6799583: LogManager shutdown hook may cause a memory leak

Reviewed-by: igor, swamyv

jdk/src/share/classes/java/util/logging/LogManager.java

@@ -215,6 +215,14 @@ public class LogManager {
     // This private class is used as a shutdown hook.
     // It does a "reset" to close all open handlers.
     private class Cleaner extends Thread {
+
+        private Cleaner() {
+            /* Set context class loader to null in order to avoid
+             * keeping a strong reference to an application classloader.
+             */
+            this.setContextClassLoader(null);
+        }
+
         public void run() {
             // This is to ensure the LogManager.<clinit> is completed
             // before synchronized block. Otherwise deadlocks are possible.

jdk/test/java/util/logging/ClassLoaderLeakTest.java

@@ -0,0 +1,190 @@
+/*
+ * Copyright 2009 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+/**
+ * @test
+ * @bug     6799583
+ *
+ * @summary Test verifes that LogManager shutdown hook does not cause
+ *          an application classloader leaks.
+ *
+ * @run     main/othervm ClassLoaderLeakTest
+ */
+
+import java.io.File;
+import java.lang.ref.WeakReference;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.concurrent.CountDownLatch;
+import java.util.logging.Logger;
+import java.util.logging.Logger;
+
+public class ClassLoaderLeakTest {
+
+    private static CountDownLatch doneSignal;
+    private static CountDownLatch launchSignal;
+    private static ThreadGroup appsThreadGroup;
+    private static Throwable launchFailure = null;
+
+    public static void main(String[] args) {
+        appsThreadGroup = new ThreadGroup("MyAppsThreadGroup");
+        doneSignal = new CountDownLatch(1);
+        launchSignal = new CountDownLatch(1);
+
+        Runnable launcher = new Runnable() {
+            public void run() {
+                try {
+                    ClassLoader cl =
+                        Thread.currentThread().getContextClassLoader();
+                    Class appMain = cl.loadClass("AppTest");
+                    Method launch =
+                        appMain.getDeclaredMethod("launch", doneSignal.getClass());
+
+                    Constructor c = appMain.getConstructor();
+
+                    Object o = c.newInstance();
+
+                    launch.invoke(o, doneSignal);
+
+                } catch (Throwable e) {
+                    launchFailure = e;
+                } finally {
+                    launchSignal.countDown();
+                }
+            }
+        };
+
+        /* prepare test  class loader */
+        URL pwd = null;
+        try {
+
+            pwd = new File(System.getProperty("test.classes",".")).toURL();
+        } catch (MalformedURLException e) {
+            throw new RuntimeException("Test failed.", e);
+        }
+        URL[] urls = new URL[] { pwd };
+
+         MyClassLoader appClassLoader = new MyClassLoader(urls, "test0");
+         WeakReference<MyClassLoader> ref =
+                 new WeakReference<MyClassLoader>(appClassLoader);
+
+
+         Thread appThread = new Thread(appsThreadGroup, launcher, "AppThread-0");
+         appThread.setContextClassLoader(appClassLoader);
+
+         appThread.start();
+         appClassLoader = null;
+         launcher = null;
+         appThread = null;
+
+         /* wait for laucnh completion */
+         try {
+             launchSignal.await();
+         } catch (InterruptedException e) {
+         }
+
+         /* check if launch failed */
+         if (launchFailure != null) {
+             throw new RuntimeException("Test failed.", launchFailure);
+         }
+
+         /* wait for test app excution completion */
+         try {
+             doneSignal.await();
+         } catch (InterruptedException e) {
+         }
+
+         /* give a chence to GC */
+         waitAndGC(5);
+
+         if (ref.get() != null) {
+             throw new RuntimeException("Test failed: classloader is still alive");
+         }
+
+         System.out.println("Test passed.");
+    }
+
+    private static class MyClassLoader extends URLClassLoader {
+
+        private static boolean verbose =
+            Boolean.getBoolean("verboseClassLoading");
+        private String uniqClassName;
+
+        public MyClassLoader(URL[] urls, String uniq) {
+            super(urls);
+
+            uniqClassName = uniq;
+        }
+
+        public Class loadClass(String name) throws ClassNotFoundException {
+            if (verbose) {
+                System.out.printf("%s: load class %s\n", uniqClassName, name);
+            }
+            if (uniqClassName.equals(name)) {
+                return Object.class;
+            }
+            return super.loadClass(name);
+        }
+
+        public String toString() {
+            return "MyClassLoader(" + uniqClassName + ")";
+        }
+    }
+
+    private static void waitAndGC(int sec) {
+        int cnt = sec;
+        System.out.print("Wait ");
+        while (cnt-- > 0) {
+            try {
+                Thread.sleep(1000);
+            } catch (InterruptedException e) {
+            }
+            // do GC every 3 seconds
+            if (cnt % 3 == 2) {
+                System.gc();
+                System.out.print("+");
+            } else {
+                System.out.print(".");
+            }
+            //checkErrors();
+        }
+        System.out.println("");
+    }
+}
+
+
+class AppTest {
+    public AppTest() {
+
+    }
+
+    public void launch(CountDownLatch done) {
+        Logger log = Logger.getLogger("app_test_logger");
+        log.fine("Test app is launched");
+
+        done.countDown();
+    }
+}