From: Kaz Kylheku <firstname.lastname@example.org>
Subject: Re: [libc-alpha] Re: PATCH: Fix ll/sc for mips
Date: Thu, 31 Jan 2002 20:02:25 -0800 (PST)
> On Fri, 1 Feb 2002, Hiroyuki Machida wrote:
> > Please note that "sc" may fail even if nobody write the
> > variable. (See P.211 "8.4.2 Load-Linked/Sotre-Conditional" of "See
> > MIPS RUN" for more detail.)
> > So, after your patch applied, compare_and_swap() may fail, even if
> > *p is equal to oldval.
> I can't think of anything that will break because of this, as long
> as the compare_and_swap eventually succeeds on some subsequent trial.
> If the atomic operation has to abort for some reason other than *p being
> unequal to oldval, that should be cool.
I mean that this patch breaks the spec of compare_and_swap().
In most case, this patch may works as Kaz said. If this patch have
no side-effect to any application, it's ok to apply the patch. But
we can't know how to use compare_and_swap() in all aplications in a
whole world. So we have to follow the spec.