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

[Geert Uytterhoeven]

On Sun, Feb 7, 2010 at 20:58, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Sun, 2010-02-07 at 20:57 +0100, Geert Uytterhoeven wrote:
>> On Mon, Feb 1, 2010 at 08:12, Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx>
>> 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@xxxxxxxxxxxxxx>
>> ---
>> Âkernel/sched.c | Â Â3 ++-
>> Â1 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)
>> Â{
>> Â Â Â unsigned long flags;
>> Â Â Â struct rq *rq;
>> - Â Â int cpu = get_cpu();
>>
>> Â#ifdef CONFIG_SMP
>> + Â Â int cpu = get_cpu();
>> +
>> Â Â Â /*
>> Â Â Â Â* Fork balancing, do it here and not earlier because:
>> Â Â Â Â* Â- 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 ;-)

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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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