forked from Minki/linux
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: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
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e3f5ed9393
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@ -24,7 +24,7 @@
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static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs);
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static DEFINE_MUTEX(dbs_data_mutex);
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static DEFINE_MUTEX(gov_dbs_data_mutex);
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/* Common sysfs tunables */
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/**
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@ -421,10 +421,10 @@ static void free_policy_dbs_info(struct policy_dbs_info *policy_dbs,
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static int cpufreq_governor_init(struct cpufreq_policy *policy)
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{
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struct dbs_governor *gov = dbs_governor_of(policy);
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struct dbs_data *dbs_data = gov->gdbs_data;
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struct dbs_data *dbs_data;
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struct policy_dbs_info *policy_dbs;
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unsigned int latency;
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int ret;
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int ret = 0;
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/* State should be equivalent to EXIT */
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if (policy->governor_data)
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@ -434,6 +434,10 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy)
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if (!policy_dbs)
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return -ENOMEM;
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/* Protect gov->gdbs_data against concurrent updates. */
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mutex_lock(&gov_dbs_data_mutex);
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dbs_data = gov->gdbs_data;
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if (dbs_data) {
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if (WARN_ON(have_governor_per_policy())) {
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ret = -EINVAL;
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@ -446,8 +450,7 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy)
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dbs_data->usage_count++;
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list_add(&policy_dbs->list, &dbs_data->policy_dbs_list);
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mutex_unlock(&dbs_data->mutex);
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return 0;
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goto out;
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}
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dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL);
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@ -488,7 +491,7 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy)
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get_governor_parent_kobj(policy),
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"%s", gov->gov.name);
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if (!ret)
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return 0;
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goto out;
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/* Failure, so roll back. */
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pr_err("cpufreq: Governor initialization failed (dbs_data kobject init error %d)\n", ret);
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@ -502,6 +505,9 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy)
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free_policy_dbs_info:
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free_policy_dbs_info(policy_dbs, gov);
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out:
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mutex_unlock(&gov_dbs_data_mutex);
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return ret;
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}
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@ -512,6 +518,9 @@ static int cpufreq_governor_exit(struct cpufreq_policy *policy)
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struct dbs_data *dbs_data = policy_dbs->dbs_data;
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int count;
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/* Protect gov->gdbs_data against concurrent updates. */
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mutex_lock(&gov_dbs_data_mutex);
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mutex_lock(&dbs_data->mutex);
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list_del(&policy_dbs->list);
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count = --dbs_data->usage_count;
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@ -533,6 +542,8 @@ static int cpufreq_governor_exit(struct cpufreq_policy *policy)
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}
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free_policy_dbs_info(policy_dbs, gov);
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mutex_unlock(&gov_dbs_data_mutex);
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return 0;
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}
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@ -599,31 +610,20 @@ static int cpufreq_governor_limits(struct cpufreq_policy *policy)
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int cpufreq_governor_dbs(struct cpufreq_policy *policy, unsigned int event)
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{
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int ret = -EINVAL;
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/* Lock governor to block concurrent initialization of governor */
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mutex_lock(&dbs_data_mutex);
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if (event == CPUFREQ_GOV_POLICY_INIT) {
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ret = cpufreq_governor_init(policy);
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return cpufreq_governor_init(policy);
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} else if (policy->governor_data) {
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switch (event) {
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case CPUFREQ_GOV_POLICY_EXIT:
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ret = cpufreq_governor_exit(policy);
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break;
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return cpufreq_governor_exit(policy);
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case CPUFREQ_GOV_START:
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ret = cpufreq_governor_start(policy);
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break;
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return cpufreq_governor_start(policy);
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case CPUFREQ_GOV_STOP:
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ret = cpufreq_governor_stop(policy);
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break;
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return cpufreq_governor_stop(policy);
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case CPUFREQ_GOV_LIMITS:
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ret = cpufreq_governor_limits(policy);
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break;
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return cpufreq_governor_limits(policy);
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}
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}
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mutex_unlock(&dbs_data_mutex);
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return ret;
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return -EINVAL;
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}
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EXPORT_SYMBOL_GPL(cpufreq_governor_dbs);
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