FreeBSD/Linux Kernel Cross Reference
sys/kernel/sched.c

     /*
      *  kernel/sched.c
      *
      *  Kernel scheduler and related syscalls
      *
      *  Copyright (C) 1991-2002  Linus Torvalds
      *
      *  1996-12-23  Modified by Dave Grothe to fix bugs in semaphores and
      *              make semaphores SMP safe
     *  1998-11-19  Implemented schedule_timeout() and related stuff
     *              by Andrea Arcangeli
     *  2002-01-04  New ultra-scalable O(1) scheduler by Ingo Molnar:
     *              hybrid priority-list and round-robin design with
     *              an array-switch method of distributing timeslices
     *              and per-CPU runqueues.  Cleanups and useful suggestions
     *              by Davide Libenzi, preemptible kernel bits by Robert Love.
     *  2003-09-03  Interactivity tuning by Con Kolivas.
     *  2004-04-02  Scheduler domains code by Nick Piggin
     *  2007-04-15  Work begun on replacing all interactivity tuning with a
     *              fair scheduling design by Con Kolivas.
     *  2007-05-05  Load balancing (smp-nice) and other improvements
     *              by Peter Williams
     *  2007-05-06  Interactivity improvements to CFS by Mike Galbraith
     *  2007-07-01  Group scheduling enhancements by Srivatsa Vaddagiri
     *  2007-11-29  RT balancing improvements by Steven Rostedt, Gregory Haskins,
     *              Thomas Gleixner, Mike Kravetz
     */
    
    #include <linux/mm.h>
    #include <linux/module.h>
    #include <linux/nmi.h>
    #include <linux/init.h>
    #include <linux/uaccess.h>
    #include <linux/highmem.h>
    #include <asm/mmu_context.h>
    #include <linux/interrupt.h>
    #include <linux/capability.h>
    #include <linux/completion.h>
    #include <linux/kernel_stat.h>
    #include <linux/debug_locks.h>
    #include <linux/perf_event.h>
    #include <linux/security.h>
    #include <linux/notifier.h>
    #include <linux/profile.h>
    #include <linux/freezer.h>
    #include <linux/vmalloc.h>
    #include <linux/blkdev.h>
    #include <linux/delay.h>
    #include <linux/pid_namespace.h>
    #include <linux/smp.h>
    #include <linux/threads.h>
    #include <linux/timer.h>
    #include <linux/rcupdate.h>
    #include <linux/cpu.h>
    #include <linux/cpuset.h>
    #include <linux/percpu.h>
    #include <linux/proc_fs.h>
    #include <linux/seq_file.h>
    #include <linux/stop_machine.h>
    #include <linux/sysctl.h>
    #include <linux/syscalls.h>
    #include <linux/times.h>
    #include <linux/tsacct_kern.h>
    #include <linux/kprobes.h>
    #include <linux/delayacct.h>
    #include <linux/unistd.h>
    #include <linux/pagemap.h>
    #include <linux/hrtimer.h>
    #include <linux/tick.h>
    #include <linux/debugfs.h>
    #include <linux/ctype.h>
    #include <linux/ftrace.h>
    #include <linux/slab.h>
    
    #include <asm/tlb.h>
    #include <asm/irq_regs.h>
    #include <asm/mutex.h>
    #ifdef CONFIG_PARAVIRT
    #include <asm/paravirt.h>
    #endif
    
    #include "sched_cpupri.h"
    #include "workqueue_sched.h"
    #include "sched_autogroup.h"
    
    #define CREATE_TRACE_POINTS
    #include <trace/events/sched.h>
    
    /*
     * Convert user-nice values [ -20 ... 0 ... 19 ]
     * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],
     * and back.
     */
    #define NICE_TO_PRIO(nice)      (MAX_RT_PRIO + (nice) + 20)
    #define PRIO_TO_NICE(prio)      ((prio) - MAX_RT_PRIO - 20)
    #define TASK_NICE(p)            PRIO_TO_NICE((p)->static_prio)
    
    /*
     * 'User priority' is the nice value converted to something we
    * can work with better when scaling various scheduler parameters,
    * it's a [ 0 ... 39 ] range.
    */
   #define USER_PRIO(p)            ((p)-MAX_RT_PRIO)
   #define TASK_USER_PRIO(p)       USER_PRIO((p)->static_prio)
   #define MAX_USER_PRIO           (USER_PRIO(MAX_PRIO))
   
   /*
    * Helpers for converting nanosecond timing to jiffy resolution
    */
   #define NS_TO_JIFFIES(TIME)     ((unsigned long)(TIME) / (NSEC_PER_SEC / HZ))
   
   #define NICE_0_LOAD             SCHED_LOAD_SCALE
   #define NICE_0_SHIFT            SCHED_LOAD_SHIFT
   
   /*
    * These are the 'tuning knobs' of the scheduler:
    *
    * default timeslice is 100 msecs (used only for SCHED_RR tasks).
    * Timeslices get refilled after they expire.
    */
   #define DEF_TIMESLICE           (100 * HZ / 1000)
   
   /*
    * single value that denotes runtime == period, ie unlimited time.
    */
   #define RUNTIME_INF     ((u64)~0ULL)
   
   static inline int rt_policy(int policy)
   {
           if (policy == SCHED_FIFO || policy == SCHED_RR)
                   return 1;
           return 0;
   }
   
   static inline int task_has_rt_policy(struct task_struct *p)
   {
           return rt_policy(p->policy);
   }
   
   /*
    * This is the priority-queue data structure of the RT scheduling class:
    */
   struct rt_prio_array {
           DECLARE_BITMAP(bitmap, MAX_RT_PRIO+1); /* include 1 bit for delimiter */
           struct list_head queue[MAX_RT_PRIO];
   };
   
   struct rt_bandwidth {
           /* nests inside the rq lock: */
           raw_spinlock_t          rt_runtime_lock;
           ktime_t                 rt_period;
           u64                     rt_runtime;
           struct hrtimer          rt_period_timer;
   };
   
   static struct rt_bandwidth def_rt_bandwidth;
   
   static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
   
   static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
   {
           struct rt_bandwidth *rt_b =
                   container_of(timer, struct rt_bandwidth, rt_period_timer);
           ktime_t now;
           int overrun;
           int idle = 0;
   
           for (;;) {
                   now = hrtimer_cb_get_time(timer);
                   overrun = hrtimer_forward(timer, now, rt_b->rt_period);
   
                   if (!overrun)
                           break;
   
                   idle = do_sched_rt_period_timer(rt_b, overrun);
           }
   
           return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
   }
   
   static
   void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
   {
           rt_b->rt_period = ns_to_ktime(period);
           rt_b->rt_runtime = runtime;
   
           raw_spin_lock_init(&rt_b->rt_runtime_lock);
   
           hrtimer_init(&rt_b->rt_period_timer,
                           CLOCK_MONOTONIC, HRTIMER_MODE_REL);
           rt_b->rt_period_timer.function = sched_rt_period_timer;
   }
   
   static inline int rt_bandwidth_enabled(void)
   {
           return sysctl_sched_rt_runtime >= 0;
   }
   
   static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
   {
           ktime_t now;
   
           if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
                   return;
   
           if (hrtimer_active(&rt_b->rt_period_timer))
                   return;
   
           raw_spin_lock(&rt_b->rt_runtime_lock);
           for (;;) {
                   unsigned long delta;
                   ktime_t soft, hard;
   
                   if (hrtimer_active(&rt_b->rt_period_timer))
                           break;
   
                   now = hrtimer_cb_get_time(&rt_b->rt_period_timer);
                   hrtimer_forward(&rt_b->rt_period_timer, now, rt_b->rt_period);
   
                   soft = hrtimer_get_softexpires(&rt_b->rt_period_timer);
                   hard = hrtimer_get_expires(&rt_b->rt_period_timer);
                   delta = ktime_to_ns(ktime_sub(hard, soft));
                   __hrtimer_start_range_ns(&rt_b->rt_period_timer, soft, delta,
                                   HRTIMER_MODE_ABS_PINNED, 0);
           }
           raw_spin_unlock(&rt_b->rt_runtime_lock);
   }
   
   #ifdef CONFIG_RT_GROUP_SCHED
   static void destroy_rt_bandwidth(struct rt_bandwidth *rt_b)
   {
           hrtimer_cancel(&rt_b->rt_period_timer);
   }
   #endif
   
   /*
    * sched_domains_mutex serializes calls to init_sched_domains,
    * detach_destroy_domains and partition_sched_domains.
    */
   static DEFINE_MUTEX(sched_domains_mutex);
   
   #ifdef CONFIG_CGROUP_SCHED
   
   #include <linux/cgroup.h>
   
   struct cfs_rq;
   
   static LIST_HEAD(task_groups);
   
   /* task group related information */
   struct task_group {
           struct cgroup_subsys_state css;
   
   #ifdef CONFIG_FAIR_GROUP_SCHED
           /* schedulable entities of this group on each cpu */
           struct sched_entity **se;
           /* runqueue "owned" by this group on each cpu */
           struct cfs_rq **cfs_rq;
           unsigned long shares;
   
           atomic_t load_weight;
   #endif
   
   #ifdef CONFIG_RT_GROUP_SCHED
           struct sched_rt_entity **rt_se;
           struct rt_rq **rt_rq;
   
           struct rt_bandwidth rt_bandwidth;
   #endif
   
           struct rcu_head rcu;
           struct list_head list;
   
           struct task_group *parent;
           struct list_head siblings;
           struct list_head children;
   
   #ifdef CONFIG_SCHED_AUTOGROUP
           struct autogroup *autogroup;
   #endif
   };
   
   /* task_group_lock serializes the addition/removal of task groups */
   static DEFINE_SPINLOCK(task_group_lock);
   
   #ifdef CONFIG_FAIR_GROUP_SCHED
   
   # define ROOT_TASK_GROUP_LOAD   NICE_0_LOAD
   
   /*
    * A weight of 0 or 1 can cause arithmetics problems.
    * A weight of a cfs_rq is the sum of weights of which entities
    * are queued on this cfs_rq, so a weight of a entity should not be
    * too large, so as the shares value of a task group.
    * (The default weight is 1024 - so there's no practical
    *  limitation from this.)
    */
   #define MIN_SHARES      (1UL <<  1)
   #define MAX_SHARES      (1UL << 18)
   
   static int root_task_group_load = ROOT_TASK_GROUP_LOAD;
   #endif
   
   /* Default task group.
    *      Every task in system belong to this group at bootup.
    */
   struct task_group root_task_group;
   
   #endif  /* CONFIG_CGROUP_SCHED */
   
   /* CFS-related fields in a runqueue */
   struct cfs_rq {
           struct load_weight load;
           unsigned long nr_running;
   
           u64 exec_clock;
           u64 min_vruntime;
   #ifndef CONFIG_64BIT
           u64 min_vruntime_copy;
   #endif
   
           struct rb_root tasks_timeline;
           struct rb_node *rb_leftmost;
   
           struct list_head tasks;
           struct list_head *balance_iterator;
   
           /*
            * 'curr' points to currently running entity on this cfs_rq.
            * It is set to NULL otherwise (i.e when none are currently running).
            */
           struct sched_entity *curr, *next, *last, *skip;
   
   #ifdef  CONFIG_SCHED_DEBUG
           unsigned int nr_spread_over;
   #endif
   
   #ifdef CONFIG_FAIR_GROUP_SCHED
           struct rq *rq;  /* cpu runqueue to which this cfs_rq is attached */
   
           /*
            * leaf cfs_rqs are those that hold tasks (lowest schedulable entity in
            * a hierarchy). Non-leaf lrqs hold other higher schedulable entities
            * (like users, containers etc.)
            *
            * leaf_cfs_rq_list ties together list of leaf cfs_rq's in a cpu. This
            * list is used during load balance.
            */
           int on_list;
           struct list_head leaf_cfs_rq_list;
           struct task_group *tg;  /* group that "owns" this runqueue */
   
   #ifdef CONFIG_SMP
           /*
            * the part of load.weight contributed by tasks
            */
           unsigned long task_weight;
   
           /*
            *   h_load = weight * f(tg)
            *
            * Where f(tg) is the recursive weight fraction assigned to
            * this group.
            */
           unsigned long h_load;
   
           /*
            * Maintaining per-cpu shares distribution for group scheduling
            *
            * load_stamp is the last time we updated the load average
            * load_last is the last time we updated the load average and saw load
            * load_unacc_exec_time is currently unaccounted execution time
            */
           u64 load_avg;
           u64 load_period;
           u64 load_stamp, load_last, load_unacc_exec_time;
   
           unsigned long load_contribution;
   #endif
   #endif
   };
   
   /* Real-Time classes' related field in a runqueue: */
   struct rt_rq {
           struct rt_prio_array active;
           unsigned long rt_nr_running;
   #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
           struct {
                   int curr; /* highest queued rt task prio */
   #ifdef CONFIG_SMP
                   int next; /* next highest */
   #endif
           } highest_prio;
   #endif
   #ifdef CONFIG_SMP
           unsigned long rt_nr_migratory;
           unsigned long rt_nr_total;
           int overloaded;
           struct plist_head pushable_tasks;
   #endif
           int rt_throttled;
           u64 rt_time;
           u64 rt_runtime;
           /* Nests inside the rq lock: */
           raw_spinlock_t rt_runtime_lock;
   
   #ifdef CONFIG_RT_GROUP_SCHED
           unsigned long rt_nr_boosted;
   
           struct rq *rq;
           struct list_head leaf_rt_rq_list;
           struct task_group *tg;
   #endif
   };
   
   #ifdef CONFIG_SMP
   
   /*
    * We add the notion of a root-domain which will be used to define per-domain
    * variables. Each exclusive cpuset essentially defines an island domain by
    * fully partitioning the member cpus from any other cpuset. Whenever a new
    * exclusive cpuset is created, we also create and attach a new root-domain
    * object.
    *
    */
   struct root_domain {
           atomic_t refcount;
           atomic_t rto_count;
           struct rcu_head rcu;
           cpumask_var_t span;
           cpumask_var_t online;
   
           /*
            * The "RT overload" flag: it gets set if a CPU has more than
            * one runnable RT task.
            */
           cpumask_var_t rto_mask;
           struct cpupri cpupri;
   };
   
   /*
    * By default the system creates a single root-domain with all cpus as
    * members (mimicking the global state we have today).
    */
   static struct root_domain def_root_domain;
   
   #endif /* CONFIG_SMP */
   
   /*
    * This is the main, per-CPU runqueue data structure.
    *
    * Locking rule: those places that want to lock multiple runqueues
    * (such as the load balancing or the thread migration code), lock
    * acquire operations must be ordered by ascending &runqueue.
    */
   struct rq {
           /* runqueue lock: */
           raw_spinlock_t lock;
   
           /*
            * nr_running and cpu_load should be in the same cacheline because
            * remote CPUs use both these fields when doing load calculation.
            */
           unsigned long nr_running;
           #define CPU_LOAD_IDX_MAX 5
           unsigned long cpu_load[CPU_LOAD_IDX_MAX];
           unsigned long last_load_update_tick;
   #ifdef CONFIG_NO_HZ
           u64 nohz_stamp;
           unsigned char nohz_balance_kick;
   #endif
           int skip_clock_update;
   
           /* capture load from *all* tasks on this cpu: */
           struct load_weight load;
           unsigned long nr_load_updates;
           u64 nr_switches;
   
           struct cfs_rq cfs;
           struct rt_rq rt;
   
   #ifdef CONFIG_FAIR_GROUP_SCHED
           /* list of leaf cfs_rq on this cpu: */
           struct list_head leaf_cfs_rq_list;
   #endif
   #ifdef CONFIG_RT_GROUP_SCHED
           struct list_head leaf_rt_rq_list;
   #endif
   
           /*
            * This is part of a global counter where only the total sum
            * over all CPUs matters. A task can increase this counter on
            * one CPU and if it got migrated afterwards it may decrease
            * it on another CPU. Always updated under the runqueue lock:
            */
           unsigned long nr_uninterruptible;
   
           struct task_struct *curr, *idle, *stop;
           unsigned long next_balance;
           struct mm_struct *prev_mm;
   
           u64 clock;
           u64 clock_task;
   
           atomic_t nr_iowait;
   
   #ifdef CONFIG_SMP
           struct root_domain *rd;
           struct sched_domain *sd;
   
           unsigned long cpu_power;
   
           unsigned char idle_at_tick;
           /* For active balancing */
           int post_schedule;
           int active_balance;
           int push_cpu;
           struct cpu_stop_work active_balance_work;
           /* cpu of this runqueue: */
           int cpu;
           int online;
   
           unsigned long avg_load_per_task;
   
           u64 rt_avg;
           u64 age_stamp;
           u64 idle_stamp;
           u64 avg_idle;
   #endif
   
   #ifdef CONFIG_IRQ_TIME_ACCOUNTING
           u64 prev_irq_time;
   #endif
   #ifdef CONFIG_PARAVIRT
           u64 prev_steal_time;
   #endif
   #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
           u64 prev_steal_time_rq;
   #endif
   
           /* calc_load related fields */
           unsigned long calc_load_update;
           long calc_load_active;
   
   #ifdef CONFIG_SCHED_HRTICK
   #ifdef CONFIG_SMP
           int hrtick_csd_pending;
           struct call_single_data hrtick_csd;
   #endif
           struct hrtimer hrtick_timer;
   #endif
   
   #ifdef CONFIG_SCHEDSTATS
           /* latency stats */
           struct sched_info rq_sched_info;
           unsigned long long rq_cpu_time;
           /* could above be rq->cfs_rq.exec_clock + rq->rt_rq.rt_runtime ? */
   
           /* sys_sched_yield() stats */
           unsigned int yld_count;
   
           /* schedule() stats */
           unsigned int sched_switch;
           unsigned int sched_count;
           unsigned int sched_goidle;
   
           /* try_to_wake_up() stats */
           unsigned int ttwu_count;
           unsigned int ttwu_local;
   #endif
   
   #ifdef CONFIG_SMP
           struct task_struct *wake_list;
   #endif
   };
   
   static DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
   
   
   static void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags);
   
   static inline int cpu_of(struct rq *rq)
   {
   #ifdef CONFIG_SMP
           return rq->cpu;
   #else
           return 0;
   #endif
   }
   
   #define rcu_dereference_check_sched_domain(p) \
           rcu_dereference_check((p), \
                                 lockdep_is_held(&sched_domains_mutex))
   
   /*
    * The domain tree (rq->sd) is protected by RCU's quiescent state transition.
    * See detach_destroy_domains: synchronize_sched for details.
    *
    * The domain tree of any CPU may only be accessed from within
    * preempt-disabled sections.
    */
   #define for_each_domain(cpu, __sd) \
           for (__sd = rcu_dereference_check_sched_domain(cpu_rq(cpu)->sd); __sd; __sd = __sd->parent)
   
   #define cpu_rq(cpu)             (&per_cpu(runqueues, (cpu)))
   #define this_rq()               (&__get_cpu_var(runqueues))
   #define task_rq(p)              cpu_rq(task_cpu(p))
   #define cpu_curr(cpu)           (cpu_rq(cpu)->curr)
   #define raw_rq()                (&__raw_get_cpu_var(runqueues))
   
   #ifdef CONFIG_CGROUP_SCHED
   
   /*
    * Return the group to which this tasks belongs.
    *
    * We use task_subsys_state_check() and extend the RCU verification with
    * pi->lock and rq->lock because cpu_cgroup_attach() holds those locks for each
    * task it moves into the cgroup. Therefore by holding either of those locks,
    * we pin the task to the current cgroup.
    */
   static inline struct task_group *task_group(struct task_struct *p)
   {
           struct task_group *tg;
           struct cgroup_subsys_state *css;
   
           css = task_subsys_state_check(p, cpu_cgroup_subsys_id,
                           lockdep_is_held(&p->pi_lock) ||
                           lockdep_is_held(&task_rq(p)->lock));
           tg = container_of(css, struct task_group, css);
   
           return autogroup_task_group(p, tg);
   }
   
   /* Change a task's cfs_rq and parent entity if it moves across CPUs/groups */
   static inline void set_task_rq(struct task_struct *p, unsigned int cpu)
   {
   #ifdef CONFIG_FAIR_GROUP_SCHED
           p->se.cfs_rq = task_group(p)->cfs_rq[cpu];
           p->se.parent = task_group(p)->se[cpu];
   #endif
   
   #ifdef CONFIG_RT_GROUP_SCHED
           p->rt.rt_rq  = task_group(p)->rt_rq[cpu];
           p->rt.parent = task_group(p)->rt_se[cpu];
   #endif
   }
   
   #else /* CONFIG_CGROUP_SCHED */
   
   static inline void set_task_rq(struct task_struct *p, unsigned int cpu) { }
   static inline struct task_group *task_group(struct task_struct *p)
   {
           return NULL;
   }
   
   #endif /* CONFIG_CGROUP_SCHED */
   
   static void update_rq_clock_task(struct rq *rq, s64 delta);
   
   static void update_rq_clock(struct rq *rq)
   {
           s64 delta;
   
           if (rq->skip_clock_update > 0)
                   return;
   
           delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
           rq->clock += delta;
           update_rq_clock_task(rq, delta);
   }
   
   /*
    * Tunables that become constants when CONFIG_SCHED_DEBUG is off:
    */
   #ifdef CONFIG_SCHED_DEBUG
   # define const_debug __read_mostly
   #else
   # define const_debug static const
   #endif
   
   /**
    * runqueue_is_locked - Returns true if the current cpu runqueue is locked
    * @cpu: the processor in question.
    *
    * This interface allows printk to be called with the runqueue lock
    * held and know whether or not it is OK to wake up the klogd.
    */
   int runqueue_is_locked(int cpu)
   {
           return raw_spin_is_locked(&cpu_rq(cpu)->lock);
   }
   
   /*
    * Debugging: various feature bits
    */
   
   #define SCHED_FEAT(name, enabled)       \
           __SCHED_FEAT_##name ,
   
   enum {
   #include "sched_features.h"
   };
   
   #undef SCHED_FEAT
   
   #define SCHED_FEAT(name, enabled)       \
           (1UL << __SCHED_FEAT_##name) * enabled |
   
   const_debug unsigned int sysctl_sched_features =
   #include "sched_features.h"
           0;
   
   #undef SCHED_FEAT
   
   #ifdef CONFIG_SCHED_DEBUG
   #define SCHED_FEAT(name, enabled)       \
           #name ,
   
   static __read_mostly char *sched_feat_names[] = {
   #include "sched_features.h"
           NULL
   };
   
   #undef SCHED_FEAT
   
   static int sched_feat_show(struct seq_file *m, void *v)
   {
           int i;
   
           for (i = 0; sched_feat_names[i]; i++) {
                   if (!(sysctl_sched_features & (1UL << i)))
                           seq_puts(m, "NO_");
                   seq_printf(m, "%s ", sched_feat_names[i]);
           }
           seq_puts(m, "\n");
   
           return 0;
   }
   
   static ssize_t
   sched_feat_write(struct file *filp, const char __user *ubuf,
                   size_t cnt, loff_t *ppos)
   {
           char buf[64];
           char *cmp;
           int neg = 0;
           int i;
   
           if (cnt > 63)
                   cnt = 63;
   
           if (copy_from_user(&buf, ubuf, cnt))
                   return -EFAULT;
   
           buf[cnt] = 0;
           cmp = strstrip(buf);
   
           if (strncmp(cmp, "NO_", 3) == 0) {
                   neg = 1;
                   cmp += 3;
           }
   
           for (i = 0; sched_feat_names[i]; i++) {
                   if (strcmp(cmp, sched_feat_names[i]) == 0) {
                           if (neg)
                                   sysctl_sched_features &= ~(1UL << i);
                           else
                                   sysctl_sched_features |= (1UL << i);
                           break;
                   }
           }
   
           if (!sched_feat_names[i])
                   return -EINVAL;
   
           *ppos += cnt;
   
           return cnt;
   }
   
   static int sched_feat_open(struct inode *inode, struct file *filp)
   {
           return single_open(filp, sched_feat_show, NULL);
   }
   
   static const struct file_operations sched_feat_fops = {
           .open           = sched_feat_open,
           .write          = sched_feat_write,
           .read           = seq_read,
           .llseek         = seq_lseek,
           .release        = single_release,
   };
   
   static __init int sched_init_debug(void)
   {
           debugfs_create_file("sched_features", 0644, NULL, NULL,
                           &sched_feat_fops);
   
           return 0;
   }
   late_initcall(sched_init_debug);
   
   #endif
   
   #define sched_feat(x) (sysctl_sched_features & (1UL << __SCHED_FEAT_##x))
   
   /*
    * Number of tasks to iterate in a single balance run.
    * Limited because this is done with IRQs disabled.
    */
   const_debug unsigned int sysctl_sched_nr_migrate = 32;
   
   /*
    * period over which we average the RT time consumption, measured
    * in ms.
    *
    * default: 1s
    */
   const_debug unsigned int sysctl_sched_time_avg = MSEC_PER_SEC;
   
   /*
    * period over which we measure -rt task cpu usage in us.
    * default: 1s
    */
   unsigned int sysctl_sched_rt_period = 1000000;
   
   static __read_mostly int scheduler_running;
   
   /*
    * part of the period that we allow rt tasks to run in us.
    * default: 0.95s
    */
   int sysctl_sched_rt_runtime = 950000;
   
   static inline u64 global_rt_period(void)
   {
           return (u64)sysctl_sched_rt_period * NSEC_PER_USEC;
   }
   
   static inline u64 global_rt_runtime(void)
   {
           if (sysctl_sched_rt_runtime < 0)
                   return RUNTIME_INF;
   
           return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC;
   }
   
   #ifndef prepare_arch_switch
   # define prepare_arch_switch(next)      do { } while (0)
   #endif
   #ifndef finish_arch_switch
   # define finish_arch_switch(prev)       do { } while (0)
   #endif
   
   static inline int task_current(struct rq *rq, struct task_struct *p)
   {
           return rq->curr == p;
   }
   
   static inline int task_running(struct rq *rq, struct task_struct *p)
   {
   #ifdef CONFIG_SMP
           return p->on_cpu;
   #else
           return task_current(rq, p);
   #endif
   }
   
   #ifndef __ARCH_WANT_UNLOCKED_CTXSW
   static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
   {
   #ifdef CONFIG_SMP
           /*
            * We can optimise this out completely for !SMP, because the
            * SMP rebalancing from interrupt is the only thing that cares
            * here.
            */
           next->on_cpu = 1;
   #endif
   }
   
   static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
   {
   #ifdef CONFIG_SMP
           /*
            * After ->on_cpu is cleared, the task can be moved to a different CPU.
            * We must ensure this doesn't happen until the switch is completely
            * finished.
            */
           smp_wmb();
           prev->on_cpu = 0;
   #endif
   #ifdef CONFIG_DEBUG_SPINLOCK
           /* this is a valid case when another task releases the spinlock */
           rq->lock.owner = current;
   #endif
           /*
            * If we are tracking spinlock dependencies then we have to
            * fix up the runqueue lock - which gets 'carried over' from
            * prev into current:
            */
           spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);
   
           raw_spin_unlock_irq(&rq->lock);
   }
   
   #else /* __ARCH_WANT_UNLOCKED_CTXSW */
   static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
   {
   #ifdef CONFIG_SMP
           /*
            * We can optimise this out completely for !SMP, because the
            * SMP rebalancing from interrupt is the only thing that cares
            * here.
            */
           next->on_cpu = 1;
   #endif
   #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
           raw_spin_unlock_irq(&rq->lock);
   #else
           raw_spin_unlock(&rq->lock);
   #endif
   }
   
   static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
   {
   #ifdef CONFIG_SMP
           /*
            * After ->on_cpu is cleared, the task can be moved to a different CPU.
            * We must ensure this doesn't happen until the switch is completely
            * finished.
            */
           smp_wmb();
           prev->on_cpu = 0;
   #endif
   #ifndef __ARCH_WANT_INTERRUPTS_ON_CTXSW
           local_irq_enable();
   #endif
   }
   #endif /* __ARCH_WANT_UNLOCKED_CTXSW */
   
   /*
    * __task_rq_lock - lock the rq @p resides on.
    */
   static inline struct rq *__task_rq_lock(struct task_struct *p)
           __acquires(rq->lock)
   {
           struct rq *rq;
   
           lockdep_assert_held(&p->pi_lock);
   
           for (;;) {
                   rq = task_rq(p);
                   raw_spin_lock(&rq->lock);
                   if (likely(rq == task_rq(p)))
                           return rq;
                   raw_spin_unlock(&rq->lock);
           }
   }
   
   /*
    * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
    */
   static struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags)
           __acquires(p->pi_lock)
           __acquires(rq->lock)
   {
           struct rq *rq;
   
           for (;;) {
                   raw_spin_lock_irqsave(&p->pi_lock, *flags);
                   rq = task_rq(p);
                   raw_spin_lock(&rq->lock);
                   if (likely(rq == task_rq(p)))
                           return rq;
                   raw_spin_unlock(&rq->lock);
                   raw_spin_unlock_irqrestore(&p->pi_lock, *flags);
           }
   }
   
   static void __task_rq_unlock(struct rq *rq)
           __releases(rq->lock)
   {
           raw_spin_unlock(&rq->lock);
   }
   
   static inline void
   task_rq_unlock(struct rq *rq, struct task_struct *p, unsigned long *flags)
           __releases(rq->lock)
           __releases(p->pi_lock)
   {
           raw_spin_unlock(&rq->lock);
           raw_spin_unlock_irqrestore(&p->pi_lock, *flags);
   }
   
   /*
    * this_rq_lock - lock this runqueue and disable interrupts.
    */
   static struct rq *this_rq_lock(void)
          __acquires(rq->lock)
  {
          struct rq *rq;
  
          local_irq_disable();
          rq = this_rq();
          raw_spin_lock(&rq->lock);
  
          return rq;
  }
  
  #ifdef CONFIG_SCHED_HRTICK
  /*
   * Use HR-timers to deliver accurate preemption points.
   *
   * Its all a bit involved since we cannot program an hrt while holding the
   * rq->lock. So what we do is store a state in in rq->hrtick_* and ask for a
   * reschedule event.
   *
   * When we get rescheduled we reprogram the hrtick_timer outside of the
   * rq->lock.
   */
  
  /*
   * Use hrtick when:
   *  - enabled by features
   *  - hrtimer is actually high res
   */
  static inline int hrtick_enabled(struct rq *rq)
  {
          if (!sched_feat(HRTICK))
                  return 0;
          if (!cpu_active(cpu_of(rq)))
                  return 0;
          return hrtimer_is_hres_active(&rq->hrtick_timer);
  }
  
  static void hrtick_clear(struct rq *rq)
  {
          if (hrtimer_active(&rq->hrtick_timer))
                  hrtimer_cancel(&rq->hrtick_timer);
  }
  
  /*
   * High-resolution timer tick.
   * Runs from hardirq context with interrupts disabled.
   */
  static enum hrtimer_restart hrtick(struct hrtimer *timer)
  {
          struct rq *rq = container_of(timer, struct rq, hrtick_timer);
  
          WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
  
          raw_spin_lock(&rq->lock);
          update_rq_clock(rq);
          rq->curr->sched_class->task_tick(rq, rq->curr, 1);
          raw_spin_unlock(&rq->lock);
  
          return HRTIMER_NORESTART;
  }
  
  #ifdef CONFIG_SMP
  /*
   * called from hardirq (IPI) context
   */
  static void __hrtick_start(void *arg)
  {
          struct rq *rq = arg;
  
          raw_spin_lock(&rq->lock);
          hrtimer_restart(&rq->hrtick_timer);
          rq->hrtick_csd_pending = 0;
          raw_spin_unlock(&rq->lock);
  }
  
  /*
   * Called to set the hrtick timer state.
   *
   * called with rq->lock held and irqs disabled
   */
  static void hrtick_start(struct rq *rq, u64 delay)
  {
          struct hrtimer *timer = &rq->hrtick_timer;
          ktime_t time = ktime_add_ns(timer->base->get_time(), delay);
  
          hrtimer_set_expires(timer, time);
  
          if (rq == this_rq()) {
                  hrtimer_restart(timer);
          } else if (!rq->hrtick_csd_pending) {
                  __smp_call_function_single(cpu_of(rq), &rq->hrtick_csd, 0);
                  rq->hrtick_csd_pending = 1;
          }
  }
  
  static int
  hotplug_hrtick(struct notifier_block *nfb, unsigned long action, void *hcpu)
  {
          int cpu = (int)(long)hcpu;
  
          switch (action) {
          case CPU_UP_CANCELED:
          case CPU_UP_CANCELED_FROZEN:
          case CPU_DOWN_PREPARE:
          case CPU_DOWN_PREPARE_FROZEN:
          case CPU_DEAD:
          case CPU_DEAD_FROZEN:
                  hrtick_clear(cpu_rq(cpu));
                  return NOTIFY_OK;
          }
  
          return NOTIFY_DONE;
  }
  
  static __init void init_hrtick(void)
  {
          hotcpu_notifier(hotplug_hrtick, 0);
  }
  #else
  /*
   * Called to set the hrtick timer state.
   *
   * called with rq->lock held and irqs disabled
   */
  static void hrtick_start(struct rq *rq, u64 delay)
  {
          __hrtimer_start_range_ns(&rq->hrtick_timer, ns_to_ktime(delay), 0,
                          HRTIMER_MODE_REL_PINNED, 0);
  }
  
  static inline void init_hrtick(void)
  {
  }
  #endif /* CONFIG_SMP */
  
  static void init_rq_hrtick(struct rq *rq)
  {
  #ifdef CONFIG_SMP
          rq->hrtick_csd_pending = 0;
  
          rq->hrtick_csd.flags = 0;
          rq->hrtick_csd.func = __hrtick_start;
          rq->hrtick_csd.info = rq;
  #endif
  
          hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
          rq->hrtick_timer.function = hrtick;
  }
  #else   /* CONFIG_SCHED_HRTICK */
  static inline void hrtick_clear(struct rq *rq)
  {
  }
  
  static inline void init_rq_hrtick(struct rq *rq)
  {
  }
  
  static inline void init_hrtick(void)
  {
  }
  #endif  /* CONFIG_SCHED_HRTICK */
  
  /*
   * resched_task - mark a task 'to be rescheduled now'.
   *
   * On UP this means the setting of the need_resched flag, on SMP it
   * might also involve a cross-CPU call to trigger the scheduler on
   * the target CPU.
   */
  #ifdef CONFIG_SMP
  
  #ifndef tsk_is_polling
  #define tsk_is_polling(t) test_tsk_thread_flag(t, TIF_POLLING_NRFLAG)
  #endif
  
  static void resched_task(struct task_struct *p)
  {
          int cpu;
  
          assert_raw_spin_locked(&task_rq(p)->lock);
  
          if (test_tsk_need_resched(p))
                  return;
  
          set_tsk_need_resched(p);
  
          cpu = task_cpu(p);
          if (cpu == smp_processor_id())
                  return;
  
          /* NEED_RESCHED must be visible before we test polling */
          smp_mb();
          if (!tsk_is_polling(p))
                  smp_send_reschedule(cpu);
  }
  
  static void resched_cpu(int cpu)
  {
          struct rq *rq = cpu_rq(cpu);
          unsigned long flags;
  
          if (!raw_spin_trylock_irqsave(&rq->lock, flags))
                  return;
          resched_task(cpu_curr(cpu));
          raw_spin_unlock_irqrestore(&rq->lock, flags);
  }
  
  #ifdef CONFIG_NO_HZ
  /*
   * In the semi idle case, use the nearest busy cpu for migrating timers
   * from an idle cpu.  This is good for power-savings.
   *
   * We don't do similar optimization for completely idle system, as
   * selecting an idle cpu will add more delays to the timers than intended
   * (as that cpu's timer base may not be uptodate wrt jiffies etc).
   */
  int get_nohz_timer_target(void)
  {
          int cpu = smp_processor_id();
          int i;
          struct sched_domain *sd;
  
          rcu_read_lock();
          for_each_domain(cpu, sd) {
                  for_each_cpu(i, sched_domain_span(sd)) {
                          if (!idle_cpu(i)) {
                                  cpu = i;
                                  goto unlock;
                          }
                  }
          }
  unlock:
          rcu_read_unlock();
          return cpu;
  }
  /*
   * When add_timer_on() enqueues a timer into the timer wheel of an
   * idle CPU then this timer might expire before the next timer event
   * which is scheduled to wake up that CPU. In case of a completely
   * idle system the next event might even be infinite time into the
   * future. wake_up_idle_cpu() ensures that the CPU is woken up and
   * leaves the inner idle loop so the newly added timer is taken into
   * account when the CPU goes back to idle and evaluates the timer
   * wheel for the next timer event.
   */
  void wake_up_idle_cpu(int cpu)
  {
          struct rq *rq = cpu_rq(cpu);
  
          if (cpu == smp_processor_id())
                  return;
  
          /*
           * This is safe, as this function is called with the timer
           * wheel base lock of (cpu) held. When the CPU is on the way
           * to idle and has not yet set rq->curr to idle then it will
           * be serialized on the timer wheel base lock and take the new
           * timer into account automatically.
           */
          if (rq->curr != rq->idle)
                  return;
  
          /*
           * We can set TIF_RESCHED on the idle task of the other CPU
           * lockless. The worst case is that the other CPU runs the
           * idle task through an additional NOOP schedule()
           */
          set_tsk_need_resched(rq->idle);
  
          /* NEED_RESCHED must be visible before we test polling */
          smp_mb();
          if (!tsk_is_polling(rq->idle))
                  smp_send_reschedule(cpu);
  }
  
  #endif /* CONFIG_NO_HZ */
  
  static u64 sched_avg_period(void)
  {
          return (u64)sysctl_sched_time_avg * NSEC_PER_MSEC / 2;
  }
  
  static void sched_avg_update(struct rq *rq)
  {
          s64 period = sched_avg_period();
  
          while ((s64)(rq->clock - rq->age_stamp) > period) {
                  /*
                   * Inline assembly required to prevent the compiler
                   * optimising this loop into a divmod call.
                   * See __iter_div_u64_rem() for another example of this.
                   */
                  asm("" : "+rm" (rq->age_stamp));
                  rq->age_stamp += period;
                  rq->rt_avg /= 2;
          }
  }
  
  static void sched_rt_avg_update(struct rq *rq, u64 rt_delta)
  {
          rq->rt_avg += rt_delta;
          sched_avg_update(rq);
  }
  
  #else /* !CONFIG_SMP */
  static void resched_task(struct task_struct *p)
  {
          assert_raw_spin_locked(&task_rq(p)->lock);
          set_tsk_need_resched(p);
  }
  
  static void sched_rt_avg_update(struct rq *rq, u64 rt_delta)
  {
  }
  
  static void sched_avg_update(struct rq *rq)
  {
  }
  #endif /* CONFIG_SMP */
  
  #if BITS_PER_LONG == 32
  # define WMULT_CONST    (~0UL)
  #else
  # define WMULT_CONST    (1UL << 32)
  #endif
  
  #define WMULT_SHIFT     32
  
  /*
   * Shift right and round:
   */
  #define SRR(x, y) (((x) + (1UL << ((y) - 1))) >> (y))
  
  /*
   * delta *= weight / lw
   */
  static unsigned long
  calc_delta_mine(unsigned long delta_exec, unsigned long weight,
                  struct load_weight *lw)
  {
          u64 tmp;
  
          /*
           * weight can be less than 2^SCHED_LOAD_RESOLUTION for task group sched
           * entities since MIN_SHARES = 2. Treat weight as 1 if less than
           * 2^SCHED_LOAD_RESOLUTION.
           */
          if (likely(weight > (1UL << SCHED_LOAD_RESOLUTION)))
                  tmp = (u64)delta_exec * scale_load_down(weight);
          else
                  tmp = (u64)delta_exec;
  
          if (!lw->inv_weight) {
                  unsigned long w = scale_load_down(lw->weight);
  
                  if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
                          lw->inv_weight = 1;
                  else if (unlikely(!w))
                          lw->inv_weight = WMULT_CONST;
                  else
                          lw->inv_weight = WMULT_CONST / w;
          }
  
          /*
           * Check whether we'd overflow the 64-bit multiplication:
           */
          if (unlikely(tmp > WMULT_CONST))
                  tmp = SRR(SRR(tmp, WMULT_SHIFT/2) * lw->inv_weight,
                          WMULT_SHIFT/2);
          else
                  tmp = SRR(tmp * lw->inv_weight, WMULT_SHIFT);
  
          return (unsigned long)min(tmp, (u64)(unsigned long)LONG_MAX);
  }
  
  static inline void update_load_add(struct load_weight *lw, unsigned long inc)
  {
          lw->weight += inc;
          lw->inv_weight = 0;
  }
  
  static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
  {
          lw->weight -= dec;
          lw->inv_weight = 0;
  }
  
  static inline void update_load_set(struct load_weight *lw, unsigned long w)
  {
          lw->weight = w;
          lw->inv_weight = 0;
  }
  
  /*
   * To aid in avoiding the subversion of "niceness" due to uneven distribution
   * of tasks with abnormal "nice" values across CPUs the contribution that
   * each task makes to its run queue's load is weighted according to its
   * scheduling class and "nice" value. For SCHED_NORMAL tasks this is just a
   * scaled version of the new time slice allocation that they receive on time
   * slice expiry etc.
   */
  
  #define WEIGHT_IDLEPRIO                3
  #define WMULT_IDLEPRIO         1431655765
  
  /*
   * Nice levels are multiplicative, with a gentle 10% change for every
   * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
   * nice 1, it will get ~10% less CPU time than another CPU-bound task
   * that remained on nice 0.
   *
   * The "10% effect" is relative and cumulative: from _any_ nice level,
   * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
   * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
   * If a task goes up by ~10% and another task goes down by ~10% then
   * the relative distance between them is ~25%.)
   */
  static const int prio_to_weight[40] = {
   /* -20 */     88761,     71755,     56483,     46273,     36291,
   /* -15 */     29154,     23254,     18705,     14949,     11916,
   /* -10 */      9548,      7620,      6100,      4904,      3906,
   /*  -5 */      3121,      2501,      1991,      1586,      1277,
   /*   0 */      1024,       820,       655,       526,       423,
   /*   5 */       335,       272,       215,       172,       137,
   /*  10 */       110,        87,        70,        56,        45,
   /*  15 */        36,        29,        23,        18,        15,
  };
  
  /*
   * Inverse (2^32/x) values of the prio_to_weight[] array, precalculated.
   *
   * In cases where the weight does not change often, we can use the
   * precalculated inverse to speed up arithmetics by turning divisions
   * into multiplications:
   */
  static const u32 prio_to_wmult[40] = {
   /* -20 */     48388,     59856,     76040,     92818,    118348,
   /* -15 */    147320,    184698,    229616,    287308,    360437,
   /* -10 */    449829,    563644,    704093,    875809,   1099582,
   /*  -5 */   1376151,   1717300,   2157191,   2708050,   3363326,
   /*   0 */   4194304,   5237765,   6557202,   8165337,  10153587,
   /*   5 */  12820798,  15790321,  19976592,  24970740,  31350126,
   /*  10 */  39045157,  49367440,  61356676,  76695844,  95443717,
   /*  15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
  };
  
  /* Time spent by the tasks of the cpu accounting group executing in ... */
  enum cpuacct_stat_index {
          CPUACCT_STAT_USER,      /* ... user mode */
          CPUACCT_STAT_SYSTEM,    /* ... kernel mode */
  
          CPUACCT_STAT_NSTATS,
  };
  
  #ifdef CONFIG_CGROUP_CPUACCT
  static void cpuacct_charge(struct task_struct *tsk, u64 cputime);
  static void cpuacct_update_stats(struct task_struct *tsk,
                  enum cpuacct_stat_index idx, cputime_t val);
  #else
  static inline void cpuacct_charge(struct task_struct *tsk, u64 cputime) {}
  static inline void cpuacct_update_stats(struct task_struct *tsk,
                  enum cpuacct_stat_index idx, cputime_t val) {}
  #endif
  
  static inline void inc_cpu_load(struct rq *rq, unsigned long load)
  {
          update_load_add(&rq->load, load);
  }
  
  static inline void dec_cpu_load(struct rq *rq, unsigned long load)
  {
          update_load_sub(&rq->load, load);
  }
  
  #if (defined(CONFIG_SMP) && defined(CONFIG_FAIR_GROUP_SCHED)) || defined(CONFIG_RT_GROUP_SCHED)
  typedef int (*tg_visitor)(struct task_group *, void *);
  
  /*
   * Iterate the full tree, calling @down when first entering a node and @up when
   * leaving it for the final time.
   */
  static int walk_tg_tree(tg_visitor down, tg_visitor up, void *data)
  {
          struct task_group *parent, *child;
          int ret;
  
          rcu_read_lock();
          parent = &root_task_group;
  down:
          ret = (*down)(parent, data);
          if (ret)
                  goto out_unlock;
          list_for_each_entry_rcu(child, &parent->children, siblings) {
                  parent = child;
                  goto down;
  
  up:
                  continue;
          }
          ret = (*up)(parent, data);
          if (ret)
                  goto out_unlock;
  
          child = parent;
          parent = parent->parent;
          if (parent)
                  goto up;
  out_unlock:
          rcu_read_unlock();
  
          return ret;
  }
  
  static int tg_nop(struct task_group *tg, void *data)
  {
          return 0;
  }
  #endif
  
  #ifdef CONFIG_SMP
  /* Used instead of source_load when we know the type == 0 */
  static unsigned long weighted_cpuload(const int cpu)
  {
          return cpu_rq(cpu)->load.weight;
  }
  
  /*
   * Return a low guess at the load of a migration-source cpu weighted
   * according to the scheduling class and "nice" value.
   *
   * We want to under-estimate the load of migration sources, to
   * balance conservatively.
   */
  static unsigned long source_load(int cpu, int type)
  {
          struct rq *rq = cpu_rq(cpu);
          unsigned long total = weighted_cpuload(cpu);
  
          if (type == 0 || !sched_feat(LB_BIAS))
                  return total;
  
          return min(rq->cpu_load[type-1], total);
  }
  
  /*
   * Return a high guess at the load of a migration-target cpu weighted
   * according to the scheduling class and "nice" value.
   */
  static unsigned long target_load(int cpu, int type)
  {
          struct rq *rq = cpu_rq(cpu);
          unsigned long total = weighted_cpuload(cpu);
  
          if (type == 0 || !sched_feat(LB_BIAS))
                  return total;
  
          return max(rq->cpu_load[type-1], total);
  }
  
  static unsigned long power_of(int cpu)
  {
          return cpu_rq(cpu)->cpu_power;
  }
  
  static int task_hot(struct task_struct *p, u64 now, struct sched_domain *sd);
  
  static unsigned long cpu_avg_load_per_task(int cpu)
  {
          struct rq *rq = cpu_rq(cpu);
          unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
  
          if (nr_running)
                  rq->avg_load_per_task = rq->load.weight / nr_running;
          else
                  rq->avg_load_per_task = 0;
  
          return rq->avg_load_per_task;
  }
  
  #ifdef CONFIG_PREEMPT
  
  static void double_rq_lock(struct rq *rq1, struct rq *rq2);
  
  /*
   * fair double_lock_balance: Safely acquires both rq->locks in a fair
   * way at the expense of forcing extra atomic operations in all
   * invocations.  This assures that the double_lock is acquired using the
   * same underlying policy as the spinlock_t on this architecture, which
   * reduces latency compared to the unfair variant below.  However, it
   * also adds more overhead and therefore may reduce throughput.
   */
  static inline int _double_lock_balance(struct rq *this_rq, struct rq *busiest)
          __releases(this_rq->lock)
          __acquires(busiest->lock)
          __acquires(this_rq->lock)
  {
          raw_spin_unlock(&this_rq->lock);
          double_rq_lock(this_rq, busiest);
  
          return 1;
  }
  
  #else
  /*
   * Unfair double_lock_balance: Optimizes throughput at the expense of
   * latency by eliminating extra atomic operations when the locks are
   * already in proper order on entry.  This favors lower cpu-ids and will
   * grant the double lock to lower cpus over higher ids under contention,
   * regardless of entry order into the function.
   */
  static int _double_lock_balance(struct rq *this_rq, struct rq *busiest)
          __releases(this_rq->lock)
          __acquires(busiest->lock)
          __acquires(this_rq->lock)
  {
          int ret = 0;
  
          if (unlikely(!raw_spin_trylock(&busiest->lock))) {
                  if (busiest < this_rq) {
                          raw_spin_unlock(&this_rq->lock);
                          raw_spin_lock(&busiest->lock);
                          raw_spin_lock_nested(&this_rq->lock,
                                                SINGLE_DEPTH_NESTING);
                          ret = 1;
                  } else
                          raw_spin_lock_nested(&busiest->lock,
                                                SINGLE_DEPTH_NESTING);
          }
          return ret;
  }
  
  #endif /* CONFIG_PREEMPT */
  
  /*
   * double_lock_balance - lock the busiest runqueue, this_rq is locked already.
   */
  static int double_lock_balance(struct rq *this_rq, struct rq *busiest)
  {
          if (unlikely(!irqs_disabled())) {
                  /* printk() doesn't work good under rq->lock */
                  raw_spin_unlock(&this_rq->lock);
                  BUG_ON(1);
          }
  
          return _double_lock_balance(this_rq, busiest);
  }
  
  static inline void double_unlock_balance(struct rq *this_rq, struct rq *busiest)
          __releases(busiest->lock)
  {
          raw_spin_unlock(&busiest->lock);
          lock_set_subclass(&this_rq->lock.dep_map, 0, _RET_IP_);
  }
  
  /*
   * double_rq_lock - safely lock two runqueues
   *
   * Note this does not disable interrupts like task_rq_lock,
   * you need to do so manually before calling.
   */
  static void double_rq_lock(struct rq *rq1, struct rq *rq2)
          __acquires(rq1->lock)
          __acquires(rq2->lock)
  {
          BUG_ON(!irqs_disabled());
          if (rq1 == rq2) {
                  raw_spin_lock(&rq1->lock);
                  __acquire(rq2->lock);   /* Fake it out ;) */
          } else {
                  if (rq1 < rq2) {
                          raw_spin_lock(&rq1->lock);
                          raw_spin_lock_nested(&rq2->lock, SINGLE_DEPTH_NESTING);
                  } else {
                          raw_spin_lock(&rq2->lock);
                          raw_spin_lock_nested(&rq1->lock, SINGLE_DEPTH_NESTING);
                  }
          }
  }
  
  /*
   * double_rq_unlock - safely unlock two runqueues
   *
   * Note this does not restore interrupts like task_rq_unlock,
   * you need to do so manually after calling.
   */
  static void double_rq_unlock(struct rq *rq1, struct rq *rq2)
          __releases(rq1->lock)
          __releases(rq2->lock)
  {
          raw_spin_unlock(&rq1->lock);
          if (rq1 != rq2)
                  raw_spin_unlock(&rq2->lock);
          else
                  __release(rq2->lock);
  }
  
  #else /* CONFIG_SMP */
  
  /*
   * double_rq_lock - safely lock two runqueues
   *
   * Note this does not disable interrupts like task_rq_lock,
   * you need to do so manually before calling.
   */
  static void double_rq_lock(struct rq *rq1, struct rq *rq2)
          __acquires(rq1->lock)
          __acquires(rq2->lock)
  {
          BUG_ON(!irqs_disabled());
          BUG_ON(rq1 != rq2);
          raw_spin_lock(&rq1->lock);
          __acquire(rq2->lock);   /* Fake it out ;) */
  }
  
  /*
   * double_rq_unlock - safely unlock two runqueues
   *
   * Note this does not restore interrupts like task_rq_unlock,
   * you need to do so manually after calling.
   */
  static void double_rq_unlock(struct rq *rq1, struct rq *rq2)
          __releases(rq1->lock)
          __releases(rq2->lock)
  {
          BUG_ON(rq1 != rq2);
          raw_spin_unlock(&rq1->lock);
          __release(rq2->lock);
  }
  
  #endif
  
  static void calc_load_account_idle(struct rq *this_rq);
  static void update_sysctl(void);
  static int get_update_sysctl_factor(void);
  static void update_cpu_load(struct rq *this_rq);
  
  static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
  {
          set_task_rq(p, cpu);
  #ifdef CONFIG_SMP
          /*
           * After ->cpu is set up to a new value, task_rq_lock(p, ...) can be
           * successfuly executed on another CPU. We must ensure that updates of
           * per-task data have been completed by this moment.
           */
          smp_wmb();
          task_thread_info(p)->cpu = cpu;
  #endif
  }
  
  static const struct sched_class rt_sched_class;
  
  #define sched_class_highest (&stop_sched_class)
  #define for_each_class(class) \
     for (class = sched_class_highest; class; class = class->next)
  
  #include "sched_stats.h"
  
  static void inc_nr_running(struct rq *rq)
  {
          rq->nr_running++;
  }
  
  static void dec_nr_running(struct rq *rq)
  {
          rq->nr_running--;
  }
  
  static void set_load_weight(struct task_struct *p)
  {
          int prio = p->static_prio - MAX_RT_PRIO;
          struct load_weight *load = &p->se.load;
  
          /*
           * SCHED_IDLE tasks get minimal weight:
           */
          if (p->policy == SCHED_IDLE) {
                  load->weight = scale_load(WEIGHT_IDLEPRIO);
                  load->inv_weight = WMULT_IDLEPRIO;
                  return;
          }
  
          load->weight = scale_load(prio_to_weight[prio]);
          load->inv_weight = prio_to_wmult[prio];
  }
  
  static void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
  {
          update_rq_clock(rq);
          sched_info_queued(p);
          p->sched_class->enqueue_task(rq, p, flags);
  }
  
  static void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
  {
          update_rq_clock(rq);
          sched_info_dequeued(p);
          p->sched_class->dequeue_task(rq, p, flags);
  }
  
  /*
   * activate_task - move a task to the runqueue.
   */
  static void activate_task(struct rq *rq, struct task_struct *p, int flags)
  {
          if (task_contributes_to_load(p))
                  rq->nr_uninterruptible--;
  
          enqueue_task(rq, p, flags);
          inc_nr_running(rq);
  }
  
  /*
   * deactivate_task - remove a task from the runqueue.
   */
  static void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
  {
          if (task_contributes_to_load(p))
                  rq->nr_uninterruptible++;
  
          dequeue_task(rq, p, flags);
          dec_nr_running(rq);
  }
  
  #ifdef CONFIG_IRQ_TIME_ACCOUNTING
  
  /*
   * There are no locks covering percpu hardirq/softirq time.
   * They are only modified in account_system_vtime, on corresponding CPU
   * with interrupts disabled. So, writes are safe.
   * They are read and saved off onto struct rq in update_rq_clock().
   * This may result in other CPU reading this CPU's irq time and can
   * race with irq/account_system_vtime on this CPU. We would either get old
   * or new value with a side effect of accounting a slice of irq time to wrong
   * task when irq is in progress while we read rq->clock. That is a worthy
   * compromise in place of having locks on each irq in account_system_time.
   */
  static DEFINE_PER_CPU(u64, cpu_hardirq_time);
  static DEFINE_PER_CPU(u64, cpu_softirq_time);
  
  static DEFINE_PER_CPU(u64, irq_start_time);
  static int sched_clock_irqtime;
  
  void enable_sched_clock_irqtime(void)
  {
          sched_clock_irqtime = 1;
  }
  
  void disable_sched_clock_irqtime(void)
  {
          sched_clock_irqtime = 0;
  }
  
  #ifndef CONFIG_64BIT
  static DEFINE_PER_CPU(seqcount_t, irq_time_seq);
  
  static inline void irq_time_write_begin(void)
  {
          __this_cpu_inc(irq_time_seq.sequence);
          smp_wmb();
  }
  
  static inline void irq_time_write_end(void)
  {
          smp_wmb();
          __this_cpu_inc(irq_time_seq.sequence);
  }
  
  static inline u64 irq_time_read(int cpu)
  {
          u64 irq_time;
          unsigned seq;
  
          do {
                  seq = read_seqcount_begin(&per_cpu(irq_time_seq, cpu));
                  irq_time = per_cpu(cpu_softirq_time, cpu) +
                             per_cpu(cpu_hardirq_time, cpu);
          } while (read_seqcount_retry(&per_cpu(irq_time_seq, cpu), seq));
  
          return irq_time;
  }
  #else /* CONFIG_64BIT */
  static inline void irq_time_write_begin(void)
  {
  }
  
  static inline void irq_time_write_end(void)
  {
  }
  
  static inline u64 irq_time_read(int cpu)
  {
          return per_cpu(cpu_softirq_time, cpu) + per_cpu(cpu_hardirq_time, cpu);
  }
  #endif /* CONFIG_64BIT */
  
  /*
   * Called before incrementing preempt_count on {soft,}irq_enter
   * and before decrementing preempt_count on {soft,}irq_exit.
   */
  void account_system_vtime(struct task_struct *curr)
  {
          unsigned long flags;
          s64 delta;
          int cpu;
  
          if (!sched_clock_irqtime)
                  return;
  
          local_irq_save(flags);
  
          cpu = smp_processor_id();
          delta = sched_clock_cpu(cpu) - __this_cpu_read(irq_start_time);
          __this_cpu_add(irq_start_time, delta);
  
          irq_time_write_begin();
          /*
           * We do not account for softirq time from ksoftirqd here.
           * We want to continue accounting softirq time to ksoftirqd thread
           * in that case, so as not to confuse scheduler with a special task
           * that do not consume any time, but still wants to run.
           */
          if (hardirq_count())
                  __this_cpu_add(cpu_hardirq_time, delta);
          else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())
                  __this_cpu_add(cpu_softirq_time, delta);
  
          irq_time_write_end();
          local_irq_restore(flags);
  }
  EXPORT_SYMBOL_GPL(account_system_vtime);
  
  #endif /* CONFIG_IRQ_TIME_ACCOUNTING */
  
  #ifdef CONFIG_PARAVIRT
  static inline u64 steal_ticks(u64 steal)
  {
          if (unlikely(steal > NSEC_PER_SEC))
                  return div_u64(steal, TICK_NSEC);
  
          return __iter_div_u64_rem(steal, TICK_NSEC, &steal);
  }
  #endif
  
  static void update_rq_clock_task(struct rq *rq, s64 delta)
  {
  /*
   * In theory, the compile should just see 0 here, and optimize out the call
   * to sched_rt_avg_update. But I don't trust it...
   */
  #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
          s64 steal = 0, irq_delta = 0;
  #endif
  #ifdef CONFIG_IRQ_TIME_ACCOUNTING
          irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
  
          /*
           * Since irq_time is only updated on {soft,}irq_exit, we might run into
           * this case when a previous update_rq_clock() happened inside a
           * {soft,}irq region.
           *
           * When this happens, we stop ->clock_task and only update the
           * prev_irq_time stamp to account for the part that fit, so that a next
           * update will consume the rest. This ensures ->clock_task is
           * monotonic.
           *
           * It does however cause some slight miss-attribution of {soft,}irq
           * time, a more accurate solution would be to update the irq_time using
           * the current rq->clock timestamp, except that would require using
           * atomic ops.
           */
          if (irq_delta > delta)
                  irq_delta = delta;
  
          rq->prev_irq_time += irq_delta;
          delta -= irq_delta;
  #endif
  #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
          if (static_branch((&paravirt_steal_rq_enabled))) {
                  u64 st;
  
                  steal = paravirt_steal_clock(cpu_of(rq));
                  steal -= rq->prev_steal_time_rq;
  
                  if (unlikely(steal > delta))
                          steal = delta;
  
                  st = steal_ticks(steal);
                  steal = st * TICK_NSEC;
  
                  rq->prev_steal_time_rq += steal;
  
                  delta -= steal;
          }
  #endif
  
          rq->clock_task += delta;
  
  #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
          if ((irq_delta + steal) && sched_feat(NONTASK_POWER))
                  sched_rt_avg_update(rq, irq_delta + steal);
  #endif
  }
  
  #ifdef CONFIG_IRQ_TIME_ACCOUNTING
  static int irqtime_account_hi_update(void)
  {
          struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
          unsigned long flags;
          u64 latest_ns;
          int ret = 0;
  
          local_irq_save(flags);
          latest_ns = this_cpu_read(cpu_hardirq_time);
          if (cputime64_gt(nsecs_to_cputime64(latest_ns), cpustat->irq))
                  ret = 1;
          local_irq_restore(flags);
          return ret;
  }
  
  static int irqtime_account_si_update(void)
  {
          struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
          unsigned long flags;
          u64 latest_ns;
          int ret = 0;
  
          local_irq_save(flags);
          latest_ns = this_cpu_read(cpu_softirq_time);
          if (cputime64_gt(nsecs_to_cputime64(latest_ns), cpustat->softirq))
                  ret = 1;
          local_irq_restore(flags);
          return ret;
  }
  
  #else /* CONFIG_IRQ_TIME_ACCOUNTING */
  
  #define sched_clock_irqtime     (0)
  
  #endif
  
  #include "sched_idletask.c"
  #include "sched_fair.c"
  #include "sched_rt.c"
  #include "sched_autogroup.c"
  #include "sched_stoptask.c"
  #ifdef CONFIG_SCHED_DEBUG
  # include "sched_debug.c"
  #endif
  
  void sched_set_stop_task(int cpu, struct task_struct *stop)
  {
          struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
          struct task_struct *old_stop = cpu_rq(cpu)->stop;
  
          if (stop) {
                  /*
                   * Make it appear like a SCHED_FIFO task, its something
                   * userspace knows about and won't get confused about.
                   *
                   * Also, it will make PI more or less work without too
                   * much confusion -- but then, stop work should not
                   * rely on PI working anyway.
                   */
                  sched_setscheduler_nocheck(stop, SCHED_FIFO, &param);
  
                  stop->sched_class = &stop_sched_class;
          }
  
          cpu_rq(cpu)->stop = stop;
  
          if (old_stop) {
                  /*
                   * Reset it back to a normal scheduling class so that
                   * it can die in pieces.
                   */
                  old_stop->sched_class = &rt_sched_class;
          }
  }
  
  /*
   * __normal_prio - return the priority that is based on the static prio
   */
  static inline int __normal_prio(struct task_struct *p)
  {
          return p->static_prio;
  }
  
  /*
   * Calculate the expected normal priority: i.e. priority
   * without taking RT-inheritance into account. Might be
   * boosted by interactivity modifiers. Changes upon fork,
   * setprio syscalls, and whenever the interactivity
   * estimator recalculates.
   */
  static inline int normal_prio(struct task_struct *p)
  {
          int prio;
  
          if (task_has_rt_policy(p))
                  prio = MAX_RT_PRIO-1 - p->rt_priority;
          else
                  prio = __normal_prio(p);
          return prio;
  }
  
  /*
   * Calculate the current priority, i.e. the priority
   * taken into account by the scheduler. This value might
   * be boosted by RT tasks, or might be boosted by
   * interactivity modifiers. Will be RT if the task got
   * RT-boosted. If not then it returns p->normal_prio.
   */
  static int effective_prio(struct task_struct *p)
  {
          p->normal_prio = normal_prio(p);
          /*
           * If we are RT tasks or we were boosted to RT priority,
           * keep the priority unchanged. Otherwise, update priority
           * to the normal priority:
           */
          if (!rt_prio(p->prio))
                  return p->normal_prio;
          return p->prio;
  }
  
  /**
   * task_curr - is this task currently executing on a CPU?
   * @p: the task in question.
   */
  inline int task_curr(const struct task_struct *p)
  {
          return cpu_curr(task_cpu(p)) == p;
  }
  
  static inline void check_class_changed(struct rq *rq, struct task_struct *p,
                                         const struct sched_class *prev_class,
                                         int oldprio)
  {
          if (prev_class != p->sched_class) {
                  if (prev_class->switched_from)
                          prev_class->switched_from(rq, p);
                  p->sched_class->switched_to(rq, p);
          } else if (oldprio != p->prio)
                  p->sched_class->prio_changed(rq, p, oldprio);
  }
  
  static void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
  {
          const struct sched_class *class;
  
          if (p->sched_class == rq->curr->sched_class) {
                  rq->curr->sched_class->check_preempt_curr(rq, p, flags);
          } else {
                  for_each_class(class) {
                          if (class == rq->curr->sched_class)
                                  break;
                          if (class == p->sched_class) {
                                  resched_task(rq->curr);
                                  break;
                          }
                  }
          }
  
          /*
           * A queue event has occurred, and we're going to schedule.  In
           * this case, we can save a useless back to back clock update.
           */
          if (rq->curr->on_rq && test_tsk_need_resched(rq->curr))
                  rq->skip_clock_update = 1;
  }
  
  #ifdef CONFIG_SMP
  /*
   * Is this task likely cache-hot:
   */
  static int
  task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
  {
          s64 delta;
  
          if (p->sched_class != &fair_sched_class)
                  return 0;
  
          if (unlikely(p->policy == SCHED_IDLE))
                  return 0;
  
          /*
           * Buddy candidates are cache hot:
           */
          if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&
                          (&p->se == cfs_rq_of(&p->se)->next ||
                           &p->se == cfs_rq_of(&p->se)->last))
                  return 1;
  
          if (sysctl_sched_migration_cost == -1)
                  return 1;
          if (sysctl_sched_migration_cost == 0)
                  return 0;
  
          delta = now - p->se.exec_start;
  
          return delta < (s64)sysctl_sched_migration_cost;
  }
  
  void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
  {
  #ifdef CONFIG_SCHED_DEBUG
          /*
           * We should never call set_task_cpu() on a blocked task,
           * ttwu() will sort out the placement.
           */
          WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
                          !(task_thread_info(p)->preempt_count & PREEMPT_ACTIVE));
  
  #ifdef CONFIG_LOCKDEP
          /*
           * The caller should hold either p->pi_lock or rq->lock, when changing
           * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
           *
           * sched_move_task() holds both and thus holding either pins the cgroup,
           * see set_task_rq().
           *
           * Furthermore, all task_rq users should acquire both locks, see
           * task_rq_lock().
           */
          WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
                                        lockdep_is_held(&task_rq(p)->lock)));
  #endif
  #endif
  
          trace_sched_migrate_task(p, new_cpu);
  
          if (task_cpu(p) != new_cpu) {
                  p->se.nr_migrations++;
                  perf_sw_event(PERF_COUNT_SW_CPU_MIGRATIONS, 1, NULL, 0);
          }
  
          __set_task_cpu(p, new_cpu);
  }
  
  struct migration_arg {
          struct task_struct *task;
          int dest_cpu;
  };
  
  static int migration_cpu_stop(void *data);
  
  /*
   * wait_task_inactive - wait for a thread to unschedule.
   *
   * If @match_state is nonzero, it's the @p->state value just checked and
   * not expected to change.  If it changes, i.e. @p might have woken up,
   * then return zero.  When we succeed in waiting for @p to be off its CPU,
   * we return a positive number (its total switch count).  If a second call
   * a short while later returns the same number, the caller can be sure that
   * @p has remained unscheduled the whole time.
   *
   * The caller must ensure that the task *will* unschedule sometime soon,
   * else this function might spin for a *long* time. This function can't
   * be called with interrupts off, or it may introduce deadlock with
   * smp_call_function() if an IPI is sent by the same process we are
   * waiting to become inactive.
   */
  unsigned long wait_task_inactive(struct task_struct *p, long match_state)
  {
          unsigned long flags;
          int running, on_rq;
          unsigned long ncsw;
          struct rq *rq;
  
          for (;;) {
                  /*
                   * We do the initial early heuristics without holding
                   * any task-queue locks at all. We'll only try to get
                   * the runqueue lock when things look like they will
                   * work out!
                   */
                  rq = task_rq(p);
  
                  /*
                   * If the task is actively running on another CPU
                   * still, just relax and busy-wait without holding
                   * any locks.
                   *
                   * NOTE! Since we don't hold any locks, it's not
                   * even sure that "rq" stays as the right runqueue!
                   * But we don't care, since "task_running()" will
                   * return false if the runqueue has changed and p
                   * is actually now running somewhere else!
                   */
                  while (task_running(rq, p)) {
                          if (match_state && unlikely(p->state != match_state))
                                  return 0;
                          cpu_relax();
                  }
  
                  /*
                   * Ok, time to look more closely! We need the rq
                   * lock now, to be *sure*. If we're wrong, we'll
                   * just go back and repeat.
                   */
                  rq = task_rq_lock(p, &flags);
                  trace_sched_wait_task(p);
                  running = task_running(rq, p);
                  on_rq = p->on_rq;
                  ncsw = 0;
                  if (!match_state || p->state == match_state)
                          ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
                  task_rq_unlock(rq, p, &flags);
  
                  /*
                   * If it changed from the expected state, bail out now.
                   */
                  if (unlikely(!ncsw))
                          break;
  
                  /*
                   * Was it really running after all now that we
                   * checked with the proper locks actually held?
                   *
                   * Oops. Go back and try again..
                   */
                  if (unlikely(running)) {
                          cpu_relax();
                          continue;
                  }
  
                  /*
                   * It's not enough that it's not actively running,
                   * it must be off the runqueue _entirely_, and not
                   * preempted!
                   *
                   * So if it was still runnable (but just not actively
                   * running right now), it's preempted, and we should
                   * yield - it could be a while.
                   */
                  if (unlikely(on_rq)) {
                          ktime_t to = ktime_set(0, NSEC_PER_SEC/HZ);
  
                          set_current_state(TASK_UNINTERRUPTIBLE);
                          schedule_hrtimeout(&to, HRTIMER_MODE_REL);
                          continue;
                  }
  
                  /*
                   * Ahh, all good. It wasn't running, and it wasn't
                   * runnable, which means that it will never become
                   * running in the future either. We're all done!
                   */
                  break;
          }
  
          return ncsw;
  }
  
  /***
   * kick_process - kick a running thread to enter/exit the kernel
   * @p: the to-be-kicked thread
   *
   * Cause a process which is running on another CPU to enter
   * kernel-mode, without any delay. (to get signals handled.)
   *
   * NOTE: this function doesn't have to take the runqueue lock,
   * because all it wants to ensure is that the remote task enters
   * the kernel. If the IPI races and the task has been migrated
   * to another CPU then no harm is done and the purpose has been
   * achieved as well.
   */
  void kick_process(struct task_struct *p)
  {
          int cpu;
  
          preempt_disable();
          cpu = task_cpu(p);
          if ((cpu != smp_processor_id()) && task_curr(p))
                  smp_send_reschedule(cpu);
          preempt_enable();
  }
  EXPORT_SYMBOL_GPL(kick_process);
  #endif /* CONFIG_SMP */
  
  #ifdef CONFIG_SMP
  /*
   * ->cpus_allowed is protected by both rq->lock and p->pi_lock
   */
  static int select_fallback_rq(int cpu, struct task_struct *p)
  {
          int dest_cpu;
          const struct cpumask *nodemask = cpumask_of_node(cpu_to_node(cpu));
  
          /* Look for allowed, online CPU in same node. */
          for_each_cpu_and(dest_cpu, nodemask, cpu_active_mask)
                  if (cpumask_test_cpu(dest_cpu, &p->cpus_allowed))
                          return dest_cpu;
  
          /* Any allowed, online CPU? */
          dest_cpu = cpumask_any_and(&p->cpus_allowed, cpu_active_mask);
          if (dest_cpu < nr_cpu_ids)
                  return dest_cpu;
  
          /* No more Mr. Nice Guy. */
          dest_cpu = cpuset_cpus_allowed_fallback(p);
          /*
           * Don't tell them about moving exiting tasks or
           * kernel threads (both mm NULL), since they never
           * leave kernel.
           */
          if (p->mm && printk_ratelimit()) {
                  printk(KERN_INFO "process %d (%s) no longer affine to cpu%d\n",
                                  task_pid_nr(p), p->comm, cpu);
          }
  
          return dest_cpu;
  }
  
  /*
   * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable.
   */
  static inline
  int select_task_rq(struct task_struct *p, int sd_flags, int wake_flags)
  {
          int cpu = p->sched_class->select_task_rq(p, sd_flags, wake_flags);
  
          /*
           * In order not to call set_task_cpu() on a blocking task we need
           * to rely on ttwu() to place the task on a valid ->cpus_allowed
           * cpu.
           *
           * Since this is common to all placement strategies, this lives here.
           *
           * [ this allows ->select_task() to simply return task_cpu(p) and
           *   not worry about this generic constraint ]
           */
          if (unlikely(!cpumask_test_cpu(cpu, &p->cpus_allowed) ||
                       !cpu_online(cpu)))
                  cpu = select_fallback_rq(task_cpu(p), p);
  
          return cpu;
  }
  
  static void update_avg(u64 *avg, u64 sample)
  {
          s64 diff = sample - *avg;
          *avg += diff >> 3;
  }
  #endif
  
  static void
  ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
  {
  #ifdef CONFIG_SCHEDSTATS
          struct rq *rq = this_rq();
  
  #ifdef CONFIG_SMP
          int this_cpu = smp_processor_id();
  
          if (cpu == this_cpu) {
                  schedstat_inc(rq, ttwu_local);
                  schedstat_inc(p, se.statistics.nr_wakeups_local);
          } else {
                  struct sched_domain *sd;
  
                  schedstat_inc(p, se.statistics.nr_wakeups_remote);
                  rcu_read_lock();
                  for_each_domain(this_cpu, sd) {
                          if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
                                  schedstat_inc(sd, ttwu_wake_remote);
                                  break;
                          }
                  }
                  rcu_read_unlock();
          }
  
          if (wake_flags & WF_MIGRATED)
                  schedstat_inc(p, se.statistics.nr_wakeups_migrate);
  
  #endif /* CONFIG_SMP */
  
          schedstat_inc(rq, ttwu_count);
          schedstat_inc(p, se.statistics.nr_wakeups);
  
          if (wake_flags & WF_SYNC)
                  schedstat_inc(p, se.statistics.nr_wakeups_sync);
  
  #endif /* CONFIG_SCHEDSTATS */
  }
  
  static void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
  {
          activate_task(rq, p, en_flags);
          p->on_rq = 1;
  
          /* if a worker is waking up, notify workqueue */
          if (p->flags & PF_WQ_WORKER)
                  wq_worker_waking_up(p, cpu_of(rq));
  }
  
  /*
   * Mark the task runnable and perform wakeup-preemption.
   */
  static void
  ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
  {
          trace_sched_wakeup(p, true);
          check_preempt_curr(rq, p, wake_flags);
  
          p->state = TASK_RUNNING;
  #ifdef CONFIG_SMP
          if (p->sched_class->task_woken)
                  p->sched_class->task_woken(rq, p);
  
          if (rq->idle_stamp) {
                  u64 delta = rq->clock - rq->idle_stamp;
                  u64 max = 2*sysctl_sched_migration_cost;
  
                  if (delta > max)
                          rq->avg_idle = max;
                  else
                          update_avg(&rq->avg_idle, delta);
                  rq->idle_stamp = 0;
          }
  #endif
  }
  
  static void
  ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags)
  {
  #ifdef CONFIG_SMP
          if (p->sched_contributes_to_load)
                  rq->nr_uninterruptible--;
  #endif
  
          ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_WAKING);
          ttwu_do_wakeup(rq, p, wake_flags);
  }
  
  /*
   * Called in case the task @p isn't fully descheduled from its runqueue,
   * in this case we must do a remote wakeup. Its a 'light' wakeup though,
   * since all we need to do is flip p->state to TASK_RUNNING, since
   * the task is still ->on_rq.
   */
  static int ttwu_remote(struct task_struct *p, int wake_flags)
  {
          struct rq *rq;
          int ret = 0;
  
          rq = __task_rq_lock(p);
          if (p->on_rq) {
                  ttwu_do_wakeup(rq, p, wake_flags);
                  ret = 1;
          }
          __task_rq_unlock(rq);
  
          return ret;
  }
  
  #ifdef CONFIG_SMP
  static void sched_ttwu_do_pending(struct task_struct *list)
  {
          struct rq *rq = this_rq();
  
          raw_spin_lock(&rq->lock);
  
          while (list) {
                  struct task_struct *p = list;
                  list = list->wake_entry;
                  ttwu_do_activate(rq, p, 0);
          }
  
          raw_spin_unlock(&rq->lock);
  }
  
  #ifdef CONFIG_HOTPLUG_CPU
  
  static void sched_ttwu_pending(void)
  {
          struct rq *rq = this_rq();
          struct task_struct *list = xchg(&rq->wake_list, NULL);
  
          if (!list)
                  return;
  
          sched_ttwu_do_pending(list);
  }
  
  #endif /* CONFIG_HOTPLUG_CPU */
  
  void scheduler_ipi(void)
  {
          struct rq *rq = this_rq();
          struct task_struct *list = xchg(&rq->wake_list, NULL);
  
          if (!list)
                  return;
  
          /*
           * Not all reschedule IPI handlers call irq_enter/irq_exit, since
           * traditionally all their work was done from the interrupt return
           * path. Now that we actually do some work, we need to make sure
           * we do call them.
           *
           * Some archs already do call them, luckily irq_enter/exit nest
           * properly.
           *
           * Arguably we should visit all archs and update all handlers,
           * however a fair share of IPIs are still resched only so this would
           * somewhat pessimize the simple resched case.
           */
          irq_enter();
          sched_ttwu_do_pending(list);
          irq_exit();
  }
  
  static void ttwu_queue_remote(struct task_struct *p, int cpu)
  {
          struct rq *rq = cpu_rq(cpu);
          struct task_struct *next = rq->wake_list;
  
          for (;;) {
                  struct task_struct *old = next;
  
                  p->wake_entry = next;
                  next = cmpxchg(&rq->wake_list, old, p);
                  if (next == old)
                          break;
          }
  
          if (!next)
                  smp_send_reschedule(cpu);
  }
  
  #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
  static int ttwu_activate_remote(struct task_struct *p, int wake_flags)
  {
          struct rq *rq;
          int ret = 0;
  
          rq = __task_rq_lock(p);
          if (p->on_cpu) {
                  ttwu_activate(rq, p, ENQUEUE_WAKEUP);
                  ttwu_do_wakeup(rq, p, wake_flags);
                  ret = 1;
          }
          __task_rq_unlock(rq);
  
          return ret;
  
  }
  #endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */
  #endif /* CONFIG_SMP */
  
  static void ttwu_queue(struct task_struct *p, int cpu)
  {
          struct rq *rq = cpu_rq(cpu);
  
  #if defined(CONFIG_SMP)
          if (sched_feat(TTWU_QUEUE) && cpu != smp_processor_id()) {
                  sched_clock_cpu(cpu); /* sync clocks x-cpu */
                  ttwu_queue_remote(p, cpu);
                  return;
          }
  #endif
  
          raw_spin_lock(&rq->lock);
          ttwu_do_activate(rq, p, 0);
          raw_spin_unlock(&rq->lock);
  }
  
  /**
   * try_to_wake_up - wake up a thread
   * @p: the thread to be awakened
   * @state: the mask of task states that can be woken
   * @wake_flags: wake modifier flags (WF_*)
   *
   * Put it on the run-queue if it's not already there. The "current"
   * thread is always on the run-queue (except when the actual
   * re-schedule is in progress), and as such you're allowed to do
   * the simpler "current->state = TASK_RUNNING" to mark yourself
   * runnable without the overhead of this.
   *
   * Returns %true if @p was woken up, %false if it was already running
   * or @state didn't match @p's state.
   */
  static int
  try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
  {
          unsigned long flags;
          int cpu, success = 0;
  
          smp_wmb();
          raw_spin_lock_irqsave(&p->pi_lock, flags);
          if (!(p->state & state))
                  goto out;
  
          success = 1; /* we're going to change ->state */
          cpu = task_cpu(p);
  
          if (p->on_rq && ttwu_remote(p, wake_flags))
                  goto stat;
  
  #ifdef CONFIG_SMP
          /*
           * If the owning (remote) cpu is still in the middle of schedule() with
           * this task as prev, wait until its done referencing the task.
           */
          while (p->on_cpu) {
  #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
                  /*
                   * In case the architecture enables interrupts in
                   * context_switch(), we cannot busy wait, since that
                   * would lead to deadlocks when an interrupt hits and
                   * tries to wake up @prev. So bail and do a complete
                   * remote wakeup.
                   */
                  if (ttwu_activate_remote(p, wake_flags))
                          goto stat;
  #else
                  cpu_relax();
  #endif
          }
          /*
           * Pairs with the smp_wmb() in finish_lock_switch().
           */
          smp_rmb();
  
          p->sched_contributes_to_load = !!task_contributes_to_load(p);
          p->state = TASK_WAKING;
  
          if (p->sched_class->task_waking)
                  p->sched_class->task_waking(p);
  
          cpu = select_task_rq(p, SD_BALANCE_WAKE, wake_flags);
          if (task_cpu(p) != cpu) {
                  wake_flags |= WF_MIGRATED;
                  set_task_cpu(p, cpu);
          }
  #endif /* CONFIG_SMP */
  
          ttwu_queue(p, cpu);
  stat:
          ttwu_stat(p, cpu, wake_flags);
  out:
          raw_spin_unlock_irqrestore(&p->pi_lock, flags);
  
          return success;
  }
  
  /**
   * try_to_wake_up_local - try to wake up a local task with rq lock held
   * @p: the thread to be awakened
   *
   * Put @p on the run-queue if it's not already there. The caller must
   * ensure that this_rq() is locked, @p is bound to this_rq() and not
   * the current task.
   */
  static void try_to_wake_up_local(struct task_struct *p)
  {
          struct rq *rq = task_rq(p);
  
          BUG_ON(rq != this_rq());
          BUG_ON(p == current);
          lockdep_assert_held(&rq->lock);
  
          if (!raw_spin_trylock(&p->pi_lock)) {
                  raw_spin_unlock(&rq->lock);
                  raw_spin_lock(&p->pi_lock);
                  raw_spin_lock(&rq->lock);
          }
  
          if (!(p->state & TASK_NORMAL))
                  goto out;
  
          if (!p->on_rq)
                  ttwu_activate(rq, p, ENQUEUE_WAKEUP);
  
          ttwu_do_wakeup(rq, p, 0);
          ttwu_stat(p, smp_processor_id(), 0);
  out:
          raw_spin_unlock(&p->pi_lock);
  }
  
  /**
   * wake_up_process - Wake up a specific process
   * @p: The process to be woken up.
   *
   * Attempt to wake up the nominated process and move it to the set of runnable
   * processes.  Returns 1 if the process was woken up, 0 if it was already
   * running.
   *
   * It may be assumed that this function implies a write memory barrier before
   * changing the task state if and only if any tasks are woken up.
   */
  int wake_up_process(struct task_struct *p)
  {
          return try_to_wake_up(p, TASK_ALL, 0);
  }
  EXPORT_SYMBOL(wake_up_process);
  
  int wake_up_state(struct task_struct *p, unsigned int state)
  {
          return try_to_wake_up(p, state, 0);
  }
  
  /*
   * Perform scheduler related setup for a newly forked process p.
   * p is forked by current.
   *
   * __sched_fork() is basic setup used by init_idle() too:
   */
  static void __sched_fork(struct task_struct *p)
  {
          p->on_rq                        = 0;
  
          p->se.on_rq                     = 0;
          p->se.exec_start                = 0;
          p->se.sum_exec_runtime          = 0;
          p->se.prev_sum_exec_runtime     = 0;
          p->se.nr_migrations             = 0;
          p->se.vruntime                  = 0;
          INIT_LIST_HEAD(&p->se.group_node);
  
  #ifdef CONFIG_SCHEDSTATS
          memset(&p->se.statistics, 0, sizeof(p->se.statistics));
  #endif
  
          INIT_LIST_HEAD(&p->rt.run_list);
  
  #ifdef CONFIG_PREEMPT_NOTIFIERS
          INIT_HLIST_HEAD(&p->preempt_notifiers);
  #endif
  }
  
  /*
   * fork()/clone()-time setup:
   */
  void sched_fork(struct task_struct *p)
  {
          unsigned long flags;
          int cpu = get_cpu();
  
          __sched_fork(p);
          /*
           * We mark the process as running here. This guarantees that
           * nobody will actually run it, and a signal or other external
           * event cannot wake it up and insert it on the runqueue either.
           */
          p->state = TASK_RUNNING;
  
          /*
           * Revert to default priority/policy on fork if requested.
           */
          if (unlikely(p->sched_reset_on_fork)) {
                  if (p->policy == SCHED_FIFO || p->policy == SCHED_RR) {
                          p->policy = SCHED_NORMAL;
                          p->normal_prio = p->static_prio;
                  }
  
                  if (PRIO_TO_NICE(p->static_prio) < 0) {
                          p->static_prio = NICE_TO_PRIO(0);
                          p->normal_prio = p->static_prio;
                          set_load_weight(p);
                  }
  
                  /*
                   * We don't need the reset flag anymore after the fork. It has
                   * fulfilled its duty:
                   */
                  p->sched_reset_on_fork = 0;
          }
  
          /*
           * Make sure we do not leak PI boosting priority to the child.
           */
          p->prio = current->normal_prio;
  
          if (!rt_prio(p->prio))
                  p->sched_class = &fair_sched_class;
  
          if (p->sched_class->task_fork)
                  p->sched_class->task_fork(p);
  
          /*
           * The child is not yet in the pid-hash so no cgroup attach races,
           * and the cgroup is pinned to this child due to cgroup_fork()
           * is ran before sched_fork().
           *
           * Silence PROVE_RCU.
           */
          raw_spin_lock_irqsave(&p->pi_lock, flags);
          set_task_cpu(p, cpu);
          raw_spin_unlock_irqrestore(&p->pi_lock, flags);
  
  #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
          if (likely(sched_info_on()))
                  memset(&p->sched_info, 0, sizeof(p->sched_info));
  #endif
  #if defined(CONFIG_SMP)
          p->on_cpu = 0;
  #endif
  #ifdef CONFIG_PREEMPT_COUNT
          /* Want to start with kernel preemption disabled. */
          task_thread_info(p)->preempt_count = 1;
  #endif
  #ifdef CONFIG_SMP
          plist_node_init(&p->pushable_tasks, MAX_PRIO);
  #endif
  
          put_cpu();
  }
  
  /*
   * wake_up_new_task - wake up a newly created task for the first time.
   *
   * This function will do some initial scheduler statistics housekeeping
   * that must be done for every newly created context, then puts the task
   * on the runqueue and wakes it.
   */
  void wake_up_new_task(struct task_struct *p)
  {
          unsigned long flags;
          struct rq *rq;
  
          raw_spin_lock_irqsave(&p->pi_lock, flags);
  #ifdef CONFIG_SMP
          /*
           * Fork balancing, do it here and not earlier because:
           *  - cpus_allowed can change in the fork path
           *  - any previously selected cpu might disappear through hotplug
           */
          set_task_cpu(p, select_task_rq(p, SD_BALANCE_FORK, 0));
  #endif
  
          rq = __task_rq_lock(p);
          activate_task(rq, p, 0);
          p->on_rq = 1;
          trace_sched_wakeup_new(p, true);
          check_preempt_curr(rq, p, WF_FORK);
  #ifdef CONFIG_SMP
          if (p->sched_class->task_woken)
                  p->sched_class->task_woken(rq, p);
  #endif
          task_rq_unlock(rq, p, &flags);
  }
  
  #ifdef CONFIG_PREEMPT_NOTIFIERS
  
  /**
   * preempt_notifier_register - tell me when current is being preempted & rescheduled
   * @notifier: notifier struct to register
   */
  void preempt_notifier_register(struct preempt_notifier *notifier)
  {
          hlist_add_head(&notifier->link, &current->preempt_notifiers);
  }
  EXPORT_SYMBOL_GPL(preempt_notifier_register);
  
  /**
   * preempt_notifier_unregister - no longer interested in preemption notifications
   * @notifier: notifier struct to unregister
   *
   * This is safe to call from within a preemption notifier.
   */
  void preempt_notifier_unregister(struct preempt_notifier *notifier)
  {
          hlist_del(&notifier->link);
  }
  EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
  
  static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
  {
          struct preempt_notifier *notifier;
          struct hlist_node *node;
  
          hlist_for_each_entry(notifier, node, &curr->preempt_notifiers, link)
                  notifier->ops->sched_in(notifier, raw_smp_processor_id());
  }
  
  static void
  fire_sched_out_preempt_notifiers(struct task_struct *curr,
                                   struct task_struct *next)
  {
          struct preempt_notifier *notifier;
          struct hlist_node *node;
  
          hlist_for_each_entry(notifier, node, &curr->preempt_notifiers, link)
                  notifier->ops->sched_out(notifier, next);
  }
  
  #else /* !CONFIG_PREEMPT_NOTIFIERS */
  
  static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
  {
  }
  
  static void
  fire_sched_out_preempt_notifiers(struct task_struct *curr,
                                   struct task_struct *next)
  {
  }
  
  #endif /* CONFIG_PREEMPT_NOTIFIERS */
  
  /**
   * prepare_task_switch - prepare to switch tasks
   * @rq: the runqueue preparing to switch
   * @prev: the current task that is being switched out
   * @next: the task we are going to switch to.
   *
   * This is called with the rq lock held and interrupts off. It must
   * be paired with a subsequent finish_task_switch after the context
   * switch.
   *
   * prepare_task_switch sets up locking and calls architecture specific
   * hooks.
   */
  static inline void
  prepare_task_switch(struct rq *rq, struct task_struct *prev,
                      struct task_struct *next)
  {
          sched_info_switch(prev, next);
          perf_event_task_sched_out(prev, next);
          fire_sched_out_preempt_notifiers(prev, next);
          prepare_lock_switch(rq, next);
          prepare_arch_switch(next);
          trace_sched_switch(prev, next);
  }
  
  /**
   * finish_task_switch - clean up after a task-switch
   * @rq: runqueue associated with task-switch
   * @prev: the thread we just switched away from.
   *
   * finish_task_switch must be called after the context switch, paired
   * with a prepare_task_switch call before the context switch.
   * finish_task_switch will reconcile locking set up by prepare_task_switch,
   * and do any other architecture-specific cleanup actions.
   *
   * Note that we may have delayed dropping an mm in context_switch(). If
   * so, we finish that here outside of the runqueue lock. (Doing it
   * with the lock held can cause deadlocks; see schedule() for
   * details.)
   */
  static void finish_task_switch(struct rq *rq, struct task_struct *prev)
          __releases(rq->lock)
  {
          struct mm_struct *mm = rq->prev_mm;
          long prev_state;
  
          rq->prev_mm = NULL;
  
          /*
           * A task struct has one reference for the use as "current".
           * If a task dies, then it sets TASK_DEAD in tsk->state and calls
           * schedule one last time. The schedule call will never return, and
           * the scheduled task must drop that reference.
           * The test for TASK_DEAD must occur while the runqueue locks are
           * still held, otherwise prev could be scheduled on another cpu, die
           * there before we look at prev->state, and then the reference would
           * be dropped twice.
           *              Manfred Spraul <manfred@colorfullife.com>
           */
          prev_state = prev->state;
          finish_arch_switch(prev);
  #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
          local_irq_disable();
  #endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */
          perf_event_task_sched_in(current);
  #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
          local_irq_enable();
  #endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */
          finish_lock_switch(rq, prev);
  
          fire_sched_in_preempt_notifiers(current);
          if (mm)
                  mmdrop(mm);
          if (unlikely(prev_state == TASK_DEAD)) {
                  /*
                   * Remove function-return probe instances associated with this
                   * task and put them back on the free list.
                   */
                  kprobe_flush_task(prev);
                  put_task_struct(prev);
          }
  }
  
  #ifdef CONFIG_SMP
  
  /* assumes rq->lock is held */
  static inline void pre_schedule(struct rq *rq, struct task_struct *prev)
  {
          if (prev->sched_class->pre_schedule)
                  prev->sched_class->pre_schedule(rq, prev);
  }
  
  /* rq->lock is NOT held, but preemption is disabled */
  static inline void post_schedule(struct rq *rq)
  {
          if (rq->post_schedule) {
                  unsigned long flags;
  
                  raw_spin_lock_irqsave(&rq->lock, flags);
                  if (rq->curr->sched_class->post_schedule)
                          rq->curr->sched_class->post_schedule(rq);
                  raw_spin_unlock_irqrestore(&rq->lock, flags);
  
                  rq->post_schedule = 0;
          }
  }
  
  #else
  
  static inline void pre_schedule(struct rq *rq, struct task_struct *p)
  {
  }
  
  static inline void post_schedule(struct rq *rq)
  {
  }
  
  #endif
  
  /**
   * schedule_tail - first thing a freshly forked thread must call.
   * @prev: the thread we just switched away from.
   */
  asmlinkage void schedule_tail(struct task_struct *prev)
          __releases(rq->lock)
  {
          struct rq *rq = this_rq();
  
          finish_task_switch(rq, prev);
  
          /*
           * FIXME: do we need to worry about rq being invalidated by the
           * task_switch?
           */
          post_schedule(rq);
  
  #ifdef __ARCH_WANT_UNLOCKED_CTXSW
          /* In this case, finish_task_switch does not reenable preemption */
          preempt_enable();
  #endif
          if (current->set_child_tid)
                  put_user(task_pid_vnr(current), current->set_child_tid);
  }
  
  /*
   * context_switch - switch to the new MM and the new
   * thread's register state.
   */
  static inline void
  context_switch(struct rq *rq, struct task_struct *prev,
                 struct task_struct *next)
  {
          struct mm_struct *mm, *oldmm;
  
          prepare_task_switch(rq, prev, next);
  
          mm = next->mm;
          oldmm = prev->active_mm;
          /*
           * For paravirt, this is coupled with an exit in switch_to to
           * combine the page table reload and the switch backend into
           * one hypercall.
           */
          arch_start_context_switch(prev);
  
          if (!mm) {
                  next->active_mm = oldmm;
                  atomic_inc(&oldmm->mm_count);
                  enter_lazy_tlb(oldmm, next);
          } else
                  switch_mm(oldmm, mm, next);
  
          if (!prev->mm) {
                  prev->active_mm = NULL;
                  rq->prev_mm = oldmm;
          }
          /*
           * Since the runqueue lock will be released by the next
           * task (which is an invalid locking op but in the case
           * of the scheduler it's an obvious special-case), so we
           * do an early lockdep release here:
           */
  #ifndef __ARCH_WANT_UNLOCKED_CTXSW
          spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
  #endif
  
          /* Here we just switch the register state and the stack. */
          switch_to(prev, next, prev);
  
          barrier();
          /*
           * this_rq must be evaluated again because prev may have moved
           * CPUs since it called schedule(), thus the 'rq' on its stack
           * frame will be invalid.
           */
          finish_task_switch(this_rq(), prev);
  }
  
  /*
   * nr_running, nr_uninterruptible and nr_context_switches:
   *
   * externally visible scheduler statistics: current number of runnable
   * threads, current number of uninterruptible-sleeping threads, total
   * number of context switches performed since bootup.
   */
  unsigned long nr_running(void)
  {
          unsigned long i, sum = 0;
  
          for_each_online_cpu(i)
                  sum += cpu_rq(i)->nr_running;
  
          return sum;
  }
  
  unsigned long nr_uninterruptible(void)
  {
          unsigned long i, sum = 0;
  
          for_each_possible_cpu(i)
                  sum += cpu_rq(i)->nr_uninterruptible;
  
          /*
           * Since we read the counters lockless, it might be slightly
           * inaccurate. Do not allow it to go below zero though:
           */
          if (unlikely((long)sum < 0))
                  sum = 0;
  
          return sum;
  }
  
  unsigned long long nr_context_switches(void)
  {
          int i;
          unsigned long long sum = 0;
  
          for_each_possible_cpu(i)
                  sum += cpu_rq(i)->nr_switches;
  
          return sum;
  }
  
  unsigned long nr_iowait(void)
  {
          unsigned long i, sum = 0;
  
          for_each_possible_cpu(i)
                  sum += atomic_read(&cpu_rq(i)->nr_iowait);
  
          return sum;
  }
  
  unsigned long nr_iowait_cpu(int cpu)
  {
          struct rq *this = cpu_rq(cpu);
          return atomic_read(&this->nr_iowait);
  }
  
  unsigned long this_cpu_load(void)
  {
          struct rq *this = this_rq();
          return this->cpu_load[0];
  }
  
  
  /* Variables and functions for calc_load */
  static atomic_long_t calc_load_tasks;
  static unsigned long calc_load_update;
  unsigned long avenrun[3];
  EXPORT_SYMBOL(avenrun);
  
  static long calc_load_fold_active(struct rq *this_rq)
  {
          long nr_active, delta = 0;
  
          nr_active = this_rq->nr_running;
          nr_active += (long) this_rq->nr_uninterruptible;
  
          if (nr_active != this_rq->calc_load_active) {
                  delta = nr_active - this_rq->calc_load_active;
                  this_rq->calc_load_active = nr_active;
          }
  
          return delta;
  }
  
  static unsigned long
  calc_load(unsigned long load, unsigned long exp, unsigned long active)
  {
          load *= exp;
          load += active * (FIXED_1 - exp);
          load += 1UL << (FSHIFT - 1);
          return load >> FSHIFT;
  }
  
  #ifdef CONFIG_NO_HZ
  /*
   * For NO_HZ we delay the active fold to the next LOAD_FREQ update.
   *
   * When making the ILB scale, we should try to pull this in as well.
   */
  static atomic_long_t calc_load_tasks_idle;
  
  static void calc_load_account_idle(struct rq *this_rq)
  {
          long delta;
  
          delta = calc_load_fold_active(this_rq);
          if (delta)
                  atomic_long_add(delta, &calc_load_tasks_idle);
  }
  
  static long calc_load_fold_idle(void)
  {
          long delta = 0;
  
          /*
           * Its got a race, we don't care...
           */
          if (atomic_long_read(&calc_load_tasks_idle))
                  delta = atomic_long_xchg(&calc_load_tasks_idle, 0);
  
          return delta;
  }
  
  /**
   * fixed_power_int - compute: x^n, in O(log n) time
   *
   * @x:         base of the power
   * @frac_bits: fractional bits of @x
   * @n:         power to raise @x to.
   *
   * By exploiting the relation between the definition of the natural power
   * function: x^n := x*x*...*x (x multiplied by itself for n times), and
   * the binary encoding of numbers used by computers: n := \Sum n_i * 2^i,
   * (where: n_i \elem {0, 1}, the binary vector representing n),
   * we find: x^n := x^(\Sum n_i * 2^i) := \Prod x^(n_i * 2^i), which is
   * of course trivially computable in O(log_2 n), the length of our binary
   * vector.
   */
  static unsigned long
  fixed_power_int(unsigned long x, unsigned int frac_bits, unsigned int n)
  {
          unsigned long result = 1UL << frac_bits;
  
          if (n) for (;;) {
                  if (n & 1) {
                          result *= x;
                          result += 1UL << (frac_bits - 1);
                          result >>= frac_bits;
                  }
                  n >>= 1;
                  if (!n)
                          break;
                  x *= x;
                  x += 1UL << (frac_bits - 1);
                  x >>= frac_bits;
          }
  
          return result;
  }
  
  /*
   * a1 = a0 * e + a * (1 - e)
   *
   * a2 = a1 * e + a * (1 - e)
   *    = (a0 * e + a * (1 - e)) * e + a * (1 - e)
   *    = a0 * e^2 + a * (1 - e) * (1 + e)
   *
   * a3 = a2 * e + a * (1 - e)
   *    = (a0 * e^2 + a * (1 - e) * (1 + e)) * e + a * (1 - e)
   *    = a0 * e^3 + a * (1 - e) * (1 + e + e^2)
   *
   *  ...
   *
   * an = a0 * e^n + a * (1 - e) * (1 + e + ... + e^n-1) [1]
   *    = a0 * e^n + a * (1 - e) * (1 - e^n)/(1 - e)
   *    = a0 * e^n + a * (1 - e^n)
   *
   * [1] application of the geometric series:
   *
   *              n         1 - x^(n+1)
   *     S_n := \Sum x^i = -------------
   *             i=0          1 - x
   */
  static unsigned long
  calc_load_n(unsigned long load, unsigned long exp,
              unsigned long active, unsigned int n)
  {
  
          return calc_load(load, fixed_power_int(exp, FSHIFT, n), active);
  }
  
  /*
   * NO_HZ can leave us missing all per-cpu ticks calling
   * calc_load_account_active(), but since an idle CPU folds its delta into
   * calc_load_tasks_idle per calc_load_account_idle(), all we need to do is fold
   * in the pending idle delta if our idle period crossed a load cycle boundary.
   *
   * Once we've updated the global active value, we need to apply the exponential
   * weights adjusted to the number of cycles missed.
   */
  static void calc_global_nohz(unsigned long ticks)
  {
          long delta, active, n;
  
          if (time_before(jiffies, calc_load_update))
                  return;
  
          /*
           * If we crossed a calc_load_update boundary, make sure to fold
           * any pending idle changes, the respective CPUs might have
           * missed the tick driven calc_load_account_active() update
           * due to NO_HZ.
           */
          delta = calc_load_fold_idle();
          if (delta)
                  atomic_long_add(delta, &calc_load_tasks);
  
          /*
           * If we were idle for multiple load cycles, apply them.
           */
          if (ticks >= LOAD_FREQ) {
                  n = ticks / LOAD_FREQ;
  
                  active = atomic_long_read(&calc_load_tasks);
                  active = active > 0 ? active * FIXED_1 : 0;
  
                  avenrun[0] = calc_load_n(avenrun[0], EXP_1, active, n);
                  avenrun[1] = calc_load_n(avenrun[1], EXP_5, active, n);
                  avenrun[2] = calc_load_n(avenrun[2], EXP_15, active, n);
  
                  calc_load_update += n * LOAD_FREQ;
          }
  
          /*
           * Its possible the remainder of the above division also crosses
           * a LOAD_FREQ period, the regular check in calc_global_load()
           * which comes after this will take care of that.
           *
           * Consider us being 11 ticks before a cycle completion, and us
           * sleeping for 4*LOAD_FREQ + 22 ticks, then the above code will
           * age us 4 cycles, and the test in calc_global_load() will
           * pick up the final one.
           */
  }
  #else
  static void calc_load_account_idle(struct rq *this_rq)
  {
  }
  
  static inline long calc_load_fold_idle(void)
  {
          return 0;
  }
  
  static void calc_global_nohz(unsigned long ticks)
  {
  }
  #endif
  
  /**
   * get_avenrun - get the load average array
   * @loads:      pointer to dest load array
   * @offset:     offset to add
   * @shift:      shift count to shift the result left
   *
   * These values are estimates at best, so no need for locking.
   */
  void get_avenrun(unsigned long *loads, unsigned long offset, int shift)
  {
          loads[0] = (avenrun[0] + offset) << shift;
          loads[1] = (avenrun[1] + offset) << shift;
          loads[2] = (avenrun[2] + offset) << shift;
  }
  
  /*
   * calc_load - update the avenrun load estimates 10 ticks after the
   * CPUs have updated calc_load_tasks.
   */
  void calc_global_load(unsigned long ticks)
  {
          long active;
  
          calc_global_nohz(ticks);
  
          if (time_before(jiffies, calc_load_update + 10))
                  return;
  
          active = atomic_long_read(&calc_load_tasks);
          active = active > 0 ? active * FIXED_1 : 0;
  
          avenrun[0] = calc_load(avenrun[0], EXP_1, active);
          avenrun[1] = calc_load(avenrun[1], EXP_5, active);
          avenrun[2] = calc_load(avenrun[2], EXP_15, active);
  
          calc_load_update += LOAD_FREQ;
  }
  
  /*
   * Called from update_cpu_load() to periodically update this CPU's
   * active count.
   */
  static void calc_load_account_active(struct rq *this_rq)
  {
          long delta;
  
          if (time_before(jiffies, this_rq->calc_load_update))
                  return;
  
          delta  = calc_load_fold_active(this_rq);
          delta += calc_load_fold_idle();
          if (delta)
                  atomic_long_add(delta, &calc_load_tasks);
  
          this_rq->calc_load_update += LOAD_FREQ;
  }
  
  /*
   * The exact cpuload at various idx values, calculated at every tick would be
   * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
   *
   * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
   * on nth tick when cpu may be busy, then we have:
   * load = ((2^idx - 1) / 2^idx)^(n-1) * load
   * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
   *
   * decay_load_missed() below does efficient calculation of
   * load = ((2^idx - 1) / 2^idx)^(n-1) * load
   * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
   *
   * The calculation is approximated on a 128 point scale.
   * degrade_zero_ticks is the number of ticks after which load at any
   * particular idx is approximated to be zero.
   * degrade_factor is a precomputed table, a row for each load idx.
   * Each column corresponds to degradation factor for a power of two ticks,
   * based on 128 point scale.
   * Example:
   * row 2, col 3 (=12) says that the degradation at load idx 2 after
   * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
   *
   * With this power of 2 load factors, we can degrade the load n times
   * by looking at 1 bits in n and doing as many mult/shift instead of
   * n mult/shifts needed by the exact degradation.
   */
  #define DEGRADE_SHIFT           7
  static const unsigned char
                  degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
  static const unsigned char
                  degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
                                          {0, 0, 0, 0, 0, 0, 0, 0},
                                          {64, 32, 8, 0, 0, 0, 0, 0},
                                          {96, 72, 40, 12, 1, 0, 0},
                                          {112, 98, 75, 43, 15, 1, 0},
                                          {120, 112, 98, 76, 45, 16, 2} };
  
  /*
   * Update cpu_load for any missed ticks, due to tickless idle. The backlog
   * would be when CPU is idle and so we just decay the old load without
   * adding any new load.
   */
  static unsigned long
  decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
  {
          int j = 0;
  
          if (!missed_updates)
                  return load;
  
          if (missed_updates >= degrade_zero_ticks[idx])
                  return 0;
  
          if (idx == 1)
                  return load >> missed_updates;
  
          while (missed_updates) {
                  if (missed_updates % 2)
                          load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
  
                  missed_updates >>= 1;
                  j++;
          }
          return load;
  }
  
  /*
   * Update rq->cpu_load[] statistics. This function is usually called every
   * scheduler tick (TICK_NSEC). With tickless idle this will not be called
   * every tick. We fix it up based on jiffies.
   */
  static void update_cpu_load(struct rq *this_rq)
  {
          unsigned long this_load = this_rq->load.weight;
          unsigned long curr_jiffies = jiffies;
          unsigned long pending_updates;
          int i, scale;
  
          this_rq->nr_load_updates++;
  
          /* Avoid repeated calls on same jiffy, when moving in and out of idle */
          if (curr_jiffies == this_rq->last_load_update_tick)
                  return;
  
          pending_updates = curr_jiffies - this_rq->last_load_update_tick;
          this_rq->last_load_update_tick = curr_jiffies;
  
          /* Update our load: */
          this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
          for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
                  unsigned long old_load, new_load;
  
                  /* scale is effectively 1 << i now, and >> i divides by scale */
  
                  old_load = this_rq->cpu_load[i];
                  old_load = decay_load_missed(old_load, pending_updates - 1, i);
                  new_load = this_load;
                  /*
                   * Round up the averaging division if load is increasing. This
                   * prevents us from getting stuck on 9 if the load is 10, for
                   * example.
                   */
                  if (new_load > old_load)
                          new_load += scale - 1;
  
                  this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
          }
  
          sched_avg_update(this_rq);
  }
  
  static void update_cpu_load_active(struct rq *this_rq)
  {
          update_cpu_load(this_rq);
  
          calc_load_account_active(this_rq);
  }
  
  #ifdef CONFIG_SMP
  
  /*
   * sched_exec - execve() is a valuable balancing opportunity, because at
   * this point the task has the smallest effective memory and cache footprint.
   */
  void sched_exec(void)
  {
          struct task_struct *p = current;
          unsigned long flags;
          int dest_cpu;
  
          raw_spin_lock_irqsave(&p->pi_lock, flags);
          dest_cpu = p->sched_class->select_task_rq(p, SD_BALANCE_EXEC, 0);
          if (dest_cpu == smp_processor_id())
                  goto unlock;
  
          if (likely(cpu_active(dest_cpu))) {
                  struct migration_arg arg = { p, dest_cpu };
  
                  raw_spin_unlock_irqrestore(&p->pi_lock, flags);
                  stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
                  return;
          }
  unlock:
          raw_spin_unlock_irqrestore(&p->pi_lock, flags);
  }
  
  #endif
  
  DEFINE_PER_CPU(struct kernel_stat, kstat);
  
  EXPORT_PER_CPU_SYMBOL(kstat);
  
  /*
   * Return any ns on the sched_clock that have not yet been accounted in
   * @p in case that task is currently running.
   *
   * Called with task_rq_lock() held on @rq.
   */
  static u64 do_task_delta_exec(struct task_struct *p, struct rq *rq)
  {
          u64 ns = 0;
  
          if (task_current(rq, p)) {
                  update_rq_clock(rq);
                  ns = rq->clock_task - p->se.exec_start;
                  if ((s64)ns < 0)
                          ns = 0;
          }
  
          return ns;
  }
  
  unsigned long long task_delta_exec(struct task_struct *p)
  {
          unsigned long flags;
          struct rq *rq;
          u64 ns = 0;
  
          rq = task_rq_lock(p, &flags);
          ns = do_task_delta_exec(p, rq);
          task_rq_unlock(rq, p, &flags);
  
          return ns;
  }
  
  /*
   * Return accounted runtime for the task.
   * In case the task is currently running, return the runtime plus current's
   * pending runtime that have not been accounted yet.
   */
  unsigned long long task_sched_runtime(struct task_struct *p)
  {
          unsigned long flags;
          struct rq *rq;
          u64 ns = 0;
  
          rq = task_rq_lock(p, &flags);
          ns = p->se.sum_exec_runtime + do_task_delta_exec(p, rq);
          task_rq_unlock(rq, p, &flags);
  
          return ns;
  }
  
  /*
   * Return sum_exec_runtime for the thread group.
   * In case the task is currently running, return the sum plus current's
   * pending runtime that have not been accounted yet.
   *
   * Note that the thread group might have other running tasks as well,
   * so the return value not includes other pending runtime that other
   * running tasks might have.
   */
  unsigned long long thread_group_sched_runtime(struct task_struct *p)
  {
          struct task_cputime totals;
          unsigned long flags;
          struct rq *rq;
          u64 ns;
  
          rq = task_rq_lock(p, &flags);
          thread_group_cputime(p, &totals);
          ns = totals.sum_exec_runtime + do_task_delta_exec(p, rq);
          task_rq_unlock(rq, p, &flags);
  
          return ns;
  }
  
  /*
   * Account user cpu time to a process.
   * @p: the process that the cpu time gets accounted to
   * @cputime: the cpu time spent in user space since the last update
   * @cputime_scaled: cputime scaled by cpu frequency
   */
  void account_user_time(struct task_struct *p, cputime_t cputime,
                         cputime_t cputime_scaled)
  {
          struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
          cputime64_t tmp;
  
          /* Add user time to process. */
          p->utime = cputime_add(p->utime, cputime);
          p->utimescaled = cputime_add(p->utimescaled, cputime_scaled);
          account_group_user_time(p, cputime);
  
          /* Add user time to cpustat. */
          tmp = cputime_to_cputime64(cputime);
          if (TASK_NICE(p) > 0)
                  cpustat->nice = cputime64_add(cpustat->nice, tmp);
          else
                  cpustat->user = cputime64_add(cpustat->user, tmp);
  
          cpuacct_update_stats(p, CPUACCT_STAT_USER, cputime);
          /* Account for user time used */
          acct_update_integrals(p);
  }
  
  /*
   * Account guest cpu time to a process.
   * @p: the process that the cpu time gets accounted to
   * @cputime: the cpu time spent in virtual machine since the last update
   * @cputime_scaled: cputime scaled by cpu frequency
   */
  static void account_guest_time(struct task_struct *p, cputime_t cputime,
                                 cputime_t cputime_scaled)
  {
          cputime64_t tmp;
          struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
  
          tmp = cputime_to_cputime64(cputime);
  
          /* Add guest time to process. */
          p->utime = cputime_add(p->utime, cputime);
          p->utimescaled = cputime_add(p->utimescaled, cputime_scaled);
          account_group_user_time(p, cputime);
          p->gtime = cputime_add(p->gtime, cputime);
  
          /* Add guest time to cpustat. */
          if (TASK_NICE(p) > 0) {
                  cpustat->nice = cputime64_add(cpustat->nice, tmp);
                  cpustat->guest_nice = cputime64_add(cpustat->guest_nice, tmp);
          } else {
                  cpustat->user = cputime64_add(cpustat->user, tmp);
                  cpustat->guest = cputime64_add(cpustat->guest, tmp);
          }
  }
  
  /*
   * Account system cpu time to a process and desired cpustat field
   * @p: the process that the cpu time gets accounted to
   * @cputime: the cpu time spent in kernel space since the last update
   * @cputime_scaled: cputime scaled by cpu frequency
   * @target_cputime64: pointer to cpustat field that has to be updated
   */
  static inline
  void __account_system_time(struct task_struct *p, cputime_t cputime,
                          cputime_t cputime_scaled, cputime64_t *target_cputime64)
  {
          cputime64_t tmp = cputime_to_cputime64(cputime);
  
          /* Add system time to process. */
          p->stime = cputime_add(p->stime, cputime);
          p->stimescaled = cputime_add(p->stimescaled, cputime_scaled);
          account_group_system_time(p, cputime);
  
          /* Add system time to cpustat. */
          *target_cputime64 = cputime64_add(*target_cputime64, tmp);
          cpuacct_update_stats(p, CPUACCT_STAT_SYSTEM, cputime);
  
          /* Account for system time used */
          acct_update_integrals(p);
  }
  
  /*
   * Account system cpu time to a process.
   * @p: the process that the cpu time gets accounted to
   * @hardirq_offset: the offset to subtract from hardirq_count()
   * @cputime: the cpu time spent in kernel space since the last update
   * @cputime_scaled: cputime scaled by cpu frequency
   */
  void account_system_time(struct task_struct *p, int hardirq_offset,
                           cputime_t cputime, cputime_t cputime_scaled)
  {
          struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
          cputime64_t *target_cputime64;
  
          if ((p->flags & PF_VCPU) && (irq_count() - hardirq_offset == 0)) {
                  account_guest_time(p, cputime, cputime_scaled);
                  return;
          }
  
          if (hardirq_count() - hardirq_offset)
                  target_cputime64 = &cpustat->irq;
          else if (in_serving_softirq())
                  target_cputime64 = &cpustat->softirq;
          else
                  target_cputime64 = &cpustat->system;
  
          __account_system_time(p, cputime, cputime_scaled, target_cputime64);
  }
  
  /*
   * Account for involuntary wait time.
   * @cputime: the cpu time spent in involuntary wait
   */
  void account_steal_time(cputime_t cputime)
  {
          struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
          cputime64_t cputime64 = cputime_to_cputime64(cputime);
  
          cpustat->steal = cputime64_add(cpustat->steal, cputime64);
  }
  
  /*
   * Account for idle time.
   * @cputime: the cpu time spent in idle wait
   */
  void account_idle_time(cputime_t cputime)
  {
          struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
          cputime64_t cputime64 = cputime_to_cputime64(cputime);
          struct rq *rq = this_rq();
  
          if (atomic_read(&rq->nr_iowait) > 0)
                  cpustat->iowait = cputime64_add(cpustat->iowait, cputime64);
          else
                  cpustat->idle = cputime64_add(cpustat->idle, cputime64);
  }
  
  static __always_inline bool steal_account_process_tick(void)
  {
  #ifdef CONFIG_PARAVIRT
          if (static_branch(&paravirt_steal_enabled)) {
                  u64 steal, st = 0;
  
                  steal = paravirt_steal_clock(smp_processor_id());
                  steal -= this_rq()->prev_steal_time;
  
                  st = steal_ticks(steal);
                  this_rq()->prev_steal_time += st * TICK_NSEC;
  
                  account_steal_time(st);
                  return st;
          }
  #endif
          return false;
  }
  
  #ifndef CONFIG_VIRT_CPU_ACCOUNTING
  
  #ifdef CONFIG_IRQ_TIME_ACCOUNTING
  /*
   * Account a tick to a process and cpustat
   * @p: the process that the cpu time gets accounted to
   * @user_tick: is the tick from userspace
   * @rq: the pointer to rq
   *
   * Tick demultiplexing follows the order
   * - pending hardirq update
   * - pending softirq update
   * - user_time
   * - idle_time
   * - system time
   *   - check for guest_time
   *   - else account as system_time
   *
   * Check for hardirq is done both for system and user time as there is
   * no timer going off while we are on hardirq and hence we may never get an
   * opportunity to update it solely in system time.
   * p->stime and friends are only updated on system time and not on irq
   * softirq as those do not count in task exec_runtime any more.
   */
  static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
                                                  struct rq *rq)
  {
          cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
          cputime64_t tmp = cputime_to_cputime64(cputime_one_jiffy);
          struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
  
          if (steal_account_process_tick())
                  return;
  
          if (irqtime_account_hi_update()) {
                  cpustat->irq = cputime64_add(cpustat->irq, tmp);
          } else if (irqtime_account_si_update()) {
                  cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
          } else if (this_cpu_ksoftirqd() == p) {
                  /*
                   * ksoftirqd time do not get accounted in cpu_softirq_time.
                   * So, we have to handle it separately here.
                   * Also, p->stime needs to be updated for ksoftirqd.
                   */
                  __account_system_time(p, cputime_one_jiffy, one_jiffy_scaled,
                                          &cpustat->softirq);
          } else if (user_tick) {
                  account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
          } else if (p == rq->idle) {
                  account_idle_time(cputime_one_jiffy);
          } else if (p->flags & PF_VCPU) { /* System time or guest time */
                  account_guest_time(p, cputime_one_jiffy, one_jiffy_scaled);
          } else {
                  __account_system_time(p, cputime_one_jiffy, one_jiffy_scaled,
                                          &cpustat->system);
          }
  }
  
  static void irqtime_account_idle_ticks(int ticks)
  {
          int i;
          struct rq *rq = this_rq();
  
          for (i = 0; i < ticks; i++)
                  irqtime_account_process_tick(current, 0, rq);
  }
  #else /* CONFIG_IRQ_TIME_ACCOUNTING */
  static void irqtime_account_idle_ticks(int ticks) {}
  static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
                                                  struct rq *rq) {}
  #endif /* CONFIG_IRQ_TIME_ACCOUNTING */
  
  /*
   * Account a single tick of cpu time.
   * @p: the process that the cpu time gets accounted to
   * @user_tick: indicates if the tick is a user or a system tick
   */
  void account_process_tick(struct task_struct *p, int user_tick)
  {
          cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
          struct rq *rq = this_rq();
  
          if (sched_clock_irqtime) {
                  irqtime_account_process_tick(p, user_tick, rq);
                  return;
          }
  
          if (steal_account_process_tick())
                  return;
  
          if (user_tick)
                  account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
          else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))
                  account_system_time(p, HARDIRQ_OFFSET, cputime_one_jiffy,
                                      one_jiffy_scaled);
          else
                  account_idle_time(cputime_one_jiffy);
  }
  
  /*
   * Account multiple ticks of steal time.
   * @p: the process from which the cpu time has been stolen
   * @ticks: number of stolen ticks
   */
  void account_steal_ticks(unsigned long ticks)
  {
          account_steal_time(jiffies_to_cputime(ticks));
  }
  
  /*
   * Account multiple ticks of idle time.
   * @ticks: number of stolen ticks
   */
  void account_idle_ticks(unsigned long ticks)
  {
  
          if (sched_clock_irqtime) {
                  irqtime_account_idle_ticks(ticks);
                  return;
          }
  
          account_idle_time(jiffies_to_cputime(ticks));
  }
  
  #endif
  
  /*
   * Use precise platform statistics if available:
   */
  #ifdef CONFIG_VIRT_CPU_ACCOUNTING
  void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
  {
          *ut = p->utime;
          *st = p->stime;
  }
  
  void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
  {
          struct task_cputime cputime;
  
          thread_group_cputime(p, &cputime);
  
          *ut = cputime.utime;
          *st = cputime.stime;
  }
  #else
  
  #ifndef nsecs_to_cputime
  # define nsecs_to_cputime(__nsecs)      nsecs_to_jiffies(__nsecs)
  #endif
  
  void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
  {
          cputime_t rtime, utime = p->utime, total = cputime_add(utime, p->stime);
  
          /*
           * Use CFS's precise accounting:
           */
          rtime = nsecs_to_cputime(p->se.sum_exec_runtime);
  
          if (total) {
                  u64 temp = rtime;
  
                  temp *= utime;
                  do_div(temp, total);
                  utime = (cputime_t)temp;
          } else
                  utime = rtime;
  
          /*
           * Compare with previous values, to keep monotonicity:
           */
          p->prev_utime = max(p->prev_utime, utime);
          p->prev_stime = max(p->prev_stime, cputime_sub(rtime, p->prev_utime));
  
          *ut = p->prev_utime;
          *st = p->prev_stime;
  }
  
  /*
   * Must be called with siglock held.
   */
  void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
  {
          struct signal_struct *sig = p->signal;
          struct task_cputime cputime;
          cputime_t rtime, utime, total;
  
          thread_group_cputime(p, &cputime);
  
          total = cputime_add(cputime.utime, cputime.stime);
          rtime = nsecs_to_cputime(cputime.sum_exec_runtime);
  
          if (total) {
                  u64 temp = rtime;
  
                  temp *= cputime.utime;
                  do_div(temp, total);
                  utime = (cputime_t)temp;
          } else
                  utime = rtime;
  
          sig->prev_utime = max(sig->prev_utime, utime);
          sig->prev_stime = max(sig->prev_stime,
                                cputime_sub(rtime, sig->prev_utime));
  
          *ut = sig->prev_utime;
          *st = sig->prev_stime;
  }
  #endif
  
  /*
   * This function gets called by the timer code, with HZ frequency.
   * We call it with interrupts disabled.
   */
  void scheduler_tick(void)
  {
          int cpu = smp_processor_id();
          struct rq *rq = cpu_rq(cpu);
          struct task_struct *curr = rq->curr;
  
          sched_clock_tick();
  
          raw_spin_lock(&rq->lock);
          update_rq_clock(rq);
          update_cpu_load_active(rq);
          curr->sched_class->task_tick(rq, curr, 0);
          raw_spin_unlock(&rq->lock);
  
          perf_event_task_tick();
  
  #ifdef CONFIG_SMP
          rq->idle_at_tick = idle_cpu(cpu);
          trigger_load_balance(rq, cpu);
  #endif
  }
  
  notrace unsigned long get_parent_ip(unsigned long addr)
  {
          if (in_lock_functions(addr)) {
                  addr = CALLER_ADDR2;
                  if (in_lock_functions(addr))
                          addr = CALLER_ADDR3;
          }
          return addr;
  }
  
  #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
                                  defined(CONFIG_PREEMPT_TRACER))
  
  void __kprobes add_preempt_count(int val)
  {
  #ifdef CONFIG_DEBUG_PREEMPT
          /*
           * Underflow?
           */
          if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
                  return;
  #endif
          preempt_count() += val;
  #ifdef CONFIG_DEBUG_PREEMPT
          /*
           * Spinlock count overflowing soon?
           */
          DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
                                  PREEMPT_MASK - 10);
  #endif
          if (preempt_count() == val)
                  trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
  }
  EXPORT_SYMBOL(add_preempt_count);
  
  void __kprobes sub_preempt_count(int val)
  {
  #ifdef CONFIG_DEBUG_PREEMPT
          /*
           * Underflow?
           */
          if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
                  return;
          /*
           * Is the spinlock portion underflowing?
           */
          if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
                          !(preempt_count() & PREEMPT_MASK)))
                  return;
  #endif
  
          if (preempt_count() == val)
                  trace_preempt_on(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
          preempt_count() -= val;
  }
  EXPORT_SYMBOL(sub_preempt_count);
  
  #endif
  
  /*
   * Print scheduling while atomic bug:
   */
  static noinline void __schedule_bug(struct task_struct *prev)
  {
          struct pt_regs *regs = get_irq_regs();
  
          printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
                  prev->comm, prev->pid, preempt_count());
  
          debug_show_held_locks(prev);
          print_modules();
          if (irqs_disabled())
                  print_irqtrace_events(prev);
  
          if (regs)
                  show_regs(regs);
          else
                  dump_stack();
  }
  
  /*
   * Various schedule()-time debugging checks and statistics:
   */
  static inline void schedule_debug(struct task_struct *prev)
  {
          /*
           * Test if we are atomic. Since do_exit() needs to call into
           * schedule() atomically, we ignore that path for now.
           * Otherwise, whine if we are scheduling when we should not be.
           */
          if (unlikely(in_atomic_preempt_off() && !prev->exit_state))
                  __schedule_bug(prev);
  
          profile_hit(SCHED_PROFILING, __builtin_return_address(0));
  
          schedstat_inc(this_rq(), sched_count);
  }
  
  static void put_prev_task(struct rq *rq, struct task_struct *prev)
  {
          if (prev->on_rq || rq->skip_clock_update < 0)
                  update_rq_clock(rq);
          prev->sched_class->put_prev_task(rq, prev);
  }
  
  /*
   * Pick up the highest-prio task:
   */
  static inline struct task_struct *
  pick_next_task(struct rq *rq)
  {
          const struct sched_class *class;
          struct task_struct *p;
  
          /*
           * Optimization: we know that if all tasks are in
           * the fair class we can call that function directly:
           */
          if (likely(rq->nr_running == rq->cfs.nr_running)) {
                  p = fair_sched_class.pick_next_task(rq);
                  if (likely(p))
                          return p;
          }
  
          for_each_class(class) {
                  p = class->pick_next_task(rq);
                  if (p)
                          return p;
          }
  
          BUG(); /* the idle class will always have a runnable task */
  }
  
  /*
   * schedule() is the main scheduler function.
   */
  asmlinkage void __sched schedule(void)
  {
          struct task_struct *prev, *next;
          unsigned long *switch_count;
          struct rq *rq;
          int cpu;
  
  need_resched:
          preempt_disable();
          cpu = smp_processor_id();
          rq = cpu_rq(cpu);
          rcu_note_context_switch(cpu);
          prev = rq->curr;
  
          schedule_debug(prev);
  
          if (sched_feat(HRTICK))
                  hrtick_clear(rq);
  
          raw_spin_lock_irq(&rq->lock);
  
          switch_count = &prev->nivcsw;
          if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
                  if (unlikely(signal_pending_state(prev->state, prev))) {
                          prev->state = TASK_RUNNING;
                  } else {
                          deactivate_task(rq, prev, DEQUEUE_SLEEP);
                          prev->on_rq = 0;
  
                          /*
                           * If a worker went to sleep, notify and ask workqueue
                           * whether it wants to wake up a task to maintain
                           * concurrency.
                           */
                          if (prev->flags & PF_WQ_WORKER) {
                                  struct task_struct *to_wakeup;
  
                                  to_wakeup = wq_worker_sleeping(prev, cpu);
                                  if (to_wakeup)
                                          try_to_wake_up_local(to_wakeup);
                          }
  
                          /*
                           * If we are going to sleep and we have plugged IO
                           * queued, make sure to submit it to avoid deadlocks.
                           */
                          if (blk_needs_flush_plug(prev)) {
                                  raw_spin_unlock(&rq->lock);
                                  blk_schedule_flush_plug(prev);
                                  raw_spin_lock(&rq->lock);
                          }
                  }
                  switch_count = &prev->nvcsw;
          }
  
          pre_schedule(rq, prev);
  
          if (unlikely(!rq->nr_running))
                  idle_balance(cpu, rq);
  
          put_prev_task(rq, prev);
          next = pick_next_task(rq);
          clear_tsk_need_resched(prev);
          rq->skip_clock_update = 0;
  
          if (likely(prev != next)) {
                  rq->nr_switches++;
                  rq->curr = next;
                  ++*switch_count;
  
                  context_switch(rq, prev, next); /* unlocks the rq */
                  /*
                   * The context switch have flipped the stack from under us
                   * and restored the local variables which were saved when
                   * this task called schedule() in the past. prev == current
                   * is still correct, but it can be moved to another cpu/rq.
                   */
                  cpu = smp_processor_id();
                  rq = cpu_rq(cpu);
          } else
                  raw_spin_unlock_irq(&rq->lock);
  
          post_schedule(rq);
  
          preempt_enable_no_resched();
          if (need_resched())
                  goto need_resched;
  }
  EXPORT_SYMBOL(schedule);
  
  #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
  
  static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
  {
          if (lock->owner != owner)
                  return false;
  
          /*
           * Ensure we emit the owner->on_cpu, dereference _after_ checking
           * lock->owner still matches owner, if that fails, owner might
           * point to free()d memory, if it still matches, the rcu_read_lock()
           * ensures the memory stays valid.
           */
          barrier();
  
          return owner->on_cpu;
  }
  
  /*
   * Look out! "owner" is an entirely speculative pointer
   * access and not reliable.
   */
  int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
  {
          if (!sched_feat(OWNER_SPIN))
                  return 0;
  
          rcu_read_lock();
          while (owner_running(lock, owner)) {
                  if (need_resched())
                          break;
  
                  arch_mutex_cpu_relax();
          }
          rcu_read_unlock();
  
          /*
           * We break out the loop above on need_resched() and when the
           * owner changed, which is a sign for heavy contention. Return
           * success only when lock->owner is NULL.
           */
          return lock->owner == NULL;
  }
  #endif
  
  #ifdef CONFIG_PREEMPT
  /*
   * this is the entry point to schedule() from in-kernel preemption
   * off of preempt_enable. Kernel preemptions off return from interrupt
   * occur there and call schedule directly.
   */
  asmlinkage void __sched notrace preempt_schedule(void)
  {
          struct thread_info *ti = current_thread_info();
  
          /*
           * If there is a non-zero preempt_count or interrupts are disabled,
           * we do not want to preempt the current task. Just return..
           */
          if (likely(ti->preempt_count || irqs_disabled()))
                  return;
  
          do {
                  add_preempt_count_notrace(PREEMPT_ACTIVE);
                  schedule();
                  sub_preempt_count_notrace(PREEMPT_ACTIVE);
  
                  /*
                   * Check again in case we missed a preemption opportunity
                   * between schedule and now.
                   */
                  barrier();
          } while (need_resched());
  }
  EXPORT_SYMBOL(preempt_schedule);
  
  /*
   * this is the entry point to schedule() from kernel preemption
   * off of irq context.
   * Note, that this is called and return with irqs disabled. This will
   * protect us against recursive calling from irq.
   */
  asmlinkage void __sched preempt_schedule_irq(void)
  {
          struct thread_info *ti = current_thread_info();
  
          /* Catch callers which need to be fixed */
          BUG_ON(ti->preempt_count || !irqs_disabled());
  
          do {
                  add_preempt_count(PREEMPT_ACTIVE);
                  local_irq_enable();
                  schedule();
                  local_irq_disable();
                  sub_preempt_count(PREEMPT_ACTIVE);
  
                  /*
                   * Check again in case we missed a preemption opportunity
                   * between schedule and now.
                   */
                  barrier();
          } while (need_resched());
  }
  
  #endif /* CONFIG_PREEMPT */
  
  int default_wake_function(wait_queue_t *curr, unsigned mode, int wake_flags,
                            void *key)
  {
          return try_to_wake_up(curr->private, mode, wake_flags);
  }
  EXPORT_SYMBOL(default_wake_function);
  
  /*
   * The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
   * wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
   * number) then we wake all the non-exclusive tasks and one exclusive task.
   *
   * There are circumstances in which we can try to wake a task which has already
   * started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
   * zero in this (rare) case, and we handle it by continuing to scan the queue.
   */
  static void __wake_up_common(wait_queue_head_t *q, unsigned int mode,
                          int nr_exclusive, int wake_flags, void *key)
  {
          wait_queue_t *curr, *next;
  
          list_for_each_entry_safe(curr, next, &q->task_list, task_list) {
                  unsigned flags = curr->flags;
  
                  if (curr->func(curr, mode, wake_flags, key) &&
                                  (flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive)
                          break;
          }
  }
  
  /**
   * __wake_up - wake up threads blocked on a waitqueue.
   * @q: the waitqueue
   * @mode: which threads
   * @nr_exclusive: how many wake-one or wake-many threads to wake up
   * @key: is directly passed to the wakeup function
   *
   * It may be assumed that this function implies a write memory barrier before
   * changing the task state if and only if any tasks are woken up.
   */
  void __wake_up(wait_queue_head_t *q, unsigned int mode,
                          int nr_exclusive, void *key)
  {
          unsigned long flags;
  
          spin_lock_irqsave(&q->lock, flags);
          __wake_up_common(q, mode, nr_exclusive, 0, key);
          spin_unlock_irqrestore(&q->lock, flags);
  }
  EXPORT_SYMBOL(__wake_up);
  
  /*
   * Same as __wake_up but called with the spinlock in wait_queue_head_t held.
   */
  void __wake_up_locked(wait_queue_head_t *q, unsigned int mode)
  {
          __wake_up_common(q, mode, 1, 0, NULL);
  }
  EXPORT_SYMBOL_GPL(__wake_up_locked);
  
  void __wake_up_locked_key(wait_queue_head_t *q, unsigned int mode, void *key)
  {
          __wake_up_common(q, mode, 1, 0, key);
  }
  EXPORT_SYMBOL_GPL(__wake_up_locked_key);
  
  /**
   * __wake_up_sync_key - wake up threads blocked on a waitqueue.
   * @q: the waitqueue
   * @mode: which threads
   * @nr_exclusive: how many wake-one or wake-many threads to wake up
   * @key: opaque value to be passed to wakeup targets
   *
   * The sync wakeup differs that the waker knows that it will schedule
   * away soon, so while the target thread will be woken up, it will not
   * be migrated to another CPU - ie. the two threads are 'synchronized'
   * with each other. This can prevent needless bouncing between CPUs.
   *
   * On UP it can prevent extra preemption.
   *
   * It may be assumed that this function implies a write memory barrier before
   * changing the task state if and only if any tasks are woken up.
   */
  void __wake_up_sync_key(wait_queue_head_t *q, unsigned int mode,
                          int nr_exclusive, void *key)
  {
          unsigned long flags;
          int wake_flags = WF_SYNC;
  
          if (unlikely(!q))
                  return;
  
          if (unlikely(!nr_exclusive))
                  wake_flags = 0;
  
          spin_lock_irqsave(&q->lock, flags);
          __wake_up_common(q, mode, nr_exclusive, wake_flags, key);
          spin_unlock_irqrestore(&q->lock, flags);
  }
  EXPORT_SYMBOL_GPL(__wake_up_sync_key);
  
  /*
   * __wake_up_sync - see __wake_up_sync_key()
   */
  void __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
  {
          __wake_up_sync_key(q, mode, nr_exclusive, NULL);
  }
  EXPORT_SYMBOL_GPL(__wake_up_sync);      /* For internal use only */
  
  /**
   * complete: - signals a single thread waiting on this completion
   * @x:  holds the state of this particular completion
   *
   * This will wake up a single thread waiting on this completion. Threads will be
   * awakened in the same order in which they were queued.
   *
   * See also complete_all(), wait_for_completion() and related routines.
   *
   * It may be assumed that this function implies a write memory barrier before
   * changing the task state if and only if any tasks are woken up.
   */
  void complete(struct completion *x)
  {
          unsigned long flags;
  
          spin_lock_irqsave(&x->wait.lock, flags);
          x->done++;
          __wake_up_common(&x->wait, TASK_NORMAL, 1, 0, NULL);
          spin_unlock_irqrestore(&x->wait.lock, flags);
  }
  EXPORT_SYMBOL(complete);
  
  /**
   * complete_all: - signals all threads waiting on this completion
   * @x:  holds the state of this particular completion
   *
   * This will wake up all threads waiting on this particular completion event.
   *
   * It may be assumed that this function implies a write memory barrier before
   * changing the task state if and only if any tasks are woken up.
   */
  void complete_all(struct completion *x)
  {
          unsigned long flags;
  
          spin_lock_irqsave(&x->wait.lock, flags);
          x->done += UINT_MAX/2;
          __wake_up_common(&x->wait, TASK_NORMAL, 0, 0, NULL);
          spin_unlock_irqrestore(&x->wait.lock, flags);
  }
  EXPORT_SYMBOL(complete_all);
  
  static inline long __sched
  do_wait_for_common(struct completion *x, long timeout, int state)
  {
          if (!x->done) {
                  DECLARE_WAITQUEUE(wait, current);
  
                  __add_wait_queue_tail_exclusive(&x->wait, &wait);
                  do {
                          if (signal_pending_state(state, current)) {
                                  timeout = -ERESTARTSYS;
                                  break;
                          }
                          __set_current_state(state);
                          spin_unlock_irq(&x->wait.lock);
                          timeout = schedule_timeout(timeout);
                          spin_lock_irq(&x->wait.lock);
                  } while (!x->done && timeout);
                  __remove_wait_queue(&x->wait, &wait);
                  if (!x->done)
                          return timeout;
          }
          x->done--;
          return timeout ?: 1;
  }
  
  static long __sched
  wait_for_common(struct completion *x, long timeout, int state)
  {
          might_sleep();
  
          spin_lock_irq(&x->wait.lock);
          timeout = do_wait_for_common(x, timeout, state);
          spin_unlock_irq(&x->wait.lock);
          return timeout;
  }
  
  /**
   * wait_for_completion: - waits for completion of a task
   * @x:  holds the state of this particular completion
   *
   * This waits to be signaled for completion of a specific task. It is NOT
   * interruptible and there is no timeout.
   *
   * See also similar routines (i.e. wait_for_completion_timeout()) with timeout
   * and interrupt capability. Also see complete().
   */
  void __sched wait_for_completion(struct completion *x)
  {
          wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
  }
  EXPORT_SYMBOL(wait_for_completion);
  
  /**
   * wait_for_completion_timeout: - waits for completion of a task (w/timeout)
   * @x:  holds the state of this particular completion
   * @timeout:  timeout value in jiffies
   *
   * This waits for either a completion of a specific task to be signaled or for a
   * specified timeout to expire. The timeout is in jiffies. It is not
   * interruptible.
   */
  unsigned long __sched
  wait_for_completion_timeout(struct completion *x, unsigned long timeout)
  {
          return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE);
  }
  EXPORT_SYMBOL(wait_for_completion_timeout);
  
  /**
   * wait_for_completion_interruptible: - waits for completion of a task (w/intr)
   * @x:  holds the state of this particular completion
   *
   * This waits for completion of a specific task to be signaled. It is
   * interruptible.
   */
  int __sched wait_for_completion_interruptible(struct completion *x)
  {
          long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE);
          if (t == -ERESTARTSYS)
                  return t;
          return 0;
  }
  EXPORT_SYMBOL(wait_for_completion_interruptible);
  
  /**
   * wait_for_completion_interruptible_timeout: - waits for completion (w/(to,intr))
   * @x:  holds the state of this particular completion
   * @timeout:  timeout value in jiffies
   *
   * This waits for either a completion of a specific task to be signaled or for a
   * specified timeout to expire. It is interruptible. The timeout is in jiffies.
   */
  long __sched
  wait_for_completion_interruptible_timeout(struct completion *x,
                                            unsigned long timeout)
  {
          return wait_for_common(x, timeout, TASK_INTERRUPTIBLE);
  }
  EXPORT_SYMBOL(wait_for_completion_interruptible_timeout);
  
  /**
   * wait_for_completion_killable: - waits for completion of a task (killable)
   * @x:  holds the state of this particular completion
   *
   * This waits to be signaled for completion of a specific task. It can be
   * interrupted by a kill signal.
   */
  int __sched wait_for_completion_killable(struct completion *x)
  {
          long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE);
          if (t == -ERESTARTSYS)
                  return t;
          return 0;
  }
  EXPORT_SYMBOL(wait_for_completion_killable);
  
  /**
   * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable))
   * @x:  holds the state of this particular completion
   * @timeout:  timeout value in jiffies
   *
   * This waits for either a completion of a specific task to be
   * signaled or for a specified timeout to expire. It can be
   * interrupted by a kill signal. The timeout is in jiffies.
   */
  long __sched
  wait_for_completion_killable_timeout(struct completion *x,
                                       unsigned long timeout)
  {
          return wait_for_common(x, timeout, TASK_KILLABLE);
  }
  EXPORT_SYMBOL(wait_for_completion_killable_timeout);
  
  /**
   *      try_wait_for_completion - try to decrement a completion without blocking
   *      @x:     completion structure
   *
   *      Returns: 0 if a decrement cannot be done without blocking
   *               1 if a decrement succeeded.
   *
   *      If a completion is being used as a counting completion,
   *      attempt to decrement the counter without blocking. This
   *      enables us to avoid waiting if the resource the completion
   *      is protecting is not available.
   */
  bool try_wait_for_completion(struct completion *x)
  {
          unsigned long flags;
          int ret = 1;
  
          spin_lock_irqsave(&x->wait.lock, flags);
          if (!x->done)
                  ret = 0;
          else
                  x->done--;
          spin_unlock_irqrestore(&x->wait.lock, flags);
          return ret;
  }
  EXPORT_SYMBOL(try_wait_for_completion);
  
  /**
   *      completion_done - Test to see if a completion has any waiters
   *      @x:     completion structure
   *
   *      Returns: 0 if there are waiters (wait_for_completion() in progress)
   *               1 if there are no waiters.
   *
   */
  bool completion_done(struct completion *x)
  {
          unsigned long flags;
          int ret = 1;
  
          spin_lock_irqsave(&x->wait.lock, flags);
          if (!x->done)
                  ret = 0;
          spin_unlock_irqrestore(&x->wait.lock, flags);
          return ret;
  }
  EXPORT_SYMBOL(completion_done);
  
  static long __sched
  sleep_on_common(wait_queue_head_t *q, int state, long timeout)
  {
          unsigned long flags;
          wait_queue_t wait;
  
          init_waitqueue_entry(&wait, current);
  
          __set_current_state(state);
  
          spin_lock_irqsave(&q->lock, flags);
          __add_wait_queue(q, &wait);
          spin_unlock(&q->lock);
          timeout = schedule_timeout(timeout);
          spin_lock_irq(&q->lock);
          __remove_wait_queue(q, &wait);
          spin_unlock_irqrestore(&q->lock, flags);
  
          return timeout;
  }
  
  void __sched interruptible_sleep_on(wait_queue_head_t *q)
  {
          sleep_on_common(q, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
  }
  EXPORT_SYMBOL(interruptible_sleep_on);
  
  long __sched
  interruptible_sleep_on_timeout(wait_queue_head_t *q, long timeout)
  {
          return sleep_on_common(q, TASK_INTERRUPTIBLE, timeout);
  }
  EXPORT_SYMBOL(interruptible_sleep_on_timeout);
  
  void __sched sleep_on(wait_queue_head_t *q)
  {
          sleep_on_common(q, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
  }
  EXPORT_SYMBOL(sleep_on);
  
  long __sched sleep_on_timeout(wait_queue_head_t *q, long timeout)
  {
          return sleep_on_common(q, TASK_UNINTERRUPTIBLE, timeout);
  }
  EXPORT_SYMBOL(sleep_on_timeout);
  
  #ifdef CONFIG_RT_MUTEXES
  
  /*
   * rt_mutex_setprio - set the current priority of a task
   * @p: task
   * @prio: prio value (kernel-internal form)
   *
   * This function changes the 'effective' priority of a task. It does
   * not touch ->normal_prio like __setscheduler().
   *
   * Used by the rt_mutex code to implement priority inheritance logic.
   */
  void rt_mutex_setprio(struct task_struct *p, int prio)
  {
          int oldprio, on_rq, running;
          struct rq *rq;
          const struct sched_class *prev_class;
  
          BUG_ON(prio < 0 || prio > MAX_PRIO);
  
          rq = __task_rq_lock(p);
  
          trace_sched_pi_setprio(p, prio);
          oldprio = p->prio;
          prev_class = p->sched_class;
          on_rq = p->on_rq;
          running = task_current(rq, p);
          if (on_rq)
                  dequeue_task(rq, p, 0);
          if (running)
                  p->sched_class->put_prev_task(rq, p);
  
          if (rt_prio(prio))
                  p->sched_class = &rt_sched_class;
          else
                  p->sched_class = &fair_sched_class;
  
          p->prio = prio;
  
          if (running)
                  p->sched_class->set_curr_task(rq);
          if (on_rq)
                  enqueue_task(rq, p, oldprio < prio ? ENQUEUE_HEAD : 0);
  
          check_class_changed(rq, p, prev_class, oldprio);
          __task_rq_unlock(rq);
  }
  
  #endif
  
  void set_user_nice(struct task_struct *p, long nice)
  {
          int old_prio, delta, on_rq;
          unsigned long flags;
          struct rq *rq;
  
          if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
                  return;
          /*
           * We have to be careful, if called from sys_setpriority(),
           * the task might be in the middle of scheduling on another CPU.
           */
          rq = task_rq_lock(p, &flags);
          /*
           * The RT priorities are set via sched_setscheduler(), but we still
           * allow the 'normal' nice value to be set - but as expected
           * it wont have any effect on scheduling until the task is
           * SCHED_FIFO/SCHED_RR:
           */
          if (task_has_rt_policy(p)) {
                  p->static_prio = NICE_TO_PRIO(nice);
                  goto out_unlock;
          }
          on_rq = p->on_rq;
          if (on_rq)
                  dequeue_task(rq, p, 0);
  
          p->static_prio = NICE_TO_PRIO(nice);
          set_load_weight(p);
          old_prio = p->prio;
          p->prio = effective_prio(p);
          delta = p->prio - old_prio;
  
          if (on_rq) {
                  enqueue_task(rq, p, 0);
                  /*
                   * If the task increased its priority or is running and
                   * lowered its priority, then reschedule its CPU:
                   */
                  if (delta < 0 || (delta > 0 && task_running(rq, p)))
                          resched_task(rq->curr);
          }
  out_unlock:
          task_rq_unlock(rq, p, &flags);
  }
  EXPORT_SYMBOL(set_user_nice);
  
  /*
   * can_nice - check if a task can reduce its nice value
   * @p: task
   * @nice: nice value
   */
  int can_nice(const struct task_struct *p, const int nice)
  {
          /* convert nice value [19,-20] to rlimit style value [1,40] */
          int nice_rlim = 20 - nice;
  
          return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
                  capable(CAP_SYS_NICE));
  }
  
  #ifdef __ARCH_WANT_SYS_NICE
  
  /*
   * sys_nice - change the priority of the current process.
   * @increment: priority increment
   *
   * sys_setpriority is a more generic, but much slower function that
   * does similar things.
   */
  SYSCALL_DEFINE1(nice, int, increment)
  {
          long nice, retval;
  
          /*
           * Setpriority might change our priority at the same moment.
           * We don't have to worry. Conceptually one call occurs first
           * and we have a single winner.
           */
          if (increment < -40)
                  increment = -40;
          if (increment > 40)
                  increment = 40;
  
          nice = TASK_NICE(current) + increment;
          if (nice < -20)
                  nice = -20;
          if (nice > 19)
                  nice = 19;
  
          if (increment < 0 && !can_nice(current, nice))
                  return -EPERM;
  
          retval = security_task_setnice(current, nice);
          if (retval)
                  return retval;
  
          set_user_nice(current, nice);
          return 0;
  }
  
  #endif
  
  /**
   * task_prio - return the priority value of a given task.
   * @p: the task in question.
   *
   * This is the priority value as seen by users in /proc.
   * RT tasks are offset by -200. Normal tasks are centered
   * around 0, value goes from -16 to +15.
   */
  int task_prio(const struct task_struct *p)
  {
          return p->prio - MAX_RT_PRIO;
  }
  
  /**
   * task_nice - return the nice value of a given task.
   * @p: the task in question.
   */
  int task_nice(const struct task_struct *p)
  {
          return TASK_NICE(p);
  }
  EXPORT_SYMBOL(task_nice);
  
  /**
   * idle_cpu - is a given cpu idle currently?
   * @cpu: the processor in question.
   */
  int idle_cpu(int cpu)
  {
          return cpu_curr(cpu) == cpu_rq(cpu)->idle;
  }
  
  /**
   * idle_task - return the idle task for a given cpu.
   * @cpu: the processor in question.
   */
  struct task_struct *idle_task(int cpu)
  {
          return cpu_rq(cpu)->idle;
  }
  
  /**
   * find_process_by_pid - find a process with a matching PID value.
   * @pid: the pid in question.
   */
  static struct task_struct *find_process_by_pid(pid_t pid)
  {
          return pid ? find_task_by_vpid(pid) : current;
  }
  
  /* Actually do priority change: must hold rq lock. */
  static void
  __setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
  {
          p->policy = policy;
          p->rt_priority = prio;
          p->normal_prio = normal_prio(p);
          /* we are holding p->pi_lock already */
          p->prio = rt_mutex_getprio(p);
          if (rt_prio(p->prio))
                  p->sched_class = &rt_sched_class;
          else
                  p->sched_class = &fair_sched_class;
          set_load_weight(p);
  }
  
  /*
   * check the target process has a UID that matches the current process's
   */
  static bool check_same_owner(struct task_struct *p)
  {
          const struct cred *cred = current_cred(), *pcred;
          bool match;
  
          rcu_read_lock();
          pcred = __task_cred(p);
          if (cred->user->user_ns == pcred->user->user_ns)
                  match = (cred->euid == pcred->euid ||
                           cred->euid == pcred->uid);
          else
                  match = false;
          rcu_read_unlock();
          return match;
  }
  
  static int __sched_setscheduler(struct task_struct *p, int policy,
                                  const struct sched_param *param, bool user)
  {
          int retval, oldprio, oldpolicy = -1, on_rq, running;
          unsigned long flags;
          const struct sched_class *prev_class;
          struct rq *rq;
          int reset_on_fork;
  
          /* may grab non-irq protected spin_locks */
          BUG_ON(in_interrupt());
  recheck:
          /* double check policy once rq lock held */
          if (policy < 0) {
                  reset_on_fork = p->sched_reset_on_fork;
                  policy = oldpolicy = p->policy;
          } else {
                  reset_on_fork = !!(policy & SCHED_RESET_ON_FORK);
                  policy &= ~SCHED_RESET_ON_FORK;
  
                  if (policy != SCHED_FIFO && policy != SCHED_RR &&
                                  policy != SCHED_NORMAL && policy != SCHED_BATCH &&
                                  policy != SCHED_IDLE)
                          return -EINVAL;
          }
  
          /*
           * Valid priorities for SCHED_FIFO and SCHED_RR are
           * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
           * SCHED_BATCH and SCHED_IDLE is 0.
           */
          if (param->sched_priority < 0 ||
              (p->mm && param->sched_priority > MAX_USER_RT_PRIO-1) ||
              (!p->mm && param->sched_priority > MAX_RT_PRIO-1))
                  return -EINVAL;
          if (rt_policy(policy) != (param->sched_priority != 0))
                  return -EINVAL;
  
          /*
           * Allow unprivileged RT tasks to decrease priority:
           */
          if (user && !capable(CAP_SYS_NICE)) {
                  if (rt_policy(policy)) {
                          unsigned long rlim_rtprio =
                                          task_rlimit(p, RLIMIT_RTPRIO);
  
                          /* can't set/change the rt policy */
                          if (policy != p->policy && !rlim_rtprio)
                                  return -EPERM;
  
                          /* can't increase priority */
                          if (param->sched_priority > p->rt_priority &&
                              param->sched_priority > rlim_rtprio)
                                  return -EPERM;
                  }
  
                  /*
                   * Treat SCHED_IDLE as nice 20. Only allow a switch to
                   * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
                   */
                  if (p->policy == SCHED_IDLE && policy != SCHED_IDLE) {
                          if (!can_nice(p, TASK_NICE(p)))
                                  return -EPERM;
                  }
  
                  /* can't change other user's priorities */
                  if (!check_same_owner(p))
                          return -EPERM;
  
                  /* Normal users shall not reset the sched_reset_on_fork flag */
                  if (p->sched_reset_on_fork && !reset_on_fork)
                          return -EPERM;
          }
  
          if (user) {
                  retval = security_task_setscheduler(p);
                  if (retval)
                          return retval;
          }
  
          /*
           * make sure no PI-waiters arrive (or leave) while we are
           * changing the priority of the task:
           *
           * To be able to change p->policy safely, the appropriate
           * runqueue lock must be held.
           */
          rq = task_rq_lock(p, &flags);
  
          /*
           * Changing the policy of the stop threads its a very bad idea
           */
          if (p == rq->stop) {
                  task_rq_unlock(rq, p, &flags);
                  return -EINVAL;
          }
  
          /*
           * If not changing anything there's no need to proceed further:
           */
          if (unlikely(policy == p->policy && (!rt_policy(policy) ||
                          param->sched_priority == p->rt_priority))) {
  
                  __task_rq_unlock(rq);
                  raw_spin_unlock_irqrestore(&p->pi_lock, flags);
                  return 0;
          }
  
  #ifdef CONFIG_RT_GROUP_SCHED
          if (user) {
                  /*
                   * Do not allow realtime tasks into groups that have no runtime
                   * assigned.
                   */
                  if (rt_bandwidth_enabled() && rt_policy(policy) &&
                                  task_group(p)->rt_bandwidth.rt_runtime == 0 &&
                                  !task_group_is_autogroup(task_group(p))) {
                          task_rq_unlock(rq, p, &flags);
                          return -EPERM;
                  }
          }
  #endif
  
          /* recheck policy now with rq lock held */
          if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
                  policy = oldpolicy = -1;
                  task_rq_unlock(rq, p, &flags);
                  goto recheck;
          }
          on_rq = p->on_rq;
          running = task_current(rq, p);
          if (on_rq)
                  deactivate_task(rq, p, 0);
          if (running)
                  p->sched_class->put_prev_task(rq, p);
  
          p->sched_reset_on_fork = reset_on_fork;
  
          oldprio = p->prio;
          prev_class = p->sched_class;
          __setscheduler(rq, p, policy, param->sched_priority);
  
          if (running)
                  p->sched_class->set_curr_task(rq);
          if (on_rq)
                  activate_task(rq, p, 0);
  
          check_class_changed(rq, p, prev_class, oldprio);
          task_rq_unlock(rq, p, &flags);
  
          rt_mutex_adjust_pi(p);
  
          return 0;
  }
  
  /**
   * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
   * @p: the task in question.
   * @policy: new policy.
   * @param: structure containing the new RT priority.
   *
   * NOTE that the task may be already dead.
   */
  int sched_setscheduler(struct task_struct *p, int policy,
                         const struct sched_param *param)
  {
          return __sched_setscheduler(p, policy, param, true);
  }
  EXPORT_SYMBOL_GPL(sched_setscheduler);
  
  /**
   * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
   * @p: the task in question.
   * @policy: new policy.
   * @param: structure containing the new RT priority.
   *
   * Just like sched_setscheduler, only don't bother checking if the
   * current context has permission.  For example, this is needed in
   * stop_machine(): we create temporary high priority worker threads,
   * but our caller might not have that capability.
   */
  int sched_setscheduler_nocheck(struct task_struct *p, int policy,
                                 const struct sched_param *param)
  {
          return __sched_setscheduler(p, policy, param, false);
  }
  
  static int
  do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
  {
          struct sched_param lparam;
          struct task_struct *p;
          int retval;
  
          if (!param || pid < 0)
                  return -EINVAL;
          if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
                  return -EFAULT;
  
          rcu_read_lock();
          retval = -ESRCH;
          p = find_process_by_pid(pid);
          if (p != NULL)
                  retval = sched_setscheduler(p, policy, &lparam);
          rcu_read_unlock();
  
          return retval;
  }
  
  /**
   * sys_sched_setscheduler - set/change the scheduler policy and RT priority
   * @pid: the pid in question.
   * @policy: new policy.
   * @param: structure containing the new RT priority.
   */
  SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy,
                  struct sched_param __user *, param)
  {
          /* negative values for policy are not valid */
          if (policy < 0)
                  return -EINVAL;
  
          return do_sched_setscheduler(pid, policy, param);
  }
  
  /**
   * sys_sched_setparam - set/change the RT priority of a thread
   * @pid: the pid in question.
   * @param: structure containing the new RT priority.
   */
  SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
  {
          return do_sched_setscheduler(pid, -1, param);
  }
  
  /**
   * sys_sched_getscheduler - get the policy (scheduling class) of a thread
   * @pid: the pid in question.
   */
  SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
  {
          struct task_struct *p;
          int retval;
  
          if (pid < 0)
                  return -EINVAL;
  
          retval = -ESRCH;
          rcu_read_lock();
          p = find_process_by_pid(pid);
          if (p) {
                  retval = security_task_getscheduler(p);
                  if (!retval)
                          retval = p->policy
                                  | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
          }
          rcu_read_unlock();
          return retval;
  }
  
  /**
   * sys_sched_getparam - get the RT priority of a thread
   * @pid: the pid in question.
   * @param: structure containing the RT priority.
   */
  SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
  {
          struct sched_param lp;
          struct task_struct *p;
          int retval;
  
          if (!param || pid < 0)
                  return -EINVAL;
  
          rcu_read_lock();
          p = find_process_by_pid(pid);
          retval = -ESRCH;
          if (!p)
                  goto out_unlock;
  
          retval = security_task_getscheduler(p);
          if (retval)
                  goto out_unlock;
  
          lp.sched_priority = p->rt_priority;
          rcu_read_unlock();
  
          /*
           * This one might sleep, we cannot do it with a spinlock held ...
           */
          retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
  
          return retval;
  
  out_unlock:
          rcu_read_unlock();
          return retval;
  }
  
  long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
  {
          cpumask_var_t cpus_allowed, new_mask;
          struct task_struct *p;
          int retval;
  
          get_online_cpus();
          rcu_read_lock();
  
          p = find_process_by_pid(pid);
          if (!p) {
                  rcu_read_unlock();
                  put_online_cpus();
                  return -ESRCH;
          }
  
          /* Prevent p going away */
          get_task_struct(p);
          rcu_read_unlock();
  
          if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
                  retval = -ENOMEM;
                  goto out_put_task;
          }
          if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
                  retval = -ENOMEM;
                  goto out_free_cpus_allowed;
          }
          retval = -EPERM;
          if (!check_same_owner(p) && !task_ns_capable(p, CAP_SYS_NICE))
                  goto out_unlock;
  
          retval = security_task_setscheduler(p);
          if (retval)
                  goto out_unlock;
  
          cpuset_cpus_allowed(p, cpus_allowed);
          cpumask_and(new_mask, in_mask, cpus_allowed);
  again:
          retval = set_cpus_allowed_ptr(p, new_mask);
  
          if (!retval) {
                  cpuset_cpus_allowed(p, cpus_allowed);
                  if (!cpumask_subset(new_mask, cpus_allowed)) {
                          /*
                           * We must have raced with a concurrent cpuset
                           * update. Just reset the cpus_allowed to the
                           * cpuset's cpus_allowed
                           */
                          cpumask_copy(new_mask, cpus_allowed);
                          goto again;
                  }
          }
  out_unlock:
          free_cpumask_var(new_mask);
  out_free_cpus_allowed:
          free_cpumask_var(cpus_allowed);
  out_put_task:
          put_task_struct(p);
          put_online_cpus();
          return retval;
  }
  
  static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
                               struct cpumask *new_mask)
  {
          if (len < cpumask_size())
                  cpumask_clear(new_mask);
          else if (len > cpumask_size())
                  len = cpumask_size();
  
          return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
  }
  
  /**
   * sys_sched_setaffinity - set the cpu affinity of a process
   * @pid: pid of the process
   * @len: length in bytes of the bitmask pointed to by user_mask_ptr
   * @user_mask_ptr: user-space pointer to the new cpu mask
   */
  SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
                  unsigned long __user *, user_mask_ptr)
  {
          cpumask_var_t new_mask;
          int retval;
  
          if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
                  return -ENOMEM;
  
          retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
          if (retval == 0)
                  retval = sched_setaffinity(pid, new_mask);
          free_cpumask_var(new_mask);
          return retval;
  }
  
  long sched_getaffinity(pid_t pid, struct cpumask *mask)
  {
          struct task_struct *p;
          unsigned long flags;
          int retval;
  
          get_online_cpus();
          rcu_read_lock();
  
          retval = -ESRCH;
          p = find_process_by_pid(pid);
          if (!p)
                  goto out_unlock;
  
          retval = security_task_getscheduler(p);
          if (retval)
                  goto out_unlock;
  
          raw_spin_lock_irqsave(&p->pi_lock, flags);
          cpumask_and(mask, &p->cpus_allowed, cpu_online_mask);
          raw_spin_unlock_irqrestore(&p->pi_lock, flags);
  
  out_unlock:
          rcu_read_unlock();
          put_online_cpus();
  
          return retval;
  }
  
  /**
   * sys_sched_getaffinity - get the cpu affinity of a process
   * @pid: pid of the process
   * @len: length in bytes of the bitmask pointed to by user_mask_ptr
   * @user_mask_ptr: user-space pointer to hold the current cpu mask
   */
  SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
                  unsigned long __user *, user_mask_ptr)
  {
          int ret;
          cpumask_var_t mask;
  
          if ((len * BITS_PER_BYTE) < nr_cpu_ids)
                  return -EINVAL;
          if (len & (sizeof(unsigned long)-1))
                  return -EINVAL;
  
          if (!alloc_cpumask_var(&mask, GFP_KERNEL))
                  return -ENOMEM;
  
          ret = sched_getaffinity(pid, mask);
          if (ret == 0) {
                  size_t retlen = min_t(size_t, len, cpumask_size());
  
                  if (copy_to_user(user_mask_ptr, mask, retlen))
                          ret = -EFAULT;
                  else
                          ret = retlen;
          }
          free_cpumask_var(mask);
  
          return ret;
  }
  
  /**
   * sys_sched_yield - yield the current processor to other threads.
   *
   * This function yields the current CPU to other tasks. If there are no
   * other threads running on this CPU then this function will return.
   */
  SYSCALL_DEFINE0(sched_yield)
  {
          struct rq *rq = this_rq_lock();
  
          schedstat_inc(rq, yld_count);
          current->sched_class->yield_task(rq);
  
          /*
           * Since we are going to call schedule() anyway, there's
           * no need to preempt or enable interrupts:
           */
          __release(rq->lock);
          spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
          do_raw_spin_unlock(&rq->lock);
          preempt_enable_no_resched();
  
          schedule();
  
          return 0;
  }
  
  static inline int should_resched(void)
  {
          return need_resched() && !(preempt_count() & PREEMPT_ACTIVE);
  }
  
  static void __cond_resched(void)
  {
          add_preempt_count(PREEMPT_ACTIVE);
          schedule();
          sub_preempt_count(PREEMPT_ACTIVE);
  }
  
  int __sched _cond_resched(void)
  {
          if (should_resched()) {
                  __cond_resched();
                  return 1;
          }
          return 0;
  }
  EXPORT_SYMBOL(_cond_resched);
  
  /*
   * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
   * call schedule, and on return reacquire the lock.
   *
   * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
   * operations here to prevent schedule() from being called twice (once via
   * spin_unlock(), once by hand).
   */
  int __cond_resched_lock(spinlock_t *lock)
  {
          int resched = should_resched();
          int ret = 0;
  
          lockdep_assert_held(lock);
  
          if (spin_needbreak(lock) || resched) {
                  spin_unlock(lock);
                  if (resched)
                          __cond_resched();
                  else
                          cpu_relax();
                  ret = 1;
                  spin_lock(lock);
          }
          return ret;
  }
  EXPORT_SYMBOL(__cond_resched_lock);
  
  int __sched __cond_resched_softirq(void)
  {
          BUG_ON(!in_softirq());
  
          if (should_resched()) {
                  local_bh_enable();
                  __cond_resched();
                  local_bh_disable();
                  return 1;
          }
          return 0;
  }
  EXPORT_SYMBOL(__cond_resched_softirq);
  
  /**
   * yield - yield the current processor to other threads.
   *
   * This is a shortcut for kernel-space yielding - it marks the
   * thread runnable and calls sys_sched_yield().
   */
  void __sched yield(void)
  {
          set_current_state(TASK_RUNNING);
          sys_sched_yield();
  }
  EXPORT_SYMBOL(yield);
  
  /**
   * yield_to - yield the current processor to another thread in
   * your thread group, or accelerate that thread toward the
   * processor it's on.
   * @p: target task
   * @preempt: whether task preemption is allowed or not
   *
   * It's the caller's job to ensure that the target task struct
   * can't go away on us before we can do any checks.
   *
   * Returns true if we indeed boosted the target task.
   */
  bool __sched yield_to(struct task_struct *p, bool preempt)
  {
          struct task_struct *curr = current;
          struct rq *rq, *p_rq;
          unsigned long flags;
          bool yielded = 0;
  
          local_irq_save(flags);
          rq = this_rq();
  
  again:
          p_rq = task_rq(p);
          double_rq_lock(rq, p_rq);
          while (task_rq(p) != p_rq) {
                  double_rq_unlock(rq, p_rq);
                  goto again;
          }
  
          if (!curr->sched_class->yield_to_task)
                  goto out;
  
          if (curr->sched_class != p->sched_class)
                  goto out;
  
          if (task_running(p_rq, p) || p->state)
                  goto out;
  
          yielded = curr->sched_class->yield_to_task(rq, p, preempt);
          if (yielded) {
                  schedstat_inc(rq, yld_count);
                  /*
                   * Make p's CPU reschedule; pick_next_entity takes care of
                   * fairness.
                   */
                  if (preempt && rq != p_rq)
                          resched_task(p_rq->curr);
          }
  
  out:
          double_rq_unlock(rq, p_rq);
          local_irq_restore(flags);
  
          if (yielded)
                  schedule();
  
          return yielded;
  }
  EXPORT_SYMBOL_GPL(yield_to);
  
  /*
   * This task is about to go to sleep on IO. Increment rq->nr_iowait so
   * that process accounting knows that this is a task in IO wait state.
   */
  void __sched io_schedule(void)
  {
          struct rq *rq = raw_rq();
  
          delayacct_blkio_start();
          atomic_inc(&rq->nr_iowait);
          blk_flush_plug(current);
          current->in_iowait = 1;
          schedule();
          current->in_iowait = 0;
          atomic_dec(&rq->nr_iowait);
          delayacct_blkio_end();
  }
  EXPORT_SYMBOL(io_schedule);
  
  long __sched io_schedule_timeout(long timeout)
  {
          struct rq *rq = raw_rq();
          long ret;
  
          delayacct_blkio_start();
          atomic_inc(&rq->nr_iowait);
          blk_flush_plug(current);
          current->in_iowait = 1;
          ret = schedule_timeout(timeout);
          current->in_iowait = 0;
          atomic_dec(&rq->nr_iowait);
          delayacct_blkio_end();
          return ret;
  }
  
  /**
   * sys_sched_get_priority_max - return maximum RT priority.
   * @policy: scheduling class.
   *
   * this syscall returns the maximum rt_priority that can be used
   * by a given scheduling class.
   */
  SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
  {
          int ret = -EINVAL;
  
          switch (policy) {
          case SCHED_FIFO:
          case SCHED_RR:
                  ret = MAX_USER_RT_PRIO-1;
                  break;
          case SCHED_NORMAL:
          case SCHED_BATCH:
          case SCHED_IDLE:
                  ret = 0;
                  break;
          }
          return ret;
  }
  
  /**
   * sys_sched_get_priority_min - return minimum RT priority.
   * @policy: scheduling class.
   *
   * this syscall returns the minimum rt_priority that can be used
   * by a given scheduling class.
   */
  SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
  {
          int ret = -EINVAL;
  
          switch (policy) {
          case SCHED_FIFO:
          case SCHED_RR:
                  ret = 1;
                  break;
          case SCHED_NORMAL:
          case SCHED_BATCH:
          case SCHED_IDLE:
                  ret = 0;
          }
          return ret;
  }
  
  /**
   * sys_sched_rr_get_interval - return the default timeslice of a process.
   * @pid: pid of the process.
   * @interval: userspace pointer to the timeslice value.
   *
   * this syscall writes the default timeslice value of a given process
   * into the user-space timespec buffer. A value of '' means infinity.
   */
  SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
                  struct timespec __user *, interval)
  {
          struct task_struct *p;
          unsigned int time_slice;
          unsigned long flags;
          struct rq *rq;
          int retval;
          struct timespec t;
  
          if (pid < 0)
                  return -EINVAL;
  
          retval = -ESRCH;
          rcu_read_lock();
          p = find_process_by_pid(pid);
          if (!p)
                  goto out_unlock;
  
          retval = security_task_getscheduler(p);
          if (retval)
                  goto out_unlock;
  
          rq = task_rq_lock(p, &flags);
          time_slice = p->sched_class->get_rr_interval(rq, p);
          task_rq_unlock(rq, p, &flags);
  
          rcu_read_unlock();
          jiffies_to_timespec(time_slice, &t);
          retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
          return retval;
  
  out_unlock:
          rcu_read_unlock();
          return retval;
  }
  
  static const char stat_nam[] = TASK_STATE_TO_CHAR_STR;
  
  void sched_show_task(struct task_struct *p)
  {
          unsigned long free = 0;
          unsigned state;
  
          state = p->state ? __ffs(p->state) + 1 : 0;
          printk(KERN_INFO "%-15.15s %c", p->comm,
                  state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
  #if BITS_PER_LONG == 32
          if (state == TASK_RUNNING)
                  printk(KERN_CONT " running  ");
          else
                  printk(KERN_CONT " %08lx ", thread_saved_pc(p));
  #else
          if (state == TASK_RUNNING)
                  printk(KERN_CONT "  running task    ");
          else
                  printk(KERN_CONT " %016lx ", thread_saved_pc(p));
  #endif
  #ifdef CONFIG_DEBUG_STACK_USAGE
          free = stack_not_used(p);
  #endif
          printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free,
                  task_pid_nr(p), task_pid_nr(p->real_parent),
                  (unsigned long)task_thread_info(p)->flags);
  
          show_stack(p, NULL);
  }
  
  void show_state_filter(unsigned long state_filter)
  {
          struct task_struct *g, *p;
  
  #if BITS_PER_LONG == 32
          printk(KERN_INFO
                  "  task                PC stack   pid father\n");
  #else
          printk(KERN_INFO
                  "  task                        PC stack   pid father\n");
  #endif
          read_lock(&tasklist_lock);
          do_each_thread(g, p) {
                  /*
                   * reset the NMI-timeout, listing all files on a slow
                   * console might take a lot of time:
                   */
                  touch_nmi_watchdog();
                  if (!state_filter || (p->state & state_filter))
                          sched_show_task(p);
          } while_each_thread(g, p);
  
          touch_all_softlockup_watchdogs();
  
  #ifdef CONFIG_SCHED_DEBUG
          sysrq_sched_debug_show();
  #endif
          read_unlock(&tasklist_lock);
          /*
           * Only show locks if all tasks are dumped:
           */
          if (!state_filter)
                  debug_show_all_locks();
  }
  
  void __cpuinit init_idle_bootup_task(struct task_struct *idle)
  {
          idle->sched_class = &idle_sched_class;
  }
  
  /**
   * init_idle - set up an idle thread for a given CPU
   * @idle: task in question
   * @cpu: cpu the idle task belongs to
   *
   * NOTE: this function does not set the idle thread's NEED_RESCHED
   * flag, to make booting more robust.
   */
  void __cpuinit init_idle(struct task_struct *idle, int cpu)
  {
          struct rq *rq = cpu_rq(cpu);
          unsigned long flags;
  
          raw_spin_lock_irqsave(&rq->lock, flags);
  
          __sched_fork(idle);
          idle->state = TASK_RUNNING;
          idle->se.exec_start = sched_clock();
  
          do_set_cpus_allowed(idle, cpumask_of(cpu));
          /*
           * We're having a chicken and egg problem, even though we are
           * holding rq->lock, the cpu isn't yet set to this cpu so the
           * lockdep check in task_group() will fail.
           *
           * Similar case to sched_fork(). / Alternatively we could
           * use task_rq_lock() here and obtain the other rq->lock.
           *
           * Silence PROVE_RCU
           */
          rcu_read_lock();
          __set_task_cpu(idle, cpu);
          rcu_read_unlock();
  
          rq->curr = rq->idle = idle;
  #if defined(CONFIG_SMP)
          idle->on_cpu = 1;
  #endif
          raw_spin_unlock_irqrestore(&rq->lock, flags);
  
          /* Set the preempt count _outside_ the spinlocks! */
          task_thread_info(idle)->preempt_count = 0;
  
          /*
           * The idle tasks have their own, simple scheduling class:
           */
          idle->sched_class = &idle_sched_class;
          ftrace_graph_init_idle_task(idle, cpu);
  }
  
  /*
   * In a system that switches off the HZ timer nohz_cpu_mask
   * indicates which cpus entered this state. This is used
   * in the rcu update to wait only for active cpus. For system
   * which do not switch off the HZ timer nohz_cpu_mask should
   * always be CPU_BITS_NONE.
   */
  cpumask_var_t nohz_cpu_mask;
  
  /*
   * Increase the granularity value when there are more CPUs,
   * because with more CPUs the 'effective latency' as visible
   * to users decreases. But the relationship is not linear,
   * so pick a second-best guess by going with the log2 of the
   * number of CPUs.
   *
   * This idea comes from the SD scheduler of Con Kolivas:
   */
  static int get_update_sysctl_factor(void)
  {
          unsigned int cpus = min_t(int, num_online_cpus(), 8);
          unsigned int factor;
  
          switch (sysctl_sched_tunable_scaling) {
          case SCHED_TUNABLESCALING_NONE:
                  factor = 1;
                  break;
          case SCHED_TUNABLESCALING_LINEAR:
                  factor = cpus;
                  break;
          case SCHED_TUNABLESCALING_LOG:
          default:
                  factor = 1 + ilog2(cpus);
                  break;
          }
  
          return factor;
  }
  
  static void update_sysctl(void)
  {
          unsigned int factor = get_update_sysctl_factor();
  
  #define SET_SYSCTL(name) \
          (sysctl_##name = (factor) * normalized_sysctl_##name)
          SET_SYSCTL(sched_min_granularity);
          SET_SYSCTL(sched_latency);
          SET_SYSCTL(sched_wakeup_granularity);
  #undef SET_SYSCTL
  }
  
  static inline void sched_init_granularity(void)
  {
          update_sysctl();
  }
  
  #ifdef CONFIG_SMP
  void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
  {
          if (p->sched_class && p->sched_class->set_cpus_allowed)
                  p->sched_class->set_cpus_allowed(p, new_mask);
          else {
                  cpumask_copy(&p->cpus_allowed, new_mask);
                  p->rt.nr_cpus_allowed = cpumask_weight(new_mask);
          }
  }
  
  /*
   * This is how migration works:
   *
   * 1) we invoke migration_cpu_stop() on the target CPU using
   *    stop_one_cpu().
   * 2) stopper starts to run (implicitly forcing the migrated thread
   *    off the CPU)
   * 3) it checks whether the migrated task is still in the wrong runqueue.
   * 4) if it's in the wrong runqueue then the migration thread removes
   *    it and puts it into the right queue.
   * 5) stopper completes and stop_one_cpu() returns and the migration
   *    is done.
   */
  
  /*
   * Change a given task's CPU affinity. Migrate the thread to a
   * proper CPU and schedule it away if the CPU it's executing on
   * is removed from the allowed bitmask.
   *
   * NOTE: the caller must have a valid reference to the task, the
   * task must not exit() & deallocate itself prematurely. The
   * call is not atomic; no spinlocks may be held.
   */
  int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
  {
          unsigned long flags;
          struct rq *rq;
          unsigned int dest_cpu;
          int ret = 0;
  
          rq = task_rq_lock(p, &flags);
  
          if (cpumask_equal(&p->cpus_allowed, new_mask))
                  goto out;
  
          if (!cpumask_intersects(new_mask, cpu_active_mask)) {
                  ret = -EINVAL;
                  goto out;
          }
  
          if (unlikely((p->flags & PF_THREAD_BOUND) && p != current)) {
                  ret = -EINVAL;
                  goto out;
          }
  
          do_set_cpus_allowed(p, new_mask);
  
          /* Can the task run on the task's current CPU? If so, we're done */
          if (cpumask_test_cpu(task_cpu(p), new_mask))
                  goto out;
  
          dest_cpu = cpumask_any_and(cpu_active_mask, new_mask);
          if (p->on_rq) {
                  struct migration_arg arg = { p, dest_cpu };
                  /* Need help from migration thread: drop lock and wait. */
                  task_rq_unlock(rq, p, &flags);
                  stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
                  tlb_migrate_finish(p->mm);
                  return 0;
          }
  out:
          task_rq_unlock(rq, p, &flags);
  
          return ret;
  }
  EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
  
  /*
   * Move (not current) task off this cpu, onto dest cpu. We're doing
   * this because either it can't run here any more (set_cpus_allowed()
   * away from this CPU, or CPU going down), or because we're
   * attempting to rebalance this task on exec (sched_exec).
   *
   * So we race with normal scheduler movements, but that's OK, as long
   * as the task is no longer on this CPU.
   *
   * Returns non-zero if task was successfully migrated.
   */
  static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
  {
          struct rq *rq_dest, *rq_src;
          int ret = 0;
  
          if (unlikely(!cpu_active(dest_cpu)))
                  return ret;
  
          rq_src = cpu_rq(src_cpu);
          rq_dest = cpu_rq(dest_cpu);
  
          raw_spin_lock(&p->pi_lock);
          double_rq_lock(rq_src, rq_dest);
          /* Already moved. */
          if (task_cpu(p) != src_cpu)
                  goto done;
          /* Affinity changed (again). */
          if (!cpumask_test_cpu(dest_cpu, &p->cpus_allowed))
                  goto fail;
  
          /*
           * If we're not on a rq, the next wake-up will ensure we're
           * placed properly.
           */
          if (p->on_rq) {
                  deactivate_task(rq_src, p, 0);
                  set_task_cpu(p, dest_cpu);
                  activate_task(rq_dest, p, 0);
                  check_preempt_curr(rq_dest, p, 0);
          }
  done:
          ret = 1;
  fail:
          double_rq_unlock(rq_src, rq_dest);
          raw_spin_unlock(&p->pi_lock);
          return ret;
  }
  
  /*
   * migration_cpu_stop - this will be executed by a highprio stopper thread
   * and performs thread migration by bumping thread off CPU then
   * 'pushing' onto another runqueue.
   */
  static int migration_cpu_stop(void *data)
  {
          struct migration_arg *arg = data;
  
          /*
           * The original target cpu might have gone down and we might
           * be on another cpu but it doesn't matter.
           */
          local_irq_disable();
          __migrate_task(arg->task, raw_smp_processor_id(), arg->dest_cpu);
          local_irq_enable();
          return 0;
  }
  
  #ifdef CONFIG_HOTPLUG_CPU
  
  /*
   * Ensures that the idle task is using init_mm right before its cpu goes
   * offline.
   */
  void idle_task_exit(void)
  {
          struct mm_struct *mm = current->active_mm;
  
          BUG_ON(cpu_online(smp_processor_id()));
  
          if (mm != &init_mm)
                  switch_mm(mm, &init_mm, current);
          mmdrop(mm);
  }
  
  /*
   * While a dead CPU has no uninterruptible tasks queued at this point,
   * it might still have a nonzero ->nr_uninterruptible counter, because
   * for performance reasons the counter is not stricly tracking tasks to
   * their home CPUs. So we just add the counter to another CPU's counter,
   * to keep the global sum constant after CPU-down:
   */
  static void migrate_nr_uninterruptible(struct rq *rq_src)
  {
          struct rq *rq_dest = cpu_rq(cpumask_any(cpu_active_mask));
  
          rq_dest->nr_uninterruptible += rq_src->nr_uninterruptible;
          rq_src->nr_uninterruptible = 0;
  }
  
  /*
   * remove the tasks which were accounted by rq from calc_load_tasks.
   */
  static void calc_global_load_remove(struct rq *rq)
  {
          atomic_long_sub(rq->calc_load_active, &calc_load_tasks);
          rq->calc_load_active = 0;
  }
  
  /*
   * Migrate all tasks from the rq, sleeping tasks will be migrated by
   * try_to_wake_up()->select_task_rq().
   *
   * Called with rq->lock held even though we'er in stop_machine() and
   * there's no concurrency possible, we hold the required locks anyway
   * because of lock validation efforts.
   */
  static void migrate_tasks(unsigned int dead_cpu)
  {
          struct rq *rq = cpu_rq(dead_cpu);
          struct task_struct *next, *stop = rq->stop;
          int dest_cpu;
  
          /*
           * Fudge the rq selection such that the below task selection loop
           * doesn't get stuck on the currently eligible stop task.
           *
           * We're currently inside stop_machine() and the rq is either stuck
           * in the stop_machine_cpu_stop() loop, or we're executing this code,
           * either way we should never end up calling schedule() until we're
           * done here.
           */
          rq->stop = NULL;
  
          for ( ; ; ) {
                  /*
                   * There's this thread running, bail when that's the only
                   * remaining thread.
                   */
                  if (rq->nr_running == 1)
                          break;
  
                  next = pick_next_task(rq);
                  BUG_ON(!next);
                  next->sched_class->put_prev_task(rq, next);
  
                  /* Find suitable destination for @next, with force if needed. */
                  dest_cpu = select_fallback_rq(dead_cpu, next);
                  raw_spin_unlock(&rq->lock);
  
                  __migrate_task(next, dead_cpu, dest_cpu);
  
                  raw_spin_lock(&rq->lock);
          }
  
          rq->stop = stop;
  }
  
  #endif /* CONFIG_HOTPLUG_CPU */
  
  #if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_SYSCTL)
  
  static struct ctl_table sd_ctl_dir[] = {
          {
                  .procname       = "sched_domain",
                  .mode           = 0555,
          },
          {}
  };
  
  static struct ctl_table sd_ctl_root[] = {
          {
                  .procname       = "kernel",
                  .mode           = 0555,
                  .child          = sd_ctl_dir,
          },
          {}
  };
  
  static struct ctl_table *sd_alloc_ctl_entry(int n)
  {
          struct ctl_table *entry =
                  kcalloc(n, sizeof(struct ctl_table), GFP_KERNEL);
  
          return entry;
  }
  
  static void sd_free_ctl_entry(struct ctl_table **tablep)
  {
          struct ctl_table *entry;
  
          /*
           * In the intermediate directories, both the child directory and
           * procname are dynamically allocated and could fail but the mode
           * will always be set. In the lowest directory the names are
           * static strings and all have proc handlers.
           */
          for (entry = *tablep; entry->mode; entry++) {
                  if (entry->child)
                          sd_free_ctl_entry(&entry->child);
                  if (entry->proc_handler == NULL)
                          kfree(entry->procname);
          }
  
          kfree(*tablep);
          *tablep = NULL;
  }
  
  static void
  set_table_entry(struct ctl_table *entry,
                  const char *procname, void *data, int maxlen,
                  mode_t mode, proc_handler *proc_handler)
  {
          entry->procname = procname;
          entry->data = data;
          entry->maxlen = maxlen;
          entry->mode = mode;
          entry->proc_handler = proc_handler;
  }
  
  static struct ctl_table *
  sd_alloc_ctl_domain_table(struct sched_domain *sd)
  {
          struct ctl_table *table = sd_alloc_ctl_entry(13);
  
          if (table == NULL)
                  return NULL;
  
          set_table_entry(&table[0], "min_interval", &sd->min_interval,
                  sizeof(long), 0644, proc_doulongvec_minmax);
          set_table_entry(&table[1], "max_interval", &sd->max_interval,
                  sizeof(long), 0644, proc_doulongvec_minmax);
          set_table_entry(&table[2], "busy_idx", &sd->busy_idx,
                  sizeof(int), 0644, proc_dointvec_minmax);
          set_table_entry(&table[3], "idle_idx", &sd->idle_idx,
                  sizeof(int), 0644, proc_dointvec_minmax);
          set_table_entry(&table[4], "newidle_idx", &sd->newidle_idx,
                  sizeof(int), 0644, proc_dointvec_minmax);
          set_table_entry(&table[5], "wake_idx", &sd->wake_idx,
                  sizeof(int), 0644, proc_dointvec_minmax);
          set_table_entry(&table[6], "forkexec_idx", &sd->forkexec_idx,
                  sizeof(int), 0644, proc_dointvec_minmax);
          set_table_entry(&table[7], "busy_factor", &sd->busy_factor,
                  sizeof(int), 0644, proc_dointvec_minmax);
          set_table_entry(&table[8], "imbalance_pct", &sd->imbalance_pct,
                  sizeof(int), 0644, proc_dointvec_minmax);
          set_table_entry(&table[9], "cache_nice_tries",
                  &sd->cache_nice_tries,
                  sizeof(int), 0644, proc_dointvec_minmax);
          set_table_entry(&table[10], "flags", &sd->flags,
                  sizeof(int), 0644, proc_dointvec_minmax);
          set_table_entry(&table[11], "name", sd->name,
                  CORENAME_MAX_SIZE, 0444, proc_dostring);
          /* &table[12] is terminator */
  
          return table;
  }
  
  static ctl_table *sd_alloc_ctl_cpu_table(int cpu)
  {
          struct ctl_table *entry, *table;
          struct sched_domain *sd;
          int domain_num = 0, i;
          char buf[32];
  
          for_each_domain(cpu, sd)
                  domain_num++;
          entry = table = sd_alloc_ctl_entry(domain_num + 1);
          if (table == NULL)
                  return NULL;
  
          i = 0;
          for_each_domain(cpu, sd) {
                  snprintf(buf, 32, "domain%d", i);
                  entry->procname = kstrdup(buf, GFP_KERNEL);
                  entry->mode = 0555;
                  entry->child = sd_alloc_ctl_domain_table(sd);
                  entry++;
                  i++;
          }
          return table;
  }
  
  static struct ctl_table_header *sd_sysctl_header;
  static void register_sched_domain_sysctl(void)
  {
          int i, cpu_num = num_possible_cpus();
          struct ctl_table *entry = sd_alloc_ctl_entry(cpu_num + 1);
          char buf[32];
  
          WARN_ON(sd_ctl_dir[0].child);
          sd_ctl_dir[0].child = entry;
  
          if (entry == NULL)
                  return;
  
          for_each_possible_cpu(i) {
                  snprintf(buf, 32, "cpu%d", i);
                  entry->procname = kstrdup(buf, GFP_KERNEL);
                  entry->mode = 0555;
                  entry->child = sd_alloc_ctl_cpu_table(i);
                  entry++;
          }
  
          WARN_ON(sd_sysctl_header);
          sd_sysctl_header = register_sysctl_table(sd_ctl_root);
  }
  
  /* may be called multiple times per register */
  static void unregister_sched_domain_sysctl(void)
  {
          if (sd_sysctl_header)
                  unregister_sysctl_table(sd_sysctl_header);
          sd_sysctl_header = NULL;
          if (sd_ctl_dir[0].child)
                  sd_free_ctl_entry(&sd_ctl_dir[0].child);
  }
  #else
  static void register_sched_domain_sysctl(void)
  {
  }
  static void unregister_sched_domain_sysctl(void)
  {
  }
  #endif
  
  static void set_rq_online(struct rq *rq)
  {
          if (!rq->online) {
                  const struct sched_class *class;
  
                  cpumask_set_cpu(rq->cpu, rq->rd->online);
                  rq->online = 1;
  
                  for_each_class(class) {
                          if (class->rq_online)
                                  class->rq_online(rq);
                  }
          }
  }
  
  static void set_rq_offline(struct rq *rq)
  {
          if (rq->online) {
                  const struct sched_class *class;
  
                  for_each_class(class) {
                          if (class->rq_offline)
                                  class->rq_offline(rq);
                  }
  
                  cpumask_clear_cpu(rq->cpu, rq->rd->online);
                  rq->online = 0;
          }
  }
  
  /*
   * migration_call - callback that gets triggered when a CPU is added.
   * Here we can start up the necessary migration thread for the new CPU.
   */
  static int __cpuinit
  migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
  {
          int cpu = (long)hcpu;
          unsigned long flags;
          struct rq *rq = cpu_rq(cpu);
  
          switch (action & ~CPU_TASKS_FROZEN) {
  
          case CPU_UP_PREPARE:
                  rq->calc_load_update = calc_load_update;
                  break;
  
          case CPU_ONLINE:
                  /* Update our root-domain */
                  raw_spin_lock_irqsave(&rq->lock, flags);
                  if (rq->rd) {
                          BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
  
                          set_rq_online(rq);
                  }
                  raw_spin_unlock_irqrestore(&rq->lock, flags);
                  break;
  
  #ifdef CONFIG_HOTPLUG_CPU
          case CPU_DYING:
                  sched_ttwu_pending();
                  /* Update our root-domain */
                  raw_spin_lock_irqsave(&rq->lock, flags);
                  if (rq->rd) {
                          BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
                          set_rq_offline(rq);
                  }
                  migrate_tasks(cpu);
                  BUG_ON(rq->nr_running != 1); /* the migration thread */
                  raw_spin_unlock_irqrestore(&rq->lock, flags);
  
                  migrate_nr_uninterruptible(rq);
                  calc_global_load_remove(rq);
                  break;
  #endif
          }
  
          update_max_interval();
  
          return NOTIFY_OK;
  }
  
  /*
   * Register at high priority so that task migration (migrate_all_tasks)
   * happens before everything else.  This has to be lower priority than
   * the notifier in the perf_event subsystem, though.
   */
  static struct notifier_block __cpuinitdata migration_notifier = {
          .notifier_call = migration_call,
          .priority = CPU_PRI_MIGRATION,
  };
  
  static int __cpuinit sched_cpu_active(struct notifier_block *nfb,
                                        unsigned long action, void *hcpu)
  {
          switch (action & ~CPU_TASKS_FROZEN) {
          case CPU_ONLINE:
          case CPU_DOWN_FAILED:
                  set_cpu_active((long)hcpu, true);
                  return NOTIFY_OK;
          default:
                  return NOTIFY_DONE;
          }
  }
  
  static int __cpuinit sched_cpu_inactive(struct notifier_block *nfb,
                                          unsigned long action, void *hcpu)
  {
          switch (action & ~CPU_TASKS_FROZEN) {
          case CPU_DOWN_PREPARE:
                  set_cpu_active((long)hcpu, false);
                  return NOTIFY_OK;
          default:
                  return NOTIFY_DONE;
          }
  }
  
  static int __init migration_init(void)
  {
          void *cpu = (void *)(long)smp_processor_id();
          int err;
  
          /* Initialize migration for the boot CPU */
          err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
          BUG_ON(err == NOTIFY_BAD);
          migration_call(&migration_notifier, CPU_ONLINE, cpu);
          register_cpu_notifier(&migration_notifier);
  
          /* Register cpu active notifiers */
          cpu_notifier(sched_cpu_active, CPU_PRI_SCHED_ACTIVE);
          cpu_notifier(sched_cpu_inactive, CPU_PRI_SCHED_INACTIVE);
  
          return 0;
  }
  early_initcall(migration_init);
  #endif
  
  #ifdef CONFIG_SMP
  
  static cpumask_var_t sched_domains_tmpmask; /* sched_domains_mutex */
  
  #ifdef CONFIG_SCHED_DEBUG
  
  static __read_mostly int sched_domain_debug_enabled;
  
  static int __init sched_domain_debug_setup(char *str)
  {
          sched_domain_debug_enabled = 1;
  
          return 0;
  }
  early_param("sched_debug", sched_domain_debug_setup);
  
  static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
                                    struct cpumask *groupmask)
  {
          struct sched_group *group = sd->groups;
          char str[256];
  
          cpulist_scnprintf(str, sizeof(str), sched_domain_span(sd));
          cpumask_clear(groupmask);
  
          printk(KERN_DEBUG "%*s domain %d: ", level, "", level);
  
          if (!(sd->flags & SD_LOAD_BALANCE)) {
                  printk("does not load-balance\n");
                  if (sd->parent)
                          printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain"
                                          " has parent");
                  return -1;
          }
  
          printk(KERN_CONT "span %s level %s\n", str, sd->name);
  
          if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) {
                  printk(KERN_ERR "ERROR: domain->span does not contain "
                                  "CPU%d\n", cpu);
          }
          if (!cpumask_test_cpu(cpu, sched_group_cpus(group))) {
                  printk(KERN_ERR "ERROR: domain->groups does not contain"
                                  " CPU%d\n", cpu);
          }
  
          printk(KERN_DEBUG "%*s groups:", level + 1, "");
          do {
                  if (!group) {
                          printk("\n");
                          printk(KERN_ERR "ERROR: group is NULL\n");
                          break;
                  }
  
                  if (!group->sgp->power) {
                          printk(KERN_CONT "\n");
                          printk(KERN_ERR "ERROR: domain->cpu_power not "
                                          "set\n");
                          break;
                  }
  
                  if (!cpumask_weight(sched_group_cpus(group))) {
                          printk(KERN_CONT "\n");
                          printk(KERN_ERR "ERROR: empty group\n");
                          break;
                  }
  
                  if (cpumask_intersects(groupmask, sched_group_cpus(group))) {
                          printk(KERN_CONT "\n");
                          printk(KERN_ERR "ERROR: repeated CPUs\n");
                          break;
                  }
  
                  cpumask_or(groupmask, groupmask, sched_group_cpus(group));
  
                  cpulist_scnprintf(str, sizeof(str), sched_group_cpus(group));
  
                  printk(KERN_CONT " %s", str);
                  if (group->sgp->power != SCHED_POWER_SCALE) {
                          printk(KERN_CONT " (cpu_power = %d)",
                                  group->sgp->power);
                  }
  
                  group = group->next;
          } while (group != sd->groups);
          printk(KERN_CONT "\n");
  
          if (!cpumask_equal(sched_domain_span(sd), groupmask))
                  printk(KERN_ERR "ERROR: groups don't span domain->span\n");
  
          if (sd->parent &&
              !cpumask_subset(groupmask, sched_domain_span(sd->parent)))
                  printk(KERN_ERR "ERROR: parent span is not a superset "
                          "of domain->span\n");
          return 0;
  }
  
  static void sched_domain_debug(struct sched_domain *sd, int cpu)
  {
          int level = 0;
  
          if (!sched_domain_debug_enabled)
                  return;
  
          if (!sd) {
                  printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu);
                  return;
          }
  
          printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu);
  
          for (;;) {
                  if (sched_domain_debug_one(sd, cpu, level, sched_domains_tmpmask))
                          break;
                  level++;
                  sd = sd->parent;
                  if (!sd)
                          break;
          }
  }
  #else /* !CONFIG_SCHED_DEBUG */
  # define sched_domain_debug(sd, cpu) do { } while (0)
  #endif /* CONFIG_SCHED_DEBUG */
  
  static int sd_degenerate(struct sched_domain *sd)
  {
          if (cpumask_weight(sched_domain_span(sd)) == 1)
                  return 1;
  
          /* Following flags need at least 2 groups */
          if (sd->flags & (SD_LOAD_BALANCE |
                           SD_BALANCE_NEWIDLE |
                           SD_BALANCE_FORK |
                           SD_BALANCE_EXEC |
                           SD_SHARE_CPUPOWER |
                           SD_SHARE_PKG_RESOURCES)) {
                  if (sd->groups != sd->groups->next)
                          return 0;
          }
  
          /* Following flags don't use groups */
          if (sd->flags & (SD_WAKE_AFFINE))
                  return 0;
  
          return 1;
  }
  
  static int
  sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
  {
          unsigned long cflags = sd->flags, pflags = parent->flags;
  
          if (sd_degenerate(parent))
                  return 1;
  
          if (!cpumask_equal(sched_domain_span(sd), sched_domain_span(parent)))
                  return 0;
  
          /* Flags needing groups don't count if only 1 group in parent */
          if (parent->groups == parent->groups->next) {
                  pflags &= ~(SD_LOAD_BALANCE |
                                  SD_BALANCE_NEWIDLE |
                                  SD_BALANCE_FORK |
                                  SD_BALANCE_EXEC |
                                  SD_SHARE_CPUPOWER |
                                  SD_SHARE_PKG_RESOURCES);
                  if (nr_node_ids == 1)
                          pflags &= ~SD_SERIALIZE;
          }
          if (~cflags & pflags)
                  return 0;
  
          return 1;
  }
  
  static void free_rootdomain(struct rcu_head *rcu)
  {
          struct root_domain *rd = container_of(rcu, struct root_domain, rcu);
  
          cpupri_cleanup(&rd->cpupri);
          free_cpumask_var(rd->rto_mask);
          free_cpumask_var(rd->online);
          free_cpumask_var(rd->span);
          kfree(rd);
  }
  
  static void rq_attach_root(struct rq *rq, struct root_domain *rd)
  {
          struct root_domain *old_rd = NULL;
          unsigned long flags;
  
          raw_spin_lock_irqsave(&rq->lock, flags);
  
          if (rq->rd) {
                  old_rd = rq->rd;
  
                  if (cpumask_test_cpu(rq->cpu, old_rd->online))
                          set_rq_offline(rq);
  
                  cpumask_clear_cpu(rq->cpu, old_rd->span);
  
                  /*
                   * If we dont want to free the old_rt yet then
                   * set old_rd to NULL to skip the freeing later
                   * in this function:
                   */
                  if (!atomic_dec_and_test(&old_rd->refcount))
                          old_rd = NULL;
          }
  
          atomic_inc(&rd->refcount);
          rq->rd = rd;
  
          cpumask_set_cpu(rq->cpu, rd->span);
          if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
                  set_rq_online(rq);
  
          raw_spin_unlock_irqrestore(&rq->lock, flags);
  
          if (old_rd)
                  call_rcu_sched(&old_rd->rcu, free_rootdomain);
  }
  
  static int init_rootdomain(struct root_domain *rd)
  {
          memset(rd, 0, sizeof(*rd));
  
          if (!alloc_cpumask_var(&rd->span, GFP_KERNEL))
                  goto out;
          if (!alloc_cpumask_var(&rd->online, GFP_KERNEL))
                  goto free_span;
          if (!alloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
                  goto free_online;
  
          if (cpupri_init(&rd->cpupri) != 0)
                  goto free_rto_mask;
          return 0;
  
  free_rto_mask:
          free_cpumask_var(rd->rto_mask);
  free_online:
          free_cpumask_var(rd->online);
  free_span:
          free_cpumask_var(rd->span);
  out:
          return -ENOMEM;
  }
  
  static void init_defrootdomain(void)
  {
          init_rootdomain(&def_root_domain);
  
          atomic_set(&def_root_domain.refcount, 1);
  }
  
  static struct root_domain *alloc_rootdomain(void)
  {
          struct root_domain *rd;
  
          rd = kmalloc(sizeof(*rd), GFP_KERNEL);
          if (!rd)
                  return NULL;
  
          if (init_rootdomain(rd) != 0) {
                  kfree(rd);
                  return NULL;
          }
  
          return rd;
  }
  
  static void free_sched_groups(struct sched_group *sg, int free_sgp)
  {
          struct sched_group *tmp, *first;
  
          if (!sg)
                  return;
  
          first = sg;
          do {
                  tmp = sg->next;
  
                  if (free_sgp && atomic_dec_and_test(&sg->sgp->ref))
                          kfree(sg->sgp);
  
                  kfree(sg);
                  sg = tmp;
          } while (sg != first);
  }
  
  static void free_sched_domain(struct rcu_head *rcu)
  {
          struct sched_domain *sd = container_of(rcu, struct sched_domain, rcu);
  
          /*
           * If its an overlapping domain it has private groups, iterate and
           * nuke them all.
           */
          if (sd->flags & SD_OVERLAP) {
                  free_sched_groups(sd->groups, 1);
          } else if (atomic_dec_and_test(&sd->groups->ref)) {
                  kfree(sd->groups->sgp);
                  kfree(sd->groups);
          }
          kfree(sd);
  }
  
  static void destroy_sched_domain(struct sched_domain *sd, int cpu)
  {
          call_rcu(&sd->rcu, free_sched_domain);
  }
  
  static void destroy_sched_domains(struct sched_domain *sd, int cpu)
  {
          for (; sd; sd = sd->parent)
                  destroy_sched_domain(sd, cpu);
  }
  
  /*
   * Attach the domain 'sd' to 'cpu' as its base domain. Callers must
   * hold the hotplug lock.
   */
  static void
  cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
  {
          struct rq *rq = cpu_rq(cpu);
          struct sched_domain *tmp;
  
          /* Remove the sched domains which do not contribute to scheduling. */
          for (tmp = sd; tmp; ) {
                  struct sched_domain *parent = tmp->parent;
                  if (!parent)
                          break;
  
                  if (sd_parent_degenerate(tmp, parent)) {
                          tmp->parent = parent->parent;
                          if (parent->parent)
                                  parent->parent->child = tmp;
                          destroy_sched_domain(parent, cpu);
                  } else
                          tmp = tmp->parent;
          }
  
          if (sd && sd_degenerate(sd)) {
                  tmp = sd;
                  sd = sd->parent;
                  destroy_sched_domain(tmp, cpu);
                  if (sd)
                          sd->child = NULL;
          }
  
          sched_domain_debug(sd, cpu);
  
          rq_attach_root(rq, rd);
          tmp = rq->sd;
          rcu_assign_pointer(rq->sd, sd);
          destroy_sched_domains(tmp, cpu);
  }
  
  /* cpus with isolated domains */
  static cpumask_var_t cpu_isolated_map;
  
  /* Setup the mask of cpus configured for isolated domains */
  static int __init isolated_cpu_setup(char *str)
  {
          alloc_bootmem_cpumask_var(&cpu_isolated_map);
          cpulist_parse(str, cpu_isolated_map);
          return 1;
  }
  
  __setup("isolcpus=", isolated_cpu_setup);
  
  #define SD_NODES_PER_DOMAIN 16
  
  #ifdef CONFIG_NUMA
  
  /**
   * find_next_best_node - find the next node to include in a sched_domain
   * @node: node whose sched_domain we're building
   * @used_nodes: nodes already in the sched_domain
   *
   * Find the next node to include in a given scheduling domain. Simply
   * finds the closest node not already in the @used_nodes map.
   *
   * Should use nodemask_t.
   */
  static int find_next_best_node(int node, nodemask_t *used_nodes)
  {
          int i, n, val, min_val, best_node = -1;
  
          min_val = INT_MAX;
  
          for (i = 0; i < nr_node_ids; i++) {
                  /* Start at @node */
                  n = (node + i) % nr_node_ids;
  
                  if (!nr_cpus_node(n))
                          continue;
  
                  /* Skip already used nodes */
                  if (node_isset(n, *used_nodes))
                          continue;
  
                  /* Simple min distance search */
                  val = node_distance(node, n);
  
                  if (val < min_val) {
                          min_val = val;
                          best_node = n;
                  }
          }
  
          if (best_node != -1)
                  node_set(best_node, *used_nodes);
          return best_node;
  }
  
  /**
   * sched_domain_node_span - get a cpumask for a node's sched_domain
   * @node: node whose cpumask we're constructing
   * @span: resulting cpumask
   *
   * Given a node, construct a good cpumask for its sched_domain to span. It
   * should be one that prevents unnecessary balancing, but also spreads tasks
   * out optimally.
   */
  static void sched_domain_node_span(int node, struct cpumask *span)
  {
          nodemask_t used_nodes;
          int i;
  
          cpumask_clear(span);
          nodes_clear(used_nodes);
  
          cpumask_or(span, span, cpumask_of_node(node));
          node_set(node, used_nodes);
  
          for (i = 1; i < SD_NODES_PER_DOMAIN; i++) {
                  int next_node = find_next_best_node(node, &used_nodes);
                  if (next_node < 0)
                          break;
                  cpumask_or(span, span, cpumask_of_node(next_node));
          }
  }
  
  static const struct cpumask *cpu_node_mask(int cpu)
  {
          lockdep_assert_held(&sched_domains_mutex);
  
          sched_domain_node_span(cpu_to_node(cpu), sched_domains_tmpmask);
  
          return sched_domains_tmpmask;
  }
  
  static const struct cpumask *cpu_allnodes_mask(int cpu)
  {
          return cpu_possible_mask;
  }
  #endif /* CONFIG_NUMA */
  
  static const struct cpumask *cpu_cpu_mask(int cpu)
  {
          return cpumask_of_node(cpu_to_node(cpu));
  }
  
  int sched_smt_power_savings = 0, sched_mc_power_savings = 0;
  
  struct sd_data {
          struct sched_domain **__percpu sd;
          struct sched_group **__percpu sg;
          struct sched_group_power **__percpu sgp;
  };
  
  struct s_data {
          struct sched_domain ** __percpu sd;
          struct root_domain      *rd;
  };
  
  enum s_alloc {
          sa_rootdomain,
          sa_sd,
          sa_sd_storage,
          sa_none,
  };
  
  struct sched_domain_topology_level;
  
  typedef struct sched_domain *(*sched_domain_init_f)(struct sched_domain_topology_level *tl, int cpu);
  typedef const struct cpumask *(*sched_domain_mask_f)(int cpu);
  
  #define SDTL_OVERLAP    0x01
  
  struct sched_domain_topology_level {
          sched_domain_init_f init;
          sched_domain_mask_f mask;
          int                 flags;
          struct sd_data      data;
  };
  
  static int
  build_overlap_sched_groups(struct sched_domain *sd, int cpu)
  {
          struct sched_group *first = NULL, *last = NULL, *groups = NULL, *sg;
          const struct cpumask *span = sched_domain_span(sd);
          struct cpumask *covered = sched_domains_tmpmask;
          struct sd_data *sdd = sd->private;
          struct sched_domain *child;
          int i;
  
          cpumask_clear(covered);
  
          for_each_cpu(i, span) {
                  struct cpumask *sg_span;
  
                  if (cpumask_test_cpu(i, covered))
                          continue;
  
                  sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
                                  GFP_KERNEL, cpu_to_node(i));
  
                  if (!sg)
                          goto fail;
  
                  sg_span = sched_group_cpus(sg);
  
                  child = *per_cpu_ptr(sdd->sd, i);
                  if (child->child) {
                          child = child->child;
                          cpumask_copy(sg_span, sched_domain_span(child));
                  } else
                          cpumask_set_cpu(i, sg_span);
  
                  cpumask_or(covered, covered, sg_span);
  
                  sg->sgp = *per_cpu_ptr(sdd->sgp, cpumask_first(sg_span));
                  atomic_inc(&sg->sgp->ref);
  
                  if (cpumask_test_cpu(cpu, sg_span))
                          groups = sg;
  
                  if (!first)
                          first = sg;
                  if (last)
                          last->next = sg;
                  last = sg;
                  last->next = first;
          }
          sd->groups = groups;
  
          return 0;
  
  fail:
          free_sched_groups(first, 0);
  
          return -ENOMEM;
  }
  
  static int get_group(int cpu, struct sd_data *sdd, struct sched_group **sg)
  {
          struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
          struct sched_domain *child = sd->child;
  
          if (child)
                  cpu = cpumask_first(sched_domain_span(child));
  
          if (sg) {
                  *sg = *per_cpu_ptr(sdd->sg, cpu);
                  (*sg)->sgp = *per_cpu_ptr(sdd->sgp, cpu);
                  atomic_set(&(*sg)->sgp->ref, 1); /* for claim_allocations */
          }
  
          return cpu;
  }
  
  /*
   * build_sched_groups will build a circular linked list of the groups
   * covered by the given span, and will set each group's ->cpumask correctly,
   * and ->cpu_power to 0.
   *
   * Assumes the sched_domain tree is fully constructed
   */
  static int
  build_sched_groups(struct sched_domain *sd, int cpu)
  {
          struct sched_group *first = NULL, *last = NULL;
          struct sd_data *sdd = sd->private;
          const struct cpumask *span = sched_domain_span(sd);
          struct cpumask *covered;
          int i;
  
          get_group(cpu, sdd, &sd->groups);
          atomic_inc(&sd->groups->ref);
  
          if (cpu != cpumask_first(sched_domain_span(sd)))
                  return 0;
  
          lockdep_assert_held(&sched_domains_mutex);
          covered = sched_domains_tmpmask;
  
          cpumask_clear(covered);
  
          for_each_cpu(i, span) {
                  struct sched_group *sg;
                  int group = get_group(i, sdd, &sg);
                  int j;
  
                  if (cpumask_test_cpu(i, covered))
                          continue;
  
                  cpumask_clear(sched_group_cpus(sg));
                  sg->sgp->power = 0;
  
                  for_each_cpu(j, span) {
                          if (get_group(j, sdd, NULL) != group)
                                  continue;
  
                          cpumask_set_cpu(j, covered);
                          cpumask_set_cpu(j, sched_group_cpus(sg));
                  }
  
                  if (!first)
                          first = sg;
                  if (last)
                          last->next = sg;
                  last = sg;
          }
          last->next = first;
  
          return 0;
  }
  
  /*
   * Initialize sched groups cpu_power.
   *
   * cpu_power indicates the capacity of sched group, which is used while
   * distributing the load between different sched groups in a sched domain.
   * Typically cpu_power for all the groups in a sched domain will be same unless
   * there are asymmetries in the topology. If there are asymmetries, group
   * having more cpu_power will pickup more load compared to the group having
   * less cpu_power.
   */
  static void init_sched_groups_power(int cpu, struct sched_domain *sd)
  {
          struct sched_group *sg = sd->groups;
  
          WARN_ON(!sd || !sg);
  
          do {
                  sg->group_weight = cpumask_weight(sched_group_cpus(sg));
                  sg = sg->next;
          } while (sg != sd->groups);
  
          if (cpu != group_first_cpu(sg))
                  return;
  
          update_group_power(sd, cpu);
  }
  
  /*
   * Initializers for schedule domains
   * Non-inlined to reduce accumulated stack pressure in build_sched_domains()
   */
  
  #ifdef CONFIG_SCHED_DEBUG
  # define SD_INIT_NAME(sd, type)         sd->name = #type
  #else
  # define SD_INIT_NAME(sd, type)         do { } while (0)
  #endif
  
  #define SD_INIT_FUNC(type)                                              \
  static noinline struct sched_domain *                                   \
  sd_init_##type(struct sched_domain_topology_level *tl, int cpu)         \
  {                                                                       \
          struct sched_domain *sd = *per_cpu_ptr(tl->data.sd, cpu);       \
          *sd = SD_##type##_INIT;                                         \
          SD_INIT_NAME(sd, type);                                         \
          sd->private = &tl->data;                                        \
          return sd;                                                      \
  }
  
  SD_INIT_FUNC(CPU)
  #ifdef CONFIG_NUMA
   SD_INIT_FUNC(ALLNODES)
   SD_INIT_FUNC(NODE)
  #endif
  #ifdef CONFIG_SCHED_SMT
   SD_INIT_FUNC(SIBLING)
  #endif
  #ifdef CONFIG_SCHED_MC
   SD_INIT_FUNC(MC)
  #endif
  #ifdef CONFIG_SCHED_BOOK
   SD_INIT_FUNC(BOOK)
  #endif
  
  static int default_relax_domain_level = -1;
  int sched_domain_level_max;
  
  static int __init setup_relax_domain_level(char *str)
  {
          unsigned long val;
  
          val = simple_strtoul(str, NULL, 0);
          if (val < sched_domain_level_max)
                  default_relax_domain_level = val;
  
          return 1;
  }
  __setup("relax_domain_level=", setup_relax_domain_level);
  
  static void set_domain_attribute(struct sched_domain *sd,
                                   struct sched_domain_attr *attr)
  {
          int request;
  
          if (!attr || attr->relax_domain_level < 0) {
                  if (default_relax_domain_level < 0)
                          return;
                  else
                          request = default_relax_domain_level;
          } else
                  request = attr->relax_domain_level;
          if (request < sd->level) {
                  /* turn off idle balance on this domain */
                  sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
          } else {
                  /* turn on idle balance on this domain */
                  sd->flags |= (SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
          }
  }
  
  static void __sdt_free(const struct cpumask *cpu_map);
  static int __sdt_alloc(const struct cpumask *cpu_map);
  
  static void __free_domain_allocs(struct s_data *d, enum s_alloc what,
                                   const struct cpumask *cpu_map)
  {
          switch (what) {
          case sa_rootdomain:
                  if (!atomic_read(&d->rd->refcount))
                          free_rootdomain(&d->rd->rcu); /* fall through */
          case sa_sd:
                  free_percpu(d->sd); /* fall through */
          case sa_sd_storage:
                  __sdt_free(cpu_map); /* fall through */
          case sa_none:
                  break;
          }
  }
  
  static enum s_alloc __visit_domain_allocation_hell(struct s_data *d,
                                                     const struct cpumask *cpu_map)
  {
          memset(d, 0, sizeof(*d));
  
          if (__sdt_alloc(cpu_map))
                  return sa_sd_storage;
          d->sd = alloc_percpu(struct sched_domain *);
          if (!d->sd)
                  return sa_sd_storage;
          d->rd = alloc_rootdomain();
          if (!d->rd)
                  return sa_sd;
          return sa_rootdomain;
  }
  
  /*
   * NULL the sd_data elements we've used to build the sched_domain and
   * sched_group structure so that the subsequent __free_domain_allocs()
   * will not free the data we're using.
   */
  static void claim_allocations(int cpu, struct sched_domain *sd)
  {
          struct sd_data *sdd = sd->private;
  
          WARN_ON_ONCE(*per_cpu_ptr(sdd->sd, cpu) != sd);
          *per_cpu_ptr(sdd->sd, cpu) = NULL;
  
          if (atomic_read(&(*per_cpu_ptr(sdd->sg, cpu))->ref))
                  *per_cpu_ptr(sdd->sg, cpu) = NULL;
  
          if (atomic_read(&(*per_cpu_ptr(sdd->sgp, cpu))->ref))
                  *per_cpu_ptr(sdd->sgp, cpu) = NULL;
  }
  
  #ifdef CONFIG_SCHED_SMT
  static const struct cpumask *cpu_smt_mask(int cpu)
  {
          return topology_thread_cpumask(cpu);
  }
  #endif
  
  /*
   * Topology list, bottom-up.
   */
  static struct sched_domain_topology_level default_topology[] = {
  #ifdef CONFIG_SCHED_SMT
          { sd_init_SIBLING, cpu_smt_mask, },
  #endif
  #ifdef CONFIG_SCHED_MC
          { sd_init_MC, cpu_coregroup_mask, },
  #endif
  #ifdef CONFIG_SCHED_BOOK
          { sd_init_BOOK, cpu_book_mask, },
  #endif
          { sd_init_CPU, cpu_cpu_mask, },
  #ifdef CONFIG_NUMA
          { sd_init_NODE, cpu_node_mask, SDTL_OVERLAP, },
          { sd_init_ALLNODES, cpu_allnodes_mask, },
  #endif
          { NULL, },
  };
  
  static struct sched_domain_topology_level *sched_domain_topology = default_topology;
  
  static int __sdt_alloc(const struct cpumask *cpu_map)
  {
          struct sched_domain_topology_level *tl;
          int j;
  
          for (tl = sched_domain_topology; tl->init; tl++) {
                  struct sd_data *sdd = &tl->data;
  
                  sdd->sd = alloc_percpu(struct sched_domain *);
                  if (!sdd->sd)
                          return -ENOMEM;
  
                  sdd->sg = alloc_percpu(struct sched_group *);
                  if (!sdd->sg)
                          return -ENOMEM;
  
                  sdd->sgp = alloc_percpu(struct sched_group_power *);
                  if (!sdd->sgp)
                          return -ENOMEM;
  
                  for_each_cpu(j, cpu_map) {
                          struct sched_domain *sd;
                          struct sched_group *sg;
                          struct sched_group_power *sgp;
  
                          sd = kzalloc_node(sizeof(struct sched_domain) + cpumask_size(),
                                          GFP_KERNEL, cpu_to_node(j));
                          if (!sd)
                                  return -ENOMEM;
  
                          *per_cpu_ptr(sdd->sd, j) = sd;
  
                          sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
                                          GFP_KERNEL, cpu_to_node(j));
                          if (!sg)
                                  return -ENOMEM;
  
                          *per_cpu_ptr(sdd->sg, j) = sg;
  
                          sgp = kzalloc_node(sizeof(struct sched_group_power),
                                          GFP_KERNEL, cpu_to_node(j));
                          if (!sgp)
                                  return -ENOMEM;
  
                          *per_cpu_ptr(sdd->sgp, j) = sgp;
                  }
          }
  
          return 0;
  }
  
  static void __sdt_free(const struct cpumask *cpu_map)
  {
          struct sched_domain_topology_level *tl;
          int j;
  
          for (tl = sched_domain_topology; tl->init; tl++) {
                  struct sd_data *sdd = &tl->data;
  
                  for_each_cpu(j, cpu_map) {
                          struct sched_domain *sd = *per_cpu_ptr(sdd->sd, j);
                          if (sd && (sd->flags & SD_OVERLAP))
                                  free_sched_groups(sd->groups, 0);
                          kfree(*per_cpu_ptr(sdd->sg, j));
                          kfree(*per_cpu_ptr(sdd->sgp, j));
                  }
                  free_percpu(sdd->sd);
                  free_percpu(sdd->sg);
                  free_percpu(sdd->sgp);
          }
  }
  
  struct sched_domain *build_sched_domain(struct sched_domain_topology_level *tl,
                  struct s_data *d, const struct cpumask *cpu_map,
                  struct sched_domain_attr *attr, struct sched_domain *child,
                  int cpu)
  {
          struct sched_domain *sd = tl->init(tl, cpu);
          if (!sd)
                  return child;
  
          set_domain_attribute(sd, attr);
          cpumask_and(sched_domain_span(sd), cpu_map, tl->mask(cpu));
          if (child) {
                  sd->level = child->level + 1;
                  sched_domain_level_max = max(sched_domain_level_max, sd->level);
                  child->parent = sd;
          }
          sd->child = child;
  
          return sd;
  }
  
  /*
   * Build sched domains for a given set of cpus and attach the sched domains
   * to the individual cpus
   */
  static int build_sched_domains(const struct cpumask *cpu_map,
                                 struct sched_domain_attr *attr)
  {
          enum s_alloc alloc_state = sa_none;
          struct sched_domain *sd;
          struct s_data d;
          int i, ret = -ENOMEM;
  
          alloc_state = __visit_domain_allocation_hell(&d, cpu_map);
          if (alloc_state != sa_rootdomain)
                  goto error;
  
          /* Set up domains for cpus specified by the cpu_map. */
          for_each_cpu(i, cpu_map) {
                  struct sched_domain_topology_level *tl;
  
                  sd = NULL;
                  for (tl = sched_domain_topology; tl->init; tl++) {
                          sd = build_sched_domain(tl, &d, cpu_map, attr, sd, i);
                          if (tl->flags & SDTL_OVERLAP || sched_feat(FORCE_SD_OVERLAP))
                                  sd->flags |= SD_OVERLAP;
                          if (cpumask_equal(cpu_map, sched_domain_span(sd)))
                                  break;
                  }
  
                  while (sd->child)
                          sd = sd->child;
  
                  *per_cpu_ptr(d.sd, i) = sd;
          }
  
          /* Build the groups for the domains */
          for_each_cpu(i, cpu_map) {
                  for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
                          sd->span_weight = cpumask_weight(sched_domain_span(sd));
                          if (sd->flags & SD_OVERLAP) {
                                  if (build_overlap_sched_groups(sd, i))
                                          goto error;
                          } else {
                                  if (build_sched_groups(sd, i))
                                          goto error;
                          }
                  }
          }
  
          /* Calculate CPU power for physical packages and nodes */
          for (i = nr_cpumask_bits-1; i >= 0; i--) {
                  if (!cpumask_test_cpu(i, cpu_map))
                          continue;
  
                  for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
                          claim_allocations(i, sd);
                          init_sched_groups_power(i, sd);
                  }
          }
  
          /* Attach the domains */
          rcu_read_lock();
          for_each_cpu(i, cpu_map) {
                  sd = *per_cpu_ptr(d.sd, i);
                  cpu_attach_domain(sd, d.rd, i);
          }
          rcu_read_unlock();
  
          ret = 0;
  error:
          __free_domain_allocs(&d, alloc_state, cpu_map);
          return ret;
  }
  
  static cpumask_var_t *doms_cur; /* current sched domains */
  static int ndoms_cur;           /* number of sched domains in 'doms_cur' */
  static struct sched_domain_attr *dattr_cur;
                                  /* attribues of custom domains in 'doms_cur' */
  
  /*
   * Special case: If a kmalloc of a doms_cur partition (array of
   * cpumask) fails, then fallback to a single sched domain,
   * as determined by the single cpumask fallback_doms.
   */
  static cpumask_var_t fallback_doms;
  
  /*
   * arch_update_cpu_topology lets virtualized architectures update the
   * cpu core maps. It is supposed to return 1 if the topology changed
   * or 0 if it stayed the same.
   */
  int __attribute__((weak)) arch_update_cpu_topology(void)
  {
          return 0;
  }
  
  cpumask_var_t *alloc_sched_domains(unsigned int ndoms)
  {
          int i;
          cpumask_var_t *doms;
  
          doms = kmalloc(sizeof(*doms) * ndoms, GFP_KERNEL);
          if (!doms)
                  return NULL;
          for (i = 0; i < ndoms; i++) {
                  if (!alloc_cpumask_var(&doms[i], GFP_KERNEL)) {
                          free_sched_domains(doms, i);
                          return NULL;
                  }
          }
          return doms;
  }
  
  void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms)
  {
          unsigned int i;
          for (i = 0; i < ndoms; i++)
                  free_cpumask_var(doms[i]);
          kfree(doms);
  }
  
  /*
   * Set up scheduler domains and groups. Callers must hold the hotplug lock.
   * For now this just excludes isolated cpus, but could be used to
   * exclude other special cases in the future.
   */
  static int init_sched_domains(const struct cpumask *cpu_map)
  {
          int err;
  
          arch_update_cpu_topology();
          ndoms_cur = 1;
          doms_cur = alloc_sched_domains(ndoms_cur);
          if (!doms_cur)
                  doms_cur = &fallback_doms;
          cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map);
          dattr_cur = NULL;
          err = build_sched_domains(doms_cur[0], NULL);
          register_sched_domain_sysctl();
  
          return err;
  }
  
  /*
   * Detach sched domains from a group of cpus specified in cpu_map
   * These cpus will now be attached to the NULL domain
   */
  static void detach_destroy_domains(const struct cpumask *cpu_map)
  {
          int i;
  
          rcu_read_lock();
          for_each_cpu(i, cpu_map)
                  cpu_attach_domain(NULL, &def_root_domain, i);
          rcu_read_unlock();
  }
  
  /* handle null as "default" */
  static int dattrs_equal(struct sched_domain_attr *cur, int idx_cur,
                          struct sched_domain_attr *new, int idx_new)
  {
          struct sched_domain_attr tmp;
  
          /* fast path */
          if (!new && !cur)
                  return 1;
  
          tmp = SD_ATTR_INIT;
          return !memcmp(cur ? (cur + idx_cur) : &tmp,
                          new ? (new + idx_new) : &tmp,
                          sizeof(struct sched_domain_attr));
  }
  
  /*
   * Partition sched domains as specified by the 'ndoms_new'
   * cpumasks in the array doms_new[] of cpumasks. This compares
   * doms_new[] to the current sched domain partitioning, doms_cur[].
   * It destroys each deleted domain and builds each new domain.
   *
   * 'doms_new' is an array of cpumask_var_t's of length 'ndoms_new'.
   * The masks don't intersect (don't overlap.) We should setup one
   * sched domain for each mask. CPUs not in any of the cpumasks will
   * not be load balanced. If the same cpumask appears both in the
   * current 'doms_cur' domains and in the new 'doms_new', we can leave
   * it as it is.
   *
   * The passed in 'doms_new' should be allocated using
   * alloc_sched_domains.  This routine takes ownership of it and will
   * free_sched_domains it when done with it. If the caller failed the
   * alloc call, then it can pass in doms_new == NULL && ndoms_new == 1,
   * and partition_sched_domains() will fallback to the single partition
   * 'fallback_doms', it also forces the domains to be rebuilt.
   *
   * If doms_new == NULL it will be replaced with cpu_online_mask.
   * ndoms_new == 0 is a special case for destroying existing domains,
   * and it will not create the default domain.
   *
   * Call with hotplug lock held
   */
  void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
                               struct sched_domain_attr *dattr_new)
  {
          int i, j, n;
          int new_topology;
  
          mutex_lock(&sched_domains_mutex);
  
          /* always unregister in case we don't destroy any domains */
          unregister_sched_domain_sysctl();
  
          /* Let architecture update cpu core mappings. */
          new_topology = arch_update_cpu_topology();
  
          n = doms_new ? ndoms_new : 0;
  
          /* Destroy deleted domains */
          for (i = 0; i < ndoms_cur; i++) {
                  for (j = 0; j < n && !new_topology; j++) {
                          if (cpumask_equal(doms_cur[i], doms_new[j])
                              && dattrs_equal(dattr_cur, i, dattr_new, j))
                                  goto match1;
                  }
                  /* no match - a current sched domain not in new doms_new[] */
                  detach_destroy_domains(doms_cur[i]);
  match1:
                  ;
          }
  
          if (doms_new == NULL) {
                  ndoms_cur = 0;
                  doms_new = &fallback_doms;
                  cpumask_andnot(doms_new[0], cpu_active_mask, cpu_isolated_map);
                  WARN_ON_ONCE(dattr_new);
          }
  
          /* Build new domains */
          for (i = 0; i < ndoms_new; i++) {
                  for (j = 0; j < ndoms_cur && !new_topology; j++) {
                          if (cpumask_equal(doms_new[i], doms_cur[j])
                              && dattrs_equal(dattr_new, i, dattr_cur, j))
                                  goto match2;
                  }
                  /* no match - add a new doms_new */
                  build_sched_domains(doms_new[i], dattr_new ? dattr_new + i : NULL);
  match2:
                  ;
          }
  
          /* Remember the new sched domains */
          if (doms_cur != &fallback_doms)
                  free_sched_domains(doms_cur, ndoms_cur);
          kfree(dattr_cur);       /* kfree(NULL) is safe */
          doms_cur = doms_new;
          dattr_cur = dattr_new;
          ndoms_cur = ndoms_new;
  
          register_sched_domain_sysctl();
  
          mutex_unlock(&sched_domains_mutex);
  }
  
  #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
  static void reinit_sched_domains(void)
  {
          get_online_cpus();
  
          /* Destroy domains first to force the rebuild */
          partition_sched_domains(0, NULL, NULL);
  
          rebuild_sched_domains();
          put_online_cpus();
  }
  
  static ssize_t sched_power_savings_store(const char *buf, size_t count, int smt)
  {
          unsigned int level = 0;
  
          if (sscanf(buf, "%u", &level) != 1)
                  return -EINVAL;
  
          /*
           * level is always be positive so don't check for
           * level < POWERSAVINGS_BALANCE_NONE which is 0
           * What happens on 0 or 1 byte write,
           * need to check for count as well?
           */
  
          if (level >= MAX_POWERSAVINGS_BALANCE_LEVELS)
                  return -EINVAL;
  
          if (smt)
                  sched_smt_power_savings = level;
          else
                  sched_mc_power_savings = level;
  
          reinit_sched_domains();
  
          return count;
  }
  
  #ifdef CONFIG_SCHED_MC
  static ssize_t sched_mc_power_savings_show(struct sysdev_class *class,
                                             struct sysdev_class_attribute *attr,
                                             char *page)
  {
          return sprintf(page, "%u\n", sched_mc_power_savings);
  }
  static ssize_t sched_mc_power_savings_store(struct sysdev_class *class,
                                              struct sysdev_class_attribute *attr,
                                              const char *buf, size_t count)
  {
          return sched_power_savings_store(buf, count, 0);
  }
  static SYSDEV_CLASS_ATTR(sched_mc_power_savings, 0644,
                           sched_mc_power_savings_show,
                           sched_mc_power_savings_store);
  #endif
  
  #ifdef CONFIG_SCHED_SMT
  static ssize_t sched_smt_power_savings_show(struct sysdev_class *dev,
                                              struct sysdev_class_attribute *attr,
                                              char *page)
  {
          return sprintf(page, "%u\n", sched_smt_power_savings);
  }
  static ssize_t sched_smt_power_savings_store(struct sysdev_class *dev,
                                               struct sysdev_class_attribute *attr,
                                               const char *buf, size_t count)
  {
          return sched_power_savings_store(buf, count, 1);
  }
  static SYSDEV_CLASS_ATTR(sched_smt_power_savings, 0644,
                     sched_smt_power_savings_show,
                     sched_smt_power_savings_store);
  #endif
  
  int __init sched_create_sysfs_power_savings_entries(struct sysdev_class *cls)
  {
          int err = 0;
  
  #ifdef CONFIG_SCHED_SMT
          if (smt_capable())
                  err = sysfs_create_file(&cls->kset.kobj,
                                          &attr_sched_smt_power_savings.attr);
  #endif
  #ifdef CONFIG_SCHED_MC
          if (!err && mc_capable())
                  err = sysfs_create_file(&cls->kset.kobj,
                                          &attr_sched_mc_power_savings.attr);
  #endif
          return err;
  }
  #endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
  
  /*
   * Update cpusets according to cpu_active mask.  If cpusets are
   * disabled, cpuset_update_active_cpus() becomes a simple wrapper
   * around partition_sched_domains().
   */
  static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
                               void *hcpu)
  {
          switch (action & ~CPU_TASKS_FROZEN) {
          case CPU_ONLINE:
          case CPU_DOWN_FAILED:
                  cpuset_update_active_cpus();
                  return NOTIFY_OK;
          default:
                  return NOTIFY_DONE;
          }
  }
  
  static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
                                 void *hcpu)
  {
          switch (action & ~CPU_TASKS_FROZEN) {
          case CPU_DOWN_PREPARE:
                  cpuset_update_active_cpus();
                  return NOTIFY_OK;
          default:
                  return NOTIFY_DONE;
          }
  }
  
  static int update_runtime(struct notifier_block *nfb,
                                  unsigned long action, void *hcpu)
  {
          int cpu = (int)(long)hcpu;
  
          switch (action) {
          case CPU_DOWN_PREPARE:
          case CPU_DOWN_PREPARE_FROZEN:
                  disable_runtime(cpu_rq(cpu));
                  return NOTIFY_OK;
  
          case CPU_DOWN_FAILED:
          case CPU_DOWN_FAILED_FROZEN:
          case CPU_ONLINE:
          case CPU_ONLINE_FROZEN:
                  enable_runtime(cpu_rq(cpu));
                  return NOTIFY_OK;
  
          default:
                  return NOTIFY_DONE;
          }
  }
  
  void __init sched_init_smp(void)
  {
          cpumask_var_t non_isolated_cpus;
  
          alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL);
          alloc_cpumask_var(&fallback_doms, GFP_KERNEL);
  
          get_online_cpus();
          mutex_lock(&sched_domains_mutex);
          init_sched_domains(cpu_active_mask);
          cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map);
          if (cpumask_empty(non_isolated_cpus))
                  cpumask_set_cpu(smp_processor_id(), non_isolated_cpus);
          mutex_unlock(&sched_domains_mutex);
          put_online_cpus();
  
          hotcpu_notifier(cpuset_cpu_active, CPU_PRI_CPUSET_ACTIVE);
          hotcpu_notifier(cpuset_cpu_inactive, CPU_PRI_CPUSET_INACTIVE);
  
          /* RT runtime code needs to handle some hotplug events */
          hotcpu_notifier(update_runtime, 0);
  
          init_hrtick();
  
          /* Move init over to a non-isolated CPU */
          if (set_cpus_allowed_ptr(current, non_isolated_cpus) < 0)
                  BUG();
          sched_init_granularity();
          free_cpumask_var(non_isolated_cpus);
  
          init_sched_rt_class();
  }
  #else
  void __init sched_init_smp(void)
  {
          sched_init_granularity();
  }
  #endif /* CONFIG_SMP */
  
  const_debug unsigned int sysctl_timer_migration = 1;
  
  int in_sched_functions(unsigned long addr)
  {
          return in_lock_functions(addr) ||
                  (addr >= (unsigned long)__sched_text_start
                  && addr < (unsigned long)__sched_text_end);
  }
  
  static void init_cfs_rq(struct cfs_rq *cfs_rq)
  {
          cfs_rq->tasks_timeline = RB_ROOT;
          INIT_LIST_HEAD(&cfs_rq->tasks);
          cfs_rq->min_vruntime = (u64)(-(1LL << 20));
  #ifndef CONFIG_64BIT
          cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
  #endif
  }
  
  static void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq)
  {
          struct rt_prio_array *array;
          int i;
  
          array = &rt_rq->active;
          for (i = 0; i < MAX_RT_PRIO; i++) {
                  INIT_LIST_HEAD(array->queue + i);
                  __clear_bit(i, array->bitmap);
          }
          /* delimiter for bitsearch: */
          __set_bit(MAX_RT_PRIO, array->bitmap);
  
  #if defined CONFIG_SMP
          rt_rq->highest_prio.curr = MAX_RT_PRIO;
          rt_rq->highest_prio.next = MAX_RT_PRIO;
          rt_rq->rt_nr_migratory = 0;
          rt_rq->overloaded = 0;
          plist_head_init(&rt_rq->pushable_tasks);
  #endif
  
          rt_rq->rt_time = 0;
          rt_rq->rt_throttled = 0;
          rt_rq->rt_runtime = 0;
          raw_spin_lock_init(&rt_rq->rt_runtime_lock);
  }
  
  #ifdef CONFIG_FAIR_GROUP_SCHED
  static void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
                                  struct sched_entity *se, int cpu,
                                  struct sched_entity *parent)
  {
          struct rq *rq = cpu_rq(cpu);
  
          cfs_rq->tg = tg;
          cfs_rq->rq = rq;
  #ifdef CONFIG_SMP
          /* allow initial update_cfs_load() to truncate */
          cfs_rq->load_stamp = 1;
  #endif
  
          tg->cfs_rq[cpu] = cfs_rq;
          tg->se[cpu] = se;
  
          /* se could be NULL for root_task_group */
          if (!se)
                  return;
  
          if (!parent)
                  se->cfs_rq = &rq->cfs;
          else
                  se->cfs_rq = parent->my_q;
  
          se->my_q = cfs_rq;
          update_load_set(&se->load, 0);
          se->parent = parent;
  }
  #endif
  
  #ifdef CONFIG_RT_GROUP_SCHED
  static void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
                  struct sched_rt_entity *rt_se, int cpu,
                  struct sched_rt_entity *parent)
  {
          struct rq *rq = cpu_rq(cpu);
  
          rt_rq->highest_prio.curr = MAX_RT_PRIO;
          rt_rq->rt_nr_boosted = 0;
          rt_rq->rq = rq;
          rt_rq->tg = tg;
  
          tg->rt_rq[cpu] = rt_rq;
          tg->rt_se[cpu] = rt_se;
  
          if (!rt_se)
                  return;
  
          if (!parent)
                  rt_se->rt_rq = &rq->rt;
          else
                  rt_se->rt_rq = parent->my_q;
  
          rt_se->my_q = rt_rq;
          rt_se->parent = parent;
          INIT_LIST_HEAD(&rt_se->run_list);
  }
  #endif
  
  void __init sched_init(void)
  {
          int i, j;
          unsigned long alloc_size = 0, ptr;
  
  #ifdef CONFIG_FAIR_GROUP_SCHED
          alloc_size += 2 * nr_cpu_ids * sizeof(void **);
  #endif
  #ifdef CONFIG_RT_GROUP_SCHED
          alloc_size += 2 * nr_cpu_ids * sizeof(void **);
  #endif
  #ifdef CONFIG_CPUMASK_OFFSTACK
          alloc_size += num_possible_cpus() * cpumask_size();
  #endif
          if (alloc_size) {
                  ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT);
  
  #ifdef CONFIG_FAIR_GROUP_SCHED
                  root_task_group.se = (struct sched_entity **)ptr;
                  ptr += nr_cpu_ids * sizeof(void **);
  
                  root_task_group.cfs_rq = (struct cfs_rq **)ptr;
                  ptr += nr_cpu_ids * sizeof(void **);
  
  #endif /* CONFIG_FAIR_GROUP_SCHED */
  #ifdef CONFIG_RT_GROUP_SCHED
                  root_task_group.rt_se = (struct sched_rt_entity **)ptr;
                  ptr += nr_cpu_ids * sizeof(void **);
  
                  root_task_group.rt_rq = (struct rt_rq **)ptr;
                  ptr += nr_cpu_ids * sizeof(void **);
  
  #endif /* CONFIG_RT_GROUP_SCHED */
  #ifdef CONFIG_CPUMASK_OFFSTACK
                  for_each_possible_cpu(i) {
                          per_cpu(load_balance_tmpmask, i) = (void *)ptr;
                          ptr += cpumask_size();
                  }
  #endif /* CONFIG_CPUMASK_OFFSTACK */
          }
  
  #ifdef CONFIG_SMP
          init_defrootdomain();
  #endif
  
          init_rt_bandwidth(&def_rt_bandwidth,
                          global_rt_period(), global_rt_runtime());
  
  #ifdef CONFIG_RT_GROUP_SCHED
          init_rt_bandwidth(&root_task_group.rt_bandwidth,
                          global_rt_period(), global_rt_runtime());
  #endif /* CONFIG_RT_GROUP_SCHED */
  
  #ifdef CONFIG_CGROUP_SCHED
          list_add(&root_task_group.list, &task_groups);
          INIT_LIST_HEAD(&root_task_group.children);
          autogroup_init(&init_task);
  #endif /* CONFIG_CGROUP_SCHED */
  
          for_each_possible_cpu(i) {
                  struct rq *rq;
  
                  rq = cpu_rq(i);
                  raw_spin_lock_init(&rq->lock);
                  rq->nr_running = 0;
                  rq->calc_load_active = 0;
                  rq->calc_load_update = jiffies + LOAD_FREQ;
                  init_cfs_rq(&rq->cfs);
                  init_rt_rq(&rq->rt, rq);
  #ifdef CONFIG_FAIR_GROUP_SCHED
                  root_task_group.shares = root_task_group_load;
                  INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
                  /*
                   * How much cpu bandwidth does root_task_group get?
                   *
                   * In case of task-groups formed thr' the cgroup filesystem, it
                   * gets 100% of the cpu resources in the system. This overall
                   * system cpu resource is divided among the tasks of
                   * root_task_group and its child task-groups in a fair manner,
                   * based on each entity's (task or task-group's) weight
                   * (se->load.weight).
                   *
                   * In other words, if root_task_group has 10 tasks of weight
                   * 1024) and two child groups A0 and A1 (of weight 1024 each),
                   * then A0's share of the cpu resource is:
                   *
                   *      A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
                   *
                   * We achieve this by letting root_task_group's tasks sit
                   * directly in rq->cfs (i.e root_task_group->se[] = NULL).
                   */
                  init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
  #endif /* CONFIG_FAIR_GROUP_SCHED */
  
                  rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
  #ifdef CONFIG_RT_GROUP_SCHED
                  INIT_LIST_HEAD(&rq->leaf_rt_rq_list);
                  init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
  #endif
  
                  for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
                          rq->cpu_load[j] = 0;
  
                  rq->last_load_update_tick = jiffies;
  
  #ifdef CONFIG_SMP
                  rq->sd = NULL;
                  rq->rd = NULL;
                  rq->cpu_power = SCHED_POWER_SCALE;
                  rq->post_schedule = 0;
                  rq->active_balance = 0;
                  rq->next_balance = jiffies;
                  rq->push_cpu = 0;
                  rq->cpu = i;
                  rq->online = 0;
                  rq->idle_stamp = 0;
                  rq->avg_idle = 2*sysctl_sched_migration_cost;
                  rq_attach_root(rq, &def_root_domain);
  #ifdef CONFIG_NO_HZ
                  rq->nohz_balance_kick = 0;
                  init_sched_softirq_csd(&per_cpu(remote_sched_softirq_cb, i));
  #endif
  #endif
                  init_rq_hrtick(rq);
                  atomic_set(&rq->nr_iowait, 0);
          }
  
          set_load_weight(&init_task);
  
  #ifdef CONFIG_PREEMPT_NOTIFIERS
          INIT_HLIST_HEAD(&init_task.preempt_notifiers);
  #endif
  
  #ifdef CONFIG_SMP
          open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
  #endif
  
  #ifdef CONFIG_RT_MUTEXES
          plist_head_init(&init_task.pi_waiters);
  #endif
  
          /*
           * The boot idle thread does lazy MMU switching as well:
           */
          atomic_inc(&init_mm.mm_count);
          enter_lazy_tlb(&init_mm, current);
  
          /*
           * Make us the idle thread. Technically, schedule() should not be
           * called from this thread, however somewhere below it might be,
           * but because we are the idle thread, we just pick up running again
           * when this runqueue becomes "idle".
           */
          init_idle(current, smp_processor_id());
  
          calc_load_update = jiffies + LOAD_FREQ;
  
          /*
           * During early bootup we pretend to be a normal task:
           */
          current->sched_class = &fair_sched_class;
  
          /* Allocate the nohz_cpu_mask if CONFIG_CPUMASK_OFFSTACK */
          zalloc_cpumask_var(&nohz_cpu_mask, GFP_NOWAIT);
  #ifdef CONFIG_SMP
          zalloc_cpumask_var(&sched_domains_tmpmask, GFP_NOWAIT);
  #ifdef CONFIG_NO_HZ
          zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
          alloc_cpumask_var(&nohz.grp_idle_mask, GFP_NOWAIT);
          atomic_set(&nohz.load_balancer, nr_cpu_ids);
          atomic_set(&nohz.first_pick_cpu, nr_cpu_ids);
          atomic_set(&nohz.second_pick_cpu, nr_cpu_ids);
  #endif
          /* May be allocated at isolcpus cmdline parse time */
          if (cpu_isolated_map == NULL)
                  zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
  #endif /* SMP */
  
          scheduler_running = 1;
  }
  
  #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
  static inline int preempt_count_equals(int preempt_offset)
  {
          int nested = (preempt_count() & ~PREEMPT_ACTIVE) + rcu_preempt_depth();
  
          return (nested == preempt_offset);
  }
  
  void __might_sleep(const char *file, int line, int preempt_offset)
  {
          static unsigned long prev_jiffy;        /* ratelimiting */
  
          if ((preempt_count_equals(preempt_offset) && !irqs_disabled()) ||
              system_state != SYSTEM_RUNNING || oops_in_progress)
                  return;
          if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
                  return;
          prev_jiffy = jiffies;
  
          printk(KERN_ERR
                  "BUG: sleeping function called from invalid context at %s:%d\n",
                          file, line);
          printk(KERN_ERR
                  "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
                          in_atomic(), irqs_disabled(),
                          current->pid, current->comm);
  
          debug_show_held_locks(current);
          if (irqs_disabled())
                  print_irqtrace_events(current);
          dump_stack();
  }
  EXPORT_SYMBOL(__might_sleep);
  #endif
  
  #ifdef CONFIG_MAGIC_SYSRQ
  static void normalize_task(struct rq *rq, struct task_struct *p)
  {
          const struct sched_class *prev_class = p->sched_class;
          int old_prio = p->prio;
          int on_rq;
  
          on_rq = p->on_rq;
          if (on_rq)
                  deactivate_task(rq, p, 0);
          __setscheduler(rq, p, SCHED_NORMAL, 0);
          if (on_rq) {
                  activate_task(rq, p, 0);
                  resched_task(rq->curr);
          }
  
          check_class_changed(rq, p, prev_class, old_prio);
  }
  
  void normalize_rt_tasks(void)
  {
          struct task_struct *g, *p;
          unsigned long flags;
          struct rq *rq;
  
          read_lock_irqsave(&tasklist_lock, flags);
          do_each_thread(g, p) {
                  /*
                   * Only normalize user tasks:
                   */
                  if (!p->mm)
                          continue;
  
                  p->se.exec_start                = 0;
  #ifdef CONFIG_SCHEDSTATS
                  p->se.statistics.wait_start     = 0;
                  p->se.statistics.sleep_start    = 0;
                  p->se.statistics.block_start    = 0;
  #endif
  
                  if (!rt_task(p)) {
                          /*
                           * Renice negative nice level userspace
                           * tasks back to 0:
                           */
                          if (TASK_NICE(p) < 0 && p->mm)
                                  set_user_nice(p, 0);
                          continue;
                  }
  
                  raw_spin_lock(&p->pi_lock);
                  rq = __task_rq_lock(p);
  
                  normalize_task(rq, p);
  
                  __task_rq_unlock(rq);
                  raw_spin_unlock(&p->pi_lock);
          } while_each_thread(g, p);
  
          read_unlock_irqrestore(&tasklist_lock, flags);
  }
  
  #endif /* CONFIG_MAGIC_SYSRQ */
  
  #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
  /*
   * These functions are only useful for the IA64 MCA handling, or kdb.
   *
   * They can only be called when the whole system has been
   * stopped - every CPU needs to be quiescent, and no scheduling
   * activity can take place. Using them for anything else would
   * be a serious bug, and as a result, they aren't even visible
   * under any other configuration.
   */
  
  /**
   * curr_task - return the current task for a given cpu.
   * @cpu: the processor in question.
   *
   * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
   */
  struct task_struct *curr_task(int cpu)
  {
          return cpu_curr(cpu);
  }
  
  #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
  
  #ifdef CONFIG_IA64
  /**
   * set_curr_task - set the current task for a given cpu.
   * @cpu: the processor in question.
   * @p: the task pointer to set.
   *
   * Description: This function must only be used when non-maskable interrupts
   * are serviced on a separate stack. It allows the architecture to switch the
   * notion of the current task on a cpu in a non-blocking manner. This function
   * must be called with all CPU's synchronized, and interrupts disabled, the
   * and caller must save the original value of the current task (see
   * curr_task() above) and restore that value before reenabling interrupts and
   * re-starting the system.
   *
   * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
   */
  void set_curr_task(int cpu, struct task_struct *p)
  {
          cpu_curr(cpu) = p;
  }
  
  #endif
  
  #ifdef CONFIG_FAIR_GROUP_SCHED
  static void free_fair_sched_group(struct task_group *tg)
  {
          int i;
  
          for_each_possible_cpu(i) {
                  if (tg->cfs_rq)
                          kfree(tg->cfs_rq[i]);
                  if (tg->se)
                          kfree(tg->se[i]);
          }
  
          kfree(tg->cfs_rq);
          kfree(tg->se);
  }
  
  static
  int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
  {
          struct cfs_rq *cfs_rq;
          struct sched_entity *se;
          int i;
  
          tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
          if (!tg->cfs_rq)
                  goto err;
          tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
          if (!tg->se)
                  goto err;
  
          tg->shares = NICE_0_LOAD;
  
          for_each_possible_cpu(i) {
                  cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
                                        GFP_KERNEL, cpu_to_node(i));
                  if (!cfs_rq)
                          goto err;
  
                  se = kzalloc_node(sizeof(struct sched_entity),
                                    GFP_KERNEL, cpu_to_node(i));
                  if (!se)
                          goto err_free_rq;
  
                  init_cfs_rq(cfs_rq);
                  init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
          }
  
          return 1;
  
  err_free_rq:
          kfree(cfs_rq);
  err:
          return 0;
  }
  
  static inline void unregister_fair_sched_group(struct task_group *tg, int cpu)
  {
          struct rq *rq = cpu_rq(cpu);
          unsigned long flags;
  
          /*
          * Only empty task groups can be destroyed; so we can speculatively
          * check on_list without danger of it being re-added.
          */
          if (!tg->cfs_rq[cpu]->on_list)
                  return;
  
          raw_spin_lock_irqsave(&rq->lock, flags);
          list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
          raw_spin_unlock_irqrestore(&rq->lock, flags);
  }
  #else /* !CONFIG_FAIR_GROUP_SCHED */
  static inline void free_fair_sched_group(struct task_group *tg)
  {
  }
  
  static inline
  int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
  {
          return 1;
  }
  
  static inline void unregister_fair_sched_group(struct task_group *tg, int cpu)
  {
  }
  #endif /* CONFIG_FAIR_GROUP_SCHED */
  
  #ifdef CONFIG_RT_GROUP_SCHED
  static void free_rt_sched_group(struct task_group *tg)
  {
          int i;
  
          if (tg->rt_se)
                  destroy_rt_bandwidth(&tg->rt_bandwidth);
  
          for_each_possible_cpu(i) {
                  if (tg->rt_rq)
                          kfree(tg->rt_rq[i]);
                  if (tg->rt_se)
                          kfree(tg->rt_se[i]);
          }
  
          kfree(tg->rt_rq);
          kfree(tg->rt_se);
  }
  
  static
  int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
  {
          struct rt_rq *rt_rq;
          struct sched_rt_entity *rt_se;
          int i;
  
          tg->rt_rq = kzalloc(sizeof(rt_rq) * nr_cpu_ids, GFP_KERNEL);
          if (!tg->rt_rq)
                  goto err;
          tg->rt_se = kzalloc(sizeof(rt_se) * nr_cpu_ids, GFP_KERNEL);
          if (!tg->rt_se)
                  goto err;
  
          init_rt_bandwidth(&tg->rt_bandwidth,
                          ktime_to_ns(def_rt_bandwidth.rt_period), 0);
  
          for_each_possible_cpu(i) {
                  rt_rq = kzalloc_node(sizeof(struct rt_rq),
                                       GFP_KERNEL, cpu_to_node(i));
                  if (!rt_rq)
                          goto err;
  
                  rt_se = kzalloc_node(sizeof(struct sched_rt_entity),
                                       GFP_KERNEL, cpu_to_node(i));
                  if (!rt_se)
                          goto err_free_rq;
  
                  init_rt_rq(rt_rq, cpu_rq(i));
                  rt_rq->rt_runtime = tg->rt_bandwidth.rt_runtime;
                  init_tg_rt_entry(tg, rt_rq, rt_se, i, parent->rt_se[i]);
          }
  
          return 1;
  
  err_free_rq:
          kfree(rt_rq);
  err:
          return 0;
  }
  #else /* !CONFIG_RT_GROUP_SCHED */
  static inline void free_rt_sched_group(struct task_group *tg)
  {
  }
  
  static inline
  int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
  {
          return 1;
  }
  #endif /* CONFIG_RT_GROUP_SCHED */
  
  #ifdef CONFIG_CGROUP_SCHED
  static void free_sched_group(struct task_group *tg)
  {
          free_fair_sched_group(tg);
          free_rt_sched_group(tg);
          autogroup_free(tg);
          kfree(tg);
  }
  
  /* allocate runqueue etc for a new task group */
  struct task_group *sched_create_group(struct task_group *parent)
  {
          struct task_group *tg;
          unsigned long flags;
  
          tg = kzalloc(sizeof(*tg), GFP_KERNEL);
          if (!tg)
                  return ERR_PTR(-ENOMEM);
  
          if (!alloc_fair_sched_group(tg, parent))
                  goto err;
  
          if (!alloc_rt_sched_group(tg, parent))
                  goto err;
  
          spin_lock_irqsave(&task_group_lock, flags);
          list_add_rcu(&tg->list, &task_groups);
  
          WARN_ON(!parent); /* root should already exist */
  
          tg->parent = parent;
          INIT_LIST_HEAD(&tg->children);
          list_add_rcu(&tg->siblings, &parent->children);
          spin_unlock_irqrestore(&task_group_lock, flags);
  
          return tg;
  
  err:
          free_sched_group(tg);
          return ERR_PTR(-ENOMEM);
  }
  
  /* rcu callback to free various structures associated with a task group */
  static void free_sched_group_rcu(struct rcu_head *rhp)
  {
          /* now it should be safe to free those cfs_rqs */
          free_sched_group(container_of(rhp, struct task_group, rcu));
  }
  
  /* Destroy runqueue etc associated with a task group */
  void sched_destroy_group(struct task_group *tg)
  {
          unsigned long flags;
          int i;
  
          /* end participation in shares distribution */
          for_each_possible_cpu(i)
                  unregister_fair_sched_group(tg, i);
  
          spin_lock_irqsave(&task_group_lock, flags);
          list_del_rcu(&tg->list);
          list_del_rcu(&tg->siblings);
          spin_unlock_irqrestore(&task_group_lock, flags);
  
          /* wait for possible concurrent references to cfs_rqs complete */
          call_rcu(&tg->rcu, free_sched_group_rcu);
  }
  
  /* change task's runqueue when it moves between groups.
   *      The caller of this function should have put the task in its new group
   *      by now. This function just updates tsk->se.cfs_rq and tsk->se.parent to
   *      reflect its new group.
   */
  void sched_move_task(struct task_struct *tsk)
  {
          int on_rq, running;
          unsigned long flags;
          struct rq *rq;
  
          rq = task_rq_lock(tsk, &flags);
  
          running = task_current(rq, tsk);
          on_rq = tsk->on_rq;
  
          if (on_rq)
                  dequeue_task(rq, tsk, 0);
          if (unlikely(running))
                  tsk->sched_class->put_prev_task(rq, tsk);
  
  #ifdef CONFIG_FAIR_GROUP_SCHED
          if (tsk->sched_class->task_move_group)
                  tsk->sched_class->task_move_group(tsk, on_rq);
          else
  #endif
                  set_task_rq(tsk, task_cpu(tsk));
  
          if (unlikely(running))
                  tsk->sched_class->set_curr_task(rq);
          if (on_rq)
                  enqueue_task(rq, tsk, 0);
  
          task_rq_unlock(rq, tsk, &flags);
  }
  #endif /* CONFIG_CGROUP_SCHED */
  
  #ifdef CONFIG_FAIR_GROUP_SCHED
  static DEFINE_MUTEX(shares_mutex);
  
  int sched_group_set_shares(struct task_group *tg, unsigned long shares)
  {
          int i;
          unsigned long flags;
  
          /*
           * We can't change the weight of the root cgroup.
           */
          if (!tg->se[0])
                  return -EINVAL;
  
          shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
  
          mutex_lock(&shares_mutex);
          if (tg->shares == shares)
                  goto done;
  
          tg->shares = shares;
          for_each_possible_cpu(i) {
                  struct rq *rq = cpu_rq(i);
                  struct sched_entity *se;
  
                  se = tg->se[i];
                  /* Propagate contribution to hierarchy */
                  raw_spin_lock_irqsave(&rq->lock, flags);
                  for_each_sched_entity(se)
                          update_cfs_shares(group_cfs_rq(se));
                  raw_spin_unlock_irqrestore(&rq->lock, flags);
          }
  
  done:
          mutex_unlock(&shares_mutex);
          return 0;
  }
  
  unsigned long sched_group_shares(struct task_group *tg)
  {
          return tg->shares;
  }
  #endif
  
  #ifdef CONFIG_RT_GROUP_SCHED
  /*
   * Ensure that the real time constraints are schedulable.
   */
  static DEFINE_MUTEX(rt_constraints_mutex);
  
  static unsigned long to_ratio(u64 period, u64 runtime)
  {
          if (runtime == RUNTIME_INF)
                  return 1ULL << 20;
  
          return div64_u64(runtime << 20, period);
  }
  
  /* Must be called with tasklist_lock held */
  static inline int tg_has_rt_tasks(struct task_group *tg)
  {
          struct task_struct *g, *p;
  
          do_each_thread(g, p) {
                  if (rt_task(p) && rt_rq_of_se(&p->rt)->tg == tg)
                          return 1;
          } while_each_thread(g, p);
  
          return 0;
  }
  
  struct rt_schedulable_data {
          struct task_group *tg;
          u64 rt_period;
          u64 rt_runtime;
  };
  
  static int tg_schedulable(struct task_group *tg, void *data)
  {
          struct rt_schedulable_data *d = data;
          struct task_group *child;
          unsigned long total, sum = 0;
          u64 period, runtime;
  
          period = ktime_to_ns(tg->rt_bandwidth.rt_period);
          runtime = tg->rt_bandwidth.rt_runtime;
  
          if (tg == d->tg) {
                  period = d->rt_period;
                  runtime = d->rt_runtime;
          }
  
          /*
           * Cannot have more runtime than the period.
           */
          if (runtime > period && runtime != RUNTIME_INF)
                  return -EINVAL;
  
          /*
           * Ensure we don't starve existing RT tasks.
           */
          if (rt_bandwidth_enabled() && !runtime && tg_has_rt_tasks(tg))
                  return -EBUSY;
  
          total = to_ratio(period, runtime);
  
          /*
           * Nobody can have more than the global setting allows.
           */
          if (total > to_ratio(global_rt_period(), global_rt_runtime()))
                  return -EINVAL;
  
          /*
           * The sum of our children's runtime should not exceed our own.
           */
          list_for_each_entry_rcu(child, &tg->children, siblings) {
                  period = ktime_to_ns(child->rt_bandwidth.rt_period);
                  runtime = child->rt_bandwidth.rt_runtime;
  
                  if (child == d->tg) {
                          period = d->rt_period;
                          runtime = d->rt_runtime;
                  }
  
                  sum += to_ratio(period, runtime);
          }
  
          if (sum > total)
                  return -EINVAL;
  
          return 0;
  }
  
  static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
  {
          struct rt_schedulable_data data = {
                  .tg = tg,
                  .rt_period = period,
                  .rt_runtime = runtime,
          };
  
          return walk_tg_tree(tg_schedulable, tg_nop, &data);
  }
  
  static int tg_set_bandwidth(struct task_group *tg,
                  u64 rt_period, u64 rt_runtime)
  {
          int i, err = 0;
  
          mutex_lock(&rt_constraints_mutex);
          read_lock(&tasklist_lock);
          err = __rt_schedulable(tg, rt_period, rt_runtime);
          if (err)
                  goto unlock;
  
          raw_spin_lock_irq(&tg->rt_bandwidth.rt_runtime_lock);
          tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period);
          tg->rt_bandwidth.rt_runtime = rt_runtime;
  
          for_each_possible_cpu(i) {
                  struct rt_rq *rt_rq = tg->rt_rq[i];
  
                  raw_spin_lock(&rt_rq->rt_runtime_lock);
                  rt_rq->rt_runtime = rt_runtime;
                  raw_spin_unlock(&rt_rq->rt_runtime_lock);
          }
          raw_spin_unlock_irq(&tg->rt_bandwidth.rt_runtime_lock);
  unlock:
          read_unlock(&tasklist_lock);
          mutex_unlock(&rt_constraints_mutex);
  
          return err;
  }
  
  int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
  {
          u64 rt_runtime, rt_period;
  
          rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period);
          rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
          if (rt_runtime_us < 0)
                  rt_runtime = RUNTIME_INF;
  
          return tg_set_bandwidth(tg, rt_period, rt_runtime);
  }
  
  long sched_group_rt_runtime(struct task_group *tg)
  {
          u64 rt_runtime_us;
  
          if (tg->rt_bandwidth.rt_runtime == RUNTIME_INF)
                  return -1;
  
          rt_runtime_us = tg->rt_bandwidth.rt_runtime;
          do_div(rt_runtime_us, NSEC_PER_USEC);
          return rt_runtime_us;
  }
  
  int sched_group_set_rt_period(struct task_group *tg, long rt_period_us)
  {
          u64 rt_runtime, rt_period;
  
          rt_period = (u64)rt_period_us * NSEC_PER_USEC;
          rt_runtime = tg->rt_bandwidth.rt_runtime;
  
          if (rt_period == 0)
                  return -EINVAL;
  
          return tg_set_bandwidth(tg, rt_period, rt_runtime);
  }
  
  long sched_group_rt_period(struct task_group *tg)
  {
          u64 rt_period_us;
  
          rt_period_us = ktime_to_ns(tg->rt_bandwidth.rt_period);
          do_div(rt_period_us, NSEC_PER_USEC);
          return rt_period_us;
  }
  
  static int sched_rt_global_constraints(void)
  {
          u64 runtime, period;
          int ret = 0;
  
          if (sysctl_sched_rt_period <= 0)
                  return -EINVAL;
  
          runtime = global_rt_runtime();
          period = global_rt_period();
  
          /*
           * Sanity check on the sysctl variables.
           */
          if (runtime > period && runtime != RUNTIME_INF)
                  return -EINVAL;
  
          mutex_lock(&rt_constraints_mutex);
          read_lock(&tasklist_lock);
          ret = __rt_schedulable(NULL, 0, 0);
          read_unlock(&tasklist_lock);
          mutex_unlock(&rt_constraints_mutex);
  
          return ret;
  }
  
  int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
  {
          /* Don't accept realtime tasks when there is no way for them to run */
          if (rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0)
                  return 0;
  
          return 1;
  }
  
  #else /* !CONFIG_RT_GROUP_SCHED */
  static int sched_rt_global_constraints(void)
  {
          unsigned long flags;
          int i;
  
          if (sysctl_sched_rt_period <= 0)
                  return -EINVAL;
  
          /*
           * There's always some RT tasks in the root group
           * -- migration, kstopmachine etc..
           */
          if (sysctl_sched_rt_runtime == 0)
                  return -EBUSY;
  
          raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
          for_each_possible_cpu(i) {
                  struct rt_rq *rt_rq = &cpu_rq(i)->rt;
  
                  raw_spin_lock(&rt_rq->rt_runtime_lock);
                  rt_rq->rt_runtime = global_rt_runtime();
                  raw_spin_unlock(&rt_rq->rt_runtime_lock);
          }
          raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
  
          return 0;
  }
  #endif /* CONFIG_RT_GROUP_SCHED */
  
  int sched_rt_handler(struct ctl_table *table, int write,
                  void __user *buffer, size_t *lenp,
                  loff_t *ppos)
  {
          int ret;
          int old_period, old_runtime;
          static DEFINE_MUTEX(mutex);
  
          mutex_lock(&mutex);
          old_period = sysctl_sched_rt_period;
          old_runtime = sysctl_sched_rt_runtime;
  
          ret = proc_dointvec(table, write, buffer, lenp, ppos);
  
          if (!ret && write) {
                  ret = sched_rt_global_constraints();
                  if (ret) {
                          sysctl_sched_rt_period = old_period;
                          sysctl_sched_rt_runtime = old_runtime;
                  } else {
                          def_rt_bandwidth.rt_runtime = global_rt_runtime();
                          def_rt_bandwidth.rt_period =
                                  ns_to_ktime(global_rt_period());
                  }
          }
          mutex_unlock(&mutex);
  
          return ret;
  }
  
  #ifdef CONFIG_CGROUP_SCHED
  
  /* return corresponding task_group object of a cgroup */
  static inline struct task_group *cgroup_tg(struct cgroup *cgrp)
  {
          return container_of(cgroup_subsys_state(cgrp, cpu_cgroup_subsys_id),
                              struct task_group, css);
  }
  
  static struct cgroup_subsys_state *
  cpu_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cgrp)
  {
          struct task_group *tg, *parent;
  
          if (!cgrp->parent) {
                  /* This is early initialization for the top cgroup */
                  return &root_task_group.css;
          }
  
          parent = cgroup_tg(cgrp->parent);
          tg = sched_create_group(parent);
          if (IS_ERR(tg))
                  return ERR_PTR(-ENOMEM);
  
          return &tg->css;
  }
  
  static void
  cpu_cgroup_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp)
  {
          struct task_group *tg = cgroup_tg(cgrp);
  
          sched_destroy_group(tg);
  }
  
  static int
  cpu_cgroup_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
  {
  #ifdef CONFIG_RT_GROUP_SCHED
          if (!sched_rt_can_attach(cgroup_tg(cgrp), tsk))
                  return -EINVAL;
  #else
          /* We don't support RT-tasks being in separate groups */
          if (tsk->sched_class != &fair_sched_class)
                  return -EINVAL;
  #endif
          return 0;
  }
  
  static void
  cpu_cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
  {
          sched_move_task(tsk);
  }
  
  static void
  cpu_cgroup_exit(struct cgroup_subsys *ss, struct cgroup *cgrp,
                  struct cgroup *old_cgrp, struct task_struct *task)
  {
          /*
           * cgroup_exit() is called in the copy_process() failure path.
           * Ignore this case since the task hasn't ran yet, this avoids
           * trying to poke a half freed task state from generic code.
           */
          if (!(task->flags & PF_EXITING))
                  return;
  
          sched_move_task(task);
  }
  
  #ifdef CONFIG_FAIR_GROUP_SCHED
  static int cpu_shares_write_u64(struct cgroup *cgrp, struct cftype *cftype,
                                  u64 shareval)
  {
          return sched_group_set_shares(cgroup_tg(cgrp), scale_load(shareval));
  }
  
  static u64 cpu_shares_read_u64(struct cgroup *cgrp, struct cftype *cft)
  {
          struct task_group *tg = cgroup_tg(cgrp);
  
          return (u64) scale_load_down(tg->shares);
  }
  #endif /* CONFIG_FAIR_GROUP_SCHED */
  
  #ifdef CONFIG_RT_GROUP_SCHED
  static int cpu_rt_runtime_write(struct cgroup *cgrp, struct cftype *cft,
                                  s64 val)
  {
          return sched_group_set_rt_runtime(cgroup_tg(cgrp), val);
  }
  
  static s64 cpu_rt_runtime_read(struct cgroup *cgrp, struct cftype *cft)
  {
          return sched_group_rt_runtime(cgroup_tg(cgrp));
  }
  
  static int cpu_rt_period_write_uint(struct cgroup *cgrp, struct cftype *cftype,
                  u64 rt_period_us)
  {
          return sched_group_set_rt_period(cgroup_tg(cgrp), rt_period_us);
  }
  
  static u64 cpu_rt_period_read_uint(struct cgroup *cgrp, struct cftype *cft)
  {
          return sched_group_rt_period(cgroup_tg(cgrp));
  }
  #endif /* CONFIG_RT_GROUP_SCHED */
  
  static struct cftype cpu_files[] = {
  #ifdef CONFIG_FAIR_GROUP_SCHED
          {
                  .name = "shares",
                  .read_u64 = cpu_shares_read_u64,
                  .write_u64 = cpu_shares_write_u64,
          },
  #endif
  #ifdef CONFIG_RT_GROUP_SCHED
          {
                  .name = "rt_runtime_us",
                  .read_s64 = cpu_rt_runtime_read,
                  .write_s64 = cpu_rt_runtime_write,
          },
          {
                  .name = "rt_period_us",
                  .read_u64 = cpu_rt_period_read_uint,
                  .write_u64 = cpu_rt_period_write_uint,
          },
  #endif
  };
  
  static int cpu_cgroup_populate(struct cgroup_subsys *ss, struct cgroup *cont)
  {
          return cgroup_add_files(cont, ss, cpu_files, ARRAY_SIZE(cpu_files));
  }
  
  struct cgroup_subsys cpu_cgroup_subsys = {
          .name           = "cpu",
          .create         = cpu_cgroup_create,
          .destroy        = cpu_cgroup_destroy,
          .can_attach_task = cpu_cgroup_can_attach_task,
          .attach_task    = cpu_cgroup_attach_task,
          .exit           = cpu_cgroup_exit,
          .populate       = cpu_cgroup_populate,
          .subsys_id      = cpu_cgroup_subsys_id,
          .early_init     = 1,
  };
  
  #endif  /* CONFIG_CGROUP_SCHED */
  
  #ifdef CONFIG_CGROUP_CPUACCT
  
  /*
   * CPU accounting code for task groups.
   *
   * Based on the work by Paul Menage (menage@google.com) and Balbir Singh
   * (balbir@in.ibm.com).
   */
  
  /* track cpu usage of a group of tasks and its child groups */
  struct cpuacct {
          struct cgroup_subsys_state css;
          /* cpuusage holds pointer to a u64-type object on every cpu */
          u64 __percpu *cpuusage;
          struct percpu_counter cpustat[CPUACCT_STAT_NSTATS];
          struct cpuacct *parent;
  };
  
  struct cgroup_subsys cpuacct_subsys;
  
  /* return cpu accounting group corresponding to this container */
  static inline struct cpuacct *cgroup_ca(struct cgroup *cgrp)
  {
          return container_of(cgroup_subsys_state(cgrp, cpuacct_subsys_id),
                              struct cpuacct, css);
  }
  
  /* return cpu accounting group to which this task belongs */
  static inline struct cpuacct *task_ca(struct task_struct *tsk)
  {
          return container_of(task_subsys_state(tsk, cpuacct_subsys_id),
                              struct cpuacct, css);
  }
  
  /* create a new cpu accounting group */
  static struct cgroup_subsys_state *cpuacct_create(
          struct cgroup_subsys *ss, struct cgroup *cgrp)
  {
          struct cpuacct *ca = kzalloc(sizeof(*ca), GFP_KERNEL);
          int i;
  
          if (!ca)
                  goto out;
  
          ca->cpuusage = alloc_percpu(u64);
          if (!ca->cpuusage)
                  goto out_free_ca;
  
          for (i = 0; i < CPUACCT_STAT_NSTATS; i++)
                  if (percpu_counter_init(&ca->cpustat[i], 0))
                          goto out_free_counters;
  
          if (cgrp->parent)
                  ca->parent = cgroup_ca(cgrp->parent);
  
          return &ca->css;
  
  out_free_counters:
          while (--i >= 0)
                  percpu_counter_destroy(&ca->cpustat[i]);
          free_percpu(ca->cpuusage);
  out_free_ca:
          kfree(ca);
  out:
          return ERR_PTR(-ENOMEM);
  }
  
  /* destroy an existing cpu accounting group */
  static void
  cpuacct_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp)
  {
          struct cpuacct *ca = cgroup_ca(cgrp);
          int i;
  
          for (i = 0; i < CPUACCT_STAT_NSTATS; i++)
                  percpu_counter_destroy(&ca->cpustat[i]);
          free_percpu(ca->cpuusage);
          kfree(ca);
  }
  
  static u64 cpuacct_cpuusage_read(struct cpuacct *ca, int cpu)
  {
          u64 *cpuusage = per_cpu_ptr(ca->cpuusage, cpu);
          u64 data;
  
  #ifndef CONFIG_64BIT
          /*
           * Take rq->lock to make 64-bit read safe on 32-bit platforms.
           */
          raw_spin_lock_irq(&cpu_rq(cpu)->lock);
          data = *cpuusage;
          raw_spin_unlock_irq(&cpu_rq(cpu)->lock);
  #else
          data = *cpuusage;
  #endif
  
          return data;
  }
  
  static void cpuacct_cpuusage_write(struct cpuacct *ca, int cpu, u64 val)
  {
          u64 *cpuusage = per_cpu_ptr(ca->cpuusage, cpu);
  
  #ifndef CONFIG_64BIT
          /*
           * Take rq->lock to make 64-bit write safe on 32-bit platforms.
           */
          raw_spin_lock_irq(&cpu_rq(cpu)->lock);
          *cpuusage = val;
          raw_spin_unlock_irq(&cpu_rq(cpu)->lock);
  #else
          *cpuusage = val;
  #endif
  }
  
  /* return total cpu usage (in nanoseconds) of a group */
  static u64 cpuusage_read(struct cgroup *cgrp, struct cftype *cft)
  {
          struct cpuacct *ca = cgroup_ca(cgrp);
          u64 totalcpuusage = 0;
          int i;
  
          for_each_present_cpu(i)
                  totalcpuusage += cpuacct_cpuusage_read(ca, i);
  
          return totalcpuusage;
  }
  
  static int cpuusage_write(struct cgroup *cgrp, struct cftype *cftype,
                                                                  u64 reset)
  {
          struct cpuacct *ca = cgroup_ca(cgrp);
          int err = 0;
          int i;
  
          if (reset) {
                  err = -EINVAL;
                  goto out;
          }
  
          for_each_present_cpu(i)
                  cpuacct_cpuusage_write(ca, i, 0);
  
  out:
          return err;
  }
  
  static int cpuacct_percpu_seq_read(struct cgroup *cgroup, struct cftype *cft,
                                     struct seq_file *m)
  {
          struct cpuacct *ca = cgroup_ca(cgroup);
          u64 percpu;
          int i;
  
          for_each_present_cpu(i) {
                  percpu = cpuacct_cpuusage_read(ca, i);
                  seq_printf(m, "%llu ", (unsigned long long) percpu);
          }
          seq_printf(m, "\n");
          return 0;
  }
  
  static const char *cpuacct_stat_desc[] = {
          [CPUACCT_STAT_USER] = "user",
          [CPUACCT_STAT_SYSTEM] = "system",
  };
  
  static int cpuacct_stats_show(struct cgroup *cgrp, struct cftype *cft,
                  struct cgroup_map_cb *cb)
  {
          struct cpuacct *ca = cgroup_ca(cgrp);
          int i;
  
          for (i = 0; i < CPUACCT_STAT_NSTATS; i++) {
                  s64 val = percpu_counter_read(&ca->cpustat[i]);
                  val = cputime64_to_clock_t(val);
                  cb->fill(cb, cpuacct_stat_desc[i], val);
          }
          return 0;
  }
  
  static struct cftype files[] = {
          {
                  .name = "usage",
                  .read_u64 = cpuusage_read,
                  .write_u64 = cpuusage_write,
          },
          {
                  .name = "usage_percpu",
                  .read_seq_string = cpuacct_percpu_seq_read,
          },
          {
                  .name = "stat",
                  .read_map = cpuacct_stats_show,
          },
  };
  
  static int cpuacct_populate(struct cgroup_subsys *ss, struct cgroup *cgrp)
  {
          return cgroup_add_files(cgrp, ss, files, ARRAY_SIZE(files));
  }
  
  /*
   * charge this task's execution time to its accounting group.
   *
   * called with rq->lock held.
   */
  static void cpuacct_charge(struct task_struct *tsk, u64 cputime)
  {
          struct cpuacct *ca;
          int cpu;
  
          if (unlikely(!cpuacct_subsys.active))
                  return;
  
          cpu = task_cpu(tsk);
  
          rcu_read_lock();
  
          ca = task_ca(tsk);
  
          for (; ca; ca = ca->parent) {
                  u64 *cpuusage = per_cpu_ptr(ca->cpuusage, cpu);
                  *cpuusage += cputime;
          }
  
          rcu_read_unlock();
  }
  
  /*
   * When CONFIG_VIRT_CPU_ACCOUNTING is enabled one jiffy can be very large
   * in cputime_t units. As a result, cpuacct_update_stats calls
   * percpu_counter_add with values large enough to always overflow the
   * per cpu batch limit causing bad SMP scalability.
   *
   * To fix this we scale percpu_counter_batch by cputime_one_jiffy so we
   * batch the same amount of time with CONFIG_VIRT_CPU_ACCOUNTING disabled
   * and enabled. We cap it at INT_MAX which is the largest allowed batch value.
   */
  #ifdef CONFIG_SMP
  #define CPUACCT_BATCH   \
          min_t(long, percpu_counter_batch * cputime_one_jiffy, INT_MAX)
  #else
  #define CPUACCT_BATCH   0
  #endif
  
  /*
   * Charge the system/user time to the task's accounting group.
   */
  static void cpuacct_update_stats(struct task_struct *tsk,
                  enum cpuacct_stat_index idx, cputime_t val)
  {
          struct cpuacct *ca;
          int batch = CPUACCT_BATCH;
  
          if (unlikely(!cpuacct_subsys.active))
                  return;
  
          rcu_read_lock();
          ca = task_ca(tsk);
  
          do {
                  __percpu_counter_add(&ca->cpustat[idx], val, batch);
                  ca = ca->parent;
          } while (ca);
          rcu_read_unlock();
  }
  
  struct cgroup_subsys cpuacct_subsys = {
          .name = "cpuacct",
          .create = cpuacct_create,
          .destroy = cpuacct_destroy,
          .populate = cpuacct_populate,
          .subsys_id = cpuacct_subsys_id,
  };
  #endif  /* CONFIG_CGROUP_CPUACCT */