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>

diff --git a/kernel/kthread.c b/kernel/kthread.c
index e29773c82b70c26fff598f864642f7dee010efab..933a625621b8dbef0564919bf6f76aa30735372f 100644 (file)
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -897,7 +897,8 @@ 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);
-       kthread_insert_work(worker, work, &worker->work_list);
+       if (!work->canceling)
+               kthread_insert_work(worker, work, &worker->work_list);
 
        raw_spin_unlock_irqrestore(&worker->lock, flags);
 }