Re: [PATCH for v3.17 2/2] vb2: fix vb2 state check when start_streaming fails

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Hans,

Thank you for the patch.

On Monday 04 August 2014 12:27:12 Hans Verkuil wrote:
> From: Hans Verkuil <hans.verkuil@cisco.com>
> 
> Commit bd994ddb2a12a3ff48cd549ec82cdceaea9614df (vb2: Fix stream start and
> buffer completion race) broke the buffer state check in vb2_buffer_done.
> 
> So accept all three possible states there since I can no longer tell the
> difference between vb2_buffer_done called from start_streaming or from
> elsewhere.
> 
> Instead add a WARN_ON at the end of start_streaming that will check whether
> any buffers were added to the done list, since that implies that the wrong
> state was used as well.
> 
> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
> Cc: stable@vger.kernel.org      # for v3.15 and up
> Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Given that I've introduced a few vb2 bugs I hope my review still has some 
value :-)

> ---
>  drivers/media/v4l2-core/videobuf2-core.c | 17 ++++++++++-------
>  1 file changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/videobuf2-core.c
> b/drivers/media/v4l2-core/videobuf2-core.c index d3f2a22..7f70fd52 100644
> --- a/drivers/media/v4l2-core/videobuf2-core.c
> +++ b/drivers/media/v4l2-core/videobuf2-core.c
> @@ -1165,13 +1165,10 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum
> vb2_buffer_state state) if (WARN_ON(vb->state != VB2_BUF_STATE_ACTIVE))
>  		return;
> 
> -	if (!q->start_streaming_called) {
> -		if (WARN_ON(state != VB2_BUF_STATE_QUEUED))
> -			state = VB2_BUF_STATE_QUEUED;
> -	} else if (WARN_ON(state != VB2_BUF_STATE_DONE &&
> -			   state != VB2_BUF_STATE_ERROR)) {
> -			state = VB2_BUF_STATE_ERROR;
> -	}
> +	if (WARN_ON(state != VB2_BUF_STATE_DONE &&
> +		    state != VB2_BUF_STATE_ERROR &&
> +		    state != VB2_BUF_STATE_QUEUED))
> +		state = VB2_BUF_STATE_ERROR;
> 
>  #ifdef CONFIG_VIDEO_ADV_DEBUG
>  	/*
> @@ -1783,6 +1780,12 @@ static int vb2_start_streaming(struct vb2_queue *q)
>  		/* Must be zero now */
>  		WARN_ON(atomic_read(&q->owned_by_drv_count));
>  	}
> +	/*
> +	 * If done_list is not empty, then start_streaming() didn't call
> +	 * vb2_buffer_done(vb, VB2_BUF_STATE_QUEUED) but STATE_ERROR or
> +	 * STATE_DONE.
> +	 */
> +	WARN_ON(!list_empty(&q->done_list));
>  	return ret;
>  }

-- 
Regards,

Laurent Pinchart