/* * 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 intsoftlock_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)		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, &param); 	/* 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 __cpuinitcpu_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);