(* MachStep that doesn't change the schedule, Reduces the set of valid schedules... *)
Inductive has_unique_running tp:Prop :=
| HasUniqueRun i (cnti : ThreadPool.containsThread tp i) q:
ThreadPool.getThreadC cnti = Krun q ->
has_unique_running tp.

Lemma schedPeek_Skip:
forall U tid
( HschedN : schedPeek U = Some tid)
( HschedS : schedSkip U = U),
False.