ubsan: disable UBSAN_TRAP for all*config
[linux-2.6-microblaze.git] / kernel / watchdog.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Detect hard and soft lockups on a system
4  *
5  * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
6  *
7  * Note: Most of this code is borrowed heavily from the original softlockup
8  * detector, so thanks to Ingo for the initial implementation.
9  * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
10  * to those contributors as well.
11  */
12
13 #define pr_fmt(fmt) "watchdog: " fmt
14
15 #include <linux/mm.h>
16 #include <linux/cpu.h>
17 #include <linux/nmi.h>
18 #include <linux/init.h>
19 #include <linux/module.h>
20 #include <linux/sysctl.h>
21 #include <linux/tick.h>
22 #include <linux/sched/clock.h>
23 #include <linux/sched/debug.h>
24 #include <linux/sched/isolation.h>
25 #include <linux/stop_machine.h>
26
27 #include <asm/irq_regs.h>
28 #include <linux/kvm_para.h>
29
30 static DEFINE_MUTEX(watchdog_mutex);
31
32 #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
33 # define WATCHDOG_DEFAULT       (SOFT_WATCHDOG_ENABLED | NMI_WATCHDOG_ENABLED)
34 # define NMI_WATCHDOG_DEFAULT   1
35 #else
36 # define WATCHDOG_DEFAULT       (SOFT_WATCHDOG_ENABLED)
37 # define NMI_WATCHDOG_DEFAULT   0
38 #endif
39
40 unsigned long __read_mostly watchdog_enabled;
41 int __read_mostly watchdog_user_enabled = 1;
42 int __read_mostly nmi_watchdog_user_enabled = NMI_WATCHDOG_DEFAULT;
43 int __read_mostly soft_watchdog_user_enabled = 1;
44 int __read_mostly watchdog_thresh = 10;
45 static int __read_mostly nmi_watchdog_available;
46
47 struct cpumask watchdog_cpumask __read_mostly;
48 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
49
50 #ifdef CONFIG_HARDLOCKUP_DETECTOR
51
52 # ifdef CONFIG_SMP
53 int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
54 # endif /* CONFIG_SMP */
55
56 /*
57  * Should we panic when a soft-lockup or hard-lockup occurs:
58  */
59 unsigned int __read_mostly hardlockup_panic =
60                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
61 /*
62  * We may not want to enable hard lockup detection by default in all cases,
63  * for example when running the kernel as a guest on a hypervisor. In these
64  * cases this function can be called to disable hard lockup detection. This
65  * function should only be executed once by the boot processor before the
66  * kernel command line parameters are parsed, because otherwise it is not
67  * possible to override this in hardlockup_panic_setup().
68  */
69 void __init hardlockup_detector_disable(void)
70 {
71         nmi_watchdog_user_enabled = 0;
72 }
73
74 static int __init hardlockup_panic_setup(char *str)
75 {
76         if (!strncmp(str, "panic", 5))
77                 hardlockup_panic = 1;
78         else if (!strncmp(str, "nopanic", 7))
79                 hardlockup_panic = 0;
80         else if (!strncmp(str, "0", 1))
81                 nmi_watchdog_user_enabled = 0;
82         else if (!strncmp(str, "1", 1))
83                 nmi_watchdog_user_enabled = 1;
84         return 1;
85 }
86 __setup("nmi_watchdog=", hardlockup_panic_setup);
87
88 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
89
90 /*
91  * These functions can be overridden if an architecture implements its
92  * own hardlockup detector.
93  *
94  * watchdog_nmi_enable/disable can be implemented to start and stop when
95  * softlockup watchdog threads start and stop. The arch must select the
96  * SOFTLOCKUP_DETECTOR Kconfig.
97  */
98 int __weak watchdog_nmi_enable(unsigned int cpu)
99 {
100         hardlockup_detector_perf_enable();
101         return 0;
102 }
103
104 void __weak watchdog_nmi_disable(unsigned int cpu)
105 {
106         hardlockup_detector_perf_disable();
107 }
108
109 /* Return 0, if a NMI watchdog is available. Error code otherwise */
110 int __weak __init watchdog_nmi_probe(void)
111 {
112         return hardlockup_detector_perf_init();
113 }
114
115 /**
116  * watchdog_nmi_stop - Stop the watchdog for reconfiguration
117  *
118  * The reconfiguration steps are:
119  * watchdog_nmi_stop();
120  * update_variables();
121  * watchdog_nmi_start();
122  */
123 void __weak watchdog_nmi_stop(void) { }
124
125 /**
126  * watchdog_nmi_start - Start the watchdog after reconfiguration
127  *
128  * Counterpart to watchdog_nmi_stop().
129  *
130  * The following variables have been updated in update_variables() and
131  * contain the currently valid configuration:
132  * - watchdog_enabled
133  * - watchdog_thresh
134  * - watchdog_cpumask
135  */
136 void __weak watchdog_nmi_start(void) { }
137
138 /**
139  * lockup_detector_update_enable - Update the sysctl enable bit
140  *
141  * Caller needs to make sure that the NMI/perf watchdogs are off, so this
142  * can't race with watchdog_nmi_disable().
143  */
144 static void lockup_detector_update_enable(void)
145 {
146         watchdog_enabled = 0;
147         if (!watchdog_user_enabled)
148                 return;
149         if (nmi_watchdog_available && nmi_watchdog_user_enabled)
150                 watchdog_enabled |= NMI_WATCHDOG_ENABLED;
151         if (soft_watchdog_user_enabled)
152                 watchdog_enabled |= SOFT_WATCHDOG_ENABLED;
153 }
154
155 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
156
157 #define SOFTLOCKUP_RESET        ULONG_MAX
158
159 #ifdef CONFIG_SMP
160 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
161 #endif
162
163 static struct cpumask watchdog_allowed_mask __read_mostly;
164
165 /* Global variables, exported for sysctl */
166 unsigned int __read_mostly softlockup_panic =
167                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
168
169 static bool softlockup_initialized __read_mostly;
170 static u64 __read_mostly sample_period;
171
172 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
173 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
174 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
175 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
176 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
177 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
178 static unsigned long soft_lockup_nmi_warn;
179
180 static int __init nowatchdog_setup(char *str)
181 {
182         watchdog_user_enabled = 0;
183         return 1;
184 }
185 __setup("nowatchdog", nowatchdog_setup);
186
187 static int __init nosoftlockup_setup(char *str)
188 {
189         soft_watchdog_user_enabled = 0;
190         return 1;
191 }
192 __setup("nosoftlockup", nosoftlockup_setup);
193
194 static int __init watchdog_thresh_setup(char *str)
195 {
196         get_option(&str, &watchdog_thresh);
197         return 1;
198 }
199 __setup("watchdog_thresh=", watchdog_thresh_setup);
200
201 static void __lockup_detector_cleanup(void);
202
203 /*
204  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
205  * lockups can have false positives under extreme conditions. So we generally
206  * want a higher threshold for soft lockups than for hard lockups. So we couple
207  * the thresholds with a factor: we make the soft threshold twice the amount of
208  * time the hard threshold is.
209  */
210 static int get_softlockup_thresh(void)
211 {
212         return watchdog_thresh * 2;
213 }
214
215 /*
216  * Returns seconds, approximately.  We don't need nanosecond
217  * resolution, and we don't need to waste time with a big divide when
218  * 2^30ns == 1.074s.
219  */
220 static unsigned long get_timestamp(void)
221 {
222         return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
223 }
224
225 static void set_sample_period(void)
226 {
227         /*
228          * convert watchdog_thresh from seconds to ns
229          * the divide by 5 is to give hrtimer several chances (two
230          * or three with the current relation between the soft
231          * and hard thresholds) to increment before the
232          * hardlockup detector generates a warning
233          */
234         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
235         watchdog_update_hrtimer_threshold(sample_period);
236 }
237
238 /* Commands for resetting the watchdog */
239 static void __touch_watchdog(void)
240 {
241         __this_cpu_write(watchdog_touch_ts, get_timestamp());
242 }
243
244 /**
245  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
246  *
247  * Call when the scheduler may have stalled for legitimate reasons
248  * preventing the watchdog task from executing - e.g. the scheduler
249  * entering idle state.  This should only be used for scheduler events.
250  * Use touch_softlockup_watchdog() for everything else.
251  */
252 notrace void touch_softlockup_watchdog_sched(void)
253 {
254         /*
255          * Preemption can be enabled.  It doesn't matter which CPU's timestamp
256          * gets zeroed here, so use the raw_ operation.
257          */
258         raw_cpu_write(watchdog_touch_ts, SOFTLOCKUP_RESET);
259 }
260
261 notrace void touch_softlockup_watchdog(void)
262 {
263         touch_softlockup_watchdog_sched();
264         wq_watchdog_touch(raw_smp_processor_id());
265 }
266 EXPORT_SYMBOL(touch_softlockup_watchdog);
267
268 void touch_all_softlockup_watchdogs(void)
269 {
270         int cpu;
271
272         /*
273          * watchdog_mutex cannpt be taken here, as this might be called
274          * from (soft)interrupt context, so the access to
275          * watchdog_allowed_cpumask might race with a concurrent update.
276          *
277          * The watchdog time stamp can race against a concurrent real
278          * update as well, the only side effect might be a cycle delay for
279          * the softlockup check.
280          */
281         for_each_cpu(cpu, &watchdog_allowed_mask)
282                 per_cpu(watchdog_touch_ts, cpu) = SOFTLOCKUP_RESET;
283         wq_watchdog_touch(-1);
284 }
285
286 void touch_softlockup_watchdog_sync(void)
287 {
288         __this_cpu_write(softlockup_touch_sync, true);
289         __this_cpu_write(watchdog_touch_ts, SOFTLOCKUP_RESET);
290 }
291
292 static int is_softlockup(unsigned long touch_ts)
293 {
294         unsigned long now = get_timestamp();
295
296         if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
297                 /* Warn about unreasonable delays. */
298                 if (time_after(now, touch_ts + get_softlockup_thresh()))
299                         return now - touch_ts;
300         }
301         return 0;
302 }
303
304 /* watchdog detector functions */
305 bool is_hardlockup(void)
306 {
307         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
308
309         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
310                 return true;
311
312         __this_cpu_write(hrtimer_interrupts_saved, hrint);
313         return false;
314 }
315
316 static void watchdog_interrupt_count(void)
317 {
318         __this_cpu_inc(hrtimer_interrupts);
319 }
320
321 static DEFINE_PER_CPU(struct completion, softlockup_completion);
322 static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
323
324 /*
325  * The watchdog thread function - touches the timestamp.
326  *
327  * It only runs once every sample_period seconds (4 seconds by
328  * default) to reset the softlockup timestamp. If this gets delayed
329  * for more than 2*watchdog_thresh seconds then the debug-printout
330  * triggers in watchdog_timer_fn().
331  */
332 static int softlockup_fn(void *data)
333 {
334         __touch_watchdog();
335         complete(this_cpu_ptr(&softlockup_completion));
336
337         return 0;
338 }
339
340 /* watchdog kicker functions */
341 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
342 {
343         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
344         struct pt_regs *regs = get_irq_regs();
345         int duration;
346         int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
347
348         if (!watchdog_enabled)
349                 return HRTIMER_NORESTART;
350
351         /* kick the hardlockup detector */
352         watchdog_interrupt_count();
353
354         /* kick the softlockup detector */
355         if (completion_done(this_cpu_ptr(&softlockup_completion))) {
356                 reinit_completion(this_cpu_ptr(&softlockup_completion));
357                 stop_one_cpu_nowait(smp_processor_id(),
358                                 softlockup_fn, NULL,
359                                 this_cpu_ptr(&softlockup_stop_work));
360         }
361
362         /* .. and repeat */
363         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
364
365         if (touch_ts == SOFTLOCKUP_RESET) {
366                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
367                         /*
368                          * If the time stamp was touched atomically
369                          * make sure the scheduler tick is up to date.
370                          */
371                         __this_cpu_write(softlockup_touch_sync, false);
372                         sched_clock_tick();
373                 }
374
375                 /* Clear the guest paused flag on watchdog reset */
376                 kvm_check_and_clear_guest_paused();
377                 __touch_watchdog();
378                 return HRTIMER_RESTART;
379         }
380
381         /* check for a softlockup
382          * This is done by making sure a high priority task is
383          * being scheduled.  The task touches the watchdog to
384          * indicate it is getting cpu time.  If it hasn't then
385          * this is a good indication some task is hogging the cpu
386          */
387         duration = is_softlockup(touch_ts);
388         if (unlikely(duration)) {
389                 /*
390                  * If a virtual machine is stopped by the host it can look to
391                  * the watchdog like a soft lockup, check to see if the host
392                  * stopped the vm before we issue the warning
393                  */
394                 if (kvm_check_and_clear_guest_paused())
395                         return HRTIMER_RESTART;
396
397                 /* only warn once */
398                 if (__this_cpu_read(soft_watchdog_warn) == true)
399                         return HRTIMER_RESTART;
400
401                 if (softlockup_all_cpu_backtrace) {
402                         /* Prevent multiple soft-lockup reports if one cpu is already
403                          * engaged in dumping cpu back traces
404                          */
405                         if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
406                                 /* Someone else will report us. Let's give up */
407                                 __this_cpu_write(soft_watchdog_warn, true);
408                                 return HRTIMER_RESTART;
409                         }
410                 }
411
412                 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
413                         smp_processor_id(), duration,
414                         current->comm, task_pid_nr(current));
415                 print_modules();
416                 print_irqtrace_events(current);
417                 if (regs)
418                         show_regs(regs);
419                 else
420                         dump_stack();
421
422                 if (softlockup_all_cpu_backtrace) {
423                         /* Avoid generating two back traces for current
424                          * given that one is already made above
425                          */
426                         trigger_allbutself_cpu_backtrace();
427
428                         clear_bit(0, &soft_lockup_nmi_warn);
429                         /* Barrier to sync with other cpus */
430                         smp_mb__after_atomic();
431                 }
432
433                 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
434                 if (softlockup_panic)
435                         panic("softlockup: hung tasks");
436                 __this_cpu_write(soft_watchdog_warn, true);
437         } else
438                 __this_cpu_write(soft_watchdog_warn, false);
439
440         return HRTIMER_RESTART;
441 }
442
443 static void watchdog_enable(unsigned int cpu)
444 {
445         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
446         struct completion *done = this_cpu_ptr(&softlockup_completion);
447
448         WARN_ON_ONCE(cpu != smp_processor_id());
449
450         init_completion(done);
451         complete(done);
452
453         /*
454          * Start the timer first to prevent the NMI watchdog triggering
455          * before the timer has a chance to fire.
456          */
457         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
458         hrtimer->function = watchdog_timer_fn;
459         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
460                       HRTIMER_MODE_REL_PINNED_HARD);
461
462         /* Initialize timestamp */
463         __touch_watchdog();
464         /* Enable the perf event */
465         if (watchdog_enabled & NMI_WATCHDOG_ENABLED)
466                 watchdog_nmi_enable(cpu);
467 }
468
469 static void watchdog_disable(unsigned int cpu)
470 {
471         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
472
473         WARN_ON_ONCE(cpu != smp_processor_id());
474
475         /*
476          * Disable the perf event first. That prevents that a large delay
477          * between disabling the timer and disabling the perf event causes
478          * the perf NMI to detect a false positive.
479          */
480         watchdog_nmi_disable(cpu);
481         hrtimer_cancel(hrtimer);
482         wait_for_completion(this_cpu_ptr(&softlockup_completion));
483 }
484
485 static int softlockup_stop_fn(void *data)
486 {
487         watchdog_disable(smp_processor_id());
488         return 0;
489 }
490
491 static void softlockup_stop_all(void)
492 {
493         int cpu;
494
495         if (!softlockup_initialized)
496                 return;
497
498         for_each_cpu(cpu, &watchdog_allowed_mask)
499                 smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
500
501         cpumask_clear(&watchdog_allowed_mask);
502 }
503
504 static int softlockup_start_fn(void *data)
505 {
506         watchdog_enable(smp_processor_id());
507         return 0;
508 }
509
510 static void softlockup_start_all(void)
511 {
512         int cpu;
513
514         cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
515         for_each_cpu(cpu, &watchdog_allowed_mask)
516                 smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
517 }
518
519 int lockup_detector_online_cpu(unsigned int cpu)
520 {
521         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
522                 watchdog_enable(cpu);
523         return 0;
524 }
525
526 int lockup_detector_offline_cpu(unsigned int cpu)
527 {
528         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
529                 watchdog_disable(cpu);
530         return 0;
531 }
532
533 static void lockup_detector_reconfigure(void)
534 {
535         cpus_read_lock();
536         watchdog_nmi_stop();
537
538         softlockup_stop_all();
539         set_sample_period();
540         lockup_detector_update_enable();
541         if (watchdog_enabled && watchdog_thresh)
542                 softlockup_start_all();
543
544         watchdog_nmi_start();
545         cpus_read_unlock();
546         /*
547          * Must be called outside the cpus locked section to prevent
548          * recursive locking in the perf code.
549          */
550         __lockup_detector_cleanup();
551 }
552
553 /*
554  * Create the watchdog thread infrastructure and configure the detector(s).
555  *
556  * The threads are not unparked as watchdog_allowed_mask is empty.  When
557  * the threads are successfully initialized, take the proper locks and
558  * unpark the threads in the watchdog_cpumask if the watchdog is enabled.
559  */
560 static __init void lockup_detector_setup(void)
561 {
562         /*
563          * If sysctl is off and watchdog got disabled on the command line,
564          * nothing to do here.
565          */
566         lockup_detector_update_enable();
567
568         if (!IS_ENABLED(CONFIG_SYSCTL) &&
569             !(watchdog_enabled && watchdog_thresh))
570                 return;
571
572         mutex_lock(&watchdog_mutex);
573         lockup_detector_reconfigure();
574         softlockup_initialized = true;
575         mutex_unlock(&watchdog_mutex);
576 }
577
578 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
579 static void lockup_detector_reconfigure(void)
580 {
581         cpus_read_lock();
582         watchdog_nmi_stop();
583         lockup_detector_update_enable();
584         watchdog_nmi_start();
585         cpus_read_unlock();
586 }
587 static inline void lockup_detector_setup(void)
588 {
589         lockup_detector_reconfigure();
590 }
591 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
592
593 static void __lockup_detector_cleanup(void)
594 {
595         lockdep_assert_held(&watchdog_mutex);
596         hardlockup_detector_perf_cleanup();
597 }
598
599 /**
600  * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
601  *
602  * Caller must not hold the cpu hotplug rwsem.
603  */
604 void lockup_detector_cleanup(void)
605 {
606         mutex_lock(&watchdog_mutex);
607         __lockup_detector_cleanup();
608         mutex_unlock(&watchdog_mutex);
609 }
610
611 /**
612  * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
613  *
614  * Special interface for parisc. It prevents lockup detector warnings from
615  * the default pm_poweroff() function which busy loops forever.
616  */
617 void lockup_detector_soft_poweroff(void)
618 {
619         watchdog_enabled = 0;
620 }
621
622 #ifdef CONFIG_SYSCTL
623
624 /* Propagate any changes to the watchdog threads */
625 static void proc_watchdog_update(void)
626 {
627         /* Remove impossible cpus to keep sysctl output clean. */
628         cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
629         lockup_detector_reconfigure();
630 }
631
632 /*
633  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
634  *
635  * caller             | table->data points to      | 'which'
636  * -------------------|----------------------------|--------------------------
637  * proc_watchdog      | watchdog_user_enabled      | NMI_WATCHDOG_ENABLED |
638  *                    |                            | SOFT_WATCHDOG_ENABLED
639  * -------------------|----------------------------|--------------------------
640  * proc_nmi_watchdog  | nmi_watchdog_user_enabled  | NMI_WATCHDOG_ENABLED
641  * -------------------|----------------------------|--------------------------
642  * proc_soft_watchdog | soft_watchdog_user_enabled | SOFT_WATCHDOG_ENABLED
643  */
644 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
645                                 void *buffer, size_t *lenp, loff_t *ppos)
646 {
647         int err, old, *param = table->data;
648
649         mutex_lock(&watchdog_mutex);
650
651         if (!write) {
652                 /*
653                  * On read synchronize the userspace interface. This is a
654                  * racy snapshot.
655                  */
656                 *param = (watchdog_enabled & which) != 0;
657                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
658         } else {
659                 old = READ_ONCE(*param);
660                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
661                 if (!err && old != READ_ONCE(*param))
662                         proc_watchdog_update();
663         }
664         mutex_unlock(&watchdog_mutex);
665         return err;
666 }
667
668 /*
669  * /proc/sys/kernel/watchdog
670  */
671 int proc_watchdog(struct ctl_table *table, int write,
672                   void *buffer, size_t *lenp, loff_t *ppos)
673 {
674         return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
675                                     table, write, buffer, lenp, ppos);
676 }
677
678 /*
679  * /proc/sys/kernel/nmi_watchdog
680  */
681 int proc_nmi_watchdog(struct ctl_table *table, int write,
682                       void *buffer, size_t *lenp, loff_t *ppos)
683 {
684         if (!nmi_watchdog_available && write)
685                 return -ENOTSUPP;
686         return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
687                                     table, write, buffer, lenp, ppos);
688 }
689
690 /*
691  * /proc/sys/kernel/soft_watchdog
692  */
693 int proc_soft_watchdog(struct ctl_table *table, int write,
694                         void *buffer, size_t *lenp, loff_t *ppos)
695 {
696         return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
697                                     table, write, buffer, lenp, ppos);
698 }
699
700 /*
701  * /proc/sys/kernel/watchdog_thresh
702  */
703 int proc_watchdog_thresh(struct ctl_table *table, int write,
704                          void *buffer, size_t *lenp, loff_t *ppos)
705 {
706         int err, old;
707
708         mutex_lock(&watchdog_mutex);
709
710         old = READ_ONCE(watchdog_thresh);
711         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
712
713         if (!err && write && old != READ_ONCE(watchdog_thresh))
714                 proc_watchdog_update();
715
716         mutex_unlock(&watchdog_mutex);
717         return err;
718 }
719
720 /*
721  * The cpumask is the mask of possible cpus that the watchdog can run
722  * on, not the mask of cpus it is actually running on.  This allows the
723  * user to specify a mask that will include cpus that have not yet
724  * been brought online, if desired.
725  */
726 int proc_watchdog_cpumask(struct ctl_table *table, int write,
727                           void *buffer, size_t *lenp, loff_t *ppos)
728 {
729         int err;
730
731         mutex_lock(&watchdog_mutex);
732
733         err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
734         if (!err && write)
735                 proc_watchdog_update();
736
737         mutex_unlock(&watchdog_mutex);
738         return err;
739 }
740 #endif /* CONFIG_SYSCTL */
741
742 void __init lockup_detector_init(void)
743 {
744         if (tick_nohz_full_enabled())
745                 pr_info("Disabling watchdog on nohz_full cores by default\n");
746
747         cpumask_copy(&watchdog_cpumask,
748                      housekeeping_cpumask(HK_FLAG_TIMER));
749
750         if (!watchdog_nmi_probe())
751                 nmi_watchdog_available = true;
752         lockup_detector_setup();
753 }