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Commit 6687a97d authored by Ingo Molnar's avatar Ingo Molnar Committed by Linus Torvalds
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[PATCH] timer-irq-driven soft-watchdog, cleanups 



Make the softlockup detector purely timer-interrupt driven, removing
softirq-context (timer) dependencies.  This means that if the softlockup
watchdog triggers, it has truly observed a longer than 10 seconds
scheduling delay of a SCHED_FIFO prio 99 task.

(the patch also turns off the softlockup detector during the initial bootup
phase and does small style fixes)

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 6a4d11c2

include/linux/sched.h

+2 −2
Original line number Diff line number Diff line
@@ -206,11 +206,11 @@ extern void update_process_times(int user); 
extern void scheduler_tick(void);



#ifdef CONFIG_DETECT_SOFTLOCKUP

extern void softlockup_tick(struct pt_regs *regs);

extern void softlockup_tick(void);

extern void spawn_softlockup_task(void);

extern void touch_softlockup_watchdog(void);

#else

static inline void softlockup_tick(struct pt_regs *regs)

static inline void softlockup_tick(void)

{

}

static inline void spawn_softlockup_task(void)

kernel/softlockup.c

+30 −24
Original line number Diff line number Diff line 
/*

 * Detect Soft Lockups

 *

 * started by Ingo Molnar, (C) 2005, Red Hat

 * 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>
@@ -17,13 +16,14 @@ 


static DEFINE_SPINLOCK(print_lock);



static DEFINE_PER_CPU(unsigned long, timestamp) = 0;

static DEFINE_PER_CPU(unsigned long, print_timestamp) = 0;

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 int softlock_panic(struct notifier_block *this, unsigned long event,

				void *ptr)



static int

softlock_panic(struct notifier_block *this, unsigned long event, void *ptr)

{

	did_panic = 1;
@@ -36,7 +36,7 @@ static struct notifier_block panic_block = { 


void touch_softlockup_watchdog(void)

{

	per_cpu(timestamp, raw_smp_processor_id()) = jiffies;

	per_cpu(touch_timestamp, raw_smp_processor_id()) = jiffies;

}

EXPORT_SYMBOL(touch_softlockup_watchdog);
@@ -44,25 +44,35 @@ 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(struct pt_regs *regs)

void softlockup_tick(void)

{

	int this_cpu = smp_processor_id();

	unsigned long timestamp = per_cpu(timestamp, this_cpu);

	unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu);



	if (per_cpu(print_timestamp, this_cpu) == timestamp)

	/* prevent double reports: */

	if (per_cpu(print_timestamp, this_cpu) == touch_timestamp ||

		did_panic ||

			!per_cpu(watchdog_task, this_cpu))

		return;



	/* Do not cause a second panic when there already was one */

	if (did_panic)

	/* 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));



	if (time_after(jiffies, timestamp + 10*HZ)) {

		per_cpu(print_timestamp, this_cpu) = timestamp;

	/* 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);

		show_regs(regs);

		dump_stack();

		spin_unlock(&print_lock);

	}

}
@@ -77,18 +87,16 @@ static int watchdog(void * __bind_cpu) 
	sched_setscheduler(current, SCHED_FIFO, &param);

	current->flags |= PF_NOFREEZE;



	set_current_state(TASK_INTERRUPTIBLE);



	/*

	 * Run briefly once per second - if this gets delayed for

	 * more than 10 seconds then the debug-printout triggers

	 * in softlockup_tick():

	 * 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()) {

		msleep_interruptible(1000);

		set_current_state(TASK_INTERRUPTIBLE);

		touch_softlockup_watchdog();

		schedule();

	}

	__set_current_state(TASK_RUNNING);



	return 0;

}
@@ -114,7 +122,6 @@ cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) 
		kthread_bind(p, hotcpu);

 		break;

	case CPU_ONLINE:



		wake_up_process(per_cpu(watchdog_task, hotcpu));

		break;

#ifdef CONFIG_HOTPLUG_CPU
@@ -146,4 +153,3 @@ __init void spawn_softlockup_task(void) 


	notifier_chain_register(&panic_notifier_list, &panic_block);

}

kernel/timer.c

+1 −1
Original line number Diff line number Diff line
@@ -915,6 +915,7 @@ static void run_timer_softirq(struct softirq_action *h) 
void run_local_timers(void)

{

	raise_softirq(TIMER_SOFTIRQ);

	softlockup_tick();

}



/*
@@ -945,7 +946,6 @@ void do_timer(struct pt_regs *regs) 
	/* prevent loading jiffies before storing new jiffies_64 value. */

	barrier();

	update_times();

	softlockup_tick(regs);

}



#ifdef __ARCH_WANT_SYS_ALARM