Commit 575c52cc authored by Alexandre Courbot's avatar Alexandre Courbot Committed by Mauro Carvalho Chehab
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media: videobuf2: always call poll_wait() on queues 



do_poll()/do_select() seem to set the _qproc member of poll_table to
NULL the first time they are called on a given table, making subsequent
calls of poll_wait() on that table no-ops. This is a problem for vb2
which calls poll_wait() on the V4L2 queues' waitqueues only when a
queue-related event is requested, which may not necessarily be the case
during the first poll.

Fix this by making the call to poll_wait() happen first thing and
unconditionally in vb2_core_poll().

Signed-off-by: default avatarAlexandre Courbot <gnurou@gmail.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab+huawei@kernel.org>
parent a45c39b8

drivers/media/common/videobuf2/videobuf2-core.c

+9 −2
Original line number Diff line number Diff line
@@ -2374,13 +2374,20 @@ __poll_t vb2_core_poll(struct vb2_queue *q, struct file *file, 
	struct vb2_buffer *vb = NULL;

	unsigned long flags;



	/*

	 * poll_wait() MUST be called on the first invocation on all the

	 * potential queues of interest, even if we are not interested in their

	 * events during this first call. Failure to do so will result in

	 * queue's events to be ignored because the poll_table won't be capable

	 * of adding new wait queues thereafter.

	 */

	poll_wait(file, &q->done_wq, wait);



	if (!q->is_output && !(req_events & (EPOLLIN | EPOLLRDNORM)))

		return 0;

	if (q->is_output && !(req_events & (EPOLLOUT | EPOLLWRNORM)))

		return 0;



	poll_wait(file, &q->done_wq, wait);



	/*

	 * Start file I/O emulator only if streaming API has not been used yet.

	 */