[rfc][icedtea-web] More shutdown fixes -- Interrupt applet threads after shutdown, fix NPE

[Adam Domurad]

ChangeLog:

2013-02-13  Adam Domurad  <adomurad at redhat.com>

     Interrupt applet threads that did not finish on normal shutdown. 
Prevent
     NPE that can occur from sun.applet.AppletPanel.
     * netx/net/sourceforge/jnlp/NetxPanel.java
     (destroyApplet): interrupt applet threads
     * netx/net/sourceforge/jnlp/runtime/JNLPClassLoader.java
     (getPermissions): avoid potential NPE if code source location is
     missing



1.) The NPE:

I had previously posted a patch for an NPE that only occurred during 
shutdown, but I had not looked into it too deeply.

Now I see the cause is:

sun.applet.AppletPanel.java:

     private AccessControlContext getAccessControlContext(final URL 
codebase) {

         PermissionCollection perms = (PermissionCollection)
             AccessController.doPrivileged(new PrivilegedAction() {
                     public Object run() {
                         Policy p = java.security.Policy.getPolicy();
                         if (p != null) {
 >>>                         return p.getPermissions(new 
CodeSource(null,         <<<
(java.security.cert.Certificate[]) null));
                         } else {
                             return null;
                         }
                     }
                 });

This occurs in PluginAppletViewer#appletShutdown, when 
p.sendEvent(AppletPanel.APPLET_QUIT); is used. A null source location 
must thus be supported as such:

diff --git a/netx/net/sourceforge/jnlp/runtime/JNLPClassLoader.java 
b/netx/net/sourceforge/jnlp/runtime/JNLPClassLoader.java
--- a/netx/net/sourceforge/jnlp/runtime/JNLPClassLoader.java
+++ b/netx/net/sourceforge/jnlp/runtime/JNLPClassLoader.java
@@ -1144,7 +1144,7 @@ public class JNLPClassLoader extends URL
              }

              // Class from host X should be allowed to connect to host X
-            if (cs.getLocation().getHost().length() > 0)
+            if (cs.getLocation() != null && 
cs.getLocation().getHost().length() > 0)
                  result.add(new 
SocketPermission(cs.getLocation().getHost(),
                          "connect, accept"));


2.) Threads seem to sometimes leak when icedtea-web is refreshed. In 
fact, this is the cause of an out-of-memory-error I was seeing a while 
back. ITW had ~ 1000 threads kicking around because they were not 
properly disposed of.

This interrupts all remaining threads, after joining with the applets 
main thread. This will be enough to shut down most threads (and fixed 
the issue I was seeing with horaoficial). It's hard to think of anything 
further that can be done, save for lots of interrupts in quick 
succession. Causing thread death was considered, but it can cause 
stability problems, I think.


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