Re: [PATCH net-next v3 5/7] mld: convert ifmcaddr6 to RCU

On 3/25/21 5:16 PM, Taehee Yoo wrote:

The ifmcaddr6 has been protected by inet6_dev->lock(rwlock) so that the critical section is atomic context. In order to switch this context, changing locking is needed. The ifmcaddr6 actually already protected by RTNL So if it's converted to use RCU, its control path context can be switched to sleepable.

I do not really understand the changelog.

You wanted to convert from RCU to RTNL, right ?

Also :

@@ -571,13 +573,9 @@ int ip6_mc_msfget(struct sock *sk, struct group_filter *gsf, if (!ipv6_addr_is_multicast(group)) return -EINVAL;

• rcu_read_lock();
• idev = ip6_mc_find_dev_rcu(net, group, gsf->gf_interface);
• if (!idev) {

• rcu_read_unlock();
  

• idev = ip6_mc_find_dev_rtnl(net, group, gsf->gf_interface);
• if (!idev) return -ENODEV;

• }

I do not see RTNL being acquired before entering ip6_mc_msfget()