kernel/watchdog.c - third_party/linux - Git at Google

 /*
  * 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 <linux/sched/rt.h>

 #include <asm/irq_regs.h>
 #include <linux/kvm_para.h>
 #include <linux/perf_event.h>

 int watchdog_user_enabled = 1;
 int __read_mostly watchdog_thresh = 10;
 static int __read_mostly watchdog_running;
 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, "0", 1))
 		watchdog_user_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_user_enabled = 0;
 	return 1;
 }
 __setup("nowatchdog", nowatchdog_setup);

 /* deprecated */
 static int __init nosoftlockup_setup(char *str)
 {
 	watchdog_user_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(void)
 {
 	return local_clock() >> 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)
 {
 	__this_cpu_write(watchdog_touch_ts, get_timestamp());
 }

 void touch_softlockup_watchdog(void)
 {
 	/*
 	 * Preemption can be enabled.  It doesn't matter which CPU's timestamp
 	 * gets zeroed here, so use the raw_ operation.
 	 */
 	raw_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)
 {
 	/*
 	 * Using __raw here because some code paths have
 	 * preemption enabled.  If preemption is enabled
 	 * then interrupts should be enabled too, in which
 	 * case we shouldn't have to worry about the watchdog
 	 * going off.
 	 */
 	__raw_get_cpu_var(watchdog_nmi_touch) = 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();

 	/* 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;

 	/* 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 void watchdog_cleanup(unsigned int cpu, bool online)
 {
 	watchdog_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 */

 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,
 	.cleanup		= watchdog_cleanup,
 	.park			= watchdog_disable,
 	.unpark			= watchdog_enable,
 };

 static void restart_watchdog_hrtimer(void *info)
 {
 	struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
 	int ret;

 	/*
 	 * No need to cancel and restart hrtimer if it is currently executing
 	 * because it will reprogram itself with the new period now.
 	 * We should never see it unqueued here because we are running per-cpu
 	 * with interrupts disabled.
 	 */
 	ret = hrtimer_try_to_cancel(hrtimer);
 	if (ret == 1)
 		hrtimer_start(hrtimer, ns_to_ktime(sample_period),
 				HRTIMER_MODE_REL_PINNED);
 }

 static void update_timers(int cpu)
 {
 	/*
 	 * Make sure that perf event counter will adopt to a new
 	 * sampling period. Updating the sampling period directly would
 	 * be much nicer but we do not have an API for that now so
 	 * let's use a big hammer.
 	 * Hrtimer will adopt the new period on the next tick but this
 	 * might be late already so we have to restart the timer as well.
 	 */
 	watchdog_nmi_disable(cpu);
 	smp_call_function_single(cpu, restart_watchdog_hrtimer, NULL, 1);
 	watchdog_nmi_enable(cpu);
 }

 static void update_timers_all_cpus(void)
 {
 	int cpu;

 	get_online_cpus();
 	preempt_disable();
 	for_each_online_cpu(cpu)
 		update_timers(cpu);
 	preempt_enable();
 	put_online_cpus();
 }

 static int watchdog_enable_all_cpus(bool sample_period_changed)
 {
 	int err = 0;

 	if (!watchdog_running) {
 		err = smpboot_register_percpu_thread(&watchdog_threads);
 		if (err)
 			pr_err("Failed to create watchdog threads, disabled\n");
 		else
 			watchdog_running = 1;
 	} else if (sample_period_changed) {
 		update_timers_all_cpus();
 	}

 	return err;
 }

 /* prepare/enable/disable routines */
 /* sysctl functions */
 #ifdef CONFIG_SYSCTL
 static void watchdog_disable_all_cpus(void)
 {
 	if (watchdog_running) {
 		watchdog_running = 0;
 		smpboot_unregister_percpu_thread(&watchdog_threads);
 	}
 }

 /*
  * 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 err, old_thresh, old_enabled;
 	static DEFINE_MUTEX(watchdog_proc_mutex);

 	mutex_lock(&watchdog_proc_mutex);
 	old_thresh = ACCESS_ONCE(watchdog_thresh);
 	old_enabled = ACCESS_ONCE(watchdog_user_enabled);

 	err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 	if (err || !write)
 		goto out;

 	set_sample_period();
 	/*
 	 * Watchdog threads shouldn't be enabled if they are
 	 * disabled. The 'watchdog_running' variable check in
 	 * watchdog_*_all_cpus() function takes care of this.
 	 */
 	if (watchdog_user_enabled && watchdog_thresh)
 		err = watchdog_enable_all_cpus(old_thresh != watchdog_thresh);
 	else
 		watchdog_disable_all_cpus();

 	/* Restore old values on failure */
 	if (err) {
 		watchdog_thresh = old_thresh;
 		watchdog_user_enabled = old_enabled;
 	}
 out:
 	mutex_unlock(&watchdog_proc_mutex);
 	return err;
 }
 #endif /* CONFIG_SYSCTL */

 void __init lockup_detector_init(void)
 {
 	set_sample_period();

 	if (watchdog_user_enabled)
 		watchdog_enable_all_cpus(false);
 }
	/*
	* 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 <linux/sched/rt.h>

	#include <asm/irq_regs.h>
	#include <linux/kvm_para.h>
	#include <linux/perf_event.h>

	int watchdog_user_enabled = 1;
	int __read_mostly watchdog_thresh = 10;
	static int __read_mostly watchdog_running;
	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, "0", 1))
	watchdog_user_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_user_enabled = 0;
	return 1;
	}
	__setup("nowatchdog", nowatchdog_setup);

	/* deprecated */
	static int __init nosoftlockup_setup(char *str)
	{
	watchdog_user_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(void)
	{
	return local_clock() >> 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)
	{
	__this_cpu_write(watchdog_touch_ts, get_timestamp());
	}

	void touch_softlockup_watchdog(void)
	{
	/*
	* Preemption can be enabled. It doesn't matter which CPU's timestamp
	* gets zeroed here, so use the raw_ operation.
	*/
	raw_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)
	{
	/*
	* Using __raw here because some code paths have
	* preemption enabled. If preemption is enabled
	* then interrupts should be enabled too, in which
	* case we shouldn't have to worry about the watchdog
	* going off.
	*/
	__raw_get_cpu_var(watchdog_nmi_touch) = 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();

	/* 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;

	/* 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 void watchdog_cleanup(unsigned int cpu, bool online)
	{
	watchdog_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 */

	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,
	.cleanup = watchdog_cleanup,
	.park = watchdog_disable,
	.unpark = watchdog_enable,
	};

	static void restart_watchdog_hrtimer(void *info)
	{
	struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
	int ret;

	/*
	* No need to cancel and restart hrtimer if it is currently executing
	* because it will reprogram itself with the new period now.
	* We should never see it unqueued here because we are running per-cpu
	* with interrupts disabled.
	*/
	ret = hrtimer_try_to_cancel(hrtimer);
	if (ret == 1)
	hrtimer_start(hrtimer, ns_to_ktime(sample_period),
	HRTIMER_MODE_REL_PINNED);
	}

	static void update_timers(int cpu)
	{
	/*
	* Make sure that perf event counter will adopt to a new
	* sampling period. Updating the sampling period directly would
	* be much nicer but we do not have an API for that now so
	* let's use a big hammer.
	* Hrtimer will adopt the new period on the next tick but this
	* might be late already so we have to restart the timer as well.
	*/
	watchdog_nmi_disable(cpu);
	smp_call_function_single(cpu, restart_watchdog_hrtimer, NULL, 1);
	watchdog_nmi_enable(cpu);
	}

	static void update_timers_all_cpus(void)
	{
	int cpu;

	get_online_cpus();
	preempt_disable();
	for_each_online_cpu(cpu)
	update_timers(cpu);
	preempt_enable();
	put_online_cpus();
	}

	static int watchdog_enable_all_cpus(bool sample_period_changed)
	{
	int err = 0;

	if (!watchdog_running) {
	err = smpboot_register_percpu_thread(&watchdog_threads);
	if (err)
	pr_err("Failed to create watchdog threads, disabled\n");
	else
	watchdog_running = 1;
	} else if (sample_period_changed) {
	update_timers_all_cpus();
	}

	return err;
	}

	/* prepare/enable/disable routines */
	/* sysctl functions */
	#ifdef CONFIG_SYSCTL
	static void watchdog_disable_all_cpus(void)
	{
	if (watchdog_running) {
	watchdog_running = 0;
	smpboot_unregister_percpu_thread(&watchdog_threads);
	}
	}

	/*
	* 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 err, old_thresh, old_enabled;
	static DEFINE_MUTEX(watchdog_proc_mutex);

	mutex_lock(&watchdog_proc_mutex);
	old_thresh = ACCESS_ONCE(watchdog_thresh);
	old_enabled = ACCESS_ONCE(watchdog_user_enabled);

	err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
	if (err \|\| !write)
	goto out;

	set_sample_period();
	/*
	* Watchdog threads shouldn't be enabled if they are
	* disabled. The 'watchdog_running' variable check in
	* watchdog_*_all_cpus() function takes care of this.
	*/
	if (watchdog_user_enabled && watchdog_thresh)
	err = watchdog_enable_all_cpus(old_thresh != watchdog_thresh);
	else
	watchdog_disable_all_cpus();

	/* Restore old values on failure */
	if (err) {
	watchdog_thresh = old_thresh;
	watchdog_user_enabled = old_enabled;
	}
	out:
	mutex_unlock(&watchdog_proc_mutex);
	return err;
	}
	#endif /* CONFIG_SYSCTL */

	void __init lockup_detector_init(void)
	{
	set_sample_period();

	if (watchdog_user_enabled)
	watchdog_enable_all_cpus(false);
	}