code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.concurrent.CyclicBarrier;
  
  /*
   * Copyright 2005-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
   * CA 95054 USA or visit www.sun.com if you need additional information or
   * have any questions.
   */
  
  /*
   * @test
   * @bug 6253848 6366811
   * @summary Basic tests for CyclicBarrier
   * @author Martin Buchholz, David Holmes
   */
  
  import java.util.*;
  import java.util.concurrent.*;
  import java.util.concurrent.atomic.AtomicInteger;
  import static java.util.concurrent.TimeUnit.*;
  
  public class Basic {
  
      private static void checkBroken(final CyclicBarrier barrier) {
          check(barrier.isBroken());
          equal(barrier.getNumberWaiting(), 0);
  
          THROWS(BrokenBarrierException.class,
                 new Fun() { public void f() throws Throwable {
                     barrier.await(); }},
                 new Fun() { public void f() throws Throwable {
                     barrier.await(100, MILLISECONDS); }});
      }
  
      private static void reset(CyclicBarrier barrier) {
          barrier.reset();
          check(! barrier.isBroken());
          equal(barrier.getNumberWaiting(), 0);
      }
  
      private static void checkResult(Awaiter a, Class<? extends Throwable> c) {
          Throwable t = a.result();
          if (! ((t == null && c == null) || (c != null && c.isInstance(t)))) {
              //      t.printStackTrace();
              fail("Mismatch in thread " +
                   a.getName() + ": " +
                   t + ", " +
                   (c == null ? "<null>" : c.getName()));
          } else {
              pass();
          }
      }
  
      //----------------------------------------------------------------
      // Mechanism to get all victim threads into "running" mode.
      // The fact that this also uses CyclicBarrier is entirely coincidental.
      //----------------------------------------------------------------
      private static final CyclicBarrier atTheStartingGate = new CyclicBarrier(3);
  
      private static void toTheStartingGate() {
          try { atTheStartingGate.await(10, SECONDS); pass(); }
          catch (Throwable t) {
              unexpected(t);
              reset(atTheStartingGate);
              throw new Error(t);
          }
      }
  
      //----------------------------------------------------------------
      // Convenience methods for creating threads that call CyclicBarrier.await
      //----------------------------------------------------------------
      private static abstract class Awaiter extends Thread {
          static AtomicInteger count = new AtomicInteger(1);
  
          {
              this.setName("Awaiter:"+count.getAndIncrement());
              this.setDaemon(true);
          }
  
          private volatile Throwable result = null;
          protected void result(Throwable result) { this.result = result; }
          public Throwable result() { return this.result; }
      }
  
      private static Awaiter awaiter(final CyclicBarrier barrier) {
          return new Awaiter() { public void run() {
              toTheStartingGate();
  
              try { barrier.await(); }
              catch (Throwable result) { result(result); }}};
      }
  
      private static Awaiter awaiter(final CyclicBarrier barrier,
                                     final long millis) {
          return new Awaiter() { public void run() {
              toTheStartingGate();
  
              try { barrier.await(millis, MILLISECONDS); }
              catch (Throwable result) { result(result); }}};
      }
  
      // Returns an infinite lazy list of all possible awaiter pair combinations.
      private static Iterator<Awaiter> awaiterIterator(final CyclicBarrier barrier) {
          return new Iterator<Awaiter>() {
              int i = 0;
              public boolean hasNext() { return true; }
              public Awaiter next() {
                  switch ((i++)&7) {
                  case 0: case 2: case 4: case 5:
                      return awaiter(barrier);
                  default:
                      return awaiter(barrier, 10 * 1000); }}
              public void remove() {throw new UnsupportedOperationException();}};
      }
  
      private static void realMain(String[] args) throws Throwable {
  
          Thread.currentThread().setName("mainThread");
  
          //----------------------------------------------------------------
          // Normal use
          //----------------------------------------------------------------
          try {
              CyclicBarrier barrier = new CyclicBarrier(3);
              equal(barrier.getParties(), 3);
              Iterator<Awaiter> awaiters = awaiterIterator(barrier);
              for (boolean doReset : new boolean[] {false, true})
                  for (int i = 0; i < 4; i++) {
                      Awaiter a1 = awaiters.next(); a1.start();
                      Awaiter a2 = awaiters.next(); a2.start();
                      toTheStartingGate();
                      barrier.await();
                      a1.join();
                      a2.join();
                      checkResult(a1, null);
                      checkResult(a2, null);
                      check(! barrier.isBroken());
                      equal(barrier.getParties(), 3);
                      equal(barrier.getNumberWaiting(), 0);
                      if (doReset) reset(barrier);
                  }
          } catch (Throwable t) { unexpected(t); }
  
          //----------------------------------------------------------------
          // One thread interrupted
          //----------------------------------------------------------------
          try {
              CyclicBarrier barrier = new CyclicBarrier(3);
              Iterator<Awaiter> awaiters = awaiterIterator(barrier);
              for (int i = 0; i < 4; i++) {
                  Awaiter a1 = awaiters.next(); a1.start();
                  Awaiter a2 = awaiters.next(); a2.start();
                  toTheStartingGate();
                  a1.interrupt();
                  a1.join();
                  a2.join();
                  checkResult(a1, InterruptedException.class);
                  checkResult(a2, BrokenBarrierException.class);
                  checkBroken(barrier);
                  reset(barrier);
              }
          } catch (Throwable t) { unexpected(t); }
  
          //----------------------------------------------------------------
          // Barrier is reset while threads are waiting
          //----------------------------------------------------------------
          try {
              CyclicBarrier barrier = new CyclicBarrier(3);
              Iterator<Awaiter> awaiters = awaiterIterator(barrier);
              for (int i = 0; i < 4; i++) {
                  Awaiter a1 = awaiters.next(); a1.start();
                  Awaiter a2 = awaiters.next(); a2.start();
                  toTheStartingGate();
                  while (barrier.getNumberWaiting() < 2) Thread.yield();
                  barrier.reset();
                  a1.join();
                  a2.join();
                  checkResult(a1, BrokenBarrierException.class);
                  checkResult(a2, BrokenBarrierException.class);
                  check(! barrier.isBroken());
                  equal(barrier.getParties(), 3);
                  equal(barrier.getNumberWaiting(), 0);
              }
          } catch (Throwable t) { unexpected(t); }
  
          //----------------------------------------------------------------
          // One thread timed out
          //----------------------------------------------------------------
          try {
              CyclicBarrier barrier = new CyclicBarrier(3);
              Iterator<Awaiter> awaiters = awaiterIterator(barrier);
              for (long timeout : new long[] { 0L, 10L }) {
                  for (int i = 0; i < 2; i++) {
                      Awaiter a1 = awaiter(barrier, timeout); a1.start();
                      Awaiter a2 = awaiters.next();           a2.start();
                      toTheStartingGate();
                      a1.join();
                      a2.join();
                      checkResult(a1, TimeoutException.class);
                      checkResult(a2, BrokenBarrierException.class);
                      checkBroken(barrier);
                      equal(barrier.getParties(), 3);
                      reset(barrier);
                  }
              }
          } catch (Throwable t) { unexpected(t); }
  
          //----------------------------------------------------------------
          // Barrier action completed normally
          //----------------------------------------------------------------
          try {
              final AtomicInteger count = new AtomicInteger(0);
              final CyclicBarrier[] kludge = new CyclicBarrier[1];
              Runnable action = new Runnable() { public void run() {
                  count.incrementAndGet();
                  equal(kludge[0].getNumberWaiting(),
                        kludge[0].getParties());
                  System.out.println("OK!"); }};
              CyclicBarrier barrier = new CyclicBarrier(3, action);
              kludge[0] = barrier;
              equal(barrier.getParties(), 3);
              Iterator<Awaiter> awaiters = awaiterIterator(barrier);
              for (int i = 0; i < 4; i++) {
                  Awaiter a1 = awaiters.next(); a1.start();
                  Awaiter a2 = awaiters.next(); a2.start();
                  toTheStartingGate();
                  while (barrier.getNumberWaiting() < 2) Thread.yield();
                  try { barrier.await(); }
                  catch (Throwable t) { unexpected(t); }
                  a1.join();
                  a2.join();
                  checkResult(a1, null);
                  checkResult(a2, null);
                  check(! barrier.isBroken());
                  equal(barrier.getNumberWaiting(), 0);
                  reset(barrier);
                  equal(count.get(), i+1);
              }
          } catch (Throwable t) { unexpected(t); }
  
          //----------------------------------------------------------------
          // Barrier action threw exception
          //----------------------------------------------------------------
          try {
              Runnable action = new Runnable() {
                      public void run() { throw new Error(); }};
              CyclicBarrier barrier = new CyclicBarrier(3, action);
              Iterator<Awaiter> awaiters = awaiterIterator(barrier);
              for (int i = 0; i < 4; i++) {
                  Awaiter a1 = awaiters.next(); a1.start();
                  Awaiter a2 = awaiters.next(); a2.start();
                  toTheStartingGate();
                  while (barrier.getNumberWaiting() < 2) Thread.yield();
                  try {
                      barrier.await();
                      fail("Expected Error not thrown"); }
                  catch (Error e) { pass(); }
                  catch (Throwable t) { unexpected(t); }
                  a1.join();
                  a2.join();
                  checkResult(a1, BrokenBarrierException.class);
                  checkResult(a2, BrokenBarrierException.class);
                  checkBroken(barrier);
                  reset(barrier);
              }
          } catch (Throwable t) { unexpected(t); }
  
          testInterrupts();
      }
  
      /**
       * Handling of extra interrupts while waiting - tests for bug 6366811
       */
      private static void testInterrupts() {
          final int N = 10;
          final CyclicBarrier startingGate = new CyclicBarrier(N+1);
  
          /**
           * A version of Awaiter that also records interrupted state.
           */
          class Waiter extends CheckedThread {
              private boolean timed;
              private CyclicBarrier barrier;
              private CountDownLatch doneSignal;
              private Throwable throwable;
              private boolean interrupted;
  
              public Waiter(boolean timed,
                            CountDownLatch doneSignal,
                            CyclicBarrier barrier) {
                  this.timed = timed;
                  this.doneSignal = doneSignal;
                  this.barrier = barrier;
              }
              Throwable throwable() { return this.throwable; }
              boolean interruptBit() { return this.interrupted; }
              void realRun() throws Throwable {
                  startingGate.await(10, SECONDS);
                  try {
                      if (timed) barrier.await(10, SECONDS);
                      else barrier.await(); }
                  catch (Throwable throwable) { this.throwable = throwable; }
  
                  try { doneSignal.await(10, SECONDS); }
                  catch (InterruptedException e) { interrupted = true; }
              }
          }
  
          //----------------------------------------------------------------
          // Interrupt occurs during barrier trip
          //----------------------------------------------------------------
          try {
              final CountDownLatch doneSignal = new CountDownLatch(1);
              final List<Waiter> waiters = new ArrayList<Waiter>(N);
  
              // work around finality of closed-over variables
              final Runnable[] realAction = new Runnable[1];
              final Runnable delegateAction =
                  new Runnable() {public void run() {realAction[0].run();}};
              final CyclicBarrier barrier = new CyclicBarrier(N+1, delegateAction);
  
              realAction[0] = new Runnable() { public void run() {
                  try {
                      for (int i = 0; i < N/2; i++)
                          waiters.get(i).interrupt();
                      // we need to try and ensure that the waiters get
                      // to process their interruption before we do the
                      // signalAll that trips the barrier. Using sleep
                      // seems to work reliably while yield does not.
                      Thread.sleep(100);
                  } catch (Throwable t) { unexpected(t); }
              }};
              for (int i = 0; i < N; i++) {
                  Waiter waiter = new Waiter(i < N/2, doneSignal, barrier);
                  waiter.start();
                  waiters.add(waiter);
              }
              startingGate.await(10, SECONDS);
              while (barrier.getNumberWaiting() < N) Thread.yield();
              barrier.await();
              doneSignal.countDown();
              int countInterrupted = 0;
              int countInterruptedException = 0;
              int countBrokenBarrierException = 0;
              for (Waiter waiter : waiters) {
                  waiter.join();
                  equal(waiter.throwable(), null);
                  if (waiter.interruptBit())
                      countInterrupted++;
              }
              equal(countInterrupted, N/2);
              check(! barrier.isBroken());
          } catch (Throwable t) { unexpected(t); }
  
          //----------------------------------------------------------------
          // Multiple interrupts occur during barrier await
          //----------------------------------------------------------------
          try {
              final CountDownLatch doneSignal = new CountDownLatch(1);
              final CyclicBarrier barrier = new CyclicBarrier(N+1);
              final List<Waiter> waiters = new ArrayList<Waiter>(N);
              for (int i = 0; i < N; i++) {
                  Waiter waiter = new Waiter(i < N/2, doneSignal, barrier);
                  waiter.start();
                  waiters.add(waiter);
              }
              startingGate.await(10, SECONDS);
              while (barrier.getNumberWaiting() < N) Thread.yield();
              for (int i = 0; i < N/2; i++)
                  waiters.get(i).interrupt();
              doneSignal.countDown();
              int countInterrupted = 0;
              int countInterruptedException = 0;
              int countBrokenBarrierException = 0;
              for (Waiter waiter : waiters) {
                  waiter.join();
                  if (waiter.throwable() instanceof InterruptedException)
                      countInterruptedException++;
                  if (waiter.throwable() instanceof BrokenBarrierException)
                      countBrokenBarrierException++;
                  if (waiter.interruptBit())
                      countInterrupted++;
              }
              equal(countInterrupted, N/2-1);
              equal(countInterruptedException, 1);
              equal(countBrokenBarrierException, N-1);
              checkBroken(barrier);
              reset(barrier);
          } catch (Throwable t) { unexpected(t); }
      }
  
      //--------------------- Infrastructure ---------------------------
      static volatile int passed = 0, failed = 0;
      static void pass() {passed++;}
      static void fail() {failed++; Thread.dumpStack();}
      static void fail(String msg) {System.out.println(msg); fail();}
      static void unexpected(Throwable t) {failed++; t.printStackTrace();}
      static void check(boolean cond) {if (cond) pass(); else fail();}
      static void equal(Object x, Object y) {
          if (x == null ? y == null : x.equals(y)) pass();
          else fail(x + " not equal to " + y);}
      public static void main(String[] args) throws Throwable {
          try {realMain(args);} catch (Throwable t) {unexpected(t);}
          System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
          if (failed > 0) throw new AssertionError("Some tests failed");}
      static abstract class Fun { abstract void f() throws Throwable; }
      private static void THROWS(Class<? extends Throwable> k, Fun... fs) {
          for (Fun f : fs)
              try { f.f(); fail("Expected " + k.getName() + " not thrown"); }
              catch (Throwable t) {
                  if (k.isAssignableFrom(t.getClass())) pass();
                  else unexpected(t);}}
      private static abstract class CheckedThread extends Thread {
          abstract void realRun() throws Throwable;
          public void run() {
              try {realRun();} catch (Throwable t) {unexpected(t);}}}
  }
  