Fix: consumer-stream: live viewers observe timestamps going backwards

[lttng-tools.git] / src / common / consumer / consumer-stream.cpp

/*
 * Copyright (C) 2011 Julien Desfossez <julien.desfossez@polymtl.ca>
 * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 * Copyright (C) 2013 David Goulet <dgoulet@efficios.com>
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 */

#define _LGPL_SOURCE
#include <inttypes.h>
#include <sys/mman.h>
#include <unistd.h>

#include <common/common.h>
#include <common/consumer/consumer-timer.h>
#include <common/consumer/consumer-timer.h>
#include <common/consumer/consumer.h>
#include <common/consumer/consumer.h>
#include <common/consumer/metadata-bucket.h>
#include <common/consumer/metadata-bucket.h>
#include <common/index/index.h>
#include <common/kernel-consumer/kernel-consumer.h>
#include <common/kernel-ctl/kernel-ctl.h>
#include <common/macros.h>
#include <common/relayd/relayd.h>
#include <common/ust-consumer/ust-consumer.h>
#include <common/utils.h>

#include "consumer-stream.h"

/*
 * RCU call to free stream. MUST only be used with call_rcu().
 */
static void free_stream_rcu(struct rcu_head *head)
{
	struct lttng_ht_node_u64 *node =
		caa_container_of(head, struct lttng_ht_node_u64, head);
	struct lttng_consumer_stream *stream =
		caa_container_of(node, struct lttng_consumer_stream, node);

	pthread_mutex_destroy(&stream->lock);
	free(stream);
}

static void consumer_stream_data_lock_all(struct lttng_consumer_stream *stream)
{
	pthread_mutex_lock(&stream->chan->lock);
	pthread_mutex_lock(&stream->lock);
}

static void consumer_stream_data_unlock_all(struct lttng_consumer_stream *stream)
{
	pthread_mutex_unlock(&stream->lock);
	pthread_mutex_unlock(&stream->chan->lock);
}

static void consumer_stream_data_assert_locked_all(struct lttng_consumer_stream *stream)
{
	ASSERT_LOCKED(stream->lock);
	ASSERT_LOCKED(stream->chan->lock);
}

static void consumer_stream_metadata_lock_all(struct lttng_consumer_stream *stream)
{
	consumer_stream_data_lock_all(stream);
	pthread_mutex_lock(&stream->metadata_rdv_lock);
}

static void consumer_stream_metadata_unlock_all(struct lttng_consumer_stream *stream)
{
	pthread_mutex_unlock(&stream->metadata_rdv_lock);
	consumer_stream_data_unlock_all(stream);
}

static void consumer_stream_metadata_assert_locked_all(struct lttng_consumer_stream *stream)
{
	ASSERT_LOCKED(stream->metadata_rdv_lock);
	consumer_stream_data_assert_locked_all(stream);
}

/* Only used for data streams. */
static int consumer_stream_update_stats(struct lttng_consumer_stream *stream,
		const struct stream_subbuffer *subbuf)
{
	int ret = 0;
	uint64_t sequence_number;
	const uint64_t discarded_events = subbuf->info.data.events_discarded;

	if (!subbuf->info.data.sequence_number.is_set) {
		/* Command not supported by the tracer. */
		sequence_number = -1ULL;
		stream->sequence_number_unavailable = true;
	} else {
		sequence_number = subbuf->info.data.sequence_number.value;
	}

	/*
	 * 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 = sequence_number;
	} else if (sequence_number > stream->last_sequence_number) {
		stream->chan->lost_packets += sequence_number -
				stream->last_sequence_number - 1;
	} else {
		/* seq <= last_sequence_number */
		ERR("Sequence number inconsistent : prev = %" PRIu64
		    ", current = %" PRIu64,
				stream->last_sequence_number, sequence_number);
		ret = -1;
		goto end;
	}
	stream->last_sequence_number = sequence_number;

	if (discarded_events < 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_events;
	} else {
		stream->chan->discarded_events += discarded_events -
						  stream->last_discarded_events;
	}
	stream->last_discarded_events = discarded_events;
	ret = 0;

end:
	return ret;
}

static
void ctf_packet_index_populate(struct ctf_packet_index *index,
		off_t offset, const struct stream_subbuffer *subbuffer)
{
	*index = (typeof(*index)){
		.offset = htobe64(offset),
		.packet_size = htobe64(subbuffer->info.data.packet_size),
		.content_size = htobe64(subbuffer->info.data.content_size),
		.timestamp_begin = htobe64(
				subbuffer->info.data.timestamp_begin),
		.timestamp_end = htobe64(
				subbuffer->info.data.timestamp_end),
		.events_discarded = htobe64(
				subbuffer->info.data.events_discarded),
		.stream_id = htobe64(subbuffer->info.data.stream_id),
		.stream_instance_id = htobe64(
				subbuffer->info.data.stream_instance_id.is_set ?
				subbuffer->info.data.stream_instance_id.value : -1ULL),
		.packet_seq_num = htobe64(
				subbuffer->info.data.sequence_number.is_set ?
				subbuffer->info.data.sequence_number.value : -1ULL),
	};
}

static ssize_t consumer_stream_consume_mmap(
		struct lttng_consumer_local_data *ctx,
		struct lttng_consumer_stream *stream,
		const struct stream_subbuffer *subbuffer)
{
	const unsigned long padding_size =
			subbuffer->info.data.padded_subbuf_size -
			subbuffer->info.data.subbuf_size;
	const ssize_t written_bytes = lttng_consumer_on_read_subbuffer_mmap(
			stream, &subbuffer->buffer.buffer, padding_size);

	if (stream->net_seq_idx == -1ULL) {
		/*
		 * When writing on disk, check that only the subbuffer (no
		 * padding) was written to disk.
		 */
		if (written_bytes != subbuffer->info.data.padded_subbuf_size) {
			DBG("Failed to write the entire padded subbuffer on disk (written_bytes: %zd, padded subbuffer size %lu)",
					written_bytes,
					subbuffer->info.data.padded_subbuf_size);
		}
	} else {
		/*
		 * When streaming over the network, check that the entire
		 * subbuffer including padding was successfully written.
		 */
		if (written_bytes != subbuffer->info.data.subbuf_size) {
			DBG("Failed to write only the subbuffer over the network (written_bytes: %zd, subbuffer size %lu)",
					written_bytes,
					subbuffer->info.data.subbuf_size);
		}
	}

	/*
	 * If `lttng_consumer_on_read_subbuffer_mmap()` returned an error, pass
	 * it along to the caller, else return zero.
	 */
	if (written_bytes < 0) {
		ERR("Error reading mmap subbuffer: %zd", written_bytes);
	}

	return written_bytes;
}

static ssize_t consumer_stream_consume_splice(
		struct lttng_consumer_local_data *ctx,
		struct lttng_consumer_stream *stream,
		const struct stream_subbuffer *subbuffer)
{
	const ssize_t written_bytes = lttng_consumer_on_read_subbuffer_splice(
			ctx, stream, subbuffer->info.data.padded_subbuf_size, 0);

	if (written_bytes != subbuffer->info.data.padded_subbuf_size) {
		DBG("Failed to write the entire padded subbuffer (written_bytes: %zd, padded subbuffer size %lu)",
				written_bytes,
				subbuffer->info.data.padded_subbuf_size);
	}

	/*
	 * If `lttng_consumer_on_read_subbuffer_splice()` returned an error,
	 * pass it along to the caller, else return zero.
	 */
	if (written_bytes < 0) {
		ERR("Error reading splice subbuffer: %zd", written_bytes);
	}

	return written_bytes;
}

static int consumer_stream_send_index(
		struct lttng_consumer_stream *stream,
		const struct stream_subbuffer *subbuffer,
		struct lttng_consumer_local_data *ctx)
{
	off_t packet_offset = 0;
	struct ctf_packet_index index = {};

	/*
	 * This is called after consuming the sub-buffer; substract the
	 * effect this sub-buffer from the offset.
	 */
	if (stream->net_seq_idx == (uint64_t) -1ULL) {
		packet_offset = stream->out_fd_offset -
				subbuffer->info.data.padded_subbuf_size;
	}

	ctf_packet_index_populate(&index, packet_offset, subbuffer);
	return consumer_stream_write_index(stream, &index);
}

/*
 * Actually do the metadata sync using the given metadata stream.
 *
 * Return 0 on success else a negative value. ENODATA can be returned also
 * indicating that there is no metadata available for that stream.
 */
static int do_sync_metadata(struct lttng_consumer_stream *metadata,
		struct lttng_consumer_local_data *ctx)
{
	int ret;
	enum sync_metadata_status status;

	LTTNG_ASSERT(metadata);
	LTTNG_ASSERT(metadata->metadata_flag);
	LTTNG_ASSERT(ctx);

	/*
	 * In UST, since we have to write the metadata from the cache packet
	 * by packet, we might need to start this procedure multiple times
	 * until all the metadata from the cache has been extracted.
	 */
	do {
		/*
		 * Steps :
		 * - Lock the metadata stream
		 * - Check if metadata stream node was deleted before locking.
		 *   - if yes, release and return success
		 * - Check if new metadata is ready (flush + snapshot pos)
		 * - If nothing : release and return.
		 * - Lock the metadata_rdv_lock
		 * - Unlock the metadata stream
		 * - cond_wait on metadata_rdv to wait the wakeup from the
		 *   metadata thread
		 * - Unlock the metadata_rdv_lock
		 */
		pthread_mutex_lock(&metadata->lock);

		/*
		 * There is a possibility that we were able to acquire a reference on the
		 * stream from the RCU hash table but between then and now, the node might
		 * have been deleted just before the lock is acquired. Thus, after locking,
		 * we make sure the metadata node has not been deleted which means that the
		 * buffers are closed.
		 *
		 * In that case, there is no need to sync the metadata hence returning a
		 * success return code.
		 */
		ret = cds_lfht_is_node_deleted(&metadata->node.node);
		if (ret) {
			ret = 0;
			goto end_unlock_mutex;
		}

		switch (ctx->type) {
		case LTTNG_CONSUMER_KERNEL:
			/*
			 * Empty the metadata cache and flush the current stream.
			 */
			status = lttng_kconsumer_sync_metadata(metadata);
			break;
		case LTTNG_CONSUMER32_UST:
		case LTTNG_CONSUMER64_UST:
			/*
			 * Ask the sessiond if we have new metadata waiting and update the
			 * consumer metadata cache.
			 */
			status = lttng_ustconsumer_sync_metadata(ctx, metadata);
			break;
		default:
			abort();
		}

		switch (status) {
		case SYNC_METADATA_STATUS_NEW_DATA:
			break;
		case SYNC_METADATA_STATUS_NO_DATA:
			ret = 0;
			goto end_unlock_mutex;
		case SYNC_METADATA_STATUS_ERROR:
			ret = -1;
			goto end_unlock_mutex;
		default:
			abort();
		}

		/*
		 * At this point, new metadata have been flushed, so we wait on the
		 * rendez-vous point for the metadata thread to wake us up when it
		 * finishes consuming the metadata and continue execution.
		 */

		pthread_mutex_lock(&metadata->metadata_rdv_lock);

		/*
		 * Release metadata stream lock so the metadata thread can process it.
		 */
		pthread_mutex_unlock(&metadata->lock);

		/*
		 * Wait on the rendez-vous point. Once woken up, it means the metadata was
		 * consumed and thus synchronization is achieved.
		 */
		pthread_cond_wait(&metadata->metadata_rdv, &metadata->metadata_rdv_lock);
		pthread_mutex_unlock(&metadata->metadata_rdv_lock);
	} while (status == SYNC_METADATA_STATUS_NEW_DATA);

	/* Success */
	return 0;

end_unlock_mutex:
	pthread_mutex_unlock(&metadata->lock);
	return ret;
}

/*
 * Synchronize the metadata using a given session ID. A successful acquisition
 * of a metadata stream will trigger a request to the session daemon and a
 * snapshot so the metadata thread can consume it.
 *
 * This function call is a rendez-vous point between the metadata thread and
 * the data thread.
 *
 * Return 0 on success or else a negative value.
 */
int consumer_stream_sync_metadata(struct lttng_consumer_local_data *ctx,
		uint64_t session_id)
{
	int ret;
	struct lttng_consumer_stream *stream = NULL;
	struct lttng_ht_iter iter;
	struct lttng_ht *ht;

	LTTNG_ASSERT(ctx);

	/* Ease our life a bit. */
	ht = the_consumer_data.stream_list_ht;

	rcu_read_lock();

	/* Search the metadata associated with the session id of the given stream. */

	cds_lfht_for_each_entry_duplicate(ht->ht,
			ht->hash_fct(&session_id, lttng_ht_seed), ht->match_fct,
			&session_id, &iter.iter, stream, node_session_id.node) {
		if (!stream->metadata_flag) {
			continue;
		}

		ret = do_sync_metadata(stream, ctx);
		if (ret < 0) {
			goto end;
		}
	}

	/*
	 * Force return code to 0 (success) since ret might be ENODATA for instance
	 * which is not an error but rather that we should come back.
	 */
	ret = 0;

end:
	rcu_read_unlock();
	return ret;
}

static int consumer_stream_sync_metadata_index(
		struct lttng_consumer_stream *stream,
		const struct stream_subbuffer *subbuffer,
		struct lttng_consumer_local_data *ctx)
{
	bool missed_metadata_flush;
	int ret;

	/* Block until all the metadata is sent. */
	pthread_mutex_lock(&stream->metadata_timer_lock);
	LTTNG_ASSERT(!stream->missed_metadata_flush);
	stream->waiting_on_metadata = true;
	pthread_mutex_unlock(&stream->metadata_timer_lock);

	ret = consumer_stream_sync_metadata(ctx, stream->session_id);

	pthread_mutex_lock(&stream->metadata_timer_lock);
	stream->waiting_on_metadata = false;
	missed_metadata_flush = stream->missed_metadata_flush;
	if (missed_metadata_flush) {
		stream->missed_metadata_flush = false;
	}
	pthread_mutex_unlock(&stream->metadata_timer_lock);
	if (ret < 0) {
		goto end;
	}

	ret = consumer_stream_send_index(stream, subbuffer, ctx);
	/*
	 * Send the live inactivity beacon to handle the situation where
	 * the live timer is prevented from sampling this stream
	 * because the stream lock was being held while this stream is
	 * waiting on metadata. This ensures live viewer progress in the
	 * unlikely scenario where a live timer would be prevented from
	 * locking a stream lock repeatedly due to a steady flow of
	 * incoming metadata, for a stream which is mostly inactive.
	 *
	 * It is important to send the inactivity beacon packet to
	 * relayd _after_ sending the index associated with the data
	 * that was just sent, otherwise this can cause live viewers to
	 * observe timestamps going backwards between an inactivity
	 * beacon and a following trace packet.
	 */
	if (missed_metadata_flush) {
		(void) stream->read_subbuffer_ops.send_live_beacon(stream);
	}
end:
	return ret;
}

/*
 * Check if the local version of the metadata stream matches with the version
 * of the metadata stream in the kernel. If it was updated, set the reset flag
 * on the stream.
 */
static
int metadata_stream_check_version(struct lttng_consumer_stream *stream,
	const struct stream_subbuffer *subbuffer)
{
	if (stream->metadata_version == subbuffer->info.metadata.version) {
		goto end;
	}

	DBG("New metadata version detected");
	consumer_stream_metadata_set_version(stream,
			subbuffer->info.metadata.version);

	if (stream->read_subbuffer_ops.reset_metadata) {
		stream->read_subbuffer_ops.reset_metadata(stream);
	}

end:
	return 0;
}

static
bool stream_is_rotating_to_null_chunk(
		const struct lttng_consumer_stream *stream)
{
	bool rotating_to_null_chunk = false;

	if (stream->rotate_position == -1ULL) {
		/* No rotation ongoing. */
		goto end;
	}

	if (stream->trace_chunk == stream->chan->trace_chunk ||
			!stream->chan->trace_chunk) {
		rotating_to_null_chunk = true;
	}
end:
	return rotating_to_null_chunk;
}

enum consumer_stream_open_packet_status consumer_stream_open_packet(
		struct lttng_consumer_stream *stream)
{
	int ret;
	enum consumer_stream_open_packet_status status;
	unsigned long produced_pos_before, produced_pos_after;

	ret = lttng_consumer_sample_snapshot_positions(stream);
	if (ret < 0) {
		ERR("Failed to snapshot positions before post-rotation empty packet flush: stream id = %" PRIu64
				", channel name = %s, session id = %" PRIu64,
				stream->key, stream->chan->name,
				stream->chan->session_id);
		status = CONSUMER_STREAM_OPEN_PACKET_STATUS_ERROR;
		goto end;
	}

	ret = lttng_consumer_get_produced_snapshot(
			stream, &produced_pos_before);
	if (ret < 0) {
		ERR("Failed to read produced position before post-rotation empty packet flush: stream id = %" PRIu64
				", channel name = %s, session id = %" PRIu64,
				stream->key, stream->chan->name,
				stream->chan->session_id);
		status = CONSUMER_STREAM_OPEN_PACKET_STATUS_ERROR;
		goto end;
	}

	ret = consumer_stream_flush_buffer(stream, 0);
	if (ret) {
		ERR("Failed to flush an empty packet at rotation point: stream id = %" PRIu64
				", channel name = %s, session id = %" PRIu64,
				stream->key, stream->chan->name,
				stream->chan->session_id);
		status = CONSUMER_STREAM_OPEN_PACKET_STATUS_ERROR;
		goto end;
	}

	ret = lttng_consumer_sample_snapshot_positions(stream);
	if (ret < 0) {
		ERR("Failed to snapshot positions after post-rotation empty packet flush: stream id = %" PRIu64
				", channel name = %s, session id = %" PRIu64,
				stream->key, stream->chan->name,
				stream->chan->session_id);
		status = CONSUMER_STREAM_OPEN_PACKET_STATUS_ERROR;
		goto end;
	}

	ret = lttng_consumer_get_produced_snapshot(stream, &produced_pos_after);
	if (ret < 0) {
		ERR("Failed to read produced position after post-rotation empty packet flush: stream id = %" PRIu64
				", channel name = %s, session id = %" PRIu64,
				stream->key, stream->chan->name,
				stream->chan->session_id);
		status = CONSUMER_STREAM_OPEN_PACKET_STATUS_ERROR;
		goto end;
	}

	/*
	 * Determine if the flush had an effect by comparing the produced
	 * positons before and after the flush.
	 */
	status = produced_pos_before != produced_pos_after ?
			CONSUMER_STREAM_OPEN_PACKET_STATUS_OPENED :
			CONSUMER_STREAM_OPEN_PACKET_STATUS_NO_SPACE;
	if (status == CONSUMER_STREAM_OPEN_PACKET_STATUS_OPENED) {
		stream->opened_packet_in_current_trace_chunk = true;
	}

end:
	return status;
}

/*
 * An attempt to open a new packet is performed after a rotation completes to
 * get a begin timestamp as close as possible to the rotation point.
 *
 * However, that initial attempt at opening a packet can fail due to a full
 * ring-buffer. In that case, a second attempt is performed after consuming
 * a packet since that will have freed enough space in the ring-buffer.
 */
static
int post_consume_open_new_packet(struct lttng_consumer_stream *stream,
		const struct stream_subbuffer *subbuffer,
		struct lttng_consumer_local_data *ctx)
{
	int ret = 0;

	if (!stream->opened_packet_in_current_trace_chunk &&
			stream->trace_chunk &&
			!stream_is_rotating_to_null_chunk(stream)) {
		const enum consumer_stream_open_packet_status status =
				consumer_stream_open_packet(stream);

		switch (status) {
		case CONSUMER_STREAM_OPEN_PACKET_STATUS_OPENED:
			DBG("Opened a packet after consuming a packet rotation: stream id = %" PRIu64
					", channel name = %s, session id = %" PRIu64,
					stream->key, stream->chan->name,
					stream->chan->session_id);
			stream->opened_packet_in_current_trace_chunk = true;
			break;
		case CONSUMER_STREAM_OPEN_PACKET_STATUS_NO_SPACE:
			/*
			 * Can't open a packet as there is no space left.
			 * This means that new events were produced, resulting
			 * in a packet being opened, which is what we want
			 * anyhow.
			 */
			DBG("No space left to open a packet after consuming a packet: stream id = %" PRIu64
					", channel name = %s, session id = %" PRIu64,
					stream->key, stream->chan->name,
					stream->chan->session_id);
			stream->opened_packet_in_current_trace_chunk = true;
			break;
		case CONSUMER_STREAM_OPEN_PACKET_STATUS_ERROR:
			/* Logged by callee. */
			ret = -1;
			goto end;
		default:
			abort();
		}

		stream->opened_packet_in_current_trace_chunk = true;
	}

end:
	return ret;
}

struct lttng_consumer_stream *consumer_stream_create(
		struct lttng_consumer_channel *channel,
		uint64_t channel_key,
		uint64_t stream_key,
		const char *channel_name,
		uint64_t relayd_id,
		uint64_t session_id,
		struct lttng_trace_chunk *trace_chunk,
		int cpu,
		int *alloc_ret,
		enum consumer_channel_type type,
		unsigned int monitor)
{
	int ret;
	struct lttng_consumer_stream *stream;

	stream = (lttng_consumer_stream *) zmalloc(sizeof(*stream));
	if (stream == NULL) {
		PERROR("malloc struct lttng_consumer_stream");
		ret = -ENOMEM;
		goto end;
	}

	rcu_read_lock();

	if (trace_chunk && !lttng_trace_chunk_get(trace_chunk)) {
		ERR("Failed to acquire trace chunk reference during the creation of a stream");
		ret = -1;
		goto error;
	}

	stream->chan = channel;
	stream->key = stream_key;
	stream->trace_chunk = trace_chunk;
	stream->out_fd = -1;
	stream->out_fd_offset = 0;
	stream->output_written = 0;
	stream->net_seq_idx = relayd_id;
	stream->session_id = session_id;
	stream->monitor = monitor;
	stream->endpoint_status = CONSUMER_ENDPOINT_ACTIVE;
	stream->index_file = NULL;
	stream->last_sequence_number = -1ULL;
	stream->rotate_position = -1ULL;
	/* Buffer is created with an open packet. */
	stream->opened_packet_in_current_trace_chunk = true;
	pthread_mutex_init(&stream->lock, NULL);
	pthread_mutex_init(&stream->metadata_timer_lock, NULL);

	/* If channel is the metadata, flag this stream as metadata. */
	if (type == CONSUMER_CHANNEL_TYPE_METADATA) {
		stream->metadata_flag = 1;
		/* Metadata is flat out. */
		strncpy(stream->name, DEFAULT_METADATA_NAME, sizeof(stream->name));
		/* Live rendez-vous point. */
		pthread_cond_init(&stream->metadata_rdv, NULL);
		pthread_mutex_init(&stream->metadata_rdv_lock, NULL);
	} else {
		/* Format stream name to <channel_name>_<cpu_number> */
		ret = snprintf(stream->name, sizeof(stream->name), "%s_%d",
				channel_name, cpu);
		if (ret < 0) {
			PERROR("snprintf stream name");
			goto error;
		}
	}

	switch (channel->output) {
	case CONSUMER_CHANNEL_SPLICE:
		stream->output = LTTNG_EVENT_SPLICE;
		ret = utils_create_pipe(stream->splice_pipe);
		if (ret < 0) {
			goto error;
		}
		break;
	case CONSUMER_CHANNEL_MMAP:
		stream->output = LTTNG_EVENT_MMAP;
		break;
	default:
		abort();
	}

	/* Key is always the wait_fd for streams. */
	lttng_ht_node_init_u64(&stream->node, stream->key);

	/* Init node per channel id key */
	lttng_ht_node_init_u64(&stream->node_channel_id, channel_key);

	/* Init session id node with the stream session id */
	lttng_ht_node_init_u64(&stream->node_session_id, stream->session_id);

	DBG3("Allocated stream %s (key %" PRIu64 ", chan_key %" PRIu64
			" relayd_id %" PRIu64 ", session_id %" PRIu64,
			stream->name, stream->key, channel_key,
			stream->net_seq_idx, stream->session_id);

	rcu_read_unlock();

	lttng_dynamic_array_init(&stream->read_subbuffer_ops.post_consume_cbs,
			sizeof(post_consume_cb), NULL);

	if (type == CONSUMER_CHANNEL_TYPE_METADATA) {
		stream->read_subbuffer_ops.lock =
				consumer_stream_metadata_lock_all;
		stream->read_subbuffer_ops.unlock =
				consumer_stream_metadata_unlock_all;
		stream->read_subbuffer_ops.assert_locked =
				consumer_stream_metadata_assert_locked_all;
		stream->read_subbuffer_ops.pre_consume_subbuffer =
				metadata_stream_check_version;
	} else {
		const post_consume_cb post_consume_index_op = channel->is_live ?
				consumer_stream_sync_metadata_index :
				consumer_stream_send_index;
		const post_consume_cb post_consume_open_new_packet_ =
				post_consume_open_new_packet;

		ret = lttng_dynamic_array_add_element(
				&stream->read_subbuffer_ops.post_consume_cbs,
				&post_consume_index_op);
		if (ret) {
			PERROR("Failed to add `send index` callback to stream's post consumption callbacks");
			goto error;
		}

		ret = lttng_dynamic_array_add_element(
				&stream->read_subbuffer_ops.post_consume_cbs,
				&post_consume_open_new_packet_);
		if (ret) {
			PERROR("Failed to add `open new packet` callback to stream's post consumption callbacks");
			goto error;
		}

		stream->read_subbuffer_ops.lock = consumer_stream_data_lock_all;
		stream->read_subbuffer_ops.unlock =
				consumer_stream_data_unlock_all;
		stream->read_subbuffer_ops.assert_locked =
				consumer_stream_data_assert_locked_all;
		stream->read_subbuffer_ops.pre_consume_subbuffer =
				consumer_stream_update_stats;
	}

	if (channel->output == CONSUMER_CHANNEL_MMAP) {
		stream->read_subbuffer_ops.consume_subbuffer =
				consumer_stream_consume_mmap;
	} else {
		stream->read_subbuffer_ops.consume_subbuffer =
				consumer_stream_consume_splice;
	}

	return stream;

error:
	rcu_read_unlock();
	lttng_trace_chunk_put(stream->trace_chunk);
	lttng_dynamic_array_reset(&stream->read_subbuffer_ops.post_consume_cbs);
	free(stream);
end:
	if (alloc_ret) {
		*alloc_ret = ret;
	}
	return NULL;
}

/*
 * Close stream on the relayd side. This call can destroy a relayd if the
 * conditions are met.
 *
 * A RCU read side lock MUST be acquired if the relayd object was looked up in
 * a hash table before calling this.
 */
void consumer_stream_relayd_close(struct lttng_consumer_stream *stream,
		struct consumer_relayd_sock_pair *relayd)
{
	int ret;

	LTTNG_ASSERT(stream);
	LTTNG_ASSERT(relayd);

	if (stream->sent_to_relayd) {
		uatomic_dec(&relayd->refcount);
		LTTNG_ASSERT(uatomic_read(&relayd->refcount) >= 0);
	}

	/* Closing streams requires to lock the control socket. */
	pthread_mutex_lock(&relayd->ctrl_sock_mutex);
	ret = relayd_send_close_stream(&relayd->control_sock,
			stream->relayd_stream_id,
			stream->next_net_seq_num - 1);
	pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
	if (ret < 0) {
		ERR("Relayd send close stream failed. Cleaning up relayd %" PRIu64 ".", relayd->net_seq_idx);
		lttng_consumer_cleanup_relayd(relayd);
	}

	/* Both conditions are met, we destroy the relayd. */
	if (uatomic_read(&relayd->refcount) == 0 &&
			uatomic_read(&relayd->destroy_flag)) {
		consumer_destroy_relayd(relayd);
	}
	stream->net_seq_idx = (uint64_t) -1ULL;
	stream->sent_to_relayd = 0;
}

/*
 * Close stream's file descriptors and, if needed, close stream also on the
 * relayd side.
 *
 * The consumer data lock MUST be acquired.
 * The stream lock MUST be acquired.
 */
void consumer_stream_close(struct lttng_consumer_stream *stream)
{
	int ret;
	struct consumer_relayd_sock_pair *relayd;

	LTTNG_ASSERT(stream);

	switch (the_consumer_data.type) {
	case LTTNG_CONSUMER_KERNEL:
		if (stream->mmap_base != NULL) {
			ret = munmap(stream->mmap_base, stream->mmap_len);
			if (ret != 0) {
				PERROR("munmap");
			}
		}

		if (stream->wait_fd >= 0) {
			ret = close(stream->wait_fd);
			if (ret) {
				PERROR("close");
			}
			stream->wait_fd = -1;
		}
		if (stream->chan->output == CONSUMER_CHANNEL_SPLICE) {
			utils_close_pipe(stream->splice_pipe);
		}
		break;
	case LTTNG_CONSUMER32_UST:
	case LTTNG_CONSUMER64_UST:
	{
		/*
		 * Special case for the metadata since the wait fd is an internal pipe
		 * polled in the metadata thread.
		 */
		if (stream->metadata_flag && stream->chan->monitor) {
			int rpipe = stream->ust_metadata_poll_pipe[0];

			/*
			 * This will stop the channel timer if one and close the write side
			 * of the metadata poll pipe.
			 */
			lttng_ustconsumer_close_metadata(stream->chan);
			if (rpipe >= 0) {
				ret = close(rpipe);
				if (ret < 0) {
					PERROR("closing metadata pipe read side");
				}
				stream->ust_metadata_poll_pipe[0] = -1;
			}
		}
		break;
	}
	default:
		ERR("Unknown consumer_data type");
		abort();
	}

	/* Close output fd. Could be a socket or local file at this point. */
	if (stream->out_fd >= 0) {
		ret = close(stream->out_fd);
		if (ret) {
			PERROR("close");
		}
		stream->out_fd = -1;
	}

	if (stream->index_file) {
		lttng_index_file_put(stream->index_file);
		stream->index_file = NULL;
	}

	lttng_trace_chunk_put(stream->trace_chunk);
	stream->trace_chunk = NULL;

	/* Check and cleanup relayd if needed. */
	rcu_read_lock();
	relayd = consumer_find_relayd(stream->net_seq_idx);
	if (relayd != NULL) {
		consumer_stream_relayd_close(stream, relayd);
	}
	rcu_read_unlock();
}

/*
 * Delete the stream from all possible hash tables.
 *
 * The consumer data lock MUST be acquired.
 * The stream lock MUST be acquired.
 */
void consumer_stream_delete(struct lttng_consumer_stream *stream,
		struct lttng_ht *ht)
{
	int ret;
	struct lttng_ht_iter iter;

	LTTNG_ASSERT(stream);
	/* Should NEVER be called not in monitor mode. */
	LTTNG_ASSERT(stream->chan->monitor);

	rcu_read_lock();

	if (ht) {
		iter.iter.node = &stream->node.node;
		ret = lttng_ht_del(ht, &iter);
		LTTNG_ASSERT(!ret);
	}

	/* Delete from stream per channel ID hash table. */
	iter.iter.node = &stream->node_channel_id.node;
	/*
	 * The returned value is of no importance. Even if the node is NOT in the
	 * hash table, we continue since we may have been called by a code path
	 * that did not add the stream to a (all) hash table. Same goes for the
	 * next call ht del call.
	 */
	(void) lttng_ht_del(the_consumer_data.stream_per_chan_id_ht, &iter);

	/* Delete from the global stream list. */
	iter.iter.node = &stream->node_session_id.node;
	/* See the previous ht del on why we ignore the returned value. */
	(void) lttng_ht_del(the_consumer_data.stream_list_ht, &iter);

	rcu_read_unlock();

	if (!stream->metadata_flag) {
		/* Decrement the stream count of the global consumer data. */
		LTTNG_ASSERT(the_consumer_data.stream_count > 0);
		the_consumer_data.stream_count--;
	}
}

/*
 * Free the given stream within a RCU call.
 */
void consumer_stream_free(struct lttng_consumer_stream *stream)
{
	LTTNG_ASSERT(stream);

	metadata_bucket_destroy(stream->metadata_bucket);
	call_rcu(&stream->node.head, free_stream_rcu);
}

/*
 * Destroy the stream's buffers of the tracer.
 */
void consumer_stream_destroy_buffers(struct lttng_consumer_stream *stream)
{
	LTTNG_ASSERT(stream);

	switch (the_consumer_data.type) {
	case LTTNG_CONSUMER_KERNEL:
		break;
	case LTTNG_CONSUMER32_UST:
	case LTTNG_CONSUMER64_UST:
		lttng_ustconsumer_del_stream(stream);
		break;
	default:
		ERR("Unknown consumer_data type");
		abort();
	}
}

/*
 * Destroy and close a already created stream.
 */
static void destroy_close_stream(struct lttng_consumer_stream *stream)
{
	LTTNG_ASSERT(stream);

	DBG("Consumer stream destroy monitored key: %" PRIu64, stream->key);

	/* Destroy tracer buffers of the stream. */
	consumer_stream_destroy_buffers(stream);
	/* Close down everything including the relayd if one. */
	consumer_stream_close(stream);
}

/*
 * Decrement the stream's channel refcount and if down to 0, return the channel
 * pointer so it can be destroyed by the caller or NULL if not.
 */
static struct lttng_consumer_channel *unref_channel(
		struct lttng_consumer_stream *stream)
{
	struct lttng_consumer_channel *free_chan = NULL;

	LTTNG_ASSERT(stream);
	LTTNG_ASSERT(stream->chan);

	/* Update refcount of channel and see if we need to destroy it. */
	if (!uatomic_sub_return(&stream->chan->refcount, 1)
			&& !uatomic_read(&stream->chan->nb_init_stream_left)) {
		free_chan = stream->chan;
	}

	return free_chan;
}

/*
 * Destroy a stream completely. This will delete, close and free the stream.
 * Once return, the stream is NO longer usable. Its channel may get destroyed
 * if conditions are met for a monitored stream.
 *
 * This MUST be called WITHOUT the consumer data and stream lock acquired if
 * the stream is in _monitor_ mode else it does not matter.
 */
void consumer_stream_destroy(struct lttng_consumer_stream *stream,
		struct lttng_ht *ht)
{
	LTTNG_ASSERT(stream);

	/* Stream is in monitor mode. */
	if (stream->monitor) {
		struct lttng_consumer_channel *free_chan = NULL;

		/*
		 * This means that the stream was successfully removed from the streams
		 * list of the channel and sent to the right thread managing this
		 * stream thus being globally visible.
		 */
		if (stream->globally_visible) {
			pthread_mutex_lock(&the_consumer_data.lock);
			pthread_mutex_lock(&stream->chan->lock);
			pthread_mutex_lock(&stream->lock);
			/* Remove every reference of the stream in the consumer. */
			consumer_stream_delete(stream, ht);

			destroy_close_stream(stream);

			/* Update channel's refcount of the stream. */
			free_chan = unref_channel(stream);

			/* Indicates that the consumer data state MUST be updated after this. */
			the_consumer_data.need_update = 1;

			pthread_mutex_unlock(&stream->lock);
			pthread_mutex_unlock(&stream->chan->lock);
			pthread_mutex_unlock(&the_consumer_data.lock);
		} else {
			/*
			 * If the stream is not visible globally, this needs to be done
			 * outside of the consumer data lock section.
			 */
			free_chan = unref_channel(stream);
		}

		if (free_chan) {
			consumer_del_channel(free_chan);
		}
	} else {
		destroy_close_stream(stream);
	}

	/* Free stream within a RCU call. */
	lttng_trace_chunk_put(stream->trace_chunk);
	stream->trace_chunk = NULL;
	lttng_dynamic_array_reset(&stream->read_subbuffer_ops.post_consume_cbs);
	consumer_stream_free(stream);
}

/*
 * Write index of a specific stream either on the relayd or local disk.
 *
 * Return 0 on success or else a negative value.
 */
int consumer_stream_write_index(struct lttng_consumer_stream *stream,
		struct ctf_packet_index *element)
{
	int ret;

	LTTNG_ASSERT(stream);
	LTTNG_ASSERT(element);

	rcu_read_lock();
	if (stream->net_seq_idx != (uint64_t) -1ULL) {
		struct consumer_relayd_sock_pair *relayd;
		relayd = consumer_find_relayd(stream->net_seq_idx);
		if (relayd) {
			pthread_mutex_lock(&relayd->ctrl_sock_mutex);
			ret = relayd_send_index(&relayd->control_sock, element,
				stream->relayd_stream_id, stream->next_net_seq_num - 1);
			if (ret < 0) {
				/*
				 * Communication error with lttng-relayd,
				 * perform cleanup now
				 */
				ERR("Relayd send index failed. Cleaning up relayd %" PRIu64 ".", relayd->net_seq_idx);
				lttng_consumer_cleanup_relayd(relayd);
				ret = -1;
			}
			pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
		} else {
			ERR("Stream %" PRIu64 " relayd ID %" PRIu64 " unknown. Can't write index.",
					stream->key, stream->net_seq_idx);
			ret = -1;
		}
	} else {
		if (lttng_index_file_write(stream->index_file, element)) {
			ret = -1;
		} else {
			ret = 0;
		}
	}
	if (ret < 0) {
		goto error;
	}

error:
	rcu_read_unlock();
	return ret;
}

int consumer_stream_create_output_files(struct lttng_consumer_stream *stream,
		bool create_index)
{
	int ret;
	enum lttng_trace_chunk_status chunk_status;
	const int flags = O_WRONLY | O_CREAT | O_TRUNC;
	const mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP;
	char stream_path[LTTNG_PATH_MAX];

	ASSERT_LOCKED(stream->lock);
	LTTNG_ASSERT(stream->trace_chunk);

	ret = utils_stream_file_path(stream->chan->pathname, stream->name,
			stream->chan->tracefile_size,
			stream->tracefile_count_current, NULL,
			stream_path, sizeof(stream_path));
	if (ret < 0) {
		goto end;
	}

	if (stream->out_fd >= 0) {
		ret = close(stream->out_fd);
		if (ret < 0) {
			PERROR("Failed to close stream file \"%s\"",
					stream->name);
			goto end;
		}
		stream->out_fd = -1;
	}

	DBG("Opening stream output file \"%s\"", stream_path);
	chunk_status = lttng_trace_chunk_open_file(stream->trace_chunk, stream_path,
			flags, mode, &stream->out_fd, false);
	if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
		ERR("Failed to open stream file \"%s\"", stream->name);
		ret = -1;
		goto end;
	}

	if (!stream->metadata_flag && (create_index || stream->index_file)) {
		if (stream->index_file) {
			lttng_index_file_put(stream->index_file);
		}
		chunk_status = lttng_index_file_create_from_trace_chunk(
				stream->trace_chunk,
				stream->chan->pathname,
				stream->name,
				stream->chan->tracefile_size,
				stream->tracefile_count_current,
				CTF_INDEX_MAJOR, CTF_INDEX_MINOR,
				false, &stream->index_file);
		if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
			ret = -1;
			goto end;
		}
	}

	/* Reset current size because we just perform a rotation. */
	stream->tracefile_size_current = 0;
	stream->out_fd_offset = 0;
end:
	return ret;
}

int consumer_stream_rotate_output_files(struct lttng_consumer_stream *stream)
{
	int ret;

	stream->tracefile_count_current++;
	if (stream->chan->tracefile_count > 0) {
		stream->tracefile_count_current %=
				stream->chan->tracefile_count;
	}

	DBG("Rotating output files of stream \"%s\"", stream->name);
	ret = consumer_stream_create_output_files(stream, true);
	if (ret) {
		goto end;
	}

end:
	return ret;
}

bool consumer_stream_is_deleted(struct lttng_consumer_stream *stream)
{
	/*
	 * This function does not take a const stream since
	 * cds_lfht_is_node_deleted was not const before liburcu 0.12.
	 */
	LTTNG_ASSERT(stream);
	return cds_lfht_is_node_deleted(&stream->node.node);
}

static ssize_t metadata_bucket_flush(
		const struct stream_subbuffer *buffer, void *data)
{
	ssize_t ret;
	struct lttng_consumer_stream *stream = (lttng_consumer_stream *) data;

	ret = consumer_stream_consume_mmap(NULL, stream, buffer);
	if (ret < 0) {
		goto end;
	}
end:
	return ret;
}

static ssize_t metadata_bucket_consume(
		struct lttng_consumer_local_data *unused,
		struct lttng_consumer_stream *stream,
		const struct stream_subbuffer *subbuffer)
{
	ssize_t ret;
	enum metadata_bucket_status status;

	status = metadata_bucket_fill(stream->metadata_bucket, subbuffer);
	switch (status) {
	case METADATA_BUCKET_STATUS_OK:
		/* Return consumed size. */
		ret = subbuffer->buffer.buffer.size;
		break;
	default:
		ret = -1;
	}

	return ret;
}

int consumer_stream_enable_metadata_bucketization(
		struct lttng_consumer_stream *stream)
{
	int ret = 0;

	LTTNG_ASSERT(stream->metadata_flag);
	LTTNG_ASSERT(!stream->metadata_bucket);
	LTTNG_ASSERT(stream->chan->output == CONSUMER_CHANNEL_MMAP);

	stream->metadata_bucket = metadata_bucket_create(
			metadata_bucket_flush, stream);
	if (!stream->metadata_bucket) {
		ret = -1;
		goto end;
	}

	stream->read_subbuffer_ops.consume_subbuffer = metadata_bucket_consume;
end:
	return ret;
}

void consumer_stream_metadata_set_version(
		struct lttng_consumer_stream *stream, uint64_t new_version)
{
	LTTNG_ASSERT(new_version > stream->metadata_version);
	stream->metadata_version = new_version;
	stream->reset_metadata_flag = 1;

	if (stream->metadata_bucket) {
		metadata_bucket_reset(stream->metadata_bucket);
	}
}

int consumer_stream_flush_buffer(struct lttng_consumer_stream *stream,
		bool producer_active)
{
	int ret = 0;

	switch (the_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) {
				/*
				 * Doing a buffer flush which does not take into
				 * account empty packets. This is not perfect,
				 * but required as a fall-back when
				 * "flush_empty" is not implemented by
				 * lttng-modules.
				 */
				ret = kernctl_buffer_flush(stream->wait_fd);
				if (ret < 0) {
					ERR("Failed to flush kernel stream");
					goto end;
				}
			}
		}
		break;
	case LTTNG_CONSUMER32_UST:
	case LTTNG_CONSUMER64_UST:
		ret = lttng_ustconsumer_flush_buffer(stream, (int) producer_active);
		break;
	default:
		ERR("Unknown consumer_data type");
		abort();
	}

end:
	return ret;
}