Message-ID: <26aa6f92-2376-51a4-bbdc-abbbd62c23d2@leemhuis.info>
Date:   Tue, 29 Aug 2023 13:28:37 +0200
From:   "Linux regression tracking (Thorsten Leemhuis)" 
        <regressions@...mhuis.info>
To:     Shreeya Patel <shreeya.patel@...labora.com>,
        Linux regressions mailing list <regressions@...ts.linux.dev>,
        Masahiro Yamada <masahiroy@...nel.org>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Maksim Panchenko <maks@...a.com>,
        Ricardo Cañuelo <ricardo.canuelo@...labora.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <llvm@...ts.linux.dev>,
        Bill Wendling <morbo@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        "gustavo.padovan@...labora.com" <gustavo.padovan@...labora.com>,
        Guillaume Charles Tucker <guillaume.tucker@...labora.com>,
        denys.f@...labora.com, Nick Desaulniers <ndesaulniers@...gle.com>,
        kernelci@...ts.linux.dev,
        Collabora Kernel ML <kernel@...labora.com>
Subject: Re: [PATCH v4] Makefile.compiler: replace cc-ifversion with
 compiler-specific macros

On 11.07.23 13:16, Shreeya Patel wrote:
> On 10/07/23 17:39, Linux regression tracking (Thorsten Leemhuis) wrote:
>> Hi, Thorsten here, the Linux kernel's regression tracker. Top-posting
>> for once, to make this easily accessible to everyone.
>>
>> Shreeya Patel, Masahiro Yamada: what's the status of this? Was any
>> progress made to address this? Or is this maybe (accidentally?) fixed
>> with 6.5-rc1?
> 
> I still see the regression happening so it doesn't seem to be fixed.
> https://linux.kernelci.org/test/case/id/64ac675a8aebf63753bb2a8c/
> 
> Masahiro had submitted a fix for this issue here.
> 
> https://lore.kernel.org/lkml/ZJEni98knMMkU%2Fcl@buildd.core.avm.de/T/#t
> 
> But I don't see any movement there. Masahiro, are you planning to send a
> v2 for it?

That was weeks ago and we didn't get a answer. :-/ Was this fixed in
between? Doesn't look like it from here, but I might be missing something.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
Everything you wanna know about Linux kernel regression tracking:
https://linux-regtracking.leemhuis.info/about/#tldr
If I did something stupid, please tell me, as explained on that page.

#regzbot poke

>> On 20.06.23 06:19, Masahiro Yamada wrote:
>>> On Mon, Jun 12, 2023 at 7:10 PM Shreeya Patel
>>> <shreeya.patel@...labora.com> wrote:
>>>> On 24/05/23 02:57, Nick Desaulniers wrote:
>>>>> On Tue, May 23, 2023 at 3:27 AM Shreeya Patel
>>>>> <shreeya.patel@...labora.com> wrote:
>>>>>> Hi Nick and Masahiro,
>>>>>>
>>>>>> On 23/05/23 01:22, Nick Desaulniers wrote:
>>>>>>> On Mon, May 22, 2023 at 9:52 AM Greg KH
>>>>>>> <gregkh@...uxfoundation.org> wrote:
>>>>>>>> On Mon, May 22, 2023 at 12:09:34PM +0200, Ricardo Cañuelo wrote:
>>>>>>>>> On vie, may 19 2023 at 08:57:24, Nick Desaulniers
>>>>>>>>> <ndesaulniers@...gle.com> wrote:
>>>>>>>>>> It could be; if the link order was changed, it's possible that
>>>>>>>>>> this
>>>>>>>>>> target may be hitting something along the lines of:
>>>>>>>>>> https://isocpp.org/wiki/faq/ctors#static-init-order i.e. the
>>>>>>>>>> "static
>>>>>>>>>> initialization order fiasco"
>>>>>>>>>>
>>>>>>>>>> I'm struggling to think of how this appears in C codebases, but I
>>>>>>>>>> swear years ago I had a discussion with GKH (maybe?) about
>>>>>>>>>> this. I
>>>>>>>>>> think I was playing with converting Kbuild to use Ninja rather
>>>>>>>>>> than
>>>>>>>>>> Make; the resulting kernel image wouldn't boot because I had
>>>>>>>>>> modified
>>>>>>>>>> the order the object files were linked in.  If you were to
>>>>>>>>>> randomly
>>>>>>>>>> shuffle the object files in the kernel, I recall some hazard
>>>>>>>>>> that may
>>>>>>>>>> prevent boot.
>>>>>>>>> I thought that was specifically a C++ problem? But then again, the
>>>>>>>>> kernel docs explicitly say that the ordering of obj-y goals in
>>>>>>>>> kbuild is
>>>>>>>>> significant in some instances [1]:
>>>>>>>> Yes, it matters, you can not change it.  If you do, systems will
>>>>>>>> break.
>>>>>>>> It is the only way we have of properly ordering our init calls
>>>>>>>> within
>>>>>>>> the same "level".
>>>>>>> Ah, right it was the initcall ordering. Thanks for the reminder.
>>>>>>>
>>>>>>> (There's a joke in there similar to the use of regexes to solve a
>>>>>>> problem resulting in two new problems; initcalls have levels for
>>>>>>> ordering, but we still have (unexpressed) dependencies between calls
>>>>>>> of the same level; brittle!).
>>>>>>>
>>>>>>> +Maksim, since that might be relevant info for the BOLT+Kernel work.
>>>>>>>
>>>>>>> Ricardo,
>>>>>>> https://elinux.org/images/e/e8/2020_ELCE_initcalls_myjosserand.pdf
>>>>>>> mentions that there's a kernel command line param `initcall_debug`.
>>>>>>> Perhaps that can be used to see if
>>>>>>> 5750121ae7382ebac8d47ce6d68012d6cd1d7926 somehow changed initcall
>>>>>>> ordering, resulting in a config that cannot boot?
>>>>>> Here are the links to Lava jobs ran with initcall_debug added to the
>>>>>> kernel command line.
>>>>>>
>>>>>> 1. Where regression happens
>>>>>> (5750121ae7382ebac8d47ce6d68012d6cd1d7926)
>>>>>> https://lava.collabora.dev/scheduler/job/10417706
>>>>>> <https://lava.collabora.dev/scheduler/job/10417706>
>>>>>>
>>>>>> 2. With a revert of the commit
>>>>>> 5750121ae7382ebac8d47ce6d68012d6cd1d7926
>>>>>> https://lava.collabora.dev/scheduler/job/10418012
>>>>>> <https://lava.collabora.dev/scheduler/job/10418012>
>>>>> Thanks!
>>>>>
>>>>> Yeah, I can see a diff in the initcall ordering as a result of
>>>>> commit 5750121ae738 ("kbuild: list sub-directories in ./Kbuild")
>>>>>
>>>>> https://gist.github.com/nickdesaulniers/c09db256e42ad06b90842a4bb85cc0f4
>>>>>
>>>>> Not just different orderings, but some initcalls seem unique to the
>>>>> before vs. after, which is troubling. (example init_events and
>>>>> init_fs_sysctls respectively)
>>>>>
>>>>> That isn't conclusive evidence that changes to initcall ordering are
>>>>> to blame, but I suspect confirming that precisely to be very very time
>>>>> consuming.
>>>>>
>>>>> Masahiro, what are your thoughts on reverting 5750121ae738? There are
>>>>> conflicts in Kbuild and Makefile when reverting 5750121ae738 on
>>>>> mainline.
>>>> I'm not sure if you followed the conversation but we are still seeing
>>>> this regression with the latest kernel builds and would like to know if
>>>> you plan to revert 5750121ae738?
>>>
>>> Reverting 5750121ae738 does not solve the issue
>>> because the issue happens even before 5750121ae738.
>>> multi_v7_defconfig + debug.config + CONFIG_MODULES=n
>>> fails to boot in the same way.
>>>
>>> The revert would hide the issue on a particular build setup.
>>>
>>>
>>> I submitted a patch to more pin-point the issue.
>>> Let's see how it goes.
>>> https://lore.kernel.org/lkml/ZJEni98knMMkU%2Fcl@buildd.core.avm.de/T/#t
>>>
>>>
>>> (BTW, the initcall order is unrelated)
>>>
>>>
>>>
>>>
>>>
>>>>
>>>> Thanks,
>>>> Shreeya Patel
>>>>
>>>>>> Thanks,
>>>>>> Shreeya Patel
>>>>>>
>>> -- 
>>> Best Regards
>>> Masahiro Yamada
>>>
>>>
> 
> 

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