Proof using.
intros.
find_apply_lem_hyp Nth_something_at_head.
break_exists_name holder. break_exists.
exists (Client holder).
remember H0 as Hlbs; clear HeqHlbs.
invcs H0.
find_eapply_lem_hyp head_grant_state_unlock; eauto.
intuition.
- (* eventually the Locked message is delivered, after which this is
the same as the next case. *)
eapply eventually_trans
with (inv := lb_step_execution lb_step_async /\_
weak_fairness
(lb_step_async(labeled_multi_params := LockServ_LabeledParams))
Silent)
(P := now (occurred (MsgLocked holder))).
all:unfold and_tl in *; intuition.
+ eauto using lb_step_execution_invar.
+ eauto using weak_fairness_invar.
+ (* need `now (MsgLocked i) -> held i = true`, then identical to next case below. *)
find_apply_lem_hyp MsgLocked_held; eauto.
destruct s.
simpl in *.
eauto using lb_step_execution_invar, weak_fairness_invar,
E_next, held_eventually_Unlock.
+ apply Locked_in_network_eventually_MsgLocked; auto.
- eauto using held_eventually_Unlock.
- eauto using E0.
Qed.

Lemma eventually_MsgUnlock :
forall n c s,
event_step_star step_async step_async_init (hd s) ->
lb_step_execution lb_step_async s ->
weak_fairness lb_step_async label_silent s ->
Nth (queue (nwState (evt_a (hd s)) Server)) (S n) c ->
eventually (now (occurred MsgUnlock)) s.