linux-kernel - Re: WARNING: CPU: 112 PID: 2041 at kernel/sched/sched.h:1453

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Date:   Mon, 2 Aug 2021 10:43:43 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Bruno Goncalves <bgoncalv@...hat.com>
Cc:     CKI Project <cki-project@...hat.com>, linux-kernel@...r.kernel.org,
        nathan@...nel.org, Memory Management <mm-qe@...hat.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: WARNING: CPU: 112 PID: 2041 at kernel/sched/sched.h:1453

On 30/07/2021 17:23, Bruno Goncalves wrote:
> On Fri, Jul 30, 2021 at 2:22 PM Dietmar Eggemann
> <dietmar.eggemann@....com> wrote:
>>
>> On 29/07/2021 16:38, Dietmar Eggemann wrote:
>>> On 29/07/2021 14:36, Bruno Goncalves wrote:
>>>> On Wed, Jul 28, 2021 at 5:55 PM Dietmar Eggemann
>>>> <dietmar.eggemann@....com> wrote:
>>>>>
>>>>> On 28/07/2021 15:11, Bruno Goncalves wrote:

[...]

>> The task causing this seem to be the new `cppc_fie` DL task introduced
>> by commit 1eb5dde674f5 "cpufreq: CPPC: Add support for frequency
>> invariance" in v5.14-rc1.
>>
>> With `CONFIG_ACPI_CPPC_CPUFREQ_FIE=y` and schedutil cpufreq governor on
>> slow-switching system:
>>
>> DL task curr=`sugov:X` makes p=`cppc_fie` migrate and since it is in
>> `non_contending` state, migrate_task_rq_dl() calls
>>
>>   sub_running_bw()->__sub_running_bw()->cpufreq_update_util()->
>>   rq_clock()->assert_clock_updated()
>>
>> on p.
>>
>> Can you try this snippet? It should fix it.
> 
> Thank you, I've tried the patch and it fixes the issue.

Thanks for testing! Let me send out a proper patch then.