how can a kernel process send some data asynchronously to a user level process

Question

I was asked this question in an interview.But the only thing I could think of is allocating a shared memory segment and by some means both kernel and user level processes to write to that segment.Even I am not satisfied with that answer.Can someone please expalin some other mechanism to do so? Any help will be appreciated.

Regards,

Answer 1

I would think they probably wanted to hear about the NetLink Interface. This interface provides an API for a kernel process and user process to communicate through which looks just like a socket, and is considered a successor to ioctl which is easier to use and asynchronous.

Overview here: http://www.linuxjournal.com/article/7356

Answer 2

They probably wanted to hear about APC (Asynchronous Procedure Call).