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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.12 by jsr166, Tue Jul 21 18:11:44 2009 UTC vs.
Revision 1.31 by dl, Wed Jul 29 22:48:54 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
23	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
24	>	* A 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
#	Line 27 | Line 34 | import java.lang.reflect.*;
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.
37	>	* activities along with ForkJoinTasks. When setting {@linkplain
38	>	* #setAsyncMode async mode}, a ForkJoinPool may also be appropriate
39	>	* for use with fine-grained tasks that are never joined. Otherwise,
40	>	* other ExecutorService implementations are typically more
41	>	* appropriate choices.
42		*
43		* <p>A ForkJoinPool may be constructed with a given parallelism level
44		* (target pool size), which it attempts to maintain by dynamically
45		* adding, suspending, or resuming threads, even if some tasks are
46		* waiting to join others. However, no such adjustments are performed
47		* in the face of blocked IO or other unmanaged synchronization. The
48	<	* nested {@code ManagedBlocker} interface enables extension of
48	>	* nested {@link ManagedBlocker} interface enables extension of
49		* the kinds of synchronization accommodated.  The target parallelism
50	<	* level may also be changed dynamically ({@code setParallelism})
50	>	* level may also be changed dynamically ({@link #setParallelism})
51		* and thread construction can be limited using methods
52	<	* {@code setMaximumPoolSize} and/or
53	<	* {@code setMaintainsParallelism}.
52	>	* {@link #setMaximumPoolSize} and/or
53	>	* {@link #setMaintainsParallelism}.
54		*
55		* <p>In addition to execution and lifecycle control methods, this
56		* class provides status check methods (for example
57	<	* {@code getStealCount}) that are intended to aid in developing,
57	>	* {@link #getStealCount}) that are intended to aid in developing,
58		* tuning, and monitoring fork/join applications. Also, method
59	<	* {@code toString} returns indications of pool state in a
59	>	* {@link #toString} returns indications of pool state in a
60		* convenient form for informal monitoring.
61		*
62		* <p><b>Implementation notes</b>: This implementation restricts the
63		* maximum number of running threads to 32767. Attempts to create
64		* pools with greater than the maximum result in
65		* IllegalArgumentExceptions.
66	+	*
67	+	* @since 1.7
68	+	* @author Doug Lea
69		*/
70		public class ForkJoinPool extends AbstractExecutorService {
71
#	Line 87 | Line 97 | public class ForkJoinPool extends Abstra
97		}
98
99		/**
100	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
100	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
101		* new ForkJoinWorkerThread.
102		*/
103		static class  DefaultForkJoinWorkerThreadFactory
#	Line 181 | Line 191 | public class ForkJoinPool extends Abstra
191		private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
192
193		/**
194	<	* Head of Treiber stack for barrier sync. See below for explanation
194	>	* Head of Treiber stack for barrier sync. See below for explanation.
195		*/
196		private volatile WaitQueueNode syncStack;
197
#	Line 216 | Line 226 | public class ForkJoinPool extends Abstra
226		* threads, packed into one int to ensure consistent snapshot when
227		* making decisions about creating and suspending spare
228		* threads. Updated only by CAS.  Note: CASes in
229	<	* updateRunningCount and preJoin running active count is in low
230	<	* word, so need to be modified if this changes
229	>	* updateRunningCount and preJoin assume that running active count
230	>	* is in low word, so need to be modified if this changes.
231		*/
232		private volatile int workerCounts;
233
#	Line 229 | Line 239 | public class ForkJoinPool extends Abstra
239		* Adds delta (which may be negative) to running count.  This must
240		* be called before (with negative arg) and after (with positive)
241		* any managed synchronization (i.e., mainly, joins).
242	+	*
243		* @param delta the number to add
244		*/
245		final void updateRunningCount(int delta) {
246		int s;
247	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
247	>	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
248		}
249
250		/**
251		* Adds delta (which may be negative) to both total and running
252		* count.  This must be called upon creation and termination of
253		* worker threads.
254	+	*
255		* @param delta the number to add
256		*/
257		private void updateWorkerCount(int delta) {
258		int d = delta + (delta << 16); // add to both lo and hi parts
259		int s;
260	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
260	>	do {} while (!casWorkerCounts(s = workerCounts, s + d));
261		}
262
263		/**
#	Line 271 | Line 283 | public class ForkJoinPool extends Abstra
283		private static int runControlFor(int r, int a)   { return (r << 16) + a; }
284
285		/**
286	<	* Try incrementing active count; fail on contention. Called by
287	<	* workers before/during executing tasks.
286	>	* Tries incrementing active count; fails on contention.
287	>	* Called by workers before/during executing tasks.
288	>	*
289		* @return true on success
290		*/
291		final boolean tryIncrementActiveCount() {
#	Line 284 | Line 297 | public class ForkJoinPool extends Abstra
297		* Tries decrementing active count; fails on contention.
298		* Possibly triggers termination on success.
299		* Called by workers when they can't find tasks.
300	+	*
301		* @return true on success
302		*/
303		final boolean tryDecrementActiveCount() {
#	Line 297 | Line 311 | public class ForkJoinPool extends Abstra
311		}
312
313		/**
314	<	* Returns true if argument represents zero active count and
315	<	* nonzero runstate, which is the triggering condition for
314	>	* Returns {@code true} if argument represents zero active count
315	>	* and nonzero runstate, which is the triggering condition for
316		* terminating on shutdown.
317		*/
318		private static boolean canTerminateOnShutdown(int c) {
319	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
319	>	// i.e. least bit is nonzero runState bit
320	>	return ((c & -c) >>> 16) != 0;
321		}
322
323		/**
#	Line 328 | Line 343 | public class ForkJoinPool extends Abstra
343
344		/**
345		* Creates a ForkJoinPool with a pool size equal to the number of
346	<	* processors available on the system and using the default
347	<	* ForkJoinWorkerThreadFactory,
346	>	* processors available on the system, using the default
347	>	* ForkJoinWorkerThreadFactory.
348	>	*
349		* @throws SecurityException if a security manager exists and
350		*         the caller is not permitted to modify threads
351		*         because it does not hold {@link
352	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
352	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
353		*/
354		public ForkJoinPool() {
355		this(Runtime.getRuntime().availableProcessors(),
#	Line 342 | Line 358 | public class ForkJoinPool extends Abstra
358
359		/**
360		* Creates a ForkJoinPool with the indicated parallelism level
361	<	* threads, and using the default ForkJoinWorkerThreadFactory,
361	>	* threads and using the default ForkJoinWorkerThreadFactory.
362	>	*
363		* @param parallelism the number of worker threads
364		* @throws IllegalArgumentException if parallelism less than or
365		* equal to zero
366		* @throws SecurityException if a security manager exists and
367		*         the caller is not permitted to modify threads
368		*         because it does not hold {@link
369	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
369	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
370		*/
371		public ForkJoinPool(int parallelism) {
372		this(parallelism, defaultForkJoinWorkerThreadFactory);
#	Line 358 | Line 375 | public class ForkJoinPool extends Abstra
375		/**
376		* Creates a ForkJoinPool with parallelism equal to the number of
377		* processors available on the system and using the given
378	<	* ForkJoinWorkerThreadFactory,
378	>	* ForkJoinWorkerThreadFactory.
379	>	*
380		* @param factory the factory for creating new threads
381		* @throws NullPointerException if factory is null
382		* @throws SecurityException if a security manager exists and
383		*         the caller is not permitted to modify threads
384		*         because it does not hold {@link
385	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
385	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
386		*/
387		public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
388		this(Runtime.getRuntime().availableProcessors(), factory);
#	Line 381 | Line 399 | public class ForkJoinPool extends Abstra
399		* @throws SecurityException if a security manager exists and
400		*         the caller is not permitted to modify threads
401		*         because it does not hold {@link
402	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
402	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
403		*/
404		public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
405		if (parallelism <= 0 || parallelism > MAX_THREADS)
#	Line 402 | Line 420 | public class ForkJoinPool extends Abstra
420		}
421
422		/**
423	<	* Create new worker using factory.
423	>	* Creates a new worker thread using factory.
424	>	*
425		* @param index the index to assign worker
426		* @return new worker, or null of factory failed
427		*/
#	Line 424 | Line 443 | public class ForkJoinPool extends Abstra
443		* Returns a good size for worker array given pool size.
444		* Currently requires size to be a power of two.
445		*/
446	<	private static int arraySizeFor(int ps) {
447	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
446	>	private static int arraySizeFor(int poolSize) {
447	>	return (poolSize <= 1) ? 1 :
448	>	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
449		}
450
451		/**
452		* Creates or resizes array if necessary to hold newLength.
453	<	* Call only under exclusion or lock.
453	>	* Call only under exclusion.
454	>	*
455		* @return the array
456		*/
457		private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
#	Line 444 | Line 465 | public class ForkJoinPool extends Abstra
465		}
466
467		/**
468	<	* Try to shrink workers into smaller array after one or more terminate
468	>	* Tries to shrink workers into smaller array after one or more terminate.
469		*/
470		private void tryShrinkWorkerArray() {
471		ForkJoinWorkerThread[] ws = workers;
#	Line 460 | Line 481 | public class ForkJoinPool extends Abstra
481		}
482
483		/**
484	<	* Initialize workers if necessary
484	>	* Initializes workers if necessary.
485		*/
486		final void ensureWorkerInitialization() {
487		ForkJoinWorkerThread[] ws = workers;
#	Line 527 | Line 548 | public class ForkJoinPool extends Abstra
548		* Common code for execute, invoke and submit
549		*/
550		private <T> void doSubmit(ForkJoinTask<T> task) {
551	+	if (task == null)
552	+	throw new NullPointerException();
553		if (isShutdown())
554		throw new RejectedExecutionException();
555		if (workers == null)
#	Line 536 | Line 559 | public class ForkJoinPool extends Abstra
559		}
560
561		/**
562	<	* Performs the given task; returning its result upon completion
562	>	* Performs the given task, returning its result upon completion.
563	>	*
564		* @param task the task
565		* @return the task's result
566		* @throws NullPointerException if task is null
#	Line 549 | Line 573 | public class ForkJoinPool extends Abstra
573
574		/**
575		* Arranges for (asynchronous) execution of the given task.
576	+	*
577		* @param task the task
578		* @throws NullPointerException if task is null
579		* @throws RejectedExecutionException if pool is shut down
#	Line 560 | Line 585 | public class ForkJoinPool extends Abstra
585		// AbstractExecutorService methods
586
587		public void execute(Runnable task) {
588	<	doSubmit(new AdaptedRunnable<Void>(task, null));
588	>	ForkJoinTask<?> job;
589	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
590	>	job = (ForkJoinTask<?>) task;
591	>	else
592	>	job = new AdaptedRunnable<Void>(task, null);
593	>	doSubmit(job);
594		}
595
596		public <T> ForkJoinTask<T> submit(Callable<T> task) {
#	Line 576 | Line 606 | public class ForkJoinPool extends Abstra
606		}
607
608		public ForkJoinTask<?> submit(Runnable task) {
609	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
609	>	ForkJoinTask<?> job;
610	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
611	>	job = (ForkJoinTask<?>) task;
612	>	else
613	>	job = new AdaptedRunnable<Void>(task, null);
614		doSubmit(job);
615		return job;
616		}
617
618		/**
619	+	* Submits a ForkJoinTask for execution.
620	+	*
621	+	* @param task the task to submit
622	+	* @return the task
623	+	* @throws RejectedExecutionException if the task cannot be
624	+	*         scheduled for execution
625	+	* @throws NullPointerException if the task is null
626	+	*/
627	+	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
628	+	doSubmit(task);
629	+	return task;
630	+	}
631	+
632	+	/**
633		* Adaptor for Runnables. This implements RunnableFuture
634	<	* to be compliant with AbstractExecutorService constraints
634	>	* to be compliant with AbstractExecutorService constraints.
635		*/
636		static final class AdaptedRunnable<T> extends ForkJoinTask<T>
637		implements RunnableFuture<T> {
#	Line 603 | Line 651 | public class ForkJoinPool extends Abstra
651		return true;
652		}
653		public void run() { invoke(); }
654	+	private static final long serialVersionUID = 5232453952276885070L;
655		}
656
657		/**
#	Line 631 | Line 680 | public class ForkJoinPool extends Abstra
680		}
681		}
682		public void run() { invoke(); }
683	+	private static final long serialVersionUID = 2838392045355241008L;
684		}
685
686		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
687	<	ArrayList<ForkJoinTask<T>> ts =
687	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
688		new ArrayList<ForkJoinTask<T>>(tasks.size());
689	<	for (Callable<T> c : tasks)
690	<	ts.add(new AdaptedCallable<T>(c));
691	<	invoke(new InvokeAll<T>(ts));
692	<	return (List<Future<T>>)(List)ts;
689	>	for (Callable<T> task : tasks)
690	>	forkJoinTasks.add(new AdaptedCallable<T>(task));
691	>	invoke(new InvokeAll<T>(forkJoinTasks));
692	>
693	>	@SuppressWarnings({"unchecked", "rawtypes"})
694	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
695	>	return futures;
696		}
697
698		static final class InvokeAll<T> extends RecursiveAction {
699		final ArrayList<ForkJoinTask<T>> tasks;
700		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
701		public void compute() {
702	<	try { invokeAll(tasks); } catch(Exception ignore) {}
702	>	try { invokeAll(tasks); }
703	>	catch (Exception ignore) {}
704		}
705	+	private static final long serialVersionUID = -7914297376763021607L;
706		}
707
708		// Configuration and status settings and queries
709
710		/**
711	<	* Returns the factory used for constructing new workers
711	>	* Returns the factory used for constructing new workers.
712		*
713		* @return the factory used for constructing new workers
714		*/
#	Line 664 | Line 719 | public class ForkJoinPool extends Abstra
719		/**
720		* Returns the handler for internal worker threads that terminate
721		* due to unrecoverable errors encountered while executing tasks.
722	<	* @return the handler, or null if none
722	>	*
723	>	* @return the handler, or {@code null} if none
724		*/
725		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
726		Thread.UncaughtExceptionHandler h;
#	Line 685 | Line 741 | public class ForkJoinPool extends Abstra
741		* as handler.
742		*
743		* @param h the new handler
744	<	* @return the old handler, or null if none
744	>	* @return the old handler, or {@code null} if none
745		* @throws SecurityException if a security manager exists and
746		*         the caller is not permitted to modify threads
747		*         because it does not hold {@link
748	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
748	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
749		*/
750		public Thread.UncaughtExceptionHandler
751		setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
#	Line 717 | Line 773 | public class ForkJoinPool extends Abstra
773
774		/**
775		* Sets the target parallelism level of this pool.
776	+	*
777		* @param parallelism the target parallelism
778		* @throws IllegalArgumentException if parallelism less than or
779		* equal to zero or greater than maximum size bounds
780		* @throws SecurityException if a security manager exists and
781		*         the caller is not permitted to modify threads
782		*         because it does not hold {@link
783	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
783	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
784		*/
785		public void setParallelism(int parallelism) {
786		checkPermission();
#	Line 758 | Line 815 | public class ForkJoinPool extends Abstra
815		/**
816		* Returns the number of worker threads that have started but not
817		* yet terminated.  This result returned by this method may differ
818	<	* from {@code getParallelism} when threads are created to
818	>	* from {@link #getParallelism} when threads are created to
819		* maintain parallelism when others are cooperatively blocked.
820		*
821		* @return the number of worker threads
#	Line 770 | Line 827 | public class ForkJoinPool extends Abstra
827		/**
828		* Returns the maximum number of threads allowed to exist in the
829		* pool, even if there are insufficient unblocked running threads.
830	+	*
831		* @return the maximum
832		*/
833		public int getMaximumPoolSize() {
#	Line 781 | Line 839 | public class ForkJoinPool extends Abstra
839		* pool, even if there are insufficient unblocked running threads.
840		* Setting this value has no effect on current pool size. It
841		* controls construction of new threads.
842	+	*
843		* @throws IllegalArgumentException if negative or greater then
844		* internal implementation limit
845		*/
#	Line 792 | Line 851 | public class ForkJoinPool extends Abstra
851
852
853		/**
854	<	* Returns true if this pool dynamically maintains its target
855	<	* parallelism level. If false, new threads are added only to
856	<	* avoid possible starvation.
857	<	* This setting is by default true;
858	<	* @return true if maintains parallelism
854	>	* Returns {@code true} if this pool dynamically maintains its
855	>	* target parallelism level. If false, new threads are added only
856	>	* to avoid possible starvation.  This setting is by default true.
857	>	*
858	>	* @return {@code true} if maintains parallelism
859		*/
860		public boolean getMaintainsParallelism() {
861		return maintainsParallelism;
#	Line 806 | Line 865 | public class ForkJoinPool extends Abstra
865		* Sets whether this pool dynamically maintains its target
866		* parallelism level. If false, new threads are added only to
867		* avoid possible starvation.
868	<	* @param enable true to maintains parallelism
868	>	*
869	>	* @param enable {@code true} to maintain parallelism
870		*/
871		public void setMaintainsParallelism(boolean enable) {
872		maintainsParallelism = enable;
#	Line 817 | Line 877 | public class ForkJoinPool extends Abstra
877		* tasks that are never joined. This mode may be more appropriate
878		* than default locally stack-based mode in applications in which
879		* worker threads only process asynchronous tasks.  This method is
880	<	* designed to be invoked only when pool is quiescent, and
880	>	* designed to be invoked only when the pool is quiescent, and
881		* typically only before any tasks are submitted. The effects of
882		* invocations at other times may be unpredictable.
883		*
884	<	* @param async if true, use locally FIFO scheduling
884	>	* @param async if {@code true}, use locally FIFO scheduling
885		* @return the previous mode
886	+	* @see #getAsyncMode
887		*/
888		public boolean setAsyncMode(boolean async) {
889		boolean oldMode = locallyFifo;
#	Line 839 | Line 900 | public class ForkJoinPool extends Abstra
900		}
901
902		/**
903	<	* Returns true if this pool uses local first-in-first-out
903	>	* Returns {@code true} if this pool uses local first-in-first-out
904		* scheduling mode for forked tasks that are never joined.
905		*
906	<	* @return true if this pool uses async mode
906	>	* @return {@code true} if this pool uses async mode
907	>	* @see #setAsyncMode
908		*/
909		public boolean getAsyncMode() {
910		return locallyFifo;
#	Line 863 | Line 925 | public class ForkJoinPool extends Abstra
925		* Returns an estimate of the number of threads that are currently
926		* stealing or executing tasks. This method may overestimate the
927		* number of active threads.
928	+	*
929		* @return the number of active threads
930		*/
931		public int getActiveThreadCount() {
#	Line 873 | Line 936 | public class ForkJoinPool extends Abstra
936		* Returns an estimate of the number of threads that are currently
937		* idle waiting for tasks. This method may underestimate the
938		* number of idle threads.
939	+	*
940		* @return the number of idle threads
941		*/
942		final int getIdleThreadCount() {
943		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
944	<	return (c <= 0)? 0 : c;
944	>	return (c <= 0) ? 0 : c;
945		}
946
947		/**
948	<	* Returns true if all worker threads are currently idle. An idle
949	<	* worker is one that cannot obtain a task to execute because none
950	<	* are available to steal from other threads, and there are no
951	<	* pending submissions to the pool. This method is conservative:
952	<	* It might not return true immediately upon idleness of all
953	<	* threads, but will eventually become true if threads remain
954	<	* inactive.
955	<	* @return true if all threads are currently idle
948	>	* Returns {@code true} if all worker threads are currently idle.
949	>	* An idle worker is one that cannot obtain a task to execute
950	>	* because none are available to steal from other threads, and
951	>	* there are no pending submissions to the pool. This method is
952	>	* conservative; it might not return {@code true} immediately upon
953	>	* idleness of all threads, but will eventually become true if
954	>	* threads remain inactive.
955	>	*
956	>	* @return {@code true} if all threads are currently idle
957		*/
958		public boolean isQuiescent() {
959		return activeCountOf(runControl) == 0;
#	Line 899 | Line 964 | public class ForkJoinPool extends Abstra
964		* one thread's work queue by another. The reported value
965		* underestimates the actual total number of steals when the pool
966		* is not quiescent. This value may be useful for monitoring and
967	<	* tuning fork/join programs: In general, steal counts should be
967	>	* tuning fork/join programs: in general, steal counts should be
968		* high enough to keep threads busy, but low enough to avoid
969		* overhead and contention across threads.
970	+	*
971		* @return the number of steals
972		*/
973		public long getStealCount() {
#	Line 909 | Line 975 | public class ForkJoinPool extends Abstra
975		}
976
977		/**
978	<	* Accumulate steal count from a worker. Call only
979	<	* when worker known to be idle.
978	>	* Accumulates steal count from a worker.
979	>	* Call only when worker known to be idle.
980		*/
981		private void updateStealCount(ForkJoinWorkerThread w) {
982		int sc = w.getAndClearStealCount();
#	Line 925 | Line 991 | public class ForkJoinPool extends Abstra
991		* an approximation, obtained by iterating across all threads in
992		* the pool. This method may be useful for tuning task
993		* granularities.
994	+	*
995		* @return the number of queued tasks
996		*/
997		public long getQueuedTaskCount() {
#	Line 944 | Line 1011 | public class ForkJoinPool extends Abstra
1011		* Returns an estimate of the number tasks submitted to this pool
1012		* that have not yet begun executing. This method takes time
1013		* proportional to the number of submissions.
1014	+	*
1015		* @return the number of queued submissions
1016		*/
1017		public int getQueuedSubmissionCount() {
#	Line 951 | Line 1019 | public class ForkJoinPool extends Abstra
1019		}
1020
1021		/**
1022	<	* Returns true if there are any tasks submitted to this pool
1023	<	* that have not yet begun executing.
1022	>	* Returns {@code true} if there are any tasks submitted to this
1023	>	* pool that have not yet begun executing.
1024	>	*
1025		* @return {@code true} if there are any queued submissions
1026		*/
1027		public boolean hasQueuedSubmissions() {
#	Line 963 | Line 1032 | public class ForkJoinPool extends Abstra
1032		* Removes and returns the next unexecuted submission if one is
1033		* available.  This method may be useful in extensions to this
1034		* class that re-assign work in systems with multiple pools.
1035	<	* @return the next submission, or null if none
1035	>	*
1036	>	* @return the next submission, or {@code null} if none
1037		*/
1038		protected ForkJoinTask<?> pollSubmission() {
1039		return submissionQueue.poll();
#	Line 982 | Line 1052 | public class ForkJoinPool extends Abstra
1052		* exception is thrown.  The behavior of this operation is
1053		* undefined if the specified collection is modified while the
1054		* operation is in progress.
1055	+	*
1056		* @param c the collection to transfer elements into
1057		* @return the number of elements transferred
1058		*/
1059	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1059	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1060		int n = submissionQueue.drainTo(c);
1061		ForkJoinWorkerThread[] ws = workers;
1062		if (ws != null) {
#	Line 1042 | Line 1113 | public class ForkJoinPool extends Abstra
1113		* Invocation has no additional effect if already shut down.
1114		* Tasks that are in the process of being submitted concurrently
1115		* during the course of this method may or may not be rejected.
1116	+	*
1117		* @throws SecurityException if a security manager exists and
1118		*         the caller is not permitted to modify threads
1119		*         because it does not hold {@link
1120	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1120	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1121		*/
1122		public void shutdown() {
1123		checkPermission();
1124		transitionRunStateTo(SHUTDOWN);
1125	<	if (canTerminateOnShutdown(runControl))
1125	>	if (canTerminateOnShutdown(runControl)) {
1126	>	if (workers == null) { // shutting down before workers created
1127	>	final ReentrantLock lock = this.workerLock;
1128	>	lock.lock();
1129	>	try {
1130	>	if (workers == null) {
1131	>	terminate();
1132	>	transitionRunStateTo(TERMINATED);
1133	>	termination.signalAll();
1134	>	}
1135	>
1136	>	} finally {
1137	>	lock.unlock();
1138	>	}
1139	>	}
1140		terminateOnShutdown();
1141	+	}
1142		}
1143
1144		/**
#	Line 1061 | Line 1148 | public class ForkJoinPool extends Abstra
1148		* method may or may not be rejected. Unlike some other executors,
1149		* this method cancels rather than collects non-executed tasks
1150		* upon termination, so always returns an empty list. However, you
1151	<	* can use method {@code drainTasksTo} before invoking this
1151	>	* can use method {@link #drainTasksTo} before invoking this
1152		* method to transfer unexecuted tasks to another collection.
1153	+	*
1154		* @return an empty list
1155		* @throws SecurityException if a security manager exists and
1156		*         the caller is not permitted to modify threads
1157		*         because it does not hold {@link
1158	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1158	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1159		*/
1160		public List<Runnable> shutdownNow() {
1161		checkPermission();
#	Line 1135 | Line 1223 | public class ForkJoinPool extends Abstra
1223		// Shutdown and termination support
1224
1225		/**
1226	<	* Callback from terminating worker. Null out the corresponding
1227	<	* workers slot, and if terminating, try to terminate, else try to
1228	<	* shrink workers array.
1226	>	* Callback from terminating worker. Nulls out the corresponding
1227	>	* workers slot, and if terminating, tries to terminate; else
1228	>	* tries to shrink workers array.
1229	>	*
1230		* @param w the worker
1231		*/
1232		final void workerTerminated(ForkJoinWorkerThread w) {
#	Line 1168 | Line 1257 | public class ForkJoinPool extends Abstra
1257		}
1258
1259		/**
1260	<	* Initiate termination.
1260	>	* Initiates termination.
1261		*/
1262		private void terminate() {
1263		if (transitionRunStateTo(TERMINATING)) {
#	Line 1345 | Line 1434 | public class ForkJoinPool extends Abstra
1434		* Ensures that no thread is waiting for count to advance from the
1435		* current value of eventCount read on entry to this method, by
1436		* releasing waiting threads if necessary.
1437	+	*
1438		* @return the count
1439		*/
1440		final long ensureSync() {
#	Line 1366 | Line 1456 | public class ForkJoinPool extends Abstra
1456		*/
1457		private void signalIdleWorkers() {
1458		long c;
1459	<	do;while (!casEventCount(c = eventCount, c+1));
1459	>	do {} while (!casEventCount(c = eventCount, c+1));
1460		ensureSync();
1461		}
1462
#	Line 1390 | Line 1480 | public class ForkJoinPool extends Abstra
1480		* Waits until event count advances from last value held by
1481		* caller, or if excess threads, caller is resumed as spare, or
1482		* caller or pool is terminating. Updates caller's event on exit.
1483	+	*
1484		* @param w the calling worker thread
1485		*/
1486		final void sync(ForkJoinWorkerThread w) {
#	Line 1417 | Line 1508 | public class ForkJoinPool extends Abstra
1508		}
1509
1510		/**
1511	<	* Returns true if worker waiting on sync can proceed:
1511	>	* Returns {@code true} if worker waiting on sync can proceed:
1512		*  - on signal (thread == null)
1513		*  - on event count advance (winning race to notify vs signaller)
1514	<	*  - on Interrupt
1514	>	*  - on interrupt
1515		*  - if the first queued node, we find work available
1516		* If node was not signalled and event count not advanced on exit,
1517		* then we also help advance event count.
1518	<	* @return true if node can be released
1518	>	*
1519	>	* @return {@code true} if node can be released
1520		*/
1521		final boolean syncIsReleasable(WaitQueueNode node) {
1522		long prev = node.count;
#	Line 1443 | Line 1535 | public class ForkJoinPool extends Abstra
1535		}
1536
1537		/**
1538	<	* Returns true if a new sync event occurred since last call to
1539	<	* sync or this method, if so, updating caller's count.
1538	>	* Returns {@code true} if a new sync event occurred since last
1539	>	* call to sync or this method, if so, updating caller's count.
1540		*/
1541		final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1542		long lc = w.lastEventCount;
#	Line 1464 | Line 1556 | public class ForkJoinPool extends Abstra
1556		* spare thread when one is about to block (and remove or
1557		* suspend it later when unblocked -- see suspendIfSpare).
1558		* However, implementing this idea requires coping with
1559	<	* several problems: We have imperfect information about the
1559	>	* several problems: we have imperfect information about the
1560		* states of threads. Some count updates can and usually do
1561		* lag run state changes, despite arrangements to keep them
1562		* accurate (for example, when possible, updating counts
#	Line 1487 | Line 1579 | public class ForkJoinPool extends Abstra
1579		* target counts, else create only to avoid starvation
1580		* @return true if joinMe known to be done
1581		*/
1582	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1582	>	final boolean preJoin(ForkJoinTask<?> joinMe,
1583	>	boolean maintainParallelism) {
1584		maintainParallelism &= maintainsParallelism; // overrride
1585		boolean dec = false;  // true when running count decremented
1586		while (spareStack == null || !tryResumeSpare(dec)) {
1587		int counts = workerCounts;
1588	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1588	>	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1589	>	// CAS cheat
1590		if (!needSpare(counts, maintainParallelism))
1591		break;
1592		if (joinMe.status < 0)
#	Line 1507 | Line 1601 | public class ForkJoinPool extends Abstra
1601		/**
1602		* Same idea as preJoin
1603		*/
1604	<	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1604	>	final boolean preBlock(ManagedBlocker blocker,
1605	>	boolean maintainParallelism) {
1606		maintainParallelism &= maintainsParallelism;
1607		boolean dec = false;
1608		while (spareStack == null || !tryResumeSpare(dec)) {
#	Line 1525 | Line 1620 | public class ForkJoinPool extends Abstra
1620		}
1621
1622		/**
1623	<	* Returns true if a spare thread appears to be needed.  If
1624	<	* maintaining parallelism, returns true when the deficit in
1623	>	* Returns {@code true} if a spare thread appears to be needed.
1624	>	* If maintaining parallelism, returns true when the deficit in
1625		* running threads is more than the surplus of total threads, and
1626		* there is apparently some work to do.  This self-limiting rule
1627		* means that the more threads that have already been added, the
1628		* less parallelism we will tolerate before adding another.
1629	+	*
1630		* @param counts current worker counts
1631		* @param maintainParallelism try to maintain parallelism
1632		*/
#	Line 1550 | Line 1646 | public class ForkJoinPool extends Abstra
1646		/**
1647		* Adds a spare worker if lock available and no more than the
1648		* expected numbers of threads exist.
1649	+	*
1650		* @return true if successful
1651		*/
1652		private boolean tryAddSpare(int expectedCounts) {
#	Line 1609 | Line 1706 | public class ForkJoinPool extends Abstra
1706		* the same WaitQueueNodes as barriers.  They are resumed mainly
1707		* in preJoin, but are also woken on pool events that require all
1708		* threads to check run state.
1709	+	*
1710		* @param w the caller
1711		*/
1712		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
#	Line 1619 | Line 1717 | public class ForkJoinPool extends Abstra
1717		node = new WaitQueueNode(0, w);
1718		if (casWorkerCounts(s, s-1)) { // representation-dependent
1719		// push onto stack
1720	<	do;while (!casSpareStack(node.next = spareStack, node));
1720	>	do {} while (!casSpareStack(node.next = spareStack, node));
1721		// block until released by resumeSpare
1722		node.awaitSpareRelease();
1723		return true;
#	Line 1630 | Line 1728 | public class ForkJoinPool extends Abstra
1728
1729		/**
1730		* Tries to pop and resume a spare thread.
1731	+	*
1732		* @param updateCount if true, increment running count on success
1733		* @return true if successful
1734		*/
#	Line 1648 | Line 1747 | public class ForkJoinPool extends Abstra
1747
1748		/**
1749		* Pops and resumes all spare threads. Same idea as ensureSync.
1750	+	*
1751		* @return true if any spares released
1752		*/
1753		private boolean resumeAllSpares() {
#	Line 1690 | Line 1790 | public class ForkJoinPool extends Abstra
1790		/**
1791		* Interface for extending managed parallelism for tasks running
1792		* in ForkJoinPools. A ManagedBlocker provides two methods.
1793	<	* Method {@code isReleasable} must return true if blocking is not
1794	<	* necessary. Method {@code block} blocks the current thread
1795	<	* if necessary (perhaps internally invoking isReleasable before
1796	<	* actually blocking.).
1793	>	* Method {@code isReleasable} must return {@code true} if
1794	>	* blocking is not necessary. Method {@code block} blocks the
1795	>	* current thread if necessary (perhaps internally invoking
1796	>	* {@code isReleasable} before actually blocking.).
1797	>	*
1798		* <p>For example, here is a ManagedBlocker based on a
1799		* ReentrantLock:
1800	<	* <pre>
1801	<	*   class ManagedLocker implements ManagedBlocker {
1802	<	*     final ReentrantLock lock;
1803	<	*     boolean hasLock = false;
1804	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1805	<	*     public boolean block() {
1806	<	*        if (!hasLock)
1807	<	*           lock.lock();
1808	<	*        return true;
1809	<	*     }
1810	<	*     public boolean isReleasable() {
1811	<	*        return hasLock || (hasLock = lock.tryLock());
1711	<	*     }
1800	>	*  <pre> {@code
1801	>	* class ManagedLocker implements ManagedBlocker {
1802	>	*   final ReentrantLock lock;
1803	>	*   boolean hasLock = false;
1804	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1805	>	*   public boolean block() {
1806	>	*     if (!hasLock)
1807	>	*       lock.lock();
1808	>	*     return true;
1809	>	*   }
1810	>	*   public boolean isReleasable() {
1811	>	*     return hasLock || (hasLock = lock.tryLock());
1812		*   }
1813	<	* </pre>
1813	>	* }}</pre>
1814		*/
1815		public static interface ManagedBlocker {
1816		/**
1817		* Possibly blocks the current thread, for example waiting for
1818		* a lock or condition.
1819	<	* @return true if no additional blocking is necessary (i.e.,
1820	<	* if isReleasable would return true)
1819	>	*
1820	>	* @return {@code true} if no additional blocking is necessary
1821	>	* (i.e., if isReleasable would return true)
1822		* @throws InterruptedException if interrupted while waiting
1823	<	* (the method is not required to do so, but is allowed to).
1823	>	* (the method is not required to do so, but is allowed to)
1824		*/
1825		boolean block() throws InterruptedException;
1826
1827		/**
1828	<	* Returns true if blocking is unnecessary.
1828	>	* Returns {@code true} if blocking is unnecessary.
1829		*/
1830		boolean isReleasable();
1831		}
#	Line 1734 | Line 1835 | public class ForkJoinPool extends Abstra
1835		* is a ForkJoinWorkerThread, this method possibly arranges for a
1836		* spare thread to be activated if necessary to ensure parallelism
1837		* while the current thread is blocked.  If
1838	<	* {@code maintainParallelism} is true and the pool supports
1838	>	* {@code maintainParallelism} is {@code true} and the pool supports
1839		* it ({@link #getMaintainsParallelism}), this method attempts to
1840	<	* maintain the pool's nominal parallelism. Otherwise if activates
1840	>	* maintain the pool's nominal parallelism. Otherwise it activates
1841		* a thread only if necessary to avoid complete starvation. This
1842		* option may be preferable when blockages use timeouts, or are
1843		* almost always brief.
1844		*
1845		* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1846		* equivalent to
1847	<	* <pre>
1848	<	*   while (!blocker.isReleasable())
1849	<	*      if (blocker.block())
1850	<	*         return;
1851	<	* </pre>
1847	>	*  <pre> {@code
1848	>	* while (!blocker.isReleasable())
1849	>	*   if (blocker.block())
1850	>	*     return;
1851	>	* }</pre>
1852		* If the caller is a ForkJoinTask, then the pool may first
1853		* be expanded to ensure parallelism, and later adjusted.
1854		*
1855		* @param blocker the blocker
1856	<	* @param maintainParallelism if true and supported by this pool,
1857	<	* attempt to maintain the pool's nominal parallelism; otherwise
1858	<	* activate a thread only if necessary to avoid complete
1859	<	* starvation.
1856	>	* @param maintainParallelism if {@code true} and supported by
1857	>	* this pool, attempt to maintain the pool's nominal parallelism;
1858	>	* otherwise activate a thread only if necessary to avoid
1859	>	* complete starvation.
1860		* @throws InterruptedException if blocker.block did so
1861		*/
1862		public static void managedBlock(ManagedBlocker blocker,
1863		boolean maintainParallelism)
1864		throws InterruptedException {
1865		Thread t = Thread.currentThread();
1866	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1867	<	((ForkJoinWorkerThread)t).pool : null);
1866	>	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1867	>	((ForkJoinWorkerThread) t).pool : null);
1868		if (!blocker.isReleasable()) {
1869		try {
1870		if (pool == null ||
#	Line 1778 | Line 1879 | public class ForkJoinPool extends Abstra
1879
1880		private static void awaitBlocker(ManagedBlocker blocker)
1881		throws InterruptedException {
1882	<	do;while (!blocker.isReleasable() && !blocker.block());
1882	>	do {} while (!blocker.isReleasable() && !blocker.block());
1883		}
1884
1885		// AbstractExecutorService overrides
1886
1887		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1888	<	return new AdaptedRunnable(runnable, value);
1888	>	return new AdaptedRunnable<T>(runnable, value);
1889		}
1890
1891		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1892	<	return new AdaptedCallable(callable);
1892	>	return new AdaptedCallable<T>(callable);
1893		}
1894
1895	+	// Unsafe mechanics
1896
1897	<	// Temporary Unsafe mechanics for preliminary release
1898	<	private static Unsafe getUnsafe() throws Throwable {
1899	<	try {
1900	<	return Unsafe.getUnsafe();
1901	<	} catch (SecurityException se) {
1902	<	try {
1903	<	return java.security.AccessController.doPrivileged
1904	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1905	<	public Unsafe run() throws Exception {
1906	<	return getUnsafePrivileged();
1907	<	}});
1806	<	} catch (java.security.PrivilegedActionException e) {
1807	<	throw e.getCause();
1808	<	}
1809	<	}
1810	<	}
1811	<
1812	<	private static Unsafe getUnsafePrivileged()
1813	<	throws NoSuchFieldException, IllegalAccessException {
1814	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1815	<	f.setAccessible(true);
1816	<	return (Unsafe) f.get(null);
1817	<	}
1818	<
1819	<	private static long fieldOffset(String fieldName)
1820	<	throws NoSuchFieldException {
1821	<	return UNSAFE.objectFieldOffset
1822	<	(ForkJoinPool.class.getDeclaredField(fieldName));
1823	<	}
1824	<
1825	<	static final Unsafe UNSAFE;
1826	<	static final long eventCountOffset;
1827	<	static final long workerCountsOffset;
1828	<	static final long runControlOffset;
1829	<	static final long syncStackOffset;
1830	<	static final long spareStackOffset;
1831	<
1832	<	static {
1833	<	try {
1834	<	UNSAFE = getUnsafe();
1835	<	eventCountOffset = fieldOffset("eventCount");
1836	<	workerCountsOffset = fieldOffset("workerCounts");
1837	<	runControlOffset = fieldOffset("runControl");
1838	<	syncStackOffset = fieldOffset("syncStack");
1839	<	spareStackOffset = fieldOffset("spareStack");
1840	<	} catch (Throwable e) {
1841	<	throw new RuntimeException("Could not initialize intrinsics", e);
1842	<	}
1843	<	}
1897	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1898	>	private static final long eventCountOffset =
1899	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1900	>	private static final long workerCountsOffset =
1901	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1902	>	private static final long runControlOffset =
1903	>	objectFieldOffset("runControl", ForkJoinPool.class);
1904	>	private static final long syncStackOffset =
1905	>	objectFieldOffset("syncStack",ForkJoinPool.class);
1906	>	private static final long spareStackOffset =
1907	>	objectFieldOffset("spareStack", ForkJoinPool.class);
1908
1909		private boolean casEventCount(long cmp, long val) {
1910		return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
#	Line 1857 | Line 1921 | public class ForkJoinPool extends Abstra
1921		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1922		return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1923		}
1924	+
1925	+	private static long objectFieldOffset(String field, Class<?> klazz) {
1926	+	try {
1927	+	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1928	+	} catch (NoSuchFieldException e) {
1929	+	// Convert Exception to corresponding Error
1930	+	NoSuchFieldError error = new NoSuchFieldError(field);
1931	+	error.initCause(e);
1932	+	throw error;
1933	+	}
1934	+	}
1935	+
1936	+	/**
1937	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1938	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1939	+	* into a jdk.
1940	+	*
1941	+	* @return a sun.misc.Unsafe
1942	+	*/
1943	+	private static sun.misc.Unsafe getUnsafe() {
1944	+	try {
1945	+	return sun.misc.Unsafe.getUnsafe();
1946	+	} catch (SecurityException se) {
1947	+	try {
1948	+	return java.security.AccessController.doPrivileged
1949	+	(new java.security
1950	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1951	+	public sun.misc.Unsafe run() throws Exception {
1952	+	java.lang.reflect.Field f = sun.misc
1953	+	.Unsafe.class.getDeclaredField("theUnsafe");
1954	+	f.setAccessible(true);
1955	+	return (sun.misc.Unsafe) f.get(null);
1956	+	}});
1957	+	} catch (java.security.PrivilegedActionException e) {
1958	+	throw new RuntimeException("Could not initialize intrinsics",
1959	+	e.getCause());
1960	+	}
1961	+	}
1962	+	}
1963		}

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