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) "NMI 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>
23 #include <asm/irq_regs.h>
24 #include <linux/kvm_para.h>
25 #include <linux/perf_event.h>
28 * The run state of the lockup detectors is controlled by the content of the
29 * 'watchdog_enabled' variable. Each lockup detector has its dedicated bit -
30 * bit 0 for the hard lockup detector and bit 1 for the soft lockup detector.
32 * 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled'
33 * are variables that are only used as an 'interface' between the parameters
34 * in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The
35 * 'watchdog_thresh' variable is handled differently because its value is not
36 * boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh'
39 #define NMI_WATCHDOG_ENABLED_BIT 0
40 #define SOFT_WATCHDOG_ENABLED_BIT 1
41 #define NMI_WATCHDOG_ENABLED (1 << NMI_WATCHDOG_ENABLED_BIT)
42 #define SOFT_WATCHDOG_ENABLED (1 << SOFT_WATCHDOG_ENABLED_BIT)
44 #ifdef CONFIG_HARDLOCKUP_DETECTOR
45 static unsigned long __read_mostly watchdog_enabled
= SOFT_WATCHDOG_ENABLED
|NMI_WATCHDOG_ENABLED
;
47 static unsigned long __read_mostly watchdog_enabled
= SOFT_WATCHDOG_ENABLED
;
49 int __read_mostly nmi_watchdog_enabled
;
50 int __read_mostly soft_watchdog_enabled
;
51 int __read_mostly watchdog_user_enabled
;
52 int __read_mostly watchdog_thresh
= 10;
55 int __read_mostly sysctl_softlockup_all_cpu_backtrace
;
57 #define sysctl_softlockup_all_cpu_backtrace 0
60 static int __read_mostly watchdog_running
;
61 static u64 __read_mostly sample_period
;
63 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts
);
64 static DEFINE_PER_CPU(struct task_struct
*, softlockup_watchdog
);
65 static DEFINE_PER_CPU(struct hrtimer
, watchdog_hrtimer
);
66 static DEFINE_PER_CPU(bool, softlockup_touch_sync
);
67 static DEFINE_PER_CPU(bool, soft_watchdog_warn
);
68 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts
);
69 static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt
);
70 static DEFINE_PER_CPU(struct task_struct
*, softlockup_task_ptr_saved
);
71 #ifdef CONFIG_HARDLOCKUP_DETECTOR
72 static DEFINE_PER_CPU(bool, hard_watchdog_warn
);
73 static DEFINE_PER_CPU(bool, watchdog_nmi_touch
);
74 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved
);
75 static DEFINE_PER_CPU(struct perf_event
*, watchdog_ev
);
77 static unsigned long soft_lockup_nmi_warn
;
81 * Should we panic when a soft-lockup or hard-lockup occurs:
83 #ifdef CONFIG_HARDLOCKUP_DETECTOR
84 static int hardlockup_panic
=
85 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE
;
87 static bool hardlockup_detector_enabled
= true;
89 * We may not want to enable hard lockup detection by default in all cases,
90 * for example when running the kernel as a guest on a hypervisor. In these
91 * cases this function can be called to disable hard lockup detection. This
92 * function should only be executed once by the boot processor before the
93 * kernel command line parameters are parsed, because otherwise it is not
94 * possible to override this in hardlockup_panic_setup().
96 void watchdog_enable_hardlockup_detector(bool val
)
98 hardlockup_detector_enabled
= val
;
101 bool watchdog_hardlockup_detector_is_enabled(void)
103 return hardlockup_detector_enabled
;
106 static int __init
hardlockup_panic_setup(char *str
)
108 if (!strncmp(str
, "panic", 5))
109 hardlockup_panic
= 1;
110 else if (!strncmp(str
, "nopanic", 7))
111 hardlockup_panic
= 0;
112 else if (!strncmp(str
, "0", 1))
113 watchdog_enabled
&= ~NMI_WATCHDOG_ENABLED
;
114 else if (!strncmp(str
, "1", 1))
115 watchdog_enabled
|= NMI_WATCHDOG_ENABLED
;
118 __setup("nmi_watchdog=", hardlockup_panic_setup
);
121 unsigned int __read_mostly softlockup_panic
=
122 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
;
124 static int __init
softlockup_panic_setup(char *str
)
126 softlockup_panic
= simple_strtoul(str
, NULL
, 0);
130 __setup("softlockup_panic=", softlockup_panic_setup
);
132 static int __init
nowatchdog_setup(char *str
)
134 watchdog_enabled
= 0;
137 __setup("nowatchdog", nowatchdog_setup
);
139 static int __init
nosoftlockup_setup(char *str
)
141 watchdog_enabled
&= ~SOFT_WATCHDOG_ENABLED
;
144 __setup("nosoftlockup", nosoftlockup_setup
);
147 static int __init
softlockup_all_cpu_backtrace_setup(char *str
)
149 sysctl_softlockup_all_cpu_backtrace
=
150 !!simple_strtol(str
, NULL
, 0);
153 __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup
);
157 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
158 * lockups can have false positives under extreme conditions. So we generally
159 * want a higher threshold for soft lockups than for hard lockups. So we couple
160 * the thresholds with a factor: we make the soft threshold twice the amount of
161 * time the hard threshold is.
163 static int get_softlockup_thresh(void)
165 return watchdog_thresh
* 2;
169 * Returns seconds, approximately. We don't need nanosecond
170 * resolution, and we don't need to waste time with a big divide when
173 static unsigned long get_timestamp(void)
175 return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
178 static void set_sample_period(void)
181 * convert watchdog_thresh from seconds to ns
182 * the divide by 5 is to give hrtimer several chances (two
183 * or three with the current relation between the soft
184 * and hard thresholds) to increment before the
185 * hardlockup detector generates a warning
187 sample_period
= get_softlockup_thresh() * ((u64
)NSEC_PER_SEC
/ 5);
190 /* Commands for resetting the watchdog */
191 static void __touch_watchdog(void)
193 __this_cpu_write(watchdog_touch_ts
, get_timestamp());
196 void touch_softlockup_watchdog(void)
199 * Preemption can be enabled. It doesn't matter which CPU's timestamp
200 * gets zeroed here, so use the raw_ operation.
202 raw_cpu_write(watchdog_touch_ts
, 0);
204 EXPORT_SYMBOL(touch_softlockup_watchdog
);
206 void touch_all_softlockup_watchdogs(void)
211 * this is done lockless
212 * do we care if a 0 races with a timestamp?
213 * all it means is the softlock check starts one cycle later
215 for_each_online_cpu(cpu
)
216 per_cpu(watchdog_touch_ts
, cpu
) = 0;
219 #ifdef CONFIG_HARDLOCKUP_DETECTOR
220 void touch_nmi_watchdog(void)
223 * Using __raw here because some code paths have
224 * preemption enabled. If preemption is enabled
225 * then interrupts should be enabled too, in which
226 * case we shouldn't have to worry about the watchdog
229 raw_cpu_write(watchdog_nmi_touch
, true);
230 touch_softlockup_watchdog();
232 EXPORT_SYMBOL(touch_nmi_watchdog
);
236 void touch_softlockup_watchdog_sync(void)
238 __this_cpu_write(softlockup_touch_sync
, true);
239 __this_cpu_write(watchdog_touch_ts
, 0);
242 #ifdef CONFIG_HARDLOCKUP_DETECTOR
243 /* watchdog detector functions */
244 static int is_hardlockup(void)
246 unsigned long hrint
= __this_cpu_read(hrtimer_interrupts
);
248 if (__this_cpu_read(hrtimer_interrupts_saved
) == hrint
)
251 __this_cpu_write(hrtimer_interrupts_saved
, hrint
);
256 static int is_softlockup(unsigned long touch_ts
)
258 unsigned long now
= get_timestamp();
260 if (watchdog_enabled
& SOFT_WATCHDOG_ENABLED
) {
261 /* Warn about unreasonable delays. */
262 if (time_after(now
, touch_ts
+ get_softlockup_thresh()))
263 return now
- touch_ts
;
268 #ifdef CONFIG_HARDLOCKUP_DETECTOR
270 static struct perf_event_attr wd_hw_attr
= {
271 .type
= PERF_TYPE_HARDWARE
,
272 .config
= PERF_COUNT_HW_CPU_CYCLES
,
273 .size
= sizeof(struct perf_event_attr
),
278 /* Callback function for perf event subsystem */
279 static void watchdog_overflow_callback(struct perf_event
*event
,
280 struct perf_sample_data
*data
,
281 struct pt_regs
*regs
)
283 /* Ensure the watchdog never gets throttled */
284 event
->hw
.interrupts
= 0;
286 if (__this_cpu_read(watchdog_nmi_touch
) == true) {
287 __this_cpu_write(watchdog_nmi_touch
, false);
291 /* check for a hardlockup
292 * This is done by making sure our timer interrupt
293 * is incrementing. The timer interrupt should have
294 * fired multiple times before we overflow'd. If it hasn't
295 * then this is a good indication the cpu is stuck
297 if (is_hardlockup()) {
298 int this_cpu
= smp_processor_id();
300 /* only print hardlockups once */
301 if (__this_cpu_read(hard_watchdog_warn
) == true)
304 if (hardlockup_panic
)
305 panic("Watchdog detected hard LOCKUP on cpu %d",
308 WARN(1, "Watchdog detected hard LOCKUP on cpu %d",
311 __this_cpu_write(hard_watchdog_warn
, true);
315 __this_cpu_write(hard_watchdog_warn
, false);
318 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
320 static void watchdog_interrupt_count(void)
322 __this_cpu_inc(hrtimer_interrupts
);
325 static int watchdog_nmi_enable(unsigned int cpu
);
326 static void watchdog_nmi_disable(unsigned int cpu
);
328 /* watchdog kicker functions */
329 static enum hrtimer_restart
watchdog_timer_fn(struct hrtimer
*hrtimer
)
331 unsigned long touch_ts
= __this_cpu_read(watchdog_touch_ts
);
332 struct pt_regs
*regs
= get_irq_regs();
334 int softlockup_all_cpu_backtrace
= sysctl_softlockup_all_cpu_backtrace
;
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
= raw_cpu_ptr(&watchdog_hrtimer
);
449 /* kick off the timer for the hardlockup detector */
450 hrtimer_init(hrtimer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
451 hrtimer
->function
= watchdog_timer_fn
;
453 /* Enable the perf event */
454 watchdog_nmi_enable(cpu
);
456 /* done here because hrtimer_start can only pin to smp_processor_id() */
457 hrtimer_start(hrtimer
, ns_to_ktime(sample_period
),
458 HRTIMER_MODE_REL_PINNED
);
460 /* initialize timestamp */
461 watchdog_set_prio(SCHED_FIFO
, MAX_RT_PRIO
- 1);
465 static void watchdog_disable(unsigned int cpu
)
467 struct hrtimer
*hrtimer
= raw_cpu_ptr(&watchdog_hrtimer
);
469 watchdog_set_prio(SCHED_NORMAL
, 0);
470 hrtimer_cancel(hrtimer
);
471 /* disable the perf event */
472 watchdog_nmi_disable(cpu
);
475 static void watchdog_cleanup(unsigned int cpu
, bool online
)
477 watchdog_disable(cpu
);
480 static int watchdog_should_run(unsigned int cpu
)
482 return __this_cpu_read(hrtimer_interrupts
) !=
483 __this_cpu_read(soft_lockup_hrtimer_cnt
);
487 * The watchdog thread function - touches the timestamp.
489 * It only runs once every sample_period seconds (4 seconds by
490 * default) to reset the softlockup timestamp. If this gets delayed
491 * for more than 2*watchdog_thresh seconds then the debug-printout
492 * triggers in watchdog_timer_fn().
494 static void watchdog(unsigned int cpu
)
496 __this_cpu_write(soft_lockup_hrtimer_cnt
,
497 __this_cpu_read(hrtimer_interrupts
));
501 * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
502 * failure path. Check for failures that can occur asynchronously -
503 * for example, when CPUs are on-lined - and shut down the hardware
504 * perf event on each CPU accordingly.
506 * The only non-obvious place this bit can be cleared is through
507 * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a
508 * pr_info here would be too noisy as it would result in a message
509 * every few seconds if the hardlockup was disabled but the softlockup
512 if (!(watchdog_enabled
& NMI_WATCHDOG_ENABLED
))
513 watchdog_nmi_disable(cpu
);
516 #ifdef CONFIG_HARDLOCKUP_DETECTOR
518 * People like the simple clean cpu node info on boot.
519 * Reduce the watchdog noise by only printing messages
520 * that are different from what cpu0 displayed.
522 static unsigned long cpu0_err
;
524 static int watchdog_nmi_enable(unsigned int cpu
)
526 struct perf_event_attr
*wd_attr
;
527 struct perf_event
*event
= per_cpu(watchdog_ev
, cpu
);
529 /* nothing to do if the hard lockup detector is disabled */
530 if (!(watchdog_enabled
& NMI_WATCHDOG_ENABLED
))
534 * Some kernels need to default hard lockup detection to
535 * 'disabled', for example a guest on a hypervisor.
537 if (!watchdog_hardlockup_detector_is_enabled()) {
538 event
= ERR_PTR(-ENOENT
);
542 /* is it already setup and enabled? */
543 if (event
&& event
->state
> PERF_EVENT_STATE_OFF
)
546 /* it is setup but not enabled */
550 wd_attr
= &wd_hw_attr
;
551 wd_attr
->sample_period
= hw_nmi_get_sample_period(watchdog_thresh
);
553 /* Try to register using hardware perf events */
554 event
= perf_event_create_kernel_counter(wd_attr
, cpu
, NULL
, watchdog_overflow_callback
, NULL
);
557 /* save cpu0 error for future comparision */
558 if (cpu
== 0 && IS_ERR(event
))
559 cpu0_err
= PTR_ERR(event
);
561 if (!IS_ERR(event
)) {
562 /* only print for cpu0 or different than cpu0 */
563 if (cpu
== 0 || cpu0_err
)
564 pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
569 * Disable the hard lockup detector if _any_ CPU fails to set up
570 * set up the hardware perf event. The watchdog() function checks
571 * the NMI_WATCHDOG_ENABLED bit periodically.
573 * The barriers are for syncing up watchdog_enabled across all the
574 * cpus, as clear_bit() does not use barriers.
576 smp_mb__before_atomic();
577 clear_bit(NMI_WATCHDOG_ENABLED_BIT
, &watchdog_enabled
);
578 smp_mb__after_atomic();
580 /* skip displaying the same error again */
581 if (cpu
> 0 && (PTR_ERR(event
) == cpu0_err
))
582 return PTR_ERR(event
);
584 /* vary the KERN level based on the returned errno */
585 if (PTR_ERR(event
) == -EOPNOTSUPP
)
586 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu
);
587 else if (PTR_ERR(event
) == -ENOENT
)
588 pr_warn("disabled (cpu%i): hardware events not enabled\n",
591 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
592 cpu
, PTR_ERR(event
));
594 pr_info("Shutting down hard lockup detector on all cpus\n");
596 return PTR_ERR(event
);
600 per_cpu(watchdog_ev
, cpu
) = event
;
602 perf_event_enable(per_cpu(watchdog_ev
, cpu
));
607 static void watchdog_nmi_disable(unsigned int cpu
)
609 struct perf_event
*event
= per_cpu(watchdog_ev
, cpu
);
612 perf_event_disable(event
);
613 per_cpu(watchdog_ev
, cpu
) = NULL
;
615 /* should be in cleanup, but blocks oprofile */
616 perf_event_release_kernel(event
);
619 /* watchdog_nmi_enable() expects this to be zero initially. */
624 static int watchdog_nmi_enable(unsigned int cpu
) { return 0; }
625 static void watchdog_nmi_disable(unsigned int cpu
) { return; }
626 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
628 static struct smp_hotplug_thread watchdog_threads
= {
629 .store
= &softlockup_watchdog
,
630 .thread_should_run
= watchdog_should_run
,
631 .thread_fn
= watchdog
,
632 .thread_comm
= "watchdog/%u",
633 .setup
= watchdog_enable
,
634 .cleanup
= watchdog_cleanup
,
635 .park
= watchdog_disable
,
636 .unpark
= watchdog_enable
,
639 static void restart_watchdog_hrtimer(void *info
)
641 struct hrtimer
*hrtimer
= raw_cpu_ptr(&watchdog_hrtimer
);
645 * No need to cancel and restart hrtimer if it is currently executing
646 * because it will reprogram itself with the new period now.
647 * We should never see it unqueued here because we are running per-cpu
648 * with interrupts disabled.
650 ret
= hrtimer_try_to_cancel(hrtimer
);
652 hrtimer_start(hrtimer
, ns_to_ktime(sample_period
),
653 HRTIMER_MODE_REL_PINNED
);
656 static void update_timers(int cpu
)
659 * Make sure that perf event counter will adopt to a new
660 * sampling period. Updating the sampling period directly would
661 * be much nicer but we do not have an API for that now so
662 * let's use a big hammer.
663 * Hrtimer will adopt the new period on the next tick but this
664 * might be late already so we have to restart the timer as well.
666 watchdog_nmi_disable(cpu
);
667 smp_call_function_single(cpu
, restart_watchdog_hrtimer
, NULL
, 1);
668 watchdog_nmi_enable(cpu
);
671 static void update_timers_all_cpus(void)
676 for_each_online_cpu(cpu
)
681 static int watchdog_enable_all_cpus(bool sample_period_changed
)
685 if (!watchdog_running
) {
686 err
= smpboot_register_percpu_thread(&watchdog_threads
);
688 pr_err("Failed to create watchdog threads, disabled\n");
690 watchdog_running
= 1;
691 } else if (sample_period_changed
) {
692 update_timers_all_cpus();
698 /* prepare/enable/disable routines */
699 /* sysctl functions */
701 static void watchdog_disable_all_cpus(void)
703 if (watchdog_running
) {
704 watchdog_running
= 0;
705 smpboot_unregister_percpu_thread(&watchdog_threads
);
710 * Update the run state of the lockup detectors.
712 static int proc_watchdog_update(void)
717 * Watchdog threads won't be started if they are already active.
718 * The 'watchdog_running' variable in watchdog_*_all_cpus() takes
719 * care of this. If those threads are already active, the sample
720 * period will be updated and the lockup detectors will be enabled
721 * or disabled 'on the fly'.
723 if (watchdog_enabled
&& watchdog_thresh
)
724 err
= watchdog_enable_all_cpus(true);
726 watchdog_disable_all_cpus();
732 static DEFINE_MUTEX(watchdog_proc_mutex
);
735 * common function for watchdog, nmi_watchdog and soft_watchdog parameter
737 * caller | table->data points to | 'which' contains the flag(s)
738 * -------------------|-----------------------|-----------------------------
739 * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
740 * | | with SOFT_WATCHDOG_ENABLED
741 * -------------------|-----------------------|-----------------------------
742 * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED
743 * -------------------|-----------------------|-----------------------------
744 * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
746 static int proc_watchdog_common(int which
, struct ctl_table
*table
, int write
,
747 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
750 int *watchdog_param
= (int *)table
->data
;
752 mutex_lock(&watchdog_proc_mutex
);
755 * If the parameter is being read return the state of the corresponding
756 * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
757 * run state of the lockup detectors.
760 *watchdog_param
= (watchdog_enabled
& which
) != 0;
761 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
763 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
768 * There is a race window between fetching the current value
769 * from 'watchdog_enabled' and storing the new value. During
770 * this race window, watchdog_nmi_enable() can sneak in and
771 * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
772 * The 'cmpxchg' detects this race and the loop retries.
775 old
= watchdog_enabled
;
777 * If the parameter value is not zero set the
778 * corresponding bit(s), else clear it(them).
784 } while (cmpxchg(&watchdog_enabled
, old
, new) != old
);
787 * Update the run state of the lockup detectors.
788 * Restore 'watchdog_enabled' on failure.
790 err
= proc_watchdog_update();
792 watchdog_enabled
= old
;
795 mutex_unlock(&watchdog_proc_mutex
);
800 * /proc/sys/kernel/watchdog
802 int proc_watchdog(struct ctl_table
*table
, int write
,
803 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
805 return proc_watchdog_common(NMI_WATCHDOG_ENABLED
|SOFT_WATCHDOG_ENABLED
,
806 table
, write
, buffer
, lenp
, ppos
);
810 * /proc/sys/kernel/nmi_watchdog
812 int proc_nmi_watchdog(struct ctl_table
*table
, int write
,
813 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
815 return proc_watchdog_common(NMI_WATCHDOG_ENABLED
,
816 table
, write
, buffer
, lenp
, ppos
);
820 * /proc/sys/kernel/soft_watchdog
822 int proc_soft_watchdog(struct ctl_table
*table
, int write
,
823 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
825 return proc_watchdog_common(SOFT_WATCHDOG_ENABLED
,
826 table
, write
, buffer
, lenp
, ppos
);
830 * /proc/sys/kernel/watchdog_thresh
832 int proc_watchdog_thresh(struct ctl_table
*table
, int write
,
833 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
837 mutex_lock(&watchdog_proc_mutex
);
839 old
= ACCESS_ONCE(watchdog_thresh
);
840 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
846 * Update the sample period.
847 * Restore 'watchdog_thresh' on failure.
850 err
= proc_watchdog_update();
852 watchdog_thresh
= old
;
854 mutex_unlock(&watchdog_proc_mutex
);
857 #endif /* CONFIG_SYSCTL */
859 void __init
lockup_detector_init(void)
863 if (watchdog_enabled
)
864 watchdog_enable_all_cpus(false);