On Thu Sep 26 05:59:06 2024 +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.
>
> This driver (and many other usb drivers) always had this problem, but it
> wasn't possible to easily fix this until the vb2_video_unregister_device()
> helper was added. So the Fixes tag points to the creation of that helper.
>
> Reviewed-by: Hans Verkuil <[email protected]>
> Suggested-by: Hans Verkuil <[email protected]>
> Signed-off-by: Ricardo Ribalda <[email protected]>
> Reviewed-by: Mauro Carvalho Chehab <[email protected]>
> Fixes: f729ef5796d8 ("media: videobuf2-v4l2.c: add
> vb2_video_unregister_device helper function")
> Cc: [email protected] # 5.10.x
> [hverkuil: add note regarding Fixes version]
> Signed-off-by: Hans Verkuil <[email protected]>
Patch committed.
Thanks,
Hans Verkuil
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 ab9cdb50e74e..a96f6ca0889f 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -1935,11 +1935,41 @@ 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);
}
