6.12-stable review patch. If anyone has any objections, please let me know.
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From: K Prateek Nayak kprateek.nayak@amd.com
[ Upstream commit 493afbd187c4c9cc1642792c0d9ba400c3d6d90d ]
Adam reports that enabling NEXT_BUDDY insta triggers a WARN in pick_next_entity().
Moving clear_buddies() up before the delayed dequeue bits ensures no ->next buddy becomes delayed. Further ensure no new ->next buddy ever starts as delayed.
Fixes: 152e11f6df29 ("sched/fair: Implement delayed dequeue") Reported-by: Adam Li adamli@os.amperecomputing.com Signed-off-by: K Prateek Nayak kprateek.nayak@amd.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Tested-by: Adam Li adamli@os.amperecomputing.com Link: https://lkml.kernel.org/r/670a0d54-e398-4b1f-8a6e-90784e2fdf89@amd.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/fair.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 782ce70ebd1b..c467e389cd6f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5484,6 +5484,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) bool sleep = flags & DEQUEUE_SLEEP;
update_curr(cfs_rq); + clear_buddies(cfs_rq, se);
if (flags & DEQUEUE_DELAYED) { SCHED_WARN_ON(!se->sched_delayed); @@ -5500,8 +5501,6 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
if (sched_feat(DELAY_DEQUEUE) && delay && !entity_eligible(cfs_rq, se)) { - if (cfs_rq->next == se) - cfs_rq->next = NULL; update_load_avg(cfs_rq, se, 0); se->sched_delayed = 1; return false; @@ -5526,8 +5525,6 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
update_stats_dequeue_fair(cfs_rq, se, flags);
- clear_buddies(cfs_rq, se); - update_entity_lag(cfs_rq, se); if (sched_feat(PLACE_REL_DEADLINE) && !sleep) { se->deadline -= se->vruntime; @@ -8786,7 +8783,7 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int if (unlikely(throttled_hierarchy(cfs_rq_of(pse)))) return;
- if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK)) { + if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK) && !pse->sched_delayed) { set_next_buddy(pse); }