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1.1 |
/* |
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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 jsr166y; |
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jsr166 |
1.9 |
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dl |
1.51 |
import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.TimeoutException; |
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jsr166 |
1.20 |
import java.util.concurrent.atomic.AtomicReference; |
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dl |
1.1 |
import java.util.concurrent.locks.LockSupport; |
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/** |
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jsr166 |
1.37 |
* A reusable synchronization barrier, similar in functionality to |
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jsr166 |
1.9 |
* {@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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1.1 |
* |
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1.38 |
* <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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1.35 |
* #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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jsr166 |
1.37 |
* 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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1.1 |
* |
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1.38 |
* <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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1.39 |
* phase number starts at zero, and advances when all parties arrive |
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1.38 |
* 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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dl |
1.1 |
* |
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* <ul> |
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* |
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1.38 |
* <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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1.39 |
* waiting thread is interrupted. Interruptible and timeout |
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* versions are also available, but exceptions encountered while |
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1.38 |
* 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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1.1 |
* </ul> |
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* |
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1.38 |
* <p> <b>Termination.</b> A {@code Phaser} may enter a |
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1.39 |
* <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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1.4 |
* |
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1.38 |
* <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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1.4 |
* numbers of parties that would otherwise experience heavy |
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1.38 |
* synchronization contention costs may instead be set up so that |
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* groups of sub-phasers share a common parent. This may greatly |
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* increase throughput even though it incurs greater per-operation |
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* overhead. |
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* |
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* <p><b>Monitoring.</b> While synchronization methods may be invoked |
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* only by registered parties, the current state of a phaser may be |
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* monitored by any caller. At any given moment there are {@link |
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1.40 |
* #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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1.42 |
* 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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1.1 |
* |
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1.4 |
* <p><b>Sample usages:</b> |
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* |
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jsr166 |
1.24 |
* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch} |
112 |
dl |
1.48 |
* 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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1.1 |
* |
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jsr166 |
1.13 |
* <pre> {@code |
117 |
jsr166 |
1.33 |
* void runTasks(List<Runnable> tasks) { |
118 |
jsr166 |
1.13 |
* final Phaser phaser = new Phaser(1); // "1" to register self |
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dl |
1.27 |
* // create and start threads |
120 |
jsr166 |
1.33 |
* for (Runnable task : tasks) { |
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jsr166 |
1.13 |
* 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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jsr166 |
1.33 |
* task.run(); |
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jsr166 |
1.13 |
* } |
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* }.start(); |
128 |
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1.4 |
* } |
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dl |
1.6 |
* |
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1.27 |
* // allow threads to start and deregister self |
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* phaser.arriveAndDeregister(); |
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jsr166 |
1.13 |
* }}</pre> |
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1.1 |
* |
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1.4 |
* <p>One way to cause a set of threads to repeatedly perform actions |
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jsr166 |
1.7 |
* for a given number of iterations is to override {@code onAdvance}: |
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dl |
1.1 |
* |
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jsr166 |
1.13 |
* <pre> {@code |
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jsr166 |
1.33 |
* void startTasks(List<Runnable> tasks, final int iterations) { |
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jsr166 |
1.13 |
* final Phaser phaser = new Phaser() { |
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dl |
1.38 |
* protected boolean onAdvance(int phase, int registeredParties) { |
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jsr166 |
1.13 |
* return phase >= iterations || registeredParties == 0; |
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* } |
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* }; |
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* phaser.register(); |
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jsr166 |
1.45 |
* for (final Runnable task : tasks) { |
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jsr166 |
1.13 |
* phaser.register(); |
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* new Thread() { |
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* public void run() { |
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* do { |
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jsr166 |
1.33 |
* task.run(); |
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jsr166 |
1.13 |
* phaser.arriveAndAwaitAdvance(); |
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jsr166 |
1.45 |
* } while (!phaser.isTerminated()); |
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dl |
1.4 |
* } |
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jsr166 |
1.13 |
* }.start(); |
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1.1 |
* } |
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1.4 |
* phaser.arriveAndDeregister(); // deregister self, don't wait |
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jsr166 |
1.13 |
* }}</pre> |
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dl |
1.1 |
* |
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dl |
1.38 |
* 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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jsr166 |
1.45 |
* <pre> {@code |
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dl |
1.38 |
* // ... |
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* phaser.register(); |
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* while (!phaser.isTerminated()) |
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jsr166 |
1.45 |
* phaser.arriveAndAwaitAdvance();}</pre> |
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dl |
1.38 |
* |
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jsr166 |
1.45 |
* <p>Related constructions may be used to await particular phase numbers |
168 |
dl |
1.38 |
* 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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jsr166 |
1.45 |
* <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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dl |
1.38 |
* } |
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jsr166 |
1.45 |
* phaser.arriveAndDeregister(); |
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* }}</pre> |
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dl |
1.38 |
* |
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* |
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jsr166 |
1.25 |
* <p>To create a set of tasks using a tree of phasers, |
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dl |
1.4 |
* you could use code of the following form, assuming a |
186 |
jsr166 |
1.24 |
* Task class with a constructor accepting a phaser that |
187 |
dl |
1.48 |
* it registers with upon construction: |
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jsr166 |
1.45 |
* |
189 |
jsr166 |
1.13 |
* <pre> {@code |
190 |
dl |
1.44 |
* void build(Task[] actions, int lo, int hi, Phaser ph) { |
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* if (hi - lo > TASKS_PER_PHASER) { |
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* for (int i = lo; i < hi; i += TASKS_PER_PHASER) { |
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* int j = Math.min(i + TASKS_PER_PHASER, hi); |
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* build(actions, i, j, new Phaser(ph)); |
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jsr166 |
1.13 |
* } |
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* } else { |
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* for (int i = lo; i < hi; ++i) |
198 |
dl |
1.44 |
* actions[i] = new Task(ph); |
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* // assumes new Task(ph) performs ph.register() |
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jsr166 |
1.13 |
* } |
201 |
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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> |
204 |
dl |
1.4 |
* |
205 |
jsr166 |
1.7 |
* The best value of {@code TASKS_PER_PHASER} depends mainly on |
206 |
dl |
1.4 |
* expected barrier synchronization rates. A value as low as four may |
207 |
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* be appropriate for extremely small per-barrier task bodies (thus |
208 |
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* high rates), or up to hundreds for extremely large ones. |
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* |
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dl |
1.1 |
* <p><b>Implementation notes</b>: This implementation restricts the |
211 |
dl |
1.4 |
* maximum number of parties to 65535. Attempts to register additional |
212 |
jsr166 |
1.32 |
* parties result in {@code IllegalStateException}. However, you can and |
213 |
dl |
1.4 |
* should create tiered phasers to accommodate arbitrarily large sets |
214 |
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* of participants. |
215 |
jsr166 |
1.16 |
* |
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* @since 1.7 |
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* @author Doug Lea |
218 |
dl |
1.1 |
*/ |
219 |
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public class Phaser { |
220 |
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/* |
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* This class implements an extension of X10 "clocks". Thanks to |
222 |
dl |
1.4 |
* Vijay Saraswat for the idea, and to Vivek Sarkar for |
223 |
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* enhancements to extend functionality. |
224 |
dl |
1.1 |
*/ |
225 |
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226 |
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/** |
227 |
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* Barrier state representation. Conceptually, a barrier contains |
228 |
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* four values: |
229 |
jsr166 |
1.3 |
* |
230 |
dl |
1.51 |
* * unarrived -- the number of parties yet to hit barrier (bits 0-15) |
231 |
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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) |
234 |
dl |
1.1 |
* |
235 |
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* However, to efficiently maintain atomicity, these values are |
236 |
dl |
1.4 |
* packed into a single (atomic) long. Termination uses the sign |
237 |
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* bit of 32 bit representation of phase, so phase is set to -1 on |
238 |
jsr166 |
1.8 |
* termination. Good performance relies on keeping state decoding |
239 |
dl |
1.4 |
* and encoding simple, and keeping race windows short. |
240 |
dl |
1.1 |
*/ |
241 |
dl |
1.4 |
private volatile long state; |
242 |
dl |
1.1 |
|
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dl |
1.55 |
private static final int MAX_PARTIES = 0xffff; |
244 |
dl |
1.51 |
private static final int MAX_PHASE = 0x7fffffff; |
245 |
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private static final int PARTIES_SHIFT = 16; |
246 |
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private static final int PHASE_SHIFT = 32; |
247 |
dl |
1.55 |
private static final int UNARRIVED_MASK = 0xffff; |
248 |
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private static final int PARTIES_MASK = 0xffff0000; |
249 |
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private static final long LPARTIES_MASK = 0xffff0000L; // long version |
250 |
dl |
1.51 |
private static final long ONE_ARRIVAL = 1L; |
251 |
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private static final long ONE_PARTY = 1L << PARTIES_SHIFT; |
252 |
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private static final long TERMINATION_PHASE = -1L << PHASE_SHIFT; |
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254 |
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// The following unpacking methods are usually manually inlined |
255 |
dl |
1.1 |
|
256 |
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private static int unarrivedOf(long s) { |
257 |
dl |
1.55 |
return ((int) s) & UNARRIVED_MASK; |
258 |
dl |
1.1 |
} |
259 |
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260 |
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private static int partiesOf(long s) { |
261 |
dl |
1.55 |
return (((int) s) & PARTIES_MASK) >>> PARTIES_SHIFT; |
262 |
dl |
1.1 |
} |
263 |
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264 |
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private static int phaseOf(long s) { |
265 |
dl |
1.51 |
return (int) (s >>> PHASE_SHIFT); |
266 |
dl |
1.1 |
} |
267 |
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268 |
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private static int arrivedOf(long s) { |
269 |
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return partiesOf(s) - unarrivedOf(s); |
270 |
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} |
271 |
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dl |
1.4 |
/** |
273 |
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* The parent of this phaser, or null if none |
274 |
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*/ |
275 |
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private final Phaser parent; |
276 |
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277 |
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/** |
278 |
jsr166 |
1.24 |
* The root of phaser tree. Equals this if not in a tree. Used to |
279 |
dl |
1.4 |
* support faster state push-down. |
280 |
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*/ |
281 |
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private final Phaser root; |
282 |
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283 |
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/** |
284 |
dl |
1.10 |
* Heads of Treiber stacks for waiting threads. To eliminate |
285 |
dl |
1.49 |
* contention when releasing some threads while adding others, we |
286 |
dl |
1.4 |
* use two of them, alternating across even and odd phases. |
287 |
dl |
1.49 |
* Subphasers share queues with root to speed up releases. |
288 |
dl |
1.4 |
*/ |
289 |
dl |
1.50 |
private final AtomicReference<QNode> evenQ; |
290 |
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private final AtomicReference<QNode> oddQ; |
291 |
dl |
1.4 |
|
292 |
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private AtomicReference<QNode> queueFor(int phase) { |
293 |
dl |
1.50 |
return ((phase & 1) == 0) ? evenQ : oddQ; |
294 |
dl |
1.4 |
} |
295 |
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/** |
297 |
dl |
1.51 |
* Main implementation for methods arrive and arriveAndDeregister. |
298 |
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* Manually tuned to speed up and minimize race windows for the |
299 |
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* common case of just decrementing unarrived field. |
300 |
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* |
301 |
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* @param adj - adjustment to apply to state -- either |
302 |
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* ONE_ARRIVAL (for arrive) or |
303 |
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* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister) |
304 |
dl |
1.4 |
*/ |
305 |
dl |
1.51 |
private int doArrive(long adj) { |
306 |
dl |
1.54 |
for (;;) { |
307 |
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long s; |
308 |
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int phase, unarrived; |
309 |
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if ((phase = (int)((s = state) >>> PHASE_SHIFT)) < 0) |
310 |
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return phase; |
311 |
dl |
1.55 |
else if ((unarrived = ((int)s) & UNARRIVED_MASK) == 0) |
312 |
dl |
1.54 |
checkBadArrive(s); |
313 |
dl |
1.55 |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) { |
314 |
dl |
1.54 |
if (unarrived == 1) { |
315 |
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Phaser par; |
316 |
dl |
1.55 |
long p = s & LPARTIES_MASK; // unshifted parties field |
317 |
dl |
1.54 |
long lu = p >>> PARTIES_SHIFT; |
318 |
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int u = (int)lu; |
319 |
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int nextPhase = (phase + 1) & MAX_PHASE; |
320 |
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long next = ((long)nextPhase << PHASE_SHIFT) | p | lu; |
321 |
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if ((par = parent) == null) { |
322 |
dl |
1.55 |
if (onAdvance(phase, u)) |
323 |
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next |= TERMINATION_PHASE; // obliterate phase |
324 |
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UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
325 |
dl |
1.54 |
releaseWaiters(phase); |
326 |
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} |
327 |
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else { |
328 |
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par.doArrive(u == 0? |
329 |
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ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL); |
330 |
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if ((int)(par.state >>> PHASE_SHIFT) != nextPhase || |
331 |
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((int)(state >>> PHASE_SHIFT) != nextPhase && |
332 |
|
|
!UNSAFE.compareAndSwapLong(this, stateOffset, |
333 |
|
|
s, next))) |
334 |
|
|
reconcileState(); |
335 |
dl |
1.51 |
} |
336 |
|
|
} |
337 |
dl |
1.54 |
return phase; |
338 |
dl |
1.51 |
} |
339 |
|
|
} |
340 |
|
|
} |
341 |
|
|
|
342 |
|
|
/** |
343 |
dl |
1.54 |
* Rechecks state and throws bounds exceptions on arrival -- called |
344 |
|
|
* only if unarrived is apparently zero. |
345 |
dl |
1.51 |
*/ |
346 |
dl |
1.54 |
private void checkBadArrive(long s) { |
347 |
|
|
if (reconcileState() == s) |
348 |
|
|
throw new IllegalStateException |
349 |
|
|
("Attempted arrival of unregistered party for " + |
350 |
|
|
stateToString(s)); |
351 |
dl |
1.4 |
} |
352 |
|
|
|
353 |
|
|
/** |
354 |
dl |
1.51 |
* Implementation of register, bulkRegister |
355 |
|
|
* |
356 |
|
|
* @param registrations number to add to both parties and unarrived fields |
357 |
|
|
*/ |
358 |
|
|
private int doRegister(int registrations) { |
359 |
|
|
long adj = (long)registrations; // adjustment to state |
360 |
|
|
adj |= adj << PARTIES_SHIFT; |
361 |
|
|
Phaser par = parent; |
362 |
dl |
1.54 |
for (;;) { |
363 |
|
|
int phase, parties; |
364 |
|
|
long s = par == null? state : reconcileState(); |
365 |
|
|
if ((phase = (int)(s >>> PHASE_SHIFT)) < 0) |
366 |
|
|
return phase; |
367 |
dl |
1.55 |
if ((parties = (((int)s) & PARTIES_MASK) >>> PARTIES_SHIFT) != 0 && |
368 |
|
|
(((int)s) & UNARRIVED_MASK) == 0) |
369 |
dl |
1.51 |
internalAwaitAdvance(phase, null); // wait for onAdvance |
370 |
dl |
1.55 |
else if (parties + registrations > MAX_PARTIES) |
371 |
dl |
1.54 |
throw new IllegalStateException(badRegister(s)); |
372 |
dl |
1.51 |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj)) |
373 |
dl |
1.54 |
return phase; |
374 |
dl |
1.51 |
} |
375 |
|
|
} |
376 |
|
|
|
377 |
|
|
/** |
378 |
dl |
1.55 |
* Returns message string for out of bounds exceptions on registration. |
379 |
dl |
1.51 |
*/ |
380 |
dl |
1.54 |
private String badRegister(long s) { |
381 |
|
|
return "Attempt to register more than " + |
382 |
dl |
1.55 |
MAX_PARTIES + " parties for " + stateToString(s); |
383 |
dl |
1.51 |
} |
384 |
|
|
|
385 |
|
|
/** |
386 |
dl |
1.55 |
* Recursively resolves lagged phase propagation from root if necessary. |
387 |
dl |
1.4 |
*/ |
388 |
|
|
private long reconcileState() { |
389 |
dl |
1.49 |
Phaser par = parent; |
390 |
dl |
1.51 |
if (par == null) |
391 |
|
|
return state; |
392 |
|
|
Phaser rt = root; |
393 |
dl |
1.54 |
for (;;) { |
394 |
|
|
long s, u; |
395 |
|
|
int phase, rPhase, pPhase; |
396 |
|
|
if ((phase = (int)((s = state)>>> PHASE_SHIFT)) < 0 || |
397 |
|
|
(rPhase = (int)(rt.state >>> PHASE_SHIFT)) == phase) |
398 |
|
|
return s; |
399 |
|
|
long pState = par.parent == null? par.state : par.reconcileState(); |
400 |
|
|
if (state == s) { |
401 |
dl |
1.55 |
if ((rPhase < 0 || (((int)s) & UNARRIVED_MASK) == 0) && |
402 |
dl |
1.54 |
((pPhase = (int)(pState >>> PHASE_SHIFT)) < 0 || |
403 |
|
|
pPhase == ((phase + 1) & MAX_PHASE))) |
404 |
|
|
UNSAFE.compareAndSwapLong |
405 |
|
|
(this, stateOffset, s, |
406 |
|
|
(((long) pPhase) << PHASE_SHIFT) | |
407 |
dl |
1.55 |
(u = s & LPARTIES_MASK) | |
408 |
dl |
1.54 |
(u >>> PARTIES_SHIFT)); // reset unarrived to parties |
409 |
|
|
else |
410 |
|
|
releaseWaiters(phase); // help release others |
411 |
dl |
1.4 |
} |
412 |
|
|
} |
413 |
dl |
1.1 |
} |
414 |
|
|
|
415 |
|
|
/** |
416 |
jsr166 |
1.24 |
* Creates a new phaser without any initially registered parties, |
417 |
dl |
1.10 |
* initial phase number 0, and no parent. Any thread using this |
418 |
jsr166 |
1.24 |
* phaser will need to first register for it. |
419 |
dl |
1.1 |
*/ |
420 |
|
|
public Phaser() { |
421 |
dl |
1.50 |
this(null, 0); |
422 |
dl |
1.1 |
} |
423 |
|
|
|
424 |
|
|
/** |
425 |
dl |
1.48 |
* Creates a new phaser with the given number of registered |
426 |
dl |
1.4 |
* unarrived parties, initial phase number 0, and no parent. |
427 |
jsr166 |
1.14 |
* |
428 |
|
|
* @param parties the number of parties required to trip barrier |
429 |
dl |
1.1 |
* @throws IllegalArgumentException if parties less than zero |
430 |
jsr166 |
1.14 |
* or greater than the maximum number of parties supported |
431 |
dl |
1.1 |
*/ |
432 |
|
|
public Phaser(int parties) { |
433 |
dl |
1.4 |
this(null, parties); |
434 |
|
|
} |
435 |
|
|
|
436 |
|
|
/** |
437 |
jsr166 |
1.24 |
* Creates a new phaser with the given parent, without any |
438 |
dl |
1.4 |
* initially registered parties. If parent is non-null this phaser |
439 |
|
|
* is registered with the parent and its initial phase number is |
440 |
|
|
* the same as that of parent phaser. |
441 |
jsr166 |
1.14 |
* |
442 |
|
|
* @param parent the parent phaser |
443 |
dl |
1.4 |
*/ |
444 |
|
|
public Phaser(Phaser parent) { |
445 |
dl |
1.50 |
this(parent, 0); |
446 |
dl |
1.4 |
} |
447 |
|
|
|
448 |
|
|
/** |
449 |
dl |
1.48 |
* Creates a new phaser with the given parent and number of |
450 |
jsr166 |
1.14 |
* registered unarrived parties. If parent is non-null, this phaser |
451 |
dl |
1.4 |
* is registered with the parent and its initial phase number is |
452 |
|
|
* the same as that of parent phaser. |
453 |
jsr166 |
1.14 |
* |
454 |
|
|
* @param parent the parent phaser |
455 |
|
|
* @param parties the number of parties required to trip barrier |
456 |
dl |
1.4 |
* @throws IllegalArgumentException if parties less than zero |
457 |
jsr166 |
1.14 |
* or greater than the maximum number of parties supported |
458 |
dl |
1.4 |
*/ |
459 |
|
|
public Phaser(Phaser parent, int parties) { |
460 |
dl |
1.55 |
if (parties >>> PARTIES_SHIFT != 0) |
461 |
dl |
1.1 |
throw new IllegalArgumentException("Illegal number of parties"); |
462 |
dl |
1.50 |
int phase; |
463 |
dl |
1.4 |
this.parent = parent; |
464 |
|
|
if (parent != null) { |
465 |
dl |
1.50 |
Phaser r = parent.root; |
466 |
|
|
this.root = r; |
467 |
|
|
this.evenQ = r.evenQ; |
468 |
|
|
this.oddQ = r.oddQ; |
469 |
dl |
1.4 |
phase = parent.register(); |
470 |
|
|
} |
471 |
dl |
1.50 |
else { |
472 |
dl |
1.4 |
this.root = this; |
473 |
dl |
1.50 |
this.evenQ = new AtomicReference<QNode>(); |
474 |
|
|
this.oddQ = new AtomicReference<QNode>(); |
475 |
|
|
phase = 0; |
476 |
|
|
} |
477 |
dl |
1.51 |
long p = (long)parties; |
478 |
dl |
1.55 |
this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT); |
479 |
dl |
1.1 |
} |
480 |
|
|
|
481 |
|
|
/** |
482 |
|
|
* Adds a new unarrived party to this phaser. |
483 |
dl |
1.49 |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
484 |
dl |
1.50 |
* this method may wait until its completion before registering. |
485 |
jsr166 |
1.14 |
* |
486 |
dl |
1.35 |
* @return the arrival phase number to which this registration applied |
487 |
dl |
1.1 |
* @throws IllegalStateException if attempting to register more |
488 |
jsr166 |
1.14 |
* than the maximum supported number of parties |
489 |
dl |
1.1 |
*/ |
490 |
dl |
1.4 |
public int register() { |
491 |
|
|
return doRegister(1); |
492 |
|
|
} |
493 |
|
|
|
494 |
|
|
/** |
495 |
|
|
* Adds the given number of new unarrived parties to this phaser. |
496 |
dl |
1.49 |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
497 |
dl |
1.50 |
* this method may wait until its completion before registering. |
498 |
jsr166 |
1.14 |
* |
499 |
dl |
1.48 |
* @param parties the number of additional parties required to trip barrier |
500 |
dl |
1.35 |
* @return the arrival phase number to which this registration applied |
501 |
dl |
1.4 |
* @throws IllegalStateException if attempting to register more |
502 |
jsr166 |
1.14 |
* than the maximum supported number of parties |
503 |
dl |
1.48 |
* @throws IllegalArgumentException if {@code parties < 0} |
504 |
dl |
1.4 |
*/ |
505 |
|
|
public int bulkRegister(int parties) { |
506 |
|
|
if (parties < 0) |
507 |
|
|
throw new IllegalArgumentException(); |
508 |
dl |
1.55 |
if (parties > MAX_PARTIES) |
509 |
dl |
1.54 |
throw new IllegalStateException(badRegister(state)); |
510 |
dl |
1.4 |
if (parties == 0) |
511 |
|
|
return getPhase(); |
512 |
|
|
return doRegister(parties); |
513 |
|
|
} |
514 |
|
|
|
515 |
|
|
/** |
516 |
dl |
1.1 |
* Arrives at the barrier, but does not wait for others. (You can |
517 |
dl |
1.38 |
* in turn wait for others via {@link #awaitAdvance}). It is an |
518 |
|
|
* unenforced usage error for an unregistered party to invoke this |
519 |
|
|
* method. |
520 |
dl |
1.1 |
* |
521 |
dl |
1.35 |
* @return the arrival phase number, or a negative value if terminated |
522 |
dl |
1.4 |
* @throws IllegalStateException if not terminated and the number |
523 |
jsr166 |
1.14 |
* of unarrived parties would become negative |
524 |
dl |
1.1 |
*/ |
525 |
dl |
1.4 |
public int arrive() { |
526 |
dl |
1.51 |
return doArrive(ONE_ARRIVAL); |
527 |
dl |
1.1 |
} |
528 |
|
|
|
529 |
|
|
/** |
530 |
dl |
1.27 |
* Arrives at the barrier and deregisters from it without waiting |
531 |
|
|
* for others. Deregistration reduces the number of parties |
532 |
dl |
1.4 |
* required to trip the barrier in future phases. If this phaser |
533 |
|
|
* has a parent, and deregistration causes this phaser to have |
534 |
dl |
1.27 |
* zero parties, this phaser also arrives at and is deregistered |
535 |
dl |
1.38 |
* from its parent. It is an unenforced usage error for an |
536 |
|
|
* unregistered party to invoke this method. |
537 |
dl |
1.1 |
* |
538 |
dl |
1.35 |
* @return the arrival phase number, or a negative value if terminated |
539 |
dl |
1.4 |
* @throws IllegalStateException if not terminated and the number |
540 |
jsr166 |
1.14 |
* of registered or unarrived parties would become negative |
541 |
dl |
1.1 |
*/ |
542 |
dl |
1.4 |
public int arriveAndDeregister() { |
543 |
dl |
1.51 |
return doArrive(ONE_ARRIVAL|ONE_PARTY); |
544 |
dl |
1.1 |
} |
545 |
|
|
|
546 |
|
|
/** |
547 |
dl |
1.4 |
* Arrives at the barrier and awaits others. Equivalent in effect |
548 |
dl |
1.27 |
* to {@code awaitAdvance(arrive())}. If you need to await with |
549 |
|
|
* interruption or timeout, you can arrange this with an analogous |
550 |
dl |
1.48 |
* construction using one of the other forms of the {@code |
551 |
|
|
* awaitAdvance} method. If instead you need to deregister upon |
552 |
|
|
* arrival, use {@link #arriveAndDeregister}. It is an unenforced |
553 |
|
|
* usage error for an unregistered party to invoke this method. |
554 |
jsr166 |
1.14 |
* |
555 |
dl |
1.35 |
* @return the arrival phase number, or a negative number if terminated |
556 |
dl |
1.4 |
* @throws IllegalStateException if not terminated and the number |
557 |
jsr166 |
1.14 |
* of unarrived parties would become negative |
558 |
dl |
1.1 |
*/ |
559 |
|
|
public int arriveAndAwaitAdvance() { |
560 |
dl |
1.4 |
return awaitAdvance(arrive()); |
561 |
dl |
1.1 |
} |
562 |
|
|
|
563 |
|
|
/** |
564 |
dl |
1.27 |
* Awaits the phase of the barrier to advance from the given phase |
565 |
dl |
1.30 |
* value, returning immediately if the current phase of the |
566 |
|
|
* barrier is not equal to the given phase value or this barrier |
567 |
dl |
1.50 |
* is terminated. |
568 |
jsr166 |
1.14 |
* |
569 |
dl |
1.35 |
* @param phase an arrival phase number, or negative value if |
570 |
|
|
* terminated; this argument is normally the value returned by a |
571 |
|
|
* previous call to {@code arrive} or its variants |
572 |
|
|
* @return the next arrival phase number, or a negative value |
573 |
|
|
* if terminated or argument is negative |
574 |
dl |
1.1 |
*/ |
575 |
|
|
public int awaitAdvance(int phase) { |
576 |
dl |
1.55 |
int p; |
577 |
dl |
1.1 |
if (phase < 0) |
578 |
|
|
return phase; |
579 |
dl |
1.55 |
else if ((p = (int)((parent == null? state : reconcileState()) |
580 |
|
|
>>> PHASE_SHIFT)) == phase) |
581 |
|
|
return internalAwaitAdvance(phase, null); |
582 |
|
|
else |
583 |
dl |
1.4 |
return p; |
584 |
dl |
1.1 |
} |
585 |
|
|
|
586 |
|
|
/** |
587 |
dl |
1.30 |
* Awaits the phase of the barrier to advance from the given phase |
588 |
dl |
1.38 |
* value, throwing {@code InterruptedException} if interrupted |
589 |
|
|
* while waiting, or returning immediately if the current phase of |
590 |
|
|
* the barrier is not equal to the given phase value or this |
591 |
dl |
1.50 |
* barrier is terminated. |
592 |
jsr166 |
1.14 |
* |
593 |
dl |
1.35 |
* @param phase an arrival phase number, or negative value if |
594 |
|
|
* terminated; this argument is normally the value returned by a |
595 |
|
|
* previous call to {@code arrive} or its variants |
596 |
|
|
* @return the next arrival phase number, or a negative value |
597 |
|
|
* if terminated or argument is negative |
598 |
dl |
1.1 |
* @throws InterruptedException if thread interrupted while waiting |
599 |
|
|
*/ |
600 |
jsr166 |
1.12 |
public int awaitAdvanceInterruptibly(int phase) |
601 |
dl |
1.10 |
throws InterruptedException { |
602 |
dl |
1.55 |
int p; |
603 |
dl |
1.1 |
if (phase < 0) |
604 |
|
|
return phase; |
605 |
dl |
1.55 |
if ((p = (int)((parent == null? state : reconcileState()) |
606 |
|
|
>>> PHASE_SHIFT)) == phase) { |
607 |
|
|
QNode node = new QNode(this, phase, true, false, 0L); |
608 |
|
|
p = internalAwaitAdvance(phase, node); |
609 |
|
|
if (node.wasInterrupted) |
610 |
|
|
throw new InterruptedException(); |
611 |
|
|
} |
612 |
|
|
return p; |
613 |
dl |
1.1 |
} |
614 |
|
|
|
615 |
|
|
/** |
616 |
dl |
1.30 |
* Awaits the phase of the barrier to advance from the given phase |
617 |
dl |
1.38 |
* value or the given timeout to elapse, throwing {@code |
618 |
|
|
* InterruptedException} if interrupted while waiting, or |
619 |
|
|
* returning immediately if the current phase of the barrier is |
620 |
|
|
* not equal to the given phase value or this barrier is |
621 |
dl |
1.50 |
* terminated. |
622 |
jsr166 |
1.14 |
* |
623 |
dl |
1.35 |
* @param phase an arrival phase number, or negative value if |
624 |
|
|
* terminated; this argument is normally the value returned by a |
625 |
|
|
* previous call to {@code arrive} or its variants |
626 |
dl |
1.31 |
* @param timeout how long to wait before giving up, in units of |
627 |
|
|
* {@code unit} |
628 |
|
|
* @param unit a {@code TimeUnit} determining how to interpret the |
629 |
|
|
* {@code timeout} parameter |
630 |
dl |
1.35 |
* @return the next arrival phase number, or a negative value |
631 |
|
|
* if terminated or argument is negative |
632 |
dl |
1.1 |
* @throws InterruptedException if thread interrupted while waiting |
633 |
|
|
* @throws TimeoutException if timed out while waiting |
634 |
|
|
*/ |
635 |
jsr166 |
1.18 |
public int awaitAdvanceInterruptibly(int phase, |
636 |
|
|
long timeout, TimeUnit unit) |
637 |
dl |
1.1 |
throws InterruptedException, TimeoutException { |
638 |
dl |
1.49 |
long nanos = unit.toNanos(timeout); |
639 |
dl |
1.55 |
int p; |
640 |
dl |
1.1 |
if (phase < 0) |
641 |
|
|
return phase; |
642 |
dl |
1.55 |
if ((p = (int)((parent == null? state : reconcileState()) |
643 |
|
|
>>> PHASE_SHIFT)) == phase) { |
644 |
|
|
QNode node = new QNode(this, phase, true, true, nanos); |
645 |
|
|
p = internalAwaitAdvance(phase, node); |
646 |
|
|
if (node.wasInterrupted) |
647 |
|
|
throw new InterruptedException(); |
648 |
|
|
else if (p == phase) |
649 |
|
|
throw new TimeoutException(); |
650 |
|
|
} |
651 |
|
|
return p; |
652 |
dl |
1.1 |
} |
653 |
|
|
|
654 |
|
|
/** |
655 |
dl |
1.55 |
* Forces this barrier to enter termination state. Counts of |
656 |
|
|
* arrived and registered parties are unaffected. If this phaser |
657 |
|
|
* is a member of a tiered set of phasers, then all of the phasers |
658 |
|
|
* in the set are terminated. If this phaser is already |
659 |
|
|
* terminated, this method has no effect. This method may be |
660 |
|
|
* useful for coordinating recovery after one or more tasks |
661 |
|
|
* encounter unexpected exceptions. |
662 |
dl |
1.1 |
*/ |
663 |
|
|
public void forceTermination() { |
664 |
dl |
1.55 |
// Only need to change root state |
665 |
|
|
final Phaser root = this.root; |
666 |
dl |
1.49 |
long s; |
667 |
dl |
1.55 |
while ((s = root.state) >= 0) { |
668 |
|
|
if (UNSAFE.compareAndSwapLong(root, stateOffset, |
669 |
|
|
s, s | TERMINATION_PHASE)) { |
670 |
|
|
releaseWaiters(0); // signal all threads |
671 |
|
|
releaseWaiters(1); |
672 |
|
|
return; |
673 |
|
|
} |
674 |
|
|
} |
675 |
dl |
1.1 |
} |
676 |
|
|
|
677 |
|
|
/** |
678 |
dl |
1.4 |
* Returns the current phase number. The maximum phase number is |
679 |
jsr166 |
1.7 |
* {@code Integer.MAX_VALUE}, after which it restarts at |
680 |
dl |
1.4 |
* zero. Upon termination, the phase number is negative. |
681 |
jsr166 |
1.14 |
* |
682 |
dl |
1.4 |
* @return the phase number, or a negative value if terminated |
683 |
dl |
1.1 |
*/ |
684 |
dl |
1.4 |
public final int getPhase() { |
685 |
dl |
1.54 |
return (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT); |
686 |
dl |
1.1 |
} |
687 |
|
|
|
688 |
|
|
/** |
689 |
|
|
* Returns the number of parties registered at this barrier. |
690 |
jsr166 |
1.14 |
* |
691 |
dl |
1.1 |
* @return the number of parties |
692 |
|
|
*/ |
693 |
|
|
public int getRegisteredParties() { |
694 |
dl |
1.54 |
return partiesOf(parent==null? state : reconcileState()); |
695 |
dl |
1.1 |
} |
696 |
|
|
|
697 |
|
|
/** |
698 |
dl |
1.36 |
* Returns the number of registered parties that have arrived at |
699 |
|
|
* the current phase of this barrier. |
700 |
jsr166 |
1.14 |
* |
701 |
dl |
1.1 |
* @return the number of arrived parties |
702 |
|
|
*/ |
703 |
|
|
public int getArrivedParties() { |
704 |
dl |
1.54 |
return arrivedOf(parent==null? state : reconcileState()); |
705 |
dl |
1.1 |
} |
706 |
|
|
|
707 |
|
|
/** |
708 |
|
|
* Returns the number of registered parties that have not yet |
709 |
|
|
* arrived at the current phase of this barrier. |
710 |
jsr166 |
1.14 |
* |
711 |
dl |
1.1 |
* @return the number of unarrived parties |
712 |
|
|
*/ |
713 |
|
|
public int getUnarrivedParties() { |
714 |
dl |
1.54 |
return unarrivedOf(parent==null? state : reconcileState()); |
715 |
dl |
1.4 |
} |
716 |
|
|
|
717 |
|
|
/** |
718 |
jsr166 |
1.23 |
* Returns the parent of this phaser, or {@code null} if none. |
719 |
jsr166 |
1.14 |
* |
720 |
jsr166 |
1.23 |
* @return the parent of this phaser, or {@code null} if none |
721 |
dl |
1.4 |
*/ |
722 |
|
|
public Phaser getParent() { |
723 |
|
|
return parent; |
724 |
|
|
} |
725 |
|
|
|
726 |
|
|
/** |
727 |
|
|
* Returns the root ancestor of this phaser, which is the same as |
728 |
|
|
* this phaser if it has no parent. |
729 |
jsr166 |
1.14 |
* |
730 |
jsr166 |
1.9 |
* @return the root ancestor of this phaser |
731 |
dl |
1.4 |
*/ |
732 |
|
|
public Phaser getRoot() { |
733 |
|
|
return root; |
734 |
dl |
1.1 |
} |
735 |
|
|
|
736 |
|
|
/** |
737 |
jsr166 |
1.9 |
* Returns {@code true} if this barrier has been terminated. |
738 |
jsr166 |
1.14 |
* |
739 |
jsr166 |
1.9 |
* @return {@code true} if this barrier has been terminated |
740 |
dl |
1.1 |
*/ |
741 |
|
|
public boolean isTerminated() { |
742 |
dl |
1.51 |
return (parent == null? state : reconcileState()) < 0; |
743 |
dl |
1.1 |
} |
744 |
|
|
|
745 |
|
|
/** |
746 |
dl |
1.43 |
* Overridable method to perform an action upon impending phase |
747 |
|
|
* advance, and to control termination. This method is invoked |
748 |
|
|
* upon arrival of the party tripping the barrier (when all other |
749 |
|
|
* waiting parties are dormant). If this method returns {@code |
750 |
|
|
* true}, then, rather than advance the phase number, this barrier |
751 |
|
|
* will be set to a final termination state, and subsequent calls |
752 |
|
|
* to {@link #isTerminated} will return true. Any (unchecked) |
753 |
|
|
* Exception or Error thrown by an invocation of this method is |
754 |
|
|
* propagated to the party attempting to trip the barrier, in |
755 |
|
|
* which case no advance occurs. |
756 |
dl |
1.42 |
* |
757 |
|
|
* <p>The arguments to this method provide the state of the phaser |
758 |
dl |
1.51 |
* prevailing for the current transition. The effects of invoking |
759 |
|
|
* arrival, registration, and waiting methods on this Phaser from |
760 |
dl |
1.50 |
* within {@code onAdvance} are unspecified and should not be |
761 |
dl |
1.51 |
* relied on. |
762 |
|
|
* |
763 |
|
|
* <p>If this Phaser is a member of a tiered set of Phasers, then |
764 |
|
|
* {@code onAdvance} is invoked only for its root Phaser on each |
765 |
|
|
* advance. |
766 |
jsr166 |
1.3 |
* |
767 |
jsr166 |
1.25 |
* <p>The default version returns {@code true} when the number of |
768 |
dl |
1.1 |
* registered parties is zero. Normally, overrides that arrange |
769 |
|
|
* termination for other reasons should also preserve this |
770 |
|
|
* property. |
771 |
|
|
* |
772 |
|
|
* @param phase the phase number on entering the barrier |
773 |
jsr166 |
1.9 |
* @param registeredParties the current number of registered parties |
774 |
|
|
* @return {@code true} if this barrier should terminate |
775 |
dl |
1.1 |
*/ |
776 |
|
|
protected boolean onAdvance(int phase, int registeredParties) { |
777 |
|
|
return registeredParties <= 0; |
778 |
|
|
} |
779 |
|
|
|
780 |
|
|
/** |
781 |
dl |
1.4 |
* Returns a string identifying this phaser, as well as its |
782 |
dl |
1.1 |
* state. The state, in brackets, includes the String {@code |
783 |
jsr166 |
1.9 |
* "phase = "} followed by the phase number, {@code "parties = "} |
784 |
dl |
1.1 |
* followed by the number of registered parties, and {@code |
785 |
jsr166 |
1.9 |
* "arrived = "} followed by the number of arrived parties. |
786 |
dl |
1.1 |
* |
787 |
|
|
* @return a string identifying this barrier, as well as its state |
788 |
|
|
*/ |
789 |
|
|
public String toString() { |
790 |
dl |
1.54 |
return stateToString(reconcileState()); |
791 |
|
|
} |
792 |
|
|
|
793 |
|
|
/** |
794 |
|
|
* Implementation of toString and string-based error messages |
795 |
|
|
*/ |
796 |
|
|
private String stateToString(long s) { |
797 |
jsr166 |
1.9 |
return super.toString() + |
798 |
|
|
"[phase = " + phaseOf(s) + |
799 |
|
|
" parties = " + partiesOf(s) + |
800 |
|
|
" arrived = " + arrivedOf(s) + "]"; |
801 |
dl |
1.1 |
} |
802 |
|
|
|
803 |
dl |
1.54 |
// Waiting mechanics |
804 |
|
|
|
805 |
dl |
1.4 |
/** |
806 |
dl |
1.51 |
* Removes and signals threads from queue for phase |
807 |
dl |
1.4 |
*/ |
808 |
|
|
private void releaseWaiters(int phase) { |
809 |
|
|
AtomicReference<QNode> head = queueFor(phase); |
810 |
|
|
QNode q; |
811 |
dl |
1.51 |
int p; |
812 |
|
|
while ((q = head.get()) != null && |
813 |
|
|
((p = q.phase) == phase || |
814 |
|
|
(int)(root.state >>> PHASE_SHIFT) != p)) { |
815 |
dl |
1.4 |
if (head.compareAndSet(q, q.next)) |
816 |
|
|
q.signal(); |
817 |
|
|
} |
818 |
|
|
} |
819 |
|
|
|
820 |
|
|
/** |
821 |
jsr166 |
1.14 |
* Tries to enqueue given node in the appropriate wait queue. |
822 |
|
|
* |
823 |
dl |
1.10 |
* @return true if successful |
824 |
|
|
*/ |
825 |
dl |
1.51 |
private boolean tryEnqueue(int phase, QNode node) { |
826 |
|
|
releaseWaiters(phase-1); // ensure old queue clean |
827 |
|
|
AtomicReference<QNode> head = queueFor(phase); |
828 |
|
|
QNode q = head.get(); |
829 |
|
|
return ((q == null || q.phase == phase) && |
830 |
|
|
(int)(root.state >>> PHASE_SHIFT) == phase && |
831 |
|
|
head.compareAndSet(node.next = q, node)); |
832 |
dl |
1.10 |
} |
833 |
|
|
|
834 |
dl |
1.51 |
/** The number of CPUs, for spin control */ |
835 |
|
|
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
836 |
|
|
|
837 |
dl |
1.10 |
/** |
838 |
dl |
1.51 |
* The number of times to spin before blocking while waiting for |
839 |
|
|
* advance, per arrival while waiting. On multiprocessors, fully |
840 |
|
|
* blocking and waking up a large number of threads all at once is |
841 |
|
|
* usually a very slow process, so we use rechargeable spins to |
842 |
|
|
* avoid it when threads regularly arrive: When a thread in |
843 |
|
|
* internalAwaitAdvance notices another arrival before blocking, |
844 |
|
|
* and there appear to be enough CPUs available, it spins |
845 |
dl |
1.55 |
* SPINS_PER_ARRIVAL more times before blocking. Plus, even on |
846 |
|
|
* uniprocessors, there is at least one intervening Thread.yield |
847 |
|
|
* before blocking. The value trades off good-citizenship vs big |
848 |
|
|
* unnecessary slowdowns. |
849 |
dl |
1.50 |
*/ |
850 |
dl |
1.55 |
static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8; |
851 |
dl |
1.50 |
|
852 |
|
|
/** |
853 |
dl |
1.51 |
* Possibly blocks and waits for phase to advance unless aborted. |
854 |
jsr166 |
1.14 |
* |
855 |
dl |
1.51 |
* @param phase current phase |
856 |
jsr166 |
1.53 |
* @param node if non-null, the wait node to track interrupt and timeout; |
857 |
dl |
1.51 |
* if null, denotes noninterruptible wait |
858 |
dl |
1.10 |
* @return current phase |
859 |
dl |
1.1 |
*/ |
860 |
dl |
1.51 |
private int internalAwaitAdvance(int phase, QNode node) { |
861 |
|
|
Phaser current = this; // to eventually wait at root if tiered |
862 |
dl |
1.54 |
boolean queued = false; // true when node is enqueued |
863 |
|
|
int lastUnarrived = -1; // to increase spins upon change |
864 |
dl |
1.51 |
int spins = SPINS_PER_ARRIVAL; |
865 |
dl |
1.54 |
for (;;) { |
866 |
|
|
int p, unarrived; |
867 |
|
|
Phaser par; |
868 |
|
|
long s = current.state; |
869 |
|
|
if ((p = (int)(s >>> PHASE_SHIFT)) != phase) { |
870 |
|
|
if (node != null) |
871 |
|
|
node.onRelease(); |
872 |
|
|
releaseWaiters(phase); |
873 |
|
|
return p; |
874 |
|
|
} |
875 |
dl |
1.55 |
else if ((unarrived = ((int)s) & UNARRIVED_MASK) == 0 && |
876 |
|
|
(par = current.parent) != null) { |
877 |
|
|
current = par; // if all arrived, use parent |
878 |
|
|
par = par.parent; |
879 |
|
|
lastUnarrived = -1; |
880 |
|
|
} |
881 |
|
|
else if (unarrived != lastUnarrived) { |
882 |
dl |
1.51 |
if ((lastUnarrived = unarrived) < NCPU) |
883 |
|
|
spins += SPINS_PER_ARRIVAL; |
884 |
|
|
} |
885 |
dl |
1.55 |
else if (spins > 0) { |
886 |
|
|
if (--spins == (SPINS_PER_ARRIVAL >>> 1)) |
887 |
|
|
Thread.yield(); // yield midway through spin |
888 |
dl |
1.50 |
} |
889 |
dl |
1.54 |
else if (node == null) // must be noninterruptible |
890 |
dl |
1.51 |
node = new QNode(this, phase, false, false, 0L); |
891 |
dl |
1.54 |
else if (node.isReleasable()) { |
892 |
|
|
if ((int)(reconcileState() >>> PHASE_SHIFT) == phase) |
893 |
|
|
return phase; // aborted |
894 |
|
|
} |
895 |
dl |
1.10 |
else if (!queued) |
896 |
dl |
1.51 |
queued = tryEnqueue(phase, node); |
897 |
|
|
else { |
898 |
|
|
try { |
899 |
|
|
ForkJoinPool.managedBlock(node); |
900 |
|
|
} catch (InterruptedException ie) { |
901 |
|
|
node.wasInterrupted = true; |
902 |
|
|
} |
903 |
|
|
} |
904 |
dl |
1.4 |
} |
905 |
|
|
} |
906 |
|
|
|
907 |
|
|
/** |
908 |
dl |
1.51 |
* Wait nodes for Treiber stack representing wait queue |
909 |
dl |
1.4 |
*/ |
910 |
dl |
1.51 |
static final class QNode implements ForkJoinPool.ManagedBlocker { |
911 |
|
|
final Phaser phaser; |
912 |
|
|
final int phase; |
913 |
|
|
final boolean interruptible; |
914 |
|
|
final boolean timed; |
915 |
|
|
boolean wasInterrupted; |
916 |
|
|
long nanos; |
917 |
|
|
long lastTime; |
918 |
|
|
volatile Thread thread; // nulled to cancel wait |
919 |
|
|
QNode next; |
920 |
|
|
|
921 |
|
|
QNode(Phaser phaser, int phase, boolean interruptible, |
922 |
|
|
boolean timed, long nanos) { |
923 |
|
|
this.phaser = phaser; |
924 |
|
|
this.phase = phase; |
925 |
|
|
this.interruptible = interruptible; |
926 |
|
|
this.nanos = nanos; |
927 |
|
|
this.timed = timed; |
928 |
|
|
this.lastTime = timed? System.nanoTime() : 0L; |
929 |
|
|
thread = Thread.currentThread(); |
930 |
|
|
} |
931 |
|
|
|
932 |
|
|
public boolean isReleasable() { |
933 |
|
|
Thread t = thread; |
934 |
|
|
if (t != null) { |
935 |
|
|
if (phaser.getPhase() != phase) |
936 |
|
|
t = null; |
937 |
|
|
else { |
938 |
|
|
if (Thread.interrupted()) |
939 |
|
|
wasInterrupted = true; |
940 |
|
|
if (interruptible && wasInterrupted) |
941 |
|
|
t = null; |
942 |
|
|
else if (timed) { |
943 |
|
|
if (nanos > 0) { |
944 |
|
|
long now = System.nanoTime(); |
945 |
|
|
nanos -= now - lastTime; |
946 |
|
|
lastTime = now; |
947 |
|
|
} |
948 |
|
|
if (nanos <= 0) |
949 |
|
|
t = null; |
950 |
|
|
} |
951 |
|
|
} |
952 |
|
|
if (t != null) |
953 |
|
|
return false; |
954 |
|
|
thread = null; |
955 |
dl |
1.50 |
} |
956 |
dl |
1.51 |
return true; |
957 |
|
|
} |
958 |
|
|
|
959 |
|
|
public boolean block() { |
960 |
|
|
if (isReleasable()) |
961 |
|
|
return true; |
962 |
|
|
else if (!timed) |
963 |
|
|
LockSupport.park(this); |
964 |
|
|
else if (nanos > 0) |
965 |
|
|
LockSupport.parkNanos(this, nanos); |
966 |
|
|
return isReleasable(); |
967 |
dl |
1.1 |
} |
968 |
|
|
|
969 |
dl |
1.51 |
void signal() { |
970 |
|
|
Thread t = thread; |
971 |
|
|
if (t != null) { |
972 |
|
|
thread = null; |
973 |
|
|
LockSupport.unpark(t); |
974 |
dl |
1.50 |
} |
975 |
dl |
1.4 |
} |
976 |
dl |
1.54 |
|
977 |
|
|
void onRelease() { // actions upon return from internalAwaitAdvance |
978 |
|
|
if (!interruptible && wasInterrupted) |
979 |
|
|
Thread.currentThread().interrupt(); |
980 |
|
|
if (thread != null) |
981 |
|
|
thread = null; |
982 |
|
|
} |
983 |
|
|
|
984 |
dl |
1.4 |
} |
985 |
|
|
|
986 |
jsr166 |
1.22 |
// Unsafe mechanics |
987 |
|
|
|
988 |
|
|
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
989 |
|
|
private static final long stateOffset = |
990 |
|
|
objectFieldOffset("state", Phaser.class); |
991 |
|
|
|
992 |
|
|
private static long objectFieldOffset(String field, Class<?> klazz) { |
993 |
|
|
try { |
994 |
|
|
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
995 |
|
|
} catch (NoSuchFieldException e) { |
996 |
|
|
// Convert Exception to corresponding Error |
997 |
|
|
NoSuchFieldError error = new NoSuchFieldError(field); |
998 |
|
|
error.initCause(e); |
999 |
|
|
throw error; |
1000 |
|
|
} |
1001 |
|
|
} |
1002 |
|
|
|
1003 |
|
|
/** |
1004 |
|
|
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1005 |
|
|
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1006 |
|
|
* into a jdk. |
1007 |
|
|
* |
1008 |
|
|
* @return a sun.misc.Unsafe |
1009 |
|
|
*/ |
1010 |
jsr166 |
1.19 |
private static sun.misc.Unsafe getUnsafe() { |
1011 |
jsr166 |
1.11 |
try { |
1012 |
jsr166 |
1.19 |
return sun.misc.Unsafe.getUnsafe(); |
1013 |
jsr166 |
1.11 |
} catch (SecurityException se) { |
1014 |
|
|
try { |
1015 |
|
|
return java.security.AccessController.doPrivileged |
1016 |
jsr166 |
1.22 |
(new java.security |
1017 |
|
|
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1018 |
jsr166 |
1.19 |
public sun.misc.Unsafe run() throws Exception { |
1019 |
jsr166 |
1.22 |
java.lang.reflect.Field f = sun.misc |
1020 |
|
|
.Unsafe.class.getDeclaredField("theUnsafe"); |
1021 |
|
|
f.setAccessible(true); |
1022 |
|
|
return (sun.misc.Unsafe) f.get(null); |
1023 |
jsr166 |
1.11 |
}}); |
1024 |
|
|
} catch (java.security.PrivilegedActionException e) { |
1025 |
jsr166 |
1.19 |
throw new RuntimeException("Could not initialize intrinsics", |
1026 |
|
|
e.getCause()); |
1027 |
jsr166 |
1.11 |
} |
1028 |
|
|
} |
1029 |
|
|
} |
1030 |
dl |
1.1 |
} |