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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.49 by dl, Fri Nov 5 23:01:47 2010 UTC vs.
Revision 1.68 by dl, Sat Dec 4 15:25:08 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	<	import java.util.concurrent.*;
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
#	Line 33 | 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 73 | 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}.  As illustrated below, when
77	>	* <p> <b>Termination.</b> A phaser may enter a <em>termination</em>
78	>	* state, that may be checked using method {@link #isTerminated}. Upon
79	>	* termination, all synchronization methods immediately return without
80	>	* waiting for advance, as indicated by a negative return
81	>	* value. Similarly, attempts to register upon termination have no
82	>	* effect.  Termination is triggered when an invocation of {@code
83	>	* onAdvance} returns {@code true}. The default implementation returns
84	>	* {@code true} if a deregistration has caused the number of
85	>	* registered parties to become zero.  As illustrated below, when
86		* phasers control actions with a fixed number of iterations, it is
87		* often convenient to override this method to cause termination when
88		* the current phase number reaches a threshold. Method {@link
89		* #forceTermination} is also available to abruptly release waiting
90		* threads and allow them to terminate.
91		*
92	<	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
93	<	* in tree structures) to reduce contention. Phasers with large
94	<	* numbers of parties that would otherwise experience heavy
92	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
93	>	* constructed in tree structures) to reduce contention. Phasers with
94	>	* large numbers of parties that would otherwise experience heavy
95		* synchronization contention costs may instead be set up so that
96		* groups of sub-phasers share a common parent.  This may greatly
97		* increase throughput even though it incurs greater per-operation
98		* overhead.
99		*
100	+	* <p>In a tree of tiered phasers, registration and deregistration of
101	+	* child phasers with their parent are managed automatically.
102	+	* Whenever the number of registered parties of a child phaser becomes
103	+	* non-zero (as established in the {@link #Phaser(Phaser,int)}
104	+	* constructor, {@link #register}, or {@link #bulkRegister}), the
105	+	* child phaser is registered with its parent.  Whenever the number of
106	+	* registered parties becomes zero as the result of an invocation of
107	+	* {@link #arriveAndDeregister}, the child phaser is deregistered
108	+	* from its parent.
109	+	*
110		* <p><b>Monitoring.</b> While synchronization methods may be invoked
111		* only by registered parties, the current state of a phaser may be
112		* monitored by any caller.  At any given moment there are {@link
#	Line 180 | Line 194 | import java.util.concurrent.locks.LockSu
194		* }}</pre>
195		*
196		*
197	<	* <p>To create a set of tasks using a tree of phasers,
198	<	* you could use code of the following form, assuming a
199	<	* Task class with a constructor accepting a phaser that
200	<	* it registers with upon construction:
197	>	* <p>To create a set of {@code n} tasks using a tree of phasers, you
198	>	* could use code of the following form, assuming a Task class with a
199	>	* constructor accepting a {@code Phaser} that it registers with upon
200	>	* construction. After invocation of {@code build(new Task[n], 0, n,
201	>	* new Phaser())}, these tasks could then be started, for example by
202	>	* submitting to a pool:
203		*
204		*  <pre> {@code
205	<	* void build(Task[] actions, int lo, int hi, Phaser ph) {
205	>	* void build(Task[] tasks, int lo, int hi, Phaser ph) {
206		*   if (hi - lo > TASKS_PER_PHASER) {
207		*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
208		*       int j = Math.min(i + TASKS_PER_PHASER, hi);
209	<	*       build(actions, i, j, new Phaser(ph));
209	>	*       build(tasks, i, j, new Phaser(ph));
210		*     }
211		*   } else {
212		*     for (int i = lo; i < hi; ++i)
213	<	*       actions[i] = new Task(ph);
213	>	*       tasks[i] = new Task(ph);
214		*       // assumes new Task(ph) performs ph.register()
215		*   }
216	<	* }
201	<	* // .. initially called, for n tasks via
202	<	* build(new Task[n], 0, n, new Phaser());}</pre>
216	>	* }}</pre>
217		*
218		* The best value of {@code TASKS_PER_PHASER} depends mainly on
219	<	* expected barrier synchronization rates. A value as low as four may
220	<	* be appropriate for extremely small per-barrier task bodies (thus
219	>	* expected synchronization rates. A value as low as four may
220	>	* be appropriate for extremely small per-phase task bodies (thus
221		* high rates), or up to hundreds for extremely large ones.
222		*
223		* <p><b>Implementation notes</b>: This implementation restricts the
#	Line 223 | Line 237 | public class Phaser {
237		*/
238
239		/**
240	<	* Barrier state representation. Conceptually, a barrier contains
227	<	* four values:
240	>	* Primary state representation, holding four fields:
241		*
242	<	* * parties -- the number of parties to wait (16 bits)
243	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
244	<	* * phase -- the generation of the barrier (31 bits)
245	<	* * terminated -- set if barrier is terminated (1 bit)
246	<	*
247	<	* However, to efficiently maintain atomicity, these values are
248	<	* packed into a single (atomic) long. Termination uses the sign
249	<	* bit of 32 bit representation of phase, so phase is set to -1 on
250	<	* termination. Good performance relies on keeping state decoding
251	<	* and encoding simple, and keeping race windows short.
252	<	*
253	<	* Note: there are some cheats in arrive() that rely on unarrived
254	<	* count being lowest 16 bits.
242	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
243	>	* * parties -- the number of parties to wait              (bits 16-31)
244	>	* * phase -- the generation of the barrier                (bits 32-62)
245	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
246	>	*
247	>	* Except that a phaser with no registered parties is
248	>	* distinguished with the otherwise illegal state of having zero
249	>	* parties and one unarrived parties (encoded as EMPTY below).
250	>	*
251	>	* To efficiently maintain atomicity, these values are packed into
252	>	* a single (atomic) long. Good performance relies on keeping
253	>	* state decoding and encoding simple, and keeping race windows
254	>	* short.
255	>	*
256	>	* All state updates are performed via CAS except initial
257	>	* registration of a sub-phaser (i.e., one with a non-null
258	>	* parent).  In this (relatively rare) case, we use built-in
259	>	* synchronization to lock while first registering with its
260	>	* parent.
261	>	*
262	>	* The phase of a subphaser is allowed to lag that of its
263	>	* ancestors until it is actually accessed.  Method reconcileState
264	>	* is usually attempted only only when the number of unarrived
265	>	* parties appears to be zero, which indicates a potential lag in
266	>	* updating phase after the root advanced.
267		*/
268		private volatile long state;
269
270	<	private static final int ushortMask = 0xffff;
271	<	private static final int phaseMask  = 0x7fffffff;
270	>	private static final int  MAX_PARTIES     = 0xffff;
271	>	private static final int  MAX_PHASE       = 0x7fffffff;
272	>	private static final int  PARTIES_SHIFT   = 16;
273	>	private static final int  PHASE_SHIFT     = 32;
274	>	private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
275	>	private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
276	>	private static final long TERMINATION_BIT = 1L << 63;
277	>
278	>	// some special values
279	>	private static final int  ONE_ARRIVAL     = 1;
280	>	private static final int  ONE_PARTY       = 1 << PARTIES_SHIFT;
281	>	private static final int  EMPTY           = 1;
282	>
283	>	// The following unpacking methods are usually manually inlined
284
285		private static int unarrivedOf(long s) {
286	<	return (int) (s & ushortMask);
286	>	int counts = (int)s;
287	>	return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK;
288		}
289
290		private static int partiesOf(long s) {
291	<	return ((int) s) >>> 16;
291	>	return (int)s >>> PARTIES_SHIFT;
292		}
293
294		private static int phaseOf(long s) {
295	<	return (int) (s >>> 32);
295	>	return (int) (s >>> PHASE_SHIFT);
296		}
297
298		private static int arrivedOf(long s) {
299	<	return partiesOf(s) - unarrivedOf(s);
300	<	}
301	<
264	<	private static long stateFor(int phase, int parties, int unarrived) {
265	<	return ((((long) phase) << 32) | (((long) parties) << 16) |
266	<	(long) unarrived);
267	<	}
268	<
269	<	private static long trippedStateFor(int phase, int parties) {
270	<	long lp = (long) parties;
271	<	return (((long) phase) << 32) | (lp << 16) | lp;
272	<	}
273	<
274	<	/**
275	<	* Returns message string for bad bounds exceptions.
276	<	*/
277	<	private static String badBounds(int parties, int unarrived) {
278	<	return ("Attempt to set " + unarrived +
279	<	" unarrived of " + parties + " parties");
299	>	int counts = (int)s;
300	>	return (counts == EMPTY) ? 0 :
301	>	(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK);
302		}
303
304		/**
#	Line 285 | Line 307 | public class Phaser {
307		private final Phaser parent;
308
309		/**
310	<	* The root of phaser tree. Equals this if not in a tree.  Used to
289	<	* support faster state push-down.
310	>	* The root of phaser tree. Equals this if not in a tree.
311		*/
312		private final Phaser root;
313
293	–	// Wait queues
294	–
314		/**
315		* Heads of Treiber stacks for waiting threads. To eliminate
316		* contention when releasing some threads while adding others, we
317		* use two of them, alternating across even and odd phases.
318		* Subphasers share queues with root to speed up releases.
319		*/
320	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
321	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
320	>	private final AtomicReference<QNode> evenQ;
321	>	private final AtomicReference<QNode> oddQ;
322
323		private AtomicReference<QNode> queueFor(int phase) {
324	<	Phaser r = root;
306	<	return ((phase & 1) == 0) ? r.evenQ : r.oddQ;
324	>	return ((phase & 1) == 0) ? evenQ : oddQ;
325		}
326
327		/**
328	<	* Returns current state, first resolving lagged propagation from
311	<	* root if necessary.
328	>	* Returns message string for bounds exceptions on arrival.
329		*/
330	<	private long getReconciledState() {
331	<	return (parent == null) ? state : reconcileState();
330	>	private String badArrive(long s) {
331	>	return "Attempted arrival of unregistered party for " +
332	>	stateToString(s);
333		}
334
335		/**
336	<	* Recursively resolves state.
336	>	* Returns message string for bounds exceptions on registration.
337		*/
338	<	private long reconcileState() {
339	<	Phaser par = parent;
340	<	long s = state;
341	<	if (par != null) {
342	<	int phase, rootPhase;
343	<	while ((phase = phaseOf(s)) >= 0 &&
344	<	(rootPhase = phaseOf(root.state)) != phase &&
345	<	(rootPhase < 0 || unarrivedOf(s) == 0)) {
346	<	long parentState = par.getReconciledState();
347	<	int parentPhase = phaseOf(parentState);
348	<	int parties = partiesOf(s);
349	<	long next = trippedStateFor(parentPhase, parties);
350	<	if (phaseOf(root.state) == rootPhase &&
351	<	parentPhase != phase &&
352	<	state == s && casState(s, next)) {
338	>	private String badRegister(long s) {
339	>	return "Attempt to register more than " +
340	>	MAX_PARTIES + " parties for " + stateToString(s);
341	>	}
342	>
343	>	/**
344	>	* Main implementation for methods arrive and arriveAndDeregister.
345	>	* Manually tuned to speed up and minimize race windows for the
346	>	* common case of just decrementing unarrived field.
347	>	*
348	>	* @param deregister false for arrive, true for arriveAndDeregister
349	>	*/
350	>	private int doArrive(boolean deregister) {
351	>	int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL;
352	>	final Phaser root = this.root;
353	>	for (;;) {
354	>	long s = (root == this) ? state : reconcileState();
355	>	int phase = (int)(s >>> PHASE_SHIFT);
356	>	int counts = (int)s;
357	>	int unarrived = (counts & UNARRIVED_MASK) - 1;
358	>	if (phase < 0)
359	>	return phase;
360	>	else if (counts == EMPTY || unarrived < 0) {
361	>	if (root == this || reconcileState() == s)
362	>	throw new IllegalStateException(badArrive(s));
363	>	}
364	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
365	>	if (unarrived == 0) {
366	>	long n = s & PARTIES_MASK;  // base of next state
367	>	int nextUnarrived = ((int)n) >>> PARTIES_SHIFT;
368	>	if (root != this)
369	>	return parent.doArrive(nextUnarrived == 0);
370	>	if (onAdvance(phase, nextUnarrived))
371	>	n |= TERMINATION_BIT;
372	>	else if (nextUnarrived == 0)
373	>	n |= EMPTY;
374	>	else
375	>	n |= nextUnarrived;
376	>	n |= ((long)((phase + 1) & MAX_PHASE)) << PHASE_SHIFT;
377	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, n);
378		releaseWaiters(phase);
379	<	if (parties == 0) // exit if the final deregistration
379	>	}
380	>	return phase;
381	>	}
382	>	}
383	>	}
384	>
385	>	/**
386	>	* Implementation of register, bulkRegister
387	>	*
388	>	* @param registrations number to add to both parties and
389	>	* unarrived fields. Must be greater than zero.
390	>	*/
391	>	private int doRegister(int registrations) {
392	>	// adjustment to state
393	>	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
394	>	Phaser par = parent;
395	>	int phase;
396	>	for (;;) {
397	>	long s = state;
398	>	int counts = (int)s;
399	>	int parties = counts >>> PARTIES_SHIFT;
400	>	int unarrived = counts & UNARRIVED_MASK;
401	>	if (registrations > MAX_PARTIES - parties)
402	>	throw new IllegalStateException(badRegister(s));
403	>	else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0)
404	>	break;
405	>	else if (counts != EMPTY) {             // not 1st registration
406	>	if (par == null || reconcileState() == s) {
407	>	if (unarrived == 0)             // wait out advance
408	>	root.internalAwaitAdvance(phase, null);
409	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset,
410	>	s, s + adj))
411	>	break;
412	>	}
413	>	}
414	>	else if (par == null) {                 // 1st root registration
415	>	long next = (((long) phase) << PHASE_SHIFT) | adj;
416	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
417	>	break;
418	>	}
419	>	else {
420	>	synchronized (this) {               // 1st sub registration
421	>	if (state == s) {               // recheck under lock
422	>	par.doRegister(1);
423	>	do {                        // force current phase
424	>	phase = (int)(root.state >>> PHASE_SHIFT);
425	>	// assert phase < 0 || (int)state == EMPTY;
426	>	} while (!UNSAFE.compareAndSwapLong
427	>	(this, stateOffset, state,
428	>	(((long) phase) << PHASE_SHIFT) | adj));
429		break;
430	+	}
431	+	}
432	+	}
433	+	}
434	+	return phase;
435	+	}
436	+
437	+	/**
438	+	* Resolves lagged phase propagation from root if necessary.
439	+	*/
440	+	private long reconcileState() {
441	+	Phaser rt = root;
442	+	long s = state;
443	+	if (rt != this) {
444	+	int phase;
445	+	while ((phase = (int)(rt.state >>> PHASE_SHIFT)) !=
446	+	(int)(s >>> PHASE_SHIFT)) {
447	+	// assert phase < 0 || unarrivedOf(s) == 0
448	+	long t;                             // to reread s
449	+	long p = s & PARTIES_MASK;          // unshifted parties field
450	+	long n = (((long) phase) << PHASE_SHIFT) | p;
451	+	if (phase >= 0) {
452	+	if (p == 0L)
453	+	n |= EMPTY;                 // reset to empty
454	+	else
455	+	n |= p >>> PARTIES_SHIFT;   // set unarr to parties
456		}
457	<	s = state;
457	>	if ((t = state) == s &&
458	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, s = n))
459	>	break;
460	>	s = t;
461		}
462		}
463		return s;
464		}
465
466		/**
467	<	* Creates a new phaser without any initially registered parties,
468	<	* initial phase number 0, and no parent. Any thread using this
467	>	* Creates a new phaser with no initially registered parties, no
468	>	* parent, and initial phase number 0. Any thread using this
469		* phaser will need to first register for it.
470		*/
471		public Phaser() {
472	<	this(null);
472	>	this(null, 0);
473		}
474
475		/**
476		* Creates a new phaser with the given number of registered
477	<	* unarrived parties, initial phase number 0, and no parent.
477	>	* unarrived parties, no parent, and initial phase number 0.
478		*
479	<	* @param parties the number of parties required to trip barrier
479	>	* @param parties the number of parties required to advance to the
480	>	* next phase
481		* @throws IllegalArgumentException if parties less than zero
482		* or greater than the maximum number of parties supported
483		*/
#	Line 364 | Line 486 | public class Phaser {
486		}
487
488		/**
489	<	* Creates a new phaser with the given parent, without any
368	<	* initially registered parties. If parent is non-null this phaser
369	<	* is registered with the parent and its initial phase number is
370	<	* the same as that of parent phaser.
489	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
490		*
491		* @param parent the parent phaser
492		*/
493		public Phaser(Phaser parent) {
494	<	int phase = 0;
376	<	this.parent = parent;
377	<	if (parent != null) {
378	<	this.root = parent.root;
379	<	phase = parent.register();
380	<	}
381	<	else
382	<	this.root = this;
383	<	this.state = trippedStateFor(phase, 0);
494	>	this(parent, 0);
495		}
496
497		/**
498		* Creates a new phaser with the given parent and number of
499	<	* registered unarrived parties. If parent is non-null, this phaser
500	<	* is registered with the parent and its initial phase number is
501	<	* the same as that of parent phaser.
499	>	* registered unarrived parties.  When the given parent is non-null
500	>	* and the given number of parties is greater than zero, this
501	>	* child phaser is registered with its parent.
502		*
503		* @param parent the parent phaser
504	<	* @param parties the number of parties required to trip barrier
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 < 0 || parties > ushortMask)
510	>	if (parties >>> PARTIES_SHIFT != 0)
511		throw new IllegalArgumentException("Illegal number of parties");
512		int phase = 0;
513		this.parent = parent;
514		if (parent != null) {
515	<	this.root = parent.root;
516	<	phase = parent.register();
515	>	final Phaser root = parent.root;
516	>	this.root = root;
517	>	this.evenQ = root.evenQ;
518	>	this.oddQ = root.oddQ;
519	>	if (parties != 0)
520	>	phase = parent.doRegister(1);
521		}
522	<	else
522	>	else {
523		this.root = this;
524	<	this.state = trippedStateFor(phase, parties);
524	>	this.evenQ = new AtomicReference<QNode>();
525	>	this.oddQ = new AtomicReference<QNode>();
526	>	}
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.
535	<	* If an ongoing invocation of {@link #onAdvance} is in progress,
536	<	* this method waits until its completion before registering.
537	<	*
538	<	* @return the arrival phase number to which this registration applied
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 child phaser is also registered with its parent. If
539	>	* this phaser is terminated, the attempt to register has
540	>	* no effect, and a negative value is returned.
541	>	*
542	>	* @return the arrival phase number to which this registration
543	>	* applied.  If this value is negative, then this phaser has
544	>	* terminated, in which casem registration has no effect.
545		* @throws IllegalStateException if attempting to register more
546		* than the maximum supported number of parties
547		*/
#	Line 424 | Line 552 | public class Phaser {
552		/**
553		* Adds the given number of new unarrived parties to this phaser.
554		* If an ongoing invocation of {@link #onAdvance} is in progress,
555	<	* this method waits until its completion before registering.
556	<	*
557	<	* @param parties the number of additional parties required to trip barrier
558	<	* @return the arrival phase number to which this registration applied
555	>	* this method may await its completion before returning.  If this
556	>	* phaser has a parent, and the given number of parties is greater
557	>	* than zero, and this phaser previously had no registered
558	>	* parties, this child phaser is also registered with its parent.
559	>	* If this phaser is terminated, the attempt to register has no
560	>	* effect, and a negative value is returned.
561	>	*
562	>	* @param parties the number of additional parties required to
563	>	* advance to the next phase
564	>	* @return the arrival phase number to which this registration
565	>	* applied.  If this value is negative, then this phaser has
566	>	* terminated, in which casem registration has no effect.
567		* @throws IllegalStateException if attempting to register more
568		* than the maximum supported number of parties
569		* @throws IllegalArgumentException if {@code parties < 0}
#	Line 441 | Line 577 | public class Phaser {
577		}
578
579		/**
580	<	* Shared code for register, bulkRegister
581	<	*/
582	<	private int doRegister(int registrations) {
583	<	Phaser par = parent;
584	<	long s;
585	<	int phase;
450	<	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
451	<	int p = partiesOf(s);
452	<	int u = unarrivedOf(s);
453	<	int unarrived = u + registrations;
454	<	int parties = p + registrations;
455	<	if (par == null || phase == phaseOf(root.state)) {
456	<	if (parties > ushortMask || unarrived > ushortMask)
457	<	throw new IllegalStateException(badBounds(parties,
458	<	unarrived));
459	<	else if (p != 0 && u == 0)       // back off if advancing
460	<	Thread.yield();              // not worth actually blocking
461	<	else if (casState(s, stateFor(phase, parties, unarrived)))
462	<	break;
463	<	}
464	<	}
465	<	return phase;
466	<	}
467	<
468	<	/**
469	<	* Arrives at the barrier, but does not wait for others.  (You can
470	<	* in turn wait for others via {@link #awaitAdvance}).  It is an
471	<	* unenforced usage error for an unregistered party to invoke this
472	<	* method.
580	>	* Arrives at this phaser, without waiting for others to arrive.
581	>	*
582	>	* <p>It is a usage error for an unregistered party to invoke this
583	>	* method.  However, this error may result in an {@code
584	>	* IllegalStateException} only upon some subsequent operation on
585	>	* this phaser, if ever.
586		*
587		* @return the arrival phase number, or a negative value if terminated
588		* @throws IllegalStateException if not terminated and the number
589		* of unarrived parties would become negative
590		*/
591		public int arrive() {
592	<	Phaser par = parent;
480	<	long s;
481	<	int phase;
482	<	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
483	<	int parties = partiesOf(s);
484	<	int unarrived = unarrivedOf(s) - 1;
485	<	if (parties == 0 || unarrived < 0)
486	<	throw new IllegalStateException(badBounds(parties,
487	<	unarrived));
488	<	else if (unarrived > 0) {           // Not the last arrival
489	<	if (casState(s, s - 1))         // s-1 adds one arrival
490	<	break;
491	<	}
492	<	else if (par == null) {             // directly trip
493	<	if (casState(s, trippedStateFor(onAdvance(phase, parties) ? -1 :
494	<	((phase + 1) & phaseMask),
495	<	parties))) {
496	<	releaseWaiters(phase);
497	<	break;
498	<	}
499	<	}
500	<	else if (phaseOf(root.state) == phase && casState(s, s - 1)) {
501	<	par.arrive();                   // cascade to parent
502	<	reconcileState();
503	<	break;
504	<	}
505	<	}
506	<	return phase;
592	>	return doArrive(false);
593		}
594
595		/**
596	<	* Arrives at the barrier and deregisters from it without waiting
597	<	* for others. Deregistration reduces the number of parties
598	<	* required to trip the barrier in future phases.  If this phaser
596	>	* Arrives at this phaser and deregisters from it without waiting
597	>	* for others to arrive. Deregistration reduces the number of
598	>	* parties required to advance in future phases.  If this phaser
599		* has a parent, and deregistration causes this phaser to have
600	<	* zero parties, this phaser also arrives at and is deregistered
601	<	* from its parent.  It is an unenforced usage error for an
602	<	* unregistered party to invoke this method.
600	>	* zero parties, this phaser is also deregistered from its parent.
601	>	*
602	>	* <p>It is a usage error for an unregistered party to invoke this
603	>	* method.  However, this error may result in an {@code
604	>	* IllegalStateException} only upon some subsequent operation on
605	>	* this phaser, if ever.
606		*
607		* @return the arrival phase number, or a negative value if terminated
608		* @throws IllegalStateException if not terminated and the number
609		* of registered or unarrived parties would become negative
610		*/
611		public int arriveAndDeregister() {
612	<	// similar to arrive, but too different to merge
524	<	Phaser par = parent;
525	<	long s;
526	<	int phase;
527	<	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
528	<	int parties = partiesOf(s) - 1;
529	<	int unarrived = unarrivedOf(s) - 1;
530	<	if (parties < 0 || unarrived < 0)
531	<	throw new IllegalStateException(badBounds(parties,
532	<	unarrived));
533	<	else if (unarrived > 0) {
534	<	if (casState(s, stateFor(phase, parties, unarrived)))
535	<	break;
536	<	}
537	<	else if (par == null) {
538	<	if (casState(s, trippedStateFor(onAdvance(phase, parties)? -1:
539	<	(phase + 1) & phaseMask,
540	<	parties))) {
541	<	releaseWaiters(phase);
542	<	break;
543	<	}
544	<	}
545	<	else if (phaseOf(root.state) == phase &&
546	<	casState(s, stateFor(phase, parties, 0))) {
547	<	if (parties == 0)
548	<	par.arriveAndDeregister();
549	<	else
550	<	par.arrive();
551	<	reconcileState();
552	<	break;
553	<	}
554	<	}
555	<	return phase;
612	>	return doArrive(true);
613		}
614
615		/**
616	<	* Arrives at the barrier and awaits others. Equivalent in effect
616	>	* Arrives at this phaser and awaits others. Equivalent in effect
617		* to {@code awaitAdvance(arrive())}.  If you need to await with
618		* interruption or timeout, you can arrange this with an analogous
619		* construction using one of the other forms of the {@code
620		* awaitAdvance} method.  If instead you need to deregister upon
621	<	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
565	<	* usage error for an unregistered party to invoke this method.
621	>	* arrival, use {@code awaitAdvance(arriveAndDeregister())}.
622		*
623	<	* @return the arrival phase number, or a negative number if terminated
623	>	* <p>It is a usage error for an unregistered party to invoke this
624	>	* method.  However, this error may result in an {@code
625	>	* IllegalStateException} only upon some subsequent operation on
626	>	* this phaser, if ever.
627	>	*
628	>	* @return the arrival phase number, or the (negative)
629	>	* {@linkplain #getPhase() current phase} if terminated
630		* @throws IllegalStateException if not terminated and the number
631		* of unarrived parties would become negative
632		*/
633		public int arriveAndAwaitAdvance() {
634	<	return awaitAdvance(arrive());
634	>	// Specialization of doArrive+awaitAdvance eliminating some reads/paths
635	>	final Phaser root = this.root;
636	>	for (;;) {
637	>	long s = (root == this) ? state : reconcileState();
638	>	int phase = (int)(s >>> PHASE_SHIFT);
639	>	int counts = (int)s;
640	>	int unarrived = (counts & UNARRIVED_MASK) - 1;
641	>	if (phase < 0)
642	>	return phase;
643	>	else if (counts == EMPTY || unarrived < 0) {
644	>	if (reconcileState() == s)
645	>	throw new IllegalStateException(badArrive(s));
646	>	}
647	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s,
648	>	s -= ONE_ARRIVAL)) {
649	>	if (unarrived != 0)
650	>	return root.internalAwaitAdvance(phase, null);
651	>	if (root != this)
652	>	return parent.arriveAndAwaitAdvance();
653	>	long n = s & PARTIES_MASK;  // base of next state
654	>	int nextUnarrived = ((int)n) >>> PARTIES_SHIFT;
655	>	if (onAdvance(phase, nextUnarrived))
656	>	n |= TERMINATION_BIT;
657	>	else if (nextUnarrived == 0)
658	>	n |= EMPTY;
659	>	else
660	>	n |= nextUnarrived;
661	>	int nextPhase = (phase + 1) & MAX_PHASE;
662	>	n |= (long)nextPhase << PHASE_SHIFT;
663	>	if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n))
664	>	return (int)(state >>> PHASE_SHIFT); // terminated
665	>	releaseWaiters(phase);
666	>	return nextPhase;
667	>	}
668	>	}
669		}
670
671		/**
672	<	* Awaits the phase of the barrier to advance from the given phase
673	<	* value, returning immediately if the current phase of the
674	<	* barrier is not equal to the given phase value or this barrier
579	<	* is terminated.  It is an unenforced usage error for an
580	<	* unregistered party to invoke this method.
672	>	* Awaits the phase of this phaser to advance from the given phase
673	>	* value, returning immediately if the current phase is not equal
674	>	* to the given phase value or this phaser is terminated.
675		*
676		* @param phase an arrival phase number, or negative value if
677		* terminated; this argument is normally the value returned by a
678	<	* previous call to {@code arrive} or its variants
679	<	* @return the next arrival phase number, or a negative value
680	<	* if terminated or argument is negative
678	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
679	>	* @return the next arrival phase number, or the argument if it is
680	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
681	>	* if terminated
682		*/
683		public int awaitAdvance(int phase) {
684	+	final Phaser root = this.root;
685	+	int p = (int)((root == this? state : reconcileState()) >>> PHASE_SHIFT);
686		if (phase < 0)
687		return phase;
688	<	int p = getPhase();
689	<	if (p != phase)
690	<	return p;
594	<	return untimedWait(phase);
688	>	if (p == phase)
689	>	return root.internalAwaitAdvance(phase, null);
690	>	return p;
691		}
692
693		/**
694	<	* Awaits the phase of the barrier to advance from the given phase
694	>	* Awaits the phase of this phaser to advance from the given phase
695		* value, throwing {@code InterruptedException} if interrupted
696	<	* while waiting, or returning immediately if the current phase of
697	<	* the barrier is not equal to the given phase value or this
698	<	* barrier is terminated. It is an unenforced usage error for an
603	<	* unregistered party to invoke this method.
696	>	* while waiting, or returning immediately if the current phase is
697	>	* not equal to the given phase value or this phaser is
698	>	* terminated.
699		*
700		* @param phase an arrival phase number, or negative value if
701		* terminated; this argument is normally the value returned by a
702	<	* previous call to {@code arrive} or its variants
703	<	* @return the next arrival phase number, or a negative value
704	<	* if terminated or argument is negative
702	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
703	>	* @return the next arrival phase number, or the argument if it is
704	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
705	>	* if terminated
706		* @throws InterruptedException if thread interrupted while waiting
707		*/
708		public int awaitAdvanceInterruptibly(int phase)
709		throws InterruptedException {
710	+	final Phaser root = this.root;
711	+	int p = (int)((root == this? state : reconcileState()) >>> PHASE_SHIFT);
712		if (phase < 0)
713		return phase;
714	<	int p = getPhase();
715	<	if (p != phase)
716	<	return p;
717	<	return interruptibleWait(phase);
714	>	if (p == phase) {
715	>	QNode node = new QNode(this, phase, true, false, 0L);
716	>	p = root.internalAwaitAdvance(phase, node);
717	>	if (node.wasInterrupted)
718	>	throw new InterruptedException();
719	>	}
720	>	return p;
721		}
722
723		/**
724	<	* Awaits the phase of the barrier to advance from the given phase
724	>	* Awaits the phase of this phaser to advance from the given phase
725		* value or the given timeout to elapse, throwing {@code
726		* InterruptedException} if interrupted while waiting, or
727	<	* returning immediately if the current phase of the barrier is
728	<	* not equal to the given phase value or this barrier is
628	<	* terminated.  It is an unenforced usage error for an
629	<	* unregistered party to invoke this method.
727	>	* returning immediately if the current phase is not equal to the
728	>	* given phase value or this phaser is terminated.
729		*
730		* @param phase an arrival phase number, or negative value if
731		* terminated; this argument is normally the value returned by a
732	<	* previous call to {@code arrive} or its variants
732	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
733		* @param timeout how long to wait before giving up, in units of
734		*        {@code unit}
735		* @param unit a {@code TimeUnit} determining how to interpret the
736		*        {@code timeout} parameter
737	<	* @return the next arrival phase number, or a negative value
738	<	* if terminated or argument is negative
737	>	* @return the next arrival phase number, or the argument if it is
738	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
739	>	* if terminated
740		* @throws InterruptedException if thread interrupted while waiting
741		* @throws TimeoutException if timed out while waiting
742		*/
#	Line 644 | Line 744 | public class Phaser {
744		long timeout, TimeUnit unit)
745		throws InterruptedException, TimeoutException {
746		long nanos = unit.toNanos(timeout);
747	+	final Phaser root = this.root;
748	+	int p = (int)((root == this? state : reconcileState()) >>> PHASE_SHIFT);
749		if (phase < 0)
750		return phase;
751	<	int p = getPhase();
752	<	if (p != phase)
753	<	return p;
754	<	return timedWait(phase, nanos);
751	>	if (p == phase) {
752	>	QNode node = new QNode(this, phase, true, true, nanos);
753	>	p = root.internalAwaitAdvance(phase, node);
754	>	if (node.wasInterrupted)
755	>	throw new InterruptedException();
756	>	else if (p == phase)
757	>	throw new TimeoutException();
758	>	}
759	>	return p;
760		}
761
762		/**
763	<	* Forces this barrier to enter termination state. Counts of
764	<	* arrived and registered parties are unaffected. If this phaser
765	<	* has a parent, it too is terminated. This method may be useful
766	<	* for coordinating recovery after one or more tasks encounter
763	>	* Forces this phaser to enter termination state.  Counts of
764	>	* registered parties are unaffected.  If this phaser is a member
765	>	* of a tiered set of phasers, then all of the phasers in the set
766	>	* are terminated.  If this phaser is already terminated, this
767	>	* method has no effect.  This method may be useful for
768	>	* coordinating recovery after one or more tasks encounter
769		* unexpected exceptions.
770		*/
771		public void forceTermination() {
772	<	Phaser r = root;    // force at root then reconcile
772	>	// Only need to change root state
773	>	final Phaser root = this.root;
774		long s;
775	<	while (phaseOf(s = r.state) >= 0)
776	<	r.casState(s, stateFor(-1, partiesOf(s), unarrivedOf(s)));
777	<	reconcileState();
778	<	releaseWaiters(0);  // ensure wakeups on both queues
779	<	releaseWaiters(1);
775	>	while ((s = root.state) >= 0) {
776	>	long next = (s & ~((long)UNARRIVED_MASK)) | TERMINATION_BIT;
777	>	if (UNSAFE.compareAndSwapLong(root, stateOffset, s, next)) {
778	>	// signal all threads
779	>	releaseWaiters(0);
780	>	releaseWaiters(1);
781	>	return;
782	>	}
783	>	}
784		}
785
786		/**
787		* Returns the current phase number. The maximum phase number is
788		* {@code Integer.MAX_VALUE}, after which it restarts at
789	<	* zero. Upon termination, the phase number is negative.
789	>	* zero. Upon termination, the phase number is negative,
790	>	* in which case the prevailing phase prior to termination
791	>	* may be obtained via {@code getPhase() + Integer.MIN_VALUE}.
792		*
793		* @return the phase number, or a negative value if terminated
794		*/
795		public final int getPhase() {
796	<	return phaseOf(getReconciledState());
796	>	return (int)(root.state >>> PHASE_SHIFT);
797		}
798
799		/**
800	<	* Returns the number of parties registered at this barrier.
800	>	* Returns the number of parties registered at this phaser.
801		*
802		* @return the number of parties
803		*/
804		public int getRegisteredParties() {
805	<	return partiesOf(getReconciledState());
805	>	return partiesOf(state);
806		}
807
808		/**
809		* Returns the number of registered parties that have arrived at
810	<	* the current phase of this barrier.
810	>	* the current phase of this phaser.
811		*
812		* @return the number of arrived parties
813		*/
814		public int getArrivedParties() {
815	<	return arrivedOf(getReconciledState());
815	>	return arrivedOf(reconcileState());
816		}
817
818		/**
819		* Returns the number of registered parties that have not yet
820	<	* arrived at the current phase of this barrier.
820	>	* arrived at the current phase of this phaser.
821		*
822		* @return the number of unarrived parties
823		*/
824		public int getUnarrivedParties() {
825	<	return unarrivedOf(getReconciledState());
825	>	return unarrivedOf(reconcileState());
826		}
827
828		/**
#	Line 729 | Line 845 | public class Phaser {
845		}
846
847		/**
848	<	* Returns {@code true} if this barrier has been terminated.
848	>	* Returns {@code true} if this phaser has been terminated.
849		*
850	<	* @return {@code true} if this barrier has been terminated
850	>	* @return {@code true} if this phaser has been terminated
851		*/
852		public boolean isTerminated() {
853	<	return getPhase() < 0;
853	>	return root.state < 0L;
854		}
855
856		/**
857		* Overridable method to perform an action upon impending phase
858		* advance, and to control termination. This method is invoked
859	<	* upon arrival of the party tripping the barrier (when all other
859	>	* upon arrival of the party advancing this phaser (when all other
860		* waiting parties are dormant).  If this method returns {@code
861	<	* true}, then, rather than advance the phase number, this barrier
862	<	* will be set to a final termination state, and subsequent calls
863	<	* to {@link #isTerminated} will return true. Any (unchecked)
864	<	* Exception or Error thrown by an invocation of this method is
865	<	* propagated to the party attempting to trip the barrier, in
866	<	* which case no advance occurs.
861	>	* true}, this phaser will be set to a final termination state
862	>	* upon advance, and subsequent calls to {@link #isTerminated}
863	>	* will return true. Any (unchecked) Exception or Error thrown by
864	>	* an invocation of this method is propagated to the party
865	>	* attempting to advance this phaser, in which case no advance
866	>	* occurs.
867		*
868		* <p>The arguments to this method provide the state of the phaser
869	<	* prevailing for the current transition. (When called from within
870	<	* an implementation of {@code onAdvance} the values returned by
871	<	* methods such as {@code getPhase} may or may not reliably
872	<	* indicate the state to which this transition applies.)
873	<	*
874	<	* <p>The default version returns {@code true} when the number of
875	<	* registered parties is zero. Normally, overrides that arrange
876	<	* termination for other reasons should also preserve this
877	<	* property.
869	>	* prevailing for the current transition.  The effects of invoking
870	>	* arrival, registration, and waiting methods on this phaser from
871	>	* within {@code onAdvance} are unspecified and should not be
872	>	* relied on.
873	>	*
874	>	* <p>If this phaser is a member of a tiered set of phasers, then
875	>	* {@code onAdvance} is invoked only for its root phaser on each
876	>	* advance.
877	>	*
878	>	* <p>To support the most common use cases, the default
879	>	* implementation of this method returns {@code true} when the
880	>	* number of registered parties has become zero as the result of a
881	>	* party invoking {@code arriveAndDeregister}.  You can disable
882	>	* this behavior, thus enabling continuation upon future
883	>	* registrations, by overriding this method to always return
884	>	* {@code false}:
885	>	*
886	>	* <pre> {@code
887	>	* Phaser phaser = new Phaser() {
888	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
889	>	* }}</pre>
890		*
891	<	* @param phase the phase number on entering the barrier
891	>	* @param phase the current phase number on entry to this method,
892	>	* before this phaser is advanced
893		* @param registeredParties the current number of registered parties
894	<	* @return {@code true} if this barrier should terminate
894	>	* @return {@code true} if this phaser should terminate
895		*/
896		protected boolean onAdvance(int phase, int registeredParties) {
897	<	return registeredParties <= 0;
897	>	return registeredParties == 0;
898		}
899
900		/**
#	Line 775 | Line 904 | public class Phaser {
904		* followed by the number of registered parties, and {@code
905		* "arrived = "} followed by the number of arrived parties.
906		*
907	<	* @return a string identifying this barrier, as well as its state
907	>	* @return a string identifying this phaser, as well as its state
908		*/
909		public String toString() {
910	<	long s = getReconciledState();
910	>	return stateToString(reconcileState());
911	>	}
912	>
913	>	/**
914	>	* Implementation of toString and string-based error messages
915	>	*/
916	>	private String stateToString(long s) {
917		return super.toString() +
918		"[phase = " + phaseOf(s) +
919		" parties = " + partiesOf(s) +
920		" arrived = " + arrivedOf(s) + "]";
921		}
922
923	<	// methods for waiting
923	>	// Waiting mechanics
924
925		/**
926	<	* Wait nodes for Treiber stack representing wait queue
926	>	* Removes and signals threads from queue for phase.
927		*/
928	<	static final class QNode implements ForkJoinPool.ManagedBlocker {
929	<	final Phaser phaser;
930	<	final int phase;
931	<	final long startTime;
932	<	final long nanos;
933	<	final boolean timed;
934	<	final boolean interruptible;
935	<	volatile boolean wasInterrupted = false;
936	<	volatile Thread thread; // nulled to cancel wait
802	<	QNode next;
803	<
804	<	QNode(Phaser phaser, int phase, boolean interruptible,
805	<	boolean timed, long startTime, long nanos) {
806	<	this.phaser = phaser;
807	<	this.phase = phase;
808	<	this.timed = timed;
809	<	this.interruptible = interruptible;
810	<	this.startTime = startTime;
811	<	this.nanos = nanos;
812	<	thread = Thread.currentThread();
813	<	}
814	<
815	<	public boolean isReleasable() {
816	<	return (thread == null ||
817	<	phaser.getPhase() != phase ||
818	<	(interruptible && wasInterrupted) ||
819	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
820	<	}
821	<
822	<	public boolean block() {
823	<	if (Thread.interrupted()) {
824	<	wasInterrupted = true;
825	<	if (interruptible)
826	<	return true;
827	<	}
828	<	if (!timed)
829	<	LockSupport.park(this);
830	<	else {
831	<	long waitTime = nanos - (System.nanoTime() - startTime);
832	<	if (waitTime <= 0)
833	<	return true;
834	<	LockSupport.parkNanos(this, waitTime);
835	<	}
836	<	return isReleasable();
837	<	}
838	<
839	<	void signal() {
840	<	Thread t = thread;
841	<	if (t != null) {
842	<	thread = null;
928	>	private void releaseWaiters(int phase) {
929	>	QNode q;   // first element of queue
930	>	Thread t;  // its thread
931	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
932	>	while ((q = head.get()) != null &&
933	>	q.phase != (int)(root.state >>> PHASE_SHIFT)) {
934	>	if (head.compareAndSet(q, q.next) &&
935	>	(t = q.thread) != null) {
936	>	q.thread = null;
937		LockSupport.unpark(t);
938		}
939		}
846	–
847	–	boolean doWait() {
848	–	if (thread != null) {
849	–	try {
850	–	ForkJoinPool.managedBlock(this);
851	–	} catch (InterruptedException ie) {
852	–	wasInterrupted = true; // can't currently happen
853	–	}
854	–	}
855	–	return wasInterrupted;
856	–	}
940		}
941
942		/**
943	<	* Removes and signals waiting threads from wait queue.
944	<	*/
945	<	private void releaseWaiters(int phase) {
946	<	AtomicReference<QNode> head = queueFor(phase);
947	<	QNode q;
948	<	while ((q = head.get()) != null) {
949	<	if (head.compareAndSet(q, q.next))
950	<	q.signal();
943	>	* Variant of releaseWaiters that additionally tries to remove any
944	>	* nodes no longer waiting for advance due to timeout or
945	>	* interrupt. Currently, nodes are removed only if they are at
946	>	* head of queue, which suffices to reduce memory footprint in
947	>	* most usages.
948	>	*
949	>	* @return current phase on exit
950	>	*/
951	>	private int abortWait(int phase) {
952	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
953	>	for (;;) {
954	>	Thread t;
955	>	QNode q = head.get();
956	>	int p = (int)(root.state >>> PHASE_SHIFT);
957	>	if (q == null || ((t = q.thread) != null && q.phase == p))
958	>	return p;
959	>	if (head.compareAndSet(q, q.next) && t != null) {
960	>	q.thread = null;
961	>	LockSupport.unpark(t);
962	>	}
963		}
964		}
965
966	+	/** The number of CPUs, for spin control */
967	+	private static final int NCPU = Runtime.getRuntime().availableProcessors();
968	+
969		/**
970	<	* Tries to enqueue given node in the appropriate wait queue.
971	<	*
972	<	* @return true if successful
970	>	* The number of times to spin before blocking while waiting for
971	>	* advance, per arrival while waiting. On multiprocessors, fully
972	>	* blocking and waking up a large number of threads all at once is
973	>	* usually a very slow process, so we use rechargeable spins to
974	>	* avoid it when threads regularly arrive: When a thread in
975	>	* internalAwaitAdvance notices another arrival before blocking,
976	>	* and there appear to be enough CPUs available, it spins
977	>	* SPINS_PER_ARRIVAL more times before blocking. The value trades
978	>	* off good-citizenship vs big unnecessary slowdowns.
979		*/
980	<	private boolean tryEnqueue(QNode node) {
877	<	AtomicReference<QNode> head = queueFor(node.phase);
878	<	return head.compareAndSet(node.next = head.get(), node);
879	<	}
980	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
981
982		/**
983	<	* Enqueues node and waits unless aborted or signalled.
983	>	* Possibly blocks and waits for phase to advance unless aborted.
984	>	* Call only from root node.
985		*
986	+	* @param phase current phase
987	+	* @param node if non-null, the wait node to track interrupt and timeout;
988	+	* if null, denotes noninterruptible wait
989		* @return current phase
990		*/
991	<	private int untimedWait(int phase) {
992	<	QNode node = null;
993	<	boolean queued = false;
994	<	boolean interrupted = false;
991	>	private int internalAwaitAdvance(int phase, QNode node) {
992	>	releaseWaiters(phase-1);          // ensure old queue clean
993	>	boolean queued = false;           // true when node is enqueued
994	>	int lastUnarrived = 0;            // to increase spins upon change
995	>	int spins = SPINS_PER_ARRIVAL;
996	>	long s;
997		int p;
998	<	while ((p = getPhase()) == phase) {
999	<	if (Thread.interrupted())
1000	<	interrupted = true;
1001	<	else if (node == null)
1002	<	node = new QNode(this, phase, false, false, 0, 0);
1003	<	else if (!queued)
1004	<	queued = tryEnqueue(node);
1005	<	else if (node.doWait())
1006	<	interrupted = true;
998	>	while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
999	>	if (node == null) {           // spinning in noninterruptible mode
1000	>	int unarrived = (int)s & UNARRIVED_MASK;
1001	>	if (unarrived != lastUnarrived &&
1002	>	(lastUnarrived = unarrived) < NCPU)
1003	>	spins += SPINS_PER_ARRIVAL;
1004	>	boolean interrupted = Thread.interrupted();
1005	>	if (interrupted || --spins < 0) { // need node to record intr
1006	>	node = new QNode(this, phase, false, false, 0L);
1007	>	node.wasInterrupted = interrupted;
1008	>	}
1009	>	}
1010	>	else if (node.isReleasable()) // done or aborted
1011	>	break;
1012	>	else if (!queued) {           // push onto queue
1013	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
1014	>	QNode q = node.next = head.get();
1015	>	if ((q == null || q.phase == phase) &&
1016	>	(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq
1017	>	queued = head.compareAndSet(q, node);
1018	>	}
1019	>	else {
1020	>	try {
1021	>	ForkJoinPool.managedBlock(node);
1022	>	} catch (InterruptedException ie) {
1023	>	node.wasInterrupted = true;
1024	>	}
1025	>	}
1026	>	}
1027	>
1028	>	if (node != null) {
1029	>	if (node.thread != null)
1030	>	node.thread = null;       // avoid need for unpark()
1031	>	if (node.wasInterrupted && !node.interruptible)
1032	>	Thread.currentThread().interrupt();
1033	>	if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase)
1034	>	return abortWait(phase); // possibly clean up on abort
1035		}
901	–	if (node != null)
902	–	node.thread = null;
1036		releaseWaiters(phase);
904	–	if (interrupted)
905	–	Thread.currentThread().interrupt();
1037		return p;
1038		}
1039
1040		/**
1041	<	* Interruptible version
911	<	* @return current phase
1041	>	* Wait nodes for Treiber stack representing wait queue
1042		*/
1043	<	private int interruptibleWait(int phase) throws InterruptedException {
1044	<	QNode node = null;
1045	<	boolean queued = false;
1046	<	boolean interrupted = false;
1047	<	int p;
1048	<	while ((p = getPhase()) == phase && !interrupted) {
1049	<	if (Thread.interrupted())
1050	<	interrupted = true;
1051	<	else if (node == null)
1052	<	node = new QNode(this, phase, true, false, 0, 0);
923	<	else if (!queued)
924	<	queued = tryEnqueue(node);
925	<	else if (node.doWait())
926	<	interrupted = true;
927	<	}
928	<	if (node != null)
929	<	node.thread = null;
930	<	if (p != phase || (p = getPhase()) != phase)
931	<	releaseWaiters(phase);
932	<	if (interrupted)
933	<	throw new InterruptedException();
934	<	return p;
935	<	}
1043	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
1044	>	final Phaser phaser;
1045	>	final int phase;
1046	>	final boolean interruptible;
1047	>	final boolean timed;
1048	>	boolean wasInterrupted;
1049	>	long nanos;
1050	>	long lastTime;
1051	>	volatile Thread thread; // nulled to cancel wait
1052	>	QNode next;
1053
1054	<	/**
1055	<	* Timeout version.
1056	<	* @return current phase
1057	<	*/
1058	<	private int timedWait(int phase, long nanos)
1059	<	throws InterruptedException, TimeoutException {
1060	<	long startTime = System.nanoTime();
1061	<	QNode node = null;
1062	<	boolean queued = false;
1063	<	boolean interrupted = false;
1064	<	int p;
1065	<	while ((p = getPhase()) == phase && !interrupted) {
1054	>	QNode(Phaser phaser, int phase, boolean interruptible,
1055	>	boolean timed, long nanos) {
1056	>	this.phaser = phaser;
1057	>	this.phase = phase;
1058	>	this.interruptible = interruptible;
1059	>	this.nanos = nanos;
1060	>	this.timed = timed;
1061	>	this.lastTime = timed ? System.nanoTime() : 0L;
1062	>	thread = Thread.currentThread();
1063	>	}
1064	>
1065	>	public boolean isReleasable() {
1066	>	if (thread == null)
1067	>	return true;
1068	>	if (phaser.getPhase() != phase) {
1069	>	thread = null;
1070	>	return true;
1071	>	}
1072		if (Thread.interrupted())
1073	<	interrupted = true;
1074	<	else if (nanos - (System.nanoTime() - startTime) <= 0)
1075	<	break;
1076	<	else if (node == null)
1077	<	node = new QNode(this, phase, true, true, startTime, nanos);
1078	<	else if (!queued)
1079	<	queued = tryEnqueue(node);
1080	<	else if (node.doWait())
1081	<	interrupted = true;
1082	<	}
1083	<	if (node != null)
1084	<	node.thread = null;
1085	<	if (p != phase || (p = getPhase()) != phase)
1086	<	releaseWaiters(phase);
1087	<	if (interrupted)
1088	<	throw new InterruptedException();
1089	<	if (p == phase)
1090	<	throw new TimeoutException();
1091	<	return p;
1073	>	wasInterrupted = true;
1074	>	if (wasInterrupted && interruptible) {
1075	>	thread = null;
1076	>	return true;
1077	>	}
1078	>	if (timed) {
1079	>	if (nanos > 0L) {
1080	>	long now = System.nanoTime();
1081	>	nanos -= now - lastTime;
1082	>	lastTime = now;
1083	>	}
1084	>	if (nanos <= 0L) {
1085	>	thread = null;
1086	>	return true;
1087	>	}
1088	>	}
1089	>	return false;
1090	>	}
1091	>
1092	>	public boolean block() {
1093	>	if (isReleasable())
1094	>	return true;
1095	>	else if (!timed)
1096	>	LockSupport.park(this);
1097	>	else if (nanos > 0)
1098	>	LockSupport.parkNanos(this, nanos);
1099	>	return isReleasable();
1100	>	}
1101		}
1102
1103		// Unsafe mechanics
#	Line 974 | Line 1106 | public class Phaser {
1106		private static final long stateOffset =
1107		objectFieldOffset("state", Phaser.class);
1108
977	–	private final boolean casState(long cmp, long val) {
978	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
979	–	}
980	–
1109		private static long objectFieldOffset(String field, Class<?> klazz) {
1110		try {
1111		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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