Following are interview questions

1) code for kernel scheduler ( I could not, he said even if some portion of code then fine I have read but reproducing them I could not do that )

2) asked to write code for Interrupt handlers (I am aware but could not reproduce code )
3)Device drivers file operations (this I was able to write)

4) Asked to explain Xen bootstrapping and architecture code (not diagrams)

I am looking for links where code has been explained.I have read such things but I some times feel difficult to understand without having a proper explanation. So in case you are aware of any such things let me know.