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*/ |
6 |
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package jsr166y; |
8 |
< |
import java.util.*; |
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> |
|
9 |
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import java.util.concurrent.*; |
10 |
< |
import java.util.concurrent.locks.*; |
11 |
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import java.util.concurrent.atomic.*; |
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import sun.misc.Unsafe; |
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import java.lang.reflect.*; |
10 |
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|
11 |
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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; |
19 |
> |
import java.util.concurrent.atomic.AtomicInteger; |
20 |
> |
import java.util.concurrent.atomic.AtomicLong; |
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|
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/** |
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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 |
25 |
< |
* non-ForkJoinTasks, as well as management and monitoring operations. |
26 |
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* Normally a single ForkJoinPool is used for a large number of |
27 |
< |
* submitted tasks. Otherwise, use would not usually outweigh the |
28 |
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* construction and bookkeeping overhead of creating a large set of |
29 |
< |
* threads. |
23 |
> |
* An {@link ExecutorService} for running {@link ForkJoinTask}s. |
24 |
> |
* A {@code ForkJoinPool} provides the entry point for submissions |
25 |
> |
* from non-{@code ForkJoinTask}s, as well as management and |
26 |
> |
* monitoring operations. Normally a single {@code ForkJoinPool} is |
27 |
> |
* used for a large number of submitted tasks. Otherwise, use would |
28 |
> |
* not usually outweigh the construction and bookkeeping overhead of |
29 |
> |
* creating a large set of threads. |
30 |
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* |
31 |
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* <p>ForkJoinPools differ from other kinds of Executors mainly in |
32 |
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* that they provide <em>work-stealing</em>: all threads in the pool |
33 |
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* attempt to find and execute subtasks created by other active tasks |
34 |
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* (eventually blocking if none exist). This makes them efficient when |
35 |
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* most tasks spawn other subtasks (as do most ForkJoinTasks), as well |
36 |
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* as the mixed execution of some plain Runnable- or Callable- based |
37 |
< |
* activities along with ForkJoinTasks. When setting |
38 |
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* <tt>setAsyncMode</tt>, 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 |
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* choices. |
31 |
> |
* <p>{@code ForkJoinPool}s differ from other kinds of {@link |
32 |
> |
* Executor}s mainly in that they provide <em>work-stealing</em>: all |
33 |
> |
* threads in the pool attempt to find and execute subtasks created by |
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> |
* other active tasks (eventually blocking if none exist). This makes |
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> |
* them efficient when most tasks spawn other subtasks (as do most |
36 |
> |
* {@code ForkJoinTask}s), as well as the mixed execution of some |
37 |
> |
* plain {@code Runnable}- or {@code Callable}- based activities along |
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> |
* with {@code ForkJoinTask}s. When setting {@linkplain #setAsyncMode |
39 |
> |
* async mode}, a {@code ForkJoinPool} may also be appropriate for use |
40 |
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* with fine-grained tasks that are never joined. Otherwise, other |
41 |
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* {@code ExecutorService} implementations are typically more |
42 |
> |
* appropriate choices. |
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* |
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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</code> interface enables extension of |
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* the kinds of synchronization accommodated. The target parallelism |
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* level may also be changed dynamically (<code>setParallelism</code>) |
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* and thread construction can be limited using methods |
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* <code>setMaximumPoolSize</code> and/or |
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* <code>setMaintainsParallelism</code>. |
44 |
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* <p>A {@code ForkJoinPool} may be constructed with a given |
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> |
* parallelism level (target pool size), which it attempts to maintain |
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> |
* by dynamically adding, suspending, or resuming threads, even if |
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* some tasks are waiting to join others. However, no such adjustments |
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> |
* are performed in the face of blocked IO or other unmanaged |
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* synchronization. The nested {@link ManagedBlocker} interface |
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* enables extension of the kinds of synchronization accommodated. |
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> |
* The target parallelism level may also be changed dynamically |
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* ({@link #setParallelism}) and thread construction can be limited |
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* using methods {@link #setMaximumPoolSize} and/or {@link |
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* #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 |
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* <code>getStealCount</code>) that are intended to aid in developing, |
58 |
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* {@link #getStealCount}) that are intended to aid in developing, |
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* tuning, and monitoring fork/join applications. Also, method |
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* <code>toString</code> returns indications of pool state in a |
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* {@link #toString} returns indications of pool state in a |
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* convenient form for informal monitoring. |
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* |
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* <p><b>Implementation notes</b>: This implementation restricts the |
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* maximum number of running threads to 32767. Attempts to create |
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* pools with greater than the maximum result in |
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* IllegalArgumentExceptions. |
66 |
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* {@code IllegalArgumentException}. |
67 |
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* |
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* @since 1.7 |
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* @author Doug Lea |
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*/ |
71 |
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public class ForkJoinPool extends AbstractExecutorService { |
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|
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private static final int MAX_THREADS = 0x7FFF; |
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|
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/** |
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* Factory for creating new ForkJoinWorkerThreads. A |
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* ForkJoinWorkerThreadFactory must be defined and used for |
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* ForkJoinWorkerThread subclasses that extend base functionality |
88 |
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* or initialize threads with different contexts. |
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> |
* Factory for creating new {@link ForkJoinWorkerThread}s. |
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* A {@code ForkJoinWorkerThreadFactory} must be defined and used |
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* for {@code ForkJoinWorkerThread} subclasses that extend base |
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* functionality or initialize threads with different contexts. |
89 |
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*/ |
90 |
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public static interface ForkJoinWorkerThreadFactory { |
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/** |
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* Returns a new worker thread operating in the given pool. |
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* |
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* @param pool the pool this thread works in |
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* @throws NullPointerException if pool is null; |
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* @throws NullPointerException if pool is null |
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*/ |
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public ForkJoinWorkerThread newThread(ForkJoinPool pool); |
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} |
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|
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/** |
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* Default ForkJoinWorkerThreadFactory implementation, creates a |
101 |
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* Default ForkJoinWorkerThreadFactory implementation; creates a |
102 |
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* new ForkJoinWorkerThread. |
103 |
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*/ |
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static class DefaultForkJoinWorkerThreadFactory |
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|
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/** |
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* The uncaught exception handler used when any worker |
167 |
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* abrupty terminates |
167 |
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* abruptly terminates |
168 |
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*/ |
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private Thread.UncaughtExceptionHandler ueh; |
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|
192 |
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private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue; |
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|
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/** |
195 |
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* Head of Treiber stack for barrier sync. See below for explanation |
195 |
> |
* Head of Treiber stack for barrier sync. See below for explanation. |
196 |
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*/ |
197 |
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private volatile WaitQueueNode syncStack; |
198 |
|
|
228 |
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* making decisions about creating and suspending spare |
229 |
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* threads. Updated only by CAS. Note: CASes in |
230 |
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* updateRunningCount and preJoin assume that running active count |
231 |
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* is in low word, so need to be modified if this changes |
231 |
> |
* is in low word, so need to be modified if this changes. |
232 |
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*/ |
233 |
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private volatile int workerCounts; |
234 |
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|
237 |
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private static int workerCountsFor(int t, int r) { return (t << 16) + r; } |
238 |
|
|
239 |
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/** |
240 |
< |
* Add delta (which may be negative) to running count. This must |
240 |
> |
* Adds delta (which may be negative) to running count. This must |
241 |
|
* be called before (with negative arg) and after (with positive) |
242 |
< |
* any managed synchronization (i.e., mainly, joins) |
242 |
> |
* any managed synchronization (i.e., mainly, joins). |
243 |
> |
* |
244 |
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* @param delta the number to add |
245 |
|
*/ |
246 |
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final void updateRunningCount(int delta) { |
247 |
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int s; |
248 |
< |
do;while (!casWorkerCounts(s = workerCounts, s + delta)); |
248 |
> |
do {} while (!casWorkerCounts(s = workerCounts, s + delta)); |
249 |
|
} |
250 |
|
|
251 |
|
/** |
252 |
< |
* Add delta (which may be negative) to both total and running |
252 |
> |
* Adds delta (which may be negative) to both total and running |
253 |
|
* count. This must be called upon creation and termination of |
254 |
|
* worker threads. |
255 |
+ |
* |
256 |
|
* @param delta the number to add |
257 |
|
*/ |
258 |
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private void updateWorkerCount(int delta) { |
259 |
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int d = delta + (delta << 16); // add to both lo and hi parts |
260 |
|
int s; |
261 |
< |
do;while (!casWorkerCounts(s = workerCounts, s + d)); |
261 |
> |
do {} while (!casWorkerCounts(s = workerCounts, s + d)); |
262 |
|
} |
263 |
|
|
264 |
|
/** |
284 |
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private static int runControlFor(int r, int a) { return (r << 16) + a; } |
285 |
|
|
286 |
|
/** |
287 |
< |
* Try incrementing active count; fail on contention. Called by |
288 |
< |
* workers before/during executing tasks. |
289 |
< |
* @return true on success; |
287 |
> |
* Tries incrementing active count; fails on contention. |
288 |
> |
* Called by workers before/during executing tasks. |
289 |
> |
* |
290 |
> |
* @return true on success |
291 |
|
*/ |
292 |
|
final boolean tryIncrementActiveCount() { |
293 |
|
int c = runControl; |
295 |
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} |
296 |
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|
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/** |
298 |
< |
* Try decrementing active count; fail on contention. |
299 |
< |
* Possibly trigger termination on success |
298 |
> |
* Tries decrementing active count; fails on contention. |
299 |
> |
* Possibly triggers termination on success. |
300 |
|
* Called by workers when they can't find tasks. |
301 |
+ |
* |
302 |
|
* @return true on success |
303 |
|
*/ |
304 |
|
final boolean tryDecrementActiveCount() { |
312 |
|
} |
313 |
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|
314 |
|
/** |
315 |
< |
* Return true if argument represents zero active count and |
316 |
< |
* nonzero runstate, which is the triggering condition for |
315 |
> |
* Returns {@code true} if argument represents zero active count |
316 |
> |
* and nonzero runstate, which is the triggering condition for |
317 |
|
* terminating on shutdown. |
318 |
|
*/ |
319 |
|
private static boolean canTerminateOnShutdown(int c) { |
320 |
< |
return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit |
320 |
> |
// i.e. least bit is nonzero runState bit |
321 |
> |
return ((c & -c) >>> 16) != 0; |
322 |
|
} |
323 |
|
|
324 |
|
/** |
344 |
|
|
345 |
|
/** |
346 |
|
* Creates a ForkJoinPool with a pool size equal to the number of |
347 |
< |
* processors available on the system and using the default |
348 |
< |
* ForkJoinWorkerThreadFactory, |
347 |
> |
* processors available on the system, using the default |
348 |
> |
* ForkJoinWorkerThreadFactory. |
349 |
> |
* |
350 |
|
* @throws SecurityException if a security manager exists and |
351 |
|
* the caller is not permitted to modify threads |
352 |
|
* because it does not hold {@link |
353 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
353 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
354 |
|
*/ |
355 |
|
public ForkJoinPool() { |
356 |
|
this(Runtime.getRuntime().availableProcessors(), |
358 |
|
} |
359 |
|
|
360 |
|
/** |
361 |
< |
* Creates a ForkJoinPool with the indicated parellelism level |
362 |
< |
* threads, and using the default ForkJoinWorkerThreadFactory, |
361 |
> |
* Creates a ForkJoinPool with the indicated parallelism level |
362 |
> |
* threads and using the default ForkJoinWorkerThreadFactory. |
363 |
> |
* |
364 |
|
* @param parallelism the number of worker threads |
365 |
|
* @throws IllegalArgumentException if parallelism less than or |
366 |
|
* equal to zero |
367 |
|
* @throws SecurityException if a security manager exists and |
368 |
|
* the caller is not permitted to modify threads |
369 |
|
* because it does not hold {@link |
370 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
370 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
371 |
|
*/ |
372 |
|
public ForkJoinPool(int parallelism) { |
373 |
|
this(parallelism, defaultForkJoinWorkerThreadFactory); |
376 |
|
/** |
377 |
|
* Creates a ForkJoinPool with parallelism equal to the number of |
378 |
|
* processors available on the system and using the given |
379 |
< |
* ForkJoinWorkerThreadFactory, |
379 |
> |
* ForkJoinWorkerThreadFactory. |
380 |
> |
* |
381 |
|
* @param factory the factory for creating new threads |
382 |
|
* @throws NullPointerException if factory is null |
383 |
|
* @throws SecurityException if a security manager exists and |
384 |
|
* the caller is not permitted to modify threads |
385 |
|
* because it does not hold {@link |
386 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
386 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
387 |
|
*/ |
388 |
|
public ForkJoinPool(ForkJoinWorkerThreadFactory factory) { |
389 |
|
this(Runtime.getRuntime().availableProcessors(), factory); |
395 |
|
* @param parallelism the targeted number of worker threads |
396 |
|
* @param factory the factory for creating new threads |
397 |
|
* @throws IllegalArgumentException if parallelism less than or |
398 |
< |
* equal to zero, or greater than implementation limit. |
398 |
> |
* equal to zero, or greater than implementation limit |
399 |
|
* @throws NullPointerException if factory is null |
400 |
|
* @throws SecurityException if a security manager exists and |
401 |
|
* the caller is not permitted to modify threads |
402 |
|
* because it does not hold {@link |
403 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
403 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
404 |
|
*/ |
405 |
|
public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) { |
406 |
|
if (parallelism <= 0 || parallelism > MAX_THREADS) |
421 |
|
} |
422 |
|
|
423 |
|
/** |
424 |
< |
* Create new worker using factory. |
424 |
> |
* Creates a new worker thread using factory. |
425 |
> |
* |
426 |
|
* @param index the index to assign worker |
427 |
|
* @return new worker, or null of factory failed |
428 |
|
*/ |
441 |
|
} |
442 |
|
|
443 |
|
/** |
444 |
< |
* Return a good size for worker array given pool size. |
444 |
> |
* Returns a good size for worker array given pool size. |
445 |
|
* Currently requires size to be a power of two. |
446 |
|
*/ |
447 |
< |
private static int arraySizeFor(int ps) { |
448 |
< |
return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1))); |
447 |
> |
private static int arraySizeFor(int poolSize) { |
448 |
> |
return (poolSize <= 1) ? 1 : |
449 |
> |
(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1))); |
450 |
|
} |
451 |
|
|
452 |
|
/** |
453 |
< |
* Create or resize array if necessary to hold newLength. |
454 |
< |
* Call only under exclusion |
453 |
> |
* Creates or resizes array if necessary to hold newLength. |
454 |
> |
* Call only under exclusion. |
455 |
> |
* |
456 |
|
* @return the array |
457 |
|
*/ |
458 |
|
private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) { |
466 |
|
} |
467 |
|
|
468 |
|
/** |
469 |
< |
* Try to shrink workers into smaller array after one or more terminate |
469 |
> |
* Tries to shrink workers into smaller array after one or more terminate. |
470 |
|
*/ |
471 |
|
private void tryShrinkWorkerArray() { |
472 |
|
ForkJoinWorkerThread[] ws = workers; |
482 |
|
} |
483 |
|
|
484 |
|
/** |
485 |
< |
* Initialize workers if necessary |
485 |
> |
* Initializes workers if necessary. |
486 |
|
*/ |
487 |
|
final void ensureWorkerInitialization() { |
488 |
|
ForkJoinWorkerThread[] ws = workers; |
549 |
|
* Common code for execute, invoke and submit |
550 |
|
*/ |
551 |
|
private <T> void doSubmit(ForkJoinTask<T> task) { |
552 |
+ |
if (task == null) |
553 |
+ |
throw new NullPointerException(); |
554 |
|
if (isShutdown()) |
555 |
|
throw new RejectedExecutionException(); |
556 |
|
if (workers == null) |
560 |
|
} |
561 |
|
|
562 |
|
/** |
563 |
< |
* Performs the given task; returning its result upon completion |
563 |
> |
* Performs the given task, returning its result upon completion. |
564 |
> |
* |
565 |
|
* @param task the task |
566 |
|
* @return the task's result |
567 |
|
* @throws NullPointerException if task is null |
574 |
|
|
575 |
|
/** |
576 |
|
* Arranges for (asynchronous) execution of the given task. |
577 |
+ |
* |
578 |
|
* @param task the task |
579 |
|
* @throws NullPointerException if task is null |
580 |
|
* @throws RejectedExecutionException if pool is shut down |
581 |
|
*/ |
582 |
< |
public <T> void execute(ForkJoinTask<T> task) { |
582 |
> |
public void execute(ForkJoinTask<?> task) { |
583 |
|
doSubmit(task); |
584 |
|
} |
585 |
|
|
586 |
|
// AbstractExecutorService methods |
587 |
|
|
588 |
|
public void execute(Runnable task) { |
589 |
< |
doSubmit(new AdaptedRunnable<Void>(task, null)); |
589 |
> |
ForkJoinTask<?> job; |
590 |
> |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
591 |
> |
job = (ForkJoinTask<?>) task; |
592 |
> |
else |
593 |
> |
job = ForkJoinTask.adapt(task, null); |
594 |
> |
doSubmit(job); |
595 |
|
} |
596 |
|
|
597 |
|
public <T> ForkJoinTask<T> submit(Callable<T> task) { |
598 |
< |
ForkJoinTask<T> job = new AdaptedCallable<T>(task); |
598 |
> |
ForkJoinTask<T> job = ForkJoinTask.adapt(task); |
599 |
|
doSubmit(job); |
600 |
|
return job; |
601 |
|
} |
602 |
|
|
603 |
|
public <T> ForkJoinTask<T> submit(Runnable task, T result) { |
604 |
< |
ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result); |
604 |
> |
ForkJoinTask<T> job = ForkJoinTask.adapt(task, result); |
605 |
|
doSubmit(job); |
606 |
|
return job; |
607 |
|
} |
608 |
|
|
609 |
|
public ForkJoinTask<?> submit(Runnable task) { |
610 |
< |
ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null); |
610 |
> |
ForkJoinTask<?> job; |
611 |
> |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
612 |
> |
job = (ForkJoinTask<?>) task; |
613 |
> |
else |
614 |
> |
job = ForkJoinTask.adapt(task, null); |
615 |
|
doSubmit(job); |
616 |
|
return job; |
617 |
|
} |
618 |
|
|
619 |
|
/** |
620 |
< |
* Adaptor for Runnables. This implements RunnableFuture |
621 |
< |
* to be compliant with AbstractExecutorService constraints |
620 |
> |
* Submits a ForkJoinTask for execution. |
621 |
> |
* |
622 |
> |
* @param task the task to submit |
623 |
> |
* @return the task |
624 |
> |
* @throws RejectedExecutionException if the task cannot be |
625 |
> |
* scheduled for execution |
626 |
> |
* @throws NullPointerException if the task is null |
627 |
|
*/ |
628 |
< |
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
629 |
< |
implements RunnableFuture<T> { |
630 |
< |
final Runnable runnable; |
591 |
< |
final T resultOnCompletion; |
592 |
< |
T result; |
593 |
< |
AdaptedRunnable(Runnable runnable, T result) { |
594 |
< |
if (runnable == null) throw new NullPointerException(); |
595 |
< |
this.runnable = runnable; |
596 |
< |
this.resultOnCompletion = result; |
597 |
< |
} |
598 |
< |
public T getRawResult() { return result; } |
599 |
< |
public void setRawResult(T v) { result = v; } |
600 |
< |
public boolean exec() { |
601 |
< |
runnable.run(); |
602 |
< |
result = resultOnCompletion; |
603 |
< |
return true; |
604 |
< |
} |
605 |
< |
public void run() { invoke(); } |
628 |
> |
public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) { |
629 |
> |
doSubmit(task); |
630 |
> |
return task; |
631 |
|
} |
632 |
|
|
608 |
– |
/** |
609 |
– |
* Adaptor for Callables |
610 |
– |
*/ |
611 |
– |
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
612 |
– |
implements RunnableFuture<T> { |
613 |
– |
final Callable<T> callable; |
614 |
– |
T result; |
615 |
– |
AdaptedCallable(Callable<T> callable) { |
616 |
– |
if (callable == null) throw new NullPointerException(); |
617 |
– |
this.callable = callable; |
618 |
– |
} |
619 |
– |
public T getRawResult() { return result; } |
620 |
– |
public void setRawResult(T v) { result = v; } |
621 |
– |
public boolean exec() { |
622 |
– |
try { |
623 |
– |
result = callable.call(); |
624 |
– |
return true; |
625 |
– |
} catch (Error err) { |
626 |
– |
throw err; |
627 |
– |
} catch (RuntimeException rex) { |
628 |
– |
throw rex; |
629 |
– |
} catch (Exception ex) { |
630 |
– |
throw new RuntimeException(ex); |
631 |
– |
} |
632 |
– |
} |
633 |
– |
public void run() { invoke(); } |
634 |
– |
} |
633 |
|
|
634 |
|
public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) { |
635 |
< |
ArrayList<ForkJoinTask<T>> ts = |
635 |
> |
ArrayList<ForkJoinTask<T>> forkJoinTasks = |
636 |
|
new ArrayList<ForkJoinTask<T>>(tasks.size()); |
637 |
< |
for (Callable<T> c : tasks) |
638 |
< |
ts.add(new AdaptedCallable<T>(c)); |
639 |
< |
invoke(new InvokeAll<T>(ts)); |
640 |
< |
return (List<Future<T>>)(List)ts; |
637 |
> |
for (Callable<T> task : tasks) |
638 |
> |
forkJoinTasks.add(ForkJoinTask.adapt(task)); |
639 |
> |
invoke(new InvokeAll<T>(forkJoinTasks)); |
640 |
> |
|
641 |
> |
@SuppressWarnings({"unchecked", "rawtypes"}) |
642 |
> |
List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks; |
643 |
> |
return futures; |
644 |
|
} |
645 |
|
|
646 |
|
static final class InvokeAll<T> extends RecursiveAction { |
647 |
|
final ArrayList<ForkJoinTask<T>> tasks; |
648 |
|
InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; } |
649 |
|
public void compute() { |
650 |
< |
try { invokeAll(tasks); } catch(Exception ignore) {} |
650 |
> |
try { invokeAll(tasks); } |
651 |
> |
catch (Exception ignore) {} |
652 |
|
} |
653 |
+ |
private static final long serialVersionUID = -7914297376763021607L; |
654 |
|
} |
655 |
|
|
656 |
|
// Configuration and status settings and queries |
657 |
|
|
658 |
|
/** |
659 |
< |
* Returns the factory used for constructing new workers |
659 |
> |
* Returns the factory used for constructing new workers. |
660 |
|
* |
661 |
|
* @return the factory used for constructing new workers |
662 |
|
*/ |
667 |
|
/** |
668 |
|
* Returns the handler for internal worker threads that terminate |
669 |
|
* due to unrecoverable errors encountered while executing tasks. |
670 |
< |
* @return the handler, or null if none |
670 |
> |
* |
671 |
> |
* @return the handler, or {@code null} if none |
672 |
|
*/ |
673 |
|
public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() { |
674 |
|
Thread.UncaughtExceptionHandler h; |
689 |
|
* as handler. |
690 |
|
* |
691 |
|
* @param h the new handler |
692 |
< |
* @return the old handler, or null if none |
692 |
> |
* @return the old handler, or {@code null} if none |
693 |
|
* @throws SecurityException if a security manager exists and |
694 |
|
* the caller is not permitted to modify threads |
695 |
|
* because it does not hold {@link |
696 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
696 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
697 |
|
*/ |
698 |
|
public Thread.UncaughtExceptionHandler |
699 |
|
setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) { |
720 |
|
|
721 |
|
|
722 |
|
/** |
723 |
< |
* Sets the target paralleism level of this pool. |
723 |
> |
* Sets the target parallelism level of this pool. |
724 |
> |
* |
725 |
|
* @param parallelism the target parallelism |
726 |
|
* @throws IllegalArgumentException if parallelism less than or |
727 |
< |
* equal to zero or greater than maximum size bounds. |
727 |
> |
* equal to zero or greater than maximum size bounds |
728 |
|
* @throws SecurityException if a security manager exists and |
729 |
|
* the caller is not permitted to modify threads |
730 |
|
* because it does not hold {@link |
731 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
731 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
732 |
|
*/ |
733 |
|
public void setParallelism(int parallelism) { |
734 |
|
checkPermission(); |
763 |
|
/** |
764 |
|
* Returns the number of worker threads that have started but not |
765 |
|
* yet terminated. This result returned by this method may differ |
766 |
< |
* from <code>getParallelism</code> when threads are created to |
766 |
> |
* from {@link #getParallelism} when threads are created to |
767 |
|
* maintain parallelism when others are cooperatively blocked. |
768 |
|
* |
769 |
|
* @return the number of worker threads |
775 |
|
/** |
776 |
|
* Returns the maximum number of threads allowed to exist in the |
777 |
|
* pool, even if there are insufficient unblocked running threads. |
778 |
+ |
* |
779 |
|
* @return the maximum |
780 |
|
*/ |
781 |
|
public int getMaximumPoolSize() { |
787 |
|
* pool, even if there are insufficient unblocked running threads. |
788 |
|
* Setting this value has no effect on current pool size. It |
789 |
|
* controls construction of new threads. |
790 |
< |
* @throws IllegalArgumentException if negative or greater then |
791 |
< |
* internal implementation limit. |
790 |
> |
* |
791 |
> |
* @throws IllegalArgumentException if negative or greater than |
792 |
> |
* internal implementation limit |
793 |
|
*/ |
794 |
|
public void setMaximumPoolSize(int newMax) { |
795 |
|
if (newMax < 0 || newMax > MAX_THREADS) |
799 |
|
|
800 |
|
|
801 |
|
/** |
802 |
< |
* Returns true if this pool dynamically maintains its target |
803 |
< |
* parallelism level. If false, new threads are added only to |
804 |
< |
* avoid possible starvation. |
805 |
< |
* This setting is by default true; |
806 |
< |
* @return true if maintains parallelism |
802 |
> |
* Returns {@code true} if this pool dynamically maintains its |
803 |
> |
* target parallelism level. If false, new threads are added only |
804 |
> |
* to avoid possible starvation. This setting is by default true. |
805 |
> |
* |
806 |
> |
* @return {@code true} if maintains parallelism |
807 |
|
*/ |
808 |
|
public boolean getMaintainsParallelism() { |
809 |
|
return maintainsParallelism; |
813 |
|
* Sets whether this pool dynamically maintains its target |
814 |
|
* parallelism level. If false, new threads are added only to |
815 |
|
* avoid possible starvation. |
816 |
< |
* @param enable true to maintains parallelism |
816 |
> |
* |
817 |
> |
* @param enable {@code true} to maintain parallelism |
818 |
|
*/ |
819 |
|
public void setMaintainsParallelism(boolean enable) { |
820 |
|
maintainsParallelism = enable; |
825 |
|
* tasks that are never joined. This mode may be more appropriate |
826 |
|
* than default locally stack-based mode in applications in which |
827 |
|
* worker threads only process asynchronous tasks. This method is |
828 |
< |
* designed to be invoked only when pool is quiescent, and |
828 |
> |
* designed to be invoked only when the pool is quiescent, and |
829 |
|
* typically only before any tasks are submitted. The effects of |
830 |
< |
* invocations at ather times may be unpredictable. |
830 |
> |
* invocations at other times may be unpredictable. |
831 |
|
* |
832 |
< |
* @param async if true, use locally FIFO scheduling |
833 |
< |
* @return the previous mode. |
832 |
> |
* @param async if {@code true}, use locally FIFO scheduling |
833 |
> |
* @return the previous mode |
834 |
> |
* @see #getAsyncMode |
835 |
|
*/ |
836 |
|
public boolean setAsyncMode(boolean async) { |
837 |
|
boolean oldMode = locallyFifo; |
848 |
|
} |
849 |
|
|
850 |
|
/** |
851 |
< |
* Returns true if this pool uses local first-in-first-out |
852 |
< |
* scheduling mode for forked tasks that are never joined. |
851 |
> |
* Returns {@code true} if this pool uses local first-in-first-out |
852 |
> |
* scheduling mode for forked tasks that are never joined. |
853 |
|
* |
854 |
< |
* @return true if this pool uses async mode. |
854 |
> |
* @return {@code true} if this pool uses async mode |
855 |
> |
* @see #setAsyncMode |
856 |
|
*/ |
857 |
|
public boolean getAsyncMode() { |
858 |
|
return locallyFifo; |
873 |
|
* Returns an estimate of the number of threads that are currently |
874 |
|
* stealing or executing tasks. This method may overestimate the |
875 |
|
* number of active threads. |
876 |
< |
* @return the number of active threads. |
876 |
> |
* |
877 |
> |
* @return the number of active threads |
878 |
|
*/ |
879 |
|
public int getActiveThreadCount() { |
880 |
|
return activeCountOf(runControl); |
884 |
|
* Returns an estimate of the number of threads that are currently |
885 |
|
* idle waiting for tasks. This method may underestimate the |
886 |
|
* number of idle threads. |
887 |
< |
* @return the number of idle threads. |
887 |
> |
* |
888 |
> |
* @return the number of idle threads |
889 |
|
*/ |
890 |
|
final int getIdleThreadCount() { |
891 |
|
int c = runningCountOf(workerCounts) - activeCountOf(runControl); |
892 |
< |
return (c <= 0)? 0 : c; |
892 |
> |
return (c <= 0) ? 0 : c; |
893 |
|
} |
894 |
|
|
895 |
|
/** |
896 |
< |
* Returns true if all worker threads are currently idle. An idle |
897 |
< |
* worker is one that cannot obtain a task to execute because none |
898 |
< |
* are available to steal from other threads, and there are no |
899 |
< |
* pending submissions to the pool. This method is conservative: |
900 |
< |
* It might not return true immediately upon idleness of all |
901 |
< |
* threads, but will eventually become true if threads remain |
902 |
< |
* inactive. |
903 |
< |
* @return true if all threads are currently idle |
896 |
> |
* Returns {@code true} if all worker threads are currently idle. |
897 |
> |
* An idle worker is one that cannot obtain a task to execute |
898 |
> |
* because none are available to steal from other threads, and |
899 |
> |
* there are no pending submissions to the pool. This method is |
900 |
> |
* conservative; it might not return {@code true} immediately upon |
901 |
> |
* idleness of all threads, but will eventually become true if |
902 |
> |
* threads remain inactive. |
903 |
> |
* |
904 |
> |
* @return {@code true} if all threads are currently idle |
905 |
|
*/ |
906 |
|
public boolean isQuiescent() { |
907 |
|
return activeCountOf(runControl) == 0; |
912 |
|
* one thread's work queue by another. The reported value |
913 |
|
* underestimates the actual total number of steals when the pool |
914 |
|
* is not quiescent. This value may be useful for monitoring and |
915 |
< |
* tuning fork/join programs: In general, steal counts should be |
915 |
> |
* tuning fork/join programs: in general, steal counts should be |
916 |
|
* high enough to keep threads busy, but low enough to avoid |
917 |
|
* overhead and contention across threads. |
918 |
< |
* @return the number of steals. |
918 |
> |
* |
919 |
> |
* @return the number of steals |
920 |
|
*/ |
921 |
|
public long getStealCount() { |
922 |
|
return stealCount.get(); |
923 |
|
} |
924 |
|
|
925 |
|
/** |
926 |
< |
* Accumulate steal count from a worker. Call only |
927 |
< |
* when worker known to be idle. |
926 |
> |
* Accumulates steal count from a worker. |
927 |
> |
* Call only when worker known to be idle. |
928 |
|
*/ |
929 |
|
private void updateStealCount(ForkJoinWorkerThread w) { |
930 |
|
int sc = w.getAndClearStealCount(); |
939 |
|
* an approximation, obtained by iterating across all threads in |
940 |
|
* the pool. This method may be useful for tuning task |
941 |
|
* granularities. |
942 |
< |
* @return the number of queued tasks. |
942 |
> |
* |
943 |
> |
* @return the number of queued tasks |
944 |
|
*/ |
945 |
|
public long getQueuedTaskCount() { |
946 |
|
long count = 0; |
956 |
|
} |
957 |
|
|
958 |
|
/** |
959 |
< |
* Returns an estimate of the number tasks submitted to this pool |
960 |
< |
* that have not yet begun executing. This method takes time |
959 |
> |
* Returns an estimate of the number of tasks submitted to this |
960 |
> |
* pool that have not yet begun executing. This method takes time |
961 |
|
* proportional to the number of submissions. |
962 |
< |
* @return the number of queued submissions. |
962 |
> |
* |
963 |
> |
* @return the number of queued submissions |
964 |
|
*/ |
965 |
|
public int getQueuedSubmissionCount() { |
966 |
|
return submissionQueue.size(); |
967 |
|
} |
968 |
|
|
969 |
|
/** |
970 |
< |
* Returns true if there are any tasks submitted to this pool |
971 |
< |
* that have not yet begun executing. |
972 |
< |
* @return <code>true</code> if there are any queued submissions. |
970 |
> |
* Returns {@code true} if there are any tasks submitted to this |
971 |
> |
* pool that have not yet begun executing. |
972 |
> |
* |
973 |
> |
* @return {@code true} if there are any queued submissions |
974 |
|
*/ |
975 |
|
public boolean hasQueuedSubmissions() { |
976 |
|
return !submissionQueue.isEmpty(); |
980 |
|
* Removes and returns the next unexecuted submission if one is |
981 |
|
* available. This method may be useful in extensions to this |
982 |
|
* class that re-assign work in systems with multiple pools. |
983 |
< |
* @return the next submission, or null if none |
983 |
> |
* |
984 |
> |
* @return the next submission, or {@code null} if none |
985 |
|
*/ |
986 |
|
protected ForkJoinTask<?> pollSubmission() { |
987 |
|
return submissionQueue.poll(); |
991 |
|
* Removes all available unexecuted submitted and forked tasks |
992 |
|
* from scheduling queues and adds them to the given collection, |
993 |
|
* without altering their execution status. These may include |
994 |
< |
* artifically generated or wrapped tasks. This method id designed |
994 |
> |
* artificially generated or wrapped tasks. This method is designed |
995 |
|
* to be invoked only when the pool is known to be |
996 |
|
* quiescent. Invocations at other times may not remove all |
997 |
|
* tasks. A failure encountered while attempting to add elements |
998 |
< |
* to collection <tt>c</tt> may result in elements being in |
998 |
> |
* to collection {@code c} may result in elements being in |
999 |
|
* neither, either or both collections when the associated |
1000 |
|
* exception is thrown. The behavior of this operation is |
1001 |
|
* undefined if the specified collection is modified while the |
1002 |
|
* operation is in progress. |
1003 |
+ |
* |
1004 |
|
* @param c the collection to transfer elements into |
1005 |
|
* @return the number of elements transferred |
1006 |
|
*/ |
1007 |
< |
protected int drainTasksTo(Collection<ForkJoinTask<?>> c) { |
1007 |
> |
protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
1008 |
|
int n = submissionQueue.drainTo(c); |
1009 |
|
ForkJoinWorkerThread[] ws = workers; |
1010 |
|
if (ws != null) { |
1061 |
|
* Invocation has no additional effect if already shut down. |
1062 |
|
* Tasks that are in the process of being submitted concurrently |
1063 |
|
* during the course of this method may or may not be rejected. |
1064 |
+ |
* |
1065 |
|
* @throws SecurityException if a security manager exists and |
1066 |
|
* the caller is not permitted to modify threads |
1067 |
|
* because it does not hold {@link |
1068 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
1068 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1069 |
|
*/ |
1070 |
|
public void shutdown() { |
1071 |
|
checkPermission(); |
1072 |
|
transitionRunStateTo(SHUTDOWN); |
1073 |
< |
if (canTerminateOnShutdown(runControl)) |
1073 |
> |
if (canTerminateOnShutdown(runControl)) { |
1074 |
> |
if (workers == null) { // shutting down before workers created |
1075 |
> |
final ReentrantLock lock = this.workerLock; |
1076 |
> |
lock.lock(); |
1077 |
> |
try { |
1078 |
> |
if (workers == null) { |
1079 |
> |
terminate(); |
1080 |
> |
transitionRunStateTo(TERMINATED); |
1081 |
> |
termination.signalAll(); |
1082 |
> |
} |
1083 |
> |
} finally { |
1084 |
> |
lock.unlock(); |
1085 |
> |
} |
1086 |
> |
} |
1087 |
|
terminateOnShutdown(); |
1088 |
+ |
} |
1089 |
|
} |
1090 |
|
|
1091 |
|
/** |
1095 |
|
* method may or may not be rejected. Unlike some other executors, |
1096 |
|
* this method cancels rather than collects non-executed tasks |
1097 |
|
* upon termination, so always returns an empty list. However, you |
1098 |
< |
* can use method <code>drainTasksTo</code> before invoking this |
1098 |
> |
* can use method {@link #drainTasksTo} before invoking this |
1099 |
|
* method to transfer unexecuted tasks to another collection. |
1100 |
+ |
* |
1101 |
|
* @return an empty list |
1102 |
|
* @throws SecurityException if a security manager exists and |
1103 |
|
* the caller is not permitted to modify threads |
1104 |
|
* because it does not hold {@link |
1105 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
1105 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1106 |
|
*/ |
1107 |
|
public List<Runnable> shutdownNow() { |
1108 |
|
checkPermission(); |
1111 |
|
} |
1112 |
|
|
1113 |
|
/** |
1114 |
< |
* Returns <code>true</code> if all tasks have completed following shut down. |
1114 |
> |
* Returns {@code true} if all tasks have completed following shut down. |
1115 |
|
* |
1116 |
< |
* @return <code>true</code> if all tasks have completed following shut down |
1116 |
> |
* @return {@code true} if all tasks have completed following shut down |
1117 |
|
*/ |
1118 |
|
public boolean isTerminated() { |
1119 |
|
return runStateOf(runControl) == TERMINATED; |
1120 |
|
} |
1121 |
|
|
1122 |
|
/** |
1123 |
< |
* Returns <code>true</code> if the process of termination has |
1123 |
> |
* Returns {@code true} if the process of termination has |
1124 |
|
* commenced but possibly not yet completed. |
1125 |
|
* |
1126 |
< |
* @return <code>true</code> if terminating |
1126 |
> |
* @return {@code true} if terminating |
1127 |
|
*/ |
1128 |
|
public boolean isTerminating() { |
1129 |
|
return runStateOf(runControl) >= TERMINATING; |
1130 |
|
} |
1131 |
|
|
1132 |
|
/** |
1133 |
< |
* Returns <code>true</code> if this pool has been shut down. |
1133 |
> |
* Returns {@code true} if this pool has been shut down. |
1134 |
|
* |
1135 |
< |
* @return <code>true</code> if this pool has been shut down |
1135 |
> |
* @return {@code true} if this pool has been shut down |
1136 |
|
*/ |
1137 |
|
public boolean isShutdown() { |
1138 |
|
return runStateOf(runControl) >= SHUTDOWN; |
1145 |
|
* |
1146 |
|
* @param timeout the maximum time to wait |
1147 |
|
* @param unit the time unit of the timeout argument |
1148 |
< |
* @return <code>true</code> if this executor terminated and |
1149 |
< |
* <code>false</code> if the timeout elapsed before termination |
1148 |
> |
* @return {@code true} if this executor terminated and |
1149 |
> |
* {@code false} if the timeout elapsed before termination |
1150 |
|
* @throws InterruptedException if interrupted while waiting |
1151 |
|
*/ |
1152 |
|
public boolean awaitTermination(long timeout, TimeUnit unit) |
1170 |
|
// Shutdown and termination support |
1171 |
|
|
1172 |
|
/** |
1173 |
< |
* Callback from terminating worker. Null out the corresponding |
1174 |
< |
* workers slot, and if terminating, try to terminate, else try to |
1175 |
< |
* shrink workers array. |
1173 |
> |
* Callback from terminating worker. Nulls out the corresponding |
1174 |
> |
* workers slot, and if terminating, tries to terminate; else |
1175 |
> |
* tries to shrink workers array. |
1176 |
> |
* |
1177 |
|
* @param w the worker |
1178 |
|
*/ |
1179 |
|
final void workerTerminated(ForkJoinWorkerThread w) { |
1204 |
|
} |
1205 |
|
|
1206 |
|
/** |
1207 |
< |
* Initiate termination. |
1207 |
> |
* Initiates termination. |
1208 |
|
*/ |
1209 |
|
private void terminate() { |
1210 |
|
if (transitionRunStateTo(TERMINATING)) { |
1219 |
|
} |
1220 |
|
|
1221 |
|
/** |
1222 |
< |
* Possibly terminate when on shutdown state |
1222 |
> |
* Possibly terminates when on shutdown state. |
1223 |
|
*/ |
1224 |
|
private void terminateOnShutdown() { |
1225 |
|
if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl)) |
1227 |
|
} |
1228 |
|
|
1229 |
|
/** |
1230 |
< |
* Clear out and cancel submissions |
1230 |
> |
* Clears out and cancels submissions. |
1231 |
|
*/ |
1232 |
|
private void cancelQueuedSubmissions() { |
1233 |
|
ForkJoinTask<?> task; |
1236 |
|
} |
1237 |
|
|
1238 |
|
/** |
1239 |
< |
* Clean out worker queues. |
1239 |
> |
* Cleans out worker queues. |
1240 |
|
*/ |
1241 |
|
private void cancelQueuedWorkerTasks() { |
1242 |
|
final ReentrantLock lock = this.workerLock; |
1256 |
|
} |
1257 |
|
|
1258 |
|
/** |
1259 |
< |
* Set each worker's status to terminating. Requires lock to avoid |
1260 |
< |
* conflicts with add/remove |
1259 |
> |
* Sets each worker's status to terminating. Requires lock to avoid |
1260 |
> |
* conflicts with add/remove. |
1261 |
|
*/ |
1262 |
|
private void stopAllWorkers() { |
1263 |
|
final ReentrantLock lock = this.workerLock; |
1277 |
|
} |
1278 |
|
|
1279 |
|
/** |
1280 |
< |
* Interrupt all unterminated workers. This is not required for |
1280 |
> |
* Interrupts all unterminated workers. This is not required for |
1281 |
|
* sake of internal control, but may help unstick user code during |
1282 |
|
* shutdown. |
1283 |
|
*/ |
1347 |
|
} |
1348 |
|
|
1349 |
|
/** |
1350 |
< |
* Wake up waiter, returning false if known to already |
1350 |
> |
* Wakes up waiter, returning false if known to already |
1351 |
|
*/ |
1352 |
|
boolean signal() { |
1353 |
|
ForkJoinWorkerThread t = thread; |
1359 |
|
} |
1360 |
|
|
1361 |
|
/** |
1362 |
< |
* Await release on sync |
1362 |
> |
* Awaits release on sync. |
1363 |
|
*/ |
1364 |
|
void awaitSyncRelease(ForkJoinPool p) { |
1365 |
|
while (thread != null && !p.syncIsReleasable(this)) |
1367 |
|
} |
1368 |
|
|
1369 |
|
/** |
1370 |
< |
* Await resumption as spare |
1370 |
> |
* Awaits resumption as spare. |
1371 |
|
*/ |
1372 |
|
void awaitSpareRelease() { |
1373 |
|
while (thread != null) { |
1381 |
|
* Ensures that no thread is waiting for count to advance from the |
1382 |
|
* current value of eventCount read on entry to this method, by |
1383 |
|
* releasing waiting threads if necessary. |
1384 |
+ |
* |
1385 |
|
* @return the count |
1386 |
|
*/ |
1387 |
|
final long ensureSync() { |
1403 |
|
*/ |
1404 |
|
private void signalIdleWorkers() { |
1405 |
|
long c; |
1406 |
< |
do;while (!casEventCount(c = eventCount, c+1)); |
1406 |
> |
do {} while (!casEventCount(c = eventCount, c+1)); |
1407 |
|
ensureSync(); |
1408 |
|
} |
1409 |
|
|
1410 |
|
/** |
1411 |
< |
* Signal threads waiting to poll a task. Because method sync |
1411 |
> |
* Signals threads waiting to poll a task. Because method sync |
1412 |
|
* rechecks availability, it is OK to only proceed if queue |
1413 |
|
* appears to be non-empty, and OK to skip under contention to |
1414 |
|
* increment count (since some other thread succeeded). |
1427 |
|
* Waits until event count advances from last value held by |
1428 |
|
* caller, or if excess threads, caller is resumed as spare, or |
1429 |
|
* caller or pool is terminating. Updates caller's event on exit. |
1430 |
+ |
* |
1431 |
|
* @param w the calling worker thread |
1432 |
|
*/ |
1433 |
|
final void sync(ForkJoinWorkerThread w) { |
1455 |
|
} |
1456 |
|
|
1457 |
|
/** |
1458 |
< |
* Returns true if worker waiting on sync can proceed: |
1458 |
> |
* Returns {@code true} if worker waiting on sync can proceed: |
1459 |
|
* - on signal (thread == null) |
1460 |
|
* - on event count advance (winning race to notify vs signaller) |
1461 |
< |
* - on Interrupt |
1461 |
> |
* - on interrupt |
1462 |
|
* - if the first queued node, we find work available |
1463 |
|
* If node was not signalled and event count not advanced on exit, |
1464 |
|
* then we also help advance event count. |
1465 |
< |
* @return true if node can be released |
1465 |
> |
* |
1466 |
> |
* @return {@code true} if node can be released |
1467 |
|
*/ |
1468 |
|
final boolean syncIsReleasable(WaitQueueNode node) { |
1469 |
|
long prev = node.count; |
1482 |
|
} |
1483 |
|
|
1484 |
|
/** |
1485 |
< |
* Returns true if a new sync event occurred since last call to |
1486 |
< |
* sync or this method, if so, updating caller's count. |
1485 |
> |
* Returns {@code true} if a new sync event occurred since last |
1486 |
> |
* call to sync or this method, if so, updating caller's count. |
1487 |
|
*/ |
1488 |
|
final boolean hasNewSyncEvent(ForkJoinWorkerThread w) { |
1489 |
|
long lc = w.lastEventCount; |
1497 |
|
// Parallelism maintenance |
1498 |
|
|
1499 |
|
/** |
1500 |
< |
* Decrement running count; if too low, add spare. |
1500 |
> |
* Decrements running count; if too low, adds spare. |
1501 |
|
* |
1502 |
|
* Conceptually, all we need to do here is add or resume a |
1503 |
|
* spare thread when one is about to block (and remove or |
1504 |
|
* suspend it later when unblocked -- see suspendIfSpare). |
1505 |
|
* However, implementing this idea requires coping with |
1506 |
< |
* several problems: We have imperfect information about the |
1506 |
> |
* several problems: we have imperfect information about the |
1507 |
|
* states of threads. Some count updates can and usually do |
1508 |
|
* lag run state changes, despite arrangements to keep them |
1509 |
|
* accurate (for example, when possible, updating counts |
1517 |
|
* only be suspended or removed when they are idle, not |
1518 |
|
* immediately when they aren't needed. So adding threads will |
1519 |
|
* raise parallelism level for longer than necessary. Also, |
1520 |
< |
* FJ applications often enounter highly transient peaks when |
1520 |
> |
* FJ applications often encounter highly transient peaks when |
1521 |
|
* many threads are blocked joining, but for less time than it |
1522 |
|
* takes to create or resume spares. |
1523 |
|
* |
1526 |
|
* target counts, else create only to avoid starvation |
1527 |
|
* @return true if joinMe known to be done |
1528 |
|
*/ |
1529 |
< |
final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) { |
1529 |
> |
final boolean preJoin(ForkJoinTask<?> joinMe, |
1530 |
> |
boolean maintainParallelism) { |
1531 |
|
maintainParallelism &= maintainsParallelism; // overrride |
1532 |
|
boolean dec = false; // true when running count decremented |
1533 |
|
while (spareStack == null || !tryResumeSpare(dec)) { |
1534 |
|
int counts = workerCounts; |
1535 |
< |
if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat |
1535 |
> |
if (dec || (dec = casWorkerCounts(counts, --counts))) { |
1536 |
> |
// CAS cheat |
1537 |
|
if (!needSpare(counts, maintainParallelism)) |
1538 |
|
break; |
1539 |
|
if (joinMe.status < 0) |
1567 |
|
} |
1568 |
|
|
1569 |
|
/** |
1570 |
< |
* Returns true if a spare thread appears to be needed. If |
1571 |
< |
* maintaining parallelism, returns true when the deficit in |
1570 |
> |
* Returns {@code true} if a spare thread appears to be needed. |
1571 |
> |
* If maintaining parallelism, returns true when the deficit in |
1572 |
|
* running threads is more than the surplus of total threads, and |
1573 |
|
* there is apparently some work to do. This self-limiting rule |
1574 |
|
* means that the more threads that have already been added, the |
1575 |
|
* less parallelism we will tolerate before adding another. |
1576 |
+ |
* |
1577 |
|
* @param counts current worker counts |
1578 |
|
* @param maintainParallelism try to maintain parallelism |
1579 |
|
*/ |
1591 |
|
} |
1592 |
|
|
1593 |
|
/** |
1594 |
< |
* Add a spare worker if lock available and no more than the |
1595 |
< |
* expected numbers of threads exist |
1594 |
> |
* Adds a spare worker if lock available and no more than the |
1595 |
> |
* expected numbers of threads exist. |
1596 |
> |
* |
1597 |
|
* @return true if successful |
1598 |
|
*/ |
1599 |
|
private boolean tryAddSpare(int expectedCounts) { |
1626 |
|
} |
1627 |
|
|
1628 |
|
/** |
1629 |
< |
* Add the kth spare worker. On entry, pool coounts are already |
1629 |
> |
* Adds the kth spare worker. On entry, pool counts are already |
1630 |
|
* adjusted to reflect addition. |
1631 |
|
*/ |
1632 |
|
private void createAndStartSpare(int k) { |
1648 |
|
} |
1649 |
|
|
1650 |
|
/** |
1651 |
< |
* Suspend calling thread w if there are excess threads. Called |
1652 |
< |
* only from sync. Spares are enqueued in a Treiber stack |
1653 |
< |
* using the same WaitQueueNodes as barriers. They are resumed |
1654 |
< |
* mainly in preJoin, but are also woken on pool events that |
1655 |
< |
* require all threads to check run state. |
1651 |
> |
* Suspends calling thread w if there are excess threads. Called |
1652 |
> |
* only from sync. Spares are enqueued in a Treiber stack using |
1653 |
> |
* the same WaitQueueNodes as barriers. They are resumed mainly |
1654 |
> |
* in preJoin, but are also woken on pool events that require all |
1655 |
> |
* threads to check run state. |
1656 |
> |
* |
1657 |
|
* @param w the caller |
1658 |
|
*/ |
1659 |
|
private boolean suspendIfSpare(ForkJoinWorkerThread w) { |
1664 |
|
node = new WaitQueueNode(0, w); |
1665 |
|
if (casWorkerCounts(s, s-1)) { // representation-dependent |
1666 |
|
// push onto stack |
1667 |
< |
do;while (!casSpareStack(node.next = spareStack, node)); |
1667 |
> |
do {} while (!casSpareStack(node.next = spareStack, node)); |
1668 |
|
// block until released by resumeSpare |
1669 |
|
node.awaitSpareRelease(); |
1670 |
|
return true; |
1674 |
|
} |
1675 |
|
|
1676 |
|
/** |
1677 |
< |
* Try to pop and resume a spare thread. |
1677 |
> |
* Tries to pop and resume a spare thread. |
1678 |
> |
* |
1679 |
|
* @param updateCount if true, increment running count on success |
1680 |
|
* @return true if successful |
1681 |
|
*/ |
1693 |
|
} |
1694 |
|
|
1695 |
|
/** |
1696 |
< |
* Pop and resume all spare threads. Same idea as ensureSync. |
1696 |
> |
* Pops and resumes all spare threads. Same idea as ensureSync. |
1697 |
> |
* |
1698 |
|
* @return true if any spares released |
1699 |
|
*/ |
1700 |
|
private boolean resumeAllSpares() { |
1712 |
|
} |
1713 |
|
|
1714 |
|
/** |
1715 |
< |
* Pop and shutdown excessive spare threads. Call only while |
1715 |
> |
* Pops and shuts down excessive spare threads. Call only while |
1716 |
|
* holding lock. This is not guaranteed to eliminate all excess |
1717 |
|
* threads, only those suspended as spares, which are the ones |
1718 |
|
* unlikely to be needed in the future. |
1736 |
|
|
1737 |
|
/** |
1738 |
|
* Interface for extending managed parallelism for tasks running |
1739 |
< |
* in ForkJoinPools. A ManagedBlocker provides two methods. |
1740 |
< |
* Method <code>isReleasable</code> must return true if blocking is not |
1741 |
< |
* necessary. Method <code>block</code> blocks the current thread |
1742 |
< |
* if necessary (perhaps internally invoking isReleasable before |
1743 |
< |
* actually blocking.). |
1739 |
> |
* in {@link ForkJoinPool}s. |
1740 |
> |
* |
1741 |
> |
* <p>A {@code ManagedBlocker} provides two methods. |
1742 |
> |
* Method {@code isReleasable} must return {@code true} if |
1743 |
> |
* blocking is not necessary. Method {@code block} blocks the |
1744 |
> |
* current thread if necessary (perhaps internally invoking |
1745 |
> |
* {@code isReleasable} before actually blocking). |
1746 |
> |
* |
1747 |
|
* <p>For example, here is a ManagedBlocker based on a |
1748 |
|
* ReentrantLock: |
1749 |
< |
* <pre> |
1750 |
< |
* class ManagedLocker implements ManagedBlocker { |
1751 |
< |
* final ReentrantLock lock; |
1752 |
< |
* boolean hasLock = false; |
1753 |
< |
* ManagedLocker(ReentrantLock lock) { this.lock = lock; } |
1754 |
< |
* public boolean block() { |
1755 |
< |
* if (!hasLock) |
1756 |
< |
* lock.lock(); |
1757 |
< |
* return true; |
1758 |
< |
* } |
1759 |
< |
* public boolean isReleasable() { |
1760 |
< |
* return hasLock || (hasLock = lock.tryLock()); |
1712 |
< |
* } |
1749 |
> |
* <pre> {@code |
1750 |
> |
* class ManagedLocker implements ManagedBlocker { |
1751 |
> |
* final ReentrantLock lock; |
1752 |
> |
* boolean hasLock = false; |
1753 |
> |
* ManagedLocker(ReentrantLock lock) { this.lock = lock; } |
1754 |
> |
* public boolean block() { |
1755 |
> |
* if (!hasLock) |
1756 |
> |
* lock.lock(); |
1757 |
> |
* return true; |
1758 |
> |
* } |
1759 |
> |
* public boolean isReleasable() { |
1760 |
> |
* return hasLock || (hasLock = lock.tryLock()); |
1761 |
|
* } |
1762 |
< |
* </pre> |
1762 |
> |
* }}</pre> |
1763 |
|
*/ |
1764 |
|
public static interface ManagedBlocker { |
1765 |
|
/** |
1766 |
|
* Possibly blocks the current thread, for example waiting for |
1767 |
|
* a lock or condition. |
1768 |
< |
* @return true if no additional blocking is necessary (i.e., |
1769 |
< |
* if isReleasable would return true). |
1768 |
> |
* |
1769 |
> |
* @return {@code true} if no additional blocking is necessary |
1770 |
> |
* (i.e., if isReleasable would return true) |
1771 |
|
* @throws InterruptedException if interrupted while waiting |
1772 |
< |
* (the method is not required to do so, but is allowe to). |
1772 |
> |
* (the method is not required to do so, but is allowed to) |
1773 |
|
*/ |
1774 |
|
boolean block() throws InterruptedException; |
1775 |
|
|
1776 |
|
/** |
1777 |
< |
* Returns true if blocking is unnecessary. |
1777 |
> |
* Returns {@code true} if blocking is unnecessary. |
1778 |
|
*/ |
1779 |
|
boolean isReleasable(); |
1780 |
|
} |
1781 |
|
|
1782 |
|
/** |
1783 |
|
* Blocks in accord with the given blocker. If the current thread |
1784 |
< |
* is a ForkJoinWorkerThread, this method possibly arranges for a |
1785 |
< |
* spare thread to be activated if necessary to ensure parallelism |
1786 |
< |
* while the current thread is blocked. If |
1787 |
< |
* <code>maintainParallelism</code> is true and the pool supports |
1788 |
< |
* it ({@link #getMaintainsParallelism}), this method attempts to |
1789 |
< |
* maintain the pool's nominal parallelism. Otherwise if activates |
1790 |
< |
* a thread only if necessary to avoid complete starvation. This |
1791 |
< |
* option may be preferable when blockages use timeouts, or are |
1792 |
< |
* almost always brief. |
1793 |
< |
* |
1794 |
< |
* <p> If the caller is not a ForkJoinTask, this method is behaviorally |
1795 |
< |
* equivalent to |
1796 |
< |
* <pre> |
1797 |
< |
* while (!blocker.isReleasable()) |
1798 |
< |
* if (blocker.block()) |
1799 |
< |
* return; |
1800 |
< |
* </pre> |
1801 |
< |
* If the caller is a ForkJoinTask, then the pool may first |
1802 |
< |
* be expanded to ensure parallelism, and later adjusted. |
1784 |
> |
* is a {@link ForkJoinWorkerThread}, this method possibly |
1785 |
> |
* arranges for a spare thread to be activated if necessary to |
1786 |
> |
* ensure parallelism while the current thread is blocked. |
1787 |
> |
* |
1788 |
> |
* <p>If {@code maintainParallelism} is {@code true} and the pool |
1789 |
> |
* supports it ({@link #getMaintainsParallelism}), this method |
1790 |
> |
* attempts to maintain the pool's nominal parallelism. Otherwise |
1791 |
> |
* it activates a thread only if necessary to avoid complete |
1792 |
> |
* starvation. This option may be preferable when blockages use |
1793 |
> |
* timeouts, or are almost always brief. |
1794 |
> |
* |
1795 |
> |
* <p>If the caller is not a {@link ForkJoinTask}, this method is |
1796 |
> |
* behaviorally equivalent to |
1797 |
> |
* <pre> {@code |
1798 |
> |
* while (!blocker.isReleasable()) |
1799 |
> |
* if (blocker.block()) |
1800 |
> |
* return; |
1801 |
> |
* }</pre> |
1802 |
> |
* |
1803 |
> |
* If the caller is a {@code ForkJoinTask}, then the pool may |
1804 |
> |
* first be expanded to ensure parallelism, and later adjusted. |
1805 |
|
* |
1806 |
|
* @param blocker the blocker |
1807 |
< |
* @param maintainParallelism if true and supported by this pool, |
1808 |
< |
* attempt to maintain the pool's nominal parallelism; otherwise |
1809 |
< |
* activate a thread only if necessary to avoid complete |
1810 |
< |
* starvation. |
1811 |
< |
* @throws InterruptedException if blocker.block did so. |
1807 |
> |
* @param maintainParallelism if {@code true} and supported by |
1808 |
> |
* this pool, attempt to maintain the pool's nominal parallelism; |
1809 |
> |
* otherwise activate a thread only if necessary to avoid |
1810 |
> |
* complete starvation. |
1811 |
> |
* @throws InterruptedException if blocker.block did so |
1812 |
|
*/ |
1813 |
|
public static void managedBlock(ManagedBlocker blocker, |
1814 |
|
boolean maintainParallelism) |
1815 |
|
throws InterruptedException { |
1816 |
|
Thread t = Thread.currentThread(); |
1817 |
< |
ForkJoinPool pool = (t instanceof ForkJoinWorkerThread? |
1818 |
< |
((ForkJoinWorkerThread)t).pool : null); |
1817 |
> |
ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ? |
1818 |
> |
((ForkJoinWorkerThread) t).pool : null); |
1819 |
|
if (!blocker.isReleasable()) { |
1820 |
|
try { |
1821 |
|
if (pool == null || |
1830 |
|
|
1831 |
|
private static void awaitBlocker(ManagedBlocker blocker) |
1832 |
|
throws InterruptedException { |
1833 |
< |
do;while (!blocker.isReleasable() && !blocker.block()); |
1833 |
> |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1834 |
|
} |
1835 |
|
|
1836 |
< |
// AbstractExecutorService overrides |
1836 |
> |
// AbstractExecutorService overrides. These rely on undocumented |
1837 |
> |
// fact that ForkJoinTask.adapt returns ForkJoinTasks that also |
1838 |
> |
// implement RunnableFuture. |
1839 |
|
|
1840 |
|
protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) { |
1841 |
< |
return new AdaptedRunnable(runnable, value); |
1841 |
> |
return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value); |
1842 |
|
} |
1843 |
|
|
1844 |
|
protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) { |
1845 |
< |
return new AdaptedCallable(callable); |
1793 |
< |
} |
1794 |
< |
|
1795 |
< |
|
1796 |
< |
// Temporary Unsafe mechanics for preliminary release |
1797 |
< |
private static Unsafe getUnsafe() throws Throwable { |
1798 |
< |
try { |
1799 |
< |
return Unsafe.getUnsafe(); |
1800 |
< |
} catch (SecurityException se) { |
1801 |
< |
try { |
1802 |
< |
return java.security.AccessController.doPrivileged |
1803 |
< |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
1804 |
< |
public Unsafe run() throws Exception { |
1805 |
< |
return getUnsafePrivileged(); |
1806 |
< |
}}); |
1807 |
< |
} catch (java.security.PrivilegedActionException e) { |
1808 |
< |
throw e.getCause(); |
1809 |
< |
} |
1810 |
< |
} |
1845 |
> |
return (RunnableFuture<T>) ForkJoinTask.adapt(callable); |
1846 |
|
} |
1847 |
|
|
1848 |
< |
private static Unsafe getUnsafePrivileged() |
1814 |
< |
throws NoSuchFieldException, IllegalAccessException { |
1815 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1816 |
< |
f.setAccessible(true); |
1817 |
< |
return (Unsafe) f.get(null); |
1818 |
< |
} |
1848 |
> |
// Unsafe mechanics |
1849 |
|
|
1850 |
< |
private static long fieldOffset(String fieldName) |
1851 |
< |
throws NoSuchFieldException { |
1852 |
< |
return _unsafe.objectFieldOffset |
1853 |
< |
(ForkJoinPool.class.getDeclaredField(fieldName)); |
1854 |
< |
} |
1855 |
< |
|
1856 |
< |
static final Unsafe _unsafe; |
1857 |
< |
static final long eventCountOffset; |
1858 |
< |
static final long workerCountsOffset; |
1859 |
< |
static final long runControlOffset; |
1860 |
< |
static final long syncStackOffset; |
1831 |
< |
static final long spareStackOffset; |
1832 |
< |
|
1833 |
< |
static { |
1834 |
< |
try { |
1835 |
< |
_unsafe = getUnsafe(); |
1836 |
< |
eventCountOffset = fieldOffset("eventCount"); |
1837 |
< |
workerCountsOffset = fieldOffset("workerCounts"); |
1838 |
< |
runControlOffset = fieldOffset("runControl"); |
1839 |
< |
syncStackOffset = fieldOffset("syncStack"); |
1840 |
< |
spareStackOffset = fieldOffset("spareStack"); |
1841 |
< |
} catch (Throwable e) { |
1842 |
< |
throw new RuntimeException("Could not initialize intrinsics", e); |
1843 |
< |
} |
1844 |
< |
} |
1850 |
> |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1851 |
> |
private static final long eventCountOffset = |
1852 |
> |
objectFieldOffset("eventCount", ForkJoinPool.class); |
1853 |
> |
private static final long workerCountsOffset = |
1854 |
> |
objectFieldOffset("workerCounts", ForkJoinPool.class); |
1855 |
> |
private static final long runControlOffset = |
1856 |
> |
objectFieldOffset("runControl", ForkJoinPool.class); |
1857 |
> |
private static final long syncStackOffset = |
1858 |
> |
objectFieldOffset("syncStack",ForkJoinPool.class); |
1859 |
> |
private static final long spareStackOffset = |
1860 |
> |
objectFieldOffset("spareStack", ForkJoinPool.class); |
1861 |
|
|
1862 |
|
private boolean casEventCount(long cmp, long val) { |
1863 |
< |
return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val); |
1863 |
> |
return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val); |
1864 |
|
} |
1865 |
|
private boolean casWorkerCounts(int cmp, int val) { |
1866 |
< |
return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val); |
1866 |
> |
return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val); |
1867 |
|
} |
1868 |
|
private boolean casRunControl(int cmp, int val) { |
1869 |
< |
return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val); |
1869 |
> |
return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val); |
1870 |
|
} |
1871 |
|
private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) { |
1872 |
< |
return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val); |
1872 |
> |
return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val); |
1873 |
|
} |
1874 |
|
private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) { |
1875 |
< |
return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val); |
1875 |
> |
return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val); |
1876 |
> |
} |
1877 |
> |
|
1878 |
> |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1879 |
> |
try { |
1880 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1881 |
> |
} catch (NoSuchFieldException e) { |
1882 |
> |
// Convert Exception to corresponding Error |
1883 |
> |
NoSuchFieldError error = new NoSuchFieldError(field); |
1884 |
> |
error.initCause(e); |
1885 |
> |
throw error; |
1886 |
> |
} |
1887 |
> |
} |
1888 |
> |
|
1889 |
> |
/** |
1890 |
> |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1891 |
> |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1892 |
> |
* into a jdk. |
1893 |
> |
* |
1894 |
> |
* @return a sun.misc.Unsafe |
1895 |
> |
*/ |
1896 |
> |
private static sun.misc.Unsafe getUnsafe() { |
1897 |
> |
try { |
1898 |
> |
return sun.misc.Unsafe.getUnsafe(); |
1899 |
> |
} catch (SecurityException se) { |
1900 |
> |
try { |
1901 |
> |
return java.security.AccessController.doPrivileged |
1902 |
> |
(new java.security |
1903 |
> |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1904 |
> |
public sun.misc.Unsafe run() throws Exception { |
1905 |
> |
java.lang.reflect.Field f = sun.misc |
1906 |
> |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1907 |
> |
f.setAccessible(true); |
1908 |
> |
return (sun.misc.Unsafe) f.get(null); |
1909 |
> |
}}); |
1910 |
> |
} catch (java.security.PrivilegedActionException e) { |
1911 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
1912 |
> |
e.getCause()); |
1913 |
> |
} |
1914 |
> |
} |
1915 |
|
} |
1916 |
|
} |