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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.3 by jsr166, Fri Jul 25 18:11:53 2008 UTC vs.
Revision 1.44 by dl, Tue Aug 25 16:32:28 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.*;
10	>
11	>	import java.util.concurrent.atomic.AtomicReference;
12		import java.util.concurrent.locks.LockSupport;
13
14		/**
15	<	* A reusable synchronization barrier, similar in functionality to a
16	<	* {@link java.util.concurrent.CyclicBarrier}, but supporting more
17	<	* flexible usage.
15	>	* A reusable synchronization barrier, similar in functionality to
16	>	* {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and
17	>	* {@link java.util.concurrent.CountDownLatch CountDownLatch}
18	>	* but supporting more flexible usage.
19		*
20	<	* <ul>
20	>	* <p> <b>Registration.</b> Unlike the case for other barriers, the
21	>	* number of parties <em>registered</em> to synchronize on a phaser
22	>	* may vary over time.  Tasks may be registered at any time (using
23	>	* methods {@link #register}, {@link #bulkRegister}, or forms of
24	>	* constructors establishing initial numbers of parties), and
25	>	* optionally deregistered upon any arrival (using {@link
26	>	* #arriveAndDeregister}).  As is the case with most basic
27	>	* synchronization constructs, registration and deregistration affect
28	>	* only internal counts; they do not establish any further internal
29	>	* bookkeeping, so tasks cannot query whether they are registered.
30	>	* (However, you can introduce such bookkeeping by subclassing this
31	>	* class.)
32		*
33	<	* <li> The number of parties synchronizing on the barrier may vary
34	<	* over time.  A task may register to be a party in a barrier at any
35	<	* time, and may deregister upon arriving at the barrier.  As is the
36	<	* case with most basic synchronization constructs, registration
37	<	* and deregistration affect only internal counts; they do not
38	<	* establish any further internal bookkeeping, so tasks cannot query
39	<	* whether they are registered.
40	<	*
41	<	* <li> Each generation has an associated phase value, starting at
42	<	* zero, and advancing when all parties reach the barrier (wrapping
43	<	* 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:
33	>	* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
34	>	* Phaser} may be repeatedly awaited.  Method {@link
35	>	* #arriveAndAwaitAdvance} has effect analogous to {@link
36	>	* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
37	>	* generation of a {@code Phaser} has an associated phase number. The
38	>	* phase number starts at zero, and advances when all parties arrive
39	>	* at the barrier, wrapping around to zero after reaching {@code
40	>	* Integer.MAX_VALUE}. The use of phase numbers enables independent
41	>	* control of actions upon arrival at a barrier and upon awaiting
42	>	* others, via two kinds of methods that may be invoked by any
43	>	* registered party:
44		*
45		* <ul>
46		*
47	<	*   <li> Arriving at a barrier. Methods <tt>arrive</tt> and
48	<	*       <tt>arriveAndDeregister</tt> do not block, but return
49	<	*       the phase value on entry to the method.
50	<	*
51	<	*   <li> Awaiting others. Method <tt>awaitAdvance</tt> requires an
52	<	*       argument indicating the entry phase, and returns when the
53	<	*       barrier advances to a new phase.
47	>	*   <li> <b>Arrival.</b> Methods {@link #arrive} and
48	>	*       {@link #arriveAndDeregister} record arrival at a
49	>	*       barrier. These methods do not block, but return an associated
50	>	*       <em>arrival phase number</em>; that is, the phase number of
51	>	*       the barrier to which the arrival applied. When the final
52	>	*       party for a given phase arrives, an optional barrier action
53	>	*       is performed and the phase advances.  Barrier actions,
54	>	*       performed by the party triggering a phase advance, are
55	>	*       arranged by overriding method {@link #onAdvance(int, int)},
56	>	*       which also controls termination. Overriding this method is
57	>	*       similar to, but more flexible than, providing a barrier
58	>	*       action to a {@code CyclicBarrier}.
59	>	*
60	>	*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
61	>	*       argument indicating an arrival phase number, and returns when
62	>	*       the barrier advances to (or is already at) a different phase.
63	>	*       Unlike similar constructions using {@code CyclicBarrier},
64	>	*       method {@code awaitAdvance} continues to wait even if the
65	>	*       waiting thread is interrupted. Interruptible and timeout
66	>	*       versions are also available, but exceptions encountered while
67	>	*       tasks wait interruptibly or with timeout do not change the
68	>	*       state of the barrier. If necessary, you can perform any
69	>	*       associated recovery within handlers of those exceptions,
70	>	*       often after invoking {@code forceTermination}.  Phasers may
71	>	*       also be used by tasks executing in a {@link ForkJoinPool},
72	>	*       which will ensure sufficient parallelism to execute tasks
73	>	*       when others are blocked waiting for a phase to advance.
74	>	*
75		* </ul>
76		*
77	+	* <p> <b>Termination.</b> A {@code Phaser} may enter a
78	+	* <em>termination</em> state in which all synchronization methods
79	+	* immediately return without updating phaser state or waiting for
80	+	* advance, and indicating (via a negative phase value) that execution
81	+	* is complete.  Termination is triggered when an invocation of {@code
82	+	* onAdvance} returns {@code true}.  As illustrated below, when
83	+	* phasers control actions with a fixed number of iterations, it is
84	+	* often convenient to override this method to cause termination when
85	+	* the current phase number reaches a threshold. Method {@link
86	+	* #forceTermination} is also available to abruptly release waiting
87	+	* threads and allow them to terminate.
88		*
89	<	* <li> Barrier actions, performed by the task triggering a phase
90	<	* advance while others may be waiting, are arranged by overriding
91	<	* method <tt>onAdvance</tt>, that also controls termination.
92	<	*
93	<	* <li> Phasers may enter a <em>termination</em> state in which all
94	<	* await actions immediately return, indicating (via a negative phase
95	<	* 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.
89	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
90	>	* in tree structures) to reduce contention. Phasers with large
91	>	* numbers of parties that would otherwise experience heavy
92	>	* synchronization contention costs may instead be set up so that
93	>	* groups of sub-phasers share a common parent.  This may greatly
94	>	* increase throughput even though it incurs greater per-operation
95	>	* overhead.
96		*
97	<	* </ul>
97	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
98	>	* only by registered parties, the current state of a phaser may be
99	>	* monitored by any caller.  At any given moment there are {@link
100	>	* #getRegisteredParties} parties in total, of which {@link
101	>	* #getArrivedParties} have arrived at the current phase ({@link
102	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
103	>	* parties arrive, the phase advances.  The values returned by these
104	>	* methods may reflect transient states and so are not in general
105	>	* useful for synchronization control.  Method {@link #toString}
106	>	* returns snapshots of these state queries in a form convenient for
107	>	* informal monitoring.
108	>	*
109	>	* <p><b>Sample usages:</b>
110	>	*
111	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
112	>	* to control a one-shot action serving a variable number of
113	>	* parties. The typical idiom is for the method setting this up to
114	>	* first register, then start the actions, then deregister, as in:
115	>	*
116	>	*  <pre> {@code
117	>	* void runTasks(List<Runnable> tasks) {
118	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
119	>	*   // create and start threads
120	>	*   for (Runnable task : tasks) {
121	>	*     phaser.register();
122	>	*     new Thread() {
123	>	*       public void run() {
124	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
125	>	*         task.run();
126	>	*       }
127	>	*     }.start();
128	>	*   }
129	>	*
130	>	*   // allow threads to start and deregister self
131	>	*   phaser.arriveAndDeregister();
132	>	* }}</pre>
133	>	*
134	>	* <p>One way to cause a set of threads to repeatedly perform actions
135	>	* for a given number of iterations is to override {@code onAdvance}:
136	>	*
137	>	*  <pre> {@code
138	>	* void startTasks(List<Runnable> tasks, final int iterations) {
139	>	*   final Phaser phaser = new Phaser() {
140	>	*     protected boolean onAdvance(int phase, int registeredParties) {
141	>	*       return phase >= iterations || registeredParties == 0;
142	>	*     }
143	>	*   };
144	>	*   phaser.register();
145	>	*   for (Runnable task : tasks) {
146	>	*     phaser.register();
147	>	*     new Thread() {
148	>	*       public void run() {
149	>	*         do {
150	>	*           task.run();
151	>	*           phaser.arriveAndAwaitAdvance();
152	>	*         } while(!phaser.isTerminated();
153	>	*       }
154	>	*     }.start();
155	>	*   }
156	>	*   phaser.arriveAndDeregister(); // deregister self, don't wait
157	>	* }}</pre>
158		*
159	<	* <p><b>Sample usage:</b>
159	>	* If the main task must later await termination, it
160	>	* may re-register and then execute a similar loop:
161	>	* <pre> {@code
162	>	*   // ...
163	>	*   phaser.register();
164	>	*   while (!phaser.isTerminated())
165	>	*     phaser.arriveAndAwaitAdvance();
166	>	* }</pre>
167		*
168	<	* <p>[todo: non-FJ example]
168	>	* Related constructions may be used to await particular phase numbers
169	>	* in contexts where you are sure that the phase will never wrap around
170	>	* {@code Integer.MAX_VALUE}. For example:
171		*
172	<	* <p> A Phaser may be used to support a style of programming in
173	<	* which a task waits for others to complete, without otherwise
174	<	* needing to keep track of which tasks it is waiting for. This is
175	<	* similar to the "sync" construct in Cilk and "clocks" in X10.
176	<	* Special constructions based on such barriers are available using
177	<	* the <tt>LinkedAsyncAction</tt> and <tt>CyclicAction</tt> classes,
178	<	* but they can be useful in other contexts as well.  For a simple
179	<	* (but not very useful) example, here is a variant of Fibonacci:
180	<	*
181	<	* <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();
172	>	* <pre> {@code
173	>	*   void awaitPhase(Phaser phaser, int phase) {
174	>	*     int p = phaser.register(); // assumes caller not already registered
175	>	*     while (p < phase) {
176	>	*       if (phaser.isTerminated())
177	>	*         // ... deal with unexpected termination
178	>	*       else
179	>	*         p = phaser.arriveAndAwaitAdvance();
180	>	*     }
181	>	*     phaser.arriveAndDeregister();
182		*   }
183	<	*   protected void compute() {
184	<	*     int n = argument;
185	<	*     if (n &lt;= 1)
186	<	*        result = n;
187	<	*     else {
188	<	*        Phaser childBarrier = new Phaser(1);
189	<	*        BarrierFibonacci f1 = new BarrierFibonacci(n - 1, childBarrier);
190	<	*        BarrierFibonacci f2 = new BarrierFibonacci(n - 2, childBarrier);
191	<	*        f1.fork();
192	<	*        f2.fork();
193	<	*        childBarrier.arriveAndAwait();
194	<	*        result = f1.result + f2.result;
183	>	* }</pre>
184	>	*
185	>	*
186	>	* <p>To create a set of tasks using a tree of phasers,
187	>	* you could use code of the following form, assuming a
188	>	* Task class with a constructor accepting a phaser that
189	>	* it registers for upon construction:
190	>	*  <pre> {@code
191	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
192	>	*   if (hi - lo > TASKS_PER_PHASER) {
193	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
194	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
195	>	*       build(actions, i, j, new Phaser(ph));
196		*     }
197	<	*     parentBarrier.arriveAndDeregister();
197	>	*   } else {
198	>	*     for (int i = lo; i < hi; ++i)
199	>	*       actions[i] = new Task(ph);
200	>	*       // assumes new Task(ph) performs ph.register()
201		*   }
202		* }
203	+	* // .. initially called, for n tasks via
204	+	* build(new Task[n], 0, n, new Phaser());}</pre>
205	+	*
206	+	* The best value of {@code TASKS_PER_PHASER} depends mainly on
207	+	* expected barrier synchronization rates. A value as low as four may
208	+	* be appropriate for extremely small per-barrier task bodies (thus
209	+	* high rates), or up to hundreds for extremely large ones.
210	+	*
211		* </pre>
212		*
213		* <p><b>Implementation notes</b>: This implementation restricts the
214	<	* maximum number of parties to 65535. Attempts to register
215	<	* additional parties result in IllegalStateExceptions.
214	>	* maximum number of parties to 65535. Attempts to register additional
215	>	* parties result in {@code IllegalStateException}. However, you can and
216	>	* should create tiered phasers to accommodate arbitrarily large sets
217	>	* of participants.
218	>	*
219	>	* @since 1.7
220	>	* @author Doug Lea
221		*/
222		public class Phaser {
223		/*
224		* This class implements an extension of X10 "clocks".  Thanks to
225	<	* Vijay Saraswat for the idea of applying it to ForkJoinTasks,
226	<	* and to Vivek Sarkar for enhancements to extend functionality.
225	>	* Vijay Saraswat for the idea, and to Vivek Sarkar for
226	>	* enhancements to extend functionality.
227		*/
228
229		/**
#	Line 133 | Line 236 | public class Phaser {
236		* * terminated -- set if barrier is terminated (1 bit)
237		*
238		* However, to efficiently maintain atomicity, these values are
239	<	* packed into a single AtomicLong. Termination uses the sign bit
240	<	* of 32 bit representation of phase, so phase is set to -1 on
241	<	* termination.
242	<	*/
243	<	private final AtomicLong state;
244	<
245	<	/**
143	<	* Head of Treiber stack for waiting nonFJ threads.
239	>	* packed into a single (atomic) long. Termination uses the sign
240	>	* bit of 32 bit representation of phase, so phase is set to -1 on
241	>	* termination. Good performance relies on keeping state decoding
242	>	* and encoding simple, and keeping race windows short.
243	>	*
244	>	* Note: there are some cheats in arrive() that rely on unarrived
245	>	* count being lowest 16 bits.
246		*/
247	<	private final AtomicReference<QNode> head = new AtomicReference<QNode>();
247	>	private volatile long state;
248
249	<	private static final int ushortBits = 16;
250	<	private static final int ushortMask =  (1 << ushortBits) - 1;
149	<	private static final int phaseMask = 0x7fffffff;
249	>	private static final int ushortMask = 0xffff;
250	>	private static final int phaseMask  = 0x7fffffff;
251
252		private static int unarrivedOf(long s) {
253	<	return (int)(s & ushortMask);
253	>	return (int) (s & ushortMask);
254		}
255
256		private static int partiesOf(long s) {
257	<	return (int)(s & (ushortMask << 16)) >>> 16;
257	>	return ((int) s) >>> 16;
258		}
259
260		private static int phaseOf(long s) {
261	<	return (int)(s >>> 32);
261	>	return (int) (s >>> 32);
262		}
263
264		private static int arrivedOf(long s) {
#	Line 165 | Line 266 | public class Phaser {
266		}
267
268		private static long stateFor(int phase, int parties, int unarrived) {
269	<	return (((long)phase) << 32) | ((parties << 16) | unarrived);
269	>	return ((((long) phase) << 32) | (((long) parties) << 16) |
270	>	(long) unarrived);
271		}
272
273	<	private static IllegalStateException badBounds(int parties, int unarrived) {
274	<	return new IllegalStateException("Attempt to set " + unarrived +
275	<	" unarrived of " + parties + " parties");
273	>	private static long trippedStateFor(int phase, int parties) {
274	>	long lp = (long) parties;
275	>	return (((long) phase) << 32) | (lp << 16) | lp;
276		}
277
278		/**
279	<	* Creates a new Phaser without any initially registered parties,
280	<	* and initial phase number 0.
279	>	* Returns message string for bad bounds exceptions.
280	>	*/
281	>	private static String badBounds(int parties, int unarrived) {
282	>	return ("Attempt to set " + unarrived +
283	>	" unarrived of " + parties + " parties");
284	>	}
285	>
286	>	/**
287	>	* The parent of this phaser, or null if none
288	>	*/
289	>	private final Phaser parent;
290	>
291	>	/**
292	>	* The root of phaser tree. Equals this if not in a tree.  Used to
293	>	* support faster state push-down.
294	>	*/
295	>	private final Phaser root;
296	>
297	>	// Wait queues
298	>
299	>	/**
300	>	* Heads of Treiber stacks for waiting threads. To eliminate
301	>	* contention while releasing some threads while adding others, we
302	>	* use two of them, alternating across even and odd phases.
303	>	*/
304	>	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
305	>	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
306	>
307	>	private AtomicReference<QNode> queueFor(int phase) {
308	>	return ((phase & 1) == 0) ? evenQ : oddQ;
309	>	}
310	>
311	>	/**
312	>	* Returns current state, first resolving lagged propagation from
313	>	* root if necessary.
314	>	*/
315	>	private long getReconciledState() {
316	>	return (parent == null) ? state : reconcileState();
317	>	}
318	>
319	>	/**
320	>	* Recursively resolves state.
321	>	*/
322	>	private long reconcileState() {
323	>	Phaser p = parent;
324	>	long s = state;
325	>	if (p != null) {
326	>	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
327	>	long parentState = p.getReconciledState();
328	>	int parentPhase = phaseOf(parentState);
329	>	int phase = phaseOf(s = state);
330	>	if (phase != parentPhase) {
331	>	long next = trippedStateFor(parentPhase, partiesOf(s));
332	>	if (casState(s, next)) {
333	>	releaseWaiters(phase);
334	>	s = next;
335	>	}
336	>	}
337	>	}
338	>	}
339	>	return s;
340	>	}
341	>
342	>	/**
343	>	* Creates a new phaser without any initially registered parties,
344	>	* initial phase number 0, and no parent. Any thread using this
345	>	* phaser will need to first register for it.
346		*/
347		public Phaser() {
348	<	state = new AtomicLong(stateFor(0, 0, 0));
348	>	this(null);
349		}
350
351		/**
352	<	* Creates a new Phaser with the given numbers of registered
353	<	* unarrived parties and initial phase number 0.
354	<	* @param parties the number of parties required to trip barrier.
352	>	* Creates a new phaser with the given numbers of registered
353	>	* unarrived parties, initial phase number 0, and no parent.
354	>	*
355	>	* @param parties the number of parties required to trip barrier
356		* @throws IllegalArgumentException if parties less than zero
357	<	* or greater than the maximum number of parties supported.
357	>	* or greater than the maximum number of parties supported
358		*/
359		public Phaser(int parties) {
360	+	this(null, parties);
361	+	}
362	+
363	+	/**
364	+	* Creates a new phaser with the given parent, without any
365	+	* initially registered parties. If parent is non-null this phaser
366	+	* is registered with the parent and its initial phase number is
367	+	* the same as that of parent phaser.
368	+	*
369	+	* @param parent the parent phaser
370	+	*/
371	+	public Phaser(Phaser parent) {
372	+	int phase = 0;
373	+	this.parent = parent;
374	+	if (parent != null) {
375	+	this.root = parent.root;
376	+	phase = parent.register();
377	+	}
378	+	else
379	+	this.root = this;
380	+	this.state = trippedStateFor(phase, 0);
381	+	}
382	+
383	+	/**
384	+	* Creates a new phaser with the given parent and numbers of
385	+	* registered unarrived parties. If parent is non-null, this phaser
386	+	* is registered with the parent and its initial phase number is
387	+	* the same as that of parent phaser.
388	+	*
389	+	* @param parent the parent phaser
390	+	* @param parties the number of parties required to trip barrier
391	+	* @throws IllegalArgumentException if parties less than zero
392	+	* or greater than the maximum number of parties supported
393	+	*/
394	+	public Phaser(Phaser parent, int parties) {
395		if (parties < 0 || parties > ushortMask)
396		throw new IllegalArgumentException("Illegal number of parties");
397	<	state = new AtomicLong(stateFor(0, parties, parties));
397	>	int phase = 0;
398	>	this.parent = parent;
399	>	if (parent != null) {
400	>	this.root = parent.root;
401	>	phase = parent.register();
402	>	}
403	>	else
404	>	this.root = this;
405	>	this.state = trippedStateFor(phase, parties);
406		}
407
408		/**
409		* Adds a new unarrived party to this phaser.
410	<	* @return the current barrier phase number upon registration
410	>	*
411	>	* @return the arrival phase number to which this registration applied
412	>	* @throws IllegalStateException if attempting to register more
413	>	* than the maximum supported number of parties
414	>	*/
415	>	public int register() {
416	>	return doRegister(1);
417	>	}
418	>
419	>	/**
420	>	* Adds the given number of new unarrived parties to this phaser.
421	>	*
422	>	* @param parties the number of 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		*/
427	<	public int register() { // increment both parties and unarrived
428	<	final AtomicLong state = this.state;
427	>	public int bulkRegister(int parties) {
428	>	if (parties < 0)
429	>	throw new IllegalArgumentException();
430	>	if (parties == 0)
431	>	return getPhase();
432	>	return doRegister(parties);
433	>	}
434	>
435	>	/**
436	>	* Shared code for register, bulkRegister
437	>	*/
438	>	private int doRegister(int registrations) {
439	>	int phase;
440		for (;;) {
441	<	long s = state.get();
442	<	int phase = phaseOf(s);
443	<	int parties = partiesOf(s) + 1;
444	<	int unarrived = unarrivedOf(s) + 1;
441	>	long s = getReconciledState();
442	>	phase = phaseOf(s);
443	>	int unarrived = unarrivedOf(s) + registrations;
444	>	int parties = partiesOf(s) + registrations;
445	>	if (phase < 0)
446	>	break;
447		if (parties > ushortMask || unarrived > ushortMask)
448	<	throw badBounds(parties, unarrived);
449	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
450	<	return phase;
448	>	throw new IllegalStateException(badBounds(parties, unarrived));
449	>	if (phase == phaseOf(root.state) &&
450	>	casState(s, stateFor(phase, parties, unarrived)))
451	>	break;
452		}
453	+	return phase;
454		}
455
456		/**
457		* Arrives at the barrier, but does not wait for others.  (You can
458	<	* in turn wait for others via {@link #awaitAdvance}).
458	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
459	>	* unenforced usage error for an unregistered party to invoke this
460	>	* method.
461		*
462	<	* @return the current barrier phase number upon entry to
463	<	* this method, or a negative value if terminated;
464	<	* @throws IllegalStateException if the number of unarrived
224	<	* parties would become negative.
462	>	* @return the arrival phase number, or a negative value if terminated
463	>	* @throws IllegalStateException if not terminated and the number
464	>	* of unarrived parties would become negative
465		*/
466	<	public int arrive() { // decrement unarrived. If zero, trip
467	<	final AtomicLong state = this.state;
466	>	public int arrive() {
467	>	int phase;
468		for (;;) {
469	<	long s = state.get();
470	<	int phase = phaseOf(s);
469	>	long s = state;
470	>	phase = phaseOf(s);
471	>	if (phase < 0)
472	>	break;
473		int parties = partiesOf(s);
474		int unarrived = unarrivedOf(s) - 1;
475	<	if (unarrived < 0)
476	<	throw badBounds(parties, unarrived);
477	<	if (unarrived == 0 && phase >= 0) {
236	<	trip(phase, parties);
237	<	return phase;
475	>	if (unarrived > 0) {        // Not the last arrival
476	>	if (casState(s, s - 1)) // s-1 adds one arrival
477	>	break;
478		}
479	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
480	<	return phase;
479	>	else if (unarrived == 0) {  // the last arrival
480	>	Phaser par = parent;
481	>	if (par == null) {      // directly trip
482	>	if (casState
483	>	(s,
484	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
485	>	((phase + 1) & phaseMask), parties))) {
486	>	releaseWaiters(phase);
487	>	break;
488	>	}
489	>	}
490	>	else {                  // cascade to parent
491	>	if (casState(s, s - 1)) { // zeroes unarrived
492	>	par.arrive();
493	>	reconcileState();
494	>	break;
495	>	}
496	>	}
497	>	}
498	>	else if (phase != phaseOf(root.state)) // or if unreconciled
499	>	reconcileState();
500	>	else
501	>	throw new IllegalStateException(badBounds(parties, unarrived));
502		}
503	+	return phase;
504		}
505
506		/**
507	<	* Arrives at the barrier, and deregisters from it, without
508	<	* waiting for others.
507	>	* Arrives at the barrier and deregisters from it without waiting
508	>	* for others. Deregistration reduces the number of parties
509	>	* required to trip the barrier in future phases.  If this phaser
510	>	* has a parent, and deregistration causes this phaser to have
511	>	* zero parties, this phaser also arrives at and is deregistered
512	>	* from its parent.  It is an unenforced usage error for an
513	>	* unregistered party to invoke this method.
514		*
515	<	* @return the current barrier phase number upon entry to
516	<	* this method, or a negative value if terminated;
517	<	* @throws IllegalStateException if the number of registered or
518	<	* unarrived parties would become negative.
519	<	*/
520	<	public int arriveAndDeregister() { // Same as arrive, plus decrement parties
521	<	final AtomicLong state = this.state;
515	>	* @return the arrival phase number, or a negative value if terminated
516	>	* @throws IllegalStateException if not terminated and the number
517	>	* of registered or unarrived parties would become negative
518	>	*/
519	>	public int arriveAndDeregister() {
520	>	// similar code to arrive, but too different to merge
521	>	Phaser par = parent;
522	>	int phase;
523		for (;;) {
524	<	long s = state.get();
525	<	int phase = phaseOf(s);
524	>	long s = state;
525	>	phase = phaseOf(s);
526	>	if (phase < 0)
527	>	break;
528		int parties = partiesOf(s) - 1;
529		int unarrived = unarrivedOf(s) - 1;
530	<	if (parties < 0 || unarrived < 0)
531	<	throw badBounds(parties, unarrived);
532	<	if (unarrived == 0 && phase >= 0) {
533	<	trip(phase, parties);
534	<	return phase;
530	>	if (parties >= 0) {
531	>	if (unarrived > 0 || (unarrived == 0 && par != null)) {
532	>	if (casState
533	>	(s,
534	>	stateFor(phase, parties, unarrived))) {
535	>	if (unarrived == 0) {
536	>	par.arriveAndDeregister();
537	>	reconcileState();
538	>	}
539	>	break;
540	>	}
541	>	continue;
542	>	}
543	>	if (unarrived == 0) {
544	>	if (casState
545	>	(s,
546	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
547	>	((phase + 1) & phaseMask), parties))) {
548	>	releaseWaiters(phase);
549	>	break;
550	>	}
551	>	continue;
552	>	}
553	>	if (par != null && phase != phaseOf(root.state)) {
554	>	reconcileState();
555	>	continue;
556	>	}
557		}
558	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
267	<	return phase;
558	>	throw new IllegalStateException(badBounds(parties, unarrived));
559		}
560	+	return phase;
561		}
562
563		/**
564	<	* Arrives at the barrier and awaits others. Unlike other arrival
565	<	* methods, this method returns the arrival index of the
566	<	* caller. The caller tripping the barrier returns zero, the
567	<	* previous caller 1, and so on.
568	<	* @return the arrival index
569	<	* @throws IllegalStateException if the number of unarrived
570	<	* parties would become negative.
564	>	* Arrives at the barrier and awaits others. Equivalent in effect
565	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
566	>	* interruption or timeout, you can arrange this with an analogous
567	>	* construction using one of the other forms of the awaitAdvance
568	>	* method.  If instead you need to deregister upon arrival use
569	>	* {@code arriveAndDeregister}. It is an unenforced usage error
570	>	* for an unregistered party to invoke this method.
571	>	*
572	>	* @return the arrival phase number, or a negative number if terminated
573	>	* @throws IllegalStateException if not terminated and the number
574	>	* of unarrived parties would become negative
575		*/
576		public int arriveAndAwaitAdvance() {
577	<	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	<	}
577	>	return awaitAdvance(arrive());
578		}
579
580		/**
581	<	* Awaits the phase of the barrier to advance from the given
582	<	* value, or returns immediately if this barrier is terminated.
583	<	* @param phase the phase on entry to this method
584	<	* @return the phase on exit from this method
581	>	* Awaits the phase of the barrier to advance from the given phase
582	>	* value, returning immediately if the current phase of the
583	>	* barrier is not equal to the given phase value or this barrier
584	>	* is terminated.  It is an unenforced usage error for an
585	>	* unregistered party to invoke this method.
586	>	*
587	>	* @param phase an arrival phase number, or negative value if
588	>	* terminated; this argument is normally the value returned by a
589	>	* previous call to {@code arrive} or its variants
590	>	* @return the next arrival phase number, or a negative value
591	>	* if terminated or argument is negative
592		*/
593		public int awaitAdvance(int phase) {
594		if (phase < 0)
595		return phase;
596	<	Thread current = Thread.currentThread();
597	<	if (current instanceof ForkJoinWorkerThread)
598	<	return helpingWait(phase);
599	<	if (untimedWait(current, phase, false))
600	<	current.interrupt();
601	<	return phaseOf(state.get());
596	>	long s = getReconciledState();
597	>	int p = phaseOf(s);
598	>	if (p != phase)
599	>	return p;
600	>	if (unarrivedOf(s) == 0 && parent != null)
601	>	parent.awaitAdvance(phase);
602	>	// Fall here even if parent waited, to reconcile and help release
603	>	return untimedWait(phase);
604		}
605
606		/**
607	<	* Awaits the phase of the barrier to advance from the given
608	<	* value, or returns immediately if this barrier is terminated, or
609	<	* throws InterruptedException if interrupted while waiting.
610	<	* @param phase the phase on entry to this method
611	<	* @return the phase on exit from this method
607	>	* Awaits the phase of the barrier to advance from the given phase
608	>	* value, throwing {@code InterruptedException} if interrupted
609	>	* while waiting, or returning immediately if the current phase of
610	>	* the barrier is not equal to the given phase value or this
611	>	* barrier is terminated. It is an unenforced usage error for an
612	>	* unregistered party to invoke this method.
613	>	*
614	>	* @param phase an arrival phase number, or negative value if
615	>	* terminated; this argument is normally the value returned by a
616	>	* previous call to {@code arrive} or its variants
617	>	* @return the next arrival phase number, or a negative value
618	>	* if terminated or argument is negative
619		* @throws InterruptedException if thread interrupted while waiting
620		*/
621	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
621	>	public int awaitAdvanceInterruptibly(int phase)
622	>	throws InterruptedException {
623		if (phase < 0)
624		return phase;
625	<	Thread current = Thread.currentThread();
626	<	if (current instanceof ForkJoinWorkerThread)
627	<	return helpingWait(phase);
628	<	else if (Thread.interrupted() || untimedWait(current, phase, true))
629	<	throw new InterruptedException();
630	<	else
631	<	return phaseOf(state.get());
625	>	long s = getReconciledState();
626	>	int p = phaseOf(s);
627	>	if (p != phase)
628	>	return p;
629	>	if (unarrivedOf(s) == 0 && parent != null)
630	>	parent.awaitAdvanceInterruptibly(phase);
631	>	return interruptibleWait(phase);
632		}
633
634		/**
635	<	* Awaits the phase of the barrier to advance from the given value
636	<	* or the given timeout elapses, or returns immediately if this
637	<	* barrier is terminated.
638	<	* @param phase the phase on entry to this method
639	<	* @return the phase on exit from this method
635	>	* Awaits the phase of the barrier to advance from the given phase
636	>	* value or the given timeout to elapse, throwing {@code
637	>	* InterruptedException} if interrupted while waiting, or
638	>	* returning immediately if the current phase of the barrier is
639	>	* not equal to the given phase value or this barrier is
640	>	* terminated.  It is an unenforced usage error for an
641	>	* unregistered party to invoke this method.
642	>	*
643	>	* @param phase an arrival phase number, or negative value if
644	>	* terminated; this argument is normally the value returned by a
645	>	* previous call to {@code arrive} or its variants
646	>	* @param timeout how long to wait before giving up, in units of
647	>	*        {@code unit}
648	>	* @param unit a {@code TimeUnit} determining how to interpret the
649	>	*        {@code timeout} parameter
650	>	* @return the next arrival phase number, or a negative value
651	>	* if terminated or argument is negative
652		* @throws InterruptedException if thread interrupted while waiting
653		* @throws TimeoutException if timed out while waiting
654		*/
655	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
655	>	public int awaitAdvanceInterruptibly(int phase,
656	>	long timeout, TimeUnit unit)
657		throws InterruptedException, TimeoutException {
658		if (phase < 0)
659		return phase;
660	<	long nanos = unit.toNanos(timeout);
661	<	Thread current = Thread.currentThread();
662	<	if (current instanceof ForkJoinWorkerThread)
663	<	return timedHelpingWait(phase, nanos);
664	<	timedWait(current, phase, nanos);
665	<	return phaseOf(state.get());
660	>	long s = getReconciledState();
661	>	int p = phaseOf(s);
662	>	if (p != phase)
663	>	return p;
664	>	if (unarrivedOf(s) == 0 && parent != null)
665	>	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
666	>	return timedWait(phase, unit.toNanos(timeout));
667		}
668
669		/**
670		* Forces this barrier to enter termination state. Counts of
671	<	* arrived and registered parties are unaffected. This method may
672	<	* be useful for coordinating recovery after one or more tasks
673	<	* encounter unexpected exceptions.
671	>	* arrived and registered parties are unaffected. If this phaser
672	>	* has a parent, it too is terminated. This method may be useful
673	>	* for coordinating recovery after one or more tasks encounter
674	>	* unexpected exceptions.
675		*/
676		public void forceTermination() {
365	–	final AtomicLong state = this.state;
677		for (;;) {
678	<	long s = state.get();
678	>	long s = getReconciledState();
679		int phase = phaseOf(s);
680		int parties = partiesOf(s);
681		int unarrived = unarrivedOf(s);
682		if (phase < 0 ||
683	<	state.compareAndSet(s, stateFor(-1, parties, unarrived))) {
684	<	if (head.get() != null)
685	<	releaseWaiters(-1);
683	>	casState(s, stateFor(-1, parties, unarrived))) {
684	>	releaseWaiters(0);
685	>	releaseWaiters(1);
686	>	if (parent != null)
687	>	parent.forceTermination();
688		return;
689		}
690		}
691		}
692
693		/**
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);
395	–	}
396	–
397	–	/**
694		* Returns the current phase number. The maximum phase number is
695	<	* <tt>Integer.MAX_VALUE</tt>, after which it restarts at
695	>	* {@code Integer.MAX_VALUE}, after which it restarts at
696		* zero. Upon termination, the phase number is negative.
697	+	*
698		* @return the phase number, or a negative value if terminated
699		*/
700	<	public int getPhase() {
701	<	return phaseOf(state.get());
700	>	public final int getPhase() {
701	>	return phaseOf(getReconciledState());
702		}
703
704		/**
705		* Returns the number of parties registered at this barrier.
706	+	*
707		* @return the number of parties
708		*/
709		public int getRegisteredParties() {
710	<	return partiesOf(state.get());
710	>	return partiesOf(state);
711		}
712
713		/**
714	<	* Returns the number of parties that have arrived at the current
715	<	* phase of this barrier.
714	>	* Returns the number of registered parties that have arrived at
715	>	* the current phase of this barrier.
716	>	*
717		* @return the number of arrived parties
718		*/
719		public int getArrivedParties() {
720	<	return arrivedOf(state.get());
720	>	return arrivedOf(state);
721		}
722
723		/**
724		* Returns the number of registered parties that have not yet
725		* arrived at the current phase of this barrier.
726	+	*
727		* @return the number of unarrived parties
728		*/
729		public int getUnarrivedParties() {
730	<	return unarrivedOf(state.get());
730	>	return unarrivedOf(state);
731		}
732
733		/**
734	<	* Returns true if this barrier has been terminated.
735	<	* @return true if this barrier has been terminated
734	>	* Returns the parent of this phaser, or {@code null} if none.
735	>	*
736	>	* @return the parent of this phaser, or {@code null} if none
737	>	*/
738	>	public Phaser getParent() {
739	>	return parent;
740	>	}
741	>
742	>	/**
743	>	* Returns the root ancestor of this phaser, which is the same as
744	>	* this phaser if it has no parent.
745	>	*
746	>	* @return the root ancestor of this phaser
747	>	*/
748	>	public Phaser getRoot() {
749	>	return root;
750	>	}
751	>
752	>	/**
753	>	* Returns {@code true} if this barrier has been terminated.
754	>	*
755	>	* @return {@code true} if this barrier has been terminated
756		*/
757		public boolean isTerminated() {
758	<	return phaseOf(state.get()) < 0;
758	>	return getPhase() < 0;
759		}
760
761		/**
762	<	* Overridable method to perform an action upon phase advance, and
763	<	* to control termination. This method is invoked whenever the
764	<	* barrier is tripped (and thus all other waiting parties are
765	<	* dormant). If it returns true, then, rather than advance the
766	<	* phase number, this barrier will be set to a final termination
767	<	* state, and subsequent calls to <tt>isTerminated</tt> will
768	<	* return true.
762	>	* Overridable method to perform an action upon impending phase
763	>	* advance, and to control termination. This method is invoked
764	>	* upon arrival of the party tripping the barrier (when all other
765	>	* waiting parties are dormant).  If this method returns {@code
766	>	* true}, then, rather than advance the phase number, this barrier
767	>	* will be set to a final termination state, and subsequent calls
768	>	* to {@link #isTerminated} will return true. Any (unchecked)
769	>	* Exception or Error thrown by an invocation of this method is
770	>	* propagated to the party attempting to trip the barrier, in
771	>	* which case no advance occurs.
772	>	*
773	>	* <p>The arguments to this method provide the state of the phaser
774	>	* prevailing for the current transition. (When called from within
775	>	* an implementation of {@code onAdvance} the values returned by
776	>	* methods such as {@code getPhase} may or may not reliably
777	>	* indicate the state to which this transition applies.)
778		*
779	<	* <p> The default version returns true when the number of
779	>	* <p>The default version returns {@code true} when the number of
780		* registered parties is zero. Normally, overrides that arrange
781		* termination for other reasons should also preserve this
782		* property.
783		*
784	+	* <p>You may override this method to perform an action with side
785	+	* effects visible to participating tasks, but doing so requires
786	+	* care: Method {@code onAdvance} may be invoked more than once
787	+	* per transition.  Further, unless all parties register before
788	+	* any arrive, and all {@link #awaitAdvance} at each phase, then
789	+	* you cannot ensure lack of interference from other parties
790	+	* during the invocation of this method.
791	+	*
792		* @param phase the phase number on entering the barrier
793	<	* @param registeredParties the current number of registered
794	<	* parties.
458	<	* @return true if this barrier should terminate
793	>	* @param registeredParties the current number of registered parties
794	>	* @return {@code true} if this barrier should terminate
795		*/
796		protected boolean onAdvance(int phase, int registeredParties) {
797		return registeredParties <= 0;
798		}
799
800		/**
801	<	* Returns a string identifying this barrier, as well as its
801	>	* Returns a string identifying this phaser, as well as its
802		* state.  The state, in brackets, includes the String {@code
803	<	* "phase ="} followed by the phase number, {@code "parties ="}
803	>	* "phase = "} followed by the phase number, {@code "parties = "}
804		* followed by the number of registered parties, and {@code
805	<	* "arrived ="} followed by the number of arrived parties
805	>	* "arrived = "} followed by the number of arrived parties.
806		*
807		* @return a string identifying this barrier, as well as its state
808		*/
809		public String toString() {
810	<	long s = state.get();
811	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
810	>	long s = getReconciledState();
811	>	return super.toString() +
812	>	"[phase = " + phaseOf(s) +
813	>	" parties = " + partiesOf(s) +
814	>	" arrived = " + arrivedOf(s) + "]";
815		}
816
817	<	// methods for tripping and waiting
817	>	// methods for waiting
818
819		/**
820	<	* Advance the current phase (or terminate)
820	>	* Wait nodes for Treiber stack representing wait queue
821		*/
822	<	private void trip(int phase, int parties) {
823	<	int next = onAdvance(phase, parties)? -1 : ((phase + 1) & phaseMask);
824	<	state.set(stateFor(next, parties, parties));
825	<	if (head.get() != null)
826	<	releaseWaiters(next);
827	<	}
828	<
829	<	private int helpingWait(int phase) {
830	<	final AtomicLong state = this.state;
831	<	int p;
832	<	while ((p = phaseOf(state.get())) == phase) {
833	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
834	<	if (t != null) {
835	<	if ((p = phaseOf(state.get())) == phase)
836	<	t.exec();
837	<	else {   // push task and exit if barrier advanced
838	<	t.fork();
839	<	break;
840	<	}
502	<	}
822	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
823	>	final Phaser phaser;
824	>	final int phase;
825	>	final long startTime;
826	>	final long nanos;
827	>	final boolean timed;
828	>	final boolean interruptible;
829	>	volatile boolean wasInterrupted = false;
830	>	volatile Thread thread; // nulled to cancel wait
831	>	QNode next;
832	>	QNode(Phaser phaser, int phase, boolean interruptible,
833	>	boolean timed, long startTime, long nanos) {
834	>	this.phaser = phaser;
835	>	this.phase = phase;
836	>	this.timed = timed;
837	>	this.interruptible = interruptible;
838	>	this.startTime = startTime;
839	>	this.nanos = nanos;
840	>	thread = Thread.currentThread();
841		}
842	<	return p;
843	<	}
844	<
845	<	private int timedHelpingWait(int phase, long nanos) throws TimeoutException {
846	<	final AtomicLong state = this.state;
847	<	long lastTime = System.nanoTime();
848	<	int p;
849	<	while ((p = phaseOf(state.get())) == phase) {
850	<	long now = System.nanoTime();
851	<	nanos -= now - lastTime;
852	<	lastTime = now;
515	<	if (nanos <= 0) {
516	<	if ((p = phaseOf(state.get())) == phase)
517	<	throw new TimeoutException();
518	<	else
519	<	break;
842	>	public boolean isReleasable() {
843	>	return (thread == null ||
844	>	phaser.getPhase() != phase ||
845	>	(interruptible && wasInterrupted) ||
846	>	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
847	>	}
848	>	public boolean block() {
849	>	if (Thread.interrupted()) {
850	>	wasInterrupted = true;
851	>	if (interruptible)
852	>	return true;
853		}
854	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
854	>	if (!timed)
855	>	LockSupport.park(this);
856	>	else {
857	>	long waitTime = nanos - (System.nanoTime() - startTime);
858	>	if (waitTime <= 0)
859	>	return true;
860	>	LockSupport.parkNanos(this, waitTime);
861	>	}
862	>	return isReleasable();
863	>	}
864	>	void signal() {
865	>	Thread t = thread;
866		if (t != null) {
867	<	if ((p = phaseOf(state.get())) == phase)
868	<	t.exec();
869	<	else {   // push task and exit if barrier advanced
870	<	t.fork();
871	<	break;
867	>	thread = null;
868	>	LockSupport.unpark(t);
869	>	}
870	>	}
871	>	boolean doWait() {
872	>	if (thread != null) {
873	>	try {
874	>	ForkJoinPool.managedBlock(this, false);
875	>	} catch (InterruptedException ie) {
876		}
877		}
878	+	return wasInterrupted;
879		}
880	<	return p;
880	>
881		}
882
883		/**
884	<	* 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.
884	>	* Removes and signals waiting threads from wait queue.
885		*/
886	<	static final class QNode {
887	<	QNode next;
888	<	volatile Thread thread; // nulled to cancel wait
889	<	final int phase;
890	<	QNode(Thread t, int c) {
891	<	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	<	}
886	>	private void releaseWaiters(int phase) {
887	>	AtomicReference<QNode> head = queueFor(phase);
888	>	QNode q;
889	>	while ((q = head.get()) != null) {
890	>	if (head.compareAndSet(q, q.next))
891	>	q.signal();
892		}
893		}
894
565	–	/** The number of CPUs, for spin control */
566	–	static final int NCPUS = Runtime.getRuntime().availableProcessors();
567	–
895		/**
896	<	* The number of times to spin before blocking in timed waits.
897	<	* The value is empirically derived.
898	<	*/
572	<	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
573	<
574	<	/**
575	<	* The number of times to spin before blocking in untimed waits.
576	<	* This is greater than timed value because untimed waits spin
577	<	* faster since they don't need to check times on each spin.
896	>	* Tries to enqueue given node in the appropriate wait queue.
897	>	*
898	>	* @return true if successful
899		*/
900	<	static final int maxUntimedSpins = maxTimedSpins * 32;
900	>	private boolean tryEnqueue(QNode node) {
901	>	AtomicReference<QNode> head = queueFor(node.phase);
902	>	return head.compareAndSet(node.next = head.get(), node);
903	>	}
904
905		/**
906	<	* The number of nanoseconds for which it is faster to spin
907	<	* rather than to use timed park. A rough estimate suffices.
906	>	* Enqueues node and waits unless aborted or signalled.
907	>	*
908	>	* @return current phase
909		*/
910	<	static final long spinForTimeoutThreshold = 1000L;
910	>	private int untimedWait(int phase) {
911	>	QNode node = null;
912	>	boolean queued = false;
913	>	boolean interrupted = false;
914	>	int p;
915	>	while ((p = getPhase()) == phase) {
916	>	if (Thread.interrupted())
917	>	interrupted = true;
918	>	else if (node == null)
919	>	node = new QNode(this, phase, false, false, 0, 0);
920	>	else if (!queued)
921	>	queued = tryEnqueue(node);
922	>	else
923	>	interrupted = node.doWait();
924	>	}
925	>	if (node != null)
926	>	node.thread = null;
927	>	releaseWaiters(phase);
928	>	if (interrupted)
929	>	Thread.currentThread().interrupt();
930	>	return p;
931	>	}
932
933		/**
934	<	* Enqueues node and waits unless aborted or signalled.
934	>	* Interruptible version
935	>	* @return current phase
936		*/
937	<	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;
937	>	private int interruptibleWait(int phase) throws InterruptedException {
938		QNode node = null;
939		boolean queued = false;
940	<	int spins = maxUntimedSpins;
941	<	while (phaseOf(state.get()) == currentPhase) {
942	<	QNode h;
943	<	if (node != null && queued) {
944	<	if (node.thread != null) {
945	<	LockSupport.park();
946	<	if (Thread.interrupted()) {
947	<	wasInterrupted = true;
948	<	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);
940	>	boolean interrupted = false;
941	>	int p;
942	>	while ((p = getPhase()) == phase && !interrupted) {
943	>	if (Thread.interrupted())
944	>	interrupted = true;
945	>	else if (node == null)
946	>	node = new QNode(this, phase, true, false, 0, 0);
947	>	else if (!queued)
948	>	queued = tryEnqueue(node);
949		else
950	<	--spins;
950	>	interrupted = node.doWait();
951		}
952		if (node != null)
953		node.thread = null;
954	<	return wasInterrupted;
954	>	if (p != phase || (p = getPhase()) != phase)
955	>	releaseWaiters(phase);
956	>	if (interrupted)
957	>	throw new InterruptedException();
958	>	return p;
959		}
960
961		/**
962	<	* Messier timeout version
962	>	* Timeout version.
963	>	* @return current phase
964		*/
965	<	private void timedWait(Thread thread, int currentPhase, long nanos)
965	>	private int timedWait(int phase, long nanos)
966		throws InterruptedException, TimeoutException {
967	<	final AtomicReference<QNode> head = this.head;
641	<	final AtomicLong state = this.state;
642	<	long lastTime = System.nanoTime();
967	>	long startTime = System.nanoTime();
968		QNode node = null;
969		boolean queued = false;
970	<	int spins = maxTimedSpins;
971	<	while (phaseOf(state.get()) == currentPhase) {
972	<	QNode h;
973	<	long now = System.nanoTime();
974	<	nanos -= now - lastTime;
975	<	lastTime = now;
976	<	if (nanos <= 0) {
977	<	if (node != null)
978	<	node.thread = null;
979	<	if (phaseOf(state.get()) == currentPhase)
980	<	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);
970	>	boolean interrupted = false;
971	>	int p;
972	>	while ((p = getPhase()) == phase && !interrupted) {
973	>	if (Thread.interrupted())
974	>	interrupted = true;
975	>	else if (nanos - (System.nanoTime() - startTime) <= 0)
976	>	break;
977	>	else if (node == null)
978	>	node = new QNode(this, phase, true, true, startTime, nanos);
979	>	else if (!queued)
980	>	queued = tryEnqueue(node);
981		else
982	<	--spins;
982	>	interrupted = node.doWait();
983		}
984		if (node != null)
985		node.thread = null;
986	+	if (p != phase || (p = getPhase()) != phase)
987	+	releaseWaiters(phase);
988	+	if (interrupted)
989	+	throw new InterruptedException();
990	+	if (p == phase)
991	+	throw new TimeoutException();
992	+	return p;
993	+	}
994	+
995	+	// Unsafe mechanics
996	+
997	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
998	+	private static final long stateOffset =
999	+	objectFieldOffset("state", Phaser.class);
1000	+
1001	+	private final boolean casState(long cmp, long val) {
1002	+	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
1003	+	}
1004	+
1005	+	private static long objectFieldOffset(String field, Class<?> klazz) {
1006	+	try {
1007	+	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1008	+	} catch (NoSuchFieldException e) {
1009	+	// Convert Exception to corresponding Error
1010	+	NoSuchFieldError error = new NoSuchFieldError(field);
1011	+	error.initCause(e);
1012	+	throw error;
1013	+	}
1014		}
1015
1016	+	/**
1017	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1018	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1019	+	* into a jdk.
1020	+	*
1021	+	* @return a sun.misc.Unsafe
1022	+	*/
1023	+	private static sun.misc.Unsafe getUnsafe() {
1024	+	try {
1025	+	return sun.misc.Unsafe.getUnsafe();
1026	+	} catch (SecurityException se) {
1027	+	try {
1028	+	return java.security.AccessController.doPrivileged
1029	+	(new java.security
1030	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1031	+	public sun.misc.Unsafe run() throws Exception {
1032	+	java.lang.reflect.Field f = sun.misc
1033	+	.Unsafe.class.getDeclaredField("theUnsafe");
1034	+	f.setAccessible(true);
1035	+	return (sun.misc.Unsafe) f.get(null);
1036	+	}});
1037	+	} catch (java.security.PrivilegedActionException e) {
1038	+	throw new RuntimeException("Could not initialize intrinsics",
1039	+	e.getCause());
1040	+	}
1041	+	}
1042	+	}
1043		}

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