[tip: sched/urgent] sched/eevdf: Update se->vprot in reweight_entity()

[tip-bot2 for Wang Tao]

The following commit has been merged into the sched/urgent branch of tip:

Commit-ID:     ff38424030f98976150e42ca35f4b00e6ab8fa23
Gitweb:        https://git.kernel.org/tip/ff38424030f98976150e42ca35f4b00e6ab8fa23
Author:        Wang Tao <wangtao554@xxxxxxxxxx>
AuthorDate:    Tue, 20 Jan 2026 12:31:13 
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 23 Feb 2026 11:19:18 +01:00

sched/eevdf: Update se->vprot in reweight_entity()

In the EEVDF framework with Run-to-Parity protection, `se->vprot` is an
independent variable defining the virtual protection timestamp.

When `reweight_entity()` is called (e.g., via nice/renice), it performs
the following actions to preserve Lag consistency:
 1. Scales `se->vlag` based on the new weight.
 2. Calls `place_entity()`, which recalculates `se->vruntime` based on
    the new weight and scaled lag.

However, the current implementation fails to update `se->vprot`, leading
to mismatches between the task's actual runtime and its expected duration.

Fixes: 63304558ba5d ("sched/eevdf: Curb wakeup-preemption")
Suggested-by: Zhang Qiao <zhangqiao22@xxxxxxxxxx>
Signed-off-by: Wang Tao <wangtao554@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Tested-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Tested-by: Shubhang Kaushik <shubhang@xxxxxxxxxxxxxxxxxxxxxx>
Link: https://patch.msgid.link/20260120123113.3518950-1-wangtao554@xxxxxxxxxx
---
 kernel/sched/fair.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f2b46c3..93fa5b8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3815,6 +3815,8 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 			    unsigned long weight)
 {
 	bool curr = cfs_rq->curr == se;
+	bool rel_vprot = false;
+	u64 vprot;
 
 	if (se->on_rq) {
 		/* commit outstanding execution time */
@@ -3822,6 +3824,11 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 		update_entity_lag(cfs_rq, se);
 		se->deadline -= se->vruntime;
 		se->rel_deadline = 1;
+		if (curr && protect_slice(se)) {
+			vprot = se->vprot - se->vruntime;
+			rel_vprot = true;
+		}
+
 		cfs_rq->nr_queued--;
 		if (!curr)
 			__dequeue_entity(cfs_rq, se);
@@ -3837,6 +3844,9 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 	if (se->rel_deadline)
 		se->deadline = div_s64(se->deadline * se->load.weight, weight);
 
+	if (rel_vprot)
+		vprot = div_s64(vprot * se->load.weight, weight);
+
 	update_load_set(&se->load, weight);
 
 	do {
@@ -3848,6 +3858,8 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 	enqueue_load_avg(cfs_rq, se);
 	if (se->on_rq) {
 		place_entity(cfs_rq, se, 0);
+		if (rel_vprot)
+			se->vprot = se->vruntime + vprot;
 		update_load_add(&cfs_rq->load, se->load.weight);
 		if (!curr)
 			__enqueue_entity(cfs_rq, se);