ViewVC Help

View File | Revision Log | Show Annotations | Download File | Root Listing

root/jsr166/jsr166/src/jsr166y/ForkJoinPool.java

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.19 by jsr166, Fri Jul 24 18:57:56 2009 UTC vs.
Revision 1.41 by jsr166, Mon Aug 3 01:11:58 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.locks.*;
11	<	import java.util.concurrent.atomic.*;
12	<	import sun.misc.Unsafe;
13	<	import java.lang.reflect.*;
10	>
11	>	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;
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
#	Line 74 | Line 82 | public class ForkJoinPool extends Abstra
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		/**
#	Line 304 | Line 312 | public class ForkJoinPool extends Abstra
312		}
313
314		/**
315	<	* Returns 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) {
#	Line 335 | Line 343 | public class ForkJoinPool extends Abstra
343		// Constructors
344
345		/**
346	<	* Creates a ForkJoinPool with a pool size equal to the number of
347	<	* processors available on the system, using the default
348	<	* ForkJoinWorkerThreadFactory.
346	>	* Creates a {@code ForkJoinPool} with a pool size equal to the
347	>	* number of processors available on the system, using the
348	>	* {@linkplain #defaultForkJoinWorkerThreadFactory default thread factory}.
349		*
350		* @throws SecurityException if a security manager exists and
351		*         the caller is not permitted to modify threads
#	Line 350 | Line 358 | public class ForkJoinPool extends Abstra
358		}
359
360		/**
361	<	* Creates a ForkJoinPool with the indicated parallelism level
362	<	* threads and using the default ForkJoinWorkerThreadFactory.
361	>	* Creates a {@code ForkJoinPool} with the indicated parallelism level
362	>	* threads and using the
363	>	* {@linkplain #defaultForkJoinWorkerThreadFactory default thread factory}.
364		*
365		* @param parallelism the number of worker threads
366		* @throws IllegalArgumentException if parallelism less than or
#	Line 366 | Line 375 | public class ForkJoinPool extends Abstra
375		}
376
377		/**
378	<	* Creates a ForkJoinPool with parallelism equal to the number of
379	<	* processors available on the system and using the given
380	<	* ForkJoinWorkerThreadFactory.
378	>	* Creates a {@code ForkJoinPool} with parallelism equal to the
379	>	* number of processors available on the system and using the
380	>	* given thread factory.
381		*
382		* @param factory the factory for creating new threads
383		* @throws NullPointerException if factory is null
#	Line 382 | Line 391 | public class ForkJoinPool extends Abstra
391		}
392
393		/**
394	<	* Creates a ForkJoinPool with the given parallelism and factory.
394	>	* Creates a {@code ForkJoinPool} with the given parallelism and
395	>	* thread factory.
396		*
397		* @param parallelism the targeted number of worker threads
398		* @param factory the factory for creating new threads
#	Line 416 | Line 426 | public class ForkJoinPool extends Abstra
426		* Creates a new worker thread using factory.
427		*
428		* @param index the index to assign worker
429	<	* @return new worker, or null of factory failed
429	>	* @return new worker, or null if factory failed
430		*/
431		private ForkJoinWorkerThread createWorker(int index) {
432		Thread.UncaughtExceptionHandler h = ueh;
#	Line 541 | Line 551 | public class ForkJoinPool extends Abstra
551		* Common code for execute, invoke and submit
552		*/
553		private <T> void doSubmit(ForkJoinTask<T> task) {
554	+	if (task == null)
555	+	throw new NullPointerException();
556		if (isShutdown())
557		throw new RejectedExecutionException();
558		if (workers == null)
#	Line 569 | Line 581 | public class ForkJoinPool extends Abstra
581		* @throws NullPointerException if task is null
582		* @throws RejectedExecutionException if pool is shut down
583		*/
584	<	public <T> void execute(ForkJoinTask<T> task) {
584	>	public void execute(ForkJoinTask<?> task) {
585		doSubmit(task);
586		}
587
588		// AbstractExecutorService methods
589
590		public void execute(Runnable task) {
591	<	doSubmit(new AdaptedRunnable<Void>(task, null));
591	>	ForkJoinTask<?> job;
592	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
593	>	job = (ForkJoinTask<?>) task;
594	>	else
595	>	job = ForkJoinTask.adapt(task, null);
596	>	doSubmit(job);
597		}
598
599		public <T> ForkJoinTask<T> submit(Callable<T> task) {
600	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
600	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
601		doSubmit(job);
602		return job;
603		}
604
605		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
606	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
606	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
607		doSubmit(job);
608		return job;
609		}
610
611		public ForkJoinTask<?> submit(Runnable task) {
612	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
612	>	ForkJoinTask<?> job;
613	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
614	>	job = (ForkJoinTask<?>) task;
615	>	else
616	>	job = ForkJoinTask.adapt(task, null);
617		doSubmit(job);
618		return job;
619		}
620
621		/**
622	<	* Adaptor for Runnables. This implements RunnableFuture
623	<	* to be compliant with AbstractExecutorService constraints.
622	>	* Submits a ForkJoinTask for execution.
623	>	*
624	>	* @param task the task to submit
625	>	* @return the task
626	>	* @throws RejectedExecutionException if the task cannot be
627	>	*         scheduled for execution
628	>	* @throws NullPointerException if the task is null
629		*/
630	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
631	<	implements RunnableFuture<T> {
632	<	final Runnable runnable;
607	<	final T resultOnCompletion;
608	<	T result;
609	<	AdaptedRunnable(Runnable runnable, T result) {
610	<	if (runnable == null) throw new NullPointerException();
611	<	this.runnable = runnable;
612	<	this.resultOnCompletion = result;
613	<	}
614	<	public T getRawResult() { return result; }
615	<	public void setRawResult(T v) { result = v; }
616	<	public boolean exec() {
617	<	runnable.run();
618	<	result = resultOnCompletion;
619	<	return true;
620	<	}
621	<	public void run() { invoke(); }
622	<	private static final long serialVersionUID = 5232453952276885070L;
630	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
631	>	doSubmit(task);
632	>	return task;
633		}
634
625	–	/**
626	–	* Adaptor for Callables
627	–	*/
628	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
629	–	implements RunnableFuture<T> {
630	–	final Callable<T> callable;
631	–	T result;
632	–	AdaptedCallable(Callable<T> callable) {
633	–	if (callable == null) throw new NullPointerException();
634	–	this.callable = callable;
635	–	}
636	–	public T getRawResult() { return result; }
637	–	public void setRawResult(T v) { result = v; }
638	–	public boolean exec() {
639	–	try {
640	–	result = callable.call();
641	–	return true;
642	–	} catch (Error err) {
643	–	throw err;
644	–	} catch (RuntimeException rex) {
645	–	throw rex;
646	–	} catch (Exception ex) {
647	–	throw new RuntimeException(ex);
648	–	}
649	–	}
650	–	public void run() { invoke(); }
651	–	private static final long serialVersionUID = 2838392045355241008L;
652	–	}
635
636		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
637	<	ArrayList<ForkJoinTask<T>> ts =
637	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
638		new ArrayList<ForkJoinTask<T>>(tasks.size());
639	<	for (Callable<T> c : tasks)
640	<	ts.add(new AdaptedCallable<T>(c));
641	<	invoke(new InvokeAll<T>(ts));
642	<	return (List<Future<T>>) (List) ts;
639	>	for (Callable<T> task : tasks)
640	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
641	>	invoke(new InvokeAll<T>(forkJoinTasks));
642	>
643	>	@SuppressWarnings({"unchecked", "rawtypes"})
644	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
645	>	return futures;
646		}
647
648		static final class InvokeAll<T> extends RecursiveAction {
#	Line 685 | Line 670 | public class ForkJoinPool extends Abstra
670		* Returns the handler for internal worker threads that terminate
671		* due to unrecoverable errors encountered while executing tasks.
672		*
673	<	* @return the handler, or null if none
673	>	* @return the handler, or {@code null} if none
674		*/
675		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
676		Thread.UncaughtExceptionHandler h;
#	Line 706 | Line 691 | public class ForkJoinPool extends Abstra
691		* as handler.
692		*
693		* @param h the new handler
694	<	* @return the old handler, or null if none
694	>	* @return the old handler, or {@code null} if none
695		* @throws SecurityException if a security manager exists and
696		*         the caller is not permitted to modify threads
697		*         because it does not hold {@link
#	Line 780 | Line 765 | public class ForkJoinPool extends Abstra
765		/**
766		* Returns the number of worker threads that have started but not
767		* yet terminated.  This result returned by this method may differ
768	<	* from {@code getParallelism} when threads are created to
768	>	* from {@link #getParallelism} when threads are created to
769		* maintain parallelism when others are cooperatively blocked.
770		*
771		* @return the number of worker threads
#	Line 805 | Line 790 | public class ForkJoinPool extends Abstra
790		* Setting this value has no effect on current pool size. It
791		* controls construction of new threads.
792		*
793	<	* @throws IllegalArgumentException if negative or greater then
793	>	* @throws IllegalArgumentException if negative or greater than
794		* internal implementation limit
795		*/
796		public void setMaximumPoolSize(int newMax) {
#	Line 816 | Line 801 | public class ForkJoinPool extends Abstra
801
802
803		/**
804	<	* Returns true if this pool dynamically maintains its target
805	<	* parallelism level. If false, new threads are added only to
806	<	* avoid possible starvation.
822	<	* This setting is by default true.
804	>	* Returns {@code true} if this pool dynamically maintains its
805	>	* target parallelism level. If false, new threads are added only
806	>	* to avoid possible starvation.  This setting is by default true.
807		*
808	<	* @return true if maintains parallelism
808	>	* @return {@code true} if maintains parallelism
809		*/
810		public boolean getMaintainsParallelism() {
811		return maintainsParallelism;
#	Line 832 | Line 816 | public class ForkJoinPool extends Abstra
816		* parallelism level. If false, new threads are added only to
817		* avoid possible starvation.
818		*
819	<	* @param enable true to maintains parallelism
819	>	* @param enable {@code true} to maintain parallelism
820		*/
821		public void setMaintainsParallelism(boolean enable) {
822		maintainsParallelism = enable;
#	Line 843 | Line 827 | public class ForkJoinPool extends Abstra
827		* tasks that are never joined. This mode may be more appropriate
828		* than default locally stack-based mode in applications in which
829		* worker threads only process asynchronous tasks.  This method is
830	<	* designed to be invoked only when pool is quiescent, and
830	>	* designed to be invoked only when the pool is quiescent, and
831		* typically only before any tasks are submitted. The effects of
832		* invocations at other times may be unpredictable.
833		*
834	<	* @param async if true, use locally FIFO scheduling
834	>	* @param async if {@code true}, use locally FIFO scheduling
835		* @return the previous mode
836	+	* @see #getAsyncMode
837		*/
838		public boolean setAsyncMode(boolean async) {
839		boolean oldMode = locallyFifo;
#	Line 865 | Line 850 | public class ForkJoinPool extends Abstra
850		}
851
852		/**
853	<	* Returns true if this pool uses local first-in-first-out
853	>	* Returns {@code true} if this pool uses local first-in-first-out
854		* scheduling mode for forked tasks that are never joined.
855		*
856	<	* @return true if this pool uses async mode
856	>	* @return {@code true} if this pool uses async mode
857	>	* @see #setAsyncMode
858		*/
859		public boolean getAsyncMode() {
860		return locallyFifo;
#	Line 909 | Line 895 | public class ForkJoinPool extends Abstra
895		}
896
897		/**
898	<	* Returns true if all worker threads are currently idle. An idle
899	<	* worker is one that cannot obtain a task to execute because none
900	<	* are available to steal from other threads, and there are no
901	<	* pending submissions to the pool. This method is conservative;
902	<	* it might not return true immediately upon idleness of all
903	<	* threads, but will eventually become true if threads remain
904	<	* inactive.
898	>	* Returns {@code true} if all worker threads are currently idle.
899	>	* An idle worker is one that cannot obtain a task to execute
900	>	* because none are available to steal from other threads, and
901	>	* there are no pending submissions to the pool. This method is
902	>	* conservative; it might not return {@code true} immediately upon
903	>	* idleness of all threads, but will eventually become true if
904	>	* threads remain inactive.
905		*
906	<	* @return true if all threads are currently idle
906	>	* @return {@code true} if all threads are currently idle
907		*/
908		public boolean isQuiescent() {
909		return activeCountOf(runControl) == 0;
#	Line 972 | Line 958 | public class ForkJoinPool extends Abstra
958		}
959
960		/**
961	<	* Returns an estimate of the number tasks submitted to this pool
962	<	* that have not yet begun executing. This method takes time
961	>	* Returns an estimate of the number of tasks submitted to this
962	>	* pool that have not yet begun executing.  This method takes time
963		* proportional to the number of submissions.
964		*
965		* @return the number of queued submissions
#	Line 983 | Line 969 | public class ForkJoinPool extends Abstra
969		}
970
971		/**
972	<	* Returns true if there are any tasks submitted to this pool
973	<	* that have not yet begun executing.
972	>	* Returns {@code true} if there are any tasks submitted to this
973	>	* pool that have not yet begun executing.
974		*
975		* @return {@code true} if there are any queued submissions
976		*/
#	Line 997 | Line 983 | public class ForkJoinPool extends Abstra
983		* available.  This method may be useful in extensions to this
984		* class that re-assign work in systems with multiple pools.
985		*
986	<	* @return the next submission, or null if none
986	>	* @return the next submission, or {@code null} if none
987		*/
988		protected ForkJoinTask<?> pollSubmission() {
989		return submissionQueue.poll();
#	Line 1007 | Line 993 | public class ForkJoinPool extends Abstra
993		* Removes all available unexecuted submitted and forked tasks
994		* from scheduling queues and adds them to the given collection,
995		* without altering their execution status. These may include
996	<	* artificially generated or wrapped tasks. This method is designed
997	<	* to be invoked only when the pool is known to be
996	>	* artificially generated or wrapped tasks. This method is
997	>	* designed to be invoked only when the pool is known to be
998		* quiescent. Invocations at other times may not remove all
999		* tasks. A failure encountered while attempting to add elements
1000		* to collection {@code c} may result in elements being in
#	Line 1020 | Line 1006 | public class ForkJoinPool extends Abstra
1006		* @param c the collection to transfer elements into
1007		* @return the number of elements transferred
1008		*/
1009	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1009	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1010		int n = submissionQueue.drainTo(c);
1011		ForkJoinWorkerThread[] ws = workers;
1012		if (ws != null) {
#	Line 1086 | Line 1072 | public class ForkJoinPool extends Abstra
1072		public void shutdown() {
1073		checkPermission();
1074		transitionRunStateTo(SHUTDOWN);
1075	<	if (canTerminateOnShutdown(runControl))
1075	>	if (canTerminateOnShutdown(runControl)) {
1076	>	if (workers == null) { // shutting down before workers created
1077	>	final ReentrantLock lock = this.workerLock;
1078	>	lock.lock();
1079	>	try {
1080	>	if (workers == null) {
1081	>	terminate();
1082	>	transitionRunStateTo(TERMINATED);
1083	>	termination.signalAll();
1084	>	}
1085	>	} finally {
1086	>	lock.unlock();
1087	>	}
1088	>	}
1089		terminateOnShutdown();
1090	+	}
1091		}
1092
1093		/**
#	Line 1097 | Line 1097 | public class ForkJoinPool extends Abstra
1097		* method may or may not be rejected. Unlike some other executors,
1098		* this method cancels rather than collects non-executed tasks
1099		* upon termination, so always returns an empty list. However, you
1100	<	* can use method {@code drainTasksTo} before invoking this
1100	>	* can use method {@link #drainTasksTo} before invoking this
1101		* method to transfer unexecuted tasks to another collection.
1102		*
1103		* @return an empty list
#	Line 1457 | Line 1457 | public class ForkJoinPool extends Abstra
1457		}
1458
1459		/**
1460	<	* Returns true if worker waiting on sync can proceed:
1460	>	* Returns {@code true} if worker waiting on sync can proceed:
1461		*  - on signal (thread == null)
1462		*  - on event count advance (winning race to notify vs signaller)
1463		*  - on interrupt
#	Line 1465 | Line 1465 | public class ForkJoinPool extends Abstra
1465		* If node was not signalled and event count not advanced on exit,
1466		* then we also help advance event count.
1467		*
1468	<	* @return true if node can be released
1468	>	* @return {@code true} if node can be released
1469		*/
1470		final boolean syncIsReleasable(WaitQueueNode node) {
1471		long prev = node.count;
#	Line 1484 | Line 1484 | public class ForkJoinPool extends Abstra
1484		}
1485
1486		/**
1487	<	* Returns true if a new sync event occurred since last call to
1488	<	* sync or this method, if so, updating caller's count.
1487	>	* Returns {@code true} if a new sync event occurred since last
1488	>	* call to sync or this method, if so, updating caller's count.
1489		*/
1490		final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1491		long lc = w.lastEventCount;
#	Line 1569 | Line 1569 | public class ForkJoinPool extends Abstra
1569		}
1570
1571		/**
1572	<	* Returns true if a spare thread appears to be needed.  If
1573	<	* maintaining parallelism, returns true when the deficit in
1572	>	* Returns {@code true} if a spare thread appears to be needed.
1573	>	* If maintaining parallelism, returns true when the deficit in
1574		* running threads is more than the surplus of total threads, and
1575		* there is apparently some work to do.  This self-limiting rule
1576		* means that the more threads that have already been added, the
#	Line 1738 | Line 1738 | public class ForkJoinPool extends Abstra
1738
1739		/**
1740		* Interface for extending managed parallelism for tasks running
1741	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1742	<	* Method {@code isReleasable} must return true if blocking is not
1743	<	* necessary. Method {@code block} blocks the current thread if
1744	<	* necessary (perhaps internally invoking {@code isReleasable}
1745	<	* before actually blocking.).
1741	>	* in {@link ForkJoinPool}s.
1742	>	*
1743	>	* <p>A {@code ManagedBlocker} provides two methods.
1744	>	* Method {@code isReleasable} must return {@code true} if
1745	>	* blocking is not necessary. Method {@code block} blocks the
1746	>	* current thread if necessary (perhaps internally invoking
1747	>	* {@code isReleasable} before actually blocking).
1748		*
1749		* <p>For example, here is a ManagedBlocker based on a
1750		* ReentrantLock:
#	Line 1766 | Line 1768 | public class ForkJoinPool extends Abstra
1768		* Possibly blocks the current thread, for example waiting for
1769		* a lock or condition.
1770		*
1771	<	* @return true if no additional blocking is necessary (i.e.,
1772	<	* if isReleasable would return true)
1771	>	* @return {@code true} if no additional blocking is necessary
1772	>	* (i.e., if isReleasable would return true)
1773		* @throws InterruptedException if interrupted while waiting
1774		* (the method is not required to do so, but is allowed to)
1775		*/
1776		boolean block() throws InterruptedException;
1777
1778		/**
1779	<	* Returns true if blocking is unnecessary.
1779	>	* Returns {@code true} if blocking is unnecessary.
1780		*/
1781		boolean isReleasable();
1782		}
1783
1784		/**
1785		* Blocks in accord with the given blocker.  If the current thread
1786	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1787	<	* spare thread to be activated if necessary to ensure parallelism
1788	<	* while the current thread is blocked.  If
1789	<	* {@code maintainParallelism} is true and the pool supports
1790	<	* it ({@link #getMaintainsParallelism}), this method attempts to
1791	<	* maintain the pool's nominal parallelism. Otherwise it activates
1792	<	* a thread only if necessary to avoid complete starvation. This
1793	<	* option may be preferable when blockages use timeouts, or are
1794	<	* almost always brief.
1786	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1787	>	* arranges for a spare thread to be activated if necessary to
1788	>	* ensure parallelism while the current thread is blocked.
1789	>	*
1790	>	* <p>If {@code maintainParallelism} is {@code true} and the pool
1791	>	* supports it ({@link #getMaintainsParallelism}), this method
1792	>	* attempts to maintain the pool's nominal parallelism. Otherwise
1793	>	* it activates a thread only if necessary to avoid complete
1794	>	* starvation. This option may be preferable when blockages use
1795	>	* timeouts, or are almost always brief.
1796		*
1797	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1798	<	* equivalent to
1797	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1798	>	* behaviorally equivalent to
1799		*  <pre> {@code
1800		* while (!blocker.isReleasable())
1801		*   if (blocker.block())
1802		*     return;
1803		* }</pre>
1804	<	* If the caller is a ForkJoinTask, then the pool may first
1805	<	* be expanded to ensure parallelism, and later adjusted.
1804	>	*
1805	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1806	>	* first be expanded to ensure parallelism, and later adjusted.
1807		*
1808		* @param blocker the blocker
1809	<	* @param maintainParallelism if true and supported by this pool,
1810	<	* attempt to maintain the pool's nominal parallelism; otherwise
1811	<	* activate a thread only if necessary to avoid complete
1812	<	* starvation.
1809	>	* @param maintainParallelism if {@code true} and supported by
1810	>	* this pool, attempt to maintain the pool's nominal parallelism;
1811	>	* otherwise activate a thread only if necessary to avoid
1812	>	* complete starvation.
1813		* @throws InterruptedException if blocker.block did so
1814		*/
1815		public static void managedBlock(ManagedBlocker blocker,
#	Line 1831 | Line 1835 | public class ForkJoinPool extends Abstra
1835		do {} while (!blocker.isReleasable() && !blocker.block());
1836		}
1837
1838	<	// AbstractExecutorService overrides
1838	>	// AbstractExecutorService overrides.  These rely on undocumented
1839	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1840	>	// implement RunnableFuture.
1841
1842		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1843	<	return new AdaptedRunnable<T>(runnable, value);
1843	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1844		}
1845
1846		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1847	<	return new AdaptedCallable<T>(callable);
1847	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1848		}
1849
1850	+	// Unsafe mechanics
1851
1852	<	// Temporary Unsafe mechanics for preliminary release
1853	<	private static Unsafe getUnsafe() throws Throwable {
1854	<	try {
1855	<	return Unsafe.getUnsafe();
1856	<	} catch (SecurityException se) {
1857	<	try {
1858	<	return java.security.AccessController.doPrivileged
1859	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1860	<	public Unsafe run() throws Exception {
1861	<	return getUnsafePrivileged();
1862	<	}});
1856	<	} catch (java.security.PrivilegedActionException e) {
1857	<	throw e.getCause();
1858	<	}
1859	<	}
1860	<	}
1861	<
1862	<	private static Unsafe getUnsafePrivileged()
1863	<	throws NoSuchFieldException, IllegalAccessException {
1864	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1865	<	f.setAccessible(true);
1866	<	return (Unsafe) f.get(null);
1867	<	}
1868	<
1869	<	private static long fieldOffset(String fieldName)
1870	<	throws NoSuchFieldException {
1871	<	return UNSAFE.objectFieldOffset
1872	<	(ForkJoinPool.class.getDeclaredField(fieldName));
1873	<	}
1874	<
1875	<	static final Unsafe UNSAFE;
1876	<	static final long eventCountOffset;
1877	<	static final long workerCountsOffset;
1878	<	static final long runControlOffset;
1879	<	static final long syncStackOffset;
1880	<	static final long spareStackOffset;
1881	<
1882	<	static {
1883	<	try {
1884	<	UNSAFE = getUnsafe();
1885	<	eventCountOffset = fieldOffset("eventCount");
1886	<	workerCountsOffset = fieldOffset("workerCounts");
1887	<	runControlOffset = fieldOffset("runControl");
1888	<	syncStackOffset = fieldOffset("syncStack");
1889	<	spareStackOffset = fieldOffset("spareStack");
1890	<	} catch (Throwable e) {
1891	<	throw new RuntimeException("Could not initialize intrinsics", e);
1892	<	}
1893	<	}
1852	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1853	>	private static final long eventCountOffset =
1854	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1855	>	private static final long workerCountsOffset =
1856	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1857	>	private static final long runControlOffset =
1858	>	objectFieldOffset("runControl", ForkJoinPool.class);
1859	>	private static final long syncStackOffset =
1860	>	objectFieldOffset("syncStack",ForkJoinPool.class);
1861	>	private static final long spareStackOffset =
1862	>	objectFieldOffset("spareStack", ForkJoinPool.class);
1863
1864		private boolean casEventCount(long cmp, long val) {
1865		return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
#	Line 1907 | Line 1876 | public class ForkJoinPool extends Abstra
1876		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1877		return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1878		}
1879	+
1880	+	private static long objectFieldOffset(String field, Class<?> klazz) {
1881	+	try {
1882	+	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1883	+	} catch (NoSuchFieldException e) {
1884	+	// Convert Exception to corresponding Error
1885	+	NoSuchFieldError error = new NoSuchFieldError(field);
1886	+	error.initCause(e);
1887	+	throw error;
1888	+	}
1889	+	}
1890	+
1891	+	/**
1892	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1893	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1894	+	* into a jdk.
1895	+	*
1896	+	* @return a sun.misc.Unsafe
1897	+	*/
1898	+	private static sun.misc.Unsafe getUnsafe() {
1899	+	try {
1900	+	return sun.misc.Unsafe.getUnsafe();
1901	+	} catch (SecurityException se) {
1902	+	try {
1903	+	return java.security.AccessController.doPrivileged
1904	+	(new java.security
1905	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1906	+	public sun.misc.Unsafe run() throws Exception {
1907	+	java.lang.reflect.Field f = sun.misc
1908	+	.Unsafe.class.getDeclaredField("theUnsafe");
1909	+	f.setAccessible(true);
1910	+	return (sun.misc.Unsafe) f.get(null);
1911	+	}});
1912	+	} catch (java.security.PrivilegedActionException e) {
1913	+	throw new RuntimeException("Could not initialize intrinsics",
1914	+	e.getCause());
1915	+	}
1916	+	}
1917	+	}
1918		}

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines