net: Introduce for_each_netdev_rcu() iterator
Adds RCU management to the list of netdevices.
Convert some for_each_netdev() users to RCU version, if
it can avoid read_lock-ing dev_base_lock
Ie:
read_lock(&dev_base_loack);
for_each_netdev(net, dev)
some_action();
read_unlock(&dev_base_lock);
becomes :
rcu_read_lock();
for_each_netdev_rcu(net, dev)
some_action();
rcu_read_unlock();
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index 76a1502..bf629ac 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -175,7 +175,7 @@
* The @dev_base_head list is protected by @dev_base_lock and the rtnl
* semaphore.
*
- * Pure readers hold dev_base_lock for reading.
+ * Pure readers hold dev_base_lock for reading, or rcu_read_lock()
*
* Writers must hold the rtnl semaphore while they loop through the
* dev_base_head list, and hold dev_base_lock for writing when they do the
@@ -212,7 +212,7 @@
ASSERT_RTNL();
write_lock_bh(&dev_base_lock);
- list_add_tail(&dev->dev_list, &net->dev_base_head);
+ list_add_tail_rcu(&dev->dev_list, &net->dev_base_head);
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));
@@ -229,7 +229,7 @@
/* Unlink dev from the device chain */
write_lock_bh(&dev_base_lock);
- list_del(&dev->dev_list);
+ list_del_rcu(&dev->dev_list);
hlist_del_rcu(&dev->name_hlist);
hlist_del_rcu(&dev->index_hlist);
write_unlock_bh(&dev_base_lock);
@@ -799,15 +799,15 @@
struct net_device *dev, *ret;
ret = NULL;
- read_lock(&dev_base_lock);
- for_each_netdev(net, dev) {
+ rcu_read_lock();
+ for_each_netdev_rcu(net, dev) {
if (((dev->flags ^ if_flags) & mask) == 0) {
dev_hold(dev);
ret = dev;
break;
}
}
- read_unlock(&dev_base_lock);
+ rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL(dev_get_by_flags);
@@ -3077,18 +3077,18 @@
* in detail.
*/
void *dev_seq_start(struct seq_file *seq, loff_t *pos)
- __acquires(dev_base_lock)
+ __acquires(RCU)
{
struct net *net = seq_file_net(seq);
loff_t off;
struct net_device *dev;
- read_lock(&dev_base_lock);
+ rcu_read_lock();
if (!*pos)
return SEQ_START_TOKEN;
off = 1;
- for_each_netdev(net, dev)
+ for_each_netdev_rcu(net, dev)
if (off++ == *pos)
return dev;
@@ -3097,16 +3097,18 @@
void *dev_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
- struct net *net = seq_file_net(seq);
+ struct net_device *dev = (v == SEQ_START_TOKEN) ?
+ first_net_device(seq_file_net(seq)) :
+ next_net_device((struct net_device *)v);
+
++*pos;
- return v == SEQ_START_TOKEN ?
- first_net_device(net) : next_net_device((struct net_device *)v);
+ return rcu_dereference(dev);
}
void dev_seq_stop(struct seq_file *seq, void *v)
- __releases(dev_base_lock)
+ __releases(RCU)
{
- read_unlock(&dev_base_lock);
+ rcu_read_unlock();
}
static void dev_seq_printf_stats(struct seq_file *seq, struct net_device *dev)