1 files changed, 393 insertions, 345 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index f0a5e2b0eb8a..5c75e3147a60 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -17,24 +17,17 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
-#include <asm/cputime.h>
-#include <linux/kernel.h>
-#include <linux/kernel_stat.h>
-#include <linux/module.h>
-#include <linux/init.h>
-#include <linux/notifier.h>
+#include <linux/cpu.h>
 #include <linux/cpufreq.h>
 #include <linux/delay.h>
-#include <linux/interrupt.h>
-#include <linux/spinlock.h>
-#include <linux/tick.h>
 #include <linux/device.h>
-#include <linux/slab.h>
-#include <linux/cpu.h>
-#include <linux/completion.h>
+#include <linux/init.h>
+#include <linux/kernel_stat.h>
+#include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/slab.h>
 #include <linux/syscore_ops.h>
-
+#include <linux/tick.h>
 #include <trace/events/power.h>
 
 /**
@@ -44,8 +37,10 @@
  */
 static struct cpufreq_driver *cpufreq_driver;
 static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data);
+static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data_fallback);
 static DEFINE_RWLOCK(cpufreq_driver_lock);
 static DEFINE_MUTEX(cpufreq_governor_lock);
+static LIST_HEAD(cpufreq_policy_list);
 
 #ifdef CONFIG_HOTPLUG_CPU
 /* This one keeps track of the previously set governor of a removed CPU */
@@ -69,15 +64,14 @@ static DEFINE_PER_CPU(char[CPUFREQ_NAME_LEN], cpufreq_cpu_governor);
  * - Lock should not be held across
  *     __cpufreq_governor(data, CPUFREQ_GOV_STOP);
  */
-static DEFINE_PER_CPU(int, cpufreq_policy_cpu);
 static DEFINE_PER_CPU(struct rw_semaphore, cpu_policy_rwsem);
 
 #define lock_policy_rwsem(mode, cpu)					\
 static int lock_policy_rwsem_##mode(int cpu)				\
 {									\
-	int policy_cpu = per_cpu(cpufreq_policy_cpu, cpu);		\
-	BUG_ON(policy_cpu == -1);					\
-	down_##mode(&per_cpu(cpu_policy_rwsem, policy_cpu));		\
+	struct cpufreq_policy *policy = per_cpu(cpufreq_cpu_data, cpu);	\
+	BUG_ON(!policy);						\
+	down_##mode(&per_cpu(cpu_policy_rwsem, policy->cpu));		\
 									\
 	return 0;							\
 }
@@ -88,14 +82,20 @@ lock_policy_rwsem(write, cpu);
 #define unlock_policy_rwsem(mode, cpu)					\
 static void unlock_policy_rwsem_##mode(int cpu)				\
 {									\
-	int policy_cpu = per_cpu(cpufreq_policy_cpu, cpu);		\
-	BUG_ON(policy_cpu == -1);					\
-	up_##mode(&per_cpu(cpu_policy_rwsem, policy_cpu));		\
+	struct cpufreq_policy *policy = per_cpu(cpufreq_cpu_data, cpu);	\
+	BUG_ON(!policy);						\
+	up_##mode(&per_cpu(cpu_policy_rwsem, policy->cpu));		\
 }
 
 unlock_policy_rwsem(read, cpu);
 unlock_policy_rwsem(write, cpu);
 
+/*
+ * rwsem to guarantee that cpufreq driver module doesn't unload during critical
+ * sections
+ */
+static DECLARE_RWSEM(cpufreq_rwsem);
+
 /* internal prototypes */
 static int __cpufreq_governor(struct cpufreq_policy *policy,
 		unsigned int event);
@@ -183,78 +183,46 @@ u64 get_cpu_idle_time(unsigned int cpu, u64 *wall, int io_busy)
 }
 EXPORT_SYMBOL_GPL(get_cpu_idle_time);
 
-static struct cpufreq_policy *__cpufreq_cpu_get(unsigned int cpu, bool sysfs)
+struct cpufreq_policy *cpufreq_cpu_get(unsigned int cpu)
 {
-	struct cpufreq_policy *data;
+	struct cpufreq_policy *policy = NULL;
 	unsigned long flags;
 
-	if (cpu >= nr_cpu_ids)
-		goto err_out;
+	if (cpufreq_disabled() || (cpu >= nr_cpu_ids))
+		return NULL;
+
+	if (!down_read_trylock(&cpufreq_rwsem))
+		return NULL;
 
 	/* get the cpufreq driver */
 	read_lock_irqsave(&cpufreq_driver_lock, flags);
 
-	if (!cpufreq_driver)
-		goto err_out_unlock;
-
-	if (!try_module_get(cpufreq_driver->owner))
-		goto err_out_unlock;
-
-	/* get the CPU */
-	data = per_cpu(cpufreq_cpu_data, cpu);
-
-	if (!data)
-		goto err_out_put_module;
-
-	if (!sysfs && !kobject_get(&data->kobj))
-		goto err_out_put_module;
+	if (cpufreq_driver) {
+		/* get the CPU */
+		policy = per_cpu(cpufreq_cpu_data, cpu);
+		if (policy)
+			kobject_get(&policy->kobj);
+	}
 
 	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
-	return data;
 
-err_out_put_module:
-	module_put(cpufreq_driver->owner);
-err_out_unlock:
-	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
-err_out:
-	return NULL;
-}
-
-struct cpufreq_policy *cpufreq_cpu_get(unsigned int cpu)
-{
-	if (cpufreq_disabled())
-		return NULL;
+	if (!policy)
+		up_read(&cpufreq_rwsem);
 
-	return __cpufreq_cpu_get(cpu, false);
+	return policy;
 }
 EXPORT_SYMBOL_GPL(cpufreq_cpu_get);
 
-static struct cpufreq_policy *cpufreq_cpu_get_sysfs(unsigned int cpu)
-{
-	return __cpufreq_cpu_get(cpu, true);
-}
-
-static void __cpufreq_cpu_put(struct cpufreq_policy *data, bool sysfs)
-{
-	if (!sysfs)
-		kobject_put(&data->kobj);
-	module_put(cpufreq_driver->owner);
-}
-
-void cpufreq_cpu_put(struct cpufreq_policy *data)
+void cpufreq_cpu_put(struct cpufreq_policy *policy)
 {
 	if (cpufreq_disabled())
 		return;
 
-	__cpufreq_cpu_put(data, false);
+	kobject_put(&policy->kobj);
+	up_read(&cpufreq_rwsem);
 }
 EXPORT_SYMBOL_GPL(cpufreq_cpu_put);
 
-static void cpufreq_cpu_put_sysfs(struct cpufreq_policy *data)
-{
-	__cpufreq_cpu_put(data, true);
-}
-
 /*********************************************************************
  *            EXTERNALLY AFFECTING FREQUENCY CHANGES                 *
  *********************************************************************/
@@ -459,8 +427,8 @@ show_one(scaling_min_freq, min);
 show_one(scaling_max_freq, max);
 show_one(scaling_cur_freq, cur);
 
-static int __cpufreq_set_policy(struct cpufreq_policy *data,
-				struct cpufreq_policy *policy);
+static int __cpufreq_set_policy(struct cpufreq_policy *policy,
+				struct cpufreq_policy *new_policy);
 
 /**
  * cpufreq_per_cpu_attr_write() / store_##file_name() - sysfs write access
@@ -699,12 +667,12 @@ static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
 	struct cpufreq_policy *policy = to_policy(kobj);
 	struct freq_attr *fattr = to_attr(attr);
 	ssize_t ret = -EINVAL;
-	policy = cpufreq_cpu_get_sysfs(policy->cpu);
-	if (!policy)
-		goto no_policy;
+
+	if (!down_read_trylock(&cpufreq_rwsem))
+		goto exit;
 
 	if (lock_policy_rwsem_read(policy->cpu) < 0)
-		goto fail;
+		goto up_read;
 
 	if (fattr->show)
 		ret = fattr->show(policy, buf);
@@ -712,9 +680,10 @@ static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
 		ret = -EIO;
 
 	unlock_policy_rwsem_read(policy->cpu);
-fail:
-	cpufreq_cpu_put_sysfs(policy);
-no_policy:
+
+up_read:
+	up_read(&cpufreq_rwsem);
+exit:
 	return ret;
 }
 
@@ -724,12 +693,12 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr,
 	struct cpufreq_policy *policy = to_policy(kobj);
 	struct freq_attr *fattr = to_attr(attr);
 	ssize_t ret = -EINVAL;
-	policy = cpufreq_cpu_get_sysfs(policy->cpu);
-	if (!policy)
-		goto no_policy;
+
+	if (!down_read_trylock(&cpufreq_rwsem))
+		goto exit;
 
 	if (lock_policy_rwsem_write(policy->cpu) < 0)
-		goto fail;
+		goto up_read;
 
 	if (fattr->store)
 		ret = fattr->store(policy, buf, count);
@@ -737,9 +706,10 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr,
 		ret = -EIO;
 
 	unlock_policy_rwsem_write(policy->cpu);
-fail:
-	cpufreq_cpu_put_sysfs(policy);
-no_policy:
+
+up_read:
+	up_read(&cpufreq_rwsem);
+exit:
 	return ret;
 }
 
@@ -805,41 +775,32 @@ void cpufreq_sysfs_remove_file(const struct attribute *attr)
 EXPORT_SYMBOL(cpufreq_sysfs_remove_file);
 
 /* symlink affected CPUs */
-static int cpufreq_add_dev_symlink(unsigned int cpu,
-				   struct cpufreq_policy *policy)
+static int cpufreq_add_dev_symlink(struct cpufreq_policy *policy)
 {
 	unsigned int j;
 	int ret = 0;
 
 	for_each_cpu(j, policy->cpus) {
-		struct cpufreq_policy *managed_policy;
 		struct device *cpu_dev;
 
-		if (j == cpu)
+		if (j == policy->cpu)
 			continue;
 
-		pr_debug("CPU %u already managed, adding link\n", j);
-		managed_policy = cpufreq_cpu_get(cpu);
+		pr_debug("Adding link for CPU: %u\n", j);
 		cpu_dev = get_cpu_device(j);
 		ret = sysfs_create_link(&cpu_dev->kobj, &policy->kobj,
 					"cpufreq");
-		if (ret) {
-			cpufreq_cpu_put(managed_policy);
-			return ret;
-		}
+		if (ret)
+			break;
 	}
 	return ret;
 }
 
-static int cpufreq_add_dev_interface(unsigned int cpu,
-				     struct cpufreq_policy *policy,
+static int cpufreq_add_dev_interface(struct cpufreq_policy *policy,
 				     struct device *dev)
 {
-	struct cpufreq_policy new_policy;
 	struct freq_attr **drv_attr;
-	unsigned long flags;
 	int ret = 0;
-	unsigned int j;
 
 	/* prepare interface data */
 	ret = kobject_init_and_add(&policy->kobj, &ktype_cpufreq,
@@ -871,18 +832,24 @@ static int cpufreq_add_dev_interface(unsigned int cpu,
 			goto err_out_kobj_put;
 	}
 
-	write_lock_irqsave(&cpufreq_driver_lock, flags);
-	for_each_cpu(j, policy->cpus) {
-		per_cpu(cpufreq_cpu_data, j) = policy;
-		per_cpu(cpufreq_policy_cpu, j) = policy->cpu;
-	}
-	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
-
-	ret = cpufreq_add_dev_symlink(cpu, policy);
+	ret = cpufreq_add_dev_symlink(policy);
 	if (ret)
 		goto err_out_kobj_put;
 
-	memcpy(&new_policy, policy, sizeof(struct cpufreq_policy));
+	return ret;
+
+err_out_kobj_put:
+	kobject_put(&policy->kobj);
+	wait_for_completion(&policy->kobj_unregister);
+	return ret;
+}
+
+static void cpufreq_init_policy(struct cpufreq_policy *policy)
+{
+	struct cpufreq_policy new_policy;
+	int ret = 0;
+
+	memcpy(&new_policy, policy, sizeof(*policy));
 	/* assure that the starting sequence is run in __cpufreq_set_policy */
 	policy->governor = NULL;
 
@@ -896,72 +863,106 @@ static int cpufreq_add_dev_interface(unsigned int cpu,
 		if (cpufreq_driver->exit)
 			cpufreq_driver->exit(policy);
 	}
-	return ret;
-
-err_out_kobj_put:
-	kobject_put(&policy->kobj);
-	wait_for_completion(&policy->kobj_unregister);
-	return ret;
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
-static int cpufreq_add_policy_cpu(unsigned int cpu, unsigned int sibling,
-				  struct device *dev)
+static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy,
+				  unsigned int cpu, struct device *dev,
+				  bool frozen)
 {
-	struct cpufreq_policy *policy;
 	int ret = 0, has_target = !!cpufreq_driver->target;
 	unsigned long flags;
 
-	policy = cpufreq_cpu_get(sibling);
-	WARN_ON(!policy);
-
-	if (has_target)
-		__cpufreq_governor(policy, CPUFREQ_GOV_STOP);
+	if (has_target) {
+		ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
+		if (ret) {
+			pr_err("%s: Failed to stop governor\n", __func__);
+			return ret;
+		}
+	}
 
-	lock_policy_rwsem_write(sibling);
+	lock_policy_rwsem_write(policy->cpu);
 
 	write_lock_irqsave(&cpufreq_driver_lock, flags);
 
 	cpumask_set_cpu(cpu, policy->cpus);
-	per_cpu(cpufreq_policy_cpu, cpu) = policy->cpu;
 	per_cpu(cpufreq_cpu_data, cpu) = policy;
 	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
-	unlock_policy_rwsem_write(sibling);
+	unlock_policy_rwsem_write(policy->cpu);
 
 	if (has_target) {
-		__cpufreq_governor(policy, CPUFREQ_GOV_START);
-		__cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
+		if ((ret = __cpufreq_governor(policy, CPUFREQ_GOV_START)) ||
+			(ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS))) {
+			pr_err("%s: Failed to start governor\n", __func__);
+			return ret;
+		}
 	}
 
-	ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");
-	if (ret) {
-		cpufreq_cpu_put(policy);
-		return ret;
-	}
+	/* Don't touch sysfs links during light-weight init */
+	if (!frozen)
+		ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");
 
-	return 0;
+	return ret;
 }
 #endif
 
-/**
- * cpufreq_add_dev - add a CPU device
- *
- * Adds the cpufreq interface for a CPU device.
- *
- * The Oracle says: try running cpufreq registration/unregistration concurrently
- * with with cpu hotplugging and all hell will break loose. Tried to clean this
- * mess up, but more thorough testing is needed. - Mathieu
- */
-static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
+static struct cpufreq_policy *cpufreq_policy_restore(unsigned int cpu)
+{
+	struct cpufreq_policy *policy;
+	unsigned long flags;
+
+	write_lock_irqsave(&cpufreq_driver_lock, flags);
+
+	policy = per_cpu(cpufreq_cpu_data_fallback, cpu);
+
+	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
+
+	return policy;
+}
+
+static struct cpufreq_policy *cpufreq_policy_alloc(void)
+{
+	struct cpufreq_policy *policy;
+
+	policy = kzalloc(sizeof(*policy), GFP_KERNEL);
+	if (!policy)
+		return NULL;
+
+	if (!alloc_cpumask_var(&policy->cpus, GFP_KERNEL))
+		goto err_free_policy;
+
+	if (!zalloc_cpumask_var(&policy->related_cpus, GFP_KERNEL))
+		goto err_free_cpumask;
+
+	INIT_LIST_HEAD(&policy->policy_list);
+	return policy;
+
+err_free_cpumask:
+	free_cpumask_var(policy->cpus);
+err_free_policy:
+	kfree(policy);
+
+	return NULL;
+}
+
+static void cpufreq_policy_free(struct cpufreq_policy *policy)
+{
+	free_cpumask_var(policy->related_cpus);
+	free_cpumask_var(policy->cpus);
+	kfree(policy);
+}
+
+static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif,
+			     bool frozen)
 {
 	unsigned int j, cpu = dev->id;
 	int ret = -ENOMEM;
 	struct cpufreq_policy *policy;
 	unsigned long flags;
 #ifdef CONFIG_HOTPLUG_CPU
+	struct cpufreq_policy *tpolicy;
 	struct cpufreq_governor *gov;
-	int sibling;
 #endif
 
 	if (cpu_is_offline(cpu))
@@ -977,43 +978,38 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
 		cpufreq_cpu_put(policy);
 		return 0;
 	}
+#endif
+
+	if (!down_read_trylock(&cpufreq_rwsem))
+		return 0;
 
 #ifdef CONFIG_HOTPLUG_CPU
 	/* Check if this cpu was hot-unplugged earlier and has siblings */
 	read_lock_irqsave(&cpufreq_driver_lock, flags);
-	for_each_online_cpu(sibling) {
-		struct cpufreq_policy *cp = per_cpu(cpufreq_cpu_data, sibling);
-		if (cp && cpumask_test_cpu(cpu, cp->related_cpus)) {
+	list_for_each_entry(tpolicy, &cpufreq_policy_list, policy_list) {
+		if (cpumask_test_cpu(cpu, tpolicy->related_cpus)) {
 			read_unlock_irqrestore(&cpufreq_driver_lock, flags);
-			return cpufreq_add_policy_cpu(cpu, sibling, dev);
+			ret = cpufreq_add_policy_cpu(tpolicy, cpu, dev, frozen);
+			up_read(&cpufreq_rwsem);
+			return ret;
 		}
 	}
 	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
 #endif
-#endif
 
-	if (!try_module_get(cpufreq_driver->owner)) {
-		ret = -EINVAL;
-		goto module_out;
-	}
+	if (frozen)
+		/* Restore the saved policy when doing light-weight init */
+		policy = cpufreq_policy_restore(cpu);
+	else
+		policy = cpufreq_policy_alloc();
 
-	policy = kzalloc(sizeof(struct cpufreq_policy), GFP_KERNEL);
 	if (!policy)
 		goto nomem_out;
 
-	if (!alloc_cpumask_var(&policy->cpus, GFP_KERNEL))
-		goto err_free_policy;
-
-	if (!zalloc_cpumask_var(&policy->related_cpus, GFP_KERNEL))
-		goto err_free_cpumask;
-
 	policy->cpu = cpu;
 	policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
 	cpumask_copy(policy->cpus, cpumask_of(cpu));
 
-	/* Initially set CPU itself as the policy_cpu */
-	per_cpu(cpufreq_policy_cpu, cpu) = cpu;
-
 	init_completion(&policy->kobj_unregister);
 	INIT_WORK(&policy->update, handle_update);
 
@@ -1050,12 +1046,26 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
 	}
 #endif
 
-	ret = cpufreq_add_dev_interface(cpu, policy, dev);
-	if (ret)
-		goto err_out_unregister;
+	write_lock_irqsave(&cpufreq_driver_lock, flags);
+	for_each_cpu(j, policy->cpus)
+		per_cpu(cpufreq_cpu_data, j) = policy;
+	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
+
+	if (!frozen) {
+		ret = cpufreq_add_dev_interface(policy, dev);
+		if (ret)
+			goto err_out_unregister;
+	}
+
+	write_lock_irqsave(&cpufreq_driver_lock, flags);
+	list_add(&policy->policy_list, &cpufreq_policy_list);
+	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
+
+	cpufreq_init_policy(policy);
 
 	kobject_uevent(&policy->kobj, KOBJ_ADD);
-	module_put(cpufreq_driver->owner);
+	up_read(&cpufreq_rwsem);
+
 	pr_debug("initialization complete\n");
 
 	return 0;
@@ -1066,32 +1076,33 @@ err_out_unregister:
 		per_cpu(cpufreq_cpu_data, j) = NULL;
 	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
-	kobject_put(&policy->kobj);
-	wait_for_completion(&policy->kobj_unregister);
-
 err_set_policy_cpu:
-	per_cpu(cpufreq_policy_cpu, cpu) = -1;
-	free_cpumask_var(policy->related_cpus);
-err_free_cpumask:
-	free_cpumask_var(policy->cpus);
-err_free_policy:
-	kfree(policy);
+	cpufreq_policy_free(policy);
 nomem_out:
-	module_put(cpufreq_driver->owner);
-module_out:
+	up_read(&cpufreq_rwsem);
+
 	return ret;
 }
 
-static void update_policy_cpu(struct cpufreq_policy *policy, unsigned int cpu)
+/**
+ * cpufreq_add_dev - add a CPU device
+ *
+ * Adds the cpufreq interface for a CPU device.
+ *
+ * The Oracle says: try running cpufreq registration/unregistration concurrently
+ * with with cpu hotplugging and all hell will break loose. Tried to clean this
+ * mess up, but more thorough testing is needed. - Mathieu
+ */
+static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
 {
-	int j;
+	return __cpufreq_add_dev(dev, sif, false);
+}
 
+static void update_policy_cpu(struct cpufreq_policy *policy, unsigned int cpu)
+{
 	policy->last_cpu = policy->cpu;
 	policy->cpu = cpu;
 
-	for_each_cpu(j, policy->cpus)
-		per_cpu(cpufreq_policy_cpu, j) = cpu;
-
 #ifdef CONFIG_CPU_FREQ_TABLE
 	cpufreq_frequency_table_update_policy_cpu(policy);
 #endif
@@ -1099,6 +1110,37 @@ static void update_policy_cpu(struct cpufreq_policy *policy, unsigned int cpu)
 			CPUFREQ_UPDATE_POLICY_CPU, policy);
 }
 
+static int cpufreq_nominate_new_policy_cpu(struct cpufreq_policy *policy,
+					   unsigned int old_cpu, bool frozen)
+{
+	struct device *cpu_dev;
+	int ret;
+
+	/* first sibling now owns the new sysfs dir */
+	cpu_dev = get_cpu_device(cpumask_first(policy->cpus));
+
+	/* Don't touch sysfs files during light-weight tear-down */
+	if (frozen)
+		return cpu_dev->id;
+
+	sysfs_remove_link(&cpu_dev->kobj, "cpufreq");
+	ret = kobject_move(&policy->kobj, &cpu_dev->kobj);
+	if (ret) {
+		pr_err("%s: Failed to move kobj: %d", __func__, ret);
+
+		WARN_ON(lock_policy_rwsem_write(old_cpu));
+		cpumask_set_cpu(old_cpu, policy->cpus);
+		unlock_policy_rwsem_write(old_cpu);
+
+		ret = sysfs_create_link(&cpu_dev->kobj, &policy->kobj,
+					"cpufreq");
+
+		return -EINVAL;
+	}
+
+	return cpu_dev->id;
+}
+
 /**
  * __cpufreq_remove_dev - remove a CPU device
  *
@@ -1107,111 +1149,126 @@ static void update_policy_cpu(struct cpufreq_policy *policy, unsigned int cpu)
  * This routine frees the rwsem before returning.
  */
 static int __cpufreq_remove_dev(struct device *dev,
-		struct subsys_interface *sif)
+				struct subsys_interface *sif, bool frozen)
 {
-	unsigned int cpu = dev->id, ret, cpus;
+	unsigned int cpu = dev->id, cpus;
+	int new_cpu, ret;
 	unsigned long flags;
-	struct cpufreq_policy *data;
+	struct cpufreq_policy *policy;
 	struct kobject *kobj;
 	struct completion *cmp;
-	struct device *cpu_dev;
 
 	pr_debug("%s: unregistering CPU %u\n", __func__, cpu);
 
 	write_lock_irqsave(&cpufreq_driver_lock, flags);
 
-	data = per_cpu(cpufreq_cpu_data, cpu);
-	per_cpu(cpufreq_cpu_data, cpu) = NULL;
+	policy = per_cpu(cpufreq_cpu_data, cpu);
+
+	/* Save the policy somewhere when doing a light-weight tear-down */
+	if (frozen)
+		per_cpu(cpufreq_cpu_data_fallback, cpu) = policy;
 
 	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
-	if (!data) {
+	if (!policy) {
 		pr_debug("%s: No cpu_data found\n", __func__);
 		return -EINVAL;
 	}
 
-	if (cpufreq_driver->target)
-		__cpufreq_governor(data, CPUFREQ_GOV_STOP);
+	if (cpufreq_driver->target) {
+		ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
+		if (ret) {
+			pr_err("%s: Failed to stop governor\n", __func__);
+			return ret;
+		}
+	}
 
 #ifdef CONFIG_HOTPLUG_CPU
 	if (!cpufreq_driver->setpolicy)
 		strncpy(per_cpu(cpufreq_cpu_governor, cpu),
-			data->governor->name, CPUFREQ_NAME_LEN);
+			policy->governor->name, CPUFREQ_NAME_LEN);
 #endif
 
 	WARN_ON(lock_policy_rwsem_write(cpu));
-	cpus = cpumask_weight(data->cpus);
+	cpus = cpumask_weight(policy->cpus);
 
 	if (cpus > 1)
-		cpumask_clear_cpu(cpu, data->cpus);
+		cpumask_clear_cpu(cpu, policy->cpus);
 	unlock_policy_rwsem_write(cpu);
 
-	if (cpu != data->cpu) {
+	if (cpu != policy->cpu && !frozen) {
 		sysfs_remove_link(&dev->kobj, "cpufreq");
 	} else if (cpus > 1) {
-		/* first sibling now owns the new sysfs dir */
-		cpu_dev = get_cpu_device(cpumask_first(data->cpus));
-		sysfs_remove_link(&cpu_dev->kobj, "cpufreq");
-		ret = kobject_move(&data->kobj, &cpu_dev->kobj);
-		if (ret) {
-			pr_err("%s: Failed to move kobj: %d", __func__, ret);
 
+		new_cpu = cpufreq_nominate_new_policy_cpu(policy, cpu, frozen);
+		if (new_cpu >= 0) {
 			WARN_ON(lock_policy_rwsem_write(cpu));
-			cpumask_set_cpu(cpu, data->cpus);
-
-			write_lock_irqsave(&cpufreq_driver_lock, flags);
-			per_cpu(cpufreq_cpu_data, cpu) = data;
-			write_unlock_irqrestore(&cpufreq_driver_lock, flags);
-
+			update_policy_cpu(policy, new_cpu);
 			unlock_policy_rwsem_write(cpu);
 
-			ret = sysfs_create_link(&cpu_dev->kobj, &data->kobj,
-					"cpufreq");
-			return -EINVAL;
+			if (!frozen) {
+				pr_debug("%s: policy Kobject moved to cpu: %d "
+					 "from: %d\n",__func__, new_cpu, cpu);
+			}
 		}
-
-		WARN_ON(lock_policy_rwsem_write(cpu));
-		update_policy_cpu(data, cpu_dev->id);
-		unlock_policy_rwsem_write(cpu);
-		pr_debug("%s: policy Kobject moved to cpu: %d from: %d\n",
-				__func__, cpu_dev->id, cpu);
 	}
 
 	/* If cpu is last user of policy, free policy */
 	if (cpus == 1) {
-		if (cpufreq_driver->target)
-			__cpufreq_governor(data, CPUFREQ_GOV_POLICY_EXIT);
-
-		lock_policy_rwsem_read(cpu);
-		kobj = &data->kobj;
-		cmp = &data->kobj_unregister;
-		unlock_policy_rwsem_read(cpu);
-		kobject_put(kobj);
-
-		/* we need to make sure that the underlying kobj is actually
-		 * not referenced anymore by anybody before we proceed with
-		 * unloading.
-		 */
-		pr_debug("waiting for dropping of refcount\n");
-		wait_for_completion(cmp);
-		pr_debug("wait complete\n");
+		if (cpufreq_driver->target) {
+			ret = __cpufreq_governor(policy,
+					CPUFREQ_GOV_POLICY_EXIT);
+			if (ret) {
+				pr_err("%s: Failed to exit governor\n",
+						__func__);
+				return ret;
+			}
+		}
+
+		if (!frozen) {
+			lock_policy_rwsem_read(cpu);
+			kobj = &policy->kobj;
+			cmp = &policy->kobj_unregister;
+			unlock_policy_rwsem_read(cpu);
+			kobject_put(kobj);
+
+			/*
+			 * We need to make sure that the underlying kobj is
+			 * actually not referenced anymore by anybody before we
+			 * proceed with unloading.
+			 */
+			pr_debug("waiting for dropping of refcount\n");
+			wait_for_completion(cmp);
+			pr_debug("wait complete\n");
+		}
 
+		/*
+		 * Perform the ->exit() even during light-weight tear-down,
+		 * since this is a core component, and is essential for the
+		 * subsequent light-weight ->init() to succeed.
+		 */
 		if (cpufreq_driver->exit)
-			cpufreq_driver->exit(data);
+			cpufreq_driver->exit(policy);
 
-		free_cpumask_var(data->related_cpus);
-		free_cpumask_var(data->cpus);
-		kfree(data);
+		/* Remove policy from list of active policies */
+		write_lock_irqsave(&cpufreq_driver_lock, flags);
+		list_del(&policy->policy_list);
+		write_unlock_irqrestore(&cpufreq_driver_lock, flags);
+
+		if (!frozen)
+			cpufreq_policy_free(policy);
 	} else {
-		pr_debug("%s: removing link, cpu: %d\n", __func__, cpu);
-		cpufreq_cpu_put(data);
 		if (cpufreq_driver->target) {
-			__cpufreq_governor(data, CPUFREQ_GOV_START);
-			__cpufreq_governor(data, CPUFREQ_GOV_LIMITS);
+			if ((ret = __cpufreq_governor(policy, CPUFREQ_GOV_START)) ||
+					(ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS))) {
+				pr_err("%s: Failed to start governor\n",
+						__func__);
+				return ret;
+			}
 		}
 	}
 
-	per_cpu(cpufreq_policy_cpu, cpu) = -1;
+	per_cpu(cpufreq_cpu_data, cpu) = NULL;
 	return 0;
 }
 
@@ -1223,7 +1280,7 @@ static int cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif)
 	if (cpu_is_offline(cpu))
 		return 0;
 
-	retval = __cpufreq_remove_dev(dev, sif);
+	retval = __cpufreq_remove_dev(dev, sif, false);
 	return retval;
 }
 
@@ -1344,10 +1401,9 @@ static unsigned int __cpufreq_get(unsigned int cpu)
 unsigned int cpufreq_get(unsigned int cpu)
 {
 	unsigned int ret_freq = 0;
-	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
 
-	if (!policy)
-		goto out;
+	if (!down_read_trylock(&cpufreq_rwsem))
+		return 0;
 
 	if (unlikely(lock_policy_rwsem_read(cpu)))
 		goto out_policy;
@@ -1357,8 +1413,8 @@ unsigned int cpufreq_get(unsigned int cpu)
 	unlock_policy_rwsem_read(cpu);
 
 out_policy:
-	cpufreq_cpu_put(policy);
-out:
+	up_read(&cpufreq_rwsem);
+
 	return ret_freq;
 }
 EXPORT_SYMBOL(cpufreq_get);
@@ -1381,23 +1437,23 @@ static int cpufreq_bp_suspend(void)
 	int ret = 0;
 
 	int cpu = smp_processor_id();
-	struct cpufreq_policy *cpu_policy;
+	struct cpufreq_policy *policy;
 
 	pr_debug("suspending cpu %u\n", cpu);
 
 	/* If there's no policy for the boot CPU, we have nothing to do. */
-	cpu_policy = cpufreq_cpu_get(cpu);
-	if (!cpu_policy)
+	policy = cpufreq_cpu_get(cpu);
+	if (!policy)
 		return 0;
 
 	if (cpufreq_driver->suspend) {
-		ret = cpufreq_driver->suspend(cpu_policy);
+		ret = cpufreq_driver->suspend(policy);
 		if (ret)
 			printk(KERN_ERR "cpufreq: suspend failed in ->suspend "
-					"step on CPU %u\n", cpu_policy->cpu);
+					"step on CPU %u\n", policy->cpu);
 	}
 
-	cpufreq_cpu_put(cpu_policy);
+	cpufreq_cpu_put(policy);
 	return ret;
 }
 
@@ -1419,28 +1475,28 @@ static void cpufreq_bp_resume(void)
 	int ret = 0;
 
 	int cpu = smp_processor_id();
-	struct cpufreq_policy *cpu_policy;
+	struct cpufreq_policy *policy;
 
 	pr_debug("resuming cpu %u\n", cpu);
 
 	/* If there's no policy for the boot CPU, we have nothing to do. */
-	cpu_policy = cpufreq_cpu_get(cpu);
-	if (!cpu_policy)
+	policy = cpufreq_cpu_get(cpu);
+	if (!policy)
 		return;
 
 	if (cpufreq_driver->resume) {
-		ret = cpufreq_driver->resume(cpu_policy);
+		ret = cpufreq_driver->resume(policy);
 		if (ret) {
 			printk(KERN_ERR "cpufreq: resume failed in ->resume "
-					"step on CPU %u\n", cpu_policy->cpu);
+					"step on CPU %u\n", policy->cpu);
 			goto fail;
 		}
 	}
 
-	schedule_work(&cpu_policy->update);
+	schedule_work(&policy->update);
 
 fail:
-	cpufreq_cpu_put(cpu_policy);
+	cpufreq_cpu_put(policy);
 }
 
 static struct syscore_ops cpufreq_syscore_ops = {
@@ -1594,18 +1650,6 @@ fail:
 }
 EXPORT_SYMBOL_GPL(cpufreq_driver_target);
 
-int __cpufreq_driver_getavg(struct cpufreq_policy *policy, unsigned int cpu)
-{
-	if (cpufreq_disabled())
-		return 0;
-
-	if (!cpufreq_driver->getavg)
-		return 0;
-
-	return cpufreq_driver->getavg(policy, cpu);
-}
-EXPORT_SYMBOL_GPL(__cpufreq_driver_getavg);
-
 /*
  * when "event" is CPUFREQ_GOV_LIMITS
  */
@@ -1640,8 +1684,9 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
 		}
 	}
 
-	if (!try_module_get(policy->governor->owner))
-		return -EINVAL;
+	if (event == CPUFREQ_GOV_POLICY_INIT)
+		if (!try_module_get(policy->governor->owner))
+			return -EINVAL;
 
 	pr_debug("__cpufreq_governor for CPU %u, event %u\n",
 						policy->cpu, event);
@@ -1677,11 +1722,8 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
 		mutex_unlock(&cpufreq_governor_lock);
 	}
 
-	/* we keep one module reference alive for
-			each CPU governed by this CPU */
-	if ((event != CPUFREQ_GOV_START) || ret)
-		module_put(policy->governor->owner);
-	if ((event == CPUFREQ_GOV_STOP) && !ret)
+	if (((event == CPUFREQ_GOV_POLICY_INIT) && ret) ||
+			((event == CPUFREQ_GOV_POLICY_EXIT) && !ret))
 		module_put(policy->governor->owner);
 
 	return ret;
@@ -1761,7 +1803,7 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu)
 	if (!cpu_policy)
 		return -EINVAL;
 
-	memcpy(policy, cpu_policy, sizeof(struct cpufreq_policy));
+	memcpy(policy, cpu_policy, sizeof(*policy));
 
 	cpufreq_cpu_put(cpu_policy);
 	return 0;
@@ -1772,95 +1814,94 @@ EXPORT_SYMBOL(cpufreq_get_policy);
  * data   : current policy.
  * policy : policy to be set.
  */
-static int __cpufreq_set_policy(struct cpufreq_policy *data,
-				struct cpufreq_policy *policy)
+static int __cpufreq_set_policy(struct cpufreq_policy *policy,
+				struct cpufreq_policy *new_policy)
 {
 	int ret = 0, failed = 1;
 
-	pr_debug("setting new policy for CPU %u: %u - %u kHz\n", policy->cpu,
-		policy->min, policy->max);
+	pr_debug("setting new policy for CPU %u: %u - %u kHz\n", new_policy->cpu,
+		new_policy->min, new_policy->max);
 
-	memcpy(&policy->cpuinfo, &data->cpuinfo,
-				sizeof(struct cpufreq_cpuinfo));
+	memcpy(&new_policy->cpuinfo, &policy->cpuinfo, sizeof(policy->cpuinfo));
 
-	if (policy->min > data->max || policy->max < data->min) {
+	if (new_policy->min > policy->max || new_policy->max < policy->min) {
 		ret = -EINVAL;
 		goto error_out;
 	}
 
 	/* verify the cpu speed can be set within this limit */
-	ret = cpufreq_driver->verify(policy);
+	ret = cpufreq_driver->verify(new_policy);
 	if (ret)
 		goto error_out;
 
 	/* adjust if necessary - all reasons */
 	blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
-			CPUFREQ_ADJUST, policy);
+			CPUFREQ_ADJUST, new_policy);
 
 	/* adjust if necessary - hardware incompatibility*/
 	blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
-			CPUFREQ_INCOMPATIBLE, policy);
+			CPUFREQ_INCOMPATIBLE, new_policy);
 
 	/*
 	 * verify the cpu speed can be set within this limit, which might be
 	 * different to the first one
 	 */
-	ret = cpufreq_driver->verify(policy);
+	ret = cpufreq_driver->verify(new_policy);
 	if (ret)
 		goto error_out;
 
 	/* notification of the new policy */
 	blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
-			CPUFREQ_NOTIFY, policy);
+			CPUFREQ_NOTIFY, new_policy);
 
-	data->min = policy->min;
-	data->max = policy->max;
+	policy->min = new_policy->min;
+	policy->max = new_policy->max;
 
 	pr_debug("new min and max freqs are %u - %u kHz\n",
-					data->min, data->max);
+					policy->min, policy->max);
 
 	if (cpufreq_driver->setpolicy) {
-		data->policy = policy->policy;
+		policy->policy = new_policy->policy;
 		pr_debug("setting range\n");
-		ret = cpufreq_driver->setpolicy(policy);
+		ret = cpufreq_driver->setpolicy(new_policy);
 	} else {
-		if (policy->governor != data->governor) {
+		if (new_policy->governor != policy->governor) {
 			/* save old, working values */
-			struct cpufreq_governor *old_gov = data->governor;
+			struct cpufreq_governor *old_gov = policy->governor;
 
 			pr_debug("governor switch\n");
 
 			/* end old governor */
-			if (data->governor) {
-				__cpufreq_governor(data, CPUFREQ_GOV_STOP);
-				unlock_policy_rwsem_write(policy->cpu);
-				__cpufreq_governor(data,
+			if (policy->governor) {
+				__cpufreq_governor(policy, CPUFREQ_GOV_STOP);
+				unlock_policy_rwsem_write(new_policy->cpu);
+				__cpufreq_governor(policy,
 						CPUFREQ_GOV_POLICY_EXIT);
-				lock_policy_rwsem_write(policy->cpu);
+				lock_policy_rwsem_write(new_policy->cpu);
 			}
 
 			/* start new governor */
-			data->governor = policy->governor;
-			if (!__cpufreq_governor(data, CPUFREQ_GOV_POLICY_INIT)) {
-				if (!__cpufreq_governor(data, CPUFREQ_GOV_START)) {
+			policy->governor = new_policy->governor;
+			if (!__cpufreq_governor(policy, CPUFREQ_GOV_POLICY_INIT)) {
+				if (!__cpufreq_governor(policy, CPUFREQ_GOV_START)) {
 					failed = 0;
 				} else {
-					unlock_policy_rwsem_write(policy->cpu);
-					__cpufreq_governor(data,
+					unlock_policy_rwsem_write(new_policy->cpu);
+					__cpufreq_governor(policy,
 							CPUFREQ_GOV_POLICY_EXIT);
-					lock_policy_rwsem_write(policy->cpu);
+					lock_policy_rwsem_write(new_policy->cpu);
 				}
 			}
 
 			if (failed) {
 				/* new governor failed, so re-start old one */
 				pr_debug("starting governor %s failed\n",
-							data->governor->name);
+							policy->governor->name);
 				if (old_gov) {
-					data->governor = old_gov;
-					__cpufreq_governor(data,
+					policy->governor = old_gov;
+					__cpufreq_governor(policy,
 							CPUFREQ_GOV_POLICY_INIT);
-					__cpufreq_governor(data,
+					__cpufreq_governor(policy,
 							   CPUFREQ_GOV_START);
 				}
 				ret = -EINVAL;
@@ -1869,7 +1910,7 @@ static int __cpufreq_set_policy(struct cpufreq_policy *data,
 			/* might be a policy change, too, so fall through */
 		}
 		pr_debug("governor: change or update limits\n");
-		__cpufreq_governor(data, CPUFREQ_GOV_LIMITS);
+		ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
 	}
 
 error_out:
@@ -1885,11 +1926,11 @@ error_out:
  */
 int cpufreq_update_policy(unsigned int cpu)
 {
-	struct cpufreq_policy *data = cpufreq_cpu_get(cpu);
-	struct cpufreq_policy policy;
+	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
+	struct cpufreq_policy new_policy;
 	int ret;
 
-	if (!data) {
+	if (!policy) {
 		ret = -ENODEV;
 		goto no_policy;
 	}
@@ -1900,34 +1941,34 @@ int cpufreq_update_policy(unsigned int cpu)
 	}
 
 	pr_debug("updating policy for CPU %u\n", cpu);
-	memcpy(&policy, data, sizeof(struct cpufreq_policy));
-	policy.min = data->user_policy.min;
-	policy.max = data->user_policy.max;
-	policy.policy = data->user_policy.policy;
-	policy.governor = data->user_policy.governor;
+	memcpy(&new_policy, policy, sizeof(*policy));
+	new_policy.min = policy->user_policy.min;
+	new_policy.max = policy->user_policy.max;
+	new_policy.policy = policy->user_policy.policy;
+	new_policy.governor = policy->user_policy.governor;
 
 	/*
 	 * BIOS might change freq behind our back
 	 * -> ask driver for current freq and notify governors about a change
 	 */
 	if (cpufreq_driver->get) {
-		policy.cur = cpufreq_driver->get(cpu);
-		if (!data->cur) {
+		new_policy.cur = cpufreq_driver->get(cpu);
+		if (!policy->cur) {
 			pr_debug("Driver did not initialize current freq");
-			data->cur = policy.cur;
+			policy->cur = new_policy.cur;
 		} else {
-			if (data->cur != policy.cur && cpufreq_driver->target)
-				cpufreq_out_of_sync(cpu, data->cur,
-								policy.cur);
+			if (policy->cur != new_policy.cur && cpufreq_driver->target)
+				cpufreq_out_of_sync(cpu, policy->cur,
+								new_policy.cur);
 		}
 	}
 
-	ret = __cpufreq_set_policy(data, &policy);
+	ret = __cpufreq_set_policy(policy, &new_policy);
 
 	unlock_policy_rwsem_write(cpu);
 
 fail:
-	cpufreq_cpu_put(data);
+	cpufreq_cpu_put(policy);
 no_policy:
 	return ret;
 }
@@ -1938,21 +1979,26 @@ static int cpufreq_cpu_callback(struct notifier_block *nfb,
 {
 	unsigned int cpu = (unsigned long)hcpu;
 	struct device *dev;
+	bool frozen = false;
 
 	dev = get_cpu_device(cpu);
 	if (dev) {
-		switch (action) {
+
+		if (action & CPU_TASKS_FROZEN)
+			frozen = true;
+
+		switch (action & ~CPU_TASKS_FROZEN) {
 		case CPU_ONLINE:
-		case CPU_ONLINE_FROZEN:
-			cpufreq_add_dev(dev, NULL);
+			__cpufreq_add_dev(dev, NULL, frozen);
+			cpufreq_update_policy(cpu);
 			break;
+
 		case CPU_DOWN_PREPARE:
-		case CPU_DOWN_PREPARE_FROZEN:
-			__cpufreq_remove_dev(dev, NULL);
+			__cpufreq_remove_dev(dev, NULL, frozen);
 			break;
+
 		case CPU_DOWN_FAILED:
-		case CPU_DOWN_FAILED_FROZEN:
-			cpufreq_add_dev(dev, NULL);
+			__cpufreq_add_dev(dev, NULL, frozen);
 			break;
 		}
 	}
@@ -2059,9 +2105,13 @@ int cpufreq_unregister_driver(struct cpufreq_driver *driver)
 	subsys_interface_unregister(&cpufreq_interface);
 	unregister_hotcpu_notifier(&cpufreq_cpu_notifier);
 
+	down_write(&cpufreq_rwsem);
 	write_lock_irqsave(&cpufreq_driver_lock, flags);
+
 	cpufreq_driver = NULL;
+
 	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
+	up_write(&cpufreq_rwsem);
 
 	return 0;
 }
@@ -2074,10 +2124,8 @@ static int __init cpufreq_core_init(void)
 	if (cpufreq_disabled())
 		return -ENODEV;
 
-	for_each_possible_cpu(cpu) {
-		per_cpu(cpufreq_policy_cpu, cpu) = -1;
+	for_each_possible_cpu(cpu)
 		init_rwsem(&per_cpu(cpu_policy_rwsem, cpu));
-	}
 
 	cpufreq_global_kobject = kobject_create();
 	BUG_ON(!cpufreq_global_kobject);