sched/fair: Fix enqueue_task_fair warning
When a cfs rq is throttled, the latter and its child are removed from the leaf list but their nr_running is not changed which includes staying higher than 1. When a task is enqueued in this throttled branch, the cfs rqs must be added back in order to ensure correct ordering in the list but this can only happens if nr_running == 1. When cfs bandwidth is used, we call unconditionnaly list_add_leaf_cfs_rq() when enqueuing an entity to make sure that the complete branch will be added. Similarly unthrottle_cfs_rq() can stop adding cfs in the list when a parent is throttled. Iterate the remaining entity to ensure that the complete branch will be added in the list. Reported-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Christian Borntraeger <borntraeger@de.ibm.com> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: stable@vger.kernel.org Cc: stable@vger.kernel.org #v5.1+ Link: https://lkml.kernel.org/r/20200306135257.25044-1-vincent.guittot@linaro.org
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@ -4136,6 +4136,7 @@ static inline void check_schedstat_required(void)
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#endif
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}
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static inline bool cfs_bandwidth_used(void);
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/*
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* MIGRATION
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@ -4214,11 +4215,17 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
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__enqueue_entity(cfs_rq, se);
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se->on_rq = 1;
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if (cfs_rq->nr_running == 1) {
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/*
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* When bandwidth control is enabled, cfs might have been removed
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* because of a parent been throttled but cfs->nr_running > 1. Try to
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* add it unconditionnally.
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*/
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if (cfs_rq->nr_running == 1 || cfs_bandwidth_used())
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list_add_leaf_cfs_rq(cfs_rq);
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if (cfs_rq->nr_running == 1)
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check_enqueue_throttle(cfs_rq);
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}
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}
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static void __clear_buddies_last(struct sched_entity *se)
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{
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@ -4808,11 +4815,22 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
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break;
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}
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assert_list_leaf_cfs_rq(rq);
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if (!se)
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add_nr_running(rq, task_delta);
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/*
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* The cfs_rq_throttled() breaks in the above iteration can result in
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* incomplete leaf list maintenance, resulting in triggering the
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* assertion below.
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*/
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for_each_sched_entity(se) {
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cfs_rq = cfs_rq_of(se);
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list_add_leaf_cfs_rq(cfs_rq);
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}
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assert_list_leaf_cfs_rq(rq);
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/* Determine whether we need to wake up potentially idle CPU: */
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if (rq->curr == rq->idle && rq->cfs.nr_running)
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resched_curr(rq);
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