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/*
* @test
* @bug 4892507 8020875 8021335
* @summary Basic Test for the following reset methods:
* - ThreadMXBean.resetPeakThreadCount()
* @author Mandy Chung
* @author Jaroslav Bachorik
*
* @modules java.management
* @build ResetPeakThreadCount
* @build ThreadDump
* @run main/othervm ResetPeakThreadCount
*/
import java.lang.management.*;
public class ResetPeakThreadCount {
// initial number of new threads started
private static final int DAEMON_THREADS_1 = 8;
private static final int EXPECTED_PEAK_DELTA_1 = 8;
// Terminate half of the threads started
private static final int TERMINATE_1 = 4;
// start new threads but expected the peak unchanged
private static final int DAEMON_THREADS_2 = 2;
private static final int EXPECTED_PEAK_DELTA_2 = 0;
// peak thread count reset before starting new threads
private static final int DAEMON_THREADS_3 = 4;
private static final int EXPECTED_PEAK_DELTA_3 = 4;
private static final int TERMINATE_2 = 8;
private static final int TERMINATE_3 = 2;
private static final int ALL_THREADS = DAEMON_THREADS_1 +
DAEMON_THREADS_2 + DAEMON_THREADS_3;
// barrier for threads communication
private static final Barrier barrier = new Barrier(DAEMON_THREADS_1);
private static final Thread allThreads[] = new Thread[ALL_THREADS];
private static final boolean live[] = new boolean[ALL_THREADS];
private static final ThreadMXBean mbean = ManagementFactory.getThreadMXBean();
private static volatile boolean testFailed = false;
public static void main(String[] argv) throws Exception {
// This test does not expect any threads to be created
// by the test harness after main() is invoked.
// The checkThreadCount() method is to produce more
// diagnostic information in case any unexpected test failure occur.
long previous = mbean.getThreadCount();
long current = previous;
// reset the peak to start from a scratch
resetPeak(current);
// start DAEMON_THREADS_1 number of threads
current = startThreads(0, DAEMON_THREADS_1, EXPECTED_PEAK_DELTA_1);
checkThreadCount(previous, current, DAEMON_THREADS_1);
previous = current;
// terminate TERMINATE_1 number of threads and reset peak
current = terminateThreads(0, TERMINATE_1);
checkThreadCount(previous, current, TERMINATE_1 * -1);
previous = current;
// start DAEMON_THREADS_2 number of threads
// expected peak is unchanged
current = startThreads(DAEMON_THREADS_1, DAEMON_THREADS_2,
EXPECTED_PEAK_DELTA_2);
checkThreadCount(previous, current, DAEMON_THREADS_2);
previous = current;
// Reset the peak
resetPeak(current);
// start DAEMON_THREADS_3 number of threads
current = startThreads(DAEMON_THREADS_1 + DAEMON_THREADS_2,
DAEMON_THREADS_3, EXPECTED_PEAK_DELTA_3);
checkThreadCount(previous, current, DAEMON_THREADS_3);
previous = current;
// terminate TERMINATE_2 number of threads and reset peak
current = terminateThreads(TERMINATE_1, TERMINATE_2);
checkThreadCount(previous, current, TERMINATE_2 * -1);
previous = current;
resetPeak(current);
// terminate TERMINATE_3 number of threads and reset peak
current = terminateThreads(TERMINATE_1 + TERMINATE_2, TERMINATE_3);
checkThreadCount(previous, current, TERMINATE_3 * -1);
resetPeak(current);
if (testFailed)
throw new RuntimeException("TEST FAILED.");
System.out.println("Test passed");
}
private static long startThreads(int from, int count, int delta) throws InterruptedException {
// get current peak thread count
long peak1 = mbean.getPeakThreadCount();
long current = mbean.getThreadCount();
// Start threads and wait to be sure they all are alive
System.out.println("Starting " + count + " threads....");
barrier.set(count);
synchronized(live) {
for (int i = from; i < (from + count); i++) {
live[i] = true;
allThreads[i] = new MyThread(i);
allThreads[i].setDaemon(true);
allThreads[i].start();
}
}
// wait until all threads have started.
barrier.await();
// get peak thread count after daemon threads have started
long peak2 = mbean.getPeakThreadCount();
System.out.println(" Current = " + mbean.getThreadCount() +
" Peak before = " + peak1 + " after: " + peak2);
if (peak2 != (peak1 + delta)) {
throw new RuntimeException("Current Peak = " + peak2 +
" Expected to be == previous peak = " + peak1 + " + " +
delta);
}
// wait until the current thread count gets incremented
while (mbean.getThreadCount() < (current + count)) {
Thread.sleep(100);
}
current = mbean.getThreadCount();
System.out.println(" Live thread count before returns " + current);
return current;
}
private static long terminateThreads(int from, int count) throws InterruptedException {
// get current peak thread count
long peak1 = mbean.getPeakThreadCount();
// Stop daemon threads and wait to be sure they all are dead
System.out.println("Terminating " + count + " threads....");
barrier.set(count);
synchronized(live) {
for (int i = from; i < (from+count); i++) {
live[i] = false;
}
live.notifyAll();
}
// wait until daemon threads terminated.
barrier.await();
// get peak thread count after daemon threads have terminated
long peak2 = mbean.getPeakThreadCount();
// assuming no system thread is added
if (peak2 != peak1) {
throw new RuntimeException("Current Peak = " + peak2 +
" Expected to be = previous peak = " + peak1);
}
for (int i = from; i < (from+count); i++) {
allThreads[i].join();
}
// there is a race in the counter update logic somewhere causing
// the thread counters go ff
// we need to give the terminated threads some extra time to really die
// JDK-8021335
Thread.sleep(500);
long current = mbean.getThreadCount();
System.out.println(" Live thread count before returns " + current);
return current;
}
private static void resetPeak(long expectedCount) {
long peak3 = mbean.getPeakThreadCount();
long current = mbean.getThreadCount();
// Nightly testing showed some intermittent failure.
// Check here to get diagnostic information if some strange
// behavior occurs.
checkThreadCount(expectedCount, current, 0);
// Reset peak thread count
mbean.resetPeakThreadCount();
long afterResetPeak = mbean.getPeakThreadCount();
long afterResetCurrent = mbean.getThreadCount();
System.out.println("Reset peak before = " + peak3 +
" current = " + current +
" after reset peak = " + afterResetPeak +
" current = " + afterResetCurrent);
if (afterResetPeak != current) {
throw new RuntimeException("Current Peak after reset = " +
afterResetPeak +
" Expected to be = current count = " + current);
}
}
private static void checkThreadCount(long previous, long current, int expectedDelta) {
if (current != previous + expectedDelta) {
ThreadDump.threadDump();
throw new RuntimeException("***** Unexpected thread count:" +
" previous = " + previous +
" current = " + current +
" delta = " + expectedDelta + "*****");
}
}
// The MyThread thread lives as long as correspondent live[i] value is true
private static class MyThread extends Thread {
int id;
MyThread(int id) {
this.id = id;
}
public void run() {
// signal started
barrier.signal();
synchronized(live) {
while (live[id]) {
try {
live.wait(100);
} catch (InterruptedException e) {
System.out.println("Unexpected exception is thrown.");
e.printStackTrace(System.out);
testFailed = true;
}
}
}
// signal about to exit
barrier.signal();
}
}
}