From Karen's code review comments:

14. ClassLoaderData::packages()
  It is not clear to me why there is an OrderAccess::storestore() - that is used
  for store X; OA::storestore; store Y to ensure stores don't float above
  I don't see any order dependencies here?
  For modules(), I could see wanting to be sure that the temp was updated
  before the _modules was set to temp