8311867: StructuredTaskScope.shutdown does not interrupt newly started threads

src/java.base/share/classes/java/util/concurrent/StructuredTaskScope.java

@@ -59,7 +59,7 @@
  * used to get the result completed successfully, or the exception if the subtask failed.
  * {@snippet lang=java :
  *     Callable<String> task1 = ...
- *     Callable<Integer> task1 = ...
+ *     Callable<Integer> task2 = ...
  *
  *     try (var scope = new StructuredTaskScope<Object>()) {
  *

src/java.base/share/classes/jdk/internal/misc/ThreadFlock.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2023, 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
@@ -451,15 +451,15 @@ public boolean isClosed() {
     }
 
     /**
-     * {@return a stream of the live threads in this flock}
+     * {@return a stream of the threads in this flock}
      * The elements of the stream are threads that were started in this flock
      * but have not terminated. The stream will reflect the set of threads in the
      * flock at some point at or since the creation of the stream. It may or may
      * not reflect changes to the set of threads subsequent to creation of the
      * stream.
      */
     public Stream<Thread> threads() {
-        return threads.stream().filter(Thread::isAlive);
+        return threads.stream();
     }
 
     /**

test/jdk/java/util/concurrent/StructuredTaskScope/StressShutdown.java

@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 2023, 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 8311867
+ * @summary Stress test of StructuredTaskScope.shutdown with running and starting threads
+ * @enablePreview
+ * @run junit StressShutdown
+ */
+
+import java.time.Duration;
+import java.util.concurrent.Callable;
+import java.util.concurrent.StructuredTaskScope;
+import java.util.concurrent.ThreadFactory;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import static org.junit.jupiter.api.Assertions.*;
+
+class StressShutdown {
+
+    static final Callable<Void> SLEEP_FOR_A_DAY = () -> {
+        Thread.sleep(Duration.ofDays(1));
+        return null;
+    };
+
+    static Stream<Arguments> testCases() {
+        Stream<ThreadFactory> factories = Stream.of(
+                Thread.ofPlatform().factory(),
+                Thread.ofVirtual().factory()
+        );
+        // 0..15 forks before shutdown, 0..15 forks after shutdown
+        return factories.flatMap(f -> IntStream.range(0, 256)
+                .mapToObj(x -> Arguments.of(f, x & 0x0F, (x & 0xF0) >> 4)));
+    }
+
+    /**
+     * Test StructuredTaskScope.shutdown with running threads and concurrently with
+     * threads that are starting. The shutdown should interrupt all threads so that
+     * join wakes up.
+     *
+     * @param factory the ThreadFactory to use
+     * @param beforeShutdown the number of subtasks to fork before shutdown
+     * @param afterShutdown the number of subtasks to fork after shutdown
+     */
+    @ParameterizedTest
+    @MethodSource("testCases")
+    void testShutdown(ThreadFactory factory, int beforeShutdown, int afterShutdown)
+        throws InterruptedException
+    {
+        try (var scope = new StructuredTaskScope<>(null, factory)) {
+            // fork subtasks
+            for (int i = 0; i < beforeShutdown; i++) {
+                scope.fork(SLEEP_FOR_A_DAY);
+            }
+
+            // fork subtask to shutdown
+            scope.fork(() -> {
+                scope.shutdown();
+                return null;
+            });
+
+            // fork after forking subtask to shutdown
+            for (int i = 0; i < afterShutdown; i++) {
+                scope.fork(SLEEP_FOR_A_DAY);
+            }
+
+            scope.join();
+        }
+    }
+}