5 |
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*/ |
6 |
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|
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package jsr166y; |
8 |
< |
import java.util.*; |
8 |
> |
|
9 |
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import java.util.concurrent.*; |
10 |
< |
import java.util.concurrent.locks.*; |
11 |
< |
import java.util.concurrent.atomic.*; |
12 |
< |
import sun.misc.Unsafe; |
13 |
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import java.lang.reflect.*; |
10 |
> |
|
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> |
import java.util.ArrayList; |
12 |
> |
import java.util.Arrays; |
13 |
> |
import java.util.Collection; |
14 |
> |
import java.util.Collections; |
15 |
> |
import java.util.List; |
16 |
> |
import java.util.concurrent.locks.Condition; |
17 |
> |
import java.util.concurrent.locks.LockSupport; |
18 |
> |
import java.util.concurrent.locks.ReentrantLock; |
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> |
import java.util.concurrent.atomic.AtomicInteger; |
20 |
> |
import java.util.concurrent.atomic.AtomicLong; |
21 |
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|
22 |
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/** |
23 |
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* An {@link ExecutorService} for running {@link ForkJoinTask}s. A |
24 |
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* ForkJoinPool provides the entry point for submissions from |
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> |
* An {@link ExecutorService} for running {@link ForkJoinTask}s. |
24 |
> |
* A ForkJoinPool provides the entry point for submissions from |
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* non-ForkJoinTasks, as well as management and monitoring operations. |
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* Normally a single ForkJoinPool is used for a large number of |
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* submitted tasks. Otherwise, use would not usually outweigh the |
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* (eventually blocking if none exist). This makes them efficient when |
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* most tasks spawn other subtasks (as do most ForkJoinTasks), as well |
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* as the mixed execution of some plain Runnable- or Callable- based |
37 |
< |
* activities along with ForkJoinTasks. When setting |
38 |
< |
* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for |
39 |
< |
* use with fine-grained tasks that are never joined. Otherwise, other |
40 |
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* ExecutorService implementations are typically more appropriate |
41 |
< |
* choices. |
37 |
> |
* activities along with ForkJoinTasks. When setting {@linkplain |
38 |
> |
* #setAsyncMode async mode}, a ForkJoinPool may also be appropriate |
39 |
> |
* for use with fine-grained tasks that are never joined. Otherwise, |
40 |
> |
* other ExecutorService implementations are typically more |
41 |
> |
* appropriate choices. |
42 |
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* |
43 |
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* <p>A ForkJoinPool may be constructed with a given parallelism level |
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* (target pool size), which it attempts to maintain by dynamically |
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* adding, suspending, or resuming threads, even if some tasks are |
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* waiting to join others. However, no such adjustments are performed |
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* in the face of blocked IO or other unmanaged synchronization. The |
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* nested {@code ManagedBlocker} interface enables extension of |
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> |
* nested {@link ManagedBlocker} interface enables extension of |
49 |
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* the kinds of synchronization accommodated. The target parallelism |
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* level may also be changed dynamically ({@code setParallelism}) |
50 |
> |
* level may also be changed dynamically ({@link #setParallelism}) |
51 |
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* and thread construction can be limited using methods |
52 |
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* {@code setMaximumPoolSize} and/or |
53 |
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* {@code setMaintainsParallelism}. |
52 |
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* {@link #setMaximumPoolSize} and/or |
53 |
> |
* {@link #setMaintainsParallelism}. |
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* |
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* <p>In addition to execution and lifecycle control methods, this |
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* class provides status check methods (for example |
57 |
< |
* {@code getStealCount}) that are intended to aid in developing, |
57 |
> |
* {@link #getStealCount}) that are intended to aid in developing, |
58 |
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* tuning, and monitoring fork/join applications. Also, method |
59 |
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* {@code toString} returns indications of pool state in a |
59 |
> |
* {@link #toString} returns indications of pool state in a |
60 |
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* convenient form for informal monitoring. |
61 |
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* |
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* <p><b>Implementation notes</b>: This implementation restricts the |
63 |
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* maximum number of running threads to 32767. Attempts to create |
64 |
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* pools with greater than the maximum result in |
65 |
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* IllegalArgumentExceptions. |
66 |
+ |
* |
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* @since 1.7 |
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+ |
* @author Doug Lea |
69 |
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*/ |
70 |
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public class ForkJoinPool extends AbstractExecutorService { |
71 |
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|
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* Returns a new worker thread operating in the given pool. |
92 |
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* |
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* @param pool the pool this thread works in |
94 |
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* @throws NullPointerException if pool is null; |
94 |
> |
* @throws NullPointerException if pool is null |
95 |
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*/ |
96 |
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public ForkJoinWorkerThread newThread(ForkJoinPool pool); |
97 |
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} |
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|
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/** |
100 |
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* Default ForkJoinWorkerThreadFactory implementation, creates a |
100 |
> |
* Default ForkJoinWorkerThreadFactory implementation; creates a |
101 |
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* new ForkJoinWorkerThread. |
102 |
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*/ |
103 |
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static class DefaultForkJoinWorkerThreadFactory |
163 |
|
|
164 |
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/** |
165 |
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* The uncaught exception handler used when any worker |
166 |
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* abrupty terminates |
166 |
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* abruptly terminates |
167 |
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*/ |
168 |
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private Thread.UncaughtExceptionHandler ueh; |
169 |
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|
191 |
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private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue; |
192 |
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|
193 |
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/** |
194 |
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* Head of Treiber stack for barrier sync. See below for explanation |
194 |
> |
* Head of Treiber stack for barrier sync. See below for explanation. |
195 |
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*/ |
196 |
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private volatile WaitQueueNode syncStack; |
197 |
|
|
226 |
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* threads, packed into one int to ensure consistent snapshot when |
227 |
|
* making decisions about creating and suspending spare |
228 |
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* threads. Updated only by CAS. Note: CASes in |
229 |
< |
* updateRunningCount and preJoin running active count is in low |
230 |
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* word, so need to be modified if this changes |
229 |
> |
* updateRunningCount and preJoin assume that running active count |
230 |
> |
* is in low word, so need to be modified if this changes. |
231 |
|
*/ |
232 |
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private volatile int workerCounts; |
233 |
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|
236 |
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private static int workerCountsFor(int t, int r) { return (t << 16) + r; } |
237 |
|
|
238 |
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/** |
239 |
< |
* Add delta (which may be negative) to running count. This must |
239 |
> |
* Adds delta (which may be negative) to running count. This must |
240 |
|
* be called before (with negative arg) and after (with positive) |
241 |
< |
* any managed synchronization (i.e., mainly, joins) |
241 |
> |
* any managed synchronization (i.e., mainly, joins). |
242 |
> |
* |
243 |
|
* @param delta the number to add |
244 |
|
*/ |
245 |
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final void updateRunningCount(int delta) { |
246 |
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int s; |
247 |
< |
do;while (!casWorkerCounts(s = workerCounts, s + delta)); |
247 |
> |
do {} while (!casWorkerCounts(s = workerCounts, s + delta)); |
248 |
|
} |
249 |
|
|
250 |
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/** |
251 |
< |
* Add delta (which may be negative) to both total and running |
251 |
> |
* Adds delta (which may be negative) to both total and running |
252 |
|
* count. This must be called upon creation and termination of |
253 |
|
* worker threads. |
254 |
+ |
* |
255 |
|
* @param delta the number to add |
256 |
|
*/ |
257 |
|
private void updateWorkerCount(int delta) { |
258 |
|
int d = delta + (delta << 16); // add to both lo and hi parts |
259 |
|
int s; |
260 |
< |
do;while (!casWorkerCounts(s = workerCounts, s + d)); |
260 |
> |
do {} while (!casWorkerCounts(s = workerCounts, s + d)); |
261 |
|
} |
262 |
|
|
263 |
|
/** |
283 |
|
private static int runControlFor(int r, int a) { return (r << 16) + a; } |
284 |
|
|
285 |
|
/** |
286 |
< |
* Try incrementing active count; fail on contention. Called by |
287 |
< |
* workers before/during executing tasks. |
288 |
< |
* @return true on success; |
286 |
> |
* Tries incrementing active count; fails on contention. |
287 |
> |
* Called by workers before/during executing tasks. |
288 |
> |
* |
289 |
> |
* @return true on success |
290 |
|
*/ |
291 |
|
final boolean tryIncrementActiveCount() { |
292 |
|
int c = runControl; |
294 |
|
} |
295 |
|
|
296 |
|
/** |
297 |
< |
* Try decrementing active count; fail on contention. |
298 |
< |
* Possibly trigger termination on success |
297 |
> |
* Tries decrementing active count; fails on contention. |
298 |
> |
* Possibly triggers termination on success. |
299 |
|
* Called by workers when they can't find tasks. |
300 |
+ |
* |
301 |
|
* @return true on success |
302 |
|
*/ |
303 |
|
final boolean tryDecrementActiveCount() { |
311 |
|
} |
312 |
|
|
313 |
|
/** |
314 |
< |
* Return true if argument represents zero active count and |
315 |
< |
* nonzero runstate, which is the triggering condition for |
314 |
> |
* Returns {@code true} if argument represents zero active count |
315 |
> |
* and nonzero runstate, which is the triggering condition for |
316 |
|
* terminating on shutdown. |
317 |
|
*/ |
318 |
|
private static boolean canTerminateOnShutdown(int c) { |
319 |
< |
return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit |
319 |
> |
// i.e. least bit is nonzero runState bit |
320 |
> |
return ((c & -c) >>> 16) != 0; |
321 |
|
} |
322 |
|
|
323 |
|
/** |
343 |
|
|
344 |
|
/** |
345 |
|
* Creates a ForkJoinPool with a pool size equal to the number of |
346 |
< |
* processors available on the system and using the default |
347 |
< |
* ForkJoinWorkerThreadFactory, |
346 |
> |
* processors available on the system, using the default |
347 |
> |
* ForkJoinWorkerThreadFactory. |
348 |
> |
* |
349 |
|
* @throws SecurityException if a security manager exists and |
350 |
|
* the caller is not permitted to modify threads |
351 |
|
* because it does not hold {@link |
352 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
352 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
353 |
|
*/ |
354 |
|
public ForkJoinPool() { |
355 |
|
this(Runtime.getRuntime().availableProcessors(), |
357 |
|
} |
358 |
|
|
359 |
|
/** |
360 |
< |
* Creates a ForkJoinPool with the indicated parellelism level |
361 |
< |
* threads, and using the default ForkJoinWorkerThreadFactory, |
360 |
> |
* Creates a ForkJoinPool with the indicated parallelism level |
361 |
> |
* threads and using the default ForkJoinWorkerThreadFactory. |
362 |
> |
* |
363 |
|
* @param parallelism the number of worker threads |
364 |
|
* @throws IllegalArgumentException if parallelism less than or |
365 |
|
* equal to zero |
366 |
|
* @throws SecurityException if a security manager exists and |
367 |
|
* the caller is not permitted to modify threads |
368 |
|
* because it does not hold {@link |
369 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
369 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
370 |
|
*/ |
371 |
|
public ForkJoinPool(int parallelism) { |
372 |
|
this(parallelism, defaultForkJoinWorkerThreadFactory); |
375 |
|
/** |
376 |
|
* Creates a ForkJoinPool with parallelism equal to the number of |
377 |
|
* processors available on the system and using the given |
378 |
< |
* ForkJoinWorkerThreadFactory, |
378 |
> |
* ForkJoinWorkerThreadFactory. |
379 |
> |
* |
380 |
|
* @param factory the factory for creating new threads |
381 |
|
* @throws NullPointerException if factory is null |
382 |
|
* @throws SecurityException if a security manager exists and |
383 |
|
* the caller is not permitted to modify threads |
384 |
|
* because it does not hold {@link |
385 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
385 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
386 |
|
*/ |
387 |
|
public ForkJoinPool(ForkJoinWorkerThreadFactory factory) { |
388 |
|
this(Runtime.getRuntime().availableProcessors(), factory); |
394 |
|
* @param parallelism the targeted number of worker threads |
395 |
|
* @param factory the factory for creating new threads |
396 |
|
* @throws IllegalArgumentException if parallelism less than or |
397 |
< |
* equal to zero, or greater than implementation limit. |
397 |
> |
* equal to zero, or greater than implementation limit |
398 |
|
* @throws NullPointerException if factory is null |
399 |
|
* @throws SecurityException if a security manager exists and |
400 |
|
* the caller is not permitted to modify threads |
401 |
|
* because it does not hold {@link |
402 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
402 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
403 |
|
*/ |
404 |
|
public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) { |
405 |
|
if (parallelism <= 0 || parallelism > MAX_THREADS) |
420 |
|
} |
421 |
|
|
422 |
|
/** |
423 |
< |
* Create new worker using factory. |
423 |
> |
* Creates a new worker thread using factory. |
424 |
> |
* |
425 |
|
* @param index the index to assign worker |
426 |
|
* @return new worker, or null of factory failed |
427 |
|
*/ |
440 |
|
} |
441 |
|
|
442 |
|
/** |
443 |
< |
* Return a good size for worker array given pool size. |
443 |
> |
* Returns a good size for worker array given pool size. |
444 |
|
* Currently requires size to be a power of two. |
445 |
|
*/ |
446 |
< |
private static int arraySizeFor(int ps) { |
447 |
< |
return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1))); |
446 |
> |
private static int arraySizeFor(int poolSize) { |
447 |
> |
return (poolSize <= 1) ? 1 : |
448 |
> |
(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1))); |
449 |
|
} |
450 |
|
|
451 |
|
/** |
452 |
< |
* Create or resize array if necessary to hold newLength. |
453 |
< |
* Call only under exlusion or lock |
452 |
> |
* Creates or resizes array if necessary to hold newLength. |
453 |
> |
* Call only under exclusion. |
454 |
> |
* |
455 |
|
* @return the array |
456 |
|
*/ |
457 |
|
private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) { |
465 |
|
} |
466 |
|
|
467 |
|
/** |
468 |
< |
* Try to shrink workers into smaller array after one or more terminate |
468 |
> |
* Tries to shrink workers into smaller array after one or more terminate. |
469 |
|
*/ |
470 |
|
private void tryShrinkWorkerArray() { |
471 |
|
ForkJoinWorkerThread[] ws = workers; |
481 |
|
} |
482 |
|
|
483 |
|
/** |
484 |
< |
* Initialize workers if necessary |
484 |
> |
* Initializes workers if necessary. |
485 |
|
*/ |
486 |
|
final void ensureWorkerInitialization() { |
487 |
|
ForkJoinWorkerThread[] ws = workers; |
548 |
|
* Common code for execute, invoke and submit |
549 |
|
*/ |
550 |
|
private <T> void doSubmit(ForkJoinTask<T> task) { |
551 |
+ |
if (task == null) |
552 |
+ |
throw new NullPointerException(); |
553 |
|
if (isShutdown()) |
554 |
|
throw new RejectedExecutionException(); |
555 |
|
if (workers == null) |
559 |
|
} |
560 |
|
|
561 |
|
/** |
562 |
< |
* Performs the given task; returning its result upon completion |
562 |
> |
* Performs the given task, returning its result upon completion. |
563 |
> |
* |
564 |
|
* @param task the task |
565 |
|
* @return the task's result |
566 |
|
* @throws NullPointerException if task is null |
573 |
|
|
574 |
|
/** |
575 |
|
* Arranges for (asynchronous) execution of the given task. |
576 |
+ |
* |
577 |
|
* @param task the task |
578 |
|
* @throws NullPointerException if task is null |
579 |
|
* @throws RejectedExecutionException if pool is shut down |
585 |
|
// AbstractExecutorService methods |
586 |
|
|
587 |
|
public void execute(Runnable task) { |
588 |
< |
doSubmit(new AdaptedRunnable<Void>(task, null)); |
588 |
> |
ForkJoinTask<?> job; |
589 |
> |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
590 |
> |
job = (ForkJoinTask<?>) task; |
591 |
> |
else |
592 |
> |
job = new AdaptedRunnable<Void>(task, null); |
593 |
> |
doSubmit(job); |
594 |
|
} |
595 |
|
|
596 |
|
public <T> ForkJoinTask<T> submit(Callable<T> task) { |
606 |
|
} |
607 |
|
|
608 |
|
public ForkJoinTask<?> submit(Runnable task) { |
609 |
< |
ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null); |
609 |
> |
ForkJoinTask<?> job; |
610 |
> |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
611 |
> |
job = (ForkJoinTask<?>) task; |
612 |
> |
else |
613 |
> |
job = new AdaptedRunnable<Void>(task, null); |
614 |
|
doSubmit(job); |
615 |
|
return job; |
616 |
|
} |
617 |
|
|
618 |
|
/** |
619 |
+ |
* Submits a ForkJoinTask for execution. |
620 |
+ |
* |
621 |
+ |
* @param task the task to submit |
622 |
+ |
* @return the task |
623 |
+ |
* @throws RejectedExecutionException if the task cannot be |
624 |
+ |
* scheduled for execution |
625 |
+ |
* @throws NullPointerException if the task is null |
626 |
+ |
*/ |
627 |
+ |
public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) { |
628 |
+ |
doSubmit(task); |
629 |
+ |
return task; |
630 |
+ |
} |
631 |
+ |
|
632 |
+ |
/** |
633 |
|
* Adaptor for Runnables. This implements RunnableFuture |
634 |
< |
* to be compliant with AbstractExecutorService constraints |
634 |
> |
* to be compliant with AbstractExecutorService constraints. |
635 |
|
*/ |
636 |
|
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
637 |
|
implements RunnableFuture<T> { |
651 |
|
return true; |
652 |
|
} |
653 |
|
public void run() { invoke(); } |
654 |
+ |
private static final long serialVersionUID = 5232453952276885070L; |
655 |
|
} |
656 |
|
|
657 |
|
/** |
680 |
|
} |
681 |
|
} |
682 |
|
public void run() { invoke(); } |
683 |
+ |
private static final long serialVersionUID = 2838392045355241008L; |
684 |
|
} |
685 |
|
|
686 |
|
public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) { |
687 |
< |
ArrayList<ForkJoinTask<T>> ts = |
687 |
> |
ArrayList<ForkJoinTask<T>> forkJoinTasks = |
688 |
|
new ArrayList<ForkJoinTask<T>>(tasks.size()); |
689 |
< |
for (Callable<T> c : tasks) |
690 |
< |
ts.add(new AdaptedCallable<T>(c)); |
691 |
< |
invoke(new InvokeAll<T>(ts)); |
692 |
< |
return (List<Future<T>>)(List)ts; |
689 |
> |
for (Callable<T> task : tasks) |
690 |
> |
forkJoinTasks.add(new AdaptedCallable<T>(task)); |
691 |
> |
invoke(new InvokeAll<T>(forkJoinTasks)); |
692 |
> |
|
693 |
> |
@SuppressWarnings({"unchecked", "rawtypes"}) |
694 |
> |
List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks; |
695 |
> |
return futures; |
696 |
|
} |
697 |
|
|
698 |
|
static final class InvokeAll<T> extends RecursiveAction { |
699 |
|
final ArrayList<ForkJoinTask<T>> tasks; |
700 |
|
InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; } |
701 |
|
public void compute() { |
702 |
< |
try { invokeAll(tasks); } catch(Exception ignore) {} |
702 |
> |
try { invokeAll(tasks); } |
703 |
> |
catch (Exception ignore) {} |
704 |
|
} |
705 |
+ |
private static final long serialVersionUID = -7914297376763021607L; |
706 |
|
} |
707 |
|
|
708 |
|
// Configuration and status settings and queries |
709 |
|
|
710 |
|
/** |
711 |
< |
* Returns the factory used for constructing new workers |
711 |
> |
* Returns the factory used for constructing new workers. |
712 |
|
* |
713 |
|
* @return the factory used for constructing new workers |
714 |
|
*/ |
719 |
|
/** |
720 |
|
* Returns the handler for internal worker threads that terminate |
721 |
|
* due to unrecoverable errors encountered while executing tasks. |
722 |
< |
* @return the handler, or null if none |
722 |
> |
* |
723 |
> |
* @return the handler, or {@code null} if none |
724 |
|
*/ |
725 |
|
public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() { |
726 |
|
Thread.UncaughtExceptionHandler h; |
741 |
|
* as handler. |
742 |
|
* |
743 |
|
* @param h the new handler |
744 |
< |
* @return the old handler, or null if none |
744 |
> |
* @return the old handler, or {@code null} if none |
745 |
|
* @throws SecurityException if a security manager exists and |
746 |
|
* the caller is not permitted to modify threads |
747 |
|
* because it does not hold {@link |
748 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
748 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
749 |
|
*/ |
750 |
|
public Thread.UncaughtExceptionHandler |
751 |
|
setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) { |
772 |
|
|
773 |
|
|
774 |
|
/** |
775 |
< |
* Sets the target paralleism level of this pool. |
775 |
> |
* Sets the target parallelism level of this pool. |
776 |
> |
* |
777 |
|
* @param parallelism the target parallelism |
778 |
|
* @throws IllegalArgumentException if parallelism less than or |
779 |
< |
* equal to zero or greater than maximum size bounds. |
779 |
> |
* equal to zero or greater than maximum size bounds |
780 |
|
* @throws SecurityException if a security manager exists and |
781 |
|
* the caller is not permitted to modify threads |
782 |
|
* because it does not hold {@link |
783 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
783 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
784 |
|
*/ |
785 |
|
public void setParallelism(int parallelism) { |
786 |
|
checkPermission(); |
815 |
|
/** |
816 |
|
* Returns the number of worker threads that have started but not |
817 |
|
* yet terminated. This result returned by this method may differ |
818 |
< |
* from {@code getParallelism} when threads are created to |
818 |
> |
* from {@link #getParallelism} when threads are created to |
819 |
|
* maintain parallelism when others are cooperatively blocked. |
820 |
|
* |
821 |
|
* @return the number of worker threads |
827 |
|
/** |
828 |
|
* Returns the maximum number of threads allowed to exist in the |
829 |
|
* pool, even if there are insufficient unblocked running threads. |
830 |
+ |
* |
831 |
|
* @return the maximum |
832 |
|
*/ |
833 |
|
public int getMaximumPoolSize() { |
839 |
|
* pool, even if there are insufficient unblocked running threads. |
840 |
|
* Setting this value has no effect on current pool size. It |
841 |
|
* controls construction of new threads. |
842 |
+ |
* |
843 |
|
* @throws IllegalArgumentException if negative or greater then |
844 |
< |
* internal implementation limit. |
844 |
> |
* internal implementation limit |
845 |
|
*/ |
846 |
|
public void setMaximumPoolSize(int newMax) { |
847 |
|
if (newMax < 0 || newMax > MAX_THREADS) |
851 |
|
|
852 |
|
|
853 |
|
/** |
854 |
< |
* Returns true if this pool dynamically maintains its target |
855 |
< |
* parallelism level. If false, new threads are added only to |
856 |
< |
* avoid possible starvation. |
857 |
< |
* This setting is by default true; |
858 |
< |
* @return true if maintains parallelism |
854 |
> |
* Returns {@code true} if this pool dynamically maintains its |
855 |
> |
* target parallelism level. If false, new threads are added only |
856 |
> |
* to avoid possible starvation. This setting is by default true. |
857 |
> |
* |
858 |
> |
* @return {@code true} if maintains parallelism |
859 |
|
*/ |
860 |
|
public boolean getMaintainsParallelism() { |
861 |
|
return maintainsParallelism; |
865 |
|
* Sets whether this pool dynamically maintains its target |
866 |
|
* parallelism level. If false, new threads are added only to |
867 |
|
* avoid possible starvation. |
868 |
< |
* @param enable true to maintains parallelism |
868 |
> |
* |
869 |
> |
* @param enable {@code true} to maintain parallelism |
870 |
|
*/ |
871 |
|
public void setMaintainsParallelism(boolean enable) { |
872 |
|
maintainsParallelism = enable; |
877 |
|
* tasks that are never joined. This mode may be more appropriate |
878 |
|
* than default locally stack-based mode in applications in which |
879 |
|
* worker threads only process asynchronous tasks. This method is |
880 |
< |
* designed to be invoked only when pool is quiescent, and |
880 |
> |
* designed to be invoked only when the pool is quiescent, and |
881 |
|
* typically only before any tasks are submitted. The effects of |
882 |
< |
* invocations at ather times may be unpredictable. |
882 |
> |
* invocations at other times may be unpredictable. |
883 |
|
* |
884 |
< |
* @param async if true, use locally FIFO scheduling |
885 |
< |
* @return the previous mode. |
884 |
> |
* @param async if {@code true}, use locally FIFO scheduling |
885 |
> |
* @return the previous mode |
886 |
> |
* @see #getAsyncMode |
887 |
|
*/ |
888 |
|
public boolean setAsyncMode(boolean async) { |
889 |
|
boolean oldMode = locallyFifo; |
900 |
|
} |
901 |
|
|
902 |
|
/** |
903 |
< |
* Returns true if this pool uses local first-in-first-out |
903 |
> |
* Returns {@code true} if this pool uses local first-in-first-out |
904 |
|
* scheduling mode for forked tasks that are never joined. |
905 |
|
* |
906 |
< |
* @return true if this pool uses async mode. |
906 |
> |
* @return {@code true} if this pool uses async mode |
907 |
> |
* @see #setAsyncMode |
908 |
|
*/ |
909 |
|
public boolean getAsyncMode() { |
910 |
|
return locallyFifo; |
925 |
|
* Returns an estimate of the number of threads that are currently |
926 |
|
* stealing or executing tasks. This method may overestimate the |
927 |
|
* number of active threads. |
928 |
< |
* @return the number of active threads. |
928 |
> |
* |
929 |
> |
* @return the number of active threads |
930 |
|
*/ |
931 |
|
public int getActiveThreadCount() { |
932 |
|
return activeCountOf(runControl); |
936 |
|
* Returns an estimate of the number of threads that are currently |
937 |
|
* idle waiting for tasks. This method may underestimate the |
938 |
|
* number of idle threads. |
939 |
< |
* @return the number of idle threads. |
939 |
> |
* |
940 |
> |
* @return the number of idle threads |
941 |
|
*/ |
942 |
|
final int getIdleThreadCount() { |
943 |
|
int c = runningCountOf(workerCounts) - activeCountOf(runControl); |
944 |
< |
return (c <= 0)? 0 : c; |
944 |
> |
return (c <= 0) ? 0 : c; |
945 |
|
} |
946 |
|
|
947 |
|
/** |
948 |
< |
* Returns true if all worker threads are currently idle. An idle |
949 |
< |
* worker is one that cannot obtain a task to execute because none |
950 |
< |
* are available to steal from other threads, and there are no |
951 |
< |
* pending submissions to the pool. This method is conservative: |
952 |
< |
* It might not return true immediately upon idleness of all |
953 |
< |
* threads, but will eventually become true if threads remain |
954 |
< |
* inactive. |
955 |
< |
* @return true if all threads are currently idle |
948 |
> |
* Returns {@code true} if all worker threads are currently idle. |
949 |
> |
* An idle worker is one that cannot obtain a task to execute |
950 |
> |
* because none are available to steal from other threads, and |
951 |
> |
* there are no pending submissions to the pool. This method is |
952 |
> |
* conservative; it might not return {@code true} immediately upon |
953 |
> |
* idleness of all threads, but will eventually become true if |
954 |
> |
* threads remain inactive. |
955 |
> |
* |
956 |
> |
* @return {@code true} if all threads are currently idle |
957 |
|
*/ |
958 |
|
public boolean isQuiescent() { |
959 |
|
return activeCountOf(runControl) == 0; |
964 |
|
* one thread's work queue by another. The reported value |
965 |
|
* underestimates the actual total number of steals when the pool |
966 |
|
* is not quiescent. This value may be useful for monitoring and |
967 |
< |
* tuning fork/join programs: In general, steal counts should be |
967 |
> |
* tuning fork/join programs: in general, steal counts should be |
968 |
|
* high enough to keep threads busy, but low enough to avoid |
969 |
|
* overhead and contention across threads. |
970 |
< |
* @return the number of steals. |
970 |
> |
* |
971 |
> |
* @return the number of steals |
972 |
|
*/ |
973 |
|
public long getStealCount() { |
974 |
|
return stealCount.get(); |
975 |
|
} |
976 |
|
|
977 |
|
/** |
978 |
< |
* Accumulate steal count from a worker. Call only |
979 |
< |
* when worker known to be idle. |
978 |
> |
* Accumulates steal count from a worker. |
979 |
> |
* Call only when worker known to be idle. |
980 |
|
*/ |
981 |
|
private void updateStealCount(ForkJoinWorkerThread w) { |
982 |
|
int sc = w.getAndClearStealCount(); |
991 |
|
* an approximation, obtained by iterating across all threads in |
992 |
|
* the pool. This method may be useful for tuning task |
993 |
|
* granularities. |
994 |
< |
* @return the number of queued tasks. |
994 |
> |
* |
995 |
> |
* @return the number of queued tasks |
996 |
|
*/ |
997 |
|
public long getQueuedTaskCount() { |
998 |
|
long count = 0; |
1011 |
|
* Returns an estimate of the number tasks submitted to this pool |
1012 |
|
* that have not yet begun executing. This method takes time |
1013 |
|
* proportional to the number of submissions. |
1014 |
< |
* @return the number of queued submissions. |
1014 |
> |
* |
1015 |
> |
* @return the number of queued submissions |
1016 |
|
*/ |
1017 |
|
public int getQueuedSubmissionCount() { |
1018 |
|
return submissionQueue.size(); |
1019 |
|
} |
1020 |
|
|
1021 |
|
/** |
1022 |
< |
* Returns true if there are any tasks submitted to this pool |
1023 |
< |
* that have not yet begun executing. |
1024 |
< |
* @return {@code true} if there are any queued submissions. |
1022 |
> |
* Returns {@code true} if there are any tasks submitted to this |
1023 |
> |
* pool that have not yet begun executing. |
1024 |
> |
* |
1025 |
> |
* @return {@code true} if there are any queued submissions |
1026 |
|
*/ |
1027 |
|
public boolean hasQueuedSubmissions() { |
1028 |
|
return !submissionQueue.isEmpty(); |
1032 |
|
* Removes and returns the next unexecuted submission if one is |
1033 |
|
* available. This method may be useful in extensions to this |
1034 |
|
* class that re-assign work in systems with multiple pools. |
1035 |
< |
* @return the next submission, or null if none |
1035 |
> |
* |
1036 |
> |
* @return the next submission, or {@code null} if none |
1037 |
|
*/ |
1038 |
|
protected ForkJoinTask<?> pollSubmission() { |
1039 |
|
return submissionQueue.poll(); |
1043 |
|
* Removes all available unexecuted submitted and forked tasks |
1044 |
|
* from scheduling queues and adds them to the given collection, |
1045 |
|
* without altering their execution status. These may include |
1046 |
< |
* artifically generated or wrapped tasks. This method id designed |
1046 |
> |
* artificially generated or wrapped tasks. This method is designed |
1047 |
|
* to be invoked only when the pool is known to be |
1048 |
|
* quiescent. Invocations at other times may not remove all |
1049 |
|
* tasks. A failure encountered while attempting to add elements |
1052 |
|
* exception is thrown. The behavior of this operation is |
1053 |
|
* undefined if the specified collection is modified while the |
1054 |
|
* operation is in progress. |
1055 |
+ |
* |
1056 |
|
* @param c the collection to transfer elements into |
1057 |
|
* @return the number of elements transferred |
1058 |
|
*/ |
1059 |
< |
protected int drainTasksTo(Collection<ForkJoinTask<?>> c) { |
1059 |
> |
protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
1060 |
|
int n = submissionQueue.drainTo(c); |
1061 |
|
ForkJoinWorkerThread[] ws = workers; |
1062 |
|
if (ws != null) { |
1113 |
|
* Invocation has no additional effect if already shut down. |
1114 |
|
* Tasks that are in the process of being submitted concurrently |
1115 |
|
* during the course of this method may or may not be rejected. |
1116 |
+ |
* |
1117 |
|
* @throws SecurityException if a security manager exists and |
1118 |
|
* the caller is not permitted to modify threads |
1119 |
|
* because it does not hold {@link |
1120 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
1120 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1121 |
|
*/ |
1122 |
|
public void shutdown() { |
1123 |
|
checkPermission(); |
1124 |
|
transitionRunStateTo(SHUTDOWN); |
1125 |
< |
if (canTerminateOnShutdown(runControl)) |
1125 |
> |
if (canTerminateOnShutdown(runControl)) { |
1126 |
> |
if (workers == null) { // shutting down before workers created |
1127 |
> |
final ReentrantLock lock = this.workerLock; |
1128 |
> |
lock.lock(); |
1129 |
> |
try { |
1130 |
> |
if (workers == null) { |
1131 |
> |
terminate(); |
1132 |
> |
transitionRunStateTo(TERMINATED); |
1133 |
> |
termination.signalAll(); |
1134 |
> |
} |
1135 |
> |
|
1136 |
> |
} finally { |
1137 |
> |
lock.unlock(); |
1138 |
> |
} |
1139 |
> |
} |
1140 |
|
terminateOnShutdown(); |
1141 |
+ |
} |
1142 |
|
} |
1143 |
|
|
1144 |
|
/** |
1148 |
|
* method may or may not be rejected. Unlike some other executors, |
1149 |
|
* this method cancels rather than collects non-executed tasks |
1150 |
|
* upon termination, so always returns an empty list. However, you |
1151 |
< |
* can use method {@code drainTasksTo} before invoking this |
1151 |
> |
* can use method {@link #drainTasksTo} before invoking this |
1152 |
|
* method to transfer unexecuted tasks to another collection. |
1153 |
+ |
* |
1154 |
|
* @return an empty list |
1155 |
|
* @throws SecurityException if a security manager exists and |
1156 |
|
* the caller is not permitted to modify threads |
1157 |
|
* because it does not hold {@link |
1158 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
1158 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1159 |
|
*/ |
1160 |
|
public List<Runnable> shutdownNow() { |
1161 |
|
checkPermission(); |
1223 |
|
// Shutdown and termination support |
1224 |
|
|
1225 |
|
/** |
1226 |
< |
* Callback from terminating worker. Null out the corresponding |
1227 |
< |
* workers slot, and if terminating, try to terminate, else try to |
1228 |
< |
* shrink workers array. |
1226 |
> |
* Callback from terminating worker. Nulls out the corresponding |
1227 |
> |
* workers slot, and if terminating, tries to terminate; else |
1228 |
> |
* tries to shrink workers array. |
1229 |
> |
* |
1230 |
|
* @param w the worker |
1231 |
|
*/ |
1232 |
|
final void workerTerminated(ForkJoinWorkerThread w) { |
1257 |
|
} |
1258 |
|
|
1259 |
|
/** |
1260 |
< |
* Initiate termination. |
1260 |
> |
* Initiates termination. |
1261 |
|
*/ |
1262 |
|
private void terminate() { |
1263 |
|
if (transitionRunStateTo(TERMINATING)) { |
1272 |
|
} |
1273 |
|
|
1274 |
|
/** |
1275 |
< |
* Possibly terminate when on shutdown state |
1275 |
> |
* Possibly terminates when on shutdown state. |
1276 |
|
*/ |
1277 |
|
private void terminateOnShutdown() { |
1278 |
|
if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl)) |
1280 |
|
} |
1281 |
|
|
1282 |
|
/** |
1283 |
< |
* Clear out and cancel submissions |
1283 |
> |
* Clears out and cancels submissions. |
1284 |
|
*/ |
1285 |
|
private void cancelQueuedSubmissions() { |
1286 |
|
ForkJoinTask<?> task; |
1289 |
|
} |
1290 |
|
|
1291 |
|
/** |
1292 |
< |
* Clean out worker queues. |
1292 |
> |
* Cleans out worker queues. |
1293 |
|
*/ |
1294 |
|
private void cancelQueuedWorkerTasks() { |
1295 |
|
final ReentrantLock lock = this.workerLock; |
1309 |
|
} |
1310 |
|
|
1311 |
|
/** |
1312 |
< |
* Set each worker's status to terminating. Requires lock to avoid |
1313 |
< |
* conflicts with add/remove |
1312 |
> |
* Sets each worker's status to terminating. Requires lock to avoid |
1313 |
> |
* conflicts with add/remove. |
1314 |
|
*/ |
1315 |
|
private void stopAllWorkers() { |
1316 |
|
final ReentrantLock lock = this.workerLock; |
1330 |
|
} |
1331 |
|
|
1332 |
|
/** |
1333 |
< |
* Interrupt all unterminated workers. This is not required for |
1333 |
> |
* Interrupts all unterminated workers. This is not required for |
1334 |
|
* sake of internal control, but may help unstick user code during |
1335 |
|
* shutdown. |
1336 |
|
*/ |
1400 |
|
} |
1401 |
|
|
1402 |
|
/** |
1403 |
< |
* Wake up waiter, returning false if known to already |
1403 |
> |
* Wakes up waiter, returning false if known to already |
1404 |
|
*/ |
1405 |
|
boolean signal() { |
1406 |
|
ForkJoinWorkerThread t = thread; |
1412 |
|
} |
1413 |
|
|
1414 |
|
/** |
1415 |
< |
* Await release on sync |
1415 |
> |
* Awaits release on sync. |
1416 |
|
*/ |
1417 |
|
void awaitSyncRelease(ForkJoinPool p) { |
1418 |
|
while (thread != null && !p.syncIsReleasable(this)) |
1420 |
|
} |
1421 |
|
|
1422 |
|
/** |
1423 |
< |
* Await resumption as spare |
1423 |
> |
* Awaits resumption as spare. |
1424 |
|
*/ |
1425 |
|
void awaitSpareRelease() { |
1426 |
|
while (thread != null) { |
1434 |
|
* Ensures that no thread is waiting for count to advance from the |
1435 |
|
* current value of eventCount read on entry to this method, by |
1436 |
|
* releasing waiting threads if necessary. |
1437 |
+ |
* |
1438 |
|
* @return the count |
1439 |
|
*/ |
1440 |
|
final long ensureSync() { |
1456 |
|
*/ |
1457 |
|
private void signalIdleWorkers() { |
1458 |
|
long c; |
1459 |
< |
do;while (!casEventCount(c = eventCount, c+1)); |
1459 |
> |
do {} while (!casEventCount(c = eventCount, c+1)); |
1460 |
|
ensureSync(); |
1461 |
|
} |
1462 |
|
|
1463 |
|
/** |
1464 |
< |
* Signal threads waiting to poll a task. Because method sync |
1464 |
> |
* Signals threads waiting to poll a task. Because method sync |
1465 |
|
* rechecks availability, it is OK to only proceed if queue |
1466 |
|
* appears to be non-empty, and OK to skip under contention to |
1467 |
|
* increment count (since some other thread succeeded). |
1480 |
|
* Waits until event count advances from last value held by |
1481 |
|
* caller, or if excess threads, caller is resumed as spare, or |
1482 |
|
* caller or pool is terminating. Updates caller's event on exit. |
1483 |
+ |
* |
1484 |
|
* @param w the calling worker thread |
1485 |
|
*/ |
1486 |
|
final void sync(ForkJoinWorkerThread w) { |
1508 |
|
} |
1509 |
|
|
1510 |
|
/** |
1511 |
< |
* Returns true if worker waiting on sync can proceed: |
1511 |
> |
* Returns {@code true} if worker waiting on sync can proceed: |
1512 |
|
* - on signal (thread == null) |
1513 |
|
* - on event count advance (winning race to notify vs signaller) |
1514 |
< |
* - on Interrupt |
1514 |
> |
* - on interrupt |
1515 |
|
* - if the first queued node, we find work available |
1516 |
|
* If node was not signalled and event count not advanced on exit, |
1517 |
|
* then we also help advance event count. |
1518 |
< |
* @return true if node can be released |
1518 |
> |
* |
1519 |
> |
* @return {@code true} if node can be released |
1520 |
|
*/ |
1521 |
|
final boolean syncIsReleasable(WaitQueueNode node) { |
1522 |
|
long prev = node.count; |
1535 |
|
} |
1536 |
|
|
1537 |
|
/** |
1538 |
< |
* Returns true if a new sync event occurred since last call to |
1539 |
< |
* sync or this method, if so, updating caller's count. |
1538 |
> |
* Returns {@code true} if a new sync event occurred since last |
1539 |
> |
* call to sync or this method, if so, updating caller's count. |
1540 |
|
*/ |
1541 |
|
final boolean hasNewSyncEvent(ForkJoinWorkerThread w) { |
1542 |
|
long lc = w.lastEventCount; |
1550 |
|
// Parallelism maintenance |
1551 |
|
|
1552 |
|
/** |
1553 |
< |
* Decrement running count; if too low, add spare. |
1553 |
> |
* Decrements running count; if too low, adds spare. |
1554 |
|
* |
1555 |
|
* Conceptually, all we need to do here is add or resume a |
1556 |
|
* spare thread when one is about to block (and remove or |
1557 |
|
* suspend it later when unblocked -- see suspendIfSpare). |
1558 |
|
* However, implementing this idea requires coping with |
1559 |
< |
* several problems: We have imperfect information about the |
1559 |
> |
* several problems: we have imperfect information about the |
1560 |
|
* states of threads. Some count updates can and usually do |
1561 |
|
* lag run state changes, despite arrangements to keep them |
1562 |
|
* accurate (for example, when possible, updating counts |
1570 |
|
* only be suspended or removed when they are idle, not |
1571 |
|
* immediately when they aren't needed. So adding threads will |
1572 |
|
* raise parallelism level for longer than necessary. Also, |
1573 |
< |
* FJ applications often enounter highly transient peaks when |
1573 |
> |
* FJ applications often encounter highly transient peaks when |
1574 |
|
* many threads are blocked joining, but for less time than it |
1575 |
|
* takes to create or resume spares. |
1576 |
|
* |
1579 |
|
* target counts, else create only to avoid starvation |
1580 |
|
* @return true if joinMe known to be done |
1581 |
|
*/ |
1582 |
< |
final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) { |
1582 |
> |
final boolean preJoin(ForkJoinTask<?> joinMe, |
1583 |
> |
boolean maintainParallelism) { |
1584 |
|
maintainParallelism &= maintainsParallelism; // overrride |
1585 |
|
boolean dec = false; // true when running count decremented |
1586 |
|
while (spareStack == null || !tryResumeSpare(dec)) { |
1587 |
|
int counts = workerCounts; |
1588 |
< |
if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat |
1588 |
> |
if (dec || (dec = casWorkerCounts(counts, --counts))) { |
1589 |
> |
// CAS cheat |
1590 |
|
if (!needSpare(counts, maintainParallelism)) |
1591 |
|
break; |
1592 |
|
if (joinMe.status < 0) |
1601 |
|
/** |
1602 |
|
* Same idea as preJoin |
1603 |
|
*/ |
1604 |
< |
final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){ |
1604 |
> |
final boolean preBlock(ManagedBlocker blocker, |
1605 |
> |
boolean maintainParallelism) { |
1606 |
|
maintainParallelism &= maintainsParallelism; |
1607 |
|
boolean dec = false; |
1608 |
|
while (spareStack == null || !tryResumeSpare(dec)) { |
1620 |
|
} |
1621 |
|
|
1622 |
|
/** |
1623 |
< |
* Returns true if a spare thread appears to be needed. If |
1624 |
< |
* maintaining parallelism, returns true when the deficit in |
1623 |
> |
* Returns {@code true} if a spare thread appears to be needed. |
1624 |
> |
* If maintaining parallelism, returns true when the deficit in |
1625 |
|
* running threads is more than the surplus of total threads, and |
1626 |
|
* there is apparently some work to do. This self-limiting rule |
1627 |
|
* means that the more threads that have already been added, the |
1628 |
|
* less parallelism we will tolerate before adding another. |
1629 |
+ |
* |
1630 |
|
* @param counts current worker counts |
1631 |
|
* @param maintainParallelism try to maintain parallelism |
1632 |
|
*/ |
1644 |
|
} |
1645 |
|
|
1646 |
|
/** |
1647 |
< |
* Add a spare worker if lock available and no more than the |
1648 |
< |
* expected numbers of threads exist |
1647 |
> |
* Adds a spare worker if lock available and no more than the |
1648 |
> |
* expected numbers of threads exist. |
1649 |
> |
* |
1650 |
|
* @return true if successful |
1651 |
|
*/ |
1652 |
|
private boolean tryAddSpare(int expectedCounts) { |
1679 |
|
} |
1680 |
|
|
1681 |
|
/** |
1682 |
< |
* Add the kth spare worker. On entry, pool coounts are already |
1682 |
> |
* Adds the kth spare worker. On entry, pool counts are already |
1683 |
|
* adjusted to reflect addition. |
1684 |
|
*/ |
1685 |
|
private void createAndStartSpare(int k) { |
1701 |
|
} |
1702 |
|
|
1703 |
|
/** |
1704 |
< |
* Suspend calling thread w if there are excess threads. Called |
1705 |
< |
* only from sync. Spares are enqueued in a Treiber stack |
1706 |
< |
* using the same WaitQueueNodes as barriers. They are resumed |
1707 |
< |
* mainly in preJoin, but are also woken on pool events that |
1708 |
< |
* require all threads to check run state. |
1704 |
> |
* Suspends calling thread w if there are excess threads. Called |
1705 |
> |
* only from sync. Spares are enqueued in a Treiber stack using |
1706 |
> |
* the same WaitQueueNodes as barriers. They are resumed mainly |
1707 |
> |
* in preJoin, but are also woken on pool events that require all |
1708 |
> |
* threads to check run state. |
1709 |
> |
* |
1710 |
|
* @param w the caller |
1711 |
|
*/ |
1712 |
|
private boolean suspendIfSpare(ForkJoinWorkerThread w) { |
1717 |
|
node = new WaitQueueNode(0, w); |
1718 |
|
if (casWorkerCounts(s, s-1)) { // representation-dependent |
1719 |
|
// push onto stack |
1720 |
< |
do;while (!casSpareStack(node.next = spareStack, node)); |
1720 |
> |
do {} while (!casSpareStack(node.next = spareStack, node)); |
1721 |
|
// block until released by resumeSpare |
1722 |
|
node.awaitSpareRelease(); |
1723 |
|
return true; |
1727 |
|
} |
1728 |
|
|
1729 |
|
/** |
1730 |
< |
* Try to pop and resume a spare thread. |
1730 |
> |
* Tries to pop and resume a spare thread. |
1731 |
> |
* |
1732 |
|
* @param updateCount if true, increment running count on success |
1733 |
|
* @return true if successful |
1734 |
|
*/ |
1746 |
|
} |
1747 |
|
|
1748 |
|
/** |
1749 |
< |
* Pop and resume all spare threads. Same idea as ensureSync. |
1749 |
> |
* Pops and resumes all spare threads. Same idea as ensureSync. |
1750 |
> |
* |
1751 |
|
* @return true if any spares released |
1752 |
|
*/ |
1753 |
|
private boolean resumeAllSpares() { |
1765 |
|
} |
1766 |
|
|
1767 |
|
/** |
1768 |
< |
* Pop and shutdown excessive spare threads. Call only while |
1768 |
> |
* Pops and shuts down excessive spare threads. Call only while |
1769 |
|
* holding lock. This is not guaranteed to eliminate all excess |
1770 |
|
* threads, only those suspended as spares, which are the ones |
1771 |
|
* unlikely to be needed in the future. |
1790 |
|
/** |
1791 |
|
* Interface for extending managed parallelism for tasks running |
1792 |
|
* in ForkJoinPools. A ManagedBlocker provides two methods. |
1793 |
< |
* Method {@code isReleasable} must return true if blocking is not |
1794 |
< |
* necessary. Method {@code block} blocks the current thread |
1795 |
< |
* if necessary (perhaps internally invoking isReleasable before |
1796 |
< |
* actually blocking.). |
1793 |
> |
* Method {@code isReleasable} must return {@code true} if |
1794 |
> |
* blocking is not necessary. Method {@code block} blocks the |
1795 |
> |
* current thread if necessary (perhaps internally invoking |
1796 |
> |
* {@code isReleasable} before actually blocking.). |
1797 |
> |
* |
1798 |
|
* <p>For example, here is a ManagedBlocker based on a |
1799 |
|
* ReentrantLock: |
1800 |
< |
* <pre> |
1801 |
< |
* class ManagedLocker implements ManagedBlocker { |
1802 |
< |
* final ReentrantLock lock; |
1803 |
< |
* boolean hasLock = false; |
1804 |
< |
* ManagedLocker(ReentrantLock lock) { this.lock = lock; } |
1805 |
< |
* public boolean block() { |
1806 |
< |
* if (!hasLock) |
1807 |
< |
* lock.lock(); |
1808 |
< |
* return true; |
1809 |
< |
* } |
1810 |
< |
* public boolean isReleasable() { |
1811 |
< |
* return hasLock || (hasLock = lock.tryLock()); |
1711 |
< |
* } |
1800 |
> |
* <pre> {@code |
1801 |
> |
* class ManagedLocker implements ManagedBlocker { |
1802 |
> |
* final ReentrantLock lock; |
1803 |
> |
* boolean hasLock = false; |
1804 |
> |
* ManagedLocker(ReentrantLock lock) { this.lock = lock; } |
1805 |
> |
* public boolean block() { |
1806 |
> |
* if (!hasLock) |
1807 |
> |
* lock.lock(); |
1808 |
> |
* return true; |
1809 |
> |
* } |
1810 |
> |
* public boolean isReleasable() { |
1811 |
> |
* return hasLock || (hasLock = lock.tryLock()); |
1812 |
|
* } |
1813 |
< |
* </pre> |
1813 |
> |
* }}</pre> |
1814 |
|
*/ |
1815 |
|
public static interface ManagedBlocker { |
1816 |
|
/** |
1817 |
|
* Possibly blocks the current thread, for example waiting for |
1818 |
|
* a lock or condition. |
1819 |
< |
* @return true if no additional blocking is necessary (i.e., |
1820 |
< |
* if isReleasable would return true). |
1819 |
> |
* |
1820 |
> |
* @return {@code true} if no additional blocking is necessary |
1821 |
> |
* (i.e., if isReleasable would return true) |
1822 |
|
* @throws InterruptedException if interrupted while waiting |
1823 |
< |
* (the method is not required to do so, but is allowe to). |
1823 |
> |
* (the method is not required to do so, but is allowed to) |
1824 |
|
*/ |
1825 |
|
boolean block() throws InterruptedException; |
1826 |
|
|
1827 |
|
/** |
1828 |
< |
* Returns true if blocking is unnecessary. |
1828 |
> |
* Returns {@code true} if blocking is unnecessary. |
1829 |
|
*/ |
1830 |
|
boolean isReleasable(); |
1831 |
|
} |
1835 |
|
* is a ForkJoinWorkerThread, this method possibly arranges for a |
1836 |
|
* spare thread to be activated if necessary to ensure parallelism |
1837 |
|
* while the current thread is blocked. If |
1838 |
< |
* {@code maintainParallelism} is true and the pool supports |
1838 |
> |
* {@code maintainParallelism} is {@code true} and the pool supports |
1839 |
|
* it ({@link #getMaintainsParallelism}), this method attempts to |
1840 |
< |
* maintain the pool's nominal parallelism. Otherwise if activates |
1840 |
> |
* maintain the pool's nominal parallelism. Otherwise it activates |
1841 |
|
* a thread only if necessary to avoid complete starvation. This |
1842 |
|
* option may be preferable when blockages use timeouts, or are |
1843 |
|
* almost always brief. |
1844 |
|
* |
1845 |
|
* <p> If the caller is not a ForkJoinTask, this method is behaviorally |
1846 |
|
* equivalent to |
1847 |
< |
* <pre> |
1848 |
< |
* while (!blocker.isReleasable()) |
1849 |
< |
* if (blocker.block()) |
1850 |
< |
* return; |
1851 |
< |
* </pre> |
1847 |
> |
* <pre> {@code |
1848 |
> |
* while (!blocker.isReleasable()) |
1849 |
> |
* if (blocker.block()) |
1850 |
> |
* return; |
1851 |
> |
* }</pre> |
1852 |
|
* If the caller is a ForkJoinTask, then the pool may first |
1853 |
|
* be expanded to ensure parallelism, and later adjusted. |
1854 |
|
* |
1855 |
|
* @param blocker the blocker |
1856 |
< |
* @param maintainParallelism if true and supported by this pool, |
1857 |
< |
* attempt to maintain the pool's nominal parallelism; otherwise |
1858 |
< |
* activate a thread only if necessary to avoid complete |
1859 |
< |
* starvation. |
1860 |
< |
* @throws InterruptedException if blocker.block did so. |
1856 |
> |
* @param maintainParallelism if {@code true} and supported by |
1857 |
> |
* this pool, attempt to maintain the pool's nominal parallelism; |
1858 |
> |
* otherwise activate a thread only if necessary to avoid |
1859 |
> |
* complete starvation. |
1860 |
> |
* @throws InterruptedException if blocker.block did so |
1861 |
|
*/ |
1862 |
|
public static void managedBlock(ManagedBlocker blocker, |
1863 |
|
boolean maintainParallelism) |
1864 |
|
throws InterruptedException { |
1865 |
|
Thread t = Thread.currentThread(); |
1866 |
< |
ForkJoinPool pool = (t instanceof ForkJoinWorkerThread? |
1867 |
< |
((ForkJoinWorkerThread)t).pool : null); |
1866 |
> |
ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ? |
1867 |
> |
((ForkJoinWorkerThread) t).pool : null); |
1868 |
|
if (!blocker.isReleasable()) { |
1869 |
|
try { |
1870 |
|
if (pool == null || |
1879 |
|
|
1880 |
|
private static void awaitBlocker(ManagedBlocker blocker) |
1881 |
|
throws InterruptedException { |
1882 |
< |
do;while (!blocker.isReleasable() && !blocker.block()); |
1882 |
> |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1883 |
|
} |
1884 |
|
|
1885 |
|
// AbstractExecutorService overrides |
1886 |
|
|
1887 |
|
protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) { |
1888 |
< |
return new AdaptedRunnable(runnable, value); |
1888 |
> |
return new AdaptedRunnable<T>(runnable, value); |
1889 |
|
} |
1890 |
|
|
1891 |
|
protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) { |
1892 |
< |
return new AdaptedCallable(callable); |
1792 |
< |
} |
1793 |
< |
|
1794 |
< |
|
1795 |
< |
// Temporary Unsafe mechanics for preliminary release |
1796 |
< |
private static Unsafe getUnsafe() throws Throwable { |
1797 |
< |
try { |
1798 |
< |
return Unsafe.getUnsafe(); |
1799 |
< |
} catch (SecurityException se) { |
1800 |
< |
try { |
1801 |
< |
return java.security.AccessController.doPrivileged |
1802 |
< |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
1803 |
< |
public Unsafe run() throws Exception { |
1804 |
< |
return getUnsafePrivileged(); |
1805 |
< |
}}); |
1806 |
< |
} catch (java.security.PrivilegedActionException e) { |
1807 |
< |
throw e.getCause(); |
1808 |
< |
} |
1809 |
< |
} |
1892 |
> |
return new AdaptedCallable<T>(callable); |
1893 |
|
} |
1894 |
|
|
1895 |
< |
private static Unsafe getUnsafePrivileged() |
1813 |
< |
throws NoSuchFieldException, IllegalAccessException { |
1814 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1815 |
< |
f.setAccessible(true); |
1816 |
< |
return (Unsafe) f.get(null); |
1817 |
< |
} |
1818 |
< |
|
1819 |
< |
private static long fieldOffset(String fieldName) |
1820 |
< |
throws NoSuchFieldException { |
1821 |
< |
return _unsafe.objectFieldOffset |
1822 |
< |
(ForkJoinPool.class.getDeclaredField(fieldName)); |
1823 |
< |
} |
1895 |
> |
// Unsafe mechanics |
1896 |
|
|
1897 |
< |
static final Unsafe _unsafe; |
1898 |
< |
static final long eventCountOffset; |
1899 |
< |
static final long workerCountsOffset; |
1900 |
< |
static final long runControlOffset; |
1901 |
< |
static final long syncStackOffset; |
1902 |
< |
static final long spareStackOffset; |
1903 |
< |
|
1904 |
< |
static { |
1905 |
< |
try { |
1906 |
< |
_unsafe = getUnsafe(); |
1907 |
< |
eventCountOffset = fieldOffset("eventCount"); |
1836 |
< |
workerCountsOffset = fieldOffset("workerCounts"); |
1837 |
< |
runControlOffset = fieldOffset("runControl"); |
1838 |
< |
syncStackOffset = fieldOffset("syncStack"); |
1839 |
< |
spareStackOffset = fieldOffset("spareStack"); |
1840 |
< |
} catch (Throwable e) { |
1841 |
< |
throw new RuntimeException("Could not initialize intrinsics", e); |
1842 |
< |
} |
1843 |
< |
} |
1897 |
> |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1898 |
> |
private static final long eventCountOffset = |
1899 |
> |
objectFieldOffset("eventCount", ForkJoinPool.class); |
1900 |
> |
private static final long workerCountsOffset = |
1901 |
> |
objectFieldOffset("workerCounts", ForkJoinPool.class); |
1902 |
> |
private static final long runControlOffset = |
1903 |
> |
objectFieldOffset("runControl", ForkJoinPool.class); |
1904 |
> |
private static final long syncStackOffset = |
1905 |
> |
objectFieldOffset("syncStack",ForkJoinPool.class); |
1906 |
> |
private static final long spareStackOffset = |
1907 |
> |
objectFieldOffset("spareStack", ForkJoinPool.class); |
1908 |
|
|
1909 |
|
private boolean casEventCount(long cmp, long val) { |
1910 |
< |
return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val); |
1910 |
> |
return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val); |
1911 |
|
} |
1912 |
|
private boolean casWorkerCounts(int cmp, int val) { |
1913 |
< |
return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val); |
1913 |
> |
return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val); |
1914 |
|
} |
1915 |
|
private boolean casRunControl(int cmp, int val) { |
1916 |
< |
return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val); |
1916 |
> |
return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val); |
1917 |
|
} |
1918 |
|
private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) { |
1919 |
< |
return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val); |
1919 |
> |
return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val); |
1920 |
|
} |
1921 |
|
private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) { |
1922 |
< |
return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val); |
1922 |
> |
return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val); |
1923 |
> |
} |
1924 |
> |
|
1925 |
> |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1926 |
> |
try { |
1927 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1928 |
> |
} catch (NoSuchFieldException e) { |
1929 |
> |
// Convert Exception to corresponding Error |
1930 |
> |
NoSuchFieldError error = new NoSuchFieldError(field); |
1931 |
> |
error.initCause(e); |
1932 |
> |
throw error; |
1933 |
> |
} |
1934 |
> |
} |
1935 |
> |
|
1936 |
> |
/** |
1937 |
> |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1938 |
> |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1939 |
> |
* into a jdk. |
1940 |
> |
* |
1941 |
> |
* @return a sun.misc.Unsafe |
1942 |
> |
*/ |
1943 |
> |
private static sun.misc.Unsafe getUnsafe() { |
1944 |
> |
try { |
1945 |
> |
return sun.misc.Unsafe.getUnsafe(); |
1946 |
> |
} catch (SecurityException se) { |
1947 |
> |
try { |
1948 |
> |
return java.security.AccessController.doPrivileged |
1949 |
> |
(new java.security |
1950 |
> |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1951 |
> |
public sun.misc.Unsafe run() throws Exception { |
1952 |
> |
java.lang.reflect.Field f = sun.misc |
1953 |
> |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1954 |
> |
f.setAccessible(true); |
1955 |
> |
return (sun.misc.Unsafe) f.get(null); |
1956 |
> |
}}); |
1957 |
> |
} catch (java.security.PrivilegedActionException e) { |
1958 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
1959 |
> |
e.getCause()); |
1960 |
> |
} |
1961 |
> |
} |
1962 |
|
} |
1963 |
|
} |