I am reading Robert Love's Book Linux Kernel Development( https://rads.stackoverflow.com/amzn/click/com/B003V4ATI0). It uses the 2.6.33 kernel for demonstration. I have been going through certain parts of the source and can't find out where is the initial definition of many things. A lot of things are just used, like "magic" without me finding the definition. One example: static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq) { struct rb_node *left = cfs_rq->rb_leftmost; if (!left) return NULL; return rb_entry(left, struct sched_entity, run_node); } static struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) { struct rb_node *last = rb_last(&cfs_rq->tasks_timeline); if (!last) return NULL; return rb_entry(last, struct sched_entity, run_node); } This in kernel/sched_fair.c lines 384 and 394 in 2.6.33 kernel. Where is the run_node coming from ? I have grep ed( https://livegrep.com/search/linuxq=run_node&fold_case=auto®ex=false&conte... <https://livegrep.com/search/linux?q=run_node&fold_case=auto®ex=false&cont...>) the entire source base over here, and I have not found any definition of run_node that would allow it to be used like this. There is a declaration( https://github.com/torvalds/linux/blob/219d54332a09e8d8741c1e1982f5eae56099d...) in the sched_entity structure, but nothing outside of it that would allow it to be used like this. I cannot understand how things are organized, its really confusing. What is going on ? -- Regards, Sreyan Chakravarty