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Commit b8eed8af authored by Viresh Kumar's avatar Viresh Kumar Committed by Rafael J. Wysocki
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cpufreq: Simplify __cpufreq_remove_dev() 



__cpufreq_remove_dev() is called on multiple occasions: cpufreq_driver
unregister and cpu removals.

Current implementation of this routine is overly complex without much need. If
the cpu to be removed is the policy->cpu, we remove the policy first and add all
other cpus again from policy->cpus and then finally call __cpufreq_remove_dev()
again to remove the cpu to be deleted. Haahhhh..

There exist a simple solution to removal of a cpu:
- Simply use the old policy structure
- update its fields like: policy->cpu, etc.
- notify any users of cpufreq, which depend on changing policy->cpu

Hence this patch, which tries to implement the above theory. It is tested well
by myself on ARM big.LITTLE TC2 SoC, which has 5 cores (2 A15 and 3 A7). Both
A15's share same struct policy and all A7's share same policy structure.

Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Tested-by: default avatarShawn Guo <shawn.guo@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent f8517804

drivers/cpufreq/cpufreq.c

+70 −91
Original line number Diff line number Diff line
@@ -1036,6 +1036,25 @@ module_out: 
	return ret;

}



static void update_policy_cpu(struct cpufreq_policy *policy, unsigned int cpu)

{

	int j;



	policy->last_cpu = policy->cpu;

	policy->cpu = cpu;



	for_each_cpu(j, policy->cpus) {

		if (!cpu_online(j))

			continue;

		per_cpu(cpufreq_policy_cpu, j) = cpu;

	}



#ifdef CONFIG_CPU_FREQ_TABLE

	cpufreq_frequency_table_update_policy_cpu(policy);

#endif

	blocking_notifier_call_chain(&cpufreq_policy_notifier_list,

			CPUFREQ_UPDATE_POLICY_CPU, policy);

}



/**

 * __cpufreq_remove_dev - remove a CPU device
@@ -1046,95 +1065,67 @@ module_out: 
 */

static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif)

{

	unsigned int cpu = dev->id;

	unsigned int cpu = dev->id, ret, cpus;

	unsigned long flags;

	struct cpufreq_policy *data;

	struct kobject *kobj;

	struct completion *cmp;

#ifdef CONFIG_SMP

	struct device *cpu_dev;

	unsigned int j;

#endif



	pr_debug("unregistering CPU %u\n", cpu);

	pr_debug("%s: unregistering CPU %u\n", __func__, cpu);



	spin_lock_irqsave(&cpufreq_driver_lock, flags);

	data = per_cpu(cpufreq_cpu_data, cpu);



	if (!data) {

		pr_debug("%s: No cpu_data found\n", __func__);

		spin_unlock_irqrestore(&cpufreq_driver_lock, flags);

		unlock_policy_rwsem_write(cpu);

		return -EINVAL;

	}

	per_cpu(cpufreq_cpu_data, cpu) = NULL;



#ifdef CONFIG_SMP

	/* if this isn't the CPU which is the parent of the kobj, we

	 * only need to unlink, put and exit

	 */

	if (unlikely(cpu != data->cpu)) {

		pr_debug("removing link\n");

	if (cpufreq_driver->target)

		__cpufreq_governor(data, CPUFREQ_GOV_STOP);

		cpumask_clear_cpu(cpu, data->cpus);

		spin_unlock_irqrestore(&cpufreq_driver_lock, flags);



		__cpufreq_governor(data, CPUFREQ_GOV_START);

		__cpufreq_governor(data, CPUFREQ_GOV_LIMITS);



		kobj = &dev->kobj;

		cpufreq_cpu_put(data);

		unlock_policy_rwsem_write(cpu);

		sysfs_remove_link(kobj, "cpufreq");

		return 0;

	}

#endif



#ifdef CONFIG_SMP



#ifdef CONFIG_HOTPLUG_CPU

	strncpy(per_cpu(cpufreq_cpu_governor, cpu), data->governor->name,

			CPUFREQ_NAME_LEN);

#endif



	/* if we have other CPUs still registered, we need to unlink them,

	 * or else wait_for_completion below will lock up. Clean the

	 * per_cpu(cpufreq_cpu_data) while holding the lock, and remove

	 * the sysfs links afterwards.

	 */

	if (unlikely(cpumask_weight(data->cpus) > 1)) {

		for_each_cpu(j, data->cpus) {

			if (j == cpu)

				continue;

			per_cpu(cpufreq_cpu_data, j) = NULL;

		}

	}

	per_cpu(cpufreq_cpu_data, cpu) = NULL;

	cpus = cpumask_weight(data->cpus);

	cpumask_clear_cpu(cpu, data->cpus);



	if (unlikely((cpu == data->cpu) && (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);

			cpumask_set_cpu(cpu, data->cpus);

			ret = sysfs_create_link(&cpu_dev->kobj, &data->kobj,

					"cpufreq");

			spin_unlock_irqrestore(&cpufreq_driver_lock, flags);



	if (unlikely(cpumask_weight(data->cpus) > 1)) {

		for_each_cpu(j, data->cpus) {

			if (j == cpu)

				continue;

			pr_debug("removing link for cpu %u\n", j);

#ifdef CONFIG_HOTPLUG_CPU

			strncpy(per_cpu(cpufreq_cpu_governor, j),

				data->governor->name, CPUFREQ_NAME_LEN);

#endif

			cpu_dev = get_cpu_device(j);

			kobj = &cpu_dev->kobj;

			unlock_policy_rwsem_write(cpu);

			sysfs_remove_link(kobj, "cpufreq");

			lock_policy_rwsem_write(cpu);

			cpufreq_cpu_put(data);

			return -EINVAL;

		}



		update_policy_cpu(data, cpu_dev->id);

		pr_debug("%s: policy Kobject moved to cpu: %d from: %d\n",

				__func__, cpu_dev->id, cpu);

	}

#else



	spin_unlock_irqrestore(&cpufreq_driver_lock, flags);

#endif



	if (cpufreq_driver->target)

		__cpufreq_governor(data, CPUFREQ_GOV_STOP);

	pr_debug("%s: removing link, cpu: %d\n", __func__, cpu);

	cpufreq_cpu_put(data);

	unlock_policy_rwsem_write(cpu);

	sysfs_remove_link(&dev->kobj, "cpufreq");



	/* If cpu is last user of policy, free policy */

	if (cpus == 1) {

		lock_policy_rwsem_write(cpu);

		kobj = &data->kobj;

		cmp = &data->kobj_unregister;

		unlock_policy_rwsem_write(cpu);
@@ -1153,25 +1144,13 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif 
			cpufreq_driver->exit(data);

		unlock_policy_rwsem_write(cpu);



#ifdef CONFIG_HOTPLUG_CPU

	/* when the CPU which is the parent of the kobj is hotplugged

	 * offline, check for siblings, and create cpufreq sysfs interface

	 * and symlinks

	 */

	if (unlikely(cpumask_weight(data->cpus) > 1)) {

		/* first sibling now owns the new sysfs dir */

		cpumask_clear_cpu(cpu, data->cpus);

		cpufreq_add_dev(get_cpu_device(cpumask_first(data->cpus)), NULL);



		/* finally remove our own symlink */

		lock_policy_rwsem_write(cpu);

		__cpufreq_remove_dev(dev, sif);

	}

#endif



		free_cpumask_var(data->related_cpus);

		free_cpumask_var(data->cpus);

		kfree(data);

	} else if (cpufreq_driver->target) {

		__cpufreq_governor(data, CPUFREQ_GOV_START);

		__cpufreq_governor(data, CPUFREQ_GOV_LIMITS);

	}



	return 0;

}

drivers/cpufreq/cpufreq_stats.c

+25 −2
Original line number Diff line number Diff line
@@ -170,12 +170,14 @@ static int freq_table_get_index(struct cpufreq_stats *stat, unsigned int freq) 
static void cpufreq_stats_free_table(unsigned int cpu)

{

	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, cpu);



	if (stat) {

		pr_debug("%s: Free stat table\n", __func__);

		kfree(stat->time_in_state);

		kfree(stat);

	}

		per_cpu(cpufreq_stats_table, cpu) = NULL;

	}

}



/* must be called early in the CPU removal sequence (before

 * cpufreq_remove_dev) so that policy is still valid.
@@ -183,8 +185,10 @@ static void cpufreq_stats_free_table(unsigned int cpu) 
static void cpufreq_stats_free_sysfs(unsigned int cpu)

{

	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);

	if (policy && policy->cpu == cpu)

	if (policy && (cpumask_weight(policy->cpus) == 1)) {

		pr_debug("%s: Free sysfs stat\n", __func__);

		sysfs_remove_group(&policy->kobj, &stats_attr_group);

	}

	if (policy)

		cpufreq_cpu_put(policy);

}
@@ -262,6 +266,19 @@ error_get_fail: 
	return ret;

}



static void cpufreq_stats_update_policy_cpu(struct cpufreq_policy *policy)

{

	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table,

			policy->last_cpu);



	pr_debug("Updating stats_table for new_cpu %u from last_cpu %u\n",

			policy->cpu, policy->last_cpu);

	per_cpu(cpufreq_stats_table, policy->cpu) = per_cpu(cpufreq_stats_table,

			policy->last_cpu);

	per_cpu(cpufreq_stats_table, policy->last_cpu) = NULL;

	stat->cpu = policy->cpu;

}



static int cpufreq_stat_notifier_policy(struct notifier_block *nb,

		unsigned long val, void *data)

{
@@ -269,6 +286,12 @@ static int cpufreq_stat_notifier_policy(struct notifier_block *nb, 
	struct cpufreq_policy *policy = data;

	struct cpufreq_frequency_table *table;

	unsigned int cpu = policy->cpu;



	if (val == CPUFREQ_UPDATE_POLICY_CPU) {

		cpufreq_stats_update_policy_cpu(policy);

		return 0;

	}



	if (val != CPUFREQ_NOTIFY)

		return 0;

	table = cpufreq_frequency_get_table(cpu);

drivers/cpufreq/freq_table.c

+9 −0
Original line number Diff line number Diff line
@@ -227,6 +227,15 @@ void cpufreq_frequency_table_put_attr(unsigned int cpu) 
}

EXPORT_SYMBOL_GPL(cpufreq_frequency_table_put_attr);



void cpufreq_frequency_table_update_policy_cpu(struct cpufreq_policy *policy)

{

	pr_debug("Updating show_table for new_cpu %u from last_cpu %u\n",

			policy->cpu, policy->last_cpu);

	per_cpu(cpufreq_show_table, policy->cpu) = per_cpu(cpufreq_show_table,

			policy->last_cpu);

	per_cpu(cpufreq_show_table, policy->last_cpu) = NULL;

}



struct cpufreq_frequency_table *cpufreq_frequency_get_table(unsigned int cpu)

{

	return per_cpu(cpufreq_show_table, cpu);

include/linux/cpufreq.h

+9 −5
Original line number Diff line number Diff line
@@ -93,7 +93,9 @@ struct cpufreq_policy { 
	cpumask_var_t		related_cpus; /* CPUs with any coordination */

	unsigned int		shared_type; /* ANY or ALL affected CPUs

						should set cpufreq */

	unsigned int		cpu;    /* cpu nr of registered CPU */

	unsigned int		cpu;    /* cpu nr of CPU managing this policy */

	unsigned int		last_cpu; /* cpu nr of previous CPU that managed

					   * this policy */

	struct cpufreq_cpuinfo	cpuinfo;/* see above */



	unsigned int		min;    /* in kHz */
@@ -116,6 +118,7 @@ struct cpufreq_policy { 
#define CPUFREQ_INCOMPATIBLE		(1)

#define CPUFREQ_NOTIFY			(2)

#define CPUFREQ_START			(3)

#define CPUFREQ_UPDATE_POLICY_CPU	(4)



#define CPUFREQ_SHARED_TYPE_NONE (0) /* None */

#define CPUFREQ_SHARED_TYPE_HW	 (1) /* HW does needed coordination */
@@ -405,6 +408,7 @@ extern struct freq_attr cpufreq_freq_attr_scaling_available_freqs; 


void cpufreq_frequency_table_get_attr(struct cpufreq_frequency_table *table,

				      unsigned int cpu);

void cpufreq_frequency_table_update_policy_cpu(struct cpufreq_policy *policy);



void cpufreq_frequency_table_put_attr(unsigned int cpu);

#endif /* _LINUX_CPUFREQ_H */