+/* Called with RCU read-side lock held. */
+static
+void ust_app_synchronize_event_notifier_rules(struct ust_app *app)
+{
+ int ret = 0;
+ enum lttng_error_code ret_code;
+ enum lttng_trigger_status t_status;
+ struct lttng_ht_iter app_trigger_iter;
+ struct lttng_triggers *triggers = NULL;
+ struct ust_app_event_notifier_rule *event_notifier_rule;
+ unsigned int count, i;
+
+ /*
+ * Currrently, registering or unregistering a trigger with an
+ * event rule condition causes a full synchronization of the event
+ * notifiers.
+ *
+ * The first step attempts to add an event notifier for all registered
+ * triggers that apply to the user space tracers. Then, the
+ * application's event notifiers rules are all checked against the list
+ * of registered triggers. Any event notifier that doesn't have a
+ * matching trigger can be assumed to have been disabled.
+ *
+ * All of this is inefficient, but is put in place to get the feature
+ * rolling as it is simpler at this moment. It will be optimized Soon™
+ * to allow the state of enabled
+ * event notifiers to be synchronized in a piece-wise way.
+ */
+
+ /* Get all triggers using uid 0 (root) */
+ ret_code = notification_thread_command_list_triggers(
+ the_notification_thread_handle, 0, &triggers);
+ if (ret_code != LTTNG_OK) {
+ ret = -1;
+ goto end;
+ }
+
+ assert(triggers);
+
+ t_status = lttng_triggers_get_count(triggers, &count);
+ if (t_status != LTTNG_TRIGGER_STATUS_OK) {
+ ret = -1;
+ goto end;
+ }
+
+ for (i = 0; i < count; i++) {
+ struct lttng_condition *condition;
+ struct lttng_event_rule *event_rule;
+ struct lttng_trigger *trigger;
+ const struct ust_app_event_notifier_rule *looked_up_event_notifier_rule;
+ enum lttng_condition_status condition_status;
+ uint64_t token;
+
+ trigger = lttng_triggers_borrow_mutable_at_index(triggers, i);
+ assert(trigger);
+
+ token = lttng_trigger_get_tracer_token(trigger);
+ condition = lttng_trigger_get_condition(trigger);
+
+ if (lttng_condition_get_type(condition) != LTTNG_CONDITION_TYPE_ON_EVENT) {
+ /* Does not apply */
+ continue;
+ }
+
+ condition_status = lttng_condition_on_event_borrow_rule_mutable(condition, &event_rule);
+ assert(condition_status == LTTNG_CONDITION_STATUS_OK);
+
+ if (lttng_event_rule_get_domain_type(event_rule) == LTTNG_DOMAIN_KERNEL) {
+ /* Skip kernel related triggers. */
+ continue;
+ }
+
+ /*
+ * Find or create the associated token event rule. The caller
+ * holds the RCU read lock, so this is safe to call without
+ * explicitly acquiring it here.
+ */
+ looked_up_event_notifier_rule = find_ust_app_event_notifier_rule(
+ app->token_to_event_notifier_rule_ht, token);
+ if (!looked_up_event_notifier_rule) {
+ ret = create_ust_app_event_notifier_rule(trigger, app);
+ if (ret < 0) {
+ goto end;
+ }
+ }
+ }
+
+ rcu_read_lock();
+ /* Remove all unknown event sources from the app. */
+ cds_lfht_for_each_entry (app->token_to_event_notifier_rule_ht->ht,
+ &app_trigger_iter.iter, event_notifier_rule,
+ node.node) {
+ const uint64_t app_token = event_notifier_rule->token;
+ bool found = false;
+
+ /*
+ * Check if the app event trigger still exists on the
+ * notification side.
+ */
+ for (i = 0; i < count; i++) {
+ uint64_t notification_thread_token;
+ const struct lttng_trigger *trigger =
+ lttng_triggers_get_at_index(
+ triggers, i);
+
+ assert(trigger);
+
+ notification_thread_token =
+ lttng_trigger_get_tracer_token(trigger);
+
+ if (notification_thread_token == app_token) {
+ found = true;
+ break;
+ }
+ }
+
+ if (found) {
+ /* Still valid. */
+ continue;
+ }
+
+ /*
+ * This trigger was unregistered, disable it on the tracer's
+ * side.
+ */
+ ret = lttng_ht_del(app->token_to_event_notifier_rule_ht,
+ &app_trigger_iter);
+ assert(ret == 0);
+
+ /* Callee logs errors. */
+ (void) disable_ust_object(app, event_notifier_rule->obj);
+
+ delete_ust_app_event_notifier_rule(
+ app->sock, event_notifier_rule, app);
+ }
+
+ rcu_read_unlock();
+
+end:
+ lttng_triggers_destroy(triggers);
+ return;
+}
+
+/*
+ * RCU read lock must be held by the caller.
+ */
+static
+void ust_app_synchronize_all_channels(struct ltt_ust_session *usess,
+ struct ust_app_session *ua_sess,
+ struct ust_app *app)
+{
+ int ret = 0;
+ struct cds_lfht_iter uchan_iter;
+ struct ltt_ust_channel *uchan;
+
+ assert(usess);
+ assert(ua_sess);
+ assert(app);
+
+ cds_lfht_for_each_entry(usess->domain_global.channels->ht, &uchan_iter,
+ uchan, node.node) {
+ struct ust_app_channel *ua_chan;
+ struct cds_lfht_iter uevent_iter;
+ struct ltt_ust_event *uevent;
+
+ /*
+ * Search for a matching ust_app_channel. If none is found,
+ * create it. Creating the channel will cause the ua_chan
+ * structure to be allocated, the channel buffers to be
+ * allocated (if necessary) and sent to the application, and
+ * all enabled contexts will be added to the channel.
+ */
+ ret = find_or_create_ust_app_channel(usess, ua_sess,
+ app, uchan, &ua_chan);
+ if (ret) {
+ /* Tracer is probably gone or ENOMEM. */
+ goto end;
+ }
+
+ if (!ua_chan) {
+ /* ua_chan will be NULL for the metadata channel */
+ continue;
+ }
+
+ cds_lfht_for_each_entry(uchan->events->ht, &uevent_iter, uevent,
+ node.node) {
+ ret = ust_app_channel_synchronize_event(ua_chan,
+ uevent, ua_sess, app);
+ if (ret) {
+ goto end;
+ }
+ }
+
+ if (ua_chan->enabled != uchan->enabled) {
+ ret = uchan->enabled ?
+ enable_ust_app_channel(ua_sess, uchan, app) :
+ disable_ust_app_channel(ua_sess, ua_chan, app);
+ if (ret) {
+ goto end;
+ }
+ }
+ }
+end:
+ return;
+}
+
+/*
+ * The caller must ensure that the application is compatible and is tracked
+ * by the process attribute trackers.
+ */
+static
+void ust_app_synchronize(struct ltt_ust_session *usess,
+ struct ust_app *app)
+{
+ int ret = 0;
+ struct ust_app_session *ua_sess = NULL;
+
+ /*
+ * The application's configuration should only be synchronized for
+ * active sessions.
+ */
+ assert(usess->active);
+
+ ret = find_or_create_ust_app_session(usess, app, &ua_sess, NULL);
+ if (ret < 0) {
+ /* Tracer is probably gone or ENOMEM. */
+ goto error;
+ }
+ assert(ua_sess);
+
+ pthread_mutex_lock(&ua_sess->lock);
+ if (ua_sess->deleted) {
+ pthread_mutex_unlock(&ua_sess->lock);
+ goto end;
+ }
+
+ rcu_read_lock();
+
+ ust_app_synchronize_all_channels(usess, ua_sess, app);
+
+ /*
+ * Create the metadata for the application. This returns gracefully if a
+ * metadata was already set for the session.
+ *
+ * The metadata channel must be created after the data channels as the
+ * consumer daemon assumes this ordering. When interacting with a relay
+ * daemon, the consumer will use this assumption to send the
+ * "STREAMS_SENT" message to the relay daemon.
+ */
+ ret = create_ust_app_metadata(ua_sess, app, usess->consumer);
+ if (ret < 0) {
+ goto error_unlock;
+ }
+
+ rcu_read_unlock();
+
+end:
+ pthread_mutex_unlock(&ua_sess->lock);
+ /* Everything went well at this point. */
+ return;
+
+error_unlock:
+ rcu_read_unlock();
+ pthread_mutex_unlock(&ua_sess->lock);
+error: