From: Taehee Yoo ap420073@gmail.com

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.

Suggested-by: Cong Wang xiyou.wangcong@gmail.com Signed-off-by: Taehee Yoo ap420073@gmail.com Signed-off-by: David S. Miller davem@davemloft.net --- This patch is already upstream. But the compat code is missing in batman-adv. So we have to find a way to call the read_lock_bh/read_unlock_bh without adding it in multicast.c and not to use rcu_dereference without removing it from multicast.c... does anyone have an idea?

net/batman-adv/multicast.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c index 28166402..1d63c8cb 100644 --- a/net/batman-adv/multicast.c +++ b/net/batman-adv/multicast.c @@ -454,8 +454,9 @@ batadv_mcast_mla_softif_get_ipv6(struct net_device *dev, return 0; }

- read_lock_bh(&in6_dev->lock); - for (pmc6 = in6_dev->mc_list; pmc6; pmc6 = pmc6->next) { + for (pmc6 = rcu_dereference(in6_dev->mc_list); + pmc6; + pmc6 = rcu_dereference(pmc6->next)) { if (IPV6_ADDR_MC_SCOPE(&pmc6->mca_addr) < IPV6_ADDR_SCOPE_LINKLOCAL) continue; @@ -484,7 +485,6 @@ batadv_mcast_mla_softif_get_ipv6(struct net_device *dev, hlist_add_head(&new->list, mcast_list); ret++; } - read_unlock_bh(&in6_dev->lock); rcu_read_unlock();

return ret;