ipv4: Suppress lockdep-RCU false positive in FIB trie (3)

Jarek Poplawski · davem330 · commit f6b085b69d1c · 2010-09-08T14:14:20.000-07:00
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: [<c125dc1f>] 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] [<c12f9aba>] ? printk+0x18/0x1e Sep 5 23:52:33 del kernel: [46044.420761] [<c1053969>] lockdep_rcu_dereference+0xa9/0xb0 Sep 5 23:52:33 del kernel: [46044.432229] [<c12b7235>] trie_firstleaf+0x65/0x70 Sep 5 23:52:33 del kernel: [46044.443941] [<c12b74d4>] fib_table_flush+0x14/0x170 Sep 5 23:52:33 del kernel: [46044.455823] [<c1033e92>] ? local_bh_enable_ip+0x62/0xd0 Sep 5 23:52:33 del kernel: [46044.467995] [<c12fc39f>] ? _raw_spin_unlock_bh+0x2f/0x40 Sep 5 23:52:33 del kernel: [46044.480404] [<c12b24d0>] ? fib_sync_down_dev+0x120/0x180 Sep 5 23:52:33 del kernel: [46044.493025] [<c12b069d>] fib_flush+0x2d/0x60 Sep 5 23:52:33 del kernel: [46044.505796] [<c12b06f5>] fib_disable_ip+0x25/0x50 Sep 5 23:52:33 del kernel: [46044.518772] [<c12b10d3>] fib_netdev_event+0x73/0xd0 Sep 5 23:52:33 del kernel: [46044.531918] [<c1048dfd>] notifier_call_chain+0x2d/0x70 Sep 5 23:52:33 del kernel: [46044.545358] [<c1048f0a>] raw_notifier_call_chain+0x1a/0x20 Sep 5 23:52:33 del kernel: [46044.559092] [<c124f687>] call_netdevice_notifiers+0x27/0x60 Sep 5 23:52:33 del kernel: [46044.573037] [<c124faec>] __dev_notify_flags+0x5c/0x80 Sep 5 23:52:33 del kernel: [46044.586489] [<c124fb47>] dev_change_flags+0x37/0x60 Sep 5 23:52:33 del kernel: [46044.599394] [<c12a8a8d>] devinet_ioctl+0x54d/0x630 Sep 5 23:52:33 del kernel: [46044.612277] [<c12aabb7>] inet_ioctl+0x97/0xc0 Sep 5 23:52:34 del kernel: [46044.625208] [<c123f6af>] sock_ioctl+0x6f/0x270 Sep 5 23:52:34 del kernel: [46044.638046] [<c109d2b0>] ? handle_mm_fault+0x420/0x6c0 Sep 5 23:52:34 del kernel: [46044.650968] [<c123f640>] ? sock_ioctl+0x0/0x270 Sep 5 23:52:34 del kernel: [46044.663865] [<c10c3188>] vfs_ioctl+0x28/0xa0 Sep 5 23:52:34 del kernel: [46044.676556] [<c10c38fa>] do_vfs_ioctl+0x6a/0x5c0 Sep 5 23:52:34 del kernel: [46044.688989] [<c1048676>] ? up_read+0x16/0x30 Sep 5 23:52:34 del kernel: [46044.701411] [<c1021376>] ? do_page_fault+0x1d6/0x3a0 Sep 5 23:52:34 del kernel: [46044.714223] [<c10b6588>] ? fget_light+0xf8/0x2f0 Sep 5 23:52:34 del kernel: [46044.726601] [<c1241f98>] ? sys_socketcall+0x208/0x2c0 Sep 5 23:52:34 del kernel: [46044.739140] [<c10c3eb3>] sys_ioctl+0x63/0x70 Sep 5 23:52:34 del kernel: [46044.751967] [<c12fca3d>] syscall_call+0x7/0xb Sep 5 23:52:34 del kernel: [46044.764734] [<c12f0000>] ? 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: [<c125dc1f>] rtnl_lock+0xf/0x20 stack backtrace: Pid: 1717, comm: pppd Not tainted 2.6.35.4a #3 Call Trace: [<c12f9aba>] ? printk+0x18/0x1e [<c1053969>] lockdep_rcu_dereference+0xa9/0xb0 [<c12b7235>] trie_firstleaf+0x65/0x70 [<c12b74d4>] 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 634a4b2 and 4eaa0e3. Signed-off-by: Jarek Poplawski <jarkao2@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git 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;

Original file line number	Diff line number	Diff line change
`@@ -186,7 +186,9 @@ static inline struct tnode node_parent_rcu(struct node node)`
`186`	`186`	`{`
`187`	`187`	`struct tnode *ret = node_parent(node);`
`188`	`188`
`189`		`- return rcu_dereference(ret);`
	`189`	`+ return rcu_dereference_check(ret,`
	`190`	`+ rcu_read_lock_held() \|\|`
	`191`	`+ lockdep_rtnl_is_held());`
`190`	`192`	`}`
`191`	`193`
`192`	`194`	`/* Same as rcu_assign_pointer`
`@@ -1753,7 +1755,9 @@ static struct leaf leaf_walk_rcu(struct tnode p, struct node *c)`
`1753`	`1755`
`1754`	`1756`	`static struct leaf trie_firstleaf(struct trie t)`
`1755`	`1757`	`{`
`1756`		`- struct tnode n = (struct tnode ) rcu_dereference(t->trie);`
	`1758`	`+ struct tnode n = (struct tnode ) rcu_dereference_check(t->trie,`
	`1759`	`+ rcu_read_lock_held() \|\|`
	`1760`	`+ lockdep_rtnl_is_held());`
`1757`	`1761`
`1758`	`1762`	`if (!n)`
`1759`	`1763`	`return NULL;`