in src/main/java/org/apache/sling/jcr/jackrabbit/base/security/PrincipalProviderTracker.java [128:133]
private void reloadProviders() {
PrincipalProvider[] providerArray = providers.values().toArray(new PrincipalProvider[providers.size()]);
synchronized (this){
this.providerArray = providerArray;
}
}