lib/tevent: Add trace point callback

Set/get a single callback function to be invoked at various trace
points.  Define "before wait" and "after wait" trace points - more
trace points can be added later if required.

CTDB wants this to log long waits and events.

Pair-programmed-with: Amitay Isaacs <amitay@gmail.com>
Signed-off-by: Martin Schwenke <martin@meltin.net>
Signed-off-by: Stefan Metzmacher <metze@samba.org>

1 files changed, 43 insertions, 0 deletions

diff --git a/lib/tevent/tevent.h b/lib/tevent/tevent.h
index c38f7c36e17..c8719fa4f19 100644
--- a/lib/tevent/tevent.h
+++ b/lib/tevent/tevent.h
@@ -501,6 +501,49 @@ int tevent_set_debug(struct tevent_context *ev,
  */
 int tevent_set_debug_stderr(struct tevent_context *ev);
 
+enum tevent_trace_point {
+	/**
+	 * Corresponds to a trace point just before waiting
+	 */
+	TEVENT_TRACE_BEFORE_WAIT,
+	/**
+	 * Corresponds to a trace point just after waiting
+	 */
+	TEVENT_TRACE_AFTER_WAIT,
+};
+
+typedef void (*tevent_trace_callback_t)(enum tevent_trace_point,
+					void *private_data);
+
+/**
+ * Register a callback to be called at certain trace points
+ *
+ * @param[in] ev             Event context
+ * @param[in] cb             Trace callback
+ * @param[in] private_data   Data to be passed to callback
+ *
+ * @note The callback will be called at trace points defined by
+ * tevent_trace_point.  Call with NULL to reset.
+ */
+void tevent_set_trace_callback(struct tevent_context *ev,
+			       tevent_trace_callback_t cb,
+			       void *private_data);
+
+/**
+ * Retrieve the current trace callback
+ *
+ * @param[in] ev             Event context
+ * @param[out] cb            Registered trace callback
+ * @param[out] private_data  Registered data to be passed to callback
+ *
+ * @note This can be used to allow one component that wants to
+ * register a callback to respect the callback that another component
+ * has already registered.
+ */
+void tevent_get_trace_callback(struct tevent_context *ev,
+			       tevent_trace_callback_t *cb,
+			       void *private_data);
+
 /**
  * @}
  */