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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.26 by jsr166, Wed Aug 5 00:54:11 2009 UTC vs.
Revision 1.60 by dl, Sun Nov 28 15:49:49 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, that 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>
55	<	*
56	<	*
57	<	* <li> Barrier actions, performed by the task triggering a phase
58	<	* advance while others may be waiting, are arranged by overriding
59	<	* method {@link #onAdvance}, that also controls termination.
60	<	* Overriding this method may be used to similar but more flexible
61	<	* effect as providing a barrier action to a {@code CyclicBarrier}.
62	<	*
63	<	* <li> Phasers may enter a <em>termination</em> state in which all
64	<	* actions immediately return without updating phaser state or waiting
65	<	* for advance, and indicating (via a negative phase value) that
66	<	* execution is complete.  Termination is triggered by executing the
67	<	* overridable {@code onAdvance} method that is invoked each time the
68	<	* barrier is about to be tripped. When a phaser is controlling an
69	<	* action with a fixed number of iterations, it is often convenient to
70	<	* override this method to cause termination when the current phase
71	<	* number reaches a threshold. Method {@link #forceTermination} is also
72	<	* available to abruptly release waiting threads and allow them to
73	<	* terminate.
70	<	*
71	<	* <li> Phasers may be tiered to reduce contention. Phasers with large
72	<	* numbers of parties that would otherwise experience heavy
73	<	* synchronization contention costs may instead be arranged in trees.
74	<	* This will typically greatly increase throughput even though it
75	<	* incurs somewhat greater per-operation overhead.
76	<	*
77	<	* <li> By default, {@code awaitAdvance} continues to wait even if
78	<	* the waiting thread is interrupted. And unlike the case in
79	<	* {@code CyclicBarrier}, exceptions encountered while tasks wait
80	<	* interruptibly or with timeout do not change the state of the
81	<	* barrier. If necessary, you can perform any associated recovery
82	<	* within handlers of those exceptions, often after invoking
83	<	* {@code forceTermination}.
84	<	*
85	<	* <li>Phasers ensure lack of starvation when used by ForkJoinTasks.
47	>	*   <li> <b>Arrival.</b> Methods {@link #arrive} and
48	>	*       {@link #arriveAndDeregister} record arrival at a
49	>	*       barrier. These methods do not block, but return an associated
50	>	*       <em>arrival phase number</em>; that is, the phase number of
51	>	*       the barrier to which the arrival applied. When the final
52	>	*       party for a given phase arrives, an optional barrier action
53	>	*       is performed and the phase advances.  Barrier actions,
54	>	*       performed by the party triggering a phase advance, are
55	>	*       arranged by overriding method {@link #onAdvance(int, int)},
56	>	*       which also controls termination. Overriding this method is
57	>	*       similar to, but more flexible than, providing a barrier
58	>	*       action to a {@code CyclicBarrier}.
59	>	*
60	>	*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
61	>	*       argument indicating an arrival phase number, and returns when
62	>	*       the barrier advances to (or is already at) a different phase.
63	>	*       Unlike similar constructions using {@code CyclicBarrier},
64	>	*       method {@code awaitAdvance} continues to wait even if the
65	>	*       waiting thread is interrupted. Interruptible and timeout
66	>	*       versions are also available, but exceptions encountered while
67	>	*       tasks wait interruptibly or with timeout do not change the
68	>	*       state of the barrier. If necessary, you can perform any
69	>	*       associated recovery within handlers of those exceptions,
70	>	*       often after invoking {@code forceTermination}.  Phasers may
71	>	*       also be used by tasks executing in a {@link ForkJoinPool},
72	>	*       which will ensure sufficient parallelism to execute tasks
73	>	*       when others are blocked waiting for a phase to advance.
74		*
75		* </ul>
76		*
77	+	* <p> <b>Termination.</b> A {@code Phaser} may enter a
78	+	* <em>termination</em> state in which all synchronization methods
79	+	* immediately return without updating Phaser state or waiting for
80	+	* advance, and indicating (via a negative phase value) that execution
81	+	* is complete.  Termination is triggered when an invocation of {@code
82	+	* onAdvance} returns {@code true}. The default implementation returns
83	+	* {@code true} if a deregistration has caused the number of
84	+	* registered parties to become zero.  As illustrated below, when
85	+	* Phasers control actions with a fixed number of iterations, it is
86	+	* often convenient to override this method to cause termination when
87	+	* the current phase number reaches a threshold. Method {@link
88	+	* #forceTermination} is also available to abruptly release waiting
89	+	* threads and allow them to terminate.
90	+	*
91	+	* <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	<	*   for (Runnable r : list) {
121	>	*   // create and start threads
122	>	*   for (Runnable task : tasks) {
123		*     phaser.register();
124		*     new Thread() {
125		*       public void run() {
126		*         phaser.arriveAndAwaitAdvance(); // await all creation
127	<	*         r.run();
105	<	*         phaser.arriveAndDeregister();   // signal completion
127	>	*         task.run();
128		*       }
129		*     }.start();
130		*   }
131		*
132	<	*   doSomethingOnBehalfOfWorkers();
133	<	*   phaser.arrive(); // allow threads to start
112	<	*   int p = phaser.arriveAndDeregister(); // deregister self  ...
113	<	*   p = phaser.awaitAdvance(p); // ... and await arrival
114	<	*   otherActions(); // do other things while tasks execute
115	<	*   phaser.awaitAdvance(p); // await final completion
132	>	*   // allow threads to start and deregister self
133	>	*   phaser.arriveAndDeregister();
134		* }}</pre>
135		*
136		* <p>One way to cause a set of threads to repeatedly perform actions
137		* for a given number of iterations is to override {@code onAdvance}:
138		*
139		*  <pre> {@code
140	<	* void startTasks(List<Runnable> 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	<	* <p>To create a set of tasks using a tree of phasers,
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:
188	>	* Task class with a constructor accepting a Phaser that
189	>	* it registers with upon construction:
190	>	*
191		*  <pre> {@code
192	<	* void build(Task[] actions, int lo, int hi, Phaser b) {
193	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
194	<	*   if (step > 1) {
195	<	*     int i = lo;
196	<	*     while (i < hi) {
153	<	*       int r = Math.min(i + step, hi);
154	<	*       build(actions, i, r, new Phaser(b));
155	<	*       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 168 | 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		*
171	–	* </pre>
172	–	*
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
215	<	* should create tiered phasers to accommodate arbitrarily large sets
214	>	* parties result in {@code IllegalStateException}. However, you can and
215	>	* should create tiered Phasers to accommodate arbitrarily large sets
216		* of participants.
217		*
218		* @since 1.7
#	Line 190 | 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.
203	–	*
204	–	* Note: there are some cheats in arrive() that rely on unarrived
205	–	* 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
229	–	private static long stateFor(int phase, int parties, int unarrived) {
230	–	return ((((long) phase) << 32) | (((long) parties) << 16) |
231	–	(long) unarrived);
232	–	}
233	–
234	–	private static long trippedStateFor(int phase, int parties) {
235	–	long lp = (long) parties;
236	–	return (((long) phase) << 32) | (lp << 16) | lp;
237	–	}
238	–
239	–	/**
240	–	* Returns message string for bad bounds exceptions.
241	–	*/
242	–	private static String badBounds(int parties, int unarrived) {
243	–	return ("Attempt to set " + unarrived +
244	–	" unarrived of " + parties + " parties");
245	–	}
246	–
273		/**
274		* The parent of this phaser, or null if none
275		*/
#	Line 255 | Line 281 | public class Phaser {
281		*/
282		private final Phaser root;
283
258	–	// Wait queues
259	–
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
274	<	* 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	+	root.internalAwaitAdvance(phase, null);
387	+	else {                               // 1st registration of child
388	+	synchronized(this) {             // register parent first
389	+	if (reconcileState() == s) { // recheck under lock
390	+	parent.doRegister(1);    // OK if throws IllegalState
391	+	for (;;) {               // simpler form of outer loop
392	+	s = reconcileState();
393	+	phase = (int)(s >>> PHASE_SHIFT);
394	+	if (phase < 0 ||
395	+	UNSAFE.compareAndSwapLong(this, stateOffset,
396	+	s, s + adj))
397	+	return phase;
398	+	}
399	+	}
400	+	}
401	+	}
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;
428		}
429
430		/**
431	<	* Creates a new phaser without any initially registered parties,
431	>	* Creates a new Phaser without any initially registered parties,
432		* initial phase number 0, and no parent. Any thread using this
433	<	* phaser will need to first register for it.
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 322 | Line 449 | public class Phaser {
449		}
450
451		/**
452	<	* Creates a new phaser with the given parent, without any
326	<	* initially registered parties. If parent is non-null this phaser
327	<	* is registered with the parent and its initial phase number is
328	<	* the same as that of parent phaser.
452	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
453		*
454	<	* @param parent the parent phaser
454	>	* @param parent the parent Phaser
455		*/
456		public Phaser(Phaser parent) {
457	<	int phase = 0;
334	<	this.parent = parent;
335	<	if (parent != null) {
336	<	this.root = parent.root;
337	<	phase = parent.register();
338	<	}
339	<	else
340	<	this.root = this;
341	<	this.state = trippedStateFor(phase, 0);
457	>	this(parent, 0);
458		}
459
460		/**
461	<	* Creates a new phaser with the given parent and numbers of
462	<	* registered unarrived parties. If parent is non-null, this phaser
463	<	* is registered with the parent and its initial phase number is
464	<	* the same as that of parent phaser.
461	>	* Creates a new Phaser with the given parent and number of
462	>	* registered unarrived parties. Registration and deregistration
463	>	* of this child Phaser with its parent are managed automatically.
464	>	* If the given parent is non-null, whenever this child Phaser has
465	>	* any registered parties (as established in this constructor,
466	>	* {@link #register}, or {@link #bulkRegister}), this child Phaser
467	>	* is registered with its parent. Whenever the number of
468	>	* registered parties becomes zero as the result of an invocation
469	>	* of {@link #arriveAndDeregister}, this child Phaser is
470	>	* deregistered from its parent.
471		*
472	<	* @param parent the parent phaser
472	>	* @param parent the parent Phaser
473		* @param parties the number of parties required to trip barrier
474		* @throws IllegalArgumentException if parties less than zero
475		* or greater than the maximum number of parties supported
476		*/
477		public Phaser(Phaser parent, int parties) {
478	<	if (parties < 0 || parties > ushortMask)
478	>	if (parties >>> PARTIES_SHIFT != 0)
479		throw new IllegalArgumentException("Illegal number of parties");
480	<	int phase = 0;
480	>	long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT);
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	>	if (parties != 0)
488	>	s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT;
489		}
490	<	else
490	>	else {
491		this.root = this;
492	<	this.state = trippedStateFor(phase, parties);
492	>	this.evenQ = new AtomicReference<QNode>();
493	>	this.oddQ = new AtomicReference<QNode>();
494	>	}
495	>	this.state = s;
496		}
497
498		/**
499	<	* Adds a new unarrived party to this phaser.
499	>	* Adds a new unarrived party to this Phaser.  If an ongoing
500	>	* invocation of {@link #onAdvance} is in progress, this method
501	>	* may await its completion before returning.  If this Phaser has
502	>	* a parent, and this Phaser previously had no registered parties,
503	>	* this Phaser is also registered with its parent.
504		*
505	<	* @return the current barrier phase number upon registration
505	>	* @return the arrival phase number to which this registration applied
506		* @throws IllegalStateException if attempting to register more
507		* than the maximum supported number of parties
508		*/
#	Line 378 | Line 511 | public class Phaser {
511		}
512
513		/**
514	<	* Adds the given number of new unarrived parties to this phaser.
514	>	* Adds the given number of new unarrived parties to this Phaser.
515	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
516	>	* this method may await its completion before returning.  If this
517	>	* Phaser has a parent, and the given number of parities is
518	>	* greater than zero, and this Phaser previously had no registered
519	>	* parties, this Phaser is also registered with its parent.
520		*
521	<	* @param parties the number of parties required to trip barrier
522	<	* @return the current barrier phase number upon registration
521	>	* @param parties the number of additional parties required to trip barrier
522	>	* @return the arrival phase number to which this registration applied
523		* @throws IllegalStateException if attempting to register more
524		* than the maximum supported number of parties
525	+	* @throws IllegalArgumentException if {@code parties < 0}
526		*/
527		public int bulkRegister(int parties) {
528		if (parties < 0)
#	Line 394 | Line 533 | public class Phaser {
533		}
534
535		/**
536	<	* Shared code for register, bulkRegister
537	<	*/
538	<	private int doRegister(int registrations) {
539	<	int phase;
540	<	for (;;) {
541	<	long s = getReconciledState();
403	<	phase = phaseOf(s);
404	<	int unarrived = unarrivedOf(s) + registrations;
405	<	int parties = partiesOf(s) + registrations;
406	<	if (phase < 0)
407	<	break;
408	<	if (parties > ushortMask || unarrived > ushortMask)
409	<	throw new IllegalStateException(badBounds(parties, unarrived));
410	<	if (phase == phaseOf(root.state) &&
411	<	casState(s, stateFor(phase, parties, unarrived)))
412	<	break;
413	<	}
414	<	return phase;
415	<	}
416	<
417	<	/**
418	<	* Arrives at the barrier, but does not wait for others.  (You can
419	<	* in turn wait for others via {@link #awaitAdvance}).
536	>	* Arrives at the barrier, without waiting for others to arrive.
537	>	*
538	>	* <p>It is a usage error for an unregistered party to invoke this
539	>	* method.  However, this error may result in an {@code
540	>	* IllegalStateException} only upon some subsequent operation on
541	>	* this Phaser, if ever.
542		*
543	<	* @return the barrier phase number upon entry to this method, or a
422	<	* 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 unarrived parties would become negative
546		*/
547		public int arrive() {
548	<	int phase;
428	<	for (;;) {
429	<	long s = state;
430	<	phase = phaseOf(s);
431	<	if (phase < 0)
432	<	break;
433	<	int parties = partiesOf(s);
434	<	int unarrived = unarrivedOf(s) - 1;
435	<	if (unarrived > 0) {        // Not the last arrival
436	<	if (casState(s, s - 1)) // s-1 adds one arrival
437	<	break;
438	<	}
439	<	else if (unarrived == 0) {  // the last arrival
440	<	Phaser par = parent;
441	<	if (par == null) {      // directly trip
442	<	if (casState
443	<	(s,
444	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
445	<	((phase + 1) & phaseMask), parties))) {
446	<	releaseWaiters(phase);
447	<	break;
448	<	}
449	<	}
450	<	else {                  // cascade to parent
451	<	if (casState(s, s - 1)) { // zeroes unarrived
452	<	par.arrive();
453	<	reconcileState();
454	<	break;
455	<	}
456	<	}
457	<	}
458	<	else if (phase != phaseOf(root.state)) // or if unreconciled
459	<	reconcileState();
460	<	else
461	<	throw new IllegalStateException(badBounds(parties, unarrived));
462	<	}
463	<	return phase;
548	>	return doArrive(ONE_ARRIVAL);
549		}
550
551		/**
552	<	* Arrives at the barrier, and deregisters from it, without
553	<	* waiting for others. Deregistration reduces number of parties
554	<	* required to trip the barrier in future phases.  If this phaser
555	<	* has a parent, and deregistration causes this phaser to have
556	<	* zero parties, this phaser is also deregistered from its parent.
552	>	* Arrives at the barrier and deregisters from it without waiting
553	>	* for others to arrive. Deregistration reduces the number of
554	>	* parties required to trip the barrier in future phases.  If this
555	>	* Phaser has a parent, and deregistration causes this Phaser to
556	>	* have zero parties, this Phaser is also deregistered from its
557	>	* parent.
558	>	*
559	>	* <p>It is a usage error for an unregistered party to invoke this
560	>	* method.  However, this error may result in an {@code
561	>	* IllegalStateException} only upon some subsequent operation on
562	>	* this Phaser, if ever.
563		*
564	<	* @return the current barrier phase number upon entry to
474	<	* this method, or a negative value if terminated
564	>	* @return the arrival phase number, or a negative value if terminated
565		* @throws IllegalStateException if not terminated and the number
566		* of registered or unarrived parties would become negative
567		*/
568		public int arriveAndDeregister() {
569	<	// similar code to arrive, but too different to merge
480	<	Phaser par = parent;
481	<	int phase;
482	<	for (;;) {
483	<	long s = state;
484	<	phase = phaseOf(s);
485	<	if (phase < 0)
486	<	break;
487	<	int parties = partiesOf(s) - 1;
488	<	int unarrived = unarrivedOf(s) - 1;
489	<	if (parties >= 0) {
490	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
491	<	if (casState
492	<	(s,
493	<	stateFor(phase, parties, unarrived))) {
494	<	if (unarrived == 0) {
495	<	par.arriveAndDeregister();
496	<	reconcileState();
497	<	}
498	<	break;
499	<	}
500	<	continue;
501	<	}
502	<	if (unarrived == 0) {
503	<	if (casState
504	<	(s,
505	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
506	<	((phase + 1) & phaseMask), parties))) {
507	<	releaseWaiters(phase);
508	<	break;
509	<	}
510	<	continue;
511	<	}
512	<	if (par != null && phase != phaseOf(root.state)) {
513	<	reconcileState();
514	<	continue;
515	<	}
516	<	}
517	<	throw new IllegalStateException(badBounds(parties, unarrived));
518	<	}
519	<	return phase;
569	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
570		}
571
572		/**
573		* Arrives at the barrier and awaits others. Equivalent in effect
574	<	* to {@code awaitAdvance(arrive())}.  If you instead need to
575	<	* await with interruption of timeout, and/or deregister upon
576	<	* arrival, you can arrange them using analogous constructions.
574	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
575	>	* interruption or timeout, you can arrange this with an analogous
576	>	* construction using one of the other forms of the {@code
577	>	* awaitAdvance} method.  If instead you need to deregister upon
578	>	* arrival, use {@code awaitAdvance(arriveAndDeregister())}.
579	>	*
580	>	* <p>It is a usage error for an unregistered party to invoke this
581	>	* method.  However, this error may result in an {@code
582	>	* IllegalStateException} only upon some subsequent operation on
583	>	* this Phaser, if ever.
584		*
585	<	* @return the 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 534 | Line 591 | public class Phaser {
591		}
592
593		/**
594	<	* Awaits the phase of the barrier to advance from the given
595	<	* value, or returns immediately if argument is negative or this
596	<	* barrier is terminated.
597	<	*
598	<	* @param phase the phase on entry to this method
599	<	* @return the phase on exit from this method
594	>	* Awaits the phase of the barrier to advance from the given phase
595	>	* value, returning immediately if the current phase of the
596	>	* barrier is not equal to the given phase value or this barrier
597	>	* is terminated.
598	>	*
599	>	* @param phase an arrival phase number, or negative value if
600	>	* terminated; this argument is normally the value returned by a
601	>	* previous call to {@code arrive} or its variants
602	>	* @return the next arrival phase number, or a negative value
603	>	* if terminated or argument is negative
604		*/
605		public int awaitAdvance(int phase) {
606	+	Phaser r;
607	+	int p = (int)(state >>> PHASE_SHIFT);
608		if (phase < 0)
609		return phase;
610	<	long s = getReconciledState();
611	<	int p = phaseOf(s);
612	<	if (p != phase)
613	<	return p;
551	<	if (unarrivedOf(s) == 0 && parent != null)
552	<	parent.awaitAdvance(phase);
553	<	// Fall here even if parent waited, to reconcile and help release
554	<	return untimedWait(phase);
610	>	if (p == phase &&
611	>	(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase)
612	>	return r.internalAwaitAdvance(phase, null);
613	>	return p;
614		}
615
616		/**
617	<	* Awaits the phase of the barrier to advance from the given
618	<	* value, or returns immediately if argument is negative or this
619	<	* barrier is terminated, or throws InterruptedException if
620	<	* interrupted while waiting.
617	>	* Awaits the phase of the barrier to advance from the given phase
618	>	* value, throwing {@code InterruptedException} if interrupted
619	>	* while waiting, or returning immediately if the current phase of
620	>	* the barrier is not equal to the given phase value or this
621	>	* barrier is terminated.
622		*
623	<	* @param phase the phase on entry to this method
624	<	* @return the phase on exit from this method
623	>	* @param phase an arrival phase number, or negative value if
624	>	* terminated; this argument is normally the value returned by a
625	>	* previous call to {@code arrive} or its variants
626	>	* @return the next arrival phase number, or a negative value
627	>	* if terminated or argument is negative
628		* @throws InterruptedException if thread interrupted while waiting
629		*/
630		public int awaitAdvanceInterruptibly(int phase)
631		throws InterruptedException {
632	+	Phaser r;
633	+	int p = (int)(state >>> PHASE_SHIFT);
634		if (phase < 0)
635		return phase;
636	<	long s = getReconciledState();
637	<	int p = phaseOf(s);
638	<	if (p != phase)
639	<	return p;
640	<	if (unarrivedOf(s) == 0 && parent != null)
641	<	parent.awaitAdvanceInterruptibly(phase);
642	<	return interruptibleWait(phase);
636	>	if (p == phase &&
637	>	(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) {
638	>	QNode node = new QNode(this, phase, true, false, 0L);
639	>	p = r.internalAwaitAdvance(phase, node);
640	>	if (node.wasInterrupted)
641	>	throw new InterruptedException();
642	>	}
643	>	return p;
644		}
645
646		/**
647	<	* Awaits the phase of the barrier to advance from the given value
648	<	* or the given timeout elapses, or returns immediately if
649	<	* argument is negative or this barrier is terminated.
650	<	*
651	<	* @param phase the phase on entry to this method
652	<	* @return the phase on exit from this method
647	>	* Awaits the phase of the barrier to advance from the given phase
648	>	* value or the given timeout to elapse, throwing {@code
649	>	* InterruptedException} if interrupted while waiting, or
650	>	* returning immediately if the current phase of the barrier is
651	>	* not equal to the given phase value or this barrier is
652	>	* terminated.
653	>	*
654	>	* @param phase an arrival phase number, or negative value if
655	>	* terminated; this argument is normally the value returned by a
656	>	* previous call to {@code arrive} or its variants
657	>	* @param timeout how long to wait before giving up, in units of
658	>	*        {@code unit}
659	>	* @param unit a {@code TimeUnit} determining how to interpret the
660	>	*        {@code timeout} parameter
661	>	* @return the next arrival phase number, or a negative value
662	>	* if terminated or argument is negative
663		* @throws InterruptedException if thread interrupted while waiting
664		* @throws TimeoutException if timed out while waiting
665		*/
666		public int awaitAdvanceInterruptibly(int phase,
667		long timeout, TimeUnit unit)
668		throws InterruptedException, TimeoutException {
669	+	long nanos = unit.toNanos(timeout);
670	+	Phaser r;
671	+	int p = (int)(state >>> PHASE_SHIFT);
672		if (phase < 0)
673		return phase;
674	<	long s = getReconciledState();
675	<	int p = phaseOf(s);
676	<	if (p != phase)
677	<	return p;
678	<	if (unarrivedOf(s) == 0 && parent != null)
679	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
680	<	return timedWait(phase, unit.toNanos(timeout));
674	>	if (p == phase &&
675	>	(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) {
676	>	QNode node = new QNode(this, phase, true, true, nanos);
677	>	p = r.internalAwaitAdvance(phase, node);
678	>	if (node.wasInterrupted)
679	>	throw new InterruptedException();
680	>	else if (p == phase)
681	>	throw new TimeoutException();
682	>	}
683	>	return p;
684		}
685
686		/**
687	<	* Forces this barrier to enter termination state. Counts of
688	<	* arrived and registered parties are unaffected. If this phaser
689	<	* has a parent, it too is terminated. This method may be useful
690	<	* for coordinating recovery after one or more tasks encounter
691	<	* unexpected exceptions.
687	>	* Forces this barrier to enter termination state.  Counts of
688	>	* arrived and registered parties are unaffected.  If this Phaser
689	>	* is a member of a tiered set of Phasers, then all of the Phasers
690	>	* in the set are terminated.  If this Phaser is already
691	>	* terminated, this method has no effect.  This method may be
692	>	* useful for coordinating recovery after one or more tasks
693	>	* encounter unexpected exceptions.
694		*/
695		public void forceTermination() {
696	<	for (;;) {
697	<	long s = getReconciledState();
698	<	int phase = phaseOf(s);
699	<	int parties = partiesOf(s);
700	<	int unarrived = unarrivedOf(s);
701	<	if (phase < 0 ||
702	<	casState(s, stateFor(-1, parties, unarrived))) {
619	<	releaseWaiters(0);
696	>	// Only need to change root state
697	>	final Phaser root = this.root;
698	>	long s;
699	>	while ((s = root.state) >= 0) {
700	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
701	>	s, s | TERMINATION_BIT)) {
702	>	releaseWaiters(0); // signal all threads
703		releaseWaiters(1);
621	–	if (parent != null)
622	–	parent.forceTermination();
704		return;
705		}
706		}
#	Line 633 | Line 714 | public class Phaser {
714		* @return the phase number, or a negative value if terminated
715		*/
716		public final int getPhase() {
717	<	return phaseOf(getReconciledState());
637	<	}
638	<
639	<	/**
640	<	* Returns {@code true} if the current phase number equals the given phase.
641	<	*
642	<	* @param phase the phase
643	<	* @return {@code true} if the current phase number equals the given phase
644	<	*/
645	<	public final boolean hasPhase(int phase) {
646	<	return phaseOf(getReconciledState()) == phase;
717	>	return (int)(root.state >>> PHASE_SHIFT);
718		}
719
720		/**
#	Line 656 | Line 727 | public class Phaser {
727		}
728
729		/**
730	<	* Returns the number of parties that have arrived at the current
731	<	* phase of this barrier.
730	>	* Returns the number of registered parties that have arrived at
731	>	* the current phase of this barrier.
732		*
733		* @return the number of arrived parties
734		*/
735		public int getArrivedParties() {
736	<	return arrivedOf(state);
736	>	long s = state;
737	>	int u = unarrivedOf(s); // only reconcile if possibly needed
738	>	return (u != 0 || parent == null) ?
739	>	partiesOf(s) - u :
740	>	arrivedOf(reconcileState());
741		}
742
743		/**
#	Line 672 | Line 747 | public class Phaser {
747		* @return the number of unarrived parties
748		*/
749		public int getUnarrivedParties() {
750	<	return unarrivedOf(state);
750	>	int u = unarrivedOf(state);
751	>	return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState());
752		}
753
754		/**
755	<	* Returns the parent of this phaser, or {@code null} if none.
755	>	* Returns the parent of this Phaser, or {@code null} if none.
756		*
757	<	* @return the parent of this phaser, or {@code null} if none
757	>	* @return the parent of this Phaser, or {@code null} if none
758		*/
759		public Phaser getParent() {
760		return parent;
761		}
762
763		/**
764	<	* Returns the root ancestor of this phaser, which is the same as
765	<	* this phaser if it has no parent.
764	>	* Returns the root ancestor of this Phaser, which is the same as
765	>	* this Phaser if it has no parent.
766		*
767	<	* @return the root ancestor of this phaser
767	>	* @return the root ancestor of this Phaser
768		*/
769		public Phaser getRoot() {
770		return root;
#	Line 700 | Line 776 | public class Phaser {
776		* @return {@code true} if this barrier has been terminated
777		*/
778		public boolean isTerminated() {
779	<	return getPhase() < 0;
779	>	return root.state < 0L;
780		}
781
782		/**
783	<	* Overridable method to perform an action upon phase advance, and
784	<	* to control termination. This method is invoked whenever the
785	<	* barrier is tripped (and thus all other waiting parties are
786	<	* dormant). If it returns {@code true}, then, rather than advance
787	<	* the phase number, this barrier will be set to a final
788	<	* termination state, and subsequent calls to {@link #isTerminated}
789	<	* will return true.
790	<	*
791	<	* <p>The default version returns {@code true} when the number of
792	<	* registered parties is zero. Normally, overrides that arrange
793	<	* termination for other reasons should also preserve this
794	<	* property.
795	<	*
796	<	* <p>You may override this method to perform an action with side
797	<	* effects visible to participating tasks, but it is in general
798	<	* only sensible to do so in designs where all parties register
799	<	* before any arrive, and all {@link #awaitAdvance} at each phase.
800	<	* Otherwise, you cannot ensure lack of interference. In
801	<	* particular, this method may be invoked more than once per
802	<	* transition if other parties successfully register while the
803	<	* invocation of this method is in progress, thus postponing the
804	<	* transition until those parties also arrive, re-triggering this
805	<	* method.
783	>	* Overridable method to perform an action upon impending phase
784	>	* advance, and to control termination. This method is invoked
785	>	* upon arrival of the party tripping the barrier (when all other
786	>	* waiting parties are dormant).  If this method returns {@code
787	>	* true}, then, rather than advance the phase number, this barrier
788	>	* will be set to a final termination state, and subsequent calls
789	>	* to {@link #isTerminated} will return true. Any (unchecked)
790	>	* Exception or Error thrown by an invocation of this method is
791	>	* propagated to the party attempting to trip the barrier, in
792	>	* which case no advance occurs.
793	>	*
794	>	* <p>The arguments to this method provide the state of the Phaser
795	>	* prevailing for the current transition.  The effects of invoking
796	>	* arrival, registration, and waiting methods on this Phaser from
797	>	* within {@code onAdvance} are unspecified and should not be
798	>	* relied on.
799	>	*
800	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
801	>	* {@code onAdvance} is invoked only for its root Phaser on each
802	>	* advance.
803	>	*
804	>	* <p>To support the most common use cases, the default
805	>	* implementation of this method returns {@code true} when the
806	>	* number of registered parties has become zero as the result of a
807	>	* party invoking {@code arriveAndDeregister}.  You can disable
808	>	* this behavior, thus enabling continuation upon future
809	>	* registrations, by overriding this method to always return
810	>	* {@code false}:
811	>	*
812	>	* <pre> {@code
813	>	* Phaser phaser = new Phaser() {
814	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
815	>	* }}</pre>
816		*
817		* @param phase the phase number on entering the barrier
818		* @param registeredParties the current number of registered parties
#	Line 737 | Line 823 | public class Phaser {
823		}
824
825		/**
826	<	* Returns a string identifying this phaser, as well as its
826	>	* Returns a string identifying this Phaser, as well as its
827		* state.  The state, in brackets, includes the String {@code
828		* "phase = "} followed by the phase number, {@code "parties = "}
829		* followed by the number of registered parties, and {@code
#	Line 746 | Line 832 | public class Phaser {
832		* @return a string identifying this barrier, as well as its state
833		*/
834		public String toString() {
835	<	long s = getReconciledState();
835	>	return stateToString(reconcileState());
836	>	}
837	>
838	>	/**
839	>	* Implementation of toString and string-based error messages
840	>	*/
841	>	private String stateToString(long s) {
842		return super.toString() +
843		"[phase = " + phaseOf(s) +
844		" parties = " + partiesOf(s) +
845		" arrived = " + arrivedOf(s) + "]";
846		}
847
848	<	// methods for waiting
848	>	// Waiting mechanics
849	>
850	>	/**
851	>	* Removes and signals threads from queue for phase.
852	>	*/
853	>	private void releaseWaiters(int phase) {
854	>	AtomicReference<QNode> head = queueFor(phase);
855	>	QNode q;
856	>	int p;
857	>	while ((q = head.get()) != null &&
858	>	((p = q.phase) == phase ||
859	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
860	>	if (head.compareAndSet(q, q.next))
861	>	q.signal();
862	>	}
863	>	}
864	>
865	>	/** The number of CPUs, for spin control */
866	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
867	>
868	>	/**
869	>	* The number of times to spin before blocking while waiting for
870	>	* advance, per arrival while waiting. On multiprocessors, fully
871	>	* blocking and waking up a large number of threads all at once is
872	>	* usually a very slow process, so we use rechargeable spins to
873	>	* avoid it when threads regularly arrive: When a thread in
874	>	* internalAwaitAdvance notices another arrival before blocking,
875	>	* and there appear to be enough CPUs available, it spins
876	>	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
877	>	* uniprocessors, there is at least one intervening Thread.yield
878	>	* before blocking. The value trades off good-citizenship vs big
879	>	* unnecessary slowdowns.
880	>	*/
881	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
882	>
883	>	/**
884	>	* Possibly blocks and waits for phase to advance unless aborted.
885	>	* Call only from root node.
886	>	*
887	>	* @param phase current phase
888	>	* @param node if non-null, the wait node to track interrupt and timeout;
889	>	* if null, denotes noninterruptible wait
890	>	* @return current phase
891	>	*/
892	>	private int internalAwaitAdvance(int phase, QNode node) {
893	>	boolean queued = false;      // true when node is enqueued
894	>	int lastUnarrived = -1;      // to increase spins upon change
895	>	int spins = SPINS_PER_ARRIVAL;
896	>	long s;
897	>	int p;
898	>	while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
899	>	int unarrived = (int)s & UNARRIVED_MASK;
900	>	if (unarrived != lastUnarrived) {
901	>	if (lastUnarrived == -1) // ensure old queue clean
902	>	releaseWaiters(phase-1);
903	>	if ((lastUnarrived = unarrived) < NCPU)
904	>	spins += SPINS_PER_ARRIVAL;
905	>	}
906	>	else if (spins > 0) {
907	>	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
908	>	Thread.yield();  // yield midway through spin
909	>	}
910	>	else if (node == null)   // must be noninterruptible
911	>	node = new QNode(this, phase, false, false, 0L);
912	>	else if (node.isReleasable()) {
913	>	p = (int)(state >>> PHASE_SHIFT);
914	>	break;               // aborted
915	>	}
916	>	else if (!queued) {      // push onto queue
917	>	AtomicReference<QNode> head = queueFor(phase);
918	>	QNode q = head.get();
919	>	if (q == null || q.phase == phase) {
920	>	node.next = q;
921	>	if ((p = (int)(state >>> PHASE_SHIFT)) != phase)
922	>	break;       // recheck to avoid stale enqueue
923	>	else
924	>	queued = head.compareAndSet(q, node);
925	>	}
926	>	}
927	>	else {
928	>	try {
929	>	ForkJoinPool.managedBlock(node);
930	>	} catch (InterruptedException ie) {
931	>	node.wasInterrupted = true;
932	>	}
933	>	}
934	>	}
935	>
936	>	if (node != null) {
937	>	if (node.thread != null)
938	>	node.thread = null; // disable unpark() in node.signal
939	>	if (!node.interruptible && node.wasInterrupted)
940	>	Thread.currentThread().interrupt();
941	>	}
942	>	if (p != phase)
943	>	releaseWaiters(phase);
944	>	return p;
945	>	}
946
947		/**
948		* Wait nodes for Treiber stack representing wait queue
#	Line 761 | Line 950 | public class Phaser {
950		static final class QNode implements ForkJoinPool.ManagedBlocker {
951		final Phaser phaser;
952		final int phase;
764	–	final long startTime;
765	–	final long nanos;
766	–	final boolean timed;
953		final boolean interruptible;
954	<	volatile boolean wasInterrupted = false;
954	>	final boolean timed;
955	>	boolean wasInterrupted;
956	>	long nanos;
957	>	long lastTime;
958		volatile Thread thread; // nulled to cancel wait
959		QNode next;
960	+
961		QNode(Phaser phaser, int phase, boolean interruptible,
962	<	boolean timed, long startTime, long nanos) {
962	>	boolean timed, long nanos) {
963		this.phaser = phaser;
964		this.phase = phase;
775	–	this.timed = timed;
965		this.interruptible = interruptible;
777	–	this.startTime = startTime;
966		this.nanos = nanos;
967	+	this.timed = timed;
968	+	this.lastTime = timed? System.nanoTime() : 0L;
969		thread = Thread.currentThread();
970		}
971	+
972		public boolean isReleasable() {
973	<	return (thread == null ||
974	<	phaser.getPhase() != phase ||
975	<	(interruptible && wasInterrupted) ||
976	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
973	>	Thread t = thread;
974	>	if (t != null) {
975	>	if (phaser.getPhase() != phase)
976	>	t = null;
977	>	else {
978	>	if (Thread.interrupted())
979	>	wasInterrupted = true;
980	>	if (interruptible && wasInterrupted)
981	>	t = null;
982	>	else if (timed) {
983	>	if (nanos > 0) {
984	>	long now = System.nanoTime();
985	>	nanos -= now - lastTime;
986	>	lastTime = now;
987	>	}
988	>	if (nanos <= 0)
989	>	t = null;
990	>	}
991	>	}
992	>	if (t != null)
993	>	return false;
994	>	thread = null;
995	>	}
996	>	return true;
997		}
998	+
999		public boolean block() {
1000	<	if (Thread.interrupted()) {
1001	<	wasInterrupted = true;
1002	<	if (interruptible)
791	<	return true;
792	<	}
793	<	if (!timed)
1000	>	if (isReleasable())
1001	>	return true;
1002	>	else if (!timed)
1003		LockSupport.park(this);
1004	<	else {
1005	<	long waitTime = nanos - (System.nanoTime() - startTime);
797	<	if (waitTime <= 0)
798	<	return true;
799	<	LockSupport.parkNanos(this, waitTime);
800	<	}
1004	>	else if (nanos > 0)
1005	>	LockSupport.parkNanos(this, nanos);
1006		return isReleasable();
1007		}
1008	+
1009		void signal() {
1010		Thread t = thread;
1011		if (t != null) {
#	Line 807 | Line 1013 | public class Phaser {
1013		LockSupport.unpark(t);
1014		}
1015		}
810	–	boolean doWait() {
811	–	if (thread != null) {
812	–	try {
813	–	ForkJoinPool.managedBlock(this, false);
814	–	} catch (InterruptedException ie) {
815	–	}
816	–	}
817	–	return wasInterrupted;
818	–	}
819	–
820	–	}
821	–
822	–	/**
823	–	* Removes and signals waiting threads from wait queue.
824	–	*/
825	–	private void releaseWaiters(int phase) {
826	–	AtomicReference<QNode> head = queueFor(phase);
827	–	QNode q;
828	–	while ((q = head.get()) != null) {
829	–	if (head.compareAndSet(q, q.next))
830	–	q.signal();
831	–	}
832	–	}
833	–
834	–	/**
835	–	* Tries to enqueue given node in the appropriate wait queue.
836	–	*
837	–	* @return true if successful
838	–	*/
839	–	private boolean tryEnqueue(QNode node) {
840	–	AtomicReference<QNode> head = queueFor(node.phase);
841	–	return head.compareAndSet(node.next = head.get(), node);
842	–	}
843	–
844	–	/**
845	–	* Enqueues node and waits unless aborted or signalled.
846	–	*
847	–	* @return current phase
848	–	*/
849	–	private int untimedWait(int phase) {
850	–	QNode node = null;
851	–	boolean queued = false;
852	–	boolean interrupted = false;
853	–	int p;
854	–	while ((p = getPhase()) == phase) {
855	–	if (Thread.interrupted())
856	–	interrupted = true;
857	–	else if (node == null)
858	–	node = new QNode(this, phase, false, false, 0, 0);
859	–	else if (!queued)
860	–	queued = tryEnqueue(node);
861	–	else
862	–	interrupted = node.doWait();
863	–	}
864	–	if (node != null)
865	–	node.thread = null;
866	–	releaseWaiters(phase);
867	–	if (interrupted)
868	–	Thread.currentThread().interrupt();
869	–	return p;
870	–	}
871	–
872	–	/**
873	–	* Interruptible version
874	–	* @return current phase
875	–	*/
876	–	private int interruptibleWait(int phase) throws InterruptedException {
877	–	QNode node = null;
878	–	boolean queued = false;
879	–	boolean interrupted = false;
880	–	int p;
881	–	while ((p = getPhase()) == phase && !interrupted) {
882	–	if (Thread.interrupted())
883	–	interrupted = true;
884	–	else if (node == null)
885	–	node = new QNode(this, phase, true, false, 0, 0);
886	–	else if (!queued)
887	–	queued = tryEnqueue(node);
888	–	else
889	–	interrupted = node.doWait();
890	–	}
891	–	if (node != null)
892	–	node.thread = null;
893	–	if (p != phase || (p = getPhase()) != phase)
894	–	releaseWaiters(phase);
895	–	if (interrupted)
896	–	throw new InterruptedException();
897	–	return p;
898	–	}
899	–
900	–	/**
901	–	* Timeout version.
902	–	* @return current phase
903	–	*/
904	–	private int timedWait(int phase, long nanos)
905	–	throws InterruptedException, TimeoutException {
906	–	long startTime = System.nanoTime();
907	–	QNode node = null;
908	–	boolean queued = false;
909	–	boolean interrupted = false;
910	–	int p;
911	–	while ((p = getPhase()) == phase && !interrupted) {
912	–	if (Thread.interrupted())
913	–	interrupted = true;
914	–	else if (nanos - (System.nanoTime() - startTime) <= 0)
915	–	break;
916	–	else if (node == null)
917	–	node = new QNode(this, phase, true, true, startTime, nanos);
918	–	else if (!queued)
919	–	queued = tryEnqueue(node);
920	–	else
921	–	interrupted = node.doWait();
922	–	}
923	–	if (node != null)
924	–	node.thread = null;
925	–	if (p != phase || (p = getPhase()) != phase)
926	–	releaseWaiters(phase);
927	–	if (interrupted)
928	–	throw new InterruptedException();
929	–	if (p == phase)
930	–	throw new TimeoutException();
931	–	return p;
1016		}
1017
1018		// Unsafe mechanics
#	Line 937 | Line 1021 | public class Phaser {
1021		private static final long stateOffset =
1022		objectFieldOffset("state", Phaser.class);
1023
940	–	private final boolean casState(long cmp, long val) {
941	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
942	–	}
943	–
1024		private static long objectFieldOffset(String field, Class<?> klazz) {
1025		try {
1026		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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