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>
diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index 4f0bd48..542c9ca 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c
@@ -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 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 @@
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 @@
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 @@
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 @@
free_policy_dbs_info:
free_policy_dbs_info(policy_dbs, gov);
+
+out:
+ mutex_unlock(&gov_dbs_data_mutex);
return ret;
}
@@ -512,6 +518,9 @@
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 @@
}
free_policy_dbs_info(policy_dbs, gov);
+
+ mutex_unlock(&gov_dbs_data_mutex);
return 0;
}
@@ -599,31 +610,20 @@
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);