From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932250AbcBHRsu (ORCPT ); Mon, 8 Feb 2016 12:48:50 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50267 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752995AbcBHRss (ORCPT ); Mon, 8 Feb 2016 12:48:48 -0500 Date: Mon, 8 Feb 2016 11:48:46 -0600 From: Josh Poimboeuf To: Jessica Yu Cc: Seth Jennings , Jiri Kosina , Vojtech Pavlik , Miroslav Benes , Rusty Russell , Steven Rostedt , Ingo Molnar , live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 0/2] Fix ordering of ftrace/livepatch calls on module load and unload Message-ID: <20160208174846.GB23106@treble.redhat.com> References: <1454728097-7106-1-git-send-email-jeyu@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1454728097-7106-1-git-send-email-jeyu@redhat.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 05, 2016 at 10:08:15PM -0500, Jessica Yu wrote: > As explained here [1], livepatch modules are failing to initialize properly > because the ftrace coming module notifier (which calls > ftrace_module_enable()) runs *after* the livepatch module notifier (which > enables the patch(es)). Thus livepatch attempts to apply patches to > modules before ftrace_module_enable() is even called for the corresponding > module(s). As a result, patch modules break. Ftrace code must run before > livepatch on module load, and the reverse is true on module unload. > > For ftrace and livepatch, order of initialization (plus exit/cleanup code) is > important for loading and unloading modules, and using module notifiers to > perform this work is not ideal since it is not always clear what gets called > when. In this patchset, dependence on the module notifier call chain is removed > in favor of hard coding the corresponding function calls in the module loader. > This promotes better code visibility and ensures that ftrace and livepatch code > get called in the correct order on patch module load and unload. > > Tested the changes with a test livepatch module that patches 9p and nilfs2, > and verified that the issue described in [1] is fixed. Since Rusty agreed to your suggested changes for splitting up complete_formation() and for setting mod->state = MODULE_STATE_GOING before calling the going notifiers in the error path, can you do a v4 with those changes? They should probably be split up like: 1. split up complete_formation() 2. set MODULE_STATE_GOING before calling going notifiers in error path 3. remove ftrace module notifier 4. remove livepatch module notifier -- Josh