linux-kernel - Re: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu

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Message-ID: <CAHk-=wi3LZ_4OGAMhvgO0JSTp-eEPOGp+siq1nJNLY1JAxdP5Q@mail.gmail.com>
Date:   Thu, 19 Oct 2023 11:06:04 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Uros Bizjak <ubizjak@...il.com>
Cc:     peterz@...radead.org, Nadav Amit <namit@...are.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu_ptr()

On Thu, 19 Oct 2023 at 10:21, Uros Bizjak <ubizjak@...il.com> wrote:
>
> > A compiler that were to rematerializes an inline asm (instead of
> > spilling) would be a bad joke. That's not an optimization, that's just
> > a crazy bad compiler with a code generation bug.
>
> But that is what the compiler does without volatile.

Do you actually have a real case of that, or are basing it purely off
insane documentation?

Because remat of inline asm really _is_ insane.

           Linus