Otherwise the following calltrace will lead to a wrong
lockdep warning:
neigh_proxy_process()
`- lock(neigh_table->proxy_queue.lock);
arp_redo /* via tbl->proxy_redo */
arp_process
neigh_event_ns
neigh_update
skb_queue_purge
`- lock(neighbor->arp_queue.lock);
This is not a deadlock actually, as neighbor table's proxy_queue
and the neighbor's arp_queue are different queues.
Lockdep thinks there is a deadlock as both queues are initialized
with skb_queue_head_init() and thus have a common class.
--- a/include/linux/skbuff.h 2007-04-09 22:52:27.000000000 +0400
+++ b/include/linux/skbuff.h 2007-04-09 22:52:32.000000000 +0400
@@ -628,6 +628,13 @@ static inline void skb_queue_head_init(s
list->qlen = 0;
}
+static inline void skb_queue_head_init_class(struct sk_buff_head *list,
+ struct lock_class_key *class)
+{
+ skb_queue_head_init(list);
+ lockdep_set_class(&list->lock, class);
+}
+
/*
* Insert an sk_buff at the start of a list.
*
--- a/net/core/neighbour.c 2007-04-09 22:52:28.000000000 +0400
+++ b/net/core/neighbour.c 2007-04-09 22:53:01.000000000 +0400
@@ -1327,6 +1327,8 @@ void neigh_parms_destroy(struct neigh_pa
kfree(parms);
}
+static struct lock_class_key neigh_table_proxy_queue_class;
+
void neigh_table_init_no_netlink(struct neigh_table *tbl)
{
unsigned long now = jiffies;
@@ -1379,7 +1381,8 @@ void neigh_table_init_no_netlink(struct
init_timer(&tbl->proxy_timer);
tbl->proxy_timer.data = (unsigned long)tbl;
tbl->proxy_timer.function = neigh_proxy_process;
- skb_queue_head_init(&tbl->proxy_queue);
+ skb_queue_head_init_class(&tbl->proxy_queue,
+ &neigh_table_proxy_queue_class);
tbl->last_flush = now;
tbl->last_rand = now + tbl->parms.reachable_time * 20;
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