[PATCH v3] kthread_worker: Prevent queuing delayed work from timer_fn when it is being canceled

[qiang.zhang]

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

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.

Reviewed-by: Petr Mladek <pmla...@suse.com>
Signed-off-by: Zqiang <qiang.zh...@windriver.com>
--- 
 v1->v2->v3:
 Change the description of the problem and add 'Reviewed-by' tags.

 kernel/kthread.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 3edaa380dc7b..85a2c9b32049 100644
--- 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);
 }
-- 
2.17.1