Vincent Guittot <vincent.guit...@linaro.org> writes:
> Although not exactly identical, unthrottle_cfs_rq() and enqueue_task_fair()
> are quite close and follow the same sequence for enqueuing an entity in the
> cfs hierarchy. Modify unthrottle_cfs_rq() to use the same pattern as
> enqueue_task_fair(). This fixes a problem already faced with the latter and
> add an optimization in the last for_each_sched_entity loop.
>
> Reported-by Tao Zhou <zohooou...@zoho.com.cn>
> Reviewed-by: Phil Auld <pa...@redhat.com>
Reveiewed-by: Ben Segall <bseg...@google.com>
> Signed-off-by: Vincent Guittot <vincent.guit...@linaro.org>
> ---
>
> v3 changes:
> - remove the unused enqueue variable
>
> kernel/sched/fair.c | 42 ++++++++++++++++++++++++++++++------------
> 1 file changed, 30 insertions(+), 12 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 4e12ba882663..9a58874ef104 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4792,7 +4792,6 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
> struct rq *rq = rq_of(cfs_rq);
> struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
> struct sched_entity *se;
> - int enqueue = 1;
> long task_delta, idle_task_delta;
>
> se = cfs_rq->tg->se[cpu_of(rq)];
> @@ -4816,26 +4815,44 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
> idle_task_delta = cfs_rq->idle_h_nr_running;
> for_each_sched_entity(se) {
> if (se->on_rq)
> - enqueue = 0;
> + break;
> + cfs_rq = cfs_rq_of(se);
> + enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
>
> + cfs_rq->h_nr_running += task_delta;
> + cfs_rq->idle_h_nr_running += idle_task_delta;
> +
> + /* end evaluation on encountering a throttled cfs_rq */
> + if (cfs_rq_throttled(cfs_rq))
> + goto unthrottle_throttle;
> + }
> +
> + for_each_sched_entity(se) {
> cfs_rq = cfs_rq_of(se);
> - if (enqueue) {
> - enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
> - } else {
> - update_load_avg(cfs_rq, se, 0);
> - se_update_runnable(se);
> - }
> +
> + update_load_avg(cfs_rq, se, UPDATE_TG);
> + se_update_runnable(se);
>
> cfs_rq->h_nr_running += task_delta;
> cfs_rq->idle_h_nr_running += idle_task_delta;
>
> +
> + /* end evaluation on encountering a throttled cfs_rq */
> if (cfs_rq_throttled(cfs_rq))
> - break;
> + goto unthrottle_throttle;
> +
> + /*
> + * One parent has been throttled and cfs_rq removed from the
> + * list. Add it back to not break the leaf list.
> + */
> + if (throttled_hierarchy(cfs_rq))
> + list_add_leaf_cfs_rq(cfs_rq);
> }
>
> - if (!se)
> - add_nr_running(rq, task_delta);
> + /* At this point se is NULL and we are at root level*/
> + add_nr_running(rq, task_delta);
>
> +unthrottle_throttle:
> /*
> * The cfs_rq_throttled() breaks in the above iteration can result in
> * incomplete leaf list maintenance, resulting in triggering the
> @@ -4844,7 +4861,8 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
> for_each_sched_entity(se) {
> cfs_rq = cfs_rq_of(se);
>
> - list_add_leaf_cfs_rq(cfs_rq);
> + if (list_add_leaf_cfs_rq(cfs_rq))
> + break;
> }
>
> assert_list_leaf_cfs_rq(rq);
