From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner+willy=40w.ods.org-S1423789AbWKPLFU@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1423789AbWKPLFU (ORCPT <rfc822;willy@w.ods.org>);
	Thu, 16 Nov 2006 06:05:20 -0500
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1423846AbWKPLFT
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Thu, 16 Nov 2006 06:05:19 -0500
Received: from aun.it.uu.se ([130.238.12.36]:44203 "EHLO aun.it.uu.se")
	by vger.kernel.org with ESMTP id S1423844AbWKPLFS (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 16 Nov 2006 06:05:18 -0500
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Message-ID: <17756.17330.974883.486535@alkaid.it.uu.se>
Date: Thu, 16 Nov 2006 11:55:46 +0100
From: Mikael Pettersson <mikpe@it.uu.se>
To: Andrew Morton <akpm@osdl.org>
Cc: ebiederm@xmission.com (Eric W. Biederman), Andi Kleen <ak@suse.de>,
       Linus Torvalds <torvalds@osdl.org>, discuss@x86-64.org,
       William Cohen <wcohen@redhat.com>, Komuro <komurojun-mbn@nifty.com>,
       Ernst Herzberg <earny@net4u.de>, Andre Noll <maan@systemlinux.org>,
       oprofile-list@lists.sourceforge.net, Jens Axboe <jens.axboe@oracle.com>,
       linux-usb-devel@lists.sourceforge.net, phil.el@wanadoo.fr,
       Adrian Bunk <bunk@stusta.de>, Ingo Molnar <mingo@redhat.com>,
       Alan Stern <stern@rowland.harvard.edu>,
       linux-pci@atrey.karlin.mff.cuni.cz,
       Stephen Hemminger <shemminger@osdl.org>,
       Prakash Punnoor <prakash@punnoor.de>, Len Brown <len.brown@intel.com>,
       Alex Romosan <romosan@sycorax.lbl.gov>, gregkh@suse.de,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Andrey Borzenkov <arvidjaar@mail.ru>
Subject: Re: [discuss] Re: 2.6.19-rc5: known regressions (v3)
In-Reply-To: <20061115133121.8d9d621f.akpm@osdl.org>
References: <Pine.LNX.4.64.0611071829340.3667@g5.osdl.org>
	<200611151945.31535.ak@suse.de>
	<Pine.LNX.4.64.0611151105560.3349@woody.osdl.org>
	<200611152023.53960.ak@suse.de>
	<20061115122118.14fa2177.akpm@osdl.org>
	<m18xic4den.fsf@ebiederm.dsl.xmission.com>
	<20061115133121.8d9d621f.akpm@osdl.org>
X-Mailer: VM 7.17 under Emacs 20.7.1
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org

Andrew Morton writes:
 > Surely the appropriate behaviour is to allow oprofile to steal the NMI and
 > to then put the NMI back to doing the watchdog thing after oprofile has
 > finished with it.

Which is _exactly_ what pre-2.6.19-rc1 kernels did. I implemented
the in-kernel API allowing real performance counter drivers like
oprofile (and perfctr) to claim the HW from the NMI watchdog,
do their work, and then release it which resumed the watchdog.

Note that oprofile (and perfctr) didn't do anything behind the
NMI watchdog's back. They went via the API. Nothing dodgy going on.