@Override
    void inMemoryCompaction() {
      try {
        super.inMemoryCompaction();
      } finally {
        try {
          inMemoryCompactionEndCyclicBarrier.await();
        } catch (Throwable e) {
          throw new RuntimeException(e);
        }

      }
    }
Only the writeAgain thread completes, in memory compact thread would exit,because we
expect that in memory compact executing only once.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHStore.java