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Commit 1112e9d8 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

cpufreq: governor: Narrow down the dbs_data_mutex coverage 



Since cpufreq_governor_dbs() is now always called with policy->rwsem
held, it cannot be executed twice in parallel for the same policy.
Thus it is not necessary to hold dbs_data_mutex around the invocations
of cpufreq_governor_start/stop/limits() from it as those functions
never modify any data that can be shared between different policies.

However, cpufreq_governor_dbs() may be executed twice in parallal
for different policies using the same gov->gdbs_data object and
dbs_data_mutex is still necessary to protect that object against
concurrent updates.

For this reason, narrow down the dbs_data_mutex locking to
cpufreq_governor_init/exit() where it is needed and rename the
mutex to gov_dbs_data_mutex to reflect its purpose.

Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
parent e3f5ed93

drivers/cpufreq/cpufreq_governor.c

+23 −23
Original line number Diff line number Diff line
@@ -24,7 +24,7 @@ 


static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs);



static DEFINE_MUTEX(dbs_data_mutex);

static DEFINE_MUTEX(gov_dbs_data_mutex);



/* Common sysfs tunables */

/**
@@ -421,10 +421,10 @@ static void free_policy_dbs_info(struct policy_dbs_info *policy_dbs, 
static int cpufreq_governor_init(struct cpufreq_policy *policy)

{

	struct dbs_governor *gov = dbs_governor_of(policy);

	struct dbs_data *dbs_data = gov->gdbs_data;

	struct dbs_data *dbs_data;

	struct policy_dbs_info *policy_dbs;

	unsigned int latency;

	int ret;

	int ret = 0;



	/* State should be equivalent to EXIT */

	if (policy->governor_data)
@@ -434,6 +434,10 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy) 
	if (!policy_dbs)

		return -ENOMEM;



	/* Protect gov->gdbs_data against concurrent updates. */

	mutex_lock(&gov_dbs_data_mutex);



	dbs_data = gov->gdbs_data;

	if (dbs_data) {

		if (WARN_ON(have_governor_per_policy())) {

			ret = -EINVAL;
@@ -446,8 +450,7 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy) 
		dbs_data->usage_count++;

		list_add(&policy_dbs->list, &dbs_data->policy_dbs_list);

		mutex_unlock(&dbs_data->mutex);



		return 0;

		goto out;

	}



	dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL);
@@ -488,7 +491,7 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy) 
				   get_governor_parent_kobj(policy),

				   "%s", gov->gov.name);

	if (!ret)

		return 0;

		goto out;



	/* Failure, so roll back. */

	pr_err("cpufreq: Governor initialization failed (dbs_data kobject init error %d)\n", ret);
@@ -502,6 +505,9 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy) 


free_policy_dbs_info:

	free_policy_dbs_info(policy_dbs, gov);



out:

	mutex_unlock(&gov_dbs_data_mutex);

	return ret;

}
@@ -512,6 +518,9 @@ static int cpufreq_governor_exit(struct cpufreq_policy *policy) 
	struct dbs_data *dbs_data = policy_dbs->dbs_data;

	int count;



	/* Protect gov->gdbs_data against concurrent updates. */

	mutex_lock(&gov_dbs_data_mutex);



	mutex_lock(&dbs_data->mutex);

	list_del(&policy_dbs->list);

	count = --dbs_data->usage_count;
@@ -533,6 +542,8 @@ static int cpufreq_governor_exit(struct cpufreq_policy *policy) 
	}



	free_policy_dbs_info(policy_dbs, gov);



	mutex_unlock(&gov_dbs_data_mutex);

	return 0;

}
@@ -599,31 +610,20 @@ static int cpufreq_governor_limits(struct cpufreq_policy *policy) 


int cpufreq_governor_dbs(struct cpufreq_policy *policy, unsigned int event)

{

	int ret = -EINVAL;



	/* Lock governor to block concurrent initialization of governor */

	mutex_lock(&dbs_data_mutex);



	if (event == CPUFREQ_GOV_POLICY_INIT) {

		ret = cpufreq_governor_init(policy);

		return cpufreq_governor_init(policy);

	} else if (policy->governor_data) {

		switch (event) {

		case CPUFREQ_GOV_POLICY_EXIT:

			ret = cpufreq_governor_exit(policy);

			break;

			return cpufreq_governor_exit(policy);

		case CPUFREQ_GOV_START:

			ret = cpufreq_governor_start(policy);

			break;

			return cpufreq_governor_start(policy);

		case CPUFREQ_GOV_STOP:

			ret = cpufreq_governor_stop(policy);

			break;

			return cpufreq_governor_stop(policy);

		case CPUFREQ_GOV_LIMITS:

			ret = cpufreq_governor_limits(policy);

			break;

			return cpufreq_governor_limits(policy);

		}

	}



	mutex_unlock(&dbs_data_mutex);

	return ret;

	return -EINVAL;

}

EXPORT_SYMBOL_GPL(cpufreq_governor_dbs);