From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner+w=401wt.eu-S1755482AbYHTBU1@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755482AbYHTBU1 (ORCPT <rfc822;w@1wt.eu>);
	Tue, 19 Aug 2008 21:20:27 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753278AbYHTBUQ
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Tue, 19 Aug 2008 21:20:16 -0400
Received: from gate.crashing.org ([63.228.1.57]:52566 "EHLO gate.crashing.org"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1752868AbYHTBUO (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Tue, 19 Aug 2008 21:20:14 -0400
Subject: Re: ftrace introduces instability into kernel 2.6.27(-rc2,-rc3)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reply-To: benh@kernel.crashing.org
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
       Steven Rostedt <rostedt@goodmis.org>,
       Scott Wood <scottwood@freescale.com>,
       Eran Liberty <liberty@extricom.com>, linux-kernel@vger.kernel.org,
       linuxppc-dev@ozlabs.org, Steven Rostedt <srostedt@redhat.com>,
       "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
       Nick Piggin <nickpiggin@yahoo.com.au>
In-Reply-To: <48AB5E36.8030400@goop.org>
References: <48A9901B.1080900@redhat.com> <20080818154746.GA26835@Krystal>
	 <48A9AFA7.8080508@freescale.com>
	 <alpine.DEB.1.10.0808181425090.796@gandalf.stny.rr.com>
	 <1219110814.8062.2.camel@pasglop>
	 <alpine.DEB.1.10.0808182208110.13401@gandalf.stny.rr.com>
	 <1219113549.8062.13.camel@pasglop>
	 <alpine.DEB.1.10.0808182240330.13401@gandalf.stny.rr.com>
	 <20080819024707.GA22659@Krystal>
	 <alpine.DEB.1.10.0808191247001.28232@gandalf.stny.rr.com>
	 <20080819173453.GA28239@Krystal> <1219182471.7826.16.camel@pasglop>
	 <48AB5E36.8030400@goop.org>
Content-Type: text/plain
Date: Wed, 20 Aug 2008 11:17:28 +1000
Message-Id: <1219195048.7826.23.camel@pasglop>
Mime-Version: 1.0
X-Mailer: Evolution 2.22.3.1 
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

On Tue, 2008-08-19 at 16:58 -0700, Jeremy Fitzhardinge wrote:
> Benjamin Herrenschmidt wrote:
> >> Ok, there are two cases where it's ok :
> >>
> >> 1 - in stop_machine, considering we are not touching code executed in
> >> NMI handlers.
> >> 2 - when using my replace_instruction_safe() which uses a temporary
> >> breakpoint when doing the instruction replacement.
> >>
> >> In those cases you could use text_poke_early().
> >>     
> >
> > Note that vmap/vunmap will be very slow.
> >   
> 
> Don't we have Nick's speedups now?

Not sure what speedups this is, but it's stlil not something you want to
do a lot ... setting up and tearing down MMU mappings isn't something
I'd like to see happening on a per-mcount basis.

Ben