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freezer: fix kthread_create vs freezer theoretical race 

kthread() sleeps in TASK_INTERRUPTIBLE state waiting for the first wakeup.  In
theory, this wakeup may come from freeze_process()->signal_wake_up(), so the
task can disappear even before kthread_create() sets its ->comm.

Change kthread() to use TASK_UNINTERRUPTIBLE.

[akpm@linux-foundation.org: s/BUG_ON/WARN_ON+recover]
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2007-05-23 13:57:27 -07:00 committed by Linus Torvalds
parent 49b12d4f5e
commit a076e4bca2
1 changed files with 5 additions and 2 deletions
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7
kernel/kthread.c
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@ -70,7 +70,7 @@ static int kthread(void *_create)
data = create->data;
/* OK, tell user we're spawned, wait for stop or wakeup */
__set_current_state(TASK_INTERRUPTIBLE);
__set_current_state(TASK_UNINTERRUPTIBLE);
complete(&create->started);
schedule();
@ -162,7 +162,10 @@ EXPORT_SYMBOL(kthread_create);
*/
void kthread_bind(struct task_struct *k, unsigned int cpu)
{
BUG_ON(k->state != TASK_INTERRUPTIBLE);
if (k->state != TASK_UNINTERRUPTIBLE) {
WARN_ON(1);
return;
}
/* Must have done schedule() in kthread() before we set_task_cpu */
wait_task_inactive(k);
set_task_cpu(k, cpu);