linux-kernel - [PATCH 1/5] media: uvcvideo: Cancel async worker earlier

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Message-Id: <20200830150443.167286-2-linux@roeck-us.net>
Date:   Sun, 30 Aug 2020 08:04:39 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@....fi>,
        linux-uvc-devel@...ts.sourceforge.net, linux-usb@...r.kernel.org,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Guenter Roeck <linux@...ck-us.net>,
        Alan Stern <stern@...land.harvard.edu>,
        Hans Verkuil <hverkuil-cisco@...all.nl>
Subject: [PATCH 1/5] 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 #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@...asonboard.com>
Cc: Alan Stern <stern@...land.harvard.edu>
Cc: Hans Verkuil <hverkuil-cisco@...all.nl>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
 drivers/media/usb/uvc/uvc_ctrl.c   | 11 +++++++----
 drivers/media/usb/uvc/uvc_driver.c |  1 +
 drivers/media/usb/uvc/uvcvideo.h   |  1 +
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index e399b9fad757..130c56e0063d 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -2340,14 +2340,17 @@ 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) {
diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index 431d86e1c94b..bfba67a69185 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -1952,6 +1952,7 @@ 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);
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index 6ab972c643e3..543afcd9fd26 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -830,6 +830,7 @@ 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,
-- 
2.17.1