tipc: use RCU to protect media_ptr pointer

Now the media_ptr pointer is protected with tipc_net_lock write lock
on write side; tipc_net_lock read lock is used to read side. As the
part of effort of eliminating tipc_net_lock, we decide to adjust the
locking policy of media_ptr pointer protection: on write side, RTNL
lock is use while on read side RCU read lock is applied.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Tested-by: Erik Hugne <erik.hugne@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index e0625e9..c24a351 100644 (file)
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -458,7 +458,7 @@ int tipc_enable_l2_media(struct tipc_bearer *b)
                return -ENODEV;
 
        /* Associate TIPC bearer with Ethernet bearer */
-       b->media_ptr = dev;
+       rcu_assign_pointer(b->media_ptr, dev);
        memset(b->bcast_addr.value, 0, sizeof(b->bcast_addr.value));
        memcpy(b->bcast_addr.value, dev->broadcast, b->media->hwaddr_len);
        b->bcast_addr.media_id = b->media->type_id;
@@ -477,7 +477,10 @@ int tipc_enable_l2_media(struct tipc_bearer *b)
  */
 void tipc_disable_l2_media(struct tipc_bearer *b)
 {
-       struct net_device *dev = (struct net_device *)b->media_ptr;
+       struct net_device *dev;
+
+       dev = (struct net_device *)rtnl_dereference(b->media_ptr);
+       RCU_INIT_POINTER(b->media_ptr, NULL);
        RCU_INIT_POINTER(dev->tipc_ptr, NULL);
        dev_put(dev);
 }
@@ -492,8 +495,12 @@ int tipc_l2_send_msg(struct sk_buff *buf, struct tipc_bearer *b,
                     struct tipc_media_addr *dest)
 {
        struct sk_buff *clone;
+       struct net_device *dev;
        int delta;
-       struct net_device *dev = (struct net_device *)b->media_ptr;
+
+       dev = (struct net_device *)rcu_dereference_rtnl(b->media_ptr);
+       if (!dev)
+               return 0;
 
        clone = skb_clone(buf, GFP_ATOMIC);
        if (!clone)

diff --git a/net/tipc/bearer.h b/net/tipc/bearer.h
index 2fa86bd..a983b30 100644 (file)
--- a/net/tipc/bearer.h
+++ b/net/tipc/bearer.h
@@ -128,7 +128,7 @@ struct tipc_media {
  * care of initializing all other fields.
  */
 struct tipc_bearer {
-       void *media_ptr;                        /* initalized by media */
+       void __rcu *media_ptr;                  /* initalized by media */
        u32 mtu;                                /* initalized by media */
        struct tipc_media_addr addr;            /* initalized by media */
        char name[TIPC_MAX_BEARER_NAME];