1 /*
  2  * Copyright (c) 2020, 2024, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
  8  *
  9  * This code is distributed in the hope that it will be useful, but WITHOUT
 10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 12  * version 2 for more details (a copy is included in the LICENSE file that
 13  * accompanied this code).
 14  *
 15  * You should have received a copy of the GNU General Public License version
 16  * 2 along with this work; if not, write to the Free Software Foundation,
 17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 18  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  */
 23 
 24 /**
 25  * @test
 26  * @summary Stress test asynchronous Thread.getStackTrace when parking
 27  * @requires vm.debug != true & vm.continuations
 28  * @modules java.base/java.lang:+open
 29  * @library /test/lib
 30  * @run main GetStackTraceALotWhenParking
 31  */
 32 
 33 /**
 34  * @test
 35  * @requires vm.debug == true & vm.continuations
 36  * @modules java.base/java.lang:+open
 37  * @library /test/lib
 38  * @run main/timeout=300 GetStackTraceALotWhenParking 1000
 39  */
 40 
 41 import java.time.Duration;
 42 import java.time.Instant;
 43 import java.util.concurrent.Executor;
 44 import java.util.concurrent.Executors;
 45 import java.util.concurrent.ExecutorService;
 46 import java.util.concurrent.ThreadFactory;
 47 import java.util.concurrent.atomic.AtomicInteger;
 48 import java.util.concurrent.locks.LockSupport;
 49 import jdk.test.lib.thread.VThreadScheduler;
 50 
 51 public class GetStackTraceALotWhenParking {
 52     static class RoundRobinExecutor implements Executor, AutoCloseable {
 53         private final ExecutorService[] executors;
 54         private int next;
 55 
 56         RoundRobinExecutor() {
 57             var factory = Thread.ofPlatform().name("worker-", 1).daemon(true).factory();
 58             var executors = new ExecutorService[2];
 59             for (int i = 0; i < executors.length; i++) {
 60                 executors[i] = Executors.newSingleThreadExecutor(factory);
 61             }
 62             this.executors = executors;
 63         }
 64 
 65         @Override
 66         public void execute(Runnable task) {
 67             executors[next].execute(task);
 68             next = (next + 1) % executors.length;
 69         }
 70 
 71         @Override
 72         public void close() {
 73             for (int i = 0; i < executors.length; i++) {
 74                 executors[i].shutdown();
 75             }
 76         }
 77     }
 78 
 79     public static void main(String[] args) throws Exception {
 80         int iterations = args.length > 0 ? Integer.parseInt(args[0])  : 10_000;
 81 
 82         final int ITERATIONS = iterations;
 83         final int SPIN_NANOS = 5000;
 84 
 85         AtomicInteger count = new AtomicInteger();
 86 
 87         try (RoundRobinExecutor executor = new RoundRobinExecutor()) {
 88             ThreadFactory factory = VThreadScheduler.virtualThreadFactory(executor);
 89 
 90             Thread thread = factory.newThread(() -> {
 91                 while (count.incrementAndGet() < ITERATIONS) {
 92                     long start = System.nanoTime();
 93                     while ((System.nanoTime() - start) < SPIN_NANOS) {
 94                         Thread.onSpinWait();
 95                     }
 96                     LockSupport.parkNanos(500_000);
 97                 }
 98             });
 99             thread.start();
100 
101             long start = System.nanoTime();
102             while (thread.isAlive()) {
103                 StackTraceElement[] stackTrace = thread.getStackTrace();
104                 // printStackTrace(stackTrace);
105                 Thread.sleep(5);
106                 if ((System.nanoTime() - start) > 500_000_000) {
107                     System.out.format("%s => %d of %d%n", Instant.now(), count.get(), ITERATIONS);
108                     start = System.nanoTime();
109                 }
110             }
111 
112             int countValue = count.get();
113             if (countValue != ITERATIONS) {
114                 throw new RuntimeException("count = " + countValue);
115             }
116         }
117     }
118 
119     static void printStackTrace(StackTraceElement[] stackTrace) {
120         if (stackTrace == null) {
121             System.out.println("NULL");
122         } else {
123             for (var e : stackTrace) {
124                 System.out.println("\t" + e);
125             }
126         }
127     }
128 }