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/cpu.h>
16 #include <linux/init.h>
17 #include <linux/irq.h>
18 #include <linux/irqdesc.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/kvm_para.h>
21 #include <linux/math64.h>
22 #include <linux/mm.h>
23 #include <linux/module.h>
24 #include <linux/nmi.h>
25 #include <linux/stop_machine.h>
26 #include <linux/sysctl.h>
27 #include <linux/tick.h>
28
29 #include <linux/sched/clock.h>
30 #include <linux/sched/debug.h>
31 #include <linux/sched/isolation.h>
32
33 #include <asm/irq_regs.h>
34
35 static DEFINE_MUTEX(watchdog_mutex);
36
37 #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HARDLOCKUP_DETECTOR_SPARC64)
38 # define WATCHDOG_HARDLOCKUP_DEFAULT 1
39 #else
40 # define WATCHDOG_HARDLOCKUP_DEFAULT 0
41 #endif
42
43 #define NUM_SAMPLE_PERIODS 5
44
45 unsigned long __read_mostly watchdog_enabled;
46 int __read_mostly watchdog_user_enabled = 1;
47 static int __read_mostly watchdog_hardlockup_user_enabled = WATCHDOG_HARDLOCKUP_DEFAULT;
48 static int __read_mostly watchdog_softlockup_user_enabled = 1;
49 int __read_mostly watchdog_thresh = 10;
50 static int __read_mostly watchdog_hardlockup_available;
51
52 struct cpumask watchdog_cpumask __read_mostly;
53 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
54
55 #ifdef CONFIG_HARDLOCKUP_DETECTOR
56
57 # ifdef CONFIG_SMP
58 int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
59 # endif /* CONFIG_SMP */
60
61 /*
62 * Should we panic when a soft-lockup or hard-lockup occurs:
63 */
64 unsigned int __read_mostly hardlockup_panic =
65 IS_ENABLED(CONFIG_BOOTPARAM_HARDLOCKUP_PANIC);
66 /*
67 * We may not want to enable hard lockup detection by default in all cases,
68 * for example when running the kernel as a guest on a hypervisor. In these
69 * cases this function can be called to disable hard lockup detection. This
70 * function should only be executed once by the boot processor before the
71 * kernel command line parameters are parsed, because otherwise it is not
72 * possible to override this in hardlockup_panic_setup().
73 */
hardlockup_detector_disable(void)74 void __init hardlockup_detector_disable(void)
75 {
76 watchdog_hardlockup_user_enabled = 0;
77 }
78
hardlockup_panic_setup(char * str)79 static int __init hardlockup_panic_setup(char *str)
80 {
81 next:
82 if (!strncmp(str, "panic", 5))
83 hardlockup_panic = 1;
84 else if (!strncmp(str, "nopanic", 7))
85 hardlockup_panic = 0;
86 else if (!strncmp(str, "0", 1))
87 watchdog_hardlockup_user_enabled = 0;
88 else if (!strncmp(str, "1", 1))
89 watchdog_hardlockup_user_enabled = 1;
90 else if (!strncmp(str, "r", 1))
91 hardlockup_config_perf_event(str + 1);
92 while (*(str++)) {
93 if (*str == ',') {
94 str++;
95 goto next;
96 }
97 }
98 return 1;
99 }
100 __setup("nmi_watchdog=", hardlockup_panic_setup);
101
102 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
103
104 #if defined(CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER)
105
106 static DEFINE_PER_CPU(atomic_t, hrtimer_interrupts);
107 static DEFINE_PER_CPU(int, hrtimer_interrupts_saved);
108 static DEFINE_PER_CPU(bool, watchdog_hardlockup_warned);
109 static DEFINE_PER_CPU(bool, watchdog_hardlockup_touched);
110 static unsigned long hard_lockup_nmi_warn;
111
arch_touch_nmi_watchdog(void)112 notrace void arch_touch_nmi_watchdog(void)
113 {
114 /*
115 * Using __raw here because some code paths have
116 * preemption enabled. If preemption is enabled
117 * then interrupts should be enabled too, in which
118 * case we shouldn't have to worry about the watchdog
119 * going off.
120 */
121 raw_cpu_write(watchdog_hardlockup_touched, true);
122 }
123 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
124
watchdog_hardlockup_touch_cpu(unsigned int cpu)125 void watchdog_hardlockup_touch_cpu(unsigned int cpu)
126 {
127 per_cpu(watchdog_hardlockup_touched, cpu) = true;
128 }
129
is_hardlockup(unsigned int cpu)130 static bool is_hardlockup(unsigned int cpu)
131 {
132 int hrint = atomic_read(&per_cpu(hrtimer_interrupts, cpu));
133
134 if (per_cpu(hrtimer_interrupts_saved, cpu) == hrint)
135 return true;
136
137 /*
138 * NOTE: we don't need any fancy atomic_t or READ_ONCE/WRITE_ONCE
139 * for hrtimer_interrupts_saved. hrtimer_interrupts_saved is
140 * written/read by a single CPU.
141 */
142 per_cpu(hrtimer_interrupts_saved, cpu) = hrint;
143
144 return false;
145 }
146
watchdog_hardlockup_kick(void)147 static void watchdog_hardlockup_kick(void)
148 {
149 int new_interrupts;
150
151 new_interrupts = atomic_inc_return(this_cpu_ptr(&hrtimer_interrupts));
152 watchdog_buddy_check_hardlockup(new_interrupts);
153 }
154
watchdog_hardlockup_check(unsigned int cpu,struct pt_regs * regs)155 void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)
156 {
157 if (per_cpu(watchdog_hardlockup_touched, cpu)) {
158 per_cpu(watchdog_hardlockup_touched, cpu) = false;
159 return;
160 }
161
162 /*
163 * Check for a hardlockup by making sure the CPU's timer
164 * interrupt is incrementing. The timer interrupt should have
165 * fired multiple times before we overflow'd. If it hasn't
166 * then this is a good indication the cpu is stuck
167 */
168 if (is_hardlockup(cpu)) {
169 unsigned int this_cpu = smp_processor_id();
170 unsigned long flags;
171
172 /* Only print hardlockups once. */
173 if (per_cpu(watchdog_hardlockup_warned, cpu))
174 return;
175
176 /*
177 * Prevent multiple hard-lockup reports if one cpu is already
178 * engaged in dumping all cpu back traces.
179 */
180 if (sysctl_hardlockup_all_cpu_backtrace) {
181 if (test_and_set_bit_lock(0, &hard_lockup_nmi_warn))
182 return;
183 }
184
185 /*
186 * NOTE: we call printk_cpu_sync_get_irqsave() after printing
187 * the lockup message. While it would be nice to serialize
188 * that printout, we really want to make sure that if some
189 * other CPU somehow locked up while holding the lock associated
190 * with printk_cpu_sync_get_irqsave() that we can still at least
191 * get the message about the lockup out.
192 */
193 pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n", cpu);
194 printk_cpu_sync_get_irqsave(flags);
195
196 print_modules();
197 print_irqtrace_events(current);
198 if (cpu == this_cpu) {
199 if (regs)
200 show_regs(regs);
201 else
202 dump_stack();
203 printk_cpu_sync_put_irqrestore(flags);
204 } else {
205 printk_cpu_sync_put_irqrestore(flags);
206 trigger_single_cpu_backtrace(cpu);
207 }
208
209 if (sysctl_hardlockup_all_cpu_backtrace) {
210 trigger_allbutcpu_cpu_backtrace(cpu);
211 if (!hardlockup_panic)
212 clear_bit_unlock(0, &hard_lockup_nmi_warn);
213 }
214
215 if (hardlockup_panic)
216 nmi_panic(regs, "Hard LOCKUP");
217
218 per_cpu(watchdog_hardlockup_warned, cpu) = true;
219 } else {
220 per_cpu(watchdog_hardlockup_warned, cpu) = false;
221 }
222 }
223
224 #else /* CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
225
watchdog_hardlockup_kick(void)226 static inline void watchdog_hardlockup_kick(void) { }
227
228 #endif /* !CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
229
230 /*
231 * These functions can be overridden based on the configured hardlockdup detector.
232 *
233 * watchdog_hardlockup_enable/disable can be implemented to start and stop when
234 * softlockup watchdog start and stop. The detector must select the
235 * SOFTLOCKUP_DETECTOR Kconfig.
236 */
watchdog_hardlockup_enable(unsigned int cpu)237 void __weak watchdog_hardlockup_enable(unsigned int cpu) { }
238
watchdog_hardlockup_disable(unsigned int cpu)239 void __weak watchdog_hardlockup_disable(unsigned int cpu) { }
240
241 /*
242 * Watchdog-detector specific API.
243 *
244 * Return 0 when hardlockup watchdog is available, negative value otherwise.
245 * Note that the negative value means that a delayed probe might
246 * succeed later.
247 */
watchdog_hardlockup_probe(void)248 int __weak __init watchdog_hardlockup_probe(void)
249 {
250 return -ENODEV;
251 }
252
253 /**
254 * watchdog_hardlockup_stop - Stop the watchdog for reconfiguration
255 *
256 * The reconfiguration steps are:
257 * watchdog_hardlockup_stop();
258 * update_variables();
259 * watchdog_hardlockup_start();
260 */
watchdog_hardlockup_stop(void)261 void __weak watchdog_hardlockup_stop(void) { }
262
263 /**
264 * watchdog_hardlockup_start - Start the watchdog after reconfiguration
265 *
266 * Counterpart to watchdog_hardlockup_stop().
267 *
268 * The following variables have been updated in update_variables() and
269 * contain the currently valid configuration:
270 * - watchdog_enabled
271 * - watchdog_thresh
272 * - watchdog_cpumask
273 */
watchdog_hardlockup_start(void)274 void __weak watchdog_hardlockup_start(void) { }
275
276 /**
277 * lockup_detector_update_enable - Update the sysctl enable bit
278 *
279 * Caller needs to make sure that the hard watchdogs are off, so this
280 * can't race with watchdog_hardlockup_disable().
281 */
lockup_detector_update_enable(void)282 static void lockup_detector_update_enable(void)
283 {
284 watchdog_enabled = 0;
285 if (!watchdog_user_enabled)
286 return;
287 if (watchdog_hardlockup_available && watchdog_hardlockup_user_enabled)
288 watchdog_enabled |= WATCHDOG_HARDLOCKUP_ENABLED;
289 if (watchdog_softlockup_user_enabled)
290 watchdog_enabled |= WATCHDOG_SOFTOCKUP_ENABLED;
291 }
292
293 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
294
295 /*
296 * Delay the soflockup report when running a known slow code.
297 * It does _not_ affect the timestamp of the last successdul reschedule.
298 */
299 #define SOFTLOCKUP_DELAY_REPORT ULONG_MAX
300
301 #ifdef CONFIG_SMP
302 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
303 #endif
304
305 static struct cpumask watchdog_allowed_mask __read_mostly;
306
307 /* Global variables, exported for sysctl */
308 unsigned int __read_mostly softlockup_panic =
309 IS_ENABLED(CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC);
310
311 static bool softlockup_initialized __read_mostly;
312 static u64 __read_mostly sample_period;
313
314 /* Timestamp taken after the last successful reschedule. */
315 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
316 /* Timestamp of the last softlockup report. */
317 static DEFINE_PER_CPU(unsigned long, watchdog_report_ts);
318 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
319 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
320 static unsigned long soft_lockup_nmi_warn;
321
softlockup_panic_setup(char * str)322 static int __init softlockup_panic_setup(char *str)
323 {
324 softlockup_panic = simple_strtoul(str, NULL, 0);
325 return 1;
326 }
327 __setup("softlockup_panic=", softlockup_panic_setup);
328
nowatchdog_setup(char * str)329 static int __init nowatchdog_setup(char *str)
330 {
331 watchdog_user_enabled = 0;
332 return 1;
333 }
334 __setup("nowatchdog", nowatchdog_setup);
335
nosoftlockup_setup(char * str)336 static int __init nosoftlockup_setup(char *str)
337 {
338 watchdog_softlockup_user_enabled = 0;
339 return 1;
340 }
341 __setup("nosoftlockup", nosoftlockup_setup);
342
watchdog_thresh_setup(char * str)343 static int __init watchdog_thresh_setup(char *str)
344 {
345 get_option(&str, &watchdog_thresh);
346 return 1;
347 }
348 __setup("watchdog_thresh=", watchdog_thresh_setup);
349
350 static void __lockup_detector_cleanup(void);
351
352 #ifdef CONFIG_SOFTLOCKUP_DETECTOR_INTR_STORM
353 enum stats_per_group {
354 STATS_SYSTEM,
355 STATS_SOFTIRQ,
356 STATS_HARDIRQ,
357 STATS_IDLE,
358 NUM_STATS_PER_GROUP,
359 };
360
361 static const enum cpu_usage_stat tracked_stats[NUM_STATS_PER_GROUP] = {
362 CPUTIME_SYSTEM,
363 CPUTIME_SOFTIRQ,
364 CPUTIME_IRQ,
365 CPUTIME_IDLE,
366 };
367
368 static DEFINE_PER_CPU(u16, cpustat_old[NUM_STATS_PER_GROUP]);
369 static DEFINE_PER_CPU(u8, cpustat_util[NUM_SAMPLE_PERIODS][NUM_STATS_PER_GROUP]);
370 static DEFINE_PER_CPU(u8, cpustat_tail);
371
372 /*
373 * We don't need nanosecond resolution. A granularity of 16ms is
374 * sufficient for our precision, allowing us to use u16 to store
375 * cpustats, which will roll over roughly every ~1000 seconds.
376 * 2^24 ~= 16 * 10^6
377 */
get_16bit_precision(u64 data_ns)378 static u16 get_16bit_precision(u64 data_ns)
379 {
380 return data_ns >> 24LL; /* 2^24ns ~= 16.8ms */
381 }
382
update_cpustat(void)383 static void update_cpustat(void)
384 {
385 int i;
386 u8 util;
387 u16 old_stat, new_stat;
388 struct kernel_cpustat kcpustat;
389 u64 *cpustat = kcpustat.cpustat;
390 u8 tail = __this_cpu_read(cpustat_tail);
391 u16 sample_period_16 = get_16bit_precision(sample_period);
392
393 kcpustat_cpu_fetch(&kcpustat, smp_processor_id());
394
395 for (i = 0; i < NUM_STATS_PER_GROUP; i++) {
396 old_stat = __this_cpu_read(cpustat_old[i]);
397 new_stat = get_16bit_precision(cpustat[tracked_stats[i]]);
398 util = DIV_ROUND_UP(100 * (new_stat - old_stat), sample_period_16);
399 __this_cpu_write(cpustat_util[tail][i], util);
400 __this_cpu_write(cpustat_old[i], new_stat);
401 }
402
403 __this_cpu_write(cpustat_tail, (tail + 1) % NUM_SAMPLE_PERIODS);
404 }
405
print_cpustat(void)406 static void print_cpustat(void)
407 {
408 int i, group;
409 u8 tail = __this_cpu_read(cpustat_tail);
410 u64 sample_period_second = sample_period;
411
412 do_div(sample_period_second, NSEC_PER_SEC);
413
414 /*
415 * Outputting the "watchdog" prefix on every line is redundant and not
416 * concise, and the original alarm information is sufficient for
417 * positioning in logs, hence here printk() is used instead of pr_crit().
418 */
419 printk(KERN_CRIT "CPU#%d Utilization every %llus during lockup:\n",
420 smp_processor_id(), sample_period_second);
421
422 for (i = 0; i < NUM_SAMPLE_PERIODS; i++) {
423 group = (tail + i) % NUM_SAMPLE_PERIODS;
424 printk(KERN_CRIT "\t#%d: %3u%% system,\t%3u%% softirq,\t"
425 "%3u%% hardirq,\t%3u%% idle\n", i + 1,
426 __this_cpu_read(cpustat_util[group][STATS_SYSTEM]),
427 __this_cpu_read(cpustat_util[group][STATS_SOFTIRQ]),
428 __this_cpu_read(cpustat_util[group][STATS_HARDIRQ]),
429 __this_cpu_read(cpustat_util[group][STATS_IDLE]));
430 }
431 }
432
433 #define HARDIRQ_PERCENT_THRESH 50
434 #define NUM_HARDIRQ_REPORT 5
435 struct irq_counts {
436 int irq;
437 u32 counts;
438 };
439
440 static DEFINE_PER_CPU(bool, snapshot_taken);
441
442 /* Tabulate the most frequent interrupts. */
tabulate_irq_count(struct irq_counts * irq_counts,int irq,u32 counts,int rank)443 static void tabulate_irq_count(struct irq_counts *irq_counts, int irq, u32 counts, int rank)
444 {
445 int i;
446 struct irq_counts new_count = {irq, counts};
447
448 for (i = 0; i < rank; i++) {
449 if (counts > irq_counts[i].counts)
450 swap(new_count, irq_counts[i]);
451 }
452 }
453
454 /*
455 * If the hardirq time exceeds HARDIRQ_PERCENT_THRESH% of the sample_period,
456 * then the cause of softlockup might be interrupt storm. In this case, it
457 * would be useful to start interrupt counting.
458 */
need_counting_irqs(void)459 static bool need_counting_irqs(void)
460 {
461 u8 util;
462 int tail = __this_cpu_read(cpustat_tail);
463
464 tail = (tail + NUM_HARDIRQ_REPORT - 1) % NUM_HARDIRQ_REPORT;
465 util = __this_cpu_read(cpustat_util[tail][STATS_HARDIRQ]);
466 return util > HARDIRQ_PERCENT_THRESH;
467 }
468
start_counting_irqs(void)469 static void start_counting_irqs(void)
470 {
471 if (!__this_cpu_read(snapshot_taken)) {
472 kstat_snapshot_irqs();
473 __this_cpu_write(snapshot_taken, true);
474 }
475 }
476
stop_counting_irqs(void)477 static void stop_counting_irqs(void)
478 {
479 __this_cpu_write(snapshot_taken, false);
480 }
481
print_irq_counts(void)482 static void print_irq_counts(void)
483 {
484 unsigned int i, count;
485 struct irq_counts irq_counts_sorted[NUM_HARDIRQ_REPORT] = {
486 {-1, 0}, {-1, 0}, {-1, 0}, {-1, 0}, {-1, 0}
487 };
488
489 if (__this_cpu_read(snapshot_taken)) {
490 for_each_active_irq(i) {
491 count = kstat_get_irq_since_snapshot(i);
492 tabulate_irq_count(irq_counts_sorted, i, count, NUM_HARDIRQ_REPORT);
493 }
494
495 /*
496 * Outputting the "watchdog" prefix on every line is redundant and not
497 * concise, and the original alarm information is sufficient for
498 * positioning in logs, hence here printk() is used instead of pr_crit().
499 */
500 printk(KERN_CRIT "CPU#%d Detect HardIRQ Time exceeds %d%%. Most frequent HardIRQs:\n",
501 smp_processor_id(), HARDIRQ_PERCENT_THRESH);
502
503 for (i = 0; i < NUM_HARDIRQ_REPORT; i++) {
504 if (irq_counts_sorted[i].irq == -1)
505 break;
506
507 printk(KERN_CRIT "\t#%u: %-10u\tirq#%d\n",
508 i + 1, irq_counts_sorted[i].counts,
509 irq_counts_sorted[i].irq);
510 }
511
512 /*
513 * If the hardirq time is less than HARDIRQ_PERCENT_THRESH% in the last
514 * sample_period, then we suspect the interrupt storm might be subsiding.
515 */
516 if (!need_counting_irqs())
517 stop_counting_irqs();
518 }
519 }
520
report_cpu_status(void)521 static void report_cpu_status(void)
522 {
523 print_cpustat();
524 print_irq_counts();
525 }
526 #else
update_cpustat(void)527 static inline void update_cpustat(void) { }
report_cpu_status(void)528 static inline void report_cpu_status(void) { }
need_counting_irqs(void)529 static inline bool need_counting_irqs(void) { return false; }
start_counting_irqs(void)530 static inline void start_counting_irqs(void) { }
stop_counting_irqs(void)531 static inline void stop_counting_irqs(void) { }
532 #endif
533
534 /*
535 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
536 * lockups can have false positives under extreme conditions. So we generally
537 * want a higher threshold for soft lockups than for hard lockups. So we couple
538 * the thresholds with a factor: we make the soft threshold twice the amount of
539 * time the hard threshold is.
540 */
get_softlockup_thresh(void)541 static int get_softlockup_thresh(void)
542 {
543 return watchdog_thresh * 2;
544 }
545
546 /*
547 * Returns seconds, approximately. We don't need nanosecond
548 * resolution, and we don't need to waste time with a big divide when
549 * 2^30ns == 1.074s.
550 */
get_timestamp(void)551 static unsigned long get_timestamp(void)
552 {
553 return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
554 }
555
set_sample_period(void)556 static void set_sample_period(void)
557 {
558 /*
559 * convert watchdog_thresh from seconds to ns
560 * the divide by 5 is to give hrtimer several chances (two
561 * or three with the current relation between the soft
562 * and hard thresholds) to increment before the
563 * hardlockup detector generates a warning
564 */
565 sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / NUM_SAMPLE_PERIODS);
566 watchdog_update_hrtimer_threshold(sample_period);
567 }
568
update_report_ts(void)569 static void update_report_ts(void)
570 {
571 __this_cpu_write(watchdog_report_ts, get_timestamp());
572 }
573
574 /* Commands for resetting the watchdog */
update_touch_ts(void)575 static void update_touch_ts(void)
576 {
577 __this_cpu_write(watchdog_touch_ts, get_timestamp());
578 update_report_ts();
579 }
580
581 /**
582 * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
583 *
584 * Call when the scheduler may have stalled for legitimate reasons
585 * preventing the watchdog task from executing - e.g. the scheduler
586 * entering idle state. This should only be used for scheduler events.
587 * Use touch_softlockup_watchdog() for everything else.
588 */
touch_softlockup_watchdog_sched(void)589 notrace void touch_softlockup_watchdog_sched(void)
590 {
591 /*
592 * Preemption can be enabled. It doesn't matter which CPU's watchdog
593 * report period gets restarted here, so use the raw_ operation.
594 */
595 raw_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
596 }
597
touch_softlockup_watchdog(void)598 notrace void touch_softlockup_watchdog(void)
599 {
600 touch_softlockup_watchdog_sched();
601 wq_watchdog_touch(raw_smp_processor_id());
602 }
603 EXPORT_SYMBOL(touch_softlockup_watchdog);
604
touch_all_softlockup_watchdogs(void)605 void touch_all_softlockup_watchdogs(void)
606 {
607 int cpu;
608
609 /*
610 * watchdog_mutex cannpt be taken here, as this might be called
611 * from (soft)interrupt context, so the access to
612 * watchdog_allowed_cpumask might race with a concurrent update.
613 *
614 * The watchdog time stamp can race against a concurrent real
615 * update as well, the only side effect might be a cycle delay for
616 * the softlockup check.
617 */
618 for_each_cpu(cpu, &watchdog_allowed_mask) {
619 per_cpu(watchdog_report_ts, cpu) = SOFTLOCKUP_DELAY_REPORT;
620 wq_watchdog_touch(cpu);
621 }
622 }
623
touch_softlockup_watchdog_sync(void)624 void touch_softlockup_watchdog_sync(void)
625 {
626 __this_cpu_write(softlockup_touch_sync, true);
627 __this_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
628 }
629
is_softlockup(unsigned long touch_ts,unsigned long period_ts,unsigned long now)630 static int is_softlockup(unsigned long touch_ts,
631 unsigned long period_ts,
632 unsigned long now)
633 {
634 if ((watchdog_enabled & WATCHDOG_SOFTOCKUP_ENABLED) && watchdog_thresh) {
635 /*
636 * If period_ts has not been updated during a sample_period, then
637 * in the subsequent few sample_periods, period_ts might also not
638 * be updated, which could indicate a potential softlockup. In
639 * this case, if we suspect the cause of the potential softlockup
640 * might be interrupt storm, then we need to count the interrupts
641 * to find which interrupt is storming.
642 */
643 if (time_after_eq(now, period_ts + get_softlockup_thresh() / NUM_SAMPLE_PERIODS) &&
644 need_counting_irqs())
645 start_counting_irqs();
646
647 /*
648 * A poorly behaving BPF scheduler can live-lock the system into
649 * soft lockups. Tell sched_ext to try ejecting the BPF
650 * scheduler when close to a soft lockup.
651 */
652 if (time_after_eq(now, period_ts + get_softlockup_thresh() * 3 / 4))
653 scx_softlockup(now - touch_ts);
654
655 /* Warn about unreasonable delays. */
656 if (time_after(now, period_ts + get_softlockup_thresh()))
657 return now - touch_ts;
658 }
659 return 0;
660 }
661
662 /* watchdog detector functions */
663 static DEFINE_PER_CPU(struct completion, softlockup_completion);
664 static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
665
666 /*
667 * The watchdog feed function - touches the timestamp.
668 *
669 * It only runs once every sample_period seconds (4 seconds by
670 * default) to reset the softlockup timestamp. If this gets delayed
671 * for more than 2*watchdog_thresh seconds then the debug-printout
672 * triggers in watchdog_timer_fn().
673 */
softlockup_fn(void * data)674 static int softlockup_fn(void *data)
675 {
676 update_touch_ts();
677 stop_counting_irqs();
678 complete(this_cpu_ptr(&softlockup_completion));
679
680 return 0;
681 }
682
683 /* watchdog kicker functions */
watchdog_timer_fn(struct hrtimer * hrtimer)684 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
685 {
686 unsigned long touch_ts, period_ts, now;
687 struct pt_regs *regs = get_irq_regs();
688 int duration;
689 int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
690 unsigned long flags;
691
692 if (!watchdog_enabled)
693 return HRTIMER_NORESTART;
694
695 watchdog_hardlockup_kick();
696
697 /* kick the softlockup detector */
698 if (completion_done(this_cpu_ptr(&softlockup_completion))) {
699 reinit_completion(this_cpu_ptr(&softlockup_completion));
700 stop_one_cpu_nowait(smp_processor_id(),
701 softlockup_fn, NULL,
702 this_cpu_ptr(&softlockup_stop_work));
703 }
704
705 /* .. and repeat */
706 hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
707
708 /*
709 * Read the current timestamp first. It might become invalid anytime
710 * when a virtual machine is stopped by the host or when the watchog
711 * is touched from NMI.
712 */
713 now = get_timestamp();
714 /*
715 * If a virtual machine is stopped by the host it can look to
716 * the watchdog like a soft lockup. This function touches the watchdog.
717 */
718 kvm_check_and_clear_guest_paused();
719 /*
720 * The stored timestamp is comparable with @now only when not touched.
721 * It might get touched anytime from NMI. Make sure that is_softlockup()
722 * uses the same (valid) value.
723 */
724 period_ts = READ_ONCE(*this_cpu_ptr(&watchdog_report_ts));
725
726 update_cpustat();
727
728 /* Reset the interval when touched by known problematic code. */
729 if (period_ts == SOFTLOCKUP_DELAY_REPORT) {
730 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
731 /*
732 * If the time stamp was touched atomically
733 * make sure the scheduler tick is up to date.
734 */
735 __this_cpu_write(softlockup_touch_sync, false);
736 sched_clock_tick();
737 }
738
739 update_report_ts();
740 return HRTIMER_RESTART;
741 }
742
743 /* Check for a softlockup. */
744 touch_ts = __this_cpu_read(watchdog_touch_ts);
745 duration = is_softlockup(touch_ts, period_ts, now);
746 if (unlikely(duration)) {
747 /*
748 * Prevent multiple soft-lockup reports if one cpu is already
749 * engaged in dumping all cpu back traces.
750 */
751 if (softlockup_all_cpu_backtrace) {
752 if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn))
753 return HRTIMER_RESTART;
754 }
755
756 /* Start period for the next softlockup warning. */
757 update_report_ts();
758
759 printk_cpu_sync_get_irqsave(flags);
760 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
761 smp_processor_id(), duration,
762 current->comm, task_pid_nr(current));
763 report_cpu_status();
764 print_modules();
765 print_irqtrace_events(current);
766 if (regs)
767 show_regs(regs);
768 else
769 dump_stack();
770 printk_cpu_sync_put_irqrestore(flags);
771
772 if (softlockup_all_cpu_backtrace) {
773 trigger_allbutcpu_cpu_backtrace(smp_processor_id());
774 if (!softlockup_panic)
775 clear_bit_unlock(0, &soft_lockup_nmi_warn);
776 }
777
778 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
779 if (softlockup_panic)
780 panic("softlockup: hung tasks");
781 }
782
783 return HRTIMER_RESTART;
784 }
785
watchdog_enable(unsigned int cpu)786 static void watchdog_enable(unsigned int cpu)
787 {
788 struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
789 struct completion *done = this_cpu_ptr(&softlockup_completion);
790
791 WARN_ON_ONCE(cpu != smp_processor_id());
792
793 init_completion(done);
794 complete(done);
795
796 /*
797 * Start the timer first to prevent the hardlockup watchdog triggering
798 * before the timer has a chance to fire.
799 */
800 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
801 hrtimer->function = watchdog_timer_fn;
802 hrtimer_start(hrtimer, ns_to_ktime(sample_period),
803 HRTIMER_MODE_REL_PINNED_HARD);
804
805 /* Initialize timestamp */
806 update_touch_ts();
807 /* Enable the hardlockup detector */
808 if (watchdog_enabled & WATCHDOG_HARDLOCKUP_ENABLED)
809 watchdog_hardlockup_enable(cpu);
810 }
811
watchdog_disable(unsigned int cpu)812 static void watchdog_disable(unsigned int cpu)
813 {
814 struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
815
816 WARN_ON_ONCE(cpu != smp_processor_id());
817
818 /*
819 * Disable the hardlockup detector first. That prevents that a large
820 * delay between disabling the timer and disabling the hardlockup
821 * detector causes a false positive.
822 */
823 watchdog_hardlockup_disable(cpu);
824 hrtimer_cancel(hrtimer);
825 wait_for_completion(this_cpu_ptr(&softlockup_completion));
826 }
827
softlockup_stop_fn(void * data)828 static int softlockup_stop_fn(void *data)
829 {
830 watchdog_disable(smp_processor_id());
831 return 0;
832 }
833
softlockup_stop_all(void)834 static void softlockup_stop_all(void)
835 {
836 int cpu;
837
838 if (!softlockup_initialized)
839 return;
840
841 for_each_cpu(cpu, &watchdog_allowed_mask)
842 smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
843
844 cpumask_clear(&watchdog_allowed_mask);
845 }
846
softlockup_start_fn(void * data)847 static int softlockup_start_fn(void *data)
848 {
849 watchdog_enable(smp_processor_id());
850 return 0;
851 }
852
softlockup_start_all(void)853 static void softlockup_start_all(void)
854 {
855 int cpu;
856
857 cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
858 for_each_cpu(cpu, &watchdog_allowed_mask)
859 smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
860 }
861
lockup_detector_online_cpu(unsigned int cpu)862 int lockup_detector_online_cpu(unsigned int cpu)
863 {
864 if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
865 watchdog_enable(cpu);
866 return 0;
867 }
868
lockup_detector_offline_cpu(unsigned int cpu)869 int lockup_detector_offline_cpu(unsigned int cpu)
870 {
871 if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
872 watchdog_disable(cpu);
873 return 0;
874 }
875
__lockup_detector_reconfigure(void)876 static void __lockup_detector_reconfigure(void)
877 {
878 cpus_read_lock();
879 watchdog_hardlockup_stop();
880
881 softlockup_stop_all();
882 set_sample_period();
883 lockup_detector_update_enable();
884 if (watchdog_enabled && watchdog_thresh)
885 softlockup_start_all();
886
887 watchdog_hardlockup_start();
888 cpus_read_unlock();
889 /*
890 * Must be called outside the cpus locked section to prevent
891 * recursive locking in the perf code.
892 */
893 __lockup_detector_cleanup();
894 }
895
lockup_detector_reconfigure(void)896 void lockup_detector_reconfigure(void)
897 {
898 mutex_lock(&watchdog_mutex);
899 __lockup_detector_reconfigure();
900 mutex_unlock(&watchdog_mutex);
901 }
902
903 /*
904 * Create the watchdog infrastructure and configure the detector(s).
905 */
lockup_detector_setup(void)906 static __init void lockup_detector_setup(void)
907 {
908 /*
909 * If sysctl is off and watchdog got disabled on the command line,
910 * nothing to do here.
911 */
912 lockup_detector_update_enable();
913
914 if (!IS_ENABLED(CONFIG_SYSCTL) &&
915 !(watchdog_enabled && watchdog_thresh))
916 return;
917
918 mutex_lock(&watchdog_mutex);
919 __lockup_detector_reconfigure();
920 softlockup_initialized = true;
921 mutex_unlock(&watchdog_mutex);
922 }
923
924 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
__lockup_detector_reconfigure(void)925 static void __lockup_detector_reconfigure(void)
926 {
927 cpus_read_lock();
928 watchdog_hardlockup_stop();
929 lockup_detector_update_enable();
930 watchdog_hardlockup_start();
931 cpus_read_unlock();
932 }
lockup_detector_reconfigure(void)933 void lockup_detector_reconfigure(void)
934 {
935 __lockup_detector_reconfigure();
936 }
lockup_detector_setup(void)937 static inline void lockup_detector_setup(void)
938 {
939 __lockup_detector_reconfigure();
940 }
941 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
942
__lockup_detector_cleanup(void)943 static void __lockup_detector_cleanup(void)
944 {
945 lockdep_assert_held(&watchdog_mutex);
946 hardlockup_detector_perf_cleanup();
947 }
948
949 /**
950 * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
951 *
952 * Caller must not hold the cpu hotplug rwsem.
953 */
lockup_detector_cleanup(void)954 void lockup_detector_cleanup(void)
955 {
956 mutex_lock(&watchdog_mutex);
957 __lockup_detector_cleanup();
958 mutex_unlock(&watchdog_mutex);
959 }
960
961 /**
962 * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
963 *
964 * Special interface for parisc. It prevents lockup detector warnings from
965 * the default pm_poweroff() function which busy loops forever.
966 */
lockup_detector_soft_poweroff(void)967 void lockup_detector_soft_poweroff(void)
968 {
969 watchdog_enabled = 0;
970 }
971
972 #ifdef CONFIG_SYSCTL
973
974 /* Propagate any changes to the watchdog infrastructure */
proc_watchdog_update(void)975 static void proc_watchdog_update(void)
976 {
977 /* Remove impossible cpus to keep sysctl output clean. */
978 cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
979 __lockup_detector_reconfigure();
980 }
981
982 /*
983 * common function for watchdog, nmi_watchdog and soft_watchdog parameter
984 *
985 * caller | table->data points to | 'which'
986 * -------------------|----------------------------------|-------------------------------
987 * proc_watchdog | watchdog_user_enabled | WATCHDOG_HARDLOCKUP_ENABLED |
988 * | | WATCHDOG_SOFTOCKUP_ENABLED
989 * -------------------|----------------------------------|-------------------------------
990 * proc_nmi_watchdog | watchdog_hardlockup_user_enabled | WATCHDOG_HARDLOCKUP_ENABLED
991 * -------------------|----------------------------------|-------------------------------
992 * proc_soft_watchdog | watchdog_softlockup_user_enabled | WATCHDOG_SOFTOCKUP_ENABLED
993 */
proc_watchdog_common(int which,const struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)994 static int proc_watchdog_common(int which, const struct ctl_table *table, int write,
995 void *buffer, size_t *lenp, loff_t *ppos)
996 {
997 int err, old, *param = table->data;
998
999 mutex_lock(&watchdog_mutex);
1000
1001 old = *param;
1002 if (!write) {
1003 /*
1004 * On read synchronize the userspace interface. This is a
1005 * racy snapshot.
1006 */
1007 *param = (watchdog_enabled & which) != 0;
1008 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
1009 *param = old;
1010 } else {
1011 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
1012 if (!err && old != READ_ONCE(*param))
1013 proc_watchdog_update();
1014 }
1015 mutex_unlock(&watchdog_mutex);
1016 return err;
1017 }
1018
1019 /*
1020 * /proc/sys/kernel/watchdog
1021 */
proc_watchdog(const struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)1022 static int proc_watchdog(const struct ctl_table *table, int write,
1023 void *buffer, size_t *lenp, loff_t *ppos)
1024 {
1025 return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED |
1026 WATCHDOG_SOFTOCKUP_ENABLED,
1027 table, write, buffer, lenp, ppos);
1028 }
1029
1030 /*
1031 * /proc/sys/kernel/nmi_watchdog
1032 */
proc_nmi_watchdog(const struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)1033 static int proc_nmi_watchdog(const struct ctl_table *table, int write,
1034 void *buffer, size_t *lenp, loff_t *ppos)
1035 {
1036 if (!watchdog_hardlockup_available && write)
1037 return -ENOTSUPP;
1038 return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED,
1039 table, write, buffer, lenp, ppos);
1040 }
1041
1042 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
1043 /*
1044 * /proc/sys/kernel/soft_watchdog
1045 */
proc_soft_watchdog(const struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)1046 static int proc_soft_watchdog(const struct ctl_table *table, int write,
1047 void *buffer, size_t *lenp, loff_t *ppos)
1048 {
1049 return proc_watchdog_common(WATCHDOG_SOFTOCKUP_ENABLED,
1050 table, write, buffer, lenp, ppos);
1051 }
1052 #endif
1053
1054 /*
1055 * /proc/sys/kernel/watchdog_thresh
1056 */
proc_watchdog_thresh(const struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)1057 static int proc_watchdog_thresh(const struct ctl_table *table, int write,
1058 void *buffer, size_t *lenp, loff_t *ppos)
1059 {
1060 int err, old;
1061
1062 mutex_lock(&watchdog_mutex);
1063
1064 old = READ_ONCE(watchdog_thresh);
1065 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
1066
1067 if (!err && write && old != READ_ONCE(watchdog_thresh))
1068 proc_watchdog_update();
1069
1070 mutex_unlock(&watchdog_mutex);
1071 return err;
1072 }
1073
1074 /*
1075 * The cpumask is the mask of possible cpus that the watchdog can run
1076 * on, not the mask of cpus it is actually running on. This allows the
1077 * user to specify a mask that will include cpus that have not yet
1078 * been brought online, if desired.
1079 */
proc_watchdog_cpumask(const struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)1080 static int proc_watchdog_cpumask(const struct ctl_table *table, int write,
1081 void *buffer, size_t *lenp, loff_t *ppos)
1082 {
1083 int err;
1084
1085 mutex_lock(&watchdog_mutex);
1086
1087 err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
1088 if (!err && write)
1089 proc_watchdog_update();
1090
1091 mutex_unlock(&watchdog_mutex);
1092 return err;
1093 }
1094
1095 static const int sixty = 60;
1096
1097 static struct ctl_table watchdog_sysctls[] = {
1098 {
1099 .procname = "watchdog",
1100 .data = &watchdog_user_enabled,
1101 .maxlen = sizeof(int),
1102 .mode = 0644,
1103 .proc_handler = proc_watchdog,
1104 .extra1 = SYSCTL_ZERO,
1105 .extra2 = SYSCTL_ONE,
1106 },
1107 {
1108 .procname = "watchdog_thresh",
1109 .data = &watchdog_thresh,
1110 .maxlen = sizeof(int),
1111 .mode = 0644,
1112 .proc_handler = proc_watchdog_thresh,
1113 .extra1 = SYSCTL_ZERO,
1114 .extra2 = (void *)&sixty,
1115 },
1116 {
1117 .procname = "watchdog_cpumask",
1118 .data = &watchdog_cpumask_bits,
1119 .maxlen = NR_CPUS,
1120 .mode = 0644,
1121 .proc_handler = proc_watchdog_cpumask,
1122 },
1123 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
1124 {
1125 .procname = "soft_watchdog",
1126 .data = &watchdog_softlockup_user_enabled,
1127 .maxlen = sizeof(int),
1128 .mode = 0644,
1129 .proc_handler = proc_soft_watchdog,
1130 .extra1 = SYSCTL_ZERO,
1131 .extra2 = SYSCTL_ONE,
1132 },
1133 {
1134 .procname = "softlockup_panic",
1135 .data = &softlockup_panic,
1136 .maxlen = sizeof(int),
1137 .mode = 0644,
1138 .proc_handler = proc_dointvec_minmax,
1139 .extra1 = SYSCTL_ZERO,
1140 .extra2 = SYSCTL_ONE,
1141 },
1142 #ifdef CONFIG_SMP
1143 {
1144 .procname = "softlockup_all_cpu_backtrace",
1145 .data = &sysctl_softlockup_all_cpu_backtrace,
1146 .maxlen = sizeof(int),
1147 .mode = 0644,
1148 .proc_handler = proc_dointvec_minmax,
1149 .extra1 = SYSCTL_ZERO,
1150 .extra2 = SYSCTL_ONE,
1151 },
1152 #endif /* CONFIG_SMP */
1153 #endif
1154 #ifdef CONFIG_HARDLOCKUP_DETECTOR
1155 {
1156 .procname = "hardlockup_panic",
1157 .data = &hardlockup_panic,
1158 .maxlen = sizeof(int),
1159 .mode = 0644,
1160 .proc_handler = proc_dointvec_minmax,
1161 .extra1 = SYSCTL_ZERO,
1162 .extra2 = SYSCTL_ONE,
1163 },
1164 #ifdef CONFIG_SMP
1165 {
1166 .procname = "hardlockup_all_cpu_backtrace",
1167 .data = &sysctl_hardlockup_all_cpu_backtrace,
1168 .maxlen = sizeof(int),
1169 .mode = 0644,
1170 .proc_handler = proc_dointvec_minmax,
1171 .extra1 = SYSCTL_ZERO,
1172 .extra2 = SYSCTL_ONE,
1173 },
1174 #endif /* CONFIG_SMP */
1175 #endif
1176 };
1177
1178 static struct ctl_table watchdog_hardlockup_sysctl[] = {
1179 {
1180 .procname = "nmi_watchdog",
1181 .data = &watchdog_hardlockup_user_enabled,
1182 .maxlen = sizeof(int),
1183 .mode = 0444,
1184 .proc_handler = proc_nmi_watchdog,
1185 .extra1 = SYSCTL_ZERO,
1186 .extra2 = SYSCTL_ONE,
1187 },
1188 };
1189
watchdog_sysctl_init(void)1190 static void __init watchdog_sysctl_init(void)
1191 {
1192 register_sysctl_init("kernel", watchdog_sysctls);
1193
1194 if (watchdog_hardlockup_available)
1195 watchdog_hardlockup_sysctl[0].mode = 0644;
1196 register_sysctl_init("kernel", watchdog_hardlockup_sysctl);
1197 }
1198
1199 #else
1200 #define watchdog_sysctl_init() do { } while (0)
1201 #endif /* CONFIG_SYSCTL */
1202
1203 static void __init lockup_detector_delay_init(struct work_struct *work);
1204 static bool allow_lockup_detector_init_retry __initdata;
1205
1206 static struct work_struct detector_work __initdata =
1207 __WORK_INITIALIZER(detector_work, lockup_detector_delay_init);
1208
lockup_detector_delay_init(struct work_struct * work)1209 static void __init lockup_detector_delay_init(struct work_struct *work)
1210 {
1211 int ret;
1212
1213 ret = watchdog_hardlockup_probe();
1214 if (ret) {
1215 if (ret == -ENODEV)
1216 pr_info("NMI not fully supported\n");
1217 else
1218 pr_info("Delayed init of the lockup detector failed: %d\n", ret);
1219 pr_info("Hard watchdog permanently disabled\n");
1220 return;
1221 }
1222
1223 allow_lockup_detector_init_retry = false;
1224
1225 watchdog_hardlockup_available = true;
1226 lockup_detector_setup();
1227 }
1228
1229 /*
1230 * lockup_detector_retry_init - retry init lockup detector if possible.
1231 *
1232 * Retry hardlockup detector init. It is useful when it requires some
1233 * functionality that has to be initialized later on a particular
1234 * platform.
1235 */
lockup_detector_retry_init(void)1236 void __init lockup_detector_retry_init(void)
1237 {
1238 /* Must be called before late init calls */
1239 if (!allow_lockup_detector_init_retry)
1240 return;
1241
1242 schedule_work(&detector_work);
1243 }
1244
1245 /*
1246 * Ensure that optional delayed hardlockup init is proceed before
1247 * the init code and memory is freed.
1248 */
lockup_detector_check(void)1249 static int __init lockup_detector_check(void)
1250 {
1251 /* Prevent any later retry. */
1252 allow_lockup_detector_init_retry = false;
1253
1254 /* Make sure no work is pending. */
1255 flush_work(&detector_work);
1256
1257 watchdog_sysctl_init();
1258
1259 return 0;
1260
1261 }
1262 late_initcall_sync(lockup_detector_check);
1263
lockup_detector_init(void)1264 void __init lockup_detector_init(void)
1265 {
1266 if (tick_nohz_full_enabled())
1267 pr_info("Disabling watchdog on nohz_full cores by default\n");
1268
1269 cpumask_copy(&watchdog_cpumask,
1270 housekeeping_cpumask(HK_TYPE_TIMER));
1271
1272 if (!watchdog_hardlockup_probe())
1273 watchdog_hardlockup_available = true;
1274 else
1275 allow_lockup_detector_init_retry = true;
1276
1277 lockup_detector_setup();
1278 }
1279