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Date: Fri, 24 Dec 2010 22:11:06 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Christoph Lameter <cl@...ux.com>
CC: Tejun Heo <tj@...nel.org>, akpm@...ux-foundation.org,
Pekka Enberg <penberg@...helsinki.fi>,
linux-kernel@...r.kernel.org,
Eric Dumazet <eric.dumazet@...il.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [cpuops cmpxchg double V1 1/4] Generic support for this_cpu_cmpxchg_double
On 12/24/2010 08:53 PM, Christoph Lameter wrote:
> On Thu, 23 Dec 2010, H. Peter Anvin wrote:
>
>> There are two return registers; two machine registers can be returned in
>> registers. [u]int128 is poorly implemented in a lot of gcc versions,
>> since it really hasn't been exercised. However, two-word structures
>> should work. I do not believe a two-word *array* works, though.
>
> Oh gosh. So we would be using a tight corner case for gcc that may only
> work with certain versions of gcc? Note that the current version does only
> return a boolean. There is no need for returning double words. I'd be
> happy if we could *pass* double words.
>
A structure is not a corner case; a uint128 would be.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
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