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: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Toshi Kani <toshi.kani@hp.com>

diff --git a/Documentation/ABI/testing/sysfs-firmware-acpi b/Documentation/ABI/testing/sysfs-firmware-acpi
index ce9bee98b43be62f84937502ed6fdfae38d43b3d..b4436cca97a83612fd3305630f5e0807eb53caeb 100644 (file)
--- a/Documentation/ABI/testing/sysfs-firmware-acpi
+++ b/Documentation/ABI/testing/sysfs-firmware-acpi
@@ -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>

diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index 6f1afd9118c806f728ce161033e932f3dcfc485f..4548f0a114ce268bb9eb882b1d334359aefa7fde 100644 (file)
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -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,

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index fe158fd4f1df401d74c04c612cca591f4a7d8eaf..4fd392005ef11c607e02debc91a248acd1ee6f4f 100644 (file)
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -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);
 }

diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
index fcae5fa2e1b322481ec2b331c4df0430bff66d53..5c5d1624fa2c261c8b6dca89a34156268a91d799 100644 (file)
--- a/drivers/acpi/sysfs.c
+++ b/drivers/acpi/sysfs.c
@@ -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;
 }

diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 98db31d9f9b410908b2056b192bf9813bc8ce4aa..4d5d3e7ba33d201652776c27f8d7bd5de468a4ad 100644 (file)
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -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 */