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package jsr166y; |
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import java.util.concurrent.*; |
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import java.util.concurrent.atomic.*; |
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import java.util.concurrent.atomic.AtomicReference; |
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import java.util.concurrent.locks.LockSupport; |
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import sun.misc.Unsafe; |
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import java.lang.reflect.*; |
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/** |
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* A reusable synchronization barrier, similar in functionality to a |
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* A reusable synchronization barrier, similar in functionality to |
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* {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and |
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* {@link java.util.concurrent.CountDownLatch CountDownLatch} |
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* but supporting more flexible usage. |
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* |
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* <ul> |
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* |
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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 |
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* 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 |
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* Phaser} may be repeatedly awaited. Method {@link |
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* #arriveAndAwaitAdvance} has effect analogous to {@link |
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* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each |
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* 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 |
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* 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> |
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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. |
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* |
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* <li> Awaiting others. Method {@code awaitAdvance} requires an |
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* argument indicating the entry phase, and returns when the |
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* barrier advances to a new phase. |
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* </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 |
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* is performed and the phase advances. Barrier actions, |
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* 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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* |
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* </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. |
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* |
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* <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 |
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* 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 |
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* 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 |
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* number reaches a threshold. Method {@code forceTermination} is also |
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* 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 |
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* advance, and indicating (via a negative phase value) that execution |
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* 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 |
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* the current phase number reaches a threshold. Method {@link |
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* #forceTermination} is also available to abruptly release waiting |
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* threads and allow them to terminate. |
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* |
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* <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 |
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* in tree structures) to reduce contention. Phasers with large |
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* numbers of parties that would otherwise experience heavy |
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* 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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* |
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* <li> By default, {@code awaitAdvance} continues to wait even if |
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* the waiting thread is interrupted. And unlike the case in |
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* CyclicBarriers, exceptions encountered while tasks wait |
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* interruptibly or with timeout do not change the state of the |
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* barrier. If necessary, you can perform any associated recovery |
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* within handlers of those exceptions, often after invoking |
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* {@code forceTermination}. |
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* |
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* <li>Phasers ensure lack of starvation when used by ForkJoinTasks. |
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* |
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* </ul> |
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* synchronization contention costs may instead be set up so that |
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* groups of sub-phasers share a common parent. This may greatly |
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* increase throughput even though it incurs greater per-operation |
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* overhead. |
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* |
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* <p><b>Monitoring.</b> While synchronization methods may be invoked |
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* 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 |
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* #getRegisteredParties} parties in total, of which {@link |
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* #getArrivedParties} have arrived at the current phase ({@link |
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* #getPhase}). When the remaining ({@link #getUnarrivedParties}) |
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* parties arrive, the phase advances. The values returned by these |
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* methods may reflect transient states and so are not in general |
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* 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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* |
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* <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 parties. |
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* The typical idiom is for the method setting this up to first |
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* 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) { |
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* void runTasks(List<Runnable> tasks) { |
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* final Phaser phaser = new Phaser(1); // "1" to register self |
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* for (Runnable r : list) { |
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* // create and start threads |
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* for (Runnable task : tasks) { |
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* phaser.register(); |
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* new Thread() { |
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* public void run() { |
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* phaser.arriveAndAwaitAdvance(); // await all creation |
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* r.run(); |
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* phaser.arriveAndDeregister(); // signal completion |
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* task.run(); |
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* } |
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* }.start(); |
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* } |
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* |
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* doSomethingOnBehalfOfWorkers(); |
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* phaser.arrive(); // allow threads to start |
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* int p = phaser.arriveAndDeregister(); // deregister self ... |
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* p = phaser.awaitAdvance(p); // ... and await arrival |
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* otherActions(); // do other things while tasks execute |
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* phaser.awaitAdvance(p); // await final completion |
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* // allow threads to start and deregister self |
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* phaser.arriveAndDeregister(); |
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* }}</pre> |
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* |
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* <p>One way to cause a set of threads to repeatedly perform actions |
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* for a given number of iterations is to override {@code onAdvance}: |
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* |
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* <pre> {@code |
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* void startTasks(List<Runnable> list, final int iterations) { |
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* void startTasks(List<Runnable> tasks, final int iterations) { |
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* final Phaser phaser = new Phaser() { |
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* public boolean onAdvance(int phase, int registeredParties) { |
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* protected boolean onAdvance(int phase, int registeredParties) { |
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* return phase >= iterations || registeredParties == 0; |
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* } |
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* }; |
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* phaser.register(); |
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* for (Runnable r : list) { |
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* for (final Runnable task : tasks) { |
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* phaser.register(); |
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* new Thread() { |
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* public void run() { |
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* do { |
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* r.run(); |
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* task.run(); |
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* phaser.arriveAndAwaitAdvance(); |
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* } while(!phaser.isTerminated(); |
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* } while (!phaser.isTerminated()); |
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* } |
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* }.start(); |
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* } |
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* phaser.arriveAndDeregister(); // deregister self, don't wait |
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* }}</pre> |
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* |
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* <p> To create a set of tasks using a tree of Phasers, |
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* If the main task must later await termination, it |
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* may re-register and then execute a similar loop: |
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* <pre> {@code |
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* // ... |
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* phaser.register(); |
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* while (!phaser.isTerminated()) |
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* phaser.arriveAndAwaitAdvance();}</pre> |
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* |
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* <p>Related constructions may be used to await particular phase numbers |
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* in contexts where you are sure that the phase will never wrap around |
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* {@code Integer.MAX_VALUE}. For example: |
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* |
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* <pre> {@code |
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* void awaitPhase(Phaser phaser, int phase) { |
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* int p = phaser.register(); // assumes caller not already registered |
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* while (p < phase) { |
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* if (phaser.isTerminated()) |
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* // ... deal with unexpected termination |
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* else |
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* p = phaser.arriveAndAwaitAdvance(); |
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* } |
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* phaser.arriveAndDeregister(); |
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* }}</pre> |
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* |
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* |
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* <p>To create a set of tasks using a tree of phasers, |
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* you could use code of the following form, assuming a |
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* Task class with a constructor accepting a Phaser that |
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* it registers for upon construction: |
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* Task class with a constructor accepting a phaser that |
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* it registers with upon construction: |
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* |
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* <pre> {@code |
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* void build(Task[] actions, int lo, int hi, Phaser b) { |
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* int step = (hi - lo) / TASKS_PER_PHASER; |
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* if (step > 1) { |
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* int i = lo; |
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* while (i < hi) { |
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* int r = Math.min(i + step, hi); |
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* build(actions, i, r, new Phaser(b)); |
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* i = r; |
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* void build(Task[] actions, int lo, int hi, Phaser ph) { |
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* if (hi - lo > TASKS_PER_PHASER) { |
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* for (int i = lo; i < hi; i += TASKS_PER_PHASER) { |
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* int j = Math.min(i + TASKS_PER_PHASER, hi); |
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* build(actions, i, j, new Phaser(ph)); |
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* } |
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* } else { |
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* for (int i = lo; i < hi; ++i) |
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* actions[i] = new Task(b); |
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* // assumes new Task(b) performs b.register() |
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* actions[i] = new Task(ph); |
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* // assumes new Task(ph) performs ph.register() |
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* } |
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* } |
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* // .. initially called, for n tasks via |
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* be appropriate for extremely small per-barrier task bodies (thus |
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* high rates), or up to hundreds for extremely large ones. |
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* |
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* </pre> |
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* |
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* <p><b>Implementation notes</b>: This implementation restricts the |
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* maximum number of parties to 65535. Attempts to register additional |
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* parties result in IllegalStateExceptions. However, you can and |
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* parties result in {@code IllegalStateException}. However, you can and |
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* should create tiered phasers to accommodate arbitrarily large sets |
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* of participants. |
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* |
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* @since 1.7 |
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* @author Doug Lea |
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*/ |
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public class Phaser { |
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/* |
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*/ |
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private volatile long state; |
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private static final int ushortBits = 16; |
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private static final int ushortMask = 0xffff; |
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private static final int phaseMask = 0x7fffffff; |
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|
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private static int unarrivedOf(long s) { |
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return (int)(s & ushortMask); |
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return (int) (s & ushortMask); |
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} |
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|
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private static int partiesOf(long s) { |
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return ((int)s) >>> 16; |
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return ((int) s) >>> 16; |
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} |
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|
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private static int phaseOf(long s) { |
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return (int)(s >>> 32); |
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return (int) (s >>> 32); |
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} |
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private static int arrivedOf(long s) { |
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} |
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private static long stateFor(int phase, int parties, int unarrived) { |
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return ((((long)phase) << 32) | (((long)parties) << 16) | |
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(long)unarrived); |
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return ((((long) phase) << 32) | (((long) parties) << 16) | |
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(long) unarrived); |
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} |
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private static long trippedStateFor(int phase, int parties) { |
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long lp = (long)parties; |
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return (((long)phase) << 32) | (lp << 16) | lp; |
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long lp = (long) parties; |
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return (((long) phase) << 32) | (lp << 16) | lp; |
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} |
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|
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/** |
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* Returns message string for bad bounds exceptions |
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* Returns message string for bad bounds exceptions. |
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*/ |
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private static String badBounds(int parties, int unarrived) { |
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return ("Attempt to set " + unarrived + |
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private final Phaser parent; |
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|
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/** |
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* The root of Phaser tree. Equals this if not in a tree. Used to |
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* The root of phaser tree. Equals this if not in a tree. Used to |
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* support faster state push-down. |
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*/ |
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private final Phaser root; |
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private final AtomicReference<QNode> oddQ = new AtomicReference<QNode>(); |
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|
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private AtomicReference<QNode> queueFor(int phase) { |
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return (phase & 1) == 0? evenQ : oddQ; |
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return ((phase & 1) == 0) ? evenQ : oddQ; |
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} |
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|
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/** |
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* root if necessary. |
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*/ |
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private long getReconciledState() { |
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return parent == null? state : reconcileState(); |
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return (parent == null) ? state : reconcileState(); |
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} |
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/** |
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} |
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|
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/** |
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* Creates a new Phaser without any initially registered parties, |
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* Creates a new phaser without any initially registered parties, |
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* initial phase number 0, and no parent. Any thread using this |
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* Phaser will need to first register for it. |
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* phaser will need to first register for it. |
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*/ |
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public Phaser() { |
345 |
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this(null); |
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} |
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|
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/** |
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* Creates a new Phaser with the given numbers of registered |
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* Creates a new phaser with the given number of registered |
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* unarrived parties, initial phase number 0, and no parent. |
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* @param parties the number of parties required to trip barrier. |
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* |
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* @param parties the number of parties required to trip barrier |
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* @throws IllegalArgumentException if parties less than zero |
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* or greater than the maximum number of parties supported. |
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* or greater than the maximum number of parties supported |
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*/ |
356 |
|
public Phaser(int parties) { |
357 |
|
this(null, parties); |
358 |
|
} |
359 |
|
|
360 |
|
/** |
361 |
< |
* Creates a new Phaser with the given parent, without any |
361 |
> |
* Creates a new phaser with the given parent, without any |
362 |
|
* initially registered parties. If parent is non-null this phaser |
363 |
|
* is registered with the parent and its initial phase number is |
364 |
|
* the same as that of parent phaser. |
365 |
< |
* @param parent the parent phaser. |
365 |
> |
* |
366 |
> |
* @param parent the parent phaser |
367 |
|
*/ |
368 |
|
public Phaser(Phaser parent) { |
369 |
|
int phase = 0; |
378 |
|
} |
379 |
|
|
380 |
|
/** |
381 |
< |
* Creates a new Phaser with the given parent and numbers of |
382 |
< |
* registered unarrived parties. If parent is non-null this phaser |
381 |
> |
* Creates a new phaser with the given parent and number of |
382 |
> |
* registered unarrived parties. If parent is non-null, this phaser |
383 |
|
* is registered with the parent and its initial phase number is |
384 |
|
* the same as that of parent phaser. |
385 |
< |
* @param parent the parent phaser. |
386 |
< |
* @param parties the number of parties required to trip barrier. |
385 |
> |
* |
386 |
> |
* @param parent the parent phaser |
387 |
> |
* @param parties the number of parties required to trip barrier |
388 |
|
* @throws IllegalArgumentException if parties less than zero |
389 |
< |
* or greater than the maximum number of parties supported. |
389 |
> |
* or greater than the maximum number of parties supported |
390 |
|
*/ |
391 |
|
public Phaser(Phaser parent, int parties) { |
392 |
|
if (parties < 0 || parties > ushortMask) |
404 |
|
|
405 |
|
/** |
406 |
|
* Adds a new unarrived party to this phaser. |
407 |
< |
* @return the current barrier phase number upon registration |
407 |
> |
* |
408 |
> |
* @return the arrival phase number to which this registration applied |
409 |
|
* @throws IllegalStateException if attempting to register more |
410 |
< |
* than the maximum supported number of parties. |
410 |
> |
* than the maximum supported number of parties |
411 |
|
*/ |
412 |
|
public int register() { |
413 |
|
return doRegister(1); |
415 |
|
|
416 |
|
/** |
417 |
|
* Adds the given number of new unarrived parties to this phaser. |
418 |
< |
* @param parties the number of parties required to trip barrier. |
419 |
< |
* @return the current barrier phase number upon registration |
418 |
> |
* |
419 |
> |
* @param parties the number of additional parties required to trip barrier |
420 |
> |
* @return the arrival phase number to which this registration applied |
421 |
|
* @throws IllegalStateException if attempting to register more |
422 |
< |
* than the maximum supported number of parties. |
422 |
> |
* than the maximum supported number of parties |
423 |
> |
* @throws IllegalArgumentException if {@code parties < 0} |
424 |
|
*/ |
425 |
|
public int bulkRegister(int parties) { |
426 |
|
if (parties < 0) |
453 |
|
|
454 |
|
/** |
455 |
|
* Arrives at the barrier, but does not wait for others. (You can |
456 |
< |
* in turn wait for others via {@link #awaitAdvance}). |
456 |
> |
* in turn wait for others via {@link #awaitAdvance}). It is an |
457 |
> |
* unenforced usage error for an unregistered party to invoke this |
458 |
> |
* method. |
459 |
|
* |
460 |
< |
* @return the barrier phase number upon entry to this method, or a |
414 |
< |
* negative value if terminated; |
460 |
> |
* @return the arrival phase number, or a negative value if terminated |
461 |
|
* @throws IllegalStateException if not terminated and the number |
462 |
< |
* of unarrived parties would become negative. |
462 |
> |
* of unarrived parties would become negative |
463 |
|
*/ |
464 |
|
public int arrive() { |
465 |
|
int phase; |
479 |
|
if (par == null) { // directly trip |
480 |
|
if (casState |
481 |
|
(s, |
482 |
< |
trippedStateFor(onAdvance(phase, parties)? -1 : |
482 |
> |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
483 |
|
((phase + 1) & phaseMask), parties))) { |
484 |
|
releaseWaiters(phase); |
485 |
|
break; |
502 |
|
} |
503 |
|
|
504 |
|
/** |
505 |
< |
* Arrives at the barrier, and deregisters from it, without |
506 |
< |
* waiting for others. Deregistration reduces number of parties |
505 |
> |
* Arrives at the barrier and deregisters from it without waiting |
506 |
> |
* for others. Deregistration reduces the number of parties |
507 |
|
* required to trip the barrier in future phases. If this phaser |
508 |
|
* has a parent, and deregistration causes this phaser to have |
509 |
< |
* zero parties, this phaser is also deregistered from its parent. |
509 |
> |
* zero parties, this phaser also arrives at and is deregistered |
510 |
> |
* from its parent. It is an unenforced usage error for an |
511 |
> |
* unregistered party to invoke this method. |
512 |
|
* |
513 |
< |
* @return the current barrier phase number upon entry to |
466 |
< |
* this method, or a negative value if terminated; |
513 |
> |
* @return the arrival phase number, or a negative value if terminated |
514 |
|
* @throws IllegalStateException if not terminated and the number |
515 |
< |
* of registered or unarrived parties would become negative. |
515 |
> |
* of registered or unarrived parties would become negative |
516 |
|
*/ |
517 |
|
public int arriveAndDeregister() { |
518 |
|
// similar code to arrive, but too different to merge |
541 |
|
if (unarrived == 0) { |
542 |
|
if (casState |
543 |
|
(s, |
544 |
< |
trippedStateFor(onAdvance(phase, parties)? -1 : |
544 |
> |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
545 |
|
((phase + 1) & phaseMask), parties))) { |
546 |
|
releaseWaiters(phase); |
547 |
|
break; |
560 |
|
|
561 |
|
/** |
562 |
|
* Arrives at the barrier and awaits others. Equivalent in effect |
563 |
< |
* to {@code awaitAdvance(arrive())}. If you instead need to |
564 |
< |
* await with interruption of timeout, and/or deregister upon |
565 |
< |
* arrival, you can arrange them using analogous constructions. |
566 |
< |
* @return the phase on entry to this method |
563 |
> |
* to {@code awaitAdvance(arrive())}. If you need to await with |
564 |
> |
* interruption or timeout, you can arrange this with an analogous |
565 |
> |
* construction using one of the other forms of the {@code |
566 |
> |
* awaitAdvance} method. If instead you need to deregister upon |
567 |
> |
* arrival, use {@link #arriveAndDeregister}. It is an unenforced |
568 |
> |
* usage error for an unregistered party to invoke this method. |
569 |
> |
* |
570 |
> |
* @return the arrival phase number, or a negative number if terminated |
571 |
|
* @throws IllegalStateException if not terminated and the number |
572 |
< |
* of unarrived parties would become negative. |
572 |
> |
* of unarrived parties would become negative |
573 |
|
*/ |
574 |
|
public int arriveAndAwaitAdvance() { |
575 |
|
return awaitAdvance(arrive()); |
576 |
|
} |
577 |
|
|
578 |
|
/** |
579 |
< |
* Awaits the phase of the barrier to advance from the given |
580 |
< |
* value, or returns immediately if argument is negative or this |
581 |
< |
* barrier is terminated. |
582 |
< |
* @param phase the phase on entry to this method |
583 |
< |
* @return the phase on exit from this method |
579 |
> |
* Awaits the phase of the barrier to advance from the given phase |
580 |
> |
* value, returning immediately if the current phase of the |
581 |
> |
* barrier is not equal to the given phase value or this barrier |
582 |
> |
* is terminated. It is an unenforced usage error for an |
583 |
> |
* unregistered party to invoke this method. |
584 |
> |
* |
585 |
> |
* @param phase an arrival phase number, or negative value if |
586 |
> |
* terminated; this argument is normally the value returned by a |
587 |
> |
* previous call to {@code arrive} or its variants |
588 |
> |
* @return the next arrival phase number, or a negative value |
589 |
> |
* if terminated or argument is negative |
590 |
|
*/ |
591 |
|
public int awaitAdvance(int phase) { |
592 |
|
if (phase < 0) |
602 |
|
} |
603 |
|
|
604 |
|
/** |
605 |
< |
* Awaits the phase of the barrier to advance from the given |
606 |
< |
* value, or returns immediately if argument is negative or this |
607 |
< |
* barrier is terminated, or throws InterruptedException if |
608 |
< |
* interrupted while waiting. |
609 |
< |
* @param phase the phase on entry to this method |
610 |
< |
* @return the phase on exit from this method |
605 |
> |
* Awaits the phase of the barrier to advance from the given phase |
606 |
> |
* value, throwing {@code InterruptedException} if interrupted |
607 |
> |
* while waiting, or returning immediately if the current phase of |
608 |
> |
* the barrier is not equal to the given phase value or this |
609 |
> |
* barrier is terminated. It is an unenforced usage error for an |
610 |
> |
* unregistered party to invoke this method. |
611 |
> |
* |
612 |
> |
* @param phase an arrival phase number, or negative value if |
613 |
> |
* terminated; this argument is normally the value returned by a |
614 |
> |
* previous call to {@code arrive} or its variants |
615 |
> |
* @return the next arrival phase number, or a negative value |
616 |
> |
* if terminated or argument is negative |
617 |
|
* @throws InterruptedException if thread interrupted while waiting |
618 |
|
*/ |
619 |
|
public int awaitAdvanceInterruptibly(int phase) |
630 |
|
} |
631 |
|
|
632 |
|
/** |
633 |
< |
* Awaits the phase of the barrier to advance from the given value |
634 |
< |
* or the given timeout elapses, or returns immediately if |
635 |
< |
* argument is negative or this barrier is terminated. |
636 |
< |
* @param phase the phase on entry to this method |
637 |
< |
* @return the phase on exit from this method |
633 |
> |
* Awaits the phase of the barrier to advance from the given phase |
634 |
> |
* value or the given timeout to elapse, throwing {@code |
635 |
> |
* InterruptedException} if interrupted while waiting, or |
636 |
> |
* returning immediately if the current phase of the barrier is |
637 |
> |
* not equal to the given phase value or this barrier is |
638 |
> |
* terminated. It is an unenforced usage error for an |
639 |
> |
* unregistered party to invoke this method. |
640 |
> |
* |
641 |
> |
* @param phase an arrival phase number, or negative value if |
642 |
> |
* terminated; this argument is normally the value returned by a |
643 |
> |
* previous call to {@code arrive} or its variants |
644 |
> |
* @param timeout how long to wait before giving up, in units of |
645 |
> |
* {@code unit} |
646 |
> |
* @param unit a {@code TimeUnit} determining how to interpret the |
647 |
> |
* {@code timeout} parameter |
648 |
> |
* @return the next arrival phase number, or a negative value |
649 |
> |
* if terminated or argument is negative |
650 |
|
* @throws InterruptedException if thread interrupted while waiting |
651 |
|
* @throws TimeoutException if timed out while waiting |
652 |
|
*/ |
653 |
< |
public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit) |
653 |
> |
public int awaitAdvanceInterruptibly(int phase, |
654 |
> |
long timeout, TimeUnit unit) |
655 |
|
throws InterruptedException, TimeoutException { |
656 |
|
if (phase < 0) |
657 |
|
return phase; |
692 |
|
* Returns the current phase number. The maximum phase number is |
693 |
|
* {@code Integer.MAX_VALUE}, after which it restarts at |
694 |
|
* zero. Upon termination, the phase number is negative. |
695 |
+ |
* |
696 |
|
* @return the phase number, or a negative value if terminated |
697 |
|
*/ |
698 |
|
public final int getPhase() { |
700 |
|
} |
701 |
|
|
702 |
|
/** |
626 |
– |
* Returns {@code true} if the current phase number equals the given phase. |
627 |
– |
* @param phase the phase |
628 |
– |
* @return {@code true} if the current phase number equals the given phase |
629 |
– |
*/ |
630 |
– |
public final boolean hasPhase(int phase) { |
631 |
– |
return phaseOf(getReconciledState()) == phase; |
632 |
– |
} |
633 |
– |
|
634 |
– |
/** |
703 |
|
* Returns the number of parties registered at this barrier. |
704 |
+ |
* |
705 |
|
* @return the number of parties |
706 |
|
*/ |
707 |
|
public int getRegisteredParties() { |
709 |
|
} |
710 |
|
|
711 |
|
/** |
712 |
< |
* Returns the number of parties that have arrived at the current |
713 |
< |
* phase of this barrier. |
712 |
> |
* Returns the number of registered parties that have arrived at |
713 |
> |
* the current phase of this barrier. |
714 |
> |
* |
715 |
|
* @return the number of arrived parties |
716 |
|
*/ |
717 |
|
public int getArrivedParties() { |
721 |
|
/** |
722 |
|
* Returns the number of registered parties that have not yet |
723 |
|
* arrived at the current phase of this barrier. |
724 |
+ |
* |
725 |
|
* @return the number of unarrived parties |
726 |
|
*/ |
727 |
|
public int getUnarrivedParties() { |
729 |
|
} |
730 |
|
|
731 |
|
/** |
732 |
< |
* Returns the parent of this phaser, or null if none. |
733 |
< |
* @return the parent of this phaser, or null if none |
732 |
> |
* Returns the parent of this phaser, or {@code null} if none. |
733 |
> |
* |
734 |
> |
* @return the parent of this phaser, or {@code null} if none |
735 |
|
*/ |
736 |
|
public Phaser getParent() { |
737 |
|
return parent; |
740 |
|
/** |
741 |
|
* Returns the root ancestor of this phaser, which is the same as |
742 |
|
* this phaser if it has no parent. |
743 |
+ |
* |
744 |
|
* @return the root ancestor of this phaser |
745 |
|
*/ |
746 |
|
public Phaser getRoot() { |
749 |
|
|
750 |
|
/** |
751 |
|
* Returns {@code true} if this barrier has been terminated. |
752 |
+ |
* |
753 |
|
* @return {@code true} if this barrier has been terminated |
754 |
|
*/ |
755 |
|
public boolean isTerminated() { |
757 |
|
} |
758 |
|
|
759 |
|
/** |
760 |
< |
* Overridable method to perform an action upon phase advance, and |
761 |
< |
* to control termination. This method is invoked whenever the |
762 |
< |
* barrier is tripped (and thus all other waiting parties are |
763 |
< |
* dormant). If it returns true, then, rather than advance the |
764 |
< |
* phase number, this barrier will be set to a final termination |
765 |
< |
* state, and subsequent calls to {@code isTerminated} will |
766 |
< |
* return true. |
760 |
> |
* Overridable method to perform an action upon impending phase |
761 |
> |
* advance, and to control termination. This method is invoked |
762 |
> |
* upon arrival of the party tripping the barrier (when all other |
763 |
> |
* waiting parties are dormant). If this method returns {@code |
764 |
> |
* true}, then, rather than advance the phase number, this barrier |
765 |
> |
* will be set to a final termination state, and subsequent calls |
766 |
> |
* to {@link #isTerminated} will return true. Any (unchecked) |
767 |
> |
* Exception or Error thrown by an invocation of this method is |
768 |
> |
* propagated to the party attempting to trip the barrier, in |
769 |
> |
* which case no advance occurs. |
770 |
> |
* |
771 |
> |
* <p>The arguments to this method provide the state of the phaser |
772 |
> |
* prevailing for the current transition. (When called from within |
773 |
> |
* an implementation of {@code onAdvance} the values returned by |
774 |
> |
* methods such as {@code getPhase} may or may not reliably |
775 |
> |
* indicate the state to which this transition applies.) |
776 |
|
* |
777 |
< |
* <p> The default version returns true when the number of |
777 |
> |
* <p>The default version returns {@code true} when the number of |
778 |
|
* registered parties is zero. Normally, overrides that arrange |
779 |
|
* termination for other reasons should also preserve this |
780 |
|
* property. |
781 |
|
* |
782 |
< |
* <p> You may override this method to perform an action with side |
783 |
< |
* effects visible to participating tasks, but it is in general |
784 |
< |
* only sensible to do so in designs where all parties register |
785 |
< |
* before any arrive, and all {@code awaitAdvance} at each phase. |
786 |
< |
* Otherwise, you cannot ensure lack of interference. In |
787 |
< |
* particular, this method may be invoked more than once per |
788 |
< |
* transition if other parties successfully register while the |
789 |
< |
* invocation of this method is in progress, thus postponing the |
707 |
< |
* transition until those parties also arrive, re-triggering this |
708 |
< |
* method. |
782 |
> |
* <p>You may override this method to perform an action with side |
783 |
> |
* effects visible to participating tasks, but it is only sensible |
784 |
> |
* to do so in designs where all parties register before any |
785 |
> |
* arrive, and all {@link #awaitAdvance} at each phase. |
786 |
> |
* Otherwise, you cannot ensure lack of interference from other |
787 |
> |
* parties during the invocation of this method. Additionally, |
788 |
> |
* method {@code onAdvance} may be invoked more than once per |
789 |
> |
* transition if registrations are intermixed with arrivals. |
790 |
|
* |
791 |
|
* @param phase the phase number on entering the barrier |
792 |
|
* @param registeredParties the current number of registered parties |
828 |
|
volatile boolean wasInterrupted = false; |
829 |
|
volatile Thread thread; // nulled to cancel wait |
830 |
|
QNode next; |
831 |
+ |
|
832 |
|
QNode(Phaser phaser, int phase, boolean interruptible, |
833 |
|
boolean timed, long startTime, long nanos) { |
834 |
|
this.phaser = phaser; |
839 |
|
this.nanos = nanos; |
840 |
|
thread = Thread.currentThread(); |
841 |
|
} |
842 |
+ |
|
843 |
|
public boolean isReleasable() { |
844 |
|
return (thread == null || |
845 |
|
phaser.getPhase() != phase || |
846 |
|
(interruptible && wasInterrupted) || |
847 |
|
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
848 |
|
} |
849 |
+ |
|
850 |
|
public boolean block() { |
851 |
|
if (Thread.interrupted()) { |
852 |
|
wasInterrupted = true; |
863 |
|
} |
864 |
|
return isReleasable(); |
865 |
|
} |
866 |
+ |
|
867 |
|
void signal() { |
868 |
|
Thread t = thread; |
869 |
|
if (t != null) { |
871 |
|
LockSupport.unpark(t); |
872 |
|
} |
873 |
|
} |
874 |
+ |
|
875 |
|
boolean doWait() { |
876 |
|
if (thread != null) { |
877 |
|
try { |
878 |
< |
ForkJoinPool.managedBlock(this, false); |
878 |
> |
ForkJoinPool.managedBlock(this); |
879 |
|
} catch (InterruptedException ie) { |
880 |
+ |
wasInterrupted = true; // can't currently happen |
881 |
|
} |
882 |
|
} |
883 |
|
return wasInterrupted; |
884 |
|
} |
798 |
– |
|
885 |
|
} |
886 |
|
|
887 |
|
/** |
888 |
< |
* Removes and signals waiting threads from wait queue |
888 |
> |
* Removes and signals waiting threads from wait queue. |
889 |
|
*/ |
890 |
|
private void releaseWaiters(int phase) { |
891 |
|
AtomicReference<QNode> head = queueFor(phase); |
897 |
|
} |
898 |
|
|
899 |
|
/** |
900 |
< |
* Tries to enqueue given node in the appropriate wait queue |
900 |
> |
* Tries to enqueue given node in the appropriate wait queue. |
901 |
> |
* |
902 |
|
* @return true if successful |
903 |
|
*/ |
904 |
|
private boolean tryEnqueue(QNode node) { |
908 |
|
|
909 |
|
/** |
910 |
|
* Enqueues node and waits unless aborted or signalled. |
911 |
+ |
* |
912 |
|
* @return current phase |
913 |
|
*/ |
914 |
|
private int untimedWait(int phase) { |
923 |
|
node = new QNode(this, phase, false, false, 0, 0); |
924 |
|
else if (!queued) |
925 |
|
queued = tryEnqueue(node); |
926 |
< |
else |
927 |
< |
interrupted = node.doWait(); |
926 |
> |
else if (node.doWait()) |
927 |
> |
interrupted = true; |
928 |
|
} |
929 |
|
if (node != null) |
930 |
|
node.thread = null; |
950 |
|
node = new QNode(this, phase, true, false, 0, 0); |
951 |
|
else if (!queued) |
952 |
|
queued = tryEnqueue(node); |
953 |
< |
else |
954 |
< |
interrupted = node.doWait(); |
953 |
> |
else if (node.doWait()) |
954 |
> |
interrupted = true; |
955 |
|
} |
956 |
|
if (node != null) |
957 |
|
node.thread = null; |
982 |
|
node = new QNode(this, phase, true, true, startTime, nanos); |
983 |
|
else if (!queued) |
984 |
|
queued = tryEnqueue(node); |
985 |
< |
else |
986 |
< |
interrupted = node.doWait(); |
985 |
> |
else if (node.doWait()) |
986 |
> |
interrupted = true; |
987 |
|
} |
988 |
|
if (node != null) |
989 |
|
node.thread = null; |
996 |
|
return p; |
997 |
|
} |
998 |
|
|
999 |
< |
// Temporary Unsafe mechanics for preliminary release |
912 |
< |
private static Unsafe getUnsafe() throws Throwable { |
913 |
< |
try { |
914 |
< |
return Unsafe.getUnsafe(); |
915 |
< |
} catch (SecurityException se) { |
916 |
< |
try { |
917 |
< |
return java.security.AccessController.doPrivileged |
918 |
< |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
919 |
< |
public Unsafe run() throws Exception { |
920 |
< |
return getUnsafePrivileged(); |
921 |
< |
}}); |
922 |
< |
} catch (java.security.PrivilegedActionException e) { |
923 |
< |
throw e.getCause(); |
924 |
< |
} |
925 |
< |
} |
926 |
< |
} |
999 |
> |
// Unsafe mechanics |
1000 |
|
|
1001 |
< |
private static Unsafe getUnsafePrivileged() |
1002 |
< |
throws NoSuchFieldException, IllegalAccessException { |
1003 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
931 |
< |
f.setAccessible(true); |
932 |
< |
return (Unsafe) f.get(null); |
933 |
< |
} |
1001 |
> |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1002 |
> |
private static final long stateOffset = |
1003 |
> |
objectFieldOffset("state", Phaser.class); |
1004 |
|
|
1005 |
< |
private static long fieldOffset(String fieldName) |
1006 |
< |
throws NoSuchFieldException { |
937 |
< |
return _unsafe.objectFieldOffset |
938 |
< |
(Phaser.class.getDeclaredField(fieldName)); |
1005 |
> |
private final boolean casState(long cmp, long val) { |
1006 |
> |
return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val); |
1007 |
|
} |
1008 |
|
|
1009 |
< |
static final Unsafe _unsafe; |
942 |
< |
static final long stateOffset; |
943 |
< |
|
944 |
< |
static { |
1009 |
> |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1010 |
|
try { |
1011 |
< |
_unsafe = getUnsafe(); |
1012 |
< |
stateOffset = fieldOffset("state"); |
1013 |
< |
} catch (Throwable e) { |
1014 |
< |
throw new RuntimeException("Could not initialize intrinsics", e); |
1011 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1012 |
> |
} catch (NoSuchFieldException e) { |
1013 |
> |
// Convert Exception to corresponding Error |
1014 |
> |
NoSuchFieldError error = new NoSuchFieldError(field); |
1015 |
> |
error.initCause(e); |
1016 |
> |
throw error; |
1017 |
|
} |
1018 |
|
} |
1019 |
|
|
1020 |
< |
final boolean casState(long cmp, long val) { |
1021 |
< |
return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val); |
1020 |
> |
/** |
1021 |
> |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1022 |
> |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1023 |
> |
* into a jdk. |
1024 |
> |
* |
1025 |
> |
* @return a sun.misc.Unsafe |
1026 |
> |
*/ |
1027 |
> |
private static sun.misc.Unsafe getUnsafe() { |
1028 |
> |
try { |
1029 |
> |
return sun.misc.Unsafe.getUnsafe(); |
1030 |
> |
} catch (SecurityException se) { |
1031 |
> |
try { |
1032 |
> |
return java.security.AccessController.doPrivileged |
1033 |
> |
(new java.security |
1034 |
> |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1035 |
> |
public sun.misc.Unsafe run() throws Exception { |
1036 |
> |
java.lang.reflect.Field f = sun.misc |
1037 |
> |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1038 |
> |
f.setAccessible(true); |
1039 |
> |
return (sun.misc.Unsafe) f.get(null); |
1040 |
> |
}}); |
1041 |
> |
} catch (java.security.PrivilegedActionException e) { |
1042 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
1043 |
> |
e.getCause()); |
1044 |
> |
} |
1045 |
> |
} |
1046 |
|
} |
1047 |
|
} |