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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 044E4C432C0 for ; Tue, 19 Nov 2019 22:50:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DA89322449 for ; Tue, 19 Nov 2019 22:50:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727394AbfKSWux (ORCPT ); Tue, 19 Nov 2019 17:50:53 -0500 Received: from shards.monkeyblade.net ([23.128.96.9]:46166 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726290AbfKSWuw (ORCPT ); Tue, 19 Nov 2019 17:50:52 -0500 Received: from localhost (unknown [IPv6:2601:601:9f00:1e2::3d5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id EC2671423DA68; Tue, 19 Nov 2019 14:50:51 -0800 (PST) Date: Tue, 19 Nov 2019 14:50:48 -0800 (PST) Message-Id: <20191119.145048.487849503145486152.davem@davemloft.net> To: anders.roxell@linaro.org Cc: kuznet@ms2.inr.ac.ru, yoshfuji@linux-ipv6.org, paulmck@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] net: ipmr: fix suspicious RCU warning From: David Miller In-Reply-To: <20191118090925.2474-1-anders.roxell@linaro.org> References: <20191118090925.2474-1-anders.roxell@linaro.org> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Tue, 19 Nov 2019 14:50:52 -0800 (PST) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Anders Roxell Date: Mon, 18 Nov 2019 10:09:25 +0100 > @@ -108,9 +108,18 @@ static void igmpmsg_netlink_event(struct mr_table *mrt, struct sk_buff *pkt); > static void mroute_clean_tables(struct mr_table *mrt, int flags); > static void ipmr_expire_process(struct timer_list *t); > > +#ifdef CONFIG_PROVE_LOCKING > +int ip_mr_initialized; > +void ip_mr_now_initialized(void) { ip_mr_initialized = 1; } > +#else > +const int ip_mr_initialized = 1; > +void ip_mr_now_initialized(void) { } > +#endif This seems excessive and a bit not so pretty. > + > #ifdef CONFIG_IP_MROUTE_MULTIPLE_TABLES > #define ipmr_for_each_table(mrt, net) \ > - list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list) > + list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list, \ > + (lockdep_rtnl_is_held() || !ip_mr_initialized)) > > static struct mr_table *ipmr_mr_table_iter(struct net *net, > struct mr_table *mrt) The problematic code path is ipmr_rules_init() done during ipmr_net_init(). You can just wrap this call around RCU locking or take the RTNL mutex. That way you don't need to rediculous ip_mr_initialized knob which frankly doesn't even seem accurate to me. It's a centralized global variable which is holding state about multiple network namespace objects which makes absolutely no sense at all, it's wrong.