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| author | Viresh Kumar <viresh.kumar@linaro.org> | 2013-08-31 17:48:23 +0530 |
|---|---|---|
| committer | Chanho Park <chanho61.park@samsung.com> | 2014-11-18 11:47:24 +0900 |
| commit | 09b15266c45c5c36150e681edb4ad0270d602d77 (patch) | |
| tree | fc5535ac2d92e744c4d1b74ca6789952bd584818 /drivers | |
| parent | ca4546d2fec11439027f48bcc0fcd1f04e754d76 (diff) | |
| download | linux-3.10-09b15266c45c5c36150e681edb4ad0270d602d77.tar.gz linux-3.10-09b15266c45c5c36150e681edb4ad0270d602d77.tar.bz2 linux-3.10-09b15266c45c5c36150e681edb4ad0270d602d77.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>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/cpufreq/cpufreq.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index ca987faf884..12d50e82b34 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; } |