Index: test/drivers/acpi/pci_root.c
===================================================================
--- test.orig/drivers/acpi/pci_root.c
+++ test/drivers/acpi/pci_root.c
@@ -600,17 +600,20 @@ static int acpi_pci_root_add(struct acpi
 	if (system_state != SYSTEM_BOOTING)
 		pci_assign_unassigned_bus_resources(root->bus);
 
+	/* need to after hot-added ioapic is registered */
+	if (system_state != SYSTEM_BOOTING)
+		pci_enable_bridges(root->bus);
+
+	pci_bus_add_devices(root->bus);
+
 	mutex_lock(&acpi_pci_root_lock);
+
 	list_for_each_entry(driver, &acpi_pci_drivers, node)
 		if (driver->add)
 			driver->add(root);
-	mutex_unlock(&acpi_pci_root_lock);
 
-	/* need to after hot-added ioapic is registered */
-	if (system_state != SYSTEM_BOOTING)
-		pci_enable_bridges(root->bus);
+	mutex_unlock(&acpi_pci_root_lock);
 
-	pci_bus_add_devices(root->bus);
 	return 1;
 
 out_del_root: