Fix: notification thread: RCU-safe reclaim of hash table nodes

[lttng-tools.git] / src / bin / lttng-sessiond / notification-thread-events.c

diff --git a/src/bin/lttng-sessiond/notification-thread-events.c b/src/bin/lttng-sessiond/notification-thread-events.c
index f29c1ef17da90762bf225d2a3e8ba8f5b81ee306..ba4e5a057eb79464835a0ae159fbc0d1f2cf3091 100644 (file)
--- a/src/bin/lttng-sessiond/notification-thread-events.c
+++ b/src/bin/lttng-sessiond/notification-thread-events.c
@@ -70,6 +70,8 @@ struct lttng_channel_trigger_list {
        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;
 };
 
 /*
@@ -116,6 +118,8 @@ struct lttng_session_trigger_list {
 struct lttng_trigger_ht_element {
        struct lttng_trigger *trigger;
        struct cds_lfht_node node;
+       /* call_rcu delayed reclaim. */
+       struct rcu_head rcu_node;
 };
 
 struct lttng_condition_list_element {
@@ -132,6 +136,8 @@ struct notification_client_list {
        const struct lttng_trigger *trigger;
        struct cds_list_head list;
        struct cds_lfht_node notification_trigger_ht_node;
+       /* call_rcu delayed reclaim. */
+       struct rcu_head rcu_node;
 };
 
 struct notification_client {
@@ -198,6 +204,8 @@ struct notification_client {
                        struct lttng_dynamic_buffer buffer;
                } outbound;
        } communication;
+       /* call_rcu delayed reclaim. */
+       struct rcu_head rcu_node;
 };
 
 struct channel_state_sample {
@@ -206,6 +214,8 @@ struct channel_state_sample {
        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);
@@ -500,6 +510,12 @@ enum lttng_object_type get_condition_binding_object(
        }
 }
 
+static
+void free_channel_info_rcu(struct rcu_head *node)
+{
+       free(caa_container_of(node, struct channel_info, rcu_node));
+}
+
 static
 void channel_info_destroy(struct channel_info *channel_info)
 {
@@ -515,7 +531,13 @@ 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. */
@@ -539,7 +561,7 @@ void session_info_destroy(void *_data)
                        &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
@@ -841,6 +863,7 @@ int evaluate_session_condition_for_client(
        switch (lttng_condition_get_type(condition)) {
        case LTTNG_CONDITION_TYPE_SESSION_ROTATION_ONGOING:
                if (!session_info->rotation.ongoing) {
+                       ret = 0;
                        goto end_session_put;
                }
 
@@ -1097,6 +1120,12 @@ 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)
@@ -1119,7 +1148,7 @@ void notification_client_destroy(struct notification_client *client,
        }
        lttng_dynamic_buffer_reset(&client->communication.inbound.buffer);
        lttng_dynamic_buffer_reset(&client->communication.outbound.buffer);
-       free(client);
+       call_rcu(&client->rcu_node, free_notification_client_rcu);
 }
 
 /*
@@ -1533,7 +1562,7 @@ int handle_notification_thread_command_add_channel(
        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;
        }
 
@@ -1543,6 +1572,7 @@ 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) {
@@ -1555,6 +1585,7 @@ 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);
@@ -1562,6 +1593,7 @@ 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);
@@ -1596,6 +1628,20 @@ 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,
@@ -1638,7 +1684,7 @@ 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,
@@ -1657,7 +1703,7 @@ 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. */
@@ -1698,7 +1744,7 @@ int handle_notification_thread_command_session_rotation(
        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. */
                ret = -1;
                cmd_result = LTTNG_ERR_NOMEM;
                goto end;
@@ -2116,6 +2162,20 @@ error:
        return ret;
 }
 
+static
+void free_notification_client_list_rcu(struct rcu_head *node)
+{
+       free(caa_container_of(node, struct notification_client_list,
+                       rcu_node));
+}
+
+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
 int handle_notification_thread_command_unregister_trigger(
                struct notification_thread_state *state,
@@ -2185,7 +2245,7 @@ int handle_notification_thread_command_unregister_trigger(
        }
        cds_lfht_del(state->notification_trigger_clients_ht,
                        &client_list->notification_trigger_ht_node);
-       free(client_list);
+       call_rcu(&client_list->rcu_node, free_notification_client_list_rcu);
 
        /* Remove trigger from triggers_ht. */
        trigger_ht_element = caa_container_of(triggers_ht_node,
@@ -2197,7 +2257,7 @@ int handle_notification_thread_command_unregister_trigger(
        action = lttng_trigger_get_action(trigger_ht_element->trigger);
        lttng_action_destroy(action);
        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) {