Index: test/drivers/acpi/scan.c
===================================================================
--- test.orig/drivers/acpi/scan.c
+++ test/drivers/acpi/scan.c
@@ -42,6 +42,18 @@ struct acpi_device_bus_id{
 	struct list_head node;
 };
 
+void acpi_scan_lock_acquire(void)
+{
+	mutex_lock(&acpi_scan_lock);
+}
+EXPORT_SYMBOL_GPL(acpi_scan_lock_acquire);
+
+void acpi_scan_lock_release(void)
+{
+	mutex_unlock(&acpi_scan_lock);
+}
+EXPORT_SYMBOL_GPL(acpi_scan_lock_release);
+
 int acpi_scan_add_handler(struct acpi_scan_handler *handler)
 {
 	if (!handler || !handler->attach)
@@ -95,8 +107,6 @@ acpi_device_modalias_show(struct device
 }
 static DEVICE_ATTR(modalias, 0444, acpi_device_modalias_show, NULL);
 
-static void __acpi_bus_trim(struct acpi_device *start);
-
 /**
  * acpi_bus_hot_remove_device: hot-remove a device and its children
  * @context: struct acpi_eject_event pointer (freed in this func)
@@ -107,7 +117,7 @@ static void __acpi_bus_trim(struct acpi_
  */
 void acpi_bus_hot_remove_device(void *context)
 {
-	struct acpi_eject_event *ej_event = (struct acpi_eject_event *) context;
+	struct acpi_eject_event *ej_event = context;
 	struct acpi_device *device = ej_event->device;
 	acpi_handle handle = device->handle;
 	acpi_handle temp;
@@ -118,11 +128,19 @@ void acpi_bus_hot_remove_device(void *co
 
 	mutex_lock(&acpi_scan_lock);
 
+	/* If there is no handle, the device node has been unregistered. */
+	if (!device->handle) {
+		dev_dbg(&device->dev, "ACPI handle missing\n");
+		put_device(&device->dev);
+		goto out;
+	}
+
 	ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 		"Hot-removing device %s...\n", dev_name(&device->dev)));
 
-	__acpi_bus_trim(device);
-	/* Device node has been released. */
+	acpi_bus_trim(device);
+	/* Device node has been unregistered. */
+	put_device(&device->dev);
 	device = NULL;
 
 	if (ACPI_SUCCESS(acpi_get_handle(handle, "_LCK", &temp))) {
@@ -151,6 +169,7 @@ void acpi_bus_hot_remove_device(void *co
 					  ost_code, NULL);
 	}
 
+ out:
 	mutex_unlock(&acpi_scan_lock);
 	kfree(context);
 	return;
@@ -212,6 +231,7 @@ acpi_eject_store(struct device *d, struc
 		goto err;
 	}
 
+	get_device(&acpi_device->dev);
 	ej_event->device = acpi_device;
 	if (acpi_device->flags.eject_pending) {
 		/* event originated from ACPI eject notification */
@@ -224,7 +244,11 @@ acpi_eject_store(struct device *d, struc
 			ej_event->event, ACPI_OST_SC_EJECT_IN_PROGRESS, NULL);
 	}
 
-	acpi_os_hotplug_execute(acpi_bus_hot_remove_device, (void *)ej_event);
+	status = acpi_os_hotplug_execute(acpi_bus_hot_remove_device, ej_event);
+	if (ACPI_FAILURE(status)) {
+		put_device(&acpi_device->dev);
+		kfree(ej_event);
+	}
 err:
 	return ret;
 }
@@ -779,6 +803,7 @@ static void acpi_device_unregister(struc
 	 * no more references.
 	 */
 	acpi_device_set_power(device, ACPI_STATE_D3_COLD);
+	device->handle = NULL;
 	put_device(&device->dev);
 }
 
@@ -1626,14 +1651,14 @@ static acpi_status acpi_bus_device_attac
  * there has been a real error.  There just have been no suitable ACPI objects
  * in the table trunk from which the kernel could create a device and add an
  * appropriate driver.
+ *
+ * Must be called under acpi_scan_lock.
  */
 int acpi_bus_scan(acpi_handle handle)
 {
 	void *device = NULL;
 	int error = 0;
 
-	mutex_lock(&acpi_scan_lock);
-
 	if (ACPI_SUCCESS(acpi_bus_check_add(handle, 0, NULL, &device)))
 		acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,
 				    acpi_bus_check_add, NULL, NULL, &device);
@@ -1644,7 +1669,6 @@ int acpi_bus_scan(acpi_handle handle)
 		acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,
 				    acpi_bus_device_attach, NULL, NULL, NULL);
 
-	mutex_unlock(&acpi_scan_lock);
 	return error;
 }
 EXPORT_SYMBOL(acpi_bus_scan);
@@ -1681,7 +1705,13 @@ static acpi_status acpi_bus_remove(acpi_
 	return AE_OK;
 }
 
-static void __acpi_bus_trim(struct acpi_device *start)
+/**
+ * acpi_bus_trim - Remove ACPI device node and all of its descendants
+ * @start: Root of the ACPI device nodes subtree to remove.
+ *
+ * Must be called under acpi_scan_lock.
+ */
+void acpi_bus_trim(struct acpi_device *start)
 {
 	/*
 	 * Execute acpi_bus_device_detach() as a post-order callback to detach
@@ -1698,13 +1728,6 @@ static void __acpi_bus_trim(struct acpi_
 			    acpi_bus_remove, NULL, NULL);
 	acpi_bus_remove(start->handle, 0, NULL, NULL);
 }
-
-void acpi_bus_trim(struct acpi_device *start)
-{
-	mutex_lock(&acpi_scan_lock);
-	__acpi_bus_trim(start);
-	mutex_unlock(&acpi_scan_lock);
-}
 EXPORT_SYMBOL_GPL(acpi_bus_trim);
 
 static int acpi_bus_scan_fixed(void)
@@ -1762,23 +1785,27 @@ int __init acpi_scan_init(void)
 	acpi_csrt_init();
 	acpi_container_init();
 
+	mutex_lock(&acpi_scan_lock);
 	/*
 	 * Enumerate devices in the ACPI namespace.
 	 */
 	result = acpi_bus_scan(ACPI_ROOT_OBJECT);
 	if (result)
-		return result;
+		goto out;
 
 	result = acpi_bus_get_device(ACPI_ROOT_OBJECT, &acpi_root);
 	if (result)
-		return result;
+		goto out;
 
 	result = acpi_bus_scan_fixed();
 	if (result) {
 		acpi_device_unregister(acpi_root);
-		return result;
+		goto out;
 	}
 
 	acpi_update_all_gpes();
-	return 0;
+
+ out:
+	mutex_unlock(&acpi_scan_lock);
+	return result;
 }
Index: test/include/acpi/acpi_bus.h
===================================================================
--- test.orig/include/acpi/acpi_bus.h
+++ test/include/acpi/acpi_bus.h
@@ -395,6 +395,9 @@ int acpi_bus_receive_event(struct acpi_b
 static inline int acpi_bus_generate_proc_event(struct acpi_device *device, u8 type, int data)
 	{ return 0; }
 #endif
+
+void acpi_scan_lock_acquire(void);
+void acpi_scan_lock_release(void);
 int acpi_scan_add_handler(struct acpi_scan_handler *handler);
 int acpi_bus_register_driver(struct acpi_driver *driver);
 void acpi_bus_unregister_driver(struct acpi_driver *driver);
Index: test/drivers/acpi/acpi_memhotplug.c
===================================================================
--- test.orig/drivers/acpi/acpi_memhotplug.c
+++ test/drivers/acpi/acpi_memhotplug.c
@@ -153,14 +153,16 @@ acpi_memory_get_device_resources(struct
 	return 0;
 }
 
-static int
-acpi_memory_get_device(acpi_handle handle,
-		       struct acpi_memory_device **mem_device)
+static int acpi_memory_get_device(acpi_handle handle,
+				  struct acpi_memory_device **mem_device)
 {
 	struct acpi_device *device = NULL;
-	int result;
+	int result = 0;
+
+	acpi_scan_lock_acquire();
 
-	if (!acpi_bus_get_device(handle, &device) && device)
+	acpi_bus_get_device(handle, &device);
+	if (device)
 		goto end;
 
 	/*
@@ -169,23 +171,28 @@ acpi_memory_get_device(acpi_handle handl
 	 */
 	result = acpi_bus_scan(handle);
 	if (result) {
-		acpi_handle_warn(handle, "Cannot add acpi bus\n");
-		return -EINVAL;
+		acpi_handle_warn(handle, "ACPI namespace scan failed\n");
+		result = -EINVAL;
+		goto out;
 	}
 	result = acpi_bus_get_device(handle, &device);
 	if (result) {
 		acpi_handle_warn(handle, "Missing device object\n");
-		return -EINVAL;
+		result = -EINVAL;
+		goto out;
 	}
 
-      end:
+ end:
 	*mem_device = acpi_driver_data(device);
 	if (!(*mem_device)) {
 		dev_err(&device->dev, "driver data not found\n");
-		return -ENODEV;
+		result = -ENODEV;
+		goto out;
 	}
 
-	return 0;
+ out:
+	acpi_scan_lock_release();
+	return result;
 }
 
 static int acpi_memory_check_device(struct acpi_memory_device *mem_device)
@@ -305,6 +312,7 @@ static void acpi_memory_device_notify(ac
 	struct acpi_device *device;
 	struct acpi_eject_event *ej_event = NULL;
 	u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; /* default */
+	acpi_status status;
 
 	switch (event) {
 	case ACPI_NOTIFY_BUS_CHECK:
@@ -327,29 +335,40 @@ static void acpi_memory_device_notify(ac
 		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 				  "\nReceived EJECT REQUEST notification for device\n"));
 
+		status = AE_ERROR;
+		acpi_scan_lock_acquire();
+
 		if (acpi_bus_get_device(handle, &device)) {
 			acpi_handle_err(handle, "Device doesn't exist\n");
-			break;
+			goto unlock;
 		}
 		mem_device = acpi_driver_data(device);
 		if (!mem_device) {
 			acpi_handle_err(handle, "Driver Data is NULL\n");
-			break;
+			goto unlock;
 		}
 
 		ej_event = kmalloc(sizeof(*ej_event), GFP_KERNEL);
 		if (!ej_event) {
 			pr_err(PREFIX "No memory, dropping EJECT\n");
-			break;
+			goto unlock;
 		}
 
+		get_device(&device->dev);
 		ej_event->device = device;
 		ej_event->event = ACPI_NOTIFY_EJECT_REQUEST;
-		acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
-					(void *)ej_event);
+		/* The eject is carried out asynchronously. */
+		status = acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
+						 ej_event);
+		if (ACPI_FAILURE(status)) {
+			put_device(&device->dev);
+			kfree(ej_event);
+		}
 
-		/* eject is performed asynchronously */
-		return;
+ unlock:
+		acpi_scan_lock_release();
+		if (ACPI_SUCCESS(status))
+			return;
 	default:
 		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 				  "Unsupported event [0x%x]\n", event));
@@ -360,7 +379,6 @@ static void acpi_memory_device_notify(ac
 
 	/* Inform firmware that the hotplug operation has completed */
 	(void) acpi_evaluate_hotplug_ost(handle, event, ost_code, NULL);
-	return;
 }
 
 static void acpi_memory_device_free(struct acpi_memory_device *mem_device)
Index: test/drivers/acpi/processor_driver.c
===================================================================
--- test.orig/drivers/acpi/processor_driver.c
+++ test/drivers/acpi/processor_driver.c
@@ -683,8 +683,11 @@ static void acpi_processor_hotplug_notif
 	struct acpi_device *device = NULL;
 	struct acpi_eject_event *ej_event = NULL;
 	u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; /* default */
+	acpi_status status;
 	int result;
 
+	acpi_scan_lock_acquire();
+
 	switch (event) {
 	case ACPI_NOTIFY_BUS_CHECK:
 	case ACPI_NOTIFY_DEVICE_CHECK:
@@ -733,25 +736,32 @@ static void acpi_processor_hotplug_notif
 			break;
 		}
 
+		get_device(&device->dev);
 		ej_event->device = device;
 		ej_event->event = ACPI_NOTIFY_EJECT_REQUEST;
-		acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
-					(void *)ej_event);
-
-		/* eject is performed asynchronously */
-		return;
+		/* The eject is carried out asynchronously. */
+		status = acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
+						 ej_event);
+		if (ACPI_FAILURE(status)) {
+			put_device(&device->dev);
+			kfree(ej_event);
+			break;
+		}
+		goto out;
 
 	default:
 		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 				  "Unsupported event [0x%x]\n", event));
 
 		/* non-hotplug event; possibly handled by other handler */
-		return;
+		goto out;
 	}
 
 	/* Inform firmware that the hotplug operation has completed */
 	(void) acpi_evaluate_hotplug_ost(handle, event, ost_code, NULL);
-	return;
+
+ out:
+	acpi_scan_lock_release();;
 }
 
 static acpi_status is_processor_device(acpi_handle handle)
Index: test/drivers/acpi/container.c
===================================================================
--- test.orig/drivers/acpi/container.c
+++ test/drivers/acpi/container.c
@@ -88,6 +88,8 @@ static void container_notify_cb(acpi_han
 	acpi_status status;
 	u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; /* default */
 
+	acpi_scan_lock_acquire();
+
 	switch (type) {
 	case ACPI_NOTIFY_BUS_CHECK:
 		/* Fall through */
@@ -130,18 +132,20 @@ static void container_notify_cb(acpi_han
 		if (!acpi_bus_get_device(handle, &device) && device) {
 			device->flags.eject_pending = 1;
 			kobject_uevent(&device->dev.kobj, KOBJ_OFFLINE);
-			return;
+			goto out;
 		}
 		break;
 
 	default:
 		/* non-hotplug event; possibly handled by other handler */
-		return;
+		goto out;
 	}
 
 	/* Inform firmware that the hotplug operation has completed */
 	(void) acpi_evaluate_hotplug_ost(handle, type, ost_code, NULL);
-	return;
+
+ out:
+	acpi_scan_lock_release();
 }
 
 static bool is_container(acpi_handle handle)
Index: test/drivers/acpi/dock.c
===================================================================
--- test.orig/drivers/acpi/dock.c
+++ test/drivers/acpi/dock.c
@@ -744,7 +744,9 @@ static void acpi_dock_deferred_cb(void *
 {
 	struct dock_data *data = context;
 
+	acpi_scan_lock_acquire();
 	dock_notify(data->handle, data->event, data->ds);
+	acpi_scan_lock_release();
 	kfree(data);
 }
 
@@ -757,20 +759,31 @@ static int acpi_dock_notifier_call(struc
 	if (event != ACPI_NOTIFY_BUS_CHECK && event != ACPI_NOTIFY_DEVICE_CHECK
 	   && event != ACPI_NOTIFY_EJECT_REQUEST)
 		return 0;
+
+	acpi_scan_lock_acquire();
+
 	list_for_each_entry(dock_station, &dock_stations, sibling) {
 		if (dock_station->handle == handle) {
 			struct dock_data *dd;
+			acpi_status status;
 
 			dd = kmalloc(sizeof(*dd), GFP_KERNEL);
 			if (!dd)
-				return 0;
+				break;
+
 			dd->handle = handle;
 			dd->event = event;
 			dd->ds = dock_station;
-			acpi_os_hotplug_execute(acpi_dock_deferred_cb, dd);
-			return 0 ;
+			status = acpi_os_hotplug_execute(acpi_dock_deferred_cb,
+							 dd);
+			if (ACPI_FAILURE(status))
+				kfree(dd);
+
+			break;
 		}
 	}
+
+	acpi_scan_lock_release();
 	return 0;
 }
 
Index: test/drivers/pci/hotplug/acpiphp_glue.c
===================================================================
--- test.orig/drivers/pci/hotplug/acpiphp_glue.c
+++ test/drivers/pci/hotplug/acpiphp_glue.c
@@ -1218,6 +1218,8 @@ static void _handle_hotplug_event_bridge
 	handle = hp_work->handle;
 	type = hp_work->type;
 
+	acpi_scan_lock_acquire();
+
 	if (acpi_bus_get_device(handle, &device)) {
 		/* This bridge must have just been physically inserted */
 		handle_bridge_insertion(handle, type);
@@ -1295,6 +1297,7 @@ static void _handle_hotplug_event_bridge
 	}
 
 out:
+	acpi_scan_lock_release();
 	kfree(hp_work); /* allocated in handle_hotplug_event_bridge */
 }
 
@@ -1341,6 +1344,8 @@ static void _handle_hotplug_event_func(s
 
 	func = (struct acpiphp_func *)context;
 
+	acpi_scan_lock_acquire();
+
 	switch (type) {
 	case ACPI_NOTIFY_BUS_CHECK:
 		/* bus re-enumerate */
@@ -1371,6 +1376,7 @@ static void _handle_hotplug_event_func(s
 		break;
 	}
 
+	acpi_scan_lock_release();
 	kfree(hp_work); /* allocated in handle_hotplug_event_func */
 }
 
Index: test/drivers/pci/hotplug/sgi_hotplug.c
===================================================================
--- test.orig/drivers/pci/hotplug/sgi_hotplug.c
+++ test/drivers/pci/hotplug/sgi_hotplug.c
@@ -425,6 +425,7 @@ static int enable_slot(struct hotplug_sl
 			pdevice = NULL;
 		}
 
+		acpi_scan_lock_acquire();
 		/*
 		 * Walk the rootbus node's immediate children looking for
 		 * the slot's device node(s). There can be more than
@@ -458,6 +459,7 @@ static int enable_slot(struct hotplug_sl
 				}
 			}
 		}
+		acpi_scan_lock_release();
 	}
 
 	/* Call the driver for the new device */
@@ -508,6 +510,7 @@ static int disable_slot(struct hotplug_s
 		/* Get the rootbus node pointer */
 		phandle = PCI_CONTROLLER(slot->pci_bus)->acpi_handle;
 
+		acpi_scan_lock_acquire();
 		/*
 		 * Walk the rootbus node's immediate children looking for
 		 * the slot's device node(s). There can be more than
@@ -538,7 +541,7 @@ static int disable_slot(struct hotplug_s
 					acpi_bus_trim(device);
 			}
 		}
-
+		acpi_scan_lock_release();
 	}
 
 	/* Free the SN resources assigned to the Linux device.*/