net: speedup netdev_set_master()

We currently force a synchronize_net() in netdev_set_master()

This seems necessary only when a slave had a master and we dismantle it.

In the other case ("ifenslave bond0 ethO"), we dont need this long
delay.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 4 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index fe2a754238a9..2d01f18f303a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3757,11 +3757,10 @@ int netdev_set_master(struct net_device *slave, struct net_device *master)
 
         slave->master = master;
 
-        synchronize_net();
-
-        if (old)
+        if (old) {
+                synchronize_net();
                 dev_put(old);
-
+        }
         if (master)
                 slave->flags |= IFF_SLAVE;
         else