Upon return, the coroutine indicates a subsequent thread that the coroutine should be executed on when the coroutine is executed a subsequent time.

A controller routine receives a request from an originating routine to execute a coroutine, and executes the coroutine on an initial thread.

The controller routine receives a response back from the coroutine when the coroutine exits based upon a return statement.

The controller routine executes the coroutine the subsequent time on the subsequent thread.

The coroutine picks up execution at a line of code following the return statement.