Fix multiple error handling for UST tracing

[lttng-tools.git] / lttng-sessiond / event.c

diff --git a/lttng-sessiond/event.c b/lttng-sessiond/event.c
index 8582d2f8fc4907e59745feb07c93473ee08c7733..1068707438082e2758e80105599c050967d3e581 100644 (file)
--- a/lttng-sessiond/event.c
+++ b/lttng-sessiond/event.c
@@ -359,7 +359,7 @@ error:
 int event_ust_enable_tracepoint(struct ltt_ust_session *usess, int domain,
                struct ltt_ust_channel *uchan, struct lttng_event *event)
 {
-       int ret, to_create = 0;
+       int ret = LTTCOMM_OK, to_create = 0;
        struct ltt_ust_event *uevent;
 
        uevent = trace_ust_find_event_by_name(uchan->events, event->name);
@@ -369,6 +369,7 @@ int event_ust_enable_tracepoint(struct ltt_ust_session *usess, int domain,
                        ret = LTTCOMM_FATAL;
                        goto error;
                }
+               /* Valid to set it after the goto error since uevent is still NULL */
                to_create = 1;
        }
 
@@ -377,6 +378,8 @@ int event_ust_enable_tracepoint(struct ltt_ust_session *usess, int domain,
                goto end;
        }
 
+       uevent->enabled = 1;
+
        switch (domain) {
        case LTTNG_DOMAIN_UST:
        {
@@ -407,10 +410,9 @@ int event_ust_enable_tracepoint(struct ltt_ust_session *usess, int domain,
                goto end;
        }
 
-       uevent->enabled = 1;
-       /* Add ltt ust event to channel */
        if (to_create) {
                rcu_read_lock();
+               /* Add ltt ust event to channel */
                lttng_ht_add_unique_str(uchan->events, &uevent->node);
                rcu_read_unlock();
        }
@@ -418,11 +420,23 @@ int event_ust_enable_tracepoint(struct ltt_ust_session *usess, int domain,
        DBG("Event UST %s %s in channel %s", uevent->attr.name,
                        to_create ? "created" : "enabled", uchan->name);
 
+       ret = LTTCOMM_OK;
+
 end:
-       return LTTCOMM_OK;
+       return ret;
 
 error:
-       trace_ust_destroy_event(uevent);
+       /*
+        * Only destroy event on creation time (not enabling time) because if the
+        * event is found in the channel (to_create == 0), it means that at some
+        * point the enable_event worked and it's thus valid to keep it alive.
+        * Destroying it also implies that we also destroy it's shadow copy to sync
+        * everyone up.
+        */
+       if (to_create) {
+               /* In this code path, the uevent was not added to the hash table */
+               trace_ust_destroy_event(uevent);
+       }
        return ret;
 }