The patch below does not apply to the 5.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 39f23ce07b9355d05a64ae303ce20d1c4b92b957 Mon Sep 17 00:00:00 2001
From: Vincent Guittot vincent.guittot@linaro.org Date: Wed, 13 May 2020 15:55:28 +0200 Subject: [PATCH] sched/fair: Fix unthrottle_cfs_rq() for leaf_cfs_rq list
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
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c6d57c334d51..538ba5d94e99 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4774,7 +4774,6 @@ 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)]; @@ -4798,26 +4797,44 @@ 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 @@ -4826,7 +4843,8 @@ 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);