/* * 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 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,}; void touch_softlockup_watchdog(void){	per_cpu(touch_timestamp, raw_smp_processor_id()) = jiffies;}EXPORT_SYMBOL(touch_softlockup_watchdog); /* * 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); 	/* prevent double reports: */	if (per_cpu(print_timestamp, this_cpu) == touch_timestamp ||		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;	} 	/* Wake up the high-prio watchdog task every second: */	if (time_after(jiffies, touch_timestamp + HZ))		wake_up_process(per_cpu(watchdog_task, this_cpu)); 	/* Warn about unreasonable 10+ seconds delays: */	if (time_after(jiffies, touch_timestamp + 10*HZ)) {		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 = 99 }; 	sched_setscheduler(current, SCHED_FIFO, &param);	current->flags |= PF_NOFREEZE; 	/*	 * 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 intcpu_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:		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) = jiffies;  		per_cpu(watchdog_task, hotcpu) = p;		kthread_bind(p, hotcpu); 		break;	case CPU_ONLINE:		wake_up_process(per_cpu(watchdog_task, hotcpu));		break;#ifdef CONFIG_HOTPLUG_CPU	case CPU_UP_CANCELED:		/* Unbind so it can run.  Fall thru. */		kthread_bind(per_cpu(watchdog_task, hotcpu),			     any_online_cpu(cpu_online_map));	case CPU_DEAD:		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 cpu_nfb = {	.notifier_call = cpu_callback}; __init void spawn_softlockup_task(void){	void *cpu = (void *)(long)smp_processor_id(); 	cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);	cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);	register_cpu_notifier(&cpu_nfb); 	atomic_notifier_chain_register(&panic_notifier_list, &panic_block);}