| 35 |
|
* #arriveAndAwaitAdvance} has effect analogous to {@link |
| 36 |
|
* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each |
| 37 |
|
* generation of a {@code Phaser} has an associated phase number. The |
| 38 |
< |
* phase number starts at zero, amd advances when all parties arrive |
| 38 |
> |
* phase number starts at zero, and advances when all parties arrive |
| 39 |
|
* at the barrier, wrapping around to zero after reaching {@code |
| 40 |
|
* Integer.MAX_VALUE}. The use of phase numbers enables independent |
| 41 |
|
* control of actions upon arrival at a barrier and upon awaiting |
| 62 |
|
* the barrier advances to (or is already at) a different phase. |
| 63 |
|
* Unlike similar constructions using {@code CyclicBarrier}, |
| 64 |
|
* method {@code awaitAdvance} continues to wait even if the |
| 65 |
< |
* waiting thread is interrupted. (Interruptible and timeout |
| 66 |
< |
* versions are also available.) Exceptions encountered while |
| 65 |
> |
* waiting thread is interrupted. Interruptible and timeout |
| 66 |
> |
* versions are also available, but exceptions encountered while |
| 67 |
|
* tasks wait interruptibly or with timeout do not change the |
| 68 |
|
* state of the barrier. If necessary, you can perform any |
| 69 |
|
* associated recovery within handlers of those exceptions, |
| 75 |
|
* </ul> |
| 76 |
|
* |
| 77 |
|
* <p> <b>Termination.</b> A {@code Phaser} may enter a |
| 78 |
< |
* <em>termination</em> state in which all actions immediately return |
| 79 |
< |
* without updating phaser state or waiting for advance, and |
| 80 |
< |
* indicating (via a negative phase value) that execution is complete. |
| 81 |
< |
* Termination is triggered when an invocation of {@code onAdvance} |
| 82 |
< |
* returns {@code true}. As illustrated below, when phasers control |
| 83 |
< |
* actions with a fixed number of iterations, it is often convenient |
| 84 |
< |
* to override this method to cause termination when the current phase |
| 85 |
< |
* number reaches a threshold. Method {@link #forceTermination} is |
| 86 |
< |
* also available to abruptly release waiting threads and allow them |
| 87 |
< |
* to terminate. |
| 78 |
> |
* <em>termination</em> state in which all synchronization methods |
| 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}. As illustrated below, when |
| 83 |
> |
* phasers control actions with a fixed number of iterations, it is |
| 84 |
> |
* often convenient to override this method to cause termination when |
| 85 |
> |
* the current phase number reaches a threshold. Method {@link |
| 86 |
> |
* #forceTermination} is also available to abruptly release waiting |
| 87 |
> |
* threads and allow them to terminate. |
| 88 |
|
* |
| 89 |
|
* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged |
| 90 |
|
* in tree structures) to reduce contention. Phasers with large |
| 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 |
|
* |
| 249 |
|
*/ |
| 250 |
|
private volatile long state; |
| 251 |
|
|
| 249 |
– |
private static final int ushortBits = 16; |
| 252 |
|
private static final int ushortMask = 0xffff; |
| 253 |
|
private static final int phaseMask = 0x7fffffff; |
| 254 |
|
|
| 763 |
|
|
| 764 |
|
/** |
| 765 |
|
* Overridable method to perform an action upon phase advance, and |
| 766 |
< |
* to control termination. This method is invoked whenever the |
| 767 |
< |
* barrier is tripped (and thus all other waiting parties are |
| 768 |
< |
* dormant). If it returns {@code true}, then, rather than advance |
| 769 |
< |
* the phase number, this barrier will be set to a final |
| 770 |
< |
* termination state, and subsequent calls to {@link #isTerminated} |
| 771 |
< |
* will return true. |
| 766 |
> |
* to control termination. This method is invoked upon arrival of |
| 767 |
> |
* the party tripping the barrier (when all other waiting parties |
| 768 |
> |
* are dormant). If this method returns {@code true}, then, |
| 769 |
> |
* rather than advance the phase number, this barrier will be set |
| 770 |
> |
* to a final termination state, and subsequent calls to {@link |
| 771 |
> |
* #isTerminated} will return true. Any (unchecked) Exception or |
| 772 |
> |
* Error thrown by an invocation of this method is propagated to |
| 773 |
> |
* the party attempting to trip the barrier, in which case no |
| 774 |
> |
* advance occurs. |
| 775 |
> |
* |
| 776 |
> |
* <p>The arguments to this method provide the state of the phaser |
| 777 |
> |
* prevailing for the current transition. (When called from within |
| 778 |
> |
* an implementation of {@code onAdvance} the values returned by |
| 779 |
> |
* methods such as {@code getPhase} may or may not reliably |
| 780 |
> |
* indicate the state to which this transition applies.) |
| 781 |
|
* |
| 782 |
|
* <p>The default version returns {@code true} when the number of |
| 783 |
|
* registered parties is zero. Normally, overrides that arrange |
