/* * 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/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 <asm/irq_regs.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 __read_mostly did_panic; int __read_mostly softlockup_thresh = 60; /* * Should we panic (and reboot, if panic_timeout= is set) when a * soft-lockup occurs: */ 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 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(int this_cpu) { return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */ } static void __touch_softlockup_watchdog(void) { int this_cpu = raw_smp_processor_id(); __raw_get_cpu_var(touch_timestamp) = get_timestamp(this_cpu); } void touch_softlockup_watchdog(void) { __raw_get_cpu_var(touch_timestamp) = 0; } 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; struct pt_regs *regs = get_irq_regs(); unsigned long now; /* Is detection switched off? */ if (!per_cpu(watchdog_task, this_cpu) || softlockup_thresh <= 0) { /* Be sure we don't false trigger if switched back on */ if (touch_timestamp) per_cpu(touch_timestamp, this_cpu) = 0; return; } 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 || did_panic) return; /* do not print during early bootup: */ if (unlikely(system_state != SYSTEM_RUNNING)) { __touch_softlockup_watchdog(); return; } now = get_timestamp(this_cpu); /* * Wake up the high-prio watchdog task twice per * threshold timespan. */ if (now > touch_timestamp + softlockup_thresh/2) wake_up_process(per_cpu(watchdog_task, this_cpu)); /* Warn about unreasonable delays: */ if (now <= (touch_timestamp + softlockup_thresh)) return; per_cpu(print_timestamp, this_cpu) = touch_timestamp; spin_lock(&print_lock); printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n", this_cpu, now - touch_timestamp, current->comm, task_pid_nr(current)); print_modules(); print_irqtrace_events(current); if (regs) show_regs(regs); else dump_stack(); spin_unlock(&print_lock); if (softlockup_panic) panic("softlockup: hung tasks"); } /* * Have a reasonable limit on the number of tasks checked: */ unsigned long __read_mostly sysctl_hung_task_check_count = 1024; /* * Zero means infinite timeout - no checking done: */ unsigned long __read_mostly sysctl_hung_task_timeout_secs = 120; unsigned long __read_mostly sysctl_hung_task_warnings = 10; /* * Only do the hung-tasks check on one CPU: */ static int check_cpu __read_mostly = -1; static void check_hung_task(struct task_struct *t, unsigned long now) { unsigned long switch_count = t->nvcsw + t->nivcsw; if (t->flags & PF_FROZEN) return; if (switch_count != t->last_switch_count || !t->last_switch_timestamp) { t->last_switch_count = switch_count; t->last_switch_timestamp = now; return; } if ((long)(now - t->last_switch_timestamp) < sysctl_hung_task_timeout_secs) return; if (sysctl_hung_task_warnings < 0) return; sysctl_hung_task_warnings--; /* * Ok, the task did not get scheduled for more than 2 minutes, * complain: */ printk(KERN_ERR "INFO: task %s:%d blocked for more than " "%ld seconds.\n", t->comm, t->pid, sysctl_hung_task_timeout_secs); printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" " disables this message.\n"); sched_show_task(t); __debug_show_held_locks(t); t->last_switch_timestamp = now; touch_nmi_watchdog(); if (softlockup_panic) panic("softlockup: blocked tasks"); } /* * Check whether a TASK_UNINTERRUPTIBLE does not get woken up for * a really long time (120 seconds). If that happens, print out * a warning. */ static void check_hung_uninterruptible_tasks(int this_cpu) { int max_count = sysctl_hung_task_check_count; unsigned long now = get_timestamp(this_cpu); struct task_struct *g, *t; /* * If the system crashed already then all bets are off, * do not report extra hung tasks: */ if (test_taint(TAINT_DIE) || did_panic) return; read_lock(&tasklist_lock); do_each_thread(g, t) { if (!--max_count) goto unlock; /* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */ if (t->state == TASK_UNINTERRUPTIBLE) check_hung_task(t, now); } while_each_thread(g, t); unlock: read_unlock(&tasklist_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 }; int this_cpu = (long)__bind_cpu; sched_setscheduler(current, SCHED_FIFO, ¶m); /* initialize timestamp */ __touch_softlockup_watchdog(); 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 * debug-printout triggers in softlockup_tick(). */ while (!kthread_should_stop()) { __touch_softlockup_watchdog(); schedule(); if (kthread_should_stop()) break; if (this_cpu == check_cpu) { if (sysctl_hung_task_timeout_secs) check_hung_uninterruptible_tasks(this_cpu); } set_current_state(TASK_INTERRUPTIBLE); } __set_current_state(TASK_RUNNING); 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(KERN_ERR "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: check_cpu = any_online_cpu(cpu_online_map); wake_up_process(per_cpu(watchdog_task, hotcpu)); break; #ifdef CONFIG_HOTPLUG_CPU case CPU_DOWN_PREPARE: case CPU_DOWN_PREPARE_FROZEN: if (hotcpu == check_cpu) { cpumask_t temp_cpu_online_map = cpu_online_map; cpu_clear(hotcpu, temp_cpu_online_map); check_cpu = any_online_cpu(temp_cpu_online_map); } break; 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 }; static int __initdata nosoftlockup; static int __init nosoftlockup_setup(char *str) { nosoftlockup = 1; return 1; } __setup("nosoftlockup", nosoftlockup_setup); static int __init spawn_softlockup_task(void) { void *cpu = (void *)(long)smp_processor_id(); int err; if (nosoftlockup) return 0; err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); if (err == NOTIFY_BAD) { BUG(); return 1; } cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); register_cpu_notifier(&cpu_nfb); atomic_notifier_chain_register(&panic_notifier_list, &panic_block); return 0; } early_initcall(spawn_softlockup_task);