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Date: Mon, 15 Sep 2014 12:24:08 -0700 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>, Hans Verkuil <hans.verkuil@...co.com>, Mauro Carvalho Chehab <m.chehab@...sung.com> Subject: [PATCH 3.16 009/158] media: v4l: vb2: Fix stream start and buffer completion race 3.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com> 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@...asonboard.com> Reviewed-by: Hans Verkuil <hans.verkuil@...co.com> Signed-off-by: Mauro Carvalho Chehab <m.chehab@...sung.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- 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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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