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

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.39 by dl, Mon Aug 24 12:15:46 2009 UTC vs.
Revision 1.54 by dl, Sat Nov 13 13:10:04 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 97 | Line 97 | import java.util.concurrent.locks.LockSu
97		* <p><b>Monitoring.</b> While synchronization methods may be invoked
98		* only by registered parties, the current state of a phaser may be
99		* monitored by any caller.  At any given moment there are {@link
100	<	* #getRegisteredParties}, where {@link #getArrivedParties} have
101	<	* arrived at the current phase ({@link #getPhase}). When the
102	<	* remaining {@link #getUnarrivedParties}) arrive, the phase
103	<	* advances. Method {@link #toString} returns snapshots of these state
104	<	* queries in a form convenient for informal monitoring.
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.  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 139 | 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 155 | 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();
163	<	* }</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();
177	<	*     }
178	<	*     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) {
193	<	*       int r = Math.min(i + step, hi);
194	<	*       build(actions, i, r, new Phaser(b));
195	<	*       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 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 ushortBits = 16;
244	<	private static final int ushortMask = 0xffff;
245	<	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
269	–	private static long stateFor(int phase, int parties, int unarrived) {
270	–	return ((((long) phase) << 32) | (((long) parties) << 16) |
271	–	(long) unarrived);
272	–	}
273	–
274	–	private static long trippedStateFor(int phase, int parties) {
275	–	long lp = (long) parties;
276	–	return (((long) phase) << 32) | (lp << 16) | lp;
277	–	}
278	–
279	–	/**
280	–	* Returns message string for bad bounds exceptions.
281	–	*/
282	–	private static String badBounds(int parties, int unarrived) {
283	–	return ("Attempt to set " + unarrived +
284	–	" unarrived of " + parties + " parties");
285	–	}
286	–
271		/**
272		* The parent of this phaser, or null if none
273		*/
#	Line 295 | Line 279 | public class Phaser {
279		*/
280		private final Phaser root;
281
298	–	// Wait queues
299	–
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 long getReconciledState() {
305	<	return (parent == null) ? state : reconcileState();
304	>	private int doArrive(long adj) {
305	>	for (;;) {
306	>	long s;
307	>	int phase, unarrived;
308	>	if ((phase = (int)((s = state) >>> PHASE_SHIFT)) < 0)
309	>	return phase;
310	>	else if ((unarrived = (int)(s & UNARRIVED_MASK)) == 0)
311	>	checkBadArrive(s);
312	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s -= adj)){
313	>	if (unarrived == 1) {
314	>	Phaser par;
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	>	if ((par = parent) == null) {
321	>	UNSAFE.compareAndSwapLong
322	>	(this, stateOffset, s, onAdvance(phase, u)?
323	>	next | TERMINATION_PHASE : next);
324	>	releaseWaiters(phase);
325	>	}
326	>	else {
327	>	par.doArrive(u == 0?
328	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
329	>	if ((int)(par.state >>> PHASE_SHIFT) != nextPhase ||
330	>	((int)(state >>> PHASE_SHIFT) != nextPhase &&
331	>	!UNSAFE.compareAndSwapLong(this, stateOffset,
332	>	s, next)))
333	>	reconcileState();
334	>	}
335	>	}
336	>	return phase;
337	>	}
338	>	}
339		}
340
341		/**
342	<	* Recursively resolves state.
342	>	* Rechecks state and throws bounds exceptions on arrival -- called
343	>	* only if unarrived is apparently zero.
344	>	*/
345	>	private void checkBadArrive(long s) {
346	>	if (reconcileState() == s)
347	>	throw new IllegalStateException
348	>	("Attempted arrival of unregistered party for " +
349	>	stateToString(s));
350	>	}
351	>
352	>	/**
353	>	* Implementation of register, bulkRegister
354	>	*
355	>	* @param registrations number to add to both parties and unarrived fields
356	>	*/
357	>	private int doRegister(int registrations) {
358	>	long adj = (long)registrations; // adjustment to state
359	>	adj |= adj << PARTIES_SHIFT;
360	>	Phaser par = parent;
361	>	for (;;) {
362	>	int phase, parties;
363	>	long s = par == null? state : reconcileState();
364	>	if ((phase = (int)(s >>> PHASE_SHIFT)) < 0)
365	>	return phase;
366	>	if ((parties = ((int)(s & PARTIES_MASK)) >>> PARTIES_SHIFT) != 0 &&
367	>	(s & UNARRIVED_MASK) == 0)
368	>	internalAwaitAdvance(phase, null); // wait for onAdvance
369	>	else if (parties + registrations > MAX_COUNT)
370	>	throw new IllegalStateException(badRegister(s));
371	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
372	>	return phase;
373	>	}
374	>	}
375	>
376	>	/**
377	>	* Returns message string for bounds exceptions on registration
378	>	*/
379	>	private String badRegister(long s) {
380	>	return "Attempt to register more than " +
381	>	MAX_COUNT + " parties for " + stateToString(s);
382	>	}
383	>
384	>	/**
385	>	* Recursively resolves lagged phase propagation from root if
386	>	* 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 || (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 & PARTIES_MASK) |
408	>	(u >>> PARTIES_SHIFT)); // reset unarrived to parties
409	>	else
410	>	releaseWaiters(phase); // help release others
411		}
412		}
340	–	return s;
413		}
414
415		/**
#	Line 346 | 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 370 | Line 442 | public class Phaser {
442		* @param parent the parent phaser
443		*/
444		public Phaser(Phaser parent) {
445	<	int phase = 0;
374	<	this.parent = parent;
375	<	if (parent != null) {
376	<	this.root = parent.root;
377	<	phase = parent.register();
378	<	}
379	<	else
380	<	this.root = this;
381	<	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 393 | 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 419 | 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(state));
510		if (parties == 0)
511		return getPhase();
512		return doRegister(parties);
513		}
514
515		/**
437	–	* Shared code for register, bulkRegister
438	–	*/
439	–	private int doRegister(int registrations) {
440	–	int phase;
441	–	for (;;) {
442	–	long s = getReconciledState();
443	–	phase = phaseOf(s);
444	–	int unarrived = unarrivedOf(s) + registrations;
445	–	int parties = partiesOf(s) + registrations;
446	–	if (phase < 0)
447	–	break;
448	–	if (parties > ushortMask || unarrived > ushortMask)
449	–	throw new IllegalStateException(badBounds(parties, unarrived));
450	–	if (phase == phaseOf(root.state) &&
451	–	casState(s, stateFor(phase, parties, unarrived)))
452	–	break;
453	–	}
454	–	return phase;
455	–	}
456	–
457	–	/**
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 465 | Line 523 | public class Phaser {
523		* of unarrived parties would become negative
524		*/
525		public int arrive() {
526	<	int phase;
469	<	for (;;) {
470	<	long s = state;
471	<	phase = phaseOf(s);
472	<	if (phase < 0)
473	<	break;
474	<	int parties = partiesOf(s);
475	<	int unarrived = unarrivedOf(s) - 1;
476	<	if (unarrived > 0) {        // Not the last arrival
477	<	if (casState(s, s - 1)) // s-1 adds one arrival
478	<	break;
479	<	}
480	<	else if (unarrived == 0) {  // the last arrival
481	<	Phaser par = parent;
482	<	if (par == null) {      // directly trip
483	<	if (casState
484	<	(s,
485	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
486	<	((phase + 1) & phaseMask), parties))) {
487	<	releaseWaiters(phase);
488	<	break;
489	<	}
490	<	}
491	<	else {                  // cascade to parent
492	<	if (casState(s, s - 1)) { // zeroes unarrived
493	<	par.arrive();
494	<	reconcileState();
495	<	break;
496	<	}
497	<	}
498	<	}
499	<	else if (phase != phaseOf(root.state)) // or if unreconciled
500	<	reconcileState();
501	<	else
502	<	throw new IllegalStateException(badBounds(parties, unarrived));
503	<	}
504	<	return phase;
526	>	return doArrive(ONE_ARRIVAL);
527		}
528
529		/**
#	Line 518 | 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
522	<	Phaser par = parent;
523	<	int phase;
524	<	for (;;) {
525	<	long s = state;
526	<	phase = phaseOf(s);
527	<	if (phase < 0)
528	<	break;
529	<	int parties = partiesOf(s) - 1;
530	<	int unarrived = unarrivedOf(s) - 1;
531	<	if (parties >= 0) {
532	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
533	<	if (casState
534	<	(s,
535	<	stateFor(phase, parties, unarrived))) {
536	<	if (unarrived == 0) {
537	<	par.arriveAndDeregister();
538	<	reconcileState();
539	<	}
540	<	break;
541	<	}
542	<	continue;
543	<	}
544	<	if (unarrived == 0) {
545	<	if (casState
546	<	(s,
547	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
548	<	((phase + 1) & phaseMask), parties))) {
549	<	releaseWaiters(phase);
550	<	break;
551	<	}
552	<	continue;
553	<	}
554	<	if (par != null && phase != phaseOf(root.state)) {
555	<	reconcileState();
556	<	continue;
557	<	}
558	<	}
559	<	throw new IllegalStateException(badBounds(parties, unarrived));
560	<	}
561	<	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 582 | 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
586	<	* 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 575 | public class Phaser {
575		public int awaitAdvance(int phase) {
576		if (phase < 0)
577		return phase;
578	<	long s = getReconciledState();
598	<	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)
602	<	parent.awaitAdvance(phase);
603	<	// Fall here even if parent waited, to reconcile and help release
604	<	return untimedWait(phase);
581	>	return internalAwaitAdvance(phase, null);
582		}
583
584		/**
#	Line 609 | 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
613	<	* 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 623 | Line 599 | public class Phaser {
599		throws InterruptedException {
600		if (phase < 0)
601		return phase;
602	<	long s = getReconciledState();
627	<	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 638 | 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
642	<	* 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 656 | 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();
662	<	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 675 | 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))) {
685	<	releaseWaiters(0);
686	<	releaseWaiters(1);
687	<	if (parent != null)
688	<	parent.forceTermination();
689	<	return;
690	<	}
691	<	}
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 699 | 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 708 | 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 718 | 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 728 | 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 756 | 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		/**
738	<	* Overridable method to perform an action upon phase advance, and
739	<	* to control termination. This method is invoked whenever the
740	<	* barrier is tripped (and thus all other waiting parties are
741	<	* dormant). If it returns {@code true}, then, rather than advance
742	<	* the phase number, this barrier will be set to a final
743	<	* termination state, and subsequent calls to {@link #isTerminated}
744	<	* will return true.
738	>	* Overridable method to perform an action upon impending phase
739	>	* advance, and to control termination. This method is invoked
740	>	* upon arrival of the party tripping the barrier (when all other
741	>	* waiting parties are dormant).  If this method returns {@code
742	>	* true}, then, rather than advance the phase number, this barrier
743	>	* will be set to a final termination state, and subsequent calls
744	>	* to {@link #isTerminated} will return true. Any (unchecked)
745	>	* Exception or Error thrown by an invocation of this method is
746	>	* propagated to the party attempting to trip the barrier, in
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.  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		*
776	–	* <p>You may override this method to perform an action with side
777	–	* effects visible to participating tasks, but it is in general
778	–	* only sensible to do so in designs where all parties register
779	–	* before any arrive, and all {@link #awaitAdvance} at each phase.
780	–	* Otherwise, you cannot ensure lack of interference from other
781	–	* parties during the invocation of this method.
782	–	*
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 798 | 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	>	return stateToString(reconcileState());
783	>	}
784	>
785	>	/**
786	>	* Implementation of toString and string-based error messages
787	>	*/
788	>	private String stateToString(long s) {
789		return super.toString() +
790		"[phase = " + phaseOf(s) +
791		" parties = " + partiesOf(s) +
792		" arrived = " + arrivedOf(s) + "]";
793		}
794
795	<	// methods for waiting
795	>	// Waiting mechanics
796	>
797	>	/**
798	>	* Removes and signals threads from queue for phase
799	>	*/
800	>	private void releaseWaiters(int phase) {
801	>	AtomicReference<QNode> head = queueFor(phase);
802	>	QNode q;
803	>	int p;
804	>	while ((q = head.get()) != null &&
805	>	((p = q.phase) == phase ||
806	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
807	>	if (head.compareAndSet(q, q.next))
808	>	q.signal();
809	>	}
810	>	}
811	>
812	>	/**
813	>	* Tries to enqueue given node in the appropriate wait queue.
814	>	*
815	>	* @return true if successful
816	>	*/
817	>	private boolean tryEnqueue(int phase, QNode node) {
818	>	releaseWaiters(phase-1); // ensure old queue clean
819	>	AtomicReference<QNode> head = queueFor(phase);
820	>	QNode q = head.get();
821	>	return ((q == null || q.phase == phase) &&
822	>	(int)(root.state >>> PHASE_SHIFT) == phase &&
823	>	head.compareAndSet(node.next = q, node));
824	>	}
825	>
826	>	/** The number of CPUs, for spin control */
827	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
828	>
829	>	/**
830	>	* The number of times to spin before blocking while waiting for
831	>	* advance, per arrival while waiting. On multiprocessors, fully
832	>	* blocking and waking up a large number of threads all at once is
833	>	* usually a very slow process, so we use rechargeable spins to
834	>	* avoid it when threads regularly arrive: When a thread in
835	>	* internalAwaitAdvance notices another arrival before blocking,
836	>	* and there appear to be enough CPUs available, it spins
837	>	* SPINS_PER_ARRIVAL more times before continuing to try to
838	>	* block. The value trades off good-citizenship vs big unnecessary
839	>	* slowdowns.
840	>	*/
841	>	static final int SPINS_PER_ARRIVAL = NCPU < 2? 1 : 1 << 8;
842	>
843	>	/**
844	>	* Possibly blocks and waits for phase to advance unless aborted.
845	>	*
846	>	* @param phase current phase
847	>	* @param node if non-null, the wait node to track interrupt and timeout;
848	>	* if null, denotes noninterruptible wait
849	>	* @return current phase
850	>	*/
851	>	private int internalAwaitAdvance(int phase, QNode node) {
852	>	Phaser current = this;       // to eventually wait at root if tiered
853	>	boolean queued = false;      // true when node is enqueued
854	>	int lastUnarrived = -1;      // to increase spins upon change
855	>	int spins = SPINS_PER_ARRIVAL;
856	>	for (;;) {
857	>	int p, unarrived;
858	>	Phaser par;
859	>	long s = current.state;
860	>	if ((p = (int)(s >>> PHASE_SHIFT)) != phase) {
861	>	if (node != null)
862	>	node.onRelease();
863	>	releaseWaiters(phase);
864	>	return p;
865	>	}
866	>	else if ((unarrived = (int)(s & UNARRIVED_MASK)) != lastUnarrived) {
867	>	if ((lastUnarrived = unarrived) < NCPU)
868	>	spins += SPINS_PER_ARRIVAL;
869	>	}
870	>	else if (unarrived == 0 && (par = current.parent) != null) {
871	>	current = par;       // if all arrived, use parent
872	>	par = par.parent;
873	>	lastUnarrived = -1;
874	>	}
875	>	else if (spins > 0)
876	>	--spins;
877	>	else if (node == null)   // must be noninterruptible
878	>	node = new QNode(this, phase, false, false, 0L);
879	>	else if (node.isReleasable()) {
880	>	if ((int)(reconcileState() >>> PHASE_SHIFT) == phase)
881	>	return phase;    // aborted
882	>	}
883	>	else if (!queued)
884	>	queued = tryEnqueue(phase, node);
885	>	else {
886	>	try {
887	>	ForkJoinPool.managedBlock(node);
888	>	} catch (InterruptedException ie) {
889	>	node.wasInterrupted = true;
890	>	}
891	>	}
892	>	}
893	>	}
894
895		/**
896		* Wait nodes for Treiber stack representing wait queue
#	Line 813 | Line 898 | public class Phaser {
898		static final class QNode implements ForkJoinPool.ManagedBlocker {
899		final Phaser phaser;
900		final int phase;
816	–	final long startTime;
817	–	final long nanos;
818	–	final boolean timed;
901		final boolean interruptible;
902	<	volatile boolean wasInterrupted = false;
902	>	final boolean timed;
903	>	boolean wasInterrupted;
904	>	long nanos;
905	>	long lastTime;
906		volatile Thread thread; // nulled to cancel wait
907		QNode next;
908	+
909		QNode(Phaser phaser, int phase, boolean interruptible,
910	<	boolean timed, long startTime, long nanos) {
910	>	boolean timed, long nanos) {
911		this.phaser = phaser;
912		this.phase = phase;
827	–	this.timed = timed;
913		this.interruptible = interruptible;
829	–	this.startTime = startTime;
914		this.nanos = nanos;
915	+	this.timed = timed;
916	+	this.lastTime = timed? System.nanoTime() : 0L;
917		thread = Thread.currentThread();
918		}
919	+
920		public boolean isReleasable() {
921	<	return (thread == null ||
922	<	phaser.getPhase() != phase ||
923	<	(interruptible && wasInterrupted) ||
924	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
921	>	Thread t = thread;
922	>	if (t != null) {
923	>	if (phaser.getPhase() != phase)
924	>	t = null;
925	>	else {
926	>	if (Thread.interrupted())
927	>	wasInterrupted = true;
928	>	if (interruptible && wasInterrupted)
929	>	t = null;
930	>	else if (timed) {
931	>	if (nanos > 0) {
932	>	long now = System.nanoTime();
933	>	nanos -= now - lastTime;
934	>	lastTime = now;
935	>	}
936	>	if (nanos <= 0)
937	>	t = null;
938	>	}
939	>	}
940	>	if (t != null)
941	>	return false;
942	>	thread = null;
943	>	}
944	>	return true;
945		}
946	+
947		public boolean block() {
948	<	if (Thread.interrupted()) {
949	<	wasInterrupted = true;
950	<	if (interruptible)
843	<	return true;
844	<	}
845	<	if (!timed)
948	>	if (isReleasable())
949	>	return true;
950	>	else if (!timed)
951		LockSupport.park(this);
952	<	else {
953	<	long waitTime = nanos - (System.nanoTime() - startTime);
849	<	if (waitTime <= 0)
850	<	return true;
851	<	LockSupport.parkNanos(this, waitTime);
852	<	}
952	>	else if (nanos > 0)
953	>	LockSupport.parkNanos(this, nanos);
954		return isReleasable();
955		}
956	+
957		void signal() {
958		Thread t = thread;
959		if (t != null) {
#	Line 859 | Line 961 | public class Phaser {
961		LockSupport.unpark(t);
962		}
963		}
862	–	boolean doWait() {
863	–	if (thread != null) {
864	–	try {
865	–	ForkJoinPool.managedBlock(this, false);
866	–	} catch (InterruptedException ie) {
867	–	}
868	–	}
869	–	return wasInterrupted;
870	–	}
871	–
872	–	}
873	–
874	–	/**
875	–	* Removes and signals waiting threads from wait queue.
876	–	*/
877	–	private void releaseWaiters(int phase) {
878	–	AtomicReference<QNode> head = queueFor(phase);
879	–	QNode q;
880	–	while ((q = head.get()) != null) {
881	–	if (head.compareAndSet(q, q.next))
882	–	q.signal();
883	–	}
884	–	}
885	–
886	–	/**
887	–	* Tries to enqueue given node in the appropriate wait queue.
888	–	*
889	–	* @return true if successful
890	–	*/
891	–	private boolean tryEnqueue(QNode node) {
892	–	AtomicReference<QNode> head = queueFor(node.phase);
893	–	return head.compareAndSet(node.next = head.get(), node);
894	–	}
964
965	<	/**
966	<	* Enqueues node and waits unless aborted or signalled.
967	<	*
968	<	* @return current phase
969	<	*/
901	<	private int untimedWait(int phase) {
902	<	QNode node = null;
903	<	boolean queued = false;
904	<	boolean interrupted = false;
905	<	int p;
906	<	while ((p = getPhase()) == phase) {
907	<	if (Thread.interrupted())
908	<	interrupted = true;
909	<	else if (node == null)
910	<	node = new QNode(this, phase, false, false, 0, 0);
911	<	else if (!queued)
912	<	queued = tryEnqueue(node);
913	<	else
914	<	interrupted = node.doWait();
965	>	void onRelease() { // actions upon return from internalAwaitAdvance
966	>	if (!interruptible && wasInterrupted)
967	>	Thread.currentThread().interrupt();
968	>	if (thread != null)
969	>	thread = null;
970		}
916	–	if (node != null)
917	–	node.thread = null;
918	–	releaseWaiters(phase);
919	–	if (interrupted)
920	–	Thread.currentThread().interrupt();
921	–	return p;
922	–	}
971
924	–	/**
925	–	* Interruptible version
926	–	* @return current phase
927	–	*/
928	–	private int interruptibleWait(int phase) throws InterruptedException {
929	–	QNode node = null;
930	–	boolean queued = false;
931	–	boolean interrupted = false;
932	–	int p;
933	–	while ((p = getPhase()) == phase && !interrupted) {
934	–	if (Thread.interrupted())
935	–	interrupted = true;
936	–	else if (node == null)
937	–	node = new QNode(this, phase, true, false, 0, 0);
938	–	else if (!queued)
939	–	queued = tryEnqueue(node);
940	–	else
941	–	interrupted = node.doWait();
942	–	}
943	–	if (node != null)
944	–	node.thread = null;
945	–	if (p != phase || (p = getPhase()) != phase)
946	–	releaseWaiters(phase);
947	–	if (interrupted)
948	–	throw new InterruptedException();
949	–	return p;
950	–	}
951	–
952	–	/**
953	–	* Timeout version.
954	–	* @return current phase
955	–	*/
956	–	private int timedWait(int phase, long nanos)
957	–	throws InterruptedException, TimeoutException {
958	–	long startTime = System.nanoTime();
959	–	QNode node = null;
960	–	boolean queued = false;
961	–	boolean interrupted = false;
962	–	int p;
963	–	while ((p = getPhase()) == phase && !interrupted) {
964	–	if (Thread.interrupted())
965	–	interrupted = true;
966	–	else if (nanos - (System.nanoTime() - startTime) <= 0)
967	–	break;
968	–	else if (node == null)
969	–	node = new QNode(this, phase, true, true, startTime, nanos);
970	–	else if (!queued)
971	–	queued = tryEnqueue(node);
972	–	else
973	–	interrupted = node.doWait();
974	–	}
975	–	if (node != null)
976	–	node.thread = null;
977	–	if (p != phase || (p = getPhase()) != phase)
978	–	releaseWaiters(phase);
979	–	if (interrupted)
980	–	throw new InterruptedException();
981	–	if (p == phase)
982	–	throw new TimeoutException();
983	–	return p;
972		}
973
974		// Unsafe mechanics
#	Line 989 | Line 977 | public class Phaser {
977		private static final long stateOffset =
978		objectFieldOffset("state", Phaser.class);
979
992	–	private final boolean casState(long cmp, long val) {
993	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
994	–	}
995	–
980		private static long objectFieldOffset(String field, Class<?> klazz) {
981		try {
982		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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