linux-kernel - Re: [RFC PATCH 17/19] cpufreq: stop checking for cpufreq_driver being present in cpufreq_cpu

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Date:	Tue, 12 Jan 2016 16:47:29 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Juri Lelli <juri.lelli@....com>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	peterz@...radead.org, rjw@...ysocki.net, mturquette@...libre.com,
	steve.muckle@...aro.org, vincent.guittot@...aro.org,
	morten.rasmussen@....com, dietmar.eggemann@....com
Subject: Re: [RFC PATCH 17/19] cpufreq: stop checking for cpufreq_driver
 being present in cpufreq_cpu_get

On 11-01-16, 17:35, Juri Lelli wrote:
> After cpufreq_driver_lock() is acquired in cpufreq_cpu_get() we are sure
> we can't race with cpufreq_policy_free() (which is in the path that ends
> up removing cpufreq_driver). We can thus safely remove check for
> cpufreq_driver being present (which is a leftover from commit
> 6eed9404ab3c ("cpufreq: Use rwsem for protecting critical sections")).
> 
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Viresh Kumar <viresh.kumar@...aro.org>
> Signed-off-by: Juri Lelli <juri.lelli@....com>
> ---
>  drivers/cpufreq/cpufreq.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 797bfae..6c9bef7 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -282,15 +282,15 @@ struct cpufreq_policy *cpufreq_cpu_get(unsigned int cpu)
>  	if (WARN_ON(cpu >= nr_cpu_ids))
>  		return NULL;
>  
> -	/* get the cpufreq driver */
>  	read_lock_irqsave(&cpufreq_driver_lock, flags);
>  
> -	if (cpufreq_driver) {
> -		/* get the CPU */
> -		policy = cpufreq_cpu_get_raw(cpu);
> -		if (policy)
> -			kobject_get(&policy->kobj);
> -	}
> +	/*
> +	 * If we get a policy, cpufreq_policy_free() didn't
> +	 * yet run.
> +	 */
> +	policy = cpufreq_cpu_get_raw(cpu);
> +	if (policy)
> +		kobject_get(&policy->kobj);
>  
>  	read_unlock_irqrestore(&cpufreq_driver_lock, flags);

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

-- 
viresh