To: Matthew Wilcox <matthew@wil.cx>
Cc: Alex Chiang <achiang@hp.com>, linux-kernel@vger.kernel.org,
       linux-arch@vger.kernel.org, linux-acpi@vger.kernel.org
Subject: Re: [PATCH 01/14] Introduce cpu_enabled_map and friends
From: Andi Kleen <andi@firstfloor.org>
References: <20080715023344.2528.1836.stgit@blender.achiang>
	<20080715023349.2528.9423.stgit@blender.achiang>
	<20080715031512.GF14894@parisc-linux.org>
Date: Tue, 15 Jul 2008 12:03:27 +0200
In-Reply-To: <20080715031512.GF14894@parisc-linux.org> (Matthew Wilcox's message of "Mon, 14 Jul 2008 21:15:12 -0600")
Message-ID: <87wsjnxy4w.fsf@basil.nowhere.org>
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Matthew Wilcox <matthew@wil.cx> writes:
>
> I don't understand why we want to know about these CPUs.  Surely they
> should be 'possible', but not 'present'?  What useful thing can Linux do
> with them?

He explained it in the intro, near the end (I nearly complained about
this too when I hadn't finished reading it completely :):

|The big picture implication is that we can allow userspace
|to interact with disabled CPUs. In this particular example,
|we provide a knob that lets a sysadmin schedule any present
|CPU for firmware deconfiguration or enablement.

The reason sounds pretty exotic, but ok.

-Andi
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