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package jsr166y; |
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import java.util.concurrent.*; |
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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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* {@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 <em>registered</em> to synchronize on a |
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* phaser may vary over time. Tasks may be registered at any time |
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* (using methods {@link #register}, {@link #bulkRegister}, or forms |
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* of constructors establishing initial numbers of parties), and may |
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* optionally be deregistered upon any arrival (using {@link |
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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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* (However, you can introduce such bookkeeping by subclassing this |
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* class.) |
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* |
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* <li> Each generation has an associated phase number. The phase |
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* number starts at zero, amd advances when all parties arrive at the |
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* barrier, wrapping around to zero after reaching {@code |
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* 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>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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* an associated <em>arrival phase number</em>; |
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* that is, the phase number of the barrier to which the |
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* arrival applied. |
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* |
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* <li> Awaiting others. Method {@link #awaitAdvance} requires an |
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* argument indicating an arrival phase number, and returns |
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* when the barrier advances to a new phase. |
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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}. 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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* {@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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* <li>The current state of a phaser may be monitored. At any given |
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* moment there are {@link #getRegisteredParties}, where {@link |
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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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* arrive, the phase advances. Method {@link #toString} returns |
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* snapshots of these state queries in a form convenient for |
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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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* </ul> |
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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> tasks) { |
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* <pre> {@code |
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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 task : tasks) { |
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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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* 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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* 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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* 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 {@code IllegalStateException}. However, you can and |
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*/ |
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private volatile long state; |
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private static final int ushortBits = 16; |
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private static final int ushortMask = 0xffff; |
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private static final int phaseMask = 0x7fffffff; |
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/** |
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* 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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* Recursively resolves state. |
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*/ |
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private long reconcileState() { |
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Phaser p = parent; |
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Phaser par = parent; |
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long s = state; |
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if (p != null) { |
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while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) { |
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long parentState = p.getReconciledState(); |
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int parentPhase = phaseOf(parentState); |
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int phase = phaseOf(s = state); |
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if (phase != parentPhase) { |
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if (par != null) { |
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int phase, rootPhase; |
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while ((phase = phaseOf(s)) >= 0 && |
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(rootPhase = phaseOf(root.state)) != phase && |
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(rootPhase < 0 || unarrivedOf(s) == 0)) { |
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int parentPhase = phaseOf(par.getReconciledState()); |
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if (parentPhase != phase) { |
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long next = trippedStateFor(parentPhase, partiesOf(s)); |
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if (casState(s, next)) { |
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releaseWaiters(phase); |
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s = next; |
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} |
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if (state == s) |
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UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
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} |
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s = state; |
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} |
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} |
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return s; |
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* phaser will need to first register for it. |
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*/ |
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public Phaser() { |
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this(null); |
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this(null, 0); |
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} |
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|
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/** |
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* Creates a new phaser with the given numbers of registered |
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* Creates a new phaser with the given number of registered |
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* unarrived parties, initial phase number 0, and no parent. |
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* |
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* @param parties the number of parties required to trip barrier |
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* @param parent the parent phaser |
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*/ |
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public Phaser(Phaser parent) { |
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int phase = 0; |
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this.parent = parent; |
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if (parent != null) { |
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this.root = parent.root; |
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phase = parent.register(); |
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} |
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else |
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this.root = this; |
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this.state = trippedStateFor(phase, 0); |
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this(parent, 0); |
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} |
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|
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/** |
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* Creates a new phaser with the given parent and numbers of |
373 |
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* Creates a new phaser with the given parent and number of |
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* registered unarrived parties. If parent is non-null, this phaser |
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* is registered with the parent and its initial phase number is |
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* the same as that of parent phaser. |
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public Phaser(Phaser parent, int parties) { |
384 |
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if (parties < 0 || parties > ushortMask) |
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throw new IllegalArgumentException("Illegal number of parties"); |
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< |
int phase = 0; |
386 |
> |
int phase; |
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this.parent = parent; |
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if (parent != null) { |
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< |
this.root = parent.root; |
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> |
Phaser r = parent.root; |
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> |
this.root = r; |
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> |
this.evenQ = r.evenQ; |
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> |
this.oddQ = r.oddQ; |
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phase = parent.register(); |
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} |
395 |
< |
else |
395 |
> |
else { |
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this.root = this; |
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+ |
this.evenQ = new AtomicReference<QNode>(); |
398 |
+ |
this.oddQ = new AtomicReference<QNode>(); |
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+ |
phase = 0; |
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+ |
} |
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this.state = trippedStateFor(phase, parties); |
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} |
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|
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/** |
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* Adds a new unarrived party to this phaser. |
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+ |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
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* this method may wait until its completion before registering. |
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* |
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* @return the arrival phase number to which this registration applied |
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* @throws IllegalStateException if attempting to register more |
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|
417 |
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/** |
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* Adds the given number of new unarrived parties to this phaser. |
419 |
+ |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
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* this method may wait until its completion before registering. |
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* |
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< |
* @param parties the number of parties required to trip barrier |
422 |
> |
* @param parties the number of additional parties required to trip barrier |
423 |
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* @return the arrival phase number to which this registration applied |
424 |
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* @throws IllegalStateException if attempting to register more |
425 |
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* than the maximum supported number of parties |
426 |
+ |
* @throws IllegalArgumentException if {@code parties < 0} |
427 |
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*/ |
428 |
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public int bulkRegister(int parties) { |
429 |
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if (parties < 0) |
437 |
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* Shared code for register, bulkRegister |
438 |
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*/ |
439 |
|
private int doRegister(int registrations) { |
440 |
+ |
Phaser par = parent; |
441 |
+ |
long s; |
442 |
|
int phase; |
443 |
< |
for (;;) { |
444 |
< |
long s = getReconciledState(); |
445 |
< |
phase = phaseOf(s); |
446 |
< |
int unarrived = unarrivedOf(s) + registrations; |
447 |
< |
int parties = partiesOf(s) + registrations; |
448 |
< |
if (phase < 0) |
449 |
< |
break; |
450 |
< |
if (parties > ushortMask || unarrived > ushortMask) |
443 |
> |
while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) { |
444 |
> |
int p = partiesOf(s); |
445 |
> |
int u = unarrivedOf(s); |
446 |
> |
int unarrived = u + registrations; |
447 |
> |
int parties = p + registrations; |
448 |
> |
if (u == 0 && p != 0) // if tripped, wait for advance |
449 |
> |
untimedWait(phase); |
450 |
> |
else if (parties > ushortMask) |
451 |
|
throw new IllegalStateException(badBounds(parties, unarrived)); |
452 |
< |
if (phase == phaseOf(root.state) && |
453 |
< |
casState(s, stateFor(phase, parties, unarrived))) |
454 |
< |
break; |
452 |
> |
else if (par == null || phaseOf(root.state) == phase) { |
453 |
> |
long next = stateFor(phase, parties, unarrived); |
454 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
455 |
> |
break; |
456 |
> |
} |
457 |
|
} |
458 |
|
return phase; |
459 |
|
} |
460 |
|
|
461 |
|
/** |
462 |
|
* Arrives at the barrier, but does not wait for others. (You can |
463 |
< |
* in turn wait for others via {@link #awaitAdvance}). |
463 |
> |
* in turn wait for others via {@link #awaitAdvance}). It is an |
464 |
> |
* unenforced usage error for an unregistered party to invoke this |
465 |
> |
* method. |
466 |
|
* |
467 |
|
* @return the arrival phase number, or a negative value if terminated |
468 |
|
* @throws IllegalStateException if not terminated and the number |
469 |
|
* of unarrived parties would become negative |
470 |
|
*/ |
471 |
|
public int arrive() { |
472 |
+ |
Phaser par = parent; |
473 |
+ |
long s; |
474 |
|
int phase; |
475 |
< |
for (;;) { |
438 |
< |
long s = state; |
439 |
< |
phase = phaseOf(s); |
440 |
< |
if (phase < 0) |
441 |
< |
break; |
475 |
> |
while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) { |
476 |
|
int parties = partiesOf(s); |
477 |
|
int unarrived = unarrivedOf(s) - 1; |
478 |
< |
if (unarrived > 0) { // Not the last arrival |
479 |
< |
if (casState(s, s - 1)) // s-1 adds one arrival |
480 |
< |
break; |
478 |
> |
if (unarrived > 0) { // Not the last arrival |
479 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s - 1)) |
480 |
> |
break; // s-1 adds one arrival |
481 |
|
} |
482 |
< |
else if (unarrived == 0) { // the last arrival |
483 |
< |
Phaser par = parent; |
484 |
< |
if (par == null) { // directly trip |
485 |
< |
if (casState |
486 |
< |
(s, |
487 |
< |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
488 |
< |
((phase + 1) & phaseMask), parties))) { |
489 |
< |
releaseWaiters(phase); |
490 |
< |
break; |
457 |
< |
} |
458 |
< |
} |
459 |
< |
else { // cascade to parent |
460 |
< |
if (casState(s, s - 1)) { // zeroes unarrived |
461 |
< |
par.arrive(); |
462 |
< |
reconcileState(); |
463 |
< |
break; |
464 |
< |
} |
482 |
> |
else if (unarrived < 0) |
483 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
484 |
> |
else if (par == null) { // directly trip |
485 |
> |
long next = trippedStateFor(onAdvance(phase, parties) ? -1 : |
486 |
> |
((phase + 1) & phaseMask), |
487 |
> |
parties); |
488 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) { |
489 |
> |
releaseWaiters(phase); |
490 |
> |
break; |
491 |
|
} |
492 |
|
} |
493 |
< |
else if (phase != phaseOf(root.state)) // or if unreconciled |
493 |
> |
else if (phaseOf(root.state) == phase && |
494 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, s, s - 1)) { |
495 |
> |
par.arrive(); // cascade to parent |
496 |
|
reconcileState(); |
497 |
< |
else |
498 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
497 |
> |
break; |
498 |
> |
} |
499 |
|
} |
500 |
|
return phase; |
501 |
|
} |
506 |
|
* required to trip the barrier in future phases. If this phaser |
507 |
|
* has a parent, and deregistration causes this phaser to have |
508 |
|
* zero parties, this phaser also arrives at and is deregistered |
509 |
< |
* from its parent. |
509 |
> |
* from its parent. It is an unenforced usage error for an |
510 |
> |
* unregistered party to invoke this method. |
511 |
|
* |
512 |
|
* @return the arrival phase number, or a negative value if terminated |
513 |
|
* @throws IllegalStateException if not terminated and the number |
514 |
|
* of registered or unarrived parties would become negative |
515 |
|
*/ |
516 |
|
public int arriveAndDeregister() { |
517 |
< |
// similar code to arrive, but too different to merge |
517 |
> |
// similar to arrive, but too different to merge |
518 |
|
Phaser par = parent; |
519 |
+ |
long s; |
520 |
|
int phase; |
521 |
< |
for (;;) { |
492 |
< |
long s = state; |
493 |
< |
phase = phaseOf(s); |
494 |
< |
if (phase < 0) |
495 |
< |
break; |
521 |
> |
while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) { |
522 |
|
int parties = partiesOf(s) - 1; |
523 |
|
int unarrived = unarrivedOf(s) - 1; |
524 |
< |
if (parties >= 0) { |
525 |
< |
if (unarrived > 0 || (unarrived == 0 && par != null)) { |
526 |
< |
if (casState |
527 |
< |
(s, |
528 |
< |
stateFor(phase, parties, unarrived))) { |
529 |
< |
if (unarrived == 0) { |
530 |
< |
par.arriveAndDeregister(); |
531 |
< |
reconcileState(); |
532 |
< |
} |
533 |
< |
break; |
534 |
< |
} |
535 |
< |
continue; |
536 |
< |
} |
537 |
< |
if (unarrived == 0) { |
512 |
< |
if (casState |
513 |
< |
(s, |
514 |
< |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
515 |
< |
((phase + 1) & phaseMask), parties))) { |
516 |
< |
releaseWaiters(phase); |
517 |
< |
break; |
518 |
< |
} |
519 |
< |
continue; |
524 |
> |
if (unarrived > 0) { |
525 |
> |
long next = stateFor(phase, parties, unarrived); |
526 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
527 |
> |
break; |
528 |
> |
} |
529 |
> |
else if (unarrived < 0) |
530 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
531 |
> |
else if (par == null) { |
532 |
> |
long next = trippedStateFor(onAdvance(phase, parties)? -1: |
533 |
> |
(phase + 1) & phaseMask, |
534 |
> |
parties); |
535 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) { |
536 |
> |
releaseWaiters(phase); |
537 |
> |
break; |
538 |
|
} |
539 |
< |
if (par != null && phase != phaseOf(root.state)) { |
539 |
> |
} |
540 |
> |
else if (phaseOf(root.state) == phase) { |
541 |
> |
long next = stateFor(phase, parties, 0); |
542 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) { |
543 |
> |
if (parties == 0) |
544 |
> |
par.arriveAndDeregister(); |
545 |
> |
else |
546 |
> |
par.arrive(); |
547 |
|
reconcileState(); |
548 |
< |
continue; |
548 |
> |
break; |
549 |
|
} |
550 |
|
} |
526 |
– |
throw new IllegalStateException(badBounds(parties, unarrived)); |
551 |
|
} |
552 |
|
return phase; |
553 |
|
} |
556 |
|
* Arrives at the barrier and awaits others. Equivalent in effect |
557 |
|
* to {@code awaitAdvance(arrive())}. If you need to await with |
558 |
|
* interruption or timeout, you can arrange this with an analogous |
559 |
< |
* construction using one of the other forms of the awaitAdvance |
560 |
< |
* method. If instead you need to deregister upon arrival use |
561 |
< |
* {@code arriveAndDeregister}. |
559 |
> |
* construction using one of the other forms of the {@code |
560 |
> |
* awaitAdvance} method. If instead you need to deregister upon |
561 |
> |
* arrival, use {@link #arriveAndDeregister}. It is an unenforced |
562 |
> |
* usage error for an unregistered party to invoke this method. |
563 |
|
* |
564 |
|
* @return the arrival phase number, or a negative number if terminated |
565 |
|
* @throws IllegalStateException if not terminated and the number |
584 |
|
public int awaitAdvance(int phase) { |
585 |
|
if (phase < 0) |
586 |
|
return phase; |
587 |
< |
long s = getReconciledState(); |
563 |
< |
int p = phaseOf(s); |
587 |
> |
int p = getPhase(); |
588 |
|
if (p != phase) |
589 |
|
return p; |
566 |
– |
if (unarrivedOf(s) == 0 && parent != null) |
567 |
– |
parent.awaitAdvance(phase); |
568 |
– |
// Fall here even if parent waited, to reconcile and help release |
590 |
|
return untimedWait(phase); |
591 |
|
} |
592 |
|
|
593 |
|
/** |
594 |
|
* Awaits the phase of the barrier to advance from the given phase |
595 |
< |
* value, throwing {@code InterruptedException} if interrupted while |
596 |
< |
* waiting, or returning immediately if the current phase of the |
597 |
< |
* barrier is not equal to the given phase value or this barrier |
598 |
< |
* is terminated. |
595 |
> |
* value, throwing {@code InterruptedException} if interrupted |
596 |
> |
* while waiting, or returning immediately if the current phase of |
597 |
> |
* the barrier is not equal to the given phase value or this |
598 |
> |
* barrier is terminated. |
599 |
|
* |
600 |
|
* @param phase an arrival phase number, or negative value if |
601 |
|
* terminated; this argument is normally the value returned by a |
608 |
|
throws InterruptedException { |
609 |
|
if (phase < 0) |
610 |
|
return phase; |
611 |
< |
long s = getReconciledState(); |
591 |
< |
int p = phaseOf(s); |
611 |
> |
int p = getPhase(); |
612 |
|
if (p != phase) |
613 |
|
return p; |
594 |
– |
if (unarrivedOf(s) == 0 && parent != null) |
595 |
– |
parent.awaitAdvanceInterruptibly(phase); |
614 |
|
return interruptibleWait(phase); |
615 |
|
} |
616 |
|
|
617 |
|
/** |
618 |
|
* Awaits the phase of the barrier to advance from the given phase |
619 |
< |
* value or the given timeout to elapse, throwing |
620 |
< |
* {@code InterruptedException} if interrupted while waiting, or |
621 |
< |
* returning immediately if the current phase of the barrier is not |
622 |
< |
* equal to the given phase value or this barrier is terminated. |
619 |
> |
* value or the given timeout to elapse, throwing {@code |
620 |
> |
* InterruptedException} if interrupted while waiting, or |
621 |
> |
* returning immediately if the current phase of the barrier is |
622 |
> |
* not equal to the given phase value or this barrier is |
623 |
> |
* terminated. |
624 |
|
* |
625 |
|
* @param phase an arrival phase number, or negative value if |
626 |
|
* terminated; this argument is normally the value returned by a |
637 |
|
public int awaitAdvanceInterruptibly(int phase, |
638 |
|
long timeout, TimeUnit unit) |
639 |
|
throws InterruptedException, TimeoutException { |
640 |
+ |
long nanos = unit.toNanos(timeout); |
641 |
|
if (phase < 0) |
642 |
|
return phase; |
643 |
< |
long s = getReconciledState(); |
624 |
< |
int p = phaseOf(s); |
643 |
> |
int p = getPhase(); |
644 |
|
if (p != phase) |
645 |
|
return p; |
646 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
628 |
< |
parent.awaitAdvanceInterruptibly(phase, timeout, unit); |
629 |
< |
return timedWait(phase, unit.toNanos(timeout)); |
646 |
> |
return timedWait(phase, nanos); |
647 |
|
} |
648 |
|
|
649 |
|
/** |
654 |
|
* unexpected exceptions. |
655 |
|
*/ |
656 |
|
public void forceTermination() { |
657 |
< |
for (;;) { |
658 |
< |
long s = getReconciledState(); |
659 |
< |
int phase = phaseOf(s); |
660 |
< |
int parties = partiesOf(s); |
661 |
< |
int unarrived = unarrivedOf(s); |
662 |
< |
if (phase < 0 || |
663 |
< |
casState(s, stateFor(-1, parties, unarrived))) { |
664 |
< |
releaseWaiters(0); |
665 |
< |
releaseWaiters(1); |
649 |
< |
if (parent != null) |
650 |
< |
parent.forceTermination(); |
651 |
< |
return; |
652 |
< |
} |
653 |
< |
} |
657 |
> |
Phaser r = root; // force at root then reconcile |
658 |
> |
long s; |
659 |
> |
while (phaseOf(s = r.state) >= 0) |
660 |
> |
UNSAFE.compareAndSwapLong(r, stateOffset, s, |
661 |
> |
stateFor(-1, partiesOf(s), |
662 |
> |
unarrivedOf(s))); |
663 |
> |
reconcileState(); |
664 |
> |
releaseWaiters(0); // ensure wakeups on both queues |
665 |
> |
releaseWaiters(1); |
666 |
|
} |
667 |
|
|
668 |
|
/** |
682 |
|
* @return the number of parties |
683 |
|
*/ |
684 |
|
public int getRegisteredParties() { |
685 |
< |
return partiesOf(state); |
685 |
> |
return partiesOf(getReconciledState()); |
686 |
|
} |
687 |
|
|
688 |
|
/** |
692 |
|
* @return the number of arrived parties |
693 |
|
*/ |
694 |
|
public int getArrivedParties() { |
695 |
< |
return arrivedOf(state); |
695 |
> |
return arrivedOf(getReconciledState()); |
696 |
|
} |
697 |
|
|
698 |
|
/** |
702 |
|
* @return the number of unarrived parties |
703 |
|
*/ |
704 |
|
public int getUnarrivedParties() { |
705 |
< |
return unarrivedOf(state); |
705 |
> |
return unarrivedOf(getReconciledState()); |
706 |
|
} |
707 |
|
|
708 |
|
/** |
734 |
|
} |
735 |
|
|
736 |
|
/** |
737 |
< |
* Overridable method to perform an action upon phase advance, and |
738 |
< |
* to control termination. This method is invoked whenever the |
739 |
< |
* barrier is tripped (and thus all other waiting parties are |
740 |
< |
* dormant). If it returns {@code true}, then, rather than advance |
741 |
< |
* the phase number, this barrier will be set to a final |
742 |
< |
* termination state, and subsequent calls to {@link #isTerminated} |
743 |
< |
* will return true. |
737 |
> |
* Overridable method to perform an action upon impending phase |
738 |
> |
* advance, and to control termination. This method is invoked |
739 |
> |
* upon arrival of the party tripping the barrier (when all other |
740 |
> |
* waiting parties are dormant). If this method returns {@code |
741 |
> |
* true}, then, rather than advance the phase number, this barrier |
742 |
> |
* will be set to a final termination state, and subsequent calls |
743 |
> |
* to {@link #isTerminated} will return true. Any (unchecked) |
744 |
> |
* Exception or Error thrown by an invocation of this method is |
745 |
> |
* propagated to the party attempting to trip the barrier, in |
746 |
> |
* which case no advance occurs. |
747 |
> |
* |
748 |
> |
* <p>The arguments to this method provide the state of the phaser |
749 |
> |
* prevailing for the current transition. The results and effects |
750 |
> |
* of invoking phase-related methods (including {@code getPhase} |
751 |
> |
* as well as arrival, registration, and waiting methods) from |
752 |
> |
* within {@code onAdvance} are unspecified and should not be |
753 |
> |
* relied on. Similarly, while it is possible to override this |
754 |
> |
* method to produce side-effects visible to participating tasks, |
755 |
> |
* it is in general safe to do so only in designs in which all |
756 |
> |
* parties register before any arrive, and all {@link |
757 |
> |
* #awaitAdvance} at each phase. |
758 |
|
* |
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 |
|
* |
738 |
– |
* <p>You may override this method to perform an action with side |
739 |
– |
* effects visible to participating tasks, but it is in general |
740 |
– |
* only sensible to do so in designs where all parties register |
741 |
– |
* before any arrive, and all {@link #awaitAdvance} at each phase. |
742 |
– |
* Otherwise, you cannot ensure lack of interference from other |
743 |
– |
* parties during the invocation of this method. |
744 |
– |
* |
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 |
801 |
|
volatile boolean wasInterrupted = false; |
802 |
|
volatile Thread thread; // nulled to cancel wait |
803 |
|
QNode next; |
804 |
+ |
|
805 |
|
QNode(Phaser phaser, int phase, boolean interruptible, |
806 |
|
boolean timed, long startTime, long nanos) { |
807 |
|
this.phaser = phaser; |
812 |
|
this.nanos = nanos; |
813 |
|
thread = Thread.currentThread(); |
814 |
|
} |
815 |
+ |
|
816 |
|
public boolean isReleasable() { |
817 |
|
return (thread == null || |
818 |
|
phaser.getPhase() != phase || |
819 |
|
(interruptible && wasInterrupted) || |
820 |
|
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
821 |
|
} |
822 |
+ |
|
823 |
|
public boolean block() { |
824 |
|
if (Thread.interrupted()) { |
825 |
|
wasInterrupted = true; |
836 |
|
} |
837 |
|
return isReleasable(); |
838 |
|
} |
839 |
+ |
|
840 |
|
void signal() { |
841 |
|
Thread t = thread; |
842 |
|
if (t != null) { |
844 |
|
LockSupport.unpark(t); |
845 |
|
} |
846 |
|
} |
847 |
+ |
|
848 |
|
boolean doWait() { |
849 |
|
if (thread != null) { |
850 |
|
try { |
851 |
< |
ForkJoinPool.managedBlock(this, false); |
851 |
> |
ForkJoinPool.managedBlock(this); |
852 |
|
} catch (InterruptedException ie) { |
853 |
+ |
wasInterrupted = true; // can't currently happen |
854 |
|
} |
855 |
|
} |
856 |
|
return wasInterrupted; |
857 |
|
} |
833 |
– |
|
858 |
|
} |
859 |
|
|
860 |
|
/** |
880 |
|
} |
881 |
|
|
882 |
|
/** |
883 |
+ |
* The number of times to spin before blocking waiting for advance. |
884 |
+ |
*/ |
885 |
+ |
static final int MAX_SPINS = |
886 |
+ |
Runtime.getRuntime().availableProcessors() == 1 ? 0 : 1 << 8; |
887 |
+ |
|
888 |
+ |
/** |
889 |
|
* Enqueues node and waits unless aborted or signalled. |
890 |
|
* |
891 |
|
* @return current phase |
894 |
|
QNode node = null; |
895 |
|
boolean queued = false; |
896 |
|
boolean interrupted = false; |
897 |
+ |
int spins = MAX_SPINS; |
898 |
|
int p; |
899 |
|
while ((p = getPhase()) == phase) { |
900 |
|
if (Thread.interrupted()) |
901 |
|
interrupted = true; |
902 |
+ |
else if (spins > 0) { |
903 |
+ |
if (--spins == 0) |
904 |
+ |
Thread.yield(); |
905 |
+ |
} |
906 |
|
else if (node == null) |
907 |
|
node = new QNode(this, phase, false, false, 0, 0); |
908 |
|
else if (!queued) |
909 |
|
queued = tryEnqueue(node); |
910 |
< |
else |
911 |
< |
interrupted = node.doWait(); |
910 |
> |
else if (node.doWait()) |
911 |
> |
interrupted = true; |
912 |
|
} |
913 |
|
if (node != null) |
914 |
|
node.thread = null; |
926 |
|
QNode node = null; |
927 |
|
boolean queued = false; |
928 |
|
boolean interrupted = false; |
929 |
+ |
int spins = MAX_SPINS; |
930 |
|
int p; |
931 |
|
while ((p = getPhase()) == phase && !interrupted) { |
932 |
|
if (Thread.interrupted()) |
933 |
|
interrupted = true; |
934 |
+ |
else if (spins > 0) { |
935 |
+ |
if (--spins == 0) |
936 |
+ |
Thread.yield(); |
937 |
+ |
} |
938 |
|
else if (node == null) |
939 |
|
node = new QNode(this, phase, true, false, 0, 0); |
940 |
|
else if (!queued) |
941 |
|
queued = tryEnqueue(node); |
942 |
< |
else |
943 |
< |
interrupted = node.doWait(); |
942 |
> |
else if (node.doWait()) |
943 |
> |
interrupted = true; |
944 |
|
} |
945 |
|
if (node != null) |
946 |
|
node.thread = null; |
961 |
|
QNode node = null; |
962 |
|
boolean queued = false; |
963 |
|
boolean interrupted = false; |
964 |
+ |
int spins = MAX_SPINS; |
965 |
|
int p; |
966 |
|
while ((p = getPhase()) == phase && !interrupted) { |
967 |
|
if (Thread.interrupted()) |
968 |
|
interrupted = true; |
969 |
|
else if (nanos - (System.nanoTime() - startTime) <= 0) |
970 |
|
break; |
971 |
+ |
else if (spins > 0) { |
972 |
+ |
if (--spins == 0) |
973 |
+ |
Thread.yield(); |
974 |
+ |
} |
975 |
|
else if (node == null) |
976 |
|
node = new QNode(this, phase, true, true, startTime, nanos); |
977 |
|
else if (!queued) |
978 |
|
queued = tryEnqueue(node); |
979 |
< |
else |
980 |
< |
interrupted = node.doWait(); |
979 |
> |
else if (node.doWait()) |
980 |
> |
interrupted = true; |
981 |
|
} |
982 |
|
if (node != null) |
983 |
|
node.thread = null; |
996 |
|
private static final long stateOffset = |
997 |
|
objectFieldOffset("state", Phaser.class); |
998 |
|
|
954 |
– |
private final boolean casState(long cmp, long val) { |
955 |
– |
return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val); |
956 |
– |
} |
957 |
– |
|
999 |
|
private static long objectFieldOffset(String field, Class<?> klazz) { |
1000 |
|
try { |
1001 |
|
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |