linux-kernel - [PATCH V2] usb: gadget: uvc_video: unlock before submitting a request to ep

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Date:   Wed, 8 Nov 2023 20:24:26 +0530
From:   Piyush Mehta <piyush.mehta@....com>
To:     <gregkh@...uxfoundation.org>, <michal.simek@....com>,
        <laurent.pinchart@...asonboard.com>
CC:     <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <dan.scally@...asonboard.com>, <s.shtylyov@....ru>,
        <khtsai@...gle.com>, <siva.durga.prasad.paladugu@....com>,
        <radhey.shyam.pandey@....com>,
        "Piyush Mehta" <piyush.mehta@....com>
Subject: [PATCH V2] usb: gadget: uvc_video: unlock before submitting a request to ep

There could be chances where the usb_ep_queue() could fail and trigger
complete() handler with error status. In this case, if usb_ep_queue()
is called with lock held and the triggered complete() handler is waiting
for the same lock to be cleared could result in a deadlock situation and
could result in system hang, so call usb_ep_queue() without the lock to
resolve this issue.

Signed-off-by: Piyush Mehta <piyush.mehta@....com>
---
Changes in V2:
- Addressed Dan and Sergey review comments:
 - Removed unwanted usb_ep_set_halt, it's alreadly call on error path.
 - Updated commit message.

Link: https://lore.kernel.org/lkml/20231102071138.828126-1-piyush.mehta@amd.com/T/
---
 drivers/usb/gadget/function/uvc_video.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
index 91af3b1ef0d4..705d762b7f5c 100644
--- a/drivers/usb/gadget/function/uvc_video.c
+++ b/drivers/usb/gadget/function/uvc_video.c
@@ -460,10 +460,10 @@ static void uvcg_video_pump(struct work_struct *work)
 			req->no_interrupt = 1;
 		}
 
-		/* Queue the USB request */
-		ret = uvcg_video_ep_queue(video, req);
 		spin_unlock_irqrestore(&queue->irqlock, flags);
 
+		/* Queue the USB request */
+		ret = uvcg_video_ep_queue(video, req);
 		if (ret < 0) {
 			uvcg_queue_cancel(queue, 0);
 			break;
-- 
2.25.1