I had a phone call with two members (one engineer and the manager) where I was asked straightforward questions about computer architecture (cache), keywords in C (static) and multithreading (definitions of mutex, thread, spinlock, etc.). They also asked me about my work and academic experiences during the interview. I then had an onsite interview which was 4-5 hours long. I had an hour long with one interviewer followed by a one hour interview with another person and so on. During each one hour session, I was asked to write code on the whiteboard. The interviewers expected competence with OS concepts and the C programming language.

they call you and ask you the your availability and typical interview goes for 3 hours if they are interested. They ask C questions and your project related questions. At last a manager comes and takes your interview.