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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Tue, 5 Jun 2018 23:28:54 +0200
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Subject: Re: [PATCH v2 2/2] x86: paravirt: make native_save_fl extern inline
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
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On Tue, Jun 5, 2018 at 7:05 PM, Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> The semantics of extern inline has changed since gnu89. This means that
> folks using GCC versions >= 5.1 may see symbol redefinition errors at
> link time for subdirs that override KBUILD_CFLAGS (making the C standard
> used implicit) regardless of this patch. This has been cleaned up
> earlier in the patch set, but is left as a note in the commit message
> for future travelers.

I think the keyword you are missing is

__attribute__((gnu_inline))

which forces the gnu89 behavior on all compiler versions. It's been supported
since gcc-4.2, so it should not cause problems on any compiler that is able
to build an x86 kernel.

       Arnd