linux-kernel - Re: [RFC/Requirements/Design] h/w error reporting

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Message-ID: <20101110184931.GI22410@elte.hu>
Date:	Wed, 10 Nov 2010 19:49:31 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	"Luck, Tony" <tony.luck@...el.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Huang, Ying" <ying.huang@...el.com>,
	"bp@...en8.de" <bp@...en8.de>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"mchehab@...hat.com" <mchehab@...hat.com>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [RFC/Requirements/Design] h/w error reporting


* Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:

> On Wed, 2010-11-10 at 10:23 -0800, Luck, Tony wrote:
> > > A few of things that pop up quickly are:
> > >
> > > 1) lockless
> > 
> > This is a clear requirement for use in h/w error
> > reporting too.  Taking locks in NMI or machine
> > check handler isn't an option.
> 
> Don't worry, lots of PMIs are NMIs, perf needs to be fully NMI safe
> otherwise things simply don't work.

Yep, in fact perf was fully NMI safe earlier than the ftrace ring-buffer.

When perf code is NMI unsafe we notice it very quickly. I regularly record millions 
of events per second.

Thanks,

	Ingo
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