This is a note to let you know that I've just added the patch titled media: v4l2-mem2mem: prevent pollerr when last_buffer_dequeued is set to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: media-v4l2-mem2mem-prevent-pollerr-when-last_buffer_.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit fc1bd72c764f197fa28f95f36ae737de33ccdec0 Author: Ming Qian <ming.qian@xxxxxxx> Date: Wed Jun 15 04:19:20 2022 +0100 media: v4l2-mem2mem: prevent pollerr when last_buffer_dequeued is set [ Upstream commit d4de27a9b1eadd33a2e40de87a646d1bf5fef756 ] If the last buffer was dequeued from the capture queue, signal userspace. DQBUF(CAPTURE) will return -EPIPE. But if output queue is empty and capture queue is empty, v4l2_m2m_poll_for_data will return EPOLLERR, This is very easy to happen in drain. When last_buffer_dequeued is set, we shouldn't return EPOLLERR, but return EPOLLIN | EPOLLRDNORM. Fixes: 1698a7f151126 ("media: v4l2-mem2mem: simplify poll logic") Signed-off-by: Ming Qian <ming.qian@xxxxxxx> Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c index 73190652c267..ad14d5214106 100644 --- a/drivers/media/v4l2-core/v4l2-mem2mem.c +++ b/drivers/media/v4l2-core/v4l2-mem2mem.c @@ -927,7 +927,7 @@ static __poll_t v4l2_m2m_poll_for_data(struct file *file, if ((!src_q->streaming || src_q->error || list_empty(&src_q->queued_list)) && (!dst_q->streaming || dst_q->error || - list_empty(&dst_q->queued_list))) + (list_empty(&dst_q->queued_list) && !dst_q->last_buffer_dequeued))) return EPOLLERR; spin_lock_irqsave(&src_q->done_lock, flags);