diff --git a/src/share/classes/sun/util/LocaleServiceProviderPool.java b/src/share/classes/sun/util/LocaleServiceProviderPool.java
index 5b6c04e883bc1b389eda7cd98619365e679a4158..c45100d75083e601102ae8940e4bd8806c2a0829 100644
--- a/src/share/classes/sun/util/LocaleServiceProviderPool.java
+++ b/src/share/classes/sun/util/LocaleServiceProviderPool.java
@@ -40,6 +40,7 @@ import java.util.ResourceBundle.Control;
 import java.util.ServiceLoader;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
 import java.util.spi.LocaleServiceProvider;
 
 import sun.util.logging.PlatformLogger;
@@ -57,8 +58,8 @@ public final class LocaleServiceProviderPool {
      * A Map that holds singleton instances of this class.  Each instance holds a
      * set of provider implementations of a particular locale sensitive service.
      */
-    private static Map<Class, LocaleServiceProviderPool> poolOfPools =
-        new ConcurrentHashMap<Class, LocaleServiceProviderPool>();
+    private static ConcurrentMap<Class, LocaleServiceProviderPool> poolOfPools =
+        new ConcurrentHashMap<>();
 
     /**
      * A Set containing locale service providers that implement the
@@ -109,7 +110,7 @@ public final class LocaleServiceProviderPool {
         if (pool == null) {
             LocaleServiceProviderPool newPool =
                 new LocaleServiceProviderPool(providerClass);
-            pool = poolOfPools.put(providerClass, newPool);
+            pool = poolOfPools.putIfAbsent(providerClass, newPool);
             if (pool == null) {
                 pool = newPool;
             }
@@ -257,10 +258,11 @@ public final class LocaleServiceProviderPool {
             synchronized (LocaleServiceProviderPool.class) {
                 if (availableJRELocales == null) {
                     Locale[] allLocales = LocaleData.getAvailableLocales();
-                    availableJRELocales = new ArrayList<Locale>(allLocales.length);
+                    List<Locale> tmpList = new ArrayList<>(allLocales.length);
                     for (Locale locale : allLocales) {
-                        availableJRELocales.add(getLookupLocale(locale));
+                        tmpList.add(getLookupLocale(locale));
                     }
+                    availableJRELocales = tmpList;
                 }
             }
         }
diff --git a/test/java/util/Locale/Bug6989440.java b/test/java/util/Locale/Bug6989440.java
index ebf62f988070a499f6813914a8cf10edfccefd81..d524d05b11dfb020db55e0efcc7f39bb6e5ece54 100644
--- a/test/java/util/Locale/Bug6989440.java
+++ b/test/java/util/Locale/Bug6989440.java
@@ -37,26 +37,49 @@ import java.util.spi.TimeZoneNameProvider;
 import sun.util.LocaleServiceProviderPool;
 
 public class Bug6989440 {
-    public static void main(String[] args) {
-        TestThread t1 = new TestThread(LocaleNameProvider.class);
-        TestThread t2 = new TestThread(TimeZoneNameProvider.class);
-        TestThread t3 = new TestThread(DateFormatProvider.class);
-
-        t1.start();
-        t2.start();
-        t3.start();
+    static volatile boolean failed;  // false
+    static final int THREADS = 50;
+
+    public static void main(String[] args) throws Exception {
+        Thread[] threads = new Thread[THREADS];
+        for (int i=0; i<threads.length; i++)
+            threads[i] = new TestThread();
+        for (int i=0; i<threads.length; i++)
+            threads[i].start();
+        for (int i=0; i<threads.length; i++)
+            threads[i].join();
+
+        if (failed)
+            throw new RuntimeException("Failed: check output");
     }
 
     static class TestThread extends Thread {
         private Class<? extends LocaleServiceProvider> cls;
+        private static int count;
 
         public TestThread(Class<? extends LocaleServiceProvider> providerClass) {
             cls = providerClass;
         }
 
+        public TestThread() {
+            int which = count++ % 3;
+            switch (which) {
+                case 0 : cls = LocaleNameProvider.class; break;
+                case 1 : cls = TimeZoneNameProvider.class; break;
+                case 2 : cls = DateFormatProvider.class; break;
+                default : throw new AssertionError("Should not reach here");
+            }
+        }
+
         public void run() {
-            LocaleServiceProviderPool pool = LocaleServiceProviderPool.getPool(cls);
-            pool.getAvailableLocales();
+            try {
+                LocaleServiceProviderPool pool = LocaleServiceProviderPool.getPool(cls);
+                pool.getAvailableLocales();
+            } catch (Exception e) {
+                System.out.println(e);
+                e.printStackTrace();
+                failed = true;
+            }
         }
     }
 }