linux-kernel - [PATCH] usb: gadget: uvc: Fix unstarted kthread worker

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Message-ID: <20250212135514.30539-1-frederic@kernel.org>
Date: Wed, 12 Feb 2025 14:55:14 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Frederic Weisbecker <frederic@...nel.org>,
	kernel test robot <oliver.sang@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Michael Grzeschik <m.grzeschik@...gutronix.de>,
	linux-usb@...r.kernel.org
Subject: [PATCH] usb: gadget: uvc: Fix unstarted kthread worker

The behaviour of kthread_create_worker() was recently changed to align
with the one of kthread_create(). The kthread worker is created but not
awaken by default. This is to allow the use of kthread_affine_preferred()
and kthread_bind[_mask]() with kthread workers. In order to keep the
old behaviour and wake the kthread up, kthread_run_worker() must be
used. All the pre-existing users have been converted, except for UVC
that was introduced in the same merge window as the API change.

This results in hangs:

	INFO: task UVCG:82 blocked for more than 491 seconds.
	Tainted: G                T  6.13.0-rc2-00014-gb04e317b5226 #1
	task:UVCG            state:D stack:0     pid:82
	 Call Trace:
	 __schedule
	 schedule
	 schedule_preempt_disabled
	 kthread
	 ? kthread_flush_work
	 ret_from_fork
	 ret_from_fork_asm
	 entry_INT80_32

Fix this with converting UVCG kworker to the new API.

Reported-by: kernel test robot <oliver.sang@...el.com>
Closes: https://lore.kernel.org/oe-lkp/202502121025.55bfa801-lkp@intel.com
Fixes: f0bbfbd16b3b ("usb: gadget: uvc: rework to enqueue in pump worker from encoded queue")
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Michael Grzeschik <m.grzeschik@...gutronix.de>
Cc: linux-usb@...r.kernel.org
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
---
 drivers/usb/gadget/function/uvc_video.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
index 79e223713d8b..fb77b0b21790 100644
--- a/drivers/usb/gadget/function/uvc_video.c
+++ b/drivers/usb/gadget/function/uvc_video.c
@@ -818,7 +818,7 @@ int uvcg_video_init(struct uvc_video *video, struct uvc_device *uvc)
 		return -EINVAL;
 
 	/* Allocate a kthread for asynchronous hw submit handler. */
-	video->kworker = kthread_create_worker(0, "UVCG");
+	video->kworker = kthread_run_worker(0, "UVCG");
 	if (IS_ERR(video->kworker)) {
 		uvcg_err(&video->uvc->func, "failed to create UVCG kworker\n");
 		return PTR_ERR(video->kworker);
-- 
2.46.0