linux-kernel - Re: [PATCH 1/2] boot: ignore early NMIs

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Message-ID: <20120312133619.GB17288@redhat.com>
Date:	Mon, 12 Mar 2012 09:36:19 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Fernando Luis Vázquez Cao 
	<fernando@....ntt.co.jp>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Don Zickus <dzickus@...hat.com>,
	linux-tip-commits@...r.kernel.org, torvalds@...ux-foundation.org,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	mingo@...hat.com, tglx@...utronix.de, mingo@...e.hu,
	Yinghai Lu <yinghai@...nel.org>, akpm@...ux-foundation.org
Subject: Re: [PATCH 1/2] boot: ignore early NMIs

On Mon, Mar 12, 2012 at 03:14:20PM +0900, Fernando Luis Vázquez Cao wrote:

[..]
> The thing is that we want to avoid playing with hardware in the kdump
> reboot patch when we can avoid it, the premise being that it cannot
> be accessed without risking a lockup or worse (as the deadlock accessing
> the I/O APIC showed).

I think there needs to be a limit to being paranoid. On one hand people
want to run panic notifiers, all the kmsg_dump() hooks in panic path, and
on the other hand we are afraid of even disabling LAPIC.

I personally think that disabling LAPIC is reasonably practical solution
to the problem until and unless somebody shows that it deadlocks easily.

Thanks
Vivek
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