[toast0]

> But other than that, doesn't it all boil down to the same thing?

> Actors serialize access/modification of state through ordered messages. Locks serialize access/modification of state through acquiring the lock. And when you have complex access or modification patterns in your code, the actor model doesn't help all that much. To me it's like each message acquires the lock to the actor state.

I think yes and no. The big thing for me is it's easy to mess up locks. I've locked one thing and modified another, or read outside the lock, then locked to write, and the value changed. I also just did something similar except there's a mix of locks and atomics (kernel side of pthread umutexes needs to use atomics to mark the mutex as contested).

Actors serialization of work via mailbox (and its implicit locking) makes it hard to make basic mistakes. Of course, complex flows are still complex.

We're definitely in agreement on re-entrant actors. On the plus side, if it doesn't work well, I expect they'll change course.