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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 1.50 by dl, Sat Nov 6 16:12:10 2010 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.*;
10	>	import java.util.concurrent.atomic.AtomicReference;
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.
14	>	* A reusable synchronization barrier, similar in functionality to
15	>	* {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and
16	>	* {@link java.util.concurrent.CountDownLatch CountDownLatch}
17	>	* but supporting more flexible usage.
18		*
19	<	* <ul>
19	>	* <p> <b>Registration.</b> Unlike the case for other barriers, the
20	>	* number of parties <em>registered</em> to synchronize on a phaser
21	>	* may vary over time.  Tasks may be registered at any time (using
22	>	* methods {@link #register}, {@link #bulkRegister}, or forms of
23	>	* constructors establishing initial numbers of parties), and
24	>	* optionally deregistered upon any arrival (using {@link
25	>	* #arriveAndDeregister}).  As is the case with most basic
26	>	* synchronization constructs, registration and deregistration affect
27	>	* only internal counts; they do not establish any further internal
28	>	* bookkeeping, so tasks cannot query whether they are registered.
29	>	* (However, you can introduce such bookkeeping by subclassing this
30	>	* class.)
31		*
32	<	* <li> The number of parties synchronizing on the barrier may vary
33	<	* over time.  A task may register to be a party in a barrier at any
34	<	* time, and may deregister upon arriving at the barrier.  As is the
35	<	* case with most basic synchronization constructs, registration
36	<	* and deregistration affect only internal counts; they do not
37	<	* establish any further internal bookkeeping, so tasks cannot query
38	<	* whether they are registered.
39	<	*
40	<	* <li> Each generation has an associated phase value, starting at
41	<	* zero, and advancing when all parties reach the barrier (wrapping
42	<	* around to zero after reaching <tt>Integer.MAX_VALUE</tt>).
31	<	*
32	<	* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited.
33	<	* Method <tt>arriveAndAwaitAdvance</tt> has effect analogous to
34	<	* <tt>CyclicBarrier.await</tt>.  However, Phasers separate two
35	<	* aspects of coordination, that may be invoked independently:
32	>	* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
33	>	* Phaser} may be repeatedly awaited.  Method {@link
34	>	* #arriveAndAwaitAdvance} has effect analogous to {@link
35	>	* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
36	>	* generation of a {@code Phaser} has an associated phase number. The
37	>	* phase number starts at zero, and advances when all parties arrive
38	>	* at the barrier, wrapping around to zero after reaching {@code
39	>	* Integer.MAX_VALUE}. The use of phase numbers enables independent
40	>	* control of actions upon arrival at a barrier and upon awaiting
41	>	* others, via two kinds of methods that may be invoked by any
42	>	* registered party:
43		*
44		* <ul>
45		*
46	<	*   <li> Arriving at a barrier. Methods <tt>arrive</tt> and
47	<	*       <tt>arriveAndDeregister</tt> do not block, but return
48	<	*       the phase value on entry to the method.
49	<	*
50	<	*   <li> Awaiting others. Method <tt>awaitAdvance</tt> requires an
51	<	*       argument indicating the entry phase, and returns when the
52	<	*       barrier advances to a new phase.
46	>	*   <li> <b>Arrival.</b> Methods {@link #arrive} and
47	>	*       {@link #arriveAndDeregister} record arrival at a
48	>	*       barrier. These methods do not block, but return an associated
49	>	*       <em>arrival phase number</em>; that is, the phase number of
50	>	*       the barrier to which the arrival applied. When the final
51	>	*       party for a given phase arrives, an optional barrier action
52	>	*       is performed and the phase advances.  Barrier actions,
53	>	*       performed by the party triggering a phase advance, are
54	>	*       arranged by overriding method {@link #onAdvance(int, int)},
55	>	*       which also controls termination. Overriding this method is
56	>	*       similar to, but more flexible than, providing a barrier
57	>	*       action to a {@code CyclicBarrier}.
58	>	*
59	>	*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
60	>	*       argument indicating an arrival phase number, and returns when
61	>	*       the barrier advances to (or is already at) a different phase.
62	>	*       Unlike similar constructions using {@code CyclicBarrier},
63	>	*       method {@code awaitAdvance} continues to wait even if the
64	>	*       waiting thread is interrupted. Interruptible and timeout
65	>	*       versions are also available, but exceptions encountered while
66	>	*       tasks wait interruptibly or with timeout do not change the
67	>	*       state of the barrier. If necessary, you can perform any
68	>	*       associated recovery within handlers of those exceptions,
69	>	*       often after invoking {@code forceTermination}.  Phasers may
70	>	*       also be used by tasks executing in a {@link ForkJoinPool},
71	>	*       which will ensure sufficient parallelism to execute tasks
72	>	*       when others are blocked waiting for a phase to advance.
73	>	*
74		* </ul>
75		*
76	+	* <p> <b>Termination.</b> A {@code Phaser} may enter a
77	+	* <em>termination</em> state in which all synchronization methods
78	+	* immediately return without updating phaser state or waiting for
79	+	* advance, and indicating (via a negative phase value) that execution
80	+	* is complete.  Termination is triggered when an invocation of {@code
81	+	* onAdvance} returns {@code true}.  As illustrated below, when
82	+	* phasers control actions with a fixed number of iterations, it is
83	+	* often convenient to override this method to cause termination when
84	+	* the current phase number reaches a threshold. Method {@link
85	+	* #forceTermination} is also available to abruptly release waiting
86	+	* threads and allow them to terminate.
87		*
88	<	* <li> Barrier actions, performed by the task triggering a phase
89	<	* advance while others may be waiting, are arranged by overriding
90	<	* method <tt>onAdvance</tt>, that also controls termination.
91	<	*
92	<	* <li> Phasers may enter a <em>termination</em> state in which all
93	<	* await actions immediately return, indicating (via a negative phase
94	<	* value) that execution is complete.  Termination is triggered by
56	<	* executing the overridable <tt>onAdvance</tt> method that is invoked
57	<	* each time the barrier is tripped. When a Phaser is controlling an
58	<	* action with a fixed number of iterations, it is often convenient to
59	<	* override this method to cause termination when the current phase
60	<	* number reaches a threshold.  Method <tt>forceTermination</tt> is
61	<	* also available to assist recovery actions upon failure.
62	<	*
63	<	* <li> Unlike most synchronizers, a Phaser may also be used with
64	<	* 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
68	<	* CyclicBarriers, exceptions encountered while tasks wait
69	<	* interruptibly or with timeout do not change the state of the
70	<	* barrier. If necessary, you can perform any associated recovery
71	<	* within handlers of those exceptions.
88	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
89	>	* in tree structures) to reduce contention. Phasers with large
90	>	* numbers of parties that would otherwise experience heavy
91	>	* synchronization contention costs may instead be set up so that
92	>	* groups of sub-phasers share a common parent.  This may greatly
93	>	* increase throughput even though it incurs greater per-operation
94	>	* overhead.
95		*
96	<	* </ul>
96	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
97	>	* only by registered parties, the current state of a phaser may be
98	>	* monitored by any caller.  At any given moment there are {@link
99	>	* #getRegisteredParties} parties in total, of which {@link
100	>	* #getArrivedParties} have arrived at the current phase ({@link
101	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
102	>	* parties arrive, the phase advances.  The values returned by these
103	>	* methods may reflect transient states and so are not in general
104	>	* useful for synchronization control.  Method {@link #toString}
105	>	* returns snapshots of these state queries in a form convenient for
106	>	* informal monitoring.
107	>	*
108	>	* <p><b>Sample usages:</b>
109	>	*
110	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
111	>	* to control a one-shot action serving a variable number of parties.
112	>	* The typical idiom is for the method setting this up to first
113	>	* register, then start the actions, then deregister, as in:
114	>	*
115	>	*  <pre> {@code
116	>	* void runTasks(List<Runnable> tasks) {
117	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
118	>	*   // create and start threads
119	>	*   for (Runnable task : tasks) {
120	>	*     phaser.register();
121	>	*     new Thread() {
122	>	*       public void run() {
123	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
124	>	*         task.run();
125	>	*       }
126	>	*     }.start();
127	>	*   }
128	>	*
129	>	*   // allow threads to start and deregister self
130	>	*   phaser.arriveAndDeregister();
131	>	* }}</pre>
132	>	*
133	>	* <p>One way to cause a set of threads to repeatedly perform actions
134	>	* for a given number of iterations is to override {@code onAdvance}:
135	>	*
136	>	*  <pre> {@code
137	>	* void startTasks(List<Runnable> tasks, final int iterations) {
138	>	*   final Phaser phaser = new Phaser() {
139	>	*     protected boolean onAdvance(int phase, int registeredParties) {
140	>	*       return phase >= iterations || registeredParties == 0;
141	>	*     }
142	>	*   };
143	>	*   phaser.register();
144	>	*   for (final Runnable task : tasks) {
145	>	*     phaser.register();
146	>	*     new Thread() {
147	>	*       public void run() {
148	>	*         do {
149	>	*           task.run();
150	>	*           phaser.arriveAndAwaitAdvance();
151	>	*         } while (!phaser.isTerminated());
152	>	*       }
153	>	*     }.start();
154	>	*   }
155	>	*   phaser.arriveAndDeregister(); // deregister self, don't wait
156	>	* }}</pre>
157		*
158	<	* <p><b>Sample usage:</b>
158	>	* If the main task must later await termination, it
159	>	* may re-register and then execute a similar loop:
160	>	*  <pre> {@code
161	>	*   // ...
162	>	*   phaser.register();
163	>	*   while (!phaser.isTerminated())
164	>	*     phaser.arriveAndAwaitAdvance();}</pre>
165		*
166	<	* <p>[todo: non-FJ example]
166	>	* <p>Related constructions may be used to await particular phase numbers
167	>	* in contexts where you are sure that the phase will never wrap around
168	>	* {@code Integer.MAX_VALUE}. For example:
169		*
170	<	* <p> A Phaser may be used to support a style of programming in
171	<	* which a task waits for others to complete, without otherwise
172	<	* needing to keep track of which tasks it is waiting for. This is
173	<	* similar to the "sync" construct in Cilk and "clocks" in X10.
174	<	* Special constructions based on such barriers are available using
175	<	* the <tt>LinkedAsyncAction</tt> and <tt>CyclicAction</tt> classes,
176	<	* but they can be useful in other contexts as well.  For a simple
177	<	* (but not very useful) example, here is a variant of Fibonacci:
87	<	*
88	<	* <pre>
89	<	* class BarrierFibonacci extends RecursiveAction {
90	<	*   int argument, result;
91	<	*   final Phaser parentBarrier;
92	<	*   BarrierFibonacci(int n, Phaser parentBarrier) {
93	<	*     this.argument = n;
94	<	*     this.parentBarrier = parentBarrier;
95	<	*     parentBarrier.register();
170	>	*  <pre> {@code
171	>	* void awaitPhase(Phaser phaser, int phase) {
172	>	*   int p = phaser.register(); // assumes caller not already registered
173	>	*   while (p < phase) {
174	>	*     if (phaser.isTerminated())
175	>	*       // ... deal with unexpected termination
176	>	*     else
177	>	*       p = phaser.arriveAndAwaitAdvance();
178		*   }
179	<	*   protected void compute() {
180	<	*     int n = argument;
181	<	*     if (n &lt;= 1)
182	<	*        result = n;
183	<	*     else {
184	<	*        Phaser childBarrier = new Phaser(1);
185	<	*        BarrierFibonacci f1 = new BarrierFibonacci(n - 1, childBarrier);
186	<	*        BarrierFibonacci f2 = new BarrierFibonacci(n - 2, childBarrier);
187	<	*        f1.fork();
188	<	*        f2.fork();
189	<	*        childBarrier.arriveAndAwait();
190	<	*        result = f1.result + f2.result;
179	>	*   phaser.arriveAndDeregister();
180	>	* }}</pre>
181	>	*
182	>	*
183	>	* <p>To create a set of tasks using a tree of phasers,
184	>	* you could use code of the following form, assuming a
185	>	* Task class with a constructor accepting a phaser that
186	>	* it registers with upon construction:
187	>	*
188	>	*  <pre> {@code
189	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
190	>	*   if (hi - lo > TASKS_PER_PHASER) {
191	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
192	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
193	>	*       build(actions, i, j, new Phaser(ph));
194		*     }
195	<	*     parentBarrier.arriveAndDeregister();
195	>	*   } else {
196	>	*     for (int i = lo; i < hi; ++i)
197	>	*       actions[i] = new Task(ph);
198	>	*       // assumes new Task(ph) performs ph.register()
199		*   }
200		* }
201	<	* </pre>
201	>	* // .. initially called, for n tasks via
202	>	* build(new Task[n], 0, n, new Phaser());}</pre>
203	>	*
204	>	* The best value of {@code TASKS_PER_PHASER} depends mainly on
205	>	* expected barrier synchronization rates. A value as low as four may
206	>	* be appropriate for extremely small per-barrier task bodies (thus
207	>	* high rates), or up to hundreds for extremely large ones.
208		*
209		* <p><b>Implementation notes</b>: This implementation restricts the
210	<	* maximum number of parties to 65535. Attempts to register
211	<	* additional parties result in IllegalStateExceptions.
210	>	* maximum number of parties to 65535. Attempts to register additional
211	>	* parties result in {@code IllegalStateException}. However, you can and
212	>	* should create tiered phasers to accommodate arbitrarily large sets
213	>	* of participants.
214	>	*
215	>	* @since 1.7
216	>	* @author Doug Lea
217		*/
218		public class Phaser {
219		/*
220		* This class implements an extension of X10 "clocks".  Thanks to
221	<	* Vijay Saraswat for the idea of applying it to ForkJoinTasks,
222	<	* and to Vivek Sarkar for enhancements to extend functionality.
221	>	* Vijay Saraswat for the idea, and to Vivek Sarkar for
222	>	* enhancements to extend functionality.
223		*/
224
225		/**
226		* Barrier state representation. Conceptually, a barrier contains
227		* four values:
228	<	*
228	>	*
229		* * parties -- the number of parties to wait (16 bits)
230		* * unarrived -- the number of parties yet to hit barrier (16 bits)
231		* * phase -- the generation of the barrier (31 bits)
232		* * terminated -- set if barrier is terminated (1 bit)
233		*
234		* However, to efficiently maintain atomicity, these values are
235	<	* packed into a single AtomicLong. Termination uses the sign bit
236	<	* of 32 bit representation of phase, so phase is set to -1 on
237	<	* termination.
238	<	*/
239	<	private final AtomicLong state;
240	<
241	<	/**
143	<	* Head of Treiber stack for waiting nonFJ threads.
235	>	* packed into a single (atomic) long. Termination uses the sign
236	>	* bit of 32 bit representation of phase, so phase is set to -1 on
237	>	* termination. Good performance relies on keeping state decoding
238	>	* and encoding simple, and keeping race windows short.
239	>	*
240	>	* Note: there are some cheats in arrive() that rely on unarrived
241	>	* count being lowest 16 bits.
242		*/
243	<	private final AtomicReference<QNode> head = new AtomicReference<QNode>();
243	>	private volatile long state;
244
245	<	private static final int ushortBits = 16;
246	<	private static final int ushortMask =  (1 << ushortBits) - 1;
149	<	private static final int phaseMask = 0x7fffffff;
245	>	private static final int ushortMask = 0xffff;
246	>	private static final int phaseMask  = 0x7fffffff;
247
248		private static int unarrivedOf(long s) {
249	<	return (int)(s & ushortMask);
249	>	return (int) (s & ushortMask);
250		}
251
252		private static int partiesOf(long s) {
253	<	return (int)(s & (ushortMask << 16)) >>> 16;
253	>	return ((int) s) >>> 16;
254		}
255
256		private static int phaseOf(long s) {
257	<	return (int)(s >>> 32);
257	>	return (int) (s >>> 32);
258		}
259
260		private static int arrivedOf(long s) {
#	Line 165 | Line 262 | public class Phaser {
262		}
263
264		private static long stateFor(int phase, int parties, int unarrived) {
265	<	return (((long)phase) << 32) | ((parties << 16) | unarrived);
265	>	return ((((long) phase) << 32) | (((long) parties) << 16) |
266	>	(long) unarrived);
267	>	}
268	>
269	>	private static long trippedStateFor(int phase, int parties) {
270	>	long lp = (long) parties;
271	>	return (((long) phase) << 32) | (lp << 16) | lp;
272		}
273
274	<	private static IllegalStateException badBounds(int parties, int unarrived) {
275	<	return new IllegalStateException("Attempt to set " + unarrived +
276	<	" unarrived of " + parties + " parties");
274	>	/**
275	>	* Returns message string for bad bounds exceptions.
276	>	*/
277	>	private static String badBounds(int parties, int unarrived) {
278	>	return ("Attempt to set " + unarrived +
279	>	" unarrived of " + parties + " parties");
280	>	}
281	>
282	>	/**
283	>	* The parent of this phaser, or null if none
284	>	*/
285	>	private final Phaser parent;
286	>
287	>	/**
288	>	* The root of phaser tree. Equals this if not in a tree.  Used to
289	>	* support faster state push-down.
290	>	*/
291	>	private final Phaser root;
292	>
293	>	// Wait queues
294	>
295	>	/**
296	>	* Heads of Treiber stacks for waiting threads. To eliminate
297	>	* contention when releasing some threads while adding others, we
298	>	* use two of them, alternating across even and odd phases.
299	>	* Subphasers share queues with root to speed up releases.
300	>	*/
301	>	private final AtomicReference<QNode> evenQ;
302	>	private final AtomicReference<QNode> oddQ;
303	>
304	>	private AtomicReference<QNode> queueFor(int phase) {
305	>	return ((phase & 1) == 0) ? evenQ : oddQ;
306	>	}
307	>
308	>	/**
309	>	* Returns current state, first resolving lagged propagation from
310	>	* root if necessary.
311	>	*/
312	>	private long getReconciledState() {
313	>	return (parent == null) ? state : reconcileState();
314	>	}
315	>
316	>	/**
317	>	* Recursively resolves state.
318	>	*/
319	>	private long reconcileState() {
320	>	Phaser par = parent;
321	>	long s = state;
322	>	if (par != null) {
323	>	int phase, rootPhase;
324	>	while ((phase = phaseOf(s)) >= 0 &&
325	>	(rootPhase = phaseOf(root.state)) != phase &&
326	>	(rootPhase < 0 || unarrivedOf(s) == 0)) {
327	>	int parentPhase = phaseOf(par.getReconciledState());
328	>	if (parentPhase != phase) {
329	>	long next = trippedStateFor(parentPhase, partiesOf(s));
330	>	if (state == s)
331	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
332	>	}
333	>	s = state;
334	>	}
335	>	}
336	>	return s;
337		}
338
339		/**
340	<	* Creates a new Phaser without any initially registered parties,
341	<	* and initial phase number 0.
340	>	* Creates a new phaser without any initially registered parties,
341	>	* initial phase number 0, and no parent. Any thread using this
342	>	* phaser will need to first register for it.
343		*/
344		public Phaser() {
345	<	state = new AtomicLong(stateFor(0, 0, 0));
345	>	this(null, 0);
346		}
347
348		/**
349	<	* Creates a new Phaser with the given numbers of registered
350	<	* unarrived parties and initial phase number 0.
351	<	* @param parties the number of parties required to trip barrier.
349	>	* Creates a new phaser with the given number of registered
350	>	* unarrived parties, initial phase number 0, and no parent.
351	>	*
352	>	* @param parties the number of parties required to trip barrier
353		* @throws IllegalArgumentException if parties less than zero
354	<	* or greater than the maximum number of parties supported.
354	>	* or greater than the maximum number of parties supported
355		*/
356		public Phaser(int parties) {
357	+	this(null, parties);
358	+	}
359	+
360	+	/**
361	+	* Creates a new phaser with the given parent, without any
362	+	* initially registered parties. If parent is non-null this phaser
363	+	* is registered with the parent and its initial phase number is
364	+	* the same as that of parent phaser.
365	+	*
366	+	* @param parent the parent phaser
367	+	*/
368	+	public Phaser(Phaser parent) {
369	+	this(parent, 0);
370	+	}
371	+
372	+	/**
373	+	* Creates a new phaser with the given parent and number of
374	+	* registered unarrived parties. If parent is non-null, this phaser
375	+	* is registered with the parent and its initial phase number is
376	+	* the same as that of parent phaser.
377	+	*
378	+	* @param parent the parent phaser
379	+	* @param parties the number of parties required to trip barrier
380	+	* @throws IllegalArgumentException if parties less than zero
381	+	* or greater than the maximum number of parties supported
382	+	*/
383	+	public Phaser(Phaser parent, int parties) {
384		if (parties < 0 || parties > ushortMask)
385		throw new IllegalArgumentException("Illegal number of parties");
386	<	state = new AtomicLong(stateFor(0, parties, parties));
386	>	int phase;
387	>	this.parent = parent;
388	>	if (parent != null) {
389	>	Phaser r = parent.root;
390	>	this.root = r;
391	>	this.evenQ = r.evenQ;
392	>	this.oddQ = r.oddQ;
393	>	phase = parent.register();
394	>	}
395	>	else {
396	>	this.root = this;
397	>	this.evenQ = new AtomicReference<QNode>();
398	>	this.oddQ = new AtomicReference<QNode>();
399	>	phase = 0;
400	>	}
401	>	this.state = trippedStateFor(phase, parties);
402		}
403
404		/**
405		* Adds a new unarrived party to this phaser.
406	<	* @return the current barrier phase number upon registration
406	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
407	>	* this method may wait until its completion before registering.
408	>	*
409	>	* @return the arrival phase number to which this registration applied
410	>	* @throws IllegalStateException if attempting to register more
411	>	* than the maximum supported number of parties
412	>	*/
413	>	public int register() {
414	>	return doRegister(1);
415	>	}
416	>
417	>	/**
418	>	* Adds the given number of new unarrived parties to this phaser.
419	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
420	>	* this method may wait until its completion before registering.
421	>	*
422	>	* @param parties the number of additional parties required to trip barrier
423	>	* @return the arrival phase number to which this registration applied
424		* @throws IllegalStateException if attempting to register more
425	<	* than the maximum supported number of parties.
425	>	* than the maximum supported number of parties
426	>	* @throws IllegalArgumentException if {@code parties < 0}
427		*/
428	<	public int register() { // increment both parties and unarrived
429	<	final AtomicLong state = this.state;
430	<	for (;;) {
431	<	long s = state.get();
432	<	int phase = phaseOf(s);
433	<	int parties = partiesOf(s) + 1;
434	<	int unarrived = unarrivedOf(s) + 1;
435	<	if (parties > ushortMask || unarrived > ushortMask)
436	<	throw badBounds(parties, unarrived);
437	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
438	<	return phase;
428	>	public int bulkRegister(int parties) {
429	>	if (parties < 0)
430	>	throw new IllegalArgumentException();
431	>	if (parties == 0)
432	>	return getPhase();
433	>	return doRegister(parties);
434	>	}
435	>
436	>	/**
437	>	* Shared code for register, bulkRegister
438	>	*/
439	>	private int doRegister(int registrations) {
440	>	Phaser par = parent;
441	>	long s;
442	>	int phase;
443	>	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
444	>	int p = partiesOf(s);
445	>	int u = unarrivedOf(s);
446	>	int unarrived = u + registrations;
447	>	int parties = p + registrations;
448	>	if (u == 0 && p != 0)  // if tripped, wait for advance
449	>	untimedWait(phase);
450	>	else if (parties > ushortMask)
451	>	throw new IllegalStateException(badBounds(parties, unarrived));
452	>	else if (par == null || phaseOf(root.state) == phase) {
453	>	long next = stateFor(phase, parties, unarrived);
454	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
455	>	break;
456	>	}
457		}
458	+	return phase;
459		}
460
461		/**
462		* Arrives at the barrier, but does not wait for others.  (You can
463	<	* in turn wait for others via {@link #awaitAdvance}).
463	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
464	>	* unenforced usage error for an unregistered party to invoke this
465	>	* method.
466		*
467	<	* @return the current barrier phase number upon entry to
468	<	* this method, or a negative value if terminated;
469	<	* @throws IllegalStateException if the number of unarrived
470	<	* parties would become negative.
471	<	*/
472	<	public int arrive() { // decrement unarrived. If zero, trip
473	<	final AtomicLong state = this.state;
474	<	for (;;) {
475	<	long s = state.get();
230	<	int phase = phaseOf(s);
467	>	* @return the arrival phase number, or a negative value if terminated
468	>	* @throws IllegalStateException if not terminated and the number
469	>	* of unarrived parties would become negative
470	>	*/
471	>	public int arrive() {
472	>	Phaser par = parent;
473	>	long s;
474	>	int phase;
475	>	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
476		int parties = partiesOf(s);
477		int unarrived = unarrivedOf(s) - 1;
478	<	if (unarrived < 0)
479	<	throw badBounds(parties, unarrived);
480	<	if (unarrived == 0 && phase >= 0) {
481	<	trip(phase, parties);
482	<	return phase;
478	>	if (unarrived > 0) {                // Not the last arrival
479	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s - 1))
480	>	break;                      // s-1 adds one arrival
481	>	}
482	>	else if (unarrived < 0)
483	>	throw new IllegalStateException(badBounds(parties, unarrived));
484	>	else if (par == null) {             // directly trip
485	>	long next = trippedStateFor(onAdvance(phase, parties) ? -1 :
486	>	((phase + 1) & phaseMask),
487	>	parties);
488	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) {
489	>	releaseWaiters(phase);
490	>	break;
491	>	}
492	>	}
493	>	else if (phaseOf(root.state) == phase &&
494	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, s - 1)) {
495	>	par.arrive();                   // cascade to parent
496	>	reconcileState();
497	>	break;
498		}
239	–	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
240	–	return phase;
499		}
500	+	return phase;
501		}
502
503		/**
504	<	* Arrives at the barrier, and deregisters from it, without
505	<	* waiting for others.
504	>	* Arrives at the barrier and deregisters from it without waiting
505	>	* for others. Deregistration reduces the number of parties
506	>	* required to trip the barrier in future phases.  If this phaser
507	>	* has a parent, and deregistration causes this phaser to have
508	>	* zero parties, this phaser also arrives at and is deregistered
509	>	* from its parent.  It is an unenforced usage error for an
510	>	* unregistered party to invoke this method.
511		*
512	<	* @return the current barrier phase number upon entry to
513	<	* this method, or a negative value if terminated;
514	<	* @throws IllegalStateException if the number of registered or
515	<	* unarrived parties would become negative.
516	<	*/
517	<	public int arriveAndDeregister() { // Same as arrive, plus decrement parties
518	<	final AtomicLong state = this.state;
519	<	for (;;) {
520	<	long s = state.get();
521	<	int phase = phaseOf(s);
512	>	* @return the arrival phase number, or a negative value if terminated
513	>	* @throws IllegalStateException if not terminated and the number
514	>	* of registered or unarrived parties would become negative
515	>	*/
516	>	public int arriveAndDeregister() {
517	>	// similar to arrive, but too different to merge
518	>	Phaser par = parent;
519	>	long s;
520	>	int phase;
521	>	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
522		int parties = partiesOf(s) - 1;
523		int unarrived = unarrivedOf(s) - 1;
524	<	if (parties < 0 || unarrived < 0)
525	<	throw badBounds(parties, unarrived);
526	<	if (unarrived == 0 && phase >= 0) {
527	<	trip(phase, parties);
528	<	return phase;
524	>	if (unarrived > 0) {
525	>	long next = stateFor(phase, parties, unarrived);
526	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
527	>	break;
528	>	}
529	>	else if (unarrived < 0)
530	>	throw new IllegalStateException(badBounds(parties, unarrived));
531	>	else if (par == null) {
532	>	long next = trippedStateFor(onAdvance(phase, parties)? -1:
533	>	(phase + 1) & phaseMask,
534	>	parties);
535	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) {
536	>	releaseWaiters(phase);
537	>	break;
538	>	}
539	>	}
540	>	else if (phaseOf(root.state) == phase) {
541	>	long next = stateFor(phase, parties, 0);
542	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) {
543	>	if (parties == 0)
544	>	par.arriveAndDeregister();
545	>	else
546	>	par.arrive();
547	>	reconcileState();
548	>	break;
549	>	}
550		}
266	–	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
267	–	return phase;
551		}
552	+	return phase;
553		}
554
555		/**
556	<	* Arrives at the barrier and awaits others. Unlike other arrival
557	<	* methods, this method returns the arrival index of the
558	<	* caller. The caller tripping the barrier returns zero, the
559	<	* previous caller 1, and so on.
560	<	* @return the arrival index
561	<	* @throws IllegalStateException if the number of unarrived
562	<	* parties would become negative.
556	>	* Arrives at the barrier and awaits others. Equivalent in effect
557	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
558	>	* interruption or timeout, you can arrange this with an analogous
559	>	* construction using one of the other forms of the {@code
560	>	* awaitAdvance} method.  If instead you need to deregister upon
561	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
562	>	* usage error for an unregistered party to invoke this method.
563	>	*
564	>	* @return the arrival phase number, or a negative number if terminated
565	>	* @throws IllegalStateException if not terminated and the number
566	>	* of unarrived parties would become negative
567		*/
568		public int arriveAndAwaitAdvance() {
569	<	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	<	}
569	>	return awaitAdvance(arrive());
570		}
571
572		/**
573	<	* Awaits the phase of the barrier to advance from the given
574	<	* value, or returns immediately if this barrier is terminated.
575	<	* @param phase the phase on entry to this method
576	<	* @return the phase on exit from this method
573	>	* Awaits the phase of the barrier to advance from the given phase
574	>	* value, returning immediately if the current phase of the
575	>	* barrier is not equal to the given phase value or this barrier
576	>	* is terminated.
577	>	*
578	>	* @param phase an arrival phase number, or negative value if
579	>	* terminated; this argument is normally the value returned by a
580	>	* previous call to {@code arrive} or its variants
581	>	* @return the next arrival phase number, or a negative value
582	>	* if terminated or argument is negative
583		*/
584		public int awaitAdvance(int phase) {
585		if (phase < 0)
586		return phase;
587	<	Thread current = Thread.currentThread();
588	<	if (current instanceof ForkJoinWorkerThread)
589	<	return helpingWait(phase);
590	<	if (untimedWait(current, phase, false))
313	<	current.interrupt();
314	<	return phaseOf(state.get());
587	>	int p = getPhase();
588	>	if (p != phase)
589	>	return p;
590	>	return untimedWait(phase);
591		}
592
593		/**
594	<	* Awaits the phase of the barrier to advance from the given
595	<	* value, or returns immediately if this barrier is terminated, or
596	<	* throws InterruptedException if interrupted while waiting.
597	<	* @param phase the phase on entry to this method
598	<	* @return the phase on exit from this method
594	>	* Awaits the phase of the barrier to advance from the given phase
595	>	* value, throwing {@code InterruptedException} if interrupted
596	>	* while waiting, or returning immediately if the current phase of
597	>	* the barrier is not equal to the given phase value or this
598	>	* barrier is terminated.
599	>	*
600	>	* @param phase an arrival phase number, or negative value if
601	>	* terminated; this argument is normally the value returned by a
602	>	* previous call to {@code arrive} or its variants
603	>	* @return the next arrival phase number, or a negative value
604	>	* if terminated or argument is negative
605		* @throws InterruptedException if thread interrupted while waiting
606		*/
607	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
607	>	public int awaitAdvanceInterruptibly(int phase)
608	>	throws InterruptedException {
609		if (phase < 0)
610		return phase;
611	<	Thread current = Thread.currentThread();
612	<	if (current instanceof ForkJoinWorkerThread)
613	<	return helpingWait(phase);
614	<	else if (Thread.interrupted() || untimedWait(current, phase, true))
332	<	throw new InterruptedException();
333	<	else
334	<	return phaseOf(state.get());
611	>	int p = getPhase();
612	>	if (p != phase)
613	>	return p;
614	>	return interruptibleWait(phase);
615		}
616
617		/**
618	<	* Awaits the phase of the barrier to advance from the given value
619	<	* or the given timeout elapses, or returns immediately if this
620	<	* barrier is terminated.
621	<	* @param phase the phase on entry to this method
622	<	* @return the phase on exit from this method
618	>	* Awaits the phase of the barrier to advance from the given phase
619	>	* value or the given timeout to elapse, throwing {@code
620	>	* InterruptedException} if interrupted while waiting, or
621	>	* returning immediately if the current phase of the barrier is
622	>	* not equal to the given phase value or this barrier is
623	>	* terminated.
624	>	*
625	>	* @param phase an arrival phase number, or negative value if
626	>	* terminated; this argument is normally the value returned by a
627	>	* previous call to {@code arrive} or its variants
628	>	* @param timeout how long to wait before giving up, in units of
629	>	*        {@code unit}
630	>	* @param unit a {@code TimeUnit} determining how to interpret the
631	>	*        {@code timeout} parameter
632	>	* @return the next arrival phase number, or a negative value
633	>	* if terminated or argument is negative
634		* @throws InterruptedException if thread interrupted while waiting
635		* @throws TimeoutException if timed out while waiting
636		*/
637	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
637	>	public int awaitAdvanceInterruptibly(int phase,
638	>	long timeout, TimeUnit unit)
639		throws InterruptedException, TimeoutException {
640	+	long nanos = unit.toNanos(timeout);
641		if (phase < 0)
642		return phase;
643	<	long nanos = unit.toNanos(timeout);
644	<	Thread current = Thread.currentThread();
645	<	if (current instanceof ForkJoinWorkerThread)
646	<	return timedHelpingWait(phase, nanos);
354	<	timedWait(current, phase, nanos);
355	<	return phaseOf(state.get());
643	>	int p = getPhase();
644	>	if (p != phase)
645	>	return p;
646	>	return timedWait(phase, nanos);
647		}
648
649		/**
650		* Forces this barrier to enter termination state. Counts of
651	<	* arrived and registered parties are unaffected. This method may
652	<	* be useful for coordinating recovery after one or more tasks
653	<	* encounter unexpected exceptions.
651	>	* arrived and registered parties are unaffected. If this phaser
652	>	* has a parent, it too is terminated. This method may be useful
653	>	* for coordinating recovery after one or more tasks encounter
654	>	* unexpected exceptions.
655		*/
656		public void forceTermination() {
657	<	final AtomicLong state = this.state;
658	<	for (;;) {
659	<	long s = state.get();
660	<	int phase = phaseOf(s);
661	<	int parties = partiesOf(s);
662	<	int unarrived = unarrivedOf(s);
663	<	if (phase < 0 ||
664	<	state.compareAndSet(s, stateFor(-1, parties, unarrived))) {
665	<	if (head.get() != null)
374	<	releaseWaiters(-1);
375	<	return;
376	<	}
377	<	}
378	<	}
379	<
380	<	/**
381	<	* Resets the barrier with the given numbers of registered unarrived
382	<	* parties and phase number 0. This method allows repeated reuse
383	<	* of this barrier, but only if it is somehow known not to be in
384	<	* use for other purposes.
385	<	* @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.
388	<	*/
389	<	public void reset(int parties) {
390	<	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);
657	>	Phaser r = root;    // force at root then reconcile
658	>	long s;
659	>	while (phaseOf(s = r.state) >= 0)
660	>	UNSAFE.compareAndSwapLong(r, stateOffset, s,
661	>	stateFor(-1, partiesOf(s),
662	>	unarrivedOf(s)));
663	>	reconcileState();
664	>	releaseWaiters(0);  // ensure wakeups on both queues
665	>	releaseWaiters(1);
666		}
667
668		/**
669		* Returns the current phase number. The maximum phase number is
670	<	* <tt>Integer.MAX_VALUE</tt>, after which it restarts at
670	>	* {@code Integer.MAX_VALUE}, after which it restarts at
671		* zero. Upon termination, the phase number is negative.
672	+	*
673		* @return the phase number, or a negative value if terminated
674		*/
675	<	public int getPhase() {
676	<	return phaseOf(state.get());
675	>	public final int getPhase() {
676	>	return phaseOf(getReconciledState());
677		}
678
679		/**
680		* Returns the number of parties registered at this barrier.
681	+	*
682		* @return the number of parties
683		*/
684		public int getRegisteredParties() {
685	<	return partiesOf(state.get());
685	>	return partiesOf(getReconciledState());
686		}
687
688		/**
689	<	* Returns the number of parties that have arrived at the current
690	<	* phase of this barrier.
689	>	* Returns the number of registered parties that have arrived at
690	>	* the current phase of this barrier.
691	>	*
692		* @return the number of arrived parties
693		*/
694		public int getArrivedParties() {
695	<	return arrivedOf(state.get());
695	>	return arrivedOf(getReconciledState());
696		}
697
698		/**
699		* Returns the number of registered parties that have not yet
700		* arrived at the current phase of this barrier.
701	+	*
702		* @return the number of unarrived parties
703		*/
704		public int getUnarrivedParties() {
705	<	return unarrivedOf(state.get());
705	>	return unarrivedOf(getReconciledState());
706		}
707
708		/**
709	<	* Returns true if this barrier has been terminated.
710	<	* @return true if this barrier has been terminated
709	>	* Returns the parent of this phaser, or {@code null} if none.
710	>	*
711	>	* @return the parent of this phaser, or {@code null} if none
712	>	*/
713	>	public Phaser getParent() {
714	>	return parent;
715	>	}
716	>
717	>	/**
718	>	* Returns the root ancestor of this phaser, which is the same as
719	>	* this phaser if it has no parent.
720	>	*
721	>	* @return the root ancestor of this phaser
722	>	*/
723	>	public Phaser getRoot() {
724	>	return root;
725	>	}
726	>
727	>	/**
728	>	* Returns {@code true} if this barrier has been terminated.
729	>	*
730	>	* @return {@code true} if this barrier has been terminated
731		*/
732		public boolean isTerminated() {
733	<	return phaseOf(state.get()) < 0;
733	>	return getPhase() < 0;
734		}
735
736		/**
737	<	* Overridable method to perform an action upon phase advance, and
738	<	* to control termination. This method is invoked whenever the
739	<	* barrier is tripped (and thus all other waiting parties are
740	<	* dormant). If it returns true, then, rather than advance the
741	<	* phase number, this barrier will be set to a final termination
742	<	* state, and subsequent calls to <tt>isTerminated</tt> will
743	<	* return true.
744	<	*
745	<	* <p> The default version returns true when the number of
737	>	* Overridable method to perform an action upon impending phase
738	>	* advance, and to control termination. This method is invoked
739	>	* upon arrival of the party tripping the barrier (when all other
740	>	* waiting parties are dormant).  If this method returns {@code
741	>	* true}, then, rather than advance the phase number, this barrier
742	>	* will be set to a final termination state, and subsequent calls
743	>	* to {@link #isTerminated} will return true. Any (unchecked)
744	>	* Exception or Error thrown by an invocation of this method is
745	>	* propagated to the party attempting to trip the barrier, in
746	>	* which case no advance occurs.
747	>	*
748	>	* <p>The arguments to this method provide the state of the phaser
749	>	* prevailing for the current transition.  The results and effects
750	>	* of invoking phase-related methods (including {@code getPhase}
751	>	* as well as arrival, registration, and waiting methods) from
752	>	* within {@code onAdvance} are unspecified and should not be
753	>	* relied on. Similarly, while it is possible to override this
754	>	* method to produce side-effects visible to participating tasks,
755	>	* it is in general safe to do so only in designs in which all
756	>	* parties register before any arrive, and all {@link
757	>	* #awaitAdvance} at each phase.
758	>	*
759	>	* <p>The default version returns {@code true} when the number of
760		* registered parties is zero. Normally, overrides that arrange
761		* termination for other reasons should also preserve this
762		* property.
763		*
764		* @param phase the phase number on entering the barrier
765	<	* @param registeredParties the current number of registered
766	<	* parties.
458	<	* @return true if this barrier should terminate
765	>	* @param registeredParties the current number of registered parties
766	>	* @return {@code true} if this barrier should terminate
767		*/
768		protected boolean onAdvance(int phase, int registeredParties) {
769		return registeredParties <= 0;
770		}
771
772		/**
773	<	* Returns a string identifying this barrier, as well as its
773	>	* Returns a string identifying this phaser, as well as its
774		* state.  The state, in brackets, includes the String {@code
775	<	* "phase ="} followed by the phase number, {@code "parties ="}
775	>	* "phase = "} followed by the phase number, {@code "parties = "}
776		* followed by the number of registered parties, and {@code
777	<	* "arrived ="} followed by the number of arrived parties
777	>	* "arrived = "} followed by the number of arrived parties.
778		*
779		* @return a string identifying this barrier, as well as its state
780		*/
781		public String toString() {
782	<	long s = state.get();
783	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
782	>	long s = getReconciledState();
783	>	return super.toString() +
784	>	"[phase = " + phaseOf(s) +
785	>	" parties = " + partiesOf(s) +
786	>	" arrived = " + arrivedOf(s) + "]";
787		}
788
789	<	// methods for tripping and waiting
789	>	// methods for waiting
790
791		/**
792	<	* Advance the current phase (or terminate)
792	>	* Wait nodes for Treiber stack representing wait queue
793		*/
794	<	private void trip(int phase, int parties) {
795	<	int next = onAdvance(phase, parties)? -1 : ((phase + 1) & phaseMask);
796	<	state.set(stateFor(next, parties, parties));
797	<	if (head.get() != null)
798	<	releaseWaiters(next);
799	<	}
794	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
795	>	final Phaser phaser;
796	>	final int phase;
797	>	final long startTime;
798	>	final long nanos;
799	>	final boolean timed;
800	>	final boolean interruptible;
801	>	volatile boolean wasInterrupted = false;
802	>	volatile Thread thread; // nulled to cancel wait
803	>	QNode next;
804
805	<	private int helpingWait(int phase) {
806	<	final AtomicLong state = this.state;
807	<	int p;
808	<	while ((p = phaseOf(state.get())) == phase) {
809	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
810	<	if (t != null) {
811	<	if ((p = phaseOf(state.get())) == phase)
812	<	t.exec();
813	<	else {   // push task and exit if barrier advanced
499	<	t.fork();
500	<	break;
501	<	}
502	<	}
805	>	QNode(Phaser phaser, int phase, boolean interruptible,
806	>	boolean timed, long startTime, long nanos) {
807	>	this.phaser = phaser;
808	>	this.phase = phase;
809	>	this.timed = timed;
810	>	this.interruptible = interruptible;
811	>	this.startTime = startTime;
812	>	this.nanos = nanos;
813	>	thread = Thread.currentThread();
814		}
504	–	return p;
505	–	}
815
816	<	private int timedHelpingWait(int phase, long nanos) throws TimeoutException {
817	<	final AtomicLong state = this.state;
818	<	long lastTime = System.nanoTime();
819	<	int p;
820	<	while ((p = phaseOf(state.get())) == phase) {
821	<	long now = System.nanoTime();
822	<	nanos -= now - lastTime;
823	<	lastTime = now;
824	<	if (nanos <= 0) {
825	<	if ((p = phaseOf(state.get())) == phase)
826	<	throw new TimeoutException();
827	<	else
519	<	break;
816	>	public boolean isReleasable() {
817	>	return (thread == null ||
818	>	phaser.getPhase() != phase ||
819	>	(interruptible && wasInterrupted) ||
820	>	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
821	>	}
822	>
823	>	public boolean block() {
824	>	if (Thread.interrupted()) {
825	>	wasInterrupted = true;
826	>	if (interruptible)
827	>	return true;
828		}
829	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
830	<	if (t != null) {
831	<	if ((p = phaseOf(state.get())) == phase)
832	<	t.exec();
833	<	else {   // push task and exit if barrier advanced
834	<	t.fork();
835	<	break;
528	<	}
829	>	if (!timed)
830	>	LockSupport.park(this);
831	>	else {
832	>	long waitTime = nanos - (System.nanoTime() - startTime);
833	>	if (waitTime <= 0)
834	>	return true;
835	>	LockSupport.parkNanos(this, waitTime);
836		}
837	+	return isReleasable();
838		}
531	–	return p;
532	–	}
839
840	<	/**
841	<	* Wait nodes for Treiber stack representing wait queue for non-FJ
842	<	* tasks. The waiting scheme is an adaptation of the one used in
843	<	* forkjoin.PoolBarrier.
844	<	*/
845	<	static final class QNode {
540	<	QNode next;
541	<	volatile Thread thread; // nulled to cancel wait
542	<	final int phase;
543	<	QNode(Thread t, int c) {
544	<	thread = t;
545	<	phase = c;
840	>	void signal() {
841	>	Thread t = thread;
842	>	if (t != null) {
843	>	thread = null;
844	>	LockSupport.unpark(t);
845	>	}
846		}
547	–	}
847
848	<	private void releaseWaiters(int currentPhase) {
849	<	final AtomicReference<QNode> head = this.head;
850	<	QNode p;
851	<	while ((p = head.get()) != null && p.phase != currentPhase) {
852	<	if (head.compareAndSet(p, null)) {
853	<	do {
854	<	Thread t = p.thread;
556	<	if (t != null) {
557	<	p.thread = null;
558	<	LockSupport.unpark(t);
559	<	}
560	<	} while ((p = p.next) != null);
848	>	boolean doWait() {
849	>	if (thread != null) {
850	>	try {
851	>	ForkJoinPool.managedBlock(this);
852	>	} catch (InterruptedException ie) {
853	>	wasInterrupted = true; // can't currently happen
854	>	}
855		}
856	+	return wasInterrupted;
857		}
858		}
859
565	–	/** The number of CPUs, for spin control */
566	–	static final int NCPUS = Runtime.getRuntime().availableProcessors();
567	–
860		/**
861	<	* The number of times to spin before blocking in timed waits.
570	<	* The value is empirically derived.
861	>	* Removes and signals waiting threads from wait queue.
862		*/
863	<	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
863	>	private void releaseWaiters(int phase) {
864	>	AtomicReference<QNode> head = queueFor(phase);
865	>	QNode q;
866	>	while ((q = head.get()) != null) {
867	>	if (head.compareAndSet(q, q.next))
868	>	q.signal();
869	>	}
870	>	}
871
872		/**
873	<	* The number of times to spin before blocking in untimed waits.
874	<	* This is greater than timed value because untimed waits spin
875	<	* faster since they don't need to check times on each spin.
873	>	* Tries to enqueue given node in the appropriate wait queue.
874	>	*
875	>	* @return true if successful
876		*/
877	<	static final int maxUntimedSpins = maxTimedSpins * 32;
877	>	private boolean tryEnqueue(QNode node) {
878	>	AtomicReference<QNode> head = queueFor(node.phase);
879	>	return head.compareAndSet(node.next = head.get(), node);
880	>	}
881
882		/**
883	<	* The number of nanoseconds for which it is faster to spin
583	<	* rather than to use timed park. A rough estimate suffices.
883	>	* The number of times to spin before blocking waiting for advance.
884		*/
885	<	static final long spinForTimeoutThreshold = 1000L;
885	>	static final int MAX_SPINS =
886	>	Runtime.getRuntime().availableProcessors() == 1 ? 0 : 1 << 8;
887
888		/**
889		* Enqueues node and waits unless aborted or signalled.
890	+	*
891	+	* @return current phase
892		*/
893	<	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;
893	>	private int untimedWait(int phase) {
894		QNode node = null;
895		boolean queued = false;
896	<	int spins = maxUntimedSpins;
897	<	while (phaseOf(state.get()) == currentPhase) {
898	<	QNode h;
899	<	if (node != null && queued) {
900	<	if (node.thread != null) {
901	<	LockSupport.park();
902	<	if (Thread.interrupted()) {
903	<	wasInterrupted = true;
904	<	if (abortOnInterrupt)
606	<	break;
607	<	}
608	<	}
896	>	boolean interrupted = false;
897	>	int spins = MAX_SPINS;
898	>	int p;
899	>	while ((p = getPhase()) == phase) {
900	>	if (Thread.interrupted())
901	>	interrupted = true;
902	>	else if (spins > 0) {
903	>	if (--spins == 0)
904	>	Thread.yield();
905		}
906	<	else if ((h = head.get()) != null && h.phase != currentPhase) {
907	<	if (phaseOf(state.get()) == currentPhase) { // must recheck
908	<	if (head.compareAndSet(h, h.next)) {
909	<	Thread t = h.thread; // help clear out old waiters
910	<	if (t != null) {
911	<	h.thread = null;
912	<	LockSupport.unpark(t);
913	<	}
914	<	}
915	<	}
916	<	else
917	<	break;
906	>	else if (node == null)
907	>	node = new QNode(this, phase, false, false, 0, 0);
908	>	else if (!queued)
909	>	queued = tryEnqueue(node);
910	>	else if (node.doWait())
911	>	interrupted = true;
912	>	}
913	>	if (node != null)
914	>	node.thread = null;
915	>	releaseWaiters(phase);
916	>	if (interrupted)
917	>	Thread.currentThread().interrupt();
918	>	return p;
919	>	}
920	>
921	>	/**
922	>	* Interruptible version
923	>	* @return current phase
924	>	*/
925	>	private int interruptibleWait(int phase) throws InterruptedException {
926	>	QNode node = null;
927	>	boolean queued = false;
928	>	boolean interrupted = false;
929	>	int spins = MAX_SPINS;
930	>	int p;
931	>	while ((p = getPhase()) == phase && !interrupted) {
932	>	if (Thread.interrupted())
933	>	interrupted = true;
934	>	else if (spins > 0) {
935	>	if (--spins == 0)
936	>	Thread.yield();
937		}
938	<	else if (node != null)
939	<	queued = head.compareAndSet(node.next = h, node);
940	<	else if (spins <= 0)
941	<	node = new QNode(thread, currentPhase);
942	<	else
943	<	--spins;
938	>	else if (node == null)
939	>	node = new QNode(this, phase, true, false, 0, 0);
940	>	else if (!queued)
941	>	queued = tryEnqueue(node);
942	>	else if (node.doWait())
943	>	interrupted = true;
944		}
945		if (node != null)
946		node.thread = null;
947	<	return wasInterrupted;
947	>	if (p != phase || (p = getPhase()) != phase)
948	>	releaseWaiters(phase);
949	>	if (interrupted)
950	>	throw new InterruptedException();
951	>	return p;
952		}
953
954		/**
955	<	* Messier timeout version
955	>	* Timeout version.
956	>	* @return current phase
957		*/
958	<	private void timedWait(Thread thread, int currentPhase, long nanos)
958	>	private int timedWait(int phase, long nanos)
959		throws InterruptedException, TimeoutException {
960	<	final AtomicReference<QNode> head = this.head;
641	<	final AtomicLong state = this.state;
642	<	long lastTime = System.nanoTime();
960	>	long startTime = System.nanoTime();
961		QNode node = null;
962		boolean queued = false;
963	<	int spins = maxTimedSpins;
964	<	while (phaseOf(state.get()) == currentPhase) {
965	<	QNode h;
966	<	long now = System.nanoTime();
967	<	nanos -= now - lastTime;
968	<	lastTime = now;
969	<	if (nanos <= 0) {
970	<	if (node != null)
971	<	node.thread = null;
972	<	if (phaseOf(state.get()) == currentPhase)
973	<	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;
963	>	boolean interrupted = false;
964	>	int spins = MAX_SPINS;
965	>	int p;
966	>	while ((p = getPhase()) == phase && !interrupted) {
967	>	if (Thread.interrupted())
968	>	interrupted = true;
969	>	else if (nanos - (System.nanoTime() - startTime) <= 0)
970	>	break;
971	>	else if (spins > 0) {
972	>	if (--spins == 0)
973	>	Thread.yield();
974		}
975	<	else if (node != null)
976	<	queued = head.compareAndSet(node.next = h, node);
977	<	else if (spins <= 0)
978	<	node = new QNode(thread, currentPhase);
979	<	else
980	<	--spins;
975	>	else if (node == null)
976	>	node = new QNode(this, phase, true, true, startTime, nanos);
977	>	else if (!queued)
978	>	queued = tryEnqueue(node);
979	>	else if (node.doWait())
980	>	interrupted = true;
981		}
982		if (node != null)
983		node.thread = null;
984	+	if (p != phase || (p = getPhase()) != phase)
985	+	releaseWaiters(phase);
986	+	if (interrupted)
987	+	throw new InterruptedException();
988	+	if (p == phase)
989	+	throw new TimeoutException();
990	+	return p;
991		}
992
993	<	}
993	>	// Unsafe mechanics
994	>
995	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
996	>	private static final long stateOffset =
997	>	objectFieldOffset("state", Phaser.class);
998	>
999	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1000	>	try {
1001	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1002	>	} catch (NoSuchFieldException e) {
1003	>	// Convert Exception to corresponding Error
1004	>	NoSuchFieldError error = new NoSuchFieldError(field);
1005	>	error.initCause(e);
1006	>	throw error;
1007	>	}
1008	>	}
1009
1010	+	/**
1011	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1012	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1013	+	* into a jdk.
1014	+	*
1015	+	* @return a sun.misc.Unsafe
1016	+	*/
1017	+	private static sun.misc.Unsafe getUnsafe() {
1018	+	try {
1019	+	return sun.misc.Unsafe.getUnsafe();
1020	+	} catch (SecurityException se) {
1021	+	try {
1022	+	return java.security.AccessController.doPrivileged
1023	+	(new java.security
1024	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1025	+	public sun.misc.Unsafe run() throws Exception {
1026	+	java.lang.reflect.Field f = sun.misc
1027	+	.Unsafe.class.getDeclaredField("theUnsafe");
1028	+	f.setAccessible(true);
1029	+	return (sun.misc.Unsafe) f.get(null);
1030	+	}});
1031	+	} catch (java.security.PrivilegedActionException e) {
1032	+	throw new RuntimeException("Could not initialize intrinsics",
1033	+	e.getCause());
1034	+	}
1035	+	}
1036	+	}
1037	+	}

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