diff -r 17a34e111667 -r fb3d408c7a7e test/hotspot/jtreg/compiler/graalunit/com.oracle.mxtool.junit/com/oracle/mxtool/junit/TimingDecorator.java
--- a/test/hotspot/jtreg/compiler/graalunit/com.oracle.mxtool.junit/com/oracle/mxtool/junit/TimingDecorator.java	Wed Oct 09 20:12:46 2019 +0200
+++ b/test/hotspot/jtreg/compiler/graalunit/com.oracle.mxtool.junit/com/oracle/mxtool/junit/TimingDecorator.java	Wed Oct 09 10:59:45 2019 -0700
@@ -22,8 +22,8 @@
  */
 package com.oracle.mxtool.junit;
 
-import java.util.HashMap;
 import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
 import org.junit.runner.Description;
 
@@ -40,8 +40,8 @@
 
     TimingDecorator(MxRunListener l) {
         super(l);
-        this.classTimes = new HashMap<>();
-        this.testTimes = new HashMap<>();
+        this.classTimes = new ConcurrentHashMap<>();
+        this.testTimes = new ConcurrentHashMap<>();
     }
 
     @Override