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
......@@ -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)
......
/*
* 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;
}
if (time_after(jiffies, timestamp + 10*HZ)) {
per_cpu(print_timestamp, this_cpu) = timestamp;
/* 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);
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);
}
......@@ -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
......
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