From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754669Ab0IVO1Z (ORCPT ); Wed, 22 Sep 2010 10:27:25 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:61585 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753456Ab0IVO1Y (ORCPT ); Wed, 22 Sep 2010 10:27:24 -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=mu7+2o+f3+wQRofYJjqBoPsvgwke0jqiY7zVf7mXVJAczepSNlX1Ms2Y/9eriv1RiG xcT7nw7nmsU97xLuywIgFXishtnG93l3mCx3FFDypvq+nGMOz1Q4Vzd7+k6v28dgrgsi zgdLv+fY1chR8N6UW2ghbegdDmzaGmzXbL3o4= Subject: Re: 2.6.36-rc5-git1 -- include/linux/netpoll.h:67 invoked rcu_dereference_check() without protection! From: Eric Dumazet To: Miles Lane Cc: Herbert Xu , "Paul E. McKenney" , LKML , "David S. Miller" , Alexey Kuznetsov , "Pekka Savola (ipv6)" , James Morris , Hideaki YOSHIFUJI , Patrick McHardy In-Reply-To: <1285137524.6378.160.camel@edumazet-laptop> References: <1285137524.6378.160.camel@edumazet-laptop> Content-Type: text/plain; charset="UTF-8" Date: Wed, 22 Sep 2010 16:27:16 +0200 Message-ID: <1285165636.2639.421.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 08:38 +0200, Eric Dumazet a écrit : > 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()) oops, I meant irqs_disabled() here, not in_irq() > > /** > * rcu_dereference_sched - fetch RCU-protected pointer, checking for RCU-sched >