linux-kernel - Re: [Linux 5.18-rc1] WARNING: CPU: 1 PID: 0 at kernel/sched/fair.c:3355 update_blocked

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Message-ID: <7f4b3fbf-c7c6-22cb-019b-520ad6a663aa@gnuweeb.org>
Date:   Thu, 7 Apr 2022 03:34:07 +0700
From:   Ammar Faizi <ammarfaizi2@...weeb.org>
To:     Dietmar Eggemann <dietmar.eggemann@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:     Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        GNU/Weeb Mailing List <gwml@...r.gnuweeb.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Mel Gorman <mgorman@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [Linux 5.18-rc1] WARNING: CPU: 1 PID: 0 at
 kernel/sched/fair.c:3355 update_blocked_averages

On 4/6/22 7:21 PM, Dietmar Eggemann wrote:
> On 05/04/2022 15:13, Ammar Faizi wrote:
>> On 4/5/22 7:21 PM, Dietmar Eggemann wrote:
>>> Tried to recreate the issue but no success so far. I used you config
>>> file, clang-14 and a Xeon CPU E5-2690 v2 (2 sockets 40 CPUs) with 20
>>> two-level cgoupv1 taskgroups '/X/Y' with 'hackbench (10 groups, 40 fds)
>>> + idling' running in all '/X/Y/'.
>>>
>>> What userspace are you running?
>>
>> HP Laptop, Intel i7-1165G7, 8 CPUs, with 16 GB of RAM. Ubuntu 21.10.
>> Just for
>> daily workstation. Compiling kernel, browsing and coding stuff.
> 
> Can you check that CFS Bandwidth control (CONFIG_CFS_BANDWIDTH=y) is
> still not used on Ubuntu desktop 21.10?
> 
> It shouldn't but I can't verify since I'm still on 20.04 LTS Desktop:
> 
> $ mount | grep "cgroup2\|\bcpu\b"
> cgroup2 on /sys/fs/cgroup/unified type cgroup2 (rw,nosuid,nodev,noexec,relatime,nsdelegate)
> cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
> 
> CPU controller is still used in cgroupv1. So cgroupv2 can't use it:
> 
> $ cat /sys/fs/cgroup/unified/cgroup.controllers
> /* empty */
> 
> And there is no cgroupv1 hierarchy under /sys/fs/cgroup/cpu,cpuacct/ .
> 
> No cpu.cfs_quota_us files with something other than -1.
> 
> So CFS Bandwidth control is not used.

Not familiar with CFS stuff, but here...

===============
ammarfaizi2@...egral2:~$ mount | grep "cgroup2\|\bcpu\b"
cgroup2 on /sys/fs/cgroup type cgroup2 (rw,nosuid,nodev,noexec,relatime,nsdelegate,memory_recursiveprot)
ammarfaizi2@...egral2:~$ cat /sys/fs/cgroup/unified/cgroup.controllers
cat: /sys/fs/cgroup/unified/cgroup.controllers: No such file or directory
ammarfaizi2@...egral2:~$ ls /sys/fs/cgroup/{cpu,cpuacct}
ls: cannot access '/sys/fs/cgroup/cpu': No such file or directory
ls: cannot access '/sys/fs/cgroup/cpuacct': No such file or directory
ammarfaizi2@...egral2:~$
ammarfaizi2@...egral2:~$ cat /etc/os-release
PRETTY_NAME="Ubuntu 21.10"
NAME="Ubuntu"
VERSION_ID="21.10"
VERSION="21.10 (Impish Indri)"
VERSION_CODENAME=impish
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=impish
ammarfaizi2@...egral2:~$
===============

Update:
So far I have been using and torturing my machine for a day, but
still couldn't reproduce the issue. It seems I hit a rarely
happened bug. I will continue using this until 5.18-rc2 before
recompile my kernel.

-- 
Ammar Faizi