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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.2 by jsr166, Fri Jul 25 18:10:41 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	<	import jsr166y.forkjoin.*;
8	>
9		import java.util.concurrent.*;
10		import java.util.concurrent.atomic.*;
11		import java.util.concurrent.locks.LockSupport;
12
13		/**
14		* A reusable synchronization barrier, similar in functionality to a
15	<	* {@link java.util.concurrent.CyclicBarrier}, but supporting more
16	<	* flexible 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		*
21	<	* <li> The number of parties synchronizing on the barrier may vary
22	<	* over time.  A task may register to be a party in a barrier at any
23	<	* time, and may deregister upon arriving at the barrier.  As is the
24	<	* case with most basic synchronization constructs, registration
25	<	* and deregistration affect only internal counts; they do not
26	<	* establish any further internal bookkeeping, so tasks cannot query
27	<	* whether they are registered.
21	>	* <li> The number of parties synchronizing on a phaser may vary over
22	>	* time.  A task may register to be a party at any time, and may
23	>	* deregister upon arriving at the barrier.  As is the case with most
24	>	* basic synchronization constructs, registration and deregistration
25	>	* affect only internal counts; they do not establish any further
26	>	* internal bookkeeping, so tasks cannot query whether they are
27	>	* registered. (However, you can introduce such bookkeeping by
28	>	* subclassing this class.)
29		*
30		* <li> Each generation has an associated phase value, starting at
31		* zero, and advancing when all parties reach the barrier (wrapping
32	<	* around to zero after reaching <tt>Integer.MAX_VALUE</tt>).
33	<	*
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
37	<	* aspects of coordination, that may be invoked independently:
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
43	<	*       the phase value on entry to the method.
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 48 | Line 50 | import java.util.concurrent.locks.LockSu
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.
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 tripped. When a Phaser is controlling an
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 <tt>forceTermination</tt> is
66	<	* also available to assist recovery actions upon failure.
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
71	>	* synchronization contention costs may instead be arranged in trees.
72	>	* This will typically greatly increase throughput even though it
73	>	* incurs somewhat greater per-operation overhead.
74		*
75	<	* <li> Unlike most synchronizers, a Phaser may also be used with
76	<	* ForkJoinTasks (as well as plain threads).
65	<	*
66	<	* <li> By default, <tt>awaitAdvance</tt> continues to wait even if
67	<	* the current thread is interrupted. And unlike the case in
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.
80	>	* within handlers of those exceptions, often after invoking
81	>	* {@code forceTermination}.
82	>	*
83	>	* <li>Phasers ensure lack of starvation when used by ForkJoinTasks.
84		*
85		* </ul>
86		*
87	<	* <p><b>Sample usage:</b>
87	>	* <p><b>Sample usages:</b>
88		*
89	<	* <p>[todo: non-FJ example]
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> {@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	<	* <p> A Phaser may be used to support a style of programming in
109	<	* which a task waits for others to complete, without otherwise
110	<	* needing to keep track of which tasks it is waiting for. This is
111	<	* similar to the "sync" construct in Cilk and "clocks" in X10.
112	<	* Special constructions based on such barriers are available using
113	<	* the <tt>LinkedAsyncAction</tt> and <tt>CyclicAction</tt> classes,
114	<	* but they can be useful in other contexts as well.  For a simple
115	<	* (but not very useful) example, here is a variant of Fibonacci:
116	<	*
117	<	* <pre>
118	<	* class BarrierFibonacci extends RecursiveAction {
119	<	*   int argument, result;
120	<	*   final Phaser parentBarrier;
121	<	*   BarrierFibonacci(int n, Phaser parentBarrier) {
122	<	*     this.argument = n;
123	<	*     this.parentBarrier = parentBarrier;
124	<	*     parentBarrier.register();
108	>	*   doSomethingOnBehalfOfWorkers();
109	>	*   phaser.arrive(); // allow threads to start
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); // 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 {@code onAdvance}:
118	>	*
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	>	*     }.start();
137		*   }
138	<	*   protected void compute() {
139	<	*     int n = argument;
140	<	*     if (n &lt;= 1)
141	<	*        result = n;
142	<	*     else {
143	<	*        Phaser childBarrier = new Phaser(1);
144	<	*        BarrierFibonacci f1 = new BarrierFibonacci(n - 1, childBarrier);
145	<	*        BarrierFibonacci f2 = new BarrierFibonacci(n - 2, childBarrier);
146	<	*        f1.fork();
147	<	*        f2.fork();
148	<	*        childBarrier.arriveAndAwait();
149	<	*        result = f1.result + f2.result;
138	>	*   phaser.arriveAndDeregister(); // deregister self, don't wait
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> {@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	<	*     parentBarrier.arriveAndDeregister();
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 {@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.
168	+	*
169		* </pre>
170		*
171		* <p><b>Implementation notes</b>: This implementation restricts the
172	<	* maximum number of parties to 65535. Attempts to register
173	<	* additional parties result in IllegalStateExceptions.
172	>	* maximum number of parties to 65535. Attempts to register additional
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		/*
182		* This class implements an extension of X10 "clocks".  Thanks to
183	<	* Vijay Saraswat for the idea of applying it to ForkJoinTasks,
184	<	* and to Vivek Sarkar for enhancements to extend functionality.
183	>	* Vijay Saraswat for the idea, and to Vivek Sarkar for
184	>	* enhancements to extend functionality.
185		*/
186
187		/**
188		* Barrier state representation. Conceptually, a barrier contains
189		* four values:
190	<	*
190	>	*
191		* * parties -- the number of parties to wait (16 bits)
192		* * unarrived -- the number of parties yet to hit barrier (16 bits)
193		* * phase -- the generation of the barrier (31 bits)
194		* * terminated -- set if barrier is terminated (1 bit)
195		*
196		* However, to efficiently maintain atomicity, these values are
197	<	* packed into a single AtomicLong. Termination uses the sign bit
198	<	* of 32 bit representation of phase, so phase is set to -1 on
199	<	* termination.
200	<	*/
201	<	private final AtomicLong state;
202	<
203	<	/**
143	<	* Head of Treiber stack for waiting nonFJ threads.
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 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	>	* count being lowest 16 bits.
204		*/
205	<	private final AtomicReference<QNode> head = new AtomicReference<QNode>();
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 165 | 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 IllegalStateException badBounds(int parties, int unarrived) {
233	<	return new IllegalStateException("Attempt to set " + unarrived +
234	<	" unarrived of " + parties + " parties");
232	>	private static long trippedStateFor(int phase, int parties) {
233	>	long lp = (long) parties;
234	>	return (((long) phase) << 32) | (lp << 16) | lp;
235	>	}
236	>
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	>	/**
246	>	* The parent of this phaser, or null if none
247	>	*/
248	>	private final Phaser parent;
249	>
250	>	/**
251	>	* The root of Phaser tree. Equals this if not in a tree.  Used to
252	>	* support faster state push-down.
253	>	*/
254	>	private final Phaser root;
255	>
256	>	// Wait queues
257	>
258	>	/**
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	>	*/
263	>	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
264	>	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
265	>
266	>	private AtomicReference<QNode> queueFor(int phase) {
267	>	return ((phase & 1) == 0) ? evenQ : oddQ;
268	>	}
269	>
270	>	/**
271	>	* Returns current state, first resolving lagged propagation from
272	>	* root if necessary.
273	>	*/
274	>	private long getReconciledState() {
275	>	return (parent == null) ? state : reconcileState();
276	>	}
277	>
278	>	/**
279	>	* Recursively resolves state.
280	>	*/
281	>	private long reconcileState() {
282	>	Phaser p = parent;
283	>	long s = state;
284	>	if (p != null) {
285	>	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
286	>	long parentState = p.getReconciledState();
287	>	int parentPhase = phaseOf(parentState);
288	>	int phase = phaseOf(s = state);
289	>	if (phase != parentPhase) {
290	>	long next = trippedStateFor(parentPhase, partiesOf(s));
291	>	if (casState(s, next)) {
292	>	releaseWaiters(phase);
293	>	s = next;
294	>	}
295	>	}
296	>	}
297	>	}
298	>	return s;
299		}
300
301		/**
302		* Creates a new Phaser without any initially registered parties,
303	<	* and initial phase number 0.
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	<	state = new AtomicLong(stateFor(0, 0, 0));
307	>	this(null);
308		}
309
310		/**
311		* Creates a new Phaser with the given numbers of registered
312	<	* unarrived parties and initial phase number 0.
313	<	* @param parties the number of parties required to trip barrier.
312	>	* unarrived parties, initial phase number 0, and no parent.
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);
320	+	}
321	+
322	+	/**
323	+	* Creates a new Phaser with the given parent, without any
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	+	*
328	+	* @param parent the parent phaser
329	+	*/
330	+	public Phaser(Phaser parent) {
331	+	int phase = 0;
332	+	this.parent = parent;
333	+	if (parent != null) {
334	+	this.root = parent.root;
335	+	phase = parent.register();
336	+	}
337	+	else
338	+	this.root = this;
339	+	this.state = trippedStateFor(phase, 0);
340	+	}
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
345	+	* is registered with the parent and its initial phase number is
346	+	* the same as that of parent phaser.
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
352	+	*/
353	+	public Phaser(Phaser parent, int parties) {
354		if (parties < 0 || parties > ushortMask)
355		throw new IllegalArgumentException("Illegal number of parties");
356	<	state = new AtomicLong(stateFor(0, parties, parties));
356	>	int phase = 0;
357	>	this.parent = parent;
358	>	if (parent != null) {
359	>	this.root = parent.root;
360	>	phase = parent.register();
361	>	}
362	>	else
363	>	this.root = this;
364	>	this.state = trippedStateFor(phase, parties);
365		}
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
373	+	*/
374	+	public int register() {
375	+	return doRegister(1);
376	+	}
377	+
378	+	/**
379	+	* Adds the given number of new unarrived parties to this phaser.
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 register() { // increment both parties and unarrived
387	<	final AtomicLong state = this.state;
386	>	public int bulkRegister(int parties) {
387	>	if (parties < 0)
388	>	throw new IllegalArgumentException();
389	>	if (parties == 0)
390	>	return getPhase();
391	>	return doRegister(parties);
392	>	}
393	>
394	>	/**
395	>	* Shared code for register, bulkRegister
396	>	*/
397	>	private int doRegister(int registrations) {
398	>	int phase;
399		for (;;) {
400	<	long s = state.get();
401	<	int phase = phaseOf(s);
402	<	int parties = partiesOf(s) + 1;
403	<	int unarrived = unarrivedOf(s) + 1;
400	>	long s = getReconciledState();
401	>	phase = phaseOf(s);
402	>	int unarrived = unarrivedOf(s) + registrations;
403	>	int parties = partiesOf(s) + registrations;
404	>	if (phase < 0)
405	>	break;
406		if (parties > ushortMask || unarrived > ushortMask)
407	<	throw badBounds(parties, unarrived);
408	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
409	<	return phase;
407	>	throw new IllegalStateException(badBounds(parties, unarrived));
408	>	if (phase == phaseOf(root.state) &&
409	>	casState(s, stateFor(phase, parties, unarrived)))
410	>	break;
411		}
412	+	return phase;
413		}
414
415		/**
416		* Arrives at the barrier, but does not wait for others.  (You can
417		* in turn wait for others via {@link #awaitAdvance}).
418		*
419	<	* @return the current barrier phase number upon entry to
420	<	* this method, or a negative value if terminated;
421	<	* @throws IllegalStateException if the number of unarrived
422	<	* parties would become negative.
419	>	* @return the barrier phase number upon entry to this method, or a
420	>	* negative value if terminated
421	>	* @throws IllegalStateException if not terminated and the number
422	>	* of unarrived parties would become negative
423		*/
424	<	public int arrive() { // decrement unarrived. If zero, trip
425	<	final AtomicLong state = this.state;
424	>	public int arrive() {
425	>	int phase;
426		for (;;) {
427	<	long s = state.get();
428	<	int phase = phaseOf(s);
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)
434	<	throw badBounds(parties, unarrived);
435	<	if (unarrived == 0 && phase >= 0) {
436	<	trip(phase, parties);
437	<	return phase;
433	>	if (unarrived > 0) {        // Not the last arrival
434	>	if (casState(s, s - 1)) // s-1 adds one arrival
435	>	break;
436	>	}
437	>	else if (unarrived == 0) {  // the last arrival
438	>	Phaser par = parent;
439	>	if (par == null) {      // directly trip
440	>	if (casState
441	>	(s,
442	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
443	>	((phase + 1) & phaseMask), parties))) {
444	>	releaseWaiters(phase);
445	>	break;
446	>	}
447	>	}
448	>	else {                  // cascade to parent
449	>	if (casState(s, s - 1)) { // zeroes unarrived
450	>	par.arrive();
451	>	reconcileState();
452	>	break;
453	>	}
454	>	}
455		}
456	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
457	<	return phase;
456	>	else if (phase != phaseOf(root.state)) // or if unreconciled
457	>	reconcileState();
458	>	else
459	>	throw new IllegalStateException(badBounds(parties, unarrived));
460		}
461	+	return phase;
462		}
463
464		/**
465		* Arrives at the barrier, and deregisters from it, without
466	<	* waiting for others.
466	>	* waiting for others. Deregistration reduces number of parties
467	>	* required to trip the barrier in future phases.  If this phaser
468	>	* has a parent, and deregistration causes this phaser to have
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;
473	<	* @throws IllegalStateException if the number of registered or
474	<	* unarrived parties would become negative.
475	<	*/
476	<	public int arriveAndDeregister() { // Same as arrive, plus decrement parties
477	<	final AtomicLong state = this.state;
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
475	>	*/
476	>	public int arriveAndDeregister() {
477	>	// similar code to arrive, but too different to merge
478	>	Phaser par = parent;
479	>	int phase;
480		for (;;) {
481	<	long s = state.get();
482	<	int phase = phaseOf(s);
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 || unarrived < 0)
488	<	throw badBounds(parties, unarrived);
489	<	if (unarrived == 0 && phase >= 0) {
490	<	trip(phase, parties);
491	<	return phase;
487	>	if (parties >= 0) {
488	>	if (unarrived > 0 || (unarrived == 0 && par != null)) {
489	>	if (casState
490	>	(s,
491	>	stateFor(phase, parties, unarrived))) {
492	>	if (unarrived == 0) {
493	>	par.arriveAndDeregister();
494	>	reconcileState();
495	>	}
496	>	break;
497	>	}
498	>	continue;
499	>	}
500	>	if (unarrived == 0) {
501	>	if (casState
502	>	(s,
503	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
504	>	((phase + 1) & phaseMask), parties))) {
505	>	releaseWaiters(phase);
506	>	break;
507	>	}
508	>	continue;
509	>	}
510	>	if (par != null && phase != phaseOf(root.state)) {
511	>	reconcileState();
512	>	continue;
513	>	}
514		}
515	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
267	<	return phase;
515	>	throw new IllegalStateException(badBounds(parties, unarrived));
516		}
517	+	return phase;
518		}
519
520		/**
521	<	* Arrives at the barrier and awaits others. Unlike other arrival
522	<	* methods, this method returns the arrival index of the
523	<	* caller. The caller tripping the barrier returns zero, the
524	<	* previous caller 1, and so on.
525	<	* @return the arrival index
526	<	* @throws IllegalStateException if the number of unarrived
527	<	* parties would become negative.
521	>	* Arrives at the barrier and awaits others. Equivalent in effect
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
529		*/
530		public int arriveAndAwaitAdvance() {
531	<	final AtomicLong state = this.state;
282	<	for (;;) {
283	<	long s = state.get();
284	<	int phase = phaseOf(s);
285	<	int parties = partiesOf(s);
286	<	int unarrived = unarrivedOf(s) - 1;
287	<	if (unarrived < 0)
288	<	throw badBounds(parties, unarrived);
289	<	if (unarrived == 0 && phase >= 0) {
290	<	trip(phase, parties);
291	<	return 0;
292	<	}
293	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) {
294	<	awaitAdvance(phase);
295	<	return unarrived;
296	<	}
297	<	}
531	>	return awaitAdvance(arrive());
532		}
533
534		/**
535		* Awaits the phase of the barrier to advance from the given
536	<	* value, or returns immediately if this barrier is terminated.
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		*/
542		public int awaitAdvance(int phase) {
543		if (phase < 0)
544		return phase;
545	<	Thread current = Thread.currentThread();
546	<	if (current instanceof ForkJoinWorkerThread)
547	<	return helpingWait(phase);
548	<	if (untimedWait(current, phase, false))
549	<	current.interrupt();
550	<	return phaseOf(state.get());
545	>	long s = getReconciledState();
546	>	int p = phaseOf(s);
547	>	if (p != phase)
548	>	return p;
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);
553		}
554
555		/**
556		* Awaits the phase of the barrier to advance from the given
557	<	* value, or returns immediately if this barrier is terminated, or
558	<	* throws InterruptedException if interrupted while waiting.
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	<	Thread current = Thread.currentThread();
570	<	if (current instanceof ForkJoinWorkerThread)
571	<	return helpingWait(phase);
572	<	else if (Thread.interrupted() || untimedWait(current, phase, true))
573	<	throw new InterruptedException();
574	<	else
575	<	return phaseOf(state.get());
569	>	long s = getReconciledState();
570	>	int p = phaseOf(s);
571	>	if (p != phase)
572	>	return p;
573	>	if (unarrivedOf(s) == 0 && parent != null)
574	>	parent.awaitAdvanceInterruptibly(phase);
575	>	return interruptibleWait(phase);
576		}
577
578		/**
579		* Awaits the phase of the barrier to advance from the given value
580	<	* or the given timeout elapses, or returns immediately if this
581	<	* barrier is terminated.
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;
593	<	long nanos = unit.toNanos(timeout);
594	<	Thread current = Thread.currentThread();
595	<	if (current instanceof ForkJoinWorkerThread)
596	<	return timedHelpingWait(phase, nanos);
597	<	timedWait(current, phase, nanos);
598	<	return phaseOf(state.get());
593	>	long s = getReconciledState();
594	>	int p = phaseOf(s);
595	>	if (p != phase)
596	>	return p;
597	>	if (unarrivedOf(s) == 0 && parent != null)
598	>	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
599	>	return timedWait(phase, unit.toNanos(timeout));
600		}
601
602		/**
603		* Forces this barrier to enter termination state. Counts of
604	<	* arrived and registered parties are unaffected. This method may
605	<	* be useful for coordinating recovery after one or more tasks
606	<	* encounter unexpected exceptions.
604	>	* arrived and registered parties are unaffected. If this phaser
605	>	* has a parent, it too is terminated. This method may be useful
606	>	* for coordinating recovery after one or more tasks encounter
607	>	* unexpected exceptions.
608		*/
609		public void forceTermination() {
365	–	final AtomicLong state = this.state;
610		for (;;) {
611	<	long s = state.get();
611	>	long s = getReconciledState();
612		int phase = phaseOf(s);
613		int parties = partiesOf(s);
614		int unarrived = unarrivedOf(s);
615		if (phase < 0 ||
616	<	state.compareAndSet(s, stateFor(-1, parties, unarrived))) {
617	<	if (head.get() != null)
618	<	releaseWaiters(-1);
616	>	casState(s, stateFor(-1, parties, unarrived))) {
617	>	releaseWaiters(0);
618	>	releaseWaiters(1);
619	>	if (parent != null)
620	>	parent.forceTermination();
621		return;
622		}
623		}
624		}
625
626		/**
627	<	* Resets the barrier with the given numbers of registered unarrived
628	<	* parties and phase number 0. This method allows repeated reuse
629	<	* of this barrier, but only if it is somehow known not to be in
630	<	* use for other purposes.
631	<	* @param parties the number of parties required to trip barrier.
386	<	* @throws IllegalArgumentException if parties less than zero
387	<	* or greater than the maximum number of parties supported.
627	>	* Returns the current phase number. The maximum phase number is
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 void reset(int parties) {
634	<	if (parties < 0 || parties > ushortMask)
391	<	throw new IllegalArgumentException("Illegal number of parties");
392	<	state.set(stateFor(0, parties, parties));
393	<	if (head.get() != null)
394	<	releaseWaiters(0);
633	>	public final int getPhase() {
634	>	return phaseOf(getReconciledState());
635		}
636
637		/**
638	<	* Returns the current phase number. The maximum phase number is
639	<	* <tt>Integer.MAX_VALUE</tt>, after which it restarts at
640	<	* zero. Upon termination, the phase number is negative.
641	<	* @return the phase number, or a negative value if terminated
638	>	* Returns {@code true} if the current phase number equals the given phase.
639	>	*
640	>	* @param phase the phase
641	>	* @return {@code true} if the current phase number equals the given phase
642		*/
643	<	public int getPhase() {
644	<	return phaseOf(state.get());
643	>	public final boolean hasPhase(int phase) {
644	>	return phaseOf(getReconciledState()) == phase;
645		}
646
647		/**
648		* Returns the number of parties registered at this barrier.
649	+	*
650		* @return the number of parties
651		*/
652		public int getRegisteredParties() {
653	<	return partiesOf(state.get());
653	>	return partiesOf(state);
654		}
655
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() {
663	<	return arrivedOf(state.get());
663	>	return arrivedOf(state);
664		}
665
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() {
673	<	return unarrivedOf(state.get());
673	>	return unarrivedOf(state);
674		}
675
676		/**
677	<	* Returns true if this barrier has been terminated.
678	<	* @return true if this barrier has been terminated
677	>	* Returns 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;
683	>	}
684	>
685	>	/**
686	>	* Returns the root ancestor of this phaser, which is the same as
687	>	* this phaser if it has no parent.
688	>	*
689	>	* @return the root ancestor of this phaser
690	>	*/
691	>	public Phaser getRoot() {
692	>	return root;
693	>	}
694	>
695	>	/**
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 phaseOf(state.get()) < 0;
701	>	return getPhase() < 0;
702		}
703
704		/**
#	Line 444 | 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	<	*
712	>	*
713		* <p> The default version returns true when the number of
714		* registered parties is zero. Normally, overrides that arrange
715		* termination for other reasons should also preserve this
716		* property.
717		*
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 {@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
725	+	* invocation of this method is in progress, thus postponing the
726	+	* transition until those parties also arrive, re-triggering this
727	+	* method.
728	+	*
729		* @param phase the phase number on entering the barrier
730	<	* @param registeredParties the current number of registered
731	<	* parties.
458	<	* @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;
735		}
736
737		/**
738	<	* Returns a string identifying this barrier, as well as its
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 = state.get();
748	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
747	>	long s = getReconciledState();
748	>	return super.toString() +
749	>	"[phase = " + phaseOf(s) +
750	>	" parties = " + partiesOf(s) +
751	>	" arrived = " + arrivedOf(s) + "]";
752		}
753
754	<	// methods for tripping and waiting
754	>	// methods for waiting
755
756		/**
757	<	* Advance the current phase (or terminate)
757	>	* Wait nodes for Treiber stack representing wait queue
758		*/
759	<	private void trip(int phase, int parties) {
760	<	int next = onAdvance(phase, parties)? -1 : ((phase + 1) & phaseMask);
761	<	state.set(stateFor(next, parties, parties));
762	<	if (head.get() != null)
763	<	releaseWaiters(next);
764	<	}
765	<
766	<	private int helpingWait(int phase) {
767	<	final AtomicLong state = this.state;
768	<	int p;
769	<	while ((p = phaseOf(state.get())) == phase) {
770	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
771	<	if (t != null) {
772	<	if ((p = phaseOf(state.get())) == phase)
773	<	t.exec();
774	<	else {   // push task and exit if barrier advanced
775	<	t.fork();
776	<	break;
777	<	}
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 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	<	return p;
802	<	}
506	<
507	<	private int timedHelpingWait(int phase, long nanos) throws TimeoutException {
508	<	final AtomicLong state = this.state;
509	<	long lastTime = System.nanoTime();
510	<	int p;
511	<	while ((p = phaseOf(state.get())) == phase) {
512	<	long now = System.nanoTime();
513	<	nanos -= now - lastTime;
514	<	lastTime = now;
515	<	if (nanos <= 0) {
516	<	if ((p = phaseOf(state.get())) == phase)
517	<	throw new TimeoutException();
518	<	else
519	<	break;
520	<	}
521	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
801	>	void signal() {
802	>	Thread t = thread;
803		if (t != null) {
804	<	if ((p = phaseOf(state.get())) == phase)
805	<	t.exec();
806	<	else {   // push task and exit if barrier advanced
807	<	t.fork();
808	<	break;
804	>	thread = null;
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	<	return p;
817	>
818		}
819
820		/**
821	<	* Wait nodes for Treiber stack representing wait queue for non-FJ
536	<	* tasks. The waiting scheme is an adaptation of the one used in
537	<	* forkjoin.PoolBarrier.
821	>	* Removes and signals waiting threads from wait queue.
822		*/
823	<	static final class QNode {
824	<	QNode next;
825	<	volatile Thread thread; // nulled to cancel wait
826	<	final int phase;
827	<	QNode(Thread t, int c) {
828	<	thread = t;
545	<	phase = c;
546	<	}
547	<	}
548	<
549	<	private void releaseWaiters(int currentPhase) {
550	<	final AtomicReference<QNode> head = this.head;
551	<	QNode p;
552	<	while ((p = head.get()) != null && p.phase != currentPhase) {
553	<	if (head.compareAndSet(p, null)) {
554	<	do {
555	<	Thread t = p.thread;
556	<	if (t != null) {
557	<	p.thread = null;
558	<	LockSupport.unpark(t);
559	<	}
560	<	} while ((p = p.next) != null);
561	<	}
823	>	private void releaseWaiters(int phase) {
824	>	AtomicReference<QNode> head = queueFor(phase);
825	>	QNode q;
826	>	while ((q = head.get()) != null) {
827	>	if (head.compareAndSet(q, q.next))
828	>	q.signal();
829		}
830		}
831
565	–	/** The number of CPUs, for spin control */
566	–	static final int NCPUS = Runtime.getRuntime().availableProcessors();
567	–
568	–	/**
569	–	* The number of times to spin before blocking in timed waits.
570	–	* The value is empirically derived.
571	–	*/
572	–	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
573	–
832		/**
833	<	* The number of times to spin before blocking in untimed waits.
834	<	* This is greater than timed value because untimed waits spin
835	<	* faster since they don't need to check times on each spin.
833	>	* Tries to enqueue given node in the appropriate wait queue.
834	>	*
835	>	* @return true if successful
836		*/
837	<	static final int maxUntimedSpins = maxTimedSpins * 32;
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	<	* The number of nanoseconds for which it is faster to spin
844	<	* rather than to use timed park. A rough estimate suffices.
843	>	* Enqueues node and waits unless aborted or signalled.
844	>	*
845	>	* @return current phase
846		*/
847	<	static final long spinForTimeoutThreshold = 1000L;
847	>	private int untimedWait(int phase) {
848	>	QNode node = null;
849	>	boolean queued = false;
850	>	boolean interrupted = false;
851	>	int p;
852	>	while ((p = getPhase()) == phase) {
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	>	interrupted = node.doWait();
861	>	}
862	>	if (node != null)
863	>	node.thread = null;
864	>	releaseWaiters(phase);
865	>	if (interrupted)
866	>	Thread.currentThread().interrupt();
867	>	return p;
868	>	}
869
870		/**
871	<	* Enqueues node and waits unless aborted or signalled.
871	>	* Interruptible version
872	>	* @return current phase
873		*/
874	<	private boolean untimedWait(Thread thread, int currentPhase,
591	<	boolean abortOnInterrupt) {
592	<	final AtomicReference<QNode> head = this.head;
593	<	final AtomicLong state = this.state;
594	<	boolean wasInterrupted = false;
874	>	private int interruptibleWait(int phase) throws InterruptedException {
875		QNode node = null;
876		boolean queued = false;
877	<	int spins = maxUntimedSpins;
878	<	while (phaseOf(state.get()) == currentPhase) {
879	<	QNode h;
880	<	if (node != null && queued) {
881	<	if (node.thread != null) {
882	<	LockSupport.park();
883	<	if (Thread.interrupted()) {
884	<	wasInterrupted = true;
885	<	if (abortOnInterrupt)
606	<	break;
607	<	}
608	<	}
609	<	}
610	<	else if ((h = head.get()) != null && h.phase != currentPhase) {
611	<	if (phaseOf(state.get()) == currentPhase) { // must recheck
612	<	if (head.compareAndSet(h, h.next)) {
613	<	Thread t = h.thread; // help clear out old waiters
614	<	if (t != null) {
615	<	h.thread = null;
616	<	LockSupport.unpark(t);
617	<	}
618	<	}
619	<	}
620	<	else
621	<	break;
622	<	}
623	<	else if (node != null)
624	<	queued = head.compareAndSet(node.next = h, node);
625	<	else if (spins <= 0)
626	<	node = new QNode(thread, currentPhase);
877	>	boolean interrupted = false;
878	>	int p;
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	<	return wasInterrupted;
891	>	if (p != phase || (p = getPhase()) != phase)
892	>	releaseWaiters(phase);
893	>	if (interrupted)
894	>	throw new InterruptedException();
895	>	return p;
896		}
897
898		/**
899	<	* Messier timeout version
899	>	* Timeout version.
900	>	* @return current phase
901		*/
902	<	private void timedWait(Thread thread, int currentPhase, long nanos)
902	>	private int timedWait(int phase, long nanos)
903		throws InterruptedException, TimeoutException {
904	<	final AtomicReference<QNode> head = this.head;
641	<	final AtomicLong state = this.state;
642	<	long lastTime = System.nanoTime();
904	>	long startTime = System.nanoTime();
905		QNode node = null;
906		boolean queued = false;
907	<	int spins = maxTimedSpins;
908	<	while (phaseOf(state.get()) == currentPhase) {
909	<	QNode h;
910	<	long now = System.nanoTime();
911	<	nanos -= now - lastTime;
912	<	lastTime = now;
913	<	if (nanos <= 0) {
914	<	if (node != null)
915	<	node.thread = null;
916	<	if (phaseOf(state.get()) == currentPhase)
917	<	throw new TimeoutException();
656	<	else
657	<	break;
658	<	}
659	<	else if (node != null && queued) {
660	<	if (node.thread != null &&
661	<	nanos > spinForTimeoutThreshold) {
662	<	//                LockSupport.parkNanos(this, nanos);
663	<	LockSupport.parkNanos(nanos);
664	<	if (Thread.interrupted()) {
665	<	node.thread = null;
666	<	throw new InterruptedException();
667	<	}
668	<	}
669	<	}
670	<	else if ((h = head.get()) != null && h.phase != currentPhase) {
671	<	if (phaseOf(state.get()) == currentPhase) { // must recheck
672	<	if (head.compareAndSet(h, h.next)) {
673	<	Thread t = h.thread; // help clear out old waiters
674	<	if (t != null) {
675	<	h.thread = null;
676	<	LockSupport.unpark(t);
677	<	}
678	<	}
679	<	}
680	<	else
681	<	break;
682	<	}
683	<	else if (node != null)
684	<	queued = head.compareAndSet(node.next = h, node);
685	<	else if (spins <= 0)
686	<	node = new QNode(thread, currentPhase);
907	>	boolean interrupted = false;
908	>	int p;
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	<	--spins;
919	>	interrupted = node.doWait();
920		}
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	<	}
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	+	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	+	private static long fieldOffset(String fieldName, Class<?> klazz) {
959	+	try {
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);
975	+	}
976	+	}

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