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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.41 by jsr166, Mon Aug 24 15:42:51 2009 UTC vs.
Revision 1.57 by dl, Fri Nov 19 16:03:24 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	<	import java.util.concurrent.*;
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 100 | Line 100 | import java.util.concurrent.locks.LockSu
100		* #getRegisteredParties} parties in total, of which {@link
101		* #getArrivedParties} have arrived at the current phase ({@link
102		* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
103	<	* parties arrive, the phase advances; thus, this value is always
104	<	* greater than zero if there are any registered parties.  The values
105	<	* returned by these methods may reflect transient states and so are
106	<	* not in general useful for synchronization control.  Method {@link
107	<	* #toString} returns snapshots of these state queries in a form
108	<	* convenient for informal monitoring.
103	>	* parties arrive, the phase advances.  The values returned by these
104	>	* methods may reflect transient states and so are not in general
105	>	* useful for synchronization control.  Method {@link #toString}
106	>	* returns snapshots of these state queries in a form convenient for
107	>	* informal monitoring.
108		*
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 143 | 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 159 | 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();
167	<	* }</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();
181	<	*     }
182	<	*     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 b) {
191	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
192	<	*   if (step > 1) {
193	<	*     int i = lo;
194	<	*     while (i < hi) {
197	<	*       int r = Math.min(i + step, hi);
198	<	*       build(actions, i, r, new Phaser(b));
199	<	*       i = r;
190	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
191	>	*   if (hi - lo > TASKS_PER_PHASER) {
192	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
193	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
194	>	*       build(actions, i, j, new Phaser(ph));
195		*     }
196		*   } else {
197		*     for (int i = lo; i < hi; ++i)
198	<	*       actions[i] = new Task(b);
199	<	*       // assumes new Task(b) performs b.register()
198	>	*       actions[i] = new Task(ph);
199	>	*       // assumes new Task(ph) performs ph.register()
200		*   }
201		* }
202		* // .. initially called, for n tasks via
#	Line 212 | 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		*
215	–	* </pre>
216	–	*
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 234 | 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.
247	–	*
248	–	* Note: there are some cheats in arrive() that rely on unarrived
249	–	* count being lowest 16 bits.
240		*/
241		private volatile long state;
242
243	<	private static final int ushortMask = 0xffff;
244	<	private static final int phaseMask  = 0x7fffffff;
243	>	private static final int  MAX_PARTIES    = 0xffff;
244	>	private static final int  MAX_PHASE      = 0x7fffffff;
245	>	private static final int  PARTIES_SHIFT  = 16;
246	>	private static final int  PHASE_SHIFT    = 32;
247	>	private static final int  UNARRIVED_MASK = 0xffff;
248	>	private static final long PARTIES_MASK   = 0xffff0000L; // for masking long
249	>	private static final long ONE_ARRIVAL    = 1L;
250	>	private static final long ONE_PARTY      = 1L << PARTIES_SHIFT;
251	>	private static final long TERMINATION_PHASE  = -1L << PHASE_SHIFT;
252	>
253	>	// The following unpacking methods are usually manually inlined
254
255		private static int unarrivedOf(long s) {
256	<	return (int) (s & ushortMask);
256	>	return (int)s & UNARRIVED_MASK;
257		}
258
259		private static int partiesOf(long s) {
260	<	return ((int) s) >>> 16;
260	>	return (int)s >>> PARTIES_SHIFT;
261		}
262
263		private static int phaseOf(long s) {
264	<	return (int) (s >>> 32);
264	>	return (int) (s >>> PHASE_SHIFT);
265		}
266
267		private static int arrivedOf(long s) {
268		return partiesOf(s) - unarrivedOf(s);
269		}
270
272	–	private static long stateFor(int phase, int parties, int unarrived) {
273	–	return ((((long) phase) << 32) | (((long) parties) << 16) |
274	–	(long) unarrived);
275	–	}
276	–
277	–	private static long trippedStateFor(int phase, int parties) {
278	–	long lp = (long) parties;
279	–	return (((long) phase) << 32) | (lp << 16) | lp;
280	–	}
281	–
282	–	/**
283	–	* Returns message string for bad bounds exceptions.
284	–	*/
285	–	private static String badBounds(int parties, int unarrived) {
286	–	return ("Attempt to set " + unarrived +
287	–	" unarrived of " + parties + " parties");
288	–	}
289	–
271		/**
272		* The parent of this phaser, or null if none
273		*/
#	Line 298 | Line 279 | public class Phaser {
279		*/
280		private final Phaser root;
281
301	–	// Wait queues
302	–
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	>	for (;;) {
306	>	long s = state;
307	>	int phase = (int)(s >>> PHASE_SHIFT);
308	>	if (phase < 0)
309	>	return phase;
310	>	int unarrived = (int)s & UNARRIVED_MASK;
311	>	if (unarrived == 0)
312	>	checkBadArrive(s);
313	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
314	>	if (unarrived == 1) {
315	>	long p = s & PARTIES_MASK; // unshifted parties field
316	>	long lu = p >>> PARTIES_SHIFT;
317	>	int u = (int)lu;
318	>	int nextPhase = (phase + 1) & MAX_PHASE;
319	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
320	>	final Phaser parent = this.parent;
321	>	if (parent == null) {
322	>	if (onAdvance(phase, u))
323	>	next |= TERMINATION_PHASE; // obliterate phase
324	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
325	>	releaseWaiters(phase);
326	>	}
327	>	else {
328	>	parent.doArrive((u == 0) ?
329	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
330	>	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase ||
331	>	((int)(state >>> PHASE_SHIFT) != nextPhase &&
332	>	!UNSAFE.compareAndSwapLong(this, stateOffset,
333	>	s, next)))
334	>	reconcileState();
335	>	}
336	>	}
337	>	return phase;
338	>	}
339	>	}
340	>	}
341	>
342	>	/**
343	>	* Rechecks state and throws bounds exceptions on arrival -- called
344	>	* only if unarrived is apparently zero.
345		*/
346	<	private long getReconciledState() {
347	<	return (parent == null) ? state : reconcileState();
346	>	private void checkBadArrive(long s) {
347	>	if (reconcileState() == s)
348	>	throw new IllegalStateException
349	>	("Attempted arrival of unregistered party for " +
350	>	stateToString(s));
351		}
352
353		/**
354	<	* Recursively resolves state.
354	>	* Implementation of register, bulkRegister
355	>	*
356	>	* @param registrations number to add to both parties and unarrived fields
357	>	*/
358	>	private int doRegister(int registrations) {
359	>	// assert registrations > 0;
360	>	// adjustment to state
361	>	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
362	>	final Phaser parent = this.parent;
363	>	for (;;) {
364	>	long s = (parent == null) ? state : reconcileState();
365	>	int phase = (int)(s >>> PHASE_SHIFT);
366	>	if (phase < 0)
367	>	return phase;
368	>	int parties = (int)s >>> PARTIES_SHIFT;
369	>	if (parties != 0 && ((int)s & UNARRIVED_MASK) == 0)
370	>	internalAwaitAdvance(phase, null); // wait for onAdvance
371	>	else if (registrations > MAX_PARTIES - parties)
372	>	throw new IllegalStateException(badRegister(s));
373	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
374	>	return phase;
375	>	}
376	>	}
377	>
378	>	/**
379	>	* Returns message string for out of bounds exceptions on registration.
380	>	*/
381	>	private String badRegister(long s) {
382	>	return "Attempt to register more than " +
383	>	MAX_PARTIES + " parties for " + stateToString(s);
384	>	}
385	>
386	>	/**
387	>	* Recursively resolves lagged phase propagation from root if necessary.
388		*/
389		private long reconcileState() {
390	<	Phaser p = parent;
390	>	Phaser par = parent;
391		long s = state;
392	<	if (p != null) {
393	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
394	<	long parentState = p.getReconciledState();
395	<	int parentPhase = phaseOf(parentState);
396	<	int phase = phaseOf(s = state);
397	<	if (phase != parentPhase) {
398	<	long next = trippedStateFor(parentPhase, partiesOf(s));
399	<	if (casState(s, next)) {
400	<	releaseWaiters(phase);
401	<	s = next;
402	<	}
392	>	if (par != null) {
393	>	Phaser rt = root;
394	>	int phase, rPhase;
395	>	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
396	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
397	>	if ((int)(par.state >>> PHASE_SHIFT) != rPhase)
398	>	par.reconcileState();
399	>	else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
400	>	long u = s & PARTIES_MASK; // reset unarrived to parties
401	>	long next = ((((long) rPhase) << PHASE_SHIFT) | u |
402	>	(u >>> PARTIES_SHIFT));
403	>	if (state == s &&
404	>	UNSAFE.compareAndSwapLong(this, stateOffset,
405	>	s, s = next))
406	>	break;
407		}
408	+	s = state;
409		}
410		}
411		return s;
#	Line 349 | Line 417 | public class Phaser {
417		* phaser will need to first register for it.
418		*/
419		public Phaser() {
420	<	this(null);
420	>	this(null, 0);
421		}
422
423		/**
424	<	* Creates a new phaser with the given numbers of registered
424	>	* Creates a new phaser with the given number of registered
425		* unarrived parties, initial phase number 0, and no parent.
426		*
427		* @param parties the number of parties required to trip barrier
#	Line 373 | Line 441 | public class Phaser {
441		* @param parent the parent phaser
442		*/
443		public Phaser(Phaser parent) {
444	<	int phase = 0;
377	<	this.parent = parent;
378	<	if (parent != null) {
379	<	this.root = parent.root;
380	<	phase = parent.register();
381	<	}
382	<	else
383	<	this.root = this;
384	<	this.state = trippedStateFor(phase, 0);
444	>	this(parent, 0);
445		}
446
447		/**
448	<	* Creates a new phaser with the given parent and numbers of
448	>	* Creates a new phaser with the given parent and number of
449		* registered unarrived parties. If parent is non-null, this phaser
450		* is registered with the parent and its initial phase number is
451		* the same as that of parent phaser.
#	Line 396 | Line 456 | public class Phaser {
456		* or greater than the maximum number of parties supported
457		*/
458		public Phaser(Phaser parent, int parties) {
459	<	if (parties < 0 || parties > ushortMask)
459	>	if (parties >>> PARTIES_SHIFT != 0)
460		throw new IllegalArgumentException("Illegal number of parties");
461	<	int phase = 0;
461	>	int phase;
462		this.parent = parent;
463		if (parent != null) {
464	<	this.root = parent.root;
464	>	Phaser r = parent.root;
465	>	this.root = r;
466	>	this.evenQ = r.evenQ;
467	>	this.oddQ = r.oddQ;
468		phase = parent.register();
469		}
470	<	else
470	>	else {
471		this.root = this;
472	<	this.state = trippedStateFor(phase, parties);
472	>	this.evenQ = new AtomicReference<QNode>();
473	>	this.oddQ = new AtomicReference<QNode>();
474	>	phase = 0;
475	>	}
476	>	long p = (long)parties;
477	>	this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
478		}
479
480		/**
481		* Adds a new unarrived party to this phaser.
482	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
483	+	* this method may wait until its completion before registering.
484		*
485		* @return the arrival phase number to which this registration applied
486		* @throws IllegalStateException if attempting to register more
#	Line 422 | Line 492 | public class Phaser {
492
493		/**
494		* Adds the given number of new unarrived parties to this phaser.
495	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
496	+	* this method may wait until its completion before registering.
497		*
498	<	* @param parties the number of parties required to trip barrier
498	>	* @param parties the number of additional parties required to trip barrier
499		* @return the arrival phase number to which this registration applied
500		* @throws IllegalStateException if attempting to register more
501		* than the maximum supported number of parties
502	+	* @throws IllegalArgumentException if {@code parties < 0}
503		*/
504		public int bulkRegister(int parties) {
505		if (parties < 0)
#	Line 437 | Line 510 | public class Phaser {
510		}
511
512		/**
440	–	* Shared code for register, bulkRegister
441	–	*/
442	–	private int doRegister(int registrations) {
443	–	int phase;
444	–	for (;;) {
445	–	long s = getReconciledState();
446	–	phase = phaseOf(s);
447	–	int unarrived = unarrivedOf(s) + registrations;
448	–	int parties = partiesOf(s) + registrations;
449	–	if (phase < 0)
450	–	break;
451	–	if (parties > ushortMask || unarrived > ushortMask)
452	–	throw new IllegalStateException(badBounds(parties, unarrived));
453	–	if (phase == phaseOf(root.state) &&
454	–	casState(s, stateFor(phase, parties, unarrived)))
455	–	break;
456	–	}
457	–	return phase;
458	–	}
459	–
460	–	/**
513		* Arrives at the barrier, but does not wait for others.  (You can
514		* in turn wait for others via {@link #awaitAdvance}).  It is an
515		* unenforced usage error for an unregistered party to invoke this
#	Line 468 | Line 520 | public class Phaser {
520		* of unarrived parties would become negative
521		*/
522		public int arrive() {
523	<	int phase;
472	<	for (;;) {
473	<	long s = state;
474	<	phase = phaseOf(s);
475	<	if (phase < 0)
476	<	break;
477	<	int parties = partiesOf(s);
478	<	int unarrived = unarrivedOf(s) - 1;
479	<	if (unarrived > 0) {        // Not the last arrival
480	<	if (casState(s, s - 1)) // s-1 adds one arrival
481	<	break;
482	<	}
483	<	else if (unarrived == 0) {  // the last arrival
484	<	Phaser par = parent;
485	<	if (par == null) {      // directly trip
486	<	if (casState
487	<	(s,
488	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
489	<	((phase + 1) & phaseMask), parties))) {
490	<	releaseWaiters(phase);
491	<	break;
492	<	}
493	<	}
494	<	else {                  // cascade to parent
495	<	if (casState(s, s - 1)) { // zeroes unarrived
496	<	par.arrive();
497	<	reconcileState();
498	<	break;
499	<	}
500	<	}
501	<	}
502	<	else if (phase != phaseOf(root.state)) // or if unreconciled
503	<	reconcileState();
504	<	else
505	<	throw new IllegalStateException(badBounds(parties, unarrived));
506	<	}
507	<	return phase;
523	>	return doArrive(ONE_ARRIVAL);
524		}
525
526		/**
#	Line 521 | Line 537 | public class Phaser {
537		* of registered or unarrived parties would become negative
538		*/
539		public int arriveAndDeregister() {
540	<	// similar code to arrive, but too different to merge
525	<	Phaser par = parent;
526	<	int phase;
527	<	for (;;) {
528	<	long s = state;
529	<	phase = phaseOf(s);
530	<	if (phase < 0)
531	<	break;
532	<	int parties = partiesOf(s) - 1;
533	<	int unarrived = unarrivedOf(s) - 1;
534	<	if (parties >= 0) {
535	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
536	<	if (casState
537	<	(s,
538	<	stateFor(phase, parties, unarrived))) {
539	<	if (unarrived == 0) {
540	<	par.arriveAndDeregister();
541	<	reconcileState();
542	<	}
543	<	break;
544	<	}
545	<	continue;
546	<	}
547	<	if (unarrived == 0) {
548	<	if (casState
549	<	(s,
550	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
551	<	((phase + 1) & phaseMask), parties))) {
552	<	releaseWaiters(phase);
553	<	break;
554	<	}
555	<	continue;
556	<	}
557	<	if (par != null && phase != phaseOf(root.state)) {
558	<	reconcileState();
559	<	continue;
560	<	}
561	<	}
562	<	throw new IllegalStateException(badBounds(parties, unarrived));
563	<	}
564	<	return phase;
540	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
541		}
542
543		/**
544		* Arrives at the barrier and awaits others. Equivalent in effect
545		* to {@code awaitAdvance(arrive())}.  If you need to await with
546		* interruption or timeout, you can arrange this with an analogous
547	<	* construction using one of the other forms of the awaitAdvance
548	<	* method.  If instead you need to deregister upon arrival use
549	<	* {@code arriveAndDeregister}. It is an unenforced usage error
550	<	* for an unregistered party to invoke this method.
547	>	* construction using one of the other forms of the {@code
548	>	* awaitAdvance} method.  If instead you need to deregister upon
549	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
550	>	* usage error for an unregistered party to invoke this method.
551		*
552		* @return the arrival phase number, or a negative number if terminated
553		* @throws IllegalStateException if not terminated and the number
#	Line 585 | Line 561 | public class Phaser {
561		* Awaits the phase of the barrier to advance from the given phase
562		* value, returning immediately if the current phase of the
563		* barrier is not equal to the given phase value or this barrier
564	<	* is terminated.  It is an unenforced usage error for an
589	<	* unregistered party to invoke this method.
564	>	* is terminated.
565		*
566		* @param phase an arrival phase number, or negative value if
567		* terminated; this argument is normally the value returned by a
#	Line 597 | Line 572 | public class Phaser {
572		public int awaitAdvance(int phase) {
573		if (phase < 0)
574		return phase;
575	<	long s = getReconciledState();
576	<	int p = phaseOf(s);
577	<	if (p != phase)
603	<	return p;
604	<	if (unarrivedOf(s) == 0 && parent != null)
605	<	parent.awaitAdvance(phase);
606	<	// Fall here even if parent waited, to reconcile and help release
607	<	return untimedWait(phase);
575	>	long s = (parent == null) ? state : reconcileState();
576	>	int p = (int)(s >>> PHASE_SHIFT);
577	>	return (p != phase) ? p : internalAwaitAdvance(phase, null);
578		}
579
580		/**
#	Line 612 | Line 582 | public class Phaser {
582		* value, throwing {@code InterruptedException} if interrupted
583		* while waiting, or returning immediately if the current phase of
584		* the barrier is not equal to the given phase value or this
585	<	* barrier is terminated. It is an unenforced usage error for an
616	<	* unregistered party to invoke this method.
585	>	* barrier is terminated.
586		*
587		* @param phase an arrival phase number, or negative value if
588		* terminated; this argument is normally the value returned by a
#	Line 626 | Line 595 | public class Phaser {
595		throws InterruptedException {
596		if (phase < 0)
597		return phase;
598	<	long s = getReconciledState();
599	<	int p = phaseOf(s);
600	<	if (p != phase)
601	<	return p;
602	<	if (unarrivedOf(s) == 0 && parent != null)
603	<	parent.awaitAdvanceInterruptibly(phase);
604	<	return interruptibleWait(phase);
598	>	long s = (parent == null) ? state : reconcileState();
599	>	int p = (int)(s >>> PHASE_SHIFT);
600	>	if (p == phase) {
601	>	QNode node = new QNode(this, phase, true, false, 0L);
602	>	p = internalAwaitAdvance(phase, node);
603	>	if (node.wasInterrupted)
604	>	throw new InterruptedException();
605	>	}
606	>	return p;
607		}
608
609		/**
#	Line 641 | Line 612 | public class Phaser {
612		* InterruptedException} if interrupted while waiting, or
613		* returning immediately if the current phase of the barrier is
614		* not equal to the given phase value or this barrier is
615	<	* terminated.  It is an unenforced usage error for an
645	<	* unregistered party to invoke this method.
615	>	* terminated.
616		*
617		* @param phase an arrival phase number, or negative value if
618		* terminated; this argument is normally the value returned by a
#	Line 661 | Line 631 | public class Phaser {
631		throws InterruptedException, TimeoutException {
632		if (phase < 0)
633		return phase;
634	<	long s = getReconciledState();
635	<	int p = phaseOf(s);
636	<	if (p != phase)
637	<	return p;
638	<	if (unarrivedOf(s) == 0 && parent != null)
639	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
640	<	return timedWait(phase, unit.toNanos(timeout));
634	>	long s = (parent == null) ? state : reconcileState();
635	>	int p = (int)(s >>> PHASE_SHIFT);
636	>	if (p == phase) {
637	>	long nanos = unit.toNanos(timeout);
638	>	QNode node = new QNode(this, phase, true, true, nanos);
639	>	p = internalAwaitAdvance(phase, node);
640	>	if (node.wasInterrupted)
641	>	throw new InterruptedException();
642	>	else if (p == phase)
643	>	throw new TimeoutException();
644	>	}
645	>	return p;
646		}
647
648		/**
649	<	* Forces this barrier to enter termination state. Counts of
650	<	* arrived and registered parties are unaffected. If this phaser
651	<	* has a parent, it too is terminated. This method may be useful
652	<	* for coordinating recovery after one or more tasks encounter
653	<	* unexpected exceptions.
649	>	* Forces this barrier to enter termination state.  Counts of
650	>	* arrived and registered parties are unaffected.  If this phaser
651	>	* is a member of a tiered set of phasers, then all of the phasers
652	>	* in the set are terminated.  If this phaser is already
653	>	* terminated, this method has no effect.  This method may be
654	>	* useful for coordinating recovery after one or more tasks
655	>	* encounter unexpected exceptions.
656		*/
657		public void forceTermination() {
658	<	for (;;) {
659	<	long s = getReconciledState();
660	<	int phase = phaseOf(s);
661	<	int parties = partiesOf(s);
662	<	int unarrived = unarrivedOf(s);
663	<	if (phase < 0 ||
664	<	casState(s, stateFor(-1, parties, unarrived))) {
688	<	releaseWaiters(0);
658	>	// Only need to change root state
659	>	final Phaser root = this.root;
660	>	long s;
661	>	while ((s = root.state) >= 0) {
662	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
663	>	s, s | TERMINATION_PHASE)) {
664	>	releaseWaiters(0); // signal all threads
665		releaseWaiters(1);
690	–	if (parent != null)
691	–	parent.forceTermination();
666		return;
667		}
668		}
#	Line 702 | Line 676 | public class Phaser {
676		* @return the phase number, or a negative value if terminated
677		*/
678		public final int getPhase() {
679	<	return phaseOf(getReconciledState());
679	>	return (int)(root.state >>> PHASE_SHIFT);
680		}
681
682		/**
#	Line 721 | Line 695 | public class Phaser {
695		* @return the number of arrived parties
696		*/
697		public int getArrivedParties() {
698	<	return arrivedOf(state);
698	>	return arrivedOf(parent==null? state : reconcileState());
699		}
700
701		/**
#	Line 731 | Line 705 | public class Phaser {
705		* @return the number of unarrived parties
706		*/
707		public int getUnarrivedParties() {
708	<	return unarrivedOf(state);
708	>	return unarrivedOf(parent==null? state : reconcileState());
709		}
710
711		/**
#	Line 759 | Line 733 | public class Phaser {
733		* @return {@code true} if this barrier has been terminated
734		*/
735		public boolean isTerminated() {
736	<	return getPhase() < 0;
736	>	return root.state < 0L;
737		}
738
739		/**
740	<	* Overridable method to perform an action upon phase advance, and
741	<	* to control termination. This method is invoked whenever the
742	<	* barrier is tripped (and thus all other waiting parties are
743	<	* dormant). If it returns {@code true}, then, rather than advance
744	<	* the phase number, this barrier will be set to a final
745	<	* termination state, and subsequent calls to {@link #isTerminated}
746	<	* will return true.
740	>	* Overridable method to perform an action upon impending phase
741	>	* advance, and to control termination. This method is invoked
742	>	* upon arrival of the party tripping the barrier (when all other
743	>	* waiting parties are dormant).  If this method returns {@code
744	>	* true}, then, rather than advance the phase number, this barrier
745	>	* will be set to a final termination state, and subsequent calls
746	>	* to {@link #isTerminated} will return true. Any (unchecked)
747	>	* Exception or Error thrown by an invocation of this method is
748	>	* propagated to the party attempting to trip the barrier, in
749	>	* which case no advance occurs.
750	>	*
751	>	* <p>The arguments to this method provide the state of the phaser
752	>	* prevailing for the current transition.  The effects of invoking
753	>	* arrival, registration, and waiting methods on this Phaser from
754	>	* within {@code onAdvance} are unspecified and should not be
755	>	* relied on.
756	>	*
757	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
758	>	* {@code onAdvance} is invoked only for its root Phaser on each
759	>	* advance.
760		*
761		* <p>The default version returns {@code true} when the number of
762		* registered parties is zero. Normally, overrides that arrange
763		* termination for other reasons should also preserve this
764		* property.
765		*
779	–	* <p>You may override this method to perform an action with side
780	–	* effects visible to participating tasks, but it is in general
781	–	* only sensible to do so in designs where all parties register
782	–	* before any arrive, and all {@link #awaitAdvance} at each phase.
783	–	* Otherwise, you cannot ensure lack of interference from other
784	–	* parties during the invocation of this method.
785	–	*
766		* @param phase the phase number on entering the barrier
767		* @param registeredParties the current number of registered parties
768		* @return {@code true} if this barrier should terminate
#	Line 801 | Line 781 | public class Phaser {
781		* @return a string identifying this barrier, as well as its state
782		*/
783		public String toString() {
784	<	long s = getReconciledState();
784	>	return stateToString(reconcileState());
785	>	}
786	>
787	>	/**
788	>	* Implementation of toString and string-based error messages
789	>	*/
790	>	private String stateToString(long s) {
791		return super.toString() +
792		"[phase = " + phaseOf(s) +
793		" parties = " + partiesOf(s) +
794		" arrived = " + arrivedOf(s) + "]";
795		}
796
797	<	// methods for waiting
797	>	// Waiting mechanics
798	>
799	>	/**
800	>	* Removes and signals threads from queue for phase.
801	>	*/
802	>	private void releaseWaiters(int phase) {
803	>	AtomicReference<QNode> head = queueFor(phase);
804	>	QNode q;
805	>	int p;
806	>	while ((q = head.get()) != null &&
807	>	((p = q.phase) == phase ||
808	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
809	>	if (head.compareAndSet(q, q.next))
810	>	q.signal();
811	>	}
812	>	}
813	>
814	>	/** The number of CPUs, for spin control */
815	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
816	>
817	>	/**
818	>	* The number of times to spin before blocking while waiting for
819	>	* advance, per arrival while waiting. On multiprocessors, fully
820	>	* blocking and waking up a large number of threads all at once is
821	>	* usually a very slow process, so we use rechargeable spins to
822	>	* avoid it when threads regularly arrive: When a thread in
823	>	* internalAwaitAdvance notices another arrival before blocking,
824	>	* and there appear to be enough CPUs available, it spins
825	>	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
826	>	* uniprocessors, there is at least one intervening Thread.yield
827	>	* before blocking. The value trades off good-citizenship vs big
828	>	* unnecessary slowdowns.
829	>	*/
830	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
831	>
832	>	/**
833	>	* Possibly blocks and waits for phase to advance unless aborted.
834	>	*
835	>	* @param phase current phase
836	>	* @param node if non-null, the wait node to track interrupt and timeout;
837	>	* if null, denotes noninterruptible wait
838	>	* @return current phase
839	>	*/
840	>	private int internalAwaitAdvance(int phase, QNode node) {
841	>	Phaser current = this;       // to eventually wait at root if tiered
842	>	boolean queued = false;      // true when node is enqueued
843	>	int lastUnarrived = -1;      // to increase spins upon change
844	>	int spins = SPINS_PER_ARRIVAL;
845	>	long s;
846	>	int p;
847	>	while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) {
848	>	Phaser par;
849	>	int unarrived = (int)s & UNARRIVED_MASK;
850	>	if (unarrived != lastUnarrived) {
851	>	if (lastUnarrived == -1) // ensure old queue clean
852	>	releaseWaiters(phase-1);
853	>	if ((lastUnarrived = unarrived) < NCPU)
854	>	spins += SPINS_PER_ARRIVAL;
855	>	}
856	>	else if (unarrived == 0 && (par = current.parent) != null) {
857	>	current = par;       // if all arrived, use parent
858	>	par = par.parent;
859	>	lastUnarrived = -1;
860	>	}
861	>	else if (spins > 0) {
862	>	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
863	>	Thread.yield();  // yield midway through spin
864	>	}
865	>	else if (node == null)   // must be noninterruptible
866	>	node = new QNode(this, phase, false, false, 0L);
867	>	else if (node.isReleasable()) {
868	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
869	>	break;
870	>	else
871	>	return phase;    // aborted
872	>	}
873	>	else if (!queued) {      // push onto queue
874	>	AtomicReference<QNode> head = queueFor(phase);
875	>	QNode q = head.get();
876	>	if (q == null || q.phase == phase) {
877	>	node.next = q;
878	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
879	>	break;       // recheck to avoid stale enqueue
880	>	else
881	>	queued = head.compareAndSet(q, node);
882	>	}
883	>	}
884	>	else {
885	>	try {
886	>	ForkJoinPool.managedBlock(node);
887	>	} catch (InterruptedException ie) {
888	>	node.wasInterrupted = true;
889	>	}
890	>	}
891	>	}
892	>	releaseWaiters(phase);
893	>	if (node != null)
894	>	node.onRelease();
895	>	return p;
896	>	}
897
898		/**
899		* Wait nodes for Treiber stack representing wait queue
#	Line 816 | Line 901 | public class Phaser {
901		static final class QNode implements ForkJoinPool.ManagedBlocker {
902		final Phaser phaser;
903		final int phase;
819	–	final long startTime;
820	–	final long nanos;
821	–	final boolean timed;
904		final boolean interruptible;
905	<	volatile boolean wasInterrupted = false;
905	>	final boolean timed;
906	>	boolean wasInterrupted;
907	>	long nanos;
908	>	long lastTime;
909		volatile Thread thread; // nulled to cancel wait
910		QNode next;
911	+
912		QNode(Phaser phaser, int phase, boolean interruptible,
913	<	boolean timed, long startTime, long nanos) {
913	>	boolean timed, long nanos) {
914		this.phaser = phaser;
915		this.phase = phase;
830	–	this.timed = timed;
916		this.interruptible = interruptible;
832	–	this.startTime = startTime;
917		this.nanos = nanos;
918	+	this.timed = timed;
919	+	this.lastTime = timed? System.nanoTime() : 0L;
920		thread = Thread.currentThread();
921		}
922	+
923		public boolean isReleasable() {
924	<	return (thread == null ||
925	<	phaser.getPhase() != phase ||
926	<	(interruptible && wasInterrupted) ||
927	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
924	>	Thread t = thread;
925	>	if (t != null) {
926	>	if (phaser.getPhase() != phase)
927	>	t = null;
928	>	else {
929	>	if (Thread.interrupted())
930	>	wasInterrupted = true;
931	>	if (interruptible && wasInterrupted)
932	>	t = null;
933	>	else if (timed) {
934	>	if (nanos > 0) {
935	>	long now = System.nanoTime();
936	>	nanos -= now - lastTime;
937	>	lastTime = now;
938	>	}
939	>	if (nanos <= 0)
940	>	t = null;
941	>	}
942	>	}
943	>	if (t != null)
944	>	return false;
945	>	thread = null;
946	>	}
947	>	return true;
948		}
949	+
950		public boolean block() {
951	<	if (Thread.interrupted()) {
952	<	wasInterrupted = true;
953	<	if (interruptible)
846	<	return true;
847	<	}
848	<	if (!timed)
951	>	if (isReleasable())
952	>	return true;
953	>	else if (!timed)
954		LockSupport.park(this);
955	<	else {
956	<	long waitTime = nanos - (System.nanoTime() - startTime);
852	<	if (waitTime <= 0)
853	<	return true;
854	<	LockSupport.parkNanos(this, waitTime);
855	<	}
955	>	else if (nanos > 0)
956	>	LockSupport.parkNanos(this, nanos);
957		return isReleasable();
958		}
959	+
960		void signal() {
961		Thread t = thread;
962		if (t != null) {
#	Line 862 | Line 964 | public class Phaser {
964		LockSupport.unpark(t);
965		}
966		}
865	–	boolean doWait() {
866	–	if (thread != null) {
867	–	try {
868	–	ForkJoinPool.managedBlock(this, false);
869	–	} catch (InterruptedException ie) {
870	–	}
871	–	}
872	–	return wasInterrupted;
873	–	}
874	–
875	–	}
876	–
877	–	/**
878	–	* Removes and signals waiting threads from wait queue.
879	–	*/
880	–	private void releaseWaiters(int phase) {
881	–	AtomicReference<QNode> head = queueFor(phase);
882	–	QNode q;
883	–	while ((q = head.get()) != null) {
884	–	if (head.compareAndSet(q, q.next))
885	–	q.signal();
886	–	}
887	–	}
888	–
889	–	/**
890	–	* Tries to enqueue given node in the appropriate wait queue.
891	–	*
892	–	* @return true if successful
893	–	*/
894	–	private boolean tryEnqueue(QNode node) {
895	–	AtomicReference<QNode> head = queueFor(node.phase);
896	–	return head.compareAndSet(node.next = head.get(), node);
897	–	}
898	–
899	–	/**
900	–	* Enqueues node and waits unless aborted or signalled.
901	–	*
902	–	* @return current phase
903	–	*/
904	–	private int untimedWait(int phase) {
905	–	QNode node = null;
906	–	boolean queued = false;
907	–	boolean interrupted = false;
908	–	int p;
909	–	while ((p = getPhase()) == phase) {
910	–	if (Thread.interrupted())
911	–	interrupted = true;
912	–	else if (node == null)
913	–	node = new QNode(this, phase, false, false, 0, 0);
914	–	else if (!queued)
915	–	queued = tryEnqueue(node);
916	–	else
917	–	interrupted = node.doWait();
918	–	}
919	–	if (node != null)
920	–	node.thread = null;
921	–	releaseWaiters(phase);
922	–	if (interrupted)
923	–	Thread.currentThread().interrupt();
924	–	return p;
925	–	}
967
968	<	/**
969	<	* Interruptible version
970	<	* @return current phase
971	<	*/
972	<	private int interruptibleWait(int phase) throws InterruptedException {
932	<	QNode node = null;
933	<	boolean queued = false;
934	<	boolean interrupted = false;
935	<	int p;
936	<	while ((p = getPhase()) == phase && !interrupted) {
937	<	if (Thread.interrupted())
938	<	interrupted = true;
939	<	else if (node == null)
940	<	node = new QNode(this, phase, true, false, 0, 0);
941	<	else if (!queued)
942	<	queued = tryEnqueue(node);
943	<	else
944	<	interrupted = node.doWait();
968	>	void onRelease() { // actions upon return from internalAwaitAdvance
969	>	if (!interruptible && wasInterrupted)
970	>	Thread.currentThread().interrupt();
971	>	if (thread != null)
972	>	thread = null;
973		}
946	–	if (node != null)
947	–	node.thread = null;
948	–	if (p != phase || (p = getPhase()) != phase)
949	–	releaseWaiters(phase);
950	–	if (interrupted)
951	–	throw new InterruptedException();
952	–	return p;
953	–	}
974
955	–	/**
956	–	* Timeout version.
957	–	* @return current phase
958	–	*/
959	–	private int timedWait(int phase, long nanos)
960	–	throws InterruptedException, TimeoutException {
961	–	long startTime = System.nanoTime();
962	–	QNode node = null;
963	–	boolean queued = false;
964	–	boolean interrupted = false;
965	–	int p;
966	–	while ((p = getPhase()) == phase && !interrupted) {
967	–	if (Thread.interrupted())
968	–	interrupted = true;
969	–	else if (nanos - (System.nanoTime() - startTime) <= 0)
970	–	break;
971	–	else if (node == null)
972	–	node = new QNode(this, phase, true, true, startTime, nanos);
973	–	else if (!queued)
974	–	queued = tryEnqueue(node);
975	–	else
976	–	interrupted = node.doWait();
977	–	}
978	–	if (node != null)
979	–	node.thread = null;
980	–	if (p != phase || (p = getPhase()) != phase)
981	–	releaseWaiters(phase);
982	–	if (interrupted)
983	–	throw new InterruptedException();
984	–	if (p == phase)
985	–	throw new TimeoutException();
986	–	return p;
975		}
976
977		// Unsafe mechanics
#	Line 992 | Line 980 | public class Phaser {
980		private static final long stateOffset =
981		objectFieldOffset("state", Phaser.class);
982
995	–	private final boolean casState(long cmp, long val) {
996	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
997	–	}
998	–
983		private static long objectFieldOffset(String field, Class<?> klazz) {
984		try {
985		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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