linux-kernel - Re: [patch] cpufreq: ondemand: Use cpumask_var

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Date:   Mon, 25 Jul 2022 16:00:53 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Zhao Liu <zhao1.liu@...ux.intel.com>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, trivial@...nel.org,
        Rusty Russell <rusty@...tcorp.com.au>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhao Liu <zhao1.liu@...el.com>
Subject: Re: [patch] cpufreq: ondemand: Use cpumask_var_t for on-stack cpu
 mask

On 22-07-22, 10:50, Zhao Liu wrote:
> A cpumask structure on the stack can cause a warning with
> CONFIG_NR_CPUS=8192 (e.g. Ubuntu 22.04 uses this):
> 
> drivers/cpufreq/cpufreq_ondemand.c: In function 'od_set_powersave_bias':
> drivers/cpufreq/cpufreq_ondemand.c:449:1: warning: the frame size of
> 	1032 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>   449 | }
>       | ^
> 
> CONFIG_CPUMASK_OFFSTACK=y is enabled by default for most distros, and
> hence we can work around the warning by using cpumask_var_t.
> 
> Signed-off-by: Zhao Liu <zhao1.liu@...ux.intel.com>
> ---
>  drivers/cpufreq/cpufreq_ondemand.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
> index e8fbf970ff07..c52d19d67557 100644
> --- a/drivers/cpufreq/cpufreq_ondemand.c
> +++ b/drivers/cpufreq/cpufreq_ondemand.c
> @@ -416,10 +416,13 @@ static struct dbs_governor od_dbs_gov = {
>  static void od_set_powersave_bias(unsigned int powersave_bias)
>  {
>  	unsigned int cpu;
> -	cpumask_t done;
> +	cpumask_var_t done;
> +
> +	if (!alloc_cpumask_var(&done, GFP_KERNEL))
> +		return;
>  
>  	default_powersave_bias = powersave_bias;
> -	cpumask_clear(&done);
> +	cpumask_clear(done);
>  
>  	cpus_read_lock();
>  	for_each_online_cpu(cpu) {
> @@ -428,7 +431,7 @@ static void od_set_powersave_bias(unsigned int powersave_bias)
>  		struct dbs_data *dbs_data;
>  		struct od_dbs_tuners *od_tuners;
>  
> -		if (cpumask_test_cpu(cpu, &done))
> +		if (cpumask_test_cpu(cpu, done))
>  			continue;
>  
>  		policy = cpufreq_cpu_get_raw(cpu);
> @@ -439,13 +442,15 @@ static void od_set_powersave_bias(unsigned int powersave_bias)
>  		if (!policy_dbs)
>  			continue;
>  
> -		cpumask_or(&done, &done, policy->cpus);
> +		cpumask_or(done, done, policy->cpus);
>  
>  		dbs_data = policy_dbs->dbs_data;
>  		od_tuners = dbs_data->tuners;
>  		od_tuners->powersave_bias = default_powersave_bias;
>  	}
>  	cpus_read_unlock();
> +
> +	free_cpumask_var(done);
>  }
>  
>  void od_register_powersave_bias_handler(unsigned int (*f)

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh