Commit afae8002 authored by Tianchen Ding's avatar Tianchen Ding Committed by Peter Zijlstra
Browse files

sched/eevdf: Fix miscalculation in reweight_entity() when se is not curr 



reweight_eevdf() only keeps V unchanged inside itself. When se !=
cfs_rq->curr, it would be dequeued from rb tree first. So that V is
changed and the result is wrong. Pass the original V to reweight_eevdf()
to fix this issue.

Fixes: eab03c23 ("sched/eevdf: Fix vruntime adjustment on reweight")
Signed-off-by: default avatarTianchen Ding <dtcccc@linux.alibaba.com>
[peterz: flip if() condition for clarity]
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarAbel Wu <wuyun.abel@bytedance.com>
Link: https://lkml.kernel.org/r/20240306022133.81008-3-dtcccc@linux.alibaba.com
parent 11b1b8bc

kernel/sched/fair.c

+6 −5
Original line number Diff line number Diff line
@@ -3676,11 +3676,10 @@ static inline void 
dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }

#endif



static void reweight_eevdf(struct cfs_rq *cfs_rq, struct sched_entity *se,

static void reweight_eevdf(struct sched_entity *se, u64 avruntime,

			   unsigned long weight)

{

	unsigned long old_weight = se->load.weight;

	u64 avruntime = avg_vruntime(cfs_rq);

	s64 vlag, vslice;



	/*
@@ -3787,24 +3786,26 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, 
			    unsigned long weight)

{

	bool curr = cfs_rq->curr == se;

	u64 avruntime;



	if (se->on_rq) {

		/* commit outstanding execution time */

		update_curr(cfs_rq);

		avruntime = avg_vruntime(cfs_rq);

		if (!curr)

			__dequeue_entity(cfs_rq, se);

		update_load_sub(&cfs_rq->load, se->load.weight);

	}

	dequeue_load_avg(cfs_rq, se);



	if (!se->on_rq) {

	if (se->on_rq) {

		reweight_eevdf(se, avruntime, weight);

	} else {

		/*

		 * Because we keep se->vlag = V - v_i, while: lag_i = w_i*(V - v_i),

		 * we need to scale se->vlag when w_i changes.

		 */

		se->vlag = div_s64(se->vlag * se->load.weight, weight);

	} else {

		reweight_eevdf(cfs_rq, se, weight);

	}



	update_load_set(&se->load, weight);