Fix: consumer: unbalanced RCU read-side lock on error

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

/*
 * 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 <assert.h>
#include <inttypes.h>
#include <sys/mman.h>
#include <unistd.h>

#include <common/common.h>
#include <common/index/index.h>
#include <common/kernel-consumer/kernel-consumer.h>
#include <common/relayd/relayd.h>
#include <common/ust-consumer/ust-consumer.h>
#include <common/utils.h>
#include <common/consumer/consumer.h>
#include <common/consumer/consumer-timer.h>
#include <common/consumer/metadata-bucket.h>
#include <common/kernel-ctl/kernel-ctl.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_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);
}

/* 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;

        assert(metadata);
        assert(metadata->metadata_flag);
        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;

        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)
{
        int ret;

        /* Block until all the metadata is sent. */
        pthread_mutex_lock(&stream->metadata_timer_lock);
        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;
        if (stream->missed_metadata_flush) {
                stream->missed_metadata_flush = false;
                pthread_mutex_unlock(&stream->metadata_timer_lock);
                (void) stream->read_subbuffer_ops.send_live_beacon(stream);
        } else {
                pthread_mutex_unlock(&stream->metadata_timer_lock);
        }
        if (ret < 0) {
                goto end;
        }

        ret = consumer_stream_send_index(stream, subbuffer, ctx);
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 = 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.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;

                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_cb) { 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.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;

        assert(stream);
        assert(relayd);

        if (stream->sent_to_relayd) {
                uatomic_dec(&relayd->refcount);
                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;

        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");
                assert(0);
        }

        /* 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;

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

        rcu_read_lock();

        if (ht) {
                iter.iter.node = &stream->node.node;
                ret = lttng_ht_del(ht, &iter);
                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. */
                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)
{
        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)
{
        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");
                assert(0);
        }
}

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

        assert(stream);
        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)
{
        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;

        assert(stream);
        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);
        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.
         */
        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 = 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;

        assert(stream->metadata_flag);
        assert(!stream->metadata_bucket);
        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)
{
        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;
}