Cooperative Threads and Preemptive Computations

A two-level model for reactive systems programming is introduced in which threads linked to the same scheduler are run cooperatively and have the possibility to escape from the scheduler control to run preemptively. We present a type and effect system to enforce a logical separation of the memory which ensures that, when running in preemptive mode, threads do not interfere with those running in cooperative mode. Thus, the atomicity property at the basis of the cooperative model is preserved.