Re: [PATCH net-next 8/8] mld: change context of mld module

MLD module's context is atomic although most logic is called from
control-path, not data path. Only a few functions are called from
datapath, most of the functions are called from the control-path.
Furthermore, MLD's response is not processed immediately because
MLD protocol is using delayed response.
It means that If a query is received, the node should have a delay
in response At this point, it could change the context.
It means most of the functions can be implemented as the sleepable
context so that mld functions can use sleepable functions.

Most resources are protected by spinlock and rwlock so the context
of mld functions is atomic. So, in order to change context, locking
scenario should be changed.
It switches from spinlock/rwlock to mutex and rcu.

Some locks are deleted and added.
1. ipv6->mc_socklist->sflock is deleted
This is rwlock and it is unnecessary.
Because it protects ipv6_mc_socklist-sflist but it is now protected
by rtnl_lock().

2. ifmcaddr6->mca_work_lock is added.
This lock protects ifmcaddr6->mca_work.
This workqueue can be used by both control-path and data-path.
It means mutex can't be used.
So mca_work_lock(spinlock) is added.

3. inet6_dev->mc_tomb_lock is deleted
This lock protects inet6_dev->mc_bom_list.
But it is protected by rtnl_lock().

4. inet6_dev->lock is used for protecting workqueues.
inet6_dev has its own workqueues(mc_gq_work, mc_ifc_work, mc_delrec_work)
and it can be started and stop by both control-path and data-path.
So, mutex can't be used.

Suggested-by: Cong Wang <redacted>
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
---
 drivers/s390/net/qeth_l3_main.c |   6 +-
 include/net/if_inet6.h          |  29 +-
 net/batman-adv/multicast.c      |   4 +-
 net/ipv6/addrconf.c             |   4 +-
 net/ipv6/mcast.c                | 785 ++++++++++++++++----------------
 5 files changed, 411 insertions(+), 417 deletions(-)

diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index e49abdeff69c..085afb24482e 100644
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c

@@ -1098,8 +1098,8 @@ static int qeth_l3_add_mcast_rtnl(struct net_device *dev, int vid, void *arg)
 	tmp.disp_flag = QETH_DISP_ADDR_ADD;
 	tmp.is_multicast = 1;
 
-	read_lock_bh(&in6_dev->lock);
-	list_for_each_entry(im6, in6_dev->mc_list, list) {
+	rcu_read_lock();
+	list_for_each_entry_rcu(im6, in6_dev->mc_list, list) {

 		tmp.u.a6.addr = im6->mca_addr;
 
 		ipm = qeth_l3_find_addr_by_ip(card, &tmp);

@@ -1117,7 +1117,7 @@ static int qeth_l3_add_mcast_rtnl(struct net_device *dev, int vid, void *arg)
 			 qeth_l3_ipaddr_hash(ipm));
 
 	}
-	read_unlock_bh(&in6_dev->lock);
+	rcu_read_unlock();
 
 out:
 	return 0;