xref: /linux/kernel/watchdog.c (revision 2b0cfa6e49566c8fa6759734cf821aa6e8271a9e)
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  */
67 void __init hardlockup_detector_disable(void)
68 {
69 	watchdog_hardlockup_user_enabled = 0;
70 }
71 
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 hard_lockup_nmi_warn;
95 
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 
109 void watchdog_hardlockup_touch_cpu(unsigned int cpu)
110 {
111 	per_cpu(watchdog_hardlockup_touched, cpu) = true;
112 }
113 
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 
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 
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 		unsigned long flags;
155 
156 		/* Only print hardlockups once. */
157 		if (per_cpu(watchdog_hardlockup_warned, cpu))
158 			return;
159 
160 		/*
161 		 * Prevent multiple hard-lockup reports if one cpu is already
162 		 * engaged in dumping all cpu back traces.
163 		 */
164 		if (sysctl_hardlockup_all_cpu_backtrace) {
165 			if (test_and_set_bit_lock(0, &hard_lockup_nmi_warn))
166 				return;
167 		}
168 
169 		/*
170 		 * NOTE: we call printk_cpu_sync_get_irqsave() after printing
171 		 * the lockup message. While it would be nice to serialize
172 		 * that printout, we really want to make sure that if some
173 		 * other CPU somehow locked up while holding the lock associated
174 		 * with printk_cpu_sync_get_irqsave() that we can still at least
175 		 * get the message about the lockup out.
176 		 */
177 		pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n", cpu);
178 		printk_cpu_sync_get_irqsave(flags);
179 
180 		print_modules();
181 		print_irqtrace_events(current);
182 		if (cpu == this_cpu) {
183 			if (regs)
184 				show_regs(regs);
185 			else
186 				dump_stack();
187 			printk_cpu_sync_put_irqrestore(flags);
188 		} else {
189 			printk_cpu_sync_put_irqrestore(flags);
190 			trigger_single_cpu_backtrace(cpu);
191 		}
192 
193 		if (sysctl_hardlockup_all_cpu_backtrace) {
194 			trigger_allbutcpu_cpu_backtrace(cpu);
195 			if (!hardlockup_panic)
196 				clear_bit_unlock(0, &hard_lockup_nmi_warn);
197 		}
198 
199 		if (hardlockup_panic)
200 			nmi_panic(regs, "Hard LOCKUP");
201 
202 		per_cpu(watchdog_hardlockup_warned, cpu) = true;
203 	} else {
204 		per_cpu(watchdog_hardlockup_warned, cpu) = false;
205 	}
206 }
207 
208 #else /* CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
209 
210 static inline void watchdog_hardlockup_kick(void) { }
211 
212 #endif /* !CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
213 
214 /*
215  * These functions can be overridden based on the configured hardlockdup detector.
216  *
217  * watchdog_hardlockup_enable/disable can be implemented to start and stop when
218  * softlockup watchdog start and stop. The detector must select the
219  * SOFTLOCKUP_DETECTOR Kconfig.
220  */
221 void __weak watchdog_hardlockup_enable(unsigned int cpu) { }
222 
223 void __weak watchdog_hardlockup_disable(unsigned int cpu) { }
224 
225 /*
226  * Watchdog-detector specific API.
227  *
228  * Return 0 when hardlockup watchdog is available, negative value otherwise.
229  * Note that the negative value means that a delayed probe might
230  * succeed later.
231  */
232 int __weak __init watchdog_hardlockup_probe(void)
233 {
234 	return -ENODEV;
235 }
236 
237 /**
238  * watchdog_hardlockup_stop - Stop the watchdog for reconfiguration
239  *
240  * The reconfiguration steps are:
241  * watchdog_hardlockup_stop();
242  * update_variables();
243  * watchdog_hardlockup_start();
244  */
245 void __weak watchdog_hardlockup_stop(void) { }
246 
247 /**
248  * watchdog_hardlockup_start - Start the watchdog after reconfiguration
249  *
250  * Counterpart to watchdog_hardlockup_stop().
251  *
252  * The following variables have been updated in update_variables() and
253  * contain the currently valid configuration:
254  * - watchdog_enabled
255  * - watchdog_thresh
256  * - watchdog_cpumask
257  */
258 void __weak watchdog_hardlockup_start(void) { }
259 
260 /**
261  * lockup_detector_update_enable - Update the sysctl enable bit
262  *
263  * Caller needs to make sure that the hard watchdogs are off, so this
264  * can't race with watchdog_hardlockup_disable().
265  */
266 static void lockup_detector_update_enable(void)
267 {
268 	watchdog_enabled = 0;
269 	if (!watchdog_user_enabled)
270 		return;
271 	if (watchdog_hardlockup_available && watchdog_hardlockup_user_enabled)
272 		watchdog_enabled |= WATCHDOG_HARDLOCKUP_ENABLED;
273 	if (watchdog_softlockup_user_enabled)
274 		watchdog_enabled |= WATCHDOG_SOFTOCKUP_ENABLED;
275 }
276 
277 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
278 
279 /*
280  * Delay the soflockup report when running a known slow code.
281  * It does _not_ affect the timestamp of the last successdul reschedule.
282  */
283 #define SOFTLOCKUP_DELAY_REPORT	ULONG_MAX
284 
285 #ifdef CONFIG_SMP
286 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
287 #endif
288 
289 static struct cpumask watchdog_allowed_mask __read_mostly;
290 
291 /* Global variables, exported for sysctl */
292 unsigned int __read_mostly softlockup_panic =
293 			IS_ENABLED(CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC);
294 
295 static bool softlockup_initialized __read_mostly;
296 static u64 __read_mostly sample_period;
297 
298 /* Timestamp taken after the last successful reschedule. */
299 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
300 /* Timestamp of the last softlockup report. */
301 static DEFINE_PER_CPU(unsigned long, watchdog_report_ts);
302 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
303 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
304 static unsigned long soft_lockup_nmi_warn;
305 
306 static int __init softlockup_panic_setup(char *str)
307 {
308 	softlockup_panic = simple_strtoul(str, NULL, 0);
309 	return 1;
310 }
311 __setup("softlockup_panic=", softlockup_panic_setup);
312 
313 static int __init nowatchdog_setup(char *str)
314 {
315 	watchdog_user_enabled = 0;
316 	return 1;
317 }
318 __setup("nowatchdog", nowatchdog_setup);
319 
320 static int __init nosoftlockup_setup(char *str)
321 {
322 	watchdog_softlockup_user_enabled = 0;
323 	return 1;
324 }
325 __setup("nosoftlockup", nosoftlockup_setup);
326 
327 static int __init watchdog_thresh_setup(char *str)
328 {
329 	get_option(&str, &watchdog_thresh);
330 	return 1;
331 }
332 __setup("watchdog_thresh=", watchdog_thresh_setup);
333 
334 static void __lockup_detector_cleanup(void);
335 
336 /*
337  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
338  * lockups can have false positives under extreme conditions. So we generally
339  * want a higher threshold for soft lockups than for hard lockups. So we couple
340  * the thresholds with a factor: we make the soft threshold twice the amount of
341  * time the hard threshold is.
342  */
343 static int get_softlockup_thresh(void)
344 {
345 	return watchdog_thresh * 2;
346 }
347 
348 /*
349  * Returns seconds, approximately.  We don't need nanosecond
350  * resolution, and we don't need to waste time with a big divide when
351  * 2^30ns == 1.074s.
352  */
353 static unsigned long get_timestamp(void)
354 {
355 	return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
356 }
357 
358 static void set_sample_period(void)
359 {
360 	/*
361 	 * convert watchdog_thresh from seconds to ns
362 	 * the divide by 5 is to give hrtimer several chances (two
363 	 * or three with the current relation between the soft
364 	 * and hard thresholds) to increment before the
365 	 * hardlockup detector generates a warning
366 	 */
367 	sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
368 	watchdog_update_hrtimer_threshold(sample_period);
369 }
370 
371 static void update_report_ts(void)
372 {
373 	__this_cpu_write(watchdog_report_ts, get_timestamp());
374 }
375 
376 /* Commands for resetting the watchdog */
377 static void update_touch_ts(void)
378 {
379 	__this_cpu_write(watchdog_touch_ts, get_timestamp());
380 	update_report_ts();
381 }
382 
383 /**
384  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
385  *
386  * Call when the scheduler may have stalled for legitimate reasons
387  * preventing the watchdog task from executing - e.g. the scheduler
388  * entering idle state.  This should only be used for scheduler events.
389  * Use touch_softlockup_watchdog() for everything else.
390  */
391 notrace void touch_softlockup_watchdog_sched(void)
392 {
393 	/*
394 	 * Preemption can be enabled.  It doesn't matter which CPU's watchdog
395 	 * report period gets restarted here, so use the raw_ operation.
396 	 */
397 	raw_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
398 }
399 
400 notrace void touch_softlockup_watchdog(void)
401 {
402 	touch_softlockup_watchdog_sched();
403 	wq_watchdog_touch(raw_smp_processor_id());
404 }
405 EXPORT_SYMBOL(touch_softlockup_watchdog);
406 
407 void touch_all_softlockup_watchdogs(void)
408 {
409 	int cpu;
410 
411 	/*
412 	 * watchdog_mutex cannpt be taken here, as this might be called
413 	 * from (soft)interrupt context, so the access to
414 	 * watchdog_allowed_cpumask might race with a concurrent update.
415 	 *
416 	 * The watchdog time stamp can race against a concurrent real
417 	 * update as well, the only side effect might be a cycle delay for
418 	 * the softlockup check.
419 	 */
420 	for_each_cpu(cpu, &watchdog_allowed_mask) {
421 		per_cpu(watchdog_report_ts, cpu) = SOFTLOCKUP_DELAY_REPORT;
422 		wq_watchdog_touch(cpu);
423 	}
424 }
425 
426 void touch_softlockup_watchdog_sync(void)
427 {
428 	__this_cpu_write(softlockup_touch_sync, true);
429 	__this_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
430 }
431 
432 static int is_softlockup(unsigned long touch_ts,
433 			 unsigned long period_ts,
434 			 unsigned long now)
435 {
436 	if ((watchdog_enabled & WATCHDOG_SOFTOCKUP_ENABLED) && watchdog_thresh) {
437 		/* Warn about unreasonable delays. */
438 		if (time_after(now, period_ts + get_softlockup_thresh()))
439 			return now - touch_ts;
440 	}
441 	return 0;
442 }
443 
444 /* watchdog detector functions */
445 static DEFINE_PER_CPU(struct completion, softlockup_completion);
446 static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
447 
448 /*
449  * The watchdog feed function - touches the timestamp.
450  *
451  * It only runs once every sample_period seconds (4 seconds by
452  * default) to reset the softlockup timestamp. If this gets delayed
453  * for more than 2*watchdog_thresh seconds then the debug-printout
454  * triggers in watchdog_timer_fn().
455  */
456 static int softlockup_fn(void *data)
457 {
458 	update_touch_ts();
459 	complete(this_cpu_ptr(&softlockup_completion));
460 
461 	return 0;
462 }
463 
464 /* watchdog kicker functions */
465 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
466 {
467 	unsigned long touch_ts, period_ts, now;
468 	struct pt_regs *regs = get_irq_regs();
469 	int duration;
470 	int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
471 	unsigned long flags;
472 
473 	if (!watchdog_enabled)
474 		return HRTIMER_NORESTART;
475 
476 	watchdog_hardlockup_kick();
477 
478 	/* kick the softlockup detector */
479 	if (completion_done(this_cpu_ptr(&softlockup_completion))) {
480 		reinit_completion(this_cpu_ptr(&softlockup_completion));
481 		stop_one_cpu_nowait(smp_processor_id(),
482 				softlockup_fn, NULL,
483 				this_cpu_ptr(&softlockup_stop_work));
484 	}
485 
486 	/* .. and repeat */
487 	hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
488 
489 	/*
490 	 * Read the current timestamp first. It might become invalid anytime
491 	 * when a virtual machine is stopped by the host or when the watchog
492 	 * is touched from NMI.
493 	 */
494 	now = get_timestamp();
495 	/*
496 	 * If a virtual machine is stopped by the host it can look to
497 	 * the watchdog like a soft lockup. This function touches the watchdog.
498 	 */
499 	kvm_check_and_clear_guest_paused();
500 	/*
501 	 * The stored timestamp is comparable with @now only when not touched.
502 	 * It might get touched anytime from NMI. Make sure that is_softlockup()
503 	 * uses the same (valid) value.
504 	 */
505 	period_ts = READ_ONCE(*this_cpu_ptr(&watchdog_report_ts));
506 
507 	/* Reset the interval when touched by known problematic code. */
508 	if (period_ts == SOFTLOCKUP_DELAY_REPORT) {
509 		if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
510 			/*
511 			 * If the time stamp was touched atomically
512 			 * make sure the scheduler tick is up to date.
513 			 */
514 			__this_cpu_write(softlockup_touch_sync, false);
515 			sched_clock_tick();
516 		}
517 
518 		update_report_ts();
519 		return HRTIMER_RESTART;
520 	}
521 
522 	/* Check for a softlockup. */
523 	touch_ts = __this_cpu_read(watchdog_touch_ts);
524 	duration = is_softlockup(touch_ts, period_ts, now);
525 	if (unlikely(duration)) {
526 		/*
527 		 * Prevent multiple soft-lockup reports if one cpu is already
528 		 * engaged in dumping all cpu back traces.
529 		 */
530 		if (softlockup_all_cpu_backtrace) {
531 			if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn))
532 				return HRTIMER_RESTART;
533 		}
534 
535 		/* Start period for the next softlockup warning. */
536 		update_report_ts();
537 
538 		printk_cpu_sync_get_irqsave(flags);
539 		pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
540 			smp_processor_id(), duration,
541 			current->comm, task_pid_nr(current));
542 		print_modules();
543 		print_irqtrace_events(current);
544 		if (regs)
545 			show_regs(regs);
546 		else
547 			dump_stack();
548 		printk_cpu_sync_put_irqrestore(flags);
549 
550 		if (softlockup_all_cpu_backtrace) {
551 			trigger_allbutcpu_cpu_backtrace(smp_processor_id());
552 			if (!softlockup_panic)
553 				clear_bit_unlock(0, &soft_lockup_nmi_warn);
554 		}
555 
556 		add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
557 		if (softlockup_panic)
558 			panic("softlockup: hung tasks");
559 	}
560 
561 	return HRTIMER_RESTART;
562 }
563 
564 static void watchdog_enable(unsigned int cpu)
565 {
566 	struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
567 	struct completion *done = this_cpu_ptr(&softlockup_completion);
568 
569 	WARN_ON_ONCE(cpu != smp_processor_id());
570 
571 	init_completion(done);
572 	complete(done);
573 
574 	/*
575 	 * Start the timer first to prevent the hardlockup watchdog triggering
576 	 * before the timer has a chance to fire.
577 	 */
578 	hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
579 	hrtimer->function = watchdog_timer_fn;
580 	hrtimer_start(hrtimer, ns_to_ktime(sample_period),
581 		      HRTIMER_MODE_REL_PINNED_HARD);
582 
583 	/* Initialize timestamp */
584 	update_touch_ts();
585 	/* Enable the hardlockup detector */
586 	if (watchdog_enabled & WATCHDOG_HARDLOCKUP_ENABLED)
587 		watchdog_hardlockup_enable(cpu);
588 }
589 
590 static void watchdog_disable(unsigned int cpu)
591 {
592 	struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
593 
594 	WARN_ON_ONCE(cpu != smp_processor_id());
595 
596 	/*
597 	 * Disable the hardlockup detector first. That prevents that a large
598 	 * delay between disabling the timer and disabling the hardlockup
599 	 * detector causes a false positive.
600 	 */
601 	watchdog_hardlockup_disable(cpu);
602 	hrtimer_cancel(hrtimer);
603 	wait_for_completion(this_cpu_ptr(&softlockup_completion));
604 }
605 
606 static int softlockup_stop_fn(void *data)
607 {
608 	watchdog_disable(smp_processor_id());
609 	return 0;
610 }
611 
612 static void softlockup_stop_all(void)
613 {
614 	int cpu;
615 
616 	if (!softlockup_initialized)
617 		return;
618 
619 	for_each_cpu(cpu, &watchdog_allowed_mask)
620 		smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
621 
622 	cpumask_clear(&watchdog_allowed_mask);
623 }
624 
625 static int softlockup_start_fn(void *data)
626 {
627 	watchdog_enable(smp_processor_id());
628 	return 0;
629 }
630 
631 static void softlockup_start_all(void)
632 {
633 	int cpu;
634 
635 	cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
636 	for_each_cpu(cpu, &watchdog_allowed_mask)
637 		smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
638 }
639 
640 int lockup_detector_online_cpu(unsigned int cpu)
641 {
642 	if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
643 		watchdog_enable(cpu);
644 	return 0;
645 }
646 
647 int lockup_detector_offline_cpu(unsigned int cpu)
648 {
649 	if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
650 		watchdog_disable(cpu);
651 	return 0;
652 }
653 
654 static void __lockup_detector_reconfigure(void)
655 {
656 	cpus_read_lock();
657 	watchdog_hardlockup_stop();
658 
659 	softlockup_stop_all();
660 	set_sample_period();
661 	lockup_detector_update_enable();
662 	if (watchdog_enabled && watchdog_thresh)
663 		softlockup_start_all();
664 
665 	watchdog_hardlockup_start();
666 	cpus_read_unlock();
667 	/*
668 	 * Must be called outside the cpus locked section to prevent
669 	 * recursive locking in the perf code.
670 	 */
671 	__lockup_detector_cleanup();
672 }
673 
674 void lockup_detector_reconfigure(void)
675 {
676 	mutex_lock(&watchdog_mutex);
677 	__lockup_detector_reconfigure();
678 	mutex_unlock(&watchdog_mutex);
679 }
680 
681 /*
682  * Create the watchdog infrastructure and configure the detector(s).
683  */
684 static __init void lockup_detector_setup(void)
685 {
686 	/*
687 	 * If sysctl is off and watchdog got disabled on the command line,
688 	 * nothing to do here.
689 	 */
690 	lockup_detector_update_enable();
691 
692 	if (!IS_ENABLED(CONFIG_SYSCTL) &&
693 	    !(watchdog_enabled && watchdog_thresh))
694 		return;
695 
696 	mutex_lock(&watchdog_mutex);
697 	__lockup_detector_reconfigure();
698 	softlockup_initialized = true;
699 	mutex_unlock(&watchdog_mutex);
700 }
701 
702 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
703 static void __lockup_detector_reconfigure(void)
704 {
705 	cpus_read_lock();
706 	watchdog_hardlockup_stop();
707 	lockup_detector_update_enable();
708 	watchdog_hardlockup_start();
709 	cpus_read_unlock();
710 }
711 void lockup_detector_reconfigure(void)
712 {
713 	__lockup_detector_reconfigure();
714 }
715 static inline void lockup_detector_setup(void)
716 {
717 	__lockup_detector_reconfigure();
718 }
719 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
720 
721 static void __lockup_detector_cleanup(void)
722 {
723 	lockdep_assert_held(&watchdog_mutex);
724 	hardlockup_detector_perf_cleanup();
725 }
726 
727 /**
728  * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
729  *
730  * Caller must not hold the cpu hotplug rwsem.
731  */
732 void lockup_detector_cleanup(void)
733 {
734 	mutex_lock(&watchdog_mutex);
735 	__lockup_detector_cleanup();
736 	mutex_unlock(&watchdog_mutex);
737 }
738 
739 /**
740  * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
741  *
742  * Special interface for parisc. It prevents lockup detector warnings from
743  * the default pm_poweroff() function which busy loops forever.
744  */
745 void lockup_detector_soft_poweroff(void)
746 {
747 	watchdog_enabled = 0;
748 }
749 
750 #ifdef CONFIG_SYSCTL
751 
752 /* Propagate any changes to the watchdog infrastructure */
753 static void proc_watchdog_update(void)
754 {
755 	/* Remove impossible cpus to keep sysctl output clean. */
756 	cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
757 	__lockup_detector_reconfigure();
758 }
759 
760 /*
761  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
762  *
763  * caller             | table->data points to            | 'which'
764  * -------------------|----------------------------------|-------------------------------
765  * proc_watchdog      | watchdog_user_enabled            | WATCHDOG_HARDLOCKUP_ENABLED |
766  *                    |                                  | WATCHDOG_SOFTOCKUP_ENABLED
767  * -------------------|----------------------------------|-------------------------------
768  * proc_nmi_watchdog  | watchdog_hardlockup_user_enabled | WATCHDOG_HARDLOCKUP_ENABLED
769  * -------------------|----------------------------------|-------------------------------
770  * proc_soft_watchdog | watchdog_softlockup_user_enabled | WATCHDOG_SOFTOCKUP_ENABLED
771  */
772 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
773 				void *buffer, size_t *lenp, loff_t *ppos)
774 {
775 	int err, old, *param = table->data;
776 
777 	mutex_lock(&watchdog_mutex);
778 
779 	if (!write) {
780 		/*
781 		 * On read synchronize the userspace interface. This is a
782 		 * racy snapshot.
783 		 */
784 		*param = (watchdog_enabled & which) != 0;
785 		err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
786 	} else {
787 		old = READ_ONCE(*param);
788 		err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
789 		if (!err && old != READ_ONCE(*param))
790 			proc_watchdog_update();
791 	}
792 	mutex_unlock(&watchdog_mutex);
793 	return err;
794 }
795 
796 /*
797  * /proc/sys/kernel/watchdog
798  */
799 int proc_watchdog(struct ctl_table *table, int write,
800 		  void *buffer, size_t *lenp, loff_t *ppos)
801 {
802 	return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED |
803 				    WATCHDOG_SOFTOCKUP_ENABLED,
804 				    table, write, buffer, lenp, ppos);
805 }
806 
807 /*
808  * /proc/sys/kernel/nmi_watchdog
809  */
810 int proc_nmi_watchdog(struct ctl_table *table, int write,
811 		      void *buffer, size_t *lenp, loff_t *ppos)
812 {
813 	if (!watchdog_hardlockup_available && write)
814 		return -ENOTSUPP;
815 	return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED,
816 				    table, write, buffer, lenp, ppos);
817 }
818 
819 /*
820  * /proc/sys/kernel/soft_watchdog
821  */
822 int proc_soft_watchdog(struct ctl_table *table, int write,
823 			void *buffer, size_t *lenp, loff_t *ppos)
824 {
825 	return proc_watchdog_common(WATCHDOG_SOFTOCKUP_ENABLED,
826 				    table, write, buffer, lenp, ppos);
827 }
828 
829 /*
830  * /proc/sys/kernel/watchdog_thresh
831  */
832 int proc_watchdog_thresh(struct ctl_table *table, int write,
833 			 void *buffer, size_t *lenp, loff_t *ppos)
834 {
835 	int err, old;
836 
837 	mutex_lock(&watchdog_mutex);
838 
839 	old = READ_ONCE(watchdog_thresh);
840 	err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
841 
842 	if (!err && write && old != READ_ONCE(watchdog_thresh))
843 		proc_watchdog_update();
844 
845 	mutex_unlock(&watchdog_mutex);
846 	return err;
847 }
848 
849 /*
850  * The cpumask is the mask of possible cpus that the watchdog can run
851  * on, not the mask of cpus it is actually running on.  This allows the
852  * user to specify a mask that will include cpus that have not yet
853  * been brought online, if desired.
854  */
855 int proc_watchdog_cpumask(struct ctl_table *table, int write,
856 			  void *buffer, size_t *lenp, loff_t *ppos)
857 {
858 	int err;
859 
860 	mutex_lock(&watchdog_mutex);
861 
862 	err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
863 	if (!err && write)
864 		proc_watchdog_update();
865 
866 	mutex_unlock(&watchdog_mutex);
867 	return err;
868 }
869 
870 static const int sixty = 60;
871 
872 static struct ctl_table watchdog_sysctls[] = {
873 	{
874 		.procname       = "watchdog",
875 		.data		= &watchdog_user_enabled,
876 		.maxlen		= sizeof(int),
877 		.mode		= 0644,
878 		.proc_handler   = proc_watchdog,
879 		.extra1		= SYSCTL_ZERO,
880 		.extra2		= SYSCTL_ONE,
881 	},
882 	{
883 		.procname	= "watchdog_thresh",
884 		.data		= &watchdog_thresh,
885 		.maxlen		= sizeof(int),
886 		.mode		= 0644,
887 		.proc_handler	= proc_watchdog_thresh,
888 		.extra1		= SYSCTL_ZERO,
889 		.extra2		= (void *)&sixty,
890 	},
891 	{
892 		.procname	= "watchdog_cpumask",
893 		.data		= &watchdog_cpumask_bits,
894 		.maxlen		= NR_CPUS,
895 		.mode		= 0644,
896 		.proc_handler	= proc_watchdog_cpumask,
897 	},
898 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
899 	{
900 		.procname       = "soft_watchdog",
901 		.data		= &watchdog_softlockup_user_enabled,
902 		.maxlen		= sizeof(int),
903 		.mode		= 0644,
904 		.proc_handler   = proc_soft_watchdog,
905 		.extra1		= SYSCTL_ZERO,
906 		.extra2		= SYSCTL_ONE,
907 	},
908 	{
909 		.procname	= "softlockup_panic",
910 		.data		= &softlockup_panic,
911 		.maxlen		= sizeof(int),
912 		.mode		= 0644,
913 		.proc_handler	= proc_dointvec_minmax,
914 		.extra1		= SYSCTL_ZERO,
915 		.extra2		= SYSCTL_ONE,
916 	},
917 #ifdef CONFIG_SMP
918 	{
919 		.procname	= "softlockup_all_cpu_backtrace",
920 		.data		= &sysctl_softlockup_all_cpu_backtrace,
921 		.maxlen		= sizeof(int),
922 		.mode		= 0644,
923 		.proc_handler	= proc_dointvec_minmax,
924 		.extra1		= SYSCTL_ZERO,
925 		.extra2		= SYSCTL_ONE,
926 	},
927 #endif /* CONFIG_SMP */
928 #endif
929 #ifdef CONFIG_HARDLOCKUP_DETECTOR
930 	{
931 		.procname	= "hardlockup_panic",
932 		.data		= &hardlockup_panic,
933 		.maxlen		= sizeof(int),
934 		.mode		= 0644,
935 		.proc_handler	= proc_dointvec_minmax,
936 		.extra1		= SYSCTL_ZERO,
937 		.extra2		= SYSCTL_ONE,
938 	},
939 #ifdef CONFIG_SMP
940 	{
941 		.procname	= "hardlockup_all_cpu_backtrace",
942 		.data		= &sysctl_hardlockup_all_cpu_backtrace,
943 		.maxlen		= sizeof(int),
944 		.mode		= 0644,
945 		.proc_handler	= proc_dointvec_minmax,
946 		.extra1		= SYSCTL_ZERO,
947 		.extra2		= SYSCTL_ONE,
948 	},
949 #endif /* CONFIG_SMP */
950 #endif
951 	{}
952 };
953 
954 static struct ctl_table watchdog_hardlockup_sysctl[] = {
955 	{
956 		.procname       = "nmi_watchdog",
957 		.data		= &watchdog_hardlockup_user_enabled,
958 		.maxlen		= sizeof(int),
959 		.mode		= 0444,
960 		.proc_handler   = proc_nmi_watchdog,
961 		.extra1		= SYSCTL_ZERO,
962 		.extra2		= SYSCTL_ONE,
963 	},
964 	{}
965 };
966 
967 static void __init watchdog_sysctl_init(void)
968 {
969 	register_sysctl_init("kernel", watchdog_sysctls);
970 
971 	if (watchdog_hardlockup_available)
972 		watchdog_hardlockup_sysctl[0].mode = 0644;
973 	register_sysctl_init("kernel", watchdog_hardlockup_sysctl);
974 }
975 
976 #else
977 #define watchdog_sysctl_init() do { } while (0)
978 #endif /* CONFIG_SYSCTL */
979 
980 static void __init lockup_detector_delay_init(struct work_struct *work);
981 static bool allow_lockup_detector_init_retry __initdata;
982 
983 static struct work_struct detector_work __initdata =
984 		__WORK_INITIALIZER(detector_work, lockup_detector_delay_init);
985 
986 static void __init lockup_detector_delay_init(struct work_struct *work)
987 {
988 	int ret;
989 
990 	ret = watchdog_hardlockup_probe();
991 	if (ret) {
992 		pr_info("Delayed init of the lockup detector failed: %d\n", ret);
993 		pr_info("Hard watchdog permanently disabled\n");
994 		return;
995 	}
996 
997 	allow_lockup_detector_init_retry = false;
998 
999 	watchdog_hardlockup_available = true;
1000 	lockup_detector_setup();
1001 }
1002 
1003 /*
1004  * lockup_detector_retry_init - retry init lockup detector if possible.
1005  *
1006  * Retry hardlockup detector init. It is useful when it requires some
1007  * functionality that has to be initialized later on a particular
1008  * platform.
1009  */
1010 void __init lockup_detector_retry_init(void)
1011 {
1012 	/* Must be called before late init calls */
1013 	if (!allow_lockup_detector_init_retry)
1014 		return;
1015 
1016 	schedule_work(&detector_work);
1017 }
1018 
1019 /*
1020  * Ensure that optional delayed hardlockup init is proceed before
1021  * the init code and memory is freed.
1022  */
1023 static int __init lockup_detector_check(void)
1024 {
1025 	/* Prevent any later retry. */
1026 	allow_lockup_detector_init_retry = false;
1027 
1028 	/* Make sure no work is pending. */
1029 	flush_work(&detector_work);
1030 
1031 	watchdog_sysctl_init();
1032 
1033 	return 0;
1034 
1035 }
1036 late_initcall_sync(lockup_detector_check);
1037 
1038 void __init lockup_detector_init(void)
1039 {
1040 	if (tick_nohz_full_enabled())
1041 		pr_info("Disabling watchdog on nohz_full cores by default\n");
1042 
1043 	cpumask_copy(&watchdog_cpumask,
1044 		     housekeeping_cpumask(HK_TYPE_TIMER));
1045 
1046 	if (!watchdog_hardlockup_probe())
1047 		watchdog_hardlockup_available = true;
1048 	else
1049 		allow_lockup_detector_init_retry = true;
1050 
1051 	lockup_detector_setup();
1052 }
1053