cpufreq: Remove cpufreq_governor_lock

We used to drop policy->rwsem just before calling __cpufreq_governor()
in some cases earlier and so it was possible that __cpufreq_governor()
ran concurrently via separate threads for the same policy.

In order to guarantee valid state transitions for governors,
'governor_enabled' was required to be protected using some locking
and cpufreq_governor_lock was added for that.

But now __cpufreq_governor() is always called under policy->rwsem,
and 'governor_enabled' is protected against races even without
cpufreq_governor_lock.

Get rid of the extra lock now.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Juri Lelli <juri.lelli@arm.com>
Tested-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
[ rjw : Changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 6928768..bc93272 100644 (file)
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -147,8 +147,6 @@ void cpufreq_update_util(u64 time, unsigned long util, unsigned long max)
        rcu_read_unlock();
 }
 
-DEFINE_MUTEX(cpufreq_governor_lock);
-
 /* Flag to suspend/resume CPUFreq governors */
 static bool cpufreq_suspended;
 
@@ -2015,11 +2013,9 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
 
        pr_debug("%s: for CPU %u, event %u\n", __func__, policy->cpu, event);
 
-       mutex_lock(&cpufreq_governor_lock);
        if ((policy->governor_enabled && event == CPUFREQ_GOV_START)
            || (!policy->governor_enabled
            && (event == CPUFREQ_GOV_LIMITS || event == CPUFREQ_GOV_STOP))) {
-               mutex_unlock(&cpufreq_governor_lock);
                return -EBUSY;
        }
 
@@ -2028,8 +2024,6 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
        else if (event == CPUFREQ_GOV_START)
                policy->governor_enabled = true;
 
-       mutex_unlock(&cpufreq_governor_lock);
-
        ret = policy->governor->governor(policy, event);
 
        if (!ret) {
@@ -2039,12 +2033,10 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
                        policy->governor->initialized--;
        } else {
                /* Restore original values */
-               mutex_lock(&cpufreq_governor_lock);
                if (event == CPUFREQ_GOV_STOP)
                        policy->governor_enabled = true;
                else if (event == CPUFREQ_GOV_START)
                        policy->governor_enabled = false;
-               mutex_unlock(&cpufreq_governor_lock);
        }
 
        if (((event == CPUFREQ_GOV_POLICY_INIT) && ret) ||

diff --git a/drivers/cpufreq/cpufreq_governor.h b/drivers/cpufreq/cpufreq_governor.h
index 8bf4775..e9ec411 100644 (file)
--- a/drivers/cpufreq/cpufreq_governor.h
+++ b/drivers/cpufreq/cpufreq_governor.h
@@ -232,7 +232,6 @@ static inline int delay_for_sampling_rate(unsigned int sampling_rate)
 }
 
 extern struct mutex dbs_data_mutex;
-extern struct mutex cpufreq_governor_lock;
 void dbs_check_cpu(struct cpufreq_policy *policy);
 int cpufreq_governor_dbs(struct cpufreq_policy *policy, unsigned int event);
 void od_register_powersave_bias_handler(unsigned int (*f)