This is a note to let you know that I've just added the patch titled
media: v4l: vb2: Fix stream start and buffer completion race
to the 3.16-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-v4l-vb2-fix-stream-start-and-buffer-completion-race.patch
and it can be found in the queue-3.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From bd994ddb2a12a3ff48cd549ec82cdceaea9614df Mon Sep 17 00:00:00 2001
From: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
Date: Mon, 23 Jun 2014 18:00:22 -0300
Subject: media: v4l: vb2: Fix stream start and buffer completion race
From: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
commit bd994ddb2a12a3ff48cd549ec82cdceaea9614df upstream.
videobuf2 stores the driver streaming state internally in the queue in
the start_streaming_called variable. The state is set right after the
driver start_stream operation returns, and checked in the
vb2_buffer_done() function, typically called from the frame completion
interrupt handler. A race condition exists if the hardware finishes
processing the first frame before the start_stream operation returns.
Fix this by setting start_streaming_called to 1 before calling the
start_stream operation, and resetting it to 0 if the operation fails.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
Reviewed-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/media/v4l2-core/videobuf2-core.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1750,12 +1750,14 @@ static int vb2_start_streaming(struct vb
__enqueue_in_driver(vb);
/* Tell the driver to start streaming */
+ q->start_streaming_called = 1;
ret = call_qop(q, start_streaming, q,
atomic_read(&q->owned_by_drv_count));
- q->start_streaming_called = ret == 0;
if (!ret)
return 0;
+ q->start_streaming_called = 0;
+
dprintk(1, "driver refused to start streaming\n");
if (WARN_ON(atomic_read(&q->owned_by_drv_count))) {
unsigned i;
Patches currently in stable-queue which might be from laurent.pinchart+renesas@xxxxxxxxxxxxxxxx are
queue-3.16/media-v4l-vb2-fix-stream-start-and-buffer-completion-race.patch
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