+ path = zmalloc(LTTNG_PATH_MAX * sizeof(char));
+ if (!path) {
+ ERR("Cannot allocate mkdir path");
+ ret = -1;
+ goto end;
+ }
+
+ ret = snprintf(path, LTTNG_PATH_MAX, "%s%s%s",
+ session_get_base_path(session),
+ output->chunk_path, output->subdir);
+ if (ret < 0 || ret >= LTTNG_PATH_MAX) {
+ ERR("Format path");
+ ret = -1;
+ goto end;
+ }
+
+ DBG("Domain mkdir %s for session %" PRIu64, path, session->id);
+ rcu_read_lock();
+ /*
+ * We have to iterate to find a socket, but we only need to send the
+ * rename command to one consumer, so we break after the first one.
+ */
+ cds_lfht_for_each_entry(output->socks->ht, &iter.iter, socket, node.node) {
+ pthread_mutex_lock(socket->lock);
+ ret = consumer_mkdir(socket, session->id, output, path, uid, gid);
+ pthread_mutex_unlock(socket->lock);
+ if (ret) {
+ ERR("Consumer mkdir");
+ ret = -1;
+ goto end_unlock;
+ }
+ break;
+ }
+
+ ret = 0;
+
+end_unlock:
+ rcu_read_unlock();
+end:
+ free(path);
+ return ret;
+}
+
+static
+int session_mkdir(const struct ltt_session *session)
+{
+ int ret;
+ struct consumer_output *output;
+ uid_t uid;
+ gid_t gid;
+
+ /*
+ * Unsupported feature in lttng-relayd before 2.11, not an error since it
+ * is only needed for session rotation and the user will get an error
+ * on rotate.
+ */
+ if (session->consumer->type == CONSUMER_DST_NET &&
+ session->consumer->relay_major_version == 2 &&
+ session->consumer->relay_minor_version < 11) {
+ ret = 0;
+ goto end;
+ }
+
+ if (session->kernel_session) {
+ output = session->kernel_session->consumer;
+ uid = session->kernel_session->uid;
+ gid = session->kernel_session->gid;
+ ret = domain_mkdir(output, session, uid, gid);
+ if (ret) {
+ ERR("Mkdir kernel");
+ goto end;
+ }
+ }
+
+ if (session->ust_session) {
+ output = session->ust_session->consumer;
+ uid = session->ust_session->uid;
+ gid = session->ust_session->gid;
+ ret = domain_mkdir(output, session, uid, gid);
+ if (ret) {
+ ERR("Mkdir UST");
+ goto end;
+ }
+ }
+
+ ret = 0;
+
+end:
+ return ret;
+}
+
+/*
+ * Command LTTNG_START_TRACE processed by the client thread.
+ *
+ * Called with session mutex held.
+ */
+int cmd_start_trace(struct ltt_session *session)
+{
+ int ret;
+ unsigned long nb_chan = 0;
+ struct ltt_kernel_session *ksession;
+ struct ltt_ust_session *usess;
+
+ assert(session);
+
+ /* Ease our life a bit ;) */
+ ksession = session->kernel_session;
+ usess = session->ust_session;
+
+ /* Is the session already started? */
+ if (session->active) {
+ ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
+ goto error;
+ }
+
+ /*
+ * Starting a session without channel is useless since after that it's not
+ * possible to enable channel thus inform the client.
+ */
+ if (usess && usess->domain_global.channels) {
+ nb_chan += lttng_ht_get_count(usess->domain_global.channels);
+ }
+ if (ksession) {
+ nb_chan += ksession->channel_count;
+ }
+ if (!nb_chan) {
+ ret = LTTNG_ERR_NO_CHANNEL;
+ goto error;
+ }
+
+ /*
+ * Record the timestamp of the first time the session is started for
+ * an eventual session rotation call.
+ */
+ if (!session->has_been_started) {
+ session->current_chunk_start_ts = time(NULL);
+ if (session->current_chunk_start_ts == (time_t) -1) {
+ PERROR("Failed to retrieve the \"%s\" session's start time",
+ session->name);
+ ret = LTTNG_ERR_FATAL;
+ goto error;
+ }
+ if (!session->snapshot_mode && session->output_traces) {
+ ret = session_mkdir(session);
+ if (ret) {
+ ERR("Failed to create the session directories");
+ ret = LTTNG_ERR_CREATE_DIR_FAIL;
+ goto error;
+ }
+ }
+ }
+
+ /* Kernel tracing */
+ if (ksession != NULL) {
+ DBG("Start kernel tracing session %s", session->name);
+ ret = start_kernel_session(ksession, kernel_tracer_fd);
+ if (ret != LTTNG_OK) {
+ goto error;
+ }
+ }
+
+ /* Flag session that trace should start automatically */
+ if (usess) {
+ /*
+ * Even though the start trace might fail, flag this session active so
+ * other application coming in are started by default.
+ */
+ usess->active = 1;
+
+ ret = ust_app_start_trace_all(usess);
+ if (ret < 0) {
+ ret = LTTNG_ERR_UST_START_FAIL;
+ goto error;
+ }
+ }
+
+ /* Flag this after a successful start. */
+ session->has_been_started = 1;
+ session->active = 1;
+
+ /*
+ * Clear the flag that indicates that a rotation was done while the
+ * session was stopped.
+ */
+ session->rotated_after_last_stop = false;
+
+ if (session->rotate_timer_period) {
+ ret = sessiond_rotate_timer_start(session,
+ session->rotate_timer_period);
+ if (ret < 0) {
+ ERR("Failed to enable rotate timer");
+ ret = LTTNG_ERR_UNK;
+ goto error;
+ }
+ }
+
+ ret = LTTNG_OK;
+
+error:
+ return ret;
+}
+
+static
+int rename_active_chunk(struct ltt_session *session)
+{
+ int ret;
+
+ session->rotate_count++;
+
+ /*
+ * The currently active tracing path is now the folder we
+ * want to rename.
+ */
+ ret = lttng_strncpy(session->rotation_chunk.current_rotate_path,
+ session->rotation_chunk.active_tracing_path,
+ sizeof(session->rotation_chunk.current_rotate_path));
+ if (ret) {
+ ERR("Failed to copy active tracing path");
+ goto end;
+ }
+
+ ret = rename_complete_chunk(session, time(NULL));
+ if (ret < 0) {
+ ERR("Failed to rename current rotate path");
+ goto end;
+ }
+
+ /*
+ * We just renamed, the folder, we didn't do an actual rotation, so
+ * the active tracing path is now the renamed folder and we have to
+ * restore the rotate count.
+ */
+ ret = lttng_strncpy(session->rotation_chunk.active_tracing_path,
+ session->rotation_chunk.current_rotate_path,
+ sizeof(session->rotation_chunk.active_tracing_path));
+ if (ret) {
+ ERR("Failed to rename active session chunk tracing path");
+ goto end;
+ }
+end:
+ session->rotate_count--;
+ return ret;
+}
+
+/*
+ * Command LTTNG_STOP_TRACE processed by the client thread.
+ */
+int cmd_stop_trace(struct ltt_session *session)
+{
+ int ret;
+ struct ltt_kernel_channel *kchan;
+ struct ltt_kernel_session *ksession;
+ struct ltt_ust_session *usess;
+ bool error_occured = false;
+
+ assert(session);
+
+ DBG("Begin stop session %s (id %" PRIu64 ")", session->name, session->id);
+ /* Short cut */