/* * 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/freezer.h>#include <linux/kthread.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 did_panic;int softlockup_thresh = 10; 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) >> 30;  /* 2^30 ~= 10^9 */} void touch_softlockup_watchdog(void){	int this_cpu = raw_smp_processor_id(); 	__raw_get_cpu_var(touch_timestamp) = get_timestamp(this_cpu);}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; 	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 &&			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(this_cpu); 	/* 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 + 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));	if (regs)		show_regs(regs);	else		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, &param); 	/* 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 __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:		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);}