linux-kernel - Re: [kthread] 40966e316f: WARNING:at_kernel/sched/core.c:#sched

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Message-ID: <87sfukuhdh.fsf@email.froward.int.ebiederm.org>
Date:   Wed, 22 Dec 2021 21:31:22 -0600
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Oliver Sang <oliver.sang@...el.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        lkp@...el.com
Subject: Re: [kthread]  40966e316f: WARNING:at_kernel/sched/core.c:#sched_init

Oliver Sang <oliver.sang@...el.com> writes:

> hi Eric,
>
> On Fri, Dec 17, 2021 at 11:01:41AM -0600, Eric W. Biederman wrote:
>> kernel test robot <oliver.sang@...el.com> writes:
>> 
>> > Greeting,
>> >
>> > FYI, we noticed the following commit (built with gcc-9):
>> >
>> > commit: 40966e316f86b8cfd83abd31ccb4df729309d3e7 ("kthread: Ensure struct kthread is present for all kthreads")
>> > https://git.kernel.org/cgit/linux/kernel/git/ebiederm/user-namespace.git signal-for-v5.17
>> >
>> > in testcase: trinity
>> > version: trinity-x86_64-608712d8-1_20211207
>> > with following parameters:
>> >
>> > 	runtime: 300s
>> >
>> > test-description: Trinity is a linux system call fuzz tester.
>> > test-url: http://codemonkey.org.uk/projects/trinity/
>> >
>> >
>> > on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
>> >
>> > caused below changes (please refer to attached dmesg/kmsg for entire
>> > log/backtrace):
>> 
>> 
>> Ok. That is very weird.  I will dig into it.
>> 
>> Silly question is there anything in this testing to cause memory
>> allocations to fail early in boot?
>
> we didn't observe it. actually test could finish for both this
> commit (though with reported warning) and parent. the only diff seems
> the reported warning.
>
> cead18552660702a 40966e316f86b8cfd83abd31ccb
> ---------------- ---------------------------
>        fail:runs  %reproduction    fail:runs
>            |             |             |
>            :8          100%           8:8     dmesg.RIP:sched_init
>            :8          100%           8:8     dmesg.WARNING:at_kernel/sched/core.c:#sched_init
>
> but could you check in dmesg we attached in original report for any suspicous
> memory issue?
>
> or could you help check the config we used (also attached in original report)
> to see if we can make some changes then to expose the possible memory issue,
> in case our current config cannot capture? Thanks

This was my bad.  I have pushed the fix out now.  I had the test
backwards in the WARN_ON.

My apologies for the noise.

Eric