SoW-2020-0002: Trace Hit Counters: trigger error reporting integration
[lttng-tools.git] / src / bin / lttng-sessiond / notification-thread-events.c
index 98757737dbfd2d13357d62f0c2a20a5b45683163..b3c64d9c77d94ab57079df681e330fbc90413fcb 100644 (file)
@@ -1,20 +1,12 @@
 /*
- * Copyright (C) 2017 Jérémie Galarneau <jeremie.galarneau@efficios.com>
+ * Copyright (C) 2017 Jérémie Galarneau <jeremie.galarneau@efficios.com>
  *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License, version 2 only, as
- * published by the Free Software Foundation.
+ * SPDX-License-Identifier: GPL-2.0-only
  *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
- * more details.
- *
- * You should have received a copy of the GNU General Public License along with
- * this program; if not, write to the Free Software Foundation, Inc., 51
- * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#include "lttng/action/action.h"
+#include "lttng/trigger/trigger-internal.h"
 #define _LGPL_SOURCE
 #include <urcu.h>
 #include <urcu/rculfhash.h>
 #include <common/macros.h>
 #include <lttng/condition/condition.h>
 #include <lttng/action/action-internal.h>
+#include <lttng/action/group-internal.h>
+#include <lttng/domain-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/condition/session-rotation-internal.h>
+#include <lttng/condition/event-rule-internal.h>
+#include <lttng/domain-internal.h>
 #include <lttng/notification/channel-internal.h>
+#include <lttng/trigger/trigger-internal.h>
 
 #include <time.h>
 #include <unistd.h>
 #include <inttypes.h>
 #include <fcntl.h>
 
+#include "condition-internal.h"
 #include "notification-thread.h"
 #include "notification-thread-events.h"
 #include "notification-thread-commands.h"
 #include "lttng-sessiond.h"
 #include "kernel.h"
+#include "trigger-error-accounting.h"
 
 #define CLIENT_POLL_MASK_IN (LPOLLIN | LPOLLERR | LPOLLHUP | LPOLLRDHUP)
 #define CLIENT_POLL_MASK_IN_OUT (CLIENT_POLL_MASK_IN | LPOLLOUT)
 
+enum lttng_object_type {
+       LTTNG_OBJECT_TYPE_UNKNOWN,
+       LTTNG_OBJECT_TYPE_NONE,
+       LTTNG_OBJECT_TYPE_CHANNEL,
+       LTTNG_OBJECT_TYPE_SESSION,
+};
+
 struct lttng_trigger_list_element {
+       /* No ownership of the trigger object is assumed. */
        struct lttng_trigger *trigger;
        struct cds_list_head node;
 };
 
 struct lttng_channel_trigger_list {
        struct channel_key channel_key;
+       /* List of struct lttng_trigger_list_element. */
        struct cds_list_head list;
+       /* Node in the channel_triggers_ht */
        struct cds_lfht_node channel_triggers_ht_node;
+       /* call_rcu delayed reclaim. */
+       struct rcu_head rcu_node;
+};
+
+/*
+ * List of triggers applying to a given session.
+ *
+ * See:
+ *   - lttng_session_trigger_list_create()
+ *   - lttng_session_trigger_list_build()
+ *   - lttng_session_trigger_list_destroy()
+ *   - lttng_session_trigger_list_add()
+ */
+struct lttng_session_trigger_list {
+       /*
+        * Not owned by this; points to the session_info structure's
+        * session name.
+        */
+       const char *session_name;
+       /* List of struct lttng_trigger_list_element. */
+       struct cds_list_head list;
+       /* Node in the session_triggers_ht */
+       struct cds_lfht_node session_triggers_ht_node;
+       /*
+        * Weak reference to the notification system's session triggers
+        * hashtable.
+        *
+        * The session trigger list structure structure is owned by
+        * the session's session_info.
+        *
+        * The session_info is kept alive the the channel_infos holding a
+        * reference to it (reference counting). When those channels are
+        * destroyed (at runtime or on teardown), the reference they hold
+        * to the session_info are released. On destruction of session_info,
+        * session_info_destroy() will remove the list of triggers applying
+        * to this session from the notification system's state.
+        *
+        * This implies that the session_triggers_ht must be destroyed
+        * after the channels.
+        */
+       struct cds_lfht *session_triggers_ht;
+       /* Used for delayed RCU reclaim. */
+       struct rcu_head rcu_node;
 };
 
 struct lttng_trigger_ht_element {
        struct lttng_trigger *trigger;
        struct cds_lfht_node node;
+       struct cds_lfht_node node_by_name_uid;
+       /* call_rcu delayed reclaim. */
+       struct rcu_head rcu_node;
 };
 
 struct lttng_condition_list_element {
@@ -71,93 +127,18 @@ struct lttng_condition_list_element {
        struct cds_list_head node;
 };
 
-struct notification_client_list_element {
-       struct notification_client *client;
-       struct cds_list_head node;
-};
-
-struct notification_client_list {
-       struct lttng_trigger *trigger;
-       struct cds_list_head list;
-       struct cds_lfht_node notification_trigger_ht_node;
-};
-
-struct notification_client {
-       int socket;
-       /* Client protocol version. */
-       uint8_t major, minor;
-       uid_t uid;
-       gid_t gid;
-       /*
-        * Indicates if the credentials and versions of the client have been
-        * checked.
-        */
-       bool validated;
-       /*
-        * Conditions to which the client's notification channel is subscribed.
-        * List of struct lttng_condition_list_node. The condition member is
-        * owned by the client.
-        */
-       struct cds_list_head condition_list;
-       struct cds_lfht_node client_socket_ht_node;
-       struct {
-               struct {
-                       /*
-                        * During the reception of a message, the reception
-                        * buffers' "size" is set to contain the current
-                        * message's complete payload.
-                        */
-                       struct lttng_dynamic_buffer buffer;
-                       /* Bytes left to receive for the current message. */
-                       size_t bytes_to_receive;
-                       /* Type of the message being received. */
-                       enum lttng_notification_channel_message_type msg_type;
-                       /*
-                        * Indicates whether or not credentials are expected
-                        * from the client.
-                        */
-                       bool expect_creds;
-                       /*
-                        * Indicates whether or not credentials were received
-                        * from the client.
-                        */
-                       bool creds_received;
-                       /* Only used during credentials reception. */
-                       lttng_sock_cred creds;
-               } inbound;
-               struct {
-                       /*
-                        * Indicates whether or not a notification addressed to
-                        * this client was dropped because a command reply was
-                        * already buffered.
-                        *
-                        * A notification is dropped whenever the buffer is not
-                        * empty.
-                        */
-                       bool dropped_notification;
-                       /*
-                        * Indicates whether or not a command reply is already
-                        * buffered. In this case, it means that the client is
-                        * not consuming command replies before emitting a new
-                        * one. This could be caused by a protocol error or a
-                        * misbehaving/malicious client.
-                        */
-                       bool queued_command_reply;
-                       struct lttng_dynamic_buffer buffer;
-               } outbound;
-       } communication;
-};
-
 struct channel_state_sample {
        struct channel_key key;
        struct cds_lfht_node channel_state_ht_node;
        uint64_t highest_usage;
        uint64_t lowest_usage;
        uint64_t channel_total_consumed;
+       /* call_rcu delayed reclaim. */
+       struct rcu_head rcu_node;
 };
 
 static unsigned long hash_channel_key(struct channel_key *key);
-static int evaluate_condition(const struct lttng_condition *condition,
+static int evaluate_buffer_condition(const struct lttng_condition *condition,
                struct lttng_evaluation **evaluation,
                const struct notification_thread_state *state,
                const struct channel_state_sample *previous_sample,
@@ -173,6 +154,7 @@ int send_evaluation_to_clients(const struct lttng_trigger *trigger,
                uid_t channel_uid, gid_t channel_gid);
 
 
+/* session_info API */
 static
 void session_info_destroy(void *_data);
 static
@@ -181,7 +163,9 @@ 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);
+               uid_t uid, gid_t gid,
+               struct lttng_session_trigger_list *trigger_list,
+               struct cds_lfht *sessions_ht);
 static
 void session_info_add_channel(struct session_info *session_info,
                struct channel_info *channel_info);
@@ -189,17 +173,51 @@ static
 void session_info_remove_channel(struct session_info *session_info,
                struct channel_info *channel_info);
 
+/* lttng_session_trigger_list API */
+static
+struct lttng_session_trigger_list *lttng_session_trigger_list_create(
+               const char *session_name,
+               struct cds_lfht *session_triggers_ht);
+static
+struct lttng_session_trigger_list *lttng_session_trigger_list_build(
+               const struct notification_thread_state *state,
+               const char *session_name);
+static
+void lttng_session_trigger_list_destroy(
+               struct lttng_session_trigger_list *list);
+static
+int lttng_session_trigger_list_add(struct lttng_session_trigger_list *list,
+               struct lttng_trigger *trigger);
+
+static
+int client_handle_transmission_status(
+               struct notification_client *client,
+               enum client_transmission_status transmission_status,
+               struct notification_thread_state *state);
+
+static
+void free_lttng_trigger_ht_element_rcu(struct rcu_head *node);
+
 static
-int match_client(struct cds_lfht_node *node, const void *key)
+int match_client_socket(struct cds_lfht_node *node, const void *key)
 {
        /* This double-cast is intended to supress pointer-to-cast warning. */
-       int socket = (int) (intptr_t) key;
-       struct notification_client *client;
+       const int socket = (int) (intptr_t) key;
+       const struct notification_client *client = caa_container_of(node,
+                       struct notification_client, client_socket_ht_node);
 
-       client = caa_container_of(node, struct notification_client,
-                       client_socket_ht_node);
+       return client->socket == socket;
+}
 
-       return !!(client->socket == socket);
+static
+int match_client_id(struct cds_lfht_node *node, const void *key)
+{
+       /* This double-cast is intended to supress pointer-to-cast warning. */
+       const notification_client_id id = *((notification_client_id *) key);
+       const struct notification_client *client = caa_container_of(
+                       node, struct notification_client, client_id_ht_node);
+
+       return client->id == id;
 }
 
 static
@@ -215,6 +233,18 @@ int match_channel_trigger_list(struct cds_lfht_node *node, const void *key)
                        (channel_key->domain == trigger_list->channel_key.domain));
 }
 
+static
+int match_session_trigger_list(struct cds_lfht_node *node, const void *key)
+{
+       const char *session_name = (const char *) key;
+       struct lttng_session_trigger_list *trigger_list;
+
+       trigger_list = caa_container_of(node, struct lttng_session_trigger_list,
+                       session_triggers_ht_node);
+
+       return !!(strcmp(trigger_list->session_name, session_name) == 0);
+}
+
 static
 int match_channel_state_sample(struct cds_lfht_node *node, const void *key)
 {
@@ -242,36 +272,26 @@ int match_channel_info(struct cds_lfht_node *node, const void *key)
 }
 
 static
-int match_condition(struct cds_lfht_node *node, const void *key)
+int match_trigger(struct cds_lfht_node *node, const void *key)
 {
-       struct lttng_condition *condition_key = (struct lttng_condition *) key;
-       struct lttng_trigger_ht_element *trigger;
-       struct lttng_condition *condition;
+       struct lttng_trigger *trigger_key = (struct lttng_trigger *) key;
+       struct lttng_trigger_ht_element *trigger_ht_element;
 
-       trigger = caa_container_of(node, struct lttng_trigger_ht_element,
+       trigger_ht_element = caa_container_of(node, struct lttng_trigger_ht_element,
                        node);
-       condition = lttng_trigger_get_condition(trigger->trigger);
-       assert(condition);
 
-       return !!lttng_condition_is_equal(condition_key, condition);
+       return !!lttng_trigger_is_equal(trigger_key, trigger_ht_element->trigger);
 }
 
 static
-int match_client_list(struct cds_lfht_node *node, const void *key)
+int match_trigger_token(struct cds_lfht_node *node, const void *key)
 {
-       struct lttng_trigger *trigger_key = (struct lttng_trigger *) key;
-       struct notification_client_list *client_list;
-       struct lttng_condition *condition;
-       struct lttng_condition *condition_key = lttng_trigger_get_condition(
-                       trigger_key);
-
-       assert(condition_key);
-
-       client_list = caa_container_of(node, struct notification_client_list,
-                       notification_trigger_ht_node);
-       condition = lttng_trigger_get_condition(client_list->trigger);
+       const uint64_t *_key = key;
+       struct notification_trigger_tokens_ht_element *element;
 
-       return !!lttng_condition_is_equal(condition_key, condition);
+       element = caa_container_of(node, struct notification_trigger_tokens_ht_element,
+                       node);
+       return *_key == element->token ;
 }
 
 static
@@ -279,99 +299,118 @@ int match_client_list_condition(struct cds_lfht_node *node, const void *key)
 {
        struct lttng_condition *condition_key = (struct lttng_condition *) key;
        struct notification_client_list *client_list;
-       struct lttng_condition *condition;
+       const struct lttng_condition *condition;
 
        assert(condition_key);
 
        client_list = caa_container_of(node, struct notification_client_list,
-                       notification_trigger_ht_node);
-       condition = lttng_trigger_get_condition(client_list->trigger);
+                       notification_trigger_clients_ht_node);
+       condition = lttng_trigger_get_const_condition(client_list->trigger);
 
        return !!lttng_condition_is_equal(condition_key, condition);
 }
 
 static
-unsigned long lttng_condition_buffer_usage_hash(
-       const struct lttng_condition *_condition)
+int match_session(struct cds_lfht_node *node, const void *key)
 {
-       unsigned long hash = 0;
-       struct lttng_condition_buffer_usage *condition;
+       const char *name = key;
+       struct session_info *session_info = caa_container_of(
+               node, struct session_info, sessions_ht_node);
 
-       condition = container_of(_condition,
-                       struct lttng_condition_buffer_usage, parent);
+       return !strcmp(session_info->name, name);
+}
 
-       if (condition->session_name) {
-               hash ^= hash_key_str(condition->session_name, lttng_ht_seed);
-       }
-       if (condition->channel_name) {
-               hash ^= hash_key_str(condition->channel_name, lttng_ht_seed);
-       }
-       if (condition->domain.set) {
-               hash ^= hash_key_ulong(
-                               (void *) condition->domain.type,
-                               lttng_ht_seed);
-       }
-       if (condition->threshold_ratio.set) {
-               uint64_t val;
+/*
+ * Match trigger based on name and credentials only.
+ * Name duplication is NOT allowed for the same uid.
+ */
+static int match_name_uid(struct cds_lfht_node *node, const void *key)
+{
+       bool match = false;
+       struct lttng_trigger_ht_element *trigger_ht_element;
+       const char *name;
+       const char *key_name;
+       enum lttng_trigger_status status;
+       const struct lttng_credentials *key_creds;
+       const struct lttng_credentials *node_creds;
+       struct lttng_trigger *trigger_key = (struct lttng_trigger *) key;
 
-               val = condition->threshold_ratio.value * (double) UINT32_MAX;
-               hash ^= hash_key_u64(&val, lttng_ht_seed);
-       } else if (condition->threshold_bytes.set) {
-               uint64_t val;
+       trigger_ht_element = caa_container_of(node, struct lttng_trigger_ht_element,
+                       node_by_name_uid);
 
-               val = condition->threshold_bytes.value;
-               hash ^= hash_key_u64(&val, lttng_ht_seed);
+       status = lttng_trigger_get_name(trigger_ht_element->trigger, &name);
+       assert(status == LTTNG_TRIGGER_STATUS_OK);
+
+       status = lttng_trigger_get_name(trigger_key, &key_name);
+       assert(status == LTTNG_TRIGGER_STATUS_OK);
+
+       if (strcmp(name, key_name) != 0) {
+               goto end;
        }
-       return hash;
+
+       /* Check the uid */
+       key_creds = lttng_trigger_get_credentials(trigger_key);
+       node_creds = lttng_trigger_get_credentials(trigger_ht_element->trigger);
+
+       match = lttng_credentials_is_equal_uid(key_creds, node_creds);
+
+end:
+       return match;
 }
 
 static
-unsigned long lttng_condition_session_consumed_size_hash(
-       const struct lttng_condition *_condition)
+unsigned long hash_channel_key(struct channel_key *key)
 {
-       unsigned long hash = 0;
-       struct lttng_condition_session_consumed_size *condition;
-       uint64_t val;
+       unsigned long key_hash = hash_key_u64(&key->key, lttng_ht_seed);
+       unsigned long domain_hash = hash_key_ulong(
+               (void *) (unsigned long) key->domain, lttng_ht_seed);
 
-       condition = container_of(_condition,
-                       struct lttng_condition_session_consumed_size, parent);
+       return key_hash ^ domain_hash;
+}
 
-       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;
+static
+unsigned long hash_client_socket(int socket)
+{
+       return hash_key_ulong((void *) (unsigned long) socket, lttng_ht_seed);
+}
+
+static
+unsigned long hash_client_id(notification_client_id id)
+{
+       return hash_key_u64(&id, lttng_ht_seed);
 }
 
 /*
- * 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.
+ * Get the type of object to which a given condition applies. Bindings let
+ * the notification system evaluate a trigger's condition when a given
+ * object's state is updated.
+ *
+ * For instance, a condition bound to a channel will be evaluated everytime
+ * the channel's state is changed by a channel monitoring sample.
  */
 static
-unsigned long lttng_condition_hash(const struct lttng_condition *condition)
+enum lttng_object_type get_condition_binding_object(
+               const struct lttng_condition *condition)
 {
-       switch (condition->type) {
+       switch (lttng_condition_get_type(condition)) {
        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);
+               return LTTNG_OBJECT_TYPE_CHANNEL;
+       case LTTNG_CONDITION_TYPE_SESSION_ROTATION_ONGOING:
+       case LTTNG_CONDITION_TYPE_SESSION_ROTATION_COMPLETED:
+               return LTTNG_OBJECT_TYPE_SESSION;
+       case LTTNG_CONDITION_TYPE_EVENT_RULE_HIT:
+               return LTTNG_OBJECT_TYPE_NONE;
        default:
-               ERR("[notification-thread] Unexpected condition type caught");
-               abort();
+               return LTTNG_OBJECT_TYPE_UNKNOWN;
        }
 }
 
 static
-unsigned long hash_channel_key(struct channel_key *key)
+void free_channel_info_rcu(struct rcu_head *node)
 {
-       unsigned long key_hash = hash_key_u64(&key->key, lttng_ht_seed);
-       unsigned long domain_hash = hash_key_ulong(
-               (void *) (unsigned long) key->domain, lttng_ht_seed);
-
-       return key_hash ^ domain_hash;
+       free(caa_container_of(node, struct channel_info, rcu_node));
 }
 
 static
@@ -389,7 +428,13 @@ void channel_info_destroy(struct channel_info *channel_info)
        if (channel_info->name) {
                free(channel_info->name);
        }
-       free(channel_info);
+       call_rcu(&channel_info->rcu_node, free_channel_info_rcu);
+}
+
+static
+void free_session_info_rcu(struct rcu_head *node)
+{
+       free(caa_container_of(node, struct session_info, rcu_node));
 }
 
 /* Don't call directly, use the ref-counting mechanism. */
@@ -406,8 +451,14 @@ void session_info_destroy(void *_data)
                        ERR("[notification-thread] Failed to destroy channel information hash table");
                }
        }
+       lttng_session_trigger_list_destroy(session_info->trigger_list);
+
+       rcu_read_lock();
+       cds_lfht_del(session_info->sessions_ht,
+                       &session_info->sessions_ht_node);
+       rcu_read_unlock();
        free(session_info->name);
-       free(session_info);
+       call_rcu(&session_info->rcu_node, free_session_info_rcu);
 }
 
 static
@@ -429,7 +480,9 @@ 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)
+struct session_info *session_info_create(const char *name, uid_t uid, gid_t gid,
+               struct lttng_session_trigger_list *trigger_list,
+               struct cds_lfht *sessions_ht)
 {
        struct session_info *session_info;
 
@@ -454,6 +507,8 @@ struct session_info *session_info_create(const char *name, uid_t uid, gid_t gid)
        }
        session_info->uid = uid;
        session_info->gid = gid;
+       session_info->trigger_list = trigger_list;
+       session_info->sessions_ht = sessions_ht;
 end:
        return session_info;
 error:
@@ -518,12 +573,123 @@ error:
        return NULL;
 }
 
-/* This function must be called with the RCU read lock held. */
+LTTNG_HIDDEN
+bool notification_client_list_get(struct notification_client_list *list)
+{
+       return urcu_ref_get_unless_zero(&list->ref);
+}
+
 static
-int evaluate_condition_for_client(struct lttng_trigger *trigger,
-               struct lttng_condition *condition,
-               struct notification_client *client,
-               struct notification_thread_state *state)
+void free_notification_client_list_rcu(struct rcu_head *node)
+{
+       free(caa_container_of(node, struct notification_client_list,
+                       rcu_node));
+}
+
+static
+void notification_client_list_release(struct urcu_ref *list_ref)
+{
+       struct notification_client_list *list =
+                       container_of(list_ref, typeof(*list), ref);
+       struct notification_client_list_element *client_list_element, *tmp;
+
+       if (list->notification_trigger_clients_ht) {
+               rcu_read_lock();
+               cds_lfht_del(list->notification_trigger_clients_ht,
+                               &list->notification_trigger_clients_ht_node);
+               rcu_read_unlock();
+               list->notification_trigger_clients_ht = NULL;
+       }
+       cds_list_for_each_entry_safe(client_list_element, tmp,
+                                    &list->list, node) {
+               free(client_list_element);
+       }
+       pthread_mutex_destroy(&list->lock);
+       call_rcu(&list->rcu_node, free_notification_client_list_rcu);
+}
+
+static
+struct notification_client_list *notification_client_list_create(
+               const struct lttng_trigger *trigger)
+{
+       struct notification_client_list *client_list =
+                       zmalloc(sizeof(*client_list));
+
+       if (!client_list) {
+               goto error;
+       }
+       pthread_mutex_init(&client_list->lock, NULL);
+       urcu_ref_init(&client_list->ref);
+       cds_lfht_node_init(&client_list->notification_trigger_clients_ht_node);
+       CDS_INIT_LIST_HEAD(&client_list->list);
+       client_list->trigger = trigger;
+error:
+       return client_list;
+}
+
+static
+void publish_notification_client_list(
+               struct notification_thread_state *state,
+               struct notification_client_list *list)
+{
+       const struct lttng_condition *condition =
+                       lttng_trigger_get_const_condition(list->trigger);
+
+       assert(!list->notification_trigger_clients_ht);
+       notification_client_list_get(list);
+
+       list->notification_trigger_clients_ht =
+                       state->notification_trigger_clients_ht;
+
+       rcu_read_lock();
+       cds_lfht_add(state->notification_trigger_clients_ht,
+                       lttng_condition_hash(condition),
+                       &list->notification_trigger_clients_ht_node);
+       rcu_read_unlock();
+}
+
+LTTNG_HIDDEN
+void notification_client_list_put(struct notification_client_list *list)
+{
+       if (!list) {
+               return;
+       }
+       return urcu_ref_put(&list->ref, notification_client_list_release);
+}
+
+/* Provides a reference to the returned list. */
+static
+struct notification_client_list *get_client_list_from_condition(
+       struct notification_thread_state *state,
+       const struct lttng_condition *condition)
+{
+       struct cds_lfht_node *node;
+       struct cds_lfht_iter iter;
+       struct notification_client_list *list = NULL;
+
+       rcu_read_lock();
+       cds_lfht_lookup(state->notification_trigger_clients_ht,
+                       lttng_condition_hash(condition),
+                       match_client_list_condition,
+                       condition,
+                       &iter);
+       node = cds_lfht_iter_get_node(&iter);
+       if (node) {
+               list = container_of(node, struct notification_client_list,
+                               notification_trigger_clients_ht_node);
+               list = notification_client_list_get(list) ? list : NULL;
+       }
+
+       rcu_read_unlock();
+       return list;
+}
+
+static
+int evaluate_channel_condition_for_client(
+               const struct lttng_condition *condition,
+               struct notification_thread_state *state,
+               struct lttng_evaluation **evaluation,
+               uid_t *session_uid, gid_t *session_gid)
 {
        int ret;
        struct cds_lfht_iter iter;
@@ -532,23 +698,17 @@ int evaluate_condition_for_client(struct lttng_trigger *trigger,
        struct channel_key *channel_key = NULL;
        struct channel_state_sample *last_sample = NULL;
        struct lttng_channel_trigger_list *channel_trigger_list = NULL;
-       struct lttng_evaluation *evaluation = NULL;
-       struct notification_client_list client_list = { 0 };
-       struct notification_client_list_element client_list_element = { 0 };
 
-       assert(trigger);
-       assert(condition);
-       assert(client);
-       assert(state);
+       rcu_read_lock();
 
-       /* Find the channel associated with the trigger. */
+       /* Find the channel associated with the condition. */
        cds_lfht_for_each_entry(state->channel_triggers_ht, &iter,
-                       channel_trigger_list , channel_triggers_ht_node) {
+                       channel_trigger_list, channel_triggers_ht_node) {
                struct lttng_trigger_list_element *element;
 
                cds_list_for_each_entry(element, &channel_trigger_list->list, node) {
                        const struct lttng_condition *current_condition =
-                               lttng_trigger_get_const_condition(
+                                       lttng_trigger_get_const_condition(
                                                element->trigger);
 
                        assert(current_condition);
@@ -569,7 +729,7 @@ int evaluate_condition_for_client(struct lttng_trigger *trigger,
 
        if (!channel_key){
                /* No channel found; normal exit. */
-               DBG("[notification-thread] No channel associated with newly subscribed-to condition");
+               DBG("[notification-thread] No known channel associated with newly subscribed-to condition");
                ret = 0;
                goto end;
        }
@@ -603,7 +763,7 @@ int evaluate_condition_for_client(struct lttng_trigger *trigger,
                goto end;
        }
 
-       ret = evaluate_condition(condition, &evaluation, state,
+       ret = evaluate_buffer_condition(condition, evaluation, state,
                        NULL, last_sample,
                        0, channel_info->session_info->consumed_data_size,
                        channel_info);
@@ -612,58 +772,207 @@ int evaluate_condition_for_client(struct lttng_trigger *trigger,
                goto end;
        }
 
-       if (!evaluation) {
-               /* Evaluation yielded nothing. Normal exit. */
-               DBG("[notification-thread] Newly subscribed-to condition evaluated to false, nothing to report to client");
-               ret = 0;
-               goto end;
-       }
-
-       /*
-        * Create a temporary client list with the client currently
-        * subscribing.
-        */
-       cds_lfht_node_init(&client_list.notification_trigger_ht_node);
-       CDS_INIT_LIST_HEAD(&client_list.list);
-       client_list.trigger = trigger;
-
-       CDS_INIT_LIST_HEAD(&client_list_element.node);
-       client_list_element.client = client;
-       cds_list_add(&client_list_element.node, &client_list.list);
-
-       /* 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->session_info->uid,
-                       channel_info->session_info->gid);
-
+       *session_uid = channel_info->session_info->uid;
+       *session_gid = channel_info->session_info->gid;
 end:
+       rcu_read_unlock();
        return ret;
 }
 
 static
-int notification_thread_client_subscribe(struct notification_client *client,
-               struct lttng_condition *condition,
-               struct notification_thread_state *state,
-               enum lttng_notification_channel_status *_status)
+const char *get_condition_session_name(const struct lttng_condition *condition)
 {
-       int ret = 0;
-       struct cds_lfht_iter iter;
-       struct cds_lfht_node *node;
-       struct notification_client_list *client_list;
-       struct lttng_condition_list_element *condition_list_element = NULL;
-       struct notification_client_list_element *client_list_element = NULL;
-       enum lttng_notification_channel_status status =
-                       LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
+       const char *session_name = NULL;
+       enum lttng_condition_status status;
 
-       /*
-        * Ensure that the client has not already subscribed to this condition
-        * before.
-        */
-       cds_list_for_each_entry(condition_list_element, &client->condition_list, node) {
-               if (lttng_condition_is_equal(condition_list_element->condition,
-                               condition)) {
-                       status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ALREADY_SUBSCRIBED;
+       switch (lttng_condition_get_type(condition)) {
+       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_LOW:
+       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_HIGH:
+               status = lttng_condition_buffer_usage_get_session_name(
+                               condition, &session_name);
+               break;
+       case LTTNG_CONDITION_TYPE_SESSION_CONSUMED_SIZE:
+               status = lttng_condition_session_consumed_size_get_session_name(
+                               condition, &session_name);
+               break;
+       case LTTNG_CONDITION_TYPE_SESSION_ROTATION_ONGOING:
+       case LTTNG_CONDITION_TYPE_SESSION_ROTATION_COMPLETED:
+               status = lttng_condition_session_rotation_get_session_name(
+                               condition, &session_name);
+               break;
+       default:
+               abort();
+       }
+       if (status != LTTNG_CONDITION_STATUS_OK) {
+               ERR("[notification-thread] Failed to retrieve session rotation condition's session name");
+               goto end;
+       }
+end:
+       return session_name;
+}
+
+static
+int evaluate_session_condition_for_client(
+               const struct lttng_condition *condition,
+               struct notification_thread_state *state,
+               struct lttng_evaluation **evaluation,
+               uid_t *session_uid, gid_t *session_gid)
+{
+       int ret;
+       struct cds_lfht_iter iter;
+       struct cds_lfht_node *node;
+       const char *session_name;
+       struct session_info *session_info = NULL;
+
+       rcu_read_lock();
+       session_name = get_condition_session_name(condition);
+
+       /* Find the session associated with the trigger. */
+       cds_lfht_lookup(state->sessions_ht,
+                       hash_key_str(session_name, lttng_ht_seed),
+                       match_session,
+                       session_name,
+                       &iter);
+       node = cds_lfht_iter_get_node(&iter);
+       if (!node) {
+               DBG("[notification-thread] No known session matching name \"%s\"",
+                               session_name);
+               ret = 0;
+               goto end;
+       }
+
+       session_info = caa_container_of(node, struct session_info,
+                       sessions_ht_node);
+       session_info_get(session_info);
+
+       /*
+        * Evaluation is performed in-line here since only one type of
+        * session-bound condition is handled for the moment.
+        */
+       switch (lttng_condition_get_type(condition)) {
+       case LTTNG_CONDITION_TYPE_SESSION_ROTATION_ONGOING:
+               if (!session_info->rotation.ongoing) {
+                       ret = 0;
+                       goto end_session_put;
+               }
+
+               *evaluation = lttng_evaluation_session_rotation_ongoing_create(
+                               session_info->rotation.id);
+               if (!*evaluation) {
+                       /* Fatal error. */
+                       ERR("[notification-thread] Failed to create session rotation ongoing evaluation for session \"%s\"",
+                                       session_info->name);
+                       ret = -1;
+                       goto end_session_put;
+               }
+               ret = 0;
+               break;
+       default:
+               ret = 0;
+               goto end_session_put;
+       }
+
+       *session_uid = session_info->uid;
+       *session_gid = session_info->gid;
+
+end_session_put:
+       session_info_put(session_info);
+end:
+       rcu_read_unlock();
+       return ret;
+}
+
+static
+int evaluate_condition_for_client(const struct lttng_trigger *trigger,
+               const struct lttng_condition *condition,
+               struct notification_client *client,
+               struct notification_thread_state *state)
+{
+       int ret;
+       struct lttng_evaluation *evaluation = NULL;
+       struct notification_client_list client_list = {
+               .lock = PTHREAD_MUTEX_INITIALIZER,
+       };
+       struct notification_client_list_element client_list_element = { 0 };
+       uid_t object_uid = 0;
+       gid_t object_gid = 0;
+
+       assert(trigger);
+       assert(condition);
+       assert(client);
+       assert(state);
+
+       switch (get_condition_binding_object(condition)) {
+       case LTTNG_OBJECT_TYPE_SESSION:
+               ret = evaluate_session_condition_for_client(condition, state,
+                               &evaluation, &object_uid, &object_gid);
+               break;
+       case LTTNG_OBJECT_TYPE_CHANNEL:
+               ret = evaluate_channel_condition_for_client(condition, state,
+                               &evaluation, &object_uid, &object_gid);
+               break;
+       case LTTNG_OBJECT_TYPE_NONE:
+               DBG("[notification-thread] Newly subscribed-to condition not binded to object, nothing to evaluate");
+               ret = 0;
+               goto end;
+       case LTTNG_OBJECT_TYPE_UNKNOWN:
+       default:
+               ret = -1;
+               goto end;
+       }
+       if (ret) {
+               /* Fatal error. */
+               goto end;
+       }
+       if (!evaluation) {
+               /* Evaluation yielded nothing. Normal exit. */
+               DBG("[notification-thread] Newly subscribed-to condition evaluated to false, nothing to report to client");
+               ret = 0;
+               goto end;
+       }
+
+       /*
+        * Create a temporary client list with the client currently
+        * subscribing.
+        */
+       cds_lfht_node_init(&client_list.notification_trigger_clients_ht_node);
+       CDS_INIT_LIST_HEAD(&client_list.list);
+       client_list.trigger = trigger;
+
+       CDS_INIT_LIST_HEAD(&client_list_element.node);
+       client_list_element.client = client;
+       cds_list_add(&client_list_element.node, &client_list.list);
+
+       /* 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, object_uid, object_gid);
+
+end:
+       return ret;
+}
+
+static
+int notification_thread_client_subscribe(struct notification_client *client,
+               struct lttng_condition *condition,
+               struct notification_thread_state *state,
+               enum lttng_notification_channel_status *_status)
+{
+       int ret = 0;
+       struct notification_client_list *client_list = NULL;
+       struct lttng_condition_list_element *condition_list_element = NULL;
+       struct notification_client_list_element *client_list_element = NULL;
+       enum lttng_notification_channel_status status =
+                       LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
+
+       /*
+        * Ensure that the client has not already subscribed to this condition
+        * before.
+        */
+       cds_list_for_each_entry(condition_list_element, &client->condition_list, node) {
+               if (lttng_condition_is_equal(condition_list_element->condition,
+                               condition)) {
+                       status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ALREADY_SUBSCRIBED;
                        goto end;
                }
        }
@@ -679,8 +988,6 @@ int notification_thread_client_subscribe(struct notification_client *client,
                goto error;
        }
 
-       rcu_read_lock();
-
        /*
         * Add the newly-subscribed condition to the client's subscription list.
         */
@@ -688,35 +995,32 @@ int notification_thread_client_subscribe(struct notification_client *client,
        condition_list_element->condition = condition;
        cds_list_add(&condition_list_element->node, &client->condition_list);
 
-       cds_lfht_lookup(state->notification_trigger_clients_ht,
-                       lttng_condition_hash(condition),
-                       match_client_list_condition,
-                       condition,
-                       &iter);
-       node = cds_lfht_iter_get_node(&iter);
-       if (!node) {
+       client_list = get_client_list_from_condition(state, condition);
+       if (!client_list) {
                /*
                 * 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;
+               goto end;
        }
 
-       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.
+        *
+        * The client_list's trigger is used without locking the list itself.
+        * This is correct since the list doesn't own the trigger and the
+        * object is immutable.
         */
        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;
+               goto end;
        }
 
        /*
@@ -726,13 +1030,17 @@ int notification_thread_client_subscribe(struct notification_client *client,
         */
        client_list_element->client = client;
        CDS_INIT_LIST_HEAD(&client_list_element->node);
+
+       pthread_mutex_lock(&client_list->lock);
        cds_list_add(&client_list_element->node, &client_list->list);
-end_unlock:
-       rcu_read_unlock();
+       pthread_mutex_unlock(&client_list->lock);
 end:
        if (_status) {
                *_status = status;
        }
+       if (client_list) {
+               notification_client_list_put(client_list);
+       }
        return ret;
 error:
        free(condition_list_element);
@@ -747,8 +1055,6 @@ int notification_thread_client_unsubscribe(
                struct notification_thread_state *state,
                enum lttng_notification_channel_status *_status)
 {
-       struct cds_lfht_iter iter;
-       struct cds_lfht_node *node;
        struct notification_client_list *client_list;
        struct lttng_condition_list_element *condition_list_element,
                        *condition_tmp;
@@ -790,30 +1096,24 @@ int notification_thread_client_unsubscribe(
         * Remove the client from the list of clients interested the trigger
         * matching the condition.
         */
-       rcu_read_lock();
-       cds_lfht_lookup(state->notification_trigger_clients_ht,
-                       lttng_condition_hash(condition),
-                       match_client_list_condition,
-                       condition,
-                       &iter);
-       node = cds_lfht_iter_get_node(&iter);
-       if (!node) {
-               goto end_unlock;
+       client_list = get_client_list_from_condition(state, condition);
+       if (!client_list) {
+               goto end;
        }
 
-       client_list = caa_container_of(node, struct notification_client_list,
-                       notification_trigger_ht_node);
+       pthread_mutex_lock(&client_list->lock);
        cds_list_for_each_entry_safe(client_list_element, client_tmp,
                        &client_list->list, node) {
-               if (client_list_element->client->socket != client->socket) {
+               if (client_list_element->client->id != client->id) {
                        continue;
                }
                cds_list_del(&client_list_element->node);
                free(client_list_element);
                break;
        }
-end_unlock:
-       rcu_read_unlock();
+       pthread_mutex_unlock(&client_list->lock);
+       notification_client_list_put(client_list);
+       client_list = NULL;
 end:
        lttng_condition_destroy(condition);
        if (_status) {
@@ -822,29 +1122,33 @@ end:
        return 0;
 }
 
+static
+void free_notification_client_rcu(struct rcu_head *node)
+{
+       free(caa_container_of(node, struct notification_client, rcu_node));
+}
+
 static
 void notification_client_destroy(struct notification_client *client,
                struct notification_thread_state *state)
 {
-       struct lttng_condition_list_element *condition_list_element, *tmp;
-
        if (!client) {
                return;
        }
 
-       /* Release all conditions to which the client was subscribed. */
-       cds_list_for_each_entry_safe(condition_list_element, tmp,
-                       &client->condition_list, node) {
-               (void) notification_thread_client_unsubscribe(client,
-                               condition_list_element->condition, state, NULL);
-       }
-
+       /*
+        * The client object is not reachable by other threads, no need to lock
+        * the client here.
+        */
        if (client->socket >= 0) {
                (void) lttcomm_close_unix_sock(client->socket);
+               client->socket = -1;
        }
-       lttng_dynamic_buffer_reset(&client->communication.inbound.buffer);
-       lttng_dynamic_buffer_reset(&client->communication.outbound.buffer);
-       free(client);
+       client->communication.active = false;
+       lttng_payload_reset(&client->communication.inbound.payload);
+       lttng_payload_reset(&client->communication.outbound.payload);
+       pthread_mutex_destroy(&client->lock);
+       call_rcu(&client->rcu_node, free_notification_client_rcu);
 }
 
 /*
@@ -860,8 +1164,8 @@ struct notification_client *get_client_from_socket(int socket,
        struct notification_client *client = NULL;
 
        cds_lfht_lookup(state->client_socket_ht,
-                       hash_key_ulong((void *) (unsigned long) socket, lttng_ht_seed),
-                       match_client,
+                       hash_client_socket(socket),
+                       match_client_socket,
                        (void *) (unsigned long) socket,
                        &iter);
        node = cds_lfht_iter_get_node(&iter);
@@ -875,10 +1179,38 @@ end:
        return client;
 }
 
+/*
+ * Call with rcu_read_lock held (and hold for the lifetime of the returned
+ * client pointer).
+ */
+static
+struct notification_client *get_client_from_id(notification_client_id id,
+               struct notification_thread_state *state)
+{
+       struct cds_lfht_iter iter;
+       struct cds_lfht_node *node;
+       struct notification_client *client = NULL;
+
+       cds_lfht_lookup(state->client_id_ht,
+                       hash_client_id(id),
+                       match_client_id,
+                       &id,
+                       &iter);
+       node = cds_lfht_iter_get_node(&iter);
+       if (!node) {
+               goto end;
+       }
+
+       client = caa_container_of(node, struct notification_client,
+                       client_id_ht_node);
+end:
+       return client;
+}
+
 static
 bool buffer_usage_condition_applies_to_channel(
-               struct lttng_condition *condition,
-               struct channel_info *channel_info)
+               const struct lttng_condition *condition,
+               const struct channel_info *channel_info)
 {
        enum lttng_condition_status status;
        enum lttng_domain_type condition_domain;
@@ -914,8 +1246,8 @@ fail:
 
 static
 bool session_consumed_size_condition_applies_to_channel(
-               struct lttng_condition *condition,
-               struct channel_info *channel_info)
+               const struct lttng_condition *condition,
+               const struct channel_info *channel_info)
 {
        enum lttng_condition_status status;
        const char *condition_session_name = NULL;
@@ -934,13 +1266,13 @@ fail:
 }
 
 static
-bool trigger_applies_to_channel(struct lttng_trigger *trigger,
-               struct channel_info *channel_info)
+bool trigger_applies_to_channel(const struct lttng_trigger *trigger,
+               const struct channel_info *channel_info)
 {
-       struct lttng_condition *condition;
+       const struct lttng_condition *condition;
        bool trigger_applies;
 
-       condition = lttng_trigger_get_condition(trigger);
+       condition = lttng_trigger_get_const_condition(trigger);
        if (!condition) {
                goto fail;
        }
@@ -983,58 +1315,255 @@ bool trigger_applies_to_client(struct lttng_trigger *trigger,
        return applies;
 }
 
+/* Must be called with RCU read lock held. */
 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 lttng_session_trigger_list *get_session_trigger_list(
                struct notification_thread_state *state,
-               const char *name, uid_t uid, gid_t gid)
+               const char *session_name)
 {
-       struct session_info *session = NULL;
+       struct lttng_session_trigger_list *list = 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,
+       cds_lfht_lookup(state->session_triggers_ht,
+                       hash_key_str(session_name, lttng_ht_seed),
+                       match_session_trigger_list,
+                       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);
+       if (!node) {
+               /*
+                * Not an error, the list of triggers applying to that session
+                * will be initialized when the session is created.
+                */
+               DBG("[notification-thread] No trigger list found for session \"%s\" as it is not yet known to the notification system",
+                               session_name);
                goto end;
        }
 
-       cds_lfht_add(state->sessions_ht, hash_key_str(name, lttng_ht_seed),
-                       &session->sessions_ht_node);
+       list = caa_container_of(node,
+                       struct lttng_session_trigger_list,
+                       session_triggers_ht_node);
 end:
-       rcu_read_unlock();
-       return session;
+       return list;
 }
 
-static
-int handle_notification_thread_command_add_channel(
+/*
+ * Allocate an empty lttng_session_trigger_list for the session named
+ * 'session_name'.
+ *
+ * No ownership of 'session_name' is assumed by the session trigger list.
+ * It is the caller's responsability to ensure the session name is alive
+ * for as long as this list is.
+ */
+static
+struct lttng_session_trigger_list *lttng_session_trigger_list_create(
+               const char *session_name,
+               struct cds_lfht *session_triggers_ht)
+{
+       struct lttng_session_trigger_list *list;
+
+       list = zmalloc(sizeof(*list));
+       if (!list) {
+               goto end;
+       }
+       list->session_name = session_name;
+       CDS_INIT_LIST_HEAD(&list->list);
+       cds_lfht_node_init(&list->session_triggers_ht_node);
+       list->session_triggers_ht = session_triggers_ht;
+
+       rcu_read_lock();
+       /* Publish the list through the session_triggers_ht. */
+       cds_lfht_add(session_triggers_ht,
+                       hash_key_str(session_name, lttng_ht_seed),
+                       &list->session_triggers_ht_node);
+       rcu_read_unlock();
+end:
+       return list;
+}
+
+static
+void free_session_trigger_list_rcu(struct rcu_head *node)
+{
+       free(caa_container_of(node, struct lttng_session_trigger_list,
+                       rcu_node));
+}
+
+static
+void lttng_session_trigger_list_destroy(struct lttng_session_trigger_list *list)
+{
+       struct lttng_trigger_list_element *trigger_list_element, *tmp;
+
+       /* Empty the list element by element, and then free the list itself. */
+       cds_list_for_each_entry_safe(trigger_list_element, tmp,
+                       &list->list, node) {
+               cds_list_del(&trigger_list_element->node);
+               free(trigger_list_element);
+       }
+       rcu_read_lock();
+       /* Unpublish the list from the session_triggers_ht. */
+       cds_lfht_del(list->session_triggers_ht,
+                       &list->session_triggers_ht_node);
+       rcu_read_unlock();
+       call_rcu(&list->rcu_node, free_session_trigger_list_rcu);
+}
+
+static
+int lttng_session_trigger_list_add(struct lttng_session_trigger_list *list,
+               struct lttng_trigger *trigger)
+{
+       int ret = 0;
+       struct lttng_trigger_list_element *new_element =
+                       zmalloc(sizeof(*new_element));
+
+       if (!new_element) {
+               ret = -1;
+               goto end;
+       }
+       CDS_INIT_LIST_HEAD(&new_element->node);
+       new_element->trigger = trigger;
+       cds_list_add(&new_element->node, &list->list);
+end:
+       return ret;
+}
+
+static
+bool trigger_applies_to_session(const struct lttng_trigger *trigger,
+               const char *session_name)
+{
+       bool applies = false;
+       const struct lttng_condition *condition;
+
+       condition = lttng_trigger_get_const_condition(trigger);
+       switch (lttng_condition_get_type(condition)) {
+       case LTTNG_CONDITION_TYPE_SESSION_ROTATION_ONGOING:
+       case LTTNG_CONDITION_TYPE_SESSION_ROTATION_COMPLETED:
+       {
+               enum lttng_condition_status condition_status;
+               const char *condition_session_name;
+
+               condition_status = lttng_condition_session_rotation_get_session_name(
+                       condition, &condition_session_name);
+               if (condition_status != LTTNG_CONDITION_STATUS_OK) {
+                       ERR("[notification-thread] Failed to retrieve session rotation condition's session name");
+                       goto end;
+               }
+
+               assert(condition_session_name);
+               applies = !strcmp(condition_session_name, session_name);
+               break;
+       }
+       default:
+               goto end;
+       }
+end:
+       return applies;
+}
+
+/*
+ * Allocate and initialize an lttng_session_trigger_list which contains
+ * all triggers that apply to the session named 'session_name'.
+ *
+ * No ownership of 'session_name' is assumed by the session trigger list.
+ * It is the caller's responsability to ensure the session name is alive
+ * for as long as this list is.
+ */
+static
+struct lttng_session_trigger_list *lttng_session_trigger_list_build(
+               const struct notification_thread_state *state,
+               const char *session_name)
+{
+       int trigger_count = 0;
+       struct lttng_session_trigger_list *session_trigger_list = NULL;
+       struct lttng_trigger_ht_element *trigger_ht_element = NULL;
+       struct cds_lfht_iter iter;
+
+       session_trigger_list = lttng_session_trigger_list_create(session_name,
+                       state->session_triggers_ht);
+
+       /* Add all triggers applying to the session named 'session_name'. */
+       cds_lfht_for_each_entry(state->triggers_ht, &iter, trigger_ht_element,
+                       node) {
+               int ret;
+
+               if (!trigger_applies_to_session(trigger_ht_element->trigger,
+                               session_name)) {
+                       continue;
+               }
+
+               ret = lttng_session_trigger_list_add(session_trigger_list,
+                               trigger_ht_element->trigger);
+               if (ret) {
+                       goto error;
+               }
+
+               trigger_count++;
+       }
+
+       DBG("[notification-thread] Found %i triggers that apply to newly created session",
+                       trigger_count);
+       return session_trigger_list;
+error:
+       lttng_session_trigger_list_destroy(session_trigger_list);
+       return NULL;
+}
+
+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;
+       struct lttng_session_trigger_list *trigger_list;
+
+       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);
+               session_info_get(session);
+               goto end;
+       }
+
+       trigger_list = lttng_session_trigger_list_build(state, name);
+       if (!trigger_list) {
+               goto error;
+       }
+
+       session = session_info_create(name, uid, gid, trigger_list,
+                       state->sessions_ht);
+       if (!session) {
+               ERR("[notification-thread] Failed to allocation session info for session \"%s\" (uid = %i, gid = %i)",
+                               name, uid, gid);
+               lttng_session_trigger_list_destroy(trigger_list);
+               goto error;
+       }
+       trigger_list = NULL;
+
+       cds_lfht_add(state->sessions_ht, hash_key_str(name, lttng_ht_seed),
+                       &session->sessions_ht_node);
+end:
+       rcu_read_unlock();
+       return session;
+error:
+       rcu_read_unlock();
+       session_info_put(session);
+       return NULL;
+}
+
+static
+int handle_notification_thread_command_add_channel(
                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,
@@ -1055,14 +1584,14 @@ int handle_notification_thread_command_add_channel(
 
        DBG("[notification-thread] Adding channel %s from session %s, channel key = %" PRIu64 " in %s domain",
                        channel_name, session_name, channel_key_int,
-                       channel_domain == LTTNG_DOMAIN_KERNEL ? "kernel" : "user space");
+                       lttng_domain_type_str(channel_domain));
 
        CDS_INIT_LIST_HEAD(&trigger_list);
 
        session_info = find_or_create_session_info(state, session_name,
                        session_uid, session_gid);
        if (!session_info) {
-               /* Allocation error or an internal error occured. */
+               /* Allocation error or an internal error occurred. */
                goto error;
        }
 
@@ -1072,6 +1601,7 @@ int handle_notification_thread_command_add_channel(
                goto error;
        }
 
+       rcu_read_lock();
        /* Build a list of all triggers applying to the new channel. */
        cds_lfht_for_each_entry(state->triggers_ht, &iter, trigger_ht_element,
                        node) {
@@ -1084,6 +1614,7 @@ int handle_notification_thread_command_add_channel(
 
                new_element = zmalloc(sizeof(*new_element));
                if (!new_element) {
+                       rcu_read_unlock();
                        goto error;
                }
                CDS_INIT_LIST_HEAD(&new_element->node);
@@ -1091,6 +1622,7 @@ int handle_notification_thread_command_add_channel(
                cds_list_add(&new_element->node, &trigger_list);
                trigger_count++;
        }
+       rcu_read_unlock();
 
        DBG("[notification-thread] Found %i triggers that apply to newly added channel",
                        trigger_count);
@@ -1116,6 +1648,7 @@ int handle_notification_thread_command_add_channel(
                        hash_channel_key(&new_channel_info->key),
                        &channel_trigger_list->channel_triggers_ht_node);
        rcu_read_unlock();
+       session_info_put(session_info);
        *cmd_result = LTTNG_OK;
        return 0;
 error:
@@ -1124,6 +1657,20 @@ error:
        return 1;
 }
 
+static
+void free_channel_trigger_list_rcu(struct rcu_head *node)
+{
+       free(caa_container_of(node, struct lttng_channel_trigger_list,
+                       rcu_node));
+}
+
+static
+void free_channel_state_sample_rcu(struct rcu_head *node)
+{
+       free(caa_container_of(node, struct channel_state_sample,
+                       rcu_node));
+}
+
 static
 int handle_notification_thread_command_remove_channel(
        struct notification_thread_state *state,
@@ -1138,7 +1685,7 @@ int handle_notification_thread_command_remove_channel(
        struct channel_info *channel_info;
 
        DBG("[notification-thread] Removing channel key = %" PRIu64 " in %s domain",
-                       channel_key, domain == LTTNG_DOMAIN_KERNEL ? "kernel" : "user space");
+                       channel_key, lttng_domain_type_str(domain));
 
        rcu_read_lock();
 
@@ -1166,7 +1713,7 @@ int handle_notification_thread_command_remove_channel(
                free(trigger_list_element);
        }
        cds_lfht_del(state->channel_triggers_ht, node);
-       free(trigger_list);
+       call_rcu(&trigger_list->rcu_node, free_channel_trigger_list_rcu);
 
        /* Free sampled channel state. */
        cds_lfht_lookup(state->channel_state_ht,
@@ -1185,7 +1732,7 @@ int handle_notification_thread_command_remove_channel(
                                channel_state_ht_node);
 
                cds_lfht_del(state->channel_state_ht, node);
-               free(sample);
+               call_rcu(&sample->rcu_node, free_channel_state_sample_rcu);
        }
 
        /* Remove the channel from the channels_ht and free it. */
@@ -1207,91 +1754,677 @@ end:
 }
 
 static
-int condition_is_supported(struct lttng_condition *condition)
+int handle_notification_thread_command_session_rotation(
+       struct notification_thread_state *state,
+       enum notification_thread_command_type cmd_type,
+       const char *session_name, uid_t session_uid, gid_t session_gid,
+       uint64_t trace_archive_chunk_id,
+       struct lttng_trace_archive_location *location,
+       enum lttng_error_code *_cmd_result)
 {
-       int ret;
+       int ret = 0;
+       enum lttng_error_code cmd_result = LTTNG_OK;
+       struct lttng_session_trigger_list *trigger_list;
+       struct lttng_trigger_list_element *trigger_list_element;
+       struct session_info *session_info;
+       const struct lttng_credentials session_creds = {
+               .uid = LTTNG_OPTIONAL_INIT_VALUE(session_uid),
+               .gid = LTTNG_OPTIONAL_INIT_VALUE(session_gid),
+       };
 
-       switch (lttng_condition_get_type(condition)) {
-       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_LOW:
-       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_HIGH:
-       {
-               enum lttng_domain_type domain;
+       rcu_read_lock();
 
-               ret = lttng_condition_buffer_usage_get_domain_type(condition,
-                               &domain);
-               if (ret) {
-                       ret = -1;
-                       goto end;
+       session_info = find_or_create_session_info(state, session_name,
+                       session_uid, session_gid);
+       if (!session_info) {
+               /* Allocation error or an internal error occurred. */
+               ret = -1;
+               cmd_result = LTTNG_ERR_NOMEM;
+               goto end;
+       }
+
+       session_info->rotation.ongoing =
+                       cmd_type == NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_ONGOING;
+       session_info->rotation.id = trace_archive_chunk_id;
+       trigger_list = get_session_trigger_list(state, session_name);
+       if (!trigger_list) {
+               DBG("[notification-thread] No triggers applying to session \"%s\" found",
+                               session_name);
+               goto end;
+       }
+
+       cds_list_for_each_entry(trigger_list_element, &trigger_list->list,
+                       node) {
+               const struct lttng_condition *condition;
+               struct lttng_trigger *trigger;
+               struct notification_client_list *client_list;
+               struct lttng_evaluation *evaluation = NULL;
+               enum lttng_condition_type condition_type;
+               enum action_executor_status executor_status;
+
+               trigger = trigger_list_element->trigger;
+               condition = lttng_trigger_get_const_condition(trigger);
+               assert(condition);
+               condition_type = lttng_condition_get_type(condition);
+
+               if (condition_type == LTTNG_CONDITION_TYPE_SESSION_ROTATION_ONGOING &&
+                               cmd_type != NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_ONGOING) {
+                       continue;
+               } else if (condition_type == LTTNG_CONDITION_TYPE_SESSION_ROTATION_COMPLETED &&
+                               cmd_type != NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_COMPLETED) {
+                       continue;
                }
 
-               if (domain != LTTNG_DOMAIN_KERNEL) {
-                       ret = 1;
-                       goto end;
+               client_list = get_client_list_from_condition(state, condition);
+               if (cmd_type == NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_ONGOING) {
+                       evaluation = lttng_evaluation_session_rotation_ongoing_create(
+                                       trace_archive_chunk_id);
+               } else {
+                       evaluation = lttng_evaluation_session_rotation_completed_create(
+                                       trace_archive_chunk_id, location);
+               }
+
+               if (!evaluation) {
+                       /* Internal error */
+                       ret = -1;
+                       cmd_result = LTTNG_ERR_UNK;
+                       goto put_list;
                }
 
                /*
-                * Older kernel tracers don't expose the API to monitor their
-                * buffers. Therefore, we reject triggers that require that
-                * mechanism to be available to be evaluated.
+                * Ownership of `evaluation` transferred to the action executor
+                * no matter the result.
                 */
-               ret = kernel_supports_ring_buffer_snapshot_sample_positions(
-                               kernel_tracer_fd);
-               break;
-       }
-       default:
-               ret = 1;
+               executor_status = action_executor_enqueue(state->executor,
+                               trigger, evaluation, &session_creds,
+                               client_list);
+               evaluation = NULL;
+               switch (executor_status) {
+               case ACTION_EXECUTOR_STATUS_OK:
+                       break;
+               case ACTION_EXECUTOR_STATUS_ERROR:
+               case ACTION_EXECUTOR_STATUS_INVALID:
+                       /*
+                        * TODO Add trigger identification (name/id) when
+                        * it is added to the API.
+                        */
+                       ERR("Fatal error occurred while enqueuing action associated with session rotation trigger");
+                       ret = -1;
+                       goto put_list;
+               case ACTION_EXECUTOR_STATUS_OVERFLOW:
+                       /*
+                        * TODO Add trigger identification (name/id) when
+                        * it is added to the API.
+                        *
+                        * Not a fatal error.
+                        */
+                       WARN("No space left when enqueuing action associated with session rotation trigger");
+                       ret = 0;
+                       goto put_list;
+               default:
+                       abort();
+               }
+
+put_list:
+               notification_client_list_put(client_list);
+               if (caa_unlikely(ret)) {
+                       break;
+               }
        }
 end:
+       session_info_put(session_info);
+       *_cmd_result = cmd_result;
+       rcu_read_unlock();
        return ret;
 }
 
-/*
- * FIXME A client's credentials are not checked when registering a trigger, nor
- *       are they stored alongside with the trigger.
- *
- * The effects of this are benign since:
- *     - The client will succeed in registering the trigger, as it is valid,
- *     - The trigger will, internally, be bound to the channel,
- *     - The notifications will not be sent since the client's credentials
- *       are checked against the channel at that moment.
- *
- * If this function returns a non-zero value, it means something is
- * 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)
+int handle_notification_thread_command_add_application(
+       struct notification_thread_handle *handle,
+       struct notification_thread_state *state,
+       int read_side_trigger_event_application_pipe,
+       enum lttng_domain_type domain_type,
+       enum lttng_error_code *_cmd_result)
 {
        int ret = 0;
-       struct lttng_condition *condition;
-       struct notification_client *client;
-       struct notification_client_list *client_list = NULL;
-       struct lttng_trigger_ht_element *trigger_ht_element = NULL;
-       struct notification_client_list_element *client_list_element, *tmp;
-       struct cds_lfht_node *node;
-       struct cds_lfht_iter iter;
-       struct channel_info *channel;
-       bool free_trigger = true;
+       enum lttng_error_code cmd_result = LTTNG_OK;
+       struct notification_event_trigger_source_element *element = NULL;
 
-       rcu_read_lock();
+       element = zmalloc(sizeof(*element));
+       if (!element) {
+               cmd_result = LTTNG_ERR_NOMEM;
+               ret = -1;
+               goto end;
+       }
 
-       condition = lttng_trigger_get_condition(trigger);
-       assert(condition);
+       CDS_INIT_LIST_HEAD(&element->node);
+       element->fd = read_side_trigger_event_application_pipe;
+       element->domain = domain_type;
+
+       pthread_mutex_lock(&handle->event_trigger_sources.lock);
+       cds_list_add(&element->node, &handle->event_trigger_sources.list);
+       pthread_mutex_unlock(&handle->event_trigger_sources.lock);
 
-       ret = condition_is_supported(condition);
+       /* TODO: remove on failure to add to list? */
+
+       /* Adding the read side pipe to the event poll */
+       ret = lttng_poll_add(&state->events,
+                       read_side_trigger_event_application_pipe,
+                       LPOLLIN | LPOLLERR);
+
+       DBG3("[notification-thread] Adding application event source from fd: %d", read_side_trigger_event_application_pipe);
        if (ret < 0) {
-               goto error;
-       } else if (ret == 0) {
+               /* TODO: what should be the value of cmd_result??? */
+               ERR("[notification-thread] Failed to add event source pipe fd to pollset");
+               goto end;
+       }
+
+end:
+       *_cmd_result = cmd_result;
+       return ret;
+}
+
+static
+int handle_notification_thread_command_remove_application(
+       struct notification_thread_handle *handle,
+       struct notification_thread_state *state,
+       int read_side_trigger_event_application_pipe,
+       enum lttng_error_code *_cmd_result)
+{
+       int ret = 0;
+       enum lttng_error_code cmd_result = LTTNG_OK;
+       /* Used for logging */
+       enum lttng_domain_type domain = LTTNG_DOMAIN_NONE;
+
+       /* TODO: missing a lock propably to revisit */
+       struct notification_event_trigger_source_element *source_element = NULL, *tmp;
+
+       cds_list_for_each_entry_safe(source_element, tmp,
+                       &handle->event_trigger_sources.list, node) {
+               if (source_element->fd != read_side_trigger_event_application_pipe) {
+                       continue;
+               }
+
+               cds_list_del(&source_element->node);
+               break;
+       }
+
+       /* It should always be found */
+       assert(source_element);
+
+       DBG3("[notification-thread] Removing application event source from fd: %d of domain: %s",
+                       read_side_trigger_event_application_pipe,
+                       lttng_domain_type_str(domain));
+       free(source_element);
+
+       /* Removing the read side pipe to the event poll */
+       ret = lttng_poll_del(&state->events,
+                       read_side_trigger_event_application_pipe);
+       if (ret < 0) {
+               /* TODO: what should be the value of cmd_result??? */
+               ERR("[notification-thread] Failed to remove event source pipe fd from pollset");
+               goto end;
+       }
+
+end:
+       *_cmd_result = cmd_result;
+       return ret;
+}
+
+static int handle_notification_thread_command_get_tokens(
+               struct notification_thread_handle *handle,
+               struct notification_thread_state *state,
+               struct lttng_triggers **triggers,
+               enum lttng_error_code *_cmd_result)
+{
+       int ret = 0, i = 0;
+       enum lttng_error_code cmd_result = LTTNG_OK;
+       struct cds_lfht_iter iter;
+       struct notification_trigger_tokens_ht_element *element;
+       struct lttng_triggers *local_triggers = NULL;
+
+       local_triggers = lttng_triggers_create();
+       if (!local_triggers) {
+               cmd_result = LTTNG_ERR_NOMEM;
+               goto end;
+       }
+
+       rcu_read_lock();
+       cds_lfht_for_each_entry (
+                       state->trigger_tokens_ht, &iter, element, node) {
+               ret = lttng_triggers_add(local_triggers, element->trigger);
+               if (ret < 0) {
+                       cmd_result = LTTNG_ERR_FATAL;
+                       ret = -1;
+                       goto end;
+               }
+
+               i++;
+       }
+
+       /* Passing ownership up */
+       *triggers = local_triggers;
+       local_triggers = NULL;
+
+end:
+       rcu_read_unlock();
+       lttng_triggers_destroy(local_triggers);
+       *_cmd_result = cmd_result;
+       return ret;
+}
+
+static
+int trigger_update_error_count(struct lttng_trigger *trigger)
+{
+       int ret = 0;
+       uint64_t error_count = 0;
+       enum trigger_error_accounting_status status;
+
+       status = trigger_error_accounting_get_count(trigger, &error_count);
+       if (status != TRIGGER_ERROR_ACCOUNTING_STATUS_OK) {
+               ERR("Error getting trigger error count");
+       }
+
+       lttng_trigger_set_error_count(trigger, error_count);
+       return ret;
+}
+
+static int handle_notification_thread_command_list_triggers(
+               struct notification_thread_handle *handle,
+               struct notification_thread_state *state,
+               uid_t uid,
+               struct lttng_triggers **triggers,
+               enum lttng_error_code *_cmd_result)
+{
+       int ret = 0, i = 0;
+       enum lttng_error_code cmd_result = LTTNG_OK;
+       struct cds_lfht_iter iter;
+       struct lttng_trigger_ht_element *trigger_ht_element;
+       struct lttng_triggers *local_triggers = NULL;
+       const struct lttng_credentials *creds;
+
+       long scb, sca;
+       unsigned long count;
+
+       rcu_read_lock();
+       cds_lfht_count_nodes(state->triggers_ht, &scb, &count, &sca);
+
+       local_triggers = lttng_triggers_create();
+       if (!local_triggers) {
+               cmd_result = LTTNG_ERR_NOMEM;
+               goto end;
+       }
+
+       cds_lfht_for_each_entry (state->triggers_ht, &iter,
+                       trigger_ht_element, node) {
+               /*
+                * Only return the trigger for which the requestion client have
+                * access.
+                * Root user have visibility over all triggers.
+                */
+               creds = lttng_trigger_get_credentials(trigger_ht_element->trigger);
+               if (uid != lttng_credentials_get_uid(creds) && uid != 0) {
+                       continue;
+               }
+
+               ret = trigger_update_error_count(trigger_ht_element->trigger);
+               assert(!ret);
+
+               ret = lttng_triggers_add(local_triggers, trigger_ht_element->trigger);
+               if (ret < 0) {
+                       ret = -1;
+                       goto end;
+               }
+
+               i++;
+       }
+
+       /* Passing ownership up */
+       *triggers = local_triggers;
+       local_triggers = NULL;
+
+end:
+       rcu_read_unlock();
+       lttng_triggers_destroy(local_triggers);
+       *_cmd_result = cmd_result;
+       return ret;
+}
+
+static
+int condition_is_supported(struct lttng_condition *condition)
+{
+       int ret;
+
+       switch (lttng_condition_get_type(condition)) {
+       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_LOW:
+       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_HIGH:
+       {
+               enum lttng_domain_type domain;
+
+               ret = lttng_condition_buffer_usage_get_domain_type(condition,
+                               &domain);
+               if (ret) {
+                       ret = -1;
+                       goto end;
+               }
+
+               if (domain != LTTNG_DOMAIN_KERNEL) {
+                       ret = 1;
+                       goto end;
+               }
+
+               /*
+                * Older kernel tracers don't expose the API to monitor their
+                * buffers. Therefore, we reject triggers that require that
+                * mechanism to be available to be evaluated.
+                */
+               ret = kernel_supports_ring_buffer_snapshot_sample_positions();
+               break;
+       }
+       case LTTNG_CONDITION_TYPE_EVENT_RULE_HIT:
+       {
+               /* TODO:
+                * Check for kernel support.
+                * Check for ust support ??
+                */
+               ret = 1;
+               break;
+       }
+       default:
+               ret = 1;
+       }
+end:
+       return ret;
+}
+
+static
+int action_is_supported(struct lttng_action *action)
+{
+       int ret;
+
+       switch (lttng_action_get_type(action)) {
+       case LTTNG_ACTION_TYPE_NOTIFY:
+       case LTTNG_ACTION_TYPE_START_SESSION:
+       case LTTNG_ACTION_TYPE_STOP_SESSION:
+       case LTTNG_ACTION_TYPE_ROTATE_SESSION:
+       case LTTNG_ACTION_TYPE_SNAPSHOT_SESSION:
+       {
+               /* TODO validate that this is true for kernel in regards to
+                * rotation and snapshot. Start stop is not a problem notify
+                * either.
+                */
+               /* For now all type of actions are supported */
+               ret = 1;
+               break;
+       }
+       case LTTNG_ACTION_TYPE_GROUP:
+       {
+               /* TODO: Iterate over all internal actions and validate that
+                * they are supported
+                */
+               ret = 1;
+               break;
+
+       }
+       default:
+               ret = 1;
+       }
+
+       return ret;
+}
+
+/* Must be called with RCU read lock held. */
+static
+int bind_trigger_to_matching_session(struct lttng_trigger *trigger,
+               struct notification_thread_state *state)
+{
+       int ret = 0;
+       const struct lttng_condition *condition;
+       const char *session_name;
+       struct lttng_session_trigger_list *trigger_list;
+
+       condition = lttng_trigger_get_const_condition(trigger);
+       switch (lttng_condition_get_type(condition)) {
+       case LTTNG_CONDITION_TYPE_SESSION_ROTATION_ONGOING:
+       case LTTNG_CONDITION_TYPE_SESSION_ROTATION_COMPLETED:
+       {
+               enum lttng_condition_status status;
+
+               status = lttng_condition_session_rotation_get_session_name(
+                               condition, &session_name);
+               if (status != LTTNG_CONDITION_STATUS_OK) {
+                       ERR("[notification-thread] Failed to bind trigger to session: unable to get 'session_rotation' condition's session name");
+                       ret = -1;
+                       goto end;
+               }
+               break;
+       }
+       default:
+               ret = -1;
+               goto end;
+       }
+
+       trigger_list = get_session_trigger_list(state, session_name);
+       if (!trigger_list) {
+               DBG("[notification-thread] Unable to bind trigger applying to session \"%s\" as it is not yet known to the notification system",
+                               session_name);
+               goto end;
+
+       }
+
+       DBG("[notification-thread] Newly registered trigger bound to session \"%s\"",
+                       session_name);
+       ret = lttng_session_trigger_list_add(trigger_list, trigger);
+end:
+       return ret;
+}
+
+/* Must be called with RCU read lock held. */
+static
+int bind_trigger_to_matching_channels(struct lttng_trigger *trigger,
+               struct notification_thread_state *state)
+{
+       int ret = 0;
+       struct cds_lfht_node *node;
+       struct cds_lfht_iter iter;
+       struct channel_info *channel;
+
+       cds_lfht_for_each_entry(state->channels_ht, &iter, channel,
+                       channels_ht_node) {
+               struct lttng_trigger_list_element *trigger_list_element;
+               struct lttng_channel_trigger_list *trigger_list;
+               struct cds_lfht_iter lookup_iter;
+
+               if (!trigger_applies_to_channel(trigger, channel)) {
+                       continue;
+               }
+
+               cds_lfht_lookup(state->channel_triggers_ht,
+                               hash_channel_key(&channel->key),
+                               match_channel_trigger_list,
+                               &channel->key,
+                               &lookup_iter);
+               node = cds_lfht_iter_get_node(&lookup_iter);
+               assert(node);
+               trigger_list = caa_container_of(node,
+                               struct lttng_channel_trigger_list,
+                               channel_triggers_ht_node);
+
+               trigger_list_element = zmalloc(sizeof(*trigger_list_element));
+               if (!trigger_list_element) {
+                       ret = -1;
+                       goto end;
+               }
+               CDS_INIT_LIST_HEAD(&trigger_list_element->node);
+               trigger_list_element->trigger = trigger;
+               cds_list_add(&trigger_list_element->node, &trigger_list->list);
+               DBG("[notification-thread] Newly registered trigger bound to channel \"%s\"",
+                               channel->name);
+       }
+end:
+       return ret;
+}
+
+static
+bool is_trigger_action_notify(const struct lttng_trigger *trigger)
+{
+       bool is_notify = false;
+       unsigned int i, count;
+       enum lttng_action_status action_status;
+       const struct lttng_action *action =
+                       lttng_trigger_get_const_action(trigger);
+       enum lttng_action_type action_type;
+
+       assert(action);
+       action_type = lttng_action_get_type(action);
+       if (action_type == LTTNG_ACTION_TYPE_NOTIFY) {
+               is_notify = true;
+               goto end;
+       } else if (action_type != LTTNG_ACTION_TYPE_GROUP) {
+               goto end;
+       }
+
+       action_status = lttng_action_group_get_count(action, &count);
+       assert(action_status == LTTNG_ACTION_STATUS_OK);
+
+       for (i = 0; i < count; i++) {
+               const struct lttng_action *inner_action =
+                               lttng_action_group_get_at_index(
+                                               action, i);
+
+               action_type = lttng_action_get_type(inner_action);
+               if (action_type == LTTNG_ACTION_TYPE_NOTIFY) {
+                       is_notify = true;
+                       goto end;
+               }
+       }
+
+end:
+       return is_notify;
+}
+
+static bool trigger_name_taken(struct notification_thread_state *state,
+               const struct lttng_trigger *trigger)
+{
+       struct cds_lfht_node *triggers_by_name_uid_ht_node;
+       struct cds_lfht_iter iter;
+
+       /*
+        * No duplicata is allowed in the triggers_by_name_uid_ht.
+        * The match is done against the trigger name and uid.
+        */
+       cds_lfht_lookup(state->triggers_by_name_uid_ht,
+                       hash_key_str(trigger->name, lttng_ht_seed),
+                       match_name_uid,
+                       trigger,
+                       &iter);
+       triggers_by_name_uid_ht_node = cds_lfht_iter_get_node(&iter);
+       if (triggers_by_name_uid_ht_node) {
+               return true;
+       } else {
+               return false;
+       }
+}
+
+static
+void generate_trigger_name(struct notification_thread_state *state, struct lttng_trigger *trigger, const char **name)
+{
+       /*
+        * Here the offset criteria guarantee an end. This will be a nice
+        * bikeshedding conversation. I would simply generate uuid and use them
+        * as trigger name.
+        */
+       bool taken = false;
+       enum lttng_trigger_status status;
+       do {
+               lttng_trigger_generate_name(trigger, state->trigger_id.name_offset);
+
+               status = lttng_trigger_get_name(trigger, name);
+               assert(status == LTTNG_TRIGGER_STATUS_OK);
+
+               taken = trigger_name_taken(state, trigger);
+               if (taken) {
+                       state->trigger_id.name_offset++;
+               }
+       } while (taken || state->trigger_id.name_offset == UINT32_MAX);
+}
+
+/*
+ * FIXME A client's credentials are not checked when registering a trigger.
+ *
+ * The effects of this are benign since:
+ *     - The client will succeed in registering the trigger, as it is valid,
+ *     - The trigger will, internally, be bound to the channel/session,
+ *     - The notifications will not be sent since the client's credentials
+ *       are checked against the channel at that moment.
+ *
+ * If this function returns a non-zero value, it means something is
+ * 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)
+{
+       int ret = 0;
+       int is_supported;
+       struct lttng_condition *condition;
+       struct lttng_action *action;
+       struct notification_client *client;
+       struct notification_client_list *client_list = NULL;
+       struct lttng_trigger_ht_element *trigger_ht_element = NULL;
+       struct notification_client_list_element *client_list_element;
+       struct notification_trigger_tokens_ht_element *trigger_tokens_ht_element = NULL;
+       struct cds_lfht_node *node;
+       struct cds_lfht_iter iter;
+       const char* trigger_name;
+       bool free_trigger = true;
+       struct lttng_evaluation *evaluation = NULL;
+       struct lttng_credentials object_creds;
+       uid_t object_uid;
+       gid_t object_gid;
+       enum action_executor_status executor_status;
+
+       rcu_read_lock();
+
+       /* Set the trigger's tracer token */
+       lttng_trigger_set_tracer_token(trigger, state->trigger_id.token_generator);
+
+       if (lttng_trigger_get_name(trigger, &trigger_name) ==
+                       LTTNG_TRIGGER_STATUS_UNSET) {
+               generate_trigger_name(state, trigger, &trigger_name);
+       } else if (trigger_name_taken(state, trigger)) {
+               /* Not a fatal error */
+               *cmd_result = LTTNG_ERR_TRIGGER_EXISTS;
+               ret = 0;
+               goto error;
+       }
+
+       condition = lttng_trigger_get_condition(trigger);
+       assert(condition);
+
+       action = lttng_trigger_get_action(trigger);
+       assert(action);
+
+       is_supported = condition_is_supported(condition);
+       if (is_supported < 0) {
+               goto error;
+       } else if (is_supported == 0) {
                *cmd_result = LTTNG_ERR_NOT_SUPPORTED;
                goto error;
-       } else {
-               /* Feature is supported, continue. */
+       }
+
+       is_supported = action_is_supported(action);
+       if (is_supported < 0) {
+               goto error;
+       } else if (is_supported == 0) {
                ret = 0;
+               *cmd_result = LTTNG_ERR_NOT_SUPPORTED;
+               goto error;
        }
 
        trigger_ht_element = zmalloc(sizeof(*trigger_ht_element));
@@ -1302,12 +2435,13 @@ int handle_notification_thread_command_register_trigger(
 
        /* Add trigger to the trigger_ht. */
        cds_lfht_node_init(&trigger_ht_element->node);
+       cds_lfht_node_init(&trigger_ht_element->node_by_name_uid);
        trigger_ht_element->trigger = trigger;
 
        node = cds_lfht_add_unique(state->triggers_ht,
                        lttng_condition_hash(condition),
-                       match_condition,
-                       condition,
+                       match_trigger,
+                       trigger,
                        &trigger_ht_element->node);
        if (node != &trigger_ht_element->node) {
                /* Not a fatal error, simply report it to the client. */
@@ -1315,10 +2449,66 @@ int handle_notification_thread_command_register_trigger(
                goto error_free_ht_element;
        }
 
+       node = cds_lfht_add_unique(state->triggers_by_name_uid_ht,
+                       hash_key_str(trigger_name, lttng_ht_seed), match_name_uid,
+                       trigger, &trigger_ht_element->node_by_name_uid);
+       if (node != &trigger_ht_element->node_by_name_uid) {
+               /* Not a fatal error, simply report it to the client. */
+               cds_lfht_del(state->triggers_ht, &trigger_ht_element->node);
+               *cmd_result = LTTNG_ERR_TRIGGER_EXISTS;
+               goto error_free_ht_element;
+       }
+
+       if (lttng_condition_get_type(condition) == LTTNG_CONDITION_TYPE_EVENT_RULE_HIT) {
+               uint64_t error_counter_index = 0;
+               enum trigger_error_accounting_status error_accounting_status;
+
+               trigger_tokens_ht_element = zmalloc(sizeof(*trigger_tokens_ht_element));
+               if (!trigger_tokens_ht_element) {
+                       ret = -1;
+                       cds_lfht_del(state->triggers_ht, &trigger_ht_element->node);
+                       cds_lfht_del(state->triggers_by_name_uid_ht, &trigger_ht_element->node_by_name_uid);
+                       goto error;
+               }
+
+               error_accounting_status = trigger_error_accounting_register_trigger(
+                               trigger, &error_counter_index);
+               if (error_accounting_status != TRIGGER_ERROR_ACCOUNTING_STATUS_OK) {
+                       ERR("Error registering trigger for error accounting");
+                       cds_lfht_del(state->triggers_ht, &trigger_ht_element->node);
+                       cds_lfht_del(state->triggers_by_name_uid_ht, &trigger_ht_element->node_by_name_uid);
+                       *cmd_result = LTTNG_ERR_TRIGGER_GROUP_ERROR_COUNTER_FULL;
+                       goto error_free_ht_element;
+               }
+
+               lttng_trigger_set_error_counter_index(trigger, error_counter_index);
+
+               /* Add trigger token to the trigger_tokens_ht. */
+               cds_lfht_node_init(&trigger_tokens_ht_element->node);
+               trigger_tokens_ht_element->token = LTTNG_OPTIONAL_GET(trigger->tracer_token);
+               trigger_tokens_ht_element->trigger = trigger;
+
+               node = cds_lfht_add_unique(state->trigger_tokens_ht,
+                               hash_key_u64(&trigger_tokens_ht_element->token, lttng_ht_seed),
+                               match_trigger_token,
+                               &trigger_tokens_ht_element->token,
+                               &trigger_tokens_ht_element->node);
+               if (node != &trigger_tokens_ht_element->node) {
+                       /* TODO: THIS IS A FATAL ERROR... should never happen */
+                       /* Not a fatal error, simply report it to the client. */
+                       *cmd_result = LTTNG_ERR_TRIGGER_EXISTS;
+                       cds_lfht_del(state->triggers_ht, &trigger_ht_element->node);
+                       cds_lfht_del(state->triggers_by_name_uid_ht, &trigger_ht_element->node_by_name_uid);
+                       trigger_error_accounting_unregister_trigger(trigger);
+                       goto error_free_ht_element;
+               }
+       }
+
        /*
         * Ownership of the trigger and of its wrapper was transfered to
-        * the triggers_ht.
+        * the triggers_ht. Same for token ht element if necessary.
         */
+       trigger_tokens_ht_element = NULL;
        trigger_ht_element = NULL;
        free_trigger = false;
 
@@ -1327,74 +2517,73 @@ int handle_notification_thread_command_register_trigger(
         * It is not skipped as this is the only action type currently
         * supported.
         */
-       client_list = zmalloc(sizeof(*client_list));
-       if (!client_list) {
-               ret = -1;
-               goto error_free_ht_element;
-       }
-       cds_lfht_node_init(&client_list->notification_trigger_ht_node);
-       CDS_INIT_LIST_HEAD(&client_list->list);
-       client_list->trigger = trigger;
-
-       /* Build a list of clients to which this new trigger applies. */
-       cds_lfht_for_each_entry(state->client_socket_ht, &iter, client,
-                       client_socket_ht_node) {
-               if (!trigger_applies_to_client(trigger, client)) {
-                       continue;
-               }
-
-               client_list_element = zmalloc(sizeof(*client_list_element));
-               if (!client_list_element) {
+       if (is_trigger_action_notify(trigger)) {
+               client_list = notification_client_list_create(trigger);
+               if (!client_list) {
                        ret = -1;
-                       goto error_free_client_list;
+                       goto error_free_ht_element;
                }
-               CDS_INIT_LIST_HEAD(&client_list_element->node);
-               client_list_element->client = client;
-               cds_list_add(&client_list_element->node, &client_list->list);
-       }
 
-       cds_lfht_add(state->notification_trigger_clients_ht,
-                       lttng_condition_hash(condition),
-                       &client_list->notification_trigger_ht_node);
+               /* Build a list of clients to which this new trigger applies. */
+               cds_lfht_for_each_entry (state->client_socket_ht, &iter, client,
+                               client_socket_ht_node) {
+                       if (!trigger_applies_to_client(trigger, client)) {
+                               continue;
+                       }
 
-       /*
-        * Add the trigger to list of triggers bound to the channels currently
-        * known.
-        */
-       cds_lfht_for_each_entry(state->channels_ht, &iter, channel,
-                       channels_ht_node) {
-               struct lttng_trigger_list_element *trigger_list_element;
-               struct lttng_channel_trigger_list *trigger_list;
+                       client_list_element =
+                                       zmalloc(sizeof(*client_list_element));
+                       if (!client_list_element) {
+                               ret = -1;
+                               goto error_put_client_list;
+                       }
 
-               if (!trigger_applies_to_channel(trigger, channel)) {
-                       continue;
+                       CDS_INIT_LIST_HEAD(&client_list_element->node);
+                       client_list_element->client = client;
+                       cds_list_add(&client_list_element->node,
+                                       &client_list->list);
                }
 
-               cds_lfht_lookup(state->channel_triggers_ht,
-                               hash_channel_key(&channel->key),
-                               match_channel_trigger_list,
-                               &channel->key,
-                               &iter);
-               node = cds_lfht_iter_get_node(&iter);
-               assert(node);
-               trigger_list = caa_container_of(node,
-                               struct lttng_channel_trigger_list,
-                               channel_triggers_ht_node);
+               /*
+                * Client list ownership transferred to the
+                * notification_trigger_clients_ht.
+                */
+               publish_notification_client_list(state, client_list);
+       }
 
-               trigger_list_element = zmalloc(sizeof(*trigger_list_element));
-               if (!trigger_list_element) {
-                       ret = -1;
-                       goto error_free_client_list;
+       switch (get_condition_binding_object(condition)) {
+       case LTTNG_OBJECT_TYPE_SESSION:
+               /* Add the trigger to the list if it matches a known session. */
+               ret = bind_trigger_to_matching_session(trigger, state);
+               if (ret) {
+                       goto error_put_client_list;
                }
-               CDS_INIT_LIST_HEAD(&trigger_list_element->node);
-               trigger_list_element->trigger = trigger;
-               cds_list_add(&trigger_list_element->node, &trigger_list->list);
+               break;
+       case LTTNG_OBJECT_TYPE_CHANNEL:
+               /*
+                * Add the trigger to list of triggers bound to the channels
+                * currently known.
+                */
+               ret = bind_trigger_to_matching_channels(trigger, state);
+               if (ret) {
+                       goto error_put_client_list;
+               }
+               break;
+       case LTTNG_OBJECT_TYPE_NONE:
+               break;
+       default:
+               ERR("Unknown object type on which to bind a newly registered trigger was encountered");
+               ret = -1;
+               goto error_put_client_list;
        }
 
        /*
-        * 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.
+        * The new trigger's condition must be evaluated against the current
+        * state.
+        *
+        * In the case of `notify` action, 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
@@ -1417,44 +2606,112 @@ int handle_notification_thread_command_register_trigger(
         * 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;
-               }
+       switch (get_condition_binding_object(condition)) {
+       case LTTNG_OBJECT_TYPE_SESSION:
+               ret = evaluate_session_condition_for_client(condition, state,
+                               &evaluation, &object_uid,
+                               &object_gid);
+               break;
+       case LTTNG_OBJECT_TYPE_CHANNEL:
+               ret = evaluate_channel_condition_for_client(condition, state,
+                               &evaluation, &object_uid,
+                               &object_gid);
+               break;
+       case LTTNG_OBJECT_TYPE_NONE:
+               ret = 0;
+               break;
+       case LTTNG_OBJECT_TYPE_UNKNOWN:
+       default:
+               ret = -1;
+               break;
+       }
+
+       if (ret) {
+               /* Fatal error. */
+               goto error_put_client_list;
+       }
+
+       LTTNG_OPTIONAL_SET(&object_creds.uid, object_uid);
+       LTTNG_OPTIONAL_SET(&object_creds.gid, object_gid);
+
+       DBG("Newly registered trigger's condition evaluated to %s",
+                       evaluation ? "true" : "false");
+       if (!evaluation) {
+               /* Evaluation yielded nothing. Normal exit. */
+               ret = 0;
+               goto end;
        }
 
        /*
-        * Client list ownership transferred to the
-        * notification_trigger_clients_ht.
+        * Ownership of `evaluation` transferred to the action executor
+        * no matter the result.
         */
-       client_list = NULL;
+       executor_status = action_executor_enqueue(state->executor, trigger,
+                       evaluation, &object_creds, client_list);
+       evaluation = NULL;
+       switch (executor_status) {
+       case ACTION_EXECUTOR_STATUS_OK:
+               break;
+       case ACTION_EXECUTOR_STATUS_ERROR:
+       case ACTION_EXECUTOR_STATUS_INVALID:
+               /*
+                * TODO Add trigger identification (name/id) when
+                * it is added to the API.
+                */
+               ERR("Fatal error occurred while enqueuing action associated to newly registered trigger");
+               ret = -1;
+               goto error_put_client_list;
+       case ACTION_EXECUTOR_STATUS_OVERFLOW:
+               /*
+                * TODO Add trigger identification (name/id) when
+                * it is added to the API.
+                *
+                * Not a fatal error.
+                */
+               WARN("No space left when enqueuing action associated to newly registered trigger");
+               ret = 0;
+               goto end;
+       default:
+               abort();
+       }
 
+end:
+       /* Increment the trigger unique id generator */
+       state->trigger_id.token_generator++;
        *cmd_result = LTTNG_OK;
-error_free_client_list:
-       if (client_list) {
-               cds_list_for_each_entry_safe(client_list_element, tmp,
-                               &client_list->list, node) {
-                       free(client_list_element);
-               }
-               free(client_list);
-       }
+
+error_put_client_list:
+       notification_client_list_put(client_list);
+
 error_free_ht_element:
-       free(trigger_ht_element);
+       if (trigger_ht_element) {
+               /* Delayed removal due to RCU constraint on delete. */
+               call_rcu(&trigger_ht_element->rcu_node, free_lttng_trigger_ht_element_rcu);
+       }
+
+       free(trigger_tokens_ht_element);
 error:
        if (free_trigger) {
-               struct lttng_action *action = lttng_trigger_get_action(trigger);
-
-               lttng_condition_destroy(condition);
-               lttng_action_destroy(action);
                lttng_trigger_destroy(trigger);
        }
        rcu_read_unlock();
        return ret;
 }
 
+static
+void free_lttng_trigger_ht_element_rcu(struct rcu_head *node)
+{
+       free(caa_container_of(node, struct lttng_trigger_ht_element,
+                       rcu_node));
+}
+
+static
+void free_notification_trigger_tokens_ht_element_rcu(struct rcu_head *node)
+{
+       free(caa_container_of(node, struct notification_trigger_tokens_ht_element,
+                       rcu_node));
+}
+
 static
 int handle_notification_thread_command_unregister_trigger(
                struct notification_thread_state *state,
@@ -1462,22 +2719,20 @@ int handle_notification_thread_command_unregister_trigger(
                enum lttng_error_code *_cmd_reply)
 {
        struct cds_lfht_iter iter;
-       struct cds_lfht_node *node, *triggers_ht_node;
+       struct cds_lfht_node *triggers_ht_node;
        struct lttng_channel_trigger_list *trigger_list;
        struct notification_client_list *client_list;
-       struct notification_client_list_element *client_list_element, *tmp;
        struct lttng_trigger_ht_element *trigger_ht_element = NULL;
        struct lttng_condition *condition = lttng_trigger_get_condition(
                        trigger);
-       struct lttng_action *action;
        enum lttng_error_code cmd_reply;
 
        rcu_read_lock();
 
        cds_lfht_lookup(state->triggers_ht,
                        lttng_condition_hash(condition),
-                       match_condition,
-                       condition,
+                       match_trigger,
+                       trigger,
                        &iter);
        triggers_ht_node = cds_lfht_iter_get_node(&iter);
        if (!triggers_ht_node) {
@@ -1494,13 +2749,7 @@ int handle_notification_thread_command_unregister_trigger(
 
                cds_list_for_each_entry_safe(trigger_element, tmp,
                                &trigger_list->list, node) {
-                       const struct lttng_condition *current_condition =
-                                       lttng_trigger_get_const_condition(
-                                               trigger_element->trigger);
-
-                       assert(current_condition);
-                       if (!lttng_condition_is_equal(condition,
-                                       current_condition)) {
+                       if (!lttng_trigger_is_equal(trigger, trigger_element->trigger)) {
                                continue;
                        }
 
@@ -1511,37 +2760,49 @@ int handle_notification_thread_command_unregister_trigger(
                }
        }
 
-       /*
-        * Remove and release the client list from
-        * notification_trigger_clients_ht.
-        */
-       cds_lfht_lookup(state->notification_trigger_clients_ht,
-                       lttng_condition_hash(condition),
-                       match_client_list,
-                       trigger,
-                       &iter);
-       node = cds_lfht_iter_get_node(&iter);
-       assert(node);
-       client_list = caa_container_of(node, struct notification_client_list,
-                       notification_trigger_ht_node);
-       cds_list_for_each_entry_safe(client_list_element, tmp,
-                       &client_list->list, node) {
-               free(client_list_element);
+       if (lttng_condition_get_type(condition) == LTTNG_CONDITION_TYPE_EVENT_RULE_HIT) {
+               struct notification_trigger_tokens_ht_element *trigger_tokens_ht_element;
+               cds_lfht_for_each_entry(state->trigger_tokens_ht, &iter, trigger_tokens_ht_element,
+                               node) {
+                       if (!lttng_trigger_is_equal(trigger, trigger_tokens_ht_element->trigger)) {
+                               continue;
+                       }
+
+                       trigger_error_accounting_unregister_trigger(trigger_tokens_ht_element->trigger);
+
+                       /* TODO talk to all app and remove it */
+                       DBG("[notification-thread] Removed trigger from tokens_ht");
+                       cds_lfht_del(state->trigger_tokens_ht,
+                                       &trigger_tokens_ht_element->node);
+                       call_rcu(&trigger_tokens_ht_element->rcu_node, free_notification_trigger_tokens_ht_element_rcu);
+
+                       break;
+               }
+       }
+
+       if (is_trigger_action_notify(trigger)) {
+               /*
+                * Remove and release the client list from
+                * notification_trigger_clients_ht.
+                */
+               client_list = get_client_list_from_condition(state, condition);
+               assert(client_list);
+
+               /* Put new reference and the hashtable's reference. */
+               notification_client_list_put(client_list);
+               notification_client_list_put(client_list);
+               client_list = NULL;
        }
-       cds_lfht_del(state->notification_trigger_clients_ht, node);
-       free(client_list);
 
        /* Remove trigger from triggers_ht. */
        trigger_ht_element = caa_container_of(triggers_ht_node,
                        struct lttng_trigger_ht_element, node);
+       cds_lfht_del(state->triggers_by_name_uid_ht, &trigger_ht_element->node_by_name_uid);
        cds_lfht_del(state->triggers_ht, triggers_ht_node);
 
-       condition = lttng_trigger_get_condition(trigger_ht_element->trigger);
-       lttng_condition_destroy(condition);
-       action = lttng_trigger_get_action(trigger_ht_element->trigger);
-       lttng_action_destroy(action);
+       /* Release the ownership of the trigger. */
        lttng_trigger_destroy(trigger_ht_element->trigger);
-       free(trigger_ht_element);
+       call_rcu(&trigger_ht_element->rcu_node, free_lttng_trigger_ht_element_rcu);
 end:
        rcu_read_unlock();
        if (_cmd_reply) {
@@ -1560,15 +2821,17 @@ int handle_notification_thread_command(
        struct notification_thread_command *cmd;
 
        /* Read the event pipe to put it back into a quiescent state. */
-       ret = read(lttng_pipe_get_readfd(handle->cmd_queue.event_pipe), &counter,
+       ret = lttng_read(lttng_pipe_get_readfd(handle->cmd_queue.event_pipe), &counter,
                        sizeof(counter));
-       if (ret == -1) {
+       if (ret != sizeof(counter)) {
                goto error;
        }
 
        pthread_mutex_lock(&handle->cmd_queue.lock);
        cmd = cds_list_first_entry(&handle->cmd_queue.list,
                        struct notification_thread_command, cmd_list_node);
+       cds_list_del(&cmd->cmd_list_node);
+       pthread_mutex_unlock(&handle->cmd_queue.lock);
        switch (cmd->type) {
        case NOTIFICATION_COMMAND_TYPE_REGISTER_TRIGGER:
                DBG("[notification-thread] Received register trigger command");
@@ -1602,11 +2865,91 @@ int handle_notification_thread_command(
                                cmd->parameters.remove_channel.domain,
                                &cmd->reply_code);
                break;
+       case NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_ONGOING:
+       case NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_COMPLETED:
+               DBG("[notification-thread] Received session rotation %s command",
+                               cmd->type == NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_ONGOING ?
+                               "ongoing" : "completed");
+               ret = handle_notification_thread_command_session_rotation(
+                               state,
+                               cmd->type,
+                               cmd->parameters.session_rotation.session_name,
+                               cmd->parameters.session_rotation.uid,
+                               cmd->parameters.session_rotation.gid,
+                               cmd->parameters.session_rotation.trace_archive_chunk_id,
+                               cmd->parameters.session_rotation.location,
+                               &cmd->reply_code);
+               break;
+       case NOTIFICATION_COMMAND_TYPE_ADD_APPLICATION:
+               ret = handle_notification_thread_command_add_application(
+                               handle,
+                               state,
+                               cmd->parameters.application.read_side_trigger_event_application_pipe,
+                               cmd->parameters.application.domain,
+                               &cmd->reply_code);
+               break;
+       case NOTIFICATION_COMMAND_TYPE_REMOVE_APPLICATION:
+               ret = handle_notification_thread_command_remove_application(
+                               handle,
+                               state,
+                               cmd->parameters.application.read_side_trigger_event_application_pipe,
+                               &cmd->reply_code);
+               break;
+       case NOTIFICATION_COMMAND_TYPE_GET_TOKENS:
+       {
+               struct lttng_triggers *triggers = NULL;
+               ret = handle_notification_thread_command_get_tokens(
+                               handle, state, &triggers, &cmd->reply_code);
+               cmd->reply.get_tokens.triggers = triggers;
+               ret = 0;
+               break;
+       }
+       case NOTIFICATION_COMMAND_TYPE_LIST_TRIGGERS:
+       {
+               struct lttng_triggers *triggers = NULL;
+               ret = handle_notification_thread_command_list_triggers(
+                               handle,
+                               state,
+                               cmd->parameters.list_triggers.uid,
+                               &triggers,
+                               &cmd->reply_code);
+               cmd->reply.list_triggers.triggers = triggers;
+               ret = 0;
+               break;
+       }
        case NOTIFICATION_COMMAND_TYPE_QUIT:
                DBG("[notification-thread] Received quit command");
                cmd->reply_code = LTTNG_OK;
                ret = 1;
                goto end;
+       case NOTIFICATION_COMMAND_TYPE_CLIENT_COMMUNICATION_UPDATE:
+       {
+               const enum client_transmission_status client_status =
+                               cmd->parameters.client_communication_update
+                                               .status;
+               const notification_client_id client_id =
+                               cmd->parameters.client_communication_update.id;
+               struct notification_client *client;
+
+               rcu_read_lock();
+               client = get_client_from_id(client_id, state);
+
+               if (!client) {
+                       /*
+                        * Client error was probably already picked-up by the
+                        * notification thread or it has disconnected
+                        * gracefully while this command was queued.
+                        */
+                       DBG("Failed to find notification client to update communication status, client id = %" PRIu64,
+                                       client_id);
+                       ret = 0;
+               } else {
+                       ret = client_handle_transmission_status(
+                                       client, client_status, state);
+               }
+               rcu_read_unlock();
+               break;
+       }
        default:
                ERR("[notification-thread] Unknown internal command received");
                goto error_unlock;
@@ -1616,26 +2959,22 @@ int handle_notification_thread_command(
                goto error_unlock;
        }
 end:
-       cds_list_del(&cmd->cmd_list_node);
-       lttng_waiter_wake_up(&cmd->reply_waiter);
-       pthread_mutex_unlock(&handle->cmd_queue.lock);
+       if (cmd->is_async) {
+               free(cmd);
+               cmd = NULL;
+       } else {
+               lttng_waiter_wake_up(&cmd->reply_waiter);
+       }
        return ret;
 error_unlock:
        /* Wake-up and return a fatal error to the calling thread. */
        lttng_waiter_wake_up(&cmd->reply_waiter);
-       pthread_mutex_unlock(&handle->cmd_queue.lock);
        cmd->reply_code = LTTNG_ERR_FATAL;
 error:
        /* Indicate a fatal error to the caller. */
        return -1;
 }
 
-static
-unsigned long hash_client_socket(int socket)
-{
-       return hash_key_ulong((void *) (unsigned long) socket, lttng_ht_seed);
-}
-
 static
 int socket_set_non_blocking(int socket)
 {
@@ -1664,9 +3003,8 @@ int client_reset_inbound_state(struct notification_client *client)
 {
        int ret;
 
-       ret = lttng_dynamic_buffer_set_size(
-                       &client->communication.inbound.buffer, 0);
-       assert(!ret);
+
+       lttng_payload_clear(&client->communication.inbound.payload);
 
        client->communication.inbound.bytes_to_receive =
                        sizeof(struct lttng_notification_channel_message);
@@ -1675,8 +3013,9 @@ int client_reset_inbound_state(struct notification_client *client)
        LTTNG_SOCK_SET_UID_CRED(&client->communication.inbound.creds, -1);
        LTTNG_SOCK_SET_GID_CRED(&client->communication.inbound.creds, -1);
        ret = lttng_dynamic_buffer_set_size(
-                       &client->communication.inbound.buffer,
+                       &client->communication.inbound.payload.buffer,
                        client->communication.inbound.bytes_to_receive);
+
        return ret;
 }
 
@@ -1694,14 +3033,18 @@ int handle_notification_thread_client_connect(
                ret = -1;
                goto error;
        }
+
+       pthread_mutex_init(&client->lock, NULL);
+       client->id = state->next_notification_client_id++;
        CDS_INIT_LIST_HEAD(&client->condition_list);
-       lttng_dynamic_buffer_init(&client->communication.inbound.buffer);
-       lttng_dynamic_buffer_init(&client->communication.outbound.buffer);
+       lttng_payload_init(&client->communication.inbound.payload);
+       lttng_payload_init(&client->communication.outbound.payload);
        client->communication.inbound.expect_creds = true;
+
        ret = client_reset_inbound_state(client);
        if (ret) {
                ERR("[notification-thread] Failed to reset client communication's inbound state");
-               ret = 0;
+               ret = 0;
                goto error;
        }
 
@@ -1742,17 +3085,60 @@ int handle_notification_thread_client_connect(
        cds_lfht_add(state->client_socket_ht,
                        hash_client_socket(client->socket),
                        &client->client_socket_ht_node);
+       cds_lfht_add(state->client_id_ht,
+                       hash_client_id(client->id),
+                       &client->client_id_ht_node);
        rcu_read_unlock();
 
        return ret;
+
 error:
        notification_client_destroy(client, state);
        return ret;
 }
 
+/*
+ * RCU read-lock must be held by the caller.
+ * Client lock must _not_ be held by the caller.
+ */
+static
+int notification_thread_client_disconnect(
+               struct notification_client *client,
+               struct notification_thread_state *state)
+{
+       int ret;
+       struct lttng_condition_list_element *condition_list_element, *tmp;
+
+       /* Acquire the client lock to disable its communication atomically. */
+       pthread_mutex_lock(&client->lock);
+       client->communication.active = false;
+       cds_lfht_del(state->client_socket_ht, &client->client_socket_ht_node);
+       cds_lfht_del(state->client_id_ht, &client->client_id_ht_node);
+       pthread_mutex_unlock(&client->lock);
+
+       ret = lttng_poll_del(&state->events, client->socket);
+       if (ret) {
+               ERR("[notification-thread] Failed to remove client socket %d from poll set",
+                               client->socket);
+       }
+
+       /* Release all conditions to which the client was subscribed. */
+       cds_list_for_each_entry_safe(condition_list_element, tmp,
+                       &client->condition_list, node) {
+               (void) notification_thread_client_unsubscribe(client,
+                               condition_list_element->condition, state, NULL);
+       }
+
+       /*
+        * Client no longer accessible to other threads (through the
+        * client lists).
+        */
+       notification_client_destroy(client, state);
+       return ret;
+}
+
 int handle_notification_thread_client_disconnect(
-               int client_socket,
-               struct notification_thread_state *state)
+               int client_socket, struct notification_thread_state *state)
 {
        int ret = 0;
        struct notification_client *client;
@@ -1769,13 +3155,7 @@ int handle_notification_thread_client_disconnect(
                goto end;
        }
 
-       ret = lttng_poll_del(&state->events, client_socket);
-       if (ret) {
-               ERR("[notification-thread] Failed to remove client socket from poll set");
-       }
-        cds_lfht_del(state->client_socket_ht,
-                       &client->client_socket_ht_node);
-       notification_client_destroy(client, state);
+       ret = notification_thread_client_disconnect(client, state);
 end:
        rcu_read_unlock();
        return ret;
@@ -1791,11 +3171,11 @@ int handle_notification_thread_client_disconnect_all(
        rcu_read_lock();
        DBG("[notification-thread] Closing all client connections");
        cds_lfht_for_each_entry(state->client_socket_ht, &iter, client,
-               client_socket_ht_node) {
+                       client_socket_ht_node) {
                int ret;
 
-               ret = handle_notification_thread_client_disconnect(
-                               client->socket, state);
+               ret = notification_thread_client_disconnect(
+                               client, state);
                if (ret) {
                        error_encoutered = true;
                }
@@ -1811,6 +3191,7 @@ int handle_notification_thread_trigger_unregister_all(
        struct cds_lfht_iter iter;
        struct lttng_trigger_ht_element *trigger_ht_element;
 
+       rcu_read_lock();
        cds_lfht_for_each_entry(state->triggers_ht, &iter, trigger_ht_element,
                        node) {
                int ret = handle_notification_thread_command_unregister_trigger(
@@ -1819,81 +3200,190 @@ int handle_notification_thread_trigger_unregister_all(
                        error_occurred = true;
                }
        }
+       rcu_read_unlock();
        return error_occurred ? -1 : 0;
 }
 
 static
-int client_flush_outgoing_queue(struct notification_client *client,
+int client_handle_transmission_status(
+               struct notification_client *client,
+               enum client_transmission_status transmission_status,
                struct notification_thread_state *state)
+{
+       int ret = 0;
+
+       switch (transmission_status) {
+       case CLIENT_TRANSMISSION_STATUS_COMPLETE:
+               ret = lttng_poll_mod(&state->events, client->socket,
+                               CLIENT_POLL_MASK_IN);
+               if (ret) {
+                       goto end;
+               }
+
+               break;
+       case CLIENT_TRANSMISSION_STATUS_QUEUED:
+               /*
+                * We want to be notified whenever there is buffer space
+                * available to send the rest of the payload.
+                */
+               ret = lttng_poll_mod(&state->events, client->socket,
+                               CLIENT_POLL_MASK_IN_OUT);
+               if (ret) {
+                       goto end;
+               }
+               break;
+       case CLIENT_TRANSMISSION_STATUS_FAIL:
+               ret = notification_thread_client_disconnect(client, state);
+               if (ret) {
+                       goto end;
+               }
+               break;
+       case CLIENT_TRANSMISSION_STATUS_ERROR:
+               ret = -1;
+               goto end;
+       default:
+               abort();
+       }
+end:
+       return ret;
+}
+
+/* Client lock must be acquired by caller. */
+static
+enum client_transmission_status client_flush_outgoing_queue(
+               struct notification_client *client)
 {
        ssize_t ret;
        size_t to_send_count;
+       enum client_transmission_status status;
+       struct lttng_payload_view pv = lttng_payload_view_from_payload(
+                       &client->communication.outbound.payload, 0, -1);
+       const int fds_to_send_count =
+                       lttng_payload_view_get_fd_handle_count(&pv);
+
+       ASSERT_LOCKED(client->lock);
+
+       if (!client->communication.active) {
+               status = CLIENT_TRANSMISSION_STATUS_FAIL;
+               goto end;
+       }
+
+       if (pv.buffer.size == 0) {
+               /*
+                * If both data and fds are equal to zero, we are in an invalid
+                * state.
+                */
+               assert(fds_to_send_count != 0);
+               goto send_fds;
+       }
 
-       assert(client->communication.outbound.buffer.size != 0);
-       to_send_count = client->communication.outbound.buffer.size;
+       /* Send data. */
+       to_send_count = pv.buffer.size;
        DBG("[notification-thread] Flushing client (socket fd = %i) outgoing queue",
                        client->socket);
 
        ret = lttcomm_send_unix_sock_non_block(client->socket,
-                       client->communication.outbound.buffer.data,
+                       pv.buffer.data,
                        to_send_count);
-       if ((ret < 0 && (errno == EAGAIN || errno == EWOULDBLOCK)) ||
-                       (ret > 0 && ret < to_send_count)) {
+       if ((ret >= 0 && ret < to_send_count)) {
                DBG("[notification-thread] Client (socket fd = %i) outgoing queue could not be completely flushed",
                                client->socket);
                to_send_count -= max(ret, 0);
 
-               memcpy(client->communication.outbound.buffer.data,
-                               client->communication.outbound.buffer.data +
-                               client->communication.outbound.buffer.size - to_send_count,
+               memmove(client->communication.outbound.payload.buffer.data,
+                               pv.buffer.data +
+                               pv.buffer.size - to_send_count,
                                to_send_count);
                ret = lttng_dynamic_buffer_set_size(
-                               &client->communication.outbound.buffer,
+                               &client->communication.outbound.payload.buffer,
                                to_send_count);
                if (ret) {
                        goto error;
                }
 
-               /*
-                * We want to be notified whenever there is buffer space
-                * available to send the rest of the payload.
-                */
-               ret = lttng_poll_mod(&state->events, client->socket,
-                               CLIENT_POLL_MASK_IN_OUT);
-               if (ret) {
-                       goto error;
-               }
+               status = CLIENT_TRANSMISSION_STATUS_QUEUED;
+               goto end;
        } else if (ret < 0) {
-               /* Generic error, disconnect the client. */
-               ERR("[notification-thread] Failed to send flush outgoing queue, disconnecting client (socket fd = %i)",
+               /* Generic error, disable the client's communication. */
+               ERR("[notification-thread] Failed to flush outgoing queue, disconnecting client (socket fd = %i)",
                                client->socket);
-               ret = handle_notification_thread_client_disconnect(
-                               client->socket, state);
-               if (ret) {
-                       goto error;
-               }
+               client->communication.active = false;
+               status = CLIENT_TRANSMISSION_STATUS_FAIL;
+               goto end;
        } else {
-               /* No error and flushed the queue completely. */
+               /*
+                * No error and flushed the queue completely.
+                *
+                * The payload buffer size is used later to
+                * check if there is notifications queued. So albeit that the
+                * direct caller knows that the transmission is complete, we
+                * need to set the buffer size to zero.
+                */
                ret = lttng_dynamic_buffer_set_size(
-                               &client->communication.outbound.buffer, 0);
-               if (ret) {
-                       goto error;
-               }
-               ret = lttng_poll_mod(&state->events, client->socket,
-                               CLIENT_POLL_MASK_IN);
+                               &client->communication.outbound.payload.buffer, 0);
                if (ret) {
                        goto error;
                }
+       }
+
+send_fds:
+       /* No fds to send, transmission is complete. */
+       if (fds_to_send_count == 0) {
+               status = CLIENT_TRANSMISSION_STATUS_COMPLETE;
+               goto end;
+       }
 
+       ret = lttcomm_send_payload_view_fds_unix_sock_non_block(
+                       client->socket, &pv);
+       if (ret < 0) {
+               /* Generic error, disable the client's communication. */
+               ERR("[notification-thread] Failed to flush outgoing fds queue, disconnecting client (socket fd = %i)",
+                               client->socket);
+               client->communication.active = false;
+               status = CLIENT_TRANSMISSION_STATUS_FAIL;
+               goto end;
+       } else if (ret == 0) {
+               /* Nothing could be sent. */
+               status = CLIENT_TRANSMISSION_STATUS_QUEUED;
+       } else {
+               /* Fd passing is an all or nothing kind of thing. */
+               status = CLIENT_TRANSMISSION_STATUS_COMPLETE;
+               /*
+                * The payload _fd_array count is used later to
+                * check if there is notifications queued. So although the
+                * direct caller knows that the transmission is complete, we
+                * need to clear the _fd_array for the queuing check.
+                */
+               lttng_dynamic_pointer_array_clear(
+                               &client->communication.outbound.payload
+                                                ._fd_handles);
+       }
+
+end:
+       if (status == CLIENT_TRANSMISSION_STATUS_COMPLETE) {
                client->communication.outbound.queued_command_reply = false;
                client->communication.outbound.dropped_notification = false;
+               lttng_payload_clear(&client->communication.outbound.payload);
        }
 
-       return 0;
+       return status;
 error:
-       return -1;
+       return CLIENT_TRANSMISSION_STATUS_ERROR;
+}
+
+static
+bool client_has_outbound_data_left(
+               const struct notification_client *client)
+{
+       const struct lttng_payload_view pv = lttng_payload_view_from_payload(
+                       &client->communication.outbound.payload, 0, -1);
+       const bool has_data = pv.buffer.size != 0;
+       const bool has_fds = lttng_payload_view_get_fd_handle_count(&pv);
+
+       return has_data || has_fds;
 }
 
+/* Client lock must _not_ be held by the caller. */
 static
 int client_send_command_reply(struct notification_client *client,
                struct notification_thread_state *state,
@@ -1908,210 +3398,266 @@ int client_send_command_reply(struct notification_client *client,
                .size = sizeof(reply),
        };
        char buffer[sizeof(msg) + sizeof(reply)];
-
-       if (client->communication.outbound.queued_command_reply) {
-               /* Protocol error. */
-               goto error;
-       }
+       enum client_transmission_status transmission_status;
 
        memcpy(buffer, &msg, sizeof(msg));
        memcpy(buffer + sizeof(msg), &reply, sizeof(reply));
        DBG("[notification-thread] Send command reply (%i)", (int) status);
 
+       pthread_mutex_lock(&client->lock);
+       if (client->communication.outbound.queued_command_reply) {
+               /* Protocol error. */
+               goto error_unlock;
+       }
+
        /* Enqueue buffer to outgoing queue and flush it. */
        ret = lttng_dynamic_buffer_append(
-                       &client->communication.outbound.buffer,
+                       &client->communication.outbound.payload.buffer,
                        buffer, sizeof(buffer));
        if (ret) {
-               goto error;
+               goto error_unlock;
        }
 
-       ret = client_flush_outgoing_queue(client, state);
-       if (ret) {
-               goto error;
-       }
+       transmission_status = client_flush_outgoing_queue(client);
 
-       if (client->communication.outbound.buffer.size != 0) {
+       if (client_has_outbound_data_left(client)) {
                /* Queue could not be emptied. */
                client->communication.outbound.queued_command_reply = true;
        }
 
+       pthread_mutex_unlock(&client->lock);
+       ret = client_handle_transmission_status(
+                       client, transmission_status, state);
+       if (ret) {
+               goto error;
+       }
+
        return 0;
+error_unlock:
+       pthread_mutex_unlock(&client->lock);
 error:
        return -1;
 }
 
 static
-int client_dispatch_message(struct notification_client *client,
+int client_handle_message_unknown(struct notification_client *client,
                struct notification_thread_state *state)
 {
-       int ret = 0;
+       int ret;
+       /*
+        * Receiving message header. The function will be called again
+        * once the rest of the message as been received and can be
+        * interpreted.
+        */
+       const struct lttng_notification_channel_message *msg;
 
-       if (client->communication.inbound.msg_type !=
-                       LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_HANDSHAKE &&
-                       client->communication.inbound.msg_type !=
-                               LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_UNKNOWN &&
-                       !client->validated) {
-               WARN("[notification-thread] client attempted a command before handshake");
+       assert(sizeof(*msg) == client->communication.inbound.payload.buffer.size);
+       msg = (const struct lttng_notification_channel_message *)
+                             client->communication.inbound.payload.buffer.data;
+
+       if (msg->size == 0 ||
+                       msg->size > DEFAULT_MAX_NOTIFICATION_CLIENT_MESSAGE_PAYLOAD_SIZE) {
+               ERR("[notification-thread] Invalid notification channel message: length = %u",
+                               msg->size);
                ret = -1;
                goto end;
        }
 
-       switch (client->communication.inbound.msg_type) {
-       case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_UNKNOWN:
-       {
-               /*
-                * Receiving message header. The function will be called again
-                * once the rest of the message as been received and can be
-                * interpreted.
-                */
-               const struct lttng_notification_channel_message *msg;
-
-               assert(sizeof(*msg) ==
-                               client->communication.inbound.buffer.size);
-               msg = (const struct lttng_notification_channel_message *)
-                               client->communication.inbound.buffer.data;
+       switch (msg->type) {
+       case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_SUBSCRIBE:
+       case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_UNSUBSCRIBE:
+       case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_HANDSHAKE:
+               break;
+       default:
+               ret = -1;
+               ERR("[notification-thread] Invalid notification channel message: unexpected message type");
+               goto end;
+       }
 
-               if (msg->size == 0 || msg->size > DEFAULT_MAX_NOTIFICATION_CLIENT_MESSAGE_PAYLOAD_SIZE) {
-                       ERR("[notification-thread] Invalid notification channel message: length = %u", msg->size);
-                       ret = -1;
-                       goto end;
-               }
+       client->communication.inbound.bytes_to_receive = msg->size;
+       client->communication.inbound.fds_to_receive = msg->fds;
+       client->communication.inbound.msg_type =
+                       (enum lttng_notification_channel_message_type) msg->type;
+       ret = lttng_dynamic_buffer_set_size(
+                       &client->communication.inbound.payload.buffer, msg->size);
 
-               switch (msg->type) {
-               case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_SUBSCRIBE:
-               case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_UNSUBSCRIBE:
-               case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_HANDSHAKE:
-                       break;
-               default:
-                       ret = -1;
-                       ERR("[notification-thread] Invalid notification channel message: unexpected message type");
-                       goto end;
-               }
+       /* msg is not valid anymore due to lttng_dynamic_buffer_set_size. */
+       msg = NULL;
+end:
+       return ret;
+}
 
-               client->communication.inbound.bytes_to_receive = msg->size;
-               client->communication.inbound.msg_type =
-                               (enum lttng_notification_channel_message_type) msg->type;
-               ret = lttng_dynamic_buffer_set_size(
-                               &client->communication.inbound.buffer, msg->size);
-               if (ret) {
-                       goto end;
-               }
-               break;
-       }
-       case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_HANDSHAKE:
-       {
-               struct lttng_notification_channel_command_handshake *handshake_client;
-               struct lttng_notification_channel_command_handshake handshake_reply = {
+static
+int client_handle_message_handshake(struct notification_client *client,
+               struct notification_thread_state *state)
+{
+       int ret;
+       struct lttng_notification_channel_command_handshake *handshake_client;
+       const struct lttng_notification_channel_command_handshake handshake_reply = {
                        .major = LTTNG_NOTIFICATION_CHANNEL_VERSION_MAJOR,
                        .minor = LTTNG_NOTIFICATION_CHANNEL_VERSION_MINOR,
-               };
-               struct lttng_notification_channel_message msg_header = {
+       };
+       const struct lttng_notification_channel_message msg_header = {
                        .type = LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_HANDSHAKE,
                        .size = sizeof(handshake_reply),
-               };
-               enum lttng_notification_channel_status status =
-                               LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
-               char send_buffer[sizeof(msg_header) + sizeof(handshake_reply)];
-
-               memcpy(send_buffer, &msg_header, sizeof(msg_header));
-               memcpy(send_buffer + sizeof(msg_header), &handshake_reply,
-                               sizeof(handshake_reply));
-
-               handshake_client =
-                               (struct lttng_notification_channel_command_handshake *)
-                                       client->communication.inbound.buffer.data;
-               client->major = handshake_client->major;
-               client->minor = handshake_client->minor;
-               if (!client->communication.inbound.creds_received) {
-                       ERR("[notification-thread] No credentials received from client");
-                       ret = -1;
-                       goto end;
-               }
+       };
+       enum lttng_notification_channel_status status =
+                       LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
+       char send_buffer[sizeof(msg_header) + sizeof(handshake_reply)];
+
+       memcpy(send_buffer, &msg_header, sizeof(msg_header));
+       memcpy(send_buffer + sizeof(msg_header), &handshake_reply,
+                       sizeof(handshake_reply));
+
+       handshake_client =
+                       (struct lttng_notification_channel_command_handshake *)
+                                       client->communication.inbound.payload.buffer
+                                                       .data;
+       client->major = handshake_client->major;
+       client->minor = handshake_client->minor;
+       if (!client->communication.inbound.creds_received) {
+               ERR("[notification-thread] No credentials received from client");
+               ret = -1;
+               goto end;
+       }
 
-               client->uid = LTTNG_SOCK_GET_UID_CRED(
-                               &client->communication.inbound.creds);
-               client->gid = LTTNG_SOCK_GET_GID_CRED(
-                               &client->communication.inbound.creds);
-               DBG("[notification-thread] Received handshake from client (uid = %u, gid = %u) with version %i.%i",
-                               client->uid, client->gid, (int) client->major,
-                               (int) client->minor);
+       client->uid = LTTNG_SOCK_GET_UID_CRED(
+                       &client->communication.inbound.creds);
+       client->gid = LTTNG_SOCK_GET_GID_CRED(
+                       &client->communication.inbound.creds);
+       DBG("[notification-thread] Received handshake from client (uid = %u, gid = %u) with version %i.%i",
+                       client->uid, client->gid, (int) client->major,
+                       (int) client->minor);
+
+       if (handshake_client->major !=
+                       LTTNG_NOTIFICATION_CHANNEL_VERSION_MAJOR) {
+               status = LTTNG_NOTIFICATION_CHANNEL_STATUS_UNSUPPORTED_VERSION;
+       }
 
-               if (handshake_client->major != LTTNG_NOTIFICATION_CHANNEL_VERSION_MAJOR) {
-                       status = LTTNG_NOTIFICATION_CHANNEL_STATUS_UNSUPPORTED_VERSION;
-               }
+       pthread_mutex_lock(&client->lock);
+       /* Outgoing queue will be flushed when the command reply is sent. */
+       ret = lttng_dynamic_buffer_append(
+                       &client->communication.outbound.payload.buffer, send_buffer,
+                       sizeof(send_buffer));
+       if (ret) {
+               ERR("[notification-thread] Failed to send protocol version to notification channel client");
+               goto end_unlock;
+       }
 
-               ret = lttng_dynamic_buffer_append(&client->communication.outbound.buffer,
-                               send_buffer, sizeof(send_buffer));
-               if (ret) {
-                       ERR("[notification-thread] Failed to send protocol version to notification channel client");
-                       goto end;
-               }
+       client->validated = true;
+       client->communication.active = true;
+       pthread_mutex_unlock(&client->lock);
 
-               ret = client_flush_outgoing_queue(client, state);
-               if (ret) {
-                       goto end;
-               }
+       /* Set reception state to receive the next message header. */
+       ret = client_reset_inbound_state(client);
+       if (ret) {
+               ERR("[notification-thread] Failed to reset client communication's inbound state");
+               goto end;
+       }
 
-               ret = client_send_command_reply(client, state, status);
-               if (ret) {
-                       ERR("[notification-thread] Failed to send reply to notification channel client");
-                       goto end;
-               }
+       /* Flushes the outgoing queue. */
+       ret = client_send_command_reply(client, state, status);
+       if (ret) {
+               ERR("[notification-thread] Failed to send reply to notification channel client");
+               goto end;
+       }
+
+       goto end;
+end_unlock:
+       pthread_mutex_unlock(&client->lock);
+end:
+       return ret;
+}
+
+static
+int client_handle_message_subscription(
+               struct notification_client *client,
+               enum lttng_notification_channel_message_type msg_type,
+               struct notification_thread_state *state)
+{
+       int ret;
+       struct lttng_condition *condition;
+       enum lttng_notification_channel_status status =
+                       LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
+       struct lttng_payload_view condition_view =
+                       lttng_payload_view_from_payload(
+                                       &client->communication.inbound.payload,
+                                       0, -1);
+       size_t expected_condition_size;
+
+       /*
+        * No need to lock client to sample the inbound state as the only
+        * other thread accessing clients (action executor) only uses the
+        * outbound state.
+        */
+       expected_condition_size = client->communication.inbound.payload.buffer.size;
+       ret = lttng_condition_create_from_payload(&condition_view, &condition);
+       if (ret != expected_condition_size) {
+               ERR("[notification-thread] Malformed condition received from client");
+               goto end;
+       }
+
+       if (msg_type == LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_SUBSCRIBE) {
+               ret = notification_thread_client_subscribe(
+                               client, condition, state, &status);
+       } else {
+               ret = notification_thread_client_unsubscribe(
+                               client, condition, state, &status);
+       }
+
+       if (ret) {
+               goto end;
+       }
+
+       /* Set reception state to receive the next message header. */
+       ret = client_reset_inbound_state(client);
+       if (ret) {
+               ERR("[notification-thread] Failed to reset client communication's inbound state");
+               goto end;
+       }
+
+       ret = client_send_command_reply(client, state, status);
+       if (ret) {
+               ERR("[notification-thread] Failed to send reply to notification channel client");
+               goto end;
+       }
+
+end:
+       return ret;
+}
+
+static
+int client_dispatch_message(struct notification_client *client,
+               struct notification_thread_state *state)
+{
+       int ret = 0;
+
+       if (client->communication.inbound.msg_type !=
+                       LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_HANDSHAKE &&
+                       client->communication.inbound.msg_type !=
+                               LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_UNKNOWN &&
+                       !client->validated) {
+               WARN("[notification-thread] client attempted a command before handshake");
+               ret = -1;
+               goto end;
+       }
 
-               /* Set reception state to receive the next message header. */
-               ret = client_reset_inbound_state(client);
-               if (ret) {
-                       ERR("[notification-thread] Failed to reset client communication's inbound state");
-                       goto end;
-               }
-               client->validated = true;
+       switch (client->communication.inbound.msg_type) {
+       case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_UNKNOWN:
+       {
+               ret = client_handle_message_unknown(client, state);
+               break;
+       }
+       case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_HANDSHAKE:
+       {
+               ret = client_handle_message_handshake(client, state);
                break;
        }
        case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_SUBSCRIBE:
        case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_UNSUBSCRIBE:
        {
-               struct lttng_condition *condition;
-               enum lttng_notification_channel_status status =
-                               LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
-               const struct lttng_buffer_view condition_view =
-                               lttng_buffer_view_from_dynamic_buffer(
-                                       &client->communication.inbound.buffer,
-                                       0, -1);
-               size_t expected_condition_size =
-                               client->communication.inbound.buffer.size;
-
-               ret = lttng_condition_create_from_buffer(&condition_view,
-                               &condition);
-               if (ret != expected_condition_size) {
-                       ERR("[notification-thread] Malformed condition received from client");
-                       goto end;
-               }
-
-               if (client->communication.inbound.msg_type ==
-                               LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_SUBSCRIBE) {
-                       ret = notification_thread_client_subscribe(client,
-                                       condition, state, &status);
-               } else {
-                       ret = notification_thread_client_unsubscribe(client,
-                                       condition, state, &status);
-               }
-               if (ret) {
-                       goto end;
-               }
-
-               ret = client_send_command_reply(client, state, status);
-               if (ret) {
-                       ERR("[notification-thread] Failed to send reply to notification channel client");
-                       goto end;
-               }
-
-               /* Set reception state to receive the next message header. */
-               ret = client_reset_inbound_state(client);
-               if (ret) {
-                       ERR("[notification-thread] Failed to reset client communication's inbound state");
-                       goto end;
-               }
+               ret = client_handle_message_subscription(client,
+                               client->communication.inbound.msg_type, state);
                break;
        }
        default:
@@ -2130,6 +3676,7 @@ int handle_notification_thread_client_in(
        ssize_t recv_ret;
        size_t offset;
 
+       rcu_read_lock();
        client = get_client_from_socket(socket, state);
        if (!client) {
                /* Internal error, abort. */
@@ -2137,11 +3684,11 @@ int handle_notification_thread_client_in(
                goto end;
        }
 
-       offset = client->communication.inbound.buffer.size -
+       offset = client->communication.inbound.payload.buffer.size -
                        client->communication.inbound.bytes_to_receive;
        if (client->communication.inbound.expect_creds) {
                recv_ret = lttcomm_recv_creds_unix_sock(socket,
-                               client->communication.inbound.buffer.data + offset,
+                               client->communication.inbound.payload.buffer.data + offset,
                                client->communication.inbound.bytes_to_receive,
                                &client->communication.inbound.creds);
                if (recv_ret > 0) {
@@ -2150,31 +3697,69 @@ int handle_notification_thread_client_in(
                }
        } else {
                recv_ret = lttcomm_recv_unix_sock_non_block(socket,
-                               client->communication.inbound.buffer.data + offset,
+                               client->communication.inbound.payload.buffer.data + offset,
                                client->communication.inbound.bytes_to_receive);
        }
-       if (recv_ret < 0) {
+       if (recv_ret >= 0) {
+               client->communication.inbound.bytes_to_receive -= recv_ret;
+       } else {
                goto error_disconnect_client;
        }
 
-       client->communication.inbound.bytes_to_receive -= recv_ret;
-       if (client->communication.inbound.bytes_to_receive == 0) {
-               ret = client_dispatch_message(client, state);
-               if (ret) {
+       if (client->communication.inbound.bytes_to_receive != 0) {
+               /* Message incomplete wait for more data. */
+               ret = 0;
+               goto end;
+       }
+
+       assert(client->communication.inbound.bytes_to_receive == 0);
+
+       /* Receive fds. */
+       if (client->communication.inbound.fds_to_receive != 0) {
+               ret = lttcomm_recv_payload_fds_unix_sock_non_block(
+                               client->socket,
+                               client->communication.inbound.fds_to_receive,
+                               &client->communication.inbound.payload);
+               if (ret > 0) {
                        /*
-                        * Only returns an error if this client must be
-                        * disconnected.
+                        * Fds received. non blocking fds passing is all
+                        * or nothing.
                         */
+                       ssize_t expected_size;
+
+                       expected_size = sizeof(int) *
+                                       client->communication.inbound
+                                                       .fds_to_receive;
+                       assert(ret == expected_size);
+                       client->communication.inbound.fds_to_receive = 0;
+               } else if (ret == 0) {
+                       /* Received nothing. */
+                       ret = 0;
+                       goto end;
+               } else {
                        goto error_disconnect_client;
                }
-       } else {
-               goto end;
        }
+
+       /* At this point the message is complete.*/
+       assert(client->communication.inbound.bytes_to_receive == 0 &&
+                       client->communication.inbound.fds_to_receive == 0);
+       ret = client_dispatch_message(client, state);
+       if (ret) {
+               /*
+                * Only returns an error if this client must be
+                * disconnected.
+                */
+               goto error_disconnect_client;
+       }
+
 end:
+       rcu_read_unlock();
        return ret;
+
 error_disconnect_client:
-       ret = handle_notification_thread_client_disconnect(socket, state);
-       return ret;
+       ret = notification_thread_client_disconnect(client, state);
+       goto end;
 }
 
 /* Client ready to receive outgoing data. */
@@ -2183,7 +3768,9 @@ int handle_notification_thread_client_out(
 {
        int ret;
        struct notification_client *client;
+       enum client_transmission_status transmission_status;
 
+       rcu_read_lock();
        client = get_client_from_socket(socket, state);
        if (!client) {
                /* Internal error, abort. */
@@ -2191,11 +3778,17 @@ int handle_notification_thread_client_out(
                goto end;
        }
 
-       ret = client_flush_outgoing_queue(client, state);
+       pthread_mutex_lock(&client->lock);
+       transmission_status = client_flush_outgoing_queue(client);
+       pthread_mutex_unlock(&client->lock);
+
+       ret = client_handle_transmission_status(
+                       client, transmission_status, state);
        if (ret) {
                goto end;
        }
 end:
+       rcu_read_unlock();
        return ret;
 }
 
@@ -2222,7 +3815,7 @@ bool evaluate_buffer_usage_condition(const struct lttng_condition *condition,
                 * forego this double-multiplication or it could be performed
                 * as fixed-point math.
                 *
-                * Note that caching should accomodate the case where the
+                * Note that caching should accommodates the case where the
                 * condition applies to multiple channels (i.e. don't assume
                 * that all channels matching my_chann* have the same size...)
                 */
@@ -2276,7 +3869,7 @@ bool evaluate_session_consumed_size_condition(
 }
 
 static
-int evaluate_condition(const struct lttng_condition *condition,
+int evaluate_buffer_condition(const struct lttng_condition *condition,
                struct lttng_evaluation **evaluation,
                const struct notification_thread_state *state,
                const struct channel_state_sample *previous_sample,
@@ -2362,48 +3955,129 @@ end:
 }
 
 static
-int client_enqueue_dropped_notification(struct notification_client *client,
-               struct notification_thread_state *state)
+int client_notification_overflow(struct notification_client *client)
 {
-       int ret;
-       struct lttng_notification_channel_message msg = {
+       int ret = 0;
+       const struct lttng_notification_channel_message msg = {
                .type = (int8_t) LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION_DROPPED,
-               .size = 0,
        };
 
+       ASSERT_LOCKED(client->lock);
+
+       DBG("Dropping notification addressed to client (socket fd = %i)",
+                       client->socket);
+       if (client->communication.outbound.dropped_notification) {
+               /*
+                * The client already has a "notification dropped" message
+                * in its outgoing queue. Nothing to do since all
+                * of those messages are coalesced.
+                */
+               goto end;
+       }
+
+       client->communication.outbound.dropped_notification = true;
        ret = lttng_dynamic_buffer_append(
-                       &client->communication.outbound.buffer, &msg,
+                       &client->communication.outbound.payload.buffer, &msg,
                        sizeof(msg));
+       if (ret) {
+               PERROR("Failed to enqueue \"dropped notification\" message in client's (socket fd = %i) outgoing queue",
+                               client->socket);
+       }
+end:
        return ret;
 }
 
+static int client_handle_transmission_status_wrapper(
+               struct notification_client *client,
+               enum client_transmission_status status,
+               void *user_data)
+{
+       return client_handle_transmission_status(client, status,
+                       (struct notification_thread_state *) user_data);
+}
+
 static
 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)
+               uid_t object_uid, gid_t object_gid)
+{
+       const struct lttng_credentials creds = {
+               .uid = LTTNG_OPTIONAL_INIT_VALUE(object_uid),
+               .gid = LTTNG_OPTIONAL_INIT_VALUE(object_gid),
+       };
+
+       return notification_client_list_send_evaluation(client_list,
+                       lttng_trigger_get_const_condition(trigger), evaluation,
+                       lttng_trigger_get_credentials(trigger),
+                       &creds,
+                       client_handle_transmission_status_wrapper, state);
+}
+
+/*
+ * Permission checks relative to notification channel clients are performed
+ * here. Notice how object, client, and trigger credentials are involved in
+ * this check.
+ *
+ * The `object` credentials are the credentials associated with the "subject"
+ * of a condition. For instance, a `rotation completed` condition applies
+ * to a session. When that condition is met, it will produce an evaluation
+ * against a session. Hence, in this case, the `object` credentials are the
+ * credentials of the "subject" session.
+ *
+ * The `trigger` credentials are the credentials of the user that registered the
+ * trigger.
+ *
+ * The `client` credentials are the credentials of the user that created a given
+ * notification channel.
+ *
+ * In terms of visibility, it is expected that non-privilieged users can only
+ * register triggers against "their" objects (their own sessions and
+ * applications they are allowed to interact with). They can then open a
+ * notification channel and subscribe to notifications associated with those
+ * triggers.
+ *
+ * As for privilieged users, they can register triggers against the objects of
+ * other users. They can then subscribe to the notifications associated to their
+ * triggers. Privilieged users _can't_ subscribe to the notifications of
+ * triggers owned by other users; they must create their own triggers.
+ *
+ * This is more a concern of usability than security. It would be difficult for
+ * a root user reliably subscribe to a specific set of conditions without
+ * interference from external users (those could, for instance, unregister
+ * their triggers).
+ */
+LTTNG_HIDDEN
+int notification_client_list_send_evaluation(
+               struct notification_client_list *client_list,
+               const struct lttng_condition *condition,
+               const struct lttng_evaluation *evaluation,
+               const struct lttng_credentials *trigger_creds,
+               const struct lttng_credentials *source_object_creds,
+               report_client_transmission_result_cb client_report,
+               void *user_data)
 {
        int ret = 0;
-       struct lttng_dynamic_buffer msg_buffer;
+       struct lttng_payload msg_payload;
        struct notification_client_list_element *client_list_element, *tmp;
        const struct lttng_notification notification = {
-               .condition = (struct lttng_condition *) lttng_trigger_get_const_condition(trigger),
+               .condition = (struct lttng_condition *) condition,
                .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);
+       lttng_payload_init(&msg_payload);
 
-       ret = lttng_dynamic_buffer_append(&msg_buffer, &msg_header,
+       ret = lttng_dynamic_buffer_append(&msg_payload.buffer, &msg_header,
                        sizeof(msg_header));
        if (ret) {
                goto end;
        }
 
-       ret = lttng_notification_serialize(&notification, &msg_buffer);
+       ret = lttng_notification_serialize(&notification, &msg_payload);
        if (ret) {
                ERR("[notification-thread] Failed to serialize notification");
                ret = -1;
@@ -2411,24 +4085,60 @@ int send_evaluation_to_clients(const struct lttng_trigger *trigger,
        }
 
        /* Update payload size. */
-       ((struct lttng_notification_channel_message * ) msg_buffer.data)->size =
-                       (uint32_t) (msg_buffer.size - sizeof(msg_header));
+       ((struct lttng_notification_channel_message *) msg_payload.buffer.data)
+                       ->size = (uint32_t)(
+                       msg_payload.buffer.size - sizeof(msg_header));
+
+       /* Update the payload number of fds. */
+       {
+               const struct lttng_payload_view pv = lttng_payload_view_from_payload(
+                               &msg_payload, 0, -1);
+
+               ((struct lttng_notification_channel_message *)
+                               msg_payload.buffer.data)->fds = (uint32_t)
+                               lttng_payload_view_get_fd_handle_count(&pv);
+       }
 
+       pthread_mutex_lock(&client_list->lock);
        cds_list_for_each_entry_safe(client_list_element, tmp,
                        &client_list->list, node) {
+               enum client_transmission_status transmission_status;
                struct notification_client *client =
                                client_list_element->client;
 
-               if (client->uid != channel_uid && client->gid != channel_gid &&
-                               client->uid != 0) {
-                       /* Client is not allowed to monitor this channel. */
-                       DBG("[notification-thread] Skipping client at it does not have the permission to receive notification for this channel");
-                       continue;
+               ret = 0;
+               pthread_mutex_lock(&client->lock);
+               if (!client->communication.active) {
+                       /*
+                        * Skip inactive client (protocol error or
+                        * disconnecting).
+                        */
+                       DBG("Skipping client at it is marked as inactive");
+                       goto skip_client;
+               }
+
+               if (source_object_creds) {
+                       if (client->uid != lttng_credentials_get_uid(source_object_creds) &&
+                                       client->gid != lttng_credentials_get_gid(source_object_creds) &&
+                                       client->uid != 0) {
+                               /*
+                                * Client is not allowed to monitor this
+                                * object.
+                                */
+                               DBG("[notification-thread] Skipping client at it does not have the object permission to receive notification for this trigger");
+                               goto skip_client;
+                       }
+               }
+
+               if (client->uid != lttng_credentials_get_uid(trigger_creds) && client->gid != lttng_credentials_get_gid(trigger_creds)) {
+                       DBG("[notification-thread] Skipping client at it does not have the permission to receive notification for this trigger");
+                       goto skip_client;
                }
 
                DBG("[notification-thread] Sending notification to client (fd = %i, %zu bytes)",
-                               client->socket, msg_buffer.size);
-               if (client->communication.outbound.buffer.size) {
+                               client->socket, msg_payload.buffer.size);
+
+               if (client_has_outbound_data_left(client)) {
                        /*
                         * Outgoing data is already buffered for this client;
                         * drop the notification and enqueue a "dropped
@@ -2436,34 +4146,309 @@ int send_evaluation_to_clients(const struct lttng_trigger *trigger,
                         * notification since the socket spilled-over to the
                         * queue.
                         */
-                       DBG("[notification-thread] Dropping notification addressed to client (socket fd = %i)",
-                                       client->socket);
-                       if (!client->communication.outbound.dropped_notification) {
-                               client->communication.outbound.dropped_notification = true;
-                               ret = client_enqueue_dropped_notification(
-                                               client, state);
-                               if (ret) {
-                                       goto end;
-                               }
+                       ret = client_notification_overflow(client);
+                       if (ret) {
+                               /* Fatal error. */
+                               goto skip_client;
                        }
-                       continue;
                }
 
-               ret = lttng_dynamic_buffer_append_buffer(
-                               &client->communication.outbound.buffer,
-                               &msg_buffer);
+               ret = lttng_payload_copy(&msg_payload, &client->communication.outbound.payload);
                if (ret) {
-                       goto end;
+                       /* Fatal error. */
+                       goto skip_client;
                }
 
-               ret = client_flush_outgoing_queue(client, state);
+               transmission_status = client_flush_outgoing_queue(client);
+               pthread_mutex_unlock(&client->lock);
+               ret = client_report(client, transmission_status, user_data);
                if (ret) {
-                       goto end;
+                       /* Fatal error. */
+                       goto end_unlock_list;
+               }
+
+               continue;
+
+skip_client:
+               pthread_mutex_unlock(&client->lock);
+               if (ret) {
+                       /* Fatal error. */
+                       goto end_unlock_list;
                }
        }
        ret = 0;
+
+end_unlock_list:
+       pthread_mutex_unlock(&client_list->lock);
+end:
+       lttng_payload_reset(&msg_payload);
+       return ret;
+}
+
+static struct lttng_trigger_notification *receive_notification(int pipe,
+               enum lttng_domain_type domain)
+{
+       int ret;
+       uint64_t id;
+       struct lttng_trigger_notification *notification = NULL;
+       char *capture_buffer = NULL;
+       size_t capture_buffer_size;
+       void *reception_buffer;
+       size_t reception_size;
+
+       struct lttng_ust_trigger_notification ust_notification;
+       struct lttng_kernel_trigger_notification kernel_notification;
+
+       /* Init lttng_trigger_notification */
+
+       switch(domain) {
+       case LTTNG_DOMAIN_UST:
+               reception_buffer = (void *) &ust_notification;
+               reception_size = sizeof(ust_notification);
+               break;
+       case LTTNG_DOMAIN_KERNEL:
+               reception_buffer = (void *) &kernel_notification;
+               reception_size = sizeof(kernel_notification);
+               break;
+       default:
+               assert(0);
+       }
+
+       /*
+        * The monitoring pipe only holds messages smaller than PIPE_BUF,
+        * ensuring that read/write of sampling messages are atomic.
+        */
+       /* TODO: should we read as much as we can ? EWOULDBLOCK? */
+
+       ret = lttng_read(pipe, reception_buffer, reception_size);
+       if (ret != reception_size) {
+               PERROR("Failed to read from event source pipe (fd = %i, size to read=%zu, ret=%d)",
+                               pipe, reception_size, ret);
+               /* TODO: Should this error out completly.
+                * This can happen when an app is killed as of today
+                * ret = -1 cause the whole thread to die and fuck up
+                * everything.
+                */
+               goto end;
+       }
+
+       switch(domain) {
+       case LTTNG_DOMAIN_UST:
+               id = ust_notification.id;
+               capture_buffer_size =
+                               ust_notification.capture_buf_size;
+               break;
+       case LTTNG_DOMAIN_KERNEL:
+               id = kernel_notification.id;
+               capture_buffer_size =
+                       kernel_notification.capture_buf_size;
+               break;
+       default:
+               assert(0);
+       }
+
+       if (capture_buffer_size == 0) {
+               capture_buffer = NULL;
+               goto skip_capture;
+       }
+
+       capture_buffer = zmalloc(capture_buffer_size);
+       if (!capture_buffer) {
+               ERR("[notification-thread] Failed to allocate capture buffer");
+               goto end;
+       }
+
+       /*
+        * Fetch additional payload (capture).
+        */
+       ret = lttng_read(pipe, capture_buffer, capture_buffer_size);
+       if (ret != capture_buffer_size) {
+               ERR("[notification-thread] Failed to read from event source pipe (fd = %i)",
+                               pipe);
+               /* TODO: Should this error out completly.
+                * This can happen when an app is killed as of today
+                * ret = -1 cause the whole thread to die and fuck up
+                * everything.
+                */
+               goto end;
+       }
+
+skip_capture:
+       notification = lttng_trigger_notification_create(
+                       id, domain, capture_buffer, capture_buffer_size);
+       if (notification == NULL) {
+               goto end;
+       }
+
+       /* Ownership transfered to the lttng_trigger_notification object */
+       capture_buffer = NULL;
+
+end:
+       free(capture_buffer);
+       return notification;
+}
+
+int handle_notification_thread_event(struct notification_thread_state *state,
+               int pipe,
+               enum lttng_domain_type domain)
+{
+       int ret;
+       enum lttng_trigger_status trigger_status;
+       struct cds_lfht_node *node;
+       struct cds_lfht_iter iter;
+       struct notification_trigger_tokens_ht_element *element;
+       struct lttng_evaluation *evaluation = NULL;
+       struct lttng_trigger_notification *notification = NULL;
+       enum action_executor_status executor_status;
+       struct notification_client_list *client_list = NULL;
+       const char *trigger_name;
+       unsigned int capture_count = 0;
+
+       notification = receive_notification(pipe, domain);
+       if (notification == NULL) {
+               ERR("[notification-thread] Error receiving notification from tracer (fd = %i, domain = %s)",
+                               pipe, lttng_domain_type_str(domain));
+               ret = -1;
+               goto end;
+       }
+
+       /* Find triggers associated with this token. */
+       rcu_read_lock();
+       cds_lfht_lookup(state->trigger_tokens_ht,
+                       hash_key_u64(&notification->id, lttng_ht_seed),
+                       match_trigger_token, &notification->id, &iter);
+       node = cds_lfht_iter_get_node(&iter);
+       if (caa_unlikely(!node)) {
+               /* TODO: is this an error? This might happen if the receive side
+                * is slow to process event from source and that the trigger was
+                * removed but the app still kicking. This yield another
+                * question on the trigger lifetime and when we can remove a
+                * trigger. How to guarantee that all event with the token idea
+                * have be processed? Do we want to provide this guarantee?
+                *
+                * Update: I have encountered this when using a trigger on
+                * sched_switch and then removing it. The frequency is quite
+                * high hence we en up exactly in the mentionned scenario.
+                * AFAIK this might be the best way to handle this.
+                */
+               ret = 0;
+               goto end_unlock;
+       }
+       element = caa_container_of(node,
+                       struct notification_trigger_tokens_ht_element,
+                       node);
+
+       if (!lttng_trigger_should_fire(element->trigger)) {
+               ret = 0;
+               goto end_unlock;
+       }
+
+       lttng_trigger_fire(element->trigger);
+
+       trigger_status = lttng_trigger_get_name(element->trigger, &trigger_name);
+       assert(trigger_status == LTTNG_TRIGGER_STATUS_OK);
+
+       if (LTTNG_CONDITION_STATUS_OK !=
+                       lttng_condition_event_rule_get_capture_descriptor_count(
+                                       lttng_trigger_get_const_condition(
+                                                       element->trigger),
+                                       &capture_count)) {
+               ERR("Get capture count");
+               ret = -1;
+               goto end;
+       }
+
+       if (!notification->capture_buffer && capture_count != 0) {
+               ERR("Expected capture but capture buffer is null");
+               ret = -1;
+               goto end;
+       }
+
+       evaluation = lttng_evaluation_event_rule_create(
+                       container_of(lttng_trigger_get_const_condition(
+                                                    element->trigger),
+                                       struct lttng_condition_event_rule,
+                                       parent),
+                       trigger_name,
+                       notification->capture_buffer,
+                       notification->capture_buf_size, false);
+
+       if (evaluation == NULL) {
+               ERR("[notification-thread] Failed to create event rule hit evaluation");
+               ret = -1;
+               goto end_unlock;
+       }
+       client_list = get_client_list_from_condition(state,
+                       lttng_trigger_get_const_condition(element->trigger));
+       executor_status = action_executor_enqueue(state->executor,
+                       element->trigger, evaluation, NULL, client_list);
+       switch (executor_status) {
+       case ACTION_EXECUTOR_STATUS_OK:
+               ret = 0;
+               break;
+       case ACTION_EXECUTOR_STATUS_OVERFLOW:
+       {
+               struct notification_client_list_element *client_list_element,
+                               *tmp;
+
+               /*
+                * Not a fatal error; this is expected and simply means the
+                * executor has too much work queued already.
+                */
+               ret = 0;
+
+               if (!client_list) {
+                       break;
+               }
+
+               /* Warn clients that a notification (or more) was dropped. */
+               pthread_mutex_lock(&client_list->lock);
+               cds_list_for_each_entry_safe(client_list_element, tmp,
+                               &client_list->list, node) {
+                       enum client_transmission_status transmission_status;
+                       struct notification_client *client =
+                                       client_list_element->client;
+
+                       pthread_mutex_lock(&client->lock);
+                       ret = client_notification_overflow(client);
+                       if (ret) {
+                               /* Fatal error. */
+                               goto next_client;
+                       }
+
+                       transmission_status =
+                                       client_flush_outgoing_queue(client);
+                       ret = client_handle_transmission_status(
+                                       client, transmission_status, state);
+                       if (ret) {
+                               /* Fatal error. */
+                               goto next_client;
+                       }
+next_client:
+                       pthread_mutex_unlock(&client->lock);
+                       if (ret) {
+                               break;
+                       }
+               }
+               pthread_mutex_unlock(&client_list->lock);
+               break;
+       }
+       case ACTION_EXECUTOR_STATUS_INVALID:
+       case ACTION_EXECUTOR_STATUS_ERROR:
+               /* Fatal error, shut down everything. */
+               ERR("Fatal error encoutered while enqueuing action");
+               ret = -1;
+               goto end_unlock;
+       default:
+               /* Unhandled error. */
+               abort();
+       }
+
+end_unlock:
+       lttng_trigger_notification_destroy(notification);
+       notification_client_list_put(client_list);
+       rcu_read_unlock();
 end:
-       lttng_dynamic_buffer_reset(&msg_buffer);
        return ret;
 }
 
@@ -2481,6 +4466,7 @@ int handle_notification_thread_channel_sample(
        bool previous_sample_available = false;
        struct channel_state_sample previous_sample, latest_sample;
        uint64_t previous_session_consumed_total, latest_session_consumed_total;
+       struct lttng_credentials channel_creds;
 
        /*
         * The monitoring pipe only holds messages smaller than PIPE_BUF,
@@ -2519,8 +4505,7 @@ int handle_notification_thread_channel_sample(
                 */
                DBG("[notification-thread] Received a sample for an unknown channel from consumerd, key = %" PRIu64 " in %s domain",
                                latest_sample.key.key,
-                               domain == LTTNG_DOMAIN_KERNEL ? "kernel" :
-                                       "user space");
+                               lttng_domain_type_str(domain));
                goto end_unlock;
        }
        channel_info = caa_container_of(node, struct channel_info,
@@ -2599,70 +4584,97 @@ int handle_notification_thread_channel_sample(
                goto end_unlock;
        }
 
+       channel_creds = (typeof(channel_creds)) {
+               .uid = LTTNG_OPTIONAL_INIT_VALUE(channel_info->session_info->uid),
+               .gid = LTTNG_OPTIONAL_INIT_VALUE(channel_info->session_info->gid),
+       };
+
        trigger_list = caa_container_of(node, struct lttng_channel_trigger_list,
                        channel_triggers_ht_node);
        cds_list_for_each_entry(trigger_list_element, &trigger_list->list,
-                       node) {
+                       node) {
                const struct lttng_condition *condition;
                const struct lttng_action *action;
-               const struct lttng_trigger *trigger;
-               struct notification_client_list *client_list;
+               struct lttng_trigger *trigger;
+               struct notification_client_list *client_list = NULL;
                struct lttng_evaluation *evaluation = NULL;
+               enum action_executor_status executor_status;
 
+               ret = 0;
                trigger = trigger_list_element->trigger;
                condition = lttng_trigger_get_const_condition(trigger);
                assert(condition);
                action = lttng_trigger_get_const_action(trigger);
 
+               if (!lttng_trigger_should_fire(trigger)) {
+                       goto put_list;
+               }
+
+               lttng_trigger_fire(trigger);
+
                /* Notify actions are the only type currently supported. */
-               assert(lttng_action_get_type_const(action) ==
+               /* TODO support other type of action */
+               assert(lttng_action_get_type(action) ==
                                LTTNG_ACTION_TYPE_NOTIFY);
 
                /*
                 * Check if any client is subscribed to the result of this
                 * evaluation.
                 */
-               cds_lfht_lookup(state->notification_trigger_clients_ht,
-                               lttng_condition_hash(condition),
-                               match_client_list,
-                               trigger,
-                               &iter);
-               node = cds_lfht_iter_get_node(&iter);
-               assert(node);
-
-               client_list = caa_container_of(node,
-                               struct notification_client_list,
-                               notification_trigger_ht_node);
-               if (cds_list_empty(&client_list->list)) {
-                       /*
-                        * No clients interested in the evaluation's result,
-                        * skip it.
-                        */
-                       continue;
-               }
+               client_list = get_client_list_from_condition(state, condition);
 
-               ret = evaluate_condition(condition, &evaluation, state,
+               ret = evaluate_buffer_condition(condition, &evaluation, state,
                                previous_sample_available ? &previous_sample : NULL,
                                &latest_sample,
                                previous_session_consumed_total,
                                latest_session_consumed_total,
                                channel_info);
                if (caa_unlikely(ret)) {
-                       goto end_unlock;
+                       goto put_list;
                }
 
                if (caa_likely(!evaluation)) {
-                       continue;
+                       goto put_list;
+               }
+
+               /*
+                * Ownership of `evaluation` transferred to the action executor
+                * no matter the result.
+                */
+               executor_status = action_executor_enqueue(state->executor,
+                               trigger, evaluation, &channel_creds,
+                               client_list);
+               evaluation = NULL;
+               switch (executor_status) {
+               case ACTION_EXECUTOR_STATUS_OK:
+                       break;
+               case ACTION_EXECUTOR_STATUS_ERROR:
+               case ACTION_EXECUTOR_STATUS_INVALID:
+                       /*
+                        * TODO Add trigger identification (name/id) when
+                        * it is added to the API.
+                        */
+                       ERR("Fatal error occurred while enqueuing action associated with buffer-condition trigger");
+                       ret = -1;
+                       goto put_list;
+               case ACTION_EXECUTOR_STATUS_OVERFLOW:
+                       /*
+                        * TODO Add trigger identification (name/id) when
+                        * it is added to the API.
+                        *
+                        * Not a fatal error.
+                        */
+                       WARN("No space left when enqueuing action associated with buffer-condition trigger");
+                       ret = 0;
+                       goto put_list;
+               default:
+                       abort();
                }
 
-               /* Dispatch evaluation result to all clients. */
-               ret = send_evaluation_to_clients(trigger_list_element->trigger,
-                               evaluation, client_list, state,
-                               channel_info->session_info->uid,
-                               channel_info->session_info->gid);
-               lttng_evaluation_destroy(evaluation);
+put_list:
+               notification_client_list_put(client_list);
                if (caa_unlikely(ret)) {
-                       goto end_unlock;
+                       break;
                }
        }
 end_unlock:
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