The following commit has been merged into the sched/urgent branch of tip: Commit-ID: b34cb07dde7c2346dec73d053ce926aeaa087303 Gitweb: https://git.kernel.org/tip/b34cb07dde7c2346dec73d053ce926aeaa087303 Author: Phil Auld <pauld@xxxxxxxxxx> AuthorDate: Tue, 12 May 2020 09:52:22 -04:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Tue, 19 May 2020 20:34:10 +02:00 sched/fair: Fix enqueue_task_fair() warning some more sched/fair: Fix enqueue_task_fair warning some more The recent patch, fe61468b2cb (sched/fair: Fix enqueue_task_fair warning) did not fully resolve the issues with the rq->tmp_alone_branch != &rq->leaf_cfs_rq_list warning in enqueue_task_fair. There is a case where the first for_each_sched_entity loop exits due to on_rq, having incompletely updated the list. In this case the second for_each_sched_entity loop can further modify se. The later code to fix up the list management fails to do what is needed because se does not point to the sched_entity which broke out of the first loop. The list is not fixed up because the throttled parent was already added back to the list by a task enqueue in a parallel child hierarchy. Address this by calling list_add_leaf_cfs_rq if there are throttled parents while doing the second for_each_sched_entity loop. Fixes: fe61468b2cb ("sched/fair: Fix enqueue_task_fair warning") Suggested-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx> Signed-off-by: Phil Auld <pauld@xxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx> Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20200512135222.GC2201@xxxxxxxxxxxxxxxxxxxxxxxxx --- kernel/sched/fair.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 02f323b..c6d57c3 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5479,6 +5479,13 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) /* end evaluation on encountering a throttled cfs_rq */ if (cfs_rq_throttled(cfs_rq)) goto enqueue_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); } enqueue_throttle:
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