--- a/emacs.rst	Fri Sep 10 16:14:36 2010 +0300
+++ b/emacs.rst	Mon Sep 13 12:29:03 2010 +0300
@@ -45,6 +45,10 @@
 know about line numbers and files - it just knows an error happened, and
 that's it.
 
+** How debug long running command?
+
+M-x debug-on-quit RET' and then just hit `C-g' next time it gets 'stuck' somewhere.
+
 *** Check if bug in ini file.
 
 First run Emacs without loading anything: