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8189387: ConcurrentLinkedDeque linearizability continued ..

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Reviewed-by: martin, psandoz, dholmes
This commit is contained in:
Doug Lea 2017-11-09 16:10:46 -08:00
parent 42ad4ec2dd
commit e2cbace23d
2 changed files with 80 additions and 44 deletions
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51
src/java.base/share/classes/java/util/concurrent/ConcurrentLinkedDeque.java
View File

@ -695,8 +695,9 @@ public class ConcurrentLinkedDeque<E>
* stale pointer that is now off the list.
*/
final Node<E> pred(Node<E> p) {
Node<E> q = p.prev;
return (p == q) ? last() : q;
if (p == (p = p.prev))
p = last();
return p;
}
/**
@ -867,31 +868,31 @@ public class ConcurrentLinkedDeque<E>
public E peekFirst() {
restart: for (;;) {
for (Node<E> first = first(), p = first;;) {
final E item;
if ((item = p.item) != null) {
// recheck for linearizability
if (first.prev != null) continue restart;
return item;
}
if ((p = succ(p)) == null)
return null;
E item;
Node<E> first = first(), p = first;
while ((item = p.item) == null) {
if (p == (p = p.next)) continue restart;
if (p == null)
break;
}
// recheck for linearizability
if (first.prev != null) continue restart;
return item;
}
}
public E peekLast() {
restart: for (;;) {
for (Node<E> last = last(), p = last;;) {
final E item;
if ((item = p.item) != null) {
// recheck for linearizability
if (last.next != null) continue restart;
return item;
}
if ((p = pred(p)) == null)
return null;
E item;
Node<E> last = last(), p = last;
while ((item = p.item) == null) {
if (p == (p = p.prev)) continue restart;
if (p == null)
break;
}
// recheck for linearizability
if (last.next != null) continue restart;
return item;
}
}
@ -921,8 +922,11 @@ public class ConcurrentLinkedDeque<E>
return item;
}
}
if ((p = succ(p)) == null)
if (p == (p = p.next)) continue restart;
if (p == null) {
if (first.prev != null) continue restart;
return null;
}
}
}
}
@ -939,8 +943,11 @@ public class ConcurrentLinkedDeque<E>
return item;
}
}
if ((p = pred(p)) == null)
if (p == (p = p.prev)) continue restart;
if (p == null) {
if (last.next != null) continue restart;
return null;
}
}
}
}

73
test/jdk/java/util/concurrent/tck/ConcurrentLinkedDequeTest.java
View File

@ -936,6 +936,14 @@ public class ConcurrentLinkedDequeTest extends JSR166TestCase {
}
}
void runAsync(Runnable r1, Runnable r2) {
boolean b = ThreadLocalRandom.current().nextBoolean();
CompletableFuture<Void> f1 = CompletableFuture.runAsync(b ? r1 : r2);
CompletableFuture<Void> f2 = CompletableFuture.runAsync(b ? r2 : r1);
f1.join();
f2.join();
}
/**
* Non-traversing Deque operations are linearizable.
* https://bugs.openjdk.java.net/browse/JDK-8188900
@ -959,18 +967,9 @@ public class ConcurrentLinkedDequeTest extends JSR166TestCase {
x, nulls.sum(), zeros.sum()));
};
Runnable adder = () -> {
d.addFirst(0);
d.addLast(42);
};
Runnable adder = () -> { d.addFirst(0); d.addLast(42); };
boolean b = rnd.nextBoolean();
Runnable r1 = b ? getter : adder;
Runnable r2 = b ? adder : getter;
CompletableFuture<Void> f1 = CompletableFuture.runAsync(r1);
CompletableFuture<Void> f2 = CompletableFuture.runAsync(r2);
f1.join();
f2.join();
runAsync(getter, adder);
}
}
@ -995,18 +994,48 @@ public class ConcurrentLinkedDequeTest extends JSR166TestCase {
x, nulls.sum(), zeros.sum()));
};
Runnable adder = () -> {
d.addLast(0);
d.addFirst(42);
};
Runnable adder = () -> { d.addLast(0); d.addFirst(42); };
boolean b = rnd.nextBoolean();
Runnable r1 = b ? getter : adder;
Runnable r2 = b ? adder : getter;
CompletableFuture<Void> f1 = CompletableFuture.runAsync(r1);
CompletableFuture<Void> f2 = CompletableFuture.runAsync(r2);
f1.join();
f2.join();
runAsync(getter, adder);
}
}
<T> T chooseRandomly(T... choices) {
return choices[ThreadLocalRandom.current().nextInt(choices.length)];
}
/**
* Non-traversing Deque operations (that return null) are linearizable.
* Don't return null when the deque is observably never empty.
* https://bugs.openjdk.java.net/browse/JDK-8189387
* ant -Djsr166.expensiveTests=true -Djsr166.tckTestClass=ConcurrentLinkedDequeTest -Djsr166.methodFilter=testBug8189387 tck
*/
public void testBug8189387() {
final ThreadLocalRandom rnd = ThreadLocalRandom.current();
Object x = new Object();
for (int n = expensiveTests ? 100_000 : 10; n--> 0; ) {
ConcurrentLinkedDeque<Object> d = new ConcurrentLinkedDeque<>();
Runnable add = chooseRandomly(
() -> d.addFirst(x),
() -> d.offerFirst(x),
() -> d.addLast(x),
() -> d.offerLast(x));
Runnable get = chooseRandomly(
() -> assertFalse(d.isEmpty()),
() -> assertSame(x, d.peekFirst()),
() -> assertSame(x, d.peekLast()),
() -> assertSame(x, d.pollFirst()),
() -> assertSame(x, d.pollLast()));
Runnable addRemove = chooseRandomly(
() -> { d.addFirst(x); d.pollLast(); },
() -> { d.offerFirst(x); d.removeFirst(); },
() -> { d.offerLast(x); d.removeLast(); },
() -> { d.addLast(x); d.pollFirst(); });
add.run();
runAsync(get, addRemove);
}
}
}