(* We could also consider an alpha-renaming axiom, although this may be unnecessary. *)

Lemma lock_inv_share_join : forall sh1 sh2 sh v R (Hsh1 : readable_share sh1) (Hsh2 : readable_share sh2)
(Hjoin : sepalg.join sh1 sh2 sh),
lock_inv sh1 v R * lock_inv sh2 v R = lock_inv sh v R.