diff options
Diffstat (limited to 'kernel/watchdog.c')
| -rw-r--r-- | kernel/watchdog.c | 759 |
1 files changed, 759 insertions, 0 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c new file mode 100644 index 000000000..78a4603e1 --- /dev/null +++ b/kernel/watchdog.c @@ -0,0 +1,759 @@ +// 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; + +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 + +static struct cpumask watchdog_allowed_mask __read_mostly; + +/* 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(unsigned long, hrtimer_interrupts); +static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); +static unsigned long soft_lockup_nmi_warn; + +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_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 update_touch_ts(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) +{ + update_touch_ts(); + 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(); + update_touch_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); + 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; + + /* + * Prevent multiple soft-lockup reports if one cpu is already + * engaged in dumping all cpu back traces. + */ + if (softlockup_all_cpu_backtrace) { + if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn)) + return HRTIMER_RESTART; + } + + /* Start period for the next softlockup warning. */ + update_touch_ts(); + + 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) { + trigger_allbutself_cpu_backtrace(); + clear_bit_unlock(0, &soft_lockup_nmi_warn); + } + + add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); + if (softlockup_panic) + panic("softlockup: hung tasks"); + } + + 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 */ + update_touch_ts(); + /* 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); + + cpumask_clear(&watchdog_allowed_mask); +} + +static int softlockup_start_fn(void *data) +{ + watchdog_enable(smp_processor_id()); + return 0; +} + +static void softlockup_start_all(void) +{ + int cpu; + + cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask); + for_each_cpu(cpu, &watchdog_allowed_mask) + smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false); +} + +int lockup_detector_online_cpu(unsigned int cpu) +{ + if (cpumask_test_cpu(cpu, &watchdog_allowed_mask)) + watchdog_enable(cpu); + return 0; +} + +int lockup_detector_offline_cpu(unsigned int cpu) +{ + if (cpumask_test_cpu(cpu, &watchdog_allowed_mask)) + watchdog_disable(cpu); + return 0; +} + +static void __lockup_detector_reconfigure(void) +{ + cpus_read_lock(); + watchdog_nmi_stop(); + + softlockup_stop_all(); + set_sample_period(); + lockup_detector_update_enable(); + if (watchdog_enabled && watchdog_thresh) + softlockup_start_all(); + + watchdog_nmi_start(); + cpus_read_unlock(); + /* + * Must be called outside the cpus locked section to prevent + * recursive locking in the perf code. + */ + __lockup_detector_cleanup(); +} + +void lockup_detector_reconfigure(void) +{ + mutex_lock(&watchdog_mutex); + __lockup_detector_reconfigure(); + mutex_unlock(&watchdog_mutex); +} + +/* + * 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. + */ +static __init void lockup_detector_setup(void) +{ + /* + * If sysctl is off and watchdog got disabled on the command line, + * nothing to do here. + */ + lockup_detector_update_enable(); + + if (!IS_ENABLED(CONFIG_SYSCTL) && + !(watchdog_enabled && watchdog_thresh)) + return; + + mutex_lock(&watchdog_mutex); + __lockup_detector_reconfigure(); + softlockup_initialized = true; + mutex_unlock(&watchdog_mutex); +} + +#else /* CONFIG_SOFTLOCKUP_DETECTOR */ +static void __lockup_detector_reconfigure(void) +{ + cpus_read_lock(); + watchdog_nmi_stop(); + lockup_detector_update_enable(); + watchdog_nmi_start(); + cpus_read_unlock(); +} +void lockup_detector_reconfigure(void) +{ + __lockup_detector_reconfigure(); +} +static inline void lockup_detector_setup(void) +{ + __lockup_detector_reconfigure(); +} +#endif /* !CONFIG_SOFTLOCKUP_DETECTOR */ + +static void __lockup_detector_cleanup(void) +{ + lockdep_assert_held(&watchdog_mutex); + hardlockup_detector_perf_cleanup(); +} + +/** + * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes + * + * Caller must not hold the cpu hotplug rwsem. + */ +void lockup_detector_cleanup(void) +{ + mutex_lock(&watchdog_mutex); + __lockup_detector_cleanup(); + mutex_unlock(&watchdog_mutex); +} + +/** + * lockup_detector_soft_poweroff - Interface to stop lockup detector(s) + * + * Special interface for parisc. It prevents lockup detector warnings from + * the default pm_poweroff() function which busy loops forever. + */ +void lockup_detector_soft_poweroff(void) +{ + watchdog_enabled = 0; +} + +#ifdef CONFIG_SYSCTL + +/* Propagate any changes to the watchdog threads */ +static void proc_watchdog_update(void) +{ + /* Remove impossible cpus to keep sysctl output clean. */ + cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask); + __lockup_detector_reconfigure(); +} + +/* + * common function for watchdog, nmi_watchdog and soft_watchdog parameter + * + * caller | table->data points to | 'which' + * -------------------|----------------------------|-------------------------- + * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED | + * | | SOFT_WATCHDOG_ENABLED + * -------------------|----------------------------|-------------------------- + * proc_nmi_watchdog | nmi_watchdog_user_enabled | NMI_WATCHDOG_ENABLED + * -------------------|----------------------------|-------------------------- + * proc_soft_watchdog | soft_watchdog_user_enabled | SOFT_WATCHDOG_ENABLED + */ +static int proc_watchdog_common(int which, struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + int err, old, *param = table->data; + + mutex_lock(&watchdog_mutex); + + if (!write) { + /* + * On read synchronize the userspace interface. This is a + * racy snapshot. + */ + *param = (watchdog_enabled & which) != 0; + err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + } else { + old = READ_ONCE(*param); + err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + if (!err && old != READ_ONCE(*param)) + proc_watchdog_update(); + } + mutex_unlock(&watchdog_mutex); + return err; +} + +/* + * /proc/sys/kernel/watchdog + */ +int proc_watchdog(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED, + table, write, buffer, lenp, ppos); +} + +/* + * /proc/sys/kernel/nmi_watchdog + */ +int proc_nmi_watchdog(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + if (!nmi_watchdog_available && write) + return -ENOTSUPP; + return proc_watchdog_common(NMI_WATCHDOG_ENABLED, + table, write, buffer, lenp, ppos); +} + +/* + * /proc/sys/kernel/soft_watchdog + */ +int proc_soft_watchdog(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + return proc_watchdog_common(SOFT_WATCHDOG_ENABLED, + table, write, buffer, lenp, ppos); +} + +/* + * /proc/sys/kernel/watchdog_thresh + */ +int proc_watchdog_thresh(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + int err, old; + + mutex_lock(&watchdog_mutex); + + old = READ_ONCE(watchdog_thresh); + err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + + if (!err && write && old != READ_ONCE(watchdog_thresh)) + proc_watchdog_update(); + + mutex_unlock(&watchdog_mutex); + return err; +} + +/* + * The cpumask is the mask of possible cpus that the watchdog can run + * on, not the mask of cpus it is actually running on. This allows the + * user to specify a mask that will include cpus that have not yet + * been brought online, if desired. + */ +int proc_watchdog_cpumask(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + int err; + + mutex_lock(&watchdog_mutex); + + err = proc_do_large_bitmap(table, write, buffer, lenp, ppos); + if (!err && write) + proc_watchdog_update(); + + mutex_unlock(&watchdog_mutex); + return err; +} +#endif /* CONFIG_SYSCTL */ + +void __init lockup_detector_init(void) +{ + if (tick_nohz_full_enabled()) + pr_info("Disabling watchdog on nohz_full cores by default\n"); + + cpumask_copy(&watchdog_cpumask, + housekeeping_cpumask(HK_FLAG_TIMER)); + + if (!watchdog_nmi_probe()) + nmi_watchdog_available = true; + lockup_detector_setup(); +} |