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>
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 87693b3..63885ab 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -308,14 +308,14 @@
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;