| 20 |
|
import java.util.concurrent.atomic.AtomicLong; |
| 21 |
|
|
| 22 |
|
/** |
| 23 |
< |
* An {@link ExecutorService} for running {@link ForkJoinTask}s. A |
| 24 |
< |
* ForkJoinPool provides the entry point for submissions from |
| 25 |
< |
* non-ForkJoinTasks, as well as management and monitoring operations. |
| 26 |
< |
* Normally a single ForkJoinPool is used for a large number of |
| 27 |
< |
* submitted tasks. Otherwise, use would not usually outweigh the |
| 28 |
< |
* 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 |
|
* |
| 31 |
< |
* <p>ForkJoinPools differ from other kinds of Executors mainly in |
| 32 |
< |
* that they provide <em>work-stealing</em>: all threads in the pool |
| 33 |
< |
* attempt to find and execute subtasks created by other active tasks |
| 34 |
< |
* (eventually blocking if none exist). This makes them efficient when |
| 35 |
< |
* most tasks spawn other subtasks (as do most ForkJoinTasks), as well |
| 36 |
< |
* 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 |
< |
* ExecutorService implementations are typically more appropriate |
| 41 |
< |
* 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 |
| 34 |
> |
* other active tasks (eventually blocking if none exist). This makes |
| 35 |
> |
* 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 |
| 38 |
> |
* with {@code ForkJoinTask}s. When setting {@linkplain #setAsyncMode |
| 39 |
> |
* async mode}, a {@code ForkJoinPool} may also be appropriate for use |
| 40 |
> |
* with fine-grained tasks that are never joined. Otherwise, other |
| 41 |
> |
* {@code ExecutorService} implementations are typically more |
| 42 |
> |
* appropriate choices. |
| 43 |
|
* |
| 44 |
< |
* <p>A ForkJoinPool may be constructed with a given parallelism level |
| 45 |
< |
* (target pool size), which it attempts to maintain by dynamically |
| 46 |
< |
* adding, suspending, or resuming threads, even if some tasks are |
| 47 |
< |
* waiting to join others. However, no such adjustments are performed |
| 48 |
< |
* in the face of blocked IO or other unmanaged synchronization. The |
| 49 |
< |
* nested {@code ManagedBlocker} interface enables extension of |
| 50 |
< |
* the kinds of synchronization accommodated. The target parallelism |
| 51 |
< |
* level may also be changed dynamically ({@code setParallelism}) |
| 52 |
< |
* and thread construction can be limited using methods |
| 53 |
< |
* {@code setMaximumPoolSize} and/or |
| 54 |
< |
* {@code setMaintainsParallelism}. |
| 44 |
> |
* <p>A {@code ForkJoinPool} may be constructed with a given |
| 45 |
> |
* parallelism level (target pool size), which it attempts to maintain |
| 46 |
> |
* by dynamically adding, suspending, or resuming threads, even if |
| 47 |
> |
* some tasks are waiting to join others. However, no such adjustments |
| 48 |
> |
* are performed in the face of blocked IO or other unmanaged |
| 49 |
> |
* synchronization. The nested {@link ManagedBlocker} interface |
| 50 |
> |
* enables extension of the kinds of synchronization accommodated. |
| 51 |
> |
* The target parallelism level may also be changed dynamically |
| 52 |
> |
* ({@link #setParallelism}) and thread construction can be limited |
| 53 |
> |
* using methods {@link #setMaximumPoolSize} and/or {@link |
| 54 |
> |
* #setMaintainsParallelism}. |
| 55 |
|
* |
| 56 |
|
* <p>In addition to execution and lifecycle control methods, this |
| 57 |
|
* class provides status check methods (for example |
| 58 |
< |
* {@code getStealCount}) that are intended to aid in developing, |
| 58 |
> |
* {@link #getStealCount}) that are intended to aid in developing, |
| 59 |
|
* tuning, and monitoring fork/join applications. Also, method |
| 60 |
< |
* {@code toString} returns indications of pool state in a |
| 60 |
> |
* {@link #toString} returns indications of pool state in a |
| 61 |
|
* convenient form for informal monitoring. |
| 62 |
|
* |
| 63 |
|
* <p><b>Implementation notes</b>: This implementation restricts the |
| 64 |
|
* maximum number of running threads to 32767. Attempts to create |
| 65 |
|
* pools with greater than the maximum result in |
| 66 |
< |
* IllegalArgumentExceptions. |
| 66 |
> |
* {@code IllegalArgumentException}. |
| 67 |
|
* |
| 68 |
|
* @since 1.7 |
| 69 |
|
* @author Doug Lea |
| 82 |
|
private static final int MAX_THREADS = 0x7FFF; |
| 83 |
|
|
| 84 |
|
/** |
| 85 |
< |
* Factory for creating new ForkJoinWorkerThreads. A |
| 86 |
< |
* ForkJoinWorkerThreadFactory must be defined and used for |
| 87 |
< |
* ForkJoinWorkerThread subclasses that extend base functionality |
| 88 |
< |
* or initialize threads with different contexts. |
| 85 |
> |
* Factory for creating new {@link ForkJoinWorkerThread}s. |
| 86 |
> |
* A {@code ForkJoinWorkerThreadFactory} must be defined and used |
| 87 |
> |
* for {@code ForkJoinWorkerThread} subclasses that extend base |
| 88 |
> |
* functionality or initialize threads with different contexts. |
| 89 |
|
*/ |
| 90 |
|
public static interface ForkJoinWorkerThreadFactory { |
| 91 |
|
/** |
| 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 |
|
|
| 590 |
|
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
| 591 |
|
job = (ForkJoinTask<?>) task; |
| 592 |
|
else |
| 593 |
< |
job = new AdaptedRunnable<Void>(task, null); |
| 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 |
|
} |
| 611 |
|
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
| 612 |
|
job = (ForkJoinTask<?>) task; |
| 613 |
|
else |
| 614 |
< |
job = new AdaptedRunnable<Void>(task, null); |
| 614 |
> |
job = ForkJoinTask.adapt(task, null); |
| 615 |
|
doSubmit(job); |
| 616 |
|
return job; |
| 617 |
|
} |
| 630 |
|
return task; |
| 631 |
|
} |
| 632 |
|
|
| 632 |
– |
/** |
| 633 |
– |
* Adaptor for Runnables. This implements RunnableFuture |
| 634 |
– |
* to be compliant with AbstractExecutorService constraints. |
| 635 |
– |
*/ |
| 636 |
– |
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
| 637 |
– |
implements RunnableFuture<T> { |
| 638 |
– |
final Runnable runnable; |
| 639 |
– |
final T resultOnCompletion; |
| 640 |
– |
T result; |
| 641 |
– |
AdaptedRunnable(Runnable runnable, T result) { |
| 642 |
– |
if (runnable == null) throw new NullPointerException(); |
| 643 |
– |
this.runnable = runnable; |
| 644 |
– |
this.resultOnCompletion = result; |
| 645 |
– |
} |
| 646 |
– |
public T getRawResult() { return result; } |
| 647 |
– |
public void setRawResult(T v) { result = v; } |
| 648 |
– |
public boolean exec() { |
| 649 |
– |
runnable.run(); |
| 650 |
– |
result = resultOnCompletion; |
| 651 |
– |
return true; |
| 652 |
– |
} |
| 653 |
– |
public void run() { invoke(); } |
| 654 |
– |
private static final long serialVersionUID = 5232453952276885070L; |
| 655 |
– |
} |
| 656 |
– |
|
| 657 |
– |
/** |
| 658 |
– |
* Adaptor for Callables |
| 659 |
– |
*/ |
| 660 |
– |
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
| 661 |
– |
implements RunnableFuture<T> { |
| 662 |
– |
final Callable<T> callable; |
| 663 |
– |
T result; |
| 664 |
– |
AdaptedCallable(Callable<T> callable) { |
| 665 |
– |
if (callable == null) throw new NullPointerException(); |
| 666 |
– |
this.callable = callable; |
| 667 |
– |
} |
| 668 |
– |
public T getRawResult() { return result; } |
| 669 |
– |
public void setRawResult(T v) { result = v; } |
| 670 |
– |
public boolean exec() { |
| 671 |
– |
try { |
| 672 |
– |
result = callable.call(); |
| 673 |
– |
return true; |
| 674 |
– |
} catch (Error err) { |
| 675 |
– |
throw err; |
| 676 |
– |
} catch (RuntimeException rex) { |
| 677 |
– |
throw rex; |
| 678 |
– |
} catch (Exception ex) { |
| 679 |
– |
throw new RuntimeException(ex); |
| 680 |
– |
} |
| 681 |
– |
} |
| 682 |
– |
public void run() { invoke(); } |
| 683 |
– |
private static final long serialVersionUID = 2838392045355241008L; |
| 684 |
– |
} |
| 633 |
|
|
| 634 |
|
public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) { |
| 635 |
|
ArrayList<ForkJoinTask<T>> forkJoinTasks = |
| 636 |
|
new ArrayList<ForkJoinTask<T>>(tasks.size()); |
| 637 |
|
for (Callable<T> task : tasks) |
| 638 |
< |
forkJoinTasks.add(new AdaptedCallable<T>(task)); |
| 638 |
> |
forkJoinTasks.add(ForkJoinTask.adapt(task)); |
| 639 |
|
invoke(new InvokeAll<T>(forkJoinTasks)); |
| 640 |
|
|
| 641 |
|
@SuppressWarnings({"unchecked", "rawtypes"}) |
| 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} 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 |
| 788 |
|
* Setting this value has no effect on current pool size. It |
| 789 |
|
* controls construction of new threads. |
| 790 |
|
* |
| 791 |
< |
* @throws IllegalArgumentException if negative or greater then |
| 791 |
> |
* @throws IllegalArgumentException if negative or greater than |
| 792 |
|
* internal implementation limit |
| 793 |
|
*/ |
| 794 |
|
public void setMaximumPoolSize(int newMax) { |
| 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 other times may be unpredictable. |
| 831 |
|
* |
| 832 |
< |
* @param async if true, use locally FIFO scheduling |
| 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; |
| 852 |
|
* scheduling mode for forked tasks that are never joined. |
| 853 |
|
* |
| 854 |
|
* @return {@code true} if this pool uses async mode |
| 855 |
+ |
* @see #setAsyncMode |
| 856 |
|
*/ |
| 857 |
|
public boolean getAsyncMode() { |
| 858 |
|
return locallyFifo; |
| 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 |
|
* |
| 963 |
|
* @return the number of queued submissions |
| 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) { |
| 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} 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 |
| 1736 |
|
|
| 1737 |
|
/** |
| 1738 |
|
* Interface for extending managed parallelism for tasks running |
| 1739 |
< |
* in ForkJoinPools. A ManagedBlocker provides two methods. |
| 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.). |
| 1745 |
> |
* {@code isReleasable} before actually blocking). |
| 1746 |
|
* |
| 1747 |
|
* <p>For example, here is a ManagedBlocker based on a |
| 1748 |
|
* ReentrantLock: |
| 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} is {@code true} and the pool supports |
| 1788 |
< |
* it ({@link #getMaintainsParallelism}), this method attempts to |
| 1789 |
< |
* maintain the pool's nominal parallelism. Otherwise it 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. |
| 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 ForkJoinTask, this method is behaviorally |
| 1796 |
< |
* equivalent to |
| 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 |
< |
* If the caller is a ForkJoinTask, then the pool may first |
| 1803 |
< |
* be expanded to ensure parallelism, and later adjusted. |
| 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 {@code true} and supported by |
| 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<T>(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<T>(callable); |
| 1845 |
> |
return (RunnableFuture<T>) ForkJoinTask.adapt(callable); |
| 1846 |
|
} |
| 1847 |
|
|
| 1848 |
|
// Unsafe mechanics |
