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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 1.59 by dl, Sat Nov 27 16:46:53 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 78 | Line 79 | import java.util.concurrent.locks.LockSu
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
82	>	* onAdvance} returns {@code true}. The default implementation returns
83	>	* {@code true} if a deregistration has caused the number of
84	>	* registered parties to become zero.  As illustrated below, when
85		* phasers control actions with a fixed number of iterations, it is
86		* often convenient to override this method to cause termination when
87		* the current phase number reaches a threshold. Method {@link
88		* #forceTermination} is also available to abruptly release waiting
89		* threads and allow them to terminate.
90		*
91	<	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
92	<	* in tree structures) to reduce contention. Phasers with large
93	<	* numbers of parties that would otherwise experience heavy
91	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
92	>	* constructed in tree structures) to reduce contention. Phasers with
93	>	* large numbers of parties that would otherwise experience heavy
94		* synchronization contention costs may instead be set up so that
95		* groups of sub-phasers share a common parent.  This may greatly
96		* increase throughput even though it incurs greater per-operation
#	Line 226 | Line 229 | public class Phaser {
229		* Barrier state representation. Conceptually, a barrier contains
230		* four values:
231		*
232	<	* * parties -- the number of parties to wait (16 bits)
233	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
234	<	* * phase -- the generation of the barrier (31 bits)
235	<	* * terminated -- set if barrier is terminated (1 bit)
232	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
233	>	* * parties -- the number of parties to wait              (bits 16-31)
234	>	* * phase -- the generation of the barrier                (bits 32-62)
235	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
236		*
237		* However, to efficiently maintain atomicity, these values are
238		* packed into a single (atomic) long. Termination uses the sign
239		* bit of 32 bit representation of phase, so phase is set to -1 on
240		* termination. Good performance relies on keeping state decoding
241		* 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.
242		*/
243		private volatile long state;
244
245	<	private static final int ushortMask = 0xffff;
246	<	private static final int phaseMask  = 0x7fffffff;
245	>	private static final int  MAX_PARTIES     = 0xffff;
246	>	private static final int  MAX_PHASE       = 0x7fffffff;
247	>	private static final int  PARTIES_SHIFT   = 16;
248	>	private static final int  PHASE_SHIFT     = 32;
249	>	private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
250	>	private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
251	>	private static final long ONE_ARRIVAL     = 1L;
252	>	private static final long ONE_PARTY       = 1L << PARTIES_SHIFT;
253	>	private static final long TERMINATION_BIT = 1L << 63;
254	>
255	>	// The following unpacking methods are usually manually inlined
256
257		private static int unarrivedOf(long s) {
258	<	return (int) (s & ushortMask);
258	>	return (int)s & UNARRIVED_MASK;
259		}
260
261		private static int partiesOf(long s) {
262	<	return ((int) s) >>> 16;
262	>	return (int)s >>> PARTIES_SHIFT;
263		}
264
265		private static int phaseOf(long s) {
266	<	return (int) (s >>> 32);
266	>	return (int) (s >>> PHASE_SHIFT);
267		}
268
269		private static int arrivedOf(long s) {
270		return partiesOf(s) - unarrivedOf(s);
271		}
272
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	–
273		/**
274		* The parent of this phaser, or null if none
275		*/
#	Line 290 | Line 281 | public class Phaser {
281		*/
282		private final Phaser root;
283
293	–	// Wait queues
294	–
284		/**
285		* Heads of Treiber stacks for waiting threads. To eliminate
286		* contention when releasing some threads while adding others, we
287		* use two of them, alternating across even and odd phases.
288		* Subphasers share queues with root to speed up releases.
289		*/
290	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
291	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
290	>	private final AtomicReference<QNode> evenQ;
291	>	private final AtomicReference<QNode> oddQ;
292
293		private AtomicReference<QNode> queueFor(int phase) {
294	<	Phaser r = root;
295	<	return ((phase & 1) == 0) ? r.evenQ : r.oddQ;
294	>	return ((phase & 1) == 0) ? evenQ : oddQ;
295	>	}
296	>
297	>	/**
298	>	* Returns message string for bounds exceptions on arrival.
299	>	*/
300	>	private String badArrive(long s) {
301	>	return "Attempted arrival of unregistered party for " +
302	>	stateToString(s);
303	>	}
304	>
305	>	/**
306	>	* Returns message string for bounds exceptions on registration.
307	>	*/
308	>	private String badRegister(long s) {
309	>	return "Attempt to register more than " +
310	>	MAX_PARTIES + " parties for " + stateToString(s);
311	>	}
312	>
313	>	/**
314	>	* Main implementation for methods arrive and arriveAndDeregister.
315	>	* Manually tuned to speed up and minimize race windows for the
316	>	* common case of just decrementing unarrived field.
317	>	*
318	>	* @param adj - adjustment to apply to state -- either
319	>	* ONE_ARRIVAL (for arrive) or
320	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
321	>	*/
322	>	private int doArrive(long adj) {
323	>	for (;;) {
324	>	long s = state;
325	>	int unarrived = (int)s & UNARRIVED_MASK;
326	>	int phase = (int)(s >>> PHASE_SHIFT);
327	>	if (phase < 0)
328	>	return phase;
329	>	else if (unarrived == 0) {
330	>	if (reconcileState() == s)     // recheck
331	>	throw new IllegalStateException(badArrive(s));
332	>	}
333	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
334	>	if (unarrived == 1) {
335	>	long p = s & PARTIES_MASK; // unshifted parties field
336	>	long lu = p >>> PARTIES_SHIFT;
337	>	int u = (int)lu;
338	>	int nextPhase = (phase + 1) & MAX_PHASE;
339	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
340	>	final Phaser parent = this.parent;
341	>	if (parent == null) {
342	>	if (onAdvance(phase, u))
343	>	next |= TERMINATION_BIT;
344	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
345	>	releaseWaiters(phase);
346	>	}
347	>	else {
348	>	parent.doArrive((u == 0) ?
349	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
350	>	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase ||
351	>	((int)(state >>> PHASE_SHIFT) != nextPhase &&
352	>	!UNSAFE.compareAndSwapLong(this, stateOffset,
353	>	s, next)))
354	>	reconcileState();
355	>	}
356	>	}
357	>	return phase;
358	>	}
359	>	}
360		}
361
362		/**
363	<	* Returns current state, first resolving lagged propagation from
364	<	* root if necessary.
363	>	* Implementation of register, bulkRegister
364	>	*
365	>	* @param registrations number to add to both parties and
366	>	* unarrived fields. Must be greater than zero.
367		*/
368	<	private long getReconciledState() {
369	<	return (parent == null) ? state : reconcileState();
368	>	private int doRegister(int registrations) {
369	>	// adjustment to state
370	>	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
371	>	final Phaser parent = this.parent;
372	>	for (;;) {
373	>	long s = (parent == null) ? state : reconcileState();
374	>	int parties = (int)s >>> PARTIES_SHIFT;
375	>	int phase = (int)(s >>> PHASE_SHIFT);
376	>	if (phase < 0)
377	>	return phase;
378	>	else if (registrations > MAX_PARTIES - parties)
379	>	throw new IllegalStateException(badRegister(s));
380	>	else if ((parties == 0 && parent == null) || // first reg of root
381	>	((int)s & UNARRIVED_MASK) != 0) {   // not advancing
382	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
383	>	return phase;
384	>	}
385	>	else if (parties != 0)               // wait for onAdvance
386	>	internalAwaitAdvance(phase, null);
387	>	else {                               // 1st registration of child
388	>	synchronized(this) {             // register parent first
389	>	if (reconcileState() == s) { // recheck under lock
390	>	parent.doRegister(1);    // OK if throws IllegalState
391	>	for (;;) {               // simpler form of outer loop
392	>	s = reconcileState();
393	>	phase = (int)(s >>> PHASE_SHIFT);
394	>	if (phase < 0 ||
395	>	UNSAFE.compareAndSwapLong(this, stateOffset,
396	>	s, s + adj))
397	>	return phase;
398	>	}
399	>	}
400	>	}
401	>	}
402	>	}
403		}
404
405		/**
406	<	* Recursively resolves state.
406	>	* Recursively resolves lagged phase propagation from root if necessary.
407		*/
408		private long reconcileState() {
409		Phaser par = parent;
410		long s = state;
411		if (par != null) {
412	<	int phase, rootPhase;
413	<	while ((phase = phaseOf(s)) >= 0 &&
414	<	(rootPhase = phaseOf(root.state)) != phase &&
415	<	(rootPhase < 0 || unarrivedOf(s) == 0)) {
416	<	long parentState = par.getReconciledState();
417	<	int parentPhase = phaseOf(parentState);
418	<	int parties = partiesOf(s);
419	<	long next = trippedStateFor(parentPhase, parties);
420	<	if (phaseOf(root.state) == rootPhase &&
421	<	parentPhase != phase &&
422	<	state == s && casState(s, next)) {
335	<	releaseWaiters(phase);
336	<	if (parties == 0) // exit if the final deregistration
337	<	break;
412	>	Phaser rt = root;
413	>	int phase, rPhase;
414	>	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
415	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
416	>	if ((int)(par.state >>> PHASE_SHIFT) != rPhase)
417	>	par.reconcileState();
418	>	else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
419	>	long u = s & PARTIES_MASK; // reset unarrived to parties
420	>	long next = ((((long) rPhase) << PHASE_SHIFT) | u |
421	>	(u >>> PARTIES_SHIFT));
422	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
423		}
424		s = state;
425		}
#	Line 348 | Line 433 | public class Phaser {
433		* phaser will need to first register for it.
434		*/
435		public Phaser() {
436	<	this(null);
436	>	this(null, 0);
437		}
438
439		/**
#	Line 364 | Line 449 | public class Phaser {
449		}
450
451		/**
452	<	* Creates a new phaser with the given parent, without any
453	<	* initially registered parties. If parent is non-null this phaser
454	<	* is registered with the parent and its initial phase number is
455	<	* the same as that of parent phaser.
452	>	* Creates a new phaser with the given parent, and without any
453	>	* initially registered parties.  Any thread using this phaser
454	>	* will need to first register for it, at which point, if the
455	>	* given parent is non-null, this phaser will also be registered
456	>	* with the parent.
457	>	*
458	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
459		*
460		* @param parent the parent phaser
461		*/
462		public Phaser(Phaser parent) {
463	<	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);
463	>	this(parent, 0);
464		}
465
466		/**
467		* Creates a new phaser with the given parent and number of
468	<	* registered unarrived parties. If parent is non-null, this phaser
469	<	* is registered with the parent and its initial phase number is
470	<	* the same as that of parent phaser.
468	>	* registered unarrived parties. If parent is non-null and
469	>	* the number of parties is non-zero, this phaser is registered
470	>	* with the parent.
471		*
472		* @param parent the parent phaser
473		* @param parties the number of parties required to trip barrier
#	Line 395 | Line 475 | public class Phaser {
475		* or greater than the maximum number of parties supported
476		*/
477		public Phaser(Phaser parent, int parties) {
478	<	if (parties < 0 || parties > ushortMask)
478	>	if (parties >>> PARTIES_SHIFT != 0)
479		throw new IllegalArgumentException("Illegal number of parties");
480	<	int phase = 0;
480	>	int phase;
481		this.parent = parent;
482		if (parent != null) {
483	<	this.root = parent.root;
484	<	phase = parent.register();
483	>	Phaser r = parent.root;
484	>	this.root = r;
485	>	this.evenQ = r.evenQ;
486	>	this.oddQ = r.oddQ;
487	>	phase = (parties == 0) ? parent.getPhase() : parent.doRegister(1);
488		}
489	<	else
489	>	else {
490		this.root = this;
491	<	this.state = trippedStateFor(phase, parties);
491	>	this.evenQ = new AtomicReference<QNode>();
492	>	this.oddQ = new AtomicReference<QNode>();
493	>	phase = 0;
494	>	}
495	>	long p = (long)parties;
496	>	this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
497		}
498
499		/**
500	<	* Adds a new unarrived party to this phaser.
501	<	* If an ongoing invocation of {@link #onAdvance} is in progress,
502	<	* this method waits until its completion before registering.
500	>	* Adds a new unarrived party to this phaser.  If an ongoing
501	>	* invocation of {@link #onAdvance} is in progress, this method
502	>	* may wait until its completion before registering.  If this
503	>	* phaser has a parent, and this phaser previously had no
504	>	* registered parties, this phaser is also registered with its
505	>	* parent.
506		*
507		* @return the arrival phase number to which this registration applied
508		* @throws IllegalStateException if attempting to register more
#	Line 424 | Line 515 | public class Phaser {
515		/**
516		* Adds the given number of new unarrived parties to this phaser.
517		* If an ongoing invocation of {@link #onAdvance} is in progress,
518	<	* this method waits until its completion before registering.
518	>	* this method may wait until its completion before registering.
519	>	* If this phaser has a parent, and the given number of parities
520	>	* is greater than zero, and this phaser previously had no
521	>	* registered parties, this phaser is also registered with its
522	>	* parent.
523		*
524		* @param parties the number of additional parties required to trip barrier
525		* @return the arrival phase number to which this registration applied
#	Line 435 | Line 530 | public class Phaser {
530		public int bulkRegister(int parties) {
531		if (parties < 0)
532		throw new IllegalArgumentException();
533	<	if (parties == 0)
533	>	else if (parties == 0)
534		return getPhase();
535		return doRegister(parties);
536		}
537
538		/**
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	–	/**
539		* Arrives at the barrier, but does not wait for others.  (You can
540	<	* in turn wait for others via {@link #awaitAdvance}).  It is an
541	<	* unenforced usage error for an unregistered party to invoke this
542	<	* method.
540	>	* in turn wait for others via {@link #awaitAdvance}).  It is a
541	>	* usage error for an unregistered party to invoke this
542	>	* method. However, it is possible that this error will result in
543	>	* an {code IllegalStateException} only when some <em>other</em>
544	>	* party arrives.
545		*
546		* @return the arrival phase number, or a negative value if terminated
547		* @throws IllegalStateException if not terminated and the number
548		* of unarrived parties would become negative
549		*/
550		public int arrive() {
551	<	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;
551	>	return doArrive(ONE_ARRIVAL);
552		}
553
554		/**
#	Line 512 | Line 557 | public class Phaser {
557		* required to trip the barrier in future phases.  If this phaser
558		* has a parent, and deregistration causes this phaser to have
559		* zero parties, this phaser also arrives at and is deregistered
560	<	* from its parent.  It is an unenforced usage error for an
561	<	* unregistered party to invoke this method.
560	>	* from its parent.  It is a usage error for an unregistered party
561	>	* to invoke this method. However, it is possible that this error
562	>	* will result in an {code IllegalStateException} only when some
563	>	* <em>other</em> party arrives.
564		*
565		* @return the arrival phase number, or a negative value if terminated
566		* @throws IllegalStateException if not terminated and the number
567		* of registered or unarrived parties would become negative
568		*/
569		public int arriveAndDeregister() {
570	<	// 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;
570	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
571		}
572
573		/**
#	Line 561 | Line 576 | public class Phaser {
576		* interruption or timeout, you can arrange this with an analogous
577		* construction using one of the other forms of the {@code
578		* awaitAdvance} method.  If instead you need to deregister upon
579	<	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
580	<	* usage error for an unregistered party to invoke this method.
579	>	* arrival, use {@link #arriveAndDeregister}.  It is a usage error
580	>	* for an unregistered party to invoke this method. However, it is
581	>	* possible that this error will result in an {code
582	>	* IllegalStateException} only when some <em>other</em> party
583	>	* arrives.
584		*
585		* @return the arrival phase number, or a negative number if terminated
586		* @throws IllegalStateException if not terminated and the number
#	Line 576 | Line 594 | public class Phaser {
594		* Awaits the phase of the barrier to advance from the given phase
595		* value, returning immediately if the current phase of the
596		* barrier is not equal to the given phase value or this barrier
597	<	* is terminated.  It is an unenforced usage error for an
580	<	* unregistered party to invoke this method.
597	>	* is terminated.
598		*
599		* @param phase an arrival phase number, or negative value if
600		* terminated; this argument is normally the value returned by a
#	Line 588 | Line 605 | public class Phaser {
605		public int awaitAdvance(int phase) {
606		if (phase < 0)
607		return phase;
608	<	int p = getPhase();
609	<	if (p != phase)
610	<	return p;
594	<	return untimedWait(phase);
608	>	long s = (parent == null) ? state : reconcileState();
609	>	int p = (int)(s >>> PHASE_SHIFT);
610	>	return (p != phase) ? p : internalAwaitAdvance(phase, null);
611		}
612
613		/**
#	Line 599 | Line 615 | public class Phaser {
615		* value, throwing {@code InterruptedException} if interrupted
616		* while waiting, or returning immediately if the current phase of
617		* the barrier is not equal to the given phase value or this
618	<	* barrier is terminated. It is an unenforced usage error for an
603	<	* unregistered party to invoke this method.
618	>	* barrier is terminated.
619		*
620		* @param phase an arrival phase number, or negative value if
621		* terminated; this argument is normally the value returned by a
#	Line 613 | Line 628 | public class Phaser {
628		throws InterruptedException {
629		if (phase < 0)
630		return phase;
631	<	int p = getPhase();
632	<	if (p != phase)
633	<	return p;
634	<	return interruptibleWait(phase);
631	>	long s = (parent == null) ? state : reconcileState();
632	>	int p = (int)(s >>> PHASE_SHIFT);
633	>	if (p == phase) {
634	>	QNode node = new QNode(this, phase, true, false, 0L);
635	>	p = internalAwaitAdvance(phase, node);
636	>	if (node.wasInterrupted)
637	>	throw new InterruptedException();
638	>	}
639	>	return p;
640		}
641
642		/**
#	Line 625 | Line 645 | public class Phaser {
645		* InterruptedException} if interrupted while waiting, or
646		* returning immediately if the current phase of the barrier is
647		* not equal to the given phase value or this barrier is
648	<	* terminated.  It is an unenforced usage error for an
629	<	* unregistered party to invoke this method.
648	>	* terminated.
649		*
650		* @param phase an arrival phase number, or negative value if
651		* terminated; this argument is normally the value returned by a
#	Line 643 | Line 662 | public class Phaser {
662		public int awaitAdvanceInterruptibly(int phase,
663		long timeout, TimeUnit unit)
664		throws InterruptedException, TimeoutException {
646	–	long nanos = unit.toNanos(timeout);
665		if (phase < 0)
666		return phase;
667	<	int p = getPhase();
668	<	if (p != phase)
669	<	return p;
670	<	return timedWait(phase, nanos);
667	>	long s = (parent == null) ? state : reconcileState();
668	>	int p = (int)(s >>> PHASE_SHIFT);
669	>	if (p == phase) {
670	>	long nanos = unit.toNanos(timeout);
671	>	QNode node = new QNode(this, phase, true, true, nanos);
672	>	p = internalAwaitAdvance(phase, node);
673	>	if (node.wasInterrupted)
674	>	throw new InterruptedException();
675	>	else if (p == phase)
676	>	throw new TimeoutException();
677	>	}
678	>	return p;
679		}
680
681		/**
682	<	* Forces this barrier to enter termination state. Counts of
683	<	* arrived and registered parties are unaffected. If this phaser
684	<	* has a parent, it too is terminated. This method may be useful
685	<	* for coordinating recovery after one or more tasks encounter
686	<	* unexpected exceptions.
682	>	* Forces this barrier to enter termination state.  Counts of
683	>	* arrived and registered parties are unaffected.  If this phaser
684	>	* is a member of a tiered set of phasers, then all of the phasers
685	>	* in the set are terminated.  If this phaser is already
686	>	* terminated, this method has no effect.  This method may be
687	>	* useful for coordinating recovery after one or more tasks
688	>	* encounter unexpected exceptions.
689		*/
690		public void forceTermination() {
691	<	Phaser r = root;    // force at root then reconcile
691	>	// Only need to change root state
692	>	final Phaser root = this.root;
693		long s;
694	<	while (phaseOf(s = r.state) >= 0)
695	<	r.casState(s, stateFor(-1, partiesOf(s), unarrivedOf(s)));
696	<	reconcileState();
697	<	releaseWaiters(0);  // ensure wakeups on both queues
698	<	releaseWaiters(1);
694	>	while ((s = root.state) >= 0) {
695	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
696	>	s, s | TERMINATION_BIT)) {
697	>	releaseWaiters(0); // signal all threads
698	>	releaseWaiters(1);
699	>	return;
700	>	}
701	>	}
702		}
703
704		/**
#	Line 677 | Line 709 | public class Phaser {
709		* @return the phase number, or a negative value if terminated
710		*/
711		public final int getPhase() {
712	<	return phaseOf(getReconciledState());
712	>	return (int)(root.state >>> PHASE_SHIFT);
713		}
714
715		/**
#	Line 686 | Line 718 | public class Phaser {
718		* @return the number of parties
719		*/
720		public int getRegisteredParties() {
721	<	return partiesOf(getReconciledState());
721	>	return partiesOf(state);
722		}
723
724		/**
#	Line 696 | Line 728 | public class Phaser {
728		* @return the number of arrived parties
729		*/
730		public int getArrivedParties() {
731	<	return arrivedOf(getReconciledState());
731	>	return arrivedOf(parent==null? state : reconcileState());
732		}
733
734		/**
#	Line 706 | Line 738 | public class Phaser {
738		* @return the number of unarrived parties
739		*/
740		public int getUnarrivedParties() {
741	<	return unarrivedOf(getReconciledState());
741	>	return unarrivedOf(parent==null? state : reconcileState());
742		}
743
744		/**
#	Line 734 | Line 766 | public class Phaser {
766		* @return {@code true} if this barrier has been terminated
767		*/
768		public boolean isTerminated() {
769	<	return getPhase() < 0;
769	>	return root.state < 0L;
770		}
771
772		/**
#	Line 750 | Line 782 | public class Phaser {
782		* which case no advance occurs.
783		*
784		* <p>The arguments to this method provide the state of the phaser
785	<	* prevailing for the current transition. (When called from within
786	<	* an implementation of {@code onAdvance} the values returned by
787	<	* methods such as {@code getPhase} may or may not reliably
788	<	* indicate the state to which this transition applies.)
789	<	*
790	<	* <p>The default version returns {@code true} when the number of
791	<	* registered parties is zero. Normally, overrides that arrange
792	<	* termination for other reasons should also preserve this
793	<	* property.
785	>	* prevailing for the current transition.  The effects of invoking
786	>	* arrival, registration, and waiting methods on this Phaser from
787	>	* within {@code onAdvance} are unspecified and should not be
788	>	* relied on.
789	>	*
790	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
791	>	* {@code onAdvance} is invoked only for its root Phaser on each
792	>	* advance.
793	>	*
794	>	* <p>To support the most common use cases, the default
795	>	* implementation of this method returns {@code true} when the
796	>	* number of registered parties has become zero as the result of a
797	>	* party invoking {@code arriveAndDeregister}.  You can disable
798	>	* this behavior, thus enabling continuation upon future
799	>	* registrations, by overriding this method to always return
800	>	* {@code false}:
801	>	*
802	>	* <pre> {@code
803	>	* Phaser phaser = new Phaser() {
804	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
805	>	* }}</pre>
806		*
807		* @param phase the phase number on entering the barrier
808		* @param registeredParties the current number of registered parties
#	Line 778 | Line 822 | public class Phaser {
822		* @return a string identifying this barrier, as well as its state
823		*/
824		public String toString() {
825	<	long s = getReconciledState();
825	>	return stateToString(reconcileState());
826	>	}
827	>
828	>	/**
829	>	* Implementation of toString and string-based error messages
830	>	*/
831	>	private String stateToString(long s) {
832		return super.toString() +
833		"[phase = " + phaseOf(s) +
834		" parties = " + partiesOf(s) +
835		" arrived = " + arrivedOf(s) + "]";
836		}
837
838	<	// methods for waiting
838	>	// Waiting mechanics
839	>
840	>	/**
841	>	* Removes and signals threads from queue for phase.
842	>	*/
843	>	private void releaseWaiters(int phase) {
844	>	AtomicReference<QNode> head = queueFor(phase);
845	>	QNode q;
846	>	int p;
847	>	while ((q = head.get()) != null &&
848	>	((p = q.phase) == phase ||
849	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
850	>	if (head.compareAndSet(q, q.next))
851	>	q.signal();
852	>	}
853	>	}
854	>
855	>	/** The number of CPUs, for spin control */
856	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
857	>
858	>	/**
859	>	* The number of times to spin before blocking while waiting for
860	>	* advance, per arrival while waiting. On multiprocessors, fully
861	>	* blocking and waking up a large number of threads all at once is
862	>	* usually a very slow process, so we use rechargeable spins to
863	>	* avoid it when threads regularly arrive: When a thread in
864	>	* internalAwaitAdvance notices another arrival before blocking,
865	>	* and there appear to be enough CPUs available, it spins
866	>	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
867	>	* uniprocessors, there is at least one intervening Thread.yield
868	>	* before blocking. The value trades off good-citizenship vs big
869	>	* unnecessary slowdowns.
870	>	*/
871	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
872	>
873	>	/**
874	>	* Possibly blocks and waits for phase to advance unless aborted.
875	>	*
876	>	* @param phase current phase
877	>	* @param node if non-null, the wait node to track interrupt and timeout;
878	>	* if null, denotes noninterruptible wait
879	>	* @return current phase
880	>	*/
881	>	private int internalAwaitAdvance(int phase, QNode node) {
882	>	Phaser current = this;       // to eventually wait at root if tiered
883	>	boolean queued = false;      // true when node is enqueued
884	>	int lastUnarrived = -1;      // to increase spins upon change
885	>	int spins = SPINS_PER_ARRIVAL;
886	>	long s;
887	>	int p;
888	>	while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) {
889	>	Phaser par;
890	>	int unarrived = (int)s & UNARRIVED_MASK;
891	>	if (unarrived != lastUnarrived) {
892	>	if (lastUnarrived == -1) // ensure old queue clean
893	>	releaseWaiters(phase-1);
894	>	if ((lastUnarrived = unarrived) < NCPU)
895	>	spins += SPINS_PER_ARRIVAL;
896	>	}
897	>	else if (unarrived == 0 && (par = current.parent) != null) {
898	>	current = par;       // if all arrived, use parent
899	>	par = par.parent;
900	>	lastUnarrived = -1;
901	>	}
902	>	else if (spins > 0) {
903	>	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
904	>	Thread.yield();  // yield midway through spin
905	>	}
906	>	else if (node == null)   // must be noninterruptible
907	>	node = new QNode(this, phase, false, false, 0L);
908	>	else if (node.isReleasable()) {
909	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
910	>	break;
911	>	else
912	>	return phase;    // aborted
913	>	}
914	>	else if (!queued) {      // push onto queue
915	>	AtomicReference<QNode> head = queueFor(phase);
916	>	QNode q = head.get();
917	>	if (q == null || q.phase == phase) {
918	>	node.next = q;
919	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
920	>	break;       // recheck to avoid stale enqueue
921	>	else
922	>	queued = head.compareAndSet(q, node);
923	>	}
924	>	}
925	>	else {
926	>	try {
927	>	ForkJoinPool.managedBlock(node);
928	>	} catch (InterruptedException ie) {
929	>	node.wasInterrupted = true;
930	>	}
931	>	}
932	>	}
933	>	releaseWaiters(phase);
934	>	if (node != null)
935	>	node.onRelease();
936	>	return p;
937	>	}
938
939		/**
940		* Wait nodes for Treiber stack representing wait queue
#	Line 793 | Line 942 | public class Phaser {
942		static final class QNode implements ForkJoinPool.ManagedBlocker {
943		final Phaser phaser;
944		final int phase;
796	–	final long startTime;
797	–	final long nanos;
798	–	final boolean timed;
945		final boolean interruptible;
946	<	volatile boolean wasInterrupted = false;
946	>	final boolean timed;
947	>	boolean wasInterrupted;
948	>	long nanos;
949	>	long lastTime;
950		volatile Thread thread; // nulled to cancel wait
951		QNode next;
952
953		QNode(Phaser phaser, int phase, boolean interruptible,
954	<	boolean timed, long startTime, long nanos) {
954	>	boolean timed, long nanos) {
955		this.phaser = phaser;
956		this.phase = phase;
808	–	this.timed = timed;
957		this.interruptible = interruptible;
810	–	this.startTime = startTime;
958		this.nanos = nanos;
959	+	this.timed = timed;
960	+	this.lastTime = timed? System.nanoTime() : 0L;
961		thread = Thread.currentThread();
962		}
963
964		public boolean isReleasable() {
965	<	return (thread == null ||
966	<	phaser.getPhase() != phase ||
967	<	(interruptible && wasInterrupted) ||
968	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
965	>	Thread t = thread;
966	>	if (t != null) {
967	>	if (phaser.getPhase() != phase)
968	>	t = null;
969	>	else {
970	>	if (Thread.interrupted())
971	>	wasInterrupted = true;
972	>	if (interruptible && wasInterrupted)
973	>	t = null;
974	>	else if (timed) {
975	>	if (nanos > 0) {
976	>	long now = System.nanoTime();
977	>	nanos -= now - lastTime;
978	>	lastTime = now;
979	>	}
980	>	if (nanos <= 0)
981	>	t = null;
982	>	}
983	>	}
984	>	if (t != null)
985	>	return false;
986	>	thread = null;
987	>	}
988	>	return true;
989		}
990
991		public boolean block() {
992	<	if (Thread.interrupted()) {
993	<	wasInterrupted = true;
994	<	if (interruptible)
826	<	return true;
827	<	}
828	<	if (!timed)
992	>	if (isReleasable())
993	>	return true;
994	>	else if (!timed)
995		LockSupport.park(this);
996	<	else {
997	<	long waitTime = nanos - (System.nanoTime() - startTime);
832	<	if (waitTime <= 0)
833	<	return true;
834	<	LockSupport.parkNanos(this, waitTime);
835	<	}
996	>	else if (nanos > 0)
997	>	LockSupport.parkNanos(this, nanos);
998		return isReleasable();
999		}
1000
#	Line 844 | Line 1006 | public class Phaser {
1006		}
1007		}
1008
1009	<	boolean doWait() {
1010	<	if (thread != null) {
1011	<	try {
1012	<	ForkJoinPool.managedBlock(this);
1013	<	} 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;
1009	>	void onRelease() { // actions upon return from internalAwaitAdvance
1010	>	if (!interruptible && wasInterrupted)
1011	>	Thread.currentThread().interrupt();
1012	>	if (thread != null)
1013	>	thread = null;
1014		}
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	–	}
1015
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;
1016		}
1017
1018		// Unsafe mechanics
#	Line 974 | Line 1021 | public class Phaser {
1021		private static final long stateOffset =
1022		objectFieldOffset("state", Phaser.class);
1023
977	–	private final boolean casState(long cmp, long val) {
978	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
979	–	}
980	–
1024		private static long objectFieldOffset(String field, Class<?> klazz) {
1025		try {
1026		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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