[icedtea-web] RFC: Fix for PR852: Classloader not being flushed after close

[Deepak Bhole]

Hi,

This patch fixes PR852. I would like to put it in 1.2 in addition to
HEAD.

ChangeLog:
2012-01-26  Deepak Bhole <dbhole at redhat.com>

    PR852: Classloader not being flushed after last applet from a site is closed
    * netx/net/sourceforge/jnlp/runtime/JNLPClassLoader.java: Added variable
    to count usage for a given ClassLoader instance.
    (getInstance): Decrement use count for a loader after it is merged with
    another. Increment loader use count before returning.
    (incrementLoaderCount): New method. Increments loader use count.
    (decrementLoaderCount): New method. Decrements loader use count.
    * java/sun/applet/PluginAppletViewer.java (appletClose): Decrement loader
    use count when applet is closed.

Okay for both?

Cheers,
Deepak
-------------- next part --------------
diff -r 41f03d932cdf NEWS
--- a/NEWS	Mon Jan 09 18:45:31 2012 -0500
+++ b/NEWS	Thu Jan 26 13:15:59 2012 -0500
@@ -22,6 +22,7 @@
   - PR749: sun.applet.PluginStreamHandler#handleMessage(String) really slow
   - PR782: Support building against npapi-sdk as well
   - PR838: IcedTea plugin crashes with chrome browser when javascript is executed
+  - PR852: Classloader not being flushed after last applet from a site is closed
   - RH586194: Unable to connect to connect with Juniper VPN client
   - RH718693: MindTerm SSH Applet doesn't work
 Common
diff -r 41f03d932cdf netx/net/sourceforge/jnlp/runtime/JNLPClassLoader.java
--- a/netx/net/sourceforge/jnlp/runtime/JNLPClassLoader.java	Mon Jan 09 18:45:31 2012 -0500
+++ b/netx/net/sourceforge/jnlp/runtime/JNLPClassLoader.java	Thu Jan 26 13:15:59 2012 -0500
@@ -173,6 +173,11 @@
     private boolean foundMainJar= false;
 
     /**
+     * Variable to track how many times this loader is in use
+     */
+    private Integer useCount = 0;
+
+    /**
      * Create a new JNLPClassLoader from the specified file.
      *
      * @param file the JNLP file
@@ -321,6 +326,7 @@
                             throw new LaunchException(file, null, R("LSFatal"), R("LCClient"), R("LSignedAppJarUsingUnsignedJar"), R("LSignedAppJarUsingUnsignedJarInfo"));
 
                     loader.merge(extLoader);
+                    decrementLoaderCount(extLoader); // loader urls have been merged, ext loader is no longer used
                 }
 
                 // loader is now current + ext. But we also need to think of
@@ -347,7 +353,11 @@
 
         // loaders are mapped to a unique key. Only extensions and parent
         // share a key, so it is safe to always share based on it
-        urlToLoader.put(uniqueKey, loader);
+        
+        incrementLoaderCount(loader);
+        synchronized(urlToLoader) {
+            urlToLoader.put(uniqueKey, loader);
+        }
 
         return loader;
     }
@@ -1762,6 +1772,46 @@
         }
         return result;
     }
+    
+    /**
+     * Increments loader use count by 1
+     * 
+     * @throws SecurityException if caller is not trusted
+     */
+    public static void incrementLoaderCount(JNLPClassLoader loader) {
+        
+        // For use by trusted code only
+        if (System.getSecurityManager() != null)
+            System.getSecurityManager().checkPermission(new AllPermission());
+        
+        synchronized(loader.useCount) {
+            loader.useCount++;
+        }
+    }
+
+    /**
+     * Decrements loader use count by 1
+     * 
+     * If count reaches 0, loader is removed from list of available loaders
+     * 
+     * @throws SecurityException if caller is not trusted
+     */
+    public static void decrementLoaderCount(JNLPClassLoader loader) {
+
+        // For use by trusted code only
+        if (System.getSecurityManager() != null)
+            System.getSecurityManager().checkPermission(new AllPermission());
+
+        synchronized(loader.useCount) {
+            loader.useCount--;
+
+            if (loader.useCount <= 0) {
+                synchronized(urlToLoader) {
+                    urlToLoader.remove(loader.file.getUniqueKey());
+                }
+            }
+        }
+    }
 
     /*
      * Helper class to expose protected URLClassLoader methods.
diff -r 41f03d932cdf plugin/icedteanp/java/sun/applet/PluginAppletViewer.java
--- a/plugin/icedteanp/java/sun/applet/PluginAppletViewer.java	Mon Jan 09 18:45:31 2012 -0500
+++ b/plugin/icedteanp/java/sun/applet/PluginAppletViewer.java	Thu Jan 26 13:15:59 2012 -0500
@@ -1625,6 +1625,9 @@
 
                 appletShutdown(p);
                 appletPanels.removeElement(p);
+                
+                // Mark classloader unusable
+                JNLPClassLoader.decrementLoaderCount((JNLPClassLoader) cl);
 
                 try {
                     SwingUtilities.invokeAndWait(new Runnable() {