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

     /*
      * Detect hard and soft lockups on a system
      *
      * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
      *
      * Note: Most of this code is borrowed heavily from the original softlockup
      * detector, so thanks to Ingo for the initial implementation.
      * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
      * to those contributors as well.
     */
    
    #define pr_fmt(fmt) "NMI watchdog: " fmt
    
    #include <linux/mm.h>
    #include <linux/cpu.h>
    #include <linux/nmi.h>
    #include <linux/init.h>
    #include <linux/delay.h>
    #include <linux/freezer.h>
    #include <linux/kthread.h>
    #include <linux/lockdep.h>
    #include <linux/notifier.h>
    #include <linux/module.h>
    #include <linux/sysctl.h>
    #include <linux/smpboot.h>
    
    #include <asm/irq_regs.h>
    #include <linux/kvm_para.h>
    #include <linux/perf_event.h>
    
    int watchdog_enabled = 1;
    int __read_mostly watchdog_thresh = 10;
    static int __read_mostly watchdog_disabled;
    static u64 __read_mostly sample_period;
    
    static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
    static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
    static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
    static DEFINE_PER_CPU(bool, softlockup_touch_sync);
    static DEFINE_PER_CPU(bool, soft_watchdog_warn);
    static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
    static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
    #ifdef CONFIG_HARDLOCKUP_DETECTOR
    static DEFINE_PER_CPU(bool, hard_watchdog_warn);
    static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
    static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
    static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
    #endif
    
    /* boot commands */
    /*
     * Should we panic when a soft-lockup or hard-lockup occurs:
     */
    #ifdef CONFIG_HARDLOCKUP_DETECTOR
    static int hardlockup_panic =
                            CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
    
    static int __init hardlockup_panic_setup(char *str)
    {
            if (!strncmp(str, "panic", 5))
                    hardlockup_panic = 1;
            else if (!strncmp(str, "nopanic", 7))
                    hardlockup_panic = 0;
            else if (!strncmp(str, "", 1))
                    watchdog_enabled = 0;
            return 1;
    }
    __setup("nmi_watchdog=", hardlockup_panic_setup);
    #endif
    
    unsigned int __read_mostly softlockup_panic =
                            CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
    
    static int __init softlockup_panic_setup(char *str)
    {
            softlockup_panic = simple_strtoul(str, NULL, 0);
    
            return 1;
    }
    __setup("softlockup_panic=", softlockup_panic_setup);
    
    static int __init nowatchdog_setup(char *str)
    {
            watchdog_enabled = 0;
            return 1;
    }
    __setup("nowatchdog", nowatchdog_setup);
    
    /* deprecated */
    static int __init nosoftlockup_setup(char *str)
    {
            watchdog_enabled = 0;
            return 1;
    }
    __setup("nosoftlockup", nosoftlockup_setup);
    /*  */
    
    /*
     * Hard-lockup warnings should be triggered after just a few seconds. Soft-
    * lockups can have false positives under extreme conditions. So we generally
    * want a higher threshold for soft lockups than for hard lockups. So we couple
    * the thresholds with a factor: we make the soft threshold twice the amount of
    * time the hard threshold is.
    */
   static int get_softlockup_thresh(void)
   {
           return watchdog_thresh * 2;
   }
   
   /*
    * Returns seconds, approximately.  We don't need nanosecond
    * resolution, and we don't need to waste time with a big divide when
    * 2^30ns == 1.074s.
    */
   static unsigned long get_timestamp(int this_cpu)
   {
           return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
   }
   
   static void set_sample_period(void)
   {
           /*
            * convert watchdog_thresh from seconds to ns
            * the divide by 5 is to give hrtimer several chances (two
            * or three with the current relation between the soft
            * and hard thresholds) to increment before the
            * hardlockup detector generates a warning
            */
           sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
   }
   
   /* Commands for resetting the watchdog */
   static void __touch_watchdog(void)
   {
           int this_cpu = smp_processor_id();
   
           __this_cpu_write(watchdog_touch_ts, get_timestamp(this_cpu));
   }
   
   void touch_softlockup_watchdog(void)
   {
           __this_cpu_write(watchdog_touch_ts, 0);
   }
   EXPORT_SYMBOL(touch_softlockup_watchdog);
   
   void touch_all_softlockup_watchdogs(void)
   {
           int cpu;
   
           /*
            * this is done lockless
            * do we care if a 0 races with a timestamp?
            * all it means is the softlock check starts one cycle later
            */
           for_each_online_cpu(cpu)
                   per_cpu(watchdog_touch_ts, cpu) = 0;
   }
   
   #ifdef CONFIG_HARDLOCKUP_DETECTOR
   void touch_nmi_watchdog(void)
   {
           if (watchdog_enabled) {
                   unsigned cpu;
   
                   for_each_present_cpu(cpu) {
                           if (per_cpu(watchdog_nmi_touch, cpu) != true)
                                   per_cpu(watchdog_nmi_touch, cpu) = true;
                   }
           }
           touch_softlockup_watchdog();
   }
   EXPORT_SYMBOL(touch_nmi_watchdog);
   
   #endif
   
   void touch_softlockup_watchdog_sync(void)
   {
           __raw_get_cpu_var(softlockup_touch_sync) = true;
           __raw_get_cpu_var(watchdog_touch_ts) = 0;
   }
   
   #ifdef CONFIG_HARDLOCKUP_DETECTOR
   /* watchdog detector functions */
   static int is_hardlockup(void)
   {
           unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
   
           if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
                   return 1;
   
           __this_cpu_write(hrtimer_interrupts_saved, hrint);
           return 0;
   }
   #endif
   
   static int is_softlockup(unsigned long touch_ts)
   {
           unsigned long now = get_timestamp(smp_processor_id());
   
           /* Warn about unreasonable delays: */
           if (time_after(now, touch_ts + get_softlockup_thresh()))
                   return now - touch_ts;
   
           return 0;
   }
   
   #ifdef CONFIG_HARDLOCKUP_DETECTOR
   
   static struct perf_event_attr wd_hw_attr = {
           .type           = PERF_TYPE_HARDWARE,
           .config         = PERF_COUNT_HW_CPU_CYCLES,
           .size           = sizeof(struct perf_event_attr),
           .pinned         = 1,
           .disabled       = 1,
   };
   
   /* Callback function for perf event subsystem */
   static void watchdog_overflow_callback(struct perf_event *event,
                    struct perf_sample_data *data,
                    struct pt_regs *regs)
   {
           /* Ensure the watchdog never gets throttled */
           event->hw.interrupts = 0;
   
           if (__this_cpu_read(watchdog_nmi_touch) == true) {
                   __this_cpu_write(watchdog_nmi_touch, false);
                   return;
           }
   
           /* check for a hardlockup
            * This is done by making sure our timer interrupt
            * is incrementing.  The timer interrupt should have
            * fired multiple times before we overflow'd.  If it hasn't
            * then this is a good indication the cpu is stuck
            */
           if (is_hardlockup()) {
                   int this_cpu = smp_processor_id();
   
                   /* only print hardlockups once */
                   if (__this_cpu_read(hard_watchdog_warn) == true)
                           return;
   
                   if (hardlockup_panic)
                           panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
                   else
                           WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
   
                   __this_cpu_write(hard_watchdog_warn, true);
                   return;
           }
   
           __this_cpu_write(hard_watchdog_warn, false);
           return;
   }
   #endif /* CONFIG_HARDLOCKUP_DETECTOR */
   
   static void watchdog_interrupt_count(void)
   {
           __this_cpu_inc(hrtimer_interrupts);
   }
   
   static int watchdog_nmi_enable(unsigned int cpu);
   static void watchdog_nmi_disable(unsigned int cpu);
   
   /* watchdog kicker functions */
   static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
   {
           unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
           struct pt_regs *regs = get_irq_regs();
           int duration;
   
           /* kick the hardlockup detector */
           watchdog_interrupt_count();
   
           /* kick the softlockup detector */
           wake_up_process(__this_cpu_read(softlockup_watchdog));
   
           /* .. and repeat */
           hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
   
           if (touch_ts == 0) {
                   if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
                           /*
                            * If the time stamp was touched atomically
                            * make sure the scheduler tick is up to date.
                            */
                           __this_cpu_write(softlockup_touch_sync, false);
                           sched_clock_tick();
                   }
   
                   /* Clear the guest paused flag on watchdog reset */
                   kvm_check_and_clear_guest_paused();
                   __touch_watchdog();
                   return HRTIMER_RESTART;
           }
   
           /* check for a softlockup
            * This is done by making sure a high priority task is
            * being scheduled.  The task touches the watchdog to
            * indicate it is getting cpu time.  If it hasn't then
            * this is a good indication some task is hogging the cpu
            */
           duration = is_softlockup(touch_ts);
           if (unlikely(duration)) {
                   /*
                    * If a virtual machine is stopped by the host it can look to
                    * the watchdog like a soft lockup, check to see if the host
                    * stopped the vm before we issue the warning
                    */
                   if (kvm_check_and_clear_guest_paused())
                           return HRTIMER_RESTART;
   
                   /* only warn once */
                   if (__this_cpu_read(soft_watchdog_warn) == true)
                           return HRTIMER_RESTART;
   
                   printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
                           smp_processor_id(), duration,
                           current->comm, task_pid_nr(current));
                   print_modules();
                   print_irqtrace_events(current);
                   if (regs)
                           show_regs(regs);
                   else
                           dump_stack();
   
                   if (softlockup_panic)
                           panic("softlockup: hung tasks");
                   __this_cpu_write(soft_watchdog_warn, true);
           } else
                   __this_cpu_write(soft_watchdog_warn, false);
   
           return HRTIMER_RESTART;
   }
   
   static void watchdog_set_prio(unsigned int policy, unsigned int prio)
   {
           struct sched_param param = { .sched_priority = prio };
   
           sched_setscheduler(current, policy, &param);
   }
   
   static void watchdog_enable(unsigned int cpu)
   {
           struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
   
           /* kick off the timer for the hardlockup detector */
           hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
           hrtimer->function = watchdog_timer_fn;
   
           if (!watchdog_enabled) {
                   kthread_park(current);
                   return;
           }
   
           /* Enable the perf event */
           watchdog_nmi_enable(cpu);
   
           /* done here because hrtimer_start can only pin to smp_processor_id() */
           hrtimer_start(hrtimer, ns_to_ktime(sample_period),
                         HRTIMER_MODE_REL_PINNED);
   
           /* initialize timestamp */
           watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
           __touch_watchdog();
   }
   
   static void watchdog_disable(unsigned int cpu)
   {
           struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
   
           watchdog_set_prio(SCHED_NORMAL, 0);
           hrtimer_cancel(hrtimer);
           /* disable the perf event */
           watchdog_nmi_disable(cpu);
   }
   
   static int watchdog_should_run(unsigned int cpu)
   {
           return __this_cpu_read(hrtimer_interrupts) !=
                   __this_cpu_read(soft_lockup_hrtimer_cnt);
   }
   
   /*
    * The watchdog thread function - touches the timestamp.
    *
    * It only runs once every sample_period seconds (4 seconds by
    * default) to reset the softlockup timestamp. If this gets delayed
    * for more than 2*watchdog_thresh seconds then the debug-printout
    * triggers in watchdog_timer_fn().
    */
   static void watchdog(unsigned int cpu)
   {
           __this_cpu_write(soft_lockup_hrtimer_cnt,
                            __this_cpu_read(hrtimer_interrupts));
           __touch_watchdog();
   }
   
   #ifdef CONFIG_HARDLOCKUP_DETECTOR
   /*
    * People like the simple clean cpu node info on boot.
    * Reduce the watchdog noise by only printing messages
    * that are different from what cpu0 displayed.
    */
   static unsigned long cpu0_err;
   
   static int watchdog_nmi_enable(unsigned int cpu)
   {
           struct perf_event_attr *wd_attr;
           struct perf_event *event = per_cpu(watchdog_ev, cpu);
   
           /* is it already setup and enabled? */
           if (event && event->state > PERF_EVENT_STATE_OFF)
                   goto out;
   
           /* it is setup but not enabled */
           if (event != NULL)
                   goto out_enable;
   
           wd_attr = &wd_hw_attr;
           wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
   
           /* Try to register using hardware perf events */
           event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
   
           /* save cpu0 error for future comparision */
           if (cpu == 0 && IS_ERR(event))
                   cpu0_err = PTR_ERR(event);
   
           if (!IS_ERR(event)) {
                   /* only print for cpu0 or different than cpu0 */
                   if (cpu == 0 || cpu0_err)
                           pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
                   goto out_save;
           }
   
           /* skip displaying the same error again */
           if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
                   return PTR_ERR(event);
   
           /* vary the KERN level based on the returned errno */
           if (PTR_ERR(event) == -EOPNOTSUPP)
                   pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
           else if (PTR_ERR(event) == -ENOENT)
                   pr_warning("disabled (cpu%i): hardware events not enabled\n",
                            cpu);
           else
                   pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
                           cpu, PTR_ERR(event));
           return PTR_ERR(event);
   
           /* success path */
   out_save:
           per_cpu(watchdog_ev, cpu) = event;
   out_enable:
           perf_event_enable(per_cpu(watchdog_ev, cpu));
   out:
           return 0;
   }
   
   static void watchdog_nmi_disable(unsigned int cpu)
   {
           struct perf_event *event = per_cpu(watchdog_ev, cpu);
   
           if (event) {
                   perf_event_disable(event);
                   per_cpu(watchdog_ev, cpu) = NULL;
   
                   /* should be in cleanup, but blocks oprofile */
                   perf_event_release_kernel(event);
           }
           return;
   }
   #else
   static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
   static void watchdog_nmi_disable(unsigned int cpu) { return; }
   #endif /* CONFIG_HARDLOCKUP_DETECTOR */
   
   /* prepare/enable/disable routines */
   /* sysctl functions */
   #ifdef CONFIG_SYSCTL
   static void watchdog_enable_all_cpus(void)
   {
           unsigned int cpu;
   
           if (watchdog_disabled) {
                   watchdog_disabled = 0;
                   for_each_online_cpu(cpu)
                           kthread_unpark(per_cpu(softlockup_watchdog, cpu));
           }
   }
   
   static void watchdog_disable_all_cpus(void)
   {
           unsigned int cpu;
   
           if (!watchdog_disabled) {
                   watchdog_disabled = 1;
                   for_each_online_cpu(cpu)
                           kthread_park(per_cpu(softlockup_watchdog, cpu));
           }
   }
   
   /*
    * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
    */
   
   int proc_dowatchdog(struct ctl_table *table, int write,
                       void __user *buffer, size_t *lenp, loff_t *ppos)
   {
           int ret;
   
           if (watchdog_disabled < 0)
                   return -ENODEV;
   
           ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
           if (ret || !write)
                   return ret;
   
           set_sample_period();
           if (watchdog_enabled && watchdog_thresh)
                   watchdog_enable_all_cpus();
           else
                   watchdog_disable_all_cpus();
   
           return ret;
   }
   #endif /* CONFIG_SYSCTL */
   
   static struct smp_hotplug_thread watchdog_threads = {
           .store                  = &softlockup_watchdog,
           .thread_should_run      = watchdog_should_run,
           .thread_fn              = watchdog,
           .thread_comm            = "watchdog/%u",
           .setup                  = watchdog_enable,
           .park                   = watchdog_disable,
           .unpark                 = watchdog_enable,
   };
   
   void __init lockup_detector_init(void)
   {
           set_sample_period();
           if (smpboot_register_percpu_thread(&watchdog_threads)) {
                   pr_err("Failed to create watchdog threads, disabled\n");
                   watchdog_disabled = -ENODEV;
           }
   }

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