From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752603Ab0IVGiy (ORCPT ); Wed, 22 Sep 2010 02:38:54 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:58087 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751963Ab0IVGix (ORCPT ); Wed, 22 Sep 2010 02:38:53 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; b=up1N6fcvJv02FeYg+rHm89U4lbX6GSUXOeQXmJYmPxOlXwX8gKlbqbkKwEcW98u617 vjFDU+/nQCet44JIcuoS9WXlGqZirawX5ru0Dp07Bv3OiHPTV69lBu6pSshR1yYsp2lp 720AmsPgxIK/eN22RxqeZp5gg7EiUjq5URdLA= Subject: Re: 2.6.36-rc5-git1 -- include/linux/netpoll.h:67 invoked rcu_dereference_check() without protection! From: Eric Dumazet To: Miles Lane , Herbert Xu Cc: "Paul E. McKenney" , LKML , "David S. Miller" , Alexey Kuznetsov , "Pekka Savola (ipv6)" , James Morris , Hideaki YOSHIFUJI , Patrick McHardy In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Date: Wed, 22 Sep 2010 08:38:44 +0200 Message-ID: <1285137524.6378.160.camel@edumazet-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le mercredi 22 septembre 2010 à 00:22 -0400, Miles Lane a écrit : > [ INFO: suspicious rcu_dereference_check() usage. ] > --------------------------------------------------- > include/linux/netpoll.h:67 invoked rcu_dereference_check() without protection! > > other info that might help us debug this: > > > rcu_scheduler_active = 1, debug_locks = 1 > 1 lock held by avahi-daemon/1597: > #0: (sk_lock-AF_INET6){+.+.+.}, at: [] > udpv6_sendmsg+0x6c2/0x9e6 [ipv6] > > stack backtrace: > Pid: 1597, comm: avahi-daemon Not tainted 2.6.36-rc5 #13 > Call Trace: > [] lockdep_rcu_dereference+0x9d/0xa6 > [] netif_rx+0x4e/0x1a7 > [] ? get_parent_ip+0x11/0x41 > [] netif_rx_ni+0x1e/0x58 > [] ip6_dev_loopback_xmit+0xc0/0xc7 [ipv6] > [] ip6_finish_output2+0x199/0x3b6 [ipv6] > [] ip6_finish_output+0xf0f/0xf27 [ipv6] > [] ? csum_partial_copy_from_user+0xb4/0xea > [] ? csum_partial_copy_fromiovecend+0x178/0x1bd > [] ip6_output+0x158/0x161 [ipv6] > [] ? get_parent_ip+0x11/0x41 > [] ip6_local_out+0x5d/0x62 [ipv6] > [] ip6_push_pending_frames+0x466/0x524 [ipv6] > [] udp_v6_push_pending_frames+0x27f/0x2fb [ipv6] > [] ? udpv6_sendmsg+0x6c2/0x9e6 [ipv6] > [] udpv6_sendmsg+0x7c5/0x9e6 [ipv6] > [] ? inet_sendmsg+0x0/0x11f > [] inet_sendmsg+0x112/0x11f > [] ? inet_sendmsg+0x0/0x11f > [] sock_sendmsg+0xe7/0x108 > [] ? might_fault+0x63/0xb3 > [] ? might_fault+0xac/0xb3 > [] ? might_fault+0x63/0xb3 > [] sys_sendmsg+0x24f/0x2d6 > [] ? get_parent_ip+0x11/0x41 > [] ? sub_preempt_count+0x92/0xa6 > [] ? __srcu_read_unlock+0x3b/0x57 > [] ? sysret_check+0x27/0x62 > [] system_call_fastpath+0x16/0x1b# Oh well. Thanks for the report. Could you please test following patch ? [PATCH] rcu: rcu_dereference_bh() is hard irq safe rcu_dereference_bh() doesnt know yet about hard irq being disabled, so lockdep can trigger in netpoll_rx() after commit f0f9deae9e7c4 (netpoll: Disable IRQ around RCU dereference in netpoll_rx) Reported-by: Miles Lane Signed-off-by: Eric Dumazet --- diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 9fbc54a..435c502 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -454,7 +454,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) * Makes rcu_dereference_check() do the dirty work. */ #define rcu_dereference_bh(p) \ - rcu_dereference_check(p, rcu_read_lock_bh_held()) + rcu_dereference_check(p, rcu_read_lock_bh_held() || in_irq()) /** * rcu_dereference_sched - fetch RCU-protected pointer, checking for RCU-sched