public Object remove(RegionEntry entry) {
      Object retVal = map.remove(entry);
      if (retVal != null) {
        atomicUpdater.addAndGet(this,
            retVal instanceof Collection ? -((Collection) retVal).size() : -1);
      }
      return retVal;
    }
We do NOT use any locks here as every remove is for a RegionEntry which is locked before
coming here. No two threads can be entering in this method together for a RegionEntry.
geode-core/src/main/java/org/apache/geode/cache/query/internal/index/AbstractIndex.java