Re: [LAD] a *simple* ring buffer, comments pls?

On Wed, Jul 13, 2011 at 9:46 AM, Olivier Guilyardi <list(a)samalyse.com> wrote: > On 07/13/2011 11:09 AM, Tim Blechmann wrote: > >> in fact, testing is not the best approach for verifying lock-free data >> structures: an implementation may work for years, if a certain condition is >> never triggered. the only reasonable way to ensure the correctness is a formal >> proof. unfortunately, most publications assume a sequencially consistent memory >> model and sometimes even avoid dealing with the ABA problem. > > To me, testing on real devices is needed, it's a pragmatic approach. But I agree > it doesn't solve the entire problem.

i don't see why this is needed. its trivial to demonstrate on a piece of paper that in a system with weak memory ordering constraints, absence of a memory barrier is incorrect for any code with coupled data values (e.g. a read index and read data). it doesn't matter if this doesn't happen very often. you don't need a simulator of any given CPU+memory model - its just demonstrably incorrect.