cpuidle acpi driver: fix oops on AC<->DC

cpuidle and acpi driver interaction bug with the way cpuidle_register_driver()
is called. Due to this bug, there will be oops on
AC<->DC on some systems, where they support C-states in one DC and not in AC.

The current code does
ON BOOT:
	Look at CST and other C-state info to see whether more than C1 is
	supported. If it is, then acpi processor_idle does a
	cpuidle_register_driver() call, which internally enables the device.

ON CST change notification (AC<->DC) and on suspend-resume:
	acpi driver temporarily disables device, updates the device with
	any new C-states, and reenables the device.

The problem is is on boot, there are no C2, C3 states supported and we skip
the register. Later on AC<->DC, we may get a CST notification and we try
to reevaluate CST and enabled the device, without actually registering it.
This causes breakage as we try to create /sys fs sub directory, without the
parent directory which is created at register time.

Thanks to Sanjeev for reporting the problem here.
http://bugzilla.kernel.org/show_bug.cgi?id=10394

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/processor_idle.c

@@ -1669,6 +1669,7 @@ static int acpi_processor_setup_cpuidle(struct acpi_processor *pr)
 		return -EINVAL;
 	}
 
+	dev->cpu = pr->id;
 	for (i = 0; i < CPUIDLE_STATE_MAX; i++) {
 		dev->states[i].name[0] = '\0';
 		dev->states[i].desc[0] = '\0';
@@ -1738,7 +1739,7 @@ static int acpi_processor_setup_cpuidle(struct acpi_processor *pr)
 
 int acpi_processor_cst_has_changed(struct acpi_processor *pr)
 {
-	int ret;
+	int ret = 0;
 
 	if (boot_option_idle_override)
 		return 0;
@@ -1756,8 +1757,10 @@ int acpi_processor_cst_has_changed(struct acpi_processor *pr)
 	cpuidle_pause_and_lock();
 	cpuidle_disable_device(&pr->power.dev);
 	acpi_processor_get_power_info(pr);
+	if (pr->flags.power) {
 		acpi_processor_setup_cpuidle(pr);
 		ret = cpuidle_enable_device(&pr->power.dev);
+	}
 	cpuidle_resume_and_unlock();
 
 	return ret;
@@ -1813,7 +1816,6 @@ int __cpuinit acpi_processor_power_init(struct acpi_processor *pr,
 	if (pr->flags.power) {
 #ifdef CONFIG_CPU_IDLE
 		acpi_processor_setup_cpuidle(pr);
-		pr->power.dev.cpu = pr->id;
 		if (cpuidle_register_device(&pr->power.dev))
 			return -EIO;
 #endif
@@ -1850,7 +1852,6 @@ int acpi_processor_power_exit(struct acpi_processor *pr,
 		return 0;
 
 #ifdef CONFIG_CPU_IDLE
-	if (pr->flags.power)
 	cpuidle_unregister_device(&pr->power.dev);
 #endif
 	pr->flags.power_setup_done = 0;

drivers/cpuidle/cpuidle.c

@@ -38,6 +38,8 @@ static void cpuidle_kick_cpus(void)
 static void cpuidle_kick_cpus(void) {}
 #endif
 
+static int __cpuidle_register_device(struct cpuidle_device *dev);
+
 /**
  * cpuidle_idle_call - the main idle loop
  *
@@ -138,6 +140,12 @@ int cpuidle_enable_device(struct cpuidle_device *dev)
 	if (!dev->state_count)
 		return -EINVAL;
 
+	if (dev->registered == 0) {
+		ret = __cpuidle_register_device(dev);
+		if (ret)
+			return ret;
+	}
+
 	if ((ret = cpuidle_add_state_sysfs(dev)))
 		return ret;
 
@@ -232,10 +240,13 @@ static void poll_idle_init(struct cpuidle_device *dev) {}
 #endif /* CONFIG_ARCH_HAS_CPU_RELAX */
 
 /**
- * cpuidle_register_device - registers a CPU's idle PM feature
+ * __cpuidle_register_device - internal register function called before register
+ * and enable routines
  * @dev: the cpu
+ *
+ * cpuidle_lock mutex must be held before this is called
  */
-int cpuidle_register_device(struct cpuidle_device *dev)
+static int __cpuidle_register_device(struct cpuidle_device *dev)
 {
 	int ret;
 	struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
@@ -247,18 +258,34 @@ int cpuidle_register_device(struct cpuidle_device *dev)
 
 	init_completion(&dev->kobj_unregister);
 
-	mutex_lock(&cpuidle_lock);
-
 	poll_idle_init(dev);
 
 	per_cpu(cpuidle_devices, dev->cpu) = dev;
 	list_add(&dev->device_list, &cpuidle_detected_devices);
 	if ((ret = cpuidle_add_sysfs(sys_dev))) {
-		mutex_unlock(&cpuidle_lock);
 		module_put(cpuidle_curr_driver->owner);
 		return ret;
 	}
 
+	dev->registered = 1;
+	return 0;
+}
+
+/**
+ * cpuidle_register_device - registers a CPU's idle PM feature
+ * @dev: the cpu
+ */
+int cpuidle_register_device(struct cpuidle_device *dev)
+{
+	int ret;
+
+	mutex_lock(&cpuidle_lock);
+
+	if ((ret = __cpuidle_register_device(dev))) {
+		mutex_unlock(&cpuidle_lock);
+		return ret;
+	}
+
 	cpuidle_enable_device(dev);
 	cpuidle_install_idle_handler();
 
@@ -278,6 +305,9 @@ void cpuidle_unregister_device(struct cpuidle_device *dev)
 {
 	struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
 
+	if (dev->registered == 0)
+		return;
+
 	cpuidle_pause_and_lock();
 
 	cpuidle_disable_device(dev);

include/linux/cpuidle.h

@@ -82,6 +82,7 @@ struct cpuidle_state_kobj {
 };
 
 struct cpuidle_device {
+	unsigned int		registered:1;
 	unsigned int		enabled:1;
 	unsigned int		cpu;