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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 {@code CyclicBarrier}, a phaser may be repeatedly |
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* awaited. Method {@link #arriveAndAwaitAdvance} has effect |
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* analogous to {@link java.util.concurrent.CyclicBarrier#await |
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* CyclicBarrier.await}. However, phasers separate two aspects of |
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* coordination, which 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 {@link #arrive} and |
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* {@link #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 {@link #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, are arranged by overriding method {@link #onAdvance(int, |
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* int)}, which also controls termination. Overriding this method is |
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* similar to, but more flexible than, providing a barrier action to a |
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* {@code 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 when an invocation |
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* of {@code onAdvance} returns {@code true}. When a phaser is |
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* controlling an action with a fixed number of iterations, it is |
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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}. The default implementation returns |
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* {@code true} if a deregistration has caused the number of |
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* registered parties to become zero. 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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* 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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* {@code CyclicBarrier}, 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 may be used to coordinate tasks executing in a {@link |
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* ForkJoinPool}, which will ensure sufficient parallelism to execute |
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* tasks when others are blocked waiting for a phase to advance. |
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* |
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* </ul> |
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* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., |
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* constructed in tree structures) to reduce contention. Phasers with |
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* large numbers of parties that would otherwise experience heavy |
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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 {@code Phaser} may be used instead of a {@code CountDownLatch} |
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* to control a one-shot action serving a variable number of |
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* parties. The typical idiom is for the method setting this up to |
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* first register, then start the actions, then deregister, as in: |
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* 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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* // create and start threads |
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* for (Runnable r : list) { |
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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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* task.run(); |
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* } |
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* }.start(); |
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* } |
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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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* should create tiered phasers to accommodate arbitrarily large sets |
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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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* 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_PARTIES = 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 int UNARRIVED_MASK = 0xffff; // to mask ints |
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private static final long PARTIES_MASK = 0xffff0000L; // to mask longs |
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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_BIT = 1L << 63; |
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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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private static int partiesOf(long s) { |
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return ((int) s) >>> 16; |
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return (int)s >>> 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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|
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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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*/ |
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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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/** |
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* Heads of Treiber stacks for waiting threads. To eliminate |
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* contention while releasing some threads while adding others, we |
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* contention when releasing some threads while adding others, we |
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* use two of them, alternating across even and odd phases. |
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* Subphasers share queues with root to speed up releases. |
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*/ |
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private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>(); |
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private final AtomicReference<QNode> oddQ = new AtomicReference<QNode>(); |
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private final AtomicReference<QNode> evenQ; |
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> |
private final AtomicReference<QNode> oddQ; |
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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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} |
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|
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/** |
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* Returns current state, first resolving lagged propagation from |
271 |
< |
* root if necessary. |
298 |
> |
* Returns message string for bounds exceptions on arrival. |
299 |
|
*/ |
300 |
< |
private long getReconciledState() { |
301 |
< |
return (parent == null) ? state : reconcileState(); |
300 |
> |
private String badArrive(long s) { |
301 |
> |
return "Attempted arrival of unregistered party for " + |
302 |
> |
stateToString(s); |
303 |
|
} |
304 |
|
|
305 |
|
/** |
306 |
< |
* Recursively resolves state. |
306 |
> |
* Returns message string for bounds exceptions on registration. |
307 |
|
*/ |
308 |
< |
private long reconcileState() { |
309 |
< |
Phaser p = parent; |
310 |
< |
long s = state; |
311 |
< |
if (p != null) { |
312 |
< |
while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) { |
313 |
< |
long parentState = p.getReconciledState(); |
314 |
< |
int parentPhase = phaseOf(parentState); |
315 |
< |
int phase = phaseOf(s = state); |
316 |
< |
if (phase != parentPhase) { |
317 |
< |
long next = trippedStateFor(parentPhase, partiesOf(s)); |
318 |
< |
if (casState(s, next)) { |
308 |
> |
private String badRegister(long s) { |
309 |
> |
return "Attempt to register more than " + |
310 |
> |
MAX_PARTIES + " parties for " + stateToString(s); |
311 |
> |
} |
312 |
> |
|
313 |
> |
/** |
314 |
> |
* Main implementation for methods arrive and arriveAndDeregister. |
315 |
> |
* Manually tuned to speed up and minimize race windows for the |
316 |
> |
* common case of just decrementing unarrived field. |
317 |
> |
* |
318 |
> |
* @param adj - adjustment to apply to state -- either |
319 |
> |
* ONE_ARRIVAL (for arrive) or |
320 |
> |
* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister) |
321 |
> |
*/ |
322 |
> |
private int doArrive(long adj) { |
323 |
> |
for (;;) { |
324 |
> |
long s = state; |
325 |
> |
int unarrived = (int)s & UNARRIVED_MASK; |
326 |
> |
int phase = (int)(s >>> PHASE_SHIFT); |
327 |
> |
if (phase < 0) |
328 |
> |
return phase; |
329 |
> |
else if (unarrived == 0) { |
330 |
> |
if (reconcileState() == s) // recheck |
331 |
> |
throw new IllegalStateException(badArrive(s)); |
332 |
> |
} |
333 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) { |
334 |
> |
if (unarrived == 1) { |
335 |
> |
long p = s & PARTIES_MASK; // unshifted parties field |
336 |
> |
long lu = p >>> PARTIES_SHIFT; |
337 |
> |
int u = (int)lu; |
338 |
> |
int nextPhase = (phase + 1) & MAX_PHASE; |
339 |
> |
long next = ((long)nextPhase << PHASE_SHIFT) | p | lu; |
340 |
> |
final Phaser parent = this.parent; |
341 |
> |
if (parent == null) { |
342 |
> |
if (onAdvance(phase, u)) |
343 |
> |
next |= TERMINATION_BIT; |
344 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
345 |
|
releaseWaiters(phase); |
292 |
– |
s = next; |
346 |
|
} |
347 |
+ |
else { |
348 |
+ |
parent.doArrive((u == 0) ? |
349 |
+ |
ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL); |
350 |
+ |
if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase || |
351 |
+ |
((int)(state >>> PHASE_SHIFT) != nextPhase && |
352 |
+ |
!UNSAFE.compareAndSwapLong(this, stateOffset, |
353 |
+ |
s, next))) |
354 |
+ |
reconcileState(); |
355 |
+ |
} |
356 |
+ |
} |
357 |
+ |
return phase; |
358 |
+ |
} |
359 |
+ |
} |
360 |
+ |
} |
361 |
+ |
|
362 |
+ |
/** |
363 |
+ |
* Implementation of register, bulkRegister |
364 |
+ |
* |
365 |
+ |
* @param registrations number to add to both parties and |
366 |
+ |
* unarrived fields. Must be greater than zero. |
367 |
+ |
*/ |
368 |
+ |
private int doRegister(int registrations) { |
369 |
+ |
// adjustment to state |
370 |
+ |
long adj = ((long)registrations << PARTIES_SHIFT) | registrations; |
371 |
+ |
final Phaser parent = this.parent; |
372 |
+ |
for (;;) { |
373 |
+ |
long s = (parent == null) ? state : reconcileState(); |
374 |
+ |
int parties = (int)s >>> PARTIES_SHIFT; |
375 |
+ |
int phase = (int)(s >>> PHASE_SHIFT); |
376 |
+ |
if (phase < 0) |
377 |
+ |
return phase; |
378 |
+ |
else if (registrations > MAX_PARTIES - parties) |
379 |
+ |
throw new IllegalStateException(badRegister(s)); |
380 |
+ |
else if ((parties == 0 && parent == null) || // first reg of root |
381 |
+ |
((int)s & UNARRIVED_MASK) != 0) { // not advancing |
382 |
+ |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj)) |
383 |
+ |
return phase; |
384 |
+ |
} |
385 |
+ |
else if (parties != 0) // wait for onAdvance |
386 |
+ |
root.internalAwaitAdvance(phase, null); |
387 |
+ |
else { // 1st registration of child |
388 |
+ |
synchronized(this) { // register parent first |
389 |
+ |
if (reconcileState() == s) { // recheck under lock |
390 |
+ |
parent.doRegister(1); // OK if throws IllegalState |
391 |
+ |
for (;;) { // simpler form of outer loop |
392 |
+ |
s = reconcileState(); |
393 |
+ |
phase = (int)(s >>> PHASE_SHIFT); |
394 |
+ |
if (phase < 0 || |
395 |
+ |
UNSAFE.compareAndSwapLong(this, stateOffset, |
396 |
+ |
s, s + adj)) |
397 |
+ |
return phase; |
398 |
+ |
} |
399 |
+ |
} |
400 |
+ |
} |
401 |
+ |
} |
402 |
+ |
} |
403 |
+ |
} |
404 |
+ |
|
405 |
+ |
/** |
406 |
+ |
* Recursively resolves lagged phase propagation from root if necessary. |
407 |
+ |
*/ |
408 |
+ |
private long reconcileState() { |
409 |
+ |
Phaser par = parent; |
410 |
+ |
long s = state; |
411 |
+ |
if (par != null) { |
412 |
+ |
Phaser rt = root; |
413 |
+ |
int phase, rPhase; |
414 |
+ |
while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 && |
415 |
+ |
(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) { |
416 |
+ |
if ((int)(par.state >>> PHASE_SHIFT) != rPhase) |
417 |
+ |
par.reconcileState(); |
418 |
+ |
else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) { |
419 |
+ |
long u = s & PARTIES_MASK; // reset unarrived to parties |
420 |
+ |
long next = ((((long) rPhase) << PHASE_SHIFT) | u | |
421 |
+ |
(u >>> PARTIES_SHIFT)); |
422 |
+ |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
423 |
|
} |
424 |
+ |
s = state; |
425 |
|
} |
426 |
|
} |
427 |
|
return s; |
428 |
|
} |
429 |
|
|
430 |
|
/** |
431 |
< |
* Creates a new phaser without any initially registered parties, |
431 |
> |
* Creates a new Phaser without any initially registered parties, |
432 |
|
* initial phase number 0, and no parent. Any thread using this |
433 |
< |
* phaser will need to first register for it. |
433 |
> |
* Phaser will need to first register for it. |
434 |
|
*/ |
435 |
|
public Phaser() { |
436 |
< |
this(null); |
436 |
> |
this(null, 0); |
437 |
|
} |
438 |
|
|
439 |
|
/** |
440 |
< |
* Creates a new phaser with the given numbers of registered |
440 |
> |
* Creates a new Phaser with the given number of registered |
441 |
|
* unarrived parties, initial phase number 0, and no parent. |
442 |
|
* |
443 |
|
* @param parties the number of parties required to trip barrier |
449 |
|
} |
450 |
|
|
451 |
|
/** |
452 |
< |
* Creates a new phaser with the given parent, without any |
323 |
< |
* initially registered parties. If parent is non-null this phaser |
324 |
< |
* is registered with the parent and its initial phase number is |
325 |
< |
* the same as that of parent phaser. |
452 |
> |
* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}. |
453 |
|
* |
454 |
< |
* @param parent the parent phaser |
454 |
> |
* @param parent the parent Phaser |
455 |
|
*/ |
456 |
|
public Phaser(Phaser parent) { |
457 |
< |
int phase = 0; |
331 |
< |
this.parent = parent; |
332 |
< |
if (parent != null) { |
333 |
< |
this.root = parent.root; |
334 |
< |
phase = parent.register(); |
335 |
< |
} |
336 |
< |
else |
337 |
< |
this.root = this; |
338 |
< |
this.state = trippedStateFor(phase, 0); |
457 |
> |
this(parent, 0); |
458 |
|
} |
459 |
|
|
460 |
|
/** |
461 |
< |
* Creates a new phaser with the given parent and numbers of |
462 |
< |
* registered unarrived parties. If parent is non-null, this phaser |
463 |
< |
* is registered with the parent and its initial phase number is |
464 |
< |
* the same as that of parent phaser. |
461 |
> |
* Creates a new Phaser with the given parent and number of |
462 |
> |
* registered unarrived parties. Registration and deregistration |
463 |
> |
* of this child Phaser with its parent are managed automatically. |
464 |
> |
* If the given parent is non-null, whenever this child Phaser has |
465 |
> |
* any registered parties (as established in this constructor, |
466 |
> |
* {@link #register}, or {@link #bulkRegister}), this child Phaser |
467 |
> |
* is registered with its parent. Whenever the number of |
468 |
> |
* registered parties becomes zero as the result of an invocation |
469 |
> |
* of {@link #arriveAndDeregister}, this child Phaser is |
470 |
> |
* deregistered from its parent. |
471 |
|
* |
472 |
< |
* @param parent the parent phaser |
472 |
> |
* @param parent the parent Phaser |
473 |
|
* @param parties the number of parties required to trip barrier |
474 |
|
* @throws IllegalArgumentException if parties less than zero |
475 |
|
* or greater than the maximum number of parties supported |
476 |
|
*/ |
477 |
|
public Phaser(Phaser parent, int parties) { |
478 |
< |
if (parties < 0 || parties > ushortMask) |
478 |
> |
if (parties >>> PARTIES_SHIFT != 0) |
479 |
|
throw new IllegalArgumentException("Illegal number of parties"); |
480 |
< |
int phase = 0; |
480 |
> |
long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT); |
481 |
|
this.parent = parent; |
482 |
|
if (parent != null) { |
483 |
< |
this.root = parent.root; |
484 |
< |
phase = parent.register(); |
483 |
> |
Phaser r = parent.root; |
484 |
> |
this.root = r; |
485 |
> |
this.evenQ = r.evenQ; |
486 |
> |
this.oddQ = r.oddQ; |
487 |
> |
if (parties != 0) |
488 |
> |
s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT; |
489 |
|
} |
490 |
< |
else |
490 |
> |
else { |
491 |
|
this.root = this; |
492 |
< |
this.state = trippedStateFor(phase, parties); |
492 |
> |
this.evenQ = new AtomicReference<QNode>(); |
493 |
> |
this.oddQ = new AtomicReference<QNode>(); |
494 |
> |
} |
495 |
> |
this.state = s; |
496 |
|
} |
497 |
|
|
498 |
|
/** |
499 |
< |
* Adds a new unarrived party to this phaser. |
499 |
> |
* Adds a new unarrived party to this Phaser. If an ongoing |
500 |
> |
* invocation of {@link #onAdvance} is in progress, this method |
501 |
> |
* may await its completion before returning. If this Phaser has |
502 |
> |
* a parent, and this Phaser previously had no registered parties, |
503 |
> |
* this Phaser is also registered with its parent. |
504 |
|
* |
505 |
< |
* @return the current barrier phase number upon registration |
505 |
> |
* @return the arrival phase number to which this registration applied |
506 |
|
* @throws IllegalStateException if attempting to register more |
507 |
|
* than the maximum supported number of parties |
508 |
|
*/ |
511 |
|
} |
512 |
|
|
513 |
|
/** |
514 |
< |
* Adds the given number of new unarrived parties to this phaser. |
514 |
> |
* Adds the given number of new unarrived parties to this Phaser. |
515 |
> |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
516 |
> |
* this method may await its completion before returning. If this |
517 |
> |
* Phaser has a parent, and the given number of parities is |
518 |
> |
* greater than zero, and this Phaser previously had no registered |
519 |
> |
* parties, this Phaser is also registered with its parent. |
520 |
|
* |
521 |
< |
* @param parties the number of parties required to trip barrier |
522 |
< |
* @return the current barrier phase number upon registration |
521 |
> |
* @param parties the number of additional parties required to trip barrier |
522 |
> |
* @return the arrival phase number to which this registration applied |
523 |
|
* @throws IllegalStateException if attempting to register more |
524 |
|
* than the maximum supported number of parties |
525 |
+ |
* @throws IllegalArgumentException if {@code parties < 0} |
526 |
|
*/ |
527 |
|
public int bulkRegister(int parties) { |
528 |
|
if (parties < 0) |
533 |
|
} |
534 |
|
|
535 |
|
/** |
536 |
< |
* Shared code for register, bulkRegister |
395 |
< |
*/ |
396 |
< |
private int doRegister(int registrations) { |
397 |
< |
int phase; |
398 |
< |
for (;;) { |
399 |
< |
long s = getReconciledState(); |
400 |
< |
phase = phaseOf(s); |
401 |
< |
int unarrived = unarrivedOf(s) + registrations; |
402 |
< |
int parties = partiesOf(s) + registrations; |
403 |
< |
if (phase < 0) |
404 |
< |
break; |
405 |
< |
if (parties > ushortMask || unarrived > ushortMask) |
406 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
407 |
< |
if (phase == phaseOf(root.state) && |
408 |
< |
casState(s, stateFor(phase, parties, unarrived))) |
409 |
< |
break; |
410 |
< |
} |
411 |
< |
return phase; |
412 |
< |
} |
413 |
< |
|
414 |
< |
/** |
415 |
< |
* Arrives at the barrier, but does not wait for others. (You can |
416 |
< |
* in turn wait for others via {@link #awaitAdvance}). |
536 |
> |
* Arrives at the barrier, without waiting for others to arrive. |
537 |
|
* |
538 |
< |
* @return the barrier phase number upon entry to this method, or a |
539 |
< |
* negative value if terminated |
538 |
> |
* <p>It is a usage error for an unregistered party to invoke this |
539 |
> |
* method. However, this error may result in an {@code |
540 |
> |
* IllegalStateException} only upon some subsequent operation on |
541 |
> |
* this Phaser, if ever. |
542 |
> |
* |
543 |
> |
* @return the arrival phase number, or a negative value if terminated |
544 |
|
* @throws IllegalStateException if not terminated and the number |
545 |
|
* of unarrived parties would become negative |
546 |
|
*/ |
547 |
|
public int arrive() { |
548 |
< |
int phase; |
425 |
< |
for (;;) { |
426 |
< |
long s = state; |
427 |
< |
phase = phaseOf(s); |
428 |
< |
if (phase < 0) |
429 |
< |
break; |
430 |
< |
int parties = partiesOf(s); |
431 |
< |
int unarrived = unarrivedOf(s) - 1; |
432 |
< |
if (unarrived > 0) { // Not the last arrival |
433 |
< |
if (casState(s, s - 1)) // s-1 adds one arrival |
434 |
< |
break; |
435 |
< |
} |
436 |
< |
else if (unarrived == 0) { // the last arrival |
437 |
< |
Phaser par = parent; |
438 |
< |
if (par == null) { // directly trip |
439 |
< |
if (casState |
440 |
< |
(s, |
441 |
< |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
442 |
< |
((phase + 1) & phaseMask), parties))) { |
443 |
< |
releaseWaiters(phase); |
444 |
< |
break; |
445 |
< |
} |
446 |
< |
} |
447 |
< |
else { // cascade to parent |
448 |
< |
if (casState(s, s - 1)) { // zeroes unarrived |
449 |
< |
par.arrive(); |
450 |
< |
reconcileState(); |
451 |
< |
break; |
452 |
< |
} |
453 |
< |
} |
454 |
< |
} |
455 |
< |
else if (phase != phaseOf(root.state)) // or if unreconciled |
456 |
< |
reconcileState(); |
457 |
< |
else |
458 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
459 |
< |
} |
460 |
< |
return phase; |
548 |
> |
return doArrive(ONE_ARRIVAL); |
549 |
|
} |
550 |
|
|
551 |
|
/** |
552 |
|
* Arrives at the barrier and deregisters from it without waiting |
553 |
< |
* for others. Deregistration reduces the number of parties |
554 |
< |
* required to trip the barrier in future phases. If this phaser |
555 |
< |
* has a parent, and deregistration causes this phaser to have |
556 |
< |
* zero parties, this phaser also arrives at and is deregistered |
557 |
< |
* from its parent. |
553 |
> |
* for others to arrive. Deregistration reduces the number of |
554 |
> |
* parties required to trip the barrier in future phases. If this |
555 |
> |
* Phaser has a parent, and deregistration causes this Phaser to |
556 |
> |
* have zero parties, this Phaser is also deregistered from its |
557 |
> |
* parent. |
558 |
> |
* |
559 |
> |
* <p>It is a usage error for an unregistered party to invoke this |
560 |
> |
* method. However, this error may result in an {@code |
561 |
> |
* IllegalStateException} only upon some subsequent operation on |
562 |
> |
* this Phaser, if ever. |
563 |
|
* |
564 |
< |
* @return the current barrier phase number upon entry to |
472 |
< |
* this method, or a negative value if terminated |
564 |
> |
* @return the arrival phase number, or a negative value if terminated |
565 |
|
* @throws IllegalStateException if not terminated and the number |
566 |
|
* of registered or unarrived parties would become negative |
567 |
|
*/ |
568 |
|
public int arriveAndDeregister() { |
569 |
< |
// similar code to arrive, but too different to merge |
478 |
< |
Phaser par = parent; |
479 |
< |
int phase; |
480 |
< |
for (;;) { |
481 |
< |
long s = state; |
482 |
< |
phase = phaseOf(s); |
483 |
< |
if (phase < 0) |
484 |
< |
break; |
485 |
< |
int parties = partiesOf(s) - 1; |
486 |
< |
int unarrived = unarrivedOf(s) - 1; |
487 |
< |
if (parties >= 0) { |
488 |
< |
if (unarrived > 0 || (unarrived == 0 && par != null)) { |
489 |
< |
if (casState |
490 |
< |
(s, |
491 |
< |
stateFor(phase, parties, unarrived))) { |
492 |
< |
if (unarrived == 0) { |
493 |
< |
par.arriveAndDeregister(); |
494 |
< |
reconcileState(); |
495 |
< |
} |
496 |
< |
break; |
497 |
< |
} |
498 |
< |
continue; |
499 |
< |
} |
500 |
< |
if (unarrived == 0) { |
501 |
< |
if (casState |
502 |
< |
(s, |
503 |
< |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
504 |
< |
((phase + 1) & phaseMask), parties))) { |
505 |
< |
releaseWaiters(phase); |
506 |
< |
break; |
507 |
< |
} |
508 |
< |
continue; |
509 |
< |
} |
510 |
< |
if (par != null && phase != phaseOf(root.state)) { |
511 |
< |
reconcileState(); |
512 |
< |
continue; |
513 |
< |
} |
514 |
< |
} |
515 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
516 |
< |
} |
517 |
< |
return phase; |
569 |
> |
return doArrive(ONE_ARRIVAL|ONE_PARTY); |
570 |
|
} |
571 |
|
|
572 |
|
/** |
573 |
|
* Arrives at the barrier and awaits others. Equivalent in effect |
574 |
|
* to {@code awaitAdvance(arrive())}. If you need to await with |
575 |
|
* interruption or timeout, you can arrange this with an analogous |
576 |
< |
* construction using one of the other forms of the awaitAdvance |
577 |
< |
* method. If instead you need to deregister upon arrival use |
578 |
< |
* {@code arriveAndDeregister}. |
576 |
> |
* construction using one of the other forms of the {@code |
577 |
> |
* awaitAdvance} method. If instead you need to deregister upon |
578 |
> |
* arrival, use {@code awaitAdvance(arriveAndDeregister())}. |
579 |
> |
* |
580 |
> |
* <p>It is a usage error for an unregistered party to invoke this |
581 |
> |
* method. However, this error may result in an {@code |
582 |
> |
* IllegalStateException} only upon some subsequent operation on |
583 |
> |
* this Phaser, if ever. |
584 |
|
* |
585 |
< |
* @return the phase on entry to this method |
585 |
> |
* @return the arrival phase number, or a negative number if terminated |
586 |
|
* @throws IllegalStateException if not terminated and the number |
587 |
|
* of unarrived parties would become negative |
588 |
|
*/ |
596 |
|
* barrier is not equal to the given phase value or this barrier |
597 |
|
* is terminated. |
598 |
|
* |
599 |
< |
* @param phase the phase on entry to this method |
600 |
< |
* @return the phase on exit from this method |
599 |
> |
* @param phase an arrival phase number, or negative value if |
600 |
> |
* terminated; this argument is normally the value returned by a |
601 |
> |
* previous call to {@code arrive} or its variants |
602 |
> |
* @return the next arrival phase number, or a negative value |
603 |
> |
* if terminated or argument is negative |
604 |
|
*/ |
605 |
|
public int awaitAdvance(int phase) { |
606 |
+ |
Phaser r; |
607 |
+ |
int p = (int)(state >>> PHASE_SHIFT); |
608 |
|
if (phase < 0) |
609 |
|
return phase; |
610 |
< |
long s = getReconciledState(); |
611 |
< |
int p = phaseOf(s); |
612 |
< |
if (p != phase) |
613 |
< |
return p; |
552 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
553 |
< |
parent.awaitAdvance(phase); |
554 |
< |
// Fall here even if parent waited, to reconcile and help release |
555 |
< |
return untimedWait(phase); |
610 |
> |
if (p == phase && |
611 |
> |
(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) |
612 |
> |
return r.internalAwaitAdvance(phase, null); |
613 |
> |
return p; |
614 |
|
} |
615 |
|
|
616 |
|
/** |
617 |
|
* Awaits the phase of the barrier to advance from the given phase |
618 |
< |
* value, throwing InterruptedException if interrupted while |
619 |
< |
* waiting, or returning immediately if the current phase of the |
620 |
< |
* barrier is not equal to the given phase value or this barrier |
621 |
< |
* is terminated |
622 |
< |
* |
623 |
< |
* @param phase the phase on entry to this method |
624 |
< |
* @return the phase on exit from this method |
618 |
> |
* value, throwing {@code InterruptedException} if interrupted |
619 |
> |
* while waiting, or returning immediately if the current phase of |
620 |
> |
* the barrier is not equal to the given phase value or this |
621 |
> |
* barrier is terminated. |
622 |
> |
* |
623 |
> |
* @param phase an arrival phase number, or negative value if |
624 |
> |
* terminated; this argument is normally the value returned by a |
625 |
> |
* previous call to {@code arrive} or its variants |
626 |
> |
* @return the next arrival phase number, or a negative value |
627 |
> |
* if terminated or argument is negative |
628 |
|
* @throws InterruptedException if thread interrupted while waiting |
629 |
|
*/ |
630 |
|
public int awaitAdvanceInterruptibly(int phase) |
631 |
|
throws InterruptedException { |
632 |
+ |
Phaser r; |
633 |
+ |
int p = (int)(state >>> PHASE_SHIFT); |
634 |
|
if (phase < 0) |
635 |
|
return phase; |
636 |
< |
long s = getReconciledState(); |
637 |
< |
int p = phaseOf(s); |
638 |
< |
if (p != phase) |
639 |
< |
return p; |
640 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
641 |
< |
parent.awaitAdvanceInterruptibly(phase); |
642 |
< |
return interruptibleWait(phase); |
636 |
> |
if (p == phase && |
637 |
> |
(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) { |
638 |
> |
QNode node = new QNode(this, phase, true, false, 0L); |
639 |
> |
p = r.internalAwaitAdvance(phase, node); |
640 |
> |
if (node.wasInterrupted) |
641 |
> |
throw new InterruptedException(); |
642 |
> |
} |
643 |
> |
return p; |
644 |
|
} |
645 |
|
|
646 |
|
/** |
647 |
|
* Awaits the phase of the barrier to advance from the given phase |
648 |
< |
* value or the given timeout elapses, throwing |
649 |
< |
* InterruptedException if interrupted while waiting, or returning |
650 |
< |
* immediately if the current phase of the barrier is not equal to |
651 |
< |
* the given phase value or this barrier is terminated. |
652 |
< |
* |
653 |
< |
* @param phase the phase on entry to this method |
654 |
< |
* @return the phase on exit from this method |
648 |
> |
* value or the given timeout to elapse, throwing {@code |
649 |
> |
* InterruptedException} if interrupted while waiting, or |
650 |
> |
* returning immediately if the current phase of the barrier is |
651 |
> |
* not equal to the given phase value or this barrier is |
652 |
> |
* terminated. |
653 |
> |
* |
654 |
> |
* @param phase an arrival phase number, or negative value if |
655 |
> |
* terminated; this argument is normally the value returned by a |
656 |
> |
* previous call to {@code arrive} or its variants |
657 |
> |
* @param timeout how long to wait before giving up, in units of |
658 |
> |
* {@code unit} |
659 |
> |
* @param unit a {@code TimeUnit} determining how to interpret the |
660 |
> |
* {@code timeout} parameter |
661 |
> |
* @return the next arrival phase number, or a negative value |
662 |
> |
* if terminated or argument is negative |
663 |
|
* @throws InterruptedException if thread interrupted while waiting |
664 |
|
* @throws TimeoutException if timed out while waiting |
665 |
|
*/ |
666 |
|
public int awaitAdvanceInterruptibly(int phase, |
667 |
|
long timeout, TimeUnit unit) |
668 |
|
throws InterruptedException, TimeoutException { |
669 |
+ |
long nanos = unit.toNanos(timeout); |
670 |
+ |
Phaser r; |
671 |
+ |
int p = (int)(state >>> PHASE_SHIFT); |
672 |
|
if (phase < 0) |
673 |
|
return phase; |
674 |
< |
long s = getReconciledState(); |
675 |
< |
int p = phaseOf(s); |
676 |
< |
if (p != phase) |
677 |
< |
return p; |
678 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
679 |
< |
parent.awaitAdvanceInterruptibly(phase, timeout, unit); |
680 |
< |
return timedWait(phase, unit.toNanos(timeout)); |
674 |
> |
if (p == phase && |
675 |
> |
(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) { |
676 |
> |
QNode node = new QNode(this, phase, true, true, nanos); |
677 |
> |
p = r.internalAwaitAdvance(phase, node); |
678 |
> |
if (node.wasInterrupted) |
679 |
> |
throw new InterruptedException(); |
680 |
> |
else if (p == phase) |
681 |
> |
throw new TimeoutException(); |
682 |
> |
} |
683 |
> |
return p; |
684 |
|
} |
685 |
|
|
686 |
|
/** |
687 |
< |
* Forces this barrier to enter termination state. Counts of |
688 |
< |
* arrived and registered parties are unaffected. If this phaser |
689 |
< |
* has a parent, it too is terminated. This method may be useful |
690 |
< |
* for coordinating recovery after one or more tasks encounter |
691 |
< |
* unexpected exceptions. |
687 |
> |
* Forces this barrier to enter termination state. Counts of |
688 |
> |
* arrived and registered parties are unaffected. If this Phaser |
689 |
> |
* is a member of a tiered set of Phasers, then all of the Phasers |
690 |
> |
* in the set are terminated. If this Phaser is already |
691 |
> |
* terminated, this method has no effect. This method may be |
692 |
> |
* useful for coordinating recovery after one or more tasks |
693 |
> |
* encounter unexpected exceptions. |
694 |
|
*/ |
695 |
|
public void forceTermination() { |
696 |
< |
for (;;) { |
697 |
< |
long s = getReconciledState(); |
698 |
< |
int phase = phaseOf(s); |
699 |
< |
int parties = partiesOf(s); |
700 |
< |
int unarrived = unarrivedOf(s); |
701 |
< |
if (phase < 0 || |
702 |
< |
casState(s, stateFor(-1, parties, unarrived))) { |
623 |
< |
releaseWaiters(0); |
696 |
> |
// Only need to change root state |
697 |
> |
final Phaser root = this.root; |
698 |
> |
long s; |
699 |
> |
while ((s = root.state) >= 0) { |
700 |
> |
if (UNSAFE.compareAndSwapLong(root, stateOffset, |
701 |
> |
s, s | TERMINATION_BIT)) { |
702 |
> |
releaseWaiters(0); // signal all threads |
703 |
|
releaseWaiters(1); |
625 |
– |
if (parent != null) |
626 |
– |
parent.forceTermination(); |
704 |
|
return; |
705 |
|
} |
706 |
|
} |
714 |
|
* @return the phase number, or a negative value if terminated |
715 |
|
*/ |
716 |
|
public final int getPhase() { |
717 |
< |
return phaseOf(getReconciledState()); |
717 |
> |
return (int)(root.state >>> PHASE_SHIFT); |
718 |
|
} |
719 |
|
|
720 |
|
/** |
727 |
|
} |
728 |
|
|
729 |
|
/** |
730 |
< |
* Returns the number of parties that have arrived at the current |
731 |
< |
* phase of this barrier. |
730 |
> |
* Returns the number of registered parties that have arrived at |
731 |
> |
* the current phase of this barrier. |
732 |
|
* |
733 |
|
* @return the number of arrived parties |
734 |
|
*/ |
735 |
|
public int getArrivedParties() { |
736 |
< |
return arrivedOf(state); |
736 |
> |
long s = state; |
737 |
> |
int u = unarrivedOf(s); // only reconcile if possibly needed |
738 |
> |
return (u != 0 || parent == null) ? |
739 |
> |
partiesOf(s) - u : |
740 |
> |
arrivedOf(reconcileState()); |
741 |
|
} |
742 |
|
|
743 |
|
/** |
747 |
|
* @return the number of unarrived parties |
748 |
|
*/ |
749 |
|
public int getUnarrivedParties() { |
750 |
< |
return unarrivedOf(state); |
750 |
> |
int u = unarrivedOf(state); |
751 |
> |
return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState()); |
752 |
|
} |
753 |
|
|
754 |
|
/** |
755 |
< |
* Returns the parent of this phaser, or {@code null} if none. |
755 |
> |
* Returns the parent of this Phaser, or {@code null} if none. |
756 |
|
* |
757 |
< |
* @return the parent of this phaser, or {@code null} if none |
757 |
> |
* @return the parent of this Phaser, or {@code null} if none |
758 |
|
*/ |
759 |
|
public Phaser getParent() { |
760 |
|
return parent; |
761 |
|
} |
762 |
|
|
763 |
|
/** |
764 |
< |
* Returns the root ancestor of this phaser, which is the same as |
765 |
< |
* this phaser if it has no parent. |
764 |
> |
* Returns the root ancestor of this Phaser, which is the same as |
765 |
> |
* this Phaser if it has no parent. |
766 |
|
* |
767 |
< |
* @return the root ancestor of this phaser |
767 |
> |
* @return the root ancestor of this Phaser |
768 |
|
*/ |
769 |
|
public Phaser getRoot() { |
770 |
|
return root; |
776 |
|
* @return {@code true} if this barrier has been terminated |
777 |
|
*/ |
778 |
|
public boolean isTerminated() { |
779 |
< |
return getPhase() < 0; |
779 |
> |
return root.state < 0L; |
780 |
|
} |
781 |
|
|
782 |
|
/** |
783 |
< |
* Overridable method to perform an action upon phase advance, and |
784 |
< |
* to control termination. This method is invoked whenever the |
785 |
< |
* barrier is tripped (and thus all other waiting parties are |
786 |
< |
* dormant). If it returns {@code true}, then, rather than advance |
787 |
< |
* the phase number, this barrier will be set to a final |
788 |
< |
* termination state, and subsequent calls to {@link #isTerminated} |
789 |
< |
* will return true. |
790 |
< |
* |
791 |
< |
* <p>The default version returns {@code true} when the number of |
792 |
< |
* registered parties is zero. Normally, overrides that arrange |
793 |
< |
* termination for other reasons should also preserve this |
794 |
< |
* property. |
795 |
< |
* |
796 |
< |
* <p>You may override this method to perform an action with side |
797 |
< |
* effects visible to participating tasks, but it is in general |
798 |
< |
* only sensible to do so in designs where all parties register |
799 |
< |
* before any arrive, and all {@link #awaitAdvance} at each phase. |
800 |
< |
* Otherwise, you cannot ensure lack of interference from other |
801 |
< |
* parties during the invocation of this method. |
783 |
> |
* Overridable method to perform an action upon impending phase |
784 |
> |
* advance, and to control termination. This method is invoked |
785 |
> |
* upon arrival of the party tripping the barrier (when all other |
786 |
> |
* waiting parties are dormant). If this method returns {@code |
787 |
> |
* true}, then, rather than advance the phase number, this barrier |
788 |
> |
* will be set to a final termination state, and subsequent calls |
789 |
> |
* to {@link #isTerminated} will return true. Any (unchecked) |
790 |
> |
* Exception or Error thrown by an invocation of this method is |
791 |
> |
* propagated to the party attempting to trip the barrier, in |
792 |
> |
* which case no advance occurs. |
793 |
> |
* |
794 |
> |
* <p>The arguments to this method provide the state of the Phaser |
795 |
> |
* prevailing for the current transition. The effects of invoking |
796 |
> |
* arrival, registration, and waiting methods on this Phaser from |
797 |
> |
* within {@code onAdvance} are unspecified and should not be |
798 |
> |
* relied on. |
799 |
> |
* |
800 |
> |
* <p>If this Phaser is a member of a tiered set of Phasers, then |
801 |
> |
* {@code onAdvance} is invoked only for its root Phaser on each |
802 |
> |
* advance. |
803 |
> |
* |
804 |
> |
* <p>To support the most common use cases, the default |
805 |
> |
* implementation of this method returns {@code true} when the |
806 |
> |
* number of registered parties has become zero as the result of a |
807 |
> |
* party invoking {@code arriveAndDeregister}. You can disable |
808 |
> |
* this behavior, thus enabling continuation upon future |
809 |
> |
* registrations, by overriding this method to always return |
810 |
> |
* {@code false}: |
811 |
> |
* |
812 |
> |
* <pre> {@code |
813 |
> |
* Phaser phaser = new Phaser() { |
814 |
> |
* protected boolean onAdvance(int phase, int parties) { return false; } |
815 |
> |
* }}</pre> |
816 |
|
* |
817 |
|
* @param phase the phase number on entering the barrier |
818 |
|
* @param registeredParties the current number of registered parties |
823 |
|
} |
824 |
|
|
825 |
|
/** |
826 |
< |
* Returns a string identifying this phaser, as well as its |
826 |
> |
* Returns a string identifying this Phaser, as well as its |
827 |
|
* state. The state, in brackets, includes the String {@code |
828 |
|
* "phase = "} followed by the phase number, {@code "parties = "} |
829 |
|
* followed by the number of registered parties, and {@code |
832 |
|
* @return a string identifying this barrier, as well as its state |
833 |
|
*/ |
834 |
|
public String toString() { |
835 |
< |
long s = getReconciledState(); |
835 |
> |
return stateToString(reconcileState()); |
836 |
> |
} |
837 |
> |
|
838 |
> |
/** |
839 |
> |
* Implementation of toString and string-based error messages |
840 |
> |
*/ |
841 |
> |
private String stateToString(long s) { |
842 |
|
return super.toString() + |
843 |
|
"[phase = " + phaseOf(s) + |
844 |
|
" parties = " + partiesOf(s) + |
845 |
|
" arrived = " + arrivedOf(s) + "]"; |
846 |
|
} |
847 |
|
|
848 |
< |
// methods for waiting |
848 |
> |
// Waiting mechanics |
849 |
> |
|
850 |
> |
/** |
851 |
> |
* Removes and signals threads from queue for phase. |
852 |
> |
*/ |
853 |
> |
private void releaseWaiters(int phase) { |
854 |
> |
AtomicReference<QNode> head = queueFor(phase); |
855 |
> |
QNode q; |
856 |
> |
int p; |
857 |
> |
while ((q = head.get()) != null && |
858 |
> |
((p = q.phase) == phase || |
859 |
> |
(int)(root.state >>> PHASE_SHIFT) != p)) { |
860 |
> |
if (head.compareAndSet(q, q.next)) |
861 |
> |
q.signal(); |
862 |
> |
} |
863 |
> |
} |
864 |
> |
|
865 |
> |
/** The number of CPUs, for spin control */ |
866 |
> |
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
867 |
> |
|
868 |
> |
/** |
869 |
> |
* The number of times to spin before blocking while waiting for |
870 |
> |
* advance, per arrival while waiting. On multiprocessors, fully |
871 |
> |
* blocking and waking up a large number of threads all at once is |
872 |
> |
* usually a very slow process, so we use rechargeable spins to |
873 |
> |
* avoid it when threads regularly arrive: When a thread in |
874 |
> |
* internalAwaitAdvance notices another arrival before blocking, |
875 |
> |
* and there appear to be enough CPUs available, it spins |
876 |
> |
* SPINS_PER_ARRIVAL more times before blocking. Plus, even on |
877 |
> |
* uniprocessors, there is at least one intervening Thread.yield |
878 |
> |
* before blocking. The value trades off good-citizenship vs big |
879 |
> |
* unnecessary slowdowns. |
880 |
> |
*/ |
881 |
> |
static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8; |
882 |
> |
|
883 |
> |
/** |
884 |
> |
* Possibly blocks and waits for phase to advance unless aborted. |
885 |
> |
* Call only from root node. |
886 |
> |
* |
887 |
> |
* @param phase current phase |
888 |
> |
* @param node if non-null, the wait node to track interrupt and timeout; |
889 |
> |
* if null, denotes noninterruptible wait |
890 |
> |
* @return current phase |
891 |
> |
*/ |
892 |
> |
private int internalAwaitAdvance(int phase, QNode node) { |
893 |
> |
boolean queued = false; // true when node is enqueued |
894 |
> |
int lastUnarrived = -1; // to increase spins upon change |
895 |
> |
int spins = SPINS_PER_ARRIVAL; |
896 |
> |
long s; |
897 |
> |
int p; |
898 |
> |
while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) { |
899 |
> |
int unarrived = (int)s & UNARRIVED_MASK; |
900 |
> |
if (unarrived != lastUnarrived) { |
901 |
> |
if (lastUnarrived == -1) // ensure old queue clean |
902 |
> |
releaseWaiters(phase-1); |
903 |
> |
if ((lastUnarrived = unarrived) < NCPU) |
904 |
> |
spins += SPINS_PER_ARRIVAL; |
905 |
> |
} |
906 |
> |
else if (spins > 0) { |
907 |
> |
if (--spins == (SPINS_PER_ARRIVAL >>> 1)) |
908 |
> |
Thread.yield(); // yield midway through spin |
909 |
> |
} |
910 |
> |
else if (node == null) // must be noninterruptible |
911 |
> |
node = new QNode(this, phase, false, false, 0L); |
912 |
> |
else if (node.isReleasable()) { |
913 |
> |
p = (int)(state >>> PHASE_SHIFT); |
914 |
> |
break; // aborted |
915 |
> |
} |
916 |
> |
else if (!queued) { // push onto queue |
917 |
> |
AtomicReference<QNode> head = queueFor(phase); |
918 |
> |
QNode q = head.get(); |
919 |
> |
if (q == null || q.phase == phase) { |
920 |
> |
node.next = q; |
921 |
> |
if ((p = (int)(state >>> PHASE_SHIFT)) != phase) |
922 |
> |
break; // recheck to avoid stale enqueue |
923 |
> |
else |
924 |
> |
queued = head.compareAndSet(q, node); |
925 |
> |
} |
926 |
> |
} |
927 |
> |
else { |
928 |
> |
try { |
929 |
> |
ForkJoinPool.managedBlock(node); |
930 |
> |
} catch (InterruptedException ie) { |
931 |
> |
node.wasInterrupted = true; |
932 |
> |
} |
933 |
> |
} |
934 |
> |
} |
935 |
> |
|
936 |
> |
if (node != null) { |
937 |
> |
if (node.thread != null) |
938 |
> |
node.thread = null; // disable unpark() in node.signal |
939 |
> |
if (!node.interruptible && node.wasInterrupted) |
940 |
> |
Thread.currentThread().interrupt(); |
941 |
> |
} |
942 |
> |
if (p != phase) |
943 |
> |
releaseWaiters(phase); |
944 |
> |
return p; |
945 |
> |
} |
946 |
|
|
947 |
|
/** |
948 |
|
* Wait nodes for Treiber stack representing wait queue |
950 |
|
static final class QNode implements ForkJoinPool.ManagedBlocker { |
951 |
|
final Phaser phaser; |
952 |
|
final int phase; |
754 |
– |
final long startTime; |
755 |
– |
final long nanos; |
756 |
– |
final boolean timed; |
953 |
|
final boolean interruptible; |
954 |
< |
volatile boolean wasInterrupted = false; |
954 |
> |
final boolean timed; |
955 |
> |
boolean wasInterrupted; |
956 |
> |
long nanos; |
957 |
> |
long lastTime; |
958 |
|
volatile Thread thread; // nulled to cancel wait |
959 |
|
QNode next; |
960 |
+ |
|
961 |
|
QNode(Phaser phaser, int phase, boolean interruptible, |
962 |
< |
boolean timed, long startTime, long nanos) { |
962 |
> |
boolean timed, long nanos) { |
963 |
|
this.phaser = phaser; |
964 |
|
this.phase = phase; |
765 |
– |
this.timed = timed; |
965 |
|
this.interruptible = interruptible; |
767 |
– |
this.startTime = startTime; |
966 |
|
this.nanos = nanos; |
967 |
+ |
this.timed = timed; |
968 |
+ |
this.lastTime = timed? System.nanoTime() : 0L; |
969 |
|
thread = Thread.currentThread(); |
970 |
|
} |
971 |
+ |
|
972 |
|
public boolean isReleasable() { |
973 |
< |
return (thread == null || |
974 |
< |
phaser.getPhase() != phase || |
975 |
< |
(interruptible && wasInterrupted) || |
976 |
< |
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
973 |
> |
Thread t = thread; |
974 |
> |
if (t != null) { |
975 |
> |
if (phaser.getPhase() != phase) |
976 |
> |
t = null; |
977 |
> |
else { |
978 |
> |
if (Thread.interrupted()) |
979 |
> |
wasInterrupted = true; |
980 |
> |
if (interruptible && wasInterrupted) |
981 |
> |
t = null; |
982 |
> |
else if (timed) { |
983 |
> |
if (nanos > 0) { |
984 |
> |
long now = System.nanoTime(); |
985 |
> |
nanos -= now - lastTime; |
986 |
> |
lastTime = now; |
987 |
> |
} |
988 |
> |
if (nanos <= 0) |
989 |
> |
t = null; |
990 |
> |
} |
991 |
> |
} |
992 |
> |
if (t != null) |
993 |
> |
return false; |
994 |
> |
thread = null; |
995 |
> |
} |
996 |
> |
return true; |
997 |
|
} |
998 |
+ |
|
999 |
|
public boolean block() { |
1000 |
< |
if (Thread.interrupted()) { |
1001 |
< |
wasInterrupted = true; |
1002 |
< |
if (interruptible) |
781 |
< |
return true; |
782 |
< |
} |
783 |
< |
if (!timed) |
1000 |
> |
if (isReleasable()) |
1001 |
> |
return true; |
1002 |
> |
else if (!timed) |
1003 |
|
LockSupport.park(this); |
1004 |
< |
else { |
1005 |
< |
long waitTime = nanos - (System.nanoTime() - startTime); |
787 |
< |
if (waitTime <= 0) |
788 |
< |
return true; |
789 |
< |
LockSupport.parkNanos(this, waitTime); |
790 |
< |
} |
1004 |
> |
else if (nanos > 0) |
1005 |
> |
LockSupport.parkNanos(this, nanos); |
1006 |
|
return isReleasable(); |
1007 |
|
} |
1008 |
+ |
|
1009 |
|
void signal() { |
1010 |
|
Thread t = thread; |
1011 |
|
if (t != null) { |
1013 |
|
LockSupport.unpark(t); |
1014 |
|
} |
1015 |
|
} |
800 |
– |
boolean doWait() { |
801 |
– |
if (thread != null) { |
802 |
– |
try { |
803 |
– |
ForkJoinPool.managedBlock(this, false); |
804 |
– |
} catch (InterruptedException ie) { |
805 |
– |
} |
806 |
– |
} |
807 |
– |
return wasInterrupted; |
808 |
– |
} |
809 |
– |
|
810 |
– |
} |
811 |
– |
|
812 |
– |
/** |
813 |
– |
* Removes and signals waiting threads from wait queue. |
814 |
– |
*/ |
815 |
– |
private void releaseWaiters(int phase) { |
816 |
– |
AtomicReference<QNode> head = queueFor(phase); |
817 |
– |
QNode q; |
818 |
– |
while ((q = head.get()) != null) { |
819 |
– |
if (head.compareAndSet(q, q.next)) |
820 |
– |
q.signal(); |
821 |
– |
} |
822 |
– |
} |
823 |
– |
|
824 |
– |
/** |
825 |
– |
* Tries to enqueue given node in the appropriate wait queue. |
826 |
– |
* |
827 |
– |
* @return true if successful |
828 |
– |
*/ |
829 |
– |
private boolean tryEnqueue(QNode node) { |
830 |
– |
AtomicReference<QNode> head = queueFor(node.phase); |
831 |
– |
return head.compareAndSet(node.next = head.get(), node); |
832 |
– |
} |
833 |
– |
|
834 |
– |
/** |
835 |
– |
* Enqueues node and waits unless aborted or signalled. |
836 |
– |
* |
837 |
– |
* @return current phase |
838 |
– |
*/ |
839 |
– |
private int untimedWait(int phase) { |
840 |
– |
QNode node = null; |
841 |
– |
boolean queued = false; |
842 |
– |
boolean interrupted = false; |
843 |
– |
int p; |
844 |
– |
while ((p = getPhase()) == phase) { |
845 |
– |
if (Thread.interrupted()) |
846 |
– |
interrupted = true; |
847 |
– |
else if (node == null) |
848 |
– |
node = new QNode(this, phase, false, false, 0, 0); |
849 |
– |
else if (!queued) |
850 |
– |
queued = tryEnqueue(node); |
851 |
– |
else |
852 |
– |
interrupted = node.doWait(); |
853 |
– |
} |
854 |
– |
if (node != null) |
855 |
– |
node.thread = null; |
856 |
– |
releaseWaiters(phase); |
857 |
– |
if (interrupted) |
858 |
– |
Thread.currentThread().interrupt(); |
859 |
– |
return p; |
860 |
– |
} |
861 |
– |
|
862 |
– |
/** |
863 |
– |
* Interruptible version |
864 |
– |
* @return current phase |
865 |
– |
*/ |
866 |
– |
private int interruptibleWait(int phase) throws InterruptedException { |
867 |
– |
QNode node = null; |
868 |
– |
boolean queued = false; |
869 |
– |
boolean interrupted = false; |
870 |
– |
int p; |
871 |
– |
while ((p = getPhase()) == phase && !interrupted) { |
872 |
– |
if (Thread.interrupted()) |
873 |
– |
interrupted = true; |
874 |
– |
else if (node == null) |
875 |
– |
node = new QNode(this, phase, true, false, 0, 0); |
876 |
– |
else if (!queued) |
877 |
– |
queued = tryEnqueue(node); |
878 |
– |
else |
879 |
– |
interrupted = node.doWait(); |
880 |
– |
} |
881 |
– |
if (node != null) |
882 |
– |
node.thread = null; |
883 |
– |
if (p != phase || (p = getPhase()) != phase) |
884 |
– |
releaseWaiters(phase); |
885 |
– |
if (interrupted) |
886 |
– |
throw new InterruptedException(); |
887 |
– |
return p; |
888 |
– |
} |
889 |
– |
|
890 |
– |
/** |
891 |
– |
* Timeout version. |
892 |
– |
* @return current phase |
893 |
– |
*/ |
894 |
– |
private int timedWait(int phase, long nanos) |
895 |
– |
throws InterruptedException, TimeoutException { |
896 |
– |
long startTime = System.nanoTime(); |
897 |
– |
QNode node = null; |
898 |
– |
boolean queued = false; |
899 |
– |
boolean interrupted = false; |
900 |
– |
int p; |
901 |
– |
while ((p = getPhase()) == phase && !interrupted) { |
902 |
– |
if (Thread.interrupted()) |
903 |
– |
interrupted = true; |
904 |
– |
else if (nanos - (System.nanoTime() - startTime) <= 0) |
905 |
– |
break; |
906 |
– |
else if (node == null) |
907 |
– |
node = new QNode(this, phase, true, true, startTime, nanos); |
908 |
– |
else if (!queued) |
909 |
– |
queued = tryEnqueue(node); |
910 |
– |
else |
911 |
– |
interrupted = node.doWait(); |
912 |
– |
} |
913 |
– |
if (node != null) |
914 |
– |
node.thread = null; |
915 |
– |
if (p != phase || (p = getPhase()) != phase) |
916 |
– |
releaseWaiters(phase); |
917 |
– |
if (interrupted) |
918 |
– |
throw new InterruptedException(); |
919 |
– |
if (p == phase) |
920 |
– |
throw new TimeoutException(); |
921 |
– |
return p; |
1016 |
|
} |
1017 |
|
|
1018 |
|
// Unsafe mechanics |
1021 |
|
private static final long stateOffset = |
1022 |
|
objectFieldOffset("state", Phaser.class); |
1023 |
|
|
930 |
– |
private final boolean casState(long cmp, long val) { |
931 |
– |
return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val); |
932 |
– |
} |
933 |
– |
|
1024 |
|
private static long objectFieldOffset(String field, Class<?> klazz) { |
1025 |
|
try { |
1026 |
|
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |