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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 10 Jan 2020 10:54:27 -0800
Message-ID: <CAHk-=wia5ppBsfHLMx648utCjO01JAZiME0K0eSHmhWuRyL+6w@mail.gmail.com>
Subject: Re: [RFC PATCH 6/8] READ_ONCE: Drop pointer qualifiers when reading
 from scalar types
To:     Will Deacon <will@kernel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Android Kernel Team <kernel-team@android.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Peter Zijlstra <peterz@infradead.org>,
        Segher Boessenkool <segher@kernel.crashing.org>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
        Arnd Bergmann <arnd@arndb.de>
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On Fri, Jan 10, 2020 at 8:56 AM Will Deacon <will@kernel.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

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