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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
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@ -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;
}
}
}
}