Notation schedule := (seq nat).(** Internal steps are just thread coresteps or resume steps or start steps,
          they mimic fine-grained internal steps *)
      Definition internal_step {tid} {tp} m (cnt: containsThread tp tid)
                 (Hcomp: mem_compatible tp m) tp' m' :=
      (exists ev, threadStep cnt Hcomp tp' m' ev) \/
      (resume_thread m cnt tp' /\ m = m') \/
      (start_thread m cnt tp' m').

Lemma containsThread_internal_execution : forall U tp m tp' m' i (Hexec: internal_execution U tp m tp' m'), containsThread tp i -> containsThread tp' i.