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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.61 by jsr166, Sun Nov 28 21:21:03 2010 UTC vs.
Revision 1.81 by jsr166, Fri Jul 15 18:49:12 2016 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 17 | Line 17 | import java.util.concurrent.locks.LockSu
17		* {@link java.util.concurrent.CountDownLatch CountDownLatch}
18		* but supporting more flexible usage.
19		*
20	<	* <p> <b>Registration.</b> Unlike the case for other barriers, the
21	<	* number of parties <em>registered</em> to synchronize on a Phaser
20	>	* <p><b>Registration.</b> Unlike the case for other barriers, the
21	>	* number of parties <em>registered</em> to synchronize on a phaser
22		* may vary over time.  Tasks may be registered at any time (using
23		* methods {@link #register}, {@link #bulkRegister}, or forms of
24		* constructors establishing initial numbers of parties), and
#	Line 30 | Line 30 | import java.util.concurrent.locks.LockSu
30		* (However, you can introduce such bookkeeping by subclassing this
31		* class.)
32		*
33	<	* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
33	>	* <p><b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
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}.
47	>	*   <li><b>Arrival.</b> Methods {@link #arrive} and
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
60	>	*   <li><b>Waiting.</b> Method {@link #awaitAdvance} requires an
61		*       argument indicating an arrival phase number, and returns when
62	<	*       the barrier advances to (or is already at) a different phase.
62	>	*       the phaser advances to (or is already at) a different phase.
63		*       Unlike similar constructions using {@code CyclicBarrier},
64		*       method {@code awaitAdvance} continues to wait even if the
65		*       waiting thread is interrupted. Interruptible and timeout
66		*       versions are also available, but exceptions encountered while
67		*       tasks wait interruptibly or with timeout do not change the
68	<	*       state of the barrier. If necessary, you can perform any
68	>	*       state of the phaser. If necessary, you can perform any
69		*       associated recovery within handlers of those exceptions,
70		*       often after invoking {@code forceTermination}.  Phasers may
71		*       also be used by tasks executing in a {@link ForkJoinPool},
#	Line 74 | Line 74 | import java.util.concurrent.locks.LockSu
74		*
75		* </ul>
76		*
77	<	* <p> <b>Termination.</b> A {@code Phaser} may enter a
78	<	* <em>termination</em> state in which all synchronization methods
79	<	* immediately return without updating Phaser state or waiting for
80	<	* advance, and indicating (via a negative phase value) that execution
81	<	* is complete.  Termination is triggered when an invocation of {@code
82	<	* onAdvance} returns {@code true}. The default implementation returns
83	<	* {@code true} if a deregistration has caused the number of
84	<	* registered parties to become zero.  As illustrated below, when
85	<	* Phasers control actions with a fixed number of iterations, it is
86	<	* often convenient to override this method to cause termination when
87	<	* the current phase number reaches a threshold. Method {@link
88	<	* #forceTermination} is also available to abruptly release waiting
89	<	* threads and allow them to terminate.
77	>	* <p><b>Termination.</b> A phaser may enter a <em>termination</em>
78	>	* state, 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
85	>	* parties to become zero.  As illustrated below, when phasers control
86	>	* actions with a fixed number of iterations, it is often convenient
87	>	* to override this method to cause termination when the current phase
88	>	* number reaches a threshold. Method {@link #forceTermination} is
89	>	* also available to abruptly release waiting threads and allow them
90	>	* to terminate.
91		*
92	<	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
92	>	* <p><b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
93		* constructed in tree structures) to reduce contention. Phasers with
94		* large numbers of parties that would otherwise experience heavy
95		* synchronization contention costs may instead be set up so that
#	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
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
113		* #getRegisteredParties} parties in total, of which {@link
114		* #getArrivedParties} have arrived at the current phase ({@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 182 | Line 193 | import java.util.concurrent.locks.LockSu
193		*   phaser.arriveAndDeregister();
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 Phaser that
200	<	* it registers with upon construction:
196	>	* <p>To create a set of {@code n} tasks using a tree of phasers, you
197	>	* could use code of the following form, assuming a Task class with a
198	>	* constructor accepting a {@code Phaser} that it registers with upon
199	>	* construction. After invocation of {@code build(new Task[n], 0, n,
200	>	* new Phaser())}, these tasks could then be started, for example by
201	>	* submitting to a pool:
202		*
203		*  <pre> {@code
204	<	* void build(Task[] actions, int lo, int hi, Phaser ph) {
204	>	* void build(Task[] tasks, int lo, int hi, Phaser ph) {
205		*   if (hi - lo > TASKS_PER_PHASER) {
206		*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
207		*       int j = Math.min(i + TASKS_PER_PHASER, hi);
208	<	*       build(actions, i, j, new Phaser(ph));
208	>	*       build(tasks, i, j, new Phaser(ph));
209		*     }
210		*   } else {
211		*     for (int i = lo; i < hi; ++i)
212	<	*       actions[i] = new Task(ph);
212	>	*       tasks[i] = new Task(ph);
213		*       // assumes new Task(ph) performs ph.register()
214		*   }
215	<	* }
204	<	* // .. initially called, for n tasks via
205	<	* build(new Task[n], 0, n, new Phaser());}</pre>
215	>	* }}</pre>
216		*
217		* The best value of {@code TASKS_PER_PHASER} depends mainly on
218	<	* expected barrier synchronization rates. A value as low as four may
219	<	* be appropriate for extremely small per-barrier task bodies (thus
218	>	* expected synchronization rates. A value as low as four may
219	>	* be appropriate for extremely small per-phase task bodies (thus
220		* high rates), or up to hundreds for extremely large ones.
221		*
222		* <p><b>Implementation notes</b>: This implementation restricts the
223		* maximum number of parties to 65535. Attempts to register additional
224		* parties result in {@code IllegalStateException}. However, you can and
225	<	* should create tiered Phasers to accommodate arbitrarily large sets
225	>	* should create tiered phasers to accommodate arbitrarily large sets
226		* of participants.
227		*
228		* @since 1.7
#	Line 226 | Line 236 | public class Phaser {
236		*/
237
238		/**
239	<	* Barrier state representation. Conceptually, a barrier contains
240	<	* four values:
239	>	* Primary state representation, holding four bit-fields:
240	>	*
241	>	* unarrived  -- the number of parties yet to hit barrier (bits  0-15)
242	>	* parties    -- the number of parties to wait            (bits 16-31)
243	>	* phase      -- the generation of the barrier            (bits 32-62)
244	>	* terminated -- set if barrier is terminated             (bit  63 / sign)
245	>	*
246	>	* Except that a phaser with no registered parties is
247	>	* distinguished by the otherwise illegal state of having zero
248	>	* parties and one unarrived parties (encoded as EMPTY below).
249	>	*
250	>	* To efficiently maintain atomicity, these values are packed into
251	>	* a single (atomic) long. Good performance relies on keeping
252	>	* state decoding and encoding simple, and keeping race windows
253	>	* short.
254	>	*
255	>	* All state updates are performed via CAS except initial
256	>	* registration of a sub-phaser (i.e., one with a non-null
257	>	* parent).  In this (relatively rare) case, we use built-in
258	>	* synchronization to lock while first registering with its
259	>	* parent.
260		*
261	<	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
262	<	* * parties -- the number of parties to wait              (bits 16-31)
263	<	* * phase -- the generation of the barrier                (bits 32-62)
235	<	* * terminated -- set if barrier is terminated            (bit  63 / sign)
236	<	*
237	<	* However, to efficiently maintain atomicity, these values are
238	<	* packed into a single (atomic) long. Termination uses the sign
239	<	* bit of 32 bit representation of phase, so phase is set to -1 on
240	<	* termination. Good performance relies on keeping state decoding
241	<	* and encoding simple, and keeping race windows short.
261	>	* The phase of a subphaser is allowed to lag that of its
262	>	* ancestors until it is actually accessed -- see method
263	>	* reconcileState.
264		*/
265		private volatile long state;
266
267		private static final int  MAX_PARTIES     = 0xffff;
268	<	private static final int  MAX_PHASE       = 0x7fffffff;
268	>	private static final int  MAX_PHASE       = Integer.MAX_VALUE;
269		private static final int  PARTIES_SHIFT   = 16;
270		private static final int  PHASE_SHIFT     = 32;
271		private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
272		private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
273	<	private static final long ONE_ARRIVAL     = 1L;
252	<	private static final long ONE_PARTY       = 1L << PARTIES_SHIFT;
273	>	private static final long COUNTS_MASK     = 0xffffffffL;
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 263 | 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 276 | 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
280	<	* 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 315 | 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;
325	<	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 ||
351	<	((int)(state >>> PHASE_SHIFT) != nextPhase &&
352	<	!UNSAFE.compareAndSwapLong(this, stateOffset,
353	<	s, next)))
354	<	reconcileState();
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 367 | 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;
378	<	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 (parties != 0)               // wait for onAdvance
422	<	root.internalAwaitAdvance(phase, null);
423	<	else {                               // 1st registration of child
424	<	synchronized (this) {            // register parent first
425	<	if (reconcileState() == s) { // recheck under lock
426	<	parent.doRegister(1);    // OK if throws IllegalState
427	<	for (;;) {               // simpler form of outer loop
428	<	s = reconcileState();
429	<	phase = (int)(s >>> PHASE_SHIFT);
430	<	if (phase < 0 ||
431	<	UNSAFE.compareAndSwapLong(this, stateOffset,
432	<	s, s + adj))
433	<	return phase;
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 {
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	>	*
457	>	* @return reconciled state
458		*/
459		private long reconcileState() {
460	<	Phaser par = parent;
460	>	final Phaser root = this.root;
461		long s = state;
462	<	if (par != null) {
463	<	Phaser rt = root;
464	<	int phase, rPhase;
465	<	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
466	<	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
467	<	if ((int)(par.state >>> PHASE_SHIFT) != rPhase)
468	<	par.reconcileState();
469	<	else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
470	<	long u = s & PARTIES_MASK; // reset unarrived to parties
471	<	long next = ((((long) rPhase) << PHASE_SHIFT) | u |
472	<	(u >>> PARTIES_SHIFT));
422	<	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
423	<	}
462	>	if (root != this) {
463	>	int phase, p;
464	>	// CAS to root phase with current parties, tripping unarrived
465	>	while ((phase = (int)(root.state >>> PHASE_SHIFT)) !=
466	>	(int)(s >>> PHASE_SHIFT) &&
467	>	!UNSAFE.compareAndSwapLong
468	>	(this, stateOffset, s,
469	>	s = (((long)phase << PHASE_SHIFT) |
470	>	((phase < 0) ? (s & COUNTS_MASK) :
471	>	(((p = (int)s >>> PARTIES_SHIFT) == 0) ? EMPTY :
472	>	((s & PARTIES_MASK) | p))))))
473		s = state;
425	–	}
474		}
475		return s;
476		}
477
478		/**
479	<	* Creates a new Phaser without any initially registered parties,
480	<	* initial phase number 0, and no parent. Any thread using this
481	<	* Phaser will need to first register for it.
479	>	* Creates a new phaser with no initially registered parties, no
480	>	* parent, and initial phase number 0. Any thread using this
481	>	* phaser will need to first register for it.
482		*/
483		public Phaser() {
484		this(null, 0);
485		}
486
487		/**
488	<	* Creates a new Phaser with the given number of registered
489	<	* unarrived parties, initial phase number 0, and no parent.
488	>	* Creates a new phaser with the given number of registered
489	>	* unarrived parties, no parent, and initial phase number 0.
490		*
491	<	* @param parties the number of parties required to trip barrier
491	>	* @param parties the number of parties required to advance to the
492	>	* next phase
493		* @throws IllegalArgumentException if parties less than zero
494		* or greater than the maximum number of parties supported
495		*/
#	Line 451 | Line 500 | public class Phaser {
500		/**
501		* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
502		*
503	<	* @param parent the parent Phaser
503	>	* @param parent the parent phaser
504		*/
505		public Phaser(Phaser parent) {
506		this(parent, 0);
507		}
508
509		/**
510	<	* Creates a new Phaser with the given parent and number of
511	<	* registered unarrived parties. Registration and deregistration
512	<	* of this child Phaser with its parent are managed automatically.
513	<	* If the given parent is non-null, whenever this child Phaser has
514	<	* any registered parties (as established in this constructor,
515	<	* {@link #register}, or {@link #bulkRegister}), this child Phaser
516	<	* is registered with its parent. Whenever the number of
517	<	* 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
510	>	* Creates a new phaser with the given parent and number of
511	>	* registered unarrived parties.  When the given parent is non-null
512	>	* and the given number of parties is greater than zero, this
513	>	* child phaser is registered with its parent.
514	>	*
515	>	* @param parent the parent phaser
516	>	* @param parties the number of parties required to advance to the
517	>	* next phase
518		* @throws IllegalArgumentException if parties less than zero
519		* or greater than the maximum number of parties supported
520		*/
521		public Phaser(Phaser parent, int parties) {
522		if (parties >>> PARTIES_SHIFT != 0)
523		throw new IllegalArgumentException("Illegal number of parties");
524	<	long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT);
524	>	int phase = 0;
525		this.parent = parent;
526		if (parent != null) {
527	<	Phaser r = parent.root;
528	<	this.root = r;
529	<	this.evenQ = r.evenQ;
530	<	this.oddQ = r.oddQ;
527	>	final Phaser root = parent.root;
528	>	this.root = root;
529	>	this.evenQ = root.evenQ;
530	>	this.oddQ = root.oddQ;
531		if (parties != 0)
532	<	s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT;
532	>	phase = parent.doRegister(1);
533		}
534		else {
535		this.root = this;
536		this.evenQ = new AtomicReference<QNode>();
537		this.oddQ = new AtomicReference<QNode>();
538		}
539	<	this.state = s;
539	>	this.state = (parties == 0) ? (long)EMPTY :
540	>	((long)phase << PHASE_SHIFT) |
541	>	((long)parties << PARTIES_SHIFT) |
542	>	((long)parties);
543		}
544
545		/**
546	<	* Adds a new unarrived party to this Phaser.  If an ongoing
546	>	* Adds a new unarrived party to this phaser.  If an ongoing
547		* invocation of {@link #onAdvance} is in progress, this method
548	<	* may await its completion before returning.  If this Phaser has
549	<	* a parent, and this Phaser previously had no registered parties,
550	<	* this Phaser is also registered with its parent.
551	<	*
552	<	* @return the arrival phase number to which this registration applied
548	>	* may await its completion before returning.  If this phaser has
549	>	* a parent, and this phaser previously had no registered parties,
550	>	* this child phaser is also registered with its parent. If
551	>	* this phaser is terminated, the attempt to register has
552	>	* no effect, and a negative value is returned.
553	>	*
554	>	* @return the arrival phase number to which this registration
555	>	* applied.  If this value is negative, then this phaser has
556	>	* terminated, in which case registration has no effect.
557		* @throws IllegalStateException if attempting to register more
558		* than the maximum supported number of parties
559		*/
#	Line 511 | Line 562 | public class Phaser {
562		}
563
564		/**
565	<	* Adds the given number of new unarrived parties to this Phaser.
565	>	* Adds the given number of new unarrived parties to this phaser.
566		* If an ongoing invocation of {@link #onAdvance} is in progress,
567		* this method may await its completion before returning.  If this
568	<	* Phaser has a parent, and the given number of parities is
569	<	* greater than zero, and this Phaser previously had no registered
570	<	* parties, this Phaser is also registered with its parent.
571	<	*
572	<	* @param parties the number of additional parties required to trip barrier
573	<	* @return the arrival phase number to which this registration applied
568	>	* phaser has a parent, and the given number of parties is greater
569	>	* than zero, and this phaser previously had no registered
570	>	* parties, this child phaser is also registered with its parent.
571	>	* If this phaser is terminated, the attempt to register has no
572	>	* effect, and a negative value is returned.
573	>	*
574	>	* @param parties the number of additional parties required to
575	>	* advance to the next phase
576	>	* @return the arrival phase number to which this registration
577	>	* applied.  If this value is negative, then this phaser has
578	>	* terminated, in which case registration has no effect.
579		* @throws IllegalStateException if attempting to register more
580		* than the maximum supported number of parties
581		* @throws IllegalArgumentException if {@code parties < 0}
#	Line 533 | Line 589 | public class Phaser {
589		}
590
591		/**
592	<	* Arrives at the barrier, without waiting for others to arrive.
592	>	* Arrives at this phaser, without waiting for others to arrive.
593		*
594		* <p>It is a usage error for an unregistered party to invoke this
595		* method.  However, this error may result in an {@code
596		* IllegalStateException} only upon some subsequent operation on
597	<	* this Phaser, if ever.
597	>	* this phaser, if ever.
598		*
599		* @return the arrival phase number, or a negative value if terminated
600		* @throws IllegalStateException if not terminated and the number
#	Line 549 | Line 605 | public class Phaser {
605		}
606
607		/**
608	<	* Arrives at the barrier and deregisters from it without waiting
608	>	* Arrives at this phaser and deregisters from it without waiting
609		* for others to arrive. Deregistration reduces the number of
610	<	* parties required to trip the barrier in future phases.  If this
611	<	* Phaser has a parent, and deregistration causes this Phaser to
612	<	* have zero parties, this Phaser is also deregistered from its
557	<	* parent.
610	>	* parties required to advance in future phases.  If this phaser
611	>	* has a parent, and deregistration causes this phaser to have
612	>	* zero parties, this phaser is also deregistered from its parent.
613		*
614		* <p>It is a usage error for an unregistered party to invoke this
615		* method.  However, this error may result in an {@code
616		* IllegalStateException} only upon some subsequent operation on
617	<	* this Phaser, if ever.
617	>	* this phaser, if ever.
618		*
619		* @return the arrival phase number, or a negative value if terminated
620		* @throws IllegalStateException if not terminated and the number
621		* of registered or unarrived parties would become negative
622		*/
623		public int arriveAndDeregister() {
624	<	return doArrive(ONE_ARRIVAL|ONE_PARTY);
624	>	return doArrive(ONE_DEREGISTER);
625		}
626
627		/**
628	<	* Arrives at the barrier and awaits others. Equivalent in effect
628	>	* Arrives at this phaser and awaits others. Equivalent in effect
629		* to {@code awaitAdvance(arrive())}.  If you need to await with
630		* interruption or timeout, you can arrange this with an analogous
631		* construction using one of the other forms of the {@code
#	Line 580 | Line 635 | public class Phaser {
635		* <p>It is a usage error for an unregistered party to invoke this
636		* method.  However, this error may result in an {@code
637		* IllegalStateException} only upon some subsequent operation on
638	<	* this Phaser, if ever.
638	>	* this phaser, if ever.
639		*
640	<	* @return the arrival phase number, or a negative number if terminated
640	>	* @return the arrival phase number, or the (negative)
641	>	* {@linkplain #getPhase() current phase} if terminated
642		* @throws IllegalStateException if not terminated and the number
643		* of unarrived parties would become negative
644		*/
645		public int arriveAndAwaitAdvance() {
646	<	return awaitAdvance(arrive());
646	>	// Specialization of doArrive+awaitAdvance eliminating some reads/paths
647	>	final Phaser root = this.root;
648	>	for (;;) {
649	>	long s = (root == this) ? state : reconcileState();
650	>	int phase = (int)(s >>> PHASE_SHIFT);
651	>	if (phase < 0)
652	>	return phase;
653	>	int counts = (int)s;
654	>	int unarrived = (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK);
655	>	if (unarrived <= 0)
656	>	throw new IllegalStateException(badArrive(s));
657	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s,
658	>	s -= ONE_ARRIVAL)) {
659	>	if (unarrived > 1)
660	>	return root.internalAwaitAdvance(phase, null);
661	>	if (root != this)
662	>	return parent.arriveAndAwaitAdvance();
663	>	long n = s & PARTIES_MASK;  // base of next state
664	>	int nextUnarrived = (int)n >>> PARTIES_SHIFT;
665	>	if (onAdvance(phase, nextUnarrived))
666	>	n |= TERMINATION_BIT;
667	>	else if (nextUnarrived == 0)
668	>	n |= EMPTY;
669	>	else
670	>	n |= nextUnarrived;
671	>	int nextPhase = (phase + 1) & MAX_PHASE;
672	>	n |= (long)nextPhase << PHASE_SHIFT;
673	>	if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n))
674	>	return (int)(state >>> PHASE_SHIFT); // terminated
675	>	releaseWaiters(phase);
676	>	return nextPhase;
677	>	}
678	>	}
679		}
680
681		/**
682	<	* Awaits the phase of the barrier to advance from the given phase
683	<	* value, returning immediately if the current phase of the
684	<	* barrier is not equal to the given phase value or this barrier
597	<	* is terminated.
682	>	* Awaits the phase of this phaser to advance from the given phase
683	>	* value, returning immediately if the current phase is not equal
684	>	* to the given phase value or this phaser is terminated.
685		*
686		* @param phase an arrival phase number, or negative value if
687		* terminated; this argument is normally the value returned by a
688	<	* previous call to {@code arrive} or its variants
689	<	* @return the next arrival phase number, or a negative value
690	<	* if terminated or argument is negative
688	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
689	>	* @return the next arrival phase number, or the argument if it is
690	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
691	>	* if terminated
692		*/
693		public int awaitAdvance(int phase) {
694	<	Phaser r;
695	<	int p = (int)(state >>> PHASE_SHIFT);
694	>	final Phaser root = this.root;
695	>	long s = (root == this) ? state : reconcileState();
696	>	int p = (int)(s >>> PHASE_SHIFT);
697		if (phase < 0)
698		return phase;
699	<	if (p == phase &&
700	<	(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase)
612	<	return r.internalAwaitAdvance(phase, null);
699	>	if (p == phase)
700	>	return root.internalAwaitAdvance(phase, null);
701		return p;
702		}
703
704		/**
705	<	* Awaits the phase of the barrier to advance from the given phase
705	>	* Awaits the phase of this phaser to advance from the given phase
706		* value, throwing {@code InterruptedException} if interrupted
707	<	* while waiting, or returning immediately if the current phase of
708	<	* the barrier is not equal to the given phase value or this
709	<	* barrier is terminated.
707	>	* while waiting, or returning immediately if the current phase is
708	>	* not equal to the given phase value or this phaser is
709	>	* terminated.
710		*
711		* @param phase an arrival phase number, or negative value if
712		* terminated; this argument is normally the value returned by a
713	<	* previous call to {@code arrive} or its variants
714	<	* @return the next arrival phase number, or a negative value
715	<	* if terminated or argument is negative
713	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
714	>	* @return the next arrival phase number, or the argument if it is
715	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
716	>	* if terminated
717		* @throws InterruptedException if thread interrupted while waiting
718		*/
719		public int awaitAdvanceInterruptibly(int phase)
720		throws InterruptedException {
721	<	Phaser r;
722	<	int p = (int)(state >>> PHASE_SHIFT);
721	>	final Phaser root = this.root;
722	>	long s = (root == this) ? state : reconcileState();
723	>	int p = (int)(s >>> PHASE_SHIFT);
724		if (phase < 0)
725		return phase;
726	<	if (p == phase &&
637	<	(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) {
726	>	if (p == phase) {
727		QNode node = new QNode(this, phase, true, false, 0L);
728	<	p = r.internalAwaitAdvance(phase, node);
728	>	p = root.internalAwaitAdvance(phase, node);
729		if (node.wasInterrupted)
730		throw new InterruptedException();
731		}
#	Line 644 | Line 733 | public class Phaser {
733		}
734
735		/**
736	<	* Awaits the phase of the barrier to advance from the given phase
736	>	* Awaits the phase of this phaser to advance from the given phase
737		* value or the given timeout to elapse, throwing {@code
738		* InterruptedException} if interrupted while waiting, or
739	<	* returning immediately if the current phase of the barrier is
740	<	* not equal to the given phase value or this barrier is
652	<	* terminated.
739	>	* returning immediately if the current phase is not equal to the
740	>	* given phase value or this phaser is terminated.
741		*
742		* @param phase an arrival phase number, or negative value if
743		* terminated; this argument is normally the value returned by a
744	<	* previous call to {@code arrive} or its variants
744	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
745		* @param timeout how long to wait before giving up, in units of
746		*        {@code unit}
747		* @param unit a {@code TimeUnit} determining how to interpret the
748		*        {@code timeout} parameter
749	<	* @return the next arrival phase number, or a negative value
750	<	* if terminated or argument is negative
749	>	* @return the next arrival phase number, or the argument if it is
750	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
751	>	* if terminated
752		* @throws InterruptedException if thread interrupted while waiting
753		* @throws TimeoutException if timed out while waiting
754		*/
#	Line 667 | Line 756 | public class Phaser {
756		long timeout, TimeUnit unit)
757		throws InterruptedException, TimeoutException {
758		long nanos = unit.toNanos(timeout);
759	<	Phaser r;
760	<	int p = (int)(state >>> PHASE_SHIFT);
759	>	final Phaser root = this.root;
760	>	long s = (root == this) ? state : reconcileState();
761	>	int p = (int)(s >>> PHASE_SHIFT);
762		if (phase < 0)
763		return phase;
764	<	if (p == phase &&
675	<	(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) {
764	>	if (p == phase) {
765		QNode node = new QNode(this, phase, true, true, nanos);
766	<	p = r.internalAwaitAdvance(phase, node);
766	>	p = root.internalAwaitAdvance(phase, node);
767		if (node.wasInterrupted)
768		throw new InterruptedException();
769		else if (p == phase)
#	Line 684 | Line 773 | public class Phaser {
773		}
774
775		/**
776	<	* Forces this barrier to enter termination state.  Counts of
777	<	* arrived and registered parties are unaffected.  If this Phaser
778	<	* is a member of a tiered set of Phasers, then all of the Phasers
779	<	* in the set are terminated.  If this Phaser is already
780	<	* terminated, this method has no effect.  This method may be
781	<	* useful for coordinating recovery after one or more tasks
782	<	* encounter unexpected exceptions.
776	>	* Forces this phaser to enter termination state.  Counts of
777	>	* registered parties are unaffected.  If this phaser is a member
778	>	* of a tiered set of phasers, then all of the phasers in the set
779	>	* are terminated.  If this phaser is already terminated, this
780	>	* method has no effect.  This method may be useful for
781	>	* coordinating recovery after one or more tasks encounter
782	>	* unexpected exceptions.
783		*/
784		public void forceTermination() {
785		// Only need to change root state
#	Line 699 | Line 788 | public class Phaser {
788		while ((s = root.state) >= 0) {
789		if (UNSAFE.compareAndSwapLong(root, stateOffset,
790		s, s | TERMINATION_BIT)) {
791	<	releaseWaiters(0); // signal all threads
792	<	releaseWaiters(1);
791	>	// signal all threads
792	>	releaseWaiters(0); // Waiters on evenQ
793	>	releaseWaiters(1); // Waiters on oddQ
794		return;
795		}
796		}
#	Line 709 | Line 799 | public class Phaser {
799		/**
800		* Returns the current phase number. The maximum phase number is
801		* {@code Integer.MAX_VALUE}, after which it restarts at
802	<	* zero. Upon termination, the phase number is negative.
802	>	* zero. Upon termination, the phase number is negative,
803	>	* in which case the prevailing phase prior to termination
804	>	* may be obtained via {@code getPhase() + Integer.MIN_VALUE}.
805		*
806		* @return the phase number, or a negative value if terminated
807		*/
#	Line 718 | Line 810 | public class Phaser {
810		}
811
812		/**
813	<	* Returns the number of parties registered at this barrier.
813	>	* Returns the number of parties registered at this phaser.
814		*
815		* @return the number of parties
816		*/
#	Line 728 | Line 820 | public class Phaser {
820
821		/**
822		* Returns the number of registered parties that have arrived at
823	<	* the current phase of this barrier.
823	>	* the current phase of this phaser. If this phaser has terminated,
824	>	* the returned value is meaningless and arbitrary.
825		*
826		* @return the number of arrived parties
827		*/
828		public int getArrivedParties() {
829	<	long s = state;
737	<	int u = unarrivedOf(s); // only reconcile if possibly needed
738	<	return (u != 0 || parent == null) ?
739	<	partiesOf(s) - u :
740	<	arrivedOf(reconcileState());
829	>	return arrivedOf(reconcileState());
830		}
831
832		/**
833		* Returns the number of registered parties that have not yet
834	<	* arrived at the current phase of this barrier.
834	>	* arrived at the current phase of this phaser. If this phaser has
835	>	* terminated, the returned value is meaningless and arbitrary.
836		*
837		* @return the number of unarrived parties
838		*/
839		public int getUnarrivedParties() {
840	<	int u = unarrivedOf(state);
751	<	return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState());
840	>	return unarrivedOf(reconcileState());
841		}
842
843		/**
844	<	* Returns the parent of this Phaser, or {@code null} if none.
844	>	* Returns the parent of this phaser, or {@code null} if none.
845		*
846	<	* @return the parent of this Phaser, or {@code null} if none
846	>	* @return the parent of this phaser, or {@code null} if none
847		*/
848		public Phaser getParent() {
849		return parent;
850		}
851
852		/**
853	<	* Returns the root ancestor of this Phaser, which is the same as
854	<	* this Phaser if it has no parent.
853	>	* Returns the root ancestor of this phaser, which is the same as
854	>	* this phaser if it has no parent.
855		*
856	<	* @return the root ancestor of this Phaser
856	>	* @return the root ancestor of this phaser
857		*/
858		public Phaser getRoot() {
859		return root;
860		}
861
862		/**
863	<	* Returns {@code true} if this barrier has been terminated.
863	>	* Returns {@code true} if this phaser has been terminated.
864		*
865	<	* @return {@code true} if this barrier has been terminated
865	>	* @return {@code true} if this phaser has been terminated
866		*/
867		public boolean isTerminated() {
868		return root.state < 0L;
#	Line 782 | Line 871 | public class Phaser {
871		/**
872		* Overridable method to perform an action upon impending phase
873		* advance, and to control termination. This method is invoked
874	<	* upon arrival of the party tripping the barrier (when all other
874	>	* upon arrival of the party advancing this phaser (when all other
875		* waiting parties are dormant).  If this method returns {@code
876	<	* true}, then, rather than advance the phase number, this barrier
877	<	* will be set to a final termination state, and subsequent calls
878	<	* to {@link #isTerminated} will return true. Any (unchecked)
879	<	* Exception or Error thrown by an invocation of this method is
880	<	* propagated to the party attempting to trip the barrier, in
881	<	* which case no advance occurs.
876	>	* true}, this phaser will be set to a final termination state
877	>	* upon advance, and subsequent calls to {@link #isTerminated}
878	>	* will return true. Any (unchecked) Exception or Error thrown by
879	>	* an invocation of this method is propagated to the party
880	>	* attempting to advance this phaser, in which case no advance
881	>	* occurs.
882		*
883	<	* <p>The arguments to this method provide the state of the Phaser
883	>	* <p>The arguments to this method provide the state of the phaser
884		* prevailing for the current transition.  The effects of invoking
885	<	* arrival, registration, and waiting methods on this Phaser from
885	>	* arrival, registration, and waiting methods on this phaser from
886		* within {@code onAdvance} are unspecified and should not be
887		* relied on.
888		*
889	<	* <p>If this Phaser is a member of a tiered set of Phasers, then
890	<	* {@code onAdvance} is invoked only for its root Phaser on each
889	>	* <p>If this phaser is a member of a tiered set of phasers, then
890	>	* {@code onAdvance} is invoked only for its root phaser on each
891		* advance.
892		*
893		* <p>To support the most common use cases, the default
#	Line 814 | Line 903 | public class Phaser {
903		*   protected boolean onAdvance(int phase, int parties) { return false; }
904		* }}</pre>
905		*
906	<	* @param phase the phase number on entering the barrier
906	>	* @param phase the current phase number on entry to this method,
907	>	* before this phaser is advanced
908		* @param registeredParties the current number of registered parties
909	<	* @return {@code true} if this barrier should terminate
909	>	* @return {@code true} if this phaser should terminate
910		*/
911		protected boolean onAdvance(int phase, int registeredParties) {
912	<	return registeredParties <= 0;
912	>	return registeredParties == 0;
913		}
914
915		/**
916	<	* Returns a string identifying this Phaser, as well as its
916	>	* Returns a string identifying this phaser, as well as its
917		* state.  The state, in brackets, includes the String {@code
918		* "phase = "} followed by the phase number, {@code "parties = "}
919		* followed by the number of registered parties, and {@code
920		* "arrived = "} followed by the number of arrived parties.
921		*
922	<	* @return a string identifying this barrier, as well as its state
922	>	* @return a string identifying this phaser, as well as its state
923		*/
924		public String toString() {
925		return stateToString(reconcileState());
#	Line 851 | Line 941 | public class Phaser {
941		* Removes and signals threads from queue for phase.
942		*/
943		private void releaseWaiters(int phase) {
944	<	AtomicReference<QNode> head = queueFor(phase);
945	<	QNode q;
946	<	int p;
944	>	QNode q;   // first element of queue
945	>	Thread t;  // its thread
946	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
947		while ((q = head.get()) != null &&
948	<	((p = q.phase) == phase ||
949	<	(int)(root.state >>> PHASE_SHIFT) != p)) {
950	<	if (head.compareAndSet(q, q.next))
951	<	q.signal();
948	>	q.phase != (int)(root.state >>> PHASE_SHIFT)) {
949	>	if (head.compareAndSet(q, q.next) &&
950	>	(t = q.thread) != null) {
951	>	q.thread = null;
952	>	LockSupport.unpark(t);
953	>	}
954	>	}
955	>	}
956	>
957	>	/**
958	>	* Variant of releaseWaiters that additionally tries to remove any
959	>	* nodes no longer waiting for advance due to timeout or
960	>	* interrupt. Currently, nodes are removed only if they are at
961	>	* head of queue, which suffices to reduce memory footprint in
962	>	* most usages.
963	>	*
964	>	* @return current phase on exit
965	>	*/
966	>	private int abortWait(int phase) {
967	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
968	>	for (;;) {
969	>	Thread t;
970	>	QNode q = head.get();
971	>	int p = (int)(root.state >>> PHASE_SHIFT);
972	>	if (q == null || ((t = q.thread) != null && q.phase == p))
973	>	return p;
974	>	if (head.compareAndSet(q, q.next) && t != null) {
975	>	q.thread = null;
976	>	LockSupport.unpark(t);
977	>	}
978		}
979		}
980
#	Line 873 | Line 989 | public class Phaser {
989		* avoid it when threads regularly arrive: When a thread in
990		* internalAwaitAdvance notices another arrival before blocking,
991		* and there appear to be enough CPUs available, it spins
992	<	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
993	<	* uniprocessors, there is at least one intervening Thread.yield
878	<	* before blocking. The value trades off good-citizenship vs big
879	<	* unnecessary slowdowns.
992	>	* SPINS_PER_ARRIVAL more times before blocking. The value trades
993	>	* off good-citizenship vs big unnecessary slowdowns.
994		*/
995		static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
996
997		/**
998		* Possibly blocks and waits for phase to advance unless aborted.
999	<	* Call only from root node.
999	>	* Call only on root phaser.
1000		*
1001		* @param phase current phase
1002		* @param node if non-null, the wait node to track interrupt and timeout;
#	Line 890 | Line 1004 | public class Phaser {
1004		* @return current phase
1005		*/
1006		private int internalAwaitAdvance(int phase, QNode node) {
1007	<	boolean queued = false;      // true when node is enqueued
1008	<	int lastUnarrived = -1;      // to increase spins upon change
1007	>	// assert root == this;
1008	>	releaseWaiters(phase-1);          // ensure old queue clean
1009	>	boolean queued = false;           // true when node is enqueued
1010	>	int lastUnarrived = 0;            // to increase spins upon change
1011		int spins = SPINS_PER_ARRIVAL;
1012		long s;
1013		int p;
1014		while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
1015	<	int unarrived = (int)s & UNARRIVED_MASK;
1016	<	if (unarrived != lastUnarrived) {
1017	<	if (lastUnarrived == -1) // ensure old queue clean
1018	<	releaseWaiters(phase-1);
903	<	if ((lastUnarrived = unarrived) < NCPU)
1015	>	if (node == null) {           // spinning in noninterruptible mode
1016	>	int unarrived = (int)s & UNARRIVED_MASK;
1017	>	if (unarrived != lastUnarrived &&
1018	>	(lastUnarrived = unarrived) < NCPU)
1019		spins += SPINS_PER_ARRIVAL;
1020	<	}
1021	<	else if (spins > 0) {
1022	<	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
1023	<	Thread.yield();  // yield midway through spin
909	<	}
910	<	else if (node == null)   // must be noninterruptible
911	<	node = new QNode(this, phase, false, false, 0L);
912	<	else if (node.isReleasable()) {
913	<	p = (int)(state >>> PHASE_SHIFT);
914	<	break;               // aborted
915	<	}
916	<	else if (!queued) {      // push onto queue
917	<	AtomicReference<QNode> head = queueFor(phase);
918	<	QNode q = head.get();
919	<	if (q == null || q.phase == phase) {
920	<	node.next = q;
921	<	if ((p = (int)(state >>> PHASE_SHIFT)) != phase)
922	<	break;       // recheck to avoid stale enqueue
923	<	else
924	<	queued = head.compareAndSet(q, node);
1020	>	boolean interrupted = Thread.interrupted();
1021	>	if (interrupted || --spins < 0) { // need node to record intr
1022	>	node = new QNode(this, phase, false, false, 0L);
1023	>	node.wasInterrupted = interrupted;
1024		}
1025		}
1026	+	else if (node.isReleasable()) // done or aborted
1027	+	break;
1028	+	else if (!queued) {           // push onto queue
1029	+	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
1030	+	QNode q = node.next = head.get();
1031	+	if ((q == null || q.phase == phase) &&
1032	+	(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq
1033	+	queued = head.compareAndSet(q, node);
1034	+	}
1035		else {
1036		try {
1037		ForkJoinPool.managedBlock(node);
#	Line 935 | Line 1043 | public class Phaser {
1043
1044		if (node != null) {
1045		if (node.thread != null)
1046	<	node.thread = null; // disable unpark() in node.signal
1047	<	if (!node.interruptible && node.wasInterrupted)
1046	>	node.thread = null;       // avoid need for unpark()
1047	>	if (node.wasInterrupted && !node.interruptible)
1048		Thread.currentThread().interrupt();
1049	+	if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase)
1050	+	return abortWait(phase); // possibly clean up on abort
1051		}
1052	<	if (p != phase)
943	<	releaseWaiters(phase);
1052	>	releaseWaiters(phase);
1053		return p;
1054		}
1055
#	Line 965 | Line 1074 | public class Phaser {
1074		this.interruptible = interruptible;
1075		this.nanos = nanos;
1076		this.timed = timed;
1077	<	this.lastTime = timed? System.nanoTime() : 0L;
1077	>	this.lastTime = timed ? System.nanoTime() : 0L;
1078		thread = Thread.currentThread();
1079		}
1080
1081		public boolean isReleasable() {
1082	<	Thread t = thread;
1083	<	if (t != null) {
1084	<	if (phaser.getPhase() != phase)
1085	<	t = null;
1086	<	else {
1087	<	if (Thread.interrupted())
1088	<	wasInterrupted = true;
1089	<	if (interruptible && wasInterrupted)
1090	<	t = null;
982	<	else if (timed) {
983	<	if (nanos > 0) {
984	<	long now = System.nanoTime();
985	<	nanos -= now - lastTime;
986	<	lastTime = now;
987	<	}
988	<	if (nanos <= 0)
989	<	t = null;
990	<	}
991	<	}
992	<	if (t != null)
993	<	return false;
1082	>	if (thread == null)
1083	>	return true;
1084	>	if (phaser.getPhase() != phase) {
1085	>	thread = null;
1086	>	return true;
1087	>	}
1088	>	if (Thread.interrupted())
1089	>	wasInterrupted = true;
1090	>	if (wasInterrupted && interruptible) {
1091		thread = null;
1092	+	return true;
1093	+	}
1094	+	if (timed) {
1095	+	if (nanos > 0L) {
1096	+	long now = System.nanoTime();
1097	+	nanos -= now - lastTime;
1098	+	lastTime = now;
1099	+	}
1100	+	if (nanos <= 0L) {
1101	+	thread = null;
1102	+	return true;
1103	+	}
1104		}
1105	<	return true;
1105	>	return false;
1106		}
1107
1108		public boolean block() {
#	Line 1005 | Line 1114 | public class Phaser {
1114		LockSupport.parkNanos(this, nanos);
1115		return isReleasable();
1116		}
1008	–
1009	–	void signal() {
1010	–	Thread t = thread;
1011	–	if (t != null) {
1012	–	thread = null;
1013	–	LockSupport.unpark(t);
1014	–	}
1015	–	}
1117		}
1118
1119		// Unsafe mechanics
1120
1121	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1122	<	private static final long stateOffset =
1123	<	objectFieldOffset("state", Phaser.class);
1023	<
1024	<	private static long objectFieldOffset(String field, Class<?> klazz) {
1121	>	private static final sun.misc.Unsafe UNSAFE;
1122	>	private static final long stateOffset;
1123	>	static {
1124		try {
1125	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1126	<	} catch (NoSuchFieldException e) {
1127	<	// Convert Exception to corresponding Error
1128	<	NoSuchFieldError error = new NoSuchFieldError(field);
1129	<	error.initCause(e);
1130	<	throw error;
1125	>	UNSAFE = getUnsafe();
1126	>	Class<?> k = Phaser.class;
1127	>	stateOffset = UNSAFE.objectFieldOffset
1128	>	(k.getDeclaredField("state"));
1129	>	} catch (Exception e) {
1130	>	throw new Error(e);
1131		}
1132		}
1133
#	Line 1042 | Line 1141 | public class Phaser {
1141		private static sun.misc.Unsafe getUnsafe() {
1142		try {
1143		return sun.misc.Unsafe.getUnsafe();
1144	<	} catch (SecurityException se) {
1145	<	try {
1146	<	return java.security.AccessController.doPrivileged
1147	<	(new java.security
1148	<	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1149	<	public sun.misc.Unsafe run() throws Exception {
1150	<	java.lang.reflect.Field f = sun.misc
1151	<	.Unsafe.class.getDeclaredField("theUnsafe");
1152	<	f.setAccessible(true);
1153	<	return (sun.misc.Unsafe) f.get(null);
1154	<	}});
1155	<	} catch (java.security.PrivilegedActionException e) {
1156	<	throw new RuntimeException("Could not initialize intrinsics",
1157	<	e.getCause());
1158	<	}
1144	>	} catch (SecurityException tryReflectionInstead) {}
1145	>	try {
1146	>	return java.security.AccessController.doPrivileged
1147	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1148	>	public sun.misc.Unsafe run() throws Exception {
1149	>	Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class;
1150	>	for (java.lang.reflect.Field f : k.getDeclaredFields()) {
1151	>	f.setAccessible(true);
1152	>	Object x = f.get(null);
1153	>	if (k.isInstance(x))
1154	>	return k.cast(x);
1155	>	}
1156	>	throw new NoSuchFieldError("the Unsafe");
1157	>	}});
1158	>	} catch (java.security.PrivilegedActionException e) {
1159	>	throw new RuntimeException("Could not initialize intrinsics",
1160	>	e.getCause());
1161		}
1162		}
1163		}

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