linux-kernel - Re: [powerpc][next-20210621] WARNING at kernel/sched/fair.c:3277 during boot

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Date:   Wed, 23 Jun 2021 17:13:11 +0200
From:   Odin Ugedal <odin@...d.al>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Odin Ugedal <odin@...d.al>,
        Sachin Sant <sachinp@...ux.vnet.ibm.com>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        linuxppc-dev@...ts.ozlabs.org,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [powerpc][next-20210621] WARNING at kernel/sched/fair.c:3277
 during boot

ons. 23. jun. 2021 kl. 15:56 skrev Vincent Guittot <vincent.guittot@...aro.org>:
>
>
> The pelt value of sched_entity is synced with  cfs and its contrib
> before being removed.

Hmm. Not sure what you mean by sched_entity here, since this is only
taking the "removed" load_avg
and removing it from cfs_rq, together with (removed.load_avg *
divider) from load_sum. (Although. ".removed" comes from
a sched entity)

> Then, we start to remove this load in update_cfs_rq_load_avg() before
> calling __update_load_avg_cfs_rq so contrib should not have change and
> we should be safe

For what it is worth, I am now able to reproduce it (maybe
CONFIG_HZ=300/250 is the thing) as reported by Sachin,
and my patch makes it disappear. Without my patch I see situations
where _sum is zero while _avg is eg. 1 or 2 or 14 (in that range).
This happens for both load, runnable and util.

Lets see what Sachin reports back.

Thanks
Odin