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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.57 by dl, Fri Nov 19 16:03:24 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}.  As illustrated below, when
83	<	* phasers control actions with a fixed number of iterations, it is
84	<	* often convenient to override this method to cause termination when
85	<	* the current phase number reaches a threshold. Method {@link
86	<	* #forceTermination} is also available to abruptly release waiting
87	<	* threads and allow them to terminate.
88	<	*
89	<	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
90	<	* in tree structures) to reduce contention. Phasers with large
91	<	* numbers of parties that would otherwise experience heavy
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
93	>	* large numbers of parties that would otherwise experience heavy
94		* synchronization contention costs may instead be set up so that
95		* groups of sub-phasers share a common parent.  This may greatly
96		* increase throughput even though it incurs greater per-operation
#	Line 183 | 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 203 | 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 224 | Line 226 | public class Phaser {
226		*/
227
228		/**
229	<	* Barrier state representation. Conceptually, a barrier contains
228	<	* 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 240 | Line 241 | public class Phaser {
241		*/
242		private volatile long state;
243
244	<	private static final int  MAX_PARTIES    = 0xffff;
245	<	private static final int  MAX_PHASE      = 0x7fffffff;
246	<	private static final int  PARTIES_SHIFT  = 16;
247	<	private static final int  PHASE_SHIFT    = 32;
248	<	private static final int  UNARRIVED_MASK = 0xffff;
249	<	private static final long PARTIES_MASK   = 0xffff0000L; // for masking long
250	<	private static final long ONE_ARRIVAL    = 1L;
251	<	private static final long ONE_PARTY      = 1L << PARTIES_SHIFT;
252	<	private static final long TERMINATION_PHASE  = -1L << PHASE_SHIFT;
244	>	private static final int  MAX_PARTIES     = 0xffff;
245	>	private static final int  MAX_PHASE       = 0x7fffffff;
246	>	private static final int  PARTIES_SHIFT   = 16;
247	>	private static final int  PHASE_SHIFT     = 32;
248	>	private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
249	>	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;
252	>	private static final long TERMINATION_BIT = 1L << 63;
253
254		// The following unpacking methods are usually manually inlined
255
#	Line 293 | Line 294 | public class Phaser {
294		}
295
296		/**
297	+	* Returns message string for bounds exceptions on arrival.
298	+	*/
299	+	private String badArrive(long s) {
300	+	return "Attempted arrival of unregistered party for " +
301	+	stateToString(s);
302	+	}
303	+
304	+	/**
305	+	* Returns message string for bounds exceptions on registration.
306	+	*/
307	+	private String badRegister(long s) {
308	+	return "Attempt to register more than " +
309	+	MAX_PARTIES + " parties for " + stateToString(s);
310	+	}
311	+
312	+	/**
313		* Main implementation for methods arrive and arriveAndDeregister.
314		* Manually tuned to speed up and minimize race windows for the
315		* common case of just decrementing unarrived field.
#	Line 304 | Line 321 | public class Phaser {
321		private int doArrive(long adj) {
322		for (;;) {
323		long s = state;
324	+	int unarrived = (int)s & UNARRIVED_MASK;
325		int phase = (int)(s >>> PHASE_SHIFT);
326		if (phase < 0)
327		return phase;
328	<	int unarrived = (int)s & UNARRIVED_MASK;
329	<	if (unarrived == 0)
330	<	checkBadArrive(s);
328	>	else if (unarrived == 0) {
329	>	if (reconcileState() == s)     // recheck
330	>	throw new IllegalStateException(badArrive(s));
331	>	}
332		else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
333		if (unarrived == 1) {
334		long p = s & PARTIES_MASK; // unshifted parties field
#	Line 320 | Line 339 | public class Phaser {
339		final Phaser parent = this.parent;
340		if (parent == null) {
341		if (onAdvance(phase, u))
342	<	next |= TERMINATION_PHASE; // obliterate phase
342	>	next |= TERMINATION_BIT;
343		UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
344		releaseWaiters(phase);
345		}
346		else {
347		parent.doArrive((u == 0) ?
348		ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
349	<	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase ||
331	<	((int)(state >>> PHASE_SHIFT) != nextPhase &&
332	<	!UNSAFE.compareAndSwapLong(this, stateOffset,
333	<	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 340 | Line 359 | public class Phaser {
359		}
360
361		/**
343	–	* Rechecks state and throws bounds exceptions on arrival -- called
344	–	* only if unarrived is apparently zero.
345	–	*/
346	–	private void checkBadArrive(long s) {
347	–	if (reconcileState() == s)
348	–	throw new IllegalStateException
349	–	("Attempted arrival of unregistered party for " +
350	–	stateToString(s));
351	–	}
352	–
353	–	/**
362		* Implementation of register, bulkRegister
363		*
364	<	* @param registrations number to add to both parties and unarrived fields
364	>	* @param registrations number to add to both parties and
365	>	* unarrived fields. Must be greater than zero.
366		*/
367		private int doRegister(int registrations) {
359	–	// assert registrations > 0;
368		// adjustment to state
369		long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
370		final Phaser parent = this.parent;
371		for (;;) {
372		long s = (parent == null) ? state : reconcileState();
373	+	int parties = (int)s >>> PARTIES_SHIFT;
374		int phase = (int)(s >>> PHASE_SHIFT);
375		if (phase < 0)
376		return phase;
368	–	int parties = (int)s >>> PARTIES_SHIFT;
369	–	if (parties != 0 && ((int)s & UNARRIVED_MASK) == 0)
370	–	internalAwaitAdvance(phase, null); // wait for onAdvance
377		else if (registrations > MAX_PARTIES - parties)
378		throw new IllegalStateException(badRegister(s));
379	<	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
380	<	return phase;
379	>	else if ((parties == 0 && parent == null) || // first reg of root
380	>	((int)s & UNARRIVED_MASK) != 0) {   // not advancing
381	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
382	>	return phase;
383	>	}
384	>	else if (parties != 0)               // wait for onAdvance
385	>	root.internalAwaitAdvance(phase, null);
386	>	else {                               // 1st registration of child
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
391	>	s = reconcileState();
392	>	phase = (int)(s >>> PHASE_SHIFT);
393	>	if (phase < 0 ||
394	>	UNSAFE.compareAndSwapLong(this, stateOffset,
395	>	s, s + adj))
396	>	return phase;
397	>	}
398	>	}
399	>	}
400	>	}
401		}
402		}
403
404		/**
379	–	* Returns message string for out of bounds exceptions on registration.
380	–	*/
381	–	private String badRegister(long s) {
382	–	return "Attempt to register more than " +
383	–	MAX_PARTIES + " parties for " + stateToString(s);
384	–	}
385	–
386	–	/**
405		* Recursively resolves lagged phase propagation from root if necessary.
406		*/
407		private long reconcileState() {
#	Line 394 | 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
419		long next = ((((long) rPhase) << PHASE_SHIFT) | u |
420		(u >>> PARTIES_SHIFT));
421	<	if (state == s &&
404	<	UNSAFE.compareAndSwapLong(this, stateOffset,
405	<	s, s = next))
406	<	break;
421	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
422		}
423		s = state;
424		}
#	Line 412 | 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 422 | 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 433 | Line 449 | public class Phaser {
449		}
450
451		/**
452	<	* Creates a new phaser with the given parent, without any
437	<	* initially registered parties. If parent is non-null this phaser
438	<	* is registered with the parent and its initial phase number is
439	<	* the same as that of parent phaser.
452	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
453		*
454		* @param parent the parent phaser
455		*/
#	Line 446 | 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, this phaser
463	<	* is registered with the parent and its initial phase number is
464	<	* the same as that of parent phaser.
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 = parent.register();
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>();
474	–	phase = 0;
495		}
496	<	long p = (long)parties;
477	<	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.
501	<	* If an ongoing invocation of {@link #onAdvance} is in progress,
502	<	* this method may wait until its completion before registering.
500	>	* Adds a new unarrived party to this phaser.  If an ongoing
501	>	* invocation of {@link #onAdvance} is in progress, this method
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 493 | 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.
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 510 | Line 535 | public class Phaser {
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 an
540	<	* unenforced usage error for an unregistered party to invoke this
541	<	* method.
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 524 | 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 an unenforced usage error for an
560	<	* unregistered party to invoke this method.
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 541 | 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 an unenforced
580	<	* usage error for an unregistered party to invoke this method.
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
564	<	* 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);
600	<	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 607 | 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
615	<	* 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 629 | 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);
636	<	if (p == phase) {
637	<	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 646 | 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 660 | Line 697 | public class Phaser {
697		long s;
698		while ((s = root.state) >= 0) {
699		if (UNSAFE.compareAndSwapLong(root, stateOffset,
700	<	s, s | TERMINATION_PHASE)) {
700	>	s, s | TERMINATION_BIT)) {
701		releaseWaiters(0); // signal all threads
702		releaseWaiters(1);
703		return;
#	Line 671 | 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 680 | 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 690 | 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 728 | 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 739 | 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>The default version returns {@code true} when the number of
806	<	* registered parties is zero. Normally, overrides that arrange
807	<	* termination for other reasons should also preserve this
808	<	* property.
805	>	* <p>To support the most common use cases, the default
806	>	* implementation of this method returns {@code true} when the
807	>	* number of registered parties has become zero as the result of a
808	>	* party invoking {@code arriveAndDeregister}.  You can disable
809	>	* this behavior, thus enabling continuation upon future
810	>	* registrations, by overriding this method to always return
811	>	* {@code false}:
812	>	*
813	>	* <pre> {@code
814	>	* Phaser phaser = new 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 778 | 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 800 | 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 822 | 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
827	<	* before blocking. The value trades off good-citizenship vs big
828	<	* 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 838 | 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
852	<	releaseWaiters(phase-1);
853	<	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;
859	<	lastUnarrived = -1;
860	<	}
861	<	else if (spins > 0) {
862	<	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
863	<	Thread.yield();  // yield midway through spin
864	<	}
865	<	else if (node == null)   // must be noninterruptible
866	<	node = new QNode(this, phase, false, false, 0L);
867	<	else if (node.isReleasable()) {
868	<	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
869	<	break;
870	<	else
871	<	return phase;    // aborted
872	<	}
873	<	else if (!queued) {      // push onto queue
874	<	AtomicReference<QNode> head = queueFor(phase);
875	<	QNode q = head.get();
876	<	if (q == null || q.phase == phase) {
877	<	node.next = q;
878	<	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
879	<	break;       // recheck to avoid stale enqueue
880	<	else
881	<	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 889 | 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);
893	–	if (node != null)
894	–	node.onRelease();
942		return p;
943		}
944
#	Line 921 | Line 968 | public class Phaser {
968		}
969
970		public boolean isReleasable() {
971	<	Thread t = thread;
972	<	if (t != null) {
973	<	if (phaser.getPhase() != phase)
927	<	t = null;
928	<	else {
929	<	if (Thread.interrupted())
930	<	wasInterrupted = true;
931	<	if (interruptible && wasInterrupted)
932	<	t = null;
933	<	else if (timed) {
934	<	if (nanos > 0) {
935	<	long now = System.nanoTime();
936	<	nanos -= now - lastTime;
937	<	lastTime = now;
938	<	}
939	<	if (nanos <= 0)
940	<	t = null;
941	<	}
942	<	}
943	<	if (t != null)
944	<	return false;
971	>	if (thread == null)
972	>	return true;
973	>	if (phaser.getPhase() != phase) {
974		thread = null;
975	+	return true;
976		}
977	<	return true;
977	>	if (Thread.interrupted())
978	>	wasInterrupted = true;
979	>	if (wasInterrupted && interruptible) {
980	>	thread = null;
981	>	return true;
982	>	}
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 956 | Line 1003 | public class Phaser {
1003		LockSupport.parkNanos(this, nanos);
1004		return isReleasable();
1005		}
959	–
960	–	void signal() {
961	–	Thread t = thread;
962	–	if (t != null) {
963	–	thread = null;
964	–	LockSupport.unpark(t);
965	–	}
966	–	}
967	–
968	–	void onRelease() { // actions upon return from internalAwaitAdvance
969	–	if (!interruptible && wasInterrupted)
970	–	Thread.currentThread().interrupt();
971	–	if (thread != null)
972	–	thread = null;
973	–	}
974	–
1006		}
1007
1008		// Unsafe mechanics

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