ipv4: get rid of ip_ra_lock

After commit 1215e51edad1 ("ipv4: fix a deadlock in ip_ra_control")
we always take RTNL lock for ip_ra_control() which is the only place
we update the list ip_ra_chain, so the ip_ra_lock is no longer needed.

As Eric points out, BH does not need to disable either, RCU readers
don't care.

Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 1d46d05efb0ff067c35750ac43be8e7babd60446..ec4fe3d4b5c9c17d53d7464b42b82a564ae48e54 100644 (file)
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -330,7 +330,6 @@ int ip_cmsg_send(struct sock *sk, struct msghdr *msg, struct ipcm_cookie *ipc,
    sent to multicast group to reach destination designated router.
  */
 struct ip_ra_chain __rcu *ip_ra_chain;
-static DEFINE_SPINLOCK(ip_ra_lock);
 
 
 static void ip_ra_destroy_rcu(struct rcu_head *head)
@@ -352,21 +351,17 @@ int ip_ra_control(struct sock *sk, unsigned char on,
 
        new_ra = on ? kmalloc(sizeof(*new_ra), GFP_KERNEL) : NULL;
 
-       spin_lock_bh(&ip_ra_lock);
        for (rap = &ip_ra_chain;
-            (ra = rcu_dereference_protected(*rap,
-                       lockdep_is_held(&ip_ra_lock))) != NULL;
+            (ra = rtnl_dereference(*rap)) != NULL;
             rap = &ra->next) {
                if (ra->sk == sk) {
                        if (on) {
-                               spin_unlock_bh(&ip_ra_lock);
                                kfree(new_ra);
                                return -EADDRINUSE;
                        }
                        /* dont let ip_call_ra_chain() use sk again */
                        ra->sk = NULL;
                        RCU_INIT_POINTER(*rap, ra->next);
-                       spin_unlock_bh(&ip_ra_lock);
 
                        if (ra->destructor)
                                ra->destructor(sk);
@@ -380,17 +375,14 @@ int ip_ra_control(struct sock *sk, unsigned char on,
                        return 0;
                }
        }
-       if (!new_ra) {
-               spin_unlock_bh(&ip_ra_lock);
+       if (!new_ra)
                return -ENOBUFS;
-       }
        new_ra->sk = sk;
        new_ra->destructor = destructor;
 
        RCU_INIT_POINTER(new_ra->next, ra);
        rcu_assign_pointer(*rap, new_ra);
        sock_hold(sk);
-       spin_unlock_bh(&ip_ra_lock);
 
        return 0;
 }