Index: if.c
===================================================================
--- if.c	(revision 223821)
+++ if.c	(working copy)
@@ -2533,18 +2534,21 @@
 		return (ENXIO);
 	}
 
+	IF_ADDR_LOCK(ifp);
+	if (ifp->if_flags & IFF_INIOCTL)
+		msleep(ifp, &ifp->if_addr_mtx, 0, "ifioctl", 0);
+	else
+		ifp->if_flags |= IFF_INIOCTL;
+	IF_ADDR_UNLOCK(ifp);
+
 	error = ifhwioctl(cmd, ifp, data, td);
-	if (error != ENOIOCTL) {
-		if_rele(ifp);
-		CURVNET_RESTORE();
-		return (error);
-	}
+	if (error != ENOIOCTL)
+		goto wakeup_out;
 
 	oif_flags = ifp->if_flags;
 	if (so->so_proto == NULL) {
-		if_rele(ifp);
-		CURVNET_RESTORE();
-		return (EOPNOTSUPP);
+		error = EOPNOTSUPP;
+		goto wakeup_out;
 	}
 #ifndef COMPAT_43
 	error = ((*so->so_proto->pr_usrreqs->pru_control)(so, cmd,
@@ -2617,6 +2621,13 @@
 		}
 #endif
 	}
+
+wakeup_out:
+	IF_ADDR_LOCK(ifp);
+	ifp->if_flags &= ~IFF_INIOCTL;
+	wakeup(ifp);
+	IF_ADDR_UNLOCK(ifp);
+
 	if_rele(ifp);
 	CURVNET_RESTORE();
 	return (error);