Notation coh := LockCoh.Definition server_send_safe (this n : nid)
           (d : dstatelet) (msg : seq nat) :=
  HServ this n /\
  exists (C : coh d), prec (getSt_server C) n msg.

Lemma server_step_def this to d msg : server_send_safe this to d msg <-> exists b pf, @server_step this to d msg pf = Some b.