On 06/24/14 01:54, Laurent Pinchart wrote:
> 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+rene...@ideasonboard.com>
Reviewed-by: Hans Verkuil <hans.verk...@cisco.com>
Good catch!
This needs a:
Cc: sta...@vger.kernel.org # for v3.15 and up
Regards,
Hans
> ---
> drivers/media/v4l2-core/videobuf2-core.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/v4l2-core/videobuf2-core.c
> b/drivers/media/v4l2-core/videobuf2-core.c
> index 7c4489c..1d67e95 100644
> --- 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 vb2_queue *q)
> __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;
>
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