Mad C Skillz OEMG

I want to jump to the next level in C. I'm a quite skilled programmer for what I do, know the whole K&R but I feel like I miss something, especially about those weird techniques proPROgrammers use in OS dev and related. Suggested readings?

>>48
multics had everything plan 9 has?
multics had zfs? hammer? ext4?
yeah, i didn't think so.