Commit d5ec8d91 authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Jakub Kicinski
Browse files

rtnetlink: Remove __rtnl_link_unregister(). 



rtnl_link_unregister() holds RTNL and calls __rtnl_link_unregister(),
where we call synchronize_srcu() to wait inflight RTM_NEWLINK requests
for per-netns RTNL.

We put synchronize_srcu() in __rtnl_link_unregister() due to ifb.ko
and dummy.ko.

However, rtnl_newlink() will acquire SRCU before RTNL later in this
series.  Then, lockdep will detect the deadlock:

   rtnl_link_unregister()       rtnl_newlink()
   ----                         ----
   lock(rtnl_mutex);
                                lock(&ops->srcu);
                                lock(rtnl_mutex);
   sync(&ops->srcu);

To avoid the problem, we must call synchronize_srcu() before RTNL in
rtnl_link_unregister().

As a preparation, let's remove __rtnl_link_unregister().

Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20241108004823.29419-2-kuniyu@amazon.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 7a3bcd39

drivers/net/dummy.c

+5 −1
Original line number Diff line number Diff line
@@ -166,6 +166,7 @@ static int __init dummy_init_one(void) 


static int __init dummy_init_module(void)

{

	bool need_unregister = false;

	int i, err = 0;



	down_write(&pernet_ops_rwsem);
@@ -179,12 +180,15 @@ static int __init dummy_init_module(void) 
		cond_resched();

	}

	if (err < 0)

		__rtnl_link_unregister(&dummy_link_ops);

		need_unregister = true;



out:

	rtnl_unlock();

	up_write(&pernet_ops_rwsem);



	if (need_unregister)

		rtnl_link_unregister(&dummy_link_ops);



	return err;

}

drivers/net/ifb.c

+5 −1
Original line number Diff line number Diff line
@@ -424,6 +424,7 @@ static int __init ifb_init_one(int index) 


static int __init ifb_init_module(void)

{

	bool need_unregister = false;

	int i, err;



	down_write(&pernet_ops_rwsem);
@@ -437,12 +438,15 @@ static int __init ifb_init_module(void) 
		cond_resched();

	}

	if (err)

		__rtnl_link_unregister(&ifb_link_ops);

		need_unregister = true;



out:

	rtnl_unlock();

	up_write(&pernet_ops_rwsem);



	if (need_unregister)

		rtnl_link_unregister(&ifb_link_ops);



	return err;

}

include/net/rtnetlink.h

+0 −1
Original line number Diff line number Diff line
@@ -165,7 +165,6 @@ struct rtnl_link_ops { 
};



int __rtnl_link_register(struct rtnl_link_ops *ops);

void __rtnl_link_unregister(struct rtnl_link_ops *ops);



int rtnl_link_register(struct rtnl_link_ops *ops);

void rtnl_link_unregister(struct rtnl_link_ops *ops);

net/core/rtnetlink.c

+10 −22
Original line number Diff line number Diff line
@@ -568,27 +568,6 @@ static void __rtnl_kill_links(struct net *net, struct rtnl_link_ops *ops) 
	unregister_netdevice_many(&list_kill);

}



/**

 * __rtnl_link_unregister - Unregister rtnl_link_ops from rtnetlink.

 * @ops: struct rtnl_link_ops * to unregister

 *

 * The caller must hold the rtnl_mutex and guarantee net_namespace_list

 * integrity (hold pernet_ops_rwsem for writing to close the race

 * with setup_net() and cleanup_net()).

 */

void __rtnl_link_unregister(struct rtnl_link_ops *ops)

{

	struct net *net;



	list_del_rcu(&ops->list);

	synchronize_srcu(&ops->srcu);

	cleanup_srcu_struct(&ops->srcu);



	for_each_net(net)

		__rtnl_kill_links(net, ops);

}

EXPORT_SYMBOL_GPL(__rtnl_link_unregister);



/* Return with the rtnl_lock held when there are no network

 * devices unregistering in any network namespace.

 */
@@ -617,10 +596,19 @@ static void rtnl_lock_unregistering_all(void) 
 */

void rtnl_link_unregister(struct rtnl_link_ops *ops)

{

	struct net *net;



	/* Close the race with setup_net() and cleanup_net() */

	down_write(&pernet_ops_rwsem);

	rtnl_lock_unregistering_all();

	__rtnl_link_unregister(ops);



	list_del_rcu(&ops->list);

	synchronize_srcu(&ops->srcu);

	cleanup_srcu_struct(&ops->srcu);



	for_each_net(net)

		__rtnl_kill_links(net, ops);



	rtnl_unlock();

	up_write(&pernet_ops_rwsem);

}