2 * Detect hard and soft lockups on a system
4 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
6 * Note: Most of this code is borrowed heavily from the original softlockup
7 * detector, so thanks to Ingo for the initial implementation.
8 * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
9 * to those contributors as well.
13 #include <linux/cpu.h>
14 #include <linux/nmi.h>
15 #include <linux/init.h>
16 #include <linux/delay.h>
17 #include <linux/freezer.h>
18 #include <linux/kthread.h>
19 #include <linux/lockdep.h>
20 #include <linux/notifier.h>
21 #include <linux/module.h>
22 #include <linux/sysctl.h>
24 #include <asm/irq_regs.h>
25 #include <linux/perf_event.h>
27 int watchdog_enabled
= 1;
28 int __read_mostly watchdog_thresh
= 10;
30 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts
);
31 static DEFINE_PER_CPU(struct task_struct
*, softlockup_watchdog
);
32 static DEFINE_PER_CPU(struct hrtimer
, watchdog_hrtimer
);
33 static DEFINE_PER_CPU(bool, softlockup_touch_sync
);
34 static DEFINE_PER_CPU(bool, soft_watchdog_warn
);
35 #ifdef CONFIG_HARDLOCKUP_DETECTOR
36 static DEFINE_PER_CPU(bool, hard_watchdog_warn
);
37 static DEFINE_PER_CPU(bool, watchdog_nmi_touch
);
38 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts
);
39 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved
);
40 static DEFINE_PER_CPU(struct perf_event
*, watchdog_ev
);
45 * Should we panic when a soft-lockup or hard-lockup occurs:
47 #ifdef CONFIG_HARDLOCKUP_DETECTOR
48 static int hardlockup_panic
=
49 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE
;
51 static int __init
hardlockup_panic_setup(char *str
)
53 if (!strncmp(str
, "panic", 5))
55 else if (!strncmp(str
, "nopanic", 7))
57 else if (!strncmp(str
, "0", 1))
61 __setup("nmi_watchdog=", hardlockup_panic_setup
);
64 unsigned int __read_mostly softlockup_panic
=
65 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
;
67 static int __init
softlockup_panic_setup(char *str
)
69 softlockup_panic
= simple_strtoul(str
, NULL
, 0);
73 __setup("softlockup_panic=", softlockup_panic_setup
);
75 static int __init
nowatchdog_setup(char *str
)
80 __setup("nowatchdog", nowatchdog_setup
);
83 static int __init
nosoftlockup_setup(char *str
)
88 __setup("nosoftlockup", nosoftlockup_setup
);
92 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
93 * lockups can have false positives under extreme conditions. So we generally
94 * want a higher threshold for soft lockups than for hard lockups. So we couple
95 * the thresholds with a factor: we make the soft threshold twice the amount of
96 * time the hard threshold is.
98 static int get_softlockup_thresh(void)
100 return watchdog_thresh
* 2;
104 * Returns seconds, approximately. We don't need nanosecond
105 * resolution, and we don't need to waste time with a big divide when
108 static unsigned long get_timestamp(int this_cpu
)
110 return cpu_clock(this_cpu
) >> 30LL; /* 2^30 ~= 10^9 */
113 static unsigned long get_sample_period(void)
116 * convert watchdog_thresh from seconds to ns
117 * the divide by 5 is to give hrtimer several chances (two
118 * or three with the current relation between the soft
119 * and hard thresholds) to increment before the
120 * hardlockup detector generates a warning
122 return get_softlockup_thresh() * (NSEC_PER_SEC
/ 5);
125 /* Commands for resetting the watchdog */
126 static void __touch_watchdog(void)
128 int this_cpu
= smp_processor_id();
130 __this_cpu_write(watchdog_touch_ts
, get_timestamp(this_cpu
));
133 void touch_softlockup_watchdog(void)
135 __this_cpu_write(watchdog_touch_ts
, 0);
137 EXPORT_SYMBOL(touch_softlockup_watchdog
);
139 void touch_all_softlockup_watchdogs(void)
144 * this is done lockless
145 * do we care if a 0 races with a timestamp?
146 * all it means is the softlock check starts one cycle later
148 for_each_online_cpu(cpu
)
149 per_cpu(watchdog_touch_ts
, cpu
) = 0;
152 #ifdef CONFIG_HARDLOCKUP_DETECTOR
153 void touch_nmi_watchdog(void)
155 if (watchdog_enabled
) {
158 for_each_present_cpu(cpu
) {
159 if (per_cpu(watchdog_nmi_touch
, cpu
) != true)
160 per_cpu(watchdog_nmi_touch
, cpu
) = true;
163 touch_softlockup_watchdog();
165 EXPORT_SYMBOL(touch_nmi_watchdog
);
169 void touch_softlockup_watchdog_sync(void)
171 __raw_get_cpu_var(softlockup_touch_sync
) = true;
172 __raw_get_cpu_var(watchdog_touch_ts
) = 0;
175 #ifdef CONFIG_HARDLOCKUP_DETECTOR
176 /* watchdog detector functions */
177 static int is_hardlockup(void)
179 unsigned long hrint
= __this_cpu_read(hrtimer_interrupts
);
181 if (__this_cpu_read(hrtimer_interrupts_saved
) == hrint
)
184 __this_cpu_write(hrtimer_interrupts_saved
, hrint
);
189 static int is_softlockup(unsigned long touch_ts
)
191 unsigned long now
= get_timestamp(smp_processor_id());
193 /* Warn about unreasonable delays: */
194 if (time_after(now
, touch_ts
+ get_softlockup_thresh()))
195 return now
- touch_ts
;
200 #ifdef CONFIG_HARDLOCKUP_DETECTOR
202 static struct perf_event_attr wd_hw_attr
= {
203 .type
= PERF_TYPE_HARDWARE
,
204 .config
= PERF_COUNT_HW_CPU_CYCLES
,
205 .size
= sizeof(struct perf_event_attr
),
210 /* Callback function for perf event subsystem */
211 static void watchdog_overflow_callback(struct perf_event
*event
,
212 struct perf_sample_data
*data
,
213 struct pt_regs
*regs
)
215 /* Ensure the watchdog never gets throttled */
216 event
->hw
.interrupts
= 0;
218 if (__this_cpu_read(watchdog_nmi_touch
) == true) {
219 __this_cpu_write(watchdog_nmi_touch
, false);
223 /* check for a hardlockup
224 * This is done by making sure our timer interrupt
225 * is incrementing. The timer interrupt should have
226 * fired multiple times before we overflow'd. If it hasn't
227 * then this is a good indication the cpu is stuck
229 if (is_hardlockup()) {
230 int this_cpu
= smp_processor_id();
232 /* only print hardlockups once */
233 if (__this_cpu_read(hard_watchdog_warn
) == true)
236 if (hardlockup_panic
)
237 panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu
);
239 WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu
);
241 __this_cpu_write(hard_watchdog_warn
, true);
245 __this_cpu_write(hard_watchdog_warn
, false);
248 static void watchdog_interrupt_count(void)
250 __this_cpu_inc(hrtimer_interrupts
);
253 static inline void watchdog_interrupt_count(void) { return; }
254 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
256 /* watchdog kicker functions */
257 static enum hrtimer_restart
watchdog_timer_fn(struct hrtimer
*hrtimer
)
259 unsigned long touch_ts
= __this_cpu_read(watchdog_touch_ts
);
260 struct pt_regs
*regs
= get_irq_regs();
263 /* kick the hardlockup detector */
264 watchdog_interrupt_count();
266 /* kick the softlockup detector */
267 wake_up_process(__this_cpu_read(softlockup_watchdog
));
270 hrtimer_forward_now(hrtimer
, ns_to_ktime(get_sample_period()));
273 if (unlikely(__this_cpu_read(softlockup_touch_sync
))) {
275 * If the time stamp was touched atomically
276 * make sure the scheduler tick is up to date.
278 __this_cpu_write(softlockup_touch_sync
, false);
282 return HRTIMER_RESTART
;
285 /* check for a softlockup
286 * This is done by making sure a high priority task is
287 * being scheduled. The task touches the watchdog to
288 * indicate it is getting cpu time. If it hasn't then
289 * this is a good indication some task is hogging the cpu
291 duration
= is_softlockup(touch_ts
);
292 if (unlikely(duration
)) {
294 if (__this_cpu_read(soft_watchdog_warn
) == true)
295 return HRTIMER_RESTART
;
297 printk(KERN_EMERG
"BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
298 smp_processor_id(), duration
,
299 current
->comm
, task_pid_nr(current
));
301 print_irqtrace_events(current
);
307 if (softlockup_panic
)
308 panic("softlockup: hung tasks");
309 __this_cpu_write(soft_watchdog_warn
, true);
311 __this_cpu_write(soft_watchdog_warn
, false);
313 return HRTIMER_RESTART
;
318 * The watchdog thread - touches the timestamp.
320 static int watchdog(void *unused
)
322 struct sched_param param
= { .sched_priority
= MAX_RT_PRIO
-1 };
323 struct hrtimer
*hrtimer
= &__raw_get_cpu_var(watchdog_hrtimer
);
325 sched_setscheduler(current
, SCHED_FIFO
, ¶m
);
327 /* initialize timestamp */
330 /* kick off the timer for the hardlockup detector */
331 /* done here because hrtimer_start can only pin to smp_processor_id() */
332 hrtimer_start(hrtimer
, ns_to_ktime(get_sample_period()),
333 HRTIMER_MODE_REL_PINNED
);
335 set_current_state(TASK_INTERRUPTIBLE
);
337 * Run briefly (kicked by the hrtimer callback function) once every
338 * get_sample_period() seconds (4 seconds by default) to reset the
339 * softlockup timestamp. If this gets delayed for more than
340 * 2*watchdog_thresh seconds then the debug-printout triggers in
341 * watchdog_timer_fn().
343 while (!kthread_should_stop()) {
347 if (kthread_should_stop())
350 set_current_state(TASK_INTERRUPTIBLE
);
352 __set_current_state(TASK_RUNNING
);
353 param
.sched_priority
= 0;
354 sched_setscheduler(current
, SCHED_NORMAL
, ¶m
);
359 #ifdef CONFIG_HARDLOCKUP_DETECTOR
360 static int watchdog_nmi_enable(int cpu
)
362 struct perf_event_attr
*wd_attr
;
363 struct perf_event
*event
= per_cpu(watchdog_ev
, cpu
);
365 /* is it already setup and enabled? */
366 if (event
&& event
->state
> PERF_EVENT_STATE_OFF
)
369 /* it is setup but not enabled */
373 wd_attr
= &wd_hw_attr
;
374 wd_attr
->sample_period
= hw_nmi_get_sample_period(watchdog_thresh
);
376 /* Try to register using hardware perf events */
377 event
= perf_event_create_kernel_counter(wd_attr
, cpu
, NULL
, watchdog_overflow_callback
, NULL
);
378 if (!IS_ERR(event
)) {
379 printk(KERN_INFO
"NMI watchdog enabled, takes one hw-pmu counter.\n");
384 /* vary the KERN level based on the returned errno */
385 if (PTR_ERR(event
) == -EOPNOTSUPP
)
386 printk(KERN_INFO
"NMI watchdog disabled (cpu%i): not supported (no LAPIC?)\n", cpu
);
387 else if (PTR_ERR(event
) == -ENOENT
)
388 printk(KERN_WARNING
"NMI watchdog disabled (cpu%i): hardware events not enabled\n", cpu
);
390 printk(KERN_ERR
"NMI watchdog disabled (cpu%i): unable to create perf event: %ld\n", cpu
, PTR_ERR(event
));
391 return PTR_ERR(event
);
395 per_cpu(watchdog_ev
, cpu
) = event
;
397 perf_event_enable(per_cpu(watchdog_ev
, cpu
));
402 static void watchdog_nmi_disable(int cpu
)
404 struct perf_event
*event
= per_cpu(watchdog_ev
, cpu
);
407 perf_event_disable(event
);
408 per_cpu(watchdog_ev
, cpu
) = NULL
;
410 /* should be in cleanup, but blocks oprofile */
411 perf_event_release_kernel(event
);
416 static int watchdog_nmi_enable(int cpu
) { return 0; }
417 static void watchdog_nmi_disable(int cpu
) { return; }
418 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
420 /* prepare/enable/disable routines */
421 static void watchdog_prepare_cpu(int cpu
)
423 struct hrtimer
*hrtimer
= &per_cpu(watchdog_hrtimer
, cpu
);
425 WARN_ON(per_cpu(softlockup_watchdog
, cpu
));
426 hrtimer_init(hrtimer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
427 hrtimer
->function
= watchdog_timer_fn
;
430 static int watchdog_enable(int cpu
)
432 struct task_struct
*p
= per_cpu(softlockup_watchdog
, cpu
);
435 /* enable the perf event */
436 err
= watchdog_nmi_enable(cpu
);
438 /* Regardless of err above, fall through and start softlockup */
440 /* create the watchdog thread */
442 p
= kthread_create_on_node(watchdog
, NULL
, cpu_to_node(cpu
), "watchdog/%d", cpu
);
444 printk(KERN_ERR
"softlockup watchdog for %i failed\n", cpu
);
446 /* if hardlockup hasn't already set this */
448 /* and disable the perf event */
449 watchdog_nmi_disable(cpu
);
453 kthread_bind(p
, cpu
);
454 per_cpu(watchdog_touch_ts
, cpu
) = 0;
455 per_cpu(softlockup_watchdog
, cpu
) = p
;
463 static void watchdog_disable(int cpu
)
465 struct task_struct
*p
= per_cpu(softlockup_watchdog
, cpu
);
466 struct hrtimer
*hrtimer
= &per_cpu(watchdog_hrtimer
, cpu
);
469 * cancel the timer first to stop incrementing the stats
470 * and waking up the kthread
472 hrtimer_cancel(hrtimer
);
474 /* disable the perf event */
475 watchdog_nmi_disable(cpu
);
477 /* stop the watchdog thread */
479 per_cpu(softlockup_watchdog
, cpu
) = NULL
;
484 /* sysctl functions */
486 static void watchdog_enable_all_cpus(void)
490 watchdog_enabled
= 0;
492 for_each_online_cpu(cpu
)
493 if (!watchdog_enable(cpu
))
494 /* if any cpu succeeds, watchdog is considered
495 enabled for the system */
496 watchdog_enabled
= 1;
498 if (!watchdog_enabled
)
499 printk(KERN_ERR
"watchdog: failed to be enabled on some cpus\n");
503 static void watchdog_disable_all_cpus(void)
507 for_each_online_cpu(cpu
)
508 watchdog_disable(cpu
);
510 /* if all watchdogs are disabled, then they are disabled for the system */
511 watchdog_enabled
= 0;
516 * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
519 int proc_dowatchdog(struct ctl_table
*table
, int write
,
520 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
524 ret
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
528 if (watchdog_enabled
&& watchdog_thresh
)
529 watchdog_enable_all_cpus();
531 watchdog_disable_all_cpus();
536 #endif /* CONFIG_SYSCTL */
540 * Create/destroy watchdog threads as CPUs come and go:
543 cpu_callback(struct notifier_block
*nfb
, unsigned long action
, void *hcpu
)
545 int hotcpu
= (unsigned long)hcpu
;
549 case CPU_UP_PREPARE_FROZEN
:
550 watchdog_prepare_cpu(hotcpu
);
553 case CPU_ONLINE_FROZEN
:
554 if (watchdog_enabled
)
555 watchdog_enable(hotcpu
);
557 #ifdef CONFIG_HOTPLUG_CPU
558 case CPU_UP_CANCELED
:
559 case CPU_UP_CANCELED_FROZEN
:
560 watchdog_disable(hotcpu
);
563 case CPU_DEAD_FROZEN
:
564 watchdog_disable(hotcpu
);
566 #endif /* CONFIG_HOTPLUG_CPU */
570 * hardlockup and softlockup are not important enough
571 * to block cpu bring up. Just always succeed and
572 * rely on printk output to flag problems.
577 static struct notifier_block __cpuinitdata cpu_nfb
= {
578 .notifier_call
= cpu_callback
581 void __init
lockup_detector_init(void)
583 void *cpu
= (void *)(long)smp_processor_id();
586 err
= cpu_callback(&cpu_nfb
, CPU_UP_PREPARE
, cpu
);
587 WARN_ON(notifier_to_errno(err
));
589 cpu_callback(&cpu_nfb
, CPU_ONLINE
, cpu
);
590 register_cpu_notifier(&cpu_nfb
);