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| author | Viresh Kumar <viresh.kumar@linaro.org> | 2013-08-31 17:48:23 +0530 |
|---|---|---|
| committer | Marek Szyprowski <m.szyprowski@samsung.com> | 2014-04-01 13:07:35 +0200 |
| commit | d4f7a025e14f89bf815855d72f4a905390cac624 (patch) | |
| tree | 6796cfea07c2a094e6f00a6b9324916f16451880 | |
| parent | 56e69b35155ea6b699c6dba228aae5521fa8d4a2 (diff) | |
| download | linux-3.10-d4f7a025e14f89bf815855d72f4a905390cac624.tar.gz linux-3.10-d4f7a025e14f89bf815855d72f4a905390cac624.tar.bz2 linux-3.10-d4f7a025e14f89bf815855d72f4a905390cac624.zip | |
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.
Change-Id: Ibae767cbd9c25c7598b39d1405fa3d98d2125101
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>
| -rw-r--r-- | drivers/cpufreq/cpufreq.c | 10 | ||||
| -rw-r--r-- | include/linux/cpufreq.h | 1 |
2 files changed, 9 insertions, 2 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 398882939cb..17267a4b459 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1635,12 +1635,15 @@ static int __cpufreq_governor(struct cpufreq_policy *policy, policy->cpu, event); mutex_lock(&cpufreq_governor_lock); - if ((!policy->governor_enabled && (event == CPUFREQ_GOV_STOP)) || - (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) @@ -1672,6 +1675,9 @@ static int __cpufreq_governor(struct cpufreq_policy *policy, if ((event == CPUFREQ_GOV_STOP) && !ret) module_put(policy->governor->owner); + mutex_lock(&cpufreq_governor_lock); + policy->governor_busy = false; + mutex_unlock(&cpufreq_governor_lock); return ret; } diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h index bd1ad374076..940f1fed44f 100644 --- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h @@ -112,6 +112,7 @@ struct cpufreq_policy { struct cpufreq_governor *governor; /* see below */ void *governor_data; bool governor_enabled; /* governor start/stop flag */ + bool governor_busy; struct work_struct update; /* if update_policy() needs to be * called, but you're in IRQ context */ |