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Commit 683058e3 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
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ACPI / hotplug: Use device offline/online for graceful hot-removal 



Modify the generic ACPI hotplug code to be able to check if devices
scheduled for hot-removal may be gracefully removed from the system
using the device offline/online mechanism introduced previously.

Namely, make acpi_scan_hot_remove() handling device hot-removal call
device_offline() for all physical companions of the ACPI device nodes
involved in the operation and check the results.  If any of the
device_offline() calls fails, the function will not progress to the
removal phase (which cannot be aborted), unless its (new) force
argument is set (in case of a failing offline it will put the devices
offlined by it back online).

In support of 'forced' device hot-removal, add a new sysfs attribute
'force_remove' that will reside under /sys/firmware/acpi/hotplug/.

Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: default avatarToshi Kani <toshi.kani@hp.com>
parent 0902a904

Documentation/ABI/testing/sysfs-firmware-acpi

+10 −0
Original line number Diff line number Diff line
@@ -44,6 +44,16 @@ Description: 
		or 0 (unset).  Attempts to write any other values to it will

		cause -EINVAL to be returned.



What:		/sys/firmware/acpi/hotplug/force_remove

Date:		May 2013

Contact:	Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Description:

		The number in this file (0 or 1) determines whether (1) or not

		(0) the ACPI subsystem will allow devices to be hot-removed even

		if they cannot be put offline gracefully (from the kernel's

		viewpoint).  That number can be changed by writing a boolean

		value to this file.



What:		/sys/firmware/acpi/interrupts/

Date:		February 2008

Contact:	Len Brown <lenb@kernel.org>

drivers/acpi/internal.h

+2 −0
Original line number Diff line number Diff line
@@ -47,6 +47,8 @@ void acpi_memory_hotplug_init(void); 
static inline void acpi_memory_hotplug_init(void) {}

#endif



extern bool acpi_force_hot_remove;



void acpi_sysfs_add_hotplug_profile(struct acpi_hotplug_profile *hotplug,

				    const char *name);

int acpi_scan_add_handler_with_hotplug(struct acpi_scan_handler *handler,

drivers/acpi/scan.c

+84 −0
Original line number Diff line number Diff line
@@ -27,6 +27,12 @@ extern struct acpi_device *acpi_root; 


#define ACPI_IS_ROOT_DEVICE(device)    (!(device)->parent)



/*

 * If set, devices will be hot-removed even if they cannot be put offline

 * gracefully (from the kernel's standpoint).

 */

bool acpi_force_hot_remove;



static const char *dummy_hid = "device";



static LIST_HEAD(acpi_device_list);
@@ -120,6 +126,59 @@ acpi_device_modalias_show(struct device *dev, struct device_attribute *attr, cha 
}

static DEVICE_ATTR(modalias, 0444, acpi_device_modalias_show, NULL);



static acpi_status acpi_bus_offline_companions(acpi_handle handle, u32 lvl,

					       void *data, void **ret_p)

{

	struct acpi_device *device = NULL;

	struct acpi_device_physical_node *pn;

	acpi_status status = AE_OK;



	if (acpi_bus_get_device(handle, &device))

		return AE_OK;



	mutex_lock(&device->physical_node_lock);



	list_for_each_entry(pn, &device->physical_node_list, node) {

		int ret;



		ret = device_offline(pn->dev);

		if (acpi_force_hot_remove)

			continue;



		if (ret < 0) {

			status = AE_ERROR;

			break;

		}

		pn->put_online = !ret;

	}



	mutex_unlock(&device->physical_node_lock);



	return status;

}



static acpi_status acpi_bus_online_companions(acpi_handle handle, u32 lvl,

					      void *data, void **ret_p)

{

	struct acpi_device *device = NULL;

	struct acpi_device_physical_node *pn;



	if (acpi_bus_get_device(handle, &device))

		return AE_OK;



	mutex_lock(&device->physical_node_lock);



	list_for_each_entry(pn, &device->physical_node_list, node)

		if (pn->put_online) {

			device_online(pn->dev);

			pn->put_online = false;

		}



	mutex_unlock(&device->physical_node_lock);



	return AE_OK;

}



static int acpi_scan_hot_remove(struct acpi_device *device)

{

	acpi_handle handle = device->handle;
@@ -136,10 +195,33 @@ static int acpi_scan_hot_remove(struct acpi_device *device) 
		return -EINVAL;

	}



	lock_device_hotplug();



	status = acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,

				     NULL, acpi_bus_offline_companions, NULL,

				     NULL);

	if (ACPI_SUCCESS(status) || acpi_force_hot_remove)

		status = acpi_bus_offline_companions(handle, 0, NULL, NULL);



	if (ACPI_FAILURE(status) && !acpi_force_hot_remove) {

		acpi_bus_online_companions(handle, 0, NULL, NULL);

		acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,

				    acpi_bus_online_companions, NULL, NULL,

				    NULL);



		unlock_device_hotplug();



		put_device(&device->dev);

		return -EBUSY;

	}



	ACPI_DEBUG_PRINT((ACPI_DB_INFO,

		"Hot-removing device %s...\n", dev_name(&device->dev)));



	acpi_bus_trim(device);



	unlock_device_hotplug();



	/* Device node has been unregistered. */

	put_device(&device->dev);

	device = NULL;
@@ -236,6 +318,7 @@ static void acpi_scan_bus_device_check(acpi_handle handle, u32 ost_source) 
	int error;



	mutex_lock(&acpi_scan_lock);

	lock_device_hotplug();



	acpi_bus_get_device(handle, &device);

	if (device) {
@@ -259,6 +342,7 @@ static void acpi_scan_bus_device_check(acpi_handle handle, u32 ost_source) 
		kobject_uevent(&device->dev.kobj, KOBJ_ONLINE);



 out:

	unlock_device_hotplug();

	acpi_evaluate_hotplug_ost(handle, ost_source, ost_code, NULL);

	mutex_unlock(&acpi_scan_lock);

}

drivers/acpi/sysfs.c

+31 −0
Original line number Diff line number Diff line
@@ -780,6 +780,33 @@ void acpi_sysfs_add_hotplug_profile(struct acpi_hotplug_profile *hotplug, 
	pr_err(PREFIX "Unable to add hotplug profile '%s'\n", name);

}



static ssize_t force_remove_show(struct kobject *kobj,

				 struct kobj_attribute *attr, char *buf)

{

	return sprintf(buf, "%d\n", !!acpi_force_hot_remove);

}



static ssize_t force_remove_store(struct kobject *kobj,

				  struct kobj_attribute *attr,

				  const char *buf, size_t size)

{

	bool val;

	int ret;



	ret = strtobool(buf, &val);

	if (ret < 0)

		return ret;



	lock_device_hotplug();

	acpi_force_hot_remove = val;

	unlock_device_hotplug();

	return size;

}



static const struct kobj_attribute force_remove_attr =

	__ATTR(force_remove, S_IRUGO | S_IWUSR, force_remove_show,

	       force_remove_store);



int __init acpi_sysfs_init(void)

{

	int result;
@@ -789,6 +816,10 @@ int __init acpi_sysfs_init(void) 
		return result;



	hotplug_kobj = kobject_create_and_add("hotplug", acpi_kobj);

	result = sysfs_create_file(hotplug_kobj, &force_remove_attr.attr);

	if (result)

		return result;



	result = sysfs_create_file(acpi_kobj, &pm_profile_attr.attr);

	return result;

}

include/acpi/acpi_bus.h

+1 −0
Original line number Diff line number Diff line
@@ -286,6 +286,7 @@ struct acpi_device_physical_node { 
	u8 node_id;

	struct list_head node;

	struct device *dev;

	bool put_online:1;

};



/* set maximum of physical nodes to 32 for expansibility */