in src/main/java/org/apache/sling/jcr/jackrabbit/base/security/PrincipalProviderTracker.java [117:126]
private void addProvider(PrincipalProvider provider,ServiceReference reference){
String providerName = getProviderName(provider,reference);
if(providers.containsKey(providerName)){
log.warn("Provider with name {} is already registered. PrincipalProvider {} " +
"would not be registered",providerName,reference);
return;
}
providers.put(providerName,provider);
refToNameMapping.put(reference,providerName);
}