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/*
* Copyright (c) 2020, 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 8284161 8289284 8322846
* @summary Basic test of debugging option to trace pinned threads
* @requires vm.continuations
* @library /test/lib
* @run junit/othervm -Djdk.tracePinnedThreads=full TracePinnedThreads
* @run junit/othervm -Djdk.tracePinnedThreads=short TracePinnedThreads
*/
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import java.time.Duration;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.LockSupport;
import jdk.test.lib.thread.VThreadRunner;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;
class TracePinnedThreads {
static final Object lock = new Object();
/**
* Parks current thread for 1 second.
*/
private static void park() {
long nanos = Duration.ofSeconds(1).toNanos();
LockSupport.parkNanos(nanos);
}
/**
* Invokes the park method through a native frame to park the current
* thread for 1 second.
*/
private static native void invokePark();
/**
* Test parking inside synchronized block.
*/
@Test
void testPinnedCausedBySynchronizedBlock() throws Exception {
String output = run(() -> {
synchronized (lock) {
park();
}
});
assertContains(output, "reason:MONITOR");
assertContains(output, "<== monitors:1");
}
/**
* Test parking with native frame on stack.
*/
@Test
void testPinnedCausedByNativeMethod() throws Exception {
System.loadLibrary("TracePinnedThreads");
String output = run(() -> invokePark());
assertContains(output, "reason:NATIVE");
assertContains(output, "(Native Method)");
}
/**
* Test parking in class initializer.
*/
@Test
void testPinnedCausedByClassInitializer() throws Exception {
class C {
static {
park();
}
}
String output = run(C::new);
assertContains(output, "reason:NATIVE");
assertContains(output, "<clinit>");
}
/**
* Test contention writing to System.out when pinned. The test creates four threads
* that write to System.out when pinned, this is enough to potentially deadlock
* without the changes in JDK-8322846.
*/
@Test
void testContention() throws Exception {
// use several classes to avoid duplicate stack traces
class C1 {
synchronized void print() {
System.out.println("hello");
}
}
class C2 {
synchronized void print() {
System.out.println("hello");
}
}
class C3 {
synchronized void print() {
System.out.println("hello");
}
}
class C4 {
synchronized void print() {
System.out.println("hello");
}
}
try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
executor.submit(() -> {
new C1().print();
});
executor.submit(() -> {
new C2().print();
});
executor.submit(() -> {
new C3().print();
});
executor.submit(() -> {
new C4().print();
});
}
}
/**
* Run a task in a virtual thread, returning a String with any output printed
* to standard output.
*/
private static String run(Runnable task) throws Exception {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
PrintStream original = System.out;
System.setOut(new PrintStream(baos, true));
try {
VThreadRunner.run(task::run);
} finally {
System.setOut(original);
}
String output = new String(baos.toByteArray());
System.out.println(output);
return output;
}
/**
* Tests that s1 contains s2.
*/
private static void assertContains(String s1, String s2) {
assertTrue(s1.contains(s2), s2 + " not found!!!");
}
/**
* Tests that s1 does not contain s2.
*/
private static void assertDoesNotContain(String s1, String s2) {
assertFalse(s1.contains(s2), s2 + " found!!");
}
}
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