| 32 |
|
* zero, and advancing when all parties reach the barrier (wrapping |
| 33 |
|
* around to zero after reaching {@code Integer.MAX_VALUE}). |
| 34 |
|
* |
| 35 |
< |
* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited. |
| 36 |
< |
* Method {@code arriveAndAwaitAdvance} has effect analogous to |
| 37 |
< |
* {@code CyclicBarrier.await}. However, Phasers separate two |
| 38 |
< |
* aspects of coordination, that may also be invoked independently: |
| 35 |
> |
* <li> Like a {@code CyclicBarrier}, a phaser may be repeatedly |
| 36 |
> |
* awaited. Method {@link #arriveAndAwaitAdvance} has effect |
| 37 |
> |
* analogous to {@link java.util.concurrent.CyclicBarrier#await |
| 38 |
> |
* CyclicBarrier.await}. However, phasers separate two aspects of |
| 39 |
> |
* coordination, which may also be invoked independently: |
| 40 |
|
* |
| 41 |
|
* <ul> |
| 42 |
|
* |
| 43 |
< |
* <li> Arriving at a barrier. Methods {@code arrive} and |
| 44 |
< |
* {@code arriveAndDeregister} do not block, but return |
| 43 |
> |
* <li> Arriving at a barrier. Methods {@link #arrive} and |
| 44 |
> |
* {@link #arriveAndDeregister} do not block, but return |
| 45 |
|
* the phase value current upon entry to the method. |
| 46 |
|
* |
| 47 |
< |
* <li> Awaiting others. Method {@code awaitAdvance} requires an |
| 47 |
> |
* <li> Awaiting others. Method {@link #awaitAdvance} requires an |
| 48 |
|
* argument indicating the entry phase, and returns when the |
| 49 |
|
* barrier advances to a new phase. |
| 50 |
|
* </ul> |
| 51 |
|
* |
| 52 |
|
* |
| 53 |
|
* <li> Barrier actions, performed by the task triggering a phase |
| 54 |
< |
* advance while others may be waiting, are arranged by overriding |
| 55 |
< |
* method {@code onAdvance}, that also controls termination. |
| 56 |
< |
* Overriding this method may be used to similar but more flexible |
| 57 |
< |
* effect as providing a barrier action to a CyclicBarrier. |
| 54 |
> |
* advance, are arranged by overriding method {@link #onAdvance(int, |
| 55 |
> |
* int)}, which also controls termination. Overriding this method is |
| 56 |
> |
* similar to, but more flexible than, providing a barrier action to a |
| 57 |
> |
* {@code CyclicBarrier}. |
| 58 |
|
* |
| 59 |
|
* <li> Phasers may enter a <em>termination</em> state in which all |
| 60 |
|
* actions immediately return without updating phaser state or waiting |
| 61 |
|
* for advance, and indicating (via a negative phase value) that |
| 62 |
< |
* execution is complete. Termination is triggered by executing the |
| 63 |
< |
* overridable {@code onAdvance} method that is invoked each time the |
| 64 |
< |
* barrier is about to be tripped. When a Phaser is controlling an |
| 65 |
< |
* action with a fixed number of iterations, it is often convenient to |
| 66 |
< |
* override this method to cause termination when the current phase |
| 67 |
< |
* number reaches a threshold. Method {@code forceTermination} is also |
| 68 |
< |
* available to abruptly release waiting threads and allow them to |
| 68 |
< |
* terminate. |
| 62 |
> |
* execution is complete. Termination is triggered when an invocation |
| 63 |
> |
* of {@code onAdvance} returns {@code true}. When a phaser is |
| 64 |
> |
* controlling an action with a fixed number of iterations, it is |
| 65 |
> |
* often convenient to override this method to cause termination when |
| 66 |
> |
* the current phase number reaches a threshold. Method {@link |
| 67 |
> |
* #forceTermination} is also available to abruptly release waiting |
| 68 |
> |
* threads and allow them to terminate. |
| 69 |
|
* |
| 70 |
|
* <li> Phasers may be tiered to reduce contention. Phasers with large |
| 71 |
|
* numbers of parties that would otherwise experience heavy |
| 75 |
|
* |
| 76 |
|
* <li> By default, {@code awaitAdvance} continues to wait even if |
| 77 |
|
* the waiting thread is interrupted. And unlike the case in |
| 78 |
< |
* CyclicBarriers, exceptions encountered while tasks wait |
| 78 |
> |
* {@code CyclicBarrier}, exceptions encountered while tasks wait |
| 79 |
|
* interruptibly or with timeout do not change the state of the |
| 80 |
|
* barrier. If necessary, you can perform any associated recovery |
| 81 |
|
* within handlers of those exceptions, often after invoking |
| 82 |
|
* {@code forceTermination}. |
| 83 |
|
* |
| 84 |
< |
* <li>Phasers ensure lack of starvation when used by ForkJoinTasks. |
| 84 |
> |
* <li>Phasers may be used to coordinate tasks executing in a {@link |
| 85 |
> |
* ForkJoinPool}, which will ensure sufficient parallelism to execute |
| 86 |
> |
* tasks when others are blocked waiting for a phase to advance. |
| 87 |
|
* |
| 88 |
|
* </ul> |
| 89 |
|
* |
| 90 |
|
* <p><b>Sample usages:</b> |
| 91 |
|
* |
| 92 |
< |
* <p>A Phaser may be used instead of a {@code CountDownLatch} to control |
| 93 |
< |
* a one-shot action serving a variable number of parties. The typical |
| 94 |
< |
* idiom is for the method setting this up to first register, then |
| 95 |
< |
* start the actions, then deregister, as in: |
| 92 |
> |
* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch} |
| 93 |
> |
* to control a one-shot action serving a variable number of |
| 94 |
> |
* parties. The typical idiom is for the method setting this up to |
| 95 |
> |
* first register, then start the actions, then deregister, as in: |
| 96 |
|
* |
| 97 |
|
* <pre> {@code |
| 98 |
|
* void runTasks(List<Runnable> list) { |
| 99 |
|
* final Phaser phaser = new Phaser(1); // "1" to register self |
| 100 |
+ |
* // create and start threads |
| 101 |
|
* for (Runnable r : list) { |
| 102 |
|
* phaser.register(); |
| 103 |
|
* new Thread() { |
| 104 |
|
* public void run() { |
| 105 |
|
* phaser.arriveAndAwaitAdvance(); // await all creation |
| 106 |
|
* r.run(); |
| 104 |
– |
* phaser.arriveAndDeregister(); // signal completion |
| 107 |
|
* } |
| 108 |
|
* }.start(); |
| 109 |
|
* } |
| 110 |
|
* |
| 111 |
< |
* doSomethingOnBehalfOfWorkers(); |
| 112 |
< |
* phaser.arrive(); // allow threads to start |
| 111 |
< |
* int p = phaser.arriveAndDeregister(); // deregister self ... |
| 112 |
< |
* p = phaser.awaitAdvance(p); // ... and await arrival |
| 113 |
< |
* otherActions(); // do other things while tasks execute |
| 114 |
< |
* phaser.awaitAdvance(p); // await final completion |
| 111 |
> |
* // allow threads to start and deregister self |
| 112 |
> |
* phaser.arriveAndDeregister(); |
| 113 |
|
* }}</pre> |
| 114 |
|
* |
| 115 |
|
* <p>One way to cause a set of threads to repeatedly perform actions |
| 137 |
|
* phaser.arriveAndDeregister(); // deregister self, don't wait |
| 138 |
|
* }}</pre> |
| 139 |
|
* |
| 140 |
< |
* <p> To create a set of tasks using a tree of Phasers, |
| 140 |
> |
* <p>To create a set of tasks using a tree of phasers, |
| 141 |
|
* you could use code of the following form, assuming a |
| 142 |
< |
* Task class with a constructor accepting a Phaser that |
| 142 |
> |
* Task class with a constructor accepting a phaser that |
| 143 |
|
* it registers for upon construction: |
| 144 |
|
* <pre> {@code |
| 145 |
|
* void build(Task[] actions, int lo, int hi, Phaser b) { |
| 169 |
|
* |
| 170 |
|
* <p><b>Implementation notes</b>: This implementation restricts the |
| 171 |
|
* maximum number of parties to 65535. Attempts to register additional |
| 172 |
< |
* parties result in IllegalStateExceptions. However, you can and |
| 172 |
> |
* parties result in {@code IllegalStateException}. However, you can and |
| 173 |
|
* should create tiered phasers to accommodate arbitrarily large sets |
| 174 |
|
* of participants. |
| 175 |
|
* |
| 247 |
|
private final Phaser parent; |
| 248 |
|
|
| 249 |
|
/** |
| 250 |
< |
* The root of Phaser tree. Equals this if not in a tree. Used to |
| 250 |
> |
* The root of phaser tree. Equals this if not in a tree. Used to |
| 251 |
|
* support faster state push-down. |
| 252 |
|
*/ |
| 253 |
|
private final Phaser root; |
| 298 |
|
} |
| 299 |
|
|
| 300 |
|
/** |
| 301 |
< |
* Creates a new Phaser without any initially registered parties, |
| 301 |
> |
* Creates a new phaser without any initially registered parties, |
| 302 |
|
* initial phase number 0, and no parent. Any thread using this |
| 303 |
< |
* Phaser will need to first register for it. |
| 303 |
> |
* phaser will need to first register for it. |
| 304 |
|
*/ |
| 305 |
|
public Phaser() { |
| 306 |
|
this(null); |
| 307 |
|
} |
| 308 |
|
|
| 309 |
|
/** |
| 310 |
< |
* Creates a new Phaser with the given numbers of registered |
| 310 |
> |
* Creates a new phaser with the given numbers of registered |
| 311 |
|
* unarrived parties, initial phase number 0, and no parent. |
| 312 |
|
* |
| 313 |
|
* @param parties the number of parties required to trip barrier |
| 319 |
|
} |
| 320 |
|
|
| 321 |
|
/** |
| 322 |
< |
* Creates a new Phaser with the given parent, without any |
| 322 |
> |
* Creates a new phaser with the given parent, without any |
| 323 |
|
* initially registered parties. If parent is non-null this phaser |
| 324 |
|
* is registered with the parent and its initial phase number is |
| 325 |
|
* the same as that of parent phaser. |
| 339 |
|
} |
| 340 |
|
|
| 341 |
|
/** |
| 342 |
< |
* Creates a new Phaser with the given parent and numbers of |
| 342 |
> |
* Creates a new phaser with the given parent and numbers of |
| 343 |
|
* registered unarrived parties. If parent is non-null, this phaser |
| 344 |
|
* is registered with the parent and its initial phase number is |
| 345 |
|
* the same as that of parent phaser. |
| 461 |
|
} |
| 462 |
|
|
| 463 |
|
/** |
| 464 |
< |
* Arrives at the barrier, and deregisters from it, without |
| 465 |
< |
* waiting for others. Deregistration reduces number of parties |
| 464 |
> |
* Arrives at the barrier and deregisters from it without waiting |
| 465 |
> |
* for others. Deregistration reduces the number of parties |
| 466 |
|
* required to trip the barrier in future phases. If this phaser |
| 467 |
|
* has a parent, and deregistration causes this phaser to have |
| 468 |
< |
* zero parties, this phaser is also deregistered from its parent. |
| 468 |
> |
* zero parties, this phaser also arrives at and is deregistered |
| 469 |
> |
* from its parent. |
| 470 |
|
* |
| 471 |
|
* @return the current barrier phase number upon entry to |
| 472 |
|
* this method, or a negative value if terminated |
| 519 |
|
|
| 520 |
|
/** |
| 521 |
|
* Arrives at the barrier and awaits others. Equivalent in effect |
| 522 |
< |
* to {@code awaitAdvance(arrive())}. If you instead need to |
| 523 |
< |
* await with interruption of timeout, and/or deregister upon |
| 524 |
< |
* arrival, you can arrange them using analogous constructions. |
| 522 |
> |
* to {@code awaitAdvance(arrive())}. If you need to await with |
| 523 |
> |
* interruption or timeout, you can arrange this with an analogous |
| 524 |
> |
* construction using one of the other forms of the awaitAdvance |
| 525 |
> |
* method. If instead you need to deregister upon arrival use |
| 526 |
> |
* {@code arriveAndDeregister}. |
| 527 |
|
* |
| 528 |
|
* @return the phase on entry to this method |
| 529 |
|
* @throws IllegalStateException if not terminated and the number |
| 534 |
|
} |
| 535 |
|
|
| 536 |
|
/** |
| 537 |
< |
* Awaits the phase of the barrier to advance from the given |
| 538 |
< |
* value, or returns immediately if argument is negative or this |
| 539 |
< |
* barrier is terminated. |
| 537 |
> |
* Awaits the phase of the barrier to advance from the given phase |
| 538 |
> |
* value, returning immediately if the current phase of the |
| 539 |
> |
* barrier is not equal to the given phase value or this barrier |
| 540 |
> |
* is terminated. |
| 541 |
|
* |
| 542 |
|
* @param phase the phase on entry to this method |
| 543 |
|
* @return the phase on exit from this method |
| 556 |
|
} |
| 557 |
|
|
| 558 |
|
/** |
| 559 |
< |
* Awaits the phase of the barrier to advance from the given |
| 560 |
< |
* value, or returns immediately if argument is negative or this |
| 561 |
< |
* barrier is terminated, or throws InterruptedException if |
| 562 |
< |
* interrupted while waiting. |
| 559 |
> |
* Awaits the phase of the barrier to advance from the given phase |
| 560 |
> |
* value, throwing {@code InterruptedException} if interrupted while |
| 561 |
> |
* waiting, or returning immediately if the current phase of the |
| 562 |
> |
* barrier is not equal to the given phase value or this barrier |
| 563 |
> |
* is terminated. |
| 564 |
|
* |
| 565 |
|
* @param phase the phase on entry to this method |
| 566 |
|
* @return the phase on exit from this method |
| 580 |
|
} |
| 581 |
|
|
| 582 |
|
/** |
| 583 |
< |
* Awaits the phase of the barrier to advance from the given value |
| 584 |
< |
* or the given timeout elapses, or returns immediately if |
| 585 |
< |
* argument is negative or this barrier is terminated. |
| 583 |
> |
* Awaits the phase of the barrier to advance from the given phase |
| 584 |
> |
* value or the given timeout to elapse, throwing |
| 585 |
> |
* {@code InterruptedException} if interrupted while waiting, or |
| 586 |
> |
* returning immediately if the current phase of the barrier is not |
| 587 |
> |
* equal to the given phase value or this barrier is terminated. |
| 588 |
|
* |
| 589 |
|
* @param phase the phase on entry to this method |
| 590 |
+ |
* @param timeout how long to wait before giving up, in units of |
| 591 |
+ |
* {@code unit} |
| 592 |
+ |
* @param unit a {@code TimeUnit} determining how to interpret the |
| 593 |
+ |
* {@code timeout} parameter |
| 594 |
|
* @return the phase on exit from this method |
| 595 |
|
* @throws InterruptedException if thread interrupted while waiting |
| 596 |
|
* @throws TimeoutException if timed out while waiting |
| 645 |
|
} |
| 646 |
|
|
| 647 |
|
/** |
| 639 |
– |
* Returns {@code true} if the current phase number equals the given phase. |
| 640 |
– |
* |
| 641 |
– |
* @param phase the phase |
| 642 |
– |
* @return {@code true} if the current phase number equals the given phase |
| 643 |
– |
*/ |
| 644 |
– |
public final boolean hasPhase(int phase) { |
| 645 |
– |
return phaseOf(getReconciledState()) == phase; |
| 646 |
– |
} |
| 647 |
– |
|
| 648 |
– |
/** |
| 648 |
|
* Returns the number of parties registered at this barrier. |
| 649 |
|
* |
| 650 |
|
* @return the number of parties |
| 674 |
|
} |
| 675 |
|
|
| 676 |
|
/** |
| 677 |
< |
* Returns the parent of this phaser, or null if none. |
| 677 |
> |
* Returns the parent of this phaser, or {@code null} if none. |
| 678 |
|
* |
| 679 |
< |
* @return the parent of this phaser, or null if none |
| 679 |
> |
* @return the parent of this phaser, or {@code null} if none |
| 680 |
|
*/ |
| 681 |
|
public Phaser getParent() { |
| 682 |
|
return parent; |
| 705 |
|
* Overridable method to perform an action upon phase advance, and |
| 706 |
|
* to control termination. This method is invoked whenever the |
| 707 |
|
* barrier is tripped (and thus all other waiting parties are |
| 708 |
< |
* dormant). If it returns true, then, rather than advance the |
| 709 |
< |
* phase number, this barrier will be set to a final termination |
| 710 |
< |
* state, and subsequent calls to {@code isTerminated} will |
| 711 |
< |
* return true. |
| 708 |
> |
* dormant). If it returns {@code true}, then, rather than advance |
| 709 |
> |
* the phase number, this barrier will be set to a final |
| 710 |
> |
* termination state, and subsequent calls to {@link #isTerminated} |
| 711 |
> |
* will return true. |
| 712 |
|
* |
| 713 |
< |
* <p> The default version returns true when the number of |
| 713 |
> |
* <p>The default version returns {@code true} when the number of |
| 714 |
|
* registered parties is zero. Normally, overrides that arrange |
| 715 |
|
* termination for other reasons should also preserve this |
| 716 |
|
* property. |
| 717 |
|
* |
| 718 |
< |
* <p> You may override this method to perform an action with side |
| 718 |
> |
* <p>You may override this method to perform an action with side |
| 719 |
|
* effects visible to participating tasks, but it is in general |
| 720 |
|
* only sensible to do so in designs where all parties register |
| 721 |
< |
* before any arrive, and all {@code awaitAdvance} at each phase. |
| 722 |
< |
* Otherwise, you cannot ensure lack of interference. In |
| 723 |
< |
* particular, this method may be invoked more than once per |
| 725 |
< |
* transition if other parties successfully register while the |
| 726 |
< |
* invocation of this method is in progress, thus postponing the |
| 727 |
< |
* transition until those parties also arrive, re-triggering this |
| 728 |
< |
* method. |
| 721 |
> |
* before any arrive, and all {@link #awaitAdvance} at each phase. |
| 722 |
> |
* Otherwise, you cannot ensure lack of interference from other |
| 723 |
> |
* parties during the invocation of this method. |
| 724 |
|
* |
| 725 |
|
* @param phase the phase number on entering the barrier |
| 726 |
|
* @param registeredParties the current number of registered parties |
