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tipc: adjust the policy of holding subscription kref

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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 <ying.xue@windriver.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ying Xue 2017-03-28 12:28:28 +02:00 committed by David S. Miller
parent 139bb36f75
commit 7efea60dcf
3 changed files with 7 additions and 6 deletions
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2
net/tipc/name_table.c
View File

@ -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);

8
net/tipc/subscr.c
View File

@ -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);
}

3
net/tipc/subscr.h
View File

@ -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