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, hard_watchdog_warn);
38 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
39 #ifdef CONFIG_PERF_EVENTS_NMI
40 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
41 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
42 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
45 static int __read_mostly did_panic;
46 static int __initdata no_watchdog;
51 * Should we panic when a soft-lockup or hard-lockup occurs:
53 #ifdef CONFIG_PERF_EVENTS_NMI
54 static int hardlockup_panic;
56 static int __init hardlockup_panic_setup(char *str)
58 if (!strncmp(str, "panic", 5))
62 __setup("nmi_watchdog=", hardlockup_panic_setup);
65 unsigned int __read_mostly softlockup_panic =
66 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
68 static int __init softlockup_panic_setup(char *str)
70 softlockup_panic = simple_strtoul(str, NULL, 0);
74 __setup("softlockup_panic=", softlockup_panic_setup);
76 static int __init nowatchdog_setup(char *str)
81 __setup("nowatchdog", nowatchdog_setup);
84 static int __init nosoftlockup_setup(char *str)
89 __setup("nosoftlockup", nosoftlockup_setup);
94 * Returns seconds, approximately. We don't need nanosecond
95 * resolution, and we don't need to waste time with a big divide when
98 static unsigned long get_timestamp(int this_cpu)
100 return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */
103 static unsigned long get_sample_period(void)
106 * convert softlockup_thresh from seconds to ns
107 * the divide by 5 is to give hrtimer 5 chances to
108 * increment before the hardlockup detector generates
111 return softlockup_thresh / 5 * NSEC_PER_SEC;
114 /* Commands for resetting the watchdog */
115 static void __touch_watchdog(void)
117 int this_cpu = raw_smp_processor_id();
119 __get_cpu_var(watchdog_touch_ts) = get_timestamp(this_cpu);
122 void touch_watchdog(void)
124 __get_cpu_var(watchdog_touch_ts) = 0;
126 EXPORT_SYMBOL(touch_watchdog);
128 void touch_all_watchdog(void)
133 * this is done lockless
134 * do we care if a 0 races with a timestamp?
135 * all it means is the softlock check starts one cycle later
137 for_each_online_cpu(cpu)
138 per_cpu(watchdog_touch_ts, cpu) = 0;
141 void touch_nmi_watchdog(void)
145 EXPORT_SYMBOL(touch_nmi_watchdog);
147 void touch_all_nmi_watchdog(void)
149 touch_all_watchdog();
152 void touch_softlockup_watchdog(void)
157 void touch_all_softlockup_watchdogs(void)
159 touch_all_watchdog();
162 void touch_softlockup_watchdog_sync(void)
164 __raw_get_cpu_var(softlockup_touch_sync) = true;
165 __raw_get_cpu_var(watchdog_touch_ts) = 0;
168 void softlockup_tick(void)
172 #ifdef CONFIG_PERF_EVENTS_NMI
173 /* watchdog detector functions */
174 static int is_hardlockup(int cpu)
176 unsigned long hrint = per_cpu(hrtimer_interrupts, cpu);
178 if (per_cpu(hrtimer_interrupts_saved, cpu) == hrint)
181 per_cpu(hrtimer_interrupts_saved, cpu) = hrint;
186 static int is_softlockup(unsigned long touch_ts, int cpu)
188 unsigned long now = get_timestamp(cpu);
190 /* Warn about unreasonable delays: */
191 if (time_after(now, touch_ts + softlockup_thresh))
192 return now - touch_ts;
198 watchdog_panic(struct notifier_block *this, unsigned long event, void *ptr)
205 static struct notifier_block panic_block = {
206 .notifier_call = watchdog_panic,
209 #ifdef CONFIG_PERF_EVENTS_NMI
210 static struct perf_event_attr wd_hw_attr = {
211 .type = PERF_TYPE_HARDWARE,
212 .config = PERF_COUNT_HW_CPU_CYCLES,
213 .size = sizeof(struct perf_event_attr),
218 /* Callback function for perf event subsystem */
219 void watchdog_overflow_callback(struct perf_event *event, int nmi,
220 struct perf_sample_data *data,
221 struct pt_regs *regs)
223 int this_cpu = smp_processor_id();
224 unsigned long touch_ts = per_cpu(watchdog_touch_ts, this_cpu);
231 /* check for a hardlockup
232 * This is done by making sure our timer interrupt
233 * is incrementing. The timer interrupt should have
234 * fired multiple times before we overflow'd. If it hasn't
235 * then this is a good indication the cpu is stuck
237 if (is_hardlockup(this_cpu)) {
238 /* only print hardlockups once */
239 if (__get_cpu_var(hard_watchdog_warn) == true)
242 if (hardlockup_panic)
243 panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
245 WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
247 __get_cpu_var(hard_watchdog_warn) = true;
251 __get_cpu_var(hard_watchdog_warn) = false;
254 static void watchdog_interrupt_count(void)
256 __get_cpu_var(hrtimer_interrupts)++;
259 static inline void watchdog_interrupt_count(void) { return; }
260 #endif /* CONFIG_PERF_EVENTS_NMI */
262 /* watchdog kicker functions */
263 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
265 int this_cpu = smp_processor_id();
266 unsigned long touch_ts = __get_cpu_var(watchdog_touch_ts);
267 struct pt_regs *regs = get_irq_regs();
270 /* kick the hardlockup detector */
271 watchdog_interrupt_count();
273 /* kick the softlockup detector */
274 wake_up_process(__get_cpu_var(softlockup_watchdog));
277 hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
280 if (unlikely(per_cpu(softlockup_touch_sync, this_cpu))) {
282 * If the time stamp was touched atomically
283 * make sure the scheduler tick is up to date.
285 per_cpu(softlockup_touch_sync, this_cpu) = false;
289 return HRTIMER_RESTART;
292 /* check for a softlockup
293 * This is done by making sure a high priority task is
294 * being scheduled. The task touches the watchdog to
295 * indicate it is getting cpu time. If it hasn't then
296 * this is a good indication some task is hogging the cpu
298 duration = is_softlockup(touch_ts, this_cpu);
299 if (unlikely(duration)) {
301 if (__get_cpu_var(soft_watchdog_warn) == true)
302 return HRTIMER_RESTART;
304 printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
306 current->comm, task_pid_nr(current));
308 print_irqtrace_events(current);
314 if (softlockup_panic)
315 panic("softlockup: hung tasks");
316 __get_cpu_var(soft_watchdog_warn) = true;
318 __get_cpu_var(soft_watchdog_warn) = false;
320 return HRTIMER_RESTART;
325 * The watchdog thread - touches the timestamp.
327 static int watchdog(void *__bind_cpu)
329 struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
330 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, (unsigned long)__bind_cpu);
332 sched_setscheduler(current, SCHED_FIFO, ¶m);
334 /* initialize timestamp */
337 /* kick off the timer for the hardlockup detector */
338 /* done here because hrtimer_start can only pin to smp_processor_id() */
339 hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
340 HRTIMER_MODE_REL_PINNED);
342 set_current_state(TASK_INTERRUPTIBLE);
344 * Run briefly once per second to reset the softlockup timestamp.
345 * If this gets delayed for more than 60 seconds then the
346 * debug-printout triggers in softlockup_tick().
348 while (!kthread_should_stop()) {
352 if (kthread_should_stop())
355 set_current_state(TASK_INTERRUPTIBLE);
357 __set_current_state(TASK_RUNNING);
363 #ifdef CONFIG_PERF_EVENTS_NMI
364 static int watchdog_nmi_enable(int cpu)
366 struct perf_event_attr *wd_attr;
367 struct perf_event *event = per_cpu(watchdog_ev, cpu);
369 /* is it already setup and enabled? */
370 if (event && event->state > PERF_EVENT_STATE_OFF)
373 /* it is setup but not enabled */
377 /* Try to register using hardware perf events */
378 wd_attr = &wd_hw_attr;
379 wd_attr->sample_period = hw_nmi_get_sample_period();
380 event = perf_event_create_kernel_counter(wd_attr, cpu, -1, watchdog_overflow_callback);
381 if (!IS_ERR(event)) {
382 printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
386 printk(KERN_ERR "NMI watchdog failed to create perf event on cpu%i: %p\n", cpu, event);
391 per_cpu(watchdog_ev, cpu) = event;
393 perf_event_enable(per_cpu(watchdog_ev, cpu));
398 static void watchdog_nmi_disable(int cpu)
400 struct perf_event *event = per_cpu(watchdog_ev, cpu);
403 perf_event_disable(event);
404 per_cpu(watchdog_ev, cpu) = NULL;
406 /* should be in cleanup, but blocks oprofile */
407 perf_event_release_kernel(event);
412 static int watchdog_nmi_enable(int cpu) { return 0; }
413 static void watchdog_nmi_disable(int cpu) { return; }
414 #endif /* CONFIG_PERF_EVENTS_NMI */
416 /* prepare/enable/disable routines */
417 static int watchdog_prepare_cpu(int cpu)
419 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
421 WARN_ON(per_cpu(softlockup_watchdog, cpu));
422 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
423 hrtimer->function = watchdog_timer_fn;
428 static int watchdog_enable(int cpu)
430 struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
432 /* enable the perf event */
433 if (watchdog_nmi_enable(cpu) != 0)
436 /* create the watchdog thread */
438 p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
440 printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
443 kthread_bind(p, cpu);
444 per_cpu(watchdog_touch_ts, cpu) = 0;
445 per_cpu(softlockup_watchdog, cpu) = p;
452 static void watchdog_disable(int cpu)
454 struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
455 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
458 * cancel the timer first to stop incrementing the stats
459 * and waking up the kthread
461 hrtimer_cancel(hrtimer);
463 /* disable the perf event */
464 watchdog_nmi_disable(cpu);
466 /* stop the watchdog thread */
468 per_cpu(softlockup_watchdog, cpu) = NULL;
472 /* if any cpu succeeds, watchdog is considered enabled for the system */
473 watchdog_enabled = 1;
476 static void watchdog_enable_all_cpus(void)
481 for_each_online_cpu(cpu)
482 result += watchdog_enable(cpu);
485 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
489 static void watchdog_disable_all_cpus(void)
493 for_each_online_cpu(cpu)
494 watchdog_disable(cpu);
496 /* if all watchdogs are disabled, then they are disabled for the system */
497 watchdog_enabled = 0;
501 /* sysctl functions */
504 * proc handler for /proc/sys/kernel/nmi_watchdog
507 int proc_dowatchdog_enabled(struct ctl_table *table, int write,
508 void __user *buffer, size_t *length, loff_t *ppos)
510 proc_dointvec(table, write, buffer, length, ppos);
512 if (watchdog_enabled)
513 watchdog_enable_all_cpus();
515 watchdog_disable_all_cpus();
519 int proc_dowatchdog_thresh(struct ctl_table *table, int write,
521 size_t *lenp, loff_t *ppos)
523 return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
527 int proc_dosoftlockup_thresh(struct ctl_table *table, int write,
529 size_t *lenp, loff_t *ppos)
531 return proc_dowatchdog_thresh(table, write, buffer, lenp, ppos);
533 /* end of stub functions */
534 #endif /* CONFIG_SYSCTL */
538 * Create/destroy watchdog threads as CPUs come and go:
541 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
543 int hotcpu = (unsigned long)hcpu;
547 case CPU_UP_PREPARE_FROZEN:
548 if (watchdog_prepare_cpu(hotcpu))
552 case CPU_ONLINE_FROZEN:
553 if (watchdog_enable(hotcpu))
556 #ifdef CONFIG_HOTPLUG_CPU
557 case CPU_UP_CANCELED:
558 case CPU_UP_CANCELED_FROZEN:
559 watchdog_disable(hotcpu);
562 case CPU_DEAD_FROZEN:
563 watchdog_disable(hotcpu);
565 #endif /* CONFIG_HOTPLUG_CPU */
570 static struct notifier_block __cpuinitdata cpu_nfb = {
571 .notifier_call = cpu_callback
574 static int __init spawn_watchdog_task(void)
576 void *cpu = (void *)(long)smp_processor_id();
582 err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
583 WARN_ON(err == NOTIFY_BAD);
585 cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
586 register_cpu_notifier(&cpu_nfb);
588 atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
592 early_initcall(spawn_watchdog_task);