93 |
|
* idiom is for the method setting this up to first register, then |
94 |
|
* start the actions, then deregister, as in: |
95 |
|
* |
96 |
< |
* <pre> |
97 |
< |
* void runTasks(List<Runnable> list) { |
98 |
< |
* final Phaser phaser = new Phaser(1); // "1" to register self |
99 |
< |
* for (Runnable r : list) { |
100 |
< |
* phaser.register(); |
101 |
< |
* new Thread() { |
102 |
< |
* public void run() { |
103 |
< |
* phaser.arriveAndAwaitAdvance(); // await all creation |
104 |
< |
* r.run(); |
105 |
< |
* phaser.arriveAndDeregister(); // signal completion |
106 |
< |
* } |
107 |
< |
* }.start(); |
96 |
> |
* <pre> {@code |
97 |
> |
* void runTasks(List<Runnable> list) { |
98 |
> |
* final Phaser phaser = new Phaser(1); // "1" to register self |
99 |
> |
* for (Runnable r : list) { |
100 |
> |
* phaser.register(); |
101 |
> |
* new Thread() { |
102 |
> |
* public void run() { |
103 |
> |
* phaser.arriveAndAwaitAdvance(); // await all creation |
104 |
> |
* r.run(); |
105 |
> |
* phaser.arriveAndDeregister(); // signal completion |
106 |
> |
* } |
107 |
> |
* }.start(); |
108 |
|
* } |
109 |
|
* |
110 |
|
* doSomethingOnBehalfOfWorkers(); |
113 |
|
* p = phaser.awaitAdvance(p); // ... and await arrival |
114 |
|
* otherActions(); // do other things while tasks execute |
115 |
|
* phaser.awaitAdvance(p); // await final completion |
116 |
< |
* } |
117 |
< |
* </pre> |
116 |
> |
* }}</pre> |
117 |
|
* |
118 |
|
* <p>One way to cause a set of threads to repeatedly perform actions |
119 |
|
* for a given number of iterations is to override {@code onAdvance}: |
120 |
|
* |
121 |
< |
* <pre> |
122 |
< |
* void startTasks(List<Runnable> list, final int iterations) { |
123 |
< |
* final Phaser phaser = new Phaser() { |
124 |
< |
* public boolean onAdvance(int phase, int registeredParties) { |
125 |
< |
* return phase >= iterations || registeredParties == 0; |
121 |
> |
* <pre> {@code |
122 |
> |
* void startTasks(List<Runnable> list, final int iterations) { |
123 |
> |
* final Phaser phaser = new Phaser() { |
124 |
> |
* public boolean onAdvance(int phase, int registeredParties) { |
125 |
> |
* return phase >= iterations || registeredParties == 0; |
126 |
> |
* } |
127 |
> |
* }; |
128 |
> |
* phaser.register(); |
129 |
> |
* for (Runnable r : list) { |
130 |
> |
* phaser.register(); |
131 |
> |
* new Thread() { |
132 |
> |
* public void run() { |
133 |
> |
* do { |
134 |
> |
* r.run(); |
135 |
> |
* phaser.arriveAndAwaitAdvance(); |
136 |
> |
* } while(!phaser.isTerminated(); |
137 |
|
* } |
138 |
< |
* }; |
129 |
< |
* phaser.register(); |
130 |
< |
* for (Runnable r : list) { |
131 |
< |
* phaser.register(); |
132 |
< |
* new Thread() { |
133 |
< |
* public void run() { |
134 |
< |
* do { |
135 |
< |
* r.run(); |
136 |
< |
* phaser.arriveAndAwaitAdvance(); |
137 |
< |
* } while(!phaser.isTerminated(); |
138 |
< |
* } |
139 |
< |
* }.start(); |
138 |
> |
* }.start(); |
139 |
|
* } |
140 |
|
* phaser.arriveAndDeregister(); // deregister self, don't wait |
141 |
< |
* } |
143 |
< |
* </pre> |
141 |
> |
* }}</pre> |
142 |
|
* |
143 |
|
* <p> To create a set of tasks using a tree of Phasers, |
144 |
|
* you could use code of the following form, assuming a |
145 |
|
* Task class with a constructor accepting a Phaser that |
146 |
|
* it registers for upon construction: |
147 |
< |
* <pre> |
148 |
< |
* void build(Task[] actions, int lo, int hi, Phaser b) { |
149 |
< |
* int step = (hi - lo) / TASKS_PER_PHASER; |
150 |
< |
* if (step > 1) { |
151 |
< |
* int i = lo; |
152 |
< |
* while (i < hi) { |
153 |
< |
* int r = Math.min(i + step, hi); |
154 |
< |
* build(actions, i, r, new Phaser(b)); |
155 |
< |
* i = r; |
156 |
< |
* } |
157 |
< |
* } |
158 |
< |
* else { |
159 |
< |
* for (int i = lo; i < hi; ++i) |
160 |
< |
* actions[i] = new Task(b); |
161 |
< |
* // assumes new Task(b) performs b.register() |
162 |
< |
* } |
163 |
< |
* } |
164 |
< |
* // .. initially called, for n tasks via |
167 |
< |
* build(new Task[n], 0, n, new Phaser()); |
168 |
< |
* </pre> |
147 |
> |
* <pre> {@code |
148 |
> |
* void build(Task[] actions, int lo, int hi, Phaser b) { |
149 |
> |
* int step = (hi - lo) / TASKS_PER_PHASER; |
150 |
> |
* if (step > 1) { |
151 |
> |
* int i = lo; |
152 |
> |
* while (i < hi) { |
153 |
> |
* int r = Math.min(i + step, hi); |
154 |
> |
* build(actions, i, r, new Phaser(b)); |
155 |
> |
* i = r; |
156 |
> |
* } |
157 |
> |
* } else { |
158 |
> |
* for (int i = lo; i < hi; ++i) |
159 |
> |
* actions[i] = new Task(b); |
160 |
> |
* // assumes new Task(b) performs b.register() |
161 |
> |
* } |
162 |
> |
* } |
163 |
> |
* // .. initially called, for n tasks via |
164 |
> |
* build(new Task[n], 0, n, new Phaser());}</pre> |
165 |
|
* |
166 |
|
* The best value of {@code TASKS_PER_PHASER} depends mainly on |
167 |
|
* expected barrier synchronization rates. A value as low as four may |
175 |
|
* parties result in IllegalStateExceptions. However, you can and |
176 |
|
* should create tiered phasers to accommodate arbitrarily large sets |
177 |
|
* of participants. |
178 |
+ |
* |
179 |
+ |
* @since 1.7 |
180 |
+ |
* @author Doug Lea |
181 |
|
*/ |
182 |
|
public class Phaser { |
183 |
|
/* |
237 |
|
} |
238 |
|
|
239 |
|
/** |
240 |
< |
* Returns message string for bad bounds exceptions |
240 |
> |
* Returns message string for bad bounds exceptions. |
241 |
|
*/ |
242 |
|
private static String badBounds(int parties, int unarrived) { |
243 |
|
return ("Attempt to set " + unarrived + |
312 |
|
/** |
313 |
|
* Creates a new Phaser with the given numbers of registered |
314 |
|
* unarrived parties, initial phase number 0, and no parent. |
315 |
< |
* @param parties the number of parties required to trip barrier. |
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); |
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 |
< |
* @param parent the parent phaser. |
329 |
> |
* |
330 |
> |
* @param parent the parent phaser |
331 |
|
*/ |
332 |
|
public Phaser(Phaser parent) { |
333 |
|
int phase = 0; |
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 |
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 |
< |
* @param parent the parent phaser. |
350 |
< |
* @param parties the number of parties required to trip barrier. |
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. |
353 |
> |
* or greater than the maximum number of parties supported |
354 |
|
*/ |
355 |
|
public Phaser(Phaser parent, int parties) { |
356 |
|
if (parties < 0 || parties > ushortMask) |
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. |
374 |
> |
* than the maximum supported number of parties |
375 |
|
*/ |
376 |
|
public int register() { |
377 |
|
return doRegister(1); |
379 |
|
|
380 |
|
/** |
381 |
|
* Adds the given number of new unarrived parties to this phaser. |
382 |
< |
* @param parties the number of parties required to trip barrier. |
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 bulkRegister(int parties) { |
389 |
|
if (parties < 0) |
419 |
|
* in turn wait for others via {@link #awaitAdvance}). |
420 |
|
* |
421 |
|
* @return the barrier phase number upon entry to this method, or a |
422 |
< |
* negative value if terminated; |
422 |
> |
* negative value if terminated |
423 |
|
* @throws IllegalStateException if not terminated and the number |
424 |
< |
* of unarrived parties would become negative. |
424 |
> |
* of unarrived parties would become negative |
425 |
|
*/ |
426 |
|
public int arrive() { |
427 |
|
int phase; |
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; |
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. |
476 |
> |
* of registered or unarrived parties would become negative |
477 |
|
*/ |
478 |
|
public int arriveAndDeregister() { |
479 |
|
// similar code to arrive, but too different to merge |
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. |
530 |
> |
* of unarrived parties would become negative |
531 |
|
*/ |
532 |
|
public int arriveAndAwaitAdvance() { |
533 |
|
return awaitAdvance(arrive()); |
537 |
|
* Awaits the phase of the barrier to advance from the given |
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 |
|
*/ |
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 |
581 |
|
* Awaits the phase of the barrier to advance from the given value |
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 |
628 |
|
* Returns the current phase number. The maximum phase number is |
629 |
|
* {@code Integer.MAX_VALUE}, after which it restarts at |
630 |
|
* zero. Upon termination, the phase number is negative. |
631 |
+ |
* |
632 |
|
* @return the phase number, or a negative value if terminated |
633 |
|
*/ |
634 |
|
public final int getPhase() { |
637 |
|
|
638 |
|
/** |
639 |
|
* Returns {@code true} if the current phase number equals the given phase. |
640 |
+ |
* |
641 |
|
* @param phase the phase |
642 |
|
* @return {@code true} if the current phase number equals the given phase |
643 |
|
*/ |
647 |
|
|
648 |
|
/** |
649 |
|
* Returns the number of parties registered at this barrier. |
650 |
+ |
* |
651 |
|
* @return the number of parties |
652 |
|
*/ |
653 |
|
public int getRegisteredParties() { |
657 |
|
/** |
658 |
|
* Returns the number of parties that have arrived at the current |
659 |
|
* phase of this barrier. |
660 |
+ |
* |
661 |
|
* @return the number of arrived parties |
662 |
|
*/ |
663 |
|
public int getArrivedParties() { |
667 |
|
/** |
668 |
|
* Returns the number of registered parties that have not yet |
669 |
|
* arrived at the current phase of this barrier. |
670 |
+ |
* |
671 |
|
* @return the number of unarrived parties |
672 |
|
*/ |
673 |
|
public int getUnarrivedParties() { |
676 |
|
|
677 |
|
/** |
678 |
|
* Returns the parent of this phaser, or null if none. |
679 |
+ |
* |
680 |
|
* @return the parent of this phaser, or null if none |
681 |
|
*/ |
682 |
|
public Phaser getParent() { |
686 |
|
/** |
687 |
|
* Returns the root ancestor of this phaser, which is the same as |
688 |
|
* this phaser if it has no parent. |
689 |
+ |
* |
690 |
|
* @return the root ancestor of this phaser |
691 |
|
*/ |
692 |
|
public Phaser getRoot() { |
695 |
|
|
696 |
|
/** |
697 |
|
* Returns {@code true} if this barrier has been terminated. |
698 |
+ |
* |
699 |
|
* @return {@code true} if this barrier has been terminated |
700 |
|
*/ |
701 |
|
public boolean isTerminated() { |
819 |
|
} |
820 |
|
|
821 |
|
/** |
822 |
< |
* Removes and signals waiting threads from wait queue |
822 |
> |
* Removes and signals waiting threads from wait queue. |
823 |
|
*/ |
824 |
|
private void releaseWaiters(int phase) { |
825 |
|
AtomicReference<QNode> head = queueFor(phase); |
831 |
|
} |
832 |
|
|
833 |
|
/** |
834 |
< |
* Tries to enqueue given node in the appropriate wait queue |
834 |
> |
* Tries to enqueue given node in the appropriate wait queue. |
835 |
> |
* |
836 |
|
* @return true if successful |
837 |
|
*/ |
838 |
|
private boolean tryEnqueue(QNode node) { |
842 |
|
|
843 |
|
/** |
844 |
|
* Enqueues node and waits unless aborted or signalled. |
845 |
+ |
* |
846 |
|
* @return current phase |
847 |
|
*/ |
848 |
|
private int untimedWait(int phase) { |
956 |
|
|
957 |
|
private static long fieldOffset(String fieldName) |
958 |
|
throws NoSuchFieldException { |
959 |
< |
return _unsafe.objectFieldOffset |
959 |
> |
return UNSAFE.objectFieldOffset |
960 |
|
(Phaser.class.getDeclaredField(fieldName)); |
961 |
|
} |
962 |
|
|
963 |
< |
static final Unsafe _unsafe; |
963 |
> |
static final Unsafe UNSAFE; |
964 |
|
static final long stateOffset; |
965 |
|
|
966 |
|
static { |
967 |
|
try { |
968 |
< |
_unsafe = getUnsafe(); |
968 |
> |
UNSAFE = getUnsafe(); |
969 |
|
stateOffset = fieldOffset("state"); |
970 |
|
} catch (Throwable e) { |
971 |
|
throw new RuntimeException("Could not initialize intrinsics", e); |
973 |
|
} |
974 |
|
|
975 |
|
final boolean casState(long cmp, long val) { |
976 |
< |
return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val); |
976 |
> |
return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val); |
977 |
|
} |
978 |
|
} |