interface IBlocked
{
  in void e();

  behaviour
  {
    on e:{}
  }
}

interface IAsync
{
  in void trigger();
  out void notify();

  behaviour
  {
    bool pending = false;
    on trigger:
    {
      [!pending] pending = true;
      [pending] illegal;
    }
    on inevitable:
    {
      [pending]{pending = false; notify;}
    }
  }
}

component Blocked
{
  provides IBlocked provided;

  requires IAsync required;

  behaviour
  {
    blocking on provided.e(): required.trigger();

    on required.notify(): provided.reply();
  }
}

component BlockedSystem2
{
  provides IBlocked port1;
  provides IBlocked port2;

  requires IAsync async1;
  requires IAsync async2;

  system
  {
    Blocked blocked1;
    Blocked blocked2;

    blocked1.provided <=> port1;
    blocked2.provided <=> port2;

    blocked1.required <=> async1;
    blocked2.required <=> async2;
  }
}