[B.A.T.M.A.N.] [PATCH 10/10] batman-adv: Use rcu locking + ref-counting for neigh_list

Linus Lüssing
2010-12-31T15:46:25Z

With this commit only spinlocking for reading/writing variables inside
a neigh_node for NDP is used. The neigh_list traversal and entry
deleting/adding is done with rcu-locking and reference counting instead
to greatly reduce the time of (concurrent) spinlocking.

Signed-off-by: Linus Lüssing <linus.luessing@ascom.ch>
---
ndp.c | 54 ++++++++++++++++++++++++++++++++++++++----------------
originator.c | 2 +-
originator.h | 1 +
routing.c | 14 +++++++++-----
types.h | 2 ++
5 files changed, 51 insertions(+), 22 deletions(-)

diff --git a/ndp.c b/ndp.c
index 9f498f9..0793564 100644
--- a/ndp.c
+++ b/ndp.c
@@ -66,19 +66,23 @@ static void ndp_send(struct work_struct *work)
ETH_ALEN);

neigh_entry = (struct neigh_entry *)(ndp_packet + 1);
- spin_lock_bh(&batman_if->neigh_list_lock);
- hlist_for_each_entry(neigh_node, node, &batman_if->neigh_list, list) {
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(neigh_node, node, &batman_if->neigh_list,
+ list) {
if (entries_len + sizeof(struct neigh_entry) >
skb_tailroom(skb))
break;

+ spin_lock_bh(&neigh_node->update_lock);
memcpy(neigh_entry->addr, neigh_node->addr, ETH_ALEN);
neigh_entry->rq = neigh_node->rq;
+ spin_unlock_bh(&neigh_node->update_lock);
+
ndp_packet->num_neighbors++;
neigh_entry++;
entries_len += sizeof(struct neigh_entry);
}
- spin_unlock_bh(&batman_if->neigh_list_lock);
+ rcu_read_unlock();
skb_put(skb, entries_len);

bat_dbg(DBG_BATMAN, bat_priv,
@@ -205,6 +209,9 @@ static struct neigh_node *ndp_create_neighbor(uint8_t my_tq, uint32_t seqno,
return NULL;

INIT_HLIST_NODE(&neigh_node->list);
+ spin_lock_init(&neigh_node->update_lock);
+ kref_init(&neigh_node->refcount);
+
memcpy(neigh_node->addr, neigh_addr, ETH_ALEN);
neigh_node->last_rq_seqno = seqno - 1;

@@ -216,6 +223,7 @@ void ndp_purge_neighbors(void)
struct neigh_node *neigh_node;
struct hlist_node *node, *node_tmp;
struct batman_if *batman_if;
+ unsigned long last_valid;

rcu_read_lock();
list_for_each_entry_rcu(batman_if, &if_list, list) {
@@ -225,13 +233,17 @@ void ndp_purge_neighbors(void)
spin_lock_bh(&batman_if->neigh_list_lock);
hlist_for_each_entry_safe(neigh_node, node, node_tmp,
&batman_if->neigh_list, list) {
- if (time_before(jiffies, neigh_node->last_valid +
+ spin_lock(&neigh_node->update_lock);
+ last_valid = neigh_node->last_valid;
+ spin_unlock(&neigh_node->update_lock);
+
+ if (time_before(jiffies, last_valid +
msecs_to_jiffies(PURGE_TIMEOUT *
1000)))
continue;

- hlist_del(&neigh_node->list);
- kfree(neigh_node);
+ hlist_del_rcu(&neigh_node->list);
+ call_rcu(&neigh_node->rcu, neigh_node_free_rcu);
}
spin_unlock_bh(&batman_if->neigh_list_lock);
}
@@ -246,16 +258,17 @@ int ndp_update_neighbor(uint8_t my_tq, uint32_t seqno,
struct hlist_node *node;
int ret = 1;

- spin_lock_bh(&batman_if->neigh_list_lock);
- /* old neighbor? */
- hlist_for_each_entry(tmp_neigh_node, node, &batman_if->neigh_list,
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(tmp_neigh_node, node, &batman_if->neigh_list,
list) {
if (!compare_orig(tmp_neigh_node->addr, neigh_addr))
continue;

neigh_node = tmp_neigh_node;
+ kref_get(&neigh_node->refcount);
break;
}
+ rcu_read_unlock();

/* new neighbor? */
if (!neigh_node) {
@@ -264,15 +277,24 @@ int ndp_update_neighbor(uint8_t my_tq, uint32_t seqno,
if (!neigh_node)
goto ret;

- hlist_add_head(&neigh_node->list, &batman_if->neigh_list);
+ ndp_update_neighbor_lq(my_tq, seqno, neigh_node, bat_priv);
+
+ spin_lock_bh(&batman_if->neigh_list_lock);
+ hlist_add_head_rcu(&neigh_node->list, &batman_if->neigh_list);
+ spin_unlock_bh(&batman_if->neigh_list_lock);
}
+ /* old neighbor? */
+ else {
+ spin_lock_bh(&neigh_node->update_lock);
+ ndp_update_neighbor_lq(my_tq, seqno, neigh_node, bat_priv);
+ spin_unlock_bh(&neigh_node->update_lock);

- ndp_update_neighbor_lq(my_tq, seqno, neigh_node, bat_priv);
+ kref_put(&neigh_node->refcount, neigh_node_free_ref);
+ }

ret = 0;

ret:
- spin_unlock_bh(&batman_if->neigh_list_lock);
return ret;
}

@@ -311,9 +333,9 @@ int ndp_seq_print_text(struct seq_file *seq, void *offset)
if (batman_if->if_status != IF_ACTIVE)
continue;

- spin_lock_bh(&batman_if->neigh_list_lock);
- hlist_for_each_entry(neigh_node, node, &batman_if->neigh_list,
- list) {
+ hlist_for_each_entry_rcu(neigh_node, node,
+ &batman_if->neigh_list, list) {
+ spin_lock_bh(&neigh_node->update_lock);
last_seen_secs = jiffies_to_msecs(jiffies -
neigh_node->last_valid) / 1000;
last_seen_msecs = jiffies_to_msecs(jiffies -
@@ -324,9 +346,9 @@ int ndp_seq_print_text(struct seq_file *seq, void *offset)
last_seen_msecs, neigh_node->tq_avg,
neigh_node->rq, batman_if->net_dev->name);

+ spin_unlock_bh(&neigh_node->update_lock);
batman_count++;
}
- spin_unlock_bh(&batman_if->neigh_list_lock);
}
rcu_read_unlock();

diff --git a/originator.c b/originator.c
index e98add5..699dbfc 100644
--- a/originator.c
+++ b/originator.c
@@ -68,7 +68,7 @@ void neigh_node_free_ref(struct kref *refcount)
kfree(neigh_node);
}

-static void neigh_node_free_rcu(struct rcu_head *rcu)
+void neigh_node_free_rcu(struct rcu_head *rcu)
{
struct neigh_node *neigh_node;

diff --git a/originator.h b/originator.h
index f3676fa..2a7d68b 100644
--- a/originator.h
+++ b/originator.h
@@ -31,6 +31,7 @@ struct neigh_node *create_neighbor(struct orig_node *orig_node,
uint8_t *neigh,
struct batman_if *if_incoming);
void neigh_node_free_ref(struct kref *refcount);
+void neigh_node_free_rcu(struct rcu_head *rcu);
int orig_seq_print_text(struct seq_file *seq, void *offset);
int orig_hash_add_if(struct batman_if *batman_if, int max_if_num);
int orig_hash_del_if(struct batman_if *batman_if, int max_if_num);
diff --git a/routing.c b/routing.c
index 8a3acfa..785ddc2 100644
--- a/routing.c
+++ b/routing.c
@@ -199,20 +199,24 @@ static int is_bidirectional_neigh(struct orig_node *orig_node,
return 0;
}

- /* note, bottom halves are already deactivated outside in
- * recv_bat_packet() */
- spin_lock(&if_incoming->neigh_list_lock);
- hlist_for_each_entry(neigh_node, node, &if_incoming->neigh_list,
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(neigh_node, node, &if_incoming->neigh_list,
list) {
if (!compare_orig(neigh_node->addr, orig_neigh_node->orig))
continue;

orig_node->last_valid = jiffies;
+
+ /* note, bottom halves are already deactivated outside in
+ * recv_bat_packet() */
+ spin_lock(&neigh_node->update_lock);
local_tq = neigh_node->tq_avg;
local_rq = neigh_node->rq;
+ spin_unlock(&neigh_node->update_lock);
+
break;
}
- spin_unlock(&if_incoming->neigh_list_lock);
+ rcu_read_unlock();

if (local_tq == 0)
return 0;
diff --git a/types.h b/types.h
index 43721cf..37c2c58 100644
--- a/types.h
+++ b/types.h
@@ -129,6 +129,8 @@ struct neigh_node {
struct rcu_head rcu;
struct orig_node *orig_node;
struct batman_if *if_incoming;
+ spinlock_t update_lock; /* protects last_rq_seqno, ndp_rq_window, rq,
+ last_valid, tq_avg for NDP */
};

struct neigh_entry {
--
1.7.1