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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.32 by jsr166, Wed Aug 19 17:44:45 2009 UTC vs.
Revision 1.58 by dl, Wed Nov 24 15:48:01 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
60	<	* actions immediately return without updating phaser state or waiting
61	<	* 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}.  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> Phasers may be tiered to reduce contention. Phasers with large
90	<	* numbers of parties that would otherwise experience heavy
91	<	* synchronization contention costs may instead be arranged in trees.
92	<	* This will typically greatly increase throughput even though it
93	<	* incurs somewhat greater per-operation overhead.
94	<	*
95	<	* <li> By default, {@code awaitAdvance} continues to wait even if
96	<	* the waiting thread is interrupted. And unlike the case in
97	<	* {@code CyclicBarrier}, exceptions encountered while tasks wait
98	<	* interruptibly or with timeout do not change the state of the
99	<	* barrier. If necessary, you can perform any associated recovery
100	<	* within handlers of those exceptions, often after invoking
101	<	* {@code forceTermination}.
102	<	*
103	<	* <li>Phasers may be used to coordinate tasks executing in a {@link
104	<	* ForkJoinPool}, which will ensure sufficient parallelism to execute
105	<	* tasks when others are blocked waiting for a phase to advance.
106	<	*
107	<	* </ul>
89	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
90	>	* constructed in tree structures) to reduce contention. Phasers with
91	>	* large 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	>	* <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 usages:</b>
110		*
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
113	<	* parties. The typical idiom is for the method setting this up to
114	<	* first register, then start the actions, then deregister, as in:
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		*  <pre> {@code
117	<	* void runTasks(List<Runnable> list) {
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 r : list) {
120	>	*   for (Runnable task : tasks) {
121		*     phaser.register();
122		*     new Thread() {
123		*       public void run() {
124		*         phaser.arriveAndAwaitAdvance(); // await all creation
125	<	*         r.run();
125	>	*         task.run();
126		*       }
127		*     }.start();
128		*   }
#	Line 116 | Line 135 | import java.util.concurrent.locks.LockSu
135		* for a given number of iterations is to override {@code onAdvance}:
136		*
137		*  <pre> {@code
138	<	* void startTasks(List<Runnable> list, final int iterations) {
138	>	* void startTasks(List<Runnable> tasks, final int iterations) {
139		*   final Phaser phaser = new Phaser() {
140	<	*     public boolean onAdvance(int phase, int registeredParties) {
140	>	*     protected boolean onAdvance(int phase, int registeredParties) {
141		*       return phase >= iterations || registeredParties == 0;
142		*     }
143		*   };
144		*   phaser.register();
145	<	*   for (Runnable r : list) {
145	>	*   for (final Runnable task : tasks) {
146		*     phaser.register();
147		*     new Thread() {
148		*       public void run() {
149		*         do {
150	<	*           r.run();
150	>	*           task.run();
151		*           phaser.arriveAndAwaitAdvance();
152	<	*         } while(!phaser.isTerminated();
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 for upon construction:
187	>	* it registers with upon construction:
188	>	*
189		*  <pre> {@code
190	<	* void build(Task[] actions, int lo, int hi, Phaser b) {
191	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
192	<	*   if (step > 1) {
193	<	*     int i = lo;
194	<	*     while (i < hi) {
150	<	*       int r = Math.min(i + step, hi);
151	<	*       build(actions, i, r, new Phaser(b));
152	<	*       i = r;
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(b);
199	<	*       // assumes new Task(b) performs b.register()
198	>	*       actions[i] = new Task(ph);
199	>	*       // assumes new Task(ph) performs ph.register()
200		*   }
201		* }
202		* // .. initially called, for n tasks via
#	Line 165 | Line 207 | import java.util.concurrent.locks.LockSu
207		* be appropriate for extremely small per-barrier task bodies (thus
208		* high rates), or up to hundreds for extremely large ones.
209		*
168	–	* </pre>
169	–	*
210		* <p><b>Implementation notes</b>: This implementation restricts the
211		* maximum number of parties to 65535. Attempts to register additional
212		* parties result in {@code IllegalStateException}. However, you can and
#	Line 187 | Line 227 | public class Phaser {
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)
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 (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.
200	–	*
201	–	* Note: there are some cheats in arrive() that rely on unarrived
202	–	* count being lowest 16 bits.
240		*/
241		private volatile long state;
242
243	<	private static final int ushortBits = 16;
244	<	private static final int ushortMask = 0xffff;
245	<	private static final int phaseMask  = 0x7fffffff;
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 long PARTIES_MASK   = 0xffff0000L; // for masking long
249	>	private static final long ONE_ARRIVAL    = 1L;
250	>	private static final long ONE_PARTY      = 1L << PARTIES_SHIFT;
251	>	private static final long TERMINATION_PHASE  = -1L << PHASE_SHIFT;
252	>
253	>	// The following unpacking methods are usually manually inlined
254
255		private static int unarrivedOf(long s) {
256	<	return (int) (s & ushortMask);
256	>	return (int)s & UNARRIVED_MASK;
257		}
258
259		private static int partiesOf(long s) {
260	<	return ((int) s) >>> 16;
260	>	return (int)s >>> PARTIES_SHIFT;
261		}
262
263		private static int phaseOf(long s) {
264	<	return (int) (s >>> 32);
264	>	return (int) (s >>> PHASE_SHIFT);
265		}
266
267		private static int arrivedOf(long s) {
268		return partiesOf(s) - unarrivedOf(s);
269		}
270
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	–
271		/**
272		* The parent of this phaser, or null if none
273		*/
#	Line 252 | Line 279 | public class Phaser {
279		*/
280		private final Phaser root;
281
255	–	// Wait queues
256	–
282		/**
283		* Heads of Treiber stacks for waiting threads. To eliminate
284	<	* contention while releasing some threads while adding others, we
284	>	* contention when releasing some threads while adding others, we
285		* use two of them, alternating across even and odd phases.
286	+	* Subphasers share queues with root to speed up releases.
287		*/
288	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
289	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
288	>	private final AtomicReference<QNode> evenQ;
289	>	private final AtomicReference<QNode> oddQ;
290
291		private AtomicReference<QNode> queueFor(int phase) {
292		return ((phase & 1) == 0) ? evenQ : oddQ;
293		}
294
295		/**
296	<	* Returns current state, first resolving lagged propagation from
297	<	* root if necessary.
296	>	* Main implementation for methods arrive and arriveAndDeregister.
297	>	* Manually tuned to speed up and minimize race windows for the
298	>	* common case of just decrementing unarrived field.
299	>	*
300	>	* @param adj - adjustment to apply to state -- either
301	>	* ONE_ARRIVAL (for arrive) or
302	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
303	>	*/
304	>	private int doArrive(long adj) {
305	>	for (;;) {
306	>	long s = state;
307	>	int phase = (int)(s >>> PHASE_SHIFT);
308	>	if (phase < 0)
309	>	return phase;
310	>	int unarrived = (int)s & UNARRIVED_MASK;
311	>	if (unarrived == 0)
312	>	checkBadArrive(s);
313	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
314	>	if (unarrived == 1) {
315	>	long p = s & PARTIES_MASK; // unshifted parties field
316	>	long lu = p >>> PARTIES_SHIFT;
317	>	int u = (int)lu;
318	>	int nextPhase = (phase + 1) & MAX_PHASE;
319	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
320	>	final Phaser parent = this.parent;
321	>	if (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	>	parent.doArrive((u == 0) ?
329	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
330	>	if ((int)(parent.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	>	* 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	>	* @param registrations number to add to both parties and
357	>	* unarrived fields. Must be greater than zero.
358	>	*/
359	>	private int doRegister(int registrations) {
360	>	// adjustment to state
361	>	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
362	>	final Phaser parent = this.parent;
363	>	for (;;) {
364	>	long s = (parent == null) ? state : reconcileState();
365	>	int parties = (int)s >>> PARTIES_SHIFT;
366	>	int phase = (int)(s >>> PHASE_SHIFT);
367	>	if (phase < 0)
368	>	return phase;
369	>	else if (parties != 0 && ((int)s & UNARRIVED_MASK) == 0)
370	>	internalAwaitAdvance(phase, null); // wait for onAdvance
371	>	else if (registrations > MAX_PARTIES - parties)
372	>	throw new IllegalStateException(badRegister(s));
373	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
374	>	return phase;
375	>	}
376	>	}
377	>
378	>	/**
379	>	* Returns message string for out of bounds exceptions on registration.
380		*/
381	<	private long getReconciledState() {
382	<	return (parent == null) ? state : reconcileState();
381	>	private String badRegister(long s) {
382	>	return "Attempt to register more than " +
383	>	MAX_PARTIES + " parties for " + stateToString(s);
384		}
385
386		/**
387	<	* Recursively resolves state.
387	>	* Recursively resolves lagged phase propagation from root if necessary.
388		*/
389		private long reconcileState() {
390	<	Phaser p = parent;
390	>	Phaser par = parent;
391		long s = state;
392	<	if (p != null) {
393	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
394	<	long parentState = p.getReconciledState();
395	<	int parentPhase = phaseOf(parentState);
396	<	int phase = phaseOf(s = state);
397	<	if (phase != parentPhase) {
398	<	long next = trippedStateFor(parentPhase, partiesOf(s));
399	<	if (casState(s, next)) {
400	<	releaseWaiters(phase);
401	<	s = next;
402	<	}
392	>	if (par != null) {
393	>	Phaser rt = root;
394	>	int phase, rPhase;
395	>	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
396	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
397	>	if ((int)(par.state >>> PHASE_SHIFT) != rPhase)
398	>	par.reconcileState();
399	>	else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
400	>	long u = s & PARTIES_MASK; // reset unarrived to parties
401	>	long next = ((((long) rPhase) << PHASE_SHIFT) | u |
402	>	(u >>> PARTIES_SHIFT));
403	>	if (state == s &&
404	>	UNSAFE.compareAndSwapLong(this, stateOffset,
405	>	s, s = next))
406	>	break;
407		}
408	+	s = state;
409		}
410		}
411		return s;
#	Line 303 | Line 417 | public class Phaser {
417		* phaser will need to first register for it.
418		*/
419		public Phaser() {
420	<	this(null);
420	>	this(null, 0);
421		}
422
423		/**
424	<	* Creates a new phaser with the given numbers of registered
424	>	* Creates a new phaser with the given number of registered
425		* unarrived parties, initial phase number 0, and no parent.
426		*
427		* @param parties the number of parties required to trip barrier
#	Line 319 | Line 433 | public class Phaser {
433		}
434
435		/**
436	<	* Creates a new phaser with the given parent, without any
323	<	* initially registered parties. If parent is non-null this phaser
324	<	* is registered with the parent and its initial phase number is
325	<	* the same as that of parent phaser.
436	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
437		*
438		* @param parent the parent phaser
439		*/
440		public Phaser(Phaser parent) {
441	<	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);
441	>	this(parent, 0);
442		}
443
444		/**
445	<	* Creates a new phaser with the given parent and numbers of
446	<	* registered unarrived parties. If parent is non-null, this phaser
447	<	* is registered with the parent and its initial phase number is
448	<	* the same as that of parent phaser.
445	>	* Creates a new phaser with the given parent and number of
446	>	* registered unarrived parties. If parent is non-null, this
447	>	* phaser is registered with the parent and its initial phase
448	>	* number is the same as that of parent phaser.  If the number of
449	>	* parties is zero, the parent phaser will not proceed until this
450	>	* child phaser registers parties and advances, or this child
451	>	* phaser deregisters with its parent, or the parent is otherwise
452	>	* terminated.  This child Phaser will be deregistered from its
453	>	* parent automatically upon any invocation of the child's {@link
454	>	* #arriveAndDeregister} method that results in the child's number
455	>	* of registered parties becoming zero. (Although rarely
456	>	* appropriate, this child may also explicity deregister from its
457	>	* parent using {@code getParent().arriveAndDeregister()}.)  After
458	>	* deregistration, the child cannot re-register. (Instead, you can
459	>	* create a new child Phaser.)
460		*
461		* @param parent the parent phaser
462		* @param parties the number of parties required to trip barrier
#	Line 350 | Line 464 | public class Phaser {
464		* or greater than the maximum number of parties supported
465		*/
466		public Phaser(Phaser parent, int parties) {
467	<	if (parties < 0 || parties > ushortMask)
467	>	if (parties >>> PARTIES_SHIFT != 0)
468		throw new IllegalArgumentException("Illegal number of parties");
469	<	int phase = 0;
469	>	int phase;
470		this.parent = parent;
471		if (parent != null) {
472	<	this.root = parent.root;
473	<	phase = parent.register();
472	>	Phaser r = parent.root;
473	>	this.root = r;
474	>	this.evenQ = r.evenQ;
475	>	this.oddQ = r.oddQ;
476	>	phase = parent.doRegister(1);
477		}
478	<	else
478	>	else {
479		this.root = this;
480	<	this.state = trippedStateFor(phase, parties);
480	>	this.evenQ = new AtomicReference<QNode>();
481	>	this.oddQ = new AtomicReference<QNode>();
482	>	phase = 0;
483	>	}
484	>	long p = (long)parties;
485	>	this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
486		}
487
488		/**
489		* Adds a new unarrived party to this phaser.
490	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
491	+	* this method may wait until its completion before registering.
492		*
493	<	* @return the current barrier phase number upon registration
493	>	* @return the arrival phase number to which this registration applied
494		* @throws IllegalStateException if attempting to register more
495		* than the maximum supported number of parties
496		*/
#	Line 376 | Line 500 | public class Phaser {
500
501		/**
502		* Adds the given number of new unarrived parties to this phaser.
503	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
504	+	* this method may wait until its completion before registering.
505		*
506	<	* @param parties the number of parties required to trip barrier
507	<	* @return the current barrier phase number upon registration
506	>	* @param parties the number of additional parties required to trip barrier
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	+	* @throws IllegalArgumentException if {@code parties < 0}
511		*/
512		public int bulkRegister(int parties) {
513		if (parties < 0)
#	Line 391 | Line 518 | public class Phaser {
518		}
519
520		/**
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	–	/**
521		* Arrives at the barrier, but does not wait for others.  (You can
522	<	* in turn wait for others via {@link #awaitAdvance}).
522	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
523	>	* unenforced usage error for an unregistered party to invoke this
524	>	* method.
525		*
526	<	* @return the barrier phase number upon entry to this method, or a
419	<	* negative value if terminated
526	>	* @return the arrival phase number, or a negative value if terminated
527		* @throws IllegalStateException if not terminated and the number
528		* of unarrived parties would become negative
529		*/
530		public int arrive() {
531	<	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;
531	>	return doArrive(ONE_ARRIVAL);
532		}
533
534		/**
#	Line 466 | Line 537 | public class Phaser {
537		* required to trip the barrier in future phases.  If this phaser
538		* has a parent, and deregistration causes this phaser to have
539		* zero parties, this phaser also arrives at and is deregistered
540	<	* from its parent.
540	>	* from its parent.  It is an unenforced usage error for an
541	>	* unregistered party to invoke this method.
542		*
543	<	* @return the current barrier phase number upon entry to
472	<	* this method, or a negative value if terminated
543	>	* @return the arrival phase number, or a negative value if terminated
544		* @throws IllegalStateException if not terminated and the number
545		* of registered or unarrived parties would become negative
546		*/
547		public int arriveAndDeregister() {
548	<	// 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;
548	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
549		}
550
551		/**
552		* Arrives at the barrier and awaits others. Equivalent in effect
553		* to {@code awaitAdvance(arrive())}.  If you need to await with
554		* interruption or timeout, you can arrange this with an analogous
555	<	* construction using one of the other forms of the awaitAdvance
556	<	* method.  If instead you need to deregister upon arrival use
557	<	* {@code arriveAndDeregister}.
555	>	* construction using one of the other forms of the {@code
556	>	* awaitAdvance} method.  If instead you need to deregister upon
557	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
558	>	* usage error for an unregistered party to invoke this method.
559		*
560	<	* @return the phase on entry to this method
560	>	* @return the arrival phase number, or a negative number if terminated
561		* @throws IllegalStateException if not terminated and the number
562		* of unarrived parties would become negative
563		*/
#	Line 539 | Line 571 | public class Phaser {
571		* barrier is not equal to the given phase value or this barrier
572		* is terminated.
573		*
574	<	* @param phase the phase on entry to this method
575	<	* @return the phase on exit from this method
574	>	* @param phase an arrival phase number, or negative value if
575	>	* terminated; this argument is normally the value returned by a
576	>	* previous call to {@code arrive} or its variants
577	>	* @return the next arrival phase number, or a negative value
578	>	* if terminated or argument is negative
579		*/
580		public int awaitAdvance(int phase) {
581		if (phase < 0)
582		return phase;
583	<	long s = getReconciledState();
584	<	int p = phaseOf(s);
585	<	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);
583	>	long s = (parent == null) ? state : reconcileState();
584	>	int p = (int)(s >>> PHASE_SHIFT);
585	>	return (p != phase) ? p : internalAwaitAdvance(phase, null);
586		}
587
588		/**
589		* Awaits the phase of the barrier to advance from the given phase
590	<	* value, throwing {@code InterruptedException} if interrupted while
591	<	* waiting, or returning immediately if the current phase of the
592	<	* barrier is not equal to the given phase value or this barrier
593	<	* is terminated.
594	<	*
595	<	* @param phase the phase on entry to this method
596	<	* @return the phase on exit from this method
590	>	* value, throwing {@code InterruptedException} if interrupted
591	>	* while waiting, or returning immediately if the current phase of
592	>	* the barrier is not equal to the given phase value or this
593	>	* barrier is terminated.
594	>	*
595	>	* @param phase an arrival phase number, or negative value if
596	>	* terminated; this argument is normally the value returned by a
597	>	* previous call to {@code arrive} or its variants
598	>	* @return the next arrival phase number, or a negative value
599	>	* if terminated or argument is negative
600		* @throws InterruptedException if thread interrupted while waiting
601		*/
602		public int awaitAdvanceInterruptibly(int phase)
603		throws InterruptedException {
604		if (phase < 0)
605		return phase;
606	<	long s = getReconciledState();
607	<	int p = phaseOf(s);
608	<	if (p != phase)
609	<	return p;
610	<	if (unarrivedOf(s) == 0 && parent != null)
611	<	parent.awaitAdvanceInterruptibly(phase);
612	<	return interruptibleWait(phase);
606	>	long s = (parent == null) ? state : reconcileState();
607	>	int p = (int)(s >>> PHASE_SHIFT);
608	>	if (p == phase) {
609	>	QNode node = new QNode(this, phase, true, false, 0L);
610	>	p = internalAwaitAdvance(phase, node);
611	>	if (node.wasInterrupted)
612	>	throw new InterruptedException();
613	>	}
614	>	return p;
615		}
616
617		/**
618		* Awaits the phase of the barrier to advance from the given phase
619	<	* value or the given timeout to elapse, throwing
620	<	* {@code InterruptedException} if interrupted while waiting, or
621	<	* returning immediately if the current phase of the barrier is not
622	<	* equal to the given phase value or this barrier is terminated.
623	<	*
624	<	* @param phase the phase on entry to this method
619	>	* value or the given timeout to elapse, throwing {@code
620	>	* InterruptedException} if interrupted while waiting, or
621	>	* returning immediately if the current phase of the barrier is
622	>	* not equal to the given phase value or this barrier is
623	>	* terminated.
624	>	*
625	>	* @param phase an arrival phase number, or negative value if
626	>	* terminated; this argument is normally the value returned by a
627	>	* previous call to {@code arrive} or its variants
628		* @param timeout how long to wait before giving up, in units of
629		*        {@code unit}
630		* @param unit a {@code TimeUnit} determining how to interpret the
631		*        {@code timeout} parameter
632	<	* @return the phase on exit from this method
632	>	* @return the next arrival phase number, or a negative value
633	>	* if terminated or argument is negative
634		* @throws InterruptedException if thread interrupted while waiting
635		* @throws TimeoutException if timed out while waiting
636		*/
#	Line 600 | Line 639 | public class Phaser {
639		throws InterruptedException, TimeoutException {
640		if (phase < 0)
641		return phase;
642	<	long s = getReconciledState();
643	<	int p = phaseOf(s);
644	<	if (p != phase)
645	<	return p;
646	<	if (unarrivedOf(s) == 0 && parent != null)
647	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
648	<	return timedWait(phase, unit.toNanos(timeout));
642	>	long s = (parent == null) ? state : reconcileState();
643	>	int p = (int)(s >>> PHASE_SHIFT);
644	>	if (p == phase) {
645	>	long nanos = unit.toNanos(timeout);
646	>	QNode node = new QNode(this, phase, true, true, nanos);
647	>	p = internalAwaitAdvance(phase, node);
648	>	if (node.wasInterrupted)
649	>	throw new InterruptedException();
650	>	else if (p == phase)
651	>	throw new TimeoutException();
652	>	}
653	>	return p;
654		}
655
656		/**
657	<	* Forces this barrier to enter termination state. Counts of
658	<	* arrived and registered parties are unaffected. If this phaser
659	<	* has a parent, it too is terminated. This method may be useful
660	<	* for coordinating recovery after one or more tasks encounter
661	<	* unexpected exceptions.
657	>	* Forces this barrier to enter termination state.  Counts of
658	>	* arrived and registered parties are unaffected.  If this phaser
659	>	* is a member of a tiered set of phasers, then all of the phasers
660	>	* in the set are terminated.  If this phaser is already
661	>	* terminated, this method has no effect.  This method may be
662	>	* useful for coordinating recovery after one or more tasks
663	>	* encounter unexpected exceptions.
664		*/
665		public void forceTermination() {
666	<	for (;;) {
667	<	long s = getReconciledState();
668	<	int phase = phaseOf(s);
669	<	int parties = partiesOf(s);
670	<	int unarrived = unarrivedOf(s);
671	<	if (phase < 0 ||
672	<	casState(s, stateFor(-1, parties, unarrived))) {
627	<	releaseWaiters(0);
666	>	// Only need to change root state
667	>	final Phaser root = this.root;
668	>	long s;
669	>	while ((s = root.state) >= 0) {
670	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
671	>	s, s | TERMINATION_PHASE)) {
672	>	releaseWaiters(0); // signal all threads
673		releaseWaiters(1);
629	–	if (parent != null)
630	–	parent.forceTermination();
674		return;
675		}
676		}
#	Line 641 | Line 684 | public class Phaser {
684		* @return the phase number, or a negative value if terminated
685		*/
686		public final int getPhase() {
687	<	return phaseOf(getReconciledState());
687	>	return (int)(root.state >>> PHASE_SHIFT);
688		}
689
690		/**
#	Line 654 | Line 697 | public class Phaser {
697		}
698
699		/**
700	<	* Returns the number of parties that have arrived at the current
701	<	* phase of this barrier.
700	>	* Returns the number of registered parties that have arrived at
701	>	* the current phase of this barrier.
702		*
703		* @return the number of arrived parties
704		*/
705		public int getArrivedParties() {
706	<	return arrivedOf(state);
706	>	return arrivedOf(parent==null? state : reconcileState());
707		}
708
709		/**
#	Line 670 | Line 713 | public class Phaser {
713		* @return the number of unarrived parties
714		*/
715		public int getUnarrivedParties() {
716	<	return unarrivedOf(state);
716	>	return unarrivedOf(parent==null? state : reconcileState());
717		}
718
719		/**
#	Line 698 | Line 741 | public class Phaser {
741		* @return {@code true} if this barrier has been terminated
742		*/
743		public boolean isTerminated() {
744	<	return getPhase() < 0;
744	>	return root.state < 0L;
745		}
746
747		/**
748	<	* Overridable method to perform an action upon phase advance, and
749	<	* to control termination. This method is invoked whenever the
750	<	* barrier is tripped (and thus all other waiting parties are
751	<	* dormant). If it returns {@code true}, then, rather than advance
752	<	* the phase number, this barrier will be set to a final
753	<	* termination state, and subsequent calls to {@link #isTerminated}
754	<	* will return true.
748	>	* Overridable method to perform an action upon impending phase
749	>	* advance, and to control termination. This method is invoked
750	>	* upon arrival of the party tripping the barrier (when all other
751	>	* waiting parties are dormant).  If this method returns {@code
752	>	* true}, then, rather than advance the phase number, this barrier
753	>	* will be set to a final termination state, and subsequent calls
754	>	* to {@link #isTerminated} will return true. Any (unchecked)
755	>	* Exception or Error thrown by an invocation of this method is
756	>	* propagated to the party attempting to trip the barrier, in
757	>	* which case no advance occurs.
758	>	*
759	>	* <p>The arguments to this method provide the state of the phaser
760	>	* prevailing for the current transition.  The effects of invoking
761	>	* arrival, registration, and waiting methods on this Phaser from
762	>	* within {@code onAdvance} are unspecified and should not be
763	>	* relied on.
764	>	*
765	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
766	>	* {@code onAdvance} is invoked only for its root Phaser on each
767	>	* advance.
768		*
769		* <p>The default version returns {@code true} when the number of
770		* registered parties is zero. Normally, overrides that arrange
771		* termination for other reasons should also preserve this
772		* property.
773		*
718	–	* <p>You may override this method to perform an action with side
719	–	* effects visible to participating tasks, but it is in general
720	–	* only sensible to do so in designs where all parties register
721	–	* before any arrive, and all {@link #awaitAdvance} at each phase.
722	–	* Otherwise, you cannot ensure lack of interference from other
723	–	* parties during the invocation of this method.
724	–	*
774		* @param phase the phase number on entering the barrier
775		* @param registeredParties the current number of registered parties
776		* @return {@code true} if this barrier should terminate
#	Line 740 | Line 789 | public class Phaser {
789		* @return a string identifying this barrier, as well as its state
790		*/
791		public String toString() {
792	<	long s = getReconciledState();
792	>	return stateToString(reconcileState());
793	>	}
794	>
795	>	/**
796	>	* Implementation of toString and string-based error messages
797	>	*/
798	>	private String stateToString(long s) {
799		return super.toString() +
800		"[phase = " + phaseOf(s) +
801		" parties = " + partiesOf(s) +
802		" arrived = " + arrivedOf(s) + "]";
803		}
804
805	<	// methods for waiting
805	>	// Waiting mechanics
806	>
807	>	/**
808	>	* Removes and signals threads from queue for phase.
809	>	*/
810	>	private void releaseWaiters(int phase) {
811	>	AtomicReference<QNode> head = queueFor(phase);
812	>	QNode q;
813	>	int p;
814	>	while ((q = head.get()) != null &&
815	>	((p = q.phase) == phase ||
816	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
817	>	if (head.compareAndSet(q, q.next))
818	>	q.signal();
819	>	}
820	>	}
821	>
822	>	/** The number of CPUs, for spin control */
823	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
824	>
825	>	/**
826	>	* The number of times to spin before blocking while waiting for
827	>	* advance, per arrival while waiting. On multiprocessors, fully
828	>	* blocking and waking up a large number of threads all at once is
829	>	* usually a very slow process, so we use rechargeable spins to
830	>	* avoid it when threads regularly arrive: When a thread in
831	>	* internalAwaitAdvance notices another arrival before blocking,
832	>	* and there appear to be enough CPUs available, it spins
833	>	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
834	>	* uniprocessors, there is at least one intervening Thread.yield
835	>	* before blocking. The value trades off good-citizenship vs big
836	>	* unnecessary slowdowns.
837	>	*/
838	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
839	>
840	>	/**
841	>	* Possibly blocks and waits for phase to advance unless aborted.
842	>	*
843	>	* @param phase current phase
844	>	* @param node if non-null, the wait node to track interrupt and timeout;
845	>	* if null, denotes noninterruptible wait
846	>	* @return current phase
847	>	*/
848	>	private int internalAwaitAdvance(int phase, QNode node) {
849	>	Phaser current = this;       // to eventually wait at root if tiered
850	>	boolean queued = false;      // true when node is enqueued
851	>	int lastUnarrived = -1;      // to increase spins upon change
852	>	int spins = SPINS_PER_ARRIVAL;
853	>	long s;
854	>	int p;
855	>	while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) {
856	>	Phaser par;
857	>	int unarrived = (int)s & UNARRIVED_MASK;
858	>	if (unarrived != lastUnarrived) {
859	>	if (lastUnarrived == -1) // ensure old queue clean
860	>	releaseWaiters(phase-1);
861	>	if ((lastUnarrived = unarrived) < NCPU)
862	>	spins += SPINS_PER_ARRIVAL;
863	>	}
864	>	else if (unarrived == 0 && (par = current.parent) != null) {
865	>	current = par;       // if all arrived, use parent
866	>	par = par.parent;
867	>	lastUnarrived = -1;
868	>	}
869	>	else if (spins > 0) {
870	>	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
871	>	Thread.yield();  // yield midway through spin
872	>	}
873	>	else if (node == null)   // must be noninterruptible
874	>	node = new QNode(this, phase, false, false, 0L);
875	>	else if (node.isReleasable()) {
876	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
877	>	break;
878	>	else
879	>	return phase;    // aborted
880	>	}
881	>	else if (!queued) {      // push onto queue
882	>	AtomicReference<QNode> head = queueFor(phase);
883	>	QNode q = head.get();
884	>	if (q == null || q.phase == phase) {
885	>	node.next = q;
886	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
887	>	break;       // recheck to avoid stale enqueue
888	>	else
889	>	queued = head.compareAndSet(q, node);
890	>	}
891	>	}
892	>	else {
893	>	try {
894	>	ForkJoinPool.managedBlock(node);
895	>	} catch (InterruptedException ie) {
896	>	node.wasInterrupted = true;
897	>	}
898	>	}
899	>	}
900	>	releaseWaiters(phase);
901	>	if (node != null)
902	>	node.onRelease();
903	>	return p;
904	>	}
905
906		/**
907		* Wait nodes for Treiber stack representing wait queue
#	Line 755 | Line 909 | public class Phaser {
909		static final class QNode implements ForkJoinPool.ManagedBlocker {
910		final Phaser phaser;
911		final int phase;
758	–	final long startTime;
759	–	final long nanos;
760	–	final boolean timed;
912		final boolean interruptible;
913	<	volatile boolean wasInterrupted = false;
913	>	final boolean timed;
914	>	boolean wasInterrupted;
915	>	long nanos;
916	>	long lastTime;
917		volatile Thread thread; // nulled to cancel wait
918		QNode next;
919	+
920		QNode(Phaser phaser, int phase, boolean interruptible,
921	<	boolean timed, long startTime, long nanos) {
921	>	boolean timed, long nanos) {
922		this.phaser = phaser;
923		this.phase = phase;
769	–	this.timed = timed;
924		this.interruptible = interruptible;
771	–	this.startTime = startTime;
925		this.nanos = nanos;
926	+	this.timed = timed;
927	+	this.lastTime = timed? System.nanoTime() : 0L;
928		thread = Thread.currentThread();
929		}
930	+
931		public boolean isReleasable() {
932	<	return (thread == null ||
933	<	phaser.getPhase() != phase ||
934	<	(interruptible && wasInterrupted) ||
935	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
932	>	Thread t = thread;
933	>	if (t != null) {
934	>	if (phaser.getPhase() != phase)
935	>	t = null;
936	>	else {
937	>	if (Thread.interrupted())
938	>	wasInterrupted = true;
939	>	if (interruptible && wasInterrupted)
940	>	t = null;
941	>	else if (timed) {
942	>	if (nanos > 0) {
943	>	long now = System.nanoTime();
944	>	nanos -= now - lastTime;
945	>	lastTime = now;
946	>	}
947	>	if (nanos <= 0)
948	>	t = null;
949	>	}
950	>	}
951	>	if (t != null)
952	>	return false;
953	>	thread = null;
954	>	}
955	>	return true;
956		}
957	+
958		public boolean block() {
959	<	if (Thread.interrupted()) {
960	<	wasInterrupted = true;
961	<	if (interruptible)
785	<	return true;
786	<	}
787	<	if (!timed)
959	>	if (isReleasable())
960	>	return true;
961	>	else if (!timed)
962		LockSupport.park(this);
963	<	else {
964	<	long waitTime = nanos - (System.nanoTime() - startTime);
791	<	if (waitTime <= 0)
792	<	return true;
793	<	LockSupport.parkNanos(this, waitTime);
794	<	}
963	>	else if (nanos > 0)
964	>	LockSupport.parkNanos(this, nanos);
965		return isReleasable();
966		}
967	+
968		void signal() {
969		Thread t = thread;
970		if (t != null) {
#	Line 801 | Line 972 | public class Phaser {
972		LockSupport.unpark(t);
973		}
974		}
804	–	boolean doWait() {
805	–	if (thread != null) {
806	–	try {
807	–	ForkJoinPool.managedBlock(this, false);
808	–	} catch (InterruptedException ie) {
809	–	}
810	–	}
811	–	return wasInterrupted;
812	–	}
813	–
814	–	}
815	–
816	–	/**
817	–	* Removes and signals waiting threads from wait queue.
818	–	*/
819	–	private void releaseWaiters(int phase) {
820	–	AtomicReference<QNode> head = queueFor(phase);
821	–	QNode q;
822	–	while ((q = head.get()) != null) {
823	–	if (head.compareAndSet(q, q.next))
824	–	q.signal();
825	–	}
826	–	}
827	–
828	–	/**
829	–	* Tries to enqueue given node in the appropriate wait queue.
830	–	*
831	–	* @return true if successful
832	–	*/
833	–	private boolean tryEnqueue(QNode node) {
834	–	AtomicReference<QNode> head = queueFor(node.phase);
835	–	return head.compareAndSet(node.next = head.get(), node);
836	–	}
837	–
838	–	/**
839	–	* Enqueues node and waits unless aborted or signalled.
840	–	*
841	–	* @return current phase
842	–	*/
843	–	private int untimedWait(int phase) {
844	–	QNode node = null;
845	–	boolean queued = false;
846	–	boolean interrupted = false;
847	–	int p;
848	–	while ((p = getPhase()) == phase) {
849	–	if (Thread.interrupted())
850	–	interrupted = true;
851	–	else if (node == null)
852	–	node = new QNode(this, phase, false, false, 0, 0);
853	–	else if (!queued)
854	–	queued = tryEnqueue(node);
855	–	else
856	–	interrupted = node.doWait();
857	–	}
858	–	if (node != null)
859	–	node.thread = null;
860	–	releaseWaiters(phase);
861	–	if (interrupted)
862	–	Thread.currentThread().interrupt();
863	–	return p;
864	–	}
975
976	<	/**
977	<	* Interruptible version
978	<	* @return current phase
979	<	*/
980	<	private int interruptibleWait(int phase) throws InterruptedException {
871	<	QNode node = null;
872	<	boolean queued = false;
873	<	boolean interrupted = false;
874	<	int p;
875	<	while ((p = getPhase()) == phase && !interrupted) {
876	<	if (Thread.interrupted())
877	<	interrupted = true;
878	<	else if (node == null)
879	<	node = new QNode(this, phase, true, false, 0, 0);
880	<	else if (!queued)
881	<	queued = tryEnqueue(node);
882	<	else
883	<	interrupted = node.doWait();
976	>	void onRelease() { // actions upon return from internalAwaitAdvance
977	>	if (!interruptible && wasInterrupted)
978	>	Thread.currentThread().interrupt();
979	>	if (thread != null)
980	>	thread = null;
981		}
885	–	if (node != null)
886	–	node.thread = null;
887	–	if (p != phase || (p = getPhase()) != phase)
888	–	releaseWaiters(phase);
889	–	if (interrupted)
890	–	throw new InterruptedException();
891	–	return p;
892	–	}
982
894	–	/**
895	–	* Timeout version.
896	–	* @return current phase
897	–	*/
898	–	private int timedWait(int phase, long nanos)
899	–	throws InterruptedException, TimeoutException {
900	–	long startTime = System.nanoTime();
901	–	QNode node = null;
902	–	boolean queued = false;
903	–	boolean interrupted = false;
904	–	int p;
905	–	while ((p = getPhase()) == phase && !interrupted) {
906	–	if (Thread.interrupted())
907	–	interrupted = true;
908	–	else if (nanos - (System.nanoTime() - startTime) <= 0)
909	–	break;
910	–	else if (node == null)
911	–	node = new QNode(this, phase, true, true, startTime, nanos);
912	–	else if (!queued)
913	–	queued = tryEnqueue(node);
914	–	else
915	–	interrupted = node.doWait();
916	–	}
917	–	if (node != null)
918	–	node.thread = null;
919	–	if (p != phase || (p = getPhase()) != phase)
920	–	releaseWaiters(phase);
921	–	if (interrupted)
922	–	throw new InterruptedException();
923	–	if (p == phase)
924	–	throw new TimeoutException();
925	–	return p;
983		}
984
985		// Unsafe mechanics
#	Line 931 | Line 988 | public class Phaser {
988		private static final long stateOffset =
989		objectFieldOffset("state", Phaser.class);
990
934	–	private final boolean casState(long cmp, long val) {
935	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
936	–	}
937	–
991		private static long objectFieldOffset(String field, Class<?> klazz) {
992		try {
993		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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