output: #fixed code
                                  @Override
      public boolean tryAdvance(Consumer<? super E> action) {
          Objects.requireNonNull(action);
          if (exhausted)
              return false;
          LinkedBlockingDeque<E> q = queue;
          ReentrantLock lock = queueLock;
          Object p = current;
          E e = null;
          lock.lock();
          try {
              if ((p != null && p != getNextNode(p)) || (p = getQueueFirst(q)) != null) {
                  e = getNodeItem(p);
                  p = getNextNode(p);
              }
          } finally {
              lock.unlock();
          }
          exhausted = ((current = p) == null);
          if (e == null)
              return false;
          action.accept(e);
          return true;
      }
input: #vulnerable code 
                                  @Override
      public boolean tryAdvance(Consumer<? super E> action) {
          Objects.requireNonNull(action);
          LinkedBlockingDeque<E> q = queue;
          ReentrantLock lock = queueLock;
          if (!exhausted) {
              E e = null;
              lock.lock();
              try {
                  if (current == null) {
                      current = getQueueFirst(q);
                  }
                  while (current != null) {
                      e = getNodeItem(current);
                      current = getNextNode(current);
                      if (e != null) {
                          break;
                      }
                  }
              } finally {
                  lock.unlock();
              }
              if (current == null) {
                  exhausted = true;
              }
              if (e != null) {
                  action.accept(e);
                  return true;
              }
          }
          return false;
      } 
                              #location 15 
                              #vulnerability type THREAD_SAFETY_VIOLATION