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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.4 by dl, Sat Sep 6 13:19:17 2008 UTC vs.
Revision 1.19 by jsr166, Fri Jul 24 23:47:01 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	+
9		import java.util.concurrent.*;
10		import java.util.concurrent.atomic.*;
11		import java.util.concurrent.locks.LockSupport;
11	–	import sun.misc.Unsafe;
12	–	import java.lang.reflect.*;
12
13		/**
14		* A reusable synchronization barrier, similar in functionality to a
15	<	* {@link java.util.concurrent.CyclicBarrier} and {@link
16	<	* java.util.concurrent.CountDownLatch} but supporting more flexible
17	<	* usage.
15	>	* {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and
16	>	* {@link java.util.concurrent.CountDownLatch CountDownLatch}
17	>	* but supporting more flexible usage.
18		*
19		* <ul>
20		*
#	Line 25 | Line 24 | import java.lang.reflect.*;
24		* basic synchronization constructs, registration and deregistration
25		* affect only internal counts; they do not establish any further
26		* internal bookkeeping, so tasks cannot query whether they are
27	<	* registered. (However, you can introduce such bookkeeping in by
27	>	* registered. (However, you can introduce such bookkeeping by
28		* subclassing this class.)
29		*
30		* <li> Each generation has an associated phase value, starting at
31		* zero, and advancing when all parties reach the barrier (wrapping
32	<	* around to zero after reaching <tt>Integer.MAX_VALUE</tt>).
32	>	* around to zero after reaching {@code Integer.MAX_VALUE}).
33		*
34		* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited.
35	<	* Method <tt>arriveAndAwaitAdvance</tt> has effect analogous to
36	<	* <tt>CyclicBarrier.await</tt>.  However, Phasers separate two
35	>	* Method {@code arriveAndAwaitAdvance} has effect analogous to
36	>	* {@code CyclicBarrier.await}.  However, Phasers separate two
37		* aspects of coordination, that may also be invoked independently:
38		*
39		* <ul>
40		*
41	<	*   <li> Arriving at a barrier. Methods <tt>arrive</tt> and
42	<	*       <tt>arriveAndDeregister</tt> do not block, but return
41	>	*   <li> Arriving at a barrier. Methods {@code arrive} and
42	>	*       {@code arriveAndDeregister} do not block, but return
43		*       the phase value current upon entry to the method.
44		*
45	<	*   <li> Awaiting others. Method <tt>awaitAdvance</tt> requires an
45	>	*   <li> Awaiting others. Method {@code awaitAdvance} requires an
46		*       argument indicating the entry phase, and returns when the
47		*       barrier advances to a new phase.
48		* </ul>
#	Line 51 | Line 50 | import java.lang.reflect.*;
50		*
51		* <li> Barrier actions, performed by the task triggering a phase
52		* advance while others may be waiting, are arranged by overriding
53	<	* method <tt>onAdvance</tt>, that also controls termination.
54	<	* Overriding this method may be used to similar but more flecible
53	>	* method {@code onAdvance}, that also controls termination.
54	>	* Overriding this method may be used to similar but more flexible
55		* effect as providing a barrier action to a CyclicBarrier.
56		*
57		* <li> Phasers may enter a <em>termination</em> state in which all
58	<	* await actions immediately return, indicating (via a negative phase
59	<	* value) that execution is complete.  Termination is triggered by
60	<	* executing the overridable <tt>onAdvance</tt> method that is invoked
61	<	* each time the barrier is about to be tripped. When a Phaser is
62	<	* controlling an action with a fixed number of iterations, it is
63	<	* often convenient to override this method to cause termination when
64	<	* the current phase number reaches a threshold. Method
65	<	* <tt>forceTermination</tt> is also available to abruptly release
66	<	* waiting threads and allow them to terminate.
58	>	* actions immediately return without updating phaser state or waiting
59	>	* for advance, and indicating (via a negative phase value) that
60	>	* execution is complete.  Termination is triggered by executing the
61	>	* overridable {@code onAdvance} method that is invoked each time the
62	>	* barrier is about to be tripped. When a Phaser is controlling an
63	>	* action with a fixed number of iterations, it is often convenient to
64	>	* override this method to cause termination when the current phase
65	>	* number reaches a threshold. Method {@code forceTermination} is also
66	>	* available to abruptly release waiting threads and allow them to
67	>	* terminate.
68		*
69		* <li> Phasers may be tiered to reduce contention. Phasers with large
70		* numbers of parties that would otherwise experience heavy
#	Line 72 | Line 72 | import java.lang.reflect.*;
72		* This will typically greatly increase throughput even though it
73		* incurs somewhat greater per-operation overhead.
74		*
75	<	* <li> By default, <tt>awaitAdvance</tt> continues to wait even if
75	>	* <li> By default, {@code awaitAdvance} continues to wait even if
76		* the waiting thread is interrupted. And unlike the case in
77		* CyclicBarriers, exceptions encountered while tasks wait
78		* interruptibly or with timeout do not change the state of the
79		* barrier. If necessary, you can perform any associated recovery
80		* within handlers of those exceptions, often after invoking
81	<	* <tt>forceTermination</tt>.
81	>	* {@code forceTermination}.
82	>	*
83	>	* <li>Phasers ensure lack of starvation when used by ForkJoinTasks.
84		*
85		* </ul>
86		*
87		* <p><b>Sample usages:</b>
88		*
89	<	* <p>A Phaser may be used instead of a <tt>CountdownLatch</tt> to control
89	>	* <p>A Phaser may be used instead of a {@code CountDownLatch} to control
90		* a one-shot action serving a variable number of parties. The typical
91		* idiom is for the method setting this up to first register, then
92		* start the actions, then deregister, as in:
93		*
94	<	* <pre>
95	<	*  void runTasks(List&lt;Runnable&gt; list) {
96	<	*    final Phaser phaser = new Phaser(1); // "1" to register self
97	<	*    for (Runnable r : list) {
98	<	*      phaser.register();
99	<	*      new Thread() {
100	<	*        public void run() {
101	<	*          phaser.arriveAndAwaitAdvance(); // await all creation
102	<	*          r.run();
103	<	*          phaser.arriveAndDeregister();   // signal completion
104	<	*        }
105	<	*      }.start();
94	>	*  <pre> {@code
95	>	* void runTasks(List<Runnable> list) {
96	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
97	>	*   for (Runnable r : list) {
98	>	*     phaser.register();
99	>	*     new Thread() {
100	>	*       public void run() {
101	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
102	>	*         r.run();
103	>	*         phaser.arriveAndDeregister();   // signal completion
104	>	*       }
105	>	*     }.start();
106		*   }
107	+	*
108	+	*   doSomethingOnBehalfOfWorkers();
109		*   phaser.arrive(); // allow threads to start
110	<	*   int p = phaser.arriveAndDeregister(); // deregister self
110	>	*   int p = phaser.arriveAndDeregister(); // deregister self  ...
111	>	*   p = phaser.awaitAdvance(p); // ... and await arrival
112		*   otherActions(); // do other things while tasks execute
113	<	*   phaser.awaitAdvance(p); // wait for all tasks to arrive
114	<	* }
110	<	* </pre>
113	>	*   phaser.awaitAdvance(p); // await final completion
114	>	* }}</pre>
115		*
116		* <p>One way to cause a set of threads to repeatedly perform actions
117	<	* for a given number of iterations is to override <tt>onAdvance</tt>:
117	>	* for a given number of iterations is to override {@code onAdvance}:
118		*
119	<	* <pre>
120	<	*  void startTasks(List&lt;Runnable&gt; list, final int iterations) {
121	<	*    final Phaser phaser = new Phaser() {
122	<	*       public boolean onAdvance(int phase, int registeredParties) {
123	<	*         return phase &gt;= iterations || registeredParties == 0;
119	>	*  <pre> {@code
120	>	* void startTasks(List<Runnable> list, final int iterations) {
121	>	*   final Phaser phaser = new Phaser() {
122	>	*     public boolean onAdvance(int phase, int registeredParties) {
123	>	*       return phase >= iterations || registeredParties == 0;
124	>	*     }
125	>	*   };
126	>	*   phaser.register();
127	>	*   for (Runnable r : list) {
128	>	*     phaser.register();
129	>	*     new Thread() {
130	>	*       public void run() {
131	>	*         do {
132	>	*           r.run();
133	>	*           phaser.arriveAndAwaitAdvance();
134	>	*         } while(!phaser.isTerminated();
135		*       }
136	<	*    };
122	<	*    phaser.register();
123	<	*    for (Runnable r : list) {
124	<	*      phaser.register();
125	<	*      new Thread() {
126	<	*        public void run() {
127	<	*           do {
128	<	*             r.run();
129	<	*             phaser.arriveAndAwaitAdvance();
130	<	*           } while(!phaser.isTerminated();
131	<	*        }
132	<	*      }.start();
136	>	*     }.start();
137		*   }
138		*   phaser.arriveAndDeregister(); // deregister self, don't wait
139	<	* }
136	<	* </pre>
139	>	* }}</pre>
140		*
141		* <p> To create a set of tasks using a tree of Phasers,
142		* you could use code of the following form, assuming a
143		* Task class with a constructor accepting a Phaser that
144		* it registers for upon construction:
145	<	* <pre>
146	<	*  void build(Task[] actions, int lo, int hi, Phaser b) {
147	<	*    int step = (hi - lo) / TASKS_PER_PHASER;
148	<	*    if (step &gt; 1) {
149	<	*       int i = lo;
150	<	*       while (i &lt; hi) {
151	<	*         int r = Math.min(i + step, hi);
152	<	*         build(actions, i, r, new Phaser(b));
153	<	*         i = r;
154	<	*       }
155	<	*    }
156	<	*    else {
157	<	*      for (int i = lo; i &lt; hi; ++i)
158	<	*        actions[i] = new Task(b);
159	<	*        // assumes new Task(b) performs b.register()
160	<	*    }
161	<	*  }
162	<	*  // .. initially called, for n tasks via
160	<	*  build(new Task[n], 0, n, new Phaser());
161	<	* </pre>
145	>	*  <pre> {@code
146	>	* void build(Task[] actions, int lo, int hi, Phaser b) {
147	>	*   int step = (hi - lo) / TASKS_PER_PHASER;
148	>	*   if (step > 1) {
149	>	*     int i = lo;
150	>	*     while (i < hi) {
151	>	*       int r = Math.min(i + step, hi);
152	>	*       build(actions, i, r, new Phaser(b));
153	>	*       i = r;
154	>	*     }
155	>	*   } else {
156	>	*     for (int i = lo; i < hi; ++i)
157	>	*       actions[i] = new Task(b);
158	>	*       // assumes new Task(b) performs b.register()
159	>	*   }
160	>	* }
161	>	* // .. initially called, for n tasks via
162	>	* build(new Task[n], 0, n, new Phaser());}</pre>
163		*
164	<	* The best value of <tt>TASKS_PER_PHASER</tt> depends mainly on
164	>	* The best value of {@code TASKS_PER_PHASER} depends mainly on
165		* expected barrier synchronization rates. A value as low as four may
166		* be appropriate for extremely small per-barrier task bodies (thus
167		* high rates), or up to hundreds for extremely large ones.
#	Line 172 | Line 173 | import java.lang.reflect.*;
173		* parties result in IllegalStateExceptions. However, you can and
174		* should create tiered phasers to accommodate arbitrarily large sets
175		* of participants.
176	+	*
177	+	* @since 1.7
178	+	* @author Doug Lea
179		*/
180		public class Phaser {
181		/*
#	Line 192 | Line 196 | public class Phaser {
196		* However, to efficiently maintain atomicity, these values are
197		* packed into a single (atomic) long. Termination uses the sign
198		* bit of 32 bit representation of phase, so phase is set to -1 on
199	<	* termination. Good performace relies on keeping state decoding
199	>	* termination. Good performance relies on keeping state decoding
200		* and encoding simple, and keeping race windows short.
201		*
202		* Note: there are some cheats in arrive() that rely on unarrived
203	<	* being lowest 16 bits.
203	>	* count being lowest 16 bits.
204		*/
205		private volatile long state;
206
207		private static final int ushortBits = 16;
208	<	private static final int ushortMask =  (1 << ushortBits) - 1;
209	<	private static final int phaseMask = 0x7fffffff;
208	>	private static final int ushortMask = 0xffff;
209	>	private static final int phaseMask  = 0x7fffffff;
210
211		private static int unarrivedOf(long s) {
212	<	return (int)(s & ushortMask);
212	>	return (int) (s & ushortMask);
213		}
214
215		private static int partiesOf(long s) {
216	<	return (int)(s & (ushortMask << 16)) >>> 16;
216	>	return ((int) s) >>> 16;
217		}
218
219		private static int phaseOf(long s) {
220	<	return (int)(s >>> 32);
220	>	return (int) (s >>> 32);
221		}
222
223		private static int arrivedOf(long s) {
#	Line 221 | Line 225 | public class Phaser {
225		}
226
227		private static long stateFor(int phase, int parties, int unarrived) {
228	<	return (((long)phase) << 32) | ((parties << 16) | unarrived);
228	>	return ((((long) phase) << 32) | (((long) parties) << 16) |
229	>	(long) unarrived);
230		}
231
232		private static long trippedStateFor(int phase, int parties) {
233	<	return (((long)phase) << 32) | ((parties << 16) | parties);
233	>	long lp = (long) parties;
234	>	return (((long) phase) << 32) | (lp << 16) | lp;
235		}
236
237	<	private static IllegalStateException badBounds(int parties, int unarrived) {
238	<	return new IllegalStateException
239	<	("Attempt to set " + unarrived +
240	<	" unarrived of " + parties + " parties");
237	>	/**
238	>	* Returns message string for bad bounds exceptions.
239	>	*/
240	>	private static String badBounds(int parties, int unarrived) {
241	>	return ("Attempt to set " + unarrived +
242	>	" unarrived of " + parties + " parties");
243		}
244
245		/**
#	Line 248 | Line 256 | public class Phaser {
256		// Wait queues
257
258		/**
259	<	* Heads of Treiber stacks waiting for nonFJ threads. To eliminate
259	>	* Heads of Treiber stacks for waiting threads. To eliminate
260		* contention while releasing some threads while adding others, we
261		* use two of them, alternating across even and odd phases.
262		*/
#	Line 256 | Line 264 | public class Phaser {
264		private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
265
266		private AtomicReference<QNode> queueFor(int phase) {
267	<	return (phase & 1) == 0? evenQ : oddQ;
267	>	return ((phase & 1) == 0) ? evenQ : oddQ;
268		}
269
270		/**
#	Line 264 | Line 272 | public class Phaser {
272		* root if necessary.
273		*/
274		private long getReconciledState() {
275	<	return parent == null? state : reconcileState();
275	>	return (parent == null) ? state : reconcileState();
276		}
277
278		/**
#	Line 292 | Line 300 | public class Phaser {
300
301		/**
302		* Creates a new Phaser without any initially registered parties,
303	<	* initial phase number 0, and no parent.
303	>	* initial phase number 0, and no parent. Any thread using this
304	>	* Phaser will need to first register for it.
305		*/
306		public Phaser() {
307		this(null);
#	Line 301 | Line 310 | public class Phaser {
310		/**
311		* Creates a new Phaser with the given numbers of registered
312		* unarrived parties, initial phase number 0, and no parent.
313	<	* @param parties the number of parties required to trip barrier.
313	>	*
314	>	* @param parties the number of parties required to trip barrier
315		* @throws IllegalArgumentException if parties less than zero
316	<	* or greater than the maximum number of parties supported.
316	>	* or greater than the maximum number of parties supported
317		*/
318		public Phaser(int parties) {
319		this(null, parties);
#	Line 314 | Line 324 | public class Phaser {
324		* initially registered parties. If parent is non-null this phaser
325		* is registered with the parent and its initial phase number is
326		* the same as that of parent phaser.
327	<	* @param parent the parent phaser.
327	>	*
328	>	* @param parent the parent phaser
329		*/
330		public Phaser(Phaser parent) {
331		int phase = 0;
#	Line 330 | Line 341 | public class Phaser {
341
342		/**
343		* Creates a new Phaser with the given parent and numbers of
344	<	* registered unarrived parties. If parent is non-null this phaser
344	>	* registered unarrived parties. If parent is non-null, this phaser
345		* is registered with the parent and its initial phase number is
346		* the same as that of parent phaser.
347	<	* @param parent the parent phaser.
348	<	* @param parties the number of parties required to trip barrier.
347	>	*
348	>	* @param parent the parent phaser
349	>	* @param parties the number of parties required to trip barrier
350		* @throws IllegalArgumentException if parties less than zero
351	<	* or greater than the maximum number of parties supported.
351	>	* or greater than the maximum number of parties supported
352		*/
353		public Phaser(Phaser parent, int parties) {
354		if (parties < 0 || parties > ushortMask)
#	Line 354 | Line 366 | public class Phaser {
366
367		/**
368		* Adds a new unarrived party to this phaser.
369	+	*
370		* @return the current barrier phase number upon registration
371		* @throws IllegalStateException if attempting to register more
372	<	* than the maximum supported number of parties.
372	>	* than the maximum supported number of parties
373		*/
374		public int register() {
375		return doRegister(1);
#	Line 364 | Line 377 | public class Phaser {
377
378		/**
379		* Adds the given number of new unarrived parties to this phaser.
380	<	* @param parties the number of parties required to trip barrier.
380	>	*
381	>	* @param parties the number of parties required to trip barrier
382		* @return the current barrier phase number upon registration
383		* @throws IllegalStateException if attempting to register more
384	<	* than the maximum supported number of parties.
384	>	* than the maximum supported number of parties
385		*/
386		public int bulkRegister(int parties) {
387		if (parties < 0)
#	Line 390 | Line 404 | public class Phaser {
404		if (phase < 0)
405		break;
406		if (parties > ushortMask || unarrived > ushortMask)
407	<	throw badBounds(parties, unarrived);
407	>	throw new IllegalStateException(badBounds(parties, unarrived));
408		if (phase == phaseOf(root.state) &&
409		casState(s, stateFor(phase, parties, unarrived)))
410		break;
#	Line 403 | Line 417 | public class Phaser {
417		* in turn wait for others via {@link #awaitAdvance}).
418		*
419		* @return the barrier phase number upon entry to this method, or a
420	<	* negative value if terminated;
420	>	* negative value if terminated
421		* @throws IllegalStateException if not terminated and the number
422	<	* of unarrived parties would become negative.
422	>	* of unarrived parties would become negative
423		*/
424		public int arrive() {
425		int phase;
426		for (;;) {
427		long s = state;
428		phase = phaseOf(s);
429	+	if (phase < 0)
430	+	break;
431		int parties = partiesOf(s);
432		int unarrived = unarrivedOf(s) - 1;
433		if (unarrived > 0) {        // Not the last arrival
#	Line 423 | Line 439 | public class Phaser {
439		if (par == null) {      // directly trip
440		if (casState
441		(s,
442	<	trippedStateFor(onAdvance(phase, parties)? -1 :
442	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
443		((phase + 1) & phaseMask), parties))) {
444		releaseWaiters(phase);
445		break;
#	Line 437 | Line 453 | public class Phaser {
453		}
454		}
455		}
440	–	else if (phase < 0) // Don't throw exception if terminated
441	–	break;
456		else if (phase != phaseOf(root.state)) // or if unreconciled
457		reconcileState();
458		else
459	<	throw badBounds(parties, unarrived);
459	>	throw new IllegalStateException(badBounds(parties, unarrived));
460		}
461		return phase;
462		}
#	Line 455 | Line 469 | public class Phaser {
469		* zero parties, this phaser is also deregistered from its parent.
470		*
471		* @return the current barrier phase number upon entry to
472	<	* this method, or a negative value if terminated;
472	>	* this method, or a negative value if terminated
473		* @throws IllegalStateException if not terminated and the number
474	<	* of registered or unarrived parties would become negative.
474	>	* of registered or unarrived parties would become negative
475		*/
476		public int arriveAndDeregister() {
477		// similar code to arrive, but too different to merge
#	Line 466 | Line 480 | public class Phaser {
480		for (;;) {
481		long s = state;
482		phase = phaseOf(s);
483	+	if (phase < 0)
484	+	break;
485		int parties = partiesOf(s) - 1;
486		int unarrived = unarrivedOf(s) - 1;
487		if (parties >= 0) {
#	Line 484 | Line 500 | public class Phaser {
500		if (unarrived == 0) {
501		if (casState
502		(s,
503	<	trippedStateFor(onAdvance(phase, parties)? -1 :
503	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
504		((phase + 1) & phaseMask), parties))) {
505		releaseWaiters(phase);
506		break;
507		}
508		continue;
509		}
494	–	if (phase < 0)
495	–	break;
510		if (par != null && phase != phaseOf(root.state)) {
511		reconcileState();
512		continue;
513		}
514		}
515	<	throw badBounds(parties, unarrived);
515	>	throw new IllegalStateException(badBounds(parties, unarrived));
516		}
517		return phase;
518		}
519
520		/**
521		* Arrives at the barrier and awaits others. Equivalent in effect
522	<	* to <tt>awaitAdvance(arrive())</tt>.  If you instead need to
522	>	* to {@code awaitAdvance(arrive())}.  If you instead need to
523		* await with interruption of timeout, and/or deregister upon
524		* arrival, you can arrange them using analogous constructions.
525	+	*
526		* @return the phase on entry to this method
527		* @throws IllegalStateException if not terminated and the number
528	<	* of unarrived parties would become negative.
528	>	* of unarrived parties would become negative
529		*/
530		public int arriveAndAwaitAdvance() {
531		return awaitAdvance(arrive());
#	Line 520 | Line 535 | public class Phaser {
535		* Awaits the phase of the barrier to advance from the given
536		* value, or returns immediately if argument is negative or this
537		* barrier is terminated.
538	+	*
539		* @param phase the phase on entry to this method
540		* @return the phase on exit from this method
541		*/
#	Line 530 | Line 546 | public class Phaser {
546		int p = phaseOf(s);
547		if (p != phase)
548		return p;
549	<	if (unarrivedOf(s) == 0)
549	>	if (unarrivedOf(s) == 0 && parent != null)
550		parent.awaitAdvance(phase);
551		// Fall here even if parent waited, to reconcile and help release
552		return untimedWait(phase);
#	Line 538 | Line 554 | public class Phaser {
554
555		/**
556		* Awaits the phase of the barrier to advance from the given
557	<	* value, or returns immediately if argumet is negative or this
557	>	* value, or returns immediately if argument is negative or this
558		* barrier is terminated, or throws InterruptedException if
559		* interrupted while waiting.
560	+	*
561		* @param phase the phase on entry to this method
562		* @return the phase on exit from this method
563		* @throws InterruptedException if thread interrupted while waiting
564		*/
565	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
565	>	public int awaitAdvanceInterruptibly(int phase)
566	>	throws InterruptedException {
567		if (phase < 0)
568		return phase;
569		long s = getReconciledState();
570		int p = phaseOf(s);
571		if (p != phase)
572		return p;
573	<	if (unarrivedOf(s) != 0)
573	>	if (unarrivedOf(s) == 0 && parent != null)
574		parent.awaitAdvanceInterruptibly(phase);
575		return interruptibleWait(phase);
576		}
#	Line 561 | Line 579 | public class Phaser {
579		* Awaits the phase of the barrier to advance from the given value
580		* or the given timeout elapses, or returns immediately if
581		* argument is negative or this barrier is terminated.
582	+	*
583		* @param phase the phase on entry to this method
584		* @return the phase on exit from this method
585		* @throws InterruptedException if thread interrupted while waiting
586		* @throws TimeoutException if timed out while waiting
587		*/
588	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
588	>	public int awaitAdvanceInterruptibly(int phase,
589	>	long timeout, TimeUnit unit)
590		throws InterruptedException, TimeoutException {
591		if (phase < 0)
592		return phase;
#	Line 574 | Line 594 | public class Phaser {
594		int p = phaseOf(s);
595		if (p != phase)
596		return p;
597	<	if (unarrivedOf(s) == 0)
597	>	if (unarrivedOf(s) == 0 && parent != null)
598		parent.awaitAdvanceInterruptibly(phase, timeout, unit);
599		return timedWait(phase, unit.toNanos(timeout));
600		}
#	Line 605 | Line 625 | public class Phaser {
625
626		/**
627		* Returns the current phase number. The maximum phase number is
628	<	* <tt>Integer.MAX_VALUE</tt>, after which it restarts at
628	>	* {@code Integer.MAX_VALUE}, after which it restarts at
629		* zero. Upon termination, the phase number is negative.
630	+	*
631		* @return the phase number, or a negative value if terminated
632		*/
633		public final int getPhase() {
#	Line 614 | Line 635 | public class Phaser {
635		}
636
637		/**
638	<	* Returns true if the current phase number equals the given phase.
638	>	* Returns {@code true} if the current phase number equals the given phase.
639	>	*
640		* @param phase the phase
641	<	* @return true if the current phase number equals the given phase.
641	>	* @return {@code true} if the current phase number equals the given phase
642		*/
643		public final boolean hasPhase(int phase) {
644		return phaseOf(getReconciledState()) == phase;
#	Line 624 | Line 646 | public class Phaser {
646
647		/**
648		* Returns the number of parties registered at this barrier.
649	+	*
650		* @return the number of parties
651		*/
652		public int getRegisteredParties() {
#	Line 633 | Line 656 | public class Phaser {
656		/**
657		* Returns the number of parties that have arrived at the current
658		* phase of this barrier.
659	+	*
660		* @return the number of arrived parties
661		*/
662		public int getArrivedParties() {
#	Line 642 | Line 666 | public class Phaser {
666		/**
667		* Returns the number of registered parties that have not yet
668		* arrived at the current phase of this barrier.
669	+	*
670		* @return the number of unarrived parties
671		*/
672		public int getUnarrivedParties() {
#	Line 650 | Line 675 | public class Phaser {
675
676		/**
677		* Returns the parent of this phaser, or null if none.
678	<	* @return the parent of this phaser, or null if none.
678	>	*
679	>	* @return the parent of this phaser, or null if none
680		*/
681		public Phaser getParent() {
682		return parent;
#	Line 659 | Line 685 | public class Phaser {
685		/**
686		* Returns the root ancestor of this phaser, which is the same as
687		* this phaser if it has no parent.
688	<	* @return the root ancestor of this phaser.
688	>	*
689	>	* @return the root ancestor of this phaser
690		*/
691		public Phaser getRoot() {
692		return root;
693		}
694
695		/**
696	<	* Returns true if this barrier has been terminated.
697	<	* @return true if this barrier has been terminated
696	>	* Returns {@code true} if this barrier has been terminated.
697	>	*
698	>	* @return {@code true} if this barrier has been terminated
699		*/
700		public boolean isTerminated() {
701		return getPhase() < 0;
#	Line 679 | Line 707 | public class Phaser {
707		* barrier is tripped (and thus all other waiting parties are
708		* dormant). If it returns true, then, rather than advance the
709		* phase number, this barrier will be set to a final termination
710	<	* state, and subsequent calls to <tt>isTerminated</tt> will
710	>	* state, and subsequent calls to {@code isTerminated} will
711		* return true.
712		*
713		* <p> The default version returns true when the number of
#	Line 690 | Line 718 | public class Phaser {
718		* <p> You may override this method to perform an action with side
719		* effects visible to participating tasks, but it is in general
720		* only sensible to do so in designs where all parties register
721	<	* before any arrive, and all <tt>awaitAdvance</tt> at each phase.
721	>	* before any arrive, and all {@code awaitAdvance} at each phase.
722		* Otherwise, you cannot ensure lack of interference. In
723		* particular, this method may be invoked more than once per
724		* transition if other parties successfully register while the
#	Line 699 | Line 727 | public class Phaser {
727		* method.
728		*
729		* @param phase the phase number on entering the barrier
730	<	* @param registeredParties the current number of registered
731	<	* parties.
704	<	* @return true if this barrier should terminate
730	>	* @param registeredParties the current number of registered parties
731	>	* @return {@code true} if this barrier should terminate
732		*/
733		protected boolean onAdvance(int phase, int registeredParties) {
734		return registeredParties <= 0;
#	Line 710 | Line 737 | public class Phaser {
737		/**
738		* Returns a string identifying this phaser, as well as its
739		* state.  The state, in brackets, includes the String {@code
740	<	* "phase ="} followed by the phase number, {@code "parties ="}
740	>	* "phase = "} followed by the phase number, {@code "parties = "}
741		* followed by the number of registered parties, and {@code
742	<	* "arrived ="} followed by the number of arrived parties
742	>	* "arrived = "} followed by the number of arrived parties.
743		*
744		* @return a string identifying this barrier, as well as its state
745		*/
746		public String toString() {
747		long s = getReconciledState();
748	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
748	>	return super.toString() +
749	>	"[phase = " + phaseOf(s) +
750	>	" parties = " + partiesOf(s) +
751	>	" arrived = " + arrivedOf(s) + "]";
752		}
753
754		// methods for waiting
755
726	–	/** The number of CPUs, for spin control */
727	–	static final int NCPUS = Runtime.getRuntime().availableProcessors();
728	–
729	–	/**
730	–	* The number of times to spin before blocking in timed waits.
731	–	* The value is empirically derived.
732	–	*/
733	–	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
734	–
735	–	/**
736	–	* The number of times to spin before blocking in untimed waits.
737	–	* This is greater than timed value because untimed waits spin
738	–	* faster since they don't need to check times on each spin.
739	–	*/
740	–	static final int maxUntimedSpins = maxTimedSpins * 32;
741	–
742	–	/**
743	–	* The number of nanoseconds for which it is faster to spin
744	–	* rather than to use timed park. A rough estimate suffices.
745	–	*/
746	–	static final long spinForTimeoutThreshold = 1000L;
747	–
756		/**
757	<	* Wait nodes for Treiber stack representing wait queue for non-FJ
750	<	* tasks.
757	>	* Wait nodes for Treiber stack representing wait queue
758		*/
759	<	static final class QNode {
760	<	QNode next;
759	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
760	>	final Phaser phaser;
761	>	final int phase;
762	>	final long startTime;
763	>	final long nanos;
764	>	final boolean timed;
765	>	final boolean interruptible;
766	>	volatile boolean wasInterrupted = false;
767		volatile Thread thread; // nulled to cancel wait
768	<	QNode() {
768	>	QNode next;
769	>	QNode(Phaser phaser, int phase, boolean interruptible,
770	>	boolean timed, long startTime, long nanos) {
771	>	this.phaser = phaser;
772	>	this.phase = phase;
773	>	this.timed = timed;
774	>	this.interruptible = interruptible;
775	>	this.startTime = startTime;
776	>	this.nanos = nanos;
777		thread = Thread.currentThread();
778		}
779	+	public boolean isReleasable() {
780	+	return (thread == null ||
781	+	phaser.getPhase() != phase ||
782	+	(interruptible && wasInterrupted) ||
783	+	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
784	+	}
785	+	public boolean block() {
786	+	if (Thread.interrupted()) {
787	+	wasInterrupted = true;
788	+	if (interruptible)
789	+	return true;
790	+	}
791	+	if (!timed)
792	+	LockSupport.park(this);
793	+	else {
794	+	long waitTime = nanos - (System.nanoTime() - startTime);
795	+	if (waitTime <= 0)
796	+	return true;
797	+	LockSupport.parkNanos(this, waitTime);
798	+	}
799	+	return isReleasable();
800	+	}
801		void signal() {
802		Thread t = thread;
803		if (t != null) {
#	Line 762 | Line 805 | public class Phaser {
805		LockSupport.unpark(t);
806		}
807		}
808	+	boolean doWait() {
809	+	if (thread != null) {
810	+	try {
811	+	ForkJoinPool.managedBlock(this, false);
812	+	} catch (InterruptedException ie) {
813	+	}
814	+	}
815	+	return wasInterrupted;
816	+	}
817	+
818		}
819
820		/**
821	<	* Removes and signals waiting threads from wait queue
821	>	* Removes and signals waiting threads from wait queue.
822		*/
823		private void releaseWaiters(int phase) {
824		AtomicReference<QNode> head = queueFor(phase);
#	Line 777 | Line 830 | public class Phaser {
830		}
831
832		/**
833	+	* Tries to enqueue given node in the appropriate wait queue.
834	+	*
835	+	* @return true if successful
836	+	*/
837	+	private boolean tryEnqueue(QNode node) {
838	+	AtomicReference<QNode> head = queueFor(node.phase);
839	+	return head.compareAndSet(node.next = head.get(), node);
840	+	}
841	+
842	+	/**
843		* Enqueues node and waits unless aborted or signalled.
844	+	*
845	+	* @return current phase
846		*/
847		private int untimedWait(int phase) {
783	–	int spins = maxUntimedSpins;
848		QNode node = null;
785	–	boolean interrupted = false;
849		boolean queued = false;
850	+	boolean interrupted = false;
851		int p;
852		while ((p = getPhase()) == phase) {
853	<	interrupted = Thread.interrupted();
854	<	if (node != null) {
855	<	if (!queued) {
856	<	AtomicReference<QNode> head = queueFor(phase);
857	<	queued = head.compareAndSet(node.next = head.get(), node);
858	<	}
795	<	else if (node.thread != null)
796	<	LockSupport.park(this);
797	<	}
798	<	else if (spins <= 0)
799	<	node = new QNode();
853	>	if (Thread.interrupted())
854	>	interrupted = true;
855	>	else if (node == null)
856	>	node = new QNode(this, phase, false, false, 0, 0);
857	>	else if (!queued)
858	>	queued = tryEnqueue(node);
859		else
860	<	--spins;
860	>	interrupted = node.doWait();
861		}
862		if (node != null)
863		node.thread = null;
864	+	releaseWaiters(phase);
865		if (interrupted)
866		Thread.currentThread().interrupt();
807	–	releaseWaiters(phase);
867		return p;
868		}
869
870		/**
871	<	* Messier interruptible version
871	>	* Interruptible version
872	>	* @return current phase
873		*/
874		private int interruptibleWait(int phase) throws InterruptedException {
815	–	int spins = maxUntimedSpins;
875		QNode node = null;
876		boolean queued = false;
877		boolean interrupted = false;
878		int p;
879	<	while ((p = getPhase()) == phase) {
880	<	if (interrupted = Thread.interrupted())
881	<	break;
882	<	if (node != null) {
883	<	if (!queued) {
884	<	AtomicReference<QNode> head = queueFor(phase);
885	<	queued = head.compareAndSet(node.next = head.get(), node);
827	<	}
828	<	else if (node.thread != null)
829	<	LockSupport.park(this);
830	<	}
831	<	else if (spins <= 0)
832	<	node = new QNode();
879	>	while ((p = getPhase()) == phase && !interrupted) {
880	>	if (Thread.interrupted())
881	>	interrupted = true;
882	>	else if (node == null)
883	>	node = new QNode(this, phase, true, false, 0, 0);
884	>	else if (!queued)
885	>	queued = tryEnqueue(node);
886		else
887	<	--spins;
887	>	interrupted = node.doWait();
888		}
889		if (node != null)
890		node.thread = null;
891	+	if (p != phase || (p = getPhase()) != phase)
892	+	releaseWaiters(phase);
893		if (interrupted)
894		throw new InterruptedException();
840	–	releaseWaiters(phase);
895		return p;
896		}
897
898		/**
899	<	* Even messier timeout version.
899	>	* Timeout version.
900	>	* @return current phase
901		*/
902		private int timedWait(int phase, long nanos)
903		throws InterruptedException, TimeoutException {
904	+	long startTime = System.nanoTime();
905	+	QNode node = null;
906	+	boolean queued = false;
907	+	boolean interrupted = false;
908		int p;
909	<	if ((p = getPhase()) == phase) {
910	<	long lastTime = System.nanoTime();
911	<	int spins = maxTimedSpins;
912	<	QNode node = null;
913	<	boolean queued = false;
914	<	boolean interrupted = false;
915	<	while ((p = getPhase()) == phase) {
916	<	if (interrupted = Thread.interrupted())
917	<	break;
918	<	long now = System.nanoTime();
919	<	if ((nanos -= now - lastTime) <= 0)
861	<	break;
862	<	lastTime = now;
863	<	if (node != null) {
864	<	if (!queued) {
865	<	AtomicReference<QNode> head = queueFor(phase);
866	<	queued = head.compareAndSet(node.next = head.get(), node);
867	<	}
868	<	else if (node.thread != null &&
869	<	nanos > spinForTimeoutThreshold) {
870	<	LockSupport.parkNanos(this, nanos);
871	<	}
872	<	}
873	<	else if (spins <= 0)
874	<	node = new QNode();
875	<	else
876	<	--spins;
877	<	}
878	<	if (node != null)
879	<	node.thread = null;
880	<	if (interrupted)
881	<	throw new InterruptedException();
882	<	if (p == phase && (p = getPhase()) == phase)
883	<	throw new TimeoutException();
909	>	while ((p = getPhase()) == phase && !interrupted) {
910	>	if (Thread.interrupted())
911	>	interrupted = true;
912	>	else if (nanos - (System.nanoTime() - startTime) <= 0)
913	>	break;
914	>	else if (node == null)
915	>	node = new QNode(this, phase, true, true, startTime, nanos);
916	>	else if (!queued)
917	>	queued = tryEnqueue(node);
918	>	else
919	>	interrupted = node.doWait();
920		}
921	<	releaseWaiters(phase);
921	>	if (node != null)
922	>	node.thread = null;
923	>	if (p != phase || (p = getPhase()) != phase)
924	>	releaseWaiters(phase);
925	>	if (interrupted)
926	>	throw new InterruptedException();
927	>	if (p == phase)
928	>	throw new TimeoutException();
929		return p;
930		}
931
932	<	// Temporary Unsafe mechanics for preliminary release
932	>	// Unsafe mechanics for jsr166y 3rd party package.
933	>	private static sun.misc.Unsafe getUnsafe() {
934	>	try {
935	>	return sun.misc.Unsafe.getUnsafe();
936	>	} catch (SecurityException se) {
937	>	try {
938	>	return java.security.AccessController.doPrivileged
939	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
940	>	public sun.misc.Unsafe run() throws Exception {
941	>	return getUnsafeByReflection();
942	>	}});
943	>	} catch (java.security.PrivilegedActionException e) {
944	>	throw new RuntimeException("Could not initialize intrinsics",
945	>	e.getCause());
946	>	}
947	>	}
948	>	}
949
950	<	static final Unsafe _unsafe;
951	<	static final long stateOffset;
950	>	private static sun.misc.Unsafe getUnsafeByReflection()
951	>	throws NoSuchFieldException, IllegalAccessException {
952	>	java.lang.reflect.Field f =
953	>	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
954	>	f.setAccessible(true);
955	>	return (sun.misc.Unsafe) f.get(null);
956	>	}
957
958	<	static {
958	>	private static long fieldOffset(String fieldName, Class<?> klazz) {
959		try {
960	<	if (Phaser.class.getClassLoader() != null) {
961	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
962	<	f.setAccessible(true);
963	<	_unsafe = (Unsafe)f.get(null);
964	<	}
965	<	else
902	<	_unsafe = Unsafe.getUnsafe();
903	<	stateOffset = _unsafe.objectFieldOffset
904	<	(Phaser.class.getDeclaredField("state"));
905	<	} catch (Exception e) {
906	<	throw new RuntimeException("Could not initialize intrinsics", e);
960	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
961	>	} catch (NoSuchFieldException e) {
962	>	// Convert Exception to Error
963	>	NoSuchFieldError error = new NoSuchFieldError(fieldName);
964	>	error.initCause(e);
965	>	throw error;
966		}
967		}
968
969	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
970	+	static final long stateOffset =
971	+	fieldOffset("state", Phaser.class);
972	+
973		final boolean casState(long cmp, long val) {
974	<	return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val);
974	>	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
975		}
976		}

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