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>

1 files changed, 35 insertions, 5 deletions

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index fc555a90bb21..23554b676d6e 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/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);