Cleanup: enforce const-correctness in notification thread
[lttng-tools.git] / src / bin / lttng-sessiond / notification-thread-events.c
index 5e53b79a1661a458e5d4bada395350b152f6d725..98757737dbfd2d13357d62f0c2a20a5b45683163 100644 (file)
 #include <common/sessiond-comm/sessiond-comm.h>
 #include <common/macros.h>
 #include <lttng/condition/condition.h>
-#include <lttng/action/action.h>
+#include <lttng/action/action-internal.h>
 #include <lttng/notification/notification-internal.h>
 #include <lttng/condition/condition-internal.h>
 #include <lttng/condition/buffer-usage-internal.h>
+#include <lttng/condition/session-consumed-size-internal.h>
 #include <lttng/notification/channel-internal.h>
 
 #include <time.h>
@@ -88,7 +89,7 @@ struct notification_client {
        uid_t uid;
        gid_t gid;
        /*
-        * Indicates if the credentials and versions of the client has been
+        * Indicates if the credentials and versions of the client have been
         * checked.
         */
        bool validated;
@@ -152,22 +153,42 @@ struct channel_state_sample {
        struct cds_lfht_node channel_state_ht_node;
        uint64_t highest_usage;
        uint64_t lowest_usage;
+       uint64_t channel_total_consumed;
 };
 
 static unsigned long hash_channel_key(struct channel_key *key);
-static int evaluate_condition(struct lttng_condition *condition,
+static int evaluate_condition(const struct lttng_condition *condition,
                struct lttng_evaluation **evaluation,
-               struct notification_thread_state *state,
-               struct channel_state_sample *previous_sample,
-               struct channel_state_sample *latest_sample,
-               uint64_t buffer_capacity);
+               const struct notification_thread_state *state,
+               const struct channel_state_sample *previous_sample,
+               const struct channel_state_sample *latest_sample,
+               uint64_t previous_session_consumed_total,
+               uint64_t latest_session_consumed_total,
+               struct channel_info *channel_info);
 static
-int send_evaluation_to_clients(struct lttng_trigger *trigger,
-               struct lttng_evaluation *evaluation,
+int send_evaluation_to_clients(const struct lttng_trigger *trigger,
+               const struct lttng_evaluation *evaluation,
                struct notification_client_list *client_list,
                struct notification_thread_state *state,
                uid_t channel_uid, gid_t channel_gid);
 
+
+static
+void session_info_destroy(void *_data);
+static
+void session_info_get(struct session_info *session_info);
+static
+void session_info_put(struct session_info *session_info);
+static
+struct session_info *session_info_create(const char *name,
+               uid_t uid, gid_t gid);
+static
+void session_info_add_channel(struct session_info *session_info,
+               struct channel_info *channel_info);
+static
+void session_info_remove_channel(struct session_info *session_info,
+               struct channel_info *channel_info);
+
 static
 int match_client(struct cds_lfht_node *node, const void *key)
 {
@@ -271,7 +292,7 @@ int match_client_list_condition(struct cds_lfht_node *node, const void *key)
 
 static
 unsigned long lttng_condition_buffer_usage_hash(
-       struct lttng_condition *_condition)
+       const struct lttng_condition *_condition)
 {
        unsigned long hash = 0;
        struct lttng_condition_buffer_usage *condition;
@@ -295,7 +316,7 @@ unsigned long lttng_condition_buffer_usage_hash(
 
                val = condition->threshold_ratio.value * (double) UINT32_MAX;
                hash ^= hash_key_u64(&val, lttng_ht_seed);
-       } else if (condition->threshold_ratio.set) {
+       } else if (condition->threshold_bytes.set) {
                uint64_t val;
 
                val = condition->threshold_bytes.value;
@@ -304,18 +325,39 @@ unsigned long lttng_condition_buffer_usage_hash(
        return hash;
 }
 
+static
+unsigned long lttng_condition_session_consumed_size_hash(
+       const struct lttng_condition *_condition)
+{
+       unsigned long hash = 0;
+       struct lttng_condition_session_consumed_size *condition;
+       uint64_t val;
+
+       condition = container_of(_condition,
+                       struct lttng_condition_session_consumed_size, parent);
+
+       if (condition->session_name) {
+               hash ^= hash_key_str(condition->session_name, lttng_ht_seed);
+       }
+       val = condition->consumed_threshold_bytes.value;
+       hash ^= hash_key_u64(&val, lttng_ht_seed);
+       return hash;
+}
+
 /*
  * The lttng_condition hashing code is kept in this file (rather than
  * condition.c) since it makes use of GPLv2 code (hashtable utils), which we
  * don't want to link in liblttng-ctl.
  */
 static
-unsigned long lttng_condition_hash(struct lttng_condition *condition)
+unsigned long lttng_condition_hash(const struct lttng_condition *condition)
 {
        switch (condition->type) {
        case LTTNG_CONDITION_TYPE_BUFFER_USAGE_LOW:
        case LTTNG_CONDITION_TYPE_BUFFER_USAGE_HIGH:
                return lttng_condition_buffer_usage_hash(condition);
+       case LTTNG_CONDITION_TYPE_SESSION_CONSUMED_SIZE:
+               return lttng_condition_session_consumed_size_hash(condition);
        default:
                ERR("[notification-thread] Unexpected condition type caught");
                abort();
@@ -339,45 +381,140 @@ void channel_info_destroy(struct channel_info *channel_info)
                return;
        }
 
-       if (channel_info->session_name) {
-               free(channel_info->session_name);
+       if (channel_info->session_info) {
+               session_info_remove_channel(channel_info->session_info,
+                               channel_info);
+               session_info_put(channel_info->session_info);
        }
-       if (channel_info->channel_name) {
-               free(channel_info->channel_name);
+       if (channel_info->name) {
+               free(channel_info->name);
        }
        free(channel_info);
 }
 
+/* Don't call directly, use the ref-counting mechanism. */
 static
-struct channel_info *channel_info_copy(struct channel_info *channel_info)
+void session_info_destroy(void *_data)
 {
-       struct channel_info *copy = zmalloc(sizeof(*channel_info));
+       struct session_info *session_info = _data;
+       int ret;
+
+       assert(session_info);
+       if (session_info->channel_infos_ht) {
+               ret = cds_lfht_destroy(session_info->channel_infos_ht, NULL);
+               if (ret) {
+                       ERR("[notification-thread] Failed to destroy channel information hash table");
+               }
+       }
+       free(session_info->name);
+       free(session_info);
+}
 
-       assert(channel_info);
-       assert(channel_info->session_name);
-       assert(channel_info->channel_name);
+static
+void session_info_get(struct session_info *session_info)
+{
+       if (!session_info) {
+               return;
+       }
+       lttng_ref_get(&session_info->ref);
+}
 
-       if (!copy) {
-               goto end;
+static
+void session_info_put(struct session_info *session_info)
+{
+       if (!session_info) {
+               return;
        }
+       lttng_ref_put(&session_info->ref);
+}
 
-       memcpy(copy, channel_info, sizeof(*channel_info));
-       copy->session_name = NULL;
-       copy->channel_name = NULL;
+static
+struct session_info *session_info_create(const char *name, uid_t uid, gid_t gid)
+{
+       struct session_info *session_info;
+
+       assert(name);
 
-       copy->session_name = strdup(channel_info->session_name);
-       if (!copy->session_name) {
+       session_info = zmalloc(sizeof(*session_info));
+       if (!session_info) {
+               goto end;
+       }
+       lttng_ref_init(&session_info->ref, session_info_destroy);
+
+       session_info->channel_infos_ht = cds_lfht_new(DEFAULT_HT_SIZE,
+                       1, 0, CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
+       if (!session_info->channel_infos_ht) {
                goto error;
        }
-       copy->channel_name = strdup(channel_info->channel_name);
-       if (!copy->channel_name) {
+
+       cds_lfht_node_init(&session_info->sessions_ht_node);
+       session_info->name = strdup(name);
+       if (!session_info->name) {
                goto error;
        }
+       session_info->uid = uid;
+       session_info->gid = gid;
+end:
+       return session_info;
+error:
+       session_info_put(session_info);
+       return NULL;
+}
+
+static
+void session_info_add_channel(struct session_info *session_info,
+               struct channel_info *channel_info)
+{
+       rcu_read_lock();
+       cds_lfht_add(session_info->channel_infos_ht,
+                       hash_channel_key(&channel_info->key),
+                       &channel_info->session_info_channels_ht_node);
+       rcu_read_unlock();
+}
+
+static
+void session_info_remove_channel(struct session_info *session_info,
+               struct channel_info *channel_info)
+{
+       rcu_read_lock();
+       cds_lfht_del(session_info->channel_infos_ht,
+                       &channel_info->session_info_channels_ht_node);
+       rcu_read_unlock();
+}
+
+static
+struct channel_info *channel_info_create(const char *channel_name,
+               struct channel_key *channel_key, uint64_t channel_capacity,
+               struct session_info *session_info)
+{
+       struct channel_info *channel_info = zmalloc(sizeof(*channel_info));
+
+       if (!channel_info) {
+               goto end;
+       }
+
        cds_lfht_node_init(&channel_info->channels_ht_node);
+       cds_lfht_node_init(&channel_info->session_info_channels_ht_node);
+       memcpy(&channel_info->key, channel_key, sizeof(*channel_key));
+       channel_info->capacity = channel_capacity;
+
+       channel_info->name = strdup(channel_name);
+       if (!channel_info->name) {
+               goto error;
+       }
+
+       /*
+        * Set the references between session and channel infos:
+        *   - channel_info holds a strong reference to session_info
+        *   - session_info holds a weak reference to channel_info
+        */
+       session_info_get(session_info);
+       session_info_add_channel(session_info, channel_info);
+       channel_info->session_info = session_info;
 end:
-       return copy;
+       return channel_info;
 error:
-       channel_info_destroy(copy);
+       channel_info_destroy(channel_info);
        return NULL;
 }
 
@@ -410,13 +547,13 @@ int evaluate_condition_for_client(struct lttng_trigger *trigger,
                struct lttng_trigger_list_element *element;
 
                cds_list_for_each_entry(element, &channel_trigger_list->list, node) {
-                       struct lttng_condition *current_condition =
-                               lttng_trigger_get_condition(
+                       const struct lttng_condition *current_condition =
+                               lttng_trigger_get_const_condition(
                                                element->trigger);
 
                        assert(current_condition);
                        if (!lttng_condition_is_equal(condition,
-                                               current_condition)) {
+                                       current_condition)) {
                                continue;
                        }
 
@@ -466,10 +603,12 @@ int evaluate_condition_for_client(struct lttng_trigger *trigger,
                goto end;
        }
 
-       ret = evaluate_condition(condition, &evaluation, state, NULL,
-                       last_sample, channel_info->capacity);
+       ret = evaluate_condition(condition, &evaluation, state,
+                       NULL, last_sample,
+                       0, channel_info->session_info->consumed_data_size,
+                       channel_info);
        if (ret) {
-               WARN("[notification-thread] Fatal error occured while evaluating a newly subscribed-to condition");
+               WARN("[notification-thread] Fatal error occurred while evaluating a newly subscribed-to condition");
                goto end;
        }
 
@@ -495,7 +634,8 @@ int evaluate_condition_for_client(struct lttng_trigger *trigger,
        /* Send evaluation result to the newly-subscribed client. */
        DBG("[notification-thread] Newly subscribed-to condition evaluated to true, notifying client");
        ret = send_evaluation_to_clients(trigger, evaluation, &client_list,
-                       state, channel_info->uid, channel_info->gid);
+                       state, channel_info->session_info->uid,
+                       channel_info->session_info->gid);
 
 end:
        return ret;
@@ -555,16 +695,27 @@ int notification_thread_client_subscribe(struct notification_client *client,
                        &iter);
        node = cds_lfht_iter_get_node(&iter);
        if (!node) {
+               /*
+                * No notification-emiting trigger registered with this
+                * condition. We don't evaluate the condition right away
+                * since this trigger is not registered yet.
+                */
                free(client_list_element);
                goto end_unlock;
        }
 
        client_list = caa_container_of(node, struct notification_client_list,
                        notification_trigger_ht_node);
+       /*
+        * The condition to which the client just subscribed is evaluated
+        * at this point so that conditions that are already TRUE result
+        * in a notification being sent out.
+        */
        if (evaluate_condition_for_client(client_list->trigger, condition,
                        client, state)) {
                WARN("[notification-thread] Evaluation of a condition on client subscription failed, aborting.");
                ret = -1;
+               free(client_list_element);
                goto end_unlock;
        }
 
@@ -725,51 +876,90 @@ end:
 }
 
 static
-bool trigger_applies_to_channel(struct lttng_trigger *trigger,
-               struct channel_info *info)
+bool buffer_usage_condition_applies_to_channel(
+               struct lttng_condition *condition,
+               struct channel_info *channel_info)
 {
        enum lttng_condition_status status;
-       struct lttng_condition *condition;
-       const char *trigger_session_name = NULL;
-       const char *trigger_channel_name = NULL;
-       enum lttng_domain_type trigger_domain;
+       enum lttng_domain_type condition_domain;
+       const char *condition_session_name = NULL;
+       const char *condition_channel_name = NULL;
 
-       condition = lttng_trigger_get_condition(trigger);
-       if (!condition) {
+       status = lttng_condition_buffer_usage_get_domain_type(condition,
+                       &condition_domain);
+       assert(status == LTTNG_CONDITION_STATUS_OK);
+       if (channel_info->key.domain != condition_domain) {
                goto fail;
        }
 
-       switch (lttng_condition_get_type(condition)) {
-       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_LOW:
-       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_HIGH:
-               break;
-       default:
+       status = lttng_condition_buffer_usage_get_session_name(
+                       condition, &condition_session_name);
+       assert((status == LTTNG_CONDITION_STATUS_OK) && condition_session_name);
+
+       status = lttng_condition_buffer_usage_get_channel_name(
+                       condition, &condition_channel_name);
+       assert((status == LTTNG_CONDITION_STATUS_OK) && condition_channel_name);
+
+       if (strcmp(channel_info->session_info->name, condition_session_name)) {
+               goto fail;
+       }
+       if (strcmp(channel_info->name, condition_channel_name)) {
                goto fail;
        }
 
-       status = lttng_condition_buffer_usage_get_domain_type(condition,
-                       &trigger_domain);
-       assert(status == LTTNG_CONDITION_STATUS_OK);
-       if (info->key.domain != trigger_domain) {
+       return true;
+fail:
+       return false;
+}
+
+static
+bool session_consumed_size_condition_applies_to_channel(
+               struct lttng_condition *condition,
+               struct channel_info *channel_info)
+{
+       enum lttng_condition_status status;
+       const char *condition_session_name = NULL;
+
+       status = lttng_condition_session_consumed_size_get_session_name(
+                       condition, &condition_session_name);
+       assert((status == LTTNG_CONDITION_STATUS_OK) && condition_session_name);
+
+       if (strcmp(channel_info->session_info->name, condition_session_name)) {
                goto fail;
        }
 
-       status = lttng_condition_buffer_usage_get_session_name(
-                       condition, &trigger_session_name);
-       assert((status == LTTNG_CONDITION_STATUS_OK) && trigger_session_name);
+       return true;
+fail:
+       return false;
+}
 
-       status = lttng_condition_buffer_usage_get_channel_name(
-                       condition, &trigger_channel_name);
-       assert((status == LTTNG_CONDITION_STATUS_OK) && trigger_channel_name);
+static
+bool trigger_applies_to_channel(struct lttng_trigger *trigger,
+               struct channel_info *channel_info)
+{
+       struct lttng_condition *condition;
+       bool trigger_applies;
 
-       if (strcmp(info->session_name, trigger_session_name)) {
+       condition = lttng_trigger_get_condition(trigger);
+       if (!condition) {
                goto fail;
        }
-       if (strcmp(info->channel_name, trigger_channel_name)) {
+
+       switch (lttng_condition_get_type(condition)) {
+       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_LOW:
+       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_HIGH:
+               trigger_applies = buffer_usage_condition_applies_to_channel(
+                               condition, channel_info);
+               break;
+       case LTTNG_CONDITION_TYPE_SESSION_CONSUMED_SIZE:
+               trigger_applies = session_consumed_size_condition_applies_to_channel(
+                               condition, channel_info);
+               break;
+       default:
                goto fail;
        }
 
-       return true;
+       return trigger_applies;
 fail:
        return false;
 }
@@ -793,32 +983,94 @@ bool trigger_applies_to_client(struct lttng_trigger *trigger,
        return applies;
 }
 
+static
+int match_session(struct cds_lfht_node *node, const void *key)
+{
+       const char *name = key;
+       struct session_info *session_info = caa_container_of(
+               node, struct session_info, sessions_ht_node);
+
+       return !strcmp(session_info->name, name);
+}
+
+static
+struct session_info *find_or_create_session_info(
+               struct notification_thread_state *state,
+               const char *name, uid_t uid, gid_t gid)
+{
+       struct session_info *session = NULL;
+       struct cds_lfht_node *node;
+       struct cds_lfht_iter iter;
+
+       rcu_read_lock();
+       cds_lfht_lookup(state->sessions_ht,
+                       hash_key_str(name, lttng_ht_seed),
+                       match_session,
+                       name,
+                       &iter);
+       node = cds_lfht_iter_get_node(&iter);
+       if (node) {
+               DBG("[notification-thread] Found session info of session \"%s\" (uid = %i, gid = %i)",
+                               name, uid, gid);
+               session = caa_container_of(node, struct session_info,
+                               sessions_ht_node);
+               assert(session->uid == uid);
+               assert(session->gid == gid);
+               goto end;
+       }
+
+       session = session_info_create(name, uid, gid);
+       if (!session) {
+               ERR("[notification-thread] Failed to allocation session info for session \"%s\" (uid = %i, gid = %i)",
+                               name, uid, gid);
+               goto end;
+       }
+
+       cds_lfht_add(state->sessions_ht, hash_key_str(name, lttng_ht_seed),
+                       &session->sessions_ht_node);
+end:
+       rcu_read_unlock();
+       return session;
+}
+
 static
 int handle_notification_thread_command_add_channel(
-       struct notification_thread_state *state,
-       struct channel_info *channel_info,
-       enum lttng_error_code *cmd_result)
+               struct notification_thread_state *state,
+               const char *session_name, uid_t session_uid, gid_t session_gid,
+               const char *channel_name, enum lttng_domain_type channel_domain,
+               uint64_t channel_key_int, uint64_t channel_capacity,
+               enum lttng_error_code *cmd_result)
 {
        struct cds_list_head trigger_list;
-       struct channel_info *new_channel_info;
-       struct channel_key *channel_key;
+       struct channel_info *new_channel_info = NULL;
+       struct channel_key channel_key = {
+               .key = channel_key_int,
+               .domain = channel_domain,
+       };
        struct lttng_channel_trigger_list *channel_trigger_list = NULL;
        struct lttng_trigger_ht_element *trigger_ht_element = NULL;
        int trigger_count = 0;
        struct cds_lfht_iter iter;
+       struct session_info *session_info = NULL;
 
        DBG("[notification-thread] Adding channel %s from session %s, channel key = %" PRIu64 " in %s domain",
-                       channel_info->channel_name, channel_info->session_name,
-                       channel_info->key.key, channel_info->key.domain == LTTNG_DOMAIN_KERNEL ? "kernel" : "user space");
+                       channel_name, session_name, channel_key_int,
+                       channel_domain == LTTNG_DOMAIN_KERNEL ? "kernel" : "user space");
 
        CDS_INIT_LIST_HEAD(&trigger_list);
 
-       new_channel_info = channel_info_copy(channel_info);
-       if (!new_channel_info) {
+       session_info = find_or_create_session_info(state, session_name,
+                       session_uid, session_gid);
+       if (!session_info) {
+               /* Allocation error or an internal error occured. */
                goto error;
        }
 
-       channel_key = &new_channel_info->key;
+       new_channel_info = channel_info_create(channel_name, &channel_key,
+                       channel_capacity, session_info);
+       if (!new_channel_info) {
+               goto error;
+       }
 
        /* Build a list of all triggers applying to the new channel. */
        cds_lfht_for_each_entry(state->triggers_ht, &iter, trigger_ht_element,
@@ -826,7 +1078,7 @@ int handle_notification_thread_command_add_channel(
                struct lttng_trigger_list_element *new_element;
 
                if (!trigger_applies_to_channel(trigger_ht_element->trigger,
-                               channel_info)) {
+                               new_channel_info)) {
                        continue;
                }
 
@@ -846,7 +1098,7 @@ int handle_notification_thread_command_add_channel(
        if (!channel_trigger_list) {
                goto error;
        }
-       channel_trigger_list->channel_key = *channel_key;
+       channel_trigger_list->channel_key = new_channel_info->key;
        CDS_INIT_LIST_HEAD(&channel_trigger_list->list);
        cds_lfht_node_init(&channel_trigger_list->channel_triggers_ht_node);
        cds_list_splice(&trigger_list, &channel_trigger_list->list);
@@ -854,21 +1106,21 @@ int handle_notification_thread_command_add_channel(
        rcu_read_lock();
        /* Add channel to the channel_ht which owns the channel_infos. */
        cds_lfht_add(state->channels_ht,
-                       hash_channel_key(channel_key),
+                       hash_channel_key(&new_channel_info->key),
                        &new_channel_info->channels_ht_node);
        /*
         * Add the list of triggers associated with this channel to the
         * channel_triggers_ht.
         */
        cds_lfht_add(state->channel_triggers_ht,
-                       hash_channel_key(channel_key),
+                       hash_channel_key(&new_channel_info->key),
                        &channel_trigger_list->channel_triggers_ht_node);
        rcu_read_unlock();
        *cmd_result = LTTNG_OK;
        return 0;
 error:
-       /* Empty trigger list */
        channel_info_destroy(new_channel_info);
+       session_info_put(session_info);
        return 1;
 }
 
@@ -1004,16 +1256,16 @@ end:
  *       are checked against the channel at that moment.
  *
  * If this function returns a non-zero value, it means something is
- * fundamentally and the whole subsystem/thread will be torn down.
+ * fundamentally broken and the whole subsystem/thread will be torn down.
  *
  * If a non-fatal error occurs, just set the cmd_result to the appropriate
  * error code.
  */
 static
 int handle_notification_thread_command_register_trigger(
-       struct notification_thread_state *state,
-       struct lttng_trigger *trigger,
-       enum lttng_error_code *cmd_result)
+               struct notification_thread_state *state,
+               struct lttng_trigger *trigger,
+               enum lttng_error_code *cmd_result)
 {
        int ret = 0;
        struct lttng_condition *condition;
@@ -1104,11 +1356,6 @@ int handle_notification_thread_command_register_trigger(
        cds_lfht_add(state->notification_trigger_clients_ht,
                        lttng_condition_hash(condition),
                        &client_list->notification_trigger_ht_node);
-       /*
-        * Client list ownership transferred to the
-        * notification_trigger_clients_ht.
-        */
-       client_list = NULL;
 
        /*
         * Add the trigger to list of triggers bound to the channels currently
@@ -1142,11 +1389,49 @@ int handle_notification_thread_command_register_trigger(
                CDS_INIT_LIST_HEAD(&trigger_list_element->node);
                trigger_list_element->trigger = trigger;
                cds_list_add(&trigger_list_element->node, &trigger_list->list);
+       }
 
-               /* A trigger can only apply to one channel. */
-               break;
+       /*
+        * Since there is nothing preventing clients from subscribing to a
+        * condition before the corresponding trigger is registered, we have
+        * to evaluate this new condition right away.
+        *
+        * At some point, we were waiting for the next "evaluation" (e.g. on
+        * reception of a channel sample) to evaluate this new condition, but
+        * that was broken.
+        *
+        * The reason it was broken is that waiting for the next sample
+        * does not allow us to properly handle transitions for edge-triggered
+        * conditions.
+        *
+        * Consider this example: when we handle a new channel sample, we
+        * evaluate each conditions twice: once with the previous state, and
+        * again with the newest state. We then use those two results to
+        * determine whether a state change happened: a condition was false and
+        * became true. If a state change happened, we have to notify clients.
+        *
+        * Now, if a client subscribes to a given notification and registers
+        * a trigger *after* that subscription, we have to make sure the
+        * condition is evaluated at this point while considering only the
+        * current state. Otherwise, the next evaluation cycle may only see
+        * that the evaluations remain the same (true for samples n-1 and n) and
+        * the client will never know that the condition has been met.
+        */
+       cds_list_for_each_entry_safe(client_list_element, tmp,
+                       &client_list->list, node) {
+               ret = evaluate_condition_for_client(trigger, condition,
+                               client_list_element->client, state);
+               if (ret) {
+                       goto error_free_client_list;
+               }
        }
 
+       /*
+        * Client list ownership transferred to the
+        * notification_trigger_clients_ht.
+        */
+       client_list = NULL;
+
        *cmd_result = LTTNG_OK;
 error_free_client_list:
        if (client_list) {
@@ -1209,8 +1494,8 @@ int handle_notification_thread_command_unregister_trigger(
 
                cds_list_for_each_entry_safe(trigger_element, tmp,
                                &trigger_list->list, node) {
-                       struct lttng_condition *current_condition =
-                                       lttng_trigger_get_condition(
+                       const struct lttng_condition *current_condition =
+                                       lttng_trigger_get_const_condition(
                                                trigger_element->trigger);
 
                        assert(current_condition);
@@ -1274,8 +1559,9 @@ int handle_notification_thread_command(
        uint64_t counter;
        struct notification_thread_command *cmd;
 
-       /* Read event_fd to put it back into a quiescent state. */
-       ret = read(handle->cmd_queue.event_fd, &counter, sizeof(counter));
+       /* Read the event pipe to put it back into a quiescent state. */
+       ret = read(lttng_pipe_get_readfd(handle->cmd_queue.event_pipe), &counter,
+                       sizeof(counter));
        if (ret == -1) {
                goto error;
        }
@@ -1299,7 +1585,14 @@ int handle_notification_thread_command(
        case NOTIFICATION_COMMAND_TYPE_ADD_CHANNEL:
                DBG("[notification-thread] Received add channel command");
                ret = handle_notification_thread_command_add_channel(
-                               state, &cmd->parameters.add_channel,
+                               state,
+                               cmd->parameters.add_channel.session.name,
+                               cmd->parameters.add_channel.session.uid,
+                               cmd->parameters.add_channel.session.gid,
+                               cmd->parameters.add_channel.channel.name,
+                               cmd->parameters.add_channel.channel.domain,
+                               cmd->parameters.add_channel.channel.key,
+                               cmd->parameters.add_channel.channel.capacity,
                                &cmd->reply_code);
                break;
        case NOTIFICATION_COMMAND_TYPE_REMOVE_CHANNEL:
@@ -1797,10 +2090,6 @@ int client_dispatch_message(struct notification_client *client,
 
                if (client->communication.inbound.msg_type ==
                                LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_SUBSCRIBE) {
-                       /*
-                        * FIXME The current state should be evaluated on
-                        * subscription.
-                        */
                        ret = notification_thread_client_subscribe(client,
                                        condition, state, &status);
                } else {
@@ -1911,20 +2200,17 @@ end:
 }
 
 static
-bool evaluate_buffer_usage_condition(struct lttng_condition *condition,
-               struct channel_state_sample *sample, uint64_t buffer_capacity)
+bool evaluate_buffer_usage_condition(const struct lttng_condition *condition,
+               const struct channel_state_sample *sample,
+               uint64_t buffer_capacity)
 {
        bool result = false;
        uint64_t threshold;
        enum lttng_condition_type condition_type;
-       struct lttng_condition_buffer_usage *use_condition = container_of(
+       const struct lttng_condition_buffer_usage *use_condition = container_of(
                        condition, struct lttng_condition_buffer_usage,
                        parent);
 
-       if (!sample) {
-               goto end;
-       }
-
        if (use_condition->threshold_bytes.set) {
                threshold = use_condition->threshold_bytes.value;
        } else {
@@ -1968,32 +2254,73 @@ bool evaluate_buffer_usage_condition(struct lttng_condition *condition,
                        result = true;
                }
        }
-end:
+
        return result;
 }
 
 static
-int evaluate_condition(struct lttng_condition *condition,
+bool evaluate_session_consumed_size_condition(
+               const struct lttng_condition *condition,
+               uint64_t session_consumed_size)
+{
+       uint64_t threshold;
+       const struct lttng_condition_session_consumed_size *size_condition =
+                       container_of(condition,
+                               struct lttng_condition_session_consumed_size,
+                               parent);
+
+       threshold = size_condition->consumed_threshold_bytes.value;
+       DBG("[notification-thread] Session consumed size condition being evaluated: threshold = %" PRIu64 ", current size = %" PRIu64,
+                       threshold, session_consumed_size);
+       return session_consumed_size >= threshold;
+}
+
+static
+int evaluate_condition(const struct lttng_condition *condition,
                struct lttng_evaluation **evaluation,
-               struct notification_thread_state *state,
-               struct channel_state_sample *previous_sample,
-               struct channel_state_sample *latest_sample,
-               uint64_t buffer_capacity)
+               const struct notification_thread_state *state,
+               const struct channel_state_sample *previous_sample,
+               const struct channel_state_sample *latest_sample,
+               uint64_t previous_session_consumed_total,
+               uint64_t latest_session_consumed_total,
+               struct channel_info *channel_info)
 {
        int ret = 0;
        enum lttng_condition_type condition_type;
-       bool previous_sample_result;
+       const bool previous_sample_available = !!previous_sample;
+       bool previous_sample_result = false;
        bool latest_sample_result;
 
        condition_type = lttng_condition_get_type(condition);
-       /* No other condition type supported for the moment. */
-       assert(condition_type == LTTNG_CONDITION_TYPE_BUFFER_USAGE_LOW ||
-                       condition_type == LTTNG_CONDITION_TYPE_BUFFER_USAGE_HIGH);
 
-       previous_sample_result = evaluate_buffer_usage_condition(condition,
-                       previous_sample, buffer_capacity);
-       latest_sample_result = evaluate_buffer_usage_condition(condition,
-                       latest_sample, buffer_capacity);
+       switch (condition_type) {
+       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_LOW:
+       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_HIGH:
+               if (caa_likely(previous_sample_available)) {
+                       previous_sample_result =
+                               evaluate_buffer_usage_condition(condition,
+                                       previous_sample, channel_info->capacity);
+               }
+               latest_sample_result = evaluate_buffer_usage_condition(
+                               condition, latest_sample,
+                               channel_info->capacity);
+               break;
+       case LTTNG_CONDITION_TYPE_SESSION_CONSUMED_SIZE:
+               if (caa_likely(previous_sample_available)) {
+                       previous_sample_result =
+                               evaluate_session_consumed_size_condition(
+                                       condition,
+                                       previous_session_consumed_total);
+               }
+               latest_sample_result =
+                               evaluate_session_consumed_size_condition(
+                                       condition,
+                                       latest_session_consumed_total);
+               break;
+       default:
+               /* Unknown condition type; internal error. */
+               abort();
+       }
 
        if (!latest_sample_result ||
                        (previous_sample_result == latest_sample_result)) {
@@ -2006,15 +2333,29 @@ int evaluate_condition(struct lttng_condition *condition,
                goto end;
        }
 
-       if (evaluation && latest_sample_result) {
+       if (!evaluation || !latest_sample_result) {
+               goto end;
+       }
+
+       switch (condition_type) {
+       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_LOW:
+       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_HIGH:
                *evaluation = lttng_evaluation_buffer_usage_create(
                                condition_type,
                                latest_sample->highest_usage,
-                               buffer_capacity);
-               if (!*evaluation) {
-                       ret = -1;
-                       goto end;
-               }
+                               channel_info->capacity);
+               break;
+       case LTTNG_CONDITION_TYPE_SESSION_CONSUMED_SIZE:
+               *evaluation = lttng_evaluation_session_consumed_size_create(
+                               latest_session_consumed_total);
+               break;
+       default:
+               abort();
+       }
+
+       if (!*evaluation) {
+               ret = -1;
+               goto end;
        }
 end:
        return ret;
@@ -2037,8 +2378,8 @@ int client_enqueue_dropped_notification(struct notification_client *client,
 }
 
 static
-int send_evaluation_to_clients(struct lttng_trigger *trigger,
-               struct lttng_evaluation *evaluation,
+int send_evaluation_to_clients(const struct lttng_trigger *trigger,
+               const struct lttng_evaluation *evaluation,
                struct notification_client_list* client_list,
                struct notification_thread_state *state,
                uid_t channel_uid, gid_t channel_gid)
@@ -2046,51 +2387,33 @@ int send_evaluation_to_clients(struct lttng_trigger *trigger,
        int ret = 0;
        struct lttng_dynamic_buffer msg_buffer;
        struct notification_client_list_element *client_list_element, *tmp;
-       struct lttng_notification *notification;
-       struct lttng_condition *condition;
-       ssize_t expected_notification_size, notification_size;
-       struct lttng_notification_channel_message msg;
+       const struct lttng_notification notification = {
+               .condition = (struct lttng_condition *) lttng_trigger_get_const_condition(trigger),
+               .evaluation = (struct lttng_evaluation *) evaluation,
+       };
+       struct lttng_notification_channel_message msg_header = {
+               .type = (int8_t) LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION,
+       };
 
        lttng_dynamic_buffer_init(&msg_buffer);
 
-       condition = lttng_trigger_get_condition(trigger);
-       assert(condition);
-
-       notification = lttng_notification_create(condition, evaluation);
-       if (!notification) {
-               ret = -1;
-               goto end;
-       }
-
-       expected_notification_size = lttng_notification_serialize(notification,
-                       NULL);
-       if (expected_notification_size < 0) {
-               ERR("[notification-thread] Failed to get size of serialized notification");
-               ret = -1;
-               goto end;
-       }
-
-       msg.type = (int8_t) LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION;
-       msg.size = (uint32_t) expected_notification_size;
-       ret = lttng_dynamic_buffer_append(&msg_buffer, &msg, sizeof(msg));
+       ret = lttng_dynamic_buffer_append(&msg_buffer, &msg_header,
+                       sizeof(msg_header));
        if (ret) {
                goto end;
        }
 
-       ret = lttng_dynamic_buffer_set_size(&msg_buffer,
-                       msg_buffer.size + expected_notification_size);
+       ret = lttng_notification_serialize(&notification, &msg_buffer);
        if (ret) {
-               goto end;
-       }
-
-       notification_size = lttng_notification_serialize(notification,
-                       msg_buffer.data + sizeof(msg));
-       if (notification_size != expected_notification_size) {
                ERR("[notification-thread] Failed to serialize notification");
                ret = -1;
                goto end;
        }
 
+       /* Update payload size. */
+       ((struct lttng_notification_channel_message * ) msg_buffer.data)->size =
+                       (uint32_t) (msg_buffer.size - sizeof(msg_header));
+
        cds_list_for_each_entry_safe(client_list_element, tmp,
                        &client_list->list, node) {
                struct notification_client *client =
@@ -2140,7 +2463,6 @@ int send_evaluation_to_clients(struct lttng_trigger *trigger,
        }
        ret = 0;
 end:
-       lttng_notification_destroy(notification);
        lttng_dynamic_buffer_reset(&msg_buffer);
        return ret;
 }
@@ -2151,13 +2473,14 @@ int handle_notification_thread_channel_sample(
 {
        int ret = 0;
        struct lttcomm_consumer_channel_monitor_msg sample_msg;
-       struct channel_state_sample previous_sample, latest_sample;
        struct channel_info *channel_info;
        struct cds_lfht_node *node;
        struct cds_lfht_iter iter;
        struct lttng_channel_trigger_list *trigger_list;
        struct lttng_trigger_list_element *trigger_list_element;
        bool previous_sample_available = false;
+       struct channel_state_sample previous_sample, latest_sample;
+       uint64_t previous_session_consumed_total, latest_session_consumed_total;
 
        /*
         * The monitoring pipe only holds messages smaller than PIPE_BUF,
@@ -2176,6 +2499,7 @@ int handle_notification_thread_channel_sample(
        latest_sample.key.domain = domain;
        latest_sample.highest_usage = sample_msg.highest;
        latest_sample.lowest_usage = sample_msg.lowest;
+       latest_sample.channel_total_consumed = sample_msg.total_consumed;
 
        rcu_read_lock();
 
@@ -2186,7 +2510,7 @@ int handle_notification_thread_channel_sample(
                        &latest_sample.key,
                        &iter);
        node = cds_lfht_iter_get_node(&iter);
-       if (!node) {
+       if (caa_unlikely(!node)) {
                /*
                 * Not an error since the consumer can push a sample to the pipe
                 * and the rest of the session daemon could notify us of the
@@ -2201,12 +2525,16 @@ int handle_notification_thread_channel_sample(
        }
        channel_info = caa_container_of(node, struct channel_info,
                        channels_ht_node);
-       DBG("[notification-thread] Handling channel sample for channel %s (key = %" PRIu64 ") in session %s (highest usage = %" PRIu64 ", lowest usage = %" PRIu64")",
-                       channel_info->channel_name,
+       DBG("[notification-thread] Handling channel sample for channel %s (key = %" PRIu64 ") in session %s (highest usage = %" PRIu64 ", lowest usage = %" PRIu64", total consumed = %" PRIu64")",
+                       channel_info->name,
                        latest_sample.key.key,
-                       channel_info->session_name,
+                       channel_info->session_info->name,
                        latest_sample.highest_usage,
-                       latest_sample.lowest_usage);
+                       latest_sample.lowest_usage,
+                       latest_sample.channel_total_consumed);
+
+       previous_session_consumed_total =
+                       channel_info->session_info->consumed_data_size;
 
        /* Retrieve the channel's last sample, if it exists, and update it. */
        cds_lfht_lookup(state->channel_state_ht,
@@ -2215,18 +2543,24 @@ int handle_notification_thread_channel_sample(
                        &latest_sample.key,
                        &iter);
        node = cds_lfht_iter_get_node(&iter);
-       if (node) {
+       if (caa_likely(node)) {
                struct channel_state_sample *stored_sample;
 
                /* Update the sample stored. */
                stored_sample = caa_container_of(node,
                                struct channel_state_sample,
                                channel_state_ht_node);
+
                memcpy(&previous_sample, stored_sample,
                                sizeof(previous_sample));
                stored_sample->highest_usage = latest_sample.highest_usage;
                stored_sample->lowest_usage = latest_sample.lowest_usage;
+               stored_sample->channel_total_consumed = latest_sample.channel_total_consumed;
                previous_sample_available = true;
+
+               latest_session_consumed_total =
+                               previous_session_consumed_total +
+                               (latest_sample.channel_total_consumed - previous_sample.channel_total_consumed);
        } else {
                /*
                 * This is the channel's first sample, allocate space for and
@@ -2245,8 +2579,15 @@ int handle_notification_thread_channel_sample(
                cds_lfht_add(state->channel_state_ht,
                                hash_channel_key(&stored_sample->key),
                                &stored_sample->channel_state_ht_node);
+
+               latest_session_consumed_total =
+                               previous_session_consumed_total +
+                               latest_sample.channel_total_consumed;
        }
 
+       channel_info->session_info->consumed_data_size =
+                       latest_session_consumed_total;
+
        /* Find triggers associated with this channel. */
        cds_lfht_lookup(state->channel_triggers_ht,
                        hash_channel_key(&latest_sample.key),
@@ -2254,7 +2595,7 @@ int handle_notification_thread_channel_sample(
                        &latest_sample.key,
                        &iter);
        node = cds_lfht_iter_get_node(&iter);
-       if (!node) {
+       if (caa_likely(!node)) {
                goto end_unlock;
        }
 
@@ -2262,19 +2603,19 @@ int handle_notification_thread_channel_sample(
                        channel_triggers_ht_node);
        cds_list_for_each_entry(trigger_list_element, &trigger_list->list,
                        node) {
-               struct lttng_condition *condition;
-               struct lttng_action *action;
-               struct lttng_trigger *trigger;
+               const struct lttng_condition *condition;
+               const struct lttng_action *action;
+               const struct lttng_trigger *trigger;
                struct notification_client_list *client_list;
                struct lttng_evaluation *evaluation = NULL;
 
                trigger = trigger_list_element->trigger;
-               condition = lttng_trigger_get_condition(trigger);
+               condition = lttng_trigger_get_const_condition(trigger);
                assert(condition);
-               action = lttng_trigger_get_action(trigger);
+               action = lttng_trigger_get_const_action(trigger);
 
                /* Notify actions are the only type currently supported. */
-               assert(lttng_action_get_type(action) ==
+               assert(lttng_action_get_type_const(action) ==
                                LTTNG_ACTION_TYPE_NOTIFY);
 
                /*
@@ -2302,20 +2643,25 @@ int handle_notification_thread_channel_sample(
 
                ret = evaluate_condition(condition, &evaluation, state,
                                previous_sample_available ? &previous_sample : NULL,
-                               &latest_sample, channel_info->capacity);
-               if (ret) {
+                               &latest_sample,
+                               previous_session_consumed_total,
+                               latest_session_consumed_total,
+                               channel_info);
+               if (caa_unlikely(ret)) {
                        goto end_unlock;
                }
 
-               if (!evaluation) {
+               if (caa_likely(!evaluation)) {
                        continue;
                }
 
                /* Dispatch evaluation result to all clients. */
                ret = send_evaluation_to_clients(trigger_list_element->trigger,
                                evaluation, client_list, state,
-                               channel_info->uid, channel_info->gid);
-               if (ret) {
+                               channel_info->session_info->uid,
+                               channel_info->session_info->gid);
+               lttng_evaluation_destroy(evaluation);
+               if (caa_unlikely(ret)) {
                        goto end_unlock;
                }
        }
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