public void expireTombstones(Map<VersionSource<?>, Long> regionGCVersions, EventID eventID,
      FilterInfo clientRouting) {
    if (!getConcurrencyChecksEnabled()) {
      return;
    }
    Set<Object> keys = null;
    if (!versionVector.containsTombstoneGCVersions(regionGCVersions)) {
      keys = cache.getTombstoneService().gcTombstones(this, regionGCVersions,
          needsTombstoneGCKeysForClients(eventID, clientRouting));
      if (keys == null) {
        // deltaGII prevented tombstone GC
        return;
      }
    }
    if (eventID != null) {
      // old members might not send an eventID
      notifyClientsOfTombstoneGC(regionGCVersions, keys, eventID, clientRouting);
    }
  }
remove any tombstones from the given member that are <= the given version

@param eventID event identifier for the GC operation
@param clientRouting routing info (if null a routing is computed)
geode-core/src/main/java/org/apache/geode/internal/cache/LocalRegion.java