Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Sender: Guenter Roeck <groeck7@gmail.com>
Message-ID: <6b05a082-41a7-f0cf-c0a4-1cced8d5a230@roeck-us.net>
Date:   Wed, 9 Aug 2023 13:38:19 -0700
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.13.0
Subject: Re: [PATCH 5.15 00/92] 5.15.126-rc1 review
Content-Language: en-US
To:     Joel Fernandes <joel@joelfernandes.org>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, patches@lists.linux.dev,
        linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
        akpm@linux-foundation.org, shuah@kernel.org, patches@kernelci.org,
        lkft-triage@lists.linaro.org, pavel@denx.de, jonathanh@nvidia.com,
        f.fainelli@gmail.com, sudipm.mukherjee@gmail.com,
        srw@sladewatkins.net, rwarsow@gmx.de, conor@kernel.org,
        paulmck@kernel.org
References: <20230809103633.485906560@linuxfoundation.org>
 <20230809135326.GE3031656@google.com>
 <f47340c6-3c41-1f91-d0f9-fe0b59a23aac@roeck-us.net>
 <CAEXW_YQ4GqPwvUF8=8CWmdj=cD56v_eEVK-EirsObQXyBDFVpg@mail.gmail.com>
 <35e4b770-2ead-4a19-ad01-fa75996adef4@roeck-us.net>
 <20230809201413.GA3374446@google.com>
From:   Guenter Roeck <linux@roeck-us.net>
In-Reply-To: <20230809201413.GA3374446@google.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk

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@roeck-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