/* * 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 <uapi/linux/sched/types.h>#include <linux/tick.h>#include <linux/workqueue.h>#include <linux/sched/clock.h>#include <linux/sched/debug.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;#elseunsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;#endifint __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_SMPint __read_mostly sysctl_softlockup_all_cpu_backtrace;int __read_mostly sysctl_hardlockup_all_cpu_backtrace;#endifstatic 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) atomic_t watchdog_park_in_progress = ATOMIC_INIT(0); /* * 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_SMPstatic 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; if (atomic_read(&watchdog_park_in_progress) != 0) return HRTIMER_NORESTART; /* 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, ¶m);} 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; atomic_set(&watchdog_park_in_progress, 1); for_each_watchdog_cpu(cpu) { ret = kthread_park(per_cpu(softlockup_watchdog, cpu)); if (ret) break; } atomic_set(&watchdog_park_in_progress, 0); 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; Lines 1–500 of 842. Load more
/* * 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 <uapi/linux/sched/types.h> #include <linux/tick.h> #include <linux/workqueue.h> #include <linux/sched/clock.h> #include <linux/sched/debug.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) atomic_t watchdog_park_in_progress = ATOMIC_INIT(0); /* * 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; if (atomic_read(&watchdog_park_in_progress) != 0) return HRTIMER_NORESTART; /* 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, ¶m); } 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; atomic_set(&watchdog_park_in_progress, 1); for_each_watchdog_cpu(cpu) { ret = kthread_park(per_cpu(softlockup_watchdog, cpu)); if (ret) break; } atomic_set(&watchdog_park_in_progress, 0); 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;