linux-kernel - Re: [PATCH] x86: show cpuinfo only for online CPUs

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Date:	Thu, 1 Nov 2007 18:35:43 +0100
From:	"Andreas Herrmann3" <andreas.herrmann3@....com>
To:	"Glauber de Oliveira Costa" <gcosta@...hat.com>
cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, tglx@...utronix.de,
	akpm@...ux-foundation.org, travis@....com
Subject: Re: [PATCH] x86: show cpuinfo only for online CPUs

On Thu, Nov 01, 2007 at 03:12:25PM -0200, Glauber de Oliveira Costa wrote:
> did you test it in a kernel without SMP compiled in ?
> 
> I'm a little afraid about what can happen here:

No I didn't, but should have done so - cpu_index exists only
in the SMP case ...

I'll come up with a corrected fix (adding some ifdefs).

> The attribuition of cpu_index only happens in a code that seems to be
> called for all cpus but the boot one.

Yes, just in identify_cpu and not in its "early_" variant.

> So it could even work, but as accident. Unless I'm wrong about it, I'd
> prefer to see an explicit attribution of cpu_index = 0 somewhere for the
> boot cpu.

Hmm, will look at this as well.

> Other than that, good catch! I didn't notice it, because all my present
> cpus were online in my box

You might be able to trigger it by using additional_cpus=<n> in your kernel
command line.
A second test is offlining a CPU: Then cpuinfo was still shown for the
offlined CPU.


Regards,

Andreas

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