From: Daniel Axtens dja@axtens.net
[ Upstream commit 10e1fdb95809ed21406f53b5b4f064673a1b9ceb ]
Currently, disconnecting a USB webcam while it is in use prints out a number of warnings, such as:
WARNING: CPU: 2 PID: 3118 at /build/linux-ezBi1T/linux-4.8.0/fs/sysfs/group.c:237 sysfs_remove_group+0x8b/0x90 sysfs group ffffffffa7cd0780 not found for kobject 'event13'
This has been noticed before. [0]
This is because of the order in which things are torn down.
If there are no streams active during a USB disconnect:
- uvc_disconnect() is invoked via device_del() through the bus notifier mechanism.
- this calls uvc_unregister_video().
- uvc_unregister_video() unregisters the video device for each stream,
- because there are no streams open, it calls uvc_delete()
- uvc_delete() calls uvc_status_cleanup(), which cleans up the status input device.
- uvc_delete() calls media_device_unregister(), which cleans up the media device
- uvc_delete(), uvc_unregister_video() and uvc_disconnect() all return, and we end up back in device_del().
- device_del() then cleans up the sysfs folder for the camera with dpm_sysfs_remove(). Because uvc_status_cleanup() and media_device_unregister() have already been called, this all works nicely.
If, on the other hand, there *are* streams active during a USB disconnect:
- uvc_disconnect() is invoked
- this calls uvc_unregister_video()
- uvc_unregister_video() unregisters the video device for each stream,
- uvc_unregister_video() and uvc_disconnect() return, and we end up back in device_del().
- device_del() then cleans up the sysfs folder for the camera with dpm_sysfs_remove(). Because the status input device and the media device are children of the USB device, this also deletes their sysfs folders.
- Sometime later, the final stream is closed, invoking uvc_release().
- uvc_release() calls uvc_delete()
- uvc_delete() calls uvc_status_cleanup(), which cleans up the status input device. Because the sysfs directory has already been removed, this causes a WARNing.
- uvc_delete() calls media_device_unregister(), which cleans up the media device. Because the sysfs directory has already been removed, this causes another WARNing.
To fix this, we need to make sure the devices are always unregistered before the end of uvc_disconnect(). To this, move the unregistration into the disconnect path:
- split uvc_status_cleanup() into two parts, one on disconnect that unregisters and one on delete that frees.
- move v4l2_device_unregister() and media_device_unregister() into the disconnect path.
[0]: https://lkml.org/lkml/2016/12/8/657
[Renamed uvc_input_cleanup() to uvc_input_unregister()]
Signed-off-by: Daniel Axtens dja@axtens.net Acked-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Laurent Pinchart laurent.pinchart@ideasonboard.com Signed-off-by: Mauro Carvalho Chehab mchehab+samsung@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/media/usb/uvc/uvc_driver.c | 13 +++++++++---- drivers/media/usb/uvc/uvc_status.c | 12 ++++++++---- drivers/media/usb/uvc/uvcvideo.h | 1 + 3 files changed, 18 insertions(+), 8 deletions(-)
diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c index d46dc432456c..361abbc00486 100644 --- a/drivers/media/usb/uvc/uvc_driver.c +++ b/drivers/media/usb/uvc/uvc_driver.c @@ -1824,11 +1824,7 @@ static void uvc_delete(struct kref *kref) usb_put_intf(dev->intf); usb_put_dev(dev->udev);
- if (dev->vdev.dev) - v4l2_device_unregister(&dev->vdev); #ifdef CONFIG_MEDIA_CONTROLLER - if (media_devnode_is_registered(dev->mdev.devnode)) - media_device_unregister(&dev->mdev); media_device_cleanup(&dev->mdev); #endif
@@ -1885,6 +1881,15 @@ static void uvc_unregister_video(struct uvc_device *dev)
uvc_debugfs_cleanup_stream(stream); } + + uvc_status_unregister(dev); + + if (dev->vdev.dev) + v4l2_device_unregister(&dev->vdev); +#ifdef CONFIG_MEDIA_CONTROLLER + if (media_devnode_is_registered(dev->mdev.devnode)) + media_device_unregister(&dev->mdev); +#endif }
int uvc_register_video_device(struct uvc_device *dev, diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c index 0722dc684378..883e4cab45e7 100644 --- a/drivers/media/usb/uvc/uvc_status.c +++ b/drivers/media/usb/uvc/uvc_status.c @@ -54,7 +54,7 @@ static int uvc_input_init(struct uvc_device *dev) return ret; }
-static void uvc_input_cleanup(struct uvc_device *dev) +static void uvc_input_unregister(struct uvc_device *dev) { if (dev->input) input_unregister_device(dev->input); @@ -71,7 +71,7 @@ static void uvc_input_report_key(struct uvc_device *dev, unsigned int code,
#else #define uvc_input_init(dev) -#define uvc_input_cleanup(dev) +#define uvc_input_unregister(dev) #define uvc_input_report_key(dev, code, value) #endif /* CONFIG_USB_VIDEO_CLASS_INPUT_EVDEV */
@@ -292,12 +292,16 @@ int uvc_status_init(struct uvc_device *dev) return 0; }
-void uvc_status_cleanup(struct uvc_device *dev) +void uvc_status_unregister(struct uvc_device *dev) { usb_kill_urb(dev->int_urb); + uvc_input_unregister(dev); +} + +void uvc_status_cleanup(struct uvc_device *dev) +{ usb_free_urb(dev->int_urb); kfree(dev->status); - uvc_input_cleanup(dev); }
int uvc_status_start(struct uvc_device *dev, gfp_t flags) diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h index e5f5d84f1d1d..a738486fd9d6 100644 --- a/drivers/media/usb/uvc/uvcvideo.h +++ b/drivers/media/usb/uvc/uvcvideo.h @@ -750,6 +750,7 @@ int uvc_register_video_device(struct uvc_device *dev,
/* Status */ int uvc_status_init(struct uvc_device *dev); +void uvc_status_unregister(struct uvc_device *dev); void uvc_status_cleanup(struct uvc_device *dev); int uvc_status_start(struct uvc_device *dev, gfp_t flags); void uvc_status_stop(struct uvc_device *dev);