linux-kernel - Re: [sched/pelt] e906550aca: WARNING:at_kernel/sched/fair.c:#update_blocked

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Date:   Thu, 3 Jun 2021 12:50:36 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     kernel test robot <oliver.sang@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Cc:     0day robot <lkp@...el.com>, LKML <linux-kernel@...r.kernel.org>,
        lkp@...ts.01.org, ltp@...ts.linux.it, mingo@...hat.com,
        peterz@...radead.org, juri.lelli@...hat.com, rostedt@...dmis.org,
        bsegall@...gle.com, mgorman@...e.de, bristot@...hat.com,
        odin@...d.al, aubrey.li@...ux.intel.com, yu.c.chen@...el.com
Subject: Re: [sched/pelt] e906550aca:
 WARNING:at_kernel/sched/fair.c:#update_blocked_averages

On 02/06/2021 08:45, kernel test robot wrote:

[...]

> kern :warn : [   40.989618] WARNING: CPU: 2 PID: 253 at kernel/sched/fair.c:8029 update_blocked_averages (kbuild/src/consumer/kernel/sched/fair.c:8029 kbuild/src/consumer/kernel/sched/fair.c:8065 kbuild/src/consumer/kernel/sched/fair.c:8152) 

Hit something like this on my Ubuntu i7-7567U as well.

With more debugging:

[    7.388006] WARNING: CPU: 1 PID: 926 at kernel/sched/fair.c:8029 update_blocked_averages+0x30d/0x7e0
...
[    7.388167] path=/autogroup-2 load_avg=1 util_avg=0 runnable_avg=1

IMHO, this is because this patch needs:

(1) sched/pelt: ensure that *_sum is always synced with *_avg (2021-06-03 Vincent Guittot)

https://lkml.kernel.org/r/20210601085832.12626-1-vincent.guittot@linaro.org

(2) sched/fair: Keep load_avg and load_sum synced (2021-06-03 Vincent Guittot)

tip/sched/urgent 7c7ad626d9a0

Using both patches underneath makes this warning go away.