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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 1.39 by jsr166, Sun Aug 2 17:55:51 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.locks.*;
11	<	import java.util.concurrent.atomic.*;
12	<	import sun.misc.Unsafe;
13	<	import java.lang.reflect.*;
10	>
11	>	import java.util.ArrayList;
12	>	import java.util.Arrays;
13	>	import java.util.Collection;
14	>	import java.util.Collections;
15	>	import java.util.List;
16	>	import java.util.concurrent.locks.Condition;
17	>	import java.util.concurrent.locks.LockSupport;
18	>	import java.util.concurrent.locks.ReentrantLock;
19	>	import java.util.concurrent.atomic.AtomicInteger;
20	>	import java.util.concurrent.atomic.AtomicLong;
21
22		/**
23	<	* Host for a group of ForkJoinWorkerThreads.  A ForkJoinPool provides
24	<	* the entry point for tasks submitted from non-ForkJoinTasks, as well
25	<	* as management and monitoring operations.  Normally a single
26	<	* ForkJoinPool is used for a large number of submitted
27	<	* tasks. Otherwise, use would not usually outweigh the construction
28	<	* and bookkeeping overhead of creating a large set of threads.
29	<	*
23	<	* <p>ForkJoinPools differ from other kinds of Executor mainly in that
24	<	* they provide <em>work-stealing</em>: all threads in the pool
25	<	* attempt to find and execute subtasks created by other active tasks
26	<	* (eventually blocking if none exist). This makes them efficient when
27	<	* most tasks spawn other subtasks (as do most ForkJoinTasks) but
28	<	* possibly less so otherwise. It is however fine to combine execution
29	<	* of some plain Runnable- or Callable- based activities with that of
30	<	* ForkJoinTasks.
23	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
24	>	* A {@code ForkJoinPool} provides the entry point for submissions
25	>	* from non-{@code ForkJoinTask}s, as well as management and
26	>	* monitoring operations.  Normally a single {@code ForkJoinPool} is
27	>	* used for a large number of submitted tasks. Otherwise, use would
28	>	* not usually outweigh the construction and bookkeeping overhead of
29	>	* creating a large set of threads.
30		*
31	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
32	<	* (target pool size), which it attempts to maintain by dynamically
33	<	* adding, suspending, or resuming threads, even if some tasks have
34	<	* blocked waiting to join others. However, no such adjustments are
35	<	* performed in the face of blocked IO or other unmanaged
36	<	* synchronization. The nested ManagedBlocker interface enables
37	<	* extension of the kinds of synchronization accommodated.
31	>	* <p>{@code ForkJoinPool}s differ from other kinds of {@link
32	>	* Executor}s mainly in that they provide <em>work-stealing</em>: all
33	>	* threads in the pool attempt to find and execute subtasks created by
34	>	* other active tasks (eventually blocking if none exist). This makes
35	>	* them efficient when most tasks spawn other subtasks (as do most
36	>	* {@code ForkJoinTask}s), as well as the mixed execution of some
37	>	* plain {@code Runnable}- or {@code Callable}- based activities along
38	>	* with {@code ForkJoinTask}s. When setting {@linkplain #setAsyncMode
39	>	* async mode}, a {@code ForkJoinPool} may also be appropriate for use
40	>	* with fine-grained tasks that are never joined. Otherwise, other
41	>	* {@code ExecutorService} implementations are typically more
42	>	* appropriate choices.
43		*
44	<	* <p>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
47	<	* <tt>setMaintainParallelism</tt>.
44	>	* <p>A {@code ForkJoinPool} may be constructed with a given
45	>	* parallelism level (target pool size), which it attempts to maintain
46	>	* by dynamically adding, suspending, or resuming threads, even if
47	>	* some tasks are waiting to join others. However, no such adjustments
48	>	* are performed in the face of blocked IO or other unmanaged
49	>	* synchronization. The nested {@link ManagedBlocker} interface
50	>	* enables extension of the kinds of synchronization accommodated.
51	>	* The target parallelism level may also be changed dynamically
52	>	* ({@link #setParallelism}) and thread construction can be limited
53	>	* using methods {@link #setMaximumPoolSize} and/or {@link
54	>	* #setMaintainsParallelism}.
55		*
56		* <p>In addition to execution and lifecycle control methods, this
57		* class provides status check methods (for example
58	<	* <tt>getStealCount</tt>) that are intended to aid in developing,
58	>	* {@link #getStealCount}) that are intended to aid in developing,
59		* tuning, and monitoring fork/join applications. Also, method
60	<	* <tt>toString</tt> returns indications of pool state in a convenient
61	<	* form for informal monitoring.
60	>	* {@link #toString} returns indications of pool state in a
61	>	* convenient form for informal monitoring.
62		*
63		* <p><b>Implementation notes</b>: This implementation restricts the
64	<	* maximum parallelism to 32767. Attempts to create pools with greater
65	<	* than the maximum result in IllegalArgumentExceptions.
64	>	* maximum number of running threads to 32767. Attempts to create
65	>	* pools with greater than the maximum result in
66	>	* {@code IllegalArgumentException}.
67	>	*
68	>	* @since 1.7
69	>	* @author Doug Lea
70		*/
71	<	public class ForkJoinPool extends AbstractExecutorService
57	<	implements ExecutorService {
71	>	public class ForkJoinPool extends AbstractExecutorService {
72
73		/*
74		* See the extended comments interspersed below for design,
#	Line 68 | Line 82 | public class ForkJoinPool extends Abstra
82		private static final int MAX_THREADS =  0x7FFF;
83
84		/**
85	<	* Factory for creating new ForkJoinWorkerThreads.  A
86	<	* ForkJoinWorkerThreadFactory must be defined and used for
87	<	* ForkJoinWorkerThread subclasses that extend base functionality
88	<	* or initialize threads with different contexts.
85	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
86	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
87	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
88	>	* functionality or initialize threads with different contexts.
89		*/
90		public static interface ForkJoinWorkerThreadFactory {
91		/**
92		* Returns a new worker thread operating in the given pool.
93		*
94		* @param pool the pool this thread works in
95	<	* @throws NullPointerException if pool is null;
95	>	* @throws NullPointerException if pool is null
96		*/
97		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
98		}
99
100		/**
101	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
101	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
102		* new ForkJoinWorkerThread.
103		*/
104	<	public static class  DefaultForkJoinWorkerThreadFactory
104	>	static class  DefaultForkJoinWorkerThreadFactory
105		implements ForkJoinWorkerThreadFactory {
106		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
107		try {
#	Line 99 | Line 113 | public class ForkJoinPool extends Abstra
113		}
114
115		/**
116	<	* The default ForkJoinWorkerThreadFactory, used unless overridden
117	<	* in ForkJoinPool constructors.
116	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
117	>	* overridden in ForkJoinPool constructors.
118		*/
119	<	private static final DefaultForkJoinWorkerThreadFactory
119	>	public static final ForkJoinWorkerThreadFactory
120		defaultForkJoinWorkerThreadFactory =
121		new DefaultForkJoinWorkerThreadFactory();
122
109	–
123		/**
124		* Permission required for callers of methods that may start or
125		* kill threads.
#	Line 131 | Line 144 | public class ForkJoinPool extends Abstra
144		new AtomicInteger();
145
146		/**
147	<	* Array holding all worker threads in the pool. Array size must
148	<	* be a power of two.  Updates and replacements are protected by
149	<	* workerLock, but it is always kept in a consistent enough state
150	<	* to be randomly accessed without locking by workers performing
151	<	* work-stealing.
147	>	* Array holding all worker threads in the pool. Initialized upon
148	>	* first use. Array size must be a power of two.  Updates and
149	>	* replacements are protected by workerLock, but it is always kept
150	>	* in a consistent enough state to be randomly accessed without
151	>	* locking by workers performing work-stealing.
152		*/
153		volatile ForkJoinWorkerThread[] workers;
154
#	Line 151 | Line 164 | public class ForkJoinPool extends Abstra
164
165		/**
166		* The uncaught exception handler used when any worker
167	<	* abrupty terminates
167	>	* abruptly terminates
168		*/
169		private Thread.UncaughtExceptionHandler ueh;
170
#	Line 179 | Line 192 | public class ForkJoinPool extends Abstra
192		private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
193
194		/**
195	<	* Head of Treiber stack for barrier sync. See below for explanation
195	>	* Head of Treiber stack for barrier sync. See below for explanation.
196		*/
197	<	private volatile WaitQueueNode barrierStack;
197	>	private volatile WaitQueueNode syncStack;
198
199		/**
200		* The count for event barrier
#	Line 204 | Line 217 | public class ForkJoinPool extends Abstra
217		private volatile int parallelism;
218
219		/**
220	+	* True if use local fifo, not default lifo, for local polling
221	+	*/
222	+	private volatile boolean locallyFifo;
223	+
224	+	/**
225		* Holds number of total (i.e., created and not yet terminated)
226		* and running (i.e., not blocked on joins or other managed sync)
227		* threads, packed into one int to ensure consistent snapshot when
228		* making decisions about creating and suspending spare
229		* threads. Updated only by CAS.  Note: CASes in
230	<	* updateRunningCount and preJoin running active count is in low
231	<	* word, so need to be modified if this changes
230	>	* updateRunningCount and preJoin assume that running active count
231	>	* is in low word, so need to be modified if this changes.
232		*/
233		private volatile int workerCounts;
234
#	Line 219 | Line 237 | public class ForkJoinPool extends Abstra
237		private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
238
239		/**
240	<	* Add delta (which may be negative) to running count.  This must
240	>	* Adds delta (which may be negative) to running count.  This must
241		* be called before (with negative arg) and after (with positive)
242	<	* any managed synchronization (i.e., mainly, joins)
242	>	* any managed synchronization (i.e., mainly, joins).
243	>	*
244		* @param delta the number to add
245		*/
246		final void updateRunningCount(int delta) {
247		int s;
248	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
248	>	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
249		}
250
251		/**
252	<	* Add delta (which may be negative) to both total and running
252	>	* Adds delta (which may be negative) to both total and running
253		* count.  This must be called upon creation and termination of
254		* worker threads.
255	+	*
256		* @param delta the number to add
257		*/
258		private void updateWorkerCount(int delta) {
259		int d = delta + (delta << 16); // add to both lo and hi parts
260		int s;
261	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
261	>	do {} while (!casWorkerCounts(s = workerCounts, s + d));
262		}
263
264		/**
#	Line 264 | Line 284 | public class ForkJoinPool extends Abstra
284		private static int runControlFor(int r, int a)   { return (r << 16) + a; }
285
286		/**
287	<	* Increment active count. Called by workers before/during
288	<	* executing tasks.
287	>	* Tries incrementing active count; fails on contention.
288	>	* Called by workers before/during executing tasks.
289	>	*
290	>	* @return true on success
291		*/
292	<	final void incrementActiveCount() {
293	<	int c;
294	<	do;while (!casRunControl(c = runControl, c+1));
292	>	final boolean tryIncrementActiveCount() {
293	>	int c = runControl;
294	>	return casRunControl(c, c+1);
295		}
296
297		/**
298	<	* Decrement active count; possibly trigger termination.
298	>	* Tries decrementing active count; fails on contention.
299	>	* Possibly triggers termination on success.
300		* Called by workers when they can't find tasks.
301	+	*
302	+	* @return true on success
303		*/
304	<	final void decrementActiveCount() {
305	<	int c, nextc;
306	<	do;while (!casRunControl(c = runControl, nextc = c-1));
304	>	final boolean tryDecrementActiveCount() {
305	>	int c = runControl;
306	>	int nextc = c - 1;
307	>	if (!casRunControl(c, nextc))
308	>	return false;
309		if (canTerminateOnShutdown(nextc))
310		terminateOnShutdown();
311	+	return true;
312		}
313
314		/**
315	<	* Return true if argument represents zero active count and
316	<	* nonzero runstate, which is the triggering condition for
315	>	* Returns {@code true} if argument represents zero active count
316	>	* and nonzero runstate, which is the triggering condition for
317		* terminating on shutdown.
318		*/
319		private static boolean canTerminateOnShutdown(int c) {
320	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
320	>	// i.e. least bit is nonzero runState bit
321	>	return ((c & -c) >>> 16) != 0;
322		}
323
324		/**
#	Line 315 | Line 344 | public class ForkJoinPool extends Abstra
344
345		/**
346		* Creates a ForkJoinPool with a pool size equal to the number of
347	<	* processors available on the system and using the default
348	<	* ForkJoinWorkerThreadFactory,
347	>	* processors available on the system, using the default
348	>	* ForkJoinWorkerThreadFactory.
349	>	*
350		* @throws SecurityException if a security manager exists and
351		*         the caller is not permitted to modify threads
352		*         because it does not hold {@link
353	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
353	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
354		*/
355		public ForkJoinPool() {
356		this(Runtime.getRuntime().availableProcessors(),
#	Line 328 | Line 358 | public class ForkJoinPool extends Abstra
358		}
359
360		/**
361	<	* Creates a ForkJoinPool with the indicated parellelism level
362	<	* threads, and using the default ForkJoinWorkerThreadFactory,
361	>	* Creates a ForkJoinPool with the indicated parallelism level
362	>	* threads and using the default ForkJoinWorkerThreadFactory.
363	>	*
364		* @param parallelism the number of worker threads
365		* @throws IllegalArgumentException if parallelism less than or
366		* equal to zero
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(int parallelism) {
373		this(parallelism, defaultForkJoinWorkerThreadFactory);
374		}
375
376		/**
377	<	* Creates a ForkJoinPool with a pool size equal to the number of
377	>	* Creates a ForkJoinPool with parallelism equal to the number of
378		* processors available on the system and using the given
379	<	* ForkJoinWorkerThreadFactory,
379	>	* ForkJoinWorkerThreadFactory.
380	>	*
381		* @param factory the factory for creating new threads
382		* @throws NullPointerException if factory is null
383		* @throws SecurityException if a security manager exists and
384		*         the caller is not permitted to modify threads
385		*         because it does not hold {@link
386	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
386	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
387		*/
388		public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
389		this(Runtime.getRuntime().availableProcessors(), factory);
390		}
391
392		/**
393	<	* Creates a ForkJoinPool with the indicated target number of
362	<	* worker threads and the given factory.
393	>	* Creates a ForkJoinPool with the given parallelism and factory.
394		*
395		* @param parallelism the targeted number of worker threads
396		* @param factory the factory for creating new threads
397		* @throws IllegalArgumentException if parallelism less than or
398	<	* equal to zero, or greater than implementation limit.
398	>	* equal to zero, or greater than implementation limit
399		* @throws NullPointerException if factory is null
400		* @throws SecurityException if a security manager exists and
401		*         the caller is not permitted to modify threads
402		*         because it does not hold {@link
403	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
403	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
404		*/
405		public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
406		if (parallelism <= 0 || parallelism > MAX_THREADS)
#	Line 386 | Line 417 | public class ForkJoinPool extends Abstra
417		this.termination = workerLock.newCondition();
418		this.stealCount = new AtomicLong();
419		this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
420	<	createAndStartInitialWorkers(parallelism);
420	>	// worker array and workers are lazily constructed
421		}
422
423		/**
424	<	* Create new worker using factory.
424	>	* Creates a new worker thread using factory.
425	>	*
426		* @param index the index to assign worker
427		* @return new worker, or null of factory failed
428		*/
#	Line 400 | Line 432 | public class ForkJoinPool extends Abstra
432		if (w != null) {
433		w.poolIndex = index;
434		w.setDaemon(true);
435	+	w.setAsyncMode(locallyFifo);
436		w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
437		if (h != null)
438		w.setUncaughtExceptionHandler(h);
#	Line 408 | Line 441 | public class ForkJoinPool extends Abstra
441		}
442
443		/**
444	<	* Return a good size for worker array given pool size.
444	>	* Returns a good size for worker array given pool size.
445		* Currently requires size to be a power of two.
446		*/
447	<	private static int arraySizeFor(int ps) {
448	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
447	>	private static int arraySizeFor(int poolSize) {
448	>	return (poolSize <= 1) ? 1 :
449	>	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
450		}
451
452		/**
453	<	* Create or resize array if necessary to hold newLength
453	>	* Creates or resizes array if necessary to hold newLength.
454	>	* Call only under exclusion.
455	>	*
456		* @return the array
457		*/
458		private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
#	Line 430 | Line 466 | public class ForkJoinPool extends Abstra
466		}
467
468		/**
469	<	* Try to shrink workers into smaller array after one or more terminate
469	>	* Tries to shrink workers into smaller array after one or more terminate.
470		*/
471		private void tryShrinkWorkerArray() {
472		ForkJoinWorkerThread[] ws = workers;
473	<	int len = ws.length;
474	<	int last = len - 1;
475	<	while (last >= 0 && ws[last] == null)
476	<	--last;
477	<	int newLength = arraySizeFor(last+1);
478	<	if (newLength < len)
479	<	workers = Arrays.copyOf(ws, newLength);
473	>	if (ws != null) {
474	>	int len = ws.length;
475	>	int last = len - 1;
476	>	while (last >= 0 && ws[last] == null)
477	>	--last;
478	>	int newLength = arraySizeFor(last+1);
479	>	if (newLength < len)
480	>	workers = Arrays.copyOf(ws, newLength);
481	>	}
482		}
483
484		/**
485	<	* 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.)
485	>	* Initializes workers if necessary.
486		*/
487	<	private void createAndStartInitialWorkers(int ps) {
488	<	final ReentrantLock lock = this.workerLock;
489	<	lock.lock();
490	<	try {
491	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
492	<	for (int i = 0; i < ps; ++i) {
493	<	ForkJoinWorkerThread w = createWorker(i);
494	<	if (w != null) {
495	<	ws[i] = w;
496	<	w.start();
497	<	updateWorkerCount(1);
487	>	final void ensureWorkerInitialization() {
488	>	ForkJoinWorkerThread[] ws = workers;
489	>	if (ws == null) {
490	>	final ReentrantLock lock = this.workerLock;
491	>	lock.lock();
492	>	try {
493	>	ws = workers;
494	>	if (ws == null) {
495	>	int ps = parallelism;
496	>	ws = ensureWorkerArrayCapacity(ps);
497	>	for (int i = 0; i < ps; ++i) {
498	>	ForkJoinWorkerThread w = createWorker(i);
499	>	if (w != null) {
500	>	ws[i] = w;
501	>	w.start();
502	>	updateWorkerCount(1);
503	>	}
504	>	}
505		}
506	+	} finally {
507	+	lock.unlock();
508		}
464	–	} finally {
465	–	lock.unlock();
509		}
510		}
511
#	Line 500 | Line 543 | public class ForkJoinPool extends Abstra
543		}
544		}
545
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	–
546		// Execution methods
547
548		/**
549		* Common code for execute, invoke and submit
550		*/
551		private <T> void doSubmit(ForkJoinTask<T> task) {
552	+	if (task == null)
553	+	throw new NullPointerException();
554		if (isShutdown())
555		throw new RejectedExecutionException();
556	+	if (workers == null)
557	+	ensureWorkerInitialization();
558		submissionQueue.offer(task);
559	<	signalIdleWorkers(true);
559	>	signalIdleWorkers();
560		}
561
562		/**
563	<	* Performs the given task; returning its result upon completion
563	>	* Performs the given task, returning its result upon completion.
564	>	*
565		* @param task the task
566		* @return the task's result
567		* @throws NullPointerException if task is null
#	Line 577 | Line 574 | public class ForkJoinPool extends Abstra
574
575		/**
576		* Arranges for (asynchronous) execution of the given task.
577	+	*
578		* @param task the task
579		* @throws NullPointerException if task is null
580		* @throws RejectedExecutionException if pool is shut down
581		*/
582	<	public <T> void execute(ForkJoinTask<T> task) {
582	>	public void execute(ForkJoinTask<?> task) {
583		doSubmit(task);
584		}
585
586		// AbstractExecutorService methods
587
588		public void execute(Runnable task) {
589	<	doSubmit(new AdaptedRunnable<Void>(task, null));
589	>	ForkJoinTask<?> job;
590	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
591	>	job = (ForkJoinTask<?>) task;
592	>	else
593	>	job = ForkJoinTask.adapt(task, null);
594	>	doSubmit(job);
595		}
596
597		public <T> ForkJoinTask<T> submit(Callable<T> task) {
598	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
598	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
599		doSubmit(job);
600		return job;
601		}
602
603		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
604	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
604	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
605		doSubmit(job);
606		return job;
607		}
608
609		public ForkJoinTask<?> submit(Runnable task) {
610	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
610	>	ForkJoinTask<?> job;
611	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
612	>	job = (ForkJoinTask<?>) task;
613	>	else
614	>	job = ForkJoinTask.adapt(task, null);
615		doSubmit(job);
616		return job;
617		}
618
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	–
619		/**
620	<	* Adaptor for Runnables. This implements RunnableFuture
621	<	* to be compliant with AbstractExecutorService constraints
620	>	* Submits a ForkJoinTask for execution.
621	>	*
622	>	* @param task the task to submit
623	>	* @return the task
624	>	* @throws RejectedExecutionException if the task cannot be
625	>	*         scheduled for execution
626	>	* @throws NullPointerException if the task is null
627		*/
628	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
629	<	implements RunnableFuture<T> {
630	<	final Runnable runnable;
627	<	final T resultOnCompletion;
628	<	T result;
629	<	AdaptedRunnable(Runnable runnable, T result) {
630	<	if (runnable == null) throw new NullPointerException();
631	<	this.runnable = runnable;
632	<	this.resultOnCompletion = result;
633	<	}
634	<	public T getRawResult() { return result; }
635	<	public void setRawResult(T v) { result = v; }
636	<	public boolean exec() {
637	<	runnable.run();
638	<	result = resultOnCompletion;
639	<	return true;
640	<	}
641	<	public void run() { invoke(); }
628	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
629	>	doSubmit(task);
630	>	return task;
631		}
632
644	–	/**
645	–	* Adaptor for Callables
646	–	*/
647	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
648	–	implements RunnableFuture<T> {
649	–	final Callable<T> callable;
650	–	T result;
651	–	AdaptedCallable(Callable<T> callable) {
652	–	if (callable == null) throw new NullPointerException();
653	–	this.callable = callable;
654	–	}
655	–	public T getRawResult() { return result; }
656	–	public void setRawResult(T v) { result = v; }
657	–	public boolean exec() {
658	–	try {
659	–	result = callable.call();
660	–	return true;
661	–	} catch (Error err) {
662	–	throw err;
663	–	} catch (RuntimeException rex) {
664	–	throw rex;
665	–	} catch (Exception ex) {
666	–	throw new RuntimeException(ex);
667	–	}
668	–	}
669	–	public void run() { invoke(); }
670	–	}
633
634		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
635	<	ArrayList<ForkJoinTask<T>> ts =
635	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
636		new ArrayList<ForkJoinTask<T>>(tasks.size());
637	<	for (Callable<T> c : tasks)
638	<	ts.add(new AdaptedCallable<T>(c));
639	<	invoke(new InvokeAll<T>(ts));
640	<	return (List<Future<T>>)(List)ts;
637	>	for (Callable<T> task : tasks)
638	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
639	>	invoke(new InvokeAll<T>(forkJoinTasks));
640	>
641	>	@SuppressWarnings({"unchecked", "rawtypes"})
642	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
643	>	return futures;
644		}
645
646		static final class InvokeAll<T> extends RecursiveAction {
647		final ArrayList<ForkJoinTask<T>> tasks;
648		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
649		public void compute() {
650	<	try { invokeAll(tasks); } catch(Exception ignore) {}
650	>	try { invokeAll(tasks); }
651	>	catch (Exception ignore) {}
652		}
653	+	private static final long serialVersionUID = -7914297376763021607L;
654		}
655
656		// Configuration and status settings and queries
657
658		/**
659	<	* Returns the factory used for constructing new workers
659	>	* Returns the factory used for constructing new workers.
660		*
661		* @return the factory used for constructing new workers
662		*/
#	Line 698 | Line 665 | public class ForkJoinPool extends Abstra
665		}
666
667		/**
668	<	* Sets the target paralleism level of this pool.
668	>	* Returns the handler for internal worker threads that terminate
669	>	* due to unrecoverable errors encountered while executing tasks.
670	>	*
671	>	* @return the handler, or {@code 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 {@code 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	>	*
725		* @param parallelism the target parallelism
726		* @throws IllegalArgumentException if parallelism less than or
727	<	* equal to zero or greater than maximum size bounds.
727	>	* equal to zero or greater than maximum size bounds
728		* @throws SecurityException if a security manager exists and
729		*         the caller is not permitted to modify threads
730		*         because it does not hold {@link
731	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
731	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
732		*/
733		public void setParallelism(int parallelism) {
734		checkPermission();
#	Line 725 | Line 748 | public class ForkJoinPool extends Abstra
748		} finally {
749		lock.unlock();
750		}
751	<	signalIdleWorkers(false);
751	>	signalIdleWorkers();
752		}
753
754		/**
755		* 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.
756		*
757		* @return the targeted number of worker threads in this pool
758		*/
#	Line 742 | Line 763 | public class ForkJoinPool extends Abstra
763		/**
764		* Returns the number of worker threads that have started but not
765		* yet terminated.  This result returned by this method may differ
766	<	* from <tt>getParallelism</tt> when threads are created to
766	>	* from {@link #getParallelism} when threads are created to
767		* maintain parallelism when others are cooperatively blocked.
768		*
769		* @return the number of worker threads
#	Line 754 | Line 775 | public class ForkJoinPool extends Abstra
775		/**
776		* Returns the maximum number of threads allowed to exist in the
777		* pool, even if there are insufficient unblocked running threads.
778	+	*
779		* @return the maximum
780		*/
781		public int getMaximumPoolSize() {
#	Line 765 | Line 787 | public class ForkJoinPool extends Abstra
787		* pool, even if there are insufficient unblocked running threads.
788		* Setting this value has no effect on current pool size. It
789		* controls construction of new threads.
790	<	* @throws IllegalArgumentException if negative or greater then
791	<	* internal implementation limit.
790	>	*
791	>	* @throws IllegalArgumentException if negative or greater than
792	>	* internal implementation limit
793		*/
794		public void setMaximumPoolSize(int newMax) {
795		if (newMax < 0 || newMax > MAX_THREADS)
#	Line 776 | Line 799 | public class ForkJoinPool extends Abstra
799
800
801		/**
802	<	* Returns true if this pool dynamically maintains its target
803	<	* parallelism level. If false, new threads are added only to
804	<	* avoid possible starvation.
805	<	* This setting is by default true;
806	<	* @return true if maintains parallelism
802	>	* Returns {@code true} if this pool dynamically maintains its
803	>	* target parallelism level. If false, new threads are added only
804	>	* to avoid possible starvation.  This setting is by default true.
805	>	*
806	>	* @return {@code true} if maintains parallelism
807		*/
808		public boolean getMaintainsParallelism() {
809		return maintainsParallelism;
#	Line 790 | Line 813 | public class ForkJoinPool extends Abstra
813		* Sets whether this pool dynamically maintains its target
814		* parallelism level. If false, new threads are added only to
815		* avoid possible starvation.
816	<	* @param enable true to maintains parallelism
816	>	*
817	>	* @param enable {@code true} to maintain parallelism
818		*/
819		public void setMaintainsParallelism(boolean enable) {
820		maintainsParallelism = enable;
821		}
822
823		/**
824	<	* Returns the approximate number of worker threads that are not
825	<	* blocked waiting to join tasks or for other managed
824	>	* Establishes local first-in-first-out scheduling mode for forked
825	>	* tasks that are never joined. This mode may be more appropriate
826	>	* than default locally stack-based mode in applications in which
827	>	* worker threads only process asynchronous tasks.  This method is
828	>	* designed to be invoked only when the pool is quiescent, and
829	>	* typically only before any tasks are submitted. The effects of
830	>	* invocations at other times may be unpredictable.
831	>	*
832	>	* @param async if {@code true}, use locally FIFO scheduling
833	>	* @return the previous mode
834	>	* @see #getAsyncMode
835	>	*/
836	>	public boolean setAsyncMode(boolean async) {
837	>	boolean oldMode = locallyFifo;
838	>	locallyFifo = async;
839	>	ForkJoinWorkerThread[] ws = workers;
840	>	if (ws != null) {
841	>	for (int i = 0; i < ws.length; ++i) {
842	>	ForkJoinWorkerThread t = ws[i];
843	>	if (t != null)
844	>	t.setAsyncMode(async);
845	>	}
846	>	}
847	>	return oldMode;
848	>	}
849	>
850	>	/**
851	>	* Returns {@code true} if this pool uses local first-in-first-out
852	>	* scheduling mode for forked tasks that are never joined.
853	>	*
854	>	* @return {@code true} if this pool uses async mode
855	>	* @see #setAsyncMode
856	>	*/
857	>	public boolean getAsyncMode() {
858	>	return locallyFifo;
859	>	}
860	>
861	>	/**
862	>	* Returns an estimate of the number of worker threads that are
863	>	* not blocked waiting to join tasks or for other managed
864		* synchronization.
865		*
866		* @return the number of worker threads
#	Line 808 | Line 870 | public class ForkJoinPool extends Abstra
870		}
871
872		/**
873	<	* Returns the approximate number of threads that are currently
873	>	* Returns an estimate of the number of threads that are currently
874		* stealing or executing tasks. This method may overestimate the
875		* number of active threads.
876	<	* @return the number of active threads.
876	>	*
877	>	* @return the number of active threads
878		*/
879		public int getActiveThreadCount() {
880		return activeCountOf(runControl);
881		}
882
883		/**
884	<	* Returns the approximate number of threads that are currently
884	>	* Returns an estimate of the number of threads that are currently
885		* idle waiting for tasks. This method may underestimate the
886		* number of idle threads.
887	<	* @return the number of idle threads.
887	>	*
888	>	* @return the number of idle threads
889		*/
890		final int getIdleThreadCount() {
891		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
892	<	return (c <= 0)? 0 : c;
892	>	return (c <= 0) ? 0 : c;
893		}
894
895		/**
896	<	* Returns true if all worker threads are currently idle. An idle
897	<	* worker is one that cannot obtain a task to execute because none
898	<	* are available to steal from other threads, and there are no
899	<	* pending submissions to the pool. This method is conservative:
900	<	* It might not return true immediately upon idleness of all
901	<	* threads, but will eventually become true if threads remain
902	<	* inactive.
903	<	* @return true if all threads are currently idle
896	>	* Returns {@code true} if all worker threads are currently idle.
897	>	* An idle worker is one that cannot obtain a task to execute
898	>	* because none are available to steal from other threads, and
899	>	* there are no pending submissions to the pool. This method is
900	>	* conservative; it might not return {@code true} immediately upon
901	>	* idleness of all threads, but will eventually become true if
902	>	* threads remain inactive.
903	>	*
904	>	* @return {@code true} if all threads are currently idle
905		*/
906		public boolean isQuiescent() {
907		return activeCountOf(runControl) == 0;
#	Line 847 | Line 912 | public class ForkJoinPool extends Abstra
912		* one thread's work queue by another. The reported value
913		* underestimates the actual total number of steals when the pool
914		* is not quiescent. This value may be useful for monitoring and
915	<	* tuning fork/join programs: In general, steal counts should be
915	>	* tuning fork/join programs: in general, steal counts should be
916		* high enough to keep threads busy, but low enough to avoid
917		* overhead and contention across threads.
918	<	* @return the number of steals.
918	>	*
919	>	* @return the number of steals
920		*/
921		public long getStealCount() {
922		return stealCount.get();
923		}
924
925		/**
926	<	* Accumulate steal count from a worker. Call only
927	<	* when worker known to be idle.
926	>	* Accumulates steal count from a worker.
927	>	* Call only when worker known to be idle.
928		*/
929		private void updateStealCount(ForkJoinWorkerThread w) {
930		int sc = w.getAndClearStealCount();
#	Line 867 | Line 933 | public class ForkJoinPool extends Abstra
933		}
934
935		/**
936	<	* Returns the total number of tasks currently held in queues by
937	<	* worker threads (but not including tasks submitted to the pool
938	<	* that have not begun executing). This value is only an
939	<	* approximation, obtained by iterating across all threads in the
940	<	* pool. This method may be useful for tuning task granularities.
941	<	* @return the number of queued tasks.
936	>	* Returns an estimate of the total number of tasks currently held
937	>	* in queues by worker threads (but not including tasks submitted
938	>	* to the pool that have not begun executing). This value is only
939	>	* an approximation, obtained by iterating across all threads in
940	>	* the pool. This method may be useful for tuning task
941	>	* granularities.
942	>	*
943	>	* @return the number of queued tasks
944		*/
945		public long getQueuedTaskCount() {
946		long count = 0;
947		ForkJoinWorkerThread[] ws = workers;
948	<	for (int i = 0; i < ws.length; ++i) {
949	<	ForkJoinWorkerThread t = ws[i];
950	<	if (t != null)
951	<	count += t.getQueueSize();
948	>	if (ws != null) {
949	>	for (int i = 0; i < ws.length; ++i) {
950	>	ForkJoinWorkerThread t = ws[i];
951	>	if (t != null)
952	>	count += t.getQueueSize();
953	>	}
954		}
955		return count;
956		}
957
958		/**
959	<	* Returns the approximate number tasks submitted to this pool
959	>	* Returns an estimate of the number tasks submitted to this pool
960		* that have not yet begun executing. This method takes time
961		* proportional to the number of submissions.
962	<	* @return the number of queued submissions.
962	>	*
963	>	* @return the number of queued submissions
964		*/
965		public int getQueuedSubmissionCount() {
966		return submissionQueue.size();
967		}
968
969		/**
970	<	* Returns true if there are any tasks submitted to this pool
971	<	* that have not yet begun executing.
972	<	* @return <tt>true</tt> if there are any queued submissions.
970	>	* Returns {@code true} if there are any tasks submitted to this
971	>	* pool that have not yet begun executing.
972	>	*
973	>	* @return {@code true} if there are any queued submissions
974		*/
975		public boolean hasQueuedSubmissions() {
976		return !submissionQueue.isEmpty();
#	Line 908 | Line 980 | public class ForkJoinPool extends Abstra
980		* Removes and returns the next unexecuted submission if one is
981		* available.  This method may be useful in extensions to this
982		* class that re-assign work in systems with multiple pools.
983	<	* @return the next submission, or null if none
983	>	*
984	>	* @return the next submission, or {@code null} if none
985		*/
986		protected ForkJoinTask<?> pollSubmission() {
987		return submissionQueue.poll();
988		}
989
990		/**
991	+	* Removes all available unexecuted submitted and forked tasks
992	+	* from scheduling queues and adds them to the given collection,
993	+	* without altering their execution status. These may include
994	+	* artificially generated or wrapped tasks. This method is designed
995	+	* to be invoked only when the pool is known to be
996	+	* quiescent. Invocations at other times may not remove all
997	+	* tasks. A failure encountered while attempting to add elements
998	+	* to collection {@code c} may result in elements being in
999	+	* neither, either or both collections when the associated
1000	+	* exception is thrown.  The behavior of this operation is
1001	+	* undefined if the specified collection is modified while the
1002	+	* operation is in progress.
1003	+	*
1004	+	* @param c the collection to transfer elements into
1005	+	* @return the number of elements transferred
1006	+	*/
1007	+	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1008	+	int n = submissionQueue.drainTo(c);
1009	+	ForkJoinWorkerThread[] ws = workers;
1010	+	if (ws != null) {
1011	+	for (int i = 0; i < ws.length; ++i) {
1012	+	ForkJoinWorkerThread w = ws[i];
1013	+	if (w != null)
1014	+	n += w.drainTasksTo(c);
1015	+	}
1016	+	}
1017	+	return n;
1018	+	}
1019	+
1020	+	/**
1021		* Returns a string identifying this pool, as well as its state,
1022		* including indications of run state, parallelism level, and
1023		* worker and task counts.
#	Line 958 | Line 1061 | public class ForkJoinPool extends Abstra
1061		* Invocation has no additional effect if already shut down.
1062		* Tasks that are in the process of being submitted concurrently
1063		* during the course of this method may or may not be rejected.
1064	+	*
1065		* @throws SecurityException if a security manager exists and
1066		*         the caller is not permitted to modify threads
1067		*         because it does not hold {@link
1068	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1068	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1069		*/
1070		public void shutdown() {
1071		checkPermission();
1072		transitionRunStateTo(SHUTDOWN);
1073	<	if (canTerminateOnShutdown(runControl))
1073	>	if (canTerminateOnShutdown(runControl)) {
1074	>	if (workers == null) { // shutting down before workers created
1075	>	final ReentrantLock lock = this.workerLock;
1076	>	lock.lock();
1077	>	try {
1078	>	if (workers == null) {
1079	>	terminate();
1080	>	transitionRunStateTo(TERMINATED);
1081	>	termination.signalAll();
1082	>	}
1083	>	} finally {
1084	>	lock.unlock();
1085	>	}
1086	>	}
1087		terminateOnShutdown();
1088	+	}
1089		}
1090
1091		/**
#	Line 975 | Line 1093 | public class ForkJoinPool extends Abstra
1093		* waiting tasks.  Tasks that are in the process of being
1094		* submitted or executed concurrently during the course of this
1095		* method may or may not be rejected. Unlike some other executors,
1096	<	* this method cancels rather than collects non-executed tasks,
1097	<	* so always returns an empty list.
1096	>	* this method cancels rather than collects non-executed tasks
1097	>	* upon termination, so always returns an empty list. However, you
1098	>	* can use method {@link #drainTasksTo} before invoking this
1099	>	* method to transfer unexecuted tasks to another collection.
1100	>	*
1101		* @return an empty list
1102		* @throws SecurityException if a security manager exists and
1103		*         the caller is not permitted to modify threads
1104		*         because it does not hold {@link
1105	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1105	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1106		*/
1107		public List<Runnable> shutdownNow() {
1108		checkPermission();
#	Line 990 | Line 1111 | public class ForkJoinPool extends Abstra
1111		}
1112
1113		/**
1114	<	* Returns <tt>true</tt> if all tasks have completed following shut down.
1114	>	* Returns {@code true} if all tasks have completed following shut down.
1115		*
1116	<	* @return <tt>true</tt> if all tasks have completed following shut down
1116	>	* @return {@code true} if all tasks have completed following shut down
1117		*/
1118		public boolean isTerminated() {
1119		return runStateOf(runControl) == TERMINATED;
1120		}
1121
1122		/**
1123	<	* Returns <tt>true</tt> if the process of termination has
1123	>	* Returns {@code true} if the process of termination has
1124		* commenced but possibly not yet completed.
1125		*
1126	<	* @return <tt>true</tt> if terminating
1126	>	* @return {@code true} if terminating
1127		*/
1128		public boolean isTerminating() {
1129		return runStateOf(runControl) >= TERMINATING;
1130		}
1131
1132		/**
1133	<	* Returns <tt>true</tt> if this pool has been shut down.
1133	>	* Returns {@code true} if this pool has been shut down.
1134		*
1135	<	* @return <tt>true</tt> if this pool has been shut down
1135	>	* @return {@code true} if this pool has been shut down
1136		*/
1137		public boolean isShutdown() {
1138		return runStateOf(runControl) >= SHUTDOWN;
#	Line 1024 | Line 1145 | public class ForkJoinPool extends Abstra
1145		*
1146		* @param timeout the maximum time to wait
1147		* @param unit the time unit of the timeout argument
1148	<	* @return <tt>true</tt> if this executor terminated and
1149	<	*         <tt>false</tt> if the timeout elapsed before termination
1148	>	* @return {@code true} if this executor terminated and
1149	>	*         {@code false} if the timeout elapsed before termination
1150		* @throws InterruptedException if interrupted while waiting
1151		*/
1152		public boolean awaitTermination(long timeout, TimeUnit unit)
#	Line 1049 | Line 1170 | public class ForkJoinPool extends Abstra
1170		// Shutdown and termination support
1171
1172		/**
1173	<	* Callback from terminating worker. Null out the corresponding
1174	<	* workers slot, and if terminating, try to terminate, else try to
1175	<	* shrink workers array.
1173	>	* Callback from terminating worker. Nulls out the corresponding
1174	>	* workers slot, and if terminating, tries to terminate; else
1175	>	* tries to shrink workers array.
1176	>	*
1177		* @param w the worker
1178		*/
1179		final void workerTerminated(ForkJoinWorkerThread w) {
#	Line 1061 | Line 1183 | public class ForkJoinPool extends Abstra
1183		lock.lock();
1184		try {
1185		ForkJoinWorkerThread[] ws = workers;
1186	<	int idx = w.poolIndex;
1187	<	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1188	<	ws[idx] = null;
1189	<	if (totalCountOf(workerCounts) == 0) {
1190	<	terminate(); // no-op if already terminating
1191	<	transitionRunStateTo(TERMINATED);
1192	<	termination.signalAll();
1193	<	}
1194	<	else if (!isTerminating()) {
1195	<	tryShrinkWorkerArray();
1196	<	tryResumeSpare(true); // allow replacement
1186	>	if (ws != null) {
1187	>	int idx = w.poolIndex;
1188	>	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1189	>	ws[idx] = null;
1190	>	if (totalCountOf(workerCounts) == 0) {
1191	>	terminate(); // no-op if already terminating
1192	>	transitionRunStateTo(TERMINATED);
1193	>	termination.signalAll();
1194	>	}
1195	>	else if (!isTerminating()) {
1196	>	tryShrinkWorkerArray();
1197	>	tryResumeSpare(true); // allow replacement
1198	>	}
1199		}
1200		} finally {
1201		lock.unlock();
1202		}
1203	<	signalIdleWorkers(false);
1203	>	signalIdleWorkers();
1204		}
1205
1206		/**
1207	<	* Initiate termination.
1207	>	* Initiates termination.
1208		*/
1209		private void terminate() {
1210		if (transitionRunStateTo(TERMINATING)) {
1211		stopAllWorkers();
1212		resumeAllSpares();
1213	<	signalIdleWorkers(true);
1213	>	signalIdleWorkers();
1214		cancelQueuedSubmissions();
1215		cancelQueuedWorkerTasks();
1216		interruptUnterminatedWorkers();
1217	<	signalIdleWorkers(true); // resignal after interrupt
1217	>	signalIdleWorkers(); // resignal after interrupt
1218		}
1219		}
1220
1221		/**
1222	<	* Possibly terminate when on shutdown state
1222	>	* Possibly terminates when on shutdown state.
1223		*/
1224		private void terminateOnShutdown() {
1225		if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
#	Line 1103 | Line 1227 | public class ForkJoinPool extends Abstra
1227		}
1228
1229		/**
1230	<	* Clear out and cancel submissions
1230	>	* Clears out and cancels submissions.
1231		*/
1232		private void cancelQueuedSubmissions() {
1233		ForkJoinTask<?> task;
#	Line 1112 | Line 1236 | public class ForkJoinPool extends Abstra
1236		}
1237
1238		/**
1239	<	* Clean out worker queues.
1239	>	* Cleans out worker queues.
1240		*/
1241		private void cancelQueuedWorkerTasks() {
1242		final ReentrantLock lock = this.workerLock;
1243		lock.lock();
1244		try {
1245		ForkJoinWorkerThread[] ws = workers;
1246	<	for (int i = 0; i < ws.length; ++i) {
1247	<	ForkJoinWorkerThread t = ws[i];
1248	<	if (t != null)
1249	<	t.cancelTasks();
1246	>	if (ws != null) {
1247	>	for (int i = 0; i < ws.length; ++i) {
1248	>	ForkJoinWorkerThread t = ws[i];
1249	>	if (t != null)
1250	>	t.cancelTasks();
1251	>	}
1252		}
1253		} finally {
1254		lock.unlock();
#	Line 1130 | Line 1256 | public class ForkJoinPool extends Abstra
1256		}
1257
1258		/**
1259	<	* Set each worker's status to terminating. Requires lock to avoid
1260	<	* conflicts with add/remove
1259	>	* Sets each worker's status to terminating. Requires lock to avoid
1260	>	* conflicts with add/remove.
1261		*/
1262		private void stopAllWorkers() {
1263		final ReentrantLock lock = this.workerLock;
1264		lock.lock();
1265		try {
1266		ForkJoinWorkerThread[] ws = workers;
1267	<	for (int i = 0; i < ws.length; ++i) {
1268	<	ForkJoinWorkerThread t = ws[i];
1269	<	if (t != null)
1270	<	t.shutdownNow();
1267	>	if (ws != null) {
1268	>	for (int i = 0; i < ws.length; ++i) {
1269	>	ForkJoinWorkerThread t = ws[i];
1270	>	if (t != null)
1271	>	t.shutdownNow();
1272	>	}
1273		}
1274		} finally {
1275		lock.unlock();
#	Line 1149 | Line 1277 | public class ForkJoinPool extends Abstra
1277		}
1278
1279		/**
1280	<	* Interrupt all unterminated workers.  This is not required for
1280	>	* Interrupts all unterminated workers.  This is not required for
1281		* sake of internal control, but may help unstick user code during
1282		* shutdown.
1283		*/
#	Line 1158 | Line 1286 | public class ForkJoinPool extends Abstra
1286		lock.lock();
1287		try {
1288		ForkJoinWorkerThread[] ws = workers;
1289	<	for (int i = 0; i < ws.length; ++i) {
1290	<	ForkJoinWorkerThread t = ws[i];
1291	<	if (t != null && !t.isTerminated()) {
1292	<	try {
1293	<	t.interrupt();
1294	<	} catch (SecurityException ignore) {
1289	>	if (ws != null) {
1290	>	for (int i = 0; i < ws.length; ++i) {
1291	>	ForkJoinWorkerThread t = ws[i];
1292	>	if (t != null && !t.isTerminated()) {
1293	>	try {
1294	>	t.interrupt();
1295	>	} catch (SecurityException ignore) {
1296	>	}
1297		}
1298		}
1299		}
#	Line 1174 | Line 1304 | public class ForkJoinPool extends Abstra
1304
1305
1306		/*
1307	<	* Nodes for event barrier to manage idle threads.
1307	>	* Nodes for event barrier to manage idle threads.  Queue nodes
1308	>	* are basic Treiber stack nodes, also used for spare stack.
1309		*
1310		* The event barrier has an event count and a wait queue (actually
1311		* a Treiber stack).  Workers are enabled to look for work when
1312	<	* the eventCount is incremented. If they fail to find some,
1313	<	* they may wait for next count. Synchronization events occur only
1314	<	* in enough contexts to maintain overall liveness:
1312	>	* the eventCount is incremented. If they fail to find work, they
1313	>	* may wait for next count. Upon release, threads help others wake
1314	>	* up.
1315	>	*
1316	>	* Synchronization events occur only in enough contexts to
1317	>	* maintain overall liveness:
1318		*
1319		*   - Submission of a new task to the pool
1320	<	*   - Creation or termination of a worker
1320	>	*   - Resizes or other changes to the workers array
1321		*   - pool termination
1322		*   - A worker pushing a task on an empty queue
1323		*
1324	<	* The last case (pushing a task) occurs often enough, and is
1325	<	* heavy enough compared to simple stack pushes to require some
1326	<	* special handling: Method signalNonEmptyWorkerQueue returns
1327	<	* without advancing count if the queue appears to be empty.  This
1328	<	* would ordinarily result in races causing some queued waiters
1329	<	* not to be woken up. To avoid this, a worker in sync
1330	<	* rescans for tasks after being enqueued if it was the first to
1331	<	* enqueue, and aborts the wait if finding one, also helping to
1332	<	* signal others. This works well because the worker has nothing
1333	<	* better to do anyway, and so might as well help alleviate the
1334	<	* overhead and contention on the threads actually doing work.
1335	<	*
1336	<	* Queue nodes are basic Treiber stack nodes, also used for spare
1337	<	* stack.
1324	>	* The case of pushing a task occurs often enough, and is heavy
1325	>	* enough compared to simple stack pushes, to require special
1326	>	* handling: Method signalWork returns without advancing count if
1327	>	* the queue appears to be empty.  This would ordinarily result in
1328	>	* races causing some queued waiters not to be woken up. To avoid
1329	>	* this, the first worker enqueued in method sync (see
1330	>	* syncIsReleasable) rescans for tasks after being enqueued, and
1331	>	* helps signal if any are found. This works well because the
1332	>	* worker has nothing better to do, and so might as well help
1333	>	* alleviate the overhead and contention on the threads actually
1334	>	* doing work.  Also, since event counts increments on task
1335	>	* availability exist to maintain liveness (rather than to force
1336	>	* refreshes etc), it is OK for callers to exit early if
1337	>	* contending with another signaller.
1338		*/
1339		static final class WaitQueueNode {
1340		WaitQueueNode next; // only written before enqueued
1341		volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1342		final long count; // unused for spare stack
1343	<	WaitQueueNode(ForkJoinWorkerThread w, long c) {
1343	>
1344	>	WaitQueueNode(long c, ForkJoinWorkerThread w) {
1345		count = c;
1346		thread = w;
1347		}
1348	<	final boolean signal() {
1348	>
1349	>	/**
1350	>	* Wakes up waiter, returning false if known to already
1351	>	*/
1352	>	boolean signal() {
1353		ForkJoinWorkerThread t = thread;
1354	+	if (t == null)
1355	+	return false;
1356		thread = null;
1357	<	if (t != null) {
1358	<	LockSupport.unpark(t);
1359	<	return true;
1357	>	LockSupport.unpark(t);
1358	>	return true;
1359	>	}
1360	>
1361	>	/**
1362	>	* Awaits release on sync.
1363	>	*/
1364	>	void awaitSyncRelease(ForkJoinPool p) {
1365	>	while (thread != null && !p.syncIsReleasable(this))
1366	>	LockSupport.park(this);
1367	>	}
1368	>
1369	>	/**
1370	>	* Awaits resumption as spare.
1371	>	*/
1372	>	void awaitSpareRelease() {
1373	>	while (thread != null) {
1374	>	if (!Thread.interrupted())
1375	>	LockSupport.park(this);
1376		}
1220	–	return false;
1377		}
1378		}
1379
1380		/**
1381	<	* Release at least one thread waiting for event count to advance,
1382	<	* if one exists. If initial attempt fails, release all threads.
1383	<	* @param all if false, at first try to only release one thread
1384	<	* @return current event
1381	>	* Ensures that no thread is waiting for count to advance from the
1382	>	* current value of eventCount read on entry to this method, by
1383	>	* releasing waiting threads if necessary.
1384	>	*
1385	>	* @return the count
1386		*/
1387	<	private long releaseIdleWorkers(boolean all) {
1388	<	long c;
1389	<	for (;;) {
1390	<	WaitQueueNode q = barrierStack;
1391	<	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)) {
1387	>	final long ensureSync() {
1388	>	long c = eventCount;
1389	>	WaitQueueNode q;
1390	>	while ((q = syncStack) != null && q.count < c) {
1391	>	if (casBarrierStack(q, null)) {
1392		do {
1393	<	q.signal();
1393	>	q.signal();
1394		} while ((q = q.next) != null);
1395		break;
1396		}
#	Line 1251 | Line 1399 | public class ForkJoinPool extends Abstra
1399		}
1400
1401		/**
1402	<	* 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
1402	>	* Increments event count and releases waiting threads.
1403		*/
1404	<	final void signalIdleWorkers(boolean all) {
1404	>	private void signalIdleWorkers() {
1405		long c;
1406	<	do;while (!casEventCount(c = eventCount, c+1));
1407	<	releaseIdleWorkers(all);
1406	>	do {} while (!casEventCount(c = eventCount, c+1));
1407	>	ensureSync();
1408		}
1409
1410		/**
1411	<	* Wake up threads waiting to steal a task. Because method
1412	<	* sync rechecks availability, it is OK to only proceed if
1413	<	* queue appears to be non-empty.
1411	>	* Signals threads waiting to poll a task. Because method sync
1412	>	* rechecks availability, it is OK to only proceed if queue
1413	>	* appears to be non-empty, and OK to skip under contention to
1414	>	* increment count (since some other thread succeeded).
1415		*/
1416	<	final void signalNonEmptyWorkerQueue() {
1280	<	// If CAS fails another signaller must have succeeded
1416	>	final void signalWork() {
1417		long c;
1418	<	if (barrierStack != null && casEventCount(c = eventCount, c+1))
1419	<	releaseIdleWorkers(false);
1418	>	WaitQueueNode q;
1419	>	if (syncStack != null &&
1420	>	casEventCount(c = eventCount, c+1) &&
1421	>	(((q = syncStack) != null && q.count <= c) &&
1422	>	(!casBarrierStack(q, q.next) || !q.signal())))
1423	>	ensureSync();
1424		}
1425
1426		/**
1427	<	* Waits until event count advances from count, or some thread is
1428	<	* waiting on a previous count, or there is stealable work
1429	<	* available. Help wake up others on release.
1427	>	* Waits until event count advances from last value held by
1428	>	* caller, or if excess threads, caller is resumed as spare, or
1429	>	* caller or pool is terminating. Updates caller's event on exit.
1430	>	*
1431		* @param w the calling worker thread
1291	–	* @param prev previous value returned by sync (or 0)
1292	–	* @return current event count
1432		*/
1433	<	final long sync(ForkJoinWorkerThread w, long prev) {
1434	<	updateStealCount(w);
1433	>	final void sync(ForkJoinWorkerThread w) {
1434	>	updateStealCount(w); // Transfer w's count while it is idle
1435
1436	<	while (!w.isShutdown() && !isTerminating() &&
1437	<	(parallelism >= runningCountOf(workerCounts) ||
1299	<	!suspendIfSpare(w))) { // prefer suspend to waiting here
1436	>	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1437	>	long prev = w.lastEventCount;
1438		WaitQueueNode node = null;
1439	<	boolean queued = false;
1440	<	for (;;) {
1441	<	if (!queued) {
1442	<	if (eventCount != prev)
1443	<	break;
1444	<	WaitQueueNode h = barrierStack;
1445	<	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);
1439	>	WaitQueueNode h;
1440	>	while (eventCount == prev &&
1441	>	((h = syncStack) == null || h.count == prev)) {
1442	>	if (node == null)
1443	>	node = new WaitQueueNode(prev, w);
1444	>	if (casBarrierStack(node.next = h, node)) {
1445	>	node.awaitSyncRelease(this);
1446		break;
1447		}
1322	–	else
1323	–	LockSupport.park(this);
1448		}
1449	+	long ec = ensureSync();
1450	+	if (ec != prev) {
1451	+	w.lastEventCount = ec;
1452	+	break;
1453	+	}
1454	+	}
1455	+	}
1456	+
1457	+	/**
1458	+	* Returns {@code true} if worker waiting on sync can proceed:
1459	+	*  - on signal (thread == null)
1460	+	*  - on event count advance (winning race to notify vs signaller)
1461	+	*  - on interrupt
1462	+	*  - if the first queued node, we find work available
1463	+	* If node was not signalled and event count not advanced on exit,
1464	+	* then we also help advance event count.
1465	+	*
1466	+	* @return {@code true} if node can be released
1467	+	*/
1468	+	final boolean syncIsReleasable(WaitQueueNode node) {
1469	+	long prev = node.count;
1470	+	if (!Thread.interrupted() && node.thread != null &&
1471	+	(node.next != null ||
1472	+	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1473	+	eventCount == prev)
1474	+	return false;
1475	+	if (node.thread != null) {
1476	+	node.thread = null;
1477		long ec = eventCount;
1478	<	if (releaseIdleWorkers(false) != prev)
1479	<	return ec;
1478	>	if (prev <= ec) // help signal
1479	>	casEventCount(ec, ec+1);
1480		}
1481	<	return prev; // return old count if aborted
1481	>	return true;
1482	>	}
1483	>
1484	>	/**
1485	>	* Returns {@code true} if a new sync event occurred since last
1486	>	* call to sync or this method, if so, updating caller's count.
1487	>	*/
1488	>	final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1489	>	long lc = w.lastEventCount;
1490	>	long ec = ensureSync();
1491	>	if (ec == lc)
1492	>	return false;
1493	>	w.lastEventCount = ec;
1494	>	return true;
1495		}
1496
1497		//  Parallelism maintenance
1498
1499		/**
1500	<	* Decrement running count; if too low, add spare.
1500	>	* Decrements running count; if too low, adds spare.
1501		*
1502		* Conceptually, all we need to do here is add or resume a
1503		* spare thread when one is about to block (and remove or
1504		* suspend it later when unblocked -- see suspendIfSpare).
1505		* However, implementing this idea requires coping with
1506	<	* several problems: We have imperfect information about the
1506	>	* several problems: we have imperfect information about the
1507		* states of threads. Some count updates can and usually do
1508		* lag run state changes, despite arrangements to keep them
1509		* accurate (for example, when possible, updating counts
#	Line 1352 | Line 1517 | public class ForkJoinPool extends Abstra
1517		* only be suspended or removed when they are idle, not
1518		* immediately when they aren't needed. So adding threads will
1519		* raise parallelism level for longer than necessary.  Also,
1520	<	* FJ applications often enounter highly transient peaks when
1520	>	* FJ applications often encounter highly transient peaks when
1521		* many threads are blocked joining, but for less time than it
1522		* takes to create or resume spares.
1523		*
#	Line 1361 | Line 1526 | public class ForkJoinPool extends Abstra
1526		* target counts, else create only to avoid starvation
1527		* @return true if joinMe known to be done
1528		*/
1529	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1529	>	final boolean preJoin(ForkJoinTask<?> joinMe,
1530	>	boolean maintainParallelism) {
1531		maintainParallelism &= maintainsParallelism; // overrride
1532		boolean dec = false;  // true when running count decremented
1533		while (spareStack == null || !tryResumeSpare(dec)) {
1534		int counts = workerCounts;
1535	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1535	>	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1536	>	// CAS cheat
1537		if (!needSpare(counts, maintainParallelism))
1538		break;
1539		if (joinMe.status < 0)
#	Line 1381 | Line 1548 | public class ForkJoinPool extends Abstra
1548		/**
1549		* Same idea as preJoin
1550		*/
1551	<	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1551	>	final boolean preBlock(ManagedBlocker blocker,
1552	>	boolean maintainParallelism) {
1553		maintainParallelism &= maintainsParallelism;
1554		boolean dec = false;
1555		while (spareStack == null || !tryResumeSpare(dec)) {
#	Line 1399 | Line 1567 | public class ForkJoinPool extends Abstra
1567		}
1568
1569		/**
1570	<	* Returns true if a spare thread appears to be needed.  If
1571	<	* maintaining parallelism, returns true when the deficit in
1570	>	* Returns {@code true} if a spare thread appears to be needed.
1571	>	* If maintaining parallelism, returns true when the deficit in
1572		* running threads is more than the surplus of total threads, and
1573		* there is apparently some work to do.  This self-limiting rule
1574		* means that the more threads that have already been added, the
1575		* less parallelism we will tolerate before adding another.
1576	+	*
1577		* @param counts current worker counts
1578		* @param maintainParallelism try to maintain parallelism
1579		*/
#	Line 1417 | Line 1586 | public class ForkJoinPool extends Abstra
1586		return (tc < maxPoolSize &&
1587		(rc == 0 || totalSurplus < 0 ||
1588		(maintainParallelism &&
1589	<	runningDeficit > totalSurplus && mayHaveQueuedWork())));
1589	>	runningDeficit > totalSurplus &&
1590	>	ForkJoinWorkerThread.hasQueuedTasks(workers))));
1591		}
1592
1593		/**
1594	<	* Returns true if at least one worker queue appears to be
1595	<	* nonempty. This is expensive but not often called. It is not
1596	<	* 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
1594	>	* Adds a spare worker if lock available and no more than the
1595	>	* expected numbers of threads exist.
1596	>	*
1597		* @return true if successful
1598		*/
1599		private boolean tryAddSpare(int expectedCounts) {
#	Line 1474 | Line 1626 | public class ForkJoinPool extends Abstra
1626		}
1627
1628		/**
1629	<	* Add the kth spare worker. On entry, pool coounts are already
1629	>	* Adds the kth spare worker. On entry, pool counts are already
1630		* adjusted to reflect addition.
1631		*/
1632		private void createAndStartSpare(int k) {
#	Line 1486 | Line 1638 | public class ForkJoinPool extends Abstra
1638		for (k = 0; k < len && ws[k] != null; ++k)
1639		;
1640		}
1641	<	if (k < len && (w = createWorker(k)) != null) {
1641	>	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1642		ws[k] = w;
1643		w.start();
1644		}
1645		else
1646		updateWorkerCount(-1); // adjust on failure
1647	<	signalIdleWorkers(false);
1647	>	signalIdleWorkers();
1648		}
1649
1650		/**
1651	<	* Suspend calling thread w if there are excess threads.  Called
1652	<	* only from sync.  Spares are enqueued in a Treiber stack
1653	<	* using the same WaitQueueNodes as barriers.  They are resumed
1654	<	* mainly in preJoin, but are also woken on pool events that
1655	<	* require all threads to check run state.
1651	>	* Suspends calling thread w if there are excess threads.  Called
1652	>	* only from sync.  Spares are enqueued in a Treiber stack using
1653	>	* the same WaitQueueNodes as barriers.  They are resumed mainly
1654	>	* in preJoin, but are also woken on pool events that require all
1655	>	* threads to check run state.
1656	>	*
1657		* @param w the caller
1658		*/
1659		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
#	Line 1508 | Line 1661 | public class ForkJoinPool extends Abstra
1661		int s;
1662		while (parallelism < runningCountOf(s = workerCounts)) {
1663		if (node == null)
1664	<	node = new WaitQueueNode(w, 0);
1664	>	node = new WaitQueueNode(0, w);
1665		if (casWorkerCounts(s, s-1)) { // representation-dependent
1666		// push onto stack
1667	<	do;while (!casSpareStack(node.next = spareStack, node));
1515	<
1667	>	do {} while (!casSpareStack(node.next = spareStack, node));
1668		// block until released by resumeSpare
1669	<	while (node.thread != null) {
1518	<	if (!Thread.interrupted())
1519	<	LockSupport.park(this);
1520	<	}
1521	<	w.activate(); // help warm up
1669	>	node.awaitSpareRelease();
1670		return true;
1671		}
1672		}
#	Line 1526 | Line 1674 | public class ForkJoinPool extends Abstra
1674		}
1675
1676		/**
1677	<	* Try to pop and resume a spare thread.
1677	>	* Tries to pop and resume a spare thread.
1678	>	*
1679		* @param updateCount if true, increment running count on success
1680		* @return true if successful
1681		*/
#	Line 1544 | Line 1693 | public class ForkJoinPool extends Abstra
1693		}
1694
1695		/**
1696	<	* Pop and resume all spare threads. Same idea as
1697	<	* releaseIdleWorkers.
1696	>	* Pops and resumes all spare threads. Same idea as ensureSync.
1697	>	*
1698		* @return true if any spares released
1699		*/
1700		private boolean resumeAllSpares() {
#	Line 1563 | Line 1712 | public class ForkJoinPool extends Abstra
1712		}
1713
1714		/**
1715	<	* Pop and shutdown excessive spare threads. Call only while
1715	>	* Pops and shuts down excessive spare threads. Call only while
1716		* holding lock. This is not guaranteed to eliminate all excess
1717		* threads, only those suspended as spares, which are the ones
1718		* unlikely to be needed in the future.
#	Line 1586 | Line 1735 | public class ForkJoinPool extends Abstra
1735		}
1736
1737		/**
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	–	/**
1738		* Interface for extending managed parallelism for tasks running
1739	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1740	<	* Method <tt>isReleasable</tt> must return true if blocking is not
1741	<	* necessary. Method <tt>block</tt> blocks the current thread
1742	<	* if necessary (perhaps internally invoking isReleasable before
1743	<	* actually blocking.).
1739	>	* in {@link ForkJoinPool}s.
1740	>	*
1741	>	* <p>A {@code ManagedBlocker} provides two methods.
1742	>	* Method {@code isReleasable} must return {@code true} if
1743	>	* blocking is not necessary. Method {@code block} blocks the
1744	>	* current thread if necessary (perhaps internally invoking
1745	>	* {@code isReleasable} before actually blocking.).
1746	>	*
1747		* <p>For example, here is a ManagedBlocker based on a
1748		* ReentrantLock:
1749	<	* <pre>
1750	<	*   class ManagedLocker implements ManagedBlocker {
1751	<	*     final ReentrantLock lock;
1752	<	*     boolean hasLock = false;
1753	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1754	<	*     public boolean block() {
1755	<	*        if (!hasLock)
1756	<	*           lock.lock();
1757	<	*        return true;
1616	<	*     }
1617	<	*     public boolean isReleasable() {
1618	<	*        return hasLock || (hasLock = lock.tryLock());
1619	<	*     }
1749	>	*  <pre> {@code
1750	>	* class ManagedLocker implements ManagedBlocker {
1751	>	*   final ReentrantLock lock;
1752	>	*   boolean hasLock = false;
1753	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1754	>	*   public boolean block() {
1755	>	*     if (!hasLock)
1756	>	*       lock.lock();
1757	>	*     return true;
1758		*   }
1759	<	* </pre>
1759	>	*   public boolean isReleasable() {
1760	>	*     return hasLock || (hasLock = lock.tryLock());
1761	>	*   }
1762	>	* }}</pre>
1763		*/
1764		public static interface ManagedBlocker {
1765		/**
1766		* Possibly blocks the current thread, for example waiting for
1767		* a lock or condition.
1768	<	* @return true if no additional blocking is necessary (i.e.,
1769	<	* if isReleasable would return true).
1768	>	*
1769	>	* @return {@code true} if no additional blocking is necessary
1770	>	* (i.e., if isReleasable would return true)
1771		* @throws InterruptedException if interrupted while waiting
1772	<	* (the method is not required to do so, but is allowe to).
1772	>	* (the method is not required to do so, but is allowed to)
1773		*/
1774		boolean block() throws InterruptedException;
1775
1776		/**
1777	<	* Returns true if blocking is unnecessary.
1777	>	* Returns {@code true} if blocking is unnecessary.
1778		*/
1779		boolean isReleasable();
1780		}
1781
1782		/**
1783		* Blocks in accord with the given blocker.  If the current thread
1784	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1785	<	* spare thread to be activated if necessary to ensure parallelism
1786	<	* while the current thread is blocked.  If
1787	<	* <tt>maintainParallelism</tt> is true and the pool supports it
1788	<	* (see <tt>getMaintainsParallelism</tt>), this method attempts to
1789	<	* maintain the pool's nominal parallelism. Otherwise if activates
1790	<	* a thread only if necessary to avoid complete starvation. This
1791	<	* option may be preferable when blockages use timeouts, or are
1792	<	* almost always brief.
1793	<	*
1794	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1795	<	* equivalent to
1796	<	* <pre>
1797	<	*   while (!blocker.isReleasable())
1798	<	*      if (blocker.block())
1799	<	*         return;
1800	<	* </pre>
1801	<	* If the caller is a ForkJoinTask, then the pool may first
1802	<	* be expanded to ensure parallelism, and later adjusted.
1784	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1785	>	* arranges for a spare thread to be activated if necessary to
1786	>	* ensure parallelism while the current thread is blocked.
1787	>	*
1788	>	* <p>If {@code maintainParallelism} is {@code true} and the pool
1789	>	* supports it ({@link #getMaintainsParallelism}), this method
1790	>	* attempts to maintain the pool's nominal parallelism. Otherwise
1791	>	* it activates a thread only if necessary to avoid complete
1792	>	* starvation. This option may be preferable when blockages use
1793	>	* timeouts, or are almost always brief.
1794	>	*
1795	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1796	>	* behaviorally equivalent to
1797	>	*  <pre> {@code
1798	>	* while (!blocker.isReleasable())
1799	>	*   if (blocker.block())
1800	>	*     return;
1801	>	* }</pre>
1802	>	*
1803	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1804	>	* first be expanded to ensure parallelism, and later adjusted.
1805		*
1806		* @param blocker the blocker
1807	<	* @param maintainParallelism if true and supported by this pool,
1808	<	* attempt to maintain the pool's nominal parallelism; otherwise
1809	<	* activate a thread only if necessary to avoid complete
1810	<	* starvation.
1811	<	* @throws InterruptedException if blocker.block did so.
1807	>	* @param maintainParallelism if {@code true} and supported by
1808	>	* this pool, attempt to maintain the pool's nominal parallelism;
1809	>	* otherwise activate a thread only if necessary to avoid
1810	>	* complete starvation.
1811	>	* @throws InterruptedException if blocker.block did so
1812		*/
1813		public static void managedBlock(ManagedBlocker blocker,
1814		boolean maintainParallelism)
1815		throws InterruptedException {
1816		Thread t = Thread.currentThread();
1817	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1818	<	((ForkJoinWorkerThread)t).pool : null);
1817	>	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1818	>	((ForkJoinWorkerThread) t).pool : null);
1819		if (!blocker.isReleasable()) {
1820		try {
1821		if (pool == null ||
#	Line 1686 | Line 1830 | public class ForkJoinPool extends Abstra
1830
1831		private static void awaitBlocker(ManagedBlocker blocker)
1832		throws InterruptedException {
1833	<	do;while (!blocker.isReleasable() && !blocker.block());
1833	>	do {} while (!blocker.isReleasable() && !blocker.block());
1834		}
1835
1836	+	// AbstractExecutorService overrides.  These rely on undocumented
1837	+	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1838	+	// implement RunnableFuture.
1839
1840	<	// Temporary Unsafe mechanics for preliminary release
1841	<
1842	<	static final Unsafe _unsafe;
1696	<	static final long eventCountOffset;
1697	<	static final long workerCountsOffset;
1698	<	static final long runControlOffset;
1699	<	static final long barrierStackOffset;
1700	<	static final long spareStackOffset;
1840	>	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1841	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1842	>	}
1843
1844	<	static {
1845	<	try {
1704	<	if (ForkJoinPool.class.getClassLoader() != null) {
1705	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1706	<	f.setAccessible(true);
1707	<	_unsafe = (Unsafe)f.get(null);
1708	<	}
1709	<	else
1710	<	_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) {
1722	<	throw new RuntimeException("Could not initialize intrinsics", e);
1723	<	}
1844	>	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1845	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1846		}
1847
1848	+	// Unsafe mechanics
1849	+
1850	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1851	+	private static final long eventCountOffset =
1852	+	objectFieldOffset("eventCount", ForkJoinPool.class);
1853	+	private static final long workerCountsOffset =
1854	+	objectFieldOffset("workerCounts", ForkJoinPool.class);
1855	+	private static final long runControlOffset =
1856	+	objectFieldOffset("runControl", ForkJoinPool.class);
1857	+	private static final long syncStackOffset =
1858	+	objectFieldOffset("syncStack",ForkJoinPool.class);
1859	+	private static final long spareStackOffset =
1860	+	objectFieldOffset("spareStack", ForkJoinPool.class);
1861	+
1862		private boolean casEventCount(long cmp, long val) {
1863	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1863	>	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1864		}
1865		private boolean casWorkerCounts(int cmp, int val) {
1866	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1866	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1867		}
1868		private boolean casRunControl(int cmp, int val) {
1869	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1869	>	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1870		}
1871		private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1872	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1872	>	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1873		}
1874		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1875	<	return _unsafe.compareAndSwapObject(this, barrierStackOffset, cmp, val);
1875	>	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1876	>	}
1877	>
1878	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1879	>	try {
1880	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1881	>	} catch (NoSuchFieldException e) {
1882	>	// Convert Exception to corresponding Error
1883	>	NoSuchFieldError error = new NoSuchFieldError(field);
1884	>	error.initCause(e);
1885	>	throw error;
1886	>	}
1887	>	}
1888	>
1889	>	/**
1890	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1891	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1892	>	* into a jdk.
1893	>	*
1894	>	* @return a sun.misc.Unsafe
1895	>	*/
1896	>	private static sun.misc.Unsafe getUnsafe() {
1897	>	try {
1898	>	return sun.misc.Unsafe.getUnsafe();
1899	>	} catch (SecurityException se) {
1900	>	try {
1901	>	return java.security.AccessController.doPrivileged
1902	>	(new java.security
1903	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1904	>	public sun.misc.Unsafe run() throws Exception {
1905	>	java.lang.reflect.Field f = sun.misc
1906	>	.Unsafe.class.getDeclaredField("theUnsafe");
1907	>	f.setAccessible(true);
1908	>	return (sun.misc.Unsafe) f.get(null);
1909	>	}});
1910	>	} catch (java.security.PrivilegedActionException e) {
1911	>	throw new RuntimeException("Could not initialize intrinsics",
1912	>	e.getCause());
1913	>	}
1914	>	}
1915		}
1916		}

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