From: Keith Owens <kaos@sgi.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Takao Indoh <indou.takao@soft.fujitsu.com>, linux-kernel@vger.kernel.org,
       Christoph Hellwig <hch@infradead.org>, Andi Kleen <ak@muc.de>
Subject: Re: [3/4] [PATCH]Diskdump - yet another crash dump function 
In-reply-to: Your message of "Thu, 17 Jun 2004 14:13:56 +0200."
             <20040617121356.GA24338@elte.hu> 
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Date: Mon, 21 Jun 2004 15:46:11 +1000
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On Thu, 17 Jun 2004 14:13:56 +0200, 
Ingo Molnar <mingo@elte.hu> wrote:
>but there's another possible method (suggested by Alan Cox) that
>requires no changes to the timer API hotpaths: 'clear' all timer lists
>upon a crash [once all CPUs have stopped and irqs are disabled] and just
>let the drivers use the normal timer APIs. Drive timer execution via a
>polling method.
>
>this basically approximates your polling based implementation but uses
>the existing kernel timer data structures and timer mechanism so should
>be robust and compatible. It doesnt rely on any previous state (because
>all currently pending timers are discarded) so it's as crash-safe as
>possible.

Don't forget live crash dumping.  The system is running and is behaving
strangely so you want to take a dump for investigation, but you do not
want to kill the system afterwards.  Live crash dumping is very useful
for problem diagnosis.

It is a little more complex than dumping after an oops because you must
not destroy any kernel data, including timer lists.

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