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From:   Alexandre Courbot <gnurou@gmail.com>
To:     Mauro Carvalho Chehab <mchehab@kernel.org>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Nicolas Dufresne <nicolas.dufresne@collabora.com>
Cc:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        Alexandre Courbot <gnurou@gmail.com>
Subject: [PATCH 0/2] media: v4l2-mem2mem: fix poll() bug
Date:   Tue, 25 Aug 2020 23:55:54 +0900
Message-Id: <20200825145556.637323-1-gnurou@gmail.com>
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This addresses a very corner case that probably nobody ever encounters,
but I have hit it when playing with vicoded so here is a tentative fix.

Patch 1/2 addresses the issue that when the last buffer of a m2m device
has been dequeued, any attempt to poll with EPOLLOUT will result in only
EPOLLIN being returned, even if OUTPUT buffers are still pending. The
issue stems from the fact that the last buffer check if done first, and
returns immediately if true.

Patch 2/2 builds on the first one to (hopefully) clean up the code a bit
and make the function flow easier to follow. Functionally speaking it is
supposed to be a no-op and it can safely be dropped if the former code
is preferred - the actual fix is in 1/2.

Alexandre Courbot (2):
  media: v4l2-mem2mem: consider OUTPUT queue first when polling
  media: v4l2-mem2mem: simplify poll logic a bit

 drivers/media/v4l2-core/v4l2-mem2mem.c | 42 +++++++++++---------------
 1 file changed, 18 insertions(+), 24 deletions(-)

-- 
2.28.0