[ramy_d]

  two process working with a shared actor share that state

I think this is where I disagree. They may share an actor but the state of the actor belongs to the actor. To say they share it implies they can always change it independently but that's not the case. Actors don't trample on each other's internal states. For example a simple mutex semaphore pattern fixes your race condition.

[lmm]

> They may share an actor but the state of the actor belongs to the actor. To say they share it implies they can always change it independently but that's not the case. Actors don't trample on each other's internal states. For example a simple mutex semaphore pattern fixes your race condition.

The actor's state is shared in the sense that both processes can change it in ways that are visible to each other. The actor can control access to it, but unless the actor never changes state in response to messages (in which case why bother with actors at all?) there's still something that changes. Constrained state is still state.