void interruptIfNecessary() {
    lock.writeLock().lock();
    try {
      for (FlushHandler flushHandler : flushHandlers) {
        if (flushHandler != null) {
          flushHandler.interrupt();
        }
      }
    } finally {
      lock.writeLock().unlock();
    }
  }
Only interrupt once it's done with a run through the work loop.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/MemStoreFlusher.java