Docs: callback comments

source/blender/blenkernel/BKE_node.h

@@ -172,7 +172,10 @@ typedef struct bNodeType {
 	/* Additional drawing on backdrop */
 	void (*draw_backdrop)(struct SpaceNode *snode, struct ImBuf *backdrop, struct bNode *node, int x, int y);
 
-	/// Optional custom label function for the node header.
+	/**
+	 * Optional custom label function for the node header.
+	 * \note Used as a fallback when #bNode.label isn't set.
+	 */
 	void (*labelfunc)(struct bNodeTree *ntree, struct bNode *node, char *label, int maxlen);
 	/// Optional custom resize handle polling.
 	int (*resize_area_func)(struct bNode *node, int x, int y);

source/blender/makesdna/DNA_node_types.h

@@ -384,6 +384,7 @@ typedef struct bNodeTree {
 	
 	/* callbacks */
 	void (*progress)(void *, float progress);
+	/** \warning may be called by different threads */
 	void (*stats_draw)(void *, const char *str);
 	int (*test_break)(void *);
 	void (*update_draw)(void *);