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DEFINITIONS
This source file includes following definitions.
- softlockup_panic_setup
- softlock_panic
- get_timestamp
- __touch_softlockup_watchdog
- touch_softlockup_watchdog
- touch_all_softlockup_watchdogs
- softlockup_tick
- check_hung_task
- check_hung_uninterruptible_tasks
- watchdog
- cpu_callback
- nosoftlockup_setup
- spawn_softlockup_task
/*
* 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, ¶m);
/* 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);