SoW-2020-0002: Trace Hit Counters: trigger error reporting integration
[lttng-tools.git] / src / common / kernel-consumer / kernel-consumer.c
index 185d42320731d026e26a167a3809a731ce597b05..b9d843714550c5821d3b091eb7fb6e390a3c6786 100644 (file)
@@ -1,20 +1,10 @@
 /*
- * 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
@@ -29,6 +19,7 @@
 #include <inttypes.h>
 #include <unistd.h>
 #include <sys/stat.h>
+#include <stdint.h>
 
 #include <bin/lttng-consumerd/health-consumerd.h>
 #include <common/common.h>
 #include <common/consumer/consumer-stream.h>
 #include <common/index/index.h>
 #include <common/consumer/consumer-timer.h>
+#include <common/optional.h>
+#include <common/buffer-view.h>
+#include <common/consumer/consumer.h>
+#include <common/consumer/metadata-bucket.h>
 
 #include "kernel-consumer.h"
 
@@ -60,7 +55,11 @@ int lttng_kconsumer_take_snapshot(struct lttng_consumer_stream *stream)
        int infd = stream->wait_fd;
 
        ret = kernctl_snapshot(infd);
-       if (ret != 0) {
+       /*
+        * -EAGAIN is not an error, it just means that there is no data to
+        *  be read.
+        */
+       if (ret != 0 && ret != -EAGAIN) {
                PERROR("Getting sub-buffer snapshot.");
        }
 
@@ -118,33 +117,49 @@ int lttng_kconsumer_get_consumed_snapshot(struct lttng_consumer_stream *stream,
        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 = stream->mmap_base;
+
+       ret = kernctl_get_mmap_read_offset(stream->wait_fd, &mmap_offset);
+       if (ret < 0) {
+               PERROR("Failed to get mmap read offset");
+               goto error;
+       }
+
+       *addr = mmap_base + mmap_offset;
+error:
+       return ret;
+}
+
 /*
  * Take a snapshot of all the stream of a channel
+ * RCU read-side lock must be held across this function to ensure existence of
+ * channel. The channel lock must be held by the caller.
  *
  * Returns 0 on success, < 0 on error
  */
-int lttng_kconsumer_snapshot_channel(uint64_t key, char *path,
-               uint64_t relayd_id, uint64_t nb_packets_per_stream,
+static int lttng_kconsumer_snapshot_channel(
+               struct lttng_consumer_channel *channel,
+               uint64_t key, char *path, uint64_t relayd_id,
+               uint64_t nb_packets_per_stream,
                struct lttng_consumer_local_data *ctx)
 {
        int ret;
-       struct lttng_consumer_channel *channel;
        struct lttng_consumer_stream *stream;
 
        DBG("Kernel consumer snapshot channel %" PRIu64, key);
 
        rcu_read_lock();
 
-       channel = consumer_find_channel(key);
-       if (!channel) {
-               ERR("No channel found for key %" PRIu64, key);
-               ret = -1;
-               goto end;
-       }
-
        /* Splice is not supported yet for channel snapshot. */
        if (channel->output != CONSUMER_CHANNEL_MMAP) {
-               ERR("Unsupported output %d", channel->output);
+               ERR("Unsupported output type for channel \"%s\": mmap output is required to record a snapshot",
+                               channel->name);
                ret = -1;
                goto end;
        }
@@ -159,6 +174,19 @@ int lttng_kconsumer_snapshot_channel(uint64_t key, char *path,
                 */
                pthread_mutex_lock(&stream->lock);
 
+               assert(channel->trace_chunk);
+               if (!lttng_trace_chunk_get(channel->trace_chunk)) {
+                       /*
+                        * Can't happen barring an internal error as the channel
+                        * holds a reference to the trace chunk.
+                        */
+                       ERR("Failed to acquire reference to channel's trace chunk");
+                       ret = -1;
+                       goto end_unlock;
+               }
+               assert(!stream->trace_chunk);
+               stream->trace_chunk = channel->trace_chunk;
+
                /*
                 * Assign the received relayd ID so we can use it for streaming. The streams
                 * are not visible to anyone so this is OK to change it.
@@ -172,20 +200,13 @@ int lttng_kconsumer_snapshot_channel(uint64_t key, char *path,
                                goto end_unlock;
                        }
                } else {
-                       ret = utils_create_stream_file(path, stream->name,
-                                       stream->chan->tracefile_size,
-                                       stream->tracefile_count_current,
-                                       stream->uid, stream->gid, NULL);
+                       ret = consumer_stream_create_output_files(stream,
+                                       false);
                        if (ret < 0) {
-                               ERR("utils_create_stream_file");
                                goto end_unlock;
                        }
-
-                       stream->out_fd = ret;
-                       stream->tracefile_size_current = 0;
-
-                       DBG("Kernel consumer snapshot stream %s/%s (%" PRIu64 ")",
-                                       path, stream->name, stream->key);
+                       DBG("Kernel consumer snapshot stream (%" PRIu64 ")",
+                                       stream->key);
                }
 
                ret = kernctl_buffer_flush_empty(stream->wait_fd);
@@ -223,25 +244,17 @@ int lttng_kconsumer_snapshot_channel(uint64_t key, char *path,
                        goto end_unlock;
                }
 
-               if (stream->max_sb_size == 0) {
-                       ret = kernctl_get_max_subbuf_size(stream->wait_fd,
-                                       &stream->max_sb_size);
-                       if (ret < 0) {
-                               ERR("Getting kernel max_sb_size");
-                               goto end_unlock;
-                       }
-               }
-
                consumed_pos = consumer_get_consume_start_pos(consumed_pos,
                                produced_pos, nb_packets_per_stream,
                                stream->max_sb_size);
 
-               while (consumed_pos < produced_pos) {
+               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("Kernel consumer taking snapshot at pos %lu", consumed_pos);
 
                        ret = kernctl_get_subbuf(stream->wait_fd, &consumed_pos);
@@ -268,8 +281,16 @@ int lttng_kconsumer_snapshot_channel(uint64_t key, char *path,
                                goto error_put_subbuf;
                        }
 
-                       read_len = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, len,
-                                       padded_len - len, NULL);
+                       ret = get_current_subbuf_addr(stream, &subbuf_addr);
+                       if (ret) {
+                               goto error_put_subbuf;
+                       }
+
+                       subbuf_view = lttng_buffer_view_init(
+                                       subbuf_addr, 0, padded_len);
+                       read_len = lttng_consumer_on_read_subbuffer_mmap(
+                                       stream, &subbuf_view,
+                                       padded_len - len);
                        /*
                         * We write the padded len in local tracefiles but the data len
                         * when using a relay. Display the error but continue processing
@@ -308,6 +329,8 @@ int lttng_kconsumer_snapshot_channel(uint64_t key, char *path,
                        close_relayd_stream(stream);
                        stream->net_seq_idx = (uint64_t) -1ULL;
                }
+               lttng_trace_chunk_put(stream->trace_chunk);
+               stream->trace_chunk = NULL;
                pthread_mutex_unlock(&stream->lock);
        }
 
@@ -329,15 +352,18 @@ end:
 
 /*
  * Read the whole metadata available for a snapshot.
+ * RCU read-side lock must be held across this function to ensure existence of
+ * metadata_channel. The channel lock must be held by the caller.
  *
  * Returns 0 on success, < 0 on error
  */
-int lttng_kconsumer_snapshot_metadata(uint64_t key, char *path,
-               uint64_t relayd_id, struct lttng_consumer_local_data *ctx)
+static int lttng_kconsumer_snapshot_metadata(
+               struct lttng_consumer_channel *metadata_channel,
+               uint64_t key, char *path, uint64_t relayd_id,
+               struct lttng_consumer_local_data *ctx)
 {
        int ret, use_relayd = 0;
        ssize_t ret_read;
-       struct lttng_consumer_channel *metadata_channel;
        struct lttng_consumer_stream *metadata_stream;
 
        assert(ctx);
@@ -347,16 +373,13 @@ int lttng_kconsumer_snapshot_metadata(uint64_t key, char *path,
 
        rcu_read_lock();
 
-       metadata_channel = consumer_find_channel(key);
-       if (!metadata_channel) {
-               ERR("Kernel snapshot metadata not found for key %" PRIu64, key);
-               ret = -1;
-               goto error;
-       }
-
        metadata_stream = metadata_channel->metadata_stream;
        assert(metadata_stream);
 
+       pthread_mutex_lock(&metadata_stream->lock);
+       assert(metadata_channel->trace_chunk);
+       assert(metadata_stream->trace_chunk);
+
        /* Flag once that we have a valid relayd for the stream. */
        if (relayd_id != (uint64_t) -1ULL) {
                use_relayd = 1;
@@ -365,28 +388,26 @@ int lttng_kconsumer_snapshot_metadata(uint64_t key, char *path,
        if (use_relayd) {
                ret = consumer_send_relayd_stream(metadata_stream, path);
                if (ret < 0) {
-                       goto error;
+                       goto error_snapshot;
                }
        } else {
-               ret = utils_create_stream_file(path, metadata_stream->name,
-                               metadata_stream->chan->tracefile_size,
-                               metadata_stream->tracefile_count_current,
-                               metadata_stream->uid, metadata_stream->gid, NULL);
+               ret = consumer_stream_create_output_files(metadata_stream,
+                               false);
                if (ret < 0) {
-                       goto error;
+                       goto error_snapshot;
                }
-               metadata_stream->out_fd = ret;
        }
 
        do {
                health_code_update();
 
-               ret_read = lttng_kconsumer_read_subbuffer(metadata_stream, ctx);
+               ret_read = lttng_consumer_read_subbuffer(metadata_stream, ctx, true);
                if (ret_read < 0) {
                        if (ret_read != -EAGAIN) {
                                ERR("Kernel snapshot reading metadata subbuffer (ret: %zd)",
                                                ret_read);
-                               goto error;
+                               ret = ret_read;
+                               goto error_snapshot;
                        }
                        /* ret_read is negative at this point so we will exit the loop. */
                        continue;
@@ -407,15 +428,17 @@ int lttng_kconsumer_snapshot_metadata(uint64_t key, char *path,
                                 */
                        }
                        metadata_stream->out_fd = -1;
+                       lttng_trace_chunk_put(metadata_stream->trace_chunk);
+                       metadata_stream->trace_chunk = NULL;
                }
        }
 
        ret = 0;
-
+error_snapshot:
+       pthread_mutex_unlock(&metadata_stream->lock);
        cds_list_del(&metadata_stream->send_node);
        consumer_stream_destroy(metadata_stream, NULL);
        metadata_channel->metadata_stream = NULL;
-error:
        rcu_read_unlock();
        return ret;
 }
@@ -467,6 +490,7 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
        {
                struct lttng_consumer_channel *new_channel;
                int ret_recv;
+               const uint64_t chunk_id = msg.u.channel.chunk_id.value;
 
                health_code_update();
 
@@ -481,13 +505,17 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 
                DBG("consumer_add_channel %" PRIu64, msg.u.channel.channel_key);
                new_channel = consumer_allocate_channel(msg.u.channel.channel_key,
-                               msg.u.channel.session_id, msg.u.channel.pathname,
-                               msg.u.channel.name, msg.u.channel.uid, msg.u.channel.gid,
+                               msg.u.channel.session_id,
+                               msg.u.channel.chunk_id.is_set ?
+                                               &chunk_id : NULL,
+                               msg.u.channel.pathname,
+                               msg.u.channel.name,
                                msg.u.channel.relayd_id, msg.u.channel.output,
                                msg.u.channel.tracefile_size,
                                msg.u.channel.tracefile_count, 0,
                                msg.u.channel.monitor,
                                msg.u.channel.live_timer_interval,
+                               msg.u.channel.is_live,
                                NULL, NULL);
                if (new_channel == NULL) {
                        lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_OUTFD_ERROR);
@@ -586,14 +614,14 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                ret = consumer_send_status_msg(sock, ret_code);
                if (ret < 0) {
                        /* Somehow, the session daemon is not responding anymore. */
-                       goto error_fatal;
+                       goto error_add_stream_fatal;
                }
 
                health_code_update();
 
                if (ret_code != LTTCOMM_CONSUMERD_SUCCESS) {
                        /* Channel was not found. */
-                       goto end_nosignal;
+                       goto error_add_stream_nosignal;
                }
 
                /* Blocking call */
@@ -601,7 +629,7 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                ret = lttng_consumer_poll_socket(consumer_sockpoll);
                health_poll_exit();
                if (ret) {
-                       goto error_fatal;
+                       goto error_add_stream_fatal;
                }
 
                health_code_update();
@@ -610,8 +638,7 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                ret = lttcomm_recv_fds_unix_sock(sock, &fd, 1);
                if (ret != sizeof(fd)) {
                        lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_ERROR_RECV_FD);
-                       rcu_read_unlock();
-                       return ret;
+                       goto end;
                }
 
                health_code_update();
@@ -624,19 +651,20 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                ret = consumer_send_status_msg(sock, ret_code);
                if (ret < 0) {
                        /* Somehow, the session daemon is not responding anymore. */
-                       goto end_nosignal;
+                       goto error_add_stream_nosignal;
                }
 
                health_code_update();
 
-               new_stream = consumer_allocate_stream(channel->key,
+               pthread_mutex_lock(&channel->lock);
+               new_stream = consumer_stream_create(
+                               channel,
+                               channel->key,
                                fd,
-                               LTTNG_CONSUMER_ACTIVE_STREAM,
                                channel->name,
-                               channel->uid,
-                               channel->gid,
                                channel->relayd_id,
                                channel->session_id,
+                               channel->trace_chunk,
                                msg.u.stream.cpu,
                                &alloc_ret,
                                channel->type,
@@ -649,27 +677,22 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                                lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_OUTFD_ERROR);
                                break;
                        }
-                       goto end_nosignal;
+                       pthread_mutex_unlock(&channel->lock);
+                       goto error_add_stream_nosignal;
                }
 
-               new_stream->chan = channel;
                new_stream->wait_fd = fd;
-               switch (channel->output) {
-               case CONSUMER_CHANNEL_SPLICE:
-                       new_stream->output = LTTNG_EVENT_SPLICE;
-                       ret = utils_create_pipe(new_stream->splice_pipe);
-                       if (ret < 0) {
-                               goto end_nosignal;
-                       }
-                       break;
-               case CONSUMER_CHANNEL_MMAP:
-                       new_stream->output = LTTNG_EVENT_MMAP;
-                       break;
-               default:
-                       ERR("Stream output unknown %d", channel->output);
-                       goto end_nosignal;
+               ret = kernctl_get_max_subbuf_size(new_stream->wait_fd,
+                               &new_stream->max_sb_size);
+               if (ret < 0) {
+                       pthread_mutex_unlock(&channel->lock);
+                       ERR("Failed to get kernel maximal subbuffer size");
+                       goto error_add_stream_nosignal;
                }
 
+               consumer_stream_update_channel_attributes(new_stream,
+                               channel);
+
                /*
                 * We've just assigned the channel to the stream so increment the
                 * refcount right now. We don't need to increment the refcount for
@@ -692,14 +715,16 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 
                health_code_update();
 
+               pthread_mutex_lock(&new_stream->lock);
                if (ctx->on_recv_stream) {
                        ret = ctx->on_recv_stream(new_stream);
                        if (ret < 0) {
+                               pthread_mutex_unlock(&new_stream->lock);
+                               pthread_mutex_unlock(&channel->lock);
                                consumer_stream_free(new_stream);
-                               goto end_nosignal;
+                               goto error_add_stream_nosignal;
                        }
                }
-
                health_code_update();
 
                if (new_stream->metadata_flag) {
@@ -712,7 +737,9 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                                        "relayd id %" PRIu64, new_stream->name,
                                        new_stream->net_seq_idx);
                        cds_list_add(&new_stream->send_node, &channel->streams.head);
-                       break;
+                       pthread_mutex_unlock(&new_stream->lock);
+                       pthread_mutex_unlock(&channel->lock);
+                       goto end_add_stream;
                }
 
                /* Send stream to relayd if the stream has an ID. */
@@ -720,8 +747,10 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                        ret = consumer_send_relayd_stream(new_stream,
                                        new_stream->chan->pathname);
                        if (ret < 0) {
+                               pthread_mutex_unlock(&new_stream->lock);
+                               pthread_mutex_unlock(&channel->lock);
                                consumer_stream_free(new_stream);
-                               goto end_nosignal;
+                               goto error_add_stream_nosignal;
                        }
 
                        /*
@@ -733,10 +762,14 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                                ret = consumer_send_relayd_streams_sent(
                                                new_stream->net_seq_idx);
                                if (ret < 0) {
-                                       goto end_nosignal;
+                                       pthread_mutex_unlock(&new_stream->lock);
+                                       pthread_mutex_unlock(&channel->lock);
+                                       goto error_add_stream_nosignal;
                                }
                        }
                }
+               pthread_mutex_unlock(&new_stream->lock);
+               pthread_mutex_unlock(&channel->lock);
 
                /* Get the right pipe where the stream will be sent. */
                if (new_stream->metadata_flag) {
@@ -762,12 +795,17 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                        } else {
                                consumer_del_stream_for_data(new_stream);
                        }
-                       goto end_nosignal;
+                       goto error_add_stream_nosignal;
                }
 
-               DBG("Kernel consumer ADD_STREAM %s (fd: %d) with relayd id %" PRIu64,
-                               new_stream->name, fd, new_stream->relayd_stream_id);
+               DBG("Kernel consumer ADD_STREAM %s (fd: %d) %s with relayd id %" PRIu64,
+                               new_stream->name, fd, new_stream->chan->pathname, new_stream->relayd_stream_id);
+end_add_stream:
                break;
+error_add_stream_nosignal:
+               goto end_nosignal;
+error_add_stream_fatal:
+               goto error_fatal;
        }
        case LTTNG_CONSUMER_STREAMS_SENT:
        {
@@ -796,7 +834,7 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                ret = consumer_send_status_msg(sock, ret_code);
                if (ret < 0 || ret_code != LTTCOMM_CONSUMERD_SUCCESS) {
                        /* Somehow, the session daemon is not responding anymore. */
-                       goto end_nosignal;
+                       goto error_streams_sent_nosignal;
                }
 
                health_code_update();
@@ -806,7 +844,7 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                 * streams in this channel.
                 */
                if (!channel->monitor) {
-                       break;
+                       goto end_error_streams_sent;
                }
 
                health_code_update();
@@ -815,11 +853,14 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                        ret = consumer_send_relayd_streams_sent(
                                        msg.u.sent_streams.net_seq_idx);
                        if (ret < 0) {
-                               goto end_nosignal;
+                               goto error_streams_sent_nosignal;
                        }
                        channel->streams_sent_to_relayd = true;
                }
+end_error_streams_sent:
                break;
+error_streams_sent_nosignal:
+               goto end_nosignal;
        }
        case LTTNG_CONSUMER_UPDATE_STREAM:
        {
@@ -890,26 +931,36 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
        }
        case LTTNG_CONSUMER_SNAPSHOT_CHANNEL:
        {
-               if (msg.u.snapshot_channel.metadata == 1) {
-                       ret = lttng_kconsumer_snapshot_metadata(msg.u.snapshot_channel.key,
-                                       msg.u.snapshot_channel.pathname,
-                                       msg.u.snapshot_channel.relayd_id, ctx);
-                       if (ret < 0) {
-                               ERR("Snapshot metadata failed");
-                               ret_code = LTTCOMM_CONSUMERD_ERROR_METADATA;
-                       }
+               struct lttng_consumer_channel *channel;
+               uint64_t key = msg.u.snapshot_channel.key;
+
+               channel = consumer_find_channel(key);
+               if (!channel) {
+                       ERR("Channel %" PRIu64 " not found", key);
+                       ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
                } else {
-                       ret = lttng_kconsumer_snapshot_channel(msg.u.snapshot_channel.key,
-                                       msg.u.snapshot_channel.pathname,
-                                       msg.u.snapshot_channel.relayd_id,
-                                       msg.u.snapshot_channel.nb_packets_per_stream,
-                                       ctx);
-                       if (ret < 0) {
-                               ERR("Snapshot channel failed");
-                               ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
+                       pthread_mutex_lock(&channel->lock);
+                       if (msg.u.snapshot_channel.metadata == 1) {
+                               ret = lttng_kconsumer_snapshot_metadata(channel, key,
+                                               msg.u.snapshot_channel.pathname,
+                                               msg.u.snapshot_channel.relayd_id, ctx);
+                               if (ret < 0) {
+                                       ERR("Snapshot metadata failed");
+                                       ret_code = LTTCOMM_CONSUMERD_SNAPSHOT_FAILED;
+                               }
+                       } else {
+                               ret = lttng_kconsumer_snapshot_channel(channel, key,
+                                               msg.u.snapshot_channel.pathname,
+                                               msg.u.snapshot_channel.relayd_id,
+                                               msg.u.snapshot_channel.nb_packets_per_stream,
+                                               ctx);
+                               if (ret < 0) {
+                                       ERR("Snapshot channel failed");
+                                       ret_code = LTTCOMM_CONSUMERD_SNAPSHOT_FAILED;
+                               }
                        }
+                       pthread_mutex_unlock(&channel->lock);
                }
-
                health_code_update();
 
                ret = consumer_send_status_msg(sock, ret_code);
@@ -935,14 +986,14 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                ret = consumer_send_status_msg(sock, ret_code);
                if (ret < 0) {
                        /* Somehow, the session daemon is not responding anymore. */
-                       goto end_nosignal;
+                       goto end_destroy_channel;
                }
 
                health_code_update();
 
                /* Stop right now if no channel was found. */
                if (!channel) {
-                       goto end_nosignal;
+                       goto end_destroy_channel;
                }
 
                /*
@@ -958,7 +1009,7 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                assert(!uatomic_sub_return(&channel->refcount, 1));
 
                consumer_del_channel(channel);
-
+end_destroy_channel:
                goto end_nosignal;
        }
        case LTTNG_CONSUMER_DISCARDED_EVENTS:
@@ -1072,47 +1123,80 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                }
                break;
        }
-       case LTTNG_CONSUMER_ROTATE_RENAME:
+       case LTTNG_CONSUMER_ROTATE_CHANNEL:
        {
-               DBG("Consumer rename session %" PRIu64 " after rotation, old path = \"%s\", new path = \"%s\"",
-                               msg.u.rotate_rename.session_id,
-                               msg.u.rotate_rename.old_path,
-                               msg.u.rotate_rename.new_path);
-               ret = lttng_consumer_rotate_rename(msg.u.rotate_rename.old_path,
-                               msg.u.rotate_rename.new_path,
-                               msg.u.rotate_rename.uid,
-                               msg.u.rotate_rename.gid,
-                               msg.u.rotate_rename.relayd_id);
-               if (ret < 0) {
-                       ERR("Rotate rename failed");
-                       ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
-               }
+               struct lttng_consumer_channel *channel;
+               uint64_t key = msg.u.rotate_channel.key;
 
-               health_code_update();
+               DBG("Consumer rotate channel %" PRIu64, key);
 
+               channel = consumer_find_channel(key);
+               if (!channel) {
+                       ERR("Channel %" PRIu64 " not found", key);
+                       ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
+               } else {
+                       /*
+                        * Sample the rotate position of all the streams in this channel.
+                        */
+                       ret = lttng_consumer_rotate_channel(channel, key,
+                                       msg.u.rotate_channel.relayd_id,
+                                       msg.u.rotate_channel.metadata,
+                                       ctx);
+                       if (ret < 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) {
                        /* Somehow, the session daemon is not responding anymore. */
-                       goto end_nosignal;
+                       goto error_rotate_channel;
+               }
+               if (channel) {
+                       /* Rotate the streams that are ready right now. */
+                       ret = lttng_consumer_rotate_ready_streams(
+                                       channel, key, ctx);
+                       if (ret < 0) {
+                               ERR("Rotate ready streams failed");
+                       }
                }
                break;
+error_rotate_channel:
+               goto end_nosignal;
        }
-       case LTTNG_CONSUMER_MKDIR:
+       case LTTNG_CONSUMER_CLEAR_CHANNEL:
        {
-               DBG("Consumer mkdir %s in session %" PRIu64,
-                               msg.u.mkdir.path,
-                               msg.u.mkdir.session_id);
-               ret = lttng_consumer_mkdir(msg.u.mkdir.path,
-                               msg.u.mkdir.uid,
-                               msg.u.mkdir.gid,
-                               msg.u.mkdir.relayd_id);
-               if (ret < 0) {
-                       ERR("consumer mkdir failed");
+               struct lttng_consumer_channel *channel;
+               uint64_t key = msg.u.clear_channel.key;
+
+               channel = consumer_find_channel(key);
+               if (!channel) {
+                       DBG("Channel %" PRIu64 " not found", key);
                        ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
+               } else {
+                       ret = lttng_consumer_clear_channel(channel);
+                       if (ret) {
+                               ERR("Clear channel failed");
+                               ret_code = ret;
+                       }
+
+                       health_code_update();
+               }
+               ret = consumer_send_status_msg(sock, ret_code);
+               if (ret < 0) {
+                       /* Somehow, the session daemon is not responding anymore. */
+                       goto end_nosignal;
                }
 
+               break;
+       }
+       case LTTNG_CONSUMER_INIT:
+       {
+               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) {
                        /* Somehow, the session daemon is not responding anymore. */
@@ -1120,464 +1204,497 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                }
                break;
        }
+       case LTTNG_CONSUMER_CREATE_TRACE_CHUNK:
+       {
+               const struct lttng_credentials credentials = {
+                       .uid = LTTNG_OPTIONAL_INIT_VALUE(msg.u.create_trace_chunk.credentials.value.uid),
+                       .gid = LTTNG_OPTIONAL_INIT_VALUE(msg.u.create_trace_chunk.credentials.value.gid),
+               };
+               const bool is_local_trace =
+                               !msg.u.create_trace_chunk.relayd_id.is_set;
+               const uint64_t relayd_id =
+                               msg.u.create_trace_chunk.relayd_id.value;
+               const char *chunk_override_name =
+                               *msg.u.create_trace_chunk.override_name ?
+                                       msg.u.create_trace_chunk.override_name :
+                                       NULL;
+               struct lttng_directory_handle *chunk_directory_handle = NULL;
+
+               /*
+                * The session daemon will only provide a chunk directory file
+                * descriptor for local traces.
+                */
+               if (is_local_trace) {
+                       int chunk_dirfd;
+
+                       /* Acnowledge the reception of the command. */
+                       ret = consumer_send_status_msg(sock,
+                                       LTTCOMM_CONSUMERD_SUCCESS);
+                       if (ret < 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");
+                               goto error_fatal;
+                       }
+
+                       DBG("Received trace chunk directory fd (%d)",
+                                       chunk_dirfd);
+                       chunk_directory_handle = lttng_directory_handle_create_from_dirfd(
+                                       chunk_dirfd);
+                       if (!chunk_directory_handle) {
+                               ERR("Failed to initialize chunk directory handle from directory file descriptor");
+                               if (close(chunk_dirfd)) {
+                                       PERROR("Failed to close chunk directory file descriptor");
+                               }
+                               goto error_fatal;
+                       }
+               }
+
+               ret_code = lttng_consumer_create_trace_chunk(
+                               !is_local_trace ? &relayd_id : NULL,
+                               msg.u.create_trace_chunk.session_id,
+                               msg.u.create_trace_chunk.chunk_id,
+                               (time_t) msg.u.create_trace_chunk
+                                               .creation_timestamp,
+                               chunk_override_name,
+                               msg.u.create_trace_chunk.credentials.is_set ?
+                                               &credentials :
+                                               NULL,
+                               chunk_directory_handle);
+               lttng_directory_handle_put(chunk_directory_handle);
+               goto end_msg_sessiond;
+       }
+       case LTTNG_CONSUMER_CLOSE_TRACE_CHUNK:
+       {
+               enum lttng_trace_chunk_command_type close_command =
+                               msg.u.close_trace_chunk.close_command.value;
+               const uint64_t relayd_id =
+                               msg.u.close_trace_chunk.relayd_id.value;
+               struct lttcomm_consumer_close_trace_chunk_reply reply;
+               char path[LTTNG_PATH_MAX];
+
+               ret_code = lttng_consumer_close_trace_chunk(
+                               msg.u.close_trace_chunk.relayd_id.is_set ?
+                                               &relayd_id :
+                                               NULL,
+                               msg.u.close_trace_chunk.session_id,
+                               msg.u.close_trace_chunk.chunk_id,
+                               (time_t) msg.u.close_trace_chunk.close_timestamp,
+                               msg.u.close_trace_chunk.close_command.is_set ?
+                                               &close_command :
+                                               NULL, path);
+               reply.ret_code = ret_code;
+               reply.path_length = strlen(path) + 1;
+               ret = lttcomm_send_unix_sock(sock, &reply, sizeof(reply));
+               if (ret != sizeof(reply)) {
+                       goto error_fatal;
+               }
+               ret = lttcomm_send_unix_sock(sock, path, reply.path_length);
+               if (ret != reply.path_length) {
+                       goto error_fatal;
+               }
+               goto end_nosignal;
+       }
+       case LTTNG_CONSUMER_TRACE_CHUNK_EXISTS:
+       {
+               const uint64_t relayd_id =
+                               msg.u.trace_chunk_exists.relayd_id.value;
+
+               ret_code = lttng_consumer_trace_chunk_exists(
+                               msg.u.trace_chunk_exists.relayd_id.is_set ?
+                                               &relayd_id : NULL,
+                               msg.u.trace_chunk_exists.session_id,
+                               msg.u.trace_chunk_exists.chunk_id);
+               goto end_msg_sessiond;
+       }
+       case LTTNG_CONSUMER_OPEN_CHANNEL_PACKETS:
+       {
+               const uint64_t key = msg.u.open_channel_packets.key;
+               struct lttng_consumer_channel *channel =
+                               consumer_find_channel(key);
+
+               if (channel) {
+                       pthread_mutex_lock(&channel->lock);
+                       ret_code = lttng_consumer_open_channel_packets(channel);
+                       pthread_mutex_unlock(&channel->lock);
+               } else {
+                       WARN("Channel %" PRIu64 " not found", key);
+                       ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
+               }
+
+               health_code_update();
+               goto end_msg_sessiond;
+       }
        default:
                goto end_nosignal;
        }
 
 end_nosignal:
-       rcu_read_unlock();
-
        /*
         * Return 1 to indicate success since the 0 value can be a socket
         * shutdown during the recv() or send() call.
         */
-       health_code_update();
-       return 1;
-
+       ret = 1;
+       goto end;
 error_fatal:
-       rcu_read_unlock();
        /* This will issue a consumer stop. */
-       return -1;
+       ret = -1;
+       goto end;
+end_msg_sessiond:
+       /*
+        * The returned value here is not useful since either way we'll return 1 to
+        * the caller because the session daemon socket management is done
+        * elsewhere. Returning a negative code or 0 will shutdown the consumer.
+        */
+       ret = consumer_send_status_msg(sock, ret_code);
+       if (ret < 0) {
+               goto error_fatal;
+       }
+       ret = 1;
+end:
+       health_code_update();
+       rcu_read_unlock();
+       return ret;
 }
 
 /*
- * Populate index values of a kernel stream. Values are set in big endian order.
+ * Sync metadata meaning request them to the session daemon and snapshot to the
+ * metadata thread can consumer them.
  *
- * Return 0 on success or else a negative value.
+ * Metadata stream lock MUST be acquired.
  */
-static int get_index_values(struct ctf_packet_index *index, int infd)
+enum sync_metadata_status lttng_kconsumer_sync_metadata(
+               struct lttng_consumer_stream *metadata)
 {
        int ret;
+       enum sync_metadata_status status;
 
-       ret = kernctl_get_timestamp_begin(infd, &index->timestamp_begin);
-       if (ret < 0) {
-               PERROR("kernctl_get_timestamp_begin");
-               goto error;
-       }
-       index->timestamp_begin = htobe64(index->timestamp_begin);
+       assert(metadata);
 
-       ret = kernctl_get_timestamp_end(infd, &index->timestamp_end);
+       ret = kernctl_buffer_flush(metadata->wait_fd);
        if (ret < 0) {
-               PERROR("kernctl_get_timestamp_end");
-               goto error;
+               ERR("Failed to flush kernel stream");
+               status = SYNC_METADATA_STATUS_ERROR;
+               goto end;
        }
-       index->timestamp_end = htobe64(index->timestamp_end);
 
-       ret = kernctl_get_events_discarded(infd, &index->events_discarded);
+       ret = kernctl_snapshot(metadata->wait_fd);
        if (ret < 0) {
-               PERROR("kernctl_get_events_discarded");
-               goto error;
+               if (errno == EAGAIN) {
+                       /* No new metadata, exit. */
+                       DBG("Sync metadata, no new kernel metadata");
+                       status = SYNC_METADATA_STATUS_NO_DATA;
+               } else {
+                       ERR("Sync metadata, taking kernel snapshot failed.");
+                       status = SYNC_METADATA_STATUS_ERROR;
+               }
+       } else {
+               status = SYNC_METADATA_STATUS_NEW_DATA;
        }
-       index->events_discarded = htobe64(index->events_discarded);
 
-       ret = kernctl_get_content_size(infd, &index->content_size);
-       if (ret < 0) {
-               PERROR("kernctl_get_content_size");
-               goto error;
-       }
-       index->content_size = htobe64(index->content_size);
+end:
+       return status;
+}
 
-       ret = kernctl_get_packet_size(infd, &index->packet_size);
-       if (ret < 0) {
-               PERROR("kernctl_get_packet_size");
-               goto error;
+static
+int extract_common_subbuffer_info(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuf)
+{
+       int ret;
+
+       ret = kernctl_get_subbuf_size(
+                       stream->wait_fd, &subbuf->info.data.subbuf_size);
+       if (ret) {
+               goto end;
        }
-       index->packet_size = htobe64(index->packet_size);
 
-       ret = kernctl_get_stream_id(infd, &index->stream_id);
-       if (ret < 0) {
-               PERROR("kernctl_get_stream_id");
-               goto error;
+       ret = kernctl_get_padded_subbuf_size(
+                       stream->wait_fd, &subbuf->info.data.padded_subbuf_size);
+       if (ret) {
+               goto end;
        }
-       index->stream_id = htobe64(index->stream_id);
 
-       ret = kernctl_get_instance_id(infd, &index->stream_instance_id);
-       if (ret < 0) {
-               if (ret == -ENOTTY) {
-                       /* Command not implemented by lttng-modules. */
-                       index->stream_instance_id = -1ULL;
-               } else {
-                       PERROR("kernctl_get_instance_id");
-                       goto error;
-               }
+end:
+       return ret;
+}
+
+static
+int extract_metadata_subbuffer_info(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuf)
+{
+       int ret;
+
+       ret = extract_common_subbuffer_info(stream, subbuf);
+       if (ret) {
+               goto end;
        }
-       index->stream_instance_id = htobe64(index->stream_instance_id);
 
-       ret = kernctl_get_sequence_number(infd, &index->packet_seq_num);
-       if (ret < 0) {
-               if (ret == -ENOTTY) {
-                       /* Command not implemented by lttng-modules. */
-                       index->packet_seq_num = -1ULL;
-                       ret = 0;
-               } else {
-                       PERROR("kernctl_get_sequence_number");
-                       goto error;
-               }
+       ret = kernctl_get_metadata_version(
+                       stream->wait_fd, &subbuf->info.metadata.version);
+       if (ret) {
+               goto end;
        }
-       index->packet_seq_num = htobe64(index->packet_seq_num);
 
-error:
+end:
        return ret;
 }
-/*
- * Sync metadata meaning request them to the session daemon and snapshot to the
- * metadata thread can consumer them.
- *
- * Metadata stream lock MUST be acquired.
- *
- * Return 0 if new metadatda is available, EAGAIN if the metadata stream
- * is empty or a negative value on error.
- */
-int lttng_kconsumer_sync_metadata(struct lttng_consumer_stream *metadata)
+
+static
+int extract_data_subbuffer_info(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuf)
 {
        int ret;
 
-       assert(metadata);
+       ret = extract_common_subbuffer_info(stream, subbuf);
+       if (ret) {
+               goto end;
+       }
 
-       ret = kernctl_buffer_flush(metadata->wait_fd);
+       ret = kernctl_get_packet_size(
+                       stream->wait_fd, &subbuf->info.data.packet_size);
        if (ret < 0) {
-               ERR("Failed to flush kernel stream");
+               PERROR("Failed to get sub-buffer packet size");
                goto end;
        }
 
-       ret = kernctl_snapshot(metadata->wait_fd);
+       ret = kernctl_get_content_size(
+                       stream->wait_fd, &subbuf->info.data.content_size);
        if (ret < 0) {
-               if (ret != -EAGAIN) {
-                       ERR("Sync metadata, taking kernel snapshot failed.");
+               PERROR("Failed to get sub-buffer content size");
+               goto end;
+       }
+
+       ret = kernctl_get_timestamp_begin(
+                       stream->wait_fd, &subbuf->info.data.timestamp_begin);
+       if (ret < 0) {
+               PERROR("Failed to get sub-buffer begin timestamp");
+               goto end;
+       }
+
+       ret = kernctl_get_timestamp_end(
+                       stream->wait_fd, &subbuf->info.data.timestamp_end);
+       if (ret < 0) {
+               PERROR("Failed to get sub-buffer end timestamp");
+               goto end;
+       }
+
+       ret = kernctl_get_events_discarded(
+                       stream->wait_fd, &subbuf->info.data.events_discarded);
+       if (ret) {
+               PERROR("Failed to get sub-buffer events discarded count");
+               goto end;
+       }
+
+       ret = kernctl_get_sequence_number(stream->wait_fd,
+                       &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;
                }
-               DBG("Sync metadata, no new kernel metadata");
-               /* No new metadata, exit. */
-               ret = ENODATA;
+       } else {
+               subbuf->info.data.sequence_number.is_set = true;
+       }
+
+       ret = kernctl_get_stream_id(
+                       stream->wait_fd, &subbuf->info.data.stream_id);
+       if (ret < 0) {
+               PERROR("Failed to get stream id");
                goto end;
        }
 
+       ret = kernctl_get_instance_id(stream->wait_fd,
+                       &subbuf->info.data.stream_instance_id.value);
+       if (ret) {
+               /* May not be supported by older LTTng-modules. */
+               if (ret != -ENOTTY) {
+                       PERROR("Failed to get stream instance id");
+                       goto end;
+               }
+       } else {
+               subbuf->info.data.stream_instance_id.is_set = true;
+       }
 end:
        return ret;
 }
 
 static
-int update_stream_stats(struct lttng_consumer_stream *stream)
+int get_subbuffer_common(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuffer)
 {
        int ret;
-       uint64_t seq, discarded;
-
-       ret = kernctl_get_sequence_number(stream->wait_fd, &seq);
-       if (ret < 0) {
-               if (ret == -ENOTTY) {
-                       /* Command not implemented by lttng-modules. */
-                       seq = -1ULL;
-               } else {
-                       PERROR("kernctl_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).
-        */
-       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;
+       ret = kernctl_get_next_subbuf(stream->wait_fd);
+       if (ret) {
                goto end;
        }
-       stream->last_sequence_number = seq;
 
-       ret = kernctl_get_events_discarded(stream->wait_fd, &discarded);
-       if (ret < 0) {
-               PERROR("kernctl_get_events_discarded");
+       ret = stream->read_subbuffer_ops.extract_subbuffer_info(
+                       stream, subbuffer);
+end:
+       return ret;
+}
+
+static
+int get_next_subbuffer_splice(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuffer)
+{
+       int ret;
+
+       ret = get_subbuffer_common(stream, subbuffer);
+       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;
-       }
-       stream->last_discarded_events = discarded;
-       ret = 0;
 
+       subbuffer->buffer.fd = stream->wait_fd;
 end:
        return ret;
 }
 
-/*
- * Check if the local version of the metadata stream matches with the version
- * of the metadata stream in the kernel. If it was updated, set the reset flag
- * on the stream.
- */
 static
-int metadata_stream_check_version(int infd, struct lttng_consumer_stream *stream)
+int get_next_subbuffer_mmap(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuffer)
 {
        int ret;
-       uint64_t cur_version;
+       const char *addr;
 
-       ret = kernctl_get_metadata_version(infd, &cur_version);
-       if (ret < 0) {
-               if (ret == -ENOTTY) {
-                       /*
-                        * LTTng-modules does not implement this
-                        * command.
-                        */
-                       ret = 0;
-                       goto end;
-               }
-               ERR("Failed to get the metadata version");
+       ret = get_subbuffer_common(stream, subbuffer);
+       if (ret) {
                goto end;
        }
 
-       if (stream->metadata_version == cur_version) {
-               ret = 0;
+       ret = get_current_subbuf_addr(stream, &addr);
+       if (ret) {
                goto end;
        }
 
-       DBG("New metadata version detected");
-       stream->metadata_version = cur_version;
-       stream->reset_metadata_flag = 1;
-       ret = 0;
-
+       subbuffer->buffer.buffer = lttng_buffer_view_init(
+                       addr, 0, subbuffer->info.data.padded_subbuf_size);
 end:
        return ret;
 }
 
-/*
- * Consume data on a file descriptor and write it on a trace file.
- */
-ssize_t lttng_kconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
-               struct lttng_consumer_local_data *ctx)
+static
+int get_next_subbuffer_metadata_check(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuffer)
 {
-       unsigned long len, subbuf_size, padding;
-       int err, write_index = 1;
-       ssize_t ret = 0;
-       int infd = stream->wait_fd;
-       struct ctf_packet_index index;
-
-       DBG("In read_subbuffer (infd : %d)", infd);
+       int ret;
+       const char *addr;
+       bool coherent;
 
-       /* Get the next subbuffer */
-       err = kernctl_get_next_subbuf(infd);
-       if (err != 0) {
-               /*
-                * 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 = err;
+       ret = kernctl_get_next_subbuf_metadata_check(stream->wait_fd,
+                       &coherent);
+       if (ret) {
                goto end;
        }
 
-       /* Get the full subbuffer size including padding */
-       err = kernctl_get_padded_subbuf_size(infd, &len);
-       if (err != 0) {
-               PERROR("Getting sub-buffer len failed.");
-               err = kernctl_put_subbuf(infd);
-               if (err != 0) {
-                       if (err == -EFAULT) {
-                               PERROR("Error in unreserving sub buffer\n");
-                       } else if (err == -EIO) {
-                               /* Should never happen with newer LTTng versions */
-                               PERROR("Reader has been pushed by the writer, last sub-buffer corrupted.");
-                       }
-                       ret = err;
-                       goto end;
-               }
-               ret = err;
+       ret = stream->read_subbuffer_ops.extract_subbuffer_info(
+                       stream, subbuffer);
+       if (ret) {
                goto end;
        }
 
-       if (!stream->metadata_flag) {
-               ret = get_index_values(&index, infd);
-               if (ret < 0) {
-                       err = kernctl_put_subbuf(infd);
-                       if (err != 0) {
-                               if (err == -EFAULT) {
-                                       PERROR("Error in unreserving sub buffer\n");
-                               } else if (err == -EIO) {
-                                       /* Should never happen with newer LTTng versions */
-                                       PERROR("Reader has been pushed by the writer, last sub-buffer corrupted.");
-                               }
-                               ret = err;
-                               goto end;
-                       }
-                       goto end;
-               }
-               ret = update_stream_stats(stream);
-               if (ret < 0) {
-                       err = kernctl_put_subbuf(infd);
-                       if (err != 0) {
-                               if (err == -EFAULT) {
-                                       PERROR("Error in unreserving sub buffer\n");
-                               } else if (err == -EIO) {
-                                       /* Should never happen with newer LTTng versions */
-                                       PERROR("Reader has been pushed by the writer, last sub-buffer corrupted.");
-                               }
-                               ret = err;
-                               goto end;
-                       }
-                       goto end;
-               }
-       } else {
-               write_index = 0;
-               ret = metadata_stream_check_version(infd, stream);
-               if (ret < 0) {
-                       err = kernctl_put_subbuf(infd);
-                       if (err != 0) {
-                               if (err == -EFAULT) {
-                                       PERROR("Error in unreserving sub buffer\n");
-                               } else if (err == -EIO) {
-                                       /* Should never happen with newer LTTng versions */
-                                       PERROR("Reader has been pushed by the writer, last sub-buffer corrupted.");
-                               }
-                               ret = err;
-                               goto end;
-                       }
-                       goto end;
-               }
+       LTTNG_OPTIONAL_SET(&subbuffer->info.metadata.coherent, coherent);
+
+       ret = get_current_subbuf_addr(stream, &addr);
+       if (ret) {
+               goto end;
        }
 
-       switch (stream->chan->output) {
-       case CONSUMER_CHANNEL_SPLICE:
-               /*
-                * XXX: The lttng-modules splice "actor" does not handle copying
-                * partial pages hence only using the subbuffer size without the
-                * padding makes the splice fail.
-                */
-               subbuf_size = len;
-               padding = 0;
+       subbuffer->buffer.buffer = lttng_buffer_view_init(
+                       addr, 0, subbuffer->info.data.padded_subbuf_size);
+       DBG("Got metadata packet with padded_subbuf_size = %lu, coherent = %s",
+                       subbuffer->info.metadata.padded_subbuf_size,
+                       coherent ? "true" : "false");
+end:
+       return ret;
+}
 
-               /* splice the subbuffer to the tracefile */
-               ret = lttng_consumer_on_read_subbuffer_splice(ctx, stream, subbuf_size,
-                               padding, &index);
-               /*
-                * XXX: Splice does not support network streaming so the return value
-                * is simply checked against subbuf_size and not like the mmap() op.
-                */
-               if (ret != subbuf_size) {
-                       /*
-                        * display the error but continue processing to try
-                        * to release the subbuffer
-                        */
-                       ERR("Error splicing to tracefile (ret: %zd != len: %lu)",
-                                       ret, subbuf_size);
-                       write_index = 0;
-               }
-               break;
-       case CONSUMER_CHANNEL_MMAP:
-               /* Get subbuffer size without padding */
-               err = kernctl_get_subbuf_size(infd, &subbuf_size);
-               if (err != 0) {
-                       PERROR("Getting sub-buffer len failed.");
-                       err = kernctl_put_subbuf(infd);
-                       if (err != 0) {
-                               if (err == -EFAULT) {
-                                       PERROR("Error in unreserving sub buffer\n");
-                               } else if (err == -EIO) {
-                                       /* Should never happen with newer LTTng versions */
-                                       PERROR("Reader has been pushed by the writer, last sub-buffer corrupted.");
-                               }
-                               ret = err;
-                               goto end;
-                       }
-                       ret = err;
-                       goto end;
+static
+int put_next_subbuffer(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuffer)
+{
+       const int ret = kernctl_put_next_subbuf(stream->wait_fd);
+
+       if (ret) {
+               if (ret == -EFAULT) {
+                       PERROR("Error in unreserving sub buffer");
+               } else if (ret == -EIO) {
+                       /* Should never happen with newer LTTng versions */
+                       PERROR("Reader has been pushed by the writer, last sub-buffer corrupted");
                }
+       }
 
-               /* Make sure the tracer is not gone mad on us! */
-               assert(len >= subbuf_size);
+       return ret;
+}
 
-               padding = len - subbuf_size;
+static
+bool is_get_next_check_metadata_available(int tracer_fd)
+{
+       return kernctl_get_next_subbuf_metadata_check(tracer_fd, NULL) !=
+                       -ENOTTY;
+}
 
-               /* 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)) {
+static
+int lttng_kconsumer_set_stream_ops(
+               struct lttng_consumer_stream *stream)
+{
+       int ret = 0;
+
+       if (stream->metadata_flag && stream->chan->is_live) {
+               DBG("Attempting to enable metadata bucketization for live consumers");
+               if (is_get_next_check_metadata_available(stream->wait_fd)) {
+                       DBG("Kernel tracer supports get_next_subbuffer_metadata_check, metadata will be accumulated until a coherent state is reached");
+                       stream->read_subbuffer_ops.get_next_subbuffer =
+                                       get_next_subbuffer_metadata_check;
+                       ret = consumer_stream_enable_metadata_bucketization(
+                                       stream);
+                       if (ret) {
+                               goto end;
+                       }
+               } else {
                        /*
-                        * Display the error but continue processing to try to release the
-                        * subbuffer. This is a DBG statement since this is possible to
-                        * happen without being a critical error.
+                        * The kernel tracer version is too old to indicate
+                        * when the metadata stream has reached a "coherent"
+                        * (parseable) point.
+                        *
+                        * This means that a live viewer may see an incoherent
+                        * sequence of metadata and fail to parse it.
                         */
-                       DBG("Error writing to tracefile "
-                                       "(ret: %zd != len: %lu != subbuf_size: %lu)",
-                                       ret, len, subbuf_size);
-                       write_index = 0;
+                       WARN("Kernel tracer does not support get_next_subbuffer_metadata_check which may cause live clients to fail to parse the metadata stream");
+                       metadata_bucket_destroy(stream->metadata_bucket);
+                       stream->metadata_bucket = NULL;
                }
-               break;
-       default:
-               ERR("Unknown output method");
-               ret = -EPERM;
-       }
-
-       err = kernctl_put_next_subbuf(infd);
-       if (err != 0) {
-               if (err == -EFAULT) {
-                       PERROR("Error in unreserving sub buffer\n");
-               } else if (err == -EIO) {
-                       /* Should never happen with newer LTTng versions */
-                       PERROR("Reader has been pushed by the writer, last sub-buffer corrupted.");
-               }
-               ret = err;
-               goto end;
        }
 
-       /* Write index if needed. */
-       if (!write_index) {
-               goto end;
-       }
-
-       if (stream->chan->live_timer_interval && !stream->metadata_flag) {
-               /*
-                * In live, block until all the metadata is sent.
-                */
-               pthread_mutex_lock(&stream->metadata_timer_lock);
-               assert(!stream->missed_metadata_flush);
-               stream->waiting_on_metadata = true;
-               pthread_mutex_unlock(&stream->metadata_timer_lock);
-
-               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_kernel_index(stream);
+       if (!stream->read_subbuffer_ops.get_next_subbuffer) {
+               if (stream->chan->output == CONSUMER_CHANNEL_MMAP) {
+                       stream->read_subbuffer_ops.get_next_subbuffer =
+                                       get_next_subbuffer_mmap;
                } else {
-                       pthread_mutex_unlock(&stream->metadata_timer_lock);
-               }
-               if (err < 0) {
-                       goto end;
+                       stream->read_subbuffer_ops.get_next_subbuffer =
+                                       get_next_subbuffer_splice;
                }
        }
 
-       err = consumer_stream_write_index(stream, &index);
-       if (err < 0) {
-               goto end;
+       if (stream->metadata_flag) {
+               stream->read_subbuffer_ops.extract_subbuffer_info =
+                               extract_metadata_subbuffer_info;
+       } else {
+               stream->read_subbuffer_ops.extract_subbuffer_info =
+                               extract_data_subbuffer_info;
+               if (stream->chan->is_live) {
+                       stream->read_subbuffer_ops.send_live_beacon =
+                                       consumer_flush_kernel_index;
+               }
        }
 
+       stream->read_subbuffer_ops.put_next_subbuffer = put_next_subbuffer;
 end:
        return ret;
 }
@@ -1589,33 +1706,15 @@ int lttng_kconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
        assert(stream);
 
        /*
-        * Don't create anything if this is set for streaming or should not be
-        * monitored.
+        * Don't create anything if this is set for streaming or if there is
+        * no current trace chunk on the parent channel.
         */
-       if (stream->net_seq_idx == (uint64_t) -1ULL && stream->chan->monitor) {
-               ret = utils_create_stream_file(stream->chan->pathname, stream->name,
-                               stream->chan->tracefile_size, stream->tracefile_count_current,
-                               stream->uid, stream->gid, NULL);
-               if (ret < 0) {
+       if (stream->net_seq_idx == (uint64_t) -1ULL && stream->chan->monitor &&
+                       stream->chan->trace_chunk) {
+               ret = consumer_stream_create_output_files(stream, true);
+               if (ret) {
                        goto error;
                }
-               stream->out_fd = ret;
-               stream->tracefile_size_current = 0;
-
-               if (!stream->metadata_flag) {
-                       struct lttng_index_file *index_file;
-
-                       index_file = lttng_index_file_create(stream->chan->pathname,
-                                       stream->name, stream->uid, stream->gid,
-                                       stream->chan->tracefile_size,
-                                       stream->tracefile_count_current,
-                                       CTF_INDEX_MAJOR, CTF_INDEX_MINOR);
-                       if (!index_file) {
-                               goto error;
-                       }
-                       assert(!stream->index_file);
-                       stream->index_file = index_file;
-               }
        }
 
        if (stream->output == LTTNG_EVENT_MMAP) {
@@ -1638,6 +1737,11 @@ int lttng_kconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
                }
        }
 
+       ret = lttng_kconsumer_set_stream_ops(stream);
+       if (ret) {
+               goto error_close_fd;
+       }
+
        /* we return 0 to let the library handle the FD internally */
        return 0;
 
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