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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: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Viresh Kumar 2015-07-18 11:31:01 +05:30 committed by Rafael J. Wysocki
parent 43e0ee361e
commit a72c49590a
1 changed files with 35 additions and 11 deletions
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46
drivers/cpufreq/cpufreq_governor.c
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@ -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,
struct dbs_data *dbs_data)
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;
@ -465,14 +479,18 @@ static int cpufreq_governor_start(struct cpufreq_policy *policy,
return 0;
}
static void cpufreq_governor_stop(struct cpufreq_policy *policy,
struct dbs_data *dbs_data)
static int cpufreq_governor_stop(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);
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,
struct dbs_data *dbs_data)
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: