linux-kernel - Re: [PATCH] futex: remove unused empty compat_exit_robust

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Date:   Sat, 14 Nov 2020 01:15:20 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Darren Hart <dvhart@...radead.org>, Arnd Bergmann <arnd@...db.de>,
        Tom Rix <trix@...hat.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lukas Bulwahn <lukas.bulwahn@...il.com>
Subject: Re: [PATCH] futex: remove unused empty compat_exit_robust_list()

Lukas,

On Fri, Nov 13 2020 at 18:20, Lukas Bulwahn wrote:
> Commit ba31c1a48538 ("futex: Move futex exit handling into futex code")
> introduced compat_exit_robust_list() with a full-fledged implementation for
> CONFIG_COMPAT, and an empty-body function for !CONFIG_COMPAT.
> However, compat_exit_robust_list() is only used in futex_mm_release() under
> ifdef CONFIG_COMPAT.
>
> Hence for !CONFIG_COMPAT, make CC=clang W=1 warns:
>
>   kernel/futex.c:314:20:
>     warning: unused function 'compat_exit_robust_list' [-Wunused-function]
>
> There is no need to declare the unused empty function for !CONFIG_COMPAT.
> Simply, remove it to address the -Wunused-function warning.

While I agree with the removal, I disagree with the reasoning.

The real argument is that the stub function is useless. Addressing the
warning is a side effect of the removal, nothing else.

Thanks,

        tglx