cpu group pick_next函数

以下代码来自 pick_next_task_fair

6739         /* 6740          * Because of the set_next_buddy() in dequeue_task_fair() it is rather 6741          * likely that a next task is from the same cgroup as the current. 6742          * 6743          * Therefore attempt to avoid putting and setting the entire cgroup 6744          * hierarchy, only change the part that actually changes. 6745          */ 6746 6747         do { 6748                 struct sched_entity *curr = cfs_rq->curr; 6749 6750                 /* 6751                  * Since we got here without doing put_prev_entity() we also 6752                  * have to consider cfs_rq->curr. If it is still a runnable 6753                  * entity, update_curr() will update its vruntime, otherwise 6754                  * forget we've ever seen it. 6755                  */ 6756                 if (curr) { 6757                         if (curr->on_rq) 6758                                 update_curr(cfs_rq); 6759                         else 6760                                 curr = NULL; 6761 6762                         /* 6763                          * This call to check_cfs_rq_runtime() will do the 6764                          * throttle and dequeue its entity in the parent(s). 6765                          * Therefore the nr_running test will indeed 6766                          * be correct. 6767                          */ 6768                         if (unlikely(check_cfs_rq_runtime(cfs_rq))) { 6769                                 cfs_rq = &rq->cfs; 6770 6771                                 if (!cfs_rq->nr_running) 6772                                         goto idle; 6773 6774                                 goto simple; 6775                         } 6776                 } 6777 6778                 **se = pick_next_entity(cfs_rq, curr);** 6779                 **cfs_rq = group_cfs_rq(se);** 6780         } while (cfs_rq);

279 /* runqueue "owned" by this group */  280 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)  281 {  282         return grp->my_q;  283 }

1）如果cpu 原始rq pick_next_entity选择的是非cgoup节点，那么6779行返回空，即 my_q为空

2）如果6778行选择的cgroup的根节点的sched_entity,那么会根据cgroup层次结构遍历一次遍历，到最后的一层节点选出的sched_entity的my_q为空，则为真正的task entity