output: #fixed code
                                @SuppressWarnings("unchecked")
    @Override
    public void run() {
      try {
        // restart the clock.
        synchronized (callLock) {
          super.run();
          // pre-fetch one more result, for performance reasons.
          adapter.request(1);
          if (rowObserver instanceof ClientResponseObserver) {
            ((ClientResponseObserver<ReadRowsRequest, FlatRow>) rowObserver).beforeStart(adapter);
          }
          lastResponseMs = clock.currentTimeMillis();
        }
      } catch (Exception e) {
        setException(e);
      }
    }
input: #vulnerable code 
                                @SuppressWarnings("unchecked")
    @Override
    public void run() {
      try {
        // restart the clock.
        this.rowMerger = new RowMerger(rowObserver);
        adapter = new CallToStreamObserverAdapter();
        synchronized (callLock) {
          super.run();
          // pre-fetch one more result, for performance reasons.
          adapter.request(1);
          if (rowObserver instanceof ClientResponseObserver) {
            ((ClientResponseObserver<ReadRowsRequest, FlatRow>) rowObserver).beforeStart(adapter);
          }
          lastResponseMs = clock.currentTimeMillis();
        }
      } catch (Exception e) {
        setException(e);
      }
    } 
                              #location 7 
                              #vulnerability type THREAD_SAFETY_VIOLATION