linux-kernel - Re: [tip:perfcounters/core] perf_counter: x86: Fix call-chain support to use NMI-safe methods

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Message-ID: <20090615224908.GA16661@Krystal>
Date:	Mon, 15 Jun 2009 18:49:08 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	mingo@...hat.com, paulus@...ba.org, acme@...hat.com,
	linux-kernel@...r.kernel.org, penberg@...helsinki.fi,
	vegard.nossum@...il.com, efault@....de, jeremy@...p.org,
	npiggin@...e.de, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perfcounters/core] perf_counter: x86: Fix call-chain
	support to use NMI-safe methods

* H. Peter Anvin (hpa@...or.com) wrote:
> Mathieu Desnoyers wrote:
> > 
> > I'm just thinking that touching or not vmalloc'd areas should not be the
> > first thing that comes into the mind of someone willing to write a
> > nmi-hooking tracer or oprofile module.
> > 
> 
> But is HAS to be.  Otherwise you're in deadlock city anyway.
> 

Where is the kernel page fault handler grabbing any lock to service
in-kernel page faults exactly ?

Those are usually considered as utterly simple page table fixups,
nothing more.

Mathieu

> 	-hpa
> 

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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