Reentrant

The global interpreter lock of the embedded scripting engine is not reentrant.

Global variables must not be altered by reentrant code.

Actor serialization […]might even lead to possible deadlock. To mitigate that risk, there's an important exception to actor serialization: actors are reentrant. This means that when an actor itself says await, then while the actor's code is waiting, its members can be accessed from outside the actor using await.