[ Upstream commit 39f23ce07b9355d05a64ae303ce20d1c4b92b957 upstream ]

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.

Fixes: fe61468b2cb (sched/fair: Fix enqueue_task_fair warning) Reported-by Tao Zhou zohooouoto@zoho.com.cn Signed-off-by: Vincent Guittot vincent.guittot@linaro.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Phil Auld pauld@redhat.com Reviewed-by: Ben Segall bsegall@google.com Link: https://lkml.kernel.org/r/20200513135528.4742-1-vincent.guittot@linaro.org ---

This is the rebase on v5.4.y / v5.4.81 of commit: b34cb07dde7c ("sched/fair: Fix enqueue_task_fair() warning some more")

kernel/sched/fair.c | 36 ++++++++++++++++++++++++++++-------- 1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 200e12110109..3dd7c10d6a58 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4580,7 +4580,6 @@ 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)]; @@ -4604,21 +4603,41 @@ 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); + 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 @@ -4627,7 +4646,8 @@ 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);