6989440: tomcat test from dacapo benchmark fails with ConcurrentModificationException

Reviewed-by: okutsu
Contributed-by: y.umaoka@gmail.com

src/share/classes/sun/util/LocaleServiceProviderPool.java

@@ -84,7 +84,7 @@ public final class LocaleServiceProviderPool {
      * static.  This could be non-static later, so that they could have
      * different sets for each locale sensitive services.
      */
-    private static List<Locale> availableJRELocales = null;
+    private static volatile List<Locale> availableJRELocales = null;
 
     /**
      * Provider locales for this locale sensitive service.
@@ -252,12 +252,16 @@ public final class LocaleServiceProviderPool {
      *
      * @return list of the available JRE locales
      */
-    private synchronized List<Locale> getJRELocales() {
+    private List<Locale> getJRELocales() {
         if (availableJRELocales == null) {
-            Locale[] allLocales = LocaleData.getAvailableLocales();
-            availableJRELocales = new ArrayList<Locale>(allLocales.length);
-            for (Locale locale : allLocales) {
-                availableJRELocales.add(getLookupLocale(locale));
+            synchronized (LocaleServiceProviderPool.class) {
+                if (availableJRELocales == null) {
+                    Locale[] allLocales = LocaleData.getAvailableLocales();
+                    availableJRELocales = new ArrayList<Locale>(allLocales.length);
+                    for (Locale locale : allLocales) {
+                        availableJRELocales.add(getLookupLocale(locale));
+                    }
+                }
             }
         }
         return availableJRELocales;

test/java/util/Locale/Bug6989440.java

+/*
+ * Copyright (c) 2010, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 6989440
+ * @summary Verify ConcurrentModificationException is not thrown with multiple
+ *     thread accesses.
+ * @compile -XDignore.symbol.file=true Bug6989440.java
+ * @run main Bug6989440
+ */
+import java.text.spi.DateFormatProvider;
+import java.util.spi.LocaleNameProvider;
+import java.util.spi.LocaleServiceProvider;
+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 class TestThread extends Thread {
+        private Class<? extends LocaleServiceProvider> cls;
+
+        public TestThread(Class<? extends LocaleServiceProvider> providerClass) {
+            cls = providerClass;
+        }
+
+        public void run() {
+            LocaleServiceProviderPool pool = LocaleServiceProviderPool.getPool(cls);
+            pool.getAvailableLocales();
+        }
+    }
+}