Date: Mon, 6 Feb 2006 02:16:39 -0800
From: Andrew Morton <akpm@osdl.org>
To: Eric Dumazet <dada1@cosmosbay.com>
Cc: bcrl@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH, V2] i386: instead of poisoning .init zone, change
 protection bits to force a fault
Message-Id: <20060206021639.2e9d9157.akpm@osdl.org>
In-Reply-To: <43E71FEC.6020506@cosmosbay.com>
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	<43DD1FDC.4080302@cosmosbay.com>
	<20060129200504.GD28400@kvack.org>
	<43DD2C15.1090800@cosmosbay.com>
	<20060204144111.7e33569f.akpm@osdl.org>
	<43E7108A.8030001@cosmosbay.com>
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Eric Dumazet <dada1@cosmosbay.com> wrote:
>
> Andrew Morton a ?crit :
> 
> > But I'm inclined to drop the whole patch - I don't see how it can detect
> > any bugs which CONFIG_DEBUG_PAGEALLOC won't find.
> > 
> 
> If CONFIG_DEBUG_PAGEALLOC is selected, does a page freed by free_page(addr); 
> guaranted not being reused later ?

No.

So with your patch, any access to the freed page will oops.  With
CONFIG_DEBUG_PAGEALLOC it'll only oops if that page is presently free.

So if enough people run with CONFIG_DEBUG_PAGEALLOC for enough time, we'll
find the same bugs.

> Anyway, the CONFIG_DEBUG_INITDATA was a temporary patch in order to track the 
> accesses to non possible cpus percpu data. So if you feel all such accesses 
> were cleaned, we can drop the patch...

I think so..
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