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root/jsr166/jsr166/src/jsr166y/LinkedTransferQueue.java

Comparing jsr166/src/jsr166y/LinkedTransferQueue.java (file contents):
Revision 1.14 by jsr166, Thu Mar 19 05:10:42 2009 UTC vs.
Revision 1.25 by jsr166, Fri Jul 24 23:48:26 2009 UTC

#	Line 10 | Line 10 | import java.util.concurrent.locks.*;
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.
#	Line 44 | Line 42 | import java.lang.reflect.*;
42		* @since 1.7
43		* @author Doug Lea
44		* @param <E> the type of elements held in this collection
47	–	*
45		*/
46		public class LinkedTransferQueue<E> extends AbstractQueue<E>
47		implements TransferQueue<E>, java.io.Serializable {
#	Line 81 | Line 78 | public class LinkedTransferQueue<E> exte
78		* seems not to vary with number of CPUs (beyond 2) so is just
79		* a constant.
80		*/
81	<	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
81	>	static final int maxTimedSpins = (NCPUS < 2) ? 0 : 32;
82
83		/**
84		* The number of times to spin before blocking in untimed waits.
#	Line 103 | Line 100 | public class LinkedTransferQueue<E> exte
100		* 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	<	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	+
122	+	final void clearNext() {
123	+	nextUpdater.lazySet(this, this);
124	+	}
125	+
126	+	private static final long serialVersionUID = -3375979862319811754L;
127		}
128
129		/**
#	Line 130 | Line 135 | public class LinkedTransferQueue<E> exte
135		// enough padding for 64bytes with 4byte refs
136		Object p0, p1, p2, p3, p4, p5, p6, p7, p8, p9, pa, pb, pc, pd, pe;
137		PaddedAtomicReference(T r) { super(r); }
138	+	private static final long serialVersionUID = 8170090609809740854L;
139		}
140
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.next = h; // forget old next
161	>	h.clearNext(); // forget old next
162		return true;
163		}
164		return false;
#	Line 161 | Line 168 | public class LinkedTransferQueue<E> exte
168		* Puts or takes an item. Used for most queue operations (except
169		* poll() and tryTransfer()). See the similar code in
170		* SynchronousQueue for detailed explanation.
171	+	*
172		* @param e the item or if null, signifies that this is a take
173		* @param mode the wait mode: NOWAIT, TIMEOUT, WAIT
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);
#	Line 191 | Line 199 | public class LinkedTransferQueue<E> exte
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		}
#	Line 207 | Line 215 | public class LinkedTransferQueue<E> exte
215
216		/**
217		* Version of xfer for poll() and tryTransfer, which
218	<	* simplifies control paths both here and in xfer
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);
#	Line 228 | Line 236 | public class LinkedTransferQueue<E> exte
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		}
#	Line 253 | Line 261 | public class LinkedTransferQueue<E> exte
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
269	<	long lastTime = (mode == TIMEOUT)? System.nanoTime() : 0;
269	>	long lastTime = (mode == TIMEOUT) ? System.nanoTime() : 0;
270		Thread w = Thread.currentThread();
271		int spins = -1; // set to desired spin count below
272		for (;;) {
#	Line 267 | Line 275 | public class LinkedTransferQueue<E> exte
275		Object x = s.get();
276		if (x != e) {                 // Node was matched or cancelled
277		advanceHead(pred, s);     // unlink if head
278	<	if (x == s) {              // was cancelled
278	>	if (x == s) {             // was cancelled
279		clean(pred, s);
280		return null;
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;
#	Line 288 | Line 296 | public class LinkedTransferQueue<E> exte
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?
301	>	((mode == TIMEOUT) ?
302		maxTimedSpins : maxUntimedSpins) : 0);
303		}
304		if (spins > 0)
#	Line 311 | Line 319 | public class LinkedTransferQueue<E> exte
319		}
320
321		/**
322	<	* Returns validated tail for use in cleaning methods
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
#	Line 334 | Line 342 | public class LinkedTransferQueue<E> exte
342
343		/**
344		* Gets rid of cancelled node s with original predecessor pred.
345	+	*
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;
353		if (w != Thread.currentThread())
354		LockSupport.unpark(w);
355		}
356	+
357	+	if (pred == null)
358	+	return;
359	+
360		/*
361		* At any given time, exactly one node on list cannot be
362		* deleted -- the last inserted node. To accommodate this, if
#	Line 353 | Line 366 | public class LinkedTransferQueue<E> exte
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		}
#	Line 369 | Line 382 | public class LinkedTransferQueue<E> exte
382		/**
383		* Tries to unsplice the cancelled node held in cleanMe that was
384		* previously uncleanable because it was at tail.
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
#	Line 383 | Line 397 | public class LinkedTransferQueue<E> exte
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);
#	Line 403 | Line 417 | public class LinkedTransferQueue<E> exte
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		/**
427		* Creates a {@code LinkedTransferQueue}
428		* initially containing the elements of the given collection,
429		* added in traversal order of the collection's iterator.
430	+	*
431		* @param c the collection of elements to initially contain
432		* @throws NullPointerException if the specified collection or any
433		*         of its elements are null
#	Line 442 | Line 457 | public class LinkedTransferQueue<E> exte
457		return true;
458		}
459
460	+	public boolean add(E e) {
461	+	if (e == null) throw new NullPointerException();
462	+	xfer(e, NOWAIT, 0);
463	+	return true;
464	+	}
465	+
466		public void transfer(E e) throws InterruptedException {
467		if (e == null) throw new NullPointerException();
468		if (xfer(e, WAIT, 0) == null) {
#	Line 468 | Line 489 | public class LinkedTransferQueue<E> exte
489		public E take() throws InterruptedException {
490		Object e = xfer(null, WAIT, 0);
491		if (e != null)
492	<	return (E)e;
492	>	return (E) e;
493		Thread.interrupted();
494		throw new InterruptedException();
495		}
#	Line 476 | Line 497 | public class LinkedTransferQueue<E> exte
497		public E poll(long timeout, TimeUnit unit) throws InterruptedException {
498		Object e = xfer(null, TIMEOUT, unit.toNanos(timeout));
499		if (e != null || !Thread.interrupted())
500	<	return (E)e;
500	>	return (E) e;
501		throw new InterruptedException();
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) {
#	Line 515 | Line 536 | public class LinkedTransferQueue<E> exte
536		// Traversal-based methods
537
538		/**
539	<	* Return head after performing any outstanding helping steps
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);
#	Line 538 | Line 559 | public class LinkedTransferQueue<E> exte
559		return h;
560		}
561		}
562	+	reclean();
563		}
564		}
565
#	Line 554 | Line 576 | public class LinkedTransferQueue<E> exte
576		* if subsequently removed.
577		*/
578		class Itr implements Iterator<E> {
579	<	QNode nextNode;    // Next node to return next
580	<	QNode currentNode; // last returned node, for remove()
581	<	QNode prevNode;    // predecessor of last returned node
582	<	E nextItem;        // Cache of next item, once commited to in next
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() {
587	<	nextNode = traversalHead();
564	<	advance();
587	>	findNext();
588		}
589
590	<	E advance() {
591	<	prevNode = currentNode;
592	<	currentNode = nextNode;
593	<	E x = nextItem;
571	<
572	<	QNode p = nextNode.next;
590	>	/**
591	>	* Ensures next points to next valid node, or null if none.
592	>	*/
593	>	void findNext() {
594		for (;;) {
595	<	if (p == null || !p.isData) {
596	<	nextNode = null;
597	<	nextItem = null;
598	<	return x;
599	<	}
600	<	Object item = p.get();
601	<	if (item != p && item != null) {
602	<	nextNode = p;
603	<	nextItem = (E)item;
604	<	return x;
595	>	Node<E> pred = pnext;
596	>	Node<E> q = next;
597	>	if (pred == null || pred == q) {
598	>	pred = traversalHead();
599	>	q = pred.next;
600	>	}
601	>	if (q == null || !q.isData) {
602	>	next = null;
603	>	return;
604	>	}
605	>	Object x = q.get();
606	>	Node<E> s = q.next;
607	>	if (x != null && q != x && q != s) {
608	>	nextItem = (E) x;
609	>	snext = s;
610	>	pnext = pred;
611	>	next = q;
612	>	return;
613		}
614	<	prevNode = p;
615	<	p = p.next;
614	>	pnext = q;
615	>	next = s;
616		}
617		}
618
619		public boolean hasNext() {
620	<	return nextNode != null;
620	>	return next != null;
621		}
622
623		public E next() {
624	<	if (nextNode == null) throw new NoSuchElementException();
625	<	return advance();
624	>	if (next == null) throw new NoSuchElementException();
625	>	pcurr = pnext;
626	>	curr = next;
627	>	pnext = next;
628	>	next = snext;
629	>	E x = nextItem;
630	>	findNext();
631	>	return x;
632		}
633
634		public void remove() {
635	<	QNode p = currentNode;
636	<	QNode prev = prevNode;
602	<	if (prev == null || p == null)
635	>	Node<E> p = curr;
636	>	if (p == null)
637		throw new IllegalStateException();
638		Object x = p.get();
639		if (x != null && x != p && p.compareAndSet(x, p))
640	<	clean(prev, p);
640	>	clean(pcurr, p);
641		}
642		}
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();
#	Line 618 | Line 652 | public class LinkedTransferQueue<E> exte
652		if (!p.isData)
653		return null;
654		if (x != null)
655	<	return (E)x;
655	>	return (E) x;
656		}
657		}
658		}
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();
#	Line 641 | Line 675 | public class LinkedTransferQueue<E> exte
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();
#	Line 665 | Line 699 | public class LinkedTransferQueue<E> exte
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
#	Line 678 | Line 712 | public class LinkedTransferQueue<E> exte
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;
#	Line 692 | Line 726 | public class LinkedTransferQueue<E> exte
726		return Integer.MAX_VALUE;
727		}
728
729	+	public boolean remove(Object o) {
730	+	if (o == null)
731	+	return false;
732	+	for (;;) {
733	+	Node<E> pred = traversalHead();
734	+	for (;;) {
735	+	Node<E> q = pred.next;
736	+	if (q == null || !q.isData)
737	+	return false;
738	+	if (q == pred) // restart
739	+	break;
740	+	Object x = q.get();
741	+	if (x != null && x != q && o.equals(x) &&
742	+	q.compareAndSet(x, q)) {
743	+	clean(pred, q);
744	+	return true;
745	+	}
746	+	pred = q;
747	+	}
748	+	}
749	+	}
750	+
751		/**
752		* Save the state to a stream (that is, serialize it).
753		*
#	Line 702 | Line 758 | public class LinkedTransferQueue<E> exte
758		private void writeObject(java.io.ObjectOutputStream s)
759		throws java.io.IOException {
760		s.defaultWriteObject();
761	<	for (Iterator<E> it = iterator(); it.hasNext(); )
762	<	s.writeObject(it.next());
761	>	for (E e : this)
762	>	s.writeObject(e);
763		// Use trailing null as sentinel
764		s.writeObject(null);
765		}
#	Line 711 | Line 767 | public class LinkedTransferQueue<E> exte
767		/**
768		* Reconstitute the Queue instance from a stream (that is,
769		* deserialize it).
770	+	*
771		* @param s the stream
772		*/
773		private void readObject(java.io.ObjectInputStream s)
#	Line 718 | Line 775 | public class LinkedTransferQueue<E> exte
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
#	Line 726 | Line 783 | public class LinkedTransferQueue<E> exte
783		}
784		}
785
729	–
786		// Support for resetting head/tail while deserializing
787		private void resetHeadAndTail() {
788	<	QNode dummy = new QNode(null, false);
789	<	_unsafe.putObjectVolatile(this, headOffset,
790	<	new PaddedAtomicReference<QNode>(dummy));
791	<	_unsafe.putObjectVolatile(this, tailOffset,
792	<	new PaddedAtomicReference<QNode>(dummy));
793	<	_unsafe.putObjectVolatile(this, cleanMeOffset,
794	<	new PaddedAtomicReference<QNode>(null));
788	>	Node<E> dummy = new Node<E>(null, false);
789	>	UNSAFE.putObjectVolatile(this, headOffset,
790	>	new PaddedAtomicReference<Node<E>>(dummy));
791	>	UNSAFE.putObjectVolatile(this, tailOffset,
792	>	new PaddedAtomicReference<Node<E>>(dummy));
793	>	UNSAFE.putObjectVolatile(this, cleanMeOffset,
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);
763	<	}
764	<
765	<	private static long fieldOffset(String fieldName)
766	<	throws NoSuchFieldException {
767	<	return _unsafe.objectFieldOffset
768	<	(LinkedTransferQueue.class.getDeclaredField(fieldName));
820	>	return (sun.misc.Unsafe) f.get(null);
821		}
822
823	<	private static final Unsafe _unsafe;
772	<	private static final long headOffset;
773	<	private static final long tailOffset;
774	<	private static final long cleanMeOffset;
775	<	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		}

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