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kernel/watchdog.c
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/* * Detect hard and soft lockups on a system * * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc. * * this code detects hard lockups: incidents in where on a CPU * the kernel does not respond to anything except NMI. * * Note: Most of this code is borrowed heavily from softlockup.c, * so thanks to Ingo for the initial implementation. * Some chunks also taken from arch/x86/kernel/apic/nmi.c, thanks * to those contributors as well. */ #include <linux/mm.h> #include <linux/cpu.h> #include <linux/nmi.h> #include <linux/init.h> #include <linux/delay.h> #include <linux/freezer.h> #include <linux/kthread.h> #include <linux/lockdep.h> #include <linux/notifier.h> #include <linux/module.h> #include <linux/sysctl.h> #include <asm/irq_regs.h> #include <linux/perf_event.h> |
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int watchdog_enabled = 1; |
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int __read_mostly softlockup_thresh = 60; 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); |
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static DEFINE_PER_CPU(bool, soft_watchdog_warn); |
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#ifdef CONFIG_HARDLOCKUP_DETECTOR |
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static DEFINE_PER_CPU(bool, hard_watchdog_warn); static DEFINE_PER_CPU(bool, watchdog_nmi_touch); |
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static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); static DEFINE_PER_CPU(struct perf_event *, watchdog_ev); #endif |
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/* boot commands */ /* * Should we panic when a soft-lockup or hard-lockup occurs: */ |
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#ifdef CONFIG_HARDLOCKUP_DETECTOR |
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static int hardlockup_panic = CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE; |
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static int __init hardlockup_panic_setup(char *str) { if (!strncmp(str, "panic", 5)) hardlockup_panic = 1; |
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else if (!strncmp(str, "nopanic", 7)) hardlockup_panic = 0; |
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else if (!strncmp(str, "0", 1)) |
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watchdog_enabled = 0; |
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return 1; } __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; } __setup("softlockup_panic=", softlockup_panic_setup); static int __init nowatchdog_setup(char *str) { |
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watchdog_enabled = 0; |
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return 1; } __setup("nowatchdog", nowatchdog_setup); /* deprecated */ static int __init nosoftlockup_setup(char *str) { |
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watchdog_enabled = 0; |
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return 1; } __setup("nosoftlockup", nosoftlockup_setup); /* */ /* * 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(int this_cpu) { return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */ } static unsigned long get_sample_period(void) { /* * convert softlockup_thresh from seconds to ns * the divide by 5 is to give hrtimer 5 chances to * increment before the hardlockup detector generates * a warning */ return softlockup_thresh / 5 * NSEC_PER_SEC; } /* Commands for resetting the watchdog */ static void __touch_watchdog(void) { |
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int this_cpu = smp_processor_id(); |
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__this_cpu_write(watchdog_touch_ts, get_timestamp(this_cpu)); |
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} |
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void touch_softlockup_watchdog(void) |
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{ |
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__this_cpu_write(watchdog_touch_ts, 0); |
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} |
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EXPORT_SYMBOL(touch_softlockup_watchdog); |
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void touch_all_softlockup_watchdogs(void) |
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{ 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_online_cpu(cpu) per_cpu(watchdog_touch_ts, cpu) = 0; } |
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#ifdef CONFIG_HARDLOCKUP_DETECTOR |
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void touch_nmi_watchdog(void) { |
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if (watchdog_enabled) { unsigned cpu; for_each_present_cpu(cpu) { if (per_cpu(watchdog_nmi_touch, cpu) != true) per_cpu(watchdog_nmi_touch, cpu) = true; } } |
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touch_softlockup_watchdog(); |
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} EXPORT_SYMBOL(touch_nmi_watchdog); |
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#endif |
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void touch_softlockup_watchdog_sync(void) { __raw_get_cpu_var(softlockup_touch_sync) = true; __raw_get_cpu_var(watchdog_touch_ts) = 0; } |
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#ifdef CONFIG_HARDLOCKUP_DETECTOR |
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/* watchdog detector functions */ |
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static int is_hardlockup(void) |
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{ |
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unsigned long hrint = __this_cpu_read(hrtimer_interrupts); |
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if (__this_cpu_read(hrtimer_interrupts_saved) == hrint) |
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return 1; |
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__this_cpu_write(hrtimer_interrupts_saved, hrint); |
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return 0; } #endif |
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static int is_softlockup(unsigned long touch_ts) |
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{ |
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unsigned long now = get_timestamp(smp_processor_id()); |
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/* Warn about unreasonable delays: */ if (time_after(now, touch_ts + softlockup_thresh)) return now - touch_ts; return 0; } |
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#ifdef CONFIG_HARDLOCKUP_DETECTOR |
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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 */ |
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static void watchdog_overflow_callback(struct perf_event *event, int nmi, |
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struct perf_sample_data *data, struct pt_regs *regs) { |
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/* Ensure the watchdog never gets throttled */ event->hw.interrupts = 0; |
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if (__this_cpu_read(watchdog_nmi_touch) == true) { __this_cpu_write(watchdog_nmi_touch, false); |
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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 */ |
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if (is_hardlockup()) { int this_cpu = smp_processor_id(); |
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/* only print hardlockups once */ |
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if (__this_cpu_read(hard_watchdog_warn) == true) |
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return; if (hardlockup_panic) panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu); else WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu); |
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__this_cpu_write(hard_watchdog_warn, true); |
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return; } |
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__this_cpu_write(hard_watchdog_warn, false); |
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return; } static void watchdog_interrupt_count(void) { |
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__this_cpu_inc(hrtimer_interrupts); |
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} #else static inline void watchdog_interrupt_count(void) { return; } |
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#endif /* CONFIG_HARDLOCKUP_DETECTOR */ |
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/* watchdog kicker functions */ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) { |
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unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts); |
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struct pt_regs *regs = get_irq_regs(); int duration; /* kick the hardlockup detector */ watchdog_interrupt_count(); /* kick the softlockup detector */ |
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wake_up_process(__this_cpu_read(softlockup_watchdog)); |
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/* .. and repeat */ hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period())); if (touch_ts == 0) { |
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if (unlikely(__this_cpu_read(softlockup_touch_sync))) { |
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/* * If the time stamp was touched atomically * make sure the scheduler tick is up to date. */ |
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__this_cpu_write(softlockup_touch_sync, false); |
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sched_clock_tick(); } __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 */ |
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duration = is_softlockup(touch_ts); |
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if (unlikely(duration)) { /* only warn once */ |
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if (__this_cpu_read(soft_watchdog_warn) == true) |
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return HRTIMER_RESTART; printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d] ", |
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smp_processor_id(), duration, |
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current->comm, task_pid_nr(current)); print_modules(); print_irqtrace_events(current); if (regs) show_regs(regs); else dump_stack(); if (softlockup_panic) panic("softlockup: hung tasks"); |
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__this_cpu_write(soft_watchdog_warn, true); |
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} else |
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__this_cpu_write(soft_watchdog_warn, false); |
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return HRTIMER_RESTART; } /* * The watchdog thread - touches the timestamp. */ |
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static int watchdog(void *unused) |
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{ |
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static struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; |
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struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer); |
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sched_setscheduler(current, SCHED_FIFO, ¶m); /* initialize timestamp */ __touch_watchdog(); /* kick off the timer for the hardlockup detector */ /* done here because hrtimer_start can only pin to smp_processor_id() */ hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()), HRTIMER_MODE_REL_PINNED); set_current_state(TASK_INTERRUPTIBLE); /* * Run briefly once per second to reset the softlockup timestamp. * If this gets delayed for more than 60 seconds then the |
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* debug-printout triggers in watchdog_timer_fn(). |
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*/ while (!kthread_should_stop()) { __touch_watchdog(); schedule(); if (kthread_should_stop()) break; set_current_state(TASK_INTERRUPTIBLE); } __set_current_state(TASK_RUNNING); return 0; } |
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#ifdef CONFIG_HARDLOCKUP_DETECTOR |
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static int watchdog_nmi_enable(int cpu) { struct perf_event_attr *wd_attr; struct perf_event *event = per_cpu(watchdog_ev, cpu); /* 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; /* Try to register using hardware perf events */ wd_attr = &wd_hw_attr; wd_attr->sample_period = hw_nmi_get_sample_period(); |
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event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback); |
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if (!IS_ERR(event)) { printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter. "); goto out_save; } |
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/* vary the KERN level based on the returned errno */ if (PTR_ERR(event) == -EOPNOTSUPP) printk(KERN_INFO "NMI watchdog disabled (cpu%i): not supported (no LAPIC?) ", cpu); else if (PTR_ERR(event) == -ENOENT) printk(KERN_WARNING "NMI watchdog disabled (cpu%i): hardware events not enabled ", cpu); else printk(KERN_ERR "NMI watchdog disabled (cpu%i): unable to create perf event: %ld ", cpu, PTR_ERR(event)); |
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return PTR_ERR(event); |
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/* success path */ out_save: per_cpu(watchdog_ev, cpu) = event; out_enable: perf_event_enable(per_cpu(watchdog_ev, cpu)); out: return 0; } static void watchdog_nmi_disable(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); } return; } #else static int watchdog_nmi_enable(int cpu) { return 0; } static void watchdog_nmi_disable(int cpu) { return; } |
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#endif /* CONFIG_HARDLOCKUP_DETECTOR */ |
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/* prepare/enable/disable routines */ static int watchdog_prepare_cpu(int cpu) { struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu); WARN_ON(per_cpu(softlockup_watchdog, cpu)); hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); hrtimer->function = watchdog_timer_fn; return 0; } static int watchdog_enable(int cpu) { struct task_struct *p = per_cpu(softlockup_watchdog, cpu); |
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int err = 0; |
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/* enable the perf event */ |
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err = watchdog_nmi_enable(cpu); |
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/* Regardless of err above, fall through and start softlockup */ |
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/* create the watchdog thread */ if (!p) { p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu); if (IS_ERR(p)) { printk(KERN_ERR "softlockup watchdog for %i failed ", cpu); |
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if (!err) /* if hardlockup hasn't already set this */ err = PTR_ERR(p); goto out; |
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} kthread_bind(p, cpu); per_cpu(watchdog_touch_ts, cpu) = 0; per_cpu(softlockup_watchdog, cpu) = p; wake_up_process(p); } |
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out: return err; |
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} static void watchdog_disable(int cpu) { struct task_struct *p = per_cpu(softlockup_watchdog, cpu); struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu); /* * cancel the timer first to stop incrementing the stats * and waking up the kthread */ hrtimer_cancel(hrtimer); /* disable the perf event */ watchdog_nmi_disable(cpu); /* stop the watchdog thread */ if (p) { per_cpu(softlockup_watchdog, cpu) = NULL; kthread_stop(p); } |
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} static void watchdog_enable_all_cpus(void) { int cpu; |
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watchdog_enabled = 0; |
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for_each_online_cpu(cpu) |
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if (!watchdog_enable(cpu)) /* if any cpu succeeds, watchdog is considered enabled for the system */ watchdog_enabled = 1; |
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|
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if (!watchdog_enabled) |
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printk(KERN_ERR "watchdog: failed to be enabled on some cpus "); } static void watchdog_disable_all_cpus(void) { int cpu; for_each_online_cpu(cpu) watchdog_disable(cpu); /* if all watchdogs are disabled, then they are disabled for the system */ watchdog_enabled = 0; } /* sysctl functions */ #ifdef CONFIG_SYSCTL /* * proc handler for /proc/sys/kernel/nmi_watchdog */ int proc_dowatchdog_enabled(struct ctl_table *table, int write, void __user *buffer, size_t *length, loff_t *ppos) { proc_dointvec(table, write, buffer, length, ppos); |
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if (write) { if (watchdog_enabled) watchdog_enable_all_cpus(); else watchdog_disable_all_cpus(); } |
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return 0; } int proc_dowatchdog_thresh(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { return proc_dointvec_minmax(table, write, buffer, lenp, ppos); } |
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#endif /* CONFIG_SYSCTL */ /* * Create/destroy watchdog threads as CPUs come and go: */ static int __cpuinit cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) { int hotcpu = (unsigned long)hcpu; |
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int err = 0; |
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switch (action) { case CPU_UP_PREPARE: case CPU_UP_PREPARE_FROZEN: |
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err = watchdog_prepare_cpu(hotcpu); |
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break; case CPU_ONLINE: case CPU_ONLINE_FROZEN: |
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if (watchdog_enabled) err = watchdog_enable(hotcpu); |
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break; #ifdef CONFIG_HOTPLUG_CPU case CPU_UP_CANCELED: case CPU_UP_CANCELED_FROZEN: watchdog_disable(hotcpu); break; case CPU_DEAD: case CPU_DEAD_FROZEN: watchdog_disable(hotcpu); break; #endif /* CONFIG_HOTPLUG_CPU */ } |
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/* * hardlockup and softlockup are not important enough * to block cpu bring up. Just always succeed and * rely on printk output to flag problems. */ return NOTIFY_OK; |
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} static struct notifier_block __cpuinitdata cpu_nfb = { .notifier_call = cpu_callback }; |
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void __init lockup_detector_init(void) |
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{ void *cpu = (void *)(long)smp_processor_id(); int err; |
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err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); |
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WARN_ON(notifier_to_errno(err)); |
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cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); register_cpu_notifier(&cpu_nfb); |
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return; |
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} |