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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.63 by dl, Mon Nov 29 15:47:19 2010 UTC vs.
Revision 1.72 by dl, Mon May 16 11:41:14 2011 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
6
7		package jsr166y;
#	Line 75 | Line 75 | import java.util.concurrent.locks.LockSu
75		* </ul>
76		*
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.
78	>	* state, that may be checked using method {@link #isTerminated}. Upon
79	>	* termination, all synchronization methods immediately return without
80	>	* waiting for advance, as indicated by a negative return value.
81	>	* Similarly, attempts to register upon termination have no effect.
82		* Termination is triggered when an invocation of {@code onAdvance}
83		* returns {@code true}. The default implementation returns {@code
84		* true} if a deregistration has caused the number of registered
#	Line 96 | Line 97 | import java.util.concurrent.locks.LockSu
97		* increase throughput even though it incurs greater per-operation
98		* overhead.
99		*
100	+	* <p>In a tree of tiered phasers, registration and deregistration of
101	+	* child phasers with their parent are managed automatically.
102	+	* Whenever the number of registered parties of a child phaser becomes
103	+	* non-zero (as established in the {@link #Phaser(Phaser,int)}
104	+	* constructor, {@link #register}, or {@link #bulkRegister}), the
105	+	* child phaser is registered with its parent.  Whenever the number of
106	+	* registered parties becomes zero as the result of an invocation of
107	+	* {@link #arriveAndDeregister}, the child phaser is deregistered
108	+	* from its parent.
109	+	*
110		* <p><b>Monitoring.</b> While synchronization methods may be invoked
111		* only by registered parties, the current state of a phaser may be
112		* monitored by any caller.  At any given moment there are {@link
#	Line 119 | Line 130 | import java.util.concurrent.locks.LockSu
130		* void runTasks(List<Runnable> tasks) {
131		*   final Phaser phaser = new Phaser(1); // "1" to register self
132		*   // create and start threads
133	<	*   for (Runnable task : tasks) {
133	>	*   for (final Runnable task : tasks) {
134		*     phaser.register();
135		*     new Thread() {
136		*       public void run() {
#	Line 183 | Line 194 | import java.util.concurrent.locks.LockSu
194		* }}</pre>
195		*
196		*
197	<	* <p>To create a set of tasks using a tree of phasers,
198	<	* you could use code of the following form, assuming a
199	<	* Task class with a constructor accepting a {@code Phaser} that
200	<	* it registers with upon construction:
197	>	* <p>To create a set of {@code n} tasks using a tree of phasers, you
198	>	* could use code of the following form, assuming a Task class with a
199	>	* constructor accepting a {@code Phaser} that it registers with upon
200	>	* construction. After invocation of {@code build(new Task[n], 0, n,
201	>	* new Phaser())}, these tasks could then be started, for example by
202	>	* submitting to a pool:
203		*
204		*  <pre> {@code
205	<	* void build(Task[] actions, int lo, int hi, Phaser ph) {
205	>	* void build(Task[] tasks, int lo, int hi, Phaser ph) {
206		*   if (hi - lo > TASKS_PER_PHASER) {
207		*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
208		*       int j = Math.min(i + TASKS_PER_PHASER, hi);
209	<	*       build(actions, i, j, new Phaser(ph));
209	>	*       build(tasks, i, j, new Phaser(ph));
210		*     }
211		*   } else {
212		*     for (int i = lo; i < hi; ++i)
213	<	*       actions[i] = new Task(ph);
213	>	*       tasks[i] = new Task(ph);
214		*       // assumes new Task(ph) performs ph.register()
215		*   }
216	<	* }
204	<	* // .. initially called, for n tasks via
205	<	* build(new Task[n], 0, n, new Phaser());}</pre>
216	>	* }}</pre>
217		*
218		* The best value of {@code TASKS_PER_PHASER} depends mainly on
219		* expected synchronization rates. A value as low as four may
#	Line 233 | Line 244 | public class Phaser {
244		* * phase -- the generation of the barrier                (bits 32-62)
245		* * terminated -- set if barrier is terminated            (bit  63 / sign)
246		*
247	<	* However, to efficiently maintain atomicity, these values are
248	<	* packed into a single (atomic) long. Termination uses the sign
249	<	* bit of 32 bit representation of phase, so phase is set to -1 on
250	<	* termination. Good performance relies on keeping state decoding
251	<	* and encoding simple, and keeping race windows short.
247	>	* Except that a phaser with no registered parties is
248	>	* distinguished with the otherwise illegal state of having zero
249	>	* parties and one unarrived parties (encoded as EMPTY below).
250	>	*
251	>	* To efficiently maintain atomicity, these values are packed into
252	>	* a single (atomic) long. Good performance relies on keeping
253	>	* state decoding and encoding simple, and keeping race windows
254	>	* short.
255	>	*
256	>	* All state updates are performed via CAS except initial
257	>	* registration of a sub-phaser (i.e., one with a non-null
258	>	* parent).  In this (relatively rare) case, we use built-in
259	>	* synchronization to lock while first registering with its
260	>	* parent.
261	>	*
262	>	* The phase of a subphaser is allowed to lag that of its
263	>	* ancestors until it is actually accessed -- see method
264	>	* reconcileState.
265		*/
266		private volatile long state;
267
#	Line 245 | Line 269 | public class Phaser {
269		private static final int  MAX_PHASE       = 0x7fffffff;
270		private static final int  PARTIES_SHIFT   = 16;
271		private static final int  PHASE_SHIFT     = 32;
272	+	private static final long PHASE_MASK      = -1L << PHASE_SHIFT;
273		private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
274		private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
250	–	private static final long ONE_ARRIVAL     = 1L;
251	–	private static final long ONE_PARTY       = 1L << PARTIES_SHIFT;
275		private static final long TERMINATION_BIT = 1L << 63;
276
277	+	// some special values
278	+	private static final int  ONE_ARRIVAL     = 1;
279	+	private static final int  ONE_PARTY       = 1 << PARTIES_SHIFT;
280	+	private static final int  EMPTY           = 1;
281	+
282		// The following unpacking methods are usually manually inlined
283
284		private static int unarrivedOf(long s) {
285	<	return (int)s & UNARRIVED_MASK;
285	>	int counts = (int)s;
286	>	return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK;
287		}
288
289		private static int partiesOf(long s) {
#	Line 266 | Line 295 | public class Phaser {
295		}
296
297		private static int arrivedOf(long s) {
298	<	return partiesOf(s) - unarrivedOf(s);
298	>	int counts = (int)s;
299	>	return (counts == EMPTY) ? 0 :
300	>	(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK);
301		}
302
303		/**
#	Line 275 | Line 306 | public class Phaser {
306		private final Phaser parent;
307
308		/**
309	<	* The root of phaser tree. Equals this if not in a tree.  Used to
279	<	* support faster state push-down.
309	>	* The root of phaser tree. Equals this if not in a tree.
310		*/
311		private final Phaser root;
312
#	Line 314 | Line 344 | public class Phaser {
344		* Manually tuned to speed up and minimize race windows for the
345		* common case of just decrementing unarrived field.
346		*
347	<	* @param adj - adjustment to apply to state -- either
318	<	* ONE_ARRIVAL (for arrive) or
319	<	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
347	>	* @param deregister false for arrive, true for arriveAndDeregister
348		*/
349	<	private int doArrive(long adj) {
349	>	private int doArrive(boolean deregister) {
350	>	int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL;
351	>	final Phaser root = this.root;
352		for (;;) {
353	<	long s = state;
324	<	int unarrived = (int)s & UNARRIVED_MASK;
353	>	long s = (root == this) ? state : reconcileState();
354		int phase = (int)(s >>> PHASE_SHIFT);
355	+	int counts = (int)s;
356	+	int unarrived = (counts & UNARRIVED_MASK) - 1;
357		if (phase < 0)
358		return phase;
359	<	else if (unarrived == 0) {
360	<	if (reconcileState() == s)     // recheck
359	>	else if (counts == EMPTY || unarrived < 0) {
360	>	if (root == this || reconcileState() == s)
361		throw new IllegalStateException(badArrive(s));
362		}
363		else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
364	<	if (unarrived == 1) {
365	<	long p = s & PARTIES_MASK; // unshifted parties field
366	<	long lu = p >>> PARTIES_SHIFT;
367	<	int u = (int)lu;
368	<	int nextPhase = (phase + 1) & MAX_PHASE;
369	<	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
370	<	final Phaser parent = this.parent;
371	<	if (parent == null) {
372	<	if (onAdvance(phase, u))
373	<	next |= TERMINATION_BIT;
374	<	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
375	<	releaseWaiters(phase);
376	<	}
377	<	else {
347	<	parent.doArrive((u == 0) ?
348	<	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
349	<	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase)
350	<	reconcileState();
351	<	else if (state == s)
352	<	UNSAFE.compareAndSwapLong(this, stateOffset, s,
353	<	next);
354	<	}
364	>	if (unarrived == 0) {
365	>	long n = s & PARTIES_MASK;  // base of next state
366	>	int nextUnarrived = ((int)n) >>> PARTIES_SHIFT;
367	>	if (root != this)
368	>	return parent.doArrive(nextUnarrived == 0);
369	>	if (onAdvance(phase, nextUnarrived))
370	>	n |= TERMINATION_BIT;
371	>	else if (nextUnarrived == 0)
372	>	n |= EMPTY;
373	>	else
374	>	n |= nextUnarrived;
375	>	n |= ((long)((phase + 1) & MAX_PHASE)) << PHASE_SHIFT;
376	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, n);
377	>	releaseWaiters(phase);
378		}
379		return phase;
380		}
#	Line 367 | Line 390 | public class Phaser {
390		private int doRegister(int registrations) {
391		// adjustment to state
392		long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
393	<	final Phaser parent = this.parent;
393	>	Phaser par = parent;
394	>	int phase;
395		for (;;) {
396	<	long s = (parent == null) ? state : reconcileState();
397	<	int parties = (int)s >>> PARTIES_SHIFT;
398	<	int phase = (int)(s >>> PHASE_SHIFT);
399	<	if (phase < 0)
400	<	return phase;
377	<	else if (registrations > MAX_PARTIES - parties)
396	>	long s = state;
397	>	int counts = (int)s;
398	>	int parties = counts >>> PARTIES_SHIFT;
399	>	int unarrived = counts & UNARRIVED_MASK;
400	>	if (registrations > MAX_PARTIES - parties)
401		throw new IllegalStateException(badRegister(s));
402	<	else if ((parties == 0 && parent == null) || // first reg of root
403	<	((int)s & UNARRIVED_MASK) != 0) {   // not advancing
404	<	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
405	<	return phase;
406	<	}
407	<	else if (parties != 0)               // wait for onAdvance
408	<	root.internalAwaitAdvance(phase, null);
409	<	else {                               // 1st registration of child
410	<	synchronized (this) {            // register parent first
411	<	if (reconcileState() == s) { // recheck under lock
412	<	parent.doRegister(1);    // OK if throws IllegalState
413	<	for (;;) {               // simpler form of outer loop
414	<	s = reconcileState();
415	<	phase = (int)(s >>> PHASE_SHIFT);
416	<	if (phase < 0 ||
417	<	UNSAFE.compareAndSwapLong(this, stateOffset,
418	<	s, s + adj))
419	<	return phase;
420	<	}
402	>	else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0)
403	>	break;
404	>	else if (counts != EMPTY) {             // not 1st registration
405	>	if (par == null || reconcileState() == s) {
406	>	if (unarrived == 0)             // wait out advance
407	>	root.internalAwaitAdvance(phase, null);
408	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset,
409	>	s, s + adj))
410	>	break;
411	>	}
412	>	}
413	>	else if (par == null) {                 // 1st root registration
414	>	long next = (((long) phase) << PHASE_SHIFT) | adj;
415	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
416	>	break;
417	>	}
418	>	else {
419	>	synchronized (this) {               // 1st sub registration
420	>	if (state == s) {               // recheck under lock
421	>	par.doRegister(1);
422	>	do {                        // force current phase
423	>	phase = (int)(root.state >>> PHASE_SHIFT);
424	>	// assert phase < 0 || (int)state == EMPTY;
425	>	} while (!UNSAFE.compareAndSwapLong
426	>	(this, stateOffset, state,
427	>	(((long) phase) << PHASE_SHIFT) | adj));
428	>	break;
429		}
430		}
431		}
432		}
433	+	return phase;
434		}
435
436		/**
437	<	* Recursively resolves lagged phase propagation from root if necessary.
437	>	* Resolves lagged phase propagation from root if necessary.
438	>	* Reconciliation normally occurs when root has advanced but
439	>	* subphasers have not yet done so, in which case they must finish
440	>	* their own advance by setting unarrived to parties (or if
441	>	* parties is zero, resetting to unregistered EMPTY state).
442	>	* However, this method may also be called when "floating"
443	>	* subphasers with possibly some unarrived parties are merely
444	>	* catching up to current phase, in which case counts are
445	>	* unaffected.
446	>	*
447	>	* @return reconciled state
448		*/
449		private long reconcileState() {
450	<	Phaser par = parent;
450	>	final Phaser root = this.root;
451		long s = state;
452	<	if (par != null) {
453	<	Phaser rt = root;
454	<	int phase, rPhase;
455	<	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
456	<	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
457	<	if (par != rt && (int)(par.state >>> PHASE_SHIFT) != rPhase)
458	<	par.reconcileState();
459	<	else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
460	<	long u = s & PARTIES_MASK; // reset unarrived to parties
461	<	long next = ((((long) rPhase) << PHASE_SHIFT) | u |
420	<	(u >>> PARTIES_SHIFT));
421	<	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
422	<	}
452	>	if (root != this) {
453	>	int phase, u, p;
454	>	// CAS root phase with current parties; possibly trip unarrived
455	>	while ((phase = (int)(root.state >>> PHASE_SHIFT)) !=
456	>	(int)(s >>> PHASE_SHIFT) &&
457	>	!UNSAFE.compareAndSwapLong
458	>	(this, stateOffset, s,
459	>	s = ((((long) phase) << PHASE_SHIFT) | (s & PARTIES_MASK) |
460	>	((p = (int)s >>> PARTIES_SHIFT) == 0 ? EMPTY :
461	>	(u = (int)s & UNARRIVED_MASK) == 0 ? p : u))))
462		s = state;
424	–	}
463		}
464		return s;
465		}
#	Line 459 | Line 497 | public class Phaser {
497
498		/**
499		* Creates a new phaser with the given parent and number of
500	<	* registered unarrived parties. Registration and deregistration
501	<	* of this child phaser with its parent are managed automatically.
502	<	* 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.
500	>	* registered unarrived parties.  When the given parent is non-null
501	>	* and the given number of parties is greater than zero, this
502	>	* child phaser is registered with its parent.
503		*
504		* @param parent the parent phaser
505		* @param parties the number of parties required to advance to the
#	Line 478 | Line 510 | public class Phaser {
510		public Phaser(Phaser parent, int parties) {
511		if (parties >>> PARTIES_SHIFT != 0)
512		throw new IllegalArgumentException("Illegal number of parties");
513	<	long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT);
513	>	int phase = 0;
514		this.parent = parent;
515		if (parent != null) {
516	<	Phaser r = parent.root;
517	<	this.root = r;
518	<	this.evenQ = r.evenQ;
519	<	this.oddQ = r.oddQ;
516	>	final Phaser root = parent.root;
517	>	this.root = root;
518	>	this.evenQ = root.evenQ;
519	>	this.oddQ = root.oddQ;
520		if (parties != 0)
521	<	s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT;
521	>	phase = parent.doRegister(1);
522		}
523		else {
524		this.root = this;
525		this.evenQ = new AtomicReference<QNode>();
526		this.oddQ = new AtomicReference<QNode>();
527		}
528	<	this.state = s;
528	>	this.state = (parties == 0) ? (long) EMPTY :
529	>	((((long) phase) << PHASE_SHIFT) |
530	>	(((long) parties) << PARTIES_SHIFT) |
531	>	((long) parties));
532		}
533
534		/**
#	Line 501 | Line 536 | public class Phaser {
536		* invocation of {@link #onAdvance} is in progress, this method
537		* may await its completion before returning.  If this phaser has
538		* a parent, and this phaser previously had no registered parties,
539	<	* this phaser is also registered with its parent.
540	<	*
541	<	* @return the arrival phase number to which this registration applied
539	>	* this child phaser is also registered with its parent. If
540	>	* this phaser is terminated, the attempt to register has
541	>	* no effect, and a negative value is returned.
542	>	*
543	>	* @return the arrival phase number to which this registration
544	>	* applied.  If this value is negative, then this phaser has
545	>	* terminated, in which case registration has no effect.
546		* @throws IllegalStateException if attempting to register more
547		* than the maximum supported number of parties
548		*/
#	Line 515 | Line 554 | public class Phaser {
554		* Adds the given number of new unarrived parties to this phaser.
555		* If an ongoing invocation of {@link #onAdvance} is in progress,
556		* this method may await its completion before returning.  If this
557	<	* phaser has a parent, and the given number of parities is
558	<	* greater than zero, and this phaser previously had no registered
559	<	* parties, this phaser is also registered with its parent.
557	>	* phaser has a parent, and the given number of parties is greater
558	>	* than zero, and this phaser previously had no registered
559	>	* parties, this child phaser is also registered with its parent.
560	>	* If this phaser is terminated, the attempt to register has no
561	>	* effect, and a negative value is returned.
562		*
563		* @param parties the number of additional parties required to
564		* advance to the next phase
565	<	* @return the arrival phase number to which this registration applied
565	>	* @return the arrival phase number to which this registration
566	>	* applied.  If this value is negative, then this phaser has
567	>	* terminated, in which case registration has no effect.
568		* @throws IllegalStateException if attempting to register more
569		* than the maximum supported number of parties
570		* @throws IllegalArgumentException if {@code parties < 0}
#	Line 547 | Line 590 | public class Phaser {
590		* of unarrived parties would become negative
591		*/
592		public int arrive() {
593	<	return doArrive(ONE_ARRIVAL);
593	>	return doArrive(false);
594		}
595
596		/**
#	Line 567 | Line 610 | public class Phaser {
610		* of registered or unarrived parties would become negative
611		*/
612		public int arriveAndDeregister() {
613	<	return doArrive(ONE_ARRIVAL|ONE_PARTY);
613	>	return doArrive(true);
614		}
615
616		/**
#	Line 583 | Line 626 | public class Phaser {
626		* IllegalStateException} only upon some subsequent operation on
627		* this phaser, if ever.
628		*
629	<	* @return the arrival phase number, or a negative number if terminated
629	>	* @return the arrival phase number, or the (negative)
630	>	* {@linkplain #getPhase() current phase} if terminated
631		* @throws IllegalStateException if not terminated and the number
632		* of unarrived parties would become negative
633		*/
634		public int arriveAndAwaitAdvance() {
635	<	return awaitAdvance(doArrive(ONE_ARRIVAL));
635	>	// Specialization of doArrive+awaitAdvance eliminating some reads/paths
636	>	final Phaser root = this.root;
637	>	for (;;) {
638	>	long s = (root == this) ? state : reconcileState();
639	>	int phase = (int)(s >>> PHASE_SHIFT);
640	>	int counts = (int)s;
641	>	int unarrived = (counts & UNARRIVED_MASK) - 1;
642	>	if (phase < 0)
643	>	return phase;
644	>	else if (counts == EMPTY || unarrived < 0) {
645	>	if (reconcileState() == s)
646	>	throw new IllegalStateException(badArrive(s));
647	>	}
648	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s,
649	>	s -= ONE_ARRIVAL)) {
650	>	if (unarrived != 0)
651	>	return root.internalAwaitAdvance(phase, null);
652	>	if (root != this)
653	>	return parent.arriveAndAwaitAdvance();
654	>	long n = s & PARTIES_MASK;  // base of next state
655	>	int nextUnarrived = ((int)n) >>> PARTIES_SHIFT;
656	>	if (onAdvance(phase, nextUnarrived))
657	>	n |= TERMINATION_BIT;
658	>	else if (nextUnarrived == 0)
659	>	n |= EMPTY;
660	>	else
661	>	n |= nextUnarrived;
662	>	int nextPhase = (phase + 1) & MAX_PHASE;
663	>	n |= (long)nextPhase << PHASE_SHIFT;
664	>	if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n))
665	>	return (int)(state >>> PHASE_SHIFT); // terminated
666	>	releaseWaiters(phase);
667	>	return nextPhase;
668	>	}
669	>	}
670		}
671
672		/**
#	Line 599 | Line 677 | public class Phaser {
677		* @param phase an arrival phase number, or negative value if
678		* terminated; this argument is normally the value returned by a
679		* previous call to {@code arrive} or {@code arriveAndDeregister}.
680	<	* @return the next arrival phase number, or a negative value
681	<	* if terminated or argument is negative
680	>	* @return the next arrival phase number, or the argument if it is
681	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
682	>	* if terminated
683		*/
684		public int awaitAdvance(int phase) {
685	<	Phaser rt;
686	<	int p = (int)(state >>> PHASE_SHIFT);
685	>	final Phaser root = this.root;
686	>	long s = (root == this) ? state : reconcileState();
687	>	int p = (int)(s >>> PHASE_SHIFT);
688		if (phase < 0)
689		return phase;
690	<	if (p == phase &&
691	<	(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase)
612	<	return rt.internalAwaitAdvance(phase, null);
690	>	if (p == phase)
691	>	return root.internalAwaitAdvance(phase, null);
692		return p;
693		}
694
#	Line 623 | Line 702 | public class Phaser {
702		* @param phase an arrival phase number, or negative value if
703		* terminated; this argument is normally the value returned by a
704		* previous call to {@code arrive} or {@code arriveAndDeregister}.
705	<	* @return the next arrival phase number, or a negative value
706	<	* if terminated or argument is negative
705	>	* @return the next arrival phase number, or the argument if it is
706	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
707	>	* if terminated
708		* @throws InterruptedException if thread interrupted while waiting
709		*/
710		public int awaitAdvanceInterruptibly(int phase)
711		throws InterruptedException {
712	<	Phaser rt;
713	<	int p = (int)(state >>> PHASE_SHIFT);
712	>	final Phaser root = this.root;
713	>	long s = (root == this) ? state : reconcileState();
714	>	int p = (int)(s >>> PHASE_SHIFT);
715		if (phase < 0)
716		return phase;
717	<	if (p == phase &&
637	<	(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
717	>	if (p == phase) {
718		QNode node = new QNode(this, phase, true, false, 0L);
719	<	p = rt.internalAwaitAdvance(phase, node);
719	>	p = root.internalAwaitAdvance(phase, node);
720		if (node.wasInterrupted)
721		throw new InterruptedException();
722		}
#	Line 657 | Line 737 | public class Phaser {
737		*        {@code unit}
738		* @param unit a {@code TimeUnit} determining how to interpret the
739		*        {@code timeout} parameter
740	<	* @return the next arrival phase number, or a negative value
741	<	* if terminated or argument is negative
740	>	* @return the next arrival phase number, or the argument if it is
741	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
742	>	* if terminated
743		* @throws InterruptedException if thread interrupted while waiting
744		* @throws TimeoutException if timed out while waiting
745		*/
#	Line 666 | Line 747 | public class Phaser {
747		long timeout, TimeUnit unit)
748		throws InterruptedException, TimeoutException {
749		long nanos = unit.toNanos(timeout);
750	<	Phaser rt;
751	<	int p = (int)(state >>> PHASE_SHIFT);
750	>	final Phaser root = this.root;
751	>	long s = (root == this) ? state : reconcileState();
752	>	int p = (int)(s >>> PHASE_SHIFT);
753		if (phase < 0)
754		return phase;
755	<	if (p == phase &&
674	<	(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
755	>	if (p == phase) {
756		QNode node = new QNode(this, phase, true, true, nanos);
757	<	p = rt.internalAwaitAdvance(phase, node);
757	>	p = root.internalAwaitAdvance(phase, node);
758		if (node.wasInterrupted)
759		throw new InterruptedException();
760		else if (p == phase)
#	Line 684 | Line 765 | public class Phaser {
765
766		/**
767		* Forces this phaser to enter termination state.  Counts of
768	<	* arrived and registered parties are unaffected.  If this phaser
769	<	* is a member of a tiered set of phasers, then all of the phasers
770	<	* in the set are terminated.  If this phaser is already
771	<	* terminated, this method has no effect.  This method may be
772	<	* useful for coordinating recovery after one or more tasks
773	<	* encounter unexpected exceptions.
768	>	* registered parties are unaffected.  If this phaser is a member
769	>	* of a tiered set of phasers, then all of the phasers in the set
770	>	* are terminated.  If this phaser is already terminated, this
771	>	* method has no effect.  This method may be useful for
772	>	* coordinating recovery after one or more tasks encounter
773	>	* unexpected exceptions.
774		*/
775		public void forceTermination() {
776		// Only need to change root state
#	Line 698 | Line 779 | public class Phaser {
779		while ((s = root.state) >= 0) {
780		if (UNSAFE.compareAndSwapLong(root, stateOffset,
781		s, s | TERMINATION_BIT)) {
782	<	releaseWaiters(0); // signal all threads
782	>	// signal all threads
783	>	releaseWaiters(0);
784		releaseWaiters(1);
785		return;
786		}
#	Line 729 | Line 811 | public class Phaser {
811
812		/**
813		* Returns the number of registered parties that have arrived at
814	<	* the current phase of this phaser.
814	>	* the current phase of this phaser. If this phaser has terminated,
815	>	* the returned value is meaningless and arbitrary.
816		*
817		* @return the number of arrived parties
818		*/
819		public int getArrivedParties() {
820	<	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());
820	>	return arrivedOf(reconcileState());
821		}
822
823		/**
824		* Returns the number of registered parties that have not yet
825	<	* arrived at the current phase of this phaser.
825	>	* arrived at the current phase of this phaser. If this phaser has
826	>	* terminated, the returned value is meaningless and arbitrary.
827		*
828		* @return the number of unarrived parties
829		*/
830		public int getUnarrivedParties() {
831	<	int u = unarrivedOf(state);
752	<	return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState());
831	>	return unarrivedOf(reconcileState());
832		}
833
834		/**
#	Line 785 | Line 864 | public class Phaser {
864		* advance, and to control termination. This method is invoked
865		* upon arrival of the party advancing this phaser (when all other
866		* waiting parties are dormant).  If this method returns {@code
867	<	* true}, then, rather than advance the phase number, this phaser
868	<	* will be set to a final termination state, and subsequent calls
869	<	* to {@link #isTerminated} will return true. Any (unchecked)
870	<	* Exception or Error thrown by an invocation of this method is
871	<	* propagated to the party attempting to advance this phaser, in
872	<	* which case no advance occurs.
867	>	* true}, this phaser will be set to a final termination state
868	>	* upon advance, and subsequent calls to {@link #isTerminated}
869	>	* will return true. Any (unchecked) Exception or Error thrown by
870	>	* an invocation of this method is propagated to the party
871	>	* attempting to advance this phaser, in which case no advance
872	>	* occurs.
873		*
874		* <p>The arguments to this method provide the state of the phaser
875		* prevailing for the current transition.  The effects of invoking
#	Line 854 | Line 933 | public class Phaser {
933		*/
934		private void releaseWaiters(int phase) {
935		QNode q;   // first element of queue
857	–	int p;     // its phase
936		Thread t;  // its thread
937		AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
938		while ((q = head.get()) != null &&
939	<	((p = q.phase) == phase ||
862	<	(int)(root.state >>> PHASE_SHIFT) != p)) {
939	>	q.phase != (int)(root.state >>> PHASE_SHIFT)) {
940		if (head.compareAndSet(q, q.next) &&
941		(t = q.thread) != null) {
942		q.thread = null;
#	Line 868 | Line 945 | public class Phaser {
945		}
946		}
947
948	+	/**
949	+	* Variant of releaseWaiters that additionally tries to remove any
950	+	* nodes no longer waiting for advance due to timeout or
951	+	* interrupt. Currently, nodes are removed only if they are at
952	+	* head of queue, which suffices to reduce memory footprint in
953	+	* most usages.
954	+	*
955	+	* @return current phase on exit
956	+	*/
957	+	private int abortWait(int phase) {
958	+	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
959	+	for (;;) {
960	+	Thread t;
961	+	QNode q = head.get();
962	+	int p = (int)(root.state >>> PHASE_SHIFT);
963	+	if (q == null || ((t = q.thread) != null && q.phase == p))
964	+	return p;
965	+	if (head.compareAndSet(q, q.next) && t != null) {
966	+	q.thread = null;
967	+	LockSupport.unpark(t);
968	+	}
969	+	}
970	+	}
971	+
972		/** The number of CPUs, for spin control */
973		private static final int NCPU = Runtime.getRuntime().availableProcessors();
974
#	Line 935 | Line 1036 | public class Phaser {
1036		node.thread = null;       // avoid need for unpark()
1037		if (node.wasInterrupted && !node.interruptible)
1038		Thread.currentThread().interrupt();
1039	<	if ((p = (int)(state >>> PHASE_SHIFT)) == phase)
1040	<	return p;                 // recheck abort
1039	>	if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase)
1040	>	return abortWait(phase); // possibly clean up on abort
1041		}
1042		releaseWaiters(phase);
1043		return p;
#	Line 963 | Line 1064 | public class Phaser {
1064		this.interruptible = interruptible;
1065		this.nanos = nanos;
1066		this.timed = timed;
1067	<	this.lastTime = timed? System.nanoTime() : 0L;
1067	>	this.lastTime = timed ? System.nanoTime() : 0L;
1068		thread = Thread.currentThread();
1069		}
1070

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