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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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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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package jsr166y; |
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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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* <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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* (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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* <p><b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code |
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* Phaser} may be repeatedly awaited. Method {@link |
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* #arriveAndAwaitAdvance} has effect analogous to {@link |
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* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each |
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* generation of a {@code Phaser} has an associated phase number. The |
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* phase number starts at zero, and advances when all parties arrive |
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* at the barrier, wrapping around to zero after reaching {@code |
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* 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 barrier and upon awaiting |
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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 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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* {@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 barrier advances to (or is already at) a different phase. |
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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 barrier. If necessary, you can perform any |
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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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* |
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* </ul> |
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* |
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* <p> <b>Termination.</b> A {@code Phaser} may enter a |
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* <em>termination</em> state in which all synchronization methods |
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* immediately return without updating phaser state or waiting for |
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* advance, and indicating (via a negative phase value) that execution |
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* is complete. Termination is triggered when an invocation of {@code |
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* onAdvance} returns {@code true}. As illustrated below, when |
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* phasers control actions with a fixed number of iterations, it is |
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* often convenient to override this method to cause termination when |
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* the current phase number reaches a threshold. Method {@link |
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* #forceTermination} is also available to abruptly release waiting |
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* threads and allow them to terminate. |
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* <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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* <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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* 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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* 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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* 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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* }}</pre> |
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* |
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* |
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* <p>To create a set of tasks using a tree of phasers, |
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* you could use code of the following form, assuming a |
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* Task class with a constructor accepting a phaser that |
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* it registers with upon construction: |
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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[] actions, int lo, int hi, Phaser ph) { |
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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(actions, i, j, new Phaser(ph)); |
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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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* actions[i] = new Task(ph); |
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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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* } |
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* // .. initially called, for n tasks via |
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* build(new Task[n], 0, n, new Phaser());}</pre> |
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* }}</pre> |
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* |
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* The best value of {@code TASKS_PER_PHASER} depends mainly on |
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* expected barrier synchronization rates. A value as low as four may |
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* be appropriate for extremely small per-barrier task bodies (thus |
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* 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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* 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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*/ |
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/** |
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* Barrier state representation. Conceptually, a barrier contains |
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* four values: |
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* Primary state representation, holding four bit-fields: |
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* |
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* * unarrived -- the number of parties yet to hit barrier (bits 0-15) |
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* * parties -- the number of parties to wait (bits 16-31) |
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* * phase -- the generation of the barrier (bits 32-62) |
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* * terminated -- set if barrier is terminated (bit 63 / sign) |
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* |
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* However, to efficiently maintain atomicity, these values are |
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* packed into a single (atomic) long. Termination uses the sign |
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* bit of 32 bit representation of phase, so phase is set to -1 on |
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* termination. Good performance relies on keeping state decoding |
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* and encoding simple, and keeping race windows short. |
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* unarrived -- the number of parties yet to hit barrier (bits 0-15) |
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* parties -- the number of parties to wait (bits 16-31) |
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* phase -- the generation of the barrier (bits 32-62) |
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* terminated -- set if barrier is terminated (bit 63 / sign) |
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* |
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* Except that a phaser with no registered parties is |
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* distinguished by 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 -- see method |
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* reconcileState. |
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*/ |
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private volatile long state; |
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|
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private static final int MAX_PARTIES = 0xffff; |
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private static final int MAX_PHASE = 0x7fffffff; |
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private static final int PARTIES_SHIFT = 16; |
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private static final int PHASE_SHIFT = 32; |
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private static final int UNARRIVED_MASK = 0xffff; |
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private static final long PARTIES_MASK = 0xffff0000L; // for masking long |
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private static final long ONE_ARRIVAL = 1L; |
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private static final long ONE_PARTY = 1L << PARTIES_SHIFT; |
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private static final long TERMINATION_PHASE = -1L << PHASE_SHIFT; |
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private static final int MAX_PARTIES = 0xffff; |
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private static final int MAX_PHASE = Integer.MAX_VALUE; |
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private static final int PARTIES_SHIFT = 16; |
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private static final int PHASE_SHIFT = 32; |
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private static final int UNARRIVED_MASK = 0xffff; // to mask ints |
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private static final long PARTIES_MASK = 0xffff0000L; // to mask longs |
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private static final long COUNTS_MASK = 0xffffffffL; |
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private static final long TERMINATION_BIT = 1L << 63; |
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|
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// 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 ONE_DEREGISTER = ONE_ARRIVAL|ONE_PARTY; |
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private static final int EMPTY = 1; |
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|
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// The following unpacking methods are usually manually inlined |
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|
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private static int unarrivedOf(long s) { |
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return (int)s & UNARRIVED_MASK; |
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int counts = (int)s; |
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> |
return (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK); |
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} |
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|
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private static int partiesOf(long s) { |
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} |
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|
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private static int phaseOf(long s) { |
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< |
return (int) (s >>> PHASE_SHIFT); |
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> |
return (int)(s >>> PHASE_SHIFT); |
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} |
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|
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private static int arrivedOf(long s) { |
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< |
return partiesOf(s) - unarrivedOf(s); |
299 |
> |
int counts = (int)s; |
300 |
> |
return (counts == EMPTY) ? 0 : |
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(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK); |
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} |
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|
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/** |
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private final Phaser parent; |
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|
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/** |
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* The root of phaser tree. Equals this if not in a tree. Used to |
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* support faster state push-down. |
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* The root of phaser tree. Equals this if not in a tree. |
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*/ |
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private final Phaser root; |
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|
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} |
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|
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/** |
328 |
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* 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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/** |
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* Returns message string for bounds exceptions on registration. |
337 |
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*/ |
338 |
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private String badRegister(long s) { |
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return "Attempt to register more than " + |
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MAX_PARTIES + " parties for " + stateToString(s); |
341 |
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} |
342 |
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|
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/** |
344 |
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* Main implementation for methods arrive and arriveAndDeregister. |
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* Manually tuned to speed up and minimize race windows for the |
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* common case of just decrementing unarrived field. |
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* |
348 |
< |
* @param adj - adjustment to apply to state -- either |
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* ONE_ARRIVAL (for arrive) or |
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* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister) |
348 |
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* @param adjust value to subtract from state; |
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* ONE_ARRIVAL for arrive, |
350 |
> |
* ONE_DEREGISTER for arriveAndDeregister |
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*/ |
352 |
< |
private int doArrive(long adj) { |
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> |
private int doArrive(int adjust) { |
353 |
> |
final Phaser root = this.root; |
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for (;;) { |
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< |
long s = state; |
355 |
> |
long s = (root == this) ? state : reconcileState(); |
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int phase = (int)(s >>> PHASE_SHIFT); |
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if (phase < 0) |
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return phase; |
359 |
< |
int unarrived = (int)s & UNARRIVED_MASK; |
360 |
< |
if (unarrived == 0) |
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< |
checkBadArrive(s); |
362 |
< |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) { |
359 |
> |
int counts = (int)s; |
360 |
> |
int unarrived = (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK); |
361 |
> |
if (unarrived <= 0) |
362 |
> |
throw new IllegalStateException(badArrive(s)); |
363 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adjust)) { |
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if (unarrived == 1) { |
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< |
long p = s & PARTIES_MASK; // unshifted parties field |
366 |
< |
long lu = p >>> PARTIES_SHIFT; |
367 |
< |
int u = (int)lu; |
368 |
< |
int nextPhase = (phase + 1) & MAX_PHASE; |
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< |
long next = ((long)nextPhase << PHASE_SHIFT) | p | lu; |
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< |
final Phaser parent = this.parent; |
371 |
< |
if (parent == null) { |
372 |
< |
if (onAdvance(phase, u)) |
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< |
next |= TERMINATION_PHASE; // obliterate phase |
374 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
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> |
long n = s & PARTIES_MASK; // base of next state |
366 |
> |
int nextUnarrived = (int)n >>> PARTIES_SHIFT; |
367 |
> |
if (root == this) { |
368 |
> |
if (onAdvance(phase, nextUnarrived)) |
369 |
> |
n |= TERMINATION_BIT; |
370 |
> |
else if (nextUnarrived == 0) |
371 |
> |
n |= EMPTY; |
372 |
> |
else |
373 |
> |
n |= nextUnarrived; |
374 |
> |
int nextPhase = (phase + 1) & MAX_PHASE; |
375 |
> |
n |= (long)nextPhase << PHASE_SHIFT; |
376 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, s, n); |
377 |
|
releaseWaiters(phase); |
378 |
|
} |
379 |
< |
else { |
380 |
< |
parent.doArrive((u == 0) ? |
381 |
< |
ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL); |
382 |
< |
if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase || |
331 |
< |
((int)(state >>> PHASE_SHIFT) != nextPhase && |
332 |
< |
!UNSAFE.compareAndSwapLong(this, stateOffset, |
333 |
< |
s, next))) |
334 |
< |
reconcileState(); |
379 |
> |
else if (nextUnarrived == 0) { // propagate deregistration |
380 |
> |
phase = parent.doArrive(ONE_DEREGISTER); |
381 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, |
382 |
> |
s, s | EMPTY); |
383 |
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} |
384 |
+ |
else |
385 |
+ |
phase = parent.doArrive(ONE_ARRIVAL); |
386 |
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} |
387 |
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return phase; |
388 |
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} |
390 |
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} |
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|
392 |
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/** |
343 |
– |
* Rechecks state and throws bounds exceptions on arrival -- called |
344 |
– |
* only if unarrived is apparently zero. |
345 |
– |
*/ |
346 |
– |
private void checkBadArrive(long s) { |
347 |
– |
if (reconcileState() == s) |
348 |
– |
throw new IllegalStateException |
349 |
– |
("Attempted arrival of unregistered party for " + |
350 |
– |
stateToString(s)); |
351 |
– |
} |
352 |
– |
|
353 |
– |
/** |
393 |
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* Implementation of register, bulkRegister |
394 |
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* |
395 |
|
* @param registrations number to add to both parties and |
397 |
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*/ |
398 |
|
private int doRegister(int registrations) { |
399 |
|
// adjustment to state |
400 |
< |
long adj = ((long)registrations << PARTIES_SHIFT) | registrations; |
400 |
> |
long adjust = ((long)registrations << PARTIES_SHIFT) | registrations; |
401 |
|
final Phaser parent = this.parent; |
402 |
+ |
int phase; |
403 |
|
for (;;) { |
404 |
|
long s = (parent == null) ? state : reconcileState(); |
405 |
< |
int parties = (int)s >>> PARTIES_SHIFT; |
406 |
< |
int phase = (int)(s >>> PHASE_SHIFT); |
407 |
< |
if (phase < 0) |
408 |
< |
return phase; |
369 |
< |
else if (parties != 0 && ((int)s & UNARRIVED_MASK) == 0) |
370 |
< |
internalAwaitAdvance(phase, null); // wait for onAdvance |
371 |
< |
else if (registrations > MAX_PARTIES - parties) |
405 |
> |
int counts = (int)s; |
406 |
> |
int parties = counts >>> PARTIES_SHIFT; |
407 |
> |
int unarrived = counts & UNARRIVED_MASK; |
408 |
> |
if (registrations > MAX_PARTIES - parties) |
409 |
|
throw new IllegalStateException(badRegister(s)); |
410 |
< |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj)) |
411 |
< |
return phase; |
410 |
> |
phase = (int)(s >>> PHASE_SHIFT); |
411 |
> |
if (phase < 0) |
412 |
> |
break; |
413 |
> |
if (counts != EMPTY) { // not 1st registration |
414 |
> |
if (parent == null || reconcileState() == s) { |
415 |
> |
if (unarrived == 0) // wait out advance |
416 |
> |
root.internalAwaitAdvance(phase, null); |
417 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, |
418 |
> |
s, s + adjust)) |
419 |
> |
break; |
420 |
> |
} |
421 |
> |
} |
422 |
> |
else if (parent == null) { // 1st root registration |
423 |
> |
long next = ((long)phase << PHASE_SHIFT) | adjust; |
424 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
425 |
> |
break; |
426 |
> |
} |
427 |
> |
else { |
428 |
> |
synchronized (this) { // 1st sub registration |
429 |
> |
if (state == s) { // recheck under lock |
430 |
> |
phase = parent.doRegister(1); |
431 |
> |
if (phase < 0) |
432 |
> |
break; |
433 |
> |
// finish registration whenever parent registration |
434 |
> |
// succeeded, even when racing with termination, |
435 |
> |
// since these are part of the same "transaction". |
436 |
> |
while (!UNSAFE.compareAndSwapLong |
437 |
> |
(this, stateOffset, s, |
438 |
> |
((long)phase << PHASE_SHIFT) | adjust)) { |
439 |
> |
s = state; |
440 |
> |
phase = (int)(root.state >>> PHASE_SHIFT); |
441 |
> |
// assert (int)s == EMPTY; |
442 |
> |
} |
443 |
> |
break; |
444 |
> |
} |
445 |
> |
} |
446 |
> |
} |
447 |
|
} |
448 |
+ |
return phase; |
449 |
|
} |
450 |
|
|
451 |
|
/** |
452 |
< |
* Returns message string for out of bounds exceptions on registration. |
453 |
< |
*/ |
454 |
< |
private String badRegister(long s) { |
455 |
< |
return "Attempt to register more than " + |
456 |
< |
MAX_PARTIES + " parties for " + stateToString(s); |
457 |
< |
} |
458 |
< |
|
386 |
< |
/** |
387 |
< |
* Recursively resolves lagged phase propagation from root if necessary. |
452 |
> |
* Resolves lagged phase propagation from root if necessary. |
453 |
> |
* Reconciliation normally occurs when root has advanced but |
454 |
> |
* subphasers have not yet done so, in which case they must finish |
455 |
> |
* their own advance by setting unarrived to parties (or if |
456 |
> |
* parties is zero, resetting to unregistered EMPTY state). |
457 |
> |
* |
458 |
> |
* @return reconciled state |
459 |
|
*/ |
460 |
|
private long reconcileState() { |
461 |
< |
Phaser par = parent; |
461 |
> |
final Phaser root = this.root; |
462 |
|
long s = state; |
463 |
< |
if (par != null) { |
464 |
< |
Phaser rt = root; |
465 |
< |
int phase, rPhase; |
466 |
< |
while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 && |
467 |
< |
(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) { |
468 |
< |
if ((int)(par.state >>> PHASE_SHIFT) != rPhase) |
469 |
< |
par.reconcileState(); |
470 |
< |
else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) { |
471 |
< |
long u = s & PARTIES_MASK; // reset unarrived to parties |
472 |
< |
long next = ((((long) rPhase) << PHASE_SHIFT) | u | |
473 |
< |
(u >>> PARTIES_SHIFT)); |
403 |
< |
if (state == s && |
404 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, |
405 |
< |
s, s = next)) |
406 |
< |
break; |
407 |
< |
} |
463 |
> |
if (root != this) { |
464 |
> |
int phase, p; |
465 |
> |
// CAS to root phase with current parties, tripping unarrived |
466 |
> |
while ((phase = (int)(root.state >>> PHASE_SHIFT)) != |
467 |
> |
(int)(s >>> PHASE_SHIFT) && |
468 |
> |
!UNSAFE.compareAndSwapLong |
469 |
> |
(this, stateOffset, s, |
470 |
> |
s = (((long)phase << PHASE_SHIFT) | |
471 |
> |
((phase < 0) ? (s & COUNTS_MASK) : |
472 |
> |
(((p = (int)s >>> PARTIES_SHIFT) == 0) ? EMPTY : |
473 |
> |
((s & PARTIES_MASK) | p)))))) |
474 |
|
s = state; |
409 |
– |
} |
475 |
|
} |
476 |
|
return s; |
477 |
|
} |
478 |
|
|
479 |
|
/** |
480 |
< |
* Creates a new phaser without any initially registered parties, |
481 |
< |
* initial phase number 0, and no parent. Any thread using this |
480 |
> |
* Creates a new phaser with no initially registered parties, no |
481 |
> |
* parent, and initial phase number 0. Any thread using this |
482 |
|
* phaser will need to first register for it. |
483 |
|
*/ |
484 |
|
public Phaser() { |
487 |
|
|
488 |
|
/** |
489 |
|
* Creates a new phaser with the given number of registered |
490 |
< |
* unarrived parties, initial phase number 0, and no parent. |
490 |
> |
* unarrived parties, no parent, and initial phase number 0. |
491 |
|
* |
492 |
< |
* @param parties the number of parties required to trip barrier |
492 |
> |
* @param parties the number of parties required to advance to the |
493 |
> |
* next phase |
494 |
|
* @throws IllegalArgumentException if parties less than zero |
495 |
|
* or greater than the maximum number of parties supported |
496 |
|
*/ |
509 |
|
|
510 |
|
/** |
511 |
|
* Creates a new phaser with the given parent and number of |
512 |
< |
* registered unarrived parties. If parent is non-null, this |
513 |
< |
* phaser is registered with the parent and its initial phase |
514 |
< |
* number is the same as that of parent phaser. If the number of |
449 |
< |
* parties is zero, the parent phaser will not proceed until this |
450 |
< |
* child phaser registers parties and advances, or this child |
451 |
< |
* phaser deregisters with its parent, or the parent is otherwise |
452 |
< |
* terminated. This child Phaser will be deregistered from its |
453 |
< |
* parent automatically upon any invocation of the child's {@link |
454 |
< |
* #arriveAndDeregister} method that results in the child's number |
455 |
< |
* of registered parties becoming zero. (Although rarely |
456 |
< |
* appropriate, this child may also explicity deregister from its |
457 |
< |
* parent using {@code getParent().arriveAndDeregister()}.) After |
458 |
< |
* deregistration, the child cannot re-register. (Instead, you can |
459 |
< |
* create a new child Phaser.) |
512 |
> |
* registered unarrived parties. When the given parent is non-null |
513 |
> |
* and the given number of parties is greater than zero, this |
514 |
> |
* child phaser is registered with its parent. |
515 |
|
* |
516 |
|
* @param parent the parent phaser |
517 |
< |
* @param parties the number of parties required to trip barrier |
517 |
> |
* @param parties the number of parties required to advance to the |
518 |
> |
* next phase |
519 |
|
* @throws IllegalArgumentException if parties less than zero |
520 |
|
* or greater than the maximum number of parties supported |
521 |
|
*/ |
522 |
|
public Phaser(Phaser parent, int parties) { |
523 |
|
if (parties >>> PARTIES_SHIFT != 0) |
524 |
|
throw new IllegalArgumentException("Illegal number of parties"); |
525 |
< |
int phase; |
525 |
> |
int phase = 0; |
526 |
|
this.parent = parent; |
527 |
|
if (parent != null) { |
528 |
< |
Phaser r = parent.root; |
529 |
< |
this.root = r; |
530 |
< |
this.evenQ = r.evenQ; |
531 |
< |
this.oddQ = r.oddQ; |
532 |
< |
phase = parent.doRegister(1); |
528 |
> |
final Phaser root = parent.root; |
529 |
> |
this.root = root; |
530 |
> |
this.evenQ = root.evenQ; |
531 |
> |
this.oddQ = root.oddQ; |
532 |
> |
if (parties != 0) |
533 |
> |
phase = parent.doRegister(1); |
534 |
|
} |
535 |
|
else { |
536 |
|
this.root = this; |
537 |
|
this.evenQ = new AtomicReference<QNode>(); |
538 |
|
this.oddQ = new AtomicReference<QNode>(); |
482 |
– |
phase = 0; |
539 |
|
} |
540 |
< |
long p = (long)parties; |
541 |
< |
this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT); |
540 |
> |
this.state = (parties == 0) ? (long)EMPTY : |
541 |
> |
((long)phase << PHASE_SHIFT) | |
542 |
> |
((long)parties << PARTIES_SHIFT) | |
543 |
> |
((long)parties); |
544 |
|
} |
545 |
|
|
546 |
|
/** |
547 |
< |
* Adds a new unarrived party to this phaser. |
548 |
< |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
549 |
< |
* this method may wait until its completion before registering. |
550 |
< |
* |
551 |
< |
* @return the arrival phase number to which this registration applied |
547 |
> |
* Adds a new unarrived party to this phaser. If an ongoing |
548 |
> |
* invocation of {@link #onAdvance} is in progress, this method |
549 |
> |
* may await its completion before returning. If this phaser has |
550 |
> |
* a parent, and this phaser previously had no registered parties, |
551 |
> |
* this child phaser is also registered with its parent. If |
552 |
> |
* this phaser is terminated, the attempt to register has |
553 |
> |
* no effect, and a negative value is returned. |
554 |
> |
* |
555 |
> |
* @return the arrival phase number to which this registration |
556 |
> |
* applied. If this value is negative, then this phaser has |
557 |
> |
* terminated, in which case registration has no effect. |
558 |
|
* @throws IllegalStateException if attempting to register more |
559 |
|
* than the maximum supported number of parties |
560 |
|
*/ |
565 |
|
/** |
566 |
|
* Adds the given number of new unarrived parties to this phaser. |
567 |
|
* If an ongoing invocation of {@link #onAdvance} is in progress, |
568 |
< |
* this method may wait until its completion before registering. |
569 |
< |
* |
570 |
< |
* @param parties the number of additional parties required to trip barrier |
571 |
< |
* @return the arrival phase number to which this registration applied |
568 |
> |
* this method may await its completion before returning. If this |
569 |
> |
* phaser has a parent, and the given number of parties is greater |
570 |
> |
* than zero, and this phaser previously had no registered |
571 |
> |
* parties, this child phaser is also registered with its parent. |
572 |
> |
* If this phaser is terminated, the attempt to register has no |
573 |
> |
* effect, and a negative value is returned. |
574 |
> |
* |
575 |
> |
* @param parties the number of additional parties required to |
576 |
> |
* advance to the next phase |
577 |
> |
* @return the arrival phase number to which this registration |
578 |
> |
* applied. If this value is negative, then this phaser has |
579 |
> |
* terminated, in which case registration has no effect. |
580 |
|
* @throws IllegalStateException if attempting to register more |
581 |
|
* than the maximum supported number of parties |
582 |
|
* @throws IllegalArgumentException if {@code parties < 0} |
590 |
|
} |
591 |
|
|
592 |
|
/** |
593 |
< |
* Arrives at the barrier, but does not wait for others. (You can |
594 |
< |
* in turn wait for others via {@link #awaitAdvance}). It is an |
595 |
< |
* unenforced usage error for an unregistered party to invoke this |
596 |
< |
* method. |
593 |
> |
* Arrives at this phaser, without waiting for others to arrive. |
594 |
> |
* |
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 |
> |
* this phaser, if ever. |
599 |
|
* |
600 |
|
* @return the arrival phase number, or a negative value if terminated |
601 |
|
* @throws IllegalStateException if not terminated and the number |
606 |
|
} |
607 |
|
|
608 |
|
/** |
609 |
< |
* Arrives at the barrier and deregisters from it without waiting |
610 |
< |
* for others. Deregistration reduces the number of parties |
611 |
< |
* required to trip the barrier in future phases. If this phaser |
609 |
> |
* Arrives at this phaser and deregisters from it without waiting |
610 |
> |
* for others to arrive. Deregistration reduces the number of |
611 |
> |
* parties required to advance in future phases. If this phaser |
612 |
|
* has a parent, and deregistration causes this phaser to have |
613 |
< |
* zero parties, this phaser also arrives at and is deregistered |
614 |
< |
* from its parent. It is an unenforced usage error for an |
615 |
< |
* unregistered party to invoke this method. |
613 |
> |
* zero parties, this phaser is also deregistered from its parent. |
614 |
> |
* |
615 |
> |
* <p>It is a usage error for an unregistered party to invoke this |
616 |
> |
* method. However, this error may result in an {@code |
617 |
> |
* IllegalStateException} only upon some subsequent operation on |
618 |
> |
* this phaser, if ever. |
619 |
|
* |
620 |
|
* @return the arrival phase number, or a negative value if terminated |
621 |
|
* @throws IllegalStateException if not terminated and the number |
622 |
|
* of registered or unarrived parties would become negative |
623 |
|
*/ |
624 |
|
public int arriveAndDeregister() { |
625 |
< |
return doArrive(ONE_ARRIVAL|ONE_PARTY); |
625 |
> |
return doArrive(ONE_DEREGISTER); |
626 |
|
} |
627 |
|
|
628 |
|
/** |
629 |
< |
* Arrives at the barrier and awaits others. Equivalent in effect |
629 |
> |
* Arrives at this phaser and awaits others. Equivalent in effect |
630 |
|
* to {@code awaitAdvance(arrive())}. If you need to await with |
631 |
|
* interruption or timeout, you can arrange this with an analogous |
632 |
|
* construction using one of the other forms of the {@code |
633 |
|
* awaitAdvance} method. If instead you need to deregister upon |
634 |
< |
* arrival, use {@link #arriveAndDeregister}. It is an unenforced |
635 |
< |
* usage error for an unregistered party to invoke this method. |
634 |
> |
* arrival, use {@code awaitAdvance(arriveAndDeregister())}. |
635 |
> |
* |
636 |
> |
* <p>It is a usage error for an unregistered party to invoke this |
637 |
> |
* method. However, this error may result in an {@code |
638 |
> |
* IllegalStateException} only upon some subsequent operation on |
639 |
> |
* this phaser, if ever. |
640 |
|
* |
641 |
< |
* @return the arrival phase number, or a negative number if terminated |
641 |
> |
* @return the arrival phase number, or the (negative) |
642 |
> |
* {@linkplain #getPhase() current phase} if terminated |
643 |
|
* @throws IllegalStateException if not terminated and the number |
644 |
|
* of unarrived parties would become negative |
645 |
|
*/ |
646 |
|
public int arriveAndAwaitAdvance() { |
647 |
< |
return awaitAdvance(arrive()); |
647 |
> |
// Specialization of doArrive+awaitAdvance eliminating some reads/paths |
648 |
> |
final Phaser root = this.root; |
649 |
> |
for (;;) { |
650 |
> |
long s = (root == this) ? state : reconcileState(); |
651 |
> |
int phase = (int)(s >>> PHASE_SHIFT); |
652 |
> |
if (phase < 0) |
653 |
> |
return phase; |
654 |
> |
int counts = (int)s; |
655 |
> |
int unarrived = (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK); |
656 |
> |
if (unarrived <= 0) |
657 |
> |
throw new IllegalStateException(badArrive(s)); |
658 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, |
659 |
> |
s -= ONE_ARRIVAL)) { |
660 |
> |
if (unarrived > 1) |
661 |
> |
return root.internalAwaitAdvance(phase, null); |
662 |
> |
if (root != this) |
663 |
> |
return parent.arriveAndAwaitAdvance(); |
664 |
> |
long n = s & PARTIES_MASK; // base of next state |
665 |
> |
int nextUnarrived = (int)n >>> PARTIES_SHIFT; |
666 |
> |
if (onAdvance(phase, nextUnarrived)) |
667 |
> |
n |= TERMINATION_BIT; |
668 |
> |
else if (nextUnarrived == 0) |
669 |
> |
n |= EMPTY; |
670 |
> |
else |
671 |
> |
n |= nextUnarrived; |
672 |
> |
int nextPhase = (phase + 1) & MAX_PHASE; |
673 |
> |
n |= (long)nextPhase << PHASE_SHIFT; |
674 |
> |
if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n)) |
675 |
> |
return (int)(state >>> PHASE_SHIFT); // terminated |
676 |
> |
releaseWaiters(phase); |
677 |
> |
return nextPhase; |
678 |
> |
} |
679 |
> |
} |
680 |
|
} |
681 |
|
|
682 |
|
/** |
683 |
< |
* Awaits the phase of the barrier to advance from the given phase |
684 |
< |
* value, returning immediately if the current phase of the |
685 |
< |
* barrier is not equal to the given phase value or this barrier |
572 |
< |
* is terminated. |
683 |
> |
* Awaits the phase of this phaser to advance from the given phase |
684 |
> |
* value, returning immediately if the current phase is not equal |
685 |
> |
* to the given phase value or this phaser is terminated. |
686 |
|
* |
687 |
|
* @param phase an arrival phase number, or negative value if |
688 |
|
* terminated; this argument is normally the value returned by a |
689 |
< |
* previous call to {@code arrive} or its variants |
690 |
< |
* @return the next arrival phase number, or a negative value |
691 |
< |
* if terminated or argument is negative |
689 |
> |
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
690 |
> |
* @return the next arrival phase number, or the argument if it is |
691 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
692 |
> |
* if terminated |
693 |
|
*/ |
694 |
|
public int awaitAdvance(int phase) { |
695 |
+ |
final Phaser root = this.root; |
696 |
+ |
long s = (root == this) ? state : reconcileState(); |
697 |
+ |
int p = (int)(s >>> PHASE_SHIFT); |
698 |
|
if (phase < 0) |
699 |
|
return phase; |
700 |
< |
long s = (parent == null) ? state : reconcileState(); |
701 |
< |
int p = (int)(s >>> PHASE_SHIFT); |
702 |
< |
return (p != phase) ? p : internalAwaitAdvance(phase, null); |
700 |
> |
if (p == phase) |
701 |
> |
return root.internalAwaitAdvance(phase, null); |
702 |
> |
return p; |
703 |
|
} |
704 |
|
|
705 |
|
/** |
706 |
< |
* Awaits the phase of the barrier to advance from the given phase |
706 |
> |
* Awaits the phase of this phaser to advance from the given phase |
707 |
|
* value, throwing {@code InterruptedException} if interrupted |
708 |
< |
* while waiting, or returning immediately if the current phase of |
709 |
< |
* the barrier is not equal to the given phase value or this |
710 |
< |
* barrier is terminated. |
708 |
> |
* while waiting, or returning immediately if the current phase is |
709 |
> |
* not equal to the given phase value or this phaser is |
710 |
> |
* terminated. |
711 |
|
* |
712 |
|
* @param phase an arrival phase number, or negative value if |
713 |
|
* terminated; this argument is normally the value returned by a |
714 |
< |
* previous call to {@code arrive} or its variants |
715 |
< |
* @return the next arrival phase number, or a negative value |
716 |
< |
* if terminated or argument is negative |
714 |
> |
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
715 |
> |
* @return the next arrival phase number, or the argument if it is |
716 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
717 |
> |
* if terminated |
718 |
|
* @throws InterruptedException if thread interrupted while waiting |
719 |
|
*/ |
720 |
|
public int awaitAdvanceInterruptibly(int phase) |
721 |
|
throws InterruptedException { |
722 |
+ |
final Phaser root = this.root; |
723 |
+ |
long s = (root == this) ? state : reconcileState(); |
724 |
+ |
int p = (int)(s >>> PHASE_SHIFT); |
725 |
|
if (phase < 0) |
726 |
|
return phase; |
606 |
– |
long s = (parent == null) ? state : reconcileState(); |
607 |
– |
int p = (int)(s >>> PHASE_SHIFT); |
727 |
|
if (p == phase) { |
728 |
|
QNode node = new QNode(this, phase, true, false, 0L); |
729 |
< |
p = internalAwaitAdvance(phase, node); |
729 |
> |
p = root.internalAwaitAdvance(phase, node); |
730 |
|
if (node.wasInterrupted) |
731 |
|
throw new InterruptedException(); |
732 |
|
} |
734 |
|
} |
735 |
|
|
736 |
|
/** |
737 |
< |
* Awaits the phase of the barrier to advance from the given phase |
737 |
> |
* Awaits the phase of this phaser to advance from the given phase |
738 |
|
* value or the given timeout to elapse, throwing {@code |
739 |
|
* InterruptedException} if interrupted while waiting, or |
740 |
< |
* returning immediately if the current phase of the barrier is |
741 |
< |
* not equal to the given phase value or this barrier is |
623 |
< |
* terminated. |
740 |
> |
* returning immediately if the current phase is not equal to the |
741 |
> |
* given phase value or this phaser is terminated. |
742 |
|
* |
743 |
|
* @param phase an arrival phase number, or negative value if |
744 |
|
* terminated; this argument is normally the value returned by a |
745 |
< |
* previous call to {@code arrive} or its variants |
745 |
> |
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
746 |
|
* @param timeout how long to wait before giving up, in units of |
747 |
|
* {@code unit} |
748 |
|
* @param unit a {@code TimeUnit} determining how to interpret the |
749 |
|
* {@code timeout} parameter |
750 |
< |
* @return the next arrival phase number, or a negative value |
751 |
< |
* if terminated or argument is negative |
750 |
> |
* @return the next arrival phase number, or the argument if it is |
751 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
752 |
> |
* if terminated |
753 |
|
* @throws InterruptedException if thread interrupted while waiting |
754 |
|
* @throws TimeoutException if timed out while waiting |
755 |
|
*/ |
756 |
|
public int awaitAdvanceInterruptibly(int phase, |
757 |
|
long timeout, TimeUnit unit) |
758 |
|
throws InterruptedException, TimeoutException { |
759 |
+ |
long nanos = unit.toNanos(timeout); |
760 |
+ |
final Phaser root = this.root; |
761 |
+ |
long s = (root == this) ? state : reconcileState(); |
762 |
+ |
int p = (int)(s >>> PHASE_SHIFT); |
763 |
|
if (phase < 0) |
764 |
|
return phase; |
642 |
– |
long s = (parent == null) ? state : reconcileState(); |
643 |
– |
int p = (int)(s >>> PHASE_SHIFT); |
765 |
|
if (p == phase) { |
645 |
– |
long nanos = unit.toNanos(timeout); |
766 |
|
QNode node = new QNode(this, phase, true, true, nanos); |
767 |
< |
p = internalAwaitAdvance(phase, node); |
767 |
> |
p = root.internalAwaitAdvance(phase, node); |
768 |
|
if (node.wasInterrupted) |
769 |
|
throw new InterruptedException(); |
770 |
|
else if (p == phase) |
774 |
|
} |
775 |
|
|
776 |
|
/** |
777 |
< |
* Forces this barrier to enter termination state. Counts of |
778 |
< |
* arrived and registered parties are unaffected. If this phaser |
779 |
< |
* is a member of a tiered set of phasers, then all of the phasers |
780 |
< |
* in the set are terminated. If this phaser is already |
781 |
< |
* terminated, this method has no effect. This method may be |
782 |
< |
* useful for coordinating recovery after one or more tasks |
783 |
< |
* encounter unexpected exceptions. |
777 |
> |
* Forces this phaser to enter termination state. Counts of |
778 |
> |
* registered parties are unaffected. If this phaser is a member |
779 |
> |
* of a tiered set of phasers, then all of the phasers in the set |
780 |
> |
* are terminated. If this phaser is already terminated, this |
781 |
> |
* method has no effect. This method may be useful for |
782 |
> |
* coordinating recovery after one or more tasks encounter |
783 |
> |
* unexpected exceptions. |
784 |
|
*/ |
785 |
|
public void forceTermination() { |
786 |
|
// Only need to change root state |
788 |
|
long s; |
789 |
|
while ((s = root.state) >= 0) { |
790 |
|
if (UNSAFE.compareAndSwapLong(root, stateOffset, |
791 |
< |
s, s | TERMINATION_PHASE)) { |
792 |
< |
releaseWaiters(0); // signal all threads |
793 |
< |
releaseWaiters(1); |
791 |
> |
s, s | TERMINATION_BIT)) { |
792 |
> |
// signal all threads |
793 |
> |
releaseWaiters(0); // Waiters on evenQ |
794 |
> |
releaseWaiters(1); // Waiters on oddQ |
795 |
|
return; |
796 |
|
} |
797 |
|
} |
800 |
|
/** |
801 |
|
* Returns the current phase number. The maximum phase number is |
802 |
|
* {@code Integer.MAX_VALUE}, after which it restarts at |
803 |
< |
* zero. Upon termination, the phase number is negative. |
803 |
> |
* zero. Upon termination, the phase number is negative, |
804 |
> |
* in which case the prevailing phase prior to termination |
805 |
> |
* may be obtained via {@code getPhase() + Integer.MIN_VALUE}. |
806 |
|
* |
807 |
|
* @return the phase number, or a negative value if terminated |
808 |
|
*/ |
811 |
|
} |
812 |
|
|
813 |
|
/** |
814 |
< |
* Returns the number of parties registered at this barrier. |
814 |
> |
* Returns the number of parties registered at this phaser. |
815 |
|
* |
816 |
|
* @return the number of parties |
817 |
|
*/ |
821 |
|
|
822 |
|
/** |
823 |
|
* Returns the number of registered parties that have arrived at |
824 |
< |
* the current phase of this barrier. |
824 |
> |
* the current phase of this phaser. If this phaser has terminated, |
825 |
> |
* the returned value is meaningless and arbitrary. |
826 |
|
* |
827 |
|
* @return the number of arrived parties |
828 |
|
*/ |
829 |
|
public int getArrivedParties() { |
830 |
< |
return arrivedOf(parent==null? state : reconcileState()); |
830 |
> |
return arrivedOf(reconcileState()); |
831 |
|
} |
832 |
|
|
833 |
|
/** |
834 |
|
* Returns the number of registered parties that have not yet |
835 |
< |
* arrived at the current phase of this barrier. |
835 |
> |
* arrived at the current phase of this phaser. If this phaser has |
836 |
> |
* terminated, the returned value is meaningless and arbitrary. |
837 |
|
* |
838 |
|
* @return the number of unarrived parties |
839 |
|
*/ |
840 |
|
public int getUnarrivedParties() { |
841 |
< |
return unarrivedOf(parent==null? state : reconcileState()); |
841 |
> |
return unarrivedOf(reconcileState()); |
842 |
|
} |
843 |
|
|
844 |
|
/** |
861 |
|
} |
862 |
|
|
863 |
|
/** |
864 |
< |
* Returns {@code true} if this barrier has been terminated. |
864 |
> |
* Returns {@code true} if this phaser has been terminated. |
865 |
|
* |
866 |
< |
* @return {@code true} if this barrier has been terminated |
866 |
> |
* @return {@code true} if this phaser has been terminated |
867 |
|
*/ |
868 |
|
public boolean isTerminated() { |
869 |
|
return root.state < 0L; |
872 |
|
/** |
873 |
|
* Overridable method to perform an action upon impending phase |
874 |
|
* advance, and to control termination. This method is invoked |
875 |
< |
* upon arrival of the party tripping the barrier (when all other |
875 |
> |
* upon arrival of the party advancing this phaser (when all other |
876 |
|
* waiting parties are dormant). If this method returns {@code |
877 |
< |
* true}, then, rather than advance the phase number, this barrier |
878 |
< |
* will be set to a final termination state, and subsequent calls |
879 |
< |
* to {@link #isTerminated} will return true. Any (unchecked) |
880 |
< |
* Exception or Error thrown by an invocation of this method is |
881 |
< |
* propagated to the party attempting to trip the barrier, in |
882 |
< |
* which case no advance occurs. |
877 |
> |
* true}, this phaser will be set to a final termination state |
878 |
> |
* upon advance, and subsequent calls to {@link #isTerminated} |
879 |
> |
* will return true. Any (unchecked) Exception or Error thrown by |
880 |
> |
* an invocation of this method is propagated to the party |
881 |
> |
* attempting to advance this phaser, in which case no advance |
882 |
> |
* occurs. |
883 |
|
* |
884 |
|
* <p>The arguments to this method provide the state of the phaser |
885 |
|
* prevailing for the current transition. The effects of invoking |
886 |
< |
* arrival, registration, and waiting methods on this Phaser from |
886 |
> |
* arrival, registration, and waiting methods on this phaser from |
887 |
|
* within {@code onAdvance} are unspecified and should not be |
888 |
|
* relied on. |
889 |
|
* |
890 |
< |
* <p>If this Phaser is a member of a tiered set of Phasers, then |
891 |
< |
* {@code onAdvance} is invoked only for its root Phaser on each |
890 |
> |
* <p>If this phaser is a member of a tiered set of phasers, then |
891 |
> |
* {@code onAdvance} is invoked only for its root phaser on each |
892 |
|
* advance. |
893 |
|
* |
894 |
< |
* <p>The default version returns {@code true} when the number of |
895 |
< |
* registered parties is zero. Normally, overrides that arrange |
896 |
< |
* termination for other reasons should also preserve this |
897 |
< |
* property. |
894 |
> |
* <p>To support the most common use cases, the default |
895 |
> |
* implementation of this method returns {@code true} when the |
896 |
> |
* number of registered parties has become zero as the result of a |
897 |
> |
* party invoking {@code arriveAndDeregister}. You can disable |
898 |
> |
* this behavior, thus enabling continuation upon future |
899 |
> |
* registrations, by overriding this method to always return |
900 |
> |
* {@code false}: |
901 |
> |
* |
902 |
> |
* <pre> {@code |
903 |
> |
* Phaser phaser = new Phaser() { |
904 |
> |
* protected boolean onAdvance(int phase, int parties) { return false; } |
905 |
> |
* }}</pre> |
906 |
|
* |
907 |
< |
* @param phase the phase number on entering the barrier |
907 |
> |
* @param phase the current phase number on entry to this method, |
908 |
> |
* before this phaser is advanced |
909 |
|
* @param registeredParties the current number of registered parties |
910 |
< |
* @return {@code true} if this barrier should terminate |
910 |
> |
* @return {@code true} if this phaser should terminate |
911 |
|
*/ |
912 |
|
protected boolean onAdvance(int phase, int registeredParties) { |
913 |
< |
return registeredParties <= 0; |
913 |
> |
return registeredParties == 0; |
914 |
|
} |
915 |
|
|
916 |
|
/** |
920 |
|
* followed by the number of registered parties, and {@code |
921 |
|
* "arrived = "} followed by the number of arrived parties. |
922 |
|
* |
923 |
< |
* @return a string identifying this barrier, as well as its state |
923 |
> |
* @return a string identifying this phaser, as well as its state |
924 |
|
*/ |
925 |
|
public String toString() { |
926 |
|
return stateToString(reconcileState()); |
942 |
|
* Removes and signals threads from queue for phase. |
943 |
|
*/ |
944 |
|
private void releaseWaiters(int phase) { |
945 |
< |
AtomicReference<QNode> head = queueFor(phase); |
946 |
< |
QNode q; |
947 |
< |
int p; |
945 |
> |
QNode q; // first element of queue |
946 |
> |
Thread t; // its thread |
947 |
> |
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
948 |
|
while ((q = head.get()) != null && |
949 |
< |
((p = q.phase) == phase || |
950 |
< |
(int)(root.state >>> PHASE_SHIFT) != p)) { |
951 |
< |
if (head.compareAndSet(q, q.next)) |
952 |
< |
q.signal(); |
949 |
> |
q.phase != (int)(root.state >>> PHASE_SHIFT)) { |
950 |
> |
if (head.compareAndSet(q, q.next) && |
951 |
> |
(t = q.thread) != null) { |
952 |
> |
q.thread = null; |
953 |
> |
LockSupport.unpark(t); |
954 |
> |
} |
955 |
> |
} |
956 |
> |
} |
957 |
> |
|
958 |
> |
/** |
959 |
> |
* Variant of releaseWaiters that additionally tries to remove any |
960 |
> |
* nodes no longer waiting for advance due to timeout or |
961 |
> |
* interrupt. Currently, nodes are removed only if they are at |
962 |
> |
* head of queue, which suffices to reduce memory footprint in |
963 |
> |
* most usages. |
964 |
> |
* |
965 |
> |
* @return current phase on exit |
966 |
> |
*/ |
967 |
> |
private int abortWait(int phase) { |
968 |
> |
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
969 |
> |
for (;;) { |
970 |
> |
Thread t; |
971 |
> |
QNode q = head.get(); |
972 |
> |
int p = (int)(root.state >>> PHASE_SHIFT); |
973 |
> |
if (q == null || ((t = q.thread) != null && q.phase == p)) |
974 |
> |
return p; |
975 |
> |
if (head.compareAndSet(q, q.next) && t != null) { |
976 |
> |
q.thread = null; |
977 |
> |
LockSupport.unpark(t); |
978 |
> |
} |
979 |
|
} |
980 |
|
} |
981 |
|
|
990 |
|
* avoid it when threads regularly arrive: When a thread in |
991 |
|
* internalAwaitAdvance notices another arrival before blocking, |
992 |
|
* and there appear to be enough CPUs available, it spins |
993 |
< |
* SPINS_PER_ARRIVAL more times before blocking. Plus, even on |
994 |
< |
* uniprocessors, there is at least one intervening Thread.yield |
835 |
< |
* before blocking. The value trades off good-citizenship vs big |
836 |
< |
* unnecessary slowdowns. |
993 |
> |
* SPINS_PER_ARRIVAL more times before blocking. The value trades |
994 |
> |
* off good-citizenship vs big unnecessary slowdowns. |
995 |
|
*/ |
996 |
|
static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8; |
997 |
|
|
998 |
|
/** |
999 |
|
* Possibly blocks and waits for phase to advance unless aborted. |
1000 |
+ |
* Call only on root phaser. |
1001 |
|
* |
1002 |
|
* @param phase current phase |
1003 |
|
* @param node if non-null, the wait node to track interrupt and timeout; |
1005 |
|
* @return current phase |
1006 |
|
*/ |
1007 |
|
private int internalAwaitAdvance(int phase, QNode node) { |
1008 |
< |
Phaser current = this; // to eventually wait at root if tiered |
1009 |
< |
boolean queued = false; // true when node is enqueued |
1010 |
< |
int lastUnarrived = -1; // to increase spins upon change |
1008 |
> |
// assert root == this; |
1009 |
> |
releaseWaiters(phase-1); // ensure old queue clean |
1010 |
> |
boolean queued = false; // true when node is enqueued |
1011 |
> |
int lastUnarrived = 0; // to increase spins upon change |
1012 |
|
int spins = SPINS_PER_ARRIVAL; |
1013 |
|
long s; |
1014 |
|
int p; |
1015 |
< |
while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) { |
1016 |
< |
Phaser par; |
1017 |
< |
int unarrived = (int)s & UNARRIVED_MASK; |
1018 |
< |
if (unarrived != lastUnarrived) { |
1019 |
< |
if (lastUnarrived == -1) // ensure old queue clean |
860 |
< |
releaseWaiters(phase-1); |
861 |
< |
if ((lastUnarrived = unarrived) < NCPU) |
1015 |
> |
while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) { |
1016 |
> |
if (node == null) { // spinning in noninterruptible mode |
1017 |
> |
int unarrived = (int)s & UNARRIVED_MASK; |
1018 |
> |
if (unarrived != lastUnarrived && |
1019 |
> |
(lastUnarrived = unarrived) < NCPU) |
1020 |
|
spins += SPINS_PER_ARRIVAL; |
1021 |
< |
} |
1022 |
< |
else if (unarrived == 0 && (par = current.parent) != null) { |
1023 |
< |
current = par; // if all arrived, use parent |
1024 |
< |
par = par.parent; |
867 |
< |
lastUnarrived = -1; |
868 |
< |
} |
869 |
< |
else if (spins > 0) { |
870 |
< |
if (--spins == (SPINS_PER_ARRIVAL >>> 1)) |
871 |
< |
Thread.yield(); // yield midway through spin |
872 |
< |
} |
873 |
< |
else if (node == null) // must be noninterruptible |
874 |
< |
node = new QNode(this, phase, false, false, 0L); |
875 |
< |
else if (node.isReleasable()) { |
876 |
< |
if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase) |
877 |
< |
break; |
878 |
< |
else |
879 |
< |
return phase; // aborted |
880 |
< |
} |
881 |
< |
else if (!queued) { // push onto queue |
882 |
< |
AtomicReference<QNode> head = queueFor(phase); |
883 |
< |
QNode q = head.get(); |
884 |
< |
if (q == null || q.phase == phase) { |
885 |
< |
node.next = q; |
886 |
< |
if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase) |
887 |
< |
break; // recheck to avoid stale enqueue |
888 |
< |
else |
889 |
< |
queued = head.compareAndSet(q, node); |
1021 |
> |
boolean interrupted = Thread.interrupted(); |
1022 |
> |
if (interrupted || --spins < 0) { // need node to record intr |
1023 |
> |
node = new QNode(this, phase, false, false, 0L); |
1024 |
> |
node.wasInterrupted = interrupted; |
1025 |
|
} |
1026 |
|
} |
1027 |
+ |
else if (node.isReleasable()) // done or aborted |
1028 |
+ |
break; |
1029 |
+ |
else if (!queued) { // push onto queue |
1030 |
+ |
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
1031 |
+ |
QNode q = node.next = head.get(); |
1032 |
+ |
if ((q == null || q.phase == phase) && |
1033 |
+ |
(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq |
1034 |
+ |
queued = head.compareAndSet(q, node); |
1035 |
+ |
} |
1036 |
|
else { |
1037 |
|
try { |
1038 |
|
ForkJoinPool.managedBlock(node); |
1041 |
|
} |
1042 |
|
} |
1043 |
|
} |
1044 |
+ |
|
1045 |
+ |
if (node != null) { |
1046 |
+ |
if (node.thread != null) |
1047 |
+ |
node.thread = null; // avoid need for unpark() |
1048 |
+ |
if (node.wasInterrupted && !node.interruptible) |
1049 |
+ |
Thread.currentThread().interrupt(); |
1050 |
+ |
if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase) |
1051 |
+ |
return abortWait(phase); // possibly clean up on abort |
1052 |
+ |
} |
1053 |
|
releaseWaiters(phase); |
901 |
– |
if (node != null) |
902 |
– |
node.onRelease(); |
1054 |
|
return p; |
1055 |
|
} |
1056 |
|
|
1075 |
|
this.interruptible = interruptible; |
1076 |
|
this.nanos = nanos; |
1077 |
|
this.timed = timed; |
1078 |
< |
this.lastTime = timed? System.nanoTime() : 0L; |
1078 |
> |
this.lastTime = timed ? System.nanoTime() : 0L; |
1079 |
|
thread = Thread.currentThread(); |
1080 |
|
} |
1081 |
|
|
1082 |
|
public boolean isReleasable() { |
1083 |
< |
Thread t = thread; |
1084 |
< |
if (t != null) { |
1085 |
< |
if (phaser.getPhase() != phase) |
1086 |
< |
t = null; |
1087 |
< |
else { |
1088 |
< |
if (Thread.interrupted()) |
1089 |
< |
wasInterrupted = true; |
1090 |
< |
if (interruptible && wasInterrupted) |
1091 |
< |
t = null; |
941 |
< |
else if (timed) { |
942 |
< |
if (nanos > 0) { |
943 |
< |
long now = System.nanoTime(); |
944 |
< |
nanos -= now - lastTime; |
945 |
< |
lastTime = now; |
946 |
< |
} |
947 |
< |
if (nanos <= 0) |
948 |
< |
t = null; |
949 |
< |
} |
950 |
< |
} |
951 |
< |
if (t != null) |
952 |
< |
return false; |
1083 |
> |
if (thread == null) |
1084 |
> |
return true; |
1085 |
> |
if (phaser.getPhase() != phase) { |
1086 |
> |
thread = null; |
1087 |
> |
return true; |
1088 |
> |
} |
1089 |
> |
if (Thread.interrupted()) |
1090 |
> |
wasInterrupted = true; |
1091 |
> |
if (wasInterrupted && interruptible) { |
1092 |
|
thread = null; |
1093 |
+ |
return true; |
1094 |
|
} |
1095 |
< |
return true; |
1095 |
> |
if (timed) { |
1096 |
> |
if (nanos > 0L) { |
1097 |
> |
long now = System.nanoTime(); |
1098 |
> |
nanos -= now - lastTime; |
1099 |
> |
lastTime = now; |
1100 |
> |
} |
1101 |
> |
if (nanos <= 0L) { |
1102 |
> |
thread = null; |
1103 |
> |
return true; |
1104 |
> |
} |
1105 |
> |
} |
1106 |
> |
return false; |
1107 |
|
} |
1108 |
|
|
1109 |
|
public boolean block() { |
1115 |
|
LockSupport.parkNanos(this, nanos); |
1116 |
|
return isReleasable(); |
1117 |
|
} |
967 |
– |
|
968 |
– |
void signal() { |
969 |
– |
Thread t = thread; |
970 |
– |
if (t != null) { |
971 |
– |
thread = null; |
972 |
– |
LockSupport.unpark(t); |
973 |
– |
} |
974 |
– |
} |
975 |
– |
|
976 |
– |
void onRelease() { // actions upon return from internalAwaitAdvance |
977 |
– |
if (!interruptible && wasInterrupted) |
978 |
– |
Thread.currentThread().interrupt(); |
979 |
– |
if (thread != null) |
980 |
– |
thread = null; |
981 |
– |
} |
982 |
– |
|
1118 |
|
} |
1119 |
|
|
1120 |
|
// Unsafe mechanics |
1121 |
|
|
1122 |
< |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1123 |
< |
private static final long stateOffset = |
1124 |
< |
objectFieldOffset("state", Phaser.class); |
990 |
< |
|
991 |
< |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1122 |
> |
private static final sun.misc.Unsafe UNSAFE; |
1123 |
> |
private static final long stateOffset; |
1124 |
> |
static { |
1125 |
|
try { |
1126 |
< |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1127 |
< |
} catch (NoSuchFieldException e) { |
1128 |
< |
// Convert Exception to corresponding Error |
1129 |
< |
NoSuchFieldError error = new NoSuchFieldError(field); |
1130 |
< |
error.initCause(e); |
1131 |
< |
throw error; |
1126 |
> |
UNSAFE = getUnsafe(); |
1127 |
> |
Class<?> k = Phaser.class; |
1128 |
> |
stateOffset = UNSAFE.objectFieldOffset |
1129 |
> |
(k.getDeclaredField("state")); |
1130 |
> |
} catch (Exception e) { |
1131 |
> |
throw new Error(e); |
1132 |
|
} |
1133 |
|
} |
1134 |
|
|
1142 |
|
private static sun.misc.Unsafe getUnsafe() { |
1143 |
|
try { |
1144 |
|
return sun.misc.Unsafe.getUnsafe(); |
1145 |
< |
} catch (SecurityException se) { |
1146 |
< |
try { |
1147 |
< |
return java.security.AccessController.doPrivileged |
1148 |
< |
(new java.security |
1149 |
< |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1150 |
< |
public sun.misc.Unsafe run() throws Exception { |
1151 |
< |
java.lang.reflect.Field f = sun.misc |
1152 |
< |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1153 |
< |
f.setAccessible(true); |
1154 |
< |
return (sun.misc.Unsafe) f.get(null); |
1155 |
< |
}}); |
1156 |
< |
} catch (java.security.PrivilegedActionException e) { |
1157 |
< |
throw new RuntimeException("Could not initialize intrinsics", |
1158 |
< |
e.getCause()); |
1159 |
< |
} |
1145 |
> |
} catch (SecurityException tryReflectionInstead) {} |
1146 |
> |
try { |
1147 |
> |
return java.security.AccessController.doPrivileged |
1148 |
> |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1149 |
> |
public sun.misc.Unsafe run() throws Exception { |
1150 |
> |
Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class; |
1151 |
> |
for (java.lang.reflect.Field f : k.getDeclaredFields()) { |
1152 |
> |
f.setAccessible(true); |
1153 |
> |
Object x = f.get(null); |
1154 |
> |
if (k.isInstance(x)) |
1155 |
> |
return k.cast(x); |
1156 |
> |
} |
1157 |
> |
throw new NoSuchFieldError("the Unsafe"); |
1158 |
> |
}}); |
1159 |
> |
} catch (java.security.PrivilegedActionException e) { |
1160 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
1161 |
> |
e.getCause()); |
1162 |
|
} |
1163 |
|
} |
1164 |
|
} |