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Revision 1.1 by dl, Mon Jul 7 16:53:30 2008 UTC vs.
Revision 1.79 by jsr166, Wed Jan 9 02:51:37 2013 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
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 phaser has an associated phase number. The phase
38	>	* number starts at zero, and advances when all parties arrive at the
39	>	* phaser, 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 phaser 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.  These methods
49	>	*       do not block, but return an associated <em>arrival phase
50	>	*       number</em>; that is, the phase number of the phaser to which
51	>	*       the arrival applied. When the final party for a given phase
52	>	*       arrives, an optional action is performed and the phase
53	>	*       advances.  These actions are performed by the party
54	>	*       triggering a phase advance, and are arranged by overriding
55	>	*       method {@link #onAdvance(int, int)}, which also controls
56	>	*       termination. Overriding this method is similar to, but more
57	>	*       flexible than, providing a barrier action to a {@code
58	>	*       CyclicBarrier}.
59	>	*
60	>	*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
61	>	*       argument indicating an arrival phase number, and returns when
62	>	*       the phaser 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 phaser. 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 phaser may enter a <em>termination</em>
78	+	* state, that may be checked using method {@link #isTerminated}. Upon
79	+	* termination, all synchronization methods immediately return without
80	+	* waiting for advance, as indicated by a negative return value.
81	+	* Similarly, attempts to register upon termination have no effect.
82	+	* Termination is triggered when an invocation of {@code onAdvance}
83	+	* returns {@code true}. The default implementation returns {@code
84	+	* true} if a deregistration has caused the number of registered
85	+	* parties to become zero.  As illustrated below, when phasers control
86	+	* actions with a fixed number of iterations, it is often convenient
87	+	* to override this method to cause termination when the current phase
88	+	* number reaches a threshold. Method {@link #forceTermination} is
89	+	* also available to abruptly release waiting threads and allow them
90	+	* to terminate.
91		*
92	<	* <li> Barrier actions, performed by the task triggering a phase
93	<	* advance while others may be waiting, are arranged by overriding
94	<	* method <tt>onAdvance</tt>, that also controls termination.
95	<	*
96	<	* <li> Phasers may enter a <em>termination</em> state in which all
97	<	* await actions immediately return, indicating (via a negative phase
98	<	* 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.
92	>	* <p><b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
93	>	* constructed in tree structures) to reduce contention. Phasers with
94	>	* large numbers of parties that would otherwise experience heavy
95	>	* synchronization contention costs may instead be set up so that
96	>	* groups of sub-phasers share a common parent.  This may greatly
97	>	* increase throughput even though it incurs greater per-operation
98	>	* overhead.
99		*
100	<	* </ul>
100	>	* <p>In a tree of tiered phasers, registration and deregistration of
101	>	* child phasers with their parent are managed automatically.
102	>	* Whenever the number of registered parties of a child phaser becomes
103	>	* non-zero (as established in the {@link #Phaser(Phaser,int)}
104	>	* constructor, {@link #register}, or {@link #bulkRegister}), the
105	>	* child phaser is registered with its parent.  Whenever the number of
106	>	* registered parties becomes zero as the result of an invocation of
107	>	* {@link #arriveAndDeregister}, the child phaser is deregistered
108	>	* from its parent.
109	>	*
110	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
111	>	* only by registered parties, the current state of a phaser may be
112	>	* monitored by any caller.  At any given moment there are {@link
113	>	* #getRegisteredParties} parties in total, of which {@link
114	>	* #getArrivedParties} have arrived at the current phase ({@link
115	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
116	>	* parties arrive, the phase advances.  The values returned by these
117	>	* methods may reflect transient states and so are not in general
118	>	* useful for synchronization control.  Method {@link #toString}
119	>	* returns snapshots of these state queries in a form convenient for
120	>	* informal monitoring.
121		*
122	<	* <p><b>Sample usage:</b>
122	>	* <p><b>Sample usages:</b>
123		*
124	<	* <p>[todo: non-FJ example]
124	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
125	>	* to control a one-shot action serving a variable number of parties.
126	>	* The typical idiom is for the method setting this up to first
127	>	* register, then start the actions, then deregister, as in:
128		*
129	<	* <p> A Phaser may be used to support a style of programming in
130	<	* which a task waits for others to complete, without otherwise
131	<	* needing to keep track of which tasks it is waiting for. This is
132	<	* similar to the "sync" construct in Cilk and "clocks" in X10.
133	<	* Special constructions based on such barriers are available using
134	<	* the <tt>LinkedAsyncAction</tt> and <tt>CyclicAction</tt> classes,
135	<	* but they can be useful in other contexts as well.  For a simple
136	<	* (but not very useful) example, here is a variant of Fibonacci:
137	<	*
138	<	* <pre>
139	<	* class BarrierFibonacci extends RecursiveAction {
140	<	*   int argument, result;
91	<	*   final Phaser parentBarrier;
92	<	*   BarrierFibonacci(int n, Phaser parentBarrier) {
93	<	*     this.argument = n;
94	<	*     this.parentBarrier = parentBarrier;
95	<	*     parentBarrier.register();
129	>	*  <pre> {@code
130	>	* void runTasks(List<Runnable> tasks) {
131	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
132	>	*   // create and start threads
133	>	*   for (final Runnable task : tasks) {
134	>	*     phaser.register();
135	>	*     new Thread() {
136	>	*       public void run() {
137	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
138	>	*         task.run();
139	>	*       }
140	>	*     }.start();
141		*   }
142	<	*   protected void compute() {
143	<	*     int n = argument;
144	<	*     if (n &lt;= 1)
145	<	*        result = n;
146	<	*     else {
147	<	*        Phaser childBarrier = new Phaser(1);
148	<	*        BarrierFibonacci f1 = new BarrierFibonacci(n - 1, childBarrier);
149	<	*        BarrierFibonacci f2 = new BarrierFibonacci(n - 2, childBarrier);
150	<	*        f1.fork();
151	<	*        f2.fork();
152	<	*        childBarrier.arriveAndAwait();
153	<	*        result = f1.result + f2.result;
142	>	*
143	>	*   // allow threads to start and deregister self
144	>	*   phaser.arriveAndDeregister();
145	>	* }}</pre>
146	>	*
147	>	* <p>One way to cause a set of threads to repeatedly perform actions
148	>	* for a given number of iterations is to override {@code onAdvance}:
149	>	*
150	>	*  <pre> {@code
151	>	* void startTasks(List<Runnable> tasks, final int iterations) {
152	>	*   final Phaser phaser = new Phaser() {
153	>	*     protected boolean onAdvance(int phase, int registeredParties) {
154	>	*       return phase >= iterations || registeredParties == 0;
155		*     }
156	<	*     parentBarrier.arriveAndDeregister();
156	>	*   };
157	>	*   phaser.register();
158	>	*   for (final Runnable task : tasks) {
159	>	*     phaser.register();
160	>	*     new Thread() {
161	>	*       public void run() {
162	>	*         do {
163	>	*           task.run();
164	>	*           phaser.arriveAndAwaitAdvance();
165	>	*         } while (!phaser.isTerminated());
166	>	*       }
167	>	*     }.start();
168		*   }
169	<	* }
170	<	* </pre>
169	>	*   phaser.arriveAndDeregister(); // deregister self, don't wait
170	>	* }}</pre>
171	>	*
172	>	* If the main task must later await termination, it
173	>	* may re-register and then execute a similar loop:
174	>	*  <pre> {@code
175	>	*   // ...
176	>	*   phaser.register();
177	>	*   while (!phaser.isTerminated())
178	>	*     phaser.arriveAndAwaitAdvance();}</pre>
179	>	*
180	>	* <p>Related constructions may be used to await particular phase numbers
181	>	* in contexts where you are sure that the phase will never wrap around
182	>	* {@code Integer.MAX_VALUE}. For example:
183	>	*
184	>	*  <pre> {@code
185	>	* void awaitPhase(Phaser phaser, int phase) {
186	>	*   int p = phaser.register(); // assumes caller not already registered
187	>	*   while (p < phase) {
188	>	*     if (phaser.isTerminated())
189	>	*       // ... deal with unexpected termination
190	>	*     else
191	>	*       p = phaser.arriveAndAwaitAdvance();
192	>	*   }
193	>	*   phaser.arriveAndDeregister();
194	>	* }}</pre>
195	>	*
196	>	*
197	>	* <p>To create a set of {@code n} tasks using a tree of phasers, you
198	>	* could use code of the following form, assuming a Task class with a
199	>	* constructor accepting a {@code Phaser} that it registers with upon
200	>	* construction. After invocation of {@code build(new Task[n], 0, n,
201	>	* new Phaser())}, these tasks could then be started, for example by
202	>	* submitting to a pool:
203	>	*
204	>	*  <pre> {@code
205	>	* void build(Task[] tasks, int lo, int hi, Phaser ph) {
206	>	*   if (hi - lo > TASKS_PER_PHASER) {
207	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
208	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
209	>	*       build(tasks, i, j, new Phaser(ph));
210	>	*     }
211	>	*   } else {
212	>	*     for (int i = lo; i < hi; ++i)
213	>	*       tasks[i] = new Task(ph);
214	>	*       // assumes new Task(ph) performs ph.register()
215	>	*   }
216	>	* }}</pre>
217	>	*
218	>	* The best value of {@code TASKS_PER_PHASER} depends mainly on
219	>	* expected synchronization rates. A value as low as four may
220	>	* be appropriate for extremely small per-phase task bodies (thus
221	>	* high rates), or up to hundreds for extremely large ones.
222		*
223		* <p><b>Implementation notes</b>: This implementation restricts the
224	<	* maximum number of parties to 65535. Attempts to register
225	<	* additional parties result in IllegalStateExceptions.
224	>	* maximum number of parties to 65535. Attempts to register additional
225	>	* parties result in {@code IllegalStateException}. However, you can and
226	>	* should create tiered phasers to accommodate arbitrarily large sets
227	>	* of participants.
228	>	*
229	>	* @since 1.7
230	>	* @author Doug Lea
231		*/
232		public class Phaser {
233		/*
234		* This class implements an extension of X10 "clocks".  Thanks to
235	<	* Vijay Saraswat for the idea of applying it to ForkJoinTasks,
236	<	* and to Vivek Sarkar for enhancements to extend functionality.
235	>	* Vijay Saraswat for the idea, and to Vivek Sarkar for
236	>	* enhancements to extend functionality.
237		*/
238
239		/**
240	<	* Barrier state representation. Conceptually, a barrier contains
128	<	* four values:
129	<	*
130	<	* * parties -- the number of parties to wait (16 bits)
131	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
132	<	* * phase -- the generation of the barrier (31 bits)
133	<	* * terminated -- set if barrier is terminated (1 bit)
240	>	* Primary state representation, holding four bit-fields:
241		*
242	<	* However, to efficiently maintain atomicity, these values are
243	<	* packed into a single AtomicLong. Termination uses the sign bit
244	<	* of 32 bit representation of phase, so phase is set to -1 on
245	<	* termination.
246	<	*/
247	<	private final AtomicLong state;
248	<
249	<	/**
250	<	* Head of Treiber stack for waiting nonFJ threads.
251	<	*/
252	<	private final AtomicReference<QNode> head = new AtomicReference<QNode>();
242	>	* unarrived  -- the number of parties yet to hit barrier (bits  0-15)
243	>	* parties    -- the number of parties to wait            (bits 16-31)
244	>	* phase      -- the generation of the barrier            (bits 32-62)
245	>	* terminated -- set if barrier is terminated             (bit  63 / sign)
246	>	*
247	>	* Except that a phaser with no registered parties is
248	>	* distinguished by the otherwise illegal state of having zero
249	>	* parties and one unarrived parties (encoded as EMPTY below).
250	>	*
251	>	* To efficiently maintain atomicity, these values are packed into
252	>	* a single (atomic) long. Good performance relies on keeping
253	>	* state decoding and encoding simple, and keeping race windows
254	>	* short.
255	>	*
256	>	* All state updates are performed via CAS except initial
257	>	* registration of a sub-phaser (i.e., one with a non-null
258	>	* parent).  In this (relatively rare) case, we use built-in
259	>	* synchronization to lock while first registering with its
260	>	* parent.
261	>	*
262	>	* The phase of a subphaser is allowed to lag that of its
263	>	* ancestors until it is actually accessed -- see method
264	>	* reconcileState.
265	>	*/
266	>	private volatile long state;
267	>
268	>	private static final int  MAX_PARTIES     = 0xffff;
269	>	private static final int  MAX_PHASE       = Integer.MAX_VALUE;
270	>	private static final int  PARTIES_SHIFT   = 16;
271	>	private static final int  PHASE_SHIFT     = 32;
272	>	private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
273	>	private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
274	>	private static final long COUNTS_MASK     = 0xffffffffL;
275	>	private static final long TERMINATION_BIT = 1L << 63;
276	>
277	>	// some special values
278	>	private static final int  ONE_ARRIVAL     = 1;
279	>	private static final int  ONE_PARTY       = 1 << PARTIES_SHIFT;
280	>	private static final int  ONE_DEREGISTER  = ONE_ARRIVAL|ONE_PARTY;
281	>	private static final int  EMPTY           = 1;
282
283	<	private static final int ushortBits = 16;
148	<	private static final int ushortMask =  (1 << ushortBits) - 1;
149	<	private static final int phaseMask = 0x7fffffff;
283	>	// The following unpacking methods are usually manually inlined
284
285		private static int unarrivedOf(long s) {
286	<	return (int)(s & ushortMask);
286	>	int counts = (int)s;
287	>	return (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK);
288		}
289
290		private static int partiesOf(long s) {
291	<	return (int)(s & (ushortMask << 16)) >>> 16;
291	>	return (int)s >>> PARTIES_SHIFT;
292		}
293
294		private static int phaseOf(long s) {
295	<	return (int)(s >>> 32);
295	>	return (int)(s >>> PHASE_SHIFT);
296		}
297
298		private static int arrivedOf(long s) {
299	<	return partiesOf(s) - unarrivedOf(s);
299	>	int counts = (int)s;
300	>	return (counts == EMPTY) ? 0 :
301	>	(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK);
302		}
303
304	<	private static long stateFor(int phase, int parties, int unarrived) {
305	<	return (((long)phase) << 32) | ((parties << 16) | unarrived);
306	<	}
304	>	/**
305	>	* The parent of this phaser, or null if none
306	>	*/
307	>	private final Phaser parent;
308	>
309	>	/**
310	>	* The root of phaser tree. Equals this if not in a tree.
311	>	*/
312	>	private final Phaser root;
313	>
314	>	/**
315	>	* Heads of Treiber stacks for waiting threads. To eliminate
316	>	* contention when releasing some threads while adding others, we
317	>	* use two of them, alternating across even and odd phases.
318	>	* Subphasers share queues with root to speed up releases.
319	>	*/
320	>	private final AtomicReference<QNode> evenQ;
321	>	private final AtomicReference<QNode> oddQ;
322
323	<	private static IllegalStateException badBounds(int parties, int unarrived) {
324	<	return new IllegalStateException("Attempt to set " + unarrived +
173	<	" unarrived of " + parties + " parties");
323	>	private AtomicReference<QNode> queueFor(int phase) {
324	>	return ((phase & 1) == 0) ? evenQ : oddQ;
325		}
326
327		/**
328	<	* Creates a new Phaser without any initially registered parties,
178	<	* and initial phase number 0.
328	>	* Returns message string for bounds exceptions on arrival.
329		*/
330	<	public Phaser() {
331	<	state = new AtomicLong(stateFor(0, 0, 0));
330	>	private String badArrive(long s) {
331	>	return "Attempted arrival of unregistered party for " +
332	>	stateToString(s);
333		}
334
335		/**
336	<	* 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.
336	>	* Returns message string for bounds exceptions on registration.
337		*/
338	<	public Phaser(int parties) {
339	<	if (parties < 0 || parties > ushortMask)
340	<	throw new IllegalArgumentException("Illegal number of parties");
194	<	state = new AtomicLong(stateFor(0, parties, parties));
338	>	private String badRegister(long s) {
339	>	return "Attempt to register more than " +
340	>	MAX_PARTIES + " parties for " + stateToString(s);
341		}
342
343		/**
344	<	* Adds a new unarrived party to this phaser.
345	<	* @return the current barrier phase number upon registration
346	<	* @throws IllegalStateException if attempting to register more
347	<	* than the maximum supported number of parties.
344	>	* Main implementation for methods arrive and arriveAndDeregister.
345	>	* Manually tuned to speed up and minimize race windows for the
346	>	* common case of just decrementing unarrived field.
347	>	*
348	>	* @param adjust value to subtract from state;
349	>	*               ONE_ARRIVAL for arrive,
350	>	*               ONE_DEREGISTER for arriveAndDeregister
351		*/
352	<	public int register() { // increment both parties and unarrived
353	<	final AtomicLong state = this.state;
352	>	private int doArrive(int adjust) {
353	>	final Phaser root = this.root;
354		for (;;) {
355	<	long s = state.get();
356	<	int phase = phaseOf(s);
357	<	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)))
355	>	long s = (root == this) ? state : reconcileState();
356	>	int phase = (int)(s >>> PHASE_SHIFT);
357	>	if (phase < 0)
358		return phase;
359	+	int counts = (int)s;
360	+	int unarrived = (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK);
361	+	if (unarrived <= 0)
362	+	throw new IllegalStateException(badArrive(s));
363	+	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adjust)) {
364	+	if (unarrived == 1) {
365	+	long n = s & PARTIES_MASK;  // base of next state
366	+	int nextUnarrived = (int)n >>> PARTIES_SHIFT;
367	+	if (root == this) {
368	+	if (onAdvance(phase, nextUnarrived))
369	+	n |= TERMINATION_BIT;
370	+	else if (nextUnarrived == 0)
371	+	n |= EMPTY;
372	+	else
373	+	n |= nextUnarrived;
374	+	int nextPhase = (phase + 1) & MAX_PHASE;
375	+	n |= (long)nextPhase << PHASE_SHIFT;
376	+	UNSAFE.compareAndSwapLong(this, stateOffset, s, n);
377	+	releaseWaiters(phase);
378	+	}
379	+	else if (nextUnarrived == 0) { // propagate deregistration
380	+	phase = parent.doArrive(ONE_DEREGISTER);
381	+	UNSAFE.compareAndSwapLong(this, stateOffset,
382	+	s, s | EMPTY);
383	+	}
384	+	else
385	+	phase = parent.doArrive(ONE_ARRIVAL);
386	+	}
387	+	return phase;
388	+	}
389		}
390		}
391
392		/**
393	<	* Arrives at the barrier, but does not wait for others.  (You can
219	<	* in turn wait for others via {@link #awaitAdvance}).
393	>	* Implementation of register, bulkRegister
394		*
395	<	* @return the current barrier phase number upon entry to
396	<	* this method, or a negative value if terminated;
223	<	* @throws IllegalStateException if the number of unarrived
224	<	* parties would become negative.
395	>	* @param registrations number to add to both parties and
396	>	* unarrived fields. Must be greater than zero.
397		*/
398	<	public int arrive() { // decrement unarrived. If zero, trip
399	<	final AtomicLong state = this.state;
398	>	private int doRegister(int registrations) {
399	>	// adjustment to state
400	>	long adjust = ((long)registrations << PARTIES_SHIFT) | registrations;
401	>	final Phaser parent = this.parent;
402	>	int phase;
403		for (;;) {
404	<	long s = state.get();
405	<	int phase = phaseOf(s);
406	<	int parties = partiesOf(s);
407	<	int unarrived = unarrivedOf(s) - 1;
408	<	if (unarrived < 0)
409	<	throw badBounds(parties, unarrived);
410	<	if (unarrived == 0 && phase >= 0) {
411	<	trip(phase, parties);
412	<	return phase;
404	>	long s = (parent == null) ? state : reconcileState();
405	>	int counts = (int)s;
406	>	int parties = counts >>> PARTIES_SHIFT;
407	>	int unarrived = counts & UNARRIVED_MASK;
408	>	if (registrations > MAX_PARTIES - parties)
409	>	throw new IllegalStateException(badRegister(s));
410	>	phase = (int)(s >>> PHASE_SHIFT);
411	>	if (phase < 0)
412	>	break;
413	>	if (counts != EMPTY) {                  // not 1st registration
414	>	if (parent == null || reconcileState() == s) {
415	>	if (unarrived == 0)             // wait out advance
416	>	root.internalAwaitAdvance(phase, null);
417	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset,
418	>	s, s + adjust))
419	>	break;
420	>	}
421	>	}
422	>	else if (parent == null) {              // 1st root registration
423	>	long next = ((long)phase << PHASE_SHIFT) | adjust;
424	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
425	>	break;
426	>	}
427	>	else {
428	>	synchronized (this) {               // 1st sub registration
429	>	if (state == s) {               // recheck under lock
430	>	phase = parent.doRegister(1);
431	>	if (phase < 0)
432	>	break;
433	>	// finish registration whenever parent registration
434	>	// succeeded, even when racing with termination,
435	>	// since these are part of the same "transaction".
436	>	while (!UNSAFE.compareAndSwapLong
437	>	(this, stateOffset, s,
438	>	((long)phase << PHASE_SHIFT) | adjust)) {
439	>	s = state;
440	>	phase = (int)(root.state >>> PHASE_SHIFT);
441	>	// assert (int)s == EMPTY;
442	>	}
443	>	break;
444	>	}
445	>	}
446		}
239	–	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
240	–	return phase;
447		}
448	+	return phase;
449		}
450
451		/**
452	<	* Arrives at the barrier, and deregisters from it, without
453	<	* waiting for others.
452	>	* Resolves lagged phase propagation from root if necessary.
453	>	* Reconciliation normally occurs when root has advanced but
454	>	* subphasers have not yet done so, in which case they must finish
455	>	* their own advance by setting unarrived to parties (or if
456	>	* parties is zero, resetting to unregistered EMPTY state).
457		*
458	<	* @return the current barrier phase number upon entry to
249	<	* this method, or a negative value if terminated;
250	<	* @throws IllegalStateException if the number of registered or
251	<	* unarrived parties would become negative.
458	>	* @return reconciled state
459		*/
460	<	public int arriveAndDeregister() { // Same as arrive, plus decrement parties
461	<	final AtomicLong state = this.state;
462	<	for (;;) {
463	<	long s = state.get();
464	<	int phase = phaseOf(s);
465	<	int parties = partiesOf(s) - 1;
466	<	int unarrived = unarrivedOf(s) - 1;
467	<	if (parties < 0 || unarrived < 0)
468	<	throw badBounds(parties, unarrived);
469	<	if (unarrived == 0 && phase >= 0) {
470	<	trip(phase, parties);
471	<	return phase;
472	<	}
473	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
474	<	return phase;
460	>	private long reconcileState() {
461	>	final Phaser root = this.root;
462	>	long s = state;
463	>	if (root != this) {
464	>	int phase, p;
465	>	// CAS to root phase with current parties, tripping unarrived
466	>	while ((phase = (int)(root.state >>> PHASE_SHIFT)) !=
467	>	(int)(s >>> PHASE_SHIFT) &&
468	>	!UNSAFE.compareAndSwapLong
469	>	(this, stateOffset, s,
470	>	s = (((long)phase << PHASE_SHIFT) |
471	>	((phase < 0) ? (s & COUNTS_MASK) :
472	>	(((p = (int)s >>> PARTIES_SHIFT) == 0) ? EMPTY :
473	>	((s & PARTIES_MASK) | p))))))
474	>	s = state;
475		}
476	+	return s;
477		}
478
479		/**
480	<	* Arrives at the barrier and awaits others. Unlike other arrival
481	<	* methods, this method returns the arrival index of the
482	<	* caller. The caller tripping the barrier returns zero, the
483	<	* previous caller 1, and so on.
484	<	* @return the arrival index
485	<	* @throws IllegalStateException if the number of unarrived
486	<	* parties would become negative.
480	>	* Creates a new phaser with no initially registered parties, no
481	>	* parent, and initial phase number 0. Any thread using this
482	>	* phaser will need to first register for it.
483	>	*/
484	>	public Phaser() {
485	>	this(null, 0);
486	>	}
487	>
488	>	/**
489	>	* Creates a new phaser with the given number of registered
490	>	* unarrived parties, no parent, and initial phase number 0.
491	>	*
492	>	* @param parties the number of parties required to advance to the
493	>	* next phase
494	>	* @throws IllegalArgumentException if parties less than zero
495	>	* or greater than the maximum number of parties supported
496	>	*/
497	>	public Phaser(int parties) {
498	>	this(null, parties);
499	>	}
500	>
501	>	/**
502	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
503	>	*
504	>	* @param parent the parent phaser
505	>	*/
506	>	public Phaser(Phaser parent) {
507	>	this(parent, 0);
508	>	}
509	>
510	>	/**
511	>	* Creates a new phaser with the given parent and number of
512	>	* registered unarrived parties.  When the given parent is non-null
513	>	* and the given number of parties is greater than zero, this
514	>	* child phaser is registered with its parent.
515	>	*
516	>	* @param parent the parent phaser
517	>	* @param parties the number of parties required to advance to the
518	>	* next phase
519	>	* @throws IllegalArgumentException if parties less than zero
520	>	* or greater than the maximum number of parties supported
521	>	*/
522	>	public Phaser(Phaser parent, int parties) {
523	>	if (parties >>> PARTIES_SHIFT != 0)
524	>	throw new IllegalArgumentException("Illegal number of parties");
525	>	int phase = 0;
526	>	this.parent = parent;
527	>	if (parent != null) {
528	>	final Phaser root = parent.root;
529	>	this.root = root;
530	>	this.evenQ = root.evenQ;
531	>	this.oddQ = root.oddQ;
532	>	if (parties != 0)
533	>	phase = parent.doRegister(1);
534	>	}
535	>	else {
536	>	this.root = this;
537	>	this.evenQ = new AtomicReference<QNode>();
538	>	this.oddQ = new AtomicReference<QNode>();
539	>	}
540	>	this.state = (parties == 0) ? (long)EMPTY :
541	>	((long)phase << PHASE_SHIFT) |
542	>	((long)parties << PARTIES_SHIFT) |
543	>	((long)parties);
544	>	}
545	>
546	>	/**
547	>	* Adds a new unarrived party to this phaser.  If an ongoing
548	>	* invocation of {@link #onAdvance} is in progress, this method
549	>	* may await its completion before returning.  If this phaser has
550	>	* a parent, and this phaser previously had no registered parties,
551	>	* this child phaser is also registered with its parent. If
552	>	* this phaser is terminated, the attempt to register has
553	>	* no effect, and a negative value is returned.
554	>	*
555	>	* @return the arrival phase number to which this registration
556	>	* applied.  If this value is negative, then this phaser has
557	>	* terminated, in which case registration has no effect.
558	>	* @throws IllegalStateException if attempting to register more
559	>	* than the maximum supported number of parties
560	>	*/
561	>	public int register() {
562	>	return doRegister(1);
563	>	}
564	>
565	>	/**
566	>	* Adds the given number of new unarrived parties to this phaser.
567	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
568	>	* this method may await its completion before returning.  If this
569	>	* phaser has a parent, and the given number of parties is greater
570	>	* than zero, and this phaser previously had no registered
571	>	* parties, this child phaser is also registered with its parent.
572	>	* If this phaser is terminated, the attempt to register has no
573	>	* effect, and a negative value is returned.
574	>	*
575	>	* @param parties the number of additional parties required to
576	>	* advance to the next phase
577	>	* @return the arrival phase number to which this registration
578	>	* applied.  If this value is negative, then this phaser has
579	>	* terminated, in which case registration has no effect.
580	>	* @throws IllegalStateException if attempting to register more
581	>	* than the maximum supported number of parties
582	>	* @throws IllegalArgumentException if {@code parties < 0}
583	>	*/
584	>	public int bulkRegister(int parties) {
585	>	if (parties < 0)
586	>	throw new IllegalArgumentException();
587	>	if (parties == 0)
588	>	return getPhase();
589	>	return doRegister(parties);
590	>	}
591	>
592	>	/**
593	>	* Arrives at this phaser, without waiting for others to arrive.
594	>	*
595	>	* <p>It is a usage error for an unregistered party to invoke this
596	>	* method.  However, this error may result in an {@code
597	>	* IllegalStateException} only upon some subsequent operation on
598	>	* this phaser, if ever.
599	>	*
600	>	* @return the arrival phase number, or a negative value if terminated
601	>	* @throws IllegalStateException if not terminated and the number
602	>	* of unarrived parties would become negative
603	>	*/
604	>	public int arrive() {
605	>	return doArrive(ONE_ARRIVAL);
606	>	}
607	>
608	>	/**
609	>	* Arrives at this phaser and deregisters from it without waiting
610	>	* for others to arrive. Deregistration reduces the number of
611	>	* parties required to advance in future phases.  If this phaser
612	>	* has a parent, and deregistration causes this phaser to have
613	>	* zero parties, this phaser is also deregistered from its parent.
614	>	*
615	>	* <p>It is a usage error for an unregistered party to invoke this
616	>	* method.  However, this error may result in an {@code
617	>	* IllegalStateException} only upon some subsequent operation on
618	>	* this phaser, if ever.
619	>	*
620	>	* @return the arrival phase number, or a negative value if terminated
621	>	* @throws IllegalStateException if not terminated and the number
622	>	* of registered or unarrived parties would become negative
623	>	*/
624	>	public int arriveAndDeregister() {
625	>	return doArrive(ONE_DEREGISTER);
626	>	}
627	>
628	>	/**
629	>	* Arrives at this phaser and awaits others. Equivalent in effect
630	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
631	>	* interruption or timeout, you can arrange this with an analogous
632	>	* construction using one of the other forms of the {@code
633	>	* awaitAdvance} method.  If instead you need to deregister upon
634	>	* arrival, use {@code awaitAdvance(arriveAndDeregister())}.
635	>	*
636	>	* <p>It is a usage error for an unregistered party to invoke this
637	>	* method.  However, this error may result in an {@code
638	>	* IllegalStateException} only upon some subsequent operation on
639	>	* this phaser, if ever.
640	>	*
641	>	* @return the arrival phase number, or the (negative)
642	>	* {@linkplain #getPhase() current phase} if terminated
643	>	* @throws IllegalStateException if not terminated and the number
644	>	* of unarrived parties would become negative
645		*/
646		public int arriveAndAwaitAdvance() {
647	<	final AtomicLong state = this.state;
647	>	// Specialization of doArrive+awaitAdvance eliminating some reads/paths
648	>	final Phaser root = this.root;
649		for (;;) {
650	<	long s = state.get();
651	<	int phase = phaseOf(s);
652	<	int parties = partiesOf(s);
653	<	int unarrived = unarrivedOf(s) - 1;
654	<	if (unarrived < 0)
655	<	throw badBounds(parties, unarrived);
656	<	if (unarrived == 0 && phase >= 0) {
657	<	trip(phase, parties);
658	<	return 0;
659	<	}
660	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) {
661	<	awaitAdvance(phase);
662	<	return unarrived;
650	>	long s = (root == this) ? state : reconcileState();
651	>	int phase = (int)(s >>> PHASE_SHIFT);
652	>	if (phase < 0)
653	>	return phase;
654	>	int counts = (int)s;
655	>	int unarrived = (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK);
656	>	if (unarrived <= 0)
657	>	throw new IllegalStateException(badArrive(s));
658	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s,
659	>	s -= ONE_ARRIVAL)) {
660	>	if (unarrived > 1)
661	>	return root.internalAwaitAdvance(phase, null);
662	>	if (root != this)
663	>	return parent.arriveAndAwaitAdvance();
664	>	long n = s & PARTIES_MASK;  // base of next state
665	>	int nextUnarrived = (int)n >>> PARTIES_SHIFT;
666	>	if (onAdvance(phase, nextUnarrived))
667	>	n |= TERMINATION_BIT;
668	>	else if (nextUnarrived == 0)
669	>	n |= EMPTY;
670	>	else
671	>	n |= nextUnarrived;
672	>	int nextPhase = (phase + 1) & MAX_PHASE;
673	>	n |= (long)nextPhase << PHASE_SHIFT;
674	>	if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n))
675	>	return (int)(state >>> PHASE_SHIFT); // terminated
676	>	releaseWaiters(phase);
677	>	return nextPhase;
678		}
679		}
680		}
681
682		/**
683	<	* Awaits the phase of the barrier to advance from the given
684	<	* value, or returns immediately if this barrier is terminated
685	<	* @param phase the phase on entry to this method
686	<	* @return the phase on exit from this method
683	>	* Awaits the phase of this phaser to advance from the given phase
684	>	* value, returning immediately if the current phase is not equal
685	>	* to the given phase value or this phaser is terminated.
686	>	*
687	>	* @param phase an arrival phase number, or negative value if
688	>	* terminated; this argument is normally the value returned by a
689	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
690	>	* @return the next arrival phase number, or the argument if it is
691	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
692	>	* if terminated
693		*/
694		public int awaitAdvance(int phase) {
695	+	final Phaser root = this.root;
696	+	long s = (root == this) ? state : reconcileState();
697	+	int p = (int)(s >>> PHASE_SHIFT);
698		if (phase < 0)
699		return phase;
700	<	Thread current = Thread.currentThread();
701	<	if (current instanceof ForkJoinWorkerThread)
702	<	return helpingWait(phase);
312	<	if (untimedWait(current, phase, false))
313	<	current.interrupt();
314	<	return phaseOf(state.get());
700	>	if (p == phase)
701	>	return root.internalAwaitAdvance(phase, null);
702	>	return p;
703		}
704
705		/**
706	<	* Awaits the phase of the barrier to advance from the given
707	<	* value, or returns immediately if this barrier is terminated, or
708	<	* throws InterruptedException if interrupted while waiting.
709	<	* @param phase the phase on entry to this method
710	<	* @return the phase on exit from this method
706	>	* Awaits the phase of this phaser to advance from the given phase
707	>	* value, throwing {@code InterruptedException} if interrupted
708	>	* while waiting, or returning immediately if the current phase is
709	>	* not equal to the given phase value or this phaser is
710	>	* terminated.
711	>	*
712	>	* @param phase an arrival phase number, or negative value if
713	>	* terminated; this argument is normally the value returned by a
714	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
715	>	* @return the next arrival phase number, or the argument if it is
716	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
717	>	* if terminated
718		* @throws InterruptedException if thread interrupted while waiting
719		*/
720	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
720	>	public int awaitAdvanceInterruptibly(int phase)
721	>	throws InterruptedException {
722	>	final Phaser root = this.root;
723	>	long s = (root == this) ? state : reconcileState();
724	>	int p = (int)(s >>> PHASE_SHIFT);
725		if (phase < 0)
726		return phase;
727	<	Thread current = Thread.currentThread();
728	<	if (current instanceof ForkJoinWorkerThread)
729	<	return helpingWait(phase);
730	<	else if (Thread.interrupted() || untimedWait(current, phase, true))
731	<	throw new InterruptedException();
732	<	else
733	<	return phaseOf(state.get());
727	>	if (p == phase) {
728	>	QNode node = new QNode(this, phase, true, false, 0L);
729	>	p = root.internalAwaitAdvance(phase, node);
730	>	if (node.wasInterrupted)
731	>	throw new InterruptedException();
732	>	}
733	>	return p;
734		}
735
736		/**
737	<	* Awaits the phase of the barrier to advance from the given value
738	<	* or the given timeout elapses, or returns immediately if this
739	<	* barrier is terminated
740	<	* @param phase the phase on entry to this method
741	<	* @return the phase on exit from this method
737	>	* Awaits the phase of this phaser to advance from the given phase
738	>	* value or the given timeout to elapse, throwing {@code
739	>	* InterruptedException} if interrupted while waiting, or
740	>	* returning immediately if the current phase is not equal to the
741	>	* given phase value or this phaser is terminated.
742	>	*
743	>	* @param phase an arrival phase number, or negative value if
744	>	* terminated; this argument is normally the value returned by a
745	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
746	>	* @param timeout how long to wait before giving up, in units of
747	>	*        {@code unit}
748	>	* @param unit a {@code TimeUnit} determining how to interpret the
749	>	*        {@code timeout} parameter
750	>	* @return the next arrival phase number, or the argument if it is
751	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
752	>	* if terminated
753		* @throws InterruptedException if thread interrupted while waiting
754		* @throws TimeoutException if timed out while waiting
755		*/
756	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
756	>	public int awaitAdvanceInterruptibly(int phase,
757	>	long timeout, TimeUnit unit)
758		throws InterruptedException, TimeoutException {
759	+	long nanos = unit.toNanos(timeout);
760	+	final Phaser root = this.root;
761	+	long s = (root == this) ? state : reconcileState();
762	+	int p = (int)(s >>> PHASE_SHIFT);
763		if (phase < 0)
764		return phase;
765	<	long nanos = unit.toNanos(timeout);
766	<	Thread current = Thread.currentThread();
767	<	if (current instanceof ForkJoinWorkerThread)
768	<	return timedHelpingWait(phase, nanos);
769	<	timedWait(current, phase, nanos);
770	<	return phaseOf(state.get());
765	>	if (p == phase) {
766	>	QNode node = new QNode(this, phase, true, true, nanos);
767	>	p = root.internalAwaitAdvance(phase, node);
768	>	if (node.wasInterrupted)
769	>	throw new InterruptedException();
770	>	else if (p == phase)
771	>	throw new TimeoutException();
772	>	}
773	>	return p;
774		}
775
776		/**
777	<	* Forces this barrier to enter termination state. Counts of
778	<	* arrived and registered parties are unaffected. This method may
779	<	* be useful for coordinating recovery after one or more tasks
780	<	* encounter unexpected exceptions.
777	>	* Forces this phaser to enter termination state.  Counts of
778	>	* registered parties are unaffected.  If this phaser is a member
779	>	* of a tiered set of phasers, then all of the phasers in the set
780	>	* are terminated.  If this phaser is already terminated, this
781	>	* method has no effect.  This method may be useful for
782	>	* coordinating recovery after one or more tasks encounter
783	>	* unexpected exceptions.
784		*/
785		public void forceTermination() {
786	<	final AtomicLong state = this.state;
787	<	for (;;) {
788	<	long s = state.get();
789	<	int phase = phaseOf(s);
790	<	int parties = partiesOf(s);
791	<	int unarrived = unarrivedOf(s);
792	<	if (phase < 0 ||
793	<	state.compareAndSet(s, stateFor(-1, parties, unarrived))) {
794	<	if (head.get() != null)
374	<	releaseWaiters(-1);
786	>	// Only need to change root state
787	>	final Phaser root = this.root;
788	>	long s;
789	>	while ((s = root.state) >= 0) {
790	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
791	>	s, s | TERMINATION_BIT)) {
792	>	// signal all threads
793	>	releaseWaiters(0); // Waiters on evenQ
794	>	releaseWaiters(1); // Waiters on oddQ
795		return;
796		}
797		}
798		}
799
800		/**
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	–	/**
801		* Returns the current phase number. The maximum phase number is
802	<	* <tt>Integer.MAX_VALUE</tt>, after which it restarts at
803	<	* zero. Upon termination, the phase number is negative.
802	>	* {@code Integer.MAX_VALUE}, after which it restarts at
803	>	* zero. Upon termination, the phase number is negative,
804	>	* in which case the prevailing phase prior to termination
805	>	* may be obtained via {@code getPhase() + Integer.MIN_VALUE}.
806	>	*
807		* @return the phase number, or a negative value if terminated
808		*/
809	<	public int getPhase() {
810	<	return phaseOf(state.get());
809	>	public final int getPhase() {
810	>	return (int)(root.state >>> PHASE_SHIFT);
811		}
812
813		/**
814	<	* Returns the number of parties registered at this barrier.
814	>	* Returns the number of parties registered at this phaser.
815	>	*
816		* @return the number of parties
817		*/
818		public int getRegisteredParties() {
819	<	return partiesOf(state.get());
819	>	return partiesOf(state);
820		}
821
822		/**
823	<	* Returns the number of parties that have arrived at the current
824	<	* phase of this barrier.
823	>	* Returns the number of registered parties that have arrived at
824	>	* the current phase of this phaser. If this phaser has terminated,
825	>	* the returned value is meaningless and arbitrary.
826	>	*
827		* @return the number of arrived parties
828		*/
829		public int getArrivedParties() {
830	<	return arrivedOf(state.get());
830	>	return arrivedOf(reconcileState());
831		}
832
833		/**
834		* Returns the number of registered parties that have not yet
835	<	* arrived at the current phase of this barrier.
835	>	* arrived at the current phase of this phaser. If this phaser has
836	>	* terminated, the returned value is meaningless and arbitrary.
837	>	*
838		* @return the number of unarrived parties
839		*/
840		public int getUnarrivedParties() {
841	<	return unarrivedOf(state.get());
841	>	return unarrivedOf(reconcileState());
842		}
843
844		/**
845	<	* Returns true if this barrier has been terminated
846	<	* @return true if this barrier has been terminated
845	>	* Returns the parent of this phaser, or {@code null} if none.
846	>	*
847	>	* @return the parent of this phaser, or {@code null} if none
848	>	*/
849	>	public Phaser getParent() {
850	>	return parent;
851	>	}
852	>
853	>	/**
854	>	* Returns the root ancestor of this phaser, which is the same as
855	>	* this phaser if it has no parent.
856	>	*
857	>	* @return the root ancestor of this phaser
858	>	*/
859	>	public Phaser getRoot() {
860	>	return root;
861	>	}
862	>
863	>	/**
864	>	* Returns {@code true} if this phaser has been terminated.
865	>	*
866	>	* @return {@code true} if this phaser has been terminated
867		*/
868		public boolean isTerminated() {
869	<	return phaseOf(state.get()) < 0;
869	>	return root.state < 0L;
870		}
871
872		/**
873	<	* Overridable method to perform an action upon phase advance, and
874	<	* to control termination. This method is invoked whenever the
875	<	* barrier is tripped (and thus all other waiting parties are
876	<	* dormant). If it returns true, then, rather than advance the
877	<	* phase number, this barrier will be set to a final termination
878	<	* state, and subsequent calls to <tt>isTerminated</tt> will
879	<	* return true.
880	<	*
881	<	* <p> The default version returns true when the number of
882	<	* registered parties is zero. Normally, overrides that arrange
883	<	* termination for other reasons should also preserve this
884	<	* property.
885	<	*
886	<	* @param phase the phase number on entering the barrier
887	<	* @param registeredParties the current number of registered
888	<	* parties.
889	<	* @return true if this barrier should terminate
873	>	* Overridable method to perform an action upon impending phase
874	>	* advance, and to control termination. This method is invoked
875	>	* upon arrival of the party advancing this phaser (when all other
876	>	* waiting parties are dormant).  If this method returns {@code
877	>	* true}, this phaser will be set to a final termination state
878	>	* upon advance, and subsequent calls to {@link #isTerminated}
879	>	* will return true. Any (unchecked) Exception or Error thrown by
880	>	* an invocation of this method is propagated to the party
881	>	* attempting to advance this phaser, in which case no advance
882	>	* occurs.
883	>	*
884	>	* <p>The arguments to this method provide the state of the phaser
885	>	* prevailing for the current transition.  The effects of invoking
886	>	* arrival, registration, and waiting methods on this phaser from
887	>	* within {@code onAdvance} are unspecified and should not be
888	>	* relied on.
889	>	*
890	>	* <p>If this phaser is a member of a tiered set of phasers, then
891	>	* {@code onAdvance} is invoked only for its root phaser on each
892	>	* advance.
893	>	*
894	>	* <p>To support the most common use cases, the default
895	>	* implementation of this method returns {@code true} when the
896	>	* number of registered parties has become zero as the result of a
897	>	* party invoking {@code arriveAndDeregister}.  You can disable
898	>	* this behavior, thus enabling continuation upon future
899	>	* registrations, by overriding this method to always return
900	>	* {@code false}:
901	>	*
902	>	* <pre> {@code
903	>	* Phaser phaser = new Phaser() {
904	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
905	>	* }}</pre>
906	>	*
907	>	* @param phase the current phase number on entry to this method,
908	>	* before this phaser is advanced
909	>	* @param registeredParties the current number of registered parties
910	>	* @return {@code true} if this phaser should terminate
911		*/
912		protected boolean onAdvance(int phase, int registeredParties) {
913	<	return registeredParties <= 0;
913	>	return registeredParties == 0;
914		}
915
916		/**
917	<	* Returns a string identifying this barrier, as well as its
917	>	* Returns a string identifying this phaser, as well as its
918		* state.  The state, in brackets, includes the String {@code
919	<	* "phase ="} followed by the phase number, {@code "parties ="}
919	>	* "phase = "} followed by the phase number, {@code "parties = "}
920		* followed by the number of registered parties, and {@code
921	<	* "arrived ="} followed by the number of arrived parties
921	>	* "arrived = "} followed by the number of arrived parties.
922		*
923	<	* @return a string identifying this barrier, as well as its state
923	>	* @return a string identifying this phaser, as well as its state
924		*/
925		public String toString() {
926	<	long s = state.get();
475	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
926	>	return stateToString(reconcileState());
927		}
928
478	–	// methods for tripping and waiting
479	–
929		/**
930	<	* Advance the current phase (or terminate)
930	>	* Implementation of toString and string-based error messages
931		*/
932	<	private void trip(int phase, int parties) {
933	<	int next = onAdvance(phase, parties)? -1 : ((phase + 1) & phaseMask);
934	<	state.set(stateFor(next, parties, parties));
935	<	if (head.get() != null)
936	<	releaseWaiters(next);
932	>	private String stateToString(long s) {
933	>	return super.toString() +
934	>	"[phase = " + phaseOf(s) +
935	>	" parties = " + partiesOf(s) +
936	>	" arrived = " + arrivedOf(s) + "]";
937		}
938
939	<	private int helpingWait(int phase) {
491	<	final AtomicLong state = this.state;
492	<	int p;
493	<	while ((p = phaseOf(state.get())) == phase) {
494	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
495	<	if (t != null) {
496	<	if ((p = phaseOf(state.get())) == phase)
497	<	t.exec();
498	<	else {   // push task and exit if barrier advanced
499	<	t.fork();
500	<	break;
501	<	}
502	<	}
503	<	}
504	<	return p;
505	<	}
939	>	// Waiting mechanics
940
941	<	private int timedHelpingWait(int phase, long nanos) throws TimeoutException {
942	<	final AtomicLong state = this.state;
943	<	long lastTime = System.nanoTime();
944	<	int p;
945	<	while ((p = phaseOf(state.get())) == phase) {
946	<	long now = System.nanoTime();
947	<	nanos -= now - lastTime;
948	<	lastTime = now;
949	<	if (nanos <= 0) {
950	<	if ((p = phaseOf(state.get())) == phase)
951	<	throw new TimeoutException();
952	<	else
953	<	break;
520	<	}
521	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
522	<	if (t != null) {
523	<	if ((p = phaseOf(state.get())) == phase)
524	<	t.exec();
525	<	else {   // push task and exit if barrier advanced
526	<	t.fork();
527	<	break;
528	<	}
941	>	/**
942	>	* Removes and signals threads from queue for phase.
943	>	*/
944	>	private void releaseWaiters(int phase) {
945	>	QNode q;   // first element of queue
946	>	Thread t;  // its thread
947	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
948	>	while ((q = head.get()) != null &&
949	>	q.phase != (int)(root.state >>> PHASE_SHIFT)) {
950	>	if (head.compareAndSet(q, q.next) &&
951	>	(t = q.thread) != null) {
952	>	q.thread = null;
953	>	LockSupport.unpark(t);
954		}
955		}
531	–	return p;
956		}
957
958		/**
959	<	* Wait nodes for Treiber stack representing wait queue for non-FJ
960	<	* tasks. The waiting scheme is an adaptation of the one used in
961	<	* forkjoin.PoolBarrier.
959	>	* Variant of releaseWaiters that additionally tries to remove any
960	>	* nodes no longer waiting for advance due to timeout or
961	>	* interrupt. Currently, nodes are removed only if they are at
962	>	* head of queue, which suffices to reduce memory footprint in
963	>	* most usages.
964	>	*
965	>	* @return current phase on exit
966		*/
967	<	static final class QNode {
968	<	QNode next;
969	<	volatile Thread thread; // nulled to cancel wait
970	<	final int phase;
971	<	QNode(Thread t, int c) {
972	<	thread = t;
973	<	phase = c;
974	<	}
975	<	}
976	<
977	<	private void releaseWaiters(int currentPhase) {
550	<	final AtomicReference<QNode> head = this.head;
551	<	QNode p;
552	<	while ((p = head.get()) != null && p.phase != currentPhase) {
553	<	if (head.compareAndSet(p, null)) {
554	<	do {
555	<	Thread t = p.thread;
556	<	if (t != null) {
557	<	p.thread = null;
558	<	LockSupport.unpark(t);
559	<	}
560	<	} while ((p = p.next) != null);
967	>	private int abortWait(int phase) {
968	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
969	>	for (;;) {
970	>	Thread t;
971	>	QNode q = head.get();
972	>	int p = (int)(root.state >>> PHASE_SHIFT);
973	>	if (q == null || ((t = q.thread) != null && q.phase == p))
974	>	return p;
975	>	if (head.compareAndSet(q, q.next) && t != null) {
976	>	q.thread = null;
977	>	LockSupport.unpark(t);
978		}
979		}
980		}
981
982		/** The number of CPUs, for spin control */
983	<	static final int NCPUS = Runtime.getRuntime().availableProcessors();
567	<
568	<	/**
569	<	* The number of times to spin before blocking in timed waits.
570	<	* The value is empirically derived
571	<	*/
572	<	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
573	<
574	<	/**
575	<	* The number of times to spin before blocking in untimed waits.
576	<	* This is greater than timed value because untimed waits spin
577	<	* faster since they don't need to check times on each spin.
578	<	*/
579	<	static final int maxUntimedSpins = maxTimedSpins * 32;
983	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
984
985		/**
986	<	* The number of nanoseconds for which it is faster to spin
987	<	* rather than to use timed park. A rough estimate suffices.
986	>	* The number of times to spin before blocking while waiting for
987	>	* advance, per arrival while waiting. On multiprocessors, fully
988	>	* blocking and waking up a large number of threads all at once is
989	>	* usually a very slow process, so we use rechargeable spins to
990	>	* avoid it when threads regularly arrive: When a thread in
991	>	* internalAwaitAdvance notices another arrival before blocking,
992	>	* and there appear to be enough CPUs available, it spins
993	>	* SPINS_PER_ARRIVAL more times before blocking. The value trades
994	>	* off good-citizenship vs big unnecessary slowdowns.
995		*/
996	<	static final long spinForTimeoutThreshold = 1000L;
996	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
997
998		/**
999	<	* Enqueues node and waits unless aborted or signalled.
1000	<	*/
1001	<	private boolean untimedWait(Thread thread, int currentPhase,
1002	<	boolean abortOnInterrupt) {
1003	<	final AtomicReference<QNode> head = this.head;
1004	<	final AtomicLong state = this.state;
1005	<	boolean wasInterrupted = false;
1006	<	QNode node = null;
1007	<	boolean queued = false;
1008	<	int spins = maxUntimedSpins;
1009	<	while (phaseOf(state.get()) == currentPhase) {
1010	<	QNode h;
1011	<	if (node != null && queued) {
1012	<	if (node.thread != null) {
1013	<	LockSupport.park();
1014	<	if (Thread.interrupted()) {
1015	<	wasInterrupted = true;
1016	<	if (abortOnInterrupt)
1017	<	break;
1018	<	}
999	>	* Possibly blocks and waits for phase to advance unless aborted.
1000	>	* Call only on root phaser.
1001	>	*
1002	>	* @param phase current phase
1003	>	* @param node if non-null, the wait node to track interrupt and timeout;
1004	>	* if null, denotes noninterruptible wait
1005	>	* @return current phase
1006	>	*/
1007	>	private int internalAwaitAdvance(int phase, QNode node) {
1008	>	// assert root == this;
1009	>	releaseWaiters(phase-1);          // ensure old queue clean
1010	>	boolean queued = false;           // true when node is enqueued
1011	>	int lastUnarrived = 0;            // to increase spins upon change
1012	>	int spins = SPINS_PER_ARRIVAL;
1013	>	long s;
1014	>	int p;
1015	>	while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
1016	>	if (node == null) {           // spinning in noninterruptible mode
1017	>	int unarrived = (int)s & UNARRIVED_MASK;
1018	>	if (unarrived != lastUnarrived &&
1019	>	(lastUnarrived = unarrived) < NCPU)
1020	>	spins += SPINS_PER_ARRIVAL;
1021	>	boolean interrupted = Thread.interrupted();
1022	>	if (interrupted || --spins < 0) { // need node to record intr
1023	>	node = new QNode(this, phase, false, false, 0L);
1024	>	node.wasInterrupted = interrupted;
1025		}
1026		}
1027	<	else if ((h = head.get()) != null && h.phase != currentPhase) {
1028	<	if (phaseOf(state.get()) == currentPhase) { // must recheck
1029	<	if (head.compareAndSet(h, h.next)) {
1030	<	Thread t = h.thread; // help clear out old waiters
1031	<	if (t != null) {
1032	<	h.thread = null;
1033	<	LockSupport.unpark(t);
1034	<	}
1035	<	}
1027	>	else if (node.isReleasable()) // done or aborted
1028	>	break;
1029	>	else if (!queued) {           // push onto queue
1030	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
1031	>	QNode q = node.next = head.get();
1032	>	if ((q == null || q.phase == phase) &&
1033	>	(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq
1034	>	queued = head.compareAndSet(q, node);
1035	>	}
1036	>	else {
1037	>	try {
1038	>	ForkJoinPool.managedBlock(node);
1039	>	} catch (InterruptedException ie) {
1040	>	node.wasInterrupted = true;
1041		}
620	–	else
621	–	break;
1042		}
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;
1043		}
1044	<	if (node != null)
1045	<	node.thread = null;
1046	<	return wasInterrupted;
1044	>
1045	>	if (node != null) {
1046	>	if (node.thread != null)
1047	>	node.thread = null;       // avoid need for unpark()
1048	>	if (node.wasInterrupted && !node.interruptible)
1049	>	Thread.currentThread().interrupt();
1050	>	if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase)
1051	>	return abortWait(phase); // possibly clean up on abort
1052	>	}
1053	>	releaseWaiters(phase);
1054	>	return p;
1055		}
1056
1057		/**
1058	<	* Messier timeout version
1058	>	* Wait nodes for Treiber stack representing wait queue
1059		*/
1060	<	private void timedWait(Thread thread, int currentPhase, long nanos)
1061	<	throws InterruptedException, TimeoutException {
1062	<	final AtomicReference<QNode> head = this.head;
1063	<	final AtomicLong state = this.state;
1064	<	long lastTime = System.nanoTime();
1065	<	QNode node = null;
1066	<	boolean queued = false;
1067	<	int spins = maxTimedSpins;
1068	<	while (phaseOf(state.get()) == currentPhase) {
1069	<	QNode h;
1070	<	long now = System.nanoTime();
1071	<	nanos -= now - lastTime;
1072	<	lastTime = now;
1073	<	if (nanos <= 0) {
1074	<	if (node != null)
1075	<	node.thread = null;
1076	<	if (phaseOf(state.get()) == currentPhase)
1077	<	throw new TimeoutException();
1078	<	else
1079	<	break;
1060	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
1061	>	final Phaser phaser;
1062	>	final int phase;
1063	>	final boolean interruptible;
1064	>	final boolean timed;
1065	>	boolean wasInterrupted;
1066	>	long nanos;
1067	>	long lastTime;
1068	>	volatile Thread thread; // nulled to cancel wait
1069	>	QNode next;
1070	>
1071	>	QNode(Phaser phaser, int phase, boolean interruptible,
1072	>	boolean timed, long nanos) {
1073	>	this.phaser = phaser;
1074	>	this.phase = phase;
1075	>	this.interruptible = interruptible;
1076	>	this.nanos = nanos;
1077	>	this.timed = timed;
1078	>	this.lastTime = timed ? System.nanoTime() : 0L;
1079	>	thread = Thread.currentThread();
1080	>	}
1081	>
1082	>	public boolean isReleasable() {
1083	>	if (thread == null)
1084	>	return true;
1085	>	if (phaser.getPhase() != phase) {
1086	>	thread = null;
1087	>	return true;
1088		}
1089	<	else if (node != null && queued) {
1090	<	if (node.thread != null &&
1091	<	nanos > spinForTimeoutThreshold) {
1092	<	//                LockSupport.parkNanos(this, nanos);
1093	<	LockSupport.parkNanos(nanos);
664	<	if (Thread.interrupted()) {
665	<	node.thread = null;
666	<	throw new InterruptedException();
667	<	}
668	<	}
1089	>	if (Thread.interrupted())
1090	>	wasInterrupted = true;
1091	>	if (wasInterrupted && interruptible) {
1092	>	thread = null;
1093	>	return true;
1094		}
1095	<	else if ((h = head.get()) != null && h.phase != currentPhase) {
1096	<	if (phaseOf(state.get()) == currentPhase) { // must recheck
1097	<	if (head.compareAndSet(h, h.next)) {
1098	<	Thread t = h.thread; // help clear out old waiters
1099	<	if (t != null) {
1100	<	h.thread = null;
1101	<	LockSupport.unpark(t);
1102	<	}
1103	<	}
1095	>	if (timed) {
1096	>	if (nanos > 0L) {
1097	>	long now = System.nanoTime();
1098	>	nanos -= now - lastTime;
1099	>	lastTime = now;
1100	>	}
1101	>	if (nanos <= 0L) {
1102	>	thread = null;
1103	>	return true;
1104		}
680	–	else
681	–	break;
1105		}
1106	<	else if (node != null)
1107	<	queued = head.compareAndSet(node.next = h, node);
1108	<	else if (spins <= 0)
1109	<	node = new QNode(thread, currentPhase);
1110	<	else
1111	<	--spins;
1106	>	return false;
1107	>	}
1108	>
1109	>	public boolean block() {
1110	>	if (isReleasable())
1111	>	return true;
1112	>	else if (!timed)
1113	>	LockSupport.park(this);
1114	>	else if (nanos > 0)
1115	>	LockSupport.parkNanos(this, nanos);
1116	>	return isReleasable();
1117		}
690	–	if (node != null)
691	–	node.thread = null;
1118		}
1119
1120	<	}
1120	>	// Unsafe mechanics
1121	>
1122	>	private static final sun.misc.Unsafe UNSAFE;
1123	>	private static final long stateOffset;
1124	>	static {
1125	>	try {
1126	>	UNSAFE = getUnsafe();
1127	>	Class<?> k = Phaser.class;
1128	>	stateOffset = UNSAFE.objectFieldOffset
1129	>	(k.getDeclaredField("state"));
1130	>	} catch (Exception e) {
1131	>	throw new Error(e);
1132	>	}
1133	>	}
1134
1135	+	/**
1136	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1137	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1138	+	* into a jdk.
1139	+	*
1140	+	* @return a sun.misc.Unsafe
1141	+	*/
1142	+	private static sun.misc.Unsafe getUnsafe() {
1143	+	try {
1144	+	return sun.misc.Unsafe.getUnsafe();
1145	+	} catch (SecurityException tryReflectionInstead) {}
1146	+	try {
1147	+	return java.security.AccessController.doPrivileged
1148	+	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1149	+	public sun.misc.Unsafe run() throws Exception {
1150	+	Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class;
1151	+	for (java.lang.reflect.Field f : k.getDeclaredFields()) {
1152	+	f.setAccessible(true);
1153	+	Object x = f.get(null);
1154	+	if (k.isInstance(x))
1155	+	return k.cast(x);
1156	+	}
1157	+	throw new NoSuchFieldError("the Unsafe");
1158	+	}});
1159	+	} catch (java.security.PrivilegedActionException e) {
1160	+	throw new RuntimeException("Could not initialize intrinsics",
1161	+	e.getCause());
1162	+	}
1163	+	}
1164	+	}

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