The reading of the hard header cache in the output path can be
made lockless using seqlock.
Signed-off-by: Stephen Hemminger <[EMAIL PROTECTED]>
---
include/linux/netdevice.h | 3 ++-
include/net/neighbour.h | 2 ++
net/core/neighbour.c | 40 +++++++++++++++++++++++++++++++++++-----
net/ipv4/ip_output.c | 13 +++----------
net/ipv6/ip6_output.c | 13 +++----------
5 files changed, 45 insertions(+), 26 deletions(-)
--- net-2.6.19.orig/include/linux/netdevice.h
+++ net-2.6.19/include/linux/netdevice.h
@@ -193,7 +193,7 @@ struct hh_cache
*/
int 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
@@ -217,6 +217,7 @@ struct hh_cache
#define LL_RESERVED_SPACE_EXTRA(dev,extra) \
((((dev)->hard_header_len+extra)&~(HH_DATA_MOD - 1)) + HH_DATA_MOD)
+
/* These flag bits are private to the generic network queueing
* layer, they may not be explicitly referenced by any other
* code.
--- net-2.6.19.orig/net/core/neighbour.c
+++ net-2.6.19/net/core/neighbour.c
@@ -591,9 +591,11 @@ void neigh_destroy(struct neighbour *nei
while ((hh = neigh->hh) != NULL) {
neigh->hh = hh->hh_next;
hh->hh_next = NULL;
- write_lock_bh(&hh->hh_lock);
+
+ write_seqlock_bh(&hh->hh_lock);
hh->hh_output = neigh_blackhole;
- write_unlock_bh(&hh->hh_lock);
+ write_sequnlock_bh(&hh->hh_lock);
+
if (atomic_dec_and_test(&hh->hh_refcnt))
kfree(hh);
}
@@ -912,9 +914,9 @@ static __inline__ void neigh_update_hhs(
if (update) {
for (hh = neigh->hh; hh; hh = hh->hh_next) {
- write_lock_bh(&hh->hh_lock);
+ write_seqlock_bh(&hh->hh_lock);
update(hh, neigh->dev, neigh->ha);
- write_unlock_bh(&hh->hh_lock);
+ write_sequnlock_bh(&hh->hh_lock);
}
}
}
@@ -1105,7 +1107,7 @@ static void neigh_hh_init(struct neighbo
break;
if (!hh && (hh = kzalloc(sizeof(*hh), GFP_ATOMIC)) != NULL) {
- rwlock_init(&hh->hh_lock);
+ seqlock_init(&hh->hh_lock);
hh->hh_type = protocol;
atomic_set(&hh->hh_refcnt, 0);
hh->hh_next = NULL;
@@ -1128,6 +1130,33 @@ static void neigh_hh_init(struct neighbo
}
}
+
+/*
+ * Add header to skb from hard header cache
+ * Handle case where cache gets changed.
+ */
+int neigh_hh_output(const struct hh_cache *hh, struct sk_buff *skb)
+{
+ int len, alen;
+ unsigned seq;
+ int (*output)(struct sk_buff *);
+
+ for(;;) {
+ seq = read_seqbegin(&hh->hh_lock);
+ len = hh->hh_len;
+ alen = HH_DATA_ALIGN(len);
+ output = hh->hh_output;
+ memcpy(skb->data - alen, hh->hh_data, alen);
+ skb_push(skb, len);
+
+ if (likely(!read_seqretry(&hh->hh_lock, seq)))
+ return output(skb);
+
+ /* undo and try again */
+ __skb_pull(skb, len);
+ }
+}
+
/* This function can be used in contexts, where only old dev_queue_xmit
worked, f.e. if you want to override normal output path (eql, shaper),
but resolution is not made yet.
@@ -2762,6 +2791,7 @@ EXPORT_SYMBOL(neigh_delete);
EXPORT_SYMBOL(neigh_destroy);
EXPORT_SYMBOL(neigh_dump_info);
EXPORT_SYMBOL(neigh_event_ns);
+EXPORT_SYMBOL(neigh_hh_output);
EXPORT_SYMBOL(neigh_ifdown);
EXPORT_SYMBOL(neigh_lookup);
EXPORT_SYMBOL(neigh_lookup_nodev);
--- net-2.6.19.orig/net/ipv4/ip_output.c
+++ net-2.6.19/net/ipv4/ip_output.c
@@ -182,16 +182,9 @@ static inline int ip_finish_output2(stru
skb = skb2;
}
- if (hh) {
- int hh_alen;
-
- read_lock_bh(&hh->hh_lock);
- hh_alen = HH_DATA_ALIGN(hh->hh_len);
- memcpy(skb->data - hh_alen, hh->hh_data, hh_alen);
- read_unlock_bh(&hh->hh_lock);
- skb_push(skb, hh->hh_len);
- return hh->hh_output(skb);
- } else if (dst->neighbour)
+ if (hh)
+ return neigh_hh_output(hh, skb);
+ else if (dst->neighbour)
return dst->neighbour->output(skb);
if (net_ratelimit())
--- net-2.6.19.orig/net/ipv6/ip6_output.c
+++ net-2.6.19/net/ipv6/ip6_output.c
@@ -76,16 +76,9 @@ static inline int ip6_output_finish(stru
struct dst_entry *dst = skb->dst;
struct hh_cache *hh = dst->hh;
- if (hh) {
- int hh_alen;
-
- read_lock_bh(&hh->hh_lock);
- hh_alen = HH_DATA_ALIGN(hh->hh_len);
- memcpy(skb->data - hh_alen, hh->hh_data, hh_alen);
- read_unlock_bh(&hh->hh_lock);
- skb_push(skb, hh->hh_len);
- return hh->hh_output(skb);
- } else if (dst->neighbour)
+ if (hh)
+ return neigh_hh_output(hh, skb);
+ else if (dst->neighbour)
return dst->neighbour->output(skb);
IP6_INC_STATS_BH(IPSTATS_MIB_OUTNOROUTES);
--- net-2.6.19.orig/include/net/neighbour.h
+++ net-2.6.19/include/net/neighbour.h
@@ -193,6 +193,8 @@ extern struct neighbour * neigh_create(s
struct net_device *dev);
extern void neigh_destroy(struct neighbour *neigh);
extern int __neigh_event_send(struct neighbour *neigh,
struct sk_buff *skb);
+extern int neigh_hh_output(const struct hh_cache *hh,
struct sk_buff *skb);
+
extern int neigh_update(struct neighbour *neigh, const u8
*lladdr, u8 new,
u32 flags);
extern void neigh_changeaddr(struct neigh_table *tbl,
struct net_device *dev);
--
-
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