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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.62 by dl, Wed Aug 11 20:28:22 2010 UTC vs.
Revision 1.78 by dl, Tue Sep 7 14:52:24 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 259 | Line 267 | public class ForkJoinPool extends Abstra
267		* workers that previously could not find a task to now find one:
268		* Submission of a new task to the pool, or another worker pushing
269		* a task onto a previously empty queue.  (We also use this
270	<	* mechanism for termination actions that require wakeups of idle
271	<	* workers).  Each worker maintains its last known event count,
272	<	* and blocks when a scan for work did not find a task AND its
273	<	* lastEventCount matches the current eventCount. Waiting idle
274	<	* workers are recorded in a variant of Treiber stack headed by
275	<	* field eventWaiters which, when nonzero, encodes the thread
276	<	* index and count awaited for by the worker thread most recently
277	<	* calling eventSync. This thread in turn has a record (field
278	<	* nextEventWaiter) for the next waiting worker.  In addition to
279	<	* allowing simpler decisions about need for wakeup, the event
280	<	* count bits in eventWaiters serve the role of tags to avoid ABA
281	<	* errors in Treiber stacks.  To reduce delays in task diffusion,
282	<	* workers not otherwise occupied may invoke method
283	<	* releaseEventWaiters, that removes and signals (unparks) workers
284	<	* not waiting on current count. To reduce stalls, To minimize
285	<	* task production stalls associate with signalling, any worker
286	<	* pushing a task on an empty queue invokes the weaker method
279	<	* signalWork, that only releases idle workers until it detects
280	<	* interference by other threads trying to release, and lets them
281	<	* take over.  The net effect is a tree-like diffusion of signals,
282	<	* where released threads (and possibly others) help with unparks.
283	<	* To further reduce contention effects a bit, failed CASes to
284	<	* increment field eventCount are tolerated without retries.
270	>	* mechanism for configuration and termination actions that
271	>	* require wakeups of idle workers).  Each worker maintains its
272	>	* last known event count, and blocks when a scan for work did not
273	>	* find a task AND its lastEventCount matches the current
274	>	* eventCount. Waiting idle workers are recorded in a variant of
275	>	* Treiber stack headed by field eventWaiters which, when nonzero,
276	>	* encodes the thread index and count awaited for by the worker
277	>	* thread most recently calling eventSync. This thread in turn has
278	>	* a record (field nextEventWaiter) for the next waiting worker.
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 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.  To avoid
310	<	* long-term build-up of spares, the oldest spare (see
311	<	* ForkJoinWorkerThread.suspendAsSpare) occasionally wakes up if
312	<	* not signalled and calls tryTrimSpare, which uses two different
313	<	* thresholds: Always killing if the number of spares is greater
314	<	* that 25% of total, and killing others only at a slower rate
315	<	* (UNUSED_SPARE_TRIM_RATE_NANOS).
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	<	* 6. Deciding when to create new workers. The main dynamic
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. The rules also
336	<	* better cope with the fact that some of the methods in this
337	<	* class tend to never become compiled (but are interpreted), so
338	<	* some components of the entire set of controls might execute 100
339	<	* times faster than others. And similarly for cases where the
340	<	* apparent lack of work is just due to GC stalls and other
335	<	* 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 347 | 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 419 | 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	+	* 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	+	30L * 1000L * 1000L * 1000L; // 2 per minute
447	+
448	+	/**
449		* Absolute bound for parallelism level. Twice this number plus
450		* one (i.e., 0xfff) must fit into a 16bit field to enable
451		* word-packing for some counts and indices.
#	Line 463 | Line 490 | public class ForkJoinPool extends Abstra
490		private volatile long stealCount;
491
492		/**
493	<	* The last nanoTime that a spare thread was trimmed
467	<	*/
468	<	private volatile long trimTime;
469	<
470	<	/**
471	<	* The rate at which to trim unused spares
472	<	*/
473	<	static final long UNUSED_SPARE_TRIM_RATE_NANOS =
474	<	1000L * 1000L * 1000L; // 1 sec
475	<
476	<	/**
477	<	* 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 514 | Line 530 | public class ForkJoinPool extends Abstra
530		* These are bundled together to ensure consistent read for
531		* termination checks (i.e., that runLevel is at least SHUTDOWN
532		* and active threads is zero).
533	+	*
534	+	* Notes: Most direct CASes are dependent on these bitfield
535	+	* positions.  Also, this field is non-private to enable direct
536	+	* performance-sensitive CASes in ForkJoinWorkerThread.
537		*/
538	<	private volatile int runState;
538	>	volatile int runState;
539
540		// Note: The order among run level values matters.
541		private static final int RUNLEVEL_SHIFT     = 16;
#	Line 523 | Line 543 | public class ForkJoinPool extends Abstra
543		private static final int TERMINATING        = 1 << (RUNLEVEL_SHIFT + 1);
544		private static final int TERMINATED         = 1 << (RUNLEVEL_SHIFT + 2);
545		private static final int ACTIVE_COUNT_MASK  = (1 << RUNLEVEL_SHIFT) - 1;
526	–	private static final int ONE_ACTIVE         = 1; // active update delta
546
547		/**
548		* Holds number of total (i.e., created and not yet terminated)
#	Line 564 | Line 583 | public class ForkJoinPool extends Abstra
583		*/
584		private final int poolNumber;
585
586	<
587	<	// Utilities for CASing fields. Note that several of these
569	<	// are manually inlined by callers
586	>	// Utilities for CASing fields. Note that most of these
587	>	// are usually manually inlined by callers
588
589		/**
590		* Increments running count part of workerCounts
#	Line 594 | 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 (;;) {
619		int wc = workerCounts;
602	–	if (wc == 0 && (runState & TERMINATED) != 0)
603	–	return; // lagging termination on a backout
620		if ((wc & RUNNING_COUNT_MASK)  - dr < 0 ||
621	<	(wc >>> TOTAL_COUNT_SHIFT) - dt < 0)
621	>	(wc >>> TOTAL_COUNT_SHIFT) - dt < 0) {
622	>	if ((runState & TERMINATED) != 0)
623	>	return; // lagging termination on a backout
624		Thread.yield();
625	+	}
626		if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
627		wc, wc - (dr + dt)))
628		return;
#	Line 611 | Line 630 | public class ForkJoinPool extends Abstra
630		}
631
632		/**
614	–	* Increments event count
615	–	*/
616	–	private void advanceEventCount() {
617	–	int c;
618	–	do {} while(!UNSAFE.compareAndSwapInt(this, eventCountOffset,
619	–	c = eventCount, c+1));
620	–	}
621	–
622	–	/**
623	–	* Tries incrementing active count; fails on contention.
624	–	* Called by workers before executing tasks.
625	–	*
626	–	* @return true on success
627	–	*/
628	–	final boolean tryIncrementActiveCount() {
629	–	int c;
630	–	return UNSAFE.compareAndSwapInt(this, runStateOffset,
631	–	c = runState, c + ONE_ACTIVE);
632	–	}
633	–
634	–	/**
633		* Tries decrementing active count; fails on contention.
634		* Called when workers cannot find tasks to run.
635		*/
636		final boolean tryDecrementActiveCount() {
637		int c;
638		return UNSAFE.compareAndSwapInt(this, runStateOffset,
639	<	c = runState, c - ONE_ACTIVE);
639	>	c = runState, c - 1);
640		}
641
642		/**
#	Line 683 | 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 699 | Line 697 | public class ForkJoinPool extends Abstra
697		}
698		}
699
702	–	// adding and removing workers
703	–
704	–	/**
705	–	* Tries to create and add new worker. Assumes that worker counts
706	–	* are already updated to accommodate the worker, so adjusts on
707	–	* failure.
708	–	*/
709	–	private void addWorker() {
710	–	ForkJoinWorkerThread w = null;
711	–	try {
712	–	w = factory.newThread(this);
713	–	} finally { // Adjust on either null or exceptional factory return
714	–	if (w == null) {
715	–	decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL);
716	–	tryTerminate(false); // in case of failure during shutdown
717	–	}
718	–	}
719	–	if (w != null)
720	–	w.start(recordWorker(w), ueh);
721	–	}
722	–
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 740 | Line 717 | public class ForkJoinPool extends Abstra
717		/**
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.
721	<	*
745	<	* @param signalling true if caller is a signalling worker so can
746	<	* exit upon (conservatively) detected contention by other threads
747	<	* who will continue to release
720	>	* avoid wasted array checks. Gives up upon a change in count or
721	>	* upon releasing two workers, letting others take over.
722		*/
723	<	private void releaseEventWaiters(boolean signalling) {
723	>	private void releaseEventWaiters() {
724		ForkJoinWorkerThread[] ws = workers;
725		int n = ws.length;
726	<	long h; // head of stack
727	<	ForkJoinWorkerThread w; int id, ec;
728	<	while ((id = ((int)((h = eventWaiters) & WAITER_ID_MASK)) - 1) >= 0 &&
729	<	(int)(h >>> EVENT_COUNT_SHIFT) != (ec = eventCount) &&
726	>	long h = eventWaiters;
727	>	int ec = eventCount;
728	>	boolean releasedOne = false;
729	>	ForkJoinWorkerThread w; int id;
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, h = w.nextWaiter))
734	>	h,  w.nextWaiter)) {
735		LockSupport.unpark(w);
736	<	if (signalling && (eventCount != ec || eventWaiters != h))
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 770 | Line 751 | public class ForkJoinPool extends Abstra
751		int c; // try to increment event count -- CAS failure OK
752		UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
753		if (eventWaiters != 0L)
754	<	releaseEventWaiters(true);
754	>	releaseEventWaiters();
755		}
756
757		/**
758	<	* Blocks worker until terminating or event count
759	<	* advances from last value held by worker
758	>	* Adds the given worker to event queue and blocks until
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) {
765	<	int wec = w.lastEventCount;
784	<	long nh = (((long)wec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1));
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)) &&
768	<	((h = eventWaiters) == 0L ||
769	<	(int)(h >>> EVENT_COUNT_SHIFT) == wec) &&
770	<	eventCount == wec) {
768	>	(((int)((h = eventWaiters) & WAITER_ID_MASK)) == 0 ||
769	>	(int)(h >>> EVENT_COUNT_SHIFT) == ec) &&
770	>	eventCount == ec) {
771		if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
772		w.nextWaiter = h, nh)) {
773	<	while (runState < TERMINATING && eventCount == wec) {
774	<	if (!tryAccumulateStealCount(w))  // transfer while idle
775	<	continue;
776	<	Thread.interrupted();             // clear/ignore interrupt
777	<	if (eventCount != wec)
778	<	break;
773	>	awaitEvent(w, ec);
774	>	break;
775	>	}
776	>	}
777	>	}
778	>
779	>	/**
780	>	* Blocks the given worker (that has already been entered as an
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	>	* minimum of one) if the pool has not been used for extended
785	>	* periods.
786	>	*
787	>	* @param w the calling worker thread
788	>	* @param ec the count
789	>	*/
790	>	private void awaitEvent(ForkJoinWorkerThread w, int ec) {
791	>	while (eventCount == ec) {
792	>	if (tryAccumulateStealCount(w)) { // transfer while idle
793	>	boolean untimed = (w.nextWaiter != 0L ||
794	>	(workerCounts & RUNNING_COUNT_MASK) <= 1);
795	>	long startTime = untimed? 0 : System.nanoTime();
796	>	Thread.interrupted();         // clear/ignore interrupt
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.runState != 0 ||
805	+	runState >= TERMINATING)
806	+	break;
807	+	if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS)
808	+	tryShutdownUnusedWorker(ec);
809		}
800	–	break;
810		}
811		}
803	–	w.lastEventCount = eventCount;
812		}
813
814	<	// 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);
820	>	int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1);
821		do {} while (!UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
822		w.nextSpare = spareWaiters,ns));
823		}
824
825		/**
826	<	* Tries (once) to resume a spare if running count is less than
827	<	* target parallelism. Fails on contention or stale workers.
826	>	* Tries (once) to resume a spare if the number of running
827	>	* threads is less than target.
828		*/
829		private void tryResumeSpare() {
830		int sw, id;
831	+	ForkJoinWorkerThread[] ws = workers;
832	+	int n = ws.length;
833		ForkJoinWorkerThread w;
834	<	ForkJoinWorkerThread[] ws;
835	<	if ((id = ((sw = spareWaiters) & SPARE_ID_MASK) - 1) >= 0 &&
836	<	id < (ws = workers).length && (w = ws[id]) != null &&
834	>	if ((sw = spareWaiters) != 0 &&
835	>	(id = (sw & SPARE_ID_MASK) - 1) >= 0 &&
836	>	id < n && (w = ws[id]) != null &&
837		(workerCounts & RUNNING_COUNT_MASK) < parallelism &&
828	–	eventWaiters == 0L &&
838		spareWaiters == sw &&
839		UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
840	<	sw, w.nextSpare) &&
841	<	w.tryUnsuspend()) {
842	<	int c; // try increment; if contended, finish after unpark
843	<	boolean inc = UNSAFE.compareAndSwapInt(this, workerCountsOffset,
844	<	c = workerCounts,
845	<	c + ONE_RUNNING);
846	<	LockSupport.unpark(w);
847	<	if (!inc) {
848	<	do {} while(!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
840	<	c = workerCounts,
841	<	c + ONE_RUNNING));
842	<	}
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
852		/**
853	<	* Callback from oldest spare occasionally waking up.  Tries
854	<	* (once) to shutdown a spare if more than 25% spare overage, or
855	<	* if UNUSED_SPARE_TRIM_RATE_NANOS have elapsed and there are at
856	<	* least #parallelism running threads. Note that we don't need CAS
857	<	* or locks here because the method is called only from the oldest
858	<	* suspended spare occasionally waking (and even misfires are OK).
859	<	*
854	<	* @param now the wake up nanoTime of caller
855	<	*/
856	<	final void tryTrimSpare(long now) {
857	<	long lastTrim = trimTime;
858	<	trimTime = now;
859	<	helpMaintainParallelism(); // first, help wake up any needed spares
860	<	int sw, id;
861	<	ForkJoinWorkerThread w;
862	<	ForkJoinWorkerThread[] ws;
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 helpMaintainParallelism() {
860		int pc = parallelism;
861	<	int wc = workerCounts;
862	<	if ((wc & RUNNING_COUNT_MASK) >= pc &&
863	<	(((wc >>> TOTAL_COUNT_SHIFT) - pc) > (pc >>> 2) + 1 ||// approx 25%
864	<	now - lastTrim >= UNUSED_SPARE_TRIM_RATE_NANOS) &&
865	<	(id = ((sw = spareWaiters) & SPARE_ID_MASK) - 1) >= 0 &&
866	<	id < (ws = workers).length && (w = ws[id]) != null &&
867	<	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
868	<	sw, w.nextSpare))
869	<	w.shutdown(false);
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	<	* Does at most one of:
898	<	*
899	<	* 1. Help wake up existing workers waiting for work via
900	<	*    releaseEventWaiters. (If any exist, then it probably doesn't
901	<	*    matter right now if under target parallelism level.)
902	<	*
903	<	* 2. If below parallelism level and a spare exists, try (once)
883	<	*    to resume it via tryResumeSpare.
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	<	* 3. If neither of the above, tries (once) to add a new
906	<	*    worker if either there are not enough total, or if all
887	<	*    existing workers are busy, there are either no running
888	<	*    workers or the deficit is at least twice the surplus.
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	<	// uglified to work better when not compiled
910	<	int pc, wc, rc, tc, rs; long h;
911	<	if ((h = eventWaiters) != 0L) {
912	<	if ((int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
913	<	releaseEventWaiters(false); // avoid useless call
914	<	}
915	<	else if ((pc = parallelism) >
916	<	(rc = ((wc = workerCounts) & RUNNING_COUNT_MASK))) {
917	<	if (spareWaiters != 0)
918	<	tryResumeSpare();
919	<	else if ((rs = runState) < TERMINATING &&
920	<	((tc = wc >>> TOTAL_COUNT_SHIFT) < pc ||
921	<	(tc == (rs & ACTIVE_COUNT_MASK) && // all busy
922	<	(rc == 0 ||                       // must add
923	<	rc < pc - ((tc - pc) << 1)) &&   // within slack
924	<	tc < MAX_WORKERS && runState == rs)) && // recheck busy
925	<	workerCounts == wc &&
926	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
927	<	wc + (ONE_RUNNING|ONE_TOTAL)))
928	<	addWorker();
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		/**
940		* Callback from workers invoked upon each top-level action (i.e.,
941	<	* stealing a task or taking a submission and running
942	<	* it). Performs one or more of the following:
918	<	*
919	<	* 1. If the worker cannot find work (misses > 0), updates its
920	<	*    active status to inactive and updates activeCount unless
921	<	*    this is the first miss and there is contention, in which
922	<	*    case it may try again (either in this or a subsequent
923	<	*    call).
924	<	*
925	<	* 2. If there are at least 2 misses, awaits the next task event
926	<	*    via eventSync
927	<	*
928	<	* 3. If there are too many running threads, suspends this worker
929	<	*    (first forcing inactivation if necessary).  If it is not
930	<	*    needed, it may be killed while suspended via
931	<	*    tryTrimSpare. Otherwise, upon resume it rechecks to make
932	<	*    sure that it is still needed.
941	>	* stealing a task or taking a submission and running it).
942	>	* Performs one or more of the following:
943		*
944	<	* 4. Helps release and/or reactivate other workers via
945	<	*    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
939	<	* (saturating at 2 just 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 (;;) {
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	<	int rc = wc & RUNNING_COUNT_MASK;
978	<	if (active && (misses > 0 || rc > pc)) {
979	<	int rs;                      // try inactivate
949	<	if (UNSAFE.compareAndSwapInt(this, runStateOffset,
950	<	rs = runState, rs - ONE_ACTIVE))
951	<	active = w.active = false;
952	<	else if (misses > 1 || rc > pc ||
953	<	(rs & ACTIVE_COUNT_MASK) >= pc)
954	<	continue;                // force inactivate
955	<	}
956	<	if (misses > 1) {
957	<	misses = 0;                  // don't re-sync
958	<	eventSync(w);                // continue loop to recheck rc
959	<	}
960	<	else if (rc > pc) {
961	<	if (workerCounts == wc &&   // try to suspend as spare
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) &&
982	<	!w.suspendAsSpare())    // false if killed
981	>	wc, wc - ONE_RUNNING))
982	>	w.suspendAsSpare();
983	>	}
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	+	else if (!(inactivate |= active))
996	+	eventSync(w, wec);         // must inactivate before sync
997		}
998	<	else {
968	<	if (rc < pc || eventWaiters != 0L)
969	<	helpMaintainParallelism();
998	>	else
999		break;
971	–	}
1000		}
1001		}
1002
1003		/**
1004		* Helps and/or blocks awaiting join of the given task.
1005	<	* Alternates between helpJoinTask() and helpMaintainParallelism()
978	<	* as many times as there is a deficit in running count (or longer
979	<	* if running count would become zero), then blocks if task still
980	<	* 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 {
1018	–	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;
1024	<	else
1025	<	advanceEventCount();
1026	<	block = false;
1027	<	}
1028	<	else
1029	<	block = UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1030	<	wc, wc - ONE_RUNNING);
1031	<	helpMaintainParallelism();
1032	<	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 1073 | Line 1101 | public class ForkJoinPool extends Abstra
1101		* Actions on transition to TERMINATING
1102		*
1103		* Runs up to four passes through workers: (0) shutting down each
1104	<	* quietly (without waking up if parked) to quickly spread
1105	<	* notifications without unnecessary bouncing around event queues
1106	<	* etc (1) wake up and help cancel tasks (2) interrupt (3) mop up
1107	<	* races with interrupted workers
1104	>	* (without waking up if parked) to quickly spread notifications
1105	>	* without unnecessary bouncing around event queues etc (1) wake
1106	>	* up and help cancel tasks (2) interrupt (3) mop up races with
1107	>	* interrupted workers
1108		*/
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;
1088	<	int n = ws.length;
1089	<	for (int i = 0; i < n; ++i) {
1090	<	ForkJoinWorkerThread w = ws[i];
1117	>	for (ForkJoinWorkerThread w : workers) {
1118		if (w != null) {
1119	<	w.shutdown(true);
1119	>	w.shutdown();
1120		if (passes > 0 && !w.isTerminated()) {
1121		w.cancelTasks();
1122		LockSupport.unpark(w);
#	Line 1106 | 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 1121 | 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 1151 | 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 1203 | 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 1237 | Line 1267 | public class ForkJoinPool extends Abstra
1267		this.workerLock = new ReentrantLock();
1268		this.termination = new Phaser(1);
1269		this.poolNumber = poolNumberGenerator.incrementAndGet();
1240	–	this.trimTime = System.nanoTime();
1270		}
1271
1272		/**
#	Line 1245 | 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 1265 | Line 1295 | public class ForkJoinPool extends Abstra
1295		if (runState >= SHUTDOWN)
1296		throw new RejectedExecutionException();
1297		submissionQueue.offer(task);
1298	<	advanceEventCount();
1299	<	helpMaintainParallelism();         // start or wake up workers
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		/**
1304		* Performs the given task, returning its result upon completion.
1274	–	* If the caller is already engaged in a fork/join computation in
1275	–	* the current pool, this method is equivalent in effect to
1276	–	* {@link ForkJoinTask#invoke}.
1305		*
1306		* @param task the task
1307		* @return the task's result
#	Line 1288 | Line 1316 | public class ForkJoinPool extends Abstra
1316
1317		/**
1318		* Arranges for (asynchronous) execution of the given task.
1291	–	* If the caller is already engaged in a fork/join computation in
1292	–	* the current pool, this method is equivalent in effect to
1293	–	* {@link ForkJoinTask#fork}.
1319		*
1320		* @param task the task
1321		* @throws NullPointerException if the task is null
#	Line 1319 | Line 1344 | public class ForkJoinPool extends Abstra
1344
1345		/**
1346		* Submits a ForkJoinTask for execution.
1322	–	* If the caller is already engaged in a fork/join computation in
1323	–	* the current pool, this method is equivalent in effect to
1324	–	* {@link ForkJoinTask#fork}.
1347		*
1348		* @param task the task to submit
1349		* @return the task
#	Line 1427 | 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 1512 | Line 1534 | public class ForkJoinPool extends Abstra
1534		*/
1535		public long getQueuedTaskCount() {
1536		long count = 0;
1537	<	ForkJoinWorkerThread[] ws = workers;
1516	<	int n = ws.length;
1517	<	for (int i = 0; i < n; ++i) {
1518	<	ForkJoinWorkerThread w = ws[i];
1537	>	for (ForkJoinWorkerThread w : workers)
1538		if (w != null)
1539		count += w.getQueueSize();
1521	–	}
1540		return count;
1541		}
1542
#	Line 1573 | 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;
1577	<	int n = ws.length;
1578	<	for (int i = 0; i < n; ++i) {
1579	<	ForkJoinWorkerThread w = ws[i];
1594	>	for (ForkJoinWorkerThread w : workers)
1595		if (w != null)
1596		count += w.drainTasksTo(c);
1582	–	}
1597		return count;
1598		}
1599
#	Line 1706 | 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 1753 | 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 1836 | 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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