About JDK-6772009

[chen zero]

Hi David,
Thank you for reminding.
I post the code here.


import java.util.Arrays;
import java.util.Collections;
import java.util.Random;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.locks.ReentrantLock;

// https://bugs.openjdk.java.net/browse/JDK-6772009

public final class CancelledLockLoops {
    static final Random rng = new Random();
    static boolean print = false;
    //static final int ITERS = 1000000;
    static final int ITERS = 10000000;

    static final long TIMEOUT = 100;

    public static void main(String[] args) throws Exception {
        int maxThreads = 5;
        if (args.length > 0) {
            maxThreads = Integer.parseInt(args[0]);
        }

        print = true;

        for (int i = 2; i <= maxThreads; i += (i+1) >>> 1) {
            System.out.print("Threads: " + i);

            try {
                new ReentrantLockLoop(i).test();
            }
            catch (BrokenBarrierException bb) {
                // OK, ignore
                bb.printStackTrace();
            }
            Thread.sleep(TIMEOUT);
        }
    }

    static final class ReentrantLockLoop implements Runnable {
        private int v = rng.nextInt();
        private int completed;
        private volatile int result = 17;
        private final ReentrantLock lock = new ReentrantLock();
        private final LoopHelpers.BarrierTimer timer = new
LoopHelpers.BarrierTimer();
        private final CyclicBarrier barrier;
        private final int nthreads;

        ReentrantLockLoop(int nthreads) {
            this.nthreads = nthreads;
            barrier = new CyclicBarrier(nthreads+1, timer);
        }

        void checkBarrierStatus() {
            if(this.barrier.isBroken()) {
                throw new Error("barrier is broken !!!");
            }
        }

        final void test() throws Exception {
            checkBarrierStatus();

            timer.run();

            Thread[] threads = new Thread[nthreads];
            for (int i = 0; i < threads.length; ++i) {
                threads[i] = new Thread(this, "th"+i);
            }

            for (int i = 0; i < threads.length; ++i) {
                threads[i].start();
            }

            Thread[] cancels =  (Thread[])(threads.clone());

            Collections.shuffle(Arrays.asList(cancels), rng);
            Thread.sleep(TIMEOUT);
            for (int i = 0; i < cancels.length-2; ++i) {
                cancels[i].interrupt();
                // make sure all OK even when cancellations spaced out
                if ((i & 3) == 0) {
                    Thread.sleep(1 + rng.nextInt(10));
                }
            }

            Thread.sleep(TIMEOUT);

            try {
                // in here, the barrier might be broken because some
working threads is interrupted.
                // so, catching the BrokenBarrierException to let testcase
continue running
                barrier.await();
            }
            catch(BrokenBarrierException e) {
                // nop
            }

            if (print) {
                // since the barrier might be broken ( the barrier action
will not run),
                // running here to ensure time is set.
                timer.run();
                long time = timer.getTime();
                double secs = (double)(time) / 1000000000.0;
                System.out.println("\t " + secs + "s run time");
            }

            int c;
            lock.lock();
            //System.out.println("main to verify completed.....");

            try {
                c = completed;
            }
            finally {
                lock.unlock();
            }
            // here the completed should not < 2, it can not guarantee that
always == 2.
            if (c < 2) {
                throw new Error("Completed < 2 : " + c);
            }

            int r = result;
            if (r == 0) { // avoid overoptimization
                System.out.println("useless result: " + r);
            }
        }

        public final void run() {
            try {
                checkBarrierStatus();

                int sum = v;
                int x = 0;
                int n = ITERS;
                do {
                    try {
                        lock.lockInterruptibly();
                    }
                    catch (InterruptedException ie) {
                        break;
                    }
                    try {
                        v = x = LoopHelpers.compute1(v);
                    }
                    finally {
                        lock.unlock();
                    }
                    sum += LoopHelpers.compute2(x);
                } while (n-- > 0);

                /*
                 * in the main thread, two threads are un-interrupted,
others threads are interrupted.
                 * this line, however, can not guarantee that only
"un-interrupted" threads can go in,
                 * but also interrupted threads can go in,
                 * so, the "completed" will not always == 2, might be > 2
                 */
                if (n < 0) {
                    lock.lock();
                    try {
                        ++completed;
                    }
                    finally {
                        lock.unlock();
                    }
                }

                result += sum;
                barrier.await();
            }
            catch(BrokenBarrierException ex) {
                //ex.printStackTrace();
            }
            catch(InterruptedException ex) {
                //ex.printStackTrace();
            }
            catch (Exception ex) {
                ex.printStackTrace();
                return;
            }
        }
    }

}


On Thu, Jan 5, 2017 at 12:20 PM, David Holmes <david.holmes at oracle.com>
wrote:

> Hi chenzero,
>
> Attachments get stripped from the mailing lists so you'll need to include
> your patch inline, or else get someone to host it for you on
> cr.openjdk.java.net
>
> Thanks,
> David
> .....
>