Re: [RFT] [SPARC] Emulate cmpxchg like parisc
On Sun, May 27, 2007 at 07:49:21PM -0700, David Miller wrote:
> From: Martin Habets <errandir_news@mph.eclipse.co.uk>
> Date: Mon, 28 May 2007 01:07:46 +0100
>
> > On Sat, May 26, 2007 at 03:59:21PM -0700, David Miller wrote:
> > > Alternatively we can have a KCONFIG variable with reversed
> > > logic, like "EMULATED_CMPXCHG" which only the atomically
> > > challenged platforms need to set.
> >
> > Like this idea, but if we're not going to build DRM I see no
> > point adding the cmpxchg emulation to sparc32. Maybe "NOARCH_CMPXCHG"
> > would be better?
>
> It is likely that we are going to have generic users of cmpxchg() in
> the kernel in the future (I think the -rt patch set has some which are
> hard to get rid of) at which point we'd probably put the emulated
> cmpxchg() in there anyways.
>
Yeah, David Howells wanted to use cmpxchg in his work struct patch, but
had to not because not everyone implements it.
>From what I can tell, very few arches actually have CAS, and others
emulate it with LL/SC type implementations.
Cheers,
Kyle
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