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package jsr166y; |
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import java.util.concurrent.*; |
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import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.TimeoutException; |
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import java.util.concurrent.atomic.AtomicReference; |
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import java.util.concurrent.locks.LockSupport; |
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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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* Barrier state representation. Conceptually, a barrier contains |
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* four values: |
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* |
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* * parties -- the number of parties to wait (16 bits) |
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* * unarrived -- the number of parties yet to hit barrier (16 bits) |
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* * phase -- the generation of the barrier (31 bits) |
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* * terminated -- set if barrier is terminated (1 bit) |
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* * unarrived -- the number of parties yet to hit barrier (bits 0-15) |
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* * parties -- the number of parties to wait (bits 16-31) |
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* * phase -- the generation of the barrier (bits 32-62) |
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* * terminated -- set if barrier is terminated (bit 63 / sign) |
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* |
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* However, to efficiently maintain atomicity, these values are |
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* packed into a single (atomic) long. Termination uses the sign |
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* bit of 32 bit representation of phase, so phase is set to -1 on |
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* termination. Good performance relies on keeping state decoding |
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* and encoding simple, and keeping race windows short. |
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* |
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* Note: there are some cheats in arrive() that rely on unarrived |
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* count being lowest 16 bits. |
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*/ |
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private volatile long state; |
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|
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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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private static final int MAX_COUNT = 0xffff; |
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private static final int MAX_PHASE = 0x7fffffff; |
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private static final int PARTIES_SHIFT = 16; |
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private static final int PHASE_SHIFT = 32; |
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private static final long UNARRIVED_MASK = 0xffffL; |
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private static final long PARTIES_MASK = 0xffff0000L; |
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private static final long ONE_ARRIVAL = 1L; |
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private static final long ONE_PARTY = 1L << PARTIES_SHIFT; |
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private static final long TERMINATION_PHASE = -1L << PHASE_SHIFT; |
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|
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// The following unpacking methods are usually manually inlined |
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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 & UNARRIVED_MASK); |
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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 & PARTIES_MASK)) >>> PARTIES_SHIFT; |
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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 >>> PHASE_SHIFT); |
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} |
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private static int arrivedOf(long s) { |
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return partiesOf(s) - unarrivedOf(s); |
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} |
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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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} |
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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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} |
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|
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/** |
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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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" unarrived of " + parties + " parties"); |
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} |
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|
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/** |
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* The parent of this phaser, or null if none |
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*/ |
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private final Phaser parent; |
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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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|
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// Wait queues |
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|
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|
/** |
283 |
|
* Heads of Treiber stacks for waiting threads. To eliminate |
284 |
< |
* contention while releasing some threads while adding others, we |
284 |
> |
* contention when releasing some threads while adding others, we |
285 |
|
* use two of them, alternating across even and odd phases. |
286 |
+ |
* Subphasers share queues with root to speed up releases. |
287 |
|
*/ |
288 |
< |
private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>(); |
289 |
< |
private final AtomicReference<QNode> oddQ = new AtomicReference<QNode>(); |
288 |
> |
private final AtomicReference<QNode> evenQ; |
289 |
> |
private final AtomicReference<QNode> oddQ; |
290 |
|
|
291 |
|
private AtomicReference<QNode> queueFor(int phase) { |
292 |
|
return ((phase & 1) == 0) ? evenQ : oddQ; |
293 |
|
} |
294 |
|
|
295 |
|
/** |
296 |
< |
* Returns current state, first resolving lagged propagation from |
297 |
< |
* root if necessary. |
296 |
> |
* Main implementation for methods arrive and arriveAndDeregister. |
297 |
> |
* Manually tuned to speed up and minimize race windows for the |
298 |
> |
* common case of just decrementing unarrived field. |
299 |
> |
* |
300 |
> |
* @param adj - adjustment to apply to state -- either |
301 |
> |
* ONE_ARRIVAL (for arrive) or |
302 |
> |
* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister) |
303 |
> |
*/ |
304 |
> |
private int doArrive(long adj) { |
305 |
> |
for (;;) { |
306 |
> |
long s; |
307 |
> |
int phase, unarrived; |
308 |
> |
if ((phase = (int)((s = state) >>> PHASE_SHIFT)) < 0) |
309 |
> |
return phase; |
310 |
> |
else if ((unarrived = (int)(s & UNARRIVED_MASK)) == 0) |
311 |
> |
checkBadArrive(s); |
312 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s -= adj)){ |
313 |
> |
if (unarrived == 1) { |
314 |
> |
Phaser par; |
315 |
> |
long p = s & PARTIES_MASK; // unshifted parties field |
316 |
> |
long lu = p >>> PARTIES_SHIFT; |
317 |
> |
int u = (int)lu; |
318 |
> |
int nextPhase = (phase + 1) & MAX_PHASE; |
319 |
> |
long next = ((long)nextPhase << PHASE_SHIFT) | p | lu; |
320 |
> |
if ((par = parent) == null) { |
321 |
> |
UNSAFE.compareAndSwapLong |
322 |
> |
(this, stateOffset, s, onAdvance(phase, u)? |
323 |
> |
next | TERMINATION_PHASE : next); |
324 |
> |
releaseWaiters(phase); |
325 |
> |
} |
326 |
> |
else { |
327 |
> |
par.doArrive(u == 0? |
328 |
> |
ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL); |
329 |
> |
if ((int)(par.state >>> PHASE_SHIFT) != nextPhase || |
330 |
> |
((int)(state >>> PHASE_SHIFT) != nextPhase && |
331 |
> |
!UNSAFE.compareAndSwapLong(this, stateOffset, |
332 |
> |
s, next))) |
333 |
> |
reconcileState(); |
334 |
> |
} |
335 |
> |
} |
336 |
> |
return phase; |
337 |
> |
} |
338 |
> |
} |
339 |
> |
} |
340 |
> |
|
341 |
> |
/** |
342 |
> |
* Rechecks state and throws bounds exceptions on arrival -- called |
343 |
> |
* only if unarrived is apparently zero. |
344 |
|
*/ |
345 |
< |
private long getReconciledState() { |
346 |
< |
return (parent == null) ? state : reconcileState(); |
345 |
> |
private void checkBadArrive(long s) { |
346 |
> |
if (reconcileState() == s) |
347 |
> |
throw new IllegalStateException |
348 |
> |
("Attempted arrival of unregistered party for " + |
349 |
> |
stateToString(s)); |
350 |
|
} |
351 |
|
|
352 |
|
/** |
353 |
< |
* Recursively resolves state. |
353 |
> |
* Implementation of register, bulkRegister |
354 |
> |
* |
355 |
> |
* @param registrations number to add to both parties and unarrived fields |
356 |
> |
*/ |
357 |
> |
private int doRegister(int registrations) { |
358 |
> |
long adj = (long)registrations; // adjustment to state |
359 |
> |
adj |= adj << PARTIES_SHIFT; |
360 |
> |
Phaser par = parent; |
361 |
> |
for (;;) { |
362 |
> |
int phase, parties; |
363 |
> |
long s = par == null? state : reconcileState(); |
364 |
> |
if ((phase = (int)(s >>> PHASE_SHIFT)) < 0) |
365 |
> |
return phase; |
366 |
> |
if ((parties = ((int)(s & PARTIES_MASK)) >>> PARTIES_SHIFT) != 0 && |
367 |
> |
(s & UNARRIVED_MASK) == 0) |
368 |
> |
internalAwaitAdvance(phase, null); // wait for onAdvance |
369 |
> |
else if (parties + registrations > MAX_COUNT) |
370 |
> |
throw new IllegalStateException(badRegister(s)); |
371 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj)) |
372 |
> |
return phase; |
373 |
> |
} |
374 |
> |
} |
375 |
> |
|
376 |
> |
/** |
377 |
> |
* Returns message string for bounds exceptions on registration |
378 |
> |
*/ |
379 |
> |
private String badRegister(long s) { |
380 |
> |
return "Attempt to register more than " + |
381 |
> |
MAX_COUNT + " parties for " + stateToString(s); |
382 |
> |
} |
383 |
> |
|
384 |
> |
/** |
385 |
> |
* Recursively resolves lagged phase propagation from root if |
386 |
> |
* necessary. |
387 |
|
*/ |
388 |
|
private long reconcileState() { |
389 |
< |
Phaser p = parent; |
390 |
< |
long s = state; |
391 |
< |
if (p != null) { |
392 |
< |
while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) { |
393 |
< |
long parentState = p.getReconciledState(); |
394 |
< |
int parentPhase = phaseOf(parentState); |
395 |
< |
int phase = phaseOf(s = state); |
396 |
< |
if (phase != parentPhase) { |
397 |
< |
long next = trippedStateFor(parentPhase, partiesOf(s)); |
398 |
< |
if (casState(s, next)) { |
399 |
< |
releaseWaiters(phase); |
400 |
< |
s = next; |
401 |
< |
} |
402 |
< |
} |
389 |
> |
Phaser par = parent; |
390 |
> |
if (par == null) |
391 |
> |
return state; |
392 |
> |
Phaser rt = root; |
393 |
> |
for (;;) { |
394 |
> |
long s, u; |
395 |
> |
int phase, rPhase, pPhase; |
396 |
> |
if ((phase = (int)((s = state)>>> PHASE_SHIFT)) < 0 || |
397 |
> |
(rPhase = (int)(rt.state >>> PHASE_SHIFT)) == phase) |
398 |
> |
return s; |
399 |
> |
long pState = par.parent == null? par.state : par.reconcileState(); |
400 |
> |
if (state == s) { |
401 |
> |
if ((rPhase < 0 || (s & UNARRIVED_MASK) == 0) && |
402 |
> |
((pPhase = (int)(pState >>> PHASE_SHIFT)) < 0 || |
403 |
> |
pPhase == ((phase + 1) & MAX_PHASE))) |
404 |
> |
UNSAFE.compareAndSwapLong |
405 |
> |
(this, stateOffset, s, |
406 |
> |
(((long) pPhase) << PHASE_SHIFT) | |
407 |
> |
(u = s & PARTIES_MASK) | |
408 |
> |
(u >>> PARTIES_SHIFT)); // reset unarrived to parties |
409 |
> |
else |
410 |
> |
releaseWaiters(phase); // help release others |
411 |
|
} |
412 |
|
} |
299 |
– |
return s; |
413 |
|
} |
414 |
|
|
415 |
|
/** |
416 |
< |
* Creates a new Phaser without any initially registered parties, |
416 |
> |
* Creates a new phaser without any initially registered parties, |
417 |
|
* initial phase number 0, and no parent. Any thread using this |
418 |
< |
* Phaser will need to first register for it. |
418 |
> |
* phaser will need to first register for it. |
419 |
|
*/ |
420 |
|
public Phaser() { |
421 |
< |
this(null); |
421 |
> |
this(null, 0); |
422 |
|
} |
423 |
|
|
424 |
|
/** |
425 |
< |
* Creates a new Phaser with the given numbers of registered |
425 |
> |
* Creates a new phaser with the given number of registered |
426 |
|
* unarrived parties, initial phase number 0, and no parent. |
427 |
|
* |
428 |
|
* @param parties the number of parties required to trip barrier |
434 |
|
} |
435 |
|
|
436 |
|
/** |
437 |
< |
* Creates a new Phaser with the given parent, without any |
437 |
> |
* Creates a new phaser with the given parent, without any |
438 |
|
* initially registered parties. If parent is non-null this phaser |
439 |
|
* is registered with the parent and its initial phase number is |
440 |
|
* the same as that of parent phaser. |
442 |
|
* @param parent the parent phaser |
443 |
|
*/ |
444 |
|
public Phaser(Phaser parent) { |
445 |
< |
int phase = 0; |
333 |
< |
this.parent = parent; |
334 |
< |
if (parent != null) { |
335 |
< |
this.root = parent.root; |
336 |
< |
phase = parent.register(); |
337 |
< |
} |
338 |
< |
else |
339 |
< |
this.root = this; |
340 |
< |
this.state = trippedStateFor(phase, 0); |
445 |
> |
this(parent, 0); |
446 |
|
} |
447 |
|
|
448 |
|
/** |
449 |
< |
* Creates a new Phaser with the given parent and numbers of |
449 |
> |
* Creates a new phaser with the given parent and number of |
450 |
|
* registered unarrived parties. If parent is non-null, this phaser |
451 |
|
* is registered with the parent and its initial phase number is |
452 |
|
* the same as that of parent phaser. |
457 |
|
* or greater than the maximum number of parties supported |
458 |
|
*/ |
459 |
|
public Phaser(Phaser parent, int parties) { |
460 |
< |
if (parties < 0 || parties > ushortMask) |
460 |
> |
if (parties < 0 || parties > MAX_COUNT) |
461 |
|
throw new IllegalArgumentException("Illegal number of parties"); |
462 |
< |
int phase = 0; |
462 |
> |
int phase; |
463 |
|
this.parent = parent; |
464 |
|
if (parent != null) { |
465 |
< |
this.root = parent.root; |
465 |
> |
Phaser r = parent.root; |
466 |
> |
this.root = r; |
467 |
> |
this.evenQ = r.evenQ; |
468 |
> |
this.oddQ = r.oddQ; |
469 |
|
phase = parent.register(); |
470 |
|
} |
471 |
< |
else |
471 |
> |
else { |
472 |
|
this.root = this; |
473 |
< |
this.state = trippedStateFor(phase, parties); |
473 |
> |
this.evenQ = new AtomicReference<QNode>(); |
474 |
> |
this.oddQ = new AtomicReference<QNode>(); |
475 |
> |
phase = 0; |
476 |
> |
} |
477 |
> |
long p = (long)parties; |
478 |
> |
this.state = (((long) phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT); |
479 |
|
} |
480 |
|
|
481 |
|
/** |
482 |
|
* Adds a new unarrived party to this phaser. |
483 |
+ |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
484 |
+ |
* this method may wait until its completion before registering. |
485 |
|
* |
486 |
< |
* @return the current barrier phase number upon registration |
486 |
> |
* @return the arrival phase number to which this registration applied |
487 |
|
* @throws IllegalStateException if attempting to register more |
488 |
|
* than the maximum supported number of parties |
489 |
|
*/ |
493 |
|
|
494 |
|
/** |
495 |
|
* Adds the given number of new unarrived parties to this phaser. |
496 |
+ |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
497 |
+ |
* this method may wait until its completion before registering. |
498 |
|
* |
499 |
< |
* @param parties the number of parties required to trip barrier |
500 |
< |
* @return the current barrier phase number upon registration |
499 |
> |
* @param parties the number of additional parties required to trip barrier |
500 |
> |
* @return the arrival phase number to which this registration applied |
501 |
|
* @throws IllegalStateException if attempting to register more |
502 |
|
* than the maximum supported number of parties |
503 |
+ |
* @throws IllegalArgumentException if {@code parties < 0} |
504 |
|
*/ |
505 |
|
public int bulkRegister(int parties) { |
506 |
|
if (parties < 0) |
507 |
|
throw new IllegalArgumentException(); |
508 |
+ |
if (parties > MAX_COUNT) |
509 |
+ |
throw new IllegalStateException(badRegister(state)); |
510 |
|
if (parties == 0) |
511 |
|
return getPhase(); |
512 |
|
return doRegister(parties); |
513 |
|
} |
514 |
|
|
515 |
|
/** |
396 |
– |
* Shared code for register, bulkRegister |
397 |
– |
*/ |
398 |
– |
private int doRegister(int registrations) { |
399 |
– |
int phase; |
400 |
– |
for (;;) { |
401 |
– |
long s = getReconciledState(); |
402 |
– |
phase = phaseOf(s); |
403 |
– |
int unarrived = unarrivedOf(s) + registrations; |
404 |
– |
int parties = partiesOf(s) + registrations; |
405 |
– |
if (phase < 0) |
406 |
– |
break; |
407 |
– |
if (parties > ushortMask || unarrived > ushortMask) |
408 |
– |
throw new IllegalStateException(badBounds(parties, unarrived)); |
409 |
– |
if (phase == phaseOf(root.state) && |
410 |
– |
casState(s, stateFor(phase, parties, unarrived))) |
411 |
– |
break; |
412 |
– |
} |
413 |
– |
return phase; |
414 |
– |
} |
415 |
– |
|
416 |
– |
/** |
516 |
|
* Arrives at the barrier, but does not wait for others. (You can |
517 |
< |
* in turn wait for others via {@link #awaitAdvance}). |
517 |
> |
* in turn wait for others via {@link #awaitAdvance}). It is an |
518 |
> |
* unenforced usage error for an unregistered party to invoke this |
519 |
> |
* method. |
520 |
|
* |
521 |
< |
* @return the barrier phase number upon entry to this method, or a |
421 |
< |
* negative value if terminated |
521 |
> |
* @return the arrival phase number, or a negative value if terminated |
522 |
|
* @throws IllegalStateException if not terminated and the number |
523 |
|
* of unarrived parties would become negative |
524 |
|
*/ |
525 |
|
public int arrive() { |
526 |
< |
int phase; |
427 |
< |
for (;;) { |
428 |
< |
long s = state; |
429 |
< |
phase = phaseOf(s); |
430 |
< |
if (phase < 0) |
431 |
< |
break; |
432 |
< |
int parties = partiesOf(s); |
433 |
< |
int unarrived = unarrivedOf(s) - 1; |
434 |
< |
if (unarrived > 0) { // Not the last arrival |
435 |
< |
if (casState(s, s - 1)) // s-1 adds one arrival |
436 |
< |
break; |
437 |
< |
} |
438 |
< |
else if (unarrived == 0) { // the last arrival |
439 |
< |
Phaser par = parent; |
440 |
< |
if (par == null) { // directly trip |
441 |
< |
if (casState |
442 |
< |
(s, |
443 |
< |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
444 |
< |
((phase + 1) & phaseMask), parties))) { |
445 |
< |
releaseWaiters(phase); |
446 |
< |
break; |
447 |
< |
} |
448 |
< |
} |
449 |
< |
else { // cascade to parent |
450 |
< |
if (casState(s, s - 1)) { // zeroes unarrived |
451 |
< |
par.arrive(); |
452 |
< |
reconcileState(); |
453 |
< |
break; |
454 |
< |
} |
455 |
< |
} |
456 |
< |
} |
457 |
< |
else if (phase != phaseOf(root.state)) // or if unreconciled |
458 |
< |
reconcileState(); |
459 |
< |
else |
460 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
461 |
< |
} |
462 |
< |
return phase; |
526 |
> |
return doArrive(ONE_ARRIVAL); |
527 |
|
} |
528 |
|
|
529 |
|
/** |
530 |
< |
* Arrives at the barrier, and deregisters from it, without |
531 |
< |
* waiting for others. Deregistration reduces number of parties |
530 |
> |
* Arrives at the barrier and deregisters from it without waiting |
531 |
> |
* for others. Deregistration reduces the number of parties |
532 |
|
* required to trip the barrier in future phases. If this phaser |
533 |
|
* has a parent, and deregistration causes this phaser to have |
534 |
< |
* zero parties, this phaser is also deregistered from its parent. |
534 |
> |
* zero parties, this phaser also arrives at and is deregistered |
535 |
> |
* from its parent. It is an unenforced usage error for an |
536 |
> |
* unregistered party to invoke this method. |
537 |
|
* |
538 |
< |
* @return the current barrier phase number upon entry to |
473 |
< |
* this method, or a negative value if terminated |
538 |
> |
* @return the arrival phase number, or a negative value if terminated |
539 |
|
* @throws IllegalStateException if not terminated and the number |
540 |
|
* of registered or unarrived parties would become negative |
541 |
|
*/ |
542 |
|
public int arriveAndDeregister() { |
543 |
< |
// similar code to arrive, but too different to merge |
479 |
< |
Phaser par = parent; |
480 |
< |
int phase; |
481 |
< |
for (;;) { |
482 |
< |
long s = state; |
483 |
< |
phase = phaseOf(s); |
484 |
< |
if (phase < 0) |
485 |
< |
break; |
486 |
< |
int parties = partiesOf(s) - 1; |
487 |
< |
int unarrived = unarrivedOf(s) - 1; |
488 |
< |
if (parties >= 0) { |
489 |
< |
if (unarrived > 0 || (unarrived == 0 && par != null)) { |
490 |
< |
if (casState |
491 |
< |
(s, |
492 |
< |
stateFor(phase, parties, unarrived))) { |
493 |
< |
if (unarrived == 0) { |
494 |
< |
par.arriveAndDeregister(); |
495 |
< |
reconcileState(); |
496 |
< |
} |
497 |
< |
break; |
498 |
< |
} |
499 |
< |
continue; |
500 |
< |
} |
501 |
< |
if (unarrived == 0) { |
502 |
< |
if (casState |
503 |
< |
(s, |
504 |
< |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
505 |
< |
((phase + 1) & phaseMask), parties))) { |
506 |
< |
releaseWaiters(phase); |
507 |
< |
break; |
508 |
< |
} |
509 |
< |
continue; |
510 |
< |
} |
511 |
< |
if (par != null && phase != phaseOf(root.state)) { |
512 |
< |
reconcileState(); |
513 |
< |
continue; |
514 |
< |
} |
515 |
< |
} |
516 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
517 |
< |
} |
518 |
< |
return phase; |
543 |
> |
return doArrive(ONE_ARRIVAL|ONE_PARTY); |
544 |
|
} |
545 |
|
|
546 |
|
/** |
547 |
|
* Arrives at the barrier and awaits others. Equivalent in effect |
548 |
< |
* to {@code awaitAdvance(arrive())}. If you instead need to |
549 |
< |
* await with interruption of timeout, and/or deregister upon |
550 |
< |
* arrival, you can arrange them using analogous constructions. |
548 |
> |
* to {@code awaitAdvance(arrive())}. If you need to await with |
549 |
> |
* interruption or timeout, you can arrange this with an analogous |
550 |
> |
* construction using one of the other forms of the {@code |
551 |
> |
* awaitAdvance} method. If instead you need to deregister upon |
552 |
> |
* arrival, use {@link #arriveAndDeregister}. It is an unenforced |
553 |
> |
* usage error for an unregistered party to invoke this method. |
554 |
|
* |
555 |
< |
* @return the phase on entry to this method |
555 |
> |
* @return the arrival phase number, or a negative number if terminated |
556 |
|
* @throws IllegalStateException if not terminated and the number |
557 |
|
* of unarrived parties would become negative |
558 |
|
*/ |
561 |
|
} |
562 |
|
|
563 |
|
/** |
564 |
< |
* Awaits the phase of the barrier to advance from the given |
565 |
< |
* value, or returns immediately if argument is negative or this |
566 |
< |
* barrier is terminated. |
567 |
< |
* |
568 |
< |
* @param phase the phase on entry to this method |
569 |
< |
* @return the phase on exit from this method |
564 |
> |
* Awaits the phase of the barrier to advance from the given phase |
565 |
> |
* value, returning immediately if the current phase of the |
566 |
> |
* barrier is not equal to the given phase value or this barrier |
567 |
> |
* is terminated. |
568 |
> |
* |
569 |
> |
* @param phase an arrival phase number, or negative value if |
570 |
> |
* terminated; this argument is normally the value returned by a |
571 |
> |
* previous call to {@code arrive} or its variants |
572 |
> |
* @return the next arrival phase number, or a negative value |
573 |
> |
* if terminated or argument is negative |
574 |
|
*/ |
575 |
|
public int awaitAdvance(int phase) { |
576 |
|
if (phase < 0) |
577 |
|
return phase; |
578 |
< |
long s = getReconciledState(); |
547 |
< |
int p = phaseOf(s); |
578 |
> |
int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT); |
579 |
|
if (p != phase) |
580 |
|
return p; |
581 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
551 |
< |
parent.awaitAdvance(phase); |
552 |
< |
// Fall here even if parent waited, to reconcile and help release |
553 |
< |
return untimedWait(phase); |
581 |
> |
return internalAwaitAdvance(phase, null); |
582 |
|
} |
583 |
|
|
584 |
|
/** |
585 |
< |
* Awaits the phase of the barrier to advance from the given |
586 |
< |
* value, or returns immediately if argument is negative or this |
587 |
< |
* barrier is terminated, or throws InterruptedException if |
588 |
< |
* interrupted while waiting. |
585 |
> |
* Awaits the phase of the barrier to advance from the given phase |
586 |
> |
* value, throwing {@code InterruptedException} if interrupted |
587 |
> |
* while waiting, or returning immediately if the current phase of |
588 |
> |
* the barrier is not equal to the given phase value or this |
589 |
> |
* barrier is terminated. |
590 |
|
* |
591 |
< |
* @param phase the phase on entry to this method |
592 |
< |
* @return the phase on exit from this method |
591 |
> |
* @param phase an arrival phase number, or negative value if |
592 |
> |
* terminated; this argument is normally the value returned by a |
593 |
> |
* previous call to {@code arrive} or its variants |
594 |
> |
* @return the next arrival phase number, or a negative value |
595 |
> |
* if terminated or argument is negative |
596 |
|
* @throws InterruptedException if thread interrupted while waiting |
597 |
|
*/ |
598 |
|
public int awaitAdvanceInterruptibly(int phase) |
599 |
|
throws InterruptedException { |
600 |
|
if (phase < 0) |
601 |
|
return phase; |
602 |
< |
long s = getReconciledState(); |
571 |
< |
int p = phaseOf(s); |
602 |
> |
int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT); |
603 |
|
if (p != phase) |
604 |
|
return p; |
605 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
606 |
< |
parent.awaitAdvanceInterruptibly(phase); |
607 |
< |
return interruptibleWait(phase); |
605 |
> |
QNode node = new QNode(this, phase, true, false, 0L); |
606 |
> |
p = internalAwaitAdvance(phase, node); |
607 |
> |
if (node.wasInterrupted) |
608 |
> |
throw new InterruptedException(); |
609 |
> |
else |
610 |
> |
return p; |
611 |
|
} |
612 |
|
|
613 |
|
/** |
614 |
< |
* Awaits the phase of the barrier to advance from the given value |
615 |
< |
* or the given timeout elapses, or returns immediately if |
616 |
< |
* argument is negative or this barrier is terminated. |
617 |
< |
* |
618 |
< |
* @param phase the phase on entry to this method |
619 |
< |
* @return the phase on exit from this method |
614 |
> |
* Awaits the phase of the barrier to advance from the given phase |
615 |
> |
* value or the given timeout to elapse, throwing {@code |
616 |
> |
* InterruptedException} if interrupted while waiting, or |
617 |
> |
* returning immediately if the current phase of the barrier is |
618 |
> |
* not equal to the given phase value or this barrier is |
619 |
> |
* terminated. |
620 |
> |
* |
621 |
> |
* @param phase an arrival phase number, or negative value if |
622 |
> |
* terminated; this argument is normally the value returned by a |
623 |
> |
* previous call to {@code arrive} or its variants |
624 |
> |
* @param timeout how long to wait before giving up, in units of |
625 |
> |
* {@code unit} |
626 |
> |
* @param unit a {@code TimeUnit} determining how to interpret the |
627 |
> |
* {@code timeout} parameter |
628 |
> |
* @return the next arrival phase number, or a negative value |
629 |
> |
* if terminated or argument is negative |
630 |
|
* @throws InterruptedException if thread interrupted while waiting |
631 |
|
* @throws TimeoutException if timed out while waiting |
632 |
|
*/ |
633 |
|
public int awaitAdvanceInterruptibly(int phase, |
634 |
|
long timeout, TimeUnit unit) |
635 |
|
throws InterruptedException, TimeoutException { |
636 |
+ |
long nanos = unit.toNanos(timeout); |
637 |
|
if (phase < 0) |
638 |
|
return phase; |
639 |
< |
long s = getReconciledState(); |
595 |
< |
int p = phaseOf(s); |
639 |
> |
int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT); |
640 |
|
if (p != phase) |
641 |
|
return p; |
642 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
643 |
< |
parent.awaitAdvanceInterruptibly(phase, timeout, unit); |
644 |
< |
return timedWait(phase, unit.toNanos(timeout)); |
642 |
> |
QNode node = new QNode(this, phase, true, true, nanos); |
643 |
> |
p = internalAwaitAdvance(phase, node); |
644 |
> |
if (node.wasInterrupted) |
645 |
> |
throw new InterruptedException(); |
646 |
> |
else if (p == phase) |
647 |
> |
throw new TimeoutException(); |
648 |
> |
else |
649 |
> |
return p; |
650 |
|
} |
651 |
|
|
652 |
|
/** |
657 |
|
* unexpected exceptions. |
658 |
|
*/ |
659 |
|
public void forceTermination() { |
660 |
< |
for (;;) { |
661 |
< |
long s = getReconciledState(); |
662 |
< |
int phase = phaseOf(s); |
663 |
< |
int parties = partiesOf(s); |
664 |
< |
int unarrived = unarrivedOf(s); |
665 |
< |
if (phase < 0 || |
666 |
< |
casState(s, stateFor(-1, parties, unarrived))) { |
618 |
< |
releaseWaiters(0); |
619 |
< |
releaseWaiters(1); |
620 |
< |
if (parent != null) |
621 |
< |
parent.forceTermination(); |
622 |
< |
return; |
623 |
< |
} |
624 |
< |
} |
660 |
> |
Phaser r = root; // force at root then reconcile |
661 |
> |
long s; |
662 |
> |
while ((s = r.state) >= 0) |
663 |
> |
UNSAFE.compareAndSwapLong(r, stateOffset, s, s | TERMINATION_PHASE); |
664 |
> |
reconcileState(); |
665 |
> |
releaseWaiters(0); // signal all threads |
666 |
> |
releaseWaiters(1); |
667 |
|
} |
668 |
|
|
669 |
|
/** |
674 |
|
* @return the phase number, or a negative value if terminated |
675 |
|
*/ |
676 |
|
public final int getPhase() { |
677 |
< |
return phaseOf(getReconciledState()); |
636 |
< |
} |
637 |
< |
|
638 |
< |
/** |
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; |
677 |
> |
return (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT); |
678 |
|
} |
679 |
|
|
680 |
|
/** |
683 |
|
* @return the number of parties |
684 |
|
*/ |
685 |
|
public int getRegisteredParties() { |
686 |
< |
return partiesOf(state); |
686 |
> |
return partiesOf(parent==null? state : reconcileState()); |
687 |
|
} |
688 |
|
|
689 |
|
/** |
690 |
< |
* Returns the number of parties that have arrived at the current |
691 |
< |
* phase of this barrier. |
690 |
> |
* Returns the number of registered parties that have arrived at |
691 |
> |
* the current phase of this barrier. |
692 |
|
* |
693 |
|
* @return the number of arrived parties |
694 |
|
*/ |
695 |
|
public int getArrivedParties() { |
696 |
< |
return arrivedOf(state); |
696 |
> |
return arrivedOf(parent==null? state : reconcileState()); |
697 |
|
} |
698 |
|
|
699 |
|
/** |
703 |
|
* @return the number of unarrived parties |
704 |
|
*/ |
705 |
|
public int getUnarrivedParties() { |
706 |
< |
return unarrivedOf(state); |
706 |
> |
return unarrivedOf(parent==null? state : reconcileState()); |
707 |
|
} |
708 |
|
|
709 |
|
/** |
710 |
< |
* Returns the parent of this phaser, or null if none. |
710 |
> |
* Returns the parent of this phaser, or {@code null} if none. |
711 |
|
* |
712 |
< |
* @return the parent of this phaser, or null if none |
712 |
> |
* @return the parent of this phaser, or {@code null} if none |
713 |
|
*/ |
714 |
|
public Phaser getParent() { |
715 |
|
return parent; |
731 |
|
* @return {@code true} if this barrier has been terminated |
732 |
|
*/ |
733 |
|
public boolean isTerminated() { |
734 |
< |
return getPhase() < 0; |
734 |
> |
return (parent == null? state : reconcileState()) < 0; |
735 |
|
} |
736 |
|
|
737 |
|
/** |
738 |
< |
* Overridable method to perform an action upon phase advance, and |
739 |
< |
* to control termination. This method is invoked whenever the |
740 |
< |
* barrier is tripped (and thus all other waiting parties are |
741 |
< |
* dormant). If it returns true, then, rather than advance the |
742 |
< |
* phase number, this barrier will be set to a final termination |
743 |
< |
* state, and subsequent calls to {@code isTerminated} will |
744 |
< |
* return true. |
738 |
> |
* Overridable method to perform an action upon impending phase |
739 |
> |
* advance, and to control termination. This method is invoked |
740 |
> |
* upon arrival of the party tripping the barrier (when all other |
741 |
> |
* waiting parties are dormant). If this method returns {@code |
742 |
> |
* true}, then, rather than advance the phase number, this barrier |
743 |
> |
* will be set to a final termination state, and subsequent calls |
744 |
> |
* to {@link #isTerminated} will return true. Any (unchecked) |
745 |
> |
* Exception or Error thrown by an invocation of this method is |
746 |
> |
* propagated to the party attempting to trip the barrier, in |
747 |
> |
* which case no advance occurs. |
748 |
> |
* |
749 |
> |
* <p>The arguments to this method provide the state of the phaser |
750 |
> |
* prevailing for the current transition. The effects of invoking |
751 |
> |
* arrival, registration, and waiting methods on this Phaser from |
752 |
> |
* within {@code onAdvance} are unspecified and should not be |
753 |
> |
* relied on. |
754 |
> |
* |
755 |
> |
* <p>If this Phaser is a member of a tiered set of Phasers, then |
756 |
> |
* {@code onAdvance} is invoked only for its root Phaser on each |
757 |
> |
* advance. |
758 |
|
* |
759 |
< |
* <p> The default version returns true when the number of |
759 |
> |
* <p>The default version returns {@code true} when the number of |
760 |
|
* registered parties is zero. Normally, overrides that arrange |
761 |
|
* termination for other reasons should also preserve this |
762 |
|
* property. |
763 |
|
* |
719 |
– |
* <p> You may override this method to perform an action with side |
720 |
– |
* effects visible to participating tasks, but it is in general |
721 |
– |
* only sensible to do so in designs where all parties register |
722 |
– |
* before any arrive, and all {@code awaitAdvance} at each phase. |
723 |
– |
* Otherwise, you cannot ensure lack of interference. In |
724 |
– |
* particular, this method may be invoked more than once per |
725 |
– |
* 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. |
729 |
– |
* |
764 |
|
* @param phase the phase number on entering the barrier |
765 |
|
* @param registeredParties the current number of registered parties |
766 |
|
* @return {@code true} if this barrier should terminate |
779 |
|
* @return a string identifying this barrier, as well as its state |
780 |
|
*/ |
781 |
|
public String toString() { |
782 |
< |
long s = getReconciledState(); |
782 |
> |
return stateToString(reconcileState()); |
783 |
> |
} |
784 |
> |
|
785 |
> |
/** |
786 |
> |
* Implementation of toString and string-based error messages |
787 |
> |
*/ |
788 |
> |
private String stateToString(long s) { |
789 |
|
return super.toString() + |
790 |
|
"[phase = " + phaseOf(s) + |
791 |
|
" parties = " + partiesOf(s) + |
792 |
|
" arrived = " + arrivedOf(s) + "]"; |
793 |
|
} |
794 |
|
|
795 |
< |
// methods for waiting |
795 |
> |
// Waiting mechanics |
796 |
> |
|
797 |
> |
/** |
798 |
> |
* Removes and signals threads from queue for phase |
799 |
> |
*/ |
800 |
> |
private void releaseWaiters(int phase) { |
801 |
> |
AtomicReference<QNode> head = queueFor(phase); |
802 |
> |
QNode q; |
803 |
> |
int p; |
804 |
> |
while ((q = head.get()) != null && |
805 |
> |
((p = q.phase) == phase || |
806 |
> |
(int)(root.state >>> PHASE_SHIFT) != p)) { |
807 |
> |
if (head.compareAndSet(q, q.next)) |
808 |
> |
q.signal(); |
809 |
> |
} |
810 |
> |
} |
811 |
> |
|
812 |
> |
/** |
813 |
> |
* Tries to enqueue given node in the appropriate wait queue. |
814 |
> |
* |
815 |
> |
* @return true if successful |
816 |
> |
*/ |
817 |
> |
private boolean tryEnqueue(int phase, QNode node) { |
818 |
> |
releaseWaiters(phase-1); // ensure old queue clean |
819 |
> |
AtomicReference<QNode> head = queueFor(phase); |
820 |
> |
QNode q = head.get(); |
821 |
> |
return ((q == null || q.phase == phase) && |
822 |
> |
(int)(root.state >>> PHASE_SHIFT) == phase && |
823 |
> |
head.compareAndSet(node.next = q, node)); |
824 |
> |
} |
825 |
> |
|
826 |
> |
/** The number of CPUs, for spin control */ |
827 |
> |
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
828 |
> |
|
829 |
> |
/** |
830 |
> |
* The number of times to spin before blocking while waiting for |
831 |
> |
* advance, per arrival while waiting. On multiprocessors, fully |
832 |
> |
* blocking and waking up a large number of threads all at once is |
833 |
> |
* usually a very slow process, so we use rechargeable spins to |
834 |
> |
* avoid it when threads regularly arrive: When a thread in |
835 |
> |
* internalAwaitAdvance notices another arrival before blocking, |
836 |
> |
* and there appear to be enough CPUs available, it spins |
837 |
> |
* SPINS_PER_ARRIVAL more times before continuing to try to |
838 |
> |
* block. The value trades off good-citizenship vs big unnecessary |
839 |
> |
* slowdowns. |
840 |
> |
*/ |
841 |
> |
static final int SPINS_PER_ARRIVAL = NCPU < 2? 1 : 1 << 8; |
842 |
> |
|
843 |
> |
/** |
844 |
> |
* Possibly blocks and waits for phase to advance unless aborted. |
845 |
> |
* |
846 |
> |
* @param phase current phase |
847 |
> |
* @param node if non-null, the wait node to track interrupt and timeout; |
848 |
> |
* if null, denotes noninterruptible wait |
849 |
> |
* @return current phase |
850 |
> |
*/ |
851 |
> |
private int internalAwaitAdvance(int phase, QNode node) { |
852 |
> |
Phaser current = this; // to eventually wait at root if tiered |
853 |
> |
boolean queued = false; // true when node is enqueued |
854 |
> |
int lastUnarrived = -1; // to increase spins upon change |
855 |
> |
int spins = SPINS_PER_ARRIVAL; |
856 |
> |
for (;;) { |
857 |
> |
int p, unarrived; |
858 |
> |
Phaser par; |
859 |
> |
long s = current.state; |
860 |
> |
if ((p = (int)(s >>> PHASE_SHIFT)) != phase) { |
861 |
> |
if (node != null) |
862 |
> |
node.onRelease(); |
863 |
> |
releaseWaiters(phase); |
864 |
> |
return p; |
865 |
> |
} |
866 |
> |
else if ((unarrived = (int)(s & UNARRIVED_MASK)) != lastUnarrived) { |
867 |
> |
if ((lastUnarrived = unarrived) < NCPU) |
868 |
> |
spins += SPINS_PER_ARRIVAL; |
869 |
> |
} |
870 |
> |
else if (unarrived == 0 && (par = current.parent) != null) { |
871 |
> |
current = par; // if all arrived, use parent |
872 |
> |
par = par.parent; |
873 |
> |
lastUnarrived = -1; |
874 |
> |
} |
875 |
> |
else if (spins > 0) |
876 |
> |
--spins; |
877 |
> |
else if (node == null) // must be noninterruptible |
878 |
> |
node = new QNode(this, phase, false, false, 0L); |
879 |
> |
else if (node.isReleasable()) { |
880 |
> |
if ((int)(reconcileState() >>> PHASE_SHIFT) == phase) |
881 |
> |
return phase; // aborted |
882 |
> |
} |
883 |
> |
else if (!queued) |
884 |
> |
queued = tryEnqueue(phase, node); |
885 |
> |
else { |
886 |
> |
try { |
887 |
> |
ForkJoinPool.managedBlock(node); |
888 |
> |
} catch (InterruptedException ie) { |
889 |
> |
node.wasInterrupted = true; |
890 |
> |
} |
891 |
> |
} |
892 |
> |
} |
893 |
> |
} |
894 |
|
|
895 |
|
/** |
896 |
|
* Wait nodes for Treiber stack representing wait queue |
898 |
|
static final class QNode implements ForkJoinPool.ManagedBlocker { |
899 |
|
final Phaser phaser; |
900 |
|
final int phase; |
763 |
– |
final long startTime; |
764 |
– |
final long nanos; |
765 |
– |
final boolean timed; |
901 |
|
final boolean interruptible; |
902 |
< |
volatile boolean wasInterrupted = false; |
902 |
> |
final boolean timed; |
903 |
> |
boolean wasInterrupted; |
904 |
> |
long nanos; |
905 |
> |
long lastTime; |
906 |
|
volatile Thread thread; // nulled to cancel wait |
907 |
|
QNode next; |
908 |
+ |
|
909 |
|
QNode(Phaser phaser, int phase, boolean interruptible, |
910 |
< |
boolean timed, long startTime, long nanos) { |
910 |
> |
boolean timed, long nanos) { |
911 |
|
this.phaser = phaser; |
912 |
|
this.phase = phase; |
774 |
– |
this.timed = timed; |
913 |
|
this.interruptible = interruptible; |
776 |
– |
this.startTime = startTime; |
914 |
|
this.nanos = nanos; |
915 |
+ |
this.timed = timed; |
916 |
+ |
this.lastTime = timed? System.nanoTime() : 0L; |
917 |
|
thread = Thread.currentThread(); |
918 |
|
} |
919 |
+ |
|
920 |
|
public boolean isReleasable() { |
921 |
< |
return (thread == null || |
922 |
< |
phaser.getPhase() != phase || |
923 |
< |
(interruptible && wasInterrupted) || |
924 |
< |
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
921 |
> |
Thread t = thread; |
922 |
> |
if (t != null) { |
923 |
> |
if (phaser.getPhase() != phase) |
924 |
> |
t = null; |
925 |
> |
else { |
926 |
> |
if (Thread.interrupted()) |
927 |
> |
wasInterrupted = true; |
928 |
> |
if (interruptible && wasInterrupted) |
929 |
> |
t = null; |
930 |
> |
else if (timed) { |
931 |
> |
if (nanos > 0) { |
932 |
> |
long now = System.nanoTime(); |
933 |
> |
nanos -= now - lastTime; |
934 |
> |
lastTime = now; |
935 |
> |
} |
936 |
> |
if (nanos <= 0) |
937 |
> |
t = null; |
938 |
> |
} |
939 |
> |
} |
940 |
> |
if (t != null) |
941 |
> |
return false; |
942 |
> |
thread = null; |
943 |
> |
} |
944 |
> |
return true; |
945 |
|
} |
946 |
+ |
|
947 |
|
public boolean block() { |
948 |
< |
if (Thread.interrupted()) { |
949 |
< |
wasInterrupted = true; |
950 |
< |
if (interruptible) |
790 |
< |
return true; |
791 |
< |
} |
792 |
< |
if (!timed) |
948 |
> |
if (isReleasable()) |
949 |
> |
return true; |
950 |
> |
else if (!timed) |
951 |
|
LockSupport.park(this); |
952 |
< |
else { |
953 |
< |
long waitTime = nanos - (System.nanoTime() - startTime); |
796 |
< |
if (waitTime <= 0) |
797 |
< |
return true; |
798 |
< |
LockSupport.parkNanos(this, waitTime); |
799 |
< |
} |
952 |
> |
else if (nanos > 0) |
953 |
> |
LockSupport.parkNanos(this, nanos); |
954 |
|
return isReleasable(); |
955 |
|
} |
956 |
+ |
|
957 |
|
void signal() { |
958 |
|
Thread t = thread; |
959 |
|
if (t != null) { |
961 |
|
LockSupport.unpark(t); |
962 |
|
} |
963 |
|
} |
964 |
< |
boolean doWait() { |
965 |
< |
if (thread != null) { |
966 |
< |
try { |
967 |
< |
ForkJoinPool.managedBlock(this, false); |
968 |
< |
} catch (InterruptedException ie) { |
969 |
< |
} |
815 |
< |
} |
816 |
< |
return wasInterrupted; |
964 |
> |
|
965 |
> |
void onRelease() { // actions upon return from internalAwaitAdvance |
966 |
> |
if (!interruptible && wasInterrupted) |
967 |
> |
Thread.currentThread().interrupt(); |
968 |
> |
if (thread != null) |
969 |
> |
thread = null; |
970 |
|
} |
971 |
|
|
972 |
|
} |
973 |
|
|
974 |
< |
/** |
822 |
< |
* Removes and signals waiting threads from wait queue. |
823 |
< |
*/ |
824 |
< |
private void releaseWaiters(int phase) { |
825 |
< |
AtomicReference<QNode> head = queueFor(phase); |
826 |
< |
QNode q; |
827 |
< |
while ((q = head.get()) != null) { |
828 |
< |
if (head.compareAndSet(q, q.next)) |
829 |
< |
q.signal(); |
830 |
< |
} |
831 |
< |
} |
974 |
> |
// Unsafe mechanics |
975 |
|
|
976 |
< |
/** |
977 |
< |
* Tries to enqueue given node in the appropriate wait queue. |
978 |
< |
* |
836 |
< |
* @return true if successful |
837 |
< |
*/ |
838 |
< |
private boolean tryEnqueue(QNode node) { |
839 |
< |
AtomicReference<QNode> head = queueFor(node.phase); |
840 |
< |
return head.compareAndSet(node.next = head.get(), node); |
841 |
< |
} |
976 |
> |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
977 |
> |
private static final long stateOffset = |
978 |
> |
objectFieldOffset("state", Phaser.class); |
979 |
|
|
980 |
< |
/** |
981 |
< |
* Enqueues node and waits unless aborted or signalled. |
982 |
< |
* |
983 |
< |
* @return current phase |
984 |
< |
*/ |
985 |
< |
private int untimedWait(int phase) { |
986 |
< |
QNode node = null; |
987 |
< |
boolean queued = false; |
851 |
< |
boolean interrupted = false; |
852 |
< |
int p; |
853 |
< |
while ((p = getPhase()) == phase) { |
854 |
< |
if (Thread.interrupted()) |
855 |
< |
interrupted = true; |
856 |
< |
else if (node == null) |
857 |
< |
node = new QNode(this, phase, false, false, 0, 0); |
858 |
< |
else if (!queued) |
859 |
< |
queued = tryEnqueue(node); |
860 |
< |
else |
861 |
< |
interrupted = node.doWait(); |
980 |
> |
private static long objectFieldOffset(String field, Class<?> klazz) { |
981 |
> |
try { |
982 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
983 |
> |
} catch (NoSuchFieldException e) { |
984 |
> |
// Convert Exception to corresponding Error |
985 |
> |
NoSuchFieldError error = new NoSuchFieldError(field); |
986 |
> |
error.initCause(e); |
987 |
> |
throw error; |
988 |
|
} |
863 |
– |
if (node != null) |
864 |
– |
node.thread = null; |
865 |
– |
releaseWaiters(phase); |
866 |
– |
if (interrupted) |
867 |
– |
Thread.currentThread().interrupt(); |
868 |
– |
return p; |
869 |
– |
} |
870 |
– |
|
871 |
– |
/** |
872 |
– |
* Interruptible version |
873 |
– |
* @return current phase |
874 |
– |
*/ |
875 |
– |
private int interruptibleWait(int phase) throws InterruptedException { |
876 |
– |
QNode node = null; |
877 |
– |
boolean queued = false; |
878 |
– |
boolean interrupted = false; |
879 |
– |
int p; |
880 |
– |
while ((p = getPhase()) == phase && !interrupted) { |
881 |
– |
if (Thread.interrupted()) |
882 |
– |
interrupted = true; |
883 |
– |
else if (node == null) |
884 |
– |
node = new QNode(this, phase, true, false, 0, 0); |
885 |
– |
else if (!queued) |
886 |
– |
queued = tryEnqueue(node); |
887 |
– |
else |
888 |
– |
interrupted = node.doWait(); |
889 |
– |
} |
890 |
– |
if (node != null) |
891 |
– |
node.thread = null; |
892 |
– |
if (p != phase || (p = getPhase()) != phase) |
893 |
– |
releaseWaiters(phase); |
894 |
– |
if (interrupted) |
895 |
– |
throw new InterruptedException(); |
896 |
– |
return p; |
989 |
|
} |
990 |
|
|
991 |
|
/** |
992 |
< |
* Timeout version. |
993 |
< |
* @return current phase |
992 |
> |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
993 |
> |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
994 |
> |
* into a jdk. |
995 |
> |
* |
996 |
> |
* @return a sun.misc.Unsafe |
997 |
|
*/ |
903 |
– |
private int timedWait(int phase, long nanos) |
904 |
– |
throws InterruptedException, TimeoutException { |
905 |
– |
long startTime = System.nanoTime(); |
906 |
– |
QNode node = null; |
907 |
– |
boolean queued = false; |
908 |
– |
boolean interrupted = false; |
909 |
– |
int p; |
910 |
– |
while ((p = getPhase()) == phase && !interrupted) { |
911 |
– |
if (Thread.interrupted()) |
912 |
– |
interrupted = true; |
913 |
– |
else if (nanos - (System.nanoTime() - startTime) <= 0) |
914 |
– |
break; |
915 |
– |
else if (node == null) |
916 |
– |
node = new QNode(this, phase, true, true, startTime, nanos); |
917 |
– |
else if (!queued) |
918 |
– |
queued = tryEnqueue(node); |
919 |
– |
else |
920 |
– |
interrupted = node.doWait(); |
921 |
– |
} |
922 |
– |
if (node != null) |
923 |
– |
node.thread = null; |
924 |
– |
if (p != phase || (p = getPhase()) != phase) |
925 |
– |
releaseWaiters(phase); |
926 |
– |
if (interrupted) |
927 |
– |
throw new InterruptedException(); |
928 |
– |
if (p == phase) |
929 |
– |
throw new TimeoutException(); |
930 |
– |
return p; |
931 |
– |
} |
932 |
– |
|
933 |
– |
// Unsafe mechanics for jsr166y 3rd party package. |
998 |
|
private static sun.misc.Unsafe getUnsafe() { |
999 |
|
try { |
1000 |
|
return sun.misc.Unsafe.getUnsafe(); |
1001 |
|
} catch (SecurityException se) { |
1002 |
|
try { |
1003 |
|
return java.security.AccessController.doPrivileged |
1004 |
< |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1004 |
> |
(new java.security |
1005 |
> |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1006 |
|
public sun.misc.Unsafe run() throws Exception { |
1007 |
< |
return getUnsafeByReflection(); |
1007 |
> |
java.lang.reflect.Field f = sun.misc |
1008 |
> |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1009 |
> |
f.setAccessible(true); |
1010 |
> |
return (sun.misc.Unsafe) f.get(null); |
1011 |
|
}}); |
1012 |
|
} catch (java.security.PrivilegedActionException e) { |
1013 |
|
throw new RuntimeException("Could not initialize intrinsics", |
1015 |
|
} |
1016 |
|
} |
1017 |
|
} |
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 |
– |
} |
1018 |
|
} |