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*/ |
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package jsr166y; |
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import jsr166y.forkjoin.*; |
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|
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import java.util.concurrent.*; |
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import java.util.concurrent.atomic.*; |
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|
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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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/** |
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* A reusable synchronization barrier, similar in functionality to a |
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* {@link java.util.concurrent.CyclicBarrier}, but supporting more |
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* flexible usage. |
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* {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and |
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* {@link java.util.concurrent.CountDownLatch CountDownLatch} |
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* but supporting more flexible usage. |
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* |
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* <ul> |
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* |
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* <li> The number of parties synchronizing on the barrier may vary |
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* over time. A task may register to be a party in a barrier at any |
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* time, and may deregister upon arriving at the barrier. As is the |
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* case with most basic synchronization constructs, registration |
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* and deregistration affect only internal counts; they do not |
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* establish any further internal bookkeeping, so tasks cannot query |
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* whether they are registered. |
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* <li> The number of parties synchronizing on a phaser may vary over |
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* time. A task may register to be a party at any time, and may |
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* deregister upon arriving at the barrier. As is the case with most |
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* basic synchronization constructs, registration and deregistration |
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* affect only internal counts; they do not establish any further |
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* internal bookkeeping, so tasks cannot query whether they are |
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* registered. (However, you can introduce such bookkeeping by |
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* subclassing this class.) |
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* |
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* <li> Each generation has an associated phase value, starting at |
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* zero, and advancing when all parties reach the barrier (wrapping |
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* around to zero after reaching <tt>Integer.MAX_VALUE</tt>). |
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* |
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* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited. |
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* Method <tt>arriveAndAwaitAdvance</tt> has effect analogous to |
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* <tt>CyclicBarrier.await</tt>. However, Phasers separate two |
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* aspects of coordination, that may be invoked independently: |
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* around to zero after reaching {@code Integer.MAX_VALUE}). |
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* |
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* <li> Like a {@code CyclicBarrier}, a Phaser may be repeatedly |
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* awaited. Method {@link #arriveAndAwaitAdvance} has effect |
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* analogous to {@link java.util.concurrent.CyclicBarrier#await |
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* CyclicBarrier.await}. However, phasers separate two aspects of |
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* coordination, that may also be invoked independently: |
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* |
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* <ul> |
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* |
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* <li> Arriving at a barrier. Methods <tt>arrive</tt> and |
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* <tt>arriveAndDeregister</tt> do not block, but return |
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* the phase value on entry to the method. |
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* <li> Arriving at a barrier. Methods {@link #arrive} and |
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* {@link #arriveAndDeregister} do not block, but return |
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* the phase value current upon entry to the method. |
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* |
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* <li> Awaiting others. Method <tt>awaitAdvance</tt> requires an |
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* <li> Awaiting others. Method {@link #awaitAdvance} requires an |
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* argument indicating the entry phase, and returns when the |
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* barrier advances to a new phase. |
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* </ul> |
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* |
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* <li> Barrier actions, performed by the task triggering a phase |
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* advance while others may be waiting, are arranged by overriding |
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* method <tt>onAdvance</tt>, that also controls termination. |
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* method {@link #onAdvance}, that also controls termination. |
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* Overriding this method may be used to similar but more flexible |
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* effect as providing a barrier action to a {@code CyclicBarrier}. |
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* |
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* <li> Phasers may enter a <em>termination</em> state in which all |
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* await actions immediately return, indicating (via a negative phase |
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* value) that execution is complete. Termination is triggered by |
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* executing the overridable <tt>onAdvance</tt> method that is invoked |
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* each time the barrier is tripped. When a Phaser is controlling an |
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* actions immediately return without updating phaser state or waiting |
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* for advance, and indicating (via a negative phase value) that |
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* execution is complete. Termination is triggered by executing the |
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* overridable {@code onAdvance} method that is invoked each time the |
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* barrier is about to be tripped. When a phaser is controlling an |
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* action with a fixed number of iterations, it is often convenient to |
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* override this method to cause termination when the current phase |
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* number reaches a threshold. Method <tt>forceTermination</tt> is |
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* also available to assist recovery actions upon failure. |
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* |
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* <li> Unlike most synchronizers, a Phaser may also be used with |
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* ForkJoinTasks (as well as plain threads). |
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* |
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* <li> By default, <tt>awaitAdvance</tt> continues to wait even if |
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* the current thread is interrupted. And unlike the case in |
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* CyclicBarriers, exceptions encountered while tasks wait |
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* number reaches a threshold. Method {@link #forceTermination} is also |
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* available to abruptly release waiting threads and allow them to |
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* terminate. |
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* |
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* <li> Phasers may be tiered to reduce contention. Phasers with large |
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* numbers of parties that would otherwise experience heavy |
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* synchronization contention costs may instead be arranged in trees. |
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* This will typically greatly increase throughput even though it |
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* incurs somewhat greater per-operation overhead. |
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* |
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* <li> By default, {@code awaitAdvance} continues to wait even if |
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* the waiting thread is interrupted. And unlike the case in |
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* {@code CyclicBarrier}, exceptions encountered while tasks wait |
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* interruptibly or with timeout do not change the state of the |
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* barrier. If necessary, you can perform any associated recovery |
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* within handlers of those exceptions. |
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* within handlers of those exceptions, often after invoking |
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* {@code forceTermination}. |
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* |
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* <li>Phasers ensure lack of starvation when used by ForkJoinTasks. |
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* |
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* </ul> |
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* |
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* <p><b>Sample usage:</b> |
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* <p><b>Sample usages:</b> |
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* |
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* <p>[todo: non-FJ example] |
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* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch} |
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* to control a one-shot action serving a variable number of |
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* parties. The typical idiom is for the method setting this up to |
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* first register, then start the actions, then deregister, as in: |
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* |
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* <pre> {@code |
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* void runTasks(List<Runnable> list) { |
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* final Phaser phaser = new Phaser(1); // "1" to register self |
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* for (Runnable r : list) { |
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* phaser.register(); |
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* new Thread() { |
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* public void run() { |
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* phaser.arriveAndAwaitAdvance(); // await all creation |
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* r.run(); |
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* phaser.arriveAndDeregister(); // signal completion |
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* } |
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* }.start(); |
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* } |
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* |
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* <p> A Phaser may be used to support a style of programming in |
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* which a task waits for others to complete, without otherwise |
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* needing to keep track of which tasks it is waiting for. This is |
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* similar to the "sync" construct in Cilk and "clocks" in X10. |
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* Special constructions based on such barriers are available using |
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* the <tt>LinkedAsyncAction</tt> and <tt>CyclicAction</tt> classes, |
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* but they can be useful in other contexts as well. For a simple |
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* (but not very useful) example, here is a variant of Fibonacci: |
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* |
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* <pre> |
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* class BarrierFibonacci extends RecursiveAction { |
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* int argument, result; |
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* final Phaser parentBarrier; |
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* BarrierFibonacci(int n, Phaser parentBarrier) { |
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* this.argument = n; |
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* this.parentBarrier = parentBarrier; |
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* parentBarrier.register(); |
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* doSomethingOnBehalfOfWorkers(); |
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* phaser.arrive(); // allow threads to start |
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* int p = phaser.arriveAndDeregister(); // deregister self ... |
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* p = phaser.awaitAdvance(p); // ... and await arrival |
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* otherActions(); // do other things while tasks execute |
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* phaser.awaitAdvance(p); // await final completion |
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* }}</pre> |
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* |
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* <p>One way to cause a set of threads to repeatedly perform actions |
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* for a given number of iterations is to override {@code onAdvance}: |
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* |
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* <pre> {@code |
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* void startTasks(List<Runnable> list, final int iterations) { |
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* final Phaser phaser = new Phaser() { |
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* public boolean onAdvance(int phase, int registeredParties) { |
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* return phase >= iterations || registeredParties == 0; |
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* } |
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* }; |
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* phaser.register(); |
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* for (Runnable r : list) { |
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* phaser.register(); |
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* new Thread() { |
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* public void run() { |
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* do { |
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* r.run(); |
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* phaser.arriveAndAwaitAdvance(); |
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* } while(!phaser.isTerminated(); |
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* } |
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* }.start(); |
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* } |
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* protected void compute() { |
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* int n = argument; |
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* if (n <= 1) |
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* result = n; |
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* else { |
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* Phaser childBarrier = new Phaser(1); |
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* BarrierFibonacci f1 = new BarrierFibonacci(n - 1, childBarrier); |
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* BarrierFibonacci f2 = new BarrierFibonacci(n - 2, childBarrier); |
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* f1.fork(); |
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* f2.fork(); |
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* childBarrier.arriveAndAwait(); |
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* result = f1.result + f2.result; |
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* phaser.arriveAndDeregister(); // deregister self, don't wait |
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* }}</pre> |
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* |
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* <p>To create a set of tasks using a tree of phasers, |
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* you could use code of the following form, assuming a |
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* Task class with a constructor accepting a phaser that |
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* it registers for upon construction: |
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* <pre> {@code |
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* void build(Task[] actions, int lo, int hi, Phaser b) { |
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* int step = (hi - lo) / TASKS_PER_PHASER; |
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* if (step > 1) { |
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* int i = lo; |
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* while (i < hi) { |
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* int r = Math.min(i + step, hi); |
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* build(actions, i, r, new Phaser(b)); |
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* i = r; |
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* } |
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* parentBarrier.arriveAndDeregister(); |
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* } else { |
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* for (int i = lo; i < hi; ++i) |
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* actions[i] = new Task(b); |
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* // assumes new Task(b) performs b.register() |
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* } |
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* } |
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* // .. initially called, for n tasks via |
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* build(new Task[n], 0, n, new Phaser());}</pre> |
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* |
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* The best value of {@code TASKS_PER_PHASER} depends mainly on |
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* expected barrier synchronization rates. A value as low as four may |
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* be appropriate for extremely small per-barrier task bodies (thus |
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* high rates), or up to hundreds for extremely large ones. |
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* |
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* </pre> |
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* |
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* <p><b>Implementation notes</b>: This implementation restricts the |
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* maximum number of parties to 65535. Attempts to register |
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* additional parties result in IllegalStateExceptions. |
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* maximum number of parties to 65535. Attempts to register additional |
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* parties result in IllegalStateExceptions. However, you can and |
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* should create tiered phasers to accommodate arbitrarily large sets |
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* of participants. |
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* |
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* @since 1.7 |
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* @author Doug Lea |
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*/ |
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public class Phaser { |
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/* |
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* This class implements an extension of X10 "clocks". Thanks to |
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* Vijay Saraswat for the idea of applying it to ForkJoinTasks, |
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* and to Vivek Sarkar for enhancements to extend functionality. |
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* Vijay Saraswat for the idea, and to Vivek Sarkar for |
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* enhancements to extend functionality. |
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*/ |
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|
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/** |
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* Barrier state representation. Conceptually, a barrier contains |
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* four values: |
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* |
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* |
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* * parties -- the number of parties to wait (16 bits) |
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* * unarrived -- the number of parties yet to hit barrier (16 bits) |
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* * phase -- the generation of the barrier (31 bits) |
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* * terminated -- set if barrier is terminated (1 bit) |
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* |
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* However, to efficiently maintain atomicity, these values are |
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* packed into a single AtomicLong. Termination uses the sign bit |
200 |
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* of 32 bit representation of phase, so phase is set to -1 on |
201 |
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* termination. |
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*/ |
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private final AtomicLong state; |
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|
205 |
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/** |
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* Head of Treiber stack for waiting nonFJ threads. |
199 |
> |
* packed into a single (atomic) long. Termination uses the sign |
200 |
> |
* bit of 32 bit representation of phase, so phase is set to -1 on |
201 |
> |
* termination. Good performance relies on keeping state decoding |
202 |
> |
* and encoding simple, and keeping race windows short. |
203 |
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* |
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* Note: there are some cheats in arrive() that rely on unarrived |
205 |
> |
* count being lowest 16 bits. |
206 |
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*/ |
207 |
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private final AtomicReference<QNode> head = new AtomicReference<QNode>(); |
207 |
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private volatile long state; |
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|
209 |
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private static final int ushortBits = 16; |
210 |
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private static final int ushortMask = (1 << ushortBits) - 1; |
211 |
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private static final int phaseMask = 0x7fffffff; |
210 |
> |
private static final int ushortMask = 0xffff; |
211 |
> |
private static final int phaseMask = 0x7fffffff; |
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|
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private static int unarrivedOf(long s) { |
214 |
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return (int)(s & ushortMask); |
214 |
> |
return (int) (s & ushortMask); |
215 |
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} |
216 |
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|
217 |
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private static int partiesOf(long s) { |
218 |
< |
return (int)(s & (ushortMask << 16)) >>> 16; |
218 |
> |
return ((int) s) >>> 16; |
219 |
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} |
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|
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private static int phaseOf(long s) { |
222 |
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return (int)(s >>> 32); |
222 |
> |
return (int) (s >>> 32); |
223 |
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} |
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|
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private static int arrivedOf(long s) { |
227 |
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} |
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|
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private static long stateFor(int phase, int parties, int unarrived) { |
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< |
return (((long)phase) << 32) | ((parties << 16) | unarrived); |
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> |
return ((((long) phase) << 32) | (((long) parties) << 16) | |
231 |
> |
(long) unarrived); |
232 |
> |
} |
233 |
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|
234 |
> |
private static long trippedStateFor(int phase, int parties) { |
235 |
> |
long lp = (long) parties; |
236 |
> |
return (((long) phase) << 32) | (lp << 16) | lp; |
237 |
> |
} |
238 |
> |
|
239 |
> |
/** |
240 |
> |
* Returns message string for bad bounds exceptions. |
241 |
> |
*/ |
242 |
> |
private static String badBounds(int parties, int unarrived) { |
243 |
> |
return ("Attempt to set " + unarrived + |
244 |
> |
" unarrived of " + parties + " parties"); |
245 |
> |
} |
246 |
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|
247 |
> |
/** |
248 |
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* The parent of this phaser, or null if none |
249 |
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*/ |
250 |
> |
private final Phaser parent; |
251 |
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|
252 |
> |
/** |
253 |
> |
* The root of phaser tree. Equals this if not in a tree. Used to |
254 |
> |
* support faster state push-down. |
255 |
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*/ |
256 |
> |
private final Phaser root; |
257 |
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|
258 |
> |
// Wait queues |
259 |
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|
260 |
> |
/** |
261 |
> |
* Heads of Treiber stacks for waiting threads. To eliminate |
262 |
> |
* contention while releasing some threads while adding others, we |
263 |
> |
* use two of them, alternating across even and odd phases. |
264 |
> |
*/ |
265 |
> |
private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>(); |
266 |
> |
private final AtomicReference<QNode> oddQ = new AtomicReference<QNode>(); |
267 |
> |
|
268 |
> |
private AtomicReference<QNode> queueFor(int phase) { |
269 |
> |
return ((phase & 1) == 0) ? evenQ : oddQ; |
270 |
|
} |
271 |
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|
272 |
< |
private static IllegalStateException badBounds(int parties, int unarrived) { |
273 |
< |
return new IllegalStateException("Attempt to set " + unarrived + |
274 |
< |
" unarrived of " + parties + " parties"); |
272 |
> |
/** |
273 |
> |
* Returns current state, first resolving lagged propagation from |
274 |
> |
* root if necessary. |
275 |
> |
*/ |
276 |
> |
private long getReconciledState() { |
277 |
> |
return (parent == null) ? state : reconcileState(); |
278 |
|
} |
279 |
|
|
280 |
|
/** |
281 |
< |
* Creates a new Phaser without any initially registered parties, |
282 |
< |
* and initial phase number 0. |
281 |
> |
* Recursively resolves state. |
282 |
> |
*/ |
283 |
> |
private long reconcileState() { |
284 |
> |
Phaser p = parent; |
285 |
> |
long s = state; |
286 |
> |
if (p != null) { |
287 |
> |
while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) { |
288 |
> |
long parentState = p.getReconciledState(); |
289 |
> |
int parentPhase = phaseOf(parentState); |
290 |
> |
int phase = phaseOf(s = state); |
291 |
> |
if (phase != parentPhase) { |
292 |
> |
long next = trippedStateFor(parentPhase, partiesOf(s)); |
293 |
> |
if (casState(s, next)) { |
294 |
> |
releaseWaiters(phase); |
295 |
> |
s = next; |
296 |
> |
} |
297 |
> |
} |
298 |
> |
} |
299 |
> |
} |
300 |
> |
return s; |
301 |
> |
} |
302 |
> |
|
303 |
> |
/** |
304 |
> |
* Creates a new phaser without any initially registered parties, |
305 |
> |
* initial phase number 0, and no parent. Any thread using this |
306 |
> |
* phaser will need to first register for it. |
307 |
|
*/ |
308 |
|
public Phaser() { |
309 |
< |
state = new AtomicLong(stateFor(0, 0, 0)); |
309 |
> |
this(null); |
310 |
|
} |
311 |
|
|
312 |
|
/** |
313 |
< |
* Creates a new Phaser with the given numbers of registered |
314 |
< |
* unarrived parties and initial phase number 0. |
315 |
< |
* @param parties the number of parties required to trip barrier. |
313 |
> |
* Creates a new phaser with the given numbers of registered |
314 |
> |
* unarrived parties, initial phase number 0, and no parent. |
315 |
> |
* |
316 |
> |
* @param parties the number of parties required to trip barrier |
317 |
|
* @throws IllegalArgumentException if parties less than zero |
318 |
< |
* or greater than the maximum number of parties supported. |
318 |
> |
* or greater than the maximum number of parties supported |
319 |
|
*/ |
320 |
|
public Phaser(int parties) { |
321 |
+ |
this(null, parties); |
322 |
+ |
} |
323 |
+ |
|
324 |
+ |
/** |
325 |
+ |
* Creates a new phaser with the given parent, without any |
326 |
+ |
* initially registered parties. If parent is non-null this phaser |
327 |
+ |
* is registered with the parent and its initial phase number is |
328 |
+ |
* the same as that of parent phaser. |
329 |
+ |
* |
330 |
+ |
* @param parent the parent phaser |
331 |
+ |
*/ |
332 |
+ |
public Phaser(Phaser parent) { |
333 |
+ |
int phase = 0; |
334 |
+ |
this.parent = parent; |
335 |
+ |
if (parent != null) { |
336 |
+ |
this.root = parent.root; |
337 |
+ |
phase = parent.register(); |
338 |
+ |
} |
339 |
+ |
else |
340 |
+ |
this.root = this; |
341 |
+ |
this.state = trippedStateFor(phase, 0); |
342 |
+ |
} |
343 |
+ |
|
344 |
+ |
/** |
345 |
+ |
* Creates a new phaser with the given parent and numbers of |
346 |
+ |
* registered unarrived parties. If parent is non-null, this phaser |
347 |
+ |
* is registered with the parent and its initial phase number is |
348 |
+ |
* the same as that of parent phaser. |
349 |
+ |
* |
350 |
+ |
* @param parent the parent phaser |
351 |
+ |
* @param parties the number of parties required to trip barrier |
352 |
+ |
* @throws IllegalArgumentException if parties less than zero |
353 |
+ |
* or greater than the maximum number of parties supported |
354 |
+ |
*/ |
355 |
+ |
public Phaser(Phaser parent, int parties) { |
356 |
|
if (parties < 0 || parties > ushortMask) |
357 |
|
throw new IllegalArgumentException("Illegal number of parties"); |
358 |
< |
state = new AtomicLong(stateFor(0, parties, parties)); |
358 |
> |
int phase = 0; |
359 |
> |
this.parent = parent; |
360 |
> |
if (parent != null) { |
361 |
> |
this.root = parent.root; |
362 |
> |
phase = parent.register(); |
363 |
> |
} |
364 |
> |
else |
365 |
> |
this.root = this; |
366 |
> |
this.state = trippedStateFor(phase, parties); |
367 |
|
} |
368 |
|
|
369 |
|
/** |
370 |
|
* Adds a new unarrived party to this phaser. |
371 |
+ |
* |
372 |
+ |
* @return the current barrier phase number upon registration |
373 |
+ |
* @throws IllegalStateException if attempting to register more |
374 |
+ |
* than the maximum supported number of parties |
375 |
+ |
*/ |
376 |
+ |
public int register() { |
377 |
+ |
return doRegister(1); |
378 |
+ |
} |
379 |
+ |
|
380 |
+ |
/** |
381 |
+ |
* Adds the given number of new unarrived parties to this phaser. |
382 |
+ |
* |
383 |
+ |
* @param parties the number of parties required to trip barrier |
384 |
|
* @return the current barrier phase number upon registration |
385 |
|
* @throws IllegalStateException if attempting to register more |
386 |
< |
* than the maximum supported number of parties. |
386 |
> |
* than the maximum supported number of parties |
387 |
|
*/ |
388 |
< |
public int register() { // increment both parties and unarrived |
389 |
< |
final AtomicLong state = this.state; |
388 |
> |
public int bulkRegister(int parties) { |
389 |
> |
if (parties < 0) |
390 |
> |
throw new IllegalArgumentException(); |
391 |
> |
if (parties == 0) |
392 |
> |
return getPhase(); |
393 |
> |
return doRegister(parties); |
394 |
> |
} |
395 |
> |
|
396 |
> |
/** |
397 |
> |
* Shared code for register, bulkRegister |
398 |
> |
*/ |
399 |
> |
private int doRegister(int registrations) { |
400 |
> |
int phase; |
401 |
|
for (;;) { |
402 |
< |
long s = state.get(); |
403 |
< |
int phase = phaseOf(s); |
404 |
< |
int parties = partiesOf(s) + 1; |
405 |
< |
int unarrived = unarrivedOf(s) + 1; |
402 |
> |
long s = getReconciledState(); |
403 |
> |
phase = phaseOf(s); |
404 |
> |
int unarrived = unarrivedOf(s) + registrations; |
405 |
> |
int parties = partiesOf(s) + registrations; |
406 |
> |
if (phase < 0) |
407 |
> |
break; |
408 |
|
if (parties > ushortMask || unarrived > ushortMask) |
409 |
< |
throw badBounds(parties, unarrived); |
410 |
< |
if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) |
411 |
< |
return phase; |
409 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
410 |
> |
if (phase == phaseOf(root.state) && |
411 |
> |
casState(s, stateFor(phase, parties, unarrived))) |
412 |
> |
break; |
413 |
|
} |
414 |
+ |
return phase; |
415 |
|
} |
416 |
|
|
417 |
|
/** |
418 |
|
* Arrives at the barrier, but does not wait for others. (You can |
419 |
|
* in turn wait for others via {@link #awaitAdvance}). |
420 |
|
* |
421 |
< |
* @return the current barrier phase number upon entry to |
422 |
< |
* this method, or a negative value if terminated; |
423 |
< |
* @throws IllegalStateException if the number of unarrived |
424 |
< |
* parties would become negative. |
421 |
> |
* @return the barrier phase number upon entry to this method, or a |
422 |
> |
* negative value if terminated |
423 |
> |
* @throws IllegalStateException if not terminated and the number |
424 |
> |
* of unarrived parties would become negative |
425 |
|
*/ |
426 |
< |
public int arrive() { // decrement unarrived. If zero, trip |
427 |
< |
final AtomicLong state = this.state; |
426 |
> |
public int arrive() { |
427 |
> |
int phase; |
428 |
|
for (;;) { |
429 |
< |
long s = state.get(); |
430 |
< |
int phase = phaseOf(s); |
429 |
> |
long s = state; |
430 |
> |
phase = phaseOf(s); |
431 |
> |
if (phase < 0) |
432 |
> |
break; |
433 |
|
int parties = partiesOf(s); |
434 |
|
int unarrived = unarrivedOf(s) - 1; |
435 |
< |
if (unarrived < 0) |
436 |
< |
throw badBounds(parties, unarrived); |
437 |
< |
if (unarrived == 0 && phase >= 0) { |
438 |
< |
trip(phase, parties); |
439 |
< |
return phase; |
435 |
> |
if (unarrived > 0) { // Not the last arrival |
436 |
> |
if (casState(s, s - 1)) // s-1 adds one arrival |
437 |
> |
break; |
438 |
> |
} |
439 |
> |
else if (unarrived == 0) { // the last arrival |
440 |
> |
Phaser par = parent; |
441 |
> |
if (par == null) { // directly trip |
442 |
> |
if (casState |
443 |
> |
(s, |
444 |
> |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
445 |
> |
((phase + 1) & phaseMask), parties))) { |
446 |
> |
releaseWaiters(phase); |
447 |
> |
break; |
448 |
> |
} |
449 |
> |
} |
450 |
> |
else { // cascade to parent |
451 |
> |
if (casState(s, s - 1)) { // zeroes unarrived |
452 |
> |
par.arrive(); |
453 |
> |
reconcileState(); |
454 |
> |
break; |
455 |
> |
} |
456 |
> |
} |
457 |
|
} |
458 |
< |
if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) |
459 |
< |
return phase; |
458 |
> |
else if (phase != phaseOf(root.state)) // or if unreconciled |
459 |
> |
reconcileState(); |
460 |
> |
else |
461 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
462 |
|
} |
463 |
+ |
return phase; |
464 |
|
} |
465 |
|
|
466 |
|
/** |
467 |
|
* Arrives at the barrier, and deregisters from it, without |
468 |
< |
* waiting for others. |
468 |
> |
* waiting for others. Deregistration reduces number of parties |
469 |
> |
* required to trip the barrier in future phases. If this phaser |
470 |
> |
* has a parent, and deregistration causes this phaser to have |
471 |
> |
* zero parties, this phaser is also deregistered from its parent. |
472 |
|
* |
473 |
|
* @return the current barrier phase number upon entry to |
474 |
< |
* this method, or a negative value if terminated; |
475 |
< |
* @throws IllegalStateException if the number of registered or |
476 |
< |
* unarrived parties would become negative. |
477 |
< |
*/ |
478 |
< |
public int arriveAndDeregister() { // Same as arrive, plus decrement parties |
479 |
< |
final AtomicLong state = this.state; |
474 |
> |
* this method, or a negative value if terminated |
475 |
> |
* @throws IllegalStateException if not terminated and the number |
476 |
> |
* of registered or unarrived parties would become negative |
477 |
> |
*/ |
478 |
> |
public int arriveAndDeregister() { |
479 |
> |
// similar code to arrive, but too different to merge |
480 |
> |
Phaser par = parent; |
481 |
> |
int phase; |
482 |
|
for (;;) { |
483 |
< |
long s = state.get(); |
484 |
< |
int phase = phaseOf(s); |
483 |
> |
long s = state; |
484 |
> |
phase = phaseOf(s); |
485 |
> |
if (phase < 0) |
486 |
> |
break; |
487 |
|
int parties = partiesOf(s) - 1; |
488 |
|
int unarrived = unarrivedOf(s) - 1; |
489 |
< |
if (parties < 0 || unarrived < 0) |
490 |
< |
throw badBounds(parties, unarrived); |
491 |
< |
if (unarrived == 0 && phase >= 0) { |
492 |
< |
trip(phase, parties); |
493 |
< |
return phase; |
489 |
> |
if (parties >= 0) { |
490 |
> |
if (unarrived > 0 || (unarrived == 0 && par != null)) { |
491 |
> |
if (casState |
492 |
> |
(s, |
493 |
> |
stateFor(phase, parties, unarrived))) { |
494 |
> |
if (unarrived == 0) { |
495 |
> |
par.arriveAndDeregister(); |
496 |
> |
reconcileState(); |
497 |
> |
} |
498 |
> |
break; |
499 |
> |
} |
500 |
> |
continue; |
501 |
> |
} |
502 |
> |
if (unarrived == 0) { |
503 |
> |
if (casState |
504 |
> |
(s, |
505 |
> |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
506 |
> |
((phase + 1) & phaseMask), parties))) { |
507 |
> |
releaseWaiters(phase); |
508 |
> |
break; |
509 |
> |
} |
510 |
> |
continue; |
511 |
> |
} |
512 |
> |
if (par != null && phase != phaseOf(root.state)) { |
513 |
> |
reconcileState(); |
514 |
> |
continue; |
515 |
> |
} |
516 |
|
} |
517 |
< |
if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) |
267 |
< |
return phase; |
517 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
518 |
|
} |
519 |
+ |
return phase; |
520 |
|
} |
521 |
|
|
522 |
|
/** |
523 |
< |
* Arrives at the barrier and awaits others. Unlike other arrival |
524 |
< |
* methods, this method returns the arrival index of the |
525 |
< |
* caller. The caller tripping the barrier returns zero, the |
526 |
< |
* previous caller 1, and so on. |
527 |
< |
* @return the arrival index |
528 |
< |
* @throws IllegalStateException if the number of unarrived |
529 |
< |
* parties would become negative. |
523 |
> |
* Arrives at the barrier and awaits others. Equivalent in effect |
524 |
> |
* to {@code awaitAdvance(arrive())}. If you instead need to |
525 |
> |
* await with interruption of timeout, and/or deregister upon |
526 |
> |
* arrival, you can arrange them using analogous constructions. |
527 |
> |
* |
528 |
> |
* @return the phase on entry to this method |
529 |
> |
* @throws IllegalStateException if not terminated and the number |
530 |
> |
* of unarrived parties would become negative |
531 |
|
*/ |
532 |
|
public int arriveAndAwaitAdvance() { |
533 |
< |
final AtomicLong state = this.state; |
282 |
< |
for (;;) { |
283 |
< |
long s = state.get(); |
284 |
< |
int phase = phaseOf(s); |
285 |
< |
int parties = partiesOf(s); |
286 |
< |
int unarrived = unarrivedOf(s) - 1; |
287 |
< |
if (unarrived < 0) |
288 |
< |
throw badBounds(parties, unarrived); |
289 |
< |
if (unarrived == 0 && phase >= 0) { |
290 |
< |
trip(phase, parties); |
291 |
< |
return 0; |
292 |
< |
} |
293 |
< |
if (state.compareAndSet(s, stateFor(phase, parties, unarrived))) { |
294 |
< |
awaitAdvance(phase); |
295 |
< |
return unarrived; |
296 |
< |
} |
297 |
< |
} |
533 |
> |
return awaitAdvance(arrive()); |
534 |
|
} |
535 |
|
|
536 |
|
/** |
537 |
|
* Awaits the phase of the barrier to advance from the given |
538 |
< |
* value, or returns immediately if this barrier is terminated |
538 |
> |
* value, or returns immediately if argument is negative or this |
539 |
> |
* barrier is terminated. |
540 |
> |
* |
541 |
|
* @param phase the phase on entry to this method |
542 |
|
* @return the phase on exit from this method |
543 |
|
*/ |
544 |
|
public int awaitAdvance(int phase) { |
545 |
|
if (phase < 0) |
546 |
|
return phase; |
547 |
< |
Thread current = Thread.currentThread(); |
548 |
< |
if (current instanceof ForkJoinWorkerThread) |
549 |
< |
return helpingWait(phase); |
550 |
< |
if (untimedWait(current, phase, false)) |
551 |
< |
current.interrupt(); |
552 |
< |
return phaseOf(state.get()); |
547 |
> |
long s = getReconciledState(); |
548 |
> |
int p = phaseOf(s); |
549 |
> |
if (p != phase) |
550 |
> |
return p; |
551 |
> |
if (unarrivedOf(s) == 0 && parent != null) |
552 |
> |
parent.awaitAdvance(phase); |
553 |
> |
// Fall here even if parent waited, to reconcile and help release |
554 |
> |
return untimedWait(phase); |
555 |
|
} |
556 |
|
|
557 |
|
/** |
558 |
|
* Awaits the phase of the barrier to advance from the given |
559 |
< |
* value, or returns immediately if this barrier is terminated, or |
560 |
< |
* throws InterruptedException if interrupted while waiting. |
559 |
> |
* value, or returns immediately if argument is negative or this |
560 |
> |
* barrier is terminated, or throws InterruptedException if |
561 |
> |
* interrupted while waiting. |
562 |
> |
* |
563 |
|
* @param phase the phase on entry to this method |
564 |
|
* @return the phase on exit from this method |
565 |
|
* @throws InterruptedException if thread interrupted while waiting |
566 |
|
*/ |
567 |
< |
public int awaitAdvanceInterruptibly(int phase) throws InterruptedException { |
567 |
> |
public int awaitAdvanceInterruptibly(int phase) |
568 |
> |
throws InterruptedException { |
569 |
|
if (phase < 0) |
570 |
|
return phase; |
571 |
< |
Thread current = Thread.currentThread(); |
572 |
< |
if (current instanceof ForkJoinWorkerThread) |
573 |
< |
return helpingWait(phase); |
574 |
< |
else if (Thread.interrupted() || untimedWait(current, phase, true)) |
575 |
< |
throw new InterruptedException(); |
576 |
< |
else |
577 |
< |
return phaseOf(state.get()); |
571 |
> |
long s = getReconciledState(); |
572 |
> |
int p = phaseOf(s); |
573 |
> |
if (p != phase) |
574 |
> |
return p; |
575 |
> |
if (unarrivedOf(s) == 0 && parent != null) |
576 |
> |
parent.awaitAdvanceInterruptibly(phase); |
577 |
> |
return interruptibleWait(phase); |
578 |
|
} |
579 |
|
|
580 |
|
/** |
581 |
|
* Awaits the phase of the barrier to advance from the given value |
582 |
< |
* or the given timeout elapses, or returns immediately if this |
583 |
< |
* barrier is terminated |
582 |
> |
* or the given timeout elapses, or returns immediately if |
583 |
> |
* argument is negative or this barrier is terminated. |
584 |
> |
* |
585 |
|
* @param phase the phase on entry to this method |
586 |
|
* @return the phase on exit from this method |
587 |
|
* @throws InterruptedException if thread interrupted while waiting |
588 |
|
* @throws TimeoutException if timed out while waiting |
589 |
|
*/ |
590 |
< |
public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit) |
590 |
> |
public int awaitAdvanceInterruptibly(int phase, |
591 |
> |
long timeout, TimeUnit unit) |
592 |
|
throws InterruptedException, TimeoutException { |
593 |
|
if (phase < 0) |
594 |
|
return phase; |
595 |
< |
long nanos = unit.toNanos(timeout); |
596 |
< |
Thread current = Thread.currentThread(); |
597 |
< |
if (current instanceof ForkJoinWorkerThread) |
598 |
< |
return timedHelpingWait(phase, nanos); |
599 |
< |
timedWait(current, phase, nanos); |
600 |
< |
return phaseOf(state.get()); |
595 |
> |
long s = getReconciledState(); |
596 |
> |
int p = phaseOf(s); |
597 |
> |
if (p != phase) |
598 |
> |
return p; |
599 |
> |
if (unarrivedOf(s) == 0 && parent != null) |
600 |
> |
parent.awaitAdvanceInterruptibly(phase, timeout, unit); |
601 |
> |
return timedWait(phase, unit.toNanos(timeout)); |
602 |
|
} |
603 |
|
|
604 |
|
/** |
605 |
|
* Forces this barrier to enter termination state. Counts of |
606 |
< |
* arrived and registered parties are unaffected. This method may |
607 |
< |
* be useful for coordinating recovery after one or more tasks |
608 |
< |
* encounter unexpected exceptions. |
606 |
> |
* arrived and registered parties are unaffected. If this phaser |
607 |
> |
* has a parent, it too is terminated. This method may be useful |
608 |
> |
* for coordinating recovery after one or more tasks encounter |
609 |
> |
* unexpected exceptions. |
610 |
|
*/ |
611 |
|
public void forceTermination() { |
365 |
– |
final AtomicLong state = this.state; |
612 |
|
for (;;) { |
613 |
< |
long s = state.get(); |
613 |
> |
long s = getReconciledState(); |
614 |
|
int phase = phaseOf(s); |
615 |
|
int parties = partiesOf(s); |
616 |
|
int unarrived = unarrivedOf(s); |
617 |
|
if (phase < 0 || |
618 |
< |
state.compareAndSet(s, stateFor(-1, parties, unarrived))) { |
619 |
< |
if (head.get() != null) |
620 |
< |
releaseWaiters(-1); |
618 |
> |
casState(s, stateFor(-1, parties, unarrived))) { |
619 |
> |
releaseWaiters(0); |
620 |
> |
releaseWaiters(1); |
621 |
> |
if (parent != null) |
622 |
> |
parent.forceTermination(); |
623 |
|
return; |
624 |
|
} |
625 |
|
} |
626 |
|
} |
627 |
|
|
628 |
|
/** |
629 |
< |
* Resets the barrier with the given numbers of registered unarrived |
630 |
< |
* parties and phase number 0. This method allows repeated reuse |
631 |
< |
* of this barrier, but only if it is somehow known not to be in |
632 |
< |
* use for other purposes. |
633 |
< |
* @param parties the number of parties required to trip barrier. |
386 |
< |
* @throws IllegalArgumentException if parties less than zero |
387 |
< |
* or greater than the maximum number of parties supported. |
629 |
> |
* Returns the current phase number. The maximum phase number is |
630 |
> |
* {@code Integer.MAX_VALUE}, after which it restarts at |
631 |
> |
* zero. Upon termination, the phase number is negative. |
632 |
> |
* |
633 |
> |
* @return the phase number, or a negative value if terminated |
634 |
|
*/ |
635 |
< |
public void reset(int parties) { |
636 |
< |
if (parties < 0 || parties > ushortMask) |
391 |
< |
throw new IllegalArgumentException("Illegal number of parties"); |
392 |
< |
state.set(stateFor(0, parties, parties)); |
393 |
< |
if (head.get() != null) |
394 |
< |
releaseWaiters(0); |
635 |
> |
public final int getPhase() { |
636 |
> |
return phaseOf(getReconciledState()); |
637 |
|
} |
638 |
|
|
639 |
|
/** |
640 |
< |
* Returns the current phase number. The maximum phase number is |
641 |
< |
* <tt>Integer.MAX_VALUE</tt>, after which it restarts at |
642 |
< |
* zero. Upon termination, the phase number is negative. |
643 |
< |
* @return the phase number, or a negative value if terminated |
640 |
> |
* Returns {@code true} if the current phase number equals the given phase. |
641 |
> |
* |
642 |
> |
* @param phase the phase |
643 |
> |
* @return {@code true} if the current phase number equals the given phase |
644 |
|
*/ |
645 |
< |
public int getPhase() { |
646 |
< |
return phaseOf(state.get()); |
645 |
> |
public final boolean hasPhase(int phase) { |
646 |
> |
return phaseOf(getReconciledState()) == phase; |
647 |
|
} |
648 |
|
|
649 |
|
/** |
650 |
|
* Returns the number of parties registered at this barrier. |
651 |
+ |
* |
652 |
|
* @return the number of parties |
653 |
|
*/ |
654 |
|
public int getRegisteredParties() { |
655 |
< |
return partiesOf(state.get()); |
655 |
> |
return partiesOf(state); |
656 |
|
} |
657 |
|
|
658 |
|
/** |
659 |
|
* Returns the number of parties that have arrived at the current |
660 |
|
* phase of this barrier. |
661 |
+ |
* |
662 |
|
* @return the number of arrived parties |
663 |
|
*/ |
664 |
|
public int getArrivedParties() { |
665 |
< |
return arrivedOf(state.get()); |
665 |
> |
return arrivedOf(state); |
666 |
|
} |
667 |
|
|
668 |
|
/** |
669 |
|
* Returns the number of registered parties that have not yet |
670 |
|
* arrived at the current phase of this barrier. |
671 |
+ |
* |
672 |
|
* @return the number of unarrived parties |
673 |
|
*/ |
674 |
|
public int getUnarrivedParties() { |
675 |
< |
return unarrivedOf(state.get()); |
675 |
> |
return unarrivedOf(state); |
676 |
|
} |
677 |
|
|
678 |
|
/** |
679 |
< |
* Returns true if this barrier has been terminated |
680 |
< |
* @return true if this barrier has been terminated |
679 |
> |
* Returns the parent of this phaser, or {@code null} if none. |
680 |
> |
* |
681 |
> |
* @return the parent of this phaser, or {@code null} if none |
682 |
> |
*/ |
683 |
> |
public Phaser getParent() { |
684 |
> |
return parent; |
685 |
> |
} |
686 |
> |
|
687 |
> |
/** |
688 |
> |
* Returns the root ancestor of this phaser, which is the same as |
689 |
> |
* this phaser if it has no parent. |
690 |
> |
* |
691 |
> |
* @return the root ancestor of this phaser |
692 |
> |
*/ |
693 |
> |
public Phaser getRoot() { |
694 |
> |
return root; |
695 |
> |
} |
696 |
> |
|
697 |
> |
/** |
698 |
> |
* Returns {@code true} if this barrier has been terminated. |
699 |
> |
* |
700 |
> |
* @return {@code true} if this barrier has been terminated |
701 |
|
*/ |
702 |
|
public boolean isTerminated() { |
703 |
< |
return phaseOf(state.get()) < 0; |
703 |
> |
return getPhase() < 0; |
704 |
|
} |
705 |
|
|
706 |
|
/** |
707 |
|
* Overridable method to perform an action upon phase advance, and |
708 |
|
* to control termination. This method is invoked whenever the |
709 |
|
* barrier is tripped (and thus all other waiting parties are |
710 |
< |
* dormant). If it returns true, then, rather than advance the |
711 |
< |
* phase number, this barrier will be set to a final termination |
712 |
< |
* state, and subsequent calls to <tt>isTerminated</tt> will |
713 |
< |
* return true. |
714 |
< |
* |
715 |
< |
* <p> The default version returns true when the number of |
710 |
> |
* dormant). If it returns {@code true}, then, rather than advance |
711 |
> |
* the phase number, this barrier will be set to a final |
712 |
> |
* termination state, and subsequent calls to {@link #isTerminated} |
713 |
> |
* will return true. |
714 |
> |
* |
715 |
> |
* <p>The default version returns {@code true} when the number of |
716 |
|
* registered parties is zero. Normally, overrides that arrange |
717 |
|
* termination for other reasons should also preserve this |
718 |
|
* property. |
719 |
|
* |
720 |
+ |
* <p>You may override this method to perform an action with side |
721 |
+ |
* effects visible to participating tasks, but it is in general |
722 |
+ |
* only sensible to do so in designs where all parties register |
723 |
+ |
* before any arrive, and all {@link #awaitAdvance} at each phase. |
724 |
+ |
* Otherwise, you cannot ensure lack of interference. In |
725 |
+ |
* particular, this method may be invoked more than once per |
726 |
+ |
* transition if other parties successfully register while the |
727 |
+ |
* invocation of this method is in progress, thus postponing the |
728 |
+ |
* transition until those parties also arrive, re-triggering this |
729 |
+ |
* method. |
730 |
+ |
* |
731 |
|
* @param phase the phase number on entering the barrier |
732 |
< |
* @param registeredParties the current number of registered |
733 |
< |
* parties. |
458 |
< |
* @return true if this barrier should terminate |
732 |
> |
* @param registeredParties the current number of registered parties |
733 |
> |
* @return {@code true} if this barrier should terminate |
734 |
|
*/ |
735 |
|
protected boolean onAdvance(int phase, int registeredParties) { |
736 |
|
return registeredParties <= 0; |
737 |
|
} |
738 |
|
|
739 |
|
/** |
740 |
< |
* Returns a string identifying this barrier, as well as its |
740 |
> |
* Returns a string identifying this phaser, as well as its |
741 |
|
* state. The state, in brackets, includes the String {@code |
742 |
< |
* "phase ="} followed by the phase number, {@code "parties ="} |
742 |
> |
* "phase = "} followed by the phase number, {@code "parties = "} |
743 |
|
* followed by the number of registered parties, and {@code |
744 |
< |
* "arrived ="} followed by the number of arrived parties |
744 |
> |
* "arrived = "} followed by the number of arrived parties. |
745 |
|
* |
746 |
|
* @return a string identifying this barrier, as well as its state |
747 |
|
*/ |
748 |
|
public String toString() { |
749 |
< |
long s = state.get(); |
750 |
< |
return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]"; |
749 |
> |
long s = getReconciledState(); |
750 |
> |
return super.toString() + |
751 |
> |
"[phase = " + phaseOf(s) + |
752 |
> |
" parties = " + partiesOf(s) + |
753 |
> |
" arrived = " + arrivedOf(s) + "]"; |
754 |
|
} |
755 |
|
|
756 |
< |
// methods for tripping and waiting |
756 |
> |
// methods for waiting |
757 |
|
|
758 |
|
/** |
759 |
< |
* Advance the current phase (or terminate) |
759 |
> |
* Wait nodes for Treiber stack representing wait queue |
760 |
|
*/ |
761 |
< |
private void trip(int phase, int parties) { |
762 |
< |
int next = onAdvance(phase, parties)? -1 : ((phase + 1) & phaseMask); |
763 |
< |
state.set(stateFor(next, parties, parties)); |
764 |
< |
if (head.get() != null) |
765 |
< |
releaseWaiters(next); |
766 |
< |
} |
767 |
< |
|
768 |
< |
private int helpingWait(int phase) { |
769 |
< |
final AtomicLong state = this.state; |
770 |
< |
int p; |
771 |
< |
while ((p = phaseOf(state.get())) == phase) { |
772 |
< |
ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask(); |
773 |
< |
if (t != null) { |
774 |
< |
if ((p = phaseOf(state.get())) == phase) |
775 |
< |
t.exec(); |
776 |
< |
else { // push task and exit if barrier advanced |
777 |
< |
t.fork(); |
778 |
< |
break; |
779 |
< |
} |
761 |
> |
static final class QNode implements ForkJoinPool.ManagedBlocker { |
762 |
> |
final Phaser phaser; |
763 |
> |
final int phase; |
764 |
> |
final long startTime; |
765 |
> |
final long nanos; |
766 |
> |
final boolean timed; |
767 |
> |
final boolean interruptible; |
768 |
> |
volatile boolean wasInterrupted = false; |
769 |
> |
volatile Thread thread; // nulled to cancel wait |
770 |
> |
QNode next; |
771 |
> |
QNode(Phaser phaser, int phase, boolean interruptible, |
772 |
> |
boolean timed, long startTime, long nanos) { |
773 |
> |
this.phaser = phaser; |
774 |
> |
this.phase = phase; |
775 |
> |
this.timed = timed; |
776 |
> |
this.interruptible = interruptible; |
777 |
> |
this.startTime = startTime; |
778 |
> |
this.nanos = nanos; |
779 |
> |
thread = Thread.currentThread(); |
780 |
> |
} |
781 |
> |
public boolean isReleasable() { |
782 |
> |
return (thread == null || |
783 |
> |
phaser.getPhase() != phase || |
784 |
> |
(interruptible && wasInterrupted) || |
785 |
> |
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
786 |
> |
} |
787 |
> |
public boolean block() { |
788 |
> |
if (Thread.interrupted()) { |
789 |
> |
wasInterrupted = true; |
790 |
> |
if (interruptible) |
791 |
> |
return true; |
792 |
> |
} |
793 |
> |
if (!timed) |
794 |
> |
LockSupport.park(this); |
795 |
> |
else { |
796 |
> |
long waitTime = nanos - (System.nanoTime() - startTime); |
797 |
> |
if (waitTime <= 0) |
798 |
> |
return true; |
799 |
> |
LockSupport.parkNanos(this, waitTime); |
800 |
|
} |
801 |
+ |
return isReleasable(); |
802 |
|
} |
803 |
< |
return p; |
804 |
< |
} |
506 |
< |
|
507 |
< |
private int timedHelpingWait(int phase, long nanos) throws TimeoutException { |
508 |
< |
final AtomicLong state = this.state; |
509 |
< |
long lastTime = System.nanoTime(); |
510 |
< |
int p; |
511 |
< |
while ((p = phaseOf(state.get())) == phase) { |
512 |
< |
long now = System.nanoTime(); |
513 |
< |
nanos -= now - lastTime; |
514 |
< |
lastTime = now; |
515 |
< |
if (nanos <= 0) { |
516 |
< |
if ((p = phaseOf(state.get())) == phase) |
517 |
< |
throw new TimeoutException(); |
518 |
< |
else |
519 |
< |
break; |
520 |
< |
} |
521 |
< |
ForkJoinTask<?> t = ForkJoinWorkerThread.pollTask(); |
803 |
> |
void signal() { |
804 |
> |
Thread t = thread; |
805 |
|
if (t != null) { |
806 |
< |
if ((p = phaseOf(state.get())) == phase) |
807 |
< |
t.exec(); |
808 |
< |
else { // push task and exit if barrier advanced |
809 |
< |
t.fork(); |
810 |
< |
break; |
806 |
> |
thread = null; |
807 |
> |
LockSupport.unpark(t); |
808 |
> |
} |
809 |
> |
} |
810 |
> |
boolean doWait() { |
811 |
> |
if (thread != null) { |
812 |
> |
try { |
813 |
> |
ForkJoinPool.managedBlock(this, false); |
814 |
> |
} catch (InterruptedException ie) { |
815 |
|
} |
816 |
|
} |
817 |
+ |
return wasInterrupted; |
818 |
|
} |
819 |
< |
return p; |
819 |
> |
|
820 |
|
} |
821 |
|
|
822 |
|
/** |
823 |
< |
* Wait nodes for Treiber stack representing wait queue for non-FJ |
536 |
< |
* tasks. The waiting scheme is an adaptation of the one used in |
537 |
< |
* forkjoin.PoolBarrier. |
823 |
> |
* Removes and signals waiting threads from wait queue. |
824 |
|
*/ |
825 |
< |
static final class QNode { |
826 |
< |
QNode next; |
827 |
< |
volatile Thread thread; // nulled to cancel wait |
828 |
< |
final int phase; |
829 |
< |
QNode(Thread t, int c) { |
830 |
< |
thread = t; |
545 |
< |
phase = c; |
825 |
> |
private void releaseWaiters(int phase) { |
826 |
> |
AtomicReference<QNode> head = queueFor(phase); |
827 |
> |
QNode q; |
828 |
> |
while ((q = head.get()) != null) { |
829 |
> |
if (head.compareAndSet(q, q.next)) |
830 |
> |
q.signal(); |
831 |
|
} |
832 |
|
} |
833 |
|
|
549 |
– |
private void releaseWaiters(int currentPhase) { |
550 |
– |
final AtomicReference<QNode> head = this.head; |
551 |
– |
QNode p; |
552 |
– |
while ((p = head.get()) != null && p.phase != currentPhase) { |
553 |
– |
if (head.compareAndSet(p, null)) { |
554 |
– |
do { |
555 |
– |
Thread t = p.thread; |
556 |
– |
if (t != null) { |
557 |
– |
p.thread = null; |
558 |
– |
LockSupport.unpark(t); |
559 |
– |
} |
560 |
– |
} while ((p = p.next) != null); |
561 |
– |
} |
562 |
– |
} |
563 |
– |
} |
564 |
– |
|
565 |
– |
/** The number of CPUs, for spin control */ |
566 |
– |
static final int NCPUS = Runtime.getRuntime().availableProcessors(); |
567 |
– |
|
834 |
|
/** |
835 |
< |
* The number of times to spin before blocking in timed waits. |
836 |
< |
* The value is empirically derived |
837 |
< |
*/ |
572 |
< |
static final int maxTimedSpins = (NCPUS < 2)? 0 : 32; |
573 |
< |
|
574 |
< |
/** |
575 |
< |
* The number of times to spin before blocking in untimed waits. |
576 |
< |
* This is greater than timed value because untimed waits spin |
577 |
< |
* faster since they don't need to check times on each spin. |
835 |
> |
* Tries to enqueue given node in the appropriate wait queue. |
836 |
> |
* |
837 |
> |
* @return true if successful |
838 |
|
*/ |
839 |
< |
static final int maxUntimedSpins = maxTimedSpins * 32; |
839 |
> |
private boolean tryEnqueue(QNode node) { |
840 |
> |
AtomicReference<QNode> head = queueFor(node.phase); |
841 |
> |
return head.compareAndSet(node.next = head.get(), node); |
842 |
> |
} |
843 |
|
|
844 |
|
/** |
845 |
< |
* The number of nanoseconds for which it is faster to spin |
846 |
< |
* rather than to use timed park. A rough estimate suffices. |
845 |
> |
* Enqueues node and waits unless aborted or signalled. |
846 |
> |
* |
847 |
> |
* @return current phase |
848 |
|
*/ |
849 |
< |
static final long spinForTimeoutThreshold = 1000L; |
849 |
> |
private int untimedWait(int phase) { |
850 |
> |
QNode node = null; |
851 |
> |
boolean queued = false; |
852 |
> |
boolean interrupted = false; |
853 |
> |
int p; |
854 |
> |
while ((p = getPhase()) == phase) { |
855 |
> |
if (Thread.interrupted()) |
856 |
> |
interrupted = true; |
857 |
> |
else if (node == null) |
858 |
> |
node = new QNode(this, phase, false, false, 0, 0); |
859 |
> |
else if (!queued) |
860 |
> |
queued = tryEnqueue(node); |
861 |
> |
else |
862 |
> |
interrupted = node.doWait(); |
863 |
> |
} |
864 |
> |
if (node != null) |
865 |
> |
node.thread = null; |
866 |
> |
releaseWaiters(phase); |
867 |
> |
if (interrupted) |
868 |
> |
Thread.currentThread().interrupt(); |
869 |
> |
return p; |
870 |
> |
} |
871 |
|
|
872 |
|
/** |
873 |
< |
* Enqueues node and waits unless aborted or signalled. |
873 |
> |
* Interruptible version |
874 |
> |
* @return current phase |
875 |
|
*/ |
876 |
< |
private boolean untimedWait(Thread thread, int currentPhase, |
591 |
< |
boolean abortOnInterrupt) { |
592 |
< |
final AtomicReference<QNode> head = this.head; |
593 |
< |
final AtomicLong state = this.state; |
594 |
< |
boolean wasInterrupted = false; |
876 |
> |
private int interruptibleWait(int phase) throws InterruptedException { |
877 |
|
QNode node = null; |
878 |
|
boolean queued = false; |
879 |
< |
int spins = maxUntimedSpins; |
880 |
< |
while (phaseOf(state.get()) == currentPhase) { |
881 |
< |
QNode h; |
882 |
< |
if (node != null && queued) { |
883 |
< |
if (node.thread != null) { |
884 |
< |
LockSupport.park(); |
885 |
< |
if (Thread.interrupted()) { |
886 |
< |
wasInterrupted = true; |
887 |
< |
if (abortOnInterrupt) |
606 |
< |
break; |
607 |
< |
} |
608 |
< |
} |
609 |
< |
} |
610 |
< |
else if ((h = head.get()) != null && h.phase != currentPhase) { |
611 |
< |
if (phaseOf(state.get()) == currentPhase) { // must recheck |
612 |
< |
if (head.compareAndSet(h, h.next)) { |
613 |
< |
Thread t = h.thread; // help clear out old waiters |
614 |
< |
if (t != null) { |
615 |
< |
h.thread = null; |
616 |
< |
LockSupport.unpark(t); |
617 |
< |
} |
618 |
< |
} |
619 |
< |
} |
620 |
< |
else |
621 |
< |
break; |
622 |
< |
} |
623 |
< |
else if (node != null) |
624 |
< |
queued = head.compareAndSet(node.next = h, node); |
625 |
< |
else if (spins <= 0) |
626 |
< |
node = new QNode(thread, currentPhase); |
879 |
> |
boolean interrupted = false; |
880 |
> |
int p; |
881 |
> |
while ((p = getPhase()) == phase && !interrupted) { |
882 |
> |
if (Thread.interrupted()) |
883 |
> |
interrupted = true; |
884 |
> |
else if (node == null) |
885 |
> |
node = new QNode(this, phase, true, false, 0, 0); |
886 |
> |
else if (!queued) |
887 |
> |
queued = tryEnqueue(node); |
888 |
|
else |
889 |
< |
--spins; |
889 |
> |
interrupted = node.doWait(); |
890 |
|
} |
891 |
|
if (node != null) |
892 |
|
node.thread = null; |
893 |
< |
return wasInterrupted; |
893 |
> |
if (p != phase || (p = getPhase()) != phase) |
894 |
> |
releaseWaiters(phase); |
895 |
> |
if (interrupted) |
896 |
> |
throw new InterruptedException(); |
897 |
> |
return p; |
898 |
|
} |
899 |
|
|
900 |
|
/** |
901 |
< |
* Messier timeout version |
901 |
> |
* Timeout version. |
902 |
> |
* @return current phase |
903 |
|
*/ |
904 |
< |
private void timedWait(Thread thread, int currentPhase, long nanos) |
904 |
> |
private int timedWait(int phase, long nanos) |
905 |
|
throws InterruptedException, TimeoutException { |
906 |
< |
final AtomicReference<QNode> head = this.head; |
641 |
< |
final AtomicLong state = this.state; |
642 |
< |
long lastTime = System.nanoTime(); |
906 |
> |
long startTime = System.nanoTime(); |
907 |
|
QNode node = null; |
908 |
|
boolean queued = false; |
909 |
< |
int spins = maxTimedSpins; |
910 |
< |
while (phaseOf(state.get()) == currentPhase) { |
911 |
< |
QNode h; |
912 |
< |
long now = System.nanoTime(); |
913 |
< |
nanos -= now - lastTime; |
914 |
< |
lastTime = now; |
915 |
< |
if (nanos <= 0) { |
916 |
< |
if (node != null) |
917 |
< |
node.thread = null; |
918 |
< |
if (phaseOf(state.get()) == currentPhase) |
919 |
< |
throw new TimeoutException(); |
656 |
< |
else |
657 |
< |
break; |
658 |
< |
} |
659 |
< |
else if (node != null && queued) { |
660 |
< |
if (node.thread != null && |
661 |
< |
nanos > spinForTimeoutThreshold) { |
662 |
< |
// LockSupport.parkNanos(this, nanos); |
663 |
< |
LockSupport.parkNanos(nanos); |
664 |
< |
if (Thread.interrupted()) { |
665 |
< |
node.thread = null; |
666 |
< |
throw new InterruptedException(); |
667 |
< |
} |
668 |
< |
} |
669 |
< |
} |
670 |
< |
else if ((h = head.get()) != null && h.phase != currentPhase) { |
671 |
< |
if (phaseOf(state.get()) == currentPhase) { // must recheck |
672 |
< |
if (head.compareAndSet(h, h.next)) { |
673 |
< |
Thread t = h.thread; // help clear out old waiters |
674 |
< |
if (t != null) { |
675 |
< |
h.thread = null; |
676 |
< |
LockSupport.unpark(t); |
677 |
< |
} |
678 |
< |
} |
679 |
< |
} |
680 |
< |
else |
681 |
< |
break; |
682 |
< |
} |
683 |
< |
else if (node != null) |
684 |
< |
queued = head.compareAndSet(node.next = h, node); |
685 |
< |
else if (spins <= 0) |
686 |
< |
node = new QNode(thread, currentPhase); |
909 |
> |
boolean interrupted = false; |
910 |
> |
int p; |
911 |
> |
while ((p = getPhase()) == phase && !interrupted) { |
912 |
> |
if (Thread.interrupted()) |
913 |
> |
interrupted = true; |
914 |
> |
else if (nanos - (System.nanoTime() - startTime) <= 0) |
915 |
> |
break; |
916 |
> |
else if (node == null) |
917 |
> |
node = new QNode(this, phase, true, true, startTime, nanos); |
918 |
> |
else if (!queued) |
919 |
> |
queued = tryEnqueue(node); |
920 |
|
else |
921 |
< |
--spins; |
921 |
> |
interrupted = node.doWait(); |
922 |
|
} |
923 |
|
if (node != null) |
924 |
|
node.thread = null; |
925 |
+ |
if (p != phase || (p = getPhase()) != phase) |
926 |
+ |
releaseWaiters(phase); |
927 |
+ |
if (interrupted) |
928 |
+ |
throw new InterruptedException(); |
929 |
+ |
if (p == phase) |
930 |
+ |
throw new TimeoutException(); |
931 |
+ |
return p; |
932 |
|
} |
933 |
|
|
934 |
< |
} |
934 |
> |
// Unsafe mechanics |
935 |
|
|
936 |
+ |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
937 |
+ |
private static final long stateOffset = |
938 |
+ |
objectFieldOffset("state", Phaser.class); |
939 |
+ |
|
940 |
+ |
private final boolean casState(long cmp, long val) { |
941 |
+ |
return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val); |
942 |
+ |
} |
943 |
+ |
|
944 |
+ |
private static long objectFieldOffset(String field, Class<?> klazz) { |
945 |
+ |
try { |
946 |
+ |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
947 |
+ |
} catch (NoSuchFieldException e) { |
948 |
+ |
// Convert Exception to corresponding Error |
949 |
+ |
NoSuchFieldError error = new NoSuchFieldError(field); |
950 |
+ |
error.initCause(e); |
951 |
+ |
throw error; |
952 |
+ |
} |
953 |
+ |
} |
954 |
+ |
|
955 |
+ |
/** |
956 |
+ |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
957 |
+ |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
958 |
+ |
* into a jdk. |
959 |
+ |
* |
960 |
+ |
* @return a sun.misc.Unsafe |
961 |
+ |
*/ |
962 |
+ |
private static sun.misc.Unsafe getUnsafe() { |
963 |
+ |
try { |
964 |
+ |
return sun.misc.Unsafe.getUnsafe(); |
965 |
+ |
} catch (SecurityException se) { |
966 |
+ |
try { |
967 |
+ |
return java.security.AccessController.doPrivileged |
968 |
+ |
(new java.security |
969 |
+ |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
970 |
+ |
public sun.misc.Unsafe run() throws Exception { |
971 |
+ |
java.lang.reflect.Field f = sun.misc |
972 |
+ |
.Unsafe.class.getDeclaredField("theUnsafe"); |
973 |
+ |
f.setAccessible(true); |
974 |
+ |
return (sun.misc.Unsafe) f.get(null); |
975 |
+ |
}}); |
976 |
+ |
} catch (java.security.PrivilegedActionException e) { |
977 |
+ |
throw new RuntimeException("Could not initialize intrinsics", |
978 |
+ |
e.getCause()); |
979 |
+ |
} |
980 |
+ |
} |
981 |
+ |
} |
982 |
+ |
} |