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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.44 by dl, Tue Aug 25 16:32:28 2009 UTC vs.
Revision 1.53 by jsr166, Sat Nov 13 05:59:25 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 109 | Line 109 | import java.util.concurrent.locks.LockSu
109		* <p><b>Sample usages:</b>
110		*
111		* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
112	<	* to control a one-shot action serving a variable number of
113	<	* parties. The typical idiom is for the method setting this up to
114	<	* first register, then start the actions, then deregister, as in:
112	>	* to control a one-shot action serving a variable number of parties.
113	>	* The typical idiom is for the method setting this up to first
114	>	* register, then start the actions, then deregister, as in:
115		*
116		*  <pre> {@code
117		* void runTasks(List<Runnable> tasks) {
#	Line 142 | Line 142 | import java.util.concurrent.locks.LockSu
142		*     }
143		*   };
144		*   phaser.register();
145	<	*   for (Runnable task : tasks) {
145	>	*   for (final Runnable task : tasks) {
146		*     phaser.register();
147		*     new Thread() {
148		*       public void run() {
149		*         do {
150		*           task.run();
151		*           phaser.arriveAndAwaitAdvance();
152	<	*         } while(!phaser.isTerminated();
152	>	*         } while (!phaser.isTerminated());
153		*       }
154		*     }.start();
155		*   }
#	Line 158 | Line 158 | import java.util.concurrent.locks.LockSu
158		*
159		* If the main task must later await termination, it
160		* may re-register and then execute a similar loop:
161	<	* <pre> {@code
161	>	*  <pre> {@code
162		*   // ...
163		*   phaser.register();
164		*   while (!phaser.isTerminated())
165	<	*     phaser.arriveAndAwaitAdvance();
166	<	* }</pre>
165	>	*     phaser.arriveAndAwaitAdvance();}</pre>
166		*
167	<	* Related constructions may be used to await particular phase numbers
167	>	* <p>Related constructions may be used to await particular phase numbers
168		* in contexts where you are sure that the phase will never wrap around
169		* {@code Integer.MAX_VALUE}. For example:
170		*
171	<	* <pre> {@code
172	<	*   void awaitPhase(Phaser phaser, int phase) {
173	<	*     int p = phaser.register(); // assumes caller not already registered
174	<	*     while (p < phase) {
175	<	*       if (phaser.isTerminated())
176	<	*         // ... deal with unexpected termination
177	<	*       else
178	<	*         p = phaser.arriveAndAwaitAdvance();
180	<	*     }
181	<	*     phaser.arriveAndDeregister();
171	>	*  <pre> {@code
172	>	* void awaitPhase(Phaser phaser, int phase) {
173	>	*   int p = phaser.register(); // assumes caller not already registered
174	>	*   while (p < phase) {
175	>	*     if (phaser.isTerminated())
176	>	*       // ... deal with unexpected termination
177	>	*     else
178	>	*       p = phaser.arriveAndAwaitAdvance();
179		*   }
180	<	* }</pre>
180	>	*   phaser.arriveAndDeregister();
181	>	* }}</pre>
182		*
183		*
184		* <p>To create a set of tasks using a tree of phasers,
185		* you could use code of the following form, assuming a
186		* Task class with a constructor accepting a phaser that
187	<	* it registers for upon construction:
187	>	* it registers with upon construction:
188	>	*
189		*  <pre> {@code
190		* void build(Task[] actions, int lo, int hi, Phaser ph) {
191		*   if (hi - lo > TASKS_PER_PHASER) {
#	Line 208 | Line 207 | import java.util.concurrent.locks.LockSu
207		* be appropriate for extremely small per-barrier task bodies (thus
208		* high rates), or up to hundreds for extremely large ones.
209		*
211	–	* </pre>
212	–	*
210		* <p><b>Implementation notes</b>: This implementation restricts the
211		* maximum number of parties to 65535. Attempts to register additional
212		* parties result in {@code IllegalStateException}. However, you can and
#	Line 230 | Line 227 | public class Phaser {
227		* Barrier state representation. Conceptually, a barrier contains
228		* four values:
229		*
230	<	* * parties -- the number of parties to wait (16 bits)
231	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
232	<	* * phase -- the generation of the barrier (31 bits)
233	<	* * terminated -- set if barrier is terminated (1 bit)
230	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
231	>	* * parties -- the number of parties to wait              (bits 16-31)
232	>	* * phase -- the generation of the barrier                (bits 32-62)
233	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
234		*
235		* However, to efficiently maintain atomicity, these values are
236		* packed into a single (atomic) long. Termination uses the sign
237		* bit of 32 bit representation of phase, so phase is set to -1 on
238		* termination. Good performance relies on keeping state decoding
239		* and encoding simple, and keeping race windows short.
243	–	*
244	–	* Note: there are some cheats in arrive() that rely on unarrived
245	–	* count being lowest 16 bits.
240		*/
241		private volatile long state;
242
243	<	private static final int ushortMask = 0xffff;
244	<	private static final int phaseMask  = 0x7fffffff;
243	>	private static final int  MAX_COUNT      = 0xffff;
244	>	private static final int  MAX_PHASE      = 0x7fffffff;
245	>	private static final int  PARTIES_SHIFT  = 16;
246	>	private static final int  PHASE_SHIFT    = 32;
247	>	private static final long UNARRIVED_MASK = 0xffffL;
248	>	private static final long PARTIES_MASK   = 0xffff0000L;
249	>	private static final long ONE_ARRIVAL    = 1L;
250	>	private static final long ONE_PARTY      = 1L << PARTIES_SHIFT;
251	>	private static final long TERMINATION_PHASE  = -1L << PHASE_SHIFT;
252	>
253	>	// The following unpacking methods are usually manually inlined
254
255		private static int unarrivedOf(long s) {
256	<	return (int) (s & ushortMask);
256	>	return (int) (s & UNARRIVED_MASK);
257		}
258
259		private static int partiesOf(long s) {
260	<	return ((int) s) >>> 16;
260	>	return ((int) (s & PARTIES_MASK)) >>> PARTIES_SHIFT;
261		}
262
263		private static int phaseOf(long s) {
264	<	return (int) (s >>> 32);
264	>	return (int) (s >>> PHASE_SHIFT);
265		}
266
267		private static int arrivedOf(long s) {
268		return partiesOf(s) - unarrivedOf(s);
269		}
270
268	–	private static long stateFor(int phase, int parties, int unarrived) {
269	–	return ((((long) phase) << 32) | (((long) parties) << 16) |
270	–	(long) unarrived);
271	–	}
272	–
273	–	private static long trippedStateFor(int phase, int parties) {
274	–	long lp = (long) parties;
275	–	return (((long) phase) << 32) | (lp << 16) | lp;
276	–	}
277	–
278	–	/**
279	–	* Returns message string for bad bounds exceptions.
280	–	*/
281	–	private static String badBounds(int parties, int unarrived) {
282	–	return ("Attempt to set " + unarrived +
283	–	" unarrived of " + parties + " parties");
284	–	}
285	–
271		/**
272		* The parent of this phaser, or null if none
273		*/
#	Line 294 | Line 279 | public class Phaser {
279		*/
280		private final Phaser root;
281
297	–	// Wait queues
298	–
282		/**
283		* Heads of Treiber stacks for waiting threads. To eliminate
284	<	* contention while releasing some threads while adding others, we
284	>	* contention when releasing some threads while adding others, we
285		* use two of them, alternating across even and odd phases.
286	+	* Subphasers share queues with root to speed up releases.
287		*/
288	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
289	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
288	>	private final AtomicReference<QNode> evenQ;
289	>	private final AtomicReference<QNode> oddQ;
290
291		private AtomicReference<QNode> queueFor(int phase) {
292		return ((phase & 1) == 0) ? evenQ : oddQ;
293		}
294
295		/**
296	<	* Returns current state, first resolving lagged propagation from
297	<	* root if necessary.
296	>	* Main implementation for methods arrive and arriveAndDeregister.
297	>	* Manually tuned to speed up and minimize race windows for the
298	>	* common case of just decrementing unarrived field.
299	>	*
300	>	* @param adj - adjustment to apply to state -- either
301	>	* ONE_ARRIVAL (for arrive) or
302	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
303	>	*/
304	>	private int doArrive(long adj) {
305	>	long s;
306	>	int phase, unarrived;
307	>	while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0) {
308	>	if ((unarrived = (int)(s & UNARRIVED_MASK)) != 0) {
309	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s -= adj)) {
310	>	if (unarrived == 1) {
311	>	Phaser par;
312	>	long p = s & PARTIES_MASK; // unshifted parties field
313	>	long lu = p >>> PARTIES_SHIFT;
314	>	int u = (int)lu;
315	>	int nextPhase = (phase + 1) & MAX_PHASE;
316	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
317	>	if ((par = parent) == null) {
318	>	UNSAFE.compareAndSwapLong
319	>	(this, stateOffset, s, onAdvance(phase, u)?
320	>	next | TERMINATION_PHASE : next);
321	>	releaseWaiters(phase);
322	>	}
323	>	else {
324	>	par.doArrive(u == 0?
325	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
326	>	if ((int)(par.state >>> PHASE_SHIFT) != nextPhase ||
327	>	((int)(state >>> PHASE_SHIFT) != nextPhase &&
328	>	!UNSAFE.compareAndSwapLong(this, stateOffset,
329	>	s, next)))
330	>	reconcileState();
331	>	}
332	>	}
333	>	break;
334	>	}
335	>	}
336	>	else if (state == s && reconcileState() == s) // recheck
337	>	throw new IllegalStateException(badArrive());
338	>	}
339	>	return phase;
340	>	}
341	>
342	>	/**
343	>	* Returns message string for bounds exceptions on arrival.
344	>	* Declared out of-line from doArrive to reduce string op bulk.
345	>	*/
346	>	private String badArrive() {
347	>	return ("Attempted arrival of unregistered party for " +
348	>	this.toString());
349	>	}
350	>
351	>	/**
352	>	* Implementation of register, bulkRegister
353	>	*
354	>	* @param registrations number to add to both parties and unarrived fields
355	>	*/
356	>	private int doRegister(int registrations) {
357	>	long adj = (long)registrations; // adjustment to state
358	>	adj |= adj << PARTIES_SHIFT;
359	>	Phaser par = parent;
360	>	long s;
361	>	int phase;
362	>	while ((phase = (int)((s = (par == null? state : reconcileState()))
363	>	>>> PHASE_SHIFT)) >= 0) {
364	>	int parties = ((int)(s & PARTIES_MASK)) >>> PARTIES_SHIFT;
365	>	if (parties != 0 && (s & UNARRIVED_MASK) == 0)
366	>	internalAwaitAdvance(phase, null); // wait for onAdvance
367	>	else if (parties + registrations > MAX_COUNT)
368	>	throw new IllegalStateException(badRegister());
369	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
370	>	break;
371	>	}
372	>	return phase;
373	>	}
374	>
375	>	/**
376	>	* Returns message string for bounds exceptions on registration
377		*/
378	<	private long getReconciledState() {
379	<	return (parent == null) ? state : reconcileState();
378	>	private String badRegister() {
379	>	return ("Attempt to register more than " + MAX_COUNT + " parties for "+
380	>	this.toString());
381		}
382
383		/**
384	<	* Recursively resolves state.
384	>	* Recursively resolves lagged phase propagation from root if
385	>	* necessary.
386		*/
387		private long reconcileState() {
388	<	Phaser p = parent;
389	<	long s = state;
390	<	if (p != null) {
391	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
392	<	long parentState = p.getReconciledState();
393	<	int parentPhase = phaseOf(parentState);
394	<	int phase = phaseOf(s = state);
395	<	if (phase != parentPhase) {
396	<	long next = trippedStateFor(parentPhase, partiesOf(s));
397	<	if (casState(s, next)) {
398	<	releaseWaiters(phase);
399	<	s = next;
400	<	}
388	>	Phaser par = parent;
389	>	if (par == null)
390	>	return state;
391	>	Phaser rt = root;
392	>	long s;
393	>	int phase, rPhase;
394	>	while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0 &&
395	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
396	>	if (rPhase < 0 || (s & UNARRIVED_MASK) == 0) {
397	>	long ps = par.parent == null? par.state : par.reconcileState();
398	>	int pPhase = (int)(ps >>> PHASE_SHIFT);
399	>	if (pPhase < 0 || pPhase == ((phase + 1) & MAX_PHASE)) {
400	>	if (state != s)
401	>	continue;
402	>	long p = s & PARTIES_MASK;
403	>	long next = ((((long) pPhase) << PHASE_SHIFT) |
404	>	(p >>> PARTIES_SHIFT) | p);
405	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
406	>	return next;
407		}
408		}
409	+	if (state == s)
410	+	releaseWaiters(phase); // help release others
411		}
412		return s;
413		}
#	Line 345 | Line 418 | public class Phaser {
418		* phaser will need to first register for it.
419		*/
420		public Phaser() {
421	<	this(null);
421	>	this(null, 0);
422		}
423
424		/**
425	<	* Creates a new phaser with the given numbers of registered
425	>	* Creates a new phaser with the given number of registered
426		* unarrived parties, initial phase number 0, and no parent.
427		*
428		* @param parties the number of parties required to trip barrier
#	Line 369 | Line 442 | public class Phaser {
442		* @param parent the parent phaser
443		*/
444		public Phaser(Phaser parent) {
445	<	int phase = 0;
373	<	this.parent = parent;
374	<	if (parent != null) {
375	<	this.root = parent.root;
376	<	phase = parent.register();
377	<	}
378	<	else
379	<	this.root = this;
380	<	this.state = trippedStateFor(phase, 0);
445	>	this(parent, 0);
446		}
447
448		/**
449	<	* Creates a new phaser with the given parent and numbers of
449	>	* Creates a new phaser with the given parent and number of
450		* registered unarrived parties. If parent is non-null, this phaser
451		* is registered with the parent and its initial phase number is
452		* the same as that of parent phaser.
#	Line 392 | Line 457 | public class Phaser {
457		* or greater than the maximum number of parties supported
458		*/
459		public Phaser(Phaser parent, int parties) {
460	<	if (parties < 0 || parties > ushortMask)
460	>	if (parties < 0 || parties > MAX_COUNT)
461		throw new IllegalArgumentException("Illegal number of parties");
462	<	int phase = 0;
462	>	int phase;
463		this.parent = parent;
464		if (parent != null) {
465	<	this.root = parent.root;
465	>	Phaser r = parent.root;
466	>	this.root = r;
467	>	this.evenQ = r.evenQ;
468	>	this.oddQ = r.oddQ;
469		phase = parent.register();
470		}
471	<	else
471	>	else {
472		this.root = this;
473	<	this.state = trippedStateFor(phase, parties);
473	>	this.evenQ = new AtomicReference<QNode>();
474	>	this.oddQ = new AtomicReference<QNode>();
475	>	phase = 0;
476	>	}
477	>	long p = (long)parties;
478	>	this.state = (((long) phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
479		}
480
481		/**
482		* Adds a new unarrived party to this phaser.
483	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
484	+	* this method may wait until its completion before registering.
485		*
486		* @return the arrival phase number to which this registration applied
487		* @throws IllegalStateException if attempting to register more
#	Line 418 | Line 493 | public class Phaser {
493
494		/**
495		* Adds the given number of new unarrived parties to this phaser.
496	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
497	+	* this method may wait until its completion before registering.
498		*
499	<	* @param parties the number of parties required to trip barrier
499	>	* @param parties the number of additional parties required to trip barrier
500		* @return the arrival phase number to which this registration applied
501		* @throws IllegalStateException if attempting to register more
502		* than the maximum supported number of parties
503	+	* @throws IllegalArgumentException if {@code parties < 0}
504		*/
505		public int bulkRegister(int parties) {
506		if (parties < 0)
507		throw new IllegalArgumentException();
508	+	if (parties > MAX_COUNT)
509	+	throw new IllegalStateException(badRegister());
510		if (parties == 0)
511		return getPhase();
512		return doRegister(parties);
513		}
514
515		/**
436	–	* Shared code for register, bulkRegister
437	–	*/
438	–	private int doRegister(int registrations) {
439	–	int phase;
440	–	for (;;) {
441	–	long s = getReconciledState();
442	–	phase = phaseOf(s);
443	–	int unarrived = unarrivedOf(s) + registrations;
444	–	int parties = partiesOf(s) + registrations;
445	–	if (phase < 0)
446	–	break;
447	–	if (parties > ushortMask || unarrived > ushortMask)
448	–	throw new IllegalStateException(badBounds(parties, unarrived));
449	–	if (phase == phaseOf(root.state) &&
450	–	casState(s, stateFor(phase, parties, unarrived)))
451	–	break;
452	–	}
453	–	return phase;
454	–	}
455	–
456	–	/**
516		* Arrives at the barrier, but does not wait for others.  (You can
517		* in turn wait for others via {@link #awaitAdvance}).  It is an
518		* unenforced usage error for an unregistered party to invoke this
#	Line 464 | Line 523 | public class Phaser {
523		* of unarrived parties would become negative
524		*/
525		public int arrive() {
526	<	int phase;
468	<	for (;;) {
469	<	long s = state;
470	<	phase = phaseOf(s);
471	<	if (phase < 0)
472	<	break;
473	<	int parties = partiesOf(s);
474	<	int unarrived = unarrivedOf(s) - 1;
475	<	if (unarrived > 0) {        // Not the last arrival
476	<	if (casState(s, s - 1)) // s-1 adds one arrival
477	<	break;
478	<	}
479	<	else if (unarrived == 0) {  // the last arrival
480	<	Phaser par = parent;
481	<	if (par == null) {      // directly trip
482	<	if (casState
483	<	(s,
484	<	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	<	}
496	<	}
497	<	}
498	<	else if (phase != phaseOf(root.state)) // or if unreconciled
499	<	reconcileState();
500	<	else
501	<	throw new IllegalStateException(badBounds(parties, unarrived));
502	<	}
503	<	return phase;
526	>	return doArrive(ONE_ARRIVAL);
527		}
528
529		/**
#	Line 517 | Line 540 | public class Phaser {
540		* of registered or unarrived parties would become negative
541		*/
542		public int arriveAndDeregister() {
543	<	// similar code to arrive, but too different to merge
521	<	Phaser par = parent;
522	<	int phase;
523	<	for (;;) {
524	<	long s = state;
525	<	phase = phaseOf(s);
526	<	if (phase < 0)
527	<	break;
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;
556	<	}
557	<	}
558	<	throw new IllegalStateException(badBounds(parties, unarrived));
559	<	}
560	<	return phase;
543	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
544		}
545
546		/**
547		* Arrives at the barrier and awaits others. Equivalent in effect
548		* to {@code awaitAdvance(arrive())}.  If you need to await with
549		* interruption or timeout, you can arrange this with an analogous
550	<	* construction using one of the other forms of the awaitAdvance
551	<	* method.  If instead you need to deregister upon arrival use
552	<	* {@code arriveAndDeregister}. It is an unenforced usage error
553	<	* for an unregistered party to invoke this method.
550	>	* construction using one of the other forms of the {@code
551	>	* awaitAdvance} method.  If instead you need to deregister upon
552	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
553	>	* usage error for an unregistered party to invoke this method.
554		*
555		* @return the arrival phase number, or a negative number if terminated
556		* @throws IllegalStateException if not terminated and the number
#	Line 581 | Line 564 | public class Phaser {
564		* Awaits the phase of the barrier to advance from the given phase
565		* value, returning immediately if the current phase of the
566		* barrier is not equal to the given phase value or this barrier
567	<	* is terminated.  It is an unenforced usage error for an
585	<	* unregistered party to invoke this method.
567	>	* is terminated.
568		*
569		* @param phase an arrival phase number, or negative value if
570		* terminated; this argument is normally the value returned by a
#	Line 593 | Line 575 | public class Phaser {
575		public int awaitAdvance(int phase) {
576		if (phase < 0)
577		return phase;
578	<	long s = getReconciledState();
597	<	int p = phaseOf(s);
578	>	int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
579		if (p != phase)
580		return p;
581	<	if (unarrivedOf(s) == 0 && parent != null)
601	<	parent.awaitAdvance(phase);
602	<	// Fall here even if parent waited, to reconcile and help release
603	<	return untimedWait(phase);
581	>	return internalAwaitAdvance(phase, null);
582		}
583
584		/**
#	Line 608 | Line 586 | public class Phaser {
586		* value, throwing {@code InterruptedException} if interrupted
587		* while waiting, or returning immediately if the current phase of
588		* the barrier is not equal to the given phase value or this
589	<	* barrier is terminated. It is an unenforced usage error for an
612	<	* unregistered party to invoke this method.
589	>	* barrier is terminated.
590		*
591		* @param phase an arrival phase number, or negative value if
592		* terminated; this argument is normally the value returned by a
#	Line 622 | Line 599 | public class Phaser {
599		throws InterruptedException {
600		if (phase < 0)
601		return phase;
602	<	long s = getReconciledState();
626	<	int p = phaseOf(s);
602	>	int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
603		if (p != phase)
604		return p;
605	<	if (unarrivedOf(s) == 0 && parent != null)
606	<	parent.awaitAdvanceInterruptibly(phase);
607	<	return interruptibleWait(phase);
605	>	QNode node = new QNode(this, phase, true, false, 0L);
606	>	p = internalAwaitAdvance(phase, node);
607	>	if (node.wasInterrupted)
608	>	throw new InterruptedException();
609	>	else
610	>	return p;
611		}
612
613		/**
#	Line 637 | Line 616 | public class Phaser {
616		* InterruptedException} if interrupted while waiting, or
617		* returning immediately if the current phase of the barrier is
618		* not equal to the given phase value or this barrier is
619	<	* terminated.  It is an unenforced usage error for an
641	<	* unregistered party to invoke this method.
619	>	* terminated.
620		*
621		* @param phase an arrival phase number, or negative value if
622		* terminated; this argument is normally the value returned by a
#	Line 655 | Line 633 | public class Phaser {
633		public int awaitAdvanceInterruptibly(int phase,
634		long timeout, TimeUnit unit)
635		throws InterruptedException, TimeoutException {
636	+	long nanos = unit.toNanos(timeout);
637		if (phase < 0)
638		return phase;
639	<	long s = getReconciledState();
661	<	int p = phaseOf(s);
639	>	int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
640		if (p != phase)
641		return p;
642	<	if (unarrivedOf(s) == 0 && parent != null)
643	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
644	<	return timedWait(phase, unit.toNanos(timeout));
642	>	QNode node = new QNode(this, phase, true, true, nanos);
643	>	p = internalAwaitAdvance(phase, node);
644	>	if (node.wasInterrupted)
645	>	throw new InterruptedException();
646	>	else if (p == phase)
647	>	throw new TimeoutException();
648	>	else
649	>	return p;
650		}
651
652		/**
#	Line 674 | Line 657 | public class Phaser {
657		* unexpected exceptions.
658		*/
659		public void forceTermination() {
660	<	for (;;) {
661	<	long s = getReconciledState();
662	<	int phase = phaseOf(s);
663	<	int parties = partiesOf(s);
664	<	int unarrived = unarrivedOf(s);
665	<	if (phase < 0 ||
666	<	casState(s, stateFor(-1, parties, unarrived))) {
684	<	releaseWaiters(0);
685	<	releaseWaiters(1);
686	<	if (parent != null)
687	<	parent.forceTermination();
688	<	return;
689	<	}
690	<	}
660	>	Phaser r = root;    // force at root then reconcile
661	>	long s;
662	>	while ((s = r.state) >= 0)
663	>	UNSAFE.compareAndSwapLong(r, stateOffset, s, s | TERMINATION_PHASE);
664	>	reconcileState();
665	>	releaseWaiters(0); // signal all threads
666	>	releaseWaiters(1);
667		}
668
669		/**
#	Line 698 | Line 674 | public class Phaser {
674		* @return the phase number, or a negative value if terminated
675		*/
676		public final int getPhase() {
677	<	return phaseOf(getReconciledState());
677	>	return (int)((parent == null? state : reconcileState()) >>> PHASE_SHIFT);
678		}
679
680		/**
#	Line 707 | Line 683 | public class Phaser {
683		* @return the number of parties
684		*/
685		public int getRegisteredParties() {
686	<	return partiesOf(state);
686	>	return partiesOf(parent == null? state : reconcileState());
687		}
688
689		/**
#	Line 717 | Line 693 | public class Phaser {
693		* @return the number of arrived parties
694		*/
695		public int getArrivedParties() {
696	<	return arrivedOf(state);
696	>	return arrivedOf(parent == null? state : reconcileState());
697		}
698
699		/**
#	Line 727 | Line 703 | public class Phaser {
703		* @return the number of unarrived parties
704		*/
705		public int getUnarrivedParties() {
706	<	return unarrivedOf(state);
706	>	return unarrivedOf(parent == null? state : reconcileState());
707		}
708
709		/**
#	Line 755 | Line 731 | public class Phaser {
731		* @return {@code true} if this barrier has been terminated
732		*/
733		public boolean isTerminated() {
734	<	return getPhase() < 0;
734	>	return (parent == null? state : reconcileState()) < 0;
735		}
736
737		/**
#	Line 771 | Line 747 | public class Phaser {
747		* which case no advance occurs.
748		*
749		* <p>The arguments to this method provide the state of the phaser
750	<	* prevailing for the current transition. (When called from within
751	<	* an implementation of {@code onAdvance} the values returned by
752	<	* methods such as {@code getPhase} may or may not reliably
753	<	* indicate the state to which this transition applies.)
750	>	* prevailing for the current transition.  The effects of invoking
751	>	* arrival, registration, and waiting methods on this Phaser from
752	>	* within {@code onAdvance} are unspecified and should not be
753	>	* relied on.
754	>	*
755	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
756	>	* {@code onAdvance} is invoked only for its root Phaser on each
757	>	* advance.
758		*
759		* <p>The default version returns {@code true} when the number of
760		* registered parties is zero. Normally, overrides that arrange
761		* termination for other reasons should also preserve this
762		* property.
763		*
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	–	*
764		* @param phase the phase number on entering the barrier
765		* @param registeredParties the current number of registered parties
766		* @return {@code true} if this barrier should terminate
#	Line 807 | Line 779 | public class Phaser {
779		* @return a string identifying this barrier, as well as its state
780		*/
781		public String toString() {
782	<	long s = getReconciledState();
782	>	long s = reconcileState();
783		return super.toString() +
784		"[phase = " + phaseOf(s) +
785		" parties = " + partiesOf(s) +
786		" arrived = " + arrivedOf(s) + "]";
787		}
788
817	–	// methods for waiting
818	–
789		/**
790	<	* Wait nodes for Treiber stack representing wait queue
821	<	*/
822	<	static final class QNode implements ForkJoinPool.ManagedBlocker {
823	<	final Phaser phaser;
824	<	final int phase;
825	<	final long startTime;
826	<	final long nanos;
827	<	final boolean timed;
828	<	final boolean interruptible;
829	<	volatile boolean wasInterrupted = false;
830	<	volatile Thread thread; // nulled to cancel wait
831	<	QNode next;
832	<	QNode(Phaser phaser, int phase, boolean interruptible,
833	<	boolean timed, long startTime, long nanos) {
834	<	this.phaser = phaser;
835	<	this.phase = phase;
836	<	this.timed = timed;
837	<	this.interruptible = interruptible;
838	<	this.startTime = startTime;
839	<	this.nanos = nanos;
840	<	thread = Thread.currentThread();
841	<	}
842	<	public boolean isReleasable() {
843	<	return (thread == null ||
844	<	phaser.getPhase() != phase ||
845	<	(interruptible && wasInterrupted) ||
846	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
847	<	}
848	<	public boolean block() {
849	<	if (Thread.interrupted()) {
850	<	wasInterrupted = true;
851	<	if (interruptible)
852	<	return true;
853	<	}
854	<	if (!timed)
855	<	LockSupport.park(this);
856	<	else {
857	<	long waitTime = nanos - (System.nanoTime() - startTime);
858	<	if (waitTime <= 0)
859	<	return true;
860	<	LockSupport.parkNanos(this, waitTime);
861	<	}
862	<	return isReleasable();
863	<	}
864	<	void signal() {
865	<	Thread t = thread;
866	<	if (t != null) {
867	<	thread = null;
868	<	LockSupport.unpark(t);
869	<	}
870	<	}
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.
790	>	* Removes and signals threads from queue for phase
791		*/
792		private void releaseWaiters(int phase) {
793		AtomicReference<QNode> head = queueFor(phase);
794		QNode q;
795	<	while ((q = head.get()) != null) {
795	>	int p;
796	>	while ((q = head.get()) != null &&
797	>	((p = q.phase) == phase ||
798	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
799		if (head.compareAndSet(q, q.next))
800		q.signal();
801		}
#	Line 897 | Line 806 | public class Phaser {
806		*
807		* @return true if successful
808		*/
809	<	private boolean tryEnqueue(QNode node) {
810	<	AtomicReference<QNode> head = queueFor(node.phase);
811	<	return head.compareAndSet(node.next = head.get(), node);
809	>	private boolean tryEnqueue(int phase, QNode node) {
810	>	releaseWaiters(phase-1); // ensure old queue clean
811	>	AtomicReference<QNode> head = queueFor(phase);
812	>	QNode q = head.get();
813	>	return ((q == null || q.phase == phase) &&
814	>	(int)(root.state >>> PHASE_SHIFT) == phase &&
815	>	head.compareAndSet(node.next = q, node));
816		}
817
818	+	/** The number of CPUs, for spin control */
819	+	private static final int NCPU = Runtime.getRuntime().availableProcessors();
820	+
821		/**
822	<	* Enqueues node and waits unless aborted or signalled.
823	<	*
824	<	* @return current phase
822	>	* The number of times to spin before blocking while waiting for
823	>	* advance, per arrival while waiting. On multiprocessors, fully
824	>	* blocking and waking up a large number of threads all at once is
825	>	* usually a very slow process, so we use rechargeable spins to
826	>	* avoid it when threads regularly arrive: When a thread in
827	>	* internalAwaitAdvance notices another arrival before blocking,
828	>	* and there appear to be enough CPUs available, it spins
829	>	* SPINS_PER_ARRIVAL more times before continuing to try to
830	>	* block. The value trades off good-citizenship vs big unnecessary
831	>	* slowdowns.
832		*/
833	<	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();
924	<	}
925	<	if (node != null)
926	<	node.thread = null;
927	<	releaseWaiters(phase);
928	<	if (interrupted)
929	<	Thread.currentThread().interrupt();
930	<	return p;
931	<	}
833	>	static final int SPINS_PER_ARRIVAL = NCPU < 2? 1 : 1 << 8;
834
835		/**
836	<	* Interruptible version
836	>	* Possibly blocks and waits for phase to advance unless aborted.
837	>	*
838	>	* @param phase current phase
839	>	* @param node if non-null, the wait node to track interrupt and timeout;
840	>	* if null, denotes noninterruptible wait
841		* @return current phase
842		*/
843	<	private int interruptibleWait(int phase) throws InterruptedException {
844	<	QNode node = null;
843	>	private int internalAwaitAdvance(int phase, QNode node) {
844	>	Phaser current = this;       // to eventually wait at root if tiered
845	>	Phaser par = parent;
846		boolean queued = false;
847	<	boolean interrupted = false;
847	>	int spins = SPINS_PER_ARRIVAL;
848	>	int lastUnarrived = -1;      // to increase spins upon change
849	>	long s;
850		int p;
851	<	while ((p = getPhase()) == phase && !interrupted) {
852	<	if (Thread.interrupted())
853	<	interrupted = true;
851	>	while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) {
852	>	int unarrived = (int)(s & UNARRIVED_MASK);
853	>	if (unarrived != lastUnarrived) {
854	>	if ((lastUnarrived = unarrived) < NCPU)
855	>	spins += SPINS_PER_ARRIVAL;
856	>	}
857	>	else if (unarrived == 0 && par != null) {
858	>	current = par;       // if all arrived, use parent
859	>	par = par.parent;
860	>	}
861	>	else if (spins > 0)
862	>	--spins;
863		else if (node == null)
864	<	node = new QNode(this, phase, true, false, 0, 0);
864	>	node = new QNode(this, phase, false, false, 0L);
865	>	else if (node.isReleasable())
866	>	break;
867		else if (!queued)
868	<	queued = tryEnqueue(node);
869	<	else
870	<	interrupted = node.doWait();
871	<	}
872	<	if (node != null)
873	<	node.thread = null;
874	<	if (p != phase || (p = getPhase()) != phase)
868	>	queued = tryEnqueue(phase, node);
869	>	else {
870	>	try {
871	>	ForkJoinPool.managedBlock(node);
872	>	} catch (InterruptedException ie) {
873	>	node.wasInterrupted = true;
874	>	}
875	>	}
876	>	}
877	>	if (node != null) {
878	>	if (node.thread != null)
879	>	node.thread = null;
880	>	if (!node.interruptible && node.wasInterrupted)
881	>	Thread.currentThread().interrupt();
882	>	}
883	>	if (p == phase)
884	>	p = (int)(reconcileState() >>> PHASE_SHIFT);
885	>	if (p != phase)
886		releaseWaiters(phase);
956	–	if (interrupted)
957	–	throw new InterruptedException();
887		return p;
888		}
889
890		/**
891	<	* Timeout version.
963	<	* @return current phase
891	>	* Wait nodes for Treiber stack representing wait queue
892		*/
893	<	private int timedWait(int phase, long nanos)
894	<	throws InterruptedException, TimeoutException {
895	<	long startTime = System.nanoTime();
896	<	QNode node = null;
897	<	boolean queued = false;
898	<	boolean interrupted = false;
899	<	int p;
900	<	while ((p = getPhase()) == phase && !interrupted) {
901	<	if (Thread.interrupted())
902	<	interrupted = true;
903	<	else if (nanos - (System.nanoTime() - startTime) <= 0)
904	<	break;
905	<	else if (node == null)
906	<	node = new QNode(this, phase, true, true, startTime, nanos);
907	<	else if (!queued)
908	<	queued = tryEnqueue(node);
909	<	else
910	<	interrupted = node.doWait();
911	<	}
912	<	if (node != null)
913	<	node.thread = null;
914	<	if (p != phase || (p = getPhase()) != phase)
915	<	releaseWaiters(phase);
916	<	if (interrupted)
917	<	throw new InterruptedException();
918	<	if (p == phase)
919	<	throw new TimeoutException();
920	<	return p;
893	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
894	>	final Phaser phaser;
895	>	final int phase;
896	>	final boolean interruptible;
897	>	final boolean timed;
898	>	boolean wasInterrupted;
899	>	long nanos;
900	>	long lastTime;
901	>	volatile Thread thread; // nulled to cancel wait
902	>	QNode next;
903	>
904	>	QNode(Phaser phaser, int phase, boolean interruptible,
905	>	boolean timed, long nanos) {
906	>	this.phaser = phaser;
907	>	this.phase = phase;
908	>	this.interruptible = interruptible;
909	>	this.nanos = nanos;
910	>	this.timed = timed;
911	>	this.lastTime = timed? System.nanoTime() : 0L;
912	>	thread = Thread.currentThread();
913	>	}
914	>
915	>	public boolean isReleasable() {
916	>	Thread t = thread;
917	>	if (t != null) {
918	>	if (phaser.getPhase() != phase)
919	>	t = null;
920	>	else {
921	>	if (Thread.interrupted())
922	>	wasInterrupted = true;
923	>	if (interruptible && wasInterrupted)
924	>	t = null;
925	>	else if (timed) {
926	>	if (nanos > 0) {
927	>	long now = System.nanoTime();
928	>	nanos -= now - lastTime;
929	>	lastTime = now;
930	>	}
931	>	if (nanos <= 0)
932	>	t = null;
933	>	}
934	>	}
935	>	if (t != null)
936	>	return false;
937	>	thread = null;
938	>	}
939	>	return true;
940	>	}
941	>
942	>	public boolean block() {
943	>	if (isReleasable())
944	>	return true;
945	>	else if (!timed)
946	>	LockSupport.park(this);
947	>	else if (nanos > 0)
948	>	LockSupport.parkNanos(this, nanos);
949	>	return isReleasable();
950	>	}
951	>
952	>	void signal() {
953	>	Thread t = thread;
954	>	if (t != null) {
955	>	thread = null;
956	>	LockSupport.unpark(t);
957	>	}
958	>	}
959		}
960
961		// Unsafe mechanics
#	Line 998 | Line 964 | public class Phaser {
964		private static final long stateOffset =
965		objectFieldOffset("state", Phaser.class);
966
1001	–	private final boolean casState(long cmp, long val) {
1002	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
1003	–	}
1004	–
967		private static long objectFieldOffset(String field, Class<?> klazz) {
968		try {
969		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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