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Merge branch 'core/softlockup' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

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* 'core/softlockup' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  softlockup: make DETECT_HUNG_TASK default depend on DETECT_SOFTLOCKUP
  softlockup: move 'one' to the softlockup section in sysctl.c
  softlockup: ensure the task has been switched out once
  softlockup: remove timestamp checking from hung_task
  softlockup: convert read_lock in hung_task to rcu_read_lock
  softlockup: check all tasks in hung_task
  softlockup: remove unused definition for spawn_softlockup_task
  softlockup: fix potential race in hung_task when resetting timeout
  softlockup: fix to allow compiling with !DETECT_HUNG_TASK
  softlockup: decouple hung tasks check from softlockup detection
This commit is contained in:
Linus Torvalds
2009-04-07 14:11:07 -07:00
parent c93f216b5b 5e34437840
commit 1551260d1f
7 changed files with 283 additions and 114 deletions
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1
kernel/Makefile
View File

@@ -74,6 +74,7 @@ obj-$(CONFIG_AUDIT_TREE) += audit_tree.o
obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_KGDB) += kgdb.o
obj-$(CONFIG_DETECT_SOFTLOCKUP) += softlockup.o
obj-$(CONFIG_DETECT_HUNG_TASK) += hung_task.o
obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
obj-$(CONFIG_SECCOMP) += seccomp.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o

8
kernel/fork.c
View File

@@ -645,6 +645,9 @@ static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
tsk->min_flt = tsk->maj_flt = 0;
tsk->nvcsw = tsk->nivcsw = 0;
#ifdef CONFIG_DETECT_HUNG_TASK
tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
#endif
tsk->mm = NULL;
tsk->active_mm = NULL;
@@ -1032,11 +1035,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
p->default_timer_slack_ns = current->timer_slack_ns;
#ifdef CONFIG_DETECT_SOFTLOCKUP
p->last_switch_count = 0;
p->last_switch_timestamp = 0;
#endif
task_io_accounting_init(&p->ioac);
acct_clear_integrals(p);

217
kernel/hung_task.c Normal file
View File

@@ -0,0 +1,217 @@
/*
* Detect Hung Task
*
* kernel/hung_task.c - kernel thread for detecting tasks stuck in D state
*
*/
#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/module.h>
#include <linux/sysctl.h>
/*
* The number of tasks checked:
*/
unsigned long __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT;
/*
* Limit number of tasks checked in a batch.
*
* This value controls the preemptibility of khungtaskd since preemption
* is disabled during the critical section. It also controls the size of
* the RCU grace period. So it needs to be upper-bound.
*/
#define HUNG_TASK_BATCHING 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;
static int __read_mostly did_panic;
static struct task_struct *watchdog_task;
/*
* Should we panic (and reboot, if panic_timeout= is set) when a
* hung task is detected:
*/
unsigned int __read_mostly sysctl_hung_task_panic =
CONFIG_BOOTPARAM_HUNG_TASK_PANIC_VALUE;
static int __init hung_task_panic_setup(char *str)
{
sysctl_hung_task_panic = simple_strtoul(str, NULL, 0);
return 1;
}
__setup("hung_task_panic=", hung_task_panic_setup);
static int
hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr)
{
did_panic = 1;
return NOTIFY_DONE;
}
static struct notifier_block panic_block = {
.notifier_call = hung_task_panic,
};
static void check_hung_task(struct task_struct *t, unsigned long timeout)
{
unsigned long switch_count = t->nvcsw + t->nivcsw;
/*
* Ensure the task is not frozen.
* Also, when a freshly created task is scheduled once, changes
* its state to TASK_UNINTERRUPTIBLE without having ever been
* switched out once, it musn't be checked.
*/
if (unlikely(t->flags & PF_FROZEN || !switch_count))
return;
if (switch_count != t->last_switch_count) {
t->last_switch_count = switch_count;
return;
}
if (!sysctl_hung_task_warnings)
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, timeout);
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);
touch_nmi_watchdog();
if (sysctl_hung_task_panic)
panic("hung_task: blocked tasks");
}
/*
* To avoid extending the RCU grace period for an unbounded amount of time,
* periodically exit the critical section and enter a new one.
*
* For preemptible RCU it is sufficient to call rcu_read_unlock in order
* exit the grace period. For classic RCU, a reschedule is required.
*/
static void rcu_lock_break(struct task_struct *g, struct task_struct *t)
{
get_task_struct(g);
get_task_struct(t);
rcu_read_unlock();
cond_resched();
rcu_read_lock();
put_task_struct(t);
put_task_struct(g);
}
/*
* 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(unsigned long timeout)
{
int max_count = sysctl_hung_task_check_count;
int batch_count = HUNG_TASK_BATCHING;
struct task_struct *g, *t;
/*
* If the system crashed already then all bets are off,
* do not report extra hung tasks:
*/
if (test_taint(TAINT_DIE) || did_panic)
return;
rcu_read_lock();
do_each_thread(g, t) {
if (!--max_count)
goto unlock;
if (!--batch_count) {
batch_count = HUNG_TASK_BATCHING;
rcu_lock_break(g, t);
/* Exit if t or g was unhashed during refresh. */
if (t->state == TASK_DEAD || g->state == TASK_DEAD)
goto unlock;
}
/* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */
if (t->state == TASK_UNINTERRUPTIBLE)
check_hung_task(t, timeout);
} while_each_thread(g, t);
unlock:
rcu_read_unlock();
}
static unsigned long timeout_jiffies(unsigned long timeout)
{
/* timeout of 0 will disable the watchdog */
return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
}
/*
* Process updating of timeout sysctl
*/
int proc_dohung_task_timeout_secs(struct ctl_table *table, int write,
struct file *filp, void __user *buffer,
size_t *lenp, loff_t *ppos)
{
int ret;
ret = proc_doulongvec_minmax(table, write, filp, buffer, lenp, ppos);
if (ret || !write)
goto out;
wake_up_process(watchdog_task);
out:
return ret;
}
/*
* kthread which checks for tasks stuck in D state
*/
static int watchdog(void *dummy)
{
set_user_nice(current, 0);
for ( ; ; ) {
unsigned long timeout = sysctl_hung_task_timeout_secs;
while (schedule_timeout_interruptible(timeout_jiffies(timeout)))
timeout = sysctl_hung_task_timeout_secs;
check_hung_uninterruptible_tasks(timeout);
}
return 0;
}
static int __init hung_task_init(void)
{
atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
watchdog_task = kthread_run(watchdog, NULL, "khungtaskd");
return 0;
}
module_init(hung_task_init);

100
kernel/softlockup.c
View File

@@ -165,98 +165,12 @@ void softlockup_tick(void)
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 = 480;
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)
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 (test_taint(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);
@@ -276,11 +190,6 @@ static int watchdog(void *__bind_cpu)
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);
@@ -312,18 +221,9 @@ cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
break;
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
check_cpu = cpumask_any(cpu_online_mask);
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) {
/* Pick any other online cpu. */
check_cpu = cpumask_any_but(cpu_online_mask, hotcpu);
}
break;
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
if (!per_cpu(watchdog_task, hotcpu))

15
kernel/sysctl.c
View File

@@ -814,6 +814,19 @@ static struct ctl_table kern_table[] = {
.extra1 = &neg_one,
.extra2 = &sixty,
},
#endif
#ifdef CONFIG_DETECT_HUNG_TASK
{
.ctl_name = CTL_UNNUMBERED,
.procname = "hung_task_panic",
.data = &sysctl_hung_task_panic,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec_minmax,
.strategy = &sysctl_intvec,
.extra1 = &zero,
.extra2 = &one,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "hung_task_check_count",
@@ -829,7 +842,7 @@ static struct ctl_table kern_table[] = {
.data = &sysctl_hung_task_timeout_secs,
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = &proc_doulongvec_minmax,
.proc_handler = &proc_dohung_task_timeout_secs,
.strategy = &sysctl_intvec,
},
{