Hi Ricardo,
Thank you for the patch.
On Fri, Jun 14, 2024 at 12:41:27PM +0000, Ricardo Ribalda wrote:
> uvc_unregister_video() can be called asynchronously from
> uvc_disconnect(). If the device is still streaming when that happens, a
> plethora of race conditions can occur.
>
> Make sure that the device has stopped streaming before exiting this
> function.
>
> If the user still holds handles to the driver's file descriptors, any
> ioctl will return -ENODEV from the v4l2 core.
>
> This change makes uvc more consistent with the rest of the v4l2 drivers
> using the vb2_fop_* and vb2_ioctl_* helpers.
As I've said many times before, this issue needs a fix in the V4L2 core,
ideally with support in the cdev core. It seems I'll have to do it
myself ?
> Reviewed-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
> Suggested-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> ---
> drivers/media/usb/uvc/uvc_driver.c | 32 +++++++++++++++++++++++++++++++-
> 1 file changed, 31 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index bbd90123a4e7..55132688e363 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -1908,11 +1908,41 @@ static void uvc_unregister_video(struct uvc_device *dev)
> struct uvc_streaming *stream;
>
> list_for_each_entry(stream, &dev->streams, list) {
> + /* Nothing to do here, continue. */
> if (!video_is_registered(&stream->vdev))
> continue;
>
> + /*
> + * For stream->vdev we follow the same logic as:
> + * vb2_video_unregister_device().
> + */
> +
> + /* 1. Take a reference to vdev */
> + get_device(&stream->vdev.dev);
> +
> + /* 2. Ensure that no new ioctls can be called. */
> video_unregister_device(&stream->vdev);
> - video_unregister_device(&stream->meta.vdev);
> +
> + /* 3. Wait for old ioctls to finish. */
> + mutex_lock(&stream->mutex);
> +
> + /* 4. Stop streaming. */
> + uvc_queue_release(&stream->queue);
> +
> + mutex_unlock(&stream->mutex);
> +
> + put_device(&stream->vdev.dev);
> +
> + /*
> + * For stream->meta.vdev we can directly call:
> + * vb2_video_unregister_device().
> + */
> + vb2_video_unregister_device(&stream->meta.vdev);
> +
> + /*
> + * Now both vdevs are not streaming and all the ioctls will
> + * return -ENODEV.
> + */
>
> uvc_debugfs_cleanup_stream(stream);
> }
--
Regards,
Laurent Pinchart
