Bluetooth: 6lowpan: Converting rwlocks to use RCU

The rwlocks are converted to use RCU. This helps performance as the
irq locks are not needed any more.

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c
index aa6ebbfc5d316249e5b13b17c3a50573ca731f89..a681247b0aee4d5b26e23698e1c21b758b8c6ab0 100644 (file)
--- a/net/bluetooth/6lowpan.c
+++ b/net/bluetooth/6lowpan.c
@@ -53,7 +53,7 @@ struct skb_cb {
  * The list contains struct lowpan_dev elements.
  */
 static LIST_HEAD(bt_6lowpan_devices);
-static DEFINE_RWLOCK(devices_lock);
+static DEFINE_SPINLOCK(devices_lock);
 
 /* If psm is set to 0 (default value), then 6lowpan is disabled.
  * Other values are used to indicate a Protocol Service Multiplexer
@@ -67,6 +67,7 @@ static struct l2cap_chan *listen_chan;
 
 struct lowpan_peer {
        struct list_head list;
+       struct rcu_head rcu;
        struct l2cap_chan *chan;
 
        /* peer addresses in various formats */
@@ -86,6 +87,13 @@ struct lowpan_dev {
        struct delayed_work notify_peers;
 };
 
+static inline void peer_free(struct rcu_head *head)
+{
+       struct lowpan_peer *e = container_of(head, struct lowpan_peer, rcu);
+
+       kfree(e);
+}
+
 static inline struct lowpan_dev *lowpan_dev(const struct net_device *netdev)
 {
        return netdev_priv(netdev);
@@ -93,13 +101,14 @@ static inline struct lowpan_dev *lowpan_dev(const struct net_device *netdev)
 
 static inline void peer_add(struct lowpan_dev *dev, struct lowpan_peer *peer)
 {
-       list_add(&peer->list, &dev->peers);
+       list_add_rcu(&peer->list, &dev->peers);
        atomic_inc(&dev->peer_count);
 }
 
 static inline bool peer_del(struct lowpan_dev *dev, struct lowpan_peer *peer)
 {
-       list_del(&peer->list);
+       list_del_rcu(&peer->list);
+       call_rcu(&peer->rcu, peer_free);
 
        module_put(THIS_MODULE);
 
@@ -114,31 +123,37 @@ static inline bool peer_del(struct lowpan_dev *dev, struct lowpan_peer *peer)
 static inline struct lowpan_peer *peer_lookup_ba(struct lowpan_dev *dev,
                                                 bdaddr_t *ba, __u8 type)
 {
-       struct lowpan_peer *peer, *tmp;
+       struct lowpan_peer *peer;
 
        BT_DBG("peers %d addr %pMR type %d", atomic_read(&dev->peer_count),
               ba, type);
 
-       list_for_each_entry_safe(peer, tmp, &dev->peers, list) {
+       rcu_read_lock();
+
+       list_for_each_entry_rcu(peer, &dev->peers, list) {
                BT_DBG("dst addr %pMR dst type %d",
                       &peer->chan->dst, peer->chan->dst_type);
 
                if (bacmp(&peer->chan->dst, ba))
                        continue;
 
-               if (type == peer->chan->dst_type)
+               if (type == peer->chan->dst_type) {
+                       rcu_read_unlock();
                        return peer;
+               }
        }
 
+       rcu_read_unlock();
+
        return NULL;
 }
 
-static inline struct lowpan_peer *peer_lookup_chan(struct lowpan_dev *dev,
-                                                  struct l2cap_chan *chan)
+static inline struct lowpan_peer *__peer_lookup_chan(struct lowpan_dev *dev,
+                                                    struct l2cap_chan *chan)
 {
-       struct lowpan_peer *peer, *tmp;
+       struct lowpan_peer *peer;
 
-       list_for_each_entry_safe(peer, tmp, &dev->peers, list) {
+       list_for_each_entry_rcu(peer, &dev->peers, list) {
                if (peer->chan == chan)
                        return peer;
        }
@@ -146,12 +161,12 @@ static inline struct lowpan_peer *peer_lookup_chan(struct lowpan_dev *dev,
        return NULL;
 }
 
-static inline struct lowpan_peer *peer_lookup_conn(struct lowpan_dev *dev,
-                                                  struct l2cap_conn *conn)
+static inline struct lowpan_peer *__peer_lookup_conn(struct lowpan_dev *dev,
+                                                    struct l2cap_conn *conn)
 {
-       struct lowpan_peer *peer, *tmp;
+       struct lowpan_peer *peer;
 
-       list_for_each_entry_safe(peer, tmp, &dev->peers, list) {
+       list_for_each_entry_rcu(peer, &dev->peers, list) {
                if (peer->chan->conn == conn)
                        return peer;
        }
@@ -163,7 +178,7 @@ static inline struct lowpan_peer *peer_lookup_dst(struct lowpan_dev *dev,
                                                  struct in6_addr *daddr,
                                                  struct sk_buff *skb)
 {
-       struct lowpan_peer *peer, *tmp;
+       struct lowpan_peer *peer;
        struct in6_addr *nexthop;
        struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
        int count = atomic_read(&dev->peer_count);
@@ -174,9 +189,13 @@ static inline struct lowpan_peer *peer_lookup_dst(struct lowpan_dev *dev,
         * send the packet. If only one peer exists, then we can send the
         * packet right away.
         */
-       if (count == 1)
-               return list_first_entry(&dev->peers, struct lowpan_peer,
-                                       list);
+       if (count == 1) {
+               rcu_read_lock();
+               peer = list_first_or_null_rcu(&dev->peers, struct lowpan_peer,
+                                             list);
+               rcu_read_unlock();
+               return peer;
+       }
 
        if (!rt) {
                nexthop = &lowpan_cb(skb)->gw;
@@ -195,53 +214,57 @@ static inline struct lowpan_peer *peer_lookup_dst(struct lowpan_dev *dev,
 
        BT_DBG("gw %pI6c", nexthop);
 
-       list_for_each_entry_safe(peer, tmp, &dev->peers, list) {
+       rcu_read_lock();
+
+       list_for_each_entry_rcu(peer, &dev->peers, list) {
                BT_DBG("dst addr %pMR dst type %d ip %pI6c",
                       &peer->chan->dst, peer->chan->dst_type,
                       &peer->peer_addr);
 
-               if (!ipv6_addr_cmp(&peer->peer_addr, nexthop))
+               if (!ipv6_addr_cmp(&peer->peer_addr, nexthop)) {
+                       rcu_read_unlock();
                        return peer;
+               }
        }
 
+       rcu_read_unlock();
+
        return NULL;
 }
 
 static struct lowpan_peer *lookup_peer(struct l2cap_conn *conn)
 {
-       struct lowpan_dev *entry, *tmp;
+       struct lowpan_dev *entry;
        struct lowpan_peer *peer = NULL;
-       unsigned long flags;
 
-       read_lock_irqsave(&devices_lock, flags);
+       rcu_read_lock();
 
-       list_for_each_entry_safe(entry, tmp, &bt_6lowpan_devices, list) {
-               peer = peer_lookup_conn(entry, conn);
+       list_for_each_entry_rcu(entry, &bt_6lowpan_devices, list) {
+               peer = __peer_lookup_conn(entry, conn);
                if (peer)
                        break;
        }
 
-       read_unlock_irqrestore(&devices_lock, flags);
+       rcu_read_unlock();
 
        return peer;
 }
 
 static struct lowpan_dev *lookup_dev(struct l2cap_conn *conn)
 {
-       struct lowpan_dev *entry, *tmp;
+       struct lowpan_dev *entry;
        struct lowpan_dev *dev = NULL;
-       unsigned long flags;
 
-       read_lock_irqsave(&devices_lock, flags);
+       rcu_read_lock();
 
-       list_for_each_entry_safe(entry, tmp, &bt_6lowpan_devices, list) {
+       list_for_each_entry_rcu(entry, &bt_6lowpan_devices, list) {
                if (conn->hcon->hdev == entry->hdev) {
                        dev = entry;
                        break;
                }
        }
 
-       read_unlock_irqrestore(&devices_lock, flags);
+       rcu_read_unlock();
 
        return dev;
 }
@@ -264,13 +287,12 @@ static int iphc_decompress(struct sk_buff *skb, struct net_device *netdev,
        u8 iphc0, iphc1;
        struct lowpan_dev *dev;
        struct lowpan_peer *peer;
-       unsigned long flags;
 
        dev = lowpan_dev(netdev);
 
-       read_lock_irqsave(&devices_lock, flags);
-       peer = peer_lookup_chan(dev, chan);
-       read_unlock_irqrestore(&devices_lock, flags);
+       rcu_read_lock();
+       peer = __peer_lookup_chan(dev, chan);
+       rcu_read_unlock();
        if (!peer)
                goto drop;
 
@@ -452,7 +474,6 @@ static int setup_header(struct sk_buff *skb, struct net_device *netdev,
        if (ipv6_addr_is_multicast(&ipv6_daddr)) {
                lowpan_cb(skb)->chan = NULL;
        } else {
-               unsigned long flags;
                u8 addr_type;
 
                /* Get destination BT device from skb.
@@ -463,19 +484,14 @@ static int setup_header(struct sk_buff *skb, struct net_device *netdev,
                BT_DBG("dest addr %pMR type %d IP %pI6c", &addr,
                       addr_type, &ipv6_daddr);
 
-               read_lock_irqsave(&devices_lock, flags);
                peer = peer_lookup_ba(dev, &addr, addr_type);
-               read_unlock_irqrestore(&devices_lock, flags);
-
                if (!peer) {
                        /* The packet might be sent to 6lowpan interface
                         * because of routing (either via default route
                         * or user set route) so get peer according to
                         * the destination address.
                         */
-                       read_lock_irqsave(&devices_lock, flags);
                        peer = peer_lookup_dst(dev, &ipv6_daddr, skb);
-                       read_unlock_irqrestore(&devices_lock, flags);
                        if (!peer) {
                                BT_DBG("no such peer %pMR found", &addr);
                                return -ENOENT;
@@ -558,14 +574,13 @@ static int send_pkt(struct l2cap_chan *chan, struct sk_buff *skb,
 static int send_mcast_pkt(struct sk_buff *skb, struct net_device *netdev)
 {
        struct sk_buff *local_skb;
-       struct lowpan_dev *entry, *tmp;
-       unsigned long flags;
+       struct lowpan_dev *entry;
        int err = 0;
 
-       read_lock_irqsave(&devices_lock, flags);
+       rcu_read_lock();
 
-       list_for_each_entry_safe(entry, tmp, &bt_6lowpan_devices, list) {
-               struct lowpan_peer *pentry, *ptmp;
+       list_for_each_entry_rcu(entry, &bt_6lowpan_devices, list) {
+               struct lowpan_peer *pentry;
                struct lowpan_dev *dev;
 
                if (entry->netdev != netdev)
@@ -573,7 +588,7 @@ static int send_mcast_pkt(struct sk_buff *skb, struct net_device *netdev)
 
                dev = lowpan_dev(entry->netdev);
 
-               list_for_each_entry_safe(pentry, ptmp, &dev->peers, list) {
+               list_for_each_entry_rcu(pentry, &dev->peers, list) {
                        int ret;
 
                        local_skb = skb_clone(skb, GFP_ATOMIC);
@@ -590,7 +605,7 @@ static int send_mcast_pkt(struct sk_buff *skb, struct net_device *netdev)
                }
        }
 
-       read_unlock_irqrestore(&devices_lock, flags);
+       rcu_read_unlock();
 
        return err;
 }
@@ -792,7 +807,6 @@ static struct l2cap_chan *add_peer_chan(struct l2cap_chan *chan,
                                        struct lowpan_dev *dev)
 {
        struct lowpan_peer *peer;
-       unsigned long flags;
 
        peer = kzalloc(sizeof(*peer), GFP_ATOMIC);
        if (!peer)
@@ -815,10 +829,10 @@ static struct l2cap_chan *add_peer_chan(struct l2cap_chan *chan,
         */
        set_ip_addr_bits(chan->dst_type, (u8 *)&peer->peer_addr.s6_addr + 8);
 
-       write_lock_irqsave(&devices_lock, flags);
+       spin_lock(&devices_lock);
        INIT_LIST_HEAD(&peer->list);
        peer_add(dev, peer);
-       write_unlock_irqrestore(&devices_lock, flags);
+       spin_unlock(&devices_lock);
 
        /* Notifying peers about us needs to be done without locks held */
        INIT_DELAYED_WORK(&dev->notify_peers, do_notify_peers);
@@ -831,7 +845,6 @@ static int setup_netdev(struct l2cap_chan *chan, struct lowpan_dev **dev)
 {
        struct net_device *netdev;
        int err = 0;
-       unsigned long flags;
 
        netdev = alloc_netdev(sizeof(struct lowpan_dev), IFACE_NAME_TEMPLATE,
                              NET_NAME_UNKNOWN, netdev_setup);
@@ -861,10 +874,10 @@ static int setup_netdev(struct l2cap_chan *chan, struct lowpan_dev **dev)
        (*dev)->hdev = chan->conn->hcon->hdev;
        INIT_LIST_HEAD(&(*dev)->peers);
 
-       write_lock_irqsave(&devices_lock, flags);
+       spin_lock(&devices_lock);
        INIT_LIST_HEAD(&(*dev)->list);
-       list_add(&(*dev)->list, &bt_6lowpan_devices);
-       write_unlock_irqrestore(&devices_lock, flags);
+       list_add_rcu(&(*dev)->list, &bt_6lowpan_devices);
+       spin_unlock(&devices_lock);
 
        return 0;
 
@@ -918,11 +931,10 @@ static void delete_netdev(struct work_struct *work)
 
 static void chan_close_cb(struct l2cap_chan *chan)
 {
-       struct lowpan_dev *entry, *tmp;
+       struct lowpan_dev *entry;
        struct lowpan_dev *dev = NULL;
        struct lowpan_peer *peer;
        int err = -ENOENT;
-       unsigned long flags;
        bool last = false, removed = true;
 
        BT_DBG("chan %p conn %p", chan, chan->conn);
@@ -937,11 +949,11 @@ static void chan_close_cb(struct l2cap_chan *chan)
                removed = false;
        }
 
-       write_lock_irqsave(&devices_lock, flags);
+       spin_lock(&devices_lock);
 
-       list_for_each_entry_safe(entry, tmp, &bt_6lowpan_devices, list) {
+       list_for_each_entry_rcu(entry, &bt_6lowpan_devices, list) {
                dev = lowpan_dev(entry->netdev);
-               peer = peer_lookup_chan(dev, chan);
+               peer = __peer_lookup_chan(dev, chan);
                if (peer) {
                        last = peer_del(dev, peer);
                        err = 0;
@@ -952,13 +964,12 @@ static void chan_close_cb(struct l2cap_chan *chan)
                               atomic_read(&chan->kref.refcount));
 
                        l2cap_chan_put(chan);
-                       kfree(peer);
                        break;
                }
        }
 
        if (!err && last && dev && !atomic_read(&dev->peer_count)) {
-               write_unlock_irqrestore(&devices_lock, flags);
+               spin_unlock(&devices_lock);
 
                cancel_delayed_work_sync(&dev->notify_peers);
 
@@ -969,7 +980,7 @@ static void chan_close_cb(struct l2cap_chan *chan)
                        schedule_work(&entry->delete_netdev);
                }
        } else {
-               write_unlock_irqrestore(&devices_lock, flags);
+               spin_unlock(&devices_lock);
        }
 
        return;
@@ -1161,10 +1172,9 @@ static int get_l2cap_conn(char *buf, bdaddr_t *addr, u8 *addr_type,
 
 static void disconnect_all_peers(void)
 {
-       struct lowpan_dev *entry, *tmp_dev;
+       struct lowpan_dev *entry;
        struct lowpan_peer *peer, *tmp_peer, *new_peer;
        struct list_head peers;
-       unsigned long flags;
 
        INIT_LIST_HEAD(&peers);
 
@@ -1173,10 +1183,10 @@ static void disconnect_all_peers(void)
         * with the same list at the same time.
         */
 
-       read_lock_irqsave(&devices_lock, flags);
+       rcu_read_lock();
 
-       list_for_each_entry_safe(entry, tmp_dev, &bt_6lowpan_devices, list) {
-               list_for_each_entry_safe(peer, tmp_peer, &entry->peers, list) {
+       list_for_each_entry_rcu(entry, &bt_6lowpan_devices, list) {
+               list_for_each_entry_rcu(peer, &entry->peers, list) {
                        new_peer = kmalloc(sizeof(*new_peer), GFP_ATOMIC);
                        if (!new_peer)
                                break;
@@ -1188,26 +1198,36 @@ static void disconnect_all_peers(void)
                }
        }
 
-       read_unlock_irqrestore(&devices_lock, flags);
+       rcu_read_unlock();
 
+       spin_lock(&devices_lock);
        list_for_each_entry_safe(peer, tmp_peer, &peers, list) {
                l2cap_chan_close(peer->chan, ENOENT);
-               kfree(peer);
+
+               list_del_rcu(&peer->list);
+               call_rcu(&peer->rcu, peer_free);
+
+               module_put(THIS_MODULE);
        }
+       spin_unlock(&devices_lock);
 }
 
-static int lowpan_psm_set(void *data, u64 val)
-{
+struct set_psm {
+       struct work_struct work;
        u16 psm;
+};
 
-       psm = val;
-       if (psm == 0 || psm_6lowpan != psm)
+static void do_psm_set(struct work_struct *work)
+{
+       struct set_psm *set_psm = container_of(work, struct set_psm, work);
+
+       if (set_psm->psm == 0 || psm_6lowpan != set_psm->psm)
                /* Disconnect existing connections if 6lowpan is
                 * disabled (psm = 0), or if psm changes.
                 */
                disconnect_all_peers();
 
-       psm_6lowpan = psm;
+       psm_6lowpan = set_psm->psm;
 
        if (listen_chan) {
                l2cap_chan_close(listen_chan, 0);
@@ -1216,6 +1236,22 @@ static int lowpan_psm_set(void *data, u64 val)
 
        listen_chan = bt_6lowpan_listen();
 
+       kfree(set_psm);
+}
+
+static int lowpan_psm_set(void *data, u64 val)
+{
+       struct set_psm *set_psm;
+
+       set_psm = kzalloc(sizeof(*set_psm), GFP_KERNEL);
+       if (!set_psm)
+               return -ENOMEM;
+
+       set_psm->psm = val;
+       INIT_WORK(&set_psm->work, do_psm_set);
+
+       schedule_work(&set_psm->work);
+
        return 0;
 }
 
@@ -1297,19 +1333,18 @@ static ssize_t lowpan_control_write(struct file *fp,
 
 static int lowpan_control_show(struct seq_file *f, void *ptr)
 {
-       struct lowpan_dev *entry, *tmp_dev;
-       struct lowpan_peer *peer, *tmp_peer;
-       unsigned long flags;
+       struct lowpan_dev *entry;
+       struct lowpan_peer *peer;
 
-       read_lock_irqsave(&devices_lock, flags);
+       spin_lock(&devices_lock);
 
-       list_for_each_entry_safe(entry, tmp_dev, &bt_6lowpan_devices, list) {
-               list_for_each_entry_safe(peer, tmp_peer, &entry->peers, list)
+       list_for_each_entry(entry, &bt_6lowpan_devices, list) {
+               list_for_each_entry(peer, &entry->peers, list)
                        seq_printf(f, "%pMR (type %u)\n",
                                   &peer->chan->dst, peer->chan->dst_type);
        }
 
-       read_unlock_irqrestore(&devices_lock, flags);
+       spin_unlock(&devices_lock);
 
        return 0;
 }
@@ -1329,9 +1364,8 @@ static const struct file_operations lowpan_control_fops = {
 
 static void disconnect_devices(void)
 {
-       struct lowpan_dev *entry, *tmp, *new_dev;
+       struct lowpan_dev *entry, *new_dev;
        struct list_head devices;
-       unsigned long flags;
 
        INIT_LIST_HEAD(&devices);
 
@@ -1340,9 +1374,9 @@ static void disconnect_devices(void)
         * devices list.
         */
 
-       read_lock_irqsave(&devices_lock, flags);
+       rcu_read_lock();
 
-       list_for_each_entry_safe(entry, tmp, &bt_6lowpan_devices, list) {
+       list_for_each_entry_rcu(entry, &bt_6lowpan_devices, list) {
                new_dev = kmalloc(sizeof(*new_dev), GFP_ATOMIC);
                if (!new_dev)
                        break;
@@ -1350,12 +1384,12 @@ static void disconnect_devices(void)
                new_dev->netdev = entry->netdev;
                INIT_LIST_HEAD(&new_dev->list);
 
-               list_add(&new_dev->list, &devices);
+               list_add_rcu(&new_dev->list, &devices);
        }
 
-       read_unlock_irqrestore(&devices_lock, flags);
+       rcu_read_unlock();
 
-       list_for_each_entry_safe(entry, tmp, &devices, list) {
+       list_for_each_entry(entry, &devices, list) {
                ifdown(entry->netdev);
                BT_DBG("Unregistering netdev %s %p",
                       entry->netdev->name, entry->netdev);
@@ -1368,17 +1402,15 @@ static int device_event(struct notifier_block *unused,
                        unsigned long event, void *ptr)
 {
        struct net_device *netdev = netdev_notifier_info_to_dev(ptr);
-       struct lowpan_dev *entry, *tmp;
-       unsigned long flags;
+       struct lowpan_dev *entry;
 
        if (netdev->type != ARPHRD_6LOWPAN)
                return NOTIFY_DONE;
 
        switch (event) {
        case NETDEV_UNREGISTER:
-               write_lock_irqsave(&devices_lock, flags);
-               list_for_each_entry_safe(entry, tmp, &bt_6lowpan_devices,
-                                        list) {
+               spin_lock(&devices_lock);
+               list_for_each_entry(entry, &bt_6lowpan_devices, list) {
                        if (entry->netdev == netdev) {
                                BT_DBG("Unregistered netdev %s %p",
                                       netdev->name, netdev);
@@ -1387,7 +1419,7 @@ static int device_event(struct notifier_block *unused,
                                break;
                        }
                }
-               write_unlock_irqrestore(&devices_lock, flags);
+               spin_unlock(&devices_lock);
                break;
        }