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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.7 by jsr166, Mon Jul 20 21:45:06 2009 UTC vs.
Revision 1.18 by jsr166, Thu Jul 23 23:23:41 2009 UTC

#	Line 28 | Line 28 | import java.lang.reflect.*;
28		* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
29		* as the mixed execution of some plain Runnable- or Callable- based
30		* activities along with ForkJoinTasks. When setting
31	<	* <tt>setAsyncMode</tt>, a ForkJoinPools may also be appropriate for
31	>	* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for
32		* use with fine-grained tasks that are never joined. Otherwise, other
33		* ExecutorService implementations are typically more appropriate
34		* choices.
#	Line 38 | Line 38 | import java.lang.reflect.*;
38		* adding, suspending, or resuming threads, even if some tasks are
39		* waiting to join others. However, no such adjustments are performed
40		* in the face of blocked IO or other unmanaged synchronization. The
41	<	* nested <code>ManagedBlocker</code> interface enables extension of
41	>	* nested {@code ManagedBlocker} interface enables extension of
42		* the kinds of synchronization accommodated.  The target parallelism
43	<	* level may also be changed dynamically (<code>setParallelism</code>)
43	>	* level may also be changed dynamically ({@code setParallelism})
44		* and thread construction can be limited using methods
45	<	* <code>setMaximumPoolSize</code> and/or
46	<	* <code>setMaintainsParallelism</code>.
45	>	* {@code setMaximumPoolSize} and/or
46	>	* {@code setMaintainsParallelism}.
47		*
48		* <p>In addition to execution and lifecycle control methods, this
49		* class provides status check methods (for example
50	<	* <code>getStealCount</code>) that are intended to aid in developing,
50	>	* {@code getStealCount}) that are intended to aid in developing,
51		* tuning, and monitoring fork/join applications. Also, method
52	<	* <code>toString</code> returns indications of pool state in a
52	>	* {@code toString} returns indications of pool state in a
53		* convenient form for informal monitoring.
54		*
55		* <p><b>Implementation notes</b>: This implementation restricts the
56		* maximum number of running threads to 32767. Attempts to create
57		* pools with greater than the maximum result in
58		* IllegalArgumentExceptions.
59	+	*
60	+	* @since 1.7
61	+	* @author Doug Lea
62		*/
63		public class ForkJoinPool extends AbstractExecutorService {
64
#	Line 81 | Line 84 | public class ForkJoinPool extends Abstra
84		* Returns a new worker thread operating in the given pool.
85		*
86		* @param pool the pool this thread works in
87	<	* @throws NullPointerException if pool is null;
87	>	* @throws NullPointerException if pool is null
88		*/
89		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
90		}
91
92		/**
93	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
93	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
94		* new ForkJoinWorkerThread.
95		*/
96		static class  DefaultForkJoinWorkerThreadFactory
#	Line 153 | Line 156 | public class ForkJoinPool extends Abstra
156
157		/**
158		* The uncaught exception handler used when any worker
159	<	* abrupty terminates
159	>	* abruptly terminates
160		*/
161		private Thread.UncaughtExceptionHandler ueh;
162
#	Line 181 | Line 184 | public class ForkJoinPool extends Abstra
184		private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
185
186		/**
187	<	* Head of Treiber stack for barrier sync. See below for explanation
187	>	* Head of Treiber stack for barrier sync. See below for explanation.
188		*/
189		private volatile WaitQueueNode syncStack;
190
#	Line 216 | Line 219 | public class ForkJoinPool extends Abstra
219		* threads, packed into one int to ensure consistent snapshot when
220		* making decisions about creating and suspending spare
221		* threads. Updated only by CAS.  Note: CASes in
222	<	* updateRunningCount and preJoin running active count is in low
223	<	* word, so need to be modified if this changes
222	>	* updateRunningCount and preJoin assume that running active count
223	>	* is in low word, so need to be modified if this changes.
224		*/
225		private volatile int workerCounts;
226
#	Line 226 | Line 229 | public class ForkJoinPool extends Abstra
229		private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
230
231		/**
232	<	* Add delta (which may be negative) to running count.  This must
232	>	* Adds delta (which may be negative) to running count.  This must
233		* be called before (with negative arg) and after (with positive)
234	<	* any managed synchronization (i.e., mainly, joins)
234	>	* any managed synchronization (i.e., mainly, joins).
235	>	*
236		* @param delta the number to add
237		*/
238		final void updateRunningCount(int delta) {
239		int s;
240	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
240	>	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
241		}
242
243		/**
244	<	* Add delta (which may be negative) to both total and running
244	>	* Adds delta (which may be negative) to both total and running
245		* count.  This must be called upon creation and termination of
246		* worker threads.
247	+	*
248		* @param delta the number to add
249		*/
250		private void updateWorkerCount(int delta) {
251		int d = delta + (delta << 16); // add to both lo and hi parts
252		int s;
253	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
253	>	do {} while (!casWorkerCounts(s = workerCounts, s + d));
254		}
255
256		/**
#	Line 271 | Line 276 | public class ForkJoinPool extends Abstra
276		private static int runControlFor(int r, int a)   { return (r << 16) + a; }
277
278		/**
279	<	* Try incrementing active count; fail on contention. Called by
280	<	* workers before/during executing tasks.
281	<	* @return true on success;
279	>	* Tries incrementing active count; fails on contention.
280	>	* Called by workers before/during executing tasks.
281	>	*
282	>	* @return true on success
283		*/
284		final boolean tryIncrementActiveCount() {
285		int c = runControl;
#	Line 281 | Line 287 | public class ForkJoinPool extends Abstra
287		}
288
289		/**
290	<	* Try decrementing active count; fail on contention.
291	<	* Possibly trigger termination on success
290	>	* Tries decrementing active count; fails on contention.
291	>	* Possibly triggers termination on success.
292		* Called by workers when they can't find tasks.
293	+	*
294		* @return true on success
295		*/
296		final boolean tryDecrementActiveCount() {
#	Line 297 | Line 304 | public class ForkJoinPool extends Abstra
304		}
305
306		/**
307	<	* Return true if argument represents zero active count and
307	>	* Returns true if argument represents zero active count and
308		* nonzero runstate, which is the triggering condition for
309		* terminating on shutdown.
310		*/
311		private static boolean canTerminateOnShutdown(int c) {
312	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
312	>	// i.e. least bit is nonzero runState bit
313	>	return ((c & -c) >>> 16) != 0;
314		}
315
316		/**
#	Line 328 | Line 336 | public class ForkJoinPool extends Abstra
336
337		/**
338		* Creates a ForkJoinPool with a pool size equal to the number of
339	<	* processors available on the system and using the default
340	<	* ForkJoinWorkerThreadFactory,
339	>	* processors available on the system, using the default
340	>	* ForkJoinWorkerThreadFactory.
341	>	*
342		* @throws SecurityException if a security manager exists and
343		*         the caller is not permitted to modify threads
344		*         because it does not hold {@link
345	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
345	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
346		*/
347		public ForkJoinPool() {
348		this(Runtime.getRuntime().availableProcessors(),
#	Line 341 | Line 350 | public class ForkJoinPool extends Abstra
350		}
351
352		/**
353	<	* Creates a ForkJoinPool with the indicated parellelism level
354	<	* threads, and using the default ForkJoinWorkerThreadFactory,
353	>	* Creates a ForkJoinPool with the indicated parallelism level
354	>	* threads and using the default ForkJoinWorkerThreadFactory.
355	>	*
356		* @param parallelism the number of worker threads
357		* @throws IllegalArgumentException if parallelism less than or
358		* equal to zero
359		* @throws SecurityException if a security manager exists and
360		*         the caller is not permitted to modify threads
361		*         because it does not hold {@link
362	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
362	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
363		*/
364		public ForkJoinPool(int parallelism) {
365		this(parallelism, defaultForkJoinWorkerThreadFactory);
#	Line 358 | Line 368 | public class ForkJoinPool extends Abstra
368		/**
369		* Creates a ForkJoinPool with parallelism equal to the number of
370		* processors available on the system and using the given
371	<	* ForkJoinWorkerThreadFactory,
371	>	* ForkJoinWorkerThreadFactory.
372	>	*
373		* @param factory the factory for creating new threads
374		* @throws NullPointerException if factory is null
375		* @throws SecurityException if a security manager exists and
376		*         the caller is not permitted to modify threads
377		*         because it does not hold {@link
378	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
378	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
379		*/
380		public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
381		this(Runtime.getRuntime().availableProcessors(), factory);
#	Line 376 | Line 387 | public class ForkJoinPool extends Abstra
387		* @param parallelism the targeted number of worker threads
388		* @param factory the factory for creating new threads
389		* @throws IllegalArgumentException if parallelism less than or
390	<	* equal to zero, or greater than implementation limit.
390	>	* equal to zero, or greater than implementation limit
391		* @throws NullPointerException if factory is null
392		* @throws SecurityException if a security manager exists and
393		*         the caller is not permitted to modify threads
394		*         because it does not hold {@link
395	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
395	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
396		*/
397		public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
398		if (parallelism <= 0 || parallelism > MAX_THREADS)
#	Line 402 | Line 413 | public class ForkJoinPool extends Abstra
413		}
414
415		/**
416	<	* Create new worker using factory.
416	>	* Creates a new worker thread using factory.
417	>	*
418		* @param index the index to assign worker
419		* @return new worker, or null of factory failed
420		*/
#	Line 421 | Line 433 | public class ForkJoinPool extends Abstra
433		}
434
435		/**
436	<	* Return a good size for worker array given pool size.
436	>	* Returns a good size for worker array given pool size.
437		* Currently requires size to be a power of two.
438		*/
439	<	private static int arraySizeFor(int ps) {
440	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
439	>	private static int arraySizeFor(int poolSize) {
440	>	return (poolSize <= 1) ? 1 :
441	>	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
442		}
443
444		/**
445	<	* Create or resize array if necessary to hold newLength.
446	<	* Call only under exlusion or lock
445	>	* Creates or resizes array if necessary to hold newLength.
446	>	* Call only under exclusion.
447	>	*
448		* @return the array
449		*/
450		private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
#	Line 444 | Line 458 | public class ForkJoinPool extends Abstra
458		}
459
460		/**
461	<	* Try to shrink workers into smaller array after one or more terminate
461	>	* Tries to shrink workers into smaller array after one or more terminate.
462		*/
463		private void tryShrinkWorkerArray() {
464		ForkJoinWorkerThread[] ws = workers;
#	Line 460 | Line 474 | public class ForkJoinPool extends Abstra
474		}
475
476		/**
477	<	* Initialize workers if necessary
477	>	* Initializes workers if necessary.
478		*/
479		final void ensureWorkerInitialization() {
480		ForkJoinWorkerThread[] ws = workers;
#	Line 536 | Line 550 | public class ForkJoinPool extends Abstra
550		}
551
552		/**
553	<	* Performs the given task; returning its result upon completion
553	>	* Performs the given task, returning its result upon completion.
554	>	*
555		* @param task the task
556		* @return the task's result
557		* @throws NullPointerException if task is null
#	Line 549 | Line 564 | public class ForkJoinPool extends Abstra
564
565		/**
566		* Arranges for (asynchronous) execution of the given task.
567	+	*
568		* @param task the task
569		* @throws NullPointerException if task is null
570		* @throws RejectedExecutionException if pool is shut down
#	Line 583 | Line 599 | public class ForkJoinPool extends Abstra
599
600		/**
601		* Adaptor for Runnables. This implements RunnableFuture
602	<	* to be compliant with AbstractExecutorService constraints
602	>	* to be compliant with AbstractExecutorService constraints.
603		*/
604		static final class AdaptedRunnable<T> extends ForkJoinTask<T>
605		implements RunnableFuture<T> {
#	Line 603 | Line 619 | public class ForkJoinPool extends Abstra
619		return true;
620		}
621		public void run() { invoke(); }
622	+	private static final long serialVersionUID = 5232453952276885070L;
623		}
624
625		/**
#	Line 631 | Line 648 | public class ForkJoinPool extends Abstra
648		}
649		}
650		public void run() { invoke(); }
651	+	private static final long serialVersionUID = 2838392045355241008L;
652		}
653
654		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
#	Line 639 | Line 657 | public class ForkJoinPool extends Abstra
657		for (Callable<T> c : tasks)
658		ts.add(new AdaptedCallable<T>(c));
659		invoke(new InvokeAll<T>(ts));
660	<	return (List<Future<T>>)(List)ts;
660	>	return (List<Future<T>>) (List) ts;
661		}
662
663		static final class InvokeAll<T> extends RecursiveAction {
664		final ArrayList<ForkJoinTask<T>> tasks;
665		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
666		public void compute() {
667	<	try { invokeAll(tasks); } catch(Exception ignore) {}
667	>	try { invokeAll(tasks); }
668	>	catch (Exception ignore) {}
669		}
670	+	private static final long serialVersionUID = -7914297376763021607L;
671		}
672
673		// Configuration and status settings and queries
674
675		/**
676	<	* Returns the factory used for constructing new workers
676	>	* Returns the factory used for constructing new workers.
677		*
678		* @return the factory used for constructing new workers
679		*/
#	Line 664 | Line 684 | public class ForkJoinPool extends Abstra
684		/**
685		* Returns the handler for internal worker threads that terminate
686		* due to unrecoverable errors encountered while executing tasks.
687	+	*
688		* @return the handler, or null if none
689		*/
690		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
#	Line 689 | Line 710 | public class ForkJoinPool extends Abstra
710		* @throws SecurityException if a security manager exists and
711		*         the caller is not permitted to modify threads
712		*         because it does not hold {@link
713	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
713	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
714		*/
715		public Thread.UncaughtExceptionHandler
716		setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
#	Line 716 | Line 737 | public class ForkJoinPool extends Abstra
737
738
739		/**
740	<	* Sets the target paralleism level of this pool.
740	>	* Sets the target parallelism level of this pool.
741	>	*
742		* @param parallelism the target parallelism
743		* @throws IllegalArgumentException if parallelism less than or
744	<	* equal to zero or greater than maximum size bounds.
744	>	* equal to zero or greater than maximum size bounds
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")</code>,
748	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
749		*/
750		public void setParallelism(int parallelism) {
751		checkPermission();
#	Line 758 | Line 780 | public class ForkJoinPool extends Abstra
780		/**
781		* Returns the number of worker threads that have started but not
782		* yet terminated.  This result returned by this method may differ
783	<	* from <code>getParallelism</code> when threads are created to
783	>	* from {@code getParallelism} when threads are created to
784		* maintain parallelism when others are cooperatively blocked.
785		*
786		* @return the number of worker threads
#	Line 770 | Line 792 | public class ForkJoinPool extends Abstra
792		/**
793		* Returns the maximum number of threads allowed to exist in the
794		* pool, even if there are insufficient unblocked running threads.
795	+	*
796		* @return the maximum
797		*/
798		public int getMaximumPoolSize() {
#	Line 781 | Line 804 | public class ForkJoinPool extends Abstra
804		* pool, even if there are insufficient unblocked running threads.
805		* Setting this value has no effect on current pool size. It
806		* controls construction of new threads.
807	+	*
808		* @throws IllegalArgumentException if negative or greater then
809	<	* internal implementation limit.
809	>	* internal implementation limit
810		*/
811		public void setMaximumPoolSize(int newMax) {
812		if (newMax < 0 || newMax > MAX_THREADS)
#	Line 795 | Line 819 | public class ForkJoinPool extends Abstra
819		* Returns true if this pool dynamically maintains its target
820		* parallelism level. If false, new threads are added only to
821		* avoid possible starvation.
822	<	* This setting is by default true;
822	>	* This setting is by default true.
823	>	*
824		* @return true if maintains parallelism
825		*/
826		public boolean getMaintainsParallelism() {
#	Line 806 | Line 831 | public class ForkJoinPool extends Abstra
831		* Sets whether this pool dynamically maintains its target
832		* parallelism level. If false, new threads are added only to
833		* avoid possible starvation.
834	+	*
835		* @param enable true to maintains parallelism
836		*/
837		public void setMaintainsParallelism(boolean enable) {
#	Line 819 | Line 845 | public class ForkJoinPool extends Abstra
845		* worker threads only process asynchronous tasks.  This method is
846		* designed to be invoked only when pool is quiescent, and
847		* typically only before any tasks are submitted. The effects of
848	<	* invocations at ather times may be unpredictable.
848	>	* invocations at other times may be unpredictable.
849		*
850		* @param async if true, use locally FIFO scheduling
851	<	* @return the previous mode.
851	>	* @return the previous mode
852		*/
853		public boolean setAsyncMode(boolean async) {
854		boolean oldMode = locallyFifo;
#	Line 842 | Line 868 | public class ForkJoinPool extends Abstra
868		* Returns true if this pool uses local first-in-first-out
869		* scheduling mode for forked tasks that are never joined.
870		*
871	<	* @return true if this pool uses async mode.
871	>	* @return true if this pool uses async mode
872		*/
873		public boolean getAsyncMode() {
874		return locallyFifo;
#	Line 863 | Line 889 | public class ForkJoinPool extends Abstra
889		* Returns an estimate of the number of threads that are currently
890		* stealing or executing tasks. This method may overestimate the
891		* number of active threads.
892	<	* @return the number of active threads.
892	>	*
893	>	* @return the number of active threads
894		*/
895		public int getActiveThreadCount() {
896		return activeCountOf(runControl);
#	Line 873 | Line 900 | public class ForkJoinPool extends Abstra
900		* Returns an estimate of the number of threads that are currently
901		* idle waiting for tasks. This method may underestimate the
902		* number of idle threads.
903	<	* @return the number of idle threads.
903	>	*
904	>	* @return the number of idle threads
905		*/
906		final int getIdleThreadCount() {
907		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
908	<	return (c <= 0)? 0 : c;
908	>	return (c <= 0) ? 0 : c;
909		}
910
911		/**
912		* Returns true if all worker threads are currently idle. An idle
913		* worker is one that cannot obtain a task to execute because none
914		* are available to steal from other threads, and there are no
915	<	* pending submissions to the pool. This method is conservative:
916	<	* It might not return true immediately upon idleness of all
915	>	* pending submissions to the pool. This method is conservative;
916	>	* it might not return true immediately upon idleness of all
917		* threads, but will eventually become true if threads remain
918		* inactive.
919	+	*
920		* @return true if all threads are currently idle
921		*/
922		public boolean isQuiescent() {
#	Line 899 | Line 928 | public class ForkJoinPool extends Abstra
928		* one thread's work queue by another. The reported value
929		* underestimates the actual total number of steals when the pool
930		* is not quiescent. This value may be useful for monitoring and
931	<	* tuning fork/join programs: In general, steal counts should be
931	>	* tuning fork/join programs: in general, steal counts should be
932		* high enough to keep threads busy, but low enough to avoid
933		* overhead and contention across threads.
934	<	* @return the number of steals.
934	>	*
935	>	* @return the number of steals
936		*/
937		public long getStealCount() {
938		return stealCount.get();
939		}
940
941		/**
942	<	* Accumulate steal count from a worker. Call only
943	<	* when worker known to be idle.
942	>	* Accumulates steal count from a worker.
943	>	* Call only when worker known to be idle.
944		*/
945		private void updateStealCount(ForkJoinWorkerThread w) {
946		int sc = w.getAndClearStealCount();
#	Line 925 | Line 955 | public class ForkJoinPool extends Abstra
955		* an approximation, obtained by iterating across all threads in
956		* the pool. This method may be useful for tuning task
957		* granularities.
958	<	* @return the number of queued tasks.
958	>	*
959	>	* @return the number of queued tasks
960		*/
961		public long getQueuedTaskCount() {
962		long count = 0;
#	Line 944 | Line 975 | public class ForkJoinPool extends Abstra
975		* Returns an estimate of the number tasks submitted to this pool
976		* that have not yet begun executing. This method takes time
977		* proportional to the number of submissions.
978	<	* @return the number of queued submissions.
978	>	*
979	>	* @return the number of queued submissions
980		*/
981		public int getQueuedSubmissionCount() {
982		return submissionQueue.size();
#	Line 953 | Line 985 | public class ForkJoinPool extends Abstra
985		/**
986		* Returns true if there are any tasks submitted to this pool
987		* that have not yet begun executing.
988	<	* @return <code>true</code> if there are any queued submissions.
988	>	*
989	>	* @return {@code true} if there are any queued submissions
990		*/
991		public boolean hasQueuedSubmissions() {
992		return !submissionQueue.isEmpty();
#	Line 963 | Line 996 | public class ForkJoinPool extends Abstra
996		* Removes and returns the next unexecuted submission if one is
997		* available.  This method may be useful in extensions to this
998		* class that re-assign work in systems with multiple pools.
999	+	*
1000		* @return the next submission, or null if none
1001		*/
1002		protected ForkJoinTask<?> pollSubmission() {
#	Line 973 | Line 1007 | public class ForkJoinPool extends Abstra
1007		* Removes all available unexecuted submitted and forked tasks
1008		* from scheduling queues and adds them to the given collection,
1009		* without altering their execution status. These may include
1010	<	* artifically generated or wrapped tasks. This method id designed
1010	>	* artificially generated or wrapped tasks. This method is designed
1011		* to be invoked only when the pool is known to be
1012		* quiescent. Invocations at other times may not remove all
1013		* tasks. A failure encountered while attempting to add elements
1014	<	* to collection <tt>c</tt> may result in elements being in
1014	>	* to collection {@code c} may result in elements being in
1015		* neither, either or both collections when the associated
1016		* exception is thrown.  The behavior of this operation is
1017		* undefined if the specified collection is modified while the
1018		* operation is in progress.
1019	+	*
1020		* @param c the collection to transfer elements into
1021		* @return the number of elements transferred
1022		*/
#	Line 1042 | Line 1077 | public class ForkJoinPool extends Abstra
1077		* Invocation has no additional effect if already shut down.
1078		* Tasks that are in the process of being submitted concurrently
1079		* during the course of this method may or may not be rejected.
1080	+	*
1081		* @throws SecurityException if a security manager exists and
1082		*         the caller is not permitted to modify threads
1083		*         because it does not hold {@link
1084	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1084	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1085		*/
1086		public void shutdown() {
1087		checkPermission();
#	Line 1061 | 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</code> before invoking this
1100	>	* can use method {@code drainTasksTo} before invoking this
1101		* method to transfer unexecuted tasks to another collection.
1102	+	*
1103		* @return an empty list
1104		* @throws SecurityException if a security manager exists and
1105		*         the caller is not permitted to modify threads
1106		*         because it does not hold {@link
1107	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1107	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1108		*/
1109		public List<Runnable> shutdownNow() {
1110		checkPermission();
#	Line 1076 | Line 1113 | public class ForkJoinPool extends Abstra
1113		}
1114
1115		/**
1116	<	* Returns <code>true</code> if all tasks have completed following shut down.
1116	>	* Returns {@code true} if all tasks have completed following shut down.
1117		*
1118	<	* @return <code>true</code> if all tasks have completed following shut down
1118	>	* @return {@code true} if all tasks have completed following shut down
1119		*/
1120		public boolean isTerminated() {
1121		return runStateOf(runControl) == TERMINATED;
1122		}
1123
1124		/**
1125	<	* Returns <code>true</code> if the process of termination has
1125	>	* Returns {@code true} if the process of termination has
1126		* commenced but possibly not yet completed.
1127		*
1128	<	* @return <code>true</code> if terminating
1128	>	* @return {@code true} if terminating
1129		*/
1130		public boolean isTerminating() {
1131		return runStateOf(runControl) >= TERMINATING;
1132		}
1133
1134		/**
1135	<	* Returns <code>true</code> if this pool has been shut down.
1135	>	* Returns {@code true} if this pool has been shut down.
1136		*
1137	<	* @return <code>true</code> if this pool has been shut down
1137	>	* @return {@code true} if this pool has been shut down
1138		*/
1139		public boolean isShutdown() {
1140		return runStateOf(runControl) >= SHUTDOWN;
#	Line 1110 | Line 1147 | public class ForkJoinPool extends Abstra
1147		*
1148		* @param timeout the maximum time to wait
1149		* @param unit the time unit of the timeout argument
1150	<	* @return <code>true</code> if this executor terminated and
1151	<	*         <code>false</code> if the timeout elapsed before termination
1150	>	* @return {@code true} if this executor terminated and
1151	>	*         {@code false} if the timeout elapsed before termination
1152		* @throws InterruptedException if interrupted while waiting
1153		*/
1154		public boolean awaitTermination(long timeout, TimeUnit unit)
#	Line 1135 | Line 1172 | public class ForkJoinPool extends Abstra
1172		// Shutdown and termination support
1173
1174		/**
1175	<	* Callback from terminating worker. Null out the corresponding
1176	<	* workers slot, and if terminating, try to terminate, else try to
1177	<	* shrink workers array.
1175	>	* Callback from terminating worker. Nulls out the corresponding
1176	>	* workers slot, and if terminating, tries to terminate; else
1177	>	* tries to shrink workers array.
1178	>	*
1179		* @param w the worker
1180		*/
1181		final void workerTerminated(ForkJoinWorkerThread w) {
#	Line 1168 | Line 1206 | public class ForkJoinPool extends Abstra
1206		}
1207
1208		/**
1209	<	* Initiate termination.
1209	>	* Initiates termination.
1210		*/
1211		private void terminate() {
1212		if (transitionRunStateTo(TERMINATING)) {
#	Line 1183 | Line 1221 | public class ForkJoinPool extends Abstra
1221		}
1222
1223		/**
1224	<	* Possibly terminate when on shutdown state
1224	>	* Possibly terminates when on shutdown state.
1225		*/
1226		private void terminateOnShutdown() {
1227		if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
#	Line 1191 | Line 1229 | public class ForkJoinPool extends Abstra
1229		}
1230
1231		/**
1232	<	* Clear out and cancel submissions
1232	>	* Clears out and cancels submissions.
1233		*/
1234		private void cancelQueuedSubmissions() {
1235		ForkJoinTask<?> task;
#	Line 1200 | Line 1238 | public class ForkJoinPool extends Abstra
1238		}
1239
1240		/**
1241	<	* Clean out worker queues.
1241	>	* Cleans out worker queues.
1242		*/
1243		private void cancelQueuedWorkerTasks() {
1244		final ReentrantLock lock = this.workerLock;
#	Line 1220 | Line 1258 | public class ForkJoinPool extends Abstra
1258		}
1259
1260		/**
1261	<	* Set each worker's status to terminating. Requires lock to avoid
1262	<	* conflicts with add/remove
1261	>	* Sets each worker's status to terminating. Requires lock to avoid
1262	>	* conflicts with add/remove.
1263		*/
1264		private void stopAllWorkers() {
1265		final ReentrantLock lock = this.workerLock;
#	Line 1241 | Line 1279 | public class ForkJoinPool extends Abstra
1279		}
1280
1281		/**
1282	<	* Interrupt all unterminated workers.  This is not required for
1282	>	* Interrupts all unterminated workers.  This is not required for
1283		* sake of internal control, but may help unstick user code during
1284		* shutdown.
1285		*/
#	Line 1311 | Line 1349 | public class ForkJoinPool extends Abstra
1349		}
1350
1351		/**
1352	<	* Wake up waiter, returning false if known to already
1352	>	* Wakes up waiter, returning false if known to already
1353		*/
1354		boolean signal() {
1355		ForkJoinWorkerThread t = thread;
#	Line 1323 | Line 1361 | public class ForkJoinPool extends Abstra
1361		}
1362
1363		/**
1364	<	* Await release on sync
1364	>	* Awaits release on sync.
1365		*/
1366		void awaitSyncRelease(ForkJoinPool p) {
1367		while (thread != null && !p.syncIsReleasable(this))
#	Line 1331 | Line 1369 | public class ForkJoinPool extends Abstra
1369		}
1370
1371		/**
1372	<	* Await resumption as spare
1372	>	* Awaits resumption as spare.
1373		*/
1374		void awaitSpareRelease() {
1375		while (thread != null) {
#	Line 1345 | Line 1383 | public class ForkJoinPool extends Abstra
1383		* Ensures that no thread is waiting for count to advance from the
1384		* current value of eventCount read on entry to this method, by
1385		* releasing waiting threads if necessary.
1386	+	*
1387		* @return the count
1388		*/
1389		final long ensureSync() {
#	Line 1366 | Line 1405 | public class ForkJoinPool extends Abstra
1405		*/
1406		private void signalIdleWorkers() {
1407		long c;
1408	<	do;while (!casEventCount(c = eventCount, c+1));
1408	>	do {} while (!casEventCount(c = eventCount, c+1));
1409		ensureSync();
1410		}
1411
1412		/**
1413	<	* Signal threads waiting to poll a task. Because method sync
1413	>	* Signals threads waiting to poll a task. Because method sync
1414		* rechecks availability, it is OK to only proceed if queue
1415		* appears to be non-empty, and OK to skip under contention to
1416		* increment count (since some other thread succeeded).
#	Line 1390 | Line 1429 | public class ForkJoinPool extends Abstra
1429		* Waits until event count advances from last value held by
1430		* caller, or if excess threads, caller is resumed as spare, or
1431		* caller or pool is terminating. Updates caller's event on exit.
1432	+	*
1433		* @param w the calling worker thread
1434		*/
1435		final void sync(ForkJoinWorkerThread w) {
#	Line 1420 | Line 1460 | public class ForkJoinPool extends Abstra
1460		* Returns 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
1463	>	*  - on interrupt
1464		*  - if the first queued node, we find work available
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
1469		*/
1470		final boolean syncIsReleasable(WaitQueueNode node) {
#	Line 1458 | Line 1499 | public class ForkJoinPool extends Abstra
1499		//  Parallelism maintenance
1500
1501		/**
1502	<	* Decrement running count; if too low, add spare.
1502	>	* Decrements running count; if too low, adds spare.
1503		*
1504		* Conceptually, all we need to do here is add or resume a
1505		* spare thread when one is about to block (and remove or
1506		* suspend it later when unblocked -- see suspendIfSpare).
1507		* However, implementing this idea requires coping with
1508	<	* several problems: We have imperfect information about the
1508	>	* several problems: we have imperfect information about the
1509		* states of threads. Some count updates can and usually do
1510		* lag run state changes, despite arrangements to keep them
1511		* accurate (for example, when possible, updating counts
#	Line 1478 | Line 1519 | public class ForkJoinPool extends Abstra
1519		* only be suspended or removed when they are idle, not
1520		* immediately when they aren't needed. So adding threads will
1521		* raise parallelism level for longer than necessary.  Also,
1522	<	* FJ applications often enounter highly transient peaks when
1522	>	* FJ applications often encounter highly transient peaks when
1523		* many threads are blocked joining, but for less time than it
1524		* takes to create or resume spares.
1525		*
#	Line 1487 | Line 1528 | public class ForkJoinPool extends Abstra
1528		* target counts, else create only to avoid starvation
1529		* @return true if joinMe known to be done
1530		*/
1531	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1531	>	final boolean preJoin(ForkJoinTask<?> joinMe,
1532	>	boolean maintainParallelism) {
1533		maintainParallelism &= maintainsParallelism; // overrride
1534		boolean dec = false;  // true when running count decremented
1535		while (spareStack == null || !tryResumeSpare(dec)) {
1536		int counts = workerCounts;
1537	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1537	>	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1538	>	// CAS cheat
1539		if (!needSpare(counts, maintainParallelism))
1540		break;
1541		if (joinMe.status < 0)
#	Line 1507 | Line 1550 | public class ForkJoinPool extends Abstra
1550		/**
1551		* Same idea as preJoin
1552		*/
1553	<	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1553	>	final boolean preBlock(ManagedBlocker blocker,
1554	>	boolean maintainParallelism) {
1555		maintainParallelism &= maintainsParallelism;
1556		boolean dec = false;
1557		while (spareStack == null || !tryResumeSpare(dec)) {
#	Line 1531 | Line 1575 | public class ForkJoinPool extends Abstra
1575		* there is apparently some work to do.  This self-limiting rule
1576		* means that the more threads that have already been added, the
1577		* less parallelism we will tolerate before adding another.
1578	+	*
1579		* @param counts current worker counts
1580		* @param maintainParallelism try to maintain parallelism
1581		*/
#	Line 1548 | Line 1593 | public class ForkJoinPool extends Abstra
1593		}
1594
1595		/**
1596	<	* Add a spare worker if lock available and no more than the
1597	<	* expected numbers of threads exist
1596	>	* Adds a spare worker if lock available and no more than the
1597	>	* expected numbers of threads exist.
1598	>	*
1599		* @return true if successful
1600		*/
1601		private boolean tryAddSpare(int expectedCounts) {
#	Line 1582 | Line 1628 | public class ForkJoinPool extends Abstra
1628		}
1629
1630		/**
1631	<	* Add the kth spare worker. On entry, pool coounts are already
1631	>	* Adds the kth spare worker. On entry, pool counts are already
1632		* adjusted to reflect addition.
1633		*/
1634		private void createAndStartSpare(int k) {
#	Line 1604 | Line 1650 | public class ForkJoinPool extends Abstra
1650		}
1651
1652		/**
1653	<	* Suspend calling thread w if there are excess threads.  Called
1654	<	* only from sync.  Spares are enqueued in a Treiber stack
1655	<	* using the same WaitQueueNodes as barriers.  They are resumed
1656	<	* mainly in preJoin, but are also woken on pool events that
1657	<	* require all threads to check run state.
1653	>	* Suspends calling thread w if there are excess threads.  Called
1654	>	* only from sync.  Spares are enqueued in a Treiber stack using
1655	>	* the same WaitQueueNodes as barriers.  They are resumed mainly
1656	>	* in preJoin, but are also woken on pool events that require all
1657	>	* threads to check run state.
1658	>	*
1659		* @param w the caller
1660		*/
1661		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
#	Line 1619 | Line 1666 | public class ForkJoinPool extends Abstra
1666		node = new WaitQueueNode(0, w);
1667		if (casWorkerCounts(s, s-1)) { // representation-dependent
1668		// push onto stack
1669	<	do;while (!casSpareStack(node.next = spareStack, node));
1669	>	do {} while (!casSpareStack(node.next = spareStack, node));
1670		// block until released by resumeSpare
1671		node.awaitSpareRelease();
1672		return true;
#	Line 1629 | Line 1676 | public class ForkJoinPool extends Abstra
1676		}
1677
1678		/**
1679	<	* Try to pop and resume a spare thread.
1679	>	* Tries to pop and resume a spare thread.
1680	>	*
1681		* @param updateCount if true, increment running count on success
1682		* @return true if successful
1683		*/
#	Line 1647 | Line 1695 | public class ForkJoinPool extends Abstra
1695		}
1696
1697		/**
1698	<	* Pop and resume all spare threads. Same idea as ensureSync.
1698	>	* Pops and resumes all spare threads. Same idea as ensureSync.
1699	>	*
1700		* @return true if any spares released
1701		*/
1702		private boolean resumeAllSpares() {
#	Line 1665 | Line 1714 | public class ForkJoinPool extends Abstra
1714		}
1715
1716		/**
1717	<	* Pop and shutdown excessive spare threads. Call only while
1717	>	* Pops and shuts down excessive spare threads. Call only while
1718		* holding lock. This is not guaranteed to eliminate all excess
1719		* threads, only those suspended as spares, which are the ones
1720		* unlikely to be needed in the future.
#	Line 1690 | Line 1739 | public class ForkJoinPool extends Abstra
1739		/**
1740		* Interface for extending managed parallelism for tasks running
1741		* in ForkJoinPools. A ManagedBlocker provides two methods.
1742	<	* Method <code>isReleasable</code> must return true if blocking is not
1743	<	* necessary. Method <code>block</code> blocks the current thread
1744	<	* if necessary (perhaps internally invoking isReleasable before
1745	<	* actually blocking.).
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.).
1746	>	*
1747		* <p>For example, here is a ManagedBlocker based on a
1748		* ReentrantLock:
1749	<	* <pre>
1750	<	*   class ManagedLocker implements ManagedBlocker {
1751	<	*     final ReentrantLock lock;
1752	<	*     boolean hasLock = false;
1753	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1754	<	*     public boolean block() {
1755	<	*        if (!hasLock)
1756	<	*           lock.lock();
1757	<	*        return true;
1708	<	*     }
1709	<	*     public boolean isReleasable() {
1710	<	*        return hasLock || (hasLock = lock.tryLock());
1711	<	*     }
1749	>	*  <pre> {@code
1750	>	* class ManagedLocker implements ManagedBlocker {
1751	>	*   final ReentrantLock lock;
1752	>	*   boolean hasLock = false;
1753	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1754	>	*   public boolean block() {
1755	>	*     if (!hasLock)
1756	>	*       lock.lock();
1757	>	*     return true;
1758		*   }
1759	<	* </pre>
1759	>	*   public boolean isReleasable() {
1760	>	*     return hasLock || (hasLock = lock.tryLock());
1761	>	*   }
1762	>	* }}</pre>
1763		*/
1764		public static interface ManagedBlocker {
1765		/**
1766		* Possibly blocks the current thread, for example waiting for
1767		* a lock or condition.
1768	+	*
1769		* @return true if no additional blocking is necessary (i.e.,
1770	<	* if isReleasable would return true).
1770	>	* if isReleasable would return true)
1771		* @throws InterruptedException if interrupted while waiting
1772	<	* (the method is not required to do so, but is allowe to).
1772	>	* (the method is not required to do so, but is allowed to)
1773		*/
1774		boolean block() throws InterruptedException;
1775
#	Line 1734 | Line 1784 | public class ForkJoinPool extends Abstra
1784		* is a ForkJoinWorkerThread, this method possibly arranges for a
1785		* spare thread to be activated if necessary to ensure parallelism
1786		* while the current thread is blocked.  If
1787	<	* <code>maintainParallelism</code> is true and the pool supports
1787	>	* {@code maintainParallelism} is true and the pool supports
1788		* it ({@link #getMaintainsParallelism}), this method attempts to
1789	<	* maintain the pool's nominal parallelism. Otherwise if activates
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.
1793		*
1794		* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1795		* equivalent to
1796	<	* <pre>
1797	<	*   while (!blocker.isReleasable())
1798	<	*      if (blocker.block())
1799	<	*         return;
1800	<	* </pre>
1796	>	*  <pre> {@code
1797	>	* while (!blocker.isReleasable())
1798	>	*   if (blocker.block())
1799	>	*     return;
1800	>	* }</pre>
1801		* If the caller is a ForkJoinTask, then the pool may first
1802		* be expanded to ensure parallelism, and later adjusted.
1803		*
#	Line 1756 | Line 1806 | public class ForkJoinPool extends Abstra
1806		* attempt to maintain the pool's nominal parallelism; otherwise
1807		* activate a thread only if necessary to avoid complete
1808		* starvation.
1809	<	* @throws InterruptedException if blocker.block did so.
1809	>	* @throws InterruptedException if blocker.block did so
1810		*/
1811		public static void managedBlock(ManagedBlocker blocker,
1812		boolean maintainParallelism)
1813		throws InterruptedException {
1814		Thread t = Thread.currentThread();
1815	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1816	<	((ForkJoinWorkerThread)t).pool : null);
1815	>	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1816	>	((ForkJoinWorkerThread) t).pool : null);
1817		if (!blocker.isReleasable()) {
1818		try {
1819		if (pool == null ||
#	Line 1778 | Line 1828 | public class ForkJoinPool extends Abstra
1828
1829		private static void awaitBlocker(ManagedBlocker blocker)
1830		throws InterruptedException {
1831	<	do;while (!blocker.isReleasable() && !blocker.block());
1831	>	do {} while (!blocker.isReleasable() && !blocker.block());
1832		}
1833
1834		// AbstractExecutorService overrides
#	Line 1818 | Line 1868 | public class ForkJoinPool extends Abstra
1868
1869		private static long fieldOffset(String fieldName)
1870		throws NoSuchFieldException {
1871	<	return _unsafe.objectFieldOffset
1871	>	return UNSAFE.objectFieldOffset
1872		(ForkJoinPool.class.getDeclaredField(fieldName));
1873		}
1874
1875	<	static final Unsafe _unsafe;
1875	>	static final Unsafe UNSAFE;
1876		static final long eventCountOffset;
1877		static final long workerCountsOffset;
1878		static final long runControlOffset;
#	Line 1831 | Line 1881 | public class ForkJoinPool extends Abstra
1881
1882		static {
1883		try {
1884	<	_unsafe = getUnsafe();
1884	>	UNSAFE = getUnsafe();
1885		eventCountOffset = fieldOffset("eventCount");
1886		workerCountsOffset = fieldOffset("workerCounts");
1887		runControlOffset = fieldOffset("runControl");
#	Line 1843 | Line 1893 | public class ForkJoinPool extends Abstra
1893		}
1894
1895		private boolean casEventCount(long cmp, long val) {
1896	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1896	>	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1897		}
1898		private boolean casWorkerCounts(int cmp, int val) {
1899	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1899	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1900		}
1901		private boolean casRunControl(int cmp, int val) {
1902	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1902	>	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1903		}
1904		private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1905	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1905	>	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1906		}
1907		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1908	<	return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val);
1908	>	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1909		}
1910		}

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