[PATCH] lockdep: annotate skb_queue_head_init

Teach special (multi-initialized) locking code to the lock validator.  Has no
effect on non-lockdep kernels.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/skbuff.h

@@ -604,9 +604,12 @@ static inline __u32 skb_queue_len(const struct sk_buff_head *list_)
 	return list_->qlen;
 }
 
+extern struct lock_class_key skb_queue_lock_key;
+
 static inline void skb_queue_head_init(struct sk_buff_head *list)
 {
 	spin_lock_init(&list->lock);
+	lockdep_set_class(&list->lock, &skb_queue_lock_key);
 	list->prev = list->next = (struct sk_buff *)list;
 	list->qlen = 0;
 }

net/core/skbuff.c

@@ -70,6 +70,13 @@
 static kmem_cache_t *skbuff_head_cache __read_mostly;
 static kmem_cache_t *skbuff_fclone_cache __read_mostly;
 
+/*
+ * lockdep: lock class key used by skb_queue_head_init():
+ */
+struct lock_class_key skb_queue_lock_key;
+
+EXPORT_SYMBOL(skb_queue_lock_key);
+
 /*
  *	Keep out-of-line to prevent kernel bloat.
  *	__builtin_return_address is not used because it is not always