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Commit 9014623c authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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sched: handle vruntime 64-bit overflow 



Handle vruntime overflow by centering the key space around min_vruntime.

( otherwise we could overflow 64-bit vruntime in a few days with SCHED_IDLE
 tasks - or in a few years with nice +19. )

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarMike Galbraith <efault@gmx.de>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 94dfb5e7

kernel/sched_fair.c

+11 −4
Original line number Diff line number Diff line
@@ -124,11 +124,18 @@ set_leftmost(struct cfs_rq *cfs_rq, struct rb_node *leftmost) 
	cfs_rq->rb_leftmost = leftmost;

	if (leftmost) {

		se = rb_entry(leftmost, struct sched_entity, run_node);

		cfs_rq->min_vruntime = max(se->vruntime,

						cfs_rq->min_vruntime);

		if ((se->vruntime > cfs_rq->min_vruntime) ||

		    (cfs_rq->min_vruntime > (1ULL << 61) &&

		     se->vruntime < (1ULL << 50)))

			cfs_rq->min_vruntime = se->vruntime;

	}

}



s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)

{

	return se->fair_key - cfs_rq->min_vruntime;

}



/*

 * Enqueue an entity into the rb-tree:

 */
@@ -138,7 +145,7 @@ __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 
	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;

	struct rb_node *parent = NULL;

	struct sched_entity *entry;

	s64 key = se->fair_key;

	s64 key = entity_key(cfs_rq, se);

	int leftmost = 1;



	/*
@@ -151,7 +158,7 @@ __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 
		 * We dont care about collisions. Nodes with

		 * the same key stay together.

		 */

		if (key - entry->fair_key < 0) {

		if (key < entity_key(cfs_rq, entry)) {

			link = &parent->rb_left;

		} else {

			link = &parent->rb_right;