6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: K Prateek Nayak <kprateek.nayak@xxxxxxx>
[ 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@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: Adam Li <adamli@xxxxxxxxxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/670a0d54-e398-4b1f-8a6e-90784e2fdf89@xxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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);
}
--
2.39.5
