Implement consumer ring buffer position sampling
[lttng-tools.git] / src / common / ust-consumer / ust-consumer.c
index df12f6b8746de71a4a1ef952359abe2158268733..147fe8aafe899a092a91ee8be58357786d7f074f 100644 (file)
@@ -1,6 +1,7 @@
 /*
  * Copyright (C) 2011 - Julien Desfossez <julien.desfossez@polymtl.ca>
  *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (C) 2017 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License, version 2 only,
@@ -16,7 +17,6 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#define _GNU_SOURCE
 #define _LGPL_SOURCE
 #include <assert.h>
 #include <lttng/ust-ctl.h>
 #include <common/relayd/relayd.h>
 #include <common/compat/fcntl.h>
 #include <common/compat/endian.h>
-#include <common/consumer-metadata-cache.h>
-#include <common/consumer-stream.h>
-#include <common/consumer-timer.h>
+#include <common/consumer/consumer-metadata-cache.h>
+#include <common/consumer/consumer-stream.h>
+#include <common/consumer/consumer-timer.h>
 #include <common/utils.h>
 #include <common/index/index.h>
 
 #include "ust-consumer.h"
 
-#define UINT_MAX_STR_LEN 11    /* includes \0 */
+#define INT_MAX_STR_LEN 12     /* includes \0 */
 
 extern struct lttng_consumer_global_data consumer_data;
 extern int consumer_poll_timeout;
@@ -82,6 +82,7 @@ static void destroy_channel(struct lttng_consumer_channel *channel)
         */
        if (channel->uchan) {
                lttng_ustconsumer_del_channel(channel);
+               lttng_ustconsumer_free_channel(channel);
        }
        free(channel);
 }
@@ -247,14 +248,14 @@ error:
 static
 int get_stream_shm_path(char *stream_shm_path, const char *shm_path, int cpu)
 {
-       char cpu_nr[UINT_MAX_STR_LEN];  /* unsigned int max len */
+       char cpu_nr[INT_MAX_STR_LEN];  /* int max len */
        int ret;
 
        strncpy(stream_shm_path, shm_path, PATH_MAX);
        stream_shm_path[PATH_MAX - 1] = '\0';
-       ret = snprintf(cpu_nr, UINT_MAX_STR_LEN, "%u", cpu);
-       if (ret != 1) {
-               ret = -1;
+       ret = snprintf(cpu_nr, INT_MAX_STR_LEN, "%i", cpu);
+       if (ret < 0) {
+               PERROR("snprintf");
                goto end;
        }
        strncat(stream_shm_path, cpu_nr,
@@ -504,14 +505,13 @@ error_open:
                        closeret = run_as_unlink(shm_path,
                                        channel->uid, channel->gid);
                        if (closeret) {
-                               errno = -closeret;
                                PERROR("unlink %s", shm_path);
                        }
                }
        }
        /* Try to rmdir all directories under shm_path root. */
        if (channel->root_shm_path[0]) {
-               (void) run_as_recursive_rmdir(channel->root_shm_path,
+               (void) run_as_rmdir_recursive(channel->root_shm_path,
                                channel->uid, channel->gid);
        }
        free(stream_fds);
@@ -768,7 +768,54 @@ static int flush_channel(uint64_t chan_key)
 
                health_code_update();
 
-               ustctl_flush_buffer(stream->ustream, 1);
+               pthread_mutex_lock(&stream->lock);
+               if (!stream->quiescent) {
+                       ustctl_flush_buffer(stream->ustream, 0);
+                       stream->quiescent = true;
+               }
+               pthread_mutex_unlock(&stream->lock);
+       }
+error:
+       rcu_read_unlock();
+       return ret;
+}
+
+/*
+ * Clear quiescent state from channel's streams using the given key to
+ * retrieve the channel.
+ *
+ * Return 0 on success else an LTTng error code.
+ */
+static int clear_quiescent_channel(uint64_t chan_key)
+{
+       int ret = 0;
+       struct lttng_consumer_channel *channel;
+       struct lttng_consumer_stream *stream;
+       struct lttng_ht *ht;
+       struct lttng_ht_iter iter;
+
+       DBG("UST consumer clear quiescent channel key %" PRIu64, chan_key);
+
+       rcu_read_lock();
+       channel = consumer_find_channel(chan_key);
+       if (!channel) {
+               ERR("UST consumer clear quiescent channel %" PRIu64 " not found", chan_key);
+               ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
+               goto error;
+       }
+
+       ht = consumer_data.stream_per_chan_id_ht;
+
+       /* For each stream of the channel id, clear quiescent state. */
+       cds_lfht_for_each_entry_duplicate(ht->ht,
+                       ht->hash_fct(&channel->key, lttng_ht_seed), ht->match_fct,
+                       &channel->key, &iter.iter, stream, node_channel_id.node) {
+
+               health_code_update();
+
+               pthread_mutex_lock(&stream->lock);
+               stream->quiescent = false;
+               pthread_mutex_unlock(&stream->lock);
        }
 error:
        rcu_read_unlock();
@@ -1030,6 +1077,8 @@ static int snapshot_channel(uint64_t key, char *path, uint64_t relayd_id,
        DBG("UST consumer snapshot channel %" PRIu64, key);
 
        cds_list_for_each_entry(stream, &channel->streams.head, send_node) {
+               /* Are we at a position _before_ the first available packet ? */
+               bool before_first_packet = true;
 
                health_code_update();
 
@@ -1063,7 +1112,13 @@ static int snapshot_channel(uint64_t key, char *path, uint64_t relayd_id,
                        }
                }
 
-               ustctl_flush_buffer(stream->ustream, 1);
+               /*
+                * If tracing is active, we want to perform a "full" buffer flush.
+                * Else, if quiescent, it has already been done by the prior stop.
+                */
+               if (!stream->quiescent) {
+                       ustctl_flush_buffer(stream->ustream, 0);
+               }
 
                ret = lttng_ustconsumer_take_snapshot(stream);
                if (ret < 0) {
@@ -1096,6 +1151,7 @@ static int snapshot_channel(uint64_t key, char *path, uint64_t relayd_id,
                while (consumed_pos < produced_pos) {
                        ssize_t read_len;
                        unsigned long len, padded_len;
+                       int lost_packet = 0;
 
                        health_code_update();
 
@@ -1109,6 +1165,15 @@ static int snapshot_channel(uint64_t key, char *path, uint64_t relayd_id,
                                }
                                DBG("UST consumer get subbuf failed. Skipping it.");
                                consumed_pos += stream->max_sb_size;
+
+                               /*
+                                * Start accounting lost packets only when we
+                                * already have extracted packets (to match the
+                                * content of the final snapshot).
+                                */
+                               if (!before_first_packet) {
+                                       lost_packet = 1;
+                               }
                                continue;
                        }
 
@@ -1144,6 +1209,16 @@ static int snapshot_channel(uint64_t key, char *path, uint64_t relayd_id,
                                goto error_close_stream;
                        }
                        consumed_pos += stream->max_sb_size;
+
+                       /*
+                        * Only account lost packets located between
+                        * succesfully extracted packets (do not account before
+                        * and after since they are not visible in the
+                        * resulting snapshot).
+                        */
+                       stream->chan->lost_packets += lost_packet;
+                       lost_packet = 0;
+                       before_first_packet = false;
                }
 
                /* Simply close the stream so we can use it on the next snapshot. */
@@ -1168,11 +1243,16 @@ error:
 }
 
 /*
- * Receive the metadata updates from the sessiond.
+ * Receive the metadata updates from the sessiond. Supports receiving
+ * overlapping metadata, but is needs to always belong to a contiguous
+ * range starting from 0.
+ * Be careful about the locks held when calling this function: it needs
+ * the metadata cache flush to concurrently progress in order to
+ * complete.
  */
 int lttng_ustconsumer_recv_metadata(int sock, uint64_t key, uint64_t offset,
-               uint64_t len, struct lttng_consumer_channel *channel,
-               int timer, int wait)
+               uint64_t len, uint64_t version,
+               struct lttng_consumer_channel *channel, int timer, int wait)
 {
        int ret, ret_code = LTTCOMM_CONSUMERD_SUCCESS;
        char *metadata_str;
@@ -1199,7 +1279,8 @@ 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, metadata_str);
+       ret = consumer_metadata_cache_write(channel, offset, len, version,
+                       metadata_str);
        if (ret < 0) {
                /* Unable to handle metadata. Notify session daemon. */
                ret_code = LTTCOMM_CONSUMERD_ERROR_METADATA;
@@ -1421,8 +1502,17 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                        consumer_timer_switch_start(channel, attr.switch_timer_interval);
                        attr.switch_timer_interval = 0;
                } else {
+                       int monitor_start_ret;
+
                        consumer_timer_live_start(channel,
                                        msg.u.ask_channel.live_timer_interval);
+                       monitor_start_ret = consumer_timer_monitor_start(
+                                       channel,
+                                       msg.u.ask_channel.monitor_timer_interval);
+                       if (monitor_start_ret < 0) {
+                               ERR("Starting channel monitoring timer failed");
+                               goto end_channel_error;
+                       }
                }
 
                health_code_update();
@@ -1445,6 +1535,9 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                        if (channel->live_timer_enabled == 1) {
                                consumer_timer_live_stop(channel);
                        }
+                       if (channel->monitor_timer_enabled == 1) {
+                               consumer_timer_monitor_stop(channel);
+                       }
                        goto end_channel_error;
                }
 
@@ -1555,12 +1648,25 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 
                goto end_msg_sessiond;
        }
+       case LTTNG_CONSUMER_CLEAR_QUIESCENT_CHANNEL:
+       {
+               int ret;
+
+               ret = clear_quiescent_channel(
+                               msg.u.clear_quiescent_channel.key);
+               if (ret != 0) {
+                       ret_code = ret;
+               }
+
+               goto end_msg_sessiond;
+       }
        case LTTNG_CONSUMER_PUSH_METADATA:
        {
                int ret;
                uint64_t len = msg.u.push_metadata.len;
                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;
 
                DBG("UST consumer push metadata key %" PRIu64 " of len %" PRIu64, key,
@@ -1582,6 +1688,15 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 
                health_code_update();
 
+               if (!len) {
+                       /*
+                        * There is nothing to receive. We have simply
+                        * checked whether the channel can be found.
+                        */
+                       ret_code = LTTCOMM_CONSUMERD_SUCCESS;
+                       goto end_msg_sessiond;
+               }
+
                /* Tell session daemon we are ready to receive the metadata. */
                ret = consumer_send_status_msg(sock, LTTCOMM_CONSUMERD_SUCCESS);
                if (ret < 0) {
@@ -1602,7 +1717,7 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                health_code_update();
 
                ret = lttng_ustconsumer_recv_metadata(sock, key, offset,
-                               len, channel, 0, 1);
+                               len, version, channel, 0, 1);
                if (ret < 0) {
                        /* error receiving from sessiond */
                        goto error_fatal;
@@ -1653,6 +1768,153 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                health_code_update();
                break;
        }
+       case LTTNG_CONSUMER_DISCARDED_EVENTS:
+       {
+               int ret = 0;
+               uint64_t discarded_events;
+               struct lttng_ht_iter iter;
+               struct lttng_ht *ht;
+               struct lttng_consumer_stream *stream;
+               uint64_t id = msg.u.discarded_events.session_id;
+               uint64_t key = msg.u.discarded_events.channel_key;
+
+               DBG("UST consumer discarded events command for session id %"
+                               PRIu64, id);
+               rcu_read_lock();
+               pthread_mutex_lock(&consumer_data.lock);
+
+               ht = consumer_data.stream_list_ht;
+
+               /*
+                * We only need a reference to the channel, but they are not
+                * directly indexed, so we just use the first matching stream
+                * to extract the information we need, we default to 0 if not
+                * found (no events are dropped if the channel is not yet in
+                * use).
+                */
+               discarded_events = 0;
+               cds_lfht_for_each_entry_duplicate(ht->ht,
+                               ht->hash_fct(&id, lttng_ht_seed),
+                               ht->match_fct, &id,
+                               &iter.iter, stream, node_session_id.node) {
+                       if (stream->chan->key == key) {
+                               discarded_events = stream->chan->discarded_events;
+                               break;
+                       }
+               }
+               pthread_mutex_unlock(&consumer_data.lock);
+               rcu_read_unlock();
+
+               DBG("UST consumer discarded events command for session id %"
+                               PRIu64 ", channel key %" PRIu64, id, key);
+
+               health_code_update();
+
+               /* Send back returned value to session daemon */
+               ret = lttcomm_send_unix_sock(sock, &discarded_events, sizeof(discarded_events));
+               if (ret < 0) {
+                       PERROR("send discarded events");
+                       goto error_fatal;
+               }
+
+               break;
+       }
+       case LTTNG_CONSUMER_LOST_PACKETS:
+       {
+               int ret;
+               uint64_t lost_packets;
+               struct lttng_ht_iter iter;
+               struct lttng_ht *ht;
+               struct lttng_consumer_stream *stream;
+               uint64_t id = msg.u.lost_packets.session_id;
+               uint64_t key = msg.u.lost_packets.channel_key;
+
+               DBG("UST consumer lost packets command for session id %"
+                               PRIu64, id);
+               rcu_read_lock();
+               pthread_mutex_lock(&consumer_data.lock);
+
+               ht = consumer_data.stream_list_ht;
+
+               /*
+                * We only need a reference to the channel, but they are not
+                * directly indexed, so we just use the first matching stream
+                * to extract the information we need, we default to 0 if not
+                * found (no packets lost if the channel is not yet in use).
+                */
+               lost_packets = 0;
+               cds_lfht_for_each_entry_duplicate(ht->ht,
+                               ht->hash_fct(&id, lttng_ht_seed),
+                               ht->match_fct, &id,
+                               &iter.iter, stream, node_session_id.node) {
+                       if (stream->chan->key == key) {
+                               lost_packets = stream->chan->lost_packets;
+                               break;
+                       }
+               }
+               pthread_mutex_unlock(&consumer_data.lock);
+               rcu_read_unlock();
+
+               DBG("UST consumer lost packets command for session id %"
+                               PRIu64 ", channel key %" PRIu64, id, key);
+
+               health_code_update();
+
+               /* Send back returned value to session daemon */
+               ret = lttcomm_send_unix_sock(sock, &lost_packets,
+                               sizeof(lost_packets));
+               if (ret < 0) {
+                       PERROR("send lost packets");
+                       goto error_fatal;
+               }
+
+               break;
+       }
+       case LTTNG_CONSUMER_SET_CHANNEL_MONITOR_PIPE:
+       {
+               int channel_monitor_pipe;
+
+               ret_code = LTTCOMM_CONSUMERD_SUCCESS;
+               /* Successfully received the command's type. */
+               ret = consumer_send_status_msg(sock, ret_code);
+               if (ret < 0) {
+                       goto error_fatal;
+               }
+
+               ret = lttcomm_recv_fds_unix_sock(sock, &channel_monitor_pipe,
+                               1);
+               if (ret != 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) {
+                       int flags;
+
+                       ret_code = LTTCOMM_CONSUMERD_SUCCESS;
+                       /* Set the pipe as non-blocking. */
+                       ret = fcntl(channel_monitor_pipe, F_GETFL, 0);
+                       if (ret == -1) {
+                               PERROR("fcntl get flags of the channel monitoring pipe");
+                               goto error_fatal;
+                       }
+                       flags = ret;
+
+                       ret = fcntl(channel_monitor_pipe, F_SETFL,
+                                       flags | O_NONBLOCK);
+                       if (ret == -1) {
+                               PERROR("fcntl set O_NONBLOCK flag of the channel monitoring pipe");
+                               goto error_fatal;
+                       }
+                       DBG("Channel monitor pipe set as non-blocking");
+               } else {
+                       ret_code = LTTCOMM_CONSUMERD_ALREADY_SET;
+               }
+               goto end_msg_sessiond;
+       }
        default:
                break;
        }
@@ -1734,7 +1996,7 @@ void *lttng_ustctl_get_mmap_base(struct lttng_consumer_stream *stream)
 }
 
 /*
- * Take a snapshot for a specific fd
+ * Take a snapshot for a specific stream.
  *
  * Returns 0 on success, < 0 on error
  */
@@ -1746,6 +2008,20 @@ int lttng_ustconsumer_take_snapshot(struct lttng_consumer_stream *stream)
        return ustctl_snapshot(stream->ustream);
 }
 
+/*
+ * Sample consumed and produced positions for a specific stream.
+ *
+ * Returns 0 on success, < 0 on error.
+ */
+int lttng_ustconsumer_sample_snapshot_positions(
+               struct lttng_consumer_stream *stream)
+{
+       assert(stream);
+       assert(stream->ustream);
+
+       return ustctl_snapshot_sample_positions(stream->ustream);
+}
+
 /*
  * Get the produced position
  *
@@ -1795,15 +2071,30 @@ int lttng_ustconsumer_get_current_timestamp(
        return ustctl_get_current_timestamp(stream->ustream, ts);
 }
 
+int lttng_ustconsumer_get_sequence_number(
+               struct lttng_consumer_stream *stream, uint64_t *seq)
+{
+       assert(stream);
+       assert(stream->ustream);
+       assert(seq);
+
+       return ustctl_get_sequence_number(stream->ustream, seq);
+}
+
 /*
- * Called when the stream signal the consumer that it has hang up.
+ * Called when the stream signals the consumer that it has hung up.
  */
 void lttng_ustconsumer_on_stream_hangup(struct lttng_consumer_stream *stream)
 {
        assert(stream);
        assert(stream->ustream);
 
-       ustctl_flush_buffer(stream->ustream, 0);
+       pthread_mutex_lock(&stream->lock);
+       if (!stream->quiescent) {
+               ustctl_flush_buffer(stream->ustream, 0);
+               stream->quiescent = true;
+       }
+       pthread_mutex_unlock(&stream->lock);
        stream->hangup_flush_done = 1;
 }
 
@@ -1817,8 +2108,6 @@ void lttng_ustconsumer_del_channel(struct lttng_consumer_channel *chan)
        if (chan->switch_timer_enabled == 1) {
                consumer_timer_switch_stop(chan);
        }
-       consumer_metadata_cache_destroy(chan);
-       ustctl_destroy_channel(chan->uchan);
        for (i = 0; i < chan->nr_stream_fds; i++) {
                int ret;
 
@@ -1835,17 +2124,25 @@ void lttng_ustconsumer_del_channel(struct lttng_consumer_channel *chan)
                        }
                        ret = run_as_unlink(shm_path, chan->uid, chan->gid);
                        if (ret) {
-                               errno = -ret;
                                PERROR("unlink %s", shm_path);
                        }
                }
        }
-       free(chan->stream_fds);
+}
+
+void lttng_ustconsumer_free_channel(struct lttng_consumer_channel *chan)
+{
+       assert(chan);
+       assert(chan->uchan);
+
+       consumer_metadata_cache_destroy(chan);
+       ustctl_destroy_channel(chan->uchan);
        /* Try to rmdir all directories under shm_path root. */
        if (chan->root_shm_path[0]) {
-               (void) run_as_recursive_rmdir(chan->root_shm_path,
+               (void) run_as_rmdir_recursive(chan->root_shm_path,
                                chan->uid, chan->gid);
        }
+       free(chan->stream_fds);
 }
 
 void lttng_ustconsumer_del_stream(struct lttng_consumer_stream *stream)
@@ -1927,10 +2224,56 @@ static int get_index_values(struct ctf_packet_index *index,
        }
        index->stream_id = htobe64(index->stream_id);
 
+       ret = ustctl_get_instance_id(ustream, &index->stream_instance_id);
+       if (ret < 0) {
+               PERROR("ustctl_get_instance_id");
+               goto error;
+       }
+       index->stream_instance_id = htobe64(index->stream_instance_id);
+
+       ret = ustctl_get_sequence_number(ustream, &index->packet_seq_num);
+       if (ret < 0) {
+               PERROR("ustctl_get_sequence_number");
+               goto error;
+       }
+       index->packet_seq_num = htobe64(index->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.
  *
@@ -1944,7 +2287,11 @@ 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->contiguous
+       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;
@@ -1952,7 +2299,7 @@ int commit_one_metadata_packet(struct lttng_consumer_stream *stream)
 
        write_len = ustctl_write_one_packet_to_channel(stream->chan->uchan,
                        &stream->chan->metadata_cache->data[stream->ust_metadata_pushed],
-                       stream->chan->metadata_cache->contiguous
+                       stream->chan->metadata_cache->max_offset
                        - stream->ust_metadata_pushed);
        assert(write_len != 0);
        if (write_len < 0) {
@@ -1962,7 +2309,7 @@ int commit_one_metadata_packet(struct lttng_consumer_stream *stream)
        }
        stream->ust_metadata_pushed += write_len;
 
-       assert(stream->chan->metadata_cache->contiguous >=
+       assert(stream->chan->metadata_cache->max_offset >=
                        stream->ust_metadata_pushed);
        ret = write_len;
 
@@ -1976,7 +2323,9 @@ end:
  * Sync metadata meaning request them to the session daemon and snapshot to the
  * metadata thread can consumer them.
  *
- * Metadata stream lock MUST be acquired.
+ * Metadata stream lock is held here, but we need to release it when
+ * interacting with sessiond, else we cause a deadlock with live
+ * awaiting on metadata to be pushed out.
  *
  * Return 0 if new metadatda is available, EAGAIN if the metadata stream
  * is empty or a negative value on error.
@@ -1990,11 +2339,13 @@ int lttng_ustconsumer_sync_metadata(struct lttng_consumer_local_data *ctx,
        assert(ctx);
        assert(metadata);
 
+       pthread_mutex_unlock(&metadata->lock);
        /*
         * Request metadata from the sessiond, but don't wait for the flush
         * because we locked the metadata thread.
         */
        ret = lttng_ustconsumer_request_metadata(ctx, metadata->chan, 0, 0);
+       pthread_mutex_lock(&metadata->lock);
        if (ret < 0) {
                goto end;
        }
@@ -2081,6 +2432,61 @@ end:
        return ret;
 }
 
+static
+int update_stream_stats(struct lttng_consumer_stream *stream)
+{
+       int ret;
+       uint64_t seq, discarded;
+
+       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).
+        */
+       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;
+       }
+       stream->last_sequence_number = seq;
+
+       ret = ustctl_get_events_discarded(stream->ustream, &discarded);
+       if (ret < 0) {
+               PERROR("kernctl_get_events_discarded");
+               goto end;
+       }
+       if (discarded < stream->last_discarded_events) {
+               /*
+                * Overflow has occurred. We assume only one wrap-around
+                * has occurred.
+                */
+               stream->chan->discarded_events +=
+                               (1ULL << (CAA_BITS_PER_LONG - 1)) -
+                               stream->last_discarded_events + discarded;
+       } else {
+               stream->chan->discarded_events += discarded -
+                               stream->last_discarded_events;
+       }
+       stream->last_discarded_events = discarded;
+       ret = 0;
+
+end:
+       return ret;
+}
+
 /*
  * Read subbuffer from the given stream.
  *
@@ -2162,6 +2568,17 @@ retry:
                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 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 end;
                }
        } else {
@@ -2224,7 +2641,23 @@ retry:
                /*
                 * In live, block until all the metadata is sent.
                 */
+               pthread_mutex_lock(&stream->metadata_timer_lock);
+               assert(!stream->missed_metadata_flush);
+               stream->waiting_on_metadata = true;
+               pthread_mutex_unlock(&stream->metadata_timer_lock);
+
                err = consumer_stream_sync_metadata(ctx, stream->session_id);
+
+               pthread_mutex_lock(&stream->metadata_timer_lock);
+               stream->waiting_on_metadata = false;
+               if (stream->missed_metadata_flush) {
+                       stream->missed_metadata_flush = false;
+                       pthread_mutex_unlock(&stream->metadata_timer_lock);
+                       (void) consumer_flush_ust_index(stream);
+               } else {
+                       pthread_mutex_unlock(&stream->metadata_timer_lock);
+               }
+
                if (err < 0) {
                        goto end;
                }
@@ -2263,14 +2696,18 @@ int lttng_ustconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
                stream->tracefile_size_current = 0;
 
                if (!stream->metadata_flag) {
-                       ret = index_create_file(stream->chan->pathname,
+                       struct lttng_index_file *index_file;
+
+                       index_file = lttng_index_file_create(stream->chan->pathname,
                                        stream->name, stream->uid, stream->gid,
                                        stream->chan->tracefile_size,
-                                       stream->tracefile_count_current);
-                       if (ret < 0) {
+                                       stream->tracefile_count_current,
+                                       CTF_INDEX_MAJOR, CTF_INDEX_MINOR);
+                       if (!index_file) {
                                goto error;
                        }
-                       stream->index_fd = ret;
+                       assert(!stream->index_file);
+                       stream->index_file = index_file;
                }
        }
        ret = 0;
@@ -2305,7 +2742,7 @@ int lttng_ustconsumer_data_pending(struct lttng_consumer_stream *stream)
                uint64_t contiguous, pushed;
 
                /* Ease our life a bit. */
-               contiguous = stream->chan->metadata_cache->contiguous;
+               contiguous = stream->chan->metadata_cache->max_offset;
                pushed = stream->ust_metadata_pushed;
 
                /*
@@ -2434,6 +2871,10 @@ void lttng_ustconsumer_close_stream_wakeup(struct lttng_consumer_stream *stream)
  * function or any of its callees. Timers have a very strict locking
  * semantic with respect to teardown. Failure to respect this semantic
  * introduces deadlocks.
+ *
+ * DON'T hold the metadata lock when calling this function, else this
+ * can cause deadlock involving consumer awaiting for metadata to be
+ * pushed out due to concurrent interaction with the session daemon.
  */
 int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
                struct lttng_consumer_channel *channel, int timer, int wait)
@@ -2441,7 +2882,7 @@ int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
        struct lttcomm_metadata_request_msg request;
        struct lttcomm_consumer_msg msg;
        enum lttcomm_return_code ret_code = LTTCOMM_CONSUMERD_SUCCESS;
-       uint64_t len, key, offset;
+       uint64_t len, key, offset, version;
        int ret;
 
        assert(channel);
@@ -2521,6 +2962,7 @@ int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
        len = msg.u.push_metadata.len;
        key = msg.u.push_metadata.key;
        offset = msg.u.push_metadata.target_offset;
+       version = msg.u.push_metadata.version;
 
        assert(key == channel->key);
        if (len == 0) {
@@ -2543,7 +2985,7 @@ int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
        health_code_update();
 
        ret = lttng_ustconsumer_recv_metadata(ctx->consumer_metadata_socket,
-                       key, offset, len, channel, timer, wait);
+                       key, offset, len, version, channel, timer, wait);
        if (ret >= 0) {
                /*
                 * Only send the status msg if the sessiond is alive meaning a positive
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