/* * 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 <linux/sysctl.h> #include <asm/irq_regs.h> static DEFINE_SPINLOCK(print_lock); static DEFINE_PER_CPU(unsigned long, softlockup_touch_ts); /* touch timestamp */static DEFINE_PER_CPU(unsigned long, softlockup_print_ts); /* print timestamp */static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);static DEFINE_PER_CPU(bool, softlock_touch_sync); 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(softlockup_touch_ts) = get_timestamp(this_cpu);} void touch_softlockup_watchdog(void){	__raw_get_cpu_var(softlockup_touch_ts) = 0;}EXPORT_SYMBOL(touch_softlockup_watchdog); void touch_softlockup_watchdog_sync(void){	__raw_get_cpu_var(softlock_touch_sync) = true;	__raw_get_cpu_var(softlockup_touch_ts) = 0;} 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(softlockup_touch_ts, cpu) = 0;}EXPORT_SYMBOL(touch_all_softlockup_watchdogs); int proc_dosoftlockup_thresh(struct ctl_table *table, int write,			     void __user *buffer,			     size_t *lenp, loff_t *ppos){	touch_all_softlockup_watchdogs();	return proc_dointvec_minmax(table, write, buffer, lenp, ppos);} /* * 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_ts = per_cpu(softlockup_touch_ts, this_cpu);	unsigned long print_ts;	struct pt_regs *regs = get_irq_regs();	unsigned long now; 	/* Is detection switched off? */	if (!per_cpu(softlockup_watchdog, this_cpu) || softlockup_thresh <= 0) {		/* Be sure we don't false trigger if switched back on */		if (touch_ts)			per_cpu(softlockup_touch_ts, this_cpu) = 0;		return;	} 	if (touch_ts == 0) {		if (unlikely(per_cpu(softlock_touch_sync, this_cpu))) {			/*			 * If the time stamp was touched atomically			 * make sure the scheduler tick is up to date.			 */			per_cpu(softlock_touch_sync, this_cpu) = false;			sched_clock_tick();		}		__touch_softlockup_watchdog();		return;	} 	print_ts = per_cpu(softlockup_print_ts, this_cpu); 	/* report at most once a second */	if (print_ts == touch_ts || 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 (time_after(now - softlockup_thresh/2, touch_ts))		wake_up_process(per_cpu(softlockup_watchdog, this_cpu)); 	/* Warn about unreasonable delays: */	if (time_before_eq(now - softlockup_thresh, touch_ts))		return; 	per_cpu(softlockup_print_ts, this_cpu) = touch_ts; 	spin_lock(&print_lock);	printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n",			this_cpu, now - touch_ts,			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");} /* * 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(); 	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; 		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(softlockup_watchdog, 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(softlockup_touch_ts, hotcpu) = 0;		per_cpu(softlockup_watchdog, hotcpu) = p;		kthread_bind(p, hotcpu);		break;	case CPU_ONLINE:	case CPU_ONLINE_FROZEN:		wake_up_process(per_cpu(softlockup_watchdog, hotcpu));		break;#ifdef CONFIG_HOTPLUG_CPU	case CPU_UP_CANCELED:	case CPU_UP_CANCELED_FROZEN:		if (!per_cpu(softlockup_watchdog, hotcpu))			break;		/* Unbind so it can run.  Fall thru. */		kthread_bind(per_cpu(softlockup_watchdog, hotcpu),			     cpumask_any(cpu_online_mask));	case CPU_DEAD:	case CPU_DEAD_FROZEN:		p = per_cpu(softlockup_watchdog, hotcpu);		per_cpu(softlockup_watchdog, 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);