+ switch (consumer_data.type) {
+ case LTTNG_CONSUMER_KERNEL:
+ if (producer_active) {
+ ret = kernctl_buffer_flush(stream->wait_fd);
+ if (ret < 0) {
+ ERR("Failed to flush kernel stream");
+ goto end;
+ }
+ } else {
+ ret = kernctl_buffer_flush_empty(stream->wait_fd);
+ if (ret < 0) {
+ ERR("Failed to flush kernel stream");
+ goto end;
+ }
+ }
+ break;
+ case LTTNG_CONSUMER32_UST:
+ case LTTNG_CONSUMER64_UST:
+ lttng_ustconsumer_flush_buffer(stream, producer_active);
+ break;
+ default:
+ ERR("Unknown consumer_data type");
+ abort();
+ }
+
+end:
+ return ret;
+}
+
+/*
+ * Sample the rotate position for all the streams of a channel. If a stream
+ * is already at the rotate position (produced == consumed), we flag it as
+ * ready for rotation. The rotation of ready streams occurs after we have
+ * replied to the session daemon that we have finished sampling the positions.
+ * Must be called with RCU read-side lock held to ensure existence of channel.
+ *
+ * Returns 0 on success, < 0 on error
+ */
+int lttng_consumer_rotate_channel(struct lttng_consumer_channel *channel,
+ uint64_t key, uint64_t relayd_id, uint32_t metadata,
+ struct lttng_consumer_local_data *ctx)
+{
+ int ret;
+ struct lttng_consumer_stream *stream;
+ struct lttng_ht_iter iter;
+ struct lttng_ht *ht = consumer_data.stream_per_chan_id_ht;
+ struct lttng_dynamic_array stream_rotation_positions;
+ uint64_t next_chunk_id, stream_count = 0;
+ enum lttng_trace_chunk_status chunk_status;
+ const bool is_local_trace = relayd_id == -1ULL;
+ struct consumer_relayd_sock_pair *relayd = NULL;
+ bool rotating_to_new_chunk = true;
+
+ DBG("Consumer sample rotate position for channel %" PRIu64, key);
+
+ lttng_dynamic_array_init(&stream_rotation_positions,
+ sizeof(struct relayd_stream_rotation_position), NULL);
+
+ rcu_read_lock();
+
+ pthread_mutex_lock(&channel->lock);
+ assert(channel->trace_chunk);
+ chunk_status = lttng_trace_chunk_get_id(channel->trace_chunk,
+ &next_chunk_id);
+ if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
+ ret = -1;
+ goto end_unlock_channel;
+ }
+
+ cds_lfht_for_each_entry_duplicate(ht->ht,
+ ht->hash_fct(&channel->key, lttng_ht_seed),
+ ht->match_fct, &channel->key, &iter.iter,
+ stream, node_channel_id.node) {
+ unsigned long produced_pos = 0, consumed_pos = 0;
+
+ health_code_update();
+
+ /*
+ * Lock stream because we are about to change its state.
+ */
+ pthread_mutex_lock(&stream->lock);
+
+ if (stream->trace_chunk == stream->chan->trace_chunk) {
+ rotating_to_new_chunk = false;
+ }
+
+ /*
+ * Do not flush an empty packet when rotating from a NULL trace
+ * chunk. The stream has no means to output data, and the prior
+ * rotation which rotated to NULL performed that side-effect already.
+ */
+ if (stream->trace_chunk) {
+ /*
+ * For metadata stream, do an active flush, which does not
+ * produce empty packets. For data streams, empty-flush;
+ * ensures we have at least one packet in each stream per trace
+ * chunk, even if no data was produced.
+ */
+ ret = consumer_flush_buffer(stream, stream->metadata_flag ? 1 : 0);
+ if (ret < 0) {
+ ERR("Failed to flush stream %" PRIu64 " during channel rotation",
+ stream->key);
+ goto end_unlock_stream;
+ }
+ }
+
+ ret = lttng_consumer_take_snapshot(stream);
+ if (ret < 0 && ret != -ENODATA && ret != -EAGAIN) {
+ ERR("Failed to sample snapshot position during channel rotation");
+ goto end_unlock_stream;
+ }
+ if (!ret) {
+ ret = lttng_consumer_get_produced_snapshot(stream,
+ &produced_pos);
+ if (ret < 0) {
+ ERR("Failed to sample produced position during channel rotation");
+ goto end_unlock_stream;
+ }
+
+ ret = lttng_consumer_get_consumed_snapshot(stream,
+ &consumed_pos);
+ if (ret < 0) {
+ ERR("Failed to sample consumed position during channel rotation");
+ goto end_unlock_stream;
+ }
+ }
+ /*
+ * Align produced position on the start-of-packet boundary of the first
+ * packet going into the next trace chunk.
+ */
+ produced_pos = ALIGN_FLOOR(produced_pos, stream->max_sb_size);
+ if (consumed_pos == produced_pos) {
+ stream->rotate_ready = true;
+ }
+ /*
+ * The rotation position is based on the packet_seq_num of the
+ * packet following the last packet that was consumed for this
+ * stream, incremented by the offset between produced and
+ * consumed positions. This rotation position is a lower bound
+ * (inclusive) at which the next trace chunk starts. Since it
+ * is a lower bound, it is OK if the packet_seq_num does not
+ * correspond exactly to the same packet identified by the
+ * consumed_pos, which can happen in overwrite mode.
+ */
+ if (stream->sequence_number_unavailable) {
+ /*
+ * Rotation should never be performed on a session which
+ * interacts with a pre-2.8 lttng-modules, which does
+ * not implement packet sequence number.
+ */
+ ERR("Failure to rotate stream %" PRIu64 ": sequence number unavailable",
+ stream->key);
+ ret = -1;
+ goto end_unlock_stream;
+ }
+ stream->rotate_position = stream->last_sequence_number + 1 +
+ ((produced_pos - consumed_pos) / stream->max_sb_size);
+
+ if (!is_local_trace) {
+ /*
+ * The relay daemon control protocol expects a rotation
+ * position as "the sequence number of the first packet
+ * _after_ the current trace chunk".
+ */
+ const struct relayd_stream_rotation_position position = {
+ .stream_id = stream->relayd_stream_id,
+ .rotate_at_seq_num = stream->rotate_position,
+ };
+
+ ret = lttng_dynamic_array_add_element(
+ &stream_rotation_positions,
+ &position);
+ if (ret) {
+ ERR("Failed to allocate stream rotation position");
+ goto end_unlock_stream;
+ }
+ stream_count++;
+ }
+ pthread_mutex_unlock(&stream->lock);
+ }
+ stream = NULL;
+ pthread_mutex_unlock(&channel->lock);
+
+ if (is_local_trace) {
+ ret = 0;