NodeSubregistry getOrCreateSubregistry(final String key) {
for (; ; ) {
final Map<String, NodeSubregistry> snapshot = childrenUpdater.get(this);
final NodeSubregistry subregistry = snapshot.get(key);
if (subregistry != null) {
return subregistry;
} else {
final NodeSubregistry newRegistry = new NodeSubregistry(key, this);
final NodeSubregistry appearing =
childrenUpdater.putAtomic(this, key, newRegistry, snapshot);
if (appearing == null) {
return newRegistry;
} else if (appearing != newRegistry) {
// someone else added one
return appearing;
}
// otherwise, retry the loop because the map changed
}
}
}
