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32 results

softlockup.c

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  • softlockup.c 8.86 KiB
    /*
     * 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 ((tainted & 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 __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);