[pypy-dev] Easy way to get access to cmpxchg?

It'd be nice to be able to do something like this in rpython: compare_and_swap(foo.bar, oldval, newval) Or basically the cmpxchg. How hard would it be to get this in? Timothy -- "One of the main causes of the fall of the Roman Empire was that-lacking zero-they had no way to indicate successful termination of their C programs." (Robert Firth)