Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756497AbYHSQsF (ORCPT ); Tue, 19 Aug 2008 12:48:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756178AbYHSQro (ORCPT ); Tue, 19 Aug 2008 12:47:44 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.124]:61245 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756156AbYHSQrm (ORCPT ); Tue, 19 Aug 2008 12:47:42 -0400 Date: Tue, 19 Aug 2008 12:47:39 -0400 (EDT) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: Mathieu Desnoyers cc: Benjamin Herrenschmidt , Scott Wood , Eran Liberty , linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, Steven Rostedt , "Paul E. McKenney" Subject: Re: ftrace introduces instability into kernel 2.6.27(-rc2,-rc3) In-Reply-To: <20080819024707.GA22659@Krystal> Message-ID: References: <48591941.4070408@extricom.com> <48A92E15.2080709@extricom.com> <48A9901B.1080900@redhat.com> <20080818154746.GA26835@Krystal> <48A9AFA7.8080508@freescale.com> <1219110814.8062.2.camel@pasglop> <1219113549.8062.13.camel@pasglop> <20080819024707.GA22659@Krystal> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1142 Lines: 33 On Mon, 18 Aug 2008, Mathieu Desnoyers wrote: > * Steven Rostedt (rostedt@goodmis.org) wrote: > > > > On Tue, 19 Aug 2008, Benjamin Herrenschmidt wrote: > > > > > > > > > Hmm, this was originally copied from x86, where we did a cmpxchg, but that > > > > is probably not needed since all of this is done in kstop_machine. Also, > > > > only the "get" is needed. If we don't fault there, we wont fault on the > > > > put (unless we have permissions wrong, and that would be a bug). > > > > > > Would it ? How do we make sure the kernel text is mapped writeable ? > > > > We map it writeable if FTRACE is enabled. > > > > Argh. See text_poke(). It's there exactly for this purpose on x86. > OK, I just tried text_poke and it unfortunately fails. The problem is that it requires that the text you are changing is aligned and fits on one page. We have no control over that. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/