src/jdk.internal.vm.ci/share/classes/jdk.vm.ci.hotspot/src/jdk/vm/ci/hotspot/HotSpotJVMCIMetaAccessContext.java
--- a/src/jdk.internal.vm.ci/share/classes/jdk.vm.ci.hotspot/src/jdk/vm/ci/hotspot/HotSpotJVMCIMetaAccessContext.java Tue Apr 30 19:34:13 2019 +0100
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,271 +0,0 @@
-/*
- * Copyright (c) 2015, 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.
- */
-package jdk.vm.ci.hotspot;
-
-import java.lang.ref.Reference;
-import java.lang.ref.ReferenceQueue;
-import java.lang.ref.WeakReference;
-import java.util.Arrays;
-import java.util.Iterator;
-
-import jdk.vm.ci.meta.JavaKind;
-import jdk.vm.ci.meta.ResolvedJavaType;
-
-/**
- * This class manages the set of metadata roots that must be scanned during garbage collection.
- * Because of class redefinition Method* and ConstantPool* can be freed if they don't appear to be
- * in use so they must be tracked when there are live references to them from Java.
- *
- * The general theory of operation is that all {@link MetaspaceWrapperObject}s are created by
- * calling into the VM which calls back out to actually create the wrapper instance. During the call
- * the VM keeps the metadata reference alive through the use of metadata handles. Once the call
- * completes the wrapper object is registered here and will be scanned during metadata scanning. The
- * weakness of the reference to the wrapper object allows them to be reclaimed when they are no
- * longer used.
- *
- */
-class HotSpotJVMCIMetaAccessContext {
-
- /**
- * The set of currently live contexts used for tracking of live metadata. Examined from the VM
- * during garbage collection.
- */
- private static WeakReference<?>[] allContexts = new WeakReference<?>[0];
-
- /**
- * This is a chunked list of metadata roots. It can be read from VM native code so it's been
- * marked volatile to ensure the order of updates are respected.
- */
- private volatile Object[] metadataRoots;
-
- private ChunkedList<WeakReference<MetaspaceWrapperObject>> list = new ChunkedList<>();
-
- /**
- * The number of weak references freed since the last time the list was shrunk.
- */
- private int freed;
-
- /**
- * The {@link ReferenceQueue} tracking the weak references created by this context.
- */
- private final ReferenceQueue<MetaspaceWrapperObject> queue = new ReferenceQueue<>();
-
- static synchronized void add(HotSpotJVMCIMetaAccessContext context) {
- for (int i = 0; i < allContexts.length; i++) {
- if (allContexts[i] == null || allContexts[i].get() == null) {
- allContexts[i] = new WeakReference<>(context);
- return;
- }
- }
- int index = allContexts.length;
- allContexts = Arrays.copyOf(allContexts, index + 2);
- allContexts[index] = new WeakReference<>(context);
- }
-
- HotSpotJVMCIMetaAccessContext() {
- add(this);
- }
-
- /**
- * Periodically trim the list of tracked metadata. A new list is created to replace the old to
- * avoid concurrent scanning issues.
- */
- private void clean() {
- Reference<?> ref = queue.poll();
- if (ref == null) {
- return;
- }
- while (ref != null) {
- freed++;
- ref = queue.poll();
- }
- if (freed > list.size() / 2) {
- ChunkedList<WeakReference<MetaspaceWrapperObject>> newList = new ChunkedList<>();
- for (WeakReference<MetaspaceWrapperObject> element : list) {
- /*
- * The referent could become null anywhere in here but it doesn't matter. It will
- * get cleaned up next time.
- */
- if (element != null && element.get() != null) {
- newList.add(element);
- }
- }
- list = newList;
- metadataRoots = list.getHead();
- freed = 0;
- }
- }
-
- /**
- * Add a {@link MetaspaceWrapperObject} to tracked by the GC. It's assumed that the caller is
- * responsible for keeping the reference alive for the duration of the call. Once registration
- * is complete then the VM will ensure it's kept alive.
- *
- * @param metaspaceObject
- */
-
- public synchronized void add(MetaspaceWrapperObject metaspaceObject) {
- clean();
- list.add(new WeakReference<>(metaspaceObject, queue));
- if (list.getHead() != metadataRoots) {
- /*
- * The list enlarged so update the head.
- */
- metadataRoots = list.getHead();
- }
- assert isRegistered(metaspaceObject);
- }
-
- protected ResolvedJavaType createClass(Class<?> javaClass) {
- if (javaClass.isPrimitive()) {
- JavaKind kind = JavaKind.fromJavaClass(javaClass);
- return new HotSpotResolvedPrimitiveType(kind);
- } else {
- return new HotSpotResolvedObjectTypeImpl(javaClass, this);
- }
- }
-
- private final ClassValue<WeakReference<ResolvedJavaType>> resolvedJavaType = new ClassValue<>() {
- @Override
- protected WeakReference<ResolvedJavaType> computeValue(Class<?> type) {
- return new WeakReference<>(createClass(type));
- }
- };
-
- /**
- * Gets the JVMCI mirror for a {@link Class} object.
- *
- * @return the {@link ResolvedJavaType} corresponding to {@code javaClass}
- */
- public ResolvedJavaType fromClass(Class<?> javaClass) {
- ResolvedJavaType javaType = null;
- while (javaType == null) {
- WeakReference<ResolvedJavaType> type = resolvedJavaType.get(javaClass);
- javaType = type.get();
- if (javaType == null) {
- /*
- * If the referent has become null, clear out the current value and let computeValue
- * above create a new value. Reload the value in a loop because in theory the
- * WeakReference referent can be reclaimed at any point.
- */
- resolvedJavaType.remove(javaClass);
- }
- }
- return javaType;
- }
-
- /**
- * A very simple append only chunked list implementation.
- */
- static class ChunkedList<T> implements Iterable<T> {
- private static final int CHUNK_SIZE = 32;
-
- private static final int NEXT_CHUNK_INDEX = CHUNK_SIZE - 1;
-
- private Object[] head;
- private int index;
- private int size;
-
- ChunkedList() {
- head = new Object[CHUNK_SIZE];
- index = 0;
- }
-
- void add(T element) {
- if (index == NEXT_CHUNK_INDEX) {
- Object[] newHead = new Object[CHUNK_SIZE];
- newHead[index] = head;
- head = newHead;
- index = 0;
- }
- head[index++] = element;
- size++;
- }
-
- Object[] getHead() {
- return head;
- }
-
- @Override
- public Iterator<T> iterator() {
- return new ChunkIterator<>();
- }
-
- int size() {
- return size;
- }
-
- class ChunkIterator<V> implements Iterator<V> {
-
- ChunkIterator() {
- currentChunk = head;
- currentIndex = -1;
- next = findNext();
- }
-
- Object[] currentChunk;
- int currentIndex;
- V next;
-
- @SuppressWarnings("unchecked")
- V findNext() {
- V result;
- do {
- currentIndex++;
- if (currentIndex == NEXT_CHUNK_INDEX) {
- currentChunk = (Object[]) currentChunk[currentIndex];
- currentIndex = 0;
- if (currentChunk == null) {
- return null;
- }
- }
- result = (V) currentChunk[currentIndex];
- } while (result == null);
- return result;
- }
-
- @Override
- public boolean hasNext() {
- return next != null;
- }
-
- @Override
- public V next() {
- V result = next;
- next = findNext();
- return result;
- }
-
- }
-
- }
-
- synchronized boolean isRegistered(MetaspaceWrapperObject wrapper) {
- for (WeakReference<MetaspaceWrapperObject> m : list) {
- if (m != null && m.get() == wrapper) {
- return true;
- }
- }
- return false;
- }
-}