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, 8 insertions, 4 deletions

diff --git a/include/linux/igmp.h b/include/linux/igmp.h
index 93fc2449af10..7d164670f264 100644
--- a/include/linux/igmp.h
+++ b/include/linux/igmp.h
@@ -167,10 +167,10 @@ struct ip_sf_socklist {
  */
 
 struct ip_mc_socklist {
-        struct ip_mc_socklist   *next;
+        struct ip_mc_socklist __rcu *next_rcu;
         struct ip_mreqn         multi;
         unsigned int            sfmode;         /* MCAST_{INCLUDE,EXCLUDE} */
-        struct ip_sf_socklist   *sflist;
+        struct ip_sf_socklist __rcu     *sflist;
         struct rcu_head         rcu;
 };
 
@@ -186,11 +186,14 @@ struct ip_sf_list {
 struct ip_mc_list {
         struct in_device        *interface;
         __be32                  multiaddr;
+        unsigned int            sfmode;
         struct ip_sf_list       *sources;
         struct ip_sf_list       *tomb;
-        unsigned int            sfmode;
         unsigned long           sfcount[2];
-        struct ip_mc_list       *next;
+        union {
+                struct ip_mc_list *next;
+                struct ip_mc_list __rcu *next_rcu;
+        };
         struct timer_list       timer;
         int                     users;
         atomic_t                refcnt;
@@ -201,6 +204,7 @@ struct ip_mc_list {
         char                    loaded;
         unsigned char           gsquery;        /* check source marks? */
         unsigned char           crcount;
+        struct rcu_head         rcu;
 };
 
 /* V3 exponential field decoding */