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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.10 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.41 by jsr166, Mon Aug 24 15:42:51 2009 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; thus, this value is always
104	>	* greater than zero if there are any registered parties.  The values
105	>	* returned by these methods may reflect transient states and so are
106	>	* not in general useful for synchronization control.  Method {@link
107	>	* #toString} returns snapshots of these state queries in a form
108	>	* convenient for informal monitoring.
109		*
110		* <p><b>Sample usages:</b>
111		*
112	<	* <p>A Phaser may be used instead of a {@code CountDownLatch} to control
113	<	* a one-shot action serving a variable number of parties. The typical
114	<	* idiom is for the method setting this up to first register, then
115	<	* start the actions, then deregister, as in:
116	<	*
117	<	* <pre>
118	<	*  void runTasks(List&lt;Runnable&gt; list) {
119	<	*    final Phaser phaser = new Phaser(1); // "1" to register self
120	<	*    for (Runnable r : list) {
121	<	*      phaser.register();
122	<	*      new Thread() {
123	<	*        public void run() {
124	<	*          phaser.arriveAndAwaitAdvance(); // await all creation
125	<	*          r.run();
126	<	*          phaser.arriveAndDeregister();   // signal completion
127	<	*        }
128	<	*      }.start();
112	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
113	>	* to control a one-shot action serving a variable number of
114	>	* parties. The typical idiom is for the method setting this up to
115	>	* first register, then start the actions, then deregister, as in:
116	>	*
117	>	*  <pre> {@code
118	>	* void runTasks(List<Runnable> tasks) {
119	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
120	>	*   // create and start threads
121	>	*   for (Runnable task : tasks) {
122	>	*     phaser.register();
123	>	*     new Thread() {
124	>	*       public void run() {
125	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
126	>	*         task.run();
127	>	*       }
128	>	*     }.start();
129		*   }
130		*
131	<	*   doSomethingOnBehalfOfWorkers();
132	<	*   phaser.arrive(); // allow threads to start
133	<	*   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>
131	>	*   // allow threads to start and deregister self
132	>	*   phaser.arriveAndDeregister();
133	>	* }}</pre>
134		*
135		* <p>One way to cause a set of threads to repeatedly perform actions
136		* for a given number of iterations is to override {@code onAdvance}:
137		*
138	<	* <pre>
139	<	*  void startTasks(List&lt;Runnable&gt; list, final int iterations) {
140	<	*    final Phaser phaser = new Phaser() {
141	<	*       public boolean onAdvance(int phase, int registeredParties) {
142	<	*         return phase &gt;= iterations || registeredParties == 0;
138	>	*  <pre> {@code
139	>	* void startTasks(List<Runnable> tasks, final int iterations) {
140	>	*   final Phaser phaser = new Phaser() {
141	>	*     protected boolean onAdvance(int phase, int registeredParties) {
142	>	*       return phase >= iterations || registeredParties == 0;
143	>	*     }
144	>	*   };
145	>	*   phaser.register();
146	>	*   for (Runnable task : tasks) {
147	>	*     phaser.register();
148	>	*     new Thread() {
149	>	*       public void run() {
150	>	*         do {
151	>	*           task.run();
152	>	*           phaser.arriveAndAwaitAdvance();
153	>	*         } while(!phaser.isTerminated();
154		*       }
155	<	*    };
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();
155	>	*     }.start();
156		*   }
157		*   phaser.arriveAndDeregister(); // deregister self, don't wait
158	<	* }
159	<	* </pre>
158	>	* }}</pre>
159	>	*
160	>	* If the main task must later await termination, it
161	>	* may re-register and then execute a similar loop:
162	>	* <pre> {@code
163	>	*   // ...
164	>	*   phaser.register();
165	>	*   while (!phaser.isTerminated())
166	>	*     phaser.arriveAndAwaitAdvance();
167	>	* }</pre>
168	>	*
169	>	* Related constructions may be used to await particular phase numbers
170	>	* in contexts where you are sure that the phase will never wrap around
171	>	* {@code Integer.MAX_VALUE}. For example:
172	>	*
173	>	* <pre> {@code
174	>	*   void awaitPhase(Phaser phaser, int phase) {
175	>	*     int p = phaser.register(); // assumes caller not already registered
176	>	*     while (p < phase) {
177	>	*       if (phaser.isTerminated())
178	>	*         // ... deal with unexpected termination
179	>	*       else
180	>	*         p = phaser.arriveAndAwaitAdvance();
181	>	*     }
182	>	*     phaser.arriveAndDeregister();
183	>	*   }
184	>	* }</pre>
185		*
186	<	* <p> To create a set of tasks using a tree of Phasers,
186	>	*
187	>	* <p>To create a set of tasks using a tree of phasers,
188		* you could use code of the following form, assuming a
189	<	* Task class with a constructor accepting a Phaser that
189	>	* Task class with a constructor accepting a phaser that
190		* it registers for upon construction:
191	<	* <pre>
192	<	*  void build(Task[] actions, int lo, int hi, Phaser b) {
193	<	*    int step = (hi - lo) / TASKS_PER_PHASER;
194	<	*    if (step &gt; 1) {
195	<	*       int i = lo;
196	<	*       while (i &lt; hi) {
197	<	*         int r = Math.min(i + step, hi);
198	<	*         build(actions, i, r, new Phaser(b));
199	<	*         i = r;
200	<	*       }
201	<	*    }
202	<	*    else {
203	<	*      for (int i = lo; i &lt; hi; ++i)
204	<	*        actions[i] = new Task(b);
205	<	*        // assumes new Task(b) performs b.register()
206	<	*    }
207	<	*  }
208	<	*  // .. initially called, for n tasks via
167	<	*  build(new Task[n], 0, n, new Phaser());
168	<	* </pre>
191	>	*  <pre> {@code
192	>	* void build(Task[] actions, int lo, int hi, Phaser b) {
193	>	*   int step = (hi - lo) / TASKS_PER_PHASER;
194	>	*   if (step > 1) {
195	>	*     int i = lo;
196	>	*     while (i < hi) {
197	>	*       int r = Math.min(i + step, hi);
198	>	*       build(actions, i, r, new Phaser(b));
199	>	*       i = r;
200	>	*     }
201	>	*   } else {
202	>	*     for (int i = lo; i < hi; ++i)
203	>	*       actions[i] = new Task(b);
204	>	*       // assumes new Task(b) performs b.register()
205	>	*   }
206	>	* }
207	>	* // .. initially called, for n tasks via
208	>	* build(new Task[n], 0, n, new Phaser());}</pre>
209		*
210		* The best value of {@code TASKS_PER_PHASER} depends mainly on
211		* expected barrier synchronization rates. A value as low as four may
#	Line 176 | Line 216 | import java.lang.reflect.*;
216		*
217		* <p><b>Implementation notes</b>: This implementation restricts the
218		* maximum number of parties to 65535. Attempts to register additional
219	<	* parties result in IllegalStateExceptions. However, you can and
219	>	* parties result in {@code IllegalStateException}. However, you can and
220		* should create tiered phasers to accommodate arbitrarily large sets
221		* of participants.
222	+	*
223	+	* @since 1.7
224	+	* @author Doug Lea
225		*/
226		public class Phaser {
227		/*
#	Line 207 | Line 250 | public class Phaser {
250		*/
251		private volatile long state;
252
210	–	private static final int ushortBits = 16;
253		private static final int ushortMask = 0xffff;
254		private static final int phaseMask  = 0x7fffffff;
255
256		private static int unarrivedOf(long s) {
257	<	return (int)(s & ushortMask);
257	>	return (int) (s & ushortMask);
258		}
259
260		private static int partiesOf(long s) {
261	<	return ((int)s) >>> 16;
261	>	return ((int) s) >>> 16;
262		}
263
264		private static int phaseOf(long s) {
265	<	return (int)(s >>> 32);
265	>	return (int) (s >>> 32);
266		}
267
268		private static int arrivedOf(long s) {
#	Line 228 | Line 270 | public class Phaser {
270		}
271
272		private static long stateFor(int phase, int parties, int unarrived) {
273	<	return ((((long)phase) << 32) | (((long)parties) << 16) |
274	<	(long)unarrived);
273	>	return ((((long) phase) << 32) | (((long) parties) << 16) |
274	>	(long) unarrived);
275		}
276
277		private static long trippedStateFor(int phase, int parties) {
278	<	long lp = (long)parties;
279	<	return (((long)phase) << 32) | (lp << 16) | lp;
278	>	long lp = (long) parties;
279	>	return (((long) phase) << 32) | (lp << 16) | lp;
280		}
281
282		/**
283	<	* Returns message string for bad bounds exceptions
283	>	* Returns message string for bad bounds exceptions.
284		*/
285		private static String badBounds(int parties, int unarrived) {
286		return ("Attempt to set " + unarrived +
#	Line 251 | Line 293 | public class Phaser {
293		private final Phaser parent;
294
295		/**
296	<	* The root of Phaser tree. Equals this if not in a tree.  Used to
296	>	* The root of phaser tree. Equals this if not in a tree.  Used to
297		* support faster state push-down.
298		*/
299		private final Phaser root;
#	Line 267 | Line 309 | public class Phaser {
309		private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
310
311		private AtomicReference<QNode> queueFor(int phase) {
312	<	return (phase & 1) == 0? evenQ : oddQ;
312	>	return ((phase & 1) == 0) ? evenQ : oddQ;
313		}
314
315		/**
#	Line 275 | Line 317 | public class Phaser {
317		* root if necessary.
318		*/
319		private long getReconciledState() {
320	<	return parent == null? state : reconcileState();
320	>	return (parent == null) ? state : reconcileState();
321		}
322
323		/**
#	Line 302 | Line 344 | public class Phaser {
344		}
345
346		/**
347	<	* Creates a new Phaser without any initially registered parties,
347	>	* Creates a new phaser without any initially registered parties,
348		* initial phase number 0, and no parent. Any thread using this
349	<	* Phaser will need to first register for it.
349	>	* phaser will need to first register for it.
350		*/
351		public Phaser() {
352		this(null);
353		}
354
355		/**
356	<	* Creates a new Phaser with the given numbers of registered
356	>	* Creates a new phaser with the given numbers of registered
357		* unarrived parties, initial phase number 0, and no parent.
358	<	* @param parties the number of parties required to trip barrier.
358	>	*
359	>	* @param parties the number of parties required to trip barrier
360		* @throws IllegalArgumentException if parties less than zero
361	<	* or greater than the maximum number of parties supported.
361	>	* or greater than the maximum number of parties supported
362		*/
363		public Phaser(int parties) {
364		this(null, parties);
365		}
366
367		/**
368	<	* Creates a new Phaser with the given parent, without any
368	>	* Creates a new phaser with the given parent, without any
369		* initially registered parties. If parent is non-null this phaser
370		* is registered with the parent and its initial phase number is
371		* the same as that of parent phaser.
372	<	* @param parent the parent phaser.
372	>	*
373	>	* @param parent the parent phaser
374		*/
375		public Phaser(Phaser parent) {
376		int phase = 0;
#	Line 341 | Line 385 | public class Phaser {
385		}
386
387		/**
388	<	* Creates a new Phaser with the given parent and numbers of
389	<	* registered unarrived parties. If parent is non-null this phaser
388	>	* Creates a new phaser with the given parent and numbers of
389	>	* registered unarrived parties. If parent is non-null, this phaser
390		* is registered with the parent and its initial phase number is
391		* the same as that of parent phaser.
392	<	* @param parent the parent phaser.
393	<	* @param parties the number of parties required to trip barrier.
392	>	*
393	>	* @param parent the parent phaser
394	>	* @param parties the number of parties required to trip barrier
395		* @throws IllegalArgumentException if parties less than zero
396	<	* or greater than the maximum number of parties supported.
396	>	* or greater than the maximum number of parties supported
397		*/
398		public Phaser(Phaser parent, int parties) {
399		if (parties < 0 || parties > ushortMask)
#	Line 366 | Line 411 | public class Phaser {
411
412		/**
413		* Adds a new unarrived party to this phaser.
414	<	* @return the current barrier phase number upon registration
414	>	*
415	>	* @return the arrival phase number to which this registration applied
416		* @throws IllegalStateException if attempting to register more
417	<	* than the maximum supported number of parties.
417	>	* than the maximum supported number of parties
418		*/
419		public int register() {
420		return doRegister(1);
#	Line 376 | Line 422 | public class Phaser {
422
423		/**
424		* Adds the given number of new unarrived parties to this phaser.
425	<	* @param parties the number of parties required to trip barrier.
426	<	* @return the current barrier phase number upon registration
425	>	*
426	>	* @param parties the number of parties required to trip barrier
427	>	* @return the arrival phase number to which this registration applied
428		* @throws IllegalStateException if attempting to register more
429	<	* than the maximum supported number of parties.
429	>	* than the maximum supported number of parties
430		*/
431		public int bulkRegister(int parties) {
432		if (parties < 0)
#	Line 399 | Line 446 | public class Phaser {
446		phase = phaseOf(s);
447		int unarrived = unarrivedOf(s) + registrations;
448		int parties = partiesOf(s) + registrations;
449	<	if (phase < 0)
449	>	if (phase < 0)
450		break;
451		if (parties > ushortMask || unarrived > ushortMask)
452		throw new IllegalStateException(badBounds(parties, unarrived));
#	Line 412 | Line 459 | public class Phaser {
459
460		/**
461		* Arrives at the barrier, but does not wait for others.  (You can
462	<	* in turn wait for others via {@link #awaitAdvance}).
462	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
463	>	* unenforced usage error for an unregistered party to invoke this
464	>	* method.
465		*
466	<	* @return the barrier phase number upon entry to this method, or a
418	<	* negative value if terminated;
466	>	* @return the arrival phase number, or a negative value if terminated
467		* @throws IllegalStateException if not terminated and the number
468	<	* of unarrived parties would become negative.
468	>	* of unarrived parties would become negative
469		*/
470		public int arrive() {
471		int phase;
#	Line 437 | Line 485 | public class Phaser {
485		if (par == null) {      // directly trip
486		if (casState
487		(s,
488	<	trippedStateFor(onAdvance(phase, parties)? -1 :
488	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
489		((phase + 1) & phaseMask), parties))) {
490		releaseWaiters(phase);
491		break;
#	Line 460 | Line 508 | public class Phaser {
508		}
509
510		/**
511	<	* Arrives at the barrier, and deregisters from it, without
512	<	* waiting for others. Deregistration reduces number of parties
511	>	* Arrives at the barrier and deregisters from it without waiting
512	>	* for others. Deregistration reduces the number of parties
513		* required to trip the barrier in future phases.  If this phaser
514		* has a parent, and deregistration causes this phaser to have
515	<	* zero parties, this phaser is also deregistered from its parent.
515	>	* zero parties, this phaser also arrives at and is deregistered
516	>	* from its parent.  It is an unenforced usage error for an
517	>	* unregistered party to invoke this method.
518		*
519	<	* @return the current barrier phase number upon entry to
470	<	* this method, or a negative value if terminated;
519	>	* @return the arrival phase number, or a negative value if terminated
520		* @throws IllegalStateException if not terminated and the number
521	<	* of registered or unarrived parties would become negative.
521	>	* of registered or unarrived parties would become negative
522		*/
523		public int arriveAndDeregister() {
524		// similar code to arrive, but too different to merge
#	Line 498 | Line 547 | public class Phaser {
547		if (unarrived == 0) {
548		if (casState
549		(s,
550	<	trippedStateFor(onAdvance(phase, parties)? -1 :
550	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
551		((phase + 1) & phaseMask), parties))) {
552		releaseWaiters(phase);
553		break;
#	Line 517 | Line 566 | public class Phaser {
566
567		/**
568		* Arrives at the barrier and awaits others. Equivalent in effect
569	<	* to {@code awaitAdvance(arrive())}.  If you instead need to
570	<	* await with interruption of timeout, and/or deregister upon
571	<	* arrival, you can arrange them using analogous constructions.
572	<	* @return the phase on entry to this method
569	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
570	>	* interruption or timeout, you can arrange this with an analogous
571	>	* construction using one of the other forms of the awaitAdvance
572	>	* method.  If instead you need to deregister upon arrival use
573	>	* {@code arriveAndDeregister}. It is an unenforced usage error
574	>	* for an unregistered party to invoke this method.
575	>	*
576	>	* @return the arrival phase number, or a negative number if terminated
577		* @throws IllegalStateException if not terminated and the number
578	<	* of unarrived parties would become negative.
578	>	* of unarrived parties would become negative
579		*/
580		public int arriveAndAwaitAdvance() {
581		return awaitAdvance(arrive());
582		}
583
584		/**
585	<	* Awaits the phase of the barrier to advance from the given
586	<	* value, or returns immediately if argument is negative or this
587	<	* barrier is terminated.
588	<	* @param phase the phase on entry to this method
589	<	* @return the phase on exit from this method
585	>	* Awaits the phase of the barrier to advance from the given phase
586	>	* value, returning immediately if the current phase of the
587	>	* barrier is not equal to the given phase value or this barrier
588	>	* is terminated.  It is an unenforced usage error for an
589	>	* unregistered party to invoke this method.
590	>	*
591	>	* @param phase an arrival phase number, or negative value if
592	>	* terminated; this argument is normally the value returned by a
593	>	* previous call to {@code arrive} or its variants
594	>	* @return the next arrival phase number, or a negative value
595	>	* if terminated or argument is negative
596		*/
597		public int awaitAdvance(int phase) {
598		if (phase < 0)
#	Line 549 | Line 608 | public class Phaser {
608		}
609
610		/**
611	<	* Awaits the phase of the barrier to advance from the given
612	<	* value, or returns immediately if argument is negative or this
613	<	* barrier is terminated, or throws InterruptedException if
614	<	* interrupted while waiting.
615	<	* @param phase the phase on entry to this method
616	<	* @return the phase on exit from this method
611	>	* Awaits the phase of the barrier to advance from the given phase
612	>	* value, throwing {@code InterruptedException} if interrupted
613	>	* while waiting, or returning immediately if the current phase of
614	>	* the barrier is not equal to the given phase value or this
615	>	* barrier is terminated. It is an unenforced usage error for an
616	>	* unregistered party to invoke this method.
617	>	*
618	>	* @param phase an arrival phase number, or negative value if
619	>	* terminated; this argument is normally the value returned by a
620	>	* previous call to {@code arrive} or its variants
621	>	* @return the next arrival phase number, or a negative value
622	>	* if terminated or argument is negative
623		* @throws InterruptedException if thread interrupted while waiting
624		*/
625	<	public int awaitAdvanceInterruptibly(int phase)
625	>	public int awaitAdvanceInterruptibly(int phase)
626		throws InterruptedException {
627		if (phase < 0)
628		return phase;
#	Line 571 | Line 636 | public class Phaser {
636		}
637
638		/**
639	<	* Awaits the phase of the barrier to advance from the given value
640	<	* or the given timeout elapses, or returns immediately if
641	<	* argument is negative or this barrier is terminated.
642	<	* @param phase the phase on entry to this method
643	<	* @return the phase on exit from this method
639	>	* Awaits the phase of the barrier to advance from the given phase
640	>	* value or the given timeout to elapse, throwing {@code
641	>	* InterruptedException} if interrupted while waiting, or
642	>	* returning immediately if the current phase of the barrier is
643	>	* not equal to the given phase value or this barrier is
644	>	* terminated.  It is an unenforced usage error for an
645	>	* unregistered party to invoke this method.
646	>	*
647	>	* @param phase an arrival phase number, or negative value if
648	>	* terminated; this argument is normally the value returned by a
649	>	* previous call to {@code arrive} or its variants
650	>	* @param timeout how long to wait before giving up, in units of
651	>	*        {@code unit}
652	>	* @param unit a {@code TimeUnit} determining how to interpret the
653	>	*        {@code timeout} parameter
654	>	* @return the next arrival phase number, or a negative value
655	>	* if terminated or argument is negative
656		* @throws InterruptedException if thread interrupted while waiting
657		* @throws TimeoutException if timed out while waiting
658		*/
659	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
659	>	public int awaitAdvanceInterruptibly(int phase,
660	>	long timeout, TimeUnit unit)
661		throws InterruptedException, TimeoutException {
662		if (phase < 0)
663		return phase;
#	Line 620 | Line 698 | public class Phaser {
698		* Returns the current phase number. The maximum phase number is
699		* {@code Integer.MAX_VALUE}, after which it restarts at
700		* zero. Upon termination, the phase number is negative.
701	+	*
702		* @return the phase number, or a negative value if terminated
703		*/
704		public final int getPhase() {
#	Line 627 | Line 706 | public class Phaser {
706		}
707
708		/**
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	–	/**
709		* Returns the number of parties registered at this barrier.
710	+	*
711		* @return the number of parties
712		*/
713		public int getRegisteredParties() {
#	Line 644 | Line 715 | public class Phaser {
715		}
716
717		/**
718	<	* Returns the number of parties that have arrived at the current
719	<	* phase of this barrier.
718	>	* Returns the number of registered parties that have arrived at
719	>	* the current phase of this barrier.
720	>	*
721		* @return the number of arrived parties
722		*/
723		public int getArrivedParties() {
#	Line 655 | Line 727 | public class Phaser {
727		/**
728		* Returns the number of registered parties that have not yet
729		* arrived at the current phase of this barrier.
730	+	*
731		* @return the number of unarrived parties
732		*/
733		public int getUnarrivedParties() {
#	Line 662 | Line 735 | public class Phaser {
735		}
736
737		/**
738	<	* Returns the parent of this phaser, or null if none.
739	<	* @return the parent of this phaser, or null if none
738	>	* Returns the parent of this phaser, or {@code null} if none.
739	>	*
740	>	* @return the parent of this phaser, or {@code null} if none
741		*/
742		public Phaser getParent() {
743		return parent;
#	Line 672 | Line 746 | public class Phaser {
746		/**
747		* Returns the root ancestor of this phaser, which is the same as
748		* this phaser if it has no parent.
749	+	*
750		* @return the root ancestor of this phaser
751		*/
752		public Phaser getRoot() {
#	Line 680 | Line 755 | public class Phaser {
755
756		/**
757		* Returns {@code true} if this barrier has been terminated.
758	+	*
759		* @return {@code true} if this barrier has been terminated
760		*/
761		public boolean isTerminated() {
#	Line 690 | Line 766 | public class Phaser {
766		* Overridable method to perform an action upon phase advance, and
767		* to control termination. This method is invoked whenever the
768		* barrier is tripped (and thus all other waiting parties are
769	<	* dormant). If it returns true, then, rather than advance the
770	<	* phase number, this barrier will be set to a final termination
771	<	* state, and subsequent calls to {@code isTerminated} will
772	<	* return true.
769	>	* dormant). If it returns {@code true}, then, rather than advance
770	>	* the phase number, this barrier will be set to a final
771	>	* termination state, and subsequent calls to {@link #isTerminated}
772	>	* will return true.
773		*
774	<	* <p> The default version returns true when the number of
774	>	* <p>The default version returns {@code true} when the number of
775		* registered parties is zero. Normally, overrides that arrange
776		* termination for other reasons should also preserve this
777		* property.
778		*
779	<	* <p> You may override this method to perform an action with side
779	>	* <p>You may override this method to perform an action with side
780		* effects visible to participating tasks, but it is in general
781		* only sensible to do so in designs where all parties register
782	<	* before any arrive, and all {@code awaitAdvance} at each phase.
783	<	* Otherwise, you cannot ensure lack of interference. In
784	<	* particular, this method may be invoked more than once per
709	<	* transition if other parties successfully register while the
710	<	* invocation of this method is in progress, thus postponing the
711	<	* transition until those parties also arrive, re-triggering this
712	<	* method.
782	>	* before any arrive, and all {@link #awaitAdvance} at each phase.
783	>	* Otherwise, you cannot ensure lack of interference from other
784	>	* parties during the invocation of this method.
785		*
786		* @param phase the phase number on entering the barrier
787		* @param registeredParties the current number of registered parties
#	Line 795 | Line 867 | public class Phaser {
867		try {
868		ForkJoinPool.managedBlock(this, false);
869		} catch (InterruptedException ie) {
870	<	}
870	>	}
871		}
872		return wasInterrupted;
873		}
#	Line 803 | Line 875 | public class Phaser {
875		}
876
877		/**
878	<	* Removes and signals waiting threads from wait queue
878	>	* Removes and signals waiting threads from wait queue.
879		*/
880		private void releaseWaiters(int phase) {
881		AtomicReference<QNode> head = queueFor(phase);
#	Line 815 | Line 887 | public class Phaser {
887		}
888
889		/**
890	<	* Tries to enqueue given node in the appropriate wait queue
890	>	* Tries to enqueue given node in the appropriate wait queue.
891	>	*
892		* @return true if successful
893		*/
894		private boolean tryEnqueue(QNode node) {
#	Line 825 | Line 898 | public class Phaser {
898
899		/**
900		* Enqueues node and waits unless aborted or signalled.
901	+	*
902		* @return current phase
903		*/
904		private int untimedWait(int phase) {
#	Line 912 | Line 986 | public class Phaser {
986		return p;
987		}
988
989	<	// Temporary Unsafe mechanics for preliminary release
989	>	// Unsafe mechanics
990
991	<	static final Unsafe _unsafe;
992	<	static final long stateOffset;
991	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
992	>	private static final long stateOffset =
993	>	objectFieldOffset("state", Phaser.class);
994
995	<	static {
995	>	private final boolean casState(long cmp, long val) {
996	>	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
997	>	}
998	>
999	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1000		try {
1001	<	if (Phaser.class.getClassLoader() != null) {
1002	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1003	<	f.setAccessible(true);
1004	<	_unsafe = (Unsafe)f.get(null);
1005	<	}
1006	<	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);
1001	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1002	>	} catch (NoSuchFieldException e) {
1003	>	// Convert Exception to corresponding Error
1004	>	NoSuchFieldError error = new NoSuchFieldError(field);
1005	>	error.initCause(e);
1006	>	throw error;
1007		}
1008		}
1009
1010	<	final boolean casState(long cmp, long val) {
1011	<	return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val);
1010	>	/**
1011	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1012	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1013	>	* into a jdk.
1014	>	*
1015	>	* @return a sun.misc.Unsafe
1016	>	*/
1017	>	private static sun.misc.Unsafe getUnsafe() {
1018	>	try {
1019	>	return sun.misc.Unsafe.getUnsafe();
1020	>	} catch (SecurityException se) {
1021	>	try {
1022	>	return java.security.AccessController.doPrivileged
1023	>	(new java.security
1024	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1025	>	public sun.misc.Unsafe run() throws Exception {
1026	>	java.lang.reflect.Field f = sun.misc
1027	>	.Unsafe.class.getDeclaredField("theUnsafe");
1028	>	f.setAccessible(true);
1029	>	return (sun.misc.Unsafe) f.get(null);
1030	>	}});
1031	>	} catch (java.security.PrivilegedActionException e) {
1032	>	throw new RuntimeException("Could not initialize intrinsics",
1033	>	e.getCause());
1034	>	}
1035	>	}
1036		}
1037		}

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