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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 2 Oct 2019 13:39:40 -0700
Message-ID: <CAHk-=wgFODvdFBHzgVf3JjoBz0z6LZhOm8xvMntsvOr66ASmZQ@mail.gmail.com>
Subject: Re: [PATCH] compiler: enable CONFIG_OPTIMIZE_INLINING forcibly
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Nick Desaulniers <ndesaulniers@google.com>,
        Russell King - ARM Linux admin <linux@armlinux.org.uk>,
        Will Deacon <will@kernel.org>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        linux-arch <linux-arch@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Stefan Wahren <wahrenst@gmx.net>,
        Kees Cook <keescook@google.com>, Arnd Bergmann <arnd@arndb.de>,
        clang-built-linux <clang-built-linux@googlegroups.com>
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On Wed, Oct 2, 2019 at 5:56 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> >
> > Then use the C preprocessor to force the inlining.  I'm sorry it's not
> > as pretty as static inline functions.
>
> Which makes us lose the baby^H^H^H^Htype checking performed
> on function parameters, requiring to add more ugly checks.

I'm 100% agreed on this.

If the inline change is being pushed by people who say "you should
have used macros instead if you wanted inlining", then I will just
revert that stupid commit that is causing problems.

No, the preprocessor is not the answer.

That said, code that relies on inlining for _correctness_ should use
"__always_inline" and possibly even have a comment about why.

But I am considering just undoing commit 9012d011660e ("compiler:
allow all arches to enable CONFIG_OPTIMIZE_INLINING") entirely. The
advantages are questionable, and when the advantages are balanced
against actual regressions and the arguments are "use macros", that
just shows how badly thought out this was.

                Linus