PM: Acquire device locks on suspend

This patch reorganizes the way suspend and resume notifications are
sent to drivers.  The major changes are that now the PM core acquires
every device semaphore before calling the methods, and calls to
device_add() during suspends will fail, while calls to device_del()
during suspends will block.

It also provides a way to safely remove a suspended device with the
help of the PM core, by using the device_pm_schedule_removal() callback
introduced specifically for this purpose, and updates two drivers (msr
and cpuid) that need to use it.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

arch/x86/kernel/cpuid.c

@@ -157,15 +157,15 @@ static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb,
 
 	switch (action) {
 	case CPU_UP_PREPARE:
-	case CPU_UP_PREPARE_FROZEN:
 		err = cpuid_device_create(cpu);
 		break;
 	case CPU_UP_CANCELED:
-	case CPU_UP_CANCELED_FROZEN:
 	case CPU_DEAD:
-	case CPU_DEAD_FROZEN:
 		cpuid_device_destroy(cpu);
 		break;
+	case CPU_UP_CANCELED_FROZEN:
+		destroy_suspended_device(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
+		break;
 	}
 	return err ? NOTIFY_BAD : NOTIFY_OK;
 }

arch/x86/kernel/msr.c

@@ -155,15 +155,15 @@ static int __cpuinit msr_class_cpu_callback(struct notifier_block *nfb,
 
 	switch (action) {
 	case CPU_UP_PREPARE:
-	case CPU_UP_PREPARE_FROZEN:
 		err = msr_device_create(cpu);
 		break;
 	case CPU_UP_CANCELED:
-	case CPU_UP_CANCELED_FROZEN:
 	case CPU_DEAD:
-	case CPU_DEAD_FROZEN:
 		msr_device_destroy(cpu);
 		break;
+	case CPU_UP_CANCELED_FROZEN:
+		destroy_suspended_device(msr_class, MKDEV(MSR_MAJOR, cpu));
+		break;
 	}
 	return err ? NOTIFY_BAD : NOTIFY_OK;
 }

drivers/base/core.c

@@ -726,11 +726,20 @@ int device_add(struct device *dev)
 {
 	struct device *parent = NULL;
 	struct class_interface *class_intf;
-	int error = -EINVAL;
+	int error;
+
+	error = pm_sleep_lock();
+	if (error) {
+		dev_warn(dev, "Suspicious %s during suspend\n", __FUNCTION__);
+		dump_stack();
+		return error;
+	}
 
 	dev = get_device(dev);
-	if (!dev || !strlen(dev->bus_id))
+	if (!dev || !strlen(dev->bus_id)) {
+		error = -EINVAL;
 		goto Error;
+	}
 
 	pr_debug("DEV: registering device: ID = '%s'\n", dev->bus_id);
 
@@ -795,6 +804,7 @@ int device_add(struct device *dev)
 	}
  Done:
 	put_device(dev);
+	pm_sleep_unlock();
 	return error;
  BusError:
 	device_pm_remove(dev);
@@ -905,6 +915,7 @@ void device_del(struct device * dev)
 	struct device * parent = dev->parent;
 	struct class_interface *class_intf;
 
+	device_pm_remove(dev);
 	if (parent)
 		klist_del(&dev->knode_parent);
 	if (MAJOR(dev->devt))
@@ -981,7 +992,6 @@ void device_del(struct device * dev)
 	if (dev->bus)
 		blocking_notifier_call_chain(&dev->bus->bus_notifier,
 					     BUS_NOTIFY_DEL_DEVICE, dev);
-	device_pm_remove(dev);
 	kobject_uevent(&dev->kobj, KOBJ_REMOVE);
 	kobject_del(&dev->kobj);
 	if (parent)
@@ -1156,14 +1166,11 @@ struct device *device_create(struct class *class, struct device *parent,
 EXPORT_SYMBOL_GPL(device_create);
 
 /**
- * device_destroy - removes a device that was created with device_create()
+ * find_device - finds a device that was created with device_create()
  * @class: pointer to the struct class that this device was registered with
  * @devt: the dev_t of the device that was previously registered
- *
- * This call unregisters and cleans up a device that was created with a
- * call to device_create().
  */
-void device_destroy(struct class *class, dev_t devt)
+static struct device *find_device(struct class *class, dev_t devt)
 {
 	struct device *dev = NULL;
 	struct device *dev_tmp;
@@ -1176,12 +1183,54 @@ void device_destroy(struct class *class, dev_t devt)
 		}
 	}
 	up(&class->sem);
+	return dev;
+}
 
+/**
+ * device_destroy - removes a device that was created with device_create()
+ * @class: pointer to the struct class that this device was registered with
+ * @devt: the dev_t of the device that was previously registered
+ *
+ * This call unregisters and cleans up a device that was created with a
+ * call to device_create().
+ */
+void device_destroy(struct class *class, dev_t devt)
+{
+	struct device *dev;
+
+	dev = find_device(class, devt);
 	if (dev)
 		device_unregister(dev);
 }
 EXPORT_SYMBOL_GPL(device_destroy);
 
+#ifdef CONFIG_PM_SLEEP
+/**
+ * destroy_suspended_device - asks the PM core to remove a suspended device
+ * @class: pointer to the struct class that this device was registered with
+ * @devt: the dev_t of the device that was previously registered
+ *
+ * This call notifies the PM core of the necessity to unregister a suspended
+ * device created with a call to device_create() (devices cannot be
+ * unregistered directly while suspended, since the PM core holds their
+ * semaphores at that time).
+ *
+ * It can only be called within the scope of a system sleep transition.  In
+ * practice this means it has to be directly or indirectly invoked either by
+ * a suspend or resume method, or by the PM core (e.g. via
+ * disable_nonboot_cpus() or enable_nonboot_cpus()).
+ */
+void destroy_suspended_device(struct class *class, dev_t devt)
+{
+	struct device *dev;
+
+	dev = find_device(class, devt);
+	if (dev)
+		device_pm_schedule_removal(dev);
+}
+EXPORT_SYMBOL_GPL(destroy_suspended_device);
+#endif /* CONFIG_PM_SLEEP */
+
 /**
  * device_rename - renames a device
  * @dev: the pointer to the struct device to be renamed