usb_del_gadget() can lead to new work being scheduled in gadget->work
workqueue. This is observed, for example, with the dwc3 driver with the
following call stack:
  device_del()
    gadget_unbind_driver()
      usb_gadget_disconnect_locked()
        dwc3_gadget_pullup()
	  dwc3_gadget_soft_disconnect()
	    usb_gadget_set_state()
	      schedule_work(&gadget->work)

Move flush_work() after device_del() to ensure the workqueue is cleaned
up.

Fixes: 1ff24d40b3c3 ("usb: dwc3: gadget: Fix incorrect UDC state after manual deconfiguration")
Signed-off-by: Roy Luo <royluo@google.com>
---
 drivers/usb/gadget/udc/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index a6f46364be65..4b3d5075621a 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -1543,8 +1543,8 @@ void usb_del_gadget(struct usb_gadget *gadget)
 
 	kobject_uevent(&udc->dev.kobj, KOBJ_REMOVE);
 	sysfs_remove_link(&udc->dev.kobj, "gadget");
-	flush_work(&gadget->work);
 	device_del(&gadget->dev);
+	flush_work(&gadget->work);
 	ida_free(&gadget_id_numbers, gadget->id_number);
 	cancel_work_sync(&udc->vbus_work);
 	device_unregister(&udc->dev);

base-commit: f286757b644c226b6b31779da95a4fa7ab245ef5
-- 
2.48.1.362.g079036d154-goog

On Tue, Feb 04, 2025, Roy Luo wrote:
> usb_del_gadget() can lead to new work being scheduled in gadget->work
> workqueue. This is observed, for example, with the dwc3 driver with the
> following call stack:
>   device_del()
>     gadget_unbind_driver()
>       usb_gadget_disconnect_locked()
>         dwc3_gadget_pullup()
> 	  dwc3_gadget_soft_disconnect()
> 	    usb_gadget_set_state()
> 	      schedule_work(&gadget->work)
> 
> Move flush_work() after device_del() to ensure the workqueue is cleaned
> up.
> 
> Fixes: 1ff24d40b3c3 ("usb: dwc3: gadget: Fix incorrect UDC state after manual deconfiguration")

The reference should be targeting the udc core. Probably want to Cc
stable also.

BR,
Thinh

> Signed-off-by: Roy Luo <royluo@google.com>
> ---
>  drivers/usb/gadget/udc/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
> index a6f46364be65..4b3d5075621a 100644
> --- a/drivers/usb/gadget/udc/core.c
> +++ b/drivers/usb/gadget/udc/core.c
> @@ -1543,8 +1543,8 @@ void usb_del_gadget(struct usb_gadget *gadget)
>  
>  	kobject_uevent(&udc->dev.kobj, KOBJ_REMOVE);
>  	sysfs_remove_link(&udc->dev.kobj, "gadget");
> -	flush_work(&gadget->work);
>  	device_del(&gadget->dev);
> +	flush_work(&gadget->work);
>  	ida_free(&gadget_id_numbers, gadget->id_number);
>  	cancel_work_sync(&udc->vbus_work);
>  	device_unregister(&udc->dev);
> 
> base-commit: f286757b644c226b6b31779da95a4fa7ab245ef5
> -- 
> 2.48.1.362.g079036d154-goog
> 

On Mon, Feb 3, 2025 at 4:55 PM Thinh Nguyen <Thinh.Nguyen@synopsys.com> wrote:
>
> On Tue, Feb 04, 2025, Roy Luo wrote:
> > usb_del_gadget() can lead to new work being scheduled in gadget->work
> > workqueue. This is observed, for example, with the dwc3 driver with the
> > following call stack:
> >   device_del()
> >     gadget_unbind_driver()
> >       usb_gadget_disconnect_locked()
> >         dwc3_gadget_pullup()
> >         dwc3_gadget_soft_disconnect()
> >           usb_gadget_set_state()
> >             schedule_work(&gadget->work)
> >
> > Move flush_work() after device_del() to ensure the workqueue is cleaned
> > up.
> >
> > Fixes: 1ff24d40b3c3 ("usb: dwc3: gadget: Fix incorrect UDC state after manual deconfiguration")
>
> The reference should be targeting the udc core. Probably want to Cc
> stable also.
>

Thanks for the review, sending out v2.

Regards,
Roy Luo