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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Detect hard and soft lockups on a system
4 *
5 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
6 *
7 * Note: Most of this code is borrowed heavily from the original softlockup
8 * detector, so thanks to Ingo for the initial implementation.
9 * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
10 * to those contributors as well.
11 */
12
13#define pr_fmt(fmt) "watchdog: " fmt
14
15#include <linux/mm.h>
16#include <linux/cpu.h>
17#include <linux/nmi.h>
18#include <linux/init.h>
19#include <linux/module.h>
20#include <linux/sysctl.h>
21#include <linux/tick.h>
22#include <linux/sched/clock.h>
23#include <linux/sched/debug.h>
24#include <linux/sched/isolation.h>
25#include <linux/stop_machine.h>
26
27#include <asm/irq_regs.h>
28#include <linux/kvm_para.h>
29
30static DEFINE_MUTEX(watchdog_mutex);
31
32#if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
33# define WATCHDOG_DEFAULT (SOFT_WATCHDOG_ENABLED | NMI_WATCHDOG_ENABLED)
34# define NMI_WATCHDOG_DEFAULT 1
35#else
36# define WATCHDOG_DEFAULT (SOFT_WATCHDOG_ENABLED)
37# define NMI_WATCHDOG_DEFAULT 0
38#endif
39
40unsigned long __read_mostly watchdog_enabled;
41int __read_mostly watchdog_user_enabled = 1;
42int __read_mostly nmi_watchdog_user_enabled = NMI_WATCHDOG_DEFAULT;
43int __read_mostly soft_watchdog_user_enabled = 1;
44int __read_mostly watchdog_thresh = 10;
45static int __read_mostly nmi_watchdog_available;
46
47struct cpumask watchdog_cpumask __read_mostly;
48unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
49
50#ifdef CONFIG_HARDLOCKUP_DETECTOR
51
52# ifdef CONFIG_SMP
53int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
54# endif /* CONFIG_SMP */
55
56/*
57 * Should we panic when a soft-lockup or hard-lockup occurs:
58 */
59unsigned int __read_mostly hardlockup_panic =
60 IS_ENABLED(CONFIG_BOOTPARAM_HARDLOCKUP_PANIC);
61/*
62 * We may not want to enable hard lockup detection by default in all cases,
63 * for example when running the kernel as a guest on a hypervisor. In these
64 * cases this function can be called to disable hard lockup detection. This
65 * function should only be executed once by the boot processor before the
66 * kernel command line parameters are parsed, because otherwise it is not
67 * possible to override this in hardlockup_panic_setup().
68 */
69void __init hardlockup_detector_disable(void)
70{
71 nmi_watchdog_user_enabled = 0;
72}
73
74static int __init hardlockup_panic_setup(char *str)
75{
76 if (!strncmp(str, "panic", 5))
77 hardlockup_panic = 1;
78 else if (!strncmp(str, "nopanic", 7))
79 hardlockup_panic = 0;
80 else if (!strncmp(str, "0", 1))
81 nmi_watchdog_user_enabled = 0;
82 else if (!strncmp(str, "1", 1))
83 nmi_watchdog_user_enabled = 1;
84 return 1;
85}
86__setup("nmi_watchdog=", hardlockup_panic_setup);
87
88#endif /* CONFIG_HARDLOCKUP_DETECTOR */
89
90/*
91 * These functions can be overridden if an architecture implements its
92 * own hardlockup detector.
93 *
94 * watchdog_nmi_enable/disable can be implemented to start and stop when
95 * softlockup watchdog start and stop. The arch must select the
96 * SOFTLOCKUP_DETECTOR Kconfig.
97 */
98int __weak watchdog_nmi_enable(unsigned int cpu)
99{
100 hardlockup_detector_perf_enable();
101 return 0;
102}
103
104void __weak watchdog_nmi_disable(unsigned int cpu)
105{
106 hardlockup_detector_perf_disable();
107}
108
109/* Return 0, if a NMI watchdog is available. Error code otherwise */
110int __weak __init watchdog_nmi_probe(void)
111{
112 return hardlockup_detector_perf_init();
113}
114
115/**
116 * watchdog_nmi_stop - Stop the watchdog for reconfiguration
117 *
118 * The reconfiguration steps are:
119 * watchdog_nmi_stop();
120 * update_variables();
121 * watchdog_nmi_start();
122 */
123void __weak watchdog_nmi_stop(void) { }
124
125/**
126 * watchdog_nmi_start - Start the watchdog after reconfiguration
127 *
128 * Counterpart to watchdog_nmi_stop().
129 *
130 * The following variables have been updated in update_variables() and
131 * contain the currently valid configuration:
132 * - watchdog_enabled
133 * - watchdog_thresh
134 * - watchdog_cpumask
135 */
136void __weak watchdog_nmi_start(void) { }
137
138/**
139 * lockup_detector_update_enable - Update the sysctl enable bit
140 *
141 * Caller needs to make sure that the NMI/perf watchdogs are off, so this
142 * can't race with watchdog_nmi_disable().
143 */
144static void lockup_detector_update_enable(void)
145{
146 watchdog_enabled = 0;
147 if (!watchdog_user_enabled)
148 return;
149 if (nmi_watchdog_available && nmi_watchdog_user_enabled)
150 watchdog_enabled |= NMI_WATCHDOG_ENABLED;
151 if (soft_watchdog_user_enabled)
152 watchdog_enabled |= SOFT_WATCHDOG_ENABLED;
153}
154
155#ifdef CONFIG_SOFTLOCKUP_DETECTOR
156
157/*
158 * Delay the soflockup report when running a known slow code.
159 * It does _not_ affect the timestamp of the last successdul reschedule.
160 */
161#define SOFTLOCKUP_DELAY_REPORT ULONG_MAX
162
163#ifdef CONFIG_SMP
164int __read_mostly sysctl_softlockup_all_cpu_backtrace;
165#endif
166
167static struct cpumask watchdog_allowed_mask __read_mostly;
168
169/* Global variables, exported for sysctl */
170unsigned int __read_mostly softlockup_panic =
171 IS_ENABLED(CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC);
172
173static bool softlockup_initialized __read_mostly;
174static u64 __read_mostly sample_period;
175
176/* Timestamp taken after the last successful reschedule. */
177static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
178/* Timestamp of the last softlockup report. */
179static DEFINE_PER_CPU(unsigned long, watchdog_report_ts);
180static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
181static DEFINE_PER_CPU(bool, softlockup_touch_sync);
182static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
183static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
184static unsigned long soft_lockup_nmi_warn;
185
186static int __init nowatchdog_setup(char *str)
187{
188 watchdog_user_enabled = 0;
189 return 1;
190}
191__setup("nowatchdog", nowatchdog_setup);
192
193static int __init nosoftlockup_setup(char *str)
194{
195 soft_watchdog_user_enabled = 0;
196 return 1;
197}
198__setup("nosoftlockup", nosoftlockup_setup);
199
200static int __init watchdog_thresh_setup(char *str)
201{
202 get_option(&str, &watchdog_thresh);
203 return 1;
204}
205__setup("watchdog_thresh=", watchdog_thresh_setup);
206
207static void __lockup_detector_cleanup(void);
208
209/*
210 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
211 * lockups can have false positives under extreme conditions. So we generally
212 * want a higher threshold for soft lockups than for hard lockups. So we couple
213 * the thresholds with a factor: we make the soft threshold twice the amount of
214 * time the hard threshold is.
215 */
216static int get_softlockup_thresh(void)
217{
218 return watchdog_thresh * 2;
219}
220
221/*
222 * Returns seconds, approximately. We don't need nanosecond
223 * resolution, and we don't need to waste time with a big divide when
224 * 2^30ns == 1.074s.
225 */
226static unsigned long get_timestamp(void)
227{
228 return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
229}
230
231static void set_sample_period(void)
232{
233 /*
234 * convert watchdog_thresh from seconds to ns
235 * the divide by 5 is to give hrtimer several chances (two
236 * or three with the current relation between the soft
237 * and hard thresholds) to increment before the
238 * hardlockup detector generates a warning
239 */
240 sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
241 watchdog_update_hrtimer_threshold(sample_period);
242}
243
244static void update_report_ts(void)
245{
246 __this_cpu_write(watchdog_report_ts, get_timestamp());
247}
248
249/* Commands for resetting the watchdog */
250static void update_touch_ts(void)
251{
252 __this_cpu_write(watchdog_touch_ts, get_timestamp());
253 update_report_ts();
254}
255
256/**
257 * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
258 *
259 * Call when the scheduler may have stalled for legitimate reasons
260 * preventing the watchdog task from executing - e.g. the scheduler
261 * entering idle state. This should only be used for scheduler events.
262 * Use touch_softlockup_watchdog() for everything else.
263 */
264notrace void touch_softlockup_watchdog_sched(void)
265{
266 /*
267 * Preemption can be enabled. It doesn't matter which CPU's watchdog
268 * report period gets restarted here, so use the raw_ operation.
269 */
270 raw_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
271}
272
273notrace void touch_softlockup_watchdog(void)
274{
275 touch_softlockup_watchdog_sched();
276 wq_watchdog_touch(raw_smp_processor_id());
277}
278EXPORT_SYMBOL(touch_softlockup_watchdog);
279
280void touch_all_softlockup_watchdogs(void)
281{
282 int cpu;
283
284 /*
285 * watchdog_mutex cannpt be taken here, as this might be called
286 * from (soft)interrupt context, so the access to
287 * watchdog_allowed_cpumask might race with a concurrent update.
288 *
289 * The watchdog time stamp can race against a concurrent real
290 * update as well, the only side effect might be a cycle delay for
291 * the softlockup check.
292 */
293 for_each_cpu(cpu, &watchdog_allowed_mask) {
294 per_cpu(watchdog_report_ts, cpu) = SOFTLOCKUP_DELAY_REPORT;
295 wq_watchdog_touch(cpu);
296 }
297}
298
299void touch_softlockup_watchdog_sync(void)
300{
301 __this_cpu_write(softlockup_touch_sync, true);
302 __this_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
303}
304
305static int is_softlockup(unsigned long touch_ts,
306 unsigned long period_ts,
307 unsigned long now)
308{
309 if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
310 /* Warn about unreasonable delays. */
311 if (time_after(now, period_ts + get_softlockup_thresh()))
312 return now - touch_ts;
313 }
314 return 0;
315}
316
317/* watchdog detector functions */
318bool is_hardlockup(void)
319{
320 unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
321
322 if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
323 return true;
324
325 __this_cpu_write(hrtimer_interrupts_saved, hrint);
326 return false;
327}
328
329static void watchdog_interrupt_count(void)
330{
331 __this_cpu_inc(hrtimer_interrupts);
332}
333
334static DEFINE_PER_CPU(struct completion, softlockup_completion);
335static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
336
337/*
338 * The watchdog feed function - touches the timestamp.
339 *
340 * It only runs once every sample_period seconds (4 seconds by
341 * default) to reset the softlockup timestamp. If this gets delayed
342 * for more than 2*watchdog_thresh seconds then the debug-printout
343 * triggers in watchdog_timer_fn().
344 */
345static int softlockup_fn(void *data)
346{
347 update_touch_ts();
348 complete(this_cpu_ptr(&softlockup_completion));
349
350 return 0;
351}
352
353/* watchdog kicker functions */
354static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
355{
356 unsigned long touch_ts, period_ts, now;
357 struct pt_regs *regs = get_irq_regs();
358 int duration;
359 int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
360
361 if (!watchdog_enabled)
362 return HRTIMER_NORESTART;
363
364 /* kick the hardlockup detector */
365 watchdog_interrupt_count();
366
367 /* kick the softlockup detector */
368 if (completion_done(this_cpu_ptr(&softlockup_completion))) {
369 reinit_completion(this_cpu_ptr(&softlockup_completion));
370 stop_one_cpu_nowait(smp_processor_id(),
371 softlockup_fn, NULL,
372 this_cpu_ptr(&softlockup_stop_work));
373 }
374
375 /* .. and repeat */
376 hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
377
378 /*
379 * Read the current timestamp first. It might become invalid anytime
380 * when a virtual machine is stopped by the host or when the watchog
381 * is touched from NMI.
382 */
383 now = get_timestamp();
384 /*
385 * If a virtual machine is stopped by the host it can look to
386 * the watchdog like a soft lockup. This function touches the watchdog.
387 */
388 kvm_check_and_clear_guest_paused();
389 /*
390 * The stored timestamp is comparable with @now only when not touched.
391 * It might get touched anytime from NMI. Make sure that is_softlockup()
392 * uses the same (valid) value.
393 */
394 period_ts = READ_ONCE(*this_cpu_ptr(&watchdog_report_ts));
395
396 /* Reset the interval when touched by known problematic code. */
397 if (period_ts == SOFTLOCKUP_DELAY_REPORT) {
398 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
399 /*
400 * If the time stamp was touched atomically
401 * make sure the scheduler tick is up to date.
402 */
403 __this_cpu_write(softlockup_touch_sync, false);
404 sched_clock_tick();
405 }
406
407 update_report_ts();
408 return HRTIMER_RESTART;
409 }
410
411 /* Check for a softlockup. */
412 touch_ts = __this_cpu_read(watchdog_touch_ts);
413 duration = is_softlockup(touch_ts, period_ts, now);
414 if (unlikely(duration)) {
415 /*
416 * Prevent multiple soft-lockup reports if one cpu is already
417 * engaged in dumping all cpu back traces.
418 */
419 if (softlockup_all_cpu_backtrace) {
420 if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn))
421 return HRTIMER_RESTART;
422 }
423
424 /* Start period for the next softlockup warning. */
425 update_report_ts();
426
427 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
428 smp_processor_id(), duration,
429 current->comm, task_pid_nr(current));
430 print_modules();
431 print_irqtrace_events(current);
432 if (regs)
433 show_regs(regs);
434 else
435 dump_stack();
436
437 if (softlockup_all_cpu_backtrace) {
438 trigger_allbutself_cpu_backtrace();
439 clear_bit_unlock(0, &soft_lockup_nmi_warn);
440 }
441
442 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
443 if (softlockup_panic)
444 panic("softlockup: hung tasks");
445 }
446
447 return HRTIMER_RESTART;
448}
449
450static void watchdog_enable(unsigned int cpu)
451{
452 struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
453 struct completion *done = this_cpu_ptr(&softlockup_completion);
454
455 WARN_ON_ONCE(cpu != smp_processor_id());
456
457 init_completion(done);
458 complete(done);
459
460 /*
461 * Start the timer first to prevent the NMI watchdog triggering
462 * before the timer has a chance to fire.
463 */
464 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
465 hrtimer->function = watchdog_timer_fn;
466 hrtimer_start(hrtimer, ns_to_ktime(sample_period),
467 HRTIMER_MODE_REL_PINNED_HARD);
468
469 /* Initialize timestamp */
470 update_touch_ts();
471 /* Enable the perf event */
472 if (watchdog_enabled & NMI_WATCHDOG_ENABLED)
473 watchdog_nmi_enable(cpu);
474}
475
476static void watchdog_disable(unsigned int cpu)
477{
478 struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
479
480 WARN_ON_ONCE(cpu != smp_processor_id());
481
482 /*
483 * Disable the perf event first. That prevents that a large delay
484 * between disabling the timer and disabling the perf event causes
485 * the perf NMI to detect a false positive.
486 */
487 watchdog_nmi_disable(cpu);
488 hrtimer_cancel(hrtimer);
489 wait_for_completion(this_cpu_ptr(&softlockup_completion));
490}
491
492static int softlockup_stop_fn(void *data)
493{
494 watchdog_disable(smp_processor_id());
495 return 0;
496}
497
498static void softlockup_stop_all(void)
499{
500 int cpu;
501
502 if (!softlockup_initialized)
503 return;
504
505 for_each_cpu(cpu, &watchdog_allowed_mask)
506 smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
507
508 cpumask_clear(&watchdog_allowed_mask);
509}
510
511static int softlockup_start_fn(void *data)
512{
513 watchdog_enable(smp_processor_id());
514 return 0;
515}
516
517static void softlockup_start_all(void)
518{
519 int cpu;
520
521 cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
522 for_each_cpu(cpu, &watchdog_allowed_mask)
523 smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
524}
525
526int lockup_detector_online_cpu(unsigned int cpu)
527{
528 if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
529 watchdog_enable(cpu);
530 return 0;
531}
532
533int lockup_detector_offline_cpu(unsigned int cpu)
534{
535 if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
536 watchdog_disable(cpu);
537 return 0;
538}
539
540static void __lockup_detector_reconfigure(void)
541{
542 cpus_read_lock();
543 watchdog_nmi_stop();
544
545 softlockup_stop_all();
546 set_sample_period();
547 lockup_detector_update_enable();
548 if (watchdog_enabled && watchdog_thresh)
549 softlockup_start_all();
550
551 watchdog_nmi_start();
552 cpus_read_unlock();
553 /*
554 * Must be called outside the cpus locked section to prevent
555 * recursive locking in the perf code.
556 */
557 __lockup_detector_cleanup();
558}
559
560void lockup_detector_reconfigure(void)
561{
562 mutex_lock(&watchdog_mutex);
563 __lockup_detector_reconfigure();
564 mutex_unlock(&watchdog_mutex);
565}
566
567/*
568 * Create the watchdog infrastructure and configure the detector(s).
569 */
570static __init void lockup_detector_setup(void)
571{
572 /*
573 * If sysctl is off and watchdog got disabled on the command line,
574 * nothing to do here.
575 */
576 lockup_detector_update_enable();
577
578 if (!IS_ENABLED(CONFIG_SYSCTL) &&
579 !(watchdog_enabled && watchdog_thresh))
580 return;
581
582 mutex_lock(&watchdog_mutex);
583 __lockup_detector_reconfigure();
584 softlockup_initialized = true;
585 mutex_unlock(&watchdog_mutex);
586}
587
588#else /* CONFIG_SOFTLOCKUP_DETECTOR */
589static void __lockup_detector_reconfigure(void)
590{
591 cpus_read_lock();
592 watchdog_nmi_stop();
593 lockup_detector_update_enable();
594 watchdog_nmi_start();
595 cpus_read_unlock();
596}
597void lockup_detector_reconfigure(void)
598{
599 __lockup_detector_reconfigure();
600}
601static inline void lockup_detector_setup(void)
602{
603 __lockup_detector_reconfigure();
604}
605#endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
606
607static void __lockup_detector_cleanup(void)
608{
609 lockdep_assert_held(&watchdog_mutex);
610 hardlockup_detector_perf_cleanup();
611}
612
613/**
614 * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
615 *
616 * Caller must not hold the cpu hotplug rwsem.
617 */
618void lockup_detector_cleanup(void)
619{
620 mutex_lock(&watchdog_mutex);
621 __lockup_detector_cleanup();
622 mutex_unlock(&watchdog_mutex);
623}
624
625/**
626 * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
627 *
628 * Special interface for parisc. It prevents lockup detector warnings from
629 * the default pm_poweroff() function which busy loops forever.
630 */
631void lockup_detector_soft_poweroff(void)
632{
633 watchdog_enabled = 0;
634}
635
636#ifdef CONFIG_SYSCTL
637
638/* Propagate any changes to the watchdog infrastructure */
639static void proc_watchdog_update(void)
640{
641 /* Remove impossible cpus to keep sysctl output clean. */
642 cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
643 __lockup_detector_reconfigure();
644}
645
646/*
647 * common function for watchdog, nmi_watchdog and soft_watchdog parameter
648 *
649 * caller | table->data points to | 'which'
650 * -------------------|----------------------------|--------------------------
651 * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED |
652 * | | SOFT_WATCHDOG_ENABLED
653 * -------------------|----------------------------|--------------------------
654 * proc_nmi_watchdog | nmi_watchdog_user_enabled | NMI_WATCHDOG_ENABLED
655 * -------------------|----------------------------|--------------------------
656 * proc_soft_watchdog | soft_watchdog_user_enabled | SOFT_WATCHDOG_ENABLED
657 */
658static int proc_watchdog_common(int which, struct ctl_table *table, int write,
659 void *buffer, size_t *lenp, loff_t *ppos)
660{
661 int err, old, *param = table->data;
662
663 mutex_lock(&watchdog_mutex);
664
665 if (!write) {
666 /*
667 * On read synchronize the userspace interface. This is a
668 * racy snapshot.
669 */
670 *param = (watchdog_enabled & which) != 0;
671 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
672 } else {
673 old = READ_ONCE(*param);
674 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
675 if (!err && old != READ_ONCE(*param))
676 proc_watchdog_update();
677 }
678 mutex_unlock(&watchdog_mutex);
679 return err;
680}
681
682/*
683 * /proc/sys/kernel/watchdog
684 */
685int proc_watchdog(struct ctl_table *table, int write,
686 void *buffer, size_t *lenp, loff_t *ppos)
687{
688 return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
689 table, write, buffer, lenp, ppos);
690}
691
692/*
693 * /proc/sys/kernel/nmi_watchdog
694 */
695int proc_nmi_watchdog(struct ctl_table *table, int write,
696 void *buffer, size_t *lenp, loff_t *ppos)
697{
698 if (!nmi_watchdog_available && write)
699 return -ENOTSUPP;
700 return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
701 table, write, buffer, lenp, ppos);
702}
703
704/*
705 * /proc/sys/kernel/soft_watchdog
706 */
707int proc_soft_watchdog(struct ctl_table *table, int write,
708 void *buffer, size_t *lenp, loff_t *ppos)
709{
710 return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
711 table, write, buffer, lenp, ppos);
712}
713
714/*
715 * /proc/sys/kernel/watchdog_thresh
716 */
717int proc_watchdog_thresh(struct ctl_table *table, int write,
718 void *buffer, size_t *lenp, loff_t *ppos)
719{
720 int err, old;
721
722 mutex_lock(&watchdog_mutex);
723
724 old = READ_ONCE(watchdog_thresh);
725 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
726
727 if (!err && write && old != READ_ONCE(watchdog_thresh))
728 proc_watchdog_update();
729
730 mutex_unlock(&watchdog_mutex);
731 return err;
732}
733
734/*
735 * The cpumask is the mask of possible cpus that the watchdog can run
736 * on, not the mask of cpus it is actually running on. This allows the
737 * user to specify a mask that will include cpus that have not yet
738 * been brought online, if desired.
739 */
740int proc_watchdog_cpumask(struct ctl_table *table, int write,
741 void *buffer, size_t *lenp, loff_t *ppos)
742{
743 int err;
744
745 mutex_lock(&watchdog_mutex);
746
747 err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
748 if (!err && write)
749 proc_watchdog_update();
750
751 mutex_unlock(&watchdog_mutex);
752 return err;
753}
754
755static const int sixty = 60;
756
757static struct ctl_table watchdog_sysctls[] = {
758 {
759 .procname = "watchdog",
760 .data = &watchdog_user_enabled,
761 .maxlen = sizeof(int),
762 .mode = 0644,
763 .proc_handler = proc_watchdog,
764 .extra1 = SYSCTL_ZERO,
765 .extra2 = SYSCTL_ONE,
766 },
767 {
768 .procname = "watchdog_thresh",
769 .data = &watchdog_thresh,
770 .maxlen = sizeof(int),
771 .mode = 0644,
772 .proc_handler = proc_watchdog_thresh,
773 .extra1 = SYSCTL_ZERO,
774 .extra2 = (void *)&sixty,
775 },
776 {
777 .procname = "nmi_watchdog",
778 .data = &nmi_watchdog_user_enabled,
779 .maxlen = sizeof(int),
780 .mode = NMI_WATCHDOG_SYSCTL_PERM,
781 .proc_handler = proc_nmi_watchdog,
782 .extra1 = SYSCTL_ZERO,
783 .extra2 = SYSCTL_ONE,
784 },
785 {
786 .procname = "watchdog_cpumask",
787 .data = &watchdog_cpumask_bits,
788 .maxlen = NR_CPUS,
789 .mode = 0644,
790 .proc_handler = proc_watchdog_cpumask,
791 },
792#ifdef CONFIG_SOFTLOCKUP_DETECTOR
793 {
794 .procname = "soft_watchdog",
795 .data = &soft_watchdog_user_enabled,
796 .maxlen = sizeof(int),
797 .mode = 0644,
798 .proc_handler = proc_soft_watchdog,
799 .extra1 = SYSCTL_ZERO,
800 .extra2 = SYSCTL_ONE,
801 },
802 {
803 .procname = "softlockup_panic",
804 .data = &softlockup_panic,
805 .maxlen = sizeof(int),
806 .mode = 0644,
807 .proc_handler = proc_dointvec_minmax,
808 .extra1 = SYSCTL_ZERO,
809 .extra2 = SYSCTL_ONE,
810 },
811#ifdef CONFIG_SMP
812 {
813 .procname = "softlockup_all_cpu_backtrace",
814 .data = &sysctl_softlockup_all_cpu_backtrace,
815 .maxlen = sizeof(int),
816 .mode = 0644,
817 .proc_handler = proc_dointvec_minmax,
818 .extra1 = SYSCTL_ZERO,
819 .extra2 = SYSCTL_ONE,
820 },
821#endif /* CONFIG_SMP */
822#endif
823#ifdef CONFIG_HARDLOCKUP_DETECTOR
824 {
825 .procname = "hardlockup_panic",
826 .data = &hardlockup_panic,
827 .maxlen = sizeof(int),
828 .mode = 0644,
829 .proc_handler = proc_dointvec_minmax,
830 .extra1 = SYSCTL_ZERO,
831 .extra2 = SYSCTL_ONE,
832 },
833#ifdef CONFIG_SMP
834 {
835 .procname = "hardlockup_all_cpu_backtrace",
836 .data = &sysctl_hardlockup_all_cpu_backtrace,
837 .maxlen = sizeof(int),
838 .mode = 0644,
839 .proc_handler = proc_dointvec_minmax,
840 .extra1 = SYSCTL_ZERO,
841 .extra2 = SYSCTL_ONE,
842 },
843#endif /* CONFIG_SMP */
844#endif
845 {}
846};
847
848static void __init watchdog_sysctl_init(void)
849{
850 register_sysctl_init("kernel", watchdog_sysctls);
851}
852#else
853#define watchdog_sysctl_init() do { } while (0)
854#endif /* CONFIG_SYSCTL */
855
856void __init lockup_detector_init(void)
857{
858 if (tick_nohz_full_enabled())
859 pr_info("Disabling watchdog on nohz_full cores by default\n");
860
861 cpumask_copy(&watchdog_cpumask,
862 housekeeping_cpumask(HK_TYPE_TIMER));
863
864 if (!watchdog_nmi_probe())
865 nmi_watchdog_available = true;
866 lockup_detector_setup();
867 watchdog_sysctl_init();
868}
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/module.h>
19#include <linux/sysctl.h>
20#include <linux/smpboot.h>
21#include <linux/sched/rt.h>
22#include <linux/tick.h>
23#include <linux/workqueue.h>
24
25#include <asm/irq_regs.h>
26#include <linux/kvm_para.h>
27#include <linux/perf_event.h>
28#include <linux/kthread.h>
29
30/*
31 * The run state of the lockup detectors is controlled by the content of the
32 * 'watchdog_enabled' variable. Each lockup detector has its dedicated bit -
33 * bit 0 for the hard lockup detector and bit 1 for the soft lockup detector.
34 *
35 * 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled'
36 * are variables that are only used as an 'interface' between the parameters
37 * in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The
38 * 'watchdog_thresh' variable is handled differently because its value is not
39 * boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh'
40 * is equal zero.
41 */
42#define NMI_WATCHDOG_ENABLED_BIT 0
43#define SOFT_WATCHDOG_ENABLED_BIT 1
44#define NMI_WATCHDOG_ENABLED (1 << NMI_WATCHDOG_ENABLED_BIT)
45#define SOFT_WATCHDOG_ENABLED (1 << SOFT_WATCHDOG_ENABLED_BIT)
46
47static DEFINE_MUTEX(watchdog_proc_mutex);
48
49#ifdef CONFIG_HARDLOCKUP_DETECTOR
50static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
51#else
52static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
53#endif
54int __read_mostly nmi_watchdog_enabled;
55int __read_mostly soft_watchdog_enabled;
56int __read_mostly watchdog_user_enabled;
57int __read_mostly watchdog_thresh = 10;
58
59#ifdef CONFIG_SMP
60int __read_mostly sysctl_softlockup_all_cpu_backtrace;
61int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
62#else
63#define sysctl_softlockup_all_cpu_backtrace 0
64#define sysctl_hardlockup_all_cpu_backtrace 0
65#endif
66static struct cpumask watchdog_cpumask __read_mostly;
67unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
68
69/* Helper for online, unparked cpus. */
70#define for_each_watchdog_cpu(cpu) \
71 for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
72
73/*
74 * The 'watchdog_running' variable is set to 1 when the watchdog threads
75 * are registered/started and is set to 0 when the watchdog threads are
76 * unregistered/stopped, so it is an indicator whether the threads exist.
77 */
78static int __read_mostly watchdog_running;
79/*
80 * If a subsystem has a need to deactivate the watchdog temporarily, it
81 * can use the suspend/resume interface to achieve this. The content of
82 * the 'watchdog_suspended' variable reflects this state. Existing threads
83 * are parked/unparked by the lockup_detector_{suspend|resume} functions
84 * (see comment blocks pertaining to those functions for further details).
85 *
86 * 'watchdog_suspended' also prevents threads from being registered/started
87 * or unregistered/stopped via parameters in /proc/sys/kernel, so the state
88 * of 'watchdog_running' cannot change while the watchdog is deactivated
89 * temporarily (see related code in 'proc' handlers).
90 */
91static int __read_mostly watchdog_suspended;
92
93static u64 __read_mostly sample_period;
94
95static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
96static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
97static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
98static DEFINE_PER_CPU(bool, softlockup_touch_sync);
99static DEFINE_PER_CPU(bool, soft_watchdog_warn);
100static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
101static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
102static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
103#ifdef CONFIG_HARDLOCKUP_DETECTOR
104static DEFINE_PER_CPU(bool, hard_watchdog_warn);
105static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
106static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
107static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
108#endif
109static unsigned long soft_lockup_nmi_warn;
110
111/* boot commands */
112/*
113 * Should we panic when a soft-lockup or hard-lockup occurs:
114 */
115#ifdef CONFIG_HARDLOCKUP_DETECTOR
116unsigned int __read_mostly hardlockup_panic =
117 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
118static unsigned long hardlockup_allcpu_dumped;
119/*
120 * We may not want to enable hard lockup detection by default in all cases,
121 * for example when running the kernel as a guest on a hypervisor. In these
122 * cases this function can be called to disable hard lockup detection. This
123 * function should only be executed once by the boot processor before the
124 * kernel command line parameters are parsed, because otherwise it is not
125 * possible to override this in hardlockup_panic_setup().
126 */
127void hardlockup_detector_disable(void)
128{
129 watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
130}
131
132static int __init hardlockup_panic_setup(char *str)
133{
134 if (!strncmp(str, "panic", 5))
135 hardlockup_panic = 1;
136 else if (!strncmp(str, "nopanic", 7))
137 hardlockup_panic = 0;
138 else if (!strncmp(str, "0", 1))
139 watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
140 else if (!strncmp(str, "1", 1))
141 watchdog_enabled |= NMI_WATCHDOG_ENABLED;
142 return 1;
143}
144__setup("nmi_watchdog=", hardlockup_panic_setup);
145#endif
146
147unsigned int __read_mostly softlockup_panic =
148 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
149
150static int __init softlockup_panic_setup(char *str)
151{
152 softlockup_panic = simple_strtoul(str, NULL, 0);
153
154 return 1;
155}
156__setup("softlockup_panic=", softlockup_panic_setup);
157
158static int __init nowatchdog_setup(char *str)
159{
160 watchdog_enabled = 0;
161 return 1;
162}
163__setup("nowatchdog", nowatchdog_setup);
164
165static int __init nosoftlockup_setup(char *str)
166{
167 watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED;
168 return 1;
169}
170__setup("nosoftlockup", nosoftlockup_setup);
171
172#ifdef CONFIG_SMP
173static int __init softlockup_all_cpu_backtrace_setup(char *str)
174{
175 sysctl_softlockup_all_cpu_backtrace =
176 !!simple_strtol(str, NULL, 0);
177 return 1;
178}
179__setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
180static int __init hardlockup_all_cpu_backtrace_setup(char *str)
181{
182 sysctl_hardlockup_all_cpu_backtrace =
183 !!simple_strtol(str, NULL, 0);
184 return 1;
185}
186__setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
187#endif
188
189/*
190 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
191 * lockups can have false positives under extreme conditions. So we generally
192 * want a higher threshold for soft lockups than for hard lockups. So we couple
193 * the thresholds with a factor: we make the soft threshold twice the amount of
194 * time the hard threshold is.
195 */
196static int get_softlockup_thresh(void)
197{
198 return watchdog_thresh * 2;
199}
200
201/*
202 * Returns seconds, approximately. We don't need nanosecond
203 * resolution, and we don't need to waste time with a big divide when
204 * 2^30ns == 1.074s.
205 */
206static unsigned long get_timestamp(void)
207{
208 return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
209}
210
211static void set_sample_period(void)
212{
213 /*
214 * convert watchdog_thresh from seconds to ns
215 * the divide by 5 is to give hrtimer several chances (two
216 * or three with the current relation between the soft
217 * and hard thresholds) to increment before the
218 * hardlockup detector generates a warning
219 */
220 sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
221}
222
223/* Commands for resetting the watchdog */
224static void __touch_watchdog(void)
225{
226 __this_cpu_write(watchdog_touch_ts, get_timestamp());
227}
228
229/**
230 * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
231 *
232 * Call when the scheduler may have stalled for legitimate reasons
233 * preventing the watchdog task from executing - e.g. the scheduler
234 * entering idle state. This should only be used for scheduler events.
235 * Use touch_softlockup_watchdog() for everything else.
236 */
237void touch_softlockup_watchdog_sched(void)
238{
239 /*
240 * Preemption can be enabled. It doesn't matter which CPU's timestamp
241 * gets zeroed here, so use the raw_ operation.
242 */
243 raw_cpu_write(watchdog_touch_ts, 0);
244}
245
246void touch_softlockup_watchdog(void)
247{
248 touch_softlockup_watchdog_sched();
249 wq_watchdog_touch(raw_smp_processor_id());
250}
251EXPORT_SYMBOL(touch_softlockup_watchdog);
252
253void touch_all_softlockup_watchdogs(void)
254{
255 int cpu;
256
257 /*
258 * this is done lockless
259 * do we care if a 0 races with a timestamp?
260 * all it means is the softlock check starts one cycle later
261 */
262 for_each_watchdog_cpu(cpu)
263 per_cpu(watchdog_touch_ts, cpu) = 0;
264 wq_watchdog_touch(-1);
265}
266
267#ifdef CONFIG_HARDLOCKUP_DETECTOR
268void touch_nmi_watchdog(void)
269{
270 /*
271 * Using __raw here because some code paths have
272 * preemption enabled. If preemption is enabled
273 * then interrupts should be enabled too, in which
274 * case we shouldn't have to worry about the watchdog
275 * going off.
276 */
277 raw_cpu_write(watchdog_nmi_touch, true);
278 touch_softlockup_watchdog();
279}
280EXPORT_SYMBOL(touch_nmi_watchdog);
281
282#endif
283
284void touch_softlockup_watchdog_sync(void)
285{
286 __this_cpu_write(softlockup_touch_sync, true);
287 __this_cpu_write(watchdog_touch_ts, 0);
288}
289
290#ifdef CONFIG_HARDLOCKUP_DETECTOR
291/* watchdog detector functions */
292static bool is_hardlockup(void)
293{
294 unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
295
296 if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
297 return true;
298
299 __this_cpu_write(hrtimer_interrupts_saved, hrint);
300 return false;
301}
302#endif
303
304static int is_softlockup(unsigned long touch_ts)
305{
306 unsigned long now = get_timestamp();
307
308 if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
309 /* Warn about unreasonable delays. */
310 if (time_after(now, touch_ts + get_softlockup_thresh()))
311 return now - touch_ts;
312 }
313 return 0;
314}
315
316#ifdef CONFIG_HARDLOCKUP_DETECTOR
317
318static struct perf_event_attr wd_hw_attr = {
319 .type = PERF_TYPE_HARDWARE,
320 .config = PERF_COUNT_HW_CPU_CYCLES,
321 .size = sizeof(struct perf_event_attr),
322 .pinned = 1,
323 .disabled = 1,
324};
325
326/* Callback function for perf event subsystem */
327static void watchdog_overflow_callback(struct perf_event *event,
328 struct perf_sample_data *data,
329 struct pt_regs *regs)
330{
331 /* Ensure the watchdog never gets throttled */
332 event->hw.interrupts = 0;
333
334 if (__this_cpu_read(watchdog_nmi_touch) == true) {
335 __this_cpu_write(watchdog_nmi_touch, false);
336 return;
337 }
338
339 /* check for a hardlockup
340 * This is done by making sure our timer interrupt
341 * is incrementing. The timer interrupt should have
342 * fired multiple times before we overflow'd. If it hasn't
343 * then this is a good indication the cpu is stuck
344 */
345 if (is_hardlockup()) {
346 int this_cpu = smp_processor_id();
347 struct pt_regs *regs = get_irq_regs();
348
349 /* only print hardlockups once */
350 if (__this_cpu_read(hard_watchdog_warn) == true)
351 return;
352
353 pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
354 print_modules();
355 print_irqtrace_events(current);
356 if (regs)
357 show_regs(regs);
358 else
359 dump_stack();
360
361 /*
362 * Perform all-CPU dump only once to avoid multiple hardlockups
363 * generating interleaving traces
364 */
365 if (sysctl_hardlockup_all_cpu_backtrace &&
366 !test_and_set_bit(0, &hardlockup_allcpu_dumped))
367 trigger_allbutself_cpu_backtrace();
368
369 if (hardlockup_panic)
370 nmi_panic(regs, "Hard LOCKUP");
371
372 __this_cpu_write(hard_watchdog_warn, true);
373 return;
374 }
375
376 __this_cpu_write(hard_watchdog_warn, false);
377 return;
378}
379#endif /* CONFIG_HARDLOCKUP_DETECTOR */
380
381static void watchdog_interrupt_count(void)
382{
383 __this_cpu_inc(hrtimer_interrupts);
384}
385
386static int watchdog_nmi_enable(unsigned int cpu);
387static void watchdog_nmi_disable(unsigned int cpu);
388
389static int watchdog_enable_all_cpus(void);
390static void watchdog_disable_all_cpus(void);
391
392/* watchdog kicker functions */
393static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
394{
395 unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
396 struct pt_regs *regs = get_irq_regs();
397 int duration;
398 int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
399
400 /* kick the hardlockup detector */
401 watchdog_interrupt_count();
402
403 /* kick the softlockup detector */
404 wake_up_process(__this_cpu_read(softlockup_watchdog));
405
406 /* .. and repeat */
407 hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
408
409 if (touch_ts == 0) {
410 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
411 /*
412 * If the time stamp was touched atomically
413 * make sure the scheduler tick is up to date.
414 */
415 __this_cpu_write(softlockup_touch_sync, false);
416 sched_clock_tick();
417 }
418
419 /* Clear the guest paused flag on watchdog reset */
420 kvm_check_and_clear_guest_paused();
421 __touch_watchdog();
422 return HRTIMER_RESTART;
423 }
424
425 /* check for a softlockup
426 * This is done by making sure a high priority task is
427 * being scheduled. The task touches the watchdog to
428 * indicate it is getting cpu time. If it hasn't then
429 * this is a good indication some task is hogging the cpu
430 */
431 duration = is_softlockup(touch_ts);
432 if (unlikely(duration)) {
433 /*
434 * If a virtual machine is stopped by the host it can look to
435 * the watchdog like a soft lockup, check to see if the host
436 * stopped the vm before we issue the warning
437 */
438 if (kvm_check_and_clear_guest_paused())
439 return HRTIMER_RESTART;
440
441 /* only warn once */
442 if (__this_cpu_read(soft_watchdog_warn) == true) {
443 /*
444 * When multiple processes are causing softlockups the
445 * softlockup detector only warns on the first one
446 * because the code relies on a full quiet cycle to
447 * re-arm. The second process prevents the quiet cycle
448 * and never gets reported. Use task pointers to detect
449 * this.
450 */
451 if (__this_cpu_read(softlockup_task_ptr_saved) !=
452 current) {
453 __this_cpu_write(soft_watchdog_warn, false);
454 __touch_watchdog();
455 }
456 return HRTIMER_RESTART;
457 }
458
459 if (softlockup_all_cpu_backtrace) {
460 /* Prevent multiple soft-lockup reports if one cpu is already
461 * engaged in dumping cpu back traces
462 */
463 if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
464 /* Someone else will report us. Let's give up */
465 __this_cpu_write(soft_watchdog_warn, true);
466 return HRTIMER_RESTART;
467 }
468 }
469
470 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
471 smp_processor_id(), duration,
472 current->comm, task_pid_nr(current));
473 __this_cpu_write(softlockup_task_ptr_saved, current);
474 print_modules();
475 print_irqtrace_events(current);
476 if (regs)
477 show_regs(regs);
478 else
479 dump_stack();
480
481 if (softlockup_all_cpu_backtrace) {
482 /* Avoid generating two back traces for current
483 * given that one is already made above
484 */
485 trigger_allbutself_cpu_backtrace();
486
487 clear_bit(0, &soft_lockup_nmi_warn);
488 /* Barrier to sync with other cpus */
489 smp_mb__after_atomic();
490 }
491
492 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
493 if (softlockup_panic)
494 panic("softlockup: hung tasks");
495 __this_cpu_write(soft_watchdog_warn, true);
496 } else
497 __this_cpu_write(soft_watchdog_warn, false);
498
499 return HRTIMER_RESTART;
500}
501
502static void watchdog_set_prio(unsigned int policy, unsigned int prio)
503{
504 struct sched_param param = { .sched_priority = prio };
505
506 sched_setscheduler(current, policy, ¶m);
507}
508
509static void watchdog_enable(unsigned int cpu)
510{
511 struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
512
513 /* kick off the timer for the hardlockup detector */
514 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
515 hrtimer->function = watchdog_timer_fn;
516
517 /* Enable the perf event */
518 watchdog_nmi_enable(cpu);
519
520 /* done here because hrtimer_start can only pin to smp_processor_id() */
521 hrtimer_start(hrtimer, ns_to_ktime(sample_period),
522 HRTIMER_MODE_REL_PINNED);
523
524 /* initialize timestamp */
525 watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
526 __touch_watchdog();
527}
528
529static void watchdog_disable(unsigned int cpu)
530{
531 struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
532
533 watchdog_set_prio(SCHED_NORMAL, 0);
534 hrtimer_cancel(hrtimer);
535 /* disable the perf event */
536 watchdog_nmi_disable(cpu);
537}
538
539static void watchdog_cleanup(unsigned int cpu, bool online)
540{
541 watchdog_disable(cpu);
542}
543
544static int watchdog_should_run(unsigned int cpu)
545{
546 return __this_cpu_read(hrtimer_interrupts) !=
547 __this_cpu_read(soft_lockup_hrtimer_cnt);
548}
549
550/*
551 * The watchdog thread function - touches the timestamp.
552 *
553 * It only runs once every sample_period seconds (4 seconds by
554 * default) to reset the softlockup timestamp. If this gets delayed
555 * for more than 2*watchdog_thresh seconds then the debug-printout
556 * triggers in watchdog_timer_fn().
557 */
558static void watchdog(unsigned int cpu)
559{
560 __this_cpu_write(soft_lockup_hrtimer_cnt,
561 __this_cpu_read(hrtimer_interrupts));
562 __touch_watchdog();
563
564 /*
565 * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
566 * failure path. Check for failures that can occur asynchronously -
567 * for example, when CPUs are on-lined - and shut down the hardware
568 * perf event on each CPU accordingly.
569 *
570 * The only non-obvious place this bit can be cleared is through
571 * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a
572 * pr_info here would be too noisy as it would result in a message
573 * every few seconds if the hardlockup was disabled but the softlockup
574 * enabled.
575 */
576 if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
577 watchdog_nmi_disable(cpu);
578}
579
580#ifdef CONFIG_HARDLOCKUP_DETECTOR
581/*
582 * People like the simple clean cpu node info on boot.
583 * Reduce the watchdog noise by only printing messages
584 * that are different from what cpu0 displayed.
585 */
586static unsigned long cpu0_err;
587
588static int watchdog_nmi_enable(unsigned int cpu)
589{
590 struct perf_event_attr *wd_attr;
591 struct perf_event *event = per_cpu(watchdog_ev, cpu);
592
593 /* nothing to do if the hard lockup detector is disabled */
594 if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
595 goto out;
596
597 /* is it already setup and enabled? */
598 if (event && event->state > PERF_EVENT_STATE_OFF)
599 goto out;
600
601 /* it is setup but not enabled */
602 if (event != NULL)
603 goto out_enable;
604
605 wd_attr = &wd_hw_attr;
606 wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
607
608 /* Try to register using hardware perf events */
609 event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
610
611 /* save cpu0 error for future comparision */
612 if (cpu == 0 && IS_ERR(event))
613 cpu0_err = PTR_ERR(event);
614
615 if (!IS_ERR(event)) {
616 /* only print for cpu0 or different than cpu0 */
617 if (cpu == 0 || cpu0_err)
618 pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
619 goto out_save;
620 }
621
622 /*
623 * Disable the hard lockup detector if _any_ CPU fails to set up
624 * set up the hardware perf event. The watchdog() function checks
625 * the NMI_WATCHDOG_ENABLED bit periodically.
626 *
627 * The barriers are for syncing up watchdog_enabled across all the
628 * cpus, as clear_bit() does not use barriers.
629 */
630 smp_mb__before_atomic();
631 clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled);
632 smp_mb__after_atomic();
633
634 /* skip displaying the same error again */
635 if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
636 return PTR_ERR(event);
637
638 /* vary the KERN level based on the returned errno */
639 if (PTR_ERR(event) == -EOPNOTSUPP)
640 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
641 else if (PTR_ERR(event) == -ENOENT)
642 pr_warn("disabled (cpu%i): hardware events not enabled\n",
643 cpu);
644 else
645 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
646 cpu, PTR_ERR(event));
647
648 pr_info("Shutting down hard lockup detector on all cpus\n");
649
650 return PTR_ERR(event);
651
652 /* success path */
653out_save:
654 per_cpu(watchdog_ev, cpu) = event;
655out_enable:
656 perf_event_enable(per_cpu(watchdog_ev, cpu));
657out:
658 return 0;
659}
660
661static void watchdog_nmi_disable(unsigned int cpu)
662{
663 struct perf_event *event = per_cpu(watchdog_ev, cpu);
664
665 if (event) {
666 perf_event_disable(event);
667 per_cpu(watchdog_ev, cpu) = NULL;
668
669 /* should be in cleanup, but blocks oprofile */
670 perf_event_release_kernel(event);
671 }
672 if (cpu == 0) {
673 /* watchdog_nmi_enable() expects this to be zero initially. */
674 cpu0_err = 0;
675 }
676}
677
678#else
679static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
680static void watchdog_nmi_disable(unsigned int cpu) { return; }
681#endif /* CONFIG_HARDLOCKUP_DETECTOR */
682
683static struct smp_hotplug_thread watchdog_threads = {
684 .store = &softlockup_watchdog,
685 .thread_should_run = watchdog_should_run,
686 .thread_fn = watchdog,
687 .thread_comm = "watchdog/%u",
688 .setup = watchdog_enable,
689 .cleanup = watchdog_cleanup,
690 .park = watchdog_disable,
691 .unpark = watchdog_enable,
692};
693
694/*
695 * park all watchdog threads that are specified in 'watchdog_cpumask'
696 *
697 * This function returns an error if kthread_park() of a watchdog thread
698 * fails. In this situation, the watchdog threads of some CPUs can already
699 * be parked and the watchdog threads of other CPUs can still be runnable.
700 * Callers are expected to handle this special condition as appropriate in
701 * their context.
702 *
703 * This function may only be called in a context that is protected against
704 * races with CPU hotplug - for example, via get_online_cpus().
705 */
706static int watchdog_park_threads(void)
707{
708 int cpu, ret = 0;
709
710 for_each_watchdog_cpu(cpu) {
711 ret = kthread_park(per_cpu(softlockup_watchdog, cpu));
712 if (ret)
713 break;
714 }
715
716 return ret;
717}
718
719/*
720 * unpark all watchdog threads that are specified in 'watchdog_cpumask'
721 *
722 * This function may only be called in a context that is protected against
723 * races with CPU hotplug - for example, via get_online_cpus().
724 */
725static void watchdog_unpark_threads(void)
726{
727 int cpu;
728
729 for_each_watchdog_cpu(cpu)
730 kthread_unpark(per_cpu(softlockup_watchdog, cpu));
731}
732
733/*
734 * Suspend the hard and soft lockup detector by parking the watchdog threads.
735 */
736int lockup_detector_suspend(void)
737{
738 int ret = 0;
739
740 get_online_cpus();
741 mutex_lock(&watchdog_proc_mutex);
742 /*
743 * Multiple suspend requests can be active in parallel (counted by
744 * the 'watchdog_suspended' variable). If the watchdog threads are
745 * running, the first caller takes care that they will be parked.
746 * The state of 'watchdog_running' cannot change while a suspend
747 * request is active (see related code in 'proc' handlers).
748 */
749 if (watchdog_running && !watchdog_suspended)
750 ret = watchdog_park_threads();
751
752 if (ret == 0)
753 watchdog_suspended++;
754 else {
755 watchdog_disable_all_cpus();
756 pr_err("Failed to suspend lockup detectors, disabled\n");
757 watchdog_enabled = 0;
758 }
759
760 mutex_unlock(&watchdog_proc_mutex);
761
762 return ret;
763}
764
765/*
766 * Resume the hard and soft lockup detector by unparking the watchdog threads.
767 */
768void lockup_detector_resume(void)
769{
770 mutex_lock(&watchdog_proc_mutex);
771
772 watchdog_suspended--;
773 /*
774 * The watchdog threads are unparked if they were previously running
775 * and if there is no more active suspend request.
776 */
777 if (watchdog_running && !watchdog_suspended)
778 watchdog_unpark_threads();
779
780 mutex_unlock(&watchdog_proc_mutex);
781 put_online_cpus();
782}
783
784static int update_watchdog_all_cpus(void)
785{
786 int ret;
787
788 ret = watchdog_park_threads();
789 if (ret)
790 return ret;
791
792 watchdog_unpark_threads();
793
794 return 0;
795}
796
797static int watchdog_enable_all_cpus(void)
798{
799 int err = 0;
800
801 if (!watchdog_running) {
802 err = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
803 &watchdog_cpumask);
804 if (err)
805 pr_err("Failed to create watchdog threads, disabled\n");
806 else
807 watchdog_running = 1;
808 } else {
809 /*
810 * Enable/disable the lockup detectors or
811 * change the sample period 'on the fly'.
812 */
813 err = update_watchdog_all_cpus();
814
815 if (err) {
816 watchdog_disable_all_cpus();
817 pr_err("Failed to update lockup detectors, disabled\n");
818 }
819 }
820
821 if (err)
822 watchdog_enabled = 0;
823
824 return err;
825}
826
827static void watchdog_disable_all_cpus(void)
828{
829 if (watchdog_running) {
830 watchdog_running = 0;
831 smpboot_unregister_percpu_thread(&watchdog_threads);
832 }
833}
834
835#ifdef CONFIG_SYSCTL
836
837/*
838 * Update the run state of the lockup detectors.
839 */
840static int proc_watchdog_update(void)
841{
842 int err = 0;
843
844 /*
845 * Watchdog threads won't be started if they are already active.
846 * The 'watchdog_running' variable in watchdog_*_all_cpus() takes
847 * care of this. If those threads are already active, the sample
848 * period will be updated and the lockup detectors will be enabled
849 * or disabled 'on the fly'.
850 */
851 if (watchdog_enabled && watchdog_thresh)
852 err = watchdog_enable_all_cpus();
853 else
854 watchdog_disable_all_cpus();
855
856 return err;
857
858}
859
860/*
861 * common function for watchdog, nmi_watchdog and soft_watchdog parameter
862 *
863 * caller | table->data points to | 'which' contains the flag(s)
864 * -------------------|-----------------------|-----------------------------
865 * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
866 * | | with SOFT_WATCHDOG_ENABLED
867 * -------------------|-----------------------|-----------------------------
868 * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED
869 * -------------------|-----------------------|-----------------------------
870 * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
871 */
872static int proc_watchdog_common(int which, struct ctl_table *table, int write,
873 void __user *buffer, size_t *lenp, loff_t *ppos)
874{
875 int err, old, new;
876 int *watchdog_param = (int *)table->data;
877
878 get_online_cpus();
879 mutex_lock(&watchdog_proc_mutex);
880
881 if (watchdog_suspended) {
882 /* no parameter changes allowed while watchdog is suspended */
883 err = -EAGAIN;
884 goto out;
885 }
886
887 /*
888 * If the parameter is being read return the state of the corresponding
889 * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
890 * run state of the lockup detectors.
891 */
892 if (!write) {
893 *watchdog_param = (watchdog_enabled & which) != 0;
894 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
895 } else {
896 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
897 if (err)
898 goto out;
899
900 /*
901 * There is a race window between fetching the current value
902 * from 'watchdog_enabled' and storing the new value. During
903 * this race window, watchdog_nmi_enable() can sneak in and
904 * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
905 * The 'cmpxchg' detects this race and the loop retries.
906 */
907 do {
908 old = watchdog_enabled;
909 /*
910 * If the parameter value is not zero set the
911 * corresponding bit(s), else clear it(them).
912 */
913 if (*watchdog_param)
914 new = old | which;
915 else
916 new = old & ~which;
917 } while (cmpxchg(&watchdog_enabled, old, new) != old);
918
919 /*
920 * Update the run state of the lockup detectors. There is _no_
921 * need to check the value returned by proc_watchdog_update()
922 * and to restore the previous value of 'watchdog_enabled' as
923 * both lockup detectors are disabled if proc_watchdog_update()
924 * returns an error.
925 */
926 if (old == new)
927 goto out;
928
929 err = proc_watchdog_update();
930 }
931out:
932 mutex_unlock(&watchdog_proc_mutex);
933 put_online_cpus();
934 return err;
935}
936
937/*
938 * /proc/sys/kernel/watchdog
939 */
940int proc_watchdog(struct ctl_table *table, int write,
941 void __user *buffer, size_t *lenp, loff_t *ppos)
942{
943 return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
944 table, write, buffer, lenp, ppos);
945}
946
947/*
948 * /proc/sys/kernel/nmi_watchdog
949 */
950int proc_nmi_watchdog(struct ctl_table *table, int write,
951 void __user *buffer, size_t *lenp, loff_t *ppos)
952{
953 return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
954 table, write, buffer, lenp, ppos);
955}
956
957/*
958 * /proc/sys/kernel/soft_watchdog
959 */
960int proc_soft_watchdog(struct ctl_table *table, int write,
961 void __user *buffer, size_t *lenp, loff_t *ppos)
962{
963 return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
964 table, write, buffer, lenp, ppos);
965}
966
967/*
968 * /proc/sys/kernel/watchdog_thresh
969 */
970int proc_watchdog_thresh(struct ctl_table *table, int write,
971 void __user *buffer, size_t *lenp, loff_t *ppos)
972{
973 int err, old, new;
974
975 get_online_cpus();
976 mutex_lock(&watchdog_proc_mutex);
977
978 if (watchdog_suspended) {
979 /* no parameter changes allowed while watchdog is suspended */
980 err = -EAGAIN;
981 goto out;
982 }
983
984 old = ACCESS_ONCE(watchdog_thresh);
985 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
986
987 if (err || !write)
988 goto out;
989
990 /*
991 * Update the sample period. Restore on failure.
992 */
993 new = ACCESS_ONCE(watchdog_thresh);
994 if (old == new)
995 goto out;
996
997 set_sample_period();
998 err = proc_watchdog_update();
999 if (err) {
1000 watchdog_thresh = old;
1001 set_sample_period();
1002 }
1003out:
1004 mutex_unlock(&watchdog_proc_mutex);
1005 put_online_cpus();
1006 return err;
1007}
1008
1009/*
1010 * The cpumask is the mask of possible cpus that the watchdog can run
1011 * on, not the mask of cpus it is actually running on. This allows the
1012 * user to specify a mask that will include cpus that have not yet
1013 * been brought online, if desired.
1014 */
1015int proc_watchdog_cpumask(struct ctl_table *table, int write,
1016 void __user *buffer, size_t *lenp, loff_t *ppos)
1017{
1018 int err;
1019
1020 get_online_cpus();
1021 mutex_lock(&watchdog_proc_mutex);
1022
1023 if (watchdog_suspended) {
1024 /* no parameter changes allowed while watchdog is suspended */
1025 err = -EAGAIN;
1026 goto out;
1027 }
1028
1029 err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
1030 if (!err && write) {
1031 /* Remove impossible cpus to keep sysctl output cleaner. */
1032 cpumask_and(&watchdog_cpumask, &watchdog_cpumask,
1033 cpu_possible_mask);
1034
1035 if (watchdog_running) {
1036 /*
1037 * Failure would be due to being unable to allocate
1038 * a temporary cpumask, so we are likely not in a
1039 * position to do much else to make things better.
1040 */
1041 if (smpboot_update_cpumask_percpu_thread(
1042 &watchdog_threads, &watchdog_cpumask) != 0)
1043 pr_err("cpumask update failed\n");
1044 }
1045 }
1046out:
1047 mutex_unlock(&watchdog_proc_mutex);
1048 put_online_cpus();
1049 return err;
1050}
1051
1052#endif /* CONFIG_SYSCTL */
1053
1054void __init lockup_detector_init(void)
1055{
1056 set_sample_period();
1057
1058#ifdef CONFIG_NO_HZ_FULL
1059 if (tick_nohz_full_enabled()) {
1060 pr_info("Disabling watchdog on nohz_full cores by default\n");
1061 cpumask_copy(&watchdog_cpumask, housekeeping_mask);
1062 } else
1063 cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
1064#else
1065 cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
1066#endif
1067
1068 if (watchdog_enabled)
1069 watchdog_enable_all_cpus();
1070}