linux-kernel - Re: WARNING: CPU: 0 PID: 12 at kernel/sched/fair.c:3306 update_blocked

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Date:   Mon, 2 Aug 2021 10:42:18 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Ammar Faizi <ammarfaizi2@...weeb.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Ammar Faizi <ammarfaizi2@...il.com>
Subject: Re: WARNING: CPU: 0 PID: 12 at kernel/sched/fair.c:3306
 update_blocked_averages+0x941/0x9a0

Hi Ammar,

On 30/07/2021 17:21, Ammar Faizi wrote:
> Hi everyone,
> 
> I compiled Linux 5.13.0 and use it on my Ubuntu. I got a kernel warning
> at kernel/sched/fair.c:3306.
> 
> Below is the system information
> Kernel: 5.13.0-icetea001-12377-gf55966571d5e

So you're running with:

9e077b52d86a - sched/pelt: Check that *_avg are null when *_sum are
(2021-06-17 Vincent Guittot)

but not with:

ceb6ba45dc80 - sched/fair: Sync load_sum with load_avg after dequeue
(2021-07-02 Vincent Guittot)

The SCHED_WARN_ON you're hitting is harmless and just tells you that the
PELT load_avg and load_sum part of one of your cfs_rq's is not aligned.
Has to be load (and not util or runnable) since load is the only one
still not fixed in f55966571d5e.

This should go away once you applied ceb6ba45dc80.

-- Dietmar