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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 1.41 by jsr166, Mon Aug 24 15:42:51 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><b>Sample usage:</b>
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	<	* <p>[todo: non-FJ example]
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> A Phaser may be used to support a style of programming in
136	<	* which a task waits for others to complete, without otherwise
137	<	* needing to keep track of which tasks it is waiting for. This is
138	<	* similar to the "sync" construct in Cilk and "clocks" in X10.
139	<	* Special constructions based on such barriers are available using
140	<	* the <tt>LinkedAsyncAction</tt> and <tt>CyclicAction</tt> classes,
141	<	* but they can be useful in other contexts as well.  For a simple
142	<	* (but not very useful) example, here is a variant of Fibonacci:
143	<	*
144	<	* <pre>
145	<	* class BarrierFibonacci extends RecursiveAction {
146	<	*   int argument, result;
147	<	*   final Phaser parentBarrier;
148	<	*   BarrierFibonacci(int n, Phaser parentBarrier) {
149	<	*     this.argument = n;
150	<	*     this.parentBarrier = parentBarrier;
151	<	*     parentBarrier.register();
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	<	*   protected void compute() {
158	<	*     int n = argument;
159	<	*     if (n &lt;= 1)
160	<	*        result = n;
161	<	*     else {
162	<	*        Phaser childBarrier = new Phaser(1);
163	<	*        BarrierFibonacci f1 = new BarrierFibonacci(n - 1, childBarrier);
164	<	*        BarrierFibonacci f2 = new BarrierFibonacci(n - 2, childBarrier);
165	<	*        f1.fork();
166	<	*        f2.fork();
167	<	*        childBarrier.arriveAndAwait();
168	<	*        result = f1.result + f2.result;
157	>	*   phaser.arriveAndDeregister(); // deregister self, don't wait
158	>	* }}</pre>
159	>	*
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	>	* 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	>	* <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	<	*     parentBarrier.arriveAndDeregister();
182	>	*     phaser.arriveAndDeregister();
183	>	*   }
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	>	*   } 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		/**
#	Line 133 | Line 240 | public class Phaser {
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;
149	<	private static final int phaseMask = 0x7fffffff;
253	>	private static final int ushortMask = 0xffff;
254	>	private static final int phaseMask  = 0x7fffffff;
255
256		private static int unarrivedOf(long s) {
257	<	return (int)(s & ushortMask);
257	>	return (int) (s & ushortMask);
258		}
259
260		private static int partiesOf(long s) {
261	<	return (int)(s & (ushortMask << 16)) >>> 16;
261	>	return ((int) s) >>> 16;
262		}
263
264		private static int phaseOf(long s) {
265	<	return (int)(s >>> 32);
265	>	return (int) (s >>> 32);
266		}
267
268		private static int arrivedOf(long s) {
#	Line 165 | Line 270 | public class Phaser {
270		}
271
272		private static long stateFor(int phase, int parties, int unarrived) {
273	<	return (((long)phase) << 32) | ((parties << 16) | unarrived);
273	>	return ((((long) phase) << 32) | (((long) parties) << 16) |
274	>	(long) unarrived);
275	>	}
276	>
277	>	private static long trippedStateFor(int phase, int parties) {
278	>	long lp = (long) parties;
279	>	return (((long) phase) << 32) | (lp << 16) | lp;
280		}
281
282	<	private static IllegalStateException badBounds(int parties, int unarrived) {
283	<	return new IllegalStateException("Attempt to set " + unarrived +
284	<	" unarrived of " + parties + " parties");
282	>	/**
283	>	* Returns message string for bad bounds exceptions.
284	>	*/
285	>	private static String badBounds(int parties, int unarrived) {
286	>	return ("Attempt to set " + unarrived +
287	>	" unarrived of " + parties + " parties");
288	>	}
289	>
290	>	/**
291	>	* The parent of this phaser, or null if none
292	>	*/
293	>	private final Phaser parent;
294	>
295	>	/**
296	>	* The root of phaser tree. Equals this if not in a tree.  Used to
297	>	* support faster state push-down.
298	>	*/
299	>	private final Phaser root;
300	>
301	>	// Wait queues
302	>
303	>	/**
304	>	* Heads of Treiber stacks for waiting threads. To eliminate
305	>	* contention while releasing some threads while adding others, we
306	>	* use two of them, alternating across even and odd phases.
307	>	*/
308	>	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
309	>	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
310	>
311	>	private AtomicReference<QNode> queueFor(int phase) {
312	>	return ((phase & 1) == 0) ? evenQ : oddQ;
313		}
314
315		/**
316	<	* Creates a new Phaser without any initially registered parties,
317	<	* and initial phase number 0.
316	>	* Returns current state, first resolving lagged propagation from
317	>	* root if necessary.
318	>	*/
319	>	private long getReconciledState() {
320	>	return (parent == null) ? state : reconcileState();
321	>	}
322	>
323	>	/**
324	>	* Recursively resolves state.
325	>	*/
326	>	private long reconcileState() {
327	>	Phaser p = parent;
328	>	long s = state;
329	>	if (p != null) {
330	>	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
331	>	long parentState = p.getReconciledState();
332	>	int parentPhase = phaseOf(parentState);
333	>	int phase = phaseOf(s = state);
334	>	if (phase != parentPhase) {
335	>	long next = trippedStateFor(parentPhase, partiesOf(s));
336	>	if (casState(s, next)) {
337	>	releaseWaiters(phase);
338	>	s = next;
339	>	}
340	>	}
341	>	}
342	>	}
343	>	return s;
344	>	}
345	>
346	>	/**
347	>	* Creates a new phaser without any initially registered parties,
348	>	* initial phase number 0, and no parent. Any thread using this
349	>	* phaser will need to first register for it.
350		*/
351		public Phaser() {
352	<	state = new AtomicLong(stateFor(0, 0, 0));
352	>	this(null);
353		}
354
355		/**
356	<	* Creates a new Phaser with the given numbers of registered
357	<	* unarrived parties and initial phase number 0.
358	<	* @param parties the number of parties required to trip barrier.
356	>	* Creates a new phaser with the given numbers of registered
357	>	* unarrived parties, initial phase number 0, and no parent.
358	>	*
359	>	* @param parties the number of parties required to trip barrier
360		* @throws IllegalArgumentException if parties less than zero
361	<	* or greater than the maximum number of parties supported.
361	>	* or greater than the maximum number of parties supported
362		*/
363		public Phaser(int parties) {
364	+	this(null, parties);
365	+	}
366	+
367	+	/**
368	+	* Creates a new phaser with the given parent, without any
369	+	* initially registered parties. If parent is non-null this phaser
370	+	* is registered with the parent and its initial phase number is
371	+	* the same as that of parent phaser.
372	+	*
373	+	* @param parent the parent phaser
374	+	*/
375	+	public Phaser(Phaser parent) {
376	+	int phase = 0;
377	+	this.parent = parent;
378	+	if (parent != null) {
379	+	this.root = parent.root;
380	+	phase = parent.register();
381	+	}
382	+	else
383	+	this.root = this;
384	+	this.state = trippedStateFor(phase, 0);
385	+	}
386	+
387	+	/**
388	+	* Creates a new phaser with the given parent and numbers of
389	+	* registered unarrived parties. If parent is non-null, this phaser
390	+	* is registered with the parent and its initial phase number is
391	+	* the same as that of parent phaser.
392	+	*
393	+	* @param parent the parent phaser
394	+	* @param parties the number of parties required to trip barrier
395	+	* @throws IllegalArgumentException if parties less than zero
396	+	* or greater than the maximum number of parties supported
397	+	*/
398	+	public Phaser(Phaser parent, int parties) {
399		if (parties < 0 || parties > ushortMask)
400		throw new IllegalArgumentException("Illegal number of parties");
401	<	state = new AtomicLong(stateFor(0, parties, parties));
401	>	int phase = 0;
402	>	this.parent = parent;
403	>	if (parent != null) {
404	>	this.root = parent.root;
405	>	phase = parent.register();
406	>	}
407	>	else
408	>	this.root = this;
409	>	this.state = trippedStateFor(phase, parties);
410		}
411
412		/**
413		* Adds a new unarrived party to this phaser.
414	<	* @return the current barrier phase number upon registration
414	>	*
415	>	* @return the arrival phase number to which this registration applied
416		* @throws IllegalStateException if attempting to register more
417	<	* than the maximum supported number of parties.
417	>	* than the maximum supported number of parties
418		*/
419	<	public int register() { // increment both parties and unarrived
420	<	final AtomicLong state = this.state;
419	>	public int register() {
420	>	return doRegister(1);
421	>	}
422	>
423	>	/**
424	>	* Adds the given number of new unarrived parties to this phaser.
425	>	*
426	>	* @param parties the number of parties required to trip barrier
427	>	* @return the arrival phase number to which this registration applied
428	>	* @throws IllegalStateException if attempting to register more
429	>	* than the maximum supported number of parties
430	>	*/
431	>	public int bulkRegister(int parties) {
432	>	if (parties < 0)
433	>	throw new IllegalArgumentException();
434	>	if (parties == 0)
435	>	return getPhase();
436	>	return doRegister(parties);
437	>	}
438	>
439	>	/**
440	>	* Shared code for register, bulkRegister
441	>	*/
442	>	private int doRegister(int registrations) {
443	>	int phase;
444		for (;;) {
445	<	long s = state.get();
446	<	int phase = phaseOf(s);
447	<	int parties = partiesOf(s) + 1;
448	<	int unarrived = unarrivedOf(s) + 1;
445	>	long s = getReconciledState();
446	>	phase = phaseOf(s);
447	>	int unarrived = unarrivedOf(s) + registrations;
448	>	int parties = partiesOf(s) + registrations;
449	>	if (phase < 0)
450	>	break;
451		if (parties > ushortMask || unarrived > ushortMask)
452	<	throw badBounds(parties, unarrived);
453	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
454	<	return phase;
452	>	throw new IllegalStateException(badBounds(parties, unarrived));
453	>	if (phase == phaseOf(root.state) &&
454	>	casState(s, stateFor(phase, parties, unarrived)))
455	>	break;
456		}
457	+	return phase;
458		}
459
460		/**
461		* Arrives at the barrier, but does not wait for others.  (You can
462	<	* in turn wait for others via {@link #awaitAdvance}).
462	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
463	>	* unenforced usage error for an unregistered party to invoke this
464	>	* method.
465		*
466	<	* @return the current barrier phase number upon entry to
467	<	* this method, or a negative value if terminated;
468	<	* @throws IllegalStateException if the number of unarrived
224	<	* parties would become negative.
466	>	* @return the arrival phase number, or a negative value if terminated
467	>	* @throws IllegalStateException if not terminated and the number
468	>	* of unarrived parties would become negative
469		*/
470	<	public int arrive() { // decrement unarrived. If zero, trip
471	<	final AtomicLong state = this.state;
470	>	public int arrive() {
471	>	int phase;
472		for (;;) {
473	<	long s = state.get();
474	<	int phase = phaseOf(s);
473	>	long s = state;
474	>	phase = phaseOf(s);
475	>	if (phase < 0)
476	>	break;
477		int parties = partiesOf(s);
478		int unarrived = unarrivedOf(s) - 1;
479	<	if (unarrived < 0)
480	<	throw badBounds(parties, unarrived);
481	<	if (unarrived == 0 && phase >= 0) {
482	<	trip(phase, parties);
483	<	return phase;
479	>	if (unarrived > 0) {        // Not the last arrival
480	>	if (casState(s, s - 1)) // s-1 adds one arrival
481	>	break;
482	>	}
483	>	else if (unarrived == 0) {  // the last arrival
484	>	Phaser par = parent;
485	>	if (par == null) {      // directly trip
486	>	if (casState
487	>	(s,
488	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
489	>	((phase + 1) & phaseMask), parties))) {
490	>	releaseWaiters(phase);
491	>	break;
492	>	}
493	>	}
494	>	else {                  // cascade to parent
495	>	if (casState(s, s - 1)) { // zeroes unarrived
496	>	par.arrive();
497	>	reconcileState();
498	>	break;
499	>	}
500	>	}
501		}
502	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
503	<	return phase;
502	>	else if (phase != phaseOf(root.state)) // or if unreconciled
503	>	reconcileState();
504	>	else
505	>	throw new IllegalStateException(badBounds(parties, unarrived));
506		}
507	+	return phase;
508		}
509
510		/**
511	<	* Arrives at the barrier, and deregisters from it, without
512	<	* waiting for others.
511	>	* Arrives at the barrier and deregisters from it without waiting
512	>	* for others. Deregistration reduces the number of parties
513	>	* required to trip the barrier in future phases.  If this phaser
514	>	* has a parent, and deregistration causes this phaser to have
515	>	* zero parties, this phaser also arrives at and is deregistered
516	>	* from its parent.  It is an unenforced usage error for an
517	>	* unregistered party to invoke this method.
518		*
519	<	* @return the current barrier phase number upon entry to
520	<	* this method, or a negative value if terminated;
521	<	* @throws IllegalStateException if the number of registered or
522	<	* unarrived parties would become negative.
523	<	*/
524	<	public int arriveAndDeregister() { // Same as arrive, plus decrement parties
525	<	final AtomicLong state = this.state;
519	>	* @return the arrival phase number, or a negative value if terminated
520	>	* @throws IllegalStateException if not terminated and the number
521	>	* of registered or unarrived parties would become negative
522	>	*/
523	>	public int arriveAndDeregister() {
524	>	// similar code to arrive, but too different to merge
525	>	Phaser par = parent;
526	>	int phase;
527		for (;;) {
528	<	long s = state.get();
529	<	int phase = phaseOf(s);
528	>	long s = state;
529	>	phase = phaseOf(s);
530	>	if (phase < 0)
531	>	break;
532		int parties = partiesOf(s) - 1;
533		int unarrived = unarrivedOf(s) - 1;
534	<	if (parties < 0 || unarrived < 0)
535	<	throw badBounds(parties, unarrived);
536	<	if (unarrived == 0 && phase >= 0) {
537	<	trip(phase, parties);
538	<	return phase;
534	>	if (parties >= 0) {
535	>	if (unarrived > 0 || (unarrived == 0 && par != null)) {
536	>	if (casState
537	>	(s,
538	>	stateFor(phase, parties, unarrived))) {
539	>	if (unarrived == 0) {
540	>	par.arriveAndDeregister();
541	>	reconcileState();
542	>	}
543	>	break;
544	>	}
545	>	continue;
546	>	}
547	>	if (unarrived == 0) {
548	>	if (casState
549	>	(s,
550	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
551	>	((phase + 1) & phaseMask), parties))) {
552	>	releaseWaiters(phase);
553	>	break;
554	>	}
555	>	continue;
556	>	}
557	>	if (par != null && phase != phaseOf(root.state)) {
558	>	reconcileState();
559	>	continue;
560	>	}
561		}
562	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
267	<	return phase;
562	>	throw new IllegalStateException(badBounds(parties, unarrived));
563		}
564	+	return phase;
565		}
566
567		/**
568	<	* Arrives at the barrier and awaits others. Unlike other arrival
569	<	* methods, this method returns the arrival index of the
570	<	* caller. The caller tripping the barrier returns zero, the
571	<	* previous caller 1, and so on.
572	<	* @return the arrival index
573	<	* @throws IllegalStateException if the number of unarrived
574	<	* parties would become negative.
568	>	* Arrives at the barrier and awaits others. Equivalent in effect
569	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
570	>	* interruption or timeout, you can arrange this with an analogous
571	>	* construction using one of the other forms of the awaitAdvance
572	>	* method.  If instead you need to deregister upon arrival use
573	>	* {@code arriveAndDeregister}. It is an unenforced usage error
574	>	* for an unregistered party to invoke this method.
575	>	*
576	>	* @return the arrival phase number, or a negative number if terminated
577	>	* @throws IllegalStateException if not terminated and the number
578	>	* of unarrived parties would become negative
579		*/
580		public int arriveAndAwaitAdvance() {
581	<	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	<	}
581	>	return awaitAdvance(arrive());
582		}
583
584		/**
585	<	* Awaits the phase of the barrier to advance from the given
586	<	* value, or returns immediately if this barrier is terminated.
587	<	* @param phase the phase on entry to this method
588	<	* @return the phase on exit from this method
585	>	* Awaits the phase of the barrier to advance from the given phase
586	>	* value, returning immediately if the current phase of the
587	>	* barrier is not equal to the given phase value or this barrier
588	>	* is terminated.  It is an unenforced usage error for an
589	>	* unregistered party to invoke this method.
590	>	*
591	>	* @param phase an arrival phase number, or negative value if
592	>	* terminated; this argument is normally the value returned by a
593	>	* previous call to {@code arrive} or its variants
594	>	* @return the next arrival phase number, or a negative value
595	>	* if terminated or argument is negative
596		*/
597		public int awaitAdvance(int phase) {
598		if (phase < 0)
599		return phase;
600	<	Thread current = Thread.currentThread();
601	<	if (current instanceof ForkJoinWorkerThread)
602	<	return helpingWait(phase);
603	<	if (untimedWait(current, phase, false))
604	<	current.interrupt();
605	<	return phaseOf(state.get());
600	>	long s = getReconciledState();
601	>	int p = phaseOf(s);
602	>	if (p != phase)
603	>	return p;
604	>	if (unarrivedOf(s) == 0 && parent != null)
605	>	parent.awaitAdvance(phase);
606	>	// Fall here even if parent waited, to reconcile and help release
607	>	return untimedWait(phase);
608		}
609
610		/**
611	<	* Awaits the phase of the barrier to advance from the given
612	<	* value, or returns immediately if this barrier is terminated, or
613	<	* throws InterruptedException if interrupted while waiting.
614	<	* @param phase the phase on entry to this method
615	<	* @return the phase on exit from this method
611	>	* Awaits the phase of the barrier to advance from the given phase
612	>	* value, throwing {@code InterruptedException} if interrupted
613	>	* while waiting, or returning immediately if the current phase of
614	>	* the barrier is not equal to the given phase value or this
615	>	* barrier is terminated. It is an unenforced usage error for an
616	>	* unregistered party to invoke this method.
617	>	*
618	>	* @param phase an arrival phase number, or negative value if
619	>	* terminated; this argument is normally the value returned by a
620	>	* previous call to {@code arrive} or its variants
621	>	* @return the next arrival phase number, or a negative value
622	>	* if terminated or argument is negative
623		* @throws InterruptedException if thread interrupted while waiting
624		*/
625	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
625	>	public int awaitAdvanceInterruptibly(int phase)
626	>	throws InterruptedException {
627		if (phase < 0)
628		return phase;
629	<	Thread current = Thread.currentThread();
630	<	if (current instanceof ForkJoinWorkerThread)
631	<	return helpingWait(phase);
632	<	else if (Thread.interrupted() || untimedWait(current, phase, true))
633	<	throw new InterruptedException();
634	<	else
635	<	return phaseOf(state.get());
629	>	long s = getReconciledState();
630	>	int p = phaseOf(s);
631	>	if (p != phase)
632	>	return p;
633	>	if (unarrivedOf(s) == 0 && parent != null)
634	>	parent.awaitAdvanceInterruptibly(phase);
635	>	return interruptibleWait(phase);
636		}
637
638		/**
639	<	* Awaits the phase of the barrier to advance from the given value
640	<	* or the given timeout elapses, or returns immediately if this
641	<	* barrier is terminated.
642	<	* @param phase the phase on entry to this method
643	<	* @return the phase on exit from this method
639	>	* Awaits the phase of the barrier to advance from the given phase
640	>	* value or the given timeout to elapse, throwing {@code
641	>	* InterruptedException} if interrupted while waiting, or
642	>	* returning immediately if the current phase of the barrier is
643	>	* not equal to the given phase value or this barrier is
644	>	* terminated.  It is an unenforced usage error for an
645	>	* unregistered party to invoke this method.
646	>	*
647	>	* @param phase an arrival phase number, or negative value if
648	>	* terminated; this argument is normally the value returned by a
649	>	* previous call to {@code arrive} or its variants
650	>	* @param timeout how long to wait before giving up, in units of
651	>	*        {@code unit}
652	>	* @param unit a {@code TimeUnit} determining how to interpret the
653	>	*        {@code timeout} parameter
654	>	* @return the next arrival phase number, or a negative value
655	>	* if terminated or argument is negative
656		* @throws InterruptedException if thread interrupted while waiting
657		* @throws TimeoutException if timed out while waiting
658		*/
659	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
659	>	public int awaitAdvanceInterruptibly(int phase,
660	>	long timeout, TimeUnit unit)
661		throws InterruptedException, TimeoutException {
662		if (phase < 0)
663		return phase;
664	<	long nanos = unit.toNanos(timeout);
665	<	Thread current = Thread.currentThread();
666	<	if (current instanceof ForkJoinWorkerThread)
667	<	return timedHelpingWait(phase, nanos);
668	<	timedWait(current, phase, nanos);
669	<	return phaseOf(state.get());
664	>	long s = getReconciledState();
665	>	int p = phaseOf(s);
666	>	if (p != phase)
667	>	return p;
668	>	if (unarrivedOf(s) == 0 && parent != null)
669	>	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
670	>	return timedWait(phase, unit.toNanos(timeout));
671		}
672
673		/**
674		* Forces this barrier to enter termination state. Counts of
675	<	* arrived and registered parties are unaffected. This method may
676	<	* be useful for coordinating recovery after one or more tasks
677	<	* encounter unexpected exceptions.
675	>	* arrived and registered parties are unaffected. If this phaser
676	>	* has a parent, it too is terminated. This method may be useful
677	>	* for coordinating recovery after one or more tasks encounter
678	>	* unexpected exceptions.
679		*/
680		public void forceTermination() {
365	–	final AtomicLong state = this.state;
681		for (;;) {
682	<	long s = state.get();
682	>	long s = getReconciledState();
683		int phase = phaseOf(s);
684		int parties = partiesOf(s);
685		int unarrived = unarrivedOf(s);
686		if (phase < 0 ||
687	<	state.compareAndSet(s, stateFor(-1, parties, unarrived))) {
688	<	if (head.get() != null)
689	<	releaseWaiters(-1);
687	>	casState(s, stateFor(-1, parties, unarrived))) {
688	>	releaseWaiters(0);
689	>	releaseWaiters(1);
690	>	if (parent != null)
691	>	parent.forceTermination();
692		return;
693		}
694		}
695		}
696
697		/**
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	–	/**
698		* Returns the current phase number. The maximum phase number is
699	<	* <tt>Integer.MAX_VALUE</tt>, after which it restarts at
699	>	* {@code Integer.MAX_VALUE}, after which it restarts at
700		* zero. Upon termination, the phase number is negative.
701	+	*
702		* @return the phase number, or a negative value if terminated
703		*/
704	<	public int getPhase() {
705	<	return phaseOf(state.get());
704	>	public final int getPhase() {
705	>	return phaseOf(getReconciledState());
706		}
707
708		/**
709		* Returns the number of parties registered at this barrier.
710	+	*
711		* @return the number of parties
712		*/
713		public int getRegisteredParties() {
714	<	return partiesOf(state.get());
714	>	return partiesOf(state);
715		}
716
717		/**
718	<	* Returns the number of parties that have arrived at the current
719	<	* phase of this barrier.
718	>	* Returns the number of registered parties that have arrived at
719	>	* the current phase of this barrier.
720	>	*
721		* @return the number of arrived parties
722		*/
723		public int getArrivedParties() {
724	<	return arrivedOf(state.get());
724	>	return arrivedOf(state);
725		}
726
727		/**
728		* Returns the number of registered parties that have not yet
729		* arrived at the current phase of this barrier.
730	+	*
731		* @return the number of unarrived parties
732		*/
733		public int getUnarrivedParties() {
734	<	return unarrivedOf(state.get());
734	>	return unarrivedOf(state);
735		}
736
737		/**
738	<	* Returns true if this barrier has been terminated.
739	<	* @return true if this barrier has been terminated
738	>	* Returns the parent of this phaser, or {@code null} if none.
739	>	*
740	>	* @return the parent of this phaser, or {@code null} if none
741	>	*/
742	>	public Phaser getParent() {
743	>	return parent;
744	>	}
745	>
746	>	/**
747	>	* Returns the root ancestor of this phaser, which is the same as
748	>	* this phaser if it has no parent.
749	>	*
750	>	* @return the root ancestor of this phaser
751	>	*/
752	>	public Phaser getRoot() {
753	>	return root;
754	>	}
755	>
756	>	/**
757	>	* Returns {@code true} if this barrier has been terminated.
758	>	*
759	>	* @return {@code true} if this barrier has been terminated
760		*/
761		public boolean isTerminated() {
762	<	return phaseOf(state.get()) < 0;
762	>	return getPhase() < 0;
763		}
764
765		/**
766		* Overridable method to perform an action upon phase advance, and
767		* to control termination. This method is invoked whenever the
768		* barrier is tripped (and thus all other waiting parties are
769	<	* dormant). If it returns true, then, rather than advance the
770	<	* phase number, this barrier will be set to a final termination
771	<	* state, and subsequent calls to <tt>isTerminated</tt> will
772	<	* return true.
769	>	* dormant). If it returns {@code true}, then, rather than advance
770	>	* the phase number, this barrier will be set to a final
771	>	* termination state, and subsequent calls to {@link #isTerminated}
772	>	* will return true.
773		*
774	<	* <p> The default version returns true when the number of
774	>	* <p>The default version returns {@code true} when the number of
775		* registered parties is zero. Normally, overrides that arrange
776		* termination for other reasons should also preserve this
777		* property.
778		*
779	+	* <p>You may override this method to perform an action with side
780	+	* effects visible to participating tasks, but it is in general
781	+	* only sensible to do so in designs where all parties register
782	+	* before any arrive, and all {@link #awaitAdvance} at each phase.
783	+	* Otherwise, you cannot ensure lack of interference from other
784	+	* parties during the invocation of this method.
785	+	*
786		* @param phase the phase number on entering the barrier
787	<	* @param registeredParties the current number of registered
788	<	* parties.
458	<	* @return true if this barrier should terminate
787	>	* @param registeredParties the current number of registered parties
788	>	* @return {@code true} if this barrier should terminate
789		*/
790		protected boolean onAdvance(int phase, int registeredParties) {
791		return registeredParties <= 0;
792		}
793
794		/**
795	<	* Returns a string identifying this barrier, as well as its
795	>	* Returns a string identifying this phaser, as well as its
796		* state.  The state, in brackets, includes the String {@code
797	<	* "phase ="} followed by the phase number, {@code "parties ="}
797	>	* "phase = "} followed by the phase number, {@code "parties = "}
798		* followed by the number of registered parties, and {@code
799	<	* "arrived ="} followed by the number of arrived parties
799	>	* "arrived = "} followed by the number of arrived parties.
800		*
801		* @return a string identifying this barrier, as well as its state
802		*/
803		public String toString() {
804	<	long s = state.get();
805	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
804	>	long s = getReconciledState();
805	>	return super.toString() +
806	>	"[phase = " + phaseOf(s) +
807	>	" parties = " + partiesOf(s) +
808	>	" arrived = " + arrivedOf(s) + "]";
809		}
810
811	<	// methods for tripping and waiting
811	>	// methods for waiting
812
813		/**
814	<	* Advance the current phase (or terminate)
814	>	* Wait nodes for Treiber stack representing wait queue
815		*/
816	<	private void trip(int phase, int parties) {
817	<	int next = onAdvance(phase, parties)? -1 : ((phase + 1) & phaseMask);
818	<	state.set(stateFor(next, parties, parties));
819	<	if (head.get() != null)
820	<	releaseWaiters(next);
821	<	}
822	<
823	<	private int helpingWait(int phase) {
824	<	final AtomicLong state = this.state;
825	<	int p;
826	<	while ((p = phaseOf(state.get())) == phase) {
827	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
828	<	if (t != null) {
829	<	if ((p = phaseOf(state.get())) == phase)
830	<	t.exec();
831	<	else {   // push task and exit if barrier advanced
832	<	t.fork();
833	<	break;
834	<	}
502	<	}
816	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
817	>	final Phaser phaser;
818	>	final int phase;
819	>	final long startTime;
820	>	final long nanos;
821	>	final boolean timed;
822	>	final boolean interruptible;
823	>	volatile boolean wasInterrupted = false;
824	>	volatile Thread thread; // nulled to cancel wait
825	>	QNode next;
826	>	QNode(Phaser phaser, int phase, boolean interruptible,
827	>	boolean timed, long startTime, long nanos) {
828	>	this.phaser = phaser;
829	>	this.phase = phase;
830	>	this.timed = timed;
831	>	this.interruptible = interruptible;
832	>	this.startTime = startTime;
833	>	this.nanos = nanos;
834	>	thread = Thread.currentThread();
835		}
836	<	return p;
837	<	}
838	<
839	<	private int timedHelpingWait(int phase, long nanos) throws TimeoutException {
840	<	final AtomicLong state = this.state;
841	<	long lastTime = System.nanoTime();
842	<	int p;
843	<	while ((p = phaseOf(state.get())) == phase) {
844	<	long now = System.nanoTime();
845	<	nanos -= now - lastTime;
846	<	lastTime = now;
515	<	if (nanos <= 0) {
516	<	if ((p = phaseOf(state.get())) == phase)
517	<	throw new TimeoutException();
518	<	else
519	<	break;
836	>	public boolean isReleasable() {
837	>	return (thread == null ||
838	>	phaser.getPhase() != phase ||
839	>	(interruptible && wasInterrupted) ||
840	>	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
841	>	}
842	>	public boolean block() {
843	>	if (Thread.interrupted()) {
844	>	wasInterrupted = true;
845	>	if (interruptible)
846	>	return true;
847		}
848	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
848	>	if (!timed)
849	>	LockSupport.park(this);
850	>	else {
851	>	long waitTime = nanos - (System.nanoTime() - startTime);
852	>	if (waitTime <= 0)
853	>	return true;
854	>	LockSupport.parkNanos(this, waitTime);
855	>	}
856	>	return isReleasable();
857	>	}
858	>	void signal() {
859	>	Thread t = thread;
860		if (t != null) {
861	<	if ((p = phaseOf(state.get())) == phase)
862	<	t.exec();
863	<	else {   // push task and exit if barrier advanced
864	<	t.fork();
865	<	break;
861	>	thread = null;
862	>	LockSupport.unpark(t);
863	>	}
864	>	}
865	>	boolean doWait() {
866	>	if (thread != null) {
867	>	try {
868	>	ForkJoinPool.managedBlock(this, false);
869	>	} catch (InterruptedException ie) {
870		}
871		}
872	+	return wasInterrupted;
873		}
874	<	return p;
874	>
875		}
876
877		/**
878	<	* 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.
878	>	* Removes and signals waiting threads from wait queue.
879		*/
880	<	static final class QNode {
881	<	QNode next;
882	<	volatile Thread thread; // nulled to cancel wait
883	<	final int phase;
884	<	QNode(Thread t, int c) {
885	<	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	<	}
880	>	private void releaseWaiters(int phase) {
881	>	AtomicReference<QNode> head = queueFor(phase);
882	>	QNode q;
883	>	while ((q = head.get()) != null) {
884	>	if (head.compareAndSet(q, q.next))
885	>	q.signal();
886		}
887		}
888
565	–	/** The number of CPUs, for spin control */
566	–	static final int NCPUS = Runtime.getRuntime().availableProcessors();
567	–
889		/**
890	<	* The number of times to spin before blocking in timed waits.
891	<	* The value is empirically derived.
892	<	*/
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.
890	>	* Tries to enqueue given node in the appropriate wait queue.
891	>	*
892	>	* @return true if successful
893		*/
894	<	static final int maxUntimedSpins = maxTimedSpins * 32;
894	>	private boolean tryEnqueue(QNode node) {
895	>	AtomicReference<QNode> head = queueFor(node.phase);
896	>	return head.compareAndSet(node.next = head.get(), node);
897	>	}
898
899		/**
900	<	* The number of nanoseconds for which it is faster to spin
901	<	* rather than to use timed park. A rough estimate suffices.
900	>	* Enqueues node and waits unless aborted or signalled.
901	>	*
902	>	* @return current phase
903		*/
904	<	static final long spinForTimeoutThreshold = 1000L;
904	>	private int untimedWait(int phase) {
905	>	QNode node = null;
906	>	boolean queued = false;
907	>	boolean interrupted = false;
908	>	int p;
909	>	while ((p = getPhase()) == phase) {
910	>	if (Thread.interrupted())
911	>	interrupted = true;
912	>	else if (node == null)
913	>	node = new QNode(this, phase, false, false, 0, 0);
914	>	else if (!queued)
915	>	queued = tryEnqueue(node);
916	>	else
917	>	interrupted = node.doWait();
918	>	}
919	>	if (node != null)
920	>	node.thread = null;
921	>	releaseWaiters(phase);
922	>	if (interrupted)
923	>	Thread.currentThread().interrupt();
924	>	return p;
925	>	}
926
927		/**
928	<	* Enqueues node and waits unless aborted or signalled.
928	>	* Interruptible version
929	>	* @return current phase
930		*/
931	<	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;
931	>	private int interruptibleWait(int phase) throws InterruptedException {
932		QNode node = null;
933		boolean queued = false;
934	<	int spins = maxUntimedSpins;
935	<	while (phaseOf(state.get()) == currentPhase) {
936	<	QNode h;
937	<	if (node != null && queued) {
938	<	if (node.thread != null) {
939	<	LockSupport.park();
940	<	if (Thread.interrupted()) {
941	<	wasInterrupted = true;
942	<	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);
934	>	boolean interrupted = false;
935	>	int p;
936	>	while ((p = getPhase()) == phase && !interrupted) {
937	>	if (Thread.interrupted())
938	>	interrupted = true;
939	>	else if (node == null)
940	>	node = new QNode(this, phase, true, false, 0, 0);
941	>	else if (!queued)
942	>	queued = tryEnqueue(node);
943		else
944	<	--spins;
944	>	interrupted = node.doWait();
945		}
946		if (node != null)
947		node.thread = null;
948	<	return wasInterrupted;
948	>	if (p != phase || (p = getPhase()) != phase)
949	>	releaseWaiters(phase);
950	>	if (interrupted)
951	>	throw new InterruptedException();
952	>	return p;
953		}
954
955		/**
956	<	* Messier timeout version
956	>	* Timeout version.
957	>	* @return current phase
958		*/
959	<	private void timedWait(Thread thread, int currentPhase, long nanos)
959	>	private int timedWait(int phase, long nanos)
960		throws InterruptedException, TimeoutException {
961	<	final AtomicReference<QNode> head = this.head;
641	<	final AtomicLong state = this.state;
642	<	long lastTime = System.nanoTime();
961	>	long startTime = System.nanoTime();
962		QNode node = null;
963		boolean queued = false;
964	<	int spins = maxTimedSpins;
965	<	while (phaseOf(state.get()) == currentPhase) {
966	<	QNode h;
967	<	long now = System.nanoTime();
968	<	nanos -= now - lastTime;
969	<	lastTime = now;
970	<	if (nanos <= 0) {
971	<	if (node != null)
972	<	node.thread = null;
973	<	if (phaseOf(state.get()) == currentPhase)
974	<	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);
964	>	boolean interrupted = false;
965	>	int p;
966	>	while ((p = getPhase()) == phase && !interrupted) {
967	>	if (Thread.interrupted())
968	>	interrupted = true;
969	>	else if (nanos - (System.nanoTime() - startTime) <= 0)
970	>	break;
971	>	else if (node == null)
972	>	node = new QNode(this, phase, true, true, startTime, nanos);
973	>	else if (!queued)
974	>	queued = tryEnqueue(node);
975		else
976	<	--spins;
976	>	interrupted = node.doWait();
977		}
978		if (node != null)
979		node.thread = null;
980	+	if (p != phase || (p = getPhase()) != phase)
981	+	releaseWaiters(phase);
982	+	if (interrupted)
983	+	throw new InterruptedException();
984	+	if (p == phase)
985	+	throw new TimeoutException();
986	+	return p;
987	+	}
988	+
989	+	// Unsafe mechanics
990	+
991	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
992	+	private static final long stateOffset =
993	+	objectFieldOffset("state", Phaser.class);
994	+
995	+	private final boolean casState(long cmp, long val) {
996	+	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
997	+	}
998	+
999	+	private static long objectFieldOffset(String field, Class<?> klazz) {
1000	+	try {
1001	+	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1002	+	} catch (NoSuchFieldException e) {
1003	+	// Convert Exception to corresponding Error
1004	+	NoSuchFieldError error = new NoSuchFieldError(field);
1005	+	error.initCause(e);
1006	+	throw error;
1007	+	}
1008		}
1009
1010	+	/**
1011	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1012	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1013	+	* into a jdk.
1014	+	*
1015	+	* @return a sun.misc.Unsafe
1016	+	*/
1017	+	private static sun.misc.Unsafe getUnsafe() {
1018	+	try {
1019	+	return sun.misc.Unsafe.getUnsafe();
1020	+	} catch (SecurityException se) {
1021	+	try {
1022	+	return java.security.AccessController.doPrivileged
1023	+	(new java.security
1024	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1025	+	public sun.misc.Unsafe run() throws Exception {
1026	+	java.lang.reflect.Field f = sun.misc
1027	+	.Unsafe.class.getDeclaredField("theUnsafe");
1028	+	f.setAccessible(true);
1029	+	return (sun.misc.Unsafe) f.get(null);
1030	+	}});
1031	+	} catch (java.security.PrivilegedActionException e) {
1032	+	throw new RuntimeException("Could not initialize intrinsics",
1033	+	e.getCause());
1034	+	}
1035	+	}
1036	+	}
1037		}

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