Cleanup: Move `create_posix_shm()` to common/shm.c
[lttng-tools.git] / src / common / ust-consumer / ust-consumer.c
index b46a505021203a017832cec88826244f02895643..aede53658736e2037d8f90bb53b050c4bb2c2997 100644 (file)
@@ -7,7 +7,6 @@
  *
  */
 
-#include <stdint.h>
 #define _LGPL_SOURCE
 #include <assert.h>
 #include <lttng/ust-ctl.h>
@@ -24,6 +23,7 @@
 #include <urcu/list.h>
 #include <signal.h>
 #include <stdbool.h>
+#include <stdint.h>
 
 #include <bin/lttng-consumerd/health-consumerd.h>
 #include <common/common.h>
@@ -36,6 +36,9 @@
 #include <common/consumer/consumer-timer.h>
 #include <common/utils.h>
 #include <common/index/index.h>
+#include <common/consumer/consumer.h>
+#include <common/shm.h>
+#include <common/optional.h>
 
 #include "ust-consumer.h"
 
@@ -76,6 +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);
 }
 
@@ -111,26 +119,6 @@ error:
        return ret;
 }
 
-/*
- * Allocate and return a consumer channel object.
- */
-static struct lttng_consumer_channel *allocate_channel(uint64_t session_id,
-               const uint64_t *chunk_id, const char *pathname, const char *name,
-               uint64_t relayd_id, uint64_t key, enum lttng_event_output output,
-               uint64_t tracefile_size, uint64_t tracefile_count,
-               uint64_t session_id_per_pid, unsigned int monitor,
-               unsigned int live_timer_interval,
-               const char *root_shm_path, const char *shm_path)
-{
-       assert(pathname);
-       assert(name);
-
-       return consumer_allocate_channel(key, session_id, chunk_id, pathname,
-                       name, relayd_id, output, tracefile_size,
-                       tracefile_count, session_id_per_pid, monitor,
-                       live_timer_interval, root_shm_path, shm_path);
-}
-
 /*
  * Allocate and return a consumer stream object. If _alloc_ret is not NULL, the
  * error value if applicable is set in it else it is kept untouched.
@@ -147,7 +135,7 @@ static struct lttng_consumer_stream *allocate_stream(int cpu, int key,
        assert(channel);
        assert(ctx);
 
-       stream = consumer_allocate_stream(
+       stream = consumer_stream_create(
                        channel,
                        channel->key,
                        key,
@@ -365,48 +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)
 {
@@ -414,7 +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) {
@@ -422,7 +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;
@@ -500,8 +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);
                        }
@@ -510,8 +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);
@@ -1060,7 +1011,7 @@ static int snapshot_metadata(struct lttng_consumer_channel *metadata_channel,
        do {
                health_code_update();
 
-               ret = lttng_consumer_read_subbuffer(metadata_stream, ctx);
+               ret = lttng_consumer_read_subbuffer(metadata_stream, ctx, true);
                if (ret < 0) {
                        goto error_stream;
                }
@@ -1249,9 +1200,8 @@ 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,
-                                       stream, &subbuf_view, padded_len - len,
-                                       NULL);
+                       read_len = lttng_consumer_on_read_subbuffer_mmap(
+                                       stream, &subbuf_view, padded_len - len);
                        if (use_relayd) {
                                if (read_len != len) {
                                        ret = -EPERM;
@@ -1292,6 +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
@@ -1306,6 +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);
 
@@ -1329,9 +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;
                /*
@@ -1339,10 +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;
@@ -1475,24 +1469,26 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                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. */
-               channel = allocate_channel(msg.u.ask_channel.session_id,
+               channel = consumer_allocate_channel(
+                               msg.u.ask_channel.key,
+                               msg.u.ask_channel.session_id,
                                msg.u.ask_channel.chunk_id.is_set ?
                                                &chunk_id : NULL,
                                msg.u.ask_channel.pathname,
                                msg.u.ask_channel.name,
                                msg.u.ask_channel.relayd_id,
-                               msg.u.ask_channel.key,
                                (enum lttng_event_output) msg.u.ask_channel.output,
                                msg.u.ask_channel.tracefile_size,
                                msg.u.ask_channel.tracefile_count,
                                msg.u.ask_channel.session_id_per_pid,
                                msg.u.ask_channel.monitor,
                                msg.u.ask_channel.live_timer_interval,
+                               msg.u.ask_channel.is_live,
                                msg.u.ask_channel.root_shm_path,
                                msg.u.ask_channel.shm_path);
                if (!channel) {
@@ -1523,15 +1519,15 @@ 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
@@ -1539,9 +1535,9 @@ 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);
@@ -1555,7 +1551,7 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                        goto end_channel_error;
                }
 
-               if (msg.u.ask_channel.type == LTTNG_UST_CHAN_METADATA) {
+               if (msg.u.ask_channel.type == LTTNG_UST_ABI_CHAN_METADATA) {
                        ret = consumer_metadata_cache_allocate(channel);
                        if (ret < 0) {
                                ERR("Allocating metadata cache");
@@ -1588,7 +1584,7 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                 */
                ret = add_channel(channel, ctx);
                if (ret < 0) {
-                       if (msg.u.ask_channel.type == LTTNG_UST_CHAN_METADATA) {
+                       if (msg.u.ask_channel.type == LTTNG_UST_ABI_CHAN_METADATA) {
                                if (channel->switch_timer_enabled == 1) {
                                        consumer_timer_switch_stop(channel);
                                }
@@ -2084,8 +2080,8 @@ 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;
@@ -2193,6 +2189,28 @@ 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 *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 {
+                       /*
+                        * 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;
        }
@@ -2392,8 +2410,10 @@ 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);
                        }
@@ -2412,8 +2432,10 @@ 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);
@@ -2446,120 +2468,11 @@ int lttng_ustconsumer_close_wakeup_fd(struct lttng_consumer_stream *stream)
        return ustctl_stream_close_wakeup_fd(stream->ustream);
 }
 
-/*
- * Populate index values of a UST stream. Values are set in big endian order.
- *
- * Return 0 on success or else a negative value.
- */
-static int get_index_values(struct ctf_packet_index *index,
-               struct ustctl_consumer_stream *ustream)
-{
-       int ret;
-       uint64_t packet_size, content_size, timestamp_begin, timestamp_end,
-                       events_discarded, stream_id, stream_instance_id,
-                       packet_seq_num;
-
-       ret = ustctl_get_timestamp_begin(ustream, &timestamp_begin);
-       if (ret < 0) {
-               PERROR("ustctl_get_timestamp_begin");
-               goto error;
-       }
-
-       ret = ustctl_get_timestamp_end(ustream, &timestamp_end);
-       if (ret < 0) {
-               PERROR("ustctl_get_timestamp_end");
-               goto error;
-       }
-
-       ret = ustctl_get_events_discarded(ustream, &events_discarded);
-       if (ret < 0) {
-               PERROR("ustctl_get_events_discarded");
-               goto error;
-       }
-
-       ret = ustctl_get_content_size(ustream, &content_size);
-       if (ret < 0) {
-               PERROR("ustctl_get_content_size");
-               goto error;
-       }
-
-       ret = ustctl_get_packet_size(ustream, &packet_size);
-       if (ret < 0) {
-               PERROR("ustctl_get_packet_size");
-               goto error;
-       }
-
-       ret = ustctl_get_stream_id(ustream, &stream_id);
-       if (ret < 0) {
-               PERROR("ustctl_get_stream_id");
-               goto error;
-       }
-
-       ret = ustctl_get_instance_id(ustream, &stream_instance_id);
-       if (ret < 0) {
-               PERROR("ustctl_get_instance_id");
-               goto error;
-       }
-
-       ret = ustctl_get_sequence_number(ustream, &packet_seq_num);
-       if (ret < 0) {
-               PERROR("ustctl_get_sequence_number");
-               goto error;
-       }
-
-       *index = (typeof(*index)) {
-               .offset = index->offset,
-               .packet_size = htobe64(packet_size),
-               .content_size = htobe64(content_size),
-               .timestamp_begin = htobe64(timestamp_begin),
-               .timestamp_end = htobe64(timestamp_end),
-               .events_discarded = htobe64(events_discarded),
-               .stream_id = htobe64(stream_id),
-               .stream_instance_id = htobe64(stream_instance_id),
-               .packet_seq_num = htobe64(packet_seq_num),
-       };
-
-error:
-       return ret;
-}
-
-static
-void metadata_stream_reset_cache(struct lttng_consumer_stream *stream,
-               struct consumer_metadata_cache *cache)
-{
-       DBG("Metadata stream update to version %" PRIu64,
-                       cache->version);
-       stream->ust_metadata_pushed = 0;
-       stream->metadata_version = cache->version;
-       stream->reset_metadata_flag = 1;
-}
-
-/*
- * Check if the version of the metadata stream and metadata cache match.
- * If the cache got updated, reset the metadata stream.
- * The stream lock and metadata cache lock MUST be held.
- * Return 0 on success, a negative value on error.
- */
-static
-int metadata_stream_check_version(struct lttng_consumer_stream *stream)
-{
-       int ret = 0;
-       struct consumer_metadata_cache *cache = stream->chan->metadata_cache;
-
-       if (cache->version == stream->metadata_version) {
-               goto end;
-       }
-       metadata_stream_reset_cache(stream, cache);
-
-end:
-       return ret;
-}
-
 /*
  * 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)
@@ -2568,29 +2481,56 @@ int commit_one_metadata_packet(struct lttng_consumer_stream *stream)
        int ret;
 
        pthread_mutex_lock(&stream->chan->metadata_cache->lock);
-       ret = metadata_stream_check_version(stream);
-       if (ret < 0) {
-               goto end;
-       }
-       if (stream->chan->metadata_cache->max_offset
-                       == stream->ust_metadata_pushed) {
-               ret = 0;
-               goto end;
+       if (stream->chan->metadata_cache->contents.size ==
+                       stream->ust_metadata_pushed) {
+               /*
+                * In the context of a user space metadata channel, a
+                * change in version can be detected in two ways:
+                *   1) During the pre-consume of the `read_subbuffer` loop,
+                *   2) When populating the metadata ring buffer (i.e. here).
+                *
+                * This function is invoked when there is no metadata
+                * available in the ring-buffer. If all data was consumed
+                * up to the size of the metadata cache, there is no metadata
+                * to insert in the ring-buffer.
+                *
+                * However, the metadata version could still have changed (a
+                * regeneration without any new data will yield the same cache
+                * size).
+                *
+                * The cache's version is checked for a version change and the
+                * consumed position is reset if one occurred.
+                *
+                * This check is only necessary for the user space domain as
+                * it has to manage the cache explicitly. If this reset was not
+                * performed, no metadata would be consumed (and no reset would
+                * occur as part of the pre-consume) until the metadata size
+                * exceeded the cache size.
+                */
+               if (stream->metadata_version !=
+                               stream->chan->metadata_cache->version) {
+                       metadata_stream_reset_cache_consumed_position(stream);
+                       consumer_stream_metadata_set_version(stream,
+                                       stream->chan->metadata_cache->version);
+               } else {
+                       ret = 0;
+                       goto end;
+               }
        }
 
        write_len = ustctl_write_one_packet_to_channel(stream->chan->uchan,
-                       &stream->chan->metadata_cache->data[stream->ust_metadata_pushed],
-                       stream->chan->metadata_cache->max_offset
-                       - stream->ust_metadata_pushed);
+                       &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;
 
@@ -2616,15 +2556,13 @@ 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);
@@ -2639,6 +2577,7 @@ 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;
        }
 
@@ -2656,38 +2595,30 @@ 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;
 }
 
 /*
@@ -2741,289 +2672,333 @@ end:
        return ret;
 }
 
-static
-int update_stream_stats(struct lttng_consumer_stream *stream)
+static int consumer_stream_ust_on_wake_up(struct lttng_consumer_stream *stream)
 {
-       int ret;
-       uint64_t seq, discarded;
+       int ret = 0;
 
-       ret = ustctl_get_sequence_number(stream->ustream, &seq);
-       if (ret < 0) {
-               PERROR("ustctl_get_sequence_number");
-               goto end;
-       }
        /*
-        * Start the sequence when we extract the first packet in case we don't
-        * start at 0 (for example if a consumer is not connected to the
-        * session immediately after the beginning).
+        * We can consume the 1 byte written into the wait_fd by
+        * UST. Don't trigger error if we cannot read this one byte
+        * (read returns 0), or if the error is EAGAIN or EWOULDBLOCK.
+        *
+        * This is only done when the stream is monitored by a thread,
+        * before the flush is done after a hangup and if the stream
+        * is not flagged with data since there might be nothing to
+        * consume in the wait fd but still have data available
+        * flagged by the consumer wake up pipe.
         */
-       if (stream->last_sequence_number == -1ULL) {
-               stream->last_sequence_number = seq;
-       } else if (seq > stream->last_sequence_number) {
-               stream->chan->lost_packets += seq -
-                               stream->last_sequence_number - 1;
-       } else {
-               /* seq <= last_sequence_number */
-               ERR("Sequence number inconsistent : prev = %" PRIu64
-                               ", current = %" PRIu64,
-                               stream->last_sequence_number, seq);
-               ret = -1;
-               goto end;
+       if (stream->monitor && !stream->hangup_flush_done && !stream->has_data) {
+               char dummy;
+               ssize_t readlen;
+
+               readlen = lttng_read(stream->wait_fd, &dummy, 1);
+               if (readlen < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
+                       ret = readlen;
+               }
        }
-       stream->last_sequence_number = seq;
 
-       ret = ustctl_get_events_discarded(stream->ustream, &discarded);
-       if (ret < 0) {
-               PERROR("kernctl_get_events_discarded");
+       return ret;
+}
+
+static int extract_common_subbuffer_info(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuf)
+{
+       int ret;
+
+       ret = ustctl_get_subbuf_size(
+                       stream->ustream, &subbuf->info.data.subbuf_size);
+       if (ret) {
                goto end;
        }
-       if (discarded < stream->last_discarded_events) {
-               /*
-                * Overflow has occurred. We assume only one wrap-around
-                * has occurred.
-                */
-               stream->chan->discarded_events +=
-                               (1ULL << (CAA_BITS_PER_LONG - 1)) -
-                               stream->last_discarded_events + discarded;
-       } else {
-               stream->chan->discarded_events += discarded -
-                               stream->last_discarded_events;
+
+       ret = ustctl_get_padded_subbuf_size(
+                       stream->ustream, &subbuf->info.data.padded_subbuf_size);
+       if (ret) {
+               goto end;
        }
-       stream->last_discarded_events = discarded;
-       ret = 0;
 
 end:
        return ret;
 }
 
-/*
- * Read subbuffer from the given stream.
- *
- * Stream and channel locks MUST be acquired by the caller.
- *
- * Return 0 on success else a negative value.
- */
-int lttng_ustconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
-               struct lttng_consumer_local_data *ctx)
+static int extract_metadata_subbuffer_info(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuf)
 {
-       unsigned long len, subbuf_size, padding;
-       int err, write_index = 1, rotation_ret;
-       long ret = 0;
-       struct ustctl_consumer_stream *ustream;
-       struct ctf_packet_index index;
-       const char *subbuf_addr;
-       struct lttng_buffer_view subbuf_view;
+       int ret;
 
-       assert(stream);
-       assert(stream->ustream);
-       assert(ctx);
+       ret = extract_common_subbuffer_info(stream, subbuf);
+       if (ret) {
+               goto end;
+       }
 
-       DBG("In UST read_subbuffer (wait_fd: %d, name: %s)", stream->wait_fd,
-                       stream->name);
+       subbuf->info.metadata.version = stream->metadata_version;
 
-       /* Ease our life for what's next. */
-       ustream = stream->ustream;
+end:
+       return ret;
+}
 
-       /*
-        * We can consume the 1 byte written into the wait_fd by UST. Don't trigger
-        * error if we cannot read this one byte (read returns 0), or if the error
-        * is EAGAIN or EWOULDBLOCK.
-        *
-        * This is only done when the stream is monitored by a thread, before the
-        * flush is done after a hangup and if the stream is not flagged with data
-        * since there might be nothing to consume in the wait fd but still have
-        * data available flagged by the consumer wake up pipe.
-        */
-       if (stream->monitor && !stream->hangup_flush_done && !stream->has_data) {
-               char dummy;
-               ssize_t readlen;
+static int extract_data_subbuffer_info(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuf)
+{
+       int ret;
 
-               readlen = lttng_read(stream->wait_fd, &dummy, 1);
-               if (readlen < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
-                       ret = readlen;
-                       goto error;
-               }
+       ret = extract_common_subbuffer_info(stream, subbuf);
+       if (ret) {
+               goto end;
        }
 
-       /*
-        * If the stream was flagged to be ready for rotation before we extract the
-        * next packet, rotate it now.
-        */
-       if (stream->rotate_ready) {
-               DBG("Rotate stream before extracting data");
-               rotation_ret = lttng_consumer_rotate_stream(ctx, stream);
-               if (rotation_ret < 0) {
-                       ERR("Stream rotation error");
-                       ret = -1;
-                       goto error;
-               }
+       ret = ustctl_get_packet_size(
+                       stream->ustream, &subbuf->info.data.packet_size);
+       if (ret < 0) {
+               PERROR("Failed to get sub-buffer packet size");
+               goto end;
        }
 
-retry:
-       /* Get the next subbuffer */
-       err = ustctl_get_next_subbuf(ustream);
-       if (err != 0) {
-               /*
-                * Populate metadata info if the existing info has
-                * already been read.
-                */
-               if (stream->metadata_flag) {
-                       ret = commit_one_metadata_packet(stream);
-                       if (ret <= 0) {
-                               goto error;
-                       }
-                       goto retry;
-               }
+       ret = ustctl_get_content_size(
+                       stream->ustream, &subbuf->info.data.content_size);
+       if (ret < 0) {
+               PERROR("Failed to get sub-buffer content size");
+               goto end;
+       }
 
-               ret = err;      /* ustctl_get_next_subbuf returns negative, caller expect positive. */
-               /*
-                * This is a debug message even for single-threaded consumer,
-                * because poll() have more relaxed criterions than get subbuf,
-                * so get_subbuf may fail for short race windows where poll()
-                * would issue wakeups.
-                */
-               DBG("Reserving sub buffer failed (everything is normal, "
-                               "it is due to concurrency) [ret: %d]", err);
-               goto error;
+       ret = ustctl_get_timestamp_begin(
+                       stream->ustream, &subbuf->info.data.timestamp_begin);
+       if (ret < 0) {
+               PERROR("Failed to get sub-buffer begin timestamp");
+               goto end;
        }
-       assert(stream->chan->output == CONSUMER_CHANNEL_MMAP);
 
-       if (!stream->metadata_flag) {
-               index.offset = htobe64(stream->out_fd_offset);
-               ret = get_index_values(&index, ustream);
-               if (ret < 0) {
-                       err = ustctl_put_subbuf(ustream);
-                       assert(err == 0);
-                       goto error;
-               }
+       ret = ustctl_get_timestamp_end(
+                       stream->ustream, &subbuf->info.data.timestamp_end);
+       if (ret < 0) {
+               PERROR("Failed to get sub-buffer end timestamp");
+               goto end;
+       }
 
-               /* Update the stream's sequence and discarded events count. */
-               ret = update_stream_stats(stream);
-               if (ret < 0) {
-                       PERROR("kernctl_get_events_discarded");
-                       err = ustctl_put_subbuf(ustream);
-                       assert(err == 0);
-                       goto error;
+       ret = ustctl_get_events_discarded(
+                       stream->ustream, &subbuf->info.data.events_discarded);
+       if (ret) {
+               PERROR("Failed to get sub-buffer events discarded count");
+               goto end;
+       }
+
+       ret = ustctl_get_sequence_number(stream->ustream,
+                       &subbuf->info.data.sequence_number.value);
+       if (ret) {
+               /* May not be supported by older LTTng-modules. */
+               if (ret != -ENOTTY) {
+                       PERROR("Failed to get sub-buffer sequence number");
+                       goto end;
                }
        } else {
-               write_index = 0;
+               subbuf->info.data.sequence_number.is_set = true;
        }
 
-       /* Get the full padded subbuffer size */
-       err = ustctl_get_padded_subbuf_size(ustream, &len);
-       assert(err == 0);
+       ret = ustctl_get_stream_id(
+                       stream->ustream, &subbuf->info.data.stream_id);
+       if (ret < 0) {
+               PERROR("Failed to get stream id");
+               goto end;
+       }
 
-       /* Get subbuffer data size (without padding) */
-       err = ustctl_get_subbuf_size(ustream, &subbuf_size);
-       assert(err == 0);
+       ret = ustctl_get_instance_id(stream->ustream,
+                       &subbuf->info.data.stream_instance_id.value);
+       if (ret) {
+               /* May not be supported by older LTTng-modules. */
+               if (ret != -ENOTTY) {
+                       PERROR("Failed to get stream instance id");
+                       goto end;
+               }
+       } else {
+               subbuf->info.data.stream_instance_id.is_set = true;
+       }
+end:
+       return ret;
+}
 
-       /* Make sure we don't get a subbuffer size bigger than the padded */
-       assert(len >= subbuf_size);
+static int get_next_subbuffer_common(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuffer)
+{
+       int ret;
+       const char *addr;
 
-       padding = len - subbuf_size;
+       ret = stream->read_subbuffer_ops.extract_subbuffer_info(
+                       stream, subbuffer);
+       if (ret) {
+               goto end;
+       }
 
-       ret = get_current_subbuf_addr(stream, &subbuf_addr);
+       ret = get_current_subbuf_addr(stream, &addr);
        if (ret) {
-               write_index = 0;
-               goto error_put_subbuf;
+               goto end;
        }
 
-       subbuf_view = lttng_buffer_view_init(subbuf_addr, 0, len);
+       subbuffer->buffer.buffer = lttng_buffer_view_init(
+                       addr, 0, subbuffer->info.data.padded_subbuf_size);
+       assert(subbuffer->buffer.buffer.data != NULL);
+end:
+       return ret;
+}
 
-       /* write the subbuffer to the tracefile */
-       ret = lttng_consumer_on_read_subbuffer_mmap(
-                       ctx, stream, &subbuf_view, 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)) {
-               /*
-                * Display the error but continue processing to try to release the
-                * subbuffer. This is a DBG statement since any unexpected kill or
-                * signal, the application gets unregistered, relayd gets closed or
-                * anything that affects the buffer lifetime will trigger this error.
-                * So, for the sake of the user, don't print this error since it can
-                * happen and it is OK with the code flow.
-                */
-               DBG("Error writing to tracefile "
-                               "(ret: %ld != len: %lu != subbuf_size: %lu)",
-                               ret, len, subbuf_size);
-               write_index = 0;
-       }
-error_put_subbuf:
-       err = ustctl_put_next_subbuf(ustream);
-       assert(err == 0);
+static int get_next_subbuffer(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuffer)
+{
+       int ret;
 
-       /*
-        * This will consumer the byte on the wait_fd if and only if there is not
-        * next subbuffer to be acquired.
-        */
-       if (!stream->metadata_flag) {
-               ret = notify_if_more_data(stream, ctx);
-               if (ret < 0) {
-                       goto error;
-               }
+       ret = ustctl_get_next_subbuf(stream->ustream);
+       if (ret) {
+               goto end;
        }
 
-       /* Write index if needed. */
-       if (!write_index) {
-               goto rotate;
+       ret = get_next_subbuffer_common(stream, subbuffer);
+       if (ret) {
+               goto end;
        }
+end:
+       return ret;
+}
+
+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;
+
+       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;
+                       }
+               }
 
-       if (stream->chan->live_timer_interval && !stream->metadata_flag) {
                /*
-                * In live, block until all the metadata is sent.
+                * Determine if the cache is empty and ensure that a sub-buffer
+                * is made available if the cache is not empty.
                 */
-               pthread_mutex_lock(&stream->metadata_timer_lock);
-               assert(!stream->missed_metadata_flush);
-               stream->waiting_on_metadata = true;
-               pthread_mutex_unlock(&stream->metadata_timer_lock);
-
-               err = consumer_stream_sync_metadata(ctx, stream->session_id);
-
-               pthread_mutex_lock(&stream->metadata_timer_lock);
-               stream->waiting_on_metadata = false;
-               if (stream->missed_metadata_flush) {
-                       stream->missed_metadata_flush = false;
-                       pthread_mutex_unlock(&stream->metadata_timer_lock);
-                       (void) consumer_flush_ust_index(stream);
+               if (!got_subbuffer) {
+                       ret = commit_one_metadata_packet(stream);
+                       if (ret < 0 && ret != -ENOBUFS) {
+                               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_unlock(&stream->metadata_timer_lock);
+                       pthread_mutex_lock(&stream->chan->metadata_cache->lock);
+                       cache_empty = stream->chan->metadata_cache->contents.size ==
+                                       stream->ust_metadata_pushed;
+                       pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
                }
+       } while (!got_subbuffer);
 
-               if (err < 0) {
-                       goto error;
-               }
+       /* Populate sub-buffer infos and view. */
+       ret = get_next_subbuffer_common(stream, subbuffer);
+       if (ret) {
+               goto end;
        }
 
-       assert(!stream->metadata_flag);
-       err = consumer_stream_write_index(stream, &index);
-       if (err < 0) {
-               goto error;
+       ret = lttng_ustconsumer_sample_snapshot_positions(stream);
+       if (ret < 0) {
+               /*
+                * -EAGAIN is not expected since we got a sub-buffer and haven't
+                * pushed the consumption position yet (on put_next).
+                */
+               PERROR("Failed to take a snapshot of metadata buffer positions");
+               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;
        }
 
-rotate:
+       /* Last sub-buffer of the ring buffer ? */
+       buffer_empty = (consumed_pos + stream->max_sb_size) == produced_pos;
+
        /*
-        * After extracting the packet, we check if the stream is now ready to be
-        * rotated and perform the action immediately.
+        * The sessiond registry lock ensures that coherent units of metadata
+        * are pushed to the consumer daemon at once. Hence, if a sub-buffer is
+        * acquired, the cache is empty, and it is the only available sub-buffer
+        * available, it is safe to assume that it is "coherent".
         */
-       rotation_ret = lttng_consumer_stream_is_rotate_ready(stream);
-       if (rotation_ret == 1) {
-               rotation_ret = lttng_consumer_rotate_stream(ctx, stream);
-               if (rotation_ret < 0) {
-                       ERR("Stream rotation error");
-                       ret = -1;
-                       goto error;
+       coherent = got_subbuffer && cache_empty && buffer_empty;
+
+       LTTNG_OPTIONAL_SET(&subbuffer->info.metadata.coherent, coherent);
+end:
+       return ret;
+}
+
+static int put_next_subbuffer(struct lttng_consumer_stream *stream,
+               struct stream_subbuffer *subbuffer)
+{
+       const int ret = ustctl_put_next_subbuf(stream->ustream);
+
+       assert(ret == 0);
+       return ret;
+}
+
+static int signal_metadata(struct lttng_consumer_stream *stream,
+               struct lttng_consumer_local_data *ctx)
+{
+       ASSERT_LOCKED(stream->metadata_rdv_lock);
+       return pthread_cond_broadcast(&stream->metadata_rdv) ? -errno : 0;
+}
+
+static int lttng_ustconsumer_set_stream_ops(
+               struct lttng_consumer_stream *stream)
+{
+       int ret = 0;
+
+       stream->read_subbuffer_ops.on_wake_up = consumer_stream_ust_on_wake_up;
+       if (stream->metadata_flag) {
+               stream->read_subbuffer_ops.get_next_subbuffer =
+                               get_next_subbuffer_metadata;
+               stream->read_subbuffer_ops.extract_subbuffer_info =
+                               extract_metadata_subbuffer_info;
+               stream->read_subbuffer_ops.reset_metadata =
+                               metadata_stream_reset_cache_consumed_position;
+               if (stream->chan->is_live) {
+                       stream->read_subbuffer_ops.on_sleep = signal_metadata;
+                       ret = consumer_stream_enable_metadata_bucketization(
+                                       stream);
+                       if (ret) {
+                               goto end;
+                       }
+               }
+       } else {
+               stream->read_subbuffer_ops.get_next_subbuffer =
+                               get_next_subbuffer;
+               stream->read_subbuffer_ops.extract_subbuffer_info =
+                               extract_data_subbuffer_info;
+               stream->read_subbuffer_ops.on_sleep = notify_if_more_data;
+               if (stream->chan->is_live) {
+                       stream->read_subbuffer_ops.send_live_beacon =
+                                       consumer_flush_ust_index;
                }
-       } else if (rotation_ret < 0) {
-               ERR("Checking if stream is ready to rotate");
-               ret = -1;
-               goto error;
        }
-error:
+
+       stream->read_subbuffer_ops.put_next_subbuffer = put_next_subbuffer;
+end:
        return ret;
 }
 
@@ -3049,6 +3024,8 @@ int lttng_ustconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
                        goto error;
                }
        }
+
+       lttng_ustconsumer_set_stream_ops(stream);
        ret = 0;
 
 error:
@@ -3069,6 +3046,7 @@ 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");
 
@@ -3081,7 +3059,9 @@ 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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