Index: sys/dev/usb/ucom.c
===================================================================
RCS file: /cvsroot/src/sys/dev/usb/ucom.c,v
retrieving revision 1.115
diff -u -p -r1.115 ucom.c
--- sys/dev/usb/ucom.c	19 Nov 2016 09:49:20 -0000	1.115
+++ sys/dev/usb/ucom.c	28 Nov 2016 16:27:31 -0000
@@ -523,7 +523,6 @@ ucom_shutdown(struct ucom_softc *sc)
 
 	UCOMHIST_FUNC(); UCOMHIST_CALLED();
 
-	KASSERT(mutex_owned(&sc->sc_lock));
 	/*
 	 * Hang up if necessary.  Wait a bit, so the other side has time to
 	 * notice even if we immediately open the port again.
@@ -531,7 +530,7 @@ ucom_shutdown(struct ucom_softc *sc)
 	if (ISSET(tp->t_cflag, HUPCL)) {
 		ucom_dtr(sc, 0);
 		/* XXX will only timeout */
-		(void) kpause(ttclos, false, hz, &sc->sc_lock);
+		(void) kpause(ttclos, false, hz, NULL);
 	}
 }
 
@@ -1644,10 +1643,10 @@ ucom_cleanup(struct ucom_softc *sc)
 		return;
 	}
 
-	ucom_shutdown(sc);
-
 	mutex_exit(&sc->sc_lock);
 
+	ucom_shutdown(sc);
+
 	if (sc->sc_bulkin_pipe != NULL) {
 		usbd_abort_pipe(sc->sc_bulkin_pipe);
 	}