(*+ CSL to progress and preservation *)
(* In this file, we use the same notion of thread safety as in the rest of VST, which is defined using specifications for external functions. In the rest of VST, we derive safety of the concurrent (juicy) machine from [progress] and [preservation] of an invariant.  We give a toy version of those definitions and proofs here, simplifying greatly problems related to step indexing, external calls and spawning. *)
(* standard files distributed with Coq *)
(* local file *)
Definition interp_lock := resourcemaps.interp_lock.
Definition islock (l : nat) (R : map -> Prop) (m : map) :=
exists lock, m l = Some (inr lock) /\ interp_lock lock = R.

Lemma islock_inj : forall v R1 R2 m, islock v R1 m -> islock v R2 m -> R1 = R2.
intros v R1 R2 m [lock1 [E1 H1]] [lock2 [E2 H2]].