Date: Fri, 22 Jun 2012 16:10:30 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: shuox.liu@intel.com
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Brown, Len" <len.brown@intel.com>,
        "Zhang, Yanmin" <yanmin.zhang@intel.com>,
        "Andrew J. Schorr" <aschorr@telemetry-investments.com>,
        Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Subject: Re: [PATCH] cpuidle: move field disable from per-driver to per-cpu
Message-Id: <20120622161030.da016ccf.akpm@linux-foundation.org>
In-Reply-To: <4FD95200.1090701@intel.com>
References: <4FD95200.1090701@intel.com>
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On Thu, 14 Jun 2012 10:52:48 +0800
ShuoX Liu <shuox.liu@intel.com> wrote:

> From: ShuoX Liu <shuox.liu@intel.com>
> 
> Andrew J.Schorr raises a question. When he changes the disable setting
> on a single CPU, it affects all the other CPUs. Basically, currently,
> the disable field is per-driver instead of per-cpu. All the C states of
> the same driver are shared by all CPU in the same machine.
> 
> Below patch changes field disable to per-cpu, so we could set this
> separately for each cpu.
> 
> ...
>
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -34,6 +34,7 @@ struct cpuidle_driver;
>  struct cpuidle_state_usage {
>  	void		*driver_data;
>  
> +	unsigned long long	disable;

hrmpf.  We're using 64 bits for this where one bit would do, afaict
because the magic macros in drivers/cpuidle/sysfs.c are using %llu.

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