clang-tidy: add Chrome-inspired checks

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

/*
 * Copyright (C) 2011 EfficiOS Inc.
 * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 * Copyright (C) 2017 Jérémie Galarneau <jeremie.galarneau@efficios.com>
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 */

#define _LGPL_SOURCE
#include "ust-consumer.hpp"

#include <common/common.hpp>
#include <common/compat/endian.hpp>
#include <common/compat/fcntl.hpp>
#include <common/consumer/consumer-metadata-cache.hpp>
#include <common/consumer/consumer-stream.hpp>
#include <common/consumer/consumer-timer.hpp>
#include <common/consumer/consumer.hpp>
#include <common/index/index.hpp>
#include <common/optional.hpp>
#include <common/relayd/relayd.hpp>
#include <common/sessiond-comm/sessiond-comm.hpp>
#include <common/shm.hpp>
#include <common/utils.hpp>

#include <lttng/ust-ctl.h>
#include <lttng/ust-sigbus.h>

#include <bin/lttng-consumerd/health-consumerd.hpp>
#include <inttypes.h>
#include <poll.h>
#include <pthread.h>
#include <signal.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <urcu/list.h>

#define INT_MAX_STR_LEN 12 /* includes \0 */

extern struct lttng_consumer_global_data the_consumer_data;
extern int consumer_poll_timeout;

LTTNG_EXPORT DEFINE_LTTNG_UST_SIGBUS_STATE();

/*
 * Add channel to internal consumer state.
 *
 * Returns 0 on success or else a negative value.
 */
static int add_channel(struct lttng_consumer_channel *channel,
                       struct lttng_consumer_local_data *ctx)
{
        int ret = 0;

        LTTNG_ASSERT(channel);
        LTTNG_ASSERT(ctx);

        if (ctx->on_recv_channel != nullptr) {
                ret = ctx->on_recv_channel(channel);
                if (ret == 0) {
                        ret = consumer_add_channel(channel, ctx);
                } else if (ret < 0) {
                        /* Most likely an ENOMEM. */
                        lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_OUTFD_ERROR);
                        goto error;
                }
        } else {
                ret = consumer_add_channel(channel, ctx);
        }

        DBG("UST consumer channel added (key: %" PRIu64 ")", channel->key);

error:
        return ret;
}

/*
 * Allocate and return a consumer stream object. If _alloc_ret is not NULL, the
 * error value if applicable is set in it else it is kept untouched.
 *
 * Return NULL on error else the newly allocated stream object.
 */
static struct lttng_consumer_stream *allocate_stream(int cpu,
                                                     int key,
                                                     struct lttng_consumer_channel *channel,
                                                     struct lttng_consumer_local_data *ctx,
                                                     int *_alloc_ret)
{
        int alloc_ret;
        struct lttng_consumer_stream *stream = nullptr;

        LTTNG_ASSERT(channel);
        LTTNG_ASSERT(ctx);

        stream = consumer_stream_create(channel,
                                        channel->key,
                                        key,
                                        channel->name,
                                        channel->relayd_id,
                                        channel->session_id,
                                        channel->trace_chunk,
                                        cpu,
                                        &alloc_ret,
                                        channel->type,
                                        channel->monitor);
        if (stream == nullptr) {
                switch (alloc_ret) {
                case -ENOENT:
                        /*
                         * We could not find the channel. Can happen if cpu hotplug
                         * happens while tearing down.
                         */
                        DBG3("Could not find channel");
                        break;
                case -ENOMEM:
                case -EINVAL:
                default:
                        lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_OUTFD_ERROR);
                        break;
                }
                goto error;
        }

        consumer_stream_update_channel_attributes(stream, channel);

error:
        if (_alloc_ret) {
                *_alloc_ret = alloc_ret;
        }
        return stream;
}

/*
 * Send the given stream pointer to the corresponding thread.
 *
 * Returns 0 on success else a negative value.
 */
static int send_stream_to_thread(struct lttng_consumer_stream *stream,
                                 struct lttng_consumer_local_data *ctx)
{
        int ret;
        struct lttng_pipe *stream_pipe;

        /* Get the right pipe where the stream will be sent. */
        if (stream->metadata_flag) {
                consumer_add_metadata_stream(stream);
                stream_pipe = ctx->consumer_metadata_pipe;
        } else {
                consumer_add_data_stream(stream);
                stream_pipe = ctx->consumer_data_pipe;
        }

        /*
         * From this point on, the stream's ownership has been moved away from
         * the channel and it becomes globally visible. Hence, remove it from
         * the local stream list to prevent the stream from being both local and
         * global.
         */
        stream->globally_visible = 1;
        cds_list_del_init(&stream->send_node);

        ret = lttng_pipe_write(stream_pipe, &stream, sizeof(stream));
        if (ret < 0) {
                ERR("Consumer write %s stream to pipe %d",
                    stream->metadata_flag ? "metadata" : "data",
                    lttng_pipe_get_writefd(stream_pipe));
                if (stream->metadata_flag) {
                        consumer_del_stream_for_metadata(stream);
                } else {
                        consumer_del_stream_for_data(stream);
                }
                goto error;
        }

error:
        return ret;
}

static int get_stream_shm_path(char *stream_shm_path, const char *shm_path, int cpu)
{
        char cpu_nr[INT_MAX_STR_LEN]; /* int max len */
        int ret;

        strncpy(stream_shm_path, shm_path, PATH_MAX);
        stream_shm_path[PATH_MAX - 1] = '\0';
        ret = snprintf(cpu_nr, INT_MAX_STR_LEN, "%i", cpu);
        if (ret < 0) {
                PERROR("snprintf");
                goto end;
        }
        strncat(stream_shm_path, cpu_nr, PATH_MAX - strlen(stream_shm_path) - 1);
        ret = 0;
end:
        return ret;
}

/*
 * Create streams for the given channel using liblttng-ust-ctl.
 * The channel lock must be acquired by the caller.
 *
 * Return 0 on success else a negative value.
 */
static int create_ust_streams(struct lttng_consumer_channel *channel,
                              struct lttng_consumer_local_data *ctx)
{
        int ret, cpu = 0;
        struct lttng_ust_ctl_consumer_stream *ustream;
        struct lttng_consumer_stream *stream;
        pthread_mutex_t *current_stream_lock = nullptr;

        LTTNG_ASSERT(channel);
        LTTNG_ASSERT(ctx);

        /*
         * While a stream is available from ustctl. When NULL is returned, we've
         * reached the end of the possible stream for the channel.
         */
        while ((ustream = lttng_ust_ctl_create_stream(channel->uchan, cpu))) {
                int wait_fd;
                int ust_metadata_pipe[2];

                health_code_update();

                if (channel->type == CONSUMER_CHANNEL_TYPE_METADATA && channel->monitor) {
                        ret = utils_create_pipe_cloexec_nonblock(ust_metadata_pipe);
                        if (ret < 0) {
                                ERR("Create ust metadata poll pipe");
                                goto error;
                        }
                        wait_fd = ust_metadata_pipe[0];
                } else {
                        wait_fd = lttng_ust_ctl_stream_get_wait_fd(ustream);
                }

                /* Allocate consumer stream object. */
                stream = allocate_stream(cpu, wait_fd, channel, ctx, &ret);
                if (!stream) {
                        goto error_alloc;
                }
                stream->ustream = ustream;
                /*
                 * Store it so we can save multiple function calls afterwards since
                 * this value is used heavily in the stream threads. This is UST
                 * specific so this is why it's done after allocation.
                 */
                stream->wait_fd = wait_fd;

                /*
                 * Increment channel refcount since the channel reference has now been
                 * assigned in the allocation process above.
                 */
                if (stream->chan->monitor) {
                        uatomic_inc(&stream->chan->refcount);
                }

                pthread_mutex_lock(&stream->lock);
                current_stream_lock = &stream->lock;
                /*
                 * Order is important this is why a list is used. On error, the caller
                 * should clean this list.
                 */
                cds_list_add_tail(&stream->send_node, &channel->streams.head);

                ret = lttng_ust_ctl_get_max_subbuf_size(stream->ustream, &stream->max_sb_size);
                if (ret < 0) {
                        ERR("lttng_ust_ctl_get_max_subbuf_size failed for stream %s", stream->name);
                        goto error;
                }

                /* Do actions once stream has been received. */
                if (ctx->on_recv_stream) {
                        ret = ctx->on_recv_stream(stream);
                        if (ret < 0) {
                                goto error;
                        }
                }

                DBG("UST consumer add stream %s (key: %" PRIu64 ") with relayd id %" PRIu64,
                    stream->name,
                    stream->key,
                    stream->relayd_stream_id);

                /* Set next CPU stream. */
                channel->streams.count = ++cpu;

                /* Keep stream reference when creating metadata. */
                if (channel->type == CONSUMER_CHANNEL_TYPE_METADATA) {
                        channel->metadata_stream = stream;
                        if (channel->monitor) {
                                /* Set metadata poll pipe if we created one */
                                memcpy(stream->ust_metadata_poll_pipe,
                                       ust_metadata_pipe,
                                       sizeof(ust_metadata_pipe));
                        }
                }
                pthread_mutex_unlock(&stream->lock);
                current_stream_lock = nullptr;
        }

        return 0;

error:
error_alloc:
        if (current_stream_lock) {
                pthread_mutex_unlock(current_stream_lock);
        }
        return ret;
}

static int open_ust_stream_fd(struct lttng_consumer_channel *channel,
                              int cpu,
                              const struct lttng_credentials *session_credentials)
{
        char shm_path[PATH_MAX];
        int ret;

        if (!channel->shm_path[0]) {
                return shm_create_anonymous("ust-consumer");
        }
        ret = get_stream_shm_path(shm_path, channel->shm_path, cpu);
        if (ret) {
                goto error_shm_path;
        }
        return run_as_open(shm_path,
                           O_RDWR | O_CREAT | O_EXCL,
                           S_IRUSR | S_IWUSR,
                           lttng_credentials_get_uid(session_credentials),
                           lttng_credentials_get_gid(session_credentials));

error_shm_path:
        return -1;
}

/*
 * Create an UST channel with the given attributes and send it to the session
 * daemon using the ust ctl API.
 *
 * Return 0 on success or else a negative value.
 */
static int create_ust_channel(struct lttng_consumer_channel *channel,
                              struct lttng_ust_ctl_consumer_channel_attr *attr,
                              struct lttng_ust_ctl_consumer_channel **ust_chanp)
{
        int ret, nr_stream_fds, i, j;
        int *stream_fds;
        struct lttng_ust_ctl_consumer_channel *ust_channel;

        LTTNG_ASSERT(channel);
        LTTNG_ASSERT(attr);
        LTTNG_ASSERT(ust_chanp);
        LTTNG_ASSERT(channel->buffer_credentials.is_set);

        DBG3("Creating channel to ustctl with attr: [overwrite: %d, "
             "subbuf_size: %" PRIu64 ", num_subbuf: %" PRIu64 ", "
             "switch_timer_interval: %u, read_timer_interval: %u, "
             "output: %d, type: %d",
             attr->overwrite,
             attr->subbuf_size,
             attr->num_subbuf,
             attr->switch_timer_interval,
             attr->read_timer_interval,
             attr->output,
             attr->type);

        if (channel->type == CONSUMER_CHANNEL_TYPE_METADATA)
                nr_stream_fds = 1;
        else
                nr_stream_fds = lttng_ust_ctl_get_nr_stream_per_channel();
        stream_fds = calloc<int>(nr_stream_fds);
        if (!stream_fds) {
                ret = -1;
                goto error_alloc;
        }
        for (i = 0; i < nr_stream_fds; i++) {
                stream_fds[i] = open_ust_stream_fd(channel, i, &channel->buffer_credentials.value);
                if (stream_fds[i] < 0) {
                        ret = -1;
                        goto error_open;
                }
        }
        ust_channel = lttng_ust_ctl_create_channel(attr, stream_fds, nr_stream_fds);
        if (!ust_channel) {
                ret = -1;
                goto error_create;
        }
        channel->nr_stream_fds = nr_stream_fds;
        channel->stream_fds = stream_fds;
        *ust_chanp = ust_channel;

        return 0;

error_create:
error_open:
        for (j = i - 1; j >= 0; j--) {
                int closeret;

                closeret = close(stream_fds[j]);
                if (closeret) {
                        PERROR("close");
                }
                if (channel->shm_path[0]) {
                        char shm_path[PATH_MAX];

                        closeret = get_stream_shm_path(shm_path, channel->shm_path, j);
                        if (closeret) {
                                ERR("Cannot get stream shm path");
                        }
                        closeret = run_as_unlink(shm_path,
                                                 lttng_credentials_get_uid(LTTNG_OPTIONAL_GET_PTR(
                                                         channel->buffer_credentials)),
                                                 lttng_credentials_get_gid(LTTNG_OPTIONAL_GET_PTR(
                                                         channel->buffer_credentials)));
                        if (closeret) {
                                PERROR("unlink %s", shm_path);
                        }
                }
        }
        /* Try to rmdir all directories under shm_path root. */
        if (channel->root_shm_path[0]) {
                (void) run_as_rmdir_recursive(channel->root_shm_path,
                                              lttng_credentials_get_uid(LTTNG_OPTIONAL_GET_PTR(
                                                      channel->buffer_credentials)),
                                              lttng_credentials_get_gid(LTTNG_OPTIONAL_GET_PTR(
                                                      channel->buffer_credentials)),
                                              LTTNG_DIRECTORY_HANDLE_SKIP_NON_EMPTY_FLAG);
        }
        free(stream_fds);
error_alloc:
        return ret;
}

/*
 * Send a single given stream to the session daemon using the sock.
 *
 * Return 0 on success else a negative value.
 */
static int send_sessiond_stream(int sock, struct lttng_consumer_stream *stream)
{
        int ret;

        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(sock >= 0);

        DBG("UST consumer sending stream %" PRIu64 " to sessiond", stream->key);

        /* Send stream to session daemon. */
        ret = lttng_ust_ctl_send_stream_to_sessiond(sock, stream->ustream);
        if (ret < 0) {
                goto error;
        }

error:
        return ret;
}

/*
 * Send channel to sessiond and relayd if applicable.
 *
 * Return 0 on success or else a negative value.
 */
static int send_channel_to_sessiond_and_relayd(int sock,
                                               struct lttng_consumer_channel *channel,
                                               struct lttng_consumer_local_data *ctx,
                                               int *relayd_error)
{
        int ret, ret_code = LTTCOMM_CONSUMERD_SUCCESS;
        struct lttng_consumer_stream *stream;
        uint64_t net_seq_idx = -1ULL;

        LTTNG_ASSERT(channel);
        LTTNG_ASSERT(ctx);
        LTTNG_ASSERT(sock >= 0);

        DBG("UST consumer sending channel %s to sessiond", channel->name);

        if (channel->relayd_id != (uint64_t) -1ULL) {
                cds_list_for_each_entry (stream, &channel->streams.head, send_node) {
                        health_code_update();

                        /* Try to send the stream to the relayd if one is available. */
                        DBG("Sending stream %" PRIu64 " of channel \"%s\" to relayd",
                            stream->key,
                            channel->name);
                        ret = consumer_send_relayd_stream(stream, stream->chan->pathname);
                        if (ret < 0) {
                                /*
                                 * Flag that the relayd was the problem here probably due to a
                                 * communicaton error on the socket.
                                 */
                                if (relayd_error) {
                                        *relayd_error = 1;
                                }
                                ret_code = LTTCOMM_CONSUMERD_RELAYD_FAIL;
                        }
                        if (net_seq_idx == -1ULL) {
                                net_seq_idx = stream->net_seq_idx;
                        }
                }
        }

        /* Inform sessiond that we are about to send channel and streams. */
        ret = consumer_send_status_msg(sock, ret_code);
        if (ret < 0 || ret_code != LTTCOMM_CONSUMERD_SUCCESS) {
                /*
                 * Either the session daemon is not responding or the relayd died so we
                 * stop now.
                 */
                goto error;
        }

        /* Send channel to sessiond. */
        ret = lttng_ust_ctl_send_channel_to_sessiond(sock, channel->uchan);
        if (ret < 0) {
                goto error;
        }

        ret = lttng_ust_ctl_channel_close_wakeup_fd(channel->uchan);
        if (ret < 0) {
                goto error;
        }

        /* The channel was sent successfully to the sessiond at this point. */
        cds_list_for_each_entry (stream, &channel->streams.head, send_node) {
                health_code_update();

                /* Send stream to session daemon. */
                ret = send_sessiond_stream(sock, stream);
                if (ret < 0) {
                        goto error;
                }
        }

        /* Tell sessiond there is no more stream. */
        ret = lttng_ust_ctl_send_stream_to_sessiond(sock, nullptr);
        if (ret < 0) {
                goto error;
        }

        DBG("UST consumer NULL stream sent to sessiond");

        return 0;

error:
        if (ret_code != LTTCOMM_CONSUMERD_SUCCESS) {
                ret = -1;
        }
        return ret;
}

/*
 * Creates a channel and streams and add the channel it to the channel internal
 * state. The created stream must ONLY be sent once the GET_CHANNEL command is
 * received.
 *
 * Return 0 on success or else, a negative value is returned and the channel
 * MUST be destroyed by consumer_del_channel().
 */
static int ask_channel(struct lttng_consumer_local_data *ctx,
                       struct lttng_consumer_channel *channel,
                       struct lttng_ust_ctl_consumer_channel_attr *attr)
{
        int ret;

        LTTNG_ASSERT(ctx);
        LTTNG_ASSERT(channel);
        LTTNG_ASSERT(attr);

        /*
         * This value is still used by the kernel consumer since for the kernel,
         * the stream ownership is not IN the consumer so we need to have the
         * number of left stream that needs to be initialized so we can know when
         * to delete the channel (see consumer.c).
         *
         * As for the user space tracer now, the consumer creates and sends the
         * stream to the session daemon which only sends them to the application
         * once every stream of a channel is received making this value useless
         * because we they will be added to the poll thread before the application
         * receives them. This ensures that a stream can not hang up during
         * initilization of a channel.
         */
        channel->nb_init_stream_left = 0;

        /* The reply msg status is handled in the following call. */
        ret = create_ust_channel(channel, attr, &channel->uchan);
        if (ret < 0) {
                goto end;
        }

        channel->wait_fd = lttng_ust_ctl_channel_get_wait_fd(channel->uchan);

        /*
         * For the snapshots (no monitor), we create the metadata streams
         * on demand, not during the channel creation.
         */
        if (channel->type == CONSUMER_CHANNEL_TYPE_METADATA && !channel->monitor) {
                ret = 0;
                goto end;
        }

        /* Open all streams for this channel. */
        pthread_mutex_lock(&channel->lock);
        ret = create_ust_streams(channel, ctx);
        pthread_mutex_unlock(&channel->lock);
        if (ret < 0) {
                goto end;
        }

end:
        return ret;
}

/*
 * Send all stream of a channel to the right thread handling it.
 *
 * On error, return a negative value else 0 on success.
 */
static int send_streams_to_thread(struct lttng_consumer_channel *channel,
                                  struct lttng_consumer_local_data *ctx)
{
        int ret = 0;
        struct lttng_consumer_stream *stream, *stmp;

        LTTNG_ASSERT(channel);
        LTTNG_ASSERT(ctx);

        /* Send streams to the corresponding thread. */
        cds_list_for_each_entry_safe (stream, stmp, &channel->streams.head, send_node) {
                health_code_update();

                /* Sending the stream to the thread. */
                ret = send_stream_to_thread(stream, ctx);
                if (ret < 0) {
                        /*
                         * If we are unable to send the stream to the thread, there is
                         * a big problem so just stop everything.
                         */
                        goto error;
                }
        }

error:
        return ret;
}

/*
 * Flush channel's streams using the given key to retrieve the channel.
 *
 * Return 0 on success else an LTTng error code.
 */
static int flush_channel(uint64_t chan_key)
{
        int ret = 0;
        struct lttng_consumer_channel *channel;
        struct lttng_consumer_stream *stream;
        struct lttng_ht *ht;
        struct lttng_ht_iter iter;

        DBG("UST consumer flush channel key %" PRIu64, chan_key);

        rcu_read_lock();
        channel = consumer_find_channel(chan_key);
        if (!channel) {
                ERR("UST consumer flush channel %" PRIu64 " not found", chan_key);
                ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
                goto error;
        }

        ht = the_consumer_data.stream_per_chan_id_ht;

        /* For each stream of the channel id, flush it. */
        cds_lfht_for_each_entry_duplicate(ht->ht,
                                          ht->hash_fct(&channel->key, lttng_ht_seed),
                                          ht->match_fct,
                                          &channel->key,
                                          &iter.iter,
                                          stream,
                                          node_channel_id.node)
        {
                health_code_update();

                pthread_mutex_lock(&stream->lock);

                /*
                 * Protect against concurrent teardown of a stream.
                 */
                if (cds_lfht_is_node_deleted(&stream->node.node)) {
                        goto next;
                }

                if (!stream->quiescent) {
                        ret = lttng_ust_ctl_flush_buffer(stream->ustream, 0);
                        if (ret) {
                                ERR("Failed to flush buffer while flushing channel: channel key = %" PRIu64
                                    ", channel name = '%s'",
                                    chan_key,
                                    channel->name);
                                ret = LTTNG_ERR_BUFFER_FLUSH_FAILED;
                                pthread_mutex_unlock(&stream->lock);
                                goto error;
                        }
                        stream->quiescent = true;
                }
        next:
                pthread_mutex_unlock(&stream->lock);
        }

        /*
         * Send one last buffer statistics update to the session daemon. This
         * ensures that the session daemon gets at least one statistics update
         * per channel even in the case of short-lived channels, such as when a
         * short-lived app is traced in per-pid mode.
         */
        sample_and_send_channel_buffer_stats(channel);
error:
        rcu_read_unlock();
        return ret;
}

/*
 * Clear quiescent state from channel's streams using the given key to
 * retrieve the channel.
 *
 * Return 0 on success else an LTTng error code.
 */
static int clear_quiescent_channel(uint64_t chan_key)
{
        int ret = 0;
        struct lttng_consumer_channel *channel;
        struct lttng_consumer_stream *stream;
        struct lttng_ht *ht;
        struct lttng_ht_iter iter;

        DBG("UST consumer clear quiescent channel key %" PRIu64, chan_key);

        rcu_read_lock();
        channel = consumer_find_channel(chan_key);
        if (!channel) {
                ERR("UST consumer clear quiescent channel %" PRIu64 " not found", chan_key);
                ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
                goto error;
        }

        ht = the_consumer_data.stream_per_chan_id_ht;

        /* For each stream of the channel id, clear quiescent state. */
        cds_lfht_for_each_entry_duplicate(ht->ht,
                                          ht->hash_fct(&channel->key, lttng_ht_seed),
                                          ht->match_fct,
                                          &channel->key,
                                          &iter.iter,
                                          stream,
                                          node_channel_id.node)
        {
                health_code_update();

                pthread_mutex_lock(&stream->lock);
                stream->quiescent = false;
                pthread_mutex_unlock(&stream->lock);
        }
error:
        rcu_read_unlock();
        return ret;
}

/*
 * Close metadata stream wakeup_fd using the given key to retrieve the channel.
 *
 * Return 0 on success else an LTTng error code.
 */
static int close_metadata(uint64_t chan_key)
{
        int ret = 0;
        struct lttng_consumer_channel *channel;
        unsigned int channel_monitor;

        DBG("UST consumer close metadata key %" PRIu64, chan_key);

        channel = consumer_find_channel(chan_key);
        if (!channel) {
                /*
                 * This is possible if the metadata thread has issue a delete because
                 * the endpoint point of the stream hung up. There is no way the
                 * session daemon can know about it thus use a DBG instead of an actual
                 * error.
                 */
                DBG("UST consumer close metadata %" PRIu64 " not found", chan_key);
                ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
                goto error;
        }

        pthread_mutex_lock(&the_consumer_data.lock);
        pthread_mutex_lock(&channel->lock);
        channel_monitor = channel->monitor;
        if (cds_lfht_is_node_deleted(&channel->node.node)) {
                goto error_unlock;
        }

        lttng_ustconsumer_close_metadata(channel);
        pthread_mutex_unlock(&channel->lock);
        pthread_mutex_unlock(&the_consumer_data.lock);

        /*
         * The ownership of a metadata channel depends on the type of
         * session to which it belongs. In effect, the monitor flag is checked
         * to determine if this metadata channel is in "snapshot" mode or not.
         *
         * In the non-snapshot case, the metadata channel is created along with
         * a single stream which will remain present until the metadata channel
         * is destroyed (on the destruction of its session). In this case, the
         * metadata stream in "monitored" by the metadata poll thread and holds
         * the ownership of its channel.
         *
         * Closing the metadata will cause the metadata stream's "metadata poll
         * pipe" to be closed. Closing this pipe will wake-up the metadata poll
         * thread which will teardown the metadata stream which, in return,
         * deletes the metadata channel.
         *
         * In the snapshot case, the metadata stream is created and destroyed
         * on every snapshot record. Since the channel doesn't have an owner
         * other than the session daemon, it is safe to destroy it immediately
         * on reception of the CLOSE_METADATA command.
         */
        if (!channel_monitor) {
                /*
                 * The channel and consumer_data locks must be
                 * released before this call since consumer_del_channel
                 * re-acquires the channel and consumer_data locks to teardown
                 * the channel and queue its reclamation by the "call_rcu"
                 * worker thread.
                 */
                consumer_del_channel(channel);
        }

        return ret;
error_unlock:
        pthread_mutex_unlock(&channel->lock);
        pthread_mutex_unlock(&the_consumer_data.lock);
error:
        return ret;
}

/*
 * RCU read side lock MUST be acquired before calling this function.
 *
 * Return 0 on success else an LTTng error code.
 */
static int setup_metadata(struct lttng_consumer_local_data *ctx, uint64_t key)
{
        int ret;
        struct lttng_consumer_channel *metadata;

        ASSERT_RCU_READ_LOCKED();

        DBG("UST consumer setup metadata key %" PRIu64, key);

        metadata = consumer_find_channel(key);
        if (!metadata) {
                ERR("UST consumer push metadata %" PRIu64 " not found", key);
                ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
                goto end;
        }

        /*
         * In no monitor mode, the metadata channel has no stream(s) so skip the
         * ownership transfer to the metadata thread.
         */
        if (!metadata->monitor) {
                DBG("Metadata channel in no monitor");
                ret = 0;
                goto end;
        }

        /*
         * Send metadata stream to relayd if one available. Availability is
         * known if the stream is still in the list of the channel.
         */
        if (cds_list_empty(&metadata->streams.head)) {
                ERR("Metadata channel key %" PRIu64 ", no stream available.", key);
                ret = LTTCOMM_CONSUMERD_ERROR_METADATA;
                goto error_no_stream;
        }

        /* Send metadata stream to relayd if needed. */
        if (metadata->metadata_stream->net_seq_idx != (uint64_t) -1ULL) {
                ret = consumer_send_relayd_stream(metadata->metadata_stream, metadata->pathname);
                if (ret < 0) {
                        ret = LTTCOMM_CONSUMERD_ERROR_METADATA;
                        goto error;
                }
                ret = consumer_send_relayd_streams_sent(metadata->metadata_stream->net_seq_idx);
                if (ret < 0) {
                        ret = LTTCOMM_CONSUMERD_RELAYD_FAIL;
                        goto error;
                }
        }

        /*
         * Ownership of metadata stream is passed along. Freeing is handled by
         * the callee.
         */
        ret = send_streams_to_thread(metadata, ctx);
        if (ret < 0) {
                /*
                 * If we are unable to send the stream to the thread, there is
                 * a big problem so just stop everything.
                 */
                ret = LTTCOMM_CONSUMERD_FATAL;
                goto send_streams_error;
        }
        /* List MUST be empty after or else it could be reused. */
        LTTNG_ASSERT(cds_list_empty(&metadata->streams.head));

        ret = 0;
        goto end;

error:
        /*
         * Delete metadata channel on error. At this point, the metadata stream can
         * NOT be monitored by the metadata thread thus having the guarantee that
         * the stream is still in the local stream list of the channel. This call
         * will make sure to clean that list.
         */
        consumer_stream_destroy(metadata->metadata_stream, nullptr);
        metadata->metadata_stream = nullptr;
send_streams_error:
error_no_stream:
end:
        return ret;
}

/*
 * Snapshot the whole metadata.
 * RCU read-side lock must be held by the caller.
 *
 * Returns 0 on success, < 0 on error
 */
static int snapshot_metadata(struct lttng_consumer_channel *metadata_channel,
                             uint64_t key,
                             char *path,
                             uint64_t relayd_id,
                             struct lttng_consumer_local_data *ctx)
{
        int ret = 0;
        struct lttng_consumer_stream *metadata_stream;

        LTTNG_ASSERT(path);
        LTTNG_ASSERT(ctx);
        ASSERT_RCU_READ_LOCKED();

        DBG("UST consumer snapshot metadata with key %" PRIu64 " at path %s", key, path);

        rcu_read_lock();

        LTTNG_ASSERT(!metadata_channel->monitor);

        health_code_update();

        /*
         * Ask the sessiond if we have new metadata waiting and update the
         * consumer metadata cache.
         */
        ret = lttng_ustconsumer_request_metadata(ctx, metadata_channel, 0, 1);
        if (ret < 0) {
                goto error;
        }

        health_code_update();

        /*
         * The metadata stream is NOT created in no monitor mode when the channel
         * is created on a sessiond ask channel command.
         */
        ret = create_ust_streams(metadata_channel, ctx);
        if (ret < 0) {
                goto error;
        }

        metadata_stream = metadata_channel->metadata_stream;
        LTTNG_ASSERT(metadata_stream);

        metadata_stream->read_subbuffer_ops.lock(metadata_stream);
        if (relayd_id != (uint64_t) -1ULL) {
                metadata_stream->net_seq_idx = relayd_id;
                ret = consumer_send_relayd_stream(metadata_stream, path);
        } else {
                ret = consumer_stream_create_output_files(metadata_stream, false);
        }
        if (ret < 0) {
                goto error_stream;
        }

        do {
                health_code_update();
                ret = lttng_consumer_read_subbuffer(metadata_stream, ctx, true);
                if (ret < 0) {
                        goto error_stream;
                }
        } while (ret > 0);

error_stream:
        metadata_stream->read_subbuffer_ops.unlock(metadata_stream);
        /*
         * Clean up the stream completely because the next snapshot will use a
         * new metadata stream.
         */
        consumer_stream_destroy(metadata_stream, nullptr);
        metadata_channel->metadata_stream = nullptr;

error:
        rcu_read_unlock();
        return ret;
}

static int get_current_subbuf_addr(struct lttng_consumer_stream *stream, const char **addr)
{
        int ret;
        unsigned long mmap_offset;
        const char *mmap_base;

        mmap_base = (const char *) lttng_ust_ctl_get_mmap_base(stream->ustream);
        if (!mmap_base) {
                ERR("Failed to get mmap base for stream `%s`", stream->name);
                ret = -EPERM;
                goto error;
        }

        ret = lttng_ust_ctl_get_mmap_read_offset(stream->ustream, &mmap_offset);
        if (ret != 0) {
                ERR("Failed to get mmap offset for stream `%s`", stream->name);
                ret = -EINVAL;
                goto error;
        }

        *addr = mmap_base + mmap_offset;
error:
        return ret;
}

/*
 * Take a snapshot of all the stream of a channel.
 * RCU read-side lock and the channel lock must be held by the caller.
 *
 * Returns 0 on success, < 0 on error
 */
static int snapshot_channel(struct lttng_consumer_channel *channel,
                            uint64_t key,
                            char *path,
                            uint64_t relayd_id,
                            uint64_t nb_packets_per_stream,
                            struct lttng_consumer_local_data *ctx)
{
        int ret;
        unsigned use_relayd = 0;
        unsigned long consumed_pos, produced_pos;
        struct lttng_consumer_stream *stream;

        LTTNG_ASSERT(path);
        LTTNG_ASSERT(ctx);
        ASSERT_RCU_READ_LOCKED();

        rcu_read_lock();

        if (relayd_id != (uint64_t) -1ULL) {
                use_relayd = 1;
        }

        LTTNG_ASSERT(!channel->monitor);
        DBG("UST consumer snapshot channel %" PRIu64, key);

        cds_list_for_each_entry (stream, &channel->streams.head, send_node) {
                health_code_update();

                /* Lock stream because we are about to change its state. */
                pthread_mutex_lock(&stream->lock);
                LTTNG_ASSERT(channel->trace_chunk);
                if (!lttng_trace_chunk_get(channel->trace_chunk)) {
                        /*
                         * Can't happen barring an internal error as the channel
                         * holds a reference to the trace chunk.
                         */
                        ERR("Failed to acquire reference to channel's trace chunk");
                        ret = -1;
                        goto error_unlock;
                }
                LTTNG_ASSERT(!stream->trace_chunk);
                stream->trace_chunk = channel->trace_chunk;

                stream->net_seq_idx = relayd_id;

                if (use_relayd) {
                        ret = consumer_send_relayd_stream(stream, path);
                        if (ret < 0) {
                                goto error_close_stream;
                        }
                } else {
                        ret = consumer_stream_create_output_files(stream, false);
                        if (ret < 0) {
                                goto error_close_stream;
                        }
                        DBG("UST consumer snapshot stream (%" PRIu64 ")", stream->key);
                }

                /*
                 * If tracing is active, we want to perform a "full" buffer flush.
                 * Else, if quiescent, it has already been done by the prior stop.
                 */
                if (!stream->quiescent) {
                        ret = lttng_ust_ctl_flush_buffer(stream->ustream, 0);
                        if (ret < 0) {
                                ERR("Failed to flush buffer during snapshot of channel: channel key = %" PRIu64
                                    ", channel name = '%s'",
                                    channel->key,
                                    channel->name);
                                goto error_unlock;
                        }
                }

                ret = lttng_ustconsumer_take_snapshot(stream);
                if (ret < 0) {
                        ERR("Taking UST snapshot");
                        goto error_close_stream;
                }

                ret = lttng_ustconsumer_get_produced_snapshot(stream, &produced_pos);
                if (ret < 0) {
                        ERR("Produced UST snapshot position");
                        goto error_close_stream;
                }

                ret = lttng_ustconsumer_get_consumed_snapshot(stream, &consumed_pos);
                if (ret < 0) {
                        ERR("Consumerd UST snapshot position");
                        goto error_close_stream;
                }

                /*
                 * The original value is sent back if max stream size is larger than
                 * the possible size of the snapshot. Also, we assume that the session
                 * daemon should never send a maximum stream size that is lower than
                 * subbuffer size.
                 */
                consumed_pos = consumer_get_consume_start_pos(
                        consumed_pos, produced_pos, nb_packets_per_stream, stream->max_sb_size);

                while ((long) (consumed_pos - produced_pos) < 0) {
                        ssize_t read_len;
                        unsigned long len, padded_len;
                        const char *subbuf_addr;
                        struct lttng_buffer_view subbuf_view;

                        health_code_update();

                        DBG("UST consumer taking snapshot at pos %lu", consumed_pos);

                        ret = lttng_ust_ctl_get_subbuf(stream->ustream, &consumed_pos);
                        if (ret < 0) {
                                if (ret != -EAGAIN) {
                                        PERROR("lttng_ust_ctl_get_subbuf snapshot");
                                        goto error_close_stream;
                                }
                                DBG("UST consumer get subbuf failed. Skipping it.");
                                consumed_pos += stream->max_sb_size;
                                stream->chan->lost_packets++;
                                continue;
                        }

                        ret = lttng_ust_ctl_get_subbuf_size(stream->ustream, &len);
                        if (ret < 0) {
                                ERR("Snapshot lttng_ust_ctl_get_subbuf_size");
                                goto error_put_subbuf;
                        }

                        ret = lttng_ust_ctl_get_padded_subbuf_size(stream->ustream, &padded_len);
                        if (ret < 0) {
                                ERR("Snapshot lttng_ust_ctl_get_padded_subbuf_size");
                                goto error_put_subbuf;
                        }

                        ret = get_current_subbuf_addr(stream, &subbuf_addr);
                        if (ret) {
                                goto error_put_subbuf;
                        }

                        subbuf_view = lttng_buffer_view_init(subbuf_addr, 0, padded_len);
                        read_len = lttng_consumer_on_read_subbuffer_mmap(
                                stream, &subbuf_view, padded_len - len);
                        if (use_relayd) {
                                if (read_len != len) {
                                        ret = -EPERM;
                                        goto error_put_subbuf;
                                }
                        } else {
                                if (read_len != padded_len) {
                                        ret = -EPERM;
                                        goto error_put_subbuf;
                                }
                        }

                        ret = lttng_ust_ctl_put_subbuf(stream->ustream);
                        if (ret < 0) {
                                ERR("Snapshot lttng_ust_ctl_put_subbuf");
                                goto error_close_stream;
                        }
                        consumed_pos += stream->max_sb_size;
                }

                /* Simply close the stream so we can use it on the next snapshot. */
                consumer_stream_close_output(stream);
                pthread_mutex_unlock(&stream->lock);
        }

        rcu_read_unlock();
        return 0;

error_put_subbuf:
        if (lttng_ust_ctl_put_subbuf(stream->ustream) < 0) {
                ERR("Snapshot lttng_ust_ctl_put_subbuf");
        }
error_close_stream:
        consumer_stream_close_output(stream);
error_unlock:
        pthread_mutex_unlock(&stream->lock);
        rcu_read_unlock();
        return ret;
}

static void metadata_stream_reset_cache_consumed_position(struct lttng_consumer_stream *stream)
{
        ASSERT_LOCKED(stream->lock);

        DBG("Reset metadata cache of session %" PRIu64, stream->chan->session_id);
        stream->ust_metadata_pushed = 0;
}

/*
 * Receive the metadata updates from the sessiond. Supports receiving
 * overlapping metadata, but is needs to always belong to a contiguous
 * range starting from 0.
 * Be careful about the locks held when calling this function: it needs
 * the metadata cache flush to concurrently progress in order to
 * complete.
 */
int lttng_ustconsumer_recv_metadata(int sock,
                                    uint64_t key,
                                    uint64_t offset,
                                    uint64_t len,
                                    uint64_t version,
                                    struct lttng_consumer_channel *channel,
                                    int timer,
                                    int wait)
{
        int ret, ret_code = LTTCOMM_CONSUMERD_SUCCESS;
        char *metadata_str;
        enum consumer_metadata_cache_write_status cache_write_status;

        DBG("UST consumer push metadata key %" PRIu64 " of len %" PRIu64, key, len);

        metadata_str = calloc<char>(len);
        if (!metadata_str) {
                PERROR("zmalloc metadata string");
                ret_code = LTTCOMM_CONSUMERD_ENOMEM;
                goto end;
        }

        health_code_update();

        /* Receive metadata string. */
        ret = lttcomm_recv_unix_sock(sock, metadata_str, len);
        if (ret < 0) {
                /* Session daemon is dead so return gracefully. */
                ret_code = ret;
                goto end_free;
        }

        health_code_update();

        pthread_mutex_lock(&channel->metadata_cache->lock);
        cache_write_status = consumer_metadata_cache_write(
                channel->metadata_cache, offset, len, version, metadata_str);
        pthread_mutex_unlock(&channel->metadata_cache->lock);
        switch (cache_write_status) {
        case CONSUMER_METADATA_CACHE_WRITE_STATUS_NO_CHANGE:
                /*
                 * The write entirely overlapped with existing contents of the
                 * same metadata version (same content); there is nothing to do.
                 */
                break;
        case CONSUMER_METADATA_CACHE_WRITE_STATUS_INVALIDATED:
                /*
                 * The metadata cache was invalidated (previously pushed
                 * content has been overwritten). Reset the stream's consumed
                 * metadata position to ensure the metadata poll thread consumes
                 * the whole cache.
                 */

                /*
                 * channel::metadata_stream can be null when the metadata
                 * channel is under a snapshot session type. No need to update
                 * the stream position in that scenario.
                 */
                if (channel->metadata_stream != nullptr) {
                        pthread_mutex_lock(&channel->metadata_stream->lock);
                        metadata_stream_reset_cache_consumed_position(channel->metadata_stream);
                        pthread_mutex_unlock(&channel->metadata_stream->lock);
                } else {
                        /* Validate we are in snapshot mode. */
                        LTTNG_ASSERT(!channel->monitor);
                }
                /* Fall-through. */
        case CONSUMER_METADATA_CACHE_WRITE_STATUS_APPENDED_CONTENT:
                /*
                 * In both cases, the metadata poll thread has new data to
                 * consume.
                 */
                ret = consumer_metadata_wakeup_pipe(channel);
                if (ret) {
                        ret_code = LTTCOMM_CONSUMERD_ERROR_METADATA;
                        goto end_free;
                }
                break;
        case CONSUMER_METADATA_CACHE_WRITE_STATUS_ERROR:
                /* Unable to handle metadata. Notify session daemon. */
                ret_code = LTTCOMM_CONSUMERD_ERROR_METADATA;
                /*
                 * Skip metadata flush on write error since the offset and len might
                 * not have been updated which could create an infinite loop below when
                 * waiting for the metadata cache to be flushed.
                 */
                goto end_free;
        default:
                abort();
        }

        if (!wait) {
                goto end_free;
        }
        while (consumer_metadata_cache_flushed(channel, offset + len, timer)) {
                DBG("Waiting for metadata to be flushed");

                health_code_update();

                usleep(DEFAULT_METADATA_AVAILABILITY_WAIT_TIME);
        }

end_free:
        free(metadata_str);
end:
        return ret_code;
}

/*
 * Receive command from session daemon and process it.
 *
 * Return 1 on success else a negative value or 0.
 */
int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                               int sock,
                               struct pollfd *consumer_sockpoll)
{
        int ret_func;
        enum lttcomm_return_code ret_code = LTTCOMM_CONSUMERD_SUCCESS;
        struct lttcomm_consumer_msg msg;
        struct lttng_consumer_channel *channel = nullptr;

        health_code_update();

        {
                ssize_t ret_recv;

                ret_recv = lttcomm_recv_unix_sock(sock, &msg, sizeof(msg));
                if (ret_recv != sizeof(msg)) {
                        DBG("Consumer received unexpected message size %zd (expects %zu)",
                            ret_recv,
                            sizeof(msg));
                        /*
                         * The ret value might 0 meaning an orderly shutdown but this is ok
                         * since the caller handles this.
                         */
                        if (ret_recv > 0) {
                                lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_ERROR_RECV_CMD);
                                ret_recv = -1;
                        }
                        return ret_recv;
                }
        }

        health_code_update();

        /* deprecated */
        LTTNG_ASSERT(msg.cmd_type != LTTNG_CONSUMER_STOP);

        health_code_update();

        /* relayd needs RCU read-side lock */
        rcu_read_lock();

        switch (msg.cmd_type) {
        case LTTNG_CONSUMER_ADD_RELAYD_SOCKET:
        {
                uint32_t major = msg.u.relayd_sock.major;
                uint32_t minor = msg.u.relayd_sock.minor;
                enum lttcomm_sock_proto protocol =
                        (enum lttcomm_sock_proto) msg.u.relayd_sock.relayd_socket_protocol;

                /* Session daemon status message are handled in the following call. */
                consumer_add_relayd_socket(msg.u.relayd_sock.net_index,
                                           msg.u.relayd_sock.type,
                                           ctx,
                                           sock,
                                           consumer_sockpoll,
                                           msg.u.relayd_sock.session_id,
                                           msg.u.relayd_sock.relayd_session_id,
                                           major,
                                           minor,
                                           protocol);
                goto end_nosignal;
        }
        case LTTNG_CONSUMER_DESTROY_RELAYD:
        {
                uint64_t index = msg.u.destroy_relayd.net_seq_idx;
                struct consumer_relayd_sock_pair *relayd;

                DBG("UST consumer destroying relayd %" PRIu64, index);

                /* Get relayd reference if exists. */
                relayd = consumer_find_relayd(index);
                if (relayd == nullptr) {
                        DBG("Unable to find relayd %" PRIu64, index);
                        ret_code = LTTCOMM_CONSUMERD_RELAYD_FAIL;
                }

                /*
                 * Each relayd socket pair has a refcount of stream attached to it
                 * which tells if the relayd is still active or not depending on the
                 * refcount value.
                 *
                 * This will set the destroy flag of the relayd object and destroy it
                 * if the refcount reaches zero when called.
                 *
                 * The destroy can happen either here or when a stream fd hangs up.
                 */
                if (relayd) {
                        consumer_flag_relayd_for_destroy(relayd);
                }

                goto end_msg_sessiond;
        }
        case LTTNG_CONSUMER_UPDATE_STREAM:
        {
                rcu_read_unlock();
                return -ENOSYS;
        }
        case LTTNG_CONSUMER_DATA_PENDING:
        {
                int is_data_pending;
                ssize_t ret_send;
                uint64_t id = msg.u.data_pending.session_id;

                DBG("UST consumer data pending command for id %" PRIu64, id);

                is_data_pending = consumer_data_pending(id);

                /* Send back returned value to session daemon */
                ret_send = lttcomm_send_unix_sock(sock, &is_data_pending, sizeof(is_data_pending));
                if (ret_send < 0) {
                        DBG("Error when sending the data pending ret code: %zd", ret_send);
                        goto error_fatal;
                }

                /*
                 * No need to send back a status message since the data pending
                 * returned value is the response.
                 */
                break;
        }
        case LTTNG_CONSUMER_ASK_CHANNEL_CREATION:
        {
                int ret_ask_channel, ret_add_channel, ret_send;
                struct lttng_ust_ctl_consumer_channel_attr attr;
                const uint64_t chunk_id = msg.u.ask_channel.chunk_id.value;
                const struct lttng_credentials buffer_credentials = {
                        .uid = LTTNG_OPTIONAL_INIT_VALUE(msg.u.ask_channel.buffer_credentials.uid),
                        .gid = LTTNG_OPTIONAL_INIT_VALUE(msg.u.ask_channel.buffer_credentials.gid),
                };

                /* Create a plain object and reserve a channel key. */
                channel = consumer_allocate_channel(
                        msg.u.ask_channel.key,
                        msg.u.ask_channel.session_id,
                        msg.u.ask_channel.chunk_id.is_set ? &chunk_id : nullptr,
                        msg.u.ask_channel.pathname,
                        msg.u.ask_channel.name,
                        msg.u.ask_channel.relayd_id,
                        (enum lttng_event_output) msg.u.ask_channel.output,
                        msg.u.ask_channel.tracefile_size,
                        msg.u.ask_channel.tracefile_count,
                        msg.u.ask_channel.session_id_per_pid,
                        msg.u.ask_channel.monitor,
                        msg.u.ask_channel.live_timer_interval,
                        msg.u.ask_channel.is_live,
                        msg.u.ask_channel.root_shm_path,
                        msg.u.ask_channel.shm_path);
                if (!channel) {
                        goto end_channel_error;
                }

                LTTNG_OPTIONAL_SET(&channel->buffer_credentials, buffer_credentials);

                /*
                 * Assign UST application UID to the channel. This value is ignored for
                 * per PID buffers. This is specific to UST thus setting this after the
                 * allocation.
                 */
                channel->ust_app_uid = msg.u.ask_channel.ust_app_uid;

                /* Build channel attributes from received message. */
                attr.subbuf_size = msg.u.ask_channel.subbuf_size;
                attr.num_subbuf = msg.u.ask_channel.num_subbuf;
                attr.overwrite = msg.u.ask_channel.overwrite;
                attr.switch_timer_interval = msg.u.ask_channel.switch_timer_interval;
                attr.read_timer_interval = msg.u.ask_channel.read_timer_interval;
                attr.chan_id = msg.u.ask_channel.chan_id;
                memcpy(attr.uuid, msg.u.ask_channel.uuid, sizeof(attr.uuid));
                attr.blocking_timeout = msg.u.ask_channel.blocking_timeout;

                /* Match channel buffer type to the UST abi. */
                switch (msg.u.ask_channel.output) {
                case LTTNG_EVENT_MMAP:
                default:
                        attr.output = LTTNG_UST_ABI_MMAP;
                        break;
                }

                /* Translate and save channel type. */
                switch (msg.u.ask_channel.type) {
                case LTTNG_UST_ABI_CHAN_PER_CPU:
                        channel->type = CONSUMER_CHANNEL_TYPE_DATA;
                        attr.type = LTTNG_UST_ABI_CHAN_PER_CPU;
                        /*
                         * Set refcount to 1 for owner. Below, we will
                         * pass ownership to the
                         * consumer_thread_channel_poll() thread.
                         */
                        channel->refcount = 1;
                        break;
                case LTTNG_UST_ABI_CHAN_METADATA:
                        channel->type = CONSUMER_CHANNEL_TYPE_METADATA;
                        attr.type = LTTNG_UST_ABI_CHAN_METADATA;
                        break;
                default:
                        abort();
                        goto error_fatal;
                };

                health_code_update();

                ret_ask_channel = ask_channel(ctx, channel, &attr);
                if (ret_ask_channel < 0) {
                        goto end_channel_error;
                }

                if (msg.u.ask_channel.type == LTTNG_UST_ABI_CHAN_METADATA) {
                        int ret_allocate;

                        ret_allocate = consumer_metadata_cache_allocate(channel);
                        if (ret_allocate < 0) {
                                ERR("Allocating metadata cache");
                                goto end_channel_error;
                        }
                        consumer_timer_switch_start(channel, attr.switch_timer_interval);
                        attr.switch_timer_interval = 0;
                } else {
                        int monitor_start_ret;

                        consumer_timer_live_start(channel, msg.u.ask_channel.live_timer_interval);
                        monitor_start_ret = consumer_timer_monitor_start(
                                channel, msg.u.ask_channel.monitor_timer_interval);
                        if (monitor_start_ret < 0) {
                                ERR("Starting channel monitoring timer failed");
                                goto end_channel_error;
                        }
                }

                health_code_update();

                /*
                 * Add the channel to the internal state AFTER all streams were created
                 * and successfully sent to session daemon. This way, all streams must
                 * be ready before this channel is visible to the threads.
                 * If add_channel succeeds, ownership of the channel is
                 * passed to consumer_thread_channel_poll().
                 */
                ret_add_channel = add_channel(channel, ctx);
                if (ret_add_channel < 0) {
                        if (msg.u.ask_channel.type == LTTNG_UST_ABI_CHAN_METADATA) {
                                if (channel->switch_timer_enabled == 1) {
                                        consumer_timer_switch_stop(channel);
                                }
                                consumer_metadata_cache_destroy(channel);
                        }
                        if (channel->live_timer_enabled == 1) {
                                consumer_timer_live_stop(channel);
                        }
                        if (channel->monitor_timer_enabled == 1) {
                                consumer_timer_monitor_stop(channel);
                        }
                        goto end_channel_error;
                }

                health_code_update();

                /*
                 * Channel and streams are now created. Inform the session daemon that
                 * everything went well and should wait to receive the channel and
                 * streams with ustctl API.
                 */
                ret_send = consumer_send_status_channel(sock, channel);
                if (ret_send < 0) {
                        /*
                         * There is probably a problem on the socket.
                         */
                        goto error_fatal;
                }

                break;
        }
        case LTTNG_CONSUMER_GET_CHANNEL:
        {
                int ret, relayd_err = 0;
                uint64_t key = msg.u.get_channel.key;
                struct lttng_consumer_channel *found_channel;

                found_channel = consumer_find_channel(key);
                if (!found_channel) {
                        ERR("UST consumer get channel key %" PRIu64 " not found", key);
                        ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
                        goto end_get_channel;
                }

                health_code_update();

                /* Send the channel to sessiond (and relayd, if applicable). */
                ret = send_channel_to_sessiond_and_relayd(sock, found_channel, ctx, &relayd_err);
                if (ret < 0) {
                        if (relayd_err) {
                                /*
                                 * We were unable to send to the relayd the stream so avoid
                                 * sending back a fatal error to the thread since this is OK
                                 * and the consumer can continue its work. The above call
                                 * has sent the error status message to the sessiond.
                                 */
                                goto end_get_channel_nosignal;
                        }
                        /*
                         * The communicaton was broken hence there is a bad state between
                         * the consumer and sessiond so stop everything.
                         */
                        goto error_get_channel_fatal;
                }

                health_code_update();

                /*
                 * In no monitor mode, the streams ownership is kept inside the channel
                 * so don't send them to the data thread.
                 */
                if (!found_channel->monitor) {
                        goto end_get_channel;
                }

                ret = send_streams_to_thread(found_channel, ctx);
                if (ret < 0) {
                        /*
                         * If we are unable to send the stream to the thread, there is
                         * a big problem so just stop everything.
                         */
                        goto error_get_channel_fatal;
                }
                /* List MUST be empty after or else it could be reused. */
                LTTNG_ASSERT(cds_list_empty(&found_channel->streams.head));
        end_get_channel:
                goto end_msg_sessiond;
        error_get_channel_fatal:
                goto error_fatal;
        end_get_channel_nosignal:
                goto end_nosignal;
        }
        case LTTNG_CONSUMER_DESTROY_CHANNEL:
        {
                uint64_t key = msg.u.destroy_channel.key;

                /*
                 * Only called if streams have not been sent to stream
                 * manager thread. However, channel has been sent to
                 * channel manager thread.
                 */
                notify_thread_del_channel(ctx, key);
                goto end_msg_sessiond;
        }
        case LTTNG_CONSUMER_CLOSE_METADATA:
        {
                int ret;

                ret = close_metadata(msg.u.close_metadata.key);
                if (ret != 0) {
                        ret_code = (lttcomm_return_code) ret;
                }

                goto end_msg_sessiond;
        }
        case LTTNG_CONSUMER_FLUSH_CHANNEL:
        {
                int ret;

                ret = flush_channel(msg.u.flush_channel.key);
                if (ret != 0) {
                        ret_code = (lttcomm_return_code) ret;
                }

                goto end_msg_sessiond;
        }
        case LTTNG_CONSUMER_CLEAR_QUIESCENT_CHANNEL:
        {
                int ret;

                ret = clear_quiescent_channel(msg.u.clear_quiescent_channel.key);
                if (ret != 0) {
                        ret_code = (lttcomm_return_code) ret;
                }

                goto end_msg_sessiond;
        }
        case LTTNG_CONSUMER_PUSH_METADATA:
        {
                int ret;
                uint64_t len = msg.u.push_metadata.len;
                uint64_t key = msg.u.push_metadata.key;
                uint64_t offset = msg.u.push_metadata.target_offset;
                uint64_t version = msg.u.push_metadata.version;
                struct lttng_consumer_channel *found_channel;

                DBG("UST consumer push metadata key %" PRIu64 " of len %" PRIu64, key, len);

                found_channel = consumer_find_channel(key);
                if (!found_channel) {
                        /*
                         * This is possible if the metadata creation on the consumer side
                         * is in flight vis-a-vis a concurrent push metadata from the
                         * session daemon.  Simply return that the channel failed and the
                         * session daemon will handle that message correctly considering
                         * that this race is acceptable thus the DBG() statement here.
                         */
                        DBG("UST consumer push metadata %" PRIu64 " not found", key);
                        ret_code = LTTCOMM_CONSUMERD_CHANNEL_FAIL;
                        goto end_push_metadata_msg_sessiond;
                }

                health_code_update();

                if (!len) {
                        /*
                         * There is nothing to receive. We have simply
                         * checked whether the channel can be found.
                         */
                        ret_code = LTTCOMM_CONSUMERD_SUCCESS;
                        goto end_push_metadata_msg_sessiond;
                }

                /* Tell session daemon we are ready to receive the metadata. */
                ret = consumer_send_status_msg(sock, LTTCOMM_CONSUMERD_SUCCESS);
                if (ret < 0) {
                        /* Somehow, the session daemon is not responding anymore. */
                        goto error_push_metadata_fatal;
                }

                health_code_update();

                /* Wait for more data. */
                health_poll_entry();
                ret = lttng_consumer_poll_socket(consumer_sockpoll);
                health_poll_exit();
                if (ret) {
                        goto error_push_metadata_fatal;
                }

                health_code_update();

                ret = lttng_ustconsumer_recv_metadata(
                        sock, key, offset, len, version, found_channel, 0, 1);
                if (ret < 0) {
                        /* error receiving from sessiond */
                        goto error_push_metadata_fatal;
                } else {
                        ret_code = (lttcomm_return_code) ret;
                        goto end_push_metadata_msg_sessiond;
                }
        end_push_metadata_msg_sessiond:
                goto end_msg_sessiond;
        error_push_metadata_fatal:
                goto error_fatal;
        }
        case LTTNG_CONSUMER_SETUP_METADATA:
        {
                int ret;

                ret = setup_metadata(ctx, msg.u.setup_metadata.key);
                if (ret) {
                        ret_code = (lttcomm_return_code) ret;
                }
                goto end_msg_sessiond;
        }
        case LTTNG_CONSUMER_SNAPSHOT_CHANNEL:
        {
                struct lttng_consumer_channel *found_channel;
                uint64_t key = msg.u.snapshot_channel.key;
                int ret_send;

                found_channel = consumer_find_channel(key);
                if (!found_channel) {
                        DBG("UST snapshot channel not found for key %" PRIu64, key);
                        ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
                } else {
                        if (msg.u.snapshot_channel.metadata) {
                                int ret_snapshot;

                                ret_snapshot = snapshot_metadata(found_channel,
                                                                 key,
                                                                 msg.u.snapshot_channel.pathname,
                                                                 msg.u.snapshot_channel.relayd_id,
                                                                 ctx);
                                if (ret_snapshot < 0) {
                                        ERR("Snapshot metadata failed");
                                        ret_code = LTTCOMM_CONSUMERD_SNAPSHOT_FAILED;
                                }
                        } else {
                                int ret_snapshot;

                                ret_snapshot = snapshot_channel(
                                        found_channel,
                                        key,
                                        msg.u.snapshot_channel.pathname,
                                        msg.u.snapshot_channel.relayd_id,
                                        msg.u.snapshot_channel.nb_packets_per_stream,
                                        ctx);
                                if (ret_snapshot < 0) {
                                        ERR("Snapshot channel failed");
                                        ret_code = LTTCOMM_CONSUMERD_SNAPSHOT_FAILED;
                                }
                        }
                }
                health_code_update();
                ret_send = consumer_send_status_msg(sock, ret_code);
                if (ret_send < 0) {
                        /* Somehow, the session daemon is not responding anymore. */
                        goto end_nosignal;
                }
                health_code_update();
                break;
        }
        case LTTNG_CONSUMER_DISCARDED_EVENTS:
        {
                int ret = 0;
                uint64_t discarded_events;
                struct lttng_ht_iter iter;
                struct lttng_ht *ht;
                struct lttng_consumer_stream *stream;
                uint64_t id = msg.u.discarded_events.session_id;
                uint64_t key = msg.u.discarded_events.channel_key;

                DBG("UST consumer discarded events command for session id %" PRIu64, id);
                rcu_read_lock();
                pthread_mutex_lock(&the_consumer_data.lock);

                ht = the_consumer_data.stream_list_ht;

                /*
                 * We only need a reference to the channel, but they are not
                 * directly indexed, so we just use the first matching stream
                 * to extract the information we need, we default to 0 if not
                 * found (no events are dropped if the channel is not yet in
                 * use).
                 */
                discarded_events = 0;
                cds_lfht_for_each_entry_duplicate(ht->ht,
                                                  ht->hash_fct(&id, lttng_ht_seed),
                                                  ht->match_fct,
                                                  &id,
                                                  &iter.iter,
                                                  stream,
                                                  node_session_id.node)
                {
                        if (stream->chan->key == key) {
                                discarded_events = stream->chan->discarded_events;
                                break;
                        }
                }
                pthread_mutex_unlock(&the_consumer_data.lock);
                rcu_read_unlock();

                DBG("UST consumer discarded events command for session id %" PRIu64
                    ", channel key %" PRIu64,
                    id,
                    key);

                health_code_update();

                /* Send back returned value to session daemon */
                ret = lttcomm_send_unix_sock(sock, &discarded_events, sizeof(discarded_events));
                if (ret < 0) {
                        PERROR("send discarded events");
                        goto error_fatal;
                }

                break;
        }
        case LTTNG_CONSUMER_LOST_PACKETS:
        {
                int ret;
                uint64_t lost_packets;
                struct lttng_ht_iter iter;
                struct lttng_ht *ht;
                struct lttng_consumer_stream *stream;
                uint64_t id = msg.u.lost_packets.session_id;
                uint64_t key = msg.u.lost_packets.channel_key;

                DBG("UST consumer lost packets command for session id %" PRIu64, id);
                rcu_read_lock();
                pthread_mutex_lock(&the_consumer_data.lock);

                ht = the_consumer_data.stream_list_ht;

                /*
                 * We only need a reference to the channel, but they are not
                 * directly indexed, so we just use the first matching stream
                 * to extract the information we need, we default to 0 if not
                 * found (no packets lost if the channel is not yet in use).
                 */
                lost_packets = 0;
                cds_lfht_for_each_entry_duplicate(ht->ht,
                                                  ht->hash_fct(&id, lttng_ht_seed),
                                                  ht->match_fct,
                                                  &id,
                                                  &iter.iter,
                                                  stream,
                                                  node_session_id.node)
                {
                        if (stream->chan->key == key) {
                                lost_packets = stream->chan->lost_packets;
                                break;
                        }
                }
                pthread_mutex_unlock(&the_consumer_data.lock);
                rcu_read_unlock();

                DBG("UST consumer lost packets command for session id %" PRIu64
                    ", channel key %" PRIu64,
                    id,
                    key);

                health_code_update();

                /* Send back returned value to session daemon */
                ret = lttcomm_send_unix_sock(sock, &lost_packets, sizeof(lost_packets));
                if (ret < 0) {
                        PERROR("send lost packets");
                        goto error_fatal;
                }

                break;
        }
        case LTTNG_CONSUMER_SET_CHANNEL_MONITOR_PIPE:
        {
                int channel_monitor_pipe, ret_send, ret_set_channel_monitor_pipe;
                ssize_t ret_recv;

                ret_code = LTTCOMM_CONSUMERD_SUCCESS;
                /* Successfully received the command's type. */
                ret_send = consumer_send_status_msg(sock, ret_code);
                if (ret_send < 0) {
                        goto error_fatal;
                }

                ret_recv = lttcomm_recv_fds_unix_sock(sock, &channel_monitor_pipe, 1);
                if (ret_recv != sizeof(channel_monitor_pipe)) {
                        ERR("Failed to receive channel monitor pipe");
                        goto error_fatal;
                }

                DBG("Received channel monitor pipe (%d)", channel_monitor_pipe);
                ret_set_channel_monitor_pipe =
                        consumer_timer_thread_set_channel_monitor_pipe(channel_monitor_pipe);
                if (!ret_set_channel_monitor_pipe) {
                        int flags;
                        int ret_fcntl;

                        ret_code = LTTCOMM_CONSUMERD_SUCCESS;
                        /* Set the pipe as non-blocking. */
                        ret_fcntl = fcntl(channel_monitor_pipe, F_GETFL, 0);
                        if (ret_fcntl == -1) {
                                PERROR("fcntl get flags of the channel monitoring pipe");
                                goto error_fatal;
                        }
                        flags = ret_fcntl;

                        ret_fcntl = fcntl(channel_monitor_pipe, F_SETFL, flags | O_NONBLOCK);
                        if (ret_fcntl == -1) {
                                PERROR("fcntl set O_NONBLOCK flag of the channel monitoring pipe");
                                goto error_fatal;
                        }
                        DBG("Channel monitor pipe set as non-blocking");
                } else {
                        ret_code = LTTCOMM_CONSUMERD_ALREADY_SET;
                }
                goto end_msg_sessiond;
        }
        case LTTNG_CONSUMER_ROTATE_CHANNEL:
        {
                struct lttng_consumer_channel *found_channel;
                uint64_t key = msg.u.rotate_channel.key;
                int ret_send_status;

                found_channel = consumer_find_channel(key);
                if (!found_channel) {
                        DBG("Channel %" PRIu64 " not found", key);
                        ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
                } else {
                        int rotate_channel;

                        /*
                         * Sample the rotate position of all the streams in
                         * this channel.
                         */
                        rotate_channel = lttng_consumer_rotate_channel(
                                found_channel, key, msg.u.rotate_channel.relayd_id);
                        if (rotate_channel < 0) {
                                ERR("Rotate channel failed");
                                ret_code = LTTCOMM_CONSUMERD_ROTATION_FAIL;
                        }

                        health_code_update();
                }

                ret_send_status = consumer_send_status_msg(sock, ret_code);
                if (ret_send_status < 0) {
                        /* Somehow, the session daemon is not responding anymore. */
                        goto end_rotate_channel_nosignal;
                }

                /*
                 * Rotate the streams that are ready right now.
                 * FIXME: this is a second consecutive iteration over the
                 * streams in a channel, there is probably a better way to
                 * handle this, but it needs to be after the
                 * consumer_send_status_msg() call.
                 */
                if (found_channel) {
                        int ret_rotate_read_streams;

                        ret_rotate_read_streams =
                                lttng_consumer_rotate_ready_streams(found_channel, key);
                        if (ret_rotate_read_streams < 0) {
                                ERR("Rotate channel failed");
                        }
                }
                break;
        end_rotate_channel_nosignal:
                goto end_nosignal;
        }
        case LTTNG_CONSUMER_CLEAR_CHANNEL:
        {
                struct lttng_consumer_channel *found_channel;
                uint64_t key = msg.u.clear_channel.key;
                int ret_send_status;

                found_channel = consumer_find_channel(key);
                if (!found_channel) {
                        DBG("Channel %" PRIu64 " not found", key);
                        ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
                } else {
                        int ret_clear_channel;

                        ret_clear_channel = lttng_consumer_clear_channel(found_channel);
                        if (ret_clear_channel) {
                                ERR("Clear channel failed key %" PRIu64, key);
                                ret_code = (lttcomm_return_code) ret_clear_channel;
                        }

                        health_code_update();
                }
                ret_send_status = consumer_send_status_msg(sock, ret_code);
                if (ret_send_status < 0) {
                        /* Somehow, the session daemon is not responding anymore. */
                        goto end_nosignal;
                }
                break;
        }
        case LTTNG_CONSUMER_INIT:
        {
                int ret_send_status;
                lttng_uuid sessiond_uuid;

                std::copy(std::begin(msg.u.init.sessiond_uuid),
                          std::end(msg.u.init.sessiond_uuid),
                          sessiond_uuid.begin());
                ret_code = lttng_consumer_init_command(ctx, sessiond_uuid);
                health_code_update();
                ret_send_status = consumer_send_status_msg(sock, ret_code);
                if (ret_send_status < 0) {
                        /* Somehow, the session daemon is not responding anymore. */
                        goto end_nosignal;
                }
                break;
        }
        case LTTNG_CONSUMER_CREATE_TRACE_CHUNK:
        {
                const struct lttng_credentials credentials = {
                        .uid = LTTNG_OPTIONAL_INIT_VALUE(
                                msg.u.create_trace_chunk.credentials.value.uid),
                        .gid = LTTNG_OPTIONAL_INIT_VALUE(
                                msg.u.create_trace_chunk.credentials.value.gid),
                };
                const bool is_local_trace = !msg.u.create_trace_chunk.relayd_id.is_set;
                const uint64_t relayd_id = msg.u.create_trace_chunk.relayd_id.value;
                const char *chunk_override_name = *msg.u.create_trace_chunk.override_name ?
                        msg.u.create_trace_chunk.override_name :
                        nullptr;
                struct lttng_directory_handle *chunk_directory_handle = nullptr;

                /*
                 * The session daemon will only provide a chunk directory file
                 * descriptor for local traces.
                 */
                if (is_local_trace) {
                        int chunk_dirfd;
                        int ret_send_status;
                        ssize_t ret_recv;

                        /* Acnowledge the reception of the command. */
                        ret_send_status = consumer_send_status_msg(sock, LTTCOMM_CONSUMERD_SUCCESS);
                        if (ret_send_status < 0) {
                                /* Somehow, the session daemon is not responding anymore. */
                                goto end_nosignal;
                        }

                        /*
                         * Receive trace chunk domain dirfd.
                         */
                        ret_recv = lttcomm_recv_fds_unix_sock(sock, &chunk_dirfd, 1);
                        if (ret_recv != sizeof(chunk_dirfd)) {
                                ERR("Failed to receive trace chunk domain directory file descriptor");
                                goto error_fatal;
                        }

                        DBG("Received trace chunk domain directory fd (%d)", chunk_dirfd);
                        chunk_directory_handle =
                                lttng_directory_handle_create_from_dirfd(chunk_dirfd);
                        if (!chunk_directory_handle) {
                                ERR("Failed to initialize chunk domain directory handle from directory file descriptor");
                                if (close(chunk_dirfd)) {
                                        PERROR("Failed to close chunk directory file descriptor");
                                }
                                goto error_fatal;
                        }
                }

                ret_code = lttng_consumer_create_trace_chunk(
                        !is_local_trace ? &relayd_id : nullptr,
                        msg.u.create_trace_chunk.session_id,
                        msg.u.create_trace_chunk.chunk_id,
                        (time_t) msg.u.create_trace_chunk.creation_timestamp,
                        chunk_override_name,
                        msg.u.create_trace_chunk.credentials.is_set ? &credentials : nullptr,
                        chunk_directory_handle);
                lttng_directory_handle_put(chunk_directory_handle);
                goto end_msg_sessiond;
        }
        case LTTNG_CONSUMER_CLOSE_TRACE_CHUNK:
        {
                enum lttng_trace_chunk_command_type close_command =
                        (lttng_trace_chunk_command_type) msg.u.close_trace_chunk.close_command.value;
                const uint64_t relayd_id = msg.u.close_trace_chunk.relayd_id.value;
                struct lttcomm_consumer_close_trace_chunk_reply reply;
                char closed_trace_chunk_path[LTTNG_PATH_MAX] = {};
                int ret;

                ret_code = lttng_consumer_close_trace_chunk(
                        msg.u.close_trace_chunk.relayd_id.is_set ? &relayd_id : nullptr,
                        msg.u.close_trace_chunk.session_id,
                        msg.u.close_trace_chunk.chunk_id,
                        (time_t) msg.u.close_trace_chunk.close_timestamp,
                        msg.u.close_trace_chunk.close_command.is_set ? &close_command : nullptr,
                        closed_trace_chunk_path);
                reply.ret_code = ret_code;
                reply.path_length = strlen(closed_trace_chunk_path) + 1;
                ret = lttcomm_send_unix_sock(sock, &reply, sizeof(reply));
                if (ret != sizeof(reply)) {
                        goto error_fatal;
                }
                ret = lttcomm_send_unix_sock(sock, closed_trace_chunk_path, reply.path_length);
                if (ret != reply.path_length) {
                        goto error_fatal;
                }
                goto end_nosignal;
        }
        case LTTNG_CONSUMER_TRACE_CHUNK_EXISTS:
        {
                const uint64_t relayd_id = msg.u.trace_chunk_exists.relayd_id.value;

                ret_code = lttng_consumer_trace_chunk_exists(
                        msg.u.trace_chunk_exists.relayd_id.is_set ? &relayd_id : nullptr,
                        msg.u.trace_chunk_exists.session_id,
                        msg.u.trace_chunk_exists.chunk_id);
                goto end_msg_sessiond;
        }
        case LTTNG_CONSUMER_OPEN_CHANNEL_PACKETS:
        {
                const uint64_t key = msg.u.open_channel_packets.key;
                struct lttng_consumer_channel *found_channel = consumer_find_channel(key);

                if (found_channel) {
                        pthread_mutex_lock(&found_channel->lock);
                        ret_code = lttng_consumer_open_channel_packets(found_channel);
                        pthread_mutex_unlock(&found_channel->lock);
                } else {
                        /*
                         * The channel could have disappeared in per-pid
                         * buffering mode.
                         */
                        DBG("Channel %" PRIu64 " not found", key);
                        ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
                }

                health_code_update();
                goto end_msg_sessiond;
        }
        default:
                break;
        }

end_nosignal:
        /*
         * Return 1 to indicate success since the 0 value can be a socket
         * shutdown during the recv() or send() call.
         */
        ret_func = 1;
        goto end;

end_msg_sessiond:
        /*
         * The returned value here is not useful since either way we'll return 1 to
         * the caller because the session daemon socket management is done
         * elsewhere. Returning a negative code or 0 will shutdown the consumer.
         */
        {
                int ret_send_status;

                ret_send_status = consumer_send_status_msg(sock, ret_code);
                if (ret_send_status < 0) {
                        goto error_fatal;
                }
        }

        ret_func = 1;
        goto end;

end_channel_error:
        if (channel) {
                consumer_del_channel(channel);
        }
        /* We have to send a status channel message indicating an error. */
        {
                int ret_send_status;

                ret_send_status = consumer_send_status_channel(sock, nullptr);
                if (ret_send_status < 0) {
                        /* Stop everything if session daemon can not be notified. */
                        goto error_fatal;
                }
        }

        ret_func = 1;
        goto end;

error_fatal:
        /* This will issue a consumer stop. */
        ret_func = -1;
        goto end;

end:
        rcu_read_unlock();
        health_code_update();
        return ret_func;
}

int lttng_ust_flush_buffer(struct lttng_consumer_stream *stream, int producer_active)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream->ustream);

        return lttng_ust_ctl_flush_buffer(stream->ustream, producer_active);
}

/*
 * Take a snapshot for a specific stream.
 *
 * Returns 0 on success, < 0 on error
 */
int lttng_ustconsumer_take_snapshot(struct lttng_consumer_stream *stream)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream->ustream);

        return lttng_ust_ctl_snapshot(stream->ustream);
}

/*
 * Sample consumed and produced positions for a specific stream.
 *
 * Returns 0 on success, < 0 on error.
 */
int lttng_ustconsumer_sample_snapshot_positions(struct lttng_consumer_stream *stream)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream->ustream);

        return lttng_ust_ctl_snapshot_sample_positions(stream->ustream);
}

/*
 * Get the produced position
 *
 * Returns 0 on success, < 0 on error
 */
int lttng_ustconsumer_get_produced_snapshot(struct lttng_consumer_stream *stream,
                                            unsigned long *pos)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream->ustream);
        LTTNG_ASSERT(pos);

        return lttng_ust_ctl_snapshot_get_produced(stream->ustream, pos);
}

/*
 * Get the consumed position
 *
 * Returns 0 on success, < 0 on error
 */
int lttng_ustconsumer_get_consumed_snapshot(struct lttng_consumer_stream *stream,
                                            unsigned long *pos)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream->ustream);
        LTTNG_ASSERT(pos);

        return lttng_ust_ctl_snapshot_get_consumed(stream->ustream, pos);
}

int lttng_ustconsumer_flush_buffer(struct lttng_consumer_stream *stream, int producer)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream->ustream);

        return lttng_ust_ctl_flush_buffer(stream->ustream, producer);
}

int lttng_ustconsumer_clear_buffer(struct lttng_consumer_stream *stream)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream->ustream);

        return lttng_ust_ctl_clear_buffer(stream->ustream);
}

int lttng_ustconsumer_get_current_timestamp(struct lttng_consumer_stream *stream, uint64_t *ts)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream->ustream);
        LTTNG_ASSERT(ts);

        return lttng_ust_ctl_get_current_timestamp(stream->ustream, ts);
}

int lttng_ustconsumer_get_sequence_number(struct lttng_consumer_stream *stream, uint64_t *seq)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream->ustream);
        LTTNG_ASSERT(seq);

        return lttng_ust_ctl_get_sequence_number(stream->ustream, seq);
}

/*
 * Called when the stream signals the consumer that it has hung up.
 */
void lttng_ustconsumer_on_stream_hangup(struct lttng_consumer_stream *stream)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream->ustream);

        pthread_mutex_lock(&stream->lock);
        if (!stream->quiescent) {
                if (lttng_ust_ctl_flush_buffer(stream->ustream, 0) < 0) {
                        ERR("Failed to flush buffer on stream hang-up");
                } else {
                        stream->quiescent = true;
                }
        }

        stream->hangup_flush_done = 1;
        pthread_mutex_unlock(&stream->lock);
}

void lttng_ustconsumer_del_channel(struct lttng_consumer_channel *chan)
{
        int i;

        LTTNG_ASSERT(chan);
        LTTNG_ASSERT(chan->uchan);
        LTTNG_ASSERT(chan->buffer_credentials.is_set);

        if (chan->switch_timer_enabled == 1) {
                consumer_timer_switch_stop(chan);
        }
        for (i = 0; i < chan->nr_stream_fds; i++) {
                int ret;

                ret = close(chan->stream_fds[i]);
                if (ret) {
                        PERROR("close");
                }
                if (chan->shm_path[0]) {
                        char shm_path[PATH_MAX];

                        ret = get_stream_shm_path(shm_path, chan->shm_path, i);
                        if (ret) {
                                ERR("Cannot get stream shm path");
                        }
                        ret = run_as_unlink(shm_path,
                                            lttng_credentials_get_uid(LTTNG_OPTIONAL_GET_PTR(
                                                    chan->buffer_credentials)),
                                            lttng_credentials_get_gid(LTTNG_OPTIONAL_GET_PTR(
                                                    chan->buffer_credentials)));
                        if (ret) {
                                PERROR("unlink %s", shm_path);
                        }
                }
        }
}

void lttng_ustconsumer_free_channel(struct lttng_consumer_channel *chan)
{
        LTTNG_ASSERT(chan);
        LTTNG_ASSERT(chan->uchan);
        LTTNG_ASSERT(chan->buffer_credentials.is_set);

        consumer_metadata_cache_destroy(chan);
        lttng_ust_ctl_destroy_channel(chan->uchan);
        /* Try to rmdir all directories under shm_path root. */
        if (chan->root_shm_path[0]) {
                (void) run_as_rmdir_recursive(
                        chan->root_shm_path,
                        lttng_credentials_get_uid(LTTNG_OPTIONAL_GET_PTR(chan->buffer_credentials)),
                        lttng_credentials_get_gid(LTTNG_OPTIONAL_GET_PTR(chan->buffer_credentials)),
                        LTTNG_DIRECTORY_HANDLE_SKIP_NON_EMPTY_FLAG);
        }
        free(chan->stream_fds);
}

void lttng_ustconsumer_del_stream(struct lttng_consumer_stream *stream)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream->ustream);

        if (stream->chan->switch_timer_enabled == 1) {
                consumer_timer_switch_stop(stream->chan);
        }
        lttng_ust_ctl_destroy_stream(stream->ustream);
}

int lttng_ustconsumer_get_wakeup_fd(struct lttng_consumer_stream *stream)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream->ustream);

        return lttng_ust_ctl_stream_get_wakeup_fd(stream->ustream);
}

int lttng_ustconsumer_close_wakeup_fd(struct lttng_consumer_stream *stream)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream->ustream);

        return lttng_ust_ctl_stream_close_wakeup_fd(stream->ustream);
}

/*
 * Write up to one packet from the metadata cache to the channel.
 *
 * Returns the number of bytes pushed from the cache into the ring buffer, 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);
        if (stream->chan->metadata_cache->contents.size == stream->ust_metadata_pushed) {
                /*
                 * In the context of a user space metadata channel, a
                 * change in version can be detected in two ways:
                 *   1) During the pre-consume of the `read_subbuffer` loop,
                 *   2) When populating the metadata ring buffer (i.e. here).
                 *
                 * This function is invoked when there is no metadata
                 * available in the ring-buffer. If all data was consumed
                 * up to the size of the metadata cache, there is no metadata
                 * to insert in the ring-buffer.
                 *
                 * However, the metadata version could still have changed (a
                 * regeneration without any new data will yield the same cache
                 * size).
                 *
                 * The cache's version is checked for a version change and the
                 * consumed position is reset if one occurred.
                 *
                 * This check is only necessary for the user space domain as
                 * it has to manage the cache explicitly. If this reset was not
                 * performed, no metadata would be consumed (and no reset would
                 * occur as part of the pre-consume) until the metadata size
                 * exceeded the cache size.
                 */
                if (stream->metadata_version != stream->chan->metadata_cache->version) {
                        metadata_stream_reset_cache_consumed_position(stream);
                        consumer_stream_metadata_set_version(stream,
                                                             stream->chan->metadata_cache->version);
                } else {
                        ret = 0;
                        goto end;
                }
        }

        write_len = lttng_ust_ctl_write_one_packet_to_channel(
                stream->chan->uchan,
                &stream->chan->metadata_cache->contents.data[stream->ust_metadata_pushed],
                stream->chan->metadata_cache->contents.size - stream->ust_metadata_pushed);
        LTTNG_ASSERT(write_len != 0);
        if (write_len < 0) {
                ERR("Writing one metadata packet");
                ret = write_len;
                goto end;
        }
        stream->ust_metadata_pushed += write_len;

        LTTNG_ASSERT(stream->chan->metadata_cache->contents.size >= 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.
         */
        if (lttng_ust_ctl_flush_buffer(stream->ustream, 1)) {
                ERR("Failed to flush buffer while committing one metadata packet");
                ret = -EIO;
        } else {
                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.
 *
 * The RCU read side lock must be held by the caller.
 */
enum sync_metadata_status
lttng_ustconsumer_sync_metadata(struct lttng_consumer_local_data *ctx,
                                struct lttng_consumer_stream *metadata_stream)
{
        int ret;
        enum sync_metadata_status status;
        struct lttng_consumer_channel *metadata_channel;

        LTTNG_ASSERT(ctx);
        LTTNG_ASSERT(metadata_stream);
        ASSERT_RCU_READ_LOCKED();

        metadata_channel = metadata_stream->chan;
        pthread_mutex_unlock(&metadata_stream->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_channel, 0, 0);
        pthread_mutex_lock(&metadata_stream->lock);
        if (ret < 0) {
                status = SYNC_METADATA_STATUS_ERROR;
                goto end;
        }

        /*
         * The metadata stream and channel can be deleted while the
         * metadata stream lock was released. The streamed is checked
         * for deletion before we use it further.
         *
         * Note that it is safe to access a logically-deleted stream since its
         * existence is still guaranteed by the RCU read side lock. However,
         * it should no longer be used. The close/deletion of the metadata
         * channel and stream already guarantees that all metadata has been
         * consumed. Therefore, there is nothing left to do in this function.
         */
        if (consumer_stream_is_deleted(metadata_stream)) {
                DBG("Metadata stream %" PRIu64 " was deleted during the metadata synchronization",
                    metadata_stream->key);
                status = SYNC_METADATA_STATUS_NO_DATA;
                goto end;
        }

        ret = commit_one_metadata_packet(metadata_stream);
        if (ret < 0) {
                status = SYNC_METADATA_STATUS_ERROR;
                goto end;
        } else if (ret > 0) {
                status = SYNC_METADATA_STATUS_NEW_DATA;
        } else /* ret == 0 */ {
                status = SYNC_METADATA_STATUS_NO_DATA;
                goto end;
        }

        ret = lttng_ust_ctl_snapshot(metadata_stream->ustream);
        if (ret < 0) {
                ERR("Failed to take a snapshot of the metadata ring-buffer positions, ret = %d",
                    ret);
                status = SYNC_METADATA_STATUS_ERROR;
                goto end;
        }

end:
        return status;
}

/*
 * 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 lttng_ust_ctl_consumer_stream *ustream;

        LTTNG_ASSERT(stream);
        LTTNG_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 = lttng_ust_ctl_get_next_subbuf(ustream);
        if (ret) {
                /* No more data found, flag the stream. */
                stream->has_data = 0;
                ret = 0;
                goto end;
        }

        ret = lttng_ust_ctl_put_subbuf(ustream);
        LTTNG_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 consumer_stream_ust_on_wake_up(struct lttng_consumer_stream *stream)
{
        int ret = 0;

        /*
         * 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;
                }
        }

        return ret;
}

static int extract_common_subbuffer_info(struct lttng_consumer_stream *stream,
                                         struct stream_subbuffer *subbuf)
{
        int ret;

        ret = lttng_ust_ctl_get_subbuf_size(stream->ustream, &subbuf->info.data.subbuf_size);
        if (ret) {
                goto end;
        }

        ret = lttng_ust_ctl_get_padded_subbuf_size(stream->ustream,
                                                   &subbuf->info.data.padded_subbuf_size);
        if (ret) {
                goto end;
        }

end:
        return ret;
}

static int extract_metadata_subbuffer_info(struct lttng_consumer_stream *stream,
                                           struct stream_subbuffer *subbuf)
{
        int ret;

        ret = extract_common_subbuffer_info(stream, subbuf);
        if (ret) {
                goto end;
        }

        subbuf->info.metadata.version = stream->metadata_version;

end:
        return ret;
}

static int extract_data_subbuffer_info(struct lttng_consumer_stream *stream,
                                       struct stream_subbuffer *subbuf)
{
        int ret;

        ret = extract_common_subbuffer_info(stream, subbuf);
        if (ret) {
                goto end;
        }

        ret = lttng_ust_ctl_get_packet_size(stream->ustream, &subbuf->info.data.packet_size);
        if (ret < 0) {
                PERROR("Failed to get sub-buffer packet size");
                goto end;
        }

        ret = lttng_ust_ctl_get_content_size(stream->ustream, &subbuf->info.data.content_size);
        if (ret < 0) {
                PERROR("Failed to get sub-buffer content size");
                goto end;
        }

        ret = lttng_ust_ctl_get_timestamp_begin(stream->ustream,
                                                &subbuf->info.data.timestamp_begin);
        if (ret < 0) {
                PERROR("Failed to get sub-buffer begin timestamp");
                goto end;
        }

        ret = lttng_ust_ctl_get_timestamp_end(stream->ustream, &subbuf->info.data.timestamp_end);
        if (ret < 0) {
                PERROR("Failed to get sub-buffer end timestamp");
                goto end;
        }

        ret = lttng_ust_ctl_get_events_discarded(stream->ustream,
                                                 &subbuf->info.data.events_discarded);
        if (ret) {
                PERROR("Failed to get sub-buffer events discarded count");
                goto end;
        }

        ret = lttng_ust_ctl_get_sequence_number(stream->ustream,
                                                &subbuf->info.data.sequence_number.value);
        if (ret) {
                /* May not be supported by older LTTng-modules. */
                if (ret != -ENOTTY) {
                        PERROR("Failed to get sub-buffer sequence number");
                        goto end;
                }
        } else {
                subbuf->info.data.sequence_number.is_set = true;
        }

        ret = lttng_ust_ctl_get_stream_id(stream->ustream, &subbuf->info.data.stream_id);
        if (ret < 0) {
                PERROR("Failed to get stream id");
                goto end;
        }

        ret = lttng_ust_ctl_get_instance_id(stream->ustream,
                                            &subbuf->info.data.stream_instance_id.value);
        if (ret) {
                /* May not be supported by older LTTng-modules. */
                if (ret != -ENOTTY) {
                        PERROR("Failed to get stream instance id");
                        goto end;
                }
        } else {
                subbuf->info.data.stream_instance_id.is_set = true;
        }
end:
        return ret;
}

static int get_next_subbuffer_common(struct lttng_consumer_stream *stream,
                                     struct stream_subbuffer *subbuffer)
{
        int ret;
        const char *addr;

        ret = stream->read_subbuffer_ops.extract_subbuffer_info(stream, subbuffer);
        if (ret) {
                goto end;
        }

        ret = get_current_subbuf_addr(stream, &addr);
        if (ret) {
                goto end;
        }

        subbuffer->buffer.buffer =
                lttng_buffer_view_init(addr, 0, subbuffer->info.data.padded_subbuf_size);
        LTTNG_ASSERT(subbuffer->buffer.buffer.data != nullptr);
end:
        return ret;
}

static enum get_next_subbuffer_status get_next_subbuffer(struct lttng_consumer_stream *stream,
                                                         struct stream_subbuffer *subbuffer)
{
        int ret;
        enum get_next_subbuffer_status status;

        ret = lttng_ust_ctl_get_next_subbuf(stream->ustream);
        switch (ret) {
        case 0:
                status = GET_NEXT_SUBBUFFER_STATUS_OK;
                break;
        case -ENODATA:
        case -EAGAIN:
                /*
                 * The caller only expects -ENODATA when there is no data to
                 * read, but the kernel tracer returns -EAGAIN when there is
                 * currently no data for a non-finalized stream, and -ENODATA
                 * when there is no data for a finalized stream. Those can be
                 * combined into a -ENODATA return value.
                 */
                status = GET_NEXT_SUBBUFFER_STATUS_NO_DATA;
                goto end;
        default:
                status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
                goto end;
        }

        ret = get_next_subbuffer_common(stream, subbuffer);
        if (ret) {
                status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
                goto end;
        }
end:
        return status;
}

static enum get_next_subbuffer_status
get_next_subbuffer_metadata(struct lttng_consumer_stream *stream,
                            struct stream_subbuffer *subbuffer)
{
        int ret;
        bool cache_empty;
        bool got_subbuffer;
        bool coherent;
        bool buffer_empty;
        unsigned long consumed_pos, produced_pos;
        enum get_next_subbuffer_status status;

        do {
                ret = lttng_ust_ctl_get_next_subbuf(stream->ustream);
                if (ret == 0) {
                        got_subbuffer = true;
                } else {
                        got_subbuffer = false;
                        if (ret != -EAGAIN) {
                                /* Fatal error. */
                                status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
                                goto end;
                        }
                }

                /*
                 * Determine if the cache is empty and ensure that a sub-buffer
                 * is made available if the cache is not empty.
                 */
                if (!got_subbuffer) {
                        ret = commit_one_metadata_packet(stream);
                        if (ret < 0 && ret != -ENOBUFS) {
                                status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
                                goto end;
                        } else if (ret == 0) {
                                /* Not an error, the cache is empty. */
                                cache_empty = true;
                                status = GET_NEXT_SUBBUFFER_STATUS_NO_DATA;
                                goto end;
                        } else {
                                cache_empty = false;
                        }
                } else {
                        pthread_mutex_lock(&stream->chan->metadata_cache->lock);
                        cache_empty = stream->chan->metadata_cache->contents.size ==
                                stream->ust_metadata_pushed;
                        pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
                }
        } while (!got_subbuffer);

        /* Populate sub-buffer infos and view. */
        ret = get_next_subbuffer_common(stream, subbuffer);
        if (ret) {
                status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
                goto end;
        }

        ret = lttng_ustconsumer_sample_snapshot_positions(stream);
        if (ret < 0) {
                /*
                 * -EAGAIN is not expected since we got a sub-buffer and haven't
                 * pushed the consumption position yet (on put_next).
                 */
                PERROR("Failed to take a snapshot of metadata buffer positions");
                status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
                goto end;
        }

        ret = lttng_ustconsumer_get_consumed_snapshot(stream, &consumed_pos);
        if (ret) {
                PERROR("Failed to get metadata consumed position");
                status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
                goto end;
        }

        ret = lttng_ustconsumer_get_produced_snapshot(stream, &produced_pos);
        if (ret) {
                PERROR("Failed to get metadata produced position");
                status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
                goto end;
        }

        /* Last sub-buffer of the ring buffer ? */
        buffer_empty = (consumed_pos + stream->max_sb_size) == produced_pos;

        /*
         * The sessiond registry lock ensures that coherent units of metadata
         * are pushed to the consumer daemon at once. Hence, if a sub-buffer is
         * acquired, the cache is empty, and it is the only available sub-buffer
         * available, it is safe to assume that it is "coherent".
         */
        coherent = got_subbuffer && cache_empty && buffer_empty;

        LTTNG_OPTIONAL_SET(&subbuffer->info.metadata.coherent, coherent);
        status = GET_NEXT_SUBBUFFER_STATUS_OK;
end:
        return status;
}

static int put_next_subbuffer(struct lttng_consumer_stream *stream,
                              struct stream_subbuffer *subbuffer __attribute__((unused)))
{
        const int ret = lttng_ust_ctl_put_next_subbuf(stream->ustream);

        LTTNG_ASSERT(ret == 0);
        return ret;
}

static int signal_metadata(struct lttng_consumer_stream *stream,
                           struct lttng_consumer_local_data *ctx __attribute__((unused)))
{
        ASSERT_LOCKED(stream->metadata_rdv_lock);
        return pthread_cond_broadcast(&stream->metadata_rdv) ? -errno : 0;
}

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

        stream->read_subbuffer_ops.on_wake_up = consumer_stream_ust_on_wake_up;
        if (stream->metadata_flag) {
                stream->read_subbuffer_ops.get_next_subbuffer = get_next_subbuffer_metadata;
                stream->read_subbuffer_ops.extract_subbuffer_info = extract_metadata_subbuffer_info;
                stream->read_subbuffer_ops.reset_metadata =
                        metadata_stream_reset_cache_consumed_position;
                if (stream->chan->is_live) {
                        stream->read_subbuffer_ops.on_sleep = signal_metadata;
                        ret = consumer_stream_enable_metadata_bucketization(stream);
                        if (ret) {
                                goto end;
                        }
                }
        } else {
                stream->read_subbuffer_ops.get_next_subbuffer = get_next_subbuffer;
                stream->read_subbuffer_ops.extract_subbuffer_info = extract_data_subbuffer_info;
                stream->read_subbuffer_ops.on_sleep = notify_if_more_data;
                if (stream->chan->is_live) {
                        stream->read_subbuffer_ops.send_live_beacon = consumer_flush_ust_index;
                }
        }

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

/*
 * Called when a stream is created.
 *
 * Return 0 on success or else a negative value.
 */
int lttng_ustconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
{
        int ret;

        LTTNG_ASSERT(stream);

        /*
         * Don't create anything if this is set for streaming or if there is
         * no current trace chunk on the parent channel.
         */
        if (stream->net_seq_idx == (uint64_t) -1ULL && stream->chan->monitor &&
            stream->chan->trace_chunk) {
                ret = consumer_stream_create_output_files(stream, true);
                if (ret) {
                        goto error;
                }
        }

        lttng_ustconsumer_set_stream_ops(stream);
        ret = 0;

error:
        return ret;
}

/*
 * Check if data is still being extracted from the buffers for a specific
 * stream. Consumer data lock MUST be acquired before calling this function
 * and the stream lock.
 *
 * Return 1 if the traced data are still getting read else 0 meaning that the
 * data is available for trace viewer reading.
 */
int lttng_ustconsumer_data_pending(struct lttng_consumer_stream *stream)
{
        int ret;

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

        DBG("UST consumer checking data pending");

        if (stream->endpoint_status != CONSUMER_ENDPOINT_ACTIVE) {
                ret = 0;
                goto end;
        }

        if (stream->chan->type == CONSUMER_CHANNEL_TYPE_METADATA) {
                uint64_t contiguous, pushed;

                /* Ease our life a bit. */
                pthread_mutex_lock(&stream->chan->metadata_cache->lock);
                contiguous = stream->chan->metadata_cache->contents.size;
                pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
                pushed = stream->ust_metadata_pushed;

                /*
                 * We can simply check whether all contiguously available data
                 * has been pushed to the ring buffer, since the push operation
                 * is performed within get_next_subbuf(), and because both
                 * get_next_subbuf() and put_next_subbuf() are issued atomically
                 * thanks to the stream lock within
                 * lttng_ustconsumer_read_subbuffer(). This basically means that
                 * whetnever ust_metadata_pushed is incremented, the associated
                 * metadata has been consumed from the metadata stream.
                 */
                DBG("UST consumer metadata pending check: contiguous %" PRIu64
                    " vs pushed %" PRIu64,
                    contiguous,
                    pushed);
                LTTNG_ASSERT(((int64_t) (contiguous - pushed)) >= 0);
                if ((contiguous != pushed) ||
                    (((int64_t) contiguous - pushed) > 0 || contiguous == 0)) {
                        ret = 1; /* Data is pending */
                        goto end;
                }
        } else {
                ret = lttng_ust_ctl_get_next_subbuf(stream->ustream);
                if (ret == 0) {
                        /*
                         * There is still data so let's put back this
                         * subbuffer.
                         */
                        ret = lttng_ust_ctl_put_subbuf(stream->ustream);
                        LTTNG_ASSERT(ret == 0);
                        ret = 1; /* Data is pending */
                        goto end;
                }
        }

        /* Data is NOT pending so ready to be read. */
        ret = 0;

end:
        return ret;
}

/*
 * Stop a given metadata channel timer if enabled and close the wait fd which
 * is the poll pipe of the metadata stream.
 *
 * This MUST be called with the metadata channel lock acquired.
 */
void lttng_ustconsumer_close_metadata(struct lttng_consumer_channel *metadata)
{
        int ret;

        LTTNG_ASSERT(metadata);
        LTTNG_ASSERT(metadata->type == CONSUMER_CHANNEL_TYPE_METADATA);

        DBG("Closing metadata channel key %" PRIu64, metadata->key);

        if (metadata->switch_timer_enabled == 1) {
                consumer_timer_switch_stop(metadata);
        }

        if (!metadata->metadata_stream) {
                goto end;
        }

        /*
         * Closing write side so the thread monitoring the stream wakes up if any
         * and clean the metadata stream.
         */
        if (metadata->metadata_stream->ust_metadata_poll_pipe[1] >= 0) {
                ret = close(metadata->metadata_stream->ust_metadata_poll_pipe[1]);
                if (ret < 0) {
                        PERROR("closing metadata pipe write side");
                }
                metadata->metadata_stream->ust_metadata_poll_pipe[1] = -1;
        }

end:
        return;
}

/*
 * Close every metadata stream wait fd of the metadata hash table. This
 * function MUST be used very carefully so not to run into a race between the
 * metadata thread handling streams and this function closing their wait fd.
 *
 * For UST, this is used when the session daemon hangs up. Its the metadata
 * producer so calling this is safe because we are assured that no state change
 * can occur in the metadata thread for the streams in the hash table.
 */
void lttng_ustconsumer_close_all_metadata(struct lttng_ht *metadata_ht)
{
        struct lttng_ht_iter iter;
        struct lttng_consumer_stream *stream;

        LTTNG_ASSERT(metadata_ht);
        LTTNG_ASSERT(metadata_ht->ht);

        DBG("UST consumer closing all metadata streams");

        rcu_read_lock();
        cds_lfht_for_each_entry (metadata_ht->ht, &iter.iter, stream, node.node) {
                health_code_update();

                pthread_mutex_lock(&stream->chan->lock);
                lttng_ustconsumer_close_metadata(stream->chan);
                pthread_mutex_unlock(&stream->chan->lock);
        }
        rcu_read_unlock();
}

void lttng_ustconsumer_close_stream_wakeup(struct lttng_consumer_stream *stream)
{
        int ret;

        ret = lttng_ust_ctl_stream_close_wakeup_fd(stream->ustream);
        if (ret < 0) {
                ERR("Unable to close wakeup fd");
        }
}

/*
 * Please refer to consumer-timer.c before adding any lock within this
 * function or any of its callees. Timers have a very strict locking
 * semantic with respect to teardown. Failure to respect this semantic
 * introduces deadlocks.
 *
 * DON'T hold the metadata lock when calling this function, else this
 * can cause deadlock involving consumer awaiting for metadata to be
 * pushed out due to concurrent interaction with the session daemon.
 */
int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
                                       struct lttng_consumer_channel *channel,
                                       int timer,
                                       int wait)
{
        struct lttcomm_metadata_request_msg request;
        struct lttcomm_consumer_msg msg;
        enum lttcomm_return_code ret_code = LTTCOMM_CONSUMERD_SUCCESS;
        uint64_t len, key, offset, version;
        int ret;

        LTTNG_ASSERT(channel);
        LTTNG_ASSERT(channel->metadata_cache);

        memset(&request, 0, sizeof(request));

        /* send the metadata request to sessiond */
        switch (the_consumer_data.type) {
        case LTTNG_CONSUMER64_UST:
                request.bits_per_long = 64;
                break;
        case LTTNG_CONSUMER32_UST:
                request.bits_per_long = 32;
                break;
        default:
                request.bits_per_long = 0;
                break;
        }

        request.session_id = channel->session_id;
        request.session_id_per_pid = channel->session_id_per_pid;
        /*
         * Request the application UID here so the metadata of that application can
         * be sent back. The channel UID corresponds to the user UID of the session
         * used for the rights on the stream file(s).
         */
        request.uid = channel->ust_app_uid;
        request.key = channel->key;

        DBG("Sending metadata request to sessiond, session id %" PRIu64 ", per-pid %" PRIu64
            ", app UID %u and channel key %" PRIu64,
            request.session_id,
            request.session_id_per_pid,
            request.uid,
            request.key);

        pthread_mutex_lock(&ctx->metadata_socket_lock);

        health_code_update();

        ret = lttcomm_send_unix_sock(ctx->consumer_metadata_socket, &request, sizeof(request));
        if (ret < 0) {
                ERR("Asking metadata to sessiond");
                goto end;
        }

        health_code_update();

        /* Receive the metadata from sessiond */
        ret = lttcomm_recv_unix_sock(ctx->consumer_metadata_socket, &msg, sizeof(msg));
        if (ret != sizeof(msg)) {
                DBG("Consumer received unexpected message size %d (expects %zu)", ret, sizeof(msg));
                lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_ERROR_RECV_CMD);
                /*
                 * The ret value might 0 meaning an orderly shutdown but this is ok
                 * since the caller handles this.
                 */
                goto end;
        }

        health_code_update();

        if (msg.cmd_type == LTTNG_ERR_UND) {
                /* No registry found */
                (void) consumer_send_status_msg(ctx->consumer_metadata_socket, ret_code);
                ret = 0;
                goto end;
        } else if (msg.cmd_type != LTTNG_CONSUMER_PUSH_METADATA) {
                ERR("Unexpected cmd_type received %d", msg.cmd_type);
                ret = -1;
                goto end;
        }

        len = msg.u.push_metadata.len;
        key = msg.u.push_metadata.key;
        offset = msg.u.push_metadata.target_offset;
        version = msg.u.push_metadata.version;

        LTTNG_ASSERT(key == channel->key);
        if (len == 0) {
                DBG("No new metadata to receive for key %" PRIu64, key);
        }

        health_code_update();

        /* Tell session daemon we are ready to receive the metadata. */
        ret = consumer_send_status_msg(ctx->consumer_metadata_socket, LTTCOMM_CONSUMERD_SUCCESS);
        if (ret < 0 || len == 0) {
                /*
                 * Somehow, the session daemon is not responding anymore or there is
                 * nothing to receive.
                 */
                goto end;
        }

        health_code_update();

        ret = lttng_ustconsumer_recv_metadata(
                ctx->consumer_metadata_socket, key, offset, len, version, channel, timer, wait);
        if (ret >= 0) {
                /*
                 * Only send the status msg if the sessiond is alive meaning a positive
                 * ret code.
                 */
                (void) consumer_send_status_msg(ctx->consumer_metadata_socket, ret);
        }
        ret = 0;

end:
        health_code_update();

        pthread_mutex_unlock(&ctx->metadata_socket_lock);
        return ret;
}

/*
 * Return the ustctl call for the get stream id.
 */
int lttng_ustconsumer_get_stream_id(struct lttng_consumer_stream *stream, uint64_t *stream_id)
{
        LTTNG_ASSERT(stream);
        LTTNG_ASSERT(stream_id);

        return lttng_ust_ctl_get_stream_id(stream->ustream, stream_id);
}

void lttng_ustconsumer_sigbus_handle(void *addr)
{
        lttng_ust_ctl_sigbus_handle(addr);
}