Eclipselink freezes fetching data from cache

Eclipselink sometimes freezes when I try to get some data (CPU usage is 100%). While debugging the code, I can see that the java vm hangs while doing the HashMap.get (Object) operation ( here is a link to stackTrace) and I will assume it is a known concurrency issue on HashMap (see this java bug report ). In particular, I can see that the cacheKeys value for org.eclipse.persistence.internal.identitymaps.UnitOfWorkIdentityMap is a HashMap instance and not a ConcurrentHashMap. Could this be the reason for the hang in my code? How can I solve this?

To better explain the issue, a hang occurs when the jackson library serializes a single JPA object, specifically when serializing a loaded LAZY list of an object rendered as @ManytoMany.