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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.43 by dl, Mon Aug 24 23:08:18 2009 UTC vs.
Revision 1.56 by dl, Wed Nov 17 10:48:59 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 b) {
191	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
192	<	*   if (step > 1) {
193	<	*     int i = lo;
194	<	*     while (i < hi) {
196	<	*       int r = Math.min(i + step, hi);
197	<	*       build(actions, i, r, new Phaser(b));
198	<	*       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 211 | 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		*
214	–	* </pre>
215	–	*
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 233 | 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.
246	–	*
247	–	* Note: there are some cheats in arrive() that rely on unarrived
248	–	* 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 int  PARTIES_MASK   = 0xffff0000;
249	>	private static final long LPARTIES_MASK  = 0xffff0000L; // long version
250	>	private static final long ONE_ARRIVAL    = 1L;
251	>	private static final long ONE_PARTY      = 1L << PARTIES_SHIFT;
252	>	private static final long TERMINATION_PHASE  = -1L << PHASE_SHIFT;
253	>
254	>	// The following unpacking methods are usually manually inlined
255
256		private static int unarrivedOf(long s) {
257	<	return (int) (s & ushortMask);
257	>	return (int)s & UNARRIVED_MASK;
258		}
259
260		private static int partiesOf(long s) {
261	<	return ((int) s) >>> 16;
261	>	return (int)s >>> PARTIES_SHIFT;
262		}
263
264		private static int phaseOf(long s) {
265	<	return (int) (s >>> 32);
265	>	return (int) (s >>> PHASE_SHIFT);
266		}
267
268		private static int arrivedOf(long s) {
269		return partiesOf(s) - unarrivedOf(s);
270		}
271
271	–	private static long stateFor(int phase, int parties, int unarrived) {
272	–	return ((((long) phase) << 32) | (((long) parties) << 16) |
273	–	(long) unarrived);
274	–	}
275	–
276	–	private static long trippedStateFor(int phase, int parties) {
277	–	long lp = (long) parties;
278	–	return (((long) phase) << 32) | (lp << 16) | lp;
279	–	}
280	–
281	–	/**
282	–	* Returns message string for bad bounds exceptions.
283	–	*/
284	–	private static String badBounds(int parties, int unarrived) {
285	–	return ("Attempt to set " + unarrived +
286	–	" unarrived of " + parties + " parties");
287	–	}
288	–
272		/**
273		* The parent of this phaser, or null if none
274		*/
#	Line 297 | Line 280 | public class Phaser {
280		*/
281		private final Phaser root;
282
300	–	// Wait queues
301	–
283		/**
284		* Heads of Treiber stacks for waiting threads. To eliminate
285	<	* contention while releasing some threads while adding others, we
285	>	* contention when releasing some threads while adding others, we
286		* use two of them, alternating across even and odd phases.
287	+	* Subphasers share queues with root to speed up releases.
288		*/
289	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
290	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
289	>	private final AtomicReference<QNode> evenQ;
290	>	private final AtomicReference<QNode> oddQ;
291
292		private AtomicReference<QNode> queueFor(int phase) {
293		return ((phase & 1) == 0) ? evenQ : oddQ;
294		}
295
296		/**
297	<	* Returns current state, first resolving lagged propagation from
298	<	* root if necessary.
297	>	* Main implementation for methods arrive and arriveAndDeregister.
298	>	* Manually tuned to speed up and minimize race windows for the
299	>	* common case of just decrementing unarrived field.
300	>	*
301	>	* @param adj - adjustment to apply to state -- either
302	>	* ONE_ARRIVAL (for arrive) or
303	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
304		*/
305	<	private long getReconciledState() {
306	<	return (parent == null) ? state : reconcileState();
305	>	private int doArrive(long adj) {
306	>	for (;;) {
307	>	long s;
308	>	int phase, unarrived;
309	>	if ((phase = (int)((s = state) >>> PHASE_SHIFT)) < 0)
310	>	return phase;
311	>	else if ((unarrived = (int)s & UNARRIVED_MASK) == 0)
312	>	checkBadArrive(s);
313	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
314	>	if (unarrived == 1) {
315	>	Phaser par;
316	>	long p = s & LPARTIES_MASK; // unshifted parties field
317	>	long lu = p >>> PARTIES_SHIFT;
318	>	int u = (int)lu;
319	>	int nextPhase = (phase + 1) & MAX_PHASE;
320	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
321	>	if ((par = 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	>	par.doArrive(u == 0?
329	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
330	>	if ((int)(par.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	<	* Recursively resolves state.
343	>	* Rechecks state and throws bounds exceptions on arrival -- called
344	>	* only if unarrived is apparently zero.
345	>	*/
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	>	* 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	>	long adj = (long)registrations; // adjustment to state
360	>	adj |= adj << PARTIES_SHIFT;
361	>	Phaser par = parent;
362	>	for (;;) {
363	>	int phase, parties;
364	>	long s = par == null? state : reconcileState();
365	>	if ((phase = (int)(s >>> PHASE_SHIFT)) < 0)
366	>	return phase;
367	>	if ((parties = (int)s >>> PARTIES_SHIFT) != 0 &&
368	>	((int)s & UNARRIVED_MASK) == 0)
369	>	internalAwaitAdvance(phase, null); // wait for onAdvance
370	>	else if (parties + registrations > MAX_PARTIES)
371	>	throw new IllegalStateException(badRegister(s));
372	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
373	>	return phase;
374	>	}
375	>	}
376	>
377	>	/**
378	>	* Returns message string for out of bounds exceptions on registration.
379	>	*/
380	>	private String badRegister(long s) {
381	>	return "Attempt to register more than " +
382	>	MAX_PARTIES + " parties for " + stateToString(s);
383	>	}
384	>
385	>	/**
386	>	* Recursively resolves lagged phase propagation from root if necessary.
387		*/
388		private long reconcileState() {
389	<	Phaser p = parent;
390	<	long s = state;
391	<	if (p != null) {
392	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
393	<	long parentState = p.getReconciledState();
394	<	int parentPhase = phaseOf(parentState);
395	<	int phase = phaseOf(s = state);
396	<	if (phase != parentPhase) {
397	<	long next = trippedStateFor(parentPhase, partiesOf(s));
398	<	if (casState(s, next)) {
399	<	releaseWaiters(phase);
400	<	s = next;
401	<	}
402	<	}
389	>	Phaser par = parent;
390	>	if (par == null)
391	>	return state;
392	>	Phaser rt = root;
393	>	for (;;) {
394	>	long s, u;
395	>	int phase, rPhase, pPhase;
396	>	if ((phase = (int)((s = state)>>> PHASE_SHIFT)) < 0 ||
397	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) == phase)
398	>	return s;
399	>	long pState = par.parent == null? par.state : par.reconcileState();
400	>	if (state == s) {
401	>	if ((rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) &&
402	>	((pPhase = (int)(pState >>> PHASE_SHIFT)) < 0 ||
403	>	pPhase == ((phase + 1) & MAX_PHASE)))
404	>	UNSAFE.compareAndSwapLong
405	>	(this, stateOffset, s,
406	>	(((long) pPhase) << PHASE_SHIFT) |
407	>	(u = s & LPARTIES_MASK) |
408	>	(u >>> PARTIES_SHIFT)); // reset unarrived to parties
409	>	else
410	>	releaseWaiters(phase); // help release others
411		}
412		}
342	–	return s;
413		}
414
415		/**
#	Line 348 | 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 372 | Line 442 | public class Phaser {
442		* @param parent the parent phaser
443		*/
444		public Phaser(Phaser parent) {
445	<	int phase = 0;
376	<	this.parent = parent;
377	<	if (parent != null) {
378	<	this.root = parent.root;
379	<	phase = parent.register();
380	<	}
381	<	else
382	<	this.root = this;
383	<	this.state = trippedStateFor(phase, 0);
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 395 | 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 >>> PARTIES_SHIFT != 0)
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 421 | 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_PARTIES)
509	+	throw new IllegalStateException(badRegister(state));
510		if (parties == 0)
511		return getPhase();
512		return doRegister(parties);
513		}
514
515		/**
439	–	* Shared code for register, bulkRegister
440	–	*/
441	–	private int doRegister(int registrations) {
442	–	int phase;
443	–	for (;;) {
444	–	long s = getReconciledState();
445	–	phase = phaseOf(s);
446	–	int unarrived = unarrivedOf(s) + registrations;
447	–	int parties = partiesOf(s) + registrations;
448	–	if (phase < 0)
449	–	break;
450	–	if (parties > ushortMask || unarrived > ushortMask)
451	–	throw new IllegalStateException(badBounds(parties, unarrived));
452	–	if (phase == phaseOf(root.state) &&
453	–	casState(s, stateFor(phase, parties, unarrived)))
454	–	break;
455	–	}
456	–	return phase;
457	–	}
458	–
459	–	/**
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 467 | Line 523 | public class Phaser {
523		* of unarrived parties would become negative
524		*/
525		public int arrive() {
526	<	int phase;
471	<	for (;;) {
472	<	long s = state;
473	<	phase = phaseOf(s);
474	<	if (phase < 0)
475	<	break;
476	<	int parties = partiesOf(s);
477	<	int unarrived = unarrivedOf(s) - 1;
478	<	if (unarrived > 0) {        // Not the last arrival
479	<	if (casState(s, s - 1)) // s-1 adds one arrival
480	<	break;
481	<	}
482	<	else if (unarrived == 0) {  // the last arrival
483	<	Phaser par = parent;
484	<	if (par == null) {      // directly trip
485	<	if (casState
486	<	(s,
487	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
488	<	((phase + 1) & phaseMask), parties))) {
489	<	releaseWaiters(phase);
490	<	break;
491	<	}
492	<	}
493	<	else {                  // cascade to parent
494	<	if (casState(s, s - 1)) { // zeroes unarrived
495	<	par.arrive();
496	<	reconcileState();
497	<	break;
498	<	}
499	<	}
500	<	}
501	<	else if (phase != phaseOf(root.state)) // or if unreconciled
502	<	reconcileState();
503	<	else
504	<	throw new IllegalStateException(badBounds(parties, unarrived));
505	<	}
506	<	return phase;
526	>	return doArrive(ONE_ARRIVAL);
527		}
528
529		/**
#	Line 520 | 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
524	<	Phaser par = parent;
525	<	int phase;
526	<	for (;;) {
527	<	long s = state;
528	<	phase = phaseOf(s);
529	<	if (phase < 0)
530	<	break;
531	<	int parties = partiesOf(s) - 1;
532	<	int unarrived = unarrivedOf(s) - 1;
533	<	if (parties >= 0) {
534	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
535	<	if (casState
536	<	(s,
537	<	stateFor(phase, parties, unarrived))) {
538	<	if (unarrived == 0) {
539	<	par.arriveAndDeregister();
540	<	reconcileState();
541	<	}
542	<	break;
543	<	}
544	<	continue;
545	<	}
546	<	if (unarrived == 0) {
547	<	if (casState
548	<	(s,
549	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
550	<	((phase + 1) & phaseMask), parties))) {
551	<	releaseWaiters(phase);
552	<	break;
553	<	}
554	<	continue;
555	<	}
556	<	if (par != null && phase != phaseOf(root.state)) {
557	<	reconcileState();
558	<	continue;
559	<	}
560	<	}
561	<	throw new IllegalStateException(badBounds(parties, unarrived));
562	<	}
563	<	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 584 | 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
588	<	* 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 594 | Line 573 | public class Phaser {
573		* if terminated or argument is negative
574		*/
575		public int awaitAdvance(int phase) {
576	+	int p;
577		if (phase < 0)
578		return phase;
579	<	long s = getReconciledState();
580	<	int p = phaseOf(s);
581	<	if (p != phase)
579	>	else if ((p = (int)((parent == null? state : reconcileState())
580	>	>>> PHASE_SHIFT)) == phase)
581	>	return internalAwaitAdvance(phase, null);
582	>	else
583		return p;
603	–	if (unarrivedOf(s) == 0 && parent != null)
604	–	parent.awaitAdvance(phase);
605	–	// Fall here even if parent waited, to reconcile and help release
606	–	return untimedWait(phase);
584		}
585
586		/**
#	Line 611 | Line 588 | public class Phaser {
588		* value, throwing {@code InterruptedException} if interrupted
589		* while waiting, or returning immediately if the current phase of
590		* the barrier is not equal to the given phase value or this
591	<	* barrier is terminated. It is an unenforced usage error for an
615	<	* unregistered party to invoke this method.
591	>	* barrier is terminated.
592		*
593		* @param phase an arrival phase number, or negative value if
594		* terminated; this argument is normally the value returned by a
#	Line 623 | Line 599 | public class Phaser {
599		*/
600		public int awaitAdvanceInterruptibly(int phase)
601		throws InterruptedException {
602	+	int p;
603		if (phase < 0)
604		return phase;
605	<	long s = getReconciledState();
606	<	int p = phaseOf(s);
607	<	if (p != phase)
608	<	return p;
609	<	if (unarrivedOf(s) == 0 && parent != null)
610	<	parent.awaitAdvanceInterruptibly(phase);
611	<	return interruptibleWait(phase);
605	>	if ((p = (int)((parent == null? state : reconcileState())
606	>	>>> PHASE_SHIFT)) == phase) {
607	>	QNode node = new QNode(this, phase, true, false, 0L);
608	>	p = internalAwaitAdvance(phase, node);
609	>	if (node.wasInterrupted)
610	>	throw new InterruptedException();
611	>	}
612	>	return p;
613		}
614
615		/**
#	Line 640 | Line 618 | public class Phaser {
618		* InterruptedException} if interrupted while waiting, or
619		* returning immediately if the current phase of the barrier is
620		* not equal to the given phase value or this barrier is
621	<	* terminated.  It is an unenforced usage error for an
644	<	* unregistered party to invoke this method.
621	>	* terminated.
622		*
623		* @param phase an arrival phase number, or negative value if
624		* terminated; this argument is normally the value returned by a
#	Line 658 | Line 635 | public class Phaser {
635		public int awaitAdvanceInterruptibly(int phase,
636		long timeout, TimeUnit unit)
637		throws InterruptedException, TimeoutException {
638	+	long nanos = unit.toNanos(timeout);
639	+	int p;
640		if (phase < 0)
641		return phase;
642	<	long s = getReconciledState();
643	<	int p = phaseOf(s);
644	<	if (p != phase)
645	<	return p;
646	<	if (unarrivedOf(s) == 0 && parent != null)
647	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
648	<	return timedWait(phase, unit.toNanos(timeout));
642	>	if ((p = (int)((parent == null? state : reconcileState())
643	>	>>> PHASE_SHIFT)) == phase) {
644	>	QNode node = new QNode(this, phase, true, true, nanos);
645	>	p = internalAwaitAdvance(phase, node);
646	>	if (node.wasInterrupted)
647	>	throw new InterruptedException();
648	>	else if (p == phase)
649	>	throw new TimeoutException();
650	>	}
651	>	return p;
652		}
653
654		/**
655	<	* Forces this barrier to enter termination state. Counts of
656	<	* arrived and registered parties are unaffected. If this phaser
657	<	* has a parent, it too is terminated. This method may be useful
658	<	* for coordinating recovery after one or more tasks encounter
659	<	* unexpected exceptions.
655	>	* Forces this barrier to enter termination state.  Counts of
656	>	* arrived and registered parties are unaffected.  If this phaser
657	>	* is a member of a tiered set of phasers, then all of the phasers
658	>	* in the set are terminated.  If this phaser is already
659	>	* terminated, this method has no effect.  This method may be
660	>	* useful for coordinating recovery after one or more tasks
661	>	* encounter unexpected exceptions.
662		*/
663		public void forceTermination() {
664	<	for (;;) {
665	<	long s = getReconciledState();
666	<	int phase = phaseOf(s);
667	<	int parties = partiesOf(s);
668	<	int unarrived = unarrivedOf(s);
669	<	if (phase < 0 ||
670	<	casState(s, stateFor(-1, parties, unarrived))) {
687	<	releaseWaiters(0);
664	>	// Only need to change root state
665	>	final Phaser root = this.root;
666	>	long s;
667	>	while ((s = root.state) >= 0) {
668	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
669	>	s, s | TERMINATION_PHASE)) {
670	>	releaseWaiters(0); // signal all threads
671		releaseWaiters(1);
689	–	if (parent != null)
690	–	parent.forceTermination();
672		return;
673		}
674		}
#	Line 701 | Line 682 | public class Phaser {
682		* @return the phase number, or a negative value if terminated
683		*/
684		public final int getPhase() {
685	<	return phaseOf(getReconciledState());
685	>	return (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
686		}
687
688		/**
#	Line 710 | Line 691 | public class Phaser {
691		* @return the number of parties
692		*/
693		public int getRegisteredParties() {
694	<	return partiesOf(state);
694	>	return partiesOf(parent==null? state : reconcileState());
695		}
696
697		/**
#	Line 720 | Line 701 | public class Phaser {
701		* @return the number of arrived parties
702		*/
703		public int getArrivedParties() {
704	<	return arrivedOf(state);
704	>	return arrivedOf(parent==null? state : reconcileState());
705		}
706
707		/**
#	Line 730 | Line 711 | public class Phaser {
711		* @return the number of unarrived parties
712		*/
713		public int getUnarrivedParties() {
714	<	return unarrivedOf(state);
714	>	return unarrivedOf(parent==null? state : reconcileState());
715		}
716
717		/**
#	Line 758 | Line 739 | public class Phaser {
739		* @return {@code true} if this barrier has been terminated
740		*/
741		public boolean isTerminated() {
742	<	return getPhase() < 0;
742	>	return (parent == null? state : reconcileState()) < 0;
743		}
744
745		/**
#	Line 774 | Line 755 | public class Phaser {
755		* which case no advance occurs.
756		*
757		* <p>The arguments to this method provide the state of the phaser
758	<	* prevailing for the current transition. (When called from within
759	<	* an implementation of {@code onAdvance} the values returned by
760	<	* methods such as {@code getPhase} may or may not reliably
761	<	* indicate the state to which this transition applies.)
758	>	* prevailing for the current transition.  The effects of invoking
759	>	* arrival, registration, and waiting methods on this Phaser from
760	>	* within {@code onAdvance} are unspecified and should not be
761	>	* relied on.
762	>	*
763	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
764	>	* {@code onAdvance} is invoked only for its root Phaser on each
765	>	* advance.
766		*
767		* <p>The default version returns {@code true} when the number of
768		* registered parties is zero. Normally, overrides that arrange
769		* termination for other reasons should also preserve this
770		* property.
771		*
787	–	* <p>You may override this method to perform an action with side
788	–	* effects visible to participating tasks, but doing so requires
789	–	* care: Method {@code onAdvance} may be invoked more than once
790	–	* per transition.  Further, unless all parties register before
791	–	* any arrive, and all {@link #awaitAdvance} at each phase, then
792	–	* you cannot ensure lack of interference from other parties
793	–	* during the invocation of this method.
794	–	*
772		* @param phase the phase number on entering the barrier
773		* @param registeredParties the current number of registered parties
774		* @return {@code true} if this barrier should terminate
#	Line 810 | Line 787 | public class Phaser {
787		* @return a string identifying this barrier, as well as its state
788		*/
789		public String toString() {
790	<	long s = getReconciledState();
790	>	return stateToString(reconcileState());
791	>	}
792	>
793	>	/**
794	>	* Implementation of toString and string-based error messages
795	>	*/
796	>	private String stateToString(long s) {
797		return super.toString() +
798		"[phase = " + phaseOf(s) +
799		" parties = " + partiesOf(s) +
800		" arrived = " + arrivedOf(s) + "]";
801		}
802
803	<	// methods for waiting
803	>	// Waiting mechanics
804	>
805	>	/**
806	>	* Removes and signals threads from queue for phase
807	>	*/
808	>	private void releaseWaiters(int phase) {
809	>	AtomicReference<QNode> head = queueFor(phase);
810	>	QNode q;
811	>	int p;
812	>	while ((q = head.get()) != null &&
813	>	((p = q.phase) == phase ||
814	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
815	>	if (head.compareAndSet(q, q.next))
816	>	q.signal();
817	>	}
818	>	}
819	>
820	>	/**
821	>	* Tries to enqueue given node in the appropriate wait queue.
822	>	*
823	>	* @return true if successful
824	>	*/
825	>	private boolean tryEnqueue(int phase, QNode node) {
826	>	releaseWaiters(phase-1); // ensure old queue clean
827	>	AtomicReference<QNode> head = queueFor(phase);
828	>	QNode q = head.get();
829	>	return ((q == null || q.phase == phase) &&
830	>	(int)(root.state >>> PHASE_SHIFT) == phase &&
831	>	head.compareAndSet(node.next = q, node));
832	>	}
833	>
834	>	/** The number of CPUs, for spin control */
835	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
836	>
837	>	/**
838	>	* The number of times to spin before blocking while waiting for
839	>	* advance, per arrival while waiting. On multiprocessors, fully
840	>	* blocking and waking up a large number of threads all at once is
841	>	* usually a very slow process, so we use rechargeable spins to
842	>	* avoid it when threads regularly arrive: When a thread in
843	>	* internalAwaitAdvance notices another arrival before blocking,
844	>	* and there appear to be enough CPUs available, it spins
845	>	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
846	>	* uniprocessors, there is at least one intervening Thread.yield
847	>	* before blocking. The value trades off good-citizenship vs big
848	>	* unnecessary slowdowns.
849	>	*/
850	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
851	>
852	>	/**
853	>	* Possibly blocks and waits for phase to advance unless aborted.
854	>	*
855	>	* @param phase current phase
856	>	* @param node if non-null, the wait node to track interrupt and timeout;
857	>	* if null, denotes noninterruptible wait
858	>	* @return current phase
859	>	*/
860	>	private int internalAwaitAdvance(int phase, QNode node) {
861	>	Phaser current = this;       // to eventually wait at root if tiered
862	>	boolean queued = false;      // true when node is enqueued
863	>	int lastUnarrived = -1;      // to increase spins upon change
864	>	int spins = SPINS_PER_ARRIVAL;
865	>	for (;;) {
866	>	int p, unarrived;
867	>	Phaser par;
868	>	long s = current.state;
869	>	if ((p = (int)(s >>> PHASE_SHIFT)) != phase) {
870	>	if (node != null)
871	>	node.onRelease();
872	>	releaseWaiters(phase);
873	>	return p;
874	>	}
875	>	else if ((unarrived = (int)s & UNARRIVED_MASK) == 0 &&
876	>	(par = current.parent) != null) {
877	>	current = par;       // if all arrived, use parent
878	>	par = par.parent;
879	>	lastUnarrived = -1;
880	>	}
881	>	else if (unarrived != lastUnarrived) {
882	>	if ((lastUnarrived = unarrived) < NCPU)
883	>	spins += SPINS_PER_ARRIVAL;
884	>	}
885	>	else if (spins > 0) {
886	>	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
887	>	Thread.yield();  // yield midway through spin
888	>	}
889	>	else if (node == null)   // must be noninterruptible
890	>	node = new QNode(this, phase, false, false, 0L);
891	>	else if (node.isReleasable()) {
892	>	if ((int)(reconcileState() >>> PHASE_SHIFT) == phase)
893	>	return phase;    // aborted
894	>	}
895	>	else if (!queued)
896	>	queued = tryEnqueue(phase, node);
897	>	else {
898	>	try {
899	>	ForkJoinPool.managedBlock(node);
900	>	} catch (InterruptedException ie) {
901	>	node.wasInterrupted = true;
902	>	}
903	>	}
904	>	}
905	>	}
906
907		/**
908		* Wait nodes for Treiber stack representing wait queue
#	Line 825 | Line 910 | public class Phaser {
910		static final class QNode implements ForkJoinPool.ManagedBlocker {
911		final Phaser phaser;
912		final int phase;
828	–	final long startTime;
829	–	final long nanos;
830	–	final boolean timed;
913		final boolean interruptible;
914	<	volatile boolean wasInterrupted = false;
914	>	final boolean timed;
915	>	boolean wasInterrupted;
916	>	long nanos;
917	>	long lastTime;
918		volatile Thread thread; // nulled to cancel wait
919		QNode next;
920	+
921		QNode(Phaser phaser, int phase, boolean interruptible,
922	<	boolean timed, long startTime, long nanos) {
922	>	boolean timed, long nanos) {
923		this.phaser = phaser;
924		this.phase = phase;
839	–	this.timed = timed;
925		this.interruptible = interruptible;
841	–	this.startTime = startTime;
926		this.nanos = nanos;
927	+	this.timed = timed;
928	+	this.lastTime = timed? System.nanoTime() : 0L;
929		thread = Thread.currentThread();
930		}
931	+
932		public boolean isReleasable() {
933	<	return (thread == null ||
934	<	phaser.getPhase() != phase ||
935	<	(interruptible && wasInterrupted) ||
936	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
933	>	Thread t = thread;
934	>	if (t != null) {
935	>	if (phaser.getPhase() != phase)
936	>	t = null;
937	>	else {
938	>	if (Thread.interrupted())
939	>	wasInterrupted = true;
940	>	if (interruptible && wasInterrupted)
941	>	t = null;
942	>	else if (timed) {
943	>	if (nanos > 0) {
944	>	long now = System.nanoTime();
945	>	nanos -= now - lastTime;
946	>	lastTime = now;
947	>	}
948	>	if (nanos <= 0)
949	>	t = null;
950	>	}
951	>	}
952	>	if (t != null)
953	>	return false;
954	>	thread = null;
955	>	}
956	>	return true;
957		}
958	+
959		public boolean block() {
960	<	if (Thread.interrupted()) {
961	<	wasInterrupted = true;
962	<	if (interruptible)
855	<	return true;
856	<	}
857	<	if (!timed)
960	>	if (isReleasable())
961	>	return true;
962	>	else if (!timed)
963		LockSupport.park(this);
964	<	else {
965	<	long waitTime = nanos - (System.nanoTime() - startTime);
861	<	if (waitTime <= 0)
862	<	return true;
863	<	LockSupport.parkNanos(this, waitTime);
864	<	}
964	>	else if (nanos > 0)
965	>	LockSupport.parkNanos(this, nanos);
966		return isReleasable();
967		}
968	+
969		void signal() {
970		Thread t = thread;
971		if (t != null) {
#	Line 871 | Line 973 | public class Phaser {
973		LockSupport.unpark(t);
974		}
975		}
874	–	boolean doWait() {
875	–	if (thread != null) {
876	–	try {
877	–	ForkJoinPool.managedBlock(this, false);
878	–	} catch (InterruptedException ie) {
879	–	}
880	–	}
881	–	return wasInterrupted;
882	–	}
976
977	<	}
978	<
979	<	/**
980	<	* Removes and signals waiting threads from wait queue.
981	<	*/
889	<	private void releaseWaiters(int phase) {
890	<	AtomicReference<QNode> head = queueFor(phase);
891	<	QNode q;
892	<	while ((q = head.get()) != null) {
893	<	if (head.compareAndSet(q, q.next))
894	<	q.signal();
977	>	void onRelease() { // actions upon return from internalAwaitAdvance
978	>	if (!interruptible && wasInterrupted)
979	>	Thread.currentThread().interrupt();
980	>	if (thread != null)
981	>	thread = null;
982		}
896	–	}
897	–
898	–	/**
899	–	* Tries to enqueue given node in the appropriate wait queue.
900	–	*
901	–	* @return true if successful
902	–	*/
903	–	private boolean tryEnqueue(QNode node) {
904	–	AtomicReference<QNode> head = queueFor(node.phase);
905	–	return head.compareAndSet(node.next = head.get(), node);
906	–	}
983
908	–	/**
909	–	* Enqueues node and waits unless aborted or signalled.
910	–	*
911	–	* @return current phase
912	–	*/
913	–	private int untimedWait(int phase) {
914	–	QNode node = null;
915	–	boolean queued = false;
916	–	boolean interrupted = false;
917	–	int p;
918	–	while ((p = getPhase()) == phase) {
919	–	if (Thread.interrupted())
920	–	interrupted = true;
921	–	else if (node == null)
922	–	node = new QNode(this, phase, false, false, 0, 0);
923	–	else if (!queued)
924	–	queued = tryEnqueue(node);
925	–	else
926	–	interrupted = node.doWait();
927	–	}
928	–	if (node != null)
929	–	node.thread = null;
930	–	releaseWaiters(phase);
931	–	if (interrupted)
932	–	Thread.currentThread().interrupt();
933	–	return p;
934	–	}
935	–
936	–	/**
937	–	* Interruptible version
938	–	* @return current phase
939	–	*/
940	–	private int interruptibleWait(int phase) throws InterruptedException {
941	–	QNode node = null;
942	–	boolean queued = false;
943	–	boolean interrupted = false;
944	–	int p;
945	–	while ((p = getPhase()) == phase && !interrupted) {
946	–	if (Thread.interrupted())
947	–	interrupted = true;
948	–	else if (node == null)
949	–	node = new QNode(this, phase, true, false, 0, 0);
950	–	else if (!queued)
951	–	queued = tryEnqueue(node);
952	–	else
953	–	interrupted = node.doWait();
954	–	}
955	–	if (node != null)
956	–	node.thread = null;
957	–	if (p != phase || (p = getPhase()) != phase)
958	–	releaseWaiters(phase);
959	–	if (interrupted)
960	–	throw new InterruptedException();
961	–	return p;
962	–	}
963	–
964	–	/**
965	–	* Timeout version.
966	–	* @return current phase
967	–	*/
968	–	private int timedWait(int phase, long nanos)
969	–	throws InterruptedException, TimeoutException {
970	–	long startTime = System.nanoTime();
971	–	QNode node = null;
972	–	boolean queued = false;
973	–	boolean interrupted = false;
974	–	int p;
975	–	while ((p = getPhase()) == phase && !interrupted) {
976	–	if (Thread.interrupted())
977	–	interrupted = true;
978	–	else if (nanos - (System.nanoTime() - startTime) <= 0)
979	–	break;
980	–	else if (node == null)
981	–	node = new QNode(this, phase, true, true, startTime, nanos);
982	–	else if (!queued)
983	–	queued = tryEnqueue(node);
984	–	else
985	–	interrupted = node.doWait();
986	–	}
987	–	if (node != null)
988	–	node.thread = null;
989	–	if (p != phase || (p = getPhase()) != phase)
990	–	releaseWaiters(phase);
991	–	if (interrupted)
992	–	throw new InterruptedException();
993	–	if (p == phase)
994	–	throw new TimeoutException();
995	–	return p;
984		}
985
986		// Unsafe mechanics
#	Line 1001 | Line 989 | public class Phaser {
989		private static final long stateOffset =
990		objectFieldOffset("state", Phaser.class);
991
1004	–	private final boolean casState(long cmp, long val) {
1005	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
1006	–	}
1007	–
992		private static long objectFieldOffset(String field, Class<?> klazz) {
993		try {
994		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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