linux-kernel - Re: [PATCH v2] hwmon (coretemp): Fix build breakage if SMP is undefined

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Message-ID: <AANLkTinDkJu2MSJM6bUpWJoB2XOD4LLf6GTPBX39wteD@mail.gmail.com>
Date:	Mon, 27 Sep 2010 16:44:01 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Guenter Roeck <guenter.roeck@...csson.com>
Cc:	Pekka Enberg <penberg@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Jean Delvare <khali@...ux-fr.org>
Subject: Re: [PATCH v2] hwmon (coretemp): Fix build breakage if SMP is undefined

On Mon, Sep 27, 2010 at 4:27 PM, Guenter Roeck
<guenter.roeck@...csson.com> wrote:
> On Mon, Sep 27, 2010 at 09:02:57AM -0400, Pekka Enberg wrote:
>> On Mon, Sep 27, 2010 at 3:59 PM, Ingo Molnar <mingo@...e.hu> wrote:
>> >
>> > * Guenter Roeck <guenter.roeck@...csson.com> wrote:
>> >
>> >> +#ifdef CONFIG_SMP
>> >> +#endif
>> >> +#ifdef CONFIG_SMP
>> >> +#endif
>> >
>> > Hm, this tickles my uglo-meter. Is there no cleaner way, preferably one
>> > that doesnt involve preprocessor directives?
>>
>> Implement cpu_sibling_mask() on UP so that the loop goes away?
>
> So what is the take ? Looks like Linus won't accept my patch without someone
> else signing off on it. If the uglo-meter prevents it from being accepted,
> I'll be happy to submit the SMP cleanup patch instead. As I mentioned
> before, I would prefer that to go into -next.

I'd _much_ rather see cpu_sibling_mask() on UP, and just have the loop go away.

But that would be a generic change. Something like the (UNTESTED!)
attached. It returns a NULL, since it would always be a bug to
actually _use_ the (nonexistent) mask. And that's fine for things like
for_each_cpu() that will then happily ignore the mask.

Ingo, does this make those randconfig things work? I think it's
prettier than the horrible "sprinkle #ifdef CONFIG_SMP around in
random places".

                        Linus

View attachment "patch.diff" of type "text/x-patch" (483 bytes)