linux-kernel - Re: [PATCH] Cpufreq: Acquire read lock in the cpufreq_policy

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Date:	Wed, 11 Sep 2013 13:39:33 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	tianyu.lan@...el.com
CC:	rjw@...k.pl, viresh.kumar@...aro.org, cpufreq@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Cpufreq: Acquire read lock in the cpufreq_policy_restore()
 rather than write lock

On 09/11/2013 12:35 PM, tianyu.lan@...el.com wrote:
> From: Lan Tianyu <tianyu.lan@...el.com>
> 
> In the cpufreq_policy_restore(), policy before system suspend is read from
> from percpu's cpufreq_cpu_data_fallback. It's read operation rather than
> write operation. So convert write lock to read lock
> 
> Signed-off-by: Lan Tianyu <tianyu.lan@...el.com>

Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>

I noticed it too yesterday, while looking at something else. Thanks for
fixing this!

> ---
>  drivers/cpufreq/cpufreq.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 81ceea6..b762f9b 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -912,11 +912,11 @@ static struct cpufreq_policy *cpufreq_policy_restore(unsigned int cpu)
>  	struct cpufreq_policy *policy;
>  	unsigned long flags;
> 
> -	write_lock_irqsave(&cpufreq_driver_lock, flags);
> +	read_lock_irqsave(&cpufreq_driver_lock, flags);
> 
>  	policy = per_cpu(cpufreq_cpu_data_fallback, cpu);
> 
> -	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
> +	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
> 
>  	return policy;
>  }
> 
 
Regards,
Srivatsa S. Bhat

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