linux-kernel - Re: [PATCH 2/3] x86: add safe_smp_processor_id for x86

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Message-ID: <20071024090128.GA4809@in.ibm.com>
Date:	Wed, 24 Oct 2007 14:31:28 +0530
From:	Vivek Goyal <vgoyal@...ibm.com>
To:	h-shimamoto@...jp.nec.com
Cc:	hbabu@...ibm.com, tglx@...utronix.de, linux-kernel@...r.kernel.org,
	kexec@...ts.infradead.org,
	Fernando Luis Vazquez Cao <fernando@...ellilink.co.jp>
Subject: Re: [PATCH 2/3] x86: add safe_smp_processor_id for x86_64

On Wed, Oct 24, 2007 at 12:01:41PM +0530, Vivek Goyal wrote:
> On Fri, Oct 19, 2007 at 06:23:02PM -0700, Hiroshi Shimamoto wrote:
> > From: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
> > 
> > Signed-off-by: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
> > ---
> >  include/asm-x86/smp_64.h |    2 ++
> >  1 files changed, 2 insertions(+), 0 deletions(-)
> > 
> > diff --git a/include/asm-x86/smp_64.h b/include/asm-x86/smp_64.h
> > index 6f0e027..ab612b0 100644
> > --- a/include/asm-x86/smp_64.h
> > +++ b/include/asm-x86/smp_64.h
> > @@ -76,6 +76,8 @@ extern unsigned __cpuinitdata disabled_cpus;
> > 
> >  #endif /* CONFIG_SMP */
> > 
> > +#define safe_smp_processor_id()		smp_processor_id()
> > +
> 
> Can you please implement a patch for safe_smp_processor_id() instead of
> using smp_processor_id(). safe_smp_processor_id() was introduced to make
> sure that we are not dependent on the stack of threads after kernel has
> crashed instead read the apic id and convert it to cpu id with other
> data structures. This helped in stack overflow case.
> 
> Hardcoding it to smp_processor_id() will give the false impression.
> 

Just now Aneesh pointed that x86_64 using pda for retrieving processor id
and not kernel stack.

I think it is fine then.

Thanks
Vivek
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