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From:   Ricardo Ribalda <ribalda@chromium.org>
Subject: [PATCH v3 0/3] uvcvideo: Attempt N to land UVC race conditions
 fixes
Date:   Tue, 21 Nov 2023 19:53:47 +0000
Message-Id: <20231121-guenter-mini-v3-0-d8a5eae2312b@chromium.org>
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To:     Mauro Carvalho Chehab <mchehab@kernel.org>
Cc:     Guenter Roeck <linux@roeck-us.net>,
        Tomasz Figa <tfiga@chromium.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        Sean Paul <seanpaul@chromium.org>,
        Ricardo Ribalda <ribalda@chromium.org>,
        Sakari Ailus <sakari.ailus@linux.intel.com>
Precedence: bulk

Back in 2020 Guenter published a set of patches to fix some race
conditions on UVC.
https://lore.kernel.org/all/20200917022547.198090-5-linux@roeck-us.net/

That kind of race conditions are not only seen on UVC, but are a common
sin on almost all the kernel, so this is what it was decided back then
that we should try to fix them at higher levels.

After that. A lot of video_is_registered() were added to the core:

```
ribalda@alco:~/work/linux$ git grep is_registered drivers/media/v4l2-core/
drivers/media/v4l2-core/v4l2-compat-ioctl32.c:  if (!video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (video_is_registered(vdev)) {
drivers/media/v4l2-core/v4l2-dev.c:             if (video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (!video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (vdev == NULL || !video_is_registered(vdev)) {
drivers/media/v4l2-core/v4l2-dev.c:             if (video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (!vdev || !video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-ioctl.c:   if (!video_is_registered(vfd)) {
drivers/media/v4l2-core/v4l2-subdev.c:  if (video_is_registered(vdev)) {
```

And recently Sakari is trying to land:
https://lore.kernel.org/linux-media/20230201214535.347075-1-sakari.ailus@linux.intel.com/

Which will make obsolete a lot of (all?) of the video_is_registered() checks on
Guenter's patches.

Besides those checks, there were some other valid races fixed on his
patches.

This series is just a rebase of what I think is missing on UVC even
if we fixed v4l2/core with all the video_is_register() checks removed.

Thanks!

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
Changes in v3:
- Introduce media: uvcvideo: Do not halt the device after disconnect
- Introduce media: uvcvideo: Always use uvc_status_stop()
- Link to v2: https://lore.kernel.org/r/20230309-guenter-mini-v2-0-e6410d590d43@chromium.org

Changes in v2:
- Actually send the series to the ML an not only to individuals.
- Link to v1: https://lore.kernel.org/r/20230309-guenter-mini-v1-0-627d10cf6e96@chromium.org

---
Guenter Roeck (1):
      media: uvcvideo: Lock video streams and queues while unregistering

Ricardo Ribalda (2):
      media: uvcvideo: Always use uvc_status_stop()
      media: uvcvideo: Do not halt the device after disconnect

 drivers/media/usb/uvc/uvc_ctrl.c   |  4 ----
 drivers/media/usb/uvc/uvc_driver.c | 11 ++++++++++
 drivers/media/usb/uvc/uvc_status.c |  2 +-
 drivers/media/usb/uvc/uvc_video.c  | 45 ++++++++++++++++++++++++--------------
 drivers/media/usb/uvc/uvcvideo.h   |  2 ++
 5 files changed, 42 insertions(+), 22 deletions(-)
---
base-commit: 98b1cc82c4affc16f5598d4fa14b1858671b2263
change-id: 20230309-guenter-mini-89861b084ef1

Best regards,
-- 
Ricardo Ribalda <ribalda@chromium.org>