On Thu, Mar 10, 2016 at 11:20 PM, Rafael J. Wysocki <[email protected]> wrote:
> On Thursday, March 10, 2016 04:10:36 PM Richard Cochran wrote:
>> The function, cpufreq_quick_get, accesses the global 'cpufreq_driver' and
>> its fields without taking the associated lock, cpufreq_driver_lock.
>>
>> Without the locking, nothing guarantees that 'cpufreq_driver' remains
>> consistent during the call. This patch fixes the issue by taking the lock
>> before accessing the data structure.
>>
>> Cc: Dirk Brandewie <[email protected]>
>> Cc: Rafael J. Wysocki <[email protected]>
>> Cc: Viresh Kumar <[email protected]>
>> Signed-off-by: Richard Cochran <[email protected]>
>
> Can you please CC PM-related patches to [email protected]? They
> are much easier to handle for me then.
>
>> ---
>> drivers/cpufreq/cpufreq.c | 10 +++++++++-
>> 1 file changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index e979ec7..ce02b2b 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -1457,9 +1457,17 @@ unsigned int cpufreq_quick_get(unsigned int cpu)
>> {
>> struct cpufreq_policy *policy;
>> unsigned int ret_freq = 0;
>> + unsigned long flags;
>> +
>> + read_lock_irqsave(&cpufreq_driver_lock, flags);
>>
>> if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get)
>> - return cpufreq_driver->get(cpu);
>> + ret_freq = cpufreq_driver->get(cpu);
>> +
>> + read_unlock_irqrestore(&cpufreq_driver_lock, flags);
>> +
>> + if (ret_freq)
>> + return ret_freq;
>>
>> policy = cpufreq_cpu_get(cpu);
>> if (policy) {
>>
>
> I would prefer something like this:
>
> read_lock_irqsave(&cpufreq_driver_lock, flags);
>
> if (cpufreq_driver && cpufreq_driver->setpolicy &&
> cpufreq_driver->get) {
> unsigned int ret_freq = cpufreq_driver->get(cpu);
Sorry, ret_freq is needed outside of this block anyway, so that would be
ret_freq = cpufreq_driver->get(cpu);
>
> read_unlock_irqrestore(&cpufreq_driver_lock, flags);
> return ret_freq;
> }
>
> read_unlock_irqrestore(&cpufreq_driver_lock, flags);
