/*
* Detect Soft Lockups
*
* started by Ingo Molnar, (C) 2005, Red Hat
*
* 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, timestamp) = 0;
static DEFINE_PER_CPU(unsigned long, print_timestamp) = 0;
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)
{
did_panic = 1;
return NOTIFY_DONE;
}
static struct notifier_block panic_block = {
.notifier_call = softlock_panic,
};
void touch_softlockup_watchdog(void)
{
per_cpu(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(struct pt_regs *regs)
{
int this_cpu = smp_processor_id();
unsigned long timestamp = per_cpu(timestamp, this_cpu);
if (per_cpu(print_timestamp, this_cpu) == timestamp)
return;
/* Do not cause a second panic when there already was one */
if (did_panic)
return;
if (time_after(jiffies, timestamp + 10*HZ)) {
per_cpu(print_timestamp, this_cpu) = timestamp;
spin_lock(&print_lock);
printk(KERN_ERR "BUG: soft lockup detected on CPU#%d!\n",
this_cpu);
show_regs(regs);
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, ¶m);
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():
*/
while (!kthread_should_stop()) {
msleep_interruptible(1000);
touch_softlockup_watchdog();
}
__set_current_state(TASK_RUNNING);
return 0;
}
/*
* Create/destroy watchdog threads as CPUs come and go:
*/
static int __devinit
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:
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(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 __devinitdata 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);
notifier_chain_register(&panic_notifier_list, &panic_block);
}
