(** A location that the machine has no access to (i.e. the permission is empty in all its resources) *)
Inductive deadLocation tp m b ofs : Prop :=
| Dead: forall
(Hvalid: Mem.valid_block m b)
(Hthreads: forall i (cnti: containsThread tp i),
(getThreadR cnti).1 !! b ofs = None /\ (getThreadR cnti).2 !! b ofs = None)
(Hresources: forall l pmap,
lockRes tp l = Some pmap ->
pmap.1 !! b ofs = None /\ pmap.2 !! b ofs = None),
deadLocation tp m b ofs.

Lemma step_deadLocation:
forall U U' tr tp m tr' tp' m' b ofs
(Hdead: deadLocation tp m b ofs)
(Hstep: MachStep (U, tr, tp) m (U',tr ++ tr', tp') m'),
deadLocation tp' m' b ofs.