From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0ACE3C04AAC for ; Mon, 20 May 2019 21:39:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC8C62173E for ; Mon, 20 May 2019 21:39:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726794AbfETVjO (ORCPT ); Mon, 20 May 2019 17:39:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:48436 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725763AbfETVjN (ORCPT ); Mon, 20 May 2019 17:39:13 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0548D2171F; Mon, 20 May 2019 21:39:11 +0000 (UTC) Date: Mon, 20 May 2019 17:39:10 -0400 From: Steven Rostedt To: Josh Poimboeuf Cc: Johannes Erdfelt , Joe Lawrence , Jessica Yu , Jiri Kosina , Miroslav Benes , Ingo Molnar , live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Oops caused by race between livepatch and ftrace Message-ID: <20190520173910.6da9ddaf@gandalf.local.home> In-Reply-To: <20190520211931.vokbqxkx5kb6k2bz@treble> References: <20190520194915.GB1646@sventech.com> <90f78070-95ec-ce49-1641-19d061abecf4@redhat.com> <20190520210905.GC1646@sventech.com> <20190520211931.vokbqxkx5kb6k2bz@treble> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 20 May 2019 16:19:31 -0500 Josh Poimboeuf wrote: > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index a12aff849c04..8259d4ba8b00 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -34,6 +34,7 @@ > #include > #include > #include > +#include > > #include > > @@ -2610,10 +2611,12 @@ static void ftrace_run_update_code(int command) > { > int ret; > > + mutex_lock(&text_mutex); > + Hmm, this may blow up with lockdep, as I believe we already have a locking dependency of: text_mutex -> ftrace_lock And this will reverses it. (kprobes appears to take the locks in this order). Perhaps have live kernel patching grab ftrace_lock? -- Steve > ret = ftrace_arch_code_modify_prepare(); > FTRACE_WARN_ON(ret); > if (ret) > - return; > + goto out_unlock; > > /* > * By default we use stop_machine() to modify the code. > @@ -2625,6 +2628,9 @@ static void ftrace_run_update_code(int command) > > ret = ftrace_arch_code_modify_post_process(); > FTRACE_WARN_ON(ret); > + > +out_unlock: > + mutex_unlock(&text_mutex); > } > > static void ftrace_run_modify_code(struct ftrace_ops *ops, int command, > @@ -5776,6 +5782,7 @@ void ftrace_module_enable(struct module *mod) > struct ftrace_page *pg; > > mutex_lock(&ftrace_lock); > + mutex_lock(&text_mutex); > > if (ftrace_disabled) > goto out_unlock; > @@ -5837,6 +5844,7 @@ void ftrace_module_enable(struct module *mod) > ftrace_arch_code_modify_post_process(); > > out_unlock: > + mutex_unlock(&text_mutex); > mutex_unlock(&ftrace_lock); > > process_cached_mods(mod->name);