forked from luck/tmp_suning_uos_patched
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>
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@ -1692,13 +1692,15 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
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policy->cpu, event);
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mutex_lock(&cpufreq_governor_lock);
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if ((policy->governor_enabled && event == CPUFREQ_GOV_START)
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if (policy->governor_busy
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|| (policy->governor_enabled && event == CPUFREQ_GOV_START)
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|| (!policy->governor_enabled
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&& (event == CPUFREQ_GOV_LIMITS || event == CPUFREQ_GOV_STOP))) {
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mutex_unlock(&cpufreq_governor_lock);
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return -EBUSY;
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}
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policy->governor_busy = true;
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if (event == CPUFREQ_GOV_STOP)
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policy->governor_enabled = false;
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else if (event == CPUFREQ_GOV_START)
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@ -1727,6 +1729,9 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
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((event == CPUFREQ_GOV_POLICY_EXIT) && !ret))
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module_put(policy->governor->owner);
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mutex_lock(&cpufreq_governor_lock);
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policy->governor_busy = false;
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mutex_unlock(&cpufreq_governor_lock);
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return ret;
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}
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@ -76,6 +76,7 @@ struct cpufreq_policy {
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struct cpufreq_governor *governor; /* see below */
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void *governor_data;
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bool governor_enabled; /* governor start/stop flag */
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bool governor_busy;
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struct work_struct update; /* if update_policy() needs to be
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* called, but you're in IRQ context */
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