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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.28 by jsr166, Wed Aug 12 02:24:35 2009 UTC vs.
Revision 1.59 by dl, Sat Nov 27 16:46:53 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	<	import java.util.concurrent.*;
10	<
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
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>
21	<	*
22	<	* <li> The number of parties synchronizing on a phaser may vary over
23	<	* time.  A task may register to be a party at any time, and may
24	<	* deregister upon arriving at the barrier.  As is the case with most
25	<	* basic synchronization constructs, registration and deregistration
26	<	* affect only internal counts; they do not establish any further
27	<	* internal bookkeeping, so tasks cannot query whether they are
28	<	* registered. (However, you can introduce such bookkeeping by
29	<	* subclassing this class.)
30	<	*
31	<	* <li> Each generation has an associated phase value, starting at
32	<	* zero, and advancing when all parties reach the barrier (wrapping
33	<	* around to zero after reaching {@code Integer.MAX_VALUE}).
34	<	*
35	<	* <li> Like a {@code CyclicBarrier}, a phaser may be repeatedly
36	<	* awaited.  Method {@link #arriveAndAwaitAdvance} has effect
37	<	* analogous to {@link java.util.concurrent.CyclicBarrier#await
38	<	* CyclicBarrier.await}.  However, phasers separate two aspects of
39	<	* coordination, which may also be invoked independently:
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	>	* <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 {@link #arrive} and
48	<	*       {@link #arriveAndDeregister} do not block, but return
49	<	*       the phase value current upon entry to the method.
50	<	*
51	<	*   <li> Awaiting others. Method {@link #awaitAdvance} requires an
52	<	*       argument indicating the entry phase, and returns when the
53	<	*       barrier advances to a new phase.
54	<	* </ul>
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	<	* <li> Barrier actions, performed by the task triggering a phase
78	<	* advance, are arranged by overriding method {@link #onAdvance(int,
79	<	* int)}, which also controls termination. Overriding this method is
80	<	* similar to, but more flexible than, providing a barrier action to a
81	<	* {@code CyclicBarrier}.
82	<	*
83	<	* <li> Phasers may enter a <em>termination</em> state in which all
84	<	* actions immediately return without updating phaser state or waiting
85	<	* for advance, and indicating (via a negative phase value) that
62	<	* execution is complete.  Termination is triggered when an invocation
63	<	* of {@code onAdvance} returns {@code true}.  When a phaser is
64	<	* controlling an action with a fixed number of iterations, it is
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> Phasers may be tiered to reduce contention. Phasers with large
92	<	* numbers of parties that would otherwise experience heavy
93	<	* synchronization contention costs may instead be arranged in trees.
94	<	* This will typically greatly increase throughput even though it
95	<	* incurs somewhat greater per-operation overhead.
96	<	*
97	<	* <li> By default, {@code awaitAdvance} continues to wait even if
98	<	* the waiting thread is interrupted. And unlike the case in
99	<	* {@code CyclicBarrier}, exceptions encountered while tasks wait
100	<	* interruptibly or with timeout do not change the state of the
101	<	* barrier. If necessary, you can perform any associated recovery
102	<	* within handlers of those exceptions, often after invoking
103	<	* {@code forceTermination}.
104	<	*
105	<	* <li>Phasers may be used to coordinate tasks executing in a {@link
106	<	* ForkJoinPool}, which will ensure sufficient parallelism to execute
107	<	* tasks when others are blocked waiting for a phase to advance.
108	<	*
109	<	* </ul>
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	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
100	>	* only by registered parties, the current state of a phaser may be
101	>	* monitored by any caller.  At any given moment there are {@link
102	>	* #getRegisteredParties} parties in total, of which {@link
103	>	* #getArrivedParties} have arrived at the current phase ({@link
104	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
105	>	* parties arrive, the phase advances.  The values returned by these
106	>	* methods may reflect transient states and so are not in general
107	>	* useful for synchronization control.  Method {@link #toString}
108	>	* returns snapshots of these state queries in a form convenient for
109	>	* informal monitoring.
110		*
111		* <p><b>Sample usages:</b>
112		*
113		* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
114	<	* to control a one-shot action serving a variable number of
115	<	* parties. The typical idiom is for the method setting this up to
116	<	* first register, then start the actions, then deregister, as in:
114	>	* to control a one-shot action serving a variable number of parties.
115	>	* The typical idiom is for the method setting this up to first
116	>	* register, then start the actions, then deregister, as in:
117		*
118		*  <pre> {@code
119	<	* void runTasks(List<Runnable> list) {
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 r : list) {
122	>	*   for (Runnable task : tasks) {
123		*     phaser.register();
124		*     new Thread() {
125		*       public void run() {
126		*         phaser.arriveAndAwaitAdvance(); // await all creation
127	<	*         r.run();
127	>	*         task.run();
128		*       }
129		*     }.start();
130		*   }
#	Line 116 | Line 137 | import java.util.concurrent.locks.LockSu
137		* for a given number of iterations is to override {@code onAdvance}:
138		*
139		*  <pre> {@code
140	<	* void startTasks(List<Runnable> list, final int iterations) {
140	>	* void startTasks(List<Runnable> tasks, final int iterations) {
141		*   final Phaser phaser = new Phaser() {
142	<	*     public boolean onAdvance(int phase, int registeredParties) {
142	>	*     protected boolean onAdvance(int phase, int registeredParties) {
143		*       return phase >= iterations || registeredParties == 0;
144		*     }
145		*   };
146		*   phaser.register();
147	<	*   for (Runnable r : list) {
147	>	*   for (final Runnable task : tasks) {
148		*     phaser.register();
149		*     new Thread() {
150		*       public void run() {
151		*         do {
152	<	*           r.run();
152	>	*           task.run();
153		*           phaser.arriveAndAwaitAdvance();
154	<	*         } while(!phaser.isTerminated();
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 for upon construction:
189	>	* it registers with upon construction:
190	>	*
191		*  <pre> {@code
192	<	* void build(Task[] actions, int lo, int hi, Phaser b) {
193	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
194	<	*   if (step > 1) {
195	<	*     int i = lo;
196	<	*     while (i < hi) {
150	<	*       int r = Math.min(i + step, hi);
151	<	*       build(actions, i, r, new Phaser(b));
152	<	*       i = r;
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(b);
201	<	*       // assumes new Task(b) performs b.register()
200	>	*       actions[i] = new Task(ph);
201	>	*       // assumes new Task(ph) performs ph.register()
202		*   }
203		* }
204		* // .. initially called, for n tasks via
#	Line 165 | Line 209 | import java.util.concurrent.locks.LockSu
209		* be appropriate for extremely small per-barrier task bodies (thus
210		* high rates), or up to hundreds for extremely large ones.
211		*
168	–	* </pre>
169	–	*
212		* <p><b>Implementation notes</b>: This implementation restricts the
213		* maximum number of parties to 65535. Attempts to register additional
214	<	* parties result in IllegalStateExceptions. However, you can and
214	>	* parties result in {@code IllegalStateException}. However, you can and
215		* should create tiered phasers to accommodate arbitrarily large sets
216		* of participants.
217		*
#	Line 187 | Line 229 | public class Phaser {
229		* Barrier state representation. Conceptually, a barrier contains
230		* four values:
231		*
232	<	* * parties -- the number of parties to wait (16 bits)
233	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
234	<	* * phase -- the generation of the barrier (31 bits)
235	<	* * terminated -- set if barrier is terminated (1 bit)
232	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
233	>	* * parties -- the number of parties to wait              (bits 16-31)
234	>	* * phase -- the generation of the barrier                (bits 32-62)
235	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
236		*
237		* However, to efficiently maintain atomicity, these values are
238		* packed into a single (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.
200	–	*
201	–	* Note: there are some cheats in arrive() that rely on unarrived
202	–	* count being lowest 16 bits.
242		*/
243		private volatile long state;
244
245	<	private static final int ushortBits = 16;
246	<	private static final int ushortMask = 0xffff;
247	<	private static final int phaseMask  = 0x7fffffff;
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	>	// 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) >>> 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
226	–	private static long stateFor(int phase, int parties, int unarrived) {
227	–	return ((((long) phase) << 32) | (((long) parties) << 16) |
228	–	(long) unarrived);
229	–	}
230	–
231	–	private static long trippedStateFor(int phase, int parties) {
232	–	long lp = (long) parties;
233	–	return (((long) phase) << 32) | (lp << 16) | lp;
234	–	}
235	–
236	–	/**
237	–	* Returns message string for bad bounds exceptions.
238	–	*/
239	–	private static String badBounds(int parties, int unarrived) {
240	–	return ("Attempt to set " + unarrived +
241	–	" unarrived of " + parties + " parties");
242	–	}
243	–
273		/**
274		* The parent of this phaser, or null if none
275		*/
#	Line 252 | Line 281 | public class Phaser {
281		*/
282		private final Phaser root;
283
255	–	// Wait queues
256	–
284		/**
285		* Heads of Treiber stacks for waiting threads. To eliminate
286	<	* contention while releasing some threads while adding others, we
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	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
291	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
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	<	* Returns current state, first resolving lagged propagation from
271	<	* root if necessary.
298	>	* Returns message string for bounds exceptions on arrival.
299		*/
300	<	private long getReconciledState() {
301	<	return (parent == null) ? state : reconcileState();
300	>	private String badArrive(long s) {
301	>	return "Attempted arrival of unregistered party for " +
302	>	stateToString(s);
303		}
304
305		/**
306	<	* Recursively resolves state.
306	>	* Returns message string for bounds exceptions on registration.
307		*/
308	<	private long reconcileState() {
309	<	Phaser p = parent;
310	<	long s = state;
311	<	if (p != null) {
312	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
313	<	long parentState = p.getReconciledState();
314	<	int parentPhase = phaseOf(parentState);
315	<	int phase = phaseOf(s = state);
316	<	if (phase != parentPhase) {
317	<	long next = trippedStateFor(parentPhase, partiesOf(s));
318	<	if (casState(s, next)) {
308	>	private String badRegister(long s) {
309	>	return "Attempt to register more than " +
310	>	MAX_PARTIES + " parties for " + stateToString(s);
311	>	}
312	>
313	>	/**
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	>	* @param adj - adjustment to apply to state -- either
319	>	* ONE_ARRIVAL (for arrive) or
320	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
321	>	*/
322	>	private int doArrive(long adj) {
323	>	for (;;) {
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	>	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	<	s = next;
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	+	* Implementation of register, bulkRegister
364	+	*
365	+	* @param registrations number to add to both parties and
366	+	* unarrived fields. Must be greater than zero.
367	+	*/
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 = (parent == null) ? state : reconcileState();
374	+	int parties = (int)s >>> PARTIES_SHIFT;
375	+	int phase = (int)(s >>> PHASE_SHIFT);
376	+	if (phase < 0)
377	+	return phase;
378	+	else if (registrations > MAX_PARTIES - parties)
379	+	throw new IllegalStateException(badRegister(s));
380	+	else if ((parties == 0 && parent == null) || // first reg of root
381	+	((int)s & UNARRIVED_MASK) != 0) {   // not advancing
382	+	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
383	+	return phase;
384	+	}
385	+	else if (parties != 0)               // wait for onAdvance
386	+	internalAwaitAdvance(phase, null);
387	+	else {                               // 1st registration of child
388	+	synchronized(this) {             // register parent first
389	+	if (reconcileState() == s) { // recheck under lock
390	+	parent.doRegister(1);    // OK if throws IllegalState
391	+	for (;;) {               // simpler form of outer loop
392	+	s = reconcileState();
393	+	phase = (int)(s >>> PHASE_SHIFT);
394	+	if (phase < 0 ||
395	+	UNSAFE.compareAndSwapLong(this, stateOffset,
396	+	s, s + adj))
397	+	return phase;
398	+	}
399	+	}
400	+	}
401	+	}
402	+	}
403	+	}
404	+
405	+	/**
406	+	* Recursively resolves lagged phase propagation from root if necessary.
407	+	*/
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;
#	Line 303 | Line 433 | public class Phaser {
433		* phaser will need to first register for it.
434		*/
435		public Phaser() {
436	<	this(null);
436	>	this(null, 0);
437		}
438
439		/**
440	<	* Creates a new phaser with the given numbers of registered
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
#	Line 319 | Line 449 | public class Phaser {
449		}
450
451		/**
452	<	* Creates a new phaser with the given parent, without any
453	<	* initially registered parties. If parent is non-null this phaser
454	<	* is registered with the parent and its initial phase number is
455	<	* the same as that of parent phaser.
452	>	* Creates a new phaser with the given parent, and without any
453	>	* initially registered parties.  Any thread using this phaser
454	>	* will need to first register for it, at which point, if the
455	>	* given parent is non-null, this phaser will also be registered
456	>	* with the parent.
457	>	*
458	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
459		*
460		* @param parent the parent phaser
461		*/
462		public Phaser(Phaser parent) {
463	<	int phase = 0;
331	<	this.parent = parent;
332	<	if (parent != null) {
333	<	this.root = parent.root;
334	<	phase = parent.register();
335	<	}
336	<	else
337	<	this.root = this;
338	<	this.state = trippedStateFor(phase, 0);
463	>	this(parent, 0);
464		}
465
466		/**
467	<	* Creates a new phaser with the given parent and numbers of
468	<	* registered unarrived parties. If parent is non-null, this phaser
469	<	* is registered with the parent and its initial phase number is
470	<	* the same as that of parent phaser.
467	>	* Creates a new phaser with the given parent and number of
468	>	* registered unarrived parties. If parent is non-null and
469	>	* the number of parties is non-zero, this phaser is registered
470	>	* with the parent.
471		*
472		* @param parent the parent phaser
473		* @param parties the number of parties required to trip barrier
#	Line 350 | Line 475 | public class Phaser {
475		* or greater than the maximum number of parties supported
476		*/
477		public Phaser(Phaser parent, int parties) {
478	<	if (parties < 0 || parties > ushortMask)
478	>	if (parties >>> PARTIES_SHIFT != 0)
479		throw new IllegalArgumentException("Illegal number of parties");
480	<	int phase = 0;
480	>	int phase;
481		this.parent = parent;
482		if (parent != null) {
483	<	this.root = parent.root;
484	<	phase = parent.register();
483	>	Phaser r = parent.root;
484	>	this.root = r;
485	>	this.evenQ = r.evenQ;
486	>	this.oddQ = r.oddQ;
487	>	phase = (parties == 0) ? parent.getPhase() : parent.doRegister(1);
488		}
489	<	else
489	>	else {
490		this.root = this;
491	<	this.state = trippedStateFor(phase, parties);
491	>	this.evenQ = new AtomicReference<QNode>();
492	>	this.oddQ = new AtomicReference<QNode>();
493	>	phase = 0;
494	>	}
495	>	long p = (long)parties;
496	>	this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
497		}
498
499		/**
500	<	* Adds a new unarrived party to this phaser.
500	>	* Adds a new unarrived party to this phaser.  If an ongoing
501	>	* invocation of {@link #onAdvance} is in progress, this method
502	>	* may wait until its completion before registering.  If this
503	>	* phaser has a parent, and this phaser previously had no
504	>	* registered parties, this phaser is also registered with its
505	>	* parent.
506		*
507	<	* @return the current barrier phase number upon registration
507	>	* @return the arrival phase number to which this registration applied
508		* @throws IllegalStateException if attempting to register more
509		* than the maximum supported number of parties
510		*/
#	Line 376 | Line 514 | public class Phaser {
514
515		/**
516		* Adds the given number of new unarrived parties to this phaser.
517	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
518	+	* this method may wait until its completion before registering.
519	+	* If this phaser has a parent, and the given number of parities
520	+	* is greater than zero, and this phaser previously had no
521	+	* registered parties, this phaser is also registered with its
522	+	* parent.
523		*
524	<	* @param parties the number of parties required to trip barrier
525	<	* @return the current barrier phase number upon registration
524	>	* @param parties the number of additional parties required to trip barrier
525	>	* @return the arrival phase number to which this registration applied
526		* @throws IllegalStateException if attempting to register more
527		* than the maximum supported number of parties
528	+	* @throws IllegalArgumentException if {@code parties < 0}
529		*/
530		public int bulkRegister(int parties) {
531		if (parties < 0)
532		throw new IllegalArgumentException();
533	<	if (parties == 0)
533	>	else if (parties == 0)
534		return getPhase();
535		return doRegister(parties);
536		}
537
538		/**
394	–	* Shared code for register, bulkRegister
395	–	*/
396	–	private int doRegister(int registrations) {
397	–	int phase;
398	–	for (;;) {
399	–	long s = getReconciledState();
400	–	phase = phaseOf(s);
401	–	int unarrived = unarrivedOf(s) + registrations;
402	–	int parties = partiesOf(s) + registrations;
403	–	if (phase < 0)
404	–	break;
405	–	if (parties > ushortMask || unarrived > ushortMask)
406	–	throw new IllegalStateException(badBounds(parties, unarrived));
407	–	if (phase == phaseOf(root.state) &&
408	–	casState(s, stateFor(phase, parties, unarrived)))
409	–	break;
410	–	}
411	–	return phase;
412	–	}
413	–
414	–	/**
539		* Arrives at the barrier, but does not wait for others.  (You can
540	<	* in turn wait for others via {@link #awaitAdvance}).
540	>	* in turn wait for others via {@link #awaitAdvance}).  It is a
541	>	* usage error for an unregistered party to invoke this
542	>	* method. However, it is possible that this error will result in
543	>	* an {code IllegalStateException} only when some <em>other</em>
544	>	* party arrives.
545		*
546	<	* @return the barrier phase number upon entry to this method, or a
419	<	* negative value if terminated
546	>	* @return the arrival phase number, or a negative value if terminated
547		* @throws IllegalStateException if not terminated and the number
548		* of unarrived parties would become negative
549		*/
550		public int arrive() {
551	<	int phase;
425	<	for (;;) {
426	<	long s = state;
427	<	phase = phaseOf(s);
428	<	if (phase < 0)
429	<	break;
430	<	int parties = partiesOf(s);
431	<	int unarrived = unarrivedOf(s) - 1;
432	<	if (unarrived > 0) {        // Not the last arrival
433	<	if (casState(s, s - 1)) // s-1 adds one arrival
434	<	break;
435	<	}
436	<	else if (unarrived == 0) {  // the last arrival
437	<	Phaser par = parent;
438	<	if (par == null) {      // directly trip
439	<	if (casState
440	<	(s,
441	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
442	<	((phase + 1) & phaseMask), parties))) {
443	<	releaseWaiters(phase);
444	<	break;
445	<	}
446	<	}
447	<	else {                  // cascade to parent
448	<	if (casState(s, s - 1)) { // zeroes unarrived
449	<	par.arrive();
450	<	reconcileState();
451	<	break;
452	<	}
453	<	}
454	<	}
455	<	else if (phase != phaseOf(root.state)) // or if unreconciled
456	<	reconcileState();
457	<	else
458	<	throw new IllegalStateException(badBounds(parties, unarrived));
459	<	}
460	<	return phase;
551	>	return doArrive(ONE_ARRIVAL);
552		}
553
554		/**
#	Line 466 | Line 557 | public class Phaser {
557		* required to trip the barrier in future phases.  If this phaser
558		* has a parent, and deregistration causes this phaser to have
559		* zero parties, this phaser also arrives at and is deregistered
560	<	* from its parent.
560	>	* from its parent.  It is a usage error for an unregistered party
561	>	* to invoke this method. However, it is possible that this error
562	>	* will result in an {code IllegalStateException} only when some
563	>	* <em>other</em> party arrives.
564		*
565	<	* @return the current barrier phase number upon entry to
472	<	* this method, or a negative value if terminated
565	>	* @return the arrival phase number, or a negative value if terminated
566		* @throws IllegalStateException if not terminated and the number
567		* of registered or unarrived parties would become negative
568		*/
569		public int arriveAndDeregister() {
570	<	// similar code to arrive, but too different to merge
478	<	Phaser par = parent;
479	<	int phase;
480	<	for (;;) {
481	<	long s = state;
482	<	phase = phaseOf(s);
483	<	if (phase < 0)
484	<	break;
485	<	int parties = partiesOf(s) - 1;
486	<	int unarrived = unarrivedOf(s) - 1;
487	<	if (parties >= 0) {
488	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
489	<	if (casState
490	<	(s,
491	<	stateFor(phase, parties, unarrived))) {
492	<	if (unarrived == 0) {
493	<	par.arriveAndDeregister();
494	<	reconcileState();
495	<	}
496	<	break;
497	<	}
498	<	continue;
499	<	}
500	<	if (unarrived == 0) {
501	<	if (casState
502	<	(s,
503	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
504	<	((phase + 1) & phaseMask), parties))) {
505	<	releaseWaiters(phase);
506	<	break;
507	<	}
508	<	continue;
509	<	}
510	<	if (par != null && phase != phaseOf(root.state)) {
511	<	reconcileState();
512	<	continue;
513	<	}
514	<	}
515	<	throw new IllegalStateException(badBounds(parties, unarrived));
516	<	}
517	<	return phase;
570	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
571		}
572
573		/**
574		* Arrives at the barrier and awaits others. Equivalent in effect
575		* to {@code awaitAdvance(arrive())}.  If you need to await with
576		* interruption or timeout, you can arrange this with an analogous
577	<	* construction using one of the other forms of the awaitAdvance
578	<	* method.  If instead you need to deregister upon arrival use
579	<	* {@code arriveAndDeregister}.
577	>	* construction using one of the other forms of the {@code
578	>	* awaitAdvance} method.  If instead you need to deregister upon
579	>	* arrival, use {@link #arriveAndDeregister}.  It is a usage error
580	>	* for an unregistered party to invoke this method. However, it is
581	>	* possible that this error will result in an {code
582	>	* IllegalStateException} only when some <em>other</em> party
583	>	* arrives.
584		*
585	<	* @return the phase on entry to this method
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		*/
#	Line 535 | Line 592 | public class Phaser {
592
593		/**
594		* Awaits the phase of the barrier to advance from the given phase
595	<	* value, or returns immediately if the current phase of the barrier
596	<	* is not equal to the given phase value or this barrier is
597	<	* terminated.
598	<	*
599	<	* @param phase the phase on entry to this method
600	<	* @return the phase on exit from this method
595	>	* value, returning immediately if the current phase of the
596	>	* barrier is not equal to the given phase value or this barrier
597	>	* is terminated.
598	>	*
599	>	* @param phase an arrival phase number, or negative value if
600	>	* terminated; this argument is normally the value returned by a
601	>	* previous call to {@code arrive} or its variants
602	>	* @return the next arrival phase number, or a negative value
603	>	* if terminated or argument is negative
604		*/
605		public int awaitAdvance(int phase) {
606		if (phase < 0)
607		return phase;
608	<	long s = getReconciledState();
609	<	int p = phaseOf(s);
610	<	if (p != phase)
551	<	return p;
552	<	if (unarrivedOf(s) == 0 && parent != null)
553	<	parent.awaitAdvance(phase);
554	<	// Fall here even if parent waited, to reconcile and help release
555	<	return untimedWait(phase);
608	>	long s = (parent == null) ? state : reconcileState();
609	>	int p = (int)(s >>> PHASE_SHIFT);
610	>	return (p != phase) ? p : internalAwaitAdvance(phase, null);
611		}
612
613		/**
614	<	* Awaits the phase of the barrier to advance from the given
615	<	* value, or returns immediately if argument is negative or this
616	<	* barrier is terminated, or throws InterruptedException if
617	<	* interrupted while waiting.
618	<	*
619	<	* @param phase the phase on entry to this method
620	<	* @return the phase on exit from this method
614	>	* Awaits the phase of the barrier to advance from the given phase
615	>	* value, throwing {@code InterruptedException} if interrupted
616	>	* while waiting, or returning immediately if the current phase of
617	>	* the barrier is not equal to the given phase value or this
618	>	* barrier is terminated.
619	>	*
620	>	* @param phase an arrival phase number, or negative value if
621	>	* terminated; this argument is normally the value returned by a
622	>	* previous call to {@code arrive} or its variants
623	>	* @return the next arrival phase number, or a negative value
624	>	* if terminated or argument is negative
625		* @throws InterruptedException if thread interrupted while waiting
626		*/
627		public int awaitAdvanceInterruptibly(int phase)
628		throws InterruptedException {
629		if (phase < 0)
630		return phase;
631	<	long s = getReconciledState();
632	<	int p = phaseOf(s);
633	<	if (p != phase)
634	<	return p;
635	<	if (unarrivedOf(s) == 0 && parent != null)
636	<	parent.awaitAdvanceInterruptibly(phase);
637	<	return interruptibleWait(phase);
631	>	long s = (parent == null) ? state : reconcileState();
632	>	int p = (int)(s >>> PHASE_SHIFT);
633	>	if (p == phase) {
634	>	QNode node = new QNode(this, phase, true, false, 0L);
635	>	p = internalAwaitAdvance(phase, node);
636	>	if (node.wasInterrupted)
637	>	throw new InterruptedException();
638	>	}
639	>	return p;
640		}
641
642		/**
643	<	* Awaits the phase of the barrier to advance from the given value
644	<	* or the given timeout elapses, or returns immediately if
645	<	* argument is negative or this barrier is terminated.
643	>	* Awaits the phase of the barrier to advance from the given phase
644	>	* value or the given timeout to elapse, throwing {@code
645	>	* InterruptedException} if interrupted while waiting, or
646	>	* returning immediately if the current phase of the barrier is
647	>	* not equal to the given phase value or this barrier is
648	>	* terminated.
649		*
650	<	* @param phase the phase on entry to this method
651	<	* @return the phase on exit from this method
650	>	* @param phase an arrival phase number, or negative value if
651	>	* terminated; this argument is normally the value returned by a
652	>	* previous call to {@code arrive} or its variants
653	>	* @param timeout how long to wait before giving up, in units of
654	>	*        {@code unit}
655	>	* @param unit a {@code TimeUnit} determining how to interpret the
656	>	*        {@code timeout} parameter
657	>	* @return the next arrival phase number, or a negative value
658	>	* if terminated or argument is negative
659		* @throws InterruptedException if thread interrupted while waiting
660		* @throws TimeoutException if timed out while waiting
661		*/
#	Line 593 | Line 664 | public class Phaser {
664		throws InterruptedException, TimeoutException {
665		if (phase < 0)
666		return phase;
667	<	long s = getReconciledState();
668	<	int p = phaseOf(s);
669	<	if (p != phase)
670	<	return p;
671	<	if (unarrivedOf(s) == 0 && parent != null)
672	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
673	<	return timedWait(phase, unit.toNanos(timeout));
667	>	long s = (parent == null) ? state : reconcileState();
668	>	int p = (int)(s >>> PHASE_SHIFT);
669	>	if (p == phase) {
670	>	long nanos = unit.toNanos(timeout);
671	>	QNode node = new QNode(this, phase, true, true, nanos);
672	>	p = internalAwaitAdvance(phase, node);
673	>	if (node.wasInterrupted)
674	>	throw new InterruptedException();
675	>	else if (p == phase)
676	>	throw new TimeoutException();
677	>	}
678	>	return p;
679		}
680
681		/**
682	<	* Forces this barrier to enter termination state. Counts of
683	<	* arrived and registered parties are unaffected. If this phaser
684	<	* has a parent, it too is terminated. This method may be useful
685	<	* for coordinating recovery after one or more tasks encounter
686	<	* unexpected exceptions.
682	>	* Forces this barrier to enter termination state.  Counts of
683	>	* arrived and registered parties are unaffected.  If this phaser
684	>	* is a member of a tiered set of phasers, then all of the phasers
685	>	* in the set are terminated.  If this phaser is already
686	>	* terminated, this method has no effect.  This method may be
687	>	* useful for coordinating recovery after one or more tasks
688	>	* encounter unexpected exceptions.
689		*/
690		public void forceTermination() {
691	<	for (;;) {
692	<	long s = getReconciledState();
693	<	int phase = phaseOf(s);
694	<	int parties = partiesOf(s);
695	<	int unarrived = unarrivedOf(s);
696	<	if (phase < 0 ||
697	<	casState(s, stateFor(-1, parties, unarrived))) {
620	<	releaseWaiters(0);
691	>	// Only need to change root state
692	>	final Phaser root = this.root;
693	>	long s;
694	>	while ((s = root.state) >= 0) {
695	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
696	>	s, s | TERMINATION_BIT)) {
697	>	releaseWaiters(0); // signal all threads
698		releaseWaiters(1);
622	–	if (parent != null)
623	–	parent.forceTermination();
699		return;
700		}
701		}
#	Line 634 | Line 709 | public class Phaser {
709		* @return the phase number, or a negative value if terminated
710		*/
711		public final int getPhase() {
712	<	return phaseOf(getReconciledState());
712	>	return (int)(root.state >>> PHASE_SHIFT);
713		}
714
715		/**
#	Line 647 | Line 722 | public class Phaser {
722		}
723
724		/**
725	<	* Returns the number of parties that have arrived at the current
726	<	* phase of this barrier.
725	>	* Returns the number of registered parties that have arrived at
726	>	* the current phase of this barrier.
727		*
728		* @return the number of arrived parties
729		*/
730		public int getArrivedParties() {
731	<	return arrivedOf(state);
731	>	return arrivedOf(parent==null? state : reconcileState());
732		}
733
734		/**
#	Line 663 | Line 738 | public class Phaser {
738		* @return the number of unarrived parties
739		*/
740		public int getUnarrivedParties() {
741	<	return unarrivedOf(state);
741	>	return unarrivedOf(parent==null? state : reconcileState());
742		}
743
744		/**
#	Line 691 | Line 766 | public class Phaser {
766		* @return {@code true} if this barrier has been terminated
767		*/
768		public boolean isTerminated() {
769	<	return getPhase() < 0;
769	>	return root.state < 0L;
770		}
771
772		/**
773	<	* Overridable method to perform an action upon phase advance, and
774	<	* to control termination. This method is invoked whenever the
775	<	* barrier is tripped (and thus all other waiting parties are
776	<	* dormant). If it returns {@code true}, then, rather than advance
777	<	* the phase number, this barrier will be set to a final
778	<	* termination state, and subsequent calls to {@link #isTerminated}
779	<	* will return true.
780	<	*
781	<	* <p>The default version returns {@code true} when the number of
782	<	* registered parties is zero. Normally, overrides that arrange
783	<	* termination for other reasons should also preserve this
784	<	* property.
785	<	*
786	<	* <p>You may override this method to perform an action with side
787	<	* effects visible to participating tasks, but it is in general
788	<	* only sensible to do so in designs where all parties register
789	<	* before any arrive, and all {@link #awaitAdvance} at each phase.
790	<	* Otherwise, you cannot ensure lack of interference from other
791	<	* parties during the the invocation of this method.
773	>	* Overridable method to perform an action upon impending phase
774	>	* advance, and to control termination. This method is invoked
775	>	* upon arrival of the party tripping the barrier (when all other
776	>	* waiting parties are dormant).  If this method returns {@code
777	>	* true}, then, rather than advance the phase number, this barrier
778	>	* will be set to a final termination state, and subsequent calls
779	>	* to {@link #isTerminated} will return true. Any (unchecked)
780	>	* Exception or Error thrown by an invocation of this method is
781	>	* propagated to the party attempting to trip the barrier, in
782	>	* which case no advance occurs.
783	>	*
784	>	* <p>The arguments to this method provide the state of the phaser
785	>	* prevailing for the current transition.  The effects of invoking
786	>	* arrival, registration, and waiting methods on this Phaser from
787	>	* within {@code onAdvance} are unspecified and should not be
788	>	* relied on.
789	>	*
790	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
791	>	* {@code onAdvance} is invoked only for its root Phaser on each
792	>	* advance.
793	>	*
794	>	* <p>To support the most common use cases, the default
795	>	* implementation of this method returns {@code true} when the
796	>	* number of registered parties has become zero as the result of a
797	>	* party invoking {@code arriveAndDeregister}.  You can disable
798	>	* this behavior, thus enabling continuation upon future
799	>	* registrations, by overriding this method to always return
800	>	* {@code false}:
801	>	*
802	>	* <pre> {@code
803	>	* Phaser phaser = new Phaser() {
804	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
805	>	* }}</pre>
806		*
807		* @param phase the phase number on entering the barrier
808		* @param registeredParties the current number of registered parties
#	Line 733 | Line 822 | public class Phaser {
822		* @return a string identifying this barrier, as well as its state
823		*/
824		public String toString() {
825	<	long s = getReconciledState();
825	>	return stateToString(reconcileState());
826	>	}
827	>
828	>	/**
829	>	* Implementation of toString and string-based error messages
830	>	*/
831	>	private String stateToString(long s) {
832		return super.toString() +
833		"[phase = " + phaseOf(s) +
834		" parties = " + partiesOf(s) +
835		" arrived = " + arrivedOf(s) + "]";
836		}
837
838	<	// methods for waiting
838	>	// Waiting mechanics
839	>
840	>	/**
841	>	* Removes and signals threads from queue for phase.
842	>	*/
843	>	private void releaseWaiters(int phase) {
844	>	AtomicReference<QNode> head = queueFor(phase);
845	>	QNode q;
846	>	int p;
847	>	while ((q = head.get()) != null &&
848	>	((p = q.phase) == phase ||
849	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
850	>	if (head.compareAndSet(q, q.next))
851	>	q.signal();
852	>	}
853	>	}
854	>
855	>	/** The number of CPUs, for spin control */
856	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
857	>
858	>	/**
859	>	* The number of times to spin before blocking while waiting for
860	>	* advance, per arrival while waiting. On multiprocessors, fully
861	>	* blocking and waking up a large number of threads all at once is
862	>	* usually a very slow process, so we use rechargeable spins to
863	>	* avoid it when threads regularly arrive: When a thread in
864	>	* internalAwaitAdvance notices another arrival before blocking,
865	>	* and there appear to be enough CPUs available, it spins
866	>	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
867	>	* uniprocessors, there is at least one intervening Thread.yield
868	>	* before blocking. The value trades off good-citizenship vs big
869	>	* unnecessary slowdowns.
870	>	*/
871	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
872	>
873	>	/**
874	>	* Possibly blocks and waits for phase to advance unless aborted.
875	>	*
876	>	* @param phase current phase
877	>	* @param node if non-null, the wait node to track interrupt and timeout;
878	>	* if null, denotes noninterruptible wait
879	>	* @return current phase
880	>	*/
881	>	private int internalAwaitAdvance(int phase, QNode node) {
882	>	Phaser current = this;       // to eventually wait at root if tiered
883	>	boolean queued = false;      // true when node is enqueued
884	>	int lastUnarrived = -1;      // to increase spins upon change
885	>	int spins = SPINS_PER_ARRIVAL;
886	>	long s;
887	>	int p;
888	>	while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) {
889	>	Phaser par;
890	>	int unarrived = (int)s & UNARRIVED_MASK;
891	>	if (unarrived != lastUnarrived) {
892	>	if (lastUnarrived == -1) // ensure old queue clean
893	>	releaseWaiters(phase-1);
894	>	if ((lastUnarrived = unarrived) < NCPU)
895	>	spins += SPINS_PER_ARRIVAL;
896	>	}
897	>	else if (unarrived == 0 && (par = current.parent) != null) {
898	>	current = par;       // if all arrived, use parent
899	>	par = par.parent;
900	>	lastUnarrived = -1;
901	>	}
902	>	else if (spins > 0) {
903	>	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
904	>	Thread.yield();  // yield midway through spin
905	>	}
906	>	else if (node == null)   // must be noninterruptible
907	>	node = new QNode(this, phase, false, false, 0L);
908	>	else if (node.isReleasable()) {
909	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
910	>	break;
911	>	else
912	>	return phase;    // aborted
913	>	}
914	>	else if (!queued) {      // push onto queue
915	>	AtomicReference<QNode> head = queueFor(phase);
916	>	QNode q = head.get();
917	>	if (q == null || q.phase == phase) {
918	>	node.next = q;
919	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
920	>	break;       // recheck to avoid stale enqueue
921	>	else
922	>	queued = head.compareAndSet(q, node);
923	>	}
924	>	}
925	>	else {
926	>	try {
927	>	ForkJoinPool.managedBlock(node);
928	>	} catch (InterruptedException ie) {
929	>	node.wasInterrupted = true;
930	>	}
931	>	}
932	>	}
933	>	releaseWaiters(phase);
934	>	if (node != null)
935	>	node.onRelease();
936	>	return p;
937	>	}
938
939		/**
940		* Wait nodes for Treiber stack representing wait queue
#	Line 748 | Line 942 | public class Phaser {
942		static final class QNode implements ForkJoinPool.ManagedBlocker {
943		final Phaser phaser;
944		final int phase;
751	–	final long startTime;
752	–	final long nanos;
753	–	final boolean timed;
945		final boolean interruptible;
946	<	volatile boolean wasInterrupted = false;
946	>	final boolean timed;
947	>	boolean wasInterrupted;
948	>	long nanos;
949	>	long lastTime;
950		volatile Thread thread; // nulled to cancel wait
951		QNode next;
952	+
953		QNode(Phaser phaser, int phase, boolean interruptible,
954	<	boolean timed, long startTime, long nanos) {
954	>	boolean timed, long nanos) {
955		this.phaser = phaser;
956		this.phase = phase;
762	–	this.timed = timed;
957		this.interruptible = interruptible;
764	–	this.startTime = startTime;
958		this.nanos = nanos;
959	+	this.timed = timed;
960	+	this.lastTime = timed? System.nanoTime() : 0L;
961		thread = Thread.currentThread();
962		}
963	+
964		public boolean isReleasable() {
965	<	return (thread == null ||
966	<	phaser.getPhase() != phase ||
967	<	(interruptible && wasInterrupted) ||
968	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
965	>	Thread t = thread;
966	>	if (t != null) {
967	>	if (phaser.getPhase() != phase)
968	>	t = null;
969	>	else {
970	>	if (Thread.interrupted())
971	>	wasInterrupted = true;
972	>	if (interruptible && wasInterrupted)
973	>	t = null;
974	>	else if (timed) {
975	>	if (nanos > 0) {
976	>	long now = System.nanoTime();
977	>	nanos -= now - lastTime;
978	>	lastTime = now;
979	>	}
980	>	if (nanos <= 0)
981	>	t = null;
982	>	}
983	>	}
984	>	if (t != null)
985	>	return false;
986	>	thread = null;
987	>	}
988	>	return true;
989		}
990	+
991		public boolean block() {
992	<	if (Thread.interrupted()) {
993	<	wasInterrupted = true;
994	<	if (interruptible)
778	<	return true;
779	<	}
780	<	if (!timed)
992	>	if (isReleasable())
993	>	return true;
994	>	else if (!timed)
995		LockSupport.park(this);
996	<	else {
997	<	long waitTime = nanos - (System.nanoTime() - startTime);
784	<	if (waitTime <= 0)
785	<	return true;
786	<	LockSupport.parkNanos(this, waitTime);
787	<	}
996	>	else if (nanos > 0)
997	>	LockSupport.parkNanos(this, nanos);
998		return isReleasable();
999		}
1000	+
1001		void signal() {
1002		Thread t = thread;
1003		if (t != null) {
#	Line 794 | Line 1005 | public class Phaser {
1005		LockSupport.unpark(t);
1006		}
1007		}
797	–	boolean doWait() {
798	–	if (thread != null) {
799	–	try {
800	–	ForkJoinPool.managedBlock(this, false);
801	–	} catch (InterruptedException ie) {
802	–	}
803	–	}
804	–	return wasInterrupted;
805	–	}
1008
1009	<	}
1010	<
1011	<	/**
1012	<	* Removes and signals waiting threads from wait queue.
1013	<	*/
812	<	private void releaseWaiters(int phase) {
813	<	AtomicReference<QNode> head = queueFor(phase);
814	<	QNode q;
815	<	while ((q = head.get()) != null) {
816	<	if (head.compareAndSet(q, q.next))
817	<	q.signal();
818	<	}
819	<	}
820	<
821	<	/**
822	<	* Tries to enqueue given node in the appropriate wait queue.
823	<	*
824	<	* @return true if successful
825	<	*/
826	<	private boolean tryEnqueue(QNode node) {
827	<	AtomicReference<QNode> head = queueFor(node.phase);
828	<	return head.compareAndSet(node.next = head.get(), node);
829	<	}
830	<
831	<	/**
832	<	* Enqueues node and waits unless aborted or signalled.
833	<	*
834	<	* @return current phase
835	<	*/
836	<	private int untimedWait(int phase) {
837	<	QNode node = null;
838	<	boolean queued = false;
839	<	boolean interrupted = false;
840	<	int p;
841	<	while ((p = getPhase()) == phase) {
842	<	if (Thread.interrupted())
843	<	interrupted = true;
844	<	else if (node == null)
845	<	node = new QNode(this, phase, false, false, 0, 0);
846	<	else if (!queued)
847	<	queued = tryEnqueue(node);
848	<	else
849	<	interrupted = node.doWait();
850	<	}
851	<	if (node != null)
852	<	node.thread = null;
853	<	releaseWaiters(phase);
854	<	if (interrupted)
855	<	Thread.currentThread().interrupt();
856	<	return p;
857	<	}
858	<
859	<	/**
860	<	* Interruptible version
861	<	* @return current phase
862	<	*/
863	<	private int interruptibleWait(int phase) throws InterruptedException {
864	<	QNode node = null;
865	<	boolean queued = false;
866	<	boolean interrupted = false;
867	<	int p;
868	<	while ((p = getPhase()) == phase && !interrupted) {
869	<	if (Thread.interrupted())
870	<	interrupted = true;
871	<	else if (node == null)
872	<	node = new QNode(this, phase, true, false, 0, 0);
873	<	else if (!queued)
874	<	queued = tryEnqueue(node);
875	<	else
876	<	interrupted = node.doWait();
1009	>	void onRelease() { // actions upon return from internalAwaitAdvance
1010	>	if (!interruptible && wasInterrupted)
1011	>	Thread.currentThread().interrupt();
1012	>	if (thread != null)
1013	>	thread = null;
1014		}
878	–	if (node != null)
879	–	node.thread = null;
880	–	if (p != phase || (p = getPhase()) != phase)
881	–	releaseWaiters(phase);
882	–	if (interrupted)
883	–	throw new InterruptedException();
884	–	return p;
885	–	}
1015
887	–	/**
888	–	* Timeout version.
889	–	* @return current phase
890	–	*/
891	–	private int timedWait(int phase, long nanos)
892	–	throws InterruptedException, TimeoutException {
893	–	long startTime = System.nanoTime();
894	–	QNode node = null;
895	–	boolean queued = false;
896	–	boolean interrupted = false;
897	–	int p;
898	–	while ((p = getPhase()) == phase && !interrupted) {
899	–	if (Thread.interrupted())
900	–	interrupted = true;
901	–	else if (nanos - (System.nanoTime() - startTime) <= 0)
902	–	break;
903	–	else if (node == null)
904	–	node = new QNode(this, phase, true, true, startTime, nanos);
905	–	else if (!queued)
906	–	queued = tryEnqueue(node);
907	–	else
908	–	interrupted = node.doWait();
909	–	}
910	–	if (node != null)
911	–	node.thread = null;
912	–	if (p != phase || (p = getPhase()) != phase)
913	–	releaseWaiters(phase);
914	–	if (interrupted)
915	–	throw new InterruptedException();
916	–	if (p == phase)
917	–	throw new TimeoutException();
918	–	return p;
1016		}
1017
1018		// Unsafe mechanics
#	Line 924 | Line 1021 | public class Phaser {
1021		private static final long stateOffset =
1022		objectFieldOffset("state", Phaser.class);
1023
927	–	private final boolean casState(long cmp, long val) {
928	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
929	–	}
930	–
1024		private static long objectFieldOffset(String field, Class<?> klazz) {
1025		try {
1026		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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