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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.9 by jsr166, Mon Jul 20 22:26:03 2009 UTC vs.
Revision 1.17 by jsr166, Thu Jul 23 23:07:57 2009 UTC

#	Line 56 | Line 56 | import java.lang.reflect.*;
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 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")},
345	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
346		*/
347		public ForkJoinPool() {
348		this(Runtime.getRuntime().availableProcessors(),
#	Line 342 | Line 351 | public class ForkJoinPool extends Abstra
351
352		/**
353		* Creates a ForkJoinPool with the indicated parallelism level
354	<	* threads, and using the default ForkJoinWorkerThreadFactory,
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")},
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")},
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")},
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 exclusion 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 639 | Line 655 | public class ForkJoinPool extends Abstra
655		for (Callable<T> c : tasks)
656		ts.add(new AdaptedCallable<T>(c));
657		invoke(new InvokeAll<T>(ts));
658	<	return (List<Future<T>>)(List)ts;
658	>	return (List<Future<T>>) (List) ts;
659		}
660
661		static final class InvokeAll<T> extends RecursiveAction {
662		final ArrayList<ForkJoinTask<T>> tasks;
663		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
664		public void compute() {
665	<	try { invokeAll(tasks); } catch(Exception ignore) {}
665	>	try { invokeAll(tasks); }
666	>	catch (Exception ignore) {}
667		}
668		}
669
670		// Configuration and status settings and queries
671
672		/**
673	<	* Returns the factory used for constructing new workers
673	>	* Returns the factory used for constructing new workers.
674		*
675		* @return the factory used for constructing new workers
676		*/
#	Line 664 | Line 681 | public class ForkJoinPool extends Abstra
681		/**
682		* Returns the handler for internal worker threads that terminate
683		* due to unrecoverable errors encountered while executing tasks.
684	+	*
685		* @return the handler, or null if none
686		*/
687		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
#	Line 689 | Line 707 | public class ForkJoinPool extends Abstra
707		* @throws SecurityException if a security manager exists and
708		*         the caller is not permitted to modify threads
709		*         because it does not hold {@link
710	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
710	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
711		*/
712		public Thread.UncaughtExceptionHandler
713		setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
#	Line 717 | Line 735 | public class ForkJoinPool extends Abstra
735
736		/**
737		* Sets the target parallelism level of this pool.
738	+	*
739		* @param parallelism the target parallelism
740		* @throws IllegalArgumentException if parallelism less than or
741	<	* equal to zero or greater than maximum size bounds.
741	>	* equal to zero or greater than maximum size bounds
742		* @throws SecurityException if a security manager exists and
743		*         the caller is not permitted to modify threads
744		*         because it does not hold {@link
745	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
745	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
746		*/
747		public void setParallelism(int parallelism) {
748		checkPermission();
#	Line 770 | Line 789 | public class ForkJoinPool extends Abstra
789		/**
790		* Returns the maximum number of threads allowed to exist in the
791		* pool, even if there are insufficient unblocked running threads.
792	+	*
793		* @return the maximum
794		*/
795		public int getMaximumPoolSize() {
#	Line 781 | Line 801 | public class ForkJoinPool extends Abstra
801		* pool, even if there are insufficient unblocked running threads.
802		* Setting this value has no effect on current pool size. It
803		* controls construction of new threads.
804	+	*
805		* @throws IllegalArgumentException if negative or greater then
806	<	* internal implementation limit.
806	>	* internal implementation limit
807		*/
808		public void setMaximumPoolSize(int newMax) {
809		if (newMax < 0 || newMax > MAX_THREADS)
#	Line 795 | Line 816 | public class ForkJoinPool extends Abstra
816		* Returns true if this pool dynamically maintains its target
817		* parallelism level. If false, new threads are added only to
818		* avoid possible starvation.
819	<	* This setting is by default true;
819	>	* This setting is by default true.
820	>	*
821		* @return true if maintains parallelism
822		*/
823		public boolean getMaintainsParallelism() {
#	Line 806 | Line 828 | public class ForkJoinPool extends Abstra
828		* Sets whether this pool dynamically maintains its target
829		* parallelism level. If false, new threads are added only to
830		* avoid possible starvation.
831	+	*
832		* @param enable true to maintains parallelism
833		*/
834		public void setMaintainsParallelism(boolean enable) {
#	Line 822 | Line 845 | public class ForkJoinPool extends Abstra
845		* invocations at other times may be unpredictable.
846		*
847		* @param async if true, use locally FIFO scheduling
848	<	* @return the previous mode.
848	>	* @return the previous mode
849		*/
850		public boolean setAsyncMode(boolean async) {
851		boolean oldMode = locallyFifo;
#	Line 842 | Line 865 | public class ForkJoinPool extends Abstra
865		* Returns true if this pool uses local first-in-first-out
866		* scheduling mode for forked tasks that are never joined.
867		*
868	<	* @return true if this pool uses async mode.
868	>	* @return true if this pool uses async mode
869		*/
870		public boolean getAsyncMode() {
871		return locallyFifo;
#	Line 863 | Line 886 | public class ForkJoinPool extends Abstra
886		* Returns an estimate of the number of threads that are currently
887		* stealing or executing tasks. This method may overestimate the
888		* number of active threads.
889	<	* @return the number of active threads.
889	>	*
890	>	* @return the number of active threads
891		*/
892		public int getActiveThreadCount() {
893		return activeCountOf(runControl);
#	Line 873 | Line 897 | public class ForkJoinPool extends Abstra
897		* Returns an estimate of the number of threads that are currently
898		* idle waiting for tasks. This method may underestimate the
899		* number of idle threads.
900	<	* @return the number of idle threads.
900	>	*
901	>	* @return the number of idle threads
902		*/
903		final int getIdleThreadCount() {
904		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
905	<	return (c <= 0)? 0 : c;
905	>	return (c <= 0) ? 0 : c;
906		}
907
908		/**
909		* Returns true if all worker threads are currently idle. An idle
910		* worker is one that cannot obtain a task to execute because none
911		* are available to steal from other threads, and there are no
912	<	* pending submissions to the pool. This method is conservative:
913	<	* It might not return true immediately upon idleness of all
912	>	* pending submissions to the pool. This method is conservative;
913	>	* it might not return true immediately upon idleness of all
914		* threads, but will eventually become true if threads remain
915		* inactive.
916	+	*
917		* @return true if all threads are currently idle
918		*/
919		public boolean isQuiescent() {
#	Line 899 | Line 925 | public class ForkJoinPool extends Abstra
925		* one thread's work queue by another. The reported value
926		* underestimates the actual total number of steals when the pool
927		* is not quiescent. This value may be useful for monitoring and
928	<	* tuning fork/join programs: In general, steal counts should be
928	>	* tuning fork/join programs: in general, steal counts should be
929		* high enough to keep threads busy, but low enough to avoid
930		* overhead and contention across threads.
931	<	* @return the number of steals.
931	>	*
932	>	* @return the number of steals
933		*/
934		public long getStealCount() {
935		return stealCount.get();
936		}
937
938		/**
939	<	* Accumulate steal count from a worker. Call only
940	<	* when worker known to be idle.
939	>	* Accumulates steal count from a worker.
940	>	* Call only when worker known to be idle.
941		*/
942		private void updateStealCount(ForkJoinWorkerThread w) {
943		int sc = w.getAndClearStealCount();
#	Line 925 | Line 952 | public class ForkJoinPool extends Abstra
952		* an approximation, obtained by iterating across all threads in
953		* the pool. This method may be useful for tuning task
954		* granularities.
955	<	* @return the number of queued tasks.
955	>	*
956	>	* @return the number of queued tasks
957		*/
958		public long getQueuedTaskCount() {
959		long count = 0;
#	Line 944 | Line 972 | public class ForkJoinPool extends Abstra
972		* Returns an estimate of the number tasks submitted to this pool
973		* that have not yet begun executing. This method takes time
974		* proportional to the number of submissions.
975	<	* @return the number of queued submissions.
975	>	*
976	>	* @return the number of queued submissions
977		*/
978		public int getQueuedSubmissionCount() {
979		return submissionQueue.size();
#	Line 953 | Line 982 | public class ForkJoinPool extends Abstra
982		/**
983		* Returns true if there are any tasks submitted to this pool
984		* that have not yet begun executing.
985	<	* @return {@code true} if there are any queued submissions.
985	>	*
986	>	* @return {@code true} if there are any queued submissions
987		*/
988		public boolean hasQueuedSubmissions() {
989		return !submissionQueue.isEmpty();
#	Line 963 | Line 993 | public class ForkJoinPool extends Abstra
993		* Removes and returns the next unexecuted submission if one is
994		* available.  This method may be useful in extensions to this
995		* class that re-assign work in systems with multiple pools.
996	+	*
997		* @return the next submission, or null if none
998		*/
999		protected ForkJoinTask<?> pollSubmission() {
#	Line 982 | Line 1013 | public class ForkJoinPool extends Abstra
1013		* exception is thrown.  The behavior of this operation is
1014		* undefined if the specified collection is modified while the
1015		* operation is in progress.
1016	+	*
1017		* @param c the collection to transfer elements into
1018		* @return the number of elements transferred
1019		*/
#	Line 1042 | Line 1074 | public class ForkJoinPool extends Abstra
1074		* Invocation has no additional effect if already shut down.
1075		* Tasks that are in the process of being submitted concurrently
1076		* during the course of this method may or may not be rejected.
1077	+	*
1078		* @throws SecurityException if a security manager exists and
1079		*         the caller is not permitted to modify threads
1080		*         because it does not hold {@link
1081	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1081	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1082		*/
1083		public void shutdown() {
1084		checkPermission();
#	Line 1063 | Line 1096 | public class ForkJoinPool extends Abstra
1096		* upon termination, so always returns an empty list. However, you
1097		* can use method {@code drainTasksTo} before invoking this
1098		* method to transfer unexecuted tasks to another collection.
1099	+	*
1100		* @return an empty list
1101		* @throws SecurityException if a security manager exists and
1102		*         the caller is not permitted to modify threads
1103		*         because it does not hold {@link
1104	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1104	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1105		*/
1106		public List<Runnable> shutdownNow() {
1107		checkPermission();
#	Line 1135 | Line 1169 | public class ForkJoinPool extends Abstra
1169		// Shutdown and termination support
1170
1171		/**
1172	<	* Callback from terminating worker. Null out the corresponding
1173	<	* workers slot, and if terminating, try to terminate, else try to
1174	<	* shrink workers array.
1172	>	* Callback from terminating worker. Nulls out the corresponding
1173	>	* workers slot, and if terminating, tries to terminate; else
1174	>	* tries to shrink workers array.
1175	>	*
1176		* @param w the worker
1177		*/
1178		final void workerTerminated(ForkJoinWorkerThread w) {
#	Line 1168 | Line 1203 | public class ForkJoinPool extends Abstra
1203		}
1204
1205		/**
1206	<	* Initiate termination.
1206	>	* Initiates termination.
1207		*/
1208		private void terminate() {
1209		if (transitionRunStateTo(TERMINATING)) {
#	Line 1183 | Line 1218 | public class ForkJoinPool extends Abstra
1218		}
1219
1220		/**
1221	<	* Possibly terminate when on shutdown state
1221	>	* Possibly terminates when on shutdown state.
1222		*/
1223		private void terminateOnShutdown() {
1224		if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
#	Line 1191 | Line 1226 | public class ForkJoinPool extends Abstra
1226		}
1227
1228		/**
1229	<	* Clear out and cancel submissions
1229	>	* Clears out and cancels submissions.
1230		*/
1231		private void cancelQueuedSubmissions() {
1232		ForkJoinTask<?> task;
#	Line 1200 | Line 1235 | public class ForkJoinPool extends Abstra
1235		}
1236
1237		/**
1238	<	* Clean out worker queues.
1238	>	* Cleans out worker queues.
1239		*/
1240		private void cancelQueuedWorkerTasks() {
1241		final ReentrantLock lock = this.workerLock;
#	Line 1220 | Line 1255 | public class ForkJoinPool extends Abstra
1255		}
1256
1257		/**
1258	<	* Set each worker's status to terminating. Requires lock to avoid
1259	<	* conflicts with add/remove
1258	>	* Sets each worker's status to terminating. Requires lock to avoid
1259	>	* conflicts with add/remove.
1260		*/
1261		private void stopAllWorkers() {
1262		final ReentrantLock lock = this.workerLock;
#	Line 1241 | Line 1276 | public class ForkJoinPool extends Abstra
1276		}
1277
1278		/**
1279	<	* Interrupt all unterminated workers.  This is not required for
1279	>	* Interrupts all unterminated workers.  This is not required for
1280		* sake of internal control, but may help unstick user code during
1281		* shutdown.
1282		*/
#	Line 1311 | Line 1346 | public class ForkJoinPool extends Abstra
1346		}
1347
1348		/**
1349	<	* Wake up waiter, returning false if known to already
1349	>	* Wakes up waiter, returning false if known to already
1350		*/
1351		boolean signal() {
1352		ForkJoinWorkerThread t = thread;
#	Line 1323 | Line 1358 | public class ForkJoinPool extends Abstra
1358		}
1359
1360		/**
1361	<	* Await release on sync
1361	>	* Awaits release on sync.
1362		*/
1363		void awaitSyncRelease(ForkJoinPool p) {
1364		while (thread != null && !p.syncIsReleasable(this))
#	Line 1331 | Line 1366 | public class ForkJoinPool extends Abstra
1366		}
1367
1368		/**
1369	<	* Await resumption as spare
1369	>	* Awaits resumption as spare.
1370		*/
1371		void awaitSpareRelease() {
1372		while (thread != null) {
#	Line 1345 | Line 1380 | public class ForkJoinPool extends Abstra
1380		* Ensures that no thread is waiting for count to advance from the
1381		* current value of eventCount read on entry to this method, by
1382		* releasing waiting threads if necessary.
1383	+	*
1384		* @return the count
1385		*/
1386		final long ensureSync() {
#	Line 1366 | Line 1402 | public class ForkJoinPool extends Abstra
1402		*/
1403		private void signalIdleWorkers() {
1404		long c;
1405	<	do;while (!casEventCount(c = eventCount, c+1));
1405	>	do {} while (!casEventCount(c = eventCount, c+1));
1406		ensureSync();
1407		}
1408
1409		/**
1410	<	* Signal threads waiting to poll a task. Because method sync
1410	>	* Signals threads waiting to poll a task. Because method sync
1411		* rechecks availability, it is OK to only proceed if queue
1412		* appears to be non-empty, and OK to skip under contention to
1413		* increment count (since some other thread succeeded).
#	Line 1390 | Line 1426 | public class ForkJoinPool extends Abstra
1426		* Waits until event count advances from last value held by
1427		* caller, or if excess threads, caller is resumed as spare, or
1428		* caller or pool is terminating. Updates caller's event on exit.
1429	+	*
1430		* @param w the calling worker thread
1431		*/
1432		final void sync(ForkJoinWorkerThread w) {
#	Line 1420 | Line 1457 | public class ForkJoinPool extends Abstra
1457		* Returns true if worker waiting on sync can proceed:
1458		*  - on signal (thread == null)
1459		*  - on event count advance (winning race to notify vs signaller)
1460	<	*  - on Interrupt
1460	>	*  - on interrupt
1461		*  - if the first queued node, we find work available
1462		* If node was not signalled and event count not advanced on exit,
1463		* then we also help advance event count.
1464	+	*
1465		* @return true if node can be released
1466		*/
1467		final boolean syncIsReleasable(WaitQueueNode node) {
#	Line 1458 | Line 1496 | public class ForkJoinPool extends Abstra
1496		//  Parallelism maintenance
1497
1498		/**
1499	<	* Decrement running count; if too low, add spare.
1499	>	* Decrements running count; if too low, adds spare.
1500		*
1501		* Conceptually, all we need to do here is add or resume a
1502		* spare thread when one is about to block (and remove or
1503		* suspend it later when unblocked -- see suspendIfSpare).
1504		* However, implementing this idea requires coping with
1505	<	* several problems: We have imperfect information about the
1505	>	* several problems: we have imperfect information about the
1506		* states of threads. Some count updates can and usually do
1507		* lag run state changes, despite arrangements to keep them
1508		* accurate (for example, when possible, updating counts
#	Line 1487 | Line 1525 | public class ForkJoinPool extends Abstra
1525		* target counts, else create only to avoid starvation
1526		* @return true if joinMe known to be done
1527		*/
1528	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1528	>	final boolean preJoin(ForkJoinTask<?> joinMe,
1529	>	boolean maintainParallelism) {
1530		maintainParallelism &= maintainsParallelism; // overrride
1531		boolean dec = false;  // true when running count decremented
1532		while (spareStack == null || !tryResumeSpare(dec)) {
1533		int counts = workerCounts;
1534	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1534	>	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1535	>	// CAS cheat
1536		if (!needSpare(counts, maintainParallelism))
1537		break;
1538		if (joinMe.status < 0)
#	Line 1507 | Line 1547 | public class ForkJoinPool extends Abstra
1547		/**
1548		* Same idea as preJoin
1549		*/
1550	<	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1550	>	final boolean preBlock(ManagedBlocker blocker,
1551	>	boolean maintainParallelism) {
1552		maintainParallelism &= maintainsParallelism;
1553		boolean dec = false;
1554		while (spareStack == null || !tryResumeSpare(dec)) {
#	Line 1531 | Line 1572 | public class ForkJoinPool extends Abstra
1572		* there is apparently some work to do.  This self-limiting rule
1573		* means that the more threads that have already been added, the
1574		* less parallelism we will tolerate before adding another.
1575	+	*
1576		* @param counts current worker counts
1577		* @param maintainParallelism try to maintain parallelism
1578		*/
#	Line 1548 | Line 1590 | public class ForkJoinPool extends Abstra
1590		}
1591
1592		/**
1593	<	* Add a spare worker if lock available and no more than the
1594	<	* expected numbers of threads exist
1593	>	* Adds a spare worker if lock available and no more than the
1594	>	* expected numbers of threads exist.
1595	>	*
1596		* @return true if successful
1597		*/
1598		private boolean tryAddSpare(int expectedCounts) {
#	Line 1582 | Line 1625 | public class ForkJoinPool extends Abstra
1625		}
1626
1627		/**
1628	<	* Add the kth spare worker. On entry, pool counts are already
1628	>	* Adds the kth spare worker. On entry, pool counts are already
1629		* adjusted to reflect addition.
1630		*/
1631		private void createAndStartSpare(int k) {
#	Line 1604 | Line 1647 | public class ForkJoinPool extends Abstra
1647		}
1648
1649		/**
1650	<	* Suspend calling thread w if there are excess threads.  Called
1651	<	* only from sync.  Spares are enqueued in a Treiber stack
1652	<	* using the same WaitQueueNodes as barriers.  They are resumed
1653	<	* mainly in preJoin, but are also woken on pool events that
1654	<	* require all threads to check run state.
1650	>	* Suspends calling thread w if there are excess threads.  Called
1651	>	* only from sync.  Spares are enqueued in a Treiber stack using
1652	>	* the same WaitQueueNodes as barriers.  They are resumed mainly
1653	>	* in preJoin, but are also woken on pool events that require all
1654	>	* threads to check run state.
1655	>	*
1656		* @param w the caller
1657		*/
1658		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
#	Line 1619 | Line 1663 | public class ForkJoinPool extends Abstra
1663		node = new WaitQueueNode(0, w);
1664		if (casWorkerCounts(s, s-1)) { // representation-dependent
1665		// push onto stack
1666	<	do;while (!casSpareStack(node.next = spareStack, node));
1666	>	do {} while (!casSpareStack(node.next = spareStack, node));
1667		// block until released by resumeSpare
1668		node.awaitSpareRelease();
1669		return true;
#	Line 1629 | Line 1673 | public class ForkJoinPool extends Abstra
1673		}
1674
1675		/**
1676	<	* Try to pop and resume a spare thread.
1676	>	* Tries to pop and resume a spare thread.
1677	>	*
1678		* @param updateCount if true, increment running count on success
1679		* @return true if successful
1680		*/
#	Line 1647 | Line 1692 | public class ForkJoinPool extends Abstra
1692		}
1693
1694		/**
1695	<	* Pop and resume all spare threads. Same idea as ensureSync.
1695	>	* Pops and resumes all spare threads. Same idea as ensureSync.
1696	>	*
1697		* @return true if any spares released
1698		*/
1699		private boolean resumeAllSpares() {
#	Line 1665 | Line 1711 | public class ForkJoinPool extends Abstra
1711		}
1712
1713		/**
1714	<	* Pop and shutdown excessive spare threads. Call only while
1714	>	* Pops and shuts down excessive spare threads. Call only while
1715		* holding lock. This is not guaranteed to eliminate all excess
1716		* threads, only those suspended as spares, which are the ones
1717		* unlikely to be needed in the future.
#	Line 1691 | Line 1737 | public class ForkJoinPool extends Abstra
1737		* Interface for extending managed parallelism for tasks running
1738		* in ForkJoinPools. A ManagedBlocker provides two methods.
1739		* Method {@code isReleasable} must return true if blocking is not
1740	<	* necessary. Method {@code block} blocks the current thread
1741	<	* if necessary (perhaps internally invoking isReleasable before
1742	<	* actually blocking.).
1740	>	* necessary. Method {@code block} blocks the current thread if
1741	>	* necessary (perhaps internally invoking {@code isReleasable}
1742	>	* before actually blocking.).
1743	>	*
1744		* <p>For example, here is a ManagedBlocker based on a
1745		* ReentrantLock:
1746	<	* <pre>
1747	<	*   class ManagedLocker implements ManagedBlocker {
1748	<	*     final ReentrantLock lock;
1749	<	*     boolean hasLock = false;
1750	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1751	<	*     public boolean block() {
1752	<	*        if (!hasLock)
1753	<	*           lock.lock();
1754	<	*        return true;
1708	<	*     }
1709	<	*     public boolean isReleasable() {
1710	<	*        return hasLock || (hasLock = lock.tryLock());
1711	<	*     }
1746	>	*  <pre> {@code
1747	>	* class ManagedLocker implements ManagedBlocker {
1748	>	*   final ReentrantLock lock;
1749	>	*   boolean hasLock = false;
1750	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1751	>	*   public boolean block() {
1752	>	*     if (!hasLock)
1753	>	*       lock.lock();
1754	>	*     return true;
1755		*   }
1756	<	* </pre>
1756	>	*   public boolean isReleasable() {
1757	>	*     return hasLock || (hasLock = lock.tryLock());
1758	>	*   }
1759	>	* }}</pre>
1760		*/
1761		public static interface ManagedBlocker {
1762		/**
1763		* Possibly blocks the current thread, for example waiting for
1764		* a lock or condition.
1765	+	*
1766		* @return true if no additional blocking is necessary (i.e.,
1767	<	* if isReleasable would return true).
1767	>	* if isReleasable would return true)
1768		* @throws InterruptedException if interrupted while waiting
1769	<	* (the method is not required to do so, but is allowed to).
1769	>	* (the method is not required to do so, but is allowed to)
1770		*/
1771		boolean block() throws InterruptedException;
1772
#	Line 1736 | Line 1783 | public class ForkJoinPool extends Abstra
1783		* while the current thread is blocked.  If
1784		* {@code maintainParallelism} is true and the pool supports
1785		* it ({@link #getMaintainsParallelism}), this method attempts to
1786	<	* maintain the pool's nominal parallelism. Otherwise if activates
1786	>	* maintain the pool's nominal parallelism. Otherwise it activates
1787		* a thread only if necessary to avoid complete starvation. This
1788		* option may be preferable when blockages use timeouts, or are
1789		* almost always brief.
1790		*
1791		* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1792		* equivalent to
1793	<	* <pre>
1794	<	*   while (!blocker.isReleasable())
1795	<	*      if (blocker.block())
1796	<	*         return;
1797	<	* </pre>
1793	>	*  <pre> {@code
1794	>	* while (!blocker.isReleasable())
1795	>	*   if (blocker.block())
1796	>	*     return;
1797	>	* }</pre>
1798		* If the caller is a ForkJoinTask, then the pool may first
1799		* be expanded to ensure parallelism, and later adjusted.
1800		*
#	Line 1756 | Line 1803 | public class ForkJoinPool extends Abstra
1803		* attempt to maintain the pool's nominal parallelism; otherwise
1804		* activate a thread only if necessary to avoid complete
1805		* starvation.
1806	<	* @throws InterruptedException if blocker.block did so.
1806	>	* @throws InterruptedException if blocker.block did so
1807		*/
1808		public static void managedBlock(ManagedBlocker blocker,
1809		boolean maintainParallelism)
1810		throws InterruptedException {
1811		Thread t = Thread.currentThread();
1812	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1813	<	((ForkJoinWorkerThread)t).pool : null);
1812	>	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1813	>	((ForkJoinWorkerThread) t).pool : null);
1814		if (!blocker.isReleasable()) {
1815		try {
1816		if (pool == null ||
#	Line 1778 | Line 1825 | public class ForkJoinPool extends Abstra
1825
1826		private static void awaitBlocker(ManagedBlocker blocker)
1827		throws InterruptedException {
1828	<	do;while (!blocker.isReleasable() && !blocker.block());
1828	>	do {} while (!blocker.isReleasable() && !blocker.block());
1829		}
1830
1831		// AbstractExecutorService overrides
#	Line 1818 | Line 1865 | public class ForkJoinPool extends Abstra
1865
1866		private static long fieldOffset(String fieldName)
1867		throws NoSuchFieldException {
1868	<	return _unsafe.objectFieldOffset
1868	>	return UNSAFE.objectFieldOffset
1869		(ForkJoinPool.class.getDeclaredField(fieldName));
1870		}
1871
1872	<	static final Unsafe _unsafe;
1872	>	static final Unsafe UNSAFE;
1873		static final long eventCountOffset;
1874		static final long workerCountsOffset;
1875		static final long runControlOffset;
#	Line 1831 | Line 1878 | public class ForkJoinPool extends Abstra
1878
1879		static {
1880		try {
1881	<	_unsafe = getUnsafe();
1881	>	UNSAFE = getUnsafe();
1882		eventCountOffset = fieldOffset("eventCount");
1883		workerCountsOffset = fieldOffset("workerCounts");
1884		runControlOffset = fieldOffset("runControl");
#	Line 1843 | Line 1890 | public class ForkJoinPool extends Abstra
1890		}
1891
1892		private boolean casEventCount(long cmp, long val) {
1893	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1893	>	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1894		}
1895		private boolean casWorkerCounts(int cmp, int val) {
1896	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1896	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1897		}
1898		private boolean casRunControl(int cmp, int val) {
1899	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1899	>	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1900		}
1901		private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1902	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1902	>	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1903		}
1904		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1905	<	return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val);
1905	>	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1906		}
1907		}

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