Index: usb-devel/drivers/usb/gadget/udc/dummy_hcd.c
===================================================================
--- usb-devel.orig/drivers/usb/gadget/udc/dummy_hcd.c
+++ usb-devel/drivers/usb/gadget/udc/dummy_hcd.c
@@ -462,8 +462,13 @@ static void set_link_state(struct dummy_
 
 		/* Report reset and disconnect events to the driver */
 		if (dum->ints_enabled && (disconnect || reset)) {
-			stop_activity(dum);
 			++dum->callback_usage;
+			/*
+			 * stop_activity() can drop dum->lock, so it must
+			 * must not come between the dum->ints_enabled test
+			 * and the ++dum->callback_usage.
+			 */
+			stop_activity(dum);
 			spin_unlock(&dum->lock);
 			if (reset)
 				usb_gadget_udc_reset(&dum->gadget, dum->driver);