MODULE main
VAR
  turn : 1..2;
  p : process user(turn, 1, 2); 
  q : process user(turn, 2, 1); 
ASSIGN
  init(turn) := 1;
SPEC -- PROGRESS
  AG (p.state = local -> EF p.state = enter )
SPEC -- MUTUAL EXCLUSION
  AG !(p.state = critical & q.state = critical)
SPEC -- DEADLOCK
  AG (p.state = enter -> AF (p.state = critical | q.state = critical))
SPEC -- INDIVIDUAL STARVATION
  AG (p.state = enter -> AF p.state = critical)

MODULE user(turnloc, myproc, otherproc)
VAR
  state : {local,enter,critical,exit};
ASSIGN
  init(state) := local;
  next(state) :=
    case
      state = local : {local, enter};
      state = enter & turnloc = myproc : critical;
      state = critical : exit;
      state = exit : local;
      TRUE : state;
    esac;
  next(turnloc) :=
    case
      state = exit : otherproc;
      TRUE : turnloc;
    esac;
FAIRNESS
  running