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root/jsr166/jsr166/src/jsr166e/ForkJoinTask.java

Comparing jsr166/src/jsr166e/ForkJoinTask.java (file contents):
Revision 1.1 by dl, Mon Aug 13 15:52:33 2012 UTC vs.
Revision 1.14 by jsr166, Sun Jul 21 06:32:28 2013 UTC

#	Line 30 | Line 30 | import java.lang.reflect.Constructor;
30		* subtasks may be hosted by a small number of actual threads in a
31		* ForkJoinPool, at the price of some usage limitations.
32		*
33	<	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
34	<	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
35	<	* start other subtasks.  As indicated by the name of this class,
36	<	* many programs using {@code ForkJoinTask} employ only methods
37	<	* {@link #fork} and {@link #join}, or derivatives such as {@link
33	>	* <p>A "main" {@code ForkJoinTask} begins execution when it is
34	>	* explicitly submitted to a {@link ForkJoinPool}, or, if not already
35	>	* engaged in a ForkJoin computation, commenced in the {@link
36	>	* ForkJoinPool#commonPool()} via {@link #fork}, {@link #invoke}, or
37	>	* related methods.  Once started, it will usually in turn start other
38	>	* subtasks.  As indicated by the name of this class, many programs
39	>	* using {@code ForkJoinTask} employ only methods {@link #fork} and
40	>	* {@link #join}, or derivatives such as {@link
41		* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
42		* provides a number of other methods that can come into play in
43	<	* advanced usages, as well as extension mechanics that allow
44	<	* support of new forms of fork/join processing.
43	>	* advanced usages, as well as extension mechanics that allow support
44	>	* of new forms of fork/join processing.
45		*
46		* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
47		* The efficiency of {@code ForkJoinTask}s stems from a set of
#	Line 52 | Line 55 | import java.lang.reflect.Constructor;
55		* minimize other blocking synchronization apart from joining other
56		* tasks or using synchronizers such as Phasers that are advertised to
57		* cooperate with fork/join scheduling. Subdividable tasks should also
58	<	* not perform blocking IO, and should ideally access variables that
58	>	* not perform blocking I/O, and should ideally access variables that
59		* are completely independent of those accessed by other running
60		* tasks. These guidelines are loosely enforced by not permitting
61		* checked exceptions such as {@code IOExceptions} to be
#	Line 70 | Line 73 | import java.lang.reflect.Constructor;
73		* <p>It is possible to define and use ForkJoinTasks that may block,
74		* but doing do requires three further considerations: (1) Completion
75		* of few if any <em>other</em> tasks should be dependent on a task
76	<	* that blocks on external synchronization or IO. Event-style async
76	>	* that blocks on external synchronization or I/O. Event-style async
77		* tasks that are never joined (for example, those subclassing {@link
78		* CountedCompleter}) often fall into this category.  (2) To minimize
79		* resource impact, tasks should be small; ideally performing only the
#	Line 123 | Line 126 | import java.lang.reflect.Constructor;
126		* other actions.  Normally, a concrete ForkJoinTask subclass declares
127		* fields comprising its parameters, established in a constructor, and
128		* then defines a {@code compute} method that somehow uses the control
129	<	* methods supplied by this base class. While these methods have
127	<	* {@code public} access (to allow instances of different task
128	<	* subclasses to call each other's methods), some of them may only be
129	<	* called from within other ForkJoinTasks (as may be determined using
130	<	* method {@link #inForkJoinPool}).  Attempts to invoke them in other
131	<	* contexts result in exceptions or errors, possibly including {@code
132	<	* ClassCastException}.
129	>	* methods supplied by this base class.
130		*
131		* <p>Method {@link #join} and its variants are appropriate for use
132		* only when completion dependencies are acyclic; that is, the
#	Line 137 | Line 134 | import java.lang.reflect.Constructor;
134		* (DAG). Otherwise, executions may encounter a form of deadlock as
135		* tasks cyclically wait for each other.  However, this framework
136		* supports other methods and techniques (for example the use of
137	<	* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
137	>	* {@link java.util.concurrent.Phaser Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
138		* may be of use in constructing custom subclasses for problems that
139	<	* are not statically structured as DAGs. To support such usages a
139	>	* are not statically structured as DAGs. To support such usages, a
140		* ForkJoinTask may be atomically <em>tagged</em> with a {@code short}
141		* value using {@link #setForkJoinTaskTag} or {@link
142		* #compareAndSetForkJoinTaskTag} and checked using {@link
#	Line 287 | Line 284 | public abstract class ForkJoinTask<V> im
284		* @return status upon completion
285		*/
286		private int externalAwaitDone() {
290	–	boolean interrupted = false;
287		int s;
288	<	while ((s = status) >= 0) {
289	<	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
290	<	synchronized (this) {
291	<	if (status >= 0) {
292	<	try {
293	<	wait();
294	<	} catch (InterruptedException ie) {
295	<	interrupted = true;
288	>	ForkJoinPool cp = ForkJoinPool.common;
289	>	if ((s = status) >= 0) {
290	>	if (cp != null) {
291	>	if (this instanceof CountedCompleter)
292	>	s = cp.externalHelpComplete((CountedCompleter<?>)this);
293	>	else if (cp.tryExternalUnpush(this))
294	>	s = doExec();
295	>	}
296	>	if (s >= 0 && (s = status) >= 0) {
297	>	boolean interrupted = false;
298	>	do {
299	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
300	>	synchronized (this) {
301	>	if (status >= 0) {
302	>	try {
303	>	wait();
304	>	} catch (InterruptedException ie) {
305	>	interrupted = true;
306	>	}
307	>	}
308	>	else
309	>	notifyAll();
310		}
311		}
312	<	else
313	<	notifyAll();
314	<	}
312	>	} while ((s = status) >= 0);
313	>	if (interrupted)
314	>	Thread.currentThread().interrupt();
315		}
316		}
307	–	if (interrupted)
308	–	Thread.currentThread().interrupt();
317		return s;
318		}
319
#	Line 314 | Line 322 | public abstract class ForkJoinTask<V> im
322		*/
323		private int externalInterruptibleAwaitDone() throws InterruptedException {
324		int s;
325	+	ForkJoinPool cp = ForkJoinPool.common;
326		if (Thread.interrupted())
327		throw new InterruptedException();
328	+	if ((s = status) >= 0 && cp != null) {
329	+	if (this instanceof CountedCompleter)
330	+	cp.externalHelpComplete((CountedCompleter<?>)this);
331	+	else if (cp.tryExternalUnpush(this))
332	+	doExec();
333	+	}
334		while ((s = status) >= 0) {
335		if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
336		synchronized (this) {
#	Line 329 | Line 344 | public abstract class ForkJoinTask<V> im
344		return s;
345		}
346
347	+
348		/**
349		* Implementation for join, get, quietlyJoin. Directly handles
350		* only cases of already-completed, external wait, and
#	Line 338 | Line 354 | public abstract class ForkJoinTask<V> im
354		*/
355		private int doJoin() {
356		int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w;
357	<	if ((s = status) >= 0) {
358	<	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
359	<	if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue).
360	<	tryUnpush(this) || (s = doExec()) >= 0)
361	<	s = wt.pool.awaitJoin(w, this);
362	<	}
347	<	else
348	<	s = externalAwaitDone();
349	<	}
350	<	return s;
357	>	return (s = status) < 0 ? s :
358	>	((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
359	>	(w = (wt = (ForkJoinWorkerThread)t).workQueue).
360	>	tryUnpush(this) && (s = doExec()) < 0 ? s :
361	>	wt.pool.awaitJoin(w, this) :
362	>	externalAwaitDone();
363		}
364
365		/**
#	Line 357 | Line 369 | public abstract class ForkJoinTask<V> im
369		*/
370		private int doInvoke() {
371		int s; Thread t; ForkJoinWorkerThread wt;
372	<	if ((s = doExec()) >= 0) {
373	<	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
374	<	s = (wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue,
375	<	this);
364	<	else
365	<	s = externalAwaitDone();
366	<	}
367	<	return s;
372	>	return (s = doExec()) < 0 ? s :
373	>	((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
374	>	(wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue, this) :
375	>	externalAwaitDone();
376		}
377
378		// Exception table support
#	Line 443 | Line 451 | public abstract class ForkJoinTask<V> im
451		}
452
453		/**
454	<	* Records exception and possibly propagates
454	>	* Records exception and possibly propagates.
455		*
456		* @return status on exit
457		*/
#	Line 476 | Line 484 | public abstract class ForkJoinTask<V> im
484		}
485
486		/**
487	<	* Removes exception node and clears status
487	>	* Removes exception node and clears status.
488		*/
489		private void clearExceptionalCompletion() {
490		int h = System.identityHashCode(this);
#	Line 606 | Line 614 | public abstract class ForkJoinTask<V> im
614		}
615
616		/**
617	+	* A version of "sneaky throw" to relay exceptions
618	+	*/
619	+	static void rethrow(Throwable ex) {
620	+	if (ex != null)
621	+	ForkJoinTask.<RuntimeException>uncheckedThrow(ex);
622	+	}
623	+
624	+	/**
625	+	* The sneaky part of sneaky throw, relying on generics
626	+	* limitations to evade compiler complaints about rethrowing
627	+	* unchecked exceptions
628	+	*/
629	+	@SuppressWarnings("unchecked") static <T extends Throwable>
630	+	void uncheckedThrow(Throwable t) throws T {
631	+	throw (T)t; // rely on vacuous cast
632	+	}
633	+
634	+	/**
635		* Throws exception, if any, associated with the given status.
636		*/
637		private void reportException(int s) {
638	<	Throwable ex = ((s == CANCELLED) ?  new CancellationException() :
639	<	(s == EXCEPTIONAL) ? getThrowableException() :
640	<	null);
641	<	if (ex != null)
616	<	U.throwException(ex);
638	>	if (s == CANCELLED)
639	>	throw new CancellationException();
640	>	if (s == EXCEPTIONAL)
641	>	rethrow(getThrowableException());
642		}
643
644		// public methods
645
646		/**
647	<	* Arranges to asynchronously execute this task.  While it is not
648	<	* necessarily enforced, it is a usage error to fork a task more
649	<	* than once unless it has completed and been reinitialized.
650	<	* Subsequent modifications to the state of this task or any data
651	<	* it operates on are not necessarily consistently observable by
652	<	* any thread other than the one executing it unless preceded by a
653	<	* call to {@link #join} or related methods, or a call to {@link
654	<	* #isDone} returning {@code true}.
655	<	*
656	<	* <p>This method may be invoked only from within {@code
657	<	* ForkJoinPool} computations (as may be determined using method
633	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
634	<	* result in exceptions or errors, possibly including {@code
635	<	* ClassCastException}.
647	>	* Arranges to asynchronously execute this task in the pool the
648	>	* current task is running in, if applicable, or using the {@link
649	>	* ForkJoinPool#commonPool()} if not {@link #inForkJoinPool}.  While
650	>	* it is not necessarily enforced, it is a usage error to fork a
651	>	* task more than once unless it has completed and been
652	>	* reinitialized.  Subsequent modifications to the state of this
653	>	* task or any data it operates on are not necessarily
654	>	* consistently observable by any thread other than the one
655	>	* executing it unless preceded by a call to {@link #join} or
656	>	* related methods, or a call to {@link #isDone} returning {@code
657	>	* true}.
658		*
659		* @return {@code this}, to simplify usage
660		*/
661		public final ForkJoinTask<V> fork() {
662	<	((ForkJoinWorkerThread)Thread.currentThread()).workQueue.push(this);
662	>	Thread t;
663	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
664	>	((ForkJoinWorkerThread)t).workQueue.push(this);
665	>	else
666	>	ForkJoinPool.common.externalPush(this);
667		return this;
668		}
669
#	Line 687 | Line 713 | public abstract class ForkJoinTask<V> im
713		* cancelled, completed normally or exceptionally, or left
714		* unprocessed.
715		*
690	–	* <p>This method may be invoked only from within {@code
691	–	* ForkJoinPool} computations (as may be determined using method
692	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
693	–	* result in exceptions or errors, possibly including {@code
694	–	* ClassCastException}.
695	–	*
716		* @param t1 the first task
717		* @param t2 the second task
718		* @throws NullPointerException if any task is null
#	Line 718 | Line 738 | public abstract class ForkJoinTask<V> im
738		* related methods to check if they have been cancelled, completed
739		* normally or exceptionally, or left unprocessed.
740		*
721	–	* <p>This method may be invoked only from within {@code
722	–	* ForkJoinPool} computations (as may be determined using method
723	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
724	–	* result in exceptions or errors, possibly including {@code
725	–	* ClassCastException}.
726	–	*
741		* @param tasks the tasks
742		* @throws NullPointerException if any task is null
743		*/
#	Line 751 | Line 765 | public abstract class ForkJoinTask<V> im
765		}
766		}
767		if (ex != null)
768	<	U.throwException(ex);
768	>	rethrow(ex);
769		}
770
771		/**
#	Line 767 | Line 781 | public abstract class ForkJoinTask<V> im
781		* cancelled, completed normally or exceptionally, or left
782		* unprocessed.
783		*
770	–	* <p>This method may be invoked only from within {@code
771	–	* ForkJoinPool} computations (as may be determined using method
772	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
773	–	* result in exceptions or errors, possibly including {@code
774	–	* ClassCastException}.
775	–	*
784		* @param tasks the collection of tasks
785	+	* @param <T> the type of the values returned from the tasks
786		* @return the tasks argument, to simplify usage
787		* @throws NullPointerException if tasks or any element are null
788		*/
#	Line 808 | Line 817 | public abstract class ForkJoinTask<V> im
817		}
818		}
819		if (ex != null)
820	<	U.throwException(ex);
820	>	rethrow(ex);
821		return tasks;
822		}
823
#	Line 831 | Line 840 | public abstract class ForkJoinTask<V> im
840		* <p>This method is designed to be invoked by <em>other</em>
841		* tasks. To terminate the current task, you can just return or
842		* throw an unchecked exception from its computation method, or
843	<	* invoke {@link #completeExceptionally}.
843	>	* invoke {@link #completeExceptionally(Throwable)}.
844		*
845		* @param mayInterruptIfRunning this value has no effect in the
846		* default implementation because interrupts are not used to
#	Line 981 | Line 990 | public abstract class ForkJoinTask<V> im
990		if (Thread.interrupted())
991		throw new InterruptedException();
992		// Messy in part because we measure in nanosecs, but wait in millisecs
993	<	int s; long ns, ms;
994	<	if ((s = status) >= 0 && (ns = unit.toNanos(timeout)) > 0L) {
993	>	int s; long ms;
994	>	long ns = unit.toNanos(timeout);
995	>	ForkJoinPool cp;
996	>	if ((s = status) >= 0 && ns > 0L) {
997		long deadline = System.nanoTime() + ns;
998		ForkJoinPool p = null;
999		ForkJoinPool.WorkQueue w = null;
#	Line 991 | Line 1002 | public abstract class ForkJoinTask<V> im
1002		ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
1003		p = wt.pool;
1004		w = wt.workQueue;
1005	<	s = p.helpJoinOnce(w, this); // no retries on failure
1005	>	p.helpJoinOnce(w, this); // no retries on failure
1006	>	}
1007	>	else if ((cp = ForkJoinPool.common) != null) {
1008	>	if (this instanceof CountedCompleter)
1009	>	cp.externalHelpComplete((CountedCompleter<?>)this);
1010	>	else if (cp.tryExternalUnpush(this))
1011	>	doExec();
1012		}
1013		boolean canBlock = false;
1014		boolean interrupted = false;
1015		try {
1016		while ((s = status) >= 0) {
1017	<	if (w != null && w.runState < 0)
1017	>	if (w != null && w.qlock < 0)
1018		cancelIgnoringExceptions(this);
1019		else if (!canBlock) {
1020	<	if (p == null || p.tryCompensate(this, null))
1020	>	if (p == null || p.tryCompensate(p.ctl))
1021		canBlock = true;
1022		}
1023		else {
#	Line 1068 | Line 1085 | public abstract class ForkJoinTask<V> im
1085		* be of use in designs in which many tasks are forked, but none
1086		* are explicitly joined, instead executing them until all are
1087		* processed.
1071	–	*
1072	–	* <p>This method may be invoked only from within {@code
1073	–	* ForkJoinPool} computations (as may be determined using method
1074	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1075	–	* result in exceptions or errors, possibly including {@code
1076	–	* ClassCastException}.
1088		*/
1089		public static void helpQuiesce() {
1090	<	ForkJoinWorkerThread wt =
1091	<	(ForkJoinWorkerThread)Thread.currentThread();
1092	<	wt.pool.helpQuiescePool(wt.workQueue);
1090	>	Thread t;
1091	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
1092	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
1093	>	wt.pool.helpQuiescePool(wt.workQueue);
1094	>	}
1095	>	else
1096	>	ForkJoinPool.quiesceCommonPool();
1097		}
1098
1099		/**
#	Line 1131 | Line 1146 | public abstract class ForkJoinTask<V> im
1146
1147		/**
1148		* Tries to unschedule this task for execution. This method will
1149	<	* typically succeed if this task is the most recently forked task
1150	<	* by the current thread, and has not commenced executing in
1151	<	* another thread.  This method may be useful when arranging
1152	<	* alternative local processing of tasks that could have been, but
1153	<	* were not, stolen.
1139	<	*
1140	<	* <p>This method may be invoked only from within {@code
1141	<	* ForkJoinPool} computations (as may be determined using method
1142	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1143	<	* result in exceptions or errors, possibly including {@code
1144	<	* ClassCastException}.
1149	>	* typically (but is not guaranteed to) succeed if this task is
1150	>	* the most recently forked task by the current thread, and has
1151	>	* not commenced executing in another thread.  This method may be
1152	>	* useful when arranging alternative local processing of tasks
1153	>	* that could have been, but were not, stolen.
1154		*
1155		* @return {@code true} if unforked
1156		*/
1157		public boolean tryUnfork() {
1158	<	return ((ForkJoinWorkerThread)Thread.currentThread())
1159	<	.workQueue.tryUnpush(this);
1158	>	Thread t;
1159	>	return (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1160	>	((ForkJoinWorkerThread)t).workQueue.tryUnpush(this) :
1161	>	ForkJoinPool.common.tryExternalUnpush(this));
1162		}
1163
1164		/**
#	Line 1156 | Line 1167 | public abstract class ForkJoinTask<V> im
1167		* value may be useful for heuristic decisions about whether to
1168		* fork other tasks.
1169		*
1159	–	* <p>This method may be invoked only from within {@code
1160	–	* ForkJoinPool} computations (as may be determined using method
1161	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1162	–	* result in exceptions or errors, possibly including {@code
1163	–	* ClassCastException}.
1164	–	*
1170		* @return the number of tasks
1171		*/
1172		public static int getQueuedTaskCount() {
1173	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1174	<	.workQueue.queueSize();
1173	>	Thread t; ForkJoinPool.WorkQueue q;
1174	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
1175	>	q = ((ForkJoinWorkerThread)t).workQueue;
1176	>	else
1177	>	q = ForkJoinPool.commonSubmitterQueue();
1178	>	return (q == null) ? 0 : q.queueSize();
1179		}
1180
1181		/**
1182		* Returns an estimate of how many more locally queued tasks are
1183		* held by the current worker thread than there are other worker
1184	<	* threads that might steal them.  This value may be useful for
1184	>	* threads that might steal them, or zero if this thread is not
1185	>	* operating in a ForkJoinPool. This value may be useful for
1186		* heuristic decisions about whether to fork other tasks. In many
1187		* usages of ForkJoinTasks, at steady state, each worker should
1188		* aim to maintain a small constant surplus (for example, 3) of
1189		* tasks, and to process computations locally if this threshold is
1190		* exceeded.
1191		*
1182	–	* <p>This method may be invoked only from within {@code
1183	–	* ForkJoinPool} computations (as may be determined using method
1184	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1185	–	* result in exceptions or errors, possibly including {@code
1186	–	* ClassCastException}.
1187	–	*
1192		* @return the surplus number of tasks, which may be negative
1193		*/
1194		public static int getSurplusQueuedTaskCount() {
1195	<	/*
1192	<	* The aim of this method is to return a cheap heuristic guide
1193	<	* for task partitioning when programmers, frameworks, tools,
1194	<	* or languages have little or no idea about task granularity.
1195	<	* In essence by offering this method, we ask users only about
1196	<	* tradeoffs in overhead vs expected throughput and its
1197	<	* variance, rather than how finely to partition tasks.
1198	<	*
1199	<	* In a steady state strict (tree-structured) computation,
1200	<	* each thread makes available for stealing enough tasks for
1201	<	* other threads to remain active. Inductively, if all threads
1202	<	* play by the same rules, each thread should make available
1203	<	* only a constant number of tasks.
1204	<	*
1205	<	* The minimum useful constant is just 1. But using a value of
1206	<	* 1 would require immediate replenishment upon each steal to
1207	<	* maintain enough tasks, which is infeasible.  Further,
1208	<	* partitionings/granularities of offered tasks should
1209	<	* minimize steal rates, which in general means that threads
1210	<	* nearer the top of computation tree should generate more
1211	<	* than those nearer the bottom. In perfect steady state, each
1212	<	* thread is at approximately the same level of computation
1213	<	* tree. However, producing extra tasks amortizes the
1214	<	* uncertainty of progress and diffusion assumptions.
1215	<	*
1216	<	* So, users will want to use values larger, but not much
1217	<	* larger than 1 to both smooth over transient shortages and
1218	<	* hedge against uneven progress; as traded off against the
1219	<	* cost of extra task overhead. We leave the user to pick a
1220	<	* threshold value to compare with the results of this call to
1221	<	* guide decisions, but recommend values such as 3.
1222	<	*
1223	<	* When all threads are active, it is on average OK to
1224	<	* estimate surplus strictly locally. In steady-state, if one
1225	<	* thread is maintaining say 2 surplus tasks, then so are
1226	<	* others. So we can just use estimated queue length.
1227	<	* However, this strategy alone leads to serious mis-estimates
1228	<	* in some non-steady-state conditions (ramp-up, ramp-down,
1229	<	* other stalls). We can detect many of these by further
1230	<	* considering the number of "idle" threads, that are known to
1231	<	* have zero queued tasks, so compensate by a factor of
1232	<	* (#idle/#active) threads.
1233	<	*/
1234	<	ForkJoinWorkerThread wt =
1235	<	(ForkJoinWorkerThread)Thread.currentThread();
1236	<	return wt.workQueue.queueSize() - wt.pool.idlePerActive();
1195	>	return ForkJoinPool.getSurplusQueuedTaskCount();
1196		}
1197
1198		// Extension methods
#	Line 1284 | Line 1243 | public abstract class ForkJoinTask<V> im
1243		* primarily to support extensions, and is unlikely to be useful
1244		* otherwise.
1245		*
1287	–	* <p>This method may be invoked only from within {@code
1288	–	* ForkJoinPool} computations (as may be determined using method
1289	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1290	–	* result in exceptions or errors, possibly including {@code
1291	–	* ClassCastException}.
1292	–	*
1246		* @return the next task, or {@code null} if none are available
1247		*/
1248		protected static ForkJoinTask<?> peekNextLocalTask() {
1249	<	return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek();
1249	>	Thread t; ForkJoinPool.WorkQueue q;
1250	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
1251	>	q = ((ForkJoinWorkerThread)t).workQueue;
1252	>	else
1253	>	q = ForkJoinPool.commonSubmitterQueue();
1254	>	return (q == null) ? null : q.peek();
1255		}
1256
1257		/**
1258		* Unschedules and returns, without executing, the next task
1259	<	* queued by the current thread but not yet executed.  This method
1260	<	* is designed primarily to support extensions, and is unlikely to
1261	<	* be useful otherwise.
1262	<	*
1305	<	* <p>This method may be invoked only from within {@code
1306	<	* ForkJoinPool} computations (as may be determined using method
1307	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1308	<	* result in exceptions or errors, possibly including {@code
1309	<	* ClassCastException}.
1259	>	* queued by the current thread but not yet executed, if the
1260	>	* current thread is operating in a ForkJoinPool.  This method is
1261	>	* designed primarily to support extensions, and is unlikely to be
1262	>	* useful otherwise.
1263		*
1264		* @return the next task, or {@code null} if none are available
1265		*/
1266		protected static ForkJoinTask<?> pollNextLocalTask() {
1267	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1268	<	.workQueue.nextLocalTask();
1267	>	Thread t;
1268	>	return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1269	>	((ForkJoinWorkerThread)t).workQueue.nextLocalTask() :
1270	>	null;
1271		}
1272
1273		/**
1274	<	* Unschedules and returns, without executing, the next task
1274	>	* If the current thread is operating in a ForkJoinPool,
1275	>	* unschedules and returns, without executing, the next task
1276		* queued by the current thread but not yet executed, if one is
1277		* available, or if not available, a task that was forked by some
1278		* other thread, if available. Availability may be transient, so a
1279	<	* {@code null} result does not necessarily imply quiescence
1280	<	* of the pool this task is operating in.  This method is designed
1279	>	* {@code null} result does not necessarily imply quiescence of
1280	>	* the pool this task is operating in.  This method is designed
1281		* primarily to support extensions, and is unlikely to be useful
1282		* otherwise.
1283		*
1328	–	* <p>This method may be invoked only from within {@code
1329	–	* ForkJoinPool} computations (as may be determined using method
1330	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1331	–	* result in exceptions or errors, possibly including {@code
1332	–	* ClassCastException}.
1333	–	*
1284		* @return a task, or {@code null} if none are available
1285		*/
1286		protected static ForkJoinTask<?> pollTask() {
1287	<	ForkJoinWorkerThread wt =
1288	<	(ForkJoinWorkerThread)Thread.currentThread();
1289	<	return wt.pool.nextTaskFor(wt.workQueue);
1287	>	Thread t; ForkJoinWorkerThread wt;
1288	>	return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1289	>	(wt = (ForkJoinWorkerThread)t).pool.nextTaskFor(wt.workQueue) :
1290	>	null;
1291		}
1292
1293		// tag operations
#	Line 1376 | Line 1327 | public abstract class ForkJoinTask<V> im
1327		*
1328		* @param e the expected tag value
1329		* @param tag the new tag value
1330	<	* @return true if successful; i.e., the current value was
1330	>	* @return {@code true} if successful; i.e., the current value was
1331		* equal to e and is now tag.
1332		* @since 1.8
1333		*/
#	Line 1429 | Line 1380 | public abstract class ForkJoinTask<V> im
1380		}
1381
1382		/**
1383	+	* Adaptor for Runnables in which failure forces worker exception
1384	+	*/
1385	+	static final class RunnableExecuteAction extends ForkJoinTask<Void> {
1386	+	final Runnable runnable;
1387	+	RunnableExecuteAction(Runnable runnable) {
1388	+	if (runnable == null) throw new NullPointerException();
1389	+	this.runnable = runnable;
1390	+	}
1391	+	public final Void getRawResult() { return null; }
1392	+	public final void setRawResult(Void v) { }
1393	+	public final boolean exec() { runnable.run(); return true; }
1394	+	void internalPropagateException(Throwable ex) {
1395	+	rethrow(ex); // rethrow outside exec() catches.
1396	+	}
1397	+	private static final long serialVersionUID = 5232453952276885070L;
1398	+	}
1399	+
1400	+	/**
1401		* Adaptor for Callables
1402		*/
1403		static final class AdaptedCallable<T> extends ForkJoinTask<T>
#	Line 1476 | Line 1445 | public abstract class ForkJoinTask<V> im
1445		*
1446		* @param runnable the runnable action
1447		* @param result the result upon completion
1448	+	* @param <T> the type of the result
1449		* @return the task
1450		*/
1451		public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
#	Line 1489 | Line 1459 | public abstract class ForkJoinTask<V> im
1459		* encountered into {@code RuntimeException}.
1460		*
1461		* @param callable the callable action
1462	+	* @param <T> the type of the callable's result
1463		* @return the task
1464		*/
1465		public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
#	Line 1525 | Line 1496 | public abstract class ForkJoinTask<V> im
1496		// Unsafe mechanics
1497		private static final sun.misc.Unsafe U;
1498		private static final long STATUS;
1499	+
1500		static {
1501		exceptionTableLock = new ReentrantLock();
1502		exceptionTableRefQueue = new ReferenceQueue<Object>();
1503		exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
1504		try {
1505		U = getUnsafe();
1506	+	Class<?> k = ForkJoinTask.class;
1507		STATUS = U.objectFieldOffset
1508	<	(ForkJoinTask.class.getDeclaredField("status"));
1508	>	(k.getDeclaredField("status"));
1509		} catch (Exception e) {
1510		throw new Error(e);
1511		}
#	Line 1548 | Line 1521 | public abstract class ForkJoinTask<V> im
1521		private static sun.misc.Unsafe getUnsafe() {
1522		try {
1523		return sun.misc.Unsafe.getUnsafe();
1524	<	} catch (SecurityException se) {
1525	<	try {
1526	<	return java.security.AccessController.doPrivileged
1527	<	(new java.security
1528	<	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1529	<	public sun.misc.Unsafe run() throws Exception {
1530	<	java.lang.reflect.Field f = sun.misc
1531	<	.Unsafe.class.getDeclaredField("theUnsafe");
1532	<	f.setAccessible(true);
1533	<	return (sun.misc.Unsafe) f.get(null);
1534	<	}});
1535	<	} catch (java.security.PrivilegedActionException e) {
1536	<	throw new RuntimeException("Could not initialize intrinsics",
1537	<	e.getCause());
1538	<	}
1524	>	} catch (SecurityException tryReflectionInstead) {}
1525	>	try {
1526	>	return java.security.AccessController.doPrivileged
1527	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1528	>	public sun.misc.Unsafe run() throws Exception {
1529	>	Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class;
1530	>	for (java.lang.reflect.Field f : k.getDeclaredFields()) {
1531	>	f.setAccessible(true);
1532	>	Object x = f.get(null);
1533	>	if (k.isInstance(x))
1534	>	return k.cast(x);
1535	>	}
1536	>	throw new NoSuchFieldError("the Unsafe");
1537	>	}});
1538	>	} catch (java.security.PrivilegedActionException e) {
1539	>	throw new RuntimeException("Could not initialize intrinsics",
1540	>	e.getCause());
1541		}
1542		}
1543		}

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