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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 1.59 by dl, Sat Nov 27 16:46:53 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import jsr166y.forkjoin.*;
9	<	import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
8	>
9	>	import java.util.concurrent.TimeUnit;
10	>	import java.util.concurrent.TimeoutException;
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}. The default implementation returns
83	+	* {@code true} if a deregistration has caused the number of
84	+	* registered parties to become zero.  As illustrated below, when
85	+	* phasers control actions with a fixed number of iterations, it is
86	+	* often convenient to override this method to cause termination when
87	+	* the current phase number reaches a threshold. Method {@link
88	+	* #forceTermination} is also available to abruptly release waiting
89	+	* threads and allow them to terminate.
90		*
91	<	* <li> Barrier actions, performed by the task triggering a phase
92	<	* advance while others may be waiting, are arranged by overriding
93	<	* method <tt>onAdvance</tt>, that also controls termination.
94	<	*
95	<	* <li> Phasers may enter a <em>termination</em> state in which all
96	<	* await actions immediately return, indicating (via a negative phase
97	<	* 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.
91	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
92	>	* constructed in tree structures) to reduce contention. Phasers with
93	>	* large numbers of parties that would otherwise experience heavy
94	>	* synchronization contention costs may instead be set up so that
95	>	* groups of sub-phasers share a common parent.  This may greatly
96	>	* increase throughput even though it incurs greater per-operation
97	>	* overhead.
98		*
99	<	* </ul>
99	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
100	>	* only by registered parties, the current state of a phaser may be
101	>	* monitored by any caller.  At any given moment there are {@link
102	>	* #getRegisteredParties} parties in total, of which {@link
103	>	* #getArrivedParties} have arrived at the current phase ({@link
104	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
105	>	* parties arrive, the phase advances.  The values returned by these
106	>	* methods may reflect transient states and so are not in general
107	>	* useful for synchronization control.  Method {@link #toString}
108	>	* returns snapshots of these state queries in a form convenient for
109	>	* informal monitoring.
110	>	*
111	>	* <p><b>Sample usages:</b>
112	>	*
113	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
114	>	* to control a one-shot action serving a variable number of parties.
115	>	* The typical idiom is for the method setting this up to first
116	>	* register, then start the actions, then deregister, as in:
117	>	*
118	>	*  <pre> {@code
119	>	* void runTasks(List<Runnable> tasks) {
120	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
121	>	*   // create and start threads
122	>	*   for (Runnable task : tasks) {
123	>	*     phaser.register();
124	>	*     new Thread() {
125	>	*       public void run() {
126	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
127	>	*         task.run();
128	>	*       }
129	>	*     }.start();
130	>	*   }
131	>	*
132	>	*   // allow threads to start and deregister self
133	>	*   phaser.arriveAndDeregister();
134	>	* }}</pre>
135	>	*
136	>	* <p>One way to cause a set of threads to repeatedly perform actions
137	>	* for a given number of iterations is to override {@code onAdvance}:
138	>	*
139	>	*  <pre> {@code
140	>	* void startTasks(List<Runnable> tasks, final int iterations) {
141	>	*   final Phaser phaser = new Phaser() {
142	>	*     protected boolean onAdvance(int phase, int registeredParties) {
143	>	*       return phase >= iterations || registeredParties == 0;
144	>	*     }
145	>	*   };
146	>	*   phaser.register();
147	>	*   for (final Runnable task : tasks) {
148	>	*     phaser.register();
149	>	*     new Thread() {
150	>	*       public void run() {
151	>	*         do {
152	>	*           task.run();
153	>	*           phaser.arriveAndAwaitAdvance();
154	>	*         } while (!phaser.isTerminated());
155	>	*       }
156	>	*     }.start();
157	>	*   }
158	>	*   phaser.arriveAndDeregister(); // deregister self, don't wait
159	>	* }}</pre>
160		*
161	<	* <p><b>Sample usage:</b>
161	>	* If the main task must later await termination, it
162	>	* may re-register and then execute a similar loop:
163	>	*  <pre> {@code
164	>	*   // ...
165	>	*   phaser.register();
166	>	*   while (!phaser.isTerminated())
167	>	*     phaser.arriveAndAwaitAdvance();}</pre>
168		*
169	<	* <p>[todo: non-FJ example]
169	>	* <p>Related constructions may be used to await particular phase numbers
170	>	* in contexts where you are sure that the phase will never wrap around
171	>	* {@code Integer.MAX_VALUE}. For example:
172		*
173	<	* <p> A Phaser may be used to support a style of programming in
174	<	* which a task waits for others to complete, without otherwise
175	<	* needing to keep track of which tasks it is waiting for. This is
176	<	* similar to the "sync" construct in Cilk and "clocks" in X10.
177	<	* Special constructions based on such barriers are available using
178	<	* the <tt>LinkedAsyncAction</tt> and <tt>CyclicAction</tt> classes,
179	<	* but they can be useful in other contexts as well.  For a simple
180	<	* (but not very useful) example, here is a variant of Fibonacci:
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();
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	<	*   protected void compute() {
183	<	*     int n = argument;
184	<	*     if (n &lt;= 1)
185	<	*        result = n;
186	<	*     else {
187	<	*        Phaser childBarrier = new Phaser(1);
188	<	*        BarrierFibonacci f1 = new BarrierFibonacci(n - 1, childBarrier);
189	<	*        BarrierFibonacci f2 = new BarrierFibonacci(n - 2, childBarrier);
190	<	*        f1.fork();
191	<	*        f2.fork();
192	<	*        childBarrier.arriveAndAwait();
193	<	*        result = f1.result + f2.result;
182	>	*   phaser.arriveAndDeregister();
183	>	* }}</pre>
184	>	*
185	>	*
186	>	* <p>To create a set of tasks using a tree of phasers,
187	>	* you could use code of the following form, assuming a
188	>	* Task class with a constructor accepting a phaser that
189	>	* it registers with upon construction:
190	>	*
191	>	*  <pre> {@code
192	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
193	>	*   if (hi - lo > TASKS_PER_PHASER) {
194	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
195	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
196	>	*       build(actions, i, j, new Phaser(ph));
197		*     }
198	<	*     parentBarrier.arriveAndDeregister();
198	>	*   } else {
199	>	*     for (int i = lo; i < hi; ++i)
200	>	*       actions[i] = new Task(ph);
201	>	*       // assumes new Task(ph) performs ph.register()
202		*   }
203		* }
204	<	* </pre>
204	>	* // .. initially called, for n tasks via
205	>	* build(new Task[n], 0, n, new Phaser());}</pre>
206	>	*
207	>	* The best value of {@code TASKS_PER_PHASER} depends mainly on
208	>	* expected barrier synchronization rates. A value as low as four may
209	>	* be appropriate for extremely small per-barrier task bodies (thus
210	>	* high rates), or up to hundreds for extremely large ones.
211		*
212		* <p><b>Implementation notes</b>: This implementation restricts the
213	<	* maximum number of parties to 65535. Attempts to register
214	<	* additional parties result in IllegalStateExceptions.
213	>	* maximum number of parties to 65535. Attempts to register additional
214	>	* parties result in {@code IllegalStateException}. However, you can and
215	>	* should create tiered phasers to accommodate arbitrarily large sets
216	>	* of participants.
217	>	*
218	>	* @since 1.7
219	>	* @author Doug Lea
220		*/
221		public class Phaser {
222		/*
223		* This class implements an extension of X10 "clocks".  Thanks to
224	<	* Vijay Saraswat for the idea of applying it to ForkJoinTasks,
225	<	* and to Vivek Sarkar for enhancements to extend functionality.
224	>	* Vijay Saraswat for the idea, and to Vivek Sarkar for
225	>	* enhancements to extend functionality.
226		*/
227
228		/**
229		* Barrier state representation. Conceptually, a barrier contains
230		* four values:
231		*
232	<	* * parties -- the number of parties to wait (16 bits)
233	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
234	<	* * phase -- the generation of the barrier (31 bits)
235	<	* * terminated -- set if barrier is terminated (1 bit)
232	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
233	>	* * parties -- the number of parties to wait              (bits 16-31)
234	>	* * phase -- the generation of the barrier                (bits 32-62)
235	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
236		*
237		* However, to efficiently maintain atomicity, these values are
238	<	* packed into a single AtomicLong. Termination uses the sign bit
239	<	* of 32 bit representation of phase, so phase is set to -1 on
240	<	* termination.
241	<	*/
242	<	private final AtomicLong state;
243	<
244	<	/**
245	<	* Head of Treiber stack for waiting nonFJ threads.
246	<	*/
247	<	private final AtomicReference<QNode> head = new AtomicReference<QNode>();
238	>	* packed into a single (atomic) long. Termination uses the sign
239	>	* bit of 32 bit representation of phase, so phase is set to -1 on
240	>	* termination. Good performance relies on keeping state decoding
241	>	* and encoding simple, and keeping race windows short.
242	>	*/
243	>	private volatile long state;
244	>
245	>	private static final int  MAX_PARTIES     = 0xffff;
246	>	private static final int  MAX_PHASE       = 0x7fffffff;
247	>	private static final int  PARTIES_SHIFT   = 16;
248	>	private static final int  PHASE_SHIFT     = 32;
249	>	private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
250	>	private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
251	>	private static final long ONE_ARRIVAL     = 1L;
252	>	private static final long ONE_PARTY       = 1L << PARTIES_SHIFT;
253	>	private static final long TERMINATION_BIT = 1L << 63;
254
255	<	private static final int ushortBits = 16;
148	<	private static final int ushortMask =  (1 << ushortBits) - 1;
149	<	private static final int phaseMask = 0x7fffffff;
255	>	// The following unpacking methods are usually manually inlined
256
257		private static int unarrivedOf(long s) {
258	<	return (int)(s & ushortMask);
258	>	return (int)s & UNARRIVED_MASK;
259		}
260
261		private static int partiesOf(long s) {
262	<	return (int)(s & (ushortMask << 16)) >>> 16;
262	>	return (int)s >>> PARTIES_SHIFT;
263		}
264
265		private static int phaseOf(long s) {
266	<	return (int)(s >>> 32);
266	>	return (int) (s >>> PHASE_SHIFT);
267		}
268
269		private static int arrivedOf(long s) {
270		return partiesOf(s) - unarrivedOf(s);
271		}
272
273	<	private static long stateFor(int phase, int parties, int unarrived) {
274	<	return (((long)phase) << 32) | ((parties << 16) | unarrived);
275	<	}
273	>	/**
274	>	* The parent of this phaser, or null if none
275	>	*/
276	>	private final Phaser parent;
277
278	<	private static IllegalStateException badBounds(int parties, int unarrived) {
279	<	return new IllegalStateException("Attempt to set " + unarrived +
280	<	" unarrived of " + parties + " parties");
281	<	}
278	>	/**
279	>	* The root of phaser tree. Equals this if not in a tree.  Used to
280	>	* support faster state push-down.
281	>	*/
282	>	private final Phaser root;
283
284		/**
285	<	* Creates a new Phaser without any initially registered parties,
286	<	* and initial phase number 0.
285	>	* Heads of Treiber stacks for waiting threads. To eliminate
286	>	* contention when releasing some threads while adding others, we
287	>	* use two of them, alternating across even and odd phases.
288	>	* Subphasers share queues with root to speed up releases.
289		*/
290	<	public Phaser() {
291	<	state = new AtomicLong(stateFor(0, 0, 0));
290	>	private final AtomicReference<QNode> evenQ;
291	>	private final AtomicReference<QNode> oddQ;
292	>
293	>	private AtomicReference<QNode> queueFor(int phase) {
294	>	return ((phase & 1) == 0) ? evenQ : oddQ;
295		}
296
297		/**
298	<	* Creates a new Phaser with the given numbers of registered
186	<	* unarrived parties and initial phase number 0.
187	<	* @param parties the number of parties required to trip barrier.
188	<	* @throws IllegalArgumentException if parties less than zero
189	<	* or greater than the maximum number of parties supported.
298	>	* Returns message string for bounds exceptions on arrival.
299		*/
300	<	public Phaser(int parties) {
301	<	if (parties < 0 || parties > ushortMask)
302	<	throw new IllegalArgumentException("Illegal number of parties");
194	<	state = new AtomicLong(stateFor(0, parties, parties));
300	>	private String badArrive(long s) {
301	>	return "Attempted arrival of unregistered party for " +
302	>	stateToString(s);
303		}
304
305		/**
306	<	* Adds a new unarrived party to this phaser.
199	<	* @return the current barrier phase number upon registration
200	<	* @throws IllegalStateException if attempting to register more
201	<	* than the maximum supported number of parties.
306	>	* Returns message string for bounds exceptions on registration.
307		*/
308	<	public int register() { // increment both parties and unarrived
309	<	final AtomicLong state = this.state;
310	<	for (;;) {
206	<	long s = state.get();
207	<	int phase = phaseOf(s);
208	<	int parties = partiesOf(s) + 1;
209	<	int unarrived = unarrivedOf(s) + 1;
210	<	if (parties > ushortMask || unarrived > ushortMask)
211	<	throw badBounds(parties, unarrived);
212	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
213	<	return phase;
214	<	}
308	>	private String badRegister(long s) {
309	>	return "Attempt to register more than " +
310	>	MAX_PARTIES + " parties for " + stateToString(s);
311		}
312
313		/**
314	<	* Arrives at the barrier, but does not wait for others.  (You can
315	<	* in turn wait for others via {@link #awaitAdvance}).
314	>	* Main implementation for methods arrive and arriveAndDeregister.
315	>	* Manually tuned to speed up and minimize race windows for the
316	>	* common case of just decrementing unarrived field.
317		*
318	<	* @return the current barrier phase number upon entry to
319	<	* this method, or a negative value if terminated;
320	<	* @throws IllegalStateException if the number of unarrived
224	<	* parties would become negative.
318	>	* @param adj - adjustment to apply to state -- either
319	>	* ONE_ARRIVAL (for arrive) or
320	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
321		*/
322	<	public int arrive() { // decrement unarrived. If zero, trip
227	<	final AtomicLong state = this.state;
322	>	private int doArrive(long adj) {
323		for (;;) {
324	<	long s = state.get();
325	<	int phase = phaseOf(s);
326	<	int parties = partiesOf(s);
327	<	int unarrived = unarrivedOf(s) - 1;
233	<	if (unarrived < 0)
234	<	throw badBounds(parties, unarrived);
235	<	if (unarrived == 0 && phase >= 0) {
236	<	trip(phase, parties);
324	>	long s = state;
325	>	int unarrived = (int)s & UNARRIVED_MASK;
326	>	int phase = (int)(s >>> PHASE_SHIFT);
327	>	if (phase < 0)
328		return phase;
329	+	else if (unarrived == 0) {
330	+	if (reconcileState() == s)     // recheck
331	+	throw new IllegalStateException(badArrive(s));
332		}
333	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
333	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
334	>	if (unarrived == 1) {
335	>	long p = s & PARTIES_MASK; // unshifted parties field
336	>	long lu = p >>> PARTIES_SHIFT;
337	>	int u = (int)lu;
338	>	int nextPhase = (phase + 1) & MAX_PHASE;
339	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
340	>	final Phaser parent = this.parent;
341	>	if (parent == null) {
342	>	if (onAdvance(phase, u))
343	>	next |= TERMINATION_BIT;
344	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
345	>	releaseWaiters(phase);
346	>	}
347	>	else {
348	>	parent.doArrive((u == 0) ?
349	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
350	>	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase ||
351	>	((int)(state >>> PHASE_SHIFT) != nextPhase &&
352	>	!UNSAFE.compareAndSwapLong(this, stateOffset,
353	>	s, next)))
354	>	reconcileState();
355	>	}
356	>	}
357		return phase;
358	+	}
359		}
360		}
361
362		/**
363	<	* Arrives at the barrier, and deregisters from it, without
246	<	* waiting for others.
363	>	* Implementation of register, bulkRegister
364		*
365	<	* @return the current barrier phase number upon entry to
366	<	* this method, or a negative value if terminated;
250	<	* @throws IllegalStateException if the number of registered or
251	<	* unarrived parties would become negative.
365	>	* @param registrations number to add to both parties and
366	>	* unarrived fields. Must be greater than zero.
367		*/
368	<	public int arriveAndDeregister() { // Same as arrive, plus decrement parties
369	<	final AtomicLong state = this.state;
368	>	private int doRegister(int registrations) {
369	>	// adjustment to state
370	>	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
371	>	final Phaser parent = this.parent;
372		for (;;) {
373	<	long s = state.get();
374	<	int phase = phaseOf(s);
375	<	int parties = partiesOf(s) - 1;
376	<	int unarrived = unarrivedOf(s) - 1;
260	<	if (parties < 0 || unarrived < 0)
261	<	throw badBounds(parties, unarrived);
262	<	if (unarrived == 0 && phase >= 0) {
263	<	trip(phase, parties);
373	>	long s = (parent == null) ? state : reconcileState();
374	>	int parties = (int)s >>> PARTIES_SHIFT;
375	>	int phase = (int)(s >>> PHASE_SHIFT);
376	>	if (phase < 0)
377		return phase;
378	+	else if (registrations > MAX_PARTIES - parties)
379	+	throw new IllegalStateException(badRegister(s));
380	+	else if ((parties == 0 && parent == null) || // first reg of root
381	+	((int)s & UNARRIVED_MASK) != 0) {   // not advancing
382	+	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
383	+	return phase;
384	+	}
385	+	else if (parties != 0)               // wait for onAdvance
386	+	internalAwaitAdvance(phase, null);
387	+	else {                               // 1st registration of child
388	+	synchronized(this) {             // register parent first
389	+	if (reconcileState() == s) { // recheck under lock
390	+	parent.doRegister(1);    // OK if throws IllegalState
391	+	for (;;) {               // simpler form of outer loop
392	+	s = reconcileState();
393	+	phase = (int)(s >>> PHASE_SHIFT);
394	+	if (phase < 0 ||
395	+	UNSAFE.compareAndSwapLong(this, stateOffset,
396	+	s, s + adj))
397	+	return phase;
398	+	}
399	+	}
400	+	}
401		}
266	–	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
267	–	return phase;
402		}
403		}
404
405		/**
406	<	* Arrives at the barrier and awaits others. Unlike other arrival
273	<	* methods, this method returns the arrival index of the
274	<	* caller. The caller tripping the barrier returns zero, the
275	<	* previous caller 1, and so on.
276	<	* @return the arrival index
277	<	* @throws IllegalStateException if the number of unarrived
278	<	* parties would become negative.
406	>	* Recursively resolves lagged phase propagation from root if necessary.
407		*/
408	<	public int arriveAndAwaitAdvance() {
409	<	final AtomicLong state = this.state;
410	<	for (;;) {
411	<	long s = state.get();
412	<	int phase = phaseOf(s);
413	<	int parties = partiesOf(s);
414	<	int unarrived = unarrivedOf(s) - 1;
415	<	if (unarrived < 0)
416	<	throw badBounds(parties, unarrived);
417	<	if (unarrived == 0 && phase >= 0) {
418	<	trip(phase, parties);
419	<	return 0;
420	<	}
421	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) {
422	<	awaitAdvance(phase);
423	<	return unarrived;
408	>	private long reconcileState() {
409	>	Phaser par = parent;
410	>	long s = state;
411	>	if (par != null) {
412	>	Phaser rt = root;
413	>	int phase, rPhase;
414	>	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
415	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
416	>	if ((int)(par.state >>> PHASE_SHIFT) != rPhase)
417	>	par.reconcileState();
418	>	else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
419	>	long u = s & PARTIES_MASK; // reset unarrived to parties
420	>	long next = ((((long) rPhase) << PHASE_SHIFT) | u |
421	>	(u >>> PARTIES_SHIFT));
422	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
423	>	}
424	>	s = state;
425		}
426		}
427	+	return s;
428	+	}
429	+
430	+	/**
431	+	* Creates a new phaser without any initially registered parties,
432	+	* initial phase number 0, and no parent. Any thread using this
433	+	* phaser will need to first register for it.
434	+	*/
435	+	public Phaser() {
436	+	this(null, 0);
437	+	}
438	+
439	+	/**
440	+	* Creates a new phaser with the given number of registered
441	+	* unarrived parties, initial phase number 0, and no parent.
442	+	*
443	+	* @param parties the number of parties required to trip barrier
444	+	* @throws IllegalArgumentException if parties less than zero
445	+	* or greater than the maximum number of parties supported
446	+	*/
447	+	public Phaser(int parties) {
448	+	this(null, parties);
449	+	}
450	+
451	+	/**
452	+	* Creates a new phaser with the given parent, and without any
453	+	* initially registered parties.  Any thread using this phaser
454	+	* will need to first register for it, at which point, if the
455	+	* given parent is non-null, this phaser will also be registered
456	+	* with the parent.
457	+	*
458	+	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
459	+	*
460	+	* @param parent the parent phaser
461	+	*/
462	+	public Phaser(Phaser parent) {
463	+	this(parent, 0);
464	+	}
465	+
466	+	/**
467	+	* Creates a new phaser with the given parent and number of
468	+	* registered unarrived parties. If parent is non-null and
469	+	* the number of parties is non-zero, this phaser is registered
470	+	* with the parent.
471	+	*
472	+	* @param parent the parent phaser
473	+	* @param parties the number of parties required to trip barrier
474	+	* @throws IllegalArgumentException if parties less than zero
475	+	* or greater than the maximum number of parties supported
476	+	*/
477	+	public Phaser(Phaser parent, int parties) {
478	+	if (parties >>> PARTIES_SHIFT != 0)
479	+	throw new IllegalArgumentException("Illegal number of parties");
480	+	int phase;
481	+	this.parent = parent;
482	+	if (parent != null) {
483	+	Phaser r = parent.root;
484	+	this.root = r;
485	+	this.evenQ = r.evenQ;
486	+	this.oddQ = r.oddQ;
487	+	phase = (parties == 0) ? parent.getPhase() : parent.doRegister(1);
488	+	}
489	+	else {
490	+	this.root = this;
491	+	this.evenQ = new AtomicReference<QNode>();
492	+	this.oddQ = new AtomicReference<QNode>();
493	+	phase = 0;
494	+	}
495	+	long p = (long)parties;
496	+	this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
497		}
498
499		/**
500	<	* Awaits the phase of the barrier to advance from the given
501	<	* value, or returns immediately if this barrier is terminated.
502	<	* @param phase the phase on entry to this method
503	<	* @return the phase on exit from this method
500	>	* Adds a new unarrived party to this phaser.  If an ongoing
501	>	* invocation of {@link #onAdvance} is in progress, this method
502	>	* may wait until its completion before registering.  If this
503	>	* phaser has a parent, and this phaser previously had no
504	>	* registered parties, this phaser is also registered with its
505	>	* parent.
506	>	*
507	>	* @return the arrival phase number to which this registration applied
508	>	* @throws IllegalStateException if attempting to register more
509	>	* than the maximum supported number of parties
510	>	*/
511	>	public int register() {
512	>	return doRegister(1);
513	>	}
514	>
515	>	/**
516	>	* Adds the given number of new unarrived parties to this phaser.
517	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
518	>	* this method may wait until its completion before registering.
519	>	* If this phaser has a parent, and the given number of parities
520	>	* is greater than zero, and this phaser previously had no
521	>	* registered parties, this phaser is also registered with its
522	>	* parent.
523	>	*
524	>	* @param parties the number of additional parties required to trip barrier
525	>	* @return the arrival phase number to which this registration applied
526	>	* @throws IllegalStateException if attempting to register more
527	>	* than the maximum supported number of parties
528	>	* @throws IllegalArgumentException if {@code parties < 0}
529	>	*/
530	>	public int bulkRegister(int parties) {
531	>	if (parties < 0)
532	>	throw new IllegalArgumentException();
533	>	else if (parties == 0)
534	>	return getPhase();
535	>	return doRegister(parties);
536	>	}
537	>
538	>	/**
539	>	* Arrives at the barrier, but does not wait for others.  (You can
540	>	* in turn wait for others via {@link #awaitAdvance}).  It is a
541	>	* usage error for an unregistered party to invoke this
542	>	* method. However, it is possible that this error will result in
543	>	* an {code IllegalStateException} only when some <em>other</em>
544	>	* party arrives.
545	>	*
546	>	* @return the arrival phase number, or a negative value if terminated
547	>	* @throws IllegalStateException if not terminated and the number
548	>	* of unarrived parties would become negative
549	>	*/
550	>	public int arrive() {
551	>	return doArrive(ONE_ARRIVAL);
552	>	}
553	>
554	>	/**
555	>	* Arrives at the barrier and deregisters from it without waiting
556	>	* for others. Deregistration reduces the number of parties
557	>	* required to trip the barrier in future phases.  If this phaser
558	>	* has a parent, and deregistration causes this phaser to have
559	>	* zero parties, this phaser also arrives at and is deregistered
560	>	* from its parent.  It is a usage error for an unregistered party
561	>	* to invoke this method. However, it is possible that this error
562	>	* will result in an {code IllegalStateException} only when some
563	>	* <em>other</em> party arrives.
564	>	*
565	>	* @return the arrival phase number, or a negative value if terminated
566	>	* @throws IllegalStateException if not terminated and the number
567	>	* of registered or unarrived parties would become negative
568	>	*/
569	>	public int arriveAndDeregister() {
570	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
571	>	}
572	>
573	>	/**
574	>	* Arrives at the barrier and awaits others. Equivalent in effect
575	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
576	>	* interruption or timeout, you can arrange this with an analogous
577	>	* construction using one of the other forms of the {@code
578	>	* awaitAdvance} method.  If instead you need to deregister upon
579	>	* arrival, use {@link #arriveAndDeregister}.  It is a usage error
580	>	* for an unregistered party to invoke this method. However, it is
581	>	* possible that this error will result in an {code
582	>	* IllegalStateException} only when some <em>other</em> party
583	>	* arrives.
584	>	*
585	>	* @return the arrival phase number, or a negative number if terminated
586	>	* @throws IllegalStateException if not terminated and the number
587	>	* of unarrived parties would become negative
588	>	*/
589	>	public int arriveAndAwaitAdvance() {
590	>	return awaitAdvance(arrive());
591	>	}
592	>
593	>	/**
594	>	* Awaits the phase of the barrier to advance from the given phase
595	>	* value, returning immediately if the current phase of the
596	>	* barrier is not equal to the given phase value or this barrier
597	>	* is terminated.
598	>	*
599	>	* @param phase an arrival phase number, or negative value if
600	>	* terminated; this argument is normally the value returned by a
601	>	* previous call to {@code arrive} or its variants
602	>	* @return the next arrival phase number, or a negative value
603	>	* if terminated or argument is negative
604		*/
605		public int awaitAdvance(int phase) {
606		if (phase < 0)
607		return phase;
608	<	Thread current = Thread.currentThread();
609	<	if (current instanceof ForkJoinWorkerThread)
610	<	return helpingWait(phase);
312	<	if (untimedWait(current, phase, false))
313	<	current.interrupt();
314	<	return phaseOf(state.get());
608	>	long s = (parent == null) ? state : reconcileState();
609	>	int p = (int)(s >>> PHASE_SHIFT);
610	>	return (p != phase) ? p : internalAwaitAdvance(phase, null);
611		}
612
613		/**
614	<	* Awaits the phase of the barrier to advance from the given
615	<	* value, or returns immediately if this barrier is terminated, or
616	<	* throws InterruptedException if interrupted while waiting.
617	<	* @param phase the phase on entry to this method
618	<	* @return the phase on exit from this method
614	>	* Awaits the phase of the barrier to advance from the given phase
615	>	* value, throwing {@code InterruptedException} if interrupted
616	>	* while waiting, or returning immediately if the current phase of
617	>	* the barrier is not equal to the given phase value or this
618	>	* barrier is terminated.
619	>	*
620	>	* @param phase an arrival phase number, or negative value if
621	>	* terminated; this argument is normally the value returned by a
622	>	* previous call to {@code arrive} or its variants
623	>	* @return the next arrival phase number, or a negative value
624	>	* if terminated or argument is negative
625		* @throws InterruptedException if thread interrupted while waiting
626		*/
627	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
627	>	public int awaitAdvanceInterruptibly(int phase)
628	>	throws InterruptedException {
629		if (phase < 0)
630		return phase;
631	<	Thread current = Thread.currentThread();
632	<	if (current instanceof ForkJoinWorkerThread)
633	<	return helpingWait(phase);
634	<	else if (Thread.interrupted() || untimedWait(current, phase, true))
635	<	throw new InterruptedException();
636	<	else
637	<	return phaseOf(state.get());
631	>	long s = (parent == null) ? state : reconcileState();
632	>	int p = (int)(s >>> PHASE_SHIFT);
633	>	if (p == phase) {
634	>	QNode node = new QNode(this, phase, true, false, 0L);
635	>	p = internalAwaitAdvance(phase, node);
636	>	if (node.wasInterrupted)
637	>	throw new InterruptedException();
638	>	}
639	>	return p;
640		}
641
642		/**
643	<	* Awaits the phase of the barrier to advance from the given value
644	<	* or the given timeout elapses, or returns immediately if this
645	<	* barrier is terminated.
646	<	* @param phase the phase on entry to this method
647	<	* @return the phase on exit from this method
643	>	* Awaits the phase of the barrier to advance from the given phase
644	>	* value or the given timeout to elapse, throwing {@code
645	>	* InterruptedException} if interrupted while waiting, or
646	>	* returning immediately if the current phase of the barrier is
647	>	* not equal to the given phase value or this barrier is
648	>	* terminated.
649	>	*
650	>	* @param phase an arrival phase number, or negative value if
651	>	* terminated; this argument is normally the value returned by a
652	>	* previous call to {@code arrive} or its variants
653	>	* @param timeout how long to wait before giving up, in units of
654	>	*        {@code unit}
655	>	* @param unit a {@code TimeUnit} determining how to interpret the
656	>	*        {@code timeout} parameter
657	>	* @return the next arrival phase number, or a negative value
658	>	* if terminated or argument is negative
659		* @throws InterruptedException if thread interrupted while waiting
660		* @throws TimeoutException if timed out while waiting
661		*/
662	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
662	>	public int awaitAdvanceInterruptibly(int phase,
663	>	long timeout, TimeUnit unit)
664		throws InterruptedException, TimeoutException {
665		if (phase < 0)
666		return phase;
667	<	long nanos = unit.toNanos(timeout);
668	<	Thread current = Thread.currentThread();
669	<	if (current instanceof ForkJoinWorkerThread)
670	<	return timedHelpingWait(phase, nanos);
671	<	timedWait(current, phase, nanos);
672	<	return phaseOf(state.get());
667	>	long s = (parent == null) ? state : reconcileState();
668	>	int p = (int)(s >>> PHASE_SHIFT);
669	>	if (p == phase) {
670	>	long nanos = unit.toNanos(timeout);
671	>	QNode node = new QNode(this, phase, true, true, nanos);
672	>	p = internalAwaitAdvance(phase, node);
673	>	if (node.wasInterrupted)
674	>	throw new InterruptedException();
675	>	else if (p == phase)
676	>	throw new TimeoutException();
677	>	}
678	>	return p;
679		}
680
681		/**
682	<	* Forces this barrier to enter termination state. Counts of
683	<	* arrived and registered parties are unaffected. This method may
684	<	* be useful for coordinating recovery after one or more tasks
682	>	* Forces this barrier to enter termination state.  Counts of
683	>	* arrived and registered parties are unaffected.  If this phaser
684	>	* is a member of a tiered set of phasers, then all of the phasers
685	>	* in the set are terminated.  If this phaser is already
686	>	* terminated, this method has no effect.  This method may be
687	>	* useful for coordinating recovery after one or more tasks
688		* encounter unexpected exceptions.
689		*/
690		public void forceTermination() {
691	<	final AtomicLong state = this.state;
692	<	for (;;) {
693	<	long s = state.get();
694	<	int phase = phaseOf(s);
695	<	int parties = partiesOf(s);
696	<	int unarrived = unarrivedOf(s);
697	<	if (phase < 0 ||
698	<	state.compareAndSet(s, stateFor(-1, parties, unarrived))) {
373	<	if (head.get() != null)
374	<	releaseWaiters(-1);
691	>	// Only need to change root state
692	>	final Phaser root = this.root;
693	>	long s;
694	>	while ((s = root.state) >= 0) {
695	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
696	>	s, s | TERMINATION_BIT)) {
697	>	releaseWaiters(0); // signal all threads
698	>	releaseWaiters(1);
699		return;
700		}
701		}
702		}
703
704		/**
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	–	/**
705		* Returns the current phase number. The maximum phase number is
706	<	* <tt>Integer.MAX_VALUE</tt>, after which it restarts at
706	>	* {@code Integer.MAX_VALUE}, after which it restarts at
707		* zero. Upon termination, the phase number is negative.
708	+	*
709		* @return the phase number, or a negative value if terminated
710		*/
711	<	public int getPhase() {
712	<	return phaseOf(state.get());
711	>	public final int getPhase() {
712	>	return (int)(root.state >>> PHASE_SHIFT);
713		}
714
715		/**
716		* Returns the number of parties registered at this barrier.
717	+	*
718		* @return the number of parties
719		*/
720		public int getRegisteredParties() {
721	<	return partiesOf(state.get());
721	>	return partiesOf(state);
722		}
723
724		/**
725	<	* Returns the number of parties that have arrived at the current
726	<	* phase of this barrier.
725	>	* Returns the number of registered parties that have arrived at
726	>	* the current phase of this barrier.
727	>	*
728		* @return the number of arrived parties
729		*/
730		public int getArrivedParties() {
731	<	return arrivedOf(state.get());
731	>	return arrivedOf(parent==null? state : reconcileState());
732		}
733
734		/**
735		* Returns the number of registered parties that have not yet
736		* arrived at the current phase of this barrier.
737	+	*
738		* @return the number of unarrived parties
739		*/
740		public int getUnarrivedParties() {
741	<	return unarrivedOf(state.get());
741	>	return unarrivedOf(parent==null? state : reconcileState());
742	>	}
743	>
744	>	/**
745	>	* Returns the parent of this phaser, or {@code null} if none.
746	>	*
747	>	* @return the parent of this phaser, or {@code null} if none
748	>	*/
749	>	public Phaser getParent() {
750	>	return parent;
751		}
752
753		/**
754	<	* Returns true if this barrier has been terminated.
755	<	* @return true if this barrier has been terminated
754	>	* Returns the root ancestor of this phaser, which is the same as
755	>	* this phaser if it has no parent.
756	>	*
757	>	* @return the root ancestor of this phaser
758	>	*/
759	>	public Phaser getRoot() {
760	>	return root;
761	>	}
762	>
763	>	/**
764	>	* Returns {@code true} if this barrier has been terminated.
765	>	*
766	>	* @return {@code true} if this barrier has been terminated
767		*/
768		public boolean isTerminated() {
769	<	return phaseOf(state.get()) < 0;
769	>	return root.state < 0L;
770		}
771
772		/**
773	<	* Overridable method to perform an action upon phase advance, and
774	<	* to control termination. This method is invoked whenever the
775	<	* barrier is tripped (and thus all other waiting parties are
776	<	* dormant). If it returns true, then, rather than advance the
777	<	* phase number, this barrier will be set to a final termination
778	<	* state, and subsequent calls to <tt>isTerminated</tt> will
779	<	* return true.
780	<	*
781	<	* <p> The default version returns true when the number of
782	<	* registered parties is zero. Normally, overrides that arrange
783	<	* termination for other reasons should also preserve this
784	<	* property.
773	>	* Overridable method to perform an action upon impending phase
774	>	* advance, and to control termination. This method is invoked
775	>	* upon arrival of the party tripping the barrier (when all other
776	>	* waiting parties are dormant).  If this method returns {@code
777	>	* true}, then, rather than advance the phase number, this barrier
778	>	* will be set to a final termination state, and subsequent calls
779	>	* to {@link #isTerminated} will return true. Any (unchecked)
780	>	* Exception or Error thrown by an invocation of this method is
781	>	* propagated to the party attempting to trip the barrier, in
782	>	* which case no advance occurs.
783	>	*
784	>	* <p>The arguments to this method provide the state of the phaser
785	>	* prevailing for the current transition.  The effects of invoking
786	>	* arrival, registration, and waiting methods on this Phaser from
787	>	* within {@code onAdvance} are unspecified and should not be
788	>	* relied on.
789	>	*
790	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
791	>	* {@code onAdvance} is invoked only for its root Phaser on each
792	>	* advance.
793	>	*
794	>	* <p>To support the most common use cases, the default
795	>	* implementation of this method returns {@code true} when the
796	>	* number of registered parties has become zero as the result of a
797	>	* party invoking {@code arriveAndDeregister}.  You can disable
798	>	* this behavior, thus enabling continuation upon future
799	>	* registrations, by overriding this method to always return
800	>	* {@code false}:
801	>	*
802	>	* <pre> {@code
803	>	* Phaser phaser = new Phaser() {
804	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
805	>	* }}</pre>
806		*
807		* @param phase the phase number on entering the barrier
808	<	* @param registeredParties the current number of registered
809	<	* parties.
458	<	* @return true if this barrier should terminate
808	>	* @param registeredParties the current number of registered parties
809	>	* @return {@code true} if this barrier should terminate
810		*/
811		protected boolean onAdvance(int phase, int registeredParties) {
812		return registeredParties <= 0;
813		}
814
815		/**
816	<	* Returns a string identifying this barrier, as well as its
816	>	* Returns a string identifying this phaser, as well as its
817		* state.  The state, in brackets, includes the String {@code
818	<	* "phase ="} followed by the phase number, {@code "parties ="}
818	>	* "phase = "} followed by the phase number, {@code "parties = "}
819		* followed by the number of registered parties, and {@code
820	<	* "arrived ="} followed by the number of arrived parties
820	>	* "arrived = "} followed by the number of arrived parties.
821		*
822		* @return a string identifying this barrier, as well as its state
823		*/
824		public String toString() {
825	<	long s = state.get();
475	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
825	>	return stateToString(reconcileState());
826		}
827
478	–	// methods for tripping and waiting
479	–
828		/**
829	<	* Advance the current phase (or terminate)
829	>	* Implementation of toString and string-based error messages
830		*/
831	<	private void trip(int phase, int parties) {
832	<	int next = onAdvance(phase, parties)? -1 : ((phase + 1) & phaseMask);
833	<	state.set(stateFor(next, parties, parties));
834	<	if (head.get() != null)
835	<	releaseWaiters(next);
831	>	private String stateToString(long s) {
832	>	return super.toString() +
833	>	"[phase = " + phaseOf(s) +
834	>	" parties = " + partiesOf(s) +
835	>	" arrived = " + arrivedOf(s) + "]";
836		}
837
838	<	private int helpingWait(int phase) {
839	<	final AtomicLong state = this.state;
838	>	// Waiting mechanics
839	>
840	>	/**
841	>	* Removes and signals threads from queue for phase.
842	>	*/
843	>	private void releaseWaiters(int phase) {
844	>	AtomicReference<QNode> head = queueFor(phase);
845	>	QNode q;
846		int p;
847	<	while ((p = phaseOf(state.get())) == phase) {
848	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
849	<	if (t != null) {
850	<	if ((p = phaseOf(state.get())) == phase)
851	<	t.exec();
498	<	else {   // push task and exit if barrier advanced
499	<	t.fork();
500	<	break;
501	<	}
502	<	}
847	>	while ((q = head.get()) != null &&
848	>	((p = q.phase) == phase ||
849	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
850	>	if (head.compareAndSet(q, q.next))
851	>	q.signal();
852		}
504	–	return p;
853		}
854
855	<	private int timedHelpingWait(int phase, long nanos) throws TimeoutException {
856	<	final AtomicLong state = this.state;
857	<	long lastTime = System.nanoTime();
855	>	/** The number of CPUs, for spin control */
856	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
857	>
858	>	/**
859	>	* The number of times to spin before blocking while waiting for
860	>	* advance, per arrival while waiting. On multiprocessors, fully
861	>	* blocking and waking up a large number of threads all at once is
862	>	* usually a very slow process, so we use rechargeable spins to
863	>	* avoid it when threads regularly arrive: When a thread in
864	>	* internalAwaitAdvance notices another arrival before blocking,
865	>	* and there appear to be enough CPUs available, it spins
866	>	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
867	>	* uniprocessors, there is at least one intervening Thread.yield
868	>	* before blocking. The value trades off good-citizenship vs big
869	>	* unnecessary slowdowns.
870	>	*/
871	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
872	>
873	>	/**
874	>	* Possibly blocks and waits for phase to advance unless aborted.
875	>	*
876	>	* @param phase current phase
877	>	* @param node if non-null, the wait node to track interrupt and timeout;
878	>	* if null, denotes noninterruptible wait
879	>	* @return current phase
880	>	*/
881	>	private int internalAwaitAdvance(int phase, QNode node) {
882	>	Phaser current = this;       // to eventually wait at root if tiered
883	>	boolean queued = false;      // true when node is enqueued
884	>	int lastUnarrived = -1;      // to increase spins upon change
885	>	int spins = SPINS_PER_ARRIVAL;
886	>	long s;
887		int p;
888	<	while ((p = phaseOf(state.get())) == phase) {
889	<	long now = System.nanoTime();
890	<	nanos -= now - lastTime;
891	<	lastTime = now;
892	<	if (nanos <= 0) {
893	<	if ((p = phaseOf(state.get())) == phase)
894	<	throw new TimeoutException();
895	<	else
519	<	break;
888	>	while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) {
889	>	Phaser par;
890	>	int unarrived = (int)s & UNARRIVED_MASK;
891	>	if (unarrived != lastUnarrived) {
892	>	if (lastUnarrived == -1) // ensure old queue clean
893	>	releaseWaiters(phase-1);
894	>	if ((lastUnarrived = unarrived) < NCPU)
895	>	spins += SPINS_PER_ARRIVAL;
896		}
897	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
898	<	if (t != null) {
899	<	if ((p = phaseOf(state.get())) == phase)
900	<	t.exec();
901	<	else {   // push task and exit if barrier advanced
902	<	t.fork();
897	>	else if (unarrived == 0 && (par = current.parent) != null) {
898	>	current = par;       // if all arrived, use parent
899	>	par = par.parent;
900	>	lastUnarrived = -1;
901	>	}
902	>	else if (spins > 0) {
903	>	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
904	>	Thread.yield();  // yield midway through spin
905	>	}
906	>	else if (node == null)   // must be noninterruptible
907	>	node = new QNode(this, phase, false, false, 0L);
908	>	else if (node.isReleasable()) {
909	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
910		break;
911	+	else
912	+	return phase;    // aborted
913	+	}
914	+	else if (!queued) {      // push onto queue
915	+	AtomicReference<QNode> head = queueFor(phase);
916	+	QNode q = head.get();
917	+	if (q == null || q.phase == phase) {
918	+	node.next = q;
919	+	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
920	+	break;       // recheck to avoid stale enqueue
921	+	else
922	+	queued = head.compareAndSet(q, node);
923	+	}
924	+	}
925	+	else {
926	+	try {
927	+	ForkJoinPool.managedBlock(node);
928	+	} catch (InterruptedException ie) {
929	+	node.wasInterrupted = true;
930		}
931		}
932		}
933	+	releaseWaiters(phase);
934	+	if (node != null)
935	+	node.onRelease();
936		return p;
937		}
938
939		/**
940	<	* 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.
940	>	* Wait nodes for Treiber stack representing wait queue
941		*/
942	<	static final class QNode {
943	<	QNode next;
541	<	volatile Thread thread; // nulled to cancel wait
942	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
943	>	final Phaser phaser;
944		final int phase;
945	<	QNode(Thread t, int c) {
946	<	thread = t;
947	<	phase = c;
945	>	final boolean interruptible;
946	>	final boolean timed;
947	>	boolean wasInterrupted;
948	>	long nanos;
949	>	long lastTime;
950	>	volatile Thread thread; // nulled to cancel wait
951	>	QNode next;
952	>
953	>	QNode(Phaser phaser, int phase, boolean interruptible,
954	>	boolean timed, long nanos) {
955	>	this.phaser = phaser;
956	>	this.phase = phase;
957	>	this.interruptible = interruptible;
958	>	this.nanos = nanos;
959	>	this.timed = timed;
960	>	this.lastTime = timed? System.nanoTime() : 0L;
961	>	thread = Thread.currentThread();
962		}
547	–	}
963
964	<	private void releaseWaiters(int currentPhase) {
965	<	final AtomicReference<QNode> head = this.head;
966	<	QNode p;
967	<	while ((p = head.get()) != null && p.phase != currentPhase) {
968	<	if (head.compareAndSet(p, null)) {
969	<	do {
970	<	Thread t = p.thread;
971	<	if (t != null) {
972	<	p.thread = null;
973	<	LockSupport.unpark(t);
964	>	public boolean isReleasable() {
965	>	Thread t = thread;
966	>	if (t != null) {
967	>	if (phaser.getPhase() != phase)
968	>	t = null;
969	>	else {
970	>	if (Thread.interrupted())
971	>	wasInterrupted = true;
972	>	if (interruptible && wasInterrupted)
973	>	t = null;
974	>	else if (timed) {
975	>	if (nanos > 0) {
976	>	long now = System.nanoTime();
977	>	nanos -= now - lastTime;
978	>	lastTime = now;
979	>	}
980	>	if (nanos <= 0)
981	>	t = null;
982		}
983	<	} while ((p = p.next) != null);
983	>	}
984	>	if (t != null)
985	>	return false;
986	>	thread = null;
987		}
988	+	return true;
989		}
563	–	}
990
991	<	/** The number of CPUs, for spin control */
992	<	static final int NCPUS = Runtime.getRuntime().availableProcessors();
991	>	public boolean block() {
992	>	if (isReleasable())
993	>	return true;
994	>	else if (!timed)
995	>	LockSupport.park(this);
996	>	else if (nanos > 0)
997	>	LockSupport.parkNanos(this, nanos);
998	>	return isReleasable();
999	>	}
1000
1001	<	/**
1002	<	* The number of times to spin before blocking in timed waits.
1003	<	* The value is empirically derived.
1004	<	*/
1005	<	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
1001	>	void signal() {
1002	>	Thread t = thread;
1003	>	if (t != null) {
1004	>	thread = null;
1005	>	LockSupport.unpark(t);
1006	>	}
1007	>	}
1008
1009	<	/**
1010	<	* The number of times to spin before blocking in untimed waits.
1011	<	* This is greater than timed value because untimed waits spin
1012	<	* faster since they don't need to check times on each spin.
1013	<	*/
1014	<	static final int maxUntimedSpins = maxTimedSpins * 32;
1009	>	void onRelease() { // actions upon return from internalAwaitAdvance
1010	>	if (!interruptible && wasInterrupted)
1011	>	Thread.currentThread().interrupt();
1012	>	if (thread != null)
1013	>	thread = null;
1014	>	}
1015
1016	<	/**
582	<	* The number of nanoseconds for which it is faster to spin
583	<	* rather than to use timed park. A rough estimate suffices.
584	<	*/
585	<	static final long spinForTimeoutThreshold = 1000L;
1016	>	}
1017
1018	<	/**
1019	<	* Enqueues node and waits unless aborted or signalled.
1020	<	*/
1021	<	private boolean untimedWait(Thread thread, int currentPhase,
1022	<	boolean abortOnInterrupt) {
1023	<	final AtomicReference<QNode> head = this.head;
1024	<	final AtomicLong state = this.state;
1025	<	boolean wasInterrupted = false;
1026	<	QNode node = null;
1027	<	boolean queued = false;
1028	<	int spins = maxUntimedSpins;
1029	<	while (phaseOf(state.get()) == currentPhase) {
1030	<	QNode h;
1031	<	if (node != null && queued) {
601	<	if (node.thread != null) {
602	<	LockSupport.park();
603	<	if (Thread.interrupted()) {
604	<	wasInterrupted = true;
605	<	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);
627	<	else
628	<	--spins;
1018	>	// Unsafe mechanics
1019	>
1020	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1021	>	private static final long stateOffset =
1022	>	objectFieldOffset("state", Phaser.class);
1023	>
1024	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1025	>	try {
1026	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1027	>	} catch (NoSuchFieldException e) {
1028	>	// Convert Exception to corresponding Error
1029	>	NoSuchFieldError error = new NoSuchFieldError(field);
1030	>	error.initCause(e);
1031	>	throw error;
1032		}
630	–	if (node != null)
631	–	node.thread = null;
632	–	return wasInterrupted;
1033		}
1034
1035		/**
1036	<	* Messier timeout version
1036	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1037	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1038	>	* into a jdk.
1039	>	*
1040	>	* @return a sun.misc.Unsafe
1041		*/
1042	<	private void timedWait(Thread thread, int currentPhase, long nanos)
1043	<	throws InterruptedException, TimeoutException {
1044	<	final AtomicReference<QNode> head = this.head;
1045	<	final AtomicLong state = this.state;
1046	<	long lastTime = System.nanoTime();
1047	<	QNode node = null;
1048	<	boolean queued = false;
1049	<	int spins = maxTimedSpins;
1050	<	while (phaseOf(state.get()) == currentPhase) {
1051	<	QNode h;
1052	<	long now = System.nanoTime();
1053	<	nanos -= now - lastTime;
1054	<	lastTime = now;
1055	<	if (nanos <= 0) {
1056	<	if (node != null)
1057	<	node.thread = null;
1058	<	if (phaseOf(state.get()) == currentPhase)
655	<	throw new TimeoutException();
656	<	else
657	<	break;
1042	>	private static sun.misc.Unsafe getUnsafe() {
1043	>	try {
1044	>	return sun.misc.Unsafe.getUnsafe();
1045	>	} catch (SecurityException se) {
1046	>	try {
1047	>	return java.security.AccessController.doPrivileged
1048	>	(new java.security
1049	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1050	>	public sun.misc.Unsafe run() throws Exception {
1051	>	java.lang.reflect.Field f = sun.misc
1052	>	.Unsafe.class.getDeclaredField("theUnsafe");
1053	>	f.setAccessible(true);
1054	>	return (sun.misc.Unsafe) f.get(null);
1055	>	}});
1056	>	} catch (java.security.PrivilegedActionException e) {
1057	>	throw new RuntimeException("Could not initialize intrinsics",
1058	>	e.getCause());
1059		}
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;
1060		}
690	–	if (node != null)
691	–	node.thread = null;
1061		}
693	–
1062		}

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