8029443: 'assert(klass->is_loader_alive(_is_alive)) failed: must be alive' during VM_CollectForMetadataAllocation

Added missing metadata relocation to 'loadConP_no_oop_cheap' on Sparc if the pointer is referring to a Klass. Added jtreg test.

Reviewed-by: kvn, roland

hotspot/src/cpu/sparc/vm/sparc.ad

@@ -6184,7 +6184,11 @@ instruct loadConP_no_oop_cheap(iRegP dst, immP_no_oop_cheap con) %{
   ins_cost(DEFAULT_COST * 3/2);
   format %{ "SET    $con,$dst\t! non-oop ptr" %}
   ins_encode %{
+    if (_opnds[1]->constant_reloc() == relocInfo::metadata_type) {
+      __ set_metadata_constant((Metadata*)$con$$constant, $dst$$Register);
+    } else {
       __ set($con$$constant, $dst$$Register);
+    }
   %}
   ins_pipe(loadConP);
 %}

hotspot/test/compiler/classUnloading/methodUnloading/TestMethodUnloading.java

@@ -0,0 +1,145 @@
+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import sun.hotspot.WhiteBox;
+
+import java.lang.reflect.Method;
+import java.net.URL;
+import java.net.URLClassLoader;
+
+/*
+ * @test MethodUnloadingTest
+ * @bug 8029443
+ * @summary "Tests the unloading of methods to to class unloading"
+ * @library /testlibrary /testlibrary/whitebox
+ * @build TestMethodUnloading
+ * @build WorkerClass
+ * @run main ClassFileInstaller sun.hotspot.WhiteBox
+ * @run main/othervm -Xbootclasspath/a:. -XX:+IgnoreUnrecognizedVMOptions -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -XX:-BackgroundCompilation -XX:-UseCompressedOops -XX:+UseParallelGC -XX:CompileOnly=TestMethodUnloading::doWork TestMethodUnloading
+ */
+public class TestMethodUnloading {
+    private static final String workerClassName = "WorkerClass";
+    private static int work = -1;
+
+    private static final WhiteBox WHITE_BOX = WhiteBox.getWhiteBox();
+    private static int COMP_LEVEL_SIMPLE = 1;
+    private static int COMP_LEVEL_FULL_OPTIMIZATION = 4;
+
+    /**
+     * Does some work by either using the workerClass or locally producing values.
+     * @param workerClass Class performing some work (will be unloaded)
+     * @param useWorker If true the workerClass is used
+     */
+    static private void doWork(Class<?> workerClass, boolean useWorker) throws InstantiationException, IllegalAccessException {
+        if (useWorker) {
+            // Create a new instance
+            Object worker = workerClass.newInstance();
+            // We would like to call a method of WorkerClass here but we cannot cast to WorkerClass
+            // because the class was loaded by a different class loader. One solution would be to use
+            // reflection but since we want C2 to implement the call as an optimized IC we call
+            // Object::hashCode() here which actually calls WorkerClass::hashCode().
+            // C2 will then implement this call as an optimized IC that points to a to-interpreter stub
+            // referencing the Method* for WorkerClass::hashCode().
+            work = worker.hashCode();
+            if (work != 42) {
+                new RuntimeException("Work not done");
+            }
+        } else {
+            // Do some important work here
+            work = 1;
+        }
+    }
+
+    /**
+     * Makes sure that method is compiled by forcing compilation if not yet compiled.
+     * @param m Method to be checked
+     */
+    static private void makeSureIsCompiled(Method m) {
+        // Make sure background compilation is disabled
+        if (WHITE_BOX.getBooleanVMFlag("BackgroundCompilation")) {
+            throw new RuntimeException("Background compilation enabled");
+        }
+
+        // Check if already compiled
+        if (!WHITE_BOX.isMethodCompiled(m)) {
+            // If not, try to compile it with C2
+            if(!WHITE_BOX.enqueueMethodForCompilation(m, COMP_LEVEL_FULL_OPTIMIZATION)) {
+                // C2 compiler not available, try to compile with C1
+                WHITE_BOX.enqueueMethodForCompilation(m, COMP_LEVEL_SIMPLE);
+            }
+            // Because background compilation is disabled, method should now be compiled
+            if(!WHITE_BOX.isMethodCompiled(m)) {
+                throw new RuntimeException(m + " not compiled");
+            }
+        }
+    }
+
+    /**
+     * This test creates stale Method* metadata in a to-interpreter stub of an optimized IC.
+     *
+     * The following steps are performed:
+     * (1) A workerClass is loaded by a custom class loader
+     * (2) The method doWork that calls a method of the workerClass is compiled. The call
+     *     is implemented as an optimized IC calling a to-interpreted stub. The to-interpreter
+     *     stub contains a Method* to a workerClass method.
+     * (3) Unloading of the workerClass is enforced. The to-interpreter stub now contains a dead Method*.
+     * (4) Depending on the implementation of the IC, the compiled version of doWork should still be
+     *     valid. We call it again without using the workerClass.
+     */
+    static public void main(String[] args) throws Exception {
+        // (1) Create a custom class loader with no parent class loader
+        URL url = TestMethodUnloading.class.getProtectionDomain().getCodeSource().getLocation();
+        URLClassLoader loader = new URLClassLoader(new URL[] {url}, null);
+
+        // Load worker class with custom class loader
+        Class<?> workerClass = Class.forName(workerClassName, true, loader);
+
+        // (2) Make sure all paths of doWork are profiled and compiled
+        for (int i = 0; i < 100000; ++i) {
+            doWork(workerClass, true);
+            doWork(workerClass, false);
+        }
+
+        // Make sure doWork is compiled now
+        Method doWork = TestMethodUnloading.class.getDeclaredMethod("doWork", Class.class, boolean.class);
+        makeSureIsCompiled(doWork);
+
+        // (3) Throw away class loader and reference to workerClass to allow unloading
+        loader.close();
+        loader = null;
+        workerClass = null;
+
+        // Force garbage collection to trigger unloading of workerClass
+        // Dead reference to WorkerClass::hashCode triggers JDK-8029443
+        WHITE_BOX.fullGC();
+
+        // (4) Depending on the implementation of the IC, the compiled version of doWork
+        // may still be valid here. Execute it without a workerClass.
+        doWork(null, false);
+        if (work != 1) {
+            throw new RuntimeException("Work not done");
+        }
+
+        doWork(Object.class, false);
+    }
+}

hotspot/test/compiler/classUnloading/methodUnloading/WorkerClass.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * Worker class that is dynamically loaded/unloaded by TestMethodUnloading.
+ */
+public class WorkerClass {
+    /**
+     * We override hashCode here to be able to access this implementation
+     * via an Object reference (we cannot cast to WorkerClass).
+     */
+    @Override
+    public int hashCode() {
+        return 42;
+    }
+}
+