linux-kernel - Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it

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Message-ID: <Pine.LNX.4.64.0612080758120.15242@schroedinger.engr.sgi.com>
Date:	Fri, 8 Dec 2006 08:06:23 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Russell King <rmk+lkml@....linux.org.uk>
cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	David Howells <dhowells@...hat.com>, torvalds@...l.org,
	akpm@...l.org, linux-arm-kernel@...ts.arm.linux.org.uk,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch
 doesn't support it

On Fri, 8 Dec 2006, Russell King wrote:

> I'm trying to suggest a better implementation for atomic ops rather
> than just bowing to this x86-centric "cmpxchg is the best, everyone
> must implement it" mentality.

cmpxchg is the simplest solution to realize many other atomic operations 
and its widely available on a wide variety of platforms. It is the most 
universal atomic instruction that I know of. Other atomic operations may 
be more efficient but certainly cmpxchg is the most universal.

Having multiple instructions with restrictions of what can be done in 
between just complicates the use and seems to be arch specific. I have not 
seen a better solution. Are you really advocating the weirdly complex 
ll/sc be adopted by other architectures?
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