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Commit a076e4bc authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

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: default avatarOleg Nesterov <oleg@tv-sign.ru>
Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 49b12d4f

kernel/kthread.c

+5 −2
Original line number Original line Diff line number Diff line
@@ -70,7 +70,7 @@ static int kthread(void *_create) 
	data = create->data;

	data = create->data;





	/* OK, tell user we're spawned, wait for stop or wakeup */

	/* OK, tell user we're spawned, wait for stop or wakeup */

	__set_current_state(TASK_INTERRUPTIBLE);

	__set_current_state(TASK_UNINTERRUPTIBLE);

	complete(&create->started);

	complete(&create->started);

	schedule();

	schedule();
@@ -162,7 +162,10 @@ EXPORT_SYMBOL(kthread_create); 
 */

 */

void kthread_bind(struct task_struct *k, unsigned int cpu)

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 */

	/* Must have done schedule() in kthread() before we set_task_cpu */

	wait_task_inactive(k);

	wait_task_inactive(k);

	set_task_cpu(k, cpu);

	set_task_cpu(k, cpu);