linux-kernel - Re: [RFC PATCH] x86 NMI-safe INT3 and Page Fault (v5)

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Message-ID: <20080419212311.GD1554@Krystal>
Date:	Sat, 19 Apr 2008 17:23:11 -0400
From:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	mingo@...e.hu, akpm@...l.org, "H. Peter Anvin" <hpa@...or.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Frank Ch. Eigler" <fche@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] x86 NMI-safe INT3 and Page Fault (v5)

* Andi Kleen (andi@...stfloor.org) wrote:
> Mathieu Desnoyers <compudj@...stal.dyndns.org> writes:
> >
> > It uses RCU-style updates and has been designed to be lockless from the
> > ground up.
> 
> RCU is not necessarily NMI safe. In most cases RCU needs writer locks
> which you cannot do with NMIs.
> 
> -Andi
> 

RCU-style updates are done outside of NMIs, in sleepable context. That's
just required when the probes connected on markers must be
registered/unregistered.

The NMI context is the RCU read side. It only have to get the probe
function pointers to call along with the private data pointers.

Mathieu


-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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