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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.10 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.48 by dl, Sun Oct 24 21:45:39 2010 UTC

#	Line 7 | Line 7
7		package jsr166y;
8
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
10	>
11	>	import java.util.concurrent.atomic.AtomicReference;
12		import java.util.concurrent.locks.LockSupport;
12	–	import sun.misc.Unsafe;
13	–	import java.lang.reflect.*;
13
14		/**
15	<	* A reusable synchronization barrier, similar in functionality to a
15	>	* A reusable synchronization barrier, similar in functionality to
16		* {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and
17		* {@link java.util.concurrent.CountDownLatch CountDownLatch}
18		* but supporting more flexible usage.
19		*
20	<	* <ul>
21	<	*
22	<	* <li> The number of parties synchronizing on a phaser may vary over
23	<	* time.  A task may register to be a party at any time, and may
24	<	* deregister upon arriving at the barrier.  As is the case with most
25	<	* basic synchronization constructs, registration and deregistration
26	<	* affect only internal counts; they do not establish any further
27	<	* internal bookkeeping, so tasks cannot query whether they are
28	<	* registered. (However, you can introduce such bookkeeping by
29	<	* subclassing this class.)
30	<	*
31	<	* <li> Each generation has an associated phase value, starting at
32	<	* zero, and advancing when all parties reach the barrier (wrapping
33	<	* around to zero after reaching {@code Integer.MAX_VALUE}).
34	<	*
35	<	* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited.
36	<	* Method {@code arriveAndAwaitAdvance} has effect analogous to
37	<	* {@code CyclicBarrier.await}.  However, Phasers separate two
38	<	* aspects of coordination, that may also be invoked independently:
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
25	>	* optionally deregistered upon any arrival (using {@link
26	>	* #arriveAndDeregister}).  As is the case with most basic
27	>	* synchronization constructs, registration and deregistration affect
28	>	* only internal counts; they do not establish any further internal
29	>	* bookkeeping, so tasks cannot query whether they are registered.
30	>	* (However, you can introduce such bookkeeping by subclassing this
31	>	* class.)
32	>	*
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
40	>	* Integer.MAX_VALUE}. The use of phase numbers enables independent
41	>	* control of actions upon arrival at a barrier 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> Arriving at a barrier. Methods {@code arrive} and
48	<	*       {@code arriveAndDeregister} do not block, but return
49	<	*       the phase value current upon entry to the method.
50	<	*
51	<	*   <li> Awaiting others. Method {@code awaitAdvance} requires an
52	<	*       argument indicating the entry phase, and returns when the
53	<	*       barrier advances to a new phase.
54	<	* </ul>
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}.
59	>	*
60	>	*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
61	>	*       argument indicating an arrival phase number, and returns when
62	>	*       the barrier advances to (or is already at) a different phase.
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
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},
72	>	*       which will ensure sufficient parallelism to execute tasks
73	>	*       when others are blocked waiting for a phase to advance.
74		*
75	+	* </ul>
76		*
77	<	* <li> Barrier actions, performed by the task triggering a phase
78	<	* advance while others may be waiting, are arranged by overriding
79	<	* method {@code onAdvance}, that also controls termination.
80	<	* Overriding this method may be used to similar but more flexible
81	<	* effect as providing a barrier action to a CyclicBarrier.
82	<	*
83	<	* <li> Phasers may enter a <em>termination</em> state in which all
84	<	* actions immediately return without updating phaser state or waiting
85	<	* for advance, and indicating (via a negative phase value) that
86	<	* execution is complete.  Termination is triggered by executing the
87	<	* overridable {@code onAdvance} method that is invoked each time the
64	<	* barrier is about to be tripped. When a Phaser is controlling an
65	<	* action with a fixed number of iterations, it is often convenient to
66	<	* override this method to cause termination when the current phase
67	<	* number reaches a threshold. Method {@code forceTermination} is also
68	<	* available to abruptly release waiting threads and allow them to
69	<	* terminate.
77	>	* <p> <b>Termination.</b> A {@code Phaser} may enter a
78	>	* <em>termination</em> state in which all synchronization methods
79	>	* immediately return without updating phaser state or waiting for
80	>	* advance, and indicating (via a negative phase value) that execution
81	>	* is complete.  Termination is triggered when an invocation of {@code
82	>	* onAdvance} returns {@code true}.  As illustrated below, when
83	>	* phasers control actions with a fixed number of iterations, it is
84	>	* often convenient to override this method to cause termination when
85	>	* the current phase number reaches a threshold. Method {@link
86	>	* #forceTermination} is also available to abruptly release waiting
87	>	* threads and allow them to terminate.
88		*
89	<	* <li> Phasers may be tiered to reduce contention. Phasers with large
89	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
90	>	* in tree structures) to reduce contention. Phasers with large
91		* numbers of parties that would otherwise experience heavy
92	<	* synchronization contention costs may instead be arranged in trees.
93	<	* This will typically greatly increase throughput even though it
94	<	* incurs somewhat greater per-operation overhead.
95	<	*
96	<	* <li> By default, {@code awaitAdvance} continues to wait even if
97	<	* the waiting thread is interrupted. And unlike the case in
98	<	* CyclicBarriers, exceptions encountered while tasks wait
99	<	* interruptibly or with timeout do not change the state of the
100	<	* barrier. If necessary, you can perform any associated recovery
101	<	* within handlers of those exceptions, often after invoking
102	<	* {@code forceTermination}.
103	<	*
104	<	* <li>Phasers ensure lack of starvation when used by ForkJoinTasks.
105	<	*
106	<	* </ul>
92	>	* synchronization contention costs may instead be set up so that
93	>	* groups of sub-phasers share a common parent.  This may greatly
94	>	* increase throughput even though it incurs greater per-operation
95	>	* overhead.
96	>	*
97	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
98	>	* only by registered parties, the current state of a phaser may be
99	>	* monitored by any caller.  At any given moment there are {@link
100	>	* #getRegisteredParties} parties in total, of which {@link
101	>	* #getArrivedParties} have arrived at the current phase ({@link
102	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
103	>	* parties arrive, the phase advances.  The values returned by these
104	>	* methods may reflect transient states and so are not in general
105	>	* useful for synchronization control.  Method {@link #toString}
106	>	* returns snapshots of these state queries in a form convenient for
107	>	* informal monitoring.
108		*
109		* <p><b>Sample usages:</b>
110		*
111	<	* <p>A Phaser may be used instead of a {@code CountDownLatch} to control
112	<	* a one-shot action serving a variable number of parties. The typical
113	<	* idiom is for the method setting this up to first register, then
114	<	* start the actions, then deregister, as in:
115	<	*
116	<	* <pre>
117	<	*  void runTasks(List&lt;Runnable&gt; list) {
118	<	*    final Phaser phaser = new Phaser(1); // "1" to register self
119	<	*    for (Runnable r : list) {
120	<	*      phaser.register();
121	<	*      new Thread() {
122	<	*        public void run() {
123	<	*          phaser.arriveAndAwaitAdvance(); // await all creation
124	<	*          r.run();
125	<	*          phaser.arriveAndDeregister();   // signal completion
126	<	*        }
127	<	*      }.start();
111	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
112	>	* to control a one-shot action serving a variable number of parties.
113	>	* The typical idiom is for the method setting this up to first
114	>	* register, then start the actions, then deregister, as in:
115	>	*
116	>	*  <pre> {@code
117	>	* void runTasks(List<Runnable> tasks) {
118	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
119	>	*   // create and start threads
120	>	*   for (Runnable task : tasks) {
121	>	*     phaser.register();
122	>	*     new Thread() {
123	>	*       public void run() {
124	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
125	>	*         task.run();
126	>	*       }
127	>	*     }.start();
128		*   }
129		*
130	<	*   doSomethingOnBehalfOfWorkers();
131	<	*   phaser.arrive(); // allow threads to start
132	<	*   int p = phaser.arriveAndDeregister(); // deregister self  ...
113	<	*   p = phaser.awaitAdvance(p); // ... and await arrival
114	<	*   otherActions(); // do other things while tasks execute
115	<	*   phaser.awaitAdvance(p); // await final completion
116	<	* }
117	<	* </pre>
130	>	*   // allow threads to start and deregister self
131	>	*   phaser.arriveAndDeregister();
132	>	* }}</pre>
133		*
134		* <p>One way to cause a set of threads to repeatedly perform actions
135		* for a given number of iterations is to override {@code onAdvance}:
136		*
137	<	* <pre>
138	<	*  void startTasks(List&lt;Runnable&gt; list, final int iterations) {
139	<	*    final Phaser phaser = new Phaser() {
140	<	*       public boolean onAdvance(int phase, int registeredParties) {
141	<	*         return phase &gt;= iterations || registeredParties == 0;
137	>	*  <pre> {@code
138	>	* void startTasks(List<Runnable> tasks, final int iterations) {
139	>	*   final Phaser phaser = new Phaser() {
140	>	*     protected boolean onAdvance(int phase, int registeredParties) {
141	>	*       return phase >= iterations || registeredParties == 0;
142	>	*     }
143	>	*   };
144	>	*   phaser.register();
145	>	*   for (final Runnable task : tasks) {
146	>	*     phaser.register();
147	>	*     new Thread() {
148	>	*       public void run() {
149	>	*         do {
150	>	*           task.run();
151	>	*           phaser.arriveAndAwaitAdvance();
152	>	*         } while (!phaser.isTerminated());
153		*       }
154	<	*    };
129	<	*    phaser.register();
130	<	*    for (Runnable r : list) {
131	<	*      phaser.register();
132	<	*      new Thread() {
133	<	*        public void run() {
134	<	*           do {
135	<	*             r.run();
136	<	*             phaser.arriveAndAwaitAdvance();
137	<	*           } while(!phaser.isTerminated();
138	<	*        }
139	<	*      }.start();
154	>	*     }.start();
155		*   }
156		*   phaser.arriveAndDeregister(); // deregister self, don't wait
157	<	* }
158	<	* </pre>
157	>	* }}</pre>
158	>	*
159	>	* If the main task must later await termination, it
160	>	* may re-register and then execute a similar loop:
161	>	*  <pre> {@code
162	>	*   // ...
163	>	*   phaser.register();
164	>	*   while (!phaser.isTerminated())
165	>	*     phaser.arriveAndAwaitAdvance();}</pre>
166	>	*
167	>	* <p>Related constructions may be used to await particular phase numbers
168	>	* in contexts where you are sure that the phase will never wrap around
169	>	* {@code Integer.MAX_VALUE}. For example:
170	>	*
171	>	*  <pre> {@code
172	>	* void awaitPhase(Phaser phaser, int phase) {
173	>	*   int p = phaser.register(); // assumes caller not already registered
174	>	*   while (p < phase) {
175	>	*     if (phaser.isTerminated())
176	>	*       // ... deal with unexpected termination
177	>	*     else
178	>	*       p = phaser.arriveAndAwaitAdvance();
179	>	*   }
180	>	*   phaser.arriveAndDeregister();
181	>	* }}</pre>
182	>	*
183		*
184	<	* <p> To create a set of tasks using a tree of Phasers,
184	>	* <p>To create a set of tasks using a tree of phasers,
185		* you could use code of the following form, assuming a
186	<	* Task class with a constructor accepting a Phaser that
187	<	* it registers for upon construction:
188	<	* <pre>
189	<	*  void build(Task[] actions, int lo, int hi, Phaser b) {
190	<	*    int step = (hi - lo) / TASKS_PER_PHASER;
191	<	*    if (step &gt; 1) {
192	<	*       int i = lo;
193	<	*       while (i &lt; hi) {
194	<	*         int r = Math.min(i + step, hi);
195	<	*         build(actions, i, r, new Phaser(b));
196	<	*         i = r;
197	<	*       }
198	<	*    }
199	<	*    else {
200	<	*      for (int i = lo; i &lt; hi; ++i)
201	<	*        actions[i] = new Task(b);
202	<	*        // assumes new Task(b) performs b.register()
203	<	*    }
165	<	*  }
166	<	*  // .. initially called, for n tasks via
167	<	*  build(new Task[n], 0, n, new Phaser());
168	<	* </pre>
186	>	* Task class with a constructor accepting a phaser that
187	>	* it registers with upon construction:
188	>	*
189	>	*  <pre> {@code
190	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
191	>	*   if (hi - lo > TASKS_PER_PHASER) {
192	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
193	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
194	>	*       build(actions, i, j, new Phaser(ph));
195	>	*     }
196	>	*   } else {
197	>	*     for (int i = lo; i < hi; ++i)
198	>	*       actions[i] = new Task(ph);
199	>	*       // assumes new Task(ph) performs ph.register()
200	>	*   }
201	>	* }
202	>	* // .. initially called, for n tasks via
203	>	* build(new Task[n], 0, n, new Phaser());}</pre>
204		*
205		* The best value of {@code TASKS_PER_PHASER} depends mainly on
206		* expected barrier synchronization rates. A value as low as four may
207		* be appropriate for extremely small per-barrier task bodies (thus
208		* high rates), or up to hundreds for extremely large ones.
209		*
175	–	* </pre>
176	–	*
210		* <p><b>Implementation notes</b>: This implementation restricts the
211		* maximum number of parties to 65535. Attempts to register additional
212	<	* parties result in IllegalStateExceptions. However, you can and
212	>	* parties result in {@code IllegalStateException}. However, you can and
213		* should create tiered phasers to accommodate arbitrarily large sets
214		* of participants.
215	+	*
216	+	* @since 1.7
217	+	* @author Doug Lea
218		*/
219		public class Phaser {
220		/*
#	Line 207 | Line 243 | public class Phaser {
243		*/
244		private volatile long state;
245
210	–	private static final int ushortBits = 16;
246		private static final int ushortMask = 0xffff;
247		private static final int phaseMask  = 0x7fffffff;
248
249		private static int unarrivedOf(long s) {
250	<	return (int)(s & ushortMask);
250	>	return (int) (s & ushortMask);
251		}
252
253		private static int partiesOf(long s) {
254	<	return ((int)s) >>> 16;
254	>	return ((int) s) >>> 16;
255		}
256
257		private static int phaseOf(long s) {
258	<	return (int)(s >>> 32);
258	>	return (int) (s >>> 32);
259		}
260
261		private static int arrivedOf(long s) {
#	Line 228 | Line 263 | public class Phaser {
263		}
264
265		private static long stateFor(int phase, int parties, int unarrived) {
266	<	return ((((long)phase) << 32) | (((long)parties) << 16) |
267	<	(long)unarrived);
266	>	return ((((long) phase) << 32) | (((long) parties) << 16) |
267	>	(long) unarrived);
268		}
269
270		private static long trippedStateFor(int phase, int parties) {
271	<	long lp = (long)parties;
272	<	return (((long)phase) << 32) | (lp << 16) | lp;
271	>	long lp = (long) parties;
272	>	return (((long) phase) << 32) | (lp << 16) | lp;
273		}
274
275		/**
276	<	* Returns message string for bad bounds exceptions
276	>	* Returns message string for bad bounds exceptions.
277		*/
278		private static String badBounds(int parties, int unarrived) {
279		return ("Attempt to set " + unarrived +
#	Line 251 | Line 286 | public class Phaser {
286		private final Phaser parent;
287
288		/**
289	<	* The root of Phaser tree. Equals this if not in a tree.  Used to
289	>	* The root of phaser tree. Equals this if not in a tree.  Used to
290		* support faster state push-down.
291		*/
292		private final Phaser root;
#	Line 267 | Line 302 | public class Phaser {
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	>	return ((phase & 1) == 0) ? evenQ : oddQ;
306		}
307
308		/**
#	Line 275 | Line 310 | public class Phaser {
310		* root if necessary.
311		*/
312		private long getReconciledState() {
313	<	return parent == null? state : reconcileState();
313	>	return (parent == null) ? state : reconcileState();
314		}
315
316		/**
#	Line 302 | Line 337 | public class Phaser {
337		}
338
339		/**
340	<	* Creates a new Phaser without any initially registered parties,
340	>	* Creates a new phaser without any initially registered parties,
341		* initial phase number 0, and no parent. Any thread using this
342	<	* Phaser will need to first register for it.
342	>	* phaser will need to first register for it.
343		*/
344		public Phaser() {
345		this(null);
346		}
347
348		/**
349	<	* Creates a new Phaser with the given numbers of registered
349	>	* Creates a new phaser with the given number of registered
350		* unarrived parties, initial phase number 0, and no parent.
351	<	* @param parties the number of parties required to trip barrier.
351	>	*
352	>	* @param parties the number of parties required to trip barrier
353		* @throws IllegalArgumentException if parties less than zero
354	<	* or greater than the maximum number of parties supported.
354	>	* or greater than the maximum number of parties supported
355		*/
356		public Phaser(int parties) {
357		this(null, parties);
358		}
359
360		/**
361	<	* Creates a new Phaser with the given parent, without any
361	>	* Creates a new phaser with the given parent, without any
362		* initially registered parties. If parent is non-null this phaser
363		* is registered with the parent and its initial phase number is
364		* the same as that of parent phaser.
365	<	* @param parent the parent phaser.
365	>	*
366	>	* @param parent the parent phaser
367		*/
368		public Phaser(Phaser parent) {
369		int phase = 0;
#	Line 341 | Line 378 | public class Phaser {
378		}
379
380		/**
381	<	* Creates a new Phaser with the given parent and numbers of
382	<	* registered unarrived parties. If parent is non-null this phaser
381	>	* Creates a new phaser with the given parent and number of
382	>	* registered unarrived parties. If parent is non-null, this phaser
383		* is registered with the parent and its initial phase number is
384		* the same as that of parent phaser.
385	<	* @param parent the parent phaser.
386	<	* @param parties the number of parties required to trip barrier.
385	>	*
386	>	* @param parent the parent phaser
387	>	* @param parties the number of parties required to trip barrier
388		* @throws IllegalArgumentException if parties less than zero
389	<	* or greater than the maximum number of parties supported.
389	>	* or greater than the maximum number of parties supported
390		*/
391		public Phaser(Phaser parent, int parties) {
392		if (parties < 0 || parties > ushortMask)
#	Line 366 | Line 404 | public class Phaser {
404
405		/**
406		* Adds a new unarrived party to this phaser.
407	<	* @return the current barrier phase number upon registration
407	>	*
408	>	* @return the arrival phase number to which this registration applied
409		* @throws IllegalStateException if attempting to register more
410	<	* than the maximum supported number of parties.
410	>	* than the maximum supported number of parties
411		*/
412		public int register() {
413		return doRegister(1);
#	Line 376 | Line 415 | public class Phaser {
415
416		/**
417		* Adds the given number of new unarrived parties to this phaser.
418	<	* @param parties the number of parties required to trip barrier.
419	<	* @return the current barrier phase number upon registration
418	>	*
419	>	* @param parties the number of additional parties required to trip barrier
420	>	* @return the arrival phase number to which this registration applied
421		* @throws IllegalStateException if attempting to register more
422	<	* than the maximum supported number of parties.
422	>	* than the maximum supported number of parties
423	>	* @throws IllegalArgumentException if {@code parties < 0}
424		*/
425		public int bulkRegister(int parties) {
426		if (parties < 0)
#	Line 399 | Line 440 | public class Phaser {
440		phase = phaseOf(s);
441		int unarrived = unarrivedOf(s) + registrations;
442		int parties = partiesOf(s) + registrations;
443	<	if (phase < 0)
443	>	if (phase < 0)
444		break;
445		if (parties > ushortMask || unarrived > ushortMask)
446		throw new IllegalStateException(badBounds(parties, unarrived));
#	Line 412 | Line 453 | public class Phaser {
453
454		/**
455		* Arrives at the barrier, but does not wait for others.  (You can
456	<	* in turn wait for others via {@link #awaitAdvance}).
456	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
457	>	* unenforced usage error for an unregistered party to invoke this
458	>	* method.
459		*
460	<	* @return the barrier phase number upon entry to this method, or a
418	<	* negative value if terminated;
460	>	* @return the arrival phase number, or a negative value if terminated
461		* @throws IllegalStateException if not terminated and the number
462	<	* of unarrived parties would become negative.
462	>	* of unarrived parties would become negative
463		*/
464		public int arrive() {
465		int phase;
#	Line 437 | Line 479 | public class Phaser {
479		if (par == null) {      // directly trip
480		if (casState
481		(s,
482	<	trippedStateFor(onAdvance(phase, parties)? -1 :
482	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
483		((phase + 1) & phaseMask), parties))) {
484		releaseWaiters(phase);
485		break;
#	Line 460 | Line 502 | public class Phaser {
502		}
503
504		/**
505	<	* Arrives at the barrier, and deregisters from it, without
506	<	* waiting for others. Deregistration reduces number of parties
505	>	* Arrives at the barrier and deregisters from it without waiting
506	>	* for others. Deregistration reduces the number of parties
507		* required to trip the barrier in future phases.  If this phaser
508		* has a parent, and deregistration causes this phaser to have
509	<	* zero parties, this phaser is also deregistered from its parent.
509	>	* zero parties, this phaser also arrives at and is deregistered
510	>	* from its parent.  It is an unenforced usage error for an
511	>	* unregistered party to invoke this method.
512		*
513	<	* @return the current barrier phase number upon entry to
470	<	* this method, or a negative value if terminated;
513	>	* @return the arrival phase number, or a negative value if terminated
514		* @throws IllegalStateException if not terminated and the number
515	<	* of registered or unarrived parties would become negative.
515	>	* of registered or unarrived parties would become negative
516		*/
517		public int arriveAndDeregister() {
518		// similar code to arrive, but too different to merge
#	Line 498 | Line 541 | public class Phaser {
541		if (unarrived == 0) {
542		if (casState
543		(s,
544	<	trippedStateFor(onAdvance(phase, parties)? -1 :
544	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
545		((phase + 1) & phaseMask), parties))) {
546		releaseWaiters(phase);
547		break;
#	Line 517 | Line 560 | public class Phaser {
560
561		/**
562		* Arrives at the barrier and awaits others. Equivalent in effect
563	<	* to {@code awaitAdvance(arrive())}.  If you instead need to
564	<	* await with interruption of timeout, and/or deregister upon
565	<	* arrival, you can arrange them using analogous constructions.
566	<	* @return the phase on entry to this method
563	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
564	>	* interruption or timeout, you can arrange this with an analogous
565	>	* construction using one of the other forms of the {@code
566	>	* awaitAdvance} method.  If instead you need to deregister upon
567	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
568	>	* usage error for an unregistered party to invoke this method.
569	>	*
570	>	* @return the arrival phase number, or a negative number if terminated
571		* @throws IllegalStateException if not terminated and the number
572	<	* of unarrived parties would become negative.
572	>	* of unarrived parties would become negative
573		*/
574		public int arriveAndAwaitAdvance() {
575		return awaitAdvance(arrive());
576		}
577
578		/**
579	<	* Awaits the phase of the barrier to advance from the given
580	<	* value, or returns immediately if argument is negative or this
581	<	* barrier is terminated.
582	<	* @param phase the phase on entry to this method
583	<	* @return the phase on exit from this method
579	>	* Awaits the phase of the barrier to advance from the given phase
580	>	* value, returning immediately if the current phase of the
581	>	* barrier is not equal to the given phase value or this barrier
582	>	* is terminated.  It is an unenforced usage error for an
583	>	* unregistered party to invoke this method.
584	>	*
585	>	* @param phase an arrival phase number, or negative value if
586	>	* terminated; this argument is normally the value returned by a
587	>	* previous call to {@code arrive} or its variants
588	>	* @return the next arrival phase number, or a negative value
589	>	* if terminated or argument is negative
590		*/
591		public int awaitAdvance(int phase) {
592		if (phase < 0)
#	Line 549 | Line 602 | public class Phaser {
602		}
603
604		/**
605	<	* Awaits the phase of the barrier to advance from the given
606	<	* value, or returns immediately if argument is negative or this
607	<	* barrier is terminated, or throws InterruptedException if
608	<	* interrupted while waiting.
609	<	* @param phase the phase on entry to this method
610	<	* @return the phase on exit from this method
605	>	* Awaits the phase of the barrier to advance from the given phase
606	>	* value, throwing {@code InterruptedException} if interrupted
607	>	* while waiting, or returning immediately if the current phase of
608	>	* the barrier is not equal to the given phase value or this
609	>	* barrier is terminated. It is an unenforced usage error for an
610	>	* unregistered party to invoke this method.
611	>	*
612	>	* @param phase an arrival phase number, or negative value if
613	>	* terminated; this argument is normally the value returned by a
614	>	* previous call to {@code arrive} or its variants
615	>	* @return the next arrival phase number, or a negative value
616	>	* if terminated or argument is negative
617		* @throws InterruptedException if thread interrupted while waiting
618		*/
619	<	public int awaitAdvanceInterruptibly(int phase)
619	>	public int awaitAdvanceInterruptibly(int phase)
620		throws InterruptedException {
621		if (phase < 0)
622		return phase;
#	Line 571 | Line 630 | public class Phaser {
630		}
631
632		/**
633	<	* Awaits the phase of the barrier to advance from the given value
634	<	* or the given timeout elapses, or returns immediately if
635	<	* argument is negative or this barrier is terminated.
636	<	* @param phase the phase on entry to this method
637	<	* @return the phase on exit from this method
633	>	* Awaits the phase of the barrier to advance from the given phase
634	>	* value or the given timeout to elapse, throwing {@code
635	>	* InterruptedException} if interrupted while waiting, or
636	>	* returning immediately if the current phase of the barrier is
637	>	* not equal to the given phase value or this barrier is
638	>	* terminated.  It is an unenforced usage error for an
639	>	* unregistered party to invoke this method.
640	>	*
641	>	* @param phase an arrival phase number, or negative value if
642	>	* terminated; this argument is normally the value returned by a
643	>	* previous call to {@code arrive} or its variants
644	>	* @param timeout how long to wait before giving up, in units of
645	>	*        {@code unit}
646	>	* @param unit a {@code TimeUnit} determining how to interpret the
647	>	*        {@code timeout} parameter
648	>	* @return the next arrival phase number, or a negative value
649	>	* if terminated or argument is negative
650		* @throws InterruptedException if thread interrupted while waiting
651		* @throws TimeoutException if timed out while waiting
652		*/
653	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
653	>	public int awaitAdvanceInterruptibly(int phase,
654	>	long timeout, TimeUnit unit)
655		throws InterruptedException, TimeoutException {
656		if (phase < 0)
657		return phase;
#	Line 620 | Line 692 | public class Phaser {
692		* Returns the current phase number. The maximum phase number is
693		* {@code Integer.MAX_VALUE}, after which it restarts at
694		* zero. Upon termination, the phase number is negative.
695	+	*
696		* @return the phase number, or a negative value if terminated
697		*/
698		public final int getPhase() {
#	Line 627 | Line 700 | public class Phaser {
700		}
701
702		/**
630	–	* Returns {@code true} if the current phase number equals the given phase.
631	–	* @param phase the phase
632	–	* @return {@code true} if the current phase number equals the given phase
633	–	*/
634	–	public final boolean hasPhase(int phase) {
635	–	return phaseOf(getReconciledState()) == phase;
636	–	}
637	–
638	–	/**
703		* Returns the number of parties registered at this barrier.
704	+	*
705		* @return the number of parties
706		*/
707		public int getRegisteredParties() {
#	Line 644 | Line 709 | public class Phaser {
709		}
710
711		/**
712	<	* Returns the number of parties that have arrived at the current
713	<	* phase of this barrier.
712	>	* Returns the number of registered parties that have arrived at
713	>	* the current phase of this barrier.
714	>	*
715		* @return the number of arrived parties
716		*/
717		public int getArrivedParties() {
#	Line 655 | Line 721 | public class Phaser {
721		/**
722		* Returns the number of registered parties that have not yet
723		* arrived at the current phase of this barrier.
724	+	*
725		* @return the number of unarrived parties
726		*/
727		public int getUnarrivedParties() {
#	Line 662 | Line 729 | public class Phaser {
729		}
730
731		/**
732	<	* Returns the parent of this phaser, or null if none.
733	<	* @return the parent of this phaser, or null if none
732	>	* Returns the parent of this phaser, or {@code null} if none.
733	>	*
734	>	* @return the parent of this phaser, or {@code null} if none
735		*/
736		public Phaser getParent() {
737		return parent;
#	Line 672 | Line 740 | public class Phaser {
740		/**
741		* Returns the root ancestor of this phaser, which is the same as
742		* this phaser if it has no parent.
743	+	*
744		* @return the root ancestor of this phaser
745		*/
746		public Phaser getRoot() {
#	Line 680 | Line 749 | public class Phaser {
749
750		/**
751		* Returns {@code true} if this barrier has been terminated.
752	+	*
753		* @return {@code true} if this barrier has been terminated
754		*/
755		public boolean isTerminated() {
#	Line 687 | Line 757 | public class Phaser {
757		}
758
759		/**
760	<	* Overridable method to perform an action upon phase advance, and
761	<	* to control termination. This method is invoked whenever the
762	<	* barrier is tripped (and thus all other waiting parties are
763	<	* dormant). If it returns true, then, rather than advance the
764	<	* phase number, this barrier will be set to a final termination
765	<	* state, and subsequent calls to {@code isTerminated} will
766	<	* return true.
760	>	* Overridable method to perform an action upon impending phase
761	>	* advance, and to control termination. This method is invoked
762	>	* upon arrival of the party tripping the barrier (when all other
763	>	* waiting parties are dormant).  If this method returns {@code
764	>	* true}, then, rather than advance the phase number, this barrier
765	>	* will be set to a final termination state, and subsequent calls
766	>	* to {@link #isTerminated} will return true. Any (unchecked)
767	>	* Exception or Error thrown by an invocation of this method is
768	>	* propagated to the party attempting to trip the barrier, in
769	>	* which case no advance occurs.
770		*
771	<	* <p> The default version returns true when the number of
771	>	* <p>The arguments to this method provide the state of the phaser
772	>	* prevailing for the current transition. (When called from within
773	>	* an implementation of {@code onAdvance} the values returned by
774	>	* methods such as {@code getPhase} may or may not reliably
775	>	* indicate the state to which this transition applies.)
776	>	*
777	>	* <p>The default version returns {@code true} when the number of
778		* registered parties is zero. Normally, overrides that arrange
779		* termination for other reasons should also preserve this
780		* property.
781		*
782	<	* <p> You may override this method to perform an action with side
783	<	* effects visible to participating tasks, but it is in general
784	<	* only sensible to do so in designs where all parties register
785	<	* before any arrive, and all {@code awaitAdvance} at each phase.
786	<	* Otherwise, you cannot ensure lack of interference. In
787	<	* particular, this method may be invoked more than once per
788	<	* transition if other parties successfully register while the
789	<	* invocation of this method is in progress, thus postponing the
711	<	* transition until those parties also arrive, re-triggering this
712	<	* method.
782	>	* <p>You may override this method to perform an action with side
783	>	* effects visible to participating tasks, but it is only sensible
784	>	* to do so in designs where all parties register before any
785	>	* arrive, and all {@link #awaitAdvance} at each phase.
786	>	* Otherwise, you cannot ensure lack of interference from other
787	>	* parties during the invocation of this method. Additionally,
788	>	* method {@code onAdvance} may be invoked more than once per
789	>	* transition if registrations are intermixed with arrivals.
790		*
791		* @param phase the phase number on entering the barrier
792		* @param registeredParties the current number of registered parties
#	Line 751 | Line 828 | public class Phaser {
828		volatile boolean wasInterrupted = false;
829		volatile Thread thread; // nulled to cancel wait
830		QNode next;
831	+
832		QNode(Phaser phaser, int phase, boolean interruptible,
833		boolean timed, long startTime, long nanos) {
834		this.phaser = phaser;
#	Line 761 | Line 839 | public class Phaser {
839		this.nanos = nanos;
840		thread = Thread.currentThread();
841		}
842	+
843		public boolean isReleasable() {
844		return (thread == null ||
845		phaser.getPhase() != phase ||
846		(interruptible && wasInterrupted) ||
847		(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
848		}
849	+
850		public boolean block() {
851		if (Thread.interrupted()) {
852		wasInterrupted = true;
#	Line 783 | Line 863 | public class Phaser {
863		}
864		return isReleasable();
865		}
866	+
867		void signal() {
868		Thread t = thread;
869		if (t != null) {
#	Line 790 | Line 871 | public class Phaser {
871		LockSupport.unpark(t);
872		}
873		}
874	+
875		boolean doWait() {
876		if (thread != null) {
877		try {
878	<	ForkJoinPool.managedBlock(this, false);
878	>	ForkJoinPool.managedBlock(this);
879		} catch (InterruptedException ie) {
880	<	}
880	>	wasInterrupted = true; // can't currently happen
881	>	}
882		}
883		return wasInterrupted;
884		}
802	–
885		}
886
887		/**
888	<	* Removes and signals waiting threads from wait queue
888	>	* Removes and signals waiting threads from wait queue.
889		*/
890		private void releaseWaiters(int phase) {
891		AtomicReference<QNode> head = queueFor(phase);
#	Line 815 | Line 897 | public class Phaser {
897		}
898
899		/**
900	<	* Tries to enqueue given node in the appropriate wait queue
900	>	* Tries to enqueue given node in the appropriate wait queue.
901	>	*
902		* @return true if successful
903		*/
904		private boolean tryEnqueue(QNode node) {
#	Line 825 | Line 908 | public class Phaser {
908
909		/**
910		* Enqueues node and waits unless aborted or signalled.
911	+	*
912		* @return current phase
913		*/
914		private int untimedWait(int phase) {
#	Line 839 | Line 923 | public class Phaser {
923		node = new QNode(this, phase, false, false, 0, 0);
924		else if (!queued)
925		queued = tryEnqueue(node);
926	<	else
927	<	interrupted = node.doWait();
926	>	else if (node.doWait())
927	>	interrupted = true;
928		}
929		if (node != null)
930		node.thread = null;
#	Line 866 | Line 950 | public class Phaser {
950		node = new QNode(this, phase, true, false, 0, 0);
951		else if (!queued)
952		queued = tryEnqueue(node);
953	<	else
954	<	interrupted = node.doWait();
953	>	else if (node.doWait())
954	>	interrupted = true;
955		}
956		if (node != null)
957		node.thread = null;
#	Line 898 | Line 982 | public class Phaser {
982		node = new QNode(this, phase, true, true, startTime, nanos);
983		else if (!queued)
984		queued = tryEnqueue(node);
985	<	else
986	<	interrupted = node.doWait();
985	>	else if (node.doWait())
986	>	interrupted = true;
987		}
988		if (node != null)
989		node.thread = null;
#	Line 912 | Line 996 | public class Phaser {
996		return p;
997		}
998
999	<	// Temporary Unsafe mechanics for preliminary release
999	>	// Unsafe mechanics
1000
1001	<	static final Unsafe _unsafe;
1002	<	static final long stateOffset;
1001	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1002	>	private static final long stateOffset =
1003	>	objectFieldOffset("state", Phaser.class);
1004	>
1005	>	private final boolean casState(long cmp, long val) {
1006	>	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
1007	>	}
1008
1009	<	static {
1009	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1010		try {
1011	<	if (Phaser.class.getClassLoader() != null) {
1012	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1013	<	f.setAccessible(true);
1014	<	_unsafe = (Unsafe)f.get(null);
1015	<	}
1016	<	else
928	<	_unsafe = Unsafe.getUnsafe();
929	<	stateOffset = _unsafe.objectFieldOffset
930	<	(Phaser.class.getDeclaredField("state"));
931	<	} catch (Exception e) {
932	<	throw new RuntimeException("Could not initialize intrinsics", e);
1011	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1012	>	} catch (NoSuchFieldException e) {
1013	>	// Convert Exception to corresponding Error
1014	>	NoSuchFieldError error = new NoSuchFieldError(field);
1015	>	error.initCause(e);
1016	>	throw error;
1017		}
1018		}
1019
1020	<	final boolean casState(long cmp, long val) {
1021	<	return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val);
1020	>	/**
1021	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1022	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1023	>	* into a jdk.
1024	>	*
1025	>	* @return a sun.misc.Unsafe
1026	>	*/
1027	>	private static sun.misc.Unsafe getUnsafe() {
1028	>	try {
1029	>	return sun.misc.Unsafe.getUnsafe();
1030	>	} catch (SecurityException se) {
1031	>	try {
1032	>	return java.security.AccessController.doPrivileged
1033	>	(new java.security
1034	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1035	>	public sun.misc.Unsafe run() throws Exception {
1036	>	java.lang.reflect.Field f = sun.misc
1037	>	.Unsafe.class.getDeclaredField("theUnsafe");
1038	>	f.setAccessible(true);
1039	>	return (sun.misc.Unsafe) f.get(null);
1040	>	}});
1041	>	} catch (java.security.PrivilegedActionException e) {
1042	>	throw new RuntimeException("Could not initialize intrinsics",
1043	>	e.getCause());
1044	>	}
1045	>	}
1046		}
1047		}

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