docs: public void registerThread(StoppableThread thread)
    {
      if (tc.isEntryEnabled())
        SibTr.entry(tc, "registerThread", thread);
        
      synchronized (this)
      {
        _threadCache.add(thread);
      } 
      
      if (tc.isEntryEnabled())
        SibTr.exit(tc, "registerThread");   
    }