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*/ |
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package jsr166y; |
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import jsr166y.forkjoin.*; |
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import java.util.concurrent.*; |
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import java.util.concurrent.atomic.*; |
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import java.util.concurrent.atomic.AtomicReference; |
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import java.util.concurrent.locks.LockSupport; |
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/** |
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* A reusable synchronization barrier, similar in functionality to a |
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* {@link java.util.concurrent.CyclicBarrier}, but supporting more |
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* flexible usage. |
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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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* <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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* <li> The number of parties synchronizing on the barrier may vary |
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* over time. A task may register to be a party in a barrier at any |
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* time, and may deregister upon arriving at the barrier. As is the |
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* case with most basic synchronization constructs, registration |
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* and deregistration affect only internal counts; they do not |
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* establish any further internal bookkeeping, so tasks cannot query |
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* whether they are registered. |
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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 <tt>Integer.MAX_VALUE</tt>). |
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* |
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* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited. |
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* Method <tt>arriveAndAwaitAdvance</tt> has effect analogous to |
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* <tt>CyclicBarrier.await</tt>. However, Phasers separate two |
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* aspects of coordination, that may 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 <tt>arrive</tt> and |
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* <tt>arriveAndDeregister</tt> do not block, but return |
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* the phase value on entry to the method. |
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* |
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* <li> Awaiting others. Method <tt>awaitAdvance</tt> 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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* <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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* <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> Barrier actions, performed by the task triggering a phase |
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* advance while others may be waiting, are arranged by overriding |
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* method <tt>onAdvance</tt>, that also controls termination. |
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* |
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* <li> Phasers may enter a <em>termination</em> state in which all |
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* await actions immediately return, indicating (via a negative phase |
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* value) that execution is complete. Termination is triggered by |
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* executing the overridable <tt>onAdvance</tt> method that is invoked |
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* each time the barrier is tripped. When a Phaser is controlling an |
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* action with a fixed number of iterations, it is often convenient to |
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* override this method to cause termination when the current phase |
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* number reaches a threshold. Method <tt>forceTermination</tt> is |
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* also available to assist recovery actions upon failure. |
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* |
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* <li> Unlike most synchronizers, a Phaser may also be used with |
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* ForkJoinTasks (as well as plain threads). |
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* |
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* <li> By default, <tt>awaitAdvance</tt> continues to wait even if |
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* the current thread is interrupted. And unlike the case in |
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* CyclicBarriers, exceptions encountered while tasks wait |
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* interruptibly or with timeout do not change the state of the |
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* barrier. If necessary, you can perform any associated recovery |
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* within handlers of those exceptions. |
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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 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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* </ul> |
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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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* |
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* <pre> {@code |
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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 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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* task.run(); |
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* } |
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* }.start(); |
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* } |
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* |
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* // allow threads to start and deregister self |
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* phaser.arriveAndDeregister(); |
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* }}</pre> |
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* |
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* <p>One way to cause a set of threads to repeatedly perform actions |
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* for a given number of iterations is to override {@code onAdvance}: |
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* |
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* <pre> {@code |
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* void startTasks(List<Runnable> tasks, final int iterations) { |
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* final Phaser phaser = new Phaser() { |
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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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* 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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* } |
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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><b>Sample usage:</b> |
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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(); |
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* }</pre> |
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* |
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* <p>[todo: non-FJ example] |
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* 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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* <p> A Phaser may be used to support a style of programming in |
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* which a task waits for others to complete, without otherwise |
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* needing to keep track of which tasks it is waiting for. This is |
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* similar to the "sync" construct in Cilk and "clocks" in X10. |
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* Special constructions based on such barriers are available using |
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* the <tt>LinkedAsyncAction</tt> and <tt>CyclicAction</tt> classes, |
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* but they can be useful in other contexts as well. For a simple |
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* (but not very useful) example, here is a variant of Fibonacci: |
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* |
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* <pre> |
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* class BarrierFibonacci extends RecursiveAction { |
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* int argument, result; |
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* final Phaser parentBarrier; |
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* BarrierFibonacci(int n, Phaser parentBarrier) { |
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* this.argument = n; |
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* this.parentBarrier = parentBarrier; |
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* parentBarrier.register(); |
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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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* } |
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* protected void compute() { |
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* int n = argument; |
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* if (n <= 1) |
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* result = n; |
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* else { |
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* Phaser childBarrier = new Phaser(1); |
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* BarrierFibonacci f1 = new BarrierFibonacci(n - 1, childBarrier); |
190 |
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* BarrierFibonacci f2 = new BarrierFibonacci(n - 2, childBarrier); |
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* f1.fork(); |
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* f2.fork(); |
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* childBarrier.arriveAndAwait(); |
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* result = f1.result + f2.result; |
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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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* <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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* } |
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* parentBarrier.arriveAndDeregister(); |
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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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* } |
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* } |
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* // .. initially called, for n tasks via |
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* build(new Task[n], 0, n, new Phaser());}</pre> |
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* |
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* The best value of {@code TASKS_PER_PHASER} depends mainly on |
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* expected barrier synchronization rates. A value as low as four may |
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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 |
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* additional parties result in IllegalStateExceptions. |
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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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* should create tiered phasers to accommodate arbitrarily large sets |
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* of participants. |
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* |
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* @since 1.7 |
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* @author Doug Lea |
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*/ |
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public class Phaser { |
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/* |
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* This class implements an extension of X10 "clocks". Thanks to |
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* Vijay Saraswat for the idea of applying it to ForkJoinTasks, |
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* and to Vivek Sarkar for enhancements to extend functionality. |
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* Vijay Saraswat for the idea, and to Vivek Sarkar for |
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* enhancements to extend functionality. |
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*/ |
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|
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/** |
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* Barrier state representation. Conceptually, a barrier contains |
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* four values: |
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* |
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* |
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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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* |
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* However, to efficiently maintain atomicity, these values are |
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* packed into a single AtomicLong. Termination uses the sign bit |
243 |
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* of 32 bit representation of phase, so phase is set to -1 on |
244 |
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* termination. |
245 |
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*/ |
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private final AtomicLong state; |
247 |
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|
248 |
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/** |
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* Head of Treiber stack for waiting nonFJ threads. |
242 |
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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 |
244 |
> |
* termination. Good performance relies on keeping state decoding |
245 |
> |
* and encoding simple, and keeping race windows short. |
246 |
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* |
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* Note: there are some cheats in arrive() that rely on unarrived |
248 |
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* count being lowest 16 bits. |
249 |
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*/ |
250 |
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private final AtomicReference<QNode> head = new AtomicReference<QNode>(); |
250 |
> |
private volatile long state; |
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|
252 |
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private static final int ushortBits = 16; |
253 |
< |
private static final int ushortMask = (1 << ushortBits) - 1; |
149 |
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private static final int phaseMask = 0x7fffffff; |
252 |
> |
private static final int ushortMask = 0xffff; |
253 |
> |
private static final int phaseMask = 0x7fffffff; |
254 |
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|
255 |
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private static int unarrivedOf(long s) { |
256 |
< |
return (int)(s & ushortMask); |
256 |
> |
return (int) (s & ushortMask); |
257 |
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} |
258 |
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|
259 |
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private static int partiesOf(long s) { |
260 |
< |
return (int)(s & (ushortMask << 16)) >>> 16; |
260 |
> |
return ((int) s) >>> 16; |
261 |
|
} |
262 |
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|
263 |
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private static int phaseOf(long s) { |
264 |
< |
return (int)(s >>> 32); |
264 |
> |
return (int) (s >>> 32); |
265 |
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} |
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|
267 |
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private static int arrivedOf(long s) { |
269 |
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} |
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|
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private static long stateFor(int phase, int parties, int unarrived) { |
272 |
< |
return (((long)phase) << 32) | ((parties << 16) | unarrived); |
272 |
> |
return ((((long) phase) << 32) | (((long) parties) << 16) | |
273 |
> |
(long) unarrived); |
274 |
|
} |
275 |
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|
276 |
< |
private static IllegalStateException badBounds(int parties, int unarrived) { |
277 |
< |
return new IllegalStateException("Attempt to set " + unarrived + |
278 |
< |
" unarrived of " + parties + " parties"); |
276 |
> |
private static long trippedStateFor(int phase, int parties) { |
277 |
> |
long lp = (long) parties; |
278 |
> |
return (((long) phase) << 32) | (lp << 16) | lp; |
279 |
|
} |
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|
281 |
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/** |
282 |
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* Creates a new Phaser without any initially registered parties, |
283 |
< |
* and initial phase number 0. |
282 |
> |
* Returns message string for bad bounds exceptions. |
283 |
> |
*/ |
284 |
> |
private static String badBounds(int parties, int unarrived) { |
285 |
> |
return ("Attempt to set " + unarrived + |
286 |
> |
" unarrived of " + parties + " parties"); |
287 |
> |
} |
288 |
> |
|
289 |
> |
/** |
290 |
> |
* The parent of this phaser, or null if none |
291 |
> |
*/ |
292 |
> |
private final Phaser parent; |
293 |
> |
|
294 |
> |
/** |
295 |
> |
* The root of phaser tree. Equals this if not in a tree. Used to |
296 |
> |
* support faster state push-down. |
297 |
> |
*/ |
298 |
> |
private final Phaser root; |
299 |
> |
|
300 |
> |
// Wait queues |
301 |
> |
|
302 |
> |
/** |
303 |
> |
* Heads of Treiber stacks for waiting threads. To eliminate |
304 |
> |
* contention while releasing some threads while adding others, we |
305 |
> |
* use two of them, alternating across even and odd phases. |
306 |
> |
*/ |
307 |
> |
private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>(); |
308 |
> |
private final AtomicReference<QNode> oddQ = new AtomicReference<QNode>(); |
309 |
> |
|
310 |
> |
private AtomicReference<QNode> queueFor(int phase) { |
311 |
> |
return ((phase & 1) == 0) ? evenQ : oddQ; |
312 |
> |
} |
313 |
> |
|
314 |
> |
/** |
315 |
> |
* Returns current state, first resolving lagged propagation from |
316 |
> |
* root if necessary. |
317 |
> |
*/ |
318 |
> |
private long getReconciledState() { |
319 |
> |
return (parent == null) ? state : reconcileState(); |
320 |
> |
} |
321 |
> |
|
322 |
> |
/** |
323 |
> |
* Recursively resolves state. |
324 |
> |
*/ |
325 |
> |
private long reconcileState() { |
326 |
> |
Phaser p = parent; |
327 |
> |
long s = state; |
328 |
> |
if (p != null) { |
329 |
> |
while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) { |
330 |
> |
long parentState = p.getReconciledState(); |
331 |
> |
int parentPhase = phaseOf(parentState); |
332 |
> |
int phase = phaseOf(s = state); |
333 |
> |
if (phase != parentPhase) { |
334 |
> |
long next = trippedStateFor(parentPhase, partiesOf(s)); |
335 |
> |
if (casState(s, next)) { |
336 |
> |
releaseWaiters(phase); |
337 |
> |
s = next; |
338 |
> |
} |
339 |
> |
} |
340 |
> |
} |
341 |
> |
} |
342 |
> |
return s; |
343 |
> |
} |
344 |
> |
|
345 |
> |
/** |
346 |
> |
* Creates a new phaser without any initially registered parties, |
347 |
> |
* initial phase number 0, and no parent. Any thread using this |
348 |
> |
* phaser will need to first register for it. |
349 |
|
*/ |
350 |
|
public Phaser() { |
351 |
< |
state = new AtomicLong(stateFor(0, 0, 0)); |
351 |
> |
this(null); |
352 |
|
} |
353 |
|
|
354 |
|
/** |
355 |
< |
* Creates a new Phaser with the given numbers of registered |
356 |
< |
* unarrived parties and initial phase number 0. |
357 |
< |
* @param parties the number of parties required to trip barrier. |
355 |
> |
* Creates a new phaser with the given numbers of registered |
356 |
> |
* unarrived parties, initial phase number 0, and no parent. |
357 |
> |
* |
358 |
> |
* @param parties the number of parties required to trip barrier |
359 |
|
* @throws IllegalArgumentException if parties less than zero |
360 |
< |
* or greater than the maximum number of parties supported. |
360 |
> |
* or greater than the maximum number of parties supported |
361 |
|
*/ |
362 |
|
public Phaser(int parties) { |
363 |
+ |
this(null, parties); |
364 |
+ |
} |
365 |
+ |
|
366 |
+ |
/** |
367 |
+ |
* Creates a new phaser with the given parent, without any |
368 |
+ |
* initially registered parties. If parent is non-null this phaser |
369 |
+ |
* is registered with the parent and its initial phase number is |
370 |
+ |
* the same as that of parent phaser. |
371 |
+ |
* |
372 |
+ |
* @param parent the parent phaser |
373 |
+ |
*/ |
374 |
+ |
public Phaser(Phaser parent) { |
375 |
+ |
int phase = 0; |
376 |
+ |
this.parent = parent; |
377 |
+ |
if (parent != null) { |
378 |
+ |
this.root = parent.root; |
379 |
+ |
phase = parent.register(); |
380 |
+ |
} |
381 |
+ |
else |
382 |
+ |
this.root = this; |
383 |
+ |
this.state = trippedStateFor(phase, 0); |
384 |
+ |
} |
385 |
+ |
|
386 |
+ |
/** |
387 |
+ |
* Creates a new phaser with the given parent and numbers of |
388 |
+ |
* registered unarrived parties. If parent is non-null, this phaser |
389 |
+ |
* is registered with the parent and its initial phase number is |
390 |
+ |
* the same as that of parent phaser. |
391 |
+ |
* |
392 |
+ |
* @param parent the parent phaser |
393 |
+ |
* @param parties the number of parties required to trip barrier |
394 |
+ |
* @throws IllegalArgumentException if parties less than zero |
395 |
+ |
* or greater than the maximum number of parties supported |
396 |
+ |
*/ |
397 |
+ |
public Phaser(Phaser parent, int parties) { |
398 |
|
if (parties < 0 || parties > ushortMask) |
399 |
|
throw new IllegalArgumentException("Illegal number of parties"); |
400 |
< |
state = new AtomicLong(stateFor(0, parties, parties)); |
400 |
> |
int phase = 0; |
401 |
> |
this.parent = parent; |
402 |
> |
if (parent != null) { |
403 |
> |
this.root = parent.root; |
404 |
> |
phase = parent.register(); |
405 |
> |
} |
406 |
> |
else |
407 |
> |
this.root = this; |
408 |
> |
this.state = trippedStateFor(phase, parties); |
409 |
|
} |
410 |
|
|
411 |
|
/** |
412 |
|
* Adds a new unarrived party to this phaser. |
413 |
< |
* @return the current barrier phase number upon registration |
413 |
> |
* |
414 |
> |
* @return the arrival phase number to which this registration applied |
415 |
> |
* @throws IllegalStateException if attempting to register more |
416 |
> |
* than the maximum supported number of parties |
417 |
> |
*/ |
418 |
> |
public int register() { |
419 |
> |
return doRegister(1); |
420 |
> |
} |
421 |
> |
|
422 |
> |
/** |
423 |
> |
* Adds the given number of new unarrived parties to this phaser. |
424 |
> |
* |
425 |
> |
* @param parties the number of parties required to trip barrier |
426 |
> |
* @return the arrival phase number to which this registration applied |
427 |
|
* @throws IllegalStateException if attempting to register more |
428 |
< |
* than the maximum supported number of parties. |
428 |
> |
* than the maximum supported number of parties |
429 |
|
*/ |
430 |
< |
public int register() { // increment both parties and unarrived |
431 |
< |
final AtomicLong state = this.state; |
430 |
> |
public int bulkRegister(int parties) { |
431 |
> |
if (parties < 0) |
432 |
> |
throw new IllegalArgumentException(); |
433 |
> |
if (parties == 0) |
434 |
> |
return getPhase(); |
435 |
> |
return doRegister(parties); |
436 |
> |
} |
437 |
> |
|
438 |
> |
/** |
439 |
> |
* Shared code for register, bulkRegister |
440 |
> |
*/ |
441 |
> |
private int doRegister(int registrations) { |
442 |
> |
int phase; |
443 |
|
for (;;) { |
444 |
< |
long s = state.get(); |
445 |
< |
int phase = phaseOf(s); |
446 |
< |
int parties = partiesOf(s) + 1; |
447 |
< |
int unarrived = unarrivedOf(s) + 1; |
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) |
451 |
< |
throw badBounds(parties, unarrived); |
452 |
< |
if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) |
453 |
< |
return phase; |
451 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
452 |
> |
if (phase == phaseOf(root.state) && |
453 |
> |
casState(s, stateFor(phase, parties, unarrived))) |
454 |
> |
break; |
455 |
|
} |
456 |
+ |
return phase; |
457 |
|
} |
458 |
|
|
459 |
|
/** |
460 |
|
* Arrives at the barrier, but does not wait for others. (You can |
461 |
< |
* in turn wait for others via {@link #awaitAdvance}). |
461 |
> |
* in turn wait for others via {@link #awaitAdvance}). It is an |
462 |
> |
* unenforced usage error for an unregistered party to invoke this |
463 |
> |
* method. |
464 |
|
* |
465 |
< |
* @return the current barrier phase number upon entry to |
466 |
< |
* this method, or a negative value if terminated; |
467 |
< |
* @throws IllegalStateException if the number of unarrived |
224 |
< |
* parties would become negative. |
465 |
> |
* @return the arrival phase number, or a negative value if terminated |
466 |
> |
* @throws IllegalStateException if not terminated and the number |
467 |
> |
* of unarrived parties would become negative |
468 |
|
*/ |
469 |
< |
public int arrive() { // decrement unarrived. If zero, trip |
470 |
< |
final AtomicLong state = this.state; |
469 |
> |
public int arrive() { |
470 |
> |
int phase; |
471 |
|
for (;;) { |
472 |
< |
long s = state.get(); |
473 |
< |
int phase = phaseOf(s); |
472 |
> |
long s = state; |
473 |
> |
phase = phaseOf(s); |
474 |
> |
if (phase < 0) |
475 |
> |
break; |
476 |
|
int parties = partiesOf(s); |
477 |
|
int unarrived = unarrivedOf(s) - 1; |
478 |
< |
if (unarrived < 0) |
479 |
< |
throw badBounds(parties, unarrived); |
480 |
< |
if (unarrived == 0 && phase >= 0) { |
236 |
< |
trip(phase, parties); |
237 |
< |
return phase; |
478 |
> |
if (unarrived > 0) { // Not the last arrival |
479 |
> |
if (casState(s, s - 1)) // s-1 adds one arrival |
480 |
> |
break; |
481 |
|
} |
482 |
< |
if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) |
483 |
< |
return phase; |
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; |
491 |
> |
} |
492 |
> |
} |
493 |
> |
else { // cascade to parent |
494 |
> |
if (casState(s, s - 1)) { // zeroes unarrived |
495 |
> |
par.arrive(); |
496 |
> |
reconcileState(); |
497 |
> |
break; |
498 |
> |
} |
499 |
> |
} |
500 |
> |
} |
501 |
> |
else if (phase != phaseOf(root.state)) // or if unreconciled |
502 |
> |
reconcileState(); |
503 |
> |
else |
504 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
505 |
|
} |
506 |
+ |
return phase; |
507 |
|
} |
508 |
|
|
509 |
|
/** |
510 |
< |
* Arrives at the barrier, and deregisters from it, without |
511 |
< |
* waiting for others. |
510 |
> |
* Arrives at the barrier and deregisters from it without waiting |
511 |
> |
* for others. Deregistration reduces the number of parties |
512 |
> |
* required to trip the barrier in future phases. If this phaser |
513 |
> |
* has a parent, and deregistration causes this phaser to have |
514 |
> |
* zero parties, this phaser also arrives at and is deregistered |
515 |
> |
* from its parent. It is an unenforced usage error for an |
516 |
> |
* unregistered party to invoke this method. |
517 |
|
* |
518 |
< |
* @return the current barrier phase number upon entry to |
519 |
< |
* this method, or a negative value if terminated; |
520 |
< |
* @throws IllegalStateException if the number of registered or |
521 |
< |
* unarrived parties would become negative. |
522 |
< |
*/ |
523 |
< |
public int arriveAndDeregister() { // Same as arrive, plus decrement parties |
524 |
< |
final AtomicLong state = this.state; |
518 |
> |
* @return the arrival phase number, or a negative value if terminated |
519 |
> |
* @throws IllegalStateException if not terminated and the number |
520 |
> |
* of registered or unarrived parties would become negative |
521 |
> |
*/ |
522 |
> |
public int arriveAndDeregister() { |
523 |
> |
// similar code to arrive, but too different to merge |
524 |
> |
Phaser par = parent; |
525 |
> |
int phase; |
526 |
|
for (;;) { |
527 |
< |
long s = state.get(); |
528 |
< |
int phase = phaseOf(s); |
527 |
> |
long s = state; |
528 |
> |
phase = phaseOf(s); |
529 |
> |
if (phase < 0) |
530 |
> |
break; |
531 |
|
int parties = partiesOf(s) - 1; |
532 |
|
int unarrived = unarrivedOf(s) - 1; |
533 |
< |
if (parties < 0 || unarrived < 0) |
534 |
< |
throw badBounds(parties, unarrived); |
535 |
< |
if (unarrived == 0 && phase >= 0) { |
536 |
< |
trip(phase, parties); |
537 |
< |
return phase; |
533 |
> |
if (parties >= 0) { |
534 |
> |
if (unarrived > 0 || (unarrived == 0 && par != null)) { |
535 |
> |
if (casState |
536 |
> |
(s, |
537 |
> |
stateFor(phase, parties, unarrived))) { |
538 |
> |
if (unarrived == 0) { |
539 |
> |
par.arriveAndDeregister(); |
540 |
> |
reconcileState(); |
541 |
> |
} |
542 |
> |
break; |
543 |
> |
} |
544 |
> |
continue; |
545 |
> |
} |
546 |
> |
if (unarrived == 0) { |
547 |
> |
if (casState |
548 |
> |
(s, |
549 |
> |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
550 |
> |
((phase + 1) & phaseMask), parties))) { |
551 |
> |
releaseWaiters(phase); |
552 |
> |
break; |
553 |
> |
} |
554 |
> |
continue; |
555 |
> |
} |
556 |
> |
if (par != null && phase != phaseOf(root.state)) { |
557 |
> |
reconcileState(); |
558 |
> |
continue; |
559 |
> |
} |
560 |
|
} |
561 |
< |
if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) |
267 |
< |
return phase; |
561 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
562 |
|
} |
563 |
+ |
return phase; |
564 |
|
} |
565 |
|
|
566 |
|
/** |
567 |
< |
* Arrives at the barrier and awaits others. Unlike other arrival |
568 |
< |
* methods, this method returns the arrival index of the |
569 |
< |
* caller. The caller tripping the barrier returns zero, the |
570 |
< |
* previous caller 1, and so on. |
571 |
< |
* @return the arrival index |
572 |
< |
* @throws IllegalStateException if the number of unarrived |
573 |
< |
* parties would become negative. |
567 |
> |
* Arrives at the barrier and awaits others. Equivalent in effect |
568 |
> |
* to {@code awaitAdvance(arrive())}. If you need to await with |
569 |
> |
* interruption or timeout, you can arrange this with an analogous |
570 |
> |
* construction using one of the other forms of the awaitAdvance |
571 |
> |
* method. If instead you need to deregister upon arrival use |
572 |
> |
* {@code arriveAndDeregister}. It is an unenforced usage error |
573 |
> |
* for an unregistered party to invoke this method. |
574 |
> |
* |
575 |
> |
* @return the arrival phase number, or a negative number if terminated |
576 |
> |
* @throws IllegalStateException if not terminated and the number |
577 |
> |
* of unarrived parties would become negative |
578 |
|
*/ |
579 |
|
public int arriveAndAwaitAdvance() { |
580 |
< |
final AtomicLong state = this.state; |
282 |
< |
for (;;) { |
283 |
< |
long s = state.get(); |
284 |
< |
int phase = phaseOf(s); |
285 |
< |
int parties = partiesOf(s); |
286 |
< |
int unarrived = unarrivedOf(s) - 1; |
287 |
< |
if (unarrived < 0) |
288 |
< |
throw badBounds(parties, unarrived); |
289 |
< |
if (unarrived == 0 && phase >= 0) { |
290 |
< |
trip(phase, parties); |
291 |
< |
return 0; |
292 |
< |
} |
293 |
< |
if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) { |
294 |
< |
awaitAdvance(phase); |
295 |
< |
return unarrived; |
296 |
< |
} |
297 |
< |
} |
580 |
> |
return awaitAdvance(arrive()); |
581 |
|
} |
582 |
|
|
583 |
|
/** |
584 |
< |
* Awaits the phase of the barrier to advance from the given |
585 |
< |
* value, or returns immediately if this barrier is terminated. |
586 |
< |
* @param phase the phase on entry to this method |
587 |
< |
* @return the phase on exit from this method |
584 |
> |
* Awaits the phase of the barrier to advance from the given phase |
585 |
> |
* value, returning immediately if the current phase of the |
586 |
> |
* barrier is not equal to the given phase value or this barrier |
587 |
> |
* is terminated. It is an unenforced usage error for an |
588 |
> |
* unregistered party to invoke this method. |
589 |
> |
* |
590 |
> |
* @param phase an arrival phase number, or negative value if |
591 |
> |
* terminated; this argument is normally the value returned by a |
592 |
> |
* previous call to {@code arrive} or its variants |
593 |
> |
* @return the next arrival phase number, or a negative value |
594 |
> |
* if terminated or argument is negative |
595 |
|
*/ |
596 |
|
public int awaitAdvance(int phase) { |
597 |
|
if (phase < 0) |
598 |
|
return phase; |
599 |
< |
Thread current = Thread.currentThread(); |
600 |
< |
if (current instanceof ForkJoinWorkerThread) |
601 |
< |
return helpingWait(phase); |
602 |
< |
if (untimedWait(current, phase, false)) |
603 |
< |
current.interrupt(); |
604 |
< |
return phaseOf(state.get()); |
599 |
> |
long s = getReconciledState(); |
600 |
> |
int p = phaseOf(s); |
601 |
> |
if (p != phase) |
602 |
> |
return p; |
603 |
> |
if (unarrivedOf(s) == 0 && parent != null) |
604 |
> |
parent.awaitAdvance(phase); |
605 |
> |
// Fall here even if parent waited, to reconcile and help release |
606 |
> |
return untimedWait(phase); |
607 |
|
} |
608 |
|
|
609 |
|
/** |
610 |
< |
* Awaits the phase of the barrier to advance from the given |
611 |
< |
* value, or returns immediately if this barrier is terminated, or |
612 |
< |
* throws InterruptedException if interrupted while waiting. |
613 |
< |
* @param phase the phase on entry to this method |
614 |
< |
* @return the phase on exit from this method |
610 |
> |
* Awaits the phase of the barrier to advance from the given phase |
611 |
> |
* value, throwing {@code InterruptedException} if interrupted |
612 |
> |
* while waiting, or returning immediately if the current phase of |
613 |
> |
* the barrier is not equal to the given phase value or this |
614 |
> |
* barrier is terminated. It is an unenforced usage error for an |
615 |
> |
* unregistered party to invoke this method. |
616 |
> |
* |
617 |
> |
* @param phase an arrival phase number, or negative value if |
618 |
> |
* terminated; this argument is normally the value returned by a |
619 |
> |
* previous call to {@code arrive} or its variants |
620 |
> |
* @return the next arrival phase number, or a negative value |
621 |
> |
* if terminated or argument is negative |
622 |
|
* @throws InterruptedException if thread interrupted while waiting |
623 |
|
*/ |
624 |
< |
public int awaitAdvanceInterruptibly(int phase) throws InterruptedException { |
624 |
> |
public int awaitAdvanceInterruptibly(int phase) |
625 |
> |
throws InterruptedException { |
626 |
|
if (phase < 0) |
627 |
|
return phase; |
628 |
< |
Thread current = Thread.currentThread(); |
629 |
< |
if (current instanceof ForkJoinWorkerThread) |
630 |
< |
return helpingWait(phase); |
631 |
< |
else if (Thread.interrupted() || untimedWait(current, phase, true)) |
632 |
< |
throw new InterruptedException(); |
633 |
< |
else |
634 |
< |
return phaseOf(state.get()); |
628 |
> |
long s = getReconciledState(); |
629 |
> |
int p = phaseOf(s); |
630 |
> |
if (p != phase) |
631 |
> |
return p; |
632 |
> |
if (unarrivedOf(s) == 0 && parent != null) |
633 |
> |
parent.awaitAdvanceInterruptibly(phase); |
634 |
> |
return interruptibleWait(phase); |
635 |
|
} |
636 |
|
|
637 |
|
/** |
638 |
< |
* Awaits the phase of the barrier to advance from the given value |
639 |
< |
* or the given timeout elapses, or returns immediately if this |
640 |
< |
* barrier is terminated. |
641 |
< |
* @param phase the phase on entry to this method |
642 |
< |
* @return the phase on exit from this method |
638 |
> |
* Awaits the phase of the barrier to advance from the given phase |
639 |
> |
* value or the given timeout to elapse, throwing {@code |
640 |
> |
* InterruptedException} if interrupted while waiting, or |
641 |
> |
* returning immediately if the current phase of the barrier is |
642 |
> |
* not equal to the given phase value or this barrier is |
643 |
> |
* terminated. It is an unenforced usage error for an |
644 |
> |
* unregistered party to invoke this method. |
645 |
> |
* |
646 |
> |
* @param phase an arrival phase number, or negative value if |
647 |
> |
* terminated; this argument is normally the value returned by a |
648 |
> |
* previous call to {@code arrive} or its variants |
649 |
> |
* @param timeout how long to wait before giving up, in units of |
650 |
> |
* {@code unit} |
651 |
> |
* @param unit a {@code TimeUnit} determining how to interpret the |
652 |
> |
* {@code timeout} parameter |
653 |
> |
* @return the next arrival phase number, or a negative value |
654 |
> |
* if terminated or argument is negative |
655 |
|
* @throws InterruptedException if thread interrupted while waiting |
656 |
|
* @throws TimeoutException if timed out while waiting |
657 |
|
*/ |
658 |
< |
public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit) |
658 |
> |
public int awaitAdvanceInterruptibly(int phase, |
659 |
> |
long timeout, TimeUnit unit) |
660 |
|
throws InterruptedException, TimeoutException { |
661 |
|
if (phase < 0) |
662 |
|
return phase; |
663 |
< |
long nanos = unit.toNanos(timeout); |
664 |
< |
Thread current = Thread.currentThread(); |
665 |
< |
if (current instanceof ForkJoinWorkerThread) |
666 |
< |
return timedHelpingWait(phase, nanos); |
667 |
< |
timedWait(current, phase, nanos); |
668 |
< |
return phaseOf(state.get()); |
663 |
> |
long s = getReconciledState(); |
664 |
> |
int p = phaseOf(s); |
665 |
> |
if (p != phase) |
666 |
> |
return p; |
667 |
> |
if (unarrivedOf(s) == 0 && parent != null) |
668 |
> |
parent.awaitAdvanceInterruptibly(phase, timeout, unit); |
669 |
> |
return timedWait(phase, unit.toNanos(timeout)); |
670 |
|
} |
671 |
|
|
672 |
|
/** |
673 |
|
* Forces this barrier to enter termination state. Counts of |
674 |
< |
* arrived and registered parties are unaffected. This method may |
675 |
< |
* be useful for coordinating recovery after one or more tasks |
676 |
< |
* encounter unexpected exceptions. |
674 |
> |
* arrived and registered parties are unaffected. If this phaser |
675 |
> |
* has a parent, it too is terminated. This method may be useful |
676 |
> |
* for coordinating recovery after one or more tasks encounter |
677 |
> |
* unexpected exceptions. |
678 |
|
*/ |
679 |
|
public void forceTermination() { |
365 |
– |
final AtomicLong state = this.state; |
680 |
|
for (;;) { |
681 |
< |
long s = state.get(); |
681 |
> |
long s = getReconciledState(); |
682 |
|
int phase = phaseOf(s); |
683 |
|
int parties = partiesOf(s); |
684 |
|
int unarrived = unarrivedOf(s); |
685 |
|
if (phase < 0 || |
686 |
< |
state.compareAndSet(s, stateFor(-1, parties, unarrived))) { |
687 |
< |
if (head.get() != null) |
688 |
< |
releaseWaiters(-1); |
686 |
> |
casState(s, stateFor(-1, parties, unarrived))) { |
687 |
> |
releaseWaiters(0); |
688 |
> |
releaseWaiters(1); |
689 |
> |
if (parent != null) |
690 |
> |
parent.forceTermination(); |
691 |
|
return; |
692 |
|
} |
693 |
|
} |
694 |
|
} |
695 |
|
|
696 |
|
/** |
381 |
– |
* Resets the barrier with the given numbers of registered unarrived |
382 |
– |
* parties and phase number 0. This method allows repeated reuse |
383 |
– |
* of this barrier, but only if it is somehow known not to be in |
384 |
– |
* use for other purposes. |
385 |
– |
* @param parties the number of parties required to trip barrier. |
386 |
– |
* @throws IllegalArgumentException if parties less than zero |
387 |
– |
* or greater than the maximum number of parties supported. |
388 |
– |
*/ |
389 |
– |
public void reset(int parties) { |
390 |
– |
if (parties < 0 || parties > ushortMask) |
391 |
– |
throw new IllegalArgumentException("Illegal number of parties"); |
392 |
– |
state.set(stateFor(0, parties, parties)); |
393 |
– |
if (head.get() != null) |
394 |
– |
releaseWaiters(0); |
395 |
– |
} |
396 |
– |
|
397 |
– |
/** |
697 |
|
* Returns the current phase number. The maximum phase number is |
698 |
< |
* <tt>Integer.MAX_VALUE</tt>, after which it restarts at |
698 |
> |
* {@code Integer.MAX_VALUE}, after which it restarts at |
699 |
|
* zero. Upon termination, the phase number is negative. |
700 |
+ |
* |
701 |
|
* @return the phase number, or a negative value if terminated |
702 |
|
*/ |
703 |
< |
public int getPhase() { |
704 |
< |
return phaseOf(state.get()); |
703 |
> |
public final int getPhase() { |
704 |
> |
return phaseOf(getReconciledState()); |
705 |
|
} |
706 |
|
|
707 |
|
/** |
708 |
|
* Returns the number of parties registered at this barrier. |
709 |
+ |
* |
710 |
|
* @return the number of parties |
711 |
|
*/ |
712 |
|
public int getRegisteredParties() { |
713 |
< |
return partiesOf(state.get()); |
713 |
> |
return partiesOf(state); |
714 |
|
} |
715 |
|
|
716 |
|
/** |
717 |
< |
* Returns the number of parties that have arrived at the current |
718 |
< |
* phase of this barrier. |
717 |
> |
* Returns the number of registered parties that have arrived at |
718 |
> |
* the current phase of this barrier. |
719 |
> |
* |
720 |
|
* @return the number of arrived parties |
721 |
|
*/ |
722 |
|
public int getArrivedParties() { |
723 |
< |
return arrivedOf(state.get()); |
723 |
> |
return arrivedOf(state); |
724 |
|
} |
725 |
|
|
726 |
|
/** |
727 |
|
* Returns the number of registered parties that have not yet |
728 |
|
* arrived at the current phase of this barrier. |
729 |
+ |
* |
730 |
|
* @return the number of unarrived parties |
731 |
|
*/ |
732 |
|
public int getUnarrivedParties() { |
733 |
< |
return unarrivedOf(state.get()); |
733 |
> |
return unarrivedOf(state); |
734 |
> |
} |
735 |
> |
|
736 |
> |
/** |
737 |
> |
* Returns the parent of this phaser, or {@code null} if none. |
738 |
> |
* |
739 |
> |
* @return the parent of this phaser, or {@code null} if none |
740 |
> |
*/ |
741 |
> |
public Phaser getParent() { |
742 |
> |
return parent; |
743 |
> |
} |
744 |
> |
|
745 |
> |
/** |
746 |
> |
* Returns the root ancestor of this phaser, which is the same as |
747 |
> |
* this phaser if it has no parent. |
748 |
> |
* |
749 |
> |
* @return the root ancestor of this phaser |
750 |
> |
*/ |
751 |
> |
public Phaser getRoot() { |
752 |
> |
return root; |
753 |
|
} |
754 |
|
|
755 |
|
/** |
756 |
< |
* Returns true if this barrier has been terminated. |
757 |
< |
* @return true if this barrier has been terminated |
756 |
> |
* Returns {@code true} if this barrier has been terminated. |
757 |
> |
* |
758 |
> |
* @return {@code true} if this barrier has been terminated |
759 |
|
*/ |
760 |
|
public boolean isTerminated() { |
761 |
< |
return phaseOf(state.get()) < 0; |
761 |
> |
return getPhase() < 0; |
762 |
|
} |
763 |
|
|
764 |
|
/** |
765 |
< |
* Overridable method to perform an action upon phase advance, and |
766 |
< |
* to control termination. This method is invoked whenever the |
767 |
< |
* barrier is tripped (and thus all other waiting parties are |
768 |
< |
* dormant). If it returns true, then, rather than advance the |
769 |
< |
* phase number, this barrier will be set to a final termination |
770 |
< |
* state, and subsequent calls to <tt>isTerminated</tt> will |
771 |
< |
* return true. |
772 |
< |
* |
773 |
< |
* <p> The default version returns true when the number of |
765 |
> |
* Overridable method to perform an action upon impending phase |
766 |
> |
* advance, and to control termination. This method is invoked |
767 |
> |
* upon arrival of the party tripping the barrier (when all other |
768 |
> |
* waiting parties are dormant). If this method returns {@code |
769 |
> |
* true}, then, rather than advance the phase number, this barrier |
770 |
> |
* will be set to a final termination state, and subsequent calls |
771 |
> |
* to {@link #isTerminated} will return true. Any (unchecked) |
772 |
> |
* Exception or Error thrown by an invocation of this method is |
773 |
> |
* propagated to the party attempting to trip the barrier, in |
774 |
> |
* which case no advance occurs. |
775 |
> |
* |
776 |
> |
* <p>The arguments to this method provide the state of the phaser |
777 |
> |
* prevailing for the current transition. (When called from within |
778 |
> |
* an implementation of {@code onAdvance} the values returned by |
779 |
> |
* methods such as {@code getPhase} may or may not reliably |
780 |
> |
* indicate the state to which this transition applies.) |
781 |
> |
* |
782 |
> |
* <p>The default version returns {@code true} when the number of |
783 |
|
* registered parties is zero. Normally, overrides that arrange |
784 |
|
* termination for other reasons should also preserve this |
785 |
|
* property. |
786 |
|
* |
787 |
+ |
* <p>You may override this method to perform an action with side |
788 |
+ |
* effects visible to participating tasks, but doing so requires |
789 |
+ |
* care: Method {@code onAdvance} may be invoked more than once |
790 |
+ |
* per transition. Further, unless all parties register before |
791 |
+ |
* any arrive, and all {@link #awaitAdvance} at each phase, then |
792 |
+ |
* you cannot ensure lack of interference from other parties |
793 |
+ |
* during the invocation of this method. |
794 |
+ |
* |
795 |
|
* @param phase the phase number on entering the barrier |
796 |
< |
* @param registeredParties the current number of registered |
797 |
< |
* parties. |
458 |
< |
* @return true if this barrier should terminate |
796 |
> |
* @param registeredParties the current number of registered parties |
797 |
> |
* @return {@code true} if this barrier should terminate |
798 |
|
*/ |
799 |
|
protected boolean onAdvance(int phase, int registeredParties) { |
800 |
|
return registeredParties <= 0; |
801 |
|
} |
802 |
|
|
803 |
|
/** |
804 |
< |
* Returns a string identifying this barrier, as well as its |
804 |
> |
* Returns a string identifying this phaser, as well as its |
805 |
|
* state. The state, in brackets, includes the String {@code |
806 |
< |
* "phase ="} followed by the phase number, {@code "parties ="} |
806 |
> |
* "phase = "} followed by the phase number, {@code "parties = "} |
807 |
|
* followed by the number of registered parties, and {@code |
808 |
< |
* "arrived ="} followed by the number of arrived parties |
808 |
> |
* "arrived = "} followed by the number of arrived parties. |
809 |
|
* |
810 |
|
* @return a string identifying this barrier, as well as its state |
811 |
|
*/ |
812 |
|
public String toString() { |
813 |
< |
long s = state.get(); |
814 |
< |
return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]"; |
813 |
> |
long s = getReconciledState(); |
814 |
> |
return super.toString() + |
815 |
> |
"[phase = " + phaseOf(s) + |
816 |
> |
" parties = " + partiesOf(s) + |
817 |
> |
" arrived = " + arrivedOf(s) + "]"; |
818 |
|
} |
819 |
|
|
820 |
< |
// methods for tripping and waiting |
820 |
> |
// methods for waiting |
821 |
|
|
822 |
|
/** |
823 |
< |
* Advance the current phase (or terminate) |
823 |
> |
* Wait nodes for Treiber stack representing wait queue |
824 |
|
*/ |
825 |
< |
private void trip(int phase, int parties) { |
826 |
< |
int next = onAdvance(phase, parties)? -1 : ((phase + 1) & phaseMask); |
827 |
< |
state.set(stateFor(next, parties, parties)); |
828 |
< |
if (head.get() != null) |
829 |
< |
releaseWaiters(next); |
830 |
< |
} |
831 |
< |
|
832 |
< |
private int helpingWait(int phase) { |
833 |
< |
final AtomicLong state = this.state; |
834 |
< |
int p; |
835 |
< |
while ((p = phaseOf(state.get())) == phase) { |
836 |
< |
ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask(); |
837 |
< |
if (t != null) { |
838 |
< |
if ((p = phaseOf(state.get())) == phase) |
839 |
< |
t.exec(); |
840 |
< |
else { // push task and exit if barrier advanced |
841 |
< |
t.fork(); |
842 |
< |
break; |
843 |
< |
} |
502 |
< |
} |
825 |
> |
static final class QNode implements ForkJoinPool.ManagedBlocker { |
826 |
> |
final Phaser phaser; |
827 |
> |
final int phase; |
828 |
> |
final long startTime; |
829 |
> |
final long nanos; |
830 |
> |
final boolean timed; |
831 |
> |
final boolean interruptible; |
832 |
> |
volatile boolean wasInterrupted = false; |
833 |
> |
volatile Thread thread; // nulled to cancel wait |
834 |
> |
QNode next; |
835 |
> |
QNode(Phaser phaser, int phase, boolean interruptible, |
836 |
> |
boolean timed, long startTime, long nanos) { |
837 |
> |
this.phaser = phaser; |
838 |
> |
this.phase = phase; |
839 |
> |
this.timed = timed; |
840 |
> |
this.interruptible = interruptible; |
841 |
> |
this.startTime = startTime; |
842 |
> |
this.nanos = nanos; |
843 |
> |
thread = Thread.currentThread(); |
844 |
|
} |
845 |
< |
return p; |
846 |
< |
} |
847 |
< |
|
848 |
< |
private int timedHelpingWait(int phase, long nanos) throws TimeoutException { |
849 |
< |
final AtomicLong state = this.state; |
850 |
< |
long lastTime = System.nanoTime(); |
851 |
< |
int p; |
852 |
< |
while ((p = phaseOf(state.get())) == phase) { |
853 |
< |
long now = System.nanoTime(); |
854 |
< |
nanos -= now - lastTime; |
855 |
< |
lastTime = now; |
515 |
< |
if (nanos <= 0) { |
516 |
< |
if ((p = phaseOf(state.get())) == phase) |
517 |
< |
throw new TimeoutException(); |
518 |
< |
else |
519 |
< |
break; |
845 |
> |
public boolean isReleasable() { |
846 |
> |
return (thread == null || |
847 |
> |
phaser.getPhase() != phase || |
848 |
> |
(interruptible && wasInterrupted) || |
849 |
> |
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
850 |
> |
} |
851 |
> |
public boolean block() { |
852 |
> |
if (Thread.interrupted()) { |
853 |
> |
wasInterrupted = true; |
854 |
> |
if (interruptible) |
855 |
> |
return true; |
856 |
|
} |
857 |
< |
ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask(); |
857 |
> |
if (!timed) |
858 |
> |
LockSupport.park(this); |
859 |
> |
else { |
860 |
> |
long waitTime = nanos - (System.nanoTime() - startTime); |
861 |
> |
if (waitTime <= 0) |
862 |
> |
return true; |
863 |
> |
LockSupport.parkNanos(this, waitTime); |
864 |
> |
} |
865 |
> |
return isReleasable(); |
866 |
> |
} |
867 |
> |
void signal() { |
868 |
> |
Thread t = thread; |
869 |
|
if (t != null) { |
870 |
< |
if ((p = phaseOf(state.get())) == phase) |
871 |
< |
t.exec(); |
872 |
< |
else { // push task and exit if barrier advanced |
873 |
< |
t.fork(); |
874 |
< |
break; |
870 |
> |
thread = null; |
871 |
> |
LockSupport.unpark(t); |
872 |
> |
} |
873 |
> |
} |
874 |
> |
boolean doWait() { |
875 |
> |
if (thread != null) { |
876 |
> |
try { |
877 |
> |
ForkJoinPool.managedBlock(this, false); |
878 |
> |
} catch (InterruptedException ie) { |
879 |
|
} |
880 |
|
} |
881 |
+ |
return wasInterrupted; |
882 |
|
} |
883 |
< |
return p; |
883 |
> |
|
884 |
|
} |
885 |
|
|
886 |
|
/** |
887 |
< |
* Wait nodes for Treiber stack representing wait queue for non-FJ |
536 |
< |
* tasks. The waiting scheme is an adaptation of the one used in |
537 |
< |
* forkjoin.PoolBarrier. |
887 |
> |
* Removes and signals waiting threads from wait queue. |
888 |
|
*/ |
889 |
< |
static final class QNode { |
890 |
< |
QNode next; |
891 |
< |
volatile Thread thread; // nulled to cancel wait |
892 |
< |
final int phase; |
893 |
< |
QNode(Thread t, int c) { |
894 |
< |
thread = t; |
545 |
< |
phase = c; |
546 |
< |
} |
547 |
< |
} |
548 |
< |
|
549 |
< |
private void releaseWaiters(int currentPhase) { |
550 |
< |
final AtomicReference<QNode> head = this.head; |
551 |
< |
QNode p; |
552 |
< |
while ((p = head.get()) != null && p.phase != currentPhase) { |
553 |
< |
if (head.compareAndSet(p, null)) { |
554 |
< |
do { |
555 |
< |
Thread t = p.thread; |
556 |
< |
if (t != null) { |
557 |
< |
p.thread = null; |
558 |
< |
LockSupport.unpark(t); |
559 |
< |
} |
560 |
< |
} while ((p = p.next) != null); |
561 |
< |
} |
889 |
> |
private void releaseWaiters(int phase) { |
890 |
> |
AtomicReference<QNode> head = queueFor(phase); |
891 |
> |
QNode q; |
892 |
> |
while ((q = head.get()) != null) { |
893 |
> |
if (head.compareAndSet(q, q.next)) |
894 |
> |
q.signal(); |
895 |
|
} |
896 |
|
} |
897 |
|
|
565 |
– |
/** The number of CPUs, for spin control */ |
566 |
– |
static final int NCPUS = Runtime.getRuntime().availableProcessors(); |
567 |
– |
|
898 |
|
/** |
899 |
< |
* The number of times to spin before blocking in timed waits. |
900 |
< |
* The value is empirically derived. |
901 |
< |
*/ |
572 |
< |
static final int maxTimedSpins = (NCPUS < 2)? 0 : 32; |
573 |
< |
|
574 |
< |
/** |
575 |
< |
* The number of times to spin before blocking in untimed waits. |
576 |
< |
* This is greater than timed value because untimed waits spin |
577 |
< |
* faster since they don't need to check times on each spin. |
899 |
> |
* Tries to enqueue given node in the appropriate wait queue. |
900 |
> |
* |
901 |
> |
* @return true if successful |
902 |
|
*/ |
903 |
< |
static final int maxUntimedSpins = maxTimedSpins * 32; |
903 |
> |
private boolean tryEnqueue(QNode node) { |
904 |
> |
AtomicReference<QNode> head = queueFor(node.phase); |
905 |
> |
return head.compareAndSet(node.next = head.get(), node); |
906 |
> |
} |
907 |
|
|
908 |
|
/** |
909 |
< |
* The number of nanoseconds for which it is faster to spin |
910 |
< |
* rather than to use timed park. A rough estimate suffices. |
909 |
> |
* Enqueues node and waits unless aborted or signalled. |
910 |
> |
* |
911 |
> |
* @return current phase |
912 |
|
*/ |
913 |
< |
static final long spinForTimeoutThreshold = 1000L; |
913 |
> |
private int untimedWait(int phase) { |
914 |
> |
QNode node = null; |
915 |
> |
boolean queued = false; |
916 |
> |
boolean interrupted = false; |
917 |
> |
int p; |
918 |
> |
while ((p = getPhase()) == phase) { |
919 |
> |
if (Thread.interrupted()) |
920 |
> |
interrupted = true; |
921 |
> |
else if (node == null) |
922 |
> |
node = new QNode(this, phase, false, false, 0, 0); |
923 |
> |
else if (!queued) |
924 |
> |
queued = tryEnqueue(node); |
925 |
> |
else |
926 |
> |
interrupted = node.doWait(); |
927 |
> |
} |
928 |
> |
if (node != null) |
929 |
> |
node.thread = null; |
930 |
> |
releaseWaiters(phase); |
931 |
> |
if (interrupted) |
932 |
> |
Thread.currentThread().interrupt(); |
933 |
> |
return p; |
934 |
> |
} |
935 |
|
|
936 |
|
/** |
937 |
< |
* Enqueues node and waits unless aborted or signalled. |
937 |
> |
* Interruptible version |
938 |
> |
* @return current phase |
939 |
|
*/ |
940 |
< |
private boolean untimedWait(Thread thread, int currentPhase, |
591 |
< |
boolean abortOnInterrupt) { |
592 |
< |
final AtomicReference<QNode> head = this.head; |
593 |
< |
final AtomicLong state = this.state; |
594 |
< |
boolean wasInterrupted = false; |
940 |
> |
private int interruptibleWait(int phase) throws InterruptedException { |
941 |
|
QNode node = null; |
942 |
|
boolean queued = false; |
943 |
< |
int spins = maxUntimedSpins; |
944 |
< |
while (phaseOf(state.get()) == currentPhase) { |
945 |
< |
QNode h; |
946 |
< |
if (node != null && queued) { |
947 |
< |
if (node.thread != null) { |
948 |
< |
LockSupport.park(); |
949 |
< |
if (Thread.interrupted()) { |
950 |
< |
wasInterrupted = true; |
951 |
< |
if (abortOnInterrupt) |
606 |
< |
break; |
607 |
< |
} |
608 |
< |
} |
609 |
< |
} |
610 |
< |
else if ((h = head.get()) != null && h.phase != currentPhase) { |
611 |
< |
if (phaseOf(state.get()) == currentPhase) { // must recheck |
612 |
< |
if (head.compareAndSet(h, h.next)) { |
613 |
< |
Thread t = h.thread; // help clear out old waiters |
614 |
< |
if (t != null) { |
615 |
< |
h.thread = null; |
616 |
< |
LockSupport.unpark(t); |
617 |
< |
} |
618 |
< |
} |
619 |
< |
} |
620 |
< |
else |
621 |
< |
break; |
622 |
< |
} |
623 |
< |
else if (node != null) |
624 |
< |
queued = head.compareAndSet(node.next = h, node); |
625 |
< |
else if (spins <= 0) |
626 |
< |
node = new QNode(thread, currentPhase); |
943 |
> |
boolean interrupted = false; |
944 |
> |
int p; |
945 |
> |
while ((p = getPhase()) == phase && !interrupted) { |
946 |
> |
if (Thread.interrupted()) |
947 |
> |
interrupted = true; |
948 |
> |
else if (node == null) |
949 |
> |
node = new QNode(this, phase, true, false, 0, 0); |
950 |
> |
else if (!queued) |
951 |
> |
queued = tryEnqueue(node); |
952 |
|
else |
953 |
< |
--spins; |
953 |
> |
interrupted = node.doWait(); |
954 |
|
} |
955 |
|
if (node != null) |
956 |
|
node.thread = null; |
957 |
< |
return wasInterrupted; |
957 |
> |
if (p != phase || (p = getPhase()) != phase) |
958 |
> |
releaseWaiters(phase); |
959 |
> |
if (interrupted) |
960 |
> |
throw new InterruptedException(); |
961 |
> |
return p; |
962 |
|
} |
963 |
|
|
964 |
|
/** |
965 |
< |
* Messier timeout version |
965 |
> |
* Timeout version. |
966 |
> |
* @return current phase |
967 |
|
*/ |
968 |
< |
private void timedWait(Thread thread, int currentPhase, long nanos) |
968 |
> |
private int timedWait(int phase, long nanos) |
969 |
|
throws InterruptedException, TimeoutException { |
970 |
< |
final AtomicReference<QNode> head = this.head; |
641 |
< |
final AtomicLong state = this.state; |
642 |
< |
long lastTime = System.nanoTime(); |
970 |
> |
long startTime = System.nanoTime(); |
971 |
|
QNode node = null; |
972 |
|
boolean queued = false; |
973 |
< |
int spins = maxTimedSpins; |
974 |
< |
while (phaseOf(state.get()) == currentPhase) { |
975 |
< |
QNode h; |
976 |
< |
long now = System.nanoTime(); |
977 |
< |
nanos -= now - lastTime; |
978 |
< |
lastTime = now; |
979 |
< |
if (nanos <= 0) { |
980 |
< |
if (node != null) |
981 |
< |
node.thread = null; |
982 |
< |
if (phaseOf(state.get()) == currentPhase) |
983 |
< |
throw new TimeoutException(); |
656 |
< |
else |
657 |
< |
break; |
658 |
< |
} |
659 |
< |
else if (node != null && queued) { |
660 |
< |
if (node.thread != null && |
661 |
< |
nanos > spinForTimeoutThreshold) { |
662 |
< |
// LockSupport.parkNanos(this, nanos); |
663 |
< |
LockSupport.parkNanos(nanos); |
664 |
< |
if (Thread.interrupted()) { |
665 |
< |
node.thread = null; |
666 |
< |
throw new InterruptedException(); |
667 |
< |
} |
668 |
< |
} |
669 |
< |
} |
670 |
< |
else if ((h = head.get()) != null && h.phase != currentPhase) { |
671 |
< |
if (phaseOf(state.get()) == currentPhase) { // must recheck |
672 |
< |
if (head.compareAndSet(h, h.next)) { |
673 |
< |
Thread t = h.thread; // help clear out old waiters |
674 |
< |
if (t != null) { |
675 |
< |
h.thread = null; |
676 |
< |
LockSupport.unpark(t); |
677 |
< |
} |
678 |
< |
} |
679 |
< |
} |
680 |
< |
else |
681 |
< |
break; |
682 |
< |
} |
683 |
< |
else if (node != null) |
684 |
< |
queued = head.compareAndSet(node.next = h, node); |
685 |
< |
else if (spins <= 0) |
686 |
< |
node = new QNode(thread, currentPhase); |
973 |
> |
boolean interrupted = false; |
974 |
> |
int p; |
975 |
> |
while ((p = getPhase()) == phase && !interrupted) { |
976 |
> |
if (Thread.interrupted()) |
977 |
> |
interrupted = true; |
978 |
> |
else if (nanos - (System.nanoTime() - startTime) <= 0) |
979 |
> |
break; |
980 |
> |
else if (node == null) |
981 |
> |
node = new QNode(this, phase, true, true, startTime, nanos); |
982 |
> |
else if (!queued) |
983 |
> |
queued = tryEnqueue(node); |
984 |
|
else |
985 |
< |
--spins; |
985 |
> |
interrupted = node.doWait(); |
986 |
|
} |
987 |
|
if (node != null) |
988 |
|
node.thread = null; |
989 |
+ |
if (p != phase || (p = getPhase()) != phase) |
990 |
+ |
releaseWaiters(phase); |
991 |
+ |
if (interrupted) |
992 |
+ |
throw new InterruptedException(); |
993 |
+ |
if (p == phase) |
994 |
+ |
throw new TimeoutException(); |
995 |
+ |
return p; |
996 |
|
} |
997 |
|
|
998 |
< |
} |
998 |
> |
// Unsafe mechanics |
999 |
|
|
1000 |
+ |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1001 |
+ |
private static final long stateOffset = |
1002 |
+ |
objectFieldOffset("state", Phaser.class); |
1003 |
+ |
|
1004 |
+ |
private final boolean casState(long cmp, long val) { |
1005 |
+ |
return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val); |
1006 |
+ |
} |
1007 |
+ |
|
1008 |
+ |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1009 |
+ |
try { |
1010 |
+ |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1011 |
+ |
} catch (NoSuchFieldException e) { |
1012 |
+ |
// Convert Exception to corresponding Error |
1013 |
+ |
NoSuchFieldError error = new NoSuchFieldError(field); |
1014 |
+ |
error.initCause(e); |
1015 |
+ |
throw error; |
1016 |
+ |
} |
1017 |
+ |
} |
1018 |
+ |
|
1019 |
+ |
/** |
1020 |
+ |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1021 |
+ |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1022 |
+ |
* into a jdk. |
1023 |
+ |
* |
1024 |
+ |
* @return a sun.misc.Unsafe |
1025 |
+ |
*/ |
1026 |
+ |
private static sun.misc.Unsafe getUnsafe() { |
1027 |
+ |
try { |
1028 |
+ |
return sun.misc.Unsafe.getUnsafe(); |
1029 |
+ |
} catch (SecurityException se) { |
1030 |
+ |
try { |
1031 |
+ |
return java.security.AccessController.doPrivileged |
1032 |
+ |
(new java.security |
1033 |
+ |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1034 |
+ |
public sun.misc.Unsafe run() throws Exception { |
1035 |
+ |
java.lang.reflect.Field f = sun.misc |
1036 |
+ |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1037 |
+ |
f.setAccessible(true); |
1038 |
+ |
return (sun.misc.Unsafe) f.get(null); |
1039 |
+ |
}}); |
1040 |
+ |
} catch (java.security.PrivilegedActionException e) { |
1041 |
+ |
throw new RuntimeException("Could not initialize intrinsics", |
1042 |
+ |
e.getCause()); |
1043 |
+ |
} |
1044 |
+ |
} |
1045 |
+ |
} |
1046 |
+ |
} |