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*/ |
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package jsr166y; |
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import java.util.concurrent.*; |
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import java.util.concurrent.atomic.*; |
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import java.util.concurrent.locks.LockSupport; |
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import sun.misc.Unsafe; |
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import java.lang.reflect.*; |
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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} and {@link |
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* java.util.concurrent.CountDownLatch} but supporting more flexible |
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* 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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* 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 in by |
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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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* around to zero after reaching {@code Integer.MAX_VALUE}). |
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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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* Method {@code arriveAndAwaitAdvance} has effect analogous to |
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* {@code CyclicBarrier.await}. However, Phasers separate two |
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* aspects of 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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* <li> Arriving at a barrier. Methods {@code arrive} and |
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* {@code 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 {@code 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 {@code 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 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 about to be tripped. When a Phaser is |
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* controlling an action 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 |
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* <tt>forceTermination</tt> is also available to abruptly release |
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* waiting threads and allow them to terminate. |
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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 {@code 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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* 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, <tt>awaitAdvance</tt> continues to wait even if |
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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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* CyclicBarriers, 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, often after invoking |
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* <tt>forceTermination</tt>. |
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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 usages:</b> |
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* |
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* <p>A Phaser may be used instead of a <tt>CountdownLatch</tt> to control |
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* <p>A Phaser may be used instead of a {@code CountDownLatch} to control |
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* a one-shot action serving a variable number of parties. The typical |
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* idiom is for the method setting this up to first register, then |
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* start the actions, then deregister, as in: |
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* |
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* <pre> |
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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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* <pre> {@code |
95 |
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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() { |
100 |
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* public void run() { |
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* phaser.arriveAndAwaitAdvance(); // await all creation |
102 |
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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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* doSomethingOnBehalfOfWorkers(); |
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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); // awit final completion |
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* } |
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* </pre> |
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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 <tt>onAdvance</tt>: |
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* for a given number of iterations is to override {@code onAdvance}: |
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* |
119 |
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* <pre> |
120 |
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* void startTasks(List<Runnable> list, final int iterations) { |
121 |
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* final Phaser phaser = new Phaser() { |
122 |
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* public boolean onAdvance(int phase, int registeredParties) { |
123 |
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* return phase >= iterations || registeredParties == 0; |
119 |
> |
* <pre> {@code |
120 |
> |
* void startTasks(List<Runnable> list, final int iterations) { |
121 |
> |
* final Phaser phaser = new Phaser() { |
122 |
> |
* public boolean onAdvance(int phase, int registeredParties) { |
123 |
> |
* return phase >= iterations || registeredParties == 0; |
124 |
> |
* } |
125 |
> |
* }; |
126 |
> |
* phaser.register(); |
127 |
> |
* for (Runnable r : list) { |
128 |
> |
* phaser.register(); |
129 |
> |
* new Thread() { |
130 |
> |
* public void run() { |
131 |
> |
* do { |
132 |
> |
* r.run(); |
133 |
> |
* phaser.arriveAndAwaitAdvance(); |
134 |
> |
* } while(!phaser.isTerminated(); |
135 |
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* } |
136 |
< |
* }; |
125 |
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* phaser.register(); |
126 |
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* for (Runnable r : list) { |
127 |
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* phaser.register(); |
128 |
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* new Thread() { |
129 |
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* public void run() { |
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* do { |
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* r.run(); |
132 |
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* phaser.arriveAndAwaitAdvance(); |
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* } while(!phaser.isTerminated(); |
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* } |
135 |
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* }.start(); |
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> |
* }.start(); |
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* } |
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* phaser.arriveAndDeregister(); // deregister self, don't wait |
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< |
* } |
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* </pre> |
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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> |
146 |
< |
* void build(Task[] actions, int lo, int hi, Phaser b) { |
147 |
< |
* int step = (hi - lo) / TASKS_PER_PHASER; |
148 |
< |
* if (step > 1) { |
149 |
< |
* int i = lo; |
150 |
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* while (i < hi) { |
151 |
< |
* int r = Math.min(i + step, hi); |
152 |
< |
* build(actions, i, r, new Phaser(b)); |
153 |
< |
* i = r; |
154 |
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* } |
155 |
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* } |
156 |
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* else { |
157 |
< |
* for (int i = lo; i < hi; ++i) |
158 |
< |
* actions[i] = new Task(b); |
159 |
< |
* // assumes new Task(b) performs b.register() |
160 |
< |
* } |
161 |
< |
* } |
162 |
< |
* // .. initially called, for n tasks via |
163 |
< |
* build(new Task[n], 0, n, new Phaser()); |
164 |
< |
* </pre> |
145 |
> |
* <pre> {@code |
146 |
> |
* void build(Task[] actions, int lo, int hi, Phaser b) { |
147 |
> |
* int step = (hi - lo) / TASKS_PER_PHASER; |
148 |
> |
* if (step > 1) { |
149 |
> |
* int i = lo; |
150 |
> |
* while (i < hi) { |
151 |
> |
* int r = Math.min(i + step, hi); |
152 |
> |
* build(actions, i, r, new Phaser(b)); |
153 |
> |
* i = r; |
154 |
> |
* } |
155 |
> |
* } else { |
156 |
> |
* for (int i = lo; i < hi; ++i) |
157 |
> |
* actions[i] = new Task(b); |
158 |
> |
* // assumes new Task(b) performs b.register() |
159 |
> |
* } |
160 |
> |
* } |
161 |
> |
* // .. initially called, for n tasks via |
162 |
> |
* build(new Task[n], 0, n, new Phaser());}</pre> |
163 |
|
* |
164 |
< |
* The best value of <tt>TASKS_PER_PHASER</tt> depends mainly on |
164 |
> |
* The best value of {@code TASKS_PER_PHASER} depends mainly on |
165 |
|
* expected barrier synchronization rates. A value as low as four may |
166 |
|
* be appropriate for extremely small per-barrier task bodies (thus |
167 |
|
* high rates), or up to hundreds for extremely large ones. |
173 |
|
* parties result in IllegalStateExceptions. However, you can and |
174 |
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* should create tiered phasers to accommodate arbitrarily large sets |
175 |
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* of participants. |
176 |
+ |
* |
177 |
+ |
* @since 1.7 |
178 |
+ |
* @author Doug Lea |
179 |
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*/ |
180 |
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public class Phaser { |
181 |
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/* |
196 |
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* However, to efficiently maintain atomicity, these values are |
197 |
|
* packed into a single (atomic) long. Termination uses the sign |
198 |
|
* bit of 32 bit representation of phase, so phase is set to -1 on |
199 |
< |
* termination. Good performace relies on keeping state decoding |
199 |
> |
* termination. Good performance relies on keeping state decoding |
200 |
|
* and encoding simple, and keeping race windows short. |
201 |
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* |
202 |
|
* Note: there are some cheats in arrive() that rely on unarrived |
203 |
< |
* being lowest 16 bits. |
203 |
> |
* count being lowest 16 bits. |
204 |
|
*/ |
205 |
|
private volatile long state; |
206 |
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|
207 |
|
private static final int ushortBits = 16; |
208 |
< |
private static final int ushortMask = (1 << ushortBits) - 1; |
209 |
< |
private static final int phaseMask = 0x7fffffff; |
208 |
> |
private static final int ushortMask = 0xffff; |
209 |
> |
private static final int phaseMask = 0x7fffffff; |
210 |
|
|
211 |
|
private static int unarrivedOf(long s) { |
212 |
< |
return (int)(s & ushortMask); |
212 |
> |
return (int) (s & ushortMask); |
213 |
|
} |
214 |
|
|
215 |
|
private static int partiesOf(long s) { |
216 |
< |
return (int)(s & (ushortMask << 16)) >>> 16; |
216 |
> |
return ((int) s) >>> 16; |
217 |
|
} |
218 |
|
|
219 |
|
private static int phaseOf(long s) { |
220 |
< |
return (int)(s >>> 32); |
220 |
> |
return (int) (s >>> 32); |
221 |
|
} |
222 |
|
|
223 |
|
private static int arrivedOf(long s) { |
225 |
|
} |
226 |
|
|
227 |
|
private static long stateFor(int phase, int parties, int unarrived) { |
228 |
< |
return (((long)phase) << 32) | ((parties << 16) | unarrived); |
228 |
> |
return ((((long) phase) << 32) | (((long) parties) << 16) | |
229 |
> |
(long) unarrived); |
230 |
|
} |
231 |
|
|
232 |
|
private static long trippedStateFor(int phase, int parties) { |
233 |
< |
return (((long)phase) << 32) | ((parties << 16) | parties); |
233 |
> |
long lp = (long) parties; |
234 |
> |
return (((long) phase) << 32) | (lp << 16) | lp; |
235 |
|
} |
236 |
|
|
237 |
< |
private static IllegalStateException badBounds(int parties, int unarrived) { |
238 |
< |
return new IllegalStateException |
239 |
< |
("Attempt to set " + unarrived + |
240 |
< |
" unarrived of " + parties + " parties"); |
237 |
> |
/** |
238 |
> |
* Returns message string for bad bounds exceptions. |
239 |
> |
*/ |
240 |
> |
private static String badBounds(int parties, int unarrived) { |
241 |
> |
return ("Attempt to set " + unarrived + |
242 |
> |
" unarrived of " + parties + " parties"); |
243 |
|
} |
244 |
|
|
245 |
|
/** |
256 |
|
// Wait queues |
257 |
|
|
258 |
|
/** |
259 |
< |
* Heads of Treiber stacks waiting for nonFJ threads. To eliminate |
259 |
> |
* Heads of Treiber stacks for waiting threads. To eliminate |
260 |
|
* contention while releasing some threads while adding others, we |
261 |
|
* use two of them, alternating across even and odd phases. |
262 |
|
*/ |
264 |
|
private final AtomicReference<QNode> oddQ = new AtomicReference<QNode>(); |
265 |
|
|
266 |
|
private AtomicReference<QNode> queueFor(int phase) { |
267 |
< |
return (phase & 1) == 0? evenQ : oddQ; |
267 |
> |
return ((phase & 1) == 0) ? evenQ : oddQ; |
268 |
|
} |
269 |
|
|
270 |
|
/** |
272 |
|
* root if necessary. |
273 |
|
*/ |
274 |
|
private long getReconciledState() { |
275 |
< |
return parent == null? state : reconcileState(); |
275 |
> |
return (parent == null) ? state : reconcileState(); |
276 |
|
} |
277 |
|
|
278 |
|
/** |
300 |
|
|
301 |
|
/** |
302 |
|
* Creates a new Phaser without any initially registered parties, |
303 |
< |
* initial phase number 0, and no parent. |
303 |
> |
* initial phase number 0, and no parent. Any thread using this |
304 |
> |
* Phaser will need to first register for it. |
305 |
|
*/ |
306 |
|
public Phaser() { |
307 |
|
this(null); |
310 |
|
/** |
311 |
|
* Creates a new Phaser with the given numbers of registered |
312 |
|
* unarrived parties, initial phase number 0, and no parent. |
313 |
< |
* @param parties the number of parties required to trip barrier. |
313 |
> |
* |
314 |
> |
* @param parties the number of parties required to trip barrier |
315 |
|
* @throws IllegalArgumentException if parties less than zero |
316 |
< |
* or greater than the maximum number of parties supported. |
316 |
> |
* or greater than the maximum number of parties supported |
317 |
|
*/ |
318 |
|
public Phaser(int parties) { |
319 |
|
this(null, parties); |
324 |
|
* initially registered parties. If parent is non-null this phaser |
325 |
|
* is registered with the parent and its initial phase number is |
326 |
|
* the same as that of parent phaser. |
327 |
< |
* @param parent the parent phaser. |
327 |
> |
* |
328 |
> |
* @param parent the parent phaser |
329 |
|
*/ |
330 |
|
public Phaser(Phaser parent) { |
331 |
|
int phase = 0; |
341 |
|
|
342 |
|
/** |
343 |
|
* Creates a new Phaser with the given parent and numbers of |
344 |
< |
* registered unarrived parties. If parent is non-null this phaser |
344 |
> |
* registered unarrived parties. If parent is non-null, this phaser |
345 |
|
* is registered with the parent and its initial phase number is |
346 |
|
* the same as that of parent phaser. |
347 |
< |
* @param parent the parent phaser. |
348 |
< |
* @param parties the number of parties required to trip barrier. |
347 |
> |
* |
348 |
> |
* @param parent the parent phaser |
349 |
> |
* @param parties the number of parties required to trip barrier |
350 |
|
* @throws IllegalArgumentException if parties less than zero |
351 |
< |
* or greater than the maximum number of parties supported. |
351 |
> |
* or greater than the maximum number of parties supported |
352 |
|
*/ |
353 |
|
public Phaser(Phaser parent, int parties) { |
354 |
|
if (parties < 0 || parties > ushortMask) |
366 |
|
|
367 |
|
/** |
368 |
|
* Adds a new unarrived party to this phaser. |
369 |
+ |
* |
370 |
|
* @return the current barrier phase number upon registration |
371 |
|
* @throws IllegalStateException if attempting to register more |
372 |
< |
* than the maximum supported number of parties. |
372 |
> |
* than the maximum supported number of parties |
373 |
|
*/ |
374 |
|
public int register() { |
375 |
|
return doRegister(1); |
377 |
|
|
378 |
|
/** |
379 |
|
* Adds the given number of new unarrived parties to this phaser. |
380 |
< |
* @param parties the number of parties required to trip barrier. |
380 |
> |
* |
381 |
> |
* @param parties the number of parties required to trip barrier |
382 |
|
* @return the current barrier phase number upon registration |
383 |
|
* @throws IllegalStateException if attempting to register more |
384 |
< |
* than the maximum supported number of parties. |
384 |
> |
* than the maximum supported number of parties |
385 |
|
*/ |
386 |
|
public int bulkRegister(int parties) { |
387 |
|
if (parties < 0) |
404 |
|
if (phase < 0) |
405 |
|
break; |
406 |
|
if (parties > ushortMask || unarrived > ushortMask) |
407 |
< |
throw badBounds(parties, unarrived); |
407 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
408 |
|
if (phase == phaseOf(root.state) && |
409 |
|
casState(s, stateFor(phase, parties, unarrived))) |
410 |
|
break; |
417 |
|
* in turn wait for others via {@link #awaitAdvance}). |
418 |
|
* |
419 |
|
* @return the barrier phase number upon entry to this method, or a |
420 |
< |
* negative value if terminated; |
420 |
> |
* negative value if terminated |
421 |
|
* @throws IllegalStateException if not terminated and the number |
422 |
< |
* of unarrived parties would become negative. |
422 |
> |
* of unarrived parties would become negative |
423 |
|
*/ |
424 |
|
public int arrive() { |
425 |
|
int phase; |
426 |
|
for (;;) { |
427 |
|
long s = state; |
428 |
|
phase = phaseOf(s); |
429 |
+ |
if (phase < 0) |
430 |
+ |
break; |
431 |
|
int parties = partiesOf(s); |
432 |
|
int unarrived = unarrivedOf(s) - 1; |
433 |
|
if (unarrived > 0) { // Not the last arrival |
439 |
|
if (par == null) { // directly trip |
440 |
|
if (casState |
441 |
|
(s, |
442 |
< |
trippedStateFor(onAdvance(phase, parties)? -1 : |
442 |
> |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
443 |
|
((phase + 1) & phaseMask), parties))) { |
444 |
|
releaseWaiters(phase); |
445 |
|
break; |
453 |
|
} |
454 |
|
} |
455 |
|
} |
443 |
– |
else if (phase < 0) // Don't throw exception if terminated |
444 |
– |
break; |
456 |
|
else if (phase != phaseOf(root.state)) // or if unreconciled |
457 |
|
reconcileState(); |
458 |
|
else |
459 |
< |
throw badBounds(parties, unarrived); |
459 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
460 |
|
} |
461 |
|
return phase; |
462 |
|
} |
469 |
|
* zero parties, this phaser is also deregistered from its parent. |
470 |
|
* |
471 |
|
* @return the current barrier phase number upon entry to |
472 |
< |
* this method, or a negative value if terminated; |
472 |
> |
* this method, or a negative value if terminated |
473 |
|
* @throws IllegalStateException if not terminated and the number |
474 |
< |
* of registered or unarrived parties would become negative. |
474 |
> |
* of registered or unarrived parties would become negative |
475 |
|
*/ |
476 |
|
public int arriveAndDeregister() { |
477 |
|
// similar code to arrive, but too different to merge |
480 |
|
for (;;) { |
481 |
|
long s = state; |
482 |
|
phase = phaseOf(s); |
483 |
+ |
if (phase < 0) |
484 |
+ |
break; |
485 |
|
int parties = partiesOf(s) - 1; |
486 |
|
int unarrived = unarrivedOf(s) - 1; |
487 |
|
if (parties >= 0) { |
500 |
|
if (unarrived == 0) { |
501 |
|
if (casState |
502 |
|
(s, |
503 |
< |
trippedStateFor(onAdvance(phase, parties)? -1 : |
503 |
> |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
504 |
|
((phase + 1) & phaseMask), parties))) { |
505 |
|
releaseWaiters(phase); |
506 |
|
break; |
507 |
|
} |
508 |
|
continue; |
509 |
|
} |
497 |
– |
if (phase < 0) |
498 |
– |
break; |
510 |
|
if (par != null && phase != phaseOf(root.state)) { |
511 |
|
reconcileState(); |
512 |
|
continue; |
513 |
|
} |
514 |
|
} |
515 |
< |
throw badBounds(parties, unarrived); |
515 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
516 |
|
} |
517 |
|
return phase; |
518 |
|
} |
519 |
|
|
520 |
|
/** |
521 |
|
* Arrives at the barrier and awaits others. Equivalent in effect |
522 |
< |
* to <tt>awaitAdvance(arrive())</tt>. If you instead need to |
522 |
> |
* to {@code awaitAdvance(arrive())}. If you instead need to |
523 |
|
* await with interruption of timeout, and/or deregister upon |
524 |
|
* arrival, you can arrange them using analogous constructions. |
525 |
+ |
* |
526 |
|
* @return the phase on entry to this method |
527 |
|
* @throws IllegalStateException if not terminated and the number |
528 |
< |
* of unarrived parties would become negative. |
528 |
> |
* of unarrived parties would become negative |
529 |
|
*/ |
530 |
|
public int arriveAndAwaitAdvance() { |
531 |
|
return awaitAdvance(arrive()); |
535 |
|
* Awaits the phase of the barrier to advance from the given |
536 |
|
* value, or returns immediately if argument is negative or this |
537 |
|
* barrier is terminated. |
538 |
+ |
* |
539 |
|
* @param phase the phase on entry to this method |
540 |
|
* @return the phase on exit from this method |
541 |
|
*/ |
546 |
|
int p = phaseOf(s); |
547 |
|
if (p != phase) |
548 |
|
return p; |
549 |
< |
if (unarrivedOf(s) == 0) |
549 |
> |
if (unarrivedOf(s) == 0 && parent != null) |
550 |
|
parent.awaitAdvance(phase); |
551 |
|
// Fall here even if parent waited, to reconcile and help release |
552 |
|
return untimedWait(phase); |
554 |
|
|
555 |
|
/** |
556 |
|
* Awaits the phase of the barrier to advance from the given |
557 |
< |
* value, or returns immediately if argumet is negative or this |
557 |
> |
* value, or returns immediately if argument is negative or this |
558 |
|
* barrier is terminated, or throws InterruptedException if |
559 |
|
* interrupted while waiting. |
560 |
+ |
* |
561 |
|
* @param phase the phase on entry to this method |
562 |
|
* @return the phase on exit from this method |
563 |
|
* @throws InterruptedException if thread interrupted while waiting |
564 |
|
*/ |
565 |
< |
public int awaitAdvanceInterruptibly(int phase) throws InterruptedException { |
565 |
> |
public int awaitAdvanceInterruptibly(int phase) |
566 |
> |
throws InterruptedException { |
567 |
|
if (phase < 0) |
568 |
|
return phase; |
569 |
|
long s = getReconciledState(); |
570 |
|
int p = phaseOf(s); |
571 |
|
if (p != phase) |
572 |
|
return p; |
573 |
< |
if (unarrivedOf(s) != 0) |
573 |
> |
if (unarrivedOf(s) == 0 && parent != null) |
574 |
|
parent.awaitAdvanceInterruptibly(phase); |
575 |
|
return interruptibleWait(phase); |
576 |
|
} |
579 |
|
* Awaits the phase of the barrier to advance from the given value |
580 |
|
* or the given timeout elapses, or returns immediately if |
581 |
|
* argument is negative or this barrier is terminated. |
582 |
+ |
* |
583 |
|
* @param phase the phase on entry to this method |
584 |
|
* @return the phase on exit from this method |
585 |
|
* @throws InterruptedException if thread interrupted while waiting |
586 |
|
* @throws TimeoutException if timed out while waiting |
587 |
|
*/ |
588 |
< |
public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit) |
588 |
> |
public int awaitAdvanceInterruptibly(int phase, |
589 |
> |
long timeout, TimeUnit unit) |
590 |
|
throws InterruptedException, TimeoutException { |
591 |
|
if (phase < 0) |
592 |
|
return phase; |
594 |
|
int p = phaseOf(s); |
595 |
|
if (p != phase) |
596 |
|
return p; |
597 |
< |
if (unarrivedOf(s) == 0) |
597 |
> |
if (unarrivedOf(s) == 0 && parent != null) |
598 |
|
parent.awaitAdvanceInterruptibly(phase, timeout, unit); |
599 |
|
return timedWait(phase, unit.toNanos(timeout)); |
600 |
|
} |
625 |
|
|
626 |
|
/** |
627 |
|
* Returns the current phase number. The maximum phase number is |
628 |
< |
* <tt>Integer.MAX_VALUE</tt>, after which it restarts at |
628 |
> |
* {@code Integer.MAX_VALUE}, after which it restarts at |
629 |
|
* zero. Upon termination, the phase number is negative. |
630 |
+ |
* |
631 |
|
* @return the phase number, or a negative value if terminated |
632 |
|
*/ |
633 |
|
public final int getPhase() { |
635 |
|
} |
636 |
|
|
637 |
|
/** |
638 |
< |
* Returns true if the current phase number equals the given phase. |
638 |
> |
* Returns {@code true} if the current phase number equals the given phase. |
639 |
> |
* |
640 |
|
* @param phase the phase |
641 |
< |
* @return true if the current phase number equals the given phase. |
641 |
> |
* @return {@code true} if the current phase number equals the given phase |
642 |
|
*/ |
643 |
|
public final boolean hasPhase(int phase) { |
644 |
|
return phaseOf(getReconciledState()) == phase; |
646 |
|
|
647 |
|
/** |
648 |
|
* Returns the number of parties registered at this barrier. |
649 |
+ |
* |
650 |
|
* @return the number of parties |
651 |
|
*/ |
652 |
|
public int getRegisteredParties() { |
656 |
|
/** |
657 |
|
* Returns the number of parties that have arrived at the current |
658 |
|
* phase of this barrier. |
659 |
+ |
* |
660 |
|
* @return the number of arrived parties |
661 |
|
*/ |
662 |
|
public int getArrivedParties() { |
666 |
|
/** |
667 |
|
* Returns the number of registered parties that have not yet |
668 |
|
* arrived at the current phase of this barrier. |
669 |
+ |
* |
670 |
|
* @return the number of unarrived parties |
671 |
|
*/ |
672 |
|
public int getUnarrivedParties() { |
675 |
|
|
676 |
|
/** |
677 |
|
* Returns the parent of this phaser, or null if none. |
678 |
< |
* @return the parent of this phaser, or null if none. |
678 |
> |
* |
679 |
> |
* @return the parent of this phaser, or null if none |
680 |
|
*/ |
681 |
|
public Phaser getParent() { |
682 |
|
return parent; |
685 |
|
/** |
686 |
|
* Returns the root ancestor of this phaser, which is the same as |
687 |
|
* this phaser if it has no parent. |
688 |
< |
* @return the root ancestor of this phaser. |
688 |
> |
* |
689 |
> |
* @return the root ancestor of this phaser |
690 |
|
*/ |
691 |
|
public Phaser getRoot() { |
692 |
|
return root; |
693 |
|
} |
694 |
|
|
695 |
|
/** |
696 |
< |
* Returns true if this barrier has been terminated. |
697 |
< |
* @return true if this barrier has been terminated |
696 |
> |
* Returns {@code true} if this barrier has been terminated. |
697 |
> |
* |
698 |
> |
* @return {@code true} if this barrier has been terminated |
699 |
|
*/ |
700 |
|
public boolean isTerminated() { |
701 |
|
return getPhase() < 0; |
707 |
|
* barrier is tripped (and thus all other waiting parties are |
708 |
|
* dormant). If it returns true, then, rather than advance the |
709 |
|
* phase number, this barrier will be set to a final termination |
710 |
< |
* state, and subsequent calls to <tt>isTerminated</tt> will |
710 |
> |
* state, and subsequent calls to {@code isTerminated} will |
711 |
|
* return true. |
712 |
|
* |
713 |
|
* <p> The default version returns true when the number of |
718 |
|
* <p> You may override this method to perform an action with side |
719 |
|
* effects visible to participating tasks, but it is in general |
720 |
|
* only sensible to do so in designs where all parties register |
721 |
< |
* before any arrive, and all <tt>awaitAdvance</tt> at each phase. |
721 |
> |
* before any arrive, and all {@code awaitAdvance} at each phase. |
722 |
|
* Otherwise, you cannot ensure lack of interference. In |
723 |
|
* particular, this method may be invoked more than once per |
724 |
|
* transition if other parties successfully register while the |
727 |
|
* method. |
728 |
|
* |
729 |
|
* @param phase the phase number on entering the barrier |
730 |
< |
* @param registeredParties the current number of registered |
731 |
< |
* parties. |
707 |
< |
* @return true if this barrier should terminate |
730 |
> |
* @param registeredParties the current number of registered parties |
731 |
> |
* @return {@code true} if this barrier should terminate |
732 |
|
*/ |
733 |
|
protected boolean onAdvance(int phase, int registeredParties) { |
734 |
|
return registeredParties <= 0; |
737 |
|
/** |
738 |
|
* Returns a string identifying this phaser, as well as its |
739 |
|
* state. The state, in brackets, includes the String {@code |
740 |
< |
* "phase ="} followed by the phase number, {@code "parties ="} |
740 |
> |
* "phase = "} followed by the phase number, {@code "parties = "} |
741 |
|
* followed by the number of registered parties, and {@code |
742 |
< |
* "arrived ="} followed by the number of arrived parties |
742 |
> |
* "arrived = "} followed by the number of arrived parties. |
743 |
|
* |
744 |
|
* @return a string identifying this barrier, as well as its state |
745 |
|
*/ |
746 |
|
public String toString() { |
747 |
|
long s = getReconciledState(); |
748 |
< |
return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]"; |
748 |
> |
return super.toString() + |
749 |
> |
"[phase = " + phaseOf(s) + |
750 |
> |
" parties = " + partiesOf(s) + |
751 |
> |
" arrived = " + arrivedOf(s) + "]"; |
752 |
|
} |
753 |
|
|
754 |
|
// methods for waiting |
755 |
|
|
729 |
– |
/** The number of CPUs, for spin control */ |
730 |
– |
static final int NCPUS = Runtime.getRuntime().availableProcessors(); |
731 |
– |
|
732 |
– |
/** |
733 |
– |
* The number of times to spin before blocking in timed waits. |
734 |
– |
* The value is empirically derived. |
735 |
– |
*/ |
736 |
– |
static final int maxTimedSpins = (NCPUS < 2)? 0 : 32; |
737 |
– |
|
738 |
– |
/** |
739 |
– |
* The number of times to spin before blocking in untimed waits. |
740 |
– |
* This is greater than timed value because untimed waits spin |
741 |
– |
* faster since they don't need to check times on each spin. |
742 |
– |
*/ |
743 |
– |
static final int maxUntimedSpins = maxTimedSpins * 32; |
744 |
– |
|
745 |
– |
/** |
746 |
– |
* The number of nanoseconds for which it is faster to spin |
747 |
– |
* rather than to use timed park. A rough estimate suffices. |
748 |
– |
*/ |
749 |
– |
static final long spinForTimeoutThreshold = 1000L; |
750 |
– |
|
756 |
|
/** |
757 |
< |
* Wait nodes for Treiber stack representing wait queue for non-FJ |
753 |
< |
* tasks. |
757 |
> |
* Wait nodes for Treiber stack representing wait queue |
758 |
|
*/ |
759 |
< |
static final class QNode { |
760 |
< |
QNode next; |
759 |
> |
static final class QNode implements ForkJoinPool.ManagedBlocker { |
760 |
> |
final Phaser phaser; |
761 |
> |
final int phase; |
762 |
> |
final long startTime; |
763 |
> |
final long nanos; |
764 |
> |
final boolean timed; |
765 |
> |
final boolean interruptible; |
766 |
> |
volatile boolean wasInterrupted = false; |
767 |
|
volatile Thread thread; // nulled to cancel wait |
768 |
< |
QNode() { |
768 |
> |
QNode next; |
769 |
> |
QNode(Phaser phaser, int phase, boolean interruptible, |
770 |
> |
boolean timed, long startTime, long nanos) { |
771 |
> |
this.phaser = phaser; |
772 |
> |
this.phase = phase; |
773 |
> |
this.timed = timed; |
774 |
> |
this.interruptible = interruptible; |
775 |
> |
this.startTime = startTime; |
776 |
> |
this.nanos = nanos; |
777 |
|
thread = Thread.currentThread(); |
778 |
|
} |
779 |
+ |
public boolean isReleasable() { |
780 |
+ |
return (thread == null || |
781 |
+ |
phaser.getPhase() != phase || |
782 |
+ |
(interruptible && wasInterrupted) || |
783 |
+ |
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
784 |
+ |
} |
785 |
+ |
public boolean block() { |
786 |
+ |
if (Thread.interrupted()) { |
787 |
+ |
wasInterrupted = true; |
788 |
+ |
if (interruptible) |
789 |
+ |
return true; |
790 |
+ |
} |
791 |
+ |
if (!timed) |
792 |
+ |
LockSupport.park(this); |
793 |
+ |
else { |
794 |
+ |
long waitTime = nanos - (System.nanoTime() - startTime); |
795 |
+ |
if (waitTime <= 0) |
796 |
+ |
return true; |
797 |
+ |
LockSupport.parkNanos(this, waitTime); |
798 |
+ |
} |
799 |
+ |
return isReleasable(); |
800 |
+ |
} |
801 |
|
void signal() { |
802 |
|
Thread t = thread; |
803 |
|
if (t != null) { |
805 |
|
LockSupport.unpark(t); |
806 |
|
} |
807 |
|
} |
808 |
+ |
boolean doWait() { |
809 |
+ |
if (thread != null) { |
810 |
+ |
try { |
811 |
+ |
ForkJoinPool.managedBlock(this, false); |
812 |
+ |
} catch (InterruptedException ie) { |
813 |
+ |
} |
814 |
+ |
} |
815 |
+ |
return wasInterrupted; |
816 |
+ |
} |
817 |
+ |
|
818 |
|
} |
819 |
|
|
820 |
|
/** |
821 |
< |
* Removes and signals waiting threads from wait queue |
821 |
> |
* Removes and signals waiting threads from wait queue. |
822 |
|
*/ |
823 |
|
private void releaseWaiters(int phase) { |
824 |
|
AtomicReference<QNode> head = queueFor(phase); |
830 |
|
} |
831 |
|
|
832 |
|
/** |
833 |
+ |
* Tries to enqueue given node in the appropriate wait queue. |
834 |
+ |
* |
835 |
+ |
* @return true if successful |
836 |
+ |
*/ |
837 |
+ |
private boolean tryEnqueue(QNode node) { |
838 |
+ |
AtomicReference<QNode> head = queueFor(node.phase); |
839 |
+ |
return head.compareAndSet(node.next = head.get(), node); |
840 |
+ |
} |
841 |
+ |
|
842 |
+ |
/** |
843 |
|
* Enqueues node and waits unless aborted or signalled. |
844 |
+ |
* |
845 |
+ |
* @return current phase |
846 |
|
*/ |
847 |
|
private int untimedWait(int phase) { |
786 |
– |
int spins = maxUntimedSpins; |
848 |
|
QNode node = null; |
788 |
– |
boolean interrupted = false; |
849 |
|
boolean queued = false; |
850 |
+ |
boolean interrupted = false; |
851 |
|
int p; |
852 |
|
while ((p = getPhase()) == phase) { |
853 |
< |
interrupted = Thread.interrupted(); |
854 |
< |
if (node != null) { |
855 |
< |
if (!queued) { |
856 |
< |
AtomicReference<QNode> head = queueFor(phase); |
857 |
< |
queued = head.compareAndSet(node.next = head.get(), node); |
858 |
< |
} |
798 |
< |
else if (node.thread != null) |
799 |
< |
LockSupport.park(this); |
800 |
< |
} |
801 |
< |
else if (spins <= 0) |
802 |
< |
node = new QNode(); |
853 |
> |
if (Thread.interrupted()) |
854 |
> |
interrupted = true; |
855 |
> |
else if (node == null) |
856 |
> |
node = new QNode(this, phase, false, false, 0, 0); |
857 |
> |
else if (!queued) |
858 |
> |
queued = tryEnqueue(node); |
859 |
|
else |
860 |
< |
--spins; |
860 |
> |
interrupted = node.doWait(); |
861 |
|
} |
862 |
|
if (node != null) |
863 |
|
node.thread = null; |
864 |
+ |
releaseWaiters(phase); |
865 |
|
if (interrupted) |
866 |
|
Thread.currentThread().interrupt(); |
810 |
– |
releaseWaiters(phase); |
867 |
|
return p; |
868 |
|
} |
869 |
|
|
870 |
|
/** |
871 |
< |
* Messier interruptible version |
871 |
> |
* Interruptible version |
872 |
> |
* @return current phase |
873 |
|
*/ |
874 |
|
private int interruptibleWait(int phase) throws InterruptedException { |
818 |
– |
int spins = maxUntimedSpins; |
875 |
|
QNode node = null; |
876 |
|
boolean queued = false; |
877 |
|
boolean interrupted = false; |
878 |
|
int p; |
879 |
< |
while ((p = getPhase()) == phase) { |
880 |
< |
if (interrupted = Thread.interrupted()) |
881 |
< |
break; |
882 |
< |
if (node != null) { |
883 |
< |
if (!queued) { |
884 |
< |
AtomicReference<QNode> head = queueFor(phase); |
885 |
< |
queued = head.compareAndSet(node.next = head.get(), node); |
830 |
< |
} |
831 |
< |
else if (node.thread != null) |
832 |
< |
LockSupport.park(this); |
833 |
< |
} |
834 |
< |
else if (spins <= 0) |
835 |
< |
node = new QNode(); |
879 |
> |
while ((p = getPhase()) == phase && !interrupted) { |
880 |
> |
if (Thread.interrupted()) |
881 |
> |
interrupted = true; |
882 |
> |
else if (node == null) |
883 |
> |
node = new QNode(this, phase, true, false, 0, 0); |
884 |
> |
else if (!queued) |
885 |
> |
queued = tryEnqueue(node); |
886 |
|
else |
887 |
< |
--spins; |
887 |
> |
interrupted = node.doWait(); |
888 |
|
} |
889 |
|
if (node != null) |
890 |
|
node.thread = null; |
891 |
+ |
if (p != phase || (p = getPhase()) != phase) |
892 |
+ |
releaseWaiters(phase); |
893 |
|
if (interrupted) |
894 |
|
throw new InterruptedException(); |
843 |
– |
releaseWaiters(phase); |
895 |
|
return p; |
896 |
|
} |
897 |
|
|
898 |
|
/** |
899 |
< |
* Even messier timeout version. |
899 |
> |
* Timeout version. |
900 |
> |
* @return current phase |
901 |
|
*/ |
902 |
|
private int timedWait(int phase, long nanos) |
903 |
|
throws InterruptedException, TimeoutException { |
904 |
+ |
long startTime = System.nanoTime(); |
905 |
+ |
QNode node = null; |
906 |
+ |
boolean queued = false; |
907 |
+ |
boolean interrupted = false; |
908 |
|
int p; |
909 |
< |
if ((p = getPhase()) == phase) { |
910 |
< |
long lastTime = System.nanoTime(); |
911 |
< |
int spins = maxTimedSpins; |
912 |
< |
QNode node = null; |
913 |
< |
boolean queued = false; |
914 |
< |
boolean interrupted = false; |
915 |
< |
while ((p = getPhase()) == phase) { |
916 |
< |
if (interrupted = Thread.interrupted()) |
917 |
< |
break; |
918 |
< |
long now = System.nanoTime(); |
919 |
< |
if ((nanos -= now - lastTime) <= 0) |
864 |
< |
break; |
865 |
< |
lastTime = now; |
866 |
< |
if (node != null) { |
867 |
< |
if (!queued) { |
868 |
< |
AtomicReference<QNode> head = queueFor(phase); |
869 |
< |
queued = head.compareAndSet(node.next = head.get(), node); |
870 |
< |
} |
871 |
< |
else if (node.thread != null && |
872 |
< |
nanos > spinForTimeoutThreshold) { |
873 |
< |
LockSupport.parkNanos(this, nanos); |
874 |
< |
} |
875 |
< |
} |
876 |
< |
else if (spins <= 0) |
877 |
< |
node = new QNode(); |
878 |
< |
else |
879 |
< |
--spins; |
880 |
< |
} |
881 |
< |
if (node != null) |
882 |
< |
node.thread = null; |
883 |
< |
if (interrupted) |
884 |
< |
throw new InterruptedException(); |
885 |
< |
if (p == phase && (p = getPhase()) == phase) |
886 |
< |
throw new TimeoutException(); |
909 |
> |
while ((p = getPhase()) == phase && !interrupted) { |
910 |
> |
if (Thread.interrupted()) |
911 |
> |
interrupted = true; |
912 |
> |
else if (nanos - (System.nanoTime() - startTime) <= 0) |
913 |
> |
break; |
914 |
> |
else if (node == null) |
915 |
> |
node = new QNode(this, phase, true, true, startTime, nanos); |
916 |
> |
else if (!queued) |
917 |
> |
queued = tryEnqueue(node); |
918 |
> |
else |
919 |
> |
interrupted = node.doWait(); |
920 |
|
} |
921 |
< |
releaseWaiters(phase); |
921 |
> |
if (node != null) |
922 |
> |
node.thread = null; |
923 |
> |
if (p != phase || (p = getPhase()) != phase) |
924 |
> |
releaseWaiters(phase); |
925 |
> |
if (interrupted) |
926 |
> |
throw new InterruptedException(); |
927 |
> |
if (p == phase) |
928 |
> |
throw new TimeoutException(); |
929 |
|
return p; |
930 |
|
} |
931 |
|
|
932 |
< |
// Temporary Unsafe mechanics for preliminary release |
932 |
> |
// Unsafe mechanics for jsr166y 3rd party package. |
933 |
> |
private static sun.misc.Unsafe getUnsafe() { |
934 |
> |
try { |
935 |
> |
return sun.misc.Unsafe.getUnsafe(); |
936 |
> |
} catch (SecurityException se) { |
937 |
> |
try { |
938 |
> |
return java.security.AccessController.doPrivileged |
939 |
> |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
940 |
> |
public sun.misc.Unsafe run() throws Exception { |
941 |
> |
return getUnsafeByReflection(); |
942 |
> |
}}); |
943 |
> |
} catch (java.security.PrivilegedActionException e) { |
944 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
945 |
> |
e.getCause()); |
946 |
> |
} |
947 |
> |
} |
948 |
> |
} |
949 |
|
|
950 |
< |
static final Unsafe _unsafe; |
951 |
< |
static final long stateOffset; |
950 |
> |
private static sun.misc.Unsafe getUnsafeByReflection() |
951 |
> |
throws NoSuchFieldException, IllegalAccessException { |
952 |
> |
java.lang.reflect.Field f = |
953 |
> |
sun.misc.Unsafe.class.getDeclaredField("theUnsafe"); |
954 |
> |
f.setAccessible(true); |
955 |
> |
return (sun.misc.Unsafe) f.get(null); |
956 |
> |
} |
957 |
|
|
958 |
< |
static { |
958 |
> |
private static long fieldOffset(String fieldName, Class<?> klazz) { |
959 |
|
try { |
960 |
< |
if (Phaser.class.getClassLoader() != null) { |
961 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
962 |
< |
f.setAccessible(true); |
963 |
< |
_unsafe = (Unsafe)f.get(null); |
964 |
< |
} |
965 |
< |
else |
905 |
< |
_unsafe = Unsafe.getUnsafe(); |
906 |
< |
stateOffset = _unsafe.objectFieldOffset |
907 |
< |
(Phaser.class.getDeclaredField("state")); |
908 |
< |
} catch (Exception e) { |
909 |
< |
throw new RuntimeException("Could not initialize intrinsics", e); |
960 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName)); |
961 |
> |
} catch (NoSuchFieldException e) { |
962 |
> |
// Convert Exception to Error |
963 |
> |
NoSuchFieldError error = new NoSuchFieldError(fieldName); |
964 |
> |
error.initCause(e); |
965 |
> |
throw error; |
966 |
|
} |
967 |
|
} |
968 |
|
|
969 |
+ |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
970 |
+ |
static final long stateOffset = |
971 |
+ |
fieldOffset("state", Phaser.class); |
972 |
+ |
|
973 |
|
final boolean casState(long cmp, long val) { |
974 |
< |
return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val); |
974 |
> |
return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val); |
975 |
|
} |
976 |
|
} |