@Override
    public void uncaughtException(Thread t, Throwable e) {
      LOG.error("Uncaught exception from " + t.getName() + ": " + e.getMessage());
      error = e;
    }
counter = 0;
Thread1 counter=1, lock, wait 3s, check counter(should be 2), counter=3, unlock
Thread2 counter=2, lock (and block), inc counter, should be 4
ql/src/test/org/apache/hadoop/hive/metastore/txn/TestTxnHandler.java