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From:   Vincent Guittot <vincent.guittot@linaro.org>
To:     mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
        dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com,
        mgorman@suse.de, bristot@redhat.com, linux-kernel@vger.kernel.org
Cc:     odin@uged.al, Vincent Guittot <vincent.guittot@linaro.org>
Subject: [PATCH] sched/pelt: check that *_avg are null when *_sum are
Date:   Tue,  1 Jun 2021 17:53:28 +0200
Message-Id: <20210601155328.19487-1-vincent.guittot@linaro.org>
Precedence: bulk

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@linaro.org>
---

This is what I used for patch 20210601085832.12626-1-vincent.guittot@linaro.org

 kernel/sched/fair.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a2c30e52de76..c17feadeafcc 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8021,6 +8021,15 @@ 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;
 }
 
-- 
2.17.1