linux-kernel - Re: [PATCH] cpufreq: Lock CPU online/offline in cpufreq_register

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Date:	Thu, 30 Jul 2015 11:18:01 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Russell King <linux@....linux.org.co.uk>
Subject: Re: [PATCH] cpufreq: Lock CPU online/offline in
 cpufreq_register_driver()

On 30-07-15, 01:45, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> To protect against races with concurrent CPU online/offline, call
> get_online_cpus() before registering a cpufreq driver.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/cpufreq/cpufreq.c |   13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> Index: linux-pm/drivers/cpufreq/cpufreq.c
> ===================================================================
> --- linux-pm.orig/drivers/cpufreq/cpufreq.c
> +++ linux-pm/drivers/cpufreq/cpufreq.c
> @@ -2471,10 +2471,14 @@ int cpufreq_register_driver(struct cpufr
>  
>  	pr_debug("trying to register driver %s\n", driver_data->name);
>  
> +	/* Protect against concurrent CPU online/offline. */
> +	get_online_cpus();
> +
>  	write_lock_irqsave(&cpufreq_driver_lock, flags);
>  	if (cpufreq_driver) {
>  		write_unlock_irqrestore(&cpufreq_driver_lock, flags);
> -		return -EEXIST;
> +		ret = -EEXIST;
> +		goto out;
>  	}
>  	cpufreq_driver = driver_data;
>  	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
> @@ -2513,7 +2517,10 @@ int cpufreq_register_driver(struct cpufr
>  	register_hotcpu_notifier(&cpufreq_cpu_notifier);
>  	pr_debug("driver %s up and running\n", driver_data->name);
>  
> -	return 0;
> +out:
> +	put_online_cpus();
> +	return ret;
> +
>  err_if_unreg:
>  	subsys_interface_unregister(&cpufreq_interface);
>  err_boost_unreg:
> @@ -2523,7 +2530,7 @@ err_null_driver:
>  	write_lock_irqsave(&cpufreq_driver_lock, flags);
>  	cpufreq_driver = NULL;
>  	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
> -	return ret;
> +	goto out;
>  }
>  EXPORT_SYMBOL_GPL(cpufreq_register_driver);

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

-- 
viresh
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