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/*
* Copyright (c) 2006, 2013, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* @test
* @bug 6503247 6574123
* @summary Test resilience to tryAcquire methods that throw
* @author Martin Buchholz
*/
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedLongSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
/**
* This uses a variant of the standard Mutex demo, except with a
* tryAcquire method that randomly throws various Throwable
* subclasses.
*/
@SuppressWarnings("serial")
public class FlakyMutex implements Lock {
static class MyError extends Error {}
static class MyException extends Exception {}
static class MyRuntimeException extends RuntimeException {}
static void checkThrowable(Throwable t) {
check((t instanceof MyError) ||
(t instanceof MyException) ||
(t instanceof MyRuntimeException));
}
static void realMain(String[] args) throws Throwable {
final int nThreads = 3;
final int iterations = 10_000;
final CyclicBarrier startingGate = new CyclicBarrier(nThreads);
final FlakyMutex mutex = new FlakyMutex();
final ExecutorService es = Executors.newFixedThreadPool(nThreads);
final Runnable task = () -> {
try {
startingGate.await();
for (int i = 0; i < iterations; i++) {
for (;;) {
try { mutex.lock(); break; }
catch (Throwable t) { checkThrowable(t); }
}
try { check(! mutex.tryLock()); }
catch (Throwable t) { checkThrowable(t); }
try { check(! mutex.tryLock(1, TimeUnit.MICROSECONDS)); }
catch (Throwable t) { checkThrowable(t); }
mutex.unlock();
}
} catch (Throwable t) { unexpected(t); }
};
for (int i = 0; i < nThreads; i++)
es.submit(task);
es.shutdown();
// Let test harness handle timeout
check(es.awaitTermination(Long.MAX_VALUE, TimeUnit.DAYS));
}
private static class FlakySync extends AbstractQueuedLongSynchronizer {
private static final long serialVersionUID = -1L;
public boolean isHeldExclusively() { return getState() == 1; }
public boolean tryAcquire(long acquires) {
// Sneak in some tests for queue state
if (hasQueuedPredecessors())
check(getFirstQueuedThread() != Thread.currentThread());
if (getFirstQueuedThread() == Thread.currentThread()) {
check(hasQueuedThreads());
check(!hasQueuedPredecessors());
} else {
// Might be true, but only transiently
do {} while (hasQueuedPredecessors() != hasQueuedThreads());
}
switch (ThreadLocalRandom.current().nextInt(10)) {
case 0: throw new MyError();
case 1: throw new MyRuntimeException();
case 2: FlakyMutex.<RuntimeException>uncheckedThrow(new MyException());
// fall through ... NOT!
default: return compareAndSetState(0, 1);
}
}
public boolean tryRelease(long releases) {
setState(0);
return true;
}
Condition newCondition() { return new ConditionObject(); }
}
private final FlakySync sync = new FlakySync();
public void lock() { sync.acquire(1); }
public boolean tryLock() { return sync.tryAcquire(1); }
public void lockInterruptibly() throws InterruptedException {
sync.acquireInterruptibly(1);
}
public boolean tryLock(long timeout, TimeUnit unit) throws InterruptedException {
return sync.tryAcquireNanos(1, unit.toNanos(timeout));
}
public void unlock() { sync.release(1); }
public Condition newCondition() { return sync.newCondition(); }
public boolean isLocked() { return sync.isHeldExclusively(); }
public boolean hasQueuedThreads() { return sync.hasQueuedThreads(); }
//--------------------- 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");}
@SuppressWarnings("unchecked")
static <T extends Throwable> void uncheckedThrow(Throwable t) throws T {
throw (T)t; // rely on vacuous cast
}
}
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