linux-kernel - Re: [V3 PATCH 2/4] panic/x86: Allow cpus to save registers even if they are looping in NMI context

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Date:	Fri, 21 Aug 2015 01:18:16 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
Cc:	Jonathan Corbet <corbet@....net>, Ingo Molnar <mingo@...nel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vivek Goyal <vgoyal@...hat.com>, linux-doc@...r.kernel.org,
	x86@...nel.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Subject: Re: [V3 PATCH 2/4] panic/x86: Allow cpus to save registers even if
 they are looping in NMI context

On Thu, Aug 06, 2015 at 02:45:43PM +0900, Hidehiro Kawai wrote:
> When cpu-A panics on NMI just after cpu-B has panicked, cpu-A loops
> infinitely in NMI context.  Especially for x86, cpu-B issues NMI IPI
> to other cpus to save their register states and do some cleanups if
> kdump is enabled, but cpu-A can't handle the NMI and fails to save
> register states.
> 
> To solve thie issue, we wait for the timing of the NMI IPI, then
> call the NMI handler which saves register states.

Sorry, I don't follow, what?
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