cregit-Linux how code gets into the kernel

Release 4.7 kernel/watchdog.c

Directory: kernel
/*
 * 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 <linux/tick.h>
#include <linux/workqueue.h>

#include <asm/irq_regs.h>
#include <linux/kvm_para.h>
#include <linux/perf_event.h>
#include <linux/kthread.h>

/*
 * The run state of the lockup detectors is controlled by the content of the
 * 'watchdog_enabled' variable. Each lockup detector has its dedicated bit -
 * bit 0 for the hard lockup detector and bit 1 for the soft lockup detector.
 *
 * 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled'
 * are variables that are only used as an 'interface' between the parameters
 * in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The
 * 'watchdog_thresh' variable is handled differently because its value is not
 * boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh'
 * is equal zero.
 */

#define NMI_WATCHDOG_ENABLED_BIT   0

#define SOFT_WATCHDOG_ENABLED_BIT  1

#define NMI_WATCHDOG_ENABLED      (1 << NMI_WATCHDOG_ENABLED_BIT)

#define SOFT_WATCHDOG_ENABLED     (1 << SOFT_WATCHDOG_ENABLED_BIT)

static DEFINE_MUTEX(watchdog_proc_mutex);

#ifdef CONFIG_HARDLOCKUP_DETECTOR

static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
#else

static 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;
#else

#define sysctl_softlockup_all_cpu_backtrace 0

#define sysctl_hardlockup_all_cpu_backtrace 0
#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)

/*
 * 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);
#ifdef CONFIG_HARDLOCKUP_DETECTOR
static DEFINE_PER_CPU(bool, hard_watchdog_warn);
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 */
/*
 * Should we panic when a soft-lockup or hard-lockup occurs:
 */
#ifdef CONFIG_HARDLOCKUP_DETECTOR

unsigned int __read_mostly hardlockup_panic =
			CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;

static unsigned long hardlockup_allcpu_dumped;
/*
 * 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 hardlockup_detector_disable(void) { watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; }

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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)) watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; else if (!strncmp(str, "1", 1)) watchdog_enabled |= NMI_WATCHDOG_ENABLED; return 1; }

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__setup("nmi_watchdog=", hardlockup_panic_setup); #endif 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; }

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__setup("softlockup_panic=", softlockup_panic_setup);
static int __init nowatchdog_setup(char *str) { watchdog_enabled = 0; return 1; }

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__setup("nowatchdog", nowatchdog_setup);
static int __init nosoftlockup_setup(char *str) { watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED; return 1; }

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__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; }

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__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; }

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__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; }

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/* * 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 */ }

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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); }

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/* Commands for resetting the watchdog */
static void __touch_watchdog(void) { __this_cpu_write(watchdog_touch_ts, get_timestamp()); }

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/** * 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); }

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void touch_softlockup_watchdog(void) { touch_softlockup_watchdog_sched(); wq_watchdog_touch(raw_smp_processor_id()); }

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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); }

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#ifdef CONFIG_HARDLOCKUP_DETECTOR
void touch_nmi_watchdog(void) { /* * 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_cpu_write(watchdog_nmi_touch, true); touch_softlockup_watchdog(); }

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EXPORT_SYMBOL(touch_nmi_watchdog); #endif
void touch_softlockup_watchdog_sync(void) { __this_cpu_write(softlockup_touch_sync, true); __this_cpu_write(watchdog_touch_ts, 0); }

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#ifdef CONFIG_HARDLOCKUP_DETECTOR /* watchdog detector functions */
static 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; }

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#endif
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; }

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#ifdef CONFIG_HARDLOCKUP_DETECTOR static struct perf_event_attr wd_hw_attr = { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_CPU_CYCLES, .size = sizeof(struct perf_event_attr), .pinned = 1, .disabled = 1, }; /* Callback function for perf event subsystem */
static void watchdog_overflow_callback(struct perf_event *event, struct perf_sample_data *data, struct pt_regs *regs) { /* Ensure the watchdog never gets throttled */ event->hw.interrupts = 0; if (__this_cpu_read(watchdog_nmi_touch) == true) { __this_cpu_write(watchdog_nmi_touch, false); return; } /* check for a hardlockup * This is done by making sure our timer interrupt * is incrementing. The timer interrupt should have * fired multiple times before we overflow'd. If it hasn't * then this is a good indication the cpu is stuck */ if (is_hardlockup()) { int this_cpu = smp_processor_id(); struct pt_regs *regs = get_irq_regs(); /* only print hardlockups once */ if (__this_cpu_read(hard_watchdog_warn) == true) return; pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu); print_modules(); print_irqtrace_events(current); if (regs) show_regs(regs); else dump_stack(); /* * Perform all-CPU dump only once to avoid multiple hardlockups * generating interleaving traces */ if (sysctl_hardlockup_all_cpu_backtrace && !test_and_set_bit(0, &hardlockup_allcpu_dumped)) trigger_allbutself_cpu_backtrace(); if (hardlockup_panic) nmi_panic(regs, "Hard LOCKUP"); __this_cpu_write(hard_watchdog_warn, true); return; } __this_cpu_write(hard_watchdog_warn, false); return; }

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#endif /* CONFIG_HARDLOCKUP_DETECTOR */
static void watchdog_interrupt_count(void) { __this_cpu_inc(hrtimer_interrupts); }

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static int watchdog_nmi_enable(unsigned int cpu); static void 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; /* 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; }

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eric b munsoneric b munson134.36%111.11%
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static void watchdog_set_prio(unsigned int policy, unsigned int prio) { struct sched_param param = { .sched_priority = prio }; sched_setscheduler(current, policy, &param); }

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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(); }

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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); }

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static void watchdog_cleanup(unsigned int cpu, bool online) { watchdog_disable(cpu); }

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static int watchdog_should_run(unsigned int cpu) { return __this_cpu_read(hrtimer_interrupts) != __this_cpu_read(soft_lockup_hrtimer_cnt); }

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/* * 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); }

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Total38100.00%2100.00%

#ifdef CONFIG_HARDLOCKUP_DETECTOR /* * People like the simple clean cpu node info on boot. * Reduce the watchdog noise by only printing messages * that are different from what cpu0 displayed. */ static unsigned long cpu0_err;
static int watchdog_nmi_enable(unsigned int cpu) { struct perf_event_attr *wd_attr; struct perf_event *event = per_cpu(watchdog_ev, cpu); /* nothing to do if the hard lockup detector is disabled */ if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) goto out; /* is it already setup and enabled? */ if (event && event->state > PERF_EVENT_STATE_OFF) goto out; /* it is setup but not enabled */ if (event != NULL) goto out_enable; wd_attr = &wd_hw_attr; wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh); /* Try to register using hardware perf events */ event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL); /* save cpu0 error for future comparision */ if (cpu == 0 && IS_ERR(event)) cpu0_err = PTR_ERR(event); if (!IS_ERR(event)) { /* only print for cpu0 or different than cpu0 */ if (cpu == 0 || cpu0_err) pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n"); goto out_save; } /* * Disable the hard lockup detector if _any_ CPU fails to set up * set up the hardware perf event. The watchdog() function checks * the NMI_WATCHDOG_ENABLED bit periodically. * * The barriers are for syncing up watchdog_enabled across all the * cpus, as clear_bit() does not use barriers. */ smp_mb__before_atomic(); clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled); smp_mb__after_atomic(); /* skip displaying the same error again */ if (cpu > 0 && (PTR_ERR(event) == cpu0_err)) return PTR_ERR(event); /* vary the KERN level based on the returned errno */ if (PTR_ERR(event) == -EOPNOTSUPP) pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu); else if (PTR_ERR(event) == -ENOENT) pr_warn("disabled (cpu%i): hardware events not enabled\n", cpu); else pr_err("disabled (cpu%i): unable to create perf event: %ld\n", cpu, PTR_ERR(event)); pr_info("Shutting down hard lockup detector on all cpus\n"); return PTR_ERR(event); /* success path */ out_save: per_cpu(watchdog_ev, cpu) = event; out_enable: perf_event_enable(per_cpu(watchdog_ev, cpu)); out: return 0; }

Contributors

PersonTokensPropCommitsCommitProp
don zickusdon zickus21179.32%320.00%
ulrich obergfellulrich obergfell3312.41%320.00%
andrew mortonandrew morton62.26%16.67%
akinobu mitaakinobu mita41.50%16.67%
mandeep singh bainesmandeep singh baines31.13%16.67%
ben hutchingsben hutchings31.13%16.67%
avi kivityavi kivity20.75%16.67%
thomas gleixnerthomas gleixner10.38%16.67%
cyrill gorcunovcyrill gorcunov10.38%16.67%
matt helsleymatt helsley10.38%16.67%
fabian frederickfabian frederick10.38%16.67%
Total266100.00%15100.00%


static void watchdog_nmi_disable(unsigned int cpu) { struct perf_event *event = per_cpu(watchdog_ev, cpu); if (event) { perf_event_disable(event); per_cpu(watchdog_ev, cpu) = NULL; /* should be in cleanup, but blocks oprofile */ perf_event_release_kernel(event); } if (cpu == 0) { /* watchdog_nmi_enable() expects this to be zero initially. */ cpu0_err = 0; } }

Contributors

PersonTokensPropCommitsCommitProp
don zickusdon zickus4777.05%133.33%
ulrich obergfellulrich obergfell1321.31%133.33%
thomas gleixnerthomas gleixner11.64%133.33%
Total61100.00%3100.00%

#else
static int watchdog_nmi_enable(unsigned int cpu) { return 0; }

Contributors

PersonTokensPropCommitsCommitProp
don zickusdon zickus1292.31%150.00%
thomas gleixnerthomas gleixner17.69%150.00%
Total13100.00%2100.00%


static void watchdog_nmi_disable(unsigned int cpu) { return; }

Contributors

PersonTokensPropCommitsCommitProp
don zickusdon zickus1090.91%150.00%
thomas gleixnerthomas gleixner19.09%150.00%
Total11100.00%2100.00%

#endif /* CONFIG_HARDLOCKUP_DETECTOR */ 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; for_each_watchdog_cpu(cpu) { ret = kthread_park(per_cpu(softlockup_watchdog, cpu)); if (ret) break; } return ret; }

Contributors

PersonTokensPropCommitsCommitProp
ulrich obergfellulrich obergfell41100.00%1100.00%
Total41100.00%1100.00%

/* * 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; for_each_watchdog_cpu(cpu) kthread_unpark(per_cpu(softlockup_watchdog, cpu)); }

Contributors

PersonTokensPropCommitsCommitProp
ulrich obergfellulrich obergfell25100.00%1100.00%
Total25100.00%1100.00%

/* * Suspend the hard and soft lockup detector by parking the watchdog threads. */
int lockup_detector_suspend(void) { int ret = 0; get_online_cpus(); mutex_lock(&watchdog_proc_mutex); /* * Multiple suspend requests can be active in parallel (counted by * the 'watchdog_suspended' variable). If the watchdog threads are * running, the first caller takes care that they will be parked. * The state of 'watchdog_running' cannot change while a suspend * request is active (see related code in 'proc' handlers). */ if (watchdog_running && !watchdog_suspended) ret = watchdog_park_threads(); if (ret == 0) watchdog_suspended++; else { watchdog_disable_all_cpus(); pr_err("Failed to suspend lockup detectors, disabled\n"); watchdog_enabled = 0; } mutex_unlock(&watchdog_proc_mutex); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
ulrich obergfellulrich obergfell67100.00%4100.00%
Total67100.00%4100.00%

/* * Resume the hard and soft lockup detector by unparking the watchdog threads. */
void lockup_detector_resume(void) { mutex_lock(&watchdog_proc_mutex); watchdog_suspended--; /* * The watchdog threads are unparked if they were previously running * and if there is no more active suspend request. */ if (watchdog_running && !watchdog_suspended) watchdog_unpark_threads(); mutex_unlock(&watchdog_proc_mutex); put_online_cpus(); }

Contributors

PersonTokensPropCommitsCommitProp
ulrich obergfellulrich obergfell36100.00%3100.00%
Total36100.00%3100.00%


static int update_watchdog_all_cpus(void) { int ret; ret = watchdog_park_threads(); if (ret) return ret; watchdog_unpark_threads(); return 0; }

Contributors

PersonTokensPropCommitsCommitProp
ulrich obergfellulrich obergfell1965.52%375.00%
michal hockomichal hocko1034.48%125.00%
Total29100.00%4100.00%


static int watchdog_enable_all_cpus(void) { int err = 0; if (!watchdog_running) { err = smpboot_register_percpu_thread_cpumask(&watchdog_threads, &watchdog_cpumask); if (err) pr_err("Failed to create watchdog threads, disabled\n"); else watchdog_running = 1; } else { /* * Enable/disable the lockup detectors or * change the sample period 'on the fly'. */ err = update_watchdog_all_cpus(); if (err) { watchdog_disable_all_cpus(); pr_err("Failed to update lockup detectors, disabled\n"); } } if (err) watchdog_enabled = 0; return err; }

Contributors

PersonTokensPropCommitsCommitProp
frederic weisbeckerfrederic weisbecker2835.44%333.33%
ulrich obergfellulrich obergfell2835.44%222.22%
don zickusdon zickus1215.19%111.11%
thomas gleixnerthomas gleixner67.59%111.11%
michal hockomichal hocko45.06%111.11%
marcin slusarzmarcin slusarz11.27%111.11%
Total79100.00%9100.00%


static void watchdog_disable_all_cpus(void) { if (watchdog_running) { watchdog_running = 0; smpboot_unregister_percpu_thread(&watchdog_threads); } }

Contributors

PersonTokensPropCommitsCommitProp
don zickusdon zickus937.50%125.00%
thomas gleixnerthomas gleixner937.50%125.00%
frederic weisbeckerfrederic weisbecker625.00%250.00%
Total24100.00%4100.00%

#ifdef CONFIG_SYSCTL /* * Update the run state of the lockup detectors. */
static int proc_watchdog_update(void) { int err = 0; /* * Watchdog threads won't be started if they are already active. * The 'watchdog_running' variable in watchdog_*_all_cpus() takes * care of this. If those threads are already active, the sample * period will be updated and the lockup detectors will be enabled * or disabled 'on the fly'. */ if (watchdog_enabled && watchdog_thresh) err = watchdog_enable_all_cpus(); else watchdog_disable_all_cpus(); return err; }

Contributors

PersonTokensPropCommitsCommitProp
ulrich obergfellulrich obergfell32100.00%2100.00%
Total32100.00%2100.00%

/* * common function for watchdog, nmi_watchdog and soft_watchdog parameter * * caller | table->data points to | 'which' contains the flag(s) * -------------------|-----------------------|----------------------------- * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed * | | with SOFT_WATCHDOG_ENABLED * -------------------|-----------------------|----------------------------- * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED * -------------------|-----------------------|----------------------------- * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED */
static int proc_watchdog_common(int which, struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { int err, old, new; int *watchdog_param = (int *)table->data; get_online_cpus(); mutex_lock(&watchdog_proc_mutex); if (watchdog_suspended) { /* no parameter changes allowed while watchdog is suspended */ err = -EAGAIN; goto out; } /* * If the parameter is being read return the state of the corresponding * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the * run state of the lockup detectors. */ if (!write) { *watchdog_param = (watchdog_enabled & which) != 0; err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); } else { err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); if (err) goto out; /* * There is a race window between fetching the current value * from 'watchdog_enabled' and storing the new value. During * this race window, watchdog_nmi_enable() can sneak in and * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'. * The 'cmpxchg' detects this race and the loop retries. */ do { old = watchdog_enabled; /* * If the parameter value is not zero set the * corresponding bit(s), else clear it(them). */ if (*watchdog_param) new = old | which; else new = old & ~which; } while (cmpxchg(&watchdog_enabled, old, new) != old); /* * Update the run state of the lockup detectors. There is _no_ * need to check the value returned by proc_watchdog_update() * and to restore the previous value of 'watchdog_enabled' as * both lockup detectors are disabled if proc_watchdog_update() * returns an error. */ if (old == new) goto out; err = proc_watchdog_update(); } out: mutex_unlock(&watchdog_proc_mutex); put_online_cpus(); return err; }

Contributors

PersonTokensPropCommitsCommitProp
ulrich obergfellulrich obergfell13465.69%538.46%
don zickusdon zickus3517.16%17.69%
michal hockomichal hocko94.41%17.69%
josh huntjosh hunt94.41%17.69%
mandeep singh bainesmandeep singh baines62.94%215.38%
frederic weisbeckerfrederic weisbecker62.94%17.69%
marcin slusarzmarcin slusarz41.96%17.69%
liu chuanshengliu chuansheng10.49%17.69%
Total204100.00%13100.00%

/* * /proc/sys/kernel/watchdog */
int proc_watchdog(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED, table, write, buffer, lenp, ppos); }

Contributors

PersonTokensPropCommitsCommitProp
ulrich obergfellulrich obergfell44100.00%1100.00%
Total44100.00%1100.00%

/* * /proc/sys/kernel/nmi_watchdog */
int proc_nmi_watchdog(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { return proc_watchdog_common(NMI_WATCHDOG_ENABLED, table, write, buffer, lenp, ppos); }

Contributors

PersonTokensPropCommitsCommitProp
ulrich obergfellulrich obergfell42100.00%1100.00%
Total42100.00%1100.00%

/* * /proc/sys/kernel/soft_watchdog */
int proc_soft_watchdog(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { return proc_watchdog_common(SOFT_WATCHDOG_ENABLED, table, write, buffer, lenp, ppos); }

Contributors

PersonTokensPropCommitsCommitProp
ulrich obergfellulrich obergfell42100.00%1100.00%
Total42100.00%1100.00%

/* * /proc/sys/kernel/watchdog_thresh */
int proc_watchdog_thresh(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { int err, old, new; get_online_cpus(); mutex_lock(&watchdog_proc_mutex); if (watchdog_suspended) { /* no parameter changes allowed while watchdog is suspended */ err = -EAGAIN; goto out; } old = ACCESS_ONCE(watchdog_thresh); err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); if (err || !write) goto out; /* * Update the sample period. Restore on failure. */ new = ACCESS_ONCE(watchdog_thresh); if (old == new) goto out; set_sample_period(); err = proc_watchdog_update(); if (err) { watchdog_thresh = old; set_sample_period(); } out: mutex_unlock(&watchdog_proc_mutex); put_online_cpus(); return err; }

Contributors

PersonTokensPropCommitsCommitProp
ulrich obergfellulrich obergfell9869.50%550.00%
josh huntjosh hunt1812.77%110.00%
michal hockomichal hocko117.80%220.00%
frederic weisbeckerfrederic weisbecker96.38%110.00%
don zickusdon zickus53.55%110.00%
Total141100.00%10100.00%

/* * 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 __user *buffer, size_t *lenp, loff_t *ppos) { int err; get_online_cpus(); mutex_lock(&watchdog_proc_mutex); if (watchdog_suspended) { /* no parameter changes allowed while watchdog is suspended */ err = -EAGAIN; goto out; } err = proc_do_large_bitmap(table, write, buffer, lenp, ppos); if (!err && write) { /* Remove impossible cpus to keep sysctl output cleaner. */ cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask); if (watchdog_running) { /* * Failure would be due to being unable to allocate * a temporary cpumask, so we are likely not in a * position to do much else to make things better. */ if (smpboot_update_cpumask_percpu_thread( &watchdog_threads, &watchdog_cpumask) != 0) pr_err("cpumask update failed\n"); } } out: mutex_unlock(&watchdog_proc_mutex); put_online_cpus(); return err; }

Contributors

PersonTokensPropCommitsCommitProp
chris metcalfchris metcalf10582.03%133.33%
ulrich obergfellulrich obergfell2317.97%266.67%
Total128100.00%3100.00%

#endif /* CONFIG_SYSCTL */
void __init lockup_detector_init(void) { set_sample_period(); #ifdef CONFIG_NO_HZ_FULL if (tick_nohz_full_enabled()) { pr_info("Disabling watchdog on nohz_full cores by default\n"); cpumask_copy(&watchdog_cpumask, housekeeping_mask); } else cpumask_copy(&watchdog_cpumask, cpu_possible_mask); #else cpumask_copy(&watchdog_cpumask, cpu_possible_mask); #endif if (watchdog_enabled) watchdog_enable_all_cpus(); }

Contributors

PersonTokensPropCommitsCommitProp
chris metcalfchris metcalf4267.74%111.11%
don zickusdon zickus69.68%111.11%
thomas gleixnerthomas gleixner46.45%111.11%
liu chuanshengliu chuansheng34.84%111.11%
frederic weisbeckerfrederic weisbecker34.84%222.22%
ulrich obergfellulrich obergfell23.23%222.22%
peter zijlstrapeter zijlstra23.23%111.11%
Total62100.00%9100.00%


Overall Contributors

PersonTokensPropCommitsCommitProp
don zickusdon zickus117938.67%1011.90%
ulrich obergfellulrich obergfell83527.39%2226.19%
chris metcalfchris metcalf1785.84%11.19%
thomas gleixnerthomas gleixner1785.84%22.38%
frederic weisbeckerfrederic weisbecker1244.07%55.95%
aaron tomlinaaron tomlin1163.80%11.19%
jiri kosinajiri kosina973.18%11.19%
christoph lameterchristoph lameter481.57%22.38%
chai wenchai wen411.34%11.19%
josh huntjosh hunt341.12%22.38%
michal hockomichal hocko341.12%22.38%
mandeep singh bainesmandeep singh baines300.98%44.76%
tejun heotejun heo270.89%22.38%
liu chuanshengliu chuansheng200.66%22.38%
peter zijlstrapeter zijlstra170.56%33.57%
eric b munsoneric b munson160.52%11.19%
bjorn morkbjorn mork160.52%11.19%
andrew mortonandrew morton150.49%22.38%
ingo molnaringo molnar80.26%22.38%
marcin slusarzmarcin slusarz60.20%33.57%
akinobu mitaakinobu mita40.13%11.19%
clark williamsclark williams30.10%11.19%
yaowei baiyaowei bai30.10%11.19%
ben hutchingsben hutchings30.10%11.19%
hidehiro kawaihidehiro kawai30.10%22.38%
namhyung kimnamhyung kim30.10%11.19%
fabian frederickfabian frederick20.07%11.19%
fernando luis vazquez caofernando luis vazquez cao20.07%11.19%
avi kivityavi kivity20.07%11.19%
ben zhangben zhang10.03%11.19%
cyrill gorcunovcyrill gorcunov10.03%11.19%
lin minglin ming10.03%11.19%
matt helsleymatt helsley10.03%11.19%
cyril burcyril bur10.03%11.19%
Total3049100.00%84100.00%
Directory: kernel
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