Commit a076e4bc authored May 23, 2007 by Oleg Nesterov Committed by Linus Torvalds May 23, 2007

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>

parent 49b12d4f

kernel/kthread.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -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);

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