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authorEric Dumazet <eric.dumazet@gmail.com>2009-10-30 07:11:27 +0000
committerDavid S. Miller <davem@davemloft.net>2009-11-01 23:55:08 -0800
commit72c9528bab94cc052d00ce241b8e85f5d71e45f0 (patch)
treefcec7a40e0242e659474a4d9f501d9213225aa55 /net
parent68d8287ce1e1da3c99881385a93e74f68c454fc2 (diff)
downloadlinux-2.6.34-ux500-72c9528bab94cc052d00ce241b8e85f5d71e45f0.tar.gz
net: Introduce dev_get_by_name_rcu()
Some workloads hit dev_base_lock rwlock pretty hard. We can use RCU lookups to avoid touching this rwlock (and avoid touching netdevice refcount) netdevices are already freed after a RCU grace period, so this patch adds no penalty at device dismantle time. However, it adds a synchronize_rcu() call in dev_change_name() Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/core/dev.c49
1 files changed, 40 insertions, 9 deletions
diff --git a/net/core/dev.c b/net/core/dev.c
index 94f42a15fff..f54d8b8a434 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -213,7 +213,7 @@ static int list_netdevice(struct net_device *dev)
write_lock_bh(&dev_base_lock);
list_add_tail(&dev->dev_list, &net->dev_base_head);
- hlist_add_head(&dev->name_hlist, dev_name_hash(net, dev->name));
+ hlist_add_head_rcu(&dev->name_hlist, dev_name_hash(net, dev->name));
hlist_add_head_rcu(&dev->index_hlist,
dev_index_hash(net, dev->ifindex));
write_unlock_bh(&dev_base_lock);
@@ -230,7 +230,7 @@ static void unlist_netdevice(struct net_device *dev)
/* Unlink dev from the device chain */
write_lock_bh(&dev_base_lock);
list_del(&dev->dev_list);
- hlist_del(&dev->name_hlist);
+ hlist_del_rcu(&dev->name_hlist);
hlist_del_rcu(&dev->index_hlist);
write_unlock_bh(&dev_base_lock);
}
@@ -599,6 +599,32 @@ struct net_device *__dev_get_by_name(struct net *net, const char *name)
EXPORT_SYMBOL(__dev_get_by_name);
/**
+ * dev_get_by_name_rcu - find a device by its name
+ * @net: the applicable net namespace
+ * @name: name to find
+ *
+ * Find an interface by name.
+ * If the name is found a pointer to the device is returned.
+ * If the name is not found then %NULL is returned.
+ * The reference counters are not incremented so the caller must be
+ * careful with locks. The caller must hold RCU lock.
+ */
+
+struct net_device *dev_get_by_name_rcu(struct net *net, const char *name)
+{
+ struct hlist_node *p;
+ struct net_device *dev;
+ struct hlist_head *head = dev_name_hash(net, name);
+
+ hlist_for_each_entry_rcu(dev, p, head, name_hlist)
+ if (!strncmp(dev->name, name, IFNAMSIZ))
+ return dev;
+
+ return NULL;
+}
+EXPORT_SYMBOL(dev_get_by_name_rcu);
+
+/**
* dev_get_by_name - find a device by its name
* @net: the applicable net namespace
* @name: name to find
@@ -614,11 +640,11 @@ struct net_device *dev_get_by_name(struct net *net, const char *name)
{
struct net_device *dev;
- read_lock(&dev_base_lock);
- dev = __dev_get_by_name(net, name);
+ rcu_read_lock();
+ dev = dev_get_by_name_rcu(net, name);
if (dev)
dev_hold(dev);
- read_unlock(&dev_base_lock);
+ rcu_read_unlock();
return dev;
}
EXPORT_SYMBOL(dev_get_by_name);
@@ -960,7 +986,12 @@ rollback:
write_lock_bh(&dev_base_lock);
hlist_del(&dev->name_hlist);
- hlist_add_head(&dev->name_hlist, dev_name_hash(net, dev->name));
+ write_unlock_bh(&dev_base_lock);
+
+ synchronize_rcu();
+
+ write_lock_bh(&dev_base_lock);
+ hlist_add_head_rcu(&dev->name_hlist, dev_name_hash(net, dev->name));
write_unlock_bh(&dev_base_lock);
ret = call_netdevice_notifiers(NETDEV_CHANGENAME, dev);
@@ -1062,9 +1093,9 @@ void dev_load(struct net *net, const char *name)
{
struct net_device *dev;
- read_lock(&dev_base_lock);
- dev = __dev_get_by_name(net, name);
- read_unlock(&dev_base_lock);
+ rcu_read_lock();
+ dev = dev_get_by_name_rcu(net, name);
+ rcu_read_unlock();
if (!dev && capable(CAP_NET_ADMIN))
request_module("%s", name);