@Override
    public void await() throws IOException {
      try {
        latch.await();
      } catch (InterruptedException e) {
        throw (InterruptedIOException) new InterruptedIOException().initCause(e);
      }

      if (exception != null) {
        throw exception;
      }
    }
Returns the singleton latch which does nothing.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/procedure/ProcedurePrepareLatch.java