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/*
* Copyright (c) 2022, 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 8292240
* @summary Test the scenario where a blocking operation pins a virtual thread to its
* carrier thread (cT1) and doesn't activate a spare. Subsequent blocking operations
* that pin a virtual thread to cT1 should attempt to activate a spare.
* @requires vm.continuations
* @run main/othervm
* -Djdk.virtualThreadScheduler.parallelism=1
* -Djdk.virtualThreadScheduler.maxPoolSize=2 ActivateSpareCarrier 100
*/
import java.time.Duration;
import java.util.Comparator;
import java.util.List;
import java.util.concurrent.ForkJoinWorkerThread;
import java.util.stream.Collectors;
public class ActivateSpareCarrier {
private static final int DEFAULT_ITERTAIONS = 10_000;
private static final Object LOCK = new Object();
public static void main(String[] args) throws Exception {
int iterations;
if (args.length == 0) {
iterations = DEFAULT_ITERTAIONS;
} else {
iterations = Integer.parseInt(args[0]);
}
for (int i = 0; i < iterations; i++) {
test(i);
}
}
/**
* This method creates 3 virtual threads:
* - thread1 blocks in Object.wait, activating a spare carrier thread
* - thread2 is started and runs on the spare carrier thread
* - thread1 is notified causing it to re-adjust the release count and terminate
* - thread3 is started and should run on the one active thread
*
* This method need invoked at least twice in the same VM.
*/
private static void test(int i) throws Exception {
System.out.printf("---- %d ----%n", i);
// thread1 blocks in wait, this triggers a tryCompensate to activate a spare thread
Thread thread1 = Thread.ofVirtual().unstarted(() -> {
System.out.println(Thread.currentThread());
synchronized (LOCK) {
try {
LOCK.wait();
} catch (InterruptedException e) { }
}
});
System.out.printf("starting waiter thread #%d%n", thread1.threadId());
thread1.start();
// wait for thread1 to block in Object.wait
while (thread1.getState() != Thread.State.WAITING) {
Thread.sleep(10);
}
// start another virtual thread, it should run on the spare carrier thread
startAndJoinVirtualThread();
// notify thread1, this releases the blocker
synchronized (LOCK) {
LOCK.notifyAll();
}
joinThread(thread1);
// start another virtual thread after counts have been re-adjusted
startAndJoinVirtualThread();
}
/**
* Start a virtual thread and wait for it to terminate.
*/
private static void startAndJoinVirtualThread() throws InterruptedException {
Thread thread = Thread.ofVirtual().unstarted(() -> {
System.out.println(Thread.currentThread());
});
System.out.format("starting #%d%n", thread.threadId());
thread.start();
joinThread(thread);
}
/**
* Wait for the give thread to terminate with diagnostic output if the thread does
* not terminate quickly.
*/
private static void joinThread(Thread thread) throws InterruptedException {
long tid = thread.threadId();
System.out.printf("Waiting for #%d to terminate%n", tid);
boolean terminated = thread.join(Duration.ofSeconds(2));
if (!terminated) {
System.out.printf("#%d did not terminate quickly, continue to wait...%n", tid);
printForkJoinWorkerThreads();
thread.join();
}
System.out.printf("#%d terminated%n", tid);
}
/**
* Print the list of ForkJoinWorkerThreads and their stack traces.
*/
private static void printForkJoinWorkerThreads() {
List<Thread> threads = Thread.getAllStackTraces().keySet().stream()
.filter(t -> t instanceof ForkJoinWorkerThread)
.sorted(Comparator.comparingLong(Thread::threadId))
.collect(Collectors.toList());
System.out.println("ForkJoinWorkerThreads:");
for (Thread t : threads) {
System.out.printf(" %s%n", t);
StackTraceElement[] stack = t.getStackTrace();
for (StackTraceElement e : stack) {
System.out.printf(" %s%n", e);
}
}
}
}
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