+ ret = ustctl_get_events_discarded(ustream, &index->events_discarded);
+ if (ret < 0) {
+ PERROR("ustctl_get_events_discarded");
+ goto error;
+ }
+ index->events_discarded = htobe64(index->events_discarded);
+
+ ret = ustctl_get_content_size(ustream, &index->content_size);
+ if (ret < 0) {
+ PERROR("ustctl_get_content_size");
+ goto error;
+ }
+ index->content_size = htobe64(index->content_size);
+
+ ret = ustctl_get_packet_size(ustream, &index->packet_size);
+ if (ret < 0) {
+ PERROR("ustctl_get_packet_size");
+ goto error;
+ }
+ index->packet_size = htobe64(index->packet_size);
+
+ ret = ustctl_get_stream_id(ustream, &index->stream_id);
+ if (ret < 0) {
+ PERROR("ustctl_get_stream_id");
+ goto error;
+ }
+ index->stream_id = htobe64(index->stream_id);
+
+ ret = ustctl_get_instance_id(ustream, &index->stream_instance_id);
+ if (ret < 0) {
+ PERROR("ustctl_get_instance_id");
+ goto error;
+ }
+ index->stream_instance_id = htobe64(index->stream_instance_id);
+
+ ret = ustctl_get_sequence_number(ustream, &index->packet_seq_num);
+ if (ret < 0) {
+ PERROR("ustctl_get_sequence_number");
+ goto error;
+ }
+ index->packet_seq_num = htobe64(index->packet_seq_num);
+
+error:
+ return ret;
+}
+
+static
+void metadata_stream_reset_cache(struct lttng_consumer_stream *stream,
+ struct consumer_metadata_cache *cache)
+{
+ DBG("Metadata stream update to version %" PRIu64,
+ cache->version);
+ stream->ust_metadata_pushed = 0;
+ stream->metadata_version = cache->version;
+ stream->reset_metadata_flag = 1;
+}
+
+/*
+ * Check if the version of the metadata stream and metadata cache match.
+ * If the cache got updated, reset the metadata stream.
+ * The stream lock and metadata cache lock MUST be held.
+ * Return 0 on success, a negative value on error.
+ */
+static
+int metadata_stream_check_version(struct lttng_consumer_stream *stream)
+{
+ int ret = 0;
+ struct consumer_metadata_cache *cache = stream->chan->metadata_cache;
+
+ if (cache->version == stream->metadata_version) {
+ goto end;
+ }
+ metadata_stream_reset_cache(stream, cache);
+
+end:
+ return ret;
+}
+
+/*
+ * Write up to one packet from the metadata cache to the channel.
+ *
+ * Returns the number of bytes pushed in the cache, or a negative value
+ * on error.
+ */
+static
+int commit_one_metadata_packet(struct lttng_consumer_stream *stream)
+{
+ ssize_t write_len;
+ int ret;
+
+ pthread_mutex_lock(&stream->chan->metadata_cache->lock);
+ ret = metadata_stream_check_version(stream);
+ if (ret < 0) {
+ goto end;
+ }
+ if (stream->chan->metadata_cache->max_offset
+ == stream->ust_metadata_pushed) {
+ ret = 0;
+ goto end;
+ }
+
+ write_len = ustctl_write_one_packet_to_channel(stream->chan->uchan,
+ &stream->chan->metadata_cache->data[stream->ust_metadata_pushed],
+ stream->chan->metadata_cache->max_offset
+ - stream->ust_metadata_pushed);
+ assert(write_len != 0);
+ if (write_len < 0) {
+ ERR("Writing one metadata packet");
+ ret = -1;
+ goto end;
+ }
+ stream->ust_metadata_pushed += write_len;
+
+ assert(stream->chan->metadata_cache->max_offset >=
+ stream->ust_metadata_pushed);
+ ret = write_len;
+
+ /*
+ * Switch packet (but don't open the next one) on every commit of
+ * a metadata packet. Since the subbuffer is fully filled (with padding,
+ * if needed), the stream is "quiescent" after this commit.
+ */
+ ustctl_flush_buffer(stream->ustream, 1);
+ stream->quiescent = true;
+end:
+ pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
+ return ret;
+}
+
+
+/*
+ * Sync metadata meaning request them to the session daemon and snapshot to the
+ * metadata thread can consumer them.
+ *
+ * Metadata stream lock is held here, but we need to release it when
+ * interacting with sessiond, else we cause a deadlock with live
+ * awaiting on metadata to be pushed out.
+ *
+ * Return 0 if new metadatda is available, EAGAIN if the metadata stream
+ * is empty or a negative value on error.
+ */
+int lttng_ustconsumer_sync_metadata(struct lttng_consumer_local_data *ctx,
+ struct lttng_consumer_stream *metadata)
+{
+ int ret;
+ int retry = 0;
+
+ assert(ctx);
+ assert(metadata);
+
+ pthread_mutex_unlock(&metadata->lock);
+ /*
+ * Request metadata from the sessiond, but don't wait for the flush
+ * because we locked the metadata thread.
+ */
+ ret = lttng_ustconsumer_request_metadata(ctx, metadata->chan, 0, 0);
+ pthread_mutex_lock(&metadata->lock);
+ if (ret < 0) {
+ goto end;
+ }
+
+ ret = commit_one_metadata_packet(metadata);
+ if (ret <= 0) {
+ goto end;
+ } else if (ret > 0) {
+ retry = 1;
+ }
+
+ ret = ustctl_snapshot(metadata->ustream);
+ if (ret < 0) {
+ if (errno != EAGAIN) {
+ ERR("Sync metadata, taking UST snapshot");
+ goto end;
+ }
+ DBG("No new metadata when syncing them.");
+ /* No new metadata, exit. */
+ ret = ENODATA;
+ goto end;
+ }
+
+ /*
+ * After this flush, we still need to extract metadata.
+ */
+ if (retry) {
+ ret = EAGAIN;
+ }
+
+end:
+ return ret;
+}
+
+/*
+ * Return 0 on success else a negative value.
+ */
+static int notify_if_more_data(struct lttng_consumer_stream *stream,
+ struct lttng_consumer_local_data *ctx)
+{
+ int ret;
+ struct ustctl_consumer_stream *ustream;
+
+ assert(stream);
+ assert(ctx);
+
+ ustream = stream->ustream;
+
+ /*
+ * First, we are going to check if there is a new subbuffer available
+ * before reading the stream wait_fd.
+ */
+ /* Get the next subbuffer */
+ ret = ustctl_get_next_subbuf(ustream);
+ if (ret) {
+ /* No more data found, flag the stream. */
+ stream->has_data = 0;
+ ret = 0;
+ goto end;
+ }
+
+ ret = ustctl_put_subbuf(ustream);
+ assert(!ret);
+
+ /* This stream still has data. Flag it and wake up the data thread. */
+ stream->has_data = 1;
+
+ if (stream->monitor && !stream->hangup_flush_done && !ctx->has_wakeup) {
+ ssize_t writelen;
+
+ writelen = lttng_pipe_write(ctx->consumer_wakeup_pipe, "!", 1);
+ if (writelen < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
+ ret = writelen;
+ goto end;
+ }
+
+ /* The wake up pipe has been notified. */
+ ctx->has_wakeup = 1;
+ }
+ ret = 0;
+
+end:
+ return ret;
+}
+
+static
+int update_stream_stats(struct lttng_consumer_stream *stream)
+{
+ int ret;
+ uint64_t seq, discarded;
+
+ ret = ustctl_get_sequence_number(stream->ustream, &seq);
+ if (ret < 0) {
+ PERROR("ustctl_get_sequence_number");
+ goto end;
+ }
+ /*
+ * Start the sequence when we extract the first packet in case we don't
+ * start at 0 (for example if a consumer is not connected to the
+ * session immediately after the beginning).
+ */
+ if (stream->last_sequence_number == -1ULL) {
+ stream->last_sequence_number = seq;
+ } else if (seq > stream->last_sequence_number) {
+ stream->chan->lost_packets += seq -
+ stream->last_sequence_number - 1;
+ } else {
+ /* seq <= last_sequence_number */
+ ERR("Sequence number inconsistent : prev = %" PRIu64
+ ", current = %" PRIu64,
+ stream->last_sequence_number, seq);
+ ret = -1;
+ goto end;
+ }
+ stream->last_sequence_number = seq;
+
+ ret = ustctl_get_events_discarded(stream->ustream, &discarded);
+ if (ret < 0) {
+ PERROR("kernctl_get_events_discarded");
+ goto end;
+ }
+ if (discarded < stream->last_discarded_events) {
+ /*
+ * Overflow has occurred. We assume only one wrap-around
+ * has occurred.
+ */
+ stream->chan->discarded_events +=
+ (1ULL << (CAA_BITS_PER_LONG - 1)) -
+ stream->last_discarded_events + discarded;
+ } else {
+ stream->chan->discarded_events += discarded -
+ stream->last_discarded_events;
+ }
+ stream->last_discarded_events = discarded;
+ ret = 0;
+
+end:
+ return ret;
+}
+
+/*
+ * Read subbuffer from the given stream.
+ *
+ * Stream and channel locks MUST be acquired by the caller.
+ *
+ * Return 0 on success else a negative value.
+ */
+int lttng_ustconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
+ struct lttng_consumer_local_data *ctx)
+{
+ unsigned long len, subbuf_size, padding;
+ int err, write_index = 1, rotation_ret;
+ long ret = 0;
+ struct ustctl_consumer_stream *ustream;
+ struct ctf_packet_index index;
+
+ assert(stream);
+ assert(stream->ustream);
+ assert(ctx);
+
+ DBG("In UST read_subbuffer (wait_fd: %d, name: %s)", stream->wait_fd,
+ stream->name);
+
+ /* Ease our life for what's next. */
+ ustream = stream->ustream;
+
+ /*
+ * We can consume the 1 byte written into the wait_fd by UST. Don't trigger
+ * error if we cannot read this one byte (read returns 0), or if the error
+ * is EAGAIN or EWOULDBLOCK.
+ *
+ * This is only done when the stream is monitored by a thread, before the
+ * flush is done after a hangup and if the stream is not flagged with data
+ * since there might be nothing to consume in the wait fd but still have
+ * data available flagged by the consumer wake up pipe.
+ */
+ if (stream->monitor && !stream->hangup_flush_done && !stream->has_data) {
+ char dummy;
+ ssize_t readlen;
+
+ readlen = lttng_read(stream->wait_fd, &dummy, 1);
+ if (readlen < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
+ ret = readlen;
+ goto error;
+ }
+ }
+
+ /*
+ * If the stream was flagged to be ready for rotation before we extract the
+ * next packet, rotate it now.
+ */
+ if (stream->rotate_ready) {
+ DBG("Rotate stream before extracting data");
+ rotation_ret = lttng_consumer_rotate_stream(ctx, stream);
+ if (rotation_ret < 0) {
+ ERR("Stream rotation error");
+ ret = -1;
+ goto error;
+ }
+ }
+
+retry:
+ /* Get the next subbuffer */
+ err = ustctl_get_next_subbuf(ustream);
+ if (err != 0) {
+ /*
+ * Populate metadata info if the existing info has
+ * already been read.
+ */
+ if (stream->metadata_flag) {
+ ret = commit_one_metadata_packet(stream);
+ if (ret <= 0) {
+ goto error;
+ }
+ goto retry;
+ }
+
+ ret = err; /* ustctl_get_next_subbuf returns negative, caller expect positive. */
+ /*
+ * This is a debug message even for single-threaded consumer,
+ * because poll() have more relaxed criterions than get subbuf,
+ * so get_subbuf may fail for short race windows where poll()
+ * would issue wakeups.
+ */
+ DBG("Reserving sub buffer failed (everything is normal, "
+ "it is due to concurrency) [ret: %d]", err);
+ goto error;
+ }
+ assert(stream->chan->output == CONSUMER_CHANNEL_MMAP);
+
+ if (!stream->metadata_flag) {
+ index.offset = htobe64(stream->out_fd_offset);
+ ret = get_index_values(&index, ustream);
+ if (ret < 0) {
+ err = ustctl_put_subbuf(ustream);
+ assert(err == 0);
+ goto error;
+ }
+
+ /* Update the stream's sequence and discarded events count. */
+ ret = update_stream_stats(stream);
+ if (ret < 0) {
+ PERROR("kernctl_get_events_discarded");
+ err = ustctl_put_subbuf(ustream);
+ assert(err == 0);
+ goto error;
+ }
+ } else {
+ write_index = 0;
+ }
+
+ /* Get the full padded subbuffer size */
+ err = ustctl_get_padded_subbuf_size(ustream, &len);
+ assert(err == 0);
+
+ /* Get subbuffer data size (without padding) */
+ err = ustctl_get_subbuf_size(ustream, &subbuf_size);
+ assert(err == 0);