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root/jsr166/jsr166/src/jsr166y/Phaser.java

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.23 by jsr166, Mon Jul 27 20:57:44 2009 UTC vs.
Revision 1.50 by dl, Sat Nov 6 16:12:10 2010 UTC

#	Line 7 | Line 7
7		package jsr166y;
8
9		import java.util.concurrent.*;
10	–
10		import java.util.concurrent.atomic.AtomicReference;
11		import java.util.concurrent.locks.LockSupport;
12
13		/**
14	<	* A reusable synchronization barrier, similar in functionality to a
14	>	* A reusable synchronization barrier, similar in functionality to
15		* {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and
16		* {@link java.util.concurrent.CountDownLatch CountDownLatch}
17		* but supporting more flexible usage.
18		*
19	<	* <ul>
20	<	*
21	<	* <li> The number of parties synchronizing on a phaser may vary over
22	<	* time.  A task may register to be a party at any time, and may
23	<	* deregister upon arriving at the barrier.  As is the case with most
24	<	* basic synchronization constructs, registration and deregistration
25	<	* affect only internal counts; they do not establish any further
26	<	* internal bookkeeping, so tasks cannot query whether they are
27	<	* registered. (However, you can introduce such bookkeeping by
28	<	* subclassing this class.)
29	<	*
30	<	* <li> Each generation has an associated phase value, starting at
31	<	* zero, and advancing when all parties reach the barrier (wrapping
32	<	* around to zero after reaching {@code Integer.MAX_VALUE}).
33	<	*
34	<	* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited.
35	<	* Method {@code arriveAndAwaitAdvance} has effect analogous to
36	<	* {@code CyclicBarrier.await}.  However, Phasers separate two
37	<	* aspects of coordination, that may also be invoked independently:
19	>	* <p> <b>Registration.</b> Unlike the case for other barriers, the
20	>	* number of parties <em>registered</em> to synchronize on a phaser
21	>	* may vary over time.  Tasks may be registered at any time (using
22	>	* methods {@link #register}, {@link #bulkRegister}, or forms of
23	>	* constructors establishing initial numbers of parties), and
24	>	* optionally deregistered upon any arrival (using {@link
25	>	* #arriveAndDeregister}).  As is the case with most basic
26	>	* synchronization constructs, registration and deregistration affect
27	>	* only internal counts; they do not establish any further internal
28	>	* bookkeeping, so tasks cannot query whether they are registered.
29	>	* (However, you can introduce such bookkeeping by subclassing this
30	>	* class.)
31	>	*
32	>	* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
33	>	* Phaser} may be repeatedly awaited.  Method {@link
34	>	* #arriveAndAwaitAdvance} has effect analogous to {@link
35	>	* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
36	>	* generation of a {@code Phaser} has an associated phase number. The
37	>	* phase number starts at zero, and advances when all parties arrive
38	>	* at the barrier, wrapping around to zero after reaching {@code
39	>	* Integer.MAX_VALUE}. The use of phase numbers enables independent
40	>	* control of actions upon arrival at a barrier and upon awaiting
41	>	* others, via two kinds of methods that may be invoked by any
42	>	* registered party:
43		*
44		* <ul>
45		*
46	<	*   <li> Arriving at a barrier. Methods {@code arrive} and
47	<	*       {@code arriveAndDeregister} do not block, but return
48	<	*       the phase value current upon entry to the method.
49	<	*
50	<	*   <li> Awaiting others. Method {@code awaitAdvance} requires an
51	<	*       argument indicating the entry phase, and returns when the
52	<	*       barrier advances to a new phase.
53	<	* </ul>
46	>	*   <li> <b>Arrival.</b> Methods {@link #arrive} and
47	>	*       {@link #arriveAndDeregister} record arrival at a
48	>	*       barrier. These methods do not block, but return an associated
49	>	*       <em>arrival phase number</em>; that is, the phase number of
50	>	*       the barrier to which the arrival applied. When the final
51	>	*       party for a given phase arrives, an optional barrier action
52	>	*       is performed and the phase advances.  Barrier actions,
53	>	*       performed by the party triggering a phase advance, are
54	>	*       arranged by overriding method {@link #onAdvance(int, int)},
55	>	*       which also controls termination. Overriding this method is
56	>	*       similar to, but more flexible than, providing a barrier
57	>	*       action to a {@code CyclicBarrier}.
58	>	*
59	>	*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
60	>	*       argument indicating an arrival phase number, and returns when
61	>	*       the barrier advances to (or is already at) a different phase.
62	>	*       Unlike similar constructions using {@code CyclicBarrier},
63	>	*       method {@code awaitAdvance} continues to wait even if the
64	>	*       waiting thread is interrupted. Interruptible and timeout
65	>	*       versions are also available, but exceptions encountered while
66	>	*       tasks wait interruptibly or with timeout do not change the
67	>	*       state of the barrier. If necessary, you can perform any
68	>	*       associated recovery within handlers of those exceptions,
69	>	*       often after invoking {@code forceTermination}.  Phasers may
70	>	*       also be used by tasks executing in a {@link ForkJoinPool},
71	>	*       which will ensure sufficient parallelism to execute tasks
72	>	*       when others are blocked waiting for a phase to advance.
73		*
74	+	* </ul>
75		*
76	<	* <li> Barrier actions, performed by the task triggering a phase
77	<	* advance while others may be waiting, are arranged by overriding
78	<	* method {@code onAdvance}, that also controls termination.
79	<	* Overriding this method may be used to similar but more flexible
80	<	* effect as providing a barrier action to a CyclicBarrier.
81	<	*
82	<	* <li> Phasers may enter a <em>termination</em> state in which all
83	<	* actions immediately return without updating phaser state or waiting
84	<	* for advance, and indicating (via a negative phase value) that
85	<	* execution is complete.  Termination is triggered by executing the
86	<	* overridable {@code onAdvance} method that is invoked each time the
63	<	* barrier is about to be tripped. When a Phaser is controlling an
64	<	* action with a fixed number of iterations, it is often convenient to
65	<	* override this method to cause termination when the current phase
66	<	* number reaches a threshold. Method {@code forceTermination} is also
67	<	* available to abruptly release waiting threads and allow them to
68	<	* terminate.
76	>	* <p> <b>Termination.</b> A {@code Phaser} may enter a
77	>	* <em>termination</em> state in which all synchronization methods
78	>	* immediately return without updating phaser state or waiting for
79	>	* advance, and indicating (via a negative phase value) that execution
80	>	* is complete.  Termination is triggered when an invocation of {@code
81	>	* onAdvance} returns {@code true}.  As illustrated below, when
82	>	* phasers control actions with a fixed number of iterations, it is
83	>	* often convenient to override this method to cause termination when
84	>	* the current phase number reaches a threshold. Method {@link
85	>	* #forceTermination} is also available to abruptly release waiting
86	>	* threads and allow them to terminate.
87		*
88	<	* <li> Phasers may be tiered to reduce contention. Phasers with large
88	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
89	>	* in tree structures) 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	<	* CyclicBarriers, 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 ensure lack of starvation when used by ForkJoinTasks.
104	<	*
105	<	* </ul>
91	>	* synchronization contention costs may instead be set up so that
92	>	* groups of sub-phasers share a common parent.  This may greatly
93	>	* increase throughput even though it incurs greater per-operation
94	>	* overhead.
95	>	*
96	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
97	>	* only by registered parties, the current state of a phaser may be
98	>	* monitored by any caller.  At any given moment there are {@link
99	>	* #getRegisteredParties} parties in total, of which {@link
100	>	* #getArrivedParties} have arrived at the current phase ({@link
101	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
102	>	* parties arrive, the phase advances.  The values returned by these
103	>	* methods may reflect transient states and so are not in general
104	>	* useful for synchronization control.  Method {@link #toString}
105	>	* returns snapshots of these state queries in a form convenient for
106	>	* informal monitoring.
107		*
108		* <p><b>Sample usages:</b>
109		*
110	<	* <p>A Phaser may be used instead of a {@code CountDownLatch} to control
111	<	* a one-shot action serving a variable number of parties. The typical
112	<	* idiom is for the method setting this up to first register, then
113	<	* start the actions, then deregister, as in:
110	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
111	>	* to control a one-shot action serving a variable number of parties.
112	>	* The typical idiom is for the method setting this up to first
113	>	* register, then start the actions, then deregister, as in:
114		*
115		*  <pre> {@code
116	<	* void runTasks(List<Runnable> list) {
116	>	* void runTasks(List<Runnable> tasks) {
117		*   final Phaser phaser = new Phaser(1); // "1" to register self
118	<	*   for (Runnable r : list) {
118	>	*   // create and start threads
119	>	*   for (Runnable task : tasks) {
120		*     phaser.register();
121		*     new Thread() {
122		*       public void run() {
123		*         phaser.arriveAndAwaitAdvance(); // await all creation
124	<	*         r.run();
104	<	*         phaser.arriveAndDeregister();   // signal completion
124	>	*         task.run();
125		*       }
126		*     }.start();
127		*   }
128		*
129	<	*   doSomethingOnBehalfOfWorkers();
130	<	*   phaser.arrive(); // allow threads to start
111	<	*   int p = phaser.arriveAndDeregister(); // deregister self  ...
112	<	*   p = phaser.awaitAdvance(p); // ... and await arrival
113	<	*   otherActions(); // do other things while tasks execute
114	<	*   phaser.awaitAdvance(p); // await final completion
129	>	*   // allow threads to start and deregister self
130	>	*   phaser.arriveAndDeregister();
131		* }}</pre>
132		*
133		* <p>One way to cause a set of threads to repeatedly perform actions
134		* for a given number of iterations is to override {@code onAdvance}:
135		*
136		*  <pre> {@code
137	<	* void startTasks(List<Runnable> list, final int iterations) {
137	>	* void startTasks(List<Runnable> tasks, final int iterations) {
138		*   final Phaser phaser = new Phaser() {
139	<	*     public boolean onAdvance(int phase, int registeredParties) {
139	>	*     protected boolean onAdvance(int phase, int registeredParties) {
140		*       return phase >= iterations || registeredParties == 0;
141		*     }
142		*   };
143		*   phaser.register();
144	<	*   for (Runnable r : list) {
144	>	*   for (final Runnable task : tasks) {
145		*     phaser.register();
146		*     new Thread() {
147		*       public void run() {
148		*         do {
149	<	*           r.run();
149	>	*           task.run();
150		*           phaser.arriveAndAwaitAdvance();
151	<	*         } while(!phaser.isTerminated();
151	>	*         } while (!phaser.isTerminated());
152		*       }
153		*     }.start();
154		*   }
155		*   phaser.arriveAndDeregister(); // deregister self, don't wait
156		* }}</pre>
157		*
158	<	* <p> To create a set of tasks using a tree of Phasers,
158	>	* If the main task must later await termination, it
159	>	* may re-register and then execute a similar loop:
160	>	*  <pre> {@code
161	>	*   // ...
162	>	*   phaser.register();
163	>	*   while (!phaser.isTerminated())
164	>	*     phaser.arriveAndAwaitAdvance();}</pre>
165	>	*
166	>	* <p>Related constructions may be used to await particular phase numbers
167	>	* in contexts where you are sure that the phase will never wrap around
168	>	* {@code Integer.MAX_VALUE}. For example:
169	>	*
170	>	*  <pre> {@code
171	>	* void awaitPhase(Phaser phaser, int phase) {
172	>	*   int p = phaser.register(); // assumes caller not already registered
173	>	*   while (p < phase) {
174	>	*     if (phaser.isTerminated())
175	>	*       // ... deal with unexpected termination
176	>	*     else
177	>	*       p = phaser.arriveAndAwaitAdvance();
178	>	*   }
179	>	*   phaser.arriveAndDeregister();
180	>	* }}</pre>
181	>	*
182	>	*
183	>	* <p>To create a set of tasks using a tree of phasers,
184		* you could use code of the following form, assuming a
185	<	* Task class with a constructor accepting a Phaser that
186	<	* it registers for upon construction:
185	>	* Task class with a constructor accepting a phaser that
186	>	* it registers with upon construction:
187	>	*
188		*  <pre> {@code
189	<	* void build(Task[] actions, int lo, int hi, Phaser b) {
190	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
191	<	*   if (step > 1) {
192	<	*     int i = lo;
193	<	*     while (i < hi) {
152	<	*       int r = Math.min(i + step, hi);
153	<	*       build(actions, i, r, new Phaser(b));
154	<	*       i = r;
189	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
190	>	*   if (hi - lo > TASKS_PER_PHASER) {
191	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
192	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
193	>	*       build(actions, i, j, new Phaser(ph));
194		*     }
195		*   } else {
196		*     for (int i = lo; i < hi; ++i)
197	<	*       actions[i] = new Task(b);
198	<	*       // assumes new Task(b) performs b.register()
197	>	*       actions[i] = new Task(ph);
198	>	*       // assumes new Task(ph) performs ph.register()
199		*   }
200		* }
201		* // .. initially called, for n tasks via
#	Line 167 | Line 206 | import java.util.concurrent.locks.LockSu
206		* be appropriate for extremely small per-barrier task bodies (thus
207		* high rates), or up to hundreds for extremely large ones.
208		*
170	–	* </pre>
171	–	*
209		* <p><b>Implementation notes</b>: This implementation restricts the
210		* maximum number of parties to 65535. Attempts to register additional
211	<	* parties result in IllegalStateExceptions. However, you can and
211	>	* parties result in {@code IllegalStateException}. However, you can and
212		* should create tiered phasers to accommodate arbitrarily large sets
213		* of participants.
214		*
#	Line 205 | Line 242 | public class Phaser {
242		*/
243		private volatile long state;
244
208	–	private static final int ushortBits = 16;
245		private static final int ushortMask = 0xffff;
246		private static final int phaseMask  = 0x7fffffff;
247
#	Line 249 | Line 285 | public class Phaser {
285		private final Phaser parent;
286
287		/**
288	<	* The root of Phaser tree. Equals this if not in a tree.  Used to
288	>	* The root of phaser tree. Equals this if not in a tree.  Used to
289		* support faster state push-down.
290		*/
291		private final Phaser root;
#	Line 258 | Line 294 | public class Phaser {
294
295		/**
296		* Heads of Treiber stacks for waiting threads. To eliminate
297	<	* contention while releasing some threads while adding others, we
297	>	* contention when releasing some threads while adding others, we
298		* use two of them, alternating across even and odd phases.
299	+	* Subphasers share queues with root to speed up releases.
300		*/
301	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
302	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
301	>	private final AtomicReference<QNode> evenQ;
302	>	private final AtomicReference<QNode> oddQ;
303
304		private AtomicReference<QNode> queueFor(int phase) {
305		return ((phase & 1) == 0) ? evenQ : oddQ;
#	Line 280 | Line 317 | public class Phaser {
317		* Recursively resolves state.
318		*/
319		private long reconcileState() {
320	<	Phaser p = parent;
320	>	Phaser par = parent;
321		long s = state;
322	<	if (p != null) {
323	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
324	<	long parentState = p.getReconciledState();
325	<	int parentPhase = phaseOf(parentState);
326	<	int phase = phaseOf(s = state);
327	<	if (phase != parentPhase) {
322	>	if (par != null) {
323	>	int phase, rootPhase;
324	>	while ((phase = phaseOf(s)) >= 0 &&
325	>	(rootPhase = phaseOf(root.state)) != phase &&
326	>	(rootPhase < 0 || unarrivedOf(s) == 0)) {
327	>	int parentPhase = phaseOf(par.getReconciledState());
328	>	if (parentPhase != phase) {
329		long next = trippedStateFor(parentPhase, partiesOf(s));
330	<	if (casState(s, next)) {
331	<	releaseWaiters(phase);
294	<	s = next;
295	<	}
330	>	if (state == s)
331	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
332		}
333	+	s = state;
334		}
335		}
336		return s;
337		}
338
339		/**
340	<	* Creates a new Phaser without any initially registered parties,
340	>	* Creates a new phaser without any initially registered parties,
341		* initial phase number 0, and no parent. Any thread using this
342	<	* Phaser will need to first register for it.
342	>	* phaser will need to first register for it.
343		*/
344		public Phaser() {
345	<	this(null);
345	>	this(null, 0);
346		}
347
348		/**
349	<	* Creates a new Phaser with the given numbers of registered
349	>	* Creates a new phaser with the given number of registered
350		* unarrived parties, initial phase number 0, and no parent.
351		*
352		* @param parties the number of parties required to trip barrier
#	Line 321 | Line 358 | public class Phaser {
358		}
359
360		/**
361	<	* Creates a new Phaser with the given parent, without any
361	>	* Creates a new phaser with the given parent, without any
362		* initially registered parties. If parent is non-null this phaser
363		* is registered with the parent and its initial phase number is
364		* the same as that of parent phaser.
#	Line 329 | Line 366 | public class Phaser {
366		* @param parent the parent phaser
367		*/
368		public Phaser(Phaser parent) {
369	<	int phase = 0;
333	<	this.parent = parent;
334	<	if (parent != null) {
335	<	this.root = parent.root;
336	<	phase = parent.register();
337	<	}
338	<	else
339	<	this.root = this;
340	<	this.state = trippedStateFor(phase, 0);
369	>	this(parent, 0);
370		}
371
372		/**
373	<	* Creates a new Phaser with the given parent and numbers of
373	>	* Creates a new phaser with the given parent and number of
374		* registered unarrived parties. If parent is non-null, this phaser
375		* is registered with the parent and its initial phase number is
376		* the same as that of parent phaser.
#	Line 354 | Line 383 | public class Phaser {
383		public Phaser(Phaser parent, int parties) {
384		if (parties < 0 || parties > ushortMask)
385		throw new IllegalArgumentException("Illegal number of parties");
386	<	int phase = 0;
386	>	int phase;
387		this.parent = parent;
388		if (parent != null) {
389	<	this.root = parent.root;
389	>	Phaser r = parent.root;
390	>	this.root = r;
391	>	this.evenQ = r.evenQ;
392	>	this.oddQ = r.oddQ;
393		phase = parent.register();
394		}
395	<	else
395	>	else {
396		this.root = this;
397	+	this.evenQ = new AtomicReference<QNode>();
398	+	this.oddQ = new AtomicReference<QNode>();
399	+	phase = 0;
400	+	}
401		this.state = trippedStateFor(phase, parties);
402		}
403
404		/**
405		* Adds a new unarrived party to this phaser.
406	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
407	+	* this method may wait until its completion before registering.
408		*
409	<	* @return the current barrier phase number upon registration
409	>	* @return the arrival phase number to which this registration applied
410		* @throws IllegalStateException if attempting to register more
411		* than the maximum supported number of parties
412		*/
#	Line 378 | Line 416 | public class Phaser {
416
417		/**
418		* Adds the given number of new unarrived parties to this phaser.
419	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
420	+	* this method may wait until its completion before registering.
421		*
422	<	* @param parties the number of parties required to trip barrier
423	<	* @return the current barrier phase number upon registration
422	>	* @param parties the number of additional parties required to trip barrier
423	>	* @return the arrival phase number to which this registration applied
424		* @throws IllegalStateException if attempting to register more
425		* than the maximum supported number of parties
426	+	* @throws IllegalArgumentException if {@code parties < 0}
427		*/
428		public int bulkRegister(int parties) {
429		if (parties < 0)
#	Line 396 | Line 437 | public class Phaser {
437		* Shared code for register, bulkRegister
438		*/
439		private int doRegister(int registrations) {
440	+	Phaser par = parent;
441	+	long s;
442		int phase;
443	<	for (;;) {
444	<	long s = getReconciledState();
445	<	phase = phaseOf(s);
446	<	int unarrived = unarrivedOf(s) + registrations;
447	<	int parties = partiesOf(s) + registrations;
448	<	if (phase < 0)
449	<	break;
450	<	if (parties > ushortMask || unarrived > ushortMask)
443	>	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
444	>	int p = partiesOf(s);
445	>	int u = unarrivedOf(s);
446	>	int unarrived = u + registrations;
447	>	int parties = p + registrations;
448	>	if (u == 0 && p != 0)  // if tripped, wait for advance
449	>	untimedWait(phase);
450	>	else if (parties > ushortMask)
451		throw new IllegalStateException(badBounds(parties, unarrived));
452	<	if (phase == phaseOf(root.state) &&
453	<	casState(s, stateFor(phase, parties, unarrived)))
454	<	break;
452	>	else if (par == null || phaseOf(root.state) == phase) {
453	>	long next = stateFor(phase, parties, unarrived);
454	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
455	>	break;
456	>	}
457		}
458		return phase;
459		}
460
461		/**
462		* Arrives at the barrier, but does not wait for others.  (You can
463	<	* in turn wait for others via {@link #awaitAdvance}).
463	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
464	>	* unenforced usage error for an unregistered party to invoke this
465	>	* method.
466		*
467	<	* @return the barrier phase number upon entry to this method, or a
421	<	* negative value if terminated
467	>	* @return the arrival phase number, or a negative value if terminated
468		* @throws IllegalStateException if not terminated and the number
469		* of unarrived parties would become negative
470		*/
471		public int arrive() {
472	+	Phaser par = parent;
473	+	long s;
474		int phase;
475	<	for (;;) {
428	<	long s = state;
429	<	phase = phaseOf(s);
430	<	if (phase < 0)
431	<	break;
475	>	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
476		int parties = partiesOf(s);
477		int unarrived = unarrivedOf(s) - 1;
478	<	if (unarrived > 0) {        // Not the last arrival
479	<	if (casState(s, s - 1)) // s-1 adds one arrival
480	<	break;
478	>	if (unarrived > 0) {                // Not the last arrival
479	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s - 1))
480	>	break;                      // s-1 adds one arrival
481		}
482	<	else if (unarrived == 0) {  // the last arrival
483	<	Phaser par = parent;
484	<	if (par == null) {      // directly trip
485	<	if (casState
486	<	(s,
487	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
488	<	((phase + 1) & phaseMask), parties))) {
489	<	releaseWaiters(phase);
490	<	break;
447	<	}
448	<	}
449	<	else {                  // cascade to parent
450	<	if (casState(s, s - 1)) { // zeroes unarrived
451	<	par.arrive();
452	<	reconcileState();
453	<	break;
454	<	}
482	>	else if (unarrived < 0)
483	>	throw new IllegalStateException(badBounds(parties, unarrived));
484	>	else if (par == null) {             // directly trip
485	>	long next = trippedStateFor(onAdvance(phase, parties) ? -1 :
486	>	((phase + 1) & phaseMask),
487	>	parties);
488	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) {
489	>	releaseWaiters(phase);
490	>	break;
491		}
492		}
493	<	else if (phase != phaseOf(root.state)) // or if unreconciled
493	>	else if (phaseOf(root.state) == phase &&
494	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, s - 1)) {
495	>	par.arrive();                   // cascade to parent
496		reconcileState();
497	<	else
498	<	throw new IllegalStateException(badBounds(parties, unarrived));
497	>	break;
498	>	}
499		}
500		return phase;
501		}
502
503		/**
504	<	* Arrives at the barrier, and deregisters from it, without
505	<	* waiting for others. Deregistration reduces number of parties
504	>	* Arrives at the barrier and deregisters from it without waiting
505	>	* for others. Deregistration reduces the number of parties
506		* required to trip the barrier in future phases.  If this phaser
507		* has a parent, and deregistration causes this phaser to have
508	<	* zero parties, this phaser is also deregistered from its parent.
508	>	* zero parties, this phaser also arrives at and is deregistered
509	>	* from its parent.  It is an unenforced usage error for an
510	>	* unregistered party to invoke this method.
511		*
512	<	* @return the current barrier phase number upon entry to
473	<	* this method, or a negative value if terminated
512	>	* @return the arrival phase number, or a negative value if terminated
513		* @throws IllegalStateException if not terminated and the number
514		* of registered or unarrived parties would become negative
515		*/
516		public int arriveAndDeregister() {
517	<	// similar code to arrive, but too different to merge
517	>	// similar to arrive, but too different to merge
518		Phaser par = parent;
519	+	long s;
520		int phase;
521	<	for (;;) {
482	<	long s = state;
483	<	phase = phaseOf(s);
484	<	if (phase < 0)
485	<	break;
521	>	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
522		int parties = partiesOf(s) - 1;
523		int unarrived = unarrivedOf(s) - 1;
524	<	if (parties >= 0) {
525	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
526	<	if (casState
527	<	(s,
528	<	stateFor(phase, parties, unarrived))) {
529	<	if (unarrived == 0) {
530	<	par.arriveAndDeregister();
531	<	reconcileState();
532	<	}
533	<	break;
534	<	}
535	<	continue;
536	<	}
537	<	if (unarrived == 0) {
502	<	if (casState
503	<	(s,
504	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
505	<	((phase + 1) & phaseMask), parties))) {
506	<	releaseWaiters(phase);
507	<	break;
508	<	}
509	<	continue;
524	>	if (unarrived > 0) {
525	>	long next = stateFor(phase, parties, unarrived);
526	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
527	>	break;
528	>	}
529	>	else if (unarrived < 0)
530	>	throw new IllegalStateException(badBounds(parties, unarrived));
531	>	else if (par == null) {
532	>	long next = trippedStateFor(onAdvance(phase, parties)? -1:
533	>	(phase + 1) & phaseMask,
534	>	parties);
535	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) {
536	>	releaseWaiters(phase);
537	>	break;
538		}
539	<	if (par != null && phase != phaseOf(root.state)) {
539	>	}
540	>	else if (phaseOf(root.state) == phase) {
541	>	long next = stateFor(phase, parties, 0);
542	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) {
543	>	if (parties == 0)
544	>	par.arriveAndDeregister();
545	>	else
546	>	par.arrive();
547		reconcileState();
548	<	continue;
548	>	break;
549		}
550		}
516	–	throw new IllegalStateException(badBounds(parties, unarrived));
551		}
552		return phase;
553		}
554
555		/**
556		* Arrives at the barrier and awaits others. Equivalent in effect
557	<	* to {@code awaitAdvance(arrive())}.  If you instead need to
558	<	* await with interruption of timeout, and/or deregister upon
559	<	* arrival, you can arrange them using analogous constructions.
557	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
558	>	* interruption or timeout, you can arrange this with an analogous
559	>	* construction using one of the other forms of the {@code
560	>	* awaitAdvance} method.  If instead you need to deregister upon
561	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
562	>	* usage error for an unregistered party to invoke this method.
563		*
564	<	* @return the phase on entry to this method
564	>	* @return the arrival phase number, or a negative number if terminated
565		* @throws IllegalStateException if not terminated and the number
566		* of unarrived parties would become negative
567		*/
#	Line 533 | Line 570 | public class Phaser {
570		}
571
572		/**
573	<	* Awaits the phase of the barrier to advance from the given
574	<	* value, or returns immediately if argument is negative or this
575	<	* barrier is terminated.
576	<	*
577	<	* @param phase the phase on entry to this method
578	<	* @return the phase on exit from this method
573	>	* Awaits the phase of the barrier to advance from the given phase
574	>	* value, returning immediately if the current phase of the
575	>	* barrier is not equal to the given phase value or this barrier
576	>	* is terminated.
577	>	*
578	>	* @param phase an arrival phase number, or negative value if
579	>	* terminated; this argument is normally the value returned by a
580	>	* previous call to {@code arrive} or its variants
581	>	* @return the next arrival phase number, or a negative value
582	>	* if terminated or argument is negative
583		*/
584		public int awaitAdvance(int phase) {
585		if (phase < 0)
586		return phase;
587	<	long s = getReconciledState();
547	<	int p = phaseOf(s);
587	>	int p = getPhase();
588		if (p != phase)
589		return p;
550	–	if (unarrivedOf(s) == 0 && parent != null)
551	–	parent.awaitAdvance(phase);
552	–	// Fall here even if parent waited, to reconcile and help release
590		return untimedWait(phase);
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, or throws InterruptedException if
597	<	* interrupted while waiting.
594	>	* Awaits the phase of the barrier to advance from the given phase
595	>	* value, throwing {@code InterruptedException} if interrupted
596	>	* while waiting, or returning immediately if the current phase of
597	>	* the barrier is not equal to the given phase value or this
598	>	* barrier is terminated.
599		*
600	<	* @param phase the phase on entry to this method
601	<	* @return the phase on exit from this method
600	>	* @param phase an arrival phase number, or negative value if
601	>	* terminated; this argument is normally the value returned by a
602	>	* previous call to {@code arrive} or its variants
603	>	* @return the next arrival phase number, or a negative value
604	>	* if terminated or argument is negative
605		* @throws InterruptedException if thread interrupted while waiting
606		*/
607		public int awaitAdvanceInterruptibly(int phase)
608		throws InterruptedException {
609		if (phase < 0)
610		return phase;
611	<	long s = getReconciledState();
571	<	int p = phaseOf(s);
611	>	int p = getPhase();
612		if (p != phase)
613		return p;
574	–	if (unarrivedOf(s) == 0 && parent != null)
575	–	parent.awaitAdvanceInterruptibly(phase);
614		return interruptibleWait(phase);
615		}
616
617		/**
618	<	* Awaits the phase of the barrier to advance from the given value
619	<	* or the given timeout elapses, or returns immediately if
620	<	* argument is negative or this barrier is terminated.
621	<	*
622	<	* @param phase the phase on entry to this method
623	<	* @return the phase on exit from this method
618	>	* Awaits the phase of the barrier to advance from the given phase
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 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		*/
637		public int awaitAdvanceInterruptibly(int phase,
638		long timeout, TimeUnit unit)
639		throws InterruptedException, TimeoutException {
640	+	long nanos = unit.toNanos(timeout);
641		if (phase < 0)
642		return phase;
643	<	long s = getReconciledState();
595	<	int p = phaseOf(s);
643	>	int p = getPhase();
644		if (p != phase)
645		return p;
646	<	if (unarrivedOf(s) == 0 && parent != null)
599	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
600	<	return timedWait(phase, unit.toNanos(timeout));
646	>	return timedWait(phase, nanos);
647		}
648
649		/**
#	Line 608 | Line 654 | public class Phaser {
654		* unexpected exceptions.
655		*/
656		public void forceTermination() {
657	<	for (;;) {
658	<	long s = getReconciledState();
659	<	int phase = phaseOf(s);
660	<	int parties = partiesOf(s);
661	<	int unarrived = unarrivedOf(s);
662	<	if (phase < 0 ||
663	<	casState(s, stateFor(-1, parties, unarrived))) {
664	<	releaseWaiters(0);
665	<	releaseWaiters(1);
620	<	if (parent != null)
621	<	parent.forceTermination();
622	<	return;
623	<	}
624	<	}
657	>	Phaser r = root;    // force at root then reconcile
658	>	long s;
659	>	while (phaseOf(s = r.state) >= 0)
660	>	UNSAFE.compareAndSwapLong(r, stateOffset, s,
661	>	stateFor(-1, partiesOf(s),
662	>	unarrivedOf(s)));
663	>	reconcileState();
664	>	releaseWaiters(0);  // ensure wakeups on both queues
665	>	releaseWaiters(1);
666		}
667
668		/**
#	Line 636 | Line 677 | public class Phaser {
677		}
678
679		/**
639	–	* Returns {@code true} if the current phase number equals the given phase.
640	–	*
641	–	* @param phase the phase
642	–	* @return {@code true} if the current phase number equals the given phase
643	–	*/
644	–	public final boolean hasPhase(int phase) {
645	–	return phaseOf(getReconciledState()) == phase;
646	–	}
647	–
648	–	/**
680		* Returns the number of parties registered at this barrier.
681		*
682		* @return the number of parties
683		*/
684		public int getRegisteredParties() {
685	<	return partiesOf(state);
685	>	return partiesOf(getReconciledState());
686		}
687
688		/**
689	<	* Returns the number of parties that have arrived at the current
690	<	* phase of this barrier.
689	>	* Returns the number of registered parties that have arrived at
690	>	* the current phase of this barrier.
691		*
692		* @return the number of arrived parties
693		*/
694		public int getArrivedParties() {
695	<	return arrivedOf(state);
695	>	return arrivedOf(getReconciledState());
696		}
697
698		/**
#	Line 671 | Line 702 | public class Phaser {
702		* @return the number of unarrived parties
703		*/
704		public int getUnarrivedParties() {
705	<	return unarrivedOf(state);
705	>	return unarrivedOf(getReconciledState());
706		}
707
708		/**
#	Line 703 | Line 734 | public class Phaser {
734		}
735
736		/**
737	<	* Overridable method to perform an action upon phase advance, and
738	<	* to control termination. This method is invoked whenever the
739	<	* barrier is tripped (and thus all other waiting parties are
740	<	* dormant). If it returns {@code true}, then, rather than advance
741	<	* the phase number, this barrier will be set to a final
742	<	* termination state, and subsequent calls to {@link #isTerminated}
743	<	* will return true.
737	>	* Overridable method to perform an action upon impending phase
738	>	* advance, and to control termination. This method is invoked
739	>	* upon arrival of the party tripping the barrier (when all other
740	>	* waiting parties are dormant).  If this method returns {@code
741	>	* true}, then, rather than advance the phase number, this barrier
742	>	* will be set to a final termination state, and subsequent calls
743	>	* to {@link #isTerminated} will return true. Any (unchecked)
744	>	* Exception or Error thrown by an invocation of this method is
745	>	* propagated to the party attempting to trip the barrier, in
746	>	* which case no advance occurs.
747	>	*
748	>	* <p>The arguments to this method provide the state of the phaser
749	>	* prevailing for the current transition.  The results and effects
750	>	* of invoking phase-related methods (including {@code getPhase}
751	>	* as well as arrival, registration, and waiting methods) from
752	>	* within {@code onAdvance} are unspecified and should not be
753	>	* relied on. Similarly, while it is possible to override this
754	>	* method to produce side-effects visible to participating tasks,
755	>	* it is in general safe to do so only in designs in which all
756	>	* parties register before any arrive, and all {@link
757	>	* #awaitAdvance} at each phase.
758		*
759	<	* <p> The default version returns {@code true} when the number of
759	>	* <p>The default version returns {@code true} when the number of
760		* registered parties is zero. Normally, overrides that arrange
761		* termination for other reasons should also preserve this
762		* property.
763		*
719	–	* <p> You may override this method to perform an action with side
720	–	* effects visible to participating tasks, but it is in general
721	–	* only sensible to do so in designs where all parties register
722	–	* before any arrive, and all {@code awaitAdvance} at each phase.
723	–	* Otherwise, you cannot ensure lack of interference. In
724	–	* particular, this method may be invoked more than once per
725	–	* transition if other parties successfully register while the
726	–	* invocation of this method is in progress, thus postponing the
727	–	* transition until those parties also arrive, re-triggering this
728	–	* method.
729	–	*
764		* @param phase the phase number on entering the barrier
765		* @param registeredParties the current number of registered parties
766		* @return {@code true} if this barrier should terminate
#	Line 767 | Line 801 | public class Phaser {
801		volatile boolean wasInterrupted = false;
802		volatile Thread thread; // nulled to cancel wait
803		QNode next;
804	+
805		QNode(Phaser phaser, int phase, boolean interruptible,
806		boolean timed, long startTime, long nanos) {
807		this.phaser = phaser;
#	Line 777 | Line 812 | public class Phaser {
812		this.nanos = nanos;
813		thread = Thread.currentThread();
814		}
815	+
816		public boolean isReleasable() {
817		return (thread == null ||
818		phaser.getPhase() != phase ||
819		(interruptible && wasInterrupted) ||
820		(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
821		}
822	+
823		public boolean block() {
824		if (Thread.interrupted()) {
825		wasInterrupted = true;
#	Line 799 | Line 836 | public class Phaser {
836		}
837		return isReleasable();
838		}
839	+
840		void signal() {
841		Thread t = thread;
842		if (t != null) {
#	Line 806 | Line 844 | public class Phaser {
844		LockSupport.unpark(t);
845		}
846		}
847	+
848		boolean doWait() {
849		if (thread != null) {
850		try {
851	<	ForkJoinPool.managedBlock(this, false);
851	>	ForkJoinPool.managedBlock(this);
852		} catch (InterruptedException ie) {
853	+	wasInterrupted = true; // can't currently happen
854		}
855		}
856		return wasInterrupted;
857		}
818	–
858		}
859
860		/**
#	Line 841 | Line 880 | public class Phaser {
880		}
881
882		/**
883	+	* The number of times to spin before blocking waiting for advance.
884	+	*/
885	+	static final int MAX_SPINS =
886	+	Runtime.getRuntime().availableProcessors() == 1 ? 0 : 1 << 8;
887	+
888	+	/**
889		* Enqueues node and waits unless aborted or signalled.
890		*
891		* @return current phase
#	Line 849 | Line 894 | public class Phaser {
894		QNode node = null;
895		boolean queued = false;
896		boolean interrupted = false;
897	+	int spins = MAX_SPINS;
898		int p;
899		while ((p = getPhase()) == phase) {
900		if (Thread.interrupted())
901		interrupted = true;
902	+	else if (spins > 0) {
903	+	if (--spins == 0)
904	+	Thread.yield();
905	+	}
906		else if (node == null)
907		node = new QNode(this, phase, false, false, 0, 0);
908		else if (!queued)
909		queued = tryEnqueue(node);
910	<	else
911	<	interrupted = node.doWait();
910	>	else if (node.doWait())
911	>	interrupted = true;
912		}
913		if (node != null)
914		node.thread = null;
#	Line 876 | Line 926 | public class Phaser {
926		QNode node = null;
927		boolean queued = false;
928		boolean interrupted = false;
929	+	int spins = MAX_SPINS;
930		int p;
931		while ((p = getPhase()) == phase && !interrupted) {
932		if (Thread.interrupted())
933		interrupted = true;
934	+	else if (spins > 0) {
935	+	if (--spins == 0)
936	+	Thread.yield();
937	+	}
938		else if (node == null)
939		node = new QNode(this, phase, true, false, 0, 0);
940		else if (!queued)
941		queued = tryEnqueue(node);
942	<	else
943	<	interrupted = node.doWait();
942	>	else if (node.doWait())
943	>	interrupted = true;
944		}
945		if (node != null)
946		node.thread = null;
#	Line 906 | Line 961 | public class Phaser {
961		QNode node = null;
962		boolean queued = false;
963		boolean interrupted = false;
964	+	int spins = MAX_SPINS;
965		int p;
966		while ((p = getPhase()) == phase && !interrupted) {
967		if (Thread.interrupted())
968		interrupted = true;
969		else if (nanos - (System.nanoTime() - startTime) <= 0)
970		break;
971	+	else if (spins > 0) {
972	+	if (--spins == 0)
973	+	Thread.yield();
974	+	}
975		else if (node == null)
976		node = new QNode(this, phase, true, true, startTime, nanos);
977		else if (!queued)
978		queued = tryEnqueue(node);
979	<	else
980	<	interrupted = node.doWait();
979	>	else if (node.doWait())
980	>	interrupted = true;
981		}
982		if (node != null)
983		node.thread = null;
#	Line 936 | Line 996 | public class Phaser {
996		private static final long stateOffset =
997		objectFieldOffset("state", Phaser.class);
998
939	–	private final boolean casState(long cmp, long val) {
940	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
941	–	}
942	–
999		private static long objectFieldOffset(String field, Class<?> klazz) {
1000		try {
1001		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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