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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.1 by dl, Mon Jul 7 16:53:30 2008 UTC vs.
Revision 1.60 by dl, Sun Nov 28 15:49:49 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import jsr166y.forkjoin.*;
9	<	import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
8	>
9	>	import java.util.concurrent.TimeUnit;
10	>	import java.util.concurrent.TimeoutException;
11	>	import java.util.concurrent.atomic.AtomicReference;
12		import java.util.concurrent.locks.LockSupport;
13
14		/**
15	<	* A reusable synchronization barrier, similar in functionality to a
16	<	* {@link java.util.concurrent.CyclicBarrier}, but supporting more
17	<	* flexible usage.
15	>	* A reusable synchronization barrier, similar in functionality to
16	>	* {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and
17	>	* {@link java.util.concurrent.CountDownLatch CountDownLatch}
18	>	* but supporting more flexible usage.
19		*
20	<	* <ul>
20	>	* <p> <b>Registration.</b> Unlike the case for other barriers, the
21	>	* number of parties <em>registered</em> to synchronize on a Phaser
22	>	* may vary over time.  Tasks may be registered at any time (using
23	>	* methods {@link #register}, {@link #bulkRegister}, or forms of
24	>	* constructors establishing initial numbers of parties), and
25	>	* optionally deregistered upon any arrival (using {@link
26	>	* #arriveAndDeregister}).  As is the case with most basic
27	>	* synchronization constructs, registration and deregistration affect
28	>	* only internal counts; they do not establish any further internal
29	>	* bookkeeping, so tasks cannot query whether they are registered.
30	>	* (However, you can introduce such bookkeeping by subclassing this
31	>	* class.)
32		*
33	<	* <li> The number of parties synchronizing on the barrier may vary
34	<	* over time.  A task may register to be a party in a barrier at any
35	<	* time, and may deregister upon arriving at the barrier.  As is the
36	<	* case with most basic synchronization constructs, registration
37	<	* and deregistration affect only internal counts; they do not
38	<	* establish any further internal bookkeeping, so tasks cannot query
39	<	* whether they are registered.
40	<	*
41	<	* <li> Each generation has an associated phase value, starting at
42	<	* zero, and advancing when all parties reach the barrier (wrapping
43	<	* around to zero after reaching <tt>Integer.MAX_VALUE</tt>).
31	<	*
32	<	* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited.
33	<	* Method <tt>arriveAndAwaitAdvance</tt> has effect analogous to
34	<	* <tt>CyclicBarrier.await</tt>.  However, Phasers separate two
35	<	* aspects of coordination, that may be invoked independently:
33	>	* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
34	>	* Phaser} may be repeatedly awaited.  Method {@link
35	>	* #arriveAndAwaitAdvance} has effect analogous to {@link
36	>	* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
37	>	* generation of a {@code Phaser} has an associated phase number. The
38	>	* phase number starts at zero, and advances when all parties arrive
39	>	* at the barrier, wrapping around to zero after reaching {@code
40	>	* Integer.MAX_VALUE}. The use of phase numbers enables independent
41	>	* control of actions upon arrival at a barrier and upon awaiting
42	>	* others, via two kinds of methods that may be invoked by any
43	>	* registered party:
44		*
45		* <ul>
46		*
47	<	*   <li> Arriving at a barrier. Methods <tt>arrive</tt> and
48	<	*       <tt>arriveAndDeregister</tt> do not block, but return
49	<	*       the phase value on entry to the method.
50	<	*
51	<	*   <li> Awaiting others. Method <tt>awaitAdvance</tt> requires an
52	<	*       argument indicating the entry phase, and returns when the
53	<	*       barrier advances to a new phase.
47	>	*   <li> <b>Arrival.</b> Methods {@link #arrive} and
48	>	*       {@link #arriveAndDeregister} record arrival at a
49	>	*       barrier. These methods do not block, but return an associated
50	>	*       <em>arrival phase number</em>; that is, the phase number of
51	>	*       the barrier to which the arrival applied. When the final
52	>	*       party for a given phase arrives, an optional barrier action
53	>	*       is performed and the phase advances.  Barrier actions,
54	>	*       performed by the party triggering a phase advance, are
55	>	*       arranged by overriding method {@link #onAdvance(int, int)},
56	>	*       which also controls termination. Overriding this method is
57	>	*       similar to, but more flexible than, providing a barrier
58	>	*       action to a {@code CyclicBarrier}.
59	>	*
60	>	*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
61	>	*       argument indicating an arrival phase number, and returns when
62	>	*       the barrier advances to (or is already at) a different phase.
63	>	*       Unlike similar constructions using {@code CyclicBarrier},
64	>	*       method {@code awaitAdvance} continues to wait even if the
65	>	*       waiting thread is interrupted. Interruptible and timeout
66	>	*       versions are also available, but exceptions encountered while
67	>	*       tasks wait interruptibly or with timeout do not change the
68	>	*       state of the barrier. If necessary, you can perform any
69	>	*       associated recovery within handlers of those exceptions,
70	>	*       often after invoking {@code forceTermination}.  Phasers may
71	>	*       also be used by tasks executing in a {@link ForkJoinPool},
72	>	*       which will ensure sufficient parallelism to execute tasks
73	>	*       when others are blocked waiting for a phase to advance.
74	>	*
75		* </ul>
76		*
77	+	* <p> <b>Termination.</b> A {@code Phaser} may enter a
78	+	* <em>termination</em> state in which all synchronization methods
79	+	* immediately return without updating Phaser state or waiting for
80	+	* advance, and indicating (via a negative phase value) that execution
81	+	* is complete.  Termination is triggered when an invocation of {@code
82	+	* onAdvance} returns {@code true}. The default implementation returns
83	+	* {@code true} if a deregistration has caused the number of
84	+	* registered parties to become zero.  As illustrated below, when
85	+	* Phasers control actions with a fixed number of iterations, it is
86	+	* often convenient to override this method to cause termination when
87	+	* the current phase number reaches a threshold. Method {@link
88	+	* #forceTermination} is also available to abruptly release waiting
89	+	* threads and allow them to terminate.
90		*
91	<	* <li> Barrier actions, performed by the task triggering a phase
92	<	* advance while others may be waiting, are arranged by overriding
93	<	* method <tt>onAdvance</tt>, that also controls termination.
94	<	*
95	<	* <li> Phasers may enter a <em>termination</em> state in which all
96	<	* await actions immediately return, indicating (via a negative phase
97	<	* value) that execution is complete.  Termination is triggered by
56	<	* executing the overridable <tt>onAdvance</tt> method that is invoked
57	<	* each time the barrier is tripped. When a Phaser is controlling an
58	<	* action with a fixed number of iterations, it is often convenient to
59	<	* override this method to cause termination when the current phase
60	<	* number reaches a threshold.  Method <tt>forceTermination</tt> is
61	<	* also available to assist recovery actions upon failure.
62	<	*
63	<	* <li> Unlike most synchronizers, a Phaser may also be used with
64	<	* ForkJoinTasks (as well as plain threads).
65	<	*
66	<	* <li> By default, <tt>awaitAdvance</tt> continues to wait even if
67	<	* the current thread is interrupted. And unlike the case in
68	<	* CyclicBarriers, exceptions encountered while tasks wait
69	<	* interruptibly or with timeout do not change the state of the
70	<	* barrier. If necessary, you can perform any associated recovery
71	<	* within handlers of those exceptions.
91	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
92	>	* constructed in tree structures) to reduce contention. Phasers with
93	>	* large numbers of parties that would otherwise experience heavy
94	>	* synchronization contention costs may instead be set up so that
95	>	* groups of sub-phasers share a common parent.  This may greatly
96	>	* increase throughput even though it incurs greater per-operation
97	>	* overhead.
98		*
99	<	* </ul>
99	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
100	>	* only by registered parties, the current state of a Phaser may be
101	>	* monitored by any caller.  At any given moment there are {@link
102	>	* #getRegisteredParties} parties in total, of which {@link
103	>	* #getArrivedParties} have arrived at the current phase ({@link
104	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
105	>	* parties arrive, the phase advances.  The values returned by these
106	>	* methods may reflect transient states and so are not in general
107	>	* useful for synchronization control.  Method {@link #toString}
108	>	* returns snapshots of these state queries in a form convenient for
109	>	* informal monitoring.
110		*
111	<	* <p><b>Sample usage:</b>
111	>	* <p><b>Sample usages:</b>
112		*
113	<	* <p>[todo: non-FJ example]
113	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
114	>	* to control a one-shot action serving a variable number of parties.
115	>	* The typical idiom is for the method setting this up to first
116	>	* register, then start the actions, then deregister, as in:
117		*
118	<	* <p> A Phaser may be used to support a style of programming in
119	<	* which a task waits for others to complete, without otherwise
120	<	* needing to keep track of which tasks it is waiting for. This is
121	<	* similar to the "sync" construct in Cilk and "clocks" in X10.
122	<	* Special constructions based on such barriers are available using
123	<	* the <tt>LinkedAsyncAction</tt> and <tt>CyclicAction</tt> classes,
124	<	* but they can be useful in other contexts as well.  For a simple
125	<	* (but not very useful) example, here is a variant of Fibonacci:
126	<	*
127	<	* <pre>
128	<	* class BarrierFibonacci extends RecursiveAction {
129	<	*   int argument, result;
91	<	*   final Phaser parentBarrier;
92	<	*   BarrierFibonacci(int n, Phaser parentBarrier) {
93	<	*     this.argument = n;
94	<	*     this.parentBarrier = parentBarrier;
95	<	*     parentBarrier.register();
118	>	*  <pre> {@code
119	>	* void runTasks(List<Runnable> tasks) {
120	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
121	>	*   // create and start threads
122	>	*   for (Runnable task : tasks) {
123	>	*     phaser.register();
124	>	*     new Thread() {
125	>	*       public void run() {
126	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
127	>	*         task.run();
128	>	*       }
129	>	*     }.start();
130		*   }
131	<	*   protected void compute() {
132	<	*     int n = argument;
133	<	*     if (n &lt;= 1)
134	<	*        result = n;
135	<	*     else {
136	<	*        Phaser childBarrier = new Phaser(1);
137	<	*        BarrierFibonacci f1 = new BarrierFibonacci(n - 1, childBarrier);
138	<	*        BarrierFibonacci f2 = new BarrierFibonacci(n - 2, childBarrier);
139	<	*        f1.fork();
140	<	*        f2.fork();
141	<	*        childBarrier.arriveAndAwait();
142	<	*        result = f1.result + f2.result;
131	>	*
132	>	*   // allow threads to start and deregister self
133	>	*   phaser.arriveAndDeregister();
134	>	* }}</pre>
135	>	*
136	>	* <p>One way to cause a set of threads to repeatedly perform actions
137	>	* for a given number of iterations is to override {@code onAdvance}:
138	>	*
139	>	*  <pre> {@code
140	>	* void startTasks(List<Runnable> tasks, final int iterations) {
141	>	*   final Phaser phaser = new Phaser() {
142	>	*     protected boolean onAdvance(int phase, int registeredParties) {
143	>	*       return phase >= iterations || registeredParties == 0;
144		*     }
145	<	*     parentBarrier.arriveAndDeregister();
145	>	*   };
146	>	*   phaser.register();
147	>	*   for (final Runnable task : tasks) {
148	>	*     phaser.register();
149	>	*     new Thread() {
150	>	*       public void run() {
151	>	*         do {
152	>	*           task.run();
153	>	*           phaser.arriveAndAwaitAdvance();
154	>	*         } while (!phaser.isTerminated());
155	>	*       }
156	>	*     }.start();
157	>	*   }
158	>	*   phaser.arriveAndDeregister(); // deregister self, don't wait
159	>	* }}</pre>
160	>	*
161	>	* If the main task must later await termination, it
162	>	* may re-register and then execute a similar loop:
163	>	*  <pre> {@code
164	>	*   // ...
165	>	*   phaser.register();
166	>	*   while (!phaser.isTerminated())
167	>	*     phaser.arriveAndAwaitAdvance();}</pre>
168	>	*
169	>	* <p>Related constructions may be used to await particular phase numbers
170	>	* in contexts where you are sure that the phase will never wrap around
171	>	* {@code Integer.MAX_VALUE}. For example:
172	>	*
173	>	*  <pre> {@code
174	>	* void awaitPhase(Phaser phaser, int phase) {
175	>	*   int p = phaser.register(); // assumes caller not already registered
176	>	*   while (p < phase) {
177	>	*     if (phaser.isTerminated())
178	>	*       // ... deal with unexpected termination
179	>	*     else
180	>	*       p = phaser.arriveAndAwaitAdvance();
181	>	*   }
182	>	*   phaser.arriveAndDeregister();
183	>	* }}</pre>
184	>	*
185	>	*
186	>	* <p>To create a set of tasks using a tree of Phasers,
187	>	* you could use code of the following form, assuming a
188	>	* Task class with a constructor accepting a Phaser that
189	>	* it registers with upon construction:
190	>	*
191	>	*  <pre> {@code
192	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
193	>	*   if (hi - lo > TASKS_PER_PHASER) {
194	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
195	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
196	>	*       build(actions, i, j, new Phaser(ph));
197	>	*     }
198	>	*   } else {
199	>	*     for (int i = lo; i < hi; ++i)
200	>	*       actions[i] = new Task(ph);
201	>	*       // assumes new Task(ph) performs ph.register()
202		*   }
203		* }
204	<	* </pre>
204	>	* // .. initially called, for n tasks via
205	>	* build(new Task[n], 0, n, new Phaser());}</pre>
206	>	*
207	>	* The best value of {@code TASKS_PER_PHASER} depends mainly on
208	>	* expected barrier synchronization rates. A value as low as four may
209	>	* be appropriate for extremely small per-barrier task bodies (thus
210	>	* high rates), or up to hundreds for extremely large ones.
211		*
212		* <p><b>Implementation notes</b>: This implementation restricts the
213	<	* maximum number of parties to 65535. Attempts to register
214	<	* additional parties result in IllegalStateExceptions.
213	>	* maximum number of parties to 65535. Attempts to register additional
214	>	* parties result in {@code IllegalStateException}. However, you can and
215	>	* should create tiered Phasers to accommodate arbitrarily large sets
216	>	* of participants.
217	>	*
218	>	* @since 1.7
219	>	* @author Doug Lea
220		*/
221		public class Phaser {
222		/*
223		* This class implements an extension of X10 "clocks".  Thanks to
224	<	* Vijay Saraswat for the idea of applying it to ForkJoinTasks,
225	<	* and to Vivek Sarkar for enhancements to extend functionality.
224	>	* Vijay Saraswat for the idea, and to Vivek Sarkar for
225	>	* enhancements to extend functionality.
226		*/
227
228		/**
229		* Barrier state representation. Conceptually, a barrier contains
230		* four values:
231	<	*
232	<	* * parties -- the number of parties to wait (16 bits)
233	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
234	<	* * phase -- the generation of the barrier (31 bits)
235	<	* * terminated -- set if barrier is terminated (1 bit)
231	>	*
232	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
233	>	* * parties -- the number of parties to wait              (bits 16-31)
234	>	* * phase -- the generation of the barrier                (bits 32-62)
235	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
236		*
237		* However, to efficiently maintain atomicity, these values are
238	<	* packed into a single AtomicLong. Termination uses the sign bit
239	<	* of 32 bit representation of phase, so phase is set to -1 on
240	<	* termination.
241	<	*/
242	<	private final AtomicLong state;
238	>	* packed into a single (atomic) long. Termination uses the sign
239	>	* bit of 32 bit representation of phase, so phase is set to -1 on
240	>	* termination. Good performance relies on keeping state decoding
241	>	* and encoding simple, and keeping race windows short.
242	>	*/
243	>	private volatile long state;
244	>
245	>	private static final int  MAX_PARTIES     = 0xffff;
246	>	private static final int  MAX_PHASE       = 0x7fffffff;
247	>	private static final int  PARTIES_SHIFT   = 16;
248	>	private static final int  PHASE_SHIFT     = 32;
249	>	private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
250	>	private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
251	>	private static final long ONE_ARRIVAL     = 1L;
252	>	private static final long ONE_PARTY       = 1L << PARTIES_SHIFT;
253	>	private static final long TERMINATION_BIT = 1L << 63;
254
255	<	/**
143	<	* Head of Treiber stack for waiting nonFJ threads.
144	<	*/
145	<	private final AtomicReference<QNode> head = new AtomicReference<QNode>();
146	<
147	<	private static final int ushortBits = 16;
148	<	private static final int ushortMask =  (1 << ushortBits) - 1;
149	<	private static final int phaseMask = 0x7fffffff;
255	>	// The following unpacking methods are usually manually inlined
256
257		private static int unarrivedOf(long s) {
258	<	return (int)(s & ushortMask);
258	>	return (int)s & UNARRIVED_MASK;
259		}
260
261		private static int partiesOf(long s) {
262	<	return (int)(s & (ushortMask << 16)) >>> 16;
262	>	return (int)s >>> PARTIES_SHIFT;
263		}
264
265		private static int phaseOf(long s) {
266	<	return (int)(s >>> 32);
266	>	return (int) (s >>> PHASE_SHIFT);
267		}
268
269		private static int arrivedOf(long s) {
270		return partiesOf(s) - unarrivedOf(s);
271		}
272
273	<	private static long stateFor(int phase, int parties, int unarrived) {
274	<	return (((long)phase) << 32) | ((parties << 16) | unarrived);
275	<	}
273	>	/**
274	>	* The parent of this phaser, or null if none
275	>	*/
276	>	private final Phaser parent;
277
278	<	private static IllegalStateException badBounds(int parties, int unarrived) {
279	<	return new IllegalStateException("Attempt to set " + unarrived +
280	<	" unarrived of " + parties + " parties");
281	<	}
278	>	/**
279	>	* The root of phaser tree. Equals this if not in a tree.  Used to
280	>	* support faster state push-down.
281	>	*/
282	>	private final Phaser root;
283
284		/**
285	<	* Creates a new Phaser without any initially registered parties,
286	<	* and initial phase number 0.
285	>	* Heads of Treiber stacks for waiting threads. To eliminate
286	>	* contention when releasing some threads while adding others, we
287	>	* use two of them, alternating across even and odd phases.
288	>	* Subphasers share queues with root to speed up releases.
289		*/
290	<	public Phaser() {
291	<	state = new AtomicLong(stateFor(0, 0, 0));
290	>	private final AtomicReference<QNode> evenQ;
291	>	private final AtomicReference<QNode> oddQ;
292	>
293	>	private AtomicReference<QNode> queueFor(int phase) {
294	>	return ((phase & 1) == 0) ? evenQ : oddQ;
295		}
296
297		/**
298	<	* Creates a new Phaser with the given numbers of registered
186	<	* unarrived parties and initial phase number 0.
187	<	* @param parties the number of parties required to trip barrier.
188	<	* @throws IllegalArgumentException if parties less than zero
189	<	* or greater than the maximum number of parties supported.
298	>	* Returns message string for bounds exceptions on arrival.
299		*/
300	<	public Phaser(int parties) {
301	<	if (parties < 0 || parties > ushortMask)
302	<	throw new IllegalArgumentException("Illegal number of parties");
194	<	state = new AtomicLong(stateFor(0, parties, parties));
300	>	private String badArrive(long s) {
301	>	return "Attempted arrival of unregistered party for " +
302	>	stateToString(s);
303		}
304
305		/**
306	<	* Adds a new unarrived party to this phaser.
199	<	* @return the current barrier phase number upon registration
200	<	* @throws IllegalStateException if attempting to register more
201	<	* than the maximum supported number of parties.
306	>	* Returns message string for bounds exceptions on registration.
307		*/
308	<	public int register() { // increment both parties and unarrived
309	<	final AtomicLong state = this.state;
310	<	for (;;) {
206	<	long s = state.get();
207	<	int phase = phaseOf(s);
208	<	int parties = partiesOf(s) + 1;
209	<	int unarrived = unarrivedOf(s) + 1;
210	<	if (parties > ushortMask || unarrived > ushortMask)
211	<	throw badBounds(parties, unarrived);
212	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
213	<	return phase;
214	<	}
308	>	private String badRegister(long s) {
309	>	return "Attempt to register more than " +
310	>	MAX_PARTIES + " parties for " + stateToString(s);
311		}
312
313		/**
314	<	* Arrives at the barrier, but does not wait for others.  (You can
315	<	* in turn wait for others via {@link #awaitAdvance}).
314	>	* Main implementation for methods arrive and arriveAndDeregister.
315	>	* Manually tuned to speed up and minimize race windows for the
316	>	* common case of just decrementing unarrived field.
317		*
318	<	* @return the current barrier phase number upon entry to
319	<	* this method, or a negative value if terminated;
320	<	* @throws IllegalStateException if the number of unarrived
224	<	* parties would become negative.
318	>	* @param adj - adjustment to apply to state -- either
319	>	* ONE_ARRIVAL (for arrive) or
320	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
321		*/
322	<	public int arrive() { // decrement unarrived. If zero, trip
227	<	final AtomicLong state = this.state;
322	>	private int doArrive(long adj) {
323		for (;;) {
324	<	long s = state.get();
325	<	int phase = phaseOf(s);
326	<	int parties = partiesOf(s);
327	<	int unarrived = unarrivedOf(s) - 1;
233	<	if (unarrived < 0)
234	<	throw badBounds(parties, unarrived);
235	<	if (unarrived == 0 && phase >= 0) {
236	<	trip(phase, parties);
324	>	long s = state;
325	>	int unarrived = (int)s & UNARRIVED_MASK;
326	>	int phase = (int)(s >>> PHASE_SHIFT);
327	>	if (phase < 0)
328		return phase;
329	+	else if (unarrived == 0) {
330	+	if (reconcileState() == s)     // recheck
331	+	throw new IllegalStateException(badArrive(s));
332		}
333	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
333	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
334	>	if (unarrived == 1) {
335	>	long p = s & PARTIES_MASK; // unshifted parties field
336	>	long lu = p >>> PARTIES_SHIFT;
337	>	int u = (int)lu;
338	>	int nextPhase = (phase + 1) & MAX_PHASE;
339	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
340	>	final Phaser parent = this.parent;
341	>	if (parent == null) {
342	>	if (onAdvance(phase, u))
343	>	next |= TERMINATION_BIT;
344	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
345	>	releaseWaiters(phase);
346	>	}
347	>	else {
348	>	parent.doArrive((u == 0) ?
349	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
350	>	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase ||
351	>	((int)(state >>> PHASE_SHIFT) != nextPhase &&
352	>	!UNSAFE.compareAndSwapLong(this, stateOffset,
353	>	s, next)))
354	>	reconcileState();
355	>	}
356	>	}
357		return phase;
358	+	}
359		}
360		}
361
362		/**
363	<	* Arrives at the barrier, and deregisters from it, without
246	<	* waiting for others.
363	>	* Implementation of register, bulkRegister
364		*
365	<	* @return the current barrier phase number upon entry to
366	<	* this method, or a negative value if terminated;
250	<	* @throws IllegalStateException if the number of registered or
251	<	* unarrived parties would become negative.
365	>	* @param registrations number to add to both parties and
366	>	* unarrived fields. Must be greater than zero.
367		*/
368	<	public int arriveAndDeregister() { // Same as arrive, plus decrement parties
369	<	final AtomicLong state = this.state;
368	>	private int doRegister(int registrations) {
369	>	// adjustment to state
370	>	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
371	>	final Phaser parent = this.parent;
372		for (;;) {
373	<	long s = state.get();
374	<	int phase = phaseOf(s);
375	<	int parties = partiesOf(s) - 1;
376	<	int unarrived = unarrivedOf(s) - 1;
260	<	if (parties < 0 || unarrived < 0)
261	<	throw badBounds(parties, unarrived);
262	<	if (unarrived == 0 && phase >= 0) {
263	<	trip(phase, parties);
373	>	long s = (parent == null) ? state : reconcileState();
374	>	int parties = (int)s >>> PARTIES_SHIFT;
375	>	int phase = (int)(s >>> PHASE_SHIFT);
376	>	if (phase < 0)
377		return phase;
378	+	else if (registrations > MAX_PARTIES - parties)
379	+	throw new IllegalStateException(badRegister(s));
380	+	else if ((parties == 0 && parent == null) || // first reg of root
381	+	((int)s & UNARRIVED_MASK) != 0) {   // not advancing
382	+	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
383	+	return phase;
384	+	}
385	+	else if (parties != 0)               // wait for onAdvance
386	+	root.internalAwaitAdvance(phase, null);
387	+	else {                               // 1st registration of child
388	+	synchronized(this) {             // register parent first
389	+	if (reconcileState() == s) { // recheck under lock
390	+	parent.doRegister(1);    // OK if throws IllegalState
391	+	for (;;) {               // simpler form of outer loop
392	+	s = reconcileState();
393	+	phase = (int)(s >>> PHASE_SHIFT);
394	+	if (phase < 0 ||
395	+	UNSAFE.compareAndSwapLong(this, stateOffset,
396	+	s, s + adj))
397	+	return phase;
398	+	}
399	+	}
400	+	}
401		}
266	–	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
267	–	return phase;
402		}
403		}
404
405		/**
406	<	* Arrives at the barrier and awaits others. Unlike other arrival
273	<	* methods, this method returns the arrival index of the
274	<	* caller. The caller tripping the barrier returns zero, the
275	<	* previous caller 1, and so on.
276	<	* @return the arrival index
277	<	* @throws IllegalStateException if the number of unarrived
278	<	* parties would become negative.
406	>	* Recursively resolves lagged phase propagation from root if necessary.
407		*/
408	<	public int arriveAndAwaitAdvance() {
409	<	final AtomicLong state = this.state;
410	<	for (;;) {
411	<	long s = state.get();
412	<	int phase = phaseOf(s);
413	<	int parties = partiesOf(s);
414	<	int unarrived = unarrivedOf(s) - 1;
415	<	if (unarrived < 0)
416	<	throw badBounds(parties, unarrived);
417	<	if (unarrived == 0 && phase >= 0) {
418	<	trip(phase, parties);
419	<	return 0;
420	<	}
421	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) {
422	<	awaitAdvance(phase);
423	<	return unarrived;
408	>	private long reconcileState() {
409	>	Phaser par = parent;
410	>	long s = state;
411	>	if (par != null) {
412	>	Phaser rt = root;
413	>	int phase, rPhase;
414	>	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
415	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
416	>	if ((int)(par.state >>> PHASE_SHIFT) != rPhase)
417	>	par.reconcileState();
418	>	else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
419	>	long u = s & PARTIES_MASK; // reset unarrived to parties
420	>	long next = ((((long) rPhase) << PHASE_SHIFT) | u |
421	>	(u >>> PARTIES_SHIFT));
422	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
423	>	}
424	>	s = state;
425		}
426		}
427	+	return s;
428		}
429
430		/**
431	<	* Awaits the phase of the barrier to advance from the given
432	<	* value, or returns immediately if this barrier is terminated
433	<	* @param phase the phase on entry to this method
434	<	* @return the phase on exit from this method
431	>	* Creates a new Phaser without any initially registered parties,
432	>	* initial phase number 0, and no parent. Any thread using this
433	>	* Phaser will need to first register for it.
434	>	*/
435	>	public Phaser() {
436	>	this(null, 0);
437	>	}
438	>
439	>	/**
440	>	* Creates a new Phaser with the given number of registered
441	>	* unarrived parties, initial phase number 0, and no parent.
442	>	*
443	>	* @param parties the number of parties required to trip barrier
444	>	* @throws IllegalArgumentException if parties less than zero
445	>	* or greater than the maximum number of parties supported
446	>	*/
447	>	public Phaser(int parties) {
448	>	this(null, parties);
449	>	}
450	>
451	>	/**
452	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
453	>	*
454	>	* @param parent the parent Phaser
455	>	*/
456	>	public Phaser(Phaser parent) {
457	>	this(parent, 0);
458	>	}
459	>
460	>	/**
461	>	* Creates a new Phaser with the given parent and number of
462	>	* registered unarrived parties. Registration and deregistration
463	>	* of this child Phaser with its parent are managed automatically.
464	>	* If the given parent is non-null, whenever this child Phaser has
465	>	* any registered parties (as established in this constructor,
466	>	* {@link #register}, or {@link #bulkRegister}), this child Phaser
467	>	* is registered with its parent. Whenever the number of
468	>	* registered parties becomes zero as the result of an invocation
469	>	* of {@link #arriveAndDeregister}, this child Phaser is
470	>	* deregistered from its parent.
471	>	*
472	>	* @param parent the parent Phaser
473	>	* @param parties the number of parties required to trip barrier
474	>	* @throws IllegalArgumentException if parties less than zero
475	>	* or greater than the maximum number of parties supported
476	>	*/
477	>	public Phaser(Phaser parent, int parties) {
478	>	if (parties >>> PARTIES_SHIFT != 0)
479	>	throw new IllegalArgumentException("Illegal number of parties");
480	>	long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT);
481	>	this.parent = parent;
482	>	if (parent != null) {
483	>	Phaser r = parent.root;
484	>	this.root = r;
485	>	this.evenQ = r.evenQ;
486	>	this.oddQ = r.oddQ;
487	>	if (parties != 0)
488	>	s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT;
489	>	}
490	>	else {
491	>	this.root = this;
492	>	this.evenQ = new AtomicReference<QNode>();
493	>	this.oddQ = new AtomicReference<QNode>();
494	>	}
495	>	this.state = s;
496	>	}
497	>
498	>	/**
499	>	* Adds a new unarrived party to this Phaser.  If an ongoing
500	>	* invocation of {@link #onAdvance} is in progress, this method
501	>	* may await its completion before returning.  If this Phaser has
502	>	* a parent, and this Phaser previously had no registered parties,
503	>	* this Phaser is also registered with its parent.
504	>	*
505	>	* @return the arrival phase number to which this registration applied
506	>	* @throws IllegalStateException if attempting to register more
507	>	* than the maximum supported number of parties
508	>	*/
509	>	public int register() {
510	>	return doRegister(1);
511	>	}
512	>
513	>	/**
514	>	* Adds the given number of new unarrived parties to this Phaser.
515	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
516	>	* this method may await its completion before returning.  If this
517	>	* Phaser has a parent, and the given number of parities is
518	>	* greater than zero, and this Phaser previously had no registered
519	>	* parties, this Phaser is also registered with its parent.
520	>	*
521	>	* @param parties the number of additional parties required to trip barrier
522	>	* @return the arrival phase number to which this registration applied
523	>	* @throws IllegalStateException if attempting to register more
524	>	* than the maximum supported number of parties
525	>	* @throws IllegalArgumentException if {@code parties < 0}
526	>	*/
527	>	public int bulkRegister(int parties) {
528	>	if (parties < 0)
529	>	throw new IllegalArgumentException();
530	>	if (parties == 0)
531	>	return getPhase();
532	>	return doRegister(parties);
533	>	}
534	>
535	>	/**
536	>	* Arrives at the barrier, without waiting for others to arrive.
537	>	*
538	>	* <p>It is a usage error for an unregistered party to invoke this
539	>	* method.  However, this error may result in an {@code
540	>	* IllegalStateException} only upon some subsequent operation on
541	>	* this Phaser, if ever.
542	>	*
543	>	* @return the arrival phase number, or a negative value if terminated
544	>	* @throws IllegalStateException if not terminated and the number
545	>	* of unarrived parties would become negative
546	>	*/
547	>	public int arrive() {
548	>	return doArrive(ONE_ARRIVAL);
549	>	}
550	>
551	>	/**
552	>	* Arrives at the barrier and deregisters from it without waiting
553	>	* for others to arrive. Deregistration reduces the number of
554	>	* parties required to trip the barrier in future phases.  If this
555	>	* Phaser has a parent, and deregistration causes this Phaser to
556	>	* have zero parties, this Phaser is also deregistered from its
557	>	* parent.
558	>	*
559	>	* <p>It is a usage error for an unregistered party to invoke this
560	>	* method.  However, this error may result in an {@code
561	>	* IllegalStateException} only upon some subsequent operation on
562	>	* this Phaser, if ever.
563	>	*
564	>	* @return the arrival phase number, or a negative value if terminated
565	>	* @throws IllegalStateException if not terminated and the number
566	>	* of registered or unarrived parties would become negative
567	>	*/
568	>	public int arriveAndDeregister() {
569	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
570	>	}
571	>
572	>	/**
573	>	* Arrives at the barrier and awaits others. Equivalent in effect
574	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
575	>	* interruption or timeout, you can arrange this with an analogous
576	>	* construction using one of the other forms of the {@code
577	>	* awaitAdvance} method.  If instead you need to deregister upon
578	>	* arrival, use {@code awaitAdvance(arriveAndDeregister())}.
579	>	*
580	>	* <p>It is a usage error for an unregistered party to invoke this
581	>	* method.  However, this error may result in an {@code
582	>	* IllegalStateException} only upon some subsequent operation on
583	>	* this Phaser, if ever.
584	>	*
585	>	* @return the arrival phase number, or a negative number if terminated
586	>	* @throws IllegalStateException if not terminated and the number
587	>	* of unarrived parties would become negative
588	>	*/
589	>	public int arriveAndAwaitAdvance() {
590	>	return awaitAdvance(arrive());
591	>	}
592	>
593	>	/**
594	>	* Awaits the phase of the barrier to advance from the given phase
595	>	* value, returning immediately if the current phase of the
596	>	* barrier is not equal to the given phase value or this barrier
597	>	* is terminated.
598	>	*
599	>	* @param phase an arrival phase number, or negative value if
600	>	* terminated; this argument is normally the value returned by a
601	>	* previous call to {@code arrive} or its variants
602	>	* @return the next arrival phase number, or a negative value
603	>	* if terminated or argument is negative
604		*/
605		public int awaitAdvance(int phase) {
606	+	Phaser r;
607	+	int p = (int)(state >>> PHASE_SHIFT);
608		if (phase < 0)
609		return phase;
610	<	Thread current = Thread.currentThread();
611	<	if (current instanceof ForkJoinWorkerThread)
612	<	return helpingWait(phase);
613	<	if (untimedWait(current, phase, false))
313	<	current.interrupt();
314	<	return phaseOf(state.get());
610	>	if (p == phase &&
611	>	(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase)
612	>	return r.internalAwaitAdvance(phase, null);
613	>	return p;
614		}
615
616		/**
617	<	* Awaits the phase of the barrier to advance from the given
618	<	* value, or returns immediately if this barrier is terminated, or
619	<	* throws InterruptedException if interrupted while waiting.
620	<	* @param phase the phase on entry to this method
621	<	* @return the phase on exit from this method
617	>	* Awaits the phase of the barrier to advance from the given phase
618	>	* value, throwing {@code InterruptedException} if interrupted
619	>	* while waiting, or returning immediately if the current phase of
620	>	* the barrier is not equal to the given phase value or this
621	>	* barrier is terminated.
622	>	*
623	>	* @param phase an arrival phase number, or negative value if
624	>	* terminated; this argument is normally the value returned by a
625	>	* previous call to {@code arrive} or its variants
626	>	* @return the next arrival phase number, or a negative value
627	>	* if terminated or argument is negative
628		* @throws InterruptedException if thread interrupted while waiting
629		*/
630	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
630	>	public int awaitAdvanceInterruptibly(int phase)
631	>	throws InterruptedException {
632	>	Phaser r;
633	>	int p = (int)(state >>> PHASE_SHIFT);
634		if (phase < 0)
635		return phase;
636	<	Thread current = Thread.currentThread();
637	<	if (current instanceof ForkJoinWorkerThread)
638	<	return helpingWait(phase);
639	<	else if (Thread.interrupted() || untimedWait(current, phase, true))
640	<	throw new InterruptedException();
641	<	else
642	<	return phaseOf(state.get());
636	>	if (p == phase &&
637	>	(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) {
638	>	QNode node = new QNode(this, phase, true, false, 0L);
639	>	p = r.internalAwaitAdvance(phase, node);
640	>	if (node.wasInterrupted)
641	>	throw new InterruptedException();
642	>	}
643	>	return p;
644		}
645
646		/**
647	<	* Awaits the phase of the barrier to advance from the given value
648	<	* or the given timeout elapses, or returns immediately if this
649	<	* barrier is terminated
650	<	* @param phase the phase on entry to this method
651	<	* @return the phase on exit from this method
647	>	* Awaits the phase of the barrier to advance from the given phase
648	>	* value or the given timeout to elapse, throwing {@code
649	>	* InterruptedException} if interrupted while waiting, or
650	>	* returning immediately if the current phase of the barrier is
651	>	* not equal to the given phase value or this barrier is
652	>	* terminated.
653	>	*
654	>	* @param phase an arrival phase number, or negative value if
655	>	* terminated; this argument is normally the value returned by a
656	>	* previous call to {@code arrive} or its variants
657	>	* @param timeout how long to wait before giving up, in units of
658	>	*        {@code unit}
659	>	* @param unit a {@code TimeUnit} determining how to interpret the
660	>	*        {@code timeout} parameter
661	>	* @return the next arrival phase number, or a negative value
662	>	* if terminated or argument is negative
663		* @throws InterruptedException if thread interrupted while waiting
664		* @throws TimeoutException if timed out while waiting
665		*/
666	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
666	>	public int awaitAdvanceInterruptibly(int phase,
667	>	long timeout, TimeUnit unit)
668		throws InterruptedException, TimeoutException {
669	+	long nanos = unit.toNanos(timeout);
670	+	Phaser r;
671	+	int p = (int)(state >>> PHASE_SHIFT);
672		if (phase < 0)
673		return phase;
674	<	long nanos = unit.toNanos(timeout);
675	<	Thread current = Thread.currentThread();
676	<	if (current instanceof ForkJoinWorkerThread)
677	<	return timedHelpingWait(phase, nanos);
678	<	timedWait(current, phase, nanos);
679	<	return phaseOf(state.get());
674	>	if (p == phase &&
675	>	(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) {
676	>	QNode node = new QNode(this, phase, true, true, nanos);
677	>	p = r.internalAwaitAdvance(phase, node);
678	>	if (node.wasInterrupted)
679	>	throw new InterruptedException();
680	>	else if (p == phase)
681	>	throw new TimeoutException();
682	>	}
683	>	return p;
684		}
685
686		/**
687	<	* Forces this barrier to enter termination state. Counts of
688	<	* arrived and registered parties are unaffected. This method may
689	<	* be useful for coordinating recovery after one or more tasks
687	>	* Forces this barrier to enter termination state.  Counts of
688	>	* arrived and registered parties are unaffected.  If this Phaser
689	>	* is a member of a tiered set of Phasers, then all of the Phasers
690	>	* in the set are terminated.  If this Phaser is already
691	>	* terminated, this method has no effect.  This method may be
692	>	* useful for coordinating recovery after one or more tasks
693		* encounter unexpected exceptions.
694		*/
695		public void forceTermination() {
696	<	final AtomicLong state = this.state;
697	<	for (;;) {
698	<	long s = state.get();
699	<	int phase = phaseOf(s);
700	<	int parties = partiesOf(s);
701	<	int unarrived = unarrivedOf(s);
702	<	if (phase < 0 ||
703	<	state.compareAndSet(s, stateFor(-1, parties, unarrived))) {
373	<	if (head.get() != null)
374	<	releaseWaiters(-1);
696	>	// Only need to change root state
697	>	final Phaser root = this.root;
698	>	long s;
699	>	while ((s = root.state) >= 0) {
700	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
701	>	s, s | TERMINATION_BIT)) {
702	>	releaseWaiters(0); // signal all threads
703	>	releaseWaiters(1);
704		return;
705		}
706		}
707		}
708
709		/**
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	–	/**
710		* Returns the current phase number. The maximum phase number is
711	<	* <tt>Integer.MAX_VALUE</tt>, after which it restarts at
711	>	* {@code Integer.MAX_VALUE}, after which it restarts at
712		* zero. Upon termination, the phase number is negative.
713	+	*
714		* @return the phase number, or a negative value if terminated
715		*/
716	<	public int getPhase() {
717	<	return phaseOf(state.get());
716	>	public final int getPhase() {
717	>	return (int)(root.state >>> PHASE_SHIFT);
718		}
719
720		/**
721		* Returns the number of parties registered at this barrier.
722	+	*
723		* @return the number of parties
724		*/
725		public int getRegisteredParties() {
726	<	return partiesOf(state.get());
726	>	return partiesOf(state);
727		}
728
729		/**
730	<	* Returns the number of parties that have arrived at the current
731	<	* phase of this barrier.
730	>	* Returns the number of registered parties that have arrived at
731	>	* the current phase of this barrier.
732	>	*
733		* @return the number of arrived parties
734		*/
735		public int getArrivedParties() {
736	<	return arrivedOf(state.get());
736	>	long s = state;
737	>	int u = unarrivedOf(s); // only reconcile if possibly needed
738	>	return (u != 0 || parent == null) ?
739	>	partiesOf(s) - u :
740	>	arrivedOf(reconcileState());
741		}
742
743		/**
744		* Returns the number of registered parties that have not yet
745		* arrived at the current phase of this barrier.
746	+	*
747		* @return the number of unarrived parties
748		*/
749		public int getUnarrivedParties() {
750	<	return unarrivedOf(state.get());
750	>	int u = unarrivedOf(state);
751	>	return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState());
752		}
753
754		/**
755	<	* Returns true if this barrier has been terminated
756	<	* @return true if this barrier has been terminated
755	>	* Returns the parent of this Phaser, or {@code null} if none.
756	>	*
757	>	* @return the parent of this Phaser, or {@code null} if none
758	>	*/
759	>	public Phaser getParent() {
760	>	return parent;
761	>	}
762	>
763	>	/**
764	>	* Returns the root ancestor of this Phaser, which is the same as
765	>	* this Phaser if it has no parent.
766	>	*
767	>	* @return the root ancestor of this Phaser
768	>	*/
769	>	public Phaser getRoot() {
770	>	return root;
771	>	}
772	>
773	>	/**
774	>	* Returns {@code true} if this barrier has been terminated.
775	>	*
776	>	* @return {@code true} if this barrier has been terminated
777		*/
778		public boolean isTerminated() {
779	<	return phaseOf(state.get()) < 0;
779	>	return root.state < 0L;
780		}
781
782		/**
783	<	* Overridable method to perform an action upon phase advance, and
784	<	* to control termination. This method is invoked whenever the
785	<	* barrier is tripped (and thus all other waiting parties are
786	<	* dormant). If it returns true, then, rather than advance the
787	<	* phase number, this barrier will be set to a final termination
788	<	* state, and subsequent calls to <tt>isTerminated</tt> will
789	<	* return true.
790	<	*
791	<	* <p> The default version returns true when the number of
792	<	* registered parties is zero. Normally, overrides that arrange
793	<	* termination for other reasons should also preserve this
794	<	* property.
783	>	* Overridable method to perform an action upon impending phase
784	>	* advance, and to control termination. This method is invoked
785	>	* upon arrival of the party tripping the barrier (when all other
786	>	* waiting parties are dormant).  If this method returns {@code
787	>	* true}, then, rather than advance the phase number, this barrier
788	>	* will be set to a final termination state, and subsequent calls
789	>	* to {@link #isTerminated} will return true. Any (unchecked)
790	>	* Exception or Error thrown by an invocation of this method is
791	>	* propagated to the party attempting to trip the barrier, in
792	>	* which case no advance occurs.
793	>	*
794	>	* <p>The arguments to this method provide the state of the Phaser
795	>	* prevailing for the current transition.  The effects of invoking
796	>	* arrival, registration, and waiting methods on this Phaser from
797	>	* within {@code onAdvance} are unspecified and should not be
798	>	* relied on.
799	>	*
800	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
801	>	* {@code onAdvance} is invoked only for its root Phaser on each
802	>	* advance.
803	>	*
804	>	* <p>To support the most common use cases, the default
805	>	* implementation of this method returns {@code true} when the
806	>	* number of registered parties has become zero as the result of a
807	>	* party invoking {@code arriveAndDeregister}.  You can disable
808	>	* this behavior, thus enabling continuation upon future
809	>	* registrations, by overriding this method to always return
810	>	* {@code false}:
811	>	*
812	>	* <pre> {@code
813	>	* Phaser phaser = new Phaser() {
814	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
815	>	* }}</pre>
816		*
817		* @param phase the phase number on entering the barrier
818	<	* @param registeredParties the current number of registered
819	<	* parties.
458	<	* @return true if this barrier should terminate
818	>	* @param registeredParties the current number of registered parties
819	>	* @return {@code true} if this barrier should terminate
820		*/
821		protected boolean onAdvance(int phase, int registeredParties) {
822		return registeredParties <= 0;
823		}
824
825		/**
826	<	* Returns a string identifying this barrier, as well as its
826	>	* Returns a string identifying this Phaser, as well as its
827		* state.  The state, in brackets, includes the String {@code
828	<	* "phase ="} followed by the phase number, {@code "parties ="}
828	>	* "phase = "} followed by the phase number, {@code "parties = "}
829		* followed by the number of registered parties, and {@code
830	<	* "arrived ="} followed by the number of arrived parties
830	>	* "arrived = "} followed by the number of arrived parties.
831		*
832		* @return a string identifying this barrier, as well as its state
833		*/
834		public String toString() {
835	<	long s = state.get();
475	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
835	>	return stateToString(reconcileState());
836		}
837
478	–	// methods for tripping and waiting
479	–
838		/**
839	<	* Advance the current phase (or terminate)
839	>	* Implementation of toString and string-based error messages
840		*/
841	<	private void trip(int phase, int parties) {
842	<	int next = onAdvance(phase, parties)? -1 : ((phase + 1) & phaseMask);
843	<	state.set(stateFor(next, parties, parties));
844	<	if (head.get() != null)
845	<	releaseWaiters(next);
841	>	private String stateToString(long s) {
842	>	return super.toString() +
843	>	"[phase = " + phaseOf(s) +
844	>	" parties = " + partiesOf(s) +
845	>	" arrived = " + arrivedOf(s) + "]";
846		}
847
848	<	private int helpingWait(int phase) {
849	<	final AtomicLong state = this.state;
848	>	// Waiting mechanics
849	>
850	>	/**
851	>	* Removes and signals threads from queue for phase.
852	>	*/
853	>	private void releaseWaiters(int phase) {
854	>	AtomicReference<QNode> head = queueFor(phase);
855	>	QNode q;
856		int p;
857	<	while ((p = phaseOf(state.get())) == phase) {
858	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
859	<	if (t != null) {
860	<	if ((p = phaseOf(state.get())) == phase)
861	<	t.exec();
498	<	else {   // push task and exit if barrier advanced
499	<	t.fork();
500	<	break;
501	<	}
502	<	}
857	>	while ((q = head.get()) != null &&
858	>	((p = q.phase) == phase ||
859	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
860	>	if (head.compareAndSet(q, q.next))
861	>	q.signal();
862		}
504	–	return p;
863		}
864
865	<	private int timedHelpingWait(int phase, long nanos) throws TimeoutException {
866	<	final AtomicLong state = this.state;
867	<	long lastTime = System.nanoTime();
865	>	/** The number of CPUs, for spin control */
866	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
867	>
868	>	/**
869	>	* The number of times to spin before blocking while waiting for
870	>	* advance, per arrival while waiting. On multiprocessors, fully
871	>	* blocking and waking up a large number of threads all at once is
872	>	* usually a very slow process, so we use rechargeable spins to
873	>	* avoid it when threads regularly arrive: When a thread in
874	>	* internalAwaitAdvance notices another arrival before blocking,
875	>	* and there appear to be enough CPUs available, it spins
876	>	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
877	>	* uniprocessors, there is at least one intervening Thread.yield
878	>	* before blocking. The value trades off good-citizenship vs big
879	>	* unnecessary slowdowns.
880	>	*/
881	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
882	>
883	>	/**
884	>	* Possibly blocks and waits for phase to advance unless aborted.
885	>	* Call only from root node.
886	>	*
887	>	* @param phase current phase
888	>	* @param node if non-null, the wait node to track interrupt and timeout;
889	>	* if null, denotes noninterruptible wait
890	>	* @return current phase
891	>	*/
892	>	private int internalAwaitAdvance(int phase, QNode node) {
893	>	boolean queued = false;      // true when node is enqueued
894	>	int lastUnarrived = -1;      // to increase spins upon change
895	>	int spins = SPINS_PER_ARRIVAL;
896	>	long s;
897		int p;
898	<	while ((p = phaseOf(state.get())) == phase) {
899	<	long now = System.nanoTime();
900	<	nanos -= now - lastTime;
901	<	lastTime = now;
902	<	if (nanos <= 0) {
903	<	if ((p = phaseOf(state.get())) == phase)
904	<	throw new TimeoutException();
518	<	else
519	<	break;
898	>	while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
899	>	int unarrived = (int)s & UNARRIVED_MASK;
900	>	if (unarrived != lastUnarrived) {
901	>	if (lastUnarrived == -1) // ensure old queue clean
902	>	releaseWaiters(phase-1);
903	>	if ((lastUnarrived = unarrived) < NCPU)
904	>	spins += SPINS_PER_ARRIVAL;
905		}
906	<	ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask();
907	<	if (t != null) {
908	<	if ((p = phaseOf(state.get())) == phase)
909	<	t.exec();
910	<	else {   // push task and exit if barrier advanced
911	<	t.fork();
912	<	break;
906	>	else if (spins > 0) {
907	>	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
908	>	Thread.yield();  // yield midway through spin
909	>	}
910	>	else if (node == null)   // must be noninterruptible
911	>	node = new QNode(this, phase, false, false, 0L);
912	>	else if (node.isReleasable()) {
913	>	p = (int)(state >>> PHASE_SHIFT);
914	>	break;               // aborted
915	>	}
916	>	else if (!queued) {      // push onto queue
917	>	AtomicReference<QNode> head = queueFor(phase);
918	>	QNode q = head.get();
919	>	if (q == null || q.phase == phase) {
920	>	node.next = q;
921	>	if ((p = (int)(state >>> PHASE_SHIFT)) != phase)
922	>	break;       // recheck to avoid stale enqueue
923	>	else
924	>	queued = head.compareAndSet(q, node);
925	>	}
926	>	}
927	>	else {
928	>	try {
929	>	ForkJoinPool.managedBlock(node);
930	>	} catch (InterruptedException ie) {
931	>	node.wasInterrupted = true;
932		}
933		}
934		}
935	+
936	+	if (node != null) {
937	+	if (node.thread != null)
938	+	node.thread = null; // disable unpark() in node.signal
939	+	if (!node.interruptible && node.wasInterrupted)
940	+	Thread.currentThread().interrupt();
941	+	}
942	+	if (p != phase)
943	+	releaseWaiters(phase);
944		return p;
945		}
946
947		/**
948	<	* Wait nodes for Treiber stack representing wait queue for non-FJ
536	<	* tasks. The waiting scheme is an adaptation of the one used in
537	<	* forkjoin.PoolBarrier.
948	>	* Wait nodes for Treiber stack representing wait queue
949		*/
950	<	static final class QNode {
951	<	QNode next;
541	<	volatile Thread thread; // nulled to cancel wait
950	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
951	>	final Phaser phaser;
952		final int phase;
953	<	QNode(Thread t, int c) {
954	<	thread = t;
955	<	phase = c;
953	>	final boolean interruptible;
954	>	final boolean timed;
955	>	boolean wasInterrupted;
956	>	long nanos;
957	>	long lastTime;
958	>	volatile Thread thread; // nulled to cancel wait
959	>	QNode next;
960	>
961	>	QNode(Phaser phaser, int phase, boolean interruptible,
962	>	boolean timed, long nanos) {
963	>	this.phaser = phaser;
964	>	this.phase = phase;
965	>	this.interruptible = interruptible;
966	>	this.nanos = nanos;
967	>	this.timed = timed;
968	>	this.lastTime = timed? System.nanoTime() : 0L;
969	>	thread = Thread.currentThread();
970		}
547	–	}
971
972	<	private void releaseWaiters(int currentPhase) {
973	<	final AtomicReference<QNode> head = this.head;
974	<	QNode p;
975	<	while ((p = head.get()) != null && p.phase != currentPhase) {
976	<	if (head.compareAndSet(p, null)) {
977	<	do {
978	<	Thread t = p.thread;
979	<	if (t != null) {
980	<	p.thread = null;
981	<	LockSupport.unpark(t);
972	>	public boolean isReleasable() {
973	>	Thread t = thread;
974	>	if (t != null) {
975	>	if (phaser.getPhase() != phase)
976	>	t = null;
977	>	else {
978	>	if (Thread.interrupted())
979	>	wasInterrupted = true;
980	>	if (interruptible && wasInterrupted)
981	>	t = null;
982	>	else if (timed) {
983	>	if (nanos > 0) {
984	>	long now = System.nanoTime();
985	>	nanos -= now - lastTime;
986	>	lastTime = now;
987	>	}
988	>	if (nanos <= 0)
989	>	t = null;
990		}
991	<	} while ((p = p.next) != null);
991	>	}
992	>	if (t != null)
993	>	return false;
994	>	thread = null;
995		}
996	+	return true;
997		}
563	–	}
998
999	<	/** The number of CPUs, for spin control */
1000	<	static final int NCPUS = Runtime.getRuntime().availableProcessors();
1001	<
1002	<	/**
1003	<	* The number of times to spin before blocking in timed waits.
1004	<	* The value is empirically derived
1005	<	*/
1006	<	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
999	>	public boolean block() {
1000	>	if (isReleasable())
1001	>	return true;
1002	>	else if (!timed)
1003	>	LockSupport.park(this);
1004	>	else if (nanos > 0)
1005	>	LockSupport.parkNanos(this, nanos);
1006	>	return isReleasable();
1007	>	}
1008
1009	<	/**
1010	<	* The number of times to spin before blocking in untimed waits.
1011	<	* This is greater than timed value because untimed waits spin
1012	<	* faster since they don't need to check times on each spin.
1013	<	*/
1014	<	static final int maxUntimedSpins = maxTimedSpins * 32;
1009	>	void signal() {
1010	>	Thread t = thread;
1011	>	if (t != null) {
1012	>	thread = null;
1013	>	LockSupport.unpark(t);
1014	>	}
1015	>	}
1016	>	}
1017
1018	<	/**
582	<	* The number of nanoseconds for which it is faster to spin
583	<	* rather than to use timed park. A rough estimate suffices.
584	<	*/
585	<	static final long spinForTimeoutThreshold = 1000L;
1018	>	// Unsafe mechanics
1019
1020	<	/**
1021	<	* Enqueues node and waits unless aborted or signalled.
1022	<	*/
1023	<	private boolean untimedWait(Thread thread, int currentPhase,
1024	<	boolean abortOnInterrupt) {
1025	<	final AtomicReference<QNode> head = this.head;
1026	<	final AtomicLong state = this.state;
1027	<	boolean wasInterrupted = false;
1028	<	QNode node = null;
1029	<	boolean queued = false;
1030	<	int spins = maxUntimedSpins;
1031	<	while (phaseOf(state.get()) == currentPhase) {
599	<	QNode h;
600	<	if (node != null && queued) {
601	<	if (node.thread != null) {
602	<	LockSupport.park();
603	<	if (Thread.interrupted()) {
604	<	wasInterrupted = true;
605	<	if (abortOnInterrupt)
606	<	break;
607	<	}
608	<	}
609	<	}
610	<	else if ((h = head.get()) != null && h.phase != currentPhase) {
611	<	if (phaseOf(state.get()) == currentPhase) { // must recheck
612	<	if (head.compareAndSet(h, h.next)) {
613	<	Thread t = h.thread; // help clear out old waiters
614	<	if (t != null) {
615	<	h.thread = null;
616	<	LockSupport.unpark(t);
617	<	}
618	<	}
619	<	}
620	<	else
621	<	break;
622	<	}
623	<	else if (node != null)
624	<	queued = head.compareAndSet(node.next = h, node);
625	<	else if (spins <= 0)
626	<	node = new QNode(thread, currentPhase);
627	<	else
628	<	--spins;
1020	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1021	>	private static final long stateOffset =
1022	>	objectFieldOffset("state", Phaser.class);
1023	>
1024	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1025	>	try {
1026	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1027	>	} catch (NoSuchFieldException e) {
1028	>	// Convert Exception to corresponding Error
1029	>	NoSuchFieldError error = new NoSuchFieldError(field);
1030	>	error.initCause(e);
1031	>	throw error;
1032		}
630	–	if (node != null)
631	–	node.thread = null;
632	–	return wasInterrupted;
1033		}
1034
1035		/**
1036	<	* Messier timeout version
1036	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1037	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1038	>	* into a jdk.
1039	>	*
1040	>	* @return a sun.misc.Unsafe
1041		*/
1042	<	private void timedWait(Thread thread, int currentPhase, long nanos)
1043	<	throws InterruptedException, TimeoutException {
1044	<	final AtomicReference<QNode> head = this.head;
1045	<	final AtomicLong state = this.state;
1046	<	long lastTime = System.nanoTime();
1047	<	QNode node = null;
1048	<	boolean queued = false;
1049	<	int spins = maxTimedSpins;
1050	<	while (phaseOf(state.get()) == currentPhase) {
1051	<	QNode h;
1052	<	long now = System.nanoTime();
1053	<	nanos -= now - lastTime;
1054	<	lastTime = now;
1055	<	if (nanos <= 0) {
1056	<	if (node != null)
1057	<	node.thread = null;
1058	<	if (phaseOf(state.get()) == currentPhase)
655	<	throw new TimeoutException();
656	<	else
657	<	break;
658	<	}
659	<	else if (node != null && queued) {
660	<	if (node.thread != null &&
661	<	nanos > spinForTimeoutThreshold) {
662	<	//                LockSupport.parkNanos(this, nanos);
663	<	LockSupport.parkNanos(nanos);
664	<	if (Thread.interrupted()) {
665	<	node.thread = null;
666	<	throw new InterruptedException();
667	<	}
668	<	}
1042	>	private static sun.misc.Unsafe getUnsafe() {
1043	>	try {
1044	>	return sun.misc.Unsafe.getUnsafe();
1045	>	} catch (SecurityException se) {
1046	>	try {
1047	>	return java.security.AccessController.doPrivileged
1048	>	(new java.security
1049	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1050	>	public sun.misc.Unsafe run() throws Exception {
1051	>	java.lang.reflect.Field f = sun.misc
1052	>	.Unsafe.class.getDeclaredField("theUnsafe");
1053	>	f.setAccessible(true);
1054	>	return (sun.misc.Unsafe) f.get(null);
1055	>	}});
1056	>	} catch (java.security.PrivilegedActionException e) {
1057	>	throw new RuntimeException("Could not initialize intrinsics",
1058	>	e.getCause());
1059		}
670	–	else if ((h = head.get()) != null && h.phase != currentPhase) {
671	–	if (phaseOf(state.get()) == currentPhase) { // must recheck
672	–	if (head.compareAndSet(h, h.next)) {
673	–	Thread t = h.thread; // help clear out old waiters
674	–	if (t != null) {
675	–	h.thread = null;
676	–	LockSupport.unpark(t);
677	–	}
678	–	}
679	–	}
680	–	else
681	–	break;
682	–	}
683	–	else if (node != null)
684	–	queued = head.compareAndSet(node.next = h, node);
685	–	else if (spins <= 0)
686	–	node = new QNode(thread, currentPhase);
687	–	else
688	–	--spins;
1060		}
690	–	if (node != null)
691	–	node.thread = null;
1061		}
693	–
1062		}
695	–

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