output: #fixed code
                                  @Override
      protected void releaseSub() {
          if (rpcClient != null) {
              try {
                  rpcClient.close();
              } catch (final Exception ex) {
                  LOGGER.error("Attempt to close RPC client failed", ex);
              }
          }
          rpcClient = null;
      }
input: #vulnerable code 
                                  @Override
      protected void releaseSub() {
          if (transceiver != null) {
              try {
                  transceiver.close();
              } catch (final IOException ioe) {
                  LOGGER.error("Attempt to clean up Avro transceiver failed", ioe);
              }
          }
          client = null;
      } 
                              #location 5 
                              #vulnerability type THREAD_SAFETY_VIOLATION