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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Detect hard and soft lockups on a system
4 *
5 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
6 *
7 * Note: Most of this code is borrowed heavily from the original softlockup
8 * detector, so thanks to Ingo for the initial implementation.
9 * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
10 * to those contributors as well.
11 */
12
13#define pr_fmt(fmt) "watchdog: " fmt
14
15#include <linux/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
35static 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
45unsigned long __read_mostly watchdog_enabled;
46int __read_mostly watchdog_user_enabled = 1;
47static int __read_mostly watchdog_hardlockup_user_enabled = WATCHDOG_HARDLOCKUP_DEFAULT;
48static int __read_mostly watchdog_softlockup_user_enabled = 1;
49int __read_mostly watchdog_thresh = 10;
50static int __read_mostly watchdog_hardlockup_available;
51
52struct cpumask watchdog_cpumask __read_mostly;
53unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
54
55#ifdef CONFIG_HARDLOCKUP_DETECTOR
56
57# ifdef CONFIG_SMP
58int __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 */
64unsigned 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 */
74void __init hardlockup_detector_disable(void)
75{
76 watchdog_hardlockup_user_enabled = 0;
77}
78
79static int __init hardlockup_panic_setup(char *str)
80{
81next:
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
106static DEFINE_PER_CPU(atomic_t, hrtimer_interrupts);
107static DEFINE_PER_CPU(int, hrtimer_interrupts_saved);
108static DEFINE_PER_CPU(bool, watchdog_hardlockup_warned);
109static DEFINE_PER_CPU(bool, watchdog_hardlockup_touched);
110static unsigned long hard_lockup_nmi_warn;
111
112notrace 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}
123EXPORT_SYMBOL(arch_touch_nmi_watchdog);
124
125void watchdog_hardlockup_touch_cpu(unsigned int cpu)
126{
127 per_cpu(watchdog_hardlockup_touched, cpu) = true;
128}
129
130static 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
147static 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
155void 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
226static 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 */
237void __weak watchdog_hardlockup_enable(unsigned int cpu) { }
238
239void __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 */
248int __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 */
261void __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 */
274void __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 */
282static 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
302int __read_mostly sysctl_softlockup_all_cpu_backtrace;
303#endif
304
305static struct cpumask watchdog_allowed_mask __read_mostly;
306
307/* Global variables, exported for sysctl */
308unsigned int __read_mostly softlockup_panic =
309 IS_ENABLED(CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC);
310
311static bool softlockup_initialized __read_mostly;
312static u64 __read_mostly sample_period;
313
314/* Timestamp taken after the last successful reschedule. */
315static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
316/* Timestamp of the last softlockup report. */
317static DEFINE_PER_CPU(unsigned long, watchdog_report_ts);
318static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
319static DEFINE_PER_CPU(bool, softlockup_touch_sync);
320static unsigned long soft_lockup_nmi_warn;
321
322static 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
329static int __init nowatchdog_setup(char *str)
330{
331 watchdog_user_enabled = 0;
332 return 1;
333}
334__setup("nowatchdog", nowatchdog_setup);
335
336static int __init nosoftlockup_setup(char *str)
337{
338 watchdog_softlockup_user_enabled = 0;
339 return 1;
340}
341__setup("nosoftlockup", nosoftlockup_setup);
342
343static 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
350static void __lockup_detector_cleanup(void);
351
352#ifdef CONFIG_SOFTLOCKUP_DETECTOR_INTR_STORM
353enum stats_per_group {
354 STATS_SYSTEM,
355 STATS_SOFTIRQ,
356 STATS_HARDIRQ,
357 STATS_IDLE,
358 NUM_STATS_PER_GROUP,
359};
360
361static 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
368static DEFINE_PER_CPU(u16, cpustat_old[NUM_STATS_PER_GROUP]);
369static DEFINE_PER_CPU(u8, cpustat_util[NUM_SAMPLE_PERIODS][NUM_STATS_PER_GROUP]);
370static 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 */
378static u16 get_16bit_precision(u64 data_ns)
379{
380 return data_ns >> 24LL; /* 2^24ns ~= 16.8ms */
381}
382
383static 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
406static 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
435struct irq_counts {
436 int irq;
437 u32 counts;
438};
439
440static DEFINE_PER_CPU(bool, snapshot_taken);
441
442/* Tabulate the most frequent interrupts. */
443static 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 */
459static 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
469static 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
477static void stop_counting_irqs(void)
478{
479 __this_cpu_write(snapshot_taken, false);
480}
481
482static 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
521static void report_cpu_status(void)
522{
523 print_cpustat();
524 print_irq_counts();
525}
526#else
527static inline void update_cpustat(void) { }
528static inline void report_cpu_status(void) { }
529static inline bool need_counting_irqs(void) { return false; }
530static inline void start_counting_irqs(void) { }
531static 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 */
541static 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 */
551static unsigned long get_timestamp(void)
552{
553 return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
554}
555
556static 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
569static void update_report_ts(void)
570{
571 __this_cpu_write(watchdog_report_ts, get_timestamp());
572}
573
574/* Commands for resetting the watchdog */
575static 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 */
589notrace 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
598notrace void touch_softlockup_watchdog(void)
599{
600 touch_softlockup_watchdog_sched();
601 wq_watchdog_touch(raw_smp_processor_id());
602}
603EXPORT_SYMBOL(touch_softlockup_watchdog);
604
605void 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
624void 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
630static 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 */
663static DEFINE_PER_CPU(struct completion, softlockup_completion);
664static 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 */
674static 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 */
684static 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
786static 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
812static 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
828static int softlockup_stop_fn(void *data)
829{
830 watchdog_disable(smp_processor_id());
831 return 0;
832}
833
834static 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
847static int softlockup_start_fn(void *data)
848{
849 watchdog_enable(smp_processor_id());
850 return 0;
851}
852
853static 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
862int 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
869int 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
876static 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
896void 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 */
906static __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 */
925static 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}
933void lockup_detector_reconfigure(void)
934{
935 __lockup_detector_reconfigure();
936}
937static inline void lockup_detector_setup(void)
938{
939 __lockup_detector_reconfigure();
940}
941#endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
942
943static 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 */
954void 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 */
967void 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 */
975static 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 */
994static 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 */
1022static 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 */
1033static 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 */
1046static 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 */
1057static 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 */
1080static 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
1095static const int sixty = 60;
1096
1097static 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
1178static 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
1190static 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
1203static void __init lockup_detector_delay_init(struct work_struct *work);
1204static bool allow_lockup_detector_init_retry __initdata;
1205
1206static struct work_struct detector_work __initdata =
1207 __WORK_INITIALIZER(detector_work, lockup_detector_delay_init);
1208
1209static 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 */
1236void __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 */
1249static 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}
1262late_initcall_sync(lockup_detector_check);
1263
1264void __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}
1/*
2 * Detect hard and soft lockups on a system
3 *
4 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
5 *
6 * Note: Most of this code is borrowed heavily from the original softlockup
7 * detector, so thanks to Ingo for the initial implementation.
8 * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
9 * to those contributors as well.
10 */
11
12#define pr_fmt(fmt) "NMI watchdog: " fmt
13
14#include <linux/mm.h>
15#include <linux/cpu.h>
16#include <linux/nmi.h>
17#include <linux/init.h>
18#include <linux/module.h>
19#include <linux/sysctl.h>
20#include <linux/smpboot.h>
21#include <linux/sched/rt.h>
22#include <linux/tick.h>
23#include <linux/workqueue.h>
24
25#include <asm/irq_regs.h>
26#include <linux/kvm_para.h>
27#include <linux/perf_event.h>
28#include <linux/kthread.h>
29
30/*
31 * The run state of the lockup detectors is controlled by the content of the
32 * 'watchdog_enabled' variable. Each lockup detector has its dedicated bit -
33 * bit 0 for the hard lockup detector and bit 1 for the soft lockup detector.
34 *
35 * 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled'
36 * are variables that are only used as an 'interface' between the parameters
37 * in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The
38 * 'watchdog_thresh' variable is handled differently because its value is not
39 * boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh'
40 * is equal zero.
41 */
42#define NMI_WATCHDOG_ENABLED_BIT 0
43#define SOFT_WATCHDOG_ENABLED_BIT 1
44#define NMI_WATCHDOG_ENABLED (1 << NMI_WATCHDOG_ENABLED_BIT)
45#define SOFT_WATCHDOG_ENABLED (1 << SOFT_WATCHDOG_ENABLED_BIT)
46
47static DEFINE_MUTEX(watchdog_proc_mutex);
48
49#ifdef CONFIG_HARDLOCKUP_DETECTOR
50static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
51#else
52static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
53#endif
54int __read_mostly nmi_watchdog_enabled;
55int __read_mostly soft_watchdog_enabled;
56int __read_mostly watchdog_user_enabled;
57int __read_mostly watchdog_thresh = 10;
58
59#ifdef CONFIG_SMP
60int __read_mostly sysctl_softlockup_all_cpu_backtrace;
61int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
62#else
63#define sysctl_softlockup_all_cpu_backtrace 0
64#define sysctl_hardlockup_all_cpu_backtrace 0
65#endif
66static struct cpumask watchdog_cpumask __read_mostly;
67unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
68
69/* Helper for online, unparked cpus. */
70#define for_each_watchdog_cpu(cpu) \
71 for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
72
73/*
74 * The 'watchdog_running' variable is set to 1 when the watchdog threads
75 * are registered/started and is set to 0 when the watchdog threads are
76 * unregistered/stopped, so it is an indicator whether the threads exist.
77 */
78static int __read_mostly watchdog_running;
79/*
80 * If a subsystem has a need to deactivate the watchdog temporarily, it
81 * can use the suspend/resume interface to achieve this. The content of
82 * the 'watchdog_suspended' variable reflects this state. Existing threads
83 * are parked/unparked by the lockup_detector_{suspend|resume} functions
84 * (see comment blocks pertaining to those functions for further details).
85 *
86 * 'watchdog_suspended' also prevents threads from being registered/started
87 * or unregistered/stopped via parameters in /proc/sys/kernel, so the state
88 * of 'watchdog_running' cannot change while the watchdog is deactivated
89 * temporarily (see related code in 'proc' handlers).
90 */
91static int __read_mostly watchdog_suspended;
92
93static u64 __read_mostly sample_period;
94
95static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
96static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
97static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
98static DEFINE_PER_CPU(bool, softlockup_touch_sync);
99static DEFINE_PER_CPU(bool, soft_watchdog_warn);
100static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
101static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
102static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
103#ifdef CONFIG_HARDLOCKUP_DETECTOR
104static DEFINE_PER_CPU(bool, hard_watchdog_warn);
105static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
106static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
107static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
108#endif
109static unsigned long soft_lockup_nmi_warn;
110
111/* boot commands */
112/*
113 * Should we panic when a soft-lockup or hard-lockup occurs:
114 */
115#ifdef CONFIG_HARDLOCKUP_DETECTOR
116unsigned int __read_mostly hardlockup_panic =
117 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
118static unsigned long hardlockup_allcpu_dumped;
119/*
120 * We may not want to enable hard lockup detection by default in all cases,
121 * for example when running the kernel as a guest on a hypervisor. In these
122 * cases this function can be called to disable hard lockup detection. This
123 * function should only be executed once by the boot processor before the
124 * kernel command line parameters are parsed, because otherwise it is not
125 * possible to override this in hardlockup_panic_setup().
126 */
127void hardlockup_detector_disable(void)
128{
129 watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
130}
131
132static int __init hardlockup_panic_setup(char *str)
133{
134 if (!strncmp(str, "panic", 5))
135 hardlockup_panic = 1;
136 else if (!strncmp(str, "nopanic", 7))
137 hardlockup_panic = 0;
138 else if (!strncmp(str, "0", 1))
139 watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
140 else if (!strncmp(str, "1", 1))
141 watchdog_enabled |= NMI_WATCHDOG_ENABLED;
142 return 1;
143}
144__setup("nmi_watchdog=", hardlockup_panic_setup);
145#endif
146
147unsigned int __read_mostly softlockup_panic =
148 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
149
150static int __init softlockup_panic_setup(char *str)
151{
152 softlockup_panic = simple_strtoul(str, NULL, 0);
153
154 return 1;
155}
156__setup("softlockup_panic=", softlockup_panic_setup);
157
158static int __init nowatchdog_setup(char *str)
159{
160 watchdog_enabled = 0;
161 return 1;
162}
163__setup("nowatchdog", nowatchdog_setup);
164
165static int __init nosoftlockup_setup(char *str)
166{
167 watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED;
168 return 1;
169}
170__setup("nosoftlockup", nosoftlockup_setup);
171
172#ifdef CONFIG_SMP
173static int __init softlockup_all_cpu_backtrace_setup(char *str)
174{
175 sysctl_softlockup_all_cpu_backtrace =
176 !!simple_strtol(str, NULL, 0);
177 return 1;
178}
179__setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
180static int __init hardlockup_all_cpu_backtrace_setup(char *str)
181{
182 sysctl_hardlockup_all_cpu_backtrace =
183 !!simple_strtol(str, NULL, 0);
184 return 1;
185}
186__setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
187#endif
188
189/*
190 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
191 * lockups can have false positives under extreme conditions. So we generally
192 * want a higher threshold for soft lockups than for hard lockups. So we couple
193 * the thresholds with a factor: we make the soft threshold twice the amount of
194 * time the hard threshold is.
195 */
196static int get_softlockup_thresh(void)
197{
198 return watchdog_thresh * 2;
199}
200
201/*
202 * Returns seconds, approximately. We don't need nanosecond
203 * resolution, and we don't need to waste time with a big divide when
204 * 2^30ns == 1.074s.
205 */
206static unsigned long get_timestamp(void)
207{
208 return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
209}
210
211static void set_sample_period(void)
212{
213 /*
214 * convert watchdog_thresh from seconds to ns
215 * the divide by 5 is to give hrtimer several chances (two
216 * or three with the current relation between the soft
217 * and hard thresholds) to increment before the
218 * hardlockup detector generates a warning
219 */
220 sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
221}
222
223/* Commands for resetting the watchdog */
224static void __touch_watchdog(void)
225{
226 __this_cpu_write(watchdog_touch_ts, get_timestamp());
227}
228
229/**
230 * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
231 *
232 * Call when the scheduler may have stalled for legitimate reasons
233 * preventing the watchdog task from executing - e.g. the scheduler
234 * entering idle state. This should only be used for scheduler events.
235 * Use touch_softlockup_watchdog() for everything else.
236 */
237void touch_softlockup_watchdog_sched(void)
238{
239 /*
240 * Preemption can be enabled. It doesn't matter which CPU's timestamp
241 * gets zeroed here, so use the raw_ operation.
242 */
243 raw_cpu_write(watchdog_touch_ts, 0);
244}
245
246void touch_softlockup_watchdog(void)
247{
248 touch_softlockup_watchdog_sched();
249 wq_watchdog_touch(raw_smp_processor_id());
250}
251EXPORT_SYMBOL(touch_softlockup_watchdog);
252
253void touch_all_softlockup_watchdogs(void)
254{
255 int cpu;
256
257 /*
258 * this is done lockless
259 * do we care if a 0 races with a timestamp?
260 * all it means is the softlock check starts one cycle later
261 */
262 for_each_watchdog_cpu(cpu)
263 per_cpu(watchdog_touch_ts, cpu) = 0;
264 wq_watchdog_touch(-1);
265}
266
267#ifdef CONFIG_HARDLOCKUP_DETECTOR
268void touch_nmi_watchdog(void)
269{
270 /*
271 * Using __raw here because some code paths have
272 * preemption enabled. If preemption is enabled
273 * then interrupts should be enabled too, in which
274 * case we shouldn't have to worry about the watchdog
275 * going off.
276 */
277 raw_cpu_write(watchdog_nmi_touch, true);
278 touch_softlockup_watchdog();
279}
280EXPORT_SYMBOL(touch_nmi_watchdog);
281
282#endif
283
284void touch_softlockup_watchdog_sync(void)
285{
286 __this_cpu_write(softlockup_touch_sync, true);
287 __this_cpu_write(watchdog_touch_ts, 0);
288}
289
290#ifdef CONFIG_HARDLOCKUP_DETECTOR
291/* watchdog detector functions */
292static bool is_hardlockup(void)
293{
294 unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
295
296 if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
297 return true;
298
299 __this_cpu_write(hrtimer_interrupts_saved, hrint);
300 return false;
301}
302#endif
303
304static int is_softlockup(unsigned long touch_ts)
305{
306 unsigned long now = get_timestamp();
307
308 if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
309 /* Warn about unreasonable delays. */
310 if (time_after(now, touch_ts + get_softlockup_thresh()))
311 return now - touch_ts;
312 }
313 return 0;
314}
315
316#ifdef CONFIG_HARDLOCKUP_DETECTOR
317
318static struct perf_event_attr wd_hw_attr = {
319 .type = PERF_TYPE_HARDWARE,
320 .config = PERF_COUNT_HW_CPU_CYCLES,
321 .size = sizeof(struct perf_event_attr),
322 .pinned = 1,
323 .disabled = 1,
324};
325
326/* Callback function for perf event subsystem */
327static void watchdog_overflow_callback(struct perf_event *event,
328 struct perf_sample_data *data,
329 struct pt_regs *regs)
330{
331 /* Ensure the watchdog never gets throttled */
332 event->hw.interrupts = 0;
333
334 if (__this_cpu_read(watchdog_nmi_touch) == true) {
335 __this_cpu_write(watchdog_nmi_touch, false);
336 return;
337 }
338
339 /* check for a hardlockup
340 * This is done by making sure our timer interrupt
341 * is incrementing. The timer interrupt should have
342 * fired multiple times before we overflow'd. If it hasn't
343 * then this is a good indication the cpu is stuck
344 */
345 if (is_hardlockup()) {
346 int this_cpu = smp_processor_id();
347 struct pt_regs *regs = get_irq_regs();
348
349 /* only print hardlockups once */
350 if (__this_cpu_read(hard_watchdog_warn) == true)
351 return;
352
353 pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
354 print_modules();
355 print_irqtrace_events(current);
356 if (regs)
357 show_regs(regs);
358 else
359 dump_stack();
360
361 /*
362 * Perform all-CPU dump only once to avoid multiple hardlockups
363 * generating interleaving traces
364 */
365 if (sysctl_hardlockup_all_cpu_backtrace &&
366 !test_and_set_bit(0, &hardlockup_allcpu_dumped))
367 trigger_allbutself_cpu_backtrace();
368
369 if (hardlockup_panic)
370 nmi_panic(regs, "Hard LOCKUP");
371
372 __this_cpu_write(hard_watchdog_warn, true);
373 return;
374 }
375
376 __this_cpu_write(hard_watchdog_warn, false);
377 return;
378}
379#endif /* CONFIG_HARDLOCKUP_DETECTOR */
380
381static void watchdog_interrupt_count(void)
382{
383 __this_cpu_inc(hrtimer_interrupts);
384}
385
386static int watchdog_nmi_enable(unsigned int cpu);
387static void watchdog_nmi_disable(unsigned int cpu);
388
389static int watchdog_enable_all_cpus(void);
390static void watchdog_disable_all_cpus(void);
391
392/* watchdog kicker functions */
393static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
394{
395 unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
396 struct pt_regs *regs = get_irq_regs();
397 int duration;
398 int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
399
400 /* kick the hardlockup detector */
401 watchdog_interrupt_count();
402
403 /* kick the softlockup detector */
404 wake_up_process(__this_cpu_read(softlockup_watchdog));
405
406 /* .. and repeat */
407 hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
408
409 if (touch_ts == 0) {
410 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
411 /*
412 * If the time stamp was touched atomically
413 * make sure the scheduler tick is up to date.
414 */
415 __this_cpu_write(softlockup_touch_sync, false);
416 sched_clock_tick();
417 }
418
419 /* Clear the guest paused flag on watchdog reset */
420 kvm_check_and_clear_guest_paused();
421 __touch_watchdog();
422 return HRTIMER_RESTART;
423 }
424
425 /* check for a softlockup
426 * This is done by making sure a high priority task is
427 * being scheduled. The task touches the watchdog to
428 * indicate it is getting cpu time. If it hasn't then
429 * this is a good indication some task is hogging the cpu
430 */
431 duration = is_softlockup(touch_ts);
432 if (unlikely(duration)) {
433 /*
434 * If a virtual machine is stopped by the host it can look to
435 * the watchdog like a soft lockup, check to see if the host
436 * stopped the vm before we issue the warning
437 */
438 if (kvm_check_and_clear_guest_paused())
439 return HRTIMER_RESTART;
440
441 /* only warn once */
442 if (__this_cpu_read(soft_watchdog_warn) == true) {
443 /*
444 * When multiple processes are causing softlockups the
445 * softlockup detector only warns on the first one
446 * because the code relies on a full quiet cycle to
447 * re-arm. The second process prevents the quiet cycle
448 * and never gets reported. Use task pointers to detect
449 * this.
450 */
451 if (__this_cpu_read(softlockup_task_ptr_saved) !=
452 current) {
453 __this_cpu_write(soft_watchdog_warn, false);
454 __touch_watchdog();
455 }
456 return HRTIMER_RESTART;
457 }
458
459 if (softlockup_all_cpu_backtrace) {
460 /* Prevent multiple soft-lockup reports if one cpu is already
461 * engaged in dumping cpu back traces
462 */
463 if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
464 /* Someone else will report us. Let's give up */
465 __this_cpu_write(soft_watchdog_warn, true);
466 return HRTIMER_RESTART;
467 }
468 }
469
470 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
471 smp_processor_id(), duration,
472 current->comm, task_pid_nr(current));
473 __this_cpu_write(softlockup_task_ptr_saved, current);
474 print_modules();
475 print_irqtrace_events(current);
476 if (regs)
477 show_regs(regs);
478 else
479 dump_stack();
480
481 if (softlockup_all_cpu_backtrace) {
482 /* Avoid generating two back traces for current
483 * given that one is already made above
484 */
485 trigger_allbutself_cpu_backtrace();
486
487 clear_bit(0, &soft_lockup_nmi_warn);
488 /* Barrier to sync with other cpus */
489 smp_mb__after_atomic();
490 }
491
492 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
493 if (softlockup_panic)
494 panic("softlockup: hung tasks");
495 __this_cpu_write(soft_watchdog_warn, true);
496 } else
497 __this_cpu_write(soft_watchdog_warn, false);
498
499 return HRTIMER_RESTART;
500}
501
502static void watchdog_set_prio(unsigned int policy, unsigned int prio)
503{
504 struct sched_param param = { .sched_priority = prio };
505
506 sched_setscheduler(current, policy, ¶m);
507}
508
509static void watchdog_enable(unsigned int cpu)
510{
511 struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
512
513 /* kick off the timer for the hardlockup detector */
514 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
515 hrtimer->function = watchdog_timer_fn;
516
517 /* Enable the perf event */
518 watchdog_nmi_enable(cpu);
519
520 /* done here because hrtimer_start can only pin to smp_processor_id() */
521 hrtimer_start(hrtimer, ns_to_ktime(sample_period),
522 HRTIMER_MODE_REL_PINNED);
523
524 /* initialize timestamp */
525 watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
526 __touch_watchdog();
527}
528
529static void watchdog_disable(unsigned int cpu)
530{
531 struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
532
533 watchdog_set_prio(SCHED_NORMAL, 0);
534 hrtimer_cancel(hrtimer);
535 /* disable the perf event */
536 watchdog_nmi_disable(cpu);
537}
538
539static void watchdog_cleanup(unsigned int cpu, bool online)
540{
541 watchdog_disable(cpu);
542}
543
544static int watchdog_should_run(unsigned int cpu)
545{
546 return __this_cpu_read(hrtimer_interrupts) !=
547 __this_cpu_read(soft_lockup_hrtimer_cnt);
548}
549
550/*
551 * The watchdog thread function - touches the timestamp.
552 *
553 * It only runs once every sample_period seconds (4 seconds by
554 * default) to reset the softlockup timestamp. If this gets delayed
555 * for more than 2*watchdog_thresh seconds then the debug-printout
556 * triggers in watchdog_timer_fn().
557 */
558static void watchdog(unsigned int cpu)
559{
560 __this_cpu_write(soft_lockup_hrtimer_cnt,
561 __this_cpu_read(hrtimer_interrupts));
562 __touch_watchdog();
563
564 /*
565 * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
566 * failure path. Check for failures that can occur asynchronously -
567 * for example, when CPUs are on-lined - and shut down the hardware
568 * perf event on each CPU accordingly.
569 *
570 * The only non-obvious place this bit can be cleared is through
571 * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a
572 * pr_info here would be too noisy as it would result in a message
573 * every few seconds if the hardlockup was disabled but the softlockup
574 * enabled.
575 */
576 if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
577 watchdog_nmi_disable(cpu);
578}
579
580#ifdef CONFIG_HARDLOCKUP_DETECTOR
581/*
582 * People like the simple clean cpu node info on boot.
583 * Reduce the watchdog noise by only printing messages
584 * that are different from what cpu0 displayed.
585 */
586static unsigned long cpu0_err;
587
588static int watchdog_nmi_enable(unsigned int cpu)
589{
590 struct perf_event_attr *wd_attr;
591 struct perf_event *event = per_cpu(watchdog_ev, cpu);
592
593 /* nothing to do if the hard lockup detector is disabled */
594 if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
595 goto out;
596
597 /* is it already setup and enabled? */
598 if (event && event->state > PERF_EVENT_STATE_OFF)
599 goto out;
600
601 /* it is setup but not enabled */
602 if (event != NULL)
603 goto out_enable;
604
605 wd_attr = &wd_hw_attr;
606 wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
607
608 /* Try to register using hardware perf events */
609 event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
610
611 /* save cpu0 error for future comparision */
612 if (cpu == 0 && IS_ERR(event))
613 cpu0_err = PTR_ERR(event);
614
615 if (!IS_ERR(event)) {
616 /* only print for cpu0 or different than cpu0 */
617 if (cpu == 0 || cpu0_err)
618 pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
619 goto out_save;
620 }
621
622 /*
623 * Disable the hard lockup detector if _any_ CPU fails to set up
624 * set up the hardware perf event. The watchdog() function checks
625 * the NMI_WATCHDOG_ENABLED bit periodically.
626 *
627 * The barriers are for syncing up watchdog_enabled across all the
628 * cpus, as clear_bit() does not use barriers.
629 */
630 smp_mb__before_atomic();
631 clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled);
632 smp_mb__after_atomic();
633
634 /* skip displaying the same error again */
635 if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
636 return PTR_ERR(event);
637
638 /* vary the KERN level based on the returned errno */
639 if (PTR_ERR(event) == -EOPNOTSUPP)
640 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
641 else if (PTR_ERR(event) == -ENOENT)
642 pr_warn("disabled (cpu%i): hardware events not enabled\n",
643 cpu);
644 else
645 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
646 cpu, PTR_ERR(event));
647
648 pr_info("Shutting down hard lockup detector on all cpus\n");
649
650 return PTR_ERR(event);
651
652 /* success path */
653out_save:
654 per_cpu(watchdog_ev, cpu) = event;
655out_enable:
656 perf_event_enable(per_cpu(watchdog_ev, cpu));
657out:
658 return 0;
659}
660
661static void watchdog_nmi_disable(unsigned int cpu)
662{
663 struct perf_event *event = per_cpu(watchdog_ev, cpu);
664
665 if (event) {
666 perf_event_disable(event);
667 per_cpu(watchdog_ev, cpu) = NULL;
668
669 /* should be in cleanup, but blocks oprofile */
670 perf_event_release_kernel(event);
671 }
672 if (cpu == 0) {
673 /* watchdog_nmi_enable() expects this to be zero initially. */
674 cpu0_err = 0;
675 }
676}
677
678#else
679static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
680static void watchdog_nmi_disable(unsigned int cpu) { return; }
681#endif /* CONFIG_HARDLOCKUP_DETECTOR */
682
683static struct smp_hotplug_thread watchdog_threads = {
684 .store = &softlockup_watchdog,
685 .thread_should_run = watchdog_should_run,
686 .thread_fn = watchdog,
687 .thread_comm = "watchdog/%u",
688 .setup = watchdog_enable,
689 .cleanup = watchdog_cleanup,
690 .park = watchdog_disable,
691 .unpark = watchdog_enable,
692};
693
694/*
695 * park all watchdog threads that are specified in 'watchdog_cpumask'
696 *
697 * This function returns an error if kthread_park() of a watchdog thread
698 * fails. In this situation, the watchdog threads of some CPUs can already
699 * be parked and the watchdog threads of other CPUs can still be runnable.
700 * Callers are expected to handle this special condition as appropriate in
701 * their context.
702 *
703 * This function may only be called in a context that is protected against
704 * races with CPU hotplug - for example, via get_online_cpus().
705 */
706static int watchdog_park_threads(void)
707{
708 int cpu, ret = 0;
709
710 for_each_watchdog_cpu(cpu) {
711 ret = kthread_park(per_cpu(softlockup_watchdog, cpu));
712 if (ret)
713 break;
714 }
715
716 return ret;
717}
718
719/*
720 * unpark all watchdog threads that are specified in 'watchdog_cpumask'
721 *
722 * This function may only be called in a context that is protected against
723 * races with CPU hotplug - for example, via get_online_cpus().
724 */
725static void watchdog_unpark_threads(void)
726{
727 int cpu;
728
729 for_each_watchdog_cpu(cpu)
730 kthread_unpark(per_cpu(softlockup_watchdog, cpu));
731}
732
733/*
734 * Suspend the hard and soft lockup detector by parking the watchdog threads.
735 */
736int lockup_detector_suspend(void)
737{
738 int ret = 0;
739
740 get_online_cpus();
741 mutex_lock(&watchdog_proc_mutex);
742 /*
743 * Multiple suspend requests can be active in parallel (counted by
744 * the 'watchdog_suspended' variable). If the watchdog threads are
745 * running, the first caller takes care that they will be parked.
746 * The state of 'watchdog_running' cannot change while a suspend
747 * request is active (see related code in 'proc' handlers).
748 */
749 if (watchdog_running && !watchdog_suspended)
750 ret = watchdog_park_threads();
751
752 if (ret == 0)
753 watchdog_suspended++;
754 else {
755 watchdog_disable_all_cpus();
756 pr_err("Failed to suspend lockup detectors, disabled\n");
757 watchdog_enabled = 0;
758 }
759
760 mutex_unlock(&watchdog_proc_mutex);
761
762 return ret;
763}
764
765/*
766 * Resume the hard and soft lockup detector by unparking the watchdog threads.
767 */
768void lockup_detector_resume(void)
769{
770 mutex_lock(&watchdog_proc_mutex);
771
772 watchdog_suspended--;
773 /*
774 * The watchdog threads are unparked if they were previously running
775 * and if there is no more active suspend request.
776 */
777 if (watchdog_running && !watchdog_suspended)
778 watchdog_unpark_threads();
779
780 mutex_unlock(&watchdog_proc_mutex);
781 put_online_cpus();
782}
783
784static int update_watchdog_all_cpus(void)
785{
786 int ret;
787
788 ret = watchdog_park_threads();
789 if (ret)
790 return ret;
791
792 watchdog_unpark_threads();
793
794 return 0;
795}
796
797static int watchdog_enable_all_cpus(void)
798{
799 int err = 0;
800
801 if (!watchdog_running) {
802 err = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
803 &watchdog_cpumask);
804 if (err)
805 pr_err("Failed to create watchdog threads, disabled\n");
806 else
807 watchdog_running = 1;
808 } else {
809 /*
810 * Enable/disable the lockup detectors or
811 * change the sample period 'on the fly'.
812 */
813 err = update_watchdog_all_cpus();
814
815 if (err) {
816 watchdog_disable_all_cpus();
817 pr_err("Failed to update lockup detectors, disabled\n");
818 }
819 }
820
821 if (err)
822 watchdog_enabled = 0;
823
824 return err;
825}
826
827static void watchdog_disable_all_cpus(void)
828{
829 if (watchdog_running) {
830 watchdog_running = 0;
831 smpboot_unregister_percpu_thread(&watchdog_threads);
832 }
833}
834
835#ifdef CONFIG_SYSCTL
836
837/*
838 * Update the run state of the lockup detectors.
839 */
840static int proc_watchdog_update(void)
841{
842 int err = 0;
843
844 /*
845 * Watchdog threads won't be started if they are already active.
846 * The 'watchdog_running' variable in watchdog_*_all_cpus() takes
847 * care of this. If those threads are already active, the sample
848 * period will be updated and the lockup detectors will be enabled
849 * or disabled 'on the fly'.
850 */
851 if (watchdog_enabled && watchdog_thresh)
852 err = watchdog_enable_all_cpus();
853 else
854 watchdog_disable_all_cpus();
855
856 return err;
857
858}
859
860/*
861 * common function for watchdog, nmi_watchdog and soft_watchdog parameter
862 *
863 * caller | table->data points to | 'which' contains the flag(s)
864 * -------------------|-----------------------|-----------------------------
865 * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
866 * | | with SOFT_WATCHDOG_ENABLED
867 * -------------------|-----------------------|-----------------------------
868 * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED
869 * -------------------|-----------------------|-----------------------------
870 * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
871 */
872static int proc_watchdog_common(int which, struct ctl_table *table, int write,
873 void __user *buffer, size_t *lenp, loff_t *ppos)
874{
875 int err, old, new;
876 int *watchdog_param = (int *)table->data;
877
878 get_online_cpus();
879 mutex_lock(&watchdog_proc_mutex);
880
881 if (watchdog_suspended) {
882 /* no parameter changes allowed while watchdog is suspended */
883 err = -EAGAIN;
884 goto out;
885 }
886
887 /*
888 * If the parameter is being read return the state of the corresponding
889 * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
890 * run state of the lockup detectors.
891 */
892 if (!write) {
893 *watchdog_param = (watchdog_enabled & which) != 0;
894 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
895 } else {
896 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
897 if (err)
898 goto out;
899
900 /*
901 * There is a race window between fetching the current value
902 * from 'watchdog_enabled' and storing the new value. During
903 * this race window, watchdog_nmi_enable() can sneak in and
904 * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
905 * The 'cmpxchg' detects this race and the loop retries.
906 */
907 do {
908 old = watchdog_enabled;
909 /*
910 * If the parameter value is not zero set the
911 * corresponding bit(s), else clear it(them).
912 */
913 if (*watchdog_param)
914 new = old | which;
915 else
916 new = old & ~which;
917 } while (cmpxchg(&watchdog_enabled, old, new) != old);
918
919 /*
920 * Update the run state of the lockup detectors. There is _no_
921 * need to check the value returned by proc_watchdog_update()
922 * and to restore the previous value of 'watchdog_enabled' as
923 * both lockup detectors are disabled if proc_watchdog_update()
924 * returns an error.
925 */
926 if (old == new)
927 goto out;
928
929 err = proc_watchdog_update();
930 }
931out:
932 mutex_unlock(&watchdog_proc_mutex);
933 put_online_cpus();
934 return err;
935}
936
937/*
938 * /proc/sys/kernel/watchdog
939 */
940int proc_watchdog(struct ctl_table *table, int write,
941 void __user *buffer, size_t *lenp, loff_t *ppos)
942{
943 return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
944 table, write, buffer, lenp, ppos);
945}
946
947/*
948 * /proc/sys/kernel/nmi_watchdog
949 */
950int proc_nmi_watchdog(struct ctl_table *table, int write,
951 void __user *buffer, size_t *lenp, loff_t *ppos)
952{
953 return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
954 table, write, buffer, lenp, ppos);
955}
956
957/*
958 * /proc/sys/kernel/soft_watchdog
959 */
960int proc_soft_watchdog(struct ctl_table *table, int write,
961 void __user *buffer, size_t *lenp, loff_t *ppos)
962{
963 return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
964 table, write, buffer, lenp, ppos);
965}
966
967/*
968 * /proc/sys/kernel/watchdog_thresh
969 */
970int proc_watchdog_thresh(struct ctl_table *table, int write,
971 void __user *buffer, size_t *lenp, loff_t *ppos)
972{
973 int err, old, new;
974
975 get_online_cpus();
976 mutex_lock(&watchdog_proc_mutex);
977
978 if (watchdog_suspended) {
979 /* no parameter changes allowed while watchdog is suspended */
980 err = -EAGAIN;
981 goto out;
982 }
983
984 old = ACCESS_ONCE(watchdog_thresh);
985 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
986
987 if (err || !write)
988 goto out;
989
990 /*
991 * Update the sample period. Restore on failure.
992 */
993 new = ACCESS_ONCE(watchdog_thresh);
994 if (old == new)
995 goto out;
996
997 set_sample_period();
998 err = proc_watchdog_update();
999 if (err) {
1000 watchdog_thresh = old;
1001 set_sample_period();
1002 }
1003out:
1004 mutex_unlock(&watchdog_proc_mutex);
1005 put_online_cpus();
1006 return err;
1007}
1008
1009/*
1010 * The cpumask is the mask of possible cpus that the watchdog can run
1011 * on, not the mask of cpus it is actually running on. This allows the
1012 * user to specify a mask that will include cpus that have not yet
1013 * been brought online, if desired.
1014 */
1015int proc_watchdog_cpumask(struct ctl_table *table, int write,
1016 void __user *buffer, size_t *lenp, loff_t *ppos)
1017{
1018 int err;
1019
1020 get_online_cpus();
1021 mutex_lock(&watchdog_proc_mutex);
1022
1023 if (watchdog_suspended) {
1024 /* no parameter changes allowed while watchdog is suspended */
1025 err = -EAGAIN;
1026 goto out;
1027 }
1028
1029 err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
1030 if (!err && write) {
1031 /* Remove impossible cpus to keep sysctl output cleaner. */
1032 cpumask_and(&watchdog_cpumask, &watchdog_cpumask,
1033 cpu_possible_mask);
1034
1035 if (watchdog_running) {
1036 /*
1037 * Failure would be due to being unable to allocate
1038 * a temporary cpumask, so we are likely not in a
1039 * position to do much else to make things better.
1040 */
1041 if (smpboot_update_cpumask_percpu_thread(
1042 &watchdog_threads, &watchdog_cpumask) != 0)
1043 pr_err("cpumask update failed\n");
1044 }
1045 }
1046out:
1047 mutex_unlock(&watchdog_proc_mutex);
1048 put_online_cpus();
1049 return err;
1050}
1051
1052#endif /* CONFIG_SYSCTL */
1053
1054void __init lockup_detector_init(void)
1055{
1056 set_sample_period();
1057
1058#ifdef CONFIG_NO_HZ_FULL
1059 if (tick_nohz_full_enabled()) {
1060 pr_info("Disabling watchdog on nohz_full cores by default\n");
1061 cpumask_copy(&watchdog_cpumask, housekeeping_mask);
1062 } else
1063 cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
1064#else
1065 cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
1066#endif
1067
1068 if (watchdog_enabled)
1069 watchdog_enable_all_cpus();
1070}