linux-kernel - Re: [PATCH 2/3] cpufreq: Initialize policy before making it available for others to use

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Message-ID: <278741659.0r4LI3yGJ4@vostro.rjw.lan>
Date:	Sat, 01 Mar 2014 02:14:35 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	skannan@...eaurora.org, linaro-kernel@...ts.linaro.org,
	cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, srivatsa.bhat@...ux.vnet.ibm.com
Subject: Re: [PATCH 2/3] cpufreq: Initialize policy before making it available for others to use

On Tuesday, February 25, 2014 02:20:10 PM Viresh Kumar wrote:
> Policy must be fully initialized before it is being made available for use by
> others.

True enough.  And the problem is?

> This patch moves some initialization code before making policy available
> for others.

So why/how exactly does this fix the problem?

> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  drivers/cpufreq/cpufreq.c | 28 ++++++++++++++--------------
>  1 file changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index cc4f244..110c0cd 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1116,6 +1116,20 @@ static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif,
>  		goto err_set_policy_cpu;
>  	}
>  
> +	/* related cpus should atleast have policy->cpus */
> +	cpumask_or(policy->related_cpus, policy->related_cpus, policy->cpus);
> +
> +	/*
> +	 * affected cpus must always be the one, which are online. We aren't
> +	 * managing offline cpus here.
> +	 */
> +	cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);
> +
> +	if (!frozen) {
> +		policy->user_policy.min = policy->min;
> +		policy->user_policy.max = policy->max;
> +	}
> +
>  	write_lock_irqsave(&cpufreq_driver_lock, flags);
>  	for_each_cpu(j, policy->cpus)
>  		per_cpu(cpufreq_cpu_data, j) = policy;
> @@ -1169,20 +1183,6 @@ static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif,
>  		}
>  	}
>  
> -	/* related cpus should atleast have policy->cpus */
> -	cpumask_or(policy->related_cpus, policy->related_cpus, policy->cpus);
> -
> -	/*
> -	 * affected cpus must always be the one, which are online. We aren't
> -	 * managing offline cpus here.
> -	 */
> -	cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);
> -
> -	if (!frozen) {
> -		policy->user_policy.min = policy->min;
> -		policy->user_policy.max = policy->max;
> -	}
> -
>  	blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
>  				     CPUFREQ_START, policy);
>  
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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