From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarek Poplawski Subject: [PATCH] ipv4: Suppress lockdep-RCU false positive in FIB trie (3) Date: Tue, 7 Sep 2010 19:51:17 +0200 Message-ID: <20100907175117.GA1993@del.dom.local> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Paul E. McKenney" , Eric Dumazet , netdev@vger.kernel.org To: David Miller Return-path: Received: from mail-ew0-f46.google.com ([209.85.215.46]:56482 "EHLO mail-ew0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932099Ab0IGRvY (ORCPT ); Tue, 7 Sep 2010 13:51:24 -0400 Received: by ewy23 with SMTP id 23so2523515ewy.19 for ; Tue, 07 Sep 2010 10:51:23 -0700 (PDT) Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: Hi, Here is one more of these warnings and a patch below: Sep 5 23:52:33 del kernel: [46044.244833] =================================================== Sep 5 23:52:33 del kernel: [46044.269681] [ INFO: suspicious rcu_dereference_check() usage. ] Sep 5 23:52:33 del kernel: [46044.277000] --------------------------------------------------- Sep 5 23:52:33 del kernel: [46044.285185] net/ipv4/fib_trie.c:1756 invoked rcu_dereference_check() without protection! Sep 5 23:52:33 del kernel: [46044.293627] Sep 5 23:52:33 del kernel: [46044.293632] other info that might help us debug this: Sep 5 23:52:33 del kernel: [46044.293634] Sep 5 23:52:33 del kernel: [46044.325333] Sep 5 23:52:33 del kernel: [46044.325335] rcu_scheduler_active = 1, debug_locks = 0 Sep 5 23:52:33 del kernel: [46044.348013] 1 lock held by pppd/1717: Sep 5 23:52:33 del kernel: [46044.357548] #0: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0xf/0x20 Sep 5 23:52:33 del kernel: [46044.367647] Sep 5 23:52:33 del kernel: [46044.367652] stack backtrace: Sep 5 23:52:33 del kernel: [46044.387429] Pid: 1717, comm: pppd Not tainted 2.6.35.4.4a #3 Sep 5 23:52:33 del kernel: [46044.398764] Call Trace: Sep 5 23:52:33 del kernel: [46044.409596] [] ? printk+0x18/0x1e Sep 5 23:52:33 del kernel: [46044.420761] [] lockdep_rcu_dereference+0xa9/0xb0 Sep 5 23:52:33 del kernel: [46044.432229] [] trie_firstleaf+0x65/0x70 Sep 5 23:52:33 del kernel: [46044.443941] [] fib_table_flush+0x14/0x170 Sep 5 23:52:33 del kernel: [46044.455823] [] ? local_bh_enable_ip+0x62/0xd0 Sep 5 23:52:33 del kernel: [46044.467995] [] ? _raw_spin_unlock_bh+0x2f/0x40 Sep 5 23:52:33 del kernel: [46044.480404] [] ? fib_sync_down_dev+0x120/0x180 Sep 5 23:52:33 del kernel: [46044.493025] [] fib_flush+0x2d/0x60 Sep 5 23:52:33 del kernel: [46044.505796] [] fib_disable_ip+0x25/0x50 Sep 5 23:52:33 del kernel: [46044.518772] [] fib_netdev_event+0x73/0xd0 Sep 5 23:52:33 del kernel: [46044.531918] [] notifier_call_chain+0x2d/0x70 Sep 5 23:52:33 del kernel: [46044.545358] [] raw_notifier_call_chain+0x1a/0x20 Sep 5 23:52:33 del kernel: [46044.559092] [] call_netdevice_notifiers+0x27/0x60 Sep 5 23:52:33 del kernel: [46044.573037] [] __dev_notify_flags+0x5c/0x80 Sep 5 23:52:33 del kernel: [46044.586489] [] dev_change_flags+0x37/0x60 Sep 5 23:52:33 del kernel: [46044.599394] [] devinet_ioctl+0x54d/0x630 Sep 5 23:52:33 del kernel: [46044.612277] [] inet_ioctl+0x97/0xc0 Sep 5 23:52:34 del kernel: [46044.625208] [] sock_ioctl+0x6f/0x270 Sep 5 23:52:34 del kernel: [46044.638046] [] ? handle_mm_fault+0x420/0x6c0 Sep 5 23:52:34 del kernel: [46044.650968] [] ? sock_ioctl+0x0/0x270 Sep 5 23:52:34 del kernel: [46044.663865] [] vfs_ioctl+0x28/0xa0 Sep 5 23:52:34 del kernel: [46044.676556] [] do_vfs_ioctl+0x6a/0x5c0 Sep 5 23:52:34 del kernel: [46044.688989] [] ? up_read+0x16/0x30 Sep 5 23:52:34 del kernel: [46044.701411] [] ? do_page_fault+0x1d6/0x3a0 Sep 5 23:52:34 del kernel: [46044.714223] [] ? fget_light+0xf8/0x2f0 Sep 5 23:52:34 del kernel: [46044.726601] [] ? sys_socketcall+0x208/0x2c0 Sep 5 23:52:34 del kernel: [46044.739140] [] sys_ioctl+0x63/0x70 Sep 5 23:52:34 del kernel: [46044.751967] [] syscall_call+0x7/0xb Sep 5 23:52:34 del kernel: [46044.764734] [] ? cookie_v6_check+0x3d0/0x630 --------------> This patch fixes the warning: =================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- net/ipv4/fib_trie.c:1756 invoked rcu_dereference_check() without protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 0 1 lock held by pppd/1717: #0: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0xf/0x20 stack backtrace: Pid: 1717, comm: pppd Not tainted 2.6.35.4a #3 Call Trace: [] ? printk+0x18/0x1e [] lockdep_rcu_dereference+0xa9/0xb0 [] trie_firstleaf+0x65/0x70 [] fib_table_flush+0x14/0x170 ... Allow trie_firstleaf() to be called either under rcu_read_lock() protection or with RTNL held. The same annotation is added to node_parent_rcu() to prevent a similar warning a bit later. Followup of commits 634a4b20 and 4eaa0e3c. Signed-off-by: Jarek Poplawski --- diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index 79d057a..4a8e370 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -186,7 +186,9 @@ static inline struct tnode *node_parent_rcu(struct node *node) { struct tnode *ret = node_parent(node); - return rcu_dereference(ret); + return rcu_dereference_check(ret, + rcu_read_lock_held() || + lockdep_rtnl_is_held()); } /* Same as rcu_assign_pointer @@ -1753,7 +1755,9 @@ static struct leaf *leaf_walk_rcu(struct tnode *p, struct node *c) static struct leaf *trie_firstleaf(struct trie *t) { - struct tnode *n = (struct tnode *) rcu_dereference(t->trie); + struct tnode *n = (struct tnode *) rcu_dereference_check(t->trie, + rcu_read_lock_held() || + lockdep_rtnl_is_held()); if (!n) return NULL;