From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760571Ab2DKPI6 (ORCPT ); Wed, 11 Apr 2012 11:08:58 -0400 Received: from smtp2.it.da.ut.ee ([193.40.5.67]:51102 "EHLO smtp2.it.da.ut.ee" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755152Ab2DKPI5 (ORCPT ); Wed, 11 Apr 2012 11:08:57 -0400 Date: Wed, 11 Apr 2012 18:08:53 +0300 (EEST) From: Meelis Roos To: David Miller cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: Re: suspicious RCU usage warnings in 3.3.0 In-Reply-To: <20120328.174559.650861844028495880.davem@davemloft.net> Message-ID: References: <20120328.174559.650861844028495880.davem@davemloft.net> User-Agent: Alpine 1.00 (SOC 882 2007-12-20) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > Is this the same RCU problem that was fixed after 3.3 (fix a potential > > rcu_read_lock() imbalance in rt6_fill_node())? My problem does not seem > > to be ipv6-only, most traces are from IPv6 but some for ip. > > It's hard to say because the ipv6 RCU problem causes the warning to > trigger somewhere away from the ipv6 code that had the RCU locking > bug. Tested todays 3.4.0-rc2-00016-ga9e1e53 on the same with flood ping and still got RCU warning: [36456.693191] [36456.712658] =============================== [36456.767614] [ INFO: suspicious RCU usage. ] [36456.822588] 3.4.0-rc2-00016-ga9e1e53 #36 Not tainted [36456.887835] ------------------------------- [36456.942804] include/linux/netpoll.h:70 suspicious rcu_dereference_check() usage! [36457.040083] [36457.040089] other info that might help us debug this: [36457.040098] [36457.145306] [36457.145312] RCU used illegally from idle CPU! [36457.145320] rcu_scheduler_active = 1, debug_locks = 0 [36457.288293] RCU used illegally from extended quiescent state! [36457.363834] no locks held by swapper/0. [36457.414221] [36457.414227] stack backtrace: [36457.471471] Call Trace: [36457.503600] [0000000000489834] lockdep_rcu_suspicious+0xd4/0x100 [36457.583727] [00000000006755a8] __netif_receive_skb+0x368/0xa80 [36457.661536] [0000000000675e6c] netif_receive_skb+0x4c/0x60 [36457.734787] [000000000063fd74] tulip_poll+0x3b4/0x6a0 [36457.802327] [00000000006794d8] net_rx_action+0x118/0x1e0 [36457.873299] [00000000004560fc] __do_softirq+0x9c/0x140 [36457.941984] [000000000042b1c4] do_softirq+0x84/0xc0 [36458.007229] [0000000000404a40] __handle_softirq+0x0/0x10 [36458.078199] [000000000042b688] cpu_idle+0x48/0x100 [36458.142314] [0000000000722db8] rest_init+0x160/0x188 [36458.208711] [00000000008c87b0] start_kernel+0x32c/0x33c [36458.278530] [0000000000722c50] tlb_fixup_done+0x88/0x90 [36458.348346] [0000000000000000] (null) -- Meelis Roos (mroos@linux.ee)