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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.61 by jsr166, Sun Nov 28 21:21:03 2010 UTC vs.
Revision 1.67 by jsr166, Fri Dec 3 21:29:34 2010 UTC

#	Line 18 | Line 18 | import java.util.concurrent.locks.LockSu
18		* but supporting more flexible usage.
19		*
20		* <p> <b>Registration.</b> Unlike the case for other barriers, the
21	<	* number of parties <em>registered</em> to synchronize on a Phaser
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
#	Line 34 | Line 34 | import java.util.concurrent.locks.LockSu
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
37	>	* generation of a phaser has an associated phase number. The phase
38	>	* number starts at zero, and advances when all parties arrive at the
39	>	* phaser, 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
41	>	* control of actions upon arrival at a phaser 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> <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}.
48	>	*       {@link #arriveAndDeregister} record arrival.  These methods
49	>	*       do not block, but return an associated <em>arrival phase
50	>	*       number</em>; that is, the phase number of the phaser to which
51	>	*       the arrival applied. When the final party for a given phase
52	>	*       arrives, an optional action is performed and the phase
53	>	*       advances.  These actions are performed by the party
54	>	*       triggering a phase advance, and are arranged by overriding
55	>	*       method {@link #onAdvance(int, int)}, which also controls
56	>	*       termination. Overriding this method is similar to, but more
57	>	*       flexible than, providing a barrier action to a {@code
58	>	*       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.
62	>	*       the phaser 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
68	>	*       state of the phaser. 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},
#	Line 74 | Line 74 | import java.util.concurrent.locks.LockSu
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.
77	>	* <p> <b>Termination.</b> A phaser may enter a <em>termination</em>
78	>	* state in which all synchronization methods immediately return
79	>	* without updating phaser state or waiting for advance, and
80	>	* indicating (via a negative phase value) that execution is complete.
81	>	* Termination is triggered when an invocation of {@code onAdvance}
82	>	* returns {@code true}. The default implementation returns {@code
83	>	* true} if a deregistration has caused the number of registered
84	>	* parties to become zero.  As illustrated below, when phasers control
85	>	* actions with a fixed number of iterations, it is often convenient
86	>	* to override this method to cause termination when the current phase
87	>	* number reaches a threshold. Method {@link #forceTermination} is
88	>	* also available to abruptly release waiting threads and allow them
89	>	* 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
#	Line 97 | Line 97 | import java.util.concurrent.locks.LockSu
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
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
#	Line 183 | Line 183 | import java.util.concurrent.locks.LockSu
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 with upon construction:
186	>	* <p>To create a set of {@code n} tasks using a tree of phasers, you
187	>	* could use code of the following form, assuming a Task class with a
188	>	* constructor accepting a {@code Phaser} that it registers with upon
189	>	* construction. After invocation of {@code build(new Task[n], 0, n,
190	>	* new Phaser())}, these tasks could then be started, for example by
191	>	* submitting to a pool:
192		*
193		*  <pre> {@code
194	<	* void build(Task[] actions, int lo, int hi, Phaser ph) {
194	>	* void build(Task[] tasks, int lo, int hi, Phaser ph) {
195		*   if (hi - lo > TASKS_PER_PHASER) {
196		*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
197		*       int j = Math.min(i + TASKS_PER_PHASER, hi);
198	<	*       build(actions, i, j, new Phaser(ph));
198	>	*       build(tasks, i, j, new Phaser(ph));
199		*     }
200		*   } else {
201		*     for (int i = lo; i < hi; ++i)
202	<	*       actions[i] = new Task(ph);
202	>	*       tasks[i] = new Task(ph);
203		*       // assumes new Task(ph) performs ph.register()
204		*   }
205	<	* }
204	<	* // .. initially called, for n tasks via
205	<	* build(new Task[n], 0, n, new Phaser());}</pre>
205	>	* }}</pre>
206		*
207		* The best value of {@code TASKS_PER_PHASER} depends mainly on
208	<	* expected barrier synchronization rates. A value as low as four may
209	<	* be appropriate for extremely small per-barrier task bodies (thus
208	>	* expected synchronization rates. A value as low as four may
209	>	* be appropriate for extremely small per-phase task bodies (thus
210		* high rates), or up to hundreds for extremely large ones.
211		*
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 {@code IllegalStateException}. However, you can and
215	<	* should create tiered Phasers to accommodate arbitrarily large sets
215	>	* should create tiered phasers to accommodate arbitrarily large sets
216		* of participants.
217		*
218		* @since 1.7
#	Line 226 | Line 226 | public class Phaser {
226		*/
227
228		/**
229	<	* Barrier state representation. Conceptually, a barrier contains
230	<	* four values:
229	>	* Primary state representation, holding four fields:
230		*
231		* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
232		* * parties -- the number of parties to wait              (bits 16-31)
233		* * phase -- the generation of the barrier                (bits 32-62)
234		* * terminated -- set if barrier is terminated            (bit  63 / sign)
235		*
236	<	* However, to efficiently maintain atomicity, these values are
237	<	* packed into a single (atomic) long. Termination uses the sign
238	<	* bit of 32 bit representation of phase, so phase is set to -1 on
239	<	* termination. Good performance relies on keeping state decoding
240	<	* and encoding simple, and keeping race windows short.
236	>	* Except that a phaser with no registered parties is
237	>	* distinguished with the otherwise illegal state of having zero
238	>	* parties and one unarrived parties (encoded as EMPTY below).
239	>	*
240	>	* To efficiently maintain atomicity, these values are packed into
241	>	* a single (atomic) long. Good performance relies on keeping
242	>	* state decoding and encoding simple, and keeping race windows
243	>	* short.
244	>	*
245	>	* All state updates are performed via CAS except initial
246	>	* registration of a sub-phaser (i.e., one with a non-null
247	>	* parent).  In this (relatively rare) case, we use built-in
248	>	* synchronization to lock while first registering with its
249	>	* parent.
250	>	*
251	>	* The phase of a subphaser is allowed to lag that of its
252	>	* ancestors until it is actually accessed.  Method reconcileState
253	>	* is usually attempted only only when the number of unarrived
254	>	* parties appears to be zero, which indicates a potential lag in
255	>	* updating phase after the root advanced.
256		*/
257		private volatile long state;
258
#	Line 248 | Line 262 | public class Phaser {
262		private static final int  PHASE_SHIFT     = 32;
263		private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
264		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;
265		private static final long TERMINATION_BIT = 1L << 63;
266
267	+	// some special values
268	+	private static final int  ONE_ARRIVAL     = 1;
269	+	private static final int  ONE_PARTY       = 1 << PARTIES_SHIFT;
270	+	private static final int  EMPTY           = 1;
271	+
272		// The following unpacking methods are usually manually inlined
273
274		private static int unarrivedOf(long s) {
275	<	return (int)s & UNARRIVED_MASK;
275	>	int counts = (int)s;
276	>	return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK;
277		}
278
279		private static int partiesOf(long s) {
280	<	return (int)s >>> PARTIES_SHIFT;
280	>	int counts = (int)s;
281	>	return (counts == EMPTY) ? 0 : counts >>> PARTIES_SHIFT;
282		}
283
284		private static int phaseOf(long s) {
#	Line 267 | Line 286 | public class Phaser {
286		}
287
288		private static int arrivedOf(long s) {
289	<	return partiesOf(s) - unarrivedOf(s);
289	>	int counts = (int)s;
290	>	return (counts == EMPTY) ? 0 :
291	>	(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK);
292		}
293
294		/**
#	Line 276 | Line 297 | public class Phaser {
297		private final Phaser parent;
298
299		/**
300	<	* The root of phaser tree. Equals this if not in a tree.  Used to
280	<	* support faster state push-down.
300	>	* The root of phaser tree. Equals this if not in a tree.
301		*/
302		private final Phaser root;
303
#	Line 315 | Line 335 | public class Phaser {
335		* Manually tuned to speed up and minimize race windows for the
336		* common case of just decrementing unarrived field.
337		*
338	<	* @param adj - adjustment to apply to state -- either
319	<	* ONE_ARRIVAL (for arrive) or
320	<	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
338	>	* @param deregister false for arrive, true for arriveAndDeregister
339		*/
340	<	private int doArrive(long adj) {
341	<	for (;;) {
342	<	long s = state;
343	<	int unarrived = (int)s & UNARRIVED_MASK;
344	<	int phase = (int)(s >>> PHASE_SHIFT);
345	<	if (phase < 0)
346	<	return phase;
347	<	else if (unarrived == 0) {
348	<	if (reconcileState() == s)     // recheck
340	>	private int doArrive(boolean deregister) {
341	>	int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL;
342	>	long s;
343	>	int phase;
344	>	while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0) {
345	>	int counts = (int)s;
346	>	int unarrived = counts & UNARRIVED_MASK;
347	>	if (counts == EMPTY || unarrived == 0) {
348	>	if (reconcileState() == s)
349		throw new IllegalStateException(badArrive(s));
350		}
351		else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
352		if (unarrived == 1) {
353	<	long p = s & PARTIES_MASK; // unshifted parties field
354	<	long lu = p >>> PARTIES_SHIFT;
355	<	int u = (int)lu;
356	<	int nextPhase = (phase + 1) & MAX_PHASE;
357	<	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
358	<	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);
353	>	long n = s & PARTIES_MASK;       // unshifted parties field
354	>	int u = ((int)n) >>> PARTIES_SHIFT;
355	>	Phaser par = parent;
356	>	if (par != null) {
357	>	par.doArrive(u == 0);
358	>	reconcileState();
359		}
360		else {
361	<	parent.doArrive((u == 0) ?
362	<	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
363	<	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase ||
364	<	((int)(state >>> PHASE_SHIFT) != nextPhase &&
365	<	!UNSAFE.compareAndSwapLong(this, stateOffset,
366	<	s, next)))
367	<	reconcileState();
361	>	n |= (((long)((phase+1) & MAX_PHASE)) << PHASE_SHIFT);
362	>	if (onAdvance(phase, u))
363	>	n |= TERMINATION_BIT;
364	>	else if (u == 0)
365	>	n |= EMPTY;             // reset to unregistered
366	>	else
367	>	n |= (long)u;           // reset unarr to parties
368	>	// assert state == s || isTerminated();
369	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, n);
370	>	releaseWaiters(phase);
371		}
372		}
373	<	return phase;
373	>	break;
374		}
375		}
376	+	return phase;
377		}
378
379		/**
#	Line 368 | Line 385 | public class Phaser {
385		private int doRegister(int registrations) {
386		// adjustment to state
387		long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
388	<	final Phaser parent = this.parent;
388	>	Phaser par = parent;
389	>	int phase;
390		for (;;) {
391	<	long s = (parent == null) ? state : reconcileState();
392	<	int parties = (int)s >>> PARTIES_SHIFT;
393	<	int phase = (int)(s >>> PHASE_SHIFT);
394	<	if (phase < 0)
395	<	return phase;
378	<	else if (registrations > MAX_PARTIES - parties)
391	>	long s = state;
392	>	int counts = (int)s;
393	>	int parties = counts >>> PARTIES_SHIFT;
394	>	int unarrived = counts & UNARRIVED_MASK;
395	>	if (registrations > MAX_PARTIES - parties)
396		throw new IllegalStateException(badRegister(s));
397	<	else if ((parties == 0 && parent == null) || // first reg of root
398	<	((int)s & UNARRIVED_MASK) != 0) {   // not advancing
399	<	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
400	<	return phase;
401	<	}
402	<	else if (parties != 0)               // wait for onAdvance
403	<	root.internalAwaitAdvance(phase, null);
404	<	else {                               // 1st registration of child
405	<	synchronized (this) {            // register parent first
406	<	if (reconcileState() == s) { // recheck under lock
407	<	parent.doRegister(1);    // OK if throws IllegalState
408	<	for (;;) {               // simpler form of outer loop
409	<	s = reconcileState();
410	<	phase = (int)(s >>> PHASE_SHIFT);
411	<	if (phase < 0 ||
412	<	UNSAFE.compareAndSwapLong(this, stateOffset,
413	<	s, s + adj))
414	<	return phase;
415	<	}
397	>	else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0)
398	>	break;
399	>	else if (counts != EMPTY) {             // not 1st registration
400	>	if (par == null || reconcileState() == s) {
401	>	if (unarrived == 0)             // wait out advance
402	>	root.internalAwaitAdvance(phase, null);
403	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset,
404	>	s, s + adj))
405	>	break;
406	>	}
407	>	}
408	>	else if (par == null) {                 // 1st root registration
409	>	long next = (((long) phase) << PHASE_SHIFT) | adj;
410	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
411	>	break;
412	>	}
413	>	else {
414	>	synchronized (this) {               // 1st sub registration
415	>	if (state == s) {               // recheck under lock
416	>	par.doRegister(1);
417	>	do {                        // force current phase
418	>	phase = (int)(root.state >>> PHASE_SHIFT);
419	>	// assert phase < 0 || (int)state == EMPTY;
420	>	} while (!UNSAFE.compareAndSwapLong
421	>	(this, stateOffset, state,
422	>	(((long) phase) << PHASE_SHIFT) | adj));
423	>	break;
424		}
425		}
426		}
427		}
428	+	return phase;
429		}
430
431		/**
432	<	* Recursively resolves lagged phase propagation from root if necessary.
432	>	* Resolves lagged phase propagation from root if necessary.
433		*/
434		private long reconcileState() {
435	<	Phaser par = parent;
435	>	Phaser rt = root;
436		long s = state;
437	<	if (par != null) {
438	<	Phaser rt = root;
439	<	int phase, rPhase;
440	<	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
441	<	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
442	<	if ((int)(par.state >>> PHASE_SHIFT) != rPhase)
443	<	par.reconcileState();
444	<	else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
445	<	long u = s & PARTIES_MASK; // reset unarrived to parties
446	<	long next = ((((long) rPhase) << PHASE_SHIFT) | u |
447	<	(u >>> PARTIES_SHIFT));
448	<	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
437	>	if (rt != this) {
438	>	int phase;
439	>	while ((phase = (int)(rt.state >>> PHASE_SHIFT)) !=
440	>	(int)(s >>> PHASE_SHIFT)) {
441	>	// assert phase < 0 || unarrivedOf(s) == 0
442	>	long t;                             // to reread s
443	>	long p = s & PARTIES_MASK;          // unshifted parties field
444	>	long n = (((long) phase) << PHASE_SHIFT) | p;
445	>	if (phase >= 0) {
446	>	if (p == 0L)
447	>	n |= EMPTY;                 // reset to empty
448	>	else
449	>	n |= p >>> PARTIES_SHIFT;   // set unarr to parties
450		}
451	<	s = state;
451	>	if ((t = state) == s &&
452	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, s = n))
453	>	break;
454	>	s = t;
455		}
456		}
457		return s;
458		}
459
460		/**
461	<	* Creates a new Phaser without any initially registered parties,
462	<	* initial phase number 0, and no parent. Any thread using this
463	<	* Phaser will need to first register for it.
461	>	* Creates a new phaser with no initially registered parties, no
462	>	* parent, and initial phase number 0. Any thread using this
463	>	* phaser will need to first register for it.
464		*/
465		public Phaser() {
466		this(null, 0);
467		}
468
469		/**
470	<	* Creates a new Phaser with the given number of registered
471	<	* unarrived parties, initial phase number 0, and no parent.
470	>	* Creates a new phaser with the given number of registered
471	>	* unarrived parties, no parent, and initial phase number 0.
472		*
473	<	* @param parties the number of parties required to trip barrier
473	>	* @param parties the number of parties required to advance to the
474	>	* next phase
475		* @throws IllegalArgumentException if parties less than zero
476		* or greater than the maximum number of parties supported
477		*/
#	Line 451 | Line 482 | public class Phaser {
482		/**
483		* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
484		*
485	<	* @param parent the parent Phaser
485	>	* @param parent the parent phaser
486		*/
487		public Phaser(Phaser parent) {
488		this(parent, 0);
489		}
490
491		/**
492	<	* Creates a new Phaser with the given parent and number of
492	>	* Creates a new phaser with the given parent and number of
493		* registered unarrived parties. Registration and deregistration
494	<	* of this child Phaser with its parent are managed automatically.
495	<	* If the given parent is non-null, whenever this child Phaser has
494	>	* of this child phaser with its parent are managed automatically.
495	>	* If the given parent is non-null, whenever this child phaser has
496		* any registered parties (as established in this constructor,
497	<	* {@link #register}, or {@link #bulkRegister}), this child Phaser
497	>	* {@link #register}, or {@link #bulkRegister}), this child phaser
498		* is registered with its parent. Whenever the number of
499		* registered parties becomes zero as the result of an invocation
500	<	* of {@link #arriveAndDeregister}, this child Phaser is
500	>	* of {@link #arriveAndDeregister}, this child phaser is
501		* deregistered from its parent.
502		*
503	<	* @param parent the parent Phaser
504	<	* @param parties the number of parties required to trip barrier
503	>	* @param parent the parent phaser
504	>	* @param parties the number of parties required to advance to the
505	>	* next phase
506		* @throws IllegalArgumentException if parties less than zero
507		* or greater than the maximum number of parties supported
508		*/
509		public Phaser(Phaser parent, int parties) {
510		if (parties >>> PARTIES_SHIFT != 0)
511		throw new IllegalArgumentException("Illegal number of parties");
512	<	long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT);
512	>	int phase = 0;
513		this.parent = parent;
514		if (parent != null) {
515		Phaser r = parent.root;
#	Line 485 | Line 517 | public class Phaser {
517		this.evenQ = r.evenQ;
518		this.oddQ = r.oddQ;
519		if (parties != 0)
520	<	s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT;
520	>	phase = parent.doRegister(1);
521		}
522		else {
523		this.root = this;
524		this.evenQ = new AtomicReference<QNode>();
525		this.oddQ = new AtomicReference<QNode>();
526		}
527	<	this.state = s;
527	>	this.state = (parties == 0) ? ((long) EMPTY) :
528	>	((((long) phase) << PHASE_SHIFT) |
529	>	(((long) parties) << PARTIES_SHIFT) |
530	>	((long) parties));
531		}
532
533		/**
534	<	* Adds a new unarrived party to this Phaser.  If an ongoing
534	>	* Adds a new unarrived party to this phaser.  If an ongoing
535		* invocation of {@link #onAdvance} is in progress, this method
536	<	* may await its completion before returning.  If this Phaser has
537	<	* a parent, and this Phaser previously had no registered parties,
538	<	* this Phaser is also registered with its parent.
536	>	* may await its completion before returning.  If this phaser has
537	>	* a parent, and this phaser previously had no registered parties,
538	>	* this phaser is also registered with its parent.
539		*
540		* @return the arrival phase number to which this registration applied
541		* @throws IllegalStateException if attempting to register more
#	Line 511 | Line 546 | public class Phaser {
546		}
547
548		/**
549	<	* Adds the given number of new unarrived parties to this Phaser.
549	>	* Adds the given number of new unarrived parties to this phaser.
550		* If an ongoing invocation of {@link #onAdvance} is in progress,
551		* this method may await its completion before returning.  If this
552	<	* Phaser has a parent, and the given number of parities is
553	<	* greater than zero, and this Phaser previously had no registered
554	<	* parties, this Phaser is also registered with its parent.
552	>	* phaser has a parent, and the given number of parties is
553	>	* greater than zero, and this phaser previously had no registered
554	>	* parties, this phaser is also registered with its parent.
555		*
556	<	* @param parties the number of additional parties required to trip barrier
556	>	* @param parties the number of additional parties required to
557	>	* advance to the next phase
558		* @return the arrival phase number to which this registration applied
559		* @throws IllegalStateException if attempting to register more
560		* than the maximum supported number of parties
#	Line 533 | Line 569 | public class Phaser {
569		}
570
571		/**
572	<	* Arrives at the barrier, without waiting for others to arrive.
572	>	* Arrives at this phaser, without waiting for others to arrive.
573		*
574		* <p>It is a usage error for an unregistered party to invoke this
575		* method.  However, this error may result in an {@code
576		* IllegalStateException} only upon some subsequent operation on
577	<	* this Phaser, if ever.
577	>	* this phaser, if ever.
578		*
579		* @return the arrival phase number, or a negative value if terminated
580		* @throws IllegalStateException if not terminated and the number
581		* of unarrived parties would become negative
582		*/
583		public int arrive() {
584	<	return doArrive(ONE_ARRIVAL);
584	>	return doArrive(false);
585		}
586
587		/**
588	<	* Arrives at the barrier and deregisters from it without waiting
588	>	* Arrives at this phaser and deregisters from it without waiting
589		* for others to arrive. Deregistration reduces the number of
590	<	* parties required to trip the barrier in future phases.  If this
591	<	* Phaser has a parent, and deregistration causes this Phaser to
592	<	* have zero parties, this Phaser is also deregistered from its
557	<	* parent.
590	>	* parties required to advance in future phases.  If this phaser
591	>	* has a parent, and deregistration causes this phaser to have
592	>	* zero parties, this phaser is also deregistered from its parent.
593		*
594		* <p>It is a usage error for an unregistered party to invoke this
595		* method.  However, this error may result in an {@code
596		* IllegalStateException} only upon some subsequent operation on
597	<	* this Phaser, if ever.
597	>	* this phaser, if ever.
598		*
599		* @return the arrival phase number, or a negative value if terminated
600		* @throws IllegalStateException if not terminated and the number
601		* of registered or unarrived parties would become negative
602		*/
603		public int arriveAndDeregister() {
604	<	return doArrive(ONE_ARRIVAL|ONE_PARTY);
604	>	return doArrive(true);
605		}
606
607		/**
608	<	* Arrives at the barrier and awaits others. Equivalent in effect
608	>	* Arrives at this phaser and awaits others. Equivalent in effect
609		* to {@code awaitAdvance(arrive())}.  If you need to await with
610		* interruption or timeout, you can arrange this with an analogous
611		* construction using one of the other forms of the {@code
#	Line 580 | Line 615 | public class Phaser {
615		* <p>It is a usage error for an unregistered party to invoke this
616		* method.  However, this error may result in an {@code
617		* IllegalStateException} only upon some subsequent operation on
618	<	* this Phaser, if ever.
618	>	* this phaser, if ever.
619		*
620		* @return the arrival phase number, or a negative number if terminated
621		* @throws IllegalStateException if not terminated and the number
622		* of unarrived parties would become negative
623		*/
624		public int arriveAndAwaitAdvance() {
625	<	return awaitAdvance(arrive());
625	>	return awaitAdvance(doArrive(false));
626		}
627
628		/**
629	<	* Awaits the phase of the barrier to advance from the given phase
630	<	* value, returning immediately if the current phase of the
631	<	* barrier is not equal to the given phase value or this barrier
597	<	* is terminated.
629	>	* Awaits the phase of this phaser to advance from the given phase
630	>	* value, returning immediately if the current phase is not equal
631	>	* to the given phase value or this phaser is terminated.
632		*
633		* @param phase an arrival phase number, or negative value if
634		* terminated; this argument is normally the value returned by a
635	<	* previous call to {@code arrive} or its variants
635	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
636		* @return the next arrival phase number, or a negative value
637		* if terminated or argument is negative
638		*/
639		public int awaitAdvance(int phase) {
640	<	Phaser r;
640	>	Phaser rt;
641		int p = (int)(state >>> PHASE_SHIFT);
642		if (phase < 0)
643		return phase;
644	<	if (p == phase &&
645	<	(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase)
646	<	return r.internalAwaitAdvance(phase, null);
644	>	if (p == phase) {
645	>	if ((p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase)
646	>	return rt.internalAwaitAdvance(phase, null);
647	>	reconcileState();
648	>	}
649		return p;
650		}
651
652		/**
653	<	* Awaits the phase of the barrier to advance from the given phase
653	>	* Awaits the phase of this phaser to advance from the given phase
654		* value, throwing {@code InterruptedException} if interrupted
655	<	* while waiting, or returning immediately if the current phase of
656	<	* the barrier is not equal to the given phase value or this
657	<	* barrier is terminated.
655	>	* while waiting, or returning immediately if the current phase is
656	>	* not equal to the given phase value or this phaser is
657	>	* terminated.
658		*
659		* @param phase an arrival phase number, or negative value if
660		* terminated; this argument is normally the value returned by a
661	<	* previous call to {@code arrive} or its variants
661	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
662		* @return the next arrival phase number, or a negative value
663		* if terminated or argument is negative
664		* @throws InterruptedException if thread interrupted while waiting
665		*/
666		public int awaitAdvanceInterruptibly(int phase)
667		throws InterruptedException {
668	<	Phaser r;
668	>	Phaser rt;
669		int p = (int)(state >>> PHASE_SHIFT);
670		if (phase < 0)
671		return phase;
672	<	if (p == phase &&
673	<	(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) {
674	<	QNode node = new QNode(this, phase, true, false, 0L);
675	<	p = r.internalAwaitAdvance(phase, node);
676	<	if (node.wasInterrupted)
677	<	throw new InterruptedException();
672	>	if (p == phase) {
673	>	if ((p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
674	>	QNode node = new QNode(this, phase, true, false, 0L);
675	>	p = rt.internalAwaitAdvance(phase, node);
676	>	if (node.wasInterrupted)
677	>	throw new InterruptedException();
678	>	}
679	>	else
680	>	reconcileState();
681		}
682		return p;
683		}
684
685		/**
686	<	* Awaits the phase of the barrier to advance from the given phase
686	>	* Awaits the phase of this phaser to advance from the given phase
687		* value or the given timeout to elapse, throwing {@code
688		* InterruptedException} if interrupted while waiting, or
689	<	* returning immediately if the current phase of the barrier is
690	<	* not equal to the given phase value or this barrier is
652	<	* terminated.
689	>	* returning immediately if the current phase is not equal to the
690	>	* given phase value or this phaser is terminated.
691		*
692		* @param phase an arrival phase number, or negative value if
693		* terminated; this argument is normally the value returned by a
694	<	* previous call to {@code arrive} or its variants
694	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
695		* @param timeout how long to wait before giving up, in units of
696		*        {@code unit}
697		* @param unit a {@code TimeUnit} determining how to interpret the
#	Line 667 | Line 705 | public class Phaser {
705		long timeout, TimeUnit unit)
706		throws InterruptedException, TimeoutException {
707		long nanos = unit.toNanos(timeout);
708	<	Phaser r;
708	>	Phaser rt;
709		int p = (int)(state >>> PHASE_SHIFT);
710		if (phase < 0)
711		return phase;
712	<	if (p == phase &&
713	<	(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) {
714	<	QNode node = new QNode(this, phase, true, true, nanos);
715	<	p = r.internalAwaitAdvance(phase, node);
716	<	if (node.wasInterrupted)
717	<	throw new InterruptedException();
718	<	else if (p == phase)
719	<	throw new TimeoutException();
712	>	if (p == phase) {
713	>	if ((p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
714	>	QNode node = new QNode(this, phase, true, true, nanos);
715	>	p = rt.internalAwaitAdvance(phase, node);
716	>	if (node.wasInterrupted)
717	>	throw new InterruptedException();
718	>	else if (p == phase)
719	>	throw new TimeoutException();
720	>	}
721	>	else
722	>	reconcileState();
723		}
724		return p;
725		}
726
727		/**
728	<	* Forces this barrier to enter termination state.  Counts of
729	<	* arrived and registered parties are unaffected.  If this Phaser
730	<	* is a member of a tiered set of Phasers, then all of the Phasers
731	<	* in the set are terminated.  If this Phaser is already
732	<	* terminated, this method has no effect.  This method may be
733	<	* useful for coordinating recovery after one or more tasks
734	<	* encounter unexpected exceptions.
728	>	* Forces this phaser to enter termination state.  Counts of
729	>	* registered parties are unaffected.  If this phaser is a member
730	>	* of a tiered set of phasers, then all of the phasers in the set
731	>	* are terminated.  If this phaser is already terminated, this
732	>	* method has no effect.  This method may be useful for
733	>	* coordinating recovery after one or more tasks encounter
734	>	* unexpected exceptions.
735		*/
736		public void forceTermination() {
737		// Only need to change root state
738		final Phaser root = this.root;
739		long s;
740		while ((s = root.state) >= 0) {
741	<	if (UNSAFE.compareAndSwapLong(root, stateOffset,
742	<	s, s | TERMINATION_BIT)) {
741	>	long next = (s & ~(long)(MAX_PARTIES)) | TERMINATION_BIT;
742	>	if (UNSAFE.compareAndSwapLong(root, stateOffset, s, next)) {
743		releaseWaiters(0); // signal all threads
744		releaseWaiters(1);
745		return;
#	Line 709 | Line 750 | public class Phaser {
750		/**
751		* Returns the current phase number. The maximum phase number is
752		* {@code Integer.MAX_VALUE}, after which it restarts at
753	<	* zero. Upon termination, the phase number is negative.
753	>	* zero. Upon termination, the phase number is negative,
754	>	* in which case the prevailing phase prior to termination
755	>	* may be obtained via {@code getPhase() + Integer.MIN_VALUE}.
756		*
757		* @return the phase number, or a negative value if terminated
758		*/
#	Line 718 | Line 761 | public class Phaser {
761		}
762
763		/**
764	<	* Returns the number of parties registered at this barrier.
764	>	* Returns the number of parties registered at this phaser.
765		*
766		* @return the number of parties
767		*/
#	Line 728 | Line 771 | public class Phaser {
771
772		/**
773		* Returns the number of registered parties that have arrived at
774	<	* the current phase of this barrier.
774	>	* the current phase of this phaser.
775		*
776		* @return the number of arrived parties
777		*/
778		public int getArrivedParties() {
779	<	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());
779	>	return arrivedOf(reconcileState());
780		}
781
782		/**
783		* Returns the number of registered parties that have not yet
784	<	* arrived at the current phase of this barrier.
784	>	* arrived at the current phase of this phaser.
785		*
786		* @return the number of unarrived parties
787		*/
788		public int getUnarrivedParties() {
789	<	int u = unarrivedOf(state);
751	<	return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState());
789	>	return unarrivedOf(reconcileState());
790		}
791
792		/**
793	<	* Returns the parent of this Phaser, or {@code null} if none.
793	>	* Returns the parent of this phaser, or {@code null} if none.
794		*
795	<	* @return the parent of this Phaser, or {@code null} if none
795	>	* @return the parent of this phaser, or {@code null} if none
796		*/
797		public Phaser getParent() {
798		return parent;
799		}
800
801		/**
802	<	* Returns the root ancestor of this Phaser, which is the same as
803	<	* this Phaser if it has no parent.
802	>	* Returns the root ancestor of this phaser, which is the same as
803	>	* this phaser if it has no parent.
804		*
805	<	* @return the root ancestor of this Phaser
805	>	* @return the root ancestor of this phaser
806		*/
807		public Phaser getRoot() {
808		return root;
809		}
810
811		/**
812	<	* Returns {@code true} if this barrier has been terminated.
812	>	* Returns {@code true} if this phaser has been terminated.
813		*
814	<	* @return {@code true} if this barrier has been terminated
814	>	* @return {@code true} if this phaser has been terminated
815		*/
816		public boolean isTerminated() {
817		return root.state < 0L;
#	Line 782 | Line 820 | public class Phaser {
820		/**
821		* Overridable method to perform an action upon impending phase
822		* advance, and to control termination. This method is invoked
823	<	* upon arrival of the party tripping the barrier (when all other
823	>	* upon arrival of the party advancing this phaser (when all other
824		* waiting parties are dormant).  If this method returns {@code
825	<	* true}, then, rather than advance the phase number, this barrier
826	<	* will be set to a final termination state, and subsequent calls
827	<	* to {@link #isTerminated} will return true. Any (unchecked)
828	<	* Exception or Error thrown by an invocation of this method is
829	<	* propagated to the party attempting to trip the barrier, in
830	<	* which case no advance occurs.
825	>	* true}, this phaser will be set to a final termination state
826	>	* upon advance, and subsequent calls to {@link #isTerminated}
827	>	* will return true. Any (unchecked) Exception or Error thrown by
828	>	* an invocation of this method is propagated to the party
829	>	* attempting to advance this phaser, in which case no advance
830	>	* occurs.
831		*
832	<	* <p>The arguments to this method provide the state of the Phaser
832	>	* <p>The arguments to this method provide the state of the phaser
833		* prevailing for the current transition.  The effects of invoking
834	<	* arrival, registration, and waiting methods on this Phaser from
834	>	* arrival, registration, and waiting methods on this phaser from
835		* within {@code onAdvance} are unspecified and should not be
836		* relied on.
837		*
838	<	* <p>If this Phaser is a member of a tiered set of Phasers, then
839	<	* {@code onAdvance} is invoked only for its root Phaser on each
838	>	* <p>If this phaser is a member of a tiered set of phasers, then
839	>	* {@code onAdvance} is invoked only for its root phaser on each
840		* advance.
841		*
842		* <p>To support the most common use cases, the default
#	Line 814 | Line 852 | public class Phaser {
852		*   protected boolean onAdvance(int phase, int parties) { return false; }
853		* }}</pre>
854		*
855	<	* @param phase the phase number on entering the barrier
855	>	* @param phase the current phase number on entry to this method,
856	>	* before this phaser is advanced
857		* @param registeredParties the current number of registered parties
858	<	* @return {@code true} if this barrier should terminate
858	>	* @return {@code true} if this phaser should terminate
859		*/
860		protected boolean onAdvance(int phase, int registeredParties) {
861	<	return registeredParties <= 0;
861	>	return registeredParties == 0;
862		}
863
864		/**
865	<	* Returns a string identifying this Phaser, as well as its
865	>	* Returns a string identifying this phaser, as well as its
866		* state.  The state, in brackets, includes the String {@code
867		* "phase = "} followed by the phase number, {@code "parties = "}
868		* followed by the number of registered parties, and {@code
869		* "arrived = "} followed by the number of arrived parties.
870		*
871	<	* @return a string identifying this barrier, as well as its state
871	>	* @return a string identifying this phaser, as well as its state
872		*/
873		public String toString() {
874		return stateToString(reconcileState());
#	Line 851 | Line 890 | public class Phaser {
890		* Removes and signals threads from queue for phase.
891		*/
892		private void releaseWaiters(int phase) {
893	<	AtomicReference<QNode> head = queueFor(phase);
894	<	QNode q;
895	<	int p;
893	>	QNode q;   // first element of queue
894	>	int p;     // its phase
895	>	Thread t;  // its thread
896	>	//        assert phase != phaseOf(root.state);
897	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
898		while ((q = head.get()) != null &&
899	<	((p = q.phase) == phase ||
900	<	(int)(root.state >>> PHASE_SHIFT) != p)) {
901	<	if (head.compareAndSet(q, q.next))
902	<	q.signal();
899	>	q.phase != (int)(root.state >>> PHASE_SHIFT)) {
900	>	if (head.compareAndSet(q, q.next) &&
901	>	(t = q.thread) != null) {
902	>	q.thread = null;
903	>	LockSupport.unpark(t);
904	>	}
905		}
906		}
907
#	Line 873 | Line 916 | public class Phaser {
916		* avoid it when threads regularly arrive: When a thread in
917		* internalAwaitAdvance notices another arrival before blocking,
918		* and there appear to be enough CPUs available, it spins
919	<	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
920	<	* uniprocessors, there is at least one intervening Thread.yield
878	<	* before blocking. The value trades off good-citizenship vs big
879	<	* unnecessary slowdowns.
919	>	* SPINS_PER_ARRIVAL more times before blocking. The value trades
920	>	* off good-citizenship vs big unnecessary slowdowns.
921		*/
922		static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
923
#	Line 890 | Line 931 | public class Phaser {
931		* @return current phase
932		*/
933		private int internalAwaitAdvance(int phase, QNode node) {
934	<	boolean queued = false;      // true when node is enqueued
935	<	int lastUnarrived = -1;      // to increase spins upon change
934	>	releaseWaiters(phase-1);          // ensure old queue clean
935	>	boolean queued = false;           // true when node is enqueued
936	>	int lastUnarrived = 0;            // to increase spins upon change
937		int spins = SPINS_PER_ARRIVAL;
938		long s;
939		int p;
940		while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
941	<	int unarrived = (int)s & UNARRIVED_MASK;
942	<	if (unarrived != lastUnarrived) {
943	<	if (lastUnarrived == -1) // ensure old queue clean
944	<	releaseWaiters(phase-1);
903	<	if ((lastUnarrived = unarrived) < NCPU)
941	>	if (node == null) {           // spinning in noninterruptible mode
942	>	int unarrived = (int)s & UNARRIVED_MASK;
943	>	if (unarrived != lastUnarrived &&
944	>	(lastUnarrived = unarrived) < NCPU)
945		spins += SPINS_PER_ARRIVAL;
946	<	}
947	<	else if (spins > 0) {
948	<	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
949	<	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);
946	>	boolean interrupted = Thread.interrupted();
947	>	if (interrupted || --spins < 0) { // need node to record intr
948	>	node = new QNode(this, phase, false, false, 0L);
949	>	node.wasInterrupted = interrupted;
950		}
951		}
952	+	else if (node.isReleasable()) // done or aborted
953	+	break;
954	+	else if (!queued) {           // push onto queue
955	+	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
956	+	QNode q = node.next = head.get();
957	+	if ((q == null || q.phase == phase) &&
958	+	(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq
959	+	queued = head.compareAndSet(q, node);
960	+	}
961		else {
962		try {
963		ForkJoinPool.managedBlock(node);
#	Line 935 | Line 969 | public class Phaser {
969
970		if (node != null) {
971		if (node.thread != null)
972	<	node.thread = null; // disable unpark() in node.signal
973	<	if (!node.interruptible && node.wasInterrupted)
972	>	node.thread = null;       // avoid need for unpark()
973	>	if (node.wasInterrupted && !node.interruptible)
974		Thread.currentThread().interrupt();
975	+	if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase)
976	+	return p;                 // recheck abort
977		}
978	<	if (p != phase)
943	<	releaseWaiters(phase);
978	>	releaseWaiters(phase);
979		return p;
980		}
981
#	Line 965 | Line 1000 | public class Phaser {
1000		this.interruptible = interruptible;
1001		this.nanos = nanos;
1002		this.timed = timed;
1003	<	this.lastTime = timed? System.nanoTime() : 0L;
1003	>	this.lastTime = timed ? System.nanoTime() : 0L;
1004		thread = Thread.currentThread();
1005		}
1006
1007		public boolean isReleasable() {
1008	<	Thread t = thread;
1009	<	if (t != null) {
1010	<	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;
1008	>	if (thread == null)
1009	>	return true;
1010	>	if (phaser.getPhase() != phase) {
1011		thread = null;
1012	+	return true;
1013		}
1014	<	return true;
1014	>	if (Thread.interrupted())
1015	>	wasInterrupted = true;
1016	>	if (wasInterrupted && interruptible) {
1017	>	thread = null;
1018	>	return true;
1019	>	}
1020	>	if (timed) {
1021	>	if (nanos > 0L) {
1022	>	long now = System.nanoTime();
1023	>	nanos -= now - lastTime;
1024	>	lastTime = now;
1025	>	}
1026	>	if (nanos <= 0L) {
1027	>	thread = null;
1028	>	return true;
1029	>	}
1030	>	}
1031	>	return false;
1032		}
1033
1034		public boolean block() {
#	Line 1005 | Line 1040 | public class Phaser {
1040		LockSupport.parkNanos(this, nanos);
1041		return isReleasable();
1042		}
1008	–
1009	–	void signal() {
1010	–	Thread t = thread;
1011	–	if (t != null) {
1012	–	thread = null;
1013	–	LockSupport.unpark(t);
1014	–	}
1015	–	}
1043		}
1044
1045		// Unsafe mechanics

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