linux-kernel - Re: [PATCH 1/1] mm: Prevent dereferencing non-allocated per

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Message-ID: <Pine.LNX.4.64.0711271522050.6713@schroedinger.engr.sgi.com>
Date:	Tue, 27 Nov 2007 15:22:56 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	andi@...stfloor.org, travis@....com, ak@...e.de,
	pageexec@...email.hu, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] mm: Prevent dereferencing non-allocated per_cpu
 variables

On Tue, 27 Nov 2007, Andrew Morton wrote:

> The prefetch however might still need some work - we can indeed do
> prefetch() against a not-possible CPU's memory here.  And I do recall that
> 4-5 years ago we did have a CPU (one of mine, iirc) which would oops when
> prefetching from a bad address.  I forget what the conclusion was on that
> matter.
> 
> If we do want to fix the prefetch-from-outer-space then we should be using
> cpu_isset(cpu, *cpumask) here rather than cpu_possible().

Generally the prefetch things have turned out to be not that useful. How 
about dropping the prefetch? I kept it because it was there.

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