+
+struct lttng_ust_ctx;
+struct lttng_ust_event_common_private;
+
+enum lttng_ust_event_type {
+ LTTNG_UST_EVENT_TYPE_RECORDER = 0,
+ LTTNG_UST_EVENT_TYPE_NOTIFIER = 1,
+};
+
+/*
+ * IMPORTANT: this structure is part of the ABI between the probe and
+ * UST. Fields need to be only added at the end, never reordered, never
+ * removed.
+ *
+ * struct lttng_ust_event_common is the common ancestor of the various
+ * public event actions. Inheritance is done by composition: The parent
+ * has a pointer to its child, and the child has a pointer to its
+ * parent. Inheritance of those public structures is done by composition
+ * to ensure both parent and child structures can be extended.
+ *
+ * The field @struct_size should be used to determine the size of the
+ * structure. It should be queried before using additional fields added
+ * at the end of the structure.
+ */
+struct lttng_ust_event_common {
+ uint32_t struct_size; /* Size of this structure. */
+
+ struct lttng_ust_event_common_private *priv; /* Private event interface */
+
+ enum lttng_ust_event_type type;
+ void *child; /* Pointer to child, for inheritance by aggregation. */
+
+ int enabled;
+ int has_enablers_without_bytecode;
+ /* list of struct lttng_ust_bytecode_runtime, sorted by seqnum */
+ struct cds_list_head filter_bytecode_runtime_head;
+
+ /* End of base ABI. Fields below should be used after checking struct_size. */
+};
+
+struct lttng_ust_event_recorder_private;
+
+/*
+ * IMPORTANT: this structure is part of the ABI between the probe and
+ * UST. Fields need to be only added at the end, never reordered, never
+ * removed.
+ *
+ * struct lttng_ust_event_recorder is the action for recording events
+ * into a ring buffer. It inherits from struct lttng_ust_event_common
+ * by composition to ensure both parent and child structure are
+ * extensible.
+ *
+ * The field @struct_size should be used to determine the size of the
+ * structure. It should be queried before using additional fields added
+ * at the end of the structure.
+ */
+struct lttng_ust_event_recorder {
+ uint32_t struct_size; /* Size of this structure. */
+
+ struct lttng_ust_event_common *parent; /* Inheritance by aggregation. */
+ struct lttng_ust_event_recorder_private *priv; /* Private event record interface */
+