rhbz#1036877: Join Java AsynchronousFinalizer thread well before exit

AsynchronousFinalizer was originally added as
870a4401c05beec3d31c1f6055a64591edd0a9d9 "INTEGRATION: CWS mtg1: #i57753# Avoid
long-running finalize methods" referring to
<https://issues.apache.org/ooo/show_bug.cgi?id=57753> " Fix JNI-UNO bridge so
that the JVM doesn't run out of memory when a destructor locks the SolarMutex."

It is unclear to me how relevant "If JVMs are getting more mature and should no
longer have problems with long-running finalize methods, this class could be
removed again" really is in practice.  After all, advice on hotspot-gc-devel is
to avoid finalize() if possible
(<http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2014-June/010215.html>
"Re: History of finalizer execution and gc progress?").  So stick with this
approach of home-grown draining for now (where a home-grown approach using
PhantomReferencens would need a dedicated draining thread, too, so would not
have much benefit over the existing code in practice).

Timely termination of AsynchronousFinalizer threads is achieved by using a
dedicated thread per bridge and joining it in the remote bridge's dispose()
resp. the JNI environment's new java_env_dispose.

Change-Id: Idcef2dbf361a1de22f60db73828f59e85711aea7

3 files changed, 60 insertions, 38 deletions

diff --git a/jurt/com/sun/star/lib/uno/bridges/java_remote/ProxyFactory.java b/jurt/com/sun/star/lib/uno/bridges/java_remote/ProxyFactory.java
index edcceca44757..e249062fa07e 100644
--- a/jurt/com/sun/star/lib/uno/bridges/java_remote/ProxyFactory.java
+++ b/jurt/com/sun/star/lib/uno/bridges/java_remote/ProxyFactory.java
@@ -57,6 +57,10 @@ final class ProxyFactory {
         }
     }
 
+    public void dispose() throws InterruptedException {
+        asynchronousFinalizer.drain();
+    }
+
     public static XBridge getBridge(Object obj) {
         if (Proxy.isProxyClass(obj.getClass())) {
             InvocationHandler h = Proxy.getInvocationHandler(obj);
@@ -126,13 +130,10 @@ final class ProxyFactory {
 
         @Override
         protected void finalize() {
-            AsynchronousFinalizer.add(new AsynchronousFinalizer.Job() {
+            decrementDebugCount();
+            asynchronousFinalizer.add(new AsynchronousFinalizer.Job() {
                     public void run() throws Throwable {
-                        try {
-                            request("release", null);
-                        } finally {
-                            decrementDebugCount();
-                        }
+                        request("release", null);
                     }
                 });
         }
@@ -187,4 +188,6 @@ final class ProxyFactory {
 
     private final RequestHandler requestHandler;
     private final XBridge bridge;
+    private final AsynchronousFinalizer asynchronousFinalizer =
+        new AsynchronousFinalizer();
 }
diff --git a/jurt/com/sun/star/lib/uno/bridges/java_remote/java_remote_bridge.java b/jurt/com/sun/star/lib/uno/bridges/java_remote/java_remote_bridge.java
index 722f825e6ba5..48784283a99a 100644
--- a/jurt/com/sun/star/lib/uno/bridges/java_remote/java_remote_bridge.java
+++ b/jurt/com/sun/star/lib/uno/bridges/java_remote/java_remote_bridge.java
@@ -499,7 +499,12 @@ public class java_remote_bridge
         try {
             _messageDispatcher.terminate();
 
-            _xConnection.close();
+            try {
+                _xConnection.close();
+            } catch (com.sun.star.io.IOException e) {
+                System.err.println(
+                    getClass().getName() + ".dispose - IOException:" + e);
+            }
 
             if (Thread.currentThread() != _messageDispatcher
                 && _messageDispatcher.isAlive())
@@ -519,6 +524,8 @@ public class java_remote_bridge
             // assert _java_environment instanceof java_environment;
             ((java_environment) _java_environment).revokeAllProxies();
 
+            proxyFactory.dispose();
+
             if (DEBUG) {
                 if (_life_count != 0) {
                     System.err.println(getClass().getName()
@@ -535,9 +542,6 @@ public class java_remote_bridge
         } catch (InterruptedException e) {
             System.err.println(getClass().getName()
                                + ".dispose - InterruptedException:" + e);
-        } catch (com.sun.star.io.IOException e) {
-            System.err.println(getClass().getName() + ".dispose - IOException:"
-                               + e);
         }
     }
 
diff --git a/jurt/com/sun/star/lib/util/AsynchronousFinalizer.java b/jurt/com/sun/star/lib/util/AsynchronousFinalizer.java
index 4dcd69a97e1f..71743b25241b 100644
--- a/jurt/com/sun/star/lib/util/AsynchronousFinalizer.java
+++ b/jurt/com/sun/star/lib/util/AsynchronousFinalizer.java
@@ -35,6 +35,37 @@ import java.util.LinkedList;
  * long-running finalize methods, this class could be removed again.</p>
  */
 public final class AsynchronousFinalizer {
+    public AsynchronousFinalizer() {
+        thread = new Thread("AsynchronousFinalizer") {
+                @Override
+                public void run() {
+                    for (;;) {
+                        Job j;
+                        synchronized (queue) {
+                            for (;;) {
+                                if (done) {
+                                    return;
+                                }
+                                if (!queue.isEmpty()) {
+                                    break;
+                                }
+                                try {
+                                    queue.wait();
+                                } catch (InterruptedException e) {
+                                    return;
+                                }
+                            }
+                            j = queue.remove(0);
+                        }
+                        try {
+                            j.run();
+                        } catch (Throwable e) {}
+                    }
+                }
+            };
+        thread.start();
+    }
+
     /**
      * Add a job to be executed asynchronously.
      *
@@ -43,7 +74,7 @@ public final class AsynchronousFinalizer {
      *
      * @param job represents the body of some finalize method; must not be null.
      */
-    public static void add(Job job) {
+    public void add(Job job) {
         synchronized (queue) {
             boolean first = queue.isEmpty();
             queue.add(job);
@@ -53,6 +84,14 @@ public final class AsynchronousFinalizer {
         }
     }
 
+    public void drain() throws InterruptedException {
+        synchronized (queue) {
+            done = true;
+            queue.notify();
+        }
+        thread.join();
+    }
+
     /**
      * An interface to represent bodies of finalize methods.
      *
@@ -65,31 +104,7 @@ public final class AsynchronousFinalizer {
         void run() throws Throwable;
     }
 
-    private static final LinkedList<Job> queue = new LinkedList<Job>();
-
-    static {
-        Thread t = new Thread("AsynchronousFinalizer") {
-                @Override
-                public void run() {
-                    for (;;) {
-                        Job j;
-                        synchronized (queue) {
-                            while (queue.isEmpty()) {
-                                try {
-                                    queue.wait();
-                                } catch (InterruptedException e) {}
-                            }
-                            j = queue.remove(0);
-                        }
-                        try {
-                            j.run();
-                        } catch (Throwable e) {}
-                    }
-                }
-            };
-        t.setDaemon(true);
-        t.start();
-    }
-
-    private AsynchronousFinalizer() {}
+    private final LinkedList<Job> queue = new LinkedList<Job>();
+    private final Thread thread;
+    private boolean done = false;
 }