/* * Detect Soft Lockups * * started by Ingo Molnar, Copyright (C) 2005, 2006 Red Hat, Inc. * * this code detects soft lockups: incidents in where on a CPU * the kernel does not reschedule for 10 seconds or more. */ #include <linux/mm.h> #include <linux/cpu.h> #include <linux/init.h> #include <linux/delay.h> #include <linux/kthread.h> #include <linux/notifier.h> #include <linux/module.h> static DEFINE_SPINLOCK(print_lock); static DEFINE_PER_CPU(unsigned long, touch_timestamp); static DEFINE_PER_CPU(unsigned long, print_timestamp); static DEFINE_PER_CPU(struct task_struct *, watchdog_task); static int did_panic = 0; static int softlock_panic(struct notifier_block *this, unsigned long event, void *ptr) { did_panic = 1; return NOTIFY_DONE; } static struct notifier_block panic_block = { .notifier_call = softlock_panic, }; /* * 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 sched_clock() >> 30; /* 2^30 ~= 10^9 */ } void touch_softlockup_watchdog(void) { __raw_get_cpu_var(touch_timestamp) = get_timestamp(); } EXPORT_SYMBOL(touch_softlockup_watchdog); void touch_all_softlockup_watchdogs(void) { int cpu; /* Cause each CPU to re-update its timestamp rather than complain */ for_each_online_cpu(cpu) per_cpu(touch_timestamp, cpu) = 0; } EXPORT_SYMBOL(touch_all_softlockup_watchdogs); /* * This callback runs from the timer interrupt, and checks * whether the watchdog thread has hung or not: */ void softlockup_tick(void) { int this_cpu = smp_processor_id(); unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu); unsigned long print_timestamp; unsigned long now; if (touch_timestamp == 0) { touch_softlockup_watchdog(); return; } print_timestamp = per_cpu(print_timestamp, this_cpu); /* report at most once a second */ if (print_timestamp < (touch_timestamp + 1) || did_panic || !per_cpu(watchdog_task, this_cpu)) return; /* do not print during early bootup: */ if (unlikely(system_state != SYSTEM_RUNNING)) { touch_softlockup_watchdog(); return; } now = get_timestamp(); /* Wake up the high-prio watchdog task every second: */ if (now > (touch_timestamp + 1)) wake_up_process(per_cpu(watchdog_task, this_cpu)); /* Warn about unreasonable 10+ seconds delays: */ if (now > (touch_timestamp + 10)) { per_cpu(print_timestamp, this_cpu) = touch_timestamp; spin_lock(&print_lock); printk(KERN_ERR "BUG: soft lockup detected on CPU#%d!\n", this_cpu); dump_stack(); spin_unlock(&print_lock); } } /* * The watchdog thread - runs every second and touches the timestamp. */ static int watchdog(void * __bind_cpu) { struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; sched_setscheduler(current, SCHED_FIFO, ¶m); current->flags |= PF_NOFREEZE; /* initialize timestamp */ touch_softlockup_watchdog(); /* * Run briefly once per second to reset the softlockup timestamp. * If this gets delayed for more than 10 seconds then the * debug-printout triggers in softlockup_tick(). */ while (!kthread_should_stop()) { set_current_state(TASK_INTERRUPTIBLE); touch_softlockup_watchdog(); schedule(); } return 0; } /* * 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; struct task_struct *p; switch (action) { case CPU_UP_PREPARE: case CPU_UP_PREPARE_FROZEN: BUG_ON(per_cpu(watchdog_task, hotcpu)); p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu); if (IS_ERR(p)) { printk("watchdog for %i failed\n", hotcpu); return NOTIFY_BAD; } per_cpu(touch_timestamp, hotcpu) = 0; per_cpu(watchdog_task, hotcpu) = p; kthread_bind(p, hotcpu); break; case CPU_ONLINE: case CPU_ONLINE_FROZEN: wake_up_process(per_cpu(watchdog_task, hotcpu)); break; #ifdef CONFIG_HOTPLUG_CPU case CPU_UP_CANCELED: case CPU_UP_CANCELED_FROZEN: if (!per_cpu(watchdog_task, hotcpu)) break; /* Unbind so it can run. Fall thru. */ kthread_bind(per_cpu(watchdog_task, hotcpu), any_online_cpu(cpu_online_map)); case CPU_DEAD: case CPU_DEAD_FROZEN: p = per_cpu(watchdog_task, hotcpu); per_cpu(watchdog_task, hotcpu) = NULL; kthread_stop(p); break; #endif /* CONFIG_HOTPLUG_CPU */ } return NOTIFY_OK; } static struct notifier_block __cpuinitdata cpu_nfb = { .notifier_call = cpu_callback }; __init void spawn_softlockup_task(void) { void *cpu = (void *)(long)smp_processor_id(); int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); BUG_ON(err == NOTIFY_BAD); cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); register_cpu_notifier(&cpu_nfb); atomic_notifier_chain_register(&panic_notifier_list, &panic_block); }