net: Do not take net_rwsem in __rtnl_link_unregister()
This function calls call_netdevice_notifier(), which also
may take net_rwsem. So, we can't use net_rwsem here.
This patch makes callers of this functions take pernet_ops_rwsem,
like register_netdevice_notifier() does. This will protect
the modifications of net_namespace_list, and allows notifiers
to take it (they won't have to care about context).
Since __rtnl_link_unregister() is used on module load
and unload (which are not frequent operations), this looks
for me better, than make all call_netdevice_notifier()
always executing in "protected net_namespace_list" context.
Also, this fixes the problem we had a deal in 328fbe747ad4
"Close race between {un, }register_netdevice_notifier and ...",
and guarantees __rtnl_link_unregister() does not skip
exitting net.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/dummy.c b/drivers/net/dummy.c
index 30b1c85..0d15a12 100644
--- a/drivers/net/dummy.c
+++ b/drivers/net/dummy.c
@@ -219,6 +219,7 @@
{
int i, err = 0;
+ down_write(&pernet_ops_rwsem);
rtnl_lock();
err = __rtnl_link_register(&dummy_link_ops);
if (err < 0)
@@ -233,6 +234,7 @@
out:
rtnl_unlock();
+ up_write(&pernet_ops_rwsem);
return err;
}