linux-kernel - Re: kernel: stop_machine: report (un)dead code (and feedback request)

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Message-ID: <20151126145234.GL23362@nuc-i3427.alporthouse.com>
Date:	Thu, 26 Nov 2015 14:52:34 +0000
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	Valentin Rothberg <valentinrothberg@...il.com>
Cc:	mingo@...nel.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org,
	Patrick Plagwitz <patrick.plagwitz@....de>,
	Andreas Ziegler <ziegler@...fau.de>,
	Daniel Lohmann <dl@...fau.de>
Subject: Re: kernel: stop_machine: report (un)dead code (and feedback request)

On Thu, Nov 26, 2015 at 03:45:59PM +0100, Valentin Rothberg wrote:
> Hi Chris,
> 
> your commit 4c477de14237 ("kernel: remove stop_machine() Kconfig
> dependency") has shown up in today's linux-next tree (20151126).
> The commit changes the #ifdef condition in kernel/stop_machine.c
> from/to:
> 
>     -#if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)
>     +#if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
> 
> Although this change fixes certain configs on X86, the condition now is
> a tautology since CONFIG_SMP is already required to compile the file:
> 
>     kernel/Makefile:65:obj-$(CONFIG_SMP) += stop_machine.o
> 
> AFAIU, we can safely remove this #ifdef?

That seems logical. The argument in favour of it would be to keep the
ifdeffery around the function defintion the same as the function
declaration in stop_machine.h.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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