linux-kernel - Re: [PATCH] Makefile: remove stale cc-option checks

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Date:   Tue, 17 Aug 2021 10:38:55 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Michal Marek <michal.lkml@...kovi.net>,
        Nathan Chancellor <nathan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Vitor Massaru Iha <vitor@...saru.org>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Daniel Latypov <dlatypov@...gle.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Naresh Kamboju <naresh.kamboju@...aro.org>
Subject: Re: [PATCH] Makefile: remove stale cc-option checks

On Tue, Aug 17, 2021 at 9:16 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> On Tue, Aug 17, 2021 at 3:36 AM Nick Desaulniers
> <ndesaulniers@...gle.com> wrote:
> >
> > On Fri, Aug 13, 2021 at 6:43 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
> > >
> > > On Wed, Aug 11, 2021 at 5:42 AM Nick Desaulniers
> > > <ndesaulniers@...gle.com> wrote:
> > > >
> > > > --param=allow-store-data-races=0 was renamed to --allow-store-data-races
> > > > in the GCC 10 release.
> > > >
> > > > diff --git a/Makefile b/Makefile
> > > > index 027fdf2a14fe..3e3fb4affba1 100644
> > > > --- a/Makefile
> > > > +++ b/Makefile
> > > > @@ -844,17 +847,17 @@ KBUILD_RUSTFLAGS += -Copt-level=z
> > > >  endif
> > > >
> > > >  # Tell gcc to never replace conditional load with a non-conditional one
> > > > -KBUILD_CFLAGS  += $(call cc-option,--param=allow-store-data-races=0)
> > > > +ifdef CONFIG_CC_IS_GCC
> > >
> > >
> > > Can you insert a comment here?
> > >
> > > # GCC 10 renamed --param=allow-store-data-races=0 to --allow-store-data-races
> > >
> > >
> > > It will remind us of dropping this conditional
> > > in the (long long distant) future.
> > >
> > >
> > >
> > >
> > > > +KBUILD_CFLAGS  += $(call cc-option,--allow-store-data-races,--param=allow-store-data-races=0)
> > > >  KBUILD_CFLAGS  += $(call cc-option,-fno-allow-store-data-races)
> > > > +endif
> >
> > This report is confusing:
> > https://lore.kernel.org/linux-mm/202108160729.Lx0IJzq3-lkp@intel.com/
> > (csky gcc-11)
> >
> > >> csky-linux-gcc: error: unrecognized command-line option '--param=allow-store-data-races=0'; did you mean '--allow-store-data-races'?
> >
> > I wonder if cc-option detection for these is broken?
>
> I do not say it is broken...
>
>
> cc-option is defined like this:
>
> cc-option = $(call __cc-option, $(CC),\
>         $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS),$(1),$(2))
>
>
> It is checking
> $(KBUILD_CPPFLAGS) + $(KBUILD_CFLAGS)
> + --allow-store-data-races
>
>
> A few lines above, I see
>
> csky-linux-gcc: error: unrecognized argument in option '-mcpu=ck860'
>
>
> It makes all the cc-option tests fail after this line:
> KBUILD_CFLAGS += -mcpu=$(CPUTYPE) -Wa,-mcpu=$(MCPU_STR)
>
>
> Then,
>
> $(call cc-option,--allow-store-data-races,--param=allow-store-data-races=0)
>
> falls back to --param=allow-store-data-races=0
>
>
>
>
> >  Perhaps I should
> > not touch these other than to wrap them in the CONFIG_CC_IS_GCC guard?
>
> I do not think so.
>
> If an unrecognized argument appears,
> all the cc-option tests that follow are unreliable.
>
>
>
> If you are not comfortable with  it,
> you can split it.
>
> KBUILD_CFLAGS  += $(call cc-option,--allow-store-data-races)
> KBUILD_CFLAGS  += $(call cc-option,--param=allow-store-data-races=0)


I read the patch in the wrong way.
This is the same as the current code.

So, your v2 is fine with me.
I will pick it up soon.





-- 
Best Regards
Masahiro Yamada