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

[Shreeya Patel]

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,
Shreeya Patel