Quelle  SuspendAtExit.java

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 *
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/**
 * @test
 * @bug 8167108 8265240 8286830
 * @summary Stress test SuspendThread at thread exit.
 * @requires vm.jvmti
 * @run main/othervm/native -agentlib:SuspendAtExit SuspendAtExit
 * @run main/othervm/native -agentlib:SuspendAtExit -XX:+UnlockDiagnosticVMOptions -XX:GuaranteedSafepointInterval=1 -XX:+HandshakeALot SuspendAtExit
 */

import java.util.concurrent.CountDownLatch;

public class SuspendAtExit extends Thread {
    private final static String AGENT_LIB = "SuspendAtExit";
    private final static int DEF_TIME_MAX = 30;  // default max # secs to test
    private final static int JVMTI_ERROR_THREAD_NOT_ALIVE = 15;

    public CountDownLatch exitSyncObj = new CountDownLatch(1);
    public CountDownLatch startSyncObj = new CountDownLatch(1);

    private static void log(String msg) { System.out.println(msg); }

    native static int resumeThread(SuspendAtExit thr);
    native static int suspendThread(SuspendAtExit thr);

    @Override
    public void run() {
        // Tell main thread we have started.
        startSyncObj.countDown();
        try {
            // Wait for main thread to tell us to race to the exit.
            exitSyncObj.await();
        } catch (InterruptedException e) {
            throw new RuntimeException("Unexpected: " + e);
        }
    }

    public static void main(String[] args) {
        try {
            System.loadLibrary(AGENT_LIB);
            log("Loaded library: " + AGENT_LIB);
        } catch (UnsatisfiedLinkError ule) {
            log("Failed to load library: " + AGENT_LIB);
            log("java.library.path: " + System.getProperty("java.library.path"));
            throw ule;
        }

        int timeMax = 0;
        if (args.length == 0) {
            timeMax = DEF_TIME_MAX;
        } else {
            try {
                timeMax = Integer.parseUnsignedInt(args[0]);
            } catch (NumberFormatException nfe) {
                System.err.println("'" + args[0] + "': invalid timeMax value.");
                    usage();
            }
        }
        timeMax /= 2;  // Split time between the two sub-tests.

        test(timeMax);

        // Fire-up deamon that just creates new threads. This generates contention on
        // Threads_lock while worker tries to exit, creating more places where target
        // can be seen as handshake safe.
        Thread threadCreator = new Thread() {
            @Override
            public void run() {
                while (true) {
                    Thread dummyThread = new Thread(() -> {});
                    dummyThread.start();
                    try {
                        dummyThread.join();
                    } catch(InterruptedException ie) {
                    }
                }
            }
        };
        threadCreator.setDaemon(true);
        threadCreator.start();
        test(timeMax);
    }

    public static void test(int timeMax) {
        System.out.println("About to execute for " + timeMax + " seconds.");

        long count = 0;
        long start_time = System.currentTimeMillis();
        while (System.currentTimeMillis() < start_time + (timeMax * 1000)) {
            count++;

            int retCode;
            SuspendAtExit thread = new SuspendAtExit();
            thread.start();
            try {
                // Wait for the worker thread to get going.
                thread.startSyncObj.await();
                // Tell the worker thread to race to the exit and the
                // SuspendThread() calls will come in during thread exit.
                thread.exitSyncObj.countDown();
                while (true) {
                    retCode = suspendThread(thread);

                    if (retCode == JVMTI_ERROR_THREAD_NOT_ALIVE) {
                        // Done with SuspendThread() calls since
                        // thread is not alive.
                        break;
                    } else if (retCode != 0) {
                        throw new RuntimeException("thread " + thread.getName()
                                                   + ": suspendThread() " +
                                                   "retCode=" + retCode +
                                                   ": unexpected value.");
                    }

                    if (!thread.isAlive()) {
                        throw new RuntimeException("thread " + thread.getName()
                                                   + ": is not alive " +
                                                   "after successful " +
                                                   "suspendThread().");
                    }
                    retCode = resumeThread(thread);
                    if (retCode != 0) {
                        throw new RuntimeException("thread " + thread.getName()
                                                   + ": resumeThread() " +
                                                   "retCode=" + retCode +
                                                   ": unexpected value.");
                    }
                }
            } catch (InterruptedException e) {
                throw new RuntimeException("Unexpected: " + e);
            }

            try {
                thread.join();
            } catch (InterruptedException e) {
                throw new RuntimeException("Unexpected: " + e);
            }
            retCode = suspendThread(thread);
            if (retCode != JVMTI_ERROR_THREAD_NOT_ALIVE) {
                throw new RuntimeException("thread " + thread.getName() +
                                           ": suspendThread() " +
                                           "retCode=" + retCode +
                                           ": unexpected value.");
            }
            retCode = resumeThread(thread);
            if (retCode != JVMTI_ERROR_THREAD_NOT_ALIVE) {
                throw new RuntimeException("thread " + thread.getName() +
                                           ": suspendThread() " +
                                           "retCode=" + retCode +
                                           ": unexpected value.");
            }
        }

        System.out.println("Executed " + count + " loops in " + timeMax +
                           " seconds.");

        String cmd = System.getProperty("sun.java.command");
        if (cmd != null && !cmd.startsWith("com.sun.javatest.regtest.agent.MainWrapper")) {
            // Exit with success in a non-JavaTest environment:
            System.exit(0);
        }
    }

    public static void usage() {
        System.err.println("Usage: " + AGENT_LIB + " [time_max]");
        System.err.println("where:");
        System.err.println("    time_max ::= max looping time in seconds");
        System.err.println("                 (default is " + DEF_TIME_MAX +
                           " seconds)");
        System.exit(1);
    }
}