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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 1.55 by dl, Mon Nov 15 12:51:54 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}.  As illustrated below, when
83	+	* phasers control actions with a fixed number of iterations, it is
84	+	* often convenient to override this method to cause termination when
85	+	* the current phase number reaches a threshold. Method {@link
86	+	* #forceTermination} is also available to abruptly release waiting
87	+	* threads and allow them to terminate.
88		*
89	<	* <li> Barrier actions, performed by the task triggering a phase
90	<	* advance while others may be waiting, are arranged by overriding
91	<	* method <tt>onAdvance</tt>, that also controls termination.
92	<	*
93	<	* <li> Phasers may enter a <em>termination</em> state in which all
94	<	* await actions immediately return, indicating (via a negative phase
95	<	* value) that execution is complete.  Termination is triggered by
56	<	* executing the overridable <tt>onAdvance</tt> method that is invoked
57	<	* each time the barrier is tripped. When a Phaser is controlling an
58	<	* action with a fixed number of iterations, it is often convenient to
59	<	* override this method to cause termination when the current phase
60	<	* number reaches a threshold.  Method <tt>forceTermination</tt> is
61	<	* also available to assist recovery actions upon failure.
62	<	*
63	<	* <li> Unlike most synchronizers, a Phaser may also be used with
64	<	* ForkJoinTasks (as well as plain threads).
65	<	*
66	<	* <li> By default, <tt>awaitAdvance</tt> continues to wait even if
67	<	* the current thread is interrupted. And unlike the case in
68	<	* CyclicBarriers, exceptions encountered while tasks wait
69	<	* interruptibly or with timeout do not change the state of the
70	<	* barrier. If necessary, you can perform any associated recovery
71	<	* within handlers of those exceptions.
89	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
90	>	* in tree structures) to reduce contention. Phasers with large
91	>	* numbers of parties that would otherwise experience heavy
92	>	* synchronization contention costs may instead be set up so that
93	>	* groups of sub-phasers share a common parent.  This may greatly
94	>	* increase throughput even though it incurs greater per-operation
95	>	* overhead.
96		*
97	<	* </ul>
97	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
98	>	* only by registered parties, the current state of a phaser may be
99	>	* monitored by any caller.  At any given moment there are {@link
100	>	* #getRegisteredParties} parties in total, of which {@link
101	>	* #getArrivedParties} have arrived at the current phase ({@link
102	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
103	>	* parties arrive, the phase advances.  The values returned by these
104	>	* methods may reflect transient states and so are not in general
105	>	* useful for synchronization control.  Method {@link #toString}
106	>	* returns snapshots of these state queries in a form convenient for
107	>	* informal monitoring.
108		*
109	<	* <p><b>Sample usage:</b>
109	>	* <p><b>Sample usages:</b>
110		*
111	<	* <p>[todo: non-FJ example]
111	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
112	>	* to control a one-shot action serving a variable number of parties.
113	>	* The typical idiom is for the method setting this up to first
114	>	* register, then start the actions, then deregister, as in:
115		*
116	<	* <p> A Phaser may be used to support a style of programming in
117	<	* which a task waits for others to complete, without otherwise
118	<	* needing to keep track of which tasks it is waiting for. This is
119	<	* similar to the "sync" construct in Cilk and "clocks" in X10.
120	<	* Special constructions based on such barriers are available using
121	<	* the <tt>LinkedAsyncAction</tt> and <tt>CyclicAction</tt> classes,
122	<	* but they can be useful in other contexts as well.  For a simple
123	<	* (but not very useful) example, here is a variant of Fibonacci:
124	<	*
125	<	* <pre>
126	<	* class BarrierFibonacci extends RecursiveAction {
127	<	*   int argument, result;
91	<	*   final Phaser parentBarrier;
92	<	*   BarrierFibonacci(int n, Phaser parentBarrier) {
93	<	*     this.argument = n;
94	<	*     this.parentBarrier = parentBarrier;
95	<	*     parentBarrier.register();
116	>	*  <pre> {@code
117	>	* void runTasks(List<Runnable> tasks) {
118	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
119	>	*   // create and start threads
120	>	*   for (Runnable task : tasks) {
121	>	*     phaser.register();
122	>	*     new Thread() {
123	>	*       public void run() {
124	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
125	>	*         task.run();
126	>	*       }
127	>	*     }.start();
128		*   }
129	<	*   protected void compute() {
130	<	*     int n = argument;
131	<	*     if (n &lt;= 1)
132	<	*        result = n;
133	<	*     else {
134	<	*        Phaser childBarrier = new Phaser(1);
135	<	*        BarrierFibonacci f1 = new BarrierFibonacci(n - 1, childBarrier);
136	<	*        BarrierFibonacci f2 = new BarrierFibonacci(n - 2, childBarrier);
137	<	*        f1.fork();
138	<	*        f2.fork();
139	<	*        childBarrier.arriveAndAwait();
140	<	*        result = f1.result + f2.result;
129	>	*
130	>	*   // allow threads to start and deregister self
131	>	*   phaser.arriveAndDeregister();
132	>	* }}</pre>
133	>	*
134	>	* <p>One way to cause a set of threads to repeatedly perform actions
135	>	* for a given number of iterations is to override {@code onAdvance}:
136	>	*
137	>	*  <pre> {@code
138	>	* void startTasks(List<Runnable> tasks, final int iterations) {
139	>	*   final Phaser phaser = new Phaser() {
140	>	*     protected boolean onAdvance(int phase, int registeredParties) {
141	>	*       return phase >= iterations || registeredParties == 0;
142		*     }
143	<	*     parentBarrier.arriveAndDeregister();
143	>	*   };
144	>	*   phaser.register();
145	>	*   for (final Runnable task : tasks) {
146	>	*     phaser.register();
147	>	*     new Thread() {
148	>	*       public void run() {
149	>	*         do {
150	>	*           task.run();
151	>	*           phaser.arriveAndAwaitAdvance();
152	>	*         } while (!phaser.isTerminated());
153	>	*       }
154	>	*     }.start();
155	>	*   }
156	>	*   phaser.arriveAndDeregister(); // deregister self, don't wait
157	>	* }}</pre>
158	>	*
159	>	* If the main task must later await termination, it
160	>	* may re-register and then execute a similar loop:
161	>	*  <pre> {@code
162	>	*   // ...
163	>	*   phaser.register();
164	>	*   while (!phaser.isTerminated())
165	>	*     phaser.arriveAndAwaitAdvance();}</pre>
166	>	*
167	>	* <p>Related constructions may be used to await particular phase numbers
168	>	* in contexts where you are sure that the phase will never wrap around
169	>	* {@code Integer.MAX_VALUE}. For example:
170	>	*
171	>	*  <pre> {@code
172	>	* void awaitPhase(Phaser phaser, int phase) {
173	>	*   int p = phaser.register(); // assumes caller not already registered
174	>	*   while (p < phase) {
175	>	*     if (phaser.isTerminated())
176	>	*       // ... deal with unexpected termination
177	>	*     else
178	>	*       p = phaser.arriveAndAwaitAdvance();
179	>	*   }
180	>	*   phaser.arriveAndDeregister();
181	>	* }}</pre>
182	>	*
183	>	*
184	>	* <p>To create a set of tasks using a tree of phasers,
185	>	* you could use code of the following form, assuming a
186	>	* Task class with a constructor accepting a phaser that
187	>	* it registers with upon construction:
188	>	*
189	>	*  <pre> {@code
190	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
191	>	*   if (hi - lo > TASKS_PER_PHASER) {
192	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
193	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
194	>	*       build(actions, i, j, new Phaser(ph));
195	>	*     }
196	>	*   } else {
197	>	*     for (int i = lo; i < hi; ++i)
198	>	*       actions[i] = new Task(ph);
199	>	*       // assumes new Task(ph) performs ph.register()
200		*   }
201		* }
202	<	* </pre>
202	>	* // .. initially called, for n tasks via
203	>	* build(new Task[n], 0, n, new Phaser());}</pre>
204	>	*
205	>	* The best value of {@code TASKS_PER_PHASER} depends mainly on
206	>	* expected barrier synchronization rates. A value as low as four may
207	>	* be appropriate for extremely small per-barrier task bodies (thus
208	>	* high rates), or up to hundreds for extremely large ones.
209		*
210		* <p><b>Implementation notes</b>: This implementation restricts the
211	<	* maximum number of parties to 65535. Attempts to register
212	<	* additional parties result in IllegalStateExceptions.
211	>	* maximum number of parties to 65535. Attempts to register additional
212	>	* parties result in {@code IllegalStateException}. However, you can and
213	>	* should create tiered phasers to accommodate arbitrarily large sets
214	>	* of participants.
215	>	*
216	>	* @since 1.7
217	>	* @author Doug Lea
218		*/
219		public class Phaser {
220		/*
221		* This class implements an extension of X10 "clocks".  Thanks to
222	<	* Vijay Saraswat for the idea of applying it to ForkJoinTasks,
223	<	* and to Vivek Sarkar for enhancements to extend functionality.
222	>	* Vijay Saraswat for the idea, and to Vivek Sarkar for
223	>	* enhancements to extend functionality.
224		*/
225
226		/**
227		* Barrier state representation. Conceptually, a barrier contains
228		* four values:
229	<	*
230	<	* * parties -- the number of parties to wait (16 bits)
231	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
232	<	* * phase -- the generation of the barrier (31 bits)
233	<	* * terminated -- set if barrier is terminated (1 bit)
229	>	*
230	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
231	>	* * parties -- the number of parties to wait              (bits 16-31)
232	>	* * phase -- the generation of the barrier                (bits 32-62)
233	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
234		*
235		* However, to efficiently maintain atomicity, these values are
236	<	* packed into a single AtomicLong. Termination uses the sign bit
237	<	* of 32 bit representation of phase, so phase is set to -1 on
238	<	* termination.
239	<	*/
240	<	private final AtomicLong state;
241	<
242	<	/**
243	<	* Head of Treiber stack for waiting nonFJ threads.
244	<	*/
245	<	private final AtomicReference<QNode> head = new AtomicReference<QNode>();
236	>	* packed into a single (atomic) long. Termination uses the sign
237	>	* bit of 32 bit representation of phase, so phase is set to -1 on
238	>	* termination. Good performance relies on keeping state decoding
239	>	* and encoding simple, and keeping race windows short.
240	>	*/
241	>	private volatile long state;
242	>
243	>	private static final int  MAX_PARTIES    = 0xffff;
244	>	private static final int  MAX_PHASE      = 0x7fffffff;
245	>	private static final int  PARTIES_SHIFT  = 16;
246	>	private static final int  PHASE_SHIFT    = 32;
247	>	private static final int  UNARRIVED_MASK = 0xffff;
248	>	private static final int  PARTIES_MASK   = 0xffff0000;
249	>	private static final long LPARTIES_MASK  = 0xffff0000L; // long version
250	>	private static final long ONE_ARRIVAL    = 1L;
251	>	private static final long ONE_PARTY      = 1L << PARTIES_SHIFT;
252	>	private static final long TERMINATION_PHASE  = -1L << PHASE_SHIFT;
253
254	<	private static final int ushortBits = 16;
148	<	private static final int ushortMask =  (1 << ushortBits) - 1;
149	<	private static final int phaseMask = 0x7fffffff;
254	>	// The following unpacking methods are usually manually inlined
255
256		private static int unarrivedOf(long s) {
257	<	return (int)(s & ushortMask);
257	>	return ((int) s) & UNARRIVED_MASK;
258		}
259
260		private static int partiesOf(long s) {
261	<	return (int)(s & (ushortMask << 16)) >>> 16;
261	>	return (((int) s) & PARTIES_MASK) >>> PARTIES_SHIFT;
262		}
263
264		private static int phaseOf(long s) {
265	<	return (int)(s >>> 32);
265	>	return (int) (s >>> PHASE_SHIFT);
266		}
267
268		private static int arrivedOf(long s) {
269		return partiesOf(s) - unarrivedOf(s);
270		}
271
272	<	private static long stateFor(int phase, int parties, int unarrived) {
273	<	return (((long)phase) << 32) | ((parties << 16) | unarrived);
274	<	}
275	<
171	<	private static IllegalStateException badBounds(int parties, int unarrived) {
172	<	return new IllegalStateException("Attempt to set " + unarrived +
173	<	" unarrived of " + parties + " parties");
174	<	}
272	>	/**
273	>	* The parent of this phaser, or null if none
274	>	*/
275	>	private final Phaser parent;
276
277		/**
278	<	* Creates a new Phaser without any initially registered parties,
279	<	* and initial phase number 0.
278	>	* The root of phaser tree. Equals this if not in a tree.  Used to
279	>	* support faster state push-down.
280		*/
281	<	public Phaser() {
181	<	state = new AtomicLong(stateFor(0, 0, 0));
182	<	}
281	>	private final Phaser root;
282
283		/**
284	<	* Creates a new Phaser with the given numbers of registered
285	<	* unarrived parties and initial phase number 0.
286	<	* @param parties the number of parties required to trip barrier.
287	<	* @throws IllegalArgumentException if parties less than zero
189	<	* or greater than the maximum number of parties supported.
284	>	* Heads of Treiber stacks for waiting threads. To eliminate
285	>	* contention when releasing some threads while adding others, we
286	>	* use two of them, alternating across even and odd phases.
287	>	* Subphasers share queues with root to speed up releases.
288		*/
289	<	public Phaser(int parties) {
290	<	if (parties < 0 || parties > ushortMask)
291	<	throw new IllegalArgumentException("Illegal number of parties");
292	<	state = new AtomicLong(stateFor(0, parties, parties));
289	>	private final AtomicReference<QNode> evenQ;
290	>	private final AtomicReference<QNode> oddQ;
291	>
292	>	private AtomicReference<QNode> queueFor(int phase) {
293	>	return ((phase & 1) == 0) ? evenQ : oddQ;
294		}
295
296		/**
297	<	* Adds a new unarrived party to this phaser.
298	<	* @return the current barrier phase number upon registration
299	<	* @throws IllegalStateException if attempting to register more
300	<	* than the maximum supported number of parties.
297	>	* Main implementation for methods arrive and arriveAndDeregister.
298	>	* Manually tuned to speed up and minimize race windows for the
299	>	* common case of just decrementing unarrived field.
300	>	*
301	>	* @param adj - adjustment to apply to state -- either
302	>	* ONE_ARRIVAL (for arrive) or
303	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
304		*/
305	<	public int register() { // increment both parties and unarrived
204	<	final AtomicLong state = this.state;
305	>	private int doArrive(long adj) {
306		for (;;) {
307	<	long s = state.get();
308	<	int phase = phaseOf(s);
309	<	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)))
307	>	long s;
308	>	int phase, unarrived;
309	>	if ((phase = (int)((s = state) >>> PHASE_SHIFT)) < 0)
310		return phase;
311	+	else if ((unarrived = ((int)s) & UNARRIVED_MASK) == 0)
312	+	checkBadArrive(s);
313	+	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
314	+	if (unarrived == 1) {
315	+	Phaser par;
316	+	long p = s & LPARTIES_MASK; // unshifted parties field
317	+	long lu = p >>> PARTIES_SHIFT;
318	+	int u = (int)lu;
319	+	int nextPhase = (phase + 1) & MAX_PHASE;
320	+	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
321	+	if ((par = parent) == null) {
322	+	if (onAdvance(phase, u))
323	+	next |= TERMINATION_PHASE; // obliterate phase
324	+	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
325	+	releaseWaiters(phase);
326	+	}
327	+	else {
328	+	par.doArrive(u == 0?
329	+	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
330	+	if ((int)(par.state >>> PHASE_SHIFT) != nextPhase ||
331	+	((int)(state >>> PHASE_SHIFT) != nextPhase &&
332	+	!UNSAFE.compareAndSwapLong(this, stateOffset,
333	+	s, next)))
334	+	reconcileState();
335	+	}
336	+	}
337	+	return phase;
338	+	}
339		}
340		}
341
342		/**
343	<	* Arrives at the barrier, but does not wait for others.  (You can
344	<	* in turn wait for others via {@link #awaitAdvance}).
343	>	* Rechecks state and throws bounds exceptions on arrival -- called
344	>	* only if unarrived is apparently zero.
345	>	*/
346	>	private void checkBadArrive(long s) {
347	>	if (reconcileState() == s)
348	>	throw new IllegalStateException
349	>	("Attempted arrival of unregistered party for " +
350	>	stateToString(s));
351	>	}
352	>
353	>	/**
354	>	* Implementation of register, bulkRegister
355		*
356	<	* @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.
356	>	* @param registrations number to add to both parties and unarrived fields
357		*/
358	<	public int arrive() { // decrement unarrived. If zero, trip
359	<	final AtomicLong state = this.state;
358	>	private int doRegister(int registrations) {
359	>	long adj = (long)registrations; // adjustment to state
360	>	adj |= adj << PARTIES_SHIFT;
361	>	Phaser par = parent;
362		for (;;) {
363	<	long s = state.get();
364	<	int phase = phaseOf(s);
365	<	int parties = partiesOf(s);
232	<	int unarrived = unarrivedOf(s) - 1;
233	<	if (unarrived < 0)
234	<	throw badBounds(parties, unarrived);
235	<	if (unarrived == 0 && phase >= 0) {
236	<	trip(phase, parties);
363	>	int phase, parties;
364	>	long s = par == null? state : reconcileState();
365	>	if ((phase = (int)(s >>> PHASE_SHIFT)) < 0)
366		return phase;
367	<	}
368	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
367	>	if ((parties = (((int)s) & PARTIES_MASK) >>> PARTIES_SHIFT) != 0 &&
368	>	(((int)s) & UNARRIVED_MASK) == 0)
369	>	internalAwaitAdvance(phase, null); // wait for onAdvance
370	>	else if (parties + registrations > MAX_PARTIES)
371	>	throw new IllegalStateException(badRegister(s));
372	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
373		return phase;
374		}
375		}
376
377		/**
378	<	* Arrives at the barrier, and deregisters from it, without
379	<	* waiting for others.
380	<	*
381	<	* @return the current barrier phase number upon entry to
382	<	* this method, or a negative value if terminated;
383	<	* @throws IllegalStateException if the number of registered or
384	<	* unarrived parties would become negative.
378	>	* Returns message string for out of bounds exceptions on registration.
379	>	*/
380	>	private String badRegister(long s) {
381	>	return "Attempt to register more than " +
382	>	MAX_PARTIES + " parties for " + stateToString(s);
383	>	}
384	>
385	>	/**
386	>	* Recursively resolves lagged phase propagation from root if necessary.
387		*/
388	<	public int arriveAndDeregister() { // Same as arrive, plus decrement parties
389	<	final AtomicLong state = this.state;
388	>	private long reconcileState() {
389	>	Phaser par = parent;
390	>	if (par == null)
391	>	return state;
392	>	Phaser rt = root;
393		for (;;) {
394	<	long s = state.get();
395	<	int phase = phaseOf(s);
396	<	int parties = partiesOf(s) - 1;
397	<	int unarrived = unarrivedOf(s) - 1;
398	<	if (parties < 0 || unarrived < 0)
399	<	throw badBounds(parties, unarrived);
400	<	if (unarrived == 0 && phase >= 0) {
401	<	trip(phase, parties);
402	<	return phase;
394	>	long s, u;
395	>	int phase, rPhase, pPhase;
396	>	if ((phase = (int)((s = state)>>> PHASE_SHIFT)) < 0 ||
397	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) == phase)
398	>	return s;
399	>	long pState = par.parent == null? par.state : par.reconcileState();
400	>	if (state == s) {
401	>	if ((rPhase < 0 || (((int)s) & UNARRIVED_MASK) == 0) &&
402	>	((pPhase = (int)(pState >>> PHASE_SHIFT)) < 0 ||
403	>	pPhase == ((phase + 1) & MAX_PHASE)))
404	>	UNSAFE.compareAndSwapLong
405	>	(this, stateOffset, s,
406	>	(((long) pPhase) << PHASE_SHIFT) |
407	>	(u = s & LPARTIES_MASK) |
408	>	(u >>> PARTIES_SHIFT)); // reset unarrived to parties
409	>	else
410	>	releaseWaiters(phase); // help release others
411		}
266	–	if (state.compareAndSet(s, stateFor(phase, parties, unarrived)))
267	–	return phase;
412		}
413		}
414
415		/**
416	<	* Arrives at the barrier and awaits others. Unlike other arrival
417	<	* methods, this method returns the arrival index of the
418	<	* 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.
416	>	* Creates a new phaser without any initially registered parties,
417	>	* initial phase number 0, and no parent. Any thread using this
418	>	* phaser will need to first register for it.
419		*/
420	<	public int arriveAndAwaitAdvance() {
421	<	final AtomicLong state = this.state;
422	<	for (;;) {
423	<	long s = state.get();
424	<	int phase = phaseOf(s);
425	<	int parties = partiesOf(s);
426	<	int unarrived = unarrivedOf(s) - 1;
427	<	if (unarrived < 0)
428	<	throw badBounds(parties, unarrived);
429	<	if (unarrived == 0 && phase >= 0) {
430	<	trip(phase, parties);
431	<	return 0;
432	<	}
433	<	if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) {
434	<	awaitAdvance(phase);
435	<	return unarrived;
436	<	}
420	>	public Phaser() {
421	>	this(null, 0);
422	>	}
423	>
424	>	/**
425	>	* Creates a new phaser with the given number of registered
426	>	* unarrived parties, initial phase number 0, and no parent.
427	>	*
428	>	* @param parties the number of parties required to trip barrier
429	>	* @throws IllegalArgumentException if parties less than zero
430	>	* or greater than the maximum number of parties supported
431	>	*/
432	>	public Phaser(int parties) {
433	>	this(null, parties);
434	>	}
435	>
436	>	/**
437	>	* Creates a new phaser with the given parent, without any
438	>	* initially registered parties. If parent is non-null this phaser
439	>	* is registered with the parent and its initial phase number is
440	>	* the same as that of parent phaser.
441	>	*
442	>	* @param parent the parent phaser
443	>	*/
444	>	public Phaser(Phaser parent) {
445	>	this(parent, 0);
446	>	}
447	>
448	>	/**
449	>	* Creates a new phaser with the given parent and number of
450	>	* registered unarrived parties. If parent is non-null, this phaser
451	>	* is registered with the parent and its initial phase number is
452	>	* the same as that of parent phaser.
453	>	*
454	>	* @param parent the parent phaser
455	>	* @param parties the number of parties required to trip barrier
456	>	* @throws IllegalArgumentException if parties less than zero
457	>	* or greater than the maximum number of parties supported
458	>	*/
459	>	public Phaser(Phaser parent, int parties) {
460	>	if (parties >>> PARTIES_SHIFT != 0)
461	>	throw new IllegalArgumentException("Illegal number of parties");
462	>	int phase;
463	>	this.parent = parent;
464	>	if (parent != null) {
465	>	Phaser r = parent.root;
466	>	this.root = r;
467	>	this.evenQ = r.evenQ;
468	>	this.oddQ = r.oddQ;
469	>	phase = parent.register();
470	>	}
471	>	else {
472	>	this.root = this;
473	>	this.evenQ = new AtomicReference<QNode>();
474	>	this.oddQ = new AtomicReference<QNode>();
475	>	phase = 0;
476		}
477	+	long p = (long)parties;
478	+	this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
479		}
480
481		/**
482	<	* Awaits the phase of the barrier to advance from the given
483	<	* value, or returns immediately if this barrier is terminated.
484	<	* @param phase the phase on entry to this method
485	<	* @return the phase on exit from this method
482	>	* Adds a new unarrived party to this phaser.
483	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
484	>	* this method may wait until its completion before registering.
485	>	*
486	>	* @return the arrival phase number to which this registration applied
487	>	* @throws IllegalStateException if attempting to register more
488	>	* than the maximum supported number of parties
489	>	*/
490	>	public int register() {
491	>	return doRegister(1);
492	>	}
493	>
494	>	/**
495	>	* Adds the given number of new unarrived parties to this phaser.
496	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
497	>	* this method may wait until its completion before registering.
498	>	*
499	>	* @param parties the number of additional parties required to trip barrier
500	>	* @return the arrival phase number to which this registration applied
501	>	* @throws IllegalStateException if attempting to register more
502	>	* than the maximum supported number of parties
503	>	* @throws IllegalArgumentException if {@code parties < 0}
504	>	*/
505	>	public int bulkRegister(int parties) {
506	>	if (parties < 0)
507	>	throw new IllegalArgumentException();
508	>	if (parties > MAX_PARTIES)
509	>	throw new IllegalStateException(badRegister(state));
510	>	if (parties == 0)
511	>	return getPhase();
512	>	return doRegister(parties);
513	>	}
514	>
515	>	/**
516	>	* Arrives at the barrier, but does not wait for others.  (You can
517	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
518	>	* unenforced usage error for an unregistered party to invoke this
519	>	* method.
520	>	*
521	>	* @return the arrival phase number, or a negative value if terminated
522	>	* @throws IllegalStateException if not terminated and the number
523	>	* of unarrived parties would become negative
524	>	*/
525	>	public int arrive() {
526	>	return doArrive(ONE_ARRIVAL);
527	>	}
528	>
529	>	/**
530	>	* Arrives at the barrier and deregisters from it without waiting
531	>	* for others. Deregistration reduces the number of parties
532	>	* required to trip the barrier in future phases.  If this phaser
533	>	* has a parent, and deregistration causes this phaser to have
534	>	* zero parties, this phaser also arrives at and is deregistered
535	>	* from its parent.  It is an unenforced usage error for an
536	>	* unregistered party to invoke this method.
537	>	*
538	>	* @return the arrival phase number, or a negative value if terminated
539	>	* @throws IllegalStateException if not terminated and the number
540	>	* of registered or unarrived parties would become negative
541	>	*/
542	>	public int arriveAndDeregister() {
543	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
544	>	}
545	>
546	>	/**
547	>	* Arrives at the barrier and awaits others. Equivalent in effect
548	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
549	>	* interruption or timeout, you can arrange this with an analogous
550	>	* construction using one of the other forms of the {@code
551	>	* awaitAdvance} method.  If instead you need to deregister upon
552	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
553	>	* usage error for an unregistered party to invoke this method.
554	>	*
555	>	* @return the arrival phase number, or a negative number if terminated
556	>	* @throws IllegalStateException if not terminated and the number
557	>	* of unarrived parties would become negative
558	>	*/
559	>	public int arriveAndAwaitAdvance() {
560	>	return awaitAdvance(arrive());
561	>	}
562	>
563	>	/**
564	>	* Awaits the phase of the barrier to advance from the given phase
565	>	* value, returning immediately if the current phase of the
566	>	* barrier is not equal to the given phase value or this barrier
567	>	* is terminated.
568	>	*
569	>	* @param phase an arrival phase number, or negative value if
570	>	* terminated; this argument is normally the value returned by a
571	>	* previous call to {@code arrive} or its variants
572	>	* @return the next arrival phase number, or a negative value
573	>	* if terminated or argument is negative
574		*/
575		public int awaitAdvance(int phase) {
576	+	int p;
577		if (phase < 0)
578		return phase;
579	<	Thread current = Thread.currentThread();
580	<	if (current instanceof ForkJoinWorkerThread)
581	<	return helpingWait(phase);
582	<	if (untimedWait(current, phase, false))
583	<	current.interrupt();
314	<	return phaseOf(state.get());
579	>	else if ((p = (int)((parent == null? state : reconcileState())
580	>	>>> PHASE_SHIFT)) == phase)
581	>	return internalAwaitAdvance(phase, null);
582	>	else
583	>	return p;
584		}
585
586		/**
587	<	* Awaits the phase of the barrier to advance from the given
588	<	* value, or returns immediately if this barrier is terminated, or
589	<	* throws InterruptedException if interrupted while waiting.
590	<	* @param phase the phase on entry to this method
591	<	* @return the phase on exit from this method
587	>	* Awaits the phase of the barrier to advance from the given phase
588	>	* value, throwing {@code InterruptedException} if interrupted
589	>	* while waiting, or returning immediately if the current phase of
590	>	* the barrier is not equal to the given phase value or this
591	>	* barrier is terminated.
592	>	*
593	>	* @param phase an arrival phase number, or negative value if
594	>	* terminated; this argument is normally the value returned by a
595	>	* previous call to {@code arrive} or its variants
596	>	* @return the next arrival phase number, or a negative value
597	>	* if terminated or argument is negative
598		* @throws InterruptedException if thread interrupted while waiting
599		*/
600	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
600	>	public int awaitAdvanceInterruptibly(int phase)
601	>	throws InterruptedException {
602	>	int p;
603		if (phase < 0)
604		return phase;
605	<	Thread current = Thread.currentThread();
606	<	if (current instanceof ForkJoinWorkerThread)
607	<	return helpingWait(phase);
608	<	else if (Thread.interrupted() || untimedWait(current, phase, true))
609	<	throw new InterruptedException();
610	<	else
611	<	return phaseOf(state.get());
605	>	if ((p = (int)((parent == null? state : reconcileState())
606	>	>>> PHASE_SHIFT)) == phase) {
607	>	QNode node = new QNode(this, phase, true, false, 0L);
608	>	p = internalAwaitAdvance(phase, node);
609	>	if (node.wasInterrupted)
610	>	throw new InterruptedException();
611	>	}
612	>	return p;
613		}
614
615		/**
616	<	* Awaits the phase of the barrier to advance from the given value
617	<	* or the given timeout elapses, or returns immediately if this
618	<	* barrier is terminated.
619	<	* @param phase the phase on entry to this method
620	<	* @return the phase on exit from this method
616	>	* Awaits the phase of the barrier to advance from the given phase
617	>	* value or the given timeout to elapse, throwing {@code
618	>	* InterruptedException} if interrupted while waiting, or
619	>	* returning immediately if the current phase of the barrier is
620	>	* not equal to the given phase value or this barrier is
621	>	* 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	>	* @param timeout how long to wait before giving up, in units of
627	>	*        {@code unit}
628	>	* @param unit a {@code TimeUnit} determining how to interpret the
629	>	*        {@code timeout} parameter
630	>	* @return the next arrival phase number, or a negative value
631	>	* if terminated or argument is negative
632		* @throws InterruptedException if thread interrupted while waiting
633		* @throws TimeoutException if timed out while waiting
634		*/
635	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
635	>	public int awaitAdvanceInterruptibly(int phase,
636	>	long timeout, TimeUnit unit)
637		throws InterruptedException, TimeoutException {
638	+	long nanos = unit.toNanos(timeout);
639	+	int p;
640		if (phase < 0)
641		return phase;
642	<	long nanos = unit.toNanos(timeout);
643	<	Thread current = Thread.currentThread();
644	<	if (current instanceof ForkJoinWorkerThread)
645	<	return timedHelpingWait(phase, nanos);
646	<	timedWait(current, phase, nanos);
647	<	return phaseOf(state.get());
642	>	if ((p = (int)((parent == null? state : reconcileState())
643	>	>>> PHASE_SHIFT)) == phase) {
644	>	QNode node = new QNode(this, phase, true, true, nanos);
645	>	p = internalAwaitAdvance(phase, node);
646	>	if (node.wasInterrupted)
647	>	throw new InterruptedException();
648	>	else if (p == phase)
649	>	throw new TimeoutException();
650	>	}
651	>	return p;
652		}
653
654		/**
655	<	* Forces this barrier to enter termination state. Counts of
656	<	* arrived and registered parties are unaffected. This method may
657	<	* be useful for coordinating recovery after one or more tasks
655	>	* Forces this barrier to enter termination state.  Counts of
656	>	* arrived and registered parties are unaffected.  If this phaser
657	>	* is a member of a tiered set of phasers, then all of the phasers
658	>	* in the set are terminated.  If this phaser is already
659	>	* terminated, this method has no effect.  This method may be
660	>	* useful for coordinating recovery after one or more tasks
661		* encounter unexpected exceptions.
662		*/
663		public void forceTermination() {
664	<	final AtomicLong state = this.state;
665	<	for (;;) {
666	<	long s = state.get();
667	<	int phase = phaseOf(s);
668	<	int parties = partiesOf(s);
669	<	int unarrived = unarrivedOf(s);
670	<	if (phase < 0 ||
671	<	state.compareAndSet(s, stateFor(-1, parties, unarrived))) {
373	<	if (head.get() != null)
374	<	releaseWaiters(-1);
664	>	// Only need to change root state
665	>	final Phaser root = this.root;
666	>	long s;
667	>	while ((s = root.state) >= 0) {
668	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
669	>	s, s | TERMINATION_PHASE)) {
670	>	releaseWaiters(0); // signal all threads
671	>	releaseWaiters(1);
672		return;
673		}
674		}
675		}
676
677		/**
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	–	/**
678		* Returns the current phase number. The maximum phase number is
679	<	* <tt>Integer.MAX_VALUE</tt>, after which it restarts at
679	>	* {@code Integer.MAX_VALUE}, after which it restarts at
680		* zero. Upon termination, the phase number is negative.
681	+	*
682		* @return the phase number, or a negative value if terminated
683		*/
684	<	public int getPhase() {
685	<	return phaseOf(state.get());
684	>	public final int getPhase() {
685	>	return (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
686		}
687
688		/**
689		* Returns the number of parties registered at this barrier.
690	+	*
691		* @return the number of parties
692		*/
693		public int getRegisteredParties() {
694	<	return partiesOf(state.get());
694	>	return partiesOf(parent==null? state : reconcileState());
695		}
696
697		/**
698	<	* Returns the number of parties that have arrived at the current
699	<	* phase of this barrier.
698	>	* Returns the number of registered parties that have arrived at
699	>	* the current phase of this barrier.
700	>	*
701		* @return the number of arrived parties
702		*/
703		public int getArrivedParties() {
704	<	return arrivedOf(state.get());
704	>	return arrivedOf(parent==null? state : reconcileState());
705		}
706
707		/**
708		* Returns the number of registered parties that have not yet
709		* arrived at the current phase of this barrier.
710	+	*
711		* @return the number of unarrived parties
712		*/
713		public int getUnarrivedParties() {
714	<	return unarrivedOf(state.get());
714	>	return unarrivedOf(parent==null? state : reconcileState());
715		}
716
717		/**
718	<	* Returns true if this barrier has been terminated.
719	<	* @return true if this barrier has been terminated
718	>	* Returns the parent of this phaser, or {@code null} if none.
719	>	*
720	>	* @return the parent of this phaser, or {@code null} if none
721	>	*/
722	>	public Phaser getParent() {
723	>	return parent;
724	>	}
725	>
726	>	/**
727	>	* Returns the root ancestor of this phaser, which is the same as
728	>	* this phaser if it has no parent.
729	>	*
730	>	* @return the root ancestor of this phaser
731	>	*/
732	>	public Phaser getRoot() {
733	>	return root;
734	>	}
735	>
736	>	/**
737	>	* Returns {@code true} if this barrier has been terminated.
738	>	*
739	>	* @return {@code true} if this barrier has been terminated
740		*/
741		public boolean isTerminated() {
742	<	return phaseOf(state.get()) < 0;
742	>	return (parent == null? state : reconcileState()) < 0;
743		}
744
745		/**
746	<	* Overridable method to perform an action upon phase advance, and
747	<	* to control termination. This method is invoked whenever the
748	<	* barrier is tripped (and thus all other waiting parties are
749	<	* dormant). If it returns true, then, rather than advance the
750	<	* phase number, this barrier will be set to a final termination
751	<	* state, and subsequent calls to <tt>isTerminated</tt> will
752	<	* return true.
753	<	*
754	<	* <p> The default version returns true when the number of
746	>	* Overridable method to perform an action upon impending phase
747	>	* advance, and to control termination. This method is invoked
748	>	* upon arrival of the party tripping the barrier (when all other
749	>	* waiting parties are dormant).  If this method returns {@code
750	>	* true}, then, rather than advance the phase number, this barrier
751	>	* will be set to a final termination state, and subsequent calls
752	>	* to {@link #isTerminated} will return true. Any (unchecked)
753	>	* Exception or Error thrown by an invocation of this method is
754	>	* propagated to the party attempting to trip the barrier, in
755	>	* which case no advance occurs.
756	>	*
757	>	* <p>The arguments to this method provide the state of the phaser
758	>	* prevailing for the current transition.  The effects of invoking
759	>	* arrival, registration, and waiting methods on this Phaser from
760	>	* within {@code onAdvance} are unspecified and should not be
761	>	* relied on.
762	>	*
763	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
764	>	* {@code onAdvance} is invoked only for its root Phaser on each
765	>	* advance.
766	>	*
767	>	* <p>The default version returns {@code true} when the number of
768		* registered parties is zero. Normally, overrides that arrange
769		* termination for other reasons should also preserve this
770		* property.
771		*
772		* @param phase the phase number on entering the barrier
773	<	* @param registeredParties the current number of registered
774	<	* parties.
458	<	* @return true if this barrier should terminate
773	>	* @param registeredParties the current number of registered parties
774	>	* @return {@code true} if this barrier should terminate
775		*/
776		protected boolean onAdvance(int phase, int registeredParties) {
777		return registeredParties <= 0;
778		}
779
780		/**
781	<	* Returns a string identifying this barrier, as well as its
781	>	* Returns a string identifying this phaser, as well as its
782		* state.  The state, in brackets, includes the String {@code
783	<	* "phase ="} followed by the phase number, {@code "parties ="}
783	>	* "phase = "} followed by the phase number, {@code "parties = "}
784		* followed by the number of registered parties, and {@code
785	<	* "arrived ="} followed by the number of arrived parties
785	>	* "arrived = "} followed by the number of arrived parties.
786		*
787		* @return a string identifying this barrier, as well as its state
788		*/
789		public String toString() {
790	<	long s = state.get();
475	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
790	>	return stateToString(reconcileState());
791		}
792
478	–	// methods for tripping and waiting
479	–
793		/**
794	<	* Advance the current phase (or terminate)
794	>	* Implementation of toString and string-based error messages
795		*/
796	<	private void trip(int phase, int parties) {
797	<	int next = onAdvance(phase, parties)? -1 : ((phase + 1) & phaseMask);
798	<	state.set(stateFor(next, parties, parties));
799	<	if (head.get() != null)
800	<	releaseWaiters(next);
796	>	private String stateToString(long s) {
797	>	return super.toString() +
798	>	"[phase = " + phaseOf(s) +
799	>	" parties = " + partiesOf(s) +
800	>	" arrived = " + arrivedOf(s) + "]";
801		}
802
803	<	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	<	}
803	>	// Waiting mechanics
804
805	<	private int timedHelpingWait(int phase, long nanos) throws TimeoutException {
806	<	final AtomicLong state = this.state;
807	<	long lastTime = System.nanoTime();
805	>	/**
806	>	* Removes and signals threads from queue for phase
807	>	*/
808	>	private void releaseWaiters(int phase) {
809	>	AtomicReference<QNode> head = queueFor(phase);
810	>	QNode q;
811		int p;
812	<	while ((p = phaseOf(state.get())) == phase) {
813	<	long now = System.nanoTime();
814	<	nanos -= now - lastTime;
815	<	lastTime = now;
816	<	if (nanos <= 0) {
516	<	if ((p = phaseOf(state.get())) == phase)
517	<	throw new TimeoutException();
518	<	else
519	<	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	<	}
529	<	}
812	>	while ((q = head.get()) != null &&
813	>	((p = q.phase) == phase ||
814	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
815	>	if (head.compareAndSet(q, q.next))
816	>	q.signal();
817		}
531	–	return p;
818		}
819
820		/**
821	<	* Wait nodes for Treiber stack representing wait queue for non-FJ
822	<	* tasks. The waiting scheme is an adaptation of the one used in
823	<	* forkjoin.PoolBarrier.
821	>	* Tries to enqueue given node in the appropriate wait queue.
822	>	*
823	>	* @return true if successful
824		*/
825	<	static final class QNode {
826	<	QNode next;
827	<	volatile Thread thread; // nulled to cancel wait
828	<	final int phase;
829	<	QNode(Thread t, int c) {
830	<	thread = t;
831	<	phase = c;
546	<	}
547	<	}
548	<
549	<	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);
561	<	}
562	<	}
825	>	private boolean tryEnqueue(int phase, QNode node) {
826	>	releaseWaiters(phase-1); // ensure old queue clean
827	>	AtomicReference<QNode> head = queueFor(phase);
828	>	QNode q = head.get();
829	>	return ((q == null || q.phase == phase) &&
830	>	(int)(root.state >>> PHASE_SHIFT) == phase &&
831	>	head.compareAndSet(node.next = q, node));
832		}
833
834		/** The number of CPUs, for spin control */
835	<	static final int NCPUS = Runtime.getRuntime().availableProcessors();
835	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
836
837		/**
838	<	* The number of times to spin before blocking in timed waits.
839	<	* The value is empirically derived.
838	>	* The number of times to spin before blocking while waiting for
839	>	* advance, per arrival while waiting. On multiprocessors, fully
840	>	* blocking and waking up a large number of threads all at once is
841	>	* usually a very slow process, so we use rechargeable spins to
842	>	* avoid it when threads regularly arrive: When a thread in
843	>	* internalAwaitAdvance notices another arrival before blocking,
844	>	* and there appear to be enough CPUs available, it spins
845	>	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
846	>	* uniprocessors, there is at least one intervening Thread.yield
847	>	* before blocking. The value trades off good-citizenship vs big
848	>	* unnecessary slowdowns.
849		*/
850	<	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
850	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
851
852		/**
853	<	* The number of times to spin before blocking in untimed waits.
854	<	* This is greater than timed value because untimed waits spin
855	<	* faster since they don't need to check times on each spin.
856	<	*/
857	<	static final int maxUntimedSpins = maxTimedSpins * 32;
853	>	* Possibly blocks and waits for phase to advance unless aborted.
854	>	*
855	>	* @param phase current phase
856	>	* @param node if non-null, the wait node to track interrupt and timeout;
857	>	* if null, denotes noninterruptible wait
858	>	* @return current phase
859	>	*/
860	>	private int internalAwaitAdvance(int phase, QNode node) {
861	>	Phaser current = this;       // to eventually wait at root if tiered
862	>	boolean queued = false;      // true when node is enqueued
863	>	int lastUnarrived = -1;      // to increase spins upon change
864	>	int spins = SPINS_PER_ARRIVAL;
865	>	for (;;) {
866	>	int p, unarrived;
867	>	Phaser par;
868	>	long s = current.state;
869	>	if ((p = (int)(s >>> PHASE_SHIFT)) != phase) {
870	>	if (node != null)
871	>	node.onRelease();
872	>	releaseWaiters(phase);
873	>	return p;
874	>	}
875	>	else if ((unarrived = ((int)s) & UNARRIVED_MASK) == 0 &&
876	>	(par = current.parent) != null) {
877	>	current = par;       // if all arrived, use parent
878	>	par = par.parent;
879	>	lastUnarrived = -1;
880	>	}
881	>	else if (unarrived != lastUnarrived) {
882	>	if ((lastUnarrived = unarrived) < NCPU)
883	>	spins += SPINS_PER_ARRIVAL;
884	>	}
885	>	else if (spins > 0) {
886	>	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
887	>	Thread.yield();  // yield midway through spin
888	>	}
889	>	else if (node == null)   // must be noninterruptible
890	>	node = new QNode(this, phase, false, false, 0L);
891	>	else if (node.isReleasable()) {
892	>	if ((int)(reconcileState() >>> PHASE_SHIFT) == phase)
893	>	return phase;    // aborted
894	>	}
895	>	else if (!queued)
896	>	queued = tryEnqueue(phase, node);
897	>	else {
898	>	try {
899	>	ForkJoinPool.managedBlock(node);
900	>	} catch (InterruptedException ie) {
901	>	node.wasInterrupted = true;
902	>	}
903	>	}
904	>	}
905	>	}
906
907		/**
908	<	* The number of nanoseconds for which it is faster to spin
583	<	* rather than to use timed park. A rough estimate suffices.
908	>	* Wait nodes for Treiber stack representing wait queue
909		*/
910	<	static final long spinForTimeoutThreshold = 1000L;
910	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
911	>	final Phaser phaser;
912	>	final int phase;
913	>	final boolean interruptible;
914	>	final boolean timed;
915	>	boolean wasInterrupted;
916	>	long nanos;
917	>	long lastTime;
918	>	volatile Thread thread; // nulled to cancel wait
919	>	QNode next;
920
921	<	/**
922	<	* Enqueues node and waits unless aborted or signalled.
923	<	*/
924	<	private boolean untimedWait(Thread thread, int currentPhase,
925	<	boolean abortOnInterrupt) {
926	<	final AtomicReference<QNode> head = this.head;
927	<	final AtomicLong state = this.state;
928	<	boolean wasInterrupted = false;
929	<	QNode node = null;
930	<	boolean queued = false;
931	<	int spins = maxUntimedSpins;
932	<	while (phaseOf(state.get()) == currentPhase) {
933	<	QNode h;
934	<	if (node != null && queued) {
935	<	if (node.thread != null) {
936	<	LockSupport.park();
937	<	if (Thread.interrupted()) {
921	>	QNode(Phaser phaser, int phase, boolean interruptible,
922	>	boolean timed, long nanos) {
923	>	this.phaser = phaser;
924	>	this.phase = phase;
925	>	this.interruptible = interruptible;
926	>	this.nanos = nanos;
927	>	this.timed = timed;
928	>	this.lastTime = timed? System.nanoTime() : 0L;
929	>	thread = Thread.currentThread();
930	>	}
931	>
932	>	public boolean isReleasable() {
933	>	Thread t = thread;
934	>	if (t != null) {
935	>	if (phaser.getPhase() != phase)
936	>	t = null;
937	>	else {
938	>	if (Thread.interrupted())
939		wasInterrupted = true;
940	<	if (abortOnInterrupt)
941	<	break;
942	<	}
943	<	}
944	<	}
945	<	else if ((h = head.get()) != null && h.phase != currentPhase) {
946	<	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);
940	>	if (interruptible && wasInterrupted)
941	>	t = null;
942	>	else if (timed) {
943	>	if (nanos > 0) {
944	>	long now = System.nanoTime();
945	>	nanos -= now - lastTime;
946	>	lastTime = now;
947		}
948	+	if (nanos <= 0)
949	+	t = null;
950		}
951		}
952	<	else
953	<	break;
952	>	if (t != null)
953	>	return false;
954	>	thread = null;
955	>	}
956	>	return true;
957	>	}
958	>
959	>	public boolean block() {
960	>	if (isReleasable())
961	>	return true;
962	>	else if (!timed)
963	>	LockSupport.park(this);
964	>	else if (nanos > 0)
965	>	LockSupport.parkNanos(this, nanos);
966	>	return isReleasable();
967	>	}
968	>
969	>	void signal() {
970	>	Thread t = thread;
971	>	if (t != null) {
972	>	thread = null;
973	>	LockSupport.unpark(t);
974		}
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;
975		}
976	<	if (node != null)
977	<	node.thread = null;
978	<	return wasInterrupted;
976	>
977	>	void onRelease() { // actions upon return from internalAwaitAdvance
978	>	if (!interruptible && wasInterrupted)
979	>	Thread.currentThread().interrupt();
980	>	if (thread != null)
981	>	thread = null;
982	>	}
983	>
984	>	}
985	>
986	>	// Unsafe mechanics
987	>
988	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
989	>	private static final long stateOffset =
990	>	objectFieldOffset("state", Phaser.class);
991	>
992	>	private static long objectFieldOffset(String field, Class<?> klazz) {
993	>	try {
994	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
995	>	} catch (NoSuchFieldException e) {
996	>	// Convert Exception to corresponding Error
997	>	NoSuchFieldError error = new NoSuchFieldError(field);
998	>	error.initCause(e);
999	>	throw error;
1000	>	}
1001		}
1002
1003		/**
1004	<	* Messier timeout version
1004	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1005	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1006	>	* into a jdk.
1007	>	*
1008	>	* @return a sun.misc.Unsafe
1009		*/
1010	<	private void timedWait(Thread thread, int currentPhase, long nanos)
1011	<	throws InterruptedException, TimeoutException {
1012	<	final AtomicReference<QNode> head = this.head;
1013	<	final AtomicLong state = this.state;
1014	<	long lastTime = System.nanoTime();
1015	<	QNode node = null;
1016	<	boolean queued = false;
1017	<	int spins = maxTimedSpins;
1018	<	while (phaseOf(state.get()) == currentPhase) {
1019	<	QNode h;
1020	<	long now = System.nanoTime();
1021	<	nanos -= now - lastTime;
1022	<	lastTime = now;
1023	<	if (nanos <= 0) {
1024	<	if (node != null)
1025	<	node.thread = null;
1026	<	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	<	}
1010	>	private static sun.misc.Unsafe getUnsafe() {
1011	>	try {
1012	>	return sun.misc.Unsafe.getUnsafe();
1013	>	} catch (SecurityException se) {
1014	>	try {
1015	>	return java.security.AccessController.doPrivileged
1016	>	(new java.security
1017	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1018	>	public sun.misc.Unsafe run() throws Exception {
1019	>	java.lang.reflect.Field f = sun.misc
1020	>	.Unsafe.class.getDeclaredField("theUnsafe");
1021	>	f.setAccessible(true);
1022	>	return (sun.misc.Unsafe) f.get(null);
1023	>	}});
1024	>	} catch (java.security.PrivilegedActionException e) {
1025	>	throw new RuntimeException("Could not initialize intrinsics",
1026	>	e.getCause());
1027		}
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;
1028		}
690	–	if (node != null)
691	–	node.thread = null;
1029		}
693	–
1030		}
695	–

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