2 * Detect hard and soft lockups on a system
4 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
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.
12 #define pr_fmt(fmt) "watchdog: " fmt
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>
28 #include <asm/irq_regs.h>
29 #include <linux/kvm_para.h>
30 #include <linux/kthread.h>
32 /* Watchdog configuration */
33 static DEFINE_MUTEX(watchdog_proc_mutex
);
35 int __read_mostly nmi_watchdog_enabled
;
37 #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
38 unsigned long __read_mostly watchdog_enabled
= SOFT_WATCHDOG_ENABLED
|
41 unsigned long __read_mostly watchdog_enabled
= SOFT_WATCHDOG_ENABLED
;
44 #ifdef CONFIG_HARDLOCKUP_DETECTOR
47 * Should we panic when a soft-lockup or hard-lockup occurs:
49 unsigned int __read_mostly hardlockup_panic
=
50 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE
;
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().
59 void hardlockup_detector_disable(void)
61 watchdog_enabled
&= ~NMI_WATCHDOG_ENABLED
;
64 static int __init
hardlockup_panic_setup(char *str
)
66 if (!strncmp(str
, "panic", 5))
68 else if (!strncmp(str
, "nopanic", 7))
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
;
76 __setup("nmi_watchdog=", hardlockup_panic_setup
);
80 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
81 int __read_mostly soft_watchdog_enabled
;
84 int __read_mostly watchdog_user_enabled
;
85 int __read_mostly watchdog_thresh
= 10;
88 int __read_mostly sysctl_softlockup_all_cpu_backtrace
;
89 int __read_mostly sysctl_hardlockup_all_cpu_backtrace
;
91 struct cpumask watchdog_cpumask __read_mostly
;
92 unsigned long *watchdog_cpumask_bits
= cpumask_bits(&watchdog_cpumask
);
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.
99 static int __read_mostly watchdog_running
;
102 * These functions can be overridden if an architecture implements its
103 * own hardlockup detector.
105 * watchdog_nmi_enable/disable can be implemented to start and stop when
106 * softlockup watchdog threads start and stop. The arch must select the
107 * SOFTLOCKUP_DETECTOR Kconfig.
109 int __weak
watchdog_nmi_enable(unsigned int cpu
)
113 void __weak
watchdog_nmi_disable(unsigned int cpu
)
118 * watchdog_nmi_reconfigure can be implemented to be notified after any
119 * watchdog configuration change. The arch hardlockup watchdog should
120 * respond to the following variables:
121 * - nmi_watchdog_enabled
124 * - sysctl_hardlockup_all_cpu_backtrace
127 void __weak
watchdog_nmi_reconfigure(void)
132 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
134 /* Helper for online, unparked cpus. */
135 #define for_each_watchdog_cpu(cpu) \
136 for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
138 atomic_t watchdog_park_in_progress
= ATOMIC_INIT(0);
140 static u64 __read_mostly sample_period
;
142 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts
);
143 static DEFINE_PER_CPU(struct task_struct
*, softlockup_watchdog
);
144 static DEFINE_PER_CPU(struct hrtimer
, watchdog_hrtimer
);
145 static DEFINE_PER_CPU(bool, softlockup_touch_sync
);
146 static DEFINE_PER_CPU(bool, soft_watchdog_warn
);
147 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts
);
148 static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt
);
149 static DEFINE_PER_CPU(struct task_struct
*, softlockup_task_ptr_saved
);
150 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved
);
151 static unsigned long soft_lockup_nmi_warn
;
153 unsigned int __read_mostly softlockup_panic
=
154 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
;
156 static int __init
softlockup_panic_setup(char *str
)
158 softlockup_panic
= simple_strtoul(str
, NULL
, 0);
162 __setup("softlockup_panic=", softlockup_panic_setup
);
164 static int __init
nowatchdog_setup(char *str
)
166 watchdog_enabled
= 0;
169 __setup("nowatchdog", nowatchdog_setup
);
171 static int __init
nosoftlockup_setup(char *str
)
173 watchdog_enabled
&= ~SOFT_WATCHDOG_ENABLED
;
176 __setup("nosoftlockup", nosoftlockup_setup
);
179 static int __init
softlockup_all_cpu_backtrace_setup(char *str
)
181 sysctl_softlockup_all_cpu_backtrace
=
182 !!simple_strtol(str
, NULL
, 0);
185 __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup
);
186 #ifdef CONFIG_HARDLOCKUP_DETECTOR
187 static int __init
hardlockup_all_cpu_backtrace_setup(char *str
)
189 sysctl_hardlockup_all_cpu_backtrace
=
190 !!simple_strtol(str
, NULL
, 0);
193 __setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup
);
198 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
199 * lockups can have false positives under extreme conditions. So we generally
200 * want a higher threshold for soft lockups than for hard lockups. So we couple
201 * the thresholds with a factor: we make the soft threshold twice the amount of
202 * time the hard threshold is.
204 static int get_softlockup_thresh(void)
206 return watchdog_thresh
* 2;
210 * Returns seconds, approximately. We don't need nanosecond
211 * resolution, and we don't need to waste time with a big divide when
214 static unsigned long get_timestamp(void)
216 return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
219 static void set_sample_period(void)
222 * convert watchdog_thresh from seconds to ns
223 * the divide by 5 is to give hrtimer several chances (two
224 * or three with the current relation between the soft
225 * and hard thresholds) to increment before the
226 * hardlockup detector generates a warning
228 sample_period
= get_softlockup_thresh() * ((u64
)NSEC_PER_SEC
/ 5);
229 watchdog_update_hrtimer_threshold(sample_period
);
232 /* Commands for resetting the watchdog */
233 static void __touch_watchdog(void)
235 __this_cpu_write(watchdog_touch_ts
, get_timestamp());
239 * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
241 * Call when the scheduler may have stalled for legitimate reasons
242 * preventing the watchdog task from executing - e.g. the scheduler
243 * entering idle state. This should only be used for scheduler events.
244 * Use touch_softlockup_watchdog() for everything else.
246 void touch_softlockup_watchdog_sched(void)
249 * Preemption can be enabled. It doesn't matter which CPU's timestamp
250 * gets zeroed here, so use the raw_ operation.
252 raw_cpu_write(watchdog_touch_ts
, 0);
255 void touch_softlockup_watchdog(void)
257 touch_softlockup_watchdog_sched();
258 wq_watchdog_touch(raw_smp_processor_id());
260 EXPORT_SYMBOL(touch_softlockup_watchdog
);
262 void touch_all_softlockup_watchdogs(void)
267 * this is done lockless
268 * do we care if a 0 races with a timestamp?
269 * all it means is the softlock check starts one cycle later
271 for_each_watchdog_cpu(cpu
)
272 per_cpu(watchdog_touch_ts
, cpu
) = 0;
273 wq_watchdog_touch(-1);
276 void touch_softlockup_watchdog_sync(void)
278 __this_cpu_write(softlockup_touch_sync
, true);
279 __this_cpu_write(watchdog_touch_ts
, 0);
282 static int is_softlockup(unsigned long touch_ts
)
284 unsigned long now
= get_timestamp();
286 if ((watchdog_enabled
& SOFT_WATCHDOG_ENABLED
) && watchdog_thresh
){
287 /* Warn about unreasonable delays. */
288 if (time_after(now
, touch_ts
+ get_softlockup_thresh()))
289 return now
- touch_ts
;
294 /* watchdog detector functions */
295 bool is_hardlockup(void)
297 unsigned long hrint
= __this_cpu_read(hrtimer_interrupts
);
299 if (__this_cpu_read(hrtimer_interrupts_saved
) == hrint
)
302 __this_cpu_write(hrtimer_interrupts_saved
, hrint
);
306 static void watchdog_interrupt_count(void)
308 __this_cpu_inc(hrtimer_interrupts
);
311 static int watchdog_enable_all_cpus(void);
312 static void watchdog_disable_all_cpus(void);
314 /* watchdog kicker functions */
315 static enum hrtimer_restart
watchdog_timer_fn(struct hrtimer
*hrtimer
)
317 unsigned long touch_ts
= __this_cpu_read(watchdog_touch_ts
);
318 struct pt_regs
*regs
= get_irq_regs();
320 int softlockup_all_cpu_backtrace
= sysctl_softlockup_all_cpu_backtrace
;
322 if (!watchdog_enabled
||
323 atomic_read(&watchdog_park_in_progress
) != 0)
324 return HRTIMER_NORESTART
;
326 /* kick the hardlockup detector */
327 watchdog_interrupt_count();
329 /* kick the softlockup detector */
330 wake_up_process(__this_cpu_read(softlockup_watchdog
));
333 hrtimer_forward_now(hrtimer
, ns_to_ktime(sample_period
));
336 if (unlikely(__this_cpu_read(softlockup_touch_sync
))) {
338 * If the time stamp was touched atomically
339 * make sure the scheduler tick is up to date.
341 __this_cpu_write(softlockup_touch_sync
, false);
345 /* Clear the guest paused flag on watchdog reset */
346 kvm_check_and_clear_guest_paused();
348 return HRTIMER_RESTART
;
351 /* check for a softlockup
352 * This is done by making sure a high priority task is
353 * being scheduled. The task touches the watchdog to
354 * indicate it is getting cpu time. If it hasn't then
355 * this is a good indication some task is hogging the cpu
357 duration
= is_softlockup(touch_ts
);
358 if (unlikely(duration
)) {
360 * If a virtual machine is stopped by the host it can look to
361 * the watchdog like a soft lockup, check to see if the host
362 * stopped the vm before we issue the warning
364 if (kvm_check_and_clear_guest_paused())
365 return HRTIMER_RESTART
;
368 if (__this_cpu_read(soft_watchdog_warn
) == true) {
370 * When multiple processes are causing softlockups the
371 * softlockup detector only warns on the first one
372 * because the code relies on a full quiet cycle to
373 * re-arm. The second process prevents the quiet cycle
374 * and never gets reported. Use task pointers to detect
377 if (__this_cpu_read(softlockup_task_ptr_saved
) !=
379 __this_cpu_write(soft_watchdog_warn
, false);
382 return HRTIMER_RESTART
;
385 if (softlockup_all_cpu_backtrace
) {
386 /* Prevent multiple soft-lockup reports if one cpu is already
387 * engaged in dumping cpu back traces
389 if (test_and_set_bit(0, &soft_lockup_nmi_warn
)) {
390 /* Someone else will report us. Let's give up */
391 __this_cpu_write(soft_watchdog_warn
, true);
392 return HRTIMER_RESTART
;
396 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
397 smp_processor_id(), duration
,
398 current
->comm
, task_pid_nr(current
));
399 __this_cpu_write(softlockup_task_ptr_saved
, current
);
401 print_irqtrace_events(current
);
407 if (softlockup_all_cpu_backtrace
) {
408 /* Avoid generating two back traces for current
409 * given that one is already made above
411 trigger_allbutself_cpu_backtrace();
413 clear_bit(0, &soft_lockup_nmi_warn
);
414 /* Barrier to sync with other cpus */
415 smp_mb__after_atomic();
418 add_taint(TAINT_SOFTLOCKUP
, LOCKDEP_STILL_OK
);
419 if (softlockup_panic
)
420 panic("softlockup: hung tasks");
421 __this_cpu_write(soft_watchdog_warn
, true);
423 __this_cpu_write(soft_watchdog_warn
, false);
425 return HRTIMER_RESTART
;
428 static void watchdog_set_prio(unsigned int policy
, unsigned int prio
)
430 struct sched_param param
= { .sched_priority
= prio
};
432 sched_setscheduler(current
, policy
, ¶m
);
435 static void watchdog_enable(unsigned int cpu
)
437 struct hrtimer
*hrtimer
= raw_cpu_ptr(&watchdog_hrtimer
);
439 /* kick off the timer for the hardlockup detector */
440 hrtimer_init(hrtimer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
441 hrtimer
->function
= watchdog_timer_fn
;
443 /* Enable the perf event */
444 watchdog_nmi_enable(cpu
);
446 /* done here because hrtimer_start can only pin to smp_processor_id() */
447 hrtimer_start(hrtimer
, ns_to_ktime(sample_period
),
448 HRTIMER_MODE_REL_PINNED
);
450 /* initialize timestamp */
451 watchdog_set_prio(SCHED_FIFO
, MAX_RT_PRIO
- 1);
455 static void watchdog_disable(unsigned int cpu
)
457 struct hrtimer
*hrtimer
= raw_cpu_ptr(&watchdog_hrtimer
);
459 watchdog_set_prio(SCHED_NORMAL
, 0);
460 hrtimer_cancel(hrtimer
);
461 /* disable the perf event */
462 watchdog_nmi_disable(cpu
);
465 static void watchdog_cleanup(unsigned int cpu
, bool online
)
467 watchdog_disable(cpu
);
470 static int watchdog_should_run(unsigned int cpu
)
472 return __this_cpu_read(hrtimer_interrupts
) !=
473 __this_cpu_read(soft_lockup_hrtimer_cnt
);
477 * The watchdog thread function - touches the timestamp.
479 * It only runs once every sample_period seconds (4 seconds by
480 * default) to reset the softlockup timestamp. If this gets delayed
481 * for more than 2*watchdog_thresh seconds then the debug-printout
482 * triggers in watchdog_timer_fn().
484 static void watchdog(unsigned int cpu
)
486 __this_cpu_write(soft_lockup_hrtimer_cnt
,
487 __this_cpu_read(hrtimer_interrupts
));
491 * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
492 * failure path. Check for failures that can occur asynchronously -
493 * for example, when CPUs are on-lined - and shut down the hardware
494 * perf event on each CPU accordingly.
496 * The only non-obvious place this bit can be cleared is through
497 * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a
498 * pr_info here would be too noisy as it would result in a message
499 * every few seconds if the hardlockup was disabled but the softlockup
502 if (!(watchdog_enabled
& NMI_WATCHDOG_ENABLED
))
503 watchdog_nmi_disable(cpu
);
506 static struct smp_hotplug_thread watchdog_threads
= {
507 .store
= &softlockup_watchdog
,
508 .thread_should_run
= watchdog_should_run
,
509 .thread_fn
= watchdog
,
510 .thread_comm
= "watchdog/%u",
511 .setup
= watchdog_enable
,
512 .cleanup
= watchdog_cleanup
,
513 .park
= watchdog_disable
,
514 .unpark
= watchdog_enable
,
518 * park all watchdog threads that are specified in 'watchdog_cpumask'
520 * This function returns an error if kthread_park() of a watchdog thread
521 * fails. In this situation, the watchdog threads of some CPUs can already
522 * be parked and the watchdog threads of other CPUs can still be runnable.
523 * Callers are expected to handle this special condition as appropriate in
526 * This function may only be called in a context that is protected against
527 * races with CPU hotplug - for example, via get_online_cpus().
529 static int watchdog_park_threads(void)
533 atomic_set(&watchdog_park_in_progress
, 1);
535 for_each_watchdog_cpu(cpu
) {
536 ret
= kthread_park(per_cpu(softlockup_watchdog
, cpu
));
541 atomic_set(&watchdog_park_in_progress
, 0);
547 * unpark all watchdog threads that are specified in 'watchdog_cpumask'
549 * This function may only be called in a context that is protected against
550 * races with CPU hotplug - for example, via get_online_cpus().
552 static void watchdog_unpark_threads(void)
556 for_each_watchdog_cpu(cpu
)
557 kthread_unpark(per_cpu(softlockup_watchdog
, cpu
));
560 static int update_watchdog_all_cpus(void)
564 ret
= watchdog_park_threads();
568 watchdog_unpark_threads();
573 static int watchdog_enable_all_cpus(void)
577 if (!watchdog_running
) {
578 err
= smpboot_register_percpu_thread_cpumask(&watchdog_threads
,
581 pr_err("Failed to create watchdog threads, disabled\n");
583 watchdog_running
= 1;
586 * Enable/disable the lockup detectors or
587 * change the sample period 'on the fly'.
589 err
= update_watchdog_all_cpus();
592 watchdog_disable_all_cpus();
593 pr_err("Failed to update lockup detectors, disabled\n");
598 watchdog_enabled
= 0;
603 static void watchdog_disable_all_cpus(void)
605 if (watchdog_running
) {
606 watchdog_running
= 0;
607 smpboot_unregister_percpu_thread(&watchdog_threads
);
612 static int watchdog_update_cpus(void)
614 return smpboot_update_cpumask_percpu_thread(
615 &watchdog_threads
, &watchdog_cpumask
);
619 #else /* SOFTLOCKUP */
620 static int watchdog_park_threads(void)
625 static void watchdog_unpark_threads(void)
629 static int watchdog_enable_all_cpus(void)
634 static void watchdog_disable_all_cpus(void)
639 static int watchdog_update_cpus(void)
645 static void set_sample_period(void)
648 #endif /* SOFTLOCKUP */
651 * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
653 * Special interface for parisc. It prevents lockup detector warnings from
654 * the default pm_poweroff() function which busy loops forever.
656 void lockup_detector_soft_poweroff(void)
658 watchdog_enabled
= 0;
664 * Update the run state of the lockup detectors.
666 static int proc_watchdog_update(void)
671 * Watchdog threads won't be started if they are already active.
672 * The 'watchdog_running' variable in watchdog_*_all_cpus() takes
673 * care of this. If those threads are already active, the sample
674 * period will be updated and the lockup detectors will be enabled
675 * or disabled 'on the fly'.
677 if (watchdog_enabled
&& watchdog_thresh
)
678 err
= watchdog_enable_all_cpus();
680 watchdog_disable_all_cpus();
682 watchdog_nmi_reconfigure();
689 * common function for watchdog, nmi_watchdog and soft_watchdog parameter
691 * caller | table->data points to | 'which' contains the flag(s)
692 * -------------------|-----------------------|-----------------------------
693 * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
694 * | | with SOFT_WATCHDOG_ENABLED
695 * -------------------|-----------------------|-----------------------------
696 * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED
697 * -------------------|-----------------------|-----------------------------
698 * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
700 static int proc_watchdog_common(int which
, struct ctl_table
*table
, int write
,
701 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
704 int *watchdog_param
= (int *)table
->data
;
706 cpu_hotplug_disable();
707 mutex_lock(&watchdog_proc_mutex
);
710 * If the parameter is being read return the state of the corresponding
711 * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
712 * run state of the lockup detectors.
715 *watchdog_param
= (watchdog_enabled
& which
) != 0;
716 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
718 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
723 * There is a race window between fetching the current value
724 * from 'watchdog_enabled' and storing the new value. During
725 * this race window, watchdog_nmi_enable() can sneak in and
726 * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
727 * The 'cmpxchg' detects this race and the loop retries.
730 old
= watchdog_enabled
;
732 * If the parameter value is not zero set the
733 * corresponding bit(s), else clear it(them).
739 } while (cmpxchg(&watchdog_enabled
, old
, new) != old
);
742 * Update the run state of the lockup detectors. There is _no_
743 * need to check the value returned by proc_watchdog_update()
744 * and to restore the previous value of 'watchdog_enabled' as
745 * both lockup detectors are disabled if proc_watchdog_update()
751 err
= proc_watchdog_update();
754 mutex_unlock(&watchdog_proc_mutex
);
755 cpu_hotplug_enable();
760 * /proc/sys/kernel/watchdog
762 int proc_watchdog(struct ctl_table
*table
, int write
,
763 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
765 return proc_watchdog_common(NMI_WATCHDOG_ENABLED
|SOFT_WATCHDOG_ENABLED
,
766 table
, write
, buffer
, lenp
, ppos
);
770 * /proc/sys/kernel/nmi_watchdog
772 int proc_nmi_watchdog(struct ctl_table
*table
, int write
,
773 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
775 return proc_watchdog_common(NMI_WATCHDOG_ENABLED
,
776 table
, write
, buffer
, lenp
, ppos
);
780 * /proc/sys/kernel/soft_watchdog
782 int proc_soft_watchdog(struct ctl_table
*table
, int write
,
783 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
785 return proc_watchdog_common(SOFT_WATCHDOG_ENABLED
,
786 table
, write
, buffer
, lenp
, ppos
);
790 * /proc/sys/kernel/watchdog_thresh
792 int proc_watchdog_thresh(struct ctl_table
*table
, int write
,
793 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
797 cpu_hotplug_disable();
798 mutex_lock(&watchdog_proc_mutex
);
800 old
= ACCESS_ONCE(watchdog_thresh
);
801 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
807 * Update the sample period. Restore on failure.
809 new = ACCESS_ONCE(watchdog_thresh
);
814 err
= proc_watchdog_update();
816 watchdog_thresh
= old
;
820 mutex_unlock(&watchdog_proc_mutex
);
821 cpu_hotplug_enable();
826 * The cpumask is the mask of possible cpus that the watchdog can run
827 * on, not the mask of cpus it is actually running on. This allows the
828 * user to specify a mask that will include cpus that have not yet
829 * been brought online, if desired.
831 int proc_watchdog_cpumask(struct ctl_table
*table
, int write
,
832 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
836 cpu_hotplug_disable();
837 mutex_lock(&watchdog_proc_mutex
);
839 err
= proc_do_large_bitmap(table
, write
, buffer
, lenp
, ppos
);
841 /* Remove impossible cpus to keep sysctl output cleaner. */
842 cpumask_and(&watchdog_cpumask
, &watchdog_cpumask
,
845 if (watchdog_running
) {
847 * Failure would be due to being unable to allocate
848 * a temporary cpumask, so we are likely not in a
849 * position to do much else to make things better.
851 if (watchdog_update_cpus() != 0)
852 pr_err("cpumask update failed\n");
855 watchdog_nmi_reconfigure();
858 mutex_unlock(&watchdog_proc_mutex
);
859 cpu_hotplug_enable();
863 #endif /* CONFIG_SYSCTL */
865 void __init
lockup_detector_init(void)
869 #ifdef CONFIG_NO_HZ_FULL
870 if (tick_nohz_full_enabled()) {
871 pr_info("Disabling watchdog on nohz_full cores by default\n");
872 cpumask_copy(&watchdog_cpumask
, housekeeping_mask
);
874 cpumask_copy(&watchdog_cpumask
, cpu_possible_mask
);
876 cpumask_copy(&watchdog_cpumask
, cpu_possible_mask
);
879 if (watchdog_enabled
)
880 watchdog_enable_all_cpus();