18 |
|
* but supporting more flexible usage. |
19 |
|
* |
20 |
|
* <p> <b>Registration.</b> Unlike the case for other barriers, the |
21 |
< |
* number of parties <em>registered</em> to synchronize on a phaser |
21 |
> |
* number of parties <em>registered</em> to synchronize on a Phaser |
22 |
|
* may vary over time. Tasks may be registered at any time (using |
23 |
|
* methods {@link #register}, {@link #bulkRegister}, or forms of |
24 |
|
* constructors establishing initial numbers of parties), and |
76 |
|
* |
77 |
|
* <p> <b>Termination.</b> A {@code Phaser} may enter a |
78 |
|
* <em>termination</em> state in which all synchronization methods |
79 |
< |
* immediately return without updating phaser state or waiting for |
79 |
> |
* immediately return without updating Phaser state or waiting for |
80 |
|
* advance, and indicating (via a negative phase value) that execution |
81 |
|
* is complete. Termination is triggered when an invocation of {@code |
82 |
|
* onAdvance} returns {@code true}. The default implementation returns |
83 |
|
* {@code true} if a deregistration has caused the number of |
84 |
|
* registered parties to become zero. As illustrated below, when |
85 |
< |
* phasers control actions with a fixed number of iterations, it is |
85 |
> |
* Phasers control actions with a fixed number of iterations, it is |
86 |
|
* often convenient to override this method to cause termination when |
87 |
|
* the current phase number reaches a threshold. Method {@link |
88 |
|
* #forceTermination} is also available to abruptly release waiting |
97 |
|
* overhead. |
98 |
|
* |
99 |
|
* <p><b>Monitoring.</b> While synchronization methods may be invoked |
100 |
< |
* only by registered parties, the current state of a phaser may be |
100 |
> |
* only by registered parties, the current state of a Phaser may be |
101 |
|
* monitored by any caller. At any given moment there are {@link |
102 |
|
* #getRegisteredParties} parties in total, of which {@link |
103 |
|
* #getArrivedParties} have arrived at the current phase ({@link |
183 |
|
* }}</pre> |
184 |
|
* |
185 |
|
* |
186 |
< |
* <p>To create a set of tasks using a tree of phasers, |
186 |
> |
* <p>To create a set of tasks using a tree of Phasers, |
187 |
|
* you could use code of the following form, assuming a |
188 |
< |
* Task class with a constructor accepting a phaser that |
188 |
> |
* Task class with a constructor accepting a Phaser that |
189 |
|
* it registers with upon construction: |
190 |
|
* |
191 |
|
* <pre> {@code |
212 |
|
* <p><b>Implementation notes</b>: This implementation restricts the |
213 |
|
* maximum number of parties to 65535. Attempts to register additional |
214 |
|
* parties result in {@code IllegalStateException}. However, you can and |
215 |
< |
* should create tiered phasers to accommodate arbitrarily large sets |
215 |
> |
* should create tiered Phasers to accommodate arbitrarily large sets |
216 |
|
* of participants. |
217 |
|
* |
218 |
|
* @since 1.7 |
383 |
|
return phase; |
384 |
|
} |
385 |
|
else if (parties != 0) // wait for onAdvance |
386 |
< |
internalAwaitAdvance(phase, null); |
386 |
> |
root.internalAwaitAdvance(phase, null); |
387 |
|
else { // 1st registration of child |
388 |
< |
synchronized(this) { // register parent first |
388 |
> |
synchronized (this) { // register parent first |
389 |
|
if (reconcileState() == s) { // recheck under lock |
390 |
|
parent.doRegister(1); // OK if throws IllegalState |
391 |
|
for (;;) { // simpler form of outer loop |
428 |
|
} |
429 |
|
|
430 |
|
/** |
431 |
< |
* Creates a new phaser without any initially registered parties, |
431 |
> |
* Creates a new Phaser without any initially registered parties, |
432 |
|
* initial phase number 0, and no parent. Any thread using this |
433 |
< |
* phaser will need to first register for it. |
433 |
> |
* Phaser will need to first register for it. |
434 |
|
*/ |
435 |
|
public Phaser() { |
436 |
|
this(null, 0); |
437 |
|
} |
438 |
|
|
439 |
|
/** |
440 |
< |
* Creates a new phaser with the given number of registered |
440 |
> |
* Creates a new Phaser with the given number of registered |
441 |
|
* unarrived parties, initial phase number 0, and no parent. |
442 |
|
* |
443 |
|
* @param parties the number of parties required to trip barrier |
449 |
|
} |
450 |
|
|
451 |
|
/** |
452 |
– |
* Creates a new phaser with the given parent, and without any |
453 |
– |
* initially registered parties. Any thread using this phaser |
454 |
– |
* will need to first register for it, at which point, if the |
455 |
– |
* given parent is non-null, this phaser will also be registered |
456 |
– |
* with the parent. |
457 |
– |
* |
452 |
|
* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}. |
453 |
|
* |
454 |
< |
* @param parent the parent phaser |
454 |
> |
* @param parent the parent Phaser |
455 |
|
*/ |
456 |
|
public Phaser(Phaser parent) { |
457 |
|
this(parent, 0); |
458 |
|
} |
459 |
|
|
460 |
|
/** |
461 |
< |
* Creates a new phaser with the given parent and number of |
462 |
< |
* registered unarrived parties. If parent is non-null and |
463 |
< |
* the number of parties is non-zero, this phaser is registered |
464 |
< |
* with the parent. |
461 |
> |
* Creates a new Phaser with the given parent and number of |
462 |
> |
* registered unarrived parties. Registration and deregistration |
463 |
> |
* of this child Phaser with its parent are managed automatically. |
464 |
> |
* If the given parent is non-null, whenever this child Phaser has |
465 |
> |
* any registered parties (as established in this constructor, |
466 |
> |
* {@link #register}, or {@link #bulkRegister}), this child Phaser |
467 |
> |
* is registered with its parent. Whenever the number of |
468 |
> |
* registered parties becomes zero as the result of an invocation |
469 |
> |
* of {@link #arriveAndDeregister}, this child Phaser is |
470 |
> |
* deregistered from its parent. |
471 |
|
* |
472 |
< |
* @param parent the parent phaser |
472 |
> |
* @param parent the parent Phaser |
473 |
|
* @param parties the number of parties required to trip barrier |
474 |
|
* @throws IllegalArgumentException if parties less than zero |
475 |
|
* or greater than the maximum number of parties supported |
477 |
|
public Phaser(Phaser parent, int parties) { |
478 |
|
if (parties >>> PARTIES_SHIFT != 0) |
479 |
|
throw new IllegalArgumentException("Illegal number of parties"); |
480 |
< |
int phase; |
480 |
> |
long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT); |
481 |
|
this.parent = parent; |
482 |
|
if (parent != null) { |
483 |
|
Phaser r = parent.root; |
484 |
|
this.root = r; |
485 |
|
this.evenQ = r.evenQ; |
486 |
|
this.oddQ = r.oddQ; |
487 |
< |
phase = (parties == 0) ? parent.getPhase() : parent.doRegister(1); |
487 |
> |
if (parties != 0) |
488 |
> |
s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT; |
489 |
|
} |
490 |
|
else { |
491 |
|
this.root = this; |
492 |
|
this.evenQ = new AtomicReference<QNode>(); |
493 |
|
this.oddQ = new AtomicReference<QNode>(); |
493 |
– |
phase = 0; |
494 |
|
} |
495 |
< |
long p = (long)parties; |
496 |
< |
this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT); |
495 |
> |
this.state = s; |
496 |
|
} |
497 |
|
|
498 |
|
/** |
499 |
< |
* Adds a new unarrived party to this phaser. If an ongoing |
499 |
> |
* Adds a new unarrived party to this Phaser. If an ongoing |
500 |
|
* invocation of {@link #onAdvance} is in progress, this method |
501 |
< |
* may wait until its completion before registering. If this |
502 |
< |
* phaser has a parent, and this phaser previously had no |
503 |
< |
* registered parties, this phaser is also registered with its |
505 |
< |
* parent. |
501 |
> |
* may await its completion before returning. If this Phaser has |
502 |
> |
* a parent, and this Phaser previously had no registered parties, |
503 |
> |
* this Phaser is also registered with its parent. |
504 |
|
* |
505 |
|
* @return the arrival phase number to which this registration applied |
506 |
|
* @throws IllegalStateException if attempting to register more |
511 |
|
} |
512 |
|
|
513 |
|
/** |
514 |
< |
* Adds the given number of new unarrived parties to this phaser. |
514 |
> |
* Adds the given number of new unarrived parties to this Phaser. |
515 |
|
* If an ongoing invocation of {@link #onAdvance} is in progress, |
516 |
< |
* this method may wait until its completion before registering. |
517 |
< |
* If this phaser has a parent, and the given number of parities |
518 |
< |
* is greater than zero, and this phaser previously had no |
519 |
< |
* registered parties, this phaser is also registered with its |
522 |
< |
* parent. |
516 |
> |
* this method may await its completion before returning. If this |
517 |
> |
* Phaser has a parent, and the given number of parities is |
518 |
> |
* greater than zero, and this Phaser previously had no registered |
519 |
> |
* parties, this Phaser is also registered with its parent. |
520 |
|
* |
521 |
|
* @param parties the number of additional parties required to trip barrier |
522 |
|
* @return the arrival phase number to which this registration applied |
527 |
|
public int bulkRegister(int parties) { |
528 |
|
if (parties < 0) |
529 |
|
throw new IllegalArgumentException(); |
530 |
< |
else if (parties == 0) |
530 |
> |
if (parties == 0) |
531 |
|
return getPhase(); |
532 |
|
return doRegister(parties); |
533 |
|
} |
534 |
|
|
535 |
|
/** |
536 |
< |
* Arrives at the barrier, but does not wait for others. (You can |
537 |
< |
* in turn wait for others via {@link #awaitAdvance}). It is a |
538 |
< |
* usage error for an unregistered party to invoke this |
539 |
< |
* method. However, it is possible that this error will result in |
540 |
< |
* an {code IllegalStateException} only when some <em>other</em> |
541 |
< |
* party arrives. |
536 |
> |
* Arrives at the barrier, without waiting for others to arrive. |
537 |
> |
* |
538 |
> |
* <p>It is a usage error for an unregistered party to invoke this |
539 |
> |
* method. However, this error may result in an {@code |
540 |
> |
* IllegalStateException} only upon some subsequent operation on |
541 |
> |
* this Phaser, if ever. |
542 |
|
* |
543 |
|
* @return the arrival phase number, or a negative value if terminated |
544 |
|
* @throws IllegalStateException if not terminated and the number |
550 |
|
|
551 |
|
/** |
552 |
|
* Arrives at the barrier and deregisters from it without waiting |
553 |
< |
* for others. Deregistration reduces the number of parties |
554 |
< |
* required to trip the barrier in future phases. If this phaser |
555 |
< |
* has a parent, and deregistration causes this phaser to have |
556 |
< |
* zero parties, this phaser also arrives at and is deregistered |
557 |
< |
* from its parent. It is a usage error for an unregistered party |
558 |
< |
* to invoke this method. However, it is possible that this error |
559 |
< |
* will result in an {code IllegalStateException} only when some |
560 |
< |
* <em>other</em> party arrives. |
553 |
> |
* for others to arrive. Deregistration reduces the number of |
554 |
> |
* parties required to trip the barrier in future phases. If this |
555 |
> |
* Phaser has a parent, and deregistration causes this Phaser to |
556 |
> |
* have zero parties, this Phaser is also deregistered from its |
557 |
> |
* parent. |
558 |
> |
* |
559 |
> |
* <p>It is a usage error for an unregistered party to invoke this |
560 |
> |
* method. However, this error may result in an {@code |
561 |
> |
* IllegalStateException} only upon some subsequent operation on |
562 |
> |
* this Phaser, if ever. |
563 |
|
* |
564 |
|
* @return the arrival phase number, or a negative value if terminated |
565 |
|
* @throws IllegalStateException if not terminated and the number |
575 |
|
* interruption or timeout, you can arrange this with an analogous |
576 |
|
* construction using one of the other forms of the {@code |
577 |
|
* awaitAdvance} method. If instead you need to deregister upon |
578 |
< |
* arrival, use {@link #arriveAndDeregister}. It is a usage error |
579 |
< |
* for an unregistered party to invoke this method. However, it is |
580 |
< |
* possible that this error will result in an {code |
581 |
< |
* IllegalStateException} only when some <em>other</em> party |
582 |
< |
* arrives. |
578 |
> |
* arrival, use {@code awaitAdvance(arriveAndDeregister())}. |
579 |
> |
* |
580 |
> |
* <p>It is a usage error for an unregistered party to invoke this |
581 |
> |
* method. However, this error may result in an {@code |
582 |
> |
* IllegalStateException} only upon some subsequent operation on |
583 |
> |
* this Phaser, if ever. |
584 |
|
* |
585 |
|
* @return the arrival phase number, or a negative number if terminated |
586 |
|
* @throws IllegalStateException if not terminated and the number |
603 |
|
* if terminated or argument is negative |
604 |
|
*/ |
605 |
|
public int awaitAdvance(int phase) { |
606 |
+ |
Phaser r; |
607 |
+ |
int p = (int)(state >>> PHASE_SHIFT); |
608 |
|
if (phase < 0) |
609 |
|
return phase; |
610 |
< |
long s = (parent == null) ? state : reconcileState(); |
611 |
< |
int p = (int)(s >>> PHASE_SHIFT); |
612 |
< |
return (p != phase) ? p : internalAwaitAdvance(phase, null); |
610 |
> |
if (p == phase && |
611 |
> |
(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) |
612 |
> |
return r.internalAwaitAdvance(phase, null); |
613 |
> |
return p; |
614 |
|
} |
615 |
|
|
616 |
|
/** |
629 |
|
*/ |
630 |
|
public int awaitAdvanceInterruptibly(int phase) |
631 |
|
throws InterruptedException { |
632 |
+ |
Phaser r; |
633 |
+ |
int p = (int)(state >>> PHASE_SHIFT); |
634 |
|
if (phase < 0) |
635 |
|
return phase; |
636 |
< |
long s = (parent == null) ? state : reconcileState(); |
637 |
< |
int p = (int)(s >>> PHASE_SHIFT); |
633 |
< |
if (p == phase) { |
636 |
> |
if (p == phase && |
637 |
> |
(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) { |
638 |
|
QNode node = new QNode(this, phase, true, false, 0L); |
639 |
< |
p = internalAwaitAdvance(phase, node); |
639 |
> |
p = r.internalAwaitAdvance(phase, node); |
640 |
|
if (node.wasInterrupted) |
641 |
|
throw new InterruptedException(); |
642 |
|
} |
666 |
|
public int awaitAdvanceInterruptibly(int phase, |
667 |
|
long timeout, TimeUnit unit) |
668 |
|
throws InterruptedException, TimeoutException { |
669 |
+ |
long nanos = unit.toNanos(timeout); |
670 |
+ |
Phaser r; |
671 |
+ |
int p = (int)(state >>> PHASE_SHIFT); |
672 |
|
if (phase < 0) |
673 |
|
return phase; |
674 |
< |
long s = (parent == null) ? state : reconcileState(); |
675 |
< |
int p = (int)(s >>> PHASE_SHIFT); |
669 |
< |
if (p == phase) { |
670 |
< |
long nanos = unit.toNanos(timeout); |
674 |
> |
if (p == phase && |
675 |
> |
(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) { |
676 |
|
QNode node = new QNode(this, phase, true, true, nanos); |
677 |
< |
p = internalAwaitAdvance(phase, node); |
677 |
> |
p = r.internalAwaitAdvance(phase, node); |
678 |
|
if (node.wasInterrupted) |
679 |
|
throw new InterruptedException(); |
680 |
|
else if (p == phase) |
685 |
|
|
686 |
|
/** |
687 |
|
* Forces this barrier to enter termination state. Counts of |
688 |
< |
* arrived and registered parties are unaffected. If this phaser |
689 |
< |
* is a member of a tiered set of phasers, then all of the phasers |
690 |
< |
* in the set are terminated. If this phaser is already |
688 |
> |
* arrived and registered parties are unaffected. If this Phaser |
689 |
> |
* is a member of a tiered set of Phasers, then all of the Phasers |
690 |
> |
* in the set are terminated. If this Phaser is already |
691 |
|
* terminated, this method has no effect. This method may be |
692 |
|
* useful for coordinating recovery after one or more tasks |
693 |
|
* encounter unexpected exceptions. |
733 |
|
* @return the number of arrived parties |
734 |
|
*/ |
735 |
|
public int getArrivedParties() { |
736 |
< |
return arrivedOf(parent==null? state : reconcileState()); |
736 |
> |
long s = state; |
737 |
> |
int u = unarrivedOf(s); // only reconcile if possibly needed |
738 |
> |
return (u != 0 || parent == null) ? |
739 |
> |
partiesOf(s) - u : |
740 |
> |
arrivedOf(reconcileState()); |
741 |
|
} |
742 |
|
|
743 |
|
/** |
747 |
|
* @return the number of unarrived parties |
748 |
|
*/ |
749 |
|
public int getUnarrivedParties() { |
750 |
< |
return unarrivedOf(parent==null? state : reconcileState()); |
750 |
> |
int u = unarrivedOf(state); |
751 |
> |
return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState()); |
752 |
|
} |
753 |
|
|
754 |
|
/** |
755 |
< |
* Returns the parent of this phaser, or {@code null} if none. |
755 |
> |
* Returns the parent of this Phaser, or {@code null} if none. |
756 |
|
* |
757 |
< |
* @return the parent of this phaser, or {@code null} if none |
757 |
> |
* @return the parent of this Phaser, or {@code null} if none |
758 |
|
*/ |
759 |
|
public Phaser getParent() { |
760 |
|
return parent; |
761 |
|
} |
762 |
|
|
763 |
|
/** |
764 |
< |
* Returns the root ancestor of this phaser, which is the same as |
765 |
< |
* this phaser if it has no parent. |
764 |
> |
* Returns the root ancestor of this Phaser, which is the same as |
765 |
> |
* this Phaser if it has no parent. |
766 |
|
* |
767 |
< |
* @return the root ancestor of this phaser |
767 |
> |
* @return the root ancestor of this Phaser |
768 |
|
*/ |
769 |
|
public Phaser getRoot() { |
770 |
|
return root; |
791 |
|
* propagated to the party attempting to trip the barrier, in |
792 |
|
* which case no advance occurs. |
793 |
|
* |
794 |
< |
* <p>The arguments to this method provide the state of the phaser |
794 |
> |
* <p>The arguments to this method provide the state of the Phaser |
795 |
|
* prevailing for the current transition. The effects of invoking |
796 |
|
* arrival, registration, and waiting methods on this Phaser from |
797 |
|
* within {@code onAdvance} are unspecified and should not be |
823 |
|
} |
824 |
|
|
825 |
|
/** |
826 |
< |
* Returns a string identifying this phaser, as well as its |
826 |
> |
* Returns a string identifying this Phaser, as well as its |
827 |
|
* state. The state, in brackets, includes the String {@code |
828 |
|
* "phase = "} followed by the phase number, {@code "parties = "} |
829 |
|
* followed by the number of registered parties, and {@code |
882 |
|
|
883 |
|
/** |
884 |
|
* Possibly blocks and waits for phase to advance unless aborted. |
885 |
+ |
* Call only from root node. |
886 |
|
* |
887 |
|
* @param phase current phase |
888 |
|
* @param node if non-null, the wait node to track interrupt and timeout; |
890 |
|
* @return current phase |
891 |
|
*/ |
892 |
|
private int internalAwaitAdvance(int phase, QNode node) { |
882 |
– |
Phaser current = this; // to eventually wait at root if tiered |
893 |
|
boolean queued = false; // true when node is enqueued |
894 |
|
int lastUnarrived = -1; // to increase spins upon change |
895 |
|
int spins = SPINS_PER_ARRIVAL; |
896 |
|
long s; |
897 |
|
int p; |
898 |
< |
while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) { |
889 |
< |
Phaser par; |
898 |
> |
while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) { |
899 |
|
int unarrived = (int)s & UNARRIVED_MASK; |
900 |
|
if (unarrived != lastUnarrived) { |
901 |
|
if (lastUnarrived == -1) // ensure old queue clean |
903 |
|
if ((lastUnarrived = unarrived) < NCPU) |
904 |
|
spins += SPINS_PER_ARRIVAL; |
905 |
|
} |
897 |
– |
else if (unarrived == 0 && (par = current.parent) != null) { |
898 |
– |
current = par; // if all arrived, use parent |
899 |
– |
par = par.parent; |
900 |
– |
lastUnarrived = -1; |
901 |
– |
} |
906 |
|
else if (spins > 0) { |
907 |
|
if (--spins == (SPINS_PER_ARRIVAL >>> 1)) |
908 |
|
Thread.yield(); // yield midway through spin |
910 |
|
else if (node == null) // must be noninterruptible |
911 |
|
node = new QNode(this, phase, false, false, 0L); |
912 |
|
else if (node.isReleasable()) { |
913 |
< |
if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase) |
914 |
< |
break; |
911 |
< |
else |
912 |
< |
return phase; // aborted |
913 |
> |
p = (int)(state >>> PHASE_SHIFT); |
914 |
> |
break; // aborted |
915 |
|
} |
916 |
|
else if (!queued) { // push onto queue |
917 |
|
AtomicReference<QNode> head = queueFor(phase); |
918 |
|
QNode q = head.get(); |
919 |
|
if (q == null || q.phase == phase) { |
920 |
|
node.next = q; |
921 |
< |
if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase) |
921 |
> |
if ((p = (int)(state >>> PHASE_SHIFT)) != phase) |
922 |
|
break; // recheck to avoid stale enqueue |
923 |
|
else |
924 |
|
queued = head.compareAndSet(q, node); |
932 |
|
} |
933 |
|
} |
934 |
|
} |
935 |
< |
releaseWaiters(phase); |
936 |
< |
if (node != null) |
937 |
< |
node.onRelease(); |
935 |
> |
|
936 |
> |
if (node != null) { |
937 |
> |
if (node.thread != null) |
938 |
> |
node.thread = null; // disable unpark() in node.signal |
939 |
> |
if (!node.interruptible && node.wasInterrupted) |
940 |
> |
Thread.currentThread().interrupt(); |
941 |
> |
} |
942 |
> |
if (p != phase) |
943 |
> |
releaseWaiters(phase); |
944 |
|
return p; |
945 |
|
} |
946 |
|
|
1013 |
|
LockSupport.unpark(t); |
1014 |
|
} |
1015 |
|
} |
1008 |
– |
|
1009 |
– |
void onRelease() { // actions upon return from internalAwaitAdvance |
1010 |
– |
if (!interruptible && wasInterrupted) |
1011 |
– |
Thread.currentThread().interrupt(); |
1012 |
– |
if (thread != null) |
1013 |
– |
thread = null; |
1014 |
– |
} |
1015 |
– |
|
1016 |
|
} |
1017 |
|
|
1018 |
|
// Unsafe mechanics |