Clean-up: ust-consumer: fix -Wshadow issues in lttng_ustconsumer_recv_cmd
[lttng-tools.git] / src / common / ust-consumer / ust-consumer.c
index 1af9840cd5184b0cfebad0bf680257fbbadac9a5..01c73f959edb7320cd5db3a92a61079ef5f64e6d 100644 (file)
@@ -37,6 +37,8 @@
 #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"
 
@@ -77,6 +79,11 @@ 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);
 }
 
@@ -346,48 +353,6 @@ 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)
 {
@@ -395,7 +360,7 @@ 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) {
@@ -403,7 +368,8 @@ 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;
@@ -481,8 +447,10 @@ 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);
                        }
@@ -491,8 +459,10 @@ 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);
@@ -1230,7 +1200,7 @@ static int snapshot_channel(struct lttng_consumer_channel *channel,
 
                        subbuf_view = lttng_buffer_view_init(
                                        subbuf_addr, 0, padded_len);
-                       read_len = lttng_consumer_on_read_subbuffer_mmap(ctx,
+                       read_len = lttng_consumer_on_read_subbuffer_mmap(
                                        stream, &subbuf_view, padded_len - len);
                        if (use_relayd) {
                                if (read_len != len) {
@@ -1272,6 +1242,17 @@ 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
@@ -1286,6 +1267,7 @@ 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);
 
@@ -1309,9 +1291,41 @@ 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;
                /*
@@ -1319,10 +1333,10 @@ 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;
@@ -1349,26 +1363,31 @@ 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();
@@ -1428,7 +1447,8 @@ 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);
@@ -1436,10 +1456,11 @@ 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;
                }
 
@@ -1451,12 +1472,12 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
        }
        case LTTNG_CONSUMER_ASK_CHANNEL_CREATION:
        {
-               int ret;
+               int ret_ask_channel, ret_add_channel, ret_send;
                struct ustctl_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. */
@@ -1505,15 +1526,15 @@ 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
@@ -1521,9 +1542,9 @@ 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);
@@ -1532,14 +1553,17 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 
                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;
                        }
@@ -1568,9 +1592,9 @@ 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);
                                }
@@ -1592,8 +1616,8 @@ 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.
                         */
@@ -1606,10 +1630,10 @@ 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;
@@ -1618,8 +1642,8 @@ 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) {
                                /*
@@ -1643,11 +1667,11 @@ 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
@@ -1656,7 +1680,7 @@ 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));
+               assert(cds_list_empty(&found_channel->streams.head));
 end_get_channel:
                goto end_msg_sessiond;
 error_get_channel_fatal:
@@ -1717,13 +1741,13 @@ 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
@@ -1766,8 +1790,8 @@ 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;
@@ -1792,38 +1816,46 @@ 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;
                }
@@ -1934,40 +1966,44 @@ 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;
                        }
@@ -1979,31 +2015,35 @@ 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;
                }
@@ -2015,10 +2055,14 @@ 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");
                        }
                }
@@ -2028,24 +2072,28 @@ end_rotate_channel_nosignal:
        }
        case LTTNG_CONSUMER_CLEAR_CHANNEL:
        {
-               struct lttng_consumer_channel *channel;
+               struct lttng_consumer_channel *found_channel;
                uint64_t key = msg.u.clear_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 {
-                       ret = lttng_consumer_clear_channel(channel);
-                       if (ret) {
+                       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;
+                               ret_code = ret_clear_channel;
                        }
 
                        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;
                }
@@ -2053,11 +2101,13 @@ end_rotate_channel_nosignal:
        }
        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;
                }
@@ -2066,8 +2116,8 @@ 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;
@@ -2085,11 +2135,13 @@ 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;
                        }
@@ -2097,8 +2149,9 @@ end_rotate_channel_nosignal:
                        /*
                         * Receive trace chunk domain dirfd.
                         */
-                       ret = lttcomm_recv_fds_unix_sock(sock, &chunk_dirfd, 1);
-                       if (ret != sizeof(chunk_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;
                        }
@@ -2175,6 +2228,29 @@ 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;
        }
@@ -2184,7 +2260,7 @@ 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:
@@ -2193,11 +2269,16 @@ 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:
@@ -2209,23 +2290,28 @@ 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;
+       return ret_func;
 }
 
 void lttng_ustctl_flush_buffer(struct lttng_consumer_stream *stream,
@@ -2374,8 +2460,10 @@ 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);
                        }
@@ -2394,8 +2482,10 @@ void lttng_ustconsumer_free_channel(struct lttng_consumer_channel *chan)
        /* 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);
@@ -2428,21 +2518,11 @@ int lttng_ustconsumer_close_wakeup_fd(struct lttng_consumer_stream *stream)
        return ustctl_stream_close_wakeup_fd(stream->ustream);
 }
 
-static
-void metadata_stream_reset_cache(struct lttng_consumer_stream *stream)
-{
-       DBG("Reset metadata cache of session %" PRIu64,
-                       stream->chan->session_id);
-       stream->ust_metadata_pushed = 0;
-       stream->metadata_version = stream->chan->metadata_cache->version;
-       stream->reset_metadata_flag = 1;
-}
-
 /*
  * 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)
@@ -2451,25 +2531,56 @@ int commit_one_metadata_packet(struct lttng_consumer_stream *stream)
        int ret;
 
        pthread_mutex_lock(&stream->chan->metadata_cache->lock);
-       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);
+                       &stream->chan->metadata_cache->contents.data[stream->ust_metadata_pushed],
+                       stream->chan->metadata_cache->contents.size -
+                                       stream->ust_metadata_pushed);
        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 >=
+       assert(stream->chan->metadata_cache->contents.size >=
                        stream->ust_metadata_pushed);
        ret = write_len;
 
@@ -2495,15 +2606,13 @@ end:
  * awaiting on metadata to be pushed out.
  *
  * The RCU read side lock must be held by the caller.
- *
- * Return 0 if new metadatda is available, EAGAIN if the metadata stream
- * is empty or a negative value on error.
  */
-int lttng_ustconsumer_sync_metadata(struct lttng_consumer_local_data *ctx,
+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);
@@ -2518,6 +2627,7 @@ int lttng_ustconsumer_sync_metadata(struct lttng_consumer_local_data *ctx,
        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;
        }
 
@@ -2535,38 +2645,30 @@ int lttng_ustconsumer_sync_metadata(struct lttng_consumer_local_data *ctx,
        if (consumer_stream_is_deleted(metadata_stream)) {
                DBG("Metadata stream %" PRIu64 " was deleted during the metadata synchronization",
                                metadata_stream->key);
-               ret = 0;
+               status = SYNC_METADATA_STATUS_NO_DATA;
                goto end;
        }
 
        ret = commit_one_metadata_packet(metadata_stream);
-       if (ret <= 0) {
+       if (ret < 0) {
+               status = SYNC_METADATA_STATUS_ERROR;
                goto end;
        } else if (ret > 0) {
-               retry = 1;
+               status = SYNC_METADATA_STATUS_NEW_DATA;
+       } else /* ret == 0 */ {
+               status = SYNC_METADATA_STATUS_NO_DATA;
+               goto end;
        }
 
        ret = ustctl_snapshot(metadata_stream->ustream);
        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;
+               ERR("Failed to take a snapshot of the metadata ring-buffer positions, ret = %d", ret);
+               status = SYNC_METADATA_STATUS_ERROR;
                goto end;
        }
 
-       /*
-        * After this flush, we still need to extract metadata.
-        */
-       if (retry) {
-               ret = EAGAIN;
-       }
-
 end:
-       return ret;
+       return status;
 }
 
 /*
@@ -2679,7 +2781,7 @@ static int extract_metadata_subbuffer_info(struct lttng_consumer_stream *stream,
                goto end;
        }
 
-       subbuf->info.metadata.version = stream->chan->metadata_cache->version;
+       subbuf->info.metadata.version = stream->metadata_version;
 
 end:
        return ret;
@@ -2810,28 +2912,88 @@ static int 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;
 
-       ret = ustctl_get_next_subbuf(stream->ustream);
-       if (ret) {
-               ret = commit_one_metadata_packet(stream);
-               if (ret < 0) {
-                       goto end;
-               } else if (ret == 0) {
-                       /* Not an error, the cache is empty. */
-                       ret = -ENODATA;
-                       goto end;
+       do {
+               ret = ustctl_get_next_subbuf(stream->ustream);
+               if (ret == 0) {
+                       got_subbuffer = true;
+               } else {
+                       got_subbuffer = false;
+                       if (ret != -EAGAIN) {
+                               /* Fatal error. */
+                               goto end;
+                       }
                }
 
-               ret = ustctl_get_next_subbuf(stream->ustream);
-               if (ret) {
-                       goto end;
+               /*
+                * Determine if the cache is empty and ensure that a sub-buffer
+                * is made available if the cache is not empty.
+                */
+               if (!got_subbuffer) {
+                       ret = commit_one_metadata_packet(stream);
+                       if (ret < 0 && ret != -ENOBUFS) {
+                               goto end;
+                       } else if (ret == 0) {
+                               /* Not an error, the cache is empty. */
+                               cache_empty = true;
+                               ret = -ENODATA;
+                               goto end;
+                       } else {
+                               cache_empty = false;
+                       }
+               } else {
+                       pthread_mutex_lock(&stream->chan->metadata_cache->lock);
+                       cache_empty = stream->chan->metadata_cache->contents.size ==
+                                       stream->ust_metadata_pushed;
+                       pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
                }
-       }
+       } while (!got_subbuffer);
 
+       /* Populate sub-buffer infos and view. */
        ret = get_next_subbuffer_common(stream, subbuffer);
        if (ret) {
                goto end;
        }
+
+       ret = lttng_ustconsumer_sample_snapshot_positions(stream);
+       if (ret < 0) {
+               /*
+                * -EAGAIN is not expected since we got a sub-buffer and haven't
+                * pushed the consumption position yet (on put_next).
+                */
+               PERROR("Failed to take a snapshot of metadata buffer positions");
+               goto end;
+       }
+
+       ret = lttng_ustconsumer_get_consumed_snapshot(stream, &consumed_pos);
+       if (ret) {
+               PERROR("Failed to get metadata consumed position");
+               goto end;
+       }
+
+       ret = lttng_ustconsumer_get_produced_snapshot(stream, &produced_pos);
+       if (ret) {
+               PERROR("Failed to get metadata produced position");
+               goto end;
+       }
+
+       /* Last sub-buffer of the ring buffer ? */
+       buffer_empty = (consumed_pos + stream->max_sb_size) == produced_pos;
+
+       /*
+        * The sessiond registry lock ensures that coherent units of metadata
+        * are pushed to the consumer daemon at once. Hence, if a sub-buffer is
+        * acquired, the cache is empty, and it is the only available sub-buffer
+        * available, it is safe to assume that it is "coherent".
+        */
+       coherent = got_subbuffer && cache_empty && buffer_empty;
+
+       LTTNG_OPTIONAL_SET(&subbuffer->info.metadata.coherent, coherent);
 end:
        return ret;
 }
@@ -2848,12 +3010,15 @@ static int put_next_subbuffer(struct lttng_consumer_stream *stream,
 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 void lttng_ustconsumer_set_stream_ops(
+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 =
@@ -2861,8 +3026,15 @@ static void lttng_ustconsumer_set_stream_ops(
                stream->read_subbuffer_ops.extract_subbuffer_info =
                                extract_metadata_subbuffer_info;
                stream->read_subbuffer_ops.reset_metadata =
-                               metadata_stream_reset_cache;
-               stream->read_subbuffer_ops.on_sleep = signal_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;
@@ -2876,6 +3048,8 @@ static void lttng_ustconsumer_set_stream_ops(
        }
 
        stream->read_subbuffer_ops.put_next_subbuffer = put_next_subbuffer;
+end:
+       return ret;
 }
 
 /*
@@ -2922,6 +3096,7 @@ int lttng_ustconsumer_data_pending(struct lttng_consumer_stream *stream)
 
        assert(stream);
        assert(stream->ustream);
+       ASSERT_LOCKED(stream->lock);
 
        DBG("UST consumer checking data pending");
 
@@ -2934,7 +3109,9 @@ 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;
 
                /*
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