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
30 static DEFINE_MUTEX(watchdog_mutex);
31
32 #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HARDLOCKUP_DETECTOR_SPARC64)
33 # define WATCHDOG_HARDLOCKUP_DEFAULT 1
34 #else
35 # define WATCHDOG_HARDLOCKUP_DEFAULT 0
36 #endif
37
38 unsigned long __read_mostly watchdog_enabled;
39 int __read_mostly watchdog_user_enabled = 1;
40 static int __read_mostly watchdog_hardlockup_user_enabled = WATCHDOG_HARDLOCKUP_DEFAULT;
41 static int __read_mostly watchdog_softlockup_user_enabled = 1;
42 int __read_mostly watchdog_thresh = 10;
43 static int __read_mostly watchdog_hardlockup_available;
44
45 struct cpumask watchdog_cpumask __read_mostly;
46 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
47
48 #ifdef CONFIG_HARDLOCKUP_DETECTOR
49
50 # ifdef CONFIG_SMP
51 int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
52 # endif /* CONFIG_SMP */
53
54 /*
55 * Should we panic when a soft-lockup or hard-lockup occurs:
56 */
57 unsigned int __read_mostly hardlockup_panic =
58 IS_ENABLED(CONFIG_BOOTPARAM_HARDLOCKUP_PANIC);
59 /*
60 * We may not want to enable hard lockup detection by default in all cases,
61 * for example when running the kernel as a guest on a hypervisor. In these
62 * cases this function can be called to disable hard lockup detection. This
63 * function should only be executed once by the boot processor before the
64 * kernel command line parameters are parsed, because otherwise it is not
65 * possible to override this in hardlockup_panic_setup().
66 */
hardlockup_detector_disable(void)67 void __init hardlockup_detector_disable(void)
68 {
69 watchdog_hardlockup_user_enabled = 0;
70 }
71
hardlockup_panic_setup(char * str)72 static int __init hardlockup_panic_setup(char *str)
73 {
74 if (!strncmp(str, "panic", 5))
75 hardlockup_panic = 1;
76 else if (!strncmp(str, "nopanic", 7))
77 hardlockup_panic = 0;
78 else if (!strncmp(str, "0", 1))
79 watchdog_hardlockup_user_enabled = 0;
80 else if (!strncmp(str, "1", 1))
81 watchdog_hardlockup_user_enabled = 1;
82 return 1;
83 }
84 __setup("nmi_watchdog=", hardlockup_panic_setup);
85
86 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
87
88 #if defined(CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER)
89
90 static DEFINE_PER_CPU(atomic_t, hrtimer_interrupts);
91 static DEFINE_PER_CPU(int, hrtimer_interrupts_saved);
92 static DEFINE_PER_CPU(bool, watchdog_hardlockup_warned);
93 static DEFINE_PER_CPU(bool, watchdog_hardlockup_touched);
94 static unsigned long watchdog_hardlockup_all_cpu_dumped;
95
arch_touch_nmi_watchdog(void)96 notrace void arch_touch_nmi_watchdog(void)
97 {
98 /*
99 * Using __raw here because some code paths have
100 * preemption enabled. If preemption is enabled
101 * then interrupts should be enabled too, in which
102 * case we shouldn't have to worry about the watchdog
103 * going off.
104 */
105 raw_cpu_write(watchdog_hardlockup_touched, true);
106 }
107 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
108
watchdog_hardlockup_touch_cpu(unsigned int cpu)109 void watchdog_hardlockup_touch_cpu(unsigned int cpu)
110 {
111 per_cpu(watchdog_hardlockup_touched, cpu) = true;
112 }
113
is_hardlockup(unsigned int cpu)114 static bool is_hardlockup(unsigned int cpu)
115 {
116 int hrint = atomic_read(&per_cpu(hrtimer_interrupts, cpu));
117
118 if (per_cpu(hrtimer_interrupts_saved, cpu) == hrint)
119 return true;
120
121 /*
122 * NOTE: we don't need any fancy atomic_t or READ_ONCE/WRITE_ONCE
123 * for hrtimer_interrupts_saved. hrtimer_interrupts_saved is
124 * written/read by a single CPU.
125 */
126 per_cpu(hrtimer_interrupts_saved, cpu) = hrint;
127
128 return false;
129 }
130
watchdog_hardlockup_kick(void)131 static void watchdog_hardlockup_kick(void)
132 {
133 int new_interrupts;
134
135 new_interrupts = atomic_inc_return(this_cpu_ptr(&hrtimer_interrupts));
136 watchdog_buddy_check_hardlockup(new_interrupts);
137 }
138
watchdog_hardlockup_check(unsigned int cpu,struct pt_regs * regs)139 void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)
140 {
141 if (per_cpu(watchdog_hardlockup_touched, cpu)) {
142 per_cpu(watchdog_hardlockup_touched, cpu) = false;
143 return;
144 }
145
146 /*
147 * Check for a hardlockup by making sure the CPU's timer
148 * interrupt is incrementing. The timer interrupt should have
149 * fired multiple times before we overflow'd. If it hasn't
150 * then this is a good indication the cpu is stuck
151 */
152 if (is_hardlockup(cpu)) {
153 unsigned int this_cpu = smp_processor_id();
154
155 /* Only print hardlockups once. */
156 if (per_cpu(watchdog_hardlockup_warned, cpu))
157 return;
158
159 pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n", cpu);
160 print_modules();
161 print_irqtrace_events(current);
162 if (cpu == this_cpu) {
163 if (regs)
164 show_regs(regs);
165 else
166 dump_stack();
167 } else {
168 trigger_single_cpu_backtrace(cpu);
169 }
170
171 /*
172 * Perform multi-CPU dump only once to avoid multiple
173 * hardlockups generating interleaving traces
174 */
175 if (sysctl_hardlockup_all_cpu_backtrace &&
176 !test_and_set_bit(0, &watchdog_hardlockup_all_cpu_dumped))
177 trigger_allbutcpu_cpu_backtrace(cpu);
178
179 if (hardlockup_panic)
180 nmi_panic(regs, "Hard LOCKUP");
181
182 per_cpu(watchdog_hardlockup_warned, cpu) = true;
183 } else {
184 per_cpu(watchdog_hardlockup_warned, cpu) = false;
185 }
186 }
187
188 #else /* CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
189
watchdog_hardlockup_kick(void)190 static inline void watchdog_hardlockup_kick(void) { }
191
192 #endif /* !CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
193
194 /*
195 * These functions can be overridden based on the configured hardlockdup detector.
196 *
197 * watchdog_hardlockup_enable/disable can be implemented to start and stop when
198 * softlockup watchdog start and stop. The detector must select the
199 * SOFTLOCKUP_DETECTOR Kconfig.
200 */
watchdog_hardlockup_enable(unsigned int cpu)201 void __weak watchdog_hardlockup_enable(unsigned int cpu) { }
202
watchdog_hardlockup_disable(unsigned int cpu)203 void __weak watchdog_hardlockup_disable(unsigned int cpu) { }
204
205 /*
206 * Watchdog-detector specific API.
207 *
208 * Return 0 when hardlockup watchdog is available, negative value otherwise.
209 * Note that the negative value means that a delayed probe might
210 * succeed later.
211 */
watchdog_hardlockup_probe(void)212 int __weak __init watchdog_hardlockup_probe(void)
213 {
214 return -ENODEV;
215 }
216
217 /**
218 * watchdog_hardlockup_stop - Stop the watchdog for reconfiguration
219 *
220 * The reconfiguration steps are:
221 * watchdog_hardlockup_stop();
222 * update_variables();
223 * watchdog_hardlockup_start();
224 */
watchdog_hardlockup_stop(void)225 void __weak watchdog_hardlockup_stop(void) { }
226
227 /**
228 * watchdog_hardlockup_start - Start the watchdog after reconfiguration
229 *
230 * Counterpart to watchdog_hardlockup_stop().
231 *
232 * The following variables have been updated in update_variables() and
233 * contain the currently valid configuration:
234 * - watchdog_enabled
235 * - watchdog_thresh
236 * - watchdog_cpumask
237 */
watchdog_hardlockup_start(void)238 void __weak watchdog_hardlockup_start(void) { }
239
240 /**
241 * lockup_detector_update_enable - Update the sysctl enable bit
242 *
243 * Caller needs to make sure that the hard watchdogs are off, so this
244 * can't race with watchdog_hardlockup_disable().
245 */
lockup_detector_update_enable(void)246 static void lockup_detector_update_enable(void)
247 {
248 watchdog_enabled = 0;
249 if (!watchdog_user_enabled)
250 return;
251 if (watchdog_hardlockup_available && watchdog_hardlockup_user_enabled)
252 watchdog_enabled |= WATCHDOG_HARDLOCKUP_ENABLED;
253 if (watchdog_softlockup_user_enabled)
254 watchdog_enabled |= WATCHDOG_SOFTOCKUP_ENABLED;
255 }
256
257 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
258
259 /*
260 * Delay the soflockup report when running a known slow code.
261 * It does _not_ affect the timestamp of the last successdul reschedule.
262 */
263 #define SOFTLOCKUP_DELAY_REPORT ULONG_MAX
264
265 #ifdef CONFIG_SMP
266 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
267 #endif
268
269 static struct cpumask watchdog_allowed_mask __read_mostly;
270
271 /* Global variables, exported for sysctl */
272 unsigned int __read_mostly softlockup_panic =
273 IS_ENABLED(CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC);
274
275 static bool softlockup_initialized __read_mostly;
276 static u64 __read_mostly sample_period;
277
278 /* Timestamp taken after the last successful reschedule. */
279 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
280 /* Timestamp of the last softlockup report. */
281 static DEFINE_PER_CPU(unsigned long, watchdog_report_ts);
282 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
283 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
284 static unsigned long soft_lockup_nmi_warn;
285
softlockup_panic_setup(char * str)286 static int __init softlockup_panic_setup(char *str)
287 {
288 softlockup_panic = simple_strtoul(str, NULL, 0);
289 return 1;
290 }
291 __setup("softlockup_panic=", softlockup_panic_setup);
292
nowatchdog_setup(char * str)293 static int __init nowatchdog_setup(char *str)
294 {
295 watchdog_user_enabled = 0;
296 return 1;
297 }
298 __setup("nowatchdog", nowatchdog_setup);
299
nosoftlockup_setup(char * str)300 static int __init nosoftlockup_setup(char *str)
301 {
302 watchdog_softlockup_user_enabled = 0;
303 return 1;
304 }
305 __setup("nosoftlockup", nosoftlockup_setup);
306
watchdog_thresh_setup(char * str)307 static int __init watchdog_thresh_setup(char *str)
308 {
309 get_option(&str, &watchdog_thresh);
310 return 1;
311 }
312 __setup("watchdog_thresh=", watchdog_thresh_setup);
313
314 static void __lockup_detector_cleanup(void);
315
316 /*
317 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
318 * lockups can have false positives under extreme conditions. So we generally
319 * want a higher threshold for soft lockups than for hard lockups. So we couple
320 * the thresholds with a factor: we make the soft threshold twice the amount of
321 * time the hard threshold is.
322 */
get_softlockup_thresh(void)323 static int get_softlockup_thresh(void)
324 {
325 return watchdog_thresh * 2;
326 }
327
328 /*
329 * Returns seconds, approximately. We don't need nanosecond
330 * resolution, and we don't need to waste time with a big divide when
331 * 2^30ns == 1.074s.
332 */
get_timestamp(void)333 static unsigned long get_timestamp(void)
334 {
335 return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
336 }
337
set_sample_period(void)338 static void set_sample_period(void)
339 {
340 /*
341 * convert watchdog_thresh from seconds to ns
342 * the divide by 5 is to give hrtimer several chances (two
343 * or three with the current relation between the soft
344 * and hard thresholds) to increment before the
345 * hardlockup detector generates a warning
346 */
347 sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
348 watchdog_update_hrtimer_threshold(sample_period);
349 }
350
update_report_ts(void)351 static void update_report_ts(void)
352 {
353 __this_cpu_write(watchdog_report_ts, get_timestamp());
354 }
355
356 /* Commands for resetting the watchdog */
update_touch_ts(void)357 static void update_touch_ts(void)
358 {
359 __this_cpu_write(watchdog_touch_ts, get_timestamp());
360 update_report_ts();
361 }
362
363 /**
364 * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
365 *
366 * Call when the scheduler may have stalled for legitimate reasons
367 * preventing the watchdog task from executing - e.g. the scheduler
368 * entering idle state. This should only be used for scheduler events.
369 * Use touch_softlockup_watchdog() for everything else.
370 */
touch_softlockup_watchdog_sched(void)371 notrace void touch_softlockup_watchdog_sched(void)
372 {
373 /*
374 * Preemption can be enabled. It doesn't matter which CPU's watchdog
375 * report period gets restarted here, so use the raw_ operation.
376 */
377 raw_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
378 }
379
touch_softlockup_watchdog(void)380 notrace void touch_softlockup_watchdog(void)
381 {
382 touch_softlockup_watchdog_sched();
383 wq_watchdog_touch(raw_smp_processor_id());
384 }
385 EXPORT_SYMBOL(touch_softlockup_watchdog);
386
touch_all_softlockup_watchdogs(void)387 void touch_all_softlockup_watchdogs(void)
388 {
389 int cpu;
390
391 /*
392 * watchdog_mutex cannpt be taken here, as this might be called
393 * from (soft)interrupt context, so the access to
394 * watchdog_allowed_cpumask might race with a concurrent update.
395 *
396 * The watchdog time stamp can race against a concurrent real
397 * update as well, the only side effect might be a cycle delay for
398 * the softlockup check.
399 */
400 for_each_cpu(cpu, &watchdog_allowed_mask) {
401 per_cpu(watchdog_report_ts, cpu) = SOFTLOCKUP_DELAY_REPORT;
402 wq_watchdog_touch(cpu);
403 }
404 }
405
touch_softlockup_watchdog_sync(void)406 void touch_softlockup_watchdog_sync(void)
407 {
408 __this_cpu_write(softlockup_touch_sync, true);
409 __this_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
410 }
411
is_softlockup(unsigned long touch_ts,unsigned long period_ts,unsigned long now)412 static int is_softlockup(unsigned long touch_ts,
413 unsigned long period_ts,
414 unsigned long now)
415 {
416 if ((watchdog_enabled & WATCHDOG_SOFTOCKUP_ENABLED) && watchdog_thresh) {
417 /* Warn about unreasonable delays. */
418 if (time_after(now, period_ts + get_softlockup_thresh()))
419 return now - touch_ts;
420 }
421 return 0;
422 }
423
424 /* watchdog detector functions */
425 static DEFINE_PER_CPU(struct completion, softlockup_completion);
426 static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
427
428 /*
429 * The watchdog feed function - touches the timestamp.
430 *
431 * It only runs once every sample_period seconds (4 seconds by
432 * default) to reset the softlockup timestamp. If this gets delayed
433 * for more than 2*watchdog_thresh seconds then the debug-printout
434 * triggers in watchdog_timer_fn().
435 */
softlockup_fn(void * data)436 static int softlockup_fn(void *data)
437 {
438 update_touch_ts();
439 complete(this_cpu_ptr(&softlockup_completion));
440
441 return 0;
442 }
443
444 /* watchdog kicker functions */
watchdog_timer_fn(struct hrtimer * hrtimer)445 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
446 {
447 unsigned long touch_ts, period_ts, now;
448 struct pt_regs *regs = get_irq_regs();
449 int duration;
450 int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
451
452 if (!watchdog_enabled)
453 return HRTIMER_NORESTART;
454
455 watchdog_hardlockup_kick();
456
457 /* kick the softlockup detector */
458 if (completion_done(this_cpu_ptr(&softlockup_completion))) {
459 reinit_completion(this_cpu_ptr(&softlockup_completion));
460 stop_one_cpu_nowait(smp_processor_id(),
461 softlockup_fn, NULL,
462 this_cpu_ptr(&softlockup_stop_work));
463 }
464
465 /* .. and repeat */
466 hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
467
468 /*
469 * Read the current timestamp first. It might become invalid anytime
470 * when a virtual machine is stopped by the host or when the watchog
471 * is touched from NMI.
472 */
473 now = get_timestamp();
474 /*
475 * If a virtual machine is stopped by the host it can look to
476 * the watchdog like a soft lockup. This function touches the watchdog.
477 */
478 kvm_check_and_clear_guest_paused();
479 /*
480 * The stored timestamp is comparable with @now only when not touched.
481 * It might get touched anytime from NMI. Make sure that is_softlockup()
482 * uses the same (valid) value.
483 */
484 period_ts = READ_ONCE(*this_cpu_ptr(&watchdog_report_ts));
485
486 /* Reset the interval when touched by known problematic code. */
487 if (period_ts == SOFTLOCKUP_DELAY_REPORT) {
488 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
489 /*
490 * If the time stamp was touched atomically
491 * make sure the scheduler tick is up to date.
492 */
493 __this_cpu_write(softlockup_touch_sync, false);
494 sched_clock_tick();
495 }
496
497 update_report_ts();
498 return HRTIMER_RESTART;
499 }
500
501 /* Check for a softlockup. */
502 touch_ts = __this_cpu_read(watchdog_touch_ts);
503 duration = is_softlockup(touch_ts, period_ts, now);
504 if (unlikely(duration)) {
505 /*
506 * Prevent multiple soft-lockup reports if one cpu is already
507 * engaged in dumping all cpu back traces.
508 */
509 if (softlockup_all_cpu_backtrace) {
510 if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn))
511 return HRTIMER_RESTART;
512 }
513
514 /* Start period for the next softlockup warning. */
515 update_report_ts();
516
517 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
518 smp_processor_id(), duration,
519 current->comm, task_pid_nr(current));
520 print_modules();
521 print_irqtrace_events(current);
522 if (regs)
523 show_regs(regs);
524 else
525 dump_stack();
526
527 if (softlockup_all_cpu_backtrace) {
528 trigger_allbutcpu_cpu_backtrace(smp_processor_id());
529 clear_bit_unlock(0, &soft_lockup_nmi_warn);
530 }
531
532 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
533 if (softlockup_panic)
534 panic("softlockup: hung tasks");
535 }
536
537 return HRTIMER_RESTART;
538 }
539
watchdog_enable(unsigned int cpu)540 static void watchdog_enable(unsigned int cpu)
541 {
542 struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
543 struct completion *done = this_cpu_ptr(&softlockup_completion);
544
545 WARN_ON_ONCE(cpu != smp_processor_id());
546
547 init_completion(done);
548 complete(done);
549
550 /*
551 * Start the timer first to prevent the hardlockup watchdog triggering
552 * before the timer has a chance to fire.
553 */
554 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
555 hrtimer->function = watchdog_timer_fn;
556 hrtimer_start(hrtimer, ns_to_ktime(sample_period),
557 HRTIMER_MODE_REL_PINNED_HARD);
558
559 /* Initialize timestamp */
560 update_touch_ts();
561 /* Enable the hardlockup detector */
562 if (watchdog_enabled & WATCHDOG_HARDLOCKUP_ENABLED)
563 watchdog_hardlockup_enable(cpu);
564 }
565
watchdog_disable(unsigned int cpu)566 static void watchdog_disable(unsigned int cpu)
567 {
568 struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
569
570 WARN_ON_ONCE(cpu != smp_processor_id());
571
572 /*
573 * Disable the hardlockup detector first. That prevents that a large
574 * delay between disabling the timer and disabling the hardlockup
575 * detector causes a false positive.
576 */
577 watchdog_hardlockup_disable(cpu);
578 hrtimer_cancel(hrtimer);
579 wait_for_completion(this_cpu_ptr(&softlockup_completion));
580 }
581
softlockup_stop_fn(void * data)582 static int softlockup_stop_fn(void *data)
583 {
584 watchdog_disable(smp_processor_id());
585 return 0;
586 }
587
softlockup_stop_all(void)588 static void softlockup_stop_all(void)
589 {
590 int cpu;
591
592 if (!softlockup_initialized)
593 return;
594
595 for_each_cpu(cpu, &watchdog_allowed_mask)
596 smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
597
598 cpumask_clear(&watchdog_allowed_mask);
599 }
600
softlockup_start_fn(void * data)601 static int softlockup_start_fn(void *data)
602 {
603 watchdog_enable(smp_processor_id());
604 return 0;
605 }
606
softlockup_start_all(void)607 static void softlockup_start_all(void)
608 {
609 int cpu;
610
611 cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
612 for_each_cpu(cpu, &watchdog_allowed_mask)
613 smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
614 }
615
lockup_detector_online_cpu(unsigned int cpu)616 int lockup_detector_online_cpu(unsigned int cpu)
617 {
618 if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
619 watchdog_enable(cpu);
620 return 0;
621 }
622
lockup_detector_offline_cpu(unsigned int cpu)623 int lockup_detector_offline_cpu(unsigned int cpu)
624 {
625 if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
626 watchdog_disable(cpu);
627 return 0;
628 }
629
__lockup_detector_reconfigure(void)630 static void __lockup_detector_reconfigure(void)
631 {
632 cpus_read_lock();
633 watchdog_hardlockup_stop();
634
635 softlockup_stop_all();
636 set_sample_period();
637 lockup_detector_update_enable();
638 if (watchdog_enabled && watchdog_thresh)
639 softlockup_start_all();
640
641 watchdog_hardlockup_start();
642 cpus_read_unlock();
643 /*
644 * Must be called outside the cpus locked section to prevent
645 * recursive locking in the perf code.
646 */
647 __lockup_detector_cleanup();
648 }
649
lockup_detector_reconfigure(void)650 void lockup_detector_reconfigure(void)
651 {
652 mutex_lock(&watchdog_mutex);
653 __lockup_detector_reconfigure();
654 mutex_unlock(&watchdog_mutex);
655 }
656
657 /*
658 * Create the watchdog infrastructure and configure the detector(s).
659 */
lockup_detector_setup(void)660 static __init void lockup_detector_setup(void)
661 {
662 /*
663 * If sysctl is off and watchdog got disabled on the command line,
664 * nothing to do here.
665 */
666 lockup_detector_update_enable();
667
668 if (!IS_ENABLED(CONFIG_SYSCTL) &&
669 !(watchdog_enabled && watchdog_thresh))
670 return;
671
672 mutex_lock(&watchdog_mutex);
673 __lockup_detector_reconfigure();
674 softlockup_initialized = true;
675 mutex_unlock(&watchdog_mutex);
676 }
677
678 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
__lockup_detector_reconfigure(void)679 static void __lockup_detector_reconfigure(void)
680 {
681 cpus_read_lock();
682 watchdog_hardlockup_stop();
683 lockup_detector_update_enable();
684 watchdog_hardlockup_start();
685 cpus_read_unlock();
686 }
lockup_detector_reconfigure(void)687 void lockup_detector_reconfigure(void)
688 {
689 __lockup_detector_reconfigure();
690 }
lockup_detector_setup(void)691 static inline void lockup_detector_setup(void)
692 {
693 __lockup_detector_reconfigure();
694 }
695 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
696
__lockup_detector_cleanup(void)697 static void __lockup_detector_cleanup(void)
698 {
699 lockdep_assert_held(&watchdog_mutex);
700 hardlockup_detector_perf_cleanup();
701 }
702
703 /**
704 * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
705 *
706 * Caller must not hold the cpu hotplug rwsem.
707 */
lockup_detector_cleanup(void)708 void lockup_detector_cleanup(void)
709 {
710 mutex_lock(&watchdog_mutex);
711 __lockup_detector_cleanup();
712 mutex_unlock(&watchdog_mutex);
713 }
714
715 /**
716 * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
717 *
718 * Special interface for parisc. It prevents lockup detector warnings from
719 * the default pm_poweroff() function which busy loops forever.
720 */
lockup_detector_soft_poweroff(void)721 void lockup_detector_soft_poweroff(void)
722 {
723 watchdog_enabled = 0;
724 }
725
726 #ifdef CONFIG_SYSCTL
727
728 /* Propagate any changes to the watchdog infrastructure */
proc_watchdog_update(void)729 static void proc_watchdog_update(void)
730 {
731 /* Remove impossible cpus to keep sysctl output clean. */
732 cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
733 __lockup_detector_reconfigure();
734 }
735
736 /*
737 * common function for watchdog, nmi_watchdog and soft_watchdog parameter
738 *
739 * caller | table->data points to | 'which'
740 * -------------------|----------------------------------|-------------------------------
741 * proc_watchdog | watchdog_user_enabled | WATCHDOG_HARDLOCKUP_ENABLED |
742 * | | WATCHDOG_SOFTOCKUP_ENABLED
743 * -------------------|----------------------------------|-------------------------------
744 * proc_nmi_watchdog | watchdog_hardlockup_user_enabled | WATCHDOG_HARDLOCKUP_ENABLED
745 * -------------------|----------------------------------|-------------------------------
746 * proc_soft_watchdog | watchdog_softlockup_user_enabled | WATCHDOG_SOFTOCKUP_ENABLED
747 */
proc_watchdog_common(int which,struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)748 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
749 void *buffer, size_t *lenp, loff_t *ppos)
750 {
751 int err, old, *param = table->data;
752
753 mutex_lock(&watchdog_mutex);
754
755 if (!write) {
756 /*
757 * On read synchronize the userspace interface. This is a
758 * racy snapshot.
759 */
760 *param = (watchdog_enabled & which) != 0;
761 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
762 } else {
763 old = READ_ONCE(*param);
764 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
765 if (!err && old != READ_ONCE(*param))
766 proc_watchdog_update();
767 }
768 mutex_unlock(&watchdog_mutex);
769 return err;
770 }
771
772 /*
773 * /proc/sys/kernel/watchdog
774 */
proc_watchdog(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)775 int proc_watchdog(struct ctl_table *table, int write,
776 void *buffer, size_t *lenp, loff_t *ppos)
777 {
778 return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED |
779 WATCHDOG_SOFTOCKUP_ENABLED,
780 table, write, buffer, lenp, ppos);
781 }
782
783 /*
784 * /proc/sys/kernel/nmi_watchdog
785 */
proc_nmi_watchdog(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)786 int proc_nmi_watchdog(struct ctl_table *table, int write,
787 void *buffer, size_t *lenp, loff_t *ppos)
788 {
789 if (!watchdog_hardlockup_available && write)
790 return -ENOTSUPP;
791 return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED,
792 table, write, buffer, lenp, ppos);
793 }
794
795 /*
796 * /proc/sys/kernel/soft_watchdog
797 */
proc_soft_watchdog(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)798 int proc_soft_watchdog(struct ctl_table *table, int write,
799 void *buffer, size_t *lenp, loff_t *ppos)
800 {
801 return proc_watchdog_common(WATCHDOG_SOFTOCKUP_ENABLED,
802 table, write, buffer, lenp, ppos);
803 }
804
805 /*
806 * /proc/sys/kernel/watchdog_thresh
807 */
proc_watchdog_thresh(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)808 int proc_watchdog_thresh(struct ctl_table *table, int write,
809 void *buffer, size_t *lenp, loff_t *ppos)
810 {
811 int err, old;
812
813 mutex_lock(&watchdog_mutex);
814
815 old = READ_ONCE(watchdog_thresh);
816 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
817
818 if (!err && write && old != READ_ONCE(watchdog_thresh))
819 proc_watchdog_update();
820
821 mutex_unlock(&watchdog_mutex);
822 return err;
823 }
824
825 /*
826 * The cpumask is the mask of possible cpus that the watchdog can run
827 * on, not the mask of cpus it is actually running on. This allows the
828 * user to specify a mask that will include cpus that have not yet
829 * been brought online, if desired.
830 */
proc_watchdog_cpumask(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)831 int proc_watchdog_cpumask(struct ctl_table *table, int write,
832 void *buffer, size_t *lenp, loff_t *ppos)
833 {
834 int err;
835
836 mutex_lock(&watchdog_mutex);
837
838 err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
839 if (!err && write)
840 proc_watchdog_update();
841
842 mutex_unlock(&watchdog_mutex);
843 return err;
844 }
845
846 static const int sixty = 60;
847
848 static struct ctl_table watchdog_sysctls[] = {
849 {
850 .procname = "watchdog",
851 .data = &watchdog_user_enabled,
852 .maxlen = sizeof(int),
853 .mode = 0644,
854 .proc_handler = proc_watchdog,
855 .extra1 = SYSCTL_ZERO,
856 .extra2 = SYSCTL_ONE,
857 },
858 {
859 .procname = "watchdog_thresh",
860 .data = &watchdog_thresh,
861 .maxlen = sizeof(int),
862 .mode = 0644,
863 .proc_handler = proc_watchdog_thresh,
864 .extra1 = SYSCTL_ZERO,
865 .extra2 = (void *)&sixty,
866 },
867 {
868 .procname = "watchdog_cpumask",
869 .data = &watchdog_cpumask_bits,
870 .maxlen = NR_CPUS,
871 .mode = 0644,
872 .proc_handler = proc_watchdog_cpumask,
873 },
874 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
875 {
876 .procname = "soft_watchdog",
877 .data = &watchdog_softlockup_user_enabled,
878 .maxlen = sizeof(int),
879 .mode = 0644,
880 .proc_handler = proc_soft_watchdog,
881 .extra1 = SYSCTL_ZERO,
882 .extra2 = SYSCTL_ONE,
883 },
884 {
885 .procname = "softlockup_panic",
886 .data = &softlockup_panic,
887 .maxlen = sizeof(int),
888 .mode = 0644,
889 .proc_handler = proc_dointvec_minmax,
890 .extra1 = SYSCTL_ZERO,
891 .extra2 = SYSCTL_ONE,
892 },
893 #ifdef CONFIG_SMP
894 {
895 .procname = "softlockup_all_cpu_backtrace",
896 .data = &sysctl_softlockup_all_cpu_backtrace,
897 .maxlen = sizeof(int),
898 .mode = 0644,
899 .proc_handler = proc_dointvec_minmax,
900 .extra1 = SYSCTL_ZERO,
901 .extra2 = SYSCTL_ONE,
902 },
903 #endif /* CONFIG_SMP */
904 #endif
905 #ifdef CONFIG_HARDLOCKUP_DETECTOR
906 {
907 .procname = "hardlockup_panic",
908 .data = &hardlockup_panic,
909 .maxlen = sizeof(int),
910 .mode = 0644,
911 .proc_handler = proc_dointvec_minmax,
912 .extra1 = SYSCTL_ZERO,
913 .extra2 = SYSCTL_ONE,
914 },
915 #ifdef CONFIG_SMP
916 {
917 .procname = "hardlockup_all_cpu_backtrace",
918 .data = &sysctl_hardlockup_all_cpu_backtrace,
919 .maxlen = sizeof(int),
920 .mode = 0644,
921 .proc_handler = proc_dointvec_minmax,
922 .extra1 = SYSCTL_ZERO,
923 .extra2 = SYSCTL_ONE,
924 },
925 #endif /* CONFIG_SMP */
926 #endif
927 {}
928 };
929
930 static struct ctl_table watchdog_hardlockup_sysctl[] = {
931 {
932 .procname = "nmi_watchdog",
933 .data = &watchdog_hardlockup_user_enabled,
934 .maxlen = sizeof(int),
935 .mode = 0444,
936 .proc_handler = proc_nmi_watchdog,
937 .extra1 = SYSCTL_ZERO,
938 .extra2 = SYSCTL_ONE,
939 },
940 {}
941 };
942
watchdog_sysctl_init(void)943 static void __init watchdog_sysctl_init(void)
944 {
945 register_sysctl_init("kernel", watchdog_sysctls);
946
947 if (watchdog_hardlockup_available)
948 watchdog_hardlockup_sysctl[0].mode = 0644;
949 register_sysctl_init("kernel", watchdog_hardlockup_sysctl);
950 }
951
952 #else
953 #define watchdog_sysctl_init() do { } while (0)
954 #endif /* CONFIG_SYSCTL */
955
956 static void __init lockup_detector_delay_init(struct work_struct *work);
957 static bool allow_lockup_detector_init_retry __initdata;
958
959 static struct work_struct detector_work __initdata =
960 __WORK_INITIALIZER(detector_work, lockup_detector_delay_init);
961
lockup_detector_delay_init(struct work_struct * work)962 static void __init lockup_detector_delay_init(struct work_struct *work)
963 {
964 int ret;
965
966 ret = watchdog_hardlockup_probe();
967 if (ret) {
968 pr_info("Delayed init of the lockup detector failed: %d\n", ret);
969 pr_info("Hard watchdog permanently disabled\n");
970 return;
971 }
972
973 allow_lockup_detector_init_retry = false;
974
975 watchdog_hardlockup_available = true;
976 lockup_detector_setup();
977 }
978
979 /*
980 * lockup_detector_retry_init - retry init lockup detector if possible.
981 *
982 * Retry hardlockup detector init. It is useful when it requires some
983 * functionality that has to be initialized later on a particular
984 * platform.
985 */
lockup_detector_retry_init(void)986 void __init lockup_detector_retry_init(void)
987 {
988 /* Must be called before late init calls */
989 if (!allow_lockup_detector_init_retry)
990 return;
991
992 schedule_work(&detector_work);
993 }
994
995 /*
996 * Ensure that optional delayed hardlockup init is proceed before
997 * the init code and memory is freed.
998 */
lockup_detector_check(void)999 static int __init lockup_detector_check(void)
1000 {
1001 /* Prevent any later retry. */
1002 allow_lockup_detector_init_retry = false;
1003
1004 /* Make sure no work is pending. */
1005 flush_work(&detector_work);
1006
1007 watchdog_sysctl_init();
1008
1009 return 0;
1010
1011 }
1012 late_initcall_sync(lockup_detector_check);
1013
lockup_detector_init(void)1014 void __init lockup_detector_init(void)
1015 {
1016 if (tick_nohz_full_enabled())
1017 pr_info("Disabling watchdog on nohz_full cores by default\n");
1018
1019 cpumask_copy(&watchdog_cpumask,
1020 housekeeping_cpumask(HK_TYPE_TIMER));
1021
1022 if (!watchdog_hardlockup_probe())
1023 watchdog_hardlockup_available = true;
1024 else
1025 allow_lockup_detector_init_retry = true;
1026
1027 lockup_detector_setup();
1028 }
1029