linux-kernel - Re: [PATCH 06/20 -v5] add notrace annotations for NMI routines

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Message-ID: <Pine.LNX.4.58.0801231650150.19550@gandalf.stny.rr.com>
Date:	Wed, 23 Jan 2008 16:58:34 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Christoph Hellwig <hch@...radead.org>,
	Gregory Haskins <ghaskins@...ell.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tim Bird <tim.bird@...sony.com>,
	Sam Ravnborg <sam@...nborg.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	John Stultz <johnstul@...ibm.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 06/20 -v5] add notrace annotations for NMI routines



On Wed, 23 Jan 2008, Mathieu Desnoyers wrote:

> * Steven Rostedt (rostedt@...dmis.org) wrote:
> > This annotates NMI functions with notrace. Some tracers may be able
> > to live with this, but some cannot. So we turn off NMI tracing.
> >
> > One solution might be to make a notrace_nmi which would only turn
> > off NMI tracing if a trace utility needed it off.
> >
> Is this still needed with the atomic clocksource read ?

This never had to do with the clocksource. The tracer itself isn't atomic
against NMIs. hmm, it may actually be. It does a tracer disable for the
CPU by an atomic_inc and this would prevent the NMI from causing harm.

I'll test without this patch and see what happens when I turn on a high
rate of NMIS.

I still want to add a bit more notraces around for the simple
reason of cleaning up the output and prehaps speeding up the code a bit.

-- Steve

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