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/*
* Copyright (c) 2023, 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 id=default
* @summary Test virtual thread with monitor enter/exit
* @modules java.base/java.lang:+open jdk.management
* @library /test/lib
* @build LockingMode
* @run junit/othervm --enable-native-access=ALL-UNNAMED MonitorEnterExit
*/
/*
* @test id=LM_LEGACY
* @modules java.base/java.lang:+open jdk.management
* @library /test/lib
* @build LockingMode
* @run junit/othervm -XX:LockingMode=1 --enable-native-access=ALL-UNNAMED MonitorEnterExit
*/
/*
* @test id=LM_LIGHTWEIGHT
* @modules java.base/java.lang:+open jdk.management
* @library /test/lib
* @build LockingMode
* @run junit/othervm -XX:LockingMode=2 --enable-native-access=ALL-UNNAMED MonitorEnterExit
*/
/*
* @test id=Xint-LM_LEGACY
* @modules java.base/java.lang:+open jdk.management
* @library /test/lib
* @build LockingMode
* @run junit/othervm -Xint -XX:LockingMode=1 --enable-native-access=ALL-UNNAMED MonitorEnterExit
*/
/*
* @test id=Xint-LM_LIGHTWEIGHT
* @modules java.base/java.lang:+open jdk.management
* @library /test/lib
* @build LockingMode
* @run junit/othervm -Xint -XX:LockingMode=2 --enable-native-access=ALL-UNNAMED MonitorEnterExit
*/
/*
* @test id=Xcomp-LM_LEGACY
* @modules java.base/java.lang:+open jdk.management
* @library /test/lib
* @build LockingMode
* @run junit/othervm -Xcomp -XX:LockingMode=1 --enable-native-access=ALL-UNNAMED MonitorEnterExit
*/
/*
* @test id=Xcomp-LM_LIGHTWEIGHT
* @modules java.base/java.lang:+open jdk.management
* @library /test/lib
* @build LockingMode
* @run junit/othervm -Xcomp -XX:LockingMode=2 --enable-native-access=ALL-UNNAMED MonitorEnterExit
*/
/*
* @test id=Xcomp-TieredStopAtLevel1-LM_LEGACY
* @modules java.base/java.lang:+open jdk.management
* @library /test/lib
* @build LockingMode
* @run junit/othervm -Xcomp -XX:TieredStopAtLevel=1 -XX:LockingMode=1 --enable-native-access=ALL-UNNAMED MonitorEnterExit
*/
/*
* @test id=Xcomp-TieredStopAtLevel1-LM_LIGHTWEIGHT
* @modules java.base/java.lang:+open jdk.management
* @library /test/lib
* @build LockingMode
* @run junit/othervm -Xcomp -XX:TieredStopAtLevel=1 -XX:LockingMode=2 --enable-native-access=ALL-UNNAMED MonitorEnterExit
*/
/*
* @test id=Xcomp-noTieredCompilation-LM_LEGACY
* @modules java.base/java.lang:+open jdk.management
* @library /test/lib
* @build LockingMode
* @run junit/othervm -Xcomp -XX:-TieredCompilation -XX:LockingMode=1 --enable-native-access=ALL-UNNAMED MonitorEnterExit
*/
/*
* @test id=Xcomp-noTieredCompilation-LM_LIGHTWEIGHT
* @modules java.base/java.lang:+open jdk.management
* @library /test/lib
* @build LockingMode
* @run junit/othervm -Xcomp -XX:-TieredCompilation -XX:LockingMode=2 --enable-native-access=ALL-UNNAMED MonitorEnterExit
*/
import java.time.Duration;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.LockSupport;
import java.util.stream.IntStream;
import java.util.stream.Stream;
import jdk.test.lib.thread.VThreadPinner;
import jdk.test.lib.thread.VThreadRunner; // ensureParallelism requires jdk.management
import jdk.test.lib.thread.VThreadScheduler;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.RepeatedTest;
import org.junit.jupiter.api.condition.DisabledIf;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.Arguments;
import org.junit.jupiter.params.provider.ValueSource;
import org.junit.jupiter.params.provider.MethodSource;
import static org.junit.jupiter.api.Assertions.*;
import static org.junit.jupiter.api.Assumptions.*;
class MonitorEnterExit {
static final int MAX_VTHREAD_COUNT = 4 * Runtime.getRuntime().availableProcessors();
static final int MAX_ENTER_DEPTH = 256;
@BeforeAll
static void setup() {
// need >=2 carriers for tests that pin
VThreadRunner.ensureParallelism(2);
}
/**
* Test monitor enter with no contention.
*/
@Test
void testEnterNoContention() throws Exception {
var lock = new Object();
VThreadRunner.run(() -> {
synchronized (lock) {
assertTrue(Thread.holdsLock(lock));
}
assertFalse(Thread.holdsLock(lock));
});
}
/**
* Test monitor enter with contention, monitor is held by platform thread.
*/
@Test
void testEnterWhenHeldByPlatformThread() throws Exception {
testEnterWithContention();
}
/**
* Test monitor enter with contention, monitor is held by virtual thread.
*/
@Test
void testEnterWhenHeldByVirtualThread() throws Exception {
VThreadRunner.run(this::testEnterWithContention);
}
/**
* Test monitor enter with contention, monitor will be held by caller thread.
*/
private void testEnterWithContention() throws Exception {
var lock = new Object();
var started = new CountDownLatch(1);
var entered = new AtomicBoolean();
var vthread = Thread.ofVirtual().unstarted(() -> {
started.countDown();
synchronized (lock) {
assertTrue(Thread.holdsLock(lock));
entered.set(true);
}
assertFalse(Thread.holdsLock(lock));
});
try {
synchronized (lock) {
vthread.start();
// wait for thread to start and block
started.await();
await(vthread, Thread.State.BLOCKED);
assertFalse(entered.get());
}
} finally {
vthread.join();
}
assertTrue(entered.get());
}
/**
* Test monitor reenter.
*/
@Test
void testReenter() throws Exception {
var lock = new Object();
VThreadRunner.run(() -> {
testReenter(lock, 0);
assertFalse(Thread.holdsLock(lock));
});
}
private void testReenter(Object lock, int depth) {
if (depth < MAX_ENTER_DEPTH) {
synchronized (lock) {
assertTrue(Thread.holdsLock(lock));
testReenter(lock, depth + 1);
assertTrue(Thread.holdsLock(lock));
}
}
}
/**
* Test monitor reenter when there are other threads blocked trying to enter.
*/
@Test
@DisabledIf("LockingMode#isLegacy")
void testReenterWithContention() throws Exception {
var lock = new Object();
VThreadRunner.run(() -> {
List<Thread> threads = new ArrayList<>();
testReenter(lock, 0, threads);
// wait for threads to terminate
for (Thread vthread : threads) {
vthread.join();
}
});
}
private void testReenter(Object lock, int depth, List<Thread> threads) throws Exception {
if (depth < MAX_ENTER_DEPTH) {
synchronized (lock) {
assertTrue(Thread.holdsLock(lock));
// start platform or virtual thread that blocks waiting to enter
var started = new CountDownLatch(1);
ThreadFactory factory = ThreadLocalRandom.current().nextBoolean()
? Thread.ofPlatform().factory()
: Thread.ofVirtual().factory();
var thread = factory.newThread(() -> {
started.countDown();
synchronized (lock) {
/* do nothing */
}
});
thread.start();
// wait for thread to start and block
started.await();
await(thread, Thread.State.BLOCKED);
threads.add(thread);
// test reenter
testReenter(lock, depth + 1, threads);
}
}
}
/**
* Test monitor enter when pinned.
*/
@Test
void testEnterWhenPinned() throws Exception {
var lock = new Object();
VThreadPinner.runPinned(() -> {
synchronized (lock) {
assertTrue(Thread.holdsLock(lock));
}
assertFalse(Thread.holdsLock(lock));
});
}
/**
* Test monitor reenter when pinned.
*/
@Test
void testReenterWhenPinned() throws Exception {
VThreadRunner.run(() -> {
var lock = new Object();
synchronized (lock) {
VThreadPinner.runPinned(() -> {
assertTrue(Thread.holdsLock(lock));
synchronized (lock) {
assertTrue(Thread.holdsLock(lock));
}
assertTrue(Thread.holdsLock(lock));
});
}
assertFalse(Thread.holdsLock(lock));
});
}
/**
* Test contended monitor enter when pinned. Monitor is held by platform thread.
*/
@Test
void testContendedEnterWhenPinnedHeldByPlatformThread() throws Exception {
testEnterWithContentionWhenPinned();
}
/**
* Test contended monitor enter when pinned. Monitor is held by virtual thread.
*/
@Test
void testContendedEnterWhenPinnedHeldByVirtualThread() throws Exception {
VThreadRunner.run(this::testEnterWithContentionWhenPinned);
}
/**
* Test contended monitor enter when pinned, monitor will be held by caller thread.
*/
private void testEnterWithContentionWhenPinned() throws Exception {
var lock = new Object();
var started = new CountDownLatch(1);
var entered = new AtomicBoolean();
Thread vthread = Thread.ofVirtual().unstarted(() -> {
VThreadPinner.runPinned(() -> {
started.countDown();
synchronized (lock) {
entered.set(true);
}
});
});
synchronized (lock) {
// start thread and wait for it to block
vthread.start();
started.await();
await(vthread, Thread.State.BLOCKED);
assertFalse(entered.get());
}
vthread.join();
// check thread entered monitor
assertTrue(entered.get());
}
/**
* Test that blocking waiting to enter a monitor releases the carrier.
*/
@Test
@DisabledIf("LockingMode#isLegacy")
void testReleaseWhenBlocked() throws Exception {
assumeTrue(VThreadScheduler.supportsCustomScheduler(), "No support for custom schedulers");
try (ExecutorService scheduler = Executors.newFixedThreadPool(1)) {
ThreadFactory factory = VThreadScheduler.virtualThreadFactory(scheduler);
var lock = new Object();
// thread enters monitor
var started = new CountDownLatch(1);
var vthread1 = factory.newThread(() -> {
started.countDown();
synchronized (lock) {
}
});
try {
synchronized (lock) {
// start thread and wait for it to block
vthread1.start();
started.await();
await(vthread1, Thread.State.BLOCKED);
// carrier should be released, use it for another thread
var executed = new AtomicBoolean();
var vthread2 = factory.newThread(() -> {
executed.set(true);
});
vthread2.start();
vthread2.join();
assertTrue(executed.get());
}
} finally {
vthread1.join();
}
}
}
/**
* Test lots of virtual threads blocked waiting to enter a monitor. If the number
* of virtual threads exceeds the number of carrier threads this test will hang if
* carriers aren't released.
*/
@Test
@DisabledIf("LockingMode#isLegacy")
void testManyBlockedThreads() throws Exception {
Thread[] vthreads = new Thread[MAX_VTHREAD_COUNT];
var lock = new Object();
synchronized (lock) {
for (int i = 0; i < MAX_VTHREAD_COUNT; i++) {
var started = new CountDownLatch(1);
var vthread = Thread.ofVirtual().start(() -> {
started.countDown();
synchronized (lock) {
}
});
// wait for thread to start and block
started.await();
await(vthread, Thread.State.BLOCKED);
vthreads[i] = vthread;
}
}
// cleanup
for (int i = 0; i < MAX_VTHREAD_COUNT; i++) {
vthreads[i].join();
}
}
/**
* Returns a stream of elements that are ordered pairs of platform and virtual thread
* counts. 0,2,4,..16 platform threads. 2,4,6,..32 virtual threads.
*/
static Stream<Arguments> threadCounts() {
return IntStream.range(0, 17)
.filter(i -> i % 2 == 0)
.mapToObj(i -> i)
.flatMap(np -> IntStream.range(2, 33)
.filter(i -> i % 2 == 0)
.mapToObj(vp -> Arguments.of(np, vp)));
}
/**
* Test mutual exclusion of monitors with platform and virtual threads.
*/
@ParameterizedTest
@MethodSource("threadCounts")
void testMutualExclusion(int nPlatformThreads, int nVirtualThreads) throws Exception {
class Counter {
int count;
synchronized void increment() {
count++;
Thread.yield();
}
}
var counter = new Counter();
int nThreads = nPlatformThreads + nVirtualThreads;
var threads = new Thread[nThreads];
int index = 0;
for (int i = 0; i < nPlatformThreads; i++) {
threads[index] = Thread.ofPlatform()
.name("platform-" + index)
.unstarted(counter::increment);
index++;
}
for (int i = 0; i < nVirtualThreads; i++) {
threads[index] = Thread.ofVirtual()
.name("virtual-" + index)
.unstarted(counter::increment);
index++;
}
// start all threads
for (Thread thread : threads) {
thread.start();
}
// wait for all threads to terminate
for (Thread thread : threads) {
thread.join();
}
assertEquals(nThreads, counter.count);
}
/**
* Test unblocking a virtual thread waiting to enter a monitor held by a platform thread.
*/
@RepeatedTest(20)
void testUnblockingByPlatformThread() throws Exception {
testUnblocking();
}
/**
* Test unblocking a virtual thread waiting to enter a monitor held by another
* virtual thread.
*/
@RepeatedTest(20)
void testUnblockingByVirtualThread() throws Exception {
VThreadRunner.run(this::testUnblocking);
}
/**
* Test unblocking a virtual thread waiting to enter a monitor, monitor will be
* initially be held by caller thread.
*/
private void testUnblocking() throws Exception {
var lock = new Object();
var started = new CountDownLatch(1);
var entered = new AtomicBoolean();
var vthread = Thread.ofVirtual().unstarted(() -> {
started.countDown();
synchronized (lock) {
entered.set(true);
}
});
try {
synchronized (lock) {
vthread.start();
started.await();
// random delay before exiting monitor
switch (ThreadLocalRandom.current().nextInt(4)) {
case 0 -> { /* no delay */}
case 1 -> Thread.onSpinWait();
case 2 -> Thread.yield();
case 3 -> await(vthread, Thread.State.BLOCKED);
default -> fail();
}
assertFalse(entered.get());
}
} finally {
vthread.join();
}
assertTrue(entered.get());
}
/**
* Test that unblocking a virtual thread waiting to enter a monitor does not consume
* the thread's parking permit.
*/
@Test
void testParkingPermitNotConsumed() throws Exception {
var lock = new Object();
var started = new CountDownLatch(1);
var vthread = Thread.ofVirtual().unstarted(() -> {
started.countDown();
LockSupport.unpark(Thread.currentThread());
synchronized (lock) { } // should block
LockSupport.park(); // should not park
});
synchronized (lock) {
vthread.start();
// wait for thread to start and block
started.await();
await(vthread, Thread.State.BLOCKED);
}
vthread.join();
}
/**
* Test that unblocking a virtual thread waiting to enter a monitor does not make
* available the thread's parking permit.
*/
@Test
void testParkingPermitNotOffered() throws Exception {
var lock = new Object();
var started = new CountDownLatch(1);
var vthread = Thread.ofVirtual().unstarted(() -> {
started.countDown();
synchronized (lock) { } // should block
LockSupport.park(); // should park
});
synchronized (lock) {
vthread.start();
// wait for thread to start and block
started.await();
await(vthread, Thread.State.BLOCKED);
}
try {
// wait for thread to park, it should not terminate
await(vthread, Thread.State.WAITING);
vthread.join(Duration.ofMillis(100));
assertEquals(Thread.State.WAITING, vthread.getState());
} finally {
LockSupport.unpark(vthread);
vthread.join();
}
}
/**
* Waits for the given thread to reach a given state.
*/
private void await(Thread thread, Thread.State expectedState) throws InterruptedException {
Thread.State state = thread.getState();
while (state != expectedState) {
assertTrue(state != Thread.State.TERMINATED, "Thread has terminated");
Thread.sleep(10);
state = thread.getState();
}
}
}
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