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[209.85.216.49]) by smtp.gmail.com with ESMTPSA id i5-20020a6561a5000000b0050bd9c8c53dsm15602909pgv.23.2023.05.01.06.30.09 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 May 2023 06:30:10 -0700 (PDT) Received: by mail-pj1-f49.google.com with SMTP id 98e67ed59e1d1-24df4ecdb87so822560a91.0 for ; Mon, 01 May 2023 06:30:09 -0700 (PDT) X-Received: by 2002:a17:90b:350b:b0:247:140b:c5d6 with SMTP id ls11-20020a17090b350b00b00247140bc5d6mr14366243pjb.45.1682947809251; Mon, 01 May 2023 06:30:09 -0700 (PDT) MIME-Version: 1.0 References: <20230309-guenter-mini-v2-0-e6410d590d43@chromium.org> <20230309-guenter-mini-v2-1-e6410d590d43@chromium.org> <20230309145757.GB1088@pendragon.ideasonboard.com> In-Reply-To: From: Ricardo Ribalda Date: Mon, 1 May 2023 15:29:58 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 1/3] media: uvcvideo: Cancel async worker earlier To: Laurent Pinchart Cc: Mauro Carvalho Chehab , Max Staudt , Alan Stern , Sakari Ailus , Guenter Roeck , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Sean Paul , Tomasz Figa , Hans Verkuil Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-2.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Laurent Friendly ping! On Tue, 28 Mar 2023 at 09:52, Ricardo Ribalda wrote: > > Hi Laurent > > I have not tested it yet... but maybe something like this might be > slightly better? > > > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c > index 5e9d3da862dd..3944404b2de2 100644 > --- a/drivers/media/usb/uvc/uvc_ctrl.c > +++ b/drivers/media/usb/uvc/uvc_ctrl.c > @@ -2762,10 +2762,6 @@ void uvc_ctrl_cleanup_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); > - > /* Free controls and control mappings for all entities. */ > list_for_each_entry(entity, &dev->entities, list) { > for (i = 0; i < entity->ncontrols; ++i) { > diff --git a/drivers/media/usb/uvc/uvc_status.c > b/drivers/media/usb/uvc/uvc_status.c > index a78a88c710e2..0208612a9f12 100644 > --- a/drivers/media/usb/uvc/uvc_status.c > +++ b/drivers/media/usb/uvc/uvc_status.c > @@ -292,7 +292,7 @@ int uvc_status_init(struct uvc_device *dev) > > void uvc_status_unregister(struct uvc_device *dev) > { > - usb_kill_urb(dev->int_urb); > + uvc_status_stop(dev); > uvc_input_unregister(dev); > } > > > The benefit from Guenter patch is that it has been tested for years... > > What do you think? Shall we try this approach instead? > > Regards! > > On Thu, 9 Mar 2023 at 15:57, Laurent Pinchart > wrote: > > > > Hi Ricardo and Guenter, > > > > Thank you for the patch. > > > > On Thu, Mar 09, 2023 at 03:44:05PM +0100, Ricardo Ribalda wrote: > > > From: Guenter Roeck > > > > > > 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 > > > Cc: Alan Stern > > > Cc: Hans Verkuil > > > Reviewed-by: Tomasz Figa > > > Reviewed-by: Sean Paul > > > Signed-off-by: Guenter Roeck > > > Signed-off-by: Ricardo Ribalda > > > --- > > > 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 5e9d3da862dd..769c1d2a2f45 100644 > > > --- a/drivers/media/usb/uvc/uvc_ctrl.c > > > +++ b/drivers/media/usb/uvc/uvc_ctrl.c > > > @@ -2757,14 +2757,17 @@ 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); > > > +} > > > > There may be an opportunity for refactoring, as we have > > uvc_status_stop() that stops the work queue, but I think this is good > > enough for now. I'm wondering, though, if there could be a race > > condition here similar to the one that the recent changes to > > uvc_status_stop() have fixed ? As uvc_ctrl_stop_device() is called at > > release time I assume that URBs have been cancelled, so there should be > > no race, but a second pair of eyeballs to confirm this would be > > appreciated. > > > > Other than that, the patch looks good to me, and fixes an issue > > independent from the rest of the series, so > > > > Reviewed-by: Laurent Pinchart > > > > I will wait for a reply regarding the race condition before queuing this > > up though. > > > > > + > > > +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 7aefa76a42b3..4be6dfeaa295 100644 > > > --- a/drivers/media/usb/uvc/uvc_driver.c > > > +++ b/drivers/media/usb/uvc/uvc_driver.c > > > @@ -1893,6 +1893,7 @@ 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 9a596c8d894a..50f171e7381b 100644 > > > --- a/drivers/media/usb/uvc/uvcvideo.h > > > +++ b/drivers/media/usb/uvc/uvcvideo.h > > > @@ -760,6 +760,7 @@ 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_async(struct urb *urb, struct uvc_video_chain *chain, > > > > -- > > Regards, > > > > Laurent Pinchart > > > > -- > Ricardo Ribalda -- Ricardo Ribalda