media: cec-adap.c: don't use flush_scheduled_work()

For some inexplicable reason I decided to call flush_scheduled_work()
instead of cancel_delayed_work_sync(). The problem with that is that
flush_scheduled_work() waits for *all* queued scheduled work to be
completed instead of just the work itself.

This can cause a deadlock if a CEC driver also schedules work that
takes the same lock. See the comments for flush_scheduled_work() in
linux/workqueue.h.

This is exactly what has been observed a few times.

This patch simply replaces flush_scheduled_work() by
cancel_delayed_work_sync().

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: <stable@vger.kernel.org>      # for v5.8 and up
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

diff --git a/drivers/media/cec/core/cec-adap.c b/drivers/media/cec/core/cec-adap.c
index 4efe801..926d65d 100644 (file)
--- a/drivers/media/cec/core/cec-adap.c
+++ b/drivers/media/cec/core/cec-adap.c
@@ -1199,7 +1199,7 @@ void cec_received_msg_ts(struct cec_adapter *adap,
                        /* Cancel the pending timeout work */
                        if (!cancel_delayed_work(&data->work)) {
                                mutex_unlock(&adap->lock);
-                               flush_scheduled_work();
+                               cancel_delayed_work_sync(&data->work);
                                mutex_lock(&adap->lock);
                        }
                        /*