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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.1 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.16 by jsr166, Thu Jul 23 19:44:46 2009 UTC

#	Line 13 | Line 13 | import sun.misc.Unsafe;
13		import java.lang.reflect.*;
14
15		/**
16	<	* Host for a group of ForkJoinWorkerThreads.  A ForkJoinPool provides
17	<	* the entry point for tasks submitted from non-ForkJoinTasks, as well
18	<	* as management and monitoring operations.  Normally a single
19	<	* ForkJoinPool is used for a large number of submitted
20	<	* tasks. Otherwise, use would not usually outweigh the construction
21	<	* and bookkeeping overhead of creating a large set of threads.
16	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.  A
17	>	* ForkJoinPool provides the entry point for submissions from
18	>	* non-ForkJoinTasks, as well as management and monitoring operations.
19	>	* Normally a single ForkJoinPool is used for a large number of
20	>	* submitted tasks. Otherwise, use would not usually outweigh the
21	>	* construction and bookkeeping overhead of creating a large set of
22	>	* threads.
23		*
24	<	* <p>ForkJoinPools differ from other kinds of Executor mainly in that
25	<	* they provide <em>work-stealing</em>: all threads in the pool
24	>	* <p>ForkJoinPools differ from other kinds of Executors mainly in
25	>	* that they provide <em>work-stealing</em>: all threads in the pool
26		* attempt to find and execute subtasks created by other active tasks
27		* (eventually blocking if none exist). This makes them efficient when
28	<	* most tasks spawn other subtasks (as do most ForkJoinTasks) but
29	<	* possibly less so otherwise. It is however fine to combine execution
30	<	* of some plain Runnable- or Callable- based activities with that of
31	<	* ForkJoinTasks.
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	>	* {@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.
35		*
36		* <p>A ForkJoinPool may be constructed with a given parallelism level
37		* (target pool size), which it attempts to maintain by dynamically
38	<	* adding, suspending, or resuming threads, even if some tasks have
39	<	* blocked waiting to join others. However, no such adjustments are
40	<	* performed in the face of blocked IO or other unmanaged
41	<	* synchronization. The nested ManagedBlocker interface enables
42	<	* extension of the kinds of synchronization accommodated.
43	<	*
44	<	* <p>The target parallelism level may also be set dynamically. You
45	<	* can limit the number of threads dynamically constructed using
46	<	* method <tt>setMaximumPoolSize</tt> and/or
43	<	* <tt>setMaintainParallelism</tt>.
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} interface enables extension of
42	>	* the kinds of synchronization accommodated.  The target parallelism
43	>	* level may also be changed dynamically ({@code setParallelism})
44	>	* and thread construction can be limited using methods
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	<	* <tt>getStealCount</tt>) 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	<	* <tt>toString</tt> returns indications of pool state in a convenient
53	<	* form for informal monitoring.
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 parallelism to 32767. Attempts to create pools with greater
57	<	* than the maximum result in IllegalArgumentExceptions.
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
57	<	implements ExecutorService {
63	>	public class ForkJoinPool extends AbstractExecutorService {
64
65		/*
66		* See the extended comments interspersed below for design,
#	Line 78 | 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		}
#	Line 87 | Line 93 | public class ForkJoinPool extends Abstra
93		* Default ForkJoinWorkerThreadFactory implementation, creates a
94		* new ForkJoinWorkerThread.
95		*/
96	<	public static class  DefaultForkJoinWorkerThreadFactory
96	>	static class  DefaultForkJoinWorkerThreadFactory
97		implements ForkJoinWorkerThreadFactory {
98		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
99		try {
#	Line 99 | Line 105 | public class ForkJoinPool extends Abstra
105		}
106
107		/**
108	<	* The default ForkJoinWorkerThreadFactory, used unless overridden
109	<	* in ForkJoinPool constructors.
108	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
109	>	* overridden in ForkJoinPool constructors.
110		*/
111	<	private static final DefaultForkJoinWorkerThreadFactory
111	>	public static final ForkJoinWorkerThreadFactory
112		defaultForkJoinWorkerThreadFactory =
113		new DefaultForkJoinWorkerThreadFactory();
114
109	–
115		/**
116		* Permission required for callers of methods that may start or
117		* kill threads.
#	Line 131 | Line 136 | public class ForkJoinPool extends Abstra
136		new AtomicInteger();
137
138		/**
139	<	* Array holding all worker threads in the pool. Array size must
140	<	* be a power of two.  Updates and replacements are protected by
141	<	* workerLock, but it is always kept in a consistent enough state
142	<	* to be randomly accessed without locking by workers performing
143	<	* work-stealing.
139	>	* Array holding all worker threads in the pool. Initialized upon
140	>	* first use. Array size must be a power of two.  Updates and
141	>	* replacements are protected by workerLock, but it is always kept
142	>	* in a consistent enough state to be randomly accessed without
143	>	* locking by workers performing work-stealing.
144		*/
145		volatile ForkJoinWorkerThread[] workers;
146
#	Line 151 | 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 186 | public class ForkJoinPool extends Abstra
186		/**
187		* Head of Treiber stack for barrier sync. See below for explanation
188		*/
189	<	private volatile WaitQueueNode barrierStack;
189	>	private volatile WaitQueueNode syncStack;
190
191		/**
192		* The count for event barrier
#	Line 204 | Line 209 | public class ForkJoinPool extends Abstra
209		private volatile int parallelism;
210
211		/**
212	+	* True if use local fifo, not default lifo, for local polling
213	+	*/
214	+	private volatile boolean locallyFifo;
215	+
216	+	/**
217		* Holds number of total (i.e., created and not yet terminated)
218		* and running (i.e., not blocked on joins or other managed sync)
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 219 | 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		* @param delta the number to add
236		*/
237		final void updateRunningCount(int delta) {
#	Line 230 | Line 240 | public class ForkJoinPool extends Abstra
240		}
241
242		/**
243	<	* Add delta (which may be negative) to both total and running
243	>	* Adds delta (which may be negative) to both total and running
244		* count.  This must be called upon creation and termination of
245		* worker threads.
246		* @param delta the number to add
#	Line 264 | Line 274 | public class ForkJoinPool extends Abstra
274		private static int runControlFor(int r, int a)   { return (r << 16) + a; }
275
276		/**
277	<	* Increment active count. Called by workers before/during
278	<	* executing tasks.
277	>	* Try incrementing active count; fail on contention. Called by
278	>	* workers before/during executing tasks.
279	>	* @return true on success
280		*/
281	<	final void incrementActiveCount() {
282	<	int c;
283	<	do;while (!casRunControl(c = runControl, c+1));
281	>	final boolean tryIncrementActiveCount() {
282	>	int c = runControl;
283	>	return casRunControl(c, c+1);
284		}
285
286		/**
287	<	* Decrement active count; possibly trigger termination.
287	>	* Tries decrementing active count; fails on contention.
288	>	* Possibly triggers termination on success.
289		* Called by workers when they can't find tasks.
290	+	* @return true on success
291		*/
292	<	final void decrementActiveCount() {
293	<	int c, nextc;
294	<	do;while (!casRunControl(c = runControl, nextc = c-1));
292	>	final boolean tryDecrementActiveCount() {
293	>	int c = runControl;
294	>	int nextc = c - 1;
295	>	if (!casRunControl(c, nextc))
296	>	return false;
297		if (canTerminateOnShutdown(nextc))
298		terminateOnShutdown();
299	+	return true;
300		}
301
302		/**
303	<	* Return true if argument represents zero active count and
303	>	* Returns true if argument represents zero active count and
304		* nonzero runstate, which is the triggering condition for
305		* terminating on shutdown.
306		*/
#	Line 320 | Line 336 | public class ForkJoinPool extends Abstra
336		* @throws SecurityException if a security manager exists and
337		*         the caller is not permitted to modify threads
338		*         because it does not hold {@link
339	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
339	>	*         java.lang.RuntimePermission}{@code ("modifyThread")},
340		*/
341		public ForkJoinPool() {
342		this(Runtime.getRuntime().availableProcessors(),
#	Line 328 | Line 344 | public class ForkJoinPool extends Abstra
344		}
345
346		/**
347	<	* Creates a ForkJoinPool with the indicated parellelism level
347	>	* Creates a ForkJoinPool with the indicated parallelism level
348		* threads, and using the default ForkJoinWorkerThreadFactory,
349		* @param parallelism the number of worker threads
350		* @throws IllegalArgumentException if parallelism less than or
#	Line 336 | Line 352 | public class ForkJoinPool extends Abstra
352		* @throws SecurityException if a security manager exists and
353		*         the caller is not permitted to modify threads
354		*         because it does not hold {@link
355	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
355	>	*         java.lang.RuntimePermission}{@code ("modifyThread")},
356		*/
357		public ForkJoinPool(int parallelism) {
358		this(parallelism, defaultForkJoinWorkerThreadFactory);
359		}
360
361		/**
362	<	* Creates a ForkJoinPool with a pool size equal to the number of
362	>	* Creates a ForkJoinPool with parallelism equal to the number of
363		* processors available on the system and using the given
364		* ForkJoinWorkerThreadFactory,
365		* @param factory the factory for creating new threads
#	Line 351 | Line 367 | public class ForkJoinPool extends Abstra
367		* @throws SecurityException if a security manager exists and
368		*         the caller is not permitted to modify threads
369		*         because it does not hold {@link
370	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
370	>	*         java.lang.RuntimePermission}{@code ("modifyThread")},
371		*/
372		public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
373		this(Runtime.getRuntime().availableProcessors(), factory);
374		}
375
376		/**
377	<	* Creates a ForkJoinPool with the indicated target number of
362	<	* worker threads and the given factory.
377	>	* Creates a ForkJoinPool with the given parallelism and factory.
378		*
379		* @param parallelism the targeted number of worker threads
380		* @param factory the factory for creating new threads
381		* @throws IllegalArgumentException if parallelism less than or
382	<	* equal to zero, or greater than implementation limit.
382	>	* equal to zero, or greater than implementation limit
383		* @throws NullPointerException if factory is null
384		* @throws SecurityException if a security manager exists and
385		*         the caller is not permitted to modify threads
386		*         because it does not hold {@link
387	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
387	>	*         java.lang.RuntimePermission}{@code ("modifyThread")},
388		*/
389		public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
390		if (parallelism <= 0 || parallelism > MAX_THREADS)
#	Line 386 | Line 401 | public class ForkJoinPool extends Abstra
401		this.termination = workerLock.newCondition();
402		this.stealCount = new AtomicLong();
403		this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
404	<	createAndStartInitialWorkers(parallelism);
404	>	// worker array and workers are lazily constructed
405		}
406
407		/**
#	Line 400 | Line 415 | public class ForkJoinPool extends Abstra
415		if (w != null) {
416		w.poolIndex = index;
417		w.setDaemon(true);
418	+	w.setAsyncMode(locallyFifo);
419		w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
420		if (h != null)
421		w.setUncaughtExceptionHandler(h);
#	Line 408 | Line 424 | public class ForkJoinPool extends Abstra
424		}
425
426		/**
427	<	* Return a good size for worker array given pool size.
427	>	* Returns a good size for worker array given pool size.
428		* Currently requires size to be a power of two.
429		*/
430		private static int arraySizeFor(int ps) {
#	Line 416 | Line 432 | public class ForkJoinPool extends Abstra
432		}
433
434		/**
435	<	* Create or resize array if necessary to hold newLength
435	>	* Creates or resizes array if necessary to hold newLength.
436	>	* Call only under exclusion.
437	>	*
438		* @return the array
439		*/
440		private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
#	Line 434 | Line 452 | public class ForkJoinPool extends Abstra
452		*/
453		private void tryShrinkWorkerArray() {
454		ForkJoinWorkerThread[] ws = workers;
455	<	int len = ws.length;
456	<	int last = len - 1;
457	<	while (last >= 0 && ws[last] == null)
458	<	--last;
459	<	int newLength = arraySizeFor(last+1);
460	<	if (newLength < len)
461	<	workers = Arrays.copyOf(ws, newLength);
455	>	if (ws != null) {
456	>	int len = ws.length;
457	>	int last = len - 1;
458	>	while (last >= 0 && ws[last] == null)
459	>	--last;
460	>	int newLength = arraySizeFor(last+1);
461	>	if (newLength < len)
462	>	workers = Arrays.copyOf(ws, newLength);
463	>	}
464		}
465
466		/**
467	<	* Initial worker array and worker creation and startup. (This
448	<	* must be done under lock to avoid interference by some of the
449	<	* newly started threads while creating others.)
467	>	* Initialize workers if necessary
468		*/
469	<	private void createAndStartInitialWorkers(int ps) {
470	<	final ReentrantLock lock = this.workerLock;
471	<	lock.lock();
472	<	try {
473	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
474	<	for (int i = 0; i < ps; ++i) {
475	<	ForkJoinWorkerThread w = createWorker(i);
476	<	if (w != null) {
477	<	ws[i] = w;
478	<	w.start();
479	<	updateWorkerCount(1);
469	>	final void ensureWorkerInitialization() {
470	>	ForkJoinWorkerThread[] ws = workers;
471	>	if (ws == null) {
472	>	final ReentrantLock lock = this.workerLock;
473	>	lock.lock();
474	>	try {
475	>	ws = workers;
476	>	if (ws == null) {
477	>	int ps = parallelism;
478	>	ws = ensureWorkerArrayCapacity(ps);
479	>	for (int i = 0; i < ps; ++i) {
480	>	ForkJoinWorkerThread w = createWorker(i);
481	>	if (w != null) {
482	>	ws[i] = w;
483	>	w.start();
484	>	updateWorkerCount(1);
485	>	}
486	>	}
487		}
488	+	} finally {
489	+	lock.unlock();
490		}
464	–	} finally {
465	–	lock.unlock();
491		}
492		}
493
#	Line 500 | Line 525 | public class ForkJoinPool extends Abstra
525		}
526		}
527
503	–	/**
504	–	* Sets the handler for internal worker threads that terminate due
505	–	* to unrecoverable errors encountered while executing tasks.
506	–	* Unless set, the current default or ThreadGroup handler is used
507	–	* as handler.
508	–	*
509	–	* @param h the new handler
510	–	* @return the old handler, or null if none
511	–	* @throws SecurityException if a security manager exists and
512	–	*         the caller is not permitted to modify threads
513	–	*         because it does not hold {@link
514	–	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
515	–	*/
516	–	public Thread.UncaughtExceptionHandler
517	–	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
518	–	checkPermission();
519	–	Thread.UncaughtExceptionHandler old = null;
520	–	final ReentrantLock lock = this.workerLock;
521	–	lock.lock();
522	–	try {
523	–	old = ueh;
524	–	ueh = h;
525	–	ForkJoinWorkerThread[] ws = workers;
526	–	for (int i = 0; i < ws.length; ++i) {
527	–	ForkJoinWorkerThread w = ws[i];
528	–	if (w != null)
529	–	w.setUncaughtExceptionHandler(h);
530	–	}
531	–	} finally {
532	–	lock.unlock();
533	–	}
534	–	return old;
535	–	}
536	–
537	–	/**
538	–	* Returns the handler for internal worker threads that terminate
539	–	* due to unrecoverable errors encountered while executing tasks.
540	–	* @return the handler, or null if none
541	–	*/
542	–	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
543	–	Thread.UncaughtExceptionHandler h;
544	–	final ReentrantLock lock = this.workerLock;
545	–	lock.lock();
546	–	try {
547	–	h = ueh;
548	–	} finally {
549	–	lock.unlock();
550	–	}
551	–	return h;
552	–	}
553	–
528		// Execution methods
529
530		/**
#	Line 559 | Line 533 | public class ForkJoinPool extends Abstra
533		private <T> void doSubmit(ForkJoinTask<T> task) {
534		if (isShutdown())
535		throw new RejectedExecutionException();
536	+	if (workers == null)
537	+	ensureWorkerInitialization();
538		submissionQueue.offer(task);
539	<	signalIdleWorkers(true);
539	>	signalIdleWorkers();
540		}
541
542		/**
#	Line 609 | Line 585 | public class ForkJoinPool extends Abstra
585		return job;
586		}
587
612	–	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
613	–	return new AdaptedRunnable(runnable, value);
614	–	}
615	–
616	–	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
617	–	return new AdaptedCallable(callable);
618	–	}
619	–
588		/**
589		* Adaptor for Runnables. This implements RunnableFuture
590		* to be compliant with AbstractExecutorService constraints
#	Line 698 | Line 666 | public class ForkJoinPool extends Abstra
666		}
667
668		/**
669	<	* Sets the target paralleism level of this pool.
669	>	* Returns the handler for internal worker threads that terminate
670	>	* due to unrecoverable errors encountered while executing tasks.
671	>	* @return the handler, or null if none
672	>	*/
673	>	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
674	>	Thread.UncaughtExceptionHandler h;
675	>	final ReentrantLock lock = this.workerLock;
676	>	lock.lock();
677	>	try {
678	>	h = ueh;
679	>	} finally {
680	>	lock.unlock();
681	>	}
682	>	return h;
683	>	}
684	>
685	>	/**
686	>	* Sets the handler for internal worker threads that terminate due
687	>	* to unrecoverable errors encountered while executing tasks.
688	>	* Unless set, the current default or ThreadGroup handler is used
689	>	* as handler.
690	>	*
691	>	* @param h the new handler
692	>	* @return the old handler, or null if none
693	>	* @throws SecurityException if a security manager exists and
694	>	*         the caller is not permitted to modify threads
695	>	*         because it does not hold {@link
696	>	*         java.lang.RuntimePermission}{@code ("modifyThread")},
697	>	*/
698	>	public Thread.UncaughtExceptionHandler
699	>	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
700	>	checkPermission();
701	>	Thread.UncaughtExceptionHandler old = null;
702	>	final ReentrantLock lock = this.workerLock;
703	>	lock.lock();
704	>	try {
705	>	old = ueh;
706	>	ueh = h;
707	>	ForkJoinWorkerThread[] ws = workers;
708	>	if (ws != null) {
709	>	for (int i = 0; i < ws.length; ++i) {
710	>	ForkJoinWorkerThread w = ws[i];
711	>	if (w != null)
712	>	w.setUncaughtExceptionHandler(h);
713	>	}
714	>	}
715	>	} finally {
716	>	lock.unlock();
717	>	}
718	>	return old;
719	>	}
720	>
721	>
722	>	/**
723	>	* Sets the target parallelism level of this pool.
724		* @param parallelism the target parallelism
725		* @throws IllegalArgumentException if parallelism less than or
726	<	* equal to zero or greater than maximum size bounds.
726	>	* equal to zero or greater than maximum size bounds
727		* @throws SecurityException if a security manager exists and
728		*         the caller is not permitted to modify threads
729		*         because it does not hold {@link
730	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
730	>	*         java.lang.RuntimePermission}{@code ("modifyThread")},
731		*/
732		public void setParallelism(int parallelism) {
733		checkPermission();
#	Line 725 | Line 747 | public class ForkJoinPool extends Abstra
747		} finally {
748		lock.unlock();
749		}
750	<	signalIdleWorkers(false);
750	>	signalIdleWorkers();
751		}
752
753		/**
754		* Returns the targeted number of worker threads in this pool.
733	–	* This value does not necessarily reflect transient changes as
734	–	* threads are added, removed, or abruptly terminate.
755		*
756		* @return the targeted number of worker threads in this pool
757		*/
#	Line 742 | Line 762 | public class ForkJoinPool extends Abstra
762		/**
763		* Returns the number of worker threads that have started but not
764		* yet terminated.  This result returned by this method may differ
765	<	* from <tt>getParallelism</tt> when threads are created to
765	>	* from {@code getParallelism} when threads are created to
766		* maintain parallelism when others are cooperatively blocked.
767		*
768		* @return the number of worker threads
#	Line 766 | Line 786 | public class ForkJoinPool extends Abstra
786		* Setting this value has no effect on current pool size. It
787		* controls construction of new threads.
788		* @throws IllegalArgumentException if negative or greater then
789	<	* internal implementation limit.
789	>	* internal implementation limit
790		*/
791		public void setMaximumPoolSize(int newMax) {
792		if (newMax < 0 || newMax > MAX_THREADS)
#	Line 797 | Line 817 | public class ForkJoinPool extends Abstra
817		}
818
819		/**
820	<	* Returns the approximate number of worker threads that are not
821	<	* blocked waiting to join tasks or for other managed
820	>	* Establishes local first-in-first-out scheduling mode for forked
821	>	* tasks that are never joined. This mode may be more appropriate
822	>	* than default locally stack-based mode in applications in which
823	>	* worker threads only process asynchronous tasks.  This method is
824	>	* designed to be invoked only when pool is quiescent, and
825	>	* typically only before any tasks are submitted. The effects of
826	>	* invocations at other times may be unpredictable.
827	>	*
828	>	* @param async if true, use locally FIFO scheduling
829	>	* @return the previous mode
830	>	*/
831	>	public boolean setAsyncMode(boolean async) {
832	>	boolean oldMode = locallyFifo;
833	>	locallyFifo = async;
834	>	ForkJoinWorkerThread[] ws = workers;
835	>	if (ws != null) {
836	>	for (int i = 0; i < ws.length; ++i) {
837	>	ForkJoinWorkerThread t = ws[i];
838	>	if (t != null)
839	>	t.setAsyncMode(async);
840	>	}
841	>	}
842	>	return oldMode;
843	>	}
844	>
845	>	/**
846	>	* Returns true if this pool uses local first-in-first-out
847	>	* scheduling mode for forked tasks that are never joined.
848	>	*
849	>	* @return true if this pool uses async mode
850	>	*/
851	>	public boolean getAsyncMode() {
852	>	return locallyFifo;
853	>	}
854	>
855	>	/**
856	>	* Returns an estimate of the number of worker threads that are
857	>	* not blocked waiting to join tasks or for other managed
858		* synchronization.
859		*
860		* @return the number of worker threads
#	Line 808 | Line 864 | public class ForkJoinPool extends Abstra
864		}
865
866		/**
867	<	* Returns the approximate number of threads that are currently
867	>	* Returns an estimate of the number of threads that are currently
868		* stealing or executing tasks. This method may overestimate the
869		* number of active threads.
870	<	* @return the number of active threads.
870	>	* @return the number of active threads
871		*/
872		public int getActiveThreadCount() {
873		return activeCountOf(runControl);
874		}
875
876		/**
877	<	* Returns the approximate number of threads that are currently
877	>	* Returns an estimate of the number of threads that are currently
878		* idle waiting for tasks. This method may underestimate the
879		* number of idle threads.
880	<	* @return the number of idle threads.
880	>	* @return the number of idle threads
881		*/
882		final int getIdleThreadCount() {
883		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
#	Line 850 | Line 906 | public class ForkJoinPool extends Abstra
906		* tuning fork/join programs: In general, steal counts should be
907		* high enough to keep threads busy, but low enough to avoid
908		* overhead and contention across threads.
909	<	* @return the number of steals.
909	>	* @return the number of steals
910		*/
911		public long getStealCount() {
912		return stealCount.get();
#	Line 867 | Line 923 | public class ForkJoinPool extends Abstra
923		}
924
925		/**
926	<	* Returns the total number of tasks currently held in queues by
927	<	* worker threads (but not including tasks submitted to the pool
928	<	* that have not begun executing). This value is only an
929	<	* approximation, obtained by iterating across all threads in the
930	<	* pool. This method may be useful for tuning task granularities.
931	<	* @return the number of queued tasks.
926	>	* Returns an estimate of the total number of tasks currently held
927	>	* in queues by worker threads (but not including tasks submitted
928	>	* to the pool that have not begun executing). This value is only
929	>	* an approximation, obtained by iterating across all threads in
930	>	* the pool. This method may be useful for tuning task
931	>	* granularities.
932	>	* @return the number of queued tasks
933		*/
934		public long getQueuedTaskCount() {
935		long count = 0;
936		ForkJoinWorkerThread[] ws = workers;
937	<	for (int i = 0; i < ws.length; ++i) {
938	<	ForkJoinWorkerThread t = ws[i];
939	<	if (t != null)
940	<	count += t.getQueueSize();
937	>	if (ws != null) {
938	>	for (int i = 0; i < ws.length; ++i) {
939	>	ForkJoinWorkerThread t = ws[i];
940	>	if (t != null)
941	>	count += t.getQueueSize();
942	>	}
943		}
944		return count;
945		}
946
947		/**
948	<	* Returns the approximate number tasks submitted to this pool
948	>	* Returns an estimate of the number tasks submitted to this pool
949		* that have not yet begun executing. This method takes time
950		* proportional to the number of submissions.
951	<	* @return the number of queued submissions.
951	>	* @return the number of queued submissions
952		*/
953		public int getQueuedSubmissionCount() {
954		return submissionQueue.size();
#	Line 898 | Line 957 | public class ForkJoinPool extends Abstra
957		/**
958		* Returns true if there are any tasks submitted to this pool
959		* that have not yet begun executing.
960	<	* @return <tt>true</tt> if there are any queued submissions.
960	>	* @return {@code true} if there are any queued submissions
961		*/
962		public boolean hasQueuedSubmissions() {
963		return !submissionQueue.isEmpty();
#	Line 915 | Line 974 | public class ForkJoinPool extends Abstra
974		}
975
976		/**
977	+	* Removes all available unexecuted submitted and forked tasks
978	+	* from scheduling queues and adds them to the given collection,
979	+	* without altering their execution status. These may include
980	+	* artificially generated or wrapped tasks. This method is designed
981	+	* to be invoked only when the pool is known to be
982	+	* quiescent. Invocations at other times may not remove all
983	+	* tasks. A failure encountered while attempting to add elements
984	+	* to collection {@code c} may result in elements being in
985	+	* neither, either or both collections when the associated
986	+	* exception is thrown.  The behavior of this operation is
987	+	* undefined if the specified collection is modified while the
988	+	* operation is in progress.
989	+	* @param c the collection to transfer elements into
990	+	* @return the number of elements transferred
991	+	*/
992	+	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
993	+	int n = submissionQueue.drainTo(c);
994	+	ForkJoinWorkerThread[] ws = workers;
995	+	if (ws != null) {
996	+	for (int i = 0; i < ws.length; ++i) {
997	+	ForkJoinWorkerThread w = ws[i];
998	+	if (w != null)
999	+	n += w.drainTasksTo(c);
1000	+	}
1001	+	}
1002	+	return n;
1003	+	}
1004	+
1005	+	/**
1006		* Returns a string identifying this pool, as well as its state,
1007		* including indications of run state, parallelism level, and
1008		* worker and task counts.
#	Line 961 | Line 1049 | public class ForkJoinPool extends Abstra
1049		* @throws SecurityException if a security manager exists and
1050		*         the caller is not permitted to modify threads
1051		*         because it does not hold {@link
1052	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1052	>	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1053		*/
1054		public void shutdown() {
1055		checkPermission();
#	Line 975 | Line 1063 | public class ForkJoinPool extends Abstra
1063		* waiting tasks.  Tasks that are in the process of being
1064		* submitted or executed concurrently during the course of this
1065		* method may or may not be rejected. Unlike some other executors,
1066	<	* this method cancels rather than collects non-executed tasks,
1067	<	* so always returns an empty list.
1066	>	* this method cancels rather than collects non-executed tasks
1067	>	* upon termination, so always returns an empty list. However, you
1068	>	* can use method {@code drainTasksTo} before invoking this
1069	>	* method to transfer unexecuted tasks to another collection.
1070		* @return an empty list
1071		* @throws SecurityException if a security manager exists and
1072		*         the caller is not permitted to modify threads
1073		*         because it does not hold {@link
1074	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1074	>	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1075		*/
1076		public List<Runnable> shutdownNow() {
1077		checkPermission();
#	Line 990 | Line 1080 | public class ForkJoinPool extends Abstra
1080		}
1081
1082		/**
1083	<	* Returns <tt>true</tt> if all tasks have completed following shut down.
1083	>	* Returns {@code true} if all tasks have completed following shut down.
1084		*
1085	<	* @return <tt>true</tt> if all tasks have completed following shut down
1085	>	* @return {@code true} if all tasks have completed following shut down
1086		*/
1087		public boolean isTerminated() {
1088		return runStateOf(runControl) == TERMINATED;
1089		}
1090
1091		/**
1092	<	* Returns <tt>true</tt> if the process of termination has
1092	>	* Returns {@code true} if the process of termination has
1093		* commenced but possibly not yet completed.
1094		*
1095	<	* @return <tt>true</tt> if terminating
1095	>	* @return {@code true} if terminating
1096		*/
1097		public boolean isTerminating() {
1098		return runStateOf(runControl) >= TERMINATING;
1099		}
1100
1101		/**
1102	<	* Returns <tt>true</tt> if this pool has been shut down.
1102	>	* Returns {@code true} if this pool has been shut down.
1103		*
1104	<	* @return <tt>true</tt> if this pool has been shut down
1104	>	* @return {@code true} if this pool has been shut down
1105		*/
1106		public boolean isShutdown() {
1107		return runStateOf(runControl) >= SHUTDOWN;
#	Line 1024 | Line 1114 | public class ForkJoinPool extends Abstra
1114		*
1115		* @param timeout the maximum time to wait
1116		* @param unit the time unit of the timeout argument
1117	<	* @return <tt>true</tt> if this executor terminated and
1118	<	*         <tt>false</tt> if the timeout elapsed before termination
1117	>	* @return {@code true} if this executor terminated and
1118	>	*         {@code false} if the timeout elapsed before termination
1119		* @throws InterruptedException if interrupted while waiting
1120		*/
1121		public boolean awaitTermination(long timeout, TimeUnit unit)
#	Line 1061 | Line 1151 | public class ForkJoinPool extends Abstra
1151		lock.lock();
1152		try {
1153		ForkJoinWorkerThread[] ws = workers;
1154	<	int idx = w.poolIndex;
1155	<	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1156	<	ws[idx] = null;
1157	<	if (totalCountOf(workerCounts) == 0) {
1158	<	terminate(); // no-op if already terminating
1159	<	transitionRunStateTo(TERMINATED);
1160	<	termination.signalAll();
1161	<	}
1162	<	else if (!isTerminating()) {
1163	<	tryShrinkWorkerArray();
1164	<	tryResumeSpare(true); // allow replacement
1154	>	if (ws != null) {
1155	>	int idx = w.poolIndex;
1156	>	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1157	>	ws[idx] = null;
1158	>	if (totalCountOf(workerCounts) == 0) {
1159	>	terminate(); // no-op if already terminating
1160	>	transitionRunStateTo(TERMINATED);
1161	>	termination.signalAll();
1162	>	}
1163	>	else if (!isTerminating()) {
1164	>	tryShrinkWorkerArray();
1165	>	tryResumeSpare(true); // allow replacement
1166	>	}
1167		}
1168		} finally {
1169		lock.unlock();
1170		}
1171	<	signalIdleWorkers(false);
1171	>	signalIdleWorkers();
1172		}
1173
1174		/**
#	Line 1086 | Line 1178 | public class ForkJoinPool extends Abstra
1178		if (transitionRunStateTo(TERMINATING)) {
1179		stopAllWorkers();
1180		resumeAllSpares();
1181	<	signalIdleWorkers(true);
1181	>	signalIdleWorkers();
1182		cancelQueuedSubmissions();
1183		cancelQueuedWorkerTasks();
1184		interruptUnterminatedWorkers();
1185	<	signalIdleWorkers(true); // resignal after interrupt
1185	>	signalIdleWorkers(); // resignal after interrupt
1186		}
1187		}
1188
1189		/**
1190	<	* Possibly terminate when on shutdown state
1190	>	* Possibly terminates when on shutdown state.
1191		*/
1192		private void terminateOnShutdown() {
1193		if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
#	Line 1103 | Line 1195 | public class ForkJoinPool extends Abstra
1195		}
1196
1197		/**
1198	<	* Clear out and cancel submissions
1198	>	* Clears out and cancels submissions.
1199		*/
1200		private void cancelQueuedSubmissions() {
1201		ForkJoinTask<?> task;
#	Line 1112 | Line 1204 | public class ForkJoinPool extends Abstra
1204		}
1205
1206		/**
1207	<	* Clean out worker queues.
1207	>	* Cleans out worker queues.
1208		*/
1209		private void cancelQueuedWorkerTasks() {
1210		final ReentrantLock lock = this.workerLock;
1211		lock.lock();
1212		try {
1213		ForkJoinWorkerThread[] ws = workers;
1214	<	for (int i = 0; i < ws.length; ++i) {
1215	<	ForkJoinWorkerThread t = ws[i];
1216	<	if (t != null)
1217	<	t.cancelTasks();
1214	>	if (ws != null) {
1215	>	for (int i = 0; i < ws.length; ++i) {
1216	>	ForkJoinWorkerThread t = ws[i];
1217	>	if (t != null)
1218	>	t.cancelTasks();
1219	>	}
1220		}
1221		} finally {
1222		lock.unlock();
#	Line 1130 | Line 1224 | public class ForkJoinPool extends Abstra
1224		}
1225
1226		/**
1227	<	* Set each worker's status to terminating. Requires lock to avoid
1228	<	* conflicts with add/remove
1227	>	* Sets each worker's status to terminating. Requires lock to avoid
1228	>	* conflicts with add/remove.
1229		*/
1230		private void stopAllWorkers() {
1231		final ReentrantLock lock = this.workerLock;
1232		lock.lock();
1233		try {
1234		ForkJoinWorkerThread[] ws = workers;
1235	<	for (int i = 0; i < ws.length; ++i) {
1236	<	ForkJoinWorkerThread t = ws[i];
1237	<	if (t != null)
1238	<	t.shutdownNow();
1235	>	if (ws != null) {
1236	>	for (int i = 0; i < ws.length; ++i) {
1237	>	ForkJoinWorkerThread t = ws[i];
1238	>	if (t != null)
1239	>	t.shutdownNow();
1240	>	}
1241		}
1242		} finally {
1243		lock.unlock();
#	Line 1149 | Line 1245 | public class ForkJoinPool extends Abstra
1245		}
1246
1247		/**
1248	<	* Interrupt all unterminated workers.  This is not required for
1248	>	* Interrupts all unterminated workers.  This is not required for
1249		* sake of internal control, but may help unstick user code during
1250		* shutdown.
1251		*/
#	Line 1158 | Line 1254 | public class ForkJoinPool extends Abstra
1254		lock.lock();
1255		try {
1256		ForkJoinWorkerThread[] ws = workers;
1257	<	for (int i = 0; i < ws.length; ++i) {
1258	<	ForkJoinWorkerThread t = ws[i];
1259	<	if (t != null && !t.isTerminated()) {
1260	<	try {
1261	<	t.interrupt();
1262	<	} catch (SecurityException ignore) {
1257	>	if (ws != null) {
1258	>	for (int i = 0; i < ws.length; ++i) {
1259	>	ForkJoinWorkerThread t = ws[i];
1260	>	if (t != null && !t.isTerminated()) {
1261	>	try {
1262	>	t.interrupt();
1263	>	} catch (SecurityException ignore) {
1264	>	}
1265		}
1266		}
1267		}
#	Line 1174 | Line 1272 | public class ForkJoinPool extends Abstra
1272
1273
1274		/*
1275	<	* Nodes for event barrier to manage idle threads.
1275	>	* Nodes for event barrier to manage idle threads.  Queue nodes
1276	>	* are basic Treiber stack nodes, also used for spare stack.
1277		*
1278		* The event barrier has an event count and a wait queue (actually
1279		* a Treiber stack).  Workers are enabled to look for work when
1280	<	* the eventCount is incremented. If they fail to find some,
1281	<	* they may wait for next count. Synchronization events occur only
1282	<	* in enough contexts to maintain overall liveness:
1280	>	* the eventCount is incremented. If they fail to find work, they
1281	>	* may wait for next count. Upon release, threads help others wake
1282	>	* up.
1283	>	*
1284	>	* Synchronization events occur only in enough contexts to
1285	>	* maintain overall liveness:
1286		*
1287		*   - Submission of a new task to the pool
1288	<	*   - Creation or termination of a worker
1288	>	*   - Resizes or other changes to the workers array
1289		*   - pool termination
1290		*   - A worker pushing a task on an empty queue
1291		*
1292	<	* The last case (pushing a task) occurs often enough, and is
1293	<	* heavy enough compared to simple stack pushes to require some
1294	<	* special handling: Method signalNonEmptyWorkerQueue returns
1295	<	* without advancing count if the queue appears to be empty.  This
1296	<	* would ordinarily result in races causing some queued waiters
1297	<	* not to be woken up. To avoid this, a worker in sync
1298	<	* rescans for tasks after being enqueued if it was the first to
1299	<	* enqueue, and aborts the wait if finding one, also helping to
1300	<	* signal others. This works well because the worker has nothing
1301	<	* better to do anyway, and so might as well help alleviate the
1302	<	* overhead and contention on the threads actually doing work.
1303	<	*
1304	<	* Queue nodes are basic Treiber stack nodes, also used for spare
1305	<	* stack.
1292	>	* The case of pushing a task occurs often enough, and is heavy
1293	>	* enough compared to simple stack pushes, to require special
1294	>	* handling: Method signalWork returns without advancing count if
1295	>	* the queue appears to be empty.  This would ordinarily result in
1296	>	* races causing some queued waiters not to be woken up. To avoid
1297	>	* this, the first worker enqueued in method sync (see
1298	>	* syncIsReleasable) rescans for tasks after being enqueued, and
1299	>	* helps signal if any are found. This works well because the
1300	>	* worker has nothing better to do, and so might as well help
1301	>	* alleviate the overhead and contention on the threads actually
1302	>	* doing work.  Also, since event counts increments on task
1303	>	* availability exist to maintain liveness (rather than to force
1304	>	* refreshes etc), it is OK for callers to exit early if
1305	>	* contending with another signaller.
1306		*/
1307		static final class WaitQueueNode {
1308		WaitQueueNode next; // only written before enqueued
1309		volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1310		final long count; // unused for spare stack
1311	<	WaitQueueNode(ForkJoinWorkerThread w, long c) {
1311	>
1312	>	WaitQueueNode(long c, ForkJoinWorkerThread w) {
1313		count = c;
1314		thread = w;
1315		}
1316	<	final boolean signal() {
1316	>
1317	>	/**
1318	>	* Wakes up waiter, returning false if known to already
1319	>	*/
1320	>	boolean signal() {
1321		ForkJoinWorkerThread t = thread;
1322	+	if (t == null)
1323	+	return false;
1324		thread = null;
1325	<	if (t != null) {
1326	<	LockSupport.unpark(t);
1327	<	return true;
1325	>	LockSupport.unpark(t);
1326	>	return true;
1327	>	}
1328	>
1329	>	/**
1330	>	* Awaits release on sync.
1331	>	*/
1332	>	void awaitSyncRelease(ForkJoinPool p) {
1333	>	while (thread != null && !p.syncIsReleasable(this))
1334	>	LockSupport.park(this);
1335	>	}
1336	>
1337	>	/**
1338	>	* Awaits resumption as spare.
1339	>	*/
1340	>	void awaitSpareRelease() {
1341	>	while (thread != null) {
1342	>	if (!Thread.interrupted())
1343	>	LockSupport.park(this);
1344		}
1220	–	return false;
1345		}
1346		}
1347
1348		/**
1349	<	* Release at least one thread waiting for event count to advance,
1350	<	* if one exists. If initial attempt fails, release all threads.
1351	<	* @param all if false, at first try to only release one thread
1352	<	* @return current event
1349	>	* Ensures that no thread is waiting for count to advance from the
1350	>	* current value of eventCount read on entry to this method, by
1351	>	* releasing waiting threads if necessary.
1352	>	* @return the count
1353		*/
1354	<	private long releaseIdleWorkers(boolean all) {
1355	<	long c;
1356	<	for (;;) {
1357	<	WaitQueueNode q = barrierStack;
1358	<	c = eventCount;
1235	<	long qc;
1236	<	if (q == null || (qc = q.count) >= c)
1237	<	break;
1238	<	if (!all) {
1239	<	if (casBarrierStack(q, q.next) && q.signal())
1240	<	break;
1241	<	all = true;
1242	<	}
1243	<	else if (casBarrierStack(q, null)) {
1354	>	final long ensureSync() {
1355	>	long c = eventCount;
1356	>	WaitQueueNode q;
1357	>	while ((q = syncStack) != null && q.count < c) {
1358	>	if (casBarrierStack(q, null)) {
1359		do {
1360	<	q.signal();
1360	>	q.signal();
1361		} while ((q = q.next) != null);
1362		break;
1363		}
#	Line 1251 | Line 1366 | public class ForkJoinPool extends Abstra
1366		}
1367
1368		/**
1369	<	* Returns current barrier event count
1255	<	* @return current barrier event count
1256	<	*/
1257	<	final long getEventCount() {
1258	<	long ec = eventCount;
1259	<	releaseIdleWorkers(true); // release to ensure accurate result
1260	<	return ec;
1261	<	}
1262	<
1263	<	/**
1264	<	* Increment event count and release at least one waiting thread,
1265	<	* if one exists (released threads will in turn wake up others).
1266	<	* @param all if true, try to wake up all
1369	>	* Increments event count and releases waiting threads.
1370		*/
1371	<	final void signalIdleWorkers(boolean all) {
1371	>	private void signalIdleWorkers() {
1372		long c;
1373		do;while (!casEventCount(c = eventCount, c+1));
1374	<	releaseIdleWorkers(all);
1374	>	ensureSync();
1375		}
1376
1377		/**
1378	<	* Wake up threads waiting to steal a task. Because method
1379	<	* sync rechecks availability, it is OK to only proceed if
1380	<	* queue appears to be non-empty.
1378	>	* Signals threads waiting to poll a task. Because method sync
1379	>	* rechecks availability, it is OK to only proceed if queue
1380	>	* appears to be non-empty, and OK to skip under contention to
1381	>	* increment count (since some other thread succeeded).
1382		*/
1383	<	final void signalNonEmptyWorkerQueue() {
1280	<	// If CAS fails another signaller must have succeeded
1383	>	final void signalWork() {
1384		long c;
1385	<	if (barrierStack != null && casEventCount(c = eventCount, c+1))
1386	<	releaseIdleWorkers(false);
1385	>	WaitQueueNode q;
1386	>	if (syncStack != null &&
1387	>	casEventCount(c = eventCount, c+1) &&
1388	>	(((q = syncStack) != null && q.count <= c) &&
1389	>	(!casBarrierStack(q, q.next) || !q.signal())))
1390	>	ensureSync();
1391		}
1392
1393		/**
1394	<	* Waits until event count advances from count, or some thread is
1395	<	* waiting on a previous count, or there is stealable work
1396	<	* available. Help wake up others on release.
1394	>	* Waits until event count advances from last value held by
1395	>	* caller, or if excess threads, caller is resumed as spare, or
1396	>	* caller or pool is terminating. Updates caller's event on exit.
1397		* @param w the calling worker thread
1291	–	* @param prev previous value returned by sync (or 0)
1292	–	* @return current event count
1398		*/
1399	<	final long sync(ForkJoinWorkerThread w, long prev) {
1400	<	updateStealCount(w);
1399	>	final void sync(ForkJoinWorkerThread w) {
1400	>	updateStealCount(w); // Transfer w's count while it is idle
1401
1402	<	while (!w.isShutdown() && !isTerminating() &&
1403	<	(parallelism >= runningCountOf(workerCounts) ||
1299	<	!suspendIfSpare(w))) { // prefer suspend to waiting here
1402	>	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1403	>	long prev = w.lastEventCount;
1404		WaitQueueNode node = null;
1405	<	boolean queued = false;
1406	<	for (;;) {
1407	<	if (!queued) {
1408	<	if (eventCount != prev)
1409	<	break;
1410	<	WaitQueueNode h = barrierStack;
1411	<	if (h != null && h.count != prev)
1308	<	break; // release below and maybe retry
1309	<	if (node == null)
1310	<	node = new WaitQueueNode(w, prev);
1311	<	queued = casBarrierStack(node.next = h, node);
1312	<	}
1313	<	else if (Thread.interrupted() ||
1314	<	node.thread == null ||
1315	<	(node.next == null && w.prescan()) ||
1316	<	eventCount != prev) {
1317	<	node.thread = null;
1318	<	if (eventCount == prev) // help trigger
1319	<	casEventCount(prev, prev+1);
1405	>	WaitQueueNode h;
1406	>	while (eventCount == prev &&
1407	>	((h = syncStack) == null || h.count == prev)) {
1408	>	if (node == null)
1409	>	node = new WaitQueueNode(prev, w);
1410	>	if (casBarrierStack(node.next = h, node)) {
1411	>	node.awaitSyncRelease(this);
1412		break;
1413		}
1322	–	else
1323	–	LockSupport.park(this);
1414		}
1415	+	long ec = ensureSync();
1416	+	if (ec != prev) {
1417	+	w.lastEventCount = ec;
1418	+	break;
1419	+	}
1420	+	}
1421	+	}
1422	+
1423	+	/**
1424	+	* Returns true if worker waiting on sync can proceed:
1425	+	*  - on signal (thread == null)
1426	+	*  - on event count advance (winning race to notify vs signaller)
1427	+	*  - on Interrupt
1428	+	*  - if the first queued node, we find work available
1429	+	* If node was not signalled and event count not advanced on exit,
1430	+	* then we also help advance event count.
1431	+	* @return true if node can be released
1432	+	*/
1433	+	final boolean syncIsReleasable(WaitQueueNode node) {
1434	+	long prev = node.count;
1435	+	if (!Thread.interrupted() && node.thread != null &&
1436	+	(node.next != null ||
1437	+	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1438	+	eventCount == prev)
1439	+	return false;
1440	+	if (node.thread != null) {
1441	+	node.thread = null;
1442		long ec = eventCount;
1443	<	if (releaseIdleWorkers(false) != prev)
1444	<	return ec;
1443	>	if (prev <= ec) // help signal
1444	>	casEventCount(ec, ec+1);
1445		}
1446	<	return prev; // return old count if aborted
1446	>	return true;
1447	>	}
1448	>
1449	>	/**
1450	>	* Returns true if a new sync event occurred since last call to
1451	>	* sync or this method, if so, updating caller's count.
1452	>	*/
1453	>	final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1454	>	long lc = w.lastEventCount;
1455	>	long ec = ensureSync();
1456	>	if (ec == lc)
1457	>	return false;
1458	>	w.lastEventCount = ec;
1459	>	return true;
1460		}
1461
1462		//  Parallelism maintenance
1463
1464		/**
1465	<	* Decrement running count; if too low, add spare.
1465	>	* Decrements running count; if too low, adds spare.
1466		*
1467		* Conceptually, all we need to do here is add or resume a
1468		* spare thread when one is about to block (and remove or
#	Line 1352 | Line 1482 | public class ForkJoinPool extends Abstra
1482		* only be suspended or removed when they are idle, not
1483		* immediately when they aren't needed. So adding threads will
1484		* raise parallelism level for longer than necessary.  Also,
1485	<	* FJ applications often enounter highly transient peaks when
1485	>	* FJ applications often encounter highly transient peaks when
1486		* many threads are blocked joining, but for less time than it
1487		* takes to create or resume spares.
1488		*
#	Line 1417 | Line 1547 | public class ForkJoinPool extends Abstra
1547		return (tc < maxPoolSize &&
1548		(rc == 0 || totalSurplus < 0 ||
1549		(maintainParallelism &&
1550	<	runningDeficit > totalSurplus && mayHaveQueuedWork())));
1550	>	runningDeficit > totalSurplus &&
1551	>	ForkJoinWorkerThread.hasQueuedTasks(workers))));
1552		}
1553
1554		/**
1555	<	* Returns true if at least one worker queue appears to be
1556	<	* nonempty. This is expensive but not often called. It is not
1426	<	* critical that this be accurate, but if not, more or fewer
1427	<	* running threads than desired might be maintained.
1428	<	*/
1429	<	private boolean mayHaveQueuedWork() {
1430	<	ForkJoinWorkerThread[] ws = workers;
1431	<	int len = ws.length;
1432	<	ForkJoinWorkerThread v;
1433	<	for (int i = 0; i < len; ++i) {
1434	<	if ((v = ws[i]) != null && v.getRawQueueSize() > 0) {
1435	<	releaseIdleWorkers(false); // help wake up stragglers
1436	<	return true;
1437	<	}
1438	<	}
1439	<	return false;
1440	<	}
1441	<
1442	<	/**
1443	<	* Add a spare worker if lock available and no more than the
1444	<	* expected numbers of threads exist
1555	>	* Adds a spare worker if lock available and no more than the
1556	>	* expected numbers of threads exist.
1557		* @return true if successful
1558		*/
1559		private boolean tryAddSpare(int expectedCounts) {
#	Line 1474 | Line 1586 | public class ForkJoinPool extends Abstra
1586		}
1587
1588		/**
1589	<	* Add the kth spare worker. On entry, pool coounts are already
1589	>	* Adds the kth spare worker. On entry, pool counts are already
1590		* adjusted to reflect addition.
1591		*/
1592		private void createAndStartSpare(int k) {
#	Line 1486 | Line 1598 | public class ForkJoinPool extends Abstra
1598		for (k = 0; k < len && ws[k] != null; ++k)
1599		;
1600		}
1601	<	if (k < len && (w = createWorker(k)) != null) {
1601	>	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1602		ws[k] = w;
1603		w.start();
1604		}
1605		else
1606		updateWorkerCount(-1); // adjust on failure
1607	<	signalIdleWorkers(false);
1607	>	signalIdleWorkers();
1608		}
1609
1610		/**
1611	<	* Suspend calling thread w if there are excess threads.  Called
1612	<	* only from sync.  Spares are enqueued in a Treiber stack
1613	<	* using the same WaitQueueNodes as barriers.  They are resumed
1614	<	* mainly in preJoin, but are also woken on pool events that
1615	<	* require all threads to check run state.
1611	>	* Suspends calling thread w if there are excess threads.  Called
1612	>	* only from sync.  Spares are enqueued in a Treiber stack using
1613	>	* the same WaitQueueNodes as barriers.  They are resumed mainly
1614	>	* in preJoin, but are also woken on pool events that require all
1615	>	* threads to check run state.
1616		* @param w the caller
1617		*/
1618		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
#	Line 1508 | Line 1620 | public class ForkJoinPool extends Abstra
1620		int s;
1621		while (parallelism < runningCountOf(s = workerCounts)) {
1622		if (node == null)
1623	<	node = new WaitQueueNode(w, 0);
1623	>	node = new WaitQueueNode(0, w);
1624		if (casWorkerCounts(s, s-1)) { // representation-dependent
1625		// push onto stack
1626		do;while (!casSpareStack(node.next = spareStack, node));
1515	–
1627		// block until released by resumeSpare
1628	<	while (node.thread != null) {
1518	<	if (!Thread.interrupted())
1519	<	LockSupport.park(this);
1520	<	}
1521	<	w.activate(); // help warm up
1628	>	node.awaitSpareRelease();
1629		return true;
1630		}
1631		}
#	Line 1526 | Line 1633 | public class ForkJoinPool extends Abstra
1633		}
1634
1635		/**
1636	<	* Try to pop and resume a spare thread.
1636	>	* Tries to pop and resume a spare thread.
1637		* @param updateCount if true, increment running count on success
1638		* @return true if successful
1639		*/
#	Line 1544 | Line 1651 | public class ForkJoinPool extends Abstra
1651		}
1652
1653		/**
1654	<	* Pop and resume all spare threads. Same idea as
1548	<	* releaseIdleWorkers.
1654	>	* Pops and resumes all spare threads. Same idea as ensureSync.
1655		* @return true if any spares released
1656		*/
1657		private boolean resumeAllSpares() {
#	Line 1563 | Line 1669 | public class ForkJoinPool extends Abstra
1669		}
1670
1671		/**
1672	<	* Pop and shutdown excessive spare threads. Call only while
1672	>	* Pops and shuts down excessive spare threads. Call only while
1673		* holding lock. This is not guaranteed to eliminate all excess
1674		* threads, only those suspended as spares, which are the ones
1675		* unlikely to be needed in the future.
#	Line 1586 | Line 1692 | public class ForkJoinPool extends Abstra
1692		}
1693
1694		/**
1589	–	* Returns approximate number of spares, just for diagnostics.
1590	–	*/
1591	–	private int countSpares() {
1592	–	int sum = 0;
1593	–	for (WaitQueueNode q = spareStack; q != null; q = q.next)
1594	–	++sum;
1595	–	return sum;
1596	–	}
1597	–
1598	–	/**
1695		* Interface for extending managed parallelism for tasks running
1696		* in ForkJoinPools. A ManagedBlocker provides two methods.
1697	<	* Method <tt>isReleasable</tt> must return true if blocking is not
1698	<	* necessary. Method <tt>block</tt> blocks the current thread
1697	>	* Method {@code isReleasable} must return true if blocking is not
1698	>	* necessary. Method {@code block} blocks the current thread
1699		* if necessary (perhaps internally invoking isReleasable before
1700		* actually blocking.).
1701		* <p>For example, here is a ManagedBlocker based on a
#	Line 1625 | Line 1721 | public class ForkJoinPool extends Abstra
1721		* Possibly blocks the current thread, for example waiting for
1722		* a lock or condition.
1723		* @return true if no additional blocking is necessary (i.e.,
1724	<	* if isReleasable would return true).
1724	>	* if isReleasable would return true)
1725		* @throws InterruptedException if interrupted while waiting
1726	<	* (the method is not required to do so, but is allowe to).
1726	>	* (the method is not required to do so, but is allowed to).
1727		*/
1728		boolean block() throws InterruptedException;
1729
#	Line 1642 | Line 1738 | public class ForkJoinPool extends Abstra
1738		* is a ForkJoinWorkerThread, this method possibly arranges for a
1739		* spare thread to be activated if necessary to ensure parallelism
1740		* while the current thread is blocked.  If
1741	<	* <tt>maintainParallelism</tt> is true and the pool supports it
1742	<	* (see <tt>getMaintainsParallelism</tt>), this method attempts to
1741	>	* {@code maintainParallelism} is true and the pool supports
1742	>	* it ({@link #getMaintainsParallelism}), this method attempts to
1743		* maintain the pool's nominal parallelism. Otherwise if activates
1744		* a thread only if necessary to avoid complete starvation. This
1745		* option may be preferable when blockages use timeouts, or are
#	Line 1664 | Line 1760 | public class ForkJoinPool extends Abstra
1760		* attempt to maintain the pool's nominal parallelism; otherwise
1761		* activate a thread only if necessary to avoid complete
1762		* starvation.
1763	<	* @throws InterruptedException if blocker.block did so.
1763	>	* @throws InterruptedException if blocker.block did so
1764		*/
1765		public static void managedBlock(ManagedBlocker blocker,
1766		boolean maintainParallelism)
#	Line 1689 | Line 1785 | public class ForkJoinPool extends Abstra
1785		do;while (!blocker.isReleasable() && !blocker.block());
1786		}
1787
1788	+	// AbstractExecutorService overrides
1789	+
1790	+	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1791	+	return new AdaptedRunnable(runnable, value);
1792	+	}
1793	+
1794	+	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1795	+	return new AdaptedCallable(callable);
1796	+	}
1797	+
1798
1799		// Temporary Unsafe mechanics for preliminary release
1800	+	private static Unsafe getUnsafe() throws Throwable {
1801	+	try {
1802	+	return Unsafe.getUnsafe();
1803	+	} catch (SecurityException se) {
1804	+	try {
1805	+	return java.security.AccessController.doPrivileged
1806	+	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1807	+	public Unsafe run() throws Exception {
1808	+	return getUnsafePrivileged();
1809	+	}});
1810	+	} catch (java.security.PrivilegedActionException e) {
1811	+	throw e.getCause();
1812	+	}
1813	+	}
1814	+	}
1815	+
1816	+	private static Unsafe getUnsafePrivileged()
1817	+	throws NoSuchFieldException, IllegalAccessException {
1818	+	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1819	+	f.setAccessible(true);
1820	+	return (Unsafe) f.get(null);
1821	+	}
1822	+
1823	+	private static long fieldOffset(String fieldName)
1824	+	throws NoSuchFieldException {
1825	+	return UNSAFE.objectFieldOffset
1826	+	(ForkJoinPool.class.getDeclaredField(fieldName));
1827	+	}
1828
1829	<	static final Unsafe _unsafe;
1829	>	static final Unsafe UNSAFE;
1830		static final long eventCountOffset;
1831		static final long workerCountsOffset;
1832		static final long runControlOffset;
1833	<	static final long barrierStackOffset;
1833	>	static final long syncStackOffset;
1834		static final long spareStackOffset;
1835
1836		static {
1837		try {
1838	<	if (ForkJoinPool.class.getClassLoader() != null) {
1839	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1840	<	f.setAccessible(true);
1841	<	_unsafe = (Unsafe)f.get(null);
1842	<	}
1843	<	else
1844	<	_unsafe = Unsafe.getUnsafe();
1711	<	eventCountOffset = _unsafe.objectFieldOffset
1712	<	(ForkJoinPool.class.getDeclaredField("eventCount"));
1713	<	workerCountsOffset = _unsafe.objectFieldOffset
1714	<	(ForkJoinPool.class.getDeclaredField("workerCounts"));
1715	<	runControlOffset = _unsafe.objectFieldOffset
1716	<	(ForkJoinPool.class.getDeclaredField("runControl"));
1717	<	barrierStackOffset = _unsafe.objectFieldOffset
1718	<	(ForkJoinPool.class.getDeclaredField("barrierStack"));
1719	<	spareStackOffset = _unsafe.objectFieldOffset
1720	<	(ForkJoinPool.class.getDeclaredField("spareStack"));
1721	<	} catch (Exception e) {
1838	>	UNSAFE = getUnsafe();
1839	>	eventCountOffset = fieldOffset("eventCount");
1840	>	workerCountsOffset = fieldOffset("workerCounts");
1841	>	runControlOffset = fieldOffset("runControl");
1842	>	syncStackOffset = fieldOffset("syncStack");
1843	>	spareStackOffset = fieldOffset("spareStack");
1844	>	} catch (Throwable e) {
1845		throw new RuntimeException("Could not initialize intrinsics", e);
1846		}
1847		}
1848
1849		private boolean casEventCount(long cmp, long val) {
1850	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1850	>	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1851		}
1852		private boolean casWorkerCounts(int cmp, int val) {
1853	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1853	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1854		}
1855		private boolean casRunControl(int cmp, int val) {
1856	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1856	>	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1857		}
1858		private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1859	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1859	>	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1860		}
1861		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1862	<	return _unsafe.compareAndSwapObject(this, barrierStackOffset, cmp, val);
1862	>	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1863		}
1864		}

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