After my last discussion about getting some multi-threading primitives, I took a look at how locks are implemented in PyPy. PyPy currently uses OS level mutexes...which is okay for most uses, but in my case, I need super fast spinlocks, and for that I need a CAS operation. What I'm looking for is a bit of direction on how to go about implementing this function (shown in C syntax):
int cas(*expected, *new, **location) This function looks at the contents of the data pointed at by **location. If the contents == *expected, the contents are replaced with *new and the function returns true. Otherwise the function returns false. There are several issues I see with implementing this in python: 1) **location must be pointer to a object pointer, is this even possible in PyPy? 2) I'd rather not call an FFI C function for this, when this entire function could be inlined with just a few lines of assembly (CAS is a single instruction on x86). So could this be created as a C function that is simply inserted into the generated C code, so that GCC could inline it at will? I'm just brainstorming here. No matter how you dice it, CAS is pretty much a prerequisite to any sort of multi-threaded programming these days. That is unless you want to spend thousands of clock cycles in context switches. 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) _______________________________________________ pypy-dev@codespeak.net http://codespeak.net/mailman/listinfo/pypy-dev
