diff options
Diffstat (limited to 'kernel/watchdog.c')
| -rw-r--r-- | kernel/watchdog.c | 227 |
1 files changed, 164 insertions, 63 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 75a2ab3d0b0..c3319bd1b04 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -23,14 +23,21 @@ #include <linux/module.h> #include <linux/sysctl.h> #include <linux/smpboot.h> +#include <linux/sched/rt.h> #include <asm/irq_regs.h> #include <linux/kvm_para.h> #include <linux/perf_event.h> -int watchdog_enabled = 1; +int watchdog_user_enabled = 1; int __read_mostly watchdog_thresh = 10; -static int __read_mostly watchdog_disabled; +#ifdef CONFIG_SMP +int __read_mostly sysctl_softlockup_all_cpu_backtrace; +#else +#define sysctl_softlockup_all_cpu_backtrace 0 +#endif + +static int __read_mostly watchdog_running; static u64 __read_mostly sample_period; static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); @@ -46,6 +53,7 @@ static DEFINE_PER_CPU(bool, watchdog_nmi_touch); static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); static DEFINE_PER_CPU(struct perf_event *, watchdog_ev); #endif +static unsigned long soft_lockup_nmi_warn; /* boot commands */ /* @@ -62,7 +70,7 @@ static int __init hardlockup_panic_setup(char *str) else if (!strncmp(str, "nopanic", 7)) hardlockup_panic = 0; else if (!strncmp(str, "0", 1)) - watchdog_enabled = 0; + watchdog_user_enabled = 0; return 1; } __setup("nmi_watchdog=", hardlockup_panic_setup); @@ -81,7 +89,7 @@ __setup("softlockup_panic=", softlockup_panic_setup); static int __init nowatchdog_setup(char *str) { - watchdog_enabled = 0; + watchdog_user_enabled = 0; return 1; } __setup("nowatchdog", nowatchdog_setup); @@ -89,11 +97,20 @@ __setup("nowatchdog", nowatchdog_setup); /* deprecated */ static int __init nosoftlockup_setup(char *str) { - watchdog_enabled = 0; + watchdog_user_enabled = 0; 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); +#endif /* * Hard-lockup warnings should be triggered after just a few seconds. Soft- @@ -112,9 +129,9 @@ static int get_softlockup_thresh(void) * resolution, and we don't need to waste time with a big divide when * 2^30ns == 1.074s. */ -static unsigned long get_timestamp(int this_cpu) +static unsigned long get_timestamp(void) { - return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */ + return local_clock() >> 30LL; /* 2^30 ~= 10^9 */ } static void set_sample_period(void) @@ -132,14 +149,16 @@ static void set_sample_period(void) /* Commands for resetting the watchdog */ static void __touch_watchdog(void) { - int this_cpu = smp_processor_id(); - - __this_cpu_write(watchdog_touch_ts, get_timestamp(this_cpu)); + __this_cpu_write(watchdog_touch_ts, get_timestamp()); } void touch_softlockup_watchdog(void) { - __this_cpu_write(watchdog_touch_ts, 0); + /* + * 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); } EXPORT_SYMBOL(touch_softlockup_watchdog); @@ -159,14 +178,14 @@ void touch_all_softlockup_watchdogs(void) #ifdef CONFIG_HARDLOCKUP_DETECTOR void touch_nmi_watchdog(void) { - if (watchdog_enabled) { - unsigned cpu; - - for_each_present_cpu(cpu) { - if (per_cpu(watchdog_nmi_touch, cpu) != true) - per_cpu(watchdog_nmi_touch, cpu) = true; - } - } + /* + * Using __raw here because some code paths have + * preemption enabled. If preemption is enabled + * then interrupts should be enabled too, in which + * case we shouldn't have to worry about the watchdog + * going off. + */ + __raw_get_cpu_var(watchdog_nmi_touch) = true; touch_softlockup_watchdog(); } EXPORT_SYMBOL(touch_nmi_watchdog); @@ -195,7 +214,7 @@ static int is_hardlockup(void) static int is_softlockup(unsigned long touch_ts) { - unsigned long now = get_timestamp(smp_processor_id()); + unsigned long now = get_timestamp(); /* Warn about unreasonable delays: */ if (time_after(now, touch_ts + get_softlockup_thresh())) @@ -268,6 +287,7 @@ 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(); @@ -314,6 +334,17 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) 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); + return HRTIMER_RESTART; + } + } + printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", smp_processor_id(), duration, current->comm, task_pid_nr(current)); @@ -324,6 +355,17 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) 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(); + } + if (softlockup_panic) panic("softlockup: hung tasks"); __this_cpu_write(soft_watchdog_warn, true); @@ -348,11 +390,6 @@ static void watchdog_enable(unsigned int cpu) hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); hrtimer->function = watchdog_timer_fn; - if (!watchdog_enabled) { - kthread_park(current); - return; - } - /* Enable the perf event */ watchdog_nmi_enable(cpu); @@ -375,6 +412,11 @@ static void watchdog_disable(unsigned int cpu) 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) != @@ -476,28 +518,84 @@ static int watchdog_nmi_enable(unsigned int cpu) { return 0; } static void watchdog_nmi_disable(unsigned int cpu) { return; } #endif /* CONFIG_HARDLOCKUP_DETECTOR */ -/* prepare/enable/disable routines */ -/* sysctl functions */ -#ifdef CONFIG_SYSCTL -static void watchdog_enable_all_cpus(void) +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, +}; + +static void restart_watchdog_hrtimer(void *info) +{ + struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer); + int ret; + + /* + * No need to cancel and restart hrtimer if it is currently executing + * because it will reprogram itself with the new period now. + * We should never see it unqueued here because we are running per-cpu + * with interrupts disabled. + */ + ret = hrtimer_try_to_cancel(hrtimer); + if (ret == 1) + hrtimer_start(hrtimer, ns_to_ktime(sample_period), + HRTIMER_MODE_REL_PINNED); +} + +static void update_timers(int cpu) +{ + /* + * Make sure that perf event counter will adopt to a new + * sampling period. Updating the sampling period directly would + * be much nicer but we do not have an API for that now so + * let's use a big hammer. + * Hrtimer will adopt the new period on the next tick but this + * might be late already so we have to restart the timer as well. + */ + watchdog_nmi_disable(cpu); + smp_call_function_single(cpu, restart_watchdog_hrtimer, NULL, 1); + watchdog_nmi_enable(cpu); +} + +static void update_timers_all_cpus(void) { - unsigned int cpu; + int cpu; + + get_online_cpus(); + for_each_online_cpu(cpu) + update_timers(cpu); + put_online_cpus(); +} - if (watchdog_disabled) { - watchdog_disabled = 0; - for_each_online_cpu(cpu) - kthread_unpark(per_cpu(softlockup_watchdog, cpu)); +static int watchdog_enable_all_cpus(bool sample_period_changed) +{ + int err = 0; + + if (!watchdog_running) { + err = smpboot_register_percpu_thread(&watchdog_threads); + if (err) + pr_err("Failed to create watchdog threads, disabled\n"); + else + watchdog_running = 1; + } else if (sample_period_changed) { + update_timers_all_cpus(); } + + return err; } +/* prepare/enable/disable routines */ +/* sysctl functions */ +#ifdef CONFIG_SYSCTL static void watchdog_disable_all_cpus(void) { - unsigned int cpu; - - if (!watchdog_disabled) { - watchdog_disabled = 1; - for_each_online_cpu(cpu) - kthread_park(per_cpu(softlockup_watchdog, cpu)); + if (watchdog_running) { + watchdog_running = 0; + smpboot_unregister_percpu_thread(&watchdog_threads); } } @@ -508,40 +606,43 @@ static void watchdog_disable_all_cpus(void) int proc_dowatchdog(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { - int ret; + int err, old_thresh, old_enabled; + static DEFINE_MUTEX(watchdog_proc_mutex); - if (watchdog_disabled < 0) - return -ENODEV; + mutex_lock(&watchdog_proc_mutex); + old_thresh = ACCESS_ONCE(watchdog_thresh); + old_enabled = ACCESS_ONCE(watchdog_user_enabled); - ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); - if (ret || !write) - return ret; + err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + if (err || !write) + goto out; set_sample_period(); - if (watchdog_enabled && watchdog_thresh) - watchdog_enable_all_cpus(); + /* + * Watchdog threads shouldn't be enabled if they are + * disabled. The 'watchdog_running' variable check in + * watchdog_*_all_cpus() function takes care of this. + */ + if (watchdog_user_enabled && watchdog_thresh) + err = watchdog_enable_all_cpus(old_thresh != watchdog_thresh); else watchdog_disable_all_cpus(); - return ret; + /* Restore old values on failure */ + if (err) { + watchdog_thresh = old_thresh; + watchdog_user_enabled = old_enabled; + } +out: + mutex_unlock(&watchdog_proc_mutex); + return err; } #endif /* CONFIG_SYSCTL */ -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, - .park = watchdog_disable, - .unpark = watchdog_enable, -}; - void __init lockup_detector_init(void) { set_sample_period(); - if (smpboot_register_percpu_thread(&watchdog_threads)) { - pr_err("Failed to create watchdog threads, disabled\n"); - watchdog_disabled = -ENODEV; - } + + if (watchdog_user_enabled) + watchdog_enable_all_cpus(false); } |