They're easy to implement; terribly difficult to reason about from a correctness point of view, which is really all that matters in performant multithreaded cod

They're easy to implement; terribly difficult to reason about from a correctness point of view, which is really all that matters in performant multithreaded code. Given that it can take weeks to debug a deadlock, I am more than happy to pay the price of some boilerplate and difficult types if that helps correctness.