Merge patch series "RISC-V: Probe for misaligned access speed"
[platform/kernel/linux-starfive.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_HARDLOCKUP_DETECTOR_SPARC64)
33 # define WATCHDOG_HARDLOCKUP_DEFAULT    1
34 #else
35 # define WATCHDOG_HARDLOCKUP_DEFAULT    0
36 #endif
37
38 unsigned long __read_mostly watchdog_enabled;
39 int __read_mostly watchdog_user_enabled = 1;
40 static int __read_mostly watchdog_hardlockup_user_enabled = WATCHDOG_HARDLOCKUP_DEFAULT;
41 static int __read_mostly watchdog_softlockup_user_enabled = 1;
42 int __read_mostly watchdog_thresh = 10;
43 static int __read_mostly watchdog_hardlockup_available;
44
45 struct cpumask watchdog_cpumask __read_mostly;
46 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
47
48 #ifdef CONFIG_HARDLOCKUP_DETECTOR
49
50 # ifdef CONFIG_SMP
51 int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
52 # endif /* CONFIG_SMP */
53
54 /*
55  * Should we panic when a soft-lockup or hard-lockup occurs:
56  */
57 unsigned int __read_mostly hardlockup_panic =
58                         IS_ENABLED(CONFIG_BOOTPARAM_HARDLOCKUP_PANIC);
59 /*
60  * We may not want to enable hard lockup detection by default in all cases,
61  * for example when running the kernel as a guest on a hypervisor. In these
62  * cases this function can be called to disable hard lockup detection. This
63  * function should only be executed once by the boot processor before the
64  * kernel command line parameters are parsed, because otherwise it is not
65  * possible to override this in hardlockup_panic_setup().
66  */
67 void __init hardlockup_detector_disable(void)
68 {
69         watchdog_hardlockup_user_enabled = 0;
70 }
71
72 static int __init hardlockup_panic_setup(char *str)
73 {
74         if (!strncmp(str, "panic", 5))
75                 hardlockup_panic = 1;
76         else if (!strncmp(str, "nopanic", 7))
77                 hardlockup_panic = 0;
78         else if (!strncmp(str, "0", 1))
79                 watchdog_hardlockup_user_enabled = 0;
80         else if (!strncmp(str, "1", 1))
81                 watchdog_hardlockup_user_enabled = 1;
82         return 1;
83 }
84 __setup("nmi_watchdog=", hardlockup_panic_setup);
85
86 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
87
88 #if defined(CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER)
89
90 static DEFINE_PER_CPU(atomic_t, hrtimer_interrupts);
91 static DEFINE_PER_CPU(int, hrtimer_interrupts_saved);
92 static DEFINE_PER_CPU(bool, watchdog_hardlockup_warned);
93 static DEFINE_PER_CPU(bool, watchdog_hardlockup_touched);
94 static unsigned long watchdog_hardlockup_all_cpu_dumped;
95
96 notrace void arch_touch_nmi_watchdog(void)
97 {
98         /*
99          * Using __raw here because some code paths have
100          * preemption enabled.  If preemption is enabled
101          * then interrupts should be enabled too, in which
102          * case we shouldn't have to worry about the watchdog
103          * going off.
104          */
105         raw_cpu_write(watchdog_hardlockup_touched, true);
106 }
107 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
108
109 void watchdog_hardlockup_touch_cpu(unsigned int cpu)
110 {
111         per_cpu(watchdog_hardlockup_touched, cpu) = true;
112 }
113
114 static bool is_hardlockup(unsigned int cpu)
115 {
116         int hrint = atomic_read(&per_cpu(hrtimer_interrupts, cpu));
117
118         if (per_cpu(hrtimer_interrupts_saved, cpu) == hrint)
119                 return true;
120
121         /*
122          * NOTE: we don't need any fancy atomic_t or READ_ONCE/WRITE_ONCE
123          * for hrtimer_interrupts_saved. hrtimer_interrupts_saved is
124          * written/read by a single CPU.
125          */
126         per_cpu(hrtimer_interrupts_saved, cpu) = hrint;
127
128         return false;
129 }
130
131 static void watchdog_hardlockup_kick(void)
132 {
133         int new_interrupts;
134
135         new_interrupts = atomic_inc_return(this_cpu_ptr(&hrtimer_interrupts));
136         watchdog_buddy_check_hardlockup(new_interrupts);
137 }
138
139 void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)
140 {
141         if (per_cpu(watchdog_hardlockup_touched, cpu)) {
142                 per_cpu(watchdog_hardlockup_touched, cpu) = false;
143                 return;
144         }
145
146         /*
147          * Check for a hardlockup by making sure the CPU's timer
148          * interrupt is incrementing. The timer interrupt should have
149          * fired multiple times before we overflow'd. If it hasn't
150          * then this is a good indication the cpu is stuck
151          */
152         if (is_hardlockup(cpu)) {
153                 unsigned int this_cpu = smp_processor_id();
154
155                 /* Only print hardlockups once. */
156                 if (per_cpu(watchdog_hardlockup_warned, cpu))
157                         return;
158
159                 pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n", cpu);
160                 print_modules();
161                 print_irqtrace_events(current);
162                 if (cpu == this_cpu) {
163                         if (regs)
164                                 show_regs(regs);
165                         else
166                                 dump_stack();
167                 } else {
168                         trigger_single_cpu_backtrace(cpu);
169                 }
170
171                 /*
172                  * Perform multi-CPU dump only once to avoid multiple
173                  * hardlockups generating interleaving traces
174                  */
175                 if (sysctl_hardlockup_all_cpu_backtrace &&
176                     !test_and_set_bit(0, &watchdog_hardlockup_all_cpu_dumped))
177                         trigger_allbutcpu_cpu_backtrace(cpu);
178
179                 if (hardlockup_panic)
180                         nmi_panic(regs, "Hard LOCKUP");
181
182                 per_cpu(watchdog_hardlockup_warned, cpu) = true;
183         } else {
184                 per_cpu(watchdog_hardlockup_warned, cpu) = false;
185         }
186 }
187
188 #else /* CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
189
190 static inline void watchdog_hardlockup_kick(void) { }
191
192 #endif /* !CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
193
194 /*
195  * These functions can be overridden based on the configured hardlockdup detector.
196  *
197  * watchdog_hardlockup_enable/disable can be implemented to start and stop when
198  * softlockup watchdog start and stop. The detector must select the
199  * SOFTLOCKUP_DETECTOR Kconfig.
200  */
201 void __weak watchdog_hardlockup_enable(unsigned int cpu) { }
202
203 void __weak watchdog_hardlockup_disable(unsigned int cpu) { }
204
205 /*
206  * Watchdog-detector specific API.
207  *
208  * Return 0 when hardlockup watchdog is available, negative value otherwise.
209  * Note that the negative value means that a delayed probe might
210  * succeed later.
211  */
212 int __weak __init watchdog_hardlockup_probe(void)
213 {
214         return -ENODEV;
215 }
216
217 /**
218  * watchdog_hardlockup_stop - Stop the watchdog for reconfiguration
219  *
220  * The reconfiguration steps are:
221  * watchdog_hardlockup_stop();
222  * update_variables();
223  * watchdog_hardlockup_start();
224  */
225 void __weak watchdog_hardlockup_stop(void) { }
226
227 /**
228  * watchdog_hardlockup_start - Start the watchdog after reconfiguration
229  *
230  * Counterpart to watchdog_hardlockup_stop().
231  *
232  * The following variables have been updated in update_variables() and
233  * contain the currently valid configuration:
234  * - watchdog_enabled
235  * - watchdog_thresh
236  * - watchdog_cpumask
237  */
238 void __weak watchdog_hardlockup_start(void) { }
239
240 /**
241  * lockup_detector_update_enable - Update the sysctl enable bit
242  *
243  * Caller needs to make sure that the hard watchdogs are off, so this
244  * can't race with watchdog_hardlockup_disable().
245  */
246 static void lockup_detector_update_enable(void)
247 {
248         watchdog_enabled = 0;
249         if (!watchdog_user_enabled)
250                 return;
251         if (watchdog_hardlockup_available && watchdog_hardlockup_user_enabled)
252                 watchdog_enabled |= WATCHDOG_HARDLOCKUP_ENABLED;
253         if (watchdog_softlockup_user_enabled)
254                 watchdog_enabled |= WATCHDOG_SOFTOCKUP_ENABLED;
255 }
256
257 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
258
259 /*
260  * Delay the soflockup report when running a known slow code.
261  * It does _not_ affect the timestamp of the last successdul reschedule.
262  */
263 #define SOFTLOCKUP_DELAY_REPORT ULONG_MAX
264
265 #ifdef CONFIG_SMP
266 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
267 #endif
268
269 static struct cpumask watchdog_allowed_mask __read_mostly;
270
271 /* Global variables, exported for sysctl */
272 unsigned int __read_mostly softlockup_panic =
273                         IS_ENABLED(CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC);
274
275 static bool softlockup_initialized __read_mostly;
276 static u64 __read_mostly sample_period;
277
278 /* Timestamp taken after the last successful reschedule. */
279 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
280 /* Timestamp of the last softlockup report. */
281 static DEFINE_PER_CPU(unsigned long, watchdog_report_ts);
282 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
283 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
284 static unsigned long soft_lockup_nmi_warn;
285
286 static int __init nowatchdog_setup(char *str)
287 {
288         watchdog_user_enabled = 0;
289         return 1;
290 }
291 __setup("nowatchdog", nowatchdog_setup);
292
293 static int __init nosoftlockup_setup(char *str)
294 {
295         watchdog_softlockup_user_enabled = 0;
296         return 1;
297 }
298 __setup("nosoftlockup", nosoftlockup_setup);
299
300 static int __init watchdog_thresh_setup(char *str)
301 {
302         get_option(&str, &watchdog_thresh);
303         return 1;
304 }
305 __setup("watchdog_thresh=", watchdog_thresh_setup);
306
307 static void __lockup_detector_cleanup(void);
308
309 /*
310  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
311  * lockups can have false positives under extreme conditions. So we generally
312  * want a higher threshold for soft lockups than for hard lockups. So we couple
313  * the thresholds with a factor: we make the soft threshold twice the amount of
314  * time the hard threshold is.
315  */
316 static int get_softlockup_thresh(void)
317 {
318         return watchdog_thresh * 2;
319 }
320
321 /*
322  * Returns seconds, approximately.  We don't need nanosecond
323  * resolution, and we don't need to waste time with a big divide when
324  * 2^30ns == 1.074s.
325  */
326 static unsigned long get_timestamp(void)
327 {
328         return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
329 }
330
331 static void set_sample_period(void)
332 {
333         /*
334          * convert watchdog_thresh from seconds to ns
335          * the divide by 5 is to give hrtimer several chances (two
336          * or three with the current relation between the soft
337          * and hard thresholds) to increment before the
338          * hardlockup detector generates a warning
339          */
340         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
341         watchdog_update_hrtimer_threshold(sample_period);
342 }
343
344 static void update_report_ts(void)
345 {
346         __this_cpu_write(watchdog_report_ts, get_timestamp());
347 }
348
349 /* Commands for resetting the watchdog */
350 static void update_touch_ts(void)
351 {
352         __this_cpu_write(watchdog_touch_ts, get_timestamp());
353         update_report_ts();
354 }
355
356 /**
357  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
358  *
359  * Call when the scheduler may have stalled for legitimate reasons
360  * preventing the watchdog task from executing - e.g. the scheduler
361  * entering idle state.  This should only be used for scheduler events.
362  * Use touch_softlockup_watchdog() for everything else.
363  */
364 notrace void touch_softlockup_watchdog_sched(void)
365 {
366         /*
367          * Preemption can be enabled.  It doesn't matter which CPU's watchdog
368          * report period gets restarted here, so use the raw_ operation.
369          */
370         raw_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
371 }
372
373 notrace void touch_softlockup_watchdog(void)
374 {
375         touch_softlockup_watchdog_sched();
376         wq_watchdog_touch(raw_smp_processor_id());
377 }
378 EXPORT_SYMBOL(touch_softlockup_watchdog);
379
380 void touch_all_softlockup_watchdogs(void)
381 {
382         int cpu;
383
384         /*
385          * watchdog_mutex cannpt be taken here, as this might be called
386          * from (soft)interrupt context, so the access to
387          * watchdog_allowed_cpumask might race with a concurrent update.
388          *
389          * The watchdog time stamp can race against a concurrent real
390          * update as well, the only side effect might be a cycle delay for
391          * the softlockup check.
392          */
393         for_each_cpu(cpu, &watchdog_allowed_mask) {
394                 per_cpu(watchdog_report_ts, cpu) = SOFTLOCKUP_DELAY_REPORT;
395                 wq_watchdog_touch(cpu);
396         }
397 }
398
399 void touch_softlockup_watchdog_sync(void)
400 {
401         __this_cpu_write(softlockup_touch_sync, true);
402         __this_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
403 }
404
405 static int is_softlockup(unsigned long touch_ts,
406                          unsigned long period_ts,
407                          unsigned long now)
408 {
409         if ((watchdog_enabled & WATCHDOG_SOFTOCKUP_ENABLED) && watchdog_thresh) {
410                 /* Warn about unreasonable delays. */
411                 if (time_after(now, period_ts + get_softlockup_thresh()))
412                         return now - touch_ts;
413         }
414         return 0;
415 }
416
417 /* watchdog detector functions */
418 static DEFINE_PER_CPU(struct completion, softlockup_completion);
419 static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
420
421 /*
422  * The watchdog feed function - touches the timestamp.
423  *
424  * It only runs once every sample_period seconds (4 seconds by
425  * default) to reset the softlockup timestamp. If this gets delayed
426  * for more than 2*watchdog_thresh seconds then the debug-printout
427  * triggers in watchdog_timer_fn().
428  */
429 static int softlockup_fn(void *data)
430 {
431         update_touch_ts();
432         complete(this_cpu_ptr(&softlockup_completion));
433
434         return 0;
435 }
436
437 /* watchdog kicker functions */
438 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
439 {
440         unsigned long touch_ts, period_ts, now;
441         struct pt_regs *regs = get_irq_regs();
442         int duration;
443         int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
444
445         if (!watchdog_enabled)
446                 return HRTIMER_NORESTART;
447
448         watchdog_hardlockup_kick();
449
450         /* kick the softlockup detector */
451         if (completion_done(this_cpu_ptr(&softlockup_completion))) {
452                 reinit_completion(this_cpu_ptr(&softlockup_completion));
453                 stop_one_cpu_nowait(smp_processor_id(),
454                                 softlockup_fn, NULL,
455                                 this_cpu_ptr(&softlockup_stop_work));
456         }
457
458         /* .. and repeat */
459         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
460
461         /*
462          * Read the current timestamp first. It might become invalid anytime
463          * when a virtual machine is stopped by the host or when the watchog
464          * is touched from NMI.
465          */
466         now = get_timestamp();
467         /*
468          * If a virtual machine is stopped by the host it can look to
469          * the watchdog like a soft lockup. This function touches the watchdog.
470          */
471         kvm_check_and_clear_guest_paused();
472         /*
473          * The stored timestamp is comparable with @now only when not touched.
474          * It might get touched anytime from NMI. Make sure that is_softlockup()
475          * uses the same (valid) value.
476          */
477         period_ts = READ_ONCE(*this_cpu_ptr(&watchdog_report_ts));
478
479         /* Reset the interval when touched by known problematic code. */
480         if (period_ts == SOFTLOCKUP_DELAY_REPORT) {
481                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
482                         /*
483                          * If the time stamp was touched atomically
484                          * make sure the scheduler tick is up to date.
485                          */
486                         __this_cpu_write(softlockup_touch_sync, false);
487                         sched_clock_tick();
488                 }
489
490                 update_report_ts();
491                 return HRTIMER_RESTART;
492         }
493
494         /* Check for a softlockup. */
495         touch_ts = __this_cpu_read(watchdog_touch_ts);
496         duration = is_softlockup(touch_ts, period_ts, now);
497         if (unlikely(duration)) {
498                 /*
499                  * Prevent multiple soft-lockup reports if one cpu is already
500                  * engaged in dumping all cpu back traces.
501                  */
502                 if (softlockup_all_cpu_backtrace) {
503                         if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn))
504                                 return HRTIMER_RESTART;
505                 }
506
507                 /* Start period for the next softlockup warning. */
508                 update_report_ts();
509
510                 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
511                         smp_processor_id(), duration,
512                         current->comm, task_pid_nr(current));
513                 print_modules();
514                 print_irqtrace_events(current);
515                 if (regs)
516                         show_regs(regs);
517                 else
518                         dump_stack();
519
520                 if (softlockup_all_cpu_backtrace) {
521                         trigger_allbutcpu_cpu_backtrace(smp_processor_id());
522                         clear_bit_unlock(0, &soft_lockup_nmi_warn);
523                 }
524
525                 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
526                 if (softlockup_panic)
527                         panic("softlockup: hung tasks");
528         }
529
530         return HRTIMER_RESTART;
531 }
532
533 static void watchdog_enable(unsigned int cpu)
534 {
535         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
536         struct completion *done = this_cpu_ptr(&softlockup_completion);
537
538         WARN_ON_ONCE(cpu != smp_processor_id());
539
540         init_completion(done);
541         complete(done);
542
543         /*
544          * Start the timer first to prevent the hardlockup watchdog triggering
545          * before the timer has a chance to fire.
546          */
547         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
548         hrtimer->function = watchdog_timer_fn;
549         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
550                       HRTIMER_MODE_REL_PINNED_HARD);
551
552         /* Initialize timestamp */
553         update_touch_ts();
554         /* Enable the hardlockup detector */
555         if (watchdog_enabled & WATCHDOG_HARDLOCKUP_ENABLED)
556                 watchdog_hardlockup_enable(cpu);
557 }
558
559 static void watchdog_disable(unsigned int cpu)
560 {
561         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
562
563         WARN_ON_ONCE(cpu != smp_processor_id());
564
565         /*
566          * Disable the hardlockup detector first. That prevents that a large
567          * delay between disabling the timer and disabling the hardlockup
568          * detector causes a false positive.
569          */
570         watchdog_hardlockup_disable(cpu);
571         hrtimer_cancel(hrtimer);
572         wait_for_completion(this_cpu_ptr(&softlockup_completion));
573 }
574
575 static int softlockup_stop_fn(void *data)
576 {
577         watchdog_disable(smp_processor_id());
578         return 0;
579 }
580
581 static void softlockup_stop_all(void)
582 {
583         int cpu;
584
585         if (!softlockup_initialized)
586                 return;
587
588         for_each_cpu(cpu, &watchdog_allowed_mask)
589                 smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
590
591         cpumask_clear(&watchdog_allowed_mask);
592 }
593
594 static int softlockup_start_fn(void *data)
595 {
596         watchdog_enable(smp_processor_id());
597         return 0;
598 }
599
600 static void softlockup_start_all(void)
601 {
602         int cpu;
603
604         cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
605         for_each_cpu(cpu, &watchdog_allowed_mask)
606                 smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
607 }
608
609 int lockup_detector_online_cpu(unsigned int cpu)
610 {
611         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
612                 watchdog_enable(cpu);
613         return 0;
614 }
615
616 int lockup_detector_offline_cpu(unsigned int cpu)
617 {
618         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
619                 watchdog_disable(cpu);
620         return 0;
621 }
622
623 static void __lockup_detector_reconfigure(void)
624 {
625         cpus_read_lock();
626         watchdog_hardlockup_stop();
627
628         softlockup_stop_all();
629         set_sample_period();
630         lockup_detector_update_enable();
631         if (watchdog_enabled && watchdog_thresh)
632                 softlockup_start_all();
633
634         watchdog_hardlockup_start();
635         cpus_read_unlock();
636         /*
637          * Must be called outside the cpus locked section to prevent
638          * recursive locking in the perf code.
639          */
640         __lockup_detector_cleanup();
641 }
642
643 void lockup_detector_reconfigure(void)
644 {
645         mutex_lock(&watchdog_mutex);
646         __lockup_detector_reconfigure();
647         mutex_unlock(&watchdog_mutex);
648 }
649
650 /*
651  * Create the watchdog infrastructure and configure the detector(s).
652  */
653 static __init void lockup_detector_setup(void)
654 {
655         /*
656          * If sysctl is off and watchdog got disabled on the command line,
657          * nothing to do here.
658          */
659         lockup_detector_update_enable();
660
661         if (!IS_ENABLED(CONFIG_SYSCTL) &&
662             !(watchdog_enabled && watchdog_thresh))
663                 return;
664
665         mutex_lock(&watchdog_mutex);
666         __lockup_detector_reconfigure();
667         softlockup_initialized = true;
668         mutex_unlock(&watchdog_mutex);
669 }
670
671 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
672 static void __lockup_detector_reconfigure(void)
673 {
674         cpus_read_lock();
675         watchdog_hardlockup_stop();
676         lockup_detector_update_enable();
677         watchdog_hardlockup_start();
678         cpus_read_unlock();
679 }
680 void lockup_detector_reconfigure(void)
681 {
682         __lockup_detector_reconfigure();
683 }
684 static inline void lockup_detector_setup(void)
685 {
686         __lockup_detector_reconfigure();
687 }
688 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
689
690 static void __lockup_detector_cleanup(void)
691 {
692         lockdep_assert_held(&watchdog_mutex);
693         hardlockup_detector_perf_cleanup();
694 }
695
696 /**
697  * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
698  *
699  * Caller must not hold the cpu hotplug rwsem.
700  */
701 void lockup_detector_cleanup(void)
702 {
703         mutex_lock(&watchdog_mutex);
704         __lockup_detector_cleanup();
705         mutex_unlock(&watchdog_mutex);
706 }
707
708 /**
709  * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
710  *
711  * Special interface for parisc. It prevents lockup detector warnings from
712  * the default pm_poweroff() function which busy loops forever.
713  */
714 void lockup_detector_soft_poweroff(void)
715 {
716         watchdog_enabled = 0;
717 }
718
719 #ifdef CONFIG_SYSCTL
720
721 /* Propagate any changes to the watchdog infrastructure */
722 static void proc_watchdog_update(void)
723 {
724         /* Remove impossible cpus to keep sysctl output clean. */
725         cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
726         __lockup_detector_reconfigure();
727 }
728
729 /*
730  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
731  *
732  * caller             | table->data points to            | 'which'
733  * -------------------|----------------------------------|-------------------------------
734  * proc_watchdog      | watchdog_user_enabled            | WATCHDOG_HARDLOCKUP_ENABLED |
735  *                    |                                  | WATCHDOG_SOFTOCKUP_ENABLED
736  * -------------------|----------------------------------|-------------------------------
737  * proc_nmi_watchdog  | watchdog_hardlockup_user_enabled | WATCHDOG_HARDLOCKUP_ENABLED
738  * -------------------|----------------------------------|-------------------------------
739  * proc_soft_watchdog | watchdog_softlockup_user_enabled | WATCHDOG_SOFTOCKUP_ENABLED
740  */
741 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
742                                 void *buffer, size_t *lenp, loff_t *ppos)
743 {
744         int err, old, *param = table->data;
745
746         mutex_lock(&watchdog_mutex);
747
748         if (!write) {
749                 /*
750                  * On read synchronize the userspace interface. This is a
751                  * racy snapshot.
752                  */
753                 *param = (watchdog_enabled & which) != 0;
754                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
755         } else {
756                 old = READ_ONCE(*param);
757                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
758                 if (!err && old != READ_ONCE(*param))
759                         proc_watchdog_update();
760         }
761         mutex_unlock(&watchdog_mutex);
762         return err;
763 }
764
765 /*
766  * /proc/sys/kernel/watchdog
767  */
768 int proc_watchdog(struct ctl_table *table, int write,
769                   void *buffer, size_t *lenp, loff_t *ppos)
770 {
771         return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED |
772                                     WATCHDOG_SOFTOCKUP_ENABLED,
773                                     table, write, buffer, lenp, ppos);
774 }
775
776 /*
777  * /proc/sys/kernel/nmi_watchdog
778  */
779 int proc_nmi_watchdog(struct ctl_table *table, int write,
780                       void *buffer, size_t *lenp, loff_t *ppos)
781 {
782         if (!watchdog_hardlockup_available && write)
783                 return -ENOTSUPP;
784         return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED,
785                                     table, write, buffer, lenp, ppos);
786 }
787
788 /*
789  * /proc/sys/kernel/soft_watchdog
790  */
791 int proc_soft_watchdog(struct ctl_table *table, int write,
792                         void *buffer, size_t *lenp, loff_t *ppos)
793 {
794         return proc_watchdog_common(WATCHDOG_SOFTOCKUP_ENABLED,
795                                     table, write, buffer, lenp, ppos);
796 }
797
798 /*
799  * /proc/sys/kernel/watchdog_thresh
800  */
801 int proc_watchdog_thresh(struct ctl_table *table, int write,
802                          void *buffer, size_t *lenp, loff_t *ppos)
803 {
804         int err, old;
805
806         mutex_lock(&watchdog_mutex);
807
808         old = READ_ONCE(watchdog_thresh);
809         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
810
811         if (!err && write && old != READ_ONCE(watchdog_thresh))
812                 proc_watchdog_update();
813
814         mutex_unlock(&watchdog_mutex);
815         return err;
816 }
817
818 /*
819  * The cpumask is the mask of possible cpus that the watchdog can run
820  * on, not the mask of cpus it is actually running on.  This allows the
821  * user to specify a mask that will include cpus that have not yet
822  * been brought online, if desired.
823  */
824 int proc_watchdog_cpumask(struct ctl_table *table, int write,
825                           void *buffer, size_t *lenp, loff_t *ppos)
826 {
827         int err;
828
829         mutex_lock(&watchdog_mutex);
830
831         err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
832         if (!err && write)
833                 proc_watchdog_update();
834
835         mutex_unlock(&watchdog_mutex);
836         return err;
837 }
838
839 static const int sixty = 60;
840
841 static struct ctl_table watchdog_sysctls[] = {
842         {
843                 .procname       = "watchdog",
844                 .data           = &watchdog_user_enabled,
845                 .maxlen         = sizeof(int),
846                 .mode           = 0644,
847                 .proc_handler   = proc_watchdog,
848                 .extra1         = SYSCTL_ZERO,
849                 .extra2         = SYSCTL_ONE,
850         },
851         {
852                 .procname       = "watchdog_thresh",
853                 .data           = &watchdog_thresh,
854                 .maxlen         = sizeof(int),
855                 .mode           = 0644,
856                 .proc_handler   = proc_watchdog_thresh,
857                 .extra1         = SYSCTL_ZERO,
858                 .extra2         = (void *)&sixty,
859         },
860         {
861                 .procname       = "watchdog_cpumask",
862                 .data           = &watchdog_cpumask_bits,
863                 .maxlen         = NR_CPUS,
864                 .mode           = 0644,
865                 .proc_handler   = proc_watchdog_cpumask,
866         },
867 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
868         {
869                 .procname       = "soft_watchdog",
870                 .data           = &watchdog_softlockup_user_enabled,
871                 .maxlen         = sizeof(int),
872                 .mode           = 0644,
873                 .proc_handler   = proc_soft_watchdog,
874                 .extra1         = SYSCTL_ZERO,
875                 .extra2         = SYSCTL_ONE,
876         },
877         {
878                 .procname       = "softlockup_panic",
879                 .data           = &softlockup_panic,
880                 .maxlen         = sizeof(int),
881                 .mode           = 0644,
882                 .proc_handler   = proc_dointvec_minmax,
883                 .extra1         = SYSCTL_ZERO,
884                 .extra2         = SYSCTL_ONE,
885         },
886 #ifdef CONFIG_SMP
887         {
888                 .procname       = "softlockup_all_cpu_backtrace",
889                 .data           = &sysctl_softlockup_all_cpu_backtrace,
890                 .maxlen         = sizeof(int),
891                 .mode           = 0644,
892                 .proc_handler   = proc_dointvec_minmax,
893                 .extra1         = SYSCTL_ZERO,
894                 .extra2         = SYSCTL_ONE,
895         },
896 #endif /* CONFIG_SMP */
897 #endif
898 #ifdef CONFIG_HARDLOCKUP_DETECTOR
899         {
900                 .procname       = "hardlockup_panic",
901                 .data           = &hardlockup_panic,
902                 .maxlen         = sizeof(int),
903                 .mode           = 0644,
904                 .proc_handler   = proc_dointvec_minmax,
905                 .extra1         = SYSCTL_ZERO,
906                 .extra2         = SYSCTL_ONE,
907         },
908 #ifdef CONFIG_SMP
909         {
910                 .procname       = "hardlockup_all_cpu_backtrace",
911                 .data           = &sysctl_hardlockup_all_cpu_backtrace,
912                 .maxlen         = sizeof(int),
913                 .mode           = 0644,
914                 .proc_handler   = proc_dointvec_minmax,
915                 .extra1         = SYSCTL_ZERO,
916                 .extra2         = SYSCTL_ONE,
917         },
918 #endif /* CONFIG_SMP */
919 #endif
920         {}
921 };
922
923 static struct ctl_table watchdog_hardlockup_sysctl[] = {
924         {
925                 .procname       = "nmi_watchdog",
926                 .data           = &watchdog_hardlockup_user_enabled,
927                 .maxlen         = sizeof(int),
928                 .mode           = 0444,
929                 .proc_handler   = proc_nmi_watchdog,
930                 .extra1         = SYSCTL_ZERO,
931                 .extra2         = SYSCTL_ONE,
932         },
933         {}
934 };
935
936 static void __init watchdog_sysctl_init(void)
937 {
938         register_sysctl_init("kernel", watchdog_sysctls);
939
940         if (watchdog_hardlockup_available)
941                 watchdog_hardlockup_sysctl[0].mode = 0644;
942         register_sysctl_init("kernel", watchdog_hardlockup_sysctl);
943 }
944
945 #else
946 #define watchdog_sysctl_init() do { } while (0)
947 #endif /* CONFIG_SYSCTL */
948
949 static void __init lockup_detector_delay_init(struct work_struct *work);
950 static bool allow_lockup_detector_init_retry __initdata;
951
952 static struct work_struct detector_work __initdata =
953                 __WORK_INITIALIZER(detector_work, lockup_detector_delay_init);
954
955 static void __init lockup_detector_delay_init(struct work_struct *work)
956 {
957         int ret;
958
959         ret = watchdog_hardlockup_probe();
960         if (ret) {
961                 pr_info("Delayed init of the lockup detector failed: %d\n", ret);
962                 pr_info("Hard watchdog permanently disabled\n");
963                 return;
964         }
965
966         allow_lockup_detector_init_retry = false;
967
968         watchdog_hardlockup_available = true;
969         lockup_detector_setup();
970 }
971
972 /*
973  * lockup_detector_retry_init - retry init lockup detector if possible.
974  *
975  * Retry hardlockup detector init. It is useful when it requires some
976  * functionality that has to be initialized later on a particular
977  * platform.
978  */
979 void __init lockup_detector_retry_init(void)
980 {
981         /* Must be called before late init calls */
982         if (!allow_lockup_detector_init_retry)
983                 return;
984
985         schedule_work(&detector_work);
986 }
987
988 /*
989  * Ensure that optional delayed hardlockup init is proceed before
990  * the init code and memory is freed.
991  */
992 static int __init lockup_detector_check(void)
993 {
994         /* Prevent any later retry. */
995         allow_lockup_detector_init_retry = false;
996
997         /* Make sure no work is pending. */
998         flush_work(&detector_work);
999
1000         watchdog_sysctl_init();
1001
1002         return 0;
1003
1004 }
1005 late_initcall_sync(lockup_detector_check);
1006
1007 void __init lockup_detector_init(void)
1008 {
1009         if (tick_nohz_full_enabled())
1010                 pr_info("Disabling watchdog on nohz_full cores by default\n");
1011
1012         cpumask_copy(&watchdog_cpumask,
1013                      housekeeping_cpumask(HK_TYPE_TIMER));
1014
1015         if (!watchdog_hardlockup_probe())
1016                 watchdog_hardlockup_available = true;
1017         else
1018                 allow_lockup_detector_init_retry = true;
1019
1020         lockup_detector_setup();
1021 }