Implement channel fd monitoring thread for UST
[lttng-tools.git] / src / common / consumer.c
index 242b05b3d6bb9c65939ea72a900a84fa74d382b7..300fd2a2fc896108ac60c43ce920a5f633be111b 100644 (file)
@@ -47,8 +47,15 @@ struct lttng_consumer_global_data consumer_data = {
        .type = LTTNG_CONSUMER_UNKNOWN,
 };
 
-/* timeout parameter, to control the polling thread grace period. */
-int consumer_poll_timeout = -1;
+enum consumer_channel_action {
+       CONSUMER_CHANNEL_ADD,
+       CONSUMER_CHANNEL_QUIT,
+};
+
+struct consumer_channel_msg {
+       enum consumer_channel_action action;
+       struct lttng_consumer_channel *chan;
+};
 
 /*
  * Flag to inform the polling thread to quit when all fd hung up. Updated by
@@ -56,30 +63,84 @@ int consumer_poll_timeout = -1;
  * Also updated by the signal handler (consumer_should_exit()). Read by the
  * polling threads.
  */
-volatile int consumer_quit = 0;
+volatile int consumer_quit;
+
+/*
+ * Global hash table containing respectively metadata and data streams. The
+ * stream element in this ht should only be updated by the metadata poll thread
+ * for the metadata and the data poll thread for the data.
+ */
+static struct lttng_ht *metadata_ht;
+static struct lttng_ht *data_ht;
+
+/*
+ * Notify a thread pipe to poll back again. This usually means that some global
+ * state has changed so we just send back the thread in a poll wait call.
+ */
+static void notify_thread_pipe(int wpipe)
+{
+       int ret;
+
+       do {
+               struct lttng_consumer_stream *null_stream = NULL;
+
+               ret = write(wpipe, &null_stream, sizeof(null_stream));
+       } while (ret < 0 && errno == EINTR);
+}
+
+static void notify_channel_pipe(struct lttng_consumer_local_data *ctx,
+               struct lttng_consumer_channel *chan,
+               enum consumer_channel_action action)
+{
+       struct consumer_channel_msg msg;
+       int ret;
+
+       msg.action = action;
+       msg.chan = chan;
+       do {
+               ret = write(ctx->consumer_channel_pipe[1], &msg, sizeof(msg));
+       } while (ret < 0 && errno == EINTR);
+}
+
+static int read_channel_pipe(struct lttng_consumer_local_data *ctx,
+               struct lttng_consumer_channel **chan,
+               enum consumer_channel_action *action)
+{
+       struct consumer_channel_msg msg;
+       int ret;
+
+       do {
+               ret = read(ctx->consumer_channel_pipe[0], &msg, sizeof(msg));
+       } while (ret < 0 && errno == EINTR);
+       if (ret > 0) {
+               *action = msg.action;
+               *chan = msg.chan;
+       }
+       return ret;
+}
 
 /*
  * Find a stream. The consumer_data.lock must be locked during this
  * call.
  */
-static struct lttng_consumer_stream *consumer_find_stream(int key,
+static struct lttng_consumer_stream *find_stream(uint64_t key,
                struct lttng_ht *ht)
 {
        struct lttng_ht_iter iter;
-       struct lttng_ht_node_ulong *node;
+       struct lttng_ht_node_u64 *node;
        struct lttng_consumer_stream *stream = NULL;
 
        assert(ht);
 
-       /* Negative keys are lookup failures */
-       if (key < 0) {
+       /* -1ULL keys are lookup failures */
+       if (key == (uint64_t) -1ULL) {
                return NULL;
        }
 
        rcu_read_lock();
 
-       lttng_ht_lookup(ht, (void *)((unsigned long) key), &iter);
-       node = lttng_ht_iter_get_node_ulong(&iter);
+       lttng_ht_lookup(ht, &key, &iter);
+       node = lttng_ht_iter_get_node_u64(&iter);
        if (node != NULL) {
                stream = caa_container_of(node, struct lttng_consumer_stream, node);
        }
@@ -89,99 +150,91 @@ static struct lttng_consumer_stream *consumer_find_stream(int key,
        return stream;
 }
 
-static void consumer_steal_stream_key(int key, struct lttng_ht *ht)
+static void steal_stream_key(int key, struct lttng_ht *ht)
 {
        struct lttng_consumer_stream *stream;
 
        rcu_read_lock();
-       stream = consumer_find_stream(key, ht);
+       stream = find_stream(key, ht);
        if (stream) {
-               stream->key = -1;
+               stream->key = -1ULL;
                /*
                 * We don't want the lookup to match, but we still need
                 * to iterate on this stream when iterating over the hash table. Just
                 * change the node key.
                 */
-               stream->node.key = -1;
+               stream->node.key = -1ULL;
        }
        rcu_read_unlock();
 }
 
-static struct lttng_consumer_channel *consumer_find_channel(int key)
+/*
+ * Return a channel object for the given key.
+ *
+ * RCU read side lock MUST be acquired before calling this function and
+ * protects the channel ptr.
+ */
+struct lttng_consumer_channel *consumer_find_channel(uint64_t key)
 {
        struct lttng_ht_iter iter;
-       struct lttng_ht_node_ulong *node;
+       struct lttng_ht_node_u64 *node;
        struct lttng_consumer_channel *channel = NULL;
 
-       /* Negative keys are lookup failures */
-       if (key < 0) {
+       /* -1ULL keys are lookup failures */
+       if (key == (uint64_t) -1ULL) {
                return NULL;
        }
 
-       rcu_read_lock();
-
-       lttng_ht_lookup(consumer_data.channel_ht, (void *)((unsigned long) key),
-                       &iter);
-       node = lttng_ht_iter_get_node_ulong(&iter);
+       lttng_ht_lookup(consumer_data.channel_ht, &key, &iter);
+       node = lttng_ht_iter_get_node_u64(&iter);
        if (node != NULL) {
                channel = caa_container_of(node, struct lttng_consumer_channel, node);
        }
 
-       rcu_read_unlock();
-
        return channel;
 }
 
-static void consumer_steal_channel_key(int key)
-{
-       struct lttng_consumer_channel *channel;
-
-       rcu_read_lock();
-       channel = consumer_find_channel(key);
-       if (channel) {
-               channel->key = -1;
-               /*
-                * We don't want the lookup to match, but we still need
-                * to iterate on this channel when iterating over the hash table. Just
-                * change the node key.
-                */
-               channel->node.key = -1;
-       }
-       rcu_read_unlock();
-}
-
-static
-void consumer_free_stream(struct rcu_head *head)
+static void free_stream_rcu(struct rcu_head *head)
 {
-       struct lttng_ht_node_ulong *node =
-               caa_container_of(head, struct lttng_ht_node_ulong, head);
+       struct lttng_ht_node_u64 *node =
+               caa_container_of(head, struct lttng_ht_node_u64, head);
        struct lttng_consumer_stream *stream =
                caa_container_of(node, struct lttng_consumer_stream, node);
 
        free(stream);
 }
 
-static
-void consumer_free_metadata_stream(struct rcu_head *head)
+static void free_channel_rcu(struct rcu_head *head)
 {
-       struct lttng_ht_node_ulong *node =
-               caa_container_of(head, struct lttng_ht_node_ulong, head);
-       struct lttng_consumer_stream *stream =
-               caa_container_of(node, struct lttng_consumer_stream, waitfd_node);
+       struct lttng_ht_node_u64 *node =
+               caa_container_of(head, struct lttng_ht_node_u64, head);
+       struct lttng_consumer_channel *channel =
+               caa_container_of(node, struct lttng_consumer_channel, node);
 
-       free(stream);
+       free(channel);
 }
 
 /*
  * RCU protected relayd socket pair free.
  */
-static void consumer_rcu_free_relayd(struct rcu_head *head)
+static void free_relayd_rcu(struct rcu_head *head)
 {
-       struct lttng_ht_node_ulong *node =
-               caa_container_of(head, struct lttng_ht_node_ulong, head);
+       struct lttng_ht_node_u64 *node =
+               caa_container_of(head, struct lttng_ht_node_u64, head);
        struct consumer_relayd_sock_pair *relayd =
                caa_container_of(node, struct consumer_relayd_sock_pair, node);
 
+       /*
+        * Close all sockets. This is done in the call RCU since we don't want the
+        * socket fds to be reassigned thus potentially creating bad state of the
+        * relayd object.
+        *
+        * We do not have to lock the control socket mutex here since at this stage
+        * there is no one referencing to this relayd object.
+        */
+       (void) relayd_close(&relayd->control_sock);
+       (void) relayd_close(&relayd->data_sock);
+
        free(relayd);
 }
 
@@ -204,18 +257,146 @@ static void destroy_relayd(struct consumer_relayd_sock_pair *relayd)
        iter.iter.node = &relayd->node.node;
        ret = lttng_ht_del(consumer_data.relayd_ht, &iter);
        if (ret != 0) {
-               /* We assume the relayd was already destroyed */
+               /* We assume the relayd is being or is destroyed */
                return;
        }
 
-       /* Close all sockets */
-       pthread_mutex_lock(&relayd->ctrl_sock_mutex);
-       (void) relayd_close(&relayd->control_sock);
-       pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
-       (void) relayd_close(&relayd->data_sock);
-
        /* RCU free() call */
-       call_rcu(&relayd->node.head, consumer_rcu_free_relayd);
+       call_rcu(&relayd->node.head, free_relayd_rcu);
+}
+
+/*
+ * Remove a channel from the global list protected by a mutex. This function is
+ * also responsible for freeing its data structures.
+ */
+void consumer_del_channel(struct lttng_consumer_channel *channel)
+{
+       int ret;
+       struct lttng_ht_iter iter;
+
+       DBG("Consumer delete channel key %" PRIu64, channel->key);
+
+       pthread_mutex_lock(&consumer_data.lock);
+
+       switch (consumer_data.type) {
+       case LTTNG_CONSUMER_KERNEL:
+               break;
+       case LTTNG_CONSUMER32_UST:
+       case LTTNG_CONSUMER64_UST:
+               lttng_ustconsumer_del_channel(channel);
+               break;
+       default:
+               ERR("Unknown consumer_data type");
+               assert(0);
+               goto end;
+       }
+
+       rcu_read_lock();
+       iter.iter.node = &channel->node.node;
+       ret = lttng_ht_del(consumer_data.channel_ht, &iter);
+       assert(!ret);
+       rcu_read_unlock();
+
+       call_rcu(&channel->node.head, free_channel_rcu);
+end:
+       pthread_mutex_unlock(&consumer_data.lock);
+}
+
+/*
+ * Iterate over the relayd hash table and destroy each element. Finally,
+ * destroy the whole hash table.
+ */
+static void cleanup_relayd_ht(void)
+{
+       struct lttng_ht_iter iter;
+       struct consumer_relayd_sock_pair *relayd;
+
+       rcu_read_lock();
+
+       cds_lfht_for_each_entry(consumer_data.relayd_ht->ht, &iter.iter, relayd,
+                       node.node) {
+               destroy_relayd(relayd);
+       }
+
+       lttng_ht_destroy(consumer_data.relayd_ht);
+
+       rcu_read_unlock();
+}
+
+/*
+ * Update the end point status of all streams having the given network sequence
+ * index (relayd index).
+ *
+ * It's atomically set without having the stream mutex locked which is fine
+ * because we handle the write/read race with a pipe wakeup for each thread.
+ */
+static void update_endpoint_status_by_netidx(int net_seq_idx,
+               enum consumer_endpoint_status status)
+{
+       struct lttng_ht_iter iter;
+       struct lttng_consumer_stream *stream;
+
+       DBG("Consumer set delete flag on stream by idx %d", net_seq_idx);
+
+       rcu_read_lock();
+
+       /* Let's begin with metadata */
+       cds_lfht_for_each_entry(metadata_ht->ht, &iter.iter, stream, node.node) {
+               if (stream->net_seq_idx == net_seq_idx) {
+                       uatomic_set(&stream->endpoint_status, status);
+                       DBG("Delete flag set to metadata stream %d", stream->wait_fd);
+               }
+       }
+
+       /* Follow up by the data streams */
+       cds_lfht_for_each_entry(data_ht->ht, &iter.iter, stream, node.node) {
+               if (stream->net_seq_idx == net_seq_idx) {
+                       uatomic_set(&stream->endpoint_status, status);
+                       DBG("Delete flag set to data stream %d", stream->wait_fd);
+               }
+       }
+       rcu_read_unlock();
+}
+
+/*
+ * Cleanup a relayd object by flagging every associated streams for deletion,
+ * destroying the object meaning removing it from the relayd hash table,
+ * closing the sockets and freeing the memory in a RCU call.
+ *
+ * If a local data context is available, notify the threads that the streams'
+ * state have changed.
+ */
+static void cleanup_relayd(struct consumer_relayd_sock_pair *relayd,
+               struct lttng_consumer_local_data *ctx)
+{
+       int netidx;
+
+       assert(relayd);
+
+       DBG("Cleaning up relayd sockets");
+
+       /* Save the net sequence index before destroying the object */
+       netidx = relayd->net_seq_idx;
+
+       /*
+        * Delete the relayd from the relayd hash table, close the sockets and free
+        * the object in a RCU call.
+        */
+       destroy_relayd(relayd);
+
+       /* Set inactive endpoint to all streams */
+       update_endpoint_status_by_netidx(netidx, CONSUMER_ENDPOINT_INACTIVE);
+
+       /*
+        * With a local data context, notify the threads that the streams' state
+        * have changed. The write() action on the pipe acts as an "implicit"
+        * memory barrier ordering the updates of the end point status from the
+        * read of this status which happens AFTER receiving this notify.
+        */
+       if (ctx) {
+               notify_thread_pipe(ctx->consumer_data_pipe[1]);
+               notify_thread_pipe(ctx->consumer_metadata_pipe[1]);
+       }
 }
 
 /*
@@ -251,12 +432,15 @@ void consumer_del_stream(struct lttng_consumer_stream *stream,
 
        assert(stream);
 
+       DBG("Consumer del stream %d", stream->wait_fd);
+
        if (ht == NULL) {
                /* Means the stream was allocated but not successfully added */
-               goto free_stream;
+               goto free_stream_rcu;
        }
 
        pthread_mutex_lock(&consumer_data.lock);
+       pthread_mutex_lock(&stream->lock);
 
        switch (consumer_data.type) {
        case LTTNG_CONSUMER_KERNEL:
@@ -282,33 +466,24 @@ void consumer_del_stream(struct lttng_consumer_stream *stream,
        ret = lttng_ht_del(ht, &iter);
        assert(!ret);
 
+       iter.iter.node = &stream->node_channel_id.node;
+       ret = lttng_ht_del(consumer_data.stream_per_chan_id_ht, &iter);
+       assert(!ret);
+
+       iter.iter.node = &stream->node_session_id.node;
+       ret = lttng_ht_del(consumer_data.stream_list_ht, &iter);
+       assert(!ret);
        rcu_read_unlock();
 
-       if (consumer_data.stream_count <= 0) {
-               goto end;
-       }
+       assert(consumer_data.stream_count > 0);
        consumer_data.stream_count--;
-       if (!stream) {
-               goto end;
-       }
+
        if (stream->out_fd >= 0) {
                ret = close(stream->out_fd);
                if (ret) {
                        PERROR("close");
                }
        }
-       if (stream->wait_fd >= 0 && !stream->wait_fd_is_copy) {
-               ret = close(stream->wait_fd);
-               if (ret) {
-                       PERROR("close");
-               }
-       }
-       if (stream->shm_fd >= 0 && stream->wait_fd != stream->shm_fd) {
-               ret = close(stream->shm_fd);
-               if (ret) {
-                       PERROR("close");
-               }
-       }
 
        /* Check and cleanup relayd */
        rcu_read_lock();
@@ -342,124 +517,129 @@ void consumer_del_stream(struct lttng_consumer_stream *stream,
 
        uatomic_dec(&stream->chan->refcount);
        if (!uatomic_read(&stream->chan->refcount)
-                       && !uatomic_read(&stream->chan->nb_init_streams)) {
+                       && !uatomic_read(&stream->chan->nb_init_stream_left)) {
                free_chan = stream->chan;
        }
 
 end:
        consumer_data.need_update = 1;
+       pthread_mutex_unlock(&stream->lock);
        pthread_mutex_unlock(&consumer_data.lock);
 
        if (free_chan) {
                consumer_del_channel(free_chan);
        }
 
-free_stream:
-       call_rcu(&stream->node.head, consumer_free_stream);
+free_stream_rcu:
+       call_rcu(&stream->node.head, free_stream_rcu);
 }
 
-struct lttng_consumer_stream *consumer_allocate_stream(
-               int channel_key, int stream_key,
-               int shm_fd, int wait_fd,
+struct lttng_consumer_stream *consumer_allocate_stream(uint64_t channel_key,
+               uint64_t stream_key,
                enum lttng_consumer_stream_state state,
-               uint64_t mmap_len,
-               enum lttng_event_output output,
-               const char *path_name,
+               const char *channel_name,
                uid_t uid,
                gid_t gid,
-               int net_index,
-               int metadata_flag,
-               int *alloc_ret)
+               int relayd_id,
+               uint64_t session_id,
+               int cpu,
+               int *alloc_ret,
+               enum consumer_channel_type type)
 {
+       int ret;
        struct lttng_consumer_stream *stream;
 
        stream = zmalloc(sizeof(*stream));
        if (stream == NULL) {
                PERROR("malloc struct lttng_consumer_stream");
-               *alloc_ret = -ENOMEM;
+               ret = -ENOMEM;
                goto end;
        }
 
-       /*
-        * Get stream's channel reference. Needed when adding the stream to the
-        * global hash table.
-        */
-       stream->chan = consumer_find_channel(channel_key);
-       if (!stream->chan) {
-               *alloc_ret = -ENOENT;
-               ERR("Unable to find channel for stream %d", stream_key);
-               goto error;
-       }
+       rcu_read_lock();
 
        stream->key = stream_key;
-       stream->shm_fd = shm_fd;
-       stream->wait_fd = wait_fd;
        stream->out_fd = -1;
        stream->out_fd_offset = 0;
        stream->state = state;
-       stream->mmap_len = mmap_len;
-       stream->mmap_base = NULL;
-       stream->output = output;
        stream->uid = uid;
        stream->gid = gid;
-       stream->net_seq_idx = net_index;
-       stream->metadata_flag = metadata_flag;
-       strncpy(stream->path_name, path_name, sizeof(stream->path_name));
-       stream->path_name[sizeof(stream->path_name) - 1] = '\0';
-       lttng_ht_node_init_ulong(&stream->waitfd_node, stream->wait_fd);
-       lttng_ht_node_init_ulong(&stream->node, stream->key);
-
-       DBG3("Allocated stream %s (key %d, shm_fd %d, wait_fd %d, mmap_len %llu,"
-                       " out_fd %d, net_seq_idx %d)", stream->path_name, stream->key,
-                       stream->shm_fd, stream->wait_fd,
-                       (unsigned long long) stream->mmap_len, stream->out_fd,
-                       stream->net_seq_idx);
+       stream->net_seq_idx = relayd_id;
+       stream->session_id = session_id;
+       pthread_mutex_init(&stream->lock, NULL);
+
+       /* If channel is the metadata, flag this stream as metadata. */
+       if (type == CONSUMER_CHANNEL_TYPE_METADATA) {
+               stream->metadata_flag = 1;
+               /* Metadata is flat out. */
+               strncpy(stream->name, DEFAULT_METADATA_NAME, sizeof(stream->name));
+       } else {
+               /* Format stream name to <channel_name>_<cpu_number> */
+               ret = snprintf(stream->name, sizeof(stream->name), "%s_%d",
+                               channel_name, cpu);
+               if (ret < 0) {
+                       PERROR("snprintf stream name");
+                       goto error;
+               }
+       }
+
+       /* Key is always the wait_fd for streams. */
+       lttng_ht_node_init_u64(&stream->node, stream->key);
+
+       /* Init node per channel id key */
+       lttng_ht_node_init_u64(&stream->node_channel_id, channel_key);
+
+       /* Init session id node with the stream session id */
+       lttng_ht_node_init_u64(&stream->node_session_id, stream->session_id);
+
+       DBG3("Allocated stream %s (key %" PRIu64 ", chan_key %" PRIu64 " relayd_id %" PRIu64 ", session_id %" PRIu64,
+                       stream->name, stream->key, channel_key, stream->net_seq_idx, stream->session_id);
+
+       rcu_read_unlock();
        return stream;
 
 error:
+       rcu_read_unlock();
        free(stream);
 end:
+       if (alloc_ret) {
+               *alloc_ret = ret;
+       }
        return NULL;
 }
 
 /*
  * Add a stream to the global list protected by a mutex.
  */
-int consumer_add_stream(struct lttng_consumer_stream *stream)
+static int add_stream(struct lttng_consumer_stream *stream,
+               struct lttng_ht *ht)
 {
        int ret = 0;
        struct consumer_relayd_sock_pair *relayd;
 
        assert(stream);
+       assert(ht);
 
-       DBG3("Adding consumer stream %d", stream->key);
+       DBG3("Adding consumer stream %" PRIu64, stream->key);
 
        pthread_mutex_lock(&consumer_data.lock);
+       pthread_mutex_lock(&stream->lock);
        rcu_read_lock();
 
-       switch (consumer_data.type) {
-       case LTTNG_CONSUMER_KERNEL:
-               break;
-       case LTTNG_CONSUMER32_UST:
-       case LTTNG_CONSUMER64_UST:
-               stream->cpu = stream->chan->cpucount++;
-               ret = lttng_ustconsumer_add_stream(stream);
-               if (ret) {
-                       ret = -EINVAL;
-                       goto error;
-               }
+       /* Steal stream identifier to avoid having streams with the same key */
+       steal_stream_key(stream->key, ht);
 
-               /* Steal stream identifier only for UST */
-               consumer_steal_stream_key(stream->key, consumer_data.stream_ht);
-               break;
-       default:
-               ERR("Unknown consumer_data type");
-               assert(0);
-               ret = -ENOSYS;
-               goto error;
-       }
+       lttng_ht_add_unique_u64(ht, &stream->node);
+
+       lttng_ht_add_u64(consumer_data.stream_per_chan_id_ht,
+                       &stream->node_channel_id);
 
-       lttng_ht_add_unique_ulong(consumer_data.stream_ht, &stream->node);
+       /*
+        * Add stream to the stream_list_ht of the consumer data. No need to steal
+        * the key since the HT does not use it and we allow to add redundant keys
+        * into this table.
+        */
+       lttng_ht_add_u64(consumer_data.stream_list_ht, &stream->node_session_id);
 
        /* Check and cleanup relayd */
        relayd = consumer_find_relayd(stream->net_seq_idx);
@@ -471,22 +651,22 @@ int consumer_add_stream(struct lttng_consumer_stream *stream)
        uatomic_inc(&stream->chan->refcount);
 
        /*
-        * When nb_init_streams reaches 0, we don't need to trigger any action in
-        * terms of destroying the associated channel, because the action that
+        * When nb_init_stream_left reaches 0, we don't need to trigger any action
+        * in terms of destroying the associated channel, because the action that
         * causes the count to become 0 also causes a stream to be added. The
         * channel deletion will thus be triggered by the following removal of this
         * stream.
         */
-       if (uatomic_read(&stream->chan->nb_init_streams) > 0) {
-               uatomic_dec(&stream->chan->nb_init_streams);
+       if (uatomic_read(&stream->chan->nb_init_stream_left) > 0) {
+               uatomic_dec(&stream->chan->nb_init_stream_left);
        }
 
        /* Update consumer data once the node is inserted. */
        consumer_data.stream_count++;
        consumer_data.need_update = 1;
 
-error:
        rcu_read_unlock();
+       pthread_mutex_unlock(&stream->lock);
        pthread_mutex_unlock(&consumer_data.lock);
 
        return ret;
@@ -499,22 +679,18 @@ error:
 static int add_relayd(struct consumer_relayd_sock_pair *relayd)
 {
        int ret = 0;
-       struct lttng_ht_node_ulong *node;
+       struct lttng_ht_node_u64 *node;
        struct lttng_ht_iter iter;
 
-       if (relayd == NULL) {
-               ret = -1;
-               goto end;
-       }
+       assert(relayd);
 
        lttng_ht_lookup(consumer_data.relayd_ht,
-                       (void *)((unsigned long) relayd->net_seq_idx), &iter);
-       node = lttng_ht_iter_get_node_ulong(&iter);
+                       &relayd->net_seq_idx, &iter);
+       node = lttng_ht_iter_get_node_u64(&iter);
        if (node != NULL) {
-               /* Relayd already exist. Ignore the insertion */
                goto end;
        }
-       lttng_ht_add_unique_ulong(consumer_data.relayd_ht, &relayd->node);
+       lttng_ht_add_unique_u64(consumer_data.relayd_ht, &relayd->node);
 
 end:
        return ret;
@@ -542,7 +718,7 @@ struct consumer_relayd_sock_pair *consumer_allocate_relayd_sock_pair(
        obj->net_seq_idx = net_seq_idx;
        obj->refcount = 0;
        obj->destroy_flag = 0;
-       lttng_ht_node_init_ulong(&obj->node, obj->net_seq_idx);
+       lttng_ht_node_init_u64(&obj->node, obj->net_seq_idx);
        pthread_mutex_init(&obj->ctrl_sock_mutex, NULL);
 
 error:
@@ -556,20 +732,20 @@ error:
  * RCU read-side lock must be held across this call and while using the
  * returned object.
  */
-struct consumer_relayd_sock_pair *consumer_find_relayd(int key)
+struct consumer_relayd_sock_pair *consumer_find_relayd(uint64_t key)
 {
        struct lttng_ht_iter iter;
-       struct lttng_ht_node_ulong *node;
+       struct lttng_ht_node_u64 *node;
        struct consumer_relayd_sock_pair *relayd = NULL;
 
        /* Negative keys are lookup failures */
-       if (key < 0) {
+       if (key == (uint64_t) -1ULL) {
                goto error;
        }
 
-       lttng_ht_lookup(consumer_data.relayd_ht, (void *)((unsigned long) key),
+       lttng_ht_lookup(consumer_data.relayd_ht, &key,
                        &iter);
-       node = lttng_ht_iter_get_node_ulong(&iter);
+       node = lttng_ht_iter_get_node_u64(&iter);
        if (node != NULL) {
                relayd = caa_container_of(node, struct consumer_relayd_sock_pair, node);
        }
@@ -612,7 +788,14 @@ static int write_relayd_stream_header(struct lttng_consumer_stream *stream,
                data_hdr.stream_id = htobe64(stream->relayd_stream_id);
                data_hdr.data_size = htobe32(data_size);
                data_hdr.padding_size = htobe32(padding);
-               data_hdr.net_seq_num = htobe64(stream->next_net_seq_num++);
+               /*
+                * Note that net_seq_num below is assigned with the *current* value of
+                * next_net_seq_num and only after that the next_net_seq_num will be
+                * increment. This is why when issuing a command on the relayd using
+                * this next value, 1 should always be substracted in order to compare
+                * the last seen sequence number on the relayd side to the last sent.
+                */
+               data_hdr.net_seq_num = htobe64(stream->next_net_seq_num);
                /* Other fields are zeroed previously */
 
                ret = relayd_send_data_hdr(&relayd->data_sock, &data_hdr,
@@ -621,6 +804,8 @@ static int write_relayd_stream_header(struct lttng_consumer_stream *stream,
                        goto error;
                }
 
+               ++stream->next_net_seq_num;
+
                /* Set to go on data socket */
                outfd = relayd->data_sock.fd;
        }
@@ -630,165 +815,89 @@ error:
 }
 
 /*
- * Update a stream according to what we just received.
+ * Allocate and return a new lttng_consumer_channel object using the given key
+ * to initialize the hash table node.
+ *
+ * On error, return NULL.
  */
-void consumer_change_stream_state(int stream_key,
-               enum lttng_consumer_stream_state state)
+struct lttng_consumer_channel *consumer_allocate_channel(unsigned long key,
+               uint64_t session_id,
+               const char *pathname,
+               const char *name,
+               uid_t uid,
+               gid_t gid,
+               int relayd_id,
+               enum lttng_event_output output)
 {
-       struct lttng_consumer_stream *stream;
+       struct lttng_consumer_channel *channel;
 
-       pthread_mutex_lock(&consumer_data.lock);
-       stream = consumer_find_stream(stream_key, consumer_data.stream_ht);
-       if (stream) {
-               stream->state = state;
+       channel = zmalloc(sizeof(*channel));
+       if (channel == NULL) {
+               PERROR("malloc struct lttng_consumer_channel");
+               goto end;
        }
-       consumer_data.need_update = 1;
-       pthread_mutex_unlock(&consumer_data.lock);
-}
 
-static
-void consumer_free_channel(struct rcu_head *head)
-{
-       struct lttng_ht_node_ulong *node =
-               caa_container_of(head, struct lttng_ht_node_ulong, head);
-       struct lttng_consumer_channel *channel =
-               caa_container_of(node, struct lttng_consumer_channel, node);
+       channel->key = key;
+       channel->refcount = 0;
+       channel->session_id = session_id;
+       channel->uid = uid;
+       channel->gid = gid;
+       channel->relayd_id = relayd_id;
+       channel->output = output;
 
-       free(channel);
+       strncpy(channel->pathname, pathname, sizeof(channel->pathname));
+       channel->pathname[sizeof(channel->pathname) - 1] = '\0';
+
+       strncpy(channel->name, name, sizeof(channel->name));
+       channel->name[sizeof(channel->name) - 1] = '\0';
+
+       lttng_ht_node_init_u64(&channel->node, channel->key);
+
+       channel->wait_fd = -1;
+
+       CDS_INIT_LIST_HEAD(&channel->streams.head);
+
+       DBG("Allocated channel (key %" PRIu64 ")", channel->key)
+
+end:
+       return channel;
 }
 
 /*
- * Remove a channel from the global list protected by a mutex. This
- * function is also responsible for freeing its data structures.
+ * Add a channel to the global list protected by a mutex.
  */
-void consumer_del_channel(struct lttng_consumer_channel *channel)
+int consumer_add_channel(struct lttng_consumer_channel *channel,
+               struct lttng_consumer_local_data *ctx)
 {
-       int ret;
+       int ret = 0;
+       struct lttng_ht_node_u64 *node;
        struct lttng_ht_iter iter;
 
        pthread_mutex_lock(&consumer_data.lock);
-
-       switch (consumer_data.type) {
-       case LTTNG_CONSUMER_KERNEL:
-               break;
-       case LTTNG_CONSUMER32_UST:
-       case LTTNG_CONSUMER64_UST:
-               lttng_ustconsumer_del_channel(channel);
-               break;
-       default:
-               ERR("Unknown consumer_data type");
-               assert(0);
-               goto end;
-       }
-
-       rcu_read_lock();
-       iter.iter.node = &channel->node.node;
-       ret = lttng_ht_del(consumer_data.channel_ht, &iter);
-       assert(!ret);
-       rcu_read_unlock();
-
-       if (channel->mmap_base != NULL) {
-               ret = munmap(channel->mmap_base, channel->mmap_len);
-               if (ret != 0) {
-                       PERROR("munmap");
-               }
-       }
-       if (channel->wait_fd >= 0 && !channel->wait_fd_is_copy) {
-               ret = close(channel->wait_fd);
-               if (ret) {
-                       PERROR("close");
-               }
-       }
-       if (channel->shm_fd >= 0 && channel->wait_fd != channel->shm_fd) {
-               ret = close(channel->shm_fd);
-               if (ret) {
-                       PERROR("close");
-               }
-       }
-
-       call_rcu(&channel->node.head, consumer_free_channel);
-end:
-       pthread_mutex_unlock(&consumer_data.lock);
-}
-
-struct lttng_consumer_channel *consumer_allocate_channel(
-               int channel_key,
-               int shm_fd, int wait_fd,
-               uint64_t mmap_len,
-               uint64_t max_sb_size,
-               unsigned int nb_init_streams)
-{
-       struct lttng_consumer_channel *channel;
-       int ret;
-
-       channel = zmalloc(sizeof(*channel));
-       if (channel == NULL) {
-               PERROR("malloc struct lttng_consumer_channel");
-               goto end;
-       }
-       channel->key = channel_key;
-       channel->shm_fd = shm_fd;
-       channel->wait_fd = wait_fd;
-       channel->mmap_len = mmap_len;
-       channel->max_sb_size = max_sb_size;
-       channel->refcount = 0;
-       channel->nb_init_streams = nb_init_streams;
-       lttng_ht_node_init_ulong(&channel->node, channel->key);
-
-       switch (consumer_data.type) {
-       case LTTNG_CONSUMER_KERNEL:
-               channel->mmap_base = NULL;
-               channel->mmap_len = 0;
-               break;
-       case LTTNG_CONSUMER32_UST:
-       case LTTNG_CONSUMER64_UST:
-               ret = lttng_ustconsumer_allocate_channel(channel);
-               if (ret) {
-                       free(channel);
-                       return NULL;
-               }
-               break;
-       default:
-               ERR("Unknown consumer_data type");
-               assert(0);
-               goto end;
-       }
-       DBG("Allocated channel (key %d, shm_fd %d, wait_fd %d, mmap_len %llu, max_sb_size %llu)",
-                       channel->key, channel->shm_fd, channel->wait_fd,
-                       (unsigned long long) channel->mmap_len,
-                       (unsigned long long) channel->max_sb_size);
-end:
-       return channel;
-}
-
-/*
- * Add a channel to the global list protected by a mutex.
- */
-int consumer_add_channel(struct lttng_consumer_channel *channel)
-{
-       struct lttng_ht_node_ulong *node;
-       struct lttng_ht_iter iter;
-
-       pthread_mutex_lock(&consumer_data.lock);
-       /* Steal channel identifier, for UST */
-       consumer_steal_channel_key(channel->key);
-       rcu_read_lock();
+       rcu_read_lock();
 
        lttng_ht_lookup(consumer_data.channel_ht,
-                       (void *)((unsigned long) channel->key), &iter);
-       node = lttng_ht_iter_get_node_ulong(&iter);
+                       &channel->key, &iter);
+       node = lttng_ht_iter_get_node_u64(&iter);
        if (node != NULL) {
                /* Channel already exist. Ignore the insertion */
+               ERR("Consumer add channel key %" PRIu64 " already exists!",
+                       channel->key);
+               ret = -1;
                goto end;
        }
 
-       lttng_ht_add_unique_ulong(consumer_data.channel_ht, &channel->node);
+       lttng_ht_add_unique_u64(consumer_data.channel_ht, &channel->node);
 
 end:
        rcu_read_unlock();
        pthread_mutex_unlock(&consumer_data.lock);
 
-       return 0;
+       if (!ret && channel->wait_fd != -1 &&
+                       channel->metadata_stream == NULL) {
+               notify_channel_pipe(ctx, channel, CONSUMER_CHANNEL_ADD);
+       }
+       return ret;
 }
 
 /*
@@ -798,19 +907,33 @@ end:
  *
  * Returns the number of fds in the structures.
  */
-int consumer_update_poll_array(
-               struct lttng_consumer_local_data *ctx, struct pollfd **pollfd,
-               struct lttng_consumer_stream **local_stream)
+static int update_poll_array(struct lttng_consumer_local_data *ctx,
+               struct pollfd **pollfd, struct lttng_consumer_stream **local_stream,
+               struct lttng_ht *ht)
 {
        int i = 0;
        struct lttng_ht_iter iter;
        struct lttng_consumer_stream *stream;
 
+       assert(ctx);
+       assert(ht);
+       assert(pollfd);
+       assert(local_stream);
+
        DBG("Updating poll fd array");
        rcu_read_lock();
-       cds_lfht_for_each_entry(consumer_data.stream_ht->ht, &iter.iter, stream,
-                       node.node) {
-               if (stream->state != LTTNG_CONSUMER_ACTIVE_STREAM) {
+       cds_lfht_for_each_entry(ht->ht, &iter.iter, stream, node.node) {
+               /*
+                * Only active streams with an active end point can be added to the
+                * poll set and local stream storage of the thread.
+                *
+                * There is a potential race here for endpoint_status to be updated
+                * just after the check. However, this is OK since the stream(s) will
+                * be deleted once the thread is notified that the end point state has
+                * changed where this function will be called back again.
+                */
+               if (stream->state != LTTNG_CONSUMER_ACTIVE_STREAM ||
+                               stream->endpoint_status == CONSUMER_ENDPOINT_INACTIVE) {
                        continue;
                }
                DBG("Active FD %d", stream->wait_fd);
@@ -822,10 +945,10 @@ int consumer_update_poll_array(
        rcu_read_unlock();
 
        /*
-        * Insert the consumer_poll_pipe at the end of the array and don't
+        * Insert the consumer_data_pipe at the end of the array and don't
         * increment i so nb_fd is the number of real FD.
         */
-       (*pollfd)[i].fd = ctx->consumer_poll_pipe[0];
+       (*pollfd)[i].fd = ctx->consumer_data_pipe[0];
        (*pollfd)[i].events = POLLIN | POLLPRI;
        return i;
 }
@@ -863,8 +986,8 @@ exit:
 /*
  * Set the error socket.
  */
-void lttng_consumer_set_error_sock(
-               struct lttng_consumer_local_data *ctx, int sock)
+void lttng_consumer_set_error_sock(struct lttng_consumer_local_data *ctx,
+               int sock)
 {
        ctx->consumer_error_socket = sock;
 }
@@ -882,8 +1005,7 @@ void lttng_consumer_set_command_sock_path(
  * Send return code to the session daemon.
  * If the socket is not defined, we return 0, it is not a fatal error
  */
-int lttng_consumer_send_error(
-               struct lttng_consumer_local_data *ctx, int cmd)
+int lttng_consumer_send_error(struct lttng_consumer_local_data *ctx, int cmd)
 {
        if (ctx->consumer_error_socket > 0) {
                return lttcomm_send_unix_sock(ctx->consumer_error_socket, &cmd,
@@ -894,38 +1016,35 @@ int lttng_consumer_send_error(
 }
 
 /*
- * Close all the tracefiles and stream fds, should be called when all instances
- * are destroyed.
+ * Close all the tracefiles and stream fds and MUST be called when all
+ * instances are destroyed i.e. when all threads were joined and are ended.
  */
 void lttng_consumer_cleanup(void)
 {
        struct lttng_ht_iter iter;
-       struct lttng_ht_node_ulong *node;
+       struct lttng_consumer_channel *channel;
 
        rcu_read_lock();
 
-       /*
-        * close all outfd. Called when there are no more threads running (after
-        * joining on the threads), no need to protect list iteration with mutex.
-        */
-       cds_lfht_for_each_entry(consumer_data.stream_ht->ht, &iter.iter, node,
-                       node) {
-               struct lttng_consumer_stream *stream =
-                       caa_container_of(node, struct lttng_consumer_stream, node);
-               consumer_del_stream(stream, consumer_data.stream_ht);
-       }
-
-       cds_lfht_for_each_entry(consumer_data.channel_ht->ht, &iter.iter, node,
-                       node) {
-               struct lttng_consumer_channel *channel =
-                       caa_container_of(node, struct lttng_consumer_channel, node);
+       cds_lfht_for_each_entry(consumer_data.channel_ht->ht, &iter.iter, channel,
+                       node.node) {
                consumer_del_channel(channel);
        }
 
        rcu_read_unlock();
 
-       lttng_ht_destroy(consumer_data.stream_ht);
        lttng_ht_destroy(consumer_data.channel_ht);
+
+       cleanup_relayd_ht();
+
+       lttng_ht_destroy(consumer_data.stream_per_chan_id_ht);
+
+       /*
+        * This HT contains streams that are freed by either the metadata thread or
+        * the data thread so we do *nothing* on the hash table and simply destroy
+        * it.
+        */
+       lttng_ht_destroy(consumer_data.stream_list_ht);
 }
 
 /*
@@ -938,9 +1057,11 @@ void lttng_consumer_should_exit(struct lttng_consumer_local_data *ctx)
        do {
                ret = write(ctx->consumer_should_quit[1], "4", 1);
        } while (ret < 0 && errno == EINTR);
-       if (ret < 0) {
+       if (ret < 0 || ret != 1) {
                PERROR("write consumer quit");
        }
+
+       DBG("Consumer flag that it should quit");
 }
 
 void lttng_consumer_sync_trace_file(struct lttng_consumer_stream *stream,
@@ -954,11 +1075,11 @@ void lttng_consumer_sync_trace_file(struct lttng_consumer_stream *stream,
         * Don't care about error values, as these are just hints and ways to
         * limit the amount of page cache used.
         */
-       if (orig_offset < stream->chan->max_sb_size) {
+       if (orig_offset < stream->max_sb_size) {
                return;
        }
-       lttng_sync_file_range(outfd, orig_offset - stream->chan->max_sb_size,
-                       stream->chan->max_sb_size,
+       lttng_sync_file_range(outfd, orig_offset - stream->max_sb_size,
+                       stream->max_sb_size,
                        SYNC_FILE_RANGE_WAIT_BEFORE
                        | SYNC_FILE_RANGE_WRITE
                        | SYNC_FILE_RANGE_WAIT_AFTER);
@@ -976,8 +1097,8 @@ void lttng_consumer_sync_trace_file(struct lttng_consumer_stream *stream,
         * defined. So it can be expected to lead to lower throughput in
         * streaming.
         */
-       posix_fadvise(outfd, orig_offset - stream->chan->max_sb_size,
-                       stream->chan->max_sb_size, POSIX_FADV_DONTNEED);
+       posix_fadvise(outfd, orig_offset - stream->max_sb_size,
+                       stream->max_sb_size, POSIX_FADV_DONTNEED);
 }
 
 /*
@@ -1002,7 +1123,7 @@ struct lttng_consumer_local_data *lttng_consumer_create(
                int (*recv_stream)(struct lttng_consumer_stream *stream),
                int (*update_stream)(int stream_key, uint32_t state))
 {
-       int ret, i;
+       int ret;
        struct lttng_consumer_local_data *ctx;
 
        assert(consumer_data.type == LTTNG_CONSUMER_UNKNOWN ||
@@ -1022,21 +1143,21 @@ struct lttng_consumer_local_data *lttng_consumer_create(
        ctx->on_recv_stream = recv_stream;
        ctx->on_update_stream = update_stream;
 
-       ret = pipe(ctx->consumer_poll_pipe);
+       ret = pipe(ctx->consumer_data_pipe);
        if (ret < 0) {
                PERROR("Error creating poll pipe");
                goto error_poll_pipe;
        }
 
        /* set read end of the pipe to non-blocking */
-       ret = fcntl(ctx->consumer_poll_pipe[0], F_SETFL, O_NONBLOCK);
+       ret = fcntl(ctx->consumer_data_pipe[0], F_SETFL, O_NONBLOCK);
        if (ret < 0) {
                PERROR("fcntl O_NONBLOCK");
                goto error_poll_fcntl;
        }
 
        /* set write end of the pipe to non-blocking */
-       ret = fcntl(ctx->consumer_poll_pipe[1], F_SETFL, O_NONBLOCK);
+       ret = fcntl(ctx->consumer_data_pipe[1], F_SETFL, O_NONBLOCK);
        if (ret < 0) {
                PERROR("fcntl O_NONBLOCK");
                goto error_poll_fcntl;
@@ -1054,6 +1175,12 @@ struct lttng_consumer_local_data *lttng_consumer_create(
                goto error_thread_pipe;
        }
 
+       ret = pipe(ctx->consumer_channel_pipe);
+       if (ret < 0) {
+               PERROR("Error creating channel pipe");
+               goto error_channel_pipe;
+       }
+
        ret = utils_create_pipe(ctx->consumer_metadata_pipe);
        if (ret < 0) {
                goto error_metadata_pipe;
@@ -1069,26 +1196,14 @@ struct lttng_consumer_local_data *lttng_consumer_create(
 error_splice_pipe:
        utils_close_pipe(ctx->consumer_metadata_pipe);
 error_metadata_pipe:
+       utils_close_pipe(ctx->consumer_channel_pipe);
+error_channel_pipe:
        utils_close_pipe(ctx->consumer_thread_pipe);
 error_thread_pipe:
-       for (i = 0; i < 2; i++) {
-               int err;
-
-               err = close(ctx->consumer_should_quit[i]);
-               if (err) {
-                       PERROR("close");
-               }
-       }
+       utils_close_pipe(ctx->consumer_should_quit);
 error_poll_fcntl:
 error_quit_pipe:
-       for (i = 0; i < 2; i++) {
-               int err;
-
-               err = close(ctx->consumer_poll_pipe[i]);
-               if (err) {
-                       PERROR("close");
-               }
-       }
+       utils_close_pipe(ctx->consumer_data_pipe);
 error_poll_pipe:
        free(ctx);
 error:
@@ -1102,34 +1217,16 @@ void lttng_consumer_destroy(struct lttng_consumer_local_data *ctx)
 {
        int ret;
 
+       DBG("Consumer destroying it. Closing everything.");
+
        ret = close(ctx->consumer_error_socket);
        if (ret) {
                PERROR("close");
        }
-       ret = close(ctx->consumer_thread_pipe[0]);
-       if (ret) {
-               PERROR("close");
-       }
-       ret = close(ctx->consumer_thread_pipe[1]);
-       if (ret) {
-               PERROR("close");
-       }
-       ret = close(ctx->consumer_poll_pipe[0]);
-       if (ret) {
-               PERROR("close");
-       }
-       ret = close(ctx->consumer_poll_pipe[1]);
-       if (ret) {
-               PERROR("close");
-       }
-       ret = close(ctx->consumer_should_quit[0]);
-       if (ret) {
-               PERROR("close");
-       }
-       ret = close(ctx->consumer_should_quit[1]);
-       if (ret) {
-               PERROR("close");
-       }
+       utils_close_pipe(ctx->consumer_thread_pipe);
+       utils_close_pipe(ctx->consumer_channel_pipe);
+       utils_close_pipe(ctx->consumer_data_pipe);
+       utils_close_pipe(ctx->consumer_should_quit);
        utils_close_pipe(ctx->consumer_splice_metadata_pipe);
 
        unlink(ctx->consumer_command_sock_path);
@@ -1141,8 +1238,7 @@ void lttng_consumer_destroy(struct lttng_consumer_local_data *ctx)
  */
 static int write_relayd_metadata_id(int fd,
                struct lttng_consumer_stream *stream,
-               struct consumer_relayd_sock_pair *relayd,
-               unsigned long padding)
+               struct consumer_relayd_sock_pair *relayd, unsigned long padding)
 {
        int ret;
        struct lttcomm_relayd_metadata_payload hdr;
@@ -1152,8 +1248,22 @@ static int write_relayd_metadata_id(int fd,
        do {
                ret = write(fd, (void *) &hdr, sizeof(hdr));
        } while (ret < 0 && errno == EINTR);
-       if (ret < 0) {
-               PERROR("write metadata stream id");
+       if (ret < 0 || ret != sizeof(hdr)) {
+               /*
+                * This error means that the fd's end is closed so ignore the perror
+                * not to clubber the error output since this can happen in a normal
+                * code path.
+                */
+               if (errno != EPIPE) {
+                       PERROR("write metadata stream id");
+               }
+               DBG3("Consumer failed to write relayd metadata id (errno: %d)", errno);
+               /*
+                * Set ret to a negative value because if ret != sizeof(hdr), we don't
+                * handle writting the missing part so report that as an error and
+                * don't lie to the caller.
+                */
+               ret = -1;
                goto end;
        }
        DBG("Metadata stream id %" PRIu64 " with padding %lu written before data",
@@ -1168,6 +1278,8 @@ end:
  * core function for writing trace buffers to either the local filesystem or
  * the network.
  *
+ * It must be called with the stream lock held.
+ *
  * Careful review MUST be put if any changes occur!
  *
  * Returns the number of bytes written
@@ -1178,11 +1290,13 @@ ssize_t lttng_consumer_on_read_subbuffer_mmap(
                unsigned long padding)
 {
        unsigned long mmap_offset;
+       void *mmap_base;
        ssize_t ret = 0, written = 0;
        off_t orig_offset = stream->out_fd_offset;
        /* Default is on the disk */
        int outfd = stream->out_fd;
        struct consumer_relayd_sock_pair *relayd = NULL;
+       unsigned int relayd_hang_up = 0;
 
        /* RCU lock for the relayd pointer */
        rcu_read_lock();
@@ -1198,12 +1312,18 @@ ssize_t lttng_consumer_on_read_subbuffer_mmap(
        /* get the offset inside the fd to mmap */
        switch (consumer_data.type) {
        case LTTNG_CONSUMER_KERNEL:
+               mmap_base = stream->mmap_base;
                ret = kernctl_get_mmap_read_offset(stream->wait_fd, &mmap_offset);
                break;
        case LTTNG_CONSUMER32_UST:
        case LTTNG_CONSUMER64_UST:
-               ret = lttng_ustctl_get_mmap_read_offset(stream->chan->handle,
-                               stream->buf, &mmap_offset);
+               mmap_base = lttng_ustctl_get_mmap_base(stream);
+               if (!mmap_base) {
+                       ERR("read mmap get mmap base for stream %s", stream->name);
+                       written = -1;
+                       goto end;
+               }
+               ret = lttng_ustctl_get_mmap_read_offset(stream, &mmap_offset);
                break;
        default:
                ERR("Unknown consumer_data type");
@@ -1240,11 +1360,22 @@ ssize_t lttng_consumer_on_read_subbuffer_mmap(
                                ret = write_relayd_metadata_id(outfd, stream, relayd, padding);
                                if (ret < 0) {
                                        written = ret;
+                                       /* Socket operation failed. We consider the relayd dead */
+                                       if (ret == -EPIPE || ret == -EINVAL) {
+                                               relayd_hang_up = 1;
+                                               goto write_error;
+                                       }
                                        goto end;
                                }
                        }
+               } else {
+                       /* Socket operation failed. We consider the relayd dead */
+                       if (ret == -EPIPE || ret == -EINVAL) {
+                               relayd_hang_up = 1;
+                               goto write_error;
+                       }
+                       /* Else, use the default set before which is the filesystem. */
                }
-               /* Else, use the default set before which is the filesystem. */
        } else {
                /* No streaming, we have to set the len with the full padding */
                len += padding;
@@ -1252,14 +1383,25 @@ ssize_t lttng_consumer_on_read_subbuffer_mmap(
 
        while (len > 0) {
                do {
-                       ret = write(outfd, stream->mmap_base + mmap_offset, len);
+                       ret = write(outfd, mmap_base + mmap_offset, len);
                } while (ret < 0 && errno == EINTR);
                DBG("Consumer mmap write() ret %zd (len %lu)", ret, len);
                if (ret < 0) {
-                       PERROR("Error in file write");
+                       /*
+                        * This is possible if the fd is closed on the other side (outfd)
+                        * or any write problem. It can be verbose a bit for a normal
+                        * execution if for instance the relayd is stopped abruptly. This
+                        * can happen so set this to a DBG statement.
+                        */
+                       DBG("Error in file write mmap");
                        if (written == 0) {
                                written = ret;
                        }
+                       /* Socket operation failed. We consider the relayd dead */
+                       if (errno == EPIPE || errno == EINVAL) {
+                               relayd_hang_up = 1;
+                               goto write_error;
+                       }
                        goto end;
                } else if (ret > len) {
                        PERROR("Error in file write (ret %zd > len %lu)", ret, len);
@@ -1281,6 +1423,15 @@ ssize_t lttng_consumer_on_read_subbuffer_mmap(
        }
        lttng_consumer_sync_trace_file(stream, orig_offset);
 
+write_error:
+       /*
+        * This is a special case that the relayd has closed its socket. Let's
+        * cleanup the relayd object and all associated streams.
+        */
+       if (relayd && relayd_hang_up) {
+               cleanup_relayd(relayd, ctx);
+       }
+
 end:
        /* Unlock only if ctrl socket used */
        if (relayd && stream->metadata_flag) {
@@ -1294,6 +1445,8 @@ end:
 /*
  * Splice the data from the ring buffer to the tracefile.
  *
+ * It must be called with the stream lock held.
+ *
  * Returns the number of bytes spliced.
  */
 ssize_t lttng_consumer_on_read_subbuffer_splice(
@@ -1309,6 +1462,7 @@ ssize_t lttng_consumer_on_read_subbuffer_splice(
        int outfd = stream->out_fd;
        struct consumer_relayd_sock_pair *relayd = NULL;
        int *splice_pipe;
+       unsigned int relayd_hang_up = 0;
 
        switch (consumer_data.type) {
        case LTTNG_CONSUMER_KERNEL:
@@ -1359,6 +1513,12 @@ ssize_t lttng_consumer_on_read_subbuffer_splice(
                                        padding);
                        if (ret < 0) {
                                written = ret;
+                               /* Socket operation failed. We consider the relayd dead */
+                               if (ret == -EBADF) {
+                                       WARN("Remote relayd disconnected. Stopping");
+                                       relayd_hang_up = 1;
+                                       goto write_error;
+                               }
                                goto end;
                        }
 
@@ -1370,7 +1530,12 @@ ssize_t lttng_consumer_on_read_subbuffer_splice(
                        /* Use the returned socket. */
                        outfd = ret;
                } else {
-                       ERR("Remote relayd disconnected. Stopping");
+                       /* Socket operation failed. We consider the relayd dead */
+                       if (ret == -EBADF) {
+                               WARN("Remote relayd disconnected. Stopping");
+                               relayd_hang_up = 1;
+                               goto write_error;
+                       }
                        goto end;
                }
        } else {
@@ -1419,6 +1584,12 @@ ssize_t lttng_consumer_on_read_subbuffer_splice(
                        if (written == 0) {
                                written = ret_splice;
                        }
+                       /* Socket operation failed. We consider the relayd dead */
+                       if (errno == EBADF || errno == EPIPE) {
+                               WARN("Remote relayd disconnected. Stopping");
+                               relayd_hang_up = 1;
+                               goto write_error;
+                       }
                        ret = errno;
                        goto splice_error;
                } else if (ret_splice > len) {
@@ -1446,12 +1617,20 @@ ssize_t lttng_consumer_on_read_subbuffer_splice(
 
        goto end;
 
+write_error:
+       /*
+        * This is a special case that the relayd has closed its socket. Let's
+        * cleanup the relayd object and all associated streams.
+        */
+       if (relayd && relayd_hang_up) {
+               cleanup_relayd(relayd, ctx);
+               /* Skip splice error so the consumer does not fail */
+               goto end;
+       }
+
 splice_error:
        /* send the appropriate error description to sessiond */
        switch (ret) {
-       case EBADF:
-               lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_SPLICE_EBADF);
-               break;
        case EINVAL:
                lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_SPLICE_EINVAL);
                break;
@@ -1477,21 +1656,19 @@ end:
  *
  * Returns 0 on success, < 0 on error
  */
-int lttng_consumer_take_snapshot(struct lttng_consumer_local_data *ctx,
-               struct lttng_consumer_stream *stream)
+int lttng_consumer_take_snapshot(struct lttng_consumer_stream *stream)
 {
        switch (consumer_data.type) {
        case LTTNG_CONSUMER_KERNEL:
-               return lttng_kconsumer_take_snapshot(ctx, stream);
+               return lttng_kconsumer_take_snapshot(stream);
        case LTTNG_CONSUMER32_UST:
        case LTTNG_CONSUMER64_UST:
-               return lttng_ustconsumer_take_snapshot(ctx, stream);
+               return lttng_ustconsumer_take_snapshot(stream);
        default:
                ERR("Unknown consumer_data type");
                assert(0);
                return -ENOSYS;
        }
-
 }
 
 /*
@@ -1499,17 +1676,15 @@ int lttng_consumer_take_snapshot(struct lttng_consumer_local_data *ctx,
  *
  * Returns 0 on success, < 0 on error
  */
-int lttng_consumer_get_produced_snapshot(
-               struct lttng_consumer_local_data *ctx,
-               struct lttng_consumer_stream *stream,
+int lttng_consumer_get_produced_snapshot(struct lttng_consumer_stream *stream,
                unsigned long *pos)
 {
        switch (consumer_data.type) {
        case LTTNG_CONSUMER_KERNEL:
-               return lttng_kconsumer_get_produced_snapshot(ctx, stream, pos);
+               return lttng_kconsumer_get_produced_snapshot(stream, pos);
        case LTTNG_CONSUMER32_UST:
        case LTTNG_CONSUMER64_UST:
-               return lttng_ustconsumer_get_produced_snapshot(ctx, stream, pos);
+               return lttng_ustconsumer_get_produced_snapshot(stream, pos);
        default:
                ERR("Unknown consumer_data type");
                assert(0);
@@ -1533,6 +1708,33 @@ int lttng_consumer_recv_cmd(struct lttng_consumer_local_data *ctx,
        }
 }
 
+/*
+ * Iterate over all streams of the hashtable and free them properly.
+ *
+ * WARNING: *MUST* be used with data stream only.
+ */
+static void destroy_data_stream_ht(struct lttng_ht *ht)
+{
+       struct lttng_ht_iter iter;
+       struct lttng_consumer_stream *stream;
+
+       if (ht == NULL) {
+               return;
+       }
+
+       rcu_read_lock();
+       cds_lfht_for_each_entry(ht->ht, &iter.iter, stream, node.node) {
+               /*
+                * Ignore return value since we are currently cleaning up so any error
+                * can't be handled.
+                */
+               (void) consumer_del_stream(stream, ht);
+       }
+       rcu_read_unlock();
+
+       lttng_ht_destroy(ht);
+}
+
 /*
  * Iterate over all streams of the hashtable and free them properly.
  *
@@ -1540,7 +1742,6 @@ int lttng_consumer_recv_cmd(struct lttng_consumer_local_data *ctx,
  */
 static void destroy_stream_ht(struct lttng_ht *ht)
 {
-       int ret;
        struct lttng_ht_iter iter;
        struct lttng_consumer_stream *stream;
 
@@ -1549,17 +1750,44 @@ static void destroy_stream_ht(struct lttng_ht *ht)
        }
 
        rcu_read_lock();
-       cds_lfht_for_each_entry(ht->ht, &iter.iter, stream, waitfd_node.node) {
-               ret = lttng_ht_del(ht, &iter);
-               assert(!ret);
-
-               call_rcu(&stream->waitfd_node.head, consumer_free_metadata_stream);
+       cds_lfht_for_each_entry(ht->ht, &iter.iter, stream, node.node) {
+               /*
+                * Ignore return value since we are currently cleaning up so any error
+                * can't be handled.
+                */
+               (void) consumer_del_metadata_stream(stream, ht);
        }
        rcu_read_unlock();
 
        lttng_ht_destroy(ht);
 }
 
+void lttng_consumer_close_metadata(void)
+{
+       switch (consumer_data.type) {
+       case LTTNG_CONSUMER_KERNEL:
+               /*
+                * The Kernel consumer has a different metadata scheme so we don't
+                * close anything because the stream will be closed by the session
+                * daemon.
+                */
+               break;
+       case LTTNG_CONSUMER32_UST:
+       case LTTNG_CONSUMER64_UST:
+               /*
+                * Close all metadata streams. The metadata hash table is passed and
+                * this call iterates over it by closing all wakeup fd. This is safe
+                * because at this point we are sure that the metadata producer is
+                * either dead or blocked.
+                */
+               lttng_ustconsumer_close_metadata(metadata_ht);
+               break;
+       default:
+               ERR("Unknown consumer_data type");
+               assert(0);
+       }
+}
+
 /*
  * Clean up a metadata stream and free its memory.
  */
@@ -1582,16 +1810,12 @@ void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
 
        if (ht == NULL) {
                /* Means the stream was allocated but not successfully added */
-               goto free_stream;
+               goto free_stream_rcu;
        }
 
-       rcu_read_lock();
-       iter.iter.node = &stream->waitfd_node.node;
-       ret = lttng_ht_del(ht, &iter);
-       assert(!ret);
-       rcu_read_unlock();
-
        pthread_mutex_lock(&consumer_data.lock);
+       pthread_mutex_lock(&stream->lock);
+
        switch (consumer_data.type) {
        case LTTNG_CONSUMER_KERNEL:
                if (stream->mmap_base != NULL) {
@@ -1611,22 +1835,22 @@ void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
                goto end;
        }
 
-       if (stream->out_fd >= 0) {
-               ret = close(stream->out_fd);
-               if (ret) {
-                       PERROR("close");
-               }
-       }
+       rcu_read_lock();
+       iter.iter.node = &stream->node.node;
+       ret = lttng_ht_del(ht, &iter);
+       assert(!ret);
 
-       if (stream->wait_fd >= 0 && !stream->wait_fd_is_copy) {
-               ret = close(stream->wait_fd);
-               if (ret) {
-                       PERROR("close");
-               }
-       }
+       iter.iter.node = &stream->node_channel_id.node;
+       ret = lttng_ht_del(consumer_data.stream_per_chan_id_ht, &iter);
+       assert(!ret);
 
-       if (stream->shm_fd >= 0 && stream->wait_fd != stream->shm_fd) {
-               ret = close(stream->shm_fd);
+       iter.iter.node = &stream->node_session_id.node;
+       ret = lttng_ht_del(consumer_data.stream_list_ht, &iter);
+       assert(!ret);
+       rcu_read_unlock();
+
+       if (stream->out_fd >= 0) {
+               ret = close(stream->out_fd);
                if (ret) {
                        PERROR("close");
                }
@@ -1664,59 +1888,42 @@ void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
        /* Atomically decrement channel refcount since other threads can use it. */
        uatomic_dec(&stream->chan->refcount);
        if (!uatomic_read(&stream->chan->refcount)
-                       && !uatomic_read(&stream->chan->nb_init_streams)) {
+                       && !uatomic_read(&stream->chan->nb_init_stream_left)) {
                /* Go for channel deletion! */
                free_chan = stream->chan;
        }
 
 end:
+       pthread_mutex_unlock(&stream->lock);
        pthread_mutex_unlock(&consumer_data.lock);
 
        if (free_chan) {
                consumer_del_channel(free_chan);
        }
 
-free_stream:
-       call_rcu(&stream->waitfd_node.head, consumer_free_metadata_stream);
+free_stream_rcu:
+       call_rcu(&stream->node.head, free_stream_rcu);
 }
 
 /*
  * Action done with the metadata stream when adding it to the consumer internal
  * data structures to handle it.
  */
-static int consumer_add_metadata_stream(struct lttng_consumer_stream *stream,
+static int add_metadata_stream(struct lttng_consumer_stream *stream,
                struct lttng_ht *ht)
 {
        int ret = 0;
        struct consumer_relayd_sock_pair *relayd;
+       struct lttng_ht_iter iter;
+       struct lttng_ht_node_u64 *node;
 
        assert(stream);
        assert(ht);
 
-       DBG3("Adding metadata stream %d to hash table", stream->wait_fd);
+       DBG3("Adding metadata stream %" PRIu64 " to hash table", stream->key);
 
        pthread_mutex_lock(&consumer_data.lock);
-
-       switch (consumer_data.type) {
-       case LTTNG_CONSUMER_KERNEL:
-               break;
-       case LTTNG_CONSUMER32_UST:
-       case LTTNG_CONSUMER64_UST:
-               ret = lttng_ustconsumer_add_stream(stream);
-               if (ret) {
-                       ret = -EINVAL;
-                       goto error;
-               }
-
-               /* Steal stream identifier only for UST */
-               consumer_steal_stream_key(stream->wait_fd, ht);
-               break;
-       default:
-               ERR("Unknown consumer_data type");
-               assert(0);
-               ret = -ENOSYS;
-               goto error;
-       }
+       pthread_mutex_lock(&stream->lock);
 
        /*
         * From here, refcounts are updated so be _careful_ when returning an error
@@ -1724,6 +1931,15 @@ static int consumer_add_metadata_stream(struct lttng_consumer_stream *stream,
         */
 
        rcu_read_lock();
+
+       /*
+        * Lookup the stream just to make sure it does not exist in our internal
+        * state. This should NEVER happen.
+        */
+       lttng_ht_lookup(ht, &stream->key, &iter);
+       node = lttng_ht_iter_get_node_u64(&iter);
+       assert(!node);
+
        /* Find relayd and, if one is found, increment refcount. */
        relayd = consumer_find_relayd(stream->net_seq_idx);
        if (relayd != NULL) {
@@ -1734,54 +1950,118 @@ static int consumer_add_metadata_stream(struct lttng_consumer_stream *stream,
        uatomic_inc(&stream->chan->refcount);
 
        /*
-        * When nb_init_streams reaches 0, we don't need to trigger any action in
-        * terms of destroying the associated channel, because the action that
+        * When nb_init_stream_left reaches 0, we don't need to trigger any action
+        * in terms of destroying the associated channel, because the action that
         * causes the count to become 0 also causes a stream to be added. The
         * channel deletion will thus be triggered by the following removal of this
         * stream.
         */
-       if (uatomic_read(&stream->chan->nb_init_streams) > 0) {
-               uatomic_dec(&stream->chan->nb_init_streams);
+       if (uatomic_read(&stream->chan->nb_init_stream_left) > 0) {
+               uatomic_dec(&stream->chan->nb_init_stream_left);
        }
 
-       lttng_ht_add_unique_ulong(ht, &stream->waitfd_node);
-       rcu_read_unlock();
+       lttng_ht_add_unique_u64(ht, &stream->node);
 
-error:
-       pthread_mutex_unlock(&consumer_data.lock);
-       return ret;
-}
+       lttng_ht_add_unique_u64(consumer_data.stream_per_chan_id_ht,
+               &stream->node_channel_id);
+
+       /*
+        * Add stream to the stream_list_ht of the consumer data. No need to steal
+        * the key since the HT does not use it and we allow to add redundant keys
+        * into this table.
+        */
+       lttng_ht_add_u64(consumer_data.stream_list_ht, &stream->node_session_id);
+
+       rcu_read_unlock();
+
+       pthread_mutex_unlock(&stream->lock);
+       pthread_mutex_unlock(&consumer_data.lock);
+       return ret;
+}
+
+/*
+ * Delete data stream that are flagged for deletion (endpoint_status).
+ */
+static void validate_endpoint_status_data_stream(void)
+{
+       struct lttng_ht_iter iter;
+       struct lttng_consumer_stream *stream;
+
+       DBG("Consumer delete flagged data stream");
+
+       rcu_read_lock();
+       cds_lfht_for_each_entry(data_ht->ht, &iter.iter, stream, node.node) {
+               /* Validate delete flag of the stream */
+               if (stream->endpoint_status == CONSUMER_ENDPOINT_ACTIVE) {
+                       continue;
+               }
+               /* Delete it right now */
+               consumer_del_stream(stream, data_ht);
+       }
+       rcu_read_unlock();
+}
+
+/*
+ * Delete metadata stream that are flagged for deletion (endpoint_status).
+ */
+static void validate_endpoint_status_metadata_stream(
+               struct lttng_poll_event *pollset)
+{
+       struct lttng_ht_iter iter;
+       struct lttng_consumer_stream *stream;
+
+       DBG("Consumer delete flagged metadata stream");
+
+       assert(pollset);
+
+       rcu_read_lock();
+       cds_lfht_for_each_entry(metadata_ht->ht, &iter.iter, stream, node.node) {
+               /* Validate delete flag of the stream */
+               if (stream->endpoint_status == CONSUMER_ENDPOINT_ACTIVE) {
+                       continue;
+               }
+               /*
+                * Remove from pollset so the metadata thread can continue without
+                * blocking on a deleted stream.
+                */
+               lttng_poll_del(pollset, stream->wait_fd);
+
+               /* Delete it right now */
+               consumer_del_metadata_stream(stream, metadata_ht);
+       }
+       rcu_read_unlock();
+}
 
 /*
  * Thread polls on metadata file descriptor and write them on disk or on the
  * network.
  */
-void *lttng_consumer_thread_poll_metadata(void *data)
+void *consumer_thread_metadata_poll(void *data)
 {
        int ret, i, pollfd;
        uint32_t revents, nb_fd;
        struct lttng_consumer_stream *stream = NULL;
        struct lttng_ht_iter iter;
-       struct lttng_ht_node_ulong *node;
-       struct lttng_ht *metadata_ht = NULL;
+       struct lttng_ht_node_u64 *node;
        struct lttng_poll_event events;
        struct lttng_consumer_local_data *ctx = data;
        ssize_t len;
 
        rcu_register_thread();
 
-       DBG("Thread metadata poll started");
-
-       metadata_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
-       if (metadata_ht == NULL) {
-               goto end;
+       metadata_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
+       if (!metadata_ht) {
+               /* ENOMEM at this point. Better to bail out. */
+               goto end_ht;
        }
 
+       DBG("Thread metadata poll started");
+
        /* Size is set to 1 for the consumer_metadata pipe */
        ret = lttng_poll_create(&events, 2, LTTNG_CLOEXEC);
        if (ret < 0) {
                ERR("Poll set creation failed");
-               goto end;
+               goto end_poll;
        }
 
        ret = lttng_poll_add(&events, ctx->consumer_metadata_pipe[0], LPOLLIN);
@@ -1793,17 +2073,13 @@ void *lttng_consumer_thread_poll_metadata(void *data)
        DBG("Metadata main loop started");
 
        while (1) {
-               lttng_poll_reset(&events);
-
-               nb_fd = LTTNG_POLL_GETNB(&events);
-
                /* Only the metadata pipe is set */
-               if (nb_fd == 0 && consumer_quit == 1) {
+               if (LTTNG_POLL_GETNB(&events) == 0 && consumer_quit == 1) {
                        goto end;
                }
 
 restart:
-               DBG("Metadata poll wait with %d fd(s)", nb_fd);
+               DBG("Metadata poll wait with %d fd(s)", LTTNG_POLL_GETNB(&events));
                ret = lttng_poll_wait(&events, -1);
                DBG("Metadata event catched in thread");
                if (ret < 0) {
@@ -1814,6 +2090,8 @@ restart:
                        goto error;
                }
 
+               nb_fd = ret;
+
                /* From here, the event is a metadata wait fd */
                for (i = 0; i < nb_fd; i++) {
                        revents = LTTNG_POLL_GETEV(&events, i);
@@ -1832,7 +2110,10 @@ restart:
                                         * since their might be data to consume.
                                         */
                                        lttng_poll_del(&events, ctx->consumer_metadata_pipe[0]);
-                                       close(ctx->consumer_metadata_pipe[0]);
+                                       ret = close(ctx->consumer_metadata_pipe[0]);
+                                       if (ret < 0) {
+                                               PERROR("close metadata pipe");
+                                       }
                                        continue;
                                } else if (revents & LPOLLIN) {
                                        do {
@@ -1849,10 +2130,17 @@ restart:
                                                continue;
                                        }
 
+                                       /* A NULL stream means that the state has changed. */
+                                       if (stream == NULL) {
+                                               /* Check for deleted streams. */
+                                               validate_endpoint_status_metadata_stream(&events);
+                                               goto restart;
+                                       }
+
                                        DBG("Adding metadata stream %d to poll set",
                                                        stream->wait_fd);
 
-                                       ret = consumer_add_metadata_stream(stream, metadata_ht);
+                                       ret = add_metadata_stream(stream, metadata_ht);
                                        if (ret) {
                                                ERR("Unable to add metadata stream");
                                                /* Stream was not setup properly. Continuing. */
@@ -1870,13 +2158,16 @@ restart:
                        }
 
                        rcu_read_lock();
-                       lttng_ht_lookup(metadata_ht, (void *)((unsigned long) pollfd),
-                                       &iter);
-                       node = lttng_ht_iter_get_node_ulong(&iter);
+                       {
+                               uint64_t tmp_id = (uint64_t) pollfd;
+
+                               lttng_ht_lookup(metadata_ht, &tmp_id, &iter);
+                       }
+                       node = lttng_ht_iter_get_node_u64(&iter);
                        assert(node);
 
                        stream = caa_container_of(node, struct lttng_consumer_stream,
-                                       waitfd_node);
+                                       node);
 
                        /* Check for error event */
                        if (revents & (LPOLLERR | LPOLLHUP)) {
@@ -1888,12 +2179,15 @@ restart:
                                        lttng_ustconsumer_on_stream_hangup(stream);
 
                                        /* We just flushed the stream now read it. */
-                                       len = ctx->on_buffer_ready(stream, ctx);
-                                       /* It's ok to have an unavailable sub-buffer */
-                                       if (len < 0 && len != -EAGAIN) {
-                                               rcu_read_unlock();
-                                               goto end;
-                                       }
+                                       do {
+                                               len = ctx->on_buffer_ready(stream, ctx);
+                                               /*
+                                                * We don't check the return value here since if we get
+                                                * a negative len, it means an error occured thus we
+                                                * simply remove it from the poll set and free the
+                                                * stream.
+                                                */
+                                       } while (len > 0);
                                }
 
                                lttng_poll_del(&events, stream->wait_fd);
@@ -1909,9 +2203,10 @@ restart:
 
                                len = ctx->on_buffer_ready(stream, ctx);
                                /* It's ok to have an unavailable sub-buffer */
-                               if (len < 0 && len != -EAGAIN) {
-                                       rcu_read_unlock();
-                                       goto end;
+                               if (len < 0 && len != -EAGAIN && len != -ENODATA) {
+                                       /* Clean up stream from consumer and free it. */
+                                       lttng_poll_del(&events, stream->wait_fd);
+                                       consumer_del_metadata_stream(stream, metadata_ht);
                                } else if (len > 0) {
                                        stream->data_read = 1;
                                }
@@ -1925,12 +2220,11 @@ restart:
 error:
 end:
        DBG("Metadata poll thread exiting");
-       lttng_poll_clean(&events);
-
-       if (metadata_ht) {
-               destroy_stream_ht(metadata_ht);
-       }
 
+       lttng_poll_clean(&events);
+end_poll:
+       destroy_stream_ht(metadata_ht);
+end_ht:
        rcu_unregister_thread();
        return NULL;
 }
@@ -1939,26 +2233,22 @@ end:
  * This thread polls the fds in the set to consume the data and write
  * it to tracefile if necessary.
  */
-void *lttng_consumer_thread_poll_fds(void *data)
+void *consumer_thread_data_poll(void *data)
 {
        int num_rdy, num_hup, high_prio, ret, i;
        struct pollfd *pollfd = NULL;
        /* local view of the streams */
-       struct lttng_consumer_stream **local_stream = NULL;
+       struct lttng_consumer_stream **local_stream = NULL, *new_stream = NULL;
        /* local view of consumer_data.fds_count */
        int nb_fd = 0;
        struct lttng_consumer_local_data *ctx = data;
        ssize_t len;
-       pthread_t metadata_thread;
-       void *status;
 
        rcu_register_thread();
 
-       /* Start metadata polling thread */
-       ret = pthread_create(&metadata_thread, NULL,
-                       lttng_consumer_thread_poll_metadata, (void *) ctx);
-       if (ret < 0) {
-               PERROR("pthread_create metadata thread");
+       data_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
+       if (data_ht == NULL) {
+               /* ENOMEM at this point. Better to bail out. */
                goto end;
        }
 
@@ -1974,16 +2264,13 @@ void *lttng_consumer_thread_poll_fds(void *data)
                 */
                pthread_mutex_lock(&consumer_data.lock);
                if (consumer_data.need_update) {
-                       if (pollfd != NULL) {
-                               free(pollfd);
-                               pollfd = NULL;
-                       }
-                       if (local_stream != NULL) {
-                               free(local_stream);
-                               local_stream = NULL;
-                       }
+                       free(pollfd);
+                       pollfd = NULL;
+
+                       free(local_stream);
+                       local_stream = NULL;
 
-                       /* allocate for all fds + 1 for the consumer_poll_pipe */
+                       /* allocate for all fds + 1 for the consumer_data_pipe */
                        pollfd = zmalloc((consumer_data.stream_count + 1) * sizeof(struct pollfd));
                        if (pollfd == NULL) {
                                PERROR("pollfd malloc");
@@ -1991,7 +2278,7 @@ void *lttng_consumer_thread_poll_fds(void *data)
                                goto end;
                        }
 
-                       /* allocate for all fds + 1 for the consumer_poll_pipe */
+                       /* allocate for all fds + 1 for the consumer_data_pipe */
                        local_stream = zmalloc((consumer_data.stream_count + 1) *
                                        sizeof(struct lttng_consumer_stream));
                        if (local_stream == NULL) {
@@ -1999,7 +2286,8 @@ void *lttng_consumer_thread_poll_fds(void *data)
                                pthread_mutex_unlock(&consumer_data.lock);
                                goto end;
                        }
-                       ret = consumer_update_poll_array(ctx, &pollfd, local_stream);
+                       ret = update_poll_array(ctx, &pollfd, local_stream,
+                                       data_ht);
                        if (ret < 0) {
                                ERR("Error in allocating pollfd or local_outfds");
                                lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_POLL_ERROR);
@@ -2018,7 +2306,7 @@ void *lttng_consumer_thread_poll_fds(void *data)
                /* poll on the array of fds */
        restart:
                DBG("polling on %d fd", nb_fd + 1);
-               num_rdy = poll(pollfd, nb_fd + 1, consumer_poll_timeout);
+               num_rdy = poll(pollfd, nb_fd + 1, -1);
                DBG("poll num_rdy : %d", num_rdy);
                if (num_rdy == -1) {
                        /*
@@ -2036,31 +2324,64 @@ void *lttng_consumer_thread_poll_fds(void *data)
                }
 
                /*
-                * If the consumer_poll_pipe triggered poll go directly to the
+                * If the consumer_data_pipe triggered poll go directly to the
                 * beginning of the loop to update the array. We want to prioritize
                 * array update over low-priority reads.
                 */
                if (pollfd[nb_fd].revents & (POLLIN | POLLPRI)) {
-                       size_t pipe_readlen;
-                       char tmp;
+                       ssize_t pipe_readlen;
 
-                       DBG("consumer_poll_pipe wake up");
+                       DBG("consumer_data_pipe wake up");
                        /* Consume 1 byte of pipe data */
                        do {
-                               pipe_readlen = read(ctx->consumer_poll_pipe[0], &tmp, 1);
+                               pipe_readlen = read(ctx->consumer_data_pipe[0], &new_stream,
+                                               sizeof(new_stream));
                        } while (pipe_readlen == -1 && errno == EINTR);
+                       if (pipe_readlen < 0) {
+                               PERROR("read consumer data pipe");
+                               /* Continue so we can at least handle the current stream(s). */
+                               continue;
+                       }
+
+                       /*
+                        * If the stream is NULL, just ignore it. It's also possible that
+                        * the sessiond poll thread changed the consumer_quit state and is
+                        * waking us up to test it.
+                        */
+                       if (new_stream == NULL) {
+                               validate_endpoint_status_data_stream();
+                               continue;
+                       }
+
+                       ret = add_stream(new_stream, data_ht);
+                       if (ret) {
+                               ERR("Consumer add stream %" PRIu64 " failed. Continuing",
+                                               new_stream->key);
+                               /*
+                                * At this point, if the add_stream fails, it is not in the
+                                * hash table thus passing the NULL value here.
+                                */
+                               consumer_del_stream(new_stream, NULL);
+                       }
+
+                       /* Continue to update the local streams and handle prio ones */
                        continue;
                }
 
                /* Take care of high priority channels first. */
                for (i = 0; i < nb_fd; i++) {
+                       if (local_stream[i] == NULL) {
+                               continue;
+                       }
                        if (pollfd[i].revents & POLLPRI) {
                                DBG("Urgent read on fd %d", pollfd[i].fd);
                                high_prio = 1;
                                len = ctx->on_buffer_ready(local_stream[i], ctx);
                                /* it's ok to have an unavailable sub-buffer */
-                               if (len < 0 && len != -EAGAIN) {
-                                       goto end;
+                               if (len < 0 && len != -EAGAIN && len != -ENODATA) {
+                                       /* Clean the stream and free it. */
+                                       consumer_del_stream(local_stream[i], data_ht);
+                                       local_stream[i] = NULL;
                                } else if (len > 0) {
                                        local_stream[i]->data_read = 1;
                                }
@@ -2077,13 +2398,18 @@ void *lttng_consumer_thread_poll_fds(void *data)
 
                /* Take care of low priority channels. */
                for (i = 0; i < nb_fd; i++) {
+                       if (local_stream[i] == NULL) {
+                               continue;
+                       }
                        if ((pollfd[i].revents & POLLIN) ||
                                        local_stream[i]->hangup_flush_done) {
                                DBG("Normal read on fd %d", pollfd[i].fd);
                                len = ctx->on_buffer_ready(local_stream[i], ctx);
                                /* it's ok to have an unavailable sub-buffer */
-                               if (len < 0 && len != -EAGAIN) {
-                                       goto end;
+                               if (len < 0 && len != -EAGAIN && len != -ENODATA) {
+                                       /* Clean the stream and free it. */
+                                       consumer_del_stream(local_stream[i], data_ht);
+                                       local_stream[i] = NULL;
                                } else if (len > 0) {
                                        local_stream[i]->data_read = 1;
                                }
@@ -2092,12 +2418,15 @@ void *lttng_consumer_thread_poll_fds(void *data)
 
                /* Handle hangup and errors */
                for (i = 0; i < nb_fd; i++) {
+                       if (local_stream[i] == NULL) {
+                               continue;
+                       }
                        if (!local_stream[i]->hangup_flush_done
                                        && (pollfd[i].revents & (POLLHUP | POLLERR | POLLNVAL))
                                        && (consumer_data.type == LTTNG_CONSUMER32_UST
                                                || consumer_data.type == LTTNG_CONSUMER64_UST)) {
                                DBG("fd %d is hup|err|nval. Attempting flush and read.",
-                                       pollfd[i].fd);
+                                               pollfd[i].fd);
                                lttng_ustconsumer_on_stream_hangup(local_stream[i]);
                                /* Attempt read again, for the data we just flushed. */
                                local_stream[i]->data_read = 1;
@@ -2110,55 +2439,266 @@ void *lttng_consumer_thread_poll_fds(void *data)
                        if ((pollfd[i].revents & POLLHUP)) {
                                DBG("Polling fd %d tells it has hung up.", pollfd[i].fd);
                                if (!local_stream[i]->data_read) {
-                                       consumer_del_stream(local_stream[i],
-                                                       consumer_data.stream_ht);
+                                       consumer_del_stream(local_stream[i], data_ht);
+                                       local_stream[i] = NULL;
                                        num_hup++;
                                }
                        } else if (pollfd[i].revents & POLLERR) {
                                ERR("Error returned in polling fd %d.", pollfd[i].fd);
                                if (!local_stream[i]->data_read) {
-                                       consumer_del_stream(local_stream[i],
-                                                       consumer_data.stream_ht);
+                                       consumer_del_stream(local_stream[i], data_ht);
+                                       local_stream[i] = NULL;
                                        num_hup++;
                                }
                        } else if (pollfd[i].revents & POLLNVAL) {
                                ERR("Polling fd %d tells fd is not open.", pollfd[i].fd);
                                if (!local_stream[i]->data_read) {
-                                       consumer_del_stream(local_stream[i],
-                                                       consumer_data.stream_ht);
+                                       consumer_del_stream(local_stream[i], data_ht);
+                                       local_stream[i] = NULL;
                                        num_hup++;
                                }
                        }
-                       local_stream[i]->data_read = 0;
+                       if (local_stream[i] != NULL) {
+                               local_stream[i]->data_read = 0;
+                       }
                }
        }
 end:
        DBG("polling thread exiting");
-       if (pollfd != NULL) {
-               free(pollfd);
-               pollfd = NULL;
-       }
-       if (local_stream != NULL) {
-               free(local_stream);
-               local_stream = NULL;
-       }
+       free(pollfd);
+       free(local_stream);
 
        /*
         * Close the write side of the pipe so epoll_wait() in
-        * lttng_consumer_thread_poll_metadata can catch it. The thread is
-        * monitoring the read side of the pipe. If we close them both, epoll_wait
-        * strangely does not return and could create a endless wait period if the
-        * pipe is the only tracked fd in the poll set. The thread will take care
-        * of closing the read side.
+        * consumer_thread_metadata_poll can catch it. The thread is monitoring the
+        * read side of the pipe. If we close them both, epoll_wait strangely does
+        * not return and could create a endless wait period if the pipe is the
+        * only tracked fd in the poll set. The thread will take care of closing
+        * the read side.
         */
-       close(ctx->consumer_metadata_pipe[1]);
-       if (ret) {
-               ret = pthread_join(metadata_thread, &status);
+       ret = close(ctx->consumer_metadata_pipe[1]);
+       if (ret < 0) {
+               PERROR("close data pipe");
+       }
+
+       destroy_data_stream_ht(data_ht);
+
+       rcu_unregister_thread();
+       return NULL;
+}
+
+/*
+ * Close wake-up end of each stream belonging to the channel. This will
+ * allow the poll() on the stream read-side to detect when the
+ * write-side (application) finally closes them.
+ */
+static
+void consumer_close_channel_streams(struct lttng_consumer_channel *channel)
+{
+       struct lttng_ht *ht;
+       struct lttng_consumer_stream *stream;
+       struct lttng_ht_iter iter;
+
+       ht = consumer_data.stream_per_chan_id_ht;
+
+       rcu_read_lock();
+       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) {
+               switch (consumer_data.type) {
+               case LTTNG_CONSUMER_KERNEL:
+                       break;
+               case LTTNG_CONSUMER32_UST:
+               case LTTNG_CONSUMER64_UST:
+                       /*
+                        * Note: a mutex is taken internally within
+                        * liblttng-ust-ctl to protect timer wakeup_fd
+                        * use from concurrent close.
+                        */
+                       lttng_ustconsumer_close_stream_wakeup(stream);
+                       break;
+               default:
+                       ERR("Unknown consumer_data type");
+                       assert(0);
+               }
+       }
+       rcu_read_unlock();
+}
+
+static void destroy_channel_ht(struct lttng_ht *ht)
+{
+       struct lttng_ht_iter iter;
+       struct lttng_consumer_channel *channel;
+       int ret;
+
+       if (ht == NULL) {
+               return;
+       }
+
+       rcu_read_lock();
+       cds_lfht_for_each_entry(ht->ht, &iter.iter, channel, wait_fd_node.node) {
+               ret = lttng_ht_del(ht, &iter);
+               assert(ret != 0);
+       }
+       rcu_read_unlock();
+
+       lttng_ht_destroy(ht);
+}
+
+/*
+ * This thread polls the channel fds to detect when they are being
+ * closed. It closes all related streams if the channel is detected as
+ * closed. It is currently only used as a shim layer for UST because the
+ * consumerd needs to keep the per-stream wakeup end of pipes open for
+ * periodical flush.
+ */
+void *consumer_thread_channel_poll(void *data)
+{
+       int ret, i, pollfd;
+       uint32_t revents, nb_fd;
+       struct lttng_consumer_channel *chan = NULL;
+       struct lttng_ht_iter iter;
+       struct lttng_ht_node_u64 *node;
+       struct lttng_poll_event events;
+       struct lttng_consumer_local_data *ctx = data;
+       struct lttng_ht *channel_ht;
+
+       rcu_register_thread();
+
+       channel_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
+       if (!channel_ht) {
+               /* ENOMEM at this point. Better to bail out. */
+               goto end_ht;
+       }
+
+       DBG("Thread channel poll started");
+
+       /* Size is set to 1 for the consumer_channel pipe */
+       ret = lttng_poll_create(&events, 2, LTTNG_CLOEXEC);
+       if (ret < 0) {
+               ERR("Poll set creation failed");
+               goto end_poll;
+       }
+
+       ret = lttng_poll_add(&events, ctx->consumer_channel_pipe[0], LPOLLIN);
+       if (ret < 0) {
+               goto end;
+       }
+
+       /* Main loop */
+       DBG("Channel main loop started");
+
+       while (1) {
+               /* Only the channel pipe is set */
+               if (LTTNG_POLL_GETNB(&events) == 0 && consumer_quit == 1) {
+                       goto end;
+               }
+
+restart:
+               DBG("Channel poll wait with %d fd(s)", LTTNG_POLL_GETNB(&events));
+               ret = lttng_poll_wait(&events, -1);
+               DBG("Channel event catched in thread");
                if (ret < 0) {
-                       PERROR("pthread_join metadata thread");
+                       if (errno == EINTR) {
+                               ERR("Poll EINTR catched");
+                               goto restart;
+                       }
+                       goto end;
+               }
+
+               nb_fd = ret;
+
+               /* From here, the event is a channel wait fd */
+               for (i = 0; i < nb_fd; i++) {
+                       revents = LTTNG_POLL_GETEV(&events, i);
+                       pollfd = LTTNG_POLL_GETFD(&events, i);
+
+                       /* Just don't waste time if no returned events for the fd */
+                       if (!revents) {
+                               continue;
+                       }
+                       if (pollfd == ctx->consumer_channel_pipe[0]) {
+                               if (revents & (LPOLLERR | LPOLLHUP)) {
+                                       DBG("Channel thread pipe hung up");
+                                       /*
+                                        * Remove the pipe from the poll set and continue the loop
+                                        * since their might be data to consume.
+                                        */
+                                       lttng_poll_del(&events, ctx->consumer_channel_pipe[0]);
+                                       continue;
+                               } else if (revents & LPOLLIN) {
+                                       enum consumer_channel_action action;
+
+                                       ret = read_channel_pipe(ctx, &chan, &action);
+                                       if (ret <= 0) {
+                                               ERR("Error reading channel pipe");
+                                               continue;
+                                       }
+
+                                       switch (action) {
+                                       case CONSUMER_CHANNEL_ADD:
+                                               DBG("Adding channel %d to poll set",
+                                                       chan->wait_fd);
+
+                                               lttng_ht_node_init_u64(&chan->wait_fd_node,
+                                                       chan->wait_fd);
+                                               lttng_ht_add_unique_u64(channel_ht,
+                                                               &chan->wait_fd_node);
+                                               /* Add channel to the global poll events list */
+                                               lttng_poll_add(&events, chan->wait_fd,
+                                                               LPOLLIN | LPOLLPRI);
+                                               break;
+                                       case CONSUMER_CHANNEL_QUIT:
+                                               /*
+                                                * Remove the pipe from the poll set and continue the loop
+                                                * since their might be data to consume.
+                                                */
+                                               lttng_poll_del(&events, ctx->consumer_channel_pipe[0]);
+                                               continue;
+                                       default:
+                                               ERR("Unknown action");
+                                               break;
+                                       }
+                               }
+
+                               /* Handle other stream */
+                               continue;
+                       }
+
+                       rcu_read_lock();
+                       {
+                               uint64_t tmp_id = (uint64_t) pollfd;
+
+                               lttng_ht_lookup(channel_ht, &tmp_id, &iter);
+                       }
+                       node = lttng_ht_iter_get_node_u64(&iter);
+                       assert(node);
+
+                       chan = caa_container_of(node, struct lttng_consumer_channel,
+                                       wait_fd_node);
+
+                       /* Check for error event */
+                       if (revents & (LPOLLERR | LPOLLHUP)) {
+                               DBG("Channel fd %d is hup|err.", pollfd);
+
+                               lttng_poll_del(&events, chan->wait_fd);
+                               ret = lttng_ht_del(channel_ht, &iter);
+                               assert(ret == 0);
+                               consumer_close_channel_streams(chan);
+                       }
+
+                       /* Release RCU lock for the channel looked up */
+                       rcu_read_unlock();
                }
        }
 
+end:
+       lttng_poll_clean(&events);
+end_poll:
+       destroy_channel_ht(channel_ht);
+end_ht:
+       DBG("Channel poll thread exiting");
        rcu_unregister_thread();
        return NULL;
 }
@@ -2167,9 +2707,9 @@ end:
  * This thread listens on the consumerd socket and receives the file
  * descriptors from the session daemon.
  */
-void *lttng_consumer_thread_receive_fds(void *data)
+void *consumer_thread_sessiond_poll(void *data)
 {
-       int sock, client_socket, ret;
+       int sock = -1, client_socket, ret;
        /*
         * structure to poll for incoming data on communication socket avoids
         * making blocking sockets.
@@ -2219,7 +2759,7 @@ void *lttng_consumer_thread_receive_fds(void *data)
 
        /* Blocking call, waiting for transmission */
        sock = lttcomm_accept_unix_sock(client_socket);
-       if (sock <= 0) {
+       if (sock < 0) {
                WARN("On accept");
                goto end;
        }
@@ -2229,6 +2769,13 @@ void *lttng_consumer_thread_receive_fds(void *data)
                goto end;
        }
 
+       /* This socket is not useful anymore. */
+       ret = close(client_socket);
+       if (ret < 0) {
+               PERROR("close client_socket");
+       }
+       client_socket = -1;
+
        /* update the polling structure to poll on the established socket */
        consumer_sockpoll[1].fd = sock;
        consumer_sockpoll[1].events = POLLIN | POLLPRI;
@@ -2255,10 +2802,18 @@ void *lttng_consumer_thread_receive_fds(void *data)
                        DBG("consumer_thread_receive_fds received quit from signal");
                        goto end;
                }
-               DBG("received fds on sock");
+               DBG("received command on sock");
        }
 end:
-       DBG("consumer_thread_receive_fds exiting");
+       DBG("Consumer thread sessiond poll exiting");
+
+       /*
+        * Close metadata streams since the producer is the session daemon which
+        * just died.
+        *
+        * NOTE: for now, this only applies to the UST tracer.
+        */
+       lttng_consumer_close_metadata();
 
        /*
         * when all fds have hung up, the polling thread
@@ -2267,26 +2822,27 @@ end:
        consumer_quit = 1;
 
        /*
-        * 2s of grace period, if no polling events occur during
-        * this period, the polling thread will exit even if there
-        * are still open FDs (should not happen, but safety mechanism).
+        * Notify the data poll thread to poll back again and test the
+        * consumer_quit state that we just set so to quit gracefully.
         */
-       consumer_poll_timeout = LTTNG_CONSUMER_POLL_TIMEOUT;
+       notify_thread_pipe(ctx->consumer_data_pipe[1]);
+
+       notify_channel_pipe(ctx, NULL, CONSUMER_CHANNEL_QUIT);
+
+       /* Cleaning up possibly open sockets. */
+       if (sock >= 0) {
+               ret = close(sock);
+               if (ret < 0) {
+                       PERROR("close sock sessiond poll");
+               }
+       }
+       if (client_socket >= 0) {
+               ret = close(sock);
+               if (ret < 0) {
+                       PERROR("close client_socket sessiond poll");
+               }
+       }
 
-       /*
-        * Wake-up the other end by writing a null byte in the pipe
-        * (non-blocking). Important note: Because writing into the
-        * pipe is non-blocking (and therefore we allow dropping wakeup
-        * data, as long as there is wakeup data present in the pipe
-        * buffer to wake up the other end), the other end should
-        * perform the following sequence for waiting:
-        * 1) empty the pipe (reads).
-        * 2) perform update operation.
-        * 3) wait on the pipe (poll).
-        */
-       do {
-               ret = write(ctx->consumer_poll_pipe[1], "", 1);
-       } while (ret < 0 && errno == EINTR);
        rcu_unregister_thread();
        return NULL;
 }
@@ -2294,17 +2850,27 @@ end:
 ssize_t lttng_consumer_read_subbuffer(struct lttng_consumer_stream *stream,
                struct lttng_consumer_local_data *ctx)
 {
+       ssize_t ret;
+
+       pthread_mutex_lock(&stream->lock);
+
        switch (consumer_data.type) {
        case LTTNG_CONSUMER_KERNEL:
-               return lttng_kconsumer_read_subbuffer(stream, ctx);
+               ret = lttng_kconsumer_read_subbuffer(stream, ctx);
+               break;
        case LTTNG_CONSUMER32_UST:
        case LTTNG_CONSUMER64_UST:
-               return lttng_ustconsumer_read_subbuffer(stream, ctx);
+               ret = lttng_ustconsumer_read_subbuffer(stream, ctx);
+               break;
        default:
                ERR("Unknown consumer_data type");
                assert(0);
-               return -ENOSYS;
+               ret = -ENOSYS;
+               break;
        }
+
+       pthread_mutex_unlock(&stream->lock);
+       return ret;
 }
 
 int lttng_consumer_on_recv_stream(struct lttng_consumer_stream *stream)
@@ -2327,9 +2893,10 @@ int lttng_consumer_on_recv_stream(struct lttng_consumer_stream *stream)
  */
 void lttng_consumer_init(void)
 {
-       consumer_data.stream_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
-       consumer_data.channel_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
-       consumer_data.relayd_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
+       consumer_data.channel_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
+       consumer_data.relayd_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
+       consumer_data.stream_list_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
+       consumer_data.stream_per_chan_id_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
 }
 
 /*
@@ -2340,13 +2907,22 @@ void lttng_consumer_init(void)
  */
 int consumer_add_relayd_socket(int net_seq_idx, int sock_type,
                struct lttng_consumer_local_data *ctx, int sock,
-               struct pollfd *consumer_sockpoll, struct lttcomm_sock *relayd_sock)
+               struct pollfd *consumer_sockpoll, struct lttcomm_sock *relayd_sock,
+               unsigned int sessiond_id)
 {
-       int fd, ret = -1;
+       int fd = -1, ret = -1, relayd_created = 0;
+       enum lttng_error_code ret_code = LTTNG_OK;
        struct consumer_relayd_sock_pair *relayd;
 
        DBG("Consumer adding relayd socket (idx: %d)", net_seq_idx);
 
+       /* First send a status message before receiving the fds. */
+       ret = consumer_send_status_msg(sock, ret_code);
+       if (ret < 0) {
+               /* Somehow, the session daemon is not responding anymore. */
+               goto error;
+       }
+
        /* Get relayd reference if exists. */
        relayd = consumer_find_relayd(net_seq_idx);
        if (relayd == NULL) {
@@ -2354,8 +2930,11 @@ int consumer_add_relayd_socket(int net_seq_idx, int sock_type,
                relayd = consumer_allocate_relayd_sock_pair(net_seq_idx);
                if (relayd == NULL) {
                        lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_OUTFD_ERROR);
+                       ret = -1;
                        goto error;
                }
+               relayd->sessiond_session_id = (uint64_t) sessiond_id;
+               relayd_created = 1;
        }
 
        /* Poll on consumer socket. */
@@ -2369,6 +2948,14 @@ int consumer_add_relayd_socket(int net_seq_idx, int sock_type,
        if (ret != sizeof(fd)) {
                lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_ERROR_RECV_FD);
                ret = -1;
+               fd = -1;        /* Just in case it gets set with an invalid value. */
+               goto error_close;
+       }
+
+       /* We have the fds without error. Send status back. */
+       ret = consumer_send_status_msg(sock, ret_code);
+       if (ret < 0) {
+               /* Somehow, the session daemon is not responding anymore. */
                goto error;
        }
 
@@ -2378,36 +2965,69 @@ int consumer_add_relayd_socket(int net_seq_idx, int sock_type,
                /* Copy received lttcomm socket */
                lttcomm_copy_sock(&relayd->control_sock, relayd_sock);
                ret = lttcomm_create_sock(&relayd->control_sock);
+               /* Immediately try to close the created socket if valid. */
+               if (relayd->control_sock.fd >= 0) {
+                       if (close(relayd->control_sock.fd)) {
+                               PERROR("close relayd control socket");
+                       }
+               }
+               /* Handle create_sock error. */
                if (ret < 0) {
                        goto error;
                }
 
-               /* Close the created socket fd which is useless */
-               close(relayd->control_sock.fd);
-
                /* Assign new file descriptor */
                relayd->control_sock.fd = fd;
+
+               /*
+                * Create a session on the relayd and store the returned id. Lock the
+                * control socket mutex if the relayd was NOT created before.
+                */
+               if (!relayd_created) {
+                       pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+               }
+               ret = relayd_create_session(&relayd->control_sock,
+                               &relayd->relayd_session_id);
+               if (!relayd_created) {
+                       pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+               }
+               if (ret < 0) {
+                       /*
+                        * Close all sockets of a relayd object. It will be freed if it was
+                        * created at the error code path or else it will be garbage
+                        * collect.
+                        */
+                       (void) relayd_close(&relayd->control_sock);
+                       (void) relayd_close(&relayd->data_sock);
+                       goto error;
+               }
+
                break;
        case LTTNG_STREAM_DATA:
                /* Copy received lttcomm socket */
                lttcomm_copy_sock(&relayd->data_sock, relayd_sock);
                ret = lttcomm_create_sock(&relayd->data_sock);
+               /* Immediately try to close the created socket if valid. */
+               if (relayd->data_sock.fd >= 0) {
+                       if (close(relayd->data_sock.fd)) {
+                               PERROR("close relayd data socket");
+                       }
+               }
+               /* Handle create_sock error. */
                if (ret < 0) {
                        goto error;
                }
 
-               /* Close the created socket fd which is useless */
-               close(relayd->data_sock.fd);
-
                /* Assign new file descriptor */
                relayd->data_sock.fd = fd;
                break;
        default:
                ERR("Unknown relayd socket type (%d)", sock_type);
+               ret = -1;
                goto error;
        }
 
-       DBG("Consumer %s socket created successfully with net idx %d (fd: %d)",
+       DBG("Consumer %s socket created successfully with net idx %" PRIu64 " (fd: %d)",
                        sock_type == LTTNG_STREAM_CONTROL ? "control" : "data",
                        relayd->net_seq_idx, fd);
 
@@ -2418,8 +3038,245 @@ int consumer_add_relayd_socket(int net_seq_idx, int sock_type,
        add_relayd(relayd);
 
        /* All good! */
-       ret = 0;
+       return 0;
 
 error:
+       /* Close received socket if valid. */
+       if (fd >= 0) {
+               if (close(fd)) {
+                       PERROR("close received socket");
+               }
+       }
+
+error_close:
+       if (relayd_created) {
+               free(relayd);
+       }
+
+       return ret;
+}
+
+/*
+ * Try to lock the stream mutex.
+ *
+ * On success, 1 is returned else 0 indicating that the mutex is NOT lock.
+ */
+static int stream_try_lock(struct lttng_consumer_stream *stream)
+{
+       int ret;
+
+       assert(stream);
+
+       /*
+        * Try to lock the stream mutex. On failure, we know that the stream is
+        * being used else where hence there is data still being extracted.
+        */
+       ret = pthread_mutex_trylock(&stream->lock);
+       if (ret) {
+               /* For both EBUSY and EINVAL error, the mutex is NOT locked. */
+               ret = 0;
+               goto end;
+       }
+
+       ret = 1;
+
+end:
        return ret;
 }
+
+/*
+ * Search for a relayd associated to the session id and return the reference.
+ *
+ * A rcu read side lock MUST be acquire before calling this function and locked
+ * until the relayd object is no longer necessary.
+ */
+static struct consumer_relayd_sock_pair *find_relayd_by_session_id(uint64_t id)
+{
+       struct lttng_ht_iter iter;
+       struct consumer_relayd_sock_pair *relayd = NULL;
+
+       /* Iterate over all relayd since they are indexed by net_seq_idx. */
+       cds_lfht_for_each_entry(consumer_data.relayd_ht->ht, &iter.iter, relayd,
+                       node.node) {
+               /*
+                * Check by sessiond id which is unique here where the relayd session
+                * id might not be when having multiple relayd.
+                */
+               if (relayd->sessiond_session_id == id) {
+                       /* Found the relayd. There can be only one per id. */
+                       goto found;
+               }
+       }
+
+       return NULL;
+
+found:
+       return relayd;
+}
+
+/*
+ * Check if for a given session id there is still data needed to be extract
+ * from the buffers.
+ *
+ * Return 1 if data is pending or else 0 meaning ready to be read.
+ */
+int consumer_data_pending(uint64_t id)
+{
+       int ret;
+       struct lttng_ht_iter iter;
+       struct lttng_ht *ht;
+       struct lttng_consumer_stream *stream;
+       struct consumer_relayd_sock_pair *relayd = NULL;
+       int (*data_pending)(struct lttng_consumer_stream *);
+
+       DBG("Consumer data pending command on session id %" PRIu64, id);
+
+       rcu_read_lock();
+       pthread_mutex_lock(&consumer_data.lock);
+
+       switch (consumer_data.type) {
+       case LTTNG_CONSUMER_KERNEL:
+               data_pending = lttng_kconsumer_data_pending;
+               break;
+       case LTTNG_CONSUMER32_UST:
+       case LTTNG_CONSUMER64_UST:
+               data_pending = lttng_ustconsumer_data_pending;
+               break;
+       default:
+               ERR("Unknown consumer data type");
+               assert(0);
+       }
+
+       /* Ease our life a bit */
+       ht = consumer_data.stream_list_ht;
+
+       relayd = find_relayd_by_session_id(id);
+       if (relayd) {
+               /* Send init command for data pending. */
+               pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+               ret = relayd_begin_data_pending(&relayd->control_sock,
+                               relayd->relayd_session_id);
+               pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+               if (ret < 0) {
+                       /* Communication error thus the relayd so no data pending. */
+                       goto data_not_pending;
+               }
+       }
+
+       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 this call fails, the stream is being used hence data pending. */
+               ret = stream_try_lock(stream);
+               if (!ret) {
+                       goto data_pending;
+               }
+
+               /*
+                * A removed node from the hash table indicates that the stream has
+                * been deleted thus having a guarantee that the buffers are closed
+                * on the consumer side. However, data can still be transmitted
+                * over the network so don't skip the relayd check.
+                */
+               ret = cds_lfht_is_node_deleted(&stream->node.node);
+               if (!ret) {
+                       /* Check the stream if there is data in the buffers. */
+                       ret = data_pending(stream);
+                       if (ret == 1) {
+                               pthread_mutex_unlock(&stream->lock);
+                               goto data_pending;
+                       }
+               }
+
+               /* Relayd check */
+               if (relayd) {
+                       pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+                       if (stream->metadata_flag) {
+                               ret = relayd_quiescent_control(&relayd->control_sock,
+                                               stream->relayd_stream_id);
+                       } else {
+                               ret = relayd_data_pending(&relayd->control_sock,
+                                               stream->relayd_stream_id,
+                                               stream->next_net_seq_num - 1);
+                       }
+                       pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+                       if (ret == 1) {
+                               pthread_mutex_unlock(&stream->lock);
+                               goto data_pending;
+                       }
+               }
+               pthread_mutex_unlock(&stream->lock);
+       }
+
+       if (relayd) {
+               unsigned int is_data_inflight = 0;
+
+               /* Send init command for data pending. */
+               pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+               ret = relayd_end_data_pending(&relayd->control_sock,
+                               relayd->relayd_session_id, &is_data_inflight);
+               pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+               if (ret < 0) {
+                       goto data_not_pending;
+               }
+               if (is_data_inflight) {
+                       goto data_pending;
+               }
+       }
+
+       /*
+        * Finding _no_ node in the hash table and no inflight data means that the
+        * stream(s) have been removed thus data is guaranteed to be available for
+        * analysis from the trace files.
+        */
+
+data_not_pending:
+       /* Data is available to be read by a viewer. */
+       pthread_mutex_unlock(&consumer_data.lock);
+       rcu_read_unlock();
+       return 0;
+
+data_pending:
+       /* Data is still being extracted from buffers. */
+       pthread_mutex_unlock(&consumer_data.lock);
+       rcu_read_unlock();
+       return 1;
+}
+
+/*
+ * Send a ret code status message to the sessiond daemon.
+ *
+ * Return the sendmsg() return value.
+ */
+int consumer_send_status_msg(int sock, int ret_code)
+{
+       struct lttcomm_consumer_status_msg msg;
+
+       msg.ret_code = ret_code;
+
+       return lttcomm_send_unix_sock(sock, &msg, sizeof(msg));
+}
+
+/*
+ * Send a channel status message to the sessiond daemon.
+ *
+ * Return the sendmsg() return value.
+ */
+int consumer_send_status_channel(int sock,
+               struct lttng_consumer_channel *channel)
+{
+       struct lttcomm_consumer_status_channel msg;
+
+       assert(sock >= 0);
+
+       if (!channel) {
+               msg.ret_code = -LTTNG_ERR_UST_CHAN_FAIL;
+       } else {
+               msg.ret_code = LTTNG_OK;
+               msg.key = channel->key;
+               msg.stream_count = channel->streams.count;
+       }
+
+       return lttcomm_send_unix_sock(sock, &msg, sizeof(msg));
+}
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