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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.1 by dl, Mon Jul 7 16:53:30 2008 UTC vs.
Revision 1.48 by dl, Sun Oct 24 21:45:39 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import jsr166y.forkjoin.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
10	>
11	>	import java.util.concurrent.atomic.AtomicReference;
12		import java.util.concurrent.locks.LockSupport;
13
14		/**
15	<	* A reusable synchronization barrier, similar in functionality to a
16	<	* {@link java.util.concurrent.CyclicBarrier}, but supporting more
17	<	* flexible usage.
15	>	* A reusable synchronization barrier, similar in functionality to
16	>	* {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and
17	>	* {@link java.util.concurrent.CountDownLatch CountDownLatch}
18	>	* but supporting more flexible usage.
19		*
20	<	* <ul>
20	>	* <p> <b>Registration.</b> Unlike the case for other barriers, the
21	>	* number of parties <em>registered</em> to synchronize on a phaser
22	>	* may vary over time.  Tasks may be registered at any time (using
23	>	* methods {@link #register}, {@link #bulkRegister}, or forms of
24	>	* constructors establishing initial numbers of parties), and
25	>	* optionally deregistered upon any arrival (using {@link
26	>	* #arriveAndDeregister}).  As is the case with most basic
27	>	* synchronization constructs, registration and deregistration affect
28	>	* only internal counts; they do not establish any further internal
29	>	* bookkeeping, so tasks cannot query whether they are registered.
30	>	* (However, you can introduce such bookkeeping by subclassing this
31	>	* class.)
32		*
33	<	* <li> The number of parties synchronizing on the barrier may vary
34	<	* over time.  A task may register to be a party in a barrier at any
35	<	* time, and may deregister upon arriving at the barrier.  As is the
36	<	* case with most basic synchronization constructs, registration
37	<	* and deregistration affect only internal counts; they do not
38	<	* establish any further internal bookkeeping, so tasks cannot query
39	<	* whether they are registered.
40	<	*
41	<	* <li> Each generation has an associated phase value, starting at
42	<	* zero, and advancing when all parties reach the barrier (wrapping
43	<	* around to zero after reaching <tt>Integer.MAX_VALUE</tt>).
31	<	*
32	<	* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited.
33	<	* Method <tt>arriveAndAwaitAdvance</tt> has effect analogous to
34	<	* <tt>CyclicBarrier.await</tt>.  However, Phasers separate two
35	<	* aspects of coordination, that may be invoked independently:
33	>	* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
34	>	* Phaser} may be repeatedly awaited.  Method {@link
35	>	* #arriveAndAwaitAdvance} has effect analogous to {@link
36	>	* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
37	>	* generation of a {@code Phaser} has an associated phase number. The
38	>	* phase number starts at zero, and advances when all parties arrive
39	>	* at the barrier, wrapping around to zero after reaching {@code
40	>	* Integer.MAX_VALUE}. The use of phase numbers enables independent
41	>	* control of actions upon arrival at a barrier and upon awaiting
42	>	* others, via two kinds of methods that may be invoked by any
43	>	* registered party:
44		*
45		* <ul>
46		*
47	<	*   <li> Arriving at a barrier. Methods <tt>arrive</tt> and
48	<	*       <tt>arriveAndDeregister</tt> do not block, but return
49	<	*       the phase value on entry to the method.
50	<	*
51	<	*   <li> Awaiting others. Method <tt>awaitAdvance</tt> requires an
52	<	*       argument indicating the entry phase, and returns when the
53	<	*       barrier advances to a new phase.
47	>	*   <li> <b>Arrival.</b> Methods {@link #arrive} and
48	>	*       {@link #arriveAndDeregister} record arrival at a
49	>	*       barrier. These methods do not block, but return an associated
50	>	*       <em>arrival phase number</em>; that is, the phase number of
51	>	*       the barrier to which the arrival applied. When the final
52	>	*       party for a given phase arrives, an optional barrier action
53	>	*       is performed and the phase advances.  Barrier actions,
54	>	*       performed by the party triggering a phase advance, are
55	>	*       arranged by overriding method {@link #onAdvance(int, int)},
56	>	*       which also controls termination. Overriding this method is
57	>	*       similar to, but more flexible than, providing a barrier
58	>	*       action to a {@code CyclicBarrier}.
59	>	*
60	>	*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
61	>	*       argument indicating an arrival phase number, and returns when
62	>	*       the barrier advances to (or is already at) a different phase.
63	>	*       Unlike similar constructions using {@code CyclicBarrier},
64	>	*       method {@code awaitAdvance} continues to wait even if the
65	>	*       waiting thread is interrupted. Interruptible and timeout
66	>	*       versions are also available, but exceptions encountered while
67	>	*       tasks wait interruptibly or with timeout do not change the
68	>	*       state of the barrier. If necessary, you can perform any
69	>	*       associated recovery within handlers of those exceptions,
70	>	*       often after invoking {@code forceTermination}.  Phasers may
71	>	*       also be used by tasks executing in a {@link ForkJoinPool},
72	>	*       which will ensure sufficient parallelism to execute tasks
73	>	*       when others are blocked waiting for a phase to advance.
74	>	*
75		* </ul>
76		*
77	+	* <p> <b>Termination.</b> A {@code Phaser} may enter a
78	+	* <em>termination</em> state in which all synchronization methods
79	+	* immediately return without updating phaser state or waiting for
80	+	* advance, and indicating (via a negative phase value) that execution
81	+	* is complete.  Termination is triggered when an invocation of {@code
82	+	* onAdvance} returns {@code true}.  As illustrated below, when
83	+	* phasers control actions with a fixed number of iterations, it is
84	+	* often convenient to override this method to cause termination when
85	+	* the current phase number reaches a threshold. Method {@link
86	+	* #forceTermination} is also available to abruptly release waiting
87	+	* threads and allow them to terminate.
88		*
89	<	* <li> Barrier actions, performed by the task triggering a phase
90	<	* advance while others may be waiting, are arranged by overriding
91	<	* method <tt>onAdvance</tt>, that also controls termination.
92	<	*
93	<	* <li> Phasers may enter a <em>termination</em> state in which all
94	<	* await actions immediately return, indicating (via a negative phase
95	<	* value) that execution is complete.  Termination is triggered by
56	<	* executing the overridable <tt>onAdvance</tt> method that is invoked
57	<	* each time the barrier is tripped. When a Phaser is controlling an
58	<	* action with a fixed number of iterations, it is often convenient to
59	<	* override this method to cause termination when the current phase
60	<	* number reaches a threshold.  Method <tt>forceTermination</tt> is
61	<	* also available to assist recovery actions upon failure.
62	<	*
63	<	* <li> Unlike most synchronizers, a Phaser may also be used with
64	<	* ForkJoinTasks (as well as plain threads).
65	<	*
66	<	* <li> By default, <tt>awaitAdvance</tt> continues to wait even if
67	<	* the current thread is interrupted. And unlike the case in
68	<	* CyclicBarriers, exceptions encountered while tasks wait
69	<	* interruptibly or with timeout do not change the state of the
70	<	* barrier. If necessary, you can perform any associated recovery
71	<	* within handlers of those exceptions.
89	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
90	>	* in tree structures) to reduce contention. Phasers with large
91	>	* numbers of parties that would otherwise experience heavy
92	>	* synchronization contention costs may instead be set up so that
93	>	* groups of sub-phasers share a common parent.  This may greatly
94	>	* increase throughput even though it incurs greater per-operation
95	>	* overhead.
96		*
97	<	* </ul>
97	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
98	>	* only by registered parties, the current state of a phaser may be
99	>	* monitored by any caller.  At any given moment there are {@link
100	>	* #getRegisteredParties} parties in total, of which {@link
101	>	* #getArrivedParties} have arrived at the current phase ({@link
102	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
103	>	* parties arrive, the phase advances.  The values returned by these
104	>	* methods may reflect transient states and so are not in general
105	>	* useful for synchronization control.  Method {@link #toString}
106	>	* returns snapshots of these state queries in a form convenient for
107	>	* informal monitoring.
108	>	*
109	>	* <p><b>Sample usages:</b>
110	>	*
111	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
112	>	* to control a one-shot action serving a variable number of parties.
113	>	* The typical idiom is for the method setting this up to first
114	>	* register, then start the actions, then deregister, as in:
115	>	*
116	>	*  <pre> {@code
117	>	* void runTasks(List<Runnable> tasks) {
118	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
119	>	*   // create and start threads
120	>	*   for (Runnable task : tasks) {
121	>	*     phaser.register();
122	>	*     new Thread() {
123	>	*       public void run() {
124	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
125	>	*         task.run();
126	>	*       }
127	>	*     }.start();
128	>	*   }
129	>	*
130	>	*   // allow threads to start and deregister self
131	>	*   phaser.arriveAndDeregister();
132	>	* }}</pre>
133	>	*
134	>	* <p>One way to cause a set of threads to repeatedly perform actions
135	>	* for a given number of iterations is to override {@code onAdvance}:
136	>	*
137	>	*  <pre> {@code
138	>	* void startTasks(List<Runnable> tasks, final int iterations) {
139	>	*   final Phaser phaser = new Phaser() {
140	>	*     protected boolean onAdvance(int phase, int registeredParties) {
141	>	*       return phase >= iterations || registeredParties == 0;
142	>	*     }
143	>	*   };
144	>	*   phaser.register();
145	>	*   for (final Runnable task : tasks) {
146	>	*     phaser.register();
147	>	*     new Thread() {
148	>	*       public void run() {
149	>	*         do {
150	>	*           task.run();
151	>	*           phaser.arriveAndAwaitAdvance();
152	>	*         } while (!phaser.isTerminated());
153	>	*       }
154	>	*     }.start();
155	>	*   }
156	>	*   phaser.arriveAndDeregister(); // deregister self, don't wait
157	>	* }}</pre>
158		*
159	<	* <p><b>Sample usage:</b>
159	>	* If the main task must later await termination, it
160	>	* may re-register and then execute a similar loop:
161	>	*  <pre> {@code
162	>	*   // ...
163	>	*   phaser.register();
164	>	*   while (!phaser.isTerminated())
165	>	*     phaser.arriveAndAwaitAdvance();}</pre>
166		*
167	<	* <p>[todo: non-FJ example]
167	>	* <p>Related constructions may be used to await particular phase numbers
168	>	* in contexts where you are sure that the phase will never wrap around
169	>	* {@code Integer.MAX_VALUE}. For example:
170		*
171	<	* <p> A Phaser may be used to support a style of programming in
172	<	* which a task waits for others to complete, without otherwise
173	<	* needing to keep track of which tasks it is waiting for. This is
174	<	* similar to the "sync" construct in Cilk and "clocks" in X10.
175	<	* Special constructions based on such barriers are available using
176	<	* the <tt>LinkedAsyncAction</tt> and <tt>CyclicAction</tt> classes,
177	<	* but they can be useful in other contexts as well.  For a simple
178	<	* (but not very useful) example, here is a variant of Fibonacci:
87	<	*
88	<	* <pre>
89	<	* class BarrierFibonacci extends RecursiveAction {
90	<	*   int argument, result;
91	<	*   final Phaser parentBarrier;
92	<	*   BarrierFibonacci(int n, Phaser parentBarrier) {
93	<	*     this.argument = n;
94	<	*     this.parentBarrier = parentBarrier;
95	<	*     parentBarrier.register();
171	>	*  <pre> {@code
172	>	* void awaitPhase(Phaser phaser, int phase) {
173	>	*   int p = phaser.register(); // assumes caller not already registered
174	>	*   while (p < phase) {
175	>	*     if (phaser.isTerminated())
176	>	*       // ... deal with unexpected termination
177	>	*     else
178	>	*       p = phaser.arriveAndAwaitAdvance();
179		*   }
180	<	*   protected void compute() {
181	<	*     int n = argument;
182	<	*     if (n &lt;= 1)
183	<	*        result = n;
184	<	*     else {
185	<	*        Phaser childBarrier = new Phaser(1);
186	<	*        BarrierFibonacci f1 = new BarrierFibonacci(n - 1, childBarrier);
187	<	*        BarrierFibonacci f2 = new BarrierFibonacci(n - 2, childBarrier);
188	<	*        f1.fork();
189	<	*        f2.fork();
190	<	*        childBarrier.arriveAndAwait();
191	<	*        result = f1.result + f2.result;
180	>	*   phaser.arriveAndDeregister();
181	>	* }}</pre>
182	>	*
183	>	*
184	>	* <p>To create a set of tasks using a tree of phasers,
185	>	* you could use code of the following form, assuming a
186	>	* Task class with a constructor accepting a phaser that
187	>	* it registers with upon construction:
188	>	*
189	>	*  <pre> {@code
190	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
191	>	*   if (hi - lo > TASKS_PER_PHASER) {
192	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
193	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
194	>	*       build(actions, i, j, new Phaser(ph));
195		*     }
196	<	*     parentBarrier.arriveAndDeregister();
196	>	*   } else {
197	>	*     for (int i = lo; i < hi; ++i)
198	>	*       actions[i] = new Task(ph);
199	>	*       // assumes new Task(ph) performs ph.register()
200		*   }
201		* }
202	<	* </pre>
202	>	* // .. initially called, for n tasks via
203	>	* build(new Task[n], 0, n, new Phaser());}</pre>
204	>	*
205	>	* The best value of {@code TASKS_PER_PHASER} depends mainly on
206	>	* expected barrier synchronization rates. A value as low as four may
207	>	* be appropriate for extremely small per-barrier task bodies (thus
208	>	* high rates), or up to hundreds for extremely large ones.
209		*
210		* <p><b>Implementation notes</b>: This implementation restricts the
211	<	* maximum number of parties to 65535. Attempts to register
212	<	* additional parties result in IllegalStateExceptions.
211	>	* maximum number of parties to 65535. Attempts to register additional
212	>	* parties result in {@code IllegalStateException}. However, you can and
213	>	* should create tiered phasers to accommodate arbitrarily large sets
214	>	* of participants.
215	>	*
216	>	* @since 1.7
217	>	* @author Doug Lea
218		*/
219		public class Phaser {
220		/*
221		* This class implements an extension of X10 "clocks".  Thanks to
222	<	* Vijay Saraswat for the idea of applying it to ForkJoinTasks,
223	<	* and to Vivek Sarkar for enhancements to extend functionality.
222	>	* Vijay Saraswat for the idea, and to Vivek Sarkar for
223	>	* enhancements to extend functionality.
224		*/
225
226		/**
227		* Barrier state representation. Conceptually, a barrier contains
228		* four values:
229	<	*
229	>	*
230		* * parties -- the number of parties to wait (16 bits)
231		* * unarrived -- the number of parties yet to hit barrier (16 bits)
232		* * phase -- the generation of the barrier (31 bits)
233		* * terminated -- set if barrier is terminated (1 bit)
234		*
235		* However, to efficiently maintain atomicity, these values are
236	<	* packed into a single AtomicLong. Termination uses the sign bit
237	<	* of 32 bit representation of phase, so phase is set to -1 on
238	<	* termination.
239	<	*/
240	<	private final AtomicLong state;
241	<
242	<	/**
143	<	* Head of Treiber stack for waiting nonFJ threads.
236	>	* packed into a single (atomic) long. Termination uses the sign
237	>	* bit of 32 bit representation of phase, so phase is set to -1 on
238	>	* termination. Good performance relies on keeping state decoding
239	>	* and encoding simple, and keeping race windows short.
240	>	*
241	>	* Note: there are some cheats in arrive() that rely on unarrived
242	>	* count being lowest 16 bits.
243		*/
244	<	private final AtomicReference<QNode> head = new AtomicReference<QNode>();
244	>	private volatile long state;
245
246	<	private static final int ushortBits = 16;
247	<	private static final int ushortMask =  (1 << ushortBits) - 1;
149	<	private static final int phaseMask = 0x7fffffff;
246	>	private static final int ushortMask = 0xffff;
247	>	private static final int phaseMask  = 0x7fffffff;
248
249		private static int unarrivedOf(long s) {
250	<	return (int)(s & ushortMask);
250	>	return (int) (s & ushortMask);
251		}
252
253		private static int partiesOf(long s) {
254	<	return (int)(s & (ushortMask << 16)) >>> 16;
254	>	return ((int) s) >>> 16;
255		}
256
257		private static int phaseOf(long s) {
258	<	return (int)(s >>> 32);
258	>	return (int) (s >>> 32);
259		}
260
261		private static int arrivedOf(long s) {
#	Line 165 | Line 263 | public class Phaser {
263		}
264
265		private static long stateFor(int phase, int parties, int unarrived) {
266	<	return (((long)phase) << 32) | ((parties << 16) | unarrived);
266	>	return ((((long) phase) << 32) | (((long) parties) << 16) |
267	>	(long) unarrived);
268		}
269
270	<	private static IllegalStateException badBounds(int parties, int unarrived) {
271	<	return new IllegalStateException("Attempt to set " + unarrived +
272	<	" unarrived of " + parties + " parties");
270	>	private static long trippedStateFor(int phase, int parties) {
271	>	long lp = (long) parties;
272	>	return (((long) phase) << 32) | (lp << 16) | lp;
273		}
274
275		/**
276	<	* Creates a new Phaser without any initially registered parties,
277	<	* and initial phase number 0.
276	>	* Returns message string for bad bounds exceptions.
277	>	*/
278	>	private static String badBounds(int parties, int unarrived) {
279	>	return ("Attempt to set " + unarrived +
280	>	" unarrived of " + parties + " parties");
281	>	}
282	>
283	>	/**
284	>	* The parent of this phaser, or null if none
285	>	*/
286	>	private final Phaser parent;
287	>
288	>	/**
289	>	* The root of phaser tree. Equals this if not in a tree.  Used to
290	>	* support faster state push-down.
291	>	*/
292	>	private final Phaser root;
293	>
294	>	// Wait queues
295	>
296	>	/**
297	>	* Heads of Treiber stacks for waiting threads. To eliminate
298	>	* contention while releasing some threads while adding others, we
299	>	* use two of them, alternating across even and odd phases.
300	>	*/
301	>	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
302	>	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
303	>
304	>	private AtomicReference<QNode> queueFor(int phase) {
305	>	return ((phase & 1) == 0) ? evenQ : oddQ;
306	>	}
307	>
308	>	/**
309	>	* Returns current state, first resolving lagged propagation from
310	>	* root if necessary.
311	>	*/
312	>	private long getReconciledState() {
313	>	return (parent == null) ? state : reconcileState();
314	>	}
315	>
316	>	/**
317	>	* Recursively resolves state.
318	>	*/
319	>	private long reconcileState() {
320	>	Phaser p = parent;
321	>	long s = state;
322	>	if (p != null) {
323	>	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
324	>	long parentState = p.getReconciledState();
325	>	int parentPhase = phaseOf(parentState);
326	>	int phase = phaseOf(s = state);
327	>	if (phase != parentPhase) {
328	>	long next = trippedStateFor(parentPhase, partiesOf(s));
329	>	if (casState(s, next)) {
330	>	releaseWaiters(phase);
331	>	s = next;
332	>	}
333	>	}
334	>	}
335	>	}
336	>	return s;
337	>	}
338	>
339	>	/**
340	>	* Creates a new phaser without any initially registered parties,
341	>	* initial phase number 0, and no parent. Any thread using this
342	>	* phaser will need to first register for it.
343		*/
344		public Phaser() {
345	<	state = new AtomicLong(stateFor(0, 0, 0));
345	>	this(null);
346		}
347
348		/**
349	<	* Creates a new Phaser with the given numbers of registered
350	<	* unarrived parties and initial phase number 0.
351	<	* @param parties the number of parties required to trip barrier.
349	>	* Creates a new phaser with the given number of registered
350	>	* unarrived parties, initial phase number 0, and no parent.
351	>	*
352	>	* @param parties the number of parties required to trip barrier
353		* @throws IllegalArgumentException if parties less than zero
354	<	* or greater than the maximum number of parties supported.
354	>	* or greater than the maximum number of parties supported
355		*/
356		public Phaser(int parties) {
357	+	this(null, parties);
358	+	}
359	+
360	+	/**
361	+	* Creates a new phaser with the given parent, without any
362	+	* initially registered parties. If parent is non-null this phaser
363	+	* is registered with the parent and its initial phase number is
364	+	* the same as that of parent phaser.
365	+	*
366	+	* @param parent the parent phaser
367	+	*/
368	+	public Phaser(Phaser parent) {
369	+	int phase = 0;
370	+	this.parent = parent;
371	+	if (parent != null) {
372	+	this.root = parent.root;
373	+	phase = parent.register();
374	+	}
375	+	else
376	+	this.root = this;
377	+	this.state = trippedStateFor(phase, 0);
378	+	}
379	+
380	+	/**
381	+	* Creates a new phaser with the given parent and number of
382	+	* registered unarrived parties. If parent is non-null, this phaser
383	+	* is registered with the parent and its initial phase number is
384	+	* the same as that of parent phaser.
385	+	*
386	+	* @param parent the parent phaser
387	+	* @param parties the number of parties required to trip barrier
388	+	* @throws IllegalArgumentException if parties less than zero
389	+	* or greater than the maximum number of parties supported
390	+	*/
391	+	public Phaser(Phaser parent, int parties) {
392		if (parties < 0 || parties > ushortMask)
393		throw new IllegalArgumentException("Illegal number of parties");
394	<	state = new AtomicLong(stateFor(0, parties, parties));
394	>	int phase = 0;
395	>	this.parent = parent;
396	>	if (parent != null) {
397	>	this.root = parent.root;
398	>	phase = parent.register();
399	>	}
400	>	else
401	>	this.root = this;
402	>	this.state = trippedStateFor(phase, parties);
403		}
404
405		/**
406		* Adds a new unarrived party to this phaser.
407	<	* @return the current barrier phase number upon registration
407	>	*
408	>	* @return the arrival phase number to which this registration applied
409	>	* @throws IllegalStateException if attempting to register more
410	>	* than the maximum supported number of parties
411	>	*/
412	>	public int register() {
413	>	return doRegister(1);
414	>	}
415	>
416	>	/**
417	>	* Adds the given number of new unarrived parties to this phaser.
418	>	*
419	>	* @param parties the number of additional parties required to trip barrier
420	>	* @return the arrival phase number to which this registration applied
421		* @throws IllegalStateException if attempting to register more
422	<	* than the maximum supported number of parties.
422	>	* than the maximum supported number of parties
423	>	* @throws IllegalArgumentException if {@code parties < 0}
424		*/
425	<	public int register() { // increment both parties and unarrived
426	<	final AtomicLong state = this.state;
425	>	public int bulkRegister(int parties) {
426	>	if (parties < 0)
427	>	throw new IllegalArgumentException();
428	>	if (parties == 0)
429	>	return getPhase();
430	>	return doRegister(parties);
431	>	}
432	>
433	>	/**
434	>	* Shared code for register, bulkRegister
435	>	*/
436	>	private int doRegister(int registrations) {
437	>	int phase;
438		for (;;) {
439	<	long s = state.get();
440	<	int phase = phaseOf(s);
441	<	int parties = partiesOf(s) + 1;
442	<	int unarrived = unarrivedOf(s) + 1;
439	>	long s = getReconciledState();
440	>	phase = phaseOf(s);
441	>	int unarrived = unarrivedOf(s) + registrations;
442	>	int parties = partiesOf(s) + registrations;
443	>	if (phase < 0)
444	>	break;
445		if (parties > ushortMask || unarrived > ushortMask)
446	<	throw badBounds(parties, unarrived);
447	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
448	<	return phase;
446	>	throw new IllegalStateException(badBounds(parties, unarrived));
447	>	if (phase == phaseOf(root.state) &&
448	>	casState(s, stateFor(phase, parties, unarrived)))
449	>	break;
450		}
451	+	return phase;
452		}
453
454		/**
455		* Arrives at the barrier, but does not wait for others.  (You can
456	<	* in turn wait for others via {@link #awaitAdvance}).
456	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
457	>	* unenforced usage error for an unregistered party to invoke this
458	>	* method.
459		*
460	<	* @return the current barrier phase number upon entry to
461	<	* this method, or a negative value if terminated;
462	<	* @throws IllegalStateException if the number of unarrived
224	<	* parties would become negative.
460	>	* @return the arrival phase number, or a negative value if terminated
461	>	* @throws IllegalStateException if not terminated and the number
462	>	* of unarrived parties would become negative
463		*/
464	<	public int arrive() { // decrement unarrived. If zero, trip
465	<	final AtomicLong state = this.state;
464	>	public int arrive() {
465	>	int phase;
466		for (;;) {
467	<	long s = state.get();
468	<	int phase = phaseOf(s);
467	>	long s = state;
468	>	phase = phaseOf(s);
469	>	if (phase < 0)
470	>	break;
471		int parties = partiesOf(s);
472		int unarrived = unarrivedOf(s) - 1;
473	<	if (unarrived < 0)
474	<	throw badBounds(parties, unarrived);
475	<	if (unarrived == 0 && phase >= 0) {
236	<	trip(phase, parties);
237	<	return phase;
473	>	if (unarrived > 0) {        // Not the last arrival
474	>	if (casState(s, s - 1)) // s-1 adds one arrival
475	>	break;
476		}
477	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
478	<	return phase;
477	>	else if (unarrived == 0) {  // the last arrival
478	>	Phaser par = parent;
479	>	if (par == null) {      // directly trip
480	>	if (casState
481	>	(s,
482	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
483	>	((phase + 1) & phaseMask), parties))) {
484	>	releaseWaiters(phase);
485	>	break;
486	>	}
487	>	}
488	>	else {                  // cascade to parent
489	>	if (casState(s, s - 1)) { // zeroes unarrived
490	>	par.arrive();
491	>	reconcileState();
492	>	break;
493	>	}
494	>	}
495	>	}
496	>	else if (phase != phaseOf(root.state)) // or if unreconciled
497	>	reconcileState();
498	>	else
499	>	throw new IllegalStateException(badBounds(parties, unarrived));
500		}
501	+	return phase;
502		}
503
504		/**
505	<	* Arrives at the barrier, and deregisters from it, without
506	<	* waiting for others.
505	>	* Arrives at the barrier and deregisters from it without waiting
506	>	* for others. Deregistration reduces the number of parties
507	>	* required to trip the barrier in future phases.  If this phaser
508	>	* has a parent, and deregistration causes this phaser to have
509	>	* zero parties, this phaser also arrives at and is deregistered
510	>	* from its parent.  It is an unenforced usage error for an
511	>	* unregistered party to invoke this method.
512		*
513	<	* @return the current barrier phase number upon entry to
514	<	* this method, or a negative value if terminated;
515	<	* @throws IllegalStateException if the number of registered or
516	<	* unarrived parties would become negative.
517	<	*/
518	<	public int arriveAndDeregister() { // Same as arrive, plus decrement parties
519	<	final AtomicLong state = this.state;
513	>	* @return the arrival phase number, or a negative value if terminated
514	>	* @throws IllegalStateException if not terminated and the number
515	>	* of registered or unarrived parties would become negative
516	>	*/
517	>	public int arriveAndDeregister() {
518	>	// similar code to arrive, but too different to merge
519	>	Phaser par = parent;
520	>	int phase;
521		for (;;) {
522	<	long s = state.get();
523	<	int phase = phaseOf(s);
522	>	long s = state;
523	>	phase = phaseOf(s);
524	>	if (phase < 0)
525	>	break;
526		int parties = partiesOf(s) - 1;
527		int unarrived = unarrivedOf(s) - 1;
528	<	if (parties < 0 || unarrived < 0)
529	<	throw badBounds(parties, unarrived);
530	<	if (unarrived == 0 && phase >= 0) {
531	<	trip(phase, parties);
532	<	return phase;
528	>	if (parties >= 0) {
529	>	if (unarrived > 0 || (unarrived == 0 && par != null)) {
530	>	if (casState
531	>	(s,
532	>	stateFor(phase, parties, unarrived))) {
533	>	if (unarrived == 0) {
534	>	par.arriveAndDeregister();
535	>	reconcileState();
536	>	}
537	>	break;
538	>	}
539	>	continue;
540	>	}
541	>	if (unarrived == 0) {
542	>	if (casState
543	>	(s,
544	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
545	>	((phase + 1) & phaseMask), parties))) {
546	>	releaseWaiters(phase);
547	>	break;
548	>	}
549	>	continue;
550	>	}
551	>	if (par != null && phase != phaseOf(root.state)) {
552	>	reconcileState();
553	>	continue;
554	>	}
555		}
556	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
267	<	return phase;
556	>	throw new IllegalStateException(badBounds(parties, unarrived));
557		}
558	+	return phase;
559		}
560
561		/**
562	<	* Arrives at the barrier and awaits others. Unlike other arrival
563	<	* methods, this method returns the arrival index of the
564	<	* caller. The caller tripping the barrier returns zero, the
565	<	* previous caller 1, and so on.
566	<	* @return the arrival index
567	<	* @throws IllegalStateException if the number of unarrived
568	<	* parties would become negative.
562	>	* Arrives at the barrier and awaits others. Equivalent in effect
563	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
564	>	* interruption or timeout, you can arrange this with an analogous
565	>	* construction using one of the other forms of the {@code
566	>	* awaitAdvance} method.  If instead you need to deregister upon
567	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
568	>	* usage error for an unregistered party to invoke this method.
569	>	*
570	>	* @return the arrival phase number, or a negative number if terminated
571	>	* @throws IllegalStateException if not terminated and the number
572	>	* of unarrived parties would become negative
573		*/
574		public int arriveAndAwaitAdvance() {
575	<	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	<	}
575	>	return awaitAdvance(arrive());
576		}
577
578		/**
579	<	* Awaits the phase of the barrier to advance from the given
580	<	* value, or returns immediately if this barrier is terminated
581	<	* @param phase the phase on entry to this method
582	<	* @return the phase on exit from this method
579	>	* Awaits the phase of the barrier to advance from the given phase
580	>	* value, returning immediately if the current phase of the
581	>	* barrier is not equal to the given phase value or this barrier
582	>	* is terminated.  It is an unenforced usage error for an
583	>	* unregistered party to invoke this method.
584	>	*
585	>	* @param phase an arrival phase number, or negative value if
586	>	* terminated; this argument is normally the value returned by a
587	>	* previous call to {@code arrive} or its variants
588	>	* @return the next arrival phase number, or a negative value
589	>	* if terminated or argument is negative
590		*/
591		public int awaitAdvance(int phase) {
592		if (phase < 0)
593		return phase;
594	<	Thread current = Thread.currentThread();
595	<	if (current instanceof ForkJoinWorkerThread)
596	<	return helpingWait(phase);
597	<	if (untimedWait(current, phase, false))
598	<	current.interrupt();
599	<	return phaseOf(state.get());
594	>	long s = getReconciledState();
595	>	int p = phaseOf(s);
596	>	if (p != phase)
597	>	return p;
598	>	if (unarrivedOf(s) == 0 && parent != null)
599	>	parent.awaitAdvance(phase);
600	>	// Fall here even if parent waited, to reconcile and help release
601	>	return untimedWait(phase);
602		}
603
604		/**
605	<	* Awaits the phase of the barrier to advance from the given
606	<	* value, or returns immediately if this barrier is terminated, or
607	<	* throws InterruptedException if interrupted while waiting.
608	<	* @param phase the phase on entry to this method
609	<	* @return the phase on exit from this method
605	>	* Awaits the phase of the barrier to advance from the given phase
606	>	* value, throwing {@code InterruptedException} if interrupted
607	>	* while waiting, or returning immediately if the current phase of
608	>	* the barrier is not equal to the given phase value or this
609	>	* barrier is terminated. It is an unenforced usage error for an
610	>	* unregistered party to invoke this method.
611	>	*
612	>	* @param phase an arrival phase number, or negative value if
613	>	* terminated; this argument is normally the value returned by a
614	>	* previous call to {@code arrive} or its variants
615	>	* @return the next arrival phase number, or a negative value
616	>	* if terminated or argument is negative
617		* @throws InterruptedException if thread interrupted while waiting
618		*/
619	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
619	>	public int awaitAdvanceInterruptibly(int phase)
620	>	throws InterruptedException {
621		if (phase < 0)
622		return phase;
623	<	Thread current = Thread.currentThread();
624	<	if (current instanceof ForkJoinWorkerThread)
625	<	return helpingWait(phase);
626	<	else if (Thread.interrupted() || untimedWait(current, phase, true))
627	<	throw new InterruptedException();
628	<	else
629	<	return phaseOf(state.get());
623	>	long s = getReconciledState();
624	>	int p = phaseOf(s);
625	>	if (p != phase)
626	>	return p;
627	>	if (unarrivedOf(s) == 0 && parent != null)
628	>	parent.awaitAdvanceInterruptibly(phase);
629	>	return interruptibleWait(phase);
630		}
631
632		/**
633	<	* Awaits the phase of the barrier to advance from the given value
634	<	* or the given timeout elapses, or returns immediately if this
635	<	* barrier is terminated
636	<	* @param phase the phase on entry to this method
637	<	* @return the phase on exit from this method
633	>	* Awaits the phase of the barrier to advance from the given phase
634	>	* value or the given timeout to elapse, throwing {@code
635	>	* InterruptedException} if interrupted while waiting, or
636	>	* returning immediately if the current phase of the barrier is
637	>	* not equal to the given phase value or this barrier is
638	>	* terminated.  It is an unenforced usage error for an
639	>	* unregistered party to invoke this method.
640	>	*
641	>	* @param phase an arrival phase number, or negative value if
642	>	* terminated; this argument is normally the value returned by a
643	>	* previous call to {@code arrive} or its variants
644	>	* @param timeout how long to wait before giving up, in units of
645	>	*        {@code unit}
646	>	* @param unit a {@code TimeUnit} determining how to interpret the
647	>	*        {@code timeout} parameter
648	>	* @return the next arrival phase number, or a negative value
649	>	* if terminated or argument is negative
650		* @throws InterruptedException if thread interrupted while waiting
651		* @throws TimeoutException if timed out while waiting
652		*/
653	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
653	>	public int awaitAdvanceInterruptibly(int phase,
654	>	long timeout, TimeUnit unit)
655		throws InterruptedException, TimeoutException {
656		if (phase < 0)
657		return phase;
658	<	long nanos = unit.toNanos(timeout);
659	<	Thread current = Thread.currentThread();
660	<	if (current instanceof ForkJoinWorkerThread)
661	<	return timedHelpingWait(phase, nanos);
662	<	timedWait(current, phase, nanos);
663	<	return phaseOf(state.get());
658	>	long s = getReconciledState();
659	>	int p = phaseOf(s);
660	>	if (p != phase)
661	>	return p;
662	>	if (unarrivedOf(s) == 0 && parent != null)
663	>	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
664	>	return timedWait(phase, unit.toNanos(timeout));
665		}
666
667		/**
668		* Forces this barrier to enter termination state. Counts of
669	<	* arrived and registered parties are unaffected. This method may
670	<	* be useful for coordinating recovery after one or more tasks
671	<	* encounter unexpected exceptions.
669	>	* arrived and registered parties are unaffected. If this phaser
670	>	* has a parent, it too is terminated. This method may be useful
671	>	* for coordinating recovery after one or more tasks encounter
672	>	* unexpected exceptions.
673		*/
674		public void forceTermination() {
365	–	final AtomicLong state = this.state;
675		for (;;) {
676	<	long s = state.get();
676	>	long s = getReconciledState();
677		int phase = phaseOf(s);
678		int parties = partiesOf(s);
679		int unarrived = unarrivedOf(s);
680		if (phase < 0 ||
681	<	state.compareAndSet(s, stateFor(-1, parties, unarrived))) {
682	<	if (head.get() != null)
683	<	releaseWaiters(-1);
681	>	casState(s, stateFor(-1, parties, unarrived))) {
682	>	releaseWaiters(0);
683	>	releaseWaiters(1);
684	>	if (parent != null)
685	>	parent.forceTermination();
686		return;
687		}
688		}
689		}
690
691		/**
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	–	/**
692		* Returns the current phase number. The maximum phase number is
693	<	* <tt>Integer.MAX_VALUE</tt>, after which it restarts at
693	>	* {@code Integer.MAX_VALUE}, after which it restarts at
694		* zero. Upon termination, the phase number is negative.
695	+	*
696		* @return the phase number, or a negative value if terminated
697		*/
698	<	public int getPhase() {
699	<	return phaseOf(state.get());
698	>	public final int getPhase() {
699	>	return phaseOf(getReconciledState());
700		}
701
702		/**
703		* Returns the number of parties registered at this barrier.
704	+	*
705		* @return the number of parties
706		*/
707		public int getRegisteredParties() {
708	<	return partiesOf(state.get());
708	>	return partiesOf(state);
709		}
710
711		/**
712	<	* Returns the number of parties that have arrived at the current
713	<	* phase of this barrier.
712	>	* Returns the number of registered parties that have arrived at
713	>	* the current phase of this barrier.
714	>	*
715		* @return the number of arrived parties
716		*/
717		public int getArrivedParties() {
718	<	return arrivedOf(state.get());
718	>	return arrivedOf(state);
719		}
720
721		/**
722		* Returns the number of registered parties that have not yet
723		* arrived at the current phase of this barrier.
724	+	*
725		* @return the number of unarrived parties
726		*/
727		public int getUnarrivedParties() {
728	<	return unarrivedOf(state.get());
728	>	return unarrivedOf(state);
729	>	}
730	>
731	>	/**
732	>	* Returns the parent of this phaser, or {@code null} if none.
733	>	*
734	>	* @return the parent of this phaser, or {@code null} if none
735	>	*/
736	>	public Phaser getParent() {
737	>	return parent;
738	>	}
739	>
740	>	/**
741	>	* Returns the root ancestor of this phaser, which is the same as
742	>	* this phaser if it has no parent.
743	>	*
744	>	* @return the root ancestor of this phaser
745	>	*/
746	>	public Phaser getRoot() {
747	>	return root;
748		}
749
750		/**
751	<	* Returns true if this barrier has been terminated
752	<	* @return true if this barrier has been terminated
751	>	* Returns {@code true} if this barrier has been terminated.
752	>	*
753	>	* @return {@code true} if this barrier has been terminated
754		*/
755		public boolean isTerminated() {
756	<	return phaseOf(state.get()) < 0;
756	>	return getPhase() < 0;
757		}
758
759		/**
760	<	* Overridable method to perform an action upon phase advance, and
761	<	* to control termination. This method is invoked whenever the
762	<	* barrier is tripped (and thus all other waiting parties are
763	<	* dormant). If it returns true, then, rather than advance the
764	<	* phase number, this barrier will be set to a final termination
765	<	* state, and subsequent calls to <tt>isTerminated</tt> will
766	<	* return true.
767	<	*
768	<	* <p> The default version returns true when the number of
760	>	* Overridable method to perform an action upon impending phase
761	>	* advance, and to control termination. This method is invoked
762	>	* upon arrival of the party tripping the barrier (when all other
763	>	* waiting parties are dormant).  If this method returns {@code
764	>	* true}, then, rather than advance the phase number, this barrier
765	>	* will be set to a final termination state, and subsequent calls
766	>	* to {@link #isTerminated} will return true. Any (unchecked)
767	>	* Exception or Error thrown by an invocation of this method is
768	>	* propagated to the party attempting to trip the barrier, in
769	>	* which case no advance occurs.
770	>	*
771	>	* <p>The arguments to this method provide the state of the phaser
772	>	* prevailing for the current transition. (When called from within
773	>	* an implementation of {@code onAdvance} the values returned by
774	>	* methods such as {@code getPhase} may or may not reliably
775	>	* indicate the state to which this transition applies.)
776	>	*
777	>	* <p>The default version returns {@code true} when the number of
778		* registered parties is zero. Normally, overrides that arrange
779		* termination for other reasons should also preserve this
780		* property.
781		*
782	+	* <p>You may override this method to perform an action with side
783	+	* effects visible to participating tasks, but it is only sensible
784	+	* to do so in designs where all parties register before any
785	+	* arrive, and all {@link #awaitAdvance} at each phase.
786	+	* Otherwise, you cannot ensure lack of interference from other
787	+	* parties during the invocation of this method. Additionally,
788	+	* method {@code onAdvance} may be invoked more than once per
789	+	* transition if registrations are intermixed with arrivals.
790	+	*
791		* @param phase the phase number on entering the barrier
792	<	* @param registeredParties the current number of registered
793	<	* parties.
458	<	* @return true if this barrier should terminate
792	>	* @param registeredParties the current number of registered parties
793	>	* @return {@code true} if this barrier should terminate
794		*/
795		protected boolean onAdvance(int phase, int registeredParties) {
796		return registeredParties <= 0;
797		}
798
799		/**
800	<	* Returns a string identifying this barrier, as well as its
800	>	* Returns a string identifying this phaser, as well as its
801		* state.  The state, in brackets, includes the String {@code
802	<	* "phase ="} followed by the phase number, {@code "parties ="}
802	>	* "phase = "} followed by the phase number, {@code "parties = "}
803		* followed by the number of registered parties, and {@code
804	<	* "arrived ="} followed by the number of arrived parties
804	>	* "arrived = "} followed by the number of arrived parties.
805		*
806		* @return a string identifying this barrier, as well as its state
807		*/
808		public String toString() {
809	<	long s = state.get();
810	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
809	>	long s = getReconciledState();
810	>	return super.toString() +
811	>	"[phase = " + phaseOf(s) +
812	>	" parties = " + partiesOf(s) +
813	>	" arrived = " + arrivedOf(s) + "]";
814		}
815
816	<	// methods for tripping and waiting
816	>	// methods for waiting
817
818		/**
819	<	* Advance the current phase (or terminate)
819	>	* Wait nodes for Treiber stack representing wait queue
820		*/
821	<	private void trip(int phase, int parties) {
822	<	int next = onAdvance(phase, parties)? -1 : ((phase + 1) & phaseMask);
823	<	state.set(stateFor(next, parties, parties));
824	<	if (head.get() != null)
825	<	releaseWaiters(next);
826	<	}
821	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
822	>	final Phaser phaser;
823	>	final int phase;
824	>	final long startTime;
825	>	final long nanos;
826	>	final boolean timed;
827	>	final boolean interruptible;
828	>	volatile boolean wasInterrupted = false;
829	>	volatile Thread thread; // nulled to cancel wait
830	>	QNode next;
831
832	<	private int helpingWait(int phase) {
833	<	final AtomicLong state = this.state;
834	<	int p;
835	<	while ((p = phaseOf(state.get())) == phase) {
836	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
837	<	if (t != null) {
838	<	if ((p = phaseOf(state.get())) == phase)
839	<	t.exec();
840	<	else {   // push task and exit if barrier advanced
499	<	t.fork();
500	<	break;
501	<	}
502	<	}
832	>	QNode(Phaser phaser, int phase, boolean interruptible,
833	>	boolean timed, long startTime, long nanos) {
834	>	this.phaser = phaser;
835	>	this.phase = phase;
836	>	this.timed = timed;
837	>	this.interruptible = interruptible;
838	>	this.startTime = startTime;
839	>	this.nanos = nanos;
840	>	thread = Thread.currentThread();
841		}
504	–	return p;
505	–	}
842
843	<	private int timedHelpingWait(int phase, long nanos) throws TimeoutException {
844	<	final AtomicLong state = this.state;
845	<	long lastTime = System.nanoTime();
846	<	int p;
847	<	while ((p = phaseOf(state.get())) == phase) {
848	<	long now = System.nanoTime();
849	<	nanos -= now - lastTime;
850	<	lastTime = now;
851	<	if (nanos <= 0) {
852	<	if ((p = phaseOf(state.get())) == phase)
853	<	throw new TimeoutException();
854	<	else
519	<	break;
843	>	public boolean isReleasable() {
844	>	return (thread == null ||
845	>	phaser.getPhase() != phase ||
846	>	(interruptible && wasInterrupted) ||
847	>	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
848	>	}
849	>
850	>	public boolean block() {
851	>	if (Thread.interrupted()) {
852	>	wasInterrupted = true;
853	>	if (interruptible)
854	>	return true;
855		}
856	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
857	<	if (t != null) {
858	<	if ((p = phaseOf(state.get())) == phase)
859	<	t.exec();
860	<	else {   // push task and exit if barrier advanced
861	<	t.fork();
862	<	break;
528	<	}
856	>	if (!timed)
857	>	LockSupport.park(this);
858	>	else {
859	>	long waitTime = nanos - (System.nanoTime() - startTime);
860	>	if (waitTime <= 0)
861	>	return true;
862	>	LockSupport.parkNanos(this, waitTime);
863		}
864	+	return isReleasable();
865		}
531	–	return p;
532	–	}
866
867	<	/**
868	<	* Wait nodes for Treiber stack representing wait queue for non-FJ
869	<	* tasks. The waiting scheme is an adaptation of the one used in
870	<	* forkjoin.PoolBarrier.
871	<	*/
872	<	static final class QNode {
540	<	QNode next;
541	<	volatile Thread thread; // nulled to cancel wait
542	<	final int phase;
543	<	QNode(Thread t, int c) {
544	<	thread = t;
545	<	phase = c;
867	>	void signal() {
868	>	Thread t = thread;
869	>	if (t != null) {
870	>	thread = null;
871	>	LockSupport.unpark(t);
872	>	}
873		}
547	–	}
874
875	<	private void releaseWaiters(int currentPhase) {
876	<	final AtomicReference<QNode> head = this.head;
877	<	QNode p;
878	<	while ((p = head.get()) != null && p.phase != currentPhase) {
879	<	if (head.compareAndSet(p, null)) {
880	<	do {
881	<	Thread t = p.thread;
556	<	if (t != null) {
557	<	p.thread = null;
558	<	LockSupport.unpark(t);
559	<	}
560	<	} while ((p = p.next) != null);
875	>	boolean doWait() {
876	>	if (thread != null) {
877	>	try {
878	>	ForkJoinPool.managedBlock(this);
879	>	} catch (InterruptedException ie) {
880	>	wasInterrupted = true; // can't currently happen
881	>	}
882		}
883	+	return wasInterrupted;
884		}
885		}
886
565	–	/** The number of CPUs, for spin control */
566	–	static final int NCPUS = Runtime.getRuntime().availableProcessors();
567	–
887		/**
888	<	* The number of times to spin before blocking in timed waits.
570	<	* The value is empirically derived
888	>	* Removes and signals waiting threads from wait queue.
889		*/
890	<	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
890	>	private void releaseWaiters(int phase) {
891	>	AtomicReference<QNode> head = queueFor(phase);
892	>	QNode q;
893	>	while ((q = head.get()) != null) {
894	>	if (head.compareAndSet(q, q.next))
895	>	q.signal();
896	>	}
897	>	}
898
899		/**
900	<	* The number of times to spin before blocking in untimed waits.
901	<	* This is greater than timed value because untimed waits spin
902	<	* faster since they don't need to check times on each spin.
900	>	* Tries to enqueue given node in the appropriate wait queue.
901	>	*
902	>	* @return true if successful
903		*/
904	<	static final int maxUntimedSpins = maxTimedSpins * 32;
904	>	private boolean tryEnqueue(QNode node) {
905	>	AtomicReference<QNode> head = queueFor(node.phase);
906	>	return head.compareAndSet(node.next = head.get(), node);
907	>	}
908
909		/**
910	<	* The number of nanoseconds for which it is faster to spin
911	<	* rather than to use timed park. A rough estimate suffices.
910	>	* Enqueues node and waits unless aborted or signalled.
911	>	*
912	>	* @return current phase
913		*/
914	<	static final long spinForTimeoutThreshold = 1000L;
914	>	private int untimedWait(int phase) {
915	>	QNode node = null;
916	>	boolean queued = false;
917	>	boolean interrupted = false;
918	>	int p;
919	>	while ((p = getPhase()) == phase) {
920	>	if (Thread.interrupted())
921	>	interrupted = true;
922	>	else if (node == null)
923	>	node = new QNode(this, phase, false, false, 0, 0);
924	>	else if (!queued)
925	>	queued = tryEnqueue(node);
926	>	else if (node.doWait())
927	>	interrupted = true;
928	>	}
929	>	if (node != null)
930	>	node.thread = null;
931	>	releaseWaiters(phase);
932	>	if (interrupted)
933	>	Thread.currentThread().interrupt();
934	>	return p;
935	>	}
936
937		/**
938	<	* Enqueues node and waits unless aborted or signalled.
938	>	* Interruptible version
939	>	* @return current phase
940		*/
941	<	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;
941	>	private int interruptibleWait(int phase) throws InterruptedException {
942		QNode node = null;
943		boolean queued = false;
944	<	int spins = maxUntimedSpins;
945	<	while (phaseOf(state.get()) == currentPhase) {
946	<	QNode h;
947	<	if (node != null && queued) {
948	<	if (node.thread != null) {
949	<	LockSupport.park();
950	<	if (Thread.interrupted()) {
951	<	wasInterrupted = true;
952	<	if (abortOnInterrupt)
953	<	break;
954	<	}
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);
627	<	else
628	<	--spins;
944	>	boolean interrupted = false;
945	>	int p;
946	>	while ((p = getPhase()) == phase && !interrupted) {
947	>	if (Thread.interrupted())
948	>	interrupted = true;
949	>	else if (node == null)
950	>	node = new QNode(this, phase, true, false, 0, 0);
951	>	else if (!queued)
952	>	queued = tryEnqueue(node);
953	>	else if (node.doWait())
954	>	interrupted = true;
955		}
956		if (node != null)
957		node.thread = null;
958	<	return wasInterrupted;
958	>	if (p != phase || (p = getPhase()) != phase)
959	>	releaseWaiters(phase);
960	>	if (interrupted)
961	>	throw new InterruptedException();
962	>	return p;
963		}
964
965		/**
966	<	* Messier timeout version
966	>	* Timeout version.
967	>	* @return current phase
968		*/
969	<	private void timedWait(Thread thread, int currentPhase, long nanos)
969	>	private int timedWait(int phase, long nanos)
970		throws InterruptedException, TimeoutException {
971	<	final AtomicReference<QNode> head = this.head;
641	<	final AtomicLong state = this.state;
642	<	long lastTime = System.nanoTime();
971	>	long startTime = System.nanoTime();
972		QNode node = null;
973		boolean queued = false;
974	<	int spins = maxTimedSpins;
975	<	while (phaseOf(state.get()) == currentPhase) {
976	<	QNode h;
977	<	long now = System.nanoTime();
978	<	nanos -= now - lastTime;
979	<	lastTime = now;
980	<	if (nanos <= 0) {
981	<	if (node != null)
982	<	node.thread = null;
983	<	if (phaseOf(state.get()) == currentPhase)
984	<	throw new TimeoutException();
985	<	else
986	<	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);
687	<	else
688	<	--spins;
974	>	boolean interrupted = false;
975	>	int p;
976	>	while ((p = getPhase()) == phase && !interrupted) {
977	>	if (Thread.interrupted())
978	>	interrupted = true;
979	>	else if (nanos - (System.nanoTime() - startTime) <= 0)
980	>	break;
981	>	else if (node == null)
982	>	node = new QNode(this, phase, true, true, startTime, nanos);
983	>	else if (!queued)
984	>	queued = tryEnqueue(node);
985	>	else if (node.doWait())
986	>	interrupted = true;
987		}
988		if (node != null)
989		node.thread = null;
990	+	if (p != phase || (p = getPhase()) != phase)
991	+	releaseWaiters(phase);
992	+	if (interrupted)
993	+	throw new InterruptedException();
994	+	if (p == phase)
995	+	throw new TimeoutException();
996	+	return p;
997		}
998
999	<	}
999	>	// Unsafe mechanics
1000
1001	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1002	+	private static final long stateOffset =
1003	+	objectFieldOffset("state", Phaser.class);
1004	+
1005	+	private final boolean casState(long cmp, long val) {
1006	+	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
1007	+	}
1008	+
1009	+	private static long objectFieldOffset(String field, Class<?> klazz) {
1010	+	try {
1011	+	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1012	+	} catch (NoSuchFieldException e) {
1013	+	// Convert Exception to corresponding Error
1014	+	NoSuchFieldError error = new NoSuchFieldError(field);
1015	+	error.initCause(e);
1016	+	throw error;
1017	+	}
1018	+	}
1019	+
1020	+	/**
1021	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1022	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1023	+	* into a jdk.
1024	+	*
1025	+	* @return a sun.misc.Unsafe
1026	+	*/
1027	+	private static sun.misc.Unsafe getUnsafe() {
1028	+	try {
1029	+	return sun.misc.Unsafe.getUnsafe();
1030	+	} catch (SecurityException se) {
1031	+	try {
1032	+	return java.security.AccessController.doPrivileged
1033	+	(new java.security
1034	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1035	+	public sun.misc.Unsafe run() throws Exception {
1036	+	java.lang.reflect.Field f = sun.misc
1037	+	.Unsafe.class.getDeclaredField("theUnsafe");
1038	+	f.setAccessible(true);
1039	+	return (sun.misc.Unsafe) f.get(null);
1040	+	}});
1041	+	} catch (java.security.PrivilegedActionException e) {
1042	+	throw new RuntimeException("Could not initialize intrinsics",
1043	+	e.getCause());
1044	+	}
1045	+	}
1046	+	}
1047	+	}

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