--- old/test/lib/jdk/test/lib/containers/cgroup/MetricsTesterCgroupV1.java	2020-01-09 20:39:21.578148107 +0100
+++ new/test/lib/jdk/test/lib/containers/cgroup/MetricsTesterCgroupV1.java	2020-01-09 20:39:21.439147961 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -126,6 +126,9 @@
         startUserVal = metrics.getCpuUserUsage();
         startUsage = metrics.getCpuUsage();
         startPerCpu = metrics.getPerCpuUsage();
+        if (startPerCpu == null) {
+            startPerCpu = new long[0];
+        }
 
         try {
             Stream<String> lines = Files.lines(Paths.get("/proc/self/mountinfo"));
@@ -149,13 +152,13 @@
             return new Scanner(new File(fname)).useDelimiter("\\Z").next();
         } catch (FileNotFoundException e) {
             System.err.println("Unable to open : " + fname);
-            return "";
+            return null;
         }
     }
 
     private static long getLongValueFromFile(Controller subSystem, String fileName) {
         String data = getFileContents(subSystem, fileName);
-        return data.isEmpty() ? 0L : convertStringToLong(data);
+        return (data == null || data.isEmpty()) ? 0L : convertStringToLong(data);
     }
 
     private static long convertStringToLong(String strval) {
@@ -332,11 +335,17 @@
             warn(Controller.CPUACCT, "cpuacct.usage", oldVal, newVal);
         }
 
-        Long[] newVals = Stream.of(getFileContents(Controller.CPUACCT, "cpuacct.usage_percpu")
+        String newValsStr = getFileContents(Controller.CPUACCT, "cpuacct.usage_percpu");
+        Long[] newVals = new Long[0];
+        if (newValsStr != null) {
+            newVals = Stream.of(newValsStr
                 .split("\\s+"))
                 .map(Long::parseLong)
                 .toArray(Long[]::new);
-        Long[] oldVals = LongStream.of(metrics.getPerCpuUsage()).boxed().toArray(Long[]::new);
+        }
+        long[] oldValsPrim = metrics.getPerCpuUsage();
+        Long[] oldVals = LongStream.of(oldValsPrim == null ? new long[0] : oldValsPrim)
+                                    .boxed().toArray(Long[]::new);
         for (int i = 0; i < oldVals.length; i++) {
             if (!CgroupMetricsTester.compareWithErrorMargin(oldVals[i], newVals[i])) {
                 warn(Controller.CPUACCT, "cpuacct.usage_percpu", oldVals[i], newVals[i]);
@@ -488,6 +497,9 @@
         long newUserVal = metrics.getCpuUserUsage();
         long newUsage = metrics.getCpuUsage();
         long[] newPerCpu = metrics.getPerCpuUsage();
+        if (newPerCpu == null) {
+            newPerCpu = new long[0];
+        }
 
         // system/user CPU usage counters may be slowly increasing.
         // allow for equal values for a pass