netns: Add an explicit rcu_barrier to unregister_pernet_{device|subsys}

This allows namespace exit methods to batch work that comes requires an
rcu barrier using call_rcu without having to treat the
unregister_pernet_operations cases specially.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 4026a4c..bd8c471 100644 (file)
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -413,8 +413,11 @@ again:
                }
        }
        error = __register_pernet_operations(list, ops);
-       if (error && ops->id)
-               ida_remove(&net_generic_ids, *ops->id);
+       if (error) {
+               rcu_barrier();
+               if (ops->id)
+                       ida_remove(&net_generic_ids, *ops->id);
+       }
 
        return error;
 }
@@ -423,6 +426,7 @@ static void unregister_pernet_operations(struct pernet_operations *ops)
 {
        
        __unregister_pernet_operations(ops);
+       rcu_barrier();
        if (ops->id)
                ida_remove(&net_generic_ids, *ops->id);
 }