linux-kernel - Re: [PATCH] thermal: use cpumask_var

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Date:   Fri, 10 Feb 2017 16:38:47 +0800
From:   Zhang Rui <rui.zhang@...el.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Amit Daniel Kachhap <amit.kachhap@...il.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Javi Merino <javi.merino@...nel.org>,
        Eduardo Valentin <edubezval@...il.com>
Cc:     "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] thermal: use cpumask_var_t for on-stack cpu masks

On Thu, 2017-02-02 at 15:46 +0100, Arnd Bergmann wrote:
> Putting a bare cpumask structure on the stack produces a warning on
> large SMP configurations:
> 
> drivers/thermal/cpu_cooling.c: In function 'cpufreq_state2power':
> drivers/thermal/cpu_cooling.c:644:1: warning: the frame size of 1056
> bytes is larger than 1024 bytes [-Wframe-larger-than=]
> drivers/thermal/cpu_cooling.c: In function
> '__cpufreq_cooling_register':
> drivers/thermal/cpu_cooling.c:898:1: warning: the frame size of 1104
> bytes is larger than 1024 bytes [-Wframe-larger-than=]
> 
> The recommended workaround is to use cpumask_var_t, which behaves
> just like
> a normal cpu mask in most cases, but turns into a dynamic allocation
> when CONFIG_CPUMASK_OFFSTACK is set.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/thermal/cpu_cooling.c | 39 ++++++++++++++++++++++++++-------
> ------
>  1 file changed, 26 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/thermal/cpu_cooling.c
> b/drivers/thermal/cpu_cooling.c
> index ca7ddaea450c..1d7f7e85f669 100644
> --- a/drivers/thermal/cpu_cooling.c
> +++ b/drivers/thermal/cpu_cooling.c
> @@ -609,31 +609,39 @@ static int cpufreq_state2power(struct
> thermal_cooling_device *cdev,
>  			       unsigned long state, u32 *power)
>  {
>  	unsigned int freq, num_cpus;
> -	cpumask_t cpumask;
> +	cpumask_var_t cpumask;
>  	u32 static_power, dynamic_power;
>  	int ret;
>  	struct cpufreq_cooling_device *cpufreq_device = cdev-
> >devdata;
>  
> -	cpumask_and(&cpumask, &cpufreq_device->allowed_cpus,
> cpu_online_mask);
> -	num_cpus = cpumask_weight(&cpumask);
> +	if (!alloc_cpumask_var(&cpumask, GFP_KERNEL))
> +		return -ENOMEM;
> +
> +	cpumask_and(cpumask, &cpufreq_device->allowed_cpus,
> cpu_online_mask);
> +	num_cpus = cpumask_weight(cpumask);
>  
>  	/* None of our cpus are online, so no power */
>  	if (num_cpus == 0) {
>  		*power = 0;
> -		return 0;
> +		ret = 0;
> +		goto out;
>  	}
>  
>  	freq = cpufreq_device->freq_table[state];
> -	if (!freq)
> -		return -EINVAL;
> +	if (!freq) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
>  
>  	dynamic_power = cpu_freq_to_power(cpufreq_device, freq) *
> num_cpus;
>  	ret = get_static_power(cpufreq_device, tz, freq,
> &static_power);
>  	if (ret)
> -		return ret;
> +		goto out;
>  
>  	*power = static_power + dynamic_power;
> -	return 0;
> +out:
> +	free_cpumask_var(cpumask);
> +	return ret;;

The patch looks good to me except that there is on redundant semicolon
here.
Patch applied with the typo fixed.

thanks,
rui
>  }
>  
>  /**
> @@ -759,16 +767,20 @@ __cpufreq_cooling_register(struct device_node
> *np,
>  	struct cpufreq_cooling_device *cpufreq_dev;
>  	char dev_name[THERMAL_NAME_LENGTH];
>  	struct cpufreq_frequency_table *pos, *table;
> -	struct cpumask temp_mask;
> +	cpumask_var_t temp_mask;
>  	unsigned int freq, i, num_cpus;
>  	int ret;
>  	struct thermal_cooling_device_ops *cooling_ops;
>  
> -	cpumask_and(&temp_mask, clip_cpus, cpu_online_mask);
> -	policy = cpufreq_cpu_get(cpumask_first(&temp_mask));
> +	if (!alloc_cpumask_var(&temp_mask, GFP_KERNEL))
> +		return ERR_PTR(-ENOMEM);
> +
> +	cpumask_and(temp_mask, clip_cpus, cpu_online_mask);
> +	policy = cpufreq_cpu_get(cpumask_first(temp_mask));
>  	if (!policy) {
>  		pr_debug("%s: CPUFreq policy not found\n",
> __func__);
> -		return ERR_PTR(-EPROBE_DEFER);
> +		cool_dev = ERR_PTR(-EPROBE_DEFER);
> +		goto free_cpumask;
>  	}
>  
>  	table = policy->freq_table;
> @@ -886,7 +898,8 @@ __cpufreq_cooling_register(struct device_node
> *np,
>  	kfree(cpufreq_dev);
>  put_policy:
>  	cpufreq_cpu_put(policy);
> -
> +free_cpumask:
> +	free_cpumask_var(temp_mask);
>  	return cool_dev;
>  }
>