Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753832AbZDUR4S (ORCPT ); Tue, 21 Apr 2009 13:56:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751615AbZDUR4F (ORCPT ); Tue, 21 Apr 2009 13:56:05 -0400 Received: from BISCAYNE-ONE-STATION.MIT.EDU ([18.7.7.80]:46483 "EHLO biscayne-one-station.mit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750970AbZDUR4D (ORCPT ); Tue, 21 Apr 2009 13:56:03 -0400 Date: Tue, 21 Apr 2009 13:51:48 -0400 (EDT) From: Tim Abbott To: Rusty Russell cc: Steven Rostedt , linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton , Thomas Gleixner , Peter Zijlstra , Frederic Weisbecker , Anders Kaseorg , Jeffrey B Arnold Subject: Re: [PATCH 1/5] ftrace: use module notifier for function tracer In-Reply-To: <200904192055.04213.rusty@rustcorp.com.au> Message-ID: References: <20090416021830.556671772@goodmis.org> <20090416021928.040177084@goodmis.org> <200904192055.04213.rusty@rustcorp.com.au> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Spam-Flag: NO X-Spam-Score: 0.00 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1271 Lines: 29 On Sun, 19 Apr 2009, Rusty Russell wrote: > I think you need to do something else in general. Share the module_mutex for > the ftrace code? The ksplice guys have a similar issue, so maybe we should > generalize this into a "kernel_text" mutex? Yes, a kernel_text mutex is on my list of things to propose once Ksplice gets merged. There are at present several systems that modify the kernel text after a machine is booted (e.g. dynamic ftrace and toggling of smp_locks when hotplugging a cpu). Currently, they avoid stepping on each other by only making changes inside stop_machine. However, Ksplice does its run-pre matching checks outside stop_machine, and Ksplice needs a way to prevent e.g. dynamic ftrace from changing the code out from under it between those checks and actually applying the patches [1]. A kernel_text mutex would be a reasonable solution to this problem. -Tim Abbott [1] At present this isn't a real problem because Ksplice and ftrace conflict with each other for unrelated reasons. -- 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/