06d3389bca0df01c8a730f7b270767f6ed35a8a9
[muen/linux.git] / kernel / watchdog.c
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) "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 <uapi/linux/sched/types.h>
23 #include <linux/tick.h>
24 #include <linux/workqueue.h>
25 #include <linux/sched/clock.h>
26 #include <linux/sched/debug.h>
27
28 #include <asm/irq_regs.h>
29 #include <linux/kvm_para.h>
30 #include <linux/kthread.h>
31
32 /* Watchdog configuration */
33 static DEFINE_MUTEX(watchdog_proc_mutex);
34
35 int __read_mostly nmi_watchdog_enabled;
36
37 #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
38 unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED |
39                                                 NMI_WATCHDOG_ENABLED;
40 #else
41 unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
42 #endif
43
44 #ifdef CONFIG_HARDLOCKUP_DETECTOR
45 /* boot commands */
46 /*
47  * Should we panic when a soft-lockup or hard-lockup occurs:
48  */
49 unsigned int __read_mostly hardlockup_panic =
50                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
51 /*
52  * We may not want to enable hard lockup detection by default in all cases,
53  * for example when running the kernel as a guest on a hypervisor. In these
54  * cases this function can be called to disable hard lockup detection. This
55  * function should only be executed once by the boot processor before the
56  * kernel command line parameters are parsed, because otherwise it is not
57  * possible to override this in hardlockup_panic_setup().
58  */
59 void hardlockup_detector_disable(void)
60 {
61         watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
62 }
63
64 static int __init hardlockup_panic_setup(char *str)
65 {
66         if (!strncmp(str, "panic", 5))
67                 hardlockup_panic = 1;
68         else if (!strncmp(str, "nopanic", 7))
69                 hardlockup_panic = 0;
70         else if (!strncmp(str, "0", 1))
71                 watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
72         else if (!strncmp(str, "1", 1))
73                 watchdog_enabled |= NMI_WATCHDOG_ENABLED;
74         return 1;
75 }
76 __setup("nmi_watchdog=", hardlockup_panic_setup);
77
78 #endif
79
80 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
81 int __read_mostly soft_watchdog_enabled;
82 #endif
83
84 int __read_mostly watchdog_user_enabled;
85 int __read_mostly watchdog_thresh = 10;
86
87 #ifdef CONFIG_SMP
88 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
89 int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
90 #endif
91 struct cpumask watchdog_cpumask __read_mostly;
92 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
93
94 /*
95  * The 'watchdog_running' variable is set to 1 when the watchdog threads
96  * are registered/started and is set to 0 when the watchdog threads are
97  * unregistered/stopped, so it is an indicator whether the threads exist.
98  */
99 static int __read_mostly watchdog_running;
100 /*
101  * If a subsystem has a need to deactivate the watchdog temporarily, it
102  * can use the suspend/resume interface to achieve this. The content of
103  * the 'watchdog_suspended' variable reflects this state. Existing threads
104  * are parked/unparked by the lockup_detector_{suspend|resume} functions
105  * (see comment blocks pertaining to those functions for further details).
106  *
107  * 'watchdog_suspended' also prevents threads from being registered/started
108  * or unregistered/stopped via parameters in /proc/sys/kernel, so the state
109  * of 'watchdog_running' cannot change while the watchdog is deactivated
110  * temporarily (see related code in 'proc' handlers).
111  */
112 int __read_mostly watchdog_suspended;
113
114 /*
115  * These functions can be overridden if an architecture implements its
116  * own hardlockup detector.
117  *
118  * watchdog_nmi_enable/disable can be implemented to start and stop when
119  * softlockup watchdog threads start and stop. The arch must select the
120  * SOFTLOCKUP_DETECTOR Kconfig.
121  */
122 int __weak watchdog_nmi_enable(unsigned int cpu)
123 {
124         return 0;
125 }
126 void __weak watchdog_nmi_disable(unsigned int cpu)
127 {
128 }
129
130 /*
131  * watchdog_nmi_reconfigure can be implemented to be notified after any
132  * watchdog configuration change. The arch hardlockup watchdog should
133  * respond to the following variables:
134  * - nmi_watchdog_enabled
135  * - watchdog_thresh
136  * - watchdog_cpumask
137  * - sysctl_hardlockup_all_cpu_backtrace
138  * - hardlockup_panic
139  * - watchdog_suspended
140  */
141 void __weak watchdog_nmi_reconfigure(void)
142 {
143 }
144
145
146 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
147
148 /* Helper for online, unparked cpus. */
149 #define for_each_watchdog_cpu(cpu) \
150         for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
151
152 atomic_t watchdog_park_in_progress = ATOMIC_INIT(0);
153
154 static u64 __read_mostly sample_period;
155
156 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
157 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
158 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
159 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
160 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
161 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
162 static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
163 static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
164 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
165 static unsigned long soft_lockup_nmi_warn;
166
167 unsigned int __read_mostly softlockup_panic =
168                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
169
170 static int __init softlockup_panic_setup(char *str)
171 {
172         softlockup_panic = simple_strtoul(str, NULL, 0);
173
174         return 1;
175 }
176 __setup("softlockup_panic=", softlockup_panic_setup);
177
178 static int __init nowatchdog_setup(char *str)
179 {
180         watchdog_enabled = 0;
181         return 1;
182 }
183 __setup("nowatchdog", nowatchdog_setup);
184
185 static int __init nosoftlockup_setup(char *str)
186 {
187         watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED;
188         return 1;
189 }
190 __setup("nosoftlockup", nosoftlockup_setup);
191
192 #ifdef CONFIG_SMP
193 static int __init softlockup_all_cpu_backtrace_setup(char *str)
194 {
195         sysctl_softlockup_all_cpu_backtrace =
196                 !!simple_strtol(str, NULL, 0);
197         return 1;
198 }
199 __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
200 #ifdef CONFIG_HARDLOCKUP_DETECTOR
201 static int __init hardlockup_all_cpu_backtrace_setup(char *str)
202 {
203         sysctl_hardlockup_all_cpu_backtrace =
204                 !!simple_strtol(str, NULL, 0);
205         return 1;
206 }
207 __setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
208 #endif
209 #endif
210
211 /*
212  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
213  * lockups can have false positives under extreme conditions. So we generally
214  * want a higher threshold for soft lockups than for hard lockups. So we couple
215  * the thresholds with a factor: we make the soft threshold twice the amount of
216  * time the hard threshold is.
217  */
218 static int get_softlockup_thresh(void)
219 {
220         return watchdog_thresh * 2;
221 }
222
223 /*
224  * Returns seconds, approximately.  We don't need nanosecond
225  * resolution, and we don't need to waste time with a big divide when
226  * 2^30ns == 1.074s.
227  */
228 static unsigned long get_timestamp(void)
229 {
230         return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
231 }
232
233 static void set_sample_period(void)
234 {
235         /*
236          * convert watchdog_thresh from seconds to ns
237          * the divide by 5 is to give hrtimer several chances (two
238          * or three with the current relation between the soft
239          * and hard thresholds) to increment before the
240          * hardlockup detector generates a warning
241          */
242         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
243 }
244
245 /* Commands for resetting the watchdog */
246 static void __touch_watchdog(void)
247 {
248         __this_cpu_write(watchdog_touch_ts, get_timestamp());
249 }
250
251 /**
252  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
253  *
254  * Call when the scheduler may have stalled for legitimate reasons
255  * preventing the watchdog task from executing - e.g. the scheduler
256  * entering idle state.  This should only be used for scheduler events.
257  * Use touch_softlockup_watchdog() for everything else.
258  */
259 void touch_softlockup_watchdog_sched(void)
260 {
261         /*
262          * Preemption can be enabled.  It doesn't matter which CPU's timestamp
263          * gets zeroed here, so use the raw_ operation.
264          */
265         raw_cpu_write(watchdog_touch_ts, 0);
266 }
267
268 void touch_softlockup_watchdog(void)
269 {
270         touch_softlockup_watchdog_sched();
271         wq_watchdog_touch(raw_smp_processor_id());
272 }
273 EXPORT_SYMBOL(touch_softlockup_watchdog);
274
275 void touch_all_softlockup_watchdogs(void)
276 {
277         int cpu;
278
279         /*
280          * this is done lockless
281          * do we care if a 0 races with a timestamp?
282          * all it means is the softlock check starts one cycle later
283          */
284         for_each_watchdog_cpu(cpu)
285                 per_cpu(watchdog_touch_ts, cpu) = 0;
286         wq_watchdog_touch(-1);
287 }
288
289 void touch_softlockup_watchdog_sync(void)
290 {
291         __this_cpu_write(softlockup_touch_sync, true);
292         __this_cpu_write(watchdog_touch_ts, 0);
293 }
294
295 static int is_softlockup(unsigned long touch_ts)
296 {
297         unsigned long now = get_timestamp();
298
299         if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
300                 /* Warn about unreasonable delays. */
301                 if (time_after(now, touch_ts + get_softlockup_thresh()))
302                         return now - touch_ts;
303         }
304         return 0;
305 }
306
307 /* watchdog detector functions */
308 bool is_hardlockup(void)
309 {
310         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
311
312         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
313                 return true;
314
315         __this_cpu_write(hrtimer_interrupts_saved, hrint);
316         return false;
317 }
318
319 static void watchdog_interrupt_count(void)
320 {
321         __this_cpu_inc(hrtimer_interrupts);
322 }
323
324 static int watchdog_enable_all_cpus(void);
325 static void watchdog_disable_all_cpus(void);
326
327 /* watchdog kicker functions */
328 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
329 {
330         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
331         struct pt_regs *regs = get_irq_regs();
332         int duration;
333         int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
334
335         if (atomic_read(&watchdog_park_in_progress) != 0)
336                 return HRTIMER_NORESTART;
337
338         /* kick the hardlockup detector */
339         watchdog_interrupt_count();
340
341         /* kick the softlockup detector */
342         wake_up_process(__this_cpu_read(softlockup_watchdog));
343
344         /* .. and repeat */
345         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
346
347         if (touch_ts == 0) {
348                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
349                         /*
350                          * If the time stamp was touched atomically
351                          * make sure the scheduler tick is up to date.
352                          */
353                         __this_cpu_write(softlockup_touch_sync, false);
354                         sched_clock_tick();
355                 }
356
357                 /* Clear the guest paused flag on watchdog reset */
358                 kvm_check_and_clear_guest_paused();
359                 __touch_watchdog();
360                 return HRTIMER_RESTART;
361         }
362
363         /* check for a softlockup
364          * This is done by making sure a high priority task is
365          * being scheduled.  The task touches the watchdog to
366          * indicate it is getting cpu time.  If it hasn't then
367          * this is a good indication some task is hogging the cpu
368          */
369         duration = is_softlockup(touch_ts);
370         if (unlikely(duration)) {
371                 /*
372                  * If a virtual machine is stopped by the host it can look to
373                  * the watchdog like a soft lockup, check to see if the host
374                  * stopped the vm before we issue the warning
375                  */
376                 if (kvm_check_and_clear_guest_paused())
377                         return HRTIMER_RESTART;
378
379                 /* only warn once */
380                 if (__this_cpu_read(soft_watchdog_warn) == true) {
381                         /*
382                          * When multiple processes are causing softlockups the
383                          * softlockup detector only warns on the first one
384                          * because the code relies on a full quiet cycle to
385                          * re-arm.  The second process prevents the quiet cycle
386                          * and never gets reported.  Use task pointers to detect
387                          * this.
388                          */
389                         if (__this_cpu_read(softlockup_task_ptr_saved) !=
390                             current) {
391                                 __this_cpu_write(soft_watchdog_warn, false);
392                                 __touch_watchdog();
393                         }
394                         return HRTIMER_RESTART;
395                 }
396
397                 if (softlockup_all_cpu_backtrace) {
398                         /* Prevent multiple soft-lockup reports if one cpu is already
399                          * engaged in dumping cpu back traces
400                          */
401                         if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
402                                 /* Someone else will report us. Let's give up */
403                                 __this_cpu_write(soft_watchdog_warn, true);
404                                 return HRTIMER_RESTART;
405                         }
406                 }
407
408                 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
409                         smp_processor_id(), duration,
410                         current->comm, task_pid_nr(current));
411                 __this_cpu_write(softlockup_task_ptr_saved, current);
412                 print_modules();
413                 print_irqtrace_events(current);
414                 if (regs)
415                         show_regs(regs);
416                 else
417                         dump_stack();
418
419                 if (softlockup_all_cpu_backtrace) {
420                         /* Avoid generating two back traces for current
421                          * given that one is already made above
422                          */
423                         trigger_allbutself_cpu_backtrace();
424
425                         clear_bit(0, &soft_lockup_nmi_warn);
426                         /* Barrier to sync with other cpus */
427                         smp_mb__after_atomic();
428                 }
429
430                 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
431                 if (softlockup_panic)
432                         panic("softlockup: hung tasks");
433                 __this_cpu_write(soft_watchdog_warn, true);
434         } else
435                 __this_cpu_write(soft_watchdog_warn, false);
436
437         return HRTIMER_RESTART;
438 }
439
440 static void watchdog_set_prio(unsigned int policy, unsigned int prio)
441 {
442         struct sched_param param = { .sched_priority = prio };
443
444         sched_setscheduler(current, policy, &param);
445 }
446
447 static void watchdog_enable(unsigned int cpu)
448 {
449         struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
450
451         /* kick off the timer for the hardlockup detector */
452         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
453         hrtimer->function = watchdog_timer_fn;
454
455         /* Enable the perf event */
456         watchdog_nmi_enable(cpu);
457
458         /* done here because hrtimer_start can only pin to smp_processor_id() */
459         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
460                       HRTIMER_MODE_REL_PINNED);
461
462         /* initialize timestamp */
463         watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
464         __touch_watchdog();
465 }
466
467 static void watchdog_disable(unsigned int cpu)
468 {
469         struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
470
471         watchdog_set_prio(SCHED_NORMAL, 0);
472         hrtimer_cancel(hrtimer);
473         /* disable the perf event */
474         watchdog_nmi_disable(cpu);
475 }
476
477 static void watchdog_cleanup(unsigned int cpu, bool online)
478 {
479         watchdog_disable(cpu);
480 }
481
482 static int watchdog_should_run(unsigned int cpu)
483 {
484         return __this_cpu_read(hrtimer_interrupts) !=
485                 __this_cpu_read(soft_lockup_hrtimer_cnt);
486 }
487
488 /*
489  * The watchdog thread function - touches the timestamp.
490  *
491  * It only runs once every sample_period seconds (4 seconds by
492  * default) to reset the softlockup timestamp. If this gets delayed
493  * for more than 2*watchdog_thresh seconds then the debug-printout
494  * triggers in watchdog_timer_fn().
495  */
496 static void watchdog(unsigned int cpu)
497 {
498         __this_cpu_write(soft_lockup_hrtimer_cnt,
499                          __this_cpu_read(hrtimer_interrupts));
500         __touch_watchdog();
501
502         /*
503          * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
504          * failure path. Check for failures that can occur asynchronously -
505          * for example, when CPUs are on-lined - and shut down the hardware
506          * perf event on each CPU accordingly.
507          *
508          * The only non-obvious place this bit can be cleared is through
509          * watchdog_nmi_enable(), so a pr_info() is placed there.  Placing a
510          * pr_info here would be too noisy as it would result in a message
511          * every few seconds if the hardlockup was disabled but the softlockup
512          * enabled.
513          */
514         if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
515                 watchdog_nmi_disable(cpu);
516 }
517
518 static struct smp_hotplug_thread watchdog_threads = {
519         .store                  = &softlockup_watchdog,
520         .thread_should_run      = watchdog_should_run,
521         .thread_fn              = watchdog,
522         .thread_comm            = "watchdog/%u",
523         .setup                  = watchdog_enable,
524         .cleanup                = watchdog_cleanup,
525         .park                   = watchdog_disable,
526         .unpark                 = watchdog_enable,
527 };
528
529 /*
530  * park all watchdog threads that are specified in 'watchdog_cpumask'
531  *
532  * This function returns an error if kthread_park() of a watchdog thread
533  * fails. In this situation, the watchdog threads of some CPUs can already
534  * be parked and the watchdog threads of other CPUs can still be runnable.
535  * Callers are expected to handle this special condition as appropriate in
536  * their context.
537  *
538  * This function may only be called in a context that is protected against
539  * races with CPU hotplug - for example, via get_online_cpus().
540  */
541 static int watchdog_park_threads(void)
542 {
543         int cpu, ret = 0;
544
545         atomic_set(&watchdog_park_in_progress, 1);
546
547         for_each_watchdog_cpu(cpu) {
548                 ret = kthread_park(per_cpu(softlockup_watchdog, cpu));
549                 if (ret)
550                         break;
551         }
552
553         atomic_set(&watchdog_park_in_progress, 0);
554
555         return ret;
556 }
557
558 /*
559  * unpark all watchdog threads that are specified in 'watchdog_cpumask'
560  *
561  * This function may only be called in a context that is protected against
562  * races with CPU hotplug - for example, via get_online_cpus().
563  */
564 static void watchdog_unpark_threads(void)
565 {
566         int cpu;
567
568         for_each_watchdog_cpu(cpu)
569                 kthread_unpark(per_cpu(softlockup_watchdog, cpu));
570 }
571
572 static int update_watchdog_all_cpus(void)
573 {
574         int ret;
575
576         ret = watchdog_park_threads();
577         if (ret)
578                 return ret;
579
580         watchdog_unpark_threads();
581
582         return 0;
583 }
584
585 static int watchdog_enable_all_cpus(void)
586 {
587         int err = 0;
588
589         if (!watchdog_running) {
590                 err = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
591                                                              &watchdog_cpumask);
592                 if (err)
593                         pr_err("Failed to create watchdog threads, disabled\n");
594                 else
595                         watchdog_running = 1;
596         } else {
597                 /*
598                  * Enable/disable the lockup detectors or
599                  * change the sample period 'on the fly'.
600                  */
601                 err = update_watchdog_all_cpus();
602
603                 if (err) {
604                         watchdog_disable_all_cpus();
605                         pr_err("Failed to update lockup detectors, disabled\n");
606                 }
607         }
608
609         if (err)
610                 watchdog_enabled = 0;
611
612         return err;
613 }
614
615 static void watchdog_disable_all_cpus(void)
616 {
617         if (watchdog_running) {
618                 watchdog_running = 0;
619                 smpboot_unregister_percpu_thread(&watchdog_threads);
620         }
621 }
622
623 #ifdef CONFIG_SYSCTL
624 static int watchdog_update_cpus(void)
625 {
626         return smpboot_update_cpumask_percpu_thread(
627                     &watchdog_threads, &watchdog_cpumask);
628 }
629 #endif
630
631 #else /* SOFTLOCKUP */
632 static int watchdog_park_threads(void)
633 {
634         return 0;
635 }
636
637 static void watchdog_unpark_threads(void)
638 {
639 }
640
641 static int watchdog_enable_all_cpus(void)
642 {
643         return 0;
644 }
645
646 static void watchdog_disable_all_cpus(void)
647 {
648 }
649
650 #ifdef CONFIG_SYSCTL
651 static int watchdog_update_cpus(void)
652 {
653         return 0;
654 }
655 #endif
656
657 static void set_sample_period(void)
658 {
659 }
660 #endif /* SOFTLOCKUP */
661
662 /*
663  * Suspend the hard and soft lockup detector by parking the watchdog threads.
664  */
665 int lockup_detector_suspend(void)
666 {
667         int ret = 0;
668
669         get_online_cpus();
670         mutex_lock(&watchdog_proc_mutex);
671         /*
672          * Multiple suspend requests can be active in parallel (counted by
673          * the 'watchdog_suspended' variable). If the watchdog threads are
674          * running, the first caller takes care that they will be parked.
675          * The state of 'watchdog_running' cannot change while a suspend
676          * request is active (see related code in 'proc' handlers).
677          */
678         if (watchdog_running && !watchdog_suspended)
679                 ret = watchdog_park_threads();
680
681         if (ret == 0)
682                 watchdog_suspended++;
683         else {
684                 watchdog_disable_all_cpus();
685                 pr_err("Failed to suspend lockup detectors, disabled\n");
686                 watchdog_enabled = 0;
687         }
688
689         watchdog_nmi_reconfigure();
690
691         mutex_unlock(&watchdog_proc_mutex);
692
693         return ret;
694 }
695
696 /*
697  * Resume the hard and soft lockup detector by unparking the watchdog threads.
698  */
699 void lockup_detector_resume(void)
700 {
701         mutex_lock(&watchdog_proc_mutex);
702
703         watchdog_suspended--;
704         /*
705          * The watchdog threads are unparked if they were previously running
706          * and if there is no more active suspend request.
707          */
708         if (watchdog_running && !watchdog_suspended)
709                 watchdog_unpark_threads();
710
711         watchdog_nmi_reconfigure();
712
713         mutex_unlock(&watchdog_proc_mutex);
714         put_online_cpus();
715 }
716
717 #ifdef CONFIG_SYSCTL
718
719 /*
720  * Update the run state of the lockup detectors.
721  */
722 static int proc_watchdog_update(void)
723 {
724         int err = 0;
725
726         /*
727          * Watchdog threads won't be started if they are already active.
728          * The 'watchdog_running' variable in watchdog_*_all_cpus() takes
729          * care of this. If those threads are already active, the sample
730          * period will be updated and the lockup detectors will be enabled
731          * or disabled 'on the fly'.
732          */
733         if (watchdog_enabled && watchdog_thresh)
734                 err = watchdog_enable_all_cpus();
735         else
736                 watchdog_disable_all_cpus();
737
738         watchdog_nmi_reconfigure();
739
740         return err;
741
742 }
743
744 /*
745  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
746  *
747  * caller             | table->data points to | 'which' contains the flag(s)
748  * -------------------|-----------------------|-----------------------------
749  * proc_watchdog      | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
750  *                    |                       | with SOFT_WATCHDOG_ENABLED
751  * -------------------|-----------------------|-----------------------------
752  * proc_nmi_watchdog  | nmi_watchdog_enabled  | NMI_WATCHDOG_ENABLED
753  * -------------------|-----------------------|-----------------------------
754  * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
755  */
756 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
757                                 void __user *buffer, size_t *lenp, loff_t *ppos)
758 {
759         int err, old, new;
760         int *watchdog_param = (int *)table->data;
761
762         get_online_cpus();
763         mutex_lock(&watchdog_proc_mutex);
764
765         if (watchdog_suspended) {
766                 /* no parameter changes allowed while watchdog is suspended */
767                 err = -EAGAIN;
768                 goto out;
769         }
770
771         /*
772          * If the parameter is being read return the state of the corresponding
773          * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
774          * run state of the lockup detectors.
775          */
776         if (!write) {
777                 *watchdog_param = (watchdog_enabled & which) != 0;
778                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
779         } else {
780                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
781                 if (err)
782                         goto out;
783
784                 /*
785                  * There is a race window between fetching the current value
786                  * from 'watchdog_enabled' and storing the new value. During
787                  * this race window, watchdog_nmi_enable() can sneak in and
788                  * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
789                  * The 'cmpxchg' detects this race and the loop retries.
790                  */
791                 do {
792                         old = watchdog_enabled;
793                         /*
794                          * If the parameter value is not zero set the
795                          * corresponding bit(s), else clear it(them).
796                          */
797                         if (*watchdog_param)
798                                 new = old | which;
799                         else
800                                 new = old & ~which;
801                 } while (cmpxchg(&watchdog_enabled, old, new) != old);
802
803                 /*
804                  * Update the run state of the lockup detectors. There is _no_
805                  * need to check the value returned by proc_watchdog_update()
806                  * and to restore the previous value of 'watchdog_enabled' as
807                  * both lockup detectors are disabled if proc_watchdog_update()
808                  * returns an error.
809                  */
810                 if (old == new)
811                         goto out;
812
813                 err = proc_watchdog_update();
814         }
815 out:
816         mutex_unlock(&watchdog_proc_mutex);
817         put_online_cpus();
818         return err;
819 }
820
821 /*
822  * /proc/sys/kernel/watchdog
823  */
824 int proc_watchdog(struct ctl_table *table, int write,
825                   void __user *buffer, size_t *lenp, loff_t *ppos)
826 {
827         return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
828                                     table, write, buffer, lenp, ppos);
829 }
830
831 /*
832  * /proc/sys/kernel/nmi_watchdog
833  */
834 int proc_nmi_watchdog(struct ctl_table *table, int write,
835                       void __user *buffer, size_t *lenp, loff_t *ppos)
836 {
837         return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
838                                     table, write, buffer, lenp, ppos);
839 }
840
841 /*
842  * /proc/sys/kernel/soft_watchdog
843  */
844 int proc_soft_watchdog(struct ctl_table *table, int write,
845                         void __user *buffer, size_t *lenp, loff_t *ppos)
846 {
847         return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
848                                     table, write, buffer, lenp, ppos);
849 }
850
851 /*
852  * /proc/sys/kernel/watchdog_thresh
853  */
854 int proc_watchdog_thresh(struct ctl_table *table, int write,
855                          void __user *buffer, size_t *lenp, loff_t *ppos)
856 {
857         int err, old, new;
858
859         get_online_cpus();
860         mutex_lock(&watchdog_proc_mutex);
861
862         if (watchdog_suspended) {
863                 /* no parameter changes allowed while watchdog is suspended */
864                 err = -EAGAIN;
865                 goto out;
866         }
867
868         old = ACCESS_ONCE(watchdog_thresh);
869         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
870
871         if (err || !write)
872                 goto out;
873
874         /*
875          * Update the sample period. Restore on failure.
876          */
877         new = ACCESS_ONCE(watchdog_thresh);
878         if (old == new)
879                 goto out;
880
881         set_sample_period();
882         err = proc_watchdog_update();
883         if (err) {
884                 watchdog_thresh = old;
885                 set_sample_period();
886         }
887 out:
888         mutex_unlock(&watchdog_proc_mutex);
889         put_online_cpus();
890         return err;
891 }
892
893 /*
894  * The cpumask is the mask of possible cpus that the watchdog can run
895  * on, not the mask of cpus it is actually running on.  This allows the
896  * user to specify a mask that will include cpus that have not yet
897  * been brought online, if desired.
898  */
899 int proc_watchdog_cpumask(struct ctl_table *table, int write,
900                           void __user *buffer, size_t *lenp, loff_t *ppos)
901 {
902         int err;
903
904         get_online_cpus();
905         mutex_lock(&watchdog_proc_mutex);
906
907         if (watchdog_suspended) {
908                 /* no parameter changes allowed while watchdog is suspended */
909                 err = -EAGAIN;
910                 goto out;
911         }
912
913         err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
914         if (!err && write) {
915                 /* Remove impossible cpus to keep sysctl output cleaner. */
916                 cpumask_and(&watchdog_cpumask, &watchdog_cpumask,
917                             cpu_possible_mask);
918
919                 if (watchdog_running) {
920                         /*
921                          * Failure would be due to being unable to allocate
922                          * a temporary cpumask, so we are likely not in a
923                          * position to do much else to make things better.
924                          */
925                         if (watchdog_update_cpus() != 0)
926                                 pr_err("cpumask update failed\n");
927                 }
928
929                 watchdog_nmi_reconfigure();
930         }
931 out:
932         mutex_unlock(&watchdog_proc_mutex);
933         put_online_cpus();
934         return err;
935 }
936
937 #endif /* CONFIG_SYSCTL */
938
939 void __init lockup_detector_init(void)
940 {
941         set_sample_period();
942
943 #ifdef CONFIG_NO_HZ_FULL
944         if (tick_nohz_full_enabled()) {
945                 pr_info("Disabling watchdog on nohz_full cores by default\n");
946                 cpumask_copy(&watchdog_cpumask, housekeeping_mask);
947         } else
948                 cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
949 #else
950         cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
951 #endif
952
953         if (watchdog_enabled)
954                 watchdog_enable_all_cpus();
955 }