linux-kernel - [PATCH 5.8 88/99] media: cec-adap.c: dont use flush_scheduled

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Message-Id: <20200929105934.069653553@linuxfoundation.org>
Date:   Tue, 29 Sep 2020 13:02:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Subject: [PATCH 5.8 88/99] media: cec-adap.c: dont use flush_scheduled_work()

From: Hans Verkuil <hverkuil-cisco@...all.nl>

commit 288eceb0858323d66bff03cf386630a797b248ad upstream.

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@...all.nl>
Cc: <stable@...r.kernel.org>      # for v5.8 and up
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/media/cec/core/cec-adap.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 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_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);
 			}
 			/*