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Message-ID: <20241107022900.70287-2-kuniyu@amazon.com>
Date: Wed, 6 Nov 2024 18:28:51 -0800
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
<pabeni@...hat.com>, Simon Horman <horms@...nel.org>
CC: Andrew Lunn <andrew+netdev@...n.ch>, Marc Kleine-Budde
<mkl@...gutronix.de>, Vincent Mailhol <mailhol.vincent@...adoo.fr>, "Daniel
Borkmann" <daniel@...earbox.net>, Nikolay Aleksandrov <razor@...ckwall.org>,
Kuniyuki Iwashima <kuniyu@...zon.com>, Kuniyuki Iwashima
<kuni1840@...il.com>, <netdev@...r.kernel.org>
Subject: [PATCH v3 net-next 01/10] 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: Kuniyuki Iwashima <kuniyu@...zon.com>
---
drivers/net/dummy.c | 6 +++++-
drivers/net/ifb.c | 6 +++++-
include/net/rtnetlink.h | 1 -
net/core/rtnetlink.c | 32 ++++++++++----------------------
4 files changed, 20 insertions(+), 25 deletions(-)
diff --git a/drivers/net/dummy.c b/drivers/net/dummy.c
index e9c5e1e11fa0..72618b6af44e 100644
--- a/drivers/net/dummy.c
+++ b/drivers/net/dummy.c
@@ -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;
}
diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
index 2c1b5def4a0b..a4b9ec4e8f30 100644
--- a/drivers/net/ifb.c
+++ b/drivers/net/ifb.c
@@ -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;
}
diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index b260c0cc9671..3ebfcc6e56fd 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -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);
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 3b33810d92a8..634732fe4c64 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -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);
}
--
2.39.5 (Apple Git-154)
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