| 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, that may also be invoked independently: |
| 39 |
> |
* coordination, which may also be invoked independently: |
| 40 |
|
* |
| 41 |
|
* <ul> |
| 42 |
|
* |
| 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 {@link #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 {@code 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 {@link #forceTermination} is also |
| 68 |
< |
* available to abruptly release waiting threads and allow them to |
| 69 |
< |
* 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 |
| 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 |
|
* |
| 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(); |
| 105 |
– |
* phaser.arriveAndDeregister(); // signal completion |
| 107 |
|
* } |
| 108 |
|
* }.start(); |
| 109 |
|
* } |
| 110 |
|
* |
| 111 |
< |
* doSomethingOnBehalfOfWorkers(); |
| 112 |
< |
* phaser.arrive(); // allow threads to start |
| 112 |
< |
* int p = phaser.arriveAndDeregister(); // deregister self ... |
| 113 |
< |
* p = phaser.awaitAdvance(p); // ... and await arrival |
| 114 |
< |
* otherActions(); // do other things while tasks execute |
| 115 |
< |
* 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 |
| 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, or returns immediately if current phase of the barrier |
| 539 |
> |
* is not equal to the given phase value or this barrier is |
| 540 |
> |
* terminated. |
| 541 |
|
* |
| 542 |
|
* @param phase the phase on entry to this method |
| 543 |
|
* @return the phase on exit from this method |
| 638 |
|
} |
| 639 |
|
|
| 640 |
|
/** |
| 640 |
– |
* Returns {@code true} if the current phase number equals the given phase. |
| 641 |
– |
* |
| 642 |
– |
* @param phase the phase |
| 643 |
– |
* @return {@code true} if the current phase number equals the given phase |
| 644 |
– |
*/ |
| 645 |
– |
public final boolean hasPhase(int phase) { |
| 646 |
– |
return phaseOf(getReconciledState()) == phase; |
| 647 |
– |
} |
| 648 |
– |
|
| 649 |
– |
/** |
| 641 |
|
* Returns the number of parties registered at this barrier. |
| 642 |
|
* |
| 643 |
|
* @return the number of parties |
| 712 |
|
* effects visible to participating tasks, but it is in general |
| 713 |
|
* only sensible to do so in designs where all parties register |
| 714 |
|
* before any arrive, and all {@link #awaitAdvance} at each phase. |
| 715 |
< |
* Otherwise, you cannot ensure lack of interference. In |
| 716 |
< |
* particular, this method may be invoked more than once per |
| 726 |
< |
* transition if other parties successfully register while the |
| 727 |
< |
* invocation of this method is in progress, thus postponing the |
| 728 |
< |
* transition until those parties also arrive, re-triggering this |
| 729 |
< |
* method. |
| 715 |
> |
* Otherwise, you cannot ensure lack of interference from other |
| 716 |
> |
* parties during the the invocation of this method. |
| 717 |
|
* |
| 718 |
|
* @param phase the phase number on entering the barrier |
| 719 |
|
* @param registeredParties the current number of registered parties |
