Re: [PATCH FOR 2.6.37] Revert "V4L/DVB: v4l2-dev: remove unnecessary lock around atomic clear_bit"

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On Monday, November 22, 2010 11:21:27 Laurent Pinchart wrote:
> Removing the mutex_lock/unlock around clear_bit allowed
> device_unregister() to race with v4l2_open(). The device can be
> unregistered  between the video_devdata() and video_get() calls.
> 
> Revert the patch to fix the problem.
> 
> This reverts commit dd0daf2a6fb6bec436a3ef68bd585ea09a2a54b7.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>

Acked-by: Hans Verkuil <hverkuil@xxxxxxxxx>

> ---
>  drivers/media/video/v4l2-dev.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
> index 03f7f46..f777da6 100644
> --- a/drivers/media/video/v4l2-dev.c
> +++ b/drivers/media/video/v4l2-dev.c
> @@ -596,7 +596,9 @@ void video_unregister_device(struct video_device *vdev)
>  	if (!vdev || !video_is_registered(vdev))
>  		return;
>  
> +	mutex_lock(&videodev_lock);
>  	clear_bit(V4L2_FL_REGISTERED, &vdev->flags);
> +	mutex_unlock(&videodev_lock);
>  	device_unregister(&vdev->dev);
>  }
>  EXPORT_SYMBOL(video_unregister_device);
> 

-- 
Hans Verkuil - video4linux developer - sponsored by Cisco
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