Resolve multiple-applet deadlock issue in JNLPClassLoader

New lock used for synchronizing JNLPClassLoader#loadClass(String) to avoid
deadlock condition when multiple applets are being loaded simultaneously.
Regression test included.

    * netx/net/sourceforge/jnlp/runtime/JNLPClassLoader.java: (loadClassLock)
    private member for locking of loadClass method. (loadClass) synchronizes
    using new lock rather than instance intrinsic lock to avoid RH976833
    deadlock
    * tests/reproducers/custom/JNLPClassLoaderDeadlock/testcases/JNLPClassLoaderDeadlockTest.java:
    new test for multiple applet deadlock condition
    * tests/reproducers/custom/JNLPClassLoaderDeadlock/resources/JNLPClassLoaderDeadlock.html:
    same
    * tests/reproducers/custom/JNLPClassLoaderDeadlock/srcs/JNLPClassLoaderDeadlock_1.java:
    same
    * tests/reproducers/custom/JNLPClassLoaderDeadlock/srcs/JNLPClassLoaderDeadlock_2.java:
    same
    * tests/reproducers/custom/JNLPClassLoaderDeadlock/srcs/Makefile: same

1 files changed, 24 insertions, 0 deletions

diff --git a/tests/reproducers/custom/JNLPClassLoaderDeadlock/srcs/JNLPClassLoaderDeadlock_1.java b/tests/reproducers/custom/JNLPClassLoaderDeadlock/srcs/JNLPClassLoaderDeadlock_1.java
new file mode 100644
index 0000000..616e5d3
--- /dev/null
+++ b/tests/reproducers/custom/JNLPClassLoaderDeadlock/srcs/JNLPClassLoaderDeadlock_1.java
@@ -0,0 +1,24 @@
+import java.applet.Applet;
+import java.awt.*;
+
+public class JNLPClassLoaderDeadlock_1 extends Applet {
+
+    @Override
+    public void init() {
+        System.out.println("JNLPClassLoaderDeadlock_1 applet initialized");
+        final String version = System.getProperty("java.version") + " (" + System.getProperty("java.vm.version") + ")";
+        final String vendor = System.getProperty("java.vendor");
+        final TextField tf = new TextField(40);
+        tf.setText(version + " -- " + vendor);
+        tf.setEditable(false);
+        tf.setBackground(Color.white);
+        setBackground(Color.white);
+        add(tf);
+        System.out.println("JNLPClassLoaderDeadlock_1 applet finished");
+        System.out.println("*** APPLET FINISHED ***");
+    }
+
+    public static void main(String[] args) {
+        new JNLPClassLoaderDeadlock_1().init();
+    }
+}