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 __initdata no_watchdog;
51 * Should we panic when a soft-lockup or hard-lockup occurs:
53 #ifdef CONFIG_HARDLOCKUP_DETECTOR
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 = smp_processor_id();
119 __get_cpu_var(watchdog_touch_ts) = get_timestamp(this_cpu);
122 void touch_softlockup_watchdog(void)
124 __raw_get_cpu_var(watchdog_touch_ts) = 0;
126 EXPORT_SYMBOL(touch_softlockup_watchdog);
128 void touch_all_softlockup_watchdogs(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 #ifdef CONFIG_HARDLOCKUP_DETECTOR
142 void touch_nmi_watchdog(void)
144 if (watchdog_enabled) {
147 for_each_present_cpu(cpu) {
148 if (per_cpu(watchdog_nmi_touch, cpu) != true)
149 per_cpu(watchdog_nmi_touch, cpu) = true;
152 touch_softlockup_watchdog();
154 EXPORT_SYMBOL(touch_nmi_watchdog);
158 void touch_softlockup_watchdog_sync(void)
160 __raw_get_cpu_var(softlockup_touch_sync) = true;
161 __raw_get_cpu_var(watchdog_touch_ts) = 0;
164 #ifdef CONFIG_HARDLOCKUP_DETECTOR
165 /* watchdog detector functions */
166 static int is_hardlockup(void)
168 unsigned long hrint = __get_cpu_var(hrtimer_interrupts);
170 if (__get_cpu_var(hrtimer_interrupts_saved) == hrint)
173 __get_cpu_var(hrtimer_interrupts_saved) = hrint;
178 static int is_softlockup(unsigned long touch_ts)
180 unsigned long now = get_timestamp(smp_processor_id());
182 /* Warn about unreasonable delays: */
183 if (time_after(now, touch_ts + softlockup_thresh))
184 return now - touch_ts;
189 #ifdef CONFIG_HARDLOCKUP_DETECTOR
190 static struct perf_event_attr wd_hw_attr = {
191 .type = PERF_TYPE_HARDWARE,
192 .config = PERF_COUNT_HW_CPU_CYCLES,
193 .size = sizeof(struct perf_event_attr),
198 /* Callback function for perf event subsystem */
199 static void watchdog_overflow_callback(struct perf_event *event, int nmi,
200 struct perf_sample_data *data,
201 struct pt_regs *regs)
203 /* Ensure the watchdog never gets throttled */
204 event->hw.interrupts = 0;
206 if (__get_cpu_var(watchdog_nmi_touch) == true) {
207 __get_cpu_var(watchdog_nmi_touch) = false;
211 /* check for a hardlockup
212 * This is done by making sure our timer interrupt
213 * is incrementing. The timer interrupt should have
214 * fired multiple times before we overflow'd. If it hasn't
215 * then this is a good indication the cpu is stuck
217 if (is_hardlockup()) {
218 int this_cpu = smp_processor_id();
220 /* only print hardlockups once */
221 if (__get_cpu_var(hard_watchdog_warn) == true)
224 if (hardlockup_panic)
225 panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
227 WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
229 __get_cpu_var(hard_watchdog_warn) = true;
233 __get_cpu_var(hard_watchdog_warn) = false;
236 static void watchdog_interrupt_count(void)
238 __get_cpu_var(hrtimer_interrupts)++;
241 static inline void watchdog_interrupt_count(void) { return; }
242 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
244 /* watchdog kicker functions */
245 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
247 unsigned long touch_ts = __get_cpu_var(watchdog_touch_ts);
248 struct pt_regs *regs = get_irq_regs();
251 /* kick the hardlockup detector */
252 watchdog_interrupt_count();
254 /* kick the softlockup detector */
255 wake_up_process(__get_cpu_var(softlockup_watchdog));
258 hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
261 if (unlikely(__get_cpu_var(softlockup_touch_sync))) {
263 * If the time stamp was touched atomically
264 * make sure the scheduler tick is up to date.
266 __get_cpu_var(softlockup_touch_sync) = false;
270 return HRTIMER_RESTART;
273 /* check for a softlockup
274 * This is done by making sure a high priority task is
275 * being scheduled. The task touches the watchdog to
276 * indicate it is getting cpu time. If it hasn't then
277 * this is a good indication some task is hogging the cpu
279 duration = is_softlockup(touch_ts);
280 if (unlikely(duration)) {
282 if (__get_cpu_var(soft_watchdog_warn) == true)
283 return HRTIMER_RESTART;
285 printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
286 smp_processor_id(), duration,
287 current->comm, task_pid_nr(current));
289 print_irqtrace_events(current);
295 if (softlockup_panic)
296 panic("softlockup: hung tasks");
297 __get_cpu_var(soft_watchdog_warn) = true;
299 __get_cpu_var(soft_watchdog_warn) = false;
301 return HRTIMER_RESTART;
306 * The watchdog thread - touches the timestamp.
308 static int watchdog(void *unused)
310 struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
311 struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
313 sched_setscheduler(current, SCHED_FIFO, ¶m);
315 /* initialize timestamp */
318 /* kick off the timer for the hardlockup detector */
319 /* done here because hrtimer_start can only pin to smp_processor_id() */
320 hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
321 HRTIMER_MODE_REL_PINNED);
323 set_current_state(TASK_INTERRUPTIBLE);
325 * Run briefly once per second to reset the softlockup timestamp.
326 * If this gets delayed for more than 60 seconds then the
327 * debug-printout triggers in watchdog_timer_fn().
329 while (!kthread_should_stop()) {
333 if (kthread_should_stop())
336 set_current_state(TASK_INTERRUPTIBLE);
338 __set_current_state(TASK_RUNNING);
344 #ifdef CONFIG_HARDLOCKUP_DETECTOR
345 static int watchdog_nmi_enable(int cpu)
347 struct perf_event_attr *wd_attr;
348 struct perf_event *event = per_cpu(watchdog_ev, cpu);
350 /* is it already setup and enabled? */
351 if (event && event->state > PERF_EVENT_STATE_OFF)
354 /* it is setup but not enabled */
358 /* Try to register using hardware perf events */
359 wd_attr = &wd_hw_attr;
360 wd_attr->sample_period = hw_nmi_get_sample_period();
361 event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback);
362 if (!IS_ERR(event)) {
363 printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
367 printk(KERN_ERR "NMI watchdog failed to create perf event on cpu%i: %p\n", cpu, event);
368 return PTR_ERR(event);
372 per_cpu(watchdog_ev, cpu) = event;
374 perf_event_enable(per_cpu(watchdog_ev, cpu));
379 static void watchdog_nmi_disable(int cpu)
381 struct perf_event *event = per_cpu(watchdog_ev, cpu);
384 perf_event_disable(event);
385 per_cpu(watchdog_ev, cpu) = NULL;
387 /* should be in cleanup, but blocks oprofile */
388 perf_event_release_kernel(event);
393 static int watchdog_nmi_enable(int cpu) { return 0; }
394 static void watchdog_nmi_disable(int cpu) { return; }
395 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
397 /* prepare/enable/disable routines */
398 static int watchdog_prepare_cpu(int cpu)
400 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
402 WARN_ON(per_cpu(softlockup_watchdog, cpu));
403 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
404 hrtimer->function = watchdog_timer_fn;
409 static int watchdog_enable(int cpu)
411 struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
414 /* enable the perf event */
415 err = watchdog_nmi_enable(cpu);
419 /* create the watchdog thread */
421 p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
423 printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
426 kthread_bind(p, cpu);
427 per_cpu(watchdog_touch_ts, cpu) = 0;
428 per_cpu(softlockup_watchdog, cpu) = p;
432 /* if any cpu succeeds, watchdog is considered enabled for the system */
433 watchdog_enabled = 1;
438 static void watchdog_disable(int cpu)
440 struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
441 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
444 * cancel the timer first to stop incrementing the stats
445 * and waking up the kthread
447 hrtimer_cancel(hrtimer);
449 /* disable the perf event */
450 watchdog_nmi_disable(cpu);
452 /* stop the watchdog thread */
454 per_cpu(softlockup_watchdog, cpu) = NULL;
459 static void watchdog_enable_all_cpus(void)
464 for_each_online_cpu(cpu)
465 result += watchdog_enable(cpu);
468 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
472 static void watchdog_disable_all_cpus(void)
479 for_each_online_cpu(cpu)
480 watchdog_disable(cpu);
482 /* if all watchdogs are disabled, then they are disabled for the system */
483 watchdog_enabled = 0;
487 /* sysctl functions */
490 * proc handler for /proc/sys/kernel/nmi_watchdog
493 int proc_dowatchdog_enabled(struct ctl_table *table, int write,
494 void __user *buffer, size_t *length, loff_t *ppos)
496 proc_dointvec(table, write, buffer, length, ppos);
498 if (watchdog_enabled)
499 watchdog_enable_all_cpus();
501 watchdog_disable_all_cpus();
505 int proc_dowatchdog_thresh(struct ctl_table *table, int write,
507 size_t *lenp, loff_t *ppos)
509 return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
511 #endif /* CONFIG_SYSCTL */
515 * Create/destroy watchdog threads as CPUs come and go:
518 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
520 int hotcpu = (unsigned long)hcpu;
525 case CPU_UP_PREPARE_FROZEN:
526 err = watchdog_prepare_cpu(hotcpu);
529 case CPU_ONLINE_FROZEN:
530 err = watchdog_enable(hotcpu);
532 #ifdef CONFIG_HOTPLUG_CPU
533 case CPU_UP_CANCELED:
534 case CPU_UP_CANCELED_FROZEN:
535 watchdog_disable(hotcpu);
538 case CPU_DEAD_FROZEN:
539 watchdog_disable(hotcpu);
541 #endif /* CONFIG_HOTPLUG_CPU */
543 return notifier_from_errno(err);
546 static struct notifier_block __cpuinitdata cpu_nfb = {
547 .notifier_call = cpu_callback
550 static int __init spawn_watchdog_task(void)
552 void *cpu = (void *)(long)smp_processor_id();
558 err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
559 WARN_ON(notifier_to_errno(err));
561 cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
562 register_cpu_notifier(&cpu_nfb);
566 early_initcall(spawn_watchdog_task);