Date:	Wed, 13 Feb 2013 12:08:02 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jiang Liu <liuj97@...il.com>, Yinghai Lu <yinghai@...nel.org>,
	Toshi Kani <toshi.kani@...com>,
	Myron Stowe <mstowe@...hat.com>, <linux-pci@...r.kernel.org>
Subject: Re: [PATCH] ACPI / hotplug: Fix concurrency issues and memory leaks

Hi Rafael,

The patch seems good.
There is a comment below.

2013/02/13 9:19, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> This changeset is aimed at fixing a few different but related
> problems in the ACPI hotplug infrastructure.
>
> First of all, since notify handlers may be run in parallel with
> acpi_bus_scan(), acpi_bus_trim() and acpi_bus_hot_remove_device()
> and some of them are installed for ACPI handles that have no struct
> acpi_device objects attached (i.e. before those objects are created),
> those notify handlers have to take acpi_scan_lock to prevent races
> from taking place (e.g. a struct acpi_device is found to be present
> for the given ACPI handle, but right after that it is removed by
> acpi_bus_trim() running in parallel to the given notify handler).
> Moreover, since some of them call acpi_bus_scan() and
> acpi_bus_trim(), this leads to the conclusion that acpi_scan_lock
> should be acquired by the callers of these two funtions rather by
> these functions themselves.
>
> For these reasons, make all notify handlers that can handle device
> addition and eject events take acpi_scan_lock and remove the
> acpi_scan_lock locking from acpi_bus_scan() and acpi_bus_trim().
> Accordingly, update all of their users to make sure that they
> are always called under acpi_scan_lock.
>
> Furthermore, since eject operations are carried out asynchronously
> with respect to the notify events that trigger them, with the help
> of acpi_bus_hot_remove_device(), even if notify handlers take the
> ACPI scan lock, it still is possible that, for example,
> acpi_bus_trim() will run between acpi_bus_hot_remove_device() and
> the notify handler that scheduled its execution and that
> acpi_bus_trim() will remove the device node passed to
> acpi_bus_hot_remove_device() for ejection.  In that case, the struct
> acpi_device object obtained by acpi_bus_hot_remove_device() will be
> invalid and not-so-funny things will ensue.  To protect agaist that,
> make the users of acpi_bus_hot_remove_device() run get_device() on
> ACPI device node objects that are about to be passed to it and make
> acpi_bus_hot_remove_device() run put_device() on them and check if
> their ACPI handles are not NULL (make acpi_device_unregister() clear
> the device nodes' ACPI handles for that check to work).
>
> Finally, observe that acpi_os_hotplug_execute() actually can fail,
> in which case its caller ought to free memory allocated for the
> context object to prevent leaks from happening.  It also needs to
> run put_device() on the device node that it ran get_device() on
> previously in that case.  Modify the code accordingly.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>
> On top of linux-pm.git/linux-next.
>
> Thanks,
> Rafael
>
> ---
>   drivers/acpi/acpi_memhotplug.c     |   56 +++++++++++++++++++-----------
>   drivers/acpi/container.c           |   10 +++--
>   drivers/acpi/dock.c                |   19 ++++++++--
>   drivers/acpi/processor_driver.c    |   24 +++++++++---
>   drivers/acpi/scan.c                |   69 +++++++++++++++++++++++++------------
>   drivers/pci/hotplug/acpiphp_glue.c |    6 +++
>   drivers/pci/hotplug/sgi_hotplug.c  |    5 ++
>   include/acpi/acpi_bus.h            |    3 +
>   8 files changed, 138 insertions(+), 54 deletions(-)
>
> 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();;

extra ";"

Thanks,
Yasuaki Ishimatsu

>   }
>
>   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.*/
>


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists