diff --git a/moo/kernel/Process.moo b/moo/kernel/Process.moo
index deaaae7..7eb4390 100644
--- a/moo/kernel/Process.moo
+++ b/moo/kernel/Process.moo
@@ -60,12 +60,21 @@ class Semaphore(Object)
 	    ioHandle      := nil,
 	    ioMask        :=   0.
 
+	var (#get,#set) signalAction := nil.
 	var(#get,#set) _group := nil.
 
 	## ==================================================================
 
 	method(#primitive) signal.
-	method(#primitive) wait.
+	method(#primitive) _wait.
+
+	method wait
+	{
+		| k |
+		k := self _wait.
+		if (self.signalAction notNil) { self.signalAction value: self }.
+		^k
+	}
 
 	## ==================================================================
 
@@ -246,7 +255,15 @@ method(#class,#abstract) xxx. => method(#class) xxx { self subclassResponsibilit
 		}
 	}
 
-	method(#primitive) wait.
+	method(#primitive) _wait.
+
+	method wait
+	{
+		| r |
+		r := self wait.
+		if (r signalAction notNil) { r signalAction value: r }.
+		^r
+	}
 
 	method waitWithTimeout: seconds
 	{
@@ -267,7 +284,8 @@ method(#class,#abstract) xxx. => method(#class) xxx { self subclassResponsibilit
 
 		## if the internal semaphore has been signaled, 
 		## arrange to return nil to indicate timeout.
-		if (r == s) { r := nil }.
+		if (r == s) { r := nil }
+		elsif (r signalAction notNil) { r signalAction value: r }.
 
 		## nullify the membership
 		s _group: nil. 
diff --git a/moo/kernel/test-002.moo b/moo/kernel/test-002.moo
index 2e3349d..2b2ef8f 100644
--- a/moo/kernel/test-002.moo
+++ b/moo/kernel/test-002.moo
@@ -7,8 +7,6 @@
 
 class MyObject(Object)
 {
-## TODO: support import in extend??
-
 	var(#class) a := 100.
 
 	method(#class) proc1
@@ -36,7 +34,6 @@ class MyObject(Object)
 		sempq deleteAt: 50.
 		sempq deleteAt: 100.
 
-	
 		a := -100.
 		[sempq size > 0] whileTrue: [
 			| sem b |
@@ -85,6 +82,27 @@ class MyObject(Object)
 		^%( v, p ) ## v must be 2000, p must be 6000
 	}
 
+(*
+	method(#class) test_sem_sig
+	{
+		| s |
+		s := Semaphore new.
+		s signalAction: [:sem | 'SIGNAL ACTION............' dump. ].
+		[ Processor sleepFor: 1. s signal ] fork.
+		s wait.
+	}
+
+	method(#class) test_semgrp
+	{
+		| sg |
+		sg := SemaphoreGroup new.
+		sg add: s1 withAction: [].
+		sg add: s2 withAction: [].
+		sg add: s3 withAction: [].
+		sg wait.
+	}
+*)
+
 	method(#class) main
 	{
 		| tc limit |
@@ -94,7 +112,9 @@ class MyObject(Object)
 			[ self proc1 == 100 ], 
 			[ Processor sleepFor: 2.  self proc1 == 200 ],
 			[ self test_semaphore_heap == true ],
-			[ self test_mutex = #(2000 6000) ]
+			[ self test_mutex = #(2000 6000) ],
+			####[ self test_sem_sig ],
+			[ a == 300 ]
 		).
 
 		limit := tc size.
@@ -105,5 +125,19 @@ class MyObject(Object)
 			System log(System.Log.INFO, idx asString, (if (tb value) { ' PASS' } else { ' FAIL' }), S'\n').
 		].
 	}
-
 }
+
+
+(*
+s1 := TcpSocket new.
+
+s1 onEvent: #connected do: [
+	s1 write: C'GET / HTTP/1.0\n\r'.
+] 
+s1 onEvent: #written do: [
+]
+
+s1 on: #read do:
+s1 connectTo: '1.2.3.4:45'.
+
+*)
diff --git a/moo/kernel/test-003.moo b/moo/kernel/test-003.moo
index db713a4..28fb155 100644
--- a/moo/kernel/test-003.moo
+++ b/moo/kernel/test-003.moo
@@ -8,36 +8,7 @@
 ## MAIN
 #################################################################
 
-## TODO: use #define to define a class or use #class to define a class.
-##       use #extend to extend a class
-##       using #class for both feels confusing.
-
-extend Apex
-{
-
-}
-
-extend SmallInteger
-{
-	method getTrue: anInteger
-	{
-		^anInteger + 9999.
-	}
-
-	method inc
-	{
-		^self + 1.
-	}
-}
-
-class TestObject(Object)
-{
-	var(#class) Q, R.
-	var(#classinst) a1, a2.
-}
-
-
-class MyObject(TestObject)
+class MyObject(Object)
 {
 	var(#classinst) t1, t2.
 
diff --git a/moo/lib/exec.c b/moo/lib/exec.c
index adf4dde..72507e2 100644
--- a/moo/lib/exec.c
+++ b/moo/lib/exec.c
@@ -4243,8 +4243,8 @@ static pf_t pftab[] =
 	{ "Process__terminate",                    { pf_process_terminate,                    0, 0 } },
 
 	{ "Semaphore_signal",                      { pf_semaphore_signal,                     0, 0 } },
-	{ "Semaphore_wait",                        { pf_semaphore_wait,                       0, 0 } },
-	{ "SemaphoreGroup_wait",                   { pf_semaphore_group_wait,                 0, 0 } },
+	{ "Semaphore__wait",                       { pf_semaphore_wait,                       0, 0 } },
+	{ "SemaphoreGroup__wait",                  { pf_semaphore_group_wait,                 0, 0 } },
 
 	{ "SmallInteger_asCharacter",              { pf_smooi_as_character,                   0, 0 } },
 	{ "SmallInteger_asError",                  { pf_smooi_as_error,                       0, 0 } },
diff --git a/moo/lib/moo.h b/moo/lib/moo.h
index 2ca74bd..330c885 100644
--- a/moo/lib/moo.h
+++ b/moo/lib/moo.h
@@ -748,7 +748,7 @@ struct moo_context_t
 typedef struct moo_process_t moo_process_t;
 typedef struct moo_process_t* moo_oop_process_t;
 
-#define MOO_SEMAPHORE_NAMED_INSTVARS 10
+#define MOO_SEMAPHORE_NAMED_INSTVARS 11
 typedef struct moo_semaphore_t moo_semaphore_t;
 typedef struct moo_semaphore_t* moo_oop_semaphore_t;
 
@@ -814,6 +814,7 @@ struct moo_semaphore_t
 	moo_oop_t io_handle;
 	moo_oop_t io_mask; /* SmallInteger */
 
+	moo_oop_t signal_action;
 	moo_oop_semaphore_group_t group; /* nil or belonging semaphore group */
 };