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).
Tackle these races by comparing making sure the state-machine never gets into any invalid state. And return 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 --- drivers/cpufreq/cpufreq_governor.c | 46 +++++++++++++++++++++++++++++--------- 1 file changed, 35 insertions(+), 11 deletions(-)
diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c index 7ed0ec2ac853..f225dc975415 100644 --- a/drivers/cpufreq/cpufreq_governor.c +++ b/drivers/cpufreq/cpufreq_governor.c @@ -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: