I use `ReactDOM.unstable_renderSubtreeIntoContainer` to render a portal.

``` javascript
class Modal extends React.Component {

componentDidMount() {
    this.node = document.createElement('div');
    document.body.appendChild(this.node);
    this.renderPortal(this.props);
}

componentWillReceiveProps(nextProps) {
    this.renderPortal(nextProps);
}

componentWillUnmount() {
    ReactDOM.unmountComponentAtNode(this.node);
    document.body.removeChild(this.node);
}

renderPortal = (props) => {
    renderSubtreeIntoContainer(this, <ModalPortal {...props} />, this.node);
}

render() {
    return null;
  }
}
```

In my root component:

``` javascript
class App extends React.Component {
    static childContextTypes = {
        highlightColor: React.PropTypes.object
    }

    getChildContext() {
        return {
            highlightColor: this.props.highlightColor
        }
    }

    ...
}
```

The context of root component will be updated and passed to children if  `this.props.highlightColor` is changed. This is right.
I can access the correct context in the `<ModalPortal/>` component in the first render.
And after that the context passed to  `<ModalPortal/>` **does not change any more** when the context of root component changed.
But I can access the correct context in the `<Modal/>`  every render.

what's wrong with my code ?

componentInstance,
  container,
  shouldReuseMarkup,
  context
) {
  var transaction = ReactUpdates.ReactReconcileTransaction.getPooled(
    
    !shouldReuseMarkup && ReactDOMFeatureFlags.useCreateElement
  );
  transaction.perform(
    mountComponentIntoNode,
    null,
    componentInstance,
    container,
    transaction,
    shouldReuseMarkup,
    context
  );
  ReactUpdates.ReactReconcileTransaction.release(transaction);
}
/**
 * Unmounts a component and removes it from the DOM.
 *
 * @param {ReactComponent} instance React component instance.
 * @param {DOMElement} container DOM element to unmount from.
 * @final
 * @internal
 * @see {ReactMount.unmountComponentAtNode}
 */
function unmountComponentFromNode(instance, container, safely) {