Date: Mon, 7 Nov 2005 00:15:05 +0000 (GMT)
From: Hugh Dickins <hugh@veritas.com>
To: Andrew Morton <akpm@osdl.org>
cc: torvalds@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: poison struct page for ptlock
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On Sun, 6 Nov 2005, Andrew Morton wrote:
> Hugh Dickins <hugh@veritas.com> wrote:
> >
> > Suppress split ptlock on arches which may use one page for multiple page
> >  tables.  Reconsider what better to do (particularly on ppc64) later on.
> 
> But why is that a problem per-se?  A few "pagetable pages" will share the
> same lock.  Deadlocky when we take two pagetable locks?

Good point, it may not be as disastrous as I was imagining.  Certainly
deadlocky in copy_page_range and mremap move at present, but that can
be easily surmounted.  However, there is the slab lru issue too: if it's
convenient for an arch to use slab cache, I'd prefer not to make life
difficult for them.  I'll come back to this but not tonight.

Hugh
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