private void basicFree(long addr, int idx,
      AtomicReferenceArray<OffHeapStoredObjectAddressStack> freeLists) {
    OffHeapStoredObjectAddressStack clq = freeLists.get(idx);
    if (clq != null) {
      clq.offer(addr);
    } else {
      clq = createFreeListForEmptySlot(freeLists, idx);
      clq.offer(addr);
      if (!freeLists.compareAndSet(idx, null, clq)) {
        clq = freeLists.get(idx);
        clq.offer(addr);
      }
    }
  }
Used by the FreeListManager to easily search its ConcurrentSkipListSet. This is not a real
OffHeapStoredObject but only used for searching.
geode-core/src/main/java/org/apache/geode/internal/offheap/FreeListManager.java