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, that 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> |
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. |
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 CyclicBarrier. |
57 |
> |
* effect as providing a barrier action to a {@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 |
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 |
67 |
> |
* number reaches a threshold. Method {@link #forceTermination} is also |
68 |
|
* available to abruptly release waiting threads and allow them to |
69 |
|
* terminate. |
70 |
|
* |
76 |
|
* |
77 |
|
* <li> By default, {@code awaitAdvance} continues to wait even if |
78 |
|
* the waiting thread is interrupted. And unlike the case in |
79 |
< |
* CyclicBarriers, exceptions encountered while tasks wait |
79 |
> |
* {@code CyclicBarrier}, exceptions encountered while tasks wait |
80 |
|
* interruptibly or with timeout do not change the state of the |
81 |
|
* barrier. If necessary, you can perform any associated recovery |
82 |
|
* within handlers of those exceptions, often after invoking |
88 |
|
* |
89 |
|
* <p><b>Sample usages:</b> |
90 |
|
* |
91 |
< |
* <p>A Phaser may be used instead of a {@code CountDownLatch} to control |
92 |
< |
* a one-shot action serving a variable number of parties. The typical |
93 |
< |
* idiom is for the method setting this up to first register, then |
94 |
< |
* start the actions, then deregister, as in: |
91 |
> |
* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch} |
92 |
> |
* to control a one-shot action serving a variable number of |
93 |
> |
* parties. The typical idiom is for the method setting this up to |
94 |
> |
* first register, then start the actions, then deregister, as in: |
95 |
|
* |
96 |
|
* <pre> {@code |
97 |
|
* void runTasks(List<Runnable> list) { |
140 |
|
* phaser.arriveAndDeregister(); // deregister self, don't wait |
141 |
|
* }}</pre> |
142 |
|
* |
143 |
< |
* <p> To create a set of tasks using a tree of Phasers, |
143 |
> |
* <p>To create a set of tasks using a tree of phasers, |
144 |
|
* you could use code of the following form, assuming a |
145 |
< |
* Task class with a constructor accepting a Phaser that |
145 |
> |
* Task class with a constructor accepting a phaser that |
146 |
|
* it registers for upon construction: |
147 |
|
* <pre> {@code |
148 |
|
* void build(Task[] actions, int lo, int hi, Phaser b) { |
250 |
|
private final Phaser parent; |
251 |
|
|
252 |
|
/** |
253 |
< |
* The root of Phaser tree. Equals this if not in a tree. Used to |
253 |
> |
* The root of phaser tree. Equals this if not in a tree. Used to |
254 |
|
* support faster state push-down. |
255 |
|
*/ |
256 |
|
private final Phaser root; |
301 |
|
} |
302 |
|
|
303 |
|
/** |
304 |
< |
* Creates a new Phaser without any initially registered parties, |
304 |
> |
* Creates a new phaser without any initially registered parties, |
305 |
|
* initial phase number 0, and no parent. Any thread using this |
306 |
< |
* Phaser will need to first register for it. |
306 |
> |
* phaser will need to first register for it. |
307 |
|
*/ |
308 |
|
public Phaser() { |
309 |
|
this(null); |
310 |
|
} |
311 |
|
|
312 |
|
/** |
313 |
< |
* Creates a new Phaser with the given numbers of registered |
313 |
> |
* Creates a new phaser with the given numbers of registered |
314 |
|
* unarrived parties, initial phase number 0, and no parent. |
315 |
|
* |
316 |
|
* @param parties the number of parties required to trip barrier |
322 |
|
} |
323 |
|
|
324 |
|
/** |
325 |
< |
* Creates a new Phaser with the given parent, without any |
325 |
> |
* Creates a new phaser with the given parent, without any |
326 |
|
* initially registered parties. If parent is non-null this phaser |
327 |
|
* is registered with the parent and its initial phase number is |
328 |
|
* the same as that of parent phaser. |
342 |
|
} |
343 |
|
|
344 |
|
/** |
345 |
< |
* Creates a new Phaser with the given parent and numbers of |
345 |
> |
* Creates a new phaser with the given parent and numbers of |
346 |
|
* registered unarrived parties. If parent is non-null, this phaser |
347 |
|
* is registered with the parent and its initial phase number is |
348 |
|
* the same as that of parent phaser. |
712 |
|
* termination state, and subsequent calls to {@link #isTerminated} |
713 |
|
* will return true. |
714 |
|
* |
715 |
< |
* <p> The default version returns {@code true} when the number of |
715 |
> |
* <p>The default version returns {@code true} when the number of |
716 |
|
* registered parties is zero. Normally, overrides that arrange |
717 |
|
* termination for other reasons should also preserve this |
718 |
|
* property. |
719 |
|
* |
720 |
< |
* <p> You may override this method to perform an action with side |
720 |
> |
* <p>You may override this method to perform an action with side |
721 |
|
* effects visible to participating tasks, but it is in general |
722 |
|
* only sensible to do so in designs where all parties register |
723 |
< |
* before any arrive, and all {@code awaitAdvance} at each phase. |
723 |
> |
* before any arrive, and all {@link #awaitAdvance} at each phase. |
724 |
|
* Otherwise, you cannot ensure lack of interference. In |
725 |
|
* particular, this method may be invoked more than once per |
726 |
|
* transition if other parties successfully register while the |