diff options
Diffstat (limited to 'kernel/watchdog.c')
| -rw-r--r-- | kernel/watchdog.c | 46 |
1 files changed, 24 insertions, 22 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 7c397907d0e9..ad912511a0c0 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -92,7 +92,7 @@ __setup("nmi_watchdog=", hardlockup_panic_setup); * 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 watchdog start and stop. The arch must select the * SOFTLOCKUP_DETECTOR Kconfig. */ int __weak watchdog_nmi_enable(unsigned int cpu) @@ -302,10 +302,10 @@ void touch_softlockup_watchdog_sync(void) __this_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT); } -static int is_softlockup(unsigned long touch_ts, unsigned long period_ts) +static int is_softlockup(unsigned long touch_ts, + unsigned long period_ts, + unsigned long now) { - unsigned long now = get_timestamp(); - if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){ /* Warn about unreasonable delays. */ if (time_after(now, period_ts + get_softlockup_thresh())) @@ -335,7 +335,7 @@ 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. + * The watchdog feed 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 @@ -353,8 +353,7 @@ static int softlockup_fn(void *data) /* watchdog kicker functions */ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) { - unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts); - unsigned long period_ts = __this_cpu_read(watchdog_report_ts); + unsigned long touch_ts, period_ts, now; struct pt_regs *regs = get_irq_regs(); int duration; int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace; @@ -377,11 +376,22 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period)); /* + * Read the current timestamp first. It might become invalid anytime + * when a virtual machine is stopped by the host or when the watchog + * is touched from NMI. + */ + now = get_timestamp(); + /* * 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 process the timestamps. + * the watchdog like a soft lockup. This function touches the watchdog. */ kvm_check_and_clear_guest_paused(); + /* + * The stored timestamp is comparable with @now only when not touched. + * It might get touched anytime from NMI. Make sure that is_softlockup() + * uses the same (valid) value. + */ + period_ts = READ_ONCE(*this_cpu_ptr(&watchdog_report_ts)); /* Reset the interval when touched by known problematic code. */ if (period_ts == SOFTLOCKUP_DELAY_REPORT) { @@ -398,13 +408,9 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) 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, period_ts); + /* Check for a softlockup. */ + touch_ts = __this_cpu_read(watchdog_touch_ts); + duration = is_softlockup(touch_ts, period_ts, now); if (unlikely(duration)) { /* * Prevent multiple soft-lockup reports if one cpu is already @@ -552,11 +558,7 @@ static void lockup_detector_reconfigure(void) } /* - * 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. + * Create the watchdog infrastructure and configure the detector(s). */ static __init void lockup_detector_setup(void) { @@ -622,7 +624,7 @@ void lockup_detector_soft_poweroff(void) #ifdef CONFIG_SYSCTL -/* Propagate any changes to the watchdog threads */ +/* Propagate any changes to the watchdog infrastructure */ static void proc_watchdog_update(void) { /* Remove impossible cpus to keep sysctl output clean. */ |