diff --git a/sys/kern/subr_bus.c b/sys/kern/subr_bus.c
--- a/sys/kern/subr_bus.c
+++ b/sys/kern/subr_bus.c
@@ -1397,6 +1397,8 @@
 	device_t dev;
 	devclass_t dc;
 
+	bus_topo_assert();
+
 	PDEBUG(("%s at %s as unit %d", name, DEVICENAME(parent), unit));
 
 	if (name) {
@@ -1511,6 +1513,8 @@
 	device_t child;
 	device_t place;
 
+	bus_topo_assert();
+
 	PDEBUG(("%s at %s with order %u as unit %d",
 	    name, DEVICENAME(dev), order, unit));
 	KASSERT(name != NULL || unit == DEVICE_UNIT_ANY,
@@ -2414,6 +2418,8 @@
 	devclass_t dc;
 	int error;
 
+	bus_topo_assert();
+
 	if (!classname) {
 		if (dev->devclass)
 			devclass_delete_device(dev->devclass, dev);
@@ -5218,6 +5224,7 @@
 {
 	switch (what) {
 	case MOD_LOAD:
+		bus_topo_lock();
 		TAILQ_INIT(&bus_data_devices);
 		kobj_class_compile((kobj_class_t) &root_driver);
 		root_bus = make_device(NULL, "root", 0);
@@ -5226,6 +5233,7 @@
 		root_bus->driver = &root_driver;
 		root_bus->state = DS_ATTACHED;
 		root_devclass = devclass_find_internal("root", NULL, FALSE);
+		bus_topo_unlock();
 		devctl2_init();
 		return (0);