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Commit a72c4959 authored by Viresh Kumar's avatar Viresh Kumar Committed by Rafael J. Wysocki
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cpufreq: governor: Avoid invalid states with additional checks 



There can be races where the request has come to a wrong state. For
example INIT followed by STOP (instead of START) or START followed by
EXIT (instead of STOP).

Address these races by making sure the state-machine never gets into
any invalid state. Also return an error if an invalid state-transition
is requested.

Reviewed-and-tested-by: default avatarPreeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 43e0ee36

drivers/cpufreq/cpufreq_governor.c

+35 −11
Original line number Diff line number Diff line
@@ -305,6 +305,10 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy, 
	unsigned int latency;

	int ret;



	/* State should be equivalent to EXIT */

	if (policy->governor_data)

		return -EBUSY;



	if (dbs_data) {

		if (WARN_ON(have_governor_per_policy()))

			return -EINVAL;
@@ -375,10 +379,15 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy, 
	return ret;

}



static void cpufreq_governor_exit(struct cpufreq_policy *policy,

static int cpufreq_governor_exit(struct cpufreq_policy *policy,

				 struct dbs_data *dbs_data)

{

	struct common_dbs_data *cdata = dbs_data->cdata;

	struct cpu_dbs_info *cdbs = cdata->get_cpu_cdbs(policy->cpu);



	/* State should be equivalent to INIT */

	if (!cdbs->shared || cdbs->shared->policy)

		return -EBUSY;



	policy->governor_data = NULL;

	if (!--dbs_data->usage_count) {
@@ -395,6 +404,7 @@ static void cpufreq_governor_exit(struct cpufreq_policy *policy, 
	}



	free_common_dbs_info(policy, cdata);

	return 0;

}



static int cpufreq_governor_start(struct cpufreq_policy *policy,
@@ -409,6 +419,10 @@ static int cpufreq_governor_start(struct cpufreq_policy *policy, 
	if (!policy->cur)

		return -EINVAL;



	/* State should be equivalent to INIT */

	if (!shared || shared->policy)

		return -EBUSY;



	if (cdata->governor == GOV_CONSERVATIVE) {

		struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
@@ -465,7 +479,7 @@ static int cpufreq_governor_start(struct cpufreq_policy *policy, 
	return 0;

}



static void cpufreq_governor_stop(struct cpufreq_policy *policy,

static int cpufreq_governor_stop(struct cpufreq_policy *policy,

				 struct dbs_data *dbs_data)

{

	struct common_dbs_data *cdata = dbs_data->cdata;
@@ -473,6 +487,10 @@ static void cpufreq_governor_stop(struct cpufreq_policy *policy, 
	struct cpu_dbs_info *cdbs = cdata->get_cpu_cdbs(cpu);

	struct cpu_common_dbs_info *shared = cdbs->shared;



	/* State should be equivalent to START */

	if (!shared || !shared->policy)

		return -EBUSY;



	gov_cancel_work(dbs_data, policy);



	if (cdata->governor == GOV_CONSERVATIVE) {
@@ -484,17 +502,19 @@ static void cpufreq_governor_stop(struct cpufreq_policy *policy, 


	shared->policy = NULL;

	mutex_destroy(&shared->timer_mutex);

	return 0;

}



static void cpufreq_governor_limits(struct cpufreq_policy *policy,

static int cpufreq_governor_limits(struct cpufreq_policy *policy,

				   struct dbs_data *dbs_data)

{

	struct common_dbs_data *cdata = dbs_data->cdata;

	unsigned int cpu = policy->cpu;

	struct cpu_dbs_info *cdbs = cdata->get_cpu_cdbs(cpu);



	/* State should be equivalent to START */

	if (!cdbs->shared || !cdbs->shared->policy)

		return;

		return -EBUSY;



	mutex_lock(&cdbs->shared->timer_mutex);

	if (policy->max < cdbs->shared->policy->cur)
@@ -505,13 +525,15 @@ static void cpufreq_governor_limits(struct cpufreq_policy *policy, 
					CPUFREQ_RELATION_L);

	dbs_check_cpu(dbs_data, cpu);

	mutex_unlock(&cdbs->shared->timer_mutex);



	return 0;

}



int cpufreq_governor_dbs(struct cpufreq_policy *policy,

			 struct common_dbs_data *cdata, unsigned int event)

{

	struct dbs_data *dbs_data;

	int ret = 0;

	int ret;



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

	mutex_lock(&cdata->mutex);
@@ -531,17 +553,19 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy, 
		ret = cpufreq_governor_init(policy, dbs_data, cdata);

		break;

	case CPUFREQ_GOV_POLICY_EXIT:

		cpufreq_governor_exit(policy, dbs_data);

		ret = cpufreq_governor_exit(policy, dbs_data);

		break;

	case CPUFREQ_GOV_START:

		ret = cpufreq_governor_start(policy, dbs_data);

		break;

	case CPUFREQ_GOV_STOP:

		cpufreq_governor_stop(policy, dbs_data);

		ret = cpufreq_governor_stop(policy, dbs_data);

		break;

	case CPUFREQ_GOV_LIMITS:

		cpufreq_governor_limits(policy, dbs_data);

		ret = cpufreq_governor_limits(policy, dbs_data);

		break;

	default:

		ret = -EINVAL;

	}



unlock: