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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.44 by dl, Tue Aug 25 16:32:28 2009 UTC vs.
Revision 1.49 by dl, Fri Nov 5 23:01:47 2010 UTC

#	Line 7 | Line 7
7		package jsr166y;
8
9		import java.util.concurrent.*;
10	–
10		import java.util.concurrent.atomic.AtomicReference;
11		import java.util.concurrent.locks.LockSupport;
12
#	Line 109 | Line 108 | import java.util.concurrent.locks.LockSu
108		* <p><b>Sample usages:</b>
109		*
110		* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
111	<	* to control a one-shot action serving a variable number of
112	<	* parties. The typical idiom is for the method setting this up to
113	<	* first register, then start the actions, then deregister, as in:
111	>	* to control a one-shot action serving a variable number of parties.
112	>	* The typical idiom is for the method setting this up to first
113	>	* register, then start the actions, then deregister, as in:
114		*
115		*  <pre> {@code
116		* void runTasks(List<Runnable> tasks) {
#	Line 142 | Line 141 | import java.util.concurrent.locks.LockSu
141		*     }
142		*   };
143		*   phaser.register();
144	<	*   for (Runnable task : tasks) {
144	>	*   for (final Runnable task : tasks) {
145		*     phaser.register();
146		*     new Thread() {
147		*       public void run() {
148		*         do {
149		*           task.run();
150		*           phaser.arriveAndAwaitAdvance();
151	<	*         } while(!phaser.isTerminated();
151	>	*         } while (!phaser.isTerminated());
152		*       }
153		*     }.start();
154		*   }
#	Line 158 | Line 157 | import java.util.concurrent.locks.LockSu
157		*
158		* If the main task must later await termination, it
159		* may re-register and then execute a similar loop:
160	<	* <pre> {@code
160	>	*  <pre> {@code
161		*   // ...
162		*   phaser.register();
163		*   while (!phaser.isTerminated())
164	<	*     phaser.arriveAndAwaitAdvance();
166	<	* }</pre>
164	>	*     phaser.arriveAndAwaitAdvance();}</pre>
165		*
166	<	* Related constructions may be used to await particular phase numbers
166	>	* <p>Related constructions may be used to await particular phase numbers
167		* in contexts where you are sure that the phase will never wrap around
168		* {@code Integer.MAX_VALUE}. For example:
169		*
170	<	* <pre> {@code
171	<	*   void awaitPhase(Phaser phaser, int phase) {
172	<	*     int p = phaser.register(); // assumes caller not already registered
173	<	*     while (p < phase) {
174	<	*       if (phaser.isTerminated())
175	<	*         // ... deal with unexpected termination
176	<	*       else
177	<	*         p = phaser.arriveAndAwaitAdvance();
180	<	*     }
181	<	*     phaser.arriveAndDeregister();
170	>	*  <pre> {@code
171	>	* void awaitPhase(Phaser phaser, int phase) {
172	>	*   int p = phaser.register(); // assumes caller not already registered
173	>	*   while (p < phase) {
174	>	*     if (phaser.isTerminated())
175	>	*       // ... deal with unexpected termination
176	>	*     else
177	>	*       p = phaser.arriveAndAwaitAdvance();
178		*   }
179	<	* }</pre>
179	>	*   phaser.arriveAndDeregister();
180	>	* }}</pre>
181		*
182		*
183		* <p>To create a set of tasks using a tree of phasers,
184		* you could use code of the following form, assuming a
185		* Task class with a constructor accepting a phaser that
186	<	* it registers for upon construction:
186	>	* it registers with upon construction:
187	>	*
188		*  <pre> {@code
189		* void build(Task[] actions, int lo, int hi, Phaser ph) {
190		*   if (hi - lo > TASKS_PER_PHASER) {
#	Line 208 | Line 206 | import java.util.concurrent.locks.LockSu
206		* be appropriate for extremely small per-barrier task bodies (thus
207		* high rates), or up to hundreds for extremely large ones.
208		*
211	–	* </pre>
212	–	*
209		* <p><b>Implementation notes</b>: This implementation restricts the
210		* maximum number of parties to 65535. Attempts to register additional
211		* parties result in {@code IllegalStateException}. However, you can and
#	Line 298 | Line 294 | public class Phaser {
294
295		/**
296		* Heads of Treiber stacks for waiting threads. To eliminate
297	<	* contention while releasing some threads while adding others, we
297	>	* contention when releasing some threads while adding others, we
298		* use two of them, alternating across even and odd phases.
299	+	* Subphasers share queues with root to speed up releases.
300		*/
301		private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
302		private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
303
304		private AtomicReference<QNode> queueFor(int phase) {
305	<	return ((phase & 1) == 0) ? evenQ : oddQ;
305	>	Phaser r = root;
306	>	return ((phase & 1) == 0) ? r.evenQ : r.oddQ;
307		}
308
309		/**
#	Line 320 | Line 318 | public class Phaser {
318		* Recursively resolves state.
319		*/
320		private long reconcileState() {
321	<	Phaser p = parent;
321	>	Phaser par = parent;
322		long s = state;
323	<	if (p != null) {
324	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
325	<	long parentState = p.getReconciledState();
323	>	if (par != null) {
324	>	int phase, rootPhase;
325	>	while ((phase = phaseOf(s)) >= 0 &&
326	>	(rootPhase = phaseOf(root.state)) != phase &&
327	>	(rootPhase < 0 || unarrivedOf(s) == 0)) {
328	>	long parentState = par.getReconciledState();
329		int parentPhase = phaseOf(parentState);
330	<	int phase = phaseOf(s = state);
331	<	if (phase != parentPhase) {
332	<	long next = trippedStateFor(parentPhase, partiesOf(s));
333	<	if (casState(s, next)) {
334	<	releaseWaiters(phase);
335	<	s = next;
336	<	}
330	>	int parties = partiesOf(s);
331	>	long next = trippedStateFor(parentPhase, parties);
332	>	if (phaseOf(root.state) == rootPhase &&
333	>	parentPhase != phase &&
334	>	state == s && casState(s, next)) {
335	>	releaseWaiters(phase);
336	>	if (parties == 0) // exit if the final deregistration
337	>	break;
338		}
339	+	s = state;
340		}
341		}
342		return s;
#	Line 349 | Line 352 | public class Phaser {
352		}
353
354		/**
355	<	* Creates a new phaser with the given numbers of registered
355	>	* Creates a new phaser with the given number of registered
356		* unarrived parties, initial phase number 0, and no parent.
357		*
358		* @param parties the number of parties required to trip barrier
#	Line 381 | Line 384 | public class Phaser {
384		}
385
386		/**
387	<	* Creates a new phaser with the given parent and numbers of
387	>	* Creates a new phaser with the given parent and number of
388		* registered unarrived parties. If parent is non-null, this phaser
389		* is registered with the parent and its initial phase number is
390		* the same as that of parent phaser.
#	Line 407 | Line 410 | public class Phaser {
410
411		/**
412		* Adds a new unarrived party to this phaser.
413	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
414	+	* this method waits until its completion before registering.
415		*
416		* @return the arrival phase number to which this registration applied
417		* @throws IllegalStateException if attempting to register more
#	Line 418 | Line 423 | public class Phaser {
423
424		/**
425		* Adds the given number of new unarrived parties to this phaser.
426	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
427	+	* this method waits until its completion before registering.
428		*
429	<	* @param parties the number of parties required to trip barrier
429	>	* @param parties the number of additional parties required to trip barrier
430		* @return the arrival phase number to which this registration applied
431		* @throws IllegalStateException if attempting to register more
432		* than the maximum supported number of parties
433	+	* @throws IllegalArgumentException if {@code parties < 0}
434		*/
435		public int bulkRegister(int parties) {
436		if (parties < 0)
#	Line 436 | Line 444 | public class Phaser {
444		* Shared code for register, bulkRegister
445		*/
446		private int doRegister(int registrations) {
447	+	Phaser par = parent;
448	+	long s;
449		int phase;
450	<	for (;;) {
451	<	long s = getReconciledState();
452	<	phase = phaseOf(s);
453	<	int unarrived = unarrivedOf(s) + registrations;
454	<	int parties = partiesOf(s) + registrations;
455	<	if (phase < 0)
456	<	break;
457	<	if (parties > ushortMask || unarrived > ushortMask)
458	<	throw new IllegalStateException(badBounds(parties, unarrived));
459	<	if (phase == phaseOf(root.state) &&
460	<	casState(s, stateFor(phase, parties, unarrived)))
461	<	break;
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		}
#	Line 464 | Line 476 | public class Phaser {
476		* of unarrived parties would become negative
477		*/
478		public int arrive() {
479	+	Phaser par = parent;
480	+	long s;
481		int phase;
482	<	for (;;) {
469	<	long s = state;
470	<	phase = phaseOf(s);
471	<	if (phase < 0)
472	<	break;
482	>	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
483		int parties = partiesOf(s);
484		int unarrived = unarrivedOf(s) - 1;
485	<	if (unarrived > 0) {        // Not the last arrival
486	<	if (casState(s, s - 1)) // s-1 adds one arrival
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 (unarrived == 0) {  // the last arrival
493	<	Phaser par = parent;
494	<	if (par == null) {      // directly trip
495	<	if (casState
496	<	(s,
497	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
485	<	((phase + 1) & phaseMask), parties))) {
486	<	releaseWaiters(phase);
487	<	break;
488	<	}
489	<	}
490	<	else {                  // cascade to parent
491	<	if (casState(s, s - 1)) { // zeroes unarrived
492	<	par.arrive();
493	<	reconcileState();
494	<	break;
495	<	}
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 (phase != phaseOf(root.state)) // or if unreconciled
500	>	else if (phaseOf(root.state) == phase && casState(s, s - 1)) {
501	>	par.arrive();                   // cascade to parent
502		reconcileState();
503	<	else
504	<	throw new IllegalStateException(badBounds(parties, unarrived));
503	>	break;
504	>	}
505		}
506		return phase;
507		}
#	Line 517 | Line 520 | public class Phaser {
520		* of registered or unarrived parties would become negative
521		*/
522		public int arriveAndDeregister() {
523	<	// similar code to arrive, but too different to merge
523	>	// similar to arrive, but too different to merge
524		Phaser par = parent;
525	+	long s;
526		int phase;
527	<	for (;;) {
524	<	long s = state;
525	<	phase = phaseOf(s);
526	<	if (phase < 0)
527	<	break;
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) {
531	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
532	<	if (casState
533	<	(s,
534	<	stateFor(phase, parties, unarrived))) {
535	<	if (unarrived == 0) {
536	<	par.arriveAndDeregister();
537	<	reconcileState();
538	<	}
539	<	break;
540	<	}
541	<	continue;
542	<	}
543	<	if (unarrived == 0) {
544	<	if (casState
545	<	(s,
546	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
547	<	((phase + 1) & phaseMask), parties))) {
548	<	releaseWaiters(phase);
549	<	break;
550	<	}
551	<	continue;
552	<	}
553	<	if (par != null && phase != phaseOf(root.state)) {
554	<	reconcileState();
555	<	continue;
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	<	throw new IllegalStateException(badBounds(parties, unarrived));
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;
556		}
#	Line 564 | Line 559 | public class Phaser {
559		* Arrives at the barrier and awaits others. Equivalent in effect
560		* to {@code awaitAdvance(arrive())}.  If you need to await with
561		* interruption or timeout, you can arrange this with an analogous
562	<	* construction using one of the other forms of the awaitAdvance
563	<	* method.  If instead you need to deregister upon arrival use
564	<	* {@code arriveAndDeregister}. It is an unenforced usage error
565	<	* for an unregistered party to invoke this method.
562	>	* construction using one of the other forms of the {@code
563	>	* awaitAdvance} method.  If instead you need to deregister upon
564	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
565	>	* usage error for an unregistered party to invoke this method.
566		*
567		* @return the arrival phase number, or a negative number if terminated
568		* @throws IllegalStateException if not terminated and the number
#	Line 593 | Line 588 | public class Phaser {
588		public int awaitAdvance(int phase) {
589		if (phase < 0)
590		return phase;
591	<	long s = getReconciledState();
597	<	int p = phaseOf(s);
591	>	int p = getPhase();
592		if (p != phase)
593		return p;
600	–	if (unarrivedOf(s) == 0 && parent != null)
601	–	parent.awaitAdvance(phase);
602	–	// Fall here even if parent waited, to reconcile and help release
594		return untimedWait(phase);
595		}
596
#	Line 622 | Line 613 | public class Phaser {
613		throws InterruptedException {
614		if (phase < 0)
615		return phase;
616	<	long s = getReconciledState();
626	<	int p = phaseOf(s);
616	>	int p = getPhase();
617		if (p != phase)
618		return p;
629	–	if (unarrivedOf(s) == 0 && parent != null)
630	–	parent.awaitAdvanceInterruptibly(phase);
619		return interruptibleWait(phase);
620		}
621
#	Line 655 | Line 643 | public class Phaser {
643		public int awaitAdvanceInterruptibly(int phase,
644		long timeout, TimeUnit unit)
645		throws InterruptedException, TimeoutException {
646	+	long nanos = unit.toNanos(timeout);
647		if (phase < 0)
648		return phase;
649	<	long s = getReconciledState();
661	<	int p = phaseOf(s);
649	>	int p = getPhase();
650		if (p != phase)
651		return p;
652	<	if (unarrivedOf(s) == 0 && parent != null)
665	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
666	<	return timedWait(phase, unit.toNanos(timeout));
652	>	return timedWait(phase, nanos);
653		}
654
655		/**
#	Line 674 | Line 660 | public class Phaser {
660		* unexpected exceptions.
661		*/
662		public void forceTermination() {
663	<	for (;;) {
664	<	long s = getReconciledState();
665	<	int phase = phaseOf(s);
666	<	int parties = partiesOf(s);
667	<	int unarrived = unarrivedOf(s);
668	<	if (phase < 0 ||
669	<	casState(s, stateFor(-1, parties, unarrived))) {
684	<	releaseWaiters(0);
685	<	releaseWaiters(1);
686	<	if (parent != null)
687	<	parent.forceTermination();
688	<	return;
689	<	}
690	<	}
663	>	Phaser r = root;    // force at root then reconcile
664	>	long s;
665	>	while (phaseOf(s = r.state) >= 0)
666	>	r.casState(s, stateFor(-1, partiesOf(s), unarrivedOf(s)));
667	>	reconcileState();
668	>	releaseWaiters(0);  // ensure wakeups on both queues
669	>	releaseWaiters(1);
670		}
671
672		/**
#	Line 707 | Line 686 | public class Phaser {
686		* @return the number of parties
687		*/
688		public int getRegisteredParties() {
689	<	return partiesOf(state);
689	>	return partiesOf(getReconciledState());
690		}
691
692		/**
#	Line 717 | Line 696 | public class Phaser {
696		* @return the number of arrived parties
697		*/
698		public int getArrivedParties() {
699	<	return arrivedOf(state);
699	>	return arrivedOf(getReconciledState());
700		}
701
702		/**
#	Line 727 | Line 706 | public class Phaser {
706		* @return the number of unarrived parties
707		*/
708		public int getUnarrivedParties() {
709	<	return unarrivedOf(state);
709	>	return unarrivedOf(getReconciledState());
710		}
711
712		/**
#	Line 781 | Line 760 | public class Phaser {
760		* termination for other reasons should also preserve this
761		* property.
762		*
784	–	* <p>You may override this method to perform an action with side
785	–	* effects visible to participating tasks, but doing so requires
786	–	* care: Method {@code onAdvance} may be invoked more than once
787	–	* per transition.  Further, unless all parties register before
788	–	* any arrive, and all {@link #awaitAdvance} at each phase, then
789	–	* you cannot ensure lack of interference from other parties
790	–	* during the invocation of this method.
791	–	*
763		* @param phase the phase number on entering the barrier
764		* @param registeredParties the current number of registered parties
765		* @return {@code true} if this barrier should terminate
#	Line 829 | Line 800 | public class Phaser {
800		volatile boolean wasInterrupted = false;
801		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;
#	Line 839 | Line 811 | public class Phaser {
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;
#	Line 861 | Line 835 | public class Phaser {
835		}
836		return isReleasable();
837		}
838	+
839		void signal() {
840		Thread t = thread;
841		if (t != null) {
#	Line 868 | Line 843 | public class Phaser {
843		LockSupport.unpark(t);
844		}
845		}
846	+
847		boolean doWait() {
848		if (thread != null) {
849		try {
850	<	ForkJoinPool.managedBlock(this, false);
850	>	ForkJoinPool.managedBlock(this);
851		} catch (InterruptedException ie) {
852	+	wasInterrupted = true; // can't currently happen
853		}
854		}
855		return wasInterrupted;
856		}
880	–
857		}
858
859		/**
#	Line 919 | Line 895 | public class Phaser {
895		node = new QNode(this, phase, false, false, 0, 0);
896		else if (!queued)
897		queued = tryEnqueue(node);
898	<	else
899	<	interrupted = node.doWait();
898	>	else if (node.doWait())
899	>	interrupted = true;
900		}
901		if (node != null)
902		node.thread = null;
#	Line 946 | Line 922 | public class Phaser {
922		node = new QNode(this, phase, true, false, 0, 0);
923		else if (!queued)
924		queued = tryEnqueue(node);
925	<	else
926	<	interrupted = node.doWait();
925	>	else if (node.doWait())
926	>	interrupted = true;
927		}
928		if (node != null)
929		node.thread = null;
#	Line 978 | Line 954 | public class Phaser {
954		node = new QNode(this, phase, true, true, startTime, nanos);
955		else if (!queued)
956		queued = tryEnqueue(node);
957	<	else
958	<	interrupted = node.doWait();
957	>	else if (node.doWait())
958	>	interrupted = true;
959		}
960		if (node != null)
961		node.thread = null;

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