igmp: RCU conversion of in_dev->mc_list

in_dev->mc_list is protected by one rwlock (in_dev->mc_list_lock).

This can easily be converted to a RCU protection.

Writers hold RTNL, so mc_list_lock is removed, not replaced by a
spinlock.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Cypher Wu <cypher.w@gmail.com>
Cc: Américo Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 3 deletions

diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
index ccd5b07d678d..380ba6bc5db1 100644
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h
@@ -52,9 +52,8 @@ struct in_device {
         atomic_t                refcnt;
         int                     dead;
         struct in_ifaddr        *ifa_list;      /* IP ifaddr chain              */
-        rwlock_t                mc_list_lock;
-        struct ip_mc_list       *mc_list;       /* IP multicast filter chain    */
-        int                     mc_count;                 /* Number of installed mcasts */
+        struct ip_mc_list __rcu *mc_list;       /* IP multicast filter chain    */
+        int                     mc_count;       /* Number of installed mcasts   */
         spinlock_t              mc_tomb_lock;
         struct ip_mc_list       *mc_tomb;
         unsigned long           mr_v1_seen;