| 12 |
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import java.util.concurrent.locks.LockSupport; |
| 13 |
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|
| 14 |
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/** |
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< |
* A reusable synchronization barrier, similar in functionality to a |
| 15 |
> |
* A reusable synchronization barrier, similar in functionality to |
| 16 |
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* {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and |
| 17 |
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* {@link java.util.concurrent.CountDownLatch CountDownLatch} |
| 18 |
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* but supporting more flexible usage. |
| 19 |
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* |
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< |
* <ul> |
| 21 |
< |
* |
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* <li> The number of parties synchronizing on a phaser may vary over |
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< |
* time. A task may register to be a party at any time, and may |
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< |
* deregister upon arriving at the barrier. As is the case with most |
| 25 |
< |
* basic synchronization constructs, registration and deregistration |
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< |
* affect only internal counts; they do not establish any further |
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< |
* internal bookkeeping, so tasks cannot query whether they are |
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< |
* registered. (However, you can introduce such bookkeeping by |
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* subclassing this class.) |
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< |
* |
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* <li> Each generation has an associated phase value, starting at |
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* zero, and advancing when all parties reach the barrier (wrapping |
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* around to zero after reaching {@code Integer.MAX_VALUE}). |
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< |
* |
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* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited. |
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< |
* Method {@code arriveAndAwaitAdvance} has effect analogous to |
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* {@code CyclicBarrier.await}. However, Phasers separate two |
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* aspects of coordination, that may also be invoked independently: |
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> |
* <p> <b>Registration.</b> Unlike the case for other barriers, the |
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> |
* number of parties <em>registered</em> to synchronize on a phaser |
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> |
* may vary over time. Tasks may be registered at any time (using |
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> |
* methods {@link #register}, {@link #bulkRegister}, or forms of |
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> |
* constructors establishing initial numbers of parties), and |
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> |
* optionally deregistered upon any arrival (using {@link |
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> |
* #arriveAndDeregister}). As is the case with most basic |
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> |
* synchronization constructs, registration and deregistration affect |
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> |
* only internal counts; they do not establish any further internal |
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> |
* bookkeeping, so tasks cannot query whether they are registered. |
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* (However, you can introduce such bookkeeping by subclassing this |
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* class.) |
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> |
* |
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> |
* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code |
| 34 |
> |
* Phaser} may be repeatedly awaited. Method {@link |
| 35 |
> |
* #arriveAndAwaitAdvance} has effect analogous to {@link |
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> |
* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each |
| 37 |
> |
* generation of a {@code Phaser} has an associated phase number. The |
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> |
* phase number starts at zero, and advances when all parties arrive |
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> |
* at the barrier, wrapping around to zero after reaching {@code |
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> |
* Integer.MAX_VALUE}. The use of phase numbers enables independent |
| 41 |
> |
* control of actions upon arrival at a barrier and upon awaiting |
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> |
* others, via two kinds of methods that may be invoked by any |
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* registered party: |
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* |
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* <ul> |
| 46 |
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* |
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< |
* <li> Arriving at a barrier. Methods {@code arrive} and |
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* {@code arriveAndDeregister} do not block, but return |
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* the phase value current upon entry to the method. |
| 50 |
< |
* |
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* <li> Awaiting others. Method {@code awaitAdvance} requires an |
| 52 |
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* argument indicating the entry phase, and returns when the |
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* barrier advances to a new phase. |
| 54 |
< |
* </ul> |
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> |
* <li> <b>Arrival.</b> Methods {@link #arrive} and |
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* {@link #arriveAndDeregister} record arrival at a |
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* barrier. These methods do not block, but return an associated |
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* <em>arrival phase number</em>; that is, the phase number of |
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> |
* the barrier to which the arrival applied. When the final |
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> |
* party for a given phase arrives, an optional barrier action |
| 53 |
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* is performed and the phase advances. Barrier actions, |
| 54 |
> |
* performed by the party triggering a phase advance, are |
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> |
* arranged by overriding method {@link #onAdvance(int, int)}, |
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* which also controls termination. Overriding this method is |
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> |
* similar to, but more flexible than, providing a barrier |
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* action to a {@code CyclicBarrier}. |
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> |
* |
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> |
* <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an |
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* argument indicating an arrival phase number, and returns when |
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> |
* the barrier advances to (or is already at) a different phase. |
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> |
* Unlike similar constructions using {@code CyclicBarrier}, |
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* method {@code awaitAdvance} continues to wait even if the |
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* waiting thread is interrupted. Interruptible and timeout |
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* versions are also available, but exceptions encountered while |
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* tasks wait interruptibly or with timeout do not change the |
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* state of the barrier. If necessary, you can perform any |
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* associated recovery within handlers of those exceptions, |
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* often after invoking {@code forceTermination}. Phasers may |
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* also be used by tasks executing in a {@link ForkJoinPool}, |
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* which will ensure sufficient parallelism to execute tasks |
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* when others are blocked waiting for a phase to advance. |
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* |
| 75 |
+ |
* </ul> |
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* |
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* <li> Barrier actions, performed by the task triggering a phase |
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* advance while others may be waiting, are arranged by overriding |
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* method {@code onAdvance}, that also controls termination. |
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* Overriding this method may be used to similar but more flexible |
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* effect as providing a barrier action to a CyclicBarrier. |
| 82 |
< |
* |
| 83 |
< |
* <li> Phasers may enter a <em>termination</em> state in which all |
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* actions immediately return without updating phaser state or waiting |
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* for advance, and indicating (via a negative phase value) that |
| 86 |
< |
* execution is complete. Termination is triggered by executing the |
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< |
* overridable {@code onAdvance} method that is invoked each time the |
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< |
* barrier is about to be tripped. When a Phaser is controlling an |
| 64 |
< |
* action with a fixed number of iterations, it is often convenient to |
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< |
* override this method to cause termination when the current phase |
| 66 |
< |
* number reaches a threshold. Method {@code forceTermination} is also |
| 67 |
< |
* available to abruptly release waiting threads and allow them to |
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< |
* terminate. |
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> |
* <p> <b>Termination.</b> A {@code Phaser} may enter a |
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> |
* <em>termination</em> state in which all synchronization methods |
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> |
* 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 |
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> |
* onAdvance} returns {@code true}. As illustrated below, when |
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> |
* phasers control actions with a fixed number of iterations, it is |
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> |
* 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 |
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> |
* threads and allow them to terminate. |
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* |
| 89 |
< |
* <li> Phasers may be tiered to reduce contention. Phasers with large |
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> |
* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged |
| 90 |
> |
* in tree structures) to reduce contention. Phasers with large |
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* numbers of parties that would otherwise experience heavy |
| 92 |
< |
* synchronization contention costs may instead be arranged in trees. |
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< |
* This will typically greatly increase throughput even though it |
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< |
* incurs somewhat greater per-operation overhead. |
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< |
* |
| 96 |
< |
* <li> By default, {@code awaitAdvance} continues to wait even if |
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< |
* the waiting thread is interrupted. And unlike the case in |
| 98 |
< |
* CyclicBarriers, exceptions encountered while tasks wait |
| 99 |
< |
* interruptibly or with timeout do not change the state of the |
| 100 |
< |
* barrier. If necessary, you can perform any associated recovery |
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< |
* within handlers of those exceptions, often after invoking |
| 102 |
< |
* {@code forceTermination}. |
| 103 |
< |
* |
| 104 |
< |
* <li>Phasers ensure lack of starvation when used by ForkJoinTasks. |
| 105 |
< |
* |
| 106 |
< |
* </ul> |
| 92 |
> |
* synchronization contention costs may instead be set up so that |
| 93 |
> |
* groups of sub-phasers share a common parent. This may greatly |
| 94 |
> |
* increase throughput even though it incurs greater per-operation |
| 95 |
> |
* overhead. |
| 96 |
> |
* |
| 97 |
> |
* <p><b>Monitoring.</b> While synchronization methods may be invoked |
| 98 |
> |
* only by registered parties, the current state of a phaser may be |
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> |
* monitored by any caller. At any given moment there are {@link |
| 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} |
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> |
* returns snapshots of these state queries in a form convenient for |
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> |
* informal monitoring. |
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* |
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* <p><b>Sample usages:</b> |
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* |
| 111 |
< |
* <p>A Phaser may be used instead of a {@code CountDownLatch} to control |
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< |
* a one-shot action serving a variable number of parties. The typical |
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< |
* idiom is for the method setting this up to first register, then |
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< |
* start the actions, then deregister, as in: |
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> |
* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch} |
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> |
* to control a one-shot action serving a variable number of |
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> |
* parties. The typical idiom is for the method setting this up to |
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> |
* first register, then start the actions, then deregister, as in: |
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* |
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|
* <pre> {@code |
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< |
* void runTasks(List<Runnable> list) { |
| 117 |
> |
* void runTasks(List<Runnable> tasks) { |
| 118 |
|
* final Phaser phaser = new Phaser(1); // "1" to register self |
| 119 |
< |
* for (Runnable r : list) { |
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> |
* // create and start threads |
| 120 |
> |
* for (Runnable task : tasks) { |
| 121 |
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* phaser.register(); |
| 122 |
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* new Thread() { |
| 123 |
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* public void run() { |
| 124 |
|
* phaser.arriveAndAwaitAdvance(); // await all creation |
| 125 |
< |
* r.run(); |
| 104 |
< |
* phaser.arriveAndDeregister(); // signal completion |
| 125 |
> |
* task.run(); |
| 126 |
|
* } |
| 127 |
|
* }.start(); |
| 128 |
|
* } |
| 129 |
|
* |
| 130 |
< |
* doSomethingOnBehalfOfWorkers(); |
| 131 |
< |
* 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 |
| 130 |
> |
* // allow threads to start and deregister self |
| 131 |
> |
* phaser.arriveAndDeregister(); |
| 132 |
|
* }}</pre> |
| 133 |
|
* |
| 134 |
|
* <p>One way to cause a set of threads to repeatedly perform actions |
| 135 |
|
* for a given number of iterations is to override {@code onAdvance}: |
| 136 |
|
* |
| 137 |
|
* <pre> {@code |
| 138 |
< |
* void startTasks(List<Runnable> list, final int iterations) { |
| 138 |
> |
* void startTasks(List<Runnable> tasks, final int iterations) { |
| 139 |
|
* final Phaser phaser = new Phaser() { |
| 140 |
< |
* public boolean onAdvance(int phase, int registeredParties) { |
| 140 |
> |
* protected boolean onAdvance(int phase, int registeredParties) { |
| 141 |
|
* return phase >= iterations || registeredParties == 0; |
| 142 |
|
* } |
| 143 |
|
* }; |
| 144 |
|
* phaser.register(); |
| 145 |
< |
* for (Runnable r : list) { |
| 145 |
> |
* for (Runnable task : tasks) { |
| 146 |
|
* phaser.register(); |
| 147 |
|
* new Thread() { |
| 148 |
|
* public void run() { |
| 149 |
|
* do { |
| 150 |
< |
* r.run(); |
| 150 |
> |
* task.run(); |
| 151 |
|
* phaser.arriveAndAwaitAdvance(); |
| 152 |
|
* } while(!phaser.isTerminated(); |
| 153 |
|
* } |
| 156 |
|
* phaser.arriveAndDeregister(); // deregister self, don't wait |
| 157 |
|
* }}</pre> |
| 158 |
|
* |
| 159 |
< |
* <p> To create a set of tasks using a tree of Phasers, |
| 159 |
> |
* If the main task must later await termination, it |
| 160 |
> |
* may re-register and then execute a similar loop: |
| 161 |
> |
* <pre> {@code |
| 162 |
> |
* // ... |
| 163 |
> |
* phaser.register(); |
| 164 |
> |
* while (!phaser.isTerminated()) |
| 165 |
> |
* phaser.arriveAndAwaitAdvance(); |
| 166 |
> |
* }</pre> |
| 167 |
> |
* |
| 168 |
> |
* Related constructions may be used to await particular phase numbers |
| 169 |
> |
* in contexts where you are sure that the phase will never wrap around |
| 170 |
> |
* {@code Integer.MAX_VALUE}. For example: |
| 171 |
> |
* |
| 172 |
> |
* <pre> {@code |
| 173 |
> |
* void awaitPhase(Phaser phaser, int phase) { |
| 174 |
> |
* int p = phaser.register(); // assumes caller not already registered |
| 175 |
> |
* while (p < phase) { |
| 176 |
> |
* if (phaser.isTerminated()) |
| 177 |
> |
* // ... deal with unexpected termination |
| 178 |
> |
* else |
| 179 |
> |
* p = phaser.arriveAndAwaitAdvance(); |
| 180 |
> |
* } |
| 181 |
> |
* phaser.arriveAndDeregister(); |
| 182 |
> |
* } |
| 183 |
> |
* }</pre> |
| 184 |
> |
* |
| 185 |
> |
* |
| 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 for upon construction: |
| 190 |
|
* <pre> {@code |
| 191 |
< |
* void build(Task[] actions, int lo, int hi, Phaser b) { |
| 192 |
< |
* int step = (hi - lo) / TASKS_PER_PHASER; |
| 193 |
< |
* if (step > 1) { |
| 194 |
< |
* int i = lo; |
| 195 |
< |
* while (i < hi) { |
| 152 |
< |
* int r = Math.min(i + step, hi); |
| 153 |
< |
* build(actions, i, r, new Phaser(b)); |
| 154 |
< |
* i = r; |
| 191 |
> |
* void build(Task[] actions, int lo, int hi, Phaser ph) { |
| 192 |
> |
* if (hi - lo > TASKS_PER_PHASER) { |
| 193 |
> |
* for (int i = lo; i < hi; i += TASKS_PER_PHASER) { |
| 194 |
> |
* int j = Math.min(i + TASKS_PER_PHASER, hi); |
| 195 |
> |
* build(actions, i, j, new Phaser(ph)); |
| 196 |
|
* } |
| 197 |
|
* } else { |
| 198 |
|
* for (int i = lo; i < hi; ++i) |
| 199 |
< |
* actions[i] = new Task(b); |
| 200 |
< |
* // assumes new Task(b) performs b.register() |
| 199 |
> |
* actions[i] = new Task(ph); |
| 200 |
> |
* // assumes new Task(ph) performs ph.register() |
| 201 |
|
* } |
| 202 |
|
* } |
| 203 |
|
* // .. initially called, for n tasks via |
| 212 |
|
* |
| 213 |
|
* <p><b>Implementation notes</b>: This implementation restricts the |
| 214 |
|
* maximum number of parties to 65535. Attempts to register additional |
| 215 |
< |
* parties result in IllegalStateExceptions. However, you can and |
| 215 |
> |
* parties result in {@code IllegalStateException}. However, you can and |
| 216 |
|
* should create tiered phasers to accommodate arbitrarily large sets |
| 217 |
|
* of participants. |
| 218 |
|
* |
| 246 |
|
*/ |
| 247 |
|
private volatile long state; |
| 248 |
|
|
| 208 |
– |
private static final int ushortBits = 16; |
| 249 |
|
private static final int ushortMask = 0xffff; |
| 250 |
|
private static final int phaseMask = 0x7fffffff; |
| 251 |
|
|
| 289 |
|
private final Phaser parent; |
| 290 |
|
|
| 291 |
|
/** |
| 292 |
< |
* The root of Phaser tree. Equals this if not in a tree. Used to |
| 292 |
> |
* The root of phaser tree. Equals this if not in a tree. Used to |
| 293 |
|
* support faster state push-down. |
| 294 |
|
*/ |
| 295 |
|
private final Phaser root; |
| 340 |
|
} |
| 341 |
|
|
| 342 |
|
/** |
| 343 |
< |
* Creates a new Phaser without any initially registered parties, |
| 343 |
> |
* Creates a new phaser without any initially registered parties, |
| 344 |
|
* initial phase number 0, and no parent. Any thread using this |
| 345 |
< |
* Phaser will need to first register for it. |
| 345 |
> |
* phaser will need to first register for it. |
| 346 |
|
*/ |
| 347 |
|
public Phaser() { |
| 348 |
|
this(null); |
| 349 |
|
} |
| 350 |
|
|
| 351 |
|
/** |
| 352 |
< |
* Creates a new Phaser with the given numbers of registered |
| 352 |
> |
* Creates a new phaser with the given numbers of registered |
| 353 |
|
* unarrived parties, initial phase number 0, and no parent. |
| 354 |
|
* |
| 355 |
|
* @param parties the number of parties required to trip barrier |
| 361 |
|
} |
| 362 |
|
|
| 363 |
|
/** |
| 364 |
< |
* Creates a new Phaser with the given parent, without any |
| 364 |
> |
* Creates a new phaser with the given parent, without any |
| 365 |
|
* initially registered parties. If parent is non-null this phaser |
| 366 |
|
* is registered with the parent and its initial phase number is |
| 367 |
|
* the same as that of parent phaser. |
| 381 |
|
} |
| 382 |
|
|
| 383 |
|
/** |
| 384 |
< |
* Creates a new Phaser with the given parent and numbers of |
| 384 |
> |
* Creates a new phaser with the given parent and numbers of |
| 385 |
|
* registered unarrived parties. If parent is non-null, this phaser |
| 386 |
|
* is registered with the parent and its initial phase number is |
| 387 |
|
* the same as that of parent phaser. |
| 408 |
|
/** |
| 409 |
|
* Adds a new unarrived party to this phaser. |
| 410 |
|
* |
| 411 |
< |
* @return the current barrier phase number upon registration |
| 411 |
> |
* @return the arrival phase number to which this registration applied |
| 412 |
|
* @throws IllegalStateException if attempting to register more |
| 413 |
|
* than the maximum supported number of parties |
| 414 |
|
*/ |
| 420 |
|
* Adds the given number of new unarrived parties to this phaser. |
| 421 |
|
* |
| 422 |
|
* @param parties the number of parties required to trip barrier |
| 423 |
< |
* @return the current barrier phase number upon registration |
| 423 |
> |
* @return the arrival phase number to which this registration applied |
| 424 |
|
* @throws IllegalStateException if attempting to register more |
| 425 |
|
* than the maximum supported number of parties |
| 426 |
|
*/ |
| 455 |
|
|
| 456 |
|
/** |
| 457 |
|
* Arrives at the barrier, but does not wait for others. (You can |
| 458 |
< |
* in turn wait for others via {@link #awaitAdvance}). |
| 458 |
> |
* in turn wait for others via {@link #awaitAdvance}). It is an |
| 459 |
> |
* unenforced usage error for an unregistered party to invoke this |
| 460 |
> |
* method. |
| 461 |
|
* |
| 462 |
< |
* @return the barrier phase number upon entry to this method, or a |
| 421 |
< |
* negative value if terminated |
| 462 |
> |
* @return the arrival phase number, or a negative value if terminated |
| 463 |
|
* @throws IllegalStateException if not terminated and the number |
| 464 |
|
* of unarrived parties would become negative |
| 465 |
|
*/ |
| 504 |
|
} |
| 505 |
|
|
| 506 |
|
/** |
| 507 |
< |
* Arrives at the barrier, and deregisters from it, without |
| 508 |
< |
* waiting for others. Deregistration reduces number of parties |
| 507 |
> |
* Arrives at the barrier and deregisters from it without waiting |
| 508 |
> |
* for others. Deregistration reduces the number of parties |
| 509 |
|
* required to trip the barrier in future phases. If this phaser |
| 510 |
|
* has a parent, and deregistration causes this phaser to have |
| 511 |
< |
* zero parties, this phaser is also deregistered from its parent. |
| 511 |
> |
* zero parties, this phaser also arrives at and is deregistered |
| 512 |
> |
* from its parent. It is an unenforced usage error for an |
| 513 |
> |
* unregistered party to invoke this method. |
| 514 |
|
* |
| 515 |
< |
* @return the current barrier phase number upon entry to |
| 473 |
< |
* this method, or a negative value if terminated |
| 515 |
> |
* @return the arrival phase number, or a negative value if terminated |
| 516 |
|
* @throws IllegalStateException if not terminated and the number |
| 517 |
|
* of registered or unarrived parties would become negative |
| 518 |
|
*/ |
| 562 |
|
|
| 563 |
|
/** |
| 564 |
|
* Arrives at the barrier and awaits others. Equivalent in effect |
| 565 |
< |
* to {@code awaitAdvance(arrive())}. If you instead need to |
| 566 |
< |
* await with interruption of timeout, and/or deregister upon |
| 567 |
< |
* arrival, you can arrange them using analogous constructions. |
| 565 |
> |
* to {@code awaitAdvance(arrive())}. If you need to await with |
| 566 |
> |
* interruption or timeout, you can arrange this with an analogous |
| 567 |
> |
* construction using one of the other forms of the awaitAdvance |
| 568 |
> |
* method. If instead you need to deregister upon arrival use |
| 569 |
> |
* {@code arriveAndDeregister}. It is an unenforced usage error |
| 570 |
> |
* for an unregistered party to invoke this method. |
| 571 |
|
* |
| 572 |
< |
* @return the phase on entry to this method |
| 572 |
> |
* @return the arrival phase number, or a negative number if terminated |
| 573 |
|
* @throws IllegalStateException if not terminated and the number |
| 574 |
|
* of unarrived parties would become negative |
| 575 |
|
*/ |
| 578 |
|
} |
| 579 |
|
|
| 580 |
|
/** |
| 581 |
< |
* Awaits the phase of the barrier to advance from the given |
| 582 |
< |
* value, or returns immediately if argument is negative or this |
| 583 |
< |
* barrier is terminated. |
| 584 |
< |
* |
| 585 |
< |
* @param phase the phase on entry to this method |
| 586 |
< |
* @return the phase on exit from this method |
| 581 |
> |
* Awaits the phase of the barrier to advance from the given phase |
| 582 |
> |
* value, returning immediately if the current phase of the |
| 583 |
> |
* barrier is not equal to the given phase value or this barrier |
| 584 |
> |
* is terminated. It is an unenforced usage error for an |
| 585 |
> |
* unregistered party to invoke this method. |
| 586 |
> |
* |
| 587 |
> |
* @param phase an arrival phase number, or negative value if |
| 588 |
> |
* terminated; this argument is normally the value returned by a |
| 589 |
> |
* previous call to {@code arrive} or its variants |
| 590 |
> |
* @return the next arrival phase number, or a negative value |
| 591 |
> |
* if terminated or argument is negative |
| 592 |
|
*/ |
| 593 |
|
public int awaitAdvance(int phase) { |
| 594 |
|
if (phase < 0) |
| 604 |
|
} |
| 605 |
|
|
| 606 |
|
/** |
| 607 |
< |
* Awaits the phase of the barrier to advance from the given |
| 608 |
< |
* value, or returns immediately if argument is negative or this |
| 609 |
< |
* barrier is terminated, or throws InterruptedException if |
| 610 |
< |
* interrupted while waiting. |
| 611 |
< |
* |
| 612 |
< |
* @param phase the phase on entry to this method |
| 613 |
< |
* @return the phase on exit from this method |
| 607 |
> |
* Awaits the phase of the barrier to advance from the given phase |
| 608 |
> |
* value, throwing {@code InterruptedException} if interrupted |
| 609 |
> |
* while waiting, or returning immediately if the current phase of |
| 610 |
> |
* the barrier is not equal to the given phase value or this |
| 611 |
> |
* barrier is terminated. It is an unenforced usage error for an |
| 612 |
> |
* unregistered party to invoke this method. |
| 613 |
> |
* |
| 614 |
> |
* @param phase an arrival phase number, or negative value if |
| 615 |
> |
* terminated; this argument is normally the value returned by a |
| 616 |
> |
* previous call to {@code arrive} or its variants |
| 617 |
> |
* @return the next arrival phase number, or a negative value |
| 618 |
> |
* if terminated or argument is negative |
| 619 |
|
* @throws InterruptedException if thread interrupted while waiting |
| 620 |
|
*/ |
| 621 |
|
public int awaitAdvanceInterruptibly(int phase) |
| 632 |
|
} |
| 633 |
|
|
| 634 |
|
/** |
| 635 |
< |
* Awaits the phase of the barrier to advance from the given value |
| 636 |
< |
* or the given timeout elapses, or returns immediately if |
| 637 |
< |
* argument is negative or this barrier is terminated. |
| 638 |
< |
* |
| 639 |
< |
* @param phase the phase on entry to this method |
| 640 |
< |
* @return the phase on exit from this method |
| 635 |
> |
* Awaits the phase of the barrier to advance from the given phase |
| 636 |
> |
* value or the given timeout to elapse, throwing {@code |
| 637 |
> |
* InterruptedException} if interrupted while waiting, or |
| 638 |
> |
* returning immediately if the current phase of the barrier is |
| 639 |
> |
* not equal to the given phase value or this barrier is |
| 640 |
> |
* terminated. It is an unenforced usage error for an |
| 641 |
> |
* unregistered party to invoke this method. |
| 642 |
> |
* |
| 643 |
> |
* @param phase an arrival phase number, or negative value if |
| 644 |
> |
* terminated; this argument is normally the value returned by a |
| 645 |
> |
* previous call to {@code arrive} or its variants |
| 646 |
> |
* @param timeout how long to wait before giving up, in units of |
| 647 |
> |
* {@code unit} |
| 648 |
> |
* @param unit a {@code TimeUnit} determining how to interpret the |
| 649 |
> |
* {@code timeout} parameter |
| 650 |
> |
* @return the next arrival phase number, or a negative value |
| 651 |
> |
* if terminated or argument is negative |
| 652 |
|
* @throws InterruptedException if thread interrupted while waiting |
| 653 |
|
* @throws TimeoutException if timed out while waiting |
| 654 |
|
*/ |
| 702 |
|
} |
| 703 |
|
|
| 704 |
|
/** |
| 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 |
– |
/** |
| 705 |
|
* Returns the number of parties registered at this barrier. |
| 706 |
|
* |
| 707 |
|
* @return the number of parties |
| 711 |
|
} |
| 712 |
|
|
| 713 |
|
/** |
| 714 |
< |
* Returns the number of parties that have arrived at the current |
| 715 |
< |
* phase of this barrier. |
| 714 |
> |
* Returns the number of registered parties that have arrived at |
| 715 |
> |
* the current phase of this barrier. |
| 716 |
|
* |
| 717 |
|
* @return the number of arrived parties |
| 718 |
|
*/ |
| 731 |
|
} |
| 732 |
|
|
| 733 |
|
/** |
| 734 |
< |
* Returns the parent of this phaser, or null if none. |
| 734 |
> |
* Returns the parent of this phaser, or {@code null} if none. |
| 735 |
|
* |
| 736 |
< |
* @return the parent of this phaser, or null if none |
| 736 |
> |
* @return the parent of this phaser, or {@code null} if none |
| 737 |
|
*/ |
| 738 |
|
public Phaser getParent() { |
| 739 |
|
return parent; |
| 759 |
|
} |
| 760 |
|
|
| 761 |
|
/** |
| 762 |
< |
* Overridable method to perform an action upon phase advance, and |
| 763 |
< |
* to control termination. This method is invoked whenever the |
| 764 |
< |
* barrier is tripped (and thus all other waiting parties are |
| 765 |
< |
* dormant). If it returns true, then, rather than advance the |
| 766 |
< |
* phase number, this barrier will be set to a final termination |
| 767 |
< |
* state, and subsequent calls to {@code isTerminated} will |
| 768 |
< |
* return true. |
| 762 |
> |
* Overridable method to perform an action upon impending phase |
| 763 |
> |
* advance, and to control termination. This method is invoked |
| 764 |
> |
* upon arrival of the party tripping the barrier (when all other |
| 765 |
> |
* waiting parties are dormant). If this method returns {@code |
| 766 |
> |
* true}, then, rather than advance the phase number, this barrier |
| 767 |
> |
* will be set to a final termination state, and subsequent calls |
| 768 |
> |
* to {@link #isTerminated} will return true. Any (unchecked) |
| 769 |
> |
* Exception or Error thrown by an invocation of this method is |
| 770 |
> |
* propagated to the party attempting to trip the barrier, in |
| 771 |
> |
* which case no advance occurs. |
| 772 |
> |
* |
| 773 |
> |
* <p>The arguments to this method provide the state of the phaser |
| 774 |
> |
* prevailing for the current transition. (When called from within |
| 775 |
> |
* an implementation of {@code onAdvance} the values returned by |
| 776 |
> |
* methods such as {@code getPhase} may or may not reliably |
| 777 |
> |
* indicate the state to which this transition applies.) |
| 778 |
|
* |
| 779 |
< |
* <p> The default version returns true when the number of |
| 779 |
> |
* <p>The default version returns {@code true} when the number of |
| 780 |
|
* registered parties is zero. Normally, overrides that arrange |
| 781 |
|
* termination for other reasons should also preserve this |
| 782 |
|
* property. |
| 783 |
|
* |
| 784 |
< |
* <p> You may override this method to perform an action with side |
| 785 |
< |
* effects visible to participating tasks, but it is in general |
| 786 |
< |
* only sensible to do so in designs where all parties register |
| 787 |
< |
* before any arrive, and all {@code awaitAdvance} at each phase. |
| 788 |
< |
* Otherwise, you cannot ensure lack of interference. In |
| 789 |
< |
* particular, this method may be invoked more than once per |
| 790 |
< |
* 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. |
| 784 |
> |
* <p>You may override this method to perform an action with side |
| 785 |
> |
* effects visible to participating tasks, but doing so requires |
| 786 |
> |
* care: Method {@code onAdvance} may be invoked more than once |
| 787 |
> |
* per transition. Further, unless all parties register before |
| 788 |
> |
* any arrive, and all {@link #awaitAdvance} at each phase, then |
| 789 |
> |
* you cannot ensure lack of interference from other parties |
| 790 |
> |
* during the invocation of this method. |
| 791 |
|
* |
| 792 |
|
* @param phase the phase number on entering the barrier |
| 793 |
|
* @param registeredParties the current number of registered parties |
| 992 |
|
return p; |
| 993 |
|
} |
| 994 |
|
|
| 995 |
< |
// Unsafe mechanics for jsr166y 3rd party package. |
| 995 |
> |
// Unsafe mechanics |
| 996 |
> |
|
| 997 |
> |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
| 998 |
> |
private static final long stateOffset = |
| 999 |
> |
objectFieldOffset("state", Phaser.class); |
| 1000 |
> |
|
| 1001 |
> |
private final boolean casState(long cmp, long val) { |
| 1002 |
> |
return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val); |
| 1003 |
> |
} |
| 1004 |
> |
|
| 1005 |
> |
private static long objectFieldOffset(String field, Class<?> klazz) { |
| 1006 |
> |
try { |
| 1007 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
| 1008 |
> |
} catch (NoSuchFieldException e) { |
| 1009 |
> |
// Convert Exception to corresponding Error |
| 1010 |
> |
NoSuchFieldError error = new NoSuchFieldError(field); |
| 1011 |
> |
error.initCause(e); |
| 1012 |
> |
throw error; |
| 1013 |
> |
} |
| 1014 |
> |
} |
| 1015 |
> |
|
| 1016 |
> |
/** |
| 1017 |
> |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
| 1018 |
> |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
| 1019 |
> |
* into a jdk. |
| 1020 |
> |
* |
| 1021 |
> |
* @return a sun.misc.Unsafe |
| 1022 |
> |
*/ |
| 1023 |
|
private static sun.misc.Unsafe getUnsafe() { |
| 1024 |
|
try { |
| 1025 |
|
return sun.misc.Unsafe.getUnsafe(); |
| 1026 |
|
} catch (SecurityException se) { |
| 1027 |
|
try { |
| 1028 |
|
return java.security.AccessController.doPrivileged |
| 1029 |
< |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
| 1029 |
> |
(new java.security |
| 1030 |
> |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
| 1031 |
|
public sun.misc.Unsafe run() throws Exception { |
| 1032 |
< |
return getUnsafeByReflection(); |
| 1032 |
> |
java.lang.reflect.Field f = sun.misc |
| 1033 |
> |
.Unsafe.class.getDeclaredField("theUnsafe"); |
| 1034 |
> |
f.setAccessible(true); |
| 1035 |
> |
return (sun.misc.Unsafe) f.get(null); |
| 1036 |
|
}}); |
| 1037 |
|
} catch (java.security.PrivilegedActionException e) { |
| 1038 |
|
throw new RuntimeException("Could not initialize intrinsics", |
| 1040 |
|
} |
| 1041 |
|
} |
| 1042 |
|
} |
| 950 |
– |
|
| 951 |
– |
private static sun.misc.Unsafe getUnsafeByReflection() |
| 952 |
– |
throws NoSuchFieldException, IllegalAccessException { |
| 953 |
– |
java.lang.reflect.Field f = |
| 954 |
– |
sun.misc.Unsafe.class.getDeclaredField("theUnsafe"); |
| 955 |
– |
f.setAccessible(true); |
| 956 |
– |
return (sun.misc.Unsafe) f.get(null); |
| 957 |
– |
} |
| 958 |
– |
|
| 959 |
– |
private static long fieldOffset(String fieldName, Class<?> klazz) { |
| 960 |
– |
try { |
| 961 |
– |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName)); |
| 962 |
– |
} catch (NoSuchFieldException e) { |
| 963 |
– |
// Convert Exception to Error |
| 964 |
– |
NoSuchFieldError error = new NoSuchFieldError(fieldName); |
| 965 |
– |
error.initCause(e); |
| 966 |
– |
throw error; |
| 967 |
– |
} |
| 968 |
– |
} |
| 969 |
– |
|
| 970 |
– |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
| 971 |
– |
static final long stateOffset = |
| 972 |
– |
fieldOffset("state", Phaser.class); |
| 973 |
– |
|
| 974 |
– |
final boolean casState(long cmp, long val) { |
| 975 |
– |
return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val); |
| 976 |
– |
} |
| 1043 |
|
} |
