usb: gadget: core: flush gadget workqueue after device removal

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 <[email protected]>

---
 drivers/usb/gadget/udc/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

drivers/usb/gadget/udc/core.c +1 -1

index a6f46364be65..4b3d5075621a 100644
@@ -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

Signature · 1 line

2.48.1.362.g079036d154-goog

Quoted 11 lines · Roy Luo

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)

Quoted 4 lines

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.