From 139bb36f754adbf6d3c836db09d6459e25167b38 Mon Sep 17 00:00:00 2001 From: Ying Xue Date: Tue, 28 Mar 2017 12:28:27 +0200 Subject: [PATCH 1/2] 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 Signed-off-by: Ying Xue Signed-off-by: Parthasarathy Bhuvaragan Signed-off-by: David S. Miller --- net/tipc/subscr.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/net/tipc/subscr.c b/net/tipc/subscr.c index 271cd66e4b3b6..0649bc29c6bb1 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; From 7efea60dcffc151870d1abbfccdb1f11cd4b7f21 Mon Sep 17 00:00:00 2001 From: Ying Xue Date: Tue, 28 Mar 2017 12:28:28 +0200 Subject: [PATCH 2/2] tipc: adjust the policy of holding subscription kref When a new subscription object is inserted into name_seq->subscriptions list, it's under name_seq->lock protection; when a subscription is deleted from the list, it's also under the same lock protection; similarly, when accessing a subscription by going through subscriptions list, the entire process is also protected by the name_seq->lock. Therefore, if subscription refcount is increased before it's inserted into subscriptions list, and its refcount is decreased after it's deleted from the list, it will be unnecessary to hold refcount at all before accessing subscription object which is obtained by going through subscriptions list under name_seq->lock protection. Signed-off-by: Ying Xue Reviewed-by: Jon Maloy Signed-off-by: David S. Miller --- net/tipc/name_table.c | 2 ++ net/tipc/subscr.c | 8 ++------ net/tipc/subscr.h | 3 +++ 3 files changed, 7 insertions(+), 6 deletions(-) diff --git a/net/tipc/name_table.c b/net/tipc/name_table.c index 9be6592e4a6fa..bd0aac87b41ac 100644 --- a/net/tipc/name_table.c +++ b/net/tipc/name_table.c @@ -416,6 +416,7 @@ static void tipc_nameseq_subscribe(struct name_seq *nseq, tipc_subscrp_convert_seq(&s->evt.s.seq, s->swap, &ns); + tipc_subscrp_get(s); list_add(&s->nameseq_list, &nseq->subscriptions); if (!sseq) @@ -787,6 +788,7 @@ void tipc_nametbl_unsubscribe(struct tipc_subscription *s) if (seq != NULL) { spin_lock_bh(&seq->lock); list_del_init(&s->nameseq_list); + tipc_subscrp_put(s); if (!seq->first_free && list_empty(&seq->subscriptions)) { hlist_del_init_rcu(&seq->ns_list); kfree(seq->sseqs); diff --git a/net/tipc/subscr.c b/net/tipc/subscr.c index 0649bc29c6bb1..0bf91cd3733cb 100644 --- a/net/tipc/subscr.c +++ b/net/tipc/subscr.c @@ -54,8 +54,6 @@ struct tipc_subscriber { static void tipc_subscrp_delete(struct tipc_subscription *sub); static void tipc_subscrb_put(struct tipc_subscriber *subscriber); -static void tipc_subscrp_put(struct tipc_subscription *subscription); -static void tipc_subscrp_get(struct tipc_subscription *subscription); /** * htohl - convert value to endianness used by destination @@ -125,7 +123,6 @@ void tipc_subscrp_report_overlap(struct tipc_subscription *sub, u32 found_lower, { struct tipc_name_seq seq; - tipc_subscrp_get(sub); tipc_subscrp_convert_seq(&sub->evt.s.seq, sub->swap, &seq); if (!tipc_subscrp_check_overlap(&seq, found_lower, found_upper)) return; @@ -135,7 +132,6 @@ void tipc_subscrp_report_overlap(struct tipc_subscription *sub, u32 found_lower, tipc_subscrp_send_event(sub, found_lower, found_upper, event, port_ref, node); - tipc_subscrp_put(sub); } static void tipc_subscrp_timeout(unsigned long data) @@ -183,12 +179,12 @@ static void tipc_subscrp_kref_release(struct kref *kref) tipc_subscrb_put(subscriber); } -static void tipc_subscrp_put(struct tipc_subscription *subscription) +void tipc_subscrp_put(struct tipc_subscription *subscription) { kref_put(&subscription->kref, tipc_subscrp_kref_release); } -static void tipc_subscrp_get(struct tipc_subscription *subscription) +void tipc_subscrp_get(struct tipc_subscription *subscription) { kref_get(&subscription->kref); } diff --git a/net/tipc/subscr.h b/net/tipc/subscr.h index ffdc214c117a9..ee52957dc9524 100644 --- a/net/tipc/subscr.h +++ b/net/tipc/subscr.h @@ -78,4 +78,7 @@ u32 tipc_subscrp_convert_seq_type(u32 type, int swap); int tipc_topsrv_start(struct net *net); void tipc_topsrv_stop(struct net *net); +void tipc_subscrp_put(struct tipc_subscription *subscription); +void tipc_subscrp_get(struct tipc_subscription *subscription); + #endif