packet: convert socket list to RCU (v3)

Convert AF_PACKET to use RCU, eliminating one more reader/writer lock.

There is no need for a real sk_del_node_init_rcu(), because sk_del_node_init
is doing the equivalent thing to hlst_del_init_rcu already; but added
some comments to try and make that obvious.

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

3 files changed, 43 insertions, 33 deletions

diff --git a/include/net/netns/packet.h b/include/net/netns/packet.h
index 637daf698884..cb4e894c0f8d 100644
--- a/include/net/netns/packet.h
+++ b/include/net/netns/packet.h
@@ -4,11 +4,11 @@
 #ifndef __NETNS_PACKET_H__
 #define __NETNS_PACKET_H__
 
-#include <linux/list.h>
+#include <linux/rculist.h>
 #include <linux/spinlock.h>
 
 struct netns_packet {
-        rwlock_t                sklist_lock;
+        spinlock_t              sklist_lock;
         struct hlist_head       sklist;
 };
 
diff --git a/include/net/sock.h b/include/net/sock.h
index 580d51fa28e9..6cb1676e409a 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -381,6 +381,7 @@ static __inline__ void __sk_del_node(struct sock *sk)
         __hlist_del(&sk->sk_node);
 }
 
+/* NB: equivalent to hlist_del_init_rcu */
 static __inline__ int __sk_del_node_init(struct sock *sk)
 {
         if (sk_hashed(sk)) {
@@ -421,6 +422,7 @@ static __inline__ int sk_del_node_init(struct sock *sk)
         }
         return rc;
 }
+#define sk_del_node_init_rcu(sk)        sk_del_node_init(sk)
 
 static __inline__ int __sk_nulls_del_node_init_rcu(struct sock *sk)
 {
@@ -454,6 +456,12 @@ static __inline__ void sk_add_node(struct sock *sk, struct hlist_head *list)
         __sk_add_node(sk, list);
 }
 
+static __inline__ void sk_add_node_rcu(struct sock *sk, struct hlist_head *list)
+{
+        sock_hold(sk);
+        hlist_add_head_rcu(&sk->sk_node, list);
+}
+
 static __inline__ void __sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_head *list)
 {
         hlist_nulls_add_head_rcu(&sk->sk_nulls_node, list);
@@ -478,6 +486,8 @@ static __inline__ void sk_add_bind_node(struct sock *sk,
 
 #define sk_for_each(__sk, node, list) \
         hlist_for_each_entry(__sk, node, list, sk_node)
+#define sk_for_each_rcu(__sk, node, list) \
+        hlist_for_each_entry_rcu(__sk, node, list, sk_node)
 #define sk_nulls_for_each(__sk, node, list) \
         hlist_nulls_for_each_entry(__sk, node, list, sk_nulls_node)
 #define sk_nulls_for_each_rcu(__sk, node, list) \
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 10f7295bcefb..2f0369367ee0 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1262,24 +1262,22 @@ static int packet_release(struct socket *sock)
         net = sock_net(sk);
         po = pkt_sk(sk);
 
-        write_lock_bh(&net->packet.sklist_lock);
-        sk_del_node_init(sk);
+        spin_lock_bh(&net->packet.sklist_lock);
+        sk_del_node_init_rcu(sk);
         sock_prot_inuse_add(net, sk->sk_prot, -1);
-        write_unlock_bh(&net->packet.sklist_lock);
-
-        /*
-         *      Unhook packet receive handler.
-         */
+        spin_unlock_bh(&net->packet.sklist_lock);
 
+        spin_lock(&po->bind_lock);
         if (po->running) {
                 /*
-                 *      Remove the protocol hook
+                 * Remove from protocol table
                  */
-                dev_remove_pack(&po->prot_hook);
                 po->running = 0;
                 po->num = 0;
+                __dev_remove_pack(&po->prot_hook);
                 __sock_put(sk);
         }
+        spin_unlock(&po->bind_lock);
 
         packet_flush_mclist(sk);
 
@@ -1291,10 +1289,10 @@ static int packet_release(struct socket *sock)
         if (po->tx_ring.pg_vec)
                 packet_set_ring(sk, &req, 1, 1);
 
+        synchronize_net();
         /*
          *      Now the socket is dead. No more input will appear.
          */
-
         sock_orphan(sk);
         sock->sk = NULL;
 
@@ -1478,10 +1476,11 @@ static int packet_create(struct net *net, struct socket *sock, int protocol,
                 po->running = 1;
         }
 
-        write_lock_bh(&net->packet.sklist_lock);
-        sk_add_node(sk, &net->packet.sklist);
+        spin_lock_bh(&net->packet.sklist_lock);
+        sk_add_node_rcu(sk, &net->packet.sklist);
         sock_prot_inuse_add(net, &packet_proto, 1);
-        write_unlock_bh(&net->packet.sklist_lock);
+        spin_unlock_bh(&net->packet.sklist_lock);
+
         return 0;
 out:
         return err;
@@ -2075,8 +2074,8 @@ static int packet_notifier(struct notifier_block *this, unsigned long msg, void
         struct net_device *dev = data;
         struct net *net = dev_net(dev);
 
-        read_lock(&net->packet.sklist_lock);
-        sk_for_each(sk, node, &net->packet.sklist) {
+        rcu_read_lock();
+        sk_for_each_rcu(sk, node, &net->packet.sklist) {
                 struct packet_sock *po = pkt_sk(sk);
 
                 switch (msg) {
@@ -2104,18 +2103,19 @@ static int packet_notifier(struct notifier_block *this, unsigned long msg, void
                         }
                         break;
                 case NETDEV_UP:
-                        spin_lock(&po->bind_lock);
-                        if (dev->ifindex == po->ifindex && po->num &&
-                            !po->running) {
-                                dev_add_pack(&po->prot_hook);
-                                sock_hold(sk);
-                                po->running = 1;
+                        if (dev->ifindex == po->ifindex) {
+                                spin_lock(&po->bind_lock);
+                                if (po->num && !po->running) {
+                                        dev_add_pack(&po->prot_hook);
+                                        sock_hold(sk);
+                                        po->running = 1;
+                                }
+                                spin_unlock(&po->bind_lock);
                         }
-                        spin_unlock(&po->bind_lock);
                         break;
                 }
         }
-        read_unlock(&net->packet.sklist_lock);
+        rcu_read_unlock();
         return NOTIFY_DONE;
 }
 
@@ -2512,24 +2512,24 @@ static struct notifier_block packet_netdev_notifier = {
 #ifdef CONFIG_PROC_FS
 
 static void *packet_seq_start(struct seq_file *seq, loff_t *pos)
-        __acquires(seq_file_net(seq)->packet.sklist_lock)
+        __acquires(RCU)
 {
         struct net *net = seq_file_net(seq);
-        read_lock(&net->packet.sklist_lock);
-        return seq_hlist_start_head(&net->packet.sklist, *pos);
+
+        rcu_read_lock();
+        return seq_hlist_start_head_rcu(&net->packet.sklist, *pos);
 }
 
 static void *packet_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
         struct net *net = seq_file_net(seq);
-        return seq_hlist_next(v, &net->packet.sklist, pos);
+        return seq_hlist_next_rcu(v, &net->packet.sklist, pos);
 }
 
 static void packet_seq_stop(struct seq_file *seq, void *v)
-        __releases(seq_file_net(seq)->packet.sklist_lock)
+        __releases(RCU)
 {
-        struct net *net = seq_file_net(seq);
-        read_unlock(&net->packet.sklist_lock);
+        rcu_read_unlock();
 }
 
 static int packet_seq_show(struct seq_file *seq, void *v)
@@ -2581,7 +2581,7 @@ static const struct file_operations packet_seq_fops = {
 
 static int __net_init packet_net_init(struct net *net)
 {
-        rwlock_init(&net->packet.sklist_lock);
+        spin_lock_init(&net->packet.sklist_lock);
         INIT_HLIST_HEAD(&net->packet.sklist);
 
         if (!proc_net_fops_create(net, "packet", 0, &packet_seq_fops))