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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 B47F1C2D0DB for ; Thu, 23 Jan 2020 12:10:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 81DCB2253D for ; Thu, 23 Jan 2020 12:10:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579781419; bh=xVC+of4wwHUmBPk3J4W40b+AoZu4hwXIqW9ignswEJM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=J9qeodCtFmoM7PHV5UpCiTYg3R/0g5g5QktR6Stk54IQ1QbnssOOBhuYsNJPGgs9i 8I84tWmlBV7XnA9fy7CUM85JMeXXxQF4SmB/RP22YgAUAW0g+CufLMDJCJGidr8fmz /GjXhPe+iSQPZumaoAKg80w07jdRpdsBLNzEcxC4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728831AbgAWMKS (ORCPT ); Thu, 23 Jan 2020 07:10:18 -0500 Received: from mail.kernel.org ([198.145.29.99]:59548 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726170AbgAWMKS (ORCPT ); Thu, 23 Jan 2020 07:10:18 -0500 Received: from linux-8ccs (x2f7fea8.dyn.telefonica.de [2.247.254.168]) (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 368AE2253D; Thu, 23 Jan 2020 12:10:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579781417; bh=xVC+of4wwHUmBPk3J4W40b+AoZu4hwXIqW9ignswEJM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=W4eKy3R8Ayy+tpLYSr62z7a1B4h4BFSIyBoED+15X/BvAa8a3ydZvATj73fi9Hpxj qd7W6qYOq1/6VmSHRnQvmcLYLykfIfdFgBFaYUrSpYGtjk1bItgtB8LfdU/HvgBf/+ 6jZidqSQ2dhAoyNEQG8i7kFw4MW+hxqJ1TbEA6NE= Date: Thu, 23 Jan 2020 13:10:10 +0100 From: Jessica Yu To: Amol Grover Cc: linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, Joel Fernandes , Madhuparna Bhowmik , "Paul E . McKenney" Subject: Re: [PATCH] kernel: module: Pass lockdep expression to RCU lists Message-ID: <20200123121010.GA9011@linux-8ccs> References: <20200121124745.14864-1-frextrite@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20200121124745.14864-1-frextrite@gmail.com> X-OS: Linux linux-8ccs 4.12.14-lp150.12.61-default x86_64 User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +++ Amol Grover [21/01/20 18:17 +0530]: >modules is traversed using list_for_each_entry_rcu outside an >RCU read-side critical section but under the protection >of module_mutex or with preemption disabled. > >Hence, add corresponding lockdep expression to silence false-positive >lockdep warnings, and harden RCU lists. > >list_for_each_entry_rcu when traversed inside a preempt disabled >section, doesn't need an explicit lockdep expression since it is >implicitly checked for. > >Add macro for the corresponding lockdep expression. > >Signed-off-by: Amol Grover Hi Amol! Masami already submitted a patch for this, it's been in linux-next for a while. See commit bf08949cc8b9 ("modules: lockdep: Suppress suspicious RCU usage warning"). Thanks! Jessica >--- > kernel/module.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > >diff --git a/kernel/module.c b/kernel/module.c >index b56f3224b161..2425f58159dd 100644 >--- a/kernel/module.c >+++ b/kernel/module.c >@@ -84,6 +84,8 @@ > * 3) module_addr_min/module_addr_max. > * (delete and add uses RCU list operations). */ > DEFINE_MUTEX(module_mutex); >+#define module_mutex_held() \ >+ lockdep_is_held(&module_mutex) > EXPORT_SYMBOL_GPL(module_mutex); > static LIST_HEAD(modules); > >@@ -214,7 +216,7 @@ static struct module *mod_find(unsigned long addr) > { > struct module *mod; > >- list_for_each_entry_rcu(mod, &modules, list) { >+ list_for_each_entry_rcu(mod, &modules, list, module_mutex_held()) { > if (within_module(addr, mod)) > return mod; > } >@@ -448,7 +450,7 @@ bool each_symbol_section(bool (*fn)(const struct symsearch *arr, > if (each_symbol_in_section(arr, ARRAY_SIZE(arr), NULL, fn, data)) > return true; > >- list_for_each_entry_rcu(mod, &modules, list) { >+ list_for_each_entry_rcu(mod, &modules, list, module_mutex_held()) { > struct symsearch arr[] = { > { mod->syms, mod->syms + mod->num_syms, mod->crcs, > NOT_GPL_ONLY, false }, >@@ -616,7 +618,7 @@ static struct module *find_module_all(const char *name, size_t len, > > module_assert_mutex_or_preempt(); > >- list_for_each_entry_rcu(mod, &modules, list) { >+ list_for_each_entry_rcu(mod, &modules, list, module_mutex_held()) { > if (!even_unformed && mod->state == MODULE_STATE_UNFORMED) > continue; > if (strlen(mod->name) == len && !memcmp(mod->name, name, len)) >@@ -2040,7 +2042,7 @@ void set_all_modules_text_rw(void) > return; > > mutex_lock(&module_mutex); >- list_for_each_entry_rcu(mod, &modules, list) { >+ list_for_each_entry_rcu(mod, &modules, list, module_mutex_held()) { > if (mod->state == MODULE_STATE_UNFORMED) > continue; > >@@ -2059,7 +2061,7 @@ void set_all_modules_text_ro(void) > return; > > mutex_lock(&module_mutex); >- list_for_each_entry_rcu(mod, &modules, list) { >+ list_for_each_entry_rcu(mod, &modules, list, module_mutex_held()) { > /* > * Ignore going modules since it's possible that ro > * protection has already been disabled, otherwise we'll >-- >2.24.1 >