private void doSerialThread(Runnable command) {
    stats.incNumSerialThreads(1);
    try {
      ConnectionTable.threadWantsSharedResources();
      runUntilShutdown(command);
    } finally {
      ConnectionTable.releaseThreadsSockets();
      stats.incNumSerialThreads(-1);
    }
  }
returns the serialThread's queue if throttling is being used, null if not
geode-core/src/main/java/org/apache/geode/distributed/internal/ClusterOperationExecutors.java