// 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> 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; static struct cpumask watchdog_allowed_mask __read_mostly; struct cpumask watchdog_cpumask __read_mostly;unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask); #ifdef CONFIG_HARDLOCKUP_DETECTOR # ifdef CONFIG_SMPint __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_SMPint __read_mostly sysctl_softlockup_all_cpu_backtrace;#endif /* 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(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; 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 __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. */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){ __touch_watchdog(); 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(); __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) 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)); 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_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 */ __touch_watchdog(); /* 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); Lines 1–500 of 753. Load more
// 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> 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; static struct cpumask watchdog_allowed_mask __read_mostly; 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 /* 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(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; 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 __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. */ 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) { __touch_watchdog(); 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(); __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) 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)); 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_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 */ __touch_watchdog(); /* 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);