Fix: sessiond: notification: unreachable code in switch-case
[lttng-tools.git] / src / bin / lttng-sessiond / notification-thread-events.c
index 5956d53ca9e6f0c4e3006ac456979a621bf5f7e6..833b550f87067672a682ccc99bcec710361c90be 100644 (file)
@@ -27,6 +27,7 @@
 #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 <lttng/event-rule/event-rule-internal.h>
@@ -37,6 +38,7 @@
 #include <inttypes.h>
 #include <fcntl.h>
 
+#include "condition-internal.h"
 #include "notification-thread.h"
 #include "notification-thread-events.h"
 #include "notification-thread-commands.h"
@@ -123,6 +125,19 @@ struct lttng_condition_list_element {
        struct cds_list_head node;
 };
 
+/*
+ * Facilities to carry the different notifications type in the action processing
+ * code path.
+ */
+struct lttng_event_notifier_notification {
+       union {
+               struct lttng_ust_event_notifier_notification *ust;
+               struct lttng_kernel_event_notifier_notification *kernel;
+       } notification;
+       uint64_t token;
+       enum lttng_domain_type type;
+};
+
 struct channel_state_sample {
        struct channel_key key;
        struct cds_lfht_node channel_state_ht_node;
@@ -279,6 +294,17 @@ int match_trigger(struct cds_lfht_node *node, const void *key)
        return !!lttng_trigger_is_equal(trigger_key, trigger_ht_element->trigger);
 }
 
+static
+int match_trigger_token(struct cds_lfht_node *node, const void *key)
+{
+       const uint64_t *_key = key;
+       struct notification_trigger_tokens_ht_element *element;
+
+       element = caa_container_of(node,
+                       struct notification_trigger_tokens_ht_element, node);
+       return *_key == element->token;
+}
+
 static
 int match_client_list_condition(struct cds_lfht_node *node, const void *key)
 {
@@ -305,6 +331,38 @@ int match_session(struct cds_lfht_node *node, const void *key)
        return !strcmp(session_info->name, name);
 }
 
+static
+const char *notification_command_type_str(
+               enum notification_thread_command_type type)
+{
+       switch (type) {
+       case NOTIFICATION_COMMAND_TYPE_REGISTER_TRIGGER:
+               return "REGISTER_TRIGGER";
+       case NOTIFICATION_COMMAND_TYPE_UNREGISTER_TRIGGER:
+               return "UNREGISTER_TRIGGER";
+       case NOTIFICATION_COMMAND_TYPE_ADD_CHANNEL:
+               return "ADD_CHANNEL";
+       case NOTIFICATION_COMMAND_TYPE_REMOVE_CHANNEL:
+               return "REMOVE_CHANNEL";
+       case NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_ONGOING:
+               return "SESSION_ROTATION_ONGOING";
+       case NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_COMPLETED:
+               return "SESSION_ROTATION_COMPLETED";
+       case NOTIFICATION_COMMAND_TYPE_ADD_TRACER_EVENT_SOURCE:
+               return "ADD_TRACER_EVENT_SOURCE";
+       case NOTIFICATION_COMMAND_TYPE_REMOVE_TRACER_EVENT_SOURCE:
+               return "REMOVE_TRACER_EVENT_SOURCE";
+       case NOTIFICATION_COMMAND_TYPE_LIST_TRIGGERS:
+               return "LIST_TRIGGERS";
+       case NOTIFICATION_COMMAND_TYPE_QUIT:
+               return "QUIT";
+       case NOTIFICATION_COMMAND_TYPE_CLIENT_COMMUNICATION_UPDATE:
+               return "CLIENT_COMMUNICATION_UPDATE";
+       default:
+               abort();
+       }
+}
+
 /*
  * Match trigger based on name and credentials only.
  * Name duplication is NOT allowed for the same uid.
@@ -370,125 +428,6 @@ unsigned long hash_trigger_by_name_uid(const struct lttng_trigger *trigger)
        return hash;
 }
 
-static
-unsigned long lttng_condition_buffer_usage_hash(
-       const struct lttng_condition *_condition)
-{
-       unsigned long hash;
-       unsigned long condition_type;
-       struct lttng_condition_buffer_usage *condition;
-
-       condition = container_of(_condition,
-                       struct lttng_condition_buffer_usage, parent);
-
-       condition_type = (unsigned long) condition->parent.type;
-       hash = hash_key_ulong((void *) condition_type, lttng_ht_seed);
-       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;
-
-               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;
-
-               val = condition->threshold_bytes.value;
-               hash ^= hash_key_u64(&val, lttng_ht_seed);
-       }
-       return hash;
-}
-
-static
-unsigned long lttng_condition_session_consumed_size_hash(
-       const struct lttng_condition *_condition)
-{
-       unsigned long hash;
-       unsigned long condition_type =
-                       (unsigned long) LTTNG_CONDITION_TYPE_SESSION_CONSUMED_SIZE;
-       struct lttng_condition_session_consumed_size *condition;
-       uint64_t val;
-
-       condition = container_of(_condition,
-                       struct lttng_condition_session_consumed_size, parent);
-
-       hash = hash_key_ulong((void *) condition_type, lttng_ht_seed);
-       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 lttng_condition_session_rotation_hash(
-       const struct lttng_condition *_condition)
-{
-       unsigned long hash, condition_type;
-       struct lttng_condition_session_rotation *condition;
-
-       condition = container_of(_condition,
-                       struct lttng_condition_session_rotation, parent);
-       condition_type = (unsigned long) condition->parent.type;
-       hash = hash_key_ulong((void *) condition_type, lttng_ht_seed);
-       assert(condition->session_name);
-       hash ^= hash_key_str(condition->session_name, lttng_ht_seed);
-       return hash;
-}
-
-static
-unsigned long lttng_condition_event_rule_hash(
-       const struct lttng_condition *condition)
-{
-       unsigned long hash, condition_type;
-       enum lttng_condition_status condition_status;
-       const struct lttng_event_rule *event_rule;
-
-       condition_type = (unsigned long) condition->type;
-
-       condition_status = lttng_condition_event_rule_get_rule(condition,
-                                                              &event_rule);
-       assert(condition_status == LTTNG_CONDITION_STATUS_OK);
-
-       hash = hash_key_ulong((void *) condition_type, lttng_ht_seed);
-       return hash ^ lttng_event_rule_hash(event_rule);
-}
-
-/*
- * The lttng_condition hashing code is kept in this file (rather than
- * condition.c) since it makes use of GPLv2 code (hashtable utils), which we
- * don't want to link in liblttng-ctl.
- */
-static
-unsigned long lttng_condition_hash(const struct lttng_condition *condition)
-{
-       switch (condition->type) {
-       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_LOW:
-       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_HIGH:
-               return lttng_condition_buffer_usage_hash(condition);
-       case LTTNG_CONDITION_TYPE_SESSION_CONSUMED_SIZE:
-               return lttng_condition_session_consumed_size_hash(condition);
-       case LTTNG_CONDITION_TYPE_SESSION_ROTATION_ONGOING:
-       case LTTNG_CONDITION_TYPE_SESSION_ROTATION_COMPLETED:
-               return lttng_condition_session_rotation_hash(condition);
-       case LTTNG_CONDITION_TYPE_EVENT_RULE_HIT:
-               return lttng_condition_event_rule_hash(condition);
-       default:
-               ERR("[notification-thread] Unexpected condition type caught");
-               abort();
-       }
-}
-
 static
 unsigned long hash_channel_key(struct channel_key *key)
 {
@@ -1043,6 +982,7 @@ int evaluate_condition_for_client(const struct lttng_trigger *trigger,
                                &evaluation, &object_uid, &object_gid);
                break;
        case LTTNG_OBJECT_TYPE_NONE:
+               DBG("[notification-thread] Newly subscribed-to condition not bound to object, nothing to evaluate");
                ret = 0;
                goto end;
        case LTTNG_OBJECT_TYPE_UNKNOWN:
@@ -2008,6 +1948,126 @@ end:
        return ret;
 }
 
+static
+int handle_notification_thread_command_add_tracer_event_source(
+               struct notification_thread_state *state,
+               int tracer_event_source_fd,
+               enum lttng_domain_type domain_type,
+               enum lttng_error_code *_cmd_result)
+{
+       int ret = 0;
+       enum lttng_error_code cmd_result = LTTNG_OK;
+       struct notification_event_tracer_event_source_element *element = NULL;
+
+       element = zmalloc(sizeof(*element));
+       if (!element) {
+               cmd_result = LTTNG_ERR_NOMEM;
+               ret = -1;
+               goto end;
+       }
+
+       element->fd = tracer_event_source_fd;
+       element->domain = domain_type;
+
+       cds_list_add(&element->node, &state->tracer_event_sources_list);
+
+       DBG3("[notification-thread] Adding tracer event source fd to poll set: tracer_event_source_fd = %d, domain = '%s'",
+                       tracer_event_source_fd,
+                       lttng_domain_type_str(domain_type));
+
+       /* Adding the read side pipe to the event poll. */
+       ret = lttng_poll_add(&state->events, tracer_event_source_fd, LPOLLIN | LPOLLERR);
+       if (ret < 0) {
+               ERR("[notification-thread] Failed to add tracer event source to poll set: tracer_event_source_fd = %d, domain = '%s'",
+                               tracer_event_source_fd,
+                               lttng_domain_type_str(element->domain));
+               cds_list_del(&element->node);
+               free(element);
+               goto end;
+       }
+
+       element->is_fd_in_poll_set = true;
+
+end:
+       *_cmd_result = cmd_result;
+       return ret;
+}
+
+static
+int handle_notification_thread_command_remove_tracer_event_source(
+               struct notification_thread_state *state,
+               int tracer_event_source_fd,
+               enum lttng_error_code *_cmd_result)
+{
+       int ret = 0;
+       bool found = false;
+       enum lttng_error_code cmd_result = LTTNG_OK;
+       struct notification_event_tracer_event_source_element *source_element = NULL, *tmp;
+
+       cds_list_for_each_entry_safe(source_element, tmp,
+                       &state->tracer_event_sources_list, node) {
+               if (source_element->fd != tracer_event_source_fd) {
+                       continue;
+               }
+
+               DBG("[notification-thread] Removed tracer event source from poll set: tracer_event_source_fd = %d, domain = '%s'",
+                               tracer_event_source_fd,
+                               lttng_domain_type_str(source_element->domain));
+               cds_list_del(&source_element->node);
+               found = true;
+               break;
+       }
+
+       if (!found) {
+               /*
+                * This is temporarily allowed since the poll activity set is
+                * not properly cleaned-up for the moment. This is adressed in
+                * an upcoming fix.
+                */
+               source_element = NULL;
+               goto end;
+       }
+
+       if (!source_element->is_fd_in_poll_set) {
+               /* Skip the poll set removal. */
+               goto end;
+       }
+
+       DBG3("[notification-thread] Removing tracer event source from poll set: tracer_event_source_fd = %d, domain = '%s'",
+                       tracer_event_source_fd,
+                       lttng_domain_type_str(source_element->domain));
+
+       /* Removing the fd from the event poll set. */
+       ret = lttng_poll_del(&state->events, tracer_event_source_fd);
+       if (ret < 0) {
+               ERR("[notification-thread] Failed to remove tracer event source from poll set: tracer_event_source_fd = %d, domain = '%s'",
+                               tracer_event_source_fd,
+                               lttng_domain_type_str(source_element->domain));
+               cmd_result = LTTNG_ERR_FATAL;
+               goto end;
+       }
+
+       source_element->is_fd_in_poll_set = false;
+
+end:
+       free(source_element);
+       *_cmd_result = cmd_result;
+       return ret;
+}
+
+int handle_notification_thread_remove_tracer_event_source_no_result(
+               struct notification_thread_state *state,
+               int tracer_event_source_fd)
+{
+       int ret;
+       enum lttng_error_code cmd_result;
+
+       ret = handle_notification_thread_command_remove_tracer_event_source(
+                       state, tracer_event_source_fd, &cmd_result);
+       (void) cmd_result;
+       return ret;
+}
+
 static int handle_notification_thread_command_list_triggers(
                struct notification_thread_handle *handle,
                struct notification_thread_state *state,
@@ -2328,6 +2388,7 @@ int handle_notification_thread_command_register_trigger(
        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;
@@ -2406,10 +2467,47 @@ int handle_notification_thread_command_register_trigger(
                goto error_free_ht_element;
        }
 
+       if (lttng_condition_get_type(condition) == LTTNG_CONDITION_TYPE_EVENT_RULE_HIT) {
+               trigger_tokens_ht_element = zmalloc(sizeof(*trigger_tokens_ht_element));
+               if (!trigger_tokens_ht_element) {
+                       /* Fatal error. */
+                       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_free_ht_element;
+               }
+
+               /* 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) {
+                       /* Internal corruption, fatal error. */
+                       ret = -1;
+                       *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);
+                       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;
 
@@ -2512,11 +2610,15 @@ int handle_notification_thread_command_register_trigger(
                ret = evaluate_session_condition_for_client(condition, state,
                                &evaluation, &object_uid,
                                &object_gid);
+               LTTNG_OPTIONAL_SET(&object_creds.uid, object_uid);
+               LTTNG_OPTIONAL_SET(&object_creds.gid, object_gid);
                break;
        case LTTNG_OBJECT_TYPE_CHANNEL:
                ret = evaluate_channel_condition_for_client(condition, state,
                                &evaluation, &object_uid,
                                &object_gid);
+               LTTNG_OPTIONAL_SET(&object_creds.uid, object_uid);
+               LTTNG_OPTIONAL_SET(&object_creds.gid, object_gid);
                break;
        case LTTNG_OBJECT_TYPE_NONE:
                ret = 0;
@@ -2532,9 +2634,6 @@ int handle_notification_thread_command_register_trigger(
                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) {
@@ -2591,6 +2690,7 @@ error_free_ht_element:
                                free_lttng_trigger_ht_element_rcu);
        }
 
+       free(trigger_tokens_ht_element);
 error:
        if (free_trigger) {
                lttng_trigger_destroy(trigger);
@@ -2606,10 +2706,17 @@ void free_lttng_trigger_ht_element_rcu(struct rcu_head *node)
                        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,
-               struct lttng_trigger *trigger,
+               const struct lttng_trigger *trigger,
                enum lttng_error_code *_cmd_reply)
 {
        struct cds_lfht_iter iter;
@@ -2617,7 +2724,7 @@ int handle_notification_thread_command_unregister_trigger(
        struct lttng_channel_trigger_list *trigger_list;
        struct notification_client_list *client_list;
        struct lttng_trigger_ht_element *trigger_ht_element = NULL;
-       struct lttng_condition *condition = lttng_trigger_get_condition(
+       const struct lttng_condition *condition = lttng_trigger_get_const_condition(
                        trigger);
        enum lttng_error_code cmd_reply;
 
@@ -2654,6 +2761,28 @@ int handle_notification_thread_command_unregister_trigger(
                }
        }
 
+       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;
+                       }
+
+                       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
@@ -2706,21 +2835,22 @@ int handle_notification_thread_command(
                        struct notification_thread_command, cmd_list_node);
        cds_list_del(&cmd->cmd_list_node);
        pthread_mutex_unlock(&handle->cmd_queue.lock);
+
+       DBG("[notification-thread] Received `%s` command",
+                       notification_command_type_str(cmd->type));
        switch (cmd->type) {
        case NOTIFICATION_COMMAND_TYPE_REGISTER_TRIGGER:
-               DBG("[notification-thread] Received register trigger command");
-               ret = handle_notification_thread_command_register_trigger(
-                               state, cmd->parameters.trigger,
+               ret = handle_notification_thread_command_register_trigger(state,
+                               cmd->parameters.register_trigger.trigger,
                                &cmd->reply_code);
                break;
        case NOTIFICATION_COMMAND_TYPE_UNREGISTER_TRIGGER:
-               DBG("[notification-thread] Received unregister trigger command");
                ret = handle_notification_thread_command_unregister_trigger(
-                               state, cmd->parameters.trigger,
+                               state,
+                               cmd->parameters.unregister_trigger.trigger,
                                &cmd->reply_code);
                break;
        case NOTIFICATION_COMMAND_TYPE_ADD_CHANNEL:
-               DBG("[notification-thread] Received add channel command");
                ret = handle_notification_thread_command_add_channel(
                                state,
                                cmd->parameters.add_channel.session.name,
@@ -2733,7 +2863,6 @@ int handle_notification_thread_command(
                                &cmd->reply_code);
                break;
        case NOTIFICATION_COMMAND_TYPE_REMOVE_CHANNEL:
-               DBG("[notification-thread] Received remove channel command");
                ret = handle_notification_thread_command_remove_channel(
                                state, cmd->parameters.remove_channel.key,
                                cmd->parameters.remove_channel.domain,
@@ -2741,9 +2870,6 @@ int handle_notification_thread_command(
                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,
@@ -2754,6 +2880,19 @@ int handle_notification_thread_command(
                                cmd->parameters.session_rotation.location,
                                &cmd->reply_code);
                break;
+       case NOTIFICATION_COMMAND_TYPE_ADD_TRACER_EVENT_SOURCE:
+               ret = handle_notification_thread_command_add_tracer_event_source(
+                               state,
+                               cmd->parameters.tracer_event_source.tracer_event_source_fd,
+                               cmd->parameters.tracer_event_source.domain,
+                               &cmd->reply_code);
+               break;
+       case NOTIFICATION_COMMAND_TYPE_REMOVE_TRACER_EVENT_SOURCE:
+               ret = handle_notification_thread_command_remove_tracer_event_source(
+                               state,
+                               cmd->parameters.tracer_event_source.tracer_event_source_fd,
+                               &cmd->reply_code);
+               break;
        case NOTIFICATION_COMMAND_TYPE_LIST_TRIGGERS:
        {
                struct lttng_triggers *triggers = NULL;
@@ -2769,7 +2908,6 @@ int handle_notification_thread_command(
                break;
        }
        case NOTIFICATION_COMMAND_TYPE_QUIT:
-               DBG("[notification-thread] Received quit command");
                cmd->reply_code = LTTNG_OK;
                ret = 1;
                goto end;
@@ -4036,6 +4174,99 @@ end:
        return ret;
 }
 
+int handle_notification_thread_event_notification(struct notification_thread_state *state,
+               int notification_pipe_read_fd,
+               enum lttng_domain_type domain)
+{
+       int ret;
+       struct lttng_ust_event_notifier_notification ust_notification;
+       struct lttng_kernel_event_notifier_notification kernel_notification;
+       struct cds_lfht_node *node;
+       struct cds_lfht_iter iter;
+       struct notification_trigger_tokens_ht_element *element;
+       enum lttng_action_type action_type;
+       const struct lttng_action *action;
+       struct lttng_event_notifier_notification notification;
+       void *reception_buffer;
+       size_t reception_size;
+
+       notification.type = domain;
+
+       switch(domain) {
+       case LTTNG_DOMAIN_UST:
+               reception_buffer = (void *) &ust_notification;
+               reception_size = sizeof(ust_notification);
+               notification.notification.ust = &ust_notification;
+               break;
+       case LTTNG_DOMAIN_KERNEL:
+               reception_buffer = (void *) &kernel_notification;
+               reception_size = sizeof(kernel_notification);
+               notification.notification.kernel = &kernel_notification;
+               break;
+       default:
+               abort();
+       }
+
+       /*
+        * The monitoring pipe only holds messages smaller than PIPE_BUF,
+        * ensuring that read/write of tracer notifications are atomic.
+        */
+       ret = lttng_read(notification_pipe_read_fd, reception_buffer,
+                       reception_size);
+       if (ret != reception_size) {
+               PERROR("Failed to read from event source notification pipe: fd = %d, size to read = %zu, ret = %d",
+                               notification_pipe_read_fd, reception_size, ret);
+               ret = -1;
+               goto end;
+       }
+
+       switch(domain) {
+       case LTTNG_DOMAIN_UST:
+               notification.token = ust_notification.token;
+               break;
+       case LTTNG_DOMAIN_KERNEL:
+               notification.token = kernel_notification.token;
+               break;
+       default:
+               abort();
+       }
+
+       /* Find triggers associated with this token. */
+       rcu_read_lock();
+       cds_lfht_lookup(state->trigger_tokens_ht,
+                       hash_key_u64(&notification.token, lttng_ht_seed),
+                       match_trigger_token, &notification.token, &iter);
+       node = cds_lfht_iter_get_node(&iter);
+       if (caa_likely(!node)) {
+               /*
+                * This is not an error, slow consumption of the pipe can lead
+                * to situations where a trigger is removed but we still get
+                * tracer notification matching to a previous trigger.
+                */
+               ret = 0;
+               goto end_unlock;
+       }
+
+       element = caa_container_of(node,
+                       struct notification_trigger_tokens_ht_element,
+                       node);
+
+       action = lttng_trigger_get_const_action(element->trigger);
+       action_type = lttng_action_get_type(action);
+       DBG("Received message from tracer event source: event source fd = %d, token = %" PRIu64 ", action type = '%s'",
+                       notification_pipe_read_fd, notification.token,
+                       lttng_action_type_string(action_type));
+
+       /* TODO: Perform actions */
+
+       ret = 0;
+
+end_unlock:
+       rcu_read_unlock();
+end:
+       return ret;
+}
+
 int handle_notification_thread_channel_sample(
                struct notification_thread_state *state, int pipe,
                enum lttng_domain_type domain)
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