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

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Date:   Wed, 26 Jun 2019 08:28:31 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Daniel Lezcano <daniel.lezcano@...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

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 ?

>  	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 ?

-- 
viresh