FROMLIST: media: uvcvideo: Cancel async worker earlier

So far the asynchronous control worker was canceled only in
uvc_ctrl_cleanup_device. This is much later than the call to
uvc_disconnect. However, after the call to uvc_disconnect returns,
there must be no more USB activity. This can result in all kinds
of problems in the USB code. One observed example:

URB ffff993e83d0bc00 submitted while active
WARNING: CPU: 0 PID: 4046 at drivers/usb/core/urb.c:364 usb_submit_urb+0x4ba/0x55e
Modules linked in: <...>
CPU: 0 PID: 4046 Comm: kworker/0:35 Not tainted 4.19.139 linux-surface#18
Hardware name: Google Phaser/Phaser, BIOS Google_Phaser.10952.0.0 08/09/2018
Workqueue: events uvc_ctrl_status_event_work [uvcvideo]
RIP: 0010:usb_submit_urb+0x4ba/0x55e
Code: <...>
RSP: 0018:ffffb08d471ebde8 EFLAGS: 00010246
RAX: a6da85d923ea5d00 RBX: ffff993e71985928 RCX: 0000000000000000
RDX: ffff993f37a1de90 RSI: ffff993f37a153d0 RDI: ffff993f37a153d0
RBP: ffffb08d471ebe28 R08: 000000000000003b R09: 001424bf85822e96
R10: 0000001000000000 R11: ffffffff975a4398 R12: ffff993e83d0b000
R13: ffff993e83d0bc00 R14: 0000000000000000 R15: 00000000fffffff0
FS:  0000000000000000(0000) GS:ffff993f37a00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000ec9c0000 CR3: 000000025b160000 CR4: 0000000000340ef0
Call Trace:
 uvc_ctrl_status_event_work+0xd6/0x107 [uvcvideo]
 process_one_work+0x19b/0x4c5
 worker_thread+0x10d/0x286
 kthread+0x138/0x140
 ? process_one_work+0x4c5/0x4c5
 ? kthread_associate_blkcg+0xc1/0xc1
 ret_from_fork+0x1f/0x40

Introduce new function uvc_ctrl_stop_device() to cancel the worker
and call it from uvc_unregister_video() to solve the problem.

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
(am from https://lore.kernel.org/patchwork/patch/1307067/)
(also found at https://lore.kernel.org/r/20200917022547.198090-2-linux@roeck-us.net)

BUG=chromium:1078293
TEST=Camera tests

Change-Id: I273ca01e09decedbf7edf8d25220fd8d0faa83f3
Signed-off-by: Guenter Roeck <groeck@chromium.org>
DisallowRecycledBuilds:  hatch-arc-r-cq
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2384024
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>

drivers/media/usb/uvc/uvc_ctrl.c

@@ -2345,14 +2345,17 @@ static void uvc_ctrl_cleanup_mappings(struct uvc_device *dev,
  }
 }
 
-void uvc_ctrl_cleanup_device(struct uvc_device *dev)
+void uvc_ctrl_stop_device(struct uvc_device *dev)
 {
- struct uvc_entity *entity;
- unsigned int i;
-
  /* Can be uninitialized if we are aborting on probe error. */
  if (dev->async_ctrl.work.func)
  cancel_work_sync(&dev->async_ctrl.work);
+}
+
+void uvc_ctrl_cleanup_device(struct uvc_device *dev)
+{
+ struct uvc_entity *entity;
+ unsigned int i;
 
  /* Free controls and control mappings for all entities. */
  list_for_each_entry(entity, &dev->entities, list) {

drivers/media/usb/uvc/uvc_driver.c

@@ -1936,6 +1936,7 @@ static void uvc_unregister_video(struct uvc_device *dev)
  }
 
  uvc_status_unregister(dev);
+ uvc_ctrl_stop_device(dev);
 
  if (dev->vdev.dev)
  v4l2_device_unregister(&dev->vdev);

drivers/media/usb/uvc/uvcvideo.h

@@ -824,6 +824,7 @@ int uvc_query_v4l2_menu(struct uvc_video_chain *chain,
 int uvc_ctrl_add_mapping(struct uvc_video_chain *chain,
  const struct uvc_control_mapping *mapping);
 int uvc_ctrl_init_device(struct uvc_device *dev);
+void uvc_ctrl_stop_device(struct uvc_device *dev);
 void uvc_ctrl_cleanup_device(struct uvc_device *dev);
 int uvc_ctrl_restore_values(struct uvc_device *dev);
 bool uvc_ctrl_status_event(struct urb *urb, struct uvc_video_chain *chain,