From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031898Ab2I1UJj (ORCPT ); Fri, 28 Sep 2012 16:09:39 -0400 Received: from mail-pa0-f46.google.com ([209.85.220.46]:51579 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758704Ab2I1SyJ (ORCPT ); Fri, 28 Sep 2012 14:54:09 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg KH , alan@lxorguk.ukuu.org.uk, Cong Wang , Ben Hutchings , "David S. Miller" Subject: [ 010/262] ipv6: addrconf: Avoid calling netdevice notifiers with RCU read-side lock Date: Fri, 28 Sep 2012 11:48:59 -0700 Message-Id: <20120928182959.183063984@linuxfoundation.org> X-Mailer: git-send-email 1.7.10.1.362.g242cab3 In-Reply-To: <20120928182957.993484211@linuxfoundation.org> References: <20120928182957.993484211@linuxfoundation.org> User-Agent: quilt/0.60-2.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Greg KH 3.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ben Hutchings [ Upstream commit 4acd4945cd1e1f92b20d14e349c6c6a52acbd42d ] Cong Wang reports that lockdep detected suspicious RCU usage while enabling IPV6 forwarding: [ 1123.310275] =============================== [ 1123.442202] [ INFO: suspicious RCU usage. ] [ 1123.558207] 3.6.0-rc1+ #109 Not tainted [ 1123.665204] ------------------------------- [ 1123.768254] include/linux/rcupdate.h:430 Illegal context switch in RCU read-side critical section! [ 1123.992320] [ 1123.992320] other info that might help us debug this: [ 1123.992320] [ 1124.307382] [ 1124.307382] rcu_scheduler_active = 1, debug_locks = 0 [ 1124.522220] 2 locks held by sysctl/5710: [ 1124.648364] #0: (rtnl_mutex){+.+.+.}, at: [] rtnl_trylock+0x15/0x17 [ 1124.882211] #1: (rcu_read_lock){.+.+.+}, at: [] rcu_lock_acquire+0x0/0x29 [ 1125.085209] [ 1125.085209] stack backtrace: [ 1125.332213] Pid: 5710, comm: sysctl Not tainted 3.6.0-rc1+ #109 [ 1125.441291] Call Trace: [ 1125.545281] [] lockdep_rcu_suspicious+0x109/0x112 [ 1125.667212] [] rcu_preempt_sleep_check+0x45/0x47 [ 1125.781838] [] __might_sleep+0x1e/0x19b [...] [ 1127.445223] [] call_netdevice_notifiers+0x4a/0x4f [...] [ 1127.772188] [] dev_disable_lro+0x32/0x6b [ 1127.885174] [] dev_forward_change+0x30/0xcb [ 1128.013214] [] addrconf_forward_change+0x85/0xc5 [...] addrconf_forward_change() uses RCU iteration over the netdev list, which is unnecessary since it already holds the RTNL lock. We also cannot reasonably require netdevice notifier functions not to sleep. Reported-by: Cong Wang Signed-off-by: Ben Hutchings Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv6/addrconf.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -493,8 +493,7 @@ static void addrconf_forward_change(stru struct net_device *dev; struct inet6_dev *idev; - rcu_read_lock(); - for_each_netdev_rcu(net, dev) { + for_each_netdev(net, dev) { idev = __in6_dev_get(dev); if (idev) { int changed = (!idev->cnf.forwarding) ^ (!newf); @@ -503,7 +502,6 @@ static void addrconf_forward_change(stru dev_forward_change(idev); } } - rcu_read_unlock(); } static int addrconf_fixup_forwarding(struct ctl_table *table, int *p, int newf)