Function service_read_only 

pub async fn service_read_only<F, R>(service: F) -> R
where
    F: FnOnce() -> R,

Run one synchronous service operation at a settled ReadOnly point.

The closure runs on the simulator thread from inside the simulator’s ReadOnly callback, after pending writes and combinational logic have reached a fixed point. It may communicate with other OS threads through ordinary synchronization primitives. While it is waiting, the simulator callback cannot return, so simulation time remains frozen. Returning the closure’s value releases the simulator to advance normally.

Blocking and cancellation

Any wait in service must be bounded by wall-clock time or use a cooperative cancellation signal. A simulation-time timeout cannot fire while this function holds ReadOnly, and RustDV cannot forcibly recover an arbitrary blocking closure. An unbounded wait will therefore wedge the simulation.

This is opt-in and transport-neutral: RustDV does not create a worker, scheduler, or server. A testbench supplies both the service closure and any channels or synchronization it needs.