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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.59 by dl, Sat Nov 27 16:46:53 2010 UTC vs.
Revision 1.63 by dl, Mon Nov 29 15:47:19 2010 UTC

#	Line 34 | Line 34 | import java.util.concurrent.locks.LockSu
34		* Phaser} may be repeatedly awaited.  Method {@link
35		* #arriveAndAwaitAdvance} has effect analogous to {@link
36		* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
37	<	* generation of a {@code Phaser} has an associated phase number. The
38	<	* phase number starts at zero, and advances when all parties arrive
39	<	* at the barrier, wrapping around to zero after reaching {@code
37	>	* generation of a phaser has an associated phase number. The phase
38	>	* number starts at zero, and advances when all parties arrive at the
39	>	* phaser, wrapping around to zero after reaching {@code
40		* Integer.MAX_VALUE}. The use of phase numbers enables independent
41	<	* control of actions upon arrival at a barrier and upon awaiting
41	>	* control of actions upon arrival at a phaser and upon awaiting
42		* others, via two kinds of methods that may be invoked by any
43		* registered party:
44		*
45		* <ul>
46		*
47		*   <li> <b>Arrival.</b> Methods {@link #arrive} and
48	<	*       {@link #arriveAndDeregister} record arrival at a
49	<	*       barrier. These methods do not block, but return an associated
50	<	*       <em>arrival phase number</em>; that is, the phase number of
51	<	*       the barrier to which the arrival applied. When the final
52	<	*       party for a given phase arrives, an optional barrier action
53	<	*       is performed and the phase advances.  Barrier actions,
54	<	*       performed by the party triggering a phase advance, are
55	<	*       arranged by overriding method {@link #onAdvance(int, int)},
56	<	*       which also controls termination. Overriding this method is
57	<	*       similar to, but more flexible than, providing a barrier
58	<	*       action to a {@code CyclicBarrier}.
48	>	*       {@link #arriveAndDeregister} record arrival.  These methods
49	>	*       do not block, but return an associated <em>arrival phase
50	>	*       number</em>; that is, the phase number of the phaser to which
51	>	*       the arrival applied. When the final party for a given phase
52	>	*       arrives, an optional action is performed and the phase
53	>	*       advances.  These actions are performed by the party
54	>	*       triggering a phase advance, and are arranged by overriding
55	>	*       method {@link #onAdvance(int, int)}, which also controls
56	>	*       termination. Overriding this method is similar to, but more
57	>	*       flexible than, providing a barrier action to a {@code
58	>	*       CyclicBarrier}.
59		*
60		*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
61		*       argument indicating an arrival phase number, and returns when
62	<	*       the barrier advances to (or is already at) a different phase.
62	>	*       the phaser advances to (or is already at) a different phase.
63		*       Unlike similar constructions using {@code CyclicBarrier},
64		*       method {@code awaitAdvance} continues to wait even if the
65		*       waiting thread is interrupted. Interruptible and timeout
66		*       versions are also available, but exceptions encountered while
67		*       tasks wait interruptibly or with timeout do not change the
68	<	*       state of the barrier. If necessary, you can perform any
68	>	*       state of the phaser. If necessary, you can perform any
69		*       associated recovery within handlers of those exceptions,
70		*       often after invoking {@code forceTermination}.  Phasers may
71		*       also be used by tasks executing in a {@link ForkJoinPool},
#	Line 74 | Line 74 | import java.util.concurrent.locks.LockSu
74		*
75		* </ul>
76		*
77	<	* <p> <b>Termination.</b> A {@code Phaser} may enter a
78	<	* <em>termination</em> state in which all synchronization methods
79	<	* immediately return without updating phaser state or waiting for
80	<	* advance, and indicating (via a negative phase value) that execution
81	<	* is complete.  Termination is triggered when an invocation of {@code
82	<	* onAdvance} returns {@code true}. The default implementation returns
83	<	* {@code true} if a deregistration has caused the number of
84	<	* registered parties to become zero.  As illustrated below, when
85	<	* phasers control actions with a fixed number of iterations, it is
86	<	* often convenient to override this method to cause termination when
87	<	* the current phase number reaches a threshold. Method {@link
88	<	* #forceTermination} is also available to abruptly release waiting
89	<	* threads and allow them to terminate.
77	>	* <p> <b>Termination.</b> A phaser may enter a <em>termination</em>
78	>	* state in which all synchronization methods immediately return
79	>	* without updating phaser state or waiting for advance, and
80	>	* indicating (via a negative phase value) that execution is complete.
81	>	* Termination is triggered when an invocation of {@code onAdvance}
82	>	* returns {@code true}. The default implementation returns {@code
83	>	* true} if a deregistration has caused the number of registered
84	>	* parties to become zero.  As illustrated below, when phasers control
85	>	* actions with a fixed number of iterations, it is often convenient
86	>	* to override this method to cause termination when the current phase
87	>	* number reaches a threshold. Method {@link #forceTermination} is
88	>	* also available to abruptly release waiting threads and allow them
89	>	* to terminate.
90		*
91		* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
92		* constructed in tree structures) to reduce contention. Phasers with
#	Line 185 | Line 185 | import java.util.concurrent.locks.LockSu
185		*
186		* <p>To create a set of tasks using a tree of phasers,
187		* you could use code of the following form, assuming a
188	<	* Task class with a constructor accepting a phaser that
188	>	* Task class with a constructor accepting a {@code Phaser} that
189		* it registers with upon construction:
190		*
191		*  <pre> {@code
#	Line 205 | Line 205 | import java.util.concurrent.locks.LockSu
205		* build(new Task[n], 0, n, new Phaser());}</pre>
206		*
207		* The best value of {@code TASKS_PER_PHASER} depends mainly on
208	<	* expected barrier synchronization rates. A value as low as four may
209	<	* be appropriate for extremely small per-barrier task bodies (thus
208	>	* expected synchronization rates. A value as low as four may
209	>	* be appropriate for extremely small per-phase task bodies (thus
210		* high rates), or up to hundreds for extremely large ones.
211		*
212		* <p><b>Implementation notes</b>: This implementation restricts the
#	Line 226 | Line 226 | public class Phaser {
226		*/
227
228		/**
229	<	* Barrier state representation. Conceptually, a barrier contains
230	<	* four values:
229	>	* Primary state representation, holding four fields:
230		*
231		* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
232		* * parties -- the number of parties to wait              (bits 16-31)
#	Line 347 | Line 346 | public class Phaser {
346		else {
347		parent.doArrive((u == 0) ?
348		ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
349	<	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase ||
351	<	((int)(state >>> PHASE_SHIFT) != nextPhase &&
352	<	!UNSAFE.compareAndSwapLong(this, stateOffset,
353	<	s, next)))
349	>	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase)
350		reconcileState();
351	+	else if (state == s)
352	+	UNSAFE.compareAndSwapLong(this, stateOffset, s,
353	+	next);
354		}
355		}
356		return phase;
#	Line 383 | Line 382 | public class Phaser {
382		return phase;
383		}
384		else if (parties != 0)               // wait for onAdvance
385	<	internalAwaitAdvance(phase, null);
385	>	root.internalAwaitAdvance(phase, null);
386		else {                               // 1st registration of child
387	<	synchronized(this) {             // register parent first
387	>	synchronized (this) {            // register parent first
388		if (reconcileState() == s) { // recheck under lock
389		parent.doRegister(1);    // OK if throws IllegalState
390		for (;;) {               // simpler form of outer loop
#	Line 413 | Line 412 | public class Phaser {
412		int phase, rPhase;
413		while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
414		(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
415	<	if ((int)(par.state >>> PHASE_SHIFT) != rPhase)
415	>	if (par != rt && (int)(par.state >>> PHASE_SHIFT) != rPhase)
416		par.reconcileState();
417		else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
418		long u = s & PARTIES_MASK; // reset unarrived to parties
#	Line 428 | Line 427 | public class Phaser {
427		}
428
429		/**
430	<	* Creates a new phaser without any initially registered parties,
431	<	* initial phase number 0, and no parent. Any thread using this
430	>	* Creates a new phaser with no initially registered parties, no
431	>	* parent, and initial phase number 0. Any thread using this
432		* phaser will need to first register for it.
433		*/
434		public Phaser() {
#	Line 438 | Line 437 | public class Phaser {
437
438		/**
439		* Creates a new phaser with the given number of registered
440	<	* unarrived parties, initial phase number 0, and no parent.
440	>	* unarrived parties, no parent, and initial phase number 0.
441		*
442	<	* @param parties the number of parties required to trip barrier
442	>	* @param parties the number of parties required to advance to the
443	>	* next phase
444		* @throws IllegalArgumentException if parties less than zero
445		* or greater than the maximum number of parties supported
446		*/
#	Line 449 | Line 449 | public class Phaser {
449		}
450
451		/**
452	–	* Creates a new phaser with the given parent, and without any
453	–	* initially registered parties.  Any thread using this phaser
454	–	* will need to first register for it, at which point, if the
455	–	* given parent is non-null, this phaser will also be registered
456	–	* with the parent.
457	–	*
452		* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
453		*
454		* @param parent the parent phaser
#	Line 465 | Line 459 | public class Phaser {
459
460		/**
461		* Creates a new phaser with the given parent and number of
462	<	* registered unarrived parties. If parent is non-null and
463	<	* the number of parties is non-zero, this phaser is registered
464	<	* with the parent.
462	>	* registered unarrived parties. Registration and deregistration
463	>	* of this child phaser with its parent are managed automatically.
464	>	* If the given parent is non-null, whenever this child phaser has
465	>	* any registered parties (as established in this constructor,
466	>	* {@link #register}, or {@link #bulkRegister}), this child phaser
467	>	* is registered with its parent. Whenever the number of
468	>	* registered parties becomes zero as the result of an invocation
469	>	* of {@link #arriveAndDeregister}, this child phaser is
470	>	* deregistered from its parent.
471		*
472		* @param parent the parent phaser
473	<	* @param parties the number of parties required to trip barrier
473	>	* @param parties the number of parties required to advance to the
474	>	* next phase
475		* @throws IllegalArgumentException if parties less than zero
476		* or greater than the maximum number of parties supported
477		*/
478		public Phaser(Phaser parent, int parties) {
479		if (parties >>> PARTIES_SHIFT != 0)
480		throw new IllegalArgumentException("Illegal number of parties");
481	<	int phase;
481	>	long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT);
482		this.parent = parent;
483		if (parent != null) {
484		Phaser r = parent.root;
485		this.root = r;
486		this.evenQ = r.evenQ;
487		this.oddQ = r.oddQ;
488	<	phase = (parties == 0) ? parent.getPhase() : parent.doRegister(1);
488	>	if (parties != 0)
489	>	s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT;
490		}
491		else {
492		this.root = this;
493		this.evenQ = new AtomicReference<QNode>();
494		this.oddQ = new AtomicReference<QNode>();
493	–	phase = 0;
495		}
496	<	long p = (long)parties;
496	<	this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
496	>	this.state = s;
497		}
498
499		/**
500		* Adds a new unarrived party to this phaser.  If an ongoing
501		* invocation of {@link #onAdvance} is in progress, this method
502	<	* may wait until its completion before registering.  If this
503	<	* phaser has a parent, and this phaser previously had no
504	<	* registered parties, this phaser is also registered with its
505	<	* parent.
502	>	* may await its completion before returning.  If this phaser has
503	>	* a parent, and this phaser previously had no registered parties,
504	>	* this phaser is also registered with its parent.
505		*
506		* @return the arrival phase number to which this registration applied
507		* @throws IllegalStateException if attempting to register more
#	Line 515 | Line 514 | public class Phaser {
514		/**
515		* Adds the given number of new unarrived parties to this phaser.
516		* If an ongoing invocation of {@link #onAdvance} is in progress,
517	<	* this method may wait until its completion before registering.
518	<	* If this phaser has a parent, and the given number of parities
519	<	* is greater than zero, and this phaser previously had no
520	<	* registered parties, this phaser is also registered with its
522	<	* parent.
517	>	* this method may await its completion before returning.  If this
518	>	* phaser has a parent, and the given number of parities is
519	>	* greater than zero, and this phaser previously had no registered
520	>	* parties, this phaser is also registered with its parent.
521		*
522	<	* @param parties the number of additional parties required to trip barrier
522	>	* @param parties the number of additional parties required to
523	>	* advance to the next phase
524		* @return the arrival phase number to which this registration applied
525		* @throws IllegalStateException if attempting to register more
526		* than the maximum supported number of parties
#	Line 530 | Line 529 | public class Phaser {
529		public int bulkRegister(int parties) {
530		if (parties < 0)
531		throw new IllegalArgumentException();
532	<	else if (parties == 0)
532	>	if (parties == 0)
533		return getPhase();
534		return doRegister(parties);
535		}
536
537		/**
538	<	* Arrives at the barrier, but does not wait for others.  (You can
539	<	* in turn wait for others via {@link #awaitAdvance}).  It is a
540	<	* usage error for an unregistered party to invoke this
541	<	* method. However, it is possible that this error will result in
542	<	* an {code IllegalStateException} only when some <em>other</em>
543	<	* party arrives.
538	>	* Arrives at this phaser, without waiting for others to arrive.
539	>	*
540	>	* <p>It is a usage error for an unregistered party to invoke this
541	>	* method.  However, this error may result in an {@code
542	>	* IllegalStateException} only upon some subsequent operation on
543	>	* this phaser, if ever.
544		*
545		* @return the arrival phase number, or a negative value if terminated
546		* @throws IllegalStateException if not terminated and the number
#	Line 552 | Line 551 | public class Phaser {
551		}
552
553		/**
554	<	* Arrives at the barrier and deregisters from it without waiting
555	<	* for others. Deregistration reduces the number of parties
556	<	* required to trip the barrier in future phases.  If this phaser
554	>	* Arrives at this phaser and deregisters from it without waiting
555	>	* for others to arrive. Deregistration reduces the number of
556	>	* parties required to advance in future phases.  If this phaser
557		* has a parent, and deregistration causes this phaser to have
558	<	* zero parties, this phaser also arrives at and is deregistered
559	<	* from its parent.  It is a usage error for an unregistered party
560	<	* to invoke this method. However, it is possible that this error
561	<	* will result in an {code IllegalStateException} only when some
562	<	* <em>other</em> party arrives.
558	>	* zero parties, this phaser is also deregistered from its parent.
559	>	*
560	>	* <p>It is a usage error for an unregistered party to invoke this
561	>	* method.  However, this error may result in an {@code
562	>	* IllegalStateException} only upon some subsequent operation on
563	>	* this phaser, if ever.
564		*
565		* @return the arrival phase number, or a negative value if terminated
566		* @throws IllegalStateException if not terminated and the number
#	Line 571 | Line 571 | public class Phaser {
571		}
572
573		/**
574	<	* Arrives at the barrier and awaits others. Equivalent in effect
574	>	* Arrives at this phaser and awaits others. Equivalent in effect
575		* to {@code awaitAdvance(arrive())}.  If you need to await with
576		* interruption or timeout, you can arrange this with an analogous
577		* construction using one of the other forms of the {@code
578		* awaitAdvance} method.  If instead you need to deregister upon
579	<	* arrival, use {@link #arriveAndDeregister}.  It is a usage error
580	<	* for an unregistered party to invoke this method. However, it is
581	<	* possible that this error will result in an {code
582	<	* IllegalStateException} only when some <em>other</em> party
583	<	* arrives.
579	>	* arrival, use {@code awaitAdvance(arriveAndDeregister())}.
580	>	*
581	>	* <p>It is a usage error for an unregistered party to invoke this
582	>	* method.  However, this error may result in an {@code
583	>	* IllegalStateException} only upon some subsequent operation on
584	>	* this phaser, if ever.
585		*
586		* @return the arrival phase number, or a negative number if terminated
587		* @throws IllegalStateException if not terminated and the number
588		* of unarrived parties would become negative
589		*/
590		public int arriveAndAwaitAdvance() {
591	<	return awaitAdvance(arrive());
591	>	return awaitAdvance(doArrive(ONE_ARRIVAL));
592		}
593
594		/**
595	<	* Awaits the phase of the barrier to advance from the given phase
596	<	* value, returning immediately if the current phase of the
597	<	* barrier is not equal to the given phase value or this barrier
597	<	* is terminated.
595	>	* Awaits the phase of this phaser to advance from the given phase
596	>	* value, returning immediately if the current phase is not equal
597	>	* to the given phase value or this phaser is terminated.
598		*
599		* @param phase an arrival phase number, or negative value if
600		* terminated; this argument is normally the value returned by a
601	<	* previous call to {@code arrive} or its variants
601	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
602		* @return the next arrival phase number, or a negative value
603		* if terminated or argument is negative
604		*/
605		public int awaitAdvance(int phase) {
606	+	Phaser rt;
607	+	int p = (int)(state >>> PHASE_SHIFT);
608		if (phase < 0)
609		return phase;
610	<	long s = (parent == null) ? state : reconcileState();
611	<	int p = (int)(s >>> PHASE_SHIFT);
612	<	return (p != phase) ? p : internalAwaitAdvance(phase, null);
610	>	if (p == phase &&
611	>	(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase)
612	>	return rt.internalAwaitAdvance(phase, null);
613	>	return p;
614		}
615
616		/**
617	<	* Awaits the phase of the barrier to advance from the given phase
617	>	* Awaits the phase of this phaser to advance from the given phase
618		* value, throwing {@code InterruptedException} if interrupted
619	<	* while waiting, or returning immediately if the current phase of
620	<	* the barrier is not equal to the given phase value or this
621	<	* barrier is terminated.
619	>	* while waiting, or returning immediately if the current phase is
620	>	* not equal to the given phase value or this phaser is
621	>	* terminated.
622		*
623		* @param phase an arrival phase number, or negative value if
624		* terminated; this argument is normally the value returned by a
625	<	* previous call to {@code arrive} or its variants
625	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
626		* @return the next arrival phase number, or a negative value
627		* if terminated or argument is negative
628		* @throws InterruptedException if thread interrupted while waiting
629		*/
630		public int awaitAdvanceInterruptibly(int phase)
631		throws InterruptedException {
632	+	Phaser rt;
633	+	int p = (int)(state >>> PHASE_SHIFT);
634		if (phase < 0)
635		return phase;
636	<	long s = (parent == null) ? state : reconcileState();
637	<	int p = (int)(s >>> PHASE_SHIFT);
633	<	if (p == phase) {
636	>	if (p == phase &&
637	>	(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
638		QNode node = new QNode(this, phase, true, false, 0L);
639	<	p = internalAwaitAdvance(phase, node);
639	>	p = rt.internalAwaitAdvance(phase, node);
640		if (node.wasInterrupted)
641		throw new InterruptedException();
642		}
#	Line 640 | Line 644 | public class Phaser {
644		}
645
646		/**
647	<	* Awaits the phase of the barrier to advance from the given phase
647	>	* Awaits the phase of this phaser to advance from the given phase
648		* value or the given timeout to elapse, throwing {@code
649		* InterruptedException} if interrupted while waiting, or
650	<	* returning immediately if the current phase of the barrier is
651	<	* not equal to the given phase value or this barrier is
648	<	* terminated.
650	>	* returning immediately if the current phase is not equal to the
651	>	* given phase value or this phaser is terminated.
652		*
653		* @param phase an arrival phase number, or negative value if
654		* terminated; this argument is normally the value returned by a
655	<	* previous call to {@code arrive} or its variants
655	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
656		* @param timeout how long to wait before giving up, in units of
657		*        {@code unit}
658		* @param unit a {@code TimeUnit} determining how to interpret the
#	Line 662 | Line 665 | public class Phaser {
665		public int awaitAdvanceInterruptibly(int phase,
666		long timeout, TimeUnit unit)
667		throws InterruptedException, TimeoutException {
668	+	long nanos = unit.toNanos(timeout);
669	+	Phaser rt;
670	+	int p = (int)(state >>> PHASE_SHIFT);
671		if (phase < 0)
672		return phase;
673	<	long s = (parent == null) ? state : reconcileState();
674	<	int p = (int)(s >>> PHASE_SHIFT);
669	<	if (p == phase) {
670	<	long nanos = unit.toNanos(timeout);
673	>	if (p == phase &&
674	>	(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
675		QNode node = new QNode(this, phase, true, true, nanos);
676	<	p = internalAwaitAdvance(phase, node);
676	>	p = rt.internalAwaitAdvance(phase, node);
677		if (node.wasInterrupted)
678		throw new InterruptedException();
679		else if (p == phase)
#	Line 679 | Line 683 | public class Phaser {
683		}
684
685		/**
686	<	* Forces this barrier to enter termination state.  Counts of
686	>	* Forces this phaser to enter termination state.  Counts of
687		* arrived and registered parties are unaffected.  If this phaser
688		* is a member of a tiered set of phasers, then all of the phasers
689		* in the set are terminated.  If this phaser is already
#	Line 704 | Line 708 | public class Phaser {
708		/**
709		* Returns the current phase number. The maximum phase number is
710		* {@code Integer.MAX_VALUE}, after which it restarts at
711	<	* zero. Upon termination, the phase number is negative.
711	>	* zero. Upon termination, the phase number is negative,
712	>	* in which case the prevailing phase prior to termination
713	>	* may be obtained via {@code getPhase() + Integer.MIN_VALUE}.
714		*
715		* @return the phase number, or a negative value if terminated
716		*/
#	Line 713 | Line 719 | public class Phaser {
719		}
720
721		/**
722	<	* Returns the number of parties registered at this barrier.
722	>	* Returns the number of parties registered at this phaser.
723		*
724		* @return the number of parties
725		*/
#	Line 723 | Line 729 | public class Phaser {
729
730		/**
731		* Returns the number of registered parties that have arrived at
732	<	* the current phase of this barrier.
732	>	* the current phase of this phaser.
733		*
734		* @return the number of arrived parties
735		*/
736		public int getArrivedParties() {
737	<	return arrivedOf(parent==null? state : reconcileState());
737	>	long s = state;
738	>	int u = unarrivedOf(s); // only reconcile if possibly needed
739	>	return (u != 0 || parent == null) ?
740	>	partiesOf(s) - u :
741	>	arrivedOf(reconcileState());
742		}
743
744		/**
745		* Returns the number of registered parties that have not yet
746	<	* arrived at the current phase of this barrier.
746	>	* arrived at the current phase of this phaser.
747		*
748		* @return the number of unarrived parties
749		*/
750		public int getUnarrivedParties() {
751	<	return unarrivedOf(parent==null? state : reconcileState());
751	>	int u = unarrivedOf(state);
752	>	return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState());
753		}
754
755		/**
#	Line 761 | Line 772 | public class Phaser {
772		}
773
774		/**
775	<	* Returns {@code true} if this barrier has been terminated.
775	>	* Returns {@code true} if this phaser has been terminated.
776		*
777	<	* @return {@code true} if this barrier has been terminated
777	>	* @return {@code true} if this phaser has been terminated
778		*/
779		public boolean isTerminated() {
780		return root.state < 0L;
#	Line 772 | Line 783 | public class Phaser {
783		/**
784		* Overridable method to perform an action upon impending phase
785		* advance, and to control termination. This method is invoked
786	<	* upon arrival of the party tripping the barrier (when all other
786	>	* upon arrival of the party advancing this phaser (when all other
787		* waiting parties are dormant).  If this method returns {@code
788	<	* true}, then, rather than advance the phase number, this barrier
788	>	* true}, then, rather than advance the phase number, this phaser
789		* will be set to a final termination state, and subsequent calls
790		* to {@link #isTerminated} will return true. Any (unchecked)
791		* Exception or Error thrown by an invocation of this method is
792	<	* propagated to the party attempting to trip the barrier, in
792	>	* propagated to the party attempting to advance this phaser, in
793		* which case no advance occurs.
794		*
795		* <p>The arguments to this method provide the state of the phaser
796		* prevailing for the current transition.  The effects of invoking
797	<	* arrival, registration, and waiting methods on this Phaser from
797	>	* arrival, registration, and waiting methods on this phaser from
798		* within {@code onAdvance} are unspecified and should not be
799		* relied on.
800		*
801	<	* <p>If this Phaser is a member of a tiered set of Phasers, then
802	<	* {@code onAdvance} is invoked only for its root Phaser on each
801	>	* <p>If this phaser is a member of a tiered set of phasers, then
802	>	* {@code onAdvance} is invoked only for its root phaser on each
803		* advance.
804		*
805		* <p>To support the most common use cases, the default
#	Line 804 | Line 815 | public class Phaser {
815		*   protected boolean onAdvance(int phase, int parties) { return false; }
816		* }}</pre>
817		*
818	<	* @param phase the phase number on entering the barrier
818	>	* @param phase the current phase number on entry to this method,
819	>	* before this phaser is advanced
820		* @param registeredParties the current number of registered parties
821	<	* @return {@code true} if this barrier should terminate
821	>	* @return {@code true} if this phaser should terminate
822		*/
823		protected boolean onAdvance(int phase, int registeredParties) {
824	<	return registeredParties <= 0;
824	>	return registeredParties == 0;
825		}
826
827		/**
#	Line 819 | Line 831 | public class Phaser {
831		* followed by the number of registered parties, and {@code
832		* "arrived = "} followed by the number of arrived parties.
833		*
834	<	* @return a string identifying this barrier, as well as its state
834	>	* @return a string identifying this phaser, as well as its state
835		*/
836		public String toString() {
837		return stateToString(reconcileState());
#	Line 841 | Line 853 | public class Phaser {
853		* Removes and signals threads from queue for phase.
854		*/
855		private void releaseWaiters(int phase) {
856	<	AtomicReference<QNode> head = queueFor(phase);
857	<	QNode q;
858	<	int p;
856	>	QNode q;   // first element of queue
857	>	int p;     // its phase
858	>	Thread t;  // its thread
859	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
860		while ((q = head.get()) != null &&
861		((p = q.phase) == phase ||
862		(int)(root.state >>> PHASE_SHIFT) != p)) {
863	<	if (head.compareAndSet(q, q.next))
864	<	q.signal();
863	>	if (head.compareAndSet(q, q.next) &&
864	>	(t = q.thread) != null) {
865	>	q.thread = null;
866	>	LockSupport.unpark(t);
867	>	}
868		}
869		}
870
#	Line 863 | Line 879 | public class Phaser {
879		* avoid it when threads regularly arrive: When a thread in
880		* internalAwaitAdvance notices another arrival before blocking,
881		* and there appear to be enough CPUs available, it spins
882	<	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
883	<	* uniprocessors, there is at least one intervening Thread.yield
868	<	* before blocking. The value trades off good-citizenship vs big
869	<	* unnecessary slowdowns.
882	>	* SPINS_PER_ARRIVAL more times before blocking. The value trades
883	>	* off good-citizenship vs big unnecessary slowdowns.
884		*/
885		static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
886
887		/**
888		* Possibly blocks and waits for phase to advance unless aborted.
889	+	* Call only from root node.
890		*
891		* @param phase current phase
892		* @param node if non-null, the wait node to track interrupt and timeout;
#	Line 879 | Line 894 | public class Phaser {
894		* @return current phase
895		*/
896		private int internalAwaitAdvance(int phase, QNode node) {
897	<	Phaser current = this;       // to eventually wait at root if tiered
898	<	boolean queued = false;      // true when node is enqueued
899	<	int lastUnarrived = -1;      // to increase spins upon change
897	>	releaseWaiters(phase-1);          // ensure old queue clean
898	>	boolean queued = false;           // true when node is enqueued
899	>	int lastUnarrived = 0;            // to increase spins upon change
900		int spins = SPINS_PER_ARRIVAL;
901		long s;
902		int p;
903	<	while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) {
904	<	Phaser par;
905	<	int unarrived = (int)s & UNARRIVED_MASK;
906	<	if (unarrived != lastUnarrived) {
907	<	if (lastUnarrived == -1) // ensure old queue clean
893	<	releaseWaiters(phase-1);
894	<	if ((lastUnarrived = unarrived) < NCPU)
903	>	while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
904	>	if (node == null) {           // spinning in noninterruptible mode
905	>	int unarrived = (int)s & UNARRIVED_MASK;
906	>	if (unarrived != lastUnarrived &&
907	>	(lastUnarrived = unarrived) < NCPU)
908		spins += SPINS_PER_ARRIVAL;
909	<	}
910	<	else if (unarrived == 0 && (par = current.parent) != null) {
911	<	current = par;       // if all arrived, use parent
912	<	par = par.parent;
900	<	lastUnarrived = -1;
901	<	}
902	<	else if (spins > 0) {
903	<	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
904	<	Thread.yield();  // yield midway through spin
905	<	}
906	<	else if (node == null)   // must be noninterruptible
907	<	node = new QNode(this, phase, false, false, 0L);
908	<	else if (node.isReleasable()) {
909	<	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
910	<	break;
911	<	else
912	<	return phase;    // aborted
913	<	}
914	<	else if (!queued) {      // push onto queue
915	<	AtomicReference<QNode> head = queueFor(phase);
916	<	QNode q = head.get();
917	<	if (q == null || q.phase == phase) {
918	<	node.next = q;
919	<	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
920	<	break;       // recheck to avoid stale enqueue
921	<	else
922	<	queued = head.compareAndSet(q, node);
909	>	boolean interrupted = Thread.interrupted();
910	>	if (interrupted || --spins < 0) { // need node to record intr
911	>	node = new QNode(this, phase, false, false, 0L);
912	>	node.wasInterrupted = interrupted;
913		}
914		}
915	+	else if (node.isReleasable()) // done or aborted
916	+	break;
917	+	else if (!queued) {           // push onto queue
918	+	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
919	+	QNode q = node.next = head.get();
920	+	if ((q == null || q.phase == phase) &&
921	+	(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq
922	+	queued = head.compareAndSet(q, node);
923	+	}
924		else {
925		try {
926		ForkJoinPool.managedBlock(node);
#	Line 930 | Line 929 | public class Phaser {
929		}
930		}
931		}
932	+
933	+	if (node != null) {
934	+	if (node.thread != null)
935	+	node.thread = null;       // avoid need for unpark()
936	+	if (node.wasInterrupted && !node.interruptible)
937	+	Thread.currentThread().interrupt();
938	+	if ((p = (int)(state >>> PHASE_SHIFT)) == phase)
939	+	return p;                 // recheck abort
940	+	}
941		releaseWaiters(phase);
934	–	if (node != null)
935	–	node.onRelease();
942		return p;
943		}
944
#	Line 962 | Line 968 | public class Phaser {
968		}
969
970		public boolean isReleasable() {
971	<	Thread t = thread;
972	<	if (t != null) {
973	<	if (phaser.getPhase() != phase)
974	<	t = null;
975	<	else {
976	<	if (Thread.interrupted())
977	<	wasInterrupted = true;
978	<	if (interruptible && wasInterrupted)
979	<	t = null;
974	<	else if (timed) {
975	<	if (nanos > 0) {
976	<	long now = System.nanoTime();
977	<	nanos -= now - lastTime;
978	<	lastTime = now;
979	<	}
980	<	if (nanos <= 0)
981	<	t = null;
982	<	}
983	<	}
984	<	if (t != null)
985	<	return false;
971	>	if (thread == null)
972	>	return true;
973	>	if (phaser.getPhase() != phase) {
974	>	thread = null;
975	>	return true;
976	>	}
977	>	if (Thread.interrupted())
978	>	wasInterrupted = true;
979	>	if (wasInterrupted && interruptible) {
980		thread = null;
981	+	return true;
982		}
983	<	return true;
983	>	if (timed) {
984	>	if (nanos > 0L) {
985	>	long now = System.nanoTime();
986	>	nanos -= now - lastTime;
987	>	lastTime = now;
988	>	}
989	>	if (nanos <= 0L) {
990	>	thread = null;
991	>	return true;
992	>	}
993	>	}
994	>	return false;
995		}
996
997		public boolean block() {
#	Line 997 | Line 1003 | public class Phaser {
1003		LockSupport.parkNanos(this, nanos);
1004		return isReleasable();
1005		}
1000	–
1001	–	void signal() {
1002	–	Thread t = thread;
1003	–	if (t != null) {
1004	–	thread = null;
1005	–	LockSupport.unpark(t);
1006	–	}
1007	–	}
1008	–
1009	–	void onRelease() { // actions upon return from internalAwaitAdvance
1010	–	if (!interruptible && wasInterrupted)
1011	–	Thread.currentThread().interrupt();
1012	–	if (thread != null)
1013	–	thread = null;
1014	–	}
1015	–
1006		}
1007
1008		// Unsafe mechanics

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