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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.64 by jsr166, Mon Nov 29 20:58:06 2010 UTC vs.
Revision 1.76 by jsr166, Sat Oct 15 21:46:25 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 226 | Line 237 | public class Phaser {
237		*/
238
239		/**
240	<	* Primary state representation, holding four fields:
240	>	* Primary state representation, holding four bit-fields:
241		*
242	<	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
243	<	* * parties -- the number of parties to wait              (bits 16-31)
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.
242	>	* unarrived  -- the number of parties yet to hit barrier (bits  0-15)
243	>	* parties    -- the number of parties to wait            (bits 16-31)
244	>	* phase      -- the generation of the barrier            (bits 32-62)
245	>	* terminated -- set if barrier is terminated             (bit  63 / sign)
246	>	*
247	>	* Except that a phaser with no registered parties is
248	>	* distinguished by 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
268		private static final int  MAX_PARTIES     = 0xffff;
269	<	private static final int  MAX_PHASE       = 0x7fffffff;
269	>	private static final int  MAX_PHASE       = Integer.MAX_VALUE;
270		private static final int  PARTIES_SHIFT   = 16;
271		private static final int  PHASE_SHIFT     = 32;
272		private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
273		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;
274		private static final long TERMINATION_BIT = 1L << 63;
275
276	+	// some special values
277	+	private static final int  ONE_ARRIVAL     = 1;
278	+	private static final int  ONE_PARTY       = 1 << PARTIES_SHIFT;
279	+	private static final int  ONE_DEREGISTER  = ONE_ARRIVAL|ONE_PARTY;
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 262 | Line 291 | public class Phaser {
291		}
292
293		private static int phaseOf(long s) {
294	<	return (int) (s >>> PHASE_SHIFT);
294	>	return (int)(s >>> PHASE_SHIFT);
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
348	<	* ONE_ARRIVAL (for arrive) or
349	<	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
347	>	* @param adjust value to subtract from state;
348	>	*               ONE_ARRIVAL for arrive,
349	>	*               ONE_DEREGISTER for arriveAndDeregister
350		*/
351	<	private int doArrive(long adj) {
351	>	private int doArrive(int adjust) {
352	>	final Phaser root = this.root;
353		for (;;) {
354	<	long s = state;
324	<	int unarrived = (int)s & UNARRIVED_MASK;
354	>	long s = (root == this) ? state : reconcileState();
355		int phase = (int)(s >>> PHASE_SHIFT);
356		if (phase < 0)
357		return phase;
358	<	else if (unarrived == 0) {
359	<	if (reconcileState() == s)     // recheck
360	<	throw new IllegalStateException(badArrive(s));
361	<	}
362	<	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
358	>	int counts = (int)s;
359	>	int unarrived = (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK);
360	>	if (unarrived <= 0)
361	>	throw new IllegalStateException(badArrive(s));
362	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adjust)) {
363		if (unarrived == 1) {
364	<	long p = s & PARTIES_MASK; // unshifted parties field
365	<	long lu = p >>> PARTIES_SHIFT;
366	<	int u = (int)lu;
367	<	int nextPhase = (phase + 1) & MAX_PHASE;
368	<	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
369	<	final Phaser parent = this.parent;
370	<	if (parent == null) {
371	<	if (onAdvance(phase, u))
372	<	next |= TERMINATION_BIT;
373	<	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
364	>	long n = s & PARTIES_MASK;  // base of next state
365	>	int nextUnarrived = (int)n >>> PARTIES_SHIFT;
366	>	if (root == this) {
367	>	if (onAdvance(phase, nextUnarrived))
368	>	n |= TERMINATION_BIT;
369	>	else if (nextUnarrived == 0)
370	>	n |= EMPTY;
371	>	else
372	>	n |= nextUnarrived;
373	>	int nextPhase = (phase + 1) & MAX_PHASE;
374	>	n |= (long)nextPhase << PHASE_SHIFT;
375	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, n);
376		releaseWaiters(phase);
377		}
378	<	else {
379	<	parent.doArrive((u == 0) ?
380	<	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
381	<	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase)
350	<	reconcileState();
351	<	else if (state == s)
352	<	UNSAFE.compareAndSwapLong(this, stateOffset, s,
353	<	next);
378	>	else if (nextUnarrived == 0) { // propagate deregistration
379	>	phase = parent.doArrive(ONE_DEREGISTER);
380	>	UNSAFE.compareAndSwapLong(this, stateOffset,
381	>	s, s | EMPTY);
382		}
383	+	else
384	+	phase = parent.doArrive(ONE_ARRIVAL);
385		}
386		return phase;
387		}
#	Line 366 | Line 396 | public class Phaser {
396		*/
397		private int doRegister(int registrations) {
398		// adjustment to state
399	<	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
399	>	long adjust = ((long)registrations << PARTIES_SHIFT) | registrations;
400		final Phaser parent = this.parent;
401	+	int phase;
402		for (;;) {
403		long s = (parent == null) ? state : reconcileState();
404	<	int parties = (int)s >>> PARTIES_SHIFT;
405	<	int phase = (int)(s >>> PHASE_SHIFT);
406	<	if (phase < 0)
407	<	return phase;
377	<	else if (registrations > MAX_PARTIES - parties)
404	>	int counts = (int)s;
405	>	int parties = counts >>> PARTIES_SHIFT;
406	>	int unarrived = counts & UNARRIVED_MASK;
407	>	if (registrations > MAX_PARTIES - parties)
408		throw new IllegalStateException(badRegister(s));
409	<	else if ((parties == 0 && parent == null) || // first reg of root
410	<	((int)s & UNARRIVED_MASK) != 0) {   // not advancing
411	<	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
412	<	return phase;
409	>	phase = (int)(s >>> PHASE_SHIFT);
410	>	if (phase < 0)
411	>	break;
412	>	if (counts != EMPTY) {                  // not 1st registration
413	>	if (parent == null || reconcileState() == s) {
414	>	if (unarrived == 0)             // wait out advance
415	>	root.internalAwaitAdvance(phase, null);
416	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset,
417	>	s, s + adjust))
418	>	break;
419	>	}
420	>	}
421	>	else if (parent == null) {              // 1st root registration
422	>	long next = ((long)phase << PHASE_SHIFT) | adjust;
423	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
424	>	break;
425		}
426	<	else if (parties != 0)               // wait for onAdvance
427	<	root.internalAwaitAdvance(phase, null);
428	<	else {                               // 1st registration of child
429	<	synchronized (this) {            // register parent first
430	<	if (reconcileState() == s) { // recheck under lock
431	<	parent.doRegister(1);    // OK if throws IllegalState
432	<	for (;;) {               // simpler form of outer loop
433	<	s = reconcileState();
434	<	phase = (int)(s >>> PHASE_SHIFT);
435	<	if (phase < 0 ||
436	<	UNSAFE.compareAndSwapLong(this, stateOffset,
437	<	s, s + adj))
438	<	return phase;
426	>	else {
427	>	synchronized (this) {               // 1st sub registration
428	>	if (state == s) {               // recheck under lock
429	>	phase = parent.doRegister(1);
430	>	if (phase < 0)
431	>	break;
432	>	// finish registration whenever parent registration
433	>	// succeeded, even when racing with termination,
434	>	// since these are part of the same "transaction".
435	>	while (!UNSAFE.compareAndSwapLong
436	>	(this, stateOffset, s,
437	>	((long)phase << PHASE_SHIFT) | adjust)) {
438	>	s = state;
439	>	phase = (int)(root.state >>> PHASE_SHIFT);
440	>	// assert (int)s == EMPTY;
441		}
442	+	break;
443		}
444		}
445		}
446		}
447	+	return phase;
448		}
449
450		/**
451	<	* Recursively resolves lagged phase propagation from root if necessary.
451	>	* Resolves lagged phase propagation from root if necessary.
452	>	* Reconciliation normally occurs when root has advanced but
453	>	* subphasers have not yet done so, in which case they must finish
454	>	* their own advance by setting unarrived to parties (or if
455	>	* parties is zero, resetting to unregistered EMPTY state).
456	>	* However, this method may also be called when "floating"
457	>	* subphasers with possibly some unarrived parties are merely
458	>	* catching up to current phase, in which case counts are
459	>	* unaffected.
460	>	*
461	>	* @return reconciled state
462		*/
463		private long reconcileState() {
464	<	Phaser par = parent;
464	>	final Phaser root = this.root;
465		long s = state;
466	<	if (par != null) {
467	<	Phaser rt = root;
468	<	int phase, rPhase;
469	<	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
470	<	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
471	<	if (par != rt && (int)(par.state >>> PHASE_SHIFT) != rPhase)
472	<	par.reconcileState();
473	<	else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
474	<	long u = s & PARTIES_MASK; // reset unarrived to parties
475	<	long next = ((((long) rPhase) << PHASE_SHIFT) | u |
476	<	(u >>> PARTIES_SHIFT));
477	<	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
422	<	}
466	>	if (root != this) {
467	>	int phase, u, p;
468	>	// CAS root phase with current parties; possibly trip unarrived
469	>	while ((phase = (int)(root.state >>> PHASE_SHIFT)) !=
470	>	(int)(s >>> PHASE_SHIFT) &&
471	>	!UNSAFE.compareAndSwapLong
472	>	(this, stateOffset, s,
473	>	s = (((long)phase << PHASE_SHIFT) |
474	>	(s & PARTIES_MASK) |
475	>	((p = (int)s >>> PARTIES_SHIFT) == 0 ? EMPTY :
476	>	((u = (int)s & UNARRIVED_MASK) == 0 && phase >= 0) ?
477	>	p : u))))
478		s = state;
424	–	}
479		}
480		return s;
481		}
#	Line 459 | Line 513 | public class Phaser {
513
514		/**
515		* Creates a new phaser with the given parent and number of
516	<	* registered unarrived parties. Registration and deregistration
517	<	* of this child phaser with its parent are managed automatically.
518	<	* 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.
516	>	* registered unarrived parties.  When the given parent is non-null
517	>	* and the given number of parties is greater than zero, this
518	>	* child phaser is registered with its parent.
519		*
520		* @param parent the parent phaser
521		* @param parties the number of parties required to advance to the
#	Line 478 | Line 526 | public class Phaser {
526		public Phaser(Phaser parent, int parties) {
527		if (parties >>> PARTIES_SHIFT != 0)
528		throw new IllegalArgumentException("Illegal number of parties");
529	<	long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT);
529	>	int phase = 0;
530		this.parent = parent;
531		if (parent != null) {
532	<	Phaser r = parent.root;
533	<	this.root = r;
534	<	this.evenQ = r.evenQ;
535	<	this.oddQ = r.oddQ;
532	>	final Phaser root = parent.root;
533	>	this.root = root;
534	>	this.evenQ = root.evenQ;
535	>	this.oddQ = root.oddQ;
536		if (parties != 0)
537	<	s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT;
537	>	phase = parent.doRegister(1);
538		}
539		else {
540		this.root = this;
541		this.evenQ = new AtomicReference<QNode>();
542		this.oddQ = new AtomicReference<QNode>();
543		}
544	<	this.state = s;
544	>	this.state = (parties == 0) ? (long)EMPTY :
545	>	((long)phase << PHASE_SHIFT) |
546	>	((long)parties << PARTIES_SHIFT) |
547	>	((long)parties);
548		}
549
550		/**
#	Line 501 | Line 552 | public class Phaser {
552		* invocation of {@link #onAdvance} is in progress, this method
553		* may await its completion before returning.  If this phaser has
554		* a parent, and this phaser previously had no registered parties,
555	<	* this phaser is also registered with its parent.
556	<	*
557	<	* @return the arrival phase number to which this registration applied
555	>	* this child phaser is also registered with its parent. If
556	>	* this phaser is terminated, the attempt to register has
557	>	* no effect, and a negative value is returned.
558	>	*
559	>	* @return the arrival phase number to which this registration
560	>	* applied.  If this value is negative, then this phaser has
561	>	* terminated, in which case registration has no effect.
562		* @throws IllegalStateException if attempting to register more
563		* than the maximum supported number of parties
564		*/
#	Line 515 | Line 570 | public class Phaser {
570		* Adds the given number of new unarrived parties to this phaser.
571		* If an ongoing invocation of {@link #onAdvance} is in progress,
572		* this method may await its completion before returning.  If this
573	<	* phaser has a parent, and the given number of parities is
574	<	* greater than zero, and this phaser previously had no registered
575	<	* parties, this phaser is also registered with its parent.
573	>	* phaser has a parent, and the given number of parties is greater
574	>	* than zero, and this phaser previously had no registered
575	>	* parties, this child phaser is also registered with its parent.
576	>	* If this phaser is terminated, the attempt to register has no
577	>	* effect, and a negative value is returned.
578		*
579		* @param parties the number of additional parties required to
580		* advance to the next phase
581	<	* @return the arrival phase number to which this registration applied
581	>	* @return the arrival phase number to which this registration
582	>	* applied.  If this value is negative, then this phaser has
583	>	* terminated, in which case registration has no effect.
584		* @throws IllegalStateException if attempting to register more
585		* than the maximum supported number of parties
586		* @throws IllegalArgumentException if {@code parties < 0}
#	Line 567 | Line 626 | public class Phaser {
626		* of registered or unarrived parties would become negative
627		*/
628		public int arriveAndDeregister() {
629	<	return doArrive(ONE_ARRIVAL|ONE_PARTY);
629	>	return doArrive(ONE_DEREGISTER);
630		}
631
632		/**
#	Line 583 | Line 642 | public class Phaser {
642		* IllegalStateException} only upon some subsequent operation on
643		* this phaser, if ever.
644		*
645	<	* @return the arrival phase number, or a negative number if terminated
645	>	* @return the arrival phase number, or the (negative)
646	>	* {@linkplain #getPhase() current phase} if terminated
647		* @throws IllegalStateException if not terminated and the number
648		* of unarrived parties would become negative
649		*/
650		public int arriveAndAwaitAdvance() {
651	<	return awaitAdvance(doArrive(ONE_ARRIVAL));
651	>	// Specialization of doArrive+awaitAdvance eliminating some reads/paths
652	>	final Phaser root = this.root;
653	>	for (;;) {
654	>	long s = (root == this) ? state : reconcileState();
655	>	int phase = (int)(s >>> PHASE_SHIFT);
656	>	if (phase < 0)
657	>	return phase;
658	>	int counts = (int)s;
659	>	int unarrived = (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK);
660	>	if (unarrived <= 0)
661	>	throw new IllegalStateException(badArrive(s));
662	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s,
663	>	s -= ONE_ARRIVAL)) {
664	>	if (unarrived > 1)
665	>	return root.internalAwaitAdvance(phase, null);
666	>	if (root != this)
667	>	return parent.arriveAndAwaitAdvance();
668	>	long n = s & PARTIES_MASK;  // base of next state
669	>	int nextUnarrived = (int)n >>> PARTIES_SHIFT;
670	>	if (onAdvance(phase, nextUnarrived))
671	>	n |= TERMINATION_BIT;
672	>	else if (nextUnarrived == 0)
673	>	n |= EMPTY;
674	>	else
675	>	n |= nextUnarrived;
676	>	int nextPhase = (phase + 1) & MAX_PHASE;
677	>	n |= (long)nextPhase << PHASE_SHIFT;
678	>	if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n))
679	>	return (int)(state >>> PHASE_SHIFT); // terminated
680	>	releaseWaiters(phase);
681	>	return nextPhase;
682	>	}
683	>	}
684		}
685
686		/**
#	Line 599 | Line 691 | public class Phaser {
691		* @param phase an arrival phase number, or negative value if
692		* terminated; this argument is normally the value returned by a
693		* previous call to {@code arrive} or {@code arriveAndDeregister}.
694	<	* @return the next arrival phase number, or a negative value
695	<	* if terminated or argument is negative
694	>	* @return the next arrival phase number, or the argument if it is
695	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
696	>	* if terminated
697		*/
698		public int awaitAdvance(int phase) {
699	<	Phaser rt;
700	<	int p = (int)(state >>> PHASE_SHIFT);
699	>	final Phaser root = this.root;
700	>	long s = (root == this) ? state : reconcileState();
701	>	int p = (int)(s >>> PHASE_SHIFT);
702		if (phase < 0)
703		return phase;
704	<	if (p == phase &&
705	<	(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase)
612	<	return rt.internalAwaitAdvance(phase, null);
704	>	if (p == phase)
705	>	return root.internalAwaitAdvance(phase, null);
706		return p;
707		}
708
#	Line 623 | Line 716 | public class Phaser {
716		* @param phase an arrival phase number, or negative value if
717		* terminated; this argument is normally the value returned by a
718		* previous call to {@code arrive} or {@code arriveAndDeregister}.
719	<	* @return the next arrival phase number, or a negative value
720	<	* if terminated or argument is negative
719	>	* @return the next arrival phase number, or the argument if it is
720	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
721	>	* if terminated
722		* @throws InterruptedException if thread interrupted while waiting
723		*/
724		public int awaitAdvanceInterruptibly(int phase)
725		throws InterruptedException {
726	<	Phaser rt;
727	<	int p = (int)(state >>> PHASE_SHIFT);
726	>	final Phaser root = this.root;
727	>	long s = (root == this) ? state : reconcileState();
728	>	int p = (int)(s >>> PHASE_SHIFT);
729		if (phase < 0)
730		return phase;
731	<	if (p == phase &&
637	<	(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
731	>	if (p == phase) {
732		QNode node = new QNode(this, phase, true, false, 0L);
733	<	p = rt.internalAwaitAdvance(phase, node);
733	>	p = root.internalAwaitAdvance(phase, node);
734		if (node.wasInterrupted)
735		throw new InterruptedException();
736		}
#	Line 657 | Line 751 | public class Phaser {
751		*        {@code unit}
752		* @param unit a {@code TimeUnit} determining how to interpret the
753		*        {@code timeout} parameter
754	<	* @return the next arrival phase number, or a negative value
755	<	* if terminated or argument is negative
754	>	* @return the next arrival phase number, or the argument if it is
755	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
756	>	* if terminated
757		* @throws InterruptedException if thread interrupted while waiting
758		* @throws TimeoutException if timed out while waiting
759		*/
#	Line 666 | Line 761 | public class Phaser {
761		long timeout, TimeUnit unit)
762		throws InterruptedException, TimeoutException {
763		long nanos = unit.toNanos(timeout);
764	<	Phaser rt;
765	<	int p = (int)(state >>> PHASE_SHIFT);
764	>	final Phaser root = this.root;
765	>	long s = (root == this) ? state : reconcileState();
766	>	int p = (int)(s >>> PHASE_SHIFT);
767		if (phase < 0)
768		return phase;
769	<	if (p == phase &&
674	<	(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
769	>	if (p == phase) {
770		QNode node = new QNode(this, phase, true, true, nanos);
771	<	p = rt.internalAwaitAdvance(phase, node);
771	>	p = root.internalAwaitAdvance(phase, node);
772		if (node.wasInterrupted)
773		throw new InterruptedException();
774		else if (p == phase)
#	Line 684 | Line 779 | public class Phaser {
779
780		/**
781		* Forces this phaser to enter termination state.  Counts of
782	<	* arrived and registered parties are unaffected.  If this phaser
783	<	* is a member of a tiered set of phasers, then all of the phasers
784	<	* in the set are terminated.  If this phaser is already
785	<	* terminated, this method has no effect.  This method may be
786	<	* useful for coordinating recovery after one or more tasks
787	<	* encounter unexpected exceptions.
782	>	* registered parties are unaffected.  If this phaser is a member
783	>	* of a tiered set of phasers, then all of the phasers in the set
784	>	* are terminated.  If this phaser is already terminated, this
785	>	* method has no effect.  This method may be useful for
786	>	* coordinating recovery after one or more tasks encounter
787	>	* unexpected exceptions.
788		*/
789		public void forceTermination() {
790		// Only need to change root state
#	Line 698 | Line 793 | public class Phaser {
793		while ((s = root.state) >= 0) {
794		if (UNSAFE.compareAndSwapLong(root, stateOffset,
795		s, s | TERMINATION_BIT)) {
796	<	releaseWaiters(0); // signal all threads
797	<	releaseWaiters(1);
796	>	// signal all threads
797	>	releaseWaiters(0); // Waiters on evenQ
798	>	releaseWaiters(1); // Waiters on oddQ
799		return;
800		}
801		}
#	Line 729 | Line 825 | public class Phaser {
825
826		/**
827		* Returns the number of registered parties that have arrived at
828	<	* the current phase of this phaser.
828	>	* the current phase of this phaser. If this phaser has terminated,
829	>	* the returned value is meaningless and arbitrary.
830		*
831		* @return the number of arrived parties
832		*/
833		public int getArrivedParties() {
834	<	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());
834	>	return arrivedOf(reconcileState());
835		}
836
837		/**
838		* Returns the number of registered parties that have not yet
839	<	* arrived at the current phase of this phaser.
839	>	* arrived at the current phase of this phaser. If this phaser has
840	>	* terminated, the returned value is meaningless and arbitrary.
841		*
842		* @return the number of unarrived parties
843		*/
844		public int getUnarrivedParties() {
845	<	int u = unarrivedOf(state);
752	<	return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState());
845	>	return unarrivedOf(reconcileState());
846		}
847
848		/**
#	Line 785 | Line 878 | public class Phaser {
878		* advance, and to control termination. This method is invoked
879		* upon arrival of the party advancing this phaser (when all other
880		* waiting parties are dormant).  If this method returns {@code
881	<	* true}, then, rather than advance the phase number, this phaser
882	<	* will be set to a final termination state, and subsequent calls
883	<	* to {@link #isTerminated} will return true. Any (unchecked)
884	<	* Exception or Error thrown by an invocation of this method is
885	<	* propagated to the party attempting to advance this phaser, in
886	<	* which case no advance occurs.
881	>	* true}, this phaser will be set to a final termination state
882	>	* upon advance, and subsequent calls to {@link #isTerminated}
883	>	* will return true. Any (unchecked) Exception or Error thrown by
884	>	* an invocation of this method is propagated to the party
885	>	* attempting to advance this phaser, in which case no advance
886	>	* occurs.
887		*
888		* <p>The arguments to this method provide the state of the phaser
889		* prevailing for the current transition.  The effects of invoking
#	Line 854 | Line 947 | public class Phaser {
947		*/
948		private void releaseWaiters(int phase) {
949		QNode q;   // first element of queue
857	–	int p;     // its phase
950		Thread t;  // its thread
951		AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
952		while ((q = head.get()) != null &&
953	<	((p = q.phase) == phase ||
862	<	(int)(root.state >>> PHASE_SHIFT) != p)) {
953	>	q.phase != (int)(root.state >>> PHASE_SHIFT)) {
954		if (head.compareAndSet(q, q.next) &&
955		(t = q.thread) != null) {
956		q.thread = null;
#	Line 868 | Line 959 | public class Phaser {
959		}
960		}
961
962	+	/**
963	+	* Variant of releaseWaiters that additionally tries to remove any
964	+	* nodes no longer waiting for advance due to timeout or
965	+	* interrupt. Currently, nodes are removed only if they are at
966	+	* head of queue, which suffices to reduce memory footprint in
967	+	* most usages.
968	+	*
969	+	* @return current phase on exit
970	+	*/
971	+	private int abortWait(int phase) {
972	+	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
973	+	for (;;) {
974	+	Thread t;
975	+	QNode q = head.get();
976	+	int p = (int)(root.state >>> PHASE_SHIFT);
977	+	if (q == null || ((t = q.thread) != null && q.phase == p))
978	+	return p;
979	+	if (head.compareAndSet(q, q.next) && t != null) {
980	+	q.thread = null;
981	+	LockSupport.unpark(t);
982	+	}
983	+	}
984	+	}
985	+
986		/** The number of CPUs, for spin control */
987		private static final int NCPU = Runtime.getRuntime().availableProcessors();
988
#	Line 886 | Line 1001 | public class Phaser {
1001
1002		/**
1003		* Possibly blocks and waits for phase to advance unless aborted.
1004	<	* Call only from root node.
1004	>	* Call only on root phaser.
1005		*
1006		* @param phase current phase
1007		* @param node if non-null, the wait node to track interrupt and timeout;
#	Line 894 | Line 1009 | public class Phaser {
1009		* @return current phase
1010		*/
1011		private int internalAwaitAdvance(int phase, QNode node) {
1012	+	// assert root == this;
1013		releaseWaiters(phase-1);          // ensure old queue clean
1014		boolean queued = false;           // true when node is enqueued
1015		int lastUnarrived = 0;            // to increase spins upon change
#	Line 935 | Line 1051 | public class Phaser {
1051		node.thread = null;       // avoid need for unpark()
1052		if (node.wasInterrupted && !node.interruptible)
1053		Thread.currentThread().interrupt();
1054	<	if ((p = (int)(state >>> PHASE_SHIFT)) == phase)
1055	<	return p;                 // recheck abort
1054	>	if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase)
1055	>	return abortWait(phase); // possibly clean up on abort
1056		}
1057		releaseWaiters(phase);
1058		return p;
#	Line 1007 | Line 1123 | public class Phaser {
1123
1124		// Unsafe mechanics
1125
1126	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1127	<	private static final long stateOffset =
1128	<	objectFieldOffset("state", Phaser.class);
1013	<
1014	<	private static long objectFieldOffset(String field, Class<?> klazz) {
1126	>	private static final sun.misc.Unsafe UNSAFE;
1127	>	private static final long stateOffset;
1128	>	static {
1129		try {
1130	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1131	<	} catch (NoSuchFieldException e) {
1132	<	// Convert Exception to corresponding Error
1133	<	NoSuchFieldError error = new NoSuchFieldError(field);
1134	<	error.initCause(e);
1135	<	throw error;
1130	>	UNSAFE = getUnsafe();
1131	>	Class<?> k = Phaser.class;
1132	>	stateOffset = UNSAFE.objectFieldOffset
1133	>	(k.getDeclaredField("state"));
1134	>	} catch (Exception e) {
1135	>	throw new Error(e);
1136		}
1137		}
1138

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