Threads Stuck On Closing Brace Of While Loop

While analyzing the thread dumps for a performance issue in our java ee web application, I see many thread dumps stuck on a closing brace of a while loop. Here is the code block of a third party library bitronix (version 1.3.3 SNAPSHOT)
 
public XAResourceHolderState findXAResourceHolderState(XAResource xaResource) throws BitronixSystemException {
        Iterator it = resources.iterator();
        while (it.hasNext()) {
            XAResourceHolderState xaResourceHolderState = (XAResourceHolderState) it.next();
            if (xaResourceHolderState.getXAResource() == xaResource)
                return xaResourceHolderState;
        }      
        return null;
    }

The thread dumps indicate that many threads are stuck in RUNNABLE state on line number 07. What could be the possible reasons on why a thread could get stuck on a closing brace of a while loop? The iterator of the while loop is a custom implementation.