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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue, 7 Mar 2023 13:19:05 -0800
Message-ID: <CAHk-=wiVP8ezgCyBTq3GV-1ebiOf03Qo_iHnVAR08NJO0jOocg@mail.gmail.com>
Subject: Re: [PATCH] x86/resctrl: avoid compiler optimization in __resctrl_sched_in
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     "Luck, Tony" <tony.luck@intel.com>,
        Jakub Jelinek <jakub@redhat.com>,
        Segher Boessenkool <segher@kernel.crashing.org>,
        Peter Zijlstra <peterz@infradead.org>,
        "Eranian, Stephane" <eranian@google.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Chatre, Reinette" <reinette.chatre@intel.com>,
        "Yu, Fenghua" <fenghua.yu@intel.com>,
        "peternewman@google.com" <peternewman@google.com>,
        "james.morse@arm.com" <james.morse@arm.com>,
        "babu.moger@amd.com" <babu.moger@amd.com>,
        "ananth.narayan@amd.com" <ananth.narayan@amd.com>,
        "vschneid@redhat.com" <vschneid@redhat.com>,
        Nathan Chancellor <nathan@kernel.org>,
        clang-built-linux <llvm@lists.linux.dev>,
        Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "linux-toolchains@vger.kernel.org" <linux-toolchains@vger.kernel.org>
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On Tue, Mar 7, 2023 at 1:16=E2=80=AFPM Nick Desaulniers <ndesaulniers@googl=
e.com> wrote:
>
> >
> > Can you expand about part "a" ... Linux has zillions of static inline f=
unctions
> > in header files to handle CONFIG options. One version is the real McCoy
> > while the other is just a stub for the CONFIG=3Dn case.
>
> Right, I had the same question.
>
> Perhaps it's more so that no one calls __resctrl_sched_in, only
> resctrl_sched_in, therefor they should be folded into one function?

If you think it should be inlined, it should be marked as such.

And if you *don't* think it should be inlined - quite possibly the
right answer here - the definition of that function damn well
shouldn't be in a header file.

So either way, that __resctrl_sched_in() was wrong, wrong, wrong.

           Linus