linux-kernel - Re: [PATCH] sched: Fix unused variable warning on UP (was: Re: linux-next: tip tree build warning)

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Message-ID: <10f740e81002071231j6977c6c7ie3f9e82bd0170f21@mail.gmail.com>
Date:	Sun, 7 Feb 2010 21:31:56 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH] sched: Fix unused variable warning on UP (was: Re: 
	linux-next: tip tree build warning)

On Sun, Feb 7, 2010 at 21:26, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> On Sun, Feb 7, 2010 at 20:58, Peter Zijlstra <peterz@...radead.org> wrote:
>> On Sun, 2010-02-07 at 20:57 +0100, Geert Uytterhoeven wrote:
>>> On Mon, Feb 1, 2010 at 08:12, Stephen Rothwell <sfr@...b.auug.org.au> wrote:
>>> > Today's linux-next build (powerpc allnoconfig) produced this warning:
>>> >
>>> > kernel/sched.c: In function 'wake_up_new_task':
>>> > kernel/sched.c:2631: warning: unused variable 'cpu'
>>> >
>>> > Introduced by commit fabf318e5e4bda0aca2b0d617b191884fda62703 ("sched:
>>> > Fix fork vs hotplug vs cpuset namespaces").
>>>
>>> And now we have it in 2.6.33-rc7, too...
>>> Patch below (FWIW, compile-tested on m68k with CONFIG_SMP=n only).
>>>
>>> ---
>>> From cbf4f334632ade9c5ed9b88728ec82af074e4ace Mon Sep 17 00:00:00 2001
>>> From: Geert Uytterhoeven <geert@...ux-m68k.org>
>>> Date: Sun, 7 Feb 2010 20:47:30 +0100
>>> Subject: [PATCH] sched: Fix unused variable warning on UP
>>>
>>> Fix warning
>>>
>>> | kernel/sched.c:2650: warning: unused variable 'cpu'
>>>
>>> if CONFIG_SMP is not set.
>>>
>>> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>>> ---
>>>  kernel/sched.c |    3 ++-
>>>  1 files changed, 2 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/kernel/sched.c b/kernel/sched.c
>>> index 3a8fb30..c47561e 100644
>>> --- a/kernel/sched.c
>>> +++ b/kernel/sched.c
>>> @@ -2647,9 +2647,10 @@ void wake_up_new_task(struct task_struct *p,
>>> unsigned long clone_flags)
>>>  {
>>>       unsigned long flags;
>>>       struct rq *rq;
>>> -     int cpu = get_cpu();
>>>
>>>  #ifdef CONFIG_SMP
>>> +     int cpu = get_cpu();
>>> +
>>>       /*
>>>        * Fork balancing, do it here and not earlier because:
>>>        *  - cpus_allowed can change in the fork path
>>
>> Which introduces a preempt imbalance... I like akpm's fix much better.
>
> Bummer, you're right. Sorry, that teaches me not to write patches
> after 2 days of FOSDEM ;-)

<trying to completely destroy my credibility>
Shouldn't put_cpu() take a (possibly dummy) `cpu' parameter, as
returned by get_cpu()?
</trying>

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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