/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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*
* 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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*/
/*
* @test
* @bug 6499848
* @library /lib/testlibrary/
* @build jdk.testlibrary.RandomFactory
* @run main GCDuringIteration
* @summary Check that iterators work properly in the presence of
* concurrent finalization and removal of elements.
* @key randomness
*/
import static java.util.concurrent.TimeUnit.SECONDS;
import java.lang.ref.WeakReference;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Random;
import java.util.WeakHashMap;
import java.util.concurrent.CountDownLatch;
import java.util.function.BooleanSupplier;
import jdk.testlibrary.RandomFactory;
public class GCDuringIteration {
/** No guarantees, but effective in practice. */
static void forceFullGc() {
CountDownLatch finalizeDone = new CountDownLatch(1);
WeakReference<?> ref = new WeakReference<Object>(new Object() {
protected void finalize() { finalizeDone.countDown(); }});
try {
for (int i = 0; i < 10; i++) {
System.gc();
if (finalizeDone.await(1L, SECONDS) && ref.get() == null) {
System.runFinalization(); // try to pick up stragglers
return;
}
}
} catch (InterruptedException unexpected) {
throw new AssertionError("unexpected InterruptedException");
}
throw new AssertionError("failed to do a \"full\" gc");
}
static void gcAwait(BooleanSupplier s) {
for (int i = 0; i < 10; i++) {
if (s.getAsBoolean())
return;
forceFullGc();
}
throw new AssertionError("failed to satisfy condition");
}
// A class with the traditional pessimal hashCode implementation,
// to ensure that all instances end up in the same bucket.
static class Foo { public int hashCode() { return 42; }}
<K,V> void put(Map<K,V> map, K k, V v) {
check(! map.containsKey(k));
equal(map.get(k), null);
equal(map.put(k, v), null);
equal(map.get(k), v);
check(map.containsKey(k));
equal(map.put(k, v), v);
equal(map.get(k), v);
check(map.containsKey(k));
check(! map.isEmpty());
equal(map.keySet().iterator().next(), k);
equal(map.values().iterator().next(), v);
}
static final Random rnd = RandomFactory.getRandom();
void checkIterator(final Iterator<Map.Entry<Foo, Integer>> it, int first) {
for (int i = first; i >= 0; --i) {
if (rnd.nextBoolean()) check(it.hasNext());
equal(it.next().getValue(), i);
}
if (rnd.nextBoolean()) {
try {
it.next();
throw new AssertionError("should throw");
} catch (NoSuchElementException success) {}
}
if (rnd.nextBoolean())
check(! it.hasNext());
}
<K,V> V firstValue(Map<K,V> map) {
return map.values().iterator().next();
}
void test(String[] args) throws Throwable {
final int n = 10;
// Create array of strong refs
final Foo[] foos = new Foo[2*n];
final Map<Foo,Integer> map = new WeakHashMap<>(foos.length);
check(map.isEmpty());
equal(map.size(), 0);
for (int i = 0; i < foos.length; i++) {
Foo foo = new Foo();
foos[i] = foo;
put(map, foo, i);
}
equal(map.size(), foos.length);
{
int first = firstValue(map);
final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
foos[first] = null;
gcAwait(() -> map.size() == first);
checkIterator(it, first-1);
equal(map.size(), first);
equal(firstValue(map), first-1);
}
{
int first = firstValue(map);
final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
it.next(); // protects first entry
System.out.println(map.values());
int oldSize = map.size();
foos[first] = null;
forceFullGc();
equal(map.size(), oldSize);
System.out.println(map.values());
checkIterator(it, first-1);
// first entry no longer protected
gcAwait(() -> map.size() == first);
equal(firstValue(map), first-1);
}
{
int first = firstValue(map);
final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
it.next(); // protects first entry
System.out.println(map.values());
foos[first] = foos[first-1] = null;
gcAwait(() -> map.size() == first);
equal(firstValue(map), first);
System.out.println(map.values());
checkIterator(it, first-2);
// first entry no longer protected
gcAwait(() -> map.size() == first-1);
equal(firstValue(map), first-2);
}
{
int first = firstValue(map);
final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
it.next(); // protects first entry
it.hasNext(); // protects second entry
System.out.println(map.values());
int oldSize = map.size();
foos[first] = foos[first-1] = null;
forceFullGc();
equal(map.size(), oldSize);
equal(firstValue(map), first);
System.out.println(map.values());
checkIterator(it, first-1);
// first entry no longer protected
gcAwait(() -> map.size() == first-1);
equal(firstValue(map), first-2);
}
{
int first = firstValue(map);
final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
it.next(); // protects first entry
System.out.println(map.values());
equal(map.size(), first+1);
foos[first] = foos[first-1] = null;
gcAwait(() -> map.size() == first);
it.remove();
equal(firstValue(map), first-2);
equal(map.size(), first-1);
System.out.println(map.values());
checkIterator(it, first-2);
// first entry no longer protected
gcAwait(() -> map.size() == first-1);
equal(firstValue(map), first-2);
}
{
int first = firstValue(map);
final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
it.next(); // protects first entry
it.remove();
it.hasNext(); // protects second entry
System.out.println(map.values());
equal(map.size(), first);
foos[first] = foos[first-1] = null;
forceFullGc();
equal(firstValue(map), first-1);
equal(map.size(), first);
System.out.println(map.values());
checkIterator(it, first-1);
gcAwait(() -> map.size() == first-1);
equal(firstValue(map), first-2);
}
{
int first = firstValue(map);
final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
it.hasNext(); // protects first entry
Arrays.fill(foos, null);
gcAwait(() -> map.size() == 1);
System.out.println(map.values());
equal(it.next().getValue(), first);
check(! it.hasNext());
gcAwait(() -> map.size() == 0);
check(map.isEmpty());
}
}
//--------------------- Infrastructure ---------------------------
volatile int passed = 0, failed = 0;
void pass() {passed++;}
void fail() {failed++; Thread.dumpStack();}
void fail(String msg) {System.err.println(msg); fail();}
void unexpected(Throwable t) {failed++; t.printStackTrace();}
void check(boolean cond) {if (cond) pass(); else fail();}
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 {
new GCDuringIteration().instanceMain(args);}
void instanceMain(String[] args) throws Throwable {
try {test(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");}
}