[PATCH] usb: gadget: uvc: Fix unstarted kthread worker

From: Frederic Weisbecker
Date: Wed Feb 12 2025 - 08:55:53 EST


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@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-lkp/202502121025.55bfa801-lkp@xxxxxxxxx
Fixes: f0bbfbd16b3b ("usb: gadget: uvc: rework to enqueue in pump worker from encoded queue")
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>
Cc: linux-usb@xxxxxxxxxxxxxxx
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
---
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