linux-kernel - Re: [tip:perf/core] x86, NMI: Rewrite NMI handler

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Message-ID: <20101017004641.GB4140@redhat.com>
Date:	Sat, 16 Oct 2010 20:46:41 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...hat.com, hpa@...or.com, ying.huang@...el.com,
	linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/core] x86, NMI: Rewrite NMI handler

On Sat, Oct 16, 2010 at 07:29:17PM +0200, Peter Zijlstra wrote:
> On Sat, 2010-10-16 at 16:36 +0000, tip-bot for Huang Ying wrote:
> > Commit-ID:  e21f3e4957f4a55f546873605a5caa59556bb144
> > Gitweb:     http://git.kernel.org/tip/e21f3e4957f4a55f546873605a5caa59556bb144
> > Author:     Huang Ying <ying.huang@...el.com>
> > AuthorDate: Fri, 15 Oct 2010 22:22:16 -0400
> > Committer:  Ingo Molnar <mingo@...e.hu>
> > CommitDate: Sat, 16 Oct 2010 15:01:27 +0200
> > 
> > x86, NMI: Rewrite NMI handler
> > 
> > The original NMI handler is quite outdated in many aspects. This
> > patch tries to fix it.
> > 
> > The order to process the NMI sources are changed as follow:
> > 
> >  notify_die(DIE_NMI_IPI);
> >  notify_die(DIE_NMI);
> >  /* process io port 0x61 */
> >  nmi_watchdog_touch();
> >  unknown_nmi();
> 
> NACK!
> 
> I object to the DIE_NMI_IPI existance..

Hmm, well to his defense, he isn't adding DIE_NMI_IPI.  That code is
already there.  He is just re-arranging it, making it look painfully
obvious the die_chain probably isn't as efficient as it should be.

I think a bunch of us agree that we need to revamp the NMI notifier to
make it less wasteful.  I was hoping we could do that in a separate patch
that would be layered on top of Huangs.

Would you object to at least consider having this patch series in a
work-in-progress git branch that we can build on top of, with the final
outcome containing an nmi notifier that meets your expectations?

Cheers,
Don

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