linux-kernel - Re: [PATCH 2/2] cpufreq: userspace: Move is_managed indicator into per-policy structure

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Message-ID: <20231005110321.ythrdcueqwjrksbq@vireshk-i7>
Date:   Thu, 5 Oct 2023 16:33:21 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Liao Chang <liaochang1@...wei.com>
Cc:     rafael@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] cpufreq: userspace: Move is_managed indicator into
 per-policy structure

On 12-09-23, 06:10, Liao Chang wrote:
> The userspace governor use the 'cpu' field of cpufreq_policy structure
> to track if it is allowed to set the speed of policy.  However, there is
> a window where the 'cpu' field is equal to the value of nr_cpus_id when
> all affected CPUs of policy are offline, which is an illegal value to
> get the per-CPU variable. To avoid this issue, this patch uses a
> per-policy indicator to track if the policy is managed.
> 
> Signed-off-by: Liao Chang <liaochang1@...wei.com>
> ---
>  drivers/cpufreq/cpufreq_userspace.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq_userspace.c b/drivers/cpufreq/cpufreq_userspace.c
> index 442e31060d62..2c42fee76daa 100644
> --- a/drivers/cpufreq/cpufreq_userspace.c
> +++ b/drivers/cpufreq/cpufreq_userspace.c
> @@ -15,9 +15,8 @@
>  #include <linux/mutex.h>
>  #include <linux/slab.h>
>  
> -static DEFINE_PER_CPU(unsigned int, cpu_is_managed);
> -
>  struct userspace_policy {
> +	unsigned int is_managed;
>  	unsigned int setspeed;
>  	struct mutex mutex;
>  };
> @@ -37,7 +36,7 @@ static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
>  	pr_debug("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);
>  
>  	mutex_lock(&userspace->mutex);
> -	if (!per_cpu(cpu_is_managed, policy->cpu))
> +	if (!userspace->is_managed)
>  		goto err;
>  
>  	userspace->setspeed = freq;
> @@ -85,7 +84,7 @@ static int cpufreq_userspace_policy_start(struct cpufreq_policy *policy)
>  	pr_debug("started managing cpu %u\n", policy->cpu);
>  
>  	mutex_lock(&userspace->mutex);
> -	per_cpu(cpu_is_managed, policy->cpu) = 1;
> +	userspace->is_managed = 1;
>  	userspace->setspeed = policy->cur;
>  	mutex_unlock(&userspace->mutex);
>  	return 0;
> @@ -98,7 +97,7 @@ static void cpufreq_userspace_policy_stop(struct cpufreq_policy *policy)
>  	pr_debug("managing cpu %u stopped\n", policy->cpu);
>  
>  	mutex_lock(&userspace->mutex);
> -	per_cpu(cpu_is_managed, policy->cpu) = 0;
> +	userspace->is_managed = 0;
>  	userspace->setspeed = 0;
>  	mutex_unlock(&userspace->mutex);
>  }

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

-- 
viresh