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

     /*
      * Performance events core code:
      *
      *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
      *  Copyright (C) 2008-2009 Red Hat, Inc., Ingo Molnar
      *  Copyright (C) 2008-2009 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
      *  Copyright  ©  2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
      *
      * For licensing details see kernel-base/COPYING
     */
    
    #include <linux/fs.h>
    #include <linux/mm.h>
    #include <linux/cpu.h>
    #include <linux/smp.h>
    #include <linux/file.h>
    #include <linux/poll.h>
    #include <linux/slab.h>
    #include <linux/hash.h>
    #include <linux/sysfs.h>
    #include <linux/dcache.h>
    #include <linux/percpu.h>
    #include <linux/ptrace.h>
    #include <linux/vmstat.h>
    #include <linux/vmalloc.h>
    #include <linux/hardirq.h>
    #include <linux/rculist.h>
    #include <linux/uaccess.h>
    #include <linux/syscalls.h>
    #include <linux/anon_inodes.h>
    #include <linux/kernel_stat.h>
    #include <linux/perf_event.h>
    #include <linux/ftrace_event.h>
    #include <linux/hw_breakpoint.h>
    
    #include <asm/irq_regs.h>
    
    /*
     * Each CPU has a list of per CPU events:
     */
    static DEFINE_PER_CPU(struct perf_cpu_context, perf_cpu_context);
    
    int perf_max_events __read_mostly = 1;
    static int perf_reserved_percpu __read_mostly;
    static int perf_overcommit __read_mostly = 1;
    
    static atomic_t nr_events __read_mostly;
    static atomic_t nr_mmap_events __read_mostly;
    static atomic_t nr_comm_events __read_mostly;
    static atomic_t nr_task_events __read_mostly;
    
    /*
     * perf event paranoia level:
     *  -1 - not paranoid at all
     *   0 - disallow raw tracepoint access for unpriv
     *   1 - disallow cpu events for unpriv
     *   2 - disallow kernel profiling for unpriv
     */
    int sysctl_perf_event_paranoid __read_mostly = 1;
    
    int sysctl_perf_event_mlock __read_mostly = 512; /* 'free' kb per user */
    
    /*
     * max perf event sample rate
     */
    int sysctl_perf_event_sample_rate __read_mostly = 100000;
    
    static atomic64_t perf_event_id;
    
    /*
     * Lock for (sysadmin-configurable) event reservations:
     */
    static DEFINE_SPINLOCK(perf_resource_lock);
    
    /*
     * Architecture provided APIs - weak aliases:
     */
    extern __weak const struct pmu *hw_perf_event_init(struct perf_event *event)
    {
            return NULL;
    }
    
    void __weak hw_perf_disable(void)               { barrier(); }
    void __weak hw_perf_enable(void)                { barrier(); }
    
    void __weak perf_event_print_debug(void)        { }
    
    static DEFINE_PER_CPU(int, perf_disable_count);
    
    void perf_disable(void)
    {
            if (!__get_cpu_var(perf_disable_count)++)
                    hw_perf_disable();
    }
    
    void perf_enable(void)
    {
            if (!--__get_cpu_var(perf_disable_count))
                    hw_perf_enable();
   }
   
   static void get_ctx(struct perf_event_context *ctx)
   {
           WARN_ON(!atomic_inc_not_zero(&ctx->refcount));
   }
   
   static void free_ctx(struct rcu_head *head)
   {
           struct perf_event_context *ctx;
   
           ctx = container_of(head, struct perf_event_context, rcu_head);
           kfree(ctx);
   }
   
   static void put_ctx(struct perf_event_context *ctx)
   {
           if (atomic_dec_and_test(&ctx->refcount)) {
                   if (ctx->parent_ctx)
                           put_ctx(ctx->parent_ctx);
                   if (ctx->task)
                           put_task_struct(ctx->task);
                   call_rcu(&ctx->rcu_head, free_ctx);
           }
   }
   
   static void unclone_ctx(struct perf_event_context *ctx)
   {
           if (ctx->parent_ctx) {
                   put_ctx(ctx->parent_ctx);
                   ctx->parent_ctx = NULL;
           }
   }
   
   /*
    * If we inherit events we want to return the parent event id
    * to userspace.
    */
   static u64 primary_event_id(struct perf_event *event)
   {
           u64 id = event->id;
   
           if (event->parent)
                   id = event->parent->id;
   
           return id;
   }
   
   /*
    * Get the perf_event_context for a task and lock it.
    * This has to cope with with the fact that until it is locked,
    * the context could get moved to another task.
    */
   static struct perf_event_context *
   perf_lock_task_context(struct task_struct *task, unsigned long *flags)
   {
           struct perf_event_context *ctx;
   
           rcu_read_lock();
    retry:
           ctx = rcu_dereference(task->perf_event_ctxp);
           if (ctx) {
                   /*
                    * If this context is a clone of another, it might
                    * get swapped for another underneath us by
                    * perf_event_task_sched_out, though the
                    * rcu_read_lock() protects us from any context
                    * getting freed.  Lock the context and check if it
                    * got swapped before we could get the lock, and retry
                    * if so.  If we locked the right context, then it
                    * can't get swapped on us any more.
                    */
                   raw_spin_lock_irqsave(&ctx->lock, *flags);
                   if (ctx != rcu_dereference(task->perf_event_ctxp)) {
                           raw_spin_unlock_irqrestore(&ctx->lock, *flags);
                           goto retry;
                   }
   
                   if (!atomic_inc_not_zero(&ctx->refcount)) {
                           raw_spin_unlock_irqrestore(&ctx->lock, *flags);
                           ctx = NULL;
                   }
           }
           rcu_read_unlock();
           return ctx;
   }
   
   /*
    * Get the context for a task and increment its pin_count so it
    * can't get swapped to another task.  This also increments its
    * reference count so that the context can't get freed.
    */
   static struct perf_event_context *perf_pin_task_context(struct task_struct *task)
   {
           struct perf_event_context *ctx;
           unsigned long flags;
   
           ctx = perf_lock_task_context(task, &flags);
           if (ctx) {
                   ++ctx->pin_count;
                   raw_spin_unlock_irqrestore(&ctx->lock, flags);
           }
           return ctx;
   }
   
   static void perf_unpin_context(struct perf_event_context *ctx)
   {
           unsigned long flags;
   
           raw_spin_lock_irqsave(&ctx->lock, flags);
           --ctx->pin_count;
           raw_spin_unlock_irqrestore(&ctx->lock, flags);
           put_ctx(ctx);
   }
   
   static inline u64 perf_clock(void)
   {
           return local_clock();
   }
   
   /*
    * Update the record of the current time in a context.
    */
   static void update_context_time(struct perf_event_context *ctx)
   {
           u64 now = perf_clock();
   
           ctx->time += now - ctx->timestamp;
           ctx->timestamp = now;
   }
   
   /*
    * Update the total_time_enabled and total_time_running fields for a event.
    */
   static void update_event_times(struct perf_event *event)
   {
           struct perf_event_context *ctx = event->ctx;
           u64 run_end;
   
           if (event->state < PERF_EVENT_STATE_INACTIVE ||
               event->group_leader->state < PERF_EVENT_STATE_INACTIVE)
                   return;
   
           if (ctx->is_active)
                   run_end = ctx->time;
           else
                   run_end = event->tstamp_stopped;
   
           event->total_time_enabled = run_end - event->tstamp_enabled;
   
           if (event->state == PERF_EVENT_STATE_INACTIVE)
                   run_end = event->tstamp_stopped;
           else
                   run_end = ctx->time;
   
           event->total_time_running = run_end - event->tstamp_running;
   }
   
   /*
    * Update total_time_enabled and total_time_running for all events in a group.
    */
   static void update_group_times(struct perf_event *leader)
   {
           struct perf_event *event;
   
           update_event_times(leader);
           list_for_each_entry(event, &leader->sibling_list, group_entry)
                   update_event_times(event);
   }
   
   static struct list_head *
   ctx_group_list(struct perf_event *event, struct perf_event_context *ctx)
   {
           if (event->attr.pinned)
                   return &ctx->pinned_groups;
           else
                   return &ctx->flexible_groups;
   }
   
   /*
    * Add a event from the lists for its context.
    * Must be called with ctx->mutex and ctx->lock held.
    */
   static void
   list_add_event(struct perf_event *event, struct perf_event_context *ctx)
   {
           WARN_ON_ONCE(event->attach_state & PERF_ATTACH_CONTEXT);
           event->attach_state |= PERF_ATTACH_CONTEXT;
   
           /*
            * If we're a stand alone event or group leader, we go to the context
            * list, group events are kept attached to the group so that
            * perf_group_detach can, at all times, locate all siblings.
            */
           if (event->group_leader == event) {
                   struct list_head *list;
   
                   if (is_software_event(event))
                           event->group_flags |= PERF_GROUP_SOFTWARE;
   
                   list = ctx_group_list(event, ctx);
                   list_add_tail(&event->group_entry, list);
           }
   
           list_add_rcu(&event->event_entry, &ctx->event_list);
           ctx->nr_events++;
           if (event->attr.inherit_stat)
                   ctx->nr_stat++;
   }
   
   static void perf_group_attach(struct perf_event *event)
   {
           struct perf_event *group_leader = event->group_leader;
   
           WARN_ON_ONCE(event->attach_state & PERF_ATTACH_GROUP);
           event->attach_state |= PERF_ATTACH_GROUP;
   
           if (group_leader == event)
                   return;
   
           if (group_leader->group_flags & PERF_GROUP_SOFTWARE &&
                           !is_software_event(event))
                   group_leader->group_flags &= ~PERF_GROUP_SOFTWARE;
   
           list_add_tail(&event->group_entry, &group_leader->sibling_list);
           group_leader->nr_siblings++;
   }
   
   /*
    * Remove a event from the lists for its context.
    * Must be called with ctx->mutex and ctx->lock held.
    */
   static void
   list_del_event(struct perf_event *event, struct perf_event_context *ctx)
   {
           /*
            * We can have double detach due to exit/hot-unplug + close.
            */
           if (!(event->attach_state & PERF_ATTACH_CONTEXT))
                   return;
   
           event->attach_state &= ~PERF_ATTACH_CONTEXT;
   
           ctx->nr_events--;
           if (event->attr.inherit_stat)
                   ctx->nr_stat--;
   
           list_del_rcu(&event->event_entry);
   
           if (event->group_leader == event)
                   list_del_init(&event->group_entry);
   
           update_group_times(event);
   
           /*
            * If event was in error state, then keep it
            * that way, otherwise bogus counts will be
            * returned on read(). The only way to get out
            * of error state is by explicit re-enabling
            * of the event
            */
           if (event->state > PERF_EVENT_STATE_OFF)
                   event->state = PERF_EVENT_STATE_OFF;
   }
   
   static void perf_group_detach(struct perf_event *event)
   {
           struct perf_event *sibling, *tmp;
           struct list_head *list = NULL;
   
           /*
            * We can have double detach due to exit/hot-unplug + close.
            */
           if (!(event->attach_state & PERF_ATTACH_GROUP))
                   return;
   
           event->attach_state &= ~PERF_ATTACH_GROUP;
   
           /*
            * If this is a sibling, remove it from its group.
            */
           if (event->group_leader != event) {
                   list_del_init(&event->group_entry);
                   event->group_leader->nr_siblings--;
                   return;
           }
   
           if (!list_empty(&event->group_entry))
                   list = &event->group_entry;
   
           /*
            * If this was a group event with sibling events then
            * upgrade the siblings to singleton events by adding them
            * to whatever list we are on.
            */
           list_for_each_entry_safe(sibling, tmp, &event->sibling_list, group_entry) {
                   if (list)
                           list_move_tail(&sibling->group_entry, list);
                   sibling->group_leader = sibling;
   
                   /* Inherit group flags from the previous leader */
                   sibling->group_flags = event->group_flags;
           }
   }
   
   static void
   event_sched_out(struct perf_event *event,
                     struct perf_cpu_context *cpuctx,
                     struct perf_event_context *ctx)
   {
           if (event->state != PERF_EVENT_STATE_ACTIVE)
                   return;
   
           event->state = PERF_EVENT_STATE_INACTIVE;
           if (event->pending_disable) {
                   event->pending_disable = 0;
                   event->state = PERF_EVENT_STATE_OFF;
           }
           event->tstamp_stopped = ctx->time;
           event->pmu->disable(event);
           event->oncpu = -1;
   
           if (!is_software_event(event))
                   cpuctx->active_oncpu--;
           ctx->nr_active--;
           if (event->attr.exclusive || !cpuctx->active_oncpu)
                   cpuctx->exclusive = 0;
   }
   
   static void
   group_sched_out(struct perf_event *group_event,
                   struct perf_cpu_context *cpuctx,
                   struct perf_event_context *ctx)
   {
           struct perf_event *event;
   
           if (group_event->state != PERF_EVENT_STATE_ACTIVE)
                   return;
   
           event_sched_out(group_event, cpuctx, ctx);
   
           /*
            * Schedule out siblings (if any):
            */
           list_for_each_entry(event, &group_event->sibling_list, group_entry)
                   event_sched_out(event, cpuctx, ctx);
   
           if (group_event->attr.exclusive)
                   cpuctx->exclusive = 0;
   }
   
   /*
    * Cross CPU call to remove a performance event
    *
    * We disable the event on the hardware level first. After that we
    * remove it from the context list.
    */
   static void __perf_event_remove_from_context(void *info)
   {
           struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
           struct perf_event *event = info;
           struct perf_event_context *ctx = event->ctx;
   
           /*
            * If this is a task context, we need to check whether it is
            * the current task context of this cpu. If not it has been
            * scheduled out before the smp call arrived.
            */
           if (ctx->task && cpuctx->task_ctx != ctx)
                   return;
   
           raw_spin_lock(&ctx->lock);
           /*
            * Protect the list operation against NMI by disabling the
            * events on a global level.
            */
           perf_disable();
   
           event_sched_out(event, cpuctx, ctx);
   
           list_del_event(event, ctx);
   
           if (!ctx->task) {
                   /*
                    * Allow more per task events with respect to the
                    * reservation:
                    */
                   cpuctx->max_pertask =
                           min(perf_max_events - ctx->nr_events,
                               perf_max_events - perf_reserved_percpu);
           }
   
           perf_enable();
           raw_spin_unlock(&ctx->lock);
   }
   
   
   /*
    * Remove the event from a task's (or a CPU's) list of events.
    *
    * Must be called with ctx->mutex held.
    *
    * CPU events are removed with a smp call. For task events we only
    * call when the task is on a CPU.
    *
    * If event->ctx is a cloned context, callers must make sure that
    * every task struct that event->ctx->task could possibly point to
    * remains valid.  This is OK when called from perf_release since
    * that only calls us on the top-level context, which can't be a clone.
    * When called from perf_event_exit_task, it's OK because the
    * context has been detached from its task.
    */
   static void perf_event_remove_from_context(struct perf_event *event)
   {
           struct perf_event_context *ctx = event->ctx;
           struct task_struct *task = ctx->task;
   
           if (!task) {
                   /*
                    * Per cpu events are removed via an smp call and
                    * the removal is always successful.
                    */
                   smp_call_function_single(event->cpu,
                                            __perf_event_remove_from_context,
                                            event, 1);
                   return;
           }
   
   retry:
           task_oncpu_function_call(task, __perf_event_remove_from_context,
                                    event);
   
           raw_spin_lock_irq(&ctx->lock);
           /*
            * If the context is active we need to retry the smp call.
            */
           if (ctx->nr_active && !list_empty(&event->group_entry)) {
                   raw_spin_unlock_irq(&ctx->lock);
                   goto retry;
           }
   
           /*
            * The lock prevents that this context is scheduled in so we
            * can remove the event safely, if the call above did not
            * succeed.
            */
           if (!list_empty(&event->group_entry))
                   list_del_event(event, ctx);
           raw_spin_unlock_irq(&ctx->lock);
   }
   
   /*
    * Cross CPU call to disable a performance event
    */
   static void __perf_event_disable(void *info)
   {
           struct perf_event *event = info;
           struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
           struct perf_event_context *ctx = event->ctx;
   
           /*
            * If this is a per-task event, need to check whether this
            * event's task is the current task on this cpu.
            */
           if (ctx->task && cpuctx->task_ctx != ctx)
                   return;
   
           raw_spin_lock(&ctx->lock);
   
           /*
            * If the event is on, turn it off.
            * If it is in error state, leave it in error state.
            */
           if (event->state >= PERF_EVENT_STATE_INACTIVE) {
                   update_context_time(ctx);
                   update_group_times(event);
                   if (event == event->group_leader)
                           group_sched_out(event, cpuctx, ctx);
                   else
                           event_sched_out(event, cpuctx, ctx);
                   event->state = PERF_EVENT_STATE_OFF;
           }
   
           raw_spin_unlock(&ctx->lock);
   }
   
   /*
    * Disable a event.
    *
    * If event->ctx is a cloned context, callers must make sure that
    * every task struct that event->ctx->task could possibly point to
    * remains valid.  This condition is satisifed when called through
    * perf_event_for_each_child or perf_event_for_each because they
    * hold the top-level event's child_mutex, so any descendant that
    * goes to exit will block in sync_child_event.
    * When called from perf_pending_event it's OK because event->ctx
    * is the current context on this CPU and preemption is disabled,
    * hence we can't get into perf_event_task_sched_out for this context.
    */
   void perf_event_disable(struct perf_event *event)
   {
           struct perf_event_context *ctx = event->ctx;
           struct task_struct *task = ctx->task;
   
           if (!task) {
                   /*
                    * Disable the event on the cpu that it's on
                    */
                   smp_call_function_single(event->cpu, __perf_event_disable,
                                            event, 1);
                   return;
           }
   
    retry:
           task_oncpu_function_call(task, __perf_event_disable, event);
   
           raw_spin_lock_irq(&ctx->lock);
           /*
            * If the event is still active, we need to retry the cross-call.
            */
           if (event->state == PERF_EVENT_STATE_ACTIVE) {
                   raw_spin_unlock_irq(&ctx->lock);
                   goto retry;
           }
   
           /*
            * Since we have the lock this context can't be scheduled
            * in, so we can change the state safely.
            */
           if (event->state == PERF_EVENT_STATE_INACTIVE) {
                   update_group_times(event);
                   event->state = PERF_EVENT_STATE_OFF;
           }
   
           raw_spin_unlock_irq(&ctx->lock);
   }
   
   static int
   event_sched_in(struct perf_event *event,
                    struct perf_cpu_context *cpuctx,
                    struct perf_event_context *ctx)
   {
           if (event->state <= PERF_EVENT_STATE_OFF)
                   return 0;
   
           event->state = PERF_EVENT_STATE_ACTIVE;
           event->oncpu = smp_processor_id();
           /*
            * The new state must be visible before we turn it on in the hardware:
            */
           smp_wmb();
   
           if (event->pmu->enable(event)) {
                   event->state = PERF_EVENT_STATE_INACTIVE;
                   event->oncpu = -1;
                   return -EAGAIN;
           }
   
           event->tstamp_running += ctx->time - event->tstamp_stopped;
   
           if (!is_software_event(event))
                   cpuctx->active_oncpu++;
           ctx->nr_active++;
   
           if (event->attr.exclusive)
                   cpuctx->exclusive = 1;
   
           return 0;
   }
   
   static int
   group_sched_in(struct perf_event *group_event,
                  struct perf_cpu_context *cpuctx,
                  struct perf_event_context *ctx)
   {
           struct perf_event *event, *partial_group = NULL;
           const struct pmu *pmu = group_event->pmu;
           bool txn = false;
   
           if (group_event->state == PERF_EVENT_STATE_OFF)
                   return 0;
   
           /* Check if group transaction availabe */
           if (pmu->start_txn)
                   txn = true;
   
           if (txn)
                   pmu->start_txn(pmu);
   
           if (event_sched_in(group_event, cpuctx, ctx)) {
                   if (txn)
                           pmu->cancel_txn(pmu);
                   return -EAGAIN;
           }
   
           /*
            * Schedule in siblings as one group (if any):
            */
           list_for_each_entry(event, &group_event->sibling_list, group_entry) {
                   if (event_sched_in(event, cpuctx, ctx)) {
                           partial_group = event;
                           goto group_error;
                   }
           }
   
           if (!txn || !pmu->commit_txn(pmu))
                   return 0;
   
   group_error:
           /*
            * Groups can be scheduled in as one unit only, so undo any
            * partial group before returning:
            */
           list_for_each_entry(event, &group_event->sibling_list, group_entry) {
                   if (event == partial_group)
                           break;
                   event_sched_out(event, cpuctx, ctx);
           }
           event_sched_out(group_event, cpuctx, ctx);
   
           if (txn)
                   pmu->cancel_txn(pmu);
   
           return -EAGAIN;
   }
   
   /*
    * Work out whether we can put this event group on the CPU now.
    */
   static int group_can_go_on(struct perf_event *event,
                              struct perf_cpu_context *cpuctx,
                              int can_add_hw)
   {
           /*
            * Groups consisting entirely of software events can always go on.
            */
           if (event->group_flags & PERF_GROUP_SOFTWARE)
                   return 1;
           /*
            * If an exclusive group is already on, no other hardware
            * events can go on.
            */
           if (cpuctx->exclusive)
                   return 0;
           /*
            * If this group is exclusive and there are already
            * events on the CPU, it can't go on.
            */
           if (event->attr.exclusive && cpuctx->active_oncpu)
                   return 0;
           /*
            * Otherwise, try to add it if all previous groups were able
            * to go on.
            */
           return can_add_hw;
   }
   
   static void add_event_to_ctx(struct perf_event *event,
                                  struct perf_event_context *ctx)
   {
           list_add_event(event, ctx);
           perf_group_attach(event);
           event->tstamp_enabled = ctx->time;
           event->tstamp_running = ctx->time;
           event->tstamp_stopped = ctx->time;
   }
   
   /*
    * Cross CPU call to install and enable a performance event
    *
    * Must be called with ctx->mutex held
    */
   static void __perf_install_in_context(void *info)
   {
           struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
           struct perf_event *event = info;
           struct perf_event_context *ctx = event->ctx;
           struct perf_event *leader = event->group_leader;
           int err;
   
           /*
            * If this is a task context, we need to check whether it is
            * the current task context of this cpu. If not it has been
            * scheduled out before the smp call arrived.
            * Or possibly this is the right context but it isn't
            * on this cpu because it had no events.
            */
           if (ctx->task && cpuctx->task_ctx != ctx) {
                   if (cpuctx->task_ctx || ctx->task != current)
                           return;
                   cpuctx->task_ctx = ctx;
           }
   
           raw_spin_lock(&ctx->lock);
           ctx->is_active = 1;
           update_context_time(ctx);
   
           /*
            * Protect the list operation against NMI by disabling the
            * events on a global level. NOP for non NMI based events.
            */
           perf_disable();
   
           add_event_to_ctx(event, ctx);
   
           if (event->cpu != -1 && event->cpu != smp_processor_id())
                   goto unlock;
   
           /*
            * Don't put the event on if it is disabled or if
            * it is in a group and the group isn't on.
            */
           if (event->state != PERF_EVENT_STATE_INACTIVE ||
               (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE))
                   goto unlock;
   
           /*
            * An exclusive event can't go on if there are already active
            * hardware events, and no hardware event can go on if there
            * is already an exclusive event on.
            */
           if (!group_can_go_on(event, cpuctx, 1))
                   err = -EEXIST;
           else
                   err = event_sched_in(event, cpuctx, ctx);
   
           if (err) {
                   /*
                    * This event couldn't go on.  If it is in a group
                    * then we have to pull the whole group off.
                    * If the event group is pinned then put it in error state.
                    */
                   if (leader != event)
                           group_sched_out(leader, cpuctx, ctx);
                   if (leader->attr.pinned) {
                           update_group_times(leader);
                           leader->state = PERF_EVENT_STATE_ERROR;
                   }
           }
   
           if (!err && !ctx->task && cpuctx->max_pertask)
                   cpuctx->max_pertask--;
   
    unlock:
           perf_enable();
   
           raw_spin_unlock(&ctx->lock);
   }
   
   /*
    * Attach a performance event to a context
    *
    * First we add the event to the list with the hardware enable bit
    * in event->hw_config cleared.
    *
    * If the event is attached to a task which is on a CPU we use a smp
    * call to enable it in the task context. The task might have been
    * scheduled away, but we check this in the smp call again.
    *
    * Must be called with ctx->mutex held.
    */
   static void
   perf_install_in_context(struct perf_event_context *ctx,
                           struct perf_event *event,
                           int cpu)
   {
           struct task_struct *task = ctx->task;
   
           if (!task) {
                   /*
                    * Per cpu events are installed via an smp call and
                    * the install is always successful.
                    */
                   smp_call_function_single(cpu, __perf_install_in_context,
                                            event, 1);
                   return;
           }
   
   retry:
           task_oncpu_function_call(task, __perf_install_in_context,
                                    event);
   
           raw_spin_lock_irq(&ctx->lock);
           /*
            * we need to retry the smp call.
            */
           if (ctx->is_active && list_empty(&event->group_entry)) {
                   raw_spin_unlock_irq(&ctx->lock);
                   goto retry;
           }
   
           /*
            * The lock prevents that this context is scheduled in so we
            * can add the event safely, if it the call above did not
            * succeed.
            */
           if (list_empty(&event->group_entry))
                   add_event_to_ctx(event, ctx);
           raw_spin_unlock_irq(&ctx->lock);
   }
   
   /*
    * Put a event into inactive state and update time fields.
    * Enabling the leader of a group effectively enables all
    * the group members that aren't explicitly disabled, so we
    * have to update their ->tstamp_enabled also.
    * Note: this works for group members as well as group leaders
    * since the non-leader members' sibling_lists will be empty.
    */
   static void __perf_event_mark_enabled(struct perf_event *event,
                                           struct perf_event_context *ctx)
   {
           struct perf_event *sub;
   
           event->state = PERF_EVENT_STATE_INACTIVE;
           event->tstamp_enabled = ctx->time - event->total_time_enabled;
           list_for_each_entry(sub, &event->sibling_list, group_entry)
                   if (sub->state >= PERF_EVENT_STATE_INACTIVE)
                           sub->tstamp_enabled =
                                   ctx->time - sub->total_time_enabled;
   }
   
   /*
    * Cross CPU call to enable a performance event
    */
   static void __perf_event_enable(void *info)
   {
           struct perf_event *event = info;
           struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
           struct perf_event_context *ctx = event->ctx;
           struct perf_event *leader = event->group_leader;
           int err;
   
           /*
            * If this is a per-task event, need to check whether this
            * event's task is the current task on this cpu.
            */
           if (ctx->task && cpuctx->task_ctx != ctx) {
                   if (cpuctx->task_ctx || ctx->task != current)
                           return;
                   cpuctx->task_ctx = ctx;
           }
   
           raw_spin_lock(&ctx->lock);
           ctx->is_active = 1;
           update_context_time(ctx);
   
           if (event->state >= PERF_EVENT_STATE_INACTIVE)
                   goto unlock;
           __perf_event_mark_enabled(event, ctx);
   
           if (event->cpu != -1 && event->cpu != smp_processor_id())
                   goto unlock;
   
           /*
            * If the event is in a group and isn't the group leader,
            * then don't put it on unless the group is on.
            */
           if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE)
                   goto unlock;
   
           if (!group_can_go_on(event, cpuctx, 1)) {
                   err = -EEXIST;
           } else {
                   perf_disable();
                   if (event == leader)
                           err = group_sched_in(event, cpuctx, ctx);
                   else
                           err = event_sched_in(event, cpuctx, ctx);
                   perf_enable();
           }
   
           if (err) {
                   /*
                    * If this event can't go on and it's part of a
                    * group, then the whole group has to come off.
                    */
                   if (leader != event)
                           group_sched_out(leader, cpuctx, ctx);
                   if (leader->attr.pinned) {
                           update_group_times(leader);
                           leader->state = PERF_EVENT_STATE_ERROR;
                   }
           }
   
    unlock:
           raw_spin_unlock(&ctx->lock);
   }
   
   /*
    * Enable a event.
    *
    * If event->ctx is a cloned context, callers must make sure that
    * every task struct that event->ctx->task could possibly point to
    * remains valid.  This condition is satisfied when called through
    * perf_event_for_each_child or perf_event_for_each as described
    * for perf_event_disable.
    */
   void perf_event_enable(struct perf_event *event)
   {
          struct perf_event_context *ctx = event->ctx;
          struct task_struct *task = ctx->task;
  
          if (!task) {
                  /*
                   * Enable the event on the cpu that it's on
                   */
                  smp_call_function_single(event->cpu, __perf_event_enable,
                                           event, 1);
                  return;
          }
  
          raw_spin_lock_irq(&ctx->lock);
          if (event->state >= PERF_EVENT_STATE_INACTIVE)
                  goto out;
  
          /*
           * If the event is in error state, clear that first.
           * That way, if we see the event in error state below, we
           * know that it has gone back into error state, as distinct
           * from the task having been scheduled away before the
           * cross-call arrived.
           */
          if (event->state == PERF_EVENT_STATE_ERROR)
                  event->state = PERF_EVENT_STATE_OFF;
  
   retry:
          raw_spin_unlock_irq(&ctx->lock);
          task_oncpu_function_call(task, __perf_event_enable, event);
  
          raw_spin_lock_irq(&ctx->lock);
  
          /*
           * If the context is active and the event is still off,
           * we need to retry the cross-call.
           */
          if (ctx->is_active && event->state == PERF_EVENT_STATE_OFF)
                  goto retry;
  
          /*
           * Since we have the lock this context can't be scheduled
           * in, so we can change the state safely.
           */
          if (event->state == PERF_EVENT_STATE_OFF)
                  __perf_event_mark_enabled(event, ctx);
  
   out:
          raw_spin_unlock_irq(&ctx->lock);
  }
  
  static int perf_event_refresh(struct perf_event *event, int refresh)
  {
          /*
           * not supported on inherited events
           */
          if (event->attr.inherit)
                  return -EINVAL;
  
          atomic_add(refresh, &event->event_limit);
          perf_event_enable(event);
  
          return 0;
  }
  
  enum event_type_t {
          EVENT_FLEXIBLE = 0x1,
          EVENT_PINNED = 0x2,
          EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED,
  };
  
  static void ctx_sched_out(struct perf_event_context *ctx,
                            struct perf_cpu_context *cpuctx,
                            enum event_type_t event_type)
  {
          struct perf_event *event;
  
          raw_spin_lock(&ctx->lock);
          ctx->is_active = 0;
          if (likely(!ctx->nr_events))
                  goto out;
          update_context_time(ctx);
  
          perf_disable();
          if (!ctx->nr_active)
                  goto out_enable;
  
          if (event_type & EVENT_PINNED)
                  list_for_each_entry(event, &ctx->pinned_groups, group_entry)
                          group_sched_out(event, cpuctx, ctx);
  
          if (event_type & EVENT_FLEXIBLE)
                  list_for_each_entry(event, &ctx->flexible_groups, group_entry)
                          group_sched_out(event, cpuctx, ctx);
  
   out_enable:
          perf_enable();
   out:
          raw_spin_unlock(&ctx->lock);
  }
  
  /*
   * Test whether two contexts are equivalent, i.e. whether they
   * have both been cloned from the same version of the same context
   * and they both have the same number of enabled events.
   * If the number of enabled events is the same, then the set
   * of enabled events should be the same, because these are both
   * inherited contexts, therefore we can't access individual events
   * in them directly with an fd; we can only enable/disable all
   * events via prctl, or enable/disable all events in a family
   * via ioctl, which will have the same effect on both contexts.
   */
  static int context_equiv(struct perf_event_context *ctx1,
                           struct perf_event_context *ctx2)
  {
          return ctx1->parent_ctx && ctx1->parent_ctx == ctx2->parent_ctx
                  && ctx1->parent_gen == ctx2->parent_gen
                  && !ctx1->pin_count && !ctx2->pin_count;
  }
  
  static void __perf_event_sync_stat(struct perf_event *event,
                                       struct perf_event *next_event)
  {
          u64 value;
  
          if (!event->attr.inherit_stat)
                  return;
  
          /*
           * Update the event value, we cannot use perf_event_read()
           * because we're in the middle of a context switch and have IRQs
           * disabled, which upsets smp_call_function_single(), however
           * we know the event must be on the current CPU, therefore we
           * don't need to use it.
           */
          switch (event->state) {
          case PERF_EVENT_STATE_ACTIVE:
                  event->pmu->read(event);
                  /* fall-through */
  
          case PERF_EVENT_STATE_INACTIVE:
                  update_event_times(event);
                  break;
  
          default:
                  break;
          }
  
          /*
           * In order to keep per-task stats reliable we need to flip the event
           * values when we flip the contexts.
           */
          value = local64_read(&next_event->count);
          value = local64_xchg(&event->count, value);
          local64_set(&next_event->count, value);
  
          swap(event->total_time_enabled, next_event->total_time_enabled);
          swap(event->total_time_running, next_event->total_time_running);
  
          /*
           * Since we swizzled the values, update the user visible data too.
           */
          perf_event_update_userpage(event);
          perf_event_update_userpage(next_event);
  }
  
  #define list_next_entry(pos, member) \
          list_entry(pos->member.next, typeof(*pos), member)
  
  static void perf_event_sync_stat(struct perf_event_context *ctx,
                                     struct perf_event_context *next_ctx)
  {
          struct perf_event *event, *next_event;
  
          if (!ctx->nr_stat)
                  return;
  
          update_context_time(ctx);
  
          event = list_first_entry(&ctx->event_list,
                                     struct perf_event, event_entry);
  
          next_event = list_first_entry(&next_ctx->event_list,
                                          struct perf_event, event_entry);
  
          while (&event->event_entry != &ctx->event_list &&
                 &next_event->event_entry != &next_ctx->event_list) {
  
                  __perf_event_sync_stat(event, next_event);
  
                  event = list_next_entry(event, event_entry);
                  next_event = list_next_entry(next_event, event_entry);
          }
  }
  
  /*
   * Called from scheduler to remove the events of the current task,
   * with interrupts disabled.
   *
   * We stop each event and update the event value in event->count.
   *
   * This does not protect us against NMI, but disable()
   * sets the disabled bit in the control field of event _before_
   * accessing the event control register. If a NMI hits, then it will
   * not restart the event.
   */
  void perf_event_task_sched_out(struct task_struct *task,
                                   struct task_struct *next)
  {
          struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
          struct perf_event_context *ctx = task->perf_event_ctxp;
          struct perf_event_context *next_ctx;
          struct perf_event_context *parent;
          int do_switch = 1;
  
          perf_sw_event(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, 1, NULL, 0);
  
          if (likely(!ctx || !cpuctx->task_ctx))
                  return;
  
          rcu_read_lock();
          parent = rcu_dereference(ctx->parent_ctx);
          next_ctx = next->perf_event_ctxp;
          if (parent && next_ctx &&
              rcu_dereference(next_ctx->parent_ctx) == parent) {
                  /*
                   * Looks like the two contexts are clones, so we might be
                   * able to optimize the context switch.  We lock both
                   * contexts and check that they are clones under the
                   * lock (including re-checking that neither has been
                   * uncloned in the meantime).  It doesn't matter which
                   * order we take the locks because no other cpu could
                   * be trying to lock both of these tasks.
                   */
                  raw_spin_lock(&ctx->lock);
                  raw_spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING);
                  if (context_equiv(ctx, next_ctx)) {
                          /*
                           * XXX do we need a memory barrier of sorts
                           * wrt to rcu_dereference() of perf_event_ctxp
                           */
                          task->perf_event_ctxp = next_ctx;
                          next->perf_event_ctxp = ctx;
                          ctx->task = next;
                          next_ctx->task = task;
                          do_switch = 0;
  
                          perf_event_sync_stat(ctx, next_ctx);
                  }
                  raw_spin_unlock(&next_ctx->lock);
                  raw_spin_unlock(&ctx->lock);
          }
          rcu_read_unlock();
  
          if (do_switch) {
                  ctx_sched_out(ctx, cpuctx, EVENT_ALL);
                  cpuctx->task_ctx = NULL;
          }
  }
  
  static void task_ctx_sched_out(struct perf_event_context *ctx,
                                 enum event_type_t event_type)
  {
          struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
  
          if (!cpuctx->task_ctx)
                  return;
  
          if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
                  return;
  
          ctx_sched_out(ctx, cpuctx, event_type);
          cpuctx->task_ctx = NULL;
  }
  
  /*
   * Called with IRQs disabled
   */
  static void __perf_event_task_sched_out(struct perf_event_context *ctx)
  {
          task_ctx_sched_out(ctx, EVENT_ALL);
  }
  
  /*
   * Called with IRQs disabled
   */
  static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx,
                                enum event_type_t event_type)
  {
          ctx_sched_out(&cpuctx->ctx, cpuctx, event_type);
  }
  
  static void
  ctx_pinned_sched_in(struct perf_event_context *ctx,
                      struct perf_cpu_context *cpuctx)
  {
          struct perf_event *event;
  
          list_for_each_entry(event, &ctx->pinned_groups, group_entry) {
                  if (event->state <= PERF_EVENT_STATE_OFF)
                          continue;
                  if (event->cpu != -1 && event->cpu != smp_processor_id())
                          continue;
  
                  if (group_can_go_on(event, cpuctx, 1))
                          group_sched_in(event, cpuctx, ctx);
  
                  /*
                   * If this pinned group hasn't been scheduled,
                   * put it in error state.
                   */
                  if (event->state == PERF_EVENT_STATE_INACTIVE) {
                          update_group_times(event);
                          event->state = PERF_EVENT_STATE_ERROR;
                  }
          }
  }
  
  static void
  ctx_flexible_sched_in(struct perf_event_context *ctx,
                        struct perf_cpu_context *cpuctx)
  {
          struct perf_event *event;
          int can_add_hw = 1;
  
          list_for_each_entry(event, &ctx->flexible_groups, group_entry) {
                  /* Ignore events in OFF or ERROR state */
                  if (event->state <= PERF_EVENT_STATE_OFF)
                          continue;
                  /*
                   * Listen to the 'cpu' scheduling filter constraint
                   * of events:
                   */
                  if (event->cpu != -1 && event->cpu != smp_processor_id())
                          continue;
  
                  if (group_can_go_on(event, cpuctx, can_add_hw))
                          if (group_sched_in(event, cpuctx, ctx))
                                  can_add_hw = 0;
          }
  }
  
  static void
  ctx_sched_in(struct perf_event_context *ctx,
               struct perf_cpu_context *cpuctx,
               enum event_type_t event_type)
  {
          raw_spin_lock(&ctx->lock);
          ctx->is_active = 1;
          if (likely(!ctx->nr_events))
                  goto out;
  
          ctx->timestamp = perf_clock();
  
          perf_disable();
  
          /*
           * First go through the list and put on any pinned groups
           * in order to give them the best chance of going on.
           */
          if (event_type & EVENT_PINNED)
                  ctx_pinned_sched_in(ctx, cpuctx);
  
          /* Then walk through the lower prio flexible groups */
          if (event_type & EVENT_FLEXIBLE)
                  ctx_flexible_sched_in(ctx, cpuctx);
  
          perf_enable();
   out:
          raw_spin_unlock(&ctx->lock);
  }
  
  static void cpu_ctx_sched_in(struct perf_cpu_context *cpuctx,
                               enum event_type_t event_type)
  {
          struct perf_event_context *ctx = &cpuctx->ctx;
  
          ctx_sched_in(ctx, cpuctx, event_type);
  }
  
  static void task_ctx_sched_in(struct task_struct *task,
                                enum event_type_t event_type)
  {
          struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
          struct perf_event_context *ctx = task->perf_event_ctxp;
  
          if (likely(!ctx))
                  return;
          if (cpuctx->task_ctx == ctx)
                  return;
          ctx_sched_in(ctx, cpuctx, event_type);
          cpuctx->task_ctx = ctx;
  }
  /*
   * Called from scheduler to add the events of the current task
   * with interrupts disabled.
   *
   * We restore the event value and then enable it.
   *
   * This does not protect us against NMI, but enable()
   * sets the enabled bit in the control field of event _before_
   * accessing the event control register. If a NMI hits, then it will
   * keep the event running.
   */
  void perf_event_task_sched_in(struct task_struct *task)
  {
          struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
          struct perf_event_context *ctx = task->perf_event_ctxp;
  
          if (likely(!ctx))
                  return;
  
          if (cpuctx->task_ctx == ctx)
                  return;
  
          perf_disable();
  
          /*
           * We want to keep the following priority order:
           * cpu pinned (that don't need to move), task pinned,
           * cpu flexible, task flexible.
           */
          cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);
  
          ctx_sched_in(ctx, cpuctx, EVENT_PINNED);
          cpu_ctx_sched_in(cpuctx, EVENT_FLEXIBLE);
          ctx_sched_in(ctx, cpuctx, EVENT_FLEXIBLE);
  
          cpuctx->task_ctx = ctx;
  
          perf_enable();
  }
  
  #define MAX_INTERRUPTS (~0ULL)
  
  static void perf_log_throttle(struct perf_event *event, int enable);
  
  static u64 perf_calculate_period(struct perf_event *event, u64 nsec, u64 count)
  {
          u64 frequency = event->attr.sample_freq;
          u64 sec = NSEC_PER_SEC;
          u64 divisor, dividend;
  
          int count_fls, nsec_fls, frequency_fls, sec_fls;
  
          count_fls = fls64(count);
          nsec_fls = fls64(nsec);
          frequency_fls = fls64(frequency);
          sec_fls = 30;
  
          /*
           * We got @count in @nsec, with a target of sample_freq HZ
           * the target period becomes:
           *
           *             @count * 10^9
           * period = -------------------
           *          @nsec * sample_freq
           *
           */
  
          /*
           * Reduce accuracy by one bit such that @a and @b converge
           * to a similar magnitude.
           */
  #define REDUCE_FLS(a, b)                \
  do {                                    \
          if (a##_fls > b##_fls) {        \
                  a >>= 1;                \
                  a##_fls--;              \
          } else {                        \
                  b >>= 1;                \
                  b##_fls--;              \
          }                               \
  } while (0)
  
          /*
           * Reduce accuracy until either term fits in a u64, then proceed with
           * the other, so that finally we can do a u64/u64 division.
           */
          while (count_fls + sec_fls > 64 && nsec_fls + frequency_fls > 64) {
                  REDUCE_FLS(nsec, frequency);
                  REDUCE_FLS(sec, count);
          }
  
          if (count_fls + sec_fls > 64) {
                  divisor = nsec * frequency;
  
                  while (count_fls + sec_fls > 64) {
                          REDUCE_FLS(count, sec);
                          divisor >>= 1;
                  }
  
                  dividend = count * sec;
          } else {
                  dividend = count * sec;
  
                  while (nsec_fls + frequency_fls > 64) {
                          REDUCE_FLS(nsec, frequency);
                          dividend >>= 1;
                  }
  
                  divisor = nsec * frequency;
          }
  
          if (!divisor)
                  return dividend;
  
          return div64_u64(dividend, divisor);
  }
  
  static void perf_event_stop(struct perf_event *event)
  {
          if (!event->pmu->stop)
                  return event->pmu->disable(event);
  
          return event->pmu->stop(event);
  }
  
  static int perf_event_start(struct perf_event *event)
  {
          if (!event->pmu->start)
                  return event->pmu->enable(event);
  
          return event->pmu->start(event);
  }
  
  static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count)
  {
          struct hw_perf_event *hwc = &event->hw;
          s64 period, sample_period;
          s64 delta;
  
          period = perf_calculate_period(event, nsec, count);
  
          delta = (s64)(period - hwc->sample_period);
          delta = (delta + 7) / 8; /* low pass filter */
  
          sample_period = hwc->sample_period + delta;
  
          if (!sample_period)
                  sample_period = 1;
  
          hwc->sample_period = sample_period;
  
          if (local64_read(&hwc->period_left) > 8*sample_period) {
                  perf_disable();
                  perf_event_stop(event);
                  local64_set(&hwc->period_left, 0);
                  perf_event_start(event);
                  perf_enable();
          }
  }
  
  static void perf_ctx_adjust_freq(struct perf_event_context *ctx)
  {
          struct perf_event *event;
          struct hw_perf_event *hwc;
          u64 interrupts, now;
          s64 delta;
  
          raw_spin_lock(&ctx->lock);
          list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
                  if (event->state != PERF_EVENT_STATE_ACTIVE)
                          continue;
  
                  if (event->cpu != -1 && event->cpu != smp_processor_id())
                          continue;
  
                  hwc = &event->hw;
  
                  interrupts = hwc->interrupts;
                  hwc->interrupts = 0;
  
                  /*
                   * unthrottle events on the tick
                   */
                  if (interrupts == MAX_INTERRUPTS) {
                          perf_log_throttle(event, 1);
                          perf_disable();
                          event->pmu->unthrottle(event);
                          perf_enable();
                  }
  
                  if (!event->attr.freq || !event->attr.sample_freq)
                          continue;
  
                  perf_disable();
                  event->pmu->read(event);
                  now = local64_read(&event->count);
                  delta = now - hwc->freq_count_stamp;
                  hwc->freq_count_stamp = now;
  
                  if (delta > 0)
                          perf_adjust_period(event, TICK_NSEC, delta);
                  perf_enable();
          }
          raw_spin_unlock(&ctx->lock);
  }
  
  /*
   * Round-robin a context's events:
   */
  static void rotate_ctx(struct perf_event_context *ctx)
  {
          raw_spin_lock(&ctx->lock);
  
          /* Rotate the first entry last of non-pinned groups */
          list_rotate_left(&ctx->flexible_groups);
  
          raw_spin_unlock(&ctx->lock);
  }
  
  void perf_event_task_tick(struct task_struct *curr)
  {
          struct perf_cpu_context *cpuctx;
          struct perf_event_context *ctx;
          int rotate = 0;
  
          if (!atomic_read(&nr_events))
                  return;
  
          cpuctx = &__get_cpu_var(perf_cpu_context);
          if (cpuctx->ctx.nr_events &&
              cpuctx->ctx.nr_events != cpuctx->ctx.nr_active)
                  rotate = 1;
  
          ctx = curr->perf_event_ctxp;
          if (ctx && ctx->nr_events && ctx->nr_events != ctx->nr_active)
                  rotate = 1;
  
          perf_ctx_adjust_freq(&cpuctx->ctx);
          if (ctx)
                  perf_ctx_adjust_freq(ctx);
  
          if (!rotate)
                  return;
  
          perf_disable();
          cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);
          if (ctx)
                  task_ctx_sched_out(ctx, EVENT_FLEXIBLE);
  
          rotate_ctx(&cpuctx->ctx);
          if (ctx)
                  rotate_ctx(ctx);
  
          cpu_ctx_sched_in(cpuctx, EVENT_FLEXIBLE);
          if (ctx)
                  task_ctx_sched_in(curr, EVENT_FLEXIBLE);
          perf_enable();
  }
  
  static int event_enable_on_exec(struct perf_event *event,
                                  struct perf_event_context *ctx)
  {
          if (!event->attr.enable_on_exec)
                  return 0;
  
          event->attr.enable_on_exec = 0;
          if (event->state >= PERF_EVENT_STATE_INACTIVE)
                  return 0;
  
          __perf_event_mark_enabled(event, ctx);
  
          return 1;
  }
  
  /*
   * Enable all of a task's events that have been marked enable-on-exec.
   * This expects task == current.
   */
  static void perf_event_enable_on_exec(struct task_struct *task)
  {
          struct perf_event_context *ctx;
          struct perf_event *event;
          unsigned long flags;
          int enabled = 0;
          int ret;
  
          local_irq_save(flags);
          ctx = task->perf_event_ctxp;
          if (!ctx || !ctx->nr_events)
                  goto out;
  
          __perf_event_task_sched_out(ctx);
  
          raw_spin_lock(&ctx->lock);
  
          list_for_each_entry(event, &ctx->pinned_groups, group_entry) {
                  ret = event_enable_on_exec(event, ctx);
                  if (ret)
                          enabled = 1;
          }
  
          list_for_each_entry(event, &ctx->flexible_groups, group_entry) {
                  ret = event_enable_on_exec(event, ctx);
                  if (ret)
                          enabled = 1;
          }
  
          /*
           * Unclone this context if we enabled any event.
           */
          if (enabled)
                  unclone_ctx(ctx);
  
          raw_spin_unlock(&ctx->lock);
  
          perf_event_task_sched_in(task);
   out:
          local_irq_restore(flags);
  }
  
  /*
   * Cross CPU call to read the hardware event
   */
  static void __perf_event_read(void *info)
  {
          struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
          struct perf_event *event = info;
          struct perf_event_context *ctx = event->ctx;
  
          /*
           * If this is a task context, we need to check whether it is
           * the current task context of this cpu.  If not it has been
           * scheduled out before the smp call arrived.  In that case
           * event->count would have been updated to a recent sample
           * when the event was scheduled out.
           */
          if (ctx->task && cpuctx->task_ctx != ctx)
                  return;
  
          raw_spin_lock(&ctx->lock);
          update_context_time(ctx);
          update_event_times(event);
          raw_spin_unlock(&ctx->lock);
  
          event->pmu->read(event);
  }
  
  static inline u64 perf_event_count(struct perf_event *event)
  {
          return local64_read(&event->count) + atomic64_read(&event->child_count);
  }
  
  static u64 perf_event_read(struct perf_event *event)
  {
          /*
           * If event is enabled and currently active on a CPU, update the
           * value in the event structure:
           */
          if (event->state == PERF_EVENT_STATE_ACTIVE) {
                  smp_call_function_single(event->oncpu,
                                           __perf_event_read, event, 1);
          } else if (event->state == PERF_EVENT_STATE_INACTIVE) {
                  struct perf_event_context *ctx = event->ctx;
                  unsigned long flags;
  
                  raw_spin_lock_irqsave(&ctx->lock, flags);
                  update_context_time(ctx);
                  update_event_times(event);
                  raw_spin_unlock_irqrestore(&ctx->lock, flags);
          }
  
          return perf_event_count(event);
  }
  
  /*
   * Initialize the perf_event context in a task_struct:
   */
  static void
  __perf_event_init_context(struct perf_event_context *ctx,
                              struct task_struct *task)
  {
          raw_spin_lock_init(&ctx->lock);
          mutex_init(&ctx->mutex);
          INIT_LIST_HEAD(&ctx->pinned_groups);
          INIT_LIST_HEAD(&ctx->flexible_groups);
          INIT_LIST_HEAD(&ctx->event_list);
          atomic_set(&ctx->refcount, 1);
          ctx->task = task;
  }
  
  static struct perf_event_context *find_get_context(pid_t pid, int cpu)
  {
          struct perf_event_context *ctx;
          struct perf_cpu_context *cpuctx;
          struct task_struct *task;
          unsigned long flags;
          int err;
  
          if (pid == -1 && cpu != -1) {
                  /* Must be root to operate on a CPU event: */
                  if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
                          return ERR_PTR(-EACCES);
  
                  if (cpu < 0 || cpu >= nr_cpumask_bits)
                          return ERR_PTR(-EINVAL);
  
                  /*
                   * We could be clever and allow to attach a event to an
                   * offline CPU and activate it when the CPU comes up, but
                   * that's for later.
                   */
                  if (!cpu_online(cpu))
                          return ERR_PTR(-ENODEV);
  
                  cpuctx = &per_cpu(perf_cpu_context, cpu);
                  ctx = &cpuctx->ctx;
                  get_ctx(ctx);
  
                  return ctx;
          }
  
          rcu_read_lock();
          if (!pid)
                  task = current;
          else
                  task = find_task_by_vpid(pid);
          if (task)
                  get_task_struct(task);
          rcu_read_unlock();
  
          if (!task)
                  return ERR_PTR(-ESRCH);
  
          /*
           * Can't attach events to a dying task.
           */
          err = -ESRCH;
          if (task->flags & PF_EXITING)
                  goto errout;
  
          /* Reuse ptrace permission checks for now. */
          err = -EACCES;
          if (!ptrace_may_access(task, PTRACE_MODE_READ))
                  goto errout;
  
   retry:
          ctx = perf_lock_task_context(task, &flags);
          if (ctx) {
                  unclone_ctx(ctx);
                  raw_spin_unlock_irqrestore(&ctx->lock, flags);
          }
  
          if (!ctx) {
                  ctx = kzalloc(sizeof(struct perf_event_context), GFP_KERNEL);
                  err = -ENOMEM;
                  if (!ctx)
                          goto errout;
                  __perf_event_init_context(ctx, task);
                  get_ctx(ctx);
                  if (cmpxchg(&task->perf_event_ctxp, NULL, ctx)) {
                          /*
                           * We raced with some other task; use
                           * the context they set.
                           */
                          kfree(ctx);
                          goto retry;
                  }
                  get_task_struct(task);
          }
  
          put_task_struct(task);
          return ctx;
  
   errout:
          put_task_struct(task);
          return ERR_PTR(err);
  }
  
  static void perf_event_free_filter(struct perf_event *event);
  
  static void free_event_rcu(struct rcu_head *head)
  {
          struct perf_event *event;
  
          event = container_of(head, struct perf_event, rcu_head);
          if (event->ns)
                  put_pid_ns(event->ns);
          perf_event_free_filter(event);
          kfree(event);
  }
  
  static void perf_pending_sync(struct perf_event *event);
  static void perf_buffer_put(struct perf_buffer *buffer);
  
  static void free_event(struct perf_event *event)
  {
          perf_pending_sync(event);
  
          if (!event->parent) {
                  atomic_dec(&nr_events);
                  if (event->attr.mmap || event->attr.mmap_data)
                          atomic_dec(&nr_mmap_events);
                  if (event->attr.comm)
                          atomic_dec(&nr_comm_events);
                  if (event->attr.task)
                          atomic_dec(&nr_task_events);
          }
  
          if (event->buffer) {
                  perf_buffer_put(event->buffer);
                  event->buffer = NULL;
          }
  
          if (event->destroy)
                  event->destroy(event);
  
          put_ctx(event->ctx);
          call_rcu(&event->rcu_head, free_event_rcu);
  }
  
  int perf_event_release_kernel(struct perf_event *event)
  {
          struct perf_event_context *ctx = event->ctx;
  
          /*
           * Remove from the PMU, can't get re-enabled since we got
           * here because the last ref went.
           */
          perf_event_disable(event);
  
          WARN_ON_ONCE(ctx->parent_ctx);
          /*
           * There are two ways this annotation is useful:
           *
           *  1) there is a lock recursion from perf_event_exit_task
           *     see the comment there.
           *
           *  2) there is a lock-inversion with mmap_sem through
           *     perf_event_read_group(), which takes faults while
           *     holding ctx->mutex, however this is called after
           *     the last filedesc died, so there is no possibility
           *     to trigger the AB-BA case.
           */
          mutex_lock_nested(&ctx->mutex, SINGLE_DEPTH_NESTING);
          raw_spin_lock_irq(&ctx->lock);
          perf_group_detach(event);
          list_del_event(event, ctx);
          raw_spin_unlock_irq(&ctx->lock);
          mutex_unlock(&ctx->mutex);
  
          mutex_lock(&event->owner->perf_event_mutex);
          list_del_init(&event->owner_entry);
          mutex_unlock(&event->owner->perf_event_mutex);
          put_task_struct(event->owner);
  
          free_event(event);
  
          return 0;
  }
  EXPORT_SYMBOL_GPL(perf_event_release_kernel);
  
  /*
   * Called when the last reference to the file is gone.
   */
  static int perf_release(struct inode *inode, struct file *file)
  {
          struct perf_event *event = file->private_data;
  
          file->private_data = NULL;
  
          return perf_event_release_kernel(event);
  }
  
  static int perf_event_read_size(struct perf_event *event)
  {
          int entry = sizeof(u64); /* value */
          int size = 0;
          int nr = 1;
  
          if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
                  size += sizeof(u64);
  
          if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
                  size += sizeof(u64);
  
          if (event->attr.read_format & PERF_FORMAT_ID)
                  entry += sizeof(u64);
  
          if (event->attr.read_format & PERF_FORMAT_GROUP) {
                  nr += event->group_leader->nr_siblings;
                  size += sizeof(u64);
          }
  
          size += entry * nr;
  
          return size;
  }
  
  u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
  {
          struct perf_event *child;
          u64 total = 0;
  
          *enabled = 0;
          *running = 0;
  
          mutex_lock(&event->child_mutex);
          total += perf_event_read(event);
          *enabled += event->total_time_enabled +
                          atomic64_read(&event->child_total_time_enabled);
          *running += event->total_time_running +
                          atomic64_read(&event->child_total_time_running);
  
          list_for_each_entry(child, &event->child_list, child_list) {
                  total += perf_event_read(child);
                  *enabled += child->total_time_enabled;
                  *running += child->total_time_running;
          }
          mutex_unlock(&event->child_mutex);
  
          return total;
  }
  EXPORT_SYMBOL_GPL(perf_event_read_value);
  
  static int perf_event_read_group(struct perf_event *event,
                                     u64 read_format, char __user *buf)
  {
          struct perf_event *leader = event->group_leader, *sub;
          int n = 0, size = 0, ret = -EFAULT;
          struct perf_event_context *ctx = leader->ctx;
          u64 values[5];
          u64 count, enabled, running;
  
          mutex_lock(&ctx->mutex);
          count = perf_event_read_value(leader, &enabled, &running);
  
          values[n++] = 1 + leader->nr_siblings;
          if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
                  values[n++] = enabled;
          if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
                  values[n++] = running;
          values[n++] = count;
          if (read_format & PERF_FORMAT_ID)
                  values[n++] = primary_event_id(leader);
  
          size = n * sizeof(u64);
  
          if (copy_to_user(buf, values, size))
                  goto unlock;
  
          ret = size;
  
          list_for_each_entry(sub, &leader->sibling_list, group_entry) {
                  n = 0;
  
                  values[n++] = perf_event_read_value(sub, &enabled, &running);
                  if (read_format & PERF_FORMAT_ID)
                          values[n++] = primary_event_id(sub);
  
                  size = n * sizeof(u64);
  
                  if (copy_to_user(buf + ret, values, size)) {
                          ret = -EFAULT;
                          goto unlock;
                  }
  
                  ret += size;
          }
  unlock:
          mutex_unlock(&ctx->mutex);
  
          return ret;
  }
  
  static int perf_event_read_one(struct perf_event *event,
                                   u64 read_format, char __user *buf)
  {
          u64 enabled, running;
          u64 values[4];
          int n = 0;
  
          values[n++] = perf_event_read_value(event, &enabled, &running);
          if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
                  values[n++] = enabled;
          if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
                  values[n++] = running;
          if (read_format & PERF_FORMAT_ID)
                  values[n++] = primary_event_id(event);
  
          if (copy_to_user(buf, values, n * sizeof(u64)))
                  return -EFAULT;
  
          return n * sizeof(u64);
  }
  
  /*
   * Read the performance event - simple non blocking version for now
   */
  static ssize_t
  perf_read_hw(struct perf_event *event, char __user *buf, size_t count)
  {
          u64 read_format = event->attr.read_format;
          int ret;
  
          /*
           * Return end-of-file for a read on a event that is in
           * error state (i.e. because it was pinned but it couldn't be
           * scheduled on to the CPU at some point).
           */
          if (event->state == PERF_EVENT_STATE_ERROR)
                  return 0;
  
          if (count < perf_event_read_size(event))
                  return -ENOSPC;
  
          WARN_ON_ONCE(event->ctx->parent_ctx);
          if (read_format & PERF_FORMAT_GROUP)
                  ret = perf_event_read_group(event, read_format, buf);
          else
                  ret = perf_event_read_one(event, read_format, buf);
  
          return ret;
  }
  
  static ssize_t
  perf_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
  {
          struct perf_event *event = file->private_data;
  
          return perf_read_hw(event, buf, count);
  }
  
  static unsigned int perf_poll(struct file *file, poll_table *wait)
  {
          struct perf_event *event = file->private_data;
          struct perf_buffer *buffer;
          unsigned int events = POLL_HUP;
  
          rcu_read_lock();
          buffer = rcu_dereference(event->buffer);
          if (buffer)
                  events = atomic_xchg(&buffer->poll, 0);
          rcu_read_unlock();
  
          poll_wait(file, &event->waitq, wait);
  
          return events;
  }
  
  static void perf_event_reset(struct perf_event *event)
  {
          (void)perf_event_read(event);
          local64_set(&event->count, 0);
          perf_event_update_userpage(event);
  }
  
  /*
   * Holding the top-level event's child_mutex means that any
   * descendant process that has inherited this event will block
   * in sync_child_event if it goes to exit, thus satisfying the
   * task existence requirements of perf_event_enable/disable.
   */
  static void perf_event_for_each_child(struct perf_event *event,
                                          void (*func)(struct perf_event *))
  {
          struct perf_event *child;
  
          WARN_ON_ONCE(event->ctx->parent_ctx);
          mutex_lock(&event->child_mutex);
          func(event);
          list_for_each_entry(child, &event->child_list, child_list)
                  func(child);
          mutex_unlock(&event->child_mutex);
  }
  
  static void perf_event_for_each(struct perf_event *event,
                                    void (*func)(struct perf_event *))
  {
          struct perf_event_context *ctx = event->ctx;
          struct perf_event *sibling;
  
          WARN_ON_ONCE(ctx->parent_ctx);
          mutex_lock(&ctx->mutex);
          event = event->group_leader;
  
          perf_event_for_each_child(event, func);
          func(event);
          list_for_each_entry(sibling, &event->sibling_list, group_entry)
                  perf_event_for_each_child(event, func);
          mutex_unlock(&ctx->mutex);
  }
  
  static int perf_event_period(struct perf_event *event, u64 __user *arg)
  {
          struct perf_event_context *ctx = event->ctx;
          unsigned long size;
          int ret = 0;
          u64 value;
  
          if (!event->attr.sample_period)
                  return -EINVAL;
  
          size = copy_from_user(&value, arg, sizeof(value));
          if (size != sizeof(value))
                  return -EFAULT;
  
          if (!value)
                  return -EINVAL;
  
          raw_spin_lock_irq(&ctx->lock);
          if (event->attr.freq) {
                  if (value > sysctl_perf_event_sample_rate) {
                          ret = -EINVAL;
                          goto unlock;
                  }
  
                  event->attr.sample_freq = value;
          } else {
                  event->attr.sample_period = value;
                  event->hw.sample_period = value;
          }
  unlock:
          raw_spin_unlock_irq(&ctx->lock);
  
          return ret;
  }
  
  static const struct file_operations perf_fops;
  
  static struct perf_event *perf_fget_light(int fd, int *fput_needed)
  {
          struct file *file;
  
          file = fget_light(fd, fput_needed);
          if (!file)
                  return ERR_PTR(-EBADF);
  
          if (file->f_op != &perf_fops) {
                  fput_light(file, *fput_needed);
                  *fput_needed = 0;
                  return ERR_PTR(-EBADF);
          }
  
          return file->private_data;
  }
  
  static int perf_event_set_output(struct perf_event *event,
                                   struct perf_event *output_event);
  static int perf_event_set_filter(struct perf_event *event, void __user *arg);
  
  static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  {
          struct perf_event *event = file->private_data;
          void (*func)(struct perf_event *);
          u32 flags = arg;
  
          switch (cmd) {
          case PERF_EVENT_IOC_ENABLE:
                  func = perf_event_enable;
                  break;
          case PERF_EVENT_IOC_DISABLE:
                  func = perf_event_disable;
                  break;
          case PERF_EVENT_IOC_RESET:
                  func = perf_event_reset;
                  break;
  
          case PERF_EVENT_IOC_REFRESH:
                  return perf_event_refresh(event, arg);
  
          case PERF_EVENT_IOC_PERIOD:
                  return perf_event_period(event, (u64 __user *)arg);
  
          case PERF_EVENT_IOC_SET_OUTPUT:
          {
                  struct perf_event *output_event = NULL;
                  int fput_needed = 0;
                  int ret;
  
                  if (arg != -1) {
                          output_event = perf_fget_light(arg, &fput_needed);
                          if (IS_ERR(output_event))
                                  return PTR_ERR(output_event);
                  }
  
                  ret = perf_event_set_output(event, output_event);
                  if (output_event)
                          fput_light(output_event->filp, fput_needed);
  
                  return ret;
          }
  
          case PERF_EVENT_IOC_SET_FILTER:
                  return perf_event_set_filter(event, (void __user *)arg);
  
          default:
                  return -ENOTTY;
          }
  
          if (flags & PERF_IOC_FLAG_GROUP)
                  perf_event_for_each(event, func);
          else
                  perf_event_for_each_child(event, func);
  
          return 0;
  }
  
  int perf_event_task_enable(void)
  {
          struct perf_event *event;
  
          mutex_lock(&current->perf_event_mutex);
          list_for_each_entry(event, &current->perf_event_list, owner_entry)
                  perf_event_for_each_child(event, perf_event_enable);
          mutex_unlock(&current->perf_event_mutex);
  
          return 0;
  }
  
  int perf_event_task_disable(void)
  {
          struct perf_event *event;
  
          mutex_lock(&current->perf_event_mutex);
          list_for_each_entry(event, &current->perf_event_list, owner_entry)
                  perf_event_for_each_child(event, perf_event_disable);
          mutex_unlock(&current->perf_event_mutex);
  
          return 0;
  }
  
  #ifndef PERF_EVENT_INDEX_OFFSET
  # define PERF_EVENT_INDEX_OFFSET 0
  #endif
  
  static int perf_event_index(struct perf_event *event)
  {
          if (event->state != PERF_EVENT_STATE_ACTIVE)
                  return 0;
  
          return event->hw.idx + 1 - PERF_EVENT_INDEX_OFFSET;
  }
  
  /*
   * Callers need to ensure there can be no nesting of this function, otherwise
   * the seqlock logic goes bad. We can not serialize this because the arch
   * code calls this from NMI context.
   */
  void perf_event_update_userpage(struct perf_event *event)
  {
          struct perf_event_mmap_page *userpg;
          struct perf_buffer *buffer;
  
          rcu_read_lock();
          buffer = rcu_dereference(event->buffer);
          if (!buffer)
                  goto unlock;
  
          userpg = buffer->user_page;
  
          /*
           * Disable preemption so as to not let the corresponding user-space
           * spin too long if we get preempted.
           */
          preempt_disable();
          ++userpg->lock;
          barrier();
          userpg->index = perf_event_index(event);
          userpg->offset = perf_event_count(event);
          if (event->state == PERF_EVENT_STATE_ACTIVE)
                  userpg->offset -= local64_read(&event->hw.prev_count);
  
          userpg->time_enabled = event->total_time_enabled +
                          atomic64_read(&event->child_total_time_enabled);
  
          userpg->time_running = event->total_time_running +
                          atomic64_read(&event->child_total_time_running);
  
          barrier();
          ++userpg->lock;
          preempt_enable();
  unlock:
          rcu_read_unlock();
  }
  
  static unsigned long perf_data_size(struct perf_buffer *buffer);
  
  static void
  perf_buffer_init(struct perf_buffer *buffer, long watermark, int flags)
  {
          long max_size = perf_data_size(buffer);
  
          if (watermark)
                  buffer->watermark = min(max_size, watermark);
  
          if (!buffer->watermark)
                  buffer->watermark = max_size / 2;
  
          if (flags & PERF_BUFFER_WRITABLE)
                  buffer->writable = 1;
  
          atomic_set(&buffer->refcount, 1);
  }
  
  #ifndef CONFIG_PERF_USE_VMALLOC
  
  /*
   * Back perf_mmap() with regular GFP_KERNEL-0 pages.
   */
  
  static struct page *
  perf_mmap_to_page(struct perf_buffer *buffer, unsigned long pgoff)
  {
          if (pgoff > buffer->nr_pages)
                  return NULL;
  
          if (pgoff == 0)
                  return virt_to_page(buffer->user_page);
  
          return virt_to_page(buffer->data_pages[pgoff - 1]);
  }
  
  static void *perf_mmap_alloc_page(int cpu)
  {
          struct page *page;
          int node;
  
          node = (cpu == -1) ? cpu : cpu_to_node(cpu);
          page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
          if (!page)
                  return NULL;
  
          return page_address(page);
  }
  
  static struct perf_buffer *
  perf_buffer_alloc(int nr_pages, long watermark, int cpu, int flags)
  {
          struct perf_buffer *buffer;
          unsigned long size;
          int i;
  
          size = sizeof(struct perf_buffer);
          size += nr_pages * sizeof(void *);
  
          buffer = kzalloc(size, GFP_KERNEL);
          if (!buffer)
                  goto fail;
  
          buffer->user_page = perf_mmap_alloc_page(cpu);
          if (!buffer->user_page)
                  goto fail_user_page;
  
          for (i = 0; i < nr_pages; i++) {
                  buffer->data_pages[i] = perf_mmap_alloc_page(cpu);
                  if (!buffer->data_pages[i])
                          goto fail_data_pages;
          }
  
          buffer->nr_pages = nr_pages;
  
          perf_buffer_init(buffer, watermark, flags);
  
          return buffer;
  
  fail_data_pages:
          for (i--; i >= 0; i--)
                  free_page((unsigned long)buffer->data_pages[i]);
  
          free_page((unsigned long)buffer->user_page);
  
  fail_user_page:
          kfree(buffer);
  
  fail:
          return NULL;
  }
  
  static void perf_mmap_free_page(unsigned long addr)
  {
          struct page *page = virt_to_page((void *)addr);
  
          page->mapping = NULL;
          __free_page(page);
  }
  
  static void perf_buffer_free(struct perf_buffer *buffer)
  {
          int i;
  
          perf_mmap_free_page((unsigned long)buffer->user_page);
          for (i = 0; i < buffer->nr_pages; i++)
                  perf_mmap_free_page((unsigned long)buffer->data_pages[i]);
          kfree(buffer);
  }
  
  static inline int page_order(struct perf_buffer *buffer)
  {
          return 0;
  }
  
  #else
  
  /*
   * Back perf_mmap() with vmalloc memory.
   *
   * Required for architectures that have d-cache aliasing issues.
   */
  
  static inline int page_order(struct perf_buffer *buffer)
  {
          return buffer->page_order;
  }
  
  static struct page *
  perf_mmap_to_page(struct perf_buffer *buffer, unsigned long pgoff)
  {
          if (pgoff > (1UL << page_order(buffer)))
                  return NULL;
  
          return vmalloc_to_page((void *)buffer->user_page + pgoff * PAGE_SIZE);
  }
  
  static void perf_mmap_unmark_page(void *addr)
  {
          struct page *page = vmalloc_to_page(addr);
  
          page->mapping = NULL;
  }
  
  static void perf_buffer_free_work(struct work_struct *work)
  {
          struct perf_buffer *buffer;
          void *base;
          int i, nr;
  
          buffer = container_of(work, struct perf_buffer, work);
          nr = 1 << page_order(buffer);
  
          base = buffer->user_page;
          for (i = 0; i < nr + 1; i++)
                  perf_mmap_unmark_page(base + (i * PAGE_SIZE));
  
          vfree(base);
          kfree(buffer);
  }
  
  static void perf_buffer_free(struct perf_buffer *buffer)
  {
          schedule_work(&buffer->work);
  }
  
  static struct perf_buffer *
  perf_buffer_alloc(int nr_pages, long watermark, int cpu, int flags)
  {
          struct perf_buffer *buffer;
          unsigned long size;
          void *all_buf;
  
          size = sizeof(struct perf_buffer);
          size += sizeof(void *);
  
          buffer = kzalloc(size, GFP_KERNEL);
          if (!buffer)
                  goto fail;
  
          INIT_WORK(&buffer->work, perf_buffer_free_work);
  
          all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
          if (!all_buf)
                  goto fail_all_buf;
  
          buffer->user_page = all_buf;
          buffer->data_pages[0] = all_buf + PAGE_SIZE;
          buffer->page_order = ilog2(nr_pages);
          buffer->nr_pages = 1;
  
          perf_buffer_init(buffer, watermark, flags);
  
          return buffer;
  
  fail_all_buf:
          kfree(buffer);
  
  fail:
          return NULL;
  }
  
  #endif
  
  static unsigned long perf_data_size(struct perf_buffer *buffer)
  {
          return buffer->nr_pages << (PAGE_SHIFT + page_order(buffer));
  }
  
  static int perf_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
  {
          struct perf_event *event = vma->vm_file->private_data;
          struct perf_buffer *buffer;
          int ret = VM_FAULT_SIGBUS;
  
          if (vmf->flags & FAULT_FLAG_MKWRITE) {
                  if (vmf->pgoff == 0)
                          ret = 0;
                  return ret;
          }
  
          rcu_read_lock();
          buffer = rcu_dereference(event->buffer);
          if (!buffer)
                  goto unlock;
  
          if (vmf->pgoff && (vmf->flags & FAULT_FLAG_WRITE))
                  goto unlock;
  
          vmf->page = perf_mmap_to_page(buffer, vmf->pgoff);
          if (!vmf->page)
                  goto unlock;
  
          get_page(vmf->page);
          vmf->page->mapping = vma->vm_file->f_mapping;
          vmf->page->index   = vmf->pgoff;
  
          ret = 0;
  unlock:
          rcu_read_unlock();
  
          return ret;
  }
  
  static void perf_buffer_free_rcu(struct rcu_head *rcu_head)
  {
          struct perf_buffer *buffer;
  
          buffer = container_of(rcu_head, struct perf_buffer, rcu_head);
          perf_buffer_free(buffer);
  }
  
  static struct perf_buffer *perf_buffer_get(struct perf_event *event)
  {
          struct perf_buffer *buffer;
  
          rcu_read_lock();
          buffer = rcu_dereference(event->buffer);
          if (buffer) {
                  if (!atomic_inc_not_zero(&buffer->refcount))
                          buffer = NULL;
          }
          rcu_read_unlock();
  
          return buffer;
  }
  
  static void perf_buffer_put(struct perf_buffer *buffer)
  {
          if (!atomic_dec_and_test(&buffer->refcount))
                  return;
  
          call_rcu(&buffer->rcu_head, perf_buffer_free_rcu);
  }
  
  static void perf_mmap_open(struct vm_area_struct *vma)
  {
          struct perf_event *event = vma->vm_file->private_data;
  
          atomic_inc(&event->mmap_count);
  }
  
  static void perf_mmap_close(struct vm_area_struct *vma)
  {
          struct perf_event *event = vma->vm_file->private_data;
  
          if (atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) {
                  unsigned long size = perf_data_size(event->buffer);
                  struct user_struct *user = event->mmap_user;
                  struct perf_buffer *buffer = event->buffer;
  
                  atomic_long_sub((size >> PAGE_SHIFT) + 1, &user->locked_vm);
                  vma->vm_mm->locked_vm -= event->mmap_locked;
                  rcu_assign_pointer(event->buffer, NULL);
                  mutex_unlock(&event->mmap_mutex);
  
                  perf_buffer_put(buffer);
                  free_uid(user);
          }
  }
  
  static const struct vm_operations_struct perf_mmap_vmops = {
          .open           = perf_mmap_open,
          .close          = perf_mmap_close,
          .fault          = perf_mmap_fault,
          .page_mkwrite   = perf_mmap_fault,
  };
  
  static int perf_mmap(struct file *file, struct vm_area_struct *vma)
  {
          struct perf_event *event = file->private_data;
          unsigned long user_locked, user_lock_limit;
          struct user_struct *user = current_user();
          unsigned long locked, lock_limit;
          struct perf_buffer *buffer;
          unsigned long vma_size;
          unsigned long nr_pages;
          long user_extra, extra;
          int ret = 0, flags = 0;
  
          /*
           * Don't allow mmap() of inherited per-task counters. This would
           * create a performance issue due to all children writing to the
           * same buffer.
           */
          if (event->cpu == -1 && event->attr.inherit)
                  return -EINVAL;
  
          if (!(vma->vm_flags & VM_SHARED))
                  return -EINVAL;
  
          vma_size = vma->vm_end - vma->vm_start;
          nr_pages = (vma_size / PAGE_SIZE) - 1;
  
          /*
           * If we have buffer pages ensure they're a power-of-two number, so we
           * can do bitmasks instead of modulo.
           */
          if (nr_pages != 0 && !is_power_of_2(nr_pages))
                  return -EINVAL;
  
          if (vma_size != PAGE_SIZE * (1 + nr_pages))
                  return -EINVAL;
  
          if (vma->vm_pgoff != 0)
                  return -EINVAL;
  
          WARN_ON_ONCE(event->ctx->parent_ctx);
          mutex_lock(&event->mmap_mutex);
          if (event->buffer) {
                  if (event->buffer->nr_pages == nr_pages)
                          atomic_inc(&event->buffer->refcount);
                  else
                          ret = -EINVAL;
                  goto unlock;
          }
  
          user_extra = nr_pages + 1;
          user_lock_limit = sysctl_perf_event_mlock >> (PAGE_SHIFT - 10);
  
          /*
           * Increase the limit linearly with more CPUs:
           */
          user_lock_limit *= num_online_cpus();
  
          user_locked = atomic_long_read(&user->locked_vm) + user_extra;
  
          extra = 0;
          if (user_locked > user_lock_limit)
                  extra = user_locked - user_lock_limit;
  
          lock_limit = rlimit(RLIMIT_MEMLOCK);
          lock_limit >>= PAGE_SHIFT;
          locked = vma->vm_mm->locked_vm + extra;
  
          if ((locked > lock_limit) && perf_paranoid_tracepoint_raw() &&
                  !capable(CAP_IPC_LOCK)) {
                  ret = -EPERM;
                  goto unlock;
          }
  
          WARN_ON(event->buffer);
  
          if (vma->vm_flags & VM_WRITE)
                  flags |= PERF_BUFFER_WRITABLE;
  
          buffer = perf_buffer_alloc(nr_pages, event->attr.wakeup_watermark,
                                     event->cpu, flags);
          if (!buffer) {
                  ret = -ENOMEM;
                  goto unlock;
          }
          rcu_assign_pointer(event->buffer, buffer);
  
          atomic_long_add(user_extra, &user->locked_vm);
          event->mmap_locked = extra;
          event->mmap_user = get_current_user();
          vma->vm_mm->locked_vm += event->mmap_locked;
  
  unlock:
          if (!ret)
                  atomic_inc(&event->mmap_count);
          mutex_unlock(&event->mmap_mutex);
  
          vma->vm_flags |= VM_RESERVED;
          vma->vm_ops = &perf_mmap_vmops;
  
          return ret;
  }
  
  static int perf_fasync(int fd, struct file *filp, int on)
  {
          struct inode *inode = filp->f_path.dentry->d_inode;
          struct perf_event *event = filp->private_data;
          int retval;
  
          mutex_lock(&inode->i_mutex);
          retval = fasync_helper(fd, filp, on, &event->fasync);
          mutex_unlock(&inode->i_mutex);
  
          if (retval < 0)
                  return retval;
  
          return 0;
  }
  
  static const struct file_operations perf_fops = {
          .llseek                 = no_llseek,
          .release                = perf_release,
          .read                   = perf_read,
          .poll                   = perf_poll,
          .unlocked_ioctl         = perf_ioctl,
          .compat_ioctl           = perf_ioctl,
          .mmap                   = perf_mmap,
          .fasync                 = perf_fasync,
  };
  
  /*
   * Perf event wakeup
   *
   * If there's data, ensure we set the poll() state and publish everything
   * to user-space before waking everybody up.
   */
  
  void perf_event_wakeup(struct perf_event *event)
  {
          wake_up_all(&event->waitq);
  
          if (event->pending_kill) {
                  kill_fasync(&event->fasync, SIGIO, event->pending_kill);
                  event->pending_kill = 0;
          }
  }
  
  /*
   * Pending wakeups
   *
   * Handle the case where we need to wakeup up from NMI (or rq->lock) context.
   *
   * The NMI bit means we cannot possibly take locks. Therefore, maintain a
   * single linked list and use cmpxchg() to add entries lockless.
   */
  
  static void perf_pending_event(struct perf_pending_entry *entry)
  {
          struct perf_event *event = container_of(entry,
                          struct perf_event, pending);
  
          if (event->pending_disable) {
                  event->pending_disable = 0;
                  __perf_event_disable(event);
          }
  
          if (event->pending_wakeup) {
                  event->pending_wakeup = 0;
                  perf_event_wakeup(event);
          }
  }
  
  #define PENDING_TAIL ((struct perf_pending_entry *)-1UL)
  
  static DEFINE_PER_CPU(struct perf_pending_entry *, perf_pending_head) = {
          PENDING_TAIL,
  };
  
  static void perf_pending_queue(struct perf_pending_entry *entry,
                                 void (*func)(struct perf_pending_entry *))
  {
          struct perf_pending_entry **head;
  
          if (cmpxchg(&entry->next, NULL, PENDING_TAIL) != NULL)
                  return;
  
          entry->func = func;
  
          head = &get_cpu_var(perf_pending_head);
  
          do {
                  entry->next = *head;
          } while (cmpxchg(head, entry->next, entry) != entry->next);
  
          set_perf_event_pending();
  
          put_cpu_var(perf_pending_head);
  }
  
  static int __perf_pending_run(void)
  {
          struct perf_pending_entry *list;
          int nr = 0;
  
          list = xchg(&__get_cpu_var(perf_pending_head), PENDING_TAIL);
          while (list != PENDING_TAIL) {
                  void (*func)(struct perf_pending_entry *);
                  struct perf_pending_entry *entry = list;
  
                  list = list->next;
  
                  func = entry->func;
                  entry->next = NULL;
                  /*
                   * Ensure we observe the unqueue before we issue the wakeup,
                   * so that we won't be waiting forever.
                   * -- see perf_not_pending().
                   */
                  smp_wmb();
  
                  func(entry);
                  nr++;
          }
  
          return nr;
  }
  
  static inline int perf_not_pending(struct perf_event *event)
  {
          /*
           * If we flush on whatever cpu we run, there is a chance we don't
           * need to wait.
           */
          get_cpu();
          __perf_pending_run();
          put_cpu();
  
          /*
           * Ensure we see the proper queue state before going to sleep
           * so that we do not miss the wakeup. -- see perf_pending_handle()
           */
          smp_rmb();
          return event->pending.next == NULL;
  }
  
  static void perf_pending_sync(struct perf_event *event)
  {
          wait_event(event->waitq, perf_not_pending(event));
  }
  
  void perf_event_do_pending(void)
  {
          __perf_pending_run();
  }
  
  /*
   * Callchain support -- arch specific
   */
  
  __weak struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
  {
          return NULL;
  }
  
  
  /*
   * We assume there is only KVM supporting the callbacks.
   * Later on, we might change it to a list if there is
   * another virtualization implementation supporting the callbacks.
   */
  struct perf_guest_info_callbacks *perf_guest_cbs;
  
  int perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
  {
          perf_guest_cbs = cbs;
          return 0;
  }
  EXPORT_SYMBOL_GPL(perf_register_guest_info_callbacks);
  
  int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
  {
          perf_guest_cbs = NULL;
          return 0;
  }
  EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks);
  
  /*
   * Output
   */
  static bool perf_output_space(struct perf_buffer *buffer, unsigned long tail,
                                unsigned long offset, unsigned long head)
  {
          unsigned long mask;
  
          if (!buffer->writable)
                  return true;
  
          mask = perf_data_size(buffer) - 1;
  
          offset = (offset - tail) & mask;
          head   = (head   - tail) & mask;
  
          if ((int)(head - offset) < 0)
                  return false;
  
          return true;
  }
  
  static void perf_output_wakeup(struct perf_output_handle *handle)
  {
          atomic_set(&handle->buffer->poll, POLL_IN);
  
          if (handle->nmi) {
                  handle->event->pending_wakeup = 1;
                  perf_pending_queue(&handle->event->pending,
                                     perf_pending_event);
          } else
                  perf_event_wakeup(handle->event);
  }
  
  /*
   * We need to ensure a later event_id doesn't publish a head when a former
   * event isn't done writing. However since we need to deal with NMIs we
   * cannot fully serialize things.
   *
   * We only publish the head (and generate a wakeup) when the outer-most
   * event completes.
   */
  static void perf_output_get_handle(struct perf_output_handle *handle)
  {
          struct perf_buffer *buffer = handle->buffer;
  
          preempt_disable();
          local_inc(&buffer->nest);
          handle->wakeup = local_read(&buffer->wakeup);
  }
  
  static void perf_output_put_handle(struct perf_output_handle *handle)
  {
          struct perf_buffer *buffer = handle->buffer;
          unsigned long head;
  
  again:
          head = local_read(&buffer->head);
  
          /*
           * IRQ/NMI can happen here, which means we can miss a head update.
           */
  
          if (!local_dec_and_test(&buffer->nest))
                  goto out;
  
          /*
           * Publish the known good head. Rely on the full barrier implied
           * by atomic_dec_and_test() order the buffer->head read and this
           * write.
           */
          buffer->user_page->data_head = head;
  
          /*
           * Now check if we missed an update, rely on the (compiler)
           * barrier in atomic_dec_and_test() to re-read buffer->head.
           */
          if (unlikely(head != local_read(&buffer->head))) {
                  local_inc(&buffer->nest);
                  goto again;
          }
  
          if (handle->wakeup != local_read(&buffer->wakeup))
                  perf_output_wakeup(handle);
  
   out:
          preempt_enable();
  }
  
  __always_inline void perf_output_copy(struct perf_output_handle *handle,
                        const void *buf, unsigned int len)
  {
          do {
                  unsigned long size = min_t(unsigned long, handle->size, len);
  
                  memcpy(handle->addr, buf, size);
  
                  len -= size;
                  handle->addr += size;
                  buf += size;
                  handle->size -= size;
                  if (!handle->size) {
                          struct perf_buffer *buffer = handle->buffer;
  
                          handle->page++;
                          handle->page &= buffer->nr_pages - 1;
                          handle->addr = buffer->data_pages[handle->page];
                          handle->size = PAGE_SIZE << page_order(buffer);
                  }
          } while (len);
  }
  
  int perf_output_begin(struct perf_output_handle *handle,
                        struct perf_event *event, unsigned int size,
                        int nmi, int sample)
  {
          struct perf_buffer *buffer;
          unsigned long tail, offset, head;
          int have_lost;
          struct {
                  struct perf_event_header header;
                  u64                      id;
                  u64                      lost;
          } lost_event;
  
          rcu_read_lock();
          /*
           * For inherited events we send all the output towards the parent.
           */
          if (event->parent)
                  event = event->parent;
  
          buffer = rcu_dereference(event->buffer);
          if (!buffer)
                  goto out;
  
          handle->buffer  = buffer;
          handle->event   = event;
          handle->nmi     = nmi;
          handle->sample  = sample;
  
          if (!buffer->nr_pages)
                  goto out;
  
          have_lost = local_read(&buffer->lost);
          if (have_lost)
                  size += sizeof(lost_event);
  
          perf_output_get_handle(handle);
  
          do {
                  /*
                   * Userspace could choose to issue a mb() before updating the
                   * tail pointer. So that all reads will be completed before the
                   * write is issued.
                   */
                  tail = ACCESS_ONCE(buffer->user_page->data_tail);
                  smp_rmb();
                  offset = head = local_read(&buffer->head);
                  head += size;
                  if (unlikely(!perf_output_space(buffer, tail, offset, head)))
                          goto fail;
          } while (local_cmpxchg(&buffer->head, offset, head) != offset);
  
          if (head - local_read(&buffer->wakeup) > buffer->watermark)
                  local_add(buffer->watermark, &buffer->wakeup);
  
          handle->page = offset >> (PAGE_SHIFT + page_order(buffer));
          handle->page &= buffer->nr_pages - 1;
          handle->size = offset & ((PAGE_SIZE << page_order(buffer)) - 1);
          handle->addr = buffer->data_pages[handle->page];
          handle->addr += handle->size;
          handle->size = (PAGE_SIZE << page_order(buffer)) - handle->size;
  
          if (have_lost) {
                  lost_event.header.type = PERF_RECORD_LOST;
                  lost_event.header.misc = 0;
                  lost_event.header.size = sizeof(lost_event);
                  lost_event.id          = event->id;
                  lost_event.lost        = local_xchg(&buffer->lost, 0);
  
                  perf_output_put(handle, lost_event);
          }
  
          return 0;
  
  fail:
          local_inc(&buffer->lost);
          perf_output_put_handle(handle);
  out:
          rcu_read_unlock();
  
          return -ENOSPC;
  }
  
  void perf_output_end(struct perf_output_handle *handle)
  {
          struct perf_event *event = handle->event;
          struct perf_buffer *buffer = handle->buffer;
  
          int wakeup_events = event->attr.wakeup_events;
  
          if (handle->sample && wakeup_events) {
                  int events = local_inc_return(&buffer->events);
                  if (events >= wakeup_events) {
                          local_sub(wakeup_events, &buffer->events);
                          local_inc(&buffer->wakeup);
                  }
          }
  
          perf_output_put_handle(handle);
          rcu_read_unlock();
  }
  
  static u32 perf_event_pid(struct perf_event *event, struct task_struct *p)
  {
          /*
           * only top level events have the pid namespace they were created in
           */
          if (event->parent)
                  event = event->parent;
  
          return task_tgid_nr_ns(p, event->ns);
  }
  
  static u32 perf_event_tid(struct perf_event *event, struct task_struct *p)
  {
          /*
           * only top level events have the pid namespace they were created in
           */
          if (event->parent)
                  event = event->parent;
  
          return task_pid_nr_ns(p, event->ns);
  }
  
  static void perf_output_read_one(struct perf_output_handle *handle,
                                   struct perf_event *event)
  {
          u64 read_format = event->attr.read_format;
          u64 values[4];
          int n = 0;
  
          values[n++] = perf_event_count(event);
          if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
                  values[n++] = event->total_time_enabled +
                          atomic64_read(&event->child_total_time_enabled);
          }
          if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {
                  values[n++] = event->total_time_running +
                          atomic64_read(&event->child_total_time_running);
          }
          if (read_format & PERF_FORMAT_ID)
                  values[n++] = primary_event_id(event);
  
          perf_output_copy(handle, values, n * sizeof(u64));
  }
  
  /*
   * XXX PERF_FORMAT_GROUP vs inherited events seems difficult.
   */
  static void perf_output_read_group(struct perf_output_handle *handle,
                              struct perf_event *event)
  {
          struct perf_event *leader = event->group_leader, *sub;
          u64 read_format = event->attr.read_format;
          u64 values[5];
          int n = 0;
  
          values[n++] = 1 + leader->nr_siblings;
  
          if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
                  values[n++] = leader->total_time_enabled;
  
          if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
                  values[n++] = leader->total_time_running;
  
          if (leader != event)
                  leader->pmu->read(leader);
  
          values[n++] = perf_event_count(leader);
          if (read_format & PERF_FORMAT_ID)
                  values[n++] = primary_event_id(leader);
  
          perf_output_copy(handle, values, n * sizeof(u64));
  
          list_for_each_entry(sub, &leader->sibling_list, group_entry) {
                  n = 0;
  
                  if (sub != event)
                          sub->pmu->read(sub);
  
                  values[n++] = perf_event_count(sub);
                  if (read_format & PERF_FORMAT_ID)
                          values[n++] = primary_event_id(sub);
  
                  perf_output_copy(handle, values, n * sizeof(u64));
          }
  }
  
  static void perf_output_read(struct perf_output_handle *handle,
                               struct perf_event *event)
  {
          if (event->attr.read_format & PERF_FORMAT_GROUP)
                  perf_output_read_group(handle, event);
          else
                  perf_output_read_one(handle, event);
  }
  
  void perf_output_sample(struct perf_output_handle *handle,
                          struct perf_event_header *header,
                          struct perf_sample_data *data,
                          struct perf_event *event)
  {
          u64 sample_type = data->type;
  
          perf_output_put(handle, *header);
  
          if (sample_type & PERF_SAMPLE_IP)
                  perf_output_put(handle, data->ip);
  
          if (sample_type & PERF_SAMPLE_TID)
                  perf_output_put(handle, data->tid_entry);
  
          if (sample_type & PERF_SAMPLE_TIME)
                  perf_output_put(handle, data->time);
  
          if (sample_type & PERF_SAMPLE_ADDR)
                  perf_output_put(handle, data->addr);
  
          if (sample_type & PERF_SAMPLE_ID)
                  perf_output_put(handle, data->id);
  
          if (sample_type & PERF_SAMPLE_STREAM_ID)
                  perf_output_put(handle, data->stream_id);
  
          if (sample_type & PERF_SAMPLE_CPU)
                  perf_output_put(handle, data->cpu_entry);
  
          if (sample_type & PERF_SAMPLE_PERIOD)
                  perf_output_put(handle, data->period);
  
          if (sample_type & PERF_SAMPLE_READ)
                  perf_output_read(handle, event);
  
          if (sample_type & PERF_SAMPLE_CALLCHAIN) {
                  if (data->callchain) {
                          int size = 1;
  
                          if (data->callchain)
                                  size += data->callchain->nr;
  
                          size *= sizeof(u64);
  
                          perf_output_copy(handle, data->callchain, size);
                  } else {
                          u64 nr = 0;
                          perf_output_put(handle, nr);
                  }
          }
  
          if (sample_type & PERF_SAMPLE_RAW) {
                  if (data->raw) {
                          perf_output_put(handle, data->raw->size);
                          perf_output_copy(handle, data->raw->data,
                                           data->raw->size);
                  } else {
                          struct {
                                  u32     size;
                                  u32     data;
                          } raw = {
                                  .size = sizeof(u32),
                                  .data = 0,
                          };
                          perf_output_put(handle, raw);
                  }
          }
  }
  
  void perf_prepare_sample(struct perf_event_header *header,
                           struct perf_sample_data *data,
                           struct perf_event *event,
                           struct pt_regs *regs)
  {
          u64 sample_type = event->attr.sample_type;
  
          data->type = sample_type;
  
          header->type = PERF_RECORD_SAMPLE;
          header->size = sizeof(*header);
  
          header->misc = 0;
          header->misc |= perf_misc_flags(regs);
  
          if (sample_type & PERF_SAMPLE_IP) {
                  data->ip = perf_instruction_pointer(regs);
  
                  header->size += sizeof(data->ip);
          }
  
          if (sample_type & PERF_SAMPLE_TID) {
                  /* namespace issues */
                  data->tid_entry.pid = perf_event_pid(event, current);
                  data->tid_entry.tid = perf_event_tid(event, current);
  
                  header->size += sizeof(data->tid_entry);
          }
  
          if (sample_type & PERF_SAMPLE_TIME) {
                  data->time = perf_clock();
  
                  header->size += sizeof(data->time);
          }
  
          if (sample_type & PERF_SAMPLE_ADDR)
                  header->size += sizeof(data->addr);
  
          if (sample_type & PERF_SAMPLE_ID) {
                  data->id = primary_event_id(event);
  
                  header->size += sizeof(data->id);
          }
  
          if (sample_type & PERF_SAMPLE_STREAM_ID) {
                  data->stream_id = event->id;
  
                  header->size += sizeof(data->stream_id);
          }
  
          if (sample_type & PERF_SAMPLE_CPU) {
                  data->cpu_entry.cpu             = raw_smp_processor_id();
                  data->cpu_entry.reserved        = 0;
  
                  header->size += sizeof(data->cpu_entry);
          }
  
          if (sample_type & PERF_SAMPLE_PERIOD)
                  header->size += sizeof(data->period);
  
          if (sample_type & PERF_SAMPLE_READ)
                  header->size += perf_event_read_size(event);
  
          if (sample_type & PERF_SAMPLE_CALLCHAIN) {
                  int size = 1;
  
                  data->callchain = perf_callchain(regs);
  
                  if (data->callchain)
                          size += data->callchain->nr;
  
                  header->size += size * sizeof(u64);
          }
  
          if (sample_type & PERF_SAMPLE_RAW) {
                  int size = sizeof(u32);
  
                  if (data->raw)
                          size += data->raw->size;
                  else
                          size += sizeof(u32);
  
                  WARN_ON_ONCE(size & (sizeof(u64)-1));
                  header->size += size;
          }
  }
  
  static void perf_event_output(struct perf_event *event, int nmi,
                                  struct perf_sample_data *data,
                                  struct pt_regs *regs)
  {
          struct perf_output_handle handle;
          struct perf_event_header header;
  
          perf_prepare_sample(&header, data, event, regs);
  
          if (perf_output_begin(&handle, event, header.size, nmi, 1))
                  return;
  
          perf_output_sample(&handle, &header, data, event);
  
          perf_output_end(&handle);
  }
  
  /*
   * read event_id
   */
  
  struct perf_read_event {
          struct perf_event_header        header;
  
          u32                             pid;
          u32                             tid;
  };
  
  static void
  perf_event_read_event(struct perf_event *event,
                          struct task_struct *task)
  {
          struct perf_output_handle handle;
          struct perf_read_event read_event = {
                  .header = {
                          .type = PERF_RECORD_READ,
                          .misc = 0,
                          .size = sizeof(read_event) + perf_event_read_size(event),
                  },
                  .pid = perf_event_pid(event, task),
                  .tid = perf_event_tid(event, task),
          };
          int ret;
  
          ret = perf_output_begin(&handle, event, read_event.header.size, 0, 0);
          if (ret)
                  return;
  
          perf_output_put(&handle, read_event);
          perf_output_read(&handle, event);
  
          perf_output_end(&handle);
  }
  
  /*
   * task tracking -- fork/exit
   *
   * enabled by: attr.comm | attr.mmap | attr.mmap_data | attr.task
   */
  
  struct perf_task_event {
          struct task_struct              *task;
          struct perf_event_context       *task_ctx;
  
          struct {
                  struct perf_event_header        header;
  
                  u32                             pid;
                  u32                             ppid;
                  u32                             tid;
                  u32                             ptid;
                  u64                             time;
          } event_id;
  };
  
  static void perf_event_task_output(struct perf_event *event,
                                       struct perf_task_event *task_event)
  {
          struct perf_output_handle handle;
          struct task_struct *task = task_event->task;
          int size, ret;
  
          size  = task_event->event_id.header.size;
          ret = perf_output_begin(&handle, event, size, 0, 0);
  
          if (ret)
                  return;
  
          task_event->event_id.pid = perf_event_pid(event, task);
          task_event->event_id.ppid = perf_event_pid(event, current);
  
          task_event->event_id.tid = perf_event_tid(event, task);
          task_event->event_id.ptid = perf_event_tid(event, current);
  
          perf_output_put(&handle, task_event->event_id);
  
          perf_output_end(&handle);
  }
  
  static int perf_event_task_match(struct perf_event *event)
  {
          if (event->state < PERF_EVENT_STATE_INACTIVE)
                  return 0;
  
          if (event->cpu != -1 && event->cpu != smp_processor_id())
                  return 0;
  
          if (event->attr.comm || event->attr.mmap ||
              event->attr.mmap_data || event->attr.task)
                  return 1;
  
          return 0;
  }
  
  static void perf_event_task_ctx(struct perf_event_context *ctx,
                                    struct perf_task_event *task_event)
  {
          struct perf_event *event;
  
          list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
                  if (perf_event_task_match(event))
                          perf_event_task_output(event, task_event);
          }
  }
  
  static void perf_event_task_event(struct perf_task_event *task_event)
  {
          struct perf_cpu_context *cpuctx;
          struct perf_event_context *ctx = task_event->task_ctx;
  
          rcu_read_lock();
          cpuctx = &get_cpu_var(perf_cpu_context);
          perf_event_task_ctx(&cpuctx->ctx, task_event);
          if (!ctx)
                  ctx = rcu_dereference(current->perf_event_ctxp);
          if (ctx)
                  perf_event_task_ctx(ctx, task_event);
          put_cpu_var(perf_cpu_context);
          rcu_read_unlock();
  }
  
  static void perf_event_task(struct task_struct *task,
                                struct perf_event_context *task_ctx,
                                int new)
  {
          struct perf_task_event task_event;
  
          if (!atomic_read(&nr_comm_events) &&
              !atomic_read(&nr_mmap_events) &&
              !atomic_read(&nr_task_events))
                  return;
  
          task_event = (struct perf_task_event){
                  .task     = task,
                  .task_ctx = task_ctx,
                  .event_id    = {
                          .header = {
                                  .type = new ? PERF_RECORD_FORK : PERF_RECORD_EXIT,
                                  .misc = 0,
                                  .size = sizeof(task_event.event_id),
                          },
                          /* .pid  */
                          /* .ppid */
                          /* .tid  */
                          /* .ptid */
                          .time = perf_clock(),
                  },
          };
  
          perf_event_task_event(&task_event);
  }
  
  void perf_event_fork(struct task_struct *task)
  {
          perf_event_task(task, NULL, 1);
  }
  
  /*
   * comm tracking
   */
  
  struct perf_comm_event {
          struct task_struct      *task;
          char                    *comm;
          int                     comm_size;
  
          struct {
                  struct perf_event_header        header;
  
                  u32                             pid;
                  u32                             tid;
          } event_id;
  };
  
  static void perf_event_comm_output(struct perf_event *event,
                                       struct perf_comm_event *comm_event)
  {
          struct perf_output_handle handle;
          int size = comm_event->event_id.header.size;
          int ret = perf_output_begin(&handle, event, size, 0, 0);
  
          if (ret)
                  return;
  
          comm_event->event_id.pid = perf_event_pid(event, comm_event->task);
          comm_event->event_id.tid = perf_event_tid(event, comm_event->task);
  
          perf_output_put(&handle, comm_event->event_id);
          perf_output_copy(&handle, comm_event->comm,
                                     comm_event->comm_size);
          perf_output_end(&handle);
  }
  
  static int perf_event_comm_match(struct perf_event *event)
  {
          if (event->state < PERF_EVENT_STATE_INACTIVE)
                  return 0;
  
          if (event->cpu != -1 && event->cpu != smp_processor_id())
                  return 0;
  
          if (event->attr.comm)
                  return 1;
  
          return 0;
  }
  
  static void perf_event_comm_ctx(struct perf_event_context *ctx,
                                    struct perf_comm_event *comm_event)
  {
          struct perf_event *event;
  
          list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
                  if (perf_event_comm_match(event))
                          perf_event_comm_output(event, comm_event);
          }
  }
  
  static void perf_event_comm_event(struct perf_comm_event *comm_event)
  {
          struct perf_cpu_context *cpuctx;
          struct perf_event_context *ctx;
          unsigned int size;
          char comm[TASK_COMM_LEN];
  
          memset(comm, 0, sizeof(comm));
          strlcpy(comm, comm_event->task->comm, sizeof(comm));
          size = ALIGN(strlen(comm)+1, sizeof(u64));
  
          comm_event->comm = comm;
          comm_event->comm_size = size;
  
          comm_event->event_id.header.size = sizeof(comm_event->event_id) + size;
  
          rcu_read_lock();
          cpuctx = &get_cpu_var(perf_cpu_context);
          perf_event_comm_ctx(&cpuctx->ctx, comm_event);
          ctx = rcu_dereference(current->perf_event_ctxp);
          if (ctx)
                  perf_event_comm_ctx(ctx, comm_event);
          put_cpu_var(perf_cpu_context);
          rcu_read_unlock();
  }
  
  void perf_event_comm(struct task_struct *task)
  {
          struct perf_comm_event comm_event;
  
          if (task->perf_event_ctxp)
                  perf_event_enable_on_exec(task);
  
          if (!atomic_read(&nr_comm_events))
                  return;
  
          comm_event = (struct perf_comm_event){
                  .task   = task,
                  /* .comm      */
                  /* .comm_size */
                  .event_id  = {
                          .header = {
                                  .type = PERF_RECORD_COMM,
                                  .misc = 0,
                                  /* .size */
                          },
                          /* .pid */
                          /* .tid */
                  },
          };
  
          perf_event_comm_event(&comm_event);
  }
  
  /*
   * mmap tracking
   */
  
  struct perf_mmap_event {
          struct vm_area_struct   *vma;
  
          const char              *file_name;
          int                     file_size;
  
          struct {
                  struct perf_event_header        header;
  
                  u32                             pid;
                  u32                             tid;
                  u64                             start;
                  u64                             len;
                  u64                             pgoff;
          } event_id;
  };
  
  static void perf_event_mmap_output(struct perf_event *event,
                                       struct perf_mmap_event *mmap_event)
  {
          struct perf_output_handle handle;
          int size = mmap_event->event_id.header.size;
          int ret = perf_output_begin(&handle, event, size, 0, 0);
  
          if (ret)
                  return;
  
          mmap_event->event_id.pid = perf_event_pid(event, current);
          mmap_event->event_id.tid = perf_event_tid(event, current);
  
          perf_output_put(&handle, mmap_event->event_id);
          perf_output_copy(&handle, mmap_event->file_name,
                                     mmap_event->file_size);
          perf_output_end(&handle);
  }
  
  static int perf_event_mmap_match(struct perf_event *event,
                                     struct perf_mmap_event *mmap_event,
                                     int executable)
  {
          if (event->state < PERF_EVENT_STATE_INACTIVE)
                  return 0;
  
          if (event->cpu != -1 && event->cpu != smp_processor_id())
                  return 0;
  
          if ((!executable && event->attr.mmap_data) ||
              (executable && event->attr.mmap))
                  return 1;
  
          return 0;
  }
  
  static void perf_event_mmap_ctx(struct perf_event_context *ctx,
                                    struct perf_mmap_event *mmap_event,
                                    int executable)
  {
          struct perf_event *event;
  
          list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
                  if (perf_event_mmap_match(event, mmap_event, executable))
                          perf_event_mmap_output(event, mmap_event);
          }
  }
  
  static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
  {
          struct perf_cpu_context *cpuctx;
          struct perf_event_context *ctx;
          struct vm_area_struct *vma = mmap_event->vma;
          struct file *file = vma->vm_file;
          unsigned int size;
          char tmp[16];
          char *buf = NULL;
          const char *name;
  
          memset(tmp, 0, sizeof(tmp));
  
          if (file) {
                  /*
                   * d_path works from the end of the buffer backwards, so we
                   * need to add enough zero bytes after the string to handle
                   * the 64bit alignment we do later.
                   */
                  buf = kzalloc(PATH_MAX + sizeof(u64), GFP_KERNEL);
                  if (!buf) {
                          name = strncpy(tmp, "//enomem", sizeof(tmp));
                          goto got_name;
                  }
                  name = d_path(&file->f_path, buf, PATH_MAX);
                  if (IS_ERR(name)) {
                          name = strncpy(tmp, "//toolong", sizeof(tmp));
                          goto got_name;
                  }
          } else {
                  if (arch_vma_name(mmap_event->vma)) {
                          name = strncpy(tmp, arch_vma_name(mmap_event->vma),
                                         sizeof(tmp));
                          goto got_name;
                  }
  
                  if (!vma->vm_mm) {
                          name = strncpy(tmp, "[vdso]", sizeof(tmp));
                          goto got_name;
                  } else if (vma->vm_start <= vma->vm_mm->start_brk &&
                                  vma->vm_end >= vma->vm_mm->brk) {
                          name = strncpy(tmp, "[heap]", sizeof(tmp));
                          goto got_name;
                  } else if (vma->vm_start <= vma->vm_mm->start_stack &&
                                  vma->vm_end >= vma->vm_mm->start_stack) {
                          name = strncpy(tmp, "[stack]", sizeof(tmp));
                          goto got_name;
                  }
  
                  name = strncpy(tmp, "//anon", sizeof(tmp));
                  goto got_name;
          }
  
  got_name:
          size = ALIGN(strlen(name)+1, sizeof(u64));
  
          mmap_event->file_name = name;
          mmap_event->file_size = size;
  
          mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;
  
          rcu_read_lock();
          cpuctx = &get_cpu_var(perf_cpu_context);
          perf_event_mmap_ctx(&cpuctx->ctx, mmap_event, vma->vm_flags & VM_EXEC);
          ctx = rcu_dereference(current->perf_event_ctxp);
          if (ctx)
                  perf_event_mmap_ctx(ctx, mmap_event, vma->vm_flags & VM_EXEC);
          put_cpu_var(perf_cpu_context);
          rcu_read_unlock();
  
          kfree(buf);
  }
  
  void perf_event_mmap(struct vm_area_struct *vma)
  {
          struct perf_mmap_event mmap_event;
  
          if (!atomic_read(&nr_mmap_events))
                  return;
  
          mmap_event = (struct perf_mmap_event){
                  .vma    = vma,
                  /* .file_name */
                  /* .file_size */
                  .event_id  = {
                          .header = {
                                  .type = PERF_RECORD_MMAP,
                                  .misc = PERF_RECORD_MISC_USER,
                                  /* .size */
                          },
                          /* .pid */
                          /* .tid */
                          .start  = vma->vm_start,
                          .len    = vma->vm_end - vma->vm_start,
                          .pgoff  = (u64)vma->vm_pgoff << PAGE_SHIFT,
                  },
          };
  
          perf_event_mmap_event(&mmap_event);
  }
  
  /*
   * IRQ throttle logging
   */
  
  static void perf_log_throttle(struct perf_event *event, int enable)
  {
          struct perf_output_handle handle;
          int ret;
  
          struct {
                  struct perf_event_header        header;
                  u64                             time;
                  u64                             id;
                  u64                             stream_id;
          } throttle_event = {
                  .header = {
                          .type = PERF_RECORD_THROTTLE,
                          .misc = 0,
                          .size = sizeof(throttle_event),
                  },
                  .time           = perf_clock(),
                  .id             = primary_event_id(event),
                  .stream_id      = event->id,
          };
  
          if (enable)
                  throttle_event.header.type = PERF_RECORD_UNTHROTTLE;
  
          ret = perf_output_begin(&handle, event, sizeof(throttle_event), 1, 0);
          if (ret)
                  return;
  
          perf_output_put(&handle, throttle_event);
          perf_output_end(&handle);
  }
  
  /*
   * Generic event overflow handling, sampling.
   */
  
  static int __perf_event_overflow(struct perf_event *event, int nmi,
                                     int throttle, struct perf_sample_data *data,
                                     struct pt_regs *regs)
  {
          int events = atomic_read(&event->event_limit);
          struct hw_perf_event *hwc = &event->hw;
          int ret = 0;
  
          throttle = (throttle && event->pmu->unthrottle != NULL);
  
          if (!throttle) {
                  hwc->interrupts++;
          } else {
                  if (hwc->interrupts != MAX_INTERRUPTS) {
                          hwc->interrupts++;
                          if (HZ * hwc->interrupts >
                                          (u64)sysctl_perf_event_sample_rate) {
                                  hwc->interrupts = MAX_INTERRUPTS;
                                  perf_log_throttle(event, 0);
                                  ret = 1;
                          }
                  } else {
                          /*
                           * Keep re-disabling events even though on the previous
                           * pass we disabled it - just in case we raced with a
                           * sched-in and the event got enabled again:
                           */
                          ret = 1;
                  }
          }
  
          if (event->attr.freq) {
                  u64 now = perf_clock();
                  s64 delta = now - hwc->freq_time_stamp;
  
                  hwc->freq_time_stamp = now;
  
                  if (delta > 0 && delta < 2*TICK_NSEC)
                          perf_adjust_period(event, delta, hwc->last_period);
          }
  
          /*
           * XXX event_limit might not quite work as expected on inherited
           * events
           */
  
          event->pending_kill = POLL_IN;
          if (events && atomic_dec_and_test(&event->event_limit)) {
                  ret = 1;
                  event->pending_kill = POLL_HUP;
                  if (nmi) {
                          event->pending_disable = 1;
                          perf_pending_queue(&event->pending,
                                             perf_pending_event);
                  } else
                          perf_event_disable(event);
          }
  
          if (event->overflow_handler)
                  event->overflow_handler(event, nmi, data, regs);
          else
                  perf_event_output(event, nmi, data, regs);
  
          return ret;
  }
  
  int perf_event_overflow(struct perf_event *event, int nmi,
                            struct perf_sample_data *data,
                            struct pt_regs *regs)
  {
          return __perf_event_overflow(event, nmi, 1, data, regs);
  }
  
  /*
   * Generic software event infrastructure
   */
  
  /*
   * We directly increment event->count and keep a second value in
   * event->hw.period_left to count intervals. This period event
   * is kept in the range [-sample_period, 0] so that we can use the
   * sign as trigger.
   */
  
  static u64 perf_swevent_set_period(struct perf_event *event)
  {
          struct hw_perf_event *hwc = &event->hw;
          u64 period = hwc->last_period;
          u64 nr, offset;
          s64 old, val;
  
          hwc->last_period = hwc->sample_period;
  
  again:
          old = val = local64_read(&hwc->period_left);
          if (val < 0)
                  return 0;
  
          nr = div64_u64(period + val, period);
          offset = nr * period;
          val -= offset;
          if (local64_cmpxchg(&hwc->period_left, old, val) != old)
                  goto again;
  
          return nr;
  }
  
  static void perf_swevent_overflow(struct perf_event *event, u64 overflow,
                                      int nmi, struct perf_sample_data *data,
                                      struct pt_regs *regs)
  {
          struct hw_perf_event *hwc = &event->hw;
          int throttle = 0;
  
          data->period = event->hw.last_period;
          if (!overflow)
                  overflow = perf_swevent_set_period(event);
  
          if (hwc->interrupts == MAX_INTERRUPTS)
                  return;
  
          for (; overflow; overflow--) {
                  if (__perf_event_overflow(event, nmi, throttle,
                                              data, regs)) {
                          /*
                           * We inhibit the overflow from happening when
                           * hwc->interrupts == MAX_INTERRUPTS.
                           */
                          break;
                  }
                  throttle = 1;
          }
  }
  
  static void perf_swevent_add(struct perf_event *event, u64 nr,
                                 int nmi, struct perf_sample_data *data,
                                 struct pt_regs *regs)
  {
          struct hw_perf_event *hwc = &event->hw;
  
          local64_add(nr, &event->count);
  
          if (!regs)
                  return;
  
          if (!hwc->sample_period)
                  return;
  
          if (nr == 1 && hwc->sample_period == 1 && !event->attr.freq)
                  return perf_swevent_overflow(event, 1, nmi, data, regs);
  
          if (local64_add_negative(nr, &hwc->period_left))
                  return;
  
          perf_swevent_overflow(event, 0, nmi, data, regs);
  }
  
  static int perf_exclude_event(struct perf_event *event,
                                struct pt_regs *regs)
  {
          if (regs) {
                  if (event->attr.exclude_user && user_mode(regs))
                          return 1;
  
                  if (event->attr.exclude_kernel && !user_mode(regs))
                          return 1;
          }
  
          return 0;
  }
  
  static int perf_swevent_match(struct perf_event *event,
                                  enum perf_type_id type,
                                  u32 event_id,
                                  struct perf_sample_data *data,
                                  struct pt_regs *regs)
  {
          if (event->attr.type != type)
                  return 0;
  
          if (event->attr.config != event_id)
                  return 0;
  
          if (perf_exclude_event(event, regs))
                  return 0;
  
          return 1;
  }
  
  static inline u64 swevent_hash(u64 type, u32 event_id)
  {
          u64 val = event_id | (type << 32);
  
          return hash_64(val, SWEVENT_HLIST_BITS);
  }
  
  static inline struct hlist_head *
  __find_swevent_head(struct swevent_hlist *hlist, u64 type, u32 event_id)
  {
          u64 hash = swevent_hash(type, event_id);
  
          return &hlist->heads[hash];
  }
  
  /* For the read side: events when they trigger */
  static inline struct hlist_head *
  find_swevent_head_rcu(struct perf_cpu_context *ctx, u64 type, u32 event_id)
  {
          struct swevent_hlist *hlist;
  
          hlist = rcu_dereference(ctx->swevent_hlist);
          if (!hlist)
                  return NULL;
  
          return __find_swevent_head(hlist, type, event_id);
  }
  
  /* For the event head insertion and removal in the hlist */
  static inline struct hlist_head *
  find_swevent_head(struct perf_cpu_context *ctx, struct perf_event *event)
  {
          struct swevent_hlist *hlist;
          u32 event_id = event->attr.config;
          u64 type = event->attr.type;
  
          /*
           * Event scheduling is always serialized against hlist allocation
           * and release. Which makes the protected version suitable here.
           * The context lock guarantees that.
           */
          hlist = rcu_dereference_protected(ctx->swevent_hlist,
                                            lockdep_is_held(&event->ctx->lock));
          if (!hlist)
                  return NULL;
  
          return __find_swevent_head(hlist, type, event_id);
  }
  
  static void do_perf_sw_event(enum perf_type_id type, u32 event_id,
                                      u64 nr, int nmi,
                                      struct perf_sample_data *data,
                                      struct pt_regs *regs)
  {
          struct perf_cpu_context *cpuctx;
          struct perf_event *event;
          struct hlist_node *node;
          struct hlist_head *head;
  
          cpuctx = &__get_cpu_var(perf_cpu_context);
  
          rcu_read_lock();
  
          head = find_swevent_head_rcu(cpuctx, type, event_id);
  
          if (!head)
                  goto end;
  
          hlist_for_each_entry_rcu(event, node, head, hlist_entry) {
                  if (perf_swevent_match(event, type, event_id, data, regs))
                          perf_swevent_add(event, nr, nmi, data, regs);
          }
  end:
          rcu_read_unlock();
  }
  
  int perf_swevent_get_recursion_context(void)
  {
          struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
          int rctx;
  
          if (in_nmi())
                  rctx = 3;
          else if (in_irq())
                  rctx = 2;
          else if (in_softirq())
                  rctx = 1;
          else
                  rctx = 0;
  
          if (cpuctx->recursion[rctx])
                  return -1;
  
          cpuctx->recursion[rctx]++;
          barrier();
  
          return rctx;
  }
  EXPORT_SYMBOL_GPL(perf_swevent_get_recursion_context);
  
  void inline perf_swevent_put_recursion_context(int rctx)
  {
          struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
          barrier();
          cpuctx->recursion[rctx]--;
  }
  
  void __perf_sw_event(u32 event_id, u64 nr, int nmi,
                              struct pt_regs *regs, u64 addr)
  {
          struct perf_sample_data data;
          int rctx;
  
          preempt_disable_notrace();
          rctx = perf_swevent_get_recursion_context();
          if (rctx < 0)
                  return;
  
          perf_sample_data_init(&data, addr);
  
          do_perf_sw_event(PERF_TYPE_SOFTWARE, event_id, nr, nmi, &data, regs);
  
          perf_swevent_put_recursion_context(rctx);
          preempt_enable_notrace();
  }
  
  static void perf_swevent_read(struct perf_event *event)
  {
  }
  
  static int perf_swevent_enable(struct perf_event *event)
  {
          struct hw_perf_event *hwc = &event->hw;
          struct perf_cpu_context *cpuctx;
          struct hlist_head *head;
  
          cpuctx = &__get_cpu_var(perf_cpu_context);
  
          if (hwc->sample_period) {
                  hwc->last_period = hwc->sample_period;
                  perf_swevent_set_period(event);
          }
  
          head = find_swevent_head(cpuctx, event);
          if (WARN_ON_ONCE(!head))
                  return -EINVAL;
  
          hlist_add_head_rcu(&event->hlist_entry, head);
  
          return 0;
  }
  
  static void perf_swevent_disable(struct perf_event *event)
  {
          hlist_del_rcu(&event->hlist_entry);
  }
  
  static void perf_swevent_void(struct perf_event *event)
  {
  }
  
  static int perf_swevent_int(struct perf_event *event)
  {
          return 0;
  }
  
  static const struct pmu perf_ops_generic = {
          .enable         = perf_swevent_enable,
          .disable        = perf_swevent_disable,
          .start          = perf_swevent_int,
          .stop           = perf_swevent_void,
          .read           = perf_swevent_read,
          .unthrottle     = perf_swevent_void, /* hwc->interrupts already reset */
  };
  
  /*
   * hrtimer based swevent callback
   */
  
  static enum hrtimer_restart perf_swevent_hrtimer(struct hrtimer *hrtimer)
  {
          enum hrtimer_restart ret = HRTIMER_RESTART;
          struct perf_sample_data data;
          struct pt_regs *regs;
          struct perf_event *event;
          u64 period;
  
          event = container_of(hrtimer, struct perf_event, hw.hrtimer);
          event->pmu->read(event);
  
          perf_sample_data_init(&data, 0);
          data.period = event->hw.last_period;
          regs = get_irq_regs();
  
          if (regs && !perf_exclude_event(event, regs)) {
                  if (!(event->attr.exclude_idle && current->pid == 0))
                          if (perf_event_overflow(event, 0, &data, regs))
                                  ret = HRTIMER_NORESTART;
          }
  
          period = max_t(u64, 10000, event->hw.sample_period);
          hrtimer_forward_now(hrtimer, ns_to_ktime(period));
  
          return ret;
  }
  
  static void perf_swevent_start_hrtimer(struct perf_event *event)
  {
          struct hw_perf_event *hwc = &event->hw;
  
          hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
          hwc->hrtimer.function = perf_swevent_hrtimer;
          if (hwc->sample_period) {
                  u64 period;
  
                  if (hwc->remaining) {
                          if (hwc->remaining < 0)
                                  period = 10000;
                          else
                                  period = hwc->remaining;
                          hwc->remaining = 0;
                  } else {
                          period = max_t(u64, 10000, hwc->sample_period);
                  }
                  __hrtimer_start_range_ns(&hwc->hrtimer,
                                  ns_to_ktime(period), 0,
                                  HRTIMER_MODE_REL, 0);
          }
  }
  
  static void perf_swevent_cancel_hrtimer(struct perf_event *event)
  {
          struct hw_perf_event *hwc = &event->hw;
  
          if (hwc->sample_period) {
                  ktime_t remaining = hrtimer_get_remaining(&hwc->hrtimer);
                  hwc->remaining = ktime_to_ns(remaining);
  
                  hrtimer_cancel(&hwc->hrtimer);
          }
  }
  
  /*
   * Software event: cpu wall time clock
   */
  
  static void cpu_clock_perf_event_update(struct perf_event *event)
  {
          int cpu = raw_smp_processor_id();
          s64 prev;
          u64 now;
  
          now = cpu_clock(cpu);
          prev = local64_xchg(&event->hw.prev_count, now);
          local64_add(now - prev, &event->count);
  }
  
  static int cpu_clock_perf_event_enable(struct perf_event *event)
  {
          struct hw_perf_event *hwc = &event->hw;
          int cpu = raw_smp_processor_id();
  
          local64_set(&hwc->prev_count, cpu_clock(cpu));
          perf_swevent_start_hrtimer(event);
  
          return 0;
  }
  
  static void cpu_clock_perf_event_disable(struct perf_event *event)
  {
          perf_swevent_cancel_hrtimer(event);
          cpu_clock_perf_event_update(event);
  }
  
  static void cpu_clock_perf_event_read(struct perf_event *event)
  {
          cpu_clock_perf_event_update(event);
  }
  
  static const struct pmu perf_ops_cpu_clock = {
          .enable         = cpu_clock_perf_event_enable,
          .disable        = cpu_clock_perf_event_disable,
          .read           = cpu_clock_perf_event_read,
  };
  
  /*
   * Software event: task time clock
   */
  
  static void task_clock_perf_event_update(struct perf_event *event, u64 now)
  {
          u64 prev;
          s64 delta;
  
          prev = local64_xchg(&event->hw.prev_count, now);
          delta = now - prev;
          local64_add(delta, &event->count);
  }
  
  static int task_clock_perf_event_enable(struct perf_event *event)
  {
          struct hw_perf_event *hwc = &event->hw;
          u64 now;
  
          now = event->ctx->time;
  
          local64_set(&hwc->prev_count, now);
  
          perf_swevent_start_hrtimer(event);
  
          return 0;
  }
  
  static void task_clock_perf_event_disable(struct perf_event *event)
  {
          perf_swevent_cancel_hrtimer(event);
          task_clock_perf_event_update(event, event->ctx->time);
  
  }
  
  static void task_clock_perf_event_read(struct perf_event *event)
  {
          u64 time;
  
          if (!in_nmi()) {
                  update_context_time(event->ctx);
                  time = event->ctx->time;
          } else {
                  u64 now = perf_clock();
                  u64 delta = now - event->ctx->timestamp;
                  time = event->ctx->time + delta;
          }
  
          task_clock_perf_event_update(event, time);
  }
  
  static const struct pmu perf_ops_task_clock = {
          .enable         = task_clock_perf_event_enable,
          .disable        = task_clock_perf_event_disable,
          .read           = task_clock_perf_event_read,
  };
  
  /* Deref the hlist from the update side */
  static inline struct swevent_hlist *
  swevent_hlist_deref(struct perf_cpu_context *cpuctx)
  {
          return rcu_dereference_protected(cpuctx->swevent_hlist,
                                           lockdep_is_held(&cpuctx->hlist_mutex));
  }
  
  static void swevent_hlist_release_rcu(struct rcu_head *rcu_head)
  {
          struct swevent_hlist *hlist;
  
          hlist = container_of(rcu_head, struct swevent_hlist, rcu_head);
          kfree(hlist);
  }
  
  static void swevent_hlist_release(struct perf_cpu_context *cpuctx)
  {
          struct swevent_hlist *hlist = swevent_hlist_deref(cpuctx);
  
          if (!hlist)
                  return;
  
          rcu_assign_pointer(cpuctx->swevent_hlist, NULL);
          call_rcu(&hlist->rcu_head, swevent_hlist_release_rcu);
  }
  
  static void swevent_hlist_put_cpu(struct perf_event *event, int cpu)
  {
          struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
  
          mutex_lock(&cpuctx->hlist_mutex);
  
          if (!--cpuctx->hlist_refcount)
                  swevent_hlist_release(cpuctx);
  
          mutex_unlock(&cpuctx->hlist_mutex);
  }
  
  static void swevent_hlist_put(struct perf_event *event)
  {
          int cpu;
  
          if (event->cpu != -1) {
                  swevent_hlist_put_cpu(event, event->cpu);
                  return;
          }
  
          for_each_possible_cpu(cpu)
                  swevent_hlist_put_cpu(event, cpu);
  }
  
  static int swevent_hlist_get_cpu(struct perf_event *event, int cpu)
  {
          struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
          int err = 0;
  
          mutex_lock(&cpuctx->hlist_mutex);
  
          if (!swevent_hlist_deref(cpuctx) && cpu_online(cpu)) {
                  struct swevent_hlist *hlist;
  
                  hlist = kzalloc(sizeof(*hlist), GFP_KERNEL);
                  if (!hlist) {
                          err = -ENOMEM;
                          goto exit;
                  }
                  rcu_assign_pointer(cpuctx->swevent_hlist, hlist);
          }
          cpuctx->hlist_refcount++;
   exit:
          mutex_unlock(&cpuctx->hlist_mutex);
  
          return err;
  }
  
  static int swevent_hlist_get(struct perf_event *event)
  {
          int err;
          int cpu, failed_cpu;
  
          if (event->cpu != -1)
                  return swevent_hlist_get_cpu(event, event->cpu);
  
          get_online_cpus();
          for_each_possible_cpu(cpu) {
                  err = swevent_hlist_get_cpu(event, cpu);
                  if (err) {
                          failed_cpu = cpu;
                          goto fail;
                  }
          }
          put_online_cpus();
  
          return 0;
   fail:
          for_each_possible_cpu(cpu) {
                  if (cpu == failed_cpu)
                          break;
                  swevent_hlist_put_cpu(event, cpu);
          }
  
          put_online_cpus();
          return err;
  }
  
  #ifdef CONFIG_EVENT_TRACING
  
  static const struct pmu perf_ops_tracepoint = {
          .enable         = perf_trace_enable,
          .disable        = perf_trace_disable,
          .start          = perf_swevent_int,
          .stop           = perf_swevent_void,
          .read           = perf_swevent_read,
          .unthrottle     = perf_swevent_void,
  };
  
  static int perf_tp_filter_match(struct perf_event *event,
                                  struct perf_sample_data *data)
  {
          void *record = data->raw->data;
  
          if (likely(!event->filter) || filter_match_preds(event->filter, record))
                  return 1;
          return 0;
  }
  
  static int perf_tp_event_match(struct perf_event *event,
                                  struct perf_sample_data *data,
                                  struct pt_regs *regs)
  {
          /*
           * All tracepoints are from kernel-space.
           */
          if (event->attr.exclude_kernel)
                  return 0;
  
          if (!perf_tp_filter_match(event, data))
                  return 0;
  
          return 1;
  }
  
  void perf_tp_event(u64 addr, u64 count, void *record, int entry_size,
                     struct pt_regs *regs, struct hlist_head *head, int rctx)
  {
          struct perf_sample_data data;
          struct perf_event *event;
          struct hlist_node *node;
  
          struct perf_raw_record raw = {
                  .size = entry_size,
                  .data = record,
          };
  
          perf_sample_data_init(&data, addr);
          data.raw = &raw;
  
          hlist_for_each_entry_rcu(event, node, head, hlist_entry) {
                  if (perf_tp_event_match(event, &data, regs))
                          perf_swevent_add(event, count, 1, &data, regs);
          }
  
          perf_swevent_put_recursion_context(rctx);
  }
  EXPORT_SYMBOL_GPL(perf_tp_event);
  
  static void tp_perf_event_destroy(struct perf_event *event)
  {
          perf_trace_destroy(event);
  }
  
  static const struct pmu *tp_perf_event_init(struct perf_event *event)
  {
          int err;
  
          /*
           * Raw tracepoint data is a severe data leak, only allow root to
           * have these.
           */
          if ((event->attr.sample_type & PERF_SAMPLE_RAW) &&
                          perf_paranoid_tracepoint_raw() &&
                          !capable(CAP_SYS_ADMIN))
                  return ERR_PTR(-EPERM);
  
          err = perf_trace_init(event);
          if (err)
                  return NULL;
  
          event->destroy = tp_perf_event_destroy;
  
          return &perf_ops_tracepoint;
  }
  
  static int perf_event_set_filter(struct perf_event *event, void __user *arg)
  {
          char *filter_str;
          int ret;
  
          if (event->attr.type != PERF_TYPE_TRACEPOINT)
                  return -EINVAL;
  
          filter_str = strndup_user(arg, PAGE_SIZE);
          if (IS_ERR(filter_str))
                  return PTR_ERR(filter_str);
  
          ret = ftrace_profile_set_filter(event, event->attr.config, filter_str);
  
          kfree(filter_str);
          return ret;
  }
  
  static void perf_event_free_filter(struct perf_event *event)
  {
          ftrace_profile_free_filter(event);
  }
  
  #else
  
  static const struct pmu *tp_perf_event_init(struct perf_event *event)
  {
          return NULL;
  }
  
  static int perf_event_set_filter(struct perf_event *event, void __user *arg)
  {
          return -ENOENT;
  }
  
  static void perf_event_free_filter(struct perf_event *event)
  {
  }
  
  #endif /* CONFIG_EVENT_TRACING */
  
  #ifdef CONFIG_HAVE_HW_BREAKPOINT
  static void bp_perf_event_destroy(struct perf_event *event)
  {
          release_bp_slot(event);
  }
  
  static const struct pmu *bp_perf_event_init(struct perf_event *bp)
  {
          int err;
  
          err = register_perf_hw_breakpoint(bp);
          if (err)
                  return ERR_PTR(err);
  
          bp->destroy = bp_perf_event_destroy;
  
          return &perf_ops_bp;
  }
  
  void perf_bp_event(struct perf_event *bp, void *data)
  {
          struct perf_sample_data sample;
          struct pt_regs *regs = data;
  
          perf_sample_data_init(&sample, bp->attr.bp_addr);
  
          if (!perf_exclude_event(bp, regs))
                  perf_swevent_add(bp, 1, 1, &sample, regs);
  }
  #else
  static const struct pmu *bp_perf_event_init(struct perf_event *bp)
  {
          return NULL;
  }
  
  void perf_bp_event(struct perf_event *bp, void *regs)
  {
  }
  #endif
  
  atomic_t perf_swevent_enabled[PERF_COUNT_SW_MAX];
  
  static void sw_perf_event_destroy(struct perf_event *event)
  {
          u64 event_id = event->attr.config;
  
          WARN_ON(event->parent);
  
          atomic_dec(&perf_swevent_enabled[event_id]);
          swevent_hlist_put(event);
  }
  
  static const struct pmu *sw_perf_event_init(struct perf_event *event)
  {
          const struct pmu *pmu = NULL;
          u64 event_id = event->attr.config;
  
          /*
           * Software events (currently) can't in general distinguish
           * between user, kernel and hypervisor events.
           * However, context switches and cpu migrations are considered
           * to be kernel events, and page faults are never hypervisor
           * events.
           */
          switch (event_id) {
          case PERF_COUNT_SW_CPU_CLOCK:
                  pmu = &perf_ops_cpu_clock;
  
                  break;
          case PERF_COUNT_SW_TASK_CLOCK:
                  /*
                   * If the user instantiates this as a per-cpu event,
                   * use the cpu_clock event instead.
                   */
                  if (event->ctx->task)
                          pmu = &perf_ops_task_clock;
                  else
                          pmu = &perf_ops_cpu_clock;
  
                  break;
          case PERF_COUNT_SW_PAGE_FAULTS:
          case PERF_COUNT_SW_PAGE_FAULTS_MIN:
          case PERF_COUNT_SW_PAGE_FAULTS_MAJ:
          case PERF_COUNT_SW_CONTEXT_SWITCHES:
          case PERF_COUNT_SW_CPU_MIGRATIONS:
          case PERF_COUNT_SW_ALIGNMENT_FAULTS:
          case PERF_COUNT_SW_EMULATION_FAULTS:
                  if (!event->parent) {
                          int err;
  
                          err = swevent_hlist_get(event);
                          if (err)
                                  return ERR_PTR(err);
  
                          atomic_inc(&perf_swevent_enabled[event_id]);
                          event->destroy = sw_perf_event_destroy;
                  }
                  pmu = &perf_ops_generic;
                  break;
          }
  
          return pmu;
  }
  
  /*
   * Allocate and initialize a event structure
   */
  static struct perf_event *
  perf_event_alloc(struct perf_event_attr *attr,
                     int cpu,
                     struct perf_event_context *ctx,
                     struct perf_event *group_leader,
                     struct perf_event *parent_event,
                     perf_overflow_handler_t overflow_handler,
                     gfp_t gfpflags)
  {
          const struct pmu *pmu;
          struct perf_event *event;
          struct hw_perf_event *hwc;
          long err;
  
          event = kzalloc(sizeof(*event), gfpflags);
          if (!event)
                  return ERR_PTR(-ENOMEM);
  
          /*
           * Single events are their own group leaders, with an
           * empty sibling list:
           */
          if (!group_leader)
                  group_leader = event;
  
          mutex_init(&event->child_mutex);
          INIT_LIST_HEAD(&event->child_list);
  
          INIT_LIST_HEAD(&event->group_entry);
          INIT_LIST_HEAD(&event->event_entry);
          INIT_LIST_HEAD(&event->sibling_list);
          init_waitqueue_head(&event->waitq);
  
          mutex_init(&event->mmap_mutex);
  
          event->cpu              = cpu;
          event->attr             = *attr;
          event->group_leader     = group_leader;
          event->pmu              = NULL;
          event->ctx              = ctx;
          event->oncpu            = -1;
  
          event->parent           = parent_event;
  
          event->ns               = get_pid_ns(current->nsproxy->pid_ns);
          event->id               = atomic64_inc_return(&perf_event_id);
  
          event->state            = PERF_EVENT_STATE_INACTIVE;
  
          if (!overflow_handler && parent_event)
                  overflow_handler = parent_event->overflow_handler;
          
          event->overflow_handler = overflow_handler;
  
          if (attr->disabled)
                  event->state = PERF_EVENT_STATE_OFF;
  
          pmu = NULL;
  
          hwc = &event->hw;
          hwc->sample_period = attr->sample_period;
          if (attr->freq && attr->sample_freq)
                  hwc->sample_period = 1;
          hwc->last_period = hwc->sample_period;
  
          local64_set(&hwc->period_left, hwc->sample_period);
  
          /*
           * we currently do not support PERF_FORMAT_GROUP on inherited events
           */
          if (attr->inherit && (attr->read_format & PERF_FORMAT_GROUP))
                  goto done;
  
          switch (attr->type) {
          case PERF_TYPE_RAW:
          case PERF_TYPE_HARDWARE:
          case PERF_TYPE_HW_CACHE:
                  pmu = hw_perf_event_init(event);
                  break;
  
          case PERF_TYPE_SOFTWARE:
                  pmu = sw_perf_event_init(event);
                  break;
  
          case PERF_TYPE_TRACEPOINT:
                  pmu = tp_perf_event_init(event);
                  break;
  
          case PERF_TYPE_BREAKPOINT:
                  pmu = bp_perf_event_init(event);
                  break;
  
  
          default:
                  break;
          }
  done:
          err = 0;
          if (!pmu)
                  err = -EINVAL;
          else if (IS_ERR(pmu))
                  err = PTR_ERR(pmu);
  
          if (err) {
                  if (event->ns)
                          put_pid_ns(event->ns);
                  kfree(event);
                  return ERR_PTR(err);
          }
  
          event->pmu = pmu;
  
          if (!event->parent) {
                  atomic_inc(&nr_events);
                  if (event->attr.mmap || event->attr.mmap_data)
                          atomic_inc(&nr_mmap_events);
                  if (event->attr.comm)
                          atomic_inc(&nr_comm_events);
                  if (event->attr.task)
                          atomic_inc(&nr_task_events);
          }
  
          return event;
  }
  
  static int perf_copy_attr(struct perf_event_attr __user *uattr,
                            struct perf_event_attr *attr)
  {
          u32 size;
          int ret;
  
          if (!access_ok(VERIFY_WRITE, uattr, PERF_ATTR_SIZE_VER0))
                  return -EFAULT;
  
          /*
           * zero the full structure, so that a short copy will be nice.
           */
          memset(attr, 0, sizeof(*attr));
  
          ret = get_user(size, &uattr->size);
          if (ret)
                  return ret;
  
          if (size > PAGE_SIZE)   /* silly large */
                  goto err_size;
  
          if (!size)              /* abi compat */
                  size = PERF_ATTR_SIZE_VER0;
  
          if (size < PERF_ATTR_SIZE_VER0)
                  goto err_size;
  
          /*
           * If we're handed a bigger struct than we know of,
           * ensure all the unknown bits are 0 - i.e. new
           * user-space does not rely on any kernel feature
           * extensions we dont know about yet.
           */
          if (size > sizeof(*attr)) {
                  unsigned char __user *addr;
                  unsigned char __user *end;
                  unsigned char val;
  
                  addr = (void __user *)uattr + sizeof(*attr);
                  end  = (void __user *)uattr + size;
  
                  for (; addr < end; addr++) {
                          ret = get_user(val, addr);
                          if (ret)
                                  return ret;
                          if (val)
                                  goto err_size;
                  }
                  size = sizeof(*attr);
          }
  
          ret = copy_from_user(attr, uattr, size);
          if (ret)
                  return -EFAULT;
  
          /*
           * If the type exists, the corresponding creation will verify
           * the attr->config.
           */
          if (attr->type >= PERF_TYPE_MAX)
                  return -EINVAL;
  
          if (attr->__reserved_1)
                  return -EINVAL;
  
          if (attr->sample_type & ~(PERF_SAMPLE_MAX-1))
                  return -EINVAL;
  
          if (attr->read_format & ~(PERF_FORMAT_MAX-1))
                  return -EINVAL;
  
  out:
          return ret;
  
  err_size:
          put_user(sizeof(*attr), &uattr->size);
          ret = -E2BIG;
          goto out;
  }
  
  static int
  perf_event_set_output(struct perf_event *event, struct perf_event *output_event)
  {
          struct perf_buffer *buffer = NULL, *old_buffer = NULL;
          int ret = -EINVAL;
  
          if (!output_event)
                  goto set;
  
          /* don't allow circular references */
          if (event == output_event)
                  goto out;
  
          /*
           * Don't allow cross-cpu buffers
           */
          if (output_event->cpu != event->cpu)
                  goto out;
  
          /*
           * If its not a per-cpu buffer, it must be the same task.
           */
          if (output_event->cpu == -1 && output_event->ctx != event->ctx)
                  goto out;
  
  set:
          mutex_lock(&event->mmap_mutex);
          /* Can't redirect output if we've got an active mmap() */
          if (atomic_read(&event->mmap_count))
                  goto unlock;
  
          if (output_event) {
                  /* get the buffer we want to redirect to */
                  buffer = perf_buffer_get(output_event);
                  if (!buffer)
                          goto unlock;
          }
  
          old_buffer = event->buffer;
          rcu_assign_pointer(event->buffer, buffer);
          ret = 0;
  unlock:
          mutex_unlock(&event->mmap_mutex);
  
          if (old_buffer)
                  perf_buffer_put(old_buffer);
  out:
          return ret;
  }
  
  /**
   * sys_perf_event_open - open a performance event, associate it to a task/cpu
   *
   * @attr_uptr:  event_id type attributes for monitoring/sampling
   * @pid:                target pid
   * @cpu:                target cpu
   * @group_fd:           group leader event fd
   */
  SYSCALL_DEFINE5(perf_event_open,
                  struct perf_event_attr __user *, attr_uptr,
                  pid_t, pid, int, cpu, int, group_fd, unsigned long, flags)
  {
          struct perf_event *event, *group_leader = NULL, *output_event = NULL;
          struct perf_event_attr attr;
          struct perf_event_context *ctx;
          struct file *event_file = NULL;
          struct file *group_file = NULL;
          int event_fd;
          int fput_needed = 0;
          int err;
  
          /* for future expandability... */
          if (flags & ~(PERF_FLAG_FD_NO_GROUP | PERF_FLAG_FD_OUTPUT))
                  return -EINVAL;
  
          err = perf_copy_attr(attr_uptr, &attr);
          if (err)
                  return err;
  
          if (!attr.exclude_kernel) {
                  if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
                          return -EACCES;
          }
  
          if (attr.freq) {
                  if (attr.sample_freq > sysctl_perf_event_sample_rate)
                          return -EINVAL;
          }
  
          event_fd = get_unused_fd_flags(O_RDWR);
          if (event_fd < 0)
                  return event_fd;
  
          /*
           * Get the target context (task or percpu):
           */
          ctx = find_get_context(pid, cpu);
          if (IS_ERR(ctx)) {
                  err = PTR_ERR(ctx);
                  goto err_fd;
          }
  
          if (group_fd != -1) {
                  group_leader = perf_fget_light(group_fd, &fput_needed);
                  if (IS_ERR(group_leader)) {
                          err = PTR_ERR(group_leader);
                          goto err_put_context;
                  }
                  group_file = group_leader->filp;
                  if (flags & PERF_FLAG_FD_OUTPUT)
                          output_event = group_leader;
                  if (flags & PERF_FLAG_FD_NO_GROUP)
                          group_leader = NULL;
          }
  
          /*
           * Look up the group leader (we will attach this event to it):
           */
          if (group_leader) {
                  err = -EINVAL;
  
                  /*
                   * Do not allow a recursive hierarchy (this new sibling
                   * becoming part of another group-sibling):
                   */
                  if (group_leader->group_leader != group_leader)
                          goto err_put_context;
                  /*
                   * Do not allow to attach to a group in a different
                   * task or CPU context:
                   */
                  if (group_leader->ctx != ctx)
                          goto err_put_context;
                  /*
                   * Only a group leader can be exclusive or pinned
                   */
                  if (attr.exclusive || attr.pinned)
                          goto err_put_context;
          }
  
          event = perf_event_alloc(&attr, cpu, ctx, group_leader,
                                       NULL, NULL, GFP_KERNEL);
          if (IS_ERR(event)) {
                  err = PTR_ERR(event);
                  goto err_put_context;
          }
  
          if (output_event) {
                  err = perf_event_set_output(event, output_event);
                  if (err)
                          goto err_free_put_context;
          }
  
          event_file = anon_inode_getfile("[perf_event]", &perf_fops, event, O_RDWR);
          if (IS_ERR(event_file)) {
                  err = PTR_ERR(event_file);
                  goto err_free_put_context;
          }
  
          event->filp = event_file;
          WARN_ON_ONCE(ctx->parent_ctx);
          mutex_lock(&ctx->mutex);
          perf_install_in_context(ctx, event, cpu);
          ++ctx->generation;
          mutex_unlock(&ctx->mutex);
  
          event->owner = current;
          get_task_struct(current);
          mutex_lock(&current->perf_event_mutex);
          list_add_tail(&event->owner_entry, &current->perf_event_list);
          mutex_unlock(&current->perf_event_mutex);
  
          /*
           * Drop the reference on the group_event after placing the
           * new event on the sibling_list. This ensures destruction
           * of the group leader will find the pointer to itself in
           * perf_group_detach().
           */
          fput_light(group_file, fput_needed);
          fd_install(event_fd, event_file);
          return event_fd;
  
  err_free_put_context:
          free_event(event);
  err_put_context:
          fput_light(group_file, fput_needed);
          put_ctx(ctx);
  err_fd:
          put_unused_fd(event_fd);
          return err;
  }
  
  /**
   * perf_event_create_kernel_counter
   *
   * @attr: attributes of the counter to create
   * @cpu: cpu in which the counter is bound
   * @pid: task to profile
   */
  struct perf_event *
  perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
                                   pid_t pid,
                                   perf_overflow_handler_t overflow_handler)
  {
          struct perf_event *event;
          struct perf_event_context *ctx;
          int err;
  
          /*
           * Get the target context (task or percpu):
           */
  
          ctx = find_get_context(pid, cpu);
          if (IS_ERR(ctx)) {
                  err = PTR_ERR(ctx);
                  goto err_exit;
          }
  
          event = perf_event_alloc(attr, cpu, ctx, NULL,
                                   NULL, overflow_handler, GFP_KERNEL);
          if (IS_ERR(event)) {
                  err = PTR_ERR(event);
                  goto err_put_context;
          }
  
          event->filp = NULL;
          WARN_ON_ONCE(ctx->parent_ctx);
          mutex_lock(&ctx->mutex);
          perf_install_in_context(ctx, event, cpu);
          ++ctx->generation;
          mutex_unlock(&ctx->mutex);
  
          event->owner = current;
          get_task_struct(current);
          mutex_lock(&current->perf_event_mutex);
          list_add_tail(&event->owner_entry, &current->perf_event_list);
          mutex_unlock(&current->perf_event_mutex);
  
          return event;
  
   err_put_context:
          put_ctx(ctx);
   err_exit:
          return ERR_PTR(err);
  }
  EXPORT_SYMBOL_GPL(perf_event_create_kernel_counter);
  
  /*
   * inherit a event from parent task to child task:
   */
  static struct perf_event *
  inherit_event(struct perf_event *parent_event,
                struct task_struct *parent,
                struct perf_event_context *parent_ctx,
                struct task_struct *child,
                struct perf_event *group_leader,
                struct perf_event_context *child_ctx)
  {
          struct perf_event *child_event;
  
          /*
           * Instead of creating recursive hierarchies of events,
           * we link inherited events back to the original parent,
           * which has a filp for sure, which we use as the reference
           * count:
           */
          if (parent_event->parent)
                  parent_event = parent_event->parent;
  
          child_event = perf_event_alloc(&parent_event->attr,
                                             parent_event->cpu, child_ctx,
                                             group_leader, parent_event,
                                             NULL, GFP_KERNEL);
          if (IS_ERR(child_event))
                  return child_event;
          get_ctx(child_ctx);
  
          /*
           * Make the child state follow the state of the parent event,
           * not its attr.disabled bit.  We hold the parent's mutex,
           * so we won't race with perf_event_{en, dis}able_family.
           */
          if (parent_event->state >= PERF_EVENT_STATE_INACTIVE)
                  child_event->state = PERF_EVENT_STATE_INACTIVE;
          else
                  child_event->state = PERF_EVENT_STATE_OFF;
  
          if (parent_event->attr.freq) {
                  u64 sample_period = parent_event->hw.sample_period;
                  struct hw_perf_event *hwc = &child_event->hw;
  
                  hwc->sample_period = sample_period;
                  hwc->last_period   = sample_period;
  
                  local64_set(&hwc->period_left, sample_period);
          }
  
          child_event->overflow_handler = parent_event->overflow_handler;
  
          /*
           * Link it up in the child's context:
           */
          add_event_to_ctx(child_event, child_ctx);
  
          /*
           * Get a reference to the parent filp - we will fput it
           * when the child event exits. This is safe to do because
           * we are in the parent and we know that the filp still
           * exists and has a nonzero count:
           */
          atomic_long_inc(&parent_event->filp->f_count);
  
          /*
           * Link this into the parent event's child list
           */
          WARN_ON_ONCE(parent_event->ctx->parent_ctx);
          mutex_lock(&parent_event->child_mutex);
          list_add_tail(&child_event->child_list, &parent_event->child_list);
          mutex_unlock(&parent_event->child_mutex);
  
          return child_event;
  }
  
  static int inherit_group(struct perf_event *parent_event,
                struct task_struct *parent,
                struct perf_event_context *parent_ctx,
                struct task_struct *child,
                struct perf_event_context *child_ctx)
  {
          struct perf_event *leader;
          struct perf_event *sub;
          struct perf_event *child_ctr;
  
          leader = inherit_event(parent_event, parent, parent_ctx,
                                   child, NULL, child_ctx);
          if (IS_ERR(leader))
                  return PTR_ERR(leader);
          list_for_each_entry(sub, &parent_event->sibling_list, group_entry) {
                  child_ctr = inherit_event(sub, parent, parent_ctx,
                                              child, leader, child_ctx);
                  if (IS_ERR(child_ctr))
                          return PTR_ERR(child_ctr);
          }
          return 0;
  }
  
  static void sync_child_event(struct perf_event *child_event,
                                 struct task_struct *child)
  {
          struct perf_event *parent_event = child_event->parent;
          u64 child_val;
  
          if (child_event->attr.inherit_stat)
                  perf_event_read_event(child_event, child);
  
          child_val = perf_event_count(child_event);
  
          /*
           * Add back the child's count to the parent's count:
           */
          atomic64_add(child_val, &parent_event->child_count);
          atomic64_add(child_event->total_time_enabled,
                       &parent_event->child_total_time_enabled);
          atomic64_add(child_event->total_time_running,
                       &parent_event->child_total_time_running);
  
          /*
           * Remove this event from the parent's list
           */
          WARN_ON_ONCE(parent_event->ctx->parent_ctx);
          mutex_lock(&parent_event->child_mutex);
          list_del_init(&child_event->child_list);
          mutex_unlock(&parent_event->child_mutex);
  
          /*
           * Release the parent event, if this was the last
           * reference to it.
           */
          fput(parent_event->filp);
  }
  
  static void
  __perf_event_exit_task(struct perf_event *child_event,
                           struct perf_event_context *child_ctx,
                           struct task_struct *child)
  {
          struct perf_event *parent_event;
  
          perf_event_remove_from_context(child_event);
  
          parent_event = child_event->parent;
          /*
           * It can happen that parent exits first, and has events
           * that are still around due to the child reference. These
           * events need to be zapped - but otherwise linger.
           */
          if (parent_event) {
                  sync_child_event(child_event, child);
                  free_event(child_event);
          }
  }
  
  /*
   * When a child task exits, feed back event values to parent events.
   */
  void perf_event_exit_task(struct task_struct *child)
  {
          struct perf_event *child_event, *tmp;
          struct perf_event_context *child_ctx;
          unsigned long flags;
  
          if (likely(!child->perf_event_ctxp)) {
                  perf_event_task(child, NULL, 0);
                  return;
          }
  
          local_irq_save(flags);
          /*
           * We can't reschedule here because interrupts are disabled,
           * and either child is current or it is a task that can't be
           * scheduled, so we are now safe from rescheduling changing
           * our context.
           */
          child_ctx = child->perf_event_ctxp;
          __perf_event_task_sched_out(child_ctx);
  
          /*
           * Take the context lock here so that if find_get_context is
           * reading child->perf_event_ctxp, we wait until it has
           * incremented the context's refcount before we do put_ctx below.
           */
          raw_spin_lock(&child_ctx->lock);
          child->perf_event_ctxp = NULL;
          /*
           * If this context is a clone; unclone it so it can't get
           * swapped to another process while we're removing all
           * the events from it.
           */
          unclone_ctx(child_ctx);
          update_context_time(child_ctx);
          raw_spin_unlock_irqrestore(&child_ctx->lock, flags);
  
          /*
           * Report the task dead after unscheduling the events so that we
           * won't get any samples after PERF_RECORD_EXIT. We can however still
           * get a few PERF_RECORD_READ events.
           */
          perf_event_task(child, child_ctx, 0);
  
          /*
           * We can recurse on the same lock type through:
           *
           *   __perf_event_exit_task()
           *     sync_child_event()
           *       fput(parent_event->filp)
           *         perf_release()
           *           mutex_lock(&ctx->mutex)
           *
           * But since its the parent context it won't be the same instance.
           */
          mutex_lock(&child_ctx->mutex);
  
  again:
          list_for_each_entry_safe(child_event, tmp, &child_ctx->pinned_groups,
                                   group_entry)
                  __perf_event_exit_task(child_event, child_ctx, child);
  
          list_for_each_entry_safe(child_event, tmp, &child_ctx->flexible_groups,
                                   group_entry)
                  __perf_event_exit_task(child_event, child_ctx, child);
  
          /*
           * If the last event was a group event, it will have appended all
           * its siblings to the list, but we obtained 'tmp' before that which
           * will still point to the list head terminating the iteration.
           */
          if (!list_empty(&child_ctx->pinned_groups) ||
              !list_empty(&child_ctx->flexible_groups))
                  goto again;
  
          mutex_unlock(&child_ctx->mutex);
  
          put_ctx(child_ctx);
  }
  
  static void perf_free_event(struct perf_event *event,
                              struct perf_event_context *ctx)
  {
          struct perf_event *parent = event->parent;
  
          if (WARN_ON_ONCE(!parent))
                  return;
  
          mutex_lock(&parent->child_mutex);
          list_del_init(&event->child_list);
          mutex_unlock(&parent->child_mutex);
  
          fput(parent->filp);
  
          perf_group_detach(event);
          list_del_event(event, ctx);
          free_event(event);
  }
  
  /*
   * free an unexposed, unused context as created by inheritance by
   * init_task below, used by fork() in case of fail.
   */
  void perf_event_free_task(struct task_struct *task)
  {
          struct perf_event_context *ctx = task->perf_event_ctxp;
          struct perf_event *event, *tmp;
  
          if (!ctx)
                  return;
  
          mutex_lock(&ctx->mutex);
  again:
          list_for_each_entry_safe(event, tmp, &ctx->pinned_groups, group_entry)
                  perf_free_event(event, ctx);
  
          list_for_each_entry_safe(event, tmp, &ctx->flexible_groups,
                                   group_entry)
                  perf_free_event(event, ctx);
  
          if (!list_empty(&ctx->pinned_groups) ||
              !list_empty(&ctx->flexible_groups))
                  goto again;
  
          mutex_unlock(&ctx->mutex);
  
          put_ctx(ctx);
  }
  
  static int
  inherit_task_group(struct perf_event *event, struct task_struct *parent,
                     struct perf_event_context *parent_ctx,
                     struct task_struct *child,
                     int *inherited_all)
  {
          int ret;
          struct perf_event_context *child_ctx = child->perf_event_ctxp;
  
          if (!event->attr.inherit) {
                  *inherited_all = 0;
                  return 0;
          }
  
          if (!child_ctx) {
                  /*
                   * This is executed from the parent task context, so
                   * inherit events that have been marked for cloning.
                   * First allocate and initialize a context for the
                   * child.
                   */
  
                  child_ctx = kzalloc(sizeof(struct perf_event_context),
                                      GFP_KERNEL);
                  if (!child_ctx)
                          return -ENOMEM;
  
                  __perf_event_init_context(child_ctx, child);
                  child->perf_event_ctxp = child_ctx;
                  get_task_struct(child);
          }
  
          ret = inherit_group(event, parent, parent_ctx,
                              child, child_ctx);
  
          if (ret)
                  *inherited_all = 0;
  
          return ret;
  }
  
  
  /*
   * Initialize the perf_event context in task_struct
   */
  int perf_event_init_task(struct task_struct *child)
  {
          struct perf_event_context *child_ctx, *parent_ctx;
          struct perf_event_context *cloned_ctx;
          struct perf_event *event;
          struct task_struct *parent = current;
          int inherited_all = 1;
          int ret = 0;
  
          child->perf_event_ctxp = NULL;
  
          mutex_init(&child->perf_event_mutex);
          INIT_LIST_HEAD(&child->perf_event_list);
  
          if (likely(!parent->perf_event_ctxp))
                  return 0;
  
          /*
           * If the parent's context is a clone, pin it so it won't get
           * swapped under us.
           */
          parent_ctx = perf_pin_task_context(parent);
  
          /*
           * No need to check if parent_ctx != NULL here; since we saw
           * it non-NULL earlier, the only reason for it to become NULL
           * is if we exit, and since we're currently in the middle of
           * a fork we can't be exiting at the same time.
           */
  
          /*
           * Lock the parent list. No need to lock the child - not PID
           * hashed yet and not running, so nobody can access it.
           */
          mutex_lock(&parent_ctx->mutex);
  
          /*
           * We dont have to disable NMIs - we are only looking at
           * the list, not manipulating it:
           */
          list_for_each_entry(event, &parent_ctx->pinned_groups, group_entry) {
                  ret = inherit_task_group(event, parent, parent_ctx, child,
                                           &inherited_all);
                  if (ret)
                          break;
          }
  
          list_for_each_entry(event, &parent_ctx->flexible_groups, group_entry) {
                  ret = inherit_task_group(event, parent, parent_ctx, child,
                                           &inherited_all);
                  if (ret)
                          break;
          }
  
          child_ctx = child->perf_event_ctxp;
  
          if (child_ctx && inherited_all) {
                  /*
                   * Mark the child context as a clone of the parent
                   * context, or of whatever the parent is a clone of.
                   * Note that if the parent is a clone, it could get
                   * uncloned at any point, but that doesn't matter
                   * because the list of events and the generation
                   * count can't have changed since we took the mutex.
                   */
                  cloned_ctx = rcu_dereference(parent_ctx->parent_ctx);
                  if (cloned_ctx) {
                          child_ctx->parent_ctx = cloned_ctx;
                          child_ctx->parent_gen = parent_ctx->parent_gen;
                  } else {
                          child_ctx->parent_ctx = parent_ctx;
                          child_ctx->parent_gen = parent_ctx->generation;
                  }
                  get_ctx(child_ctx->parent_ctx);
          }
  
          mutex_unlock(&parent_ctx->mutex);
  
          perf_unpin_context(parent_ctx);
  
          return ret;
  }
  
  static void __init perf_event_init_all_cpus(void)
  {
          int cpu;
          struct perf_cpu_context *cpuctx;
  
          for_each_possible_cpu(cpu) {
                  cpuctx = &per_cpu(perf_cpu_context, cpu);
                  mutex_init(&cpuctx->hlist_mutex);
                  __perf_event_init_context(&cpuctx->ctx, NULL);
          }
  }
  
  static void __cpuinit perf_event_init_cpu(int cpu)
  {
          struct perf_cpu_context *cpuctx;
  
          cpuctx = &per_cpu(perf_cpu_context, cpu);
  
          spin_lock(&perf_resource_lock);
          cpuctx->max_pertask = perf_max_events - perf_reserved_percpu;
          spin_unlock(&perf_resource_lock);
  
          mutex_lock(&cpuctx->hlist_mutex);
          if (cpuctx->hlist_refcount > 0) {
                  struct swevent_hlist *hlist;
  
                  hlist = kzalloc(sizeof(*hlist), GFP_KERNEL);
                  WARN_ON_ONCE(!hlist);
                  rcu_assign_pointer(cpuctx->swevent_hlist, hlist);
          }
          mutex_unlock(&cpuctx->hlist_mutex);
  }
  
  #ifdef CONFIG_HOTPLUG_CPU
  static void __perf_event_exit_cpu(void *info)
  {
          struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
          struct perf_event_context *ctx = &cpuctx->ctx;
          struct perf_event *event, *tmp;
  
          list_for_each_entry_safe(event, tmp, &ctx->pinned_groups, group_entry)
                  __perf_event_remove_from_context(event);
          list_for_each_entry_safe(event, tmp, &ctx->flexible_groups, group_entry)
                  __perf_event_remove_from_context(event);
  }
  static void perf_event_exit_cpu(int cpu)
  {
          struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
          struct perf_event_context *ctx = &cpuctx->ctx;
  
          mutex_lock(&cpuctx->hlist_mutex);
          swevent_hlist_release(cpuctx);
          mutex_unlock(&cpuctx->hlist_mutex);
  
          mutex_lock(&ctx->mutex);
          smp_call_function_single(cpu, __perf_event_exit_cpu, NULL, 1);
          mutex_unlock(&ctx->mutex);
  }
  #else
  static inline void perf_event_exit_cpu(int cpu) { }
  #endif
  
  static int __cpuinit
  perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
  {
          unsigned int cpu = (long)hcpu;
  
          switch (action) {
  
          case CPU_UP_PREPARE:
          case CPU_UP_PREPARE_FROZEN:
                  perf_event_init_cpu(cpu);
                  break;
  
          case CPU_DOWN_PREPARE:
          case CPU_DOWN_PREPARE_FROZEN:
                  perf_event_exit_cpu(cpu);
                  break;
  
          default:
                  break;
          }
  
          return NOTIFY_OK;
  }
  
  /*
   * This has to have a higher priority than migration_notifier in sched.c.
   */
  static struct notifier_block __cpuinitdata perf_cpu_nb = {
          .notifier_call          = perf_cpu_notify,
          .priority               = 20,
  };
  
  void __init perf_event_init(void)
  {
          perf_event_init_all_cpus();
          perf_cpu_notify(&perf_cpu_nb, (unsigned long)CPU_UP_PREPARE,
                          (void *)(long)smp_processor_id());
          perf_cpu_notify(&perf_cpu_nb, (unsigned long)CPU_ONLINE,
                          (void *)(long)smp_processor_id());
          register_cpu_notifier(&perf_cpu_nb);
  }
  
  static ssize_t perf_show_reserve_percpu(struct sysdev_class *class,
                                          struct sysdev_class_attribute *attr,
                                          char *buf)
  {
          return sprintf(buf, "%d\n", perf_reserved_percpu);
  }
  
  static ssize_t
  perf_set_reserve_percpu(struct sysdev_class *class,
                          struct sysdev_class_attribute *attr,
                          const char *buf,
                          size_t count)
  {
          struct perf_cpu_context *cpuctx;
          unsigned long val;
          int err, cpu, mpt;
  
          err = strict_strtoul(buf, 10, &val);
          if (err)
                  return err;
          if (val > perf_max_events)
                  return -EINVAL;
  
          spin_lock(&perf_resource_lock);
          perf_reserved_percpu = val;
          for_each_online_cpu(cpu) {
                  cpuctx = &per_cpu(perf_cpu_context, cpu);
                  raw_spin_lock_irq(&cpuctx->ctx.lock);
                  mpt = min(perf_max_events - cpuctx->ctx.nr_events,
                            perf_max_events - perf_reserved_percpu);
                  cpuctx->max_pertask = mpt;
                  raw_spin_unlock_irq(&cpuctx->ctx.lock);
          }
          spin_unlock(&perf_resource_lock);
  
          return count;
  }
  
  static ssize_t perf_show_overcommit(struct sysdev_class *class,
                                      struct sysdev_class_attribute *attr,
                                      char *buf)
  {
          return sprintf(buf, "%d\n", perf_overcommit);
  }
  
  static ssize_t
  perf_set_overcommit(struct sysdev_class *class,
                      struct sysdev_class_attribute *attr,
                      const char *buf, size_t count)
  {
          unsigned long val;
          int err;
  
          err = strict_strtoul(buf, 10, &val);
          if (err)
                  return err;
          if (val > 1)
                  return -EINVAL;
  
          spin_lock(&perf_resource_lock);
          perf_overcommit = val;
          spin_unlock(&perf_resource_lock);
  
          return count;
  }
  
  static SYSDEV_CLASS_ATTR(
                                  reserve_percpu,
                                  0644,
                                  perf_show_reserve_percpu,
                                  perf_set_reserve_percpu
                          );
  
  static SYSDEV_CLASS_ATTR(
                                  overcommit,
                                  0644,
                                  perf_show_overcommit,
                                  perf_set_overcommit
                          );
  
  static struct attribute *perfclass_attrs[] = {
          &attr_reserve_percpu.attr,
          &attr_overcommit.attr,
          NULL
  };
  
  static struct attribute_group perfclass_attr_group = {
          .attrs                  = perfclass_attrs,
          .name                   = "perf_events",
  };
  
  static int __init perf_event_sysfs_init(void)
  {
          return sysfs_create_group(&cpu_sysdev_class.kset.kobj,
                                    &perfclass_attr_group);
  }
  device_initcall(perf_event_sysfs_init);