linux-kernel - Re: [PATCH v3 3/5] media: uvcvideo: Handle locks in uvc_queue_return

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Message-ID: <09cc5598-ade2-42c4-8a64-0981e4575d1b@kernel.org>
Date: Mon, 16 Jun 2025 15:38:47 +0200
From: Hans de Goede <hansg@...nel.org>
To: Ricardo Ribalda <ribalda@...omium.org>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Hans Verkuil <hans@...erkuil.nl>, Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/5] media: uvcvideo: Handle locks in
 uvc_queue_return_buffers

Hi Ricardo,

On 2-Jun-25 18:06, Ricardo Ribalda wrote:
> Most of the calls to uvc_queue_return_buffers() wrap the call with
> spin_lock_irq()/spin_unlock_irq().
> 
> Rename uvc_queue_return_buffers to __uvc_queue_return_buffers to
> indicate that this is the version that does not handle locks and create
> a new version of the function that handles the lock.
> 
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>

Thanks, patch looks good to me:

Reviewed-by: Hans de Goede <hansg@...nel.org>

Regards,

Hans


> ---
>  drivers/media/usb/uvc/uvc_queue.c | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_queue.c b/drivers/media/usb/uvc/uvc_queue.c
> index 72c5494dee9f46ff61072e7d293bfaddda40e615..8f9737ac729546683ca48f5e71ce3dfacbae2926 100644
> --- a/drivers/media/usb/uvc/uvc_queue.c
> +++ b/drivers/media/usb/uvc/uvc_queue.c
> @@ -42,13 +42,15 @@ static inline struct uvc_buffer *uvc_vbuf_to_buffer(struct vb2_v4l2_buffer *buf)
>   *
>   * This function must be called with the queue spinlock held.
>   */
> -static void uvc_queue_return_buffers(struct uvc_video_queue *queue,
> -			       enum uvc_buffer_state state)
> +static void __uvc_queue_return_buffers(struct uvc_video_queue *queue,
> +				       enum uvc_buffer_state state)
>  {
>  	enum vb2_buffer_state vb2_state = state == UVC_BUF_STATE_ERROR
>  					? VB2_BUF_STATE_ERROR
>  					: VB2_BUF_STATE_QUEUED;
>  
> +	lockdep_assert_held(&queue->irqlock);
> +
>  	while (!list_empty(&queue->irqqueue)) {
>  		struct uvc_buffer *buf = list_first_entry(&queue->irqqueue,
>  							  struct uvc_buffer,
> @@ -59,6 +61,14 @@ static void uvc_queue_return_buffers(struct uvc_video_queue *queue,
>  	}
>  }
>  
> +static void uvc_queue_return_buffers(struct uvc_video_queue *queue,
> +				     enum uvc_buffer_state state)
> +{
> +	spin_lock_irq(&queue->irqlock);
> +	__uvc_queue_return_buffers(queue, state);
> +	spin_unlock_irq(&queue->irqlock);
> +}
> +
>  /* -----------------------------------------------------------------------------
>   * videobuf2 queue operations
>   */
> @@ -171,9 +181,7 @@ static int uvc_start_streaming(struct vb2_queue *vq, unsigned int count)
>  	if (ret == 0)
>  		return 0;
>  
> -	spin_lock_irq(&queue->irqlock);
>  	uvc_queue_return_buffers(queue, UVC_BUF_STATE_QUEUED);
> -	spin_unlock_irq(&queue->irqlock);
>  
>  	return ret;
>  }
> @@ -187,9 +195,7 @@ static void uvc_stop_streaming(struct vb2_queue *vq)
>  	if (vq->type != V4L2_BUF_TYPE_META_CAPTURE)
>  		uvc_video_stop_streaming(uvc_queue_to_stream(queue));
>  
> -	spin_lock_irq(&queue->irqlock);
>  	uvc_queue_return_buffers(queue, UVC_BUF_STATE_ERROR);
> -	spin_unlock_irq(&queue->irqlock);
>  }
>  
>  static const struct vb2_ops uvc_queue_qops = {
> @@ -263,7 +269,7 @@ void uvc_queue_cancel(struct uvc_video_queue *queue, int disconnect)
>  	unsigned long flags;
>  
>  	spin_lock_irqsave(&queue->irqlock, flags);
> -	uvc_queue_return_buffers(queue, UVC_BUF_STATE_ERROR);
> +	__uvc_queue_return_buffers(queue, UVC_BUF_STATE_ERROR);
>  	/*
>  	 * This must be protected by the irqlock spinlock to avoid race
>  	 * conditions between uvc_buffer_queue and the disconnection event that
>