tools lib traceevent: Add pevent_unregister_print_function()

When a plugin unloaded it needs to unregister its print handler from
pevent.

So add an unregister function to do it.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1389839478-5887-3-git-send-email-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/traceevent/event-parse.c

@@ -5560,6 +5560,29 @@ int pevent_register_print_function(struct pevent *pevent,
 	return ret;
 }
 
+/**
+ * pevent_unregister_print_function - unregister a helper function
+ * @pevent: the handle to the pevent
+ * @func: the function to process the helper function
+ * @name: the name of the helper function
+ *
+ * This function removes existing print handler for function @name.
+ *
+ * Returns 0 if the handler was removed successully, -1 otherwise.
+ */
+int pevent_unregister_print_function(struct pevent *pevent,
+				     pevent_func_handler func, char *name)
+{
+	struct pevent_function_handler *func_handle;
+
+	func_handle = find_func_handler(pevent, name);
+	if (func_handle && func_handle->func == func) {
+		remove_func_handler(pevent, name);
+		return 0;
+	}
+	return -1;
+}
+
 static struct event_format *pevent_search_event(struct pevent *pevent, int id,
 						const char *sys_name,
 						const char *event_name)

tools/lib/traceevent/event-parse.h

@@ -631,6 +631,8 @@ int pevent_register_print_function(struct pevent *pevent,
 				   pevent_func_handler func,
 				   enum pevent_func_arg_type ret_type,
 				   char *name, ...);
+int pevent_unregister_print_function(struct pevent *pevent,
+				     pevent_func_handler func, char *name);
 
 struct format_field *pevent_find_common_field(struct event_format *event, const char *name);
 struct format_field *pevent_find_field(struct event_format *event, const char *name);