[tip: sched/core] sched/pelt: Check that *_avg are null when *_sum are

[tip-bot2 for Vincent Guittot]

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

Commit-ID:     9e077b52d86ac364a295b05c916c7478a16865b2
Gitweb:        https://git.kernel.org/tip/9e077b52d86ac364a295b05c916c7478a16865b2
Author:        Vincent Guittot <vincent.guittot@xxxxxxxxxx>
AuthorDate:    Tue, 01 Jun 2021 17:53:28 +02:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Thu, 17 Jun 2021 14:11:42 +02:00

sched/pelt: Check that *_avg are null when *_sum are

Check that we never break the rule that pelt's avg values are null if
pelt's sum are.

Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Acked-by: Odin Ugedal <odin@xxxxxxx>
Link: https://lore.kernel.org/r/20210601155328.19487-1-vincent.guittot@xxxxxxxxxx
---
 kernel/sched/fair.c |  9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ce625bf..198514d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8026,6 +8026,15 @@ static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
 	if (cfs_rq->avg.runnable_sum)
 		return false;
 
+	/*
+	 * _avg must be null when _sum are null because _avg = _sum / divider
+	 * Make sure that rounding and/or propagation of PELT values never
+	 * break this.
+	 */
+	SCHED_WARN_ON(cfs_rq->avg.load_avg ||
+		      cfs_rq->avg.util_avg ||
+		      cfs_rq->avg.runnable_avg);
+
 	return true;
 }