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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 1.57 by dl, Fri Nov 19 16:03:24 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 226 | Line 227 | public class Phaser {
227		* Barrier state representation. Conceptually, a barrier contains
228		* four values:
229		*
230	<	* * parties -- the number of parties to wait (16 bits)
231	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
232	<	* * phase -- the generation of the barrier (31 bits)
233	<	* * terminated -- set if barrier is terminated (1 bit)
230	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
231	>	* * parties -- the number of parties to wait              (bits 16-31)
232	>	* * phase -- the generation of the barrier                (bits 32-62)
233	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
234		*
235		* However, to efficiently maintain atomicity, these values are
236		* packed into a single (atomic) long. Termination uses the sign
237		* bit of 32 bit representation of phase, so phase is set to -1 on
238		* termination. Good performance relies on keeping state decoding
239		* and encoding simple, and keeping race windows short.
239	–	*
240	–	* Note: there are some cheats in arrive() that rely on unarrived
241	–	* count being lowest 16 bits.
240		*/
241		private volatile long state;
242
243	<	private static final int ushortMask = 0xffff;
244	<	private static final int phaseMask  = 0x7fffffff;
243	>	private static final int  MAX_PARTIES    = 0xffff;
244	>	private static final int  MAX_PHASE      = 0x7fffffff;
245	>	private static final int  PARTIES_SHIFT  = 16;
246	>	private static final int  PHASE_SHIFT    = 32;
247	>	private static final int  UNARRIVED_MASK = 0xffff;
248	>	private static final long PARTIES_MASK   = 0xffff0000L; // for masking long
249	>	private static final long ONE_ARRIVAL    = 1L;
250	>	private static final long ONE_PARTY      = 1L << PARTIES_SHIFT;
251	>	private static final long TERMINATION_PHASE  = -1L << PHASE_SHIFT;
252	>
253	>	// The following unpacking methods are usually manually inlined
254
255		private static int unarrivedOf(long s) {
256	<	return (int) (s & ushortMask);
256	>	return (int)s & UNARRIVED_MASK;
257		}
258
259		private static int partiesOf(long s) {
260	<	return ((int) s) >>> 16;
260	>	return (int)s >>> PARTIES_SHIFT;
261		}
262
263		private static int phaseOf(long s) {
264	<	return (int) (s >>> 32);
264	>	return (int) (s >>> PHASE_SHIFT);
265		}
266
267		private static int arrivedOf(long s) {
268		return partiesOf(s) - unarrivedOf(s);
269		}
270
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");
280	–	}
281	–
271		/**
272		* The parent of this phaser, or null if none
273		*/
#	Line 290 | Line 279 | public class Phaser {
279		*/
280		private final Phaser root;
281
293	–	// Wait queues
294	–
282		/**
283		* Heads of Treiber stacks for waiting threads. To eliminate
284		* contention when releasing some threads while adding others, we
285		* use two of them, alternating across even and odd phases.
286		* Subphasers share queues with root to speed up releases.
287		*/
288	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
289	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
288	>	private final AtomicReference<QNode> evenQ;
289	>	private final AtomicReference<QNode> oddQ;
290
291		private AtomicReference<QNode> queueFor(int phase) {
292	<	Phaser r = root;
293	<	return ((phase & 1) == 0) ? r.evenQ : r.oddQ;
292	>	return ((phase & 1) == 0) ? evenQ : oddQ;
293	>	}
294	>
295	>	/**
296	>	* Main implementation for methods arrive and arriveAndDeregister.
297	>	* Manually tuned to speed up and minimize race windows for the
298	>	* common case of just decrementing unarrived field.
299	>	*
300	>	* @param adj - adjustment to apply to state -- either
301	>	* ONE_ARRIVAL (for arrive) or
302	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
303	>	*/
304	>	private int doArrive(long adj) {
305	>	for (;;) {
306	>	long s = state;
307	>	int phase = (int)(s >>> PHASE_SHIFT);
308	>	if (phase < 0)
309	>	return phase;
310	>	int unarrived = (int)s & UNARRIVED_MASK;
311	>	if (unarrived == 0)
312	>	checkBadArrive(s);
313	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
314	>	if (unarrived == 1) {
315	>	long p = s & PARTIES_MASK; // unshifted parties field
316	>	long lu = p >>> PARTIES_SHIFT;
317	>	int u = (int)lu;
318	>	int nextPhase = (phase + 1) & MAX_PHASE;
319	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
320	>	final Phaser parent = this.parent;
321	>	if (parent == null) {
322	>	if (onAdvance(phase, u))
323	>	next |= TERMINATION_PHASE; // obliterate phase
324	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
325	>	releaseWaiters(phase);
326	>	}
327	>	else {
328	>	parent.doArrive((u == 0) ?
329	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
330	>	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase ||
331	>	((int)(state >>> PHASE_SHIFT) != nextPhase &&
332	>	!UNSAFE.compareAndSwapLong(this, stateOffset,
333	>	s, next)))
334	>	reconcileState();
335	>	}
336	>	}
337	>	return phase;
338	>	}
339	>	}
340	>	}
341	>
342	>	/**
343	>	* Rechecks state and throws bounds exceptions on arrival -- called
344	>	* only if unarrived is apparently zero.
345	>	*/
346	>	private void checkBadArrive(long s) {
347	>	if (reconcileState() == s)
348	>	throw new IllegalStateException
349	>	("Attempted arrival of unregistered party for " +
350	>	stateToString(s));
351	>	}
352	>
353	>	/**
354	>	* Implementation of register, bulkRegister
355	>	*
356	>	* @param registrations number to add to both parties and unarrived fields
357	>	*/
358	>	private int doRegister(int registrations) {
359	>	// assert registrations > 0;
360	>	// adjustment to state
361	>	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
362	>	final Phaser parent = this.parent;
363	>	for (;;) {
364	>	long s = (parent == null) ? state : reconcileState();
365	>	int phase = (int)(s >>> PHASE_SHIFT);
366	>	if (phase < 0)
367	>	return phase;
368	>	int parties = (int)s >>> PARTIES_SHIFT;
369	>	if (parties != 0 && ((int)s & UNARRIVED_MASK) == 0)
370	>	internalAwaitAdvance(phase, null); // wait for onAdvance
371	>	else if (registrations > MAX_PARTIES - parties)
372	>	throw new IllegalStateException(badRegister(s));
373	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
374	>	return phase;
375	>	}
376		}
377
378		/**
379	<	* Returns current state, first resolving lagged propagation from
311	<	* root if necessary.
379	>	* Returns message string for out of bounds exceptions on registration.
380		*/
381	<	private long getReconciledState() {
382	<	return (parent == null) ? state : reconcileState();
381	>	private String badRegister(long s) {
382	>	return "Attempt to register more than " +
383	>	MAX_PARTIES + " parties for " + stateToString(s);
384		}
385
386		/**
387	<	* Recursively resolves state.
387	>	* Recursively resolves lagged phase propagation from root if necessary.
388		*/
389		private long reconcileState() {
390		Phaser par = parent;
391		long s = state;
392		if (par != null) {
393	<	int phase, rootPhase;
394	<	while ((phase = phaseOf(s)) >= 0 &&
395	<	(rootPhase = phaseOf(root.state)) != phase &&
396	<	(rootPhase < 0 || unarrivedOf(s) == 0)) {
397	<	long parentState = par.getReconciledState();
398	<	int parentPhase = phaseOf(parentState);
399	<	int parties = partiesOf(s);
400	<	long next = trippedStateFor(parentPhase, parties);
401	<	if (phaseOf(root.state) == rootPhase &&
402	<	parentPhase != phase &&
403	<	state == s && casState(s, next)) {
404	<	releaseWaiters(phase);
405	<	if (parties == 0) // exit if the final deregistration
393	>	Phaser rt = root;
394	>	int phase, rPhase;
395	>	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
396	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
397	>	if ((int)(par.state >>> PHASE_SHIFT) != rPhase)
398	>	par.reconcileState();
399	>	else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
400	>	long u = s & PARTIES_MASK; // reset unarrived to parties
401	>	long next = ((((long) rPhase) << PHASE_SHIFT) | u |
402	>	(u >>> PARTIES_SHIFT));
403	>	if (state == s &&
404	>	UNSAFE.compareAndSwapLong(this, stateOffset,
405	>	s, s = next))
406		break;
407		}
408		s = state;
#	Line 348 | Line 417 | public class Phaser {
417		* phaser will need to first register for it.
418		*/
419		public Phaser() {
420	<	this(null);
420	>	this(null, 0);
421		}
422
423		/**
#	Line 372 | Line 441 | public class Phaser {
441		* @param parent the parent phaser
442		*/
443		public Phaser(Phaser parent) {
444	<	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);
444	>	this(parent, 0);
445		}
446
447		/**
#	Line 395 | Line 456 | public class Phaser {
456		* or greater than the maximum number of parties supported
457		*/
458		public Phaser(Phaser parent, int parties) {
459	<	if (parties < 0 || parties > ushortMask)
459	>	if (parties >>> PARTIES_SHIFT != 0)
460		throw new IllegalArgumentException("Illegal number of parties");
461	<	int phase = 0;
461	>	int phase;
462		this.parent = parent;
463		if (parent != null) {
464	<	this.root = parent.root;
464	>	Phaser r = parent.root;
465	>	this.root = r;
466	>	this.evenQ = r.evenQ;
467	>	this.oddQ = r.oddQ;
468		phase = parent.register();
469		}
470	<	else
470	>	else {
471		this.root = this;
472	<	this.state = trippedStateFor(phase, parties);
472	>	this.evenQ = new AtomicReference<QNode>();
473	>	this.oddQ = new AtomicReference<QNode>();
474	>	phase = 0;
475	>	}
476	>	long p = (long)parties;
477	>	this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
478		}
479
480		/**
481		* Adds a new unarrived party to this phaser.
482		* If an ongoing invocation of {@link #onAdvance} is in progress,
483	<	* this method waits until its completion before registering.
483	>	* this method may wait until its completion before registering.
484		*
485		* @return the arrival phase number to which this registration applied
486		* @throws IllegalStateException if attempting to register more
#	Line 424 | Line 493 | public class Phaser {
493		/**
494		* Adds the given number of new unarrived parties to this phaser.
495		* If an ongoing invocation of {@link #onAdvance} is in progress,
496	<	* this method waits until its completion before registering.
496	>	* this method may wait until its completion before registering.
497		*
498		* @param parties the number of additional parties required to trip barrier
499		* @return the arrival phase number to which this registration applied
#	Line 441 | Line 510 | public class Phaser {
510		}
511
512		/**
444	–	* Shared code for register, bulkRegister
445	–	*/
446	–	private int doRegister(int registrations) {
447	–	Phaser par = parent;
448	–	long s;
449	–	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	–	/**
513		* Arrives at the barrier, but does not wait for others.  (You can
514		* in turn wait for others via {@link #awaitAdvance}).  It is an
515		* unenforced usage error for an unregistered party to invoke this
#	Line 476 | Line 520 | public class Phaser {
520		* of unarrived parties would become negative
521		*/
522		public int arrive() {
523	<	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;
523	>	return doArrive(ONE_ARRIVAL);
524		}
525
526		/**
#	Line 520 | Line 537 | public class Phaser {
537		* of registered or unarrived parties would become negative
538		*/
539		public int arriveAndDeregister() {
540	<	// 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;
540	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
541		}
542
543		/**
#	Line 576 | Line 561 | public class Phaser {
561		* Awaits the phase of the barrier to advance from the given phase
562		* value, returning immediately if the current phase of the
563		* barrier is not equal to the given phase value or this barrier
564	<	* is terminated.  It is an unenforced usage error for an
580	<	* unregistered party to invoke this method.
564	>	* is terminated.
565		*
566		* @param phase an arrival phase number, or negative value if
567		* terminated; this argument is normally the value returned by a
#	Line 588 | Line 572 | public class Phaser {
572		public int awaitAdvance(int phase) {
573		if (phase < 0)
574		return phase;
575	<	int p = getPhase();
576	<	if (p != phase)
577	<	return p;
594	<	return untimedWait(phase);
575	>	long s = (parent == null) ? state : reconcileState();
576	>	int p = (int)(s >>> PHASE_SHIFT);
577	>	return (p != phase) ? p : internalAwaitAdvance(phase, null);
578		}
579
580		/**
#	Line 599 | Line 582 | public class Phaser {
582		* value, throwing {@code InterruptedException} if interrupted
583		* while waiting, or returning immediately if the current phase of
584		* the barrier is not equal to the given phase value or this
585	<	* barrier is terminated. It is an unenforced usage error for an
603	<	* unregistered party to invoke this method.
585	>	* barrier is terminated.
586		*
587		* @param phase an arrival phase number, or negative value if
588		* terminated; this argument is normally the value returned by a
#	Line 613 | Line 595 | public class Phaser {
595		throws InterruptedException {
596		if (phase < 0)
597		return phase;
598	<	int p = getPhase();
599	<	if (p != phase)
600	<	return p;
601	<	return interruptibleWait(phase);
598	>	long s = (parent == null) ? state : reconcileState();
599	>	int p = (int)(s >>> PHASE_SHIFT);
600	>	if (p == phase) {
601	>	QNode node = new QNode(this, phase, true, false, 0L);
602	>	p = internalAwaitAdvance(phase, node);
603	>	if (node.wasInterrupted)
604	>	throw new InterruptedException();
605	>	}
606	>	return p;
607		}
608
609		/**
#	Line 625 | Line 612 | public class Phaser {
612		* InterruptedException} if interrupted while waiting, or
613		* returning immediately if the current phase of the barrier is
614		* not equal to the given phase value or this barrier is
615	<	* terminated.  It is an unenforced usage error for an
629	<	* unregistered party to invoke this method.
615	>	* terminated.
616		*
617		* @param phase an arrival phase number, or negative value if
618		* terminated; this argument is normally the value returned by a
#	Line 643 | Line 629 | public class Phaser {
629		public int awaitAdvanceInterruptibly(int phase,
630		long timeout, TimeUnit unit)
631		throws InterruptedException, TimeoutException {
646	–	long nanos = unit.toNanos(timeout);
632		if (phase < 0)
633		return phase;
634	<	int p = getPhase();
635	<	if (p != phase)
636	<	return p;
637	<	return timedWait(phase, nanos);
634	>	long s = (parent == null) ? state : reconcileState();
635	>	int p = (int)(s >>> PHASE_SHIFT);
636	>	if (p == phase) {
637	>	long nanos = unit.toNanos(timeout);
638	>	QNode node = new QNode(this, phase, true, true, nanos);
639	>	p = internalAwaitAdvance(phase, node);
640	>	if (node.wasInterrupted)
641	>	throw new InterruptedException();
642	>	else if (p == phase)
643	>	throw new TimeoutException();
644	>	}
645	>	return p;
646		}
647
648		/**
649	<	* Forces this barrier to enter termination state. Counts of
650	<	* arrived and registered parties are unaffected. If this phaser
651	<	* has a parent, it too is terminated. This method may be useful
652	<	* for coordinating recovery after one or more tasks encounter
653	<	* unexpected exceptions.
649	>	* Forces this barrier to enter termination state.  Counts of
650	>	* arrived and registered parties are unaffected.  If this phaser
651	>	* is a member of a tiered set of phasers, then all of the phasers
652	>	* in the set are terminated.  If this phaser is already
653	>	* terminated, this method has no effect.  This method may be
654	>	* useful for coordinating recovery after one or more tasks
655	>	* encounter unexpected exceptions.
656		*/
657		public void forceTermination() {
658	<	Phaser r = root;    // force at root then reconcile
658	>	// Only need to change root state
659	>	final Phaser root = this.root;
660		long s;
661	<	while (phaseOf(s = r.state) >= 0)
662	<	r.casState(s, stateFor(-1, partiesOf(s), unarrivedOf(s)));
663	<	reconcileState();
664	<	releaseWaiters(0);  // ensure wakeups on both queues
665	<	releaseWaiters(1);
661	>	while ((s = root.state) >= 0) {
662	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
663	>	s, s | TERMINATION_PHASE)) {
664	>	releaseWaiters(0); // signal all threads
665	>	releaseWaiters(1);
666	>	return;
667	>	}
668	>	}
669		}
670
671		/**
#	Line 677 | Line 676 | public class Phaser {
676		* @return the phase number, or a negative value if terminated
677		*/
678		public final int getPhase() {
679	<	return phaseOf(getReconciledState());
679	>	return (int)(root.state >>> PHASE_SHIFT);
680		}
681
682		/**
#	Line 686 | Line 685 | public class Phaser {
685		* @return the number of parties
686		*/
687		public int getRegisteredParties() {
688	<	return partiesOf(getReconciledState());
688	>	return partiesOf(state);
689		}
690
691		/**
#	Line 696 | Line 695 | public class Phaser {
695		* @return the number of arrived parties
696		*/
697		public int getArrivedParties() {
698	<	return arrivedOf(getReconciledState());
698	>	return arrivedOf(parent==null? state : reconcileState());
699		}
700
701		/**
#	Line 706 | Line 705 | public class Phaser {
705		* @return the number of unarrived parties
706		*/
707		public int getUnarrivedParties() {
708	<	return unarrivedOf(getReconciledState());
708	>	return unarrivedOf(parent==null? state : reconcileState());
709		}
710
711		/**
#	Line 734 | Line 733 | public class Phaser {
733		* @return {@code true} if this barrier has been terminated
734		*/
735		public boolean isTerminated() {
736	<	return getPhase() < 0;
736	>	return root.state < 0L;
737		}
738
739		/**
#	Line 750 | Line 749 | public class Phaser {
749		* which case no advance occurs.
750		*
751		* <p>The arguments to this method provide the state of the phaser
752	<	* prevailing for the current transition. (When called from within
753	<	* an implementation of {@code onAdvance} the values returned by
754	<	* methods such as {@code getPhase} may or may not reliably
755	<	* indicate the state to which this transition applies.)
752	>	* prevailing for the current transition.  The effects of invoking
753	>	* arrival, registration, and waiting methods on this Phaser from
754	>	* within {@code onAdvance} are unspecified and should not be
755	>	* relied on.
756	>	*
757	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
758	>	* {@code onAdvance} is invoked only for its root Phaser on each
759	>	* advance.
760		*
761		* <p>The default version returns {@code true} when the number of
762		* registered parties is zero. Normally, overrides that arrange
#	Line 778 | Line 781 | public class Phaser {
781		* @return a string identifying this barrier, as well as its state
782		*/
783		public String toString() {
784	<	long s = getReconciledState();
784	>	return stateToString(reconcileState());
785	>	}
786	>
787	>	/**
788	>	* Implementation of toString and string-based error messages
789	>	*/
790	>	private String stateToString(long s) {
791		return super.toString() +
792		"[phase = " + phaseOf(s) +
793		" parties = " + partiesOf(s) +
794		" arrived = " + arrivedOf(s) + "]";
795		}
796
797	<	// methods for waiting
797	>	// Waiting mechanics
798	>
799	>	/**
800	>	* Removes and signals threads from queue for phase.
801	>	*/
802	>	private void releaseWaiters(int phase) {
803	>	AtomicReference<QNode> head = queueFor(phase);
804	>	QNode q;
805	>	int p;
806	>	while ((q = head.get()) != null &&
807	>	((p = q.phase) == phase ||
808	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
809	>	if (head.compareAndSet(q, q.next))
810	>	q.signal();
811	>	}
812	>	}
813	>
814	>	/** The number of CPUs, for spin control */
815	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
816	>
817	>	/**
818	>	* The number of times to spin before blocking while waiting for
819	>	* advance, per arrival while waiting. On multiprocessors, fully
820	>	* blocking and waking up a large number of threads all at once is
821	>	* usually a very slow process, so we use rechargeable spins to
822	>	* avoid it when threads regularly arrive: When a thread in
823	>	* internalAwaitAdvance notices another arrival before blocking,
824	>	* and there appear to be enough CPUs available, it spins
825	>	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
826	>	* uniprocessors, there is at least one intervening Thread.yield
827	>	* before blocking. The value trades off good-citizenship vs big
828	>	* unnecessary slowdowns.
829	>	*/
830	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
831	>
832	>	/**
833	>	* Possibly blocks and waits for phase to advance unless aborted.
834	>	*
835	>	* @param phase current phase
836	>	* @param node if non-null, the wait node to track interrupt and timeout;
837	>	* if null, denotes noninterruptible wait
838	>	* @return current phase
839	>	*/
840	>	private int internalAwaitAdvance(int phase, QNode node) {
841	>	Phaser current = this;       // to eventually wait at root if tiered
842	>	boolean queued = false;      // true when node is enqueued
843	>	int lastUnarrived = -1;      // to increase spins upon change
844	>	int spins = SPINS_PER_ARRIVAL;
845	>	long s;
846	>	int p;
847	>	while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) {
848	>	Phaser par;
849	>	int unarrived = (int)s & UNARRIVED_MASK;
850	>	if (unarrived != lastUnarrived) {
851	>	if (lastUnarrived == -1) // ensure old queue clean
852	>	releaseWaiters(phase-1);
853	>	if ((lastUnarrived = unarrived) < NCPU)
854	>	spins += SPINS_PER_ARRIVAL;
855	>	}
856	>	else if (unarrived == 0 && (par = current.parent) != null) {
857	>	current = par;       // if all arrived, use parent
858	>	par = par.parent;
859	>	lastUnarrived = -1;
860	>	}
861	>	else if (spins > 0) {
862	>	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
863	>	Thread.yield();  // yield midway through spin
864	>	}
865	>	else if (node == null)   // must be noninterruptible
866	>	node = new QNode(this, phase, false, false, 0L);
867	>	else if (node.isReleasable()) {
868	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
869	>	break;
870	>	else
871	>	return phase;    // aborted
872	>	}
873	>	else if (!queued) {      // push onto queue
874	>	AtomicReference<QNode> head = queueFor(phase);
875	>	QNode q = head.get();
876	>	if (q == null || q.phase == phase) {
877	>	node.next = q;
878	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
879	>	break;       // recheck to avoid stale enqueue
880	>	else
881	>	queued = head.compareAndSet(q, node);
882	>	}
883	>	}
884	>	else {
885	>	try {
886	>	ForkJoinPool.managedBlock(node);
887	>	} catch (InterruptedException ie) {
888	>	node.wasInterrupted = true;
889	>	}
890	>	}
891	>	}
892	>	releaseWaiters(phase);
893	>	if (node != null)
894	>	node.onRelease();
895	>	return p;
896	>	}
897
898		/**
899		* Wait nodes for Treiber stack representing wait queue
#	Line 793 | Line 901 | public class Phaser {
901		static final class QNode implements ForkJoinPool.ManagedBlocker {
902		final Phaser phaser;
903		final int phase;
796	–	final long startTime;
797	–	final long nanos;
798	–	final boolean timed;
904		final boolean interruptible;
905	<	volatile boolean wasInterrupted = false;
905	>	final boolean timed;
906	>	boolean wasInterrupted;
907	>	long nanos;
908	>	long lastTime;
909		volatile Thread thread; // nulled to cancel wait
910		QNode next;
911
912		QNode(Phaser phaser, int phase, boolean interruptible,
913	<	boolean timed, long startTime, long nanos) {
913	>	boolean timed, long nanos) {
914		this.phaser = phaser;
915		this.phase = phase;
808	–	this.timed = timed;
916		this.interruptible = interruptible;
810	–	this.startTime = startTime;
917		this.nanos = nanos;
918	+	this.timed = timed;
919	+	this.lastTime = timed? System.nanoTime() : 0L;
920		thread = Thread.currentThread();
921		}
922
923		public boolean isReleasable() {
924	<	return (thread == null ||
925	<	phaser.getPhase() != phase ||
926	<	(interruptible && wasInterrupted) ||
927	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
924	>	Thread t = thread;
925	>	if (t != null) {
926	>	if (phaser.getPhase() != phase)
927	>	t = null;
928	>	else {
929	>	if (Thread.interrupted())
930	>	wasInterrupted = true;
931	>	if (interruptible && wasInterrupted)
932	>	t = null;
933	>	else if (timed) {
934	>	if (nanos > 0) {
935	>	long now = System.nanoTime();
936	>	nanos -= now - lastTime;
937	>	lastTime = now;
938	>	}
939	>	if (nanos <= 0)
940	>	t = null;
941	>	}
942	>	}
943	>	if (t != null)
944	>	return false;
945	>	thread = null;
946	>	}
947	>	return true;
948		}
949
950		public boolean block() {
951	<	if (Thread.interrupted()) {
952	<	wasInterrupted = true;
953	<	if (interruptible)
826	<	return true;
827	<	}
828	<	if (!timed)
951	>	if (isReleasable())
952	>	return true;
953	>	else if (!timed)
954		LockSupport.park(this);
955	<	else {
956	<	long waitTime = nanos - (System.nanoTime() - startTime);
832	<	if (waitTime <= 0)
833	<	return true;
834	<	LockSupport.parkNanos(this, waitTime);
835	<	}
955	>	else if (nanos > 0)
956	>	LockSupport.parkNanos(this, nanos);
957		return isReleasable();
958		}
959
#	Line 844 | Line 965 | public class Phaser {
965		}
966		}
967
968	<	boolean doWait() {
969	<	if (thread != null) {
970	<	try {
971	<	ForkJoinPool.managedBlock(this);
972	<	} catch (InterruptedException ie) {
852	<	wasInterrupted = true; // can't currently happen
853	<	}
854	<	}
855	<	return wasInterrupted;
856	<	}
857	<	}
858	<
859	<	/**
860	<	* Removes and signals waiting threads from wait queue.
861	<	*/
862	<	private void releaseWaiters(int phase) {
863	<	AtomicReference<QNode> head = queueFor(phase);
864	<	QNode q;
865	<	while ((q = head.get()) != null) {
866	<	if (head.compareAndSet(q, q.next))
867	<	q.signal();
868	<	}
869	<	}
870	<
871	<	/**
872	<	* Tries to enqueue given node in the appropriate wait queue.
873	<	*
874	<	* @return true if successful
875	<	*/
876	<	private boolean tryEnqueue(QNode node) {
877	<	AtomicReference<QNode> head = queueFor(node.phase);
878	<	return head.compareAndSet(node.next = head.get(), node);
879	<	}
880	<
881	<	/**
882	<	* Enqueues node and waits unless aborted or signalled.
883	<	*
884	<	* @return current phase
885	<	*/
886	<	private int untimedWait(int phase) {
887	<	QNode node = null;
888	<	boolean queued = false;
889	<	boolean interrupted = false;
890	<	int p;
891	<	while ((p = getPhase()) == phase) {
892	<	if (Thread.interrupted())
893	<	interrupted = true;
894	<	else if (node == null)
895	<	node = new QNode(this, phase, false, false, 0, 0);
896	<	else if (!queued)
897	<	queued = tryEnqueue(node);
898	<	else if (node.doWait())
899	<	interrupted = true;
900	<	}
901	<	if (node != null)
902	<	node.thread = null;
903	<	releaseWaiters(phase);
904	<	if (interrupted)
905	<	Thread.currentThread().interrupt();
906	<	return p;
907	<	}
908	<
909	<	/**
910	<	* Interruptible version
911	<	* @return current phase
912	<	*/
913	<	private int interruptibleWait(int phase) throws InterruptedException {
914	<	QNode node = null;
915	<	boolean queued = false;
916	<	boolean interrupted = false;
917	<	int p;
918	<	while ((p = getPhase()) == phase && !interrupted) {
919	<	if (Thread.interrupted())
920	<	interrupted = true;
921	<	else if (node == null)
922	<	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;
968	>	void onRelease() { // actions upon return from internalAwaitAdvance
969	>	if (!interruptible && wasInterrupted)
970	>	Thread.currentThread().interrupt();
971	>	if (thread != null)
972	>	thread = null;
973		}
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	–	}
974
937	–	/**
938	–	* Timeout version.
939	–	* @return current phase
940	–	*/
941	–	private int timedWait(int phase, long nanos)
942	–	throws InterruptedException, TimeoutException {
943	–	long startTime = System.nanoTime();
944	–	QNode node = null;
945	–	boolean queued = false;
946	–	boolean interrupted = false;
947	–	int p;
948	–	while ((p = getPhase()) == phase && !interrupted) {
949	–	if (Thread.interrupted())
950	–	interrupted = true;
951	–	else if (nanos - (System.nanoTime() - startTime) <= 0)
952	–	break;
953	–	else if (node == null)
954	–	node = new QNode(this, phase, true, true, startTime, nanos);
955	–	else if (!queued)
956	–	queued = tryEnqueue(node);
957	–	else if (node.doWait())
958	–	interrupted = true;
959	–	}
960	–	if (node != null)
961	–	node.thread = null;
962	–	if (p != phase || (p = getPhase()) != phase)
963	–	releaseWaiters(phase);
964	–	if (interrupted)
965	–	throw new InterruptedException();
966	–	if (p == phase)
967	–	throw new TimeoutException();
968	–	return p;
975		}
976
977		// Unsafe mechanics
#	Line 974 | Line 980 | public class Phaser {
980		private static final long stateOffset =
981		objectFieldOffset("state", Phaser.class);
982
977	–	private final boolean casState(long cmp, long val) {
978	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
979	–	}
980	–
983		private static long objectFieldOffset(String field, Class<?> klazz) {
984		try {
985		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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