Re: [PATCH 1/1] Use RCU for the UDP hash lock

Corey Minyard
2008-09-25T19:22:33Z

Jarek Poplawski wrote:
>
> ...
>
>> @@ -1094,7 +1103,7 @@ static int __udp4_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
>> struct sock *sk;
>> int dif;
>>
>> - read_lock(&udp_hash_lock);
>> + rcu_read_lock();
>> sk = sk_head(&udptable[udp_hashfn(net, ntohs(uh->dest))]);
>>
>
> Probably sk_head_rcu() is needed too.
>
Yes, it is.
>
>> dif = skb->dev->ifindex;
>> sk = udp_v4_mcast_next(sk, uh->dest, daddr, uh->source, saddr, dif);
>> @@ -1120,7 +1129,7 @@ static int __udp4_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
>> } while (sknext);
>> } else
>> kfree_skb(skb);
>> - read_unlock(&udp_hash_lock);
>> + rcu_read_unlock();
>> return 0;
>> }
>>
> ...
>
> Aren't other functions like sk_next() or sk_unhashed() used on the
> read side and need _rcu versions?
>
It also needs sk_next_rcu(). sk_unhashed() is only used on the update
side, so an rcu version is not needed there.

Thanks for pointing this out.

-corey