8208362: (bf) Long chains created by direct Buffer::slice

Reviewed-by: mr, psandoz, alanb

src/java.base/share/classes/java/nio/Direct-X-Buffer.java.template

@@ -194,7 +194,8 @@ class Direct$Type$Buffer$RW$$BO$
 #if[byte]
         cleaner = null;
 #end[byte]
-        att = db;
+        Object attachment = db.attachment();
+        att = (attachment == null ? db : attachment);
 #else[rw]
         super(db, mark, pos, lim, cap, off);
         this.isReadOnly = true;

test/jdk/java/nio/Buffer/ReachabilityTest.java

@@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 2018, 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.
+ */
+
+/* @test
+ * @bug 8208362
+ * @summary Tests reachability from source to dependent direct byte buffers
+ * @run testng ReachabilityTest
+ */
+
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+import java.lang.ref.Reference;
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.WeakReference;
+import java.nio.Buffer;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.concurrent.CountDownLatch;
+import java.util.function.UnaryOperator;
+
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+
+public class ReachabilityTest {
+
+    @Test
+    public void testDuplicate() {
+        testReachability(ByteBuffer.allocateDirect(16384),
+                         ByteBuffer::duplicate);
+    }
+
+    @Test
+    public void testSlice() {
+        testReachability(ByteBuffer.allocateDirect(16384),
+                         ByteBuffer::slice);
+    }
+
+    @Test
+    public void testViewDuplicate() {
+        testReachability(ByteBuffer.allocateDirect(16384),
+                         (Buffer b) -> b instanceof ByteBuffer
+                                ? ((ByteBuffer) b).asIntBuffer()
+                                : b.duplicate()
+        );
+    }
+
+    @Test
+    public void testViewSlice() {
+        testReachability(ByteBuffer.allocateDirect(16384),
+                         (Buffer b) -> b instanceof ByteBuffer
+                                       ? ((ByteBuffer) b).asIntBuffer()
+                                       : b.slice()
+        );
+    }
+
+    <T> void testReachability(T t, UnaryOperator<T> b) {
+        WeakReference<T> root = new WeakReference<>(t);
+
+        ReferenceQueue<Object> queue = new ReferenceQueue<>();
+        List<WeakReference<T>> refs = new ArrayList<>();
+        for (int i = 0; i < 1000; i++) {
+            t = b.apply(t);
+            refs.add(new WeakReference<>(t, queue));
+        }
+        t = b.apply(t);
+
+        boolean collected = false;
+        long timeoutMillis = 100L;
+        try {
+            for (int tries = 0; tries < 3 && !collected; tries++) {
+                System.gc();
+                collected = refs.stream().map(Reference::get).anyMatch(Objects::isNull);
+                if (!collected) {
+                    collected = queue.remove(timeoutMillis) != null;
+                    timeoutMillis *= 4;
+                }
+            }
+        } catch (InterruptedException unexpected) {
+            throw new AssertionError("unexpected InterruptedException");
+        }
+
+        // Some or all of the intermediate values must be GC'ed
+        Assert.assertTrue(collected);
+        // The root should never be GC'ed
+        Assert.assertNotNull(root.get());
+
+        Reference.reachabilityFence(t);
+    }
+}