Commit 6993d0fd authored Nov 01, 2020 by Zqiang Committed by Linus Torvalds Nov 02, 2020

kthread_worker: prevent queuing delayed work from timer_fn when it is being canceled



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>

parent a77eedbc

kernel/kthread.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -897,6 +897,7 @@ void kthread_delayed_work_timer_fn(struct timer_list *t)
		/* Move the work from worker->delayed_work_list. */
		WARN_ON_ONCE(list_empty(&work->node));
		list_del_init(&work->node);
		if (!work->canceling)
		kthread_insert_work(worker, work, &worker->work_list);

		raw_spin_unlock_irqrestore(&worker->lock, flags);

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