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authorViresh Kumar <viresh.kumar@linaro.org>2013-08-31 17:48:23 +0530
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-09-10 02:49:46 +0200
commit19c763031acb831a5ab9c1a701b7fedda073eb3f (patch)
tree86ddfcb2266d1cc4946d7b24f2a6320277517cc2 /drivers/cpufreq/cpufreq.c
parentf73d39338444d9915c746403bd98b145ff9d2ba4 (diff)
cpufreq: serialize calls to __cpufreq_governor()
We can't take a big lock around __cpufreq_governor() as this causes recursive locking for some cases. But calls to this routine must be serialized for every policy. Otherwise we can see some unpredictable events. For example, consider following scenario: __cpufreq_remove_dev() __cpufreq_governor(policy, CPUFREQ_GOV_STOP); policy->governor->governor(policy, CPUFREQ_GOV_STOP); cpufreq_governor_dbs() case CPUFREQ_GOV_STOP: mutex_destroy(&cpu_cdbs->timer_mutex) cpu_cdbs->cur_policy = NULL; <PREEMPT> store() __cpufreq_set_policy() __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS); policy->governor->governor(policy, CPUFREQ_GOV_LIMITS); case CPUFREQ_GOV_LIMITS: mutex_lock(&cpu_cdbs->timer_mutex); <-- Warning (destroyed mutex) if (policy->max < cpu_cdbs->cur_policy->cur) <- cur_policy == NULL And so store() will eventually result in a crash if cur_policy is NULL at this point. Introduce an additional variable which would guarantee serialization here. Reported-by: Stephen Boyd <sboyd@codeaurora.org> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/cpufreq/cpufreq.c')
-rw-r--r--drivers/cpufreq/cpufreq.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 06a2496d2075..7e6baa58a7f2 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1692,13 +1692,15 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
policy->cpu, event);
mutex_lock(&cpufreq_governor_lock);
- if ((policy->governor_enabled && event == CPUFREQ_GOV_START)
+ if (policy->governor_busy
+ || (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;
}
+ policy->governor_busy = true;
if (event == CPUFREQ_GOV_STOP)
policy->governor_enabled = false;
else if (event == CPUFREQ_GOV_START)
@@ -1727,6 +1729,9 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
((event == CPUFREQ_GOV_POLICY_EXIT) && !ret))
module_put(policy->governor->owner);
+ mutex_lock(&cpufreq_governor_lock);
+ policy->governor_busy = false;
+ mutex_unlock(&cpufreq_governor_lock);
return ret;
}