In one of our client deployments on WebLogic 9.2 we observed JackRabbit sessions going stale in a load test. This was observed against release 1.6.1 (to which we migrated due to concurrency related issues
JCR-2081 and JCR-2237). Same effect with 2.0.0.
I could finally reproduce this issue locally. And it seems to boil down to WLS invoking the sequence of <prepare> ... <release> ... <commit> on one XA session from multiple threads, as it seems breaking assumptions of the thread-bound java.util.concurrent-RWLock based DefaultISMLocking class.
Effectively the setActiveXid(..) method on DefaultISMLocking$RWLock fails as the old active XID was not yet cleared. With the result of more and more sessions deadlocking in below's invocation stack.