diff --git a/kern/conf/DUMBVM b/kern/conf/DUMBVM
index 7862c64..2a19bee 100644
--- a/kern/conf/DUMBVM
+++ b/kern/conf/DUMBVM
@@ -3,7 +3,9 @@
 
 include conf/conf.kern		# get definitions of available options
 
-debug				# Compile with debug info.
+debug				# Compile with debug info and -Og.
+#debugonly			# Compile with debug info only (no -Og).
+#options hangman 		# Deadlock detection. (off by default)
 
 #
 # Device drivers for hardware.
diff --git a/kern/conf/DUMBVM-OPT b/kern/conf/DUMBVM-OPT
index e878c35..115016f 100644
--- a/kern/conf/DUMBVM-OPT
+++ b/kern/conf/DUMBVM-OPT
@@ -7,6 +7,7 @@
 include conf/conf.kern		# get definitions of available options
 
 #debug				# Optimizing compile (no debug).
+#debugonly
 options noasserts		# Disable assertions.
 
 #
diff --git a/kern/conf/GENERIC b/kern/conf/GENERIC
index 13ff40e..a726c3c 100644
--- a/kern/conf/GENERIC
+++ b/kern/conf/GENERIC
@@ -5,6 +5,8 @@
 include conf/conf.kern		# get definitions of available options
 
 debug				# Compile with debug info.
+#debugonly			# Compile with debug info only (no -Og).
+#options hangman 		# Deadlock detection. (off by default)
 
 #
 # Device drivers for hardware.
diff --git a/kern/conf/GENERIC-OPT b/kern/conf/GENERIC-OPT
index f78637d..7bdc740 100644
--- a/kern/conf/GENERIC-OPT
+++ b/kern/conf/GENERIC-OPT
@@ -7,6 +7,7 @@
 include conf/conf.kern		# get definitions of available options
 
 #debug				# Optimizing compile (no debug).
+#debugonly
 options noasserts		# Disable assertions.
 
 #
diff --git a/kern/conf/conf.kern b/kern/conf/conf.kern
index 48ed457..ad58977 100644
--- a/kern/conf/conf.kern
+++ b/kern/conf/conf.kern
@@ -326,6 +326,9 @@ file      thread/synch.c
 file      thread/thread.c
 file      thread/threadlist.c
 
+defoption hangman
+optfile   hangman thread/hangman.c
+
 #
 # Process system
 #
diff --git a/kern/conf/config b/kern/conf/config
index 01bca35..f49c4ab 100755
--- a/kern/conf/config
+++ b/kern/conf/config
@@ -12,7 +12,8 @@
 # Recognized directives:
 #
 #    file <filename>          use source file
-#    debug                    turn on debug info
+#    debug                    turn on debug info and -Og
+#    debugonly                turn on debug info without -Og
 #    defoption <sym>          define an option
 #    optfile <sym> <file>     if option <sym> is enabled, use file <file>
 #    optofffile <sym> <file>  if option <sym> is disabled, use file <file>
@@ -97,6 +98,7 @@ echo "$CONFNAME" $CONFTMP | awk '
 	nfields["include"] = 2;
 	nfields["file"] = 2;
 	nfields["debug"] = 1;
+	nfields["debugonly"] = 1;
 	nfields["defoption"] = 2;
 	nfields["optfile"] = 3;
 	nfields["optofffile"] = 3;
@@ -776,6 +778,9 @@ echo -n ' files.mk'
 	# Default: optimize.
 	BEGIN { debugflags="-O2"; }
 	$1=="debug" {
+	    debugflags="-g -Og";
+	}
+	$1=="debugonly" {
 	    debugflags="-g";
 	}