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

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Message-ID: <CAFpoUr01xb9ZJF9mb2nmZDpUHXFH3VSbY3AU8-1owV-_7wVTPg@mail.gmail.com>
Date:   Wed, 23 Jun 2021 14:18:16 +0200
From:   Odin Ugedal <odin@...d.al>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Sachin Sant <sachinp@...ux.vnet.ibm.com>,
        Odin Ugedal <odin@...d.al>,
        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

Hi,

Wouldn't the attached diff below also help when load is removed,
Vincent? Isn't there a theoretical chance that x_sum ends up at zero
while x_load ends up as a positive value (without this patch)? Can
post as a separate patch if it works for Sachin.


diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bfaa6e1f6067..def48bc2e90b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3688,15 +3688,15 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)

                r = removed_load;
                sub_positive(&sa->load_avg, r);
-               sub_positive(&sa->load_sum, r * divider);
+               sa->load_sum = sa->load_avg * divider;

                r = removed_util;
                sub_positive(&sa->util_avg, r);
-               sub_positive(&sa->util_sum, r * divider);
+               sa->util_sum = sa->util_avg * divider;

                r = removed_runnable;
                sub_positive(&sa->runnable_avg, r);
-               sub_positive(&sa->runnable_sum, r * divider);
+               sa->runnable_sum = sa->runnable_avg * divider;

                /*
                 * removed_runnable is the unweighted version of
removed_load so we