1 files changed, 42 insertions, 25 deletions

diff --git a/net/can/af_can.c b/net/can/af_can.c
index 733d66f1b05a..094fc5332d42 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -84,8 +84,8 @@ static DEFINE_SPINLOCK(can_rcvlists_lock);
 static struct kmem_cache *rcv_cache __read_mostly;
 
 /* table of registered CAN protocols */
-static struct can_proto *proto_tab[CAN_NPROTO] __read_mostly;
-static DEFINE_SPINLOCK(proto_tab_lock);
+static const struct can_proto *proto_tab[CAN_NPROTO] __read_mostly;
+static DEFINE_MUTEX(proto_tab_lock);
 
 struct timer_list can_stattimer;   /* timer for statistics update */
 struct s_stats    can_stats;       /* packet statistics */
@@ -115,11 +115,29 @@ static void can_sock_destruct(struct sock *sk)
         skb_queue_purge(&sk->sk_receive_queue);
 }
 
+static const struct can_proto *can_get_proto(int protocol)
+{
+        const struct can_proto *cp;
+
+        rcu_read_lock();
+        cp = rcu_dereference(proto_tab[protocol]);
+        if (cp && !try_module_get(cp->prot->owner))
+                cp = NULL;
+        rcu_read_unlock();
+
+        return cp;
+}
+
+static inline void can_put_proto(const struct can_proto *cp)
+{
+        module_put(cp->prot->owner);
+}
+
 static int can_create(struct net *net, struct socket *sock, int protocol,
                       int kern)
 {
         struct sock *sk;
-        struct can_proto *cp;
+        const struct can_proto *cp;
         int err = 0;
 
         sock->state = SS_UNCONNECTED;
@@ -130,9 +148,12 @@ static int can_create(struct net *net, struct socket *sock, int protocol,
         if (!net_eq(net, &init_net))
                 return -EAFNOSUPPORT;
 
+        cp = can_get_proto(protocol);
+
 #ifdef CONFIG_MODULES
-        /* try to load protocol module kernel is modular */
-        if (!proto_tab[protocol]) {
+        if (!cp) {
+                /* try to load protocol module if kernel is modular */
+
                 err = request_module("can-proto-%d", protocol);
 
                 /*
@@ -143,22 +164,18 @@ static int can_create(struct net *net, struct socket *sock, int protocol,
                 if (err && printk_ratelimit())
                         printk(KERN_ERR "can: request_module "
                                "(can-proto-%d) failed.\n", protocol);
+
+                cp = can_get_proto(protocol);
         }
 #endif
 
-        spin_lock(&proto_tab_lock);
-        cp = proto_tab[protocol];
-        if (cp && !try_module_get(cp->prot->owner))
-                cp = NULL;
-        spin_unlock(&proto_tab_lock);
-
         /* check for available protocol and correct usage */
 
         if (!cp)
                 return -EPROTONOSUPPORT;
 
         if (cp->type != sock->type) {
-                err = -EPROTONOSUPPORT;
+                err = -EPROTOTYPE;
                 goto errout;
         }
 
@@ -183,7 +200,7 @@ static int can_create(struct net *net, struct socket *sock, int protocol,
         }
 
  errout:
-        module_put(cp->prot->owner);
+        can_put_proto(cp);
         return err;
 }
 
@@ -679,7 +696,7 @@ drop:
  *  -EBUSY  protocol already in use
  *  -ENOBUF if proto_register() fails
  */
-int can_proto_register(struct can_proto *cp)
+int can_proto_register(const struct can_proto *cp)
 {
         int proto = cp->protocol;
         int err = 0;
@@ -694,15 +711,16 @@ int can_proto_register(struct can_proto *cp)
         if (err < 0)
                 return err;
 
-        spin_lock(&proto_tab_lock);
+        mutex_lock(&proto_tab_lock);
+
         if (proto_tab[proto]) {
                 printk(KERN_ERR "can: protocol %d already registered\n",
                        proto);
                 err = -EBUSY;
         } else
-                proto_tab[proto] = cp;
+                rcu_assign_pointer(proto_tab[proto], cp);
 
-        spin_unlock(&proto_tab_lock);
+        mutex_unlock(&proto_tab_lock);
 
         if (err < 0)
                 proto_unregister(cp->prot);
@@ -715,17 +733,16 @@ EXPORT_SYMBOL(can_proto_register);
  * can_proto_unregister - unregister CAN transport protocol
  * @cp: pointer to CAN protocol structure
  */
-void can_proto_unregister(struct can_proto *cp)
+void can_proto_unregister(const struct can_proto *cp)
 {
         int proto = cp->protocol;
 
-        spin_lock(&proto_tab_lock);
-        if (!proto_tab[proto]) {
-                printk(KERN_ERR "BUG: can: protocol %d is not registered\n",
-                       proto);
-        }
-        proto_tab[proto] = NULL;
-        spin_unlock(&proto_tab_lock);
+        mutex_lock(&proto_tab_lock);
+        BUG_ON(proto_tab[proto] != cp);
+        rcu_assign_pointer(proto_tab[proto], NULL);
+        mutex_unlock(&proto_tab_lock);
+
+        synchronize_rcu();
 
         proto_unregister(cp->prot);
 }