linux-kernel - Re: [PATCH] mm: add config NUMA stub to all architectures

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Message-ID: <CAMuHMdUYCGoZoUHWMtMCwAJ2ofweaeLF3U89P5EvrNGcn=6apw@mail.gmail.com>
Date:	Sun, 19 Feb 2012 18:01:33 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH] mm: add config NUMA stub to all architectures

On Fri, Feb 17, 2012 at 21:30, Andrew Morton <akpm@...ux-foundation.org> wrote:
> On Fri, 17 Feb 2012 16:08:15 +0400
> Konstantin Khlebnikov <khlebnikov@...nvz.org> wrote:
>
>> Config NUMA must be defined for all architectures,
>> otherwise IS_ENABLED(CONFIG_NUMA) does not work.
>> Some arch-specific Kconfig already has this stub.
>> This patch adds it to all remaining.
>
> It would be better to teach IS_ENABLED() to handle this situation.  I
> don't think there's a way of doing this with cpp :(
>
> This limitation makes IS_ENABLED pretty dangerous, doesn't it?  It
> makes it very easy to introduce build breakage with unexpected Kconfig
> combinations.

Indeed. Recently I discovered IS_ENABLED() and started recommending it
to people for new code. But now I've seen the CONFIG_NUMA breakage,
I no longer think this is a good recommendation.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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