Re: [PATCH for v6.10] Revert "media: v4l2-ctrls: show all owned controls in log_status"

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Hi Hans,

Thank you for the patch.

On Fri, May 10, 2024 at 09:11:46AM +0200, Hans Verkuil wrote:
> This reverts commit 9801b5b28c6929139d6fceeee8d739cc67bb2739.
> 
> This patch introduced a potential deadlock scenario:
> 
> [Wed May  8 10:02:06 2024]  Possible unsafe locking scenario:
> 
> [Wed May  8 10:02:06 2024]        CPU0                    CPU1
> [Wed May  8 10:02:06 2024]        ----                    ----
> [Wed May  8 10:02:06 2024]   lock(vivid_ctrls:1620:(hdl_vid_cap)->_lock);
> [Wed May  8 10:02:06 2024]                                lock(vivid_ctrls:1608:(hdl_user_vid)->_lock);
> [Wed May  8 10:02:06 2024]                                lock(vivid_ctrls:1620:(hdl_vid_cap)->_lock);
> [Wed May  8 10:02:06 2024]   lock(vivid_ctrls:1608:(hdl_user_vid)->_lock);
> 
> For now just revert.
> 
> Fixes: 9801b5b28c69 ("media: v4l2-ctrls: show all owned controls in log_status")
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>

Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>

> ---
>  drivers/media/v4l2-core/v4l2-ctrls-core.c | 18 +++++-------------
>  1 file changed, 5 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-core.c b/drivers/media/v4l2-core/v4l2-ctrls-core.c
> index c59dd691f79f6..eeab6a5eb7bac 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls-core.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls-core.c
> @@ -2507,8 +2507,7 @@ int v4l2_ctrl_handler_setup(struct v4l2_ctrl_handler *hdl)
>  EXPORT_SYMBOL(v4l2_ctrl_handler_setup);
> 
>  /* Log the control name and value */
> -static void log_ctrl(const struct v4l2_ctrl_handler *hdl,
> -		     struct v4l2_ctrl *ctrl,
> +static void log_ctrl(const struct v4l2_ctrl *ctrl,
>  		     const char *prefix, const char *colon)
>  {
>  	if (ctrl->flags & (V4L2_CTRL_FLAG_DISABLED | V4L2_CTRL_FLAG_WRITE_ONLY))
> @@ -2518,11 +2517,7 @@ static void log_ctrl(const struct v4l2_ctrl_handler *hdl,
> 
>  	pr_info("%s%s%s: ", prefix, colon, ctrl->name);
> 
> -	if (ctrl->handler != hdl)
> -		v4l2_ctrl_lock(ctrl);
>  	ctrl->type_ops->log(ctrl);
> -	if (ctrl->handler != hdl)
> -		v4l2_ctrl_unlock(ctrl);
> 
>  	if (ctrl->flags & (V4L2_CTRL_FLAG_INACTIVE |
>  			   V4L2_CTRL_FLAG_GRABBED |
> @@ -2541,7 +2536,7 @@ static void log_ctrl(const struct v4l2_ctrl_handler *hdl,
>  void v4l2_ctrl_handler_log_status(struct v4l2_ctrl_handler *hdl,
>  				  const char *prefix)
>  {
> -	struct v4l2_ctrl_ref *ref;
> +	struct v4l2_ctrl *ctrl;
>  	const char *colon = "";
>  	int len;
> 
> @@ -2553,12 +2548,9 @@ void v4l2_ctrl_handler_log_status(struct v4l2_ctrl_handler *hdl,
>  	if (len && prefix[len - 1] != ' ')
>  		colon = ": ";
>  	mutex_lock(hdl->lock);
> -	list_for_each_entry(ref, &hdl->ctrl_refs, node) {
> -		if (ref->from_other_dev ||
> -		    (ref->ctrl->flags & V4L2_CTRL_FLAG_DISABLED))
> -			continue;
> -		log_ctrl(hdl, ref->ctrl, prefix, colon);
> -	}
> +	list_for_each_entry(ctrl, &hdl->ctrls, node)
> +		if (!(ctrl->flags & V4L2_CTRL_FLAG_DISABLED))
> +			log_ctrl(ctrl, prefix, colon);
>  	mutex_unlock(hdl->lock);
>  }
>  EXPORT_SYMBOL(v4l2_ctrl_handler_log_status);

-- 
Regards,

Laurent Pinchart




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