static volatile bool ping_pauseAll;
static int ping_sleep = 100; // poll pauseAll flag every 100
static volatile bool ping_anyActions;
static Map<Thread, O> ping_actions = synchroMap(new WeakHashMap);

// always returns true
static bool ping() ctex {
  if (ping_pauseAll && !isAWTThread()) {
    do
      Thread.sleep(ping_sleep);
    while (ping_pauseAll);
  }
  
  if (ping_anyActions) {
    O action;
    synchronized(mc()) {
      action = ping_actions.get(currentThread());
      if (action instanceof Runnable)
        ping_actions.remove(currentThread());
      if (ping_actions.isEmpty()) ping_anyActions = false;
    }
    
    if (action instanceof Runnable)
      ((Runnable) action).run();
    else if (eq(action, "cancelled"))
      fail("Thread cancelled.");
  }
  
  true;
}