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// SPDX-License-Identifier: GPL-2.0
/*
* 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) "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/tick.h>
#include <linux/sched/clock.h>
#include <linux/sched/debug.h>
#include <linux/sched/isolation.h>
#include <linux/stop_machine.h>
#include <asm/irq_regs.h>
#include <linux/kvm_para.h>
#include <trace/hooks/softlockup.h>
static DEFINE_MUTEX(watchdog_mutex);
#if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
# define WATCHDOG_DEFAULT (SOFT_WATCHDOG_ENABLED | NMI_WATCHDOG_ENABLED)
# define NMI_WATCHDOG_DEFAULT 1
#else
# define WATCHDOG_DEFAULT (SOFT_WATCHDOG_ENABLED)
# define NMI_WATCHDOG_DEFAULT 0
#endif
unsigned long __read_mostly watchdog_enabled;
int __read_mostly watchdog_user_enabled = 1;
int __read_mostly nmi_watchdog_user_enabled = NMI_WATCHDOG_DEFAULT;
int __read_mostly soft_watchdog_user_enabled = 1;
int __read_mostly watchdog_thresh = 10;
static int __read_mostly nmi_watchdog_available;
struct cpumask watchdog_cpumask __read_mostly;
unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
#ifdef CONFIG_HARDLOCKUP_DETECTOR
# ifdef CONFIG_SMP
int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
# endif /* CONFIG_SMP */
/*
* Should we panic when a soft-lockup or hard-lockup occurs:
*/
unsigned int __read_mostly hardlockup_panic =
CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
/*
* We may not want to enable hard lockup detection by default in all cases,
* for example when running the kernel as a guest on a hypervisor. In these
* cases this function can be called to disable hard lockup detection. This
* function should only be executed once by the boot processor before the
* kernel command line parameters are parsed, because otherwise it is not
* possible to override this in hardlockup_panic_setup().
*/
void __init hardlockup_detector_disable(void)
{
nmi_watchdog_user_enabled = 0;
}
static int __init hardlockup_panic_setup(char *str)
{
if (!strncmp(str, "panic", 5))
hardlockup_panic = 1;
else if (!strncmp(str, "nopanic", 7))
hardlockup_panic = 0;
else if (!strncmp(str, "0", 1))
nmi_watchdog_user_enabled = 0;
else if (!strncmp(str, "1", 1))
nmi_watchdog_user_enabled = 1;
return 1;
}
__setup("nmi_watchdog=", hardlockup_panic_setup);
#endif /* CONFIG_HARDLOCKUP_DETECTOR */
/*
* These functions can be overridden if an architecture implements its
* own hardlockup detector.
*
* watchdog_nmi_enable/disable can be implemented to start and stop when
* softlockup watchdog threads start and stop. The arch must select the
* SOFTLOCKUP_DETECTOR Kconfig.
*/
int __weak watchdog_nmi_enable(unsigned int cpu)
{
hardlockup_detector_perf_enable();
return 0;
}
void __weak watchdog_nmi_disable(unsigned int cpu)
{
hardlockup_detector_perf_disable();
}
/* Return 0, if a NMI watchdog is available. Error code otherwise */
int __weak __init watchdog_nmi_probe(void)
{
return hardlockup_detector_perf_init();
}
/**
* watchdog_nmi_stop - Stop the watchdog for reconfiguration
*
* The reconfiguration steps are:
* watchdog_nmi_stop();
* update_variables();
* watchdog_nmi_start();
*/
void __weak watchdog_nmi_stop(void) { }
/**
* watchdog_nmi_start - Start the watchdog after reconfiguration
*
* Counterpart to watchdog_nmi_stop().
*
* The following variables have been updated in update_variables() and
* contain the currently valid configuration:
* - watchdog_enabled
* - watchdog_thresh
* - watchdog_cpumask
*/
void __weak watchdog_nmi_start(void) { }
/**
* lockup_detector_update_enable - Update the sysctl enable bit
*
* Caller needs to make sure that the NMI/perf watchdogs are off, so this
* can't race with watchdog_nmi_disable().
*/
static void lockup_detector_update_enable(void)
{
watchdog_enabled = 0;
if (!watchdog_user_enabled)
return;
if (nmi_watchdog_available && nmi_watchdog_user_enabled)
watchdog_enabled |= NMI_WATCHDOG_ENABLED;
if (soft_watchdog_user_enabled)
watchdog_enabled |= SOFT_WATCHDOG_ENABLED;
}
#ifdef CONFIG_SOFTLOCKUP_DETECTOR
#define SOFTLOCKUP_RESET ULONG_MAX
#ifdef CONFIG_SMP
int __read_mostly sysctl_softlockup_all_cpu_backtrace;
#endif
static struct cpumask watchdog_allowed_mask __read_mostly;
/* Global variables, exported for sysctl */
unsigned int __read_mostly softlockup_panic =
CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
static bool softlockup_initialized __read_mostly;
static u64 __read_mostly sample_period;
static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
static DEFINE_PER_CPU(bool, softlockup_touch_sync);
static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
static unsigned long soft_lockup_nmi_warn;
static int __init nowatchdog_setup(char *str)
{
watchdog_user_enabled = 0;
return 1;
}
__setup("nowatchdog", nowatchdog_setup);
static int __init nosoftlockup_setup(char *str)
{
soft_watchdog_user_enabled = 0;
return 1;
}
__setup("nosoftlockup", nosoftlockup_setup);
static int __init watchdog_thresh_setup(char *str)
{
get_option(&str, &watchdog_thresh);
return 1;
}
__setup("watchdog_thresh=", watchdog_thresh_setup);
static void __lockup_detector_cleanup(void);
/*
* 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);
watchdog_update_hrtimer_threshold(sample_period);
}
/* Commands for resetting the watchdog */
static void update_touch_ts(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.
*/
notrace 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, SOFTLOCKUP_RESET);
}
notrace 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;
/*
* watchdog_mutex cannpt be taken here, as this might be called
* from (soft)interrupt context, so the access to
* watchdog_allowed_cpumask might race with a concurrent update.
*
* The watchdog time stamp can race against a concurrent real
* update as well, the only side effect might be a cycle delay for
* the softlockup check.
*/
for_each_cpu(cpu, &watchdog_allowed_mask)
per_cpu(watchdog_touch_ts, cpu) = SOFTLOCKUP_RESET;
wq_watchdog_touch(-1);
}
void touch_softlockup_watchdog_sync(void)
{
__this_cpu_write(softlockup_touch_sync, true);
__this_cpu_write(watchdog_touch_ts, SOFTLOCKUP_RESET);
}
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;
}
/* 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 void watchdog_interrupt_count(void)
{
__this_cpu_inc(hrtimer_interrupts);
}
static DEFINE_PER_CPU(struct completion, softlockup_completion);
static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
/*
* 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 int softlockup_fn(void *data)
{
update_touch_ts();
complete(this_cpu_ptr(&softlockup_completion));
return 0;
}
/* 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;
if (!watchdog_enabled)
return HRTIMER_NORESTART;
/* kick the hardlockup detector */
watchdog_interrupt_count();
/* kick the softlockup detector */
if (completion_done(this_cpu_ptr(&softlockup_completion))) {
reinit_completion(this_cpu_ptr(&softlockup_completion));
stop_one_cpu_nowait(smp_processor_id(),
softlockup_fn, NULL,
this_cpu_ptr(&softlockup_stop_work));
}
/* .. and repeat */
hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
if (touch_ts == SOFTLOCKUP_RESET) {
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();
update_touch_ts();
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;
/*
* Prevent multiple soft-lockup reports if one cpu is already
* engaged in dumping all cpu back traces.
*/
if (softlockup_all_cpu_backtrace) {
if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn))
return HRTIMER_RESTART;
}
/* Start period for the next softlockup warning. */
update_touch_ts();
pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
smp_processor_id(), duration,
current->comm, task_pid_nr(current));
print_modules();
print_irqtrace_events(current);
if (regs)
show_regs(regs);
else
dump_stack();
if (softlockup_all_cpu_backtrace) {
trigger_allbutself_cpu_backtrace();
clear_bit_unlock(0, &soft_lockup_nmi_warn);
}
trace_android_vh_watchdog_timer_softlockup(duration, regs, !!softlockup_panic);
add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
if (softlockup_panic)
panic("softlockup: hung tasks");
}
return HRTIMER_RESTART;
}
static void watchdog_enable(unsigned int cpu)
{
struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
struct completion *done = this_cpu_ptr(&softlockup_completion);
WARN_ON_ONCE(cpu != smp_processor_id());
init_completion(done);
complete(done);
/*
* Start the timer first to prevent the NMI watchdog triggering
* before the timer has a chance to fire.
*/
hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
hrtimer->function = watchdog_timer_fn;
hrtimer_start(hrtimer, ns_to_ktime(sample_period),
HRTIMER_MODE_REL_PINNED_HARD);
/* Initialize timestamp */
update_touch_ts();
/* Enable the perf event */
if (watchdog_enabled & NMI_WATCHDOG_ENABLED)
watchdog_nmi_enable(cpu);
}
static void watchdog_disable(unsigned int cpu)
{
struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
WARN_ON_ONCE(cpu != smp_processor_id());
/*
* Disable the perf event first. That prevents that a large delay
* between disabling the timer and disabling the perf event causes
* the perf NMI to detect a false positive.
*/
watchdog_nmi_disable(cpu);
hrtimer_cancel(hrtimer);
wait_for_completion(this_cpu_ptr(&softlockup_completion));
}
static int softlockup_stop_fn(void *data)
{
watchdog_disable(smp_processor_id());
return 0;
}
static void softlockup_stop_all(void)
{
int cpu;
if (!softlockup_initialized)
return;
for_each_cpu(cpu, &watchdog_allowed_mask)
smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
cpumask_clear(&watchdog_allowed_mask);
}
static int softlockup_start_fn(void *data)
{
watchdog_enable(smp_processor_id());
return 0;
}
static void softlockup_start_all(void)
{
int cpu;
cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
for_each_cpu(cpu, &watchdog_allowed_mask)
smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
}
int lockup_detector_online_cpu(unsigned int cpu)
{
if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
watchdog_enable(cpu);
return 0;
}
int lockup_detector_offline_cpu(unsigned int cpu)
{
if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
watchdog_disable(cpu);
return 0;
}
static void lockup_detector_reconfigure(void)
{
cpus_read_lock();
watchdog_nmi_stop();
softlockup_stop_all();
set_sample_period();
lockup_detector_update_enable();
if (watchdog_enabled && watchdog_thresh)
softlockup_start_all();
watchdog_nmi_start();
cpus_read_unlock();
/*
* Must be called outside the cpus locked section to prevent
* recursive locking in the perf code.
*/
__lockup_detector_cleanup();
}
/*
* Create the watchdog thread infrastructure and configure the detector(s).
*
* The threads are not unparked as watchdog_allowed_mask is empty. When
* the threads are successfully initialized, take the proper locks and
* unpark the threads in the watchdog_cpumask if the watchdog is enabled.
*/
static __init void lockup_detector_setup(void)
{
/*
* If sysctl is off and watchdog got disabled on the command line,
* nothing to do here.
*/
lockup_detector_update_enable();
if (!IS_ENABLED(CONFIG_SYSCTL) &&
!(watchdog_enabled && watchdog_thresh))
return;
mutex_lock(&watchdog_mutex);
lockup_detector_reconfigure();
softlockup_initialized = true;
mutex_unlock(&watchdog_mutex);
}
#else /* CONFIG_SOFTLOCKUP_DETECTOR */
static void lockup_detector_reconfigure(void)
{
cpus_read_lock();
watchdog_nmi_stop();
lockup_detector_update_enable();
watchdog_nmi_start();
cpus_read_unlock();
}
static inline void lockup_detector_setup(void)
{
lockup_detector_reconfigure();
}
#endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
static void __lockup_detector_cleanup(void)
{
lockdep_assert_held(&watchdog_mutex);
hardlockup_detector_perf_cleanup();
}
/**
* lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
*
* Caller must not hold the cpu hotplug rwsem.
*/
void lockup_detector_cleanup(void)
{
mutex_lock(&watchdog_mutex);
__lockup_detector_cleanup();
mutex_unlock(&watchdog_mutex);
}
/**
* lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
*
* Special interface for parisc. It prevents lockup detector warnings from
* the default pm_poweroff() function which busy loops forever.
*/
void lockup_detector_soft_poweroff(void)
{
watchdog_enabled = 0;
}
#ifdef CONFIG_SYSCTL
/* Propagate any changes to the watchdog threads */
static void proc_watchdog_update(void)
{
/* Remove impossible cpus to keep sysctl output clean. */
cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
lockup_detector_reconfigure();
}
/*
* common function for watchdog, nmi_watchdog and soft_watchdog parameter
*
* caller | table->data points to | 'which'
* -------------------|----------------------------|--------------------------
* proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED |
* | | SOFT_WATCHDOG_ENABLED
* -------------------|----------------------------|--------------------------
* proc_nmi_watchdog | nmi_watchdog_user_enabled | NMI_WATCHDOG_ENABLED
* -------------------|----------------------------|--------------------------
* proc_soft_watchdog | soft_watchdog_user_enabled | SOFT_WATCHDOG_ENABLED
*/
static int proc_watchdog_common(int which, struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
int err, old, *param = table->data;
mutex_lock(&watchdog_mutex);
if (!write) {
/*
* On read synchronize the userspace interface. This is a
* racy snapshot.
*/
*param = (watchdog_enabled & which) != 0;
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
} else {
old = READ_ONCE(*param);
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (!err && old != READ_ONCE(*param))
proc_watchdog_update();
}
mutex_unlock(&watchdog_mutex);
return err;
}
/*
* /proc/sys/kernel/watchdog
*/
int proc_watchdog(struct ctl_table *table, int write,
void *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 *buffer, size_t *lenp, loff_t *ppos)
{
if (!nmi_watchdog_available && write)
return -ENOTSUPP;
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 *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 *buffer, size_t *lenp, loff_t *ppos)
{
int err, old;
mutex_lock(&watchdog_mutex);
old = READ_ONCE(watchdog_thresh);
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (!err && write && old != READ_ONCE(watchdog_thresh))
proc_watchdog_update();
mutex_unlock(&watchdog_mutex);
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 *buffer, size_t *lenp, loff_t *ppos)
{
int err;
mutex_lock(&watchdog_mutex);
err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
if (!err && write)
proc_watchdog_update();
mutex_unlock(&watchdog_mutex);
return err;
}
#endif /* CONFIG_SYSCTL */
void __init lockup_detector_init(void)
{
if (tick_nohz_full_enabled())
pr_info("Disabling watchdog on nohz_full cores by default\n");
cpumask_copy(&watchdog_cpumask,
housekeeping_cpumask(HK_FLAG_TIMER));
if (!watchdog_nmi_probe())
nmi_watchdog_available = true;
lockup_detector_setup();
}