linux-kernel - Re: [RFC PATCH 3/6] perf: Generalize some arch callchain code

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Message-ID: <1277999482.1917.219.camel@laptop>
Date:	Thu, 01 Jul 2010 17:51:22 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	David Miller <davem@...emloft.net>,
	Paul Mundt <lethal@...ux-sh.org>,
	Will Deacon <will.deacon@....com>,
	Borislav Petkov <bp@...64.org>
Subject: Re: [RFC PATCH 3/6] perf: Generalize some arch callchain code

On Thu, 2010-07-01 at 17:49 +0200, Frederic Weisbecker wrote:
> On Thu, Jul 01, 2010 at 05:46:01PM +0200, Peter Zijlstra wrote:
> > On Thu, 2010-07-01 at 17:35 +0200, Frederic Weisbecker wrote:
> > > - Most archs use one callchain buffer per cpu, except x86 that needs
> > >   to deal with NMIs. Provide a default perf_callchain_buffer()
> > >   implementation that x86 overrides. 
> > 
> > sparc and power also have NMI like contexts.
> 
> 
> Ah and the comments suggest it's because pmu interrupts can't nest or so.
> Anyway, that's notwithstanding the race that 5th patch fixes.

Right, but they could interrupt a software event or the like.

But yeah, the whole callchain thing can nest issue is real, thanks for
fixing that.
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