datapath: Don't use RCU for internal dev vport.

The vports are now attached and ready to go when they are allocated,
so we don't have to worry about future changes.  As a result, we can
directly store the pointer in the internal dev's netdevice private
space before it is registered.  The registration process will handle
the necessary write memory barriers and anyone who has a reference
to the netdev will have done the read side barriers, we don't need
to use RCU at all.

Signed-off-by: Jesse Gross <jesse@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>

diff --git a/datapath/vport-internal_dev.c b/datapath/vport-internal_dev.c
index 86171db..c88fb3b 100644 (file)
--- a/datapath/vport-internal_dev.c
+++ b/datapath/vport-internal_dev.c
@@ -10,7 +10,6 @@
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/ethtool.h>
-#include <linux/rcupdate.h>
 #include <linux/skbuff.h>
 #include <linux/version.h>
 
@@ -72,13 +71,10 @@ static int internal_dev_mac_addr(struct net_device *dev, void *p)
 /* Called with rcu_read_lock and bottom-halves disabled. */
 static int internal_dev_xmit(struct sk_buff *skb, struct net_device *netdev)
 {
-       struct internal_dev *internal_dev = internal_dev_priv(netdev);
-       struct vport *vport = rcu_dereference(internal_dev->vport);
-
        compute_ip_summed(skb, true);
        OVS_CB(skb)->flow = NULL;
 
-       vport_receive(vport, skb);
+       vport_receive(internal_dev_priv(netdev)->vport, skb);
        return 0;
 }
 
@@ -197,7 +193,7 @@ static struct vport *internal_dev_create(const struct vport_parms *parms)
        }
 
        internal_dev = internal_dev_priv(netdev_vport->dev);
-       rcu_assign_pointer(internal_dev->vport, vport);
+       internal_dev->vport = vport;
 
        err = register_netdevice(netdev_vport->dev);
        if (err)
@@ -288,11 +284,8 @@ int is_internal_vport(const struct vport *vport)
 
 struct vport *internal_dev_get_vport(struct net_device *netdev)
 {
-       struct internal_dev *internal_dev;
-
        if (!is_internal_dev(netdev))
                return NULL;
 
-       internal_dev = internal_dev_priv(netdev);
-       return rcu_dereference(internal_dev->vport);
+       return internal_dev_priv(netdev)->vport;
 }