net: RCU conversion of dev_getbyhwaddr() and arp_ioctl()
Le dimanche 05 décembre 2010 à 09:19 +0100, Eric Dumazet a écrit :
> Hmm..
>
> If somebody can explain why RTNL is held in arp_ioctl() (and therefore
> in arp_req_delete()), we might first remove RTNL use in arp_ioctl() so
> that your patch can be applied.
>
> Right now it is not good, because RTNL wont be necessarly held when you
> are going to call arp_invalidate() ?
While doing this analysis, I found a refcount bug in llc, I'll send a
patch for net-2.6
Meanwhile, here is the patch for net-next-2.6
Your patch then can be applied after mine.
Thanks
[PATCH] net: RCU conversion of dev_getbyhwaddr() and arp_ioctl()
dev_getbyhwaddr() was called under RTNL.
Rename it to dev_getbyhwaddr_rcu() and change all its caller to now use
RCU locking instead of RTNL.
Change arp_ioctl() to use RCU instead of RTNL locking.
Note: this fix a dev refcount bug in llc
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 5826129..dfd3a64 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -316,9 +316,9 @@
if (unlikely(addr->sllc_family != AF_LLC))
goto out;
rc = -ENODEV;
- rtnl_lock();
+ rcu_read_lock();
if (sk->sk_bound_dev_if) {
- llc->dev = dev_get_by_index(&init_net, sk->sk_bound_dev_if);
+ llc->dev = dev_get_by_index_rcu(&init_net, sk->sk_bound_dev_if);
if (llc->dev) {
if (!addr->sllc_arphrd)
addr->sllc_arphrd = llc->dev->type;
@@ -329,14 +329,15 @@
!llc_mac_match(addr->sllc_mac,
llc->dev->dev_addr)) {
rc = -EINVAL;
- dev_put(llc->dev);
llc->dev = NULL;
}
}
} else
- llc->dev = dev_getbyhwaddr(&init_net, addr->sllc_arphrd,
+ llc->dev = dev_getbyhwaddr_rcu(&init_net, addr->sllc_arphrd,
addr->sllc_mac);
- rtnl_unlock();
+ if (llc->dev)
+ dev_hold(llc->dev);
+ rcu_read_unlock();
if (!llc->dev)
goto out;
if (!addr->sllc_sap) {