linux-kernel - Re: [rfc] optimise unlock

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Date:	Sun, 13 May 2007 05:39:03 +0100 (BST)
From:	Hugh Dickins <hugh@...itas.com>
To:	Nick Piggin <npiggin@...e.de>
cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linux-arch@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [rfc] optimise unlock_page

On Sun, 13 May 2007, Nick Piggin wrote:
> On Fri, May 11, 2007 at 02:15:03PM +0100, Hugh Dickins wrote:
> 
> > Hmm, well, I think that's fairly horrid, and would it even be
> > guaranteed to work on all architectures?  Playing with one char
> > of an unsigned long in one way, while playing with the whole of
> > the unsigned long in another way (bitops) sounds very dodgy to me.
> 
> Of course not, but they can just use a regular atomic word sized
> bitop. The problem with i386 is that its atomic ops also imply
> memory barriers that you obviously don't need on unlock.

But is it even a valid procedure on i386?

Hugh
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