jdk-24/jdk/test/java/nio/channels/Selector/Wakeup.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
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 * 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.
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 * questions.
 */

/* @test
 * @bug 6405995
 * @summary Unit test for selector wakeup and interruption
 * @library ..
 */

import java.io.*;
import java.net.*;
import java.nio.*;
import java.nio.channels.*;
import java.util.Random;

public class Wakeup {

    static void sleep(int millis) {
        try {
            Thread.sleep(millis);
        } catch (InterruptedException x) {
            x.printStackTrace();
        }
    }

    static class Sleeper extends TestThread {
        volatile boolean started = false;
        volatile int entries = 0;
        volatile int wakeups = 0;
        volatile boolean wantInterrupt = false;
        volatile boolean gotInterrupt = false;
        volatile Exception exception = null;
        volatile boolean closed = false;
        Object gate = new Object();

        Selector sel;

        Sleeper(Selector sel) {
            super("Sleeper", System.err);
            this.sel = sel;
        }

        public void go() throws Exception {
            started = true;
            for (;;) {
                synchronized (gate) { }
                entries++;
                try {
                    sel.select();
                } catch (ClosedSelectorException x) {
                    closed = true;
                }
                boolean intr = Thread.currentThread().isInterrupted();
                wakeups++;
                System.err.println("Wakeup " + wakeups
                                   + (closed ? " (closed)" : "")
                                   + (intr ? " (intr)" : ""));
                if (wakeups > 1000)
                    throw new Exception("Too many wakeups");
                if (closed)
                    return;
                if (wantInterrupt) {
                    while (!Thread.interrupted())
                        Thread.yield();
                    gotInterrupt = true;
                    wantInterrupt = false;
                }
            }
        }

    }

    private static int checkedWakeups = 0;

    private static void check(Sleeper sleeper, boolean intr)
        throws Exception
    {
        checkedWakeups++;
        if (sleeper.wakeups > checkedWakeups) {
            sleeper.finish(100);
            throw new Exception("Sleeper has run ahead");
        }
        int n = 0;
        while (sleeper.wakeups < checkedWakeups) {
            sleep(50);
            if ((n += 50) > 1000) {
                sleeper.finish(100);
                throw new Exception("Sleeper appears to be dead ("
                                    + checkedWakeups + ")");
            }
        }
        if (sleeper.wakeups > checkedWakeups) {
            sleeper.finish(100);
            throw new Exception("Too many wakeups: Expected "
                                + checkedWakeups
                                + ", got " + sleeper.wakeups);
        }
        if (intr) {
            n = 0;
            // Interrupts can sometimes be delayed, so wait
            while (!sleeper.gotInterrupt) {
                sleep(50);
                if ((n += 50) > 1000) {
                    sleeper.finish(100);
                    throw new Exception("Interrupt never delivered");
                }
            }
            sleeper.gotInterrupt = false;
        }
        System.err.println("Check " + checkedWakeups
                           + (intr ? " (intr " + n + ")" : ""));
    }

    public static void main(String[] args) throws Exception {

        Selector sel = Selector.open();

        // Wakeup before select
        sel.wakeup();

        Sleeper sleeper = new Sleeper(sel);

        sleeper.start();
        while (!sleeper.started)
            sleep(50);

        check(sleeper, false);          // 1

        for (int i = 2; i < 5; i++) {
            // Wakeup during select
            sel.wakeup();
            check(sleeper, false);      // 2 .. 4
        }

        // Double wakeup
        synchronized (sleeper.gate) {
            sel.wakeup();
            check(sleeper, false);      // 5
            sel.wakeup();
            sel.wakeup();
        }
        check(sleeper, false);          // 6

        // Interrupt
        synchronized (sleeper.gate) {
            sleeper.wantInterrupt = true;
            sleeper.interrupt();
            check(sleeper, true);       // 7
        }

        // Interrupt before select
        while (sleeper.entries < 8)
            Thread.yield();
        synchronized (sleeper.gate) {
            sel.wakeup();
            check(sleeper, false);      // 8
            sleeper.wantInterrupt = true;
            sleeper.interrupt();
            sleep(50);
        }
        check(sleeper, true);           // 9

        // Close during select
        while (sleeper.entries < 10)
            Thread.yield();
        synchronized (sleeper.gate) {
            sel.close();
            check(sleeper, false);      // 10
        }

        if (sleeper.finish(200) == 0)
            throw new Exception("Test failed");
        if (!sleeper.closed)
            throw new Exception("Selector not closed");
    }

}