linux-kernel - Re: [cpuops cmpxchg double V2 1/4] Generic support for this_cpu_cmpxchg

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Date:	Fri, 25 Feb 2011 15:09:26 +0200
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Tejun Heo <tj@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Christoph Lameter <cl@...ux.com>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [cpuops cmpxchg double V2 1/4] Generic support for this_cpu_cmpxchg_double

On Fri, Jan 21, 2011 at 09:13:41AM -0800, H. Peter Anvin wrote:
>>> We could do cmpxchg with a structure... the problem with a lon int
>>> type is that Cristoph ran into bugs with __int128 on 64 bits.

On 01/21/2011 09:19 AM, Tejun Heo wrote:
>> But, IIRC, the problem with int128 was with passing it as parameter
>> and return value. We don't have to do that. We'll be just using it
>> as a data storage / container type. Or even that is broken?

On 1/24/11 8:01 AM, H. Peter Anvin wrote:
> Well, part of the point was to pass in registers.
>
> No idea on the data storage type.

Ping? The current situation is that we're unable to merge a perfectly 
good SLUB performance optimization because we can't seem to agree on the 
this_cpu_cmpxchg_double() API.

			Pekka
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