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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.29 by jsr166, Wed Aug 12 04:02:45 2009 UTC vs.
Revision 1.49 by dl, Fri Nov 5 23:01:47 2010 UTC

#	Line 7 | Line 7
7		package jsr166y;
8
9		import java.util.concurrent.*;
10	–
10		import java.util.concurrent.atomic.AtomicReference;
11		import java.util.concurrent.locks.LockSupport;
12
13		/**
14	<	* A reusable synchronization barrier, similar in functionality to a
14	>	* A reusable synchronization barrier, similar in functionality to
15		* {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and
16		* {@link java.util.concurrent.CountDownLatch CountDownLatch}
17		* but supporting more flexible usage.
18		*
19	<	* <ul>
20	<	*
21	<	* <li> The number of parties synchronizing on a phaser may vary over
22	<	* time.  A task may register to be a party at any time, and may
23	<	* deregister upon arriving at the barrier.  As is the case with most
24	<	* basic synchronization constructs, registration and deregistration
25	<	* affect only internal counts; they do not establish any further
26	<	* internal bookkeeping, so tasks cannot query whether they are
27	<	* registered. (However, you can introduce such bookkeeping by
28	<	* subclassing this class.)
29	<	*
30	<	* <li> Each generation has an associated phase value, starting at
31	<	* zero, and advancing when all parties reach the barrier (wrapping
32	<	* around to zero after reaching {@code Integer.MAX_VALUE}).
33	<	*
34	<	* <li> Like a {@code CyclicBarrier}, a phaser may be repeatedly
35	<	* awaited.  Method {@link #arriveAndAwaitAdvance} has effect
36	<	* analogous to {@link java.util.concurrent.CyclicBarrier#await
37	<	* CyclicBarrier.await}.  However, phasers separate two aspects of
38	<	* coordination, which may also be invoked independently:
19	>	* <p> <b>Registration.</b> Unlike the case for other barriers, the
20	>	* number of parties <em>registered</em> to synchronize on a phaser
21	>	* may vary over time.  Tasks may be registered at any time (using
22	>	* methods {@link #register}, {@link #bulkRegister}, or forms of
23	>	* constructors establishing initial numbers of parties), and
24	>	* optionally deregistered upon any arrival (using {@link
25	>	* #arriveAndDeregister}).  As is the case with most basic
26	>	* synchronization constructs, registration and deregistration affect
27	>	* only internal counts; they do not establish any further internal
28	>	* bookkeeping, so tasks cannot query whether they are registered.
29	>	* (However, you can introduce such bookkeeping by subclassing this
30	>	* class.)
31	>	*
32	>	* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
33	>	* Phaser} may be repeatedly awaited.  Method {@link
34	>	* #arriveAndAwaitAdvance} has effect analogous to {@link
35	>	* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
36	>	* generation of a {@code Phaser} has an associated phase number. The
37	>	* phase number starts at zero, and advances when all parties arrive
38	>	* at the barrier, wrapping around to zero after reaching {@code
39	>	* Integer.MAX_VALUE}. The use of phase numbers enables independent
40	>	* control of actions upon arrival at a barrier and upon awaiting
41	>	* others, via two kinds of methods that may be invoked by any
42	>	* registered party:
43		*
44		* <ul>
45		*
46	<	*   <li> Arriving at a barrier. Methods {@link #arrive} and
47	<	*       {@link #arriveAndDeregister} do not block, but return
48	<	*       the phase value current upon entry to the method.
49	<	*
50	<	*   <li> Awaiting others. Method {@link #awaitAdvance} requires an
51	<	*       argument indicating the entry phase, and returns when the
52	<	*       barrier advances to a new phase.
53	<	* </ul>
46	>	*   <li> <b>Arrival.</b> Methods {@link #arrive} and
47	>	*       {@link #arriveAndDeregister} record arrival at a
48	>	*       barrier. These methods do not block, but return an associated
49	>	*       <em>arrival phase number</em>; that is, the phase number of
50	>	*       the barrier to which the arrival applied. When the final
51	>	*       party for a given phase arrives, an optional barrier action
52	>	*       is performed and the phase advances.  Barrier actions,
53	>	*       performed by the party triggering a phase advance, are
54	>	*       arranged by overriding method {@link #onAdvance(int, int)},
55	>	*       which also controls termination. Overriding this method is
56	>	*       similar to, but more flexible than, providing a barrier
57	>	*       action to a {@code CyclicBarrier}.
58	>	*
59	>	*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
60	>	*       argument indicating an arrival phase number, and returns when
61	>	*       the barrier advances to (or is already at) a different phase.
62	>	*       Unlike similar constructions using {@code CyclicBarrier},
63	>	*       method {@code awaitAdvance} continues to wait even if the
64	>	*       waiting thread is interrupted. Interruptible and timeout
65	>	*       versions are also available, but exceptions encountered while
66	>	*       tasks wait interruptibly or with timeout do not change the
67	>	*       state of the barrier. If necessary, you can perform any
68	>	*       associated recovery within handlers of those exceptions,
69	>	*       often after invoking {@code forceTermination}.  Phasers may
70	>	*       also be used by tasks executing in a {@link ForkJoinPool},
71	>	*       which will ensure sufficient parallelism to execute tasks
72	>	*       when others are blocked waiting for a phase to advance.
73		*
74	+	* </ul>
75		*
76	<	* <li> Barrier actions, performed by the task triggering a phase
77	<	* advance, are arranged by overriding method {@link #onAdvance(int,
78	<	* int)}, which also controls termination. Overriding this method is
79	<	* similar to, but more flexible than, providing a barrier action to a
80	<	* {@code CyclicBarrier}.
81	<	*
82	<	* <li> Phasers may enter a <em>termination</em> state in which all
60	<	* actions immediately return without updating phaser state or waiting
61	<	* for advance, and indicating (via a negative phase value) that
62	<	* execution is complete.  Termination is triggered when an invocation
63	<	* of {@code onAdvance} returns {@code true}.  When a phaser is
64	<	* controlling an action with a fixed number of iterations, it is
76	>	* <p> <b>Termination.</b> A {@code Phaser} may enter a
77	>	* <em>termination</em> state in which all synchronization methods
78	>	* immediately return without updating phaser state or waiting for
79	>	* advance, and indicating (via a negative phase value) that execution
80	>	* is complete.  Termination is triggered when an invocation of {@code
81	>	* onAdvance} returns {@code true}.  As illustrated below, when
82	>	* phasers control actions with a fixed number of iterations, it is
83		* often convenient to override this method to cause termination when
84		* the current phase number reaches a threshold. Method {@link
85		* #forceTermination} is also available to abruptly release waiting
86		* threads and allow them to terminate.
87		*
88	<	* <li> Phasers may be tiered to reduce contention. Phasers with large
88	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
89	>	* in tree structures) to reduce contention. Phasers with large
90		* numbers of parties that would otherwise experience heavy
91	<	* synchronization contention costs may instead be arranged in trees.
92	<	* This will typically greatly increase throughput even though it
93	<	* incurs somewhat greater per-operation overhead.
94	<	*
95	<	* <li> By default, {@code awaitAdvance} continues to wait even if
96	<	* the waiting thread is interrupted. And unlike the case in
97	<	* {@code CyclicBarrier}, exceptions encountered while tasks wait
98	<	* interruptibly or with timeout do not change the state of the
99	<	* barrier. If necessary, you can perform any associated recovery
100	<	* within handlers of those exceptions, often after invoking
101	<	* {@code forceTermination}.
102	<	*
103	<	* <li>Phasers may be used to coordinate tasks executing in a {@link
104	<	* ForkJoinPool}, which will ensure sufficient parallelism to execute
105	<	* tasks when others are blocked waiting for a phase to advance.
106	<	*
88	<	* </ul>
91	>	* synchronization contention costs may instead be set up so that
92	>	* groups of sub-phasers share a common parent.  This may greatly
93	>	* increase throughput even though it incurs greater per-operation
94	>	* overhead.
95	>	*
96	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
97	>	* only by registered parties, the current state of a phaser may be
98	>	* monitored by any caller.  At any given moment there are {@link
99	>	* #getRegisteredParties} parties in total, of which {@link
100	>	* #getArrivedParties} have arrived at the current phase ({@link
101	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
102	>	* parties arrive, the phase advances.  The values returned by these
103	>	* methods may reflect transient states and so are not in general
104	>	* useful for synchronization control.  Method {@link #toString}
105	>	* returns snapshots of these state queries in a form convenient for
106	>	* informal monitoring.
107		*
108		* <p><b>Sample usages:</b>
109		*
110		* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
111	<	* to control a one-shot action serving a variable number of
112	<	* parties. The typical idiom is for the method setting this up to
113	<	* first register, then start the actions, then deregister, as in:
111	>	* to control a one-shot action serving a variable number of parties.
112	>	* The typical idiom is for the method setting this up to first
113	>	* register, then start the actions, then deregister, as in:
114		*
115		*  <pre> {@code
116	<	* void runTasks(List<Runnable> list) {
116	>	* void runTasks(List<Runnable> tasks) {
117		*   final Phaser phaser = new Phaser(1); // "1" to register self
118		*   // create and start threads
119	<	*   for (Runnable r : list) {
119	>	*   for (Runnable task : tasks) {
120		*     phaser.register();
121		*     new Thread() {
122		*       public void run() {
123		*         phaser.arriveAndAwaitAdvance(); // await all creation
124	<	*         r.run();
124	>	*         task.run();
125		*       }
126		*     }.start();
127		*   }
#	Line 116 | Line 134 | import java.util.concurrent.locks.LockSu
134		* for a given number of iterations is to override {@code onAdvance}:
135		*
136		*  <pre> {@code
137	<	* void startTasks(List<Runnable> list, final int iterations) {
137	>	* void startTasks(List<Runnable> tasks, final int iterations) {
138		*   final Phaser phaser = new Phaser() {
139	<	*     public boolean onAdvance(int phase, int registeredParties) {
139	>	*     protected boolean onAdvance(int phase, int registeredParties) {
140		*       return phase >= iterations || registeredParties == 0;
141		*     }
142		*   };
143		*   phaser.register();
144	<	*   for (Runnable r : list) {
144	>	*   for (final Runnable task : tasks) {
145		*     phaser.register();
146		*     new Thread() {
147		*       public void run() {
148		*         do {
149	<	*           r.run();
149	>	*           task.run();
150		*           phaser.arriveAndAwaitAdvance();
151	<	*         } while(!phaser.isTerminated();
151	>	*         } while (!phaser.isTerminated());
152		*       }
153		*     }.start();
154		*   }
155		*   phaser.arriveAndDeregister(); // deregister self, don't wait
156		* }}</pre>
157		*
158	+	* If the main task must later await termination, it
159	+	* may re-register and then execute a similar loop:
160	+	*  <pre> {@code
161	+	*   // ...
162	+	*   phaser.register();
163	+	*   while (!phaser.isTerminated())
164	+	*     phaser.arriveAndAwaitAdvance();}</pre>
165	+	*
166	+	* <p>Related constructions may be used to await particular phase numbers
167	+	* in contexts where you are sure that the phase will never wrap around
168	+	* {@code Integer.MAX_VALUE}. For example:
169	+	*
170	+	*  <pre> {@code
171	+	* void awaitPhase(Phaser phaser, int phase) {
172	+	*   int p = phaser.register(); // assumes caller not already registered
173	+	*   while (p < phase) {
174	+	*     if (phaser.isTerminated())
175	+	*       // ... deal with unexpected termination
176	+	*     else
177	+	*       p = phaser.arriveAndAwaitAdvance();
178	+	*   }
179	+	*   phaser.arriveAndDeregister();
180	+	* }}</pre>
181	+	*
182	+	*
183		* <p>To create a set of tasks using a tree of phasers,
184		* you could use code of the following form, assuming a
185		* Task class with a constructor accepting a phaser that
186	<	* it registers for upon construction:
186	>	* it registers with upon construction:
187	>	*
188		*  <pre> {@code
189	<	* void build(Task[] actions, int lo, int hi, Phaser b) {
190	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
191	<	*   if (step > 1) {
192	<	*     int i = lo;
193	<	*     while (i < hi) {
150	<	*       int r = Math.min(i + step, hi);
151	<	*       build(actions, i, r, new Phaser(b));
152	<	*       i = r;
189	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
190	>	*   if (hi - lo > TASKS_PER_PHASER) {
191	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
192	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
193	>	*       build(actions, i, j, new Phaser(ph));
194		*     }
195		*   } else {
196		*     for (int i = lo; i < hi; ++i)
197	<	*       actions[i] = new Task(b);
198	<	*       // assumes new Task(b) performs b.register()
197	>	*       actions[i] = new Task(ph);
198	>	*       // assumes new Task(ph) performs ph.register()
199		*   }
200		* }
201		* // .. initially called, for n tasks via
#	Line 165 | Line 206 | import java.util.concurrent.locks.LockSu
206		* be appropriate for extremely small per-barrier task bodies (thus
207		* high rates), or up to hundreds for extremely large ones.
208		*
168	–	* </pre>
169	–	*
209		* <p><b>Implementation notes</b>: This implementation restricts the
210		* maximum number of parties to 65535. Attempts to register additional
211	<	* parties result in IllegalStateExceptions. However, you can and
211	>	* parties result in {@code IllegalStateException}. However, you can and
212		* should create tiered phasers to accommodate arbitrarily large sets
213		* of participants.
214		*
#	Line 203 | Line 242 | public class Phaser {
242		*/
243		private volatile long state;
244
206	–	private static final int ushortBits = 16;
245		private static final int ushortMask = 0xffff;
246		private static final int phaseMask  = 0x7fffffff;
247
#	Line 256 | Line 294 | public class Phaser {
294
295		/**
296		* Heads of Treiber stacks for waiting threads. To eliminate
297	<	* contention while releasing some threads while adding others, we
297	>	* contention when releasing some threads while adding others, we
298		* use two of them, alternating across even and odd phases.
299	+	* Subphasers share queues with root to speed up releases.
300		*/
301		private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
302		private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
303
304		private AtomicReference<QNode> queueFor(int phase) {
305	<	return ((phase & 1) == 0) ? evenQ : oddQ;
305	>	Phaser r = root;
306	>	return ((phase & 1) == 0) ? r.evenQ : r.oddQ;
307		}
308
309		/**
#	Line 278 | Line 318 | public class Phaser {
318		* Recursively resolves state.
319		*/
320		private long reconcileState() {
321	<	Phaser p = parent;
321	>	Phaser par = parent;
322		long s = state;
323	<	if (p != null) {
324	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
325	<	long parentState = p.getReconciledState();
323	>	if (par != null) {
324	>	int phase, rootPhase;
325	>	while ((phase = phaseOf(s)) >= 0 &&
326	>	(rootPhase = phaseOf(root.state)) != phase &&
327	>	(rootPhase < 0 || unarrivedOf(s) == 0)) {
328	>	long parentState = par.getReconciledState();
329		int parentPhase = phaseOf(parentState);
330	<	int phase = phaseOf(s = state);
331	<	if (phase != parentPhase) {
332	<	long next = trippedStateFor(parentPhase, partiesOf(s));
333	<	if (casState(s, next)) {
334	<	releaseWaiters(phase);
335	<	s = next;
336	<	}
330	>	int parties = partiesOf(s);
331	>	long next = trippedStateFor(parentPhase, parties);
332	>	if (phaseOf(root.state) == rootPhase &&
333	>	parentPhase != phase &&
334	>	state == s && casState(s, next)) {
335	>	releaseWaiters(phase);
336	>	if (parties == 0) // exit if the final deregistration
337	>	break;
338		}
339	+	s = state;
340		}
341		}
342		return s;
#	Line 307 | Line 352 | public class Phaser {
352		}
353
354		/**
355	<	* Creates a new phaser with the given numbers of registered
355	>	* Creates a new phaser with the given number of registered
356		* unarrived parties, initial phase number 0, and no parent.
357		*
358		* @param parties the number of parties required to trip barrier
#	Line 339 | Line 384 | public class Phaser {
384		}
385
386		/**
387	<	* Creates a new phaser with the given parent and numbers of
387	>	* Creates a new phaser with the given parent and number of
388		* registered unarrived parties. If parent is non-null, this phaser
389		* is registered with the parent and its initial phase number is
390		* the same as that of parent phaser.
#	Line 365 | Line 410 | public class Phaser {
410
411		/**
412		* Adds a new unarrived party to this phaser.
413	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
414	+	* this method waits until its completion before registering.
415		*
416	<	* @return the current barrier phase number upon registration
416	>	* @return the arrival phase number to which this registration applied
417		* @throws IllegalStateException if attempting to register more
418		* than the maximum supported number of parties
419		*/
#	Line 376 | Line 423 | public class Phaser {
423
424		/**
425		* Adds the given number of new unarrived parties to this phaser.
426	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
427	+	* this method waits until its completion before registering.
428		*
429	<	* @param parties the number of parties required to trip barrier
430	<	* @return the current barrier phase number upon registration
429	>	* @param parties the number of additional parties required to trip barrier
430	>	* @return the arrival phase number to which this registration applied
431		* @throws IllegalStateException if attempting to register more
432		* than the maximum supported number of parties
433	+	* @throws IllegalArgumentException if {@code parties < 0}
434		*/
435		public int bulkRegister(int parties) {
436		if (parties < 0)
#	Line 394 | Line 444 | public class Phaser {
444		* Shared code for register, bulkRegister
445		*/
446		private int doRegister(int registrations) {
447	+	Phaser par = parent;
448	+	long s;
449		int phase;
450	<	for (;;) {
451	<	long s = getReconciledState();
452	<	phase = phaseOf(s);
453	<	int unarrived = unarrivedOf(s) + registrations;
454	<	int parties = partiesOf(s) + registrations;
455	<	if (phase < 0)
456	<	break;
457	<	if (parties > ushortMask || unarrived > ushortMask)
458	<	throw new IllegalStateException(badBounds(parties, unarrived));
459	<	if (phase == phaseOf(root.state) &&
460	<	casState(s, stateFor(phase, parties, unarrived)))
461	<	break;
450	>	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
451	>	int p = partiesOf(s);
452	>	int u = unarrivedOf(s);
453	>	int unarrived = u + registrations;
454	>	int parties = p + registrations;
455	>	if (par == null || phase == phaseOf(root.state)) {
456	>	if (parties > ushortMask || unarrived > ushortMask)
457	>	throw new IllegalStateException(badBounds(parties,
458	>	unarrived));
459	>	else if (p != 0 && u == 0)       // back off if advancing
460	>	Thread.yield();              // not worth actually blocking
461	>	else if (casState(s, stateFor(phase, parties, unarrived)))
462	>	break;
463	>	}
464		}
465		return phase;
466		}
467
468		/**
469		* Arrives at the barrier, but does not wait for others.  (You can
470	<	* in turn wait for others via {@link #awaitAdvance}).
470	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
471	>	* unenforced usage error for an unregistered party to invoke this
472	>	* method.
473		*
474	<	* @return the barrier phase number upon entry to this method, or a
419	<	* negative value if terminated
474	>	* @return the arrival phase number, or a negative value if terminated
475		* @throws IllegalStateException if not terminated and the number
476		* of unarrived parties would become negative
477		*/
478		public int arrive() {
479	+	Phaser par = parent;
480	+	long s;
481		int phase;
482	<	for (;;) {
426	<	long s = state;
427	<	phase = phaseOf(s);
428	<	if (phase < 0)
429	<	break;
482	>	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
483		int parties = partiesOf(s);
484		int unarrived = unarrivedOf(s) - 1;
485	<	if (unarrived > 0) {        // Not the last arrival
486	<	if (casState(s, s - 1)) // s-1 adds one arrival
485	>	if (parties == 0 || unarrived < 0)
486	>	throw new IllegalStateException(badBounds(parties,
487	>	unarrived));
488	>	else if (unarrived > 0) {           // Not the last arrival
489	>	if (casState(s, s - 1))         // s-1 adds one arrival
490		break;
491		}
492	<	else if (unarrived == 0) {  // the last arrival
493	<	Phaser par = parent;
494	<	if (par == null) {      // directly trip
495	<	if (casState
496	<	(s,
497	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
442	<	((phase + 1) & phaseMask), parties))) {
443	<	releaseWaiters(phase);
444	<	break;
445	<	}
446	<	}
447	<	else {                  // cascade to parent
448	<	if (casState(s, s - 1)) { // zeroes unarrived
449	<	par.arrive();
450	<	reconcileState();
451	<	break;
452	<	}
492	>	else if (par == null) {             // directly trip
493	>	if (casState(s, trippedStateFor(onAdvance(phase, parties) ? -1 :
494	>	((phase + 1) & phaseMask),
495	>	parties))) {
496	>	releaseWaiters(phase);
497	>	break;
498		}
499		}
500	<	else if (phase != phaseOf(root.state)) // or if unreconciled
500	>	else if (phaseOf(root.state) == phase && casState(s, s - 1)) {
501	>	par.arrive();                   // cascade to parent
502		reconcileState();
503	<	else
504	<	throw new IllegalStateException(badBounds(parties, unarrived));
503	>	break;
504	>	}
505		}
506		return phase;
507		}
#	Line 466 | Line 512 | public class Phaser {
512		* required to trip the barrier in future phases.  If this phaser
513		* has a parent, and deregistration causes this phaser to have
514		* zero parties, this phaser also arrives at and is deregistered
515	<	* from its parent.
515	>	* from its parent.  It is an unenforced usage error for an
516	>	* unregistered party to invoke this method.
517		*
518	<	* @return the current barrier phase number upon entry to
472	<	* this method, or a negative value if terminated
518	>	* @return the arrival phase number, or a negative value if terminated
519		* @throws IllegalStateException if not terminated and the number
520		* of registered or unarrived parties would become negative
521		*/
522		public int arriveAndDeregister() {
523	<	// similar code to arrive, but too different to merge
523	>	// similar to arrive, but too different to merge
524		Phaser par = parent;
525	+	long s;
526		int phase;
527	<	for (;;) {
481	<	long s = state;
482	<	phase = phaseOf(s);
483	<	if (phase < 0)
484	<	break;
527	>	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
528		int parties = partiesOf(s) - 1;
529		int unarrived = unarrivedOf(s) - 1;
530	<	if (parties >= 0) {
531	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
532	<	if (casState
533	<	(s,
534	<	stateFor(phase, parties, unarrived))) {
535	<	if (unarrived == 0) {
536	<	par.arriveAndDeregister();
537	<	reconcileState();
538	<	}
539	<	break;
540	<	}
541	<	continue;
542	<	}
500	<	if (unarrived == 0) {
501	<	if (casState
502	<	(s,
503	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
504	<	((phase + 1) & phaseMask), parties))) {
505	<	releaseWaiters(phase);
506	<	break;
507	<	}
508	<	continue;
509	<	}
510	<	if (par != null && phase != phaseOf(root.state)) {
511	<	reconcileState();
512	<	continue;
530	>	if (parties < 0 || unarrived < 0)
531	>	throw new IllegalStateException(badBounds(parties,
532	>	unarrived));
533	>	else if (unarrived > 0) {
534	>	if (casState(s, stateFor(phase, parties, unarrived)))
535	>	break;
536	>	}
537	>	else if (par == null) {
538	>	if (casState(s, trippedStateFor(onAdvance(phase, parties)? -1:
539	>	(phase + 1) & phaseMask,
540	>	parties))) {
541	>	releaseWaiters(phase);
542	>	break;
543		}
544		}
545	<	throw new IllegalStateException(badBounds(parties, unarrived));
545	>	else if (phaseOf(root.state) == phase &&
546	>	casState(s, stateFor(phase, parties, 0))) {
547	>	if (parties == 0)
548	>	par.arriveAndDeregister();
549	>	else
550	>	par.arrive();
551	>	reconcileState();
552	>	break;
553	>	}
554		}
555		return phase;
556		}
#	Line 521 | Line 559 | public class Phaser {
559		* Arrives at the barrier and awaits others. Equivalent in effect
560		* to {@code awaitAdvance(arrive())}.  If you need to await with
561		* interruption or timeout, you can arrange this with an analogous
562	<	* construction using one of the other forms of the awaitAdvance
563	<	* method.  If instead you need to deregister upon arrival use
564	<	* {@code arriveAndDeregister}.
562	>	* construction using one of the other forms of the {@code
563	>	* awaitAdvance} method.  If instead you need to deregister upon
564	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
565	>	* usage error for an unregistered party to invoke this method.
566		*
567	<	* @return the phase on entry to this method
567	>	* @return the arrival phase number, or a negative number if terminated
568		* @throws IllegalStateException if not terminated and the number
569		* of unarrived parties would become negative
570		*/
#	Line 535 | Line 574 | public class Phaser {
574
575		/**
576		* Awaits the phase of the barrier to advance from the given phase
577	<	* value, or returns immediately if the current phase of the barrier
578	<	* is not equal to the given phase value or this barrier is
579	<	* terminated.
580	<	*
581	<	* @param phase the phase on entry to this method
582	<	* @return the phase on exit from this method
577	>	* value, returning immediately if the current phase of the
578	>	* barrier is not equal to the given phase value or this barrier
579	>	* is terminated.  It is an unenforced usage error for an
580	>	* unregistered party to invoke this method.
581	>	*
582	>	* @param phase an arrival phase number, or negative value if
583	>	* terminated; this argument is normally the value returned by a
584	>	* previous call to {@code arrive} or its variants
585	>	* @return the next arrival phase number, or a negative value
586	>	* if terminated or argument is negative
587		*/
588		public int awaitAdvance(int phase) {
589		if (phase < 0)
590		return phase;
591	<	long s = getReconciledState();
549	<	int p = phaseOf(s);
591	>	int p = getPhase();
592		if (p != phase)
593		return p;
552	–	if (unarrivedOf(s) == 0 && parent != null)
553	–	parent.awaitAdvance(phase);
554	–	// Fall here even if parent waited, to reconcile and help release
594		return untimedWait(phase);
595		}
596
597		/**
598	<	* Awaits the phase of the barrier to advance from the given
599	<	* value, or returns immediately if argument is negative or this
600	<	* barrier is terminated, or throws InterruptedException if
601	<	* interrupted while waiting.
602	<	*
603	<	* @param phase the phase on entry to this method
604	<	* @return the phase on exit from this method
598	>	* Awaits the phase of the barrier to advance from the given phase
599	>	* value, throwing {@code InterruptedException} if interrupted
600	>	* while waiting, or returning immediately if the current phase of
601	>	* the barrier is not equal to the given phase value or this
602	>	* barrier is terminated. It is an unenforced usage error for an
603	>	* unregistered party to invoke this method.
604	>	*
605	>	* @param phase an arrival phase number, or negative value if
606	>	* terminated; this argument is normally the value returned by a
607	>	* previous call to {@code arrive} or its variants
608	>	* @return the next arrival phase number, or a negative value
609	>	* if terminated or argument is negative
610		* @throws InterruptedException if thread interrupted while waiting
611		*/
612		public int awaitAdvanceInterruptibly(int phase)
613		throws InterruptedException {
614		if (phase < 0)
615		return phase;
616	<	long s = getReconciledState();
573	<	int p = phaseOf(s);
616	>	int p = getPhase();
617		if (p != phase)
618		return p;
576	–	if (unarrivedOf(s) == 0 && parent != null)
577	–	parent.awaitAdvanceInterruptibly(phase);
619		return interruptibleWait(phase);
620		}
621
622		/**
623	<	* Awaits the phase of the barrier to advance from the given value
624	<	* or the given timeout elapses, or returns immediately if
625	<	* argument is negative or this barrier is terminated.
626	<	*
627	<	* @param phase the phase on entry to this method
628	<	* @return the phase on exit from this method
623	>	* Awaits the phase of the barrier to advance from the given phase
624	>	* value or the given timeout to elapse, throwing {@code
625	>	* InterruptedException} if interrupted while waiting, or
626	>	* returning immediately if the current phase of the barrier is
627	>	* not equal to the given phase value or this barrier is
628	>	* terminated.  It is an unenforced usage error for an
629	>	* unregistered party to invoke this method.
630	>	*
631	>	* @param phase an arrival phase number, or negative value if
632	>	* terminated; this argument is normally the value returned by a
633	>	* previous call to {@code arrive} or its variants
634	>	* @param timeout how long to wait before giving up, in units of
635	>	*        {@code unit}
636	>	* @param unit a {@code TimeUnit} determining how to interpret the
637	>	*        {@code timeout} parameter
638	>	* @return the next arrival phase number, or a negative value
639	>	* if terminated or argument is negative
640		* @throws InterruptedException if thread interrupted while waiting
641		* @throws TimeoutException if timed out while waiting
642		*/
643		public int awaitAdvanceInterruptibly(int phase,
644		long timeout, TimeUnit unit)
645		throws InterruptedException, TimeoutException {
646	+	long nanos = unit.toNanos(timeout);
647		if (phase < 0)
648		return phase;
649	<	long s = getReconciledState();
597	<	int p = phaseOf(s);
649	>	int p = getPhase();
650		if (p != phase)
651		return p;
652	<	if (unarrivedOf(s) == 0 && parent != null)
601	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
602	<	return timedWait(phase, unit.toNanos(timeout));
652	>	return timedWait(phase, nanos);
653		}
654
655		/**
#	Line 610 | Line 660 | public class Phaser {
660		* unexpected exceptions.
661		*/
662		public void forceTermination() {
663	<	for (;;) {
664	<	long s = getReconciledState();
665	<	int phase = phaseOf(s);
666	<	int parties = partiesOf(s);
667	<	int unarrived = unarrivedOf(s);
668	<	if (phase < 0 ||
669	<	casState(s, stateFor(-1, parties, unarrived))) {
620	<	releaseWaiters(0);
621	<	releaseWaiters(1);
622	<	if (parent != null)
623	<	parent.forceTermination();
624	<	return;
625	<	}
626	<	}
663	>	Phaser r = root;    // force at root then reconcile
664	>	long s;
665	>	while (phaseOf(s = r.state) >= 0)
666	>	r.casState(s, stateFor(-1, partiesOf(s), unarrivedOf(s)));
667	>	reconcileState();
668	>	releaseWaiters(0);  // ensure wakeups on both queues
669	>	releaseWaiters(1);
670		}
671
672		/**
#	Line 643 | Line 686 | public class Phaser {
686		* @return the number of parties
687		*/
688		public int getRegisteredParties() {
689	<	return partiesOf(state);
689	>	return partiesOf(getReconciledState());
690		}
691
692		/**
693	<	* Returns the number of parties that have arrived at the current
694	<	* phase of this barrier.
693	>	* Returns the number of registered parties that have arrived at
694	>	* the current phase of this barrier.
695		*
696		* @return the number of arrived parties
697		*/
698		public int getArrivedParties() {
699	<	return arrivedOf(state);
699	>	return arrivedOf(getReconciledState());
700		}
701
702		/**
#	Line 663 | Line 706 | public class Phaser {
706		* @return the number of unarrived parties
707		*/
708		public int getUnarrivedParties() {
709	<	return unarrivedOf(state);
709	>	return unarrivedOf(getReconciledState());
710		}
711
712		/**
#	Line 695 | Line 738 | public class Phaser {
738		}
739
740		/**
741	<	* Overridable method to perform an action upon phase advance, and
742	<	* to control termination. This method is invoked whenever the
743	<	* barrier is tripped (and thus all other waiting parties are
744	<	* dormant). If it returns {@code true}, then, rather than advance
745	<	* the phase number, this barrier will be set to a final
746	<	* termination state, and subsequent calls to {@link #isTerminated}
747	<	* will return true.
741	>	* Overridable method to perform an action upon impending phase
742	>	* advance, and to control termination. This method is invoked
743	>	* upon arrival of the party tripping the barrier (when all other
744	>	* waiting parties are dormant).  If this method returns {@code
745	>	* true}, then, rather than advance the phase number, this barrier
746	>	* will be set to a final termination state, and subsequent calls
747	>	* to {@link #isTerminated} will return true. Any (unchecked)
748	>	* Exception or Error thrown by an invocation of this method is
749	>	* propagated to the party attempting to trip the barrier, in
750	>	* which case no advance occurs.
751	>	*
752	>	* <p>The arguments to this method provide the state of the phaser
753	>	* prevailing for the current transition. (When called from within
754	>	* an implementation of {@code onAdvance} the values returned by
755	>	* methods such as {@code getPhase} may or may not reliably
756	>	* indicate the state to which this transition applies.)
757		*
758		* <p>The default version returns {@code true} when the number of
759		* registered parties is zero. Normally, overrides that arrange
760		* termination for other reasons should also preserve this
761		* property.
762		*
711	–	* <p>You may override this method to perform an action with side
712	–	* effects visible to participating tasks, but it is in general
713	–	* only sensible to do so in designs where all parties register
714	–	* before any arrive, and all {@link #awaitAdvance} at each phase.
715	–	* Otherwise, you cannot ensure lack of interference from other
716	–	* parties during the invocation of this method.
717	–	*
763		* @param phase the phase number on entering the barrier
764		* @param registeredParties the current number of registered parties
765		* @return {@code true} if this barrier should terminate
#	Line 755 | Line 800 | public class Phaser {
800		volatile boolean wasInterrupted = false;
801		volatile Thread thread; // nulled to cancel wait
802		QNode next;
803	+
804		QNode(Phaser phaser, int phase, boolean interruptible,
805		boolean timed, long startTime, long nanos) {
806		this.phaser = phaser;
#	Line 765 | Line 811 | public class Phaser {
811		this.nanos = nanos;
812		thread = Thread.currentThread();
813		}
814	+
815		public boolean isReleasable() {
816		return (thread == null ||
817		phaser.getPhase() != phase ||
818		(interruptible && wasInterrupted) ||
819		(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
820		}
821	+
822		public boolean block() {
823		if (Thread.interrupted()) {
824		wasInterrupted = true;
#	Line 787 | Line 835 | public class Phaser {
835		}
836		return isReleasable();
837		}
838	+
839		void signal() {
840		Thread t = thread;
841		if (t != null) {
#	Line 794 | Line 843 | public class Phaser {
843		LockSupport.unpark(t);
844		}
845		}
846	+
847		boolean doWait() {
848		if (thread != null) {
849		try {
850	<	ForkJoinPool.managedBlock(this, false);
850	>	ForkJoinPool.managedBlock(this);
851		} catch (InterruptedException ie) {
852	+	wasInterrupted = true; // can't currently happen
853		}
854		}
855		return wasInterrupted;
856		}
806	–
857		}
858
859		/**
#	Line 845 | Line 895 | public class Phaser {
895		node = new QNode(this, phase, false, false, 0, 0);
896		else if (!queued)
897		queued = tryEnqueue(node);
898	<	else
899	<	interrupted = node.doWait();
898	>	else if (node.doWait())
899	>	interrupted = true;
900		}
901		if (node != null)
902		node.thread = null;
#	Line 872 | Line 922 | public class Phaser {
922		node = new QNode(this, phase, true, false, 0, 0);
923		else if (!queued)
924		queued = tryEnqueue(node);
925	<	else
926	<	interrupted = node.doWait();
925	>	else if (node.doWait())
926	>	interrupted = true;
927		}
928		if (node != null)
929		node.thread = null;
#	Line 904 | Line 954 | public class Phaser {
954		node = new QNode(this, phase, true, true, startTime, nanos);
955		else if (!queued)
956		queued = tryEnqueue(node);
957	<	else
958	<	interrupted = node.doWait();
957	>	else if (node.doWait())
958	>	interrupted = true;
959		}
960		if (node != null)
961		node.thread = null;

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