[PATCH] sched/fair: align proxy wakeup buddy handling with EEVDF

[zhidao su (Xiaomi)]

Proxy execution still nominates a newly woken task as NEXT_BUDDY
before the wakeup path has passed the same policy and EEVDF
eligibility gates used by the updated fair scheduler wakeup logic.

Move the NEXT_BUDDY nomination later in check_preempt_wakeup_fair()
so throttled, already-rescheduled, disabled-preemption, idle-class,
and non-normal wakeups return before updating cfs_rq->next.

Also clear stale buddy state when PREEMPT_SHORT overrides slice
protection.

Signed-off-by: zhidao su (Xiaomi) <soolaugust@xxxxxxxxx>
---
 kernel/sched/fair.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1f1c53c7deb2b..6a6cf8019be90 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8755,10 +8755,6 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int
 	if (task_is_throttled(p))
 		return;
 
-	if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK) && !pse->sched_delayed) {
-		set_next_buddy(pse);
-	}
-
 	/*
 	 * We can come here with TIF_NEED_RESCHED already set from new task
 	 * wake up path.
@@ -8811,6 +8807,9 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int
 	 */
 	do_preempt_short = sched_feat(PREEMPT_SHORT) && (pse->slice < se->slice);
 
+	if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK) && !pse->sched_delayed)
+		set_next_buddy(pse);
+
 	/*
 	 * If @p has become the most eligible task, force preemption.
 	 */
@@ -8823,8 +8822,10 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int
 	return;
 
 preempt:
-	if (do_preempt_short)
+	if (do_preempt_short) {
 		cancel_protect_slice(se);
+		clear_buddies(cfs_rq, se);
+	}
 
 	resched_curr_lazy(rq);
 }
-- 
2.43.0