lib: compile liblttng-ctl as C++
[lttng-tools.git] / src / common / ust-consumer / ust-consumer.c
index f8706d0ba88528e3dbf1e698de96eec9c4d5073d..310b670b15ed4194904c0a7d5f95802c4df0f7e3 100644 (file)
@@ -1,25 +1,15 @@
 /*
- * Copyright (C) 2011 Julien Desfossez <julien.desfossez@polymtl.ca>
- *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- * Copyright (C) 2017 Jérémie Galarneau <jeremie.galarneau@efficios.com>
+ * Copyright (C) 2011 Julien Desfossez <julien.desfossez@polymtl.ca>
+ * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (C) 2017 Jérémie Galarneau <jeremie.galarneau@efficios.com>
  *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License, version 2 only,
- * as published by the Free Software Foundation.
+ * SPDX-License-Identifier: GPL-2.0-only
  *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
 #define _LGPL_SOURCE
-#include <assert.h>
 #include <lttng/ust-ctl.h>
+#include <lttng/ust-sigbus.h>
 #include <poll.h>
 #include <pthread.h>
 #include <stdlib.h>
@@ -33,6 +23,7 @@
 #include <urcu/list.h>
 #include <signal.h>
 #include <stdbool.h>
+#include <stdint.h>
 
 #include <bin/lttng-consumerd/health-consumerd.h>
 #include <common/common.h>
 #include <common/consumer/consumer-timer.h>
 #include <common/utils.h>
 #include <common/index/index.h>
+#include <common/consumer/consumer.h>
+#include <common/shm.h>
+#include <common/optional.h>
 
 #include "ust-consumer.h"
 
 #define INT_MAX_STR_LEN 12     /* includes \0 */
 
-extern struct lttng_consumer_global_data consumer_data;
+extern struct lttng_consumer_global_data the_consumer_data;
 extern int consumer_poll_timeout;
 
+LTTNG_EXPORT DEFINE_LTTNG_UST_SIGBUS_STATE();
+
 /*
  * Free channel object and all streams associated with it. This MUST be used
  * only and only if the channel has _NEVER_ been added to the global channel
@@ -62,7 +58,7 @@ static void destroy_channel(struct lttng_consumer_channel *channel)
 {
        struct lttng_consumer_stream *stream, *stmp;
 
-       assert(channel);
+       LTTNG_ASSERT(channel);
 
        DBG("UST consumer cleaning stream list");
 
@@ -72,7 +68,7 @@ static void destroy_channel(struct lttng_consumer_channel *channel)
                health_code_update();
 
                cds_list_del(&stream->send_node);
-               ustctl_destroy_stream(stream->ustream);
+               lttng_ust_ctl_destroy_stream(stream->ustream);
                lttng_trace_chunk_put(stream->trace_chunk);
                free(stream);
        }
@@ -85,6 +81,11 @@ static void destroy_channel(struct lttng_consumer_channel *channel)
                lttng_ustconsumer_del_channel(channel);
                lttng_ustconsumer_free_channel(channel);
        }
+
+       if (channel->trace_chunk) {
+               lttng_trace_chunk_put(channel->trace_chunk);
+       }
+
        free(channel);
 }
 
@@ -98,8 +99,8 @@ static int add_channel(struct lttng_consumer_channel *channel,
 {
        int ret = 0;
 
-       assert(channel);
-       assert(ctx);
+       LTTNG_ASSERT(channel);
+       LTTNG_ASSERT(ctx);
 
        if (ctx->on_recv_channel != NULL) {
                ret = ctx->on_recv_channel(channel);
@@ -120,26 +121,6 @@ error:
        return ret;
 }
 
-/*
- * Allocate and return a consumer channel object.
- */
-static struct lttng_consumer_channel *allocate_channel(uint64_t session_id,
-               const uint64_t *chunk_id, const char *pathname, const char *name,
-               uint64_t relayd_id, uint64_t key, enum lttng_event_output output,
-               uint64_t tracefile_size, uint64_t tracefile_count,
-               uint64_t session_id_per_pid, unsigned int monitor,
-               unsigned int live_timer_interval,
-               const char *root_shm_path, const char *shm_path)
-{
-       assert(pathname);
-       assert(name);
-
-       return consumer_allocate_channel(key, session_id, chunk_id, pathname,
-                       name, relayd_id, output, tracefile_size,
-                       tracefile_count, session_id_per_pid, monitor,
-                       live_timer_interval, root_shm_path, shm_path);
-}
-
 /*
  * Allocate and return a consumer stream object. If _alloc_ret is not NULL, the
  * error value if applicable is set in it else it is kept untouched.
@@ -153,10 +134,12 @@ static struct lttng_consumer_stream *allocate_stream(int cpu, int key,
        int alloc_ret;
        struct lttng_consumer_stream *stream = NULL;
 
-       assert(channel);
-       assert(ctx);
+       LTTNG_ASSERT(channel);
+       LTTNG_ASSERT(ctx);
 
-       stream = consumer_allocate_stream(channel->key,
+       stream = consumer_stream_create(
+                       channel,
+                       channel->key,
                        key,
                        channel->name,
                        channel->relayd_id,
@@ -185,7 +168,6 @@ static struct lttng_consumer_stream *allocate_stream(int cpu, int key,
        }
 
        consumer_stream_update_channel_attributes(stream, channel);
-       stream->chan = channel;
 
 error:
        if (_alloc_ret) {
@@ -270,18 +252,18 @@ static int create_ust_streams(struct lttng_consumer_channel *channel,
                struct lttng_consumer_local_data *ctx)
 {
        int ret, cpu = 0;
-       struct ustctl_consumer_stream *ustream;
+       struct lttng_ust_ctl_consumer_stream *ustream;
        struct lttng_consumer_stream *stream;
        pthread_mutex_t *current_stream_lock = NULL;
 
-       assert(channel);
-       assert(ctx);
+       LTTNG_ASSERT(channel);
+       LTTNG_ASSERT(ctx);
 
        /*
         * While a stream is available from ustctl. When NULL is returned, we've
         * reached the end of the possible stream for the channel.
         */
-       while ((ustream = ustctl_create_stream(channel->uchan, cpu))) {
+       while ((ustream = lttng_ust_ctl_create_stream(channel->uchan, cpu))) {
                int wait_fd;
                int ust_metadata_pipe[2];
 
@@ -295,7 +277,7 @@ static int create_ust_streams(struct lttng_consumer_channel *channel,
                        }
                        wait_fd = ust_metadata_pipe[0];
                } else {
-                       wait_fd = ustctl_stream_get_wait_fd(ustream);
+                       wait_fd = lttng_ust_ctl_stream_get_wait_fd(ustream);
                }
 
                /* Allocate consumer stream object. */
@@ -327,10 +309,10 @@ static int create_ust_streams(struct lttng_consumer_channel *channel,
                 */
                cds_list_add_tail(&stream->send_node, &channel->streams.head);
 
-               ret = ustctl_get_max_subbuf_size(stream->ustream,
+               ret = lttng_ust_ctl_get_max_subbuf_size(stream->ustream,
                                &stream->max_sb_size);
                if (ret < 0) {
-                       ERR("ustctl_get_max_subbuf_size failed for stream %s",
+                       ERR("lttng_ust_ctl_get_max_subbuf_size failed for stream %s",
                                        stream->name);
                        goto error;
                }
@@ -373,48 +355,6 @@ error_alloc:
        return ret;
 }
 
-/*
- * create_posix_shm is never called concurrently within a process.
- */
-static
-int create_posix_shm(void)
-{
-       char tmp_name[NAME_MAX];
-       int shmfd, ret;
-
-       ret = snprintf(tmp_name, NAME_MAX, "/ust-shm-consumer-%d", getpid());
-       if (ret < 0) {
-               PERROR("snprintf");
-               return -1;
-       }
-       /*
-        * Allocate shm, and immediately unlink its shm oject, keeping
-        * only the file descriptor as a reference to the object.
-        * We specifically do _not_ use the / at the beginning of the
-        * pathname so that some OS implementations can keep it local to
-        * the process (POSIX leaves this implementation-defined).
-        */
-       shmfd = shm_open(tmp_name, O_CREAT | O_EXCL | O_RDWR, 0700);
-       if (shmfd < 0) {
-               PERROR("shm_open");
-               goto error_shm_open;
-       }
-       ret = shm_unlink(tmp_name);
-       if (ret < 0 && errno != ENOENT) {
-               PERROR("shm_unlink");
-               goto error_shm_release;
-       }
-       return shmfd;
-
-error_shm_release:
-       ret = close(shmfd);
-       if (ret) {
-               PERROR("close");
-       }
-error_shm_open:
-       return -1;
-}
-
 static int open_ust_stream_fd(struct lttng_consumer_channel *channel, int cpu,
                const struct lttng_credentials *session_credentials)
 {
@@ -422,7 +362,7 @@ static int open_ust_stream_fd(struct lttng_consumer_channel *channel, int cpu,
        int ret;
 
        if (!channel->shm_path[0]) {
-               return create_posix_shm();
+               return shm_create_anonymous("ust-consumer");
        }
        ret = get_stream_shm_path(shm_path, channel->shm_path, cpu);
        if (ret) {
@@ -430,7 +370,8 @@ static int open_ust_stream_fd(struct lttng_consumer_channel *channel, int cpu,
        }
        return run_as_open(shm_path,
                O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR,
-               session_credentials->uid, session_credentials->gid);
+               lttng_credentials_get_uid(session_credentials),
+               lttng_credentials_get_gid(session_credentials));
 
 error_shm_path:
        return -1;
@@ -443,17 +384,17 @@ error_shm_path:
  * Return 0 on success or else a negative value.
  */
 static int create_ust_channel(struct lttng_consumer_channel *channel,
-               struct ustctl_consumer_channel_attr *attr,
-               struct ustctl_consumer_channel **ust_chanp)
+               struct lttng_ust_ctl_consumer_channel_attr *attr,
+               struct lttng_ust_ctl_consumer_channel **ust_chanp)
 {
        int ret, nr_stream_fds, i, j;
        int *stream_fds;
-       struct ustctl_consumer_channel *ust_channel;
+       struct lttng_ust_ctl_consumer_channel *ust_channel;
 
-       assert(channel);
-       assert(attr);
-       assert(ust_chanp);
-       assert(channel->buffer_credentials.is_set);
+       LTTNG_ASSERT(channel);
+       LTTNG_ASSERT(attr);
+       LTTNG_ASSERT(ust_chanp);
+       LTTNG_ASSERT(channel->buffer_credentials.is_set);
 
        DBG3("Creating channel to ustctl with attr: [overwrite: %d, "
                        "subbuf_size: %" PRIu64 ", num_subbuf: %" PRIu64 ", "
@@ -465,7 +406,7 @@ static int create_ust_channel(struct lttng_consumer_channel *channel,
        if (channel->type == CONSUMER_CHANNEL_TYPE_METADATA)
                nr_stream_fds = 1;
        else
-               nr_stream_fds = ustctl_get_nr_stream_per_channel();
+               nr_stream_fds = lttng_ust_ctl_get_nr_stream_per_channel();
        stream_fds = zmalloc(nr_stream_fds * sizeof(*stream_fds));
        if (!stream_fds) {
                ret = -1;
@@ -479,7 +420,7 @@ static int create_ust_channel(struct lttng_consumer_channel *channel,
                        goto error_open;
                }
        }
-       ust_channel = ustctl_create_channel(attr, stream_fds, nr_stream_fds);
+       ust_channel = lttng_ust_ctl_create_channel(attr, stream_fds, nr_stream_fds);
        if (!ust_channel) {
                ret = -1;
                goto error_create;
@@ -508,8 +449,10 @@ error_open:
                                ERR("Cannot get stream shm path");
                        }
                        closeret = run_as_unlink(shm_path,
-                                       channel->buffer_credentials.value.uid,
-                                       channel->buffer_credentials.value.gid);
+                                       lttng_credentials_get_uid(LTTNG_OPTIONAL_GET_PTR(
+                                                       channel->buffer_credentials)),
+                                       lttng_credentials_get_gid(LTTNG_OPTIONAL_GET_PTR(
+                                                       channel->buffer_credentials)));
                        if (closeret) {
                                PERROR("unlink %s", shm_path);
                        }
@@ -518,8 +461,10 @@ error_open:
        /* Try to rmdir all directories under shm_path root. */
        if (channel->root_shm_path[0]) {
                (void) run_as_rmdir_recursive(channel->root_shm_path,
-                               channel->buffer_credentials.value.uid,
-                               channel->buffer_credentials.value.gid,
+                               lttng_credentials_get_uid(LTTNG_OPTIONAL_GET_PTR(
+                                               channel->buffer_credentials)),
+                               lttng_credentials_get_gid(LTTNG_OPTIONAL_GET_PTR(
+                                               channel->buffer_credentials)),
                                LTTNG_DIRECTORY_HANDLE_SKIP_NON_EMPTY_FLAG);
        }
        free(stream_fds);
@@ -536,13 +481,13 @@ static int send_sessiond_stream(int sock, struct lttng_consumer_stream *stream)
 {
        int ret;
 
-       assert(stream);
-       assert(sock >= 0);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(sock >= 0);
 
        DBG("UST consumer sending stream %" PRIu64 " to sessiond", stream->key);
 
        /* Send stream to session daemon. */
-       ret = ustctl_send_stream_to_sessiond(sock, stream->ustream);
+       ret = lttng_ust_ctl_send_stream_to_sessiond(sock, stream->ustream);
        if (ret < 0) {
                goto error;
        }
@@ -564,9 +509,9 @@ static int send_channel_to_sessiond_and_relayd(int sock,
        struct lttng_consumer_stream *stream;
        uint64_t net_seq_idx = -1ULL;
 
-       assert(channel);
-       assert(ctx);
-       assert(sock >= 0);
+       LTTNG_ASSERT(channel);
+       LTTNG_ASSERT(ctx);
+       LTTNG_ASSERT(sock >= 0);
 
        DBG("UST consumer sending channel %s to sessiond", channel->name);
 
@@ -606,12 +551,12 @@ static int send_channel_to_sessiond_and_relayd(int sock,
        }
 
        /* Send channel to sessiond. */
-       ret = ustctl_send_channel_to_sessiond(sock, channel->uchan);
+       ret = lttng_ust_ctl_send_channel_to_sessiond(sock, channel->uchan);
        if (ret < 0) {
                goto error;
        }
 
-       ret = ustctl_channel_close_wakeup_fd(channel->uchan);
+       ret = lttng_ust_ctl_channel_close_wakeup_fd(channel->uchan);
        if (ret < 0) {
                goto error;
        }
@@ -629,7 +574,7 @@ static int send_channel_to_sessiond_and_relayd(int sock,
        }
 
        /* Tell sessiond there is no more stream. */
-       ret = ustctl_send_stream_to_sessiond(sock, NULL);
+       ret = lttng_ust_ctl_send_stream_to_sessiond(sock, NULL);
        if (ret < 0) {
                goto error;
        }
@@ -655,13 +600,13 @@ error:
  */
 static int ask_channel(struct lttng_consumer_local_data *ctx,
                struct lttng_consumer_channel *channel,
-               struct ustctl_consumer_channel_attr *attr)
+               struct lttng_ust_ctl_consumer_channel_attr *attr)
 {
        int ret;
 
-       assert(ctx);
-       assert(channel);
-       assert(attr);
+       LTTNG_ASSERT(ctx);
+       LTTNG_ASSERT(channel);
+       LTTNG_ASSERT(attr);
 
        /*
         * This value is still used by the kernel consumer since for the kernel,
@@ -684,7 +629,7 @@ static int ask_channel(struct lttng_consumer_local_data *ctx,
                goto end;
        }
 
-       channel->wait_fd = ustctl_channel_get_wait_fd(channel->uchan);
+       channel->wait_fd = lttng_ust_ctl_channel_get_wait_fd(channel->uchan);
 
        /*
         * For the snapshots (no monitor), we create the metadata streams
@@ -718,8 +663,8 @@ static int send_streams_to_thread(struct lttng_consumer_channel *channel,
        int ret = 0;
        struct lttng_consumer_stream *stream, *stmp;
 
-       assert(channel);
-       assert(ctx);
+       LTTNG_ASSERT(channel);
+       LTTNG_ASSERT(ctx);
 
        /* Send streams to the corresponding thread. */
        cds_list_for_each_entry_safe(stream, stmp, &channel->streams.head,
@@ -765,7 +710,7 @@ static int flush_channel(uint64_t chan_key)
                goto error;
        }
 
-       ht = consumer_data.stream_per_chan_id_ht;
+       ht = the_consumer_data.stream_per_chan_id_ht;
 
        /* For each stream of the channel id, flush it. */
        cds_lfht_for_each_entry_duplicate(ht->ht,
@@ -784,7 +729,14 @@ static int flush_channel(uint64_t chan_key)
                }
 
                if (!stream->quiescent) {
-                       ustctl_flush_buffer(stream->ustream, 0);
+                       ret = lttng_ust_ctl_flush_buffer(stream->ustream, 0);
+                       if (ret) {
+                               ERR("Failed to flush buffer while flushing channel: channel key = %" PRIu64 ", channel name = '%s'",
+                                               chan_key, channel->name);
+                               ret = LTTNG_ERR_BUFFER_FLUSH_FAILED;
+                               pthread_mutex_unlock(&stream->lock);
+                               goto error;
+                       }
                        stream->quiescent = true;
                }
 next:
@@ -819,7 +771,7 @@ static int clear_quiescent_channel(uint64_t chan_key)
                goto error;
        }
 
-       ht = consumer_data.stream_per_chan_id_ht;
+       ht = the_consumer_data.stream_per_chan_id_ht;
 
        /* For each stream of the channel id, clear quiescent state. */
        cds_lfht_for_each_entry_duplicate(ht->ht,
@@ -863,7 +815,7 @@ static int close_metadata(uint64_t chan_key)
                goto error;
        }
 
-       pthread_mutex_lock(&consumer_data.lock);
+       pthread_mutex_lock(&the_consumer_data.lock);
        pthread_mutex_lock(&channel->lock);
        channel_monitor = channel->monitor;
        if (cds_lfht_is_node_deleted(&channel->node.node)) {
@@ -872,7 +824,7 @@ static int close_metadata(uint64_t chan_key)
 
        lttng_ustconsumer_close_metadata(channel);
        pthread_mutex_unlock(&channel->lock);
-       pthread_mutex_unlock(&consumer_data.lock);
+       pthread_mutex_unlock(&the_consumer_data.lock);
 
        /*
         * The ownership of a metadata channel depends on the type of
@@ -909,7 +861,7 @@ static int close_metadata(uint64_t chan_key)
        return ret;
 error_unlock:
        pthread_mutex_unlock(&channel->lock);
-       pthread_mutex_unlock(&consumer_data.lock);
+       pthread_mutex_unlock(&the_consumer_data.lock);
 error:
        return ret;
 }
@@ -983,7 +935,7 @@ static int setup_metadata(struct lttng_consumer_local_data *ctx, uint64_t key)
                goto send_streams_error;
        }
        /* List MUST be empty after or else it could be reused. */
-       assert(cds_list_empty(&metadata->streams.head));
+       LTTNG_ASSERT(cds_list_empty(&metadata->streams.head));
 
        ret = 0;
        goto end;
@@ -1017,15 +969,15 @@ static int snapshot_metadata(struct lttng_consumer_channel *metadata_channel,
        int ret = 0;
        struct lttng_consumer_stream *metadata_stream;
 
-       assert(path);
-       assert(ctx);
+       LTTNG_ASSERT(path);
+       LTTNG_ASSERT(ctx);
 
        DBG("UST consumer snapshot metadata with key %" PRIu64 " at path %s",
                        key, path);
 
        rcu_read_lock();
 
-       assert(!metadata_channel->monitor);
+       LTTNG_ASSERT(!metadata_channel->monitor);
 
        health_code_update();
 
@@ -1050,7 +1002,7 @@ static int snapshot_metadata(struct lttng_consumer_channel *metadata_channel,
        }
 
        metadata_stream = metadata_channel->metadata_stream;
-       assert(metadata_stream);
+       LTTNG_ASSERT(metadata_stream);
 
        pthread_mutex_lock(&metadata_stream->lock);
        if (relayd_id != (uint64_t) -1ULL) {
@@ -1068,7 +1020,7 @@ static int snapshot_metadata(struct lttng_consumer_channel *metadata_channel,
        do {
                health_code_update();
 
-               ret = lttng_consumer_read_subbuffer(metadata_stream, ctx);
+               ret = lttng_consumer_read_subbuffer(metadata_stream, ctx, true);
                if (ret < 0) {
                        goto error_stream;
                }
@@ -1088,6 +1040,35 @@ error:
        return ret;
 }
 
+static
+int get_current_subbuf_addr(struct lttng_consumer_stream *stream,
+               const char **addr)
+{
+       int ret;
+       unsigned long mmap_offset;
+       const char *mmap_base;
+
+       mmap_base = lttng_ust_ctl_get_mmap_base(stream->ustream);
+       if (!mmap_base) {
+               ERR("Failed to get mmap base for stream `%s`",
+                               stream->name);
+               ret = -EPERM;
+               goto error;
+       }
+
+       ret = lttng_ust_ctl_get_mmap_read_offset(stream->ustream, &mmap_offset);
+       if (ret != 0) {
+               ERR("Failed to get mmap offset for stream `%s`", stream->name);
+               ret = -EINVAL;
+               goto error;
+       }
+
+       *addr = mmap_base + mmap_offset;
+error:
+       return ret;
+
+}
+
 /*
  * Take a snapshot of all the stream of a channel.
  * RCU read-side lock and the channel lock must be held by the caller.
@@ -1104,8 +1085,8 @@ static int snapshot_channel(struct lttng_consumer_channel *channel,
        unsigned long consumed_pos, produced_pos;
        struct lttng_consumer_stream *stream;
 
-       assert(path);
-       assert(ctx);
+       LTTNG_ASSERT(path);
+       LTTNG_ASSERT(ctx);
 
        rcu_read_lock();
 
@@ -1113,7 +1094,7 @@ static int snapshot_channel(struct lttng_consumer_channel *channel,
                use_relayd = 1;
        }
 
-       assert(!channel->monitor);
+       LTTNG_ASSERT(!channel->monitor);
        DBG("UST consumer snapshot channel %" PRIu64, key);
 
        cds_list_for_each_entry(stream, &channel->streams.head, send_node) {
@@ -1121,7 +1102,7 @@ static int snapshot_channel(struct lttng_consumer_channel *channel,
 
                /* Lock stream because we are about to change its state. */
                pthread_mutex_lock(&stream->lock);
-               assert(channel->trace_chunk);
+               LTTNG_ASSERT(channel->trace_chunk);
                if (!lttng_trace_chunk_get(channel->trace_chunk)) {
                        /*
                         * Can't happen barring an internal error as the channel
@@ -1131,7 +1112,7 @@ static int snapshot_channel(struct lttng_consumer_channel *channel,
                        ret = -1;
                        goto error_unlock;
                }
-               assert(!stream->trace_chunk);
+               LTTNG_ASSERT(!stream->trace_chunk);
                stream->trace_chunk = channel->trace_chunk;
 
                stream->net_seq_idx = relayd_id;
@@ -1156,7 +1137,12 @@ static int snapshot_channel(struct lttng_consumer_channel *channel,
                 * Else, if quiescent, it has already been done by the prior stop.
                 */
                if (!stream->quiescent) {
-                       ustctl_flush_buffer(stream->ustream, 0);
+                       ret = lttng_ust_ctl_flush_buffer(stream->ustream, 0);
+                       if (ret < 0) {
+                               ERR("Failed to flush buffer during snapshot of channel: channel key = %" PRIu64 ", channel name = '%s'",
+                                               channel->key, channel->name);
+                               goto error_unlock;
+                       }
                }
 
                ret = lttng_ustconsumer_take_snapshot(stream);
@@ -1190,15 +1176,17 @@ static int snapshot_channel(struct lttng_consumer_channel *channel,
                while ((long) (consumed_pos - produced_pos) < 0) {
                        ssize_t read_len;
                        unsigned long len, padded_len;
+                       const char *subbuf_addr;
+                       struct lttng_buffer_view subbuf_view;
 
                        health_code_update();
 
                        DBG("UST consumer taking snapshot at pos %lu", consumed_pos);
 
-                       ret = ustctl_get_subbuf(stream->ustream, &consumed_pos);
+                       ret = lttng_ust_ctl_get_subbuf(stream->ustream, &consumed_pos);
                        if (ret < 0) {
                                if (ret != -EAGAIN) {
-                                       PERROR("ustctl_get_subbuf snapshot");
+                                       PERROR("lttng_ust_ctl_get_subbuf snapshot");
                                        goto error_close_stream;
                                }
                                DBG("UST consumer get subbuf failed. Skipping it.");
@@ -1207,20 +1195,27 @@ static int snapshot_channel(struct lttng_consumer_channel *channel,
                                continue;
                        }
 
-                       ret = ustctl_get_subbuf_size(stream->ustream, &len);
+                       ret = lttng_ust_ctl_get_subbuf_size(stream->ustream, &len);
                        if (ret < 0) {
-                               ERR("Snapshot ustctl_get_subbuf_size");
+                               ERR("Snapshot lttng_ust_ctl_get_subbuf_size");
                                goto error_put_subbuf;
                        }
 
-                       ret = ustctl_get_padded_subbuf_size(stream->ustream, &padded_len);
+                       ret = lttng_ust_ctl_get_padded_subbuf_size(stream->ustream, &padded_len);
                        if (ret < 0) {
-                               ERR("Snapshot ustctl_get_padded_subbuf_size");
+                               ERR("Snapshot lttng_ust_ctl_get_padded_subbuf_size");
+                               goto error_put_subbuf;
+                       }
+
+                       ret = get_current_subbuf_addr(stream, &subbuf_addr);
+                       if (ret) {
                                goto error_put_subbuf;
                        }
 
-                       read_len = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, len,
-                                       padded_len - len, NULL);
+                       subbuf_view = lttng_buffer_view_init(
+                                       subbuf_addr, 0, padded_len);
+                       read_len = lttng_consumer_on_read_subbuffer_mmap(
+                                       stream, &subbuf_view, padded_len - len);
                        if (use_relayd) {
                                if (read_len != len) {
                                        ret = -EPERM;
@@ -1233,9 +1228,9 @@ static int snapshot_channel(struct lttng_consumer_channel *channel,
                                }
                        }
 
-                       ret = ustctl_put_subbuf(stream->ustream);
+                       ret = lttng_ust_ctl_put_subbuf(stream->ustream);
                        if (ret < 0) {
-                               ERR("Snapshot ustctl_put_subbuf");
+                               ERR("Snapshot lttng_ust_ctl_put_subbuf");
                                goto error_close_stream;
                        }
                        consumed_pos += stream->max_sb_size;
@@ -1250,8 +1245,8 @@ static int snapshot_channel(struct lttng_consumer_channel *channel,
        return 0;
 
 error_put_subbuf:
-       if (ustctl_put_subbuf(stream->ustream) < 0) {
-               ERR("Snapshot ustctl_put_subbuf");
+       if (lttng_ust_ctl_put_subbuf(stream->ustream) < 0) {
+               ERR("Snapshot lttng_ust_ctl_put_subbuf");
        }
 error_close_stream:
        consumer_stream_close(stream);
@@ -1261,6 +1256,17 @@ error_unlock:
        return ret;
 }
 
+static
+void metadata_stream_reset_cache_consumed_position(
+               struct lttng_consumer_stream *stream)
+{
+       ASSERT_LOCKED(stream->lock);
+
+       DBG("Reset metadata cache of session %" PRIu64,
+                       stream->chan->session_id);
+       stream->ust_metadata_pushed = 0;
+}
+
 /*
  * Receive the metadata updates from the sessiond. Supports receiving
  * overlapping metadata, but is needs to always belong to a contiguous
@@ -1275,6 +1281,7 @@ int lttng_ustconsumer_recv_metadata(int sock, uint64_t key, uint64_t offset,
 {
        int ret, ret_code = LTTCOMM_CONSUMERD_SUCCESS;
        char *metadata_str;
+       enum consumer_metadata_cache_write_status cache_write_status;
 
        DBG("UST consumer push metadata key %" PRIu64 " of len %" PRIu64, key, len);
 
@@ -1298,9 +1305,41 @@ int lttng_ustconsumer_recv_metadata(int sock, uint64_t key, uint64_t offset,
        health_code_update();
 
        pthread_mutex_lock(&channel->metadata_cache->lock);
-       ret = consumer_metadata_cache_write(channel, offset, len, version,
+       cache_write_status = consumer_metadata_cache_write(
+                       channel->metadata_cache, offset, len, version,
                        metadata_str);
-       if (ret < 0) {
+       pthread_mutex_unlock(&channel->metadata_cache->lock);
+       switch (cache_write_status) {
+       case CONSUMER_METADATA_CACHE_WRITE_STATUS_NO_CHANGE:
+               /*
+                * The write entirely overlapped with existing contents of the
+                * same metadata version (same content); there is nothing to do.
+                */
+               break;
+       case CONSUMER_METADATA_CACHE_WRITE_STATUS_INVALIDATED:
+               /*
+                * The metadata cache was invalidated (previously pushed
+                * content has been overwritten). Reset the stream's consumed
+                * metadata position to ensure the metadata poll thread consumes
+                * the whole cache.
+                */
+               pthread_mutex_lock(&channel->metadata_stream->lock);
+               metadata_stream_reset_cache_consumed_position(
+                               channel->metadata_stream);
+               pthread_mutex_unlock(&channel->metadata_stream->lock);
+               /* Fall-through. */
+       case CONSUMER_METADATA_CACHE_WRITE_STATUS_APPENDED_CONTENT:
+               /*
+                * In both cases, the metadata poll thread has new data to
+                * consume.
+                */
+               ret = consumer_metadata_wakeup_pipe(channel);
+               if (ret) {
+                       ret_code = LTTCOMM_CONSUMERD_ERROR_METADATA;
+                       goto end_free;
+               }
+               break;
+       case CONSUMER_METADATA_CACHE_WRITE_STATUS_ERROR:
                /* Unable to handle metadata. Notify session daemon. */
                ret_code = LTTCOMM_CONSUMERD_ERROR_METADATA;
                /*
@@ -1308,10 +1347,10 @@ int lttng_ustconsumer_recv_metadata(int sock, uint64_t key, uint64_t offset,
                 * not have been updated which could create an infinite loop below when
                 * waiting for the metadata cache to be flushed.
                 */
-               pthread_mutex_unlock(&channel->metadata_cache->lock);
                goto end_free;
+       default:
+               abort();
        }
-       pthread_mutex_unlock(&channel->metadata_cache->lock);
 
        if (!wait) {
                goto end_free;
@@ -1338,32 +1377,37 @@ end:
 int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                int sock, struct pollfd *consumer_sockpoll)
 {
-       ssize_t ret;
+       int ret_func;
        enum lttcomm_return_code ret_code = LTTCOMM_CONSUMERD_SUCCESS;
        struct lttcomm_consumer_msg msg;
        struct lttng_consumer_channel *channel = NULL;
 
        health_code_update();
 
-       ret = lttcomm_recv_unix_sock(sock, &msg, sizeof(msg));
-       if (ret != sizeof(msg)) {
-               DBG("Consumer received unexpected message size %zd (expects %zu)",
-                       ret, sizeof(msg));
-               /*
-                * The ret value might 0 meaning an orderly shutdown but this is ok
-                * since the caller handles this.
-                */
-               if (ret > 0) {
-                       lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_ERROR_RECV_CMD);
-                       ret = -1;
+       {
+               ssize_t ret_recv;
+
+               ret_recv = lttcomm_recv_unix_sock(sock, &msg, sizeof(msg));
+               if (ret_recv != sizeof(msg)) {
+                       DBG("Consumer received unexpected message size %zd (expects %zu)",
+                                       ret_recv, sizeof(msg));
+                       /*
+                        * The ret value might 0 meaning an orderly shutdown but this is ok
+                        * since the caller handles this.
+                        */
+                       if (ret_recv > 0) {
+                               lttng_consumer_send_error(ctx,
+                                               LTTCOMM_CONSUMERD_ERROR_RECV_CMD);
+                               ret_recv = -1;
+                       }
+                       return ret_recv;
                }
-               return ret;
        }
 
        health_code_update();
 
        /* deprecated */
-       assert(msg.cmd_type != LTTNG_CONSUMER_STOP);
+       LTTNG_ASSERT(msg.cmd_type != LTTNG_CONSUMER_STOP);
 
        health_code_update();
 
@@ -1417,7 +1461,8 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
        }
        case LTTNG_CONSUMER_DATA_PENDING:
        {
-               int ret, is_data_pending;
+               int is_data_pending;
+               ssize_t ret_send;
                uint64_t id = msg.u.data_pending.session_id;
 
                DBG("UST consumer data pending command for id %" PRIu64, id);
@@ -1425,10 +1470,11 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                is_data_pending = consumer_data_pending(id);
 
                /* Send back returned value to session daemon */
-               ret = lttcomm_send_unix_sock(sock, &is_data_pending,
+               ret_send = lttcomm_send_unix_sock(sock, &is_data_pending,
                                sizeof(is_data_pending));
-               if (ret < 0) {
-                       DBG("Error when sending the data pending ret code: %d", ret);
+               if (ret_send < 0) {
+                       DBG("Error when sending the data pending ret code: %zd",
+                                       ret_send);
                        goto error_fatal;
                }
 
@@ -1440,28 +1486,30 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
        }
        case LTTNG_CONSUMER_ASK_CHANNEL_CREATION:
        {
-               int ret;
-               struct ustctl_consumer_channel_attr attr;
+               int ret_ask_channel, ret_add_channel, ret_send;
+               struct lttng_ust_ctl_consumer_channel_attr attr;
                const uint64_t chunk_id = msg.u.ask_channel.chunk_id.value;
                const struct lttng_credentials buffer_credentials = {
-                       .uid = msg.u.ask_channel.buffer_credentials.uid,
-                       .gid = msg.u.ask_channel.buffer_credentials.gid,
+                       .uid = LTTNG_OPTIONAL_INIT_VALUE(msg.u.ask_channel.buffer_credentials.uid),
+                       .gid = LTTNG_OPTIONAL_INIT_VALUE(msg.u.ask_channel.buffer_credentials.gid),
                };
 
                /* Create a plain object and reserve a channel key. */
-               channel = allocate_channel(msg.u.ask_channel.session_id,
+               channel = consumer_allocate_channel(
+                               msg.u.ask_channel.key,
+                               msg.u.ask_channel.session_id,
                                msg.u.ask_channel.chunk_id.is_set ?
                                                &chunk_id : NULL,
                                msg.u.ask_channel.pathname,
                                msg.u.ask_channel.name,
                                msg.u.ask_channel.relayd_id,
-                               msg.u.ask_channel.key,
                                (enum lttng_event_output) msg.u.ask_channel.output,
                                msg.u.ask_channel.tracefile_size,
                                msg.u.ask_channel.tracefile_count,
                                msg.u.ask_channel.session_id_per_pid,
                                msg.u.ask_channel.monitor,
                                msg.u.ask_channel.live_timer_interval,
+                               msg.u.ask_channel.is_live,
                                msg.u.ask_channel.root_shm_path,
                                msg.u.ask_channel.shm_path);
                if (!channel) {
@@ -1492,15 +1540,15 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                switch (msg.u.ask_channel.output) {
                case LTTNG_EVENT_MMAP:
                default:
-                       attr.output = LTTNG_UST_MMAP;
+                       attr.output = LTTNG_UST_ABI_MMAP;
                        break;
                }
 
                /* Translate and save channel type. */
                switch (msg.u.ask_channel.type) {
-               case LTTNG_UST_CHAN_PER_CPU:
+               case LTTNG_UST_ABI_CHAN_PER_CPU:
                        channel->type = CONSUMER_CHANNEL_TYPE_DATA;
-                       attr.type = LTTNG_UST_CHAN_PER_CPU;
+                       attr.type = LTTNG_UST_ABI_CHAN_PER_CPU;
                        /*
                         * Set refcount to 1 for owner. Below, we will
                         * pass ownership to the
@@ -1508,25 +1556,28 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                         */
                        channel->refcount = 1;
                        break;
-               case LTTNG_UST_CHAN_METADATA:
+               case LTTNG_UST_ABI_CHAN_METADATA:
                        channel->type = CONSUMER_CHANNEL_TYPE_METADATA;
-                       attr.type = LTTNG_UST_CHAN_METADATA;
+                       attr.type = LTTNG_UST_ABI_CHAN_METADATA;
                        break;
                default:
-                       assert(0);
+                       abort();
                        goto error_fatal;
                };
 
                health_code_update();
 
-               ret = ask_channel(ctx, channel, &attr);
-               if (ret < 0) {
+               ret_ask_channel = ask_channel(ctx, channel, &attr);
+               if (ret_ask_channel < 0) {
                        goto end_channel_error;
                }
 
-               if (msg.u.ask_channel.type == LTTNG_UST_CHAN_METADATA) {
-                       ret = consumer_metadata_cache_allocate(channel);
-                       if (ret < 0) {
+               if (msg.u.ask_channel.type == LTTNG_UST_ABI_CHAN_METADATA) {
+                       int ret_allocate;
+
+                       ret_allocate = consumer_metadata_cache_allocate(
+                                       channel);
+                       if (ret_allocate < 0) {
                                ERR("Allocating metadata cache");
                                goto end_channel_error;
                        }
@@ -1555,9 +1606,9 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                 * If add_channel succeeds, ownership of the channel is
                 * passed to consumer_thread_channel_poll().
                 */
-               ret = add_channel(channel, ctx);
-               if (ret < 0) {
-                       if (msg.u.ask_channel.type == LTTNG_UST_CHAN_METADATA) {
+               ret_add_channel = add_channel(channel, ctx);
+               if (ret_add_channel < 0) {
+                       if (msg.u.ask_channel.type == LTTNG_UST_ABI_CHAN_METADATA) {
                                if (channel->switch_timer_enabled == 1) {
                                        consumer_timer_switch_stop(channel);
                                }
@@ -1579,8 +1630,8 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                 * everything went well and should wait to receive the channel and
                 * streams with ustctl API.
                 */
-               ret = consumer_send_status_channel(sock, channel);
-               if (ret < 0) {
+               ret_send = consumer_send_status_channel(sock, channel);
+               if (ret_send < 0) {
                        /*
                         * There is probably a problem on the socket.
                         */
@@ -1593,10 +1644,10 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
        {
                int ret, relayd_err = 0;
                uint64_t key = msg.u.get_channel.key;
-               struct lttng_consumer_channel *channel;
+               struct lttng_consumer_channel *found_channel;
 
-               channel = consumer_find_channel(key);
-               if (!channel) {
+               found_channel = consumer_find_channel(key);
+               if (!found_channel) {
                        ERR("UST consumer get channel key %" PRIu64 " not found", key);
                        ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
                        goto end_get_channel;
@@ -1605,8 +1656,8 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                health_code_update();
 
                /* Send the channel to sessiond (and relayd, if applicable). */
-               ret = send_channel_to_sessiond_and_relayd(sock, channel, ctx,
-                               &relayd_err);
+               ret = send_channel_to_sessiond_and_relayd(
+                               sock, found_channel, ctx, &relayd_err);
                if (ret < 0) {
                        if (relayd_err) {
                                /*
@@ -1630,11 +1681,11 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                 * In no monitor mode, the streams ownership is kept inside the channel
                 * so don't send them to the data thread.
                 */
-               if (!channel->monitor) {
+               if (!found_channel->monitor) {
                        goto end_get_channel;
                }
 
-               ret = send_streams_to_thread(channel, ctx);
+               ret = send_streams_to_thread(found_channel, ctx);
                if (ret < 0) {
                        /*
                         * If we are unable to send the stream to the thread, there is
@@ -1643,7 +1694,7 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                        goto error_get_channel_fatal;
                }
                /* List MUST be empty after or else it could be reused. */
-               assert(cds_list_empty(&channel->streams.head));
+               LTTNG_ASSERT(cds_list_empty(&found_channel->streams.head));
 end_get_channel:
                goto end_msg_sessiond;
 error_get_channel_fatal:
@@ -1704,13 +1755,13 @@ end_get_channel_nosignal:
                uint64_t key = msg.u.push_metadata.key;
                uint64_t offset = msg.u.push_metadata.target_offset;
                uint64_t version = msg.u.push_metadata.version;
-               struct lttng_consumer_channel *channel;
+               struct lttng_consumer_channel *found_channel;
 
                DBG("UST consumer push metadata key %" PRIu64 " of len %" PRIu64, key,
                                len);
 
-               channel = consumer_find_channel(key);
-               if (!channel) {
+               found_channel = consumer_find_channel(key);
+               if (!found_channel) {
                        /*
                         * This is possible if the metadata creation on the consumer side
                         * is in flight vis-a-vis a concurrent push metadata from the
@@ -1753,8 +1804,8 @@ end_get_channel_nosignal:
 
                health_code_update();
 
-               ret = lttng_ustconsumer_recv_metadata(sock, key, offset,
-                               len, version, channel, 0, 1);
+               ret = lttng_ustconsumer_recv_metadata(sock, key, offset, len,
+                               version, found_channel, 0, 1);
                if (ret < 0) {
                        /* error receiving from sessiond */
                        goto error_push_metadata_fatal;
@@ -1779,38 +1830,46 @@ error_push_metadata_fatal:
        }
        case LTTNG_CONSUMER_SNAPSHOT_CHANNEL:
        {
-               struct lttng_consumer_channel *channel;
+               struct lttng_consumer_channel *found_channel;
                uint64_t key = msg.u.snapshot_channel.key;
+               int ret_send;
 
-               channel = consumer_find_channel(key);
-               if (!channel) {
+               found_channel = consumer_find_channel(key);
+               if (!found_channel) {
                        DBG("UST snapshot channel not found for key %" PRIu64, key);
                        ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
                } else {
                        if (msg.u.snapshot_channel.metadata) {
-                               ret = snapshot_metadata(channel, key,
+                               int ret_snapshot;
+
+                               ret_snapshot = snapshot_metadata(found_channel,
+                                               key,
                                                msg.u.snapshot_channel.pathname,
                                                msg.u.snapshot_channel.relayd_id,
                                                ctx);
-                               if (ret < 0) {
+                               if (ret_snapshot < 0) {
                                        ERR("Snapshot metadata failed");
                                        ret_code = LTTCOMM_CONSUMERD_SNAPSHOT_FAILED;
                                }
                        } else {
-                               ret = snapshot_channel(channel, key,
+                               int ret_snapshot;
+
+                               ret_snapshot = snapshot_channel(found_channel,
+                                               key,
                                                msg.u.snapshot_channel.pathname,
                                                msg.u.snapshot_channel.relayd_id,
-                                               msg.u.snapshot_channel.nb_packets_per_stream,
+                                               msg.u.snapshot_channel
+                                                               .nb_packets_per_stream,
                                                ctx);
-                               if (ret < 0) {
+                               if (ret_snapshot < 0) {
                                        ERR("Snapshot channel failed");
                                        ret_code = LTTCOMM_CONSUMERD_SNAPSHOT_FAILED;
                                }
                        }
                }
                health_code_update();
-               ret = consumer_send_status_msg(sock, ret_code);
-               if (ret < 0) {
+               ret_send = consumer_send_status_msg(sock, ret_code);
+               if (ret_send < 0) {
                        /* Somehow, the session daemon is not responding anymore. */
                        goto end_nosignal;
                }
@@ -1830,9 +1889,9 @@ error_push_metadata_fatal:
                DBG("UST consumer discarded events command for session id %"
                                PRIu64, id);
                rcu_read_lock();
-               pthread_mutex_lock(&consumer_data.lock);
+               pthread_mutex_lock(&the_consumer_data.lock);
 
-               ht = consumer_data.stream_list_ht;
+               ht = the_consumer_data.stream_list_ht;
 
                /*
                 * We only need a reference to the channel, but they are not
@@ -1851,7 +1910,7 @@ error_push_metadata_fatal:
                                break;
                        }
                }
-               pthread_mutex_unlock(&consumer_data.lock);
+               pthread_mutex_unlock(&the_consumer_data.lock);
                rcu_read_unlock();
 
                DBG("UST consumer discarded events command for session id %"
@@ -1881,9 +1940,9 @@ error_push_metadata_fatal:
                DBG("UST consumer lost packets command for session id %"
                                PRIu64, id);
                rcu_read_lock();
-               pthread_mutex_lock(&consumer_data.lock);
+               pthread_mutex_lock(&the_consumer_data.lock);
 
-               ht = consumer_data.stream_list_ht;
+               ht = the_consumer_data.stream_list_ht;
 
                /*
                 * We only need a reference to the channel, but they are not
@@ -1901,7 +1960,7 @@ error_push_metadata_fatal:
                                break;
                        }
                }
-               pthread_mutex_unlock(&consumer_data.lock);
+               pthread_mutex_unlock(&the_consumer_data.lock);
                rcu_read_unlock();
 
                DBG("UST consumer lost packets command for session id %"
@@ -1921,40 +1980,44 @@ error_push_metadata_fatal:
        }
        case LTTNG_CONSUMER_SET_CHANNEL_MONITOR_PIPE:
        {
-               int channel_monitor_pipe;
+               int channel_monitor_pipe, ret_send,
+                               ret_set_channel_monitor_pipe;
+               ssize_t ret_recv;
 
                ret_code = LTTCOMM_CONSUMERD_SUCCESS;
                /* Successfully received the command's type. */
-               ret = consumer_send_status_msg(sock, ret_code);
-               if (ret < 0) {
+               ret_send = consumer_send_status_msg(sock, ret_code);
+               if (ret_send < 0) {
                        goto error_fatal;
                }
 
-               ret = lttcomm_recv_fds_unix_sock(sock, &channel_monitor_pipe,
-                               1);
-               if (ret != sizeof(channel_monitor_pipe)) {
+               ret_recv = lttcomm_recv_fds_unix_sock(
+                               sock, &channel_monitor_pipe, 1);
+               if (ret_recv != sizeof(channel_monitor_pipe)) {
                        ERR("Failed to receive channel monitor pipe");
                        goto error_fatal;
                }
 
                DBG("Received channel monitor pipe (%d)", channel_monitor_pipe);
-               ret = consumer_timer_thread_set_channel_monitor_pipe(
-                               channel_monitor_pipe);
-               if (!ret) {
+               ret_set_channel_monitor_pipe =
+                               consumer_timer_thread_set_channel_monitor_pipe(
+                                               channel_monitor_pipe);
+               if (!ret_set_channel_monitor_pipe) {
                        int flags;
+                       int ret_fcntl;
 
                        ret_code = LTTCOMM_CONSUMERD_SUCCESS;
                        /* Set the pipe as non-blocking. */
-                       ret = fcntl(channel_monitor_pipe, F_GETFL, 0);
-                       if (ret == -1) {
+                       ret_fcntl = fcntl(channel_monitor_pipe, F_GETFL, 0);
+                       if (ret_fcntl == -1) {
                                PERROR("fcntl get flags of the channel monitoring pipe");
                                goto error_fatal;
                        }
-                       flags = ret;
+                       flags = ret_fcntl;
 
-                       ret = fcntl(channel_monitor_pipe, F_SETFL,
+                       ret_fcntl = fcntl(channel_monitor_pipe, F_SETFL,
                                        flags | O_NONBLOCK);
-                       if (ret == -1) {
+                       if (ret_fcntl == -1) {
                                PERROR("fcntl set O_NONBLOCK flag of the channel monitoring pipe");
                                goto error_fatal;
                        }
@@ -1966,31 +2029,35 @@ error_push_metadata_fatal:
        }
        case LTTNG_CONSUMER_ROTATE_CHANNEL:
        {
-               struct lttng_consumer_channel *channel;
+               struct lttng_consumer_channel *found_channel;
                uint64_t key = msg.u.rotate_channel.key;
+               int ret_send_status;
 
-               channel = consumer_find_channel(key);
-               if (!channel) {
+               found_channel = consumer_find_channel(key);
+               if (!found_channel) {
                        DBG("Channel %" PRIu64 " not found", key);
                        ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
                } else {
+                       int rotate_channel;
+
                        /*
                         * Sample the rotate position of all the streams in
                         * this channel.
                         */
-                       ret = lttng_consumer_rotate_channel(channel, key,
+                       rotate_channel = lttng_consumer_rotate_channel(
+                                       found_channel, key,
                                        msg.u.rotate_channel.relayd_id,
-                                       msg.u.rotate_channel.metadata,
-                                       ctx);
-                       if (ret < 0) {
+                                       msg.u.rotate_channel.metadata, ctx);
+                       if (rotate_channel < 0) {
                                ERR("Rotate channel failed");
                                ret_code = LTTCOMM_CONSUMERD_ROTATION_FAIL;
                        }
 
                        health_code_update();
                }
-               ret = consumer_send_status_msg(sock, ret_code);
-               if (ret < 0) {
+
+               ret_send_status = consumer_send_status_msg(sock, ret_code);
+               if (ret_send_status < 0) {
                        /* Somehow, the session daemon is not responding anymore. */
                        goto end_rotate_channel_nosignal;
                }
@@ -2002,10 +2069,14 @@ error_push_metadata_fatal:
                 * handle this, but it needs to be after the
                 * consumer_send_status_msg() call.
                 */
-               if (channel) {
-                       ret = lttng_consumer_rotate_ready_streams(
-                                       channel, key, ctx);
-                       if (ret < 0) {
+               if (found_channel) {
+                       int ret_rotate_read_streams;
+
+                       ret_rotate_read_streams =
+                                       lttng_consumer_rotate_ready_streams(
+                                                       found_channel, key,
+                                                       ctx);
+                       if (ret_rotate_read_streams < 0) {
                                ERR("Rotate channel failed");
                        }
                }
@@ -2013,13 +2084,44 @@ error_push_metadata_fatal:
 end_rotate_channel_nosignal:
                goto end_nosignal;
        }
+       case LTTNG_CONSUMER_CLEAR_CHANNEL:
+       {
+               struct lttng_consumer_channel *found_channel;
+               uint64_t key = msg.u.clear_channel.key;
+               int ret_send_status;
+
+               found_channel = consumer_find_channel(key);
+               if (!found_channel) {
+                       DBG("Channel %" PRIu64 " not found", key);
+                       ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
+               } else {
+                       int ret_clear_channel;
+
+                       ret_clear_channel = lttng_consumer_clear_channel(
+                                       found_channel);
+                       if (ret_clear_channel) {
+                               ERR("Clear channel failed key %" PRIu64, key);
+                               ret_code = ret_clear_channel;
+                       }
+
+                       health_code_update();
+               }
+               ret_send_status = consumer_send_status_msg(sock, ret_code);
+               if (ret_send_status < 0) {
+                       /* Somehow, the session daemon is not responding anymore. */
+                       goto end_nosignal;
+               }
+               break;
+       }
        case LTTNG_CONSUMER_INIT:
        {
+               int ret_send_status;
+
                ret_code = lttng_consumer_init_command(ctx,
                                msg.u.init.sessiond_uuid);
                health_code_update();
-               ret = consumer_send_status_msg(sock, ret_code);
-               if (ret < 0) {
+               ret_send_status = consumer_send_status_msg(sock, ret_code);
+               if (ret_send_status < 0) {
                        /* Somehow, the session daemon is not responding anymore. */
                        goto end_nosignal;
                }
@@ -2028,8 +2130,8 @@ end_rotate_channel_nosignal:
        case LTTNG_CONSUMER_CREATE_TRACE_CHUNK:
        {
                const struct lttng_credentials credentials = {
-                       .uid = msg.u.create_trace_chunk.credentials.value.uid,
-                       .gid = msg.u.create_trace_chunk.credentials.value.gid,
+                       .uid = LTTNG_OPTIONAL_INIT_VALUE(msg.u.create_trace_chunk.credentials.value.uid),
+                       .gid = LTTNG_OPTIONAL_INIT_VALUE(msg.u.create_trace_chunk.credentials.value.gid),
                };
                const bool is_local_trace =
                                !msg.u.create_trace_chunk.relayd_id.is_set;
@@ -2039,8 +2141,7 @@ end_rotate_channel_nosignal:
                                *msg.u.create_trace_chunk.override_name ?
                                        msg.u.create_trace_chunk.override_name :
                                        NULL;
-               LTTNG_OPTIONAL(struct lttng_directory_handle) chunk_directory_handle =
-                               LTTNG_OPTIONAL_INIT;
+               struct lttng_directory_handle *chunk_directory_handle = NULL;
 
                /*
                 * The session daemon will only provide a chunk directory file
@@ -2048,34 +2149,38 @@ end_rotate_channel_nosignal:
                 */
                if (is_local_trace) {
                        int chunk_dirfd;
+                       int ret_send_status;
+                       ssize_t ret_recv;
 
                        /* Acnowledge the reception of the command. */
-                       ret = consumer_send_status_msg(sock,
-                                       LTTCOMM_CONSUMERD_SUCCESS);
-                       if (ret < 0) {
+                       ret_send_status = consumer_send_status_msg(
+                                       sock, LTTCOMM_CONSUMERD_SUCCESS);
+                       if (ret_send_status < 0) {
                                /* Somehow, the session daemon is not responding anymore. */
                                goto end_nosignal;
                        }
 
-                       ret = lttcomm_recv_fds_unix_sock(sock, &chunk_dirfd, 1);
-                       if (ret != sizeof(chunk_dirfd)) {
-                               ERR("Failed to receive trace chunk directory file descriptor");
+                       /*
+                        * Receive trace chunk domain dirfd.
+                        */
+                       ret_recv = lttcomm_recv_fds_unix_sock(
+                                       sock, &chunk_dirfd, 1);
+                       if (ret_recv != sizeof(chunk_dirfd)) {
+                               ERR("Failed to receive trace chunk domain directory file descriptor");
                                goto error_fatal;
                        }
 
-                       DBG("Received trace chunk directory fd (%d)",
+                       DBG("Received trace chunk domain directory fd (%d)",
                                        chunk_dirfd);
-                       ret = lttng_directory_handle_init_from_dirfd(
-                                       &chunk_directory_handle.value,
+                       chunk_directory_handle = lttng_directory_handle_create_from_dirfd(
                                        chunk_dirfd);
-                       if (ret) {
-                               ERR("Failed to initialize chunk directory handle from directory file descriptor");
+                       if (!chunk_directory_handle) {
+                               ERR("Failed to initialize chunk domain directory handle from directory file descriptor");
                                if (close(chunk_dirfd)) {
                                        PERROR("Failed to close chunk directory file descriptor");
                                }
                                goto error_fatal;
                        }
-                       chunk_directory_handle.is_set = true;
                }
 
                ret_code = lttng_consumer_create_trace_chunk(
@@ -2088,14 +2193,8 @@ end_rotate_channel_nosignal:
                                msg.u.create_trace_chunk.credentials.is_set ?
                                                &credentials :
                                                NULL,
-                               chunk_directory_handle.is_set ?
-                                               &chunk_directory_handle.value :
-                                               NULL);
-
-               if (chunk_directory_handle.is_set) {
-                       lttng_directory_handle_fini(
-                                       &chunk_directory_handle.value);
-               }
+                               chunk_directory_handle);
+               lttng_directory_handle_put(chunk_directory_handle);
                goto end_msg_sessiond;
        }
        case LTTNG_CONSUMER_CLOSE_TRACE_CHUNK:
@@ -2105,7 +2204,7 @@ end_rotate_channel_nosignal:
                const uint64_t relayd_id =
                                msg.u.close_trace_chunk.relayd_id.value;
                struct lttcomm_consumer_close_trace_chunk_reply reply;
-               char closed_trace_chunk_path[LTTNG_PATH_MAX];
+               char closed_trace_chunk_path[LTTNG_PATH_MAX] = {};
                int ret;
 
                ret_code = lttng_consumer_close_trace_chunk(
@@ -2143,6 +2242,29 @@ end_rotate_channel_nosignal:
                                msg.u.trace_chunk_exists.chunk_id);
                goto end_msg_sessiond;
        }
+       case LTTNG_CONSUMER_OPEN_CHANNEL_PACKETS:
+       {
+               const uint64_t key = msg.u.open_channel_packets.key;
+               struct lttng_consumer_channel *found_channel =
+                               consumer_find_channel(key);
+
+               if (found_channel) {
+                       pthread_mutex_lock(&found_channel->lock);
+                       ret_code = lttng_consumer_open_channel_packets(
+                                       found_channel);
+                       pthread_mutex_unlock(&found_channel->lock);
+               } else {
+                       /*
+                        * The channel could have disappeared in per-pid
+                        * buffering mode.
+                        */
+                       DBG("Channel %" PRIu64 " not found", key);
+                       ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
+               }
+
+               health_code_update();
+               goto end_msg_sessiond;
+       }
        default:
                break;
        }
@@ -2152,7 +2274,7 @@ end_nosignal:
         * Return 1 to indicate success since the 0 value can be a socket
         * shutdown during the recv() or send() call.
         */
-       ret = 1;
+       ret_func = 1;
        goto end;
 
 end_msg_sessiond:
@@ -2161,16 +2283,20 @@ end_msg_sessiond:
         * the caller because the session daemon socket management is done
         * elsewhere. Returning a negative code or 0 will shutdown the consumer.
         */
-       ret = consumer_send_status_msg(sock, ret_code);
-       if (ret < 0) {
-               goto error_fatal;
+       {
+               int ret_send_status;
+
+               ret_send_status = consumer_send_status_msg(sock, ret_code);
+               if (ret_send_status < 0) {
+                       goto error_fatal;
+               }
        }
-       ret = 1;
+
+       ret_func = 1;
        goto end;
 
 end_channel_error:
        if (channel) {
-               pthread_mutex_unlock(&channel->lock);
                /*
                 * Free channel here since no one has a reference to it. We don't
                 * free after that because a stream can store this pointer.
@@ -2178,57 +2304,37 @@ end_channel_error:
                destroy_channel(channel);
        }
        /* We have to send a status channel message indicating an error. */
-       ret = consumer_send_status_channel(sock, NULL);
-       if (ret < 0) {
-               /* Stop everything if session daemon can not be notified. */
-               goto error_fatal;
+       {
+               int ret_send_status;
+
+               ret_send_status = consumer_send_status_channel(sock, NULL);
+               if (ret_send_status < 0) {
+                       /* Stop everything if session daemon can not be notified. */
+                       goto error_fatal;
+               }
        }
-       ret = 1;
+
+       ret_func = 1;
        goto end;
 
 error_fatal:
        /* This will issue a consumer stop. */
-       ret = -1;
+       ret_func = -1;
        goto end;
 
 end:
        rcu_read_unlock();
        health_code_update();
-       return ret;
-}
-
-/*
- * Wrapper over the mmap() read offset from ust-ctl library. Since this can be
- * compiled out, we isolate it in this library.
- */
-int lttng_ustctl_get_mmap_read_offset(struct lttng_consumer_stream *stream,
-               unsigned long *off)
-{
-       assert(stream);
-       assert(stream->ustream);
-
-       return ustctl_get_mmap_read_offset(stream->ustream, off);
+       return ret_func;
 }
 
-/*
- * Wrapper over the mmap() read offset from ust-ctl library. Since this can be
- * compiled out, we isolate it in this library.
- */
-void *lttng_ustctl_get_mmap_base(struct lttng_consumer_stream *stream)
-{
-       assert(stream);
-       assert(stream->ustream);
-
-       return ustctl_get_mmap_base(stream->ustream);
-}
-
-void lttng_ustctl_flush_buffer(struct lttng_consumer_stream *stream,
+int lttng_ust_flush_buffer(struct lttng_consumer_stream *stream,
                int producer_active)
 {
-       assert(stream);
-       assert(stream->ustream);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
 
-       ustctl_flush_buffer(stream->ustream, producer_active);
+       return lttng_ust_ctl_flush_buffer(stream->ustream, producer_active);
 }
 
 /*
@@ -2238,10 +2344,10 @@ void lttng_ustctl_flush_buffer(struct lttng_consumer_stream *stream,
  */
 int lttng_ustconsumer_take_snapshot(struct lttng_consumer_stream *stream)
 {
-       assert(stream);
-       assert(stream->ustream);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
 
-       return ustctl_snapshot(stream->ustream);
+       return lttng_ust_ctl_snapshot(stream->ustream);
 }
 
 /*
@@ -2252,10 +2358,10 @@ int lttng_ustconsumer_take_snapshot(struct lttng_consumer_stream *stream)
 int lttng_ustconsumer_sample_snapshot_positions(
                struct lttng_consumer_stream *stream)
 {
-       assert(stream);
-       assert(stream->ustream);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
 
-       return ustctl_snapshot_sample_positions(stream->ustream);
+       return lttng_ust_ctl_snapshot_sample_positions(stream->ustream);
 }
 
 /*
@@ -2266,11 +2372,11 @@ int lttng_ustconsumer_sample_snapshot_positions(
 int lttng_ustconsumer_get_produced_snapshot(
                struct lttng_consumer_stream *stream, unsigned long *pos)
 {
-       assert(stream);
-       assert(stream->ustream);
-       assert(pos);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
+       LTTNG_ASSERT(pos);
 
-       return ustctl_snapshot_get_produced(stream->ustream, pos);
+       return lttng_ust_ctl_snapshot_get_produced(stream->ustream, pos);
 }
 
 /*
@@ -2281,40 +2387,48 @@ int lttng_ustconsumer_get_produced_snapshot(
 int lttng_ustconsumer_get_consumed_snapshot(
                struct lttng_consumer_stream *stream, unsigned long *pos)
 {
-       assert(stream);
-       assert(stream->ustream);
-       assert(pos);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
+       LTTNG_ASSERT(pos);
 
-       return ustctl_snapshot_get_consumed(stream->ustream, pos);
+       return lttng_ust_ctl_snapshot_get_consumed(stream->ustream, pos);
 }
 
-void lttng_ustconsumer_flush_buffer(struct lttng_consumer_stream *stream,
+int lttng_ustconsumer_flush_buffer(struct lttng_consumer_stream *stream,
                int producer)
 {
-       assert(stream);
-       assert(stream->ustream);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
 
-       ustctl_flush_buffer(stream->ustream, producer);
+       return lttng_ust_ctl_flush_buffer(stream->ustream, producer);
+}
+
+int lttng_ustconsumer_clear_buffer(struct lttng_consumer_stream *stream)
+{
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
+
+       return lttng_ust_ctl_clear_buffer(stream->ustream);
 }
 
 int lttng_ustconsumer_get_current_timestamp(
                struct lttng_consumer_stream *stream, uint64_t *ts)
 {
-       assert(stream);
-       assert(stream->ustream);
-       assert(ts);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
+       LTTNG_ASSERT(ts);
 
-       return ustctl_get_current_timestamp(stream->ustream, ts);
+       return lttng_ust_ctl_get_current_timestamp(stream->ustream, ts);
 }
 
 int lttng_ustconsumer_get_sequence_number(
                struct lttng_consumer_stream *stream, uint64_t *seq)
 {
-       assert(stream);
-       assert(stream->ustream);
-       assert(seq);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
+       LTTNG_ASSERT(seq);
 
-       return ustctl_get_sequence_number(stream->ustream, seq);
+       return lttng_ust_ctl_get_sequence_number(stream->ustream, seq);
 }
 
 /*
@@ -2322,13 +2436,16 @@ int lttng_ustconsumer_get_sequence_number(
  */
 void lttng_ustconsumer_on_stream_hangup(struct lttng_consumer_stream *stream)
 {
-       assert(stream);
-       assert(stream->ustream);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
 
        pthread_mutex_lock(&stream->lock);
        if (!stream->quiescent) {
-               ustctl_flush_buffer(stream->ustream, 0);
-               stream->quiescent = true;
+               if (lttng_ust_ctl_flush_buffer(stream->ustream, 0) < 0) {
+                       ERR("Failed to flush buffer on stream hang-up");
+               } else {
+                       stream->quiescent = true;
+               }
        }
        pthread_mutex_unlock(&stream->lock);
        stream->hangup_flush_done = 1;
@@ -2338,9 +2455,9 @@ void lttng_ustconsumer_del_channel(struct lttng_consumer_channel *chan)
 {
        int i;
 
-       assert(chan);
-       assert(chan->uchan);
-       assert(chan->buffer_credentials.is_set);
+       LTTNG_ASSERT(chan);
+       LTTNG_ASSERT(chan->uchan);
+       LTTNG_ASSERT(chan->buffer_credentials.is_set);
 
        if (chan->switch_timer_enabled == 1) {
                consumer_timer_switch_stop(chan);
@@ -2360,8 +2477,10 @@ void lttng_ustconsumer_del_channel(struct lttng_consumer_channel *chan)
                                ERR("Cannot get stream shm path");
                        }
                        ret = run_as_unlink(shm_path,
-                                       chan->buffer_credentials.value.uid,
-                                       chan->buffer_credentials.value.gid);
+                                       lttng_credentials_get_uid(LTTNG_OPTIONAL_GET_PTR(
+                                                       chan->buffer_credentials)),
+                                       lttng_credentials_get_gid(LTTNG_OPTIONAL_GET_PTR(
+                                                       chan->buffer_credentials)));
                        if (ret) {
                                PERROR("unlink %s", shm_path);
                        }
@@ -2371,17 +2490,19 @@ void lttng_ustconsumer_del_channel(struct lttng_consumer_channel *chan)
 
 void lttng_ustconsumer_free_channel(struct lttng_consumer_channel *chan)
 {
-       assert(chan);
-       assert(chan->uchan);
-       assert(chan->buffer_credentials.is_set);
+       LTTNG_ASSERT(chan);
+       LTTNG_ASSERT(chan->uchan);
+       LTTNG_ASSERT(chan->buffer_credentials.is_set);
 
        consumer_metadata_cache_destroy(chan);
-       ustctl_destroy_channel(chan->uchan);
+       lttng_ust_ctl_destroy_channel(chan->uchan);
        /* Try to rmdir all directories under shm_path root. */
        if (chan->root_shm_path[0]) {
                (void) run_as_rmdir_recursive(chan->root_shm_path,
-                               chan->buffer_credentials.value.uid,
-                               chan->buffer_credentials.value.gid,
+                               lttng_credentials_get_uid(LTTNG_OPTIONAL_GET_PTR(
+                                               chan->buffer_credentials)),
+                               lttng_credentials_get_gid(LTTNG_OPTIONAL_GET_PTR(
+                                               chan->buffer_credentials)),
                                LTTNG_DIRECTORY_HANDLE_SKIP_NON_EMPTY_FLAG);
        }
        free(chan->stream_fds);
@@ -2389,145 +2510,36 @@ void lttng_ustconsumer_free_channel(struct lttng_consumer_channel *chan)
 
 void lttng_ustconsumer_del_stream(struct lttng_consumer_stream *stream)
 {
-       assert(stream);
-       assert(stream->ustream);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
 
        if (stream->chan->switch_timer_enabled == 1) {
                consumer_timer_switch_stop(stream->chan);
        }
-       ustctl_destroy_stream(stream->ustream);
+       lttng_ust_ctl_destroy_stream(stream->ustream);
 }
 
 int lttng_ustconsumer_get_wakeup_fd(struct lttng_consumer_stream *stream)
 {
-       assert(stream);
-       assert(stream->ustream);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
 
-       return ustctl_stream_get_wakeup_fd(stream->ustream);
+       return lttng_ust_ctl_stream_get_wakeup_fd(stream->ustream);
 }
 
 int lttng_ustconsumer_close_wakeup_fd(struct lttng_consumer_stream *stream)
 {
-       assert(stream);
-       assert(stream->ustream);
-
-       return ustctl_stream_close_wakeup_fd(stream->ustream);
-}
-
-/*
- * Populate index values of a UST stream. Values are set in big endian order.
- *
- * Return 0 on success or else a negative value.
- */
-static int get_index_values(struct ctf_packet_index *index,
-               struct ustctl_consumer_stream *ustream)
-{
-       int ret;
-       uint64_t packet_size, content_size, timestamp_begin, timestamp_end,
-                       events_discarded, stream_id, stream_instance_id,
-                       packet_seq_num;
-
-       ret = ustctl_get_timestamp_begin(ustream, &timestamp_begin);
-       if (ret < 0) {
-               PERROR("ustctl_get_timestamp_begin");
-               goto error;
-       }
-
-       ret = ustctl_get_timestamp_end(ustream, &timestamp_end);
-       if (ret < 0) {
-               PERROR("ustctl_get_timestamp_end");
-               goto error;
-       }
-
-       ret = ustctl_get_events_discarded(ustream, &events_discarded);
-       if (ret < 0) {
-               PERROR("ustctl_get_events_discarded");
-               goto error;
-       }
-
-       ret = ustctl_get_content_size(ustream, &content_size);
-       if (ret < 0) {
-               PERROR("ustctl_get_content_size");
-               goto error;
-       }
-
-       ret = ustctl_get_packet_size(ustream, &packet_size);
-       if (ret < 0) {
-               PERROR("ustctl_get_packet_size");
-               goto error;
-       }
-
-       ret = ustctl_get_stream_id(ustream, &stream_id);
-       if (ret < 0) {
-               PERROR("ustctl_get_stream_id");
-               goto error;
-       }
-
-       ret = ustctl_get_instance_id(ustream, &stream_instance_id);
-       if (ret < 0) {
-               PERROR("ustctl_get_instance_id");
-               goto error;
-       }
-
-       ret = ustctl_get_sequence_number(ustream, &packet_seq_num);
-       if (ret < 0) {
-               PERROR("ustctl_get_sequence_number");
-               goto error;
-       }
-
-       *index = (typeof(*index)) {
-               .offset = index->offset,
-               .packet_size = htobe64(packet_size),
-               .content_size = htobe64(content_size),
-               .timestamp_begin = htobe64(timestamp_begin),
-               .timestamp_end = htobe64(timestamp_end),
-               .events_discarded = htobe64(events_discarded),
-               .stream_id = htobe64(stream_id),
-               .stream_instance_id = htobe64(stream_instance_id),
-               .packet_seq_num = htobe64(packet_seq_num),
-       };
-
-error:
-       return ret;
-}
-
-static
-void metadata_stream_reset_cache(struct lttng_consumer_stream *stream,
-               struct consumer_metadata_cache *cache)
-{
-       DBG("Metadata stream update to version %" PRIu64,
-                       cache->version);
-       stream->ust_metadata_pushed = 0;
-       stream->metadata_version = cache->version;
-       stream->reset_metadata_flag = 1;
-}
-
-/*
- * Check if the version of the metadata stream and metadata cache match.
- * If the cache got updated, reset the metadata stream.
- * The stream lock and metadata cache lock MUST be held.
- * Return 0 on success, a negative value on error.
- */
-static
-int metadata_stream_check_version(struct lttng_consumer_stream *stream)
-{
-       int ret = 0;
-       struct consumer_metadata_cache *cache = stream->chan->metadata_cache;
-
-       if (cache->version == stream->metadata_version) {
-               goto end;
-       }
-       metadata_stream_reset_cache(stream, cache);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
 
-end:
-       return ret;
+       return lttng_ust_ctl_stream_close_wakeup_fd(stream->ustream);
 }
 
 /*
  * Write up to one packet from the metadata cache to the channel.
  *
- * Returns the number of bytes pushed in the cache, or a negative value
- * on error.
+ * Returns the number of bytes pushed from the cache into the ring buffer, or a
+ * negative value on error.
  */
 static
 int commit_one_metadata_packet(struct lttng_consumer_stream *stream)
@@ -2536,29 +2548,56 @@ int commit_one_metadata_packet(struct lttng_consumer_stream *stream)
        int ret;
 
        pthread_mutex_lock(&stream->chan->metadata_cache->lock);
-       ret = metadata_stream_check_version(stream);
-       if (ret < 0) {
-               goto end;
-       }
-       if (stream->chan->metadata_cache->max_offset
-                       == stream->ust_metadata_pushed) {
-               ret = 0;
-               goto end;
+       if (stream->chan->metadata_cache->contents.size ==
+                       stream->ust_metadata_pushed) {
+               /*
+                * In the context of a user space metadata channel, a
+                * change in version can be detected in two ways:
+                *   1) During the pre-consume of the `read_subbuffer` loop,
+                *   2) When populating the metadata ring buffer (i.e. here).
+                *
+                * This function is invoked when there is no metadata
+                * available in the ring-buffer. If all data was consumed
+                * up to the size of the metadata cache, there is no metadata
+                * to insert in the ring-buffer.
+                *
+                * However, the metadata version could still have changed (a
+                * regeneration without any new data will yield the same cache
+                * size).
+                *
+                * The cache's version is checked for a version change and the
+                * consumed position is reset if one occurred.
+                *
+                * This check is only necessary for the user space domain as
+                * it has to manage the cache explicitly. If this reset was not
+                * performed, no metadata would be consumed (and no reset would
+                * occur as part of the pre-consume) until the metadata size
+                * exceeded the cache size.
+                */
+               if (stream->metadata_version !=
+                               stream->chan->metadata_cache->version) {
+                       metadata_stream_reset_cache_consumed_position(stream);
+                       consumer_stream_metadata_set_version(stream,
+                                       stream->chan->metadata_cache->version);
+               } else {
+                       ret = 0;
+                       goto end;
+               }
        }
 
-       write_len = ustctl_write_one_packet_to_channel(stream->chan->uchan,
-                       &stream->chan->metadata_cache->data[stream->ust_metadata_pushed],
-                       stream->chan->metadata_cache->max_offset
-                       - stream->ust_metadata_pushed);
-       assert(write_len != 0);
+       write_len = lttng_ust_ctl_write_one_packet_to_channel(stream->chan->uchan,
+                       &stream->chan->metadata_cache->contents.data[stream->ust_metadata_pushed],
+                       stream->chan->metadata_cache->contents.size -
+                                       stream->ust_metadata_pushed);
+       LTTNG_ASSERT(write_len != 0);
        if (write_len < 0) {
                ERR("Writing one metadata packet");
-               ret = -1;
+               ret = write_len;
                goto end;
        }
        stream->ust_metadata_pushed += write_len;
 
-       assert(stream->chan->metadata_cache->max_offset >=
+       LTTNG_ASSERT(stream->chan->metadata_cache->contents.size >=
                        stream->ust_metadata_pushed);
        ret = write_len;
 
@@ -2567,8 +2606,12 @@ int commit_one_metadata_packet(struct lttng_consumer_stream *stream)
         * a metadata packet. Since the subbuffer is fully filled (with padding,
         * if needed), the stream is "quiescent" after this commit.
         */
-       ustctl_flush_buffer(stream->ustream, 1);
-       stream->quiescent = true;
+       if (lttng_ust_ctl_flush_buffer(stream->ustream, 1)) {
+               ERR("Failed to flush buffer while commiting one metadata packet");
+               ret = -EIO;
+       } else {
+               stream->quiescent = true;
+       }
 end:
        pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
        return ret;
@@ -2583,57 +2626,70 @@ end:
  * interacting with sessiond, else we cause a deadlock with live
  * awaiting on metadata to be pushed out.
  *
- * Return 0 if new metadatda is available, EAGAIN if the metadata stream
- * is empty or a negative value on error.
+ * The RCU read side lock must be held by the caller.
  */
-int lttng_ustconsumer_sync_metadata(struct lttng_consumer_local_data *ctx,
-               struct lttng_consumer_stream *metadata)
+enum sync_metadata_status lttng_ustconsumer_sync_metadata(
+               struct lttng_consumer_local_data *ctx,
+               struct lttng_consumer_stream *metadata_stream)
 {
        int ret;
-       int retry = 0;
+       enum sync_metadata_status status;
+       struct lttng_consumer_channel *metadata_channel;
 
-       assert(ctx);
-       assert(metadata);
+       LTTNG_ASSERT(ctx);
+       LTTNG_ASSERT(metadata_stream);
 
-       pthread_mutex_unlock(&metadata->lock);
+       metadata_channel = metadata_stream->chan;
+       pthread_mutex_unlock(&metadata_stream->lock);
        /*
         * Request metadata from the sessiond, but don't wait for the flush
         * because we locked the metadata thread.
         */
-       ret = lttng_ustconsumer_request_metadata(ctx, metadata->chan, 0, 0);
-       pthread_mutex_lock(&metadata->lock);
+       ret = lttng_ustconsumer_request_metadata(ctx, metadata_channel, 0, 0);
+       pthread_mutex_lock(&metadata_stream->lock);
        if (ret < 0) {
+               status = SYNC_METADATA_STATUS_ERROR;
                goto end;
        }
 
-       ret = commit_one_metadata_packet(metadata);
-       if (ret <= 0) {
+       /*
+        * The metadata stream and channel can be deleted while the
+        * metadata stream lock was released. The streamed is checked
+        * for deletion before we use it further.
+        *
+        * Note that it is safe to access a logically-deleted stream since its
+        * existence is still guaranteed by the RCU read side lock. However,
+        * it should no longer be used. The close/deletion of the metadata
+        * channel and stream already guarantees that all metadata has been
+        * consumed. Therefore, there is nothing left to do in this function.
+        */
+       if (consumer_stream_is_deleted(metadata_stream)) {
+               DBG("Metadata stream %" PRIu64 " was deleted during the metadata synchronization",
+                               metadata_stream->key);
+               status = SYNC_METADATA_STATUS_NO_DATA;
                goto end;
-       } else if (ret > 0) {
-               retry = 1;
        }
 
-       ret = ustctl_snapshot(metadata->ustream);
+       ret = commit_one_metadata_packet(metadata_stream);
        if (ret < 0) {
-               if (errno != EAGAIN) {
-                       ERR("Sync metadata, taking UST snapshot");
-                       goto end;
-               }
-               DBG("No new metadata when syncing them.");
-               /* No new metadata, exit. */
-               ret = ENODATA;
+               status = SYNC_METADATA_STATUS_ERROR;
+               goto end;
+       } else if (ret > 0) {
+               status = SYNC_METADATA_STATUS_NEW_DATA;
+       } else /* ret == 0 */ {
+               status = SYNC_METADATA_STATUS_NO_DATA;
                goto end;
        }
 
-       /*
-        * After this flush, we still need to extract metadata.
-        */
-       if (retry) {
-               ret = EAGAIN;
+       ret = lttng_ust_ctl_snapshot(metadata_stream->ustream);
+       if (ret < 0) {
+               ERR("Failed to take a snapshot of the metadata ring-buffer positions, ret = %d", ret);
+               status = SYNC_METADATA_STATUS_ERROR;
+               goto end;
        }
 
 end:
-       return ret;
+       return status;
 }
 
 /*
@@ -2643,10 +2699,10 @@ static int notify_if_more_data(struct lttng_consumer_stream *stream,
                struct lttng_consumer_local_data *ctx)
 {
        int ret;
-       struct ustctl_consumer_stream *ustream;
+       struct lttng_ust_ctl_consumer_stream *ustream;
 
-       assert(stream);
-       assert(ctx);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(ctx);
 
        ustream = stream->ustream;
 
@@ -2655,7 +2711,7 @@ static int notify_if_more_data(struct lttng_consumer_stream *stream,
         * before reading the stream wait_fd.
         */
        /* Get the next subbuffer */
-       ret = ustctl_get_next_subbuf(ustream);
+       ret = lttng_ust_ctl_get_next_subbuf(ustream);
        if (ret) {
                /* No more data found, flag the stream. */
                stream->has_data = 0;
@@ -2663,8 +2719,8 @@ static int notify_if_more_data(struct lttng_consumer_stream *stream,
                goto end;
        }
 
-       ret = ustctl_put_subbuf(ustream);
-       assert(!ret);
+       ret = lttng_ust_ctl_put_subbuf(ustream);
+       LTTNG_ASSERT(!ret);
 
        /* This stream still has data. Flag it and wake up the data thread. */
        stream->has_data = 1;
@@ -2687,276 +2743,361 @@ end:
        return ret;
 }
 
-static
-int update_stream_stats(struct lttng_consumer_stream *stream)
+static int consumer_stream_ust_on_wake_up(struct lttng_consumer_stream *stream)
 {
-       int ret;
-       uint64_t seq, discarded;
+       int ret = 0;
 
-       ret = ustctl_get_sequence_number(stream->ustream, &seq);
-       if (ret < 0) {
-               PERROR("ustctl_get_sequence_number");
-               goto end;
-       }
        /*
-        * Start the sequence when we extract the first packet in case we don't
-        * start at 0 (for example if a consumer is not connected to the
-        * session immediately after the beginning).
+        * We can consume the 1 byte written into the wait_fd by
+        * UST. Don't trigger error if we cannot read this one byte
+        * (read returns 0), or if the error is EAGAIN or EWOULDBLOCK.
+        *
+        * This is only done when the stream is monitored by a thread,
+        * before the flush is done after a hangup and if the stream
+        * is not flagged with data since there might be nothing to
+        * consume in the wait fd but still have data available
+        * flagged by the consumer wake up pipe.
         */
-       if (stream->last_sequence_number == -1ULL) {
-               stream->last_sequence_number = seq;
-       } else if (seq > stream->last_sequence_number) {
-               stream->chan->lost_packets += seq -
-                               stream->last_sequence_number - 1;
-       } else {
-               /* seq <= last_sequence_number */
-               ERR("Sequence number inconsistent : prev = %" PRIu64
-                               ", current = %" PRIu64,
-                               stream->last_sequence_number, seq);
-               ret = -1;
-               goto end;
+       if (stream->monitor && !stream->hangup_flush_done && !stream->has_data) {
+               char dummy;
+               ssize_t readlen;
+
+               readlen = lttng_read(stream->wait_fd, &dummy, 1);
+               if (readlen < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
+                       ret = readlen;
+               }
        }
-       stream->last_sequence_number = seq;
 
-       ret = ustctl_get_events_discarded(stream->ustream, &discarded);
-       if (ret < 0) {
-               PERROR("kernctl_get_events_discarded");
+       return ret;
+}
+
+static int extract_common_subbuffer_info(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuf)
+{
+       int ret;
+
+       ret = lttng_ust_ctl_get_subbuf_size(
+                       stream->ustream, &subbuf->info.data.subbuf_size);
+       if (ret) {
                goto end;
        }
-       if (discarded < stream->last_discarded_events) {
-               /*
-                * Overflow has occurred. We assume only one wrap-around
-                * has occurred.
-                */
-               stream->chan->discarded_events +=
-                               (1ULL << (CAA_BITS_PER_LONG - 1)) -
-                               stream->last_discarded_events + discarded;
-       } else {
-               stream->chan->discarded_events += discarded -
-                               stream->last_discarded_events;
+
+       ret = lttng_ust_ctl_get_padded_subbuf_size(
+                       stream->ustream, &subbuf->info.data.padded_subbuf_size);
+       if (ret) {
+               goto end;
        }
-       stream->last_discarded_events = discarded;
-       ret = 0;
 
 end:
        return ret;
 }
 
-/*
- * Read subbuffer from the given stream.
- *
- * Stream and channel locks MUST be acquired by the caller.
- *
- * Return 0 on success else a negative value.
- */
-int lttng_ustconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
-               struct lttng_consumer_local_data *ctx)
+static int extract_metadata_subbuffer_info(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuf)
 {
-       unsigned long len, subbuf_size, padding;
-       int err, write_index = 1, rotation_ret;
-       long ret = 0;
-       struct ustctl_consumer_stream *ustream;
-       struct ctf_packet_index index;
+       int ret;
 
-       assert(stream);
-       assert(stream->ustream);
-       assert(ctx);
+       ret = extract_common_subbuffer_info(stream, subbuf);
+       if (ret) {
+               goto end;
+       }
 
-       DBG("In UST read_subbuffer (wait_fd: %d, name: %s)", stream->wait_fd,
-                       stream->name);
+       subbuf->info.metadata.version = stream->metadata_version;
 
-       /* Ease our life for what's next. */
-       ustream = stream->ustream;
+end:
+       return ret;
+}
 
-       /*
-        * We can consume the 1 byte written into the wait_fd by UST. Don't trigger
-        * error if we cannot read this one byte (read returns 0), or if the error
-        * is EAGAIN or EWOULDBLOCK.
-        *
-        * This is only done when the stream is monitored by a thread, before the
-        * flush is done after a hangup and if the stream is not flagged with data
-        * since there might be nothing to consume in the wait fd but still have
-        * data available flagged by the consumer wake up pipe.
-        */
-       if (stream->monitor && !stream->hangup_flush_done && !stream->has_data) {
-               char dummy;
-               ssize_t readlen;
+static int extract_data_subbuffer_info(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuf)
+{
+       int ret;
 
-               readlen = lttng_read(stream->wait_fd, &dummy, 1);
-               if (readlen < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
-                       ret = readlen;
-                       goto error;
-               }
+       ret = extract_common_subbuffer_info(stream, subbuf);
+       if (ret) {
+               goto end;
        }
 
-       /*
-        * If the stream was flagged to be ready for rotation before we extract the
-        * next packet, rotate it now.
-        */
-       if (stream->rotate_ready) {
-               DBG("Rotate stream before extracting data");
-               rotation_ret = lttng_consumer_rotate_stream(ctx, stream);
-               if (rotation_ret < 0) {
-                       ERR("Stream rotation error");
-                       ret = -1;
-                       goto error;
-               }
+       ret = lttng_ust_ctl_get_packet_size(
+                       stream->ustream, &subbuf->info.data.packet_size);
+       if (ret < 0) {
+               PERROR("Failed to get sub-buffer packet size");
+               goto end;
        }
 
-retry:
-       /* Get the next subbuffer */
-       err = ustctl_get_next_subbuf(ustream);
-       if (err != 0) {
-               /*
-                * Populate metadata info if the existing info has
-                * already been read.
-                */
-               if (stream->metadata_flag) {
-                       ret = commit_one_metadata_packet(stream);
-                       if (ret <= 0) {
-                               goto error;
-                       }
-                       goto retry;
-               }
+       ret = lttng_ust_ctl_get_content_size(
+                       stream->ustream, &subbuf->info.data.content_size);
+       if (ret < 0) {
+               PERROR("Failed to get sub-buffer content size");
+               goto end;
+       }
 
-               ret = err;      /* ustctl_get_next_subbuf returns negative, caller expect positive. */
-               /*
-                * This is a debug message even for single-threaded consumer,
-                * because poll() have more relaxed criterions than get subbuf,
-                * so get_subbuf may fail for short race windows where poll()
-                * would issue wakeups.
-                */
-               DBG("Reserving sub buffer failed (everything is normal, "
-                               "it is due to concurrency) [ret: %d]", err);
-               goto error;
+       ret = lttng_ust_ctl_get_timestamp_begin(
+                       stream->ustream, &subbuf->info.data.timestamp_begin);
+       if (ret < 0) {
+               PERROR("Failed to get sub-buffer begin timestamp");
+               goto end;
        }
-       assert(stream->chan->output == CONSUMER_CHANNEL_MMAP);
 
-       if (!stream->metadata_flag) {
-               index.offset = htobe64(stream->out_fd_offset);
-               ret = get_index_values(&index, ustream);
-               if (ret < 0) {
-                       err = ustctl_put_subbuf(ustream);
-                       assert(err == 0);
-                       goto error;
+       ret = lttng_ust_ctl_get_timestamp_end(
+                       stream->ustream, &subbuf->info.data.timestamp_end);
+       if (ret < 0) {
+               PERROR("Failed to get sub-buffer end timestamp");
+               goto end;
+       }
+
+       ret = lttng_ust_ctl_get_events_discarded(
+                       stream->ustream, &subbuf->info.data.events_discarded);
+       if (ret) {
+               PERROR("Failed to get sub-buffer events discarded count");
+               goto end;
+       }
+
+       ret = lttng_ust_ctl_get_sequence_number(stream->ustream,
+                       &subbuf->info.data.sequence_number.value);
+       if (ret) {
+               /* May not be supported by older LTTng-modules. */
+               if (ret != -ENOTTY) {
+                       PERROR("Failed to get sub-buffer sequence number");
+                       goto end;
                }
+       } else {
+               subbuf->info.data.sequence_number.is_set = true;
+       }
 
-               /* Update the stream's sequence and discarded events count. */
-               ret = update_stream_stats(stream);
-               if (ret < 0) {
-                       PERROR("kernctl_get_events_discarded");
-                       err = ustctl_put_subbuf(ustream);
-                       assert(err == 0);
-                       goto error;
+       ret = lttng_ust_ctl_get_stream_id(
+                       stream->ustream, &subbuf->info.data.stream_id);
+       if (ret < 0) {
+               PERROR("Failed to get stream id");
+               goto end;
+       }
+
+       ret = lttng_ust_ctl_get_instance_id(stream->ustream,
+                       &subbuf->info.data.stream_instance_id.value);
+       if (ret) {
+               /* May not be supported by older LTTng-modules. */
+               if (ret != -ENOTTY) {
+                       PERROR("Failed to get stream instance id");
+                       goto end;
                }
        } else {
-               write_index = 0;
+               subbuf->info.data.stream_instance_id.is_set = true;
        }
+end:
+       return ret;
+}
 
-       /* Get the full padded subbuffer size */
-       err = ustctl_get_padded_subbuf_size(ustream, &len);
-       assert(err == 0);
+static int get_next_subbuffer_common(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuffer)
+{
+       int ret;
+       const char *addr;
+
+       ret = stream->read_subbuffer_ops.extract_subbuffer_info(
+                       stream, subbuffer);
+       if (ret) {
+               goto end;
+       }
 
-       /* Get subbuffer data size (without padding) */
-       err = ustctl_get_subbuf_size(ustream, &subbuf_size);
-       assert(err == 0);
+       ret = get_current_subbuf_addr(stream, &addr);
+       if (ret) {
+               goto end;
+       }
 
-       /* Make sure we don't get a subbuffer size bigger than the padded */
-       assert(len >= subbuf_size);
+       subbuffer->buffer.buffer = lttng_buffer_view_init(
+                       addr, 0, subbuffer->info.data.padded_subbuf_size);
+       LTTNG_ASSERT(subbuffer->buffer.buffer.data != NULL);
+end:
+       return ret;
+}
 
-       padding = len - subbuf_size;
+static enum get_next_subbuffer_status get_next_subbuffer(
+               struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuffer)
+{
+       int ret;
+       enum get_next_subbuffer_status status;
 
-       /* write the subbuffer to the tracefile */
-       ret = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, subbuf_size, padding, &index);
-       /*
-        * The mmap operation should write subbuf_size amount of data when network
-        * streaming or the full padding (len) size when we are _not_ streaming.
-        */
-       if ((ret != subbuf_size && stream->net_seq_idx != (uint64_t) -1ULL) ||
-                       (ret != len && stream->net_seq_idx == (uint64_t) -1ULL)) {
+       ret = lttng_ust_ctl_get_next_subbuf(stream->ustream);
+       switch (ret) {
+       case 0:
+               status = GET_NEXT_SUBBUFFER_STATUS_OK;
+               break;
+       case -ENODATA:
+               case -EAGAIN:
                /*
-                * Display the error but continue processing to try to release the
-                * subbuffer. This is a DBG statement since any unexpected kill or
-                * signal, the application gets unregistered, relayd gets closed or
-                * anything that affects the buffer lifetime will trigger this error.
-                * So, for the sake of the user, don't print this error since it can
-                * happen and it is OK with the code flow.
+                * The caller only expects -ENODATA when there is no data to
+                * read, but the kernel tracer returns -EAGAIN when there is
+                * currently no data for a non-finalized stream, and -ENODATA
+                * when there is no data for a finalized stream. Those can be
+                * combined into a -ENODATA return value.
                 */
-               DBG("Error writing to tracefile "
-                               "(ret: %ld != len: %lu != subbuf_size: %lu)",
-                               ret, len, subbuf_size);
-               write_index = 0;
+               status = GET_NEXT_SUBBUFFER_STATUS_NO_DATA;
+               goto end;
+       default:
+               status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
+               goto end;
        }
-       err = ustctl_put_next_subbuf(ustream);
-       assert(err == 0);
 
-       /*
-        * This will consumer the byte on the wait_fd if and only if there is not
-        * next subbuffer to be acquired.
-        */
-       if (!stream->metadata_flag) {
-               ret = notify_if_more_data(stream, ctx);
-               if (ret < 0) {
-                       goto error;
-               }
+       ret = get_next_subbuffer_common(stream, subbuffer);
+       if (ret) {
+               status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
+               goto end;
        }
+end:
+       return status;
+}
 
-       /* Write index if needed. */
-       if (!write_index) {
-               goto rotate;
-       }
+static enum get_next_subbuffer_status get_next_subbuffer_metadata(
+               struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuffer)
+{
+       int ret;
+       bool cache_empty;
+       bool got_subbuffer;
+       bool coherent;
+       bool buffer_empty;
+       unsigned long consumed_pos, produced_pos;
+       enum get_next_subbuffer_status status;
+
+       do {
+               ret = lttng_ust_ctl_get_next_subbuf(stream->ustream);
+               if (ret == 0) {
+                       got_subbuffer = true;
+               } else {
+                       got_subbuffer = false;
+                       if (ret != -EAGAIN) {
+                               /* Fatal error. */
+                               status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
+                               goto end;
+                       }
+               }
 
-       if (stream->chan->live_timer_interval && !stream->metadata_flag) {
                /*
-                * In live, block until all the metadata is sent.
+                * Determine if the cache is empty and ensure that a sub-buffer
+                * is made available if the cache is not empty.
                 */
-               pthread_mutex_lock(&stream->metadata_timer_lock);
-               assert(!stream->missed_metadata_flush);
-               stream->waiting_on_metadata = true;
-               pthread_mutex_unlock(&stream->metadata_timer_lock);
-
-               err = consumer_stream_sync_metadata(ctx, stream->session_id);
-
-               pthread_mutex_lock(&stream->metadata_timer_lock);
-               stream->waiting_on_metadata = false;
-               if (stream->missed_metadata_flush) {
-                       stream->missed_metadata_flush = false;
-                       pthread_mutex_unlock(&stream->metadata_timer_lock);
-                       (void) consumer_flush_ust_index(stream);
+               if (!got_subbuffer) {
+                       ret = commit_one_metadata_packet(stream);
+                       if (ret < 0 && ret != -ENOBUFS) {
+                               status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
+                               goto end;
+                       } else if (ret == 0) {
+                               /* Not an error, the cache is empty. */
+                               cache_empty = true;
+                               status = GET_NEXT_SUBBUFFER_STATUS_NO_DATA;
+                               goto end;
+                       } else {
+                               cache_empty = false;
+                       }
                } else {
-                       pthread_mutex_unlock(&stream->metadata_timer_lock);
+                       pthread_mutex_lock(&stream->chan->metadata_cache->lock);
+                       cache_empty = stream->chan->metadata_cache->contents.size ==
+                                       stream->ust_metadata_pushed;
+                       pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
                }
+       } while (!got_subbuffer);
 
-               if (err < 0) {
-                       goto error;
-               }
+       /* Populate sub-buffer infos and view. */
+       ret = get_next_subbuffer_common(stream, subbuffer);
+       if (ret) {
+               status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
+               goto end;
        }
 
-       assert(!stream->metadata_flag);
-       err = consumer_stream_write_index(stream, &index);
-       if (err < 0) {
-               goto error;
+       ret = lttng_ustconsumer_sample_snapshot_positions(stream);
+       if (ret < 0) {
+               /*
+                * -EAGAIN is not expected since we got a sub-buffer and haven't
+                * pushed the consumption position yet (on put_next).
+                */
+               PERROR("Failed to take a snapshot of metadata buffer positions");
+               status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
+               goto end;
+       }
+
+       ret = lttng_ustconsumer_get_consumed_snapshot(stream, &consumed_pos);
+       if (ret) {
+               PERROR("Failed to get metadata consumed position");
+               status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
+               goto end;
        }
 
-rotate:
+       ret = lttng_ustconsumer_get_produced_snapshot(stream, &produced_pos);
+       if (ret) {
+               PERROR("Failed to get metadata produced position");
+               status = GET_NEXT_SUBBUFFER_STATUS_ERROR;
+               goto end;
+       }
+
+       /* Last sub-buffer of the ring buffer ? */
+       buffer_empty = (consumed_pos + stream->max_sb_size) == produced_pos;
+
        /*
-        * After extracting the packet, we check if the stream is now ready to be
-        * rotated and perform the action immediately.
+        * The sessiond registry lock ensures that coherent units of metadata
+        * are pushed to the consumer daemon at once. Hence, if a sub-buffer is
+        * acquired, the cache is empty, and it is the only available sub-buffer
+        * available, it is safe to assume that it is "coherent".
         */
-       rotation_ret = lttng_consumer_stream_is_rotate_ready(stream);
-       if (rotation_ret == 1) {
-               rotation_ret = lttng_consumer_rotate_stream(ctx, stream);
-               if (rotation_ret < 0) {
-                       ERR("Stream rotation error");
-                       ret = -1;
-                       goto error;
+       coherent = got_subbuffer && cache_empty && buffer_empty;
+
+       LTTNG_OPTIONAL_SET(&subbuffer->info.metadata.coherent, coherent);
+       status = GET_NEXT_SUBBUFFER_STATUS_OK;
+end:
+       return status;
+}
+
+static int put_next_subbuffer(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuffer)
+{
+       const int ret = lttng_ust_ctl_put_next_subbuf(stream->ustream);
+
+       LTTNG_ASSERT(ret == 0);
+       return ret;
+}
+
+static int signal_metadata(struct lttng_consumer_stream *stream,
+               struct lttng_consumer_local_data *ctx)
+{
+       ASSERT_LOCKED(stream->metadata_rdv_lock);
+       return pthread_cond_broadcast(&stream->metadata_rdv) ? -errno : 0;
+}
+
+static int lttng_ustconsumer_set_stream_ops(
+               struct lttng_consumer_stream *stream)
+{
+       int ret = 0;
+
+       stream->read_subbuffer_ops.on_wake_up = consumer_stream_ust_on_wake_up;
+       if (stream->metadata_flag) {
+               stream->read_subbuffer_ops.get_next_subbuffer =
+                               get_next_subbuffer_metadata;
+               stream->read_subbuffer_ops.extract_subbuffer_info =
+                               extract_metadata_subbuffer_info;
+               stream->read_subbuffer_ops.reset_metadata =
+                               metadata_stream_reset_cache_consumed_position;
+               if (stream->chan->is_live) {
+                       stream->read_subbuffer_ops.on_sleep = signal_metadata;
+                       ret = consumer_stream_enable_metadata_bucketization(
+                                       stream);
+                       if (ret) {
+                               goto end;
+                       }
+               }
+       } else {
+               stream->read_subbuffer_ops.get_next_subbuffer =
+                               get_next_subbuffer;
+               stream->read_subbuffer_ops.extract_subbuffer_info =
+                               extract_data_subbuffer_info;
+               stream->read_subbuffer_ops.on_sleep = notify_if_more_data;
+               if (stream->chan->is_live) {
+                       stream->read_subbuffer_ops.send_live_beacon =
+                                       consumer_flush_ust_index;
                }
-       } else if (rotation_ret < 0) {
-               ERR("Checking if stream is ready to rotate");
-               ret = -1;
-               goto error;
        }
-error:
+
+       stream->read_subbuffer_ops.put_next_subbuffer = put_next_subbuffer;
+end:
        return ret;
 }
 
@@ -2969,7 +3110,7 @@ int lttng_ustconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
 {
        int ret;
 
-       assert(stream);
+       LTTNG_ASSERT(stream);
 
        /*
         * Don't create anything if this is set for streaming or if there is
@@ -2982,6 +3123,8 @@ int lttng_ustconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
                        goto error;
                }
        }
+
+       lttng_ustconsumer_set_stream_ops(stream);
        ret = 0;
 
 error:
@@ -3000,8 +3143,9 @@ int lttng_ustconsumer_data_pending(struct lttng_consumer_stream *stream)
 {
        int ret;
 
-       assert(stream);
-       assert(stream->ustream);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream->ustream);
+       ASSERT_LOCKED(stream->lock);
 
        DBG("UST consumer checking data pending");
 
@@ -3014,7 +3158,9 @@ int lttng_ustconsumer_data_pending(struct lttng_consumer_stream *stream)
                uint64_t contiguous, pushed;
 
                /* Ease our life a bit. */
-               contiguous = stream->chan->metadata_cache->max_offset;
+               pthread_mutex_lock(&stream->chan->metadata_cache->lock);
+               contiguous = stream->chan->metadata_cache->contents.size;
+               pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
                pushed = stream->ust_metadata_pushed;
 
                /*
@@ -3029,21 +3175,21 @@ int lttng_ustconsumer_data_pending(struct lttng_consumer_stream *stream)
                 */
                DBG("UST consumer metadata pending check: contiguous %" PRIu64 " vs pushed %" PRIu64,
                                contiguous, pushed);
-               assert(((int64_t) (contiguous - pushed)) >= 0);
+               LTTNG_ASSERT(((int64_t) (contiguous - pushed)) >= 0);
                if ((contiguous != pushed) ||
                                (((int64_t) contiguous - pushed) > 0 || contiguous == 0)) {
                        ret = 1;        /* Data is pending */
                        goto end;
                }
        } else {
-               ret = ustctl_get_next_subbuf(stream->ustream);
+               ret = lttng_ust_ctl_get_next_subbuf(stream->ustream);
                if (ret == 0) {
                        /*
                         * There is still data so let's put back this
                         * subbuffer.
                         */
-                       ret = ustctl_put_subbuf(stream->ustream);
-                       assert(ret == 0);
+                       ret = lttng_ust_ctl_put_subbuf(stream->ustream);
+                       LTTNG_ASSERT(ret == 0);
                        ret = 1;        /* Data is pending */
                        goto end;
                }
@@ -3066,8 +3212,8 @@ void lttng_ustconsumer_close_metadata(struct lttng_consumer_channel *metadata)
 {
        int ret;
 
-       assert(metadata);
-       assert(metadata->type == CONSUMER_CHANNEL_TYPE_METADATA);
+       LTTNG_ASSERT(metadata);
+       LTTNG_ASSERT(metadata->type == CONSUMER_CHANNEL_TYPE_METADATA);
 
        DBG("Closing metadata channel key %" PRIu64, metadata->key);
 
@@ -3109,8 +3255,8 @@ void lttng_ustconsumer_close_all_metadata(struct lttng_ht *metadata_ht)
        struct lttng_ht_iter iter;
        struct lttng_consumer_stream *stream;
 
-       assert(metadata_ht);
-       assert(metadata_ht->ht);
+       LTTNG_ASSERT(metadata_ht);
+       LTTNG_ASSERT(metadata_ht->ht);
 
        DBG("UST consumer closing all metadata streams");
 
@@ -3132,7 +3278,7 @@ void lttng_ustconsumer_close_stream_wakeup(struct lttng_consumer_stream *stream)
 {
        int ret;
 
-       ret = ustctl_stream_close_wakeup_fd(stream->ustream);
+       ret = lttng_ust_ctl_stream_close_wakeup_fd(stream->ustream);
        if (ret < 0) {
                ERR("Unable to close wakeup fd");
        }
@@ -3157,13 +3303,13 @@ int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
        uint64_t len, key, offset, version;
        int ret;
 
-       assert(channel);
-       assert(channel->metadata_cache);
+       LTTNG_ASSERT(channel);
+       LTTNG_ASSERT(channel->metadata_cache);
 
        memset(&request, 0, sizeof(request));
 
        /* send the metadata request to sessiond */
-       switch (consumer_data.type) {
+       switch (the_consumer_data.type) {
        case LTTNG_CONSUMER64_UST:
                request.bits_per_long = 64;
                break;
@@ -3236,7 +3382,7 @@ int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
        offset = msg.u.push_metadata.target_offset;
        version = msg.u.push_metadata.version;
 
-       assert(key == channel->key);
+       LTTNG_ASSERT(key == channel->key);
        if (len == 0) {
                DBG("No new metadata to receive for key %" PRIu64, key);
        }
@@ -3280,8 +3426,13 @@ end:
 int lttng_ustconsumer_get_stream_id(struct lttng_consumer_stream *stream,
                uint64_t *stream_id)
 {
-       assert(stream);
-       assert(stream_id);
+       LTTNG_ASSERT(stream);
+       LTTNG_ASSERT(stream_id);
 
-       return ustctl_get_stream_id(stream->ustream, stream_id);
+       return lttng_ust_ctl_get_stream_id(stream->ustream, stream_id);
+}
+
+void lttng_ustconsumer_sigbus_handle(void *addr)
+{
+       lttng_ust_ctl_sigbus_handle(addr);
 }
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