linux-kernel - Re: [PATCH V3 2/3] thermal/drivers/cpu_cooling: Unregister with the policy

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Date:   Wed, 26 Jun 2019 08:02:04 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     rjw@...ysocki.net, edubezval@...il.com,
        linux-kernel@...r.kernel.org, Sudeep Holla <sudeep.holla@....com>,
        Amit Daniel Kachhap <amit.kachhap@...il.com>,
        Javi Merino <javi.merino@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Keerthy <j-keerthy@...com>,
        "open list:CPU FREQUENCY DRIVERS - ARM BIG LITTLE" 
        <linux-pm@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:TI BANDGAP AND THERMAL DRIVER" 
        <linux-omap@...r.kernel.org>
Subject: Re: [PATCH V3 2/3] thermal/drivers/cpu_cooling: Unregister with the
 policy


Hi Viresh,


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.

>>  	pr_debug("initialization complete\n");
>>  
>>  	return 0;
>> @@ -1468,10 +1468,8 @@ static int cpufreq_offline(unsigned int cpu)
>>  		goto unlock;
>>  	}
>>  
>> -	if (cpufreq_thermal_control_enabled(cpufreq_driver)) {
>> -		cpufreq_cooling_unregister(policy->cdev);
>> -		policy->cdev = NULL;
>> -	}
>> +	if (cpufreq_thermal_control_enabled(cpufreq_driver))
>> +		cpufreq_cooling_unregister(policy);
> 
> And we unregister unconditionally, even if we failed ? What if this
> routine prints error messages for such an case ?
>>  
>>  	if (cpufreq_driver->stop_cpu)
>>  		cpufreq_driver->stop_cpu(policy);
>> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
>> index 83486775e593..007c7c6bf845 100644
>> --- a/drivers/thermal/cpu_cooling.c
>> +++ b/drivers/thermal/cpu_cooling.c
>> @@ -78,6 +78,7 @@ struct cpufreq_cooling_device {
>>  	struct cpufreq_policy *policy;
>>  	struct list_head node;
>>  	struct time_in_idle *idle_time;
>> +	struct thermal_cooling_device *cdev;
>>  };
>>  
>>  static DEFINE_IDA(cpufreq_ida);
>> @@ -606,6 +607,7 @@ __cpufreq_cooling_register(struct device_node *np,
>>  		goto remove_ida;
>>  
>>  	cpufreq_cdev->clipped_freq = get_state_freq(cpufreq_cdev, 0);
>> +	cpufreq_cdev->cdev = cdev;
>>  
>>  	mutex_lock(&cooling_list_lock);
>>  	/* Register the notifier for first cpufreq cooling device */
>> @@ -699,18 +701,18 @@ EXPORT_SYMBOL_GPL(of_cpufreq_cooling_register);
>>   *
>>   * This interface function unregisters the "thermal-cpufreq-%x" cooling device.
>>   */
>> -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;
>> -
>> -	cpufreq_cdev = cdev->devdata;
>> -
>>  	mutex_lock(&cooling_list_lock);
>> -	list_del(&cpufreq_cdev->node);
>> +	list_for_each_entry(cpufreq_cdev, &cpufreq_cdev_list, node) {
>> +		if (cpufreq_cdev->policy == policy) {
>> +			list_del(&cpufreq_cdev->node);
>> +			break;
>> +		}
>> +	}
> 
> What if we reach here without a match for the policy ? We shouldn't
> continue and error out, right ? Print an error message as well ?
> 


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