linux-kernel - Re: [PATCH 4/9] x86, NMI: Remove DIE_NMI

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Date:	Wed, 1 Dec 2010 22:30:34 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Don Zickus <dzickus@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Robert Richter <robert.richter@....com>, ying.huang@...el.com,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/9] x86, NMI: Remove DIE_NMI_IPI and add priorties to
 handlers

On Wed, Dec 01, 2010 at 09:41:28PM +0300, Cyrill Gorcunov wrote:
> On Tue, Nov 30, 2010 at 05:27:25PM -0500, Don Zickus wrote:
> > When re-ordering how the NMI handles its callbacks, a conversation started
> > asking what DIE_NMI_IPI meant.  No one could answer it.
> 
> It should have came from commit
> 
>  | commit c4b2bffee2a4115fed2825530f2b906ee2f17bd7
>  | Author: Andi Kleen <ak@...e.de>
>  | Date:   Fri Jan 23 18:46:40 2004 -0800
>  |
>  |   [PATCH] x86-64 merge
>  |   
>  |   Mainly lots of bug fixes and a few minor features. One change is that
>  |   it uses drivers/Kconfig now like i386. This requires a few minor changes in
>  |   outside Kconfig files which I am sending separately.
>  ...
> 
> Andi do you remember what the initial idea was? Didn't find any user of it
> even in this old commit. Just curious.

The original die names were pretty much a 1:1 conversion of the hooks
used by both the external KDB and KGDB patchkits floating around
at that time.

IIRC DIE_NMI_IPI was the one that was early in the NMI handler
and DIE_NMI late when everything else failed.

So you could use NMI_IPI when you just wanted to stop
all CPUs with a broadcast NMI and can check that reliable
through some memory location, and NMI when you wanted
to drop into the debugger as a last resort.


-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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