projects/linux·blob v3.13 · refs

608 lines · 15.6 KiB

1/*
2 * Detect hard and soft lockups on a system
3 *
4 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
5 *
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.
10 */
11
12#define pr_fmt(fmt) "NMI watchdog: " fmt
13
14#include <linux/mm.h>
15#include <linux/cpu.h>
16#include <linux/nmi.h>
17#include <linux/init.h>
18#include <linux/delay.h>
19#include <linux/freezer.h>
20#include <linux/kthread.h>
21#include <linux/lockdep.h>
22#include <linux/notifier.h>
23#include <linux/module.h>
24#include <linux/sysctl.h>
25#include <linux/smpboot.h>
26#include <linux/sched/rt.h>
27
28#include <asm/irq_regs.h>
29#include <linux/kvm_para.h>
30#include <linux/perf_event.h>
31
32int watchdog_user_enabled = 1;
33int __read_mostly watchdog_thresh = 10;
34static int __read_mostly watchdog_running;
35static u64 __read_mostly sample_period;
36
37static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
38static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
39static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
40static DEFINE_PER_CPU(bool, softlockup_touch_sync);
41static DEFINE_PER_CPU(bool, soft_watchdog_warn);
42static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
43static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
44#ifdef CONFIG_HARDLOCKUP_DETECTOR
45static DEFINE_PER_CPU(bool, hard_watchdog_warn);
46static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
47static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
48static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
49#endif
50
51/* boot commands */
52/*
53 * Should we panic when a soft-lockup or hard-lockup occurs:
54 */
55#ifdef CONFIG_HARDLOCKUP_DETECTOR
56static int hardlockup_panic =
57 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
58
59static int __init hardlockup_panic_setup(char *str)
60{
61 if (!strncmp(str, "panic", 5))
62 hardlockup_panic = 1;
63 else if (!strncmp(str, "nopanic", 7))
64 hardlockup_panic = 0;
65 else if (!strncmp(str, "0", 1))
66 watchdog_user_enabled = 0;
67 return 1;
68}
69__setup("nmi_watchdog=", hardlockup_panic_setup);
70#endif
71
72unsigned int __read_mostly softlockup_panic =
73 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
74
75static int __init softlockup_panic_setup(char *str)
76{
77 softlockup_panic = simple_strtoul(str, NULL, 0);
78
79 return 1;
80}
81__setup("softlockup_panic=", softlockup_panic_setup);
82
83static int __init nowatchdog_setup(char *str)
84{
85 watchdog_user_enabled = 0;
86 return 1;
87}
88__setup("nowatchdog", nowatchdog_setup);
89
90/* deprecated */
91static int __init nosoftlockup_setup(char *str)
92{
93 watchdog_user_enabled = 0;
94 return 1;
95}
96__setup("nosoftlockup", nosoftlockup_setup);
97/* */
98
99/*
100 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
101 * lockups can have false positives under extreme conditions. So we generally
102 * want a higher threshold for soft lockups than for hard lockups. So we couple
103 * the thresholds with a factor: we make the soft threshold twice the amount of
104 * time the hard threshold is.
105 */
106static int get_softlockup_thresh(void)
107{
108 return watchdog_thresh * 2;
109}
110
111/*
112 * Returns seconds, approximately. We don't need nanosecond
113 * resolution, and we don't need to waste time with a big divide when
114 * 2^30ns == 1.074s.
115 */
116static unsigned long get_timestamp(void)
117{
118 return local_clock() >> 30LL; /* 2^30 ~= 10^9 */
119}
120
121static void set_sample_period(void)
122{
123 /*
124 * convert watchdog_thresh from seconds to ns
125 * the divide by 5 is to give hrtimer several chances (two
126 * or three with the current relation between the soft
127 * and hard thresholds) to increment before the
128 * hardlockup detector generates a warning
129 */
130 sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
131}
132
133/* Commands for resetting the watchdog */
134static void __touch_watchdog(void)
135{
136 __this_cpu_write(watchdog_touch_ts, get_timestamp());
137}
138
139void touch_softlockup_watchdog(void)
140{
141 __this_cpu_write(watchdog_touch_ts, 0);
142}
143EXPORT_SYMBOL(touch_softlockup_watchdog);
144
145void touch_all_softlockup_watchdogs(void)
146{
147 int cpu;
148
149 /*
150 * this is done lockless
151 * do we care if a 0 races with a timestamp?
152 * all it means is the softlock check starts one cycle later
153 */
154 for_each_online_cpu(cpu)
155 per_cpu(watchdog_touch_ts, cpu) = 0;
156}
157
158#ifdef CONFIG_HARDLOCKUP_DETECTOR
159void touch_nmi_watchdog(void)
160{
161 if (watchdog_user_enabled) {
162 unsigned cpu;
163
164 for_each_present_cpu(cpu) {
165 if (per_cpu(watchdog_nmi_touch, cpu) != true)
166 per_cpu(watchdog_nmi_touch, cpu) = true;
167 }
168 }
169 touch_softlockup_watchdog();
170}
171EXPORT_SYMBOL(touch_nmi_watchdog);
172
173#endif
174
175void touch_softlockup_watchdog_sync(void)
176{
177 __raw_get_cpu_var(softlockup_touch_sync) = true;
178 __raw_get_cpu_var(watchdog_touch_ts) = 0;
179}
180
181#ifdef CONFIG_HARDLOCKUP_DETECTOR
182/* watchdog detector functions */
183static int is_hardlockup(void)
184{
185 unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
186
187 if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
188 return 1;
189
190 __this_cpu_write(hrtimer_interrupts_saved, hrint);
191 return 0;
192}
193#endif
194
195static int is_softlockup(unsigned long touch_ts)
196{
197 unsigned long now = get_timestamp();
198
199 /* Warn about unreasonable delays: */
200 if (time_after(now, touch_ts + get_softlockup_thresh()))
201 return now - touch_ts;
202
203 return 0;
204}
205
206#ifdef CONFIG_HARDLOCKUP_DETECTOR
207
208static struct perf_event_attr wd_hw_attr = {
209 .type = PERF_TYPE_HARDWARE,
210 .config = PERF_COUNT_HW_CPU_CYCLES,
211 .size = sizeof(struct perf_event_attr),
212 .pinned = 1,
213 .disabled = 1,
214};
215
216/* Callback function for perf event subsystem */
217static void watchdog_overflow_callback(struct perf_event *event,
218 struct perf_sample_data *data,
219 struct pt_regs *regs)
220{
221 /* Ensure the watchdog never gets throttled */
222 event->hw.interrupts = 0;
223
224 if (__this_cpu_read(watchdog_nmi_touch) == true) {
225 __this_cpu_write(watchdog_nmi_touch, false);
226 return;
227 }
228
229 /* check for a hardlockup
230 * This is done by making sure our timer interrupt
231 * is incrementing. The timer interrupt should have
232 * fired multiple times before we overflow'd. If it hasn't
233 * then this is a good indication the cpu is stuck
234 */
235 if (is_hardlockup()) {
236 int this_cpu = smp_processor_id();
237
238 /* only print hardlockups once */
239 if (__this_cpu_read(hard_watchdog_warn) == true)
240 return;
241
242 if (hardlockup_panic)
243 panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
244 else
245 WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
246
247 __this_cpu_write(hard_watchdog_warn, true);
248 return;
249 }
250
251 __this_cpu_write(hard_watchdog_warn, false);
252 return;
253}
254#endif /* CONFIG_HARDLOCKUP_DETECTOR */
255
256static void watchdog_interrupt_count(void)
257{
258 __this_cpu_inc(hrtimer_interrupts);
259}
260
261static int watchdog_nmi_enable(unsigned int cpu);
262static void watchdog_nmi_disable(unsigned int cpu);
263
264/* watchdog kicker functions */
265static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
266{
267 unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
268 struct pt_regs *regs = get_irq_regs();
269 int duration;
270
271 /* kick the hardlockup detector */
272 watchdog_interrupt_count();
273
274 /* kick the softlockup detector */
275 wake_up_process(__this_cpu_read(softlockup_watchdog));
276
277 /* .. and repeat */
278 hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
279
280 if (touch_ts == 0) {
281 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
282 /*
283 * If the time stamp was touched atomically
284 * make sure the scheduler tick is up to date.
285 */
286 __this_cpu_write(softlockup_touch_sync, false);
287 sched_clock_tick();
288 }
289
290 /* Clear the guest paused flag on watchdog reset */
291 kvm_check_and_clear_guest_paused();
292 __touch_watchdog();
293 return HRTIMER_RESTART;
294 }
295
296 /* check for a softlockup
297 * This is done by making sure a high priority task is
298 * being scheduled. The task touches the watchdog to
299 * indicate it is getting cpu time. If it hasn't then
300 * this is a good indication some task is hogging the cpu
301 */
302 duration = is_softlockup(touch_ts);
303 if (unlikely(duration)) {
304 /*
305 * If a virtual machine is stopped by the host it can look to
306 * the watchdog like a soft lockup, check to see if the host
307 * stopped the vm before we issue the warning
308 */
309 if (kvm_check_and_clear_guest_paused())
310 return HRTIMER_RESTART;
311
312 /* only warn once */
313 if (__this_cpu_read(soft_watchdog_warn) == true)
314 return HRTIMER_RESTART;
315
316 printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
317 smp_processor_id(), duration,
318 current->comm, task_pid_nr(current));
319 print_modules();
320 print_irqtrace_events(current);
321 if (regs)
322 show_regs(regs);
323 else
324 dump_stack();
325
326 if (softlockup_panic)
327 panic("softlockup: hung tasks");
328 __this_cpu_write(soft_watchdog_warn, true);
329 } else
330 __this_cpu_write(soft_watchdog_warn, false);
331
332 return HRTIMER_RESTART;
333}
334
335static void watchdog_set_prio(unsigned int policy, unsigned int prio)
336{
337 struct sched_param param = { .sched_priority = prio };
338
339 sched_setscheduler(current, policy, &param);
340}
341
342static void watchdog_enable(unsigned int cpu)
343{
344 struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
345
346 /* kick off the timer for the hardlockup detector */
347 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
348 hrtimer->function = watchdog_timer_fn;
349
350 /* Enable the perf event */
351 watchdog_nmi_enable(cpu);
352
353 /* done here because hrtimer_start can only pin to smp_processor_id() */
354 hrtimer_start(hrtimer, ns_to_ktime(sample_period),
355 HRTIMER_MODE_REL_PINNED);
356
357 /* initialize timestamp */
358 watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
359 __touch_watchdog();
360}
361
362static void watchdog_disable(unsigned int cpu)
363{
364 struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
365
366 watchdog_set_prio(SCHED_NORMAL, 0);
367 hrtimer_cancel(hrtimer);
368 /* disable the perf event */
369 watchdog_nmi_disable(cpu);
370}
371
372static void watchdog_cleanup(unsigned int cpu, bool online)
373{
374 watchdog_disable(cpu);
375}
376
377static int watchdog_should_run(unsigned int cpu)
378{
379 return __this_cpu_read(hrtimer_interrupts) !=
380 __this_cpu_read(soft_lockup_hrtimer_cnt);
381}
382
383/*
384 * The watchdog thread function - touches the timestamp.
385 *
386 * It only runs once every sample_period seconds (4 seconds by
387 * default) to reset the softlockup timestamp. If this gets delayed
388 * for more than 2*watchdog_thresh seconds then the debug-printout
389 * triggers in watchdog_timer_fn().
390 */
391static void watchdog(unsigned int cpu)
392{
393 __this_cpu_write(soft_lockup_hrtimer_cnt,
394 __this_cpu_read(hrtimer_interrupts));
395 __touch_watchdog();
396}
397
398#ifdef CONFIG_HARDLOCKUP_DETECTOR
399/*
400 * People like the simple clean cpu node info on boot.
401 * Reduce the watchdog noise by only printing messages
402 * that are different from what cpu0 displayed.
403 */
404static unsigned long cpu0_err;
405
406static int watchdog_nmi_enable(unsigned int cpu)
407{
408 struct perf_event_attr *wd_attr;
409 struct perf_event *event = per_cpu(watchdog_ev, cpu);
410
411 /* is it already setup and enabled? */
412 if (event && event->state > PERF_EVENT_STATE_OFF)
413 goto out;
414
415 /* it is setup but not enabled */
416 if (event != NULL)
417 goto out_enable;
418
419 wd_attr = &wd_hw_attr;
420 wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
421
422 /* Try to register using hardware perf events */
423 event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
424
425 /* save cpu0 error for future comparision */
426 if (cpu == 0 && IS_ERR(event))
427 cpu0_err = PTR_ERR(event);
428
429 if (!IS_ERR(event)) {
430 /* only print for cpu0 or different than cpu0 */
431 if (cpu == 0 || cpu0_err)
432 pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
433 goto out_save;
434 }
435
436 /* skip displaying the same error again */
437 if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
438 return PTR_ERR(event);
439
440 /* vary the KERN level based on the returned errno */
441 if (PTR_ERR(event) == -EOPNOTSUPP)
442 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
443 else if (PTR_ERR(event) == -ENOENT)
444 pr_warning("disabled (cpu%i): hardware events not enabled\n",
445 cpu);
446 else
447 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
448 cpu, PTR_ERR(event));
449 return PTR_ERR(event);
450
451 /* success path */
452out_save:
453 per_cpu(watchdog_ev, cpu) = event;
454out_enable:
455 perf_event_enable(per_cpu(watchdog_ev, cpu));
456out:
457 return 0;
458}
459
460static void watchdog_nmi_disable(unsigned int cpu)
461{
462 struct perf_event *event = per_cpu(watchdog_ev, cpu);
463
464 if (event) {
465 perf_event_disable(event);
466 per_cpu(watchdog_ev, cpu) = NULL;
467
468 /* should be in cleanup, but blocks oprofile */
469 perf_event_release_kernel(event);
470 }
471 return;
472}
473#else
474static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
475static void watchdog_nmi_disable(unsigned int cpu) { return; }
476#endif /* CONFIG_HARDLOCKUP_DETECTOR */
477
478static struct smp_hotplug_thread watchdog_threads = {
479 .store = &softlockup_watchdog,
480 .thread_should_run = watchdog_should_run,
481 .thread_fn = watchdog,
482 .thread_comm = "watchdog/%u",
483 .setup = watchdog_enable,
484 .cleanup = watchdog_cleanup,
485 .park = watchdog_disable,
486 .unpark = watchdog_enable,
487};
488
489static void restart_watchdog_hrtimer(void *info)
490{
491 struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
492 int ret;
493
494 /*
495 * No need to cancel and restart hrtimer if it is currently executing
496 * because it will reprogram itself with the new period now.
497 * We should never see it unqueued here because we are running per-cpu
498 * with interrupts disabled.
499 */
500 ret = hrtimer_try_to_cancel(hrtimer);
501 if (ret == 1)
502 hrtimer_start(hrtimer, ns_to_ktime(sample_period),
503 HRTIMER_MODE_REL_PINNED);
504}
505
506static void update_timers(int cpu)
507{
508 struct call_single_data data = {.func = restart_watchdog_hrtimer};
509 /*
510 * Make sure that perf event counter will adopt to a new
511 * sampling period. Updating the sampling period directly would
512 * be much nicer but we do not have an API for that now so
513 * let's use a big hammer.
514 * Hrtimer will adopt the new period on the next tick but this
515 * might be late already so we have to restart the timer as well.
516 */
517 watchdog_nmi_disable(cpu);
518 __smp_call_function_single(cpu, &data, 1);
519 watchdog_nmi_enable(cpu);
520}
521
522static void update_timers_all_cpus(void)
523{
524 int cpu;
525
526 get_online_cpus();
527 preempt_disable();
528 for_each_online_cpu(cpu)
529 update_timers(cpu);
530 preempt_enable();
531 put_online_cpus();
532}
533
534static int watchdog_enable_all_cpus(bool sample_period_changed)
535{
536 int err = 0;
537
538 if (!watchdog_running) {
539 err = smpboot_register_percpu_thread(&watchdog_threads);
540 if (err)
541 pr_err("Failed to create watchdog threads, disabled\n");
542 else
543 watchdog_running = 1;
544 } else if (sample_period_changed) {
545 update_timers_all_cpus();
546 }
547
548 return err;
549}
550
551/* prepare/enable/disable routines */
552/* sysctl functions */
553#ifdef CONFIG_SYSCTL
554static void watchdog_disable_all_cpus(void)
555{
556 if (watchdog_running) {
557 watchdog_running = 0;
558 smpboot_unregister_percpu_thread(&watchdog_threads);
559 }
560}
561
562/*
563 * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
564 */
565
566int proc_dowatchdog(struct ctl_table *table, int write,
567 void __user *buffer, size_t *lenp, loff_t *ppos)
568{
569 int err, old_thresh, old_enabled;
570 static DEFINE_MUTEX(watchdog_proc_mutex);
571
572 mutex_lock(&watchdog_proc_mutex);
573 old_thresh = ACCESS_ONCE(watchdog_thresh);
574 old_enabled = ACCESS_ONCE(watchdog_user_enabled);
575
576 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
577 if (err || !write)
578 goto out;
579
580 set_sample_period();
581 /*
582 * Watchdog threads shouldn't be enabled if they are
583 * disabled. The 'watchdog_running' variable check in
584 * watchdog_*_all_cpus() function takes care of this.
585 */
586 if (watchdog_user_enabled && watchdog_thresh)
587 err = watchdog_enable_all_cpus(old_thresh != watchdog_thresh);
588 else
589 watchdog_disable_all_cpus();
590
591 /* Restore old values on failure */
592 if (err) {
593 watchdog_thresh = old_thresh;
594 watchdog_user_enabled = old_enabled;
595 }
596out:
597 mutex_unlock(&watchdog_proc_mutex);
598 return err;
599}
600#endif /* CONFIG_SYSCTL */
601
602void __init lockup_detector_init(void)
603{
604 set_sample_period();
605
606 if (watchdog_user_enabled)
607 watchdog_enable_all_cpus(false);
608}