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From:   Masahiro Yamada <yamada.masahiro@socionext.com>
Date:   Thu, 26 Sep 2019 18:02:16 +0900
Message-ID: <CAK7LNAR1eHPhf0eBNDd8bNVAUhfKrob0EvxHvAQHa8mqPnMbzw@mail.gmail.com>
Subject: Re: [PATCH] compiler: enable CONFIG_OPTIMIZE_INLINING forcibly
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        linux-arch <linux-arch@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        noreply@ellerman.id.au
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Hi Geert,

On Thu, Sep 26, 2019 at 5:54 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Yamada-san,
>
> On Fri, Aug 30, 2019 at 5:44 AM Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
> > Commit 9012d011660e ("compiler: allow all arches to enable
> > CONFIG_OPTIMIZE_INLINING") allowed all architectures to enable
> > this option. A couple of build errors were reported by randconfig,
> > but all of them have been ironed out.
> >
> > Towards the goal of removing CONFIG_OPTIMIZE_INLINING entirely
> > (and it will simplify the 'inline' macro in compiler_types.h),
> > this commit changes it to always-on option. Going forward, the
> > compiler will always be allowed to not inline functions marked
> > 'inline'.
> >
> > This is not a problem for x86 since it has been long used by
> > arch/x86/configs/{x86_64,i386}_defconfig.
> >
> > I am keeping the config option just in case any problem crops up for
> > other architectures.
> >
> > The code clean-up will be done after confirming this is solid.
> >
> > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
>
> This breaks compiling drivers/video/fbdev/c2p*, as the functions in
> drivers/video/fbdev/c2p_core.h are no longer inlined, leading to calls
> to the non-existent function c2p_unsupported(), as reported by KISSKB:
>
> On Thu, Sep 26, 2019 at 5:02 AM <noreply@ellerman.id.au> wrote:
> > FAILED linux-next/m68k-defconfig/m68k Thu Sep 26, 12:58
> >
> > http://kisskb.ellerman.id.au/kisskb/buildresult/13973194/
> >
> > Commit:   Add linux-next specific files for 20190925
> >           d47175169c28eedd2cc2ab8c01f38764cb0269cc
> > Compiler: m68k-linux-gcc (GCC) 4.6.3 / GNU ld (GNU Binutils) 2.22
> >
> > Possible errors
> > ---------------
> >
> > c2p_planar.c:(.text+0xd6): undefined reference to `c2p_unsupported'
> > c2p_planar.c:(.text+0x1dc): undefined reference to `c2p_unsupported'
> > c2p_iplan2.c:(.text+0xc4): undefined reference to `c2p_unsupported'
> > c2p_iplan2.c:(.text+0x150): undefined reference to `c2p_unsupported'
> > make[1]: *** [Makefile:1074: vmlinux] Error 1
> > make: *** [Makefile:179: sub-make] Error 2
>
> I managed to reproduce this with gcc version 8.3.0 (Ubuntu
> 8.3.0-6ubuntu1~18.04.1) , and bisected the failure to commit
> 025f072e5823947c ("compiler: enable CONFIG_OPTIMIZE_INLINING forcibly") .
>
> Marking the functions __always_inline instead of inline fixes that.
> Shall I send a patch to do that?


Yes, please.

But you do not need to touch _transp() or comp().
Only functions that call c2p_unsupported().


BTW, c2p_unsupported() can be replaced with BUILD_BUG().
This will break the build earlier in case
it cannot be optimized out.


-- 
Best Regards
Masahiro Yamada