6832540: IllegalArgumentException in ClassLoader.definePackage when classes are loaded in parallel

Summary: Modified to handle race condition for parallel-capable classloaders by re-trying/re-verifying package
Reviewed-by: alanb

src/share/classes/java/net/URLClassLoader.java

@@ -306,18 +306,13 @@ public class URLClassLoader extends SecureClassLoader implements Closeable {
     }
 
     /*
-     * Defines a Class using the class bytes obtained from the specified
-     * Resource. The resulting Class must be resolved before it can be
-     * used.
+     * Retrieve the package using the specified package name.
+     * If non-null, verify the package using the specified code
+     * source and manifest.
      */
-    private Class defineClass(String name, Resource res) throws IOException {
-        int i = name.lastIndexOf('.');
-        URL url = res.getCodeSourceURL();
-        if (i != -1) {
-            String pkgname = name.substring(0, i);
-            // Check if package already loaded.
+    private Package getAndVerifyPackage(String pkgname,
+                                        Manifest man, URL url) {
         Package pkg = getPackage(pkgname);
-            Manifest man = res.getManifest();
         if (pkg != null) {
             // Package found, so check package sealing.
             if (pkg.isSealed()) {
@@ -326,7 +321,6 @@ public class URLClassLoader extends SecureClassLoader implements Closeable {
                     throw new SecurityException(
                         "sealing violation: package " + pkgname + " is sealed");
                 }
-
             } else {
                 // Make sure we are not attempting to seal the package
                 // at this code source URL.
@@ -336,12 +330,38 @@ public class URLClassLoader extends SecureClassLoader implements Closeable {
                         ": already loaded");
                 }
             }
-            } else {
+        }
+        return pkg;
+    }
+
+    /*
+     * Defines a Class using the class bytes obtained from the specified
+     * Resource. The resulting Class must be resolved before it can be
+     * used.
+     */
+    private Class defineClass(String name, Resource res) throws IOException {
+        int i = name.lastIndexOf('.');
+        URL url = res.getCodeSourceURL();
+        if (i != -1) {
+            String pkgname = name.substring(0, i);
+            // Check if package already loaded.
+            Manifest man = res.getManifest();
+            if (getAndVerifyPackage(pkgname, man, url) == null) {
+                try {
                     if (man != null) {
                         definePackage(pkgname, man, url);
                     } else {
                         definePackage(pkgname, null, null, null, null, null, null, null);
                     }
+                } catch (IllegalArgumentException iae) {
+                    // parallel-capable class loaders: re-verify in case of a
+                    // race condition
+                    if (getAndVerifyPackage(pkgname, man, url) == null) {
+                        // Should never happen
+                        throw new AssertionError("Cannot find package " +
+                                                 pkgname);
+                    }
+                }
             }
         }
         // Now read the class bytes and define the class