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 static DEFINE_MUTEX(watchdog_mutex
);
34 #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
35 # define WATCHDOG_DEFAULT (SOFT_WATCHDOG_ENABLED | NMI_WATCHDOG_ENABLED)
36 # define NMI_WATCHDOG_DEFAULT 1
38 # define WATCHDOG_DEFAULT (SOFT_WATCHDOG_ENABLED)
39 # define NMI_WATCHDOG_DEFAULT 0
42 unsigned long __read_mostly watchdog_enabled
;
43 int __read_mostly watchdog_user_enabled
= 1;
44 int __read_mostly nmi_watchdog_user_enabled
= NMI_WATCHDOG_DEFAULT
;
45 int __read_mostly soft_watchdog_user_enabled
= 1;
46 int __read_mostly watchdog_thresh
= 10;
48 struct cpumask watchdog_allowed_mask __read_mostly
;
49 static bool softlockup_threads_initialized __read_mostly
;
51 struct cpumask watchdog_cpumask __read_mostly
;
52 unsigned long *watchdog_cpumask_bits
= cpumask_bits(&watchdog_cpumask
);
54 #ifdef CONFIG_HARDLOCKUP_DETECTOR
56 * Should we panic when a soft-lockup or hard-lockup occurs:
58 unsigned int __read_mostly hardlockup_panic
=
59 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE
;
61 * We may not want to enable hard lockup detection by default in all cases,
62 * for example when running the kernel as a guest on a hypervisor. In these
63 * cases this function can be called to disable hard lockup detection. This
64 * function should only be executed once by the boot processor before the
65 * kernel command line parameters are parsed, because otherwise it is not
66 * possible to override this in hardlockup_panic_setup().
68 void __init
hardlockup_detector_disable(void)
70 nmi_watchdog_user_enabled
= 0;
73 static int __init
hardlockup_panic_setup(char *str
)
75 if (!strncmp(str
, "panic", 5))
77 else if (!strncmp(str
, "nopanic", 7))
79 else if (!strncmp(str
, "0", 1))
80 nmi_watchdog_user_enabled
= 0;
81 else if (!strncmp(str
, "1", 1))
82 nmi_watchdog_user_enabled
= 1;
85 __setup("nmi_watchdog=", hardlockup_panic_setup
);
88 int __read_mostly sysctl_hardlockup_all_cpu_backtrace
;
90 static int __init
hardlockup_all_cpu_backtrace_setup(char *str
)
92 sysctl_hardlockup_all_cpu_backtrace
= !!simple_strtol(str
, NULL
, 0);
95 __setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup
);
96 # endif /* CONFIG_SMP */
97 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
100 * These functions can be overridden if an architecture implements its
101 * own hardlockup detector.
103 * watchdog_nmi_enable/disable can be implemented to start and stop when
104 * softlockup watchdog threads start and stop. The arch must select the
105 * SOFTLOCKUP_DETECTOR Kconfig.
107 int __weak
watchdog_nmi_enable(unsigned int cpu
)
112 void __weak
watchdog_nmi_disable(unsigned int cpu
)
114 hardlockup_detector_perf_disable();
118 * watchdog_nmi_reconfigure - Optional function to reconfigure NMI watchdogs
119 * @run: If false stop the watchdogs on all enabled CPUs
120 * If true start the watchdogs on all enabled CPUs
122 * The core call order is:
123 * watchdog_nmi_reconfigure(false);
124 * update_variables();
125 * watchdog_nmi_reconfigure(true);
127 * The second call which starts the watchdogs again guarantees that the
128 * following variables are stable across the call.
133 * After the call the variables can be changed again.
135 void __weak
watchdog_nmi_reconfigure(bool run
) { }
138 * lockup_detector_update_enable - Update the sysctl enable bit
140 * Caller needs to make sure that the NMI/perf watchdogs are off, so this
141 * can't race with watchdog_nmi_disable().
143 static void lockup_detector_update_enable(void)
145 watchdog_enabled
= 0;
146 if (!watchdog_user_enabled
)
148 if (nmi_watchdog_user_enabled
)
149 watchdog_enabled
|= NMI_WATCHDOG_ENABLED
;
150 if (soft_watchdog_user_enabled
)
151 watchdog_enabled
|= SOFT_WATCHDOG_ENABLED
;
154 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
156 /* Global variables, exported for sysctl */
157 unsigned int __read_mostly softlockup_panic
=
158 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
;
160 static u64 __read_mostly sample_period
;
162 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts
);
163 static DEFINE_PER_CPU(struct task_struct
*, softlockup_watchdog
);
164 static DEFINE_PER_CPU(struct hrtimer
, watchdog_hrtimer
);
165 static DEFINE_PER_CPU(bool, softlockup_touch_sync
);
166 static DEFINE_PER_CPU(bool, soft_watchdog_warn
);
167 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts
);
168 static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt
);
169 static DEFINE_PER_CPU(struct task_struct
*, softlockup_task_ptr_saved
);
170 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved
);
171 static unsigned long soft_lockup_nmi_warn
;
173 static int __init
softlockup_panic_setup(char *str
)
175 softlockup_panic
= simple_strtoul(str
, NULL
, 0);
178 __setup("softlockup_panic=", softlockup_panic_setup
);
180 static int __init
nowatchdog_setup(char *str
)
182 watchdog_user_enabled
= 0;
185 __setup("nowatchdog", nowatchdog_setup
);
187 static int __init
nosoftlockup_setup(char *str
)
189 soft_watchdog_user_enabled
= 0;
192 __setup("nosoftlockup", nosoftlockup_setup
);
195 int __read_mostly sysctl_softlockup_all_cpu_backtrace
;
197 static int __init
softlockup_all_cpu_backtrace_setup(char *str
)
199 sysctl_softlockup_all_cpu_backtrace
= !!simple_strtol(str
, NULL
, 0);
202 __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup
);
205 static void __lockup_detector_cleanup(void);
208 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
209 * lockups can have false positives under extreme conditions. So we generally
210 * want a higher threshold for soft lockups than for hard lockups. So we couple
211 * the thresholds with a factor: we make the soft threshold twice the amount of
212 * time the hard threshold is.
214 static int get_softlockup_thresh(void)
216 return watchdog_thresh
* 2;
220 * Returns seconds, approximately. We don't need nanosecond
221 * resolution, and we don't need to waste time with a big divide when
224 static unsigned long get_timestamp(void)
226 return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
229 static void set_sample_period(void)
232 * convert watchdog_thresh from seconds to ns
233 * the divide by 5 is to give hrtimer several chances (two
234 * or three with the current relation between the soft
235 * and hard thresholds) to increment before the
236 * hardlockup detector generates a warning
238 sample_period
= get_softlockup_thresh() * ((u64
)NSEC_PER_SEC
/ 5);
239 watchdog_update_hrtimer_threshold(sample_period
);
242 /* Commands for resetting the watchdog */
243 static void __touch_watchdog(void)
245 __this_cpu_write(watchdog_touch_ts
, get_timestamp());
249 * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
251 * Call when the scheduler may have stalled for legitimate reasons
252 * preventing the watchdog task from executing - e.g. the scheduler
253 * entering idle state. This should only be used for scheduler events.
254 * Use touch_softlockup_watchdog() for everything else.
256 void touch_softlockup_watchdog_sched(void)
259 * Preemption can be enabled. It doesn't matter which CPU's timestamp
260 * gets zeroed here, so use the raw_ operation.
262 raw_cpu_write(watchdog_touch_ts
, 0);
265 void touch_softlockup_watchdog(void)
267 touch_softlockup_watchdog_sched();
268 wq_watchdog_touch(raw_smp_processor_id());
270 EXPORT_SYMBOL(touch_softlockup_watchdog
);
272 void touch_all_softlockup_watchdogs(void)
277 * watchdog_mutex cannpt be taken here, as this might be called
278 * from (soft)interrupt context, so the access to
279 * watchdog_allowed_cpumask might race with a concurrent update.
281 * The watchdog time stamp can race against a concurrent real
282 * update as well, the only side effect might be a cycle delay for
283 * the softlockup check.
285 for_each_cpu(cpu
, &watchdog_allowed_mask
)
286 per_cpu(watchdog_touch_ts
, cpu
) = 0;
287 wq_watchdog_touch(-1);
290 void touch_softlockup_watchdog_sync(void)
292 __this_cpu_write(softlockup_touch_sync
, true);
293 __this_cpu_write(watchdog_touch_ts
, 0);
296 static int is_softlockup(unsigned long touch_ts
)
298 unsigned long now
= get_timestamp();
300 if ((watchdog_enabled
& SOFT_WATCHDOG_ENABLED
) && watchdog_thresh
){
301 /* Warn about unreasonable delays. */
302 if (time_after(now
, touch_ts
+ get_softlockup_thresh()))
303 return now
- touch_ts
;
308 /* watchdog detector functions */
309 bool is_hardlockup(void)
311 unsigned long hrint
= __this_cpu_read(hrtimer_interrupts
);
313 if (__this_cpu_read(hrtimer_interrupts_saved
) == hrint
)
316 __this_cpu_write(hrtimer_interrupts_saved
, hrint
);
320 static void watchdog_interrupt_count(void)
322 __this_cpu_inc(hrtimer_interrupts
);
325 /* watchdog kicker functions */
326 static enum hrtimer_restart
watchdog_timer_fn(struct hrtimer
*hrtimer
)
328 unsigned long touch_ts
= __this_cpu_read(watchdog_touch_ts
);
329 struct pt_regs
*regs
= get_irq_regs();
331 int softlockup_all_cpu_backtrace
= sysctl_softlockup_all_cpu_backtrace
;
333 if (!watchdog_enabled
)
334 return HRTIMER_NORESTART
;
336 /* kick the hardlockup detector */
337 watchdog_interrupt_count();
339 /* kick the softlockup detector */
340 wake_up_process(__this_cpu_read(softlockup_watchdog
));
343 hrtimer_forward_now(hrtimer
, ns_to_ktime(sample_period
));
346 if (unlikely(__this_cpu_read(softlockup_touch_sync
))) {
348 * If the time stamp was touched atomically
349 * make sure the scheduler tick is up to date.
351 __this_cpu_write(softlockup_touch_sync
, false);
355 /* Clear the guest paused flag on watchdog reset */
356 kvm_check_and_clear_guest_paused();
358 return HRTIMER_RESTART
;
361 /* check for a softlockup
362 * This is done by making sure a high priority task is
363 * being scheduled. The task touches the watchdog to
364 * indicate it is getting cpu time. If it hasn't then
365 * this is a good indication some task is hogging the cpu
367 duration
= is_softlockup(touch_ts
);
368 if (unlikely(duration
)) {
370 * If a virtual machine is stopped by the host it can look to
371 * the watchdog like a soft lockup, check to see if the host
372 * stopped the vm before we issue the warning
374 if (kvm_check_and_clear_guest_paused())
375 return HRTIMER_RESTART
;
378 if (__this_cpu_read(soft_watchdog_warn
) == true) {
380 * When multiple processes are causing softlockups the
381 * softlockup detector only warns on the first one
382 * because the code relies on a full quiet cycle to
383 * re-arm. The second process prevents the quiet cycle
384 * and never gets reported. Use task pointers to detect
387 if (__this_cpu_read(softlockup_task_ptr_saved
) !=
389 __this_cpu_write(soft_watchdog_warn
, false);
392 return HRTIMER_RESTART
;
395 if (softlockup_all_cpu_backtrace
) {
396 /* Prevent multiple soft-lockup reports if one cpu is already
397 * engaged in dumping cpu back traces
399 if (test_and_set_bit(0, &soft_lockup_nmi_warn
)) {
400 /* Someone else will report us. Let's give up */
401 __this_cpu_write(soft_watchdog_warn
, true);
402 return HRTIMER_RESTART
;
406 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
407 smp_processor_id(), duration
,
408 current
->comm
, task_pid_nr(current
));
409 __this_cpu_write(softlockup_task_ptr_saved
, current
);
411 print_irqtrace_events(current
);
417 if (softlockup_all_cpu_backtrace
) {
418 /* Avoid generating two back traces for current
419 * given that one is already made above
421 trigger_allbutself_cpu_backtrace();
423 clear_bit(0, &soft_lockup_nmi_warn
);
424 /* Barrier to sync with other cpus */
425 smp_mb__after_atomic();
428 add_taint(TAINT_SOFTLOCKUP
, LOCKDEP_STILL_OK
);
429 if (softlockup_panic
)
430 panic("softlockup: hung tasks");
431 __this_cpu_write(soft_watchdog_warn
, true);
433 __this_cpu_write(soft_watchdog_warn
, false);
435 return HRTIMER_RESTART
;
438 static void watchdog_set_prio(unsigned int policy
, unsigned int prio
)
440 struct sched_param param
= { .sched_priority
= prio
};
442 sched_setscheduler(current
, policy
, ¶m
);
445 static void watchdog_enable(unsigned int cpu
)
447 struct hrtimer
*hrtimer
= this_cpu_ptr(&watchdog_hrtimer
);
450 * Start the timer first to prevent the NMI watchdog triggering
451 * before the timer has a chance to fire.
453 hrtimer_init(hrtimer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
454 hrtimer
->function
= watchdog_timer_fn
;
455 hrtimer_start(hrtimer
, ns_to_ktime(sample_period
),
456 HRTIMER_MODE_REL_PINNED
);
458 /* Initialize timestamp */
460 /* Enable the perf event */
461 watchdog_nmi_enable(cpu
);
463 watchdog_set_prio(SCHED_FIFO
, MAX_RT_PRIO
- 1);
466 static void watchdog_disable(unsigned int cpu
)
468 struct hrtimer
*hrtimer
= this_cpu_ptr(&watchdog_hrtimer
);
470 watchdog_set_prio(SCHED_NORMAL
, 0);
472 * Disable the perf event first. That prevents that a large delay
473 * between disabling the timer and disabling the perf event causes
474 * the perf NMI to detect a false positive.
476 watchdog_nmi_disable(cpu
);
477 hrtimer_cancel(hrtimer
);
480 static void watchdog_cleanup(unsigned int cpu
, bool online
)
482 watchdog_disable(cpu
);
485 static int watchdog_should_run(unsigned int cpu
)
487 return __this_cpu_read(hrtimer_interrupts
) !=
488 __this_cpu_read(soft_lockup_hrtimer_cnt
);
492 * The watchdog thread function - touches the timestamp.
494 * It only runs once every sample_period seconds (4 seconds by
495 * default) to reset the softlockup timestamp. If this gets delayed
496 * for more than 2*watchdog_thresh seconds then the debug-printout
497 * triggers in watchdog_timer_fn().
499 static void watchdog(unsigned int cpu
)
501 __this_cpu_write(soft_lockup_hrtimer_cnt
,
502 __this_cpu_read(hrtimer_interrupts
));
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
,
517 static void softlockup_update_smpboot_threads(void)
519 lockdep_assert_held(&watchdog_mutex
);
521 if (!softlockup_threads_initialized
)
524 smpboot_update_cpumask_percpu_thread(&watchdog_threads
,
525 &watchdog_allowed_mask
);
526 __lockup_detector_cleanup();
529 /* Temporarily park all watchdog threads */
530 static void softlockup_park_all_threads(void)
532 cpumask_clear(&watchdog_allowed_mask
);
533 softlockup_update_smpboot_threads();
536 /* Unpark enabled threads */
537 static void softlockup_unpark_threads(void)
539 cpumask_copy(&watchdog_allowed_mask
, &watchdog_cpumask
);
540 softlockup_update_smpboot_threads();
543 static void softlockup_reconfigure_threads(void)
545 watchdog_nmi_reconfigure(false);
546 softlockup_park_all_threads();
548 lockup_detector_update_enable();
549 if (watchdog_enabled
&& watchdog_thresh
)
550 softlockup_unpark_threads();
551 watchdog_nmi_reconfigure(true);
555 * Create the watchdog thread infrastructure.
557 * The threads are not unparked as watchdog_allowed_mask is empty. When
558 * the threads are sucessfully initialized, take the proper locks and
559 * unpark the threads in the watchdog_cpumask if the watchdog is enabled.
561 static __init
void softlockup_init_threads(void)
566 * If sysctl is off and watchdog got disabled on the command line,
567 * nothing to do here.
569 lockup_detector_update_enable();
571 if (!IS_ENABLED(CONFIG_SYSCTL
) &&
572 !(watchdog_enabled
&& watchdog_thresh
))
575 ret
= smpboot_register_percpu_thread_cpumask(&watchdog_threads
,
576 &watchdog_allowed_mask
);
578 pr_err("Failed to initialize soft lockup detector threads\n");
582 mutex_lock(&watchdog_mutex
);
583 softlockup_threads_initialized
= true;
584 softlockup_reconfigure_threads();
585 mutex_unlock(&watchdog_mutex
);
588 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
589 static inline int watchdog_park_threads(void) { return 0; }
590 static inline void watchdog_unpark_threads(void) { }
591 static inline int watchdog_enable_all_cpus(void) { return 0; }
592 static inline void watchdog_disable_all_cpus(void) { }
593 static inline void softlockup_init_threads(void) { }
594 static void softlockup_reconfigure_threads(void)
596 watchdog_nmi_reconfigure(false);
597 lockup_detector_update_enable();
598 watchdog_nmi_reconfigure(true);
600 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
602 static void __lockup_detector_cleanup(void)
604 lockdep_assert_held(&watchdog_mutex
);
605 hardlockup_detector_perf_cleanup();
609 * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
611 * Caller must not hold the cpu hotplug rwsem.
613 void lockup_detector_cleanup(void)
615 mutex_lock(&watchdog_mutex
);
616 __lockup_detector_cleanup();
617 mutex_unlock(&watchdog_mutex
);
621 * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
623 * Special interface for parisc. It prevents lockup detector warnings from
624 * the default pm_poweroff() function which busy loops forever.
626 void lockup_detector_soft_poweroff(void)
628 watchdog_enabled
= 0;
633 /* Propagate any changes to the watchdog threads */
634 static void proc_watchdog_update(void)
636 /* Remove impossible cpus to keep sysctl output clean. */
637 cpumask_and(&watchdog_cpumask
, &watchdog_cpumask
, cpu_possible_mask
);
638 softlockup_reconfigure_threads();
642 * common function for watchdog, nmi_watchdog and soft_watchdog parameter
644 * caller | table->data points to | 'which'
645 * -------------------|----------------------------|--------------------------
646 * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED |
647 * | | SOFT_WATCHDOG_ENABLED
648 * -------------------|----------------------------|--------------------------
649 * proc_nmi_watchdog | nmi_watchdog_user_enabled | NMI_WATCHDOG_ENABLED
650 * -------------------|----------------------------|--------------------------
651 * proc_soft_watchdog | soft_watchdog_user_enabled | SOFT_WATCHDOG_ENABLED
653 static int proc_watchdog_common(int which
, struct ctl_table
*table
, int write
,
654 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
656 int err
, old
, *param
= table
->data
;
658 cpu_hotplug_disable();
659 mutex_lock(&watchdog_mutex
);
663 * On read synchronize the userspace interface. This is a
666 *param
= (watchdog_enabled
& which
) != 0;
667 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
669 old
= READ_ONCE(*param
);
670 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
671 if (!err
&& old
!= READ_ONCE(*param
))
672 proc_watchdog_update();
674 mutex_unlock(&watchdog_mutex
);
675 cpu_hotplug_enable();
680 * /proc/sys/kernel/watchdog
682 int proc_watchdog(struct ctl_table
*table
, int write
,
683 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
685 return proc_watchdog_common(NMI_WATCHDOG_ENABLED
|SOFT_WATCHDOG_ENABLED
,
686 table
, write
, buffer
, lenp
, ppos
);
690 * /proc/sys/kernel/nmi_watchdog
692 int proc_nmi_watchdog(struct ctl_table
*table
, int write
,
693 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
695 return proc_watchdog_common(NMI_WATCHDOG_ENABLED
,
696 table
, write
, buffer
, lenp
, ppos
);
700 * /proc/sys/kernel/soft_watchdog
702 int proc_soft_watchdog(struct ctl_table
*table
, int write
,
703 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
705 return proc_watchdog_common(SOFT_WATCHDOG_ENABLED
,
706 table
, write
, buffer
, lenp
, ppos
);
710 * /proc/sys/kernel/watchdog_thresh
712 int proc_watchdog_thresh(struct ctl_table
*table
, int write
,
713 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
717 cpu_hotplug_disable();
718 mutex_lock(&watchdog_mutex
);
720 old
= READ_ONCE(watchdog_thresh
);
721 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
723 if (!err
&& write
&& old
!= READ_ONCE(watchdog_thresh
))
724 proc_watchdog_update();
726 mutex_unlock(&watchdog_mutex
);
727 cpu_hotplug_enable();
732 * The cpumask is the mask of possible cpus that the watchdog can run
733 * on, not the mask of cpus it is actually running on. This allows the
734 * user to specify a mask that will include cpus that have not yet
735 * been brought online, if desired.
737 int proc_watchdog_cpumask(struct ctl_table
*table
, int write
,
738 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
742 cpu_hotplug_disable();
743 mutex_lock(&watchdog_mutex
);
745 err
= proc_do_large_bitmap(table
, write
, buffer
, lenp
, ppos
);
747 proc_watchdog_update();
749 mutex_unlock(&watchdog_mutex
);
750 cpu_hotplug_enable();
753 #endif /* CONFIG_SYSCTL */
755 void __init
lockup_detector_init(void)
757 #ifdef CONFIG_NO_HZ_FULL
758 if (tick_nohz_full_enabled()) {
759 pr_info("Disabling watchdog on nohz_full cores by default\n");
760 cpumask_copy(&watchdog_cpumask
, housekeeping_mask
);
762 cpumask_copy(&watchdog_cpumask
, cpu_possible_mask
);
764 cpumask_copy(&watchdog_cpumask
, cpu_possible_mask
);
767 softlockup_init_threads();