Date: Fri, 24 Feb 2006 12:55:39 +0000 (GMT)
From: Hugh Dickins <hugh@veritas.com>
To: Andi Kleen <ak@suse.de>
cc: Nick Piggin <nickpiggin@yahoo.com.au>, Ingo Molnar <mingo@elte.hu>,
       Arjan van de Ven <arjan@intel.linux.com>, linux-kernel@vger.kernel.org,
       akpm@osdl.org
Subject: Re: [Patch 3/3] prepopulate/cache cleared pages
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On Fri, 24 Feb 2006, Andi Kleen wrote:
> On Friday 24 February 2006 08:01, Nick Piggin wrote:
> > 
> > Yeah, as I said above, the newly allocated page is fine, it is the
> > page table pages I'm worried about.
> 
> page tables are easy because we zero them on free (as a side effect
> of all the pte_clears)

But once the page table is freed, it's likely to get used for something
else, whether for another page table or something different doesn't 
matter: this mm can no longer blindly mess with the entries within in.

Nick's point is that it's mmap_sem (or mm_users 0) guarding against
the page table being freed.

Hugh
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