diff --git a/src/share/classes/java/util/concurrent/LinkedTransferQueue.java b/src/share/classes/java/util/concurrent/LinkedTransferQueue.java index 5ebd04923d4c5d453816240081a052dbee289e29..b59042653e70c995482a256c6a866b236101b628 100644 --- a/src/share/classes/java/util/concurrent/LinkedTransferQueue.java +++ b/src/share/classes/java/util/concurrent/LinkedTransferQueue.java @@ -780,7 +780,9 @@ public class LinkedTransferQueue extends AbstractQueue } /** - * Version of firstOfMode used by Spliterator + * Version of firstOfMode used by Spliterator. Callers must + * recheck if the returned node's item field is null or + * self-linked before using. */ final Node firstDataNode() { for (Node p = head; p != null;) { @@ -953,11 +955,12 @@ public class LinkedTransferQueue extends AbstractQueue Object[] a = new Object[n]; int i = 0; do { - if ((a[i] = p.item) != null) + Object e = p.item; + if (e != p && (a[i] = e) != null) ++i; if (p == (p = p.next)) p = q.firstDataNode(); - } while (p != null && i < n); + } while (p != null && i < n && p.isData); if ((current = p) == null) exhausted = true; if (i > 0) { @@ -980,11 +983,11 @@ public class LinkedTransferQueue extends AbstractQueue exhausted = true; do { Object e = p.item; + if (e != null && e != p) + action.accept((E)e); if (p == (p = p.next)) p = q.firstDataNode(); - if (e != null) - action.accept((E)e); - } while (p != null); + } while (p != null && p.isData); } } @@ -997,10 +1000,11 @@ public class LinkedTransferQueue extends AbstractQueue ((p = current) != null || (p = q.firstDataNode()) != null)) { Object e; do { - e = p.item; + if ((e = p.item) == p) + e = null; if (p == (p = p.next)) p = q.firstDataNode(); - } while (e == null && p != null); + } while (e == null && p != null && p.isData); if ((current = p) == null) exhausted = true; if (e != null) { diff --git a/test/java/util/concurrent/LinkedTransferQueue/SpliteratorTraverseAddRemoveTest.java b/test/java/util/concurrent/LinkedTransferQueue/SpliteratorTraverseAddRemoveTest.java new file mode 100644 index 0000000000000000000000000000000000000000..4d288a27845573a1b0fd0a64ed70768abcaef5ff --- /dev/null +++ b/test/java/util/concurrent/LinkedTransferQueue/SpliteratorTraverseAddRemoveTest.java @@ -0,0 +1,114 @@ +/* + * 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. + */ + +/* + * @test + * @run testng SpliteratorTraverseAddRemoveTest + * @bug 8085978 + * @summary repeatedly traverse the queue using the spliterator while + * concurrently adding and removing an element to test that self-linked + * nodes are never erroneously reported on traversal + */ + +import org.testng.Assert; +import org.testng.annotations.DataProvider; +import org.testng.annotations.Test; + +import java.util.ArrayList; +import java.util.List; +import java.util.Queue; +import java.util.Spliterator; +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.LinkedTransferQueue; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicBoolean; +import java.util.function.Consumer; + +@Test +public class SpliteratorTraverseAddRemoveTest { + + static Object[] of(String desc, Consumer> c) { + return new Object[]{desc, c}; + } + + static void assertIsString(Object e) { + Assert.assertTrue(e instanceof String, + String.format("Object instanceof %s (actual: instanceof %s)", + String.class.getName(), + e.getClass().getName())); + } + + @DataProvider() + public static Object[][] spliteratorTraversers() { + return new Object[][]{ + of("forEachRemaining", q -> { + q.spliterator().forEachRemaining(SpliteratorTraverseAddRemoveTest::assertIsString); + }), + of("tryAdvance", q -> { + Spliterator s = q.spliterator(); + while (s.tryAdvance(SpliteratorTraverseAddRemoveTest::assertIsString)) + ; + }), + of("trySplit then forEachRemaining", q -> { + Spliterator r = q.spliterator(); + + List> ss = new ArrayList<>(); + Spliterator l; + while ((l = r.trySplit()) != null) { + ss.add(l); + } + ss.add(r); + + ss.forEach(s -> s.forEachRemaining(SpliteratorTraverseAddRemoveTest::assertIsString)); + }), + }; + } + + @Test(dataProvider = "spliteratorTraversers") + public void testQueue(String desc, Consumer> c) + throws InterruptedException { + AtomicBoolean done = new AtomicBoolean(false); + Queue msgs = new LinkedTransferQueue<>(); + + CompletableFuture traversalTask = CompletableFuture.runAsync(() -> { + while (!done.get()) { + // Traversal will fail if self-linked nodes of + // LinkedTransferQueue are erroneously reported + c.accept(msgs); + } + }); + CompletableFuture addAndRemoveTask = CompletableFuture.runAsync(() -> { + while (!traversalTask.isDone()) { + msgs.add("msg"); + msgs.remove("msg"); + } + }); + + Thread.sleep(TimeUnit.SECONDS.toMillis(1)); + done.set(true); + + addAndRemoveTask.join(); + Assert.assertTrue(traversalTask.isDone()); + traversalTask.join(); + } +}