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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 1.40 by dl, Mon Aug 24 12:49:39 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; thus, this value is always
104	>	* greater than zero if there are any registered parties.  The values
105	>	* returned by these methods may reflect transient states and so are
106	>	* not in general useful for synchronization control.  Method {@link
107	>	* #toString} returns snapshots of these state queries in a form
108	>	* convenient for informal monitoring.
109	>	*
110	>	* <p><b>Sample usages:</b>
111	>	*
112	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
113	>	* to control a one-shot action serving a variable number of
114	>	* parties. The typical idiom is for the method setting this up to
115	>	* first register, then start the actions, then deregister, as in:
116	>	*
117	>	*  <pre> {@code
118	>	* void runTasks(List<Runnable> tasks) {
119	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
120	>	*   // create and start threads
121	>	*   for (Runnable task : tasks) {
122	>	*     phaser.register();
123	>	*     new Thread() {
124	>	*       public void run() {
125	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
126	>	*         task.run();
127	>	*       }
128	>	*     }.start();
129	>	*   }
130	>	*
131	>	*   // allow threads to start and deregister self
132	>	*   phaser.arriveAndDeregister();
133	>	* }}</pre>
134	>	*
135	>	* <p>One way to cause a set of threads to repeatedly perform actions
136	>	* for a given number of iterations is to override {@code onAdvance}:
137	>	*
138	>	*  <pre> {@code
139	>	* void startTasks(List<Runnable> tasks, final int iterations) {
140	>	*   final Phaser phaser = new Phaser() {
141	>	*     protected boolean onAdvance(int phase, int registeredParties) {
142	>	*       return phase >= iterations || registeredParties == 0;
143	>	*     }
144	>	*   };
145	>	*   phaser.register();
146	>	*   for (Runnable task : tasks) {
147	>	*     phaser.register();
148	>	*     new Thread() {
149	>	*       public void run() {
150	>	*         do {
151	>	*           task.run();
152	>	*           phaser.arriveAndAwaitAdvance();
153	>	*         } while(!phaser.isTerminated();
154	>	*       }
155	>	*     }.start();
156	>	*   }
157	>	*   phaser.arriveAndDeregister(); // deregister self, don't wait
158	>	* }}</pre>
159		*
160	<	* <p><b>Sample usage:</b>
160	>	* If the main task must later await termination, it
161	>	* may re-register and then execute a similar loop:
162	>	* <pre> {@code
163	>	*   // ...
164	>	*   phaser.register();
165	>	*   while (!phaser.isTerminated())
166	>	*     phaser.arriveAndAwaitAdvance();
167	>	* }</pre>
168		*
169	<	* <p>[todo: non-FJ example]
169	>	* Related constructions may be used to await particular phase numbers
170	>	* in contexts where you are sure that the phase will never wrap around
171	>	* {@code Integer.MAX_VALUE}. For example:
172		*
173	<	* <p> A Phaser may be used to support a style of programming in
174	<	* which a task waits for others to complete, without otherwise
175	<	* needing to keep track of which tasks it is waiting for. This is
176	<	* similar to the "sync" construct in Cilk and "clocks" in X10.
177	<	* Special constructions based on such barriers are available using
178	<	* the <tt>LinkedAsyncAction</tt> and <tt>CyclicAction</tt> classes,
179	<	* but they can be useful in other contexts as well.  For a simple
180	<	* (but not very useful) example, here is a variant of Fibonacci:
181	<	*
182	<	* <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();
173	>	* <pre> {@code
174	>	*   void awaitPhase(Phaser phaser, int phase) {
175	>	*     int p = phaser.register(); // assumes caller not already registered
176	>	*     while (p < phase) {
177	>	*       if (phaser.isTerminated())
178	>	*         // ... deal with unexpected termination
179	>	*       else
180	>	*         p = phaser.arriveAndAwaitAdvance();
181	>	*     }
182	>	*     phaser.arriveAndDeregister();
183		*   }
184	<	*   protected void compute() {
185	<	*     int n = argument;
186	<	*     if (n &lt;= 1)
187	<	*        result = n;
188	<	*     else {
189	<	*        Phaser childBarrier = new Phaser(1);
190	<	*        BarrierFibonacci f1 = new BarrierFibonacci(n - 1, childBarrier);
191	<	*        BarrierFibonacci f2 = new BarrierFibonacci(n - 2, childBarrier);
192	<	*        f1.fork();
193	<	*        f2.fork();
194	<	*        childBarrier.arriveAndAwait();
195	<	*        result = f1.result + f2.result;
184	>	* }</pre>
185	>	*
186	>	*
187	>	* <p>To create a set of tasks using a tree of phasers,
188	>	* you could use code of the following form, assuming a
189	>	* Task class with a constructor accepting a phaser that
190	>	* it registers for upon construction:
191	>	*  <pre> {@code
192	>	* void build(Task[] actions, int lo, int hi, Phaser b) {
193	>	*   int step = (hi - lo) / TASKS_PER_PHASER;
194	>	*   if (step > 1) {
195	>	*     int i = lo;
196	>	*     while (i < hi) {
197	>	*       int r = Math.min(i + step, hi);
198	>	*       build(actions, i, r, new Phaser(b));
199	>	*       i = r;
200		*     }
201	<	*     parentBarrier.arriveAndDeregister();
201	>	*   } else {
202	>	*     for (int i = lo; i < hi; ++i)
203	>	*       actions[i] = new Task(b);
204	>	*       // assumes new Task(b) performs b.register()
205		*   }
206		* }
207	+	* // .. initially called, for n tasks via
208	+	* build(new Task[n], 0, n, new Phaser());}</pre>
209	+	*
210	+	* The best value of {@code TASKS_PER_PHASER} depends mainly on
211	+	* expected barrier synchronization rates. A value as low as four may
212	+	* be appropriate for extremely small per-barrier task bodies (thus
213	+	* high rates), or up to hundreds for extremely large ones.
214	+	*
215		* </pre>
216		*
217		* <p><b>Implementation notes</b>: This implementation restricts the
218	<	* maximum number of parties to 65535. Attempts to register
219	<	* additional parties result in IllegalStateExceptions.
218	>	* maximum number of parties to 65535. Attempts to register additional
219	>	* parties result in {@code IllegalStateException}. However, you can and
220	>	* should create tiered phasers to accommodate arbitrarily large sets
221	>	* of participants.
222	>	*
223	>	* @since 1.7
224	>	* @author Doug Lea
225		*/
226		public class Phaser {
227		/*
228		* This class implements an extension of X10 "clocks".  Thanks to
229	<	* Vijay Saraswat for the idea of applying it to ForkJoinTasks,
230	<	* and to Vivek Sarkar for enhancements to extend functionality.
229	>	* Vijay Saraswat for the idea, and to Vivek Sarkar for
230	>	* enhancements to extend functionality.
231		*/
232
233		/**
234		* Barrier state representation. Conceptually, a barrier contains
235		* four values:
236	<	*
236	>	*
237		* * parties -- the number of parties to wait (16 bits)
238		* * unarrived -- the number of parties yet to hit barrier (16 bits)
239		* * phase -- the generation of the barrier (31 bits)
240		* * terminated -- set if barrier is terminated (1 bit)
241		*
242		* However, to efficiently maintain atomicity, these values are
243	<	* packed into a single AtomicLong. Termination uses the sign bit
244	<	* of 32 bit representation of phase, so phase is set to -1 on
245	<	* termination.
246	<	*/
247	<	private final AtomicLong state;
248	<
249	<	/**
143	<	* Head of Treiber stack for waiting nonFJ threads.
243	>	* packed into a single (atomic) long. Termination uses the sign
244	>	* bit of 32 bit representation of phase, so phase is set to -1 on
245	>	* termination. Good performance relies on keeping state decoding
246	>	* and encoding simple, and keeping race windows short.
247	>	*
248	>	* Note: there are some cheats in arrive() that rely on unarrived
249	>	* count being lowest 16 bits.
250		*/
251	<	private final AtomicReference<QNode> head = new AtomicReference<QNode>();
251	>	private volatile long state;
252
253		private static final int ushortBits = 16;
254	<	private static final int ushortMask =  (1 << ushortBits) - 1;
255	<	private static final int phaseMask = 0x7fffffff;
254	>	private static final int ushortMask = 0xffff;
255	>	private static final int phaseMask  = 0x7fffffff;
256
257		private static int unarrivedOf(long s) {
258	<	return (int)(s & ushortMask);
258	>	return (int) (s & ushortMask);
259		}
260
261		private static int partiesOf(long s) {
262	<	return (int)(s & (ushortMask << 16)) >>> 16;
262	>	return ((int) s) >>> 16;
263		}
264
265		private static int phaseOf(long s) {
266	<	return (int)(s >>> 32);
266	>	return (int) (s >>> 32);
267		}
268
269		private static int arrivedOf(long s) {
#	Line 165 | Line 271 | public class Phaser {
271		}
272
273		private static long stateFor(int phase, int parties, int unarrived) {
274	<	return (((long)phase) << 32) | ((parties << 16) | unarrived);
274	>	return ((((long) phase) << 32) | (((long) parties) << 16) |
275	>	(long) unarrived);
276		}
277
278	<	private static IllegalStateException badBounds(int parties, int unarrived) {
279	<	return new IllegalStateException("Attempt to set " + unarrived +
280	<	" unarrived of " + parties + " parties");
278	>	private static long trippedStateFor(int phase, int parties) {
279	>	long lp = (long) parties;
280	>	return (((long) phase) << 32) | (lp << 16) | lp;
281		}
282
283		/**
284	<	* Creates a new Phaser without any initially registered parties,
285	<	* and initial phase number 0.
284	>	* Returns message string for bad bounds exceptions.
285	>	*/
286	>	private static String badBounds(int parties, int unarrived) {
287	>	return ("Attempt to set " + unarrived +
288	>	" unarrived of " + parties + " parties");
289	>	}
290	>
291	>	/**
292	>	* The parent of this phaser, or null if none
293	>	*/
294	>	private final Phaser parent;
295	>
296	>	/**
297	>	* The root of phaser tree. Equals this if not in a tree.  Used to
298	>	* support faster state push-down.
299	>	*/
300	>	private final Phaser root;
301	>
302	>	// Wait queues
303	>
304	>	/**
305	>	* Heads of Treiber stacks for waiting threads. To eliminate
306	>	* contention while releasing some threads while adding others, we
307	>	* use two of them, alternating across even and odd phases.
308	>	*/
309	>	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
310	>	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
311	>
312	>	private AtomicReference<QNode> queueFor(int phase) {
313	>	return ((phase & 1) == 0) ? evenQ : oddQ;
314	>	}
315	>
316	>	/**
317	>	* Returns current state, first resolving lagged propagation from
318	>	* root if necessary.
319	>	*/
320	>	private long getReconciledState() {
321	>	return (parent == null) ? state : reconcileState();
322	>	}
323	>
324	>	/**
325	>	* Recursively resolves state.
326	>	*/
327	>	private long reconcileState() {
328	>	Phaser p = parent;
329	>	long s = state;
330	>	if (p != null) {
331	>	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
332	>	long parentState = p.getReconciledState();
333	>	int parentPhase = phaseOf(parentState);
334	>	int phase = phaseOf(s = state);
335	>	if (phase != parentPhase) {
336	>	long next = trippedStateFor(parentPhase, partiesOf(s));
337	>	if (casState(s, next)) {
338	>	releaseWaiters(phase);
339	>	s = next;
340	>	}
341	>	}
342	>	}
343	>	}
344	>	return s;
345	>	}
346	>
347	>	/**
348	>	* Creates a new phaser without any initially registered parties,
349	>	* initial phase number 0, and no parent. Any thread using this
350	>	* phaser will need to first register for it.
351		*/
352		public Phaser() {
353	<	state = new AtomicLong(stateFor(0, 0, 0));
353	>	this(null);
354		}
355
356		/**
357	<	* Creates a new Phaser with the given numbers of registered
358	<	* unarrived parties and initial phase number 0.
359	<	* @param parties the number of parties required to trip barrier.
357	>	* Creates a new phaser with the given numbers of registered
358	>	* unarrived parties, initial phase number 0, and no parent.
359	>	*
360	>	* @param parties the number of parties required to trip barrier
361		* @throws IllegalArgumentException if parties less than zero
362	<	* or greater than the maximum number of parties supported.
362	>	* or greater than the maximum number of parties supported
363		*/
364		public Phaser(int parties) {
365	+	this(null, parties);
366	+	}
367	+
368	+	/**
369	+	* Creates a new phaser with the given parent, without any
370	+	* initially registered parties. If parent is non-null this phaser
371	+	* is registered with the parent and its initial phase number is
372	+	* the same as that of parent phaser.
373	+	*
374	+	* @param parent the parent phaser
375	+	*/
376	+	public Phaser(Phaser parent) {
377	+	int phase = 0;
378	+	this.parent = parent;
379	+	if (parent != null) {
380	+	this.root = parent.root;
381	+	phase = parent.register();
382	+	}
383	+	else
384	+	this.root = this;
385	+	this.state = trippedStateFor(phase, 0);
386	+	}
387	+
388	+	/**
389	+	* Creates a new phaser with the given parent and numbers of
390	+	* registered unarrived parties. If parent is non-null, this phaser
391	+	* is registered with the parent and its initial phase number is
392	+	* the same as that of parent phaser.
393	+	*
394	+	* @param parent the parent phaser
395	+	* @param parties the number of parties required to trip barrier
396	+	* @throws IllegalArgumentException if parties less than zero
397	+	* or greater than the maximum number of parties supported
398	+	*/
399	+	public Phaser(Phaser parent, int parties) {
400		if (parties < 0 || parties > ushortMask)
401		throw new IllegalArgumentException("Illegal number of parties");
402	<	state = new AtomicLong(stateFor(0, parties, parties));
402	>	int phase = 0;
403	>	this.parent = parent;
404	>	if (parent != null) {
405	>	this.root = parent.root;
406	>	phase = parent.register();
407	>	}
408	>	else
409	>	this.root = this;
410	>	this.state = trippedStateFor(phase, parties);
411		}
412
413		/**
414		* Adds a new unarrived party to this phaser.
415	<	* @return the current barrier phase number upon registration
415	>	*
416	>	* @return the arrival phase number to which this registration applied
417	>	* @throws IllegalStateException if attempting to register more
418	>	* than the maximum supported number of parties
419	>	*/
420	>	public int register() {
421	>	return doRegister(1);
422	>	}
423	>
424	>	/**
425	>	* Adds the given number of new unarrived parties to this phaser.
426	>	*
427	>	* @param parties the number of parties required to trip barrier
428	>	* @return the arrival phase number to which this registration applied
429		* @throws IllegalStateException if attempting to register more
430	<	* than the maximum supported number of parties.
430	>	* than the maximum supported number of parties
431		*/
432	<	public int register() { // increment both parties and unarrived
433	<	final AtomicLong state = this.state;
432	>	public int bulkRegister(int parties) {
433	>	if (parties < 0)
434	>	throw new IllegalArgumentException();
435	>	if (parties == 0)
436	>	return getPhase();
437	>	return doRegister(parties);
438	>	}
439	>
440	>	/**
441	>	* Shared code for register, bulkRegister
442	>	*/
443	>	private int doRegister(int registrations) {
444	>	int phase;
445		for (;;) {
446	<	long s = state.get();
447	<	int phase = phaseOf(s);
448	<	int parties = partiesOf(s) + 1;
449	<	int unarrived = unarrivedOf(s) + 1;
446	>	long s = getReconciledState();
447	>	phase = phaseOf(s);
448	>	int unarrived = unarrivedOf(s) + registrations;
449	>	int parties = partiesOf(s) + registrations;
450	>	if (phase < 0)
451	>	break;
452		if (parties > ushortMask || unarrived > ushortMask)
453	<	throw badBounds(parties, unarrived);
454	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
455	<	return phase;
453	>	throw new IllegalStateException(badBounds(parties, unarrived));
454	>	if (phase == phaseOf(root.state) &&
455	>	casState(s, stateFor(phase, parties, unarrived)))
456	>	break;
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
224	<	* parties would become negative.
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() { // decrement unarrived. If zero, trip
472	<	final AtomicLong state = this.state;
471	>	public int arrive() {
472	>	int phase;
473		for (;;) {
474	<	long s = state.get();
475	<	int phase = phaseOf(s);
474	>	long s = state;
475	>	phase = phaseOf(s);
476	>	if (phase < 0)
477	>	break;
478		int parties = partiesOf(s);
479		int unarrived = unarrivedOf(s) - 1;
480	<	if (unarrived < 0)
481	<	throw badBounds(parties, unarrived);
482	<	if (unarrived == 0 && phase >= 0) {
236	<	trip(phase, parties);
237	<	return phase;
480	>	if (unarrived > 0) {        // Not the last arrival
481	>	if (casState(s, s - 1)) // s-1 adds one arrival
482	>	break;
483		}
484	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
485	<	return phase;
484	>	else if (unarrived == 0) {  // the last arrival
485	>	Phaser par = parent;
486	>	if (par == null) {      // directly trip
487	>	if (casState
488	>	(s,
489	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
490	>	((phase + 1) & phaseMask), parties))) {
491	>	releaseWaiters(phase);
492	>	break;
493	>	}
494	>	}
495	>	else {                  // cascade to parent
496	>	if (casState(s, s - 1)) { // zeroes unarrived
497	>	par.arrive();
498	>	reconcileState();
499	>	break;
500	>	}
501	>	}
502	>	}
503	>	else if (phase != phaseOf(root.state)) // or if unreconciled
504	>	reconcileState();
505	>	else
506	>	throw new IllegalStateException(badBounds(parties, unarrived));
507		}
508	+	return phase;
509		}
510
511		/**
512	<	* Arrives at the barrier, and deregisters from it, without
513	<	* waiting for others.
512	>	* Arrives at the barrier and deregisters from it without waiting
513	>	* for others. Deregistration reduces the number of parties
514	>	* required to trip the barrier in future phases.  If this phaser
515	>	* has a parent, and deregistration causes this phaser to have
516	>	* zero parties, this phaser also arrives at and is deregistered
517	>	* from its parent.  It is an unenforced usage error for an
518	>	* unregistered party to invoke this method.
519		*
520	<	* @return the current barrier phase number upon entry to
521	<	* this method, or a negative value if terminated;
522	<	* @throws IllegalStateException if the number of registered or
523	<	* unarrived parties would become negative.
524	<	*/
525	<	public int arriveAndDeregister() { // Same as arrive, plus decrement parties
526	<	final AtomicLong state = this.state;
520	>	* @return the arrival phase number, or a negative value if terminated
521	>	* @throws IllegalStateException if not terminated and the number
522	>	* of registered or unarrived parties would become negative
523	>	*/
524	>	public int arriveAndDeregister() {
525	>	// similar code to arrive, but too different to merge
526	>	Phaser par = parent;
527	>	int phase;
528		for (;;) {
529	<	long s = state.get();
530	<	int phase = phaseOf(s);
529	>	long s = state;
530	>	phase = phaseOf(s);
531	>	if (phase < 0)
532	>	break;
533		int parties = partiesOf(s) - 1;
534		int unarrived = unarrivedOf(s) - 1;
535	<	if (parties < 0 || unarrived < 0)
536	<	throw badBounds(parties, unarrived);
537	<	if (unarrived == 0 && phase >= 0) {
538	<	trip(phase, parties);
539	<	return phase;
535	>	if (parties >= 0) {
536	>	if (unarrived > 0 || (unarrived == 0 && par != null)) {
537	>	if (casState
538	>	(s,
539	>	stateFor(phase, parties, unarrived))) {
540	>	if (unarrived == 0) {
541	>	par.arriveAndDeregister();
542	>	reconcileState();
543	>	}
544	>	break;
545	>	}
546	>	continue;
547	>	}
548	>	if (unarrived == 0) {
549	>	if (casState
550	>	(s,
551	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
552	>	((phase + 1) & phaseMask), parties))) {
553	>	releaseWaiters(phase);
554	>	break;
555	>	}
556	>	continue;
557	>	}
558	>	if (par != null && phase != phaseOf(root.state)) {
559	>	reconcileState();
560	>	continue;
561	>	}
562		}
563	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
267	<	return phase;
563	>	throw new IllegalStateException(badBounds(parties, unarrived));
564		}
565	+	return phase;
566		}
567
568		/**
569	<	* Arrives at the barrier and awaits others. Unlike other arrival
570	<	* methods, this method returns the arrival index of the
571	<	* caller. The caller tripping the barrier returns zero, the
572	<	* previous caller 1, and so on.
573	<	* @return the arrival index
574	<	* @throws IllegalStateException if the number of unarrived
575	<	* parties would become negative.
569	>	* Arrives at the barrier and awaits others. Equivalent in effect
570	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
571	>	* interruption or timeout, you can arrange this with an analogous
572	>	* construction using one of the other forms of the awaitAdvance
573	>	* method.  If instead you need to deregister upon arrival use
574	>	* {@code arriveAndDeregister}. It is an unenforced usage error
575	>	* for an unregistered party to invoke this method.
576	>	*
577	>	* @return the arrival phase number, or a negative number if terminated
578	>	* @throws IllegalStateException if not terminated and the number
579	>	* of unarrived parties would become negative
580		*/
581		public int arriveAndAwaitAdvance() {
582	<	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	<	}
582	>	return awaitAdvance(arrive());
583		}
584
585		/**
586	<	* Awaits the phase of the barrier to advance from the given
587	<	* value, or returns immediately if this barrier is terminated.
588	<	* @param phase the phase on entry to this method
589	<	* @return the phase on exit from this method
586	>	* Awaits the phase of the barrier to advance from the given phase
587	>	* value, returning immediately if the current phase of the
588	>	* barrier is not equal to the given phase value or this barrier
589	>	* is terminated.  It is an unenforced usage error for an
590	>	* unregistered party to invoke this method.
591	>	*
592	>	* @param phase an arrival phase number, or negative value if
593	>	* terminated; this argument is normally the value returned by a
594	>	* previous call to {@code arrive} or its variants
595	>	* @return the next arrival phase number, or a negative value
596	>	* if terminated or argument is negative
597		*/
598		public int awaitAdvance(int phase) {
599		if (phase < 0)
600		return phase;
601	<	Thread current = Thread.currentThread();
602	<	if (current instanceof ForkJoinWorkerThread)
603	<	return helpingWait(phase);
604	<	if (untimedWait(current, phase, false))
605	<	current.interrupt();
606	<	return phaseOf(state.get());
601	>	long s = getReconciledState();
602	>	int p = phaseOf(s);
603	>	if (p != phase)
604	>	return p;
605	>	if (unarrivedOf(s) == 0 && parent != null)
606	>	parent.awaitAdvance(phase);
607	>	// Fall here even if parent waited, to reconcile and help release
608	>	return untimedWait(phase);
609		}
610
611		/**
612	<	* Awaits the phase of the barrier to advance from the given
613	<	* value, or returns immediately if this barrier is terminated, or
614	<	* throws InterruptedException if interrupted while waiting.
615	<	* @param phase the phase on entry to this method
616	<	* @return the phase on exit from this method
612	>	* Awaits the phase of the barrier to advance from the given phase
613	>	* value, throwing {@code InterruptedException} if interrupted
614	>	* while waiting, or returning immediately if the current phase of
615	>	* the barrier is not equal to the given phase value or this
616	>	* barrier is terminated. It is an unenforced usage error for an
617	>	* unregistered party to invoke this method.
618	>	*
619	>	* @param phase an arrival phase number, or negative value if
620	>	* terminated; this argument is normally the value returned by a
621	>	* previous call to {@code arrive} or its variants
622	>	* @return the next arrival phase number, or a negative value
623	>	* if terminated or argument is negative
624		* @throws InterruptedException if thread interrupted while waiting
625		*/
626	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
626	>	public int awaitAdvanceInterruptibly(int phase)
627	>	throws InterruptedException {
628		if (phase < 0)
629		return phase;
630	<	Thread current = Thread.currentThread();
631	<	if (current instanceof ForkJoinWorkerThread)
632	<	return helpingWait(phase);
633	<	else if (Thread.interrupted() || untimedWait(current, phase, true))
634	<	throw new InterruptedException();
635	<	else
636	<	return phaseOf(state.get());
630	>	long s = getReconciledState();
631	>	int p = phaseOf(s);
632	>	if (p != phase)
633	>	return p;
634	>	if (unarrivedOf(s) == 0 && parent != null)
635	>	parent.awaitAdvanceInterruptibly(phase);
636	>	return interruptibleWait(phase);
637		}
638
639		/**
640	<	* Awaits the phase of the barrier to advance from the given value
641	<	* or the given timeout elapses, or returns immediately if this
642	<	* barrier is terminated.
643	<	* @param phase the phase on entry to this method
644	<	* @return the phase on exit from this method
640	>	* Awaits the phase of the barrier to advance from the given phase
641	>	* value or the given timeout to elapse, throwing {@code
642	>	* InterruptedException} if interrupted while waiting, or
643	>	* returning immediately if the current phase of the barrier is
644	>	* not equal to the given phase value or this barrier is
645	>	* terminated.  It is an unenforced usage error for an
646	>	* unregistered party to invoke this method.
647	>	*
648	>	* @param phase an arrival phase number, or negative value if
649	>	* terminated; this argument is normally the value returned by a
650	>	* previous call to {@code arrive} or its variants
651	>	* @param timeout how long to wait before giving up, in units of
652	>	*        {@code unit}
653	>	* @param unit a {@code TimeUnit} determining how to interpret the
654	>	*        {@code timeout} parameter
655	>	* @return the next arrival phase number, or a negative value
656	>	* if terminated or argument is negative
657		* @throws InterruptedException if thread interrupted while waiting
658		* @throws TimeoutException if timed out while waiting
659		*/
660	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
660	>	public int awaitAdvanceInterruptibly(int phase,
661	>	long timeout, TimeUnit unit)
662		throws InterruptedException, TimeoutException {
663		if (phase < 0)
664		return phase;
665	<	long nanos = unit.toNanos(timeout);
666	<	Thread current = Thread.currentThread();
667	<	if (current instanceof ForkJoinWorkerThread)
668	<	return timedHelpingWait(phase, nanos);
669	<	timedWait(current, phase, nanos);
670	<	return phaseOf(state.get());
665	>	long s = getReconciledState();
666	>	int p = phaseOf(s);
667	>	if (p != phase)
668	>	return p;
669	>	if (unarrivedOf(s) == 0 && parent != null)
670	>	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
671	>	return timedWait(phase, unit.toNanos(timeout));
672		}
673
674		/**
675		* Forces this barrier to enter termination state. Counts of
676	<	* arrived and registered parties are unaffected. This method may
677	<	* be useful for coordinating recovery after one or more tasks
678	<	* encounter unexpected exceptions.
676	>	* arrived and registered parties are unaffected. If this phaser
677	>	* has a parent, it too is terminated. This method may be useful
678	>	* for coordinating recovery after one or more tasks encounter
679	>	* unexpected exceptions.
680		*/
681		public void forceTermination() {
365	–	final AtomicLong state = this.state;
682		for (;;) {
683	<	long s = state.get();
683	>	long s = getReconciledState();
684		int phase = phaseOf(s);
685		int parties = partiesOf(s);
686		int unarrived = unarrivedOf(s);
687		if (phase < 0 ||
688	<	state.compareAndSet(s, stateFor(-1, parties, unarrived))) {
689	<	if (head.get() != null)
690	<	releaseWaiters(-1);
688	>	casState(s, stateFor(-1, parties, unarrived))) {
689	>	releaseWaiters(0);
690	>	releaseWaiters(1);
691	>	if (parent != null)
692	>	parent.forceTermination();
693		return;
694		}
695		}
696		}
697
698		/**
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	–	/**
699		* Returns the current phase number. The maximum phase number is
700	<	* <tt>Integer.MAX_VALUE</tt>, after which it restarts at
700	>	* {@code Integer.MAX_VALUE}, after which it restarts at
701		* zero. Upon termination, the phase number is negative.
702	+	*
703		* @return the phase number, or a negative value if terminated
704		*/
705	<	public int getPhase() {
706	<	return phaseOf(state.get());
705	>	public final int getPhase() {
706	>	return phaseOf(getReconciledState());
707		}
708
709		/**
710		* Returns the number of parties registered at this barrier.
711	+	*
712		* @return the number of parties
713		*/
714		public int getRegisteredParties() {
715	<	return partiesOf(state.get());
715	>	return partiesOf(state);
716		}
717
718		/**
719	<	* Returns the number of parties that have arrived at the current
720	<	* phase of this barrier.
719	>	* Returns the number of registered parties that have arrived at
720	>	* the current phase of this barrier.
721	>	*
722		* @return the number of arrived parties
723		*/
724		public int getArrivedParties() {
725	<	return arrivedOf(state.get());
725	>	return arrivedOf(state);
726		}
727
728		/**
729		* Returns the number of registered parties that have not yet
730		* arrived at the current phase of this barrier.
731	+	*
732		* @return the number of unarrived parties
733		*/
734		public int getUnarrivedParties() {
735	<	return unarrivedOf(state.get());
735	>	return unarrivedOf(state);
736	>	}
737	>
738	>	/**
739	>	* Returns the parent of this phaser, or {@code null} if none.
740	>	*
741	>	* @return the parent of this phaser, or {@code null} if none
742	>	*/
743	>	public Phaser getParent() {
744	>	return parent;
745	>	}
746	>
747	>	/**
748	>	* Returns the root ancestor of this phaser, which is the same as
749	>	* this phaser if it has no parent.
750	>	*
751	>	* @return the root ancestor of this phaser
752	>	*/
753	>	public Phaser getRoot() {
754	>	return root;
755		}
756
757		/**
758	<	* Returns true if this barrier has been terminated.
759	<	* @return true if this barrier has been terminated
758	>	* Returns {@code true} if this barrier has been terminated.
759	>	*
760	>	* @return {@code true} if this barrier has been terminated
761		*/
762		public boolean isTerminated() {
763	<	return phaseOf(state.get()) < 0;
763	>	return getPhase() < 0;
764		}
765
766		/**
767		* Overridable method to perform an action upon phase advance, and
768		* to control termination. This method is invoked whenever the
769		* barrier is tripped (and thus all other waiting parties are
770	<	* dormant). If it returns true, then, rather than advance the
771	<	* phase number, this barrier will be set to a final termination
772	<	* state, and subsequent calls to <tt>isTerminated</tt> will
773	<	* return true.
774	<	*
775	<	* <p> The default version returns true when the number of
770	>	* dormant). If it returns {@code true}, then, rather than advance
771	>	* the phase number, this barrier will be set to a final
772	>	* termination state, and subsequent calls to {@link #isTerminated}
773	>	* will return true.
774	>	*
775	>	* <p>The default version returns {@code true} when the number of
776		* registered parties is zero. Normally, overrides that arrange
777		* termination for other reasons should also preserve this
778		* property.
779		*
780	+	* <p>You may override this method to perform an action with side
781	+	* effects visible to participating tasks, but it is in general
782	+	* only sensible to do so in designs where all parties register
783	+	* before any arrive, and all {@link #awaitAdvance} at each phase.
784	+	* Otherwise, you cannot ensure lack of interference from other
785	+	* parties during the invocation of this method.
786	+	*
787		* @param phase the phase number on entering the barrier
788	<	* @param registeredParties the current number of registered
789	<	* parties.
458	<	* @return true if this barrier should terminate
788	>	* @param registeredParties the current number of registered parties
789	>	* @return {@code true} if this barrier should terminate
790		*/
791		protected boolean onAdvance(int phase, int registeredParties) {
792		return registeredParties <= 0;
793		}
794
795		/**
796	<	* Returns a string identifying this barrier, as well as its
796	>	* Returns a string identifying this phaser, as well as its
797		* state.  The state, in brackets, includes the String {@code
798	<	* "phase ="} followed by the phase number, {@code "parties ="}
798	>	* "phase = "} followed by the phase number, {@code "parties = "}
799		* followed by the number of registered parties, and {@code
800	<	* "arrived ="} followed by the number of arrived parties
800	>	* "arrived = "} followed by the number of arrived parties.
801		*
802		* @return a string identifying this barrier, as well as its state
803		*/
804		public String toString() {
805	<	long s = state.get();
806	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
805	>	long s = getReconciledState();
806	>	return super.toString() +
807	>	"[phase = " + phaseOf(s) +
808	>	" parties = " + partiesOf(s) +
809	>	" arrived = " + arrivedOf(s) + "]";
810		}
811
812	<	// methods for tripping and waiting
812	>	// methods for waiting
813
814		/**
815	<	* Advance the current phase (or terminate)
815	>	* Wait nodes for Treiber stack representing wait queue
816		*/
817	<	private void trip(int phase, int parties) {
818	<	int next = onAdvance(phase, parties)? -1 : ((phase + 1) & phaseMask);
819	<	state.set(stateFor(next, parties, parties));
820	<	if (head.get() != null)
821	<	releaseWaiters(next);
822	<	}
823	<
824	<	private int helpingWait(int phase) {
825	<	final AtomicLong state = this.state;
826	<	int p;
827	<	while ((p = phaseOf(state.get())) == phase) {
828	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
829	<	if (t != null) {
830	<	if ((p = phaseOf(state.get())) == phase)
831	<	t.exec();
832	<	else {   // push task and exit if barrier advanced
833	<	t.fork();
834	<	break;
835	<	}
502	<	}
817	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
818	>	final Phaser phaser;
819	>	final int phase;
820	>	final long startTime;
821	>	final long nanos;
822	>	final boolean timed;
823	>	final boolean interruptible;
824	>	volatile boolean wasInterrupted = false;
825	>	volatile Thread thread; // nulled to cancel wait
826	>	QNode next;
827	>	QNode(Phaser phaser, int phase, boolean interruptible,
828	>	boolean timed, long startTime, long nanos) {
829	>	this.phaser = phaser;
830	>	this.phase = phase;
831	>	this.timed = timed;
832	>	this.interruptible = interruptible;
833	>	this.startTime = startTime;
834	>	this.nanos = nanos;
835	>	thread = Thread.currentThread();
836		}
837	<	return p;
838	<	}
839	<
840	<	private int timedHelpingWait(int phase, long nanos) throws TimeoutException {
841	<	final AtomicLong state = this.state;
842	<	long lastTime = System.nanoTime();
843	<	int p;
844	<	while ((p = phaseOf(state.get())) == phase) {
845	<	long now = System.nanoTime();
846	<	nanos -= now - lastTime;
847	<	lastTime = now;
848	<	if (nanos <= 0) {
849	<	if ((p = phaseOf(state.get())) == phase)
850	<	throw new TimeoutException();
851	<	else
852	<	break;
837	>	public boolean isReleasable() {
838	>	return (thread == null ||
839	>	phaser.getPhase() != phase ||
840	>	(interruptible && wasInterrupted) ||
841	>	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
842	>	}
843	>	public boolean block() {
844	>	if (Thread.interrupted()) {
845	>	wasInterrupted = true;
846	>	if (interruptible)
847	>	return true;
848	>	}
849	>	if (!timed)
850	>	LockSupport.park(this);
851	>	else {
852	>	long waitTime = nanos - (System.nanoTime() - startTime);
853	>	if (waitTime <= 0)
854	>	return true;
855	>	LockSupport.parkNanos(this, waitTime);
856		}
857	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
857	>	return isReleasable();
858	>	}
859	>	void signal() {
860	>	Thread t = thread;
861		if (t != null) {
862	<	if ((p = phaseOf(state.get())) == phase)
863	<	t.exec();
864	<	else {   // push task and exit if barrier advanced
865	<	t.fork();
866	<	break;
862	>	thread = null;
863	>	LockSupport.unpark(t);
864	>	}
865	>	}
866	>	boolean doWait() {
867	>	if (thread != null) {
868	>	try {
869	>	ForkJoinPool.managedBlock(this, false);
870	>	} catch (InterruptedException ie) {
871		}
872		}
873	+	return wasInterrupted;
874		}
875	<	return p;
875	>
876		}
877
878		/**
879	<	* 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.
879	>	* Removes and signals waiting threads from wait queue.
880		*/
881	<	static final class QNode {
882	<	QNode next;
883	<	volatile Thread thread; // nulled to cancel wait
884	<	final int phase;
885	<	QNode(Thread t, int c) {
886	<	thread = t;
545	<	phase = c;
881	>	private void releaseWaiters(int phase) {
882	>	AtomicReference<QNode> head = queueFor(phase);
883	>	QNode q;
884	>	while ((q = head.get()) != null) {
885	>	if (head.compareAndSet(q, q.next))
886	>	q.signal();
887		}
888		}
889
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	–	}
562	–	}
563	–	}
564	–
565	–	/** The number of CPUs, for spin control */
566	–	static final int NCPUS = Runtime.getRuntime().availableProcessors();
567	–
890		/**
891	<	* The number of times to spin before blocking in timed waits.
892	<	* The value is empirically derived.
893	<	*/
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.
891	>	* Tries to enqueue given node in the appropriate wait queue.
892	>	*
893	>	* @return true if successful
894		*/
895	<	static final int maxUntimedSpins = maxTimedSpins * 32;
895	>	private boolean tryEnqueue(QNode node) {
896	>	AtomicReference<QNode> head = queueFor(node.phase);
897	>	return head.compareAndSet(node.next = head.get(), node);
898	>	}
899
900		/**
901	<	* The number of nanoseconds for which it is faster to spin
902	<	* rather than to use timed park. A rough estimate suffices.
901	>	* Enqueues node and waits unless aborted or signalled.
902	>	*
903	>	* @return current phase
904		*/
905	<	static final long spinForTimeoutThreshold = 1000L;
905	>	private int untimedWait(int phase) {
906	>	QNode node = null;
907	>	boolean queued = false;
908	>	boolean interrupted = false;
909	>	int p;
910	>	while ((p = getPhase()) == phase) {
911	>	if (Thread.interrupted())
912	>	interrupted = true;
913	>	else if (node == null)
914	>	node = new QNode(this, phase, false, false, 0, 0);
915	>	else if (!queued)
916	>	queued = tryEnqueue(node);
917	>	else
918	>	interrupted = node.doWait();
919	>	}
920	>	if (node != null)
921	>	node.thread = null;
922	>	releaseWaiters(phase);
923	>	if (interrupted)
924	>	Thread.currentThread().interrupt();
925	>	return p;
926	>	}
927
928		/**
929	<	* Enqueues node and waits unless aborted or signalled.
929	>	* Interruptible version
930	>	* @return current phase
931		*/
932	<	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;
932	>	private int interruptibleWait(int phase) throws InterruptedException {
933		QNode node = null;
934		boolean queued = false;
935	<	int spins = maxUntimedSpins;
936	<	while (phaseOf(state.get()) == currentPhase) {
937	<	QNode h;
938	<	if (node != null && queued) {
939	<	if (node.thread != null) {
940	<	LockSupport.park();
941	<	if (Thread.interrupted()) {
942	<	wasInterrupted = true;
943	<	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);
935	>	boolean interrupted = false;
936	>	int p;
937	>	while ((p = getPhase()) == phase && !interrupted) {
938	>	if (Thread.interrupted())
939	>	interrupted = true;
940	>	else if (node == null)
941	>	node = new QNode(this, phase, true, false, 0, 0);
942	>	else if (!queued)
943	>	queued = tryEnqueue(node);
944		else
945	<	--spins;
945	>	interrupted = node.doWait();
946		}
947		if (node != null)
948		node.thread = null;
949	<	return wasInterrupted;
949	>	if (p != phase || (p = getPhase()) != phase)
950	>	releaseWaiters(phase);
951	>	if (interrupted)
952	>	throw new InterruptedException();
953	>	return p;
954		}
955
956		/**
957	<	* Messier timeout version
957	>	* Timeout version.
958	>	* @return current phase
959		*/
960	<	private void timedWait(Thread thread, int currentPhase, long nanos)
960	>	private int timedWait(int phase, long nanos)
961		throws InterruptedException, TimeoutException {
962	<	final AtomicReference<QNode> head = this.head;
641	<	final AtomicLong state = this.state;
642	<	long lastTime = System.nanoTime();
962	>	long startTime = System.nanoTime();
963		QNode node = null;
964		boolean queued = false;
965	<	int spins = maxTimedSpins;
966	<	while (phaseOf(state.get()) == currentPhase) {
967	<	QNode h;
968	<	long now = System.nanoTime();
969	<	nanos -= now - lastTime;
970	<	lastTime = now;
971	<	if (nanos <= 0) {
972	<	if (node != null)
973	<	node.thread = null;
974	<	if (phaseOf(state.get()) == currentPhase)
975	<	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);
965	>	boolean interrupted = false;
966	>	int p;
967	>	while ((p = getPhase()) == phase && !interrupted) {
968	>	if (Thread.interrupted())
969	>	interrupted = true;
970	>	else if (nanos - (System.nanoTime() - startTime) <= 0)
971	>	break;
972	>	else if (node == null)
973	>	node = new QNode(this, phase, true, true, startTime, nanos);
974	>	else if (!queued)
975	>	queued = tryEnqueue(node);
976		else
977	<	--spins;
977	>	interrupted = node.doWait();
978		}
979		if (node != null)
980		node.thread = null;
981	+	if (p != phase || (p = getPhase()) != phase)
982	+	releaseWaiters(phase);
983	+	if (interrupted)
984	+	throw new InterruptedException();
985	+	if (p == phase)
986	+	throw new TimeoutException();
987	+	return p;
988		}
989
990	<	}
990	>	// Unsafe mechanics
991
992	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
993	+	private static final long stateOffset =
994	+	objectFieldOffset("state", Phaser.class);
995	+
996	+	private final boolean casState(long cmp, long val) {
997	+	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
998	+	}
999	+
1000	+	private static long objectFieldOffset(String field, Class<?> klazz) {
1001	+	try {
1002	+	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1003	+	} catch (NoSuchFieldException e) {
1004	+	// Convert Exception to corresponding Error
1005	+	NoSuchFieldError error = new NoSuchFieldError(field);
1006	+	error.initCause(e);
1007	+	throw error;
1008	+	}
1009	+	}
1010	+
1011	+	/**
1012	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1013	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1014	+	* into a jdk.
1015	+	*
1016	+	* @return a sun.misc.Unsafe
1017	+	*/
1018	+	private static sun.misc.Unsafe getUnsafe() {
1019	+	try {
1020	+	return sun.misc.Unsafe.getUnsafe();
1021	+	} catch (SecurityException se) {
1022	+	try {
1023	+	return java.security.AccessController.doPrivileged
1024	+	(new java.security
1025	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1026	+	public sun.misc.Unsafe run() throws Exception {
1027	+	java.lang.reflect.Field f = sun.misc
1028	+	.Unsafe.class.getDeclaredField("theUnsafe");
1029	+	f.setAccessible(true);
1030	+	return (sun.misc.Unsafe) f.get(null);
1031	+	}});
1032	+	} catch (java.security.PrivilegedActionException e) {
1033	+	throw new RuntimeException("Could not initialize intrinsics",
1034	+	e.getCause());
1035	+	}
1036	+	}
1037	+	}
1038	+	}

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