linux-kernel - Re: [RFC PATCH 6/8] READ_ONCE: Drop pointer qualifiers when reading from scalar types

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Message-ID: <CAHk-=wia5ppBsfHLMx648utCjO01JAZiME0K0eSHmhWuRyL+6w@mail.gmail.com>
Date:   Fri, 10 Jan 2020 10:54:27 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Will Deacon <will@...nel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Peter Zijlstra <peterz@...radead.org>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [RFC PATCH 6/8] READ_ONCE: Drop pointer qualifiers when reading
 from scalar types

On Fri, Jan 10, 2020 at 8:56 AM Will Deacon <will@...nel.org> wrote:
>
> +/* Declare an unqualified scalar type. Leaves non-scalar types unchanged. */
> +#define __unqual_scalar_typeof(x) typeof(                                      \

Ugh. My eyes. That's horrendous.

I can't see any better alternatives, but it does make me go "Eww".

Well, I do see one possible alternative: just re-write the bitop
implementations in terms of "atomic_long_t", and just avoid the issue
entirely.

IOW, do something like the attached (but fleshed out and tested - this
patch has not seen a compiler, much less any thought at all).

                   Linus

View attachment "patch.diff" of type "text/x-patch" (1107 bytes)