diff options
Diffstat (limited to 'kernel/watchdog.c')
| -rw-r--r-- | kernel/watchdog.c | 129 |
1 files changed, 66 insertions, 63 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 71109065bd8e..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) @@ -154,7 +154,11 @@ static void lockup_detector_update_enable(void) #ifdef CONFIG_SOFTLOCKUP_DETECTOR -#define SOFTLOCKUP_RESET ULONG_MAX +/* + * Delay the soflockup report when running a known slow code. + * It does _not_ affect the timestamp of the last successdul reschedule. + */ +#define SOFTLOCKUP_DELAY_REPORT ULONG_MAX #ifdef CONFIG_SMP int __read_mostly sysctl_softlockup_all_cpu_backtrace; @@ -169,10 +173,12 @@ unsigned int __read_mostly softlockup_panic = static bool softlockup_initialized __read_mostly; static u64 __read_mostly sample_period; +/* Timestamp taken after the last successful reschedule. */ static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); +/* Timestamp of the last softlockup report. */ +static DEFINE_PER_CPU(unsigned long, watchdog_report_ts); 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, hrtimer_interrupts_saved); static unsigned long soft_lockup_nmi_warn; @@ -235,10 +241,16 @@ static void set_sample_period(void) watchdog_update_hrtimer_threshold(sample_period); } +static void update_report_ts(void) +{ + __this_cpu_write(watchdog_report_ts, get_timestamp()); +} + /* Commands for resetting the watchdog */ -static void __touch_watchdog(void) +static void update_touch_ts(void) { __this_cpu_write(watchdog_touch_ts, get_timestamp()); + update_report_ts(); } /** @@ -252,10 +264,10 @@ static void __touch_watchdog(void) 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. + * Preemption can be enabled. It doesn't matter which CPU's watchdog + * report period gets restarted here, so use the raw_ operation. */ - raw_cpu_write(watchdog_touch_ts, SOFTLOCKUP_RESET); + raw_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT); } notrace void touch_softlockup_watchdog(void) @@ -278,24 +290,25 @@ void touch_all_softlockup_watchdogs(void) * 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); + for_each_cpu(cpu, &watchdog_allowed_mask) { + per_cpu(watchdog_report_ts, cpu) = SOFTLOCKUP_DELAY_REPORT; + wq_watchdog_touch(cpu); + } } void touch_softlockup_watchdog_sync(void) { __this_cpu_write(softlockup_touch_sync, true); - __this_cpu_write(watchdog_touch_ts, SOFTLOCKUP_RESET); + __this_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT); } -static int is_softlockup(unsigned long touch_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, touch_ts + get_softlockup_thresh())) + if (time_after(now, period_ts + get_softlockup_thresh())) return now - touch_ts; } return 0; @@ -322,7 +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 @@ -331,7 +344,7 @@ static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work); */ static int softlockup_fn(void *data) { - __touch_watchdog(); + update_touch_ts(); complete(this_cpu_ptr(&softlockup_completion)); return 0; @@ -340,7 +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 touch_ts, period_ts, now; struct pt_regs *regs = get_irq_regs(); int duration; int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace; @@ -362,7 +375,26 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) /* .. and repeat */ hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period)); - if (touch_ts == SOFTLOCKUP_RESET) { + /* + * 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. 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) { if (unlikely(__this_cpu_read(softlockup_touch_sync))) { /* * If the time stamp was touched atomically @@ -372,43 +404,26 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) sched_clock_tick(); } - /* Clear the guest paused flag on watchdog reset */ - kvm_check_and_clear_guest_paused(); - __touch_watchdog(); + update_report_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); + /* Check for a softlockup. */ + touch_ts = __this_cpu_read(watchdog_touch_ts); + duration = is_softlockup(touch_ts, period_ts, now); 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 + * Prevent multiple soft-lockup reports if one cpu is already + * engaged in dumping all cpu back traces. */ - if (kvm_check_and_clear_guest_paused()) - return HRTIMER_RESTART; - - /* only warn once */ - if (__this_cpu_read(soft_watchdog_warn) == true) - 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); + if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn)) return HRTIMER_RESTART; - } } + /* Start period for the next softlockup warning. */ + update_report_ts(); + pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", smp_processor_id(), duration, current->comm, task_pid_nr(current)); @@ -420,22 +435,14 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) 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(); + clear_bit_unlock(0, &soft_lockup_nmi_warn); } 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; } @@ -460,7 +467,7 @@ static void watchdog_enable(unsigned int cpu) HRTIMER_MODE_REL_PINNED_HARD); /* Initialize timestamp */ - __touch_watchdog(); + update_touch_ts(); /* Enable the perf event */ if (watchdog_enabled & NMI_WATCHDOG_ENABLED) watchdog_nmi_enable(cpu); @@ -551,11 +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) { @@ -621,7 +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. */ |