#vulnerable code 
                                public String pop() throws IOException {
        if (getRun() == null) {
            LOGGER.warning("run is null, cannot pop");
            return null;
        }
        synchronized (getRun()) {
            BulkChange bc = new BulkChange(getRun());
            try {
                AbstractInvisibleRunAction2 action = getRun().getAction(AbstractInvisibleRunAction2.class);
                if (action == null) {
                    action = new AbstractInvisibleRunAction2(getRun());
                    getRun().addAction(action);
                }
                String template = action.stack.pop();
                bc.commit();
                return template;
            } finally {
                bc.abort();
            }
        }
    } 
                            #location 6 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                public String pop() throws IOException {
        if (run == null) {
            LOGGER.warning("run is null, cannot pop");
            return null;
        }
        synchronized (getRun()) {
            BulkChange bc = new BulkChange(getRun());
            try {
                AbstractInvisibleRunAction2 action = getRun().getAction(this.getClass());
                if (action == null) {
                    action = createAction(getRun());
                    getRun().addAction(action);
                }
                String item = action.stack.pop();
                LOGGER.log(Level.INFO, "Popped item {0} from action {1} in run {2}",
                        new Object[] { item, action, run });
                bc.commit();
                return item;
            } finally {
                bc.abort();
            }
        }
    }