| 13 |
|
/** |
| 14 |
|
* A thread managed by a {@link ForkJoinPool}. This class is |
| 15 |
|
* subclassable solely for the sake of adding functionality -- there |
| 16 |
< |
* are no overridable methods dealing with scheduling or |
| 17 |
< |
* execution. However, you can override initialization and termination |
| 18 |
< |
* methods surrounding the main task processing loop. If you do |
| 19 |
< |
* create such a subclass, you will also need to supply a custom |
| 20 |
< |
* ForkJoinWorkerThreadFactory to use it in a ForkJoinPool. |
| 16 |
> |
* are no overridable methods dealing with scheduling or execution. |
| 17 |
> |
* However, you can override initialization and termination methods |
| 18 |
> |
* surrounding the main task processing loop. If you do create such a |
| 19 |
> |
* subclass, you will also need to supply a custom {@link |
| 20 |
> |
* ForkJoinWorkerThreadFactory} to use it in a {@code ForkJoinPool}. |
| 21 |
|
* |
| 22 |
|
* @since 1.7 |
| 23 |
|
* @author Doug Lea |
| 65 |
|
* which gives threads a chance to activate if necessary before |
| 66 |
|
* stealing (see below). |
| 67 |
|
* |
| 68 |
+ |
* This approach also enables support for "async mode" where local |
| 69 |
+ |
* task processing is in FIFO, not LIFO order; simply by using a |
| 70 |
+ |
* version of deq rather than pop when locallyFifo is true (as set |
| 71 |
+ |
* by the ForkJoinPool). This allows use in message-passing |
| 72 |
+ |
* frameworks in which tasks are never joined. |
| 73 |
+ |
* |
| 74 |
|
* Efficient implementation of this approach currently relies on |
| 75 |
|
* an uncomfortable amount of "Unsafe" mechanics. To maintain |
| 76 |
|
* correct orderings, reads and writes of variable base require |
| 271 |
|
final boolean shutdownNow() { return transitionRunStateTo(TERMINATING); } |
| 272 |
|
|
| 273 |
|
/** |
| 274 |
< |
* Transitions to at least the given state. Returns true if not |
| 275 |
< |
* already at least at given state. |
| 274 |
> |
* Transitions to at least the given state. |
| 275 |
> |
* |
| 276 |
> |
* @return {@code true} if not already at least at given state |
| 277 |
|
*/ |
| 278 |
|
private boolean transitionRunStateTo(int state) { |
| 279 |
|
for (;;) { |
| 315 |
|
* one. Marsaglia xor-shift is cheap and works well. |
| 316 |
|
*/ |
| 317 |
|
private static int xorShift(int r) { |
| 318 |
< |
r ^= r << 1; |
| 319 |
< |
r ^= r >>> 3; |
| 320 |
< |
r ^= r << 10; |
| 314 |
< |
return r; |
| 318 |
> |
r ^= (r << 13); |
| 319 |
> |
r ^= (r >>> 17); |
| 320 |
> |
return r ^ (r << 5); |
| 321 |
|
} |
| 322 |
|
|
| 323 |
|
// Lifecycle methods |
| 378 |
|
* {@code super.onTermination} at the end of the overridden method. |
| 379 |
|
* |
| 380 |
|
* @param exception the exception causing this thread to abort due |
| 381 |
< |
* to an unrecoverable error, or null if completed normally |
| 381 |
> |
* to an unrecoverable error, or {@code null} if completed normally |
| 382 |
|
*/ |
| 383 |
|
protected void onTermination(Throwable exception) { |
| 384 |
|
// Execute remaining local tasks unless aborting or terminating |
| 475 |
|
} |
| 476 |
|
|
| 477 |
|
/** |
| 478 |
+ |
* Tries to take a task from the base of own queue, activating if |
| 479 |
+ |
* necessary, failing only if empty. Called only by current thread. |
| 480 |
+ |
* |
| 481 |
+ |
* @return a task, or null if none |
| 482 |
+ |
*/ |
| 483 |
+ |
final ForkJoinTask<?> locallyDeqTask() { |
| 484 |
+ |
int b; |
| 485 |
+ |
while (sp != (b = base)) { |
| 486 |
+ |
if (tryActivate()) { |
| 487 |
+ |
ForkJoinTask<?>[] q = queue; |
| 488 |
+ |
int i = (q.length - 1) & b; |
| 489 |
+ |
ForkJoinTask<?> t = q[i]; |
| 490 |
+ |
if (t != null && casSlotNull(q, i, t)) { |
| 491 |
+ |
base = b + 1; |
| 492 |
+ |
return t; |
| 493 |
+ |
} |
| 494 |
+ |
} |
| 495 |
+ |
} |
| 496 |
+ |
return null; |
| 497 |
+ |
} |
| 498 |
+ |
|
| 499 |
+ |
/** |
| 500 |
|
* Returns a popped task, or null if empty. Ensures active status |
| 501 |
|
* if non-null. Called only by current thread. |
| 502 |
|
*/ |
| 536 |
|
} |
| 537 |
|
|
| 538 |
|
/** |
| 539 |
< |
* Returns next task. |
| 539 |
> |
* Returns next task or null if empty or contended |
| 540 |
|
*/ |
| 541 |
|
final ForkJoinTask<?> peekTask() { |
| 542 |
|
ForkJoinTask<?>[] q = queue; |
| 627 |
|
* @return a task, if available |
| 628 |
|
*/ |
| 629 |
|
final ForkJoinTask<?> pollTask() { |
| 630 |
< |
ForkJoinTask<?> t = locallyFifo ? deqTask() : popTask(); |
| 630 |
> |
ForkJoinTask<?> t = locallyFifo ? locallyDeqTask() : popTask(); |
| 631 |
|
if (t == null && (t = scan()) != null) |
| 632 |
|
++stealCount; |
| 633 |
|
return t; |
| 639 |
|
* @return a task, if available |
| 640 |
|
*/ |
| 641 |
|
final ForkJoinTask<?> pollLocalTask() { |
| 642 |
< |
return locallyFifo ? deqTask() : popTask(); |
| 642 |
> |
return locallyFifo ? locallyDeqTask() : popTask(); |
| 643 |
|
} |
| 644 |
|
|
| 645 |
|
/** |
| 674 |
|
* |
| 675 |
|
* @return the number of tasks drained |
| 676 |
|
*/ |
| 677 |
< |
final int drainTasksTo(Collection<ForkJoinTask<?>> c) { |
| 677 |
> |
final int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
| 678 |
|
int n = 0; |
| 679 |
|
ForkJoinTask<?> t; |
| 680 |
|
while (base != sp && (t = deqTask()) != null) { |
| 695 |
|
} |
| 696 |
|
|
| 697 |
|
/** |
| 698 |
< |
* Returns true if at least one worker in the given array appears |
| 699 |
< |
* to have at least one queued task. |
| 698 |
> |
* Returns {@code true} if at least one worker in the given array |
| 699 |
> |
* appears to have at least one queued task. |
| 700 |
|
* |
| 701 |
|
* @param ws array of workers |
| 702 |
|
*/ |
