From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner+w=401wt.eu-S1755356AbZFPBcd@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755356AbZFPBcd (ORCPT <rfc822;w@1wt.eu>);
	Mon, 15 Jun 2009 21:32:33 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751548AbZFPBcZ
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Mon, 15 Jun 2009 21:32:25 -0400
Received: from terminus.zytor.com ([198.137.202.10]:59653 "EHLO
	terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751428AbZFPBcY (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 15 Jun 2009 21:32:24 -0400
Message-ID: <4A36F520.6020604@zytor.com>
Date: Mon, 15 Jun 2009 18:28:00 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
User-Agent: Thunderbird 2.0.0.14 (X11/20080501)
MIME-Version: 1.0
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Linus Torvalds <torvalds@linux-foundation.org>, mingo@redhat.com,
       paulus@samba.org, acme@redhat.com, linux-kernel@vger.kernel.org,
       penberg@cs.helsinki.fi, vegard.nossum@gmail.com, efault@gmx.de,
       jeremy@goop.org, npiggin@suse.de, tglx@linutronix.de,
       linux-tip-commits@vger.kernel.org
Subject: Re: [tip:perfcounters/core] perf_counter: x86: Fix call-chain	support
 to use NMI-safe methods
References: <4A36A1C7.6080005@zytor.com> <20090615210119.GD24554@elte.hu> <20090615211207.GB12919@Krystal> <20090615211605.GC27100@elte.hu> <20090615213429.GD12919@Krystal> <4A36BF61.10901@zytor.com> <20090615215420.GE12919@Krystal> <4A36C953.8060906@zytor.com> <20090615223038.GA15903@Krystal> <4A36CCFC.8070908@zytor.com> <20090615224908.GA16661@Krystal>
In-Reply-To: <20090615224908.GA16661@Krystal>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Mathieu Desnoyers wrote:
> 
> 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.
> 

It doesn't, *because it doesn't have to*.  Your proposal requires that
page faults can be handled inside the page fault handler, and that's a
pretty tall order.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.