5 |
|
*/ |
6 |
|
|
7 |
|
package jsr166y; |
8 |
+ |
|
9 |
|
import java.util.concurrent.*; |
10 |
< |
import java.util.concurrent.locks.*; |
11 |
< |
import java.util.concurrent.atomic.*; |
12 |
< |
import java.util.*; |
13 |
< |
import java.io.*; |
14 |
< |
import sun.misc.Unsafe; |
15 |
< |
import java.lang.reflect.*; |
10 |
> |
|
11 |
> |
import java.util.AbstractQueue; |
12 |
> |
import java.util.Collection; |
13 |
> |
import java.util.Iterator; |
14 |
> |
import java.util.NoSuchElementException; |
15 |
> |
import java.util.concurrent.locks.LockSupport; |
16 |
> |
import java.util.concurrent.atomic.AtomicReference; |
17 |
> |
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; |
18 |
|
|
19 |
|
/** |
20 |
|
* An unbounded {@linkplain TransferQueue} based on linked nodes. |
105 |
|
* garbage retention. Similarly, setting the next field to this is |
106 |
|
* used as sentinel that node is off list. |
107 |
|
*/ |
108 |
< |
static final class QNode extends AtomicReference<Object> { |
109 |
< |
volatile QNode next; |
108 |
> |
static final class Node<E> extends AtomicReference<Object> { |
109 |
> |
volatile Node<E> next; |
110 |
|
volatile Thread waiter; // to control park/unpark |
111 |
|
final boolean isData; |
112 |
< |
QNode(Object item, boolean isData) { |
112 |
> |
|
113 |
> |
Node(E item, boolean isData) { |
114 |
|
super(item); |
115 |
|
this.isData = isData; |
116 |
|
} |
117 |
|
|
118 |
< |
static final AtomicReferenceFieldUpdater<QNode, QNode> |
118 |
> |
@SuppressWarnings("rawtypes") |
119 |
> |
static final AtomicReferenceFieldUpdater<Node, Node> |
120 |
|
nextUpdater = AtomicReferenceFieldUpdater.newUpdater |
121 |
< |
(QNode.class, QNode.class, "next"); |
121 |
> |
(Node.class, Node.class, "next"); |
122 |
|
|
123 |
< |
final boolean casNext(QNode cmp, QNode val) { |
123 |
> |
final boolean casNext(Node<E> cmp, Node<E> val) { |
124 |
|
return nextUpdater.compareAndSet(this, cmp, val); |
125 |
|
} |
126 |
|
|
145 |
|
|
146 |
|
|
147 |
|
/** head of the queue */ |
148 |
< |
private transient final PaddedAtomicReference<QNode> head; |
148 |
> |
private transient final PaddedAtomicReference<Node<E>> head; |
149 |
|
|
150 |
|
/** tail of the queue */ |
151 |
< |
private transient final PaddedAtomicReference<QNode> tail; |
151 |
> |
private transient final PaddedAtomicReference<Node<E>> tail; |
152 |
|
|
153 |
|
/** |
154 |
|
* Reference to a cancelled node that might not yet have been |
155 |
|
* unlinked from queue because it was the last inserted node |
156 |
|
* when it cancelled. |
157 |
|
*/ |
158 |
< |
private transient final PaddedAtomicReference<QNode> cleanMe; |
158 |
> |
private transient final PaddedAtomicReference<Node<E>> cleanMe; |
159 |
|
|
160 |
|
/** |
161 |
|
* Tries to cas nh as new head; if successful, unlink |
162 |
|
* old head's next node to avoid garbage retention. |
163 |
|
*/ |
164 |
< |
private boolean advanceHead(QNode h, QNode nh) { |
164 |
> |
private boolean advanceHead(Node<E> h, Node<E> nh) { |
165 |
|
if (h == head.get() && head.compareAndSet(h, nh)) { |
166 |
|
h.clearNext(); // forget old next |
167 |
|
return true; |
179 |
|
* @param nanos timeout in nanosecs, used only if mode is TIMEOUT |
180 |
|
* @return an item, or null on failure |
181 |
|
*/ |
182 |
< |
private Object xfer(Object e, int mode, long nanos) { |
182 |
> |
private E xfer(E e, int mode, long nanos) { |
183 |
|
boolean isData = (e != null); |
184 |
< |
QNode s = null; |
185 |
< |
final PaddedAtomicReference<QNode> head = this.head; |
186 |
< |
final PaddedAtomicReference<QNode> tail = this.tail; |
184 |
> |
Node<E> s = null; |
185 |
> |
final PaddedAtomicReference<Node<E>> head = this.head; |
186 |
> |
final PaddedAtomicReference<Node<E>> tail = this.tail; |
187 |
|
|
188 |
|
for (;;) { |
189 |
< |
QNode t = tail.get(); |
190 |
< |
QNode h = head.get(); |
189 |
> |
Node<E> t = tail.get(); |
190 |
> |
Node<E> h = head.get(); |
191 |
|
|
192 |
|
if (t != null && (t == h || t.isData == isData)) { |
193 |
|
if (s == null) |
194 |
< |
s = new QNode(e, isData); |
195 |
< |
QNode last = t.next; |
194 |
> |
s = new Node<E>(e, isData); |
195 |
> |
Node<E> last = t.next; |
196 |
|
if (last != null) { |
197 |
|
if (t == tail.get()) |
198 |
|
tail.compareAndSet(t, last); |
204 |
|
} |
205 |
|
|
206 |
|
else if (h != null) { |
207 |
< |
QNode first = h.next; |
207 |
> |
Node<E> first = h.next; |
208 |
|
if (t == tail.get() && first != null && |
209 |
|
advanceHead(h, first)) { |
210 |
|
Object x = first.get(); |
211 |
|
if (x != first && first.compareAndSet(x, e)) { |
212 |
|
LockSupport.unpark(first.waiter); |
213 |
< |
return isData ? e : x; |
213 |
> |
return isData ? e : (E) x; |
214 |
|
} |
215 |
|
} |
216 |
|
} |
222 |
|
* Version of xfer for poll() and tryTransfer, which |
223 |
|
* simplifies control paths both here and in xfer. |
224 |
|
*/ |
225 |
< |
private Object fulfill(Object e) { |
225 |
> |
private E fulfill(E e) { |
226 |
|
boolean isData = (e != null); |
227 |
< |
final PaddedAtomicReference<QNode> head = this.head; |
228 |
< |
final PaddedAtomicReference<QNode> tail = this.tail; |
227 |
> |
final PaddedAtomicReference<Node<E>> head = this.head; |
228 |
> |
final PaddedAtomicReference<Node<E>> tail = this.tail; |
229 |
|
|
230 |
|
for (;;) { |
231 |
< |
QNode t = tail.get(); |
232 |
< |
QNode h = head.get(); |
231 |
> |
Node<E> t = tail.get(); |
232 |
> |
Node<E> h = head.get(); |
233 |
|
|
234 |
|
if (t != null && (t == h || t.isData == isData)) { |
235 |
< |
QNode last = t.next; |
235 |
> |
Node<E> last = t.next; |
236 |
|
if (t == tail.get()) { |
237 |
|
if (last != null) |
238 |
|
tail.compareAndSet(t, last); |
241 |
|
} |
242 |
|
} |
243 |
|
else if (h != null) { |
244 |
< |
QNode first = h.next; |
244 |
> |
Node<E> first = h.next; |
245 |
|
if (t == tail.get() && |
246 |
|
first != null && |
247 |
|
advanceHead(h, first)) { |
248 |
|
Object x = first.get(); |
249 |
|
if (x != first && first.compareAndSet(x, e)) { |
250 |
|
LockSupport.unpark(first.waiter); |
251 |
< |
return isData ? e : x; |
251 |
> |
return isData ? e : (E) x; |
252 |
|
} |
253 |
|
} |
254 |
|
} |
266 |
|
* @param nanos timeout value |
267 |
|
* @return matched item, or s if cancelled |
268 |
|
*/ |
269 |
< |
private Object awaitFulfill(QNode pred, QNode s, Object e, |
270 |
< |
int mode, long nanos) { |
269 |
> |
private E awaitFulfill(Node<E> pred, Node<E> s, E e, |
270 |
> |
int mode, long nanos) { |
271 |
|
if (mode == NOWAIT) |
272 |
|
return null; |
273 |
|
|
286 |
|
} |
287 |
|
else if (x != null) { |
288 |
|
s.set(s); // avoid garbage retention |
289 |
< |
return x; |
289 |
> |
return (E) x; |
290 |
|
} |
291 |
|
else |
292 |
|
return e; |
301 |
|
} |
302 |
|
} |
303 |
|
if (spins < 0) { |
304 |
< |
QNode h = head.get(); // only spin if at head |
304 |
> |
Node<E> h = head.get(); // only spin if at head |
305 |
|
spins = ((h != null && h.next == s) ? |
306 |
|
((mode == TIMEOUT) ? |
307 |
|
maxTimedSpins : maxUntimedSpins) : 0); |
326 |
|
/** |
327 |
|
* Returns validated tail for use in cleaning methods. |
328 |
|
*/ |
329 |
< |
private QNode getValidatedTail() { |
329 |
> |
private Node<E> getValidatedTail() { |
330 |
|
for (;;) { |
331 |
< |
QNode h = head.get(); |
332 |
< |
QNode first = h.next; |
331 |
> |
Node<E> h = head.get(); |
332 |
> |
Node<E> first = h.next; |
333 |
|
if (first != null && first.next == first) { // help advance |
334 |
|
advanceHead(h, first); |
335 |
|
continue; |
336 |
|
} |
337 |
< |
QNode t = tail.get(); |
338 |
< |
QNode last = t.next; |
337 |
> |
Node<E> t = tail.get(); |
338 |
> |
Node<E> last = t.next; |
339 |
|
if (t == tail.get()) { |
340 |
|
if (last != null) |
341 |
|
tail.compareAndSet(t, last); // help advance |
351 |
|
* @param pred predecessor of cancelled node |
352 |
|
* @param s the cancelled node |
353 |
|
*/ |
354 |
< |
private void clean(QNode pred, QNode s) { |
354 |
> |
private void clean(Node<E> pred, Node<E> s) { |
355 |
|
Thread w = s.waiter; |
356 |
|
if (w != null) { // Wake up thread |
357 |
|
s.waiter = null; |
371 |
|
* processed, so this always terminates. |
372 |
|
*/ |
373 |
|
while (pred.next == s) { |
374 |
< |
QNode oldpred = reclean(); // First, help get rid of cleanMe |
375 |
< |
QNode t = getValidatedTail(); |
374 |
> |
Node<E> oldpred = reclean(); // First, help get rid of cleanMe |
375 |
> |
Node<E> t = getValidatedTail(); |
376 |
|
if (s != t) { // If not tail, try to unsplice |
377 |
< |
QNode sn = s.next; // s.next == s means s already off list |
377 |
> |
Node<E> sn = s.next; // s.next == s means s already off list |
378 |
|
if (sn == s || pred.casNext(s, sn)) |
379 |
|
break; |
380 |
|
} |
390 |
|
* |
391 |
|
* @return current cleanMe node (or null) |
392 |
|
*/ |
393 |
< |
private QNode reclean() { |
393 |
> |
private Node<E> reclean() { |
394 |
|
/* |
395 |
|
* cleanMe is, or at one time was, predecessor of cancelled |
396 |
|
* node s that was the tail so could not be unspliced. If s |
402 |
|
* This can loop only due to contention on casNext or |
403 |
|
* clearing cleanMe. |
404 |
|
*/ |
405 |
< |
QNode pred; |
405 |
> |
Node<E> pred; |
406 |
|
while ((pred = cleanMe.get()) != null) { |
407 |
< |
QNode t = getValidatedTail(); |
408 |
< |
QNode s = pred.next; |
407 |
> |
Node<E> t = getValidatedTail(); |
408 |
> |
Node<E> s = pred.next; |
409 |
|
if (s != t) { |
410 |
< |
QNode sn; |
410 |
> |
Node<E> sn; |
411 |
|
if (s == null || s == pred || s.get() != s || |
412 |
|
(sn = s.next) == s || pred.casNext(s, sn)) |
413 |
|
cleanMe.compareAndSet(pred, null); |
422 |
|
* Creates an initially empty {@code LinkedTransferQueue}. |
423 |
|
*/ |
424 |
|
public LinkedTransferQueue() { |
425 |
< |
QNode dummy = new QNode(null, false); |
426 |
< |
head = new PaddedAtomicReference<QNode>(dummy); |
427 |
< |
tail = new PaddedAtomicReference<QNode>(dummy); |
428 |
< |
cleanMe = new PaddedAtomicReference<QNode>(null); |
425 |
> |
Node<E> dummy = new Node<E>(null, false); |
426 |
> |
head = new PaddedAtomicReference<Node<E>>(dummy); |
427 |
> |
tail = new PaddedAtomicReference<Node<E>>(dummy); |
428 |
> |
cleanMe = new PaddedAtomicReference<Node<E>>(null); |
429 |
|
} |
430 |
|
|
431 |
|
/** |
507 |
|
} |
508 |
|
|
509 |
|
public E poll() { |
510 |
< |
return (E) fulfill(null); |
510 |
> |
return fulfill(null); |
511 |
|
} |
512 |
|
|
513 |
|
public int drainTo(Collection<? super E> c) { |
543 |
|
/** |
544 |
|
* Returns head after performing any outstanding helping steps. |
545 |
|
*/ |
546 |
< |
private QNode traversalHead() { |
546 |
> |
private Node<E> traversalHead() { |
547 |
|
for (;;) { |
548 |
< |
QNode t = tail.get(); |
549 |
< |
QNode h = head.get(); |
548 |
> |
Node<E> t = tail.get(); |
549 |
> |
Node<E> h = head.get(); |
550 |
|
if (h != null && t != null) { |
551 |
< |
QNode last = t.next; |
552 |
< |
QNode first = h.next; |
551 |
> |
Node<E> last = t.next; |
552 |
> |
Node<E> first = h.next; |
553 |
|
if (t == tail.get()) { |
554 |
|
if (last != null) |
555 |
|
tail.compareAndSet(t, last); |
581 |
|
* if subsequently removed. |
582 |
|
*/ |
583 |
|
class Itr implements Iterator<E> { |
584 |
< |
QNode next; // node to return next |
585 |
< |
QNode pnext; // predecessor of next |
586 |
< |
QNode snext; // successor of next |
587 |
< |
QNode curr; // last returned node, for remove() |
588 |
< |
QNode pcurr; // predecessor of curr, for remove() |
584 |
> |
Node<E> next; // node to return next |
585 |
> |
Node<E> pnext; // predecessor of next |
586 |
> |
Node<E> snext; // successor of next |
587 |
> |
Node<E> curr; // last returned node, for remove() |
588 |
> |
Node<E> pcurr; // predecessor of curr, for remove() |
589 |
|
E nextItem; // Cache of next item, once committed to in next |
590 |
|
|
591 |
|
Itr() { |
597 |
|
*/ |
598 |
|
void findNext() { |
599 |
|
for (;;) { |
600 |
< |
QNode pred = pnext; |
601 |
< |
QNode q = next; |
600 |
> |
Node<E> pred = pnext; |
601 |
> |
Node<E> q = next; |
602 |
|
if (pred == null || pred == q) { |
603 |
|
pred = traversalHead(); |
604 |
|
q = pred.next; |
608 |
|
return; |
609 |
|
} |
610 |
|
Object x = q.get(); |
611 |
< |
QNode s = q.next; |
611 |
> |
Node<E> s = q.next; |
612 |
|
if (x != null && q != x && q != s) { |
613 |
|
nextItem = (E) x; |
614 |
|
snext = s; |
637 |
|
} |
638 |
|
|
639 |
|
public void remove() { |
640 |
< |
QNode p = curr; |
640 |
> |
Node<E> p = curr; |
641 |
|
if (p == null) |
642 |
|
throw new IllegalStateException(); |
643 |
|
Object x = p.get(); |
648 |
|
|
649 |
|
public E peek() { |
650 |
|
for (;;) { |
651 |
< |
QNode h = traversalHead(); |
652 |
< |
QNode p = h.next; |
651 |
> |
Node<E> h = traversalHead(); |
652 |
> |
Node<E> p = h.next; |
653 |
|
if (p == null) |
654 |
|
return null; |
655 |
|
Object x = p.get(); |
664 |
|
|
665 |
|
public boolean isEmpty() { |
666 |
|
for (;;) { |
667 |
< |
QNode h = traversalHead(); |
668 |
< |
QNode p = h.next; |
667 |
> |
Node<E> h = traversalHead(); |
668 |
> |
Node<E> p = h.next; |
669 |
|
if (p == null) |
670 |
|
return true; |
671 |
|
Object x = p.get(); |
680 |
|
|
681 |
|
public boolean hasWaitingConsumer() { |
682 |
|
for (;;) { |
683 |
< |
QNode h = traversalHead(); |
684 |
< |
QNode p = h.next; |
683 |
> |
Node<E> h = traversalHead(); |
684 |
> |
Node<E> p = h.next; |
685 |
|
if (p == null) |
686 |
|
return false; |
687 |
|
Object x = p.get(); |
704 |
|
*/ |
705 |
|
public int size() { |
706 |
|
int count = 0; |
707 |
< |
QNode h = traversalHead(); |
708 |
< |
for (QNode p = h.next; p != null && p.isData; p = p.next) { |
707 |
> |
Node<E> h = traversalHead(); |
708 |
> |
for (Node<E> p = h.next; p != null && p.isData; p = p.next) { |
709 |
|
Object x = p.get(); |
710 |
|
if (x != null && x != p) { |
711 |
|
if (++count == Integer.MAX_VALUE) // saturated |
717 |
|
|
718 |
|
public int getWaitingConsumerCount() { |
719 |
|
int count = 0; |
720 |
< |
QNode h = traversalHead(); |
721 |
< |
for (QNode p = h.next; p != null && !p.isData; p = p.next) { |
720 |
> |
Node<E> h = traversalHead(); |
721 |
> |
for (Node<E> p = h.next; p != null && !p.isData; p = p.next) { |
722 |
|
if (p.get() == null) { |
723 |
|
if (++count == Integer.MAX_VALUE) |
724 |
|
break; |
735 |
|
if (o == null) |
736 |
|
return false; |
737 |
|
for (;;) { |
738 |
< |
QNode pred = traversalHead(); |
738 |
> |
Node<E> pred = traversalHead(); |
739 |
|
for (;;) { |
740 |
< |
QNode q = pred.next; |
740 |
> |
Node<E> q = pred.next; |
741 |
|
if (q == null || !q.isData) |
742 |
|
return false; |
743 |
|
if (q == pred) // restart |
780 |
|
s.defaultReadObject(); |
781 |
|
resetHeadAndTail(); |
782 |
|
for (;;) { |
783 |
< |
E item = (E) s.readObject(); |
783 |
> |
@SuppressWarnings("unchecked") E item = (E) s.readObject(); |
784 |
|
if (item == null) |
785 |
|
break; |
786 |
|
else |
788 |
|
} |
789 |
|
} |
790 |
|
|
786 |
– |
|
791 |
|
// Support for resetting head/tail while deserializing |
792 |
|
private void resetHeadAndTail() { |
793 |
< |
QNode dummy = new QNode(null, false); |
793 |
> |
Node<E> dummy = new Node<E>(null, false); |
794 |
|
UNSAFE.putObjectVolatile(this, headOffset, |
795 |
< |
new PaddedAtomicReference<QNode>(dummy)); |
795 |
> |
new PaddedAtomicReference<Node<E>>(dummy)); |
796 |
|
UNSAFE.putObjectVolatile(this, tailOffset, |
797 |
< |
new PaddedAtomicReference<QNode>(dummy)); |
797 |
> |
new PaddedAtomicReference<Node<E>>(dummy)); |
798 |
|
UNSAFE.putObjectVolatile(this, cleanMeOffset, |
799 |
< |
new PaddedAtomicReference<QNode>(null)); |
799 |
> |
new PaddedAtomicReference<Node<E>>(null)); |
800 |
|
} |
801 |
|
|
802 |
< |
// Temporary Unsafe mechanics for preliminary release |
803 |
< |
private static Unsafe getUnsafe() throws Throwable { |
802 |
> |
// Unsafe mechanics for jsr166y 3rd party package. |
803 |
> |
private static sun.misc.Unsafe getUnsafe() { |
804 |
|
try { |
805 |
< |
return Unsafe.getUnsafe(); |
805 |
> |
return sun.misc.Unsafe.getUnsafe(); |
806 |
|
} catch (SecurityException se) { |
807 |
|
try { |
808 |
|
return java.security.AccessController.doPrivileged |
809 |
< |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
810 |
< |
public Unsafe run() throws Exception { |
811 |
< |
return getUnsafePrivileged(); |
809 |
> |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
810 |
> |
public sun.misc.Unsafe run() throws Exception { |
811 |
> |
return getUnsafeByReflection(); |
812 |
|
}}); |
813 |
|
} catch (java.security.PrivilegedActionException e) { |
814 |
< |
throw e.getCause(); |
814 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
815 |
> |
e.getCause()); |
816 |
|
} |
817 |
|
} |
818 |
|
} |
819 |
|
|
820 |
< |
private static Unsafe getUnsafePrivileged() |
820 |
> |
private static sun.misc.Unsafe getUnsafeByReflection() |
821 |
|
throws NoSuchFieldException, IllegalAccessException { |
822 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
822 |
> |
java.lang.reflect.Field f = |
823 |
> |
sun.misc.Unsafe.class.getDeclaredField("theUnsafe"); |
824 |
|
f.setAccessible(true); |
825 |
< |
return (Unsafe) f.get(null); |
820 |
< |
} |
821 |
< |
|
822 |
< |
private static long fieldOffset(String fieldName) |
823 |
< |
throws NoSuchFieldException { |
824 |
< |
return UNSAFE.objectFieldOffset |
825 |
< |
(LinkedTransferQueue.class.getDeclaredField(fieldName)); |
825 |
> |
return (sun.misc.Unsafe) f.get(null); |
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 { |
828 |
> |
private static long fieldOffset(String fieldName, Class<?> klazz) { |
829 |
|
try { |
830 |
< |
UNSAFE = getUnsafe(); |
831 |
< |
headOffset = fieldOffset("head"); |
832 |
< |
tailOffset = fieldOffset("tail"); |
833 |
< |
cleanMeOffset = fieldOffset("cleanMe"); |
834 |
< |
} catch (Throwable e) { |
835 |
< |
throw new RuntimeException("Could not initialize intrinsics", e); |
830 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName)); |
831 |
> |
} catch (NoSuchFieldException e) { |
832 |
> |
// Convert Exception to Error |
833 |
> |
NoSuchFieldError error = new NoSuchFieldError(fieldName); |
834 |
> |
error.initCause(e); |
835 |
> |
throw error; |
836 |
|
} |
837 |
|
} |
838 |
|
|
839 |
+ |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
840 |
+ |
static final long headOffset = |
841 |
+ |
fieldOffset("head", LinkedTransferQueue.class); |
842 |
+ |
static final long tailOffset = |
843 |
+ |
fieldOffset("tail", LinkedTransferQueue.class); |
844 |
+ |
static final long cleanMeOffset = |
845 |
+ |
fieldOffset("cleanMe", LinkedTransferQueue.class); |
846 |
+ |
|
847 |
|
} |