[NET]: Convert hh_lock to seqlock.

The hard header cache is in the main output path, so using
seqlock instead of reader/writer lock should reduce overhead.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 19 insertions, 1 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index c57088f575a3..631cec4ff5e1 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -199,7 +199,7 @@ struct hh_cache
                                          */
         u16             hh_len;         /* length of header */
         int             (*hh_output)(struct sk_buff *skb);
-        rwlock_t        hh_lock;
+        seqlock_t       hh_lock;
 
         /* cached hardware header; allow for machine alignment needs.        */
 #define HH_DATA_MOD     16
diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index 23967031ddb7..3725b93c52f3 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -309,6 +309,24 @@ static inline int neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
         return 0;
 }
 
+static inline int neigh_hh_output(struct hh_cache *hh, struct sk_buff *skb)
+{
+        unsigned seq;
+        int hh_len;
+
+        do {
+                int hh_alen;
+
+                seq = read_seqbegin(&hh->hh_lock);
+                hh_len = hh->hh_len;
+                hh_alen = HH_DATA_ALIGN(hh_len);
+                memcpy(skb->data - hh_alen, hh->hh_data, hh_alen);
+        } while (read_seqretry(&hh->hh_lock, seq));
+
+        skb_push(skb, hh_len);
+        return hh->hh_output(skb);
+}
+
 static inline struct neighbour *
 __neigh_lookup(struct neigh_table *tbl, const void *pkey, struct net_device *dev, int creat)
 {