I have encountered another problem during timeout induced rollback scenario. When the thread rolls back the transaction immediately after the reaper they both end in ControlWrapper#rollback method. This should be synchronized: if it is not both threads may call TransactionImple#rollback method which is not expected and leads to IllegalStateException error. In synchronized scenario second thread in ControlWrapper#rollback method see that the TransactionImple has already been disassociated with the thread and throws TRANSACTION_ROLLEDBACK exception which is expected.