tipc: advance the time of deleting subscription from subscriber->subscrp_list

After a subscription object is created, it's inserted into its
subscriber subscrp_list list under subscriber lock protection,
similarly, before it's destroyed, it should be first removed from
its subscriber->subscrp_list. Since the subscription list is
accessed with subscriber lock, all the subscriptions are valid
during the lock duration. Hence in tipc_subscrb_subscrp_delete(), we
remove subscription get/put and the extra subscriber unlock/lock.

After this change, the subscriptions refcount cleanup is very simple
and does not access any lock.

Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 7 deletions

diff --git a/net/tipc/subscr.c b/net/tipc/subscr.c
index 271cd66e4b3b..0649bc29c6bb 100644
--- a/net/tipc/subscr.c
+++ b/net/tipc/subscr.c
@@ -145,6 +145,7 @@ static void tipc_subscrp_timeout(unsigned long data)
 
         spin_lock_bh(&subscriber->lock);
         tipc_nametbl_unsubscribe(sub);
+        list_del(&sub->subscrp_list);
         spin_unlock_bh(&subscriber->lock);
 
         /* Notify subscriber of timeout */
@@ -177,10 +178,7 @@ static void tipc_subscrp_kref_release(struct kref *kref)
         struct tipc_net *tn = net_generic(sub->net, tipc_net_id);
         struct tipc_subscriber *subscriber = sub->subscriber;
 
-        spin_lock_bh(&subscriber->lock);
-        list_del(&sub->subscrp_list);
         atomic_dec(&tn->subscription_count);
-        spin_unlock_bh(&subscriber->lock);
         kfree(sub);
         tipc_subscrb_put(subscriber);
 }
@@ -210,11 +208,8 @@ static void tipc_subscrb_subscrp_delete(struct tipc_subscriber *subscriber,
                         continue;
 
                 tipc_nametbl_unsubscribe(sub);
-                tipc_subscrp_get(sub);
-                spin_unlock_bh(&subscriber->lock);
+                list_del(&sub->subscrp_list);
                 tipc_subscrp_delete(sub);
-                tipc_subscrp_put(sub);
-                spin_lock_bh(&subscriber->lock);
 
                 if (s)
                         break;