Re: [libc-alpha] Re: PATCH: Fix ll/sc for mips

["H . J . Lu" <hjl at lucon dot org>]

On Thu, Jan 31, 2002 at 08:02:25PM -0800, Kaz Kylheku wrote:
> 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.

Maybe we should document it in glibc, something like

compare_and_swap compares the contents of a variable with an old value.
If the values are equal and a new value is stored in the variable
atomically, 1 is returned; otherwise, 1 is returned.


H.J.