boolean containsKey(final Object key, final int hash) {
      if (count != 0) { // read-volatile
        // Geode change to acquire the read lock on list updates
        final ReentrantReadWriteLock.ReadLock listLock = listUpdateLock.readLock();
        listLock.lock();
        HashEntry<K, V> e = getFirst(hash);
        try {
          while (e != null) {
            if (e.getEntryHash() == hash && equalityKeyCompare(key, e)) {
              return true;
            }
            e = e.getNextEntry();
          }
        } finally {
          listLock.unlock();
        }
      }
      return false;
    }
Added for GemFire since it stores some keys inline.
geode-core/src/main/java/org/apache/geode/internal/util/concurrent/CustomEntryConcurrentHashMap.java