linux-kernel - Re: [PATCH RFC V10 15/18] kvm : Paravirtual ticketlocks support for linux guests running on KVM hypervisor

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Message-ID: <20130716154852.GN23818@dyad.programming.kicks-ass.net>
Date:	Tue, 16 Jul 2013 17:48:52 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	mingo@...hat.com, jeremy@...p.org, x86@...nel.org,
	konrad.wilk@...cle.com, hpa@...or.com, pbonzini@...hat.com,
	linux-doc@...r.kernel.org, habanero@...ux.vnet.ibm.com,
	xen-devel@...ts.xensource.com, mtosatti@...hat.com,
	stefano.stabellini@...citrix.com, andi@...stfloor.org,
	attilio.rao@...rix.com, ouyang@...pitt.edu, gregkh@...e.de,
	agraf@...e.de, chegu_vinod@...com, torvalds@...ux-foundation.org,
	avi.kivity@...il.com, tglx@...utronix.de, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, stephan.diestelhorst@....com,
	riel@...hat.com, drjones@...hat.com,
	virtualization@...ts.linux-foundation.org,
	srivatsa.vaddagiri@...il.com
Subject: Re: [PATCH RFC V10 15/18] kvm : Paravirtual ticketlocks support for
 linux guests running on KVM hypervisor

On Tue, Jul 16, 2013 at 09:02:15AM +0300, Gleb Natapov wrote:
> BTW can NMI handler take spinlocks? 

No -- that is, yes you can using trylock, but you still shouldn't.

> If it can what happens if NMI is
> delivered in a section protected by local_irq_save()/local_irq_restore()?

You deadlock.
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