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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.50 by dl, Sat Nov 6 16:12:10 2010 UTC vs.
Revision 1.63 by dl, Mon Nov 29 15:47:19 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	<	import java.util.concurrent.*;
9	>	import java.util.concurrent.TimeUnit;
10	>	import java.util.concurrent.TimeoutException;
11		import java.util.concurrent.atomic.AtomicReference;
12		import java.util.concurrent.locks.LockSupport;
13
#	Line 33 | 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 73 | 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 182 | 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 202 | 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 223 | Line 226 | public class Phaser {
226		*/
227
228		/**
229	<	* Barrier state representation. Conceptually, a barrier contains
227	<	* four values:
229	>	* Primary state representation, holding four fields:
230		*
231	<	* * parties -- the number of parties to wait (16 bits)
232	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
233	<	* * phase -- the generation of the barrier (31 bits)
234	<	* * terminated -- set if barrier is terminated (1 bit)
231	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
232	>	* * parties -- the number of parties to wait              (bits 16-31)
233	>	* * phase -- the generation of the barrier                (bits 32-62)
234	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
235		*
236		* However, to efficiently maintain atomicity, these values are
237		* packed into a single (atomic) long. Termination uses the sign
238		* bit of 32 bit representation of phase, so phase is set to -1 on
239		* termination. Good performance relies on keeping state decoding
240		* and encoding simple, and keeping race windows short.
239	–	*
240	–	* Note: there are some cheats in arrive() that rely on unarrived
241	–	* count being lowest 16 bits.
241		*/
242		private volatile long state;
243
244	<	private static final int ushortMask = 0xffff;
245	<	private static final int phaseMask  = 0x7fffffff;
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
256		private static int unarrivedOf(long s) {
257	<	return (int) (s & ushortMask);
257	>	return (int)s & UNARRIVED_MASK;
258		}
259
260		private static int partiesOf(long s) {
261	<	return ((int) s) >>> 16;
261	>	return (int)s >>> PARTIES_SHIFT;
262		}
263
264		private static int phaseOf(long s) {
265	<	return (int) (s >>> 32);
265	>	return (int) (s >>> PHASE_SHIFT);
266		}
267
268		private static int arrivedOf(long s) {
269		return partiesOf(s) - unarrivedOf(s);
270		}
271
264	–	private static long stateFor(int phase, int parties, int unarrived) {
265	–	return ((((long) phase) << 32) | (((long) parties) << 16) |
266	–	(long) unarrived);
267	–	}
268	–
269	–	private static long trippedStateFor(int phase, int parties) {
270	–	long lp = (long) parties;
271	–	return (((long) phase) << 32) | (lp << 16) | lp;
272	–	}
273	–
274	–	/**
275	–	* Returns message string for bad bounds exceptions.
276	–	*/
277	–	private static String badBounds(int parties, int unarrived) {
278	–	return ("Attempt to set " + unarrived +
279	–	" unarrived of " + parties + " parties");
280	–	}
281	–
272		/**
273		* The parent of this phaser, or null if none
274		*/
#	Line 290 | Line 280 | public class Phaser {
280		*/
281		private final Phaser root;
282
293	–	// Wait queues
294	–
283		/**
284		* Heads of Treiber stacks for waiting threads. To eliminate
285		* contention when releasing some threads while adding others, we
#	Line 306 | Line 294 | public class Phaser {
294		}
295
296		/**
297	<	* Returns current state, first resolving lagged propagation from
298	<	* root if necessary.
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.
316	>	*
317	>	* @param adj - adjustment to apply to state -- either
318	>	* ONE_ARRIVAL (for arrive) or
319	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
320	>	*/
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	>	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
335	>	long lu = p >>> PARTIES_SHIFT;
336	>	int u = (int)lu;
337	>	int nextPhase = (phase + 1) & MAX_PHASE;
338	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
339	>	final Phaser parent = this.parent;
340	>	if (parent == null) {
341	>	if (onAdvance(phase, u))
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)
350	>	reconcileState();
351	>	else if (state == s)
352	>	UNSAFE.compareAndSwapLong(this, stateOffset, s,
353	>	next);
354	>	}
355	>	}
356	>	return phase;
357	>	}
358	>	}
359	>	}
360	>
361	>	/**
362	>	* Implementation of register, bulkRegister
363	>	*
364	>	* @param registrations number to add to both parties and
365	>	* unarrived fields. Must be greater than zero.
366		*/
367	<	private long getReconciledState() {
368	<	return (parent == null) ? state : reconcileState();
367	>	private int doRegister(int registrations) {
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;
377	>	else if (registrations > MAX_PARTIES - parties)
378	>	throw new IllegalStateException(badRegister(s));
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		/**
405	<	* Recursively resolves state.
405	>	* Recursively resolves lagged phase propagation from root if necessary.
406		*/
407		private long reconcileState() {
408		Phaser par = parent;
409		long s = state;
410		if (par != null) {
411	<	int phase, rootPhase;
412	<	while ((phase = phaseOf(s)) >= 0 &&
413	<	(rootPhase = phaseOf(root.state)) != phase &&
414	<	(rootPhase < 0 || unarrivedOf(s) == 0)) {
415	<	int parentPhase = phaseOf(par.getReconciledState());
416	<	if (parentPhase != phase) {
417	<	long next = trippedStateFor(parentPhase, partiesOf(s));
418	<	if (state == s)
419	<	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
411	>	Phaser rt = root;
412	>	int phase, rPhase;
413	>	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
414	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
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	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
422		}
423		s = state;
424		}
#	Line 337 | 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 347 | 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 358 | Line 449 | public class Phaser {
449		}
450
451		/**
452	<	* Creates a new phaser with the given parent, without any
362	<	* initially registered parties. If parent is non-null this phaser
363	<	* is registered with the parent and its initial phase number is
364	<	* 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 371 | 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 < 0 || parties > ushortMask)
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>();
399	–	phase = 0;
495		}
496	<	this.state = trippedStateFor(phase, parties);
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 417 | 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 434 | Line 535 | public class Phaser {
535		}
536
537		/**
538	<	* Shared code for register, bulkRegister
539	<	*/
540	<	private int doRegister(int registrations) {
541	<	Phaser par = parent;
542	<	long s;
543	<	int phase;
443	<	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
444	<	int p = partiesOf(s);
445	<	int u = unarrivedOf(s);
446	<	int unarrived = u + registrations;
447	<	int parties = p + registrations;
448	<	if (u == 0 && p != 0)  // if tripped, wait for advance
449	<	untimedWait(phase);
450	<	else if (parties > ushortMask)
451	<	throw new IllegalStateException(badBounds(parties, unarrived));
452	<	else if (par == null || phaseOf(root.state) == phase) {
453	<	long next = stateFor(phase, parties, unarrived);
454	<	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
455	<	break;
456	<	}
457	<	}
458	<	return phase;
459	<	}
460	<
461	<	/**
462	<	* Arrives at the barrier, but does not wait for others.  (You can
463	<	* in turn wait for others via {@link #awaitAdvance}).  It is an
464	<	* unenforced usage error for an unregistered party to invoke this
465	<	* 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
547		* of unarrived parties would become negative
548		*/
549		public int arrive() {
550	<	Phaser par = parent;
473	<	long s;
474	<	int phase;
475	<	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
476	<	int parties = partiesOf(s);
477	<	int unarrived = unarrivedOf(s) - 1;
478	<	if (unarrived > 0) {                // Not the last arrival
479	<	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s - 1))
480	<	break;                      // s-1 adds one arrival
481	<	}
482	<	else if (unarrived < 0)
483	<	throw new IllegalStateException(badBounds(parties, unarrived));
484	<	else if (par == null) {             // directly trip
485	<	long next = trippedStateFor(onAdvance(phase, parties) ? -1 :
486	<	((phase + 1) & phaseMask),
487	<	parties);
488	<	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) {
489	<	releaseWaiters(phase);
490	<	break;
491	<	}
492	<	}
493	<	else if (phaseOf(root.state) == phase &&
494	<	UNSAFE.compareAndSwapLong(this, stateOffset, s, s - 1)) {
495	<	par.arrive();                   // cascade to parent
496	<	reconcileState();
497	<	break;
498	<	}
499	<	}
500	<	return phase;
550	>	return doArrive(ONE_ARRIVAL);
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
567		* of registered or unarrived parties would become negative
568		*/
569		public int arriveAndDeregister() {
570	<	// similar to arrive, but too different to merge
518	<	Phaser par = parent;
519	<	long s;
520	<	int phase;
521	<	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
522	<	int parties = partiesOf(s) - 1;
523	<	int unarrived = unarrivedOf(s) - 1;
524	<	if (unarrived > 0) {
525	<	long next = stateFor(phase, parties, unarrived);
526	<	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
527	<	break;
528	<	}
529	<	else if (unarrived < 0)
530	<	throw new IllegalStateException(badBounds(parties, unarrived));
531	<	else if (par == null) {
532	<	long next = trippedStateFor(onAdvance(phase, parties)? -1:
533	<	(phase + 1) & phaseMask,
534	<	parties);
535	<	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) {
536	<	releaseWaiters(phase);
537	<	break;
538	<	}
539	<	}
540	<	else if (phaseOf(root.state) == phase) {
541	<	long next = stateFor(phase, parties, 0);
542	<	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) {
543	<	if (parties == 0)
544	<	par.arriveAndDeregister();
545	<	else
546	<	par.arrive();
547	<	reconcileState();
548	<	break;
549	<	}
550	<	}
551	<	}
552	<	return phase;
570	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
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
576	<	* 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	<	int p = getPhase();
611	<	if (p != phase)
612	<	return p;
613	<	return untimedWait(phase);
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	<	int p = getPhase();
637	<	if (p != phase)
638	<	return p;
639	<	return interruptibleWait(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 = rt.internalAwaitAdvance(phase, node);
640	>	if (node.wasInterrupted)
641	>	throw new InterruptedException();
642	>	}
643	>	return p;
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
623	<	* 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 638 | Line 666 | public class Phaser {
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	<	int p = getPhase();
674	<	if (p != phase)
675	<	return p;
676	<	return timedWait(phase, nanos);
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 = rt.internalAwaitAdvance(phase, node);
677	>	if (node.wasInterrupted)
678	>	throw new InterruptedException();
679	>	else if (p == phase)
680	>	throw new TimeoutException();
681	>	}
682	>	return p;
683		}
684
685		/**
686	<	* Forces this barrier to enter termination state. Counts of
687	<	* arrived and registered parties are unaffected. If this phaser
688	<	* has a parent, it too is terminated. This method may be useful
689	<	* for coordinating recovery after one or more tasks encounter
690	<	* unexpected exceptions.
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
690	>	* terminated, this method has no effect.  This method may be
691	>	* useful for coordinating recovery after one or more tasks
692	>	* encounter unexpected exceptions.
693		*/
694		public void forceTermination() {
695	<	Phaser r = root;    // force at root then reconcile
695	>	// Only need to change root state
696	>	final Phaser root = this.root;
697		long s;
698	<	while (phaseOf(s = r.state) >= 0)
699	<	UNSAFE.compareAndSwapLong(r, stateOffset, s,
700	<	stateFor(-1, partiesOf(s),
701	<	unarrivedOf(s)));
702	<	reconcileState();
703	<	releaseWaiters(0);  // ensure wakeups on both queues
704	<	releaseWaiters(1);
698	>	while ((s = root.state) >= 0) {
699	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
700	>	s, s | TERMINATION_BIT)) {
701	>	releaseWaiters(0); // signal all threads
702	>	releaseWaiters(1);
703	>	return;
704	>	}
705	>	}
706		}
707
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		*/
717		public final int getPhase() {
718	<	return phaseOf(getReconciledState());
718	>	return (int)(root.state >>> PHASE_SHIFT);
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		*/
726		public int getRegisteredParties() {
727	<	return partiesOf(getReconciledState());
727	>	return partiesOf(state);
728		}
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(getReconciledState());
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(getReconciledState());
751	>	int u = unarrivedOf(state);
752	>	return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState());
753		}
754
755		/**
#	Line 725 | 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 getPhase() < 0;
780	>	return root.state < 0L;
781		}
782
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 results and effects
797	<	* of invoking phase-related methods (including {@code getPhase}
751	<	* as well as arrival, registration, and waiting methods) from
796	>	* prevailing for the current transition.  The effects of invoking
797	>	* arrival, registration, and waiting methods on this phaser from
798		* within {@code onAdvance} are unspecified and should not be
799	<	* relied on. Similarly, while it is possible to override this
754	<	* method to produce side-effects visible to participating tasks,
755	<	* it is in general safe to do so only in designs in which all
756	<	* parties register before any arrive, and all {@link
757	<	* #awaitAdvance} at each phase.
758	<	*
759	<	* <p>The default version returns {@code true} when the number of
760	<	* registered parties is zero. Normally, overrides that arrange
761	<	* termination for other reasons should also preserve this
762	<	* property.
799	>	* relied on.
800		*
801	<	* @param phase the phase number on entering the barrier
801	>	* <p>If this phaser is a member of a tiered set of phasers, then
802	>	* {@code onAdvance} is invoked only for its root phaser on each
803	>	* advance.
804	>	*
805	>	* <p>To support the most common use cases, the default
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 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 776 | 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	<	long s = getReconciledState();
837	>	return stateToString(reconcileState());
838	>	}
839	>
840	>	/**
841	>	* Implementation of toString and string-based error messages
842	>	*/
843	>	private String stateToString(long s) {
844		return super.toString() +
845		"[phase = " + phaseOf(s) +
846		" parties = " + partiesOf(s) +
847		" arrived = " + arrivedOf(s) + "]";
848		}
849
850	<	// methods for waiting
850	>	// Waiting mechanics
851	>
852	>	/**
853	>	* Removes and signals threads from queue for phase.
854	>	*/
855	>	private void releaseWaiters(int phase) {
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	>	(t = q.thread) != null) {
865	>	q.thread = null;
866	>	LockSupport.unpark(t);
867	>	}
868	>	}
869	>	}
870	>
871	>	/** The number of CPUs, for spin control */
872	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
873	>
874	>	/**
875	>	* The number of times to spin before blocking while waiting for
876	>	* advance, per arrival while waiting. On multiprocessors, fully
877	>	* blocking and waking up a large number of threads all at once is
878	>	* usually a very slow process, so we use rechargeable spins to
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. 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;
893	>	* if null, denotes noninterruptible wait
894	>	* @return current phase
895	>	*/
896	>	private int internalAwaitAdvance(int phase, QNode node) {
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 = 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	>	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);
927	>	} catch (InterruptedException ie) {
928	>	node.wasInterrupted = true;
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);
942	>	return p;
943	>	}
944
945		/**
946		* Wait nodes for Treiber stack representing wait queue
#	Line 794 | Line 948 | public class Phaser {
948		static final class QNode implements ForkJoinPool.ManagedBlocker {
949		final Phaser phaser;
950		final int phase;
797	–	final long startTime;
798	–	final long nanos;
799	–	final boolean timed;
951		final boolean interruptible;
952	<	volatile boolean wasInterrupted = false;
952	>	final boolean timed;
953	>	boolean wasInterrupted;
954	>	long nanos;
955	>	long lastTime;
956		volatile Thread thread; // nulled to cancel wait
957		QNode next;
958
959		QNode(Phaser phaser, int phase, boolean interruptible,
960	<	boolean timed, long startTime, long nanos) {
960	>	boolean timed, long nanos) {
961		this.phaser = phaser;
962		this.phase = phase;
809	–	this.timed = timed;
963		this.interruptible = interruptible;
811	–	this.startTime = startTime;
964		this.nanos = nanos;
965	+	this.timed = timed;
966	+	this.lastTime = timed? System.nanoTime() : 0L;
967		thread = Thread.currentThread();
968		}
969
970		public boolean isReleasable() {
971	<	return (thread == null ||
972	<	phaser.getPhase() != phase ||
973	<	(interruptible && wasInterrupted) ||
974	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
975	<	}
822	<
823	<	public boolean block() {
824	<	if (Thread.interrupted()) {
825	<	wasInterrupted = true;
826	<	if (interruptible)
827	<	return true;
828	<	}
829	<	if (!timed)
830	<	LockSupport.park(this);
831	<	else {
832	<	long waitTime = nanos - (System.nanoTime() - startTime);
833	<	if (waitTime <= 0)
834	<	return true;
835	<	LockSupport.parkNanos(this, waitTime);
971	>	if (thread == null)
972	>	return true;
973	>	if (phaser.getPhase() != phase) {
974	>	thread = null;
975	>	return true;
976		}
977	<	return isReleasable();
978	<	}
979	<
840	<	void signal() {
841	<	Thread t = thread;
842	<	if (t != null) {
977	>	if (Thread.interrupted())
978	>	wasInterrupted = true;
979	>	if (wasInterrupted && interruptible) {
980		thread = null;
981	<	LockSupport.unpark(t);
981	>	return true;
982		}
983	<	}
984	<
985	<	boolean doWait() {
986	<	if (thread != null) {
987	<	try {
988	<	ForkJoinPool.managedBlock(this);
989	<	} catch (InterruptedException ie) {
990	<	wasInterrupted = true; // can't currently happen
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 wasInterrupted;
994	>	return false;
995		}
858	–	}
996
997	<	/**
998	<	* Removes and signals waiting threads from wait queue.
999	<	*/
1000	<	private void releaseWaiters(int phase) {
1001	<	AtomicReference<QNode> head = queueFor(phase);
1002	<	QNode q;
1003	<	while ((q = head.get()) != null) {
1004	<	if (head.compareAndSet(q, q.next))
868	<	q.signal();
869	<	}
870	<	}
871	<
872	<	/**
873	<	* Tries to enqueue given node in the appropriate wait queue.
874	<	*
875	<	* @return true if successful
876	<	*/
877	<	private boolean tryEnqueue(QNode node) {
878	<	AtomicReference<QNode> head = queueFor(node.phase);
879	<	return head.compareAndSet(node.next = head.get(), node);
880	<	}
881	<
882	<	/**
883	<	* The number of times to spin before blocking waiting for advance.
884	<	*/
885	<	static final int MAX_SPINS =
886	<	Runtime.getRuntime().availableProcessors() == 1 ? 0 : 1 << 8;
887	<
888	<	/**
889	<	* Enqueues node and waits unless aborted or signalled.
890	<	*
891	<	* @return current phase
892	<	*/
893	<	private int untimedWait(int phase) {
894	<	QNode node = null;
895	<	boolean queued = false;
896	<	boolean interrupted = false;
897	<	int spins = MAX_SPINS;
898	<	int p;
899	<	while ((p = getPhase()) == phase) {
900	<	if (Thread.interrupted())
901	<	interrupted = true;
902	<	else if (spins > 0) {
903	<	if (--spins == 0)
904	<	Thread.yield();
905	<	}
906	<	else if (node == null)
907	<	node = new QNode(this, phase, false, false, 0, 0);
908	<	else if (!queued)
909	<	queued = tryEnqueue(node);
910	<	else if (node.doWait())
911	<	interrupted = true;
997	>	public boolean block() {
998	>	if (isReleasable())
999	>	return true;
1000	>	else if (!timed)
1001	>	LockSupport.park(this);
1002	>	else if (nanos > 0)
1003	>	LockSupport.parkNanos(this, nanos);
1004	>	return isReleasable();
1005		}
913	–	if (node != null)
914	–	node.thread = null;
915	–	releaseWaiters(phase);
916	–	if (interrupted)
917	–	Thread.currentThread().interrupt();
918	–	return p;
919	–	}
920	–
921	–	/**
922	–	* Interruptible version
923	–	* @return current phase
924	–	*/
925	–	private int interruptibleWait(int phase) throws InterruptedException {
926	–	QNode node = null;
927	–	boolean queued = false;
928	–	boolean interrupted = false;
929	–	int spins = MAX_SPINS;
930	–	int p;
931	–	while ((p = getPhase()) == phase && !interrupted) {
932	–	if (Thread.interrupted())
933	–	interrupted = true;
934	–	else if (spins > 0) {
935	–	if (--spins == 0)
936	–	Thread.yield();
937	–	}
938	–	else if (node == null)
939	–	node = new QNode(this, phase, true, false, 0, 0);
940	–	else if (!queued)
941	–	queued = tryEnqueue(node);
942	–	else if (node.doWait())
943	–	interrupted = true;
944	–	}
945	–	if (node != null)
946	–	node.thread = null;
947	–	if (p != phase || (p = getPhase()) != phase)
948	–	releaseWaiters(phase);
949	–	if (interrupted)
950	–	throw new InterruptedException();
951	–	return p;
952	–	}
953	–
954	–	/**
955	–	* Timeout version.
956	–	* @return current phase
957	–	*/
958	–	private int timedWait(int phase, long nanos)
959	–	throws InterruptedException, TimeoutException {
960	–	long startTime = System.nanoTime();
961	–	QNode node = null;
962	–	boolean queued = false;
963	–	boolean interrupted = false;
964	–	int spins = MAX_SPINS;
965	–	int p;
966	–	while ((p = getPhase()) == phase && !interrupted) {
967	–	if (Thread.interrupted())
968	–	interrupted = true;
969	–	else if (nanos - (System.nanoTime() - startTime) <= 0)
970	–	break;
971	–	else if (spins > 0) {
972	–	if (--spins == 0)
973	–	Thread.yield();
974	–	}
975	–	else if (node == null)
976	–	node = new QNode(this, phase, true, true, startTime, nanos);
977	–	else if (!queued)
978	–	queued = tryEnqueue(node);
979	–	else if (node.doWait())
980	–	interrupted = true;
981	–	}
982	–	if (node != null)
983	–	node.thread = null;
984	–	if (p != phase || (p = getPhase()) != phase)
985	–	releaseWaiters(phase);
986	–	if (interrupted)
987	–	throw new InterruptedException();
988	–	if (p == phase)
989	–	throw new TimeoutException();
990	–	return p;
1006		}
1007
1008		// Unsafe mechanics

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