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root/jsr166/jsr166/src/jsr166y/Phaser.java

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.40 by dl, Mon Aug 24 12:49:39 2009 UTC vs.
Revision 1.50 by dl, Sat Nov 6 16:12:10 2010 UTC

#	Line 7 | Line 7
7		package jsr166y;
8
9		import java.util.concurrent.*;
10	–
10		import java.util.concurrent.atomic.AtomicReference;
11		import java.util.concurrent.locks.LockSupport;
12
#	Line 100 | Line 99 | import java.util.concurrent.locks.LockSu
99		* #getRegisteredParties} parties in total, of which {@link
100		* #getArrivedParties} have arrived at the current phase ({@link
101		* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
102	<	* parties arrive, the phase advances; thus, this value is always
103	<	* greater than zero if there are any registered parties.  The values
104	<	* returned by these methods may reflect transient states and so are
105	<	* not in general useful for synchronization control.  Method {@link
106	<	* #toString} returns snapshots of these state queries in a form
108	<	* convenient for informal monitoring.
102	>	* parties arrive, the phase advances.  The values returned by these
103	>	* methods may reflect transient states and so are not in general
104	>	* useful for synchronization control.  Method {@link #toString}
105	>	* returns snapshots of these state queries in a form convenient for
106	>	* informal monitoring.
107		*
108		* <p><b>Sample usages:</b>
109		*
110		* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
111	<	* to control a one-shot action serving a variable number of
112	<	* parties. The typical idiom is for the method setting this up to
113	<	* first register, then start the actions, then deregister, as in:
111	>	* to control a one-shot action serving a variable number of parties.
112	>	* The typical idiom is for the method setting this up to first
113	>	* register, then start the actions, then deregister, as in:
114		*
115		*  <pre> {@code
116		* void runTasks(List<Runnable> tasks) {
#	Line 143 | Line 141 | import java.util.concurrent.locks.LockSu
141		*     }
142		*   };
143		*   phaser.register();
144	<	*   for (Runnable task : tasks) {
144	>	*   for (final Runnable task : tasks) {
145		*     phaser.register();
146		*     new Thread() {
147		*       public void run() {
148		*         do {
149		*           task.run();
150		*           phaser.arriveAndAwaitAdvance();
151	<	*         } while(!phaser.isTerminated();
151	>	*         } while (!phaser.isTerminated());
152		*       }
153		*     }.start();
154		*   }
#	Line 159 | Line 157 | import java.util.concurrent.locks.LockSu
157		*
158		* If the main task must later await termination, it
159		* may re-register and then execute a similar loop:
160	<	* <pre> {@code
160	>	*  <pre> {@code
161		*   // ...
162		*   phaser.register();
163		*   while (!phaser.isTerminated())
164	<	*     phaser.arriveAndAwaitAdvance();
167	<	* }</pre>
164	>	*     phaser.arriveAndAwaitAdvance();}</pre>
165		*
166	<	* Related constructions may be used to await particular phase numbers
166	>	* <p>Related constructions may be used to await particular phase numbers
167		* in contexts where you are sure that the phase will never wrap around
168		* {@code Integer.MAX_VALUE}. For example:
169		*
170	<	* <pre> {@code
171	<	*   void awaitPhase(Phaser phaser, int phase) {
172	<	*     int p = phaser.register(); // assumes caller not already registered
173	<	*     while (p < phase) {
174	<	*       if (phaser.isTerminated())
175	<	*         // ... deal with unexpected termination
176	<	*       else
177	<	*         p = phaser.arriveAndAwaitAdvance();
181	<	*     }
182	<	*     phaser.arriveAndDeregister();
170	>	*  <pre> {@code
171	>	* void awaitPhase(Phaser phaser, int phase) {
172	>	*   int p = phaser.register(); // assumes caller not already registered
173	>	*   while (p < phase) {
174	>	*     if (phaser.isTerminated())
175	>	*       // ... deal with unexpected termination
176	>	*     else
177	>	*       p = phaser.arriveAndAwaitAdvance();
178		*   }
179	<	* }</pre>
179	>	*   phaser.arriveAndDeregister();
180	>	* }}</pre>
181		*
182		*
183		* <p>To create a set of tasks using a tree of phasers,
184		* you could use code of the following form, assuming a
185		* Task class with a constructor accepting a phaser that
186	<	* it registers for upon construction:
186	>	* it registers with upon construction:
187	>	*
188		*  <pre> {@code
189	<	* void build(Task[] actions, int lo, int hi, Phaser b) {
190	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
191	<	*   if (step > 1) {
192	<	*     int i = lo;
193	<	*     while (i < hi) {
197	<	*       int r = Math.min(i + step, hi);
198	<	*       build(actions, i, r, new Phaser(b));
199	<	*       i = r;
189	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
190	>	*   if (hi - lo > TASKS_PER_PHASER) {
191	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
192	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
193	>	*       build(actions, i, j, new Phaser(ph));
194		*     }
195		*   } else {
196		*     for (int i = lo; i < hi; ++i)
197	<	*       actions[i] = new Task(b);
198	<	*       // assumes new Task(b) performs b.register()
197	>	*       actions[i] = new Task(ph);
198	>	*       // assumes new Task(ph) performs ph.register()
199		*   }
200		* }
201		* // .. initially called, for n tasks via
#	Line 212 | Line 206 | import java.util.concurrent.locks.LockSu
206		* be appropriate for extremely small per-barrier task bodies (thus
207		* high rates), or up to hundreds for extremely large ones.
208		*
215	–	* </pre>
216	–	*
209		* <p><b>Implementation notes</b>: This implementation restricts the
210		* maximum number of parties to 65535. Attempts to register additional
211		* parties result in {@code IllegalStateException}. However, you can and
#	Line 250 | Line 242 | public class Phaser {
242		*/
243		private volatile long state;
244
253	–	private static final int ushortBits = 16;
245		private static final int ushortMask = 0xffff;
246		private static final int phaseMask  = 0x7fffffff;
247
#	Line 303 | Line 294 | public class Phaser {
294
295		/**
296		* Heads of Treiber stacks for waiting threads. To eliminate
297	<	* contention while releasing some threads while adding others, we
297	>	* contention when releasing some threads while adding others, we
298		* use two of them, alternating across even and odd phases.
299	+	* Subphasers share queues with root to speed up releases.
300		*/
301	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
302	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
301	>	private final AtomicReference<QNode> evenQ;
302	>	private final AtomicReference<QNode> oddQ;
303
304		private AtomicReference<QNode> queueFor(int phase) {
305		return ((phase & 1) == 0) ? evenQ : oddQ;
#	Line 325 | Line 317 | public class Phaser {
317		* Recursively resolves state.
318		*/
319		private long reconcileState() {
320	<	Phaser p = parent;
320	>	Phaser par = parent;
321		long s = state;
322	<	if (p != null) {
323	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
324	<	long parentState = p.getReconciledState();
325	<	int parentPhase = phaseOf(parentState);
326	<	int phase = phaseOf(s = state);
327	<	if (phase != parentPhase) {
322	>	if (par != null) {
323	>	int phase, rootPhase;
324	>	while ((phase = phaseOf(s)) >= 0 &&
325	>	(rootPhase = phaseOf(root.state)) != phase &&
326	>	(rootPhase < 0 || unarrivedOf(s) == 0)) {
327	>	int parentPhase = phaseOf(par.getReconciledState());
328	>	if (parentPhase != phase) {
329		long next = trippedStateFor(parentPhase, partiesOf(s));
330	<	if (casState(s, next)) {
331	<	releaseWaiters(phase);
339	<	s = next;
340	<	}
330	>	if (state == s)
331	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
332		}
333	+	s = state;
334		}
335		}
336		return s;
#	Line 350 | Line 342 | public class Phaser {
342		* phaser will need to first register for it.
343		*/
344		public Phaser() {
345	<	this(null);
345	>	this(null, 0);
346		}
347
348		/**
349	<	* Creates a new phaser with the given numbers of registered
349	>	* Creates a new phaser with the given number of registered
350		* unarrived parties, initial phase number 0, and no parent.
351		*
352		* @param parties the number of parties required to trip barrier
#	Line 374 | Line 366 | public class Phaser {
366		* @param parent the parent phaser
367		*/
368		public Phaser(Phaser parent) {
369	<	int phase = 0;
378	<	this.parent = parent;
379	<	if (parent != null) {
380	<	this.root = parent.root;
381	<	phase = parent.register();
382	<	}
383	<	else
384	<	this.root = this;
385	<	this.state = trippedStateFor(phase, 0);
369	>	this(parent, 0);
370		}
371
372		/**
373	<	* Creates a new phaser with the given parent and numbers of
373	>	* Creates a new phaser with the given parent and number of
374		* registered unarrived parties. If parent is non-null, this phaser
375		* is registered with the parent and its initial phase number is
376		* the same as that of parent phaser.
#	Line 399 | Line 383 | public class Phaser {
383		public Phaser(Phaser parent, int parties) {
384		if (parties < 0 || parties > ushortMask)
385		throw new IllegalArgumentException("Illegal number of parties");
386	<	int phase = 0;
386	>	int phase;
387		this.parent = parent;
388		if (parent != null) {
389	<	this.root = parent.root;
389	>	Phaser r = parent.root;
390	>	this.root = r;
391	>	this.evenQ = r.evenQ;
392	>	this.oddQ = r.oddQ;
393		phase = parent.register();
394		}
395	<	else
395	>	else {
396		this.root = this;
397	+	this.evenQ = new AtomicReference<QNode>();
398	+	this.oddQ = new AtomicReference<QNode>();
399	+	phase = 0;
400	+	}
401		this.state = trippedStateFor(phase, parties);
402		}
403
404		/**
405		* Adds a new unarrived party to this phaser.
406	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
407	+	* this method may wait until its completion before registering.
408		*
409		* @return the arrival phase number to which this registration applied
410		* @throws IllegalStateException if attempting to register more
#	Line 423 | Line 416 | public class Phaser {
416
417		/**
418		* Adds the given number of new unarrived parties to this phaser.
419	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
420	+	* this method may wait until its completion before registering.
421		*
422	<	* @param parties the number of parties required to trip barrier
422	>	* @param parties the number of additional parties required to trip barrier
423		* @return the arrival phase number to which this registration applied
424		* @throws IllegalStateException if attempting to register more
425		* than the maximum supported number of parties
426	+	* @throws IllegalArgumentException if {@code parties < 0}
427		*/
428		public int bulkRegister(int parties) {
429		if (parties < 0)
#	Line 441 | Line 437 | public class Phaser {
437		* Shared code for register, bulkRegister
438		*/
439		private int doRegister(int registrations) {
440	+	Phaser par = parent;
441	+	long s;
442		int phase;
443	<	for (;;) {
444	<	long s = getReconciledState();
445	<	phase = phaseOf(s);
446	<	int unarrived = unarrivedOf(s) + registrations;
447	<	int parties = partiesOf(s) + registrations;
448	<	if (phase < 0)
449	<	break;
450	<	if (parties > ushortMask || unarrived > ushortMask)
443	>	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
444	>	int p = partiesOf(s);
445	>	int u = unarrivedOf(s);
446	>	int unarrived = u + registrations;
447	>	int parties = p + registrations;
448	>	if (u == 0 && p != 0)  // if tripped, wait for advance
449	>	untimedWait(phase);
450	>	else if (parties > ushortMask)
451		throw new IllegalStateException(badBounds(parties, unarrived));
452	<	if (phase == phaseOf(root.state) &&
453	<	casState(s, stateFor(phase, parties, unarrived)))
454	<	break;
452	>	else if (par == null || phaseOf(root.state) == phase) {
453	>	long next = stateFor(phase, parties, unarrived);
454	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
455	>	break;
456	>	}
457		}
458		return phase;
459		}
#	Line 469 | Line 469 | public class Phaser {
469		* of unarrived parties would become negative
470		*/
471		public int arrive() {
472	+	Phaser par = parent;
473	+	long s;
474		int phase;
475	<	for (;;) {
474	<	long s = state;
475	<	phase = phaseOf(s);
476	<	if (phase < 0)
477	<	break;
475	>	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
476		int parties = partiesOf(s);
477		int unarrived = unarrivedOf(s) - 1;
478	<	if (unarrived > 0) {        // Not the last arrival
479	<	if (casState(s, s - 1)) // s-1 adds one arrival
480	<	break;
478	>	if (unarrived > 0) {                // Not the last arrival
479	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s - 1))
480	>	break;                      // s-1 adds one arrival
481		}
482	<	else if (unarrived == 0) {  // the last arrival
483	<	Phaser par = parent;
484	<	if (par == null) {      // directly trip
485	<	if (casState
486	<	(s,
487	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
488	<	((phase + 1) & phaseMask), parties))) {
489	<	releaseWaiters(phase);
490	<	break;
493	<	}
494	<	}
495	<	else {                  // cascade to parent
496	<	if (casState(s, s - 1)) { // zeroes unarrived
497	<	par.arrive();
498	<	reconcileState();
499	<	break;
500	<	}
482	>	else if (unarrived < 0)
483	>	throw new IllegalStateException(badBounds(parties, unarrived));
484	>	else if (par == null) {             // directly trip
485	>	long next = trippedStateFor(onAdvance(phase, parties) ? -1 :
486	>	((phase + 1) & phaseMask),
487	>	parties);
488	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) {
489	>	releaseWaiters(phase);
490	>	break;
491		}
492		}
493	<	else if (phase != phaseOf(root.state)) // or if unreconciled
493	>	else if (phaseOf(root.state) == phase &&
494	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, s - 1)) {
495	>	par.arrive();                   // cascade to parent
496		reconcileState();
497	<	else
498	<	throw new IllegalStateException(badBounds(parties, unarrived));
497	>	break;
498	>	}
499		}
500		return phase;
501		}
#	Line 522 | Line 514 | public class Phaser {
514		* of registered or unarrived parties would become negative
515		*/
516		public int arriveAndDeregister() {
517	<	// similar code to arrive, but too different to merge
517	>	// similar to arrive, but too different to merge
518		Phaser par = parent;
519	+	long s;
520		int phase;
521	<	for (;;) {
529	<	long s = state;
530	<	phase = phaseOf(s);
531	<	if (phase < 0)
532	<	break;
521	>	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
522		int parties = partiesOf(s) - 1;
523		int unarrived = unarrivedOf(s) - 1;
524	<	if (parties >= 0) {
525	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
526	<	if (casState
527	<	(s,
528	<	stateFor(phase, parties, unarrived))) {
529	<	if (unarrived == 0) {
530	<	par.arriveAndDeregister();
531	<	reconcileState();
532	<	}
533	<	break;
534	<	}
535	<	continue;
536	<	}
537	<	if (unarrived == 0) {
549	<	if (casState
550	<	(s,
551	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
552	<	((phase + 1) & phaseMask), parties))) {
553	<	releaseWaiters(phase);
554	<	break;
555	<	}
556	<	continue;
524	>	if (unarrived > 0) {
525	>	long next = stateFor(phase, parties, unarrived);
526	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
527	>	break;
528	>	}
529	>	else if (unarrived < 0)
530	>	throw new IllegalStateException(badBounds(parties, unarrived));
531	>	else if (par == null) {
532	>	long next = trippedStateFor(onAdvance(phase, parties)? -1:
533	>	(phase + 1) & phaseMask,
534	>	parties);
535	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) {
536	>	releaseWaiters(phase);
537	>	break;
538		}
539	<	if (par != null && phase != phaseOf(root.state)) {
539	>	}
540	>	else if (phaseOf(root.state) == phase) {
541	>	long next = stateFor(phase, parties, 0);
542	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) {
543	>	if (parties == 0)
544	>	par.arriveAndDeregister();
545	>	else
546	>	par.arrive();
547		reconcileState();
548	<	continue;
548	>	break;
549		}
550		}
563	–	throw new IllegalStateException(badBounds(parties, unarrived));
551		}
552		return phase;
553		}
#	Line 569 | Line 556 | public class Phaser {
556		* Arrives at the barrier and awaits others. Equivalent in effect
557		* to {@code awaitAdvance(arrive())}.  If you need to await with
558		* interruption or timeout, you can arrange this with an analogous
559	<	* construction using one of the other forms of the awaitAdvance
560	<	* method.  If instead you need to deregister upon arrival use
561	<	* {@code arriveAndDeregister}. It is an unenforced usage error
562	<	* for an unregistered party to invoke this method.
559	>	* construction using one of the other forms of the {@code
560	>	* awaitAdvance} method.  If instead you need to deregister upon
561	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
562	>	* usage error for an unregistered party to invoke this method.
563		*
564		* @return the arrival phase number, or a negative number if terminated
565		* @throws IllegalStateException if not terminated and the number
#	Line 586 | Line 573 | public class Phaser {
573		* Awaits the phase of the barrier to advance from the given phase
574		* value, returning immediately if the current phase of the
575		* barrier is not equal to the given phase value or this barrier
576	<	* is terminated.  It is an unenforced usage error for an
590	<	* unregistered party to invoke this method.
576	>	* is terminated.
577		*
578		* @param phase an arrival phase number, or negative value if
579		* terminated; this argument is normally the value returned by a
#	Line 598 | Line 584 | public class Phaser {
584		public int awaitAdvance(int phase) {
585		if (phase < 0)
586		return phase;
587	<	long s = getReconciledState();
602	<	int p = phaseOf(s);
587	>	int p = getPhase();
588		if (p != phase)
589		return p;
605	–	if (unarrivedOf(s) == 0 && parent != null)
606	–	parent.awaitAdvance(phase);
607	–	// Fall here even if parent waited, to reconcile and help release
590		return untimedWait(phase);
591		}
592
#	Line 613 | Line 595 | public class Phaser {
595		* value, throwing {@code InterruptedException} if interrupted
596		* while waiting, or returning immediately if the current phase of
597		* the barrier is not equal to the given phase value or this
598	<	* barrier is terminated. It is an unenforced usage error for an
617	<	* unregistered party to invoke this method.
598	>	* barrier is terminated.
599		*
600		* @param phase an arrival phase number, or negative value if
601		* terminated; this argument is normally the value returned by a
#	Line 627 | Line 608 | public class Phaser {
608		throws InterruptedException {
609		if (phase < 0)
610		return phase;
611	<	long s = getReconciledState();
631	<	int p = phaseOf(s);
611	>	int p = getPhase();
612		if (p != phase)
613		return p;
634	–	if (unarrivedOf(s) == 0 && parent != null)
635	–	parent.awaitAdvanceInterruptibly(phase);
614		return interruptibleWait(phase);
615		}
616
#	Line 642 | Line 620 | public class Phaser {
620		* InterruptedException} if interrupted while waiting, or
621		* returning immediately if the current phase of the barrier is
622		* not equal to the given phase value or this barrier is
623	<	* terminated.  It is an unenforced usage error for an
646	<	* unregistered party to invoke this method.
623	>	* terminated.
624		*
625		* @param phase an arrival phase number, or negative value if
626		* terminated; this argument is normally the value returned by a
#	Line 660 | Line 637 | public class Phaser {
637		public int awaitAdvanceInterruptibly(int phase,
638		long timeout, TimeUnit unit)
639		throws InterruptedException, TimeoutException {
640	+	long nanos = unit.toNanos(timeout);
641		if (phase < 0)
642		return phase;
643	<	long s = getReconciledState();
666	<	int p = phaseOf(s);
643	>	int p = getPhase();
644		if (p != phase)
645		return p;
646	<	if (unarrivedOf(s) == 0 && parent != null)
670	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
671	<	return timedWait(phase, unit.toNanos(timeout));
646	>	return timedWait(phase, nanos);
647		}
648
649		/**
#	Line 679 | Line 654 | public class Phaser {
654		* unexpected exceptions.
655		*/
656		public void forceTermination() {
657	<	for (;;) {
658	<	long s = getReconciledState();
659	<	int phase = phaseOf(s);
660	<	int parties = partiesOf(s);
661	<	int unarrived = unarrivedOf(s);
662	<	if (phase < 0 ||
663	<	casState(s, stateFor(-1, parties, unarrived))) {
664	<	releaseWaiters(0);
665	<	releaseWaiters(1);
691	<	if (parent != null)
692	<	parent.forceTermination();
693	<	return;
694	<	}
695	<	}
657	>	Phaser r = root;    // force at root then reconcile
658	>	long s;
659	>	while (phaseOf(s = r.state) >= 0)
660	>	UNSAFE.compareAndSwapLong(r, stateOffset, s,
661	>	stateFor(-1, partiesOf(s),
662	>	unarrivedOf(s)));
663	>	reconcileState();
664	>	releaseWaiters(0);  // ensure wakeups on both queues
665	>	releaseWaiters(1);
666		}
667
668		/**
#	Line 712 | Line 682 | public class Phaser {
682		* @return the number of parties
683		*/
684		public int getRegisteredParties() {
685	<	return partiesOf(state);
685	>	return partiesOf(getReconciledState());
686		}
687
688		/**
#	Line 722 | Line 692 | public class Phaser {
692		* @return the number of arrived parties
693		*/
694		public int getArrivedParties() {
695	<	return arrivedOf(state);
695	>	return arrivedOf(getReconciledState());
696		}
697
698		/**
#	Line 732 | Line 702 | public class Phaser {
702		* @return the number of unarrived parties
703		*/
704		public int getUnarrivedParties() {
705	<	return unarrivedOf(state);
705	>	return unarrivedOf(getReconciledState());
706		}
707
708		/**
#	Line 764 | Line 734 | public class Phaser {
734		}
735
736		/**
737	<	* Overridable method to perform an action upon phase advance, and
738	<	* to control termination. This method is invoked whenever the
739	<	* barrier is tripped (and thus all other waiting parties are
740	<	* dormant). If it returns {@code true}, then, rather than advance
741	<	* the phase number, this barrier will be set to a final
742	<	* termination state, and subsequent calls to {@link #isTerminated}
743	<	* will return true.
737	>	* Overridable method to perform an action upon impending phase
738	>	* advance, and to control termination. This method is invoked
739	>	* upon arrival of the party tripping the barrier (when all other
740	>	* waiting parties are dormant).  If this method returns {@code
741	>	* true}, then, rather than advance the phase number, this barrier
742	>	* will be set to a final termination state, and subsequent calls
743	>	* to {@link #isTerminated} will return true. Any (unchecked)
744	>	* Exception or Error thrown by an invocation of this method is
745	>	* propagated to the party attempting to trip the barrier, in
746	>	* which case no advance occurs.
747	>	*
748	>	* <p>The arguments to this method provide the state of the phaser
749	>	* prevailing for the current transition.  The results and effects
750	>	* of invoking phase-related methods (including {@code getPhase}
751	>	* as well as arrival, registration, and waiting methods) from
752	>	* within {@code onAdvance} are unspecified and should not be
753	>	* relied on. Similarly, while it is possible to override this
754	>	* method to produce side-effects visible to participating tasks,
755	>	* it is in general safe to do so only in designs in which all
756	>	* parties register before any arrive, and all {@link
757	>	* #awaitAdvance} at each phase.
758		*
759		* <p>The default version returns {@code true} when the number of
760		* registered parties is zero. Normally, overrides that arrange
761		* termination for other reasons should also preserve this
762		* property.
763		*
780	–	* <p>You may override this method to perform an action with side
781	–	* effects visible to participating tasks, but it is in general
782	–	* only sensible to do so in designs where all parties register
783	–	* before any arrive, and all {@link #awaitAdvance} at each phase.
784	–	* Otherwise, you cannot ensure lack of interference from other
785	–	* parties during the invocation of this method.
786	–	*
764		* @param phase the phase number on entering the barrier
765		* @param registeredParties the current number of registered parties
766		* @return {@code true} if this barrier should terminate
#	Line 824 | Line 801 | public class Phaser {
801		volatile boolean wasInterrupted = false;
802		volatile Thread thread; // nulled to cancel wait
803		QNode next;
804	+
805		QNode(Phaser phaser, int phase, boolean interruptible,
806		boolean timed, long startTime, long nanos) {
807		this.phaser = phaser;
#	Line 834 | Line 812 | public class Phaser {
812		this.nanos = nanos;
813		thread = Thread.currentThread();
814		}
815	+
816		public boolean isReleasable() {
817		return (thread == null ||
818		phaser.getPhase() != phase ||
819		(interruptible && wasInterrupted) ||
820		(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
821		}
822	+
823		public boolean block() {
824		if (Thread.interrupted()) {
825		wasInterrupted = true;
#	Line 856 | Line 836 | public class Phaser {
836		}
837		return isReleasable();
838		}
839	+
840		void signal() {
841		Thread t = thread;
842		if (t != null) {
#	Line 863 | Line 844 | public class Phaser {
844		LockSupport.unpark(t);
845		}
846		}
847	+
848		boolean doWait() {
849		if (thread != null) {
850		try {
851	<	ForkJoinPool.managedBlock(this, false);
851	>	ForkJoinPool.managedBlock(this);
852		} catch (InterruptedException ie) {
853	+	wasInterrupted = true; // can't currently happen
854		}
855		}
856		return wasInterrupted;
857		}
875	–
858		}
859
860		/**
#	Line 898 | Line 880 | public class Phaser {
880		}
881
882		/**
883	+	* The number of times to spin before blocking waiting for advance.
884	+	*/
885	+	static final int MAX_SPINS =
886	+	Runtime.getRuntime().availableProcessors() == 1 ? 0 : 1 << 8;
887	+
888	+	/**
889		* Enqueues node and waits unless aborted or signalled.
890		*
891		* @return current phase
#	Line 906 | Line 894 | public class Phaser {
894		QNode node = null;
895		boolean queued = false;
896		boolean interrupted = false;
897	+	int spins = MAX_SPINS;
898		int p;
899		while ((p = getPhase()) == phase) {
900		if (Thread.interrupted())
901		interrupted = true;
902	+	else if (spins > 0) {
903	+	if (--spins == 0)
904	+	Thread.yield();
905	+	}
906		else if (node == null)
907		node = new QNode(this, phase, false, false, 0, 0);
908		else if (!queued)
909		queued = tryEnqueue(node);
910	<	else
911	<	interrupted = node.doWait();
910	>	else if (node.doWait())
911	>	interrupted = true;
912		}
913		if (node != null)
914		node.thread = null;
#	Line 933 | Line 926 | public class Phaser {
926		QNode node = null;
927		boolean queued = false;
928		boolean interrupted = false;
929	+	int spins = MAX_SPINS;
930		int p;
931		while ((p = getPhase()) == phase && !interrupted) {
932		if (Thread.interrupted())
933		interrupted = true;
934	+	else if (spins > 0) {
935	+	if (--spins == 0)
936	+	Thread.yield();
937	+	}
938		else if (node == null)
939		node = new QNode(this, phase, true, false, 0, 0);
940		else if (!queued)
941		queued = tryEnqueue(node);
942	<	else
943	<	interrupted = node.doWait();
942	>	else if (node.doWait())
943	>	interrupted = true;
944		}
945		if (node != null)
946		node.thread = null;
#	Line 963 | Line 961 | public class Phaser {
961		QNode node = null;
962		boolean queued = false;
963		boolean interrupted = false;
964	+	int spins = MAX_SPINS;
965		int p;
966		while ((p = getPhase()) == phase && !interrupted) {
967		if (Thread.interrupted())
968		interrupted = true;
969		else if (nanos - (System.nanoTime() - startTime) <= 0)
970		break;
971	+	else if (spins > 0) {
972	+	if (--spins == 0)
973	+	Thread.yield();
974	+	}
975		else if (node == null)
976		node = new QNode(this, phase, true, true, startTime, nanos);
977		else if (!queued)
978		queued = tryEnqueue(node);
979	<	else
980	<	interrupted = node.doWait();
979	>	else if (node.doWait())
980	>	interrupted = true;
981		}
982		if (node != null)
983		node.thread = null;
#	Line 993 | Line 996 | public class Phaser {
996		private static final long stateOffset =
997		objectFieldOffset("state", Phaser.class);
998
996	–	private final boolean casState(long cmp, long val) {
997	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
998	–	}
999	–
999		private static long objectFieldOffset(String field, Class<?> klazz) {
1000		try {
1001		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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