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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.16 by jsr166, Wed Jul 22 01:36:51 2009 UTC vs.
Revision 1.46 by dl, Sun Aug 30 11:08:25 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.  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:
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
113	>	* parties. The typical idiom is for the method setting this up to
114	>	* first register, then start the actions, then deregister, as in:
115		*
116		*  <pre> {@code
117	<	* void runTasks(List<Runnable> list) {
117	>	* void runTasks(List<Runnable> tasks) {
118		*   final Phaser phaser = new Phaser(1); // "1" to register self
119	<	*   for (Runnable r : list) {
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	<	*         r.run();
105	<	*         phaser.arriveAndDeregister();   // signal completion
125	>	*         task.run();
126		*       }
127		*     }.start();
128		*   }
129		*
130	<	*   doSomethingOnBehalfOfWorkers();
131	<	*   phaser.arrive(); // allow threads to start
112	<	*   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
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> {@code
138	<	* void startTasks(List<Runnable> list, final int iterations) {
138	>	* void startTasks(List<Runnable> tasks, final int iterations) {
139		*   final Phaser phaser = new Phaser() {
140	<	*     public boolean onAdvance(int phase, int registeredParties) {
140	>	*     protected boolean onAdvance(int phase, int registeredParties) {
141		*       return phase >= iterations || registeredParties == 0;
142		*     }
143		*   };
144		*   phaser.register();
145	<	*   for (Runnable r : list) {
145	>	*   for (final Runnable task : tasks) {
146		*     phaser.register();
147		*     new Thread() {
148		*       public void run() {
149		*         do {
150	<	*           r.run();
150	>	*           task.run();
151		*           phaser.arriveAndAwaitAdvance();
152	<	*         } while(!phaser.isTerminated();
152	>	*         } while (!phaser.isTerminated());
153		*       }
154		*     }.start();
155		*   }
156		*   phaser.arriveAndDeregister(); // deregister self, don't wait
157		* }}</pre>
158		*
159	<	* <p> To create a set of tasks using a tree of Phasers,
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,
185		* you could use code of the following form, assuming a
186	<	* Task class with a constructor accepting a Phaser that
186	>	* Task class with a constructor accepting a phaser that
187		* it registers for upon construction:
188	+	*
189		*  <pre> {@code
190	<	* void build(Task[] actions, int lo, int hi, Phaser b) {
191	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
192	<	*   if (step > 1) {
193	<	*     int i = lo;
194	<	*     while (i < hi) {
153	<	*       int r = Math.min(i + step, hi);
154	<	*       build(actions, i, r, new Phaser(b));
155	<	*       i = r;
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(b);
199	<	*       // assumes new Task(b) performs b.register()
198	>	*       actions[i] = new Task(ph);
199	>	*       // assumes new Task(ph) performs ph.register()
200		*   }
201		* }
202		* // .. initially called, for n tasks via
#	Line 172 | Line 211 | import java.lang.reflect.*;
211		*
212		* <p><b>Implementation notes</b>: This implementation restricts the
213		* maximum number of parties to 65535. Attempts to register additional
214	<	* parties result in IllegalStateExceptions. However, you can and
214	>	* parties result in {@code IllegalStateException}. However, you can and
215		* should create tiered phasers to accommodate arbitrarily large sets
216		* of participants.
217		*
#	Line 206 | Line 245 | public class Phaser {
245		*/
246		private volatile long state;
247
209	–	private static final int ushortBits = 16;
248		private static final int ushortMask = 0xffff;
249		private static final int phaseMask  = 0x7fffffff;
250
251		private static int unarrivedOf(long s) {
252	<	return (int)(s & ushortMask);
252	>	return (int) (s & ushortMask);
253		}
254
255		private static int partiesOf(long s) {
256	<	return ((int)s) >>> 16;
256	>	return ((int) s) >>> 16;
257		}
258
259		private static int phaseOf(long s) {
260	<	return (int)(s >>> 32);
260	>	return (int) (s >>> 32);
261		}
262
263		private static int arrivedOf(long s) {
#	Line 227 | Line 265 | public class Phaser {
265		}
266
267		private static long stateFor(int phase, int parties, int unarrived) {
268	<	return ((((long)phase) << 32) | (((long)parties) << 16) |
269	<	(long)unarrived);
268	>	return ((((long) phase) << 32) | (((long) parties) << 16) |
269	>	(long) unarrived);
270		}
271
272		private static long trippedStateFor(int phase, int parties) {
273	<	long lp = (long)parties;
274	<	return (((long)phase) << 32) | (lp << 16) | lp;
273	>	long lp = (long) parties;
274	>	return (((long) phase) << 32) | (lp << 16) | lp;
275		}
276
277		/**
#	Line 250 | Line 288 | public class Phaser {
288		private final Phaser parent;
289
290		/**
291	<	* The root of Phaser tree. Equals this if not in a tree.  Used to
291	>	* The root of phaser tree. Equals this if not in a tree.  Used to
292		* support faster state push-down.
293		*/
294		private final Phaser root;
#	Line 266 | Line 304 | public class Phaser {
304		private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
305
306		private AtomicReference<QNode> queueFor(int phase) {
307	<	return (phase & 1) == 0? evenQ : oddQ;
307	>	return ((phase & 1) == 0) ? evenQ : oddQ;
308		}
309
310		/**
#	Line 274 | Line 312 | public class Phaser {
312		* root if necessary.
313		*/
314		private long getReconciledState() {
315	<	return parent == null? state : reconcileState();
315	>	return (parent == null) ? state : reconcileState();
316		}
317
318		/**
#	Line 301 | Line 339 | public class Phaser {
339		}
340
341		/**
342	<	* Creates a new Phaser without any initially registered parties,
342	>	* Creates a new phaser without any initially registered parties,
343		* initial phase number 0, and no parent. Any thread using this
344	<	* Phaser will need to first register for it.
344	>	* phaser will need to first register for it.
345		*/
346		public Phaser() {
347		this(null);
348		}
349
350		/**
351	<	* Creates a new Phaser with the given numbers of registered
351	>	* Creates a new phaser with the given numbers of registered
352		* unarrived parties, initial phase number 0, and no parent.
353		*
354		* @param parties the number of parties required to trip barrier
#	Line 322 | Line 360 | public class Phaser {
360		}
361
362		/**
363	<	* Creates a new Phaser with the given parent, without any
363	>	* Creates a new phaser with the given parent, without any
364		* initially registered parties. If parent is non-null this phaser
365		* is registered with the parent and its initial phase number is
366		* the same as that of parent phaser.
#	Line 342 | Line 380 | public class Phaser {
380		}
381
382		/**
383	<	* Creates a new Phaser with the given parent and numbers of
383	>	* Creates a new phaser with the given parent and numbers of
384		* registered unarrived parties. If parent is non-null, this phaser
385		* is registered with the parent and its initial phase number is
386		* the same as that of parent phaser.
#	Line 369 | Line 407 | public class Phaser {
407		/**
408		* Adds a new unarrived party to this phaser.
409		*
410	<	* @return the current barrier phase number upon registration
410	>	* @return the arrival phase number to which this registration applied
411		* @throws IllegalStateException if attempting to register more
412		* than the maximum supported number of parties
413		*/
#	Line 381 | Line 419 | public class Phaser {
419		* Adds the given number of new unarrived parties to this phaser.
420		*
421		* @param parties the number of parties required to trip barrier
422	<	* @return the current barrier phase number upon registration
422	>	* @return the arrival phase number to which this registration applied
423		* @throws IllegalStateException if attempting to register more
424		* than the maximum supported number of parties
425		*/
#	Line 416 | Line 454 | public class Phaser {
454
455		/**
456		* Arrives at the barrier, but does not wait for others.  (You can
457	<	* in turn wait for others via {@link #awaitAdvance}).
457	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
458	>	* unenforced usage error for an unregistered party to invoke this
459	>	* method.
460		*
461	<	* @return the barrier phase number upon entry to this method, or a
422	<	* negative value if terminated
461	>	* @return the arrival phase number, or a negative value if terminated
462		* @throws IllegalStateException if not terminated and the number
463		* of unarrived parties would become negative
464		*/
#	Line 441 | Line 480 | public class Phaser {
480		if (par == null) {      // directly trip
481		if (casState
482		(s,
483	<	trippedStateFor(onAdvance(phase, parties)? -1 :
483	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
484		((phase + 1) & phaseMask), parties))) {
485		releaseWaiters(phase);
486		break;
#	Line 464 | Line 503 | public class Phaser {
503		}
504
505		/**
506	<	* Arrives at the barrier, and deregisters from it, without
507	<	* waiting for others. Deregistration reduces number of parties
506	>	* Arrives at the barrier and deregisters from it without waiting
507	>	* for others. Deregistration reduces the number of parties
508		* required to trip the barrier in future phases.  If this phaser
509		* has a parent, and deregistration causes this phaser to have
510	<	* zero parties, this phaser is also deregistered from its parent.
510	>	* zero parties, this phaser also arrives at and is deregistered
511	>	* from its parent.  It is an unenforced usage error for an
512	>	* unregistered party to invoke this method.
513		*
514	<	* @return the current barrier phase number upon entry to
474	<	* this method, or a negative value if terminated
514	>	* @return the arrival phase number, or a negative value if terminated
515		* @throws IllegalStateException if not terminated and the number
516		* of registered or unarrived parties would become negative
517		*/
#	Line 502 | Line 542 | public class Phaser {
542		if (unarrived == 0) {
543		if (casState
544		(s,
545	<	trippedStateFor(onAdvance(phase, parties)? -1 :
545	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
546		((phase + 1) & phaseMask), parties))) {
547		releaseWaiters(phase);
548		break;
#	Line 521 | Line 561 | public class Phaser {
561
562		/**
563		* Arrives at the barrier and awaits others. Equivalent in effect
564	<	* to {@code awaitAdvance(arrive())}.  If you instead need to
565	<	* await with interruption of timeout, and/or deregister upon
566	<	* arrival, you can arrange them using analogous constructions.
564	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
565	>	* interruption or timeout, you can arrange this with an analogous
566	>	* construction using one of the other forms of the awaitAdvance
567	>	* method.  If instead you need to deregister upon arrival use
568	>	* {@code arriveAndDeregister}. It is an unenforced usage error
569	>	* for an unregistered party to invoke this method.
570		*
571	<	* @return the phase on entry to this method
571	>	* @return the arrival phase number, or a negative number if terminated
572		* @throws IllegalStateException if not terminated and the number
573		* of unarrived parties would become negative
574		*/
#	Line 534 | Line 577 | public class Phaser {
577		}
578
579		/**
580	<	* Awaits the phase of the barrier to advance from the given
581	<	* value, or returns immediately if argument is negative or this
582	<	* barrier is terminated.
583	<	*
584	<	* @param phase the phase on entry to this method
585	<	* @return the phase on exit from this method
580	>	* Awaits the phase of the barrier to advance from the given phase
581	>	* value, returning immediately if the current phase of the
582	>	* barrier is not equal to the given phase value or this barrier
583	>	* is terminated.  It is an unenforced usage error for an
584	>	* unregistered party to invoke this method.
585	>	*
586	>	* @param phase an arrival phase number, or negative value if
587	>	* terminated; this argument is normally the value returned by a
588	>	* previous call to {@code arrive} or its variants
589	>	* @return the next arrival phase number, or a negative value
590	>	* if terminated or argument is negative
591		*/
592		public int awaitAdvance(int phase) {
593		if (phase < 0)
#	Line 555 | Line 603 | public class Phaser {
603		}
604
605		/**
606	<	* Awaits the phase of the barrier to advance from the given
607	<	* value, or returns immediately if argument is negative or this
608	<	* barrier is terminated, or throws InterruptedException if
609	<	* interrupted while waiting.
610	<	*
611	<	* @param phase the phase on entry to this method
612	<	* @return the phase on exit from this method
606	>	* Awaits the phase of the barrier to advance from the given phase
607	>	* value, throwing {@code InterruptedException} if interrupted
608	>	* while waiting, or returning immediately if the current phase of
609	>	* the barrier is not equal to the given phase value or this
610	>	* barrier is terminated. It is an unenforced usage error for an
611	>	* unregistered party to invoke this method.
612	>	*
613	>	* @param phase an arrival phase number, or negative value if
614	>	* terminated; this argument is normally the value returned by a
615	>	* previous call to {@code arrive} or its variants
616	>	* @return the next arrival phase number, or a negative value
617	>	* if terminated or argument is negative
618		* @throws InterruptedException if thread interrupted while waiting
619		*/
620		public int awaitAdvanceInterruptibly(int phase)
#	Line 578 | Line 631 | public class Phaser {
631		}
632
633		/**
634	<	* Awaits the phase of the barrier to advance from the given value
635	<	* or the given timeout elapses, or returns immediately if
636	<	* argument is negative or this barrier is terminated.
637	<	*
638	<	* @param phase the phase on entry to this method
639	<	* @return the phase on exit from this method
634	>	* Awaits the phase of the barrier to advance from the given phase
635	>	* value or the given timeout to elapse, throwing {@code
636	>	* InterruptedException} if interrupted while waiting, or
637	>	* returning immediately if the current phase of the barrier is
638	>	* not equal to the given phase value or this barrier is
639	>	* terminated.  It is an unenforced usage error for an
640	>	* unregistered party to invoke this method.
641	>	*
642	>	* @param phase an arrival phase number, or negative value if
643	>	* terminated; this argument is normally the value returned by a
644	>	* previous call to {@code arrive} or its variants
645	>	* @param timeout how long to wait before giving up, in units of
646	>	*        {@code unit}
647	>	* @param unit a {@code TimeUnit} determining how to interpret the
648	>	*        {@code timeout} parameter
649	>	* @return the next arrival phase number, or a negative value
650	>	* if terminated or argument is negative
651		* @throws InterruptedException if thread interrupted while waiting
652		* @throws TimeoutException if timed out while waiting
653		*/
654	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
654	>	public int awaitAdvanceInterruptibly(int phase,
655	>	long timeout, TimeUnit unit)
656		throws InterruptedException, TimeoutException {
657		if (phase < 0)
658		return phase;
#	Line 636 | Line 701 | public class Phaser {
701		}
702
703		/**
639	–	* Returns {@code true} if the current phase number equals the given phase.
640	–	*
641	–	* @param phase the phase
642	–	* @return {@code true} if the current phase number equals the given phase
643	–	*/
644	–	public final boolean hasPhase(int phase) {
645	–	return phaseOf(getReconciledState()) == phase;
646	–	}
647	–
648	–	/**
704		* Returns the number of parties registered at this barrier.
705		*
706		* @return the number of parties
#	Line 655 | Line 710 | public class Phaser {
710		}
711
712		/**
713	<	* Returns the number of parties that have arrived at the current
714	<	* phase of this barrier.
713	>	* Returns the number of registered parties that have arrived at
714	>	* the current phase of this barrier.
715		*
716		* @return the number of arrived parties
717		*/
#	Line 675 | Line 730 | public class Phaser {
730		}
731
732		/**
733	<	* Returns the parent of this phaser, or null if none.
733	>	* Returns the parent of this phaser, or {@code null} if none.
734		*
735	<	* @return the parent of this phaser, or null if none
735	>	* @return the parent of this phaser, or {@code null} if none
736		*/
737		public Phaser getParent() {
738		return parent;
#	Line 703 | Line 758 | public class Phaser {
758		}
759
760		/**
761	<	* Overridable method to perform an action upon phase advance, and
762	<	* to control termination. This method is invoked whenever the
763	<	* barrier is tripped (and thus all other waiting parties are
764	<	* dormant). If it returns true, then, rather than advance the
765	<	* phase number, this barrier will be set to a final termination
766	<	* state, and subsequent calls to {@code isTerminated} will
767	<	* return true.
761	>	* Overridable method to perform an action upon impending phase
762	>	* advance, and to control termination. This method is invoked
763	>	* upon arrival of the party tripping the barrier (when all other
764	>	* waiting parties are dormant).  If this method returns {@code
765	>	* true}, then, rather than advance the phase number, this barrier
766	>	* will be set to a final termination state, and subsequent calls
767	>	* to {@link #isTerminated} will return true. Any (unchecked)
768	>	* Exception or Error thrown by an invocation of this method is
769	>	* propagated to the party attempting to trip the barrier, in
770	>	* which case no advance occurs.
771	>	*
772	>	* <p>The arguments to this method provide the state of the phaser
773	>	* prevailing for the current transition. (When called from within
774	>	* an implementation of {@code onAdvance} the values returned by
775	>	* methods such as {@code getPhase} may or may not reliably
776	>	* indicate the state to which this transition applies.)
777		*
778	<	* <p> The default version returns true when the number of
778	>	* <p>The default version returns {@code true} when the number of
779		* registered parties is zero. Normally, overrides that arrange
780		* termination for other reasons should also preserve this
781		* property.
782		*
783	<	* <p> You may override this method to perform an action with side
784	<	* effects visible to participating tasks, but it is in general
785	<	* only sensible to do so in designs where all parties register
786	<	* before any arrive, and all {@code awaitAdvance} at each phase.
787	<	* Otherwise, you cannot ensure lack of interference. In
788	<	* particular, this method may be invoked more than once per
789	<	* transition if other parties successfully register while the
790	<	* invocation of this method is in progress, thus postponing the
727	<	* transition until those parties also arrive, re-triggering this
728	<	* method.
783	>	* <p>You may override this method to perform an action with side
784	>	* effects visible to participating tasks, but it is only sensible
785	>	* to do so in designs where all parties register before any
786	>	* arrive, and all {@link #awaitAdvance} at each phase.
787	>	* Otherwise, you cannot ensure lack of interference from other
788	>	* parties during the invocation of this method. Additionally,
789	>	* method {@code onAdvance} may be invoked more than once per
790	>	* transition if registrations are intermixed with arrivals.
791		*
792		* @param phase the phase number on entering the barrier
793		* @param registeredParties the current number of registered parties
#	Line 930 | Line 992 | public class Phaser {
992		return p;
993		}
994
995	<	// Temporary Unsafe mechanics for preliminary release
934	<	private static Unsafe getUnsafe() throws Throwable {
935	<	try {
936	<	return Unsafe.getUnsafe();
937	<	} catch (SecurityException se) {
938	<	try {
939	<	return java.security.AccessController.doPrivileged
940	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
941	<	public Unsafe run() throws Exception {
942	<	return getUnsafePrivileged();
943	<	}});
944	<	} catch (java.security.PrivilegedActionException e) {
945	<	throw e.getCause();
946	<	}
947	<	}
948	<	}
995	>	// Unsafe mechanics
996
997	<	private static Unsafe getUnsafePrivileged()
998	<	throws NoSuchFieldException, IllegalAccessException {
999	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
953	<	f.setAccessible(true);
954	<	return (Unsafe) f.get(null);
955	<	}
997	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
998	>	private static final long stateOffset =
999	>	objectFieldOffset("state", Phaser.class);
1000
1001	<	private static long fieldOffset(String fieldName)
1002	<	throws NoSuchFieldException {
959	<	return UNSAFE.objectFieldOffset
960	<	(Phaser.class.getDeclaredField(fieldName));
1001	>	private final boolean casState(long cmp, long val) {
1002	>	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
1003		}
1004
1005	<	static final Unsafe UNSAFE;
964	<	static final long stateOffset;
965	<
966	<	static {
1005	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1006		try {
1007	<	UNSAFE = getUnsafe();
1008	<	stateOffset = fieldOffset("state");
1009	<	} catch (Throwable e) {
1010	<	throw new RuntimeException("Could not initialize intrinsics", e);
1007	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1008	>	} catch (NoSuchFieldException e) {
1009	>	// Convert Exception to corresponding Error
1010	>	NoSuchFieldError error = new NoSuchFieldError(field);
1011	>	error.initCause(e);
1012	>	throw error;
1013		}
1014		}
1015
1016	<	final boolean casState(long cmp, long val) {
1017	<	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
1016	>	/**
1017	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1018	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1019	>	* into a jdk.
1020	>	*
1021	>	* @return a sun.misc.Unsafe
1022	>	*/
1023	>	private static sun.misc.Unsafe getUnsafe() {
1024	>	try {
1025	>	return sun.misc.Unsafe.getUnsafe();
1026	>	} catch (SecurityException se) {
1027	>	try {
1028	>	return java.security.AccessController.doPrivileged
1029	>	(new java.security
1030	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1031	>	public sun.misc.Unsafe run() throws Exception {
1032	>	java.lang.reflect.Field f = sun.misc
1033	>	.Unsafe.class.getDeclaredField("theUnsafe");
1034	>	f.setAccessible(true);
1035	>	return (sun.misc.Unsafe) f.get(null);
1036	>	}});
1037	>	} catch (java.security.PrivilegedActionException e) {
1038	>	throw new RuntimeException("Could not initialize intrinsics",
1039	>	e.getCause());
1040	>	}
1041	>	}
1042		}
1043		}

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