Re: [PATCH v4] Makefile.compiler: replace cc-ifversion with compiler-specific macros

[Shreeya Patel]

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?

Hi Thorsten,

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@xxxxxxxxxxxxxxxxxx/T/#t

But I don't see any movement there. Masahiro, are you planning to send a 
v2 for it?


Thanks,
Shreeya Patel

> 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@xxxxxxxxxxxxx> wrote:
> > > On 24/05/23 02:57, Nick Desaulniers wrote:
> > > > On Tue, May 23, 2023 at 3:27 AM Shreeya Patel
> > > > <shreeya.patel@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxx/T/#t
> >
> >
> > (BTW, the initcall order is unrelated)
> >
> >
> >
> >
> >
> > > Thanks,
> > > Shreeya Patel
> > >
> > > > > Thanks,
> > > > > Shreeya Patel
> > --
> > Best Regards
> > Masahiro Yamada