10 |
|
import java.util.concurrent.atomic.*; |
11 |
|
import java.util.*; |
12 |
|
import java.io.*; |
13 |
– |
import sun.misc.Unsafe; |
14 |
– |
import java.lang.reflect.*; |
13 |
|
|
14 |
|
/** |
15 |
|
* An unbounded {@linkplain TransferQueue} based on linked nodes. |
100 |
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* garbage retention. Similarly, setting the next field to this is |
101 |
|
* used as sentinel that node is off list. |
102 |
|
*/ |
103 |
< |
static final class QNode extends AtomicReference<Object> { |
104 |
< |
volatile QNode next; |
103 |
> |
static final class Node<E> extends AtomicReference<Object> { |
104 |
> |
volatile Node<E> next; |
105 |
|
volatile Thread waiter; // to control park/unpark |
106 |
|
final boolean isData; |
107 |
< |
QNode(Object item, boolean isData) { |
107 |
> |
|
108 |
> |
Node(E item, boolean isData) { |
109 |
|
super(item); |
110 |
|
this.isData = isData; |
111 |
|
} |
112 |
|
|
113 |
< |
static final AtomicReferenceFieldUpdater<QNode, QNode> |
113 |
> |
@SuppressWarnings("rawtypes") |
114 |
> |
static final AtomicReferenceFieldUpdater<Node, Node> |
115 |
|
nextUpdater = AtomicReferenceFieldUpdater.newUpdater |
116 |
< |
(QNode.class, QNode.class, "next"); |
116 |
> |
(Node.class, Node.class, "next"); |
117 |
|
|
118 |
< |
final boolean casNext(QNode cmp, QNode val) { |
118 |
> |
final boolean casNext(Node<E> cmp, Node<E> val) { |
119 |
|
return nextUpdater.compareAndSet(this, cmp, val); |
120 |
|
} |
121 |
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|
140 |
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|
141 |
|
|
142 |
|
/** head of the queue */ |
143 |
< |
private transient final PaddedAtomicReference<QNode> head; |
143 |
> |
private transient final PaddedAtomicReference<Node<E>> head; |
144 |
|
|
145 |
|
/** tail of the queue */ |
146 |
< |
private transient final PaddedAtomicReference<QNode> tail; |
146 |
> |
private transient final PaddedAtomicReference<Node<E>> tail; |
147 |
|
|
148 |
|
/** |
149 |
|
* Reference to a cancelled node that might not yet have been |
150 |
|
* unlinked from queue because it was the last inserted node |
151 |
|
* when it cancelled. |
152 |
|
*/ |
153 |
< |
private transient final PaddedAtomicReference<QNode> cleanMe; |
153 |
> |
private transient final PaddedAtomicReference<Node<E>> cleanMe; |
154 |
|
|
155 |
|
/** |
156 |
|
* Tries to cas nh as new head; if successful, unlink |
157 |
|
* old head's next node to avoid garbage retention. |
158 |
|
*/ |
159 |
< |
private boolean advanceHead(QNode h, QNode nh) { |
159 |
> |
private boolean advanceHead(Node<E> h, Node<E> nh) { |
160 |
|
if (h == head.get() && head.compareAndSet(h, nh)) { |
161 |
|
h.clearNext(); // forget old next |
162 |
|
return true; |
174 |
|
* @param nanos timeout in nanosecs, used only if mode is TIMEOUT |
175 |
|
* @return an item, or null on failure |
176 |
|
*/ |
177 |
< |
private Object xfer(Object e, int mode, long nanos) { |
177 |
> |
private E xfer(E e, int mode, long nanos) { |
178 |
|
boolean isData = (e != null); |
179 |
< |
QNode s = null; |
180 |
< |
final PaddedAtomicReference<QNode> head = this.head; |
181 |
< |
final PaddedAtomicReference<QNode> tail = this.tail; |
179 |
> |
Node<E> s = null; |
180 |
> |
final PaddedAtomicReference<Node<E>> head = this.head; |
181 |
> |
final PaddedAtomicReference<Node<E>> tail = this.tail; |
182 |
|
|
183 |
|
for (;;) { |
184 |
< |
QNode t = tail.get(); |
185 |
< |
QNode h = head.get(); |
184 |
> |
Node<E> t = tail.get(); |
185 |
> |
Node<E> h = head.get(); |
186 |
|
|
187 |
|
if (t != null && (t == h || t.isData == isData)) { |
188 |
|
if (s == null) |
189 |
< |
s = new QNode(e, isData); |
190 |
< |
QNode last = t.next; |
189 |
> |
s = new Node<E>(e, isData); |
190 |
> |
Node<E> last = t.next; |
191 |
|
if (last != null) { |
192 |
|
if (t == tail.get()) |
193 |
|
tail.compareAndSet(t, last); |
199 |
|
} |
200 |
|
|
201 |
|
else if (h != null) { |
202 |
< |
QNode first = h.next; |
202 |
> |
Node<E> first = h.next; |
203 |
|
if (t == tail.get() && first != null && |
204 |
|
advanceHead(h, first)) { |
205 |
|
Object x = first.get(); |
206 |
|
if (x != first && first.compareAndSet(x, e)) { |
207 |
|
LockSupport.unpark(first.waiter); |
208 |
< |
return isData ? e : x; |
208 |
> |
return isData ? e : (E) x; |
209 |
|
} |
210 |
|
} |
211 |
|
} |
217 |
|
* Version of xfer for poll() and tryTransfer, which |
218 |
|
* simplifies control paths both here and in xfer. |
219 |
|
*/ |
220 |
< |
private Object fulfill(Object e) { |
220 |
> |
private E fulfill(E e) { |
221 |
|
boolean isData = (e != null); |
222 |
< |
final PaddedAtomicReference<QNode> head = this.head; |
223 |
< |
final PaddedAtomicReference<QNode> tail = this.tail; |
222 |
> |
final PaddedAtomicReference<Node<E>> head = this.head; |
223 |
> |
final PaddedAtomicReference<Node<E>> tail = this.tail; |
224 |
|
|
225 |
|
for (;;) { |
226 |
< |
QNode t = tail.get(); |
227 |
< |
QNode h = head.get(); |
226 |
> |
Node<E> t = tail.get(); |
227 |
> |
Node<E> h = head.get(); |
228 |
|
|
229 |
|
if (t != null && (t == h || t.isData == isData)) { |
230 |
< |
QNode last = t.next; |
230 |
> |
Node<E> last = t.next; |
231 |
|
if (t == tail.get()) { |
232 |
|
if (last != null) |
233 |
|
tail.compareAndSet(t, last); |
236 |
|
} |
237 |
|
} |
238 |
|
else if (h != null) { |
239 |
< |
QNode first = h.next; |
239 |
> |
Node<E> first = h.next; |
240 |
|
if (t == tail.get() && |
241 |
|
first != null && |
242 |
|
advanceHead(h, first)) { |
243 |
|
Object x = first.get(); |
244 |
|
if (x != first && first.compareAndSet(x, e)) { |
245 |
|
LockSupport.unpark(first.waiter); |
246 |
< |
return isData ? e : x; |
246 |
> |
return isData ? e : (E) x; |
247 |
|
} |
248 |
|
} |
249 |
|
} |
261 |
|
* @param nanos timeout value |
262 |
|
* @return matched item, or s if cancelled |
263 |
|
*/ |
264 |
< |
private Object awaitFulfill(QNode pred, QNode s, Object e, |
265 |
< |
int mode, long nanos) { |
264 |
> |
private E awaitFulfill(Node<E> pred, Node<E> s, E e, |
265 |
> |
int mode, long nanos) { |
266 |
|
if (mode == NOWAIT) |
267 |
|
return null; |
268 |
|
|
281 |
|
} |
282 |
|
else if (x != null) { |
283 |
|
s.set(s); // avoid garbage retention |
284 |
< |
return x; |
284 |
> |
return (E) x; |
285 |
|
} |
286 |
|
else |
287 |
|
return e; |
296 |
|
} |
297 |
|
} |
298 |
|
if (spins < 0) { |
299 |
< |
QNode h = head.get(); // only spin if at head |
299 |
> |
Node<E> h = head.get(); // only spin if at head |
300 |
|
spins = ((h != null && h.next == s) ? |
301 |
|
((mode == TIMEOUT) ? |
302 |
|
maxTimedSpins : maxUntimedSpins) : 0); |
321 |
|
/** |
322 |
|
* Returns validated tail for use in cleaning methods. |
323 |
|
*/ |
324 |
< |
private QNode getValidatedTail() { |
324 |
> |
private Node<E> getValidatedTail() { |
325 |
|
for (;;) { |
326 |
< |
QNode h = head.get(); |
327 |
< |
QNode first = h.next; |
326 |
> |
Node<E> h = head.get(); |
327 |
> |
Node<E> first = h.next; |
328 |
|
if (first != null && first.next == first) { // help advance |
329 |
|
advanceHead(h, first); |
330 |
|
continue; |
331 |
|
} |
332 |
< |
QNode t = tail.get(); |
333 |
< |
QNode last = t.next; |
332 |
> |
Node<E> t = tail.get(); |
333 |
> |
Node<E> last = t.next; |
334 |
|
if (t == tail.get()) { |
335 |
|
if (last != null) |
336 |
|
tail.compareAndSet(t, last); // help advance |
346 |
|
* @param pred predecessor of cancelled node |
347 |
|
* @param s the cancelled node |
348 |
|
*/ |
349 |
< |
private void clean(QNode pred, QNode s) { |
349 |
> |
private void clean(Node<E> pred, Node<E> s) { |
350 |
|
Thread w = s.waiter; |
351 |
|
if (w != null) { // Wake up thread |
352 |
|
s.waiter = null; |
366 |
|
* processed, so this always terminates. |
367 |
|
*/ |
368 |
|
while (pred.next == s) { |
369 |
< |
QNode oldpred = reclean(); // First, help get rid of cleanMe |
370 |
< |
QNode t = getValidatedTail(); |
369 |
> |
Node<E> oldpred = reclean(); // First, help get rid of cleanMe |
370 |
> |
Node<E> t = getValidatedTail(); |
371 |
|
if (s != t) { // If not tail, try to unsplice |
372 |
< |
QNode sn = s.next; // s.next == s means s already off list |
372 |
> |
Node<E> sn = s.next; // s.next == s means s already off list |
373 |
|
if (sn == s || pred.casNext(s, sn)) |
374 |
|
break; |
375 |
|
} |
385 |
|
* |
386 |
|
* @return current cleanMe node (or null) |
387 |
|
*/ |
388 |
< |
private QNode reclean() { |
388 |
> |
private Node<E> reclean() { |
389 |
|
/* |
390 |
|
* cleanMe is, or at one time was, predecessor of cancelled |
391 |
|
* node s that was the tail so could not be unspliced. If s |
397 |
|
* This can loop only due to contention on casNext or |
398 |
|
* clearing cleanMe. |
399 |
|
*/ |
400 |
< |
QNode pred; |
400 |
> |
Node<E> pred; |
401 |
|
while ((pred = cleanMe.get()) != null) { |
402 |
< |
QNode t = getValidatedTail(); |
403 |
< |
QNode s = pred.next; |
402 |
> |
Node<E> t = getValidatedTail(); |
403 |
> |
Node<E> s = pred.next; |
404 |
|
if (s != t) { |
405 |
< |
QNode sn; |
405 |
> |
Node<E> sn; |
406 |
|
if (s == null || s == pred || s.get() != s || |
407 |
|
(sn = s.next) == s || pred.casNext(s, sn)) |
408 |
|
cleanMe.compareAndSet(pred, null); |
417 |
|
* Creates an initially empty {@code LinkedTransferQueue}. |
418 |
|
*/ |
419 |
|
public LinkedTransferQueue() { |
420 |
< |
QNode dummy = new QNode(null, false); |
421 |
< |
head = new PaddedAtomicReference<QNode>(dummy); |
422 |
< |
tail = new PaddedAtomicReference<QNode>(dummy); |
423 |
< |
cleanMe = new PaddedAtomicReference<QNode>(null); |
420 |
> |
Node<E> dummy = new Node<E>(null, false); |
421 |
> |
head = new PaddedAtomicReference<Node<E>>(dummy); |
422 |
> |
tail = new PaddedAtomicReference<Node<E>>(dummy); |
423 |
> |
cleanMe = new PaddedAtomicReference<Node<E>>(null); |
424 |
|
} |
425 |
|
|
426 |
|
/** |
502 |
|
} |
503 |
|
|
504 |
|
public E poll() { |
505 |
< |
return (E) fulfill(null); |
505 |
> |
return fulfill(null); |
506 |
|
} |
507 |
|
|
508 |
|
public int drainTo(Collection<? super E> c) { |
538 |
|
/** |
539 |
|
* Returns head after performing any outstanding helping steps. |
540 |
|
*/ |
541 |
< |
private QNode traversalHead() { |
541 |
> |
private Node<E> traversalHead() { |
542 |
|
for (;;) { |
543 |
< |
QNode t = tail.get(); |
544 |
< |
QNode h = head.get(); |
543 |
> |
Node<E> t = tail.get(); |
544 |
> |
Node<E> h = head.get(); |
545 |
|
if (h != null && t != null) { |
546 |
< |
QNode last = t.next; |
547 |
< |
QNode first = h.next; |
546 |
> |
Node<E> last = t.next; |
547 |
> |
Node<E> first = h.next; |
548 |
|
if (t == tail.get()) { |
549 |
|
if (last != null) |
550 |
|
tail.compareAndSet(t, last); |
576 |
|
* if subsequently removed. |
577 |
|
*/ |
578 |
|
class Itr implements Iterator<E> { |
579 |
< |
QNode next; // node to return next |
580 |
< |
QNode pnext; // predecessor of next |
581 |
< |
QNode snext; // successor of next |
582 |
< |
QNode curr; // last returned node, for remove() |
583 |
< |
QNode pcurr; // predecessor of curr, for remove() |
579 |
> |
Node<E> next; // node to return next |
580 |
> |
Node<E> pnext; // predecessor of next |
581 |
> |
Node<E> snext; // successor of next |
582 |
> |
Node<E> curr; // last returned node, for remove() |
583 |
> |
Node<E> pcurr; // predecessor of curr, for remove() |
584 |
|
E nextItem; // Cache of next item, once committed to in next |
585 |
|
|
586 |
|
Itr() { |
592 |
|
*/ |
593 |
|
void findNext() { |
594 |
|
for (;;) { |
595 |
< |
QNode pred = pnext; |
596 |
< |
QNode q = next; |
595 |
> |
Node<E> pred = pnext; |
596 |
> |
Node<E> q = next; |
597 |
|
if (pred == null || pred == q) { |
598 |
|
pred = traversalHead(); |
599 |
|
q = pred.next; |
603 |
|
return; |
604 |
|
} |
605 |
|
Object x = q.get(); |
606 |
< |
QNode s = q.next; |
606 |
> |
Node<E> s = q.next; |
607 |
|
if (x != null && q != x && q != s) { |
608 |
|
nextItem = (E) x; |
609 |
|
snext = s; |
632 |
|
} |
633 |
|
|
634 |
|
public void remove() { |
635 |
< |
QNode p = curr; |
635 |
> |
Node<E> p = curr; |
636 |
|
if (p == null) |
637 |
|
throw new IllegalStateException(); |
638 |
|
Object x = p.get(); |
643 |
|
|
644 |
|
public E peek() { |
645 |
|
for (;;) { |
646 |
< |
QNode h = traversalHead(); |
647 |
< |
QNode p = h.next; |
646 |
> |
Node<E> h = traversalHead(); |
647 |
> |
Node<E> p = h.next; |
648 |
|
if (p == null) |
649 |
|
return null; |
650 |
|
Object x = p.get(); |
659 |
|
|
660 |
|
public boolean isEmpty() { |
661 |
|
for (;;) { |
662 |
< |
QNode h = traversalHead(); |
663 |
< |
QNode p = h.next; |
662 |
> |
Node<E> h = traversalHead(); |
663 |
> |
Node<E> p = h.next; |
664 |
|
if (p == null) |
665 |
|
return true; |
666 |
|
Object x = p.get(); |
675 |
|
|
676 |
|
public boolean hasWaitingConsumer() { |
677 |
|
for (;;) { |
678 |
< |
QNode h = traversalHead(); |
679 |
< |
QNode p = h.next; |
678 |
> |
Node<E> h = traversalHead(); |
679 |
> |
Node<E> p = h.next; |
680 |
|
if (p == null) |
681 |
|
return false; |
682 |
|
Object x = p.get(); |
699 |
|
*/ |
700 |
|
public int size() { |
701 |
|
int count = 0; |
702 |
< |
QNode h = traversalHead(); |
703 |
< |
for (QNode p = h.next; p != null && p.isData; p = p.next) { |
702 |
> |
Node<E> h = traversalHead(); |
703 |
> |
for (Node<E> p = h.next; p != null && p.isData; p = p.next) { |
704 |
|
Object x = p.get(); |
705 |
|
if (x != null && x != p) { |
706 |
|
if (++count == Integer.MAX_VALUE) // saturated |
712 |
|
|
713 |
|
public int getWaitingConsumerCount() { |
714 |
|
int count = 0; |
715 |
< |
QNode h = traversalHead(); |
716 |
< |
for (QNode p = h.next; p != null && !p.isData; p = p.next) { |
715 |
> |
Node<E> h = traversalHead(); |
716 |
> |
for (Node<E> p = h.next; p != null && !p.isData; p = p.next) { |
717 |
|
if (p.get() == null) { |
718 |
|
if (++count == Integer.MAX_VALUE) |
719 |
|
break; |
730 |
|
if (o == null) |
731 |
|
return false; |
732 |
|
for (;;) { |
733 |
< |
QNode pred = traversalHead(); |
733 |
> |
Node<E> pred = traversalHead(); |
734 |
|
for (;;) { |
735 |
< |
QNode q = pred.next; |
735 |
> |
Node<E> q = pred.next; |
736 |
|
if (q == null || !q.isData) |
737 |
|
return false; |
738 |
|
if (q == pred) // restart |
775 |
|
s.defaultReadObject(); |
776 |
|
resetHeadAndTail(); |
777 |
|
for (;;) { |
778 |
< |
E item = (E) s.readObject(); |
778 |
> |
@SuppressWarnings("unchecked") E item = (E) s.readObject(); |
779 |
|
if (item == null) |
780 |
|
break; |
781 |
|
else |
783 |
|
} |
784 |
|
} |
785 |
|
|
786 |
– |
|
786 |
|
// Support for resetting head/tail while deserializing |
787 |
|
private void resetHeadAndTail() { |
788 |
< |
QNode dummy = new QNode(null, false); |
788 |
> |
Node<E> dummy = new Node<E>(null, false); |
789 |
|
UNSAFE.putObjectVolatile(this, headOffset, |
790 |
< |
new PaddedAtomicReference<QNode>(dummy)); |
790 |
> |
new PaddedAtomicReference<Node<E>>(dummy)); |
791 |
|
UNSAFE.putObjectVolatile(this, tailOffset, |
792 |
< |
new PaddedAtomicReference<QNode>(dummy)); |
792 |
> |
new PaddedAtomicReference<Node<E>>(dummy)); |
793 |
|
UNSAFE.putObjectVolatile(this, cleanMeOffset, |
794 |
< |
new PaddedAtomicReference<QNode>(null)); |
794 |
> |
new PaddedAtomicReference<Node<E>>(null)); |
795 |
|
} |
796 |
|
|
797 |
< |
// Temporary Unsafe mechanics for preliminary release |
798 |
< |
private static Unsafe getUnsafe() throws Throwable { |
797 |
> |
// Unsafe mechanics for jsr166y 3rd party package. |
798 |
> |
private static sun.misc.Unsafe getUnsafe() { |
799 |
|
try { |
800 |
< |
return Unsafe.getUnsafe(); |
800 |
> |
return sun.misc.Unsafe.getUnsafe(); |
801 |
|
} catch (SecurityException se) { |
802 |
|
try { |
803 |
|
return java.security.AccessController.doPrivileged |
804 |
< |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
805 |
< |
public Unsafe run() throws Exception { |
806 |
< |
return getUnsafePrivileged(); |
804 |
> |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
805 |
> |
public sun.misc.Unsafe run() throws Exception { |
806 |
> |
return getUnsafeByReflection(); |
807 |
|
}}); |
808 |
|
} catch (java.security.PrivilegedActionException e) { |
809 |
< |
throw e.getCause(); |
809 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
810 |
> |
e.getCause()); |
811 |
|
} |
812 |
|
} |
813 |
|
} |
814 |
|
|
815 |
< |
private static Unsafe getUnsafePrivileged() |
815 |
> |
private static sun.misc.Unsafe getUnsafeByReflection() |
816 |
|
throws NoSuchFieldException, IllegalAccessException { |
817 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
817 |
> |
java.lang.reflect.Field f = |
818 |
> |
sun.misc.Unsafe.class.getDeclaredField("theUnsafe"); |
819 |
|
f.setAccessible(true); |
820 |
< |
return (Unsafe) f.get(null); |
820 |
> |
return (sun.misc.Unsafe) f.get(null); |
821 |
|
} |
822 |
|
|
823 |
< |
private static long fieldOffset(String fieldName) |
823 |
< |
throws NoSuchFieldException { |
824 |
< |
return UNSAFE.objectFieldOffset |
825 |
< |
(LinkedTransferQueue.class.getDeclaredField(fieldName)); |
826 |
< |
} |
827 |
< |
|
828 |
< |
private static final Unsafe UNSAFE; |
829 |
< |
private static final long headOffset; |
830 |
< |
private static final long tailOffset; |
831 |
< |
private static final long cleanMeOffset; |
832 |
< |
static { |
823 |
> |
private static long fieldOffset(String fieldName, Class<?> klazz) { |
824 |
|
try { |
825 |
< |
UNSAFE = getUnsafe(); |
826 |
< |
headOffset = fieldOffset("head"); |
827 |
< |
tailOffset = fieldOffset("tail"); |
828 |
< |
cleanMeOffset = fieldOffset("cleanMe"); |
829 |
< |
} catch (Throwable e) { |
830 |
< |
throw new RuntimeException("Could not initialize intrinsics", e); |
825 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName)); |
826 |
> |
} catch (NoSuchFieldException e) { |
827 |
> |
// Convert Exception to Error |
828 |
> |
NoSuchFieldError error = new NoSuchFieldError(fieldName); |
829 |
> |
error.initCause(e); |
830 |
> |
throw error; |
831 |
|
} |
832 |
|
} |
833 |
|
|
834 |
+ |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
835 |
+ |
static final long headOffset = |
836 |
+ |
fieldOffset("head", LinkedTransferQueue.class); |
837 |
+ |
static final long tailOffset = |
838 |
+ |
fieldOffset("tail", LinkedTransferQueue.class); |
839 |
+ |
static final long cleanMeOffset = |
840 |
+ |
fieldOffset("cleanMe", LinkedTransferQueue.class); |
841 |
+ |
|
842 |
|
} |