Since the two threads have their own private address space, they can’t share variables and thus the only way to share data is through messages.

Are there any pros/cons of using this message passing model regarding speed and utilization?

No explicit lock is required for mutual exclusion as there is no shared resource in the message passing paradigm

Technically, doesn't the message passing system itself need some kind of mutex though? Internally?

I think synchronization is done in the form of blocking calls to send/receive and barriers as opposed to mutexes. There is no need for mutexes as there are no shared data.

@jasonalouda, we can be more selective which data we are sharing between threads instead of instantiating everything that can be shared between threads.