--- a/OperationQueue.st	Wed May 08 14:41:45 2019 +0200
+++ b/OperationQueue.st	Thu May 16 14:54:03 2019 +0200
@@ -1,3 +1,5 @@
+"{ Encoding: utf8 }"
+
 "
  COPYRIGHT (c) 2000 by eXept Software AG
               All Rights Reserved
@@ -160,13 +162,15 @@
     ].
     opInQ operationResult:rslt.
 
-    opInQ operationPerformedSema signalForAll.
+    opInQ operationPerformedSema signal.
 
     [
         queue isEmpty ifTrue:[
             self stopConsumerProcess
         ]
     ] valueUninterruptably
+
+    "Modified: / 16-05-2019 / 14:52:55 / Stefan Vogel"
 !
 
 startConsumerProcess
@@ -261,7 +265,8 @@
             "/ if not, create a new one and enqueue
             myOpInQ isNil ifTrue:[
                 myOpInQ := OperationInQueue new.
-                myOpInQ operationPerformedSema:(Semaphore new).
+                "/ use an EventSemaphore to protect against races between signal and wait
+                myOpInQ operationPerformedSema:(EventSemaphore new).
                 myOpInQ operation:anotherOperation.
                 [
                     queue nextPut:myOpInQ.
@@ -290,6 +295,7 @@
     ^ myOpInQ operationResult
 
     "Modified (format): / 22-05-2017 / 12:08:05 / mawalch"
+    "Modified: / 16-05-2019 / 14:51:57 / Stefan Vogel"
 ! !
 
 !OperationQueue methodsFor:'queries'!