decnet: RCU conversion and get rid of dev_base_lock

While tracking dev_base_lock users, I found decnet used it in
dnet_select_source(), but for a wrong purpose:

Writers only hold RTNL, not dev_base_lock, so readers must use RCU if
they cannot use RTNL.

Adds an rcu_head in struct dn_ifaddr and handle proper RCU management.

Adds __rcu annotation in dn_route as well.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

8 files changed, 127 insertions, 88 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index d8fd2c23a1b9..578debb801f4 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -951,7 +951,7 @@ struct net_device {
 #endif
         void                    *atalk_ptr;     /* AppleTalk link       */
         struct in_device __rcu  *ip_ptr;        /* IPv4 specific data   */
-        void                    *dn_ptr;        /* DECnet specific data */
+        struct dn_dev __rcu     *dn_ptr;        /* DECnet specific data */
         struct inet6_dev __rcu  *ip6_ptr;       /* IPv6 specific data */
         void                    *ec_ptr;        /* Econet specific data */
         void                    *ax25_ptr;      /* AX.25 specific data */
diff --git a/include/net/dn_dev.h b/include/net/dn_dev.h
index 0916bbf3bdff..b9e32db03f20 100644
--- a/include/net/dn_dev.h
+++ b/include/net/dn_dev.h
@@ -5,13 +5,14 @@
 struct dn_dev;
 
 struct dn_ifaddr {
-        struct dn_ifaddr *ifa_next;
+        struct dn_ifaddr __rcu *ifa_next;
         struct dn_dev    *ifa_dev;
         __le16            ifa_local;
         __le16            ifa_address;
         __u8              ifa_flags;
         __u8              ifa_scope;
         char              ifa_label[IFNAMSIZ];
+        struct rcu_head   rcu;
 };
 
 #define DN_DEV_S_RU  0 /* Run - working normally   */
@@ -83,7 +84,7 @@ struct dn_dev_parms {
 
 
 struct dn_dev {
-        struct dn_ifaddr *ifa_list;
+        struct dn_ifaddr __rcu *ifa_list;
         struct net_device *dev;
         struct dn_dev_parms parms;
         char use_long;
@@ -171,19 +172,27 @@ extern int unregister_dnaddr_notifier(struct notifier_block *nb);
 
 static inline int dn_dev_islocal(struct net_device *dev, __le16 addr)
 {
-        struct dn_dev *dn_db = dev->dn_ptr;
+        struct dn_dev *dn_db;
         struct dn_ifaddr *ifa;
+        int res = 0;
 
+        rcu_read_lock();
+        dn_db = rcu_dereference(dev->dn_ptr);
         if (dn_db == NULL) {
                 printk(KERN_DEBUG "dn_dev_islocal: Called for non DECnet device\n");
-                return 0;
+                goto out;
         }
 
-        for(ifa = dn_db->ifa_list; ifa; ifa = ifa->ifa_next)
-                if ((addr ^ ifa->ifa_local) == 0)
-                        return 1;
-
-        return 0;
+        for (ifa = rcu_dereference(dn_db->ifa_list);
+             ifa != NULL;
+             ifa = rcu_dereference(ifa->ifa_next))
+                if ((addr ^ ifa->ifa_local) == 0) {
+                        res = 1;
+                        break;
+                }
+out:
+        rcu_read_unlock();
+        return res;
 }
 
 #endif /* _NET_DN_DEV_H */
diff --git a/include/net/dst.h b/include/net/dst.h
index ffe9cb719c0e..a5bd72646d65 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -94,10 +94,10 @@ struct dst_entry {
         int                     __use;
         unsigned long           lastuse;
         union {
-                struct dst_entry *next;
-                struct rtable __rcu *rt_next;
-                struct rt6_info   *rt6_next;
-                struct dn_route  *dn_next;
+                struct dst_entry        *next;
+                struct rtable __rcu     *rt_next;
+                struct rt6_info         *rt6_next;
+                struct dn_route __rcu   *dn_next;
         };
 };
 
diff --git a/net/decnet/af_decnet.c b/net/decnet/af_decnet.c
index d6b93d19790f..18b8a2cbdf77 100644
--- a/net/decnet/af_decnet.c
+++ b/net/decnet/af_decnet.c
@@ -1848,7 +1848,7 @@ unsigned dn_mss_from_pmtu(struct net_device *dev, int mtu)
 {
         unsigned mss = 230 - DN_MAX_NSP_DATA_HEADER;
         if (dev) {
-                struct dn_dev *dn_db = dev->dn_ptr;
+                struct dn_dev *dn_db = rcu_dereference_raw(dev->dn_ptr);
                 mtu -= LL_RESERVED_SPACE(dev);
                 if (dn_db->use_long)
                         mtu -= 21;
diff --git a/net/decnet/dn_dev.c b/net/decnet/dn_dev.c
index 4c409b46aa35..0ba15633c418 100644
--- a/net/decnet/dn_dev.c
+++ b/net/decnet/dn_dev.c
@@ -267,7 +267,7 @@ static int dn_forwarding_proc(ctl_table *table, int write,
         if (table->extra1 == NULL)
                 return -EINVAL;
 
-        dn_db = dev->dn_ptr;
+        dn_db = rcu_dereference_raw(dev->dn_ptr);
         old = dn_db->parms.forwarding;
 
         err = proc_dointvec(table, write, buffer, lenp, ppos);
@@ -332,14 +332,19 @@ static struct dn_ifaddr *dn_dev_alloc_ifa(void)
         return ifa;
 }
 
-static __inline__ void dn_dev_free_ifa(struct dn_ifaddr *ifa)
+static void dn_dev_free_ifa_rcu(struct rcu_head *head)
 {
-        kfree(ifa);
+        kfree(container_of(head, struct dn_ifaddr, rcu));
 }
 
-static void dn_dev_del_ifa(struct dn_dev *dn_db, struct dn_ifaddr **ifap, int destroy)
+static void dn_dev_free_ifa(struct dn_ifaddr *ifa)
 {
-        struct dn_ifaddr *ifa1 = *ifap;
+        call_rcu(&ifa->rcu, dn_dev_free_ifa_rcu);
+}
+
+static void dn_dev_del_ifa(struct dn_dev *dn_db, struct dn_ifaddr __rcu **ifap, int destroy)
+{
+        struct dn_ifaddr *ifa1 = rtnl_dereference(*ifap);
         unsigned char mac_addr[6];
         struct net_device *dev = dn_db->dev;
 
@@ -373,7 +378,9 @@ static int dn_dev_insert_ifa(struct dn_dev *dn_db, struct dn_ifaddr *ifa)
         ASSERT_RTNL();
 
         /* Check for duplicates */
-        for(ifa1 = dn_db->ifa_list; ifa1; ifa1 = ifa1->ifa_next) {
+        for (ifa1 = rtnl_dereference(dn_db->ifa_list);
+             ifa1 != NULL;
+             ifa1 = rtnl_dereference(ifa1->ifa_next)) {
                 if (ifa1->ifa_local == ifa->ifa_local)
                         return -EEXIST;
         }
@@ -386,7 +393,7 @@ static int dn_dev_insert_ifa(struct dn_dev *dn_db, struct dn_ifaddr *ifa)
         }
 
         ifa->ifa_next = dn_db->ifa_list;
-        dn_db->ifa_list = ifa;
+        rcu_assign_pointer(dn_db->ifa_list, ifa);
 
         dn_ifaddr_notify(RTM_NEWADDR, ifa);
         blocking_notifier_call_chain(&dnaddr_chain, NETDEV_UP, ifa);
@@ -396,7 +403,7 @@ static int dn_dev_insert_ifa(struct dn_dev *dn_db, struct dn_ifaddr *ifa)
 
 static int dn_dev_set_ifa(struct net_device *dev, struct dn_ifaddr *ifa)
 {
-        struct dn_dev *dn_db = dev->dn_ptr;
+        struct dn_dev *dn_db = rtnl_dereference(dev->dn_ptr);
         int rv;
 
         if (dn_db == NULL) {
@@ -425,7 +432,8 @@ int dn_dev_ioctl(unsigned int cmd, void __user *arg)
         struct sockaddr_dn *sdn = (struct sockaddr_dn *)&ifr->ifr_addr;
         struct dn_dev *dn_db;
         struct net_device *dev;
-        struct dn_ifaddr *ifa = NULL, **ifap = NULL;
+        struct dn_ifaddr *ifa = NULL;
+        struct dn_ifaddr __rcu **ifap = NULL;
         int ret = 0;
 
         if (copy_from_user(ifr, arg, DN_IFREQ_SIZE))
@@ -454,8 +462,10 @@ int dn_dev_ioctl(unsigned int cmd, void __user *arg)
                 goto done;
         }
 
-        if ((dn_db = dev->dn_ptr) != NULL) {
-                for (ifap = &dn_db->ifa_list; (ifa=*ifap) != NULL; ifap = &ifa->ifa_next)
+        if ((dn_db = rtnl_dereference(dev->dn_ptr)) != NULL) {
+                for (ifap = &dn_db->ifa_list;
+                     (ifa = rtnl_dereference(*ifap)) != NULL;
+                     ifap = &ifa->ifa_next)
                         if (strcmp(ifr->ifr_name, ifa->ifa_label) == 0)
                                 break;
         }
@@ -558,7 +568,7 @@ static struct dn_dev *dn_dev_by_index(int ifindex)
 
         dev = __dev_get_by_index(&init_net, ifindex);
         if (dev)
-                dn_dev = dev->dn_ptr;
+                dn_dev = rtnl_dereference(dev->dn_ptr);
 
         return dn_dev;
 }
@@ -576,7 +586,8 @@ static int dn_nl_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
         struct nlattr *tb[IFA_MAX+1];
         struct dn_dev *dn_db;
         struct ifaddrmsg *ifm;
-        struct dn_ifaddr *ifa, **ifap;
+        struct dn_ifaddr *ifa;
+        struct dn_ifaddr __rcu **ifap;
         int err = -EINVAL;
 
         if (!net_eq(net, &init_net))
@@ -592,7 +603,9 @@ static int dn_nl_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
                 goto errout;
 
         err = -EADDRNOTAVAIL;
-        for (ifap = &dn_db->ifa_list; (ifa = *ifap); ifap = &ifa->ifa_next) {
+        for (ifap = &dn_db->ifa_list;
+             (ifa = rtnl_dereference(*ifap)) != NULL;
+             ifap = &ifa->ifa_next) {
                 if (tb[IFA_LOCAL] &&
                     nla_memcmp(tb[IFA_LOCAL], &ifa->ifa_local, 2))
                         continue;
@@ -632,7 +645,7 @@ static int dn_nl_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
         if ((dev = __dev_get_by_index(&init_net, ifm->ifa_index)) == NULL)
                 return -ENODEV;
 
-        if ((dn_db = dev->dn_ptr) == NULL) {
+        if ((dn_db = rtnl_dereference(dev->dn_ptr)) == NULL) {
                 dn_db = dn_dev_create(dev, &err);
                 if (!dn_db)
                         return err;
@@ -748,11 +761,11 @@ static int dn_nl_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
                         skip_naddr = 0;
                 }
 
-                if ((dn_db = dev->dn_ptr) == NULL)
+                if ((dn_db = rtnl_dereference(dev->dn_ptr)) == NULL)
                         goto cont;
 
-                for (ifa = dn_db->ifa_list, dn_idx = 0; ifa;
-                     ifa = ifa->ifa_next, dn_idx++) {
+                for (ifa = rtnl_dereference(dn_db->ifa_list), dn_idx = 0; ifa;
+                     ifa = rtnl_dereference(ifa->ifa_next), dn_idx++) {
                         if (dn_idx < skip_naddr)
                                 continue;
 
@@ -773,21 +786,22 @@ done:
 
 static int dn_dev_get_first(struct net_device *dev, __le16 *addr)
 {
-        struct dn_dev *dn_db = (struct dn_dev *)dev->dn_ptr;
+        struct dn_dev *dn_db;
         struct dn_ifaddr *ifa;
         int rv = -ENODEV;
 
+        rcu_read_lock();
+        dn_db = rcu_dereference(dev->dn_ptr);
         if (dn_db == NULL)
                 goto out;
 
-        rtnl_lock();
-        ifa = dn_db->ifa_list;
+        ifa = rcu_dereference(dn_db->ifa_list);
         if (ifa != NULL) {
                 *addr = ifa->ifa_local;
                 rv = 0;
         }
-        rtnl_unlock();
 out:
+        rcu_read_unlock();
         return rv;
 }
 
@@ -823,7 +837,7 @@ static void dn_send_endnode_hello(struct net_device *dev, struct dn_ifaddr *ifa)
         struct endnode_hello_message *msg;
         struct sk_buff *skb = NULL;
         __le16 *pktlen;
-        struct dn_dev *dn_db = (struct dn_dev *)dev->dn_ptr;
+        struct dn_dev *dn_db = rcu_dereference_raw(dev->dn_ptr);
 
         if ((skb = dn_alloc_skb(NULL, sizeof(*msg), GFP_ATOMIC)) == NULL)
                 return;
@@ -889,7 +903,7 @@ static int dn_am_i_a_router(struct dn_neigh *dn, struct dn_dev *dn_db, struct dn
 static void dn_send_router_hello(struct net_device *dev, struct dn_ifaddr *ifa)
 {
         int n;
-        struct dn_dev *dn_db = dev->dn_ptr;
+        struct dn_dev *dn_db = rcu_dereference_raw(dev->dn_ptr);
         struct dn_neigh *dn = (struct dn_neigh *)dn_db->router;
         struct sk_buff *skb;
         size_t size;
@@ -960,7 +974,7 @@ static void dn_send_router_hello(struct net_device *dev, struct dn_ifaddr *ifa)
 
 static void dn_send_brd_hello(struct net_device *dev, struct dn_ifaddr *ifa)
 {
-        struct dn_dev *dn_db = (struct dn_dev *)dev->dn_ptr;
+        struct dn_dev *dn_db = rcu_dereference_raw(dev->dn_ptr);
 
         if (dn_db->parms.forwarding == 0)
                 dn_send_endnode_hello(dev, ifa);
@@ -998,7 +1012,7 @@ static void dn_send_ptp_hello(struct net_device *dev, struct dn_ifaddr *ifa)
 
 static int dn_eth_up(struct net_device *dev)
 {
-        struct dn_dev *dn_db = dev->dn_ptr;
+        struct dn_dev *dn_db = rcu_dereference_raw(dev->dn_ptr);
 
         if (dn_db->parms.forwarding == 0)
                 dev_mc_add(dev, dn_rt_all_end_mcast);
@@ -1012,7 +1026,7 @@ static int dn_eth_up(struct net_device *dev)
 
 static void dn_eth_down(struct net_device *dev)
 {
-        struct dn_dev *dn_db = dev->dn_ptr;
+        struct dn_dev *dn_db = rcu_dereference_raw(dev->dn_ptr);
 
         if (dn_db->parms.forwarding == 0)
                 dev_mc_del(dev, dn_rt_all_end_mcast);
@@ -1025,12 +1039,16 @@ static void dn_dev_set_timer(struct net_device *dev);
 static void dn_dev_timer_func(unsigned long arg)
 {
         struct net_device *dev = (struct net_device *)arg;
-        struct dn_dev *dn_db = dev->dn_ptr;
+        struct dn_dev *dn_db;
         struct dn_ifaddr *ifa;
 
+        rcu_read_lock();
+        dn_db = rcu_dereference(dev->dn_ptr);
         if (dn_db->t3 <= dn_db->parms.t2) {
                 if (dn_db->parms.timer3) {
-                        for(ifa = dn_db->ifa_list; ifa; ifa = ifa->ifa_next) {
+                        for (ifa = rcu_dereference(dn_db->ifa_list);
+                             ifa;
+                             ifa = rcu_dereference(ifa->ifa_next)) {
                                 if (!(ifa->ifa_flags & IFA_F_SECONDARY))
                                         dn_db->parms.timer3(dev, ifa);
                         }
@@ -1039,13 +1057,13 @@ static void dn_dev_timer_func(unsigned long arg)
         } else {
                 dn_db->t3 -= dn_db->parms.t2;
         }
-
+        rcu_read_unlock();
         dn_dev_set_timer(dev);
 }
 
 static void dn_dev_set_timer(struct net_device *dev)
 {
-        struct dn_dev *dn_db = dev->dn_ptr;
+        struct dn_dev *dn_db = rcu_dereference_raw(dev->dn_ptr);
 
         if (dn_db->parms.t2 > dn_db->parms.t3)
                 dn_db->parms.t2 = dn_db->parms.t3;
@@ -1077,8 +1095,8 @@ static struct dn_dev *dn_dev_create(struct net_device *dev, int *err)
                 return NULL;
 
         memcpy(&dn_db->parms, p, sizeof(struct dn_dev_parms));
-        smp_wmb();
-        dev->dn_ptr = dn_db;
+
+        rcu_assign_pointer(dev->dn_ptr, dn_db);
         dn_db->dev = dev;
         init_timer(&dn_db->timer);
 
@@ -1086,7 +1104,7 @@ static struct dn_dev *dn_dev_create(struct net_device *dev, int *err)
 
         dn_db->neigh_parms = neigh_parms_alloc(dev, &dn_neigh_table);
         if (!dn_db->neigh_parms) {
-                dev->dn_ptr = NULL;
+                rcu_assign_pointer(dev->dn_ptr, NULL);
                 kfree(dn_db);
                 return NULL;
         }
@@ -1125,7 +1143,7 @@ void dn_dev_up(struct net_device *dev)
         struct dn_ifaddr *ifa;
         __le16 addr = decnet_address;
         int maybe_default = 0;
-        struct dn_dev *dn_db = (struct dn_dev *)dev->dn_ptr;
+        struct dn_dev *dn_db = rtnl_dereference(dev->dn_ptr);
 
         if ((dev->type != ARPHRD_ETHER) && (dev->type != ARPHRD_LOOPBACK))
                 return;
@@ -1176,7 +1194,7 @@ void dn_dev_up(struct net_device *dev)
 
 static void dn_dev_delete(struct net_device *dev)
 {
-        struct dn_dev *dn_db = dev->dn_ptr;
+        struct dn_dev *dn_db = rtnl_dereference(dev->dn_ptr);
 
         if (dn_db == NULL)
                 return;
@@ -1204,13 +1222,13 @@ static void dn_dev_delete(struct net_device *dev)
 
 void dn_dev_down(struct net_device *dev)
 {
-        struct dn_dev *dn_db = dev->dn_ptr;
+        struct dn_dev *dn_db = rtnl_dereference(dev->dn_ptr);
         struct dn_ifaddr *ifa;
 
         if (dn_db == NULL)
                 return;
 
-        while((ifa = dn_db->ifa_list) != NULL) {
+        while ((ifa = rtnl_dereference(dn_db->ifa_list)) != NULL) {
                 dn_dev_del_ifa(dn_db, &dn_db->ifa_list, 0);
                 dn_dev_free_ifa(ifa);
         }
@@ -1270,7 +1288,7 @@ static inline int is_dn_dev(struct net_device *dev)
 }
 
 static void *dn_dev_seq_start(struct seq_file *seq, loff_t *pos)
-        __acquires(rcu)
+        __acquires(RCU)
 {
         int i;
         struct net_device *dev;
@@ -1313,7 +1331,7 @@ static void *dn_dev_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 }
 
 static void dn_dev_seq_stop(struct seq_file *seq, void *v)
-        __releases(rcu)
+        __releases(RCU)
 {
         rcu_read_unlock();
 }
@@ -1340,7 +1358,7 @@ static int dn_dev_seq_show(struct seq_file *seq, void *v)
                 struct net_device *dev = v;
                 char peer_buf[DN_ASCBUF_LEN];
                 char router_buf[DN_ASCBUF_LEN];
-                struct dn_dev *dn_db = dev->dn_ptr;
+                struct dn_dev *dn_db = rcu_dereference(dev->dn_ptr);
 
                 seq_printf(seq, "%-8s %1s     %04u %04u   %04lu %04lu"
                                 "   %04hu    %03d %02x    %-10s %-7s %-7s\n",
diff --git a/net/decnet/dn_fib.c b/net/decnet/dn_fib.c
index 4ab96c15166d..0ef0a81bcd72 100644
--- a/net/decnet/dn_fib.c
+++ b/net/decnet/dn_fib.c
@@ -610,10 +610,12 @@ static void dn_fib_del_ifaddr(struct dn_ifaddr *ifa)
         /* Scan device list */
         rcu_read_lock();
         for_each_netdev_rcu(&init_net, dev) {
-                dn_db = dev->dn_ptr;
+                dn_db = rcu_dereference(dev->dn_ptr);
                 if (dn_db == NULL)
                         continue;
-                for(ifa2 = dn_db->ifa_list; ifa2; ifa2 = ifa2->ifa_next) {
+                for (ifa2 = rcu_dereference(dn_db->ifa_list);
+                     ifa2 != NULL;
+                     ifa2 = rcu_dereference(ifa2->ifa_next)) {
                         if (ifa2->ifa_local == ifa->ifa_local) {
                                 found_it = 1;
                                 break;
diff --git a/net/decnet/dn_neigh.c b/net/decnet/dn_neigh.c
index a085dbcf5c7f..602dade7e9a3 100644
--- a/net/decnet/dn_neigh.c
+++ b/net/decnet/dn_neigh.c
@@ -391,7 +391,7 @@ int dn_neigh_router_hello(struct sk_buff *skb)
                 write_lock(&neigh->lock);
 
                 neigh->used = jiffies;
-                dn_db = (struct dn_dev *)neigh->dev->dn_ptr;
+                dn_db = rcu_dereference(neigh->dev->dn_ptr);
 
                 if (!(neigh->nud_state & NUD_PERMANENT)) {
                         neigh->updated = jiffies;
diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index df0f3e54ff8a..94a9eb1d313e 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -93,7 +93,7 @@
 
 struct dn_rt_hash_bucket
 {
-        struct dn_route *chain;
+        struct dn_route __rcu *chain;
         spinlock_t lock;
 };
 
@@ -157,15 +157,17 @@ static inline void dnrt_drop(struct dn_route *rt)
 static void dn_dst_check_expire(unsigned long dummy)
 {
         int i;
-        struct dn_route *rt, **rtp;
+        struct dn_route *rt;
+        struct dn_route __rcu **rtp;
         unsigned long now = jiffies;
         unsigned long expire = 120 * HZ;
 
-        for(i = 0; i <= dn_rt_hash_mask; i++) {
+        for (i = 0; i <= dn_rt_hash_mask; i++) {
                 rtp = &dn_rt_hash_table[i].chain;
 
                 spin_lock(&dn_rt_hash_table[i].lock);
-                while((rt=*rtp) != NULL) {
+                while ((rt = rcu_dereference_protected(*rtp,
+                                                lockdep_is_held(&dn_rt_hash_table[i].lock))) != NULL) {
                         if (atomic_read(&rt->dst.__refcnt) ||
                                         (now - rt->dst.lastuse) < expire) {
                                 rtp = &rt->dst.dn_next;
@@ -186,17 +188,19 @@ static void dn_dst_check_expire(unsigned long dummy)
 
 static int dn_dst_gc(struct dst_ops *ops)
 {
-        struct dn_route *rt, **rtp;
+        struct dn_route *rt;
+        struct dn_route __rcu **rtp;
         int i;
         unsigned long now = jiffies;
         unsigned long expire = 10 * HZ;
 
-        for(i = 0; i <= dn_rt_hash_mask; i++) {
+        for (i = 0; i <= dn_rt_hash_mask; i++) {
 
                 spin_lock_bh(&dn_rt_hash_table[i].lock);
                 rtp = &dn_rt_hash_table[i].chain;
 
-                while((rt=*rtp) != NULL) {
+                while ((rt = rcu_dereference_protected(*rtp,
+                                                lockdep_is_held(&dn_rt_hash_table[i].lock))) != NULL) {
                         if (atomic_read(&rt->dst.__refcnt) ||
                                         (now - rt->dst.lastuse) < expire) {
                                 rtp = &rt->dst.dn_next;
@@ -227,7 +231,7 @@ static void dn_dst_update_pmtu(struct dst_entry *dst, u32 mtu)
 {
         u32 min_mtu = 230;
         struct dn_dev *dn = dst->neighbour ?
-                            (struct dn_dev *)dst->neighbour->dev->dn_ptr : NULL;
+                            rcu_dereference_raw(dst->neighbour->dev->dn_ptr) : NULL;
 
         if (dn && dn->use_long == 0)
                 min_mtu -= 6;
@@ -277,13 +281,15 @@ static inline int compare_keys(struct flowi *fl1, struct flowi *fl2)
 
 static int dn_insert_route(struct dn_route *rt, unsigned hash, struct dn_route **rp)
 {
-        struct dn_route *rth, **rthp;
+        struct dn_route *rth;
+        struct dn_route __rcu **rthp;
         unsigned long now = jiffies;
 
         rthp = &dn_rt_hash_table[hash].chain;
 
         spin_lock_bh(&dn_rt_hash_table[hash].lock);
-        while((rth = *rthp) != NULL) {
+        while ((rth = rcu_dereference_protected(*rthp,
+                                                lockdep_is_held(&dn_rt_hash_table[hash].lock))) != NULL) {
                 if (compare_keys(&rth->fl, &rt->fl)) {
                         /* Put it first */
                         *rthp = rth->dst.dn_next;
@@ -315,15 +321,15 @@ static void dn_run_flush(unsigned long dummy)
         int i;
         struct dn_route *rt, *next;
 
-        for(i = 0; i < dn_rt_hash_mask; i++) {
+        for (i = 0; i < dn_rt_hash_mask; i++) {
                 spin_lock_bh(&dn_rt_hash_table[i].lock);
 
-                if ((rt = xchg(&dn_rt_hash_table[i].chain, NULL)) == NULL)
+                if ((rt = xchg((struct dn_route **)&dn_rt_hash_table[i].chain, NULL)) == NULL)
                         goto nothing_to_declare;
 
-                for(; rt; rt=next) {
-                        next = rt->dst.dn_next;
-                        rt->dst.dn_next = NULL;
+                for(; rt; rt = next) {
+                        next = rcu_dereference_raw(rt->dst.dn_next);
+                        RCU_INIT_POINTER(rt->dst.dn_next, NULL);
                         dst_free((struct dst_entry *)rt);
                 }
 
@@ -458,15 +464,16 @@ static int dn_return_long(struct sk_buff *skb)
  */
 static int dn_route_rx_packet(struct sk_buff *skb)
 {
-        struct dn_skb_cb *cb = DN_SKB_CB(skb);
+        struct dn_skb_cb *cb;
         int err;
 
         if ((err = dn_route_input(skb)) == 0)
                 return dst_input(skb);
 
+        cb = DN_SKB_CB(skb);
         if (decnet_debug_level & 4) {
                 char *devname = skb->dev ? skb->dev->name : "???";
-                struct dn_skb_cb *cb = DN_SKB_CB(skb);
+
                 printk(KERN_DEBUG
                         "DECnet: dn_route_rx_packet: rt_flags=0x%02x dev=%s len=%d src=0x%04hx dst=0x%04hx err=%d type=%d\n",
                         (int)cb->rt_flags, devname, skb->len,
@@ -573,7 +580,7 @@ int dn_route_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type
         struct dn_skb_cb *cb;
         unsigned char flags = 0;
         __u16 len = le16_to_cpu(*(__le16 *)skb->data);
-        struct dn_dev *dn = (struct dn_dev *)dev->dn_ptr;
+        struct dn_dev *dn = rcu_dereference(dev->dn_ptr);
         unsigned char padlen = 0;
 
         if (!net_eq(dev_net(dev), &init_net))
@@ -728,7 +735,7 @@ static int dn_forward(struct sk_buff *skb)
 {
         struct dn_skb_cb *cb = DN_SKB_CB(skb);
         struct dst_entry *dst = skb_dst(skb);
-        struct dn_dev *dn_db = dst->dev->dn_ptr;
+        struct dn_dev *dn_db = rcu_dereference(dst->dev->dn_ptr);
         struct dn_route *rt;
         struct neighbour *neigh = dst->neighbour;
         int header_len;
@@ -835,13 +842,16 @@ static inline int dn_match_addr(__le16 addr1, __le16 addr2)
 static __le16 dnet_select_source(const struct net_device *dev, __le16 daddr, int scope)
 {
         __le16 saddr = 0;
-        struct dn_dev *dn_db = dev->dn_ptr;
+        struct dn_dev *dn_db;
         struct dn_ifaddr *ifa;
         int best_match = 0;
         int ret;
 
-        read_lock(&dev_base_lock);
-        for(ifa = dn_db->ifa_list; ifa; ifa = ifa->ifa_next) {
+        rcu_read_lock();
+        dn_db = rcu_dereference(dev->dn_ptr);
+        for (ifa = rcu_dereference(dn_db->ifa_list);
+             ifa != NULL;
+             ifa = rcu_dereference(ifa->ifa_next)) {
                 if (ifa->ifa_scope > scope)
                         continue;
                 if (!daddr) {
@@ -854,7 +864,7 @@ static __le16 dnet_select_source(const struct net_device *dev, __le16 daddr, int
                 if (best_match == 0)
                         saddr = ifa->ifa_local;
         }
-        read_unlock(&dev_base_lock);
+        rcu_read_unlock();
 
         return saddr;
 }
@@ -1020,7 +1030,7 @@ source_ok:
                 err = -ENODEV;
                 if (dev_out == NULL)
                         goto out;
-                dn_db = dev_out->dn_ptr;
+                dn_db = rcu_dereference_raw(dev_out->dn_ptr);
                 /* Possible improvement - check all devices for local addr */
                 if (dn_dev_islocal(dev_out, fl.fld_dst)) {
                         dev_put(dev_out);
@@ -1233,7 +1243,7 @@ static int dn_route_input_slow(struct sk_buff *skb)
 
         dev_hold(in_dev);
 
-        if ((dn_db = in_dev->dn_ptr) == NULL)
+        if ((dn_db = rcu_dereference(in_dev->dn_ptr)) == NULL)
                 goto out;
 
         /* Zero source addresses are not allowed */
@@ -1677,15 +1687,15 @@ static struct dn_route *dn_rt_cache_get_next(struct seq_file *seq, struct dn_rou
 {
         struct dn_rt_cache_iter_state *s = seq->private;
 
-        rt = rt->dst.dn_next;
-        while(!rt) {
+        rt = rcu_dereference_bh(rt->dst.dn_next);
+        while (!rt) {
                 rcu_read_unlock_bh();
                 if (--s->bucket < 0)
                         break;
                 rcu_read_lock_bh();
-                rt = dn_rt_hash_table[s->bucket].chain;
+                rt = rcu_dereference_bh(dn_rt_hash_table[s->bucket].chain);
         }
-        return rcu_dereference_bh(rt);
+        return rt;
 }
 
 static void *dn_rt_cache_seq_start(struct seq_file *seq, loff_t *pos)