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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.64 by dl, Tue Aug 17 18:30:32 2010 UTC vs.
Revision 1.79 by jsr166, Tue Sep 7 23:49:30 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	–	import java.util.concurrent.*;
10	–
9		import java.util.ArrayList;
10		import java.util.Arrays;
11		import java.util.Collection;
12		import java.util.Collections;
13		import java.util.List;
14	+	import java.util.concurrent.AbstractExecutorService;
15	+	import java.util.concurrent.Callable;
16	+	import java.util.concurrent.CountDownLatch;
17	+	import java.util.concurrent.ExecutorService;
18	+	import java.util.concurrent.Future;
19	+	import java.util.concurrent.RejectedExecutionException;
20	+	import java.util.concurrent.RunnableFuture;
21	+	import java.util.concurrent.TimeUnit;
22	+	import java.util.concurrent.TimeoutException;
23	+	import java.util.concurrent.atomic.AtomicInteger;
24		import java.util.concurrent.locks.LockSupport;
25		import java.util.concurrent.locks.ReentrantLock;
18	–	import java.util.concurrent.atomic.AtomicInteger;
19	–	import java.util.concurrent.CountDownLatch;
26
27		/**
28		* An {@link ExecutorService} for running {@link ForkJoinTask}s.
#	Line 69 | Line 75 | import java.util.concurrent.CountDownLat
75		*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
76		*  </tr>
77		*  <tr>
78	<	*    <td> <b>Arange async execution</td>
78	>	*    <td> <b>Arrange async execution</td>
79		*    <td> {@link #execute(ForkJoinTask)}</td>
80		*    <td> {@link ForkJoinTask#fork}</td>
81		*  </tr>
#	Line 140 | Line 146 | public class ForkJoinPool extends Abstra
146		* Beyond work-stealing support and essential bookkeeping, the
147		* main responsibility of this framework is to take actions when
148		* one worker is waiting to join a task stolen (or always held by)
149	<	* another.  Becauae we are multiplexing many tasks on to a pool
149	>	* another.  Because we are multiplexing many tasks on to a pool
150		* of workers, we can't just let them block (as in Thread.join).
151		* We also cannot just reassign the joiner's run-time stack with
152		* another and replace it later, which would be a form of
#	Line 157 | Line 163 | public class ForkJoinPool extends Abstra
163		*      links to try to find such a task.
164		*
165		*   Compensating: Unless there are already enough live threads,
166	<	*      method helpMaintainParallelism() may create or or
166	>	*      method helpMaintainParallelism() may create or
167		*      re-activate a spare thread to compensate for blocked
168		*      joiners until they unblock.
169		*
170	<	* Because the determining existence of conservatively safe
171	<	* helping targets, the availability of already-created spares,
172	<	* and the apparent need to create new spares are all racy and
173	<	* require heuristic guidance, we rely on multiple retries of
174	<	* each. Further, because it is impossible to keep exactly the
175	<	* target (parallelism) number of threads running at any given
176	<	* time, we allow compensation during joins to fail, and enlist
177	<	* all other threads to help out whenever they are not otherwise
178	<	* occupied (i.e., mainly in method preStep).
170	>	* It is impossible to keep exactly the target (parallelism)
171	>	* number of threads running at any given time.  Determining
172	>	* existence of conservatively safe helping targets, the
173	>	* availability of already-created spares, and the apparent need
174	>	* to create new spares are all racy and require heuristic
175	>	* guidance, so we rely on multiple retries of each.  Compensation
176	>	* occurs in slow-motion. It is triggered only upon timeouts of
177	>	* Object.wait used for joins. This reduces poor decisions that
178	>	* would otherwise be made when threads are waiting for others
179	>	* that are stalled because of unrelated activities such as
180	>	* garbage collection.
181		*
182		* The ManagedBlocker extension API can't use helping so relies
183		* only on compensation in method awaitBlocker.
#	Line 224 | Line 232 | public class ForkJoinPool extends Abstra
232		* ManagedBlocker), we may create or resume others to take their
233		* place until they unblock (see below). Implementing this
234		* requires counts of the number of "running" threads (i.e., those
235	<	* that are neither blocked nor artifically suspended) as well as
235	>	* that are neither blocked nor artificially suspended) as well as
236		* the total number.  These two values are packed into one field,
237		* "workerCounts" because we need accurate snapshots when deciding
238		* to create, resume or suspend.  Note however that the
239	<	* correspondance of these counts to reality is not guaranteed. In
239	>	* correspondence of these counts to reality is not guaranteed. In
240		* particular updates for unblocked threads may lag until they
241		* actually wake up.
242		*
#	Line 271 | Line 279 | public class ForkJoinPool extends Abstra
279		* In addition to allowing simpler decisions about need for
280		* wakeup, the event count bits in eventWaiters serve the role of
281		* tags to avoid ABA errors in Treiber stacks. Upon any wakeup,
282	<	* released threads also try to release others (but give up upon
283	<	* contention to reduce useless flailing).  The net effect is a
284	<	* tree-like diffusion of signals, where released threads (and
285	<	* possibly others) help with unparks.  To further reduce
286	<	* contention effects a bit, failed CASes to increment field
279	<	* eventCount are tolerated without retries in signalWork.
282	>	* released threads also try to release at most two others.  The
283	>	* net effect is a tree-like diffusion of signals, where released
284	>	* threads (and possibly others) help with unparks.  To further
285	>	* reduce contention effects a bit, failed CASes to increment
286	>	* field eventCount are tolerated without retries in signalWork.
287		* Conceptually they are merged into the same event, which is OK
288		* when their only purpose is to enable workers to scan for work.
289		*
290	<	* 5. Managing suspension of extra workers. When a worker is about
291	<	* to block waiting for a join (or via ManagedBlockers), we may
292	<	* create a new thread to maintain parallelism level, or at least
293	<	* avoid starvation. Usually, extra threads are needed for only
294	<	* very short periods, yet join dependencies are such that we
295	<	* sometimes need them in bursts. Rather than create new threads
296	<	* each time this happens, we suspend no-longer-needed extra ones
297	<	* as "spares". For most purposes, we don't distinguish "extra"
298	<	* spare threads from normal "core" threads: On each call to
299	<	* preStep (the only point at which we can do this) a worker
300	<	* checks to see if there are now too many running workers, and if
301	<	* so, suspends itself.  Method helpMaintainParallelism looks for
302	<	* suspended threads to resume before considering creating a new
303	<	* replacement. The spares themselves are encoded on another
304	<	* variant of a Treiber Stack, headed at field "spareWaiters".
305	<	* Note that the use of spares is intrinsically racy.  One thread
306	<	* may become a spare at about the same time as another is
307	<	* needlessly being created. We counteract this and related slop
308	<	* in part by requiring resumed spares to immediately recheck (in
309	<	* preStep) to see whether they they should re-suspend.
310	<	*
311	<	* 6. Killing off unneeded workers. The Spare and Event queues use
312	<	* similar mechanisms to shed unused workers: The oldest (first)
313	<	* waiter uses a timed rather than hard wait. When this wait times
314	<	* out without a normal wakeup, it tries to shutdown any one (for
315	<	* convenience the newest) other waiter via tryShutdownSpare or
316	<	* tryShutdownWaiter, respectively. The wakeup rates for spares
317	<	* are much shorter than for waiters. Together, they will
318	<	* eventually reduce the number of worker threads to a minimum of
319	<	* one after a long enough period without use.
290	>	* 5. Managing suspension of extra workers. When a worker notices
291	>	* (usually upon timeout of a wait()) that there are too few
292	>	* running threads, we may create a new thread to maintain
293	>	* parallelism level, or at least avoid starvation. Usually, extra
294	>	* threads are needed for only very short periods, yet join
295	>	* dependencies are such that we sometimes need them in
296	>	* bursts. Rather than create new threads each time this happens,
297	>	* we suspend no-longer-needed extra ones as "spares". For most
298	>	* purposes, we don't distinguish "extra" spare threads from
299	>	* normal "core" threads: On each call to preStep (the only point
300	>	* at which we can do this) a worker checks to see if there are
301	>	* now too many running workers, and if so, suspends itself.
302	>	* Method helpMaintainParallelism looks for suspended threads to
303	>	* resume before considering creating a new replacement. The
304	>	* spares themselves are encoded on another variant of a Treiber
305	>	* Stack, headed at field "spareWaiters".  Note that the use of
306	>	* spares is intrinsically racy.  One thread may become a spare at
307	>	* about the same time as another is needlessly being created. We
308	>	* counteract this and related slop in part by requiring resumed
309	>	* spares to immediately recheck (in preStep) to see whether they
310	>	* should re-suspend.
311	>	*
312	>	* 6. Killing off unneeded workers. A timeout mechanism is used to
313	>	* shed unused workers: The oldest (first) event queue waiter uses
314	>	* a timed rather than hard wait. When this wait times out without
315	>	* a normal wakeup, it tries to shutdown any one (for convenience
316	>	* the newest) other spare or event waiter via
317	>	* tryShutdownUnusedWorker. This eventually reduces the number of
318	>	* worker threads to a minimum of one after a long enough period
319	>	* without use.
320		*
321		* 7. Deciding when to create new workers. The main dynamic
322		* control in this class is deciding when to create extra threads
323		* in method helpMaintainParallelism. We would like to keep
324	<	* exactly #parallelism threads running, which is an impossble
324	>	* exactly #parallelism threads running, which is an impossible
325		* task. We always need to create one when the number of running
326		* threads would become zero and all workers are busy. Beyond
327	<	* this, we must rely on heuristics that work well in the the
328	<	* presence of transients phenomena such as GC stalls, dynamic
327	>	* this, we must rely on heuristics that work well in the
328	>	* presence of transient phenomena such as GC stalls, dynamic
329		* compilation, and wake-up lags. These transients are extremely
330		* common -- we are normally trying to fully saturate the CPUs on
331		* a machine, so almost any activity other than running tasks
332	<	* impedes accuracy. Our main defense is to allow some slack in
333	<	* creation thresholds, using rules that reflect the fact that the
334	<	* more threads we have running, the more likely that we are
335	<	* underestimating the number running threads. (We also include
336	<	* some heuristic use of Thread.yield when all workers appear to
337	<	* be busy, to improve likelihood of counts settling.) The rules
338	<	* also better cope with the fact that some of the methods in this
339	<	* class tend to never become compiled (but are interpreted), so
340	<	* some components of the entire set of controls might execute 100
334	<	* times faster than others. And similarly for cases where the
335	<	* apparent lack of work is just due to GC stalls and other
336	<	* transient system activity.
332	>	* impedes accuracy. Our main defense is to allow parallelism to
333	>	* lapse for a while during joins, and use a timeout to see if,
334	>	* after the resulting settling, there is still a need for
335	>	* additional workers.  This also better copes with the fact that
336	>	* some of the methods in this class tend to never become compiled
337	>	* (but are interpreted), so some components of the entire set of
338	>	* controls might execute 100 times faster than others. And
339	>	* similarly for cases where the apparent lack of work is just due
340	>	* to GC stalls and other transient system activity.
341		*
342		* Beware that there is a lot of representation-level coupling
343		* among classes ForkJoinPool, ForkJoinWorkerThread, and
#	Line 348 | Line 352 | public class ForkJoinPool extends Abstra
352		* "while ((local = field) != 0)") which are usually the simplest
353		* way to ensure the required read orderings (which are sometimes
354		* critical). Also several occurrences of the unusual "do {}
355	<	* while(!cas...)" which is the simplest way to force an update of
355	>	* while (!cas...)" which is the simplest way to force an update of
356		* a CAS'ed variable. There are also other coding oddities that
357		* help some methods perform reasonably even when interpreted (not
358		* compiled), at the expense of some messy constructions that
#	Line 420 | Line 424 | public class ForkJoinPool extends Abstra
424		new AtomicInteger();
425
426		/**
427	+	* The time to block in a join (see awaitJoin) before checking if
428	+	* a new worker should be (re)started to maintain parallelism
429	+	* level. The value should be short enough to maintain global
430	+	* responsiveness and progress but long enough to avoid
431	+	* counterproductive firings during GC stalls or unrelated system
432	+	* activity, and to not bog down systems with continual re-firings
433	+	* on GCs or legitimately long waits.
434	+	*/
435	+	private static final long JOIN_TIMEOUT_MILLIS = 250L; // 4 per second
436	+
437	+	/**
438		* The wakeup interval (in nanoseconds) for the oldest worker
439	<	* worker waiting for an event invokes tryShutdownWaiter to shrink
440	<	* the number of workers.  The exact value does not matter too
441	<	* much, but should be long enough to slowly release resources
442	<	* during long periods without use without disrupting normal use.
439	>	* waiting for an event to invoke tryShutdownUnusedWorker to
440	>	* shrink the number of workers.  The exact value does not matter
441	>	* too much. It must be short enough to release resources during
442	>	* sustained periods of idleness, but not so short that threads
443	>	* are continually re-created.
444		*/
445		private static final long SHRINK_RATE_NANOS =
446	<	60L * 1000L * 1000L * 1000L; // one minute
446	>	30L * 1000L * 1000L * 1000L; // 2 per minute
447
448		/**
449		* Absolute bound for parallelism level. Twice this number plus
#	Line 474 | Line 490 | public class ForkJoinPool extends Abstra
490		private volatile long stealCount;
491
492		/**
493	<	* Encoded record of top of treiber stack of threads waiting for
493	>	* Encoded record of top of Treiber stack of threads waiting for
494		* events. The top 32 bits contain the count being waited for. The
495		* bottom 16 bits contains one plus the pool index of waiting
496		* worker thread. (Bits 16-31 are unused.)
#	Line 493 | Line 509 | public class ForkJoinPool extends Abstra
509		private volatile int eventCount;
510
511		/**
512	<	* Encoded record of top of treiber stack of spare threads waiting
512	>	* Encoded record of top of Treiber stack of spare threads waiting
513		* for resumption. The top 16 bits contain an arbitrary count to
514		* avoid ABA effects. The bottom 16bits contains one plus the pool
515		* index of waiting worker thread.
#	Line 507 | Line 523 | public class ForkJoinPool extends Abstra
523		* Lifecycle control. The low word contains the number of workers
524		* that are (probably) executing tasks. This value is atomically
525		* incremented before a worker gets a task to run, and decremented
526	<	* when worker has no tasks and cannot find any.  Bits 16-18
526	>	* when a worker has no tasks and cannot find any.  Bits 16-18
527		* contain runLevel value. When all are zero, the pool is
528		* running. Level transitions are monotonic (running -> shutdown
529		* -> terminating -> terminated) so each transition adds a bit.
#	Line 567 | Line 583 | public class ForkJoinPool extends Abstra
583		*/
584		private final int poolNumber;
585
570	–
586		// Utilities for CASing fields. Note that most of these
587		// are usually manually inlined by callers
588
#	Line 597 | Line 612 | public class ForkJoinPool extends Abstra
612		* (rarely) necessary when other count updates lag.
613		*
614		* @param dr -- either zero or ONE_RUNNING
615	<	* @param dt == either zero or ONE_TOTAL
615	>	* @param dt -- either zero or ONE_TOTAL
616		*/
617		private void decrementWorkerCounts(int dr, int dt) {
618		for (;;) {
#	Line 615 | Line 630 | public class ForkJoinPool extends Abstra
630		}
631
632		/**
618	–	* Increments event count
619	–	*/
620	–	private void advanceEventCount() {
621	–	int c;
622	–	do {} while(!UNSAFE.compareAndSwapInt(this, eventCountOffset,
623	–	c = eventCount, c+1));
624	–	}
625	–
626	–	/**
627	–	* Tries incrementing active count; fails on contention.
628	–	* Called by workers before executing tasks.
629	–	*
630	–	* @return true on success
631	–	*/
632	–	final boolean tryIncrementActiveCount() {
633	–	int c;
634	–	return UNSAFE.compareAndSwapInt(this, runStateOffset,
635	–	c = runState, c + 1);
636	–	}
637	–
638	–	/**
633		* Tries decrementing active count; fails on contention.
634		* Called when workers cannot find tasks to run.
635		*/
#	Line 687 | Line 681 | public class ForkJoinPool extends Abstra
681		}
682
683		/**
684	<	* Nulls out record of worker in workers array
684	>	* Nulls out record of worker in workers array.
685		*/
686		private void forgetWorker(ForkJoinWorkerThread w) {
687		int idx = w.poolIndex;
688	<	// Locking helps method recordWorker avoid unecessary expansion
688	>	// Locking helps method recordWorker avoid unnecessary expansion
689		final ReentrantLock lock = this.workerLock;
690		lock.lock();
691		try {
#	Line 703 | Line 697 | public class ForkJoinPool extends Abstra
697		}
698		}
699
706	–	// adding and removing workers
707	–
708	–	/**
709	–	* Tries to create and add new worker. Assumes that worker counts
710	–	* are already updated to accommodate the worker, so adjusts on
711	–	* failure.
712	–	*
713	–	* @return the worker, or null on failure
714	–	*/
715	–	private ForkJoinWorkerThread addWorker() {
716	–	ForkJoinWorkerThread w = null;
717	–	try {
718	–	w = factory.newThread(this);
719	–	} finally { // Adjust on either null or exceptional factory return
720	–	if (w == null) {
721	–	decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL);
722	–	tryTerminate(false); // in case of failure during shutdown
723	–	}
724	–	}
725	–	if (w != null) {
726	–	w.start(recordWorker(w), ueh);
727	–	advanceEventCount();
728	–	}
729	–	return w;
730	–	}
731	–
700		/**
701		* Final callback from terminating worker.  Removes record of
702		* worker from array, and adjusts counts. If pool is shutting
703	<	* down, tries to complete terminatation.
703	>	* down, tries to complete termination.
704		*
705		* @param w the worker
706		*/
#	Line 750 | Line 718 | public class ForkJoinPool extends Abstra
718		* Releases workers blocked on a count not equal to current count.
719		* Normally called after precheck that eventWaiters isn't zero to
720		* avoid wasted array checks. Gives up upon a change in count or
721	<	* contention, letting other workers take over.
721	>	* upon releasing two workers, letting others take over.
722		*/
723		private void releaseEventWaiters() {
724		ForkJoinWorkerThread[] ws = workers;
725		int n = ws.length;
726		long h = eventWaiters;
727		int ec = eventCount;
728	+	boolean releasedOne = false;
729		ForkJoinWorkerThread w; int id;
730	<	while ((int)(h >>> EVENT_COUNT_SHIFT) != ec &&
731	<	(id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 &&
732	<	id < n && (w = ws[id]) != null &&
733	<	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
734	<	h,  h = w.nextWaiter)) {
735	<	LockSupport.unpark(w);
736	<	if (eventWaiters != h || eventCount != ec)
730	>	while ((id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 &&
731	>	(int)(h >>> EVENT_COUNT_SHIFT) != ec &&
732	>	id < n && (w = ws[id]) != null) {
733	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
734	>	h,  w.nextWaiter)) {
735	>	LockSupport.unpark(w);
736	>	if (releasedOne) // exit on second release
737	>	break;
738	>	releasedOne = true;
739	>	}
740	>	if (eventCount != ec)
741		break;
742	+	h = eventWaiters;
743		}
744		}
745
#	Line 782 | Line 756 | public class ForkJoinPool extends Abstra
756
757		/**
758		* Adds the given worker to event queue and blocks until
759	<	* terminating or event count advances from the workers
786	<	* lastEventCount value
759	>	* terminating or event count advances from the given value
760		*
761		* @param w the calling worker thread
762	+	* @param ec the count
763		*/
764	<	private void eventSync(ForkJoinWorkerThread w) {
791	<	int ec = w.lastEventCount;
764	>	private void eventSync(ForkJoinWorkerThread w, int ec) {
765		long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1));
766		long h;
767		while ((runState < SHUTDOWN || !tryTerminate(false)) &&
#	Line 808 | Line 781 | public class ForkJoinPool extends Abstra
781		* event waiter) until terminating or event count advances from
782		* the given value. The oldest (first) waiter uses a timed wait to
783		* occasionally one-by-one shrink the number of workers (to a
784	<	* minumum of one) if the pool has not been used for extended
784	>	* minimum of one) if the pool has not been used for extended
785		* periods.
786		*
787		* @param w the calling worker thread
#	Line 821 | Line 794 | public class ForkJoinPool extends Abstra
794		(workerCounts & RUNNING_COUNT_MASK) <= 1);
795		long startTime = untimed? 0 : System.nanoTime();
796		Thread.interrupted();         // clear/ignore interrupt
797	<	if (eventCount != ec || !w.isRunning() ||
797	>	if (eventCount != ec || w.runState != 0 ||
798		runState >= TERMINATING)  // recheck after clear
799		break;
800		if (untimed)
801		LockSupport.park(w);
802		else {
803		LockSupport.parkNanos(w, SHRINK_RATE_NANOS);
804	<	if (eventCount != ec || !w.isRunning() ||
804	>	if (eventCount != ec || w.runState != 0 ||
805		runState >= TERMINATING)
806		break;
807		if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS)
808	<	tryShutdownWaiter(ec);
808	>	tryShutdownUnusedWorker(ec);
809		}
810		}
811		}
812		}
813
814	<	/**
842	<	* Callback from the oldest waiter in awaitEvent waking up after a
843	<	* period of non-use. Tries (once) to shutdown an event waiter (or
844	<	* a spare, if one exists). Note that we don't need CAS or locks
845	<	* here because the method is called only from one thread
846	<	* occasionally waking (and even misfires are OK). Note that
847	<	* until the shutdown worker fully terminates, workerCounts
848	<	* will overestimate total count, which is tolerable.
849	<	*
850	<	* @param ec the event count waited on by caller (to abort
851	<	* attempt if count has since changed).
852	<	*/
853	<	private void tryShutdownWaiter(int ec) {
854	<	if (spareWaiters != 0) { // prefer killing spares
855	<	tryShutdownSpare();
856	<	return;
857	<	}
858	<	ForkJoinWorkerThread[] ws = workers;
859	<	int n = ws.length;
860	<	long h = eventWaiters;
861	<	ForkJoinWorkerThread w; int id; long nh;
862	<	if (runState == 0 &&
863	<	submissionQueue.isEmpty() &&
864	<	eventCount == ec &&
865	<	(id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 &&
866	<	id < n && (w = ws[id]) != null &&
867	<	(nh = w.nextWaiter) != 0L && // keep at least one worker
868	<	UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh)) {
869	<	w.shutdown();
870	<	LockSupport.unpark(w);
871	<	}
872	<	releaseEventWaiters();
873	<	}
874	<
875	<	// Maintaining spares
814	>	// Maintaining parallelism
815
816		/**
817	<	* Pushes worker onto the spare stack
817	>	* Pushes worker onto the spare stack.
818		*/
819		final void pushSpare(ForkJoinWorkerThread w) {
820		int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1);
#	Line 884 | Line 823 | public class ForkJoinPool extends Abstra
823		}
824
825		/**
826	<	* Callback from oldest spare occasionally waking up.  Tries
827	<	* (once) to shutdown a spare. Same idea as tryShutdownWaiter.
826	>	* Tries (once) to resume a spare if the number of running
827	>	* threads is less than target.
828		*/
829	<	final void tryShutdownSpare() {
829	>	private void tryResumeSpare() {
830		int sw, id;
892	–	ForkJoinWorkerThread w;
893	–	ForkJoinWorkerThread[] ws;
894	–	if ((id = ((sw = spareWaiters) & SPARE_ID_MASK) - 1) >= 0 &&
895	–	id < (ws = workers).length && (w = ws[id]) != null &&
896	–	(workerCounts & RUNNING_COUNT_MASK) >= parallelism &&
897	–	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
898	–	sw, w.nextSpare)) {
899	–	w.shutdown();
900	–	LockSupport.unpark(w);
901	–	advanceEventCount();
902	–	}
903	–	}
904	–
905	–	/**
906	–	* Tries (once) to resume a spare if worker counts match
907	–	* the given count.
908	–	*
909	–	* @param wc workerCounts value on invocation of this method
910	–	*/
911	–	private void tryResumeSpare(int wc) {
831		ForkJoinWorkerThread[] ws = workers;
832		int n = ws.length;
833	<	int sw, id, rs;  ForkJoinWorkerThread w;
834	<	if ((id = ((sw = spareWaiters) & SPARE_ID_MASK) - 1) >= 0 &&
833	>	ForkJoinWorkerThread w;
834	>	if ((sw = spareWaiters) != 0 &&
835	>	(id = (sw & SPARE_ID_MASK) - 1) >= 0 &&
836		id < n && (w = ws[id]) != null &&
837	<	(rs = runState) < TERMINATING &&
838	<	eventWaiters == 0L && workerCounts == wc) {
839	<	// In case all workers busy, heuristically back off to let settle
840	<	Thread.yield();
841	<	if (eventWaiters == 0L && runState == rs && // recheck
842	<	workerCounts == wc && spareWaiters == sw &&
843	<	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
844	<	sw, w.nextSpare)) {
845	<	int c;              // increment running count before resume
846	<	do {} while(!UNSAFE.compareAndSwapInt
847	<	(this, workerCountsOffset,
848	<	c = workerCounts, c + ONE_RUNNING));
929	<	if (w.tryUnsuspend())
930	<	LockSupport.unpark(w);
931	<	else               // back out if w was shutdown
932	<	decrementWorkerCounts(ONE_RUNNING, 0);
933	<	}
837	>	(workerCounts & RUNNING_COUNT_MASK) < parallelism &&
838	>	spareWaiters == sw &&
839	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
840	>	sw, w.nextSpare)) {
841	>	int c; // increment running count before resume
842	>	do {} while (!UNSAFE.compareAndSwapInt
843	>	(this, workerCountsOffset,
844	>	c = workerCounts, c + ONE_RUNNING));
845	>	if (w.tryUnsuspend())
846	>	LockSupport.unpark(w);
847	>	else   // back out if w was shutdown
848	>	decrementWorkerCounts(ONE_RUNNING, 0);
849		}
850		}
851
937	–	// adding workers on demand
938	–
852		/**
853	<	* Adds one or more workers if needed to establish target parallelism.
854	<	* Retries upon contention.
853	>	* Tries to increase the number of running workers if below target
854	>	* parallelism: If a spare exists tries to resume it via
855	>	* tryResumeSpare.  Otherwise, if not enough total workers or all
856	>	* existing workers are busy, adds a new worker. In all cases also
857	>	* helps wake up releasable workers waiting for work.
858		*/
859	<	private void addWorkerIfBelowTarget() {
859	>	private void helpMaintainParallelism() {
860		int pc = parallelism;
861	<	int wc;
862	<	while (((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < pc &&
863	<	runState < TERMINATING) {
864	<	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
865	<	wc + (ONE_RUNNING|ONE_TOTAL))) {
866	<	if (addWorker() == null)
861	>	int wc, rs, tc;
862	>	while (((wc = workerCounts) & RUNNING_COUNT_MASK) < pc &&
863	>	(rs = runState) < TERMINATING) {
864	>	if (spareWaiters != 0)
865	>	tryResumeSpare();
866	>	else if ((tc = wc >>> TOTAL_COUNT_SHIFT) >= MAX_WORKERS ||
867	>	(tc >= pc && (rs & ACTIVE_COUNT_MASK) != tc))
868	>	break;   // enough total
869	>	else if (runState == rs && workerCounts == wc &&
870	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
871	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
872	>	ForkJoinWorkerThread w = null;
873	>	try {
874	>	w = factory.newThread(this);
875	>	} finally { // adjust on null or exceptional factory return
876	>	if (w == null) {
877	>	decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL);
878	>	tryTerminate(false); // handle failure during shutdown
879	>	}
880	>	}
881	>	if (w == null)
882		break;
883	+	w.start(recordWorker(w), ueh);
884	+	if ((workerCounts >>> TOTAL_COUNT_SHIFT) >= pc) {
885	+	int c; // advance event count
886	+	UNSAFE.compareAndSwapInt(this, eventCountOffset,
887	+	c = eventCount, c+1);
888	+	break; // add at most one unless total below target
889	+	}
890		}
891		}
892	+	if (eventWaiters != 0L)
893	+	releaseEventWaiters();
894		}
895
896		/**
897	<	* Tries (once) to add a new worker if all existing workers are
898	<	* busy, and there are either no running workers or the deficit is
899	<	* at least twice the surplus.
900	<	*
901	<	* @param wc workerCounts value on invocation of this method
902	<	*/
903	<	private void tryAddWorkerIfBusy(int wc) {
964	<	int tc, rc, rs;
965	<	int pc = parallelism;
966	<	if ((tc = wc >>> TOTAL_COUNT_SHIFT) < MAX_WORKERS &&
967	<	((rc = wc & RUNNING_COUNT_MASK) == 0 ||
968	<	rc < pc - ((tc - pc) << 1)) &&
969	<	(rs = runState) < TERMINATING &&
970	<	(rs & ACTIVE_COUNT_MASK) == tc) {
971	<	// Since all workers busy, heuristically back off to let settle
972	<	Thread.yield();
973	<	if (eventWaiters == 0L && spareWaiters == 0 && // recheck
974	<	runState == rs && workerCounts == wc &&
975	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
976	<	wc + (ONE_RUNNING|ONE_TOTAL)))
977	<	addWorker();
978	<	}
979	<	}
980	<
981	<	/**
982	<	* Does at most one of:
983	<	*
984	<	* 1. Help wake up existing workers waiting for work via
985	<	*    releaseEventWaiters. (If any exist, then it doesn't
986	<	*    matter right now if under target parallelism level.)
987	<	*
988	<	* 2. If a spare exists, try (once) to resume it via tryResumeSpare.
989	<	*
990	<	* 3. If there are not enough total workers, add some
991	<	*    via addWorkerIfBelowTarget;
897	>	* Callback from the oldest waiter in awaitEvent waking up after a
898	>	* period of non-use. If all workers are idle, tries (once) to
899	>	* shutdown an event waiter or a spare, if one exists. Note that
900	>	* we don't need CAS or locks here because the method is called
901	>	* only from one thread occasionally waking (and even misfires are
902	>	* OK). Note that until the shutdown worker fully terminates,
903	>	* workerCounts will overestimate total count, which is tolerable.
904		*
905	<	* 4. Try (once) to add a new worker if all existing workers
906	<	*     are busy, via tryAddWorkerIfBusy
905	>	* @param ec the event count waited on by caller (to abort
906	>	* attempt if count has since changed).
907		*/
908	<	private void helpMaintainParallelism() {
909	<	long h; int pc, wc;
910	<	if (((int)((h = eventWaiters) & WAITER_ID_MASK)) != 0) {
911	<	if ((int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
912	<	releaseEventWaiters(); // avoid useless call
913	<	}
914	<	else if ((pc = parallelism) >
915	<	((wc = workerCounts) & RUNNING_COUNT_MASK)) {
916	<	if (spareWaiters != 0)
917	<	tryResumeSpare(wc);
918	<	else if ((wc >>> TOTAL_COUNT_SHIFT) < pc)
919	<	addWorkerIfBelowTarget();
920	<	else
921	<	tryAddWorkerIfBusy(wc);
908	>	private void tryShutdownUnusedWorker(int ec) {
909	>	if (runState == 0 && eventCount == ec) { // only trigger if all idle
910	>	ForkJoinWorkerThread[] ws = workers;
911	>	int n = ws.length;
912	>	ForkJoinWorkerThread w = null;
913	>	boolean shutdown = false;
914	>	int sw;
915	>	long h;
916	>	if ((sw = spareWaiters) != 0) { // prefer killing spares
917	>	int id = (sw & SPARE_ID_MASK) - 1;
918	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
919	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
920	>	sw, w.nextSpare))
921	>	shutdown = true;
922	>	}
923	>	else if ((h = eventWaiters) != 0L) {
924	>	long nh;
925	>	int id = ((int)(h & WAITER_ID_MASK)) - 1;
926	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
927	>	(nh = w.nextWaiter) != 0L && // keep at least one worker
928	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh))
929	>	shutdown = true;
930	>	}
931	>	if (w != null && shutdown) {
932	>	w.shutdown();
933	>	LockSupport.unpark(w);
934	>	}
935		}
936	+	releaseEventWaiters(); // in case of interference
937		}
938
939		/**
#	Line 1015 | Line 941 | public class ForkJoinPool extends Abstra
941		* stealing a task or taking a submission and running it).
942		* Performs one or more of the following:
943		*
944	<	* 1. If the worker is active, try to set its active status to
945	<	*    inactive and update activeCount. On contention, we may try
946	<	*    again on this or subsequent call.
947	<	*
948	<	* 2. Release any existing event waiters that are now relesable
949	<	*
950	<	* 3. If there are too many running threads, suspend this worker
951	<	*    (first forcing inactive if necessary).  If it is not
952	<	*    needed, it may be killed while suspended via
953	<	*    tryShutdownSpare. Otherwise, upon resume it rechecks to make
954	<	*    sure that it is still needed.
955	<	*
956	<	* 4. If more than 1 miss, await the next task event via
957	<	*    eventSync (first forcing inactivation if necessary), upon
958	<	*    which worker may also be killed, via tryShutdownWaiter.
959	<	*
960	<	* 5. Help reactivate other workers via helpMaintainParallelism
944	>	* 1. If the worker is active and either did not run a task
945	>	*    or there are too many workers, try to set its active status
946	>	*    to inactive and update activeCount. On contention, we may
947	>	*    try again in this or a subsequent call.
948	>	*
949	>	* 2. If not enough total workers, help create some.
950	>	*
951	>	* 3. If there are too many running workers, suspend this worker
952	>	*    (first forcing inactive if necessary).  If it is not needed,
953	>	*    it may be shutdown while suspended (via
954	>	*    tryShutdownUnusedWorker).  Otherwise, upon resume it
955	>	*    rechecks running thread count and need for event sync.
956	>	*
957	>	* 4. If worker did not run a task, await the next task event via
958	>	*    eventSync if necessary (first forcing inactivation), upon
959	>	*    which the worker may be shutdown via
960	>	*    tryShutdownUnusedWorker.  Otherwise, help release any
961	>	*    existing event waiters that are now releasable,
962		*
963		* @param w the worker
964	<	* @param misses the number of scans by caller failing to find work
1038	<	* (saturating at 2 to avoid wraparound)
964	>	* @param ran true if worker ran a task since last call to this method
965		*/
966	<	final void preStep(ForkJoinWorkerThread w, int misses) {
966	>	final void preStep(ForkJoinWorkerThread w, boolean ran) {
967	>	int wec = w.lastEventCount;
968		boolean active = w.active;
969	+	boolean inactivate = false;
970		int pc = parallelism;
971	<	for (;;) {
972	<	int rs, wc, rc, ec; long h;
973	<	if (active && UNSAFE.compareAndSwapInt(this, runStateOffset,
974	<	rs = runState, rs - 1))
975	<	active = w.active = false;
976	<	if (((int)((h = eventWaiters) & WAITER_ID_MASK)) != 0 &&
977	<	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount) {
978	<	releaseEventWaiters();
1051	<	if (misses > 1)
1052	<	continue;                  // clear before sync below
1053	<	}
1054	<	if ((rc = ((wc = workerCounts) & RUNNING_COUNT_MASK)) > pc) {
1055	<	if (!active &&                 // must inactivate to suspend
971	>	int rs;
972	>	while (w.runState == 0 && (rs = runState) < TERMINATING) {
973	>	if ((inactivate || (active && (rs & ACTIVE_COUNT_MASK) >= pc)) &&
974	>	UNSAFE.compareAndSwapInt(this, runStateOffset, rs, rs - 1))
975	>	inactivate = active = w.active = false;
976	>	int wc = workerCounts;
977	>	if ((wc & RUNNING_COUNT_MASK) > pc) {
978	>	if (!(inactivate |= active) && // must inactivate to suspend
979		workerCounts == wc &&      // try to suspend as spare
980		UNSAFE.compareAndSwapInt(this, workerCountsOffset,
981	<	wc, wc - ONE_RUNNING)) {
981	>	wc, wc - ONE_RUNNING))
982		w.suspendAsSpare();
1060	–	if (!w.isRunning())
1061	–	break;                 // was killed while spare
1062	–	}
1063	–	continue;
983		}
984	<	if (misses > 0) {
985	<	if ((ec = eventCount) == w.lastEventCount && misses > 1) {
986	<	if (!active) {             // must inactivate to sync
987	<	eventSync(w);
988	<	if (w.isRunning())
989	<	misses = 1;        // don't re-sync
990	<	else
991	<	break;             // was killed while waiting
992	<	}
993	<	continue;
984	>	else if ((wc >>> TOTAL_COUNT_SHIFT) < pc)
985	>	helpMaintainParallelism();     // not enough workers
986	>	else if (!ran) {
987	>	long h = eventWaiters;
988	>	int ec = eventCount;
989	>	if (h != 0L && (int)(h >>> EVENT_COUNT_SHIFT) != ec)
990	>	releaseEventWaiters();     // release others before waiting
991	>	else if (ec != wec) {
992	>	w.lastEventCount = ec;     // no need to wait
993	>	break;
994		}
995	<	w.lastEventCount = ec;
995	>	else if (!(inactivate |= active))
996	>	eventSync(w, wec);         // must inactivate before sync
997		}
998	<	if (rc < pc)
999	<	helpMaintainParallelism();
1080	<	break;
998	>	else
999	>	break;
1000		}
1001		}
1002
1003		/**
1004		* Helps and/or blocks awaiting join of the given task.
1005	<	* Alternates between helpJoinTask() and helpMaintainParallelism()
1087	<	* as many times as there is a deficit in running count (or longer
1088	<	* if running count would become zero), then blocks if task still
1089	<	* not done.
1005	>	* See above for explanation.
1006		*
1007		* @param joinMe the task to join
1008	+	* @param worker the current worker thread
1009		*/
1010		final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker) {
1011	<	int threshold = parallelism;         // descend blocking thresholds
1011	>	int retries = 2 + (parallelism >> 2); // #helpJoins before blocking
1012		while (joinMe.status >= 0) {
1013	<	boolean block; int wc;
1013	>	int wc;
1014		worker.helpJoinTask(joinMe);
1015		if (joinMe.status < 0)
1016		break;
1017	<	if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= threshold) {
1018	<	if (threshold > 0)
1019	<	--threshold;
1020	<	else
1021	<	advanceEventCount(); // force release
1022	<	block = false;
1023	<	}
1024	<	else
1025	<	block = UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1026	<	wc, wc - ONE_RUNNING);
1027	<	helpMaintainParallelism();
1028	<	if (block) {
1029	<	int c;
1030	<	joinMe.internalAwaitDone();
1017	>	else if (retries > 0)
1018	>	--retries;
1019	>	else if (((wc = workerCounts) & RUNNING_COUNT_MASK) != 0 &&
1020	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1021	>	wc, wc - ONE_RUNNING)) {
1022	>	int stat, c; long h;
1023	>	while ((stat = joinMe.status) >= 0 &&
1024	>	(h = eventWaiters) != 0L && // help release others
1025	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1026	>	releaseEventWaiters();
1027	>	if (stat >= 0 &&
1028	>	((workerCounts & RUNNING_COUNT_MASK) == 0 ||
1029	>	(stat =
1030	>	joinMe.internalAwaitDone(JOIN_TIMEOUT_MILLIS)) >= 0))
1031	>	helpMaintainParallelism(); // timeout or no running workers
1032		do {} while (!UNSAFE.compareAndSwapInt
1033		(this, workerCountsOffset,
1034		c = workerCounts, c + ONE_RUNNING));
1035	<	break;
1035	>	if (stat < 0)
1036	>	break;   // else restart
1037		}
1038		}
1039		}
1040
1041		/**
1042	<	* Same idea as awaitJoin, but no helping
1042	>	* Same idea as awaitJoin, but no helping, retries, or timeouts.
1043		*/
1044		final void awaitBlocker(ManagedBlocker blocker)
1045		throws InterruptedException {
1127	–	int threshold = parallelism;
1046		while (!blocker.isReleasable()) {
1047	<	boolean block; int wc;
1048	<	if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= threshold) {
1049	<	if (threshold > 0)
1050	<	--threshold;
1133	<	else
1134	<	advanceEventCount();
1135	<	block = false;
1136	<	}
1137	<	else
1138	<	block = UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1139	<	wc, wc - ONE_RUNNING);
1140	<	helpMaintainParallelism();
1141	<	if (block) {
1047	>	int wc = workerCounts;
1048	>	if ((wc & RUNNING_COUNT_MASK) != 0 &&
1049	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1050	>	wc, wc - ONE_RUNNING)) {
1051		try {
1052	<	do {} while (!blocker.isReleasable() && !blocker.block());
1052	>	while (!blocker.isReleasable()) {
1053	>	long h = eventWaiters;
1054	>	if (h != 0L &&
1055	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1056	>	releaseEventWaiters();
1057	>	else if ((workerCounts & RUNNING_COUNT_MASK) == 0 &&
1058	>	runState < TERMINATING)
1059	>	helpMaintainParallelism();
1060	>	else if (blocker.block())
1061	>	break;
1062	>	}
1063		} finally {
1064		int c;
1065		do {} while (!UNSAFE.compareAndSwapInt
#	Line 1190 | Line 1109 | public class ForkJoinPool extends Abstra
1109		private void startTerminating() {
1110		cancelSubmissions();
1111		for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) {
1112	<	advanceEventCount();
1112	>	int c; // advance event count
1113	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
1114	>	c = eventCount, c+1);
1115		eventWaiters = 0L; // clobber lists
1116		spareWaiters = 0;
1117	<	ForkJoinWorkerThread[] ws = workers;
1197	<	int n = ws.length;
1198	<	for (int i = 0; i < n; ++i) {
1199	<	ForkJoinWorkerThread w = ws[i];
1117	>	for (ForkJoinWorkerThread w : workers) {
1118		if (w != null) {
1119		w.shutdown();
1120		if (passes > 0 && !w.isTerminated()) {
#	Line 1215 | Line 1133 | public class ForkJoinPool extends Abstra
1133		}
1134
1135		/**
1136	<	* Clear out and cancel submissions, ignoring exceptions
1136	>	* Clears out and cancels submissions, ignoring exceptions.
1137		*/
1138		private void cancelSubmissions() {
1139		ForkJoinTask<?> task;
#	Line 1230 | Line 1148 | public class ForkJoinPool extends Abstra
1148		// misc support for ForkJoinWorkerThread
1149
1150		/**
1151	<	* Returns pool number
1151	>	* Returns pool number.
1152		*/
1153		final int getPoolNumber() {
1154		return poolNumber;
1155		}
1156
1157		/**
1158	<	* Tries to accumulates steal count from a worker, clearing
1159	<	* the worker's value.
1158	>	* Tries to accumulate steal count from a worker, clearing
1159	>	* the worker's value if successful.
1160		*
1161		* @return true if worker steal count now zero
1162		*/
#	Line 1260 | Line 1178 | public class ForkJoinPool extends Abstra
1178		*/
1179		final int idlePerActive() {
1180		int pc = parallelism; // use parallelism, not rc
1181	<	int ac = runState;    // no mask -- artifically boosts during shutdown
1181	>	int ac = runState;    // no mask -- artificially boosts during shutdown
1182		// Use exact results for small values, saturate past 4
1183	<	return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
1183	>	return ((pc <= ac) ? 0 :
1184	>	(pc >>> 1 <= ac) ? 1 :
1185	>	(pc >>> 2 <= ac) ? 3 :
1186	>	pc >>> 3);
1187		}
1188
1189		// Public and protected methods
#	Line 1312 | Line 1233 | public class ForkJoinPool extends Abstra
1233		* use {@link #defaultForkJoinWorkerThreadFactory}.
1234		* @param handler the handler for internal worker threads that
1235		* terminate due to unrecoverable errors encountered while executing
1236	<	* tasks. For default value, use <code>null</code>.
1236	>	* tasks. For default value, use {@code null}.
1237		* @param asyncMode if true,
1238		* establishes local first-in-first-out scheduling mode for forked
1239		* tasks that are never joined. This mode may be more appropriate
1240		* than default locally stack-based mode in applications in which
1241		* worker threads only process event-style asynchronous tasks.
1242	<	* For default value, use <code>false</code>.
1242	>	* For default value, use {@code false}.
1243		* @throws IllegalArgumentException if parallelism less than or
1244		*         equal to zero, or greater than implementation limit
1245		* @throws NullPointerException if the factory is null
#	Line 1353 | Line 1274 | public class ForkJoinPool extends Abstra
1274		* @param pc the initial parallelism level
1275		*/
1276		private static int initialArraySizeFor(int pc) {
1277	<	// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16)
1277	>	// If possible, initially allocate enough space for one spare
1278		int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS;
1279	+	// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16)
1280		size |= size >>> 1;
1281		size |= size >>> 2;
1282		size |= size >>> 4;
#	Line 1373 | Line 1295 | public class ForkJoinPool extends Abstra
1295		if (runState >= SHUTDOWN)
1296		throw new RejectedExecutionException();
1297		submissionQueue.offer(task);
1298	<	advanceEventCount();
1299	<	if (eventWaiters != 0L)
1300	<	releaseEventWaiters();
1379	<	if ((workerCounts >>> TOTAL_COUNT_SHIFT) < parallelism)
1380	<	addWorkerIfBelowTarget();
1298	>	int c; // try to increment event count -- CAS failure OK
1299	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
1300	>	helpMaintainParallelism(); // create, start, or resume some workers
1301		}
1302
1303		/**
#	Line 1529 | Line 1449 | public class ForkJoinPool extends Abstra
1449
1450		/**
1451		* Returns the number of worker threads that have started but not
1452	<	* yet terminated.  This result returned by this method may differ
1452	>	* yet terminated.  The result returned by this method may differ
1453		* from {@link #getParallelism} when threads are created to
1454		* maintain parallelism when others are cooperatively blocked.
1455		*
#	Line 1614 | Line 1534 | public class ForkJoinPool extends Abstra
1534		*/
1535		public long getQueuedTaskCount() {
1536		long count = 0;
1537	<	ForkJoinWorkerThread[] ws = workers;
1618	<	int n = ws.length;
1619	<	for (int i = 0; i < n; ++i) {
1620	<	ForkJoinWorkerThread w = ws[i];
1537	>	for (ForkJoinWorkerThread w : workers)
1538		if (w != null)
1539		count += w.getQueueSize();
1623	–	}
1540		return count;
1541		}
1542
#	Line 1675 | Line 1591 | public class ForkJoinPool extends Abstra
1591		*/
1592		protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1593		int count = submissionQueue.drainTo(c);
1594	<	ForkJoinWorkerThread[] ws = workers;
1679	<	int n = ws.length;
1680	<	for (int i = 0; i < n; ++i) {
1681	<	ForkJoinWorkerThread w = ws[i];
1594	>	for (ForkJoinWorkerThread w : workers)
1595		if (w != null)
1596		count += w.drainTasksTo(c);
1684	–	}
1597		return count;
1598		}
1599
#	Line 1808 | Line 1720 | public class ForkJoinPool extends Abstra
1720		throws InterruptedException {
1721		try {
1722		return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1723	<	} catch(TimeoutException ex) {
1723	>	} catch (TimeoutException ex) {
1724		return false;
1725		}
1726		}
#	Line 1855 | Line 1767 | public class ForkJoinPool extends Abstra
1767		*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
1768		*   public boolean block() throws InterruptedException {
1769		*     if (item == null)
1770	<	*       item = queue.take
1770	>	*       item = queue.take();
1771		*     return true;
1772		*   }
1773		*   public boolean isReleasable() {
1774	<	*     return item != null || (item = queue.poll) != null;
1774	>	*     return item != null || (item = queue.poll()) != null;
1775		*   }
1776		*   public E getItem() { // call after pool.managedBlock completes
1777		*     return item;
#	Line 1938 | Line 1850 | public class ForkJoinPool extends Abstra
1850		private static final long eventCountOffset =
1851		objectFieldOffset("eventCount", ForkJoinPool.class);
1852		private static final long eventWaitersOffset =
1853	<	objectFieldOffset("eventWaiters",ForkJoinPool.class);
1853	>	objectFieldOffset("eventWaiters", ForkJoinPool.class);
1854		private static final long stealCountOffset =
1855	<	objectFieldOffset("stealCount",ForkJoinPool.class);
1855	>	objectFieldOffset("stealCount", ForkJoinPool.class);
1856		private static final long spareWaitersOffset =
1857	<	objectFieldOffset("spareWaiters",ForkJoinPool.class);
1857	>	objectFieldOffset("spareWaiters", ForkJoinPool.class);
1858
1859		private static long objectFieldOffset(String field, Class<?> klazz) {
1860		try {

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