linux-kernel - Re: [PATCH 5.15 00/92] 5.15.126-rc1 review

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Date:   Wed, 9 Aug 2023 13:38:19 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, patches@...ts.linux.dev,
        linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        akpm@...ux-foundation.org, shuah@...nel.org, patches@...nelci.org,
        lkft-triage@...ts.linaro.org, pavel@...x.de, jonathanh@...dia.com,
        f.fainelli@...il.com, sudipm.mukherjee@...il.com,
        srw@...dewatkins.net, rwarsow@....de, conor@...nel.org,
        paulmck@...nel.org
Subject: Re: [PATCH 5.15 00/92] 5.15.126-rc1 review

On 8/9/23 13:14, Joel Fernandes wrote:
> On Wed, Aug 09, 2023 at 12:25:48PM -0700, Guenter Roeck wrote:
>> On Wed, Aug 09, 2023 at 02:35:59PM -0400, Joel Fernandes wrote:
>>> On Wed, Aug 9, 2023 at 12:18 PM Guenter Roeck <linux@...ck-us.net> wrote:
>>>>
>>>> On 8/9/23 06:53, Joel Fernandes wrote:
>>>>> On Wed, Aug 09, 2023 at 12:40:36PM +0200, Greg Kroah-Hartman wrote:
>>>>>> This is the start of the stable review cycle for the 5.15.126 release.
>>>>>> There are 92 patches in this series, all will be posted as a response
>>>>>> to this one.  If anyone has any issues with these being applied, please
>>>>>> let me know.
>>>>>>
>>>>>> Responses should be made by Fri, 11 Aug 2023 10:36:10 +0000.
>>>>>> Anything received after that time might be too late.
>>>>>>
>>>>>> The whole patch series can be found in one patch at:
>>>>>>       https://www.kernel.org/pub/linux/kernel/v5.x/stable-review/patch-5.15.126-rc1.gz
>>>>>> or in the git tree and branch at:
>>>>>>       git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-5.15.y
>>>>>> and the diffstat can be found below.
>>>>>
>>>>> Not necesscarily new with 5.15 stable but 3 of the 19 rcutorture scenarios
>>>>> hang with this -rc: TREE04, TREE07, TASKS03.
>>>>>
>>>>> 5.15 has a known stop machine issue where it hangs after 1.5 hours with cpu
>>>>> hotplug rcutorture testing. Me and tglx are continuing to debug this. The
>>>>> issue does not show up on anything but 5.15 stable kernels and neither on
>>>>> mainline.
>>>>>
>>>>
>>>> Do you by any have a crash pattern that we could possibly use to find the crash
>>>> in ChromeOS crash logs ? No idea if that would help, but it could provide some
>>>> additional data points.
>>>
>>> The pattern shows as a hard hang, the system is unresponsive and all CPUs
>>> are stuck in stop_machine. Sometimes it recovers on its own from the
>>> hang and then RCU immediately gives stall warnings. It takes 1.5 hour
>>> to reproduce and sometimes never happens for several hours.
>>>
>>> It appears related to CPU hotplug since gdb showed me most of the CPUs
>>> are spinning in multi_cpu_stop() / stop machine after the hang.
>>>
>>
>> Hmm, we do see lots of soft lockups with multi_cpu_stop() in the backtrace,
>> but not with v5.15.y but with v5.4.y. The actual hang is in stop_machine_yield().
> 
> Interesting. It looks similar as far as the stack dump in gdb goes, here are
> the stacks I dumped with the hang I referred to:
> https://paste.debian.net/1288308/
> 

That link gives me "Entry not found".

Guenter