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Commit 99522fe6 authored by Viresh Kumar's avatar Viresh Kumar Committed by Rafael J. Wysocki
Browse files

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: default avatarViresh Kumar <viresh.kumar@linaro.org>
Tested-by: default avatarJuri Lelli <juri.lelli@arm.com>
Tested-by: default avatarShilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
[ rjw : Changelog ]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 49f18560

drivers/cpufreq/cpufreq.c

+0 −8
Original line number Diff line number Diff line
@@ -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) ||

drivers/cpufreq/cpufreq_governor.h

+0 −1
Original line number Diff line number Diff line
@@ -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)