Commit 85f4186a authored May 09, 2007 by Oleg Nesterov Committed by Linus Torvalds May 09, 2007

worker_thread: fix racy try_to_freeze() usage



worker_thread() can miss freeze_process()->signal_wake_up() if it happens
between try_to_freeze() and prepare_to_wait().  We should check freezing()
before entering schedule().

This race was introduced by me in

	[PATCH 1/1] workqueue: don't migrate pending works from the dead CPU

Looks like mm/vmscan.c:kswapd() has the same race.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent b9aac8e0

kernel/workqueue.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -308,14 +308,14 @@ static int worker_thread(void *__cwq)
		do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);

		for (;;) {
		if (cwq->wq->freezeable)
		try_to_freeze();

		prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);
		if (!cwq->should_stop && list_empty(&cwq->worklist))
		if (!freezing(current) && !cwq->should_stop
		&& list_empty(&cwq->worklist))
		schedule();
		finish_wait(&cwq->more_work, &wait);

		try_to_freeze();

		if (cwq_should_stop(cwq))
		break;