@Override
  public void clear() {
    fullyLock();
    try {
      for (Node<E> p, h = head; (p = h.next) != null; h = p) {
        h.next = h;
        p.item = null;
      }
      head = last;
      // assert head.item == null && head.next == null;
      if (count.getAndSet(0) >= capacity) // GEMFIRE changed == to >=
      {
        notFull.signal();
      }
    } finally {
      fullyUnlock();
    }
  }
Atomically removes all of the elements from this queue. The queue will be empty after this call
returns.
geode-core/src/main/java/org/apache/geode/internal/cache/ForceableLinkedBlockingQueue.java