linux-kernel - Re: [PATCH 1/3] x86: only call smp_processor

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Date:	Thu, 18 Nov 2010 15:49:21 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Don Zickus <dzickus@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 1/3] x86: only call smp_processor_id in non-preempt cases


* Don Zickus <dzickus@...hat.com> wrote:

> On Thu, Nov 18, 2010 at 09:14:07AM +0100, Ingo Molnar wrote:
> > 
> > * Don Zickus <dzickus@...hat.com> wrote:
> > 
> > > There are some paths that walk the die_chain with preemption on.
> > 
> > What are those codepaths? At minimum it's worth documenting them.
> 
> Well the one that caused the bug was do_general_protection which walks the
> die_chain with DIE_GPF.
> 
> I can document them, though it might be time consuming to audit them and hope they 
> don't change.

Listing one example is enough.

> [...]  I guess my bigger question is, is it expected that anyone who calls the 
> die_chain to have preemption disabled?  If not, then does it matter if we document 
> it?

Yes, it might be a bug to call those handlers with preemption on (or even with irqs 
on). But if the code is fine as-is then documenting a single example would be nice.

Thanks,

	Ingo
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