class SynchronizationCallbackCoordinatorImpl implements SynchronizationCallbackCoordinator {
    private int registrationThreadId;
    private int delayedCompletionHandlingStatus;

    ...

    public SynchronizationCallbackCoordinatorImpl(TransactionCoordinator transactionCoordinator) {
        ...
        registrationThreadId = Thread.currentThread().getId();
    }

    public void reset() {
        ...
        delayedCompletionHandlingStatus = Status.NO_STATUS
    }


    public void afterCompletion(int status) {
        if ( isNonRegistrationThread() ) {
            // for callbacks coming from a thread different than the one used for registration, 
            // we need to delay the completion handling
            delayedCompletionHandlingStatus = status;
        }
        else {
            // otherwise, we do the completion handling immediately
            doAfterCompletion( status );
        }
    }

    private boolean isNonRegistrationThread() {
        return registrationThreadId == Thread.currentThread().getId();
    }

    private void doAfterCompletion(int status) {
        ...
        try {
            afterCompletionAction.doAction( transactionCoordinator, status );
            transactionCoordinator.afterTransaction( null, status );
        }
        finally {
            reset();
            if ( transactionContext().shouldAutoClose() && !transactionContext().isClosed() ) {
                LOG.trace( "Automatically closing session" );
                transactionContext().managedClose();
            }
            
        }
     }