8322732: ForkJoinPool may underutilize cores in async mode

8327854: Test java/util/stream/test/org/openjdk/tests/java/util/stream/WhileOpStatefulTest.java failed with RuntimeException

Reviewed-by: alanb

test/jdk/java/util/concurrent/forkjoin/Starvation.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2004, 2024, 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 8322732
+ * @summary ForkJoinPool utilizes available workers even with arbitrary task dependencies
+ */
+import java.util.concurrent.Callable;
+import java.util.concurrent.ForkJoinPool;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class Starvation {
+    static final AtomicInteger count = new AtomicInteger();
+    static final Callable<Void> noop = new Callable<Void>() {
+            public Void call() {
+                return null; }};
+    static final class AwaitCount implements Callable<Void> {
+        private int c;
+        AwaitCount(int c) { this.c = c; }
+        public Void call() {
+            while (count.get() == c) Thread.onSpinWait();
+            return null; }};
+
+    public static void main(String[] args) throws Exception {
+        try (var pool = new ForkJoinPool(2)) {
+            for (int i = 0; i < 100_000; i++) {
+                var future1 = pool.submit(new AwaitCount(i));
+                var future2 = pool.submit(noop);
+                future2.get();
+                count.set(i + 1);
+                future1.get();
+            }
+        }
+    }
+}