2 * Detect hard and soft lockups on a system
4 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
6 * this code detects hard lockups: incidents in where on a CPU
7 * the kernel does not respond to anything except NMI.
9 * Note: Most of this code is borrowed heavily from softlockup.c,
10 * so thanks to Ingo for the initial implementation.
11 * Some chunks also taken from arch/x86/kernel/apic/nmi.c, thanks
12 * to those contributors as well.
16 #include <linux/cpu.h>
17 #include <linux/nmi.h>
18 #include <linux/init.h>
19 #include <linux/delay.h>
20 #include <linux/freezer.h>
21 #include <linux/kthread.h>
22 #include <linux/lockdep.h>
23 #include <linux/notifier.h>
24 #include <linux/module.h>
25 #include <linux/sysctl.h>
27 #include <asm/irq_regs.h>
28 #include <linux/perf_event.h>
31 int __read_mostly softlockup_thresh = 60;
33 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
34 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
35 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
36 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
37 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
38 #ifdef CONFIG_HARDLOCKUP_DETECTOR
39 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
40 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
41 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
42 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
43 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
46 static int __read_mostly did_panic;
47 static int __initdata no_watchdog;
52 * Should we panic when a soft-lockup or hard-lockup occurs:
54 #ifdef CONFIG_HARDLOCKUP_DETECTOR
55 static int hardlockup_panic;
57 static int __init hardlockup_panic_setup(char *str)
59 if (!strncmp(str, "panic", 5))
63 __setup("nmi_watchdog=", hardlockup_panic_setup);
66 unsigned int __read_mostly softlockup_panic =
67 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
69 static int __init softlockup_panic_setup(char *str)
71 softlockup_panic = simple_strtoul(str, NULL, 0);
75 __setup("softlockup_panic=", softlockup_panic_setup);
77 static int __init nowatchdog_setup(char *str)
82 __setup("nowatchdog", nowatchdog_setup);
85 static int __init nosoftlockup_setup(char *str)
90 __setup("nosoftlockup", nosoftlockup_setup);
95 * Returns seconds, approximately. We don't need nanosecond
96 * resolution, and we don't need to waste time with a big divide when
99 static unsigned long get_timestamp(int this_cpu)
101 return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */
104 static unsigned long get_sample_period(void)
107 * convert softlockup_thresh from seconds to ns
108 * the divide by 5 is to give hrtimer 5 chances to
109 * increment before the hardlockup detector generates
112 return softlockup_thresh / 5 * NSEC_PER_SEC;
115 /* Commands for resetting the watchdog */
116 static void __touch_watchdog(void)
118 int this_cpu = smp_processor_id();
120 __get_cpu_var(watchdog_touch_ts) = get_timestamp(this_cpu);
123 void touch_softlockup_watchdog(void)
125 __get_cpu_var(watchdog_touch_ts) = 0;
127 EXPORT_SYMBOL(touch_softlockup_watchdog);
129 void touch_all_softlockup_watchdogs(void)
134 * this is done lockless
135 * do we care if a 0 races with a timestamp?
136 * all it means is the softlock check starts one cycle later
138 for_each_online_cpu(cpu)
139 per_cpu(watchdog_touch_ts, cpu) = 0;
142 #ifdef CONFIG_HARDLOCKUP_DETECTOR
143 void touch_nmi_watchdog(void)
145 __get_cpu_var(watchdog_nmi_touch) = true;
146 touch_softlockup_watchdog();
148 EXPORT_SYMBOL(touch_nmi_watchdog);
152 void touch_softlockup_watchdog_sync(void)
154 __raw_get_cpu_var(softlockup_touch_sync) = true;
155 __raw_get_cpu_var(watchdog_touch_ts) = 0;
158 #ifdef CONFIG_HARDLOCKUP_DETECTOR
159 /* watchdog detector functions */
160 static int is_hardlockup(void)
162 unsigned long hrint = __get_cpu_var(hrtimer_interrupts);
164 if (__get_cpu_var(hrtimer_interrupts_saved) == hrint)
167 __get_cpu_var(hrtimer_interrupts_saved) = hrint;
172 static int is_softlockup(unsigned long touch_ts)
174 unsigned long now = get_timestamp(smp_processor_id());
176 /* Warn about unreasonable delays: */
177 if (time_after(now, touch_ts + softlockup_thresh))
178 return now - touch_ts;
184 watchdog_panic(struct notifier_block *this, unsigned long event, void *ptr)
191 static struct notifier_block panic_block = {
192 .notifier_call = watchdog_panic,
195 #ifdef CONFIG_HARDLOCKUP_DETECTOR
196 static struct perf_event_attr wd_hw_attr = {
197 .type = PERF_TYPE_HARDWARE,
198 .config = PERF_COUNT_HW_CPU_CYCLES,
199 .size = sizeof(struct perf_event_attr),
204 /* Callback function for perf event subsystem */
205 void watchdog_overflow_callback(struct perf_event *event, int nmi,
206 struct perf_sample_data *data,
207 struct pt_regs *regs)
209 /* Ensure the watchdog never gets throttled */
210 event->hw.interrupts = 0;
212 if (__get_cpu_var(watchdog_nmi_touch) == true) {
213 __get_cpu_var(watchdog_nmi_touch) = false;
217 /* check for a hardlockup
218 * This is done by making sure our timer interrupt
219 * is incrementing. The timer interrupt should have
220 * fired multiple times before we overflow'd. If it hasn't
221 * then this is a good indication the cpu is stuck
223 if (is_hardlockup()) {
224 int this_cpu = smp_processor_id();
226 /* only print hardlockups once */
227 if (__get_cpu_var(hard_watchdog_warn) == true)
230 if (hardlockup_panic)
231 panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
233 WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
235 __get_cpu_var(hard_watchdog_warn) = true;
239 __get_cpu_var(hard_watchdog_warn) = false;
242 static void watchdog_interrupt_count(void)
244 __get_cpu_var(hrtimer_interrupts)++;
247 static inline void watchdog_interrupt_count(void) { return; }
248 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
250 /* watchdog kicker functions */
251 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
253 unsigned long touch_ts = __get_cpu_var(watchdog_touch_ts);
254 struct pt_regs *regs = get_irq_regs();
257 /* kick the hardlockup detector */
258 watchdog_interrupt_count();
260 /* kick the softlockup detector */
261 wake_up_process(__get_cpu_var(softlockup_watchdog));
264 hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
267 if (unlikely(__get_cpu_var(softlockup_touch_sync))) {
269 * If the time stamp was touched atomically
270 * make sure the scheduler tick is up to date.
272 __get_cpu_var(softlockup_touch_sync) = false;
276 return HRTIMER_RESTART;
279 /* check for a softlockup
280 * This is done by making sure a high priority task is
281 * being scheduled. The task touches the watchdog to
282 * indicate it is getting cpu time. If it hasn't then
283 * this is a good indication some task is hogging the cpu
285 duration = is_softlockup(touch_ts);
286 if (unlikely(duration)) {
288 if (__get_cpu_var(soft_watchdog_warn) == true)
289 return HRTIMER_RESTART;
291 printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
292 smp_processor_id(), duration,
293 current->comm, task_pid_nr(current));
295 print_irqtrace_events(current);
301 if (softlockup_panic)
302 panic("softlockup: hung tasks");
303 __get_cpu_var(soft_watchdog_warn) = true;
305 __get_cpu_var(soft_watchdog_warn) = false;
307 return HRTIMER_RESTART;
312 * The watchdog thread - touches the timestamp.
314 static int watchdog(void *unused)
316 struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
317 struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
319 sched_setscheduler(current, SCHED_FIFO, ¶m);
321 /* initialize timestamp */
324 /* kick off the timer for the hardlockup detector */
325 /* done here because hrtimer_start can only pin to smp_processor_id() */
326 hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
327 HRTIMER_MODE_REL_PINNED);
329 set_current_state(TASK_INTERRUPTIBLE);
331 * Run briefly once per second to reset the softlockup timestamp.
332 * If this gets delayed for more than 60 seconds then the
333 * debug-printout triggers in watchdog_timer_fn().
335 while (!kthread_should_stop()) {
339 if (kthread_should_stop())
342 set_current_state(TASK_INTERRUPTIBLE);
344 __set_current_state(TASK_RUNNING);
350 #ifdef CONFIG_HARDLOCKUP_DETECTOR
351 static int watchdog_nmi_enable(int cpu)
353 struct perf_event_attr *wd_attr;
354 struct perf_event *event = per_cpu(watchdog_ev, cpu);
356 /* is it already setup and enabled? */
357 if (event && event->state > PERF_EVENT_STATE_OFF)
360 /* it is setup but not enabled */
364 /* Try to register using hardware perf events */
365 wd_attr = &wd_hw_attr;
366 wd_attr->sample_period = hw_nmi_get_sample_period();
367 event = perf_event_create_kernel_counter(wd_attr, cpu, -1, watchdog_overflow_callback);
368 if (!IS_ERR(event)) {
369 printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
373 printk(KERN_ERR "NMI watchdog failed to create perf event on cpu%i: %p\n", cpu, event);
374 return PTR_ERR(event);
378 per_cpu(watchdog_ev, cpu) = event;
380 perf_event_enable(per_cpu(watchdog_ev, cpu));
385 static void watchdog_nmi_disable(int cpu)
387 struct perf_event *event = per_cpu(watchdog_ev, cpu);
390 perf_event_disable(event);
391 per_cpu(watchdog_ev, cpu) = NULL;
393 /* should be in cleanup, but blocks oprofile */
394 perf_event_release_kernel(event);
399 static int watchdog_nmi_enable(int cpu) { return 0; }
400 static void watchdog_nmi_disable(int cpu) { return; }
401 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
403 /* prepare/enable/disable routines */
404 static int watchdog_prepare_cpu(int cpu)
406 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
408 WARN_ON(per_cpu(softlockup_watchdog, cpu));
409 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
410 hrtimer->function = watchdog_timer_fn;
415 static int watchdog_enable(int cpu)
417 struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
420 /* enable the perf event */
421 err = watchdog_nmi_enable(cpu);
425 /* create the watchdog thread */
427 p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
429 printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
432 kthread_bind(p, cpu);
433 per_cpu(watchdog_touch_ts, cpu) = 0;
434 per_cpu(softlockup_watchdog, cpu) = p;
441 static void watchdog_disable(int cpu)
443 struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
444 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
447 * cancel the timer first to stop incrementing the stats
448 * and waking up the kthread
450 hrtimer_cancel(hrtimer);
452 /* disable the perf event */
453 watchdog_nmi_disable(cpu);
455 /* stop the watchdog thread */
457 per_cpu(softlockup_watchdog, cpu) = NULL;
461 /* if any cpu succeeds, watchdog is considered enabled for the system */
462 watchdog_enabled = 1;
465 static void watchdog_enable_all_cpus(void)
470 for_each_online_cpu(cpu)
471 result += watchdog_enable(cpu);
474 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
478 static void watchdog_disable_all_cpus(void)
482 for_each_online_cpu(cpu)
483 watchdog_disable(cpu);
485 /* if all watchdogs are disabled, then they are disabled for the system */
486 watchdog_enabled = 0;
490 /* sysctl functions */
493 * proc handler for /proc/sys/kernel/nmi_watchdog
496 int proc_dowatchdog_enabled(struct ctl_table *table, int write,
497 void __user *buffer, size_t *length, loff_t *ppos)
499 proc_dointvec(table, write, buffer, length, ppos);
501 if (watchdog_enabled)
502 watchdog_enable_all_cpus();
504 watchdog_disable_all_cpus();
508 int proc_dowatchdog_thresh(struct ctl_table *table, int write,
510 size_t *lenp, loff_t *ppos)
512 return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
514 #endif /* CONFIG_SYSCTL */
518 * Create/destroy watchdog threads as CPUs come and go:
521 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
523 int hotcpu = (unsigned long)hcpu;
528 case CPU_UP_PREPARE_FROZEN:
529 err = watchdog_prepare_cpu(hotcpu);
532 case CPU_ONLINE_FROZEN:
533 err = watchdog_enable(hotcpu);
535 #ifdef CONFIG_HOTPLUG_CPU
536 case CPU_UP_CANCELED:
537 case CPU_UP_CANCELED_FROZEN:
538 watchdog_disable(hotcpu);
541 case CPU_DEAD_FROZEN:
542 watchdog_disable(hotcpu);
544 #endif /* CONFIG_HOTPLUG_CPU */
546 return notifier_from_errno(err);
549 static struct notifier_block __cpuinitdata cpu_nfb = {
550 .notifier_call = cpu_callback
553 static int __init spawn_watchdog_task(void)
555 void *cpu = (void *)(long)smp_processor_id();
561 err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
562 WARN_ON(notifier_to_errno(err));
564 cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
565 register_cpu_notifier(&cpu_nfb);
567 atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
571 early_initcall(spawn_watchdog_task);