linux-kernel - Re: [PATCH v3 1/3] media: uvcvideo: Always use uvc_status

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Date:   Wed, 22 Nov 2023 16:21:08 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Ricardo Ribalda <ribalda@...omium.org>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Tomasz Figa <tfiga@...omium.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sean Paul <seanpaul@...omium.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: Re: [PATCH v3 1/3] media: uvcvideo: Always use uvc_status_stop()

On (23/11/21 19:53), Ricardo Ribalda wrote:
> uvc_status_stop() handles properly the race conditions with the
> asynchronous worker.
> Let's use uvc_status_stop() for all the code paths that require stopping
> it.
> 
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
>  drivers/media/usb/uvc/uvc_ctrl.c   | 4 ----
>  drivers/media/usb/uvc/uvc_status.c | 2 +-
>  2 files changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index e59a463c2761..8e22a07e3e7b 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -2765,10 +2765,6 @@ void uvc_ctrl_cleanup_device(struct uvc_device *dev)
>  	struct uvc_entity *entity;
>  	unsigned int i;
>  
> -	/* Can be uninitialized if we are aborting on probe error. */
> -	if (dev->async_ctrl.work.func)
> -		cancel_work_sync(&dev->async_ctrl.work);
> -
>  	/* Free controls and control mappings for all entities. */
>  	list_for_each_entry(entity, &dev->entities, list) {
>  		for (i = 0; i < entity->ncontrols; ++i) {
> diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c
> index a78a88c710e2..0208612a9f12 100644
> --- a/drivers/media/usb/uvc/uvc_status.c
> +++ b/drivers/media/usb/uvc/uvc_status.c
> @@ -292,7 +292,7 @@ int uvc_status_init(struct uvc_device *dev)
>  
>  void uvc_status_unregister(struct uvc_device *dev)
>  {
> -	usb_kill_urb(dev->int_urb);
> +	uvc_status_stop(dev);

Sort of feels like this needs dev->lock somewhere here. Should we move 3/3
to the head of the series?

The question is, can this be called in parallel with uvc_v4l2_release(),
for instance?

>  	uvc_input_unregister(dev);
>  }