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

Russell King
2006-12-08T16:32:13Z

On Fri, Dec 08, 2006 at 08:06:23AM -0800, Christoph Lameter wrote:
> 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?

You're advocating cmpxchg is adopted by all architectures. It isn't
available on many architectures, and those which it can be requires
unnecessarily complicated coding.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/