sched/fair: Fix enqueue_task_fair warning (fe61468b) · Commits · 戴 / test

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

kernel/sched/fair.c

+22 −4

Original line number	Diff line number	Diff line
		@@ -4136,6 +4136,7 @@ static inline void check_schedstat_required(void)
		#endif
		}

		static inline bool cfs_bandwidth_used(void);

		/*
		* MIGRATION
		@@ -4214,11 +4215,17 @@ enqueue_entity(struct cfs_rq cfs_rq, struct sched_entity se, int flags)
		__enqueue_entity(cfs_rq, se);
		se->on_rq = 1;

		if (cfs_rq->nr_running == 1) {
		/*
		* When bandwidth control is enabled, cfs might have been removed
		* because of a parent been throttled but cfs->nr_running > 1. Try to
		* add it unconditionnally.
		*/
		if (cfs_rq->nr_running == 1 \|\| cfs_bandwidth_used())
		list_add_leaf_cfs_rq(cfs_rq);

		if (cfs_rq->nr_running == 1)
		check_enqueue_throttle(cfs_rq);
		}
		}

		static void __clear_buddies_last(struct sched_entity *se)
		{
		@@ -4808,11 +4815,22 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
		break;
		}

		assert_list_leaf_cfs_rq(rq);

		if (!se)
		add_nr_running(rq, task_delta);

		/*
		* The cfs_rq_throttled() breaks in the above iteration can result in
		* incomplete leaf list maintenance, resulting in triggering the
		* assertion below.
		*/
		for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);

		list_add_leaf_cfs_rq(cfs_rq);
		}

		assert_list_leaf_cfs_rq(rq);

		/* Determine whether we need to wake up potentially idle CPU: */
		if (rq->curr == rq->idle && rq->cfs.nr_running)
		resched_curr(rq);

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