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package jsr166y; |
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import java.util.concurrent.*; |
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import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.TimeoutException; |
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import java.util.concurrent.atomic.AtomicReference; |
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import java.util.concurrent.locks.LockSupport; |
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|
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* 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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* |
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* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged |
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* in tree structures) to reduce contention. Phasers with large |
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* numbers of parties that would otherwise experience heavy |
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* <p> <b>Termination.</b> A phaser may enter a <em>termination</em> |
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* state in which all synchronization methods immediately return |
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* without updating phaser state or waiting for advance, and |
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* indicating (via a negative phase value) that execution is complete. |
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* Termination is triggered when an invocation of {@code onAdvance} |
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* returns {@code true}. The default implementation returns {@code |
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* true} if a deregistration has caused the number of registered |
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* parties to become zero. As illustrated below, when phasers control |
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* actions with a fixed number of iterations, it is often convenient |
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* to override this method to cause termination when the current phase |
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* number reaches a threshold. Method {@link #forceTermination} is |
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* also available to abruptly release waiting threads and allow them |
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* to terminate. |
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* |
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* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., |
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* constructed in tree structures) to reduce contention. Phasers with |
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* large numbers of parties that would otherwise experience heavy |
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* synchronization contention costs may instead be set up so that |
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* groups of sub-phasers share a common parent. This may greatly |
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* increase throughput even though it incurs greater per-operation |
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* <p><b>Sample usages:</b> |
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* |
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* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch} |
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* to control a one-shot action serving a variable number of |
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* parties. The typical idiom is for the method setting this up to |
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* first register, then start the actions, then deregister, as in: |
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* to control a one-shot action serving a variable number of parties. |
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* The typical idiom is for the method setting this up to first |
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* register, then start the actions, then deregister, as in: |
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* |
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* <pre> {@code |
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* void runTasks(List<Runnable> tasks) { |
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* }}</pre> |
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* |
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* |
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* <p>To create a set of tasks using a tree of phasers, |
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* you could use code of the following form, assuming a |
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* Task class with a constructor accepting a phaser that |
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* it registers for upon construction: |
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* <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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* </pre> |
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* |
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* <p><b>Implementation notes</b>: This implementation restricts the |
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* maximum number of parties to 65535. Attempts to register additional |
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* parties result in {@code IllegalStateException}. However, you can and |
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*/ |
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|
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/** |
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* Barrier state representation. Conceptually, a barrier contains |
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* four values: |
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* |
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* * parties -- the number of parties to wait (16 bits) |
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* * unarrived -- the number of parties yet to hit barrier (16 bits) |
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* * phase -- the generation of the barrier (31 bits) |
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* * terminated -- set if barrier is terminated (1 bit) |
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* |
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* However, to efficiently maintain atomicity, these values are |
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* packed into a single (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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* Primary state representation, holding four fields: |
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* |
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* Note: there are some cheats in arrive() that rely on unarrived |
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* count being lowest 16 bits. |
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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 with the otherwise illegal state of having zero |
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* parties and one unarrived parties (encoded as EMPTY below). |
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* |
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* To efficiently maintain atomicity, these values are packed into |
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* a single (atomic) long. Good performance relies on keeping |
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* state decoding and encoding simple, and keeping race windows |
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* short. |
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* |
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* All state updates are performed via CAS except initial |
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* registration of a sub-phaser (i.e., one with a non-null |
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* parent). In this (relatively rare) case, we use built-in |
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* synchronization to lock while first registering with its |
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* parent. |
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* |
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* The phase of a subphaser is allowed to lag that of its |
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* ancestors until it is actually accessed. Method reconcileState |
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* is usually attempted only only when the number of unarrived |
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* parties appears to be zero, which indicates a potential lag in |
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* updating phase after the root advanced. |
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*/ |
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private volatile long state; |
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|
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< |
private static final int ushortMask = 0xffff; |
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private static final int phaseMask = 0x7fffffff; |
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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; // to mask ints |
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private static final long PARTIES_MASK = 0xffff0000L; // to mask longs |
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> |
private static final long TERMINATION_BIT = 1L << 63; |
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> |
|
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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 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 & ushortMask); |
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> |
int counts = (int)s; |
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> |
return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK; |
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} |
278 |
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|
279 |
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private static int partiesOf(long s) { |
280 |
< |
return ((int) s) >>> 16; |
280 |
> |
int counts = (int)s; |
281 |
> |
return (counts == EMPTY) ? 0 : counts >>> PARTIES_SHIFT; |
282 |
|
} |
283 |
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|
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private static int phaseOf(long s) { |
285 |
< |
return (int) (s >>> 32); |
285 |
> |
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); |
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< |
} |
291 |
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|
267 |
< |
private static long stateFor(int phase, int parties, int unarrived) { |
268 |
< |
return ((((long) phase) << 32) | (((long) parties) << 16) | |
269 |
< |
(long) unarrived); |
270 |
< |
} |
271 |
< |
|
272 |
< |
private static long trippedStateFor(int phase, int parties) { |
273 |
< |
long lp = (long) parties; |
274 |
< |
return (((long) phase) << 32) | (lp << 16) | lp; |
275 |
< |
} |
276 |
< |
|
277 |
< |
/** |
278 |
< |
* Returns message string for bad bounds exceptions. |
279 |
< |
*/ |
280 |
< |
private static String badBounds(int parties, int unarrived) { |
281 |
< |
return ("Attempt to set " + unarrived + |
282 |
< |
" unarrived of " + parties + " parties"); |
289 |
> |
int counts = (int)s; |
290 |
> |
return (counts == EMPTY) ? 0 : |
291 |
> |
(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK); |
292 |
|
} |
293 |
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|
294 |
|
/** |
297 |
|
private final Phaser parent; |
298 |
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|
299 |
|
/** |
300 |
< |
* The root of phaser tree. Equals this if not in a tree. Used to |
292 |
< |
* support faster state push-down. |
300 |
> |
* The root of phaser tree. Equals this if not in a tree. |
301 |
|
*/ |
302 |
|
private final Phaser root; |
303 |
|
|
296 |
– |
// Wait queues |
297 |
– |
|
304 |
|
/** |
305 |
|
* Heads of Treiber stacks for waiting threads. To eliminate |
306 |
< |
* contention while releasing some threads while adding others, we |
306 |
> |
* contention when releasing some threads while adding others, we |
307 |
|
* use two of them, alternating across even and odd phases. |
308 |
+ |
* Subphasers share queues with root to speed up releases. |
309 |
|
*/ |
310 |
< |
private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>(); |
311 |
< |
private final AtomicReference<QNode> oddQ = new AtomicReference<QNode>(); |
310 |
> |
private final AtomicReference<QNode> evenQ; |
311 |
> |
private final AtomicReference<QNode> oddQ; |
312 |
|
|
313 |
|
private AtomicReference<QNode> queueFor(int phase) { |
314 |
|
return ((phase & 1) == 0) ? evenQ : oddQ; |
315 |
|
} |
316 |
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|
317 |
|
/** |
318 |
< |
* Returns current state, first resolving lagged propagation from |
312 |
< |
* root if necessary. |
318 |
> |
* Returns message string for bounds exceptions on arrival. |
319 |
|
*/ |
320 |
< |
private long getReconciledState() { |
321 |
< |
return (parent == null) ? state : reconcileState(); |
320 |
> |
private String badArrive(long s) { |
321 |
> |
return "Attempted arrival of unregistered party for " + |
322 |
> |
stateToString(s); |
323 |
|
} |
324 |
|
|
325 |
|
/** |
326 |
< |
* Recursively resolves state. |
326 |
> |
* Returns message string for bounds exceptions on registration. |
327 |
|
*/ |
328 |
< |
private long reconcileState() { |
329 |
< |
Phaser p = parent; |
330 |
< |
long s = state; |
331 |
< |
if (p != null) { |
332 |
< |
while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) { |
333 |
< |
long parentState = p.getReconciledState(); |
334 |
< |
int parentPhase = phaseOf(parentState); |
335 |
< |
int phase = phaseOf(s = state); |
336 |
< |
if (phase != parentPhase) { |
337 |
< |
long next = trippedStateFor(parentPhase, partiesOf(s)); |
338 |
< |
if (casState(s, next)) { |
328 |
> |
private String badRegister(long s) { |
329 |
> |
return "Attempt to register more than " + |
330 |
> |
MAX_PARTIES + " parties for " + stateToString(s); |
331 |
> |
} |
332 |
> |
|
333 |
> |
/** |
334 |
> |
* Main implementation for methods arrive and arriveAndDeregister. |
335 |
> |
* Manually tuned to speed up and minimize race windows for the |
336 |
> |
* common case of just decrementing unarrived field. |
337 |
> |
* |
338 |
> |
* @param deregister false for arrive, true for arriveAndDeregister |
339 |
> |
*/ |
340 |
> |
private int doArrive(boolean deregister) { |
341 |
> |
int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL; |
342 |
> |
long s; |
343 |
> |
int phase; |
344 |
> |
while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0) { |
345 |
> |
int counts = (int)s; |
346 |
> |
int unarrived = counts & UNARRIVED_MASK; |
347 |
> |
if (counts == EMPTY || unarrived == 0) { |
348 |
> |
if (reconcileState() == s) |
349 |
> |
throw new IllegalStateException(badArrive(s)); |
350 |
> |
} |
351 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) { |
352 |
> |
if (unarrived == 1) { |
353 |
> |
long n = s & PARTIES_MASK; // unshifted parties field |
354 |
> |
int u = ((int)n) >>> PARTIES_SHIFT; |
355 |
> |
Phaser par = parent; |
356 |
> |
if (par != null) { |
357 |
> |
par.doArrive(u == 0); |
358 |
> |
reconcileState(); |
359 |
> |
} |
360 |
> |
else { |
361 |
> |
n |= (((long)((phase+1) & MAX_PHASE)) << PHASE_SHIFT); |
362 |
> |
if (onAdvance(phase, u)) |
363 |
> |
n |= TERMINATION_BIT; |
364 |
> |
else if (u == 0) |
365 |
> |
n |= EMPTY; // reset to unregistered |
366 |
> |
else |
367 |
> |
n |= (long)u; // reset unarr to parties |
368 |
> |
// assert state == s || isTerminated(); |
369 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, s, n); |
370 |
|
releaseWaiters(phase); |
333 |
– |
s = next; |
371 |
|
} |
372 |
|
} |
373 |
+ |
break; |
374 |
+ |
} |
375 |
+ |
} |
376 |
+ |
return phase; |
377 |
+ |
} |
378 |
+ |
|
379 |
+ |
/** |
380 |
+ |
* Implementation of register, bulkRegister |
381 |
+ |
* |
382 |
+ |
* @param registrations number to add to both parties and |
383 |
+ |
* unarrived fields. Must be greater than zero. |
384 |
+ |
*/ |
385 |
+ |
private int doRegister(int registrations) { |
386 |
+ |
// adjustment to state |
387 |
+ |
long adj = ((long)registrations << PARTIES_SHIFT) | registrations; |
388 |
+ |
Phaser par = parent; |
389 |
+ |
int phase; |
390 |
+ |
for (;;) { |
391 |
+ |
long s = state; |
392 |
+ |
int counts = (int)s; |
393 |
+ |
int parties = counts >>> PARTIES_SHIFT; |
394 |
+ |
int unarrived = counts & UNARRIVED_MASK; |
395 |
+ |
if (registrations > MAX_PARTIES - parties) |
396 |
+ |
throw new IllegalStateException(badRegister(s)); |
397 |
+ |
else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0) |
398 |
+ |
break; |
399 |
+ |
else if (counts != EMPTY) { // not 1st registration |
400 |
+ |
if (par == null || reconcileState() == s) { |
401 |
+ |
if (unarrived == 0) // wait out advance |
402 |
+ |
root.internalAwaitAdvance(phase, null); |
403 |
+ |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, |
404 |
+ |
s, s + adj)) |
405 |
+ |
break; |
406 |
+ |
} |
407 |
+ |
} |
408 |
+ |
else if (par == null) { // 1st root registration |
409 |
+ |
long next = (((long) phase) << PHASE_SHIFT) | adj; |
410 |
+ |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
411 |
+ |
break; |
412 |
+ |
} |
413 |
+ |
else { |
414 |
+ |
synchronized (this) { // 1st sub registration |
415 |
+ |
if (state == s) { // recheck under lock |
416 |
+ |
par.doRegister(1); |
417 |
+ |
do { // force current phase |
418 |
+ |
phase = (int)(root.state >>> PHASE_SHIFT); |
419 |
+ |
// assert phase < 0 || (int)state == EMPTY; |
420 |
+ |
} while (!UNSAFE.compareAndSwapLong |
421 |
+ |
(this, stateOffset, state, |
422 |
+ |
(((long) phase) << PHASE_SHIFT) | adj)); |
423 |
+ |
break; |
424 |
+ |
} |
425 |
+ |
} |
426 |
+ |
} |
427 |
+ |
} |
428 |
+ |
return phase; |
429 |
+ |
} |
430 |
+ |
|
431 |
+ |
/** |
432 |
+ |
* Resolves lagged phase propagation from root if necessary. |
433 |
+ |
*/ |
434 |
+ |
private long reconcileState() { |
435 |
+ |
Phaser rt = root; |
436 |
+ |
long s = state; |
437 |
+ |
if (rt != this) { |
438 |
+ |
int phase; |
439 |
+ |
while ((phase = (int)(rt.state >>> PHASE_SHIFT)) != |
440 |
+ |
(int)(s >>> PHASE_SHIFT)) { |
441 |
+ |
// assert phase < 0 || unarrivedOf(s) == 0 |
442 |
+ |
long t; // to reread s |
443 |
+ |
long p = s & PARTIES_MASK; // unshifted parties field |
444 |
+ |
long n = (((long) phase) << PHASE_SHIFT) | p; |
445 |
+ |
if (phase >= 0) { |
446 |
+ |
if (p == 0L) |
447 |
+ |
n |= EMPTY; // reset to empty |
448 |
+ |
else |
449 |
+ |
n |= p >>> PARTIES_SHIFT; // set unarr to parties |
450 |
+ |
} |
451 |
+ |
if ((t = state) == s && |
452 |
+ |
UNSAFE.compareAndSwapLong(this, stateOffset, s, s = n)) |
453 |
+ |
break; |
454 |
+ |
s = t; |
455 |
|
} |
456 |
|
} |
457 |
|
return s; |
458 |
|
} |
459 |
|
|
460 |
|
/** |
461 |
< |
* Creates a new phaser without any initially registered parties, |
462 |
< |
* initial phase number 0, and no parent. Any thread using this |
461 |
> |
* Creates a new phaser with no initially registered parties, no |
462 |
> |
* parent, and initial phase number 0. Any thread using this |
463 |
|
* phaser will need to first register for it. |
464 |
|
*/ |
465 |
|
public Phaser() { |
466 |
< |
this(null); |
466 |
> |
this(null, 0); |
467 |
|
} |
468 |
|
|
469 |
|
/** |
470 |
< |
* Creates a new phaser with the given numbers of registered |
471 |
< |
* unarrived parties, initial phase number 0, and no parent. |
470 |
> |
* Creates a new phaser with the given number of registered |
471 |
> |
* unarrived parties, no parent, and initial phase number 0. |
472 |
|
* |
473 |
< |
* @param parties the number of parties required to trip barrier |
473 |
> |
* @param parties the number of parties required to advance to the |
474 |
> |
* next phase |
475 |
|
* @throws IllegalArgumentException if parties less than zero |
476 |
|
* or greater than the maximum number of parties supported |
477 |
|
*/ |
480 |
|
} |
481 |
|
|
482 |
|
/** |
483 |
< |
* Creates a new phaser with the given parent, without any |
364 |
< |
* initially registered parties. If parent is non-null this phaser |
365 |
< |
* is registered with the parent and its initial phase number is |
366 |
< |
* the same as that of parent phaser. |
483 |
> |
* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}. |
484 |
|
* |
485 |
|
* @param parent the parent phaser |
486 |
|
*/ |
487 |
|
public Phaser(Phaser parent) { |
488 |
< |
int phase = 0; |
372 |
< |
this.parent = parent; |
373 |
< |
if (parent != null) { |
374 |
< |
this.root = parent.root; |
375 |
< |
phase = parent.register(); |
376 |
< |
} |
377 |
< |
else |
378 |
< |
this.root = this; |
379 |
< |
this.state = trippedStateFor(phase, 0); |
488 |
> |
this(parent, 0); |
489 |
|
} |
490 |
|
|
491 |
|
/** |
492 |
< |
* Creates a new phaser with the given parent and numbers of |
493 |
< |
* registered unarrived parties. If parent is non-null, this phaser |
494 |
< |
* is registered with the parent and its initial phase number is |
495 |
< |
* the same as that of parent phaser. |
492 |
> |
* Creates a new phaser with the given parent and number of |
493 |
> |
* registered unarrived parties. Registration and deregistration |
494 |
> |
* of this child phaser with its parent are managed automatically. |
495 |
> |
* If the given parent is non-null, whenever this child phaser has |
496 |
> |
* any registered parties (as established in this constructor, |
497 |
> |
* {@link #register}, or {@link #bulkRegister}), this child phaser |
498 |
> |
* is registered with its parent. Whenever the number of |
499 |
> |
* registered parties becomes zero as the result of an invocation |
500 |
> |
* of {@link #arriveAndDeregister}, this child phaser is |
501 |
> |
* deregistered from its parent. |
502 |
|
* |
503 |
|
* @param parent the parent phaser |
504 |
< |
* @param parties the number of parties required to trip barrier |
504 |
> |
* @param parties the number of parties required to advance to the |
505 |
> |
* next phase |
506 |
|
* @throws IllegalArgumentException if parties less than zero |
507 |
|
* or greater than the maximum number of parties supported |
508 |
|
*/ |
509 |
|
public Phaser(Phaser parent, int parties) { |
510 |
< |
if (parties < 0 || parties > ushortMask) |
510 |
> |
if (parties >>> PARTIES_SHIFT != 0) |
511 |
|
throw new IllegalArgumentException("Illegal number of parties"); |
512 |
|
int phase = 0; |
513 |
|
this.parent = parent; |
514 |
|
if (parent != null) { |
515 |
< |
this.root = parent.root; |
516 |
< |
phase = parent.register(); |
515 |
> |
Phaser r = parent.root; |
516 |
> |
this.root = r; |
517 |
> |
this.evenQ = r.evenQ; |
518 |
> |
this.oddQ = r.oddQ; |
519 |
> |
if (parties != 0) |
520 |
> |
phase = parent.doRegister(1); |
521 |
|
} |
522 |
< |
else |
522 |
> |
else { |
523 |
|
this.root = this; |
524 |
< |
this.state = trippedStateFor(phase, parties); |
524 |
> |
this.evenQ = new AtomicReference<QNode>(); |
525 |
> |
this.oddQ = new AtomicReference<QNode>(); |
526 |
> |
} |
527 |
> |
this.state = (parties == 0) ? ((long) EMPTY) : |
528 |
> |
((((long) phase) << PHASE_SHIFT) | |
529 |
> |
(((long) parties) << PARTIES_SHIFT) | |
530 |
> |
((long) parties)); |
531 |
|
} |
532 |
|
|
533 |
|
/** |
534 |
< |
* Adds a new unarrived party to this phaser. |
534 |
> |
* Adds a new unarrived party to this phaser. If an ongoing |
535 |
> |
* invocation of {@link #onAdvance} is in progress, this method |
536 |
> |
* may await its completion before returning. If this phaser has |
537 |
> |
* a parent, and this phaser previously had no registered parties, |
538 |
> |
* this phaser is also registered with its parent. |
539 |
|
* |
540 |
|
* @return the arrival phase number to which this registration applied |
541 |
|
* @throws IllegalStateException if attempting to register more |
547 |
|
|
548 |
|
/** |
549 |
|
* Adds the given number of new unarrived parties to this phaser. |
550 |
+ |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
551 |
+ |
* this method may await its completion before returning. If this |
552 |
+ |
* phaser has a parent, and the given number of parities is |
553 |
+ |
* greater than zero, and this phaser previously had no registered |
554 |
+ |
* parties, this phaser is also registered with its parent. |
555 |
|
* |
556 |
< |
* @param parties the number of parties required to trip barrier |
556 |
> |
* @param parties the number of additional parties required to |
557 |
> |
* advance to the next phase |
558 |
|
* @return the arrival phase number to which this registration applied |
559 |
|
* @throws IllegalStateException if attempting to register more |
560 |
|
* than the maximum supported number of parties |
561 |
+ |
* @throws IllegalArgumentException if {@code parties < 0} |
562 |
|
*/ |
563 |
|
public int bulkRegister(int parties) { |
564 |
|
if (parties < 0) |
569 |
|
} |
570 |
|
|
571 |
|
/** |
572 |
< |
* Shared code for register, bulkRegister |
573 |
< |
*/ |
574 |
< |
private int doRegister(int registrations) { |
575 |
< |
int phase; |
576 |
< |
for (;;) { |
577 |
< |
long s = getReconciledState(); |
441 |
< |
phase = phaseOf(s); |
442 |
< |
int unarrived = unarrivedOf(s) + registrations; |
443 |
< |
int parties = partiesOf(s) + registrations; |
444 |
< |
if (phase < 0) |
445 |
< |
break; |
446 |
< |
if (parties > ushortMask || unarrived > ushortMask) |
447 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
448 |
< |
if (phase == phaseOf(root.state) && |
449 |
< |
casState(s, stateFor(phase, parties, unarrived))) |
450 |
< |
break; |
451 |
< |
} |
452 |
< |
return phase; |
453 |
< |
} |
454 |
< |
|
455 |
< |
/** |
456 |
< |
* Arrives at the barrier, but does not wait for others. (You can |
457 |
< |
* in turn wait for others via {@link #awaitAdvance}). It is an |
458 |
< |
* unenforced usage error for an unregistered party to invoke this |
459 |
< |
* method. |
572 |
> |
* Arrives at this phaser, without waiting for others to arrive. |
573 |
> |
* |
574 |
> |
* <p>It is a usage error for an unregistered party to invoke this |
575 |
> |
* method. However, this error may result in an {@code |
576 |
> |
* IllegalStateException} only upon some subsequent operation on |
577 |
> |
* this phaser, if ever. |
578 |
|
* |
579 |
|
* @return the arrival phase number, or a negative value if terminated |
580 |
|
* @throws IllegalStateException if not terminated and the number |
581 |
|
* of unarrived parties would become negative |
582 |
|
*/ |
583 |
|
public int arrive() { |
584 |
< |
int phase; |
467 |
< |
for (;;) { |
468 |
< |
long s = state; |
469 |
< |
phase = phaseOf(s); |
470 |
< |
if (phase < 0) |
471 |
< |
break; |
472 |
< |
int parties = partiesOf(s); |
473 |
< |
int unarrived = unarrivedOf(s) - 1; |
474 |
< |
if (unarrived > 0) { // Not the last arrival |
475 |
< |
if (casState(s, s - 1)) // s-1 adds one arrival |
476 |
< |
break; |
477 |
< |
} |
478 |
< |
else if (unarrived == 0) { // the last arrival |
479 |
< |
Phaser par = parent; |
480 |
< |
if (par == null) { // directly trip |
481 |
< |
if (casState |
482 |
< |
(s, |
483 |
< |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
484 |
< |
((phase + 1) & phaseMask), parties))) { |
485 |
< |
releaseWaiters(phase); |
486 |
< |
break; |
487 |
< |
} |
488 |
< |
} |
489 |
< |
else { // cascade to parent |
490 |
< |
if (casState(s, s - 1)) { // zeroes unarrived |
491 |
< |
par.arrive(); |
492 |
< |
reconcileState(); |
493 |
< |
break; |
494 |
< |
} |
495 |
< |
} |
496 |
< |
} |
497 |
< |
else if (phase != phaseOf(root.state)) // or if unreconciled |
498 |
< |
reconcileState(); |
499 |
< |
else |
500 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
501 |
< |
} |
502 |
< |
return phase; |
584 |
> |
return doArrive(false); |
585 |
|
} |
586 |
|
|
587 |
|
/** |
588 |
< |
* Arrives at the barrier and deregisters from it without waiting |
589 |
< |
* for others. Deregistration reduces the number of parties |
590 |
< |
* required to trip the barrier in future phases. If this phaser |
588 |
> |
* Arrives at this phaser and deregisters from it without waiting |
589 |
> |
* for others to arrive. Deregistration reduces the number of |
590 |
> |
* parties required to advance in future phases. If this phaser |
591 |
|
* has a parent, and deregistration causes this phaser to have |
592 |
< |
* zero parties, this phaser also arrives at and is deregistered |
593 |
< |
* from its parent. It is an unenforced usage error for an |
594 |
< |
* unregistered party to invoke this method. |
592 |
> |
* zero parties, this phaser is also deregistered from its parent. |
593 |
> |
* |
594 |
> |
* <p>It is a usage error for an unregistered party to invoke this |
595 |
> |
* method. However, this error may result in an {@code |
596 |
> |
* IllegalStateException} only upon some subsequent operation on |
597 |
> |
* this phaser, if ever. |
598 |
|
* |
599 |
|
* @return the arrival phase number, or a negative value if terminated |
600 |
|
* @throws IllegalStateException if not terminated and the number |
601 |
|
* of registered or unarrived parties would become negative |
602 |
|
*/ |
603 |
|
public int arriveAndDeregister() { |
604 |
< |
// similar code to arrive, but too different to merge |
520 |
< |
Phaser par = parent; |
521 |
< |
int phase; |
522 |
< |
for (;;) { |
523 |
< |
long s = state; |
524 |
< |
phase = phaseOf(s); |
525 |
< |
if (phase < 0) |
526 |
< |
break; |
527 |
< |
int parties = partiesOf(s) - 1; |
528 |
< |
int unarrived = unarrivedOf(s) - 1; |
529 |
< |
if (parties >= 0) { |
530 |
< |
if (unarrived > 0 || (unarrived == 0 && par != null)) { |
531 |
< |
if (casState |
532 |
< |
(s, |
533 |
< |
stateFor(phase, parties, unarrived))) { |
534 |
< |
if (unarrived == 0) { |
535 |
< |
par.arriveAndDeregister(); |
536 |
< |
reconcileState(); |
537 |
< |
} |
538 |
< |
break; |
539 |
< |
} |
540 |
< |
continue; |
541 |
< |
} |
542 |
< |
if (unarrived == 0) { |
543 |
< |
if (casState |
544 |
< |
(s, |
545 |
< |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
546 |
< |
((phase + 1) & phaseMask), parties))) { |
547 |
< |
releaseWaiters(phase); |
548 |
< |
break; |
549 |
< |
} |
550 |
< |
continue; |
551 |
< |
} |
552 |
< |
if (par != null && phase != phaseOf(root.state)) { |
553 |
< |
reconcileState(); |
554 |
< |
continue; |
555 |
< |
} |
556 |
< |
} |
557 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
558 |
< |
} |
559 |
< |
return phase; |
604 |
> |
return doArrive(true); |
605 |
|
} |
606 |
|
|
607 |
|
/** |
608 |
< |
* Arrives at the barrier and awaits others. Equivalent in effect |
608 |
> |
* Arrives at this phaser and awaits others. Equivalent in effect |
609 |
|
* to {@code awaitAdvance(arrive())}. If you need to await with |
610 |
|
* interruption or timeout, you can arrange this with an analogous |
611 |
< |
* construction using one of the other forms of the awaitAdvance |
612 |
< |
* method. If instead you need to deregister upon arrival use |
613 |
< |
* {@code arriveAndDeregister}. It is an unenforced usage error |
614 |
< |
* for an unregistered party to invoke this method. |
611 |
> |
* construction using one of the other forms of the {@code |
612 |
> |
* awaitAdvance} method. If instead you need to deregister upon |
613 |
> |
* arrival, use {@code awaitAdvance(arriveAndDeregister())}. |
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 number if terminated |
621 |
|
* @throws IllegalStateException if not terminated and the number |
622 |
|
* of unarrived parties would become negative |
623 |
|
*/ |
624 |
|
public int arriveAndAwaitAdvance() { |
625 |
< |
return awaitAdvance(arrive()); |
625 |
> |
return awaitAdvance(doArrive(false)); |
626 |
|
} |
627 |
|
|
628 |
|
/** |
629 |
< |
* Awaits the phase of the barrier to advance from the given phase |
630 |
< |
* value, returning immediately if the current phase of the |
631 |
< |
* barrier is not equal to the given phase value or this barrier |
583 |
< |
* is terminated. It is an unenforced usage error for an |
584 |
< |
* unregistered party to invoke this method. |
629 |
> |
* Awaits the phase of this phaser to advance from the given phase |
630 |
> |
* value, returning immediately if the current phase is not equal |
631 |
> |
* to the given phase value or this phaser is terminated. |
632 |
|
* |
633 |
|
* @param phase an arrival phase number, or negative value if |
634 |
|
* terminated; this argument is normally the value returned by a |
635 |
< |
* previous call to {@code arrive} or its variants |
635 |
> |
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
636 |
|
* @return the next arrival phase number, or a negative value |
637 |
|
* if terminated or argument is negative |
638 |
|
*/ |
639 |
|
public int awaitAdvance(int phase) { |
640 |
+ |
Phaser rt; |
641 |
+ |
int p = (int)(state >>> PHASE_SHIFT); |
642 |
|
if (phase < 0) |
643 |
|
return phase; |
644 |
< |
long s = getReconciledState(); |
645 |
< |
int p = phaseOf(s); |
646 |
< |
if (p != phase) |
647 |
< |
return p; |
648 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
649 |
< |
parent.awaitAdvance(phase); |
601 |
< |
// Fall here even if parent waited, to reconcile and help release |
602 |
< |
return untimedWait(phase); |
644 |
> |
if (p == phase) { |
645 |
> |
if ((p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) |
646 |
> |
return rt.internalAwaitAdvance(phase, null); |
647 |
> |
reconcileState(); |
648 |
> |
} |
649 |
> |
return p; |
650 |
|
} |
651 |
|
|
652 |
|
/** |
653 |
< |
* Awaits the phase of the barrier to advance from the given phase |
653 |
> |
* Awaits the phase of this phaser to advance from the given phase |
654 |
|
* value, throwing {@code InterruptedException} if interrupted |
655 |
< |
* while waiting, or returning immediately if the current phase of |
656 |
< |
* the barrier is not equal to the given phase value or this |
657 |
< |
* barrier is terminated. It is an unenforced usage error for an |
611 |
< |
* unregistered party to invoke this method. |
655 |
> |
* while waiting, or returning immediately if the current phase is |
656 |
> |
* not equal to the given phase value or this phaser is |
657 |
> |
* terminated. |
658 |
|
* |
659 |
|
* @param phase an arrival phase number, or negative value if |
660 |
|
* terminated; this argument is normally the value returned by a |
661 |
< |
* previous call to {@code arrive} or its variants |
661 |
> |
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
662 |
|
* @return the next arrival phase number, or a negative value |
663 |
|
* if terminated or argument is negative |
664 |
|
* @throws InterruptedException if thread interrupted while waiting |
665 |
|
*/ |
666 |
|
public int awaitAdvanceInterruptibly(int phase) |
667 |
|
throws InterruptedException { |
668 |
+ |
Phaser rt; |
669 |
+ |
int p = (int)(state >>> PHASE_SHIFT); |
670 |
|
if (phase < 0) |
671 |
|
return phase; |
672 |
< |
long s = getReconciledState(); |
673 |
< |
int p = phaseOf(s); |
674 |
< |
if (p != phase) |
675 |
< |
return p; |
676 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
677 |
< |
parent.awaitAdvanceInterruptibly(phase); |
678 |
< |
return interruptibleWait(phase); |
672 |
> |
if (p == phase) { |
673 |
> |
if ((p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) { |
674 |
> |
QNode node = new QNode(this, phase, true, false, 0L); |
675 |
> |
p = rt.internalAwaitAdvance(phase, node); |
676 |
> |
if (node.wasInterrupted) |
677 |
> |
throw new InterruptedException(); |
678 |
> |
} |
679 |
> |
else |
680 |
> |
reconcileState(); |
681 |
> |
} |
682 |
> |
return p; |
683 |
|
} |
684 |
|
|
685 |
|
/** |
686 |
< |
* Awaits the phase of the barrier to advance from the given phase |
686 |
> |
* Awaits the phase of this phaser to advance from the given phase |
687 |
|
* value or the given timeout to elapse, throwing {@code |
688 |
|
* InterruptedException} if interrupted while waiting, or |
689 |
< |
* returning immediately if the current phase of the barrier is |
690 |
< |
* not equal to the given phase value or this barrier is |
639 |
< |
* terminated. It is an unenforced usage error for an |
640 |
< |
* unregistered party to invoke this method. |
689 |
> |
* returning immediately if the current phase is not equal to the |
690 |
> |
* given phase value or this phaser is terminated. |
691 |
|
* |
692 |
|
* @param phase an arrival phase number, or negative value if |
693 |
|
* terminated; this argument is normally the value returned by a |
694 |
< |
* previous call to {@code arrive} or its variants |
694 |
> |
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
695 |
|
* @param timeout how long to wait before giving up, in units of |
696 |
|
* {@code unit} |
697 |
|
* @param unit a {@code TimeUnit} determining how to interpret the |
704 |
|
public int awaitAdvanceInterruptibly(int phase, |
705 |
|
long timeout, TimeUnit unit) |
706 |
|
throws InterruptedException, TimeoutException { |
707 |
+ |
long nanos = unit.toNanos(timeout); |
708 |
+ |
Phaser rt; |
709 |
+ |
int p = (int)(state >>> PHASE_SHIFT); |
710 |
|
if (phase < 0) |
711 |
|
return phase; |
712 |
< |
long s = getReconciledState(); |
713 |
< |
int p = phaseOf(s); |
714 |
< |
if (p != phase) |
715 |
< |
return p; |
716 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
717 |
< |
parent.awaitAdvanceInterruptibly(phase, timeout, unit); |
718 |
< |
return timedWait(phase, unit.toNanos(timeout)); |
712 |
> |
if (p == phase) { |
713 |
> |
if ((p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) { |
714 |
> |
QNode node = new QNode(this, phase, true, true, nanos); |
715 |
> |
p = rt.internalAwaitAdvance(phase, node); |
716 |
> |
if (node.wasInterrupted) |
717 |
> |
throw new InterruptedException(); |
718 |
> |
else if (p == phase) |
719 |
> |
throw new TimeoutException(); |
720 |
> |
} |
721 |
> |
else |
722 |
> |
reconcileState(); |
723 |
> |
} |
724 |
> |
return p; |
725 |
|
} |
726 |
|
|
727 |
|
/** |
728 |
< |
* Forces this barrier to enter termination state. Counts of |
729 |
< |
* arrived and registered parties are unaffected. If this phaser |
730 |
< |
* has a parent, it too is terminated. This method may be useful |
731 |
< |
* for coordinating recovery after one or more tasks encounter |
728 |
> |
* Forces this phaser to enter termination state. Counts of |
729 |
> |
* registered parties are unaffected. If this phaser is a member |
730 |
> |
* of a tiered set of phasers, then all of the phasers in the set |
731 |
> |
* are terminated. If this phaser is already terminated, this |
732 |
> |
* method has no effect. This method may be useful for |
733 |
> |
* coordinating recovery after one or more tasks encounter |
734 |
|
* unexpected exceptions. |
735 |
|
*/ |
736 |
|
public void forceTermination() { |
737 |
< |
for (;;) { |
738 |
< |
long s = getReconciledState(); |
739 |
< |
int phase = phaseOf(s); |
740 |
< |
int parties = partiesOf(s); |
741 |
< |
int unarrived = unarrivedOf(s); |
742 |
< |
if (phase < 0 || |
743 |
< |
casState(s, stateFor(-1, parties, unarrived))) { |
683 |
< |
releaseWaiters(0); |
737 |
> |
// Only need to change root state |
738 |
> |
final Phaser root = this.root; |
739 |
> |
long s; |
740 |
> |
while ((s = root.state) >= 0) { |
741 |
> |
long next = (s & ~(long)(MAX_PARTIES)) | TERMINATION_BIT; |
742 |
> |
if (UNSAFE.compareAndSwapLong(root, stateOffset, s, next)) { |
743 |
> |
releaseWaiters(0); // signal all threads |
744 |
|
releaseWaiters(1); |
685 |
– |
if (parent != null) |
686 |
– |
parent.forceTermination(); |
745 |
|
return; |
746 |
|
} |
747 |
|
} |
750 |
|
/** |
751 |
|
* Returns the current phase number. The maximum phase number is |
752 |
|
* {@code Integer.MAX_VALUE}, after which it restarts at |
753 |
< |
* zero. Upon termination, the phase number is negative. |
753 |
> |
* zero. Upon termination, the phase number is negative, |
754 |
> |
* in which case the prevailing phase prior to termination |
755 |
> |
* may be obtained via {@code getPhase() + Integer.MIN_VALUE}. |
756 |
|
* |
757 |
|
* @return the phase number, or a negative value if terminated |
758 |
|
*/ |
759 |
|
public final int getPhase() { |
760 |
< |
return phaseOf(getReconciledState()); |
760 |
> |
return (int)(root.state >>> PHASE_SHIFT); |
761 |
|
} |
762 |
|
|
763 |
|
/** |
764 |
< |
* Returns the number of parties registered at this barrier. |
764 |
> |
* Returns the number of parties registered at this phaser. |
765 |
|
* |
766 |
|
* @return the number of parties |
767 |
|
*/ |
771 |
|
|
772 |
|
/** |
773 |
|
* Returns the number of registered parties that have arrived at |
774 |
< |
* the current phase of this barrier. |
774 |
> |
* the current phase of this phaser. |
775 |
|
* |
776 |
|
* @return the number of arrived parties |
777 |
|
*/ |
778 |
|
public int getArrivedParties() { |
779 |
< |
return arrivedOf(state); |
779 |
> |
return arrivedOf(reconcileState()); |
780 |
|
} |
781 |
|
|
782 |
|
/** |
783 |
|
* Returns the number of registered parties that have not yet |
784 |
< |
* arrived at the current phase of this barrier. |
784 |
> |
* arrived at the current phase of this phaser. |
785 |
|
* |
786 |
|
* @return the number of unarrived parties |
787 |
|
*/ |
788 |
|
public int getUnarrivedParties() { |
789 |
< |
return unarrivedOf(state); |
789 |
> |
return unarrivedOf(reconcileState()); |
790 |
|
} |
791 |
|
|
792 |
|
/** |
809 |
|
} |
810 |
|
|
811 |
|
/** |
812 |
< |
* Returns {@code true} if this barrier has been terminated. |
812 |
> |
* Returns {@code true} if this phaser has been terminated. |
813 |
|
* |
814 |
< |
* @return {@code true} if this barrier has been terminated |
814 |
> |
* @return {@code true} if this phaser has been terminated |
815 |
|
*/ |
816 |
|
public boolean isTerminated() { |
817 |
< |
return getPhase() < 0; |
817 |
> |
return root.state < 0L; |
818 |
|
} |
819 |
|
|
820 |
|
/** |
821 |
|
* Overridable method to perform an action upon impending phase |
822 |
|
* advance, and to control termination. This method is invoked |
823 |
< |
* upon arrival of the party tripping the barrier (when all other |
823 |
> |
* upon arrival of the party advancing this phaser (when all other |
824 |
|
* waiting parties are dormant). If this method returns {@code |
825 |
< |
* true}, then, rather than advance the phase number, this barrier |
826 |
< |
* will be set to a final termination state, and subsequent calls |
827 |
< |
* to {@link #isTerminated} will return true. Any (unchecked) |
828 |
< |
* Exception or Error thrown by an invocation of this method is |
829 |
< |
* propagated to the party attempting to trip the barrier, in |
830 |
< |
* which case no advance occurs. |
825 |
> |
* true}, this phaser will be set to a final termination state |
826 |
> |
* upon advance, and subsequent calls to {@link #isTerminated} |
827 |
> |
* will return true. Any (unchecked) Exception or Error thrown by |
828 |
> |
* an invocation of this method is propagated to the party |
829 |
> |
* attempting to advance this phaser, in which case no advance |
830 |
> |
* occurs. |
831 |
|
* |
832 |
|
* <p>The arguments to this method provide the state of the phaser |
833 |
< |
* prevailing for the current transition. (When called from within |
834 |
< |
* an implementation of {@code onAdvance} the values returned by |
835 |
< |
* methods such as {@code getPhase} may or may not reliably |
836 |
< |
* indicate the state to which this transition applies.) |
837 |
< |
* |
838 |
< |
* <p>The default version returns {@code true} when the number of |
839 |
< |
* registered parties is zero. Normally, overrides that arrange |
840 |
< |
* termination for other reasons should also preserve this |
841 |
< |
* property. |
842 |
< |
* |
843 |
< |
* <p>You may override this method to perform an action with side |
844 |
< |
* effects visible to participating tasks, but doing so requires |
845 |
< |
* care: Method {@code onAdvance} may be invoked more than once |
846 |
< |
* per transition. Further, unless all parties register before |
847 |
< |
* any arrive, and all {@link #awaitAdvance} at each phase, then |
848 |
< |
* you cannot ensure lack of interference from other parties |
849 |
< |
* during the invocation of this method. |
833 |
> |
* prevailing for the current transition. The effects of invoking |
834 |
> |
* arrival, registration, and waiting methods on this phaser from |
835 |
> |
* within {@code onAdvance} are unspecified and should not be |
836 |
> |
* relied on. |
837 |
> |
* |
838 |
> |
* <p>If this phaser is a member of a tiered set of phasers, then |
839 |
> |
* {@code onAdvance} is invoked only for its root phaser on each |
840 |
> |
* advance. |
841 |
> |
* |
842 |
> |
* <p>To support the most common use cases, the default |
843 |
> |
* implementation of this method returns {@code true} when the |
844 |
> |
* number of registered parties has become zero as the result of a |
845 |
> |
* party invoking {@code arriveAndDeregister}. You can disable |
846 |
> |
* this behavior, thus enabling continuation upon future |
847 |
> |
* registrations, by overriding this method to always return |
848 |
> |
* {@code false}: |
849 |
> |
* |
850 |
> |
* <pre> {@code |
851 |
> |
* Phaser phaser = new Phaser() { |
852 |
> |
* protected boolean onAdvance(int phase, int parties) { return false; } |
853 |
> |
* }}</pre> |
854 |
|
* |
855 |
< |
* @param phase the phase number on entering the barrier |
855 |
> |
* @param phase the current phase number on entry to this method, |
856 |
> |
* before this phaser is advanced |
857 |
|
* @param registeredParties the current number of registered parties |
858 |
< |
* @return {@code true} if this barrier should terminate |
858 |
> |
* @return {@code true} if this phaser should terminate |
859 |
|
*/ |
860 |
|
protected boolean onAdvance(int phase, int registeredParties) { |
861 |
< |
return registeredParties <= 0; |
861 |
> |
return registeredParties == 0; |
862 |
|
} |
863 |
|
|
864 |
|
/** |
868 |
|
* followed by the number of registered parties, and {@code |
869 |
|
* "arrived = "} followed by the number of arrived parties. |
870 |
|
* |
871 |
< |
* @return a string identifying this barrier, as well as its state |
871 |
> |
* @return a string identifying this phaser, as well as its state |
872 |
|
*/ |
873 |
|
public String toString() { |
874 |
< |
long s = getReconciledState(); |
874 |
> |
return stateToString(reconcileState()); |
875 |
> |
} |
876 |
> |
|
877 |
> |
/** |
878 |
> |
* Implementation of toString and string-based error messages |
879 |
> |
*/ |
880 |
> |
private String stateToString(long s) { |
881 |
|
return super.toString() + |
882 |
|
"[phase = " + phaseOf(s) + |
883 |
|
" parties = " + partiesOf(s) + |
884 |
|
" arrived = " + arrivedOf(s) + "]"; |
885 |
|
} |
886 |
|
|
887 |
< |
// methods for waiting |
887 |
> |
// Waiting mechanics |
888 |
|
|
889 |
|
/** |
890 |
< |
* Wait nodes for Treiber stack representing wait queue |
890 |
> |
* Removes and signals threads from queue for phase. |
891 |
|
*/ |
892 |
< |
static final class QNode implements ForkJoinPool.ManagedBlocker { |
893 |
< |
final Phaser phaser; |
894 |
< |
final int phase; |
895 |
< |
final long startTime; |
896 |
< |
final long nanos; |
897 |
< |
final boolean timed; |
898 |
< |
final boolean interruptible; |
899 |
< |
volatile boolean wasInterrupted = false; |
900 |
< |
volatile Thread thread; // nulled to cancel wait |
901 |
< |
QNode next; |
902 |
< |
QNode(Phaser phaser, int phase, boolean interruptible, |
832 |
< |
boolean timed, long startTime, long nanos) { |
833 |
< |
this.phaser = phaser; |
834 |
< |
this.phase = phase; |
835 |
< |
this.timed = timed; |
836 |
< |
this.interruptible = interruptible; |
837 |
< |
this.startTime = startTime; |
838 |
< |
this.nanos = nanos; |
839 |
< |
thread = Thread.currentThread(); |
840 |
< |
} |
841 |
< |
public boolean isReleasable() { |
842 |
< |
return (thread == null || |
843 |
< |
phaser.getPhase() != phase || |
844 |
< |
(interruptible && wasInterrupted) || |
845 |
< |
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
846 |
< |
} |
847 |
< |
public boolean block() { |
848 |
< |
if (Thread.interrupted()) { |
849 |
< |
wasInterrupted = true; |
850 |
< |
if (interruptible) |
851 |
< |
return true; |
852 |
< |
} |
853 |
< |
if (!timed) |
854 |
< |
LockSupport.park(this); |
855 |
< |
else { |
856 |
< |
long waitTime = nanos - (System.nanoTime() - startTime); |
857 |
< |
if (waitTime <= 0) |
858 |
< |
return true; |
859 |
< |
LockSupport.parkNanos(this, waitTime); |
860 |
< |
} |
861 |
< |
return isReleasable(); |
862 |
< |
} |
863 |
< |
void signal() { |
864 |
< |
Thread t = thread; |
865 |
< |
if (t != null) { |
866 |
< |
thread = null; |
892 |
> |
private void releaseWaiters(int phase) { |
893 |
> |
QNode q; // first element of queue |
894 |
> |
int p; // its phase |
895 |
> |
Thread t; // its thread |
896 |
> |
// assert phase != phaseOf(root.state); |
897 |
> |
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
898 |
> |
while ((q = head.get()) != null && |
899 |
> |
q.phase != (int)(root.state >>> PHASE_SHIFT)) { |
900 |
> |
if (head.compareAndSet(q, q.next) && |
901 |
> |
(t = q.thread) != null) { |
902 |
> |
q.thread = null; |
903 |
|
LockSupport.unpark(t); |
904 |
|
} |
905 |
|
} |
870 |
– |
boolean doWait() { |
871 |
– |
if (thread != null) { |
872 |
– |
try { |
873 |
– |
ForkJoinPool.managedBlock(this, false); |
874 |
– |
} catch (InterruptedException ie) { |
875 |
– |
} |
876 |
– |
} |
877 |
– |
return wasInterrupted; |
878 |
– |
} |
879 |
– |
|
906 |
|
} |
907 |
|
|
908 |
< |
/** |
909 |
< |
* Removes and signals waiting threads from wait queue. |
884 |
< |
*/ |
885 |
< |
private void releaseWaiters(int phase) { |
886 |
< |
AtomicReference<QNode> head = queueFor(phase); |
887 |
< |
QNode q; |
888 |
< |
while ((q = head.get()) != null) { |
889 |
< |
if (head.compareAndSet(q, q.next)) |
890 |
< |
q.signal(); |
891 |
< |
} |
892 |
< |
} |
908 |
> |
/** The number of CPUs, for spin control */ |
909 |
> |
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
910 |
|
|
911 |
|
/** |
912 |
< |
* Tries to enqueue given node in the appropriate wait queue. |
913 |
< |
* |
914 |
< |
* @return true if successful |
912 |
> |
* The number of times to spin before blocking while waiting for |
913 |
> |
* advance, per arrival while waiting. On multiprocessors, fully |
914 |
> |
* blocking and waking up a large number of threads all at once is |
915 |
> |
* usually a very slow process, so we use rechargeable spins to |
916 |
> |
* avoid it when threads regularly arrive: When a thread in |
917 |
> |
* internalAwaitAdvance notices another arrival before blocking, |
918 |
> |
* and there appear to be enough CPUs available, it spins |
919 |
> |
* SPINS_PER_ARRIVAL more times before blocking. The value trades |
920 |
> |
* off good-citizenship vs big unnecessary slowdowns. |
921 |
|
*/ |
922 |
< |
private boolean tryEnqueue(QNode node) { |
900 |
< |
AtomicReference<QNode> head = queueFor(node.phase); |
901 |
< |
return head.compareAndSet(node.next = head.get(), node); |
902 |
< |
} |
922 |
> |
static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8; |
923 |
|
|
924 |
|
/** |
925 |
< |
* Enqueues node and waits unless aborted or signalled. |
925 |
> |
* Possibly blocks and waits for phase to advance unless aborted. |
926 |
> |
* Call only from root node. |
927 |
|
* |
928 |
+ |
* @param phase current phase |
929 |
+ |
* @param node if non-null, the wait node to track interrupt and timeout; |
930 |
+ |
* if null, denotes noninterruptible wait |
931 |
|
* @return current phase |
932 |
|
*/ |
933 |
< |
private int untimedWait(int phase) { |
934 |
< |
QNode node = null; |
935 |
< |
boolean queued = false; |
936 |
< |
boolean interrupted = false; |
933 |
> |
private int internalAwaitAdvance(int phase, QNode node) { |
934 |
> |
releaseWaiters(phase-1); // ensure old queue clean |
935 |
> |
boolean queued = false; // true when node is enqueued |
936 |
> |
int lastUnarrived = 0; // to increase spins upon change |
937 |
> |
int spins = SPINS_PER_ARRIVAL; |
938 |
> |
long s; |
939 |
|
int p; |
940 |
< |
while ((p = getPhase()) == phase) { |
941 |
< |
if (Thread.interrupted()) |
942 |
< |
interrupted = true; |
943 |
< |
else if (node == null) |
944 |
< |
node = new QNode(this, phase, false, false, 0, 0); |
945 |
< |
else if (!queued) |
946 |
< |
queued = tryEnqueue(node); |
947 |
< |
else |
948 |
< |
interrupted = node.doWait(); |
940 |
> |
while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) { |
941 |
> |
if (node == null) { // spinning in noninterruptible mode |
942 |
> |
int unarrived = (int)s & UNARRIVED_MASK; |
943 |
> |
if (unarrived != lastUnarrived && |
944 |
> |
(lastUnarrived = unarrived) < NCPU) |
945 |
> |
spins += SPINS_PER_ARRIVAL; |
946 |
> |
boolean interrupted = Thread.interrupted(); |
947 |
> |
if (interrupted || --spins < 0) { // need node to record intr |
948 |
> |
node = new QNode(this, phase, false, false, 0L); |
949 |
> |
node.wasInterrupted = interrupted; |
950 |
> |
} |
951 |
> |
} |
952 |
> |
else if (node.isReleasable()) // done or aborted |
953 |
> |
break; |
954 |
> |
else if (!queued) { // push onto queue |
955 |
> |
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
956 |
> |
QNode q = node.next = head.get(); |
957 |
> |
if ((q == null || q.phase == phase) && |
958 |
> |
(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq |
959 |
> |
queued = head.compareAndSet(q, node); |
960 |
> |
} |
961 |
> |
else { |
962 |
> |
try { |
963 |
> |
ForkJoinPool.managedBlock(node); |
964 |
> |
} catch (InterruptedException ie) { |
965 |
> |
node.wasInterrupted = true; |
966 |
> |
} |
967 |
> |
} |
968 |
> |
} |
969 |
> |
|
970 |
> |
if (node != null) { |
971 |
> |
if (node.thread != null) |
972 |
> |
node.thread = null; // avoid need for unpark() |
973 |
> |
if (node.wasInterrupted && !node.interruptible) |
974 |
> |
Thread.currentThread().interrupt(); |
975 |
> |
if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase) |
976 |
> |
return p; // recheck abort |
977 |
|
} |
924 |
– |
if (node != null) |
925 |
– |
node.thread = null; |
978 |
|
releaseWaiters(phase); |
927 |
– |
if (interrupted) |
928 |
– |
Thread.currentThread().interrupt(); |
979 |
|
return p; |
980 |
|
} |
981 |
|
|
982 |
|
/** |
983 |
< |
* Interruptible version |
934 |
< |
* @return current phase |
983 |
> |
* Wait nodes for Treiber stack representing wait queue |
984 |
|
*/ |
985 |
< |
private int interruptibleWait(int phase) throws InterruptedException { |
986 |
< |
QNode node = null; |
987 |
< |
boolean queued = false; |
988 |
< |
boolean interrupted = false; |
989 |
< |
int p; |
990 |
< |
while ((p = getPhase()) == phase && !interrupted) { |
991 |
< |
if (Thread.interrupted()) |
992 |
< |
interrupted = true; |
993 |
< |
else if (node == null) |
994 |
< |
node = new QNode(this, phase, true, false, 0, 0); |
995 |
< |
else if (!queued) |
996 |
< |
queued = tryEnqueue(node); |
997 |
< |
else |
998 |
< |
interrupted = node.doWait(); |
985 |
> |
static final class QNode implements ForkJoinPool.ManagedBlocker { |
986 |
> |
final Phaser phaser; |
987 |
> |
final int phase; |
988 |
> |
final boolean interruptible; |
989 |
> |
final boolean timed; |
990 |
> |
boolean wasInterrupted; |
991 |
> |
long nanos; |
992 |
> |
long lastTime; |
993 |
> |
volatile Thread thread; // nulled to cancel wait |
994 |
> |
QNode next; |
995 |
> |
|
996 |
> |
QNode(Phaser phaser, int phase, boolean interruptible, |
997 |
> |
boolean timed, long nanos) { |
998 |
> |
this.phaser = phaser; |
999 |
> |
this.phase = phase; |
1000 |
> |
this.interruptible = interruptible; |
1001 |
> |
this.nanos = nanos; |
1002 |
> |
this.timed = timed; |
1003 |
> |
this.lastTime = timed ? System.nanoTime() : 0L; |
1004 |
> |
thread = Thread.currentThread(); |
1005 |
|
} |
951 |
– |
if (node != null) |
952 |
– |
node.thread = null; |
953 |
– |
if (p != phase || (p = getPhase()) != phase) |
954 |
– |
releaseWaiters(phase); |
955 |
– |
if (interrupted) |
956 |
– |
throw new InterruptedException(); |
957 |
– |
return p; |
958 |
– |
} |
1006 |
|
|
1007 |
< |
/** |
1008 |
< |
* Timeout version. |
1009 |
< |
* @return current phase |
1010 |
< |
*/ |
1011 |
< |
private int timedWait(int phase, long nanos) |
1012 |
< |
throws InterruptedException, TimeoutException { |
1013 |
< |
long startTime = System.nanoTime(); |
967 |
< |
QNode node = null; |
968 |
< |
boolean queued = false; |
969 |
< |
boolean interrupted = false; |
970 |
< |
int p; |
971 |
< |
while ((p = getPhase()) == phase && !interrupted) { |
1007 |
> |
public boolean isReleasable() { |
1008 |
> |
if (thread == null) |
1009 |
> |
return true; |
1010 |
> |
if (phaser.getPhase() != phase) { |
1011 |
> |
thread = null; |
1012 |
> |
return true; |
1013 |
> |
} |
1014 |
|
if (Thread.interrupted()) |
1015 |
< |
interrupted = true; |
1016 |
< |
else if (nanos - (System.nanoTime() - startTime) <= 0) |
1017 |
< |
break; |
1018 |
< |
else if (node == null) |
1019 |
< |
node = new QNode(this, phase, true, true, startTime, nanos); |
1020 |
< |
else if (!queued) |
1021 |
< |
queued = tryEnqueue(node); |
1022 |
< |
else |
1023 |
< |
interrupted = node.doWait(); |
1015 |
> |
wasInterrupted = true; |
1016 |
> |
if (wasInterrupted && interruptible) { |
1017 |
> |
thread = null; |
1018 |
> |
return true; |
1019 |
> |
} |
1020 |
> |
if (timed) { |
1021 |
> |
if (nanos > 0L) { |
1022 |
> |
long now = System.nanoTime(); |
1023 |
> |
nanos -= now - lastTime; |
1024 |
> |
lastTime = now; |
1025 |
> |
} |
1026 |
> |
if (nanos <= 0L) { |
1027 |
> |
thread = null; |
1028 |
> |
return true; |
1029 |
> |
} |
1030 |
> |
} |
1031 |
> |
return false; |
1032 |
> |
} |
1033 |
> |
|
1034 |
> |
public boolean block() { |
1035 |
> |
if (isReleasable()) |
1036 |
> |
return true; |
1037 |
> |
else if (!timed) |
1038 |
> |
LockSupport.park(this); |
1039 |
> |
else if (nanos > 0) |
1040 |
> |
LockSupport.parkNanos(this, nanos); |
1041 |
> |
return isReleasable(); |
1042 |
|
} |
983 |
– |
if (node != null) |
984 |
– |
node.thread = null; |
985 |
– |
if (p != phase || (p = getPhase()) != phase) |
986 |
– |
releaseWaiters(phase); |
987 |
– |
if (interrupted) |
988 |
– |
throw new InterruptedException(); |
989 |
– |
if (p == phase) |
990 |
– |
throw new TimeoutException(); |
991 |
– |
return p; |
1043 |
|
} |
1044 |
|
|
1045 |
|
// Unsafe mechanics |
1048 |
|
private static final long stateOffset = |
1049 |
|
objectFieldOffset("state", Phaser.class); |
1050 |
|
|
1000 |
– |
private final boolean casState(long cmp, long val) { |
1001 |
– |
return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val); |
1002 |
– |
} |
1003 |
– |
|
1051 |
|
private static long objectFieldOffset(String field, Class<?> klazz) { |
1052 |
|
try { |
1053 |
|
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |