From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 08/13] xen/pvticketlock: disable interrupts
 while blocking
Date: Fri, 02 Sep 2011 22:47:48 +0200
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References: <cover.1314922370.git.jeremy.fitzhardinge@citrix.com>
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	<1314974826.1861.1.camel@twins> <4E612EA1.20007@goop.org>
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To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Xen Devel <xen-devel@lists.xensource.com>, Marcelo Tosatti <mtosatti@redhat.com>, Nick Piggin <npiggin@kernel.dk>, KVM <kvm@vger.kernel.org>, maintainers <x86@kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Andi Kleen <andi@firstfloor.org>, Avi Kivity <avi@redhat.com>, Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>, "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@elte.hu>, Linus Torvalds <torvalds@linux-foundation.org>, the
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On Fri, 2011-09-02 at 12:29 -0700, Jeremy Fitzhardinge wrote:
>=20
> > I know that its generally considered bad form, but there's at least one
> > spinlock that's only taken from NMI context and thus hasn't got any
> > deadlock potential.
>=20
> Which one?=20

arch/x86/kernel/traps.c:nmi_reason_lock

It serializes NMI access to the NMI reason port across CPUs.