From 6993d0fdbee0eb38bfac350aa016f65ad11ed3b1 Mon Sep 17 00:00:00 2001

From: Zqiang <qiang.zhang@windriver.com>

Date: Sun, 1 Nov 2020 17:07:53 -0800

Subject: [PATCH] kthread_worker: prevent queuing delayed work from timer_fn when it is being canceled

Git-commit: 6993d0fdbee0eb38bfac350aa016f65ad11ed3b1

Patch-mainline: v5.10-rc3

References: git-fixes

There is a small race window when a delayed work is being canceled and

the work still might be queued from the timer_fn:

	CPU0						CPU1

kthread_cancel_delayed_work_sync()

   __kthread_cancel_work_sync()

     __kthread_cancel_work()

        work->canceling++;

					      kthread_delayed_work_timer_fn()

						   kthread_insert_work();

Bug: kthread_insert_work() should not get called when work->canceling is

set.

Signed-off-by: Zqiang <qiang.zhang@windriver.com>

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Reviewed-by: Petr Mladek <pmladek@suse.com>

Acked-by: Tejun Heo <tj@kernel.org>

Cc: <stable@vger.kernel.org>

Link: https://lkml.kernel.org/r/20201014083030.16895-1-qiang.zhang@windriver.com

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 kernel/kthread.c |    3 ++-

 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/kernel/kthread.c

+++ b/kernel/kthread.c

@@ -837,7 +837,8 @@ void kthread_delayed_work_timer_fn(unsig

 	/* Move the work from worker->delayed_work_list. */

 	WARN_ON_ONCE(list_empty(&work->node));

 	list_del_init(&work->node);

-	kthread_insert_work(worker, work, &worker->work_list);

+	if (!work->canceling)

+		kthread_insert_work(worker, work, &worker->work_list);

 	spin_unlock(&worker->lock);

 }