Andrew Haley writes:
> Phil Endecott writes:
> > Dear Experts,
> >
> > I believe that ARM's swap instruction can be used to implement the
> > __sync_lock_test_and_set builtin, yet as far as I can see it is not
> > implemented. Can anyone please confirm if (a) it is implemented but
> > I'm doing something wrong, or (b) there's some reason why it can't be
> > done? FWIW here is some asm that I am currently using for this:
> >
> > asm volatile ("swp\t%0, %1, [%2]"
> > :"=r" (oldval)
> > :"r" (newval),
> > "r" (&mem)
> > :"memory");
>
> Looks fine to me.
I forgot: SWP is deprecated on ARM. Use LDREX and STREX instead.
See http://lkml.org/lkml/2006/12/6/180
Andrew.
