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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.2 by jsr166, Fri Jul 25 18:10:41 2008 UTC vs.
Revision 1.68 by dl, Sat Dec 4 15:25:08 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 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
81	+	* value. Similarly, attempts to register upon termination have no
82	+	* effect.  Termination is triggered when an invocation of {@code
83	+	* onAdvance} returns {@code true}. The default implementation returns
84	+	* {@code true} if a deregistration has caused the number of
85	+	* registered parties to become zero.  As illustrated below, when
86	+	* phasers control actions with a fixed number of iterations, it is
87	+	* often convenient to override this method to cause termination when
88	+	* the current phase number reaches a threshold. Method {@link
89	+	* #forceTermination} is also available to abruptly release waiting
90	+	* threads and allow them 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 usages:</b>
123	>	*
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	>	*  <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 (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	>	*
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	>	*   };
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	>	*   phaser.arriveAndDeregister(); // deregister self, don't wait
170	>	* }}</pre>
171		*
172	<	* <p><b>Sample usage:</b>
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>[todo: non-FJ example]
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	<	* <p> A Phaser may be used to support a style of programming in
185	<	* which a task waits for others to complete, without otherwise
186	<	* needing to keep track of which tasks it is waiting for. This is
187	<	* similar to the "sync" construct in Cilk and "clocks" in X10.
188	<	* Special constructions based on such barriers are available using
189	<	* the <tt>LinkedAsyncAction</tt> and <tt>CyclicAction</tt> classes,
190	<	* but they can be useful in other contexts as well.  For a simple
191	<	* (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();
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	<	*   protected void compute() {
194	<	*     int n = argument;
195	<	*     if (n &lt;= 1)
196	<	*        result = n;
197	<	*     else {
198	<	*        Phaser childBarrier = new Phaser(1);
199	<	*        BarrierFibonacci f1 = new BarrierFibonacci(n - 1, childBarrier);
200	<	*        BarrierFibonacci f2 = new BarrierFibonacci(n - 2, childBarrier);
201	<	*        f1.fork();
202	<	*        f2.fork();
203	<	*        childBarrier.arriveAndAwait();
204	<	*        result = f1.result + f2.result;
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	<	*     parentBarrier.arriveAndDeregister();
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	<	* }
217	<	* </pre>
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 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 with 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.  Method reconcileState
264	>	* is usually attempted only only when the number of unarrived
265	>	* parties appears to be zero, which indicates a potential lag in
266	>	* updating phase after the root advanced.
267	>	*/
268	>	private volatile long state;
269	>
270	>	private static final int  MAX_PARTIES     = 0xffff;
271	>	private static final int  MAX_PHASE       = 0x7fffffff;
272	>	private static final int  PARTIES_SHIFT   = 16;
273	>	private static final int  PHASE_SHIFT     = 32;
274	>	private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
275	>	private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
276	>	private static final long TERMINATION_BIT = 1L << 63;
277	>
278	>	// some special values
279	>	private static final int  ONE_ARRIVAL     = 1;
280	>	private static final int  ONE_PARTY       = 1 << PARTIES_SHIFT;
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	<	private static IllegalStateException badBounds(int parties, int unarrived) {
310	<	return new IllegalStateException("Attempt to set " + unarrived +
311	<	" unarrived of " + parties + " parties");
312	<	}
309	>	/**
310	>	* The root of phaser tree. Equals this if not in a tree.
311	>	*/
312	>	private final Phaser root;
313
314		/**
315	<	* Creates a new Phaser without any initially registered parties,
316	<	* and initial phase number 0.
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	<	public Phaser() {
321	<	state = new AtomicLong(stateFor(0, 0, 0));
320	>	private final AtomicReference<QNode> evenQ;
321	>	private final AtomicReference<QNode> oddQ;
322	>
323	>	private AtomicReference<QNode> queueFor(int phase) {
324	>	return ((phase & 1) == 0) ? evenQ : oddQ;
325		}
326
327		/**
328	<	* 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.
328	>	* Returns message string for bounds exceptions on arrival.
329		*/
330	<	public Phaser(int parties) {
331	<	if (parties < 0 || parties > ushortMask)
332	<	throw new IllegalArgumentException("Illegal number of parties");
194	<	state = new AtomicLong(stateFor(0, parties, parties));
330	>	private String badArrive(long s) {
331	>	return "Attempted arrival of unregistered party for " +
332	>	stateToString(s);
333		}
334
335		/**
336	<	* 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.
336	>	* Returns message string for bounds exceptions on registration.
337		*/
338	<	public int register() { // increment both parties and unarrived
339	<	final AtomicLong state = this.state;
340	<	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	<	}
338	>	private String badRegister(long s) {
339	>	return "Attempt to register more than " +
340	>	MAX_PARTIES + " parties for " + stateToString(s);
341		}
342
343		/**
344	<	* Arrives at the barrier, but does not wait for others.  (You can
345	<	* in turn wait for others via {@link #awaitAdvance}).
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	<	* @return the current barrier phase number upon entry to
222	<	* this method, or a negative value if terminated;
223	<	* @throws IllegalStateException if the number of unarrived
224	<	* parties would become negative.
348	>	* @param deregister false for arrive, true for arriveAndDeregister
349		*/
350	<	public int arrive() { // decrement unarrived. If zero, trip
351	<	final AtomicLong state = this.state;
350	>	private int doArrive(boolean deregister) {
351	>	int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL;
352	>	final Phaser root = this.root;
353		for (;;) {
354	<	long s = state.get();
355	<	int phase = phaseOf(s);
356	<	int parties = partiesOf(s);
357	<	int unarrived = unarrivedOf(s) - 1;
358	<	if (unarrived < 0)
234	<	throw badBounds(parties, unarrived);
235	<	if (unarrived == 0 && phase >= 0) {
236	<	trip(phase, parties);
354	>	long s = (root == this) ? state : reconcileState();
355	>	int phase = (int)(s >>> PHASE_SHIFT);
356	>	int counts = (int)s;
357	>	int unarrived = (counts & UNARRIVED_MASK) - 1;
358	>	if (phase < 0)
359		return phase;
360	+	else if (counts == EMPTY || unarrived < 0) {
361	+	if (root == this || reconcileState() == s)
362	+	throw new IllegalStateException(badArrive(s));
363		}
364	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
364	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
365	>	if (unarrived == 0) {
366	>	long n = s & PARTIES_MASK;  // base of next state
367	>	int nextUnarrived = ((int)n) >>> PARTIES_SHIFT;
368	>	if (root != this)
369	>	return parent.doArrive(nextUnarrived == 0);
370	>	if (onAdvance(phase, nextUnarrived))
371	>	n |= TERMINATION_BIT;
372	>	else if (nextUnarrived == 0)
373	>	n |= EMPTY;
374	>	else
375	>	n |= nextUnarrived;
376	>	n |= ((long)((phase + 1) & MAX_PHASE)) << PHASE_SHIFT;
377	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, n);
378	>	releaseWaiters(phase);
379	>	}
380		return phase;
381	+	}
382		}
383		}
384
385		/**
386	<	* Arrives at the barrier, and deregisters from it, without
246	<	* waiting for others.
386	>	* Implementation of register, bulkRegister
387		*
388	<	* @return the current barrier phase number upon entry to
389	<	* this method, or a negative value if terminated;
250	<	* @throws IllegalStateException if the number of registered or
251	<	* unarrived parties would become negative.
388	>	* @param registrations number to add to both parties and
389	>	* unarrived fields. Must be greater than zero.
390		*/
391	<	public int arriveAndDeregister() { // Same as arrive, plus decrement parties
392	<	final AtomicLong state = this.state;
391	>	private int doRegister(int registrations) {
392	>	// adjustment to state
393	>	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
394	>	Phaser par = parent;
395	>	int phase;
396		for (;;) {
397	<	long s = state.get();
398	<	int phase = phaseOf(s);
399	<	int parties = partiesOf(s) - 1;
400	<	int unarrived = unarrivedOf(s) - 1;
401	<	if (parties < 0 || unarrived < 0)
402	<	throw badBounds(parties, unarrived);
403	<	if (unarrived == 0 && phase >= 0) {
404	<	trip(phase, parties);
405	<	return phase;
397	>	long s = state;
398	>	int counts = (int)s;
399	>	int parties = counts >>> PARTIES_SHIFT;
400	>	int unarrived = counts & UNARRIVED_MASK;
401	>	if (registrations > MAX_PARTIES - parties)
402	>	throw new IllegalStateException(badRegister(s));
403	>	else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0)
404	>	break;
405	>	else if (counts != EMPTY) {             // not 1st registration
406	>	if (par == null || reconcileState() == s) {
407	>	if (unarrived == 0)             // wait out advance
408	>	root.internalAwaitAdvance(phase, null);
409	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset,
410	>	s, s + adj))
411	>	break;
412	>	}
413		}
414	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
415	<	return phase;
414	>	else if (par == null) {                 // 1st root registration
415	>	long next = (((long) phase) << PHASE_SHIFT) | adj;
416	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
417	>	break;
418	>	}
419	>	else {
420	>	synchronized (this) {               // 1st sub registration
421	>	if (state == s) {               // recheck under lock
422	>	par.doRegister(1);
423	>	do {                        // force current phase
424	>	phase = (int)(root.state >>> PHASE_SHIFT);
425	>	// assert phase < 0 || (int)state == EMPTY;
426	>	} while (!UNSAFE.compareAndSwapLong
427	>	(this, stateOffset, state,
428	>	(((long) phase) << PHASE_SHIFT) | adj));
429	>	break;
430	>	}
431	>	}
432	>	}
433	>	}
434	>	return phase;
435	>	}
436	>
437	>	/**
438	>	* Resolves lagged phase propagation from root if necessary.
439	>	*/
440	>	private long reconcileState() {
441	>	Phaser rt = root;
442	>	long s = state;
443	>	if (rt != this) {
444	>	int phase;
445	>	while ((phase = (int)(rt.state >>> PHASE_SHIFT)) !=
446	>	(int)(s >>> PHASE_SHIFT)) {
447	>	// assert phase < 0 || unarrivedOf(s) == 0
448	>	long t;                             // to reread s
449	>	long p = s & PARTIES_MASK;          // unshifted parties field
450	>	long n = (((long) phase) << PHASE_SHIFT) | p;
451	>	if (phase >= 0) {
452	>	if (p == 0L)
453	>	n |= EMPTY;                 // reset to empty
454	>	else
455	>	n |= p >>> PARTIES_SHIFT;   // set unarr to parties
456	>	}
457	>	if ((t = state) == s &&
458	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, s = n))
459	>	break;
460	>	s = t;
461	>	}
462	>	}
463	>	return s;
464	>	}
465	>
466	>	/**
467	>	* Creates a new phaser with no initially registered parties, no
468	>	* parent, and initial phase number 0. Any thread using this
469	>	* phaser will need to first register for it.
470	>	*/
471	>	public Phaser() {
472	>	this(null, 0);
473	>	}
474	>
475	>	/**
476	>	* Creates a new phaser with the given number of registered
477	>	* unarrived parties, no parent, and initial phase number 0.
478	>	*
479	>	* @param parties the number of parties required to advance to the
480	>	* next phase
481	>	* @throws IllegalArgumentException if parties less than zero
482	>	* or greater than the maximum number of parties supported
483	>	*/
484	>	public Phaser(int parties) {
485	>	this(null, parties);
486	>	}
487	>
488	>	/**
489	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
490	>	*
491	>	* @param parent the parent phaser
492	>	*/
493	>	public Phaser(Phaser parent) {
494	>	this(parent, 0);
495	>	}
496	>
497	>	/**
498	>	* Creates a new phaser with the given parent and number of
499	>	* registered unarrived parties.  When the given parent is non-null
500	>	* and the given number of parties is greater than zero, this
501	>	* child phaser is registered with its parent.
502	>	*
503	>	* @param parent the parent phaser
504	>	* @param parties the number of parties required to advance to the
505	>	* next phase
506	>	* @throws IllegalArgumentException if parties less than zero
507	>	* or greater than the maximum number of parties supported
508	>	*/
509	>	public Phaser(Phaser parent, int parties) {
510	>	if (parties >>> PARTIES_SHIFT != 0)
511	>	throw new IllegalArgumentException("Illegal number of parties");
512	>	int phase = 0;
513	>	this.parent = parent;
514	>	if (parent != null) {
515	>	final Phaser root = parent.root;
516	>	this.root = root;
517	>	this.evenQ = root.evenQ;
518	>	this.oddQ = root.oddQ;
519	>	if (parties != 0)
520	>	phase = parent.doRegister(1);
521		}
522	+	else {
523	+	this.root = this;
524	+	this.evenQ = new AtomicReference<QNode>();
525	+	this.oddQ = new AtomicReference<QNode>();
526	+	}
527	+	this.state = (parties == 0) ? (long) EMPTY :
528	+	((((long) phase) << PHASE_SHIFT) |
529	+	(((long) parties) << PARTIES_SHIFT) |
530	+	((long) parties));
531	+	}
532	+
533	+	/**
534	+	* Adds a new unarrived party to this phaser.  If an ongoing
535	+	* invocation of {@link #onAdvance} is in progress, this method
536	+	* may await its completion before returning.  If this phaser has
537	+	* a parent, and this phaser previously had no registered parties,
538	+	* this child phaser is also registered with its parent. If
539	+	* this phaser is terminated, the attempt to register has
540	+	* no effect, and a negative value is returned.
541	+	*
542	+	* @return the arrival phase number to which this registration
543	+	* applied.  If this value is negative, then this phaser has
544	+	* terminated, in which casem registration has no effect.
545	+	* @throws IllegalStateException if attempting to register more
546	+	* than the maximum supported number of parties
547	+	*/
548	+	public int register() {
549	+	return doRegister(1);
550	+	}
551	+
552	+	/**
553	+	* Adds the given number of new unarrived parties to this phaser.
554	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
555	+	* this method may await its completion before returning.  If this
556	+	* phaser has a parent, and the given number of parties is greater
557	+	* than zero, and this phaser previously had no registered
558	+	* parties, this child phaser is also registered with its parent.
559	+	* If this phaser is terminated, the attempt to register has no
560	+	* effect, and a negative value is returned.
561	+	*
562	+	* @param parties the number of additional parties required to
563	+	* advance to the next phase
564	+	* @return the arrival phase number to which this registration
565	+	* applied.  If this value is negative, then this phaser has
566	+	* terminated, in which casem registration has no effect.
567	+	* @throws IllegalStateException if attempting to register more
568	+	* than the maximum supported number of parties
569	+	* @throws IllegalArgumentException if {@code parties < 0}
570	+	*/
571	+	public int bulkRegister(int parties) {
572	+	if (parties < 0)
573	+	throw new IllegalArgumentException();
574	+	if (parties == 0)
575	+	return getPhase();
576	+	return doRegister(parties);
577	+	}
578	+
579	+	/**
580	+	* Arrives at this phaser, without waiting for others to arrive.
581	+	*
582	+	* <p>It is a usage error for an unregistered party to invoke this
583	+	* method.  However, this error may result in an {@code
584	+	* IllegalStateException} only upon some subsequent operation on
585	+	* this phaser, if ever.
586	+	*
587	+	* @return the arrival phase number, or a negative value if terminated
588	+	* @throws IllegalStateException if not terminated and the number
589	+	* of unarrived parties would become negative
590	+	*/
591	+	public int arrive() {
592	+	return doArrive(false);
593		}
594
595		/**
596	<	* Arrives at the barrier and awaits others. Unlike other arrival
597	<	* methods, this method returns the arrival index of the
598	<	* caller. The caller tripping the barrier returns zero, the
599	<	* previous caller 1, and so on.
600	<	* @return the arrival index
601	<	* @throws IllegalStateException if the number of unarrived
602	<	* parties would become negative.
596	>	* Arrives at this phaser and deregisters from it without waiting
597	>	* for others to arrive. Deregistration reduces the number of
598	>	* parties required to advance in future phases.  If this phaser
599	>	* has a parent, and deregistration causes this phaser to have
600	>	* zero parties, this phaser is also deregistered from its parent.
601	>	*
602	>	* <p>It is a usage error for an unregistered party to invoke this
603	>	* method.  However, this error may result in an {@code
604	>	* IllegalStateException} only upon some subsequent operation on
605	>	* this phaser, if ever.
606	>	*
607	>	* @return the arrival phase number, or a negative value if terminated
608	>	* @throws IllegalStateException if not terminated and the number
609	>	* of registered or unarrived parties would become negative
610	>	*/
611	>	public int arriveAndDeregister() {
612	>	return doArrive(true);
613	>	}
614	>
615	>	/**
616	>	* Arrives at this phaser and awaits others. Equivalent in effect
617	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
618	>	* interruption or timeout, you can arrange this with an analogous
619	>	* construction using one of the other forms of the {@code
620	>	* awaitAdvance} method.  If instead you need to deregister upon
621	>	* arrival, use {@code awaitAdvance(arriveAndDeregister())}.
622	>	*
623	>	* <p>It is a usage error for an unregistered party to invoke this
624	>	* method.  However, this error may result in an {@code
625	>	* IllegalStateException} only upon some subsequent operation on
626	>	* this phaser, if ever.
627	>	*
628	>	* @return the arrival phase number, or the (negative)
629	>	* {@linkplain #getPhase() current phase} if terminated
630	>	* @throws IllegalStateException if not terminated and the number
631	>	* of unarrived parties would become negative
632		*/
633		public int arriveAndAwaitAdvance() {
634	<	final AtomicLong state = this.state;
634	>	// Specialization of doArrive+awaitAdvance eliminating some reads/paths
635	>	final Phaser root = this.root;
636		for (;;) {
637	<	long s = state.get();
638	<	int phase = phaseOf(s);
639	<	int parties = partiesOf(s);
640	<	int unarrived = unarrivedOf(s) - 1;
641	<	if (unarrived < 0)
642	<	throw badBounds(parties, unarrived);
643	<	if (unarrived == 0 && phase >= 0) {
644	<	trip(phase, parties);
645	<	return 0;
637	>	long s = (root == this) ? state : reconcileState();
638	>	int phase = (int)(s >>> PHASE_SHIFT);
639	>	int counts = (int)s;
640	>	int unarrived = (counts & UNARRIVED_MASK) - 1;
641	>	if (phase < 0)
642	>	return phase;
643	>	else if (counts == EMPTY || unarrived < 0) {
644	>	if (reconcileState() == s)
645	>	throw new IllegalStateException(badArrive(s));
646		}
647	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) {
648	<	awaitAdvance(phase);
649	<	return unarrived;
647	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s,
648	>	s -= ONE_ARRIVAL)) {
649	>	if (unarrived != 0)
650	>	return root.internalAwaitAdvance(phase, null);
651	>	if (root != this)
652	>	return parent.arriveAndAwaitAdvance();
653	>	long n = s & PARTIES_MASK;  // base of next state
654	>	int nextUnarrived = ((int)n) >>> PARTIES_SHIFT;
655	>	if (onAdvance(phase, nextUnarrived))
656	>	n |= TERMINATION_BIT;
657	>	else if (nextUnarrived == 0)
658	>	n |= EMPTY;
659	>	else
660	>	n |= nextUnarrived;
661	>	int nextPhase = (phase + 1) & MAX_PHASE;
662	>	n |= (long)nextPhase << PHASE_SHIFT;
663	>	if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n))
664	>	return (int)(state >>> PHASE_SHIFT); // terminated
665	>	releaseWaiters(phase);
666	>	return nextPhase;
667		}
668		}
669		}
670
671		/**
672	<	* Awaits the phase of the barrier to advance from the given
673	<	* value, or returns immediately if this barrier is terminated.
674	<	* @param phase the phase on entry to this method
675	<	* @return the phase on exit from this method
672	>	* Awaits the phase of this phaser to advance from the given phase
673	>	* value, returning immediately if the current phase is not equal
674	>	* to the given phase value or this phaser is terminated.
675	>	*
676	>	* @param phase an arrival phase number, or negative value if
677	>	* terminated; this argument is normally the value returned by a
678	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
679	>	* @return the next arrival phase number, or the argument if it is
680	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
681	>	* if terminated
682		*/
683		public int awaitAdvance(int phase) {
684	+	final Phaser root = this.root;
685	+	int p = (int)((root == this? state : reconcileState()) >>> PHASE_SHIFT);
686		if (phase < 0)
687		return phase;
688	<	Thread current = Thread.currentThread();
689	<	if (current instanceof ForkJoinWorkerThread)
690	<	return helpingWait(phase);
312	<	if (untimedWait(current, phase, false))
313	<	current.interrupt();
314	<	return phaseOf(state.get());
688	>	if (p == phase)
689	>	return root.internalAwaitAdvance(phase, null);
690	>	return p;
691		}
692
693		/**
694	<	* Awaits the phase of the barrier to advance from the given
695	<	* value, or returns immediately if this barrier is terminated, or
696	<	* throws InterruptedException if interrupted while waiting.
697	<	* @param phase the phase on entry to this method
698	<	* @return the phase on exit from this method
694	>	* Awaits the phase of this phaser to advance from the given phase
695	>	* value, throwing {@code InterruptedException} if interrupted
696	>	* while waiting, or returning immediately if the current phase is
697	>	* not equal to the given phase value or this phaser is
698	>	* terminated.
699	>	*
700	>	* @param phase an arrival phase number, or negative value if
701	>	* terminated; this argument is normally the value returned by a
702	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
703	>	* @return the next arrival phase number, or the argument if it is
704	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
705	>	* if terminated
706		* @throws InterruptedException if thread interrupted while waiting
707		*/
708	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
708	>	public int awaitAdvanceInterruptibly(int phase)
709	>	throws InterruptedException {
710	>	final Phaser root = this.root;
711	>	int p = (int)((root == this? state : reconcileState()) >>> PHASE_SHIFT);
712		if (phase < 0)
713		return phase;
714	<	Thread current = Thread.currentThread();
715	<	if (current instanceof ForkJoinWorkerThread)
716	<	return helpingWait(phase);
717	<	else if (Thread.interrupted() || untimedWait(current, phase, true))
718	<	throw new InterruptedException();
719	<	else
720	<	return phaseOf(state.get());
714	>	if (p == phase) {
715	>	QNode node = new QNode(this, phase, true, false, 0L);
716	>	p = root.internalAwaitAdvance(phase, node);
717	>	if (node.wasInterrupted)
718	>	throw new InterruptedException();
719	>	}
720	>	return p;
721		}
722
723		/**
724	<	* Awaits the phase of the barrier to advance from the given value
725	<	* or the given timeout elapses, or returns immediately if this
726	<	* barrier is terminated.
727	<	* @param phase the phase on entry to this method
728	<	* @return the phase on exit from this method
724	>	* Awaits the phase of this phaser to advance from the given phase
725	>	* value or the given timeout to elapse, throwing {@code
726	>	* InterruptedException} if interrupted while waiting, or
727	>	* returning immediately if the current phase is not equal to the
728	>	* given phase value or this phaser is terminated.
729	>	*
730	>	* @param phase an arrival phase number, or negative value if
731	>	* terminated; this argument is normally the value returned by a
732	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
733	>	* @param timeout how long to wait before giving up, in units of
734	>	*        {@code unit}
735	>	* @param unit a {@code TimeUnit} determining how to interpret the
736	>	*        {@code timeout} parameter
737	>	* @return the next arrival phase number, or the argument if it is
738	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
739	>	* if terminated
740		* @throws InterruptedException if thread interrupted while waiting
741		* @throws TimeoutException if timed out while waiting
742		*/
743	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
743	>	public int awaitAdvanceInterruptibly(int phase,
744	>	long timeout, TimeUnit unit)
745		throws InterruptedException, TimeoutException {
746	+	long nanos = unit.toNanos(timeout);
747	+	final Phaser root = this.root;
748	+	int p = (int)((root == this? state : reconcileState()) >>> PHASE_SHIFT);
749		if (phase < 0)
750		return phase;
751	<	long nanos = unit.toNanos(timeout);
752	<	Thread current = Thread.currentThread();
753	<	if (current instanceof ForkJoinWorkerThread)
754	<	return timedHelpingWait(phase, nanos);
755	<	timedWait(current, phase, nanos);
756	<	return phaseOf(state.get());
751	>	if (p == phase) {
752	>	QNode node = new QNode(this, phase, true, true, nanos);
753	>	p = root.internalAwaitAdvance(phase, node);
754	>	if (node.wasInterrupted)
755	>	throw new InterruptedException();
756	>	else if (p == phase)
757	>	throw new TimeoutException();
758	>	}
759	>	return p;
760		}
761
762		/**
763	<	* Forces this barrier to enter termination state. Counts of
764	<	* arrived and registered parties are unaffected. This method may
765	<	* be useful for coordinating recovery after one or more tasks
766	<	* encounter unexpected exceptions.
763	>	* Forces this phaser to enter termination state.  Counts of
764	>	* registered parties are unaffected.  If this phaser is a member
765	>	* of a tiered set of phasers, then all of the phasers in the set
766	>	* are terminated.  If this phaser is already terminated, this
767	>	* method has no effect.  This method may be useful for
768	>	* coordinating recovery after one or more tasks encounter
769	>	* unexpected exceptions.
770		*/
771		public void forceTermination() {
772	<	final AtomicLong state = this.state;
773	<	for (;;) {
774	<	long s = state.get();
775	<	int phase = phaseOf(s);
776	<	int parties = partiesOf(s);
777	<	int unarrived = unarrivedOf(s);
778	<	if (phase < 0 ||
779	<	state.compareAndSet(s, stateFor(-1, parties, unarrived))) {
780	<	if (head.get() != null)
374	<	releaseWaiters(-1);
772	>	// Only need to change root state
773	>	final Phaser root = this.root;
774	>	long s;
775	>	while ((s = root.state) >= 0) {
776	>	long next = (s & ~((long)UNARRIVED_MASK)) | TERMINATION_BIT;
777	>	if (UNSAFE.compareAndSwapLong(root, stateOffset, s, next)) {
778	>	// signal all threads
779	>	releaseWaiters(0);
780	>	releaseWaiters(1);
781		return;
782		}
783		}
784		}
785
786		/**
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	–	/**
787		* Returns the current phase number. The maximum phase number is
788	<	* <tt>Integer.MAX_VALUE</tt>, after which it restarts at
789	<	* zero. Upon termination, the phase number is negative.
788	>	* {@code Integer.MAX_VALUE}, after which it restarts at
789	>	* zero. Upon termination, the phase number is negative,
790	>	* in which case the prevailing phase prior to termination
791	>	* may be obtained via {@code getPhase() + Integer.MIN_VALUE}.
792	>	*
793		* @return the phase number, or a negative value if terminated
794		*/
795	<	public int getPhase() {
796	<	return phaseOf(state.get());
795	>	public final int getPhase() {
796	>	return (int)(root.state >>> PHASE_SHIFT);
797		}
798
799		/**
800	<	* Returns the number of parties registered at this barrier.
800	>	* Returns the number of parties registered at this phaser.
801	>	*
802		* @return the number of parties
803		*/
804		public int getRegisteredParties() {
805	<	return partiesOf(state.get());
805	>	return partiesOf(state);
806		}
807
808		/**
809	<	* Returns the number of parties that have arrived at the current
810	<	* phase of this barrier.
809	>	* Returns the number of registered parties that have arrived at
810	>	* the current phase of this phaser.
811	>	*
812		* @return the number of arrived parties
813		*/
814		public int getArrivedParties() {
815	<	return arrivedOf(state.get());
815	>	return arrivedOf(reconcileState());
816		}
817
818		/**
819		* Returns the number of registered parties that have not yet
820	<	* arrived at the current phase of this barrier.
820	>	* arrived at the current phase of this phaser.
821	>	*
822		* @return the number of unarrived parties
823		*/
824		public int getUnarrivedParties() {
825	<	return unarrivedOf(state.get());
825	>	return unarrivedOf(reconcileState());
826	>	}
827	>
828	>	/**
829	>	* Returns the parent of this phaser, or {@code null} if none.
830	>	*
831	>	* @return the parent of this phaser, or {@code null} if none
832	>	*/
833	>	public Phaser getParent() {
834	>	return parent;
835		}
836
837		/**
838	<	* Returns true if this barrier has been terminated.
839	<	* @return true if this barrier has been terminated
838	>	* Returns the root ancestor of this phaser, which is the same as
839	>	* this phaser if it has no parent.
840	>	*
841	>	* @return the root ancestor of this phaser
842	>	*/
843	>	public Phaser getRoot() {
844	>	return root;
845	>	}
846	>
847	>	/**
848	>	* Returns {@code true} if this phaser has been terminated.
849	>	*
850	>	* @return {@code true} if this phaser has been terminated
851		*/
852		public boolean isTerminated() {
853	<	return phaseOf(state.get()) < 0;
853	>	return root.state < 0L;
854		}
855
856		/**
857	<	* Overridable method to perform an action upon phase advance, and
858	<	* to control termination. This method is invoked whenever the
859	<	* barrier is tripped (and thus all other waiting parties are
860	<	* dormant). If it returns true, then, rather than advance the
861	<	* phase number, this barrier will be set to a final termination
862	<	* state, and subsequent calls to <tt>isTerminated</tt> will
863	<	* return true.
864	<	*
865	<	* <p> The default version returns true when the number of
866	<	* registered parties is zero. Normally, overrides that arrange
867	<	* termination for other reasons should also preserve this
868	<	* property.
869	<	*
870	<	* @param phase the phase number on entering the barrier
871	<	* @param registeredParties the current number of registered
872	<	* parties.
873	<	* @return true if this barrier should terminate
857	>	* Overridable method to perform an action upon impending phase
858	>	* advance, and to control termination. This method is invoked
859	>	* upon arrival of the party advancing this phaser (when all other
860	>	* waiting parties are dormant).  If this method returns {@code
861	>	* true}, this phaser will be set to a final termination state
862	>	* upon advance, and subsequent calls to {@link #isTerminated}
863	>	* will return true. Any (unchecked) Exception or Error thrown by
864	>	* an invocation of this method is propagated to the party
865	>	* attempting to advance this phaser, in which case no advance
866	>	* occurs.
867	>	*
868	>	* <p>The arguments to this method provide the state of the phaser
869	>	* prevailing for the current transition.  The effects of invoking
870	>	* arrival, registration, and waiting methods on this phaser from
871	>	* within {@code onAdvance} are unspecified and should not be
872	>	* relied on.
873	>	*
874	>	* <p>If this phaser is a member of a tiered set of phasers, then
875	>	* {@code onAdvance} is invoked only for its root phaser on each
876	>	* advance.
877	>	*
878	>	* <p>To support the most common use cases, the default
879	>	* implementation of this method returns {@code true} when the
880	>	* number of registered parties has become zero as the result of a
881	>	* party invoking {@code arriveAndDeregister}.  You can disable
882	>	* this behavior, thus enabling continuation upon future
883	>	* registrations, by overriding this method to always return
884	>	* {@code false}:
885	>	*
886	>	* <pre> {@code
887	>	* Phaser phaser = new Phaser() {
888	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
889	>	* }}</pre>
890	>	*
891	>	* @param phase the current phase number on entry to this method,
892	>	* before this phaser is advanced
893	>	* @param registeredParties the current number of registered parties
894	>	* @return {@code true} if this phaser should terminate
895		*/
896		protected boolean onAdvance(int phase, int registeredParties) {
897	<	return registeredParties <= 0;
897	>	return registeredParties == 0;
898		}
899
900		/**
901	<	* Returns a string identifying this barrier, as well as its
901	>	* Returns a string identifying this phaser, as well as its
902		* state.  The state, in brackets, includes the String {@code
903	<	* "phase ="} followed by the phase number, {@code "parties ="}
903	>	* "phase = "} followed by the phase number, {@code "parties = "}
904		* followed by the number of registered parties, and {@code
905	<	* "arrived ="} followed by the number of arrived parties
905	>	* "arrived = "} followed by the number of arrived parties.
906		*
907	<	* @return a string identifying this barrier, as well as its state
907	>	* @return a string identifying this phaser, as well as its state
908		*/
909		public String toString() {
910	<	long s = state.get();
475	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
910	>	return stateToString(reconcileState());
911		}
912
478	–	// methods for tripping and waiting
479	–
913		/**
914	<	* Advance the current phase (or terminate)
914	>	* Implementation of toString and string-based error messages
915		*/
916	<	private void trip(int phase, int parties) {
917	<	int next = onAdvance(phase, parties)? -1 : ((phase + 1) & phaseMask);
918	<	state.set(stateFor(next, parties, parties));
919	<	if (head.get() != null)
920	<	releaseWaiters(next);
916	>	private String stateToString(long s) {
917	>	return super.toString() +
918	>	"[phase = " + phaseOf(s) +
919	>	" parties = " + partiesOf(s) +
920	>	" arrived = " + arrivedOf(s) + "]";
921		}
922
923	<	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	<	}
923	>	// Waiting mechanics
924
925	<	private int timedHelpingWait(int phase, long nanos) throws TimeoutException {
926	<	final AtomicLong state = this.state;
927	<	long lastTime = System.nanoTime();
928	<	int p;
929	<	while ((p = phaseOf(state.get())) == phase) {
930	<	long now = System.nanoTime();
931	<	nanos -= now - lastTime;
932	<	lastTime = now;
933	<	if (nanos <= 0) {
934	<	if ((p = phaseOf(state.get())) == phase)
935	<	throw new TimeoutException();
936	<	else
937	<	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	<	}
925	>	/**
926	>	* Removes and signals threads from queue for phase.
927	>	*/
928	>	private void releaseWaiters(int phase) {
929	>	QNode q;   // first element of queue
930	>	Thread t;  // its thread
931	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
932	>	while ((q = head.get()) != null &&
933	>	q.phase != (int)(root.state >>> PHASE_SHIFT)) {
934	>	if (head.compareAndSet(q, q.next) &&
935	>	(t = q.thread) != null) {
936	>	q.thread = null;
937	>	LockSupport.unpark(t);
938		}
939		}
531	–	return p;
940		}
941
942		/**
943	<	* Wait nodes for Treiber stack representing wait queue for non-FJ
944	<	* tasks. The waiting scheme is an adaptation of the one used in
945	<	* forkjoin.PoolBarrier.
943	>	* Variant of releaseWaiters that additionally tries to remove any
944	>	* nodes no longer waiting for advance due to timeout or
945	>	* interrupt. Currently, nodes are removed only if they are at
946	>	* head of queue, which suffices to reduce memory footprint in
947	>	* most usages.
948	>	*
949	>	* @return current phase on exit
950		*/
951	<	static final class QNode {
952	<	QNode next;
953	<	volatile Thread thread; // nulled to cancel wait
954	<	final int phase;
955	<	QNode(Thread t, int c) {
956	<	thread = t;
957	<	phase = c;
958	<	}
959	<	}
960	<
961	<	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);
951	>	private int abortWait(int phase) {
952	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
953	>	for (;;) {
954	>	Thread t;
955	>	QNode q = head.get();
956	>	int p = (int)(root.state >>> PHASE_SHIFT);
957	>	if (q == null || ((t = q.thread) != null && q.phase == p))
958	>	return p;
959	>	if (head.compareAndSet(q, q.next) && t != null) {
960	>	q.thread = null;
961	>	LockSupport.unpark(t);
962		}
963		}
964		}
965
966		/** The number of CPUs, for spin control */
967	<	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;
967	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
968
969		/**
970	<	* The number of nanoseconds for which it is faster to spin
971	<	* rather than to use timed park. A rough estimate suffices.
970	>	* The number of times to spin before blocking while waiting for
971	>	* advance, per arrival while waiting. On multiprocessors, fully
972	>	* blocking and waking up a large number of threads all at once is
973	>	* usually a very slow process, so we use rechargeable spins to
974	>	* avoid it when threads regularly arrive: When a thread in
975	>	* internalAwaitAdvance notices another arrival before blocking,
976	>	* and there appear to be enough CPUs available, it spins
977	>	* SPINS_PER_ARRIVAL more times before blocking. The value trades
978	>	* off good-citizenship vs big unnecessary slowdowns.
979		*/
980	<	static final long spinForTimeoutThreshold = 1000L;
980	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
981
982		/**
983	<	* Enqueues node and waits unless aborted or signalled.
984	<	*/
985	<	private boolean untimedWait(Thread thread, int currentPhase,
986	<	boolean abortOnInterrupt) {
987	<	final AtomicReference<QNode> head = this.head;
988	<	final AtomicLong state = this.state;
989	<	boolean wasInterrupted = false;
990	<	QNode node = null;
991	<	boolean queued = false;
992	<	int spins = maxUntimedSpins;
993	<	while (phaseOf(state.get()) == currentPhase) {
994	<	QNode h;
995	<	if (node != null && queued) {
996	<	if (node.thread != null) {
997	<	LockSupport.park();
998	<	if (Thread.interrupted()) {
999	<	wasInterrupted = true;
1000	<	if (abortOnInterrupt)
1001	<	break;
1002	<	}
983	>	* Possibly blocks and waits for phase to advance unless aborted.
984	>	* Call only from root node.
985	>	*
986	>	* @param phase current phase
987	>	* @param node if non-null, the wait node to track interrupt and timeout;
988	>	* if null, denotes noninterruptible wait
989	>	* @return current phase
990	>	*/
991	>	private int internalAwaitAdvance(int phase, QNode node) {
992	>	releaseWaiters(phase-1);          // ensure old queue clean
993	>	boolean queued = false;           // true when node is enqueued
994	>	int lastUnarrived = 0;            // to increase spins upon change
995	>	int spins = SPINS_PER_ARRIVAL;
996	>	long s;
997	>	int p;
998	>	while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
999	>	if (node == null) {           // spinning in noninterruptible mode
1000	>	int unarrived = (int)s & UNARRIVED_MASK;
1001	>	if (unarrived != lastUnarrived &&
1002	>	(lastUnarrived = unarrived) < NCPU)
1003	>	spins += SPINS_PER_ARRIVAL;
1004	>	boolean interrupted = Thread.interrupted();
1005	>	if (interrupted || --spins < 0) { // need node to record intr
1006	>	node = new QNode(this, phase, false, false, 0L);
1007	>	node.wasInterrupted = interrupted;
1008		}
1009		}
1010	<	else if ((h = head.get()) != null && h.phase != currentPhase) {
1011	<	if (phaseOf(state.get()) == currentPhase) { // must recheck
1012	<	if (head.compareAndSet(h, h.next)) {
1013	<	Thread t = h.thread; // help clear out old waiters
1014	<	if (t != null) {
1015	<	h.thread = null;
1016	<	LockSupport.unpark(t);
1017	<	}
1018	<	}
1010	>	else if (node.isReleasable()) // done or aborted
1011	>	break;
1012	>	else if (!queued) {           // push onto queue
1013	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
1014	>	QNode q = node.next = head.get();
1015	>	if ((q == null || q.phase == phase) &&
1016	>	(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq
1017	>	queued = head.compareAndSet(q, node);
1018	>	}
1019	>	else {
1020	>	try {
1021	>	ForkJoinPool.managedBlock(node);
1022	>	} catch (InterruptedException ie) {
1023	>	node.wasInterrupted = true;
1024		}
620	–	else
621	–	break;
1025		}
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;
1026		}
1027	<	if (node != null)
1028	<	node.thread = null;
1029	<	return wasInterrupted;
1027	>
1028	>	if (node != null) {
1029	>	if (node.thread != null)
1030	>	node.thread = null;       // avoid need for unpark()
1031	>	if (node.wasInterrupted && !node.interruptible)
1032	>	Thread.currentThread().interrupt();
1033	>	if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase)
1034	>	return abortWait(phase); // possibly clean up on abort
1035	>	}
1036	>	releaseWaiters(phase);
1037	>	return p;
1038		}
1039
1040		/**
1041	<	* Messier timeout version
1041	>	* Wait nodes for Treiber stack representing wait queue
1042		*/
1043	<	private void timedWait(Thread thread, int currentPhase, long nanos)
1044	<	throws InterruptedException, TimeoutException {
1045	<	final AtomicReference<QNode> head = this.head;
1046	<	final AtomicLong state = this.state;
1047	<	long lastTime = System.nanoTime();
1048	<	QNode node = null;
1049	<	boolean queued = false;
1050	<	int spins = maxTimedSpins;
1051	<	while (phaseOf(state.get()) == currentPhase) {
1052	<	QNode h;
1053	<	long now = System.nanoTime();
1054	<	nanos -= now - lastTime;
1055	<	lastTime = now;
1056	<	if (nanos <= 0) {
1057	<	if (node != null)
1058	<	node.thread = null;
1059	<	if (phaseOf(state.get()) == currentPhase)
1060	<	throw new TimeoutException();
1061	<	else
1062	<	break;
1043	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
1044	>	final Phaser phaser;
1045	>	final int phase;
1046	>	final boolean interruptible;
1047	>	final boolean timed;
1048	>	boolean wasInterrupted;
1049	>	long nanos;
1050	>	long lastTime;
1051	>	volatile Thread thread; // nulled to cancel wait
1052	>	QNode next;
1053	>
1054	>	QNode(Phaser phaser, int phase, boolean interruptible,
1055	>	boolean timed, long nanos) {
1056	>	this.phaser = phaser;
1057	>	this.phase = phase;
1058	>	this.interruptible = interruptible;
1059	>	this.nanos = nanos;
1060	>	this.timed = timed;
1061	>	this.lastTime = timed ? System.nanoTime() : 0L;
1062	>	thread = Thread.currentThread();
1063	>	}
1064	>
1065	>	public boolean isReleasable() {
1066	>	if (thread == null)
1067	>	return true;
1068	>	if (phaser.getPhase() != phase) {
1069	>	thread = null;
1070	>	return true;
1071		}
1072	<	else if (node != null && queued) {
1073	<	if (node.thread != null &&
1074	<	nanos > spinForTimeoutThreshold) {
1075	<	//                LockSupport.parkNanos(this, nanos);
1076	<	LockSupport.parkNanos(nanos);
664	<	if (Thread.interrupted()) {
665	<	node.thread = null;
666	<	throw new InterruptedException();
667	<	}
668	<	}
1072	>	if (Thread.interrupted())
1073	>	wasInterrupted = true;
1074	>	if (wasInterrupted && interruptible) {
1075	>	thread = null;
1076	>	return true;
1077		}
1078	<	else if ((h = head.get()) != null && h.phase != currentPhase) {
1079	<	if (phaseOf(state.get()) == currentPhase) { // must recheck
1080	<	if (head.compareAndSet(h, h.next)) {
1081	<	Thread t = h.thread; // help clear out old waiters
1082	<	if (t != null) {
1083	<	h.thread = null;
1084	<	LockSupport.unpark(t);
1085	<	}
1086	<	}
1078	>	if (timed) {
1079	>	if (nanos > 0L) {
1080	>	long now = System.nanoTime();
1081	>	nanos -= now - lastTime;
1082	>	lastTime = now;
1083	>	}
1084	>	if (nanos <= 0L) {
1085	>	thread = null;
1086	>	return true;
1087		}
680	–	else
681	–	break;
1088		}
1089	<	else if (node != null)
1090	<	queued = head.compareAndSet(node.next = h, node);
1091	<	else if (spins <= 0)
1092	<	node = new QNode(thread, currentPhase);
1093	<	else
1094	<	--spins;
1089	>	return false;
1090	>	}
1091	>
1092	>	public boolean block() {
1093	>	if (isReleasable())
1094	>	return true;
1095	>	else if (!timed)
1096	>	LockSupport.park(this);
1097	>	else if (nanos > 0)
1098	>	LockSupport.parkNanos(this, nanos);
1099	>	return isReleasable();
1100		}
690	–	if (node != null)
691	–	node.thread = null;
1101		}
1102
1103	<	}
1103	>	// Unsafe mechanics
1104
1105	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1106	+	private static final long stateOffset =
1107	+	objectFieldOffset("state", Phaser.class);
1108	+
1109	+	private static long objectFieldOffset(String field, Class<?> klazz) {
1110	+	try {
1111	+	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1112	+	} catch (NoSuchFieldException e) {
1113	+	// Convert Exception to corresponding Error
1114	+	NoSuchFieldError error = new NoSuchFieldError(field);
1115	+	error.initCause(e);
1116	+	throw error;
1117	+	}
1118	+	}
1119	+
1120	+	/**
1121	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1122	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1123	+	* into a jdk.
1124	+	*
1125	+	* @return a sun.misc.Unsafe
1126	+	*/
1127	+	private static sun.misc.Unsafe getUnsafe() {
1128	+	try {
1129	+	return sun.misc.Unsafe.getUnsafe();
1130	+	} catch (SecurityException se) {
1131	+	try {
1132	+	return java.security.AccessController.doPrivileged
1133	+	(new java.security
1134	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1135	+	public sun.misc.Unsafe run() throws Exception {
1136	+	java.lang.reflect.Field f = sun.misc
1137	+	.Unsafe.class.getDeclaredField("theUnsafe");
1138	+	f.setAccessible(true);
1139	+	return (sun.misc.Unsafe) f.get(null);
1140	+	}});
1141	+	} catch (java.security.PrivilegedActionException e) {
1142	+	throw new RuntimeException("Could not initialize intrinsics",
1143	+	e.getCause());
1144	+	}
1145	+	}
1146	+	}
1147	+	}

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