linux/kernel/watchdog.c
Babu Moger 73ce0511c4 kernel/watchdog.c: move hardlockup detector to separate file
Separate hardlockup code from watchdog.c and move it to watchdog_hld.c.
It is mostly straight forward.  Remove everything inside
CONFIG_HARDLOCKUP_DETECTORS.  This code will go to file watchdog_hld.c.
Also update the makefile accordigly.

Link: http://lkml.kernel.org/r/1478034826-43888-3-git-send-email-babu.moger@oracle.com
Signed-off-by: Babu Moger <babu.moger@oracle.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Yaowei Bai <baiyaowei@cmss.chinamobile.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Josh Hunt <johunt@akamai.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-12-14 16:04:08 -08:00

831 lines
22 KiB
C

/*
* Detect hard and soft lockups on a system
*
* started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
*
* Note: Most of this code is borrowed heavily from the original softlockup
* detector, so thanks to Ingo for the initial implementation.
* Some chunks also taken from the old x86-specific nmi watchdog code, thanks
* to those contributors as well.
*/
#define pr_fmt(fmt) "NMI watchdog: " fmt
#include <linux/mm.h>
#include <linux/cpu.h>
#include <linux/nmi.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/sysctl.h>
#include <linux/smpboot.h>
#include <linux/sched/rt.h>
#include <linux/tick.h>
#include <linux/workqueue.h>
#include <asm/irq_regs.h>
#include <linux/kvm_para.h>
#include <linux/kthread.h>
static DEFINE_MUTEX(watchdog_proc_mutex);
#if defined(CONFIG_HAVE_NMI_WATCHDOG) || defined(CONFIG_HARDLOCKUP_DETECTOR)
unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
#else
unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
#endif
int __read_mostly nmi_watchdog_enabled;
int __read_mostly soft_watchdog_enabled;
int __read_mostly watchdog_user_enabled;
int __read_mostly watchdog_thresh = 10;
#ifdef CONFIG_SMP
int __read_mostly sysctl_softlockup_all_cpu_backtrace;
int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
#endif
static struct cpumask watchdog_cpumask __read_mostly;
unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
/* Helper for online, unparked cpus. */
#define for_each_watchdog_cpu(cpu) \
for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
/*
* The 'watchdog_running' variable is set to 1 when the watchdog threads
* are registered/started and is set to 0 when the watchdog threads are
* unregistered/stopped, so it is an indicator whether the threads exist.
*/
static int __read_mostly watchdog_running;
/*
* If a subsystem has a need to deactivate the watchdog temporarily, it
* can use the suspend/resume interface to achieve this. The content of
* the 'watchdog_suspended' variable reflects this state. Existing threads
* are parked/unparked by the lockup_detector_{suspend|resume} functions
* (see comment blocks pertaining to those functions for further details).
*
* 'watchdog_suspended' also prevents threads from being registered/started
* or unregistered/stopped via parameters in /proc/sys/kernel, so the state
* of 'watchdog_running' cannot change while the watchdog is deactivated
* temporarily (see related code in 'proc' handlers).
*/
static int __read_mostly watchdog_suspended;
static u64 __read_mostly sample_period;
static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
static DEFINE_PER_CPU(bool, softlockup_touch_sync);
static DEFINE_PER_CPU(bool, soft_watchdog_warn);
static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
static unsigned long soft_lockup_nmi_warn;
unsigned int __read_mostly softlockup_panic =
CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
static int __init softlockup_panic_setup(char *str)
{
softlockup_panic = simple_strtoul(str, NULL, 0);
return 1;
}
__setup("softlockup_panic=", softlockup_panic_setup);
static int __init nowatchdog_setup(char *str)
{
watchdog_enabled = 0;
return 1;
}
__setup("nowatchdog", nowatchdog_setup);
static int __init nosoftlockup_setup(char *str)
{
watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED;
return 1;
}
__setup("nosoftlockup", nosoftlockup_setup);
#ifdef CONFIG_SMP
static int __init softlockup_all_cpu_backtrace_setup(char *str)
{
sysctl_softlockup_all_cpu_backtrace =
!!simple_strtol(str, NULL, 0);
return 1;
}
__setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
static int __init hardlockup_all_cpu_backtrace_setup(char *str)
{
sysctl_hardlockup_all_cpu_backtrace =
!!simple_strtol(str, NULL, 0);
return 1;
}
__setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
#endif
/*
* Hard-lockup warnings should be triggered after just a few seconds. Soft-
* lockups can have false positives under extreme conditions. So we generally
* want a higher threshold for soft lockups than for hard lockups. So we couple
* the thresholds with a factor: we make the soft threshold twice the amount of
* time the hard threshold is.
*/
static int get_softlockup_thresh(void)
{
return watchdog_thresh * 2;
}
/*
* Returns seconds, approximately. We don't need nanosecond
* resolution, and we don't need to waste time with a big divide when
* 2^30ns == 1.074s.
*/
static unsigned long get_timestamp(void)
{
return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
}
static void set_sample_period(void)
{
/*
* convert watchdog_thresh from seconds to ns
* the divide by 5 is to give hrtimer several chances (two
* or three with the current relation between the soft
* and hard thresholds) to increment before the
* hardlockup detector generates a warning
*/
sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
}
/* Commands for resetting the watchdog */
static void __touch_watchdog(void)
{
__this_cpu_write(watchdog_touch_ts, get_timestamp());
}
/**
* touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
*
* Call when the scheduler may have stalled for legitimate reasons
* preventing the watchdog task from executing - e.g. the scheduler
* entering idle state. This should only be used for scheduler events.
* Use touch_softlockup_watchdog() for everything else.
*/
void touch_softlockup_watchdog_sched(void)
{
/*
* Preemption can be enabled. It doesn't matter which CPU's timestamp
* gets zeroed here, so use the raw_ operation.
*/
raw_cpu_write(watchdog_touch_ts, 0);
}
void touch_softlockup_watchdog(void)
{
touch_softlockup_watchdog_sched();
wq_watchdog_touch(raw_smp_processor_id());
}
EXPORT_SYMBOL(touch_softlockup_watchdog);
void touch_all_softlockup_watchdogs(void)
{
int cpu;
/*
* this is done lockless
* do we care if a 0 races with a timestamp?
* all it means is the softlock check starts one cycle later
*/
for_each_watchdog_cpu(cpu)
per_cpu(watchdog_touch_ts, cpu) = 0;
wq_watchdog_touch(-1);
}
void touch_softlockup_watchdog_sync(void)
{
__this_cpu_write(softlockup_touch_sync, true);
__this_cpu_write(watchdog_touch_ts, 0);
}
/* watchdog detector functions */
bool is_hardlockup(void)
{
unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
return true;
__this_cpu_write(hrtimer_interrupts_saved, hrint);
return false;
}
static int is_softlockup(unsigned long touch_ts)
{
unsigned long now = get_timestamp();
if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
/* Warn about unreasonable delays. */
if (time_after(now, touch_ts + get_softlockup_thresh()))
return now - touch_ts;
}
return 0;
}
static void watchdog_interrupt_count(void)
{
__this_cpu_inc(hrtimer_interrupts);
}
/*
* These two functions are mostly architecture specific
* defining them as weak here.
*/
int __weak watchdog_nmi_enable(unsigned int cpu)
{
return 0;
}
void __weak watchdog_nmi_disable(unsigned int cpu)
{
}
static int watchdog_enable_all_cpus(void);
static void watchdog_disable_all_cpus(void);
/* watchdog kicker functions */
static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
{
unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
struct pt_regs *regs = get_irq_regs();
int duration;
int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
/* kick the hardlockup detector */
watchdog_interrupt_count();
/* kick the softlockup detector */
wake_up_process(__this_cpu_read(softlockup_watchdog));
/* .. and repeat */
hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
if (touch_ts == 0) {
if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
/*
* If the time stamp was touched atomically
* make sure the scheduler tick is up to date.
*/
__this_cpu_write(softlockup_touch_sync, false);
sched_clock_tick();
}
/* Clear the guest paused flag on watchdog reset */
kvm_check_and_clear_guest_paused();
__touch_watchdog();
return HRTIMER_RESTART;
}
/* check for a softlockup
* This is done by making sure a high priority task is
* being scheduled. The task touches the watchdog to
* indicate it is getting cpu time. If it hasn't then
* this is a good indication some task is hogging the cpu
*/
duration = is_softlockup(touch_ts);
if (unlikely(duration)) {
/*
* If a virtual machine is stopped by the host it can look to
* the watchdog like a soft lockup, check to see if the host
* stopped the vm before we issue the warning
*/
if (kvm_check_and_clear_guest_paused())
return HRTIMER_RESTART;
/* only warn once */
if (__this_cpu_read(soft_watchdog_warn) == true) {
/*
* When multiple processes are causing softlockups the
* softlockup detector only warns on the first one
* because the code relies on a full quiet cycle to
* re-arm. The second process prevents the quiet cycle
* and never gets reported. Use task pointers to detect
* this.
*/
if (__this_cpu_read(softlockup_task_ptr_saved) !=
current) {
__this_cpu_write(soft_watchdog_warn, false);
__touch_watchdog();
}
return HRTIMER_RESTART;
}
if (softlockup_all_cpu_backtrace) {
/* Prevent multiple soft-lockup reports if one cpu is already
* engaged in dumping cpu back traces
*/
if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
/* Someone else will report us. Let's give up */
__this_cpu_write(soft_watchdog_warn, true);
return HRTIMER_RESTART;
}
}
pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
smp_processor_id(), duration,
current->comm, task_pid_nr(current));
__this_cpu_write(softlockup_task_ptr_saved, current);
print_modules();
print_irqtrace_events(current);
if (regs)
show_regs(regs);
else
dump_stack();
if (softlockup_all_cpu_backtrace) {
/* Avoid generating two back traces for current
* given that one is already made above
*/
trigger_allbutself_cpu_backtrace();
clear_bit(0, &soft_lockup_nmi_warn);
/* Barrier to sync with other cpus */
smp_mb__after_atomic();
}
add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
if (softlockup_panic)
panic("softlockup: hung tasks");
__this_cpu_write(soft_watchdog_warn, true);
} else
__this_cpu_write(soft_watchdog_warn, false);
return HRTIMER_RESTART;
}
static void watchdog_set_prio(unsigned int policy, unsigned int prio)
{
struct sched_param param = { .sched_priority = prio };
sched_setscheduler(current, policy, &param);
}
static void watchdog_enable(unsigned int cpu)
{
struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
/* kick off the timer for the hardlockup detector */
hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
hrtimer->function = watchdog_timer_fn;
/* Enable the perf event */
watchdog_nmi_enable(cpu);
/* done here because hrtimer_start can only pin to smp_processor_id() */
hrtimer_start(hrtimer, ns_to_ktime(sample_period),
HRTIMER_MODE_REL_PINNED);
/* initialize timestamp */
watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
__touch_watchdog();
}
static void watchdog_disable(unsigned int cpu)
{
struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
watchdog_set_prio(SCHED_NORMAL, 0);
hrtimer_cancel(hrtimer);
/* disable the perf event */
watchdog_nmi_disable(cpu);
}
static void watchdog_cleanup(unsigned int cpu, bool online)
{
watchdog_disable(cpu);
}
static int watchdog_should_run(unsigned int cpu)
{
return __this_cpu_read(hrtimer_interrupts) !=
__this_cpu_read(soft_lockup_hrtimer_cnt);
}
/*
* The watchdog thread function - touches the timestamp.
*
* It only runs once every sample_period seconds (4 seconds by
* default) to reset the softlockup timestamp. If this gets delayed
* for more than 2*watchdog_thresh seconds then the debug-printout
* triggers in watchdog_timer_fn().
*/
static void watchdog(unsigned int cpu)
{
__this_cpu_write(soft_lockup_hrtimer_cnt,
__this_cpu_read(hrtimer_interrupts));
__touch_watchdog();
/*
* watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
* failure path. Check for failures that can occur asynchronously -
* for example, when CPUs are on-lined - and shut down the hardware
* perf event on each CPU accordingly.
*
* The only non-obvious place this bit can be cleared is through
* watchdog_nmi_enable(), so a pr_info() is placed there. Placing a
* pr_info here would be too noisy as it would result in a message
* every few seconds if the hardlockup was disabled but the softlockup
* enabled.
*/
if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
watchdog_nmi_disable(cpu);
}
static struct smp_hotplug_thread watchdog_threads = {
.store = &softlockup_watchdog,
.thread_should_run = watchdog_should_run,
.thread_fn = watchdog,
.thread_comm = "watchdog/%u",
.setup = watchdog_enable,
.cleanup = watchdog_cleanup,
.park = watchdog_disable,
.unpark = watchdog_enable,
};
/*
* park all watchdog threads that are specified in 'watchdog_cpumask'
*
* This function returns an error if kthread_park() of a watchdog thread
* fails. In this situation, the watchdog threads of some CPUs can already
* be parked and the watchdog threads of other CPUs can still be runnable.
* Callers are expected to handle this special condition as appropriate in
* their context.
*
* This function may only be called in a context that is protected against
* races with CPU hotplug - for example, via get_online_cpus().
*/
static int watchdog_park_threads(void)
{
int cpu, ret = 0;
for_each_watchdog_cpu(cpu) {
ret = kthread_park(per_cpu(softlockup_watchdog, cpu));
if (ret)
break;
}
return ret;
}
/*
* unpark all watchdog threads that are specified in 'watchdog_cpumask'
*
* This function may only be called in a context that is protected against
* races with CPU hotplug - for example, via get_online_cpus().
*/
static void watchdog_unpark_threads(void)
{
int cpu;
for_each_watchdog_cpu(cpu)
kthread_unpark(per_cpu(softlockup_watchdog, cpu));
}
/*
* Suspend the hard and soft lockup detector by parking the watchdog threads.
*/
int lockup_detector_suspend(void)
{
int ret = 0;
get_online_cpus();
mutex_lock(&watchdog_proc_mutex);
/*
* Multiple suspend requests can be active in parallel (counted by
* the 'watchdog_suspended' variable). If the watchdog threads are
* running, the first caller takes care that they will be parked.
* The state of 'watchdog_running' cannot change while a suspend
* request is active (see related code in 'proc' handlers).
*/
if (watchdog_running && !watchdog_suspended)
ret = watchdog_park_threads();
if (ret == 0)
watchdog_suspended++;
else {
watchdog_disable_all_cpus();
pr_err("Failed to suspend lockup detectors, disabled\n");
watchdog_enabled = 0;
}
mutex_unlock(&watchdog_proc_mutex);
return ret;
}
/*
* Resume the hard and soft lockup detector by unparking the watchdog threads.
*/
void lockup_detector_resume(void)
{
mutex_lock(&watchdog_proc_mutex);
watchdog_suspended--;
/*
* The watchdog threads are unparked if they were previously running
* and if there is no more active suspend request.
*/
if (watchdog_running && !watchdog_suspended)
watchdog_unpark_threads();
mutex_unlock(&watchdog_proc_mutex);
put_online_cpus();
}
static int update_watchdog_all_cpus(void)
{
int ret;
ret = watchdog_park_threads();
if (ret)
return ret;
watchdog_unpark_threads();
return 0;
}
static int watchdog_enable_all_cpus(void)
{
int err = 0;
if (!watchdog_running) {
err = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
&watchdog_cpumask);
if (err)
pr_err("Failed to create watchdog threads, disabled\n");
else
watchdog_running = 1;
} else {
/*
* Enable/disable the lockup detectors or
* change the sample period 'on the fly'.
*/
err = update_watchdog_all_cpus();
if (err) {
watchdog_disable_all_cpus();
pr_err("Failed to update lockup detectors, disabled\n");
}
}
if (err)
watchdog_enabled = 0;
return err;
}
static void watchdog_disable_all_cpus(void)
{
if (watchdog_running) {
watchdog_running = 0;
smpboot_unregister_percpu_thread(&watchdog_threads);
}
}
#ifdef CONFIG_SYSCTL
/*
* Update the run state of the lockup detectors.
*/
static int proc_watchdog_update(void)
{
int err = 0;
/*
* Watchdog threads won't be started if they are already active.
* The 'watchdog_running' variable in watchdog_*_all_cpus() takes
* care of this. If those threads are already active, the sample
* period will be updated and the lockup detectors will be enabled
* or disabled 'on the fly'.
*/
if (watchdog_enabled && watchdog_thresh)
err = watchdog_enable_all_cpus();
else
watchdog_disable_all_cpus();
return err;
}
/*
* common function for watchdog, nmi_watchdog and soft_watchdog parameter
*
* caller | table->data points to | 'which' contains the flag(s)
* -------------------|-----------------------|-----------------------------
* proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
* | | with SOFT_WATCHDOG_ENABLED
* -------------------|-----------------------|-----------------------------
* proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED
* -------------------|-----------------------|-----------------------------
* proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
*/
static int proc_watchdog_common(int which, struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
int err, old, new;
int *watchdog_param = (int *)table->data;
get_online_cpus();
mutex_lock(&watchdog_proc_mutex);
if (watchdog_suspended) {
/* no parameter changes allowed while watchdog is suspended */
err = -EAGAIN;
goto out;
}
/*
* If the parameter is being read return the state of the corresponding
* bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
* run state of the lockup detectors.
*/
if (!write) {
*watchdog_param = (watchdog_enabled & which) != 0;
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
} else {
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (err)
goto out;
/*
* There is a race window between fetching the current value
* from 'watchdog_enabled' and storing the new value. During
* this race window, watchdog_nmi_enable() can sneak in and
* clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
* The 'cmpxchg' detects this race and the loop retries.
*/
do {
old = watchdog_enabled;
/*
* If the parameter value is not zero set the
* corresponding bit(s), else clear it(them).
*/
if (*watchdog_param)
new = old | which;
else
new = old & ~which;
} while (cmpxchg(&watchdog_enabled, old, new) != old);
/*
* Update the run state of the lockup detectors. There is _no_
* need to check the value returned by proc_watchdog_update()
* and to restore the previous value of 'watchdog_enabled' as
* both lockup detectors are disabled if proc_watchdog_update()
* returns an error.
*/
if (old == new)
goto out;
err = proc_watchdog_update();
}
out:
mutex_unlock(&watchdog_proc_mutex);
put_online_cpus();
return err;
}
/*
* /proc/sys/kernel/watchdog
*/
int proc_watchdog(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
table, write, buffer, lenp, ppos);
}
/*
* /proc/sys/kernel/nmi_watchdog
*/
int proc_nmi_watchdog(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
table, write, buffer, lenp, ppos);
}
/*
* /proc/sys/kernel/soft_watchdog
*/
int proc_soft_watchdog(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
table, write, buffer, lenp, ppos);
}
/*
* /proc/sys/kernel/watchdog_thresh
*/
int proc_watchdog_thresh(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
int err, old, new;
get_online_cpus();
mutex_lock(&watchdog_proc_mutex);
if (watchdog_suspended) {
/* no parameter changes allowed while watchdog is suspended */
err = -EAGAIN;
goto out;
}
old = ACCESS_ONCE(watchdog_thresh);
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (err || !write)
goto out;
/*
* Update the sample period. Restore on failure.
*/
new = ACCESS_ONCE(watchdog_thresh);
if (old == new)
goto out;
set_sample_period();
err = proc_watchdog_update();
if (err) {
watchdog_thresh = old;
set_sample_period();
}
out:
mutex_unlock(&watchdog_proc_mutex);
put_online_cpus();
return err;
}
/*
* The cpumask is the mask of possible cpus that the watchdog can run
* on, not the mask of cpus it is actually running on. This allows the
* user to specify a mask that will include cpus that have not yet
* been brought online, if desired.
*/
int proc_watchdog_cpumask(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
int err;
get_online_cpus();
mutex_lock(&watchdog_proc_mutex);
if (watchdog_suspended) {
/* no parameter changes allowed while watchdog is suspended */
err = -EAGAIN;
goto out;
}
err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
if (!err && write) {
/* Remove impossible cpus to keep sysctl output cleaner. */
cpumask_and(&watchdog_cpumask, &watchdog_cpumask,
cpu_possible_mask);
if (watchdog_running) {
/*
* Failure would be due to being unable to allocate
* a temporary cpumask, so we are likely not in a
* position to do much else to make things better.
*/
if (smpboot_update_cpumask_percpu_thread(
&watchdog_threads, &watchdog_cpumask) != 0)
pr_err("cpumask update failed\n");
}
}
out:
mutex_unlock(&watchdog_proc_mutex);
put_online_cpus();
return err;
}
#endif /* CONFIG_SYSCTL */
void __init lockup_detector_init(void)
{
set_sample_period();
#ifdef CONFIG_NO_HZ_FULL
if (tick_nohz_full_enabled()) {
pr_info("Disabling watchdog on nohz_full cores by default\n");
cpumask_copy(&watchdog_cpumask, housekeeping_mask);
} else
cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
#else
cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
#endif
if (watchdog_enabled)
watchdog_enable_all_cpus();
}