- rcu_read_lock();
-
- switch (domain->type) {
- case LTTNG_DOMAIN_KERNEL:
- {
- struct ltt_kernel_channel *kchan;
-
- /*
- * If a non-default channel has been created in the
- * session, explicitely require that -c chan_name needs
- * to be provided.
- */
- if (session->kernel_session->has_non_default_channel
- && channel_name[0] == '\0') {
- ret = LTTNG_ERR_NEED_CHANNEL_NAME;
- goto error;
- }
-
- kchan = trace_kernel_get_channel_by_name(channel_name,
- session->kernel_session);
- if (kchan == NULL) {
- attr = channel_new_default_attr(LTTNG_DOMAIN_KERNEL,
- LTTNG_BUFFER_GLOBAL);
- if (attr == NULL) {
- ret = LTTNG_ERR_FATAL;
- goto error;
- }
- strncpy(attr->name, channel_name, sizeof(attr->name));
-
- ret = cmd_enable_channel(session, domain, attr, wpipe);
- if (ret != LTTNG_OK) {
- free(attr);
- goto error;
- }
- free(attr);
-
- channel_created = 1;
- }
-
- /* Get the newly created kernel channel pointer */
- kchan = trace_kernel_get_channel_by_name(channel_name,
- session->kernel_session);
- if (kchan == NULL) {
- /* This sould not happen... */
- ret = LTTNG_ERR_FATAL;
- goto error;
- }
-
- ret = event_kernel_enable_tracepoint(kchan, event);
- if (ret != LTTNG_OK) {
- if (channel_created) {
- /* Let's not leak a useless channel. */
- kernel_destroy_channel(kchan);
- }
- goto error;
- }
-
- kernel_wait_quiescent(kernel_tracer_fd);
- break;
- }
- case LTTNG_DOMAIN_UST:
- {
- struct ltt_ust_channel *uchan;
- struct ltt_ust_session *usess = session->ust_session;
-
- assert(usess);
-
- /*
- * If a non-default channel has been created in the
- * session, explicitely require that -c chan_name needs
- * to be provided.
- */
- if (usess->has_non_default_channel && channel_name[0] == '\0') {
- ret = LTTNG_ERR_NEED_CHANNEL_NAME;
- goto error;
- }
-
- /* Get channel from global UST domain */
- uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
- channel_name);
- if (uchan == NULL) {
- /* Create default channel */
- attr = channel_new_default_attr(LTTNG_DOMAIN_UST,
- usess->buffer_type);
- if (attr == NULL) {
- ret = LTTNG_ERR_FATAL;
- goto error;
- }
- strncpy(attr->name, channel_name, sizeof(attr->name));
-
- ret = cmd_enable_channel(session, domain, attr, wpipe);
- if (ret != LTTNG_OK) {
- free(attr);
- goto error;
- }
- free(attr);
-
- /* Get the newly created channel reference back */
- uchan = trace_ust_find_channel_by_name(
- usess->domain_global.channels, channel_name);
- assert(uchan);
- }
-
- /* At this point, the session and channel exist on the tracer */
- ret = event_ust_enable_tracepoint(usess, uchan, event,
- filter_expression, filter, exclusion);
- if (ret != LTTNG_OK) {
- goto error;
- }
- break;
- }
- case LTTNG_DOMAIN_JUL:
- {
- struct lttng_event uevent;
- struct lttng_domain tmp_dom;
- struct ltt_ust_session *usess = session->ust_session;
-
- assert(usess);