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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.46 by dl, Sun Aug 30 11:08:25 2009 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.*;
10	<
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 79 | 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 109 | Line 111 | import java.util.concurrent.locks.LockSu
111		* <p><b>Sample usages:</b>
112		*
113		* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
114	<	* to control a one-shot action serving a variable number of
115	<	* parties. The typical idiom is for the method setting this up to
116	<	* first register, then start the actions, then deregister, as in:
114	>	* to control a one-shot action serving a variable number of parties.
115	>	* The typical idiom is for the method setting this up to first
116	>	* register, then start the actions, then deregister, as in:
117		*
118		*  <pre> {@code
119		* void runTasks(List<Runnable> tasks) {
#	Line 184 | Line 186 | import java.util.concurrent.locks.LockSu
186		* <p>To create a set of tasks using a tree of phasers,
187		* you could use code of the following form, assuming a
188		* Task class with a constructor accepting a phaser that
189	<	* it registers for upon construction:
189	>	* it registers with upon construction:
190		*
191		*  <pre> {@code
192		* void build(Task[] actions, int lo, int hi, Phaser ph) {
#	Line 207 | Line 209 | import java.util.concurrent.locks.LockSu
209		* be appropriate for extremely small per-barrier task bodies (thus
210		* high rates), or up to hundreds for extremely large ones.
211		*
210	–	* </pre>
211	–	*
212		* <p><b>Implementation notes</b>: This implementation restricts the
213		* maximum number of parties to 65535. Attempts to register additional
214		* parties result in {@code IllegalStateException}. However, you can and
#	Line 229 | 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.
242	–	*
243	–	* Note: there are some cheats in arrive() that rely on unarrived
244	–	* 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
267	–	private static long stateFor(int phase, int parties, int unarrived) {
268	–	return ((((long) phase) << 32) | (((long) parties) << 16) |
269	–	(long) unarrived);
270	–	}
271	–
272	–	private static long trippedStateFor(int phase, int parties) {
273	–	long lp = (long) parties;
274	–	return (((long) phase) << 32) | (lp << 16) | lp;
275	–	}
276	–
277	–	/**
278	–	* Returns message string for bad bounds exceptions.
279	–	*/
280	–	private static String badBounds(int parties, int unarrived) {
281	–	return ("Attempt to set " + unarrived +
282	–	" unarrived of " + parties + " parties");
283	–	}
284	–
273		/**
274		* The parent of this phaser, or null if none
275		*/
#	Line 293 | Line 281 | public class Phaser {
281		*/
282		private final Phaser root;
283
296	–	// Wait queues
297	–
284		/**
285		* Heads of Treiber stacks for waiting threads. To eliminate
286	<	* contention while releasing some threads while adding others, we
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		return ((phase & 1) == 0) ? evenQ : oddQ;
295		}
296
297		/**
298	<	* Returns current state, first resolving lagged propagation from
312	<	* root if necessary.
298	>	* Returns message string for bounds exceptions on arrival.
299		*/
300	<	private long getReconciledState() {
301	<	return (parent == null) ? state : reconcileState();
300	>	private String badArrive(long s) {
301	>	return "Attempted arrival of unregistered party for " +
302	>	stateToString(s);
303		}
304
305		/**
306	<	* Recursively resolves state.
306	>	* Returns message string for bounds exceptions on registration.
307		*/
308	<	private long reconcileState() {
309	<	Phaser p = parent;
310	<	long s = state;
311	<	if (p != null) {
312	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
313	<	long parentState = p.getReconciledState();
314	<	int parentPhase = phaseOf(parentState);
315	<	int phase = phaseOf(s = state);
316	<	if (phase != parentPhase) {
317	<	long next = trippedStateFor(parentPhase, partiesOf(s));
318	<	if (casState(s, next)) {
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	<	s = next;
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	+	* 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 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 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	+	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		}
426		}
427		return s;
#	Line 344 | 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		/**
440	<	* Creates a new phaser with the given numbers of registered
440	>	* Creates a new phaser with the given number of registered
441		* unarrived parties, initial phase number 0, and no parent.
442		*
443		* @param parties the number of parties required to trip barrier
#	Line 360 | 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;
372	<	this.parent = parent;
373	<	if (parent != null) {
374	<	this.root = parent.root;
375	<	phase = parent.register();
376	<	}
377	<	else
378	<	this.root = this;
379	<	this.state = trippedStateFor(phase, 0);
463	>	this(parent, 0);
464		}
465
466		/**
467	<	* Creates a new phaser with the given parent and numbers 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.
467	>	* Creates a new phaser with the given parent and number of
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 391 | 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.
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 417 | Line 514 | public class Phaser {
514
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 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 parties required to trip barrier
524	>	* @param parties the number of additional parties required to trip barrier
525		* @return the arrival phase number to which this registration applied
526		* @throws IllegalStateException if attempting to register more
527		* than the maximum supported number of parties
528	+	* @throws IllegalArgumentException if {@code parties < 0}
529		*/
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		/**
435	–	* Shared code for register, bulkRegister
436	–	*/
437	–	private int doRegister(int registrations) {
438	–	int phase;
439	–	for (;;) {
440	–	long s = getReconciledState();
441	–	phase = phaseOf(s);
442	–	int unarrived = unarrivedOf(s) + registrations;
443	–	int parties = partiesOf(s) + registrations;
444	–	if (phase < 0)
445	–	break;
446	–	if (parties > ushortMask || unarrived > ushortMask)
447	–	throw new IllegalStateException(badBounds(parties, unarrived));
448	–	if (phase == phaseOf(root.state) &&
449	–	casState(s, stateFor(phase, parties, unarrived)))
450	–	break;
451	–	}
452	–	return phase;
453	–	}
454	–
455	–	/**
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	<	int phase;
467	<	for (;;) {
468	<	long s = state;
469	<	phase = phaseOf(s);
470	<	if (phase < 0)
471	<	break;
472	<	int parties = partiesOf(s);
473	<	int unarrived = unarrivedOf(s) - 1;
474	<	if (unarrived > 0) {        // Not the last arrival
475	<	if (casState(s, s - 1)) // s-1 adds one arrival
476	<	break;
477	<	}
478	<	else if (unarrived == 0) {  // the last arrival
479	<	Phaser par = parent;
480	<	if (par == null) {      // directly trip
481	<	if (casState
482	<	(s,
483	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
484	<	((phase + 1) & phaseMask), parties))) {
485	<	releaseWaiters(phase);
486	<	break;
487	<	}
488	<	}
489	<	else {                  // cascade to parent
490	<	if (casState(s, s - 1)) { // zeroes unarrived
491	<	par.arrive();
492	<	reconcileState();
493	<	break;
494	<	}
495	<	}
496	<	}
497	<	else if (phase != phaseOf(root.state)) // or if unreconciled
498	<	reconcileState();
499	<	else
500	<	throw new IllegalStateException(badBounds(parties, unarrived));
501	<	}
502	<	return phase;
551	>	return doArrive(ONE_ARRIVAL);
552		}
553
554		/**
#	Line 508 | 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 code to arrive, but too different to merge
520	<	Phaser par = parent;
521	<	int phase;
522	<	for (;;) {
523	<	long s = state;
524	<	phase = phaseOf(s);
525	<	if (phase < 0)
526	<	break;
527	<	int parties = partiesOf(s) - 1;
528	<	int unarrived = unarrivedOf(s) - 1;
529	<	if (parties >= 0) {
530	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
531	<	if (casState
532	<	(s,
533	<	stateFor(phase, parties, unarrived))) {
534	<	if (unarrived == 0) {
535	<	par.arriveAndDeregister();
536	<	reconcileState();
537	<	}
538	<	break;
539	<	}
540	<	continue;
541	<	}
542	<	if (unarrived == 0) {
543	<	if (casState
544	<	(s,
545	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
546	<	((phase + 1) & phaseMask), parties))) {
547	<	releaseWaiters(phase);
548	<	break;
549	<	}
550	<	continue;
551	<	}
552	<	if (par != null && phase != phaseOf(root.state)) {
553	<	reconcileState();
554	<	continue;
555	<	}
556	<	}
557	<	throw new IllegalStateException(badBounds(parties, unarrived));
558	<	}
559	<	return phase;
570	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
571		}
572
573		/**
574		* Arrives at the barrier and awaits others. Equivalent in effect
575		* to {@code awaitAdvance(arrive())}.  If you need to await with
576		* interruption or timeout, you can arrange this with an analogous
577	<	* construction using one of the other forms of the awaitAdvance
578	<	* method.  If instead you need to deregister upon arrival use
579	<	* {@code arriveAndDeregister}. It is an unenforced usage error
580	<	* for an unregistered party to invoke this method.
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 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 580 | 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
584	<	* 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 592 | Line 605 | public class Phaser {
605		public int awaitAdvance(int phase) {
606		if (phase < 0)
607		return phase;
608	<	long s = getReconciledState();
609	<	int p = phaseOf(s);
610	<	if (p != phase)
598	<	return p;
599	<	if (unarrivedOf(s) == 0 && parent != null)
600	<	parent.awaitAdvance(phase);
601	<	// Fall here even if parent waited, to reconcile and help release
602	<	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 607 | 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
611	<	* 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 621 | Line 628 | public class Phaser {
628		throws InterruptedException {
629		if (phase < 0)
630		return phase;
631	<	long s = getReconciledState();
632	<	int p = phaseOf(s);
633	<	if (p != phase)
634	<	return p;
635	<	if (unarrivedOf(s) == 0 && parent != null)
636	<	parent.awaitAdvanceInterruptibly(phase);
637	<	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 636 | 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
640	<	* 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 656 | Line 664 | public class Phaser {
664		throws InterruptedException, TimeoutException {
665		if (phase < 0)
666		return phase;
667	<	long s = getReconciledState();
668	<	int p = phaseOf(s);
669	<	if (p != phase)
670	<	return p;
671	<	if (unarrivedOf(s) == 0 && parent != null)
672	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
673	<	return timedWait(phase, unit.toNanos(timeout));
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	<	for (;;) {
692	<	long s = getReconciledState();
693	<	int phase = phaseOf(s);
694	<	int parties = partiesOf(s);
695	<	int unarrived = unarrivedOf(s);
696	<	if (phase < 0 ||
697	<	casState(s, stateFor(-1, parties, unarrived))) {
683	<	releaseWaiters(0);
691	>	// Only need to change root state
692	>	final Phaser root = this.root;
693	>	long s;
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);
685	–	if (parent != null)
686	–	parent.forceTermination();
699		return;
700		}
701		}
#	Line 697 | 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 716 | Line 728 | public class Phaser {
728		* @return the number of arrived parties
729		*/
730		public int getArrivedParties() {
731	<	return arrivedOf(state);
731	>	return arrivedOf(parent==null? state : reconcileState());
732		}
733
734		/**
#	Line 726 | Line 738 | public class Phaser {
738		* @return the number of unarrived parties
739		*/
740		public int getUnarrivedParties() {
741	<	return unarrivedOf(state);
741	>	return unarrivedOf(parent==null? state : reconcileState());
742		}
743
744		/**
#	Line 754 | 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 770 | 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.
794	<	*
795	<	* <p>You may override this method to perform an action with side
796	<	* effects visible to participating tasks, but it is only sensible
797	<	* to do so in designs where all parties register before any
798	<	* arrive, and all {@link #awaitAdvance} at each phase.
799	<	* Otherwise, you cannot ensure lack of interference from other
800	<	* parties during the invocation of this method. Additionally,
801	<	* method {@code onAdvance} may be invoked more than once per
802	<	* transition if registrations are intermixed with arrivals.
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 807 | 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 822 | Line 942 | public class Phaser {
942		static final class QNode implements ForkJoinPool.ManagedBlocker {
943		final Phaser phaser;
944		final int phase;
825	–	final long startTime;
826	–	final long nanos;
827	–	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;
836	–	this.timed = timed;
957		this.interruptible = interruptible;
838	–	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)
852	<	return true;
853	<	}
854	<	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);
858	<	if (waitTime <= 0)
859	<	return true;
860	<	LockSupport.parkNanos(this, waitTime);
861	<	}
996	>	else if (nanos > 0)
997	>	LockSupport.parkNanos(this, nanos);
998		return isReleasable();
999		}
1000	+
1001		void signal() {
1002		Thread t = thread;
1003		if (t != null) {
#	Line 868 | Line 1005 | public class Phaser {
1005		LockSupport.unpark(t);
1006		}
1007		}
871	–	boolean doWait() {
872	–	if (thread != null) {
873	–	try {
874	–	ForkJoinPool.managedBlock(this, false);
875	–	} catch (InterruptedException ie) {
876	–	}
877	–	}
878	–	return wasInterrupted;
879	–	}
880	–
881	–	}
882	–
883	–	/**
884	–	* Removes and signals waiting threads from wait queue.
885	–	*/
886	–	private void releaseWaiters(int phase) {
887	–	AtomicReference<QNode> head = queueFor(phase);
888	–	QNode q;
889	–	while ((q = head.get()) != null) {
890	–	if (head.compareAndSet(q, q.next))
891	–	q.signal();
892	–	}
893	–	}
1008
1009	<	/**
1010	<	* Tries to enqueue given node in the appropriate wait queue.
1011	<	*
1012	<	* @return true if successful
1013	<	*/
900	<	private boolean tryEnqueue(QNode node) {
901	<	AtomicReference<QNode> head = queueFor(node.phase);
902	<	return head.compareAndSet(node.next = head.get(), node);
903	<	}
904	<
905	<	/**
906	<	* Enqueues node and waits unless aborted or signalled.
907	<	*
908	<	* @return current phase
909	<	*/
910	<	private int untimedWait(int phase) {
911	<	QNode node = null;
912	<	boolean queued = false;
913	<	boolean interrupted = false;
914	<	int p;
915	<	while ((p = getPhase()) == phase) {
916	<	if (Thread.interrupted())
917	<	interrupted = true;
918	<	else if (node == null)
919	<	node = new QNode(this, phase, false, false, 0, 0);
920	<	else if (!queued)
921	<	queued = tryEnqueue(node);
922	<	else
923	<	interrupted = node.doWait();
1009	>	void onRelease() { // actions upon return from internalAwaitAdvance
1010	>	if (!interruptible && wasInterrupted)
1011	>	Thread.currentThread().interrupt();
1012	>	if (thread != null)
1013	>	thread = null;
1014		}
925	–	if (node != null)
926	–	node.thread = null;
927	–	releaseWaiters(phase);
928	–	if (interrupted)
929	–	Thread.currentThread().interrupt();
930	–	return p;
931	–	}
1015
933	–	/**
934	–	* Interruptible version
935	–	* @return current phase
936	–	*/
937	–	private int interruptibleWait(int phase) throws InterruptedException {
938	–	QNode node = null;
939	–	boolean queued = false;
940	–	boolean interrupted = false;
941	–	int p;
942	–	while ((p = getPhase()) == phase && !interrupted) {
943	–	if (Thread.interrupted())
944	–	interrupted = true;
945	–	else if (node == null)
946	–	node = new QNode(this, phase, true, false, 0, 0);
947	–	else if (!queued)
948	–	queued = tryEnqueue(node);
949	–	else
950	–	interrupted = node.doWait();
951	–	}
952	–	if (node != null)
953	–	node.thread = null;
954	–	if (p != phase || (p = getPhase()) != phase)
955	–	releaseWaiters(phase);
956	–	if (interrupted)
957	–	throw new InterruptedException();
958	–	return p;
959	–	}
960	–
961	–	/**
962	–	* Timeout version.
963	–	* @return current phase
964	–	*/
965	–	private int timedWait(int phase, long nanos)
966	–	throws InterruptedException, TimeoutException {
967	–	long startTime = System.nanoTime();
968	–	QNode node = null;
969	–	boolean queued = false;
970	–	boolean interrupted = false;
971	–	int p;
972	–	while ((p = getPhase()) == phase && !interrupted) {
973	–	if (Thread.interrupted())
974	–	interrupted = true;
975	–	else if (nanos - (System.nanoTime() - startTime) <= 0)
976	–	break;
977	–	else if (node == null)
978	–	node = new QNode(this, phase, true, true, startTime, nanos);
979	–	else if (!queued)
980	–	queued = tryEnqueue(node);
981	–	else
982	–	interrupted = node.doWait();
983	–	}
984	–	if (node != null)
985	–	node.thread = null;
986	–	if (p != phase || (p = getPhase()) != phase)
987	–	releaseWaiters(phase);
988	–	if (interrupted)
989	–	throw new InterruptedException();
990	–	if (p == phase)
991	–	throw new TimeoutException();
992	–	return p;
1016		}
1017
1018		// Unsafe mechanics
#	Line 998 | Line 1021 | public class Phaser {
1021		private static final long stateOffset =
1022		objectFieldOffset("state", Phaser.class);
1023
1001	–	private final boolean casState(long cmp, long val) {
1002	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
1003	–	}
1004	–
1024		private static long objectFieldOffset(String field, Class<?> klazz) {
1025		try {
1026		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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