On 26/06/2019 13:28, Rafael J. Wysocki wrote:
> On Wed, Jun 26, 2019 at 12:19 PM Daniel Lezcano
> <daniel.lezcano@xxxxxxxxxx> wrote:
>>
>> On 26/06/2019 11:06, Rafael J. Wysocki wrote:
>>> On Wed, Jun 26, 2019 at 8:37 AM Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
>>>>
>>>> On 26-06-19, 08:02, Daniel Lezcano wrote:
>>>>> On 26/06/2019 04:58, Viresh Kumar wrote:
>>>>>> On 25-06-19, 13:32, Daniel Lezcano wrote:
>>>>>>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>>>>>>> index aee024e42618..f07454249fbc 100644
>>>>>>> --- a/drivers/cpufreq/cpufreq.c
>>>>>>> +++ b/drivers/cpufreq/cpufreq.c
>>>>>>> @@ -1379,8 +1379,8 @@ static int cpufreq_online(unsigned int cpu)
>>>>>>> cpufreq_driver->ready(policy);
>>>>>>>
>>>>>>> if (cpufreq_thermal_control_enabled(cpufreq_driver))
>>>>>>> - policy->cdev = of_cpufreq_cooling_register(policy);
>>>>>>> -
>>>>>>> + of_cpufreq_cooling_register(policy);
>>>>>>> +
>>>>>>
>>>>>> We don't need any error checking here anymore ?
>>>>>
>>>>> There was no error checking initially. This comment and the others below
>>>>> are for an additional patch IMO, not a change in this one.
>>>>
>>>> right, but ...
>>>>
>>>>>>> -void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
>>>>>>> +void cpufreq_cooling_unregister(struct cpufreq_policy *policy)
>>>>>>> {
>>>>>>> struct cpufreq_cooling_device *cpufreq_cdev;
>>>>>>> bool last;
>>>>>>>
>>>>>>> - if (!cdev)
>>>>>>> - return;
>>>>
>>>> we used to return without any errors from here. Now we will have
>>>> problems if regsitering fails for some reason.
>>>
>>> Specifically, the last cpufreq_cdev in the list will be unregistered
>>> AFAICS, and without removing it from the list for that matter, which
>>> isn't what the caller wants.
>>
>> Indeed,
>>
>> What about the resulting code above:
>>
>> void __cpufreq_cooling_unregister(struct cpufreq_cooling_device
>> *cpufreq_cdev, int last)
>> {
>> /* Unregister the notifier for the last cpufreq cooling device */
>> if (last)
>> cpufreq_unregister_notifier(&thermal_cpufreq_notifier_block,
>> CPUFREQ_POLICY_NOTIFIER);
>>
>
> Doesn't the notifier need to be unregistered under cooling_list_lock ?
I don't think so because the element is no longer in the list and we
don't touch the list anymore. Do you see another possible race?
>> thermal_cooling_device_unregister(cpufreq_cdev->cdev);
>> ida_simple_remove(&cpufreq_ida, cpufreq_cdev->id);
>> kfree(cpufreq_cdev->idle_time);
>> kfree(cpufreq_cdev);
>> }
>>
>> /**
>>
>> * cpufreq_cooling_unregister - function to remove cpufreq cooling
>> device.
>> * @cdev: thermal cooling device pointer.
>>
>> *
>>
>> * This interface function unregisters the "thermal-cpufreq-%x" cooling
>> device.
>> */
>> void cpufreq_cooling_unregister(struct cpufreq_policy *policy)
>> {
>> struct cpufreq_cooling_device *cpufreq_cdev;
>> bool last;
>>
>> mutex_lock(&cooling_list_lock);
>> list_for_each_entry(cpufreq_cdev, &cpufreq_cdev_list, node) {
>> if (cpufreq_cdev->policy == policy) {
>> list_del(&cpufreq_cdev->node);
>> last = list_empty(&cpufreq_cdev_list);
>> break;
>> }
>> }
>> mutex_unlock(&cooling_list_lock);
>>
>> if (cpufreq_cdev->policy == policy)
>> __cpufreq_cooling_unregister(cpufreq_cdev, last);
>> }
>> EXPORT_SYMBOL_GPL(cpufreq_cooling_unregister);
>>
>>
>>
>>
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