linux-kernel - Re: objtool warning "uses BP as a scratch register" with clang-9

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Message-ID: <CAHk-=wgcQBYjs-bX-v4CQUaT_bh_41EzEw4PmvSjBmAxGbr3OQ@mail.gmail.com>
Date:   Fri, 30 Aug 2019 09:03:33 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Ilie Halip <ilie.halip@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: objtool warning "uses BP as a scratch register" with clang-9

On Fri, Aug 30, 2019 at 8:14 AM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>
> What about just adding a couple of WRITE_ONCE's to sas_ss_reset()?  That
> would probably be the least disruptive option.

I think that WRITE_ONCE() with a comment about why is a good idea.

The reason I dislike WRITE_ONCE() in general is not because it's
wrong, it's because people often use it mindlessly and the rationale
for it isn't clear.

But with a comment about why, that issue obviously goes away.

            Linus