8145138: CyclicBarrier/Basic.java failed with "3 not equal to 4"
Reviewed-by: martin, alanb
/*
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*
* 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
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*
* This code is distributed in the hope that it will be useful, but WITHOUT
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* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 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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*/
/*
* @test
* @bug 6253848 6366811
* @summary Basic tests for CyclicBarrier
* @library /test/lib
* @author Martin Buchholz, David Holmes
*/
import static java.util.concurrent.TimeUnit.MILLISECONDS;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicInteger;
import jdk.test.lib.Utils;
public class Basic {
static final long LONG_DELAY_MS = Utils.adjustTimeout(10_000);
private static void checkBroken(final CyclicBarrier barrier) {
check(barrier.isBroken());
equal(barrier.getNumberWaiting(), 0);
THROWS(BrokenBarrierException.class,
() -> barrier.await(),
() -> 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(LONG_DELAY_MS, MILLISECONDS); pass(); }
catch (Throwable t) {
unexpected(t);
reset(atTheStartingGate);
throw new Error(t);
}
}
//----------------------------------------------------------------
// Convenience methods for creating threads that call CyclicBarrier.await
//----------------------------------------------------------------
private abstract static 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 = ThreadLocalRandom.current().nextInt(2, 10);
final CyclicBarrier startingGate = new CyclicBarrier(N+1);
/**
* A version of Awaiter that also records interrupted state.
*/
class Waiter extends CheckedThread {
private final boolean timed;
private final CyclicBarrier barrier;
private final CountDownLatch doneSignal;
volatile Throwable throwable;
volatile boolean interruptStatusSetAfterAwait;
public Waiter(CountDownLatch doneSignal, CyclicBarrier barrier) {
this.timed = ThreadLocalRandom.current().nextBoolean();
this.doneSignal = doneSignal;
this.barrier = barrier;
}
void realRun() throws Throwable {
startingGate.await(LONG_DELAY_MS, MILLISECONDS);
try {
if (timed) barrier.await(LONG_DELAY_MS, MILLISECONDS);
else barrier.await();
} catch (Throwable throwable) {
this.throwable = throwable;
}
try {
check(doneSignal.await(LONG_DELAY_MS, MILLISECONDS));
if (Thread.interrupted())
interruptStatusSetAfterAwait = true;
} catch (InterruptedException e) {
interruptStatusSetAfterAwait = true;
}
}
}
//----------------------------------------------------------------
// Interrupt occurs during barrier trip
//----------------------------------------------------------------
try {
final CountDownLatch doneSignal = new CountDownLatch(1);
final List<Waiter> waiters = new ArrayList<>(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(doneSignal, barrier);
waiter.start();
waiters.add(waiter);
}
startingGate.await(LONG_DELAY_MS, MILLISECONDS);
while (barrier.getNumberWaiting() < N) Thread.yield();
barrier.await();
doneSignal.countDown();
int countInterruptStatusSetAfterAwait = 0;
for (Waiter waiter : waiters) {
waiter.join();
equal(waiter.throwable, null);
if (waiter.interruptStatusSetAfterAwait)
countInterruptStatusSetAfterAwait++;
}
equal(countInterruptStatusSetAfterAwait, 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<>(N);
for (int i = 0; i < N; i++) {
Waiter waiter = new Waiter(doneSignal, barrier);
waiter.start();
waiters.add(waiter);
}
startingGate.await(LONG_DELAY_MS, MILLISECONDS);
while (barrier.getNumberWaiting() < N) Thread.yield();
for (int i = 0; i < N/2; i++) {
Thread waiter = waiters.get(i);
waiter.interrupt();
}
doneSignal.countDown();
int countInterruptedException = 0;
int countBrokenBarrierException = 0;
int countInterruptStatusSetAfterAwait = 0;
for (Waiter waiter : waiters) {
waiter.join();
if (waiter.throwable instanceof InterruptedException)
countInterruptedException++;
if (waiter.throwable instanceof BrokenBarrierException)
countBrokenBarrierException++;
if (waiter.interruptStatusSetAfterAwait)
countInterruptStatusSetAfterAwait++;
}
equal(countInterruptedException, 1);
equal(countBrokenBarrierException, N-1);
checkBroken(barrier);
equal(countInterruptStatusSetAfterAwait, N/2-1);
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");}
interface Fun {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 abstract static class CheckedThread extends Thread {
abstract void realRun() throws Throwable;
public void run() {
try {realRun();} catch (Throwable t) {unexpected(t);}}}
}