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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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*/ |
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package java.util.concurrent; |
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import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.TimeoutException; |
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import java.util.concurrent.atomic.AtomicReference; |
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import java.util.concurrent.locks.LockSupport; |
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/** |
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* A reusable synchronization barrier, similar in functionality to |
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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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* <p> <b>Registration.</b> Unlike the case for other barriers, the |
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* number of parties <em>registered</em> to synchronize on a phaser |
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* may vary over time. Tasks may be registered at any time (using |
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* methods {@link #register}, {@link #bulkRegister}, or forms of |
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* constructors establishing initial numbers of parties), and |
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* optionally deregistered upon any arrival (using {@link |
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* #arriveAndDeregister}). As is the case with most basic |
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* synchronization constructs, registration and deregistration affect |
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* only internal counts; they do not establish any further internal |
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* bookkeeping, so tasks cannot query whether they are registered. |
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* (However, you can introduce such bookkeeping by subclassing this |
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* class.) |
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* |
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* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code |
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* Phaser} may be repeatedly awaited. Method {@link |
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* #arriveAndAwaitAdvance} has effect analogous to {@link |
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* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each |
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* generation of a phaser has an associated phase number. The phase |
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* number starts at zero, and advances when all parties arrive at the |
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* phaser, 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 phaser 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> <b>Arrival.</b> Methods {@link #arrive} and |
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* {@link #arriveAndDeregister} record arrival. These methods |
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* do not block, but return an associated <em>arrival phase |
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* number</em>; that is, the phase number of the phaser to which |
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* the arrival applied. When the final party for a given phase |
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* arrives, an optional action is performed and the phase |
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* advances. These actions are performed by the party |
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* triggering a phase advance, and are arranged by overriding |
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* method {@link #onAdvance(int, int)}, which also controls |
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* termination. Overriding this method is similar to, but more |
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* flexible than, providing a barrier action to a {@code |
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* 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 phaser 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 phaser. 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 phaser may enter a <em>termination</em> |
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* state, that may be checked using method {@link #isTerminated}. Upon |
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* termination, all synchronization methods immediately return without |
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* waiting for advance, as indicated by a negative return value. |
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* Similarly, attempts to register upon termination have no effect. |
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* Termination is triggered when an invocation of {@code onAdvance} |
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* returns {@code true}. The default implementation returns {@code |
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* true} if a deregistration has caused the number of registered |
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* parties to become zero. As illustrated below, when phasers control |
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* actions with a fixed number of iterations, it is often convenient |
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* to override this method to cause termination when the current phase |
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* number reaches a threshold. Method {@link #forceTermination} is |
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* also available to abruptly release waiting threads and allow them |
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* to terminate. |
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* |
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* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., |
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* constructed in tree structures) to reduce contention. Phasers with |
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* large numbers of parties that would otherwise experience heavy |
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* synchronization contention costs may instead be set up so that |
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* groups of sub-phasers share a common parent. This may greatly |
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* increase throughput even though it incurs greater per-operation |
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* overhead. |
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* |
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* <p>In a tree of tiered phasers, registration and deregistration of |
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* child phasers with their parent are managed automatically. |
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* Whenever the number of registered parties of a child phaser becomes |
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* non-zero (as established in the {@link #Phaser(Phaser,int)} |
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* constructor, {@link #register}, or {@link #bulkRegister}), the |
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* child phaser is registered with its parent. Whenever the number of |
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* registered parties becomes zero as the result of an invocation of |
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* {@link #arriveAndDeregister}, the child phaser is deregistered |
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* from its parent. |
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* |
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* <p><b>Monitoring.</b> While synchronization methods may be invoked |
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* only by registered parties, the current state of a phaser may be |
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* monitored by any caller. At any given moment there are {@link |
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* #getRegisteredParties} parties in total, of which {@link |
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* #getArrivedParties} have arrived at the current phase ({@link |
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* #getPhase}). When the remaining ({@link #getUnarrivedParties}) |
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* parties arrive, the phase advances. The values returned by these |
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* methods may reflect transient states and so are not in general |
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* useful for synchronization control. Method {@link #toString} |
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* returns snapshots of these state queries in a form convenient for |
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* informal monitoring. |
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* |
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* <p><b>Sample usages:</b> |
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* |
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* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch} |
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* to control a one-shot action serving a variable number of 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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* 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 (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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* } |
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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 {@code n} tasks using a tree of phasers, you |
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* could use code of the following form, assuming a Task class with a |
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* constructor accepting a {@code Phaser} that it registers with upon |
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* construction. After invocation of {@code build(new Task[n], 0, n, |
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* new Phaser())}, these tasks could then be started, for example by |
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* submitting to a pool: |
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* |
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* <pre> {@code |
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* void build(Task[] tasks, 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(tasks, 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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* tasks[i] = new Task(ph); |
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* // assumes new Task(ph) performs ph.register() |
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* } |
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* }}</pre> |
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1.1 |
* |
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* The best value of {@code TASKS_PER_PHASER} depends mainly on |
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1.37 |
* expected synchronization rates. A value as low as four may |
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* be appropriate for extremely small per-phase task bodies (thus |
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1.1 |
* high rates), or up to hundreds for extremely large ones. |
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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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1.8 |
* parties result in {@code IllegalStateException}. However, you can and |
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dl |
1.37 |
* should create tiered phasers to accommodate arbitrarily large sets |
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1.1 |
* 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, 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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dl |
1.37 |
* Primary state representation, holding four fields: |
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1.1 |
* |
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dl |
1.17 |
* * unarrived -- the number of parties yet to hit barrier (bits 0-15) |
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* * parties -- the number of parties to wait (bits 16-31) |
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* * phase -- the generation of the barrier (bits 32-62) |
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* * terminated -- set if barrier is terminated (bit 63 / sign) |
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jsr166 |
1.1 |
* |
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dl |
1.39 |
* Except that a phaser with no registered parties is |
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* distinguished with the otherwise illegal state of having zero |
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* parties and one unarrived parties (encoded as EMPTY below). |
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* |
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* To efficiently maintain atomicity, these values are packed into |
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* a single (atomic) long. Good performance relies on keeping |
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* state decoding and encoding simple, and keeping race windows |
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* short. |
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* |
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* All state updates are performed via CAS except initial |
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* registration of a sub-phaser (i.e., one with a non-null |
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* parent). In this (relatively rare) case, we use built-in |
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* synchronization to lock while first registering with its |
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* parent. |
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* |
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* The phase of a subphaser is allowed to lag that of its |
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* ancestors until it is actually accessed. Method reconcileState |
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* is usually attempted only only when the number of unarrived |
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* parties appears to be zero, which indicates a potential lag in |
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* updating phase after the root advanced. |
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1.1 |
*/ |
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private volatile long state; |
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dl |
1.33 |
private static final int MAX_PARTIES = 0xffff; |
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private static final int MAX_PHASE = 0x7fffffff; |
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private static final int PARTIES_SHIFT = 16; |
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private static final int PHASE_SHIFT = 32; |
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1.52 |
private static final long PHASE_MASK = -1L << PHASE_SHIFT; |
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dl |
1.33 |
private static final int UNARRIVED_MASK = 0xffff; // to mask ints |
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private static final long PARTIES_MASK = 0xffff0000L; // to mask longs |
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private static final long TERMINATION_BIT = 1L << 63; |
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dl |
1.17 |
|
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1.39 |
// some special values |
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private static final int ONE_ARRIVAL = 1; |
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private static final int ONE_PARTY = 1 << PARTIES_SHIFT; |
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private static final int EMPTY = 1; |
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|
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1.17 |
// The following unpacking methods are usually manually inlined |
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1.1 |
|
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private static int unarrivedOf(long s) { |
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dl |
1.39 |
int counts = (int)s; |
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1.40 |
return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK; |
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1.1 |
} |
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private static int partiesOf(long s) { |
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1.41 |
return (int)s >>> PARTIES_SHIFT; |
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jsr166 |
1.1 |
} |
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private static int phaseOf(long s) { |
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1.17 |
return (int) (s >>> PHASE_SHIFT); |
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jsr166 |
1.1 |
} |
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private static int arrivedOf(long s) { |
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dl |
1.39 |
int counts = (int)s; |
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jsr166 |
1.40 |
return (counts == EMPTY) ? 0 : |
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1.39 |
(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK); |
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jsr166 |
1.1 |
} |
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/** |
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* The parent of this phaser, or null if none |
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*/ |
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private final Phaser parent; |
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/** |
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dl |
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* The root of phaser tree. Equals this if not in a tree. |
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1.1 |
*/ |
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private final Phaser root; |
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/** |
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* Heads of Treiber stacks for waiting threads. To eliminate |
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dl |
1.14 |
* contention when releasing some threads while adding others, we |
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jsr166 |
1.1 |
* use two of them, alternating across even and odd phases. |
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dl |
1.14 |
* Subphasers share queues with root to speed up releases. |
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jsr166 |
1.1 |
*/ |
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dl |
1.15 |
private final AtomicReference<QNode> evenQ; |
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private final AtomicReference<QNode> oddQ; |
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jsr166 |
1.1 |
|
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private AtomicReference<QNode> queueFor(int phase) { |
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dl |
1.15 |
return ((phase & 1) == 0) ? evenQ : oddQ; |
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jsr166 |
1.1 |
} |
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/** |
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dl |
1.33 |
* Returns message string for bounds exceptions on arrival. |
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*/ |
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private String badArrive(long s) { |
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return "Attempted arrival of unregistered party for " + |
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stateToString(s); |
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} |
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/** |
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|
|
* Returns message string for bounds exceptions on registration. |
338 |
|
|
*/ |
339 |
|
|
private String badRegister(long s) { |
340 |
|
|
return "Attempt to register more than " + |
341 |
|
|
MAX_PARTIES + " parties for " + stateToString(s); |
342 |
|
|
} |
343 |
|
|
|
344 |
|
|
/** |
345 |
dl |
1.17 |
* Main implementation for methods arrive and arriveAndDeregister. |
346 |
|
|
* Manually tuned to speed up and minimize race windows for the |
347 |
|
|
* common case of just decrementing unarrived field. |
348 |
|
|
* |
349 |
dl |
1.39 |
* @param deregister false for arrive, true for arriveAndDeregister |
350 |
dl |
1.17 |
*/ |
351 |
dl |
1.39 |
private int doArrive(boolean deregister) { |
352 |
|
|
int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL; |
353 |
dl |
1.50 |
final Phaser root = this.root; |
354 |
|
|
for (;;) { |
355 |
|
|
long s = (root == this) ? state : reconcileState(); |
356 |
|
|
int phase = (int)(s >>> PHASE_SHIFT); |
357 |
dl |
1.39 |
int counts = (int)s; |
358 |
dl |
1.50 |
int unarrived = (counts & UNARRIVED_MASK) - 1; |
359 |
|
|
if (phase < 0) |
360 |
|
|
return phase; |
361 |
|
|
else if (counts == EMPTY || unarrived < 0) { |
362 |
|
|
if (root == this || reconcileState() == s) |
363 |
dl |
1.33 |
throw new IllegalStateException(badArrive(s)); |
364 |
|
|
} |
365 |
dl |
1.24 |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) { |
366 |
dl |
1.50 |
if (unarrived == 0) { |
367 |
|
|
long n = s & PARTIES_MASK; // base of next state |
368 |
|
|
int nextUnarrived = ((int)n) >>> PARTIES_SHIFT; |
369 |
|
|
if (root != this) |
370 |
|
|
return parent.doArrive(nextUnarrived == 0); |
371 |
|
|
if (onAdvance(phase, nextUnarrived)) |
372 |
|
|
n |= TERMINATION_BIT; |
373 |
|
|
else if (nextUnarrived == 0) |
374 |
|
|
n |= EMPTY; |
375 |
|
|
else |
376 |
|
|
n |= nextUnarrived; |
377 |
|
|
n |= ((long)((phase + 1) & MAX_PHASE)) << PHASE_SHIFT; |
378 |
|
|
UNSAFE.compareAndSwapLong(this, stateOffset, s, n); |
379 |
|
|
releaseWaiters(phase); |
380 |
dl |
1.17 |
} |
381 |
dl |
1.50 |
return phase; |
382 |
dl |
1.17 |
} |
383 |
|
|
} |
384 |
|
|
} |
385 |
|
|
|
386 |
|
|
/** |
387 |
|
|
* Implementation of register, bulkRegister |
388 |
|
|
* |
389 |
dl |
1.32 |
* @param registrations number to add to both parties and |
390 |
|
|
* unarrived fields. Must be greater than zero. |
391 |
jsr166 |
1.1 |
*/ |
392 |
dl |
1.17 |
private int doRegister(int registrations) { |
393 |
jsr166 |
1.26 |
// adjustment to state |
394 |
|
|
long adj = ((long)registrations << PARTIES_SHIFT) | registrations; |
395 |
dl |
1.39 |
Phaser par = parent; |
396 |
|
|
int phase; |
397 |
dl |
1.21 |
for (;;) { |
398 |
dl |
1.39 |
long s = state; |
399 |
|
|
int counts = (int)s; |
400 |
|
|
int parties = counts >>> PARTIES_SHIFT; |
401 |
|
|
int unarrived = counts & UNARRIVED_MASK; |
402 |
|
|
if (registrations > MAX_PARTIES - parties) |
403 |
dl |
1.21 |
throw new IllegalStateException(badRegister(s)); |
404 |
dl |
1.39 |
else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0) |
405 |
|
|
break; |
406 |
|
|
else if (counts != EMPTY) { // not 1st registration |
407 |
|
|
if (par == null || reconcileState() == s) { |
408 |
|
|
if (unarrived == 0) // wait out advance |
409 |
|
|
root.internalAwaitAdvance(phase, null); |
410 |
|
|
else if (UNSAFE.compareAndSwapLong(this, stateOffset, |
411 |
|
|
s, s + adj)) |
412 |
|
|
break; |
413 |
|
|
} |
414 |
|
|
} |
415 |
|
|
else if (par == null) { // 1st root registration |
416 |
|
|
long next = (((long) phase) << PHASE_SHIFT) | adj; |
417 |
|
|
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
418 |
|
|
break; |
419 |
|
|
} |
420 |
|
|
else { |
421 |
jsr166 |
1.40 |
synchronized (this) { // 1st sub registration |
422 |
dl |
1.39 |
if (state == s) { // recheck under lock |
423 |
|
|
par.doRegister(1); |
424 |
|
|
do { // force current phase |
425 |
|
|
phase = (int)(root.state >>> PHASE_SHIFT); |
426 |
|
|
// assert phase < 0 || (int)state == EMPTY; |
427 |
|
|
} while (!UNSAFE.compareAndSwapLong |
428 |
|
|
(this, stateOffset, state, |
429 |
|
|
(((long) phase) << PHASE_SHIFT) | adj)); |
430 |
|
|
break; |
431 |
dl |
1.33 |
} |
432 |
|
|
} |
433 |
|
|
} |
434 |
dl |
1.17 |
} |
435 |
dl |
1.39 |
return phase; |
436 |
dl |
1.17 |
} |
437 |
|
|
|
438 |
|
|
/** |
439 |
dl |
1.39 |
* Resolves lagged phase propagation from root if necessary. |
440 |
jsr166 |
1.1 |
*/ |
441 |
|
|
private long reconcileState() { |
442 |
jsr166 |
1.52 |
final Phaser root = this.root; |
443 |
dl |
1.31 |
long s = state; |
444 |
jsr166 |
1.52 |
if (root != this) { |
445 |
|
|
for (long rs; ((rs = root.state) ^ s) >>> PHASE_SHIFT != 0;) { |
446 |
|
|
// assert rs < 0 || (s != state) || unarrivedOf(s) == 0; |
447 |
|
|
long lp = s & PARTIES_MASK; |
448 |
|
|
long n = (rs & PHASE_MASK) | lp; |
449 |
|
|
if (rs >= 0) |
450 |
|
|
n |= (lp == 0L) ? EMPTY : (lp >>> PARTIES_SHIFT); |
451 |
|
|
if (s == (s = state) && |
452 |
|
|
UNSAFE.compareAndSwapLong(this, stateOffset, s, n)) |
453 |
|
|
return n; |
454 |
jsr166 |
1.1 |
} |
455 |
|
|
} |
456 |
dl |
1.31 |
return s; |
457 |
jsr166 |
1.1 |
} |
458 |
|
|
|
459 |
|
|
/** |
460 |
dl |
1.37 |
* Creates a new phaser with no initially registered parties, no |
461 |
|
|
* parent, and initial phase number 0. Any thread using this |
462 |
|
|
* phaser will need to first register for it. |
463 |
jsr166 |
1.1 |
*/ |
464 |
|
|
public Phaser() { |
465 |
dl |
1.15 |
this(null, 0); |
466 |
jsr166 |
1.1 |
} |
467 |
|
|
|
468 |
|
|
/** |
469 |
dl |
1.37 |
* Creates a new phaser with the given number of registered |
470 |
|
|
* unarrived parties, no parent, and initial phase number 0. |
471 |
jsr166 |
1.1 |
* |
472 |
dl |
1.37 |
* @param parties the number of parties required to advance to the |
473 |
|
|
* next phase |
474 |
jsr166 |
1.1 |
* @throws IllegalArgumentException if parties less than zero |
475 |
|
|
* or greater than the maximum number of parties supported |
476 |
|
|
*/ |
477 |
|
|
public Phaser(int parties) { |
478 |
|
|
this(null, parties); |
479 |
|
|
} |
480 |
|
|
|
481 |
|
|
/** |
482 |
dl |
1.32 |
* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}. |
483 |
jsr166 |
1.1 |
* |
484 |
dl |
1.37 |
* @param parent the parent phaser |
485 |
jsr166 |
1.1 |
*/ |
486 |
|
|
public Phaser(Phaser parent) { |
487 |
dl |
1.15 |
this(parent, 0); |
488 |
jsr166 |
1.1 |
} |
489 |
|
|
|
490 |
|
|
/** |
491 |
dl |
1.37 |
* Creates a new phaser with the given parent and number of |
492 |
dl |
1.50 |
* registered unarrived parties. When the given parent is non-null |
493 |
jsr166 |
1.44 |
* and the given number of parties is greater than zero, this |
494 |
|
|
* child phaser is registered with its parent. |
495 |
jsr166 |
1.1 |
* |
496 |
dl |
1.37 |
* @param parent the parent phaser |
497 |
|
|
* @param parties the number of parties required to advance to the |
498 |
|
|
* next phase |
499 |
jsr166 |
1.1 |
* @throws IllegalArgumentException if parties less than zero |
500 |
|
|
* or greater than the maximum number of parties supported |
501 |
|
|
*/ |
502 |
|
|
public Phaser(Phaser parent, int parties) { |
503 |
dl |
1.24 |
if (parties >>> PARTIES_SHIFT != 0) |
504 |
jsr166 |
1.1 |
throw new IllegalArgumentException("Illegal number of parties"); |
505 |
dl |
1.39 |
int phase = 0; |
506 |
jsr166 |
1.1 |
this.parent = parent; |
507 |
|
|
if (parent != null) { |
508 |
jsr166 |
1.42 |
final Phaser root = parent.root; |
509 |
|
|
this.root = root; |
510 |
|
|
this.evenQ = root.evenQ; |
511 |
|
|
this.oddQ = root.oddQ; |
512 |
dl |
1.34 |
if (parties != 0) |
513 |
dl |
1.39 |
phase = parent.doRegister(1); |
514 |
jsr166 |
1.1 |
} |
515 |
dl |
1.15 |
else { |
516 |
jsr166 |
1.1 |
this.root = this; |
517 |
dl |
1.15 |
this.evenQ = new AtomicReference<QNode>(); |
518 |
|
|
this.oddQ = new AtomicReference<QNode>(); |
519 |
|
|
} |
520 |
jsr166 |
1.42 |
this.state = (parties == 0) ? (long) EMPTY : |
521 |
dl |
1.39 |
((((long) phase) << PHASE_SHIFT) | |
522 |
|
|
(((long) parties) << PARTIES_SHIFT) | |
523 |
|
|
((long) parties)); |
524 |
jsr166 |
1.1 |
} |
525 |
|
|
|
526 |
|
|
/** |
527 |
dl |
1.37 |
* Adds a new unarrived party to this phaser. If an ongoing |
528 |
dl |
1.33 |
* invocation of {@link #onAdvance} is in progress, this method |
529 |
dl |
1.37 |
* may await its completion before returning. If this phaser has |
530 |
|
|
* a parent, and this phaser previously had no registered parties, |
531 |
dl |
1.50 |
* this child phaser is also registered with its parent. If |
532 |
|
|
* this phaser is terminated, the attempt to register has |
533 |
|
|
* no effect, and a negative value is returned. |
534 |
|
|
* |
535 |
|
|
* @return the arrival phase number to which this registration |
536 |
|
|
* applied. If this value is negative, then this phaser has |
537 |
jsr166 |
1.51 |
* terminated, in which case registration has no effect. |
538 |
jsr166 |
1.1 |
* @throws IllegalStateException if attempting to register more |
539 |
|
|
* than the maximum supported number of parties |
540 |
|
|
*/ |
541 |
|
|
public int register() { |
542 |
|
|
return doRegister(1); |
543 |
|
|
} |
544 |
|
|
|
545 |
|
|
/** |
546 |
dl |
1.37 |
* Adds the given number of new unarrived parties to this phaser. |
547 |
dl |
1.14 |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
548 |
dl |
1.34 |
* this method may await its completion before returning. If this |
549 |
dl |
1.50 |
* phaser has a parent, and the given number of parties is greater |
550 |
|
|
* than zero, and this phaser previously had no registered |
551 |
jsr166 |
1.44 |
* parties, this child phaser is also registered with its parent. |
552 |
dl |
1.50 |
* If this phaser is terminated, the attempt to register has no |
553 |
|
|
* effect, and a negative value is returned. |
554 |
jsr166 |
1.1 |
* |
555 |
dl |
1.37 |
* @param parties the number of additional parties required to |
556 |
|
|
* advance to the next phase |
557 |
dl |
1.50 |
* @return the arrival phase number to which this registration |
558 |
|
|
* applied. If this value is negative, then this phaser has |
559 |
jsr166 |
1.51 |
* terminated, in which case registration has no effect. |
560 |
jsr166 |
1.1 |
* @throws IllegalStateException if attempting to register more |
561 |
|
|
* than the maximum supported number of parties |
562 |
dl |
1.13 |
* @throws IllegalArgumentException if {@code parties < 0} |
563 |
jsr166 |
1.1 |
*/ |
564 |
|
|
public int bulkRegister(int parties) { |
565 |
|
|
if (parties < 0) |
566 |
|
|
throw new IllegalArgumentException(); |
567 |
dl |
1.34 |
if (parties == 0) |
568 |
jsr166 |
1.1 |
return getPhase(); |
569 |
|
|
return doRegister(parties); |
570 |
|
|
} |
571 |
|
|
|
572 |
|
|
/** |
573 |
dl |
1.37 |
* Arrives at this phaser, without waiting for others to arrive. |
574 |
dl |
1.34 |
* |
575 |
|
|
* <p>It is a usage error for an unregistered party to invoke this |
576 |
|
|
* method. However, this error may result in an {@code |
577 |
|
|
* IllegalStateException} only upon some subsequent operation on |
578 |
dl |
1.37 |
* this phaser, if ever. |
579 |
jsr166 |
1.1 |
* |
580 |
jsr166 |
1.10 |
* @return the arrival phase number, or a negative value if terminated |
581 |
jsr166 |
1.1 |
* @throws IllegalStateException if not terminated and the number |
582 |
|
|
* of unarrived parties would become negative |
583 |
|
|
*/ |
584 |
|
|
public int arrive() { |
585 |
dl |
1.39 |
return doArrive(false); |
586 |
jsr166 |
1.1 |
} |
587 |
|
|
|
588 |
|
|
/** |
589 |
dl |
1.37 |
* Arrives at this phaser and deregisters from it without waiting |
590 |
dl |
1.34 |
* for others to arrive. Deregistration reduces the number of |
591 |
dl |
1.37 |
* parties required to advance in future phases. If this phaser |
592 |
|
|
* has a parent, and deregistration causes this phaser to have |
593 |
|
|
* zero parties, this phaser is also deregistered from its parent. |
594 |
dl |
1.34 |
* |
595 |
|
|
* <p>It is a usage error for an unregistered party to invoke this |
596 |
|
|
* method. However, this error may result in an {@code |
597 |
|
|
* IllegalStateException} only upon some subsequent operation on |
598 |
dl |
1.37 |
* this phaser, if ever. |
599 |
jsr166 |
1.1 |
* |
600 |
jsr166 |
1.10 |
* @return the arrival phase number, or a negative value if terminated |
601 |
jsr166 |
1.1 |
* @throws IllegalStateException if not terminated and the number |
602 |
|
|
* of registered or unarrived parties would become negative |
603 |
|
|
*/ |
604 |
|
|
public int arriveAndDeregister() { |
605 |
dl |
1.39 |
return doArrive(true); |
606 |
jsr166 |
1.1 |
} |
607 |
|
|
|
608 |
|
|
/** |
609 |
dl |
1.37 |
* Arrives at this phaser and awaits others. Equivalent in effect |
610 |
jsr166 |
1.7 |
* to {@code awaitAdvance(arrive())}. If you need to await with |
611 |
|
|
* interruption or timeout, you can arrange this with an analogous |
612 |
jsr166 |
1.12 |
* construction using one of the other forms of the {@code |
613 |
|
|
* awaitAdvance} method. If instead you need to deregister upon |
614 |
dl |
1.34 |
* arrival, use {@code awaitAdvance(arriveAndDeregister())}. |
615 |
|
|
* |
616 |
|
|
* <p>It is a usage error for an unregistered party to invoke this |
617 |
|
|
* method. However, this error may result in an {@code |
618 |
|
|
* IllegalStateException} only upon some subsequent operation on |
619 |
dl |
1.37 |
* this phaser, if ever. |
620 |
jsr166 |
1.1 |
* |
621 |
jsr166 |
1.49 |
* @return the arrival phase number, or the (negative) |
622 |
|
|
* {@linkplain #getPhase() current phase} if terminated |
623 |
jsr166 |
1.1 |
* @throws IllegalStateException if not terminated and the number |
624 |
|
|
* of unarrived parties would become negative |
625 |
|
|
*/ |
626 |
|
|
public int arriveAndAwaitAdvance() { |
627 |
dl |
1.50 |
// Specialization of doArrive+awaitAdvance eliminating some reads/paths |
628 |
|
|
final Phaser root = this.root; |
629 |
|
|
for (;;) { |
630 |
|
|
long s = (root == this) ? state : reconcileState(); |
631 |
|
|
int phase = (int)(s >>> PHASE_SHIFT); |
632 |
|
|
int counts = (int)s; |
633 |
|
|
int unarrived = (counts & UNARRIVED_MASK) - 1; |
634 |
|
|
if (phase < 0) |
635 |
|
|
return phase; |
636 |
|
|
else if (counts == EMPTY || unarrived < 0) { |
637 |
|
|
if (reconcileState() == s) |
638 |
|
|
throw new IllegalStateException(badArrive(s)); |
639 |
|
|
} |
640 |
|
|
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, |
641 |
|
|
s -= ONE_ARRIVAL)) { |
642 |
|
|
if (unarrived != 0) |
643 |
|
|
return root.internalAwaitAdvance(phase, null); |
644 |
|
|
if (root != this) |
645 |
|
|
return parent.arriveAndAwaitAdvance(); |
646 |
|
|
long n = s & PARTIES_MASK; // base of next state |
647 |
|
|
int nextUnarrived = ((int)n) >>> PARTIES_SHIFT; |
648 |
|
|
if (onAdvance(phase, nextUnarrived)) |
649 |
|
|
n |= TERMINATION_BIT; |
650 |
|
|
else if (nextUnarrived == 0) |
651 |
|
|
n |= EMPTY; |
652 |
|
|
else |
653 |
|
|
n |= nextUnarrived; |
654 |
|
|
int nextPhase = (phase + 1) & MAX_PHASE; |
655 |
|
|
n |= (long)nextPhase << PHASE_SHIFT; |
656 |
|
|
if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n)) |
657 |
|
|
return (int)(state >>> PHASE_SHIFT); // terminated |
658 |
|
|
releaseWaiters(phase); |
659 |
|
|
return nextPhase; |
660 |
|
|
} |
661 |
|
|
} |
662 |
jsr166 |
1.1 |
} |
663 |
|
|
|
664 |
|
|
/** |
665 |
dl |
1.37 |
* Awaits the phase of this phaser to advance from the given phase |
666 |
|
|
* value, returning immediately if the current phase is not equal |
667 |
|
|
* to the given phase value or this phaser is terminated. |
668 |
jsr166 |
1.1 |
* |
669 |
jsr166 |
1.10 |
* @param phase an arrival phase number, or negative value if |
670 |
|
|
* terminated; this argument is normally the value returned by a |
671 |
dl |
1.37 |
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
672 |
jsr166 |
1.48 |
* @return the next arrival phase number, or the argument if it is |
673 |
|
|
* negative, or the (negative) {@linkplain #getPhase() current phase} |
674 |
|
|
* if terminated |
675 |
jsr166 |
1.1 |
*/ |
676 |
|
|
public int awaitAdvance(int phase) { |
677 |
dl |
1.50 |
final Phaser root = this.root; |
678 |
jsr166 |
1.51 |
long s = (root == this) ? state : reconcileState(); |
679 |
|
|
int p = (int)(s >>> PHASE_SHIFT); |
680 |
jsr166 |
1.1 |
if (phase < 0) |
681 |
|
|
return phase; |
682 |
dl |
1.50 |
if (p == phase) |
683 |
|
|
return root.internalAwaitAdvance(phase, null); |
684 |
dl |
1.34 |
return p; |
685 |
jsr166 |
1.1 |
} |
686 |
|
|
|
687 |
|
|
/** |
688 |
dl |
1.37 |
* Awaits the phase of this phaser to advance from the given phase |
689 |
jsr166 |
1.10 |
* value, throwing {@code InterruptedException} if interrupted |
690 |
dl |
1.37 |
* while waiting, or returning immediately if the current phase is |
691 |
|
|
* not equal to the given phase value or this phaser is |
692 |
|
|
* terminated. |
693 |
jsr166 |
1.10 |
* |
694 |
|
|
* @param phase an arrival phase number, or negative value if |
695 |
|
|
* terminated; this argument is normally the value returned by a |
696 |
dl |
1.37 |
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
697 |
jsr166 |
1.48 |
* @return the next arrival phase number, or the argument if it is |
698 |
|
|
* negative, or the (negative) {@linkplain #getPhase() current phase} |
699 |
|
|
* if terminated |
700 |
jsr166 |
1.1 |
* @throws InterruptedException if thread interrupted while waiting |
701 |
|
|
*/ |
702 |
|
|
public int awaitAdvanceInterruptibly(int phase) |
703 |
|
|
throws InterruptedException { |
704 |
dl |
1.50 |
final Phaser root = this.root; |
705 |
jsr166 |
1.51 |
long s = (root == this) ? state : reconcileState(); |
706 |
|
|
int p = (int)(s >>> PHASE_SHIFT); |
707 |
jsr166 |
1.1 |
if (phase < 0) |
708 |
|
|
return phase; |
709 |
dl |
1.39 |
if (p == phase) { |
710 |
dl |
1.50 |
QNode node = new QNode(this, phase, true, false, 0L); |
711 |
|
|
p = root.internalAwaitAdvance(phase, node); |
712 |
|
|
if (node.wasInterrupted) |
713 |
|
|
throw new InterruptedException(); |
714 |
dl |
1.24 |
} |
715 |
|
|
return p; |
716 |
jsr166 |
1.1 |
} |
717 |
|
|
|
718 |
|
|
/** |
719 |
dl |
1.37 |
* Awaits the phase of this phaser to advance from the given phase |
720 |
jsr166 |
1.10 |
* value or the given timeout to elapse, throwing {@code |
721 |
|
|
* InterruptedException} if interrupted while waiting, or |
722 |
dl |
1.37 |
* returning immediately if the current phase is not equal to the |
723 |
|
|
* given phase value or this phaser is terminated. |
724 |
jsr166 |
1.10 |
* |
725 |
|
|
* @param phase an arrival phase number, or negative value if |
726 |
|
|
* terminated; this argument is normally the value returned by a |
727 |
dl |
1.37 |
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
728 |
jsr166 |
1.8 |
* @param timeout how long to wait before giving up, in units of |
729 |
|
|
* {@code unit} |
730 |
|
|
* @param unit a {@code TimeUnit} determining how to interpret the |
731 |
|
|
* {@code timeout} parameter |
732 |
jsr166 |
1.48 |
* @return the next arrival phase number, or the argument if it is |
733 |
|
|
* negative, or the (negative) {@linkplain #getPhase() current phase} |
734 |
|
|
* if terminated |
735 |
jsr166 |
1.1 |
* @throws InterruptedException if thread interrupted while waiting |
736 |
|
|
* @throws TimeoutException if timed out while waiting |
737 |
|
|
*/ |
738 |
|
|
public int awaitAdvanceInterruptibly(int phase, |
739 |
|
|
long timeout, TimeUnit unit) |
740 |
|
|
throws InterruptedException, TimeoutException { |
741 |
dl |
1.50 |
long nanos = unit.toNanos(timeout); |
742 |
|
|
final Phaser root = this.root; |
743 |
jsr166 |
1.51 |
long s = (root == this) ? state : reconcileState(); |
744 |
|
|
int p = (int)(s >>> PHASE_SHIFT); |
745 |
jsr166 |
1.47 |
if (phase < 0) |
746 |
|
|
return phase; |
747 |
dl |
1.39 |
if (p == phase) { |
748 |
dl |
1.50 |
QNode node = new QNode(this, phase, true, true, nanos); |
749 |
|
|
p = root.internalAwaitAdvance(phase, node); |
750 |
|
|
if (node.wasInterrupted) |
751 |
|
|
throw new InterruptedException(); |
752 |
|
|
else if (p == phase) |
753 |
|
|
throw new TimeoutException(); |
754 |
dl |
1.24 |
} |
755 |
|
|
return p; |
756 |
jsr166 |
1.1 |
} |
757 |
|
|
|
758 |
|
|
/** |
759 |
dl |
1.37 |
* Forces this phaser to enter termination state. Counts of |
760 |
dl |
1.39 |
* registered parties are unaffected. If this phaser is a member |
761 |
|
|
* of a tiered set of phasers, then all of the phasers in the set |
762 |
|
|
* are terminated. If this phaser is already terminated, this |
763 |
|
|
* method has no effect. This method may be useful for |
764 |
|
|
* coordinating recovery after one or more tasks encounter |
765 |
|
|
* unexpected exceptions. |
766 |
jsr166 |
1.1 |
*/ |
767 |
|
|
public void forceTermination() { |
768 |
jsr166 |
1.23 |
// Only need to change root state |
769 |
|
|
final Phaser root = this.root; |
770 |
dl |
1.14 |
long s; |
771 |
jsr166 |
1.23 |
while ((s = root.state) >= 0) { |
772 |
jsr166 |
1.46 |
long next = (s & ~((long)UNARRIVED_MASK)) | TERMINATION_BIT; |
773 |
dl |
1.39 |
if (UNSAFE.compareAndSwapLong(root, stateOffset, s, next)) { |
774 |
jsr166 |
1.45 |
// signal all threads |
775 |
|
|
releaseWaiters(0); |
776 |
jsr166 |
1.23 |
releaseWaiters(1); |
777 |
|
|
return; |
778 |
|
|
} |
779 |
|
|
} |
780 |
jsr166 |
1.1 |
} |
781 |
|
|
|
782 |
|
|
/** |
783 |
|
|
* Returns the current phase number. The maximum phase number is |
784 |
|
|
* {@code Integer.MAX_VALUE}, after which it restarts at |
785 |
dl |
1.37 |
* zero. Upon termination, the phase number is negative, |
786 |
|
|
* in which case the prevailing phase prior to termination |
787 |
|
|
* may be obtained via {@code getPhase() + Integer.MIN_VALUE}. |
788 |
jsr166 |
1.1 |
* |
789 |
|
|
* @return the phase number, or a negative value if terminated |
790 |
|
|
*/ |
791 |
|
|
public final int getPhase() { |
792 |
dl |
1.31 |
return (int)(root.state >>> PHASE_SHIFT); |
793 |
jsr166 |
1.1 |
} |
794 |
|
|
|
795 |
|
|
/** |
796 |
dl |
1.37 |
* Returns the number of parties registered at this phaser. |
797 |
jsr166 |
1.1 |
* |
798 |
|
|
* @return the number of parties |
799 |
|
|
*/ |
800 |
|
|
public int getRegisteredParties() { |
801 |
dl |
1.31 |
return partiesOf(state); |
802 |
jsr166 |
1.1 |
} |
803 |
|
|
|
804 |
|
|
/** |
805 |
jsr166 |
1.10 |
* Returns the number of registered parties that have arrived at |
806 |
dl |
1.37 |
* the current phase of this phaser. |
807 |
jsr166 |
1.1 |
* |
808 |
|
|
* @return the number of arrived parties |
809 |
|
|
*/ |
810 |
|
|
public int getArrivedParties() { |
811 |
dl |
1.39 |
return arrivedOf(reconcileState()); |
812 |
jsr166 |
1.1 |
} |
813 |
|
|
|
814 |
|
|
/** |
815 |
|
|
* Returns the number of registered parties that have not yet |
816 |
dl |
1.37 |
* arrived at the current phase of this phaser. |
817 |
jsr166 |
1.1 |
* |
818 |
|
|
* @return the number of unarrived parties |
819 |
|
|
*/ |
820 |
|
|
public int getUnarrivedParties() { |
821 |
dl |
1.39 |
return unarrivedOf(reconcileState()); |
822 |
jsr166 |
1.1 |
} |
823 |
|
|
|
824 |
|
|
/** |
825 |
dl |
1.37 |
* Returns the parent of this phaser, or {@code null} if none. |
826 |
jsr166 |
1.1 |
* |
827 |
dl |
1.37 |
* @return the parent of this phaser, or {@code null} if none |
828 |
jsr166 |
1.1 |
*/ |
829 |
|
|
public Phaser getParent() { |
830 |
|
|
return parent; |
831 |
|
|
} |
832 |
|
|
|
833 |
|
|
/** |
834 |
dl |
1.37 |
* Returns the root ancestor of this phaser, which is the same as |
835 |
|
|
* this phaser if it has no parent. |
836 |
jsr166 |
1.1 |
* |
837 |
dl |
1.37 |
* @return the root ancestor of this phaser |
838 |
jsr166 |
1.1 |
*/ |
839 |
|
|
public Phaser getRoot() { |
840 |
|
|
return root; |
841 |
|
|
} |
842 |
|
|
|
843 |
|
|
/** |
844 |
dl |
1.37 |
* Returns {@code true} if this phaser has been terminated. |
845 |
jsr166 |
1.1 |
* |
846 |
dl |
1.37 |
* @return {@code true} if this phaser has been terminated |
847 |
jsr166 |
1.1 |
*/ |
848 |
|
|
public boolean isTerminated() { |
849 |
dl |
1.31 |
return root.state < 0L; |
850 |
jsr166 |
1.1 |
} |
851 |
|
|
|
852 |
|
|
/** |
853 |
jsr166 |
1.10 |
* Overridable method to perform an action upon impending phase |
854 |
|
|
* advance, and to control termination. This method is invoked |
855 |
dl |
1.37 |
* upon arrival of the party advancing this phaser (when all other |
856 |
jsr166 |
1.10 |
* waiting parties are dormant). If this method returns {@code |
857 |
dl |
1.39 |
* true}, this phaser will be set to a final termination state |
858 |
|
|
* upon advance, and subsequent calls to {@link #isTerminated} |
859 |
|
|
* will return true. Any (unchecked) Exception or Error thrown by |
860 |
|
|
* an invocation of this method is propagated to the party |
861 |
|
|
* attempting to advance this phaser, in which case no advance |
862 |
|
|
* occurs. |
863 |
jsr166 |
1.10 |
* |
864 |
dl |
1.37 |
* <p>The arguments to this method provide the state of the phaser |
865 |
dl |
1.17 |
* prevailing for the current transition. The effects of invoking |
866 |
dl |
1.37 |
* arrival, registration, and waiting methods on this phaser from |
867 |
dl |
1.15 |
* within {@code onAdvance} are unspecified and should not be |
868 |
dl |
1.17 |
* relied on. |
869 |
|
|
* |
870 |
dl |
1.37 |
* <p>If this phaser is a member of a tiered set of phasers, then |
871 |
|
|
* {@code onAdvance} is invoked only for its root phaser on each |
872 |
dl |
1.17 |
* advance. |
873 |
jsr166 |
1.1 |
* |
874 |
dl |
1.33 |
* <p>To support the most common use cases, the default |
875 |
|
|
* implementation of this method returns {@code true} when the |
876 |
|
|
* number of registered parties has become zero as the result of a |
877 |
|
|
* party invoking {@code arriveAndDeregister}. You can disable |
878 |
|
|
* this behavior, thus enabling continuation upon future |
879 |
|
|
* registrations, by overriding this method to always return |
880 |
|
|
* {@code false}: |
881 |
|
|
* |
882 |
|
|
* <pre> {@code |
883 |
|
|
* Phaser phaser = new Phaser() { |
884 |
|
|
* protected boolean onAdvance(int phase, int parties) { return false; } |
885 |
|
|
* }}</pre> |
886 |
jsr166 |
1.1 |
* |
887 |
dl |
1.37 |
* @param phase the current phase number on entry to this method, |
888 |
|
|
* before this phaser is advanced |
889 |
jsr166 |
1.1 |
* @param registeredParties the current number of registered parties |
890 |
dl |
1.37 |
* @return {@code true} if this phaser should terminate |
891 |
jsr166 |
1.1 |
*/ |
892 |
|
|
protected boolean onAdvance(int phase, int registeredParties) { |
893 |
dl |
1.36 |
return registeredParties == 0; |
894 |
jsr166 |
1.1 |
} |
895 |
|
|
|
896 |
|
|
/** |
897 |
dl |
1.37 |
* Returns a string identifying this phaser, as well as its |
898 |
dl |
1.21 |
* state. The state, in brackets, includes the String {@code |
899 |
|
|
* "phase = "} followed by the phase number, {@code "parties = "} |
900 |
|
|
* followed by the number of registered parties, and {@code |
901 |
|
|
* "arrived = "} followed by the number of arrived parties. |
902 |
jsr166 |
1.1 |
* |
903 |
dl |
1.37 |
* @return a string identifying this phaser, as well as its state |
904 |
jsr166 |
1.1 |
*/ |
905 |
|
|
public String toString() { |
906 |
dl |
1.21 |
return stateToString(reconcileState()); |
907 |
|
|
} |
908 |
|
|
|
909 |
|
|
/** |
910 |
|
|
* Implementation of toString and string-based error messages |
911 |
|
|
*/ |
912 |
|
|
private String stateToString(long s) { |
913 |
jsr166 |
1.1 |
return super.toString() + |
914 |
|
|
"[phase = " + phaseOf(s) + |
915 |
|
|
" parties = " + partiesOf(s) + |
916 |
|
|
" arrived = " + arrivedOf(s) + "]"; |
917 |
|
|
} |
918 |
|
|
|
919 |
dl |
1.21 |
// Waiting mechanics |
920 |
|
|
|
921 |
jsr166 |
1.1 |
/** |
922 |
jsr166 |
1.30 |
* Removes and signals threads from queue for phase. |
923 |
jsr166 |
1.1 |
*/ |
924 |
|
|
private void releaseWaiters(int phase) { |
925 |
dl |
1.37 |
QNode q; // first element of queue |
926 |
|
|
Thread t; // its thread |
927 |
dl |
1.36 |
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
928 |
dl |
1.17 |
while ((q = head.get()) != null && |
929 |
dl |
1.39 |
q.phase != (int)(root.state >>> PHASE_SHIFT)) { |
930 |
dl |
1.37 |
if (head.compareAndSet(q, q.next) && |
931 |
|
|
(t = q.thread) != null) { |
932 |
|
|
q.thread = null; |
933 |
|
|
LockSupport.unpark(t); |
934 |
|
|
} |
935 |
jsr166 |
1.1 |
} |
936 |
|
|
} |
937 |
|
|
|
938 |
dl |
1.50 |
/** |
939 |
|
|
* Variant of releaseWaiters that additionally tries to remove any |
940 |
|
|
* nodes no longer waiting for advance due to timeout or |
941 |
|
|
* interrupt. Currently, nodes are removed only if they are at |
942 |
|
|
* head of queue, which suffices to reduce memory footprint in |
943 |
|
|
* most usages. |
944 |
|
|
* |
945 |
|
|
* @return current phase on exit |
946 |
|
|
*/ |
947 |
|
|
private int abortWait(int phase) { |
948 |
|
|
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
949 |
|
|
for (;;) { |
950 |
|
|
Thread t; |
951 |
|
|
QNode q = head.get(); |
952 |
|
|
int p = (int)(root.state >>> PHASE_SHIFT); |
953 |
|
|
if (q == null || ((t = q.thread) != null && q.phase == p)) |
954 |
|
|
return p; |
955 |
|
|
if (head.compareAndSet(q, q.next) && t != null) { |
956 |
|
|
q.thread = null; |
957 |
|
|
LockSupport.unpark(t); |
958 |
|
|
} |
959 |
|
|
} |
960 |
|
|
} |
961 |
|
|
|
962 |
dl |
1.17 |
/** The number of CPUs, for spin control */ |
963 |
|
|
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
964 |
|
|
|
965 |
jsr166 |
1.1 |
/** |
966 |
dl |
1.17 |
* The number of times to spin before blocking while waiting for |
967 |
|
|
* advance, per arrival while waiting. On multiprocessors, fully |
968 |
|
|
* blocking and waking up a large number of threads all at once is |
969 |
|
|
* usually a very slow process, so we use rechargeable spins to |
970 |
|
|
* avoid it when threads regularly arrive: When a thread in |
971 |
|
|
* internalAwaitAdvance notices another arrival before blocking, |
972 |
|
|
* and there appear to be enough CPUs available, it spins |
973 |
dl |
1.36 |
* SPINS_PER_ARRIVAL more times before blocking. The value trades |
974 |
|
|
* off good-citizenship vs big unnecessary slowdowns. |
975 |
dl |
1.15 |
*/ |
976 |
jsr166 |
1.22 |
static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8; |
977 |
dl |
1.15 |
|
978 |
|
|
/** |
979 |
dl |
1.17 |
* Possibly blocks and waits for phase to advance unless aborted. |
980 |
dl |
1.34 |
* Call only from root node. |
981 |
jsr166 |
1.1 |
* |
982 |
dl |
1.17 |
* @param phase current phase |
983 |
jsr166 |
1.22 |
* @param node if non-null, the wait node to track interrupt and timeout; |
984 |
dl |
1.17 |
* if null, denotes noninterruptible wait |
985 |
jsr166 |
1.1 |
* @return current phase |
986 |
|
|
*/ |
987 |
dl |
1.17 |
private int internalAwaitAdvance(int phase, QNode node) { |
988 |
dl |
1.37 |
releaseWaiters(phase-1); // ensure old queue clean |
989 |
|
|
boolean queued = false; // true when node is enqueued |
990 |
|
|
int lastUnarrived = 0; // to increase spins upon change |
991 |
dl |
1.17 |
int spins = SPINS_PER_ARRIVAL; |
992 |
dl |
1.31 |
long s; |
993 |
|
|
int p; |
994 |
dl |
1.34 |
while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) { |
995 |
dl |
1.37 |
if (node == null) { // spinning in noninterruptible mode |
996 |
|
|
int unarrived = (int)s & UNARRIVED_MASK; |
997 |
|
|
if (unarrived != lastUnarrived && |
998 |
|
|
(lastUnarrived = unarrived) < NCPU) |
999 |
dl |
1.31 |
spins += SPINS_PER_ARRIVAL; |
1000 |
dl |
1.37 |
boolean interrupted = Thread.interrupted(); |
1001 |
|
|
if (interrupted || --spins < 0) { // need node to record intr |
1002 |
|
|
node = new QNode(this, phase, false, false, 0L); |
1003 |
|
|
node.wasInterrupted = interrupted; |
1004 |
|
|
} |
1005 |
dl |
1.21 |
} |
1006 |
dl |
1.37 |
else if (node.isReleasable()) // done or aborted |
1007 |
|
|
break; |
1008 |
|
|
else if (!queued) { // push onto queue |
1009 |
dl |
1.36 |
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
1010 |
dl |
1.37 |
QNode q = node.next = head.get(); |
1011 |
|
|
if ((q == null || q.phase == phase) && |
1012 |
|
|
(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq |
1013 |
dl |
1.36 |
queued = head.compareAndSet(q, node); |
1014 |
dl |
1.31 |
} |
1015 |
dl |
1.17 |
else { |
1016 |
|
|
try { |
1017 |
|
|
ForkJoinPool.managedBlock(node); |
1018 |
|
|
} catch (InterruptedException ie) { |
1019 |
|
|
node.wasInterrupted = true; |
1020 |
|
|
} |
1021 |
|
|
} |
1022 |
|
|
} |
1023 |
dl |
1.34 |
|
1024 |
|
|
if (node != null) { |
1025 |
|
|
if (node.thread != null) |
1026 |
dl |
1.37 |
node.thread = null; // avoid need for unpark() |
1027 |
dl |
1.36 |
if (node.wasInterrupted && !node.interruptible) |
1028 |
dl |
1.34 |
Thread.currentThread().interrupt(); |
1029 |
dl |
1.39 |
if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase) |
1030 |
dl |
1.50 |
return abortWait(phase); // possibly clean up on abort |
1031 |
dl |
1.34 |
} |
1032 |
dl |
1.37 |
releaseWaiters(phase); |
1033 |
dl |
1.31 |
return p; |
1034 |
jsr166 |
1.1 |
} |
1035 |
|
|
|
1036 |
|
|
/** |
1037 |
dl |
1.17 |
* Wait nodes for Treiber stack representing wait queue |
1038 |
jsr166 |
1.1 |
*/ |
1039 |
dl |
1.17 |
static final class QNode implements ForkJoinPool.ManagedBlocker { |
1040 |
|
|
final Phaser phaser; |
1041 |
|
|
final int phase; |
1042 |
|
|
final boolean interruptible; |
1043 |
|
|
final boolean timed; |
1044 |
|
|
boolean wasInterrupted; |
1045 |
|
|
long nanos; |
1046 |
|
|
long lastTime; |
1047 |
|
|
volatile Thread thread; // nulled to cancel wait |
1048 |
|
|
QNode next; |
1049 |
|
|
|
1050 |
|
|
QNode(Phaser phaser, int phase, boolean interruptible, |
1051 |
|
|
boolean timed, long nanos) { |
1052 |
|
|
this.phaser = phaser; |
1053 |
|
|
this.phase = phase; |
1054 |
|
|
this.interruptible = interruptible; |
1055 |
|
|
this.nanos = nanos; |
1056 |
|
|
this.timed = timed; |
1057 |
jsr166 |
1.38 |
this.lastTime = timed ? System.nanoTime() : 0L; |
1058 |
dl |
1.17 |
thread = Thread.currentThread(); |
1059 |
|
|
} |
1060 |
|
|
|
1061 |
|
|
public boolean isReleasable() { |
1062 |
dl |
1.37 |
if (thread == null) |
1063 |
|
|
return true; |
1064 |
|
|
if (phaser.getPhase() != phase) { |
1065 |
|
|
thread = null; |
1066 |
|
|
return true; |
1067 |
|
|
} |
1068 |
|
|
if (Thread.interrupted()) |
1069 |
|
|
wasInterrupted = true; |
1070 |
|
|
if (wasInterrupted && interruptible) { |
1071 |
|
|
thread = null; |
1072 |
|
|
return true; |
1073 |
|
|
} |
1074 |
|
|
if (timed) { |
1075 |
|
|
if (nanos > 0L) { |
1076 |
|
|
long now = System.nanoTime(); |
1077 |
|
|
nanos -= now - lastTime; |
1078 |
|
|
lastTime = now; |
1079 |
|
|
} |
1080 |
|
|
if (nanos <= 0L) { |
1081 |
|
|
thread = null; |
1082 |
|
|
return true; |
1083 |
dl |
1.17 |
} |
1084 |
dl |
1.15 |
} |
1085 |
dl |
1.37 |
return false; |
1086 |
dl |
1.17 |
} |
1087 |
|
|
|
1088 |
|
|
public boolean block() { |
1089 |
|
|
if (isReleasable()) |
1090 |
|
|
return true; |
1091 |
|
|
else if (!timed) |
1092 |
|
|
LockSupport.park(this); |
1093 |
|
|
else if (nanos > 0) |
1094 |
|
|
LockSupport.parkNanos(this, nanos); |
1095 |
|
|
return isReleasable(); |
1096 |
|
|
} |
1097 |
jsr166 |
1.1 |
} |
1098 |
|
|
|
1099 |
|
|
// Unsafe mechanics |
1100 |
|
|
|
1101 |
|
|
private static final sun.misc.Unsafe UNSAFE = sun.misc.Unsafe.getUnsafe(); |
1102 |
jsr166 |
1.2 |
private static final long stateOffset = |
1103 |
jsr166 |
1.3 |
objectFieldOffset("state", Phaser.class); |
1104 |
jsr166 |
1.1 |
|
1105 |
jsr166 |
1.3 |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1106 |
|
|
try { |
1107 |
|
|
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1108 |
|
|
} catch (NoSuchFieldException e) { |
1109 |
|
|
// Convert Exception to corresponding Error |
1110 |
|
|
NoSuchFieldError error = new NoSuchFieldError(field); |
1111 |
|
|
error.initCause(e); |
1112 |
|
|
throw error; |
1113 |
|
|
} |
1114 |
|
|
} |
1115 |
jsr166 |
1.1 |
} |