Index: ifq.c
===================================================================
RCS file: /cvs/src/sys/net/ifq.c,v
retrieving revision 1.33
diff -u -p -r1.33 ifq.c
--- ifq.c	3 Jul 2019 10:19:45 -0000	1.33
+++ ifq.c	8 Aug 2019 00:48:53 -0000
@@ -122,7 +122,10 @@ ifq_is_serialized(struct ifqueue *ifq)
 void
 ifq_start(struct ifqueue *ifq)
 {
-	if (ifq_len(ifq) >= min(ifq->ifq_if->if_txmit, ifq->ifq_maxlen)) {
+	struct ifnet *ifp = ifq->ifq_if;
+
+	if (ISSET(ifp->if_xflags, IFXF_MPSAFE) &&
+	    ifq_len(ifq) >= min(ifp->if_txmit, ifq->ifq_maxlen)) {
 		task_del(ifq->ifq_softnet, &ifq->ifq_bundle);
 		ifq_run_start(ifq);
 	} else
@@ -192,7 +195,8 @@ void
 ifq_init(struct ifqueue *ifq, struct ifnet *ifp, unsigned int idx)
 {
 	ifq->ifq_if = ifp;
-	ifq->ifq_softnet = net_tq(ifp->if_index); /* + idx */
+	ifq->ifq_softnet = ISSET(ifp->if_xflags, IFXF_MPSAFE) ?
+	    net_tq(ifp->if_index /* + idx */) : systq;
 	ifq->ifq_softc = NULL;
 
 	mtx_init(&ifq->ifq_mtx, IPL_NET);