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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.60 by dl, Sat Jul 24 20:28:18 2010 UTC vs.
Revision 1.83 by dl, Sun Oct 24 19:37:26 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.ExecutorService;
17	+	import java.util.concurrent.Future;
18	+	import java.util.concurrent.RejectedExecutionException;
19	+	import java.util.concurrent.RunnableFuture;
20	+	import java.util.concurrent.TimeUnit;
21	+	import java.util.concurrent.TimeoutException;
22	+	import java.util.concurrent.atomic.AtomicInteger;
23		import java.util.concurrent.locks.LockSupport;
24		import java.util.concurrent.locks.ReentrantLock;
18	–	import java.util.concurrent.atomic.AtomicInteger;
19	–	import java.util.concurrent.CountDownLatch;
25
26		/**
27		* An {@link ExecutorService} for running {@link ForkJoinTask}s.
#	Line 69 | Line 74 | import java.util.concurrent.CountDownLat
74		*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
75		*  </tr>
76		*  <tr>
77	<	*    <td> <b>Arange async execution</td>
77	>	*    <td> <b>Arrange async execution</td>
78		*    <td> {@link #execute(ForkJoinTask)}</td>
79		*    <td> {@link ForkJoinTask#fork}</td>
80		*  </tr>
#	Line 110 | Line 115 | import java.util.concurrent.CountDownLat
115		*
116		* <p>This implementation rejects submitted tasks (that is, by throwing
117		* {@link RejectedExecutionException}) only when the pool is shut down
118	<	* or internal resources have been exhuasted.
118	>	* or internal resources have been exhausted.
119		*
120		* @since 1.7
121		* @author Doug Lea
#	Line 140 | Line 145 | public class ForkJoinPool extends Abstra
145		* Beyond work-stealing support and essential bookkeeping, the
146		* main responsibility of this framework is to take actions when
147		* one worker is waiting to join a task stolen (or always held by)
148	<	* another.  Becauae we are multiplexing many tasks on to a pool
148	>	* another.  Because we are multiplexing many tasks on to a pool
149		* of workers, we can't just let them block (as in Thread.join).
150		* We also cannot just reassign the joiner's run-time stack with
151		* another and replace it later, which would be a form of
#	Line 156 | Line 161 | public class ForkJoinPool extends Abstra
161		*      ForkJoinWorkerThread.helpJoinTask tracks joining->stealing
162		*      links to try to find such a task.
163		*
164	<	*   Compensating: Unless there are already enough live threads,
165	<	*      creating or or re-activating a spare thread to compensate
166	<	*      for the (blocked) joiner until it unblocks.  Spares then
167	<	*      suspend at their next opportunity or eventually die if
168	<	*      unused for too long.  See below and the internal
169	<	*      documentation for tryAwaitJoin for more details about
170	<	*      compensation rules.
171	<	*
172	<	* Because the determining existence of conservatively safe
173	<	* helping targets, the availability of already-created spares,
174	<	* and the apparent need to create new spares are all racy and
175	<	* require heuristic guidance, joins (in
176	<	* ForkJoinWorkerThread.joinTask) interleave these options until
177	<	* successful.  Creating a new spare always succeeds, but also
178	<	* increases application footprint, so we try to avoid it, within
179	<	* reason.
164	>	*   Compensating: Unless there are already enough live threads,
165	>	*      method helpMaintainParallelism() may create or
166	>	*      re-activate a spare thread to compensate for blocked
167	>	*      joiners until they unblock.
168	>	*
169	>	* It is impossible to keep exactly the target (parallelism)
170	>	* number of threads running at any given time.  Determining
171	>	* existence of conservatively safe helping targets, the
172	>	* availability of already-created spares, and the apparent need
173	>	* to create new spares are all racy and require heuristic
174	>	* guidance, so we rely on multiple retries of each.  Compensation
175	>	* occurs in slow-motion. It is triggered only upon timeouts of
176	>	* Object.wait used for joins. This reduces poor decisions that
177	>	* would otherwise be made when threads are waiting for others
178	>	* that are stalled because of unrelated activities such as
179	>	* garbage collection.
180		*
181	<	* The ManagedBlocker extension API can't use helping so uses a
182	<	* special version of compensation in method awaitBlocker.
181	>	* The ManagedBlocker extension API can't use helping so relies
182	>	* only on compensation in method awaitBlocker.
183		*
184		* The main throughput advantages of work-stealing stem from
185		* decentralized control -- workers mostly steal tasks from each
#	Line 207 | Line 212 | public class ForkJoinPool extends Abstra
212		* blocked workers. However, all other support code is set up to
213		* work with other policies.
214		*
215	+	* To ensure that we do not hold on to worker references that
216	+	* would prevent GC, ALL accesses to workers are via indices into
217	+	* the workers array (which is one source of some of the unusual
218	+	* code constructions here). In essence, the workers array serves
219	+	* as a WeakReference mechanism. Thus for example the event queue
220	+	* stores worker indices, not worker references. Access to the
221	+	* workers in associated methods (for example releaseEventWaiters)
222	+	* must both index-check and null-check the IDs. All such accesses
223	+	* ignore bad IDs by returning out early from what they are doing,
224	+	* since this can only be associated with shutdown, in which case
225	+	* it is OK to give up. On termination, we just clobber these
226	+	* data structures without trying to use them.
227	+	*
228		* 2. Bookkeeping for dynamically adding and removing workers. We
229		* aim to approximately maintain the given level of parallelism.
230		* When some workers are known to be blocked (on joins or via
231		* ManagedBlocker), we may create or resume others to take their
232		* place until they unblock (see below). Implementing this
233		* requires counts of the number of "running" threads (i.e., those
234	<	* that are neither blocked nor artifically suspended) as well as
234	>	* that are neither blocked nor artificially suspended) as well as
235		* the total number.  These two values are packed into one field,
236		* "workerCounts" because we need accurate snapshots when deciding
237		* to create, resume or suspend.  Note however that the
238	<	* correspondance of these counts to reality is not guaranteed. In
238	>	* correspondence of these counts to reality is not guaranteed. In
239		* particular updates for unblocked threads may lag until they
240		* actually wake up.
241		*
#	Line 248 | Line 266 | public class ForkJoinPool extends Abstra
266		* workers that previously could not find a task to now find one:
267		* Submission of a new task to the pool, or another worker pushing
268		* a task onto a previously empty queue.  (We also use this
269	<	* mechanism for termination and reconfiguration actions that
269	>	* mechanism for configuration and termination actions that
270		* require wakeups of idle workers).  Each worker maintains its
271		* last known event count, and blocks when a scan for work did not
272		* find a task AND its lastEventCount matches the current
#	Line 259 | Line 277 | public class ForkJoinPool extends Abstra
277		* a record (field nextEventWaiter) for the next waiting worker.
278		* In addition to allowing simpler decisions about need for
279		* wakeup, the event count bits in eventWaiters serve the role of
280	<	* tags to avoid ABA errors in Treiber stacks.  To reduce delays
281	<	* in task diffusion, workers not otherwise occupied may invoke
282	<	* method releaseWaiters, that removes and signals (unparks)
283	<	* workers not waiting on current count. To minimize task
284	<	* production stalls associate with signalling, any worker pushing
285	<	* a task on an empty queue invokes the weaker method signalWork,
268	<	* that only releases idle workers until it detects interference
269	<	* by other threads trying to release, and lets them take
270	<	* over. The net effect is a tree-like diffusion of signals, where
271	<	* released threads (and possibly others) help with unparks.  To
272	<	* further reduce contention effects a bit, failed CASes to
273	<	* increment field eventCount are tolerated without retries.
280	>	* tags to avoid ABA errors in Treiber stacks. Upon any wakeup,
281	>	* released threads also try to release at most two others.  The
282	>	* net effect is a tree-like diffusion of signals, where released
283	>	* threads (and possibly others) help with unparks.  To further
284	>	* reduce contention effects a bit, failed CASes to increment
285	>	* field eventCount are tolerated without retries in signalWork.
286		* Conceptually they are merged into the same event, which is OK
287		* when their only purpose is to enable workers to scan for work.
288		*
289	<	* 5. Managing suspension of extra workers. When a worker is about
290	<	* to block waiting for a join (or via ManagedBlockers), we may
291	<	* create a new thread to maintain parallelism level, or at least
292	<	* avoid starvation. Usually, extra threads are needed for only
293	<	* very short periods, yet join dependencies are such that we
294	<	* sometimes need them in bursts. Rather than create new threads
295	<	* each time this happens, we suspend no-longer-needed extra ones
296	<	* as "spares". For most purposes, we don't distinguish "extra"
297	<	* spare threads from normal "core" threads: On each call to
298	<	* preStep (the only point at which we can do this) a worker
299	<	* checks to see if there are now too many running workers, and if
300	<	* so, suspends itself.  Methods tryAwaitJoin and awaitBlocker
301	<	* look for suspended threads to resume before considering
302	<	* creating a new replacement. We don't need a special data
303	<	* structure to maintain spares; simply scanning the workers array
304	<	* looking for worker.isSuspended() is fine because the calling
305	<	* thread is otherwise not doing anything useful anyway; we are at
306	<	* least as happy if after locating a spare, the caller doesn't
307	<	* actually block because the join is ready before we try to
308	<	* adjust and compensate.  Note that this is intrinsically racy.
309	<	* One thread may become a spare at about the same time as another
310	<	* is needlessly being created. We counteract this and related
311	<	* slop in part by requiring resumed spares to immediately recheck
312	<	* (in preStep) to see whether they they should re-suspend. The
313	<	* only effective difference between "extra" and "core" threads is
314	<	* that we allow the "extra" ones to time out and die if they are
315	<	* not resumed within a keep-alive interval of a few seconds. This
316	<	* is implemented mainly within ForkJoinWorkerThread, but requires
317	<	* some coordination (isTrimmed() -- meaning killed while
318	<	* suspended) to correctly maintain pool counts.
319	<	*
320	<	* 6. Deciding when to create new workers. The main dynamic
321	<	* control in this class is deciding when to create extra threads,
322	<	* in methods awaitJoin and awaitBlocker. We always need to create
323	<	* one when the number of running threads would become zero and
324	<	* all workers are busy. However, this is not easy to detect
325	<	* reliably in the presence of transients so we use retries and
326	<	* allow slack (in tryAwaitJoin) to reduce false alarms.  These
327	<	* effectively reduce churn at the price of systematically
328	<	* undershooting target parallelism when many threads are blocked.
329	<	* However, biasing toward undeshooting partially compensates for
330	<	* the above mechanics to suspend extra threads, that normally
331	<	* lead to overshoot because we can only suspend workers
332	<	* in-between top-level actions. It also better copes with the
333	<	* fact that some of the methods in this class tend to never
334	<	* become compiled (but are interpreted), so some components of
335	<	* the entire set of controls might execute many times faster than
336	<	* others. And similarly for cases where the apparent lack of work
337	<	* is just due to GC stalls and other transient system activity.
289	>	* 5. Managing suspension of extra workers. When a worker notices
290	>	* (usually upon timeout of a wait()) that there are too few
291	>	* running threads, we may create a new thread to maintain
292	>	* parallelism level, or at least avoid starvation. Usually, extra
293	>	* threads are needed for only very short periods, yet join
294	>	* dependencies are such that we sometimes need them in
295	>	* bursts. Rather than create new threads each time this happens,
296	>	* we suspend no-longer-needed extra ones as "spares". For most
297	>	* purposes, we don't distinguish "extra" spare threads from
298	>	* normal "core" threads: On each call to preStep (the only point
299	>	* at which we can do this) a worker checks to see if there are
300	>	* now too many running workers, and if so, suspends itself.
301	>	* Method helpMaintainParallelism looks for suspended threads to
302	>	* resume before considering creating a new replacement. The
303	>	* spares themselves are encoded on another variant of a Treiber
304	>	* Stack, headed at field "spareWaiters".  Note that the use of
305	>	* spares is intrinsically racy.  One thread may become a spare at
306	>	* about the same time as another is needlessly being created. We
307	>	* counteract this and related slop in part by requiring resumed
308	>	* spares to immediately recheck (in preStep) to see whether they
309	>	* should re-suspend.
310	>	*
311	>	* 6. Killing off unneeded workers. A timeout mechanism is used to
312	>	* shed unused workers: The oldest (first) event queue waiter uses
313	>	* a timed rather than hard wait. When this wait times out without
314	>	* a normal wakeup, it tries to shutdown any one (for convenience
315	>	* the newest) other spare or event waiter via
316	>	* tryShutdownUnusedWorker. This eventually reduces the number of
317	>	* worker threads to a minimum of one after a long enough period
318	>	* without use.
319	>	*
320	>	* 7. Deciding when to create new workers. The main dynamic
321	>	* control in this class is deciding when to create extra threads
322	>	* in method helpMaintainParallelism. We would like to keep
323	>	* exactly #parallelism threads running, which is an impossible
324	>	* task. We always need to create one when the number of running
325	>	* threads would become zero and all workers are busy. Beyond
326	>	* this, we must rely on heuristics that work well in the
327	>	* presence of transient phenomena such as GC stalls, dynamic
328	>	* compilation, and wake-up lags. These transients are extremely
329	>	* common -- we are normally trying to fully saturate the CPUs on
330	>	* a machine, so almost any activity other than running tasks
331	>	* impedes accuracy. Our main defense is to allow parallelism to
332	>	* lapse for a while during joins, and use a timeout to see if,
333	>	* after the resulting settling, there is still a need for
334	>	* additional workers.  This also better copes with the fact that
335	>	* some of the methods in this class tend to never become compiled
336	>	* (but are interpreted), so some components of the entire set of
337	>	* controls might execute 100 times faster than others. And
338	>	* similarly for cases where the apparent lack of work is just due
339	>	* to GC stalls and other transient system activity.
340		*
341		* Beware that there is a lot of representation-level coupling
342		* among classes ForkJoinPool, ForkJoinWorkerThread, and
#	Line 335 | Line 349 | public class ForkJoinPool extends Abstra
349		*
350		* Style notes: There are lots of inline assignments (of form
351		* "while ((local = field) != 0)") which are usually the simplest
352	<	* way to ensure read orderings. Also several occurrences of the
353	<	* unusual "do {} while(!cas...)" which is the simplest way to
354	<	* force an update of a CAS'ed variable. There are also other
355	<	* coding oddities that help some methods perform reasonably even
356	<	* when interpreted (not compiled), at the expense of messiness.
352	>	* way to ensure the required read orderings (which are sometimes
353	>	* critical). Also several occurrences of the unusual "do {}
354	>	* while (!cas...)" which is the simplest way to force an update of
355	>	* a CAS'ed variable. There are also other coding oddities that
356	>	* help some methods perform reasonably even when interpreted (not
357	>	* compiled), at the expense of some messy constructions that
358	>	* reduce byte code counts.
359		*
360		* The order of declarations in this file is: (1) statics (2)
361		* fields (along with constants used when unpacking some of them)
#	Line 407 | Line 423 | public class ForkJoinPool extends Abstra
423		new AtomicInteger();
424
425		/**
426	<	* Absolute bound for parallelism level. Twice this number must
427	<	* fit into a 16bit field to enable word-packing for some counts.
426	>	* The time to block in a join (see awaitJoin) before checking if
427	>	* a new worker should be (re)started to maintain parallelism
428	>	* level. The value should be short enough to maintain global
429	>	* responsiveness and progress but long enough to avoid
430	>	* counterproductive firings during GC stalls or unrelated system
431	>	* activity, and to not bog down systems with continual re-firings
432	>	* on GCs or legitimately long waits.
433	>	*/
434	>	private static final long JOIN_TIMEOUT_MILLIS = 250L; // 4 per second
435	>
436	>	/**
437	>	* The wakeup interval (in nanoseconds) for the oldest worker
438	>	* waiting for an event to invoke tryShutdownUnusedWorker to
439	>	* shrink the number of workers.  The exact value does not matter
440	>	* too much. It must be short enough to release resources during
441	>	* sustained periods of idleness, but not so short that threads
442	>	* are continually re-created.
443	>	*/
444	>	private static final long SHRINK_RATE_NANOS =
445	>	30L * 1000L * 1000L * 1000L; // 2 per minute
446	>
447	>	/**
448	>	* Absolute bound for parallelism level. Twice this number plus
449	>	* one (i.e., 0xfff) must fit into a 16bit field to enable
450	>	* word-packing for some counts and indices.
451		*/
452	<	private static final int MAX_THREADS = 0x7fff;
452	>	private static final int MAX_WORKERS   = 0x7fff;
453
454		/**
455		* Array holding all worker threads in the pool.  Array size must
#	Line 450 | Line 489 | public class ForkJoinPool extends Abstra
489		private volatile long stealCount;
490
491		/**
492	<	* Encoded record of top of treiber stack of threads waiting for
492	>	* Encoded record of top of Treiber stack of threads waiting for
493		* events. The top 32 bits contain the count being waited for. The
494	<	* bottom word contains one plus the pool index of waiting worker
495	<	* thread.
494	>	* bottom 16 bits contains one plus the pool index of waiting
495	>	* worker thread. (Bits 16-31 are unused.)
496		*/
497		private volatile long eventWaiters;
498
499		private static final int  EVENT_COUNT_SHIFT = 32;
500	<	private static final long WAITER_ID_MASK = (1L << EVENT_COUNT_SHIFT)-1L;
500	>	private static final long WAITER_ID_MASK    = (1L << 16) - 1L;
501
502		/**
503		* A counter for events that may wake up worker threads:
504		*   - Submission of a new task to the pool
505		*   - A worker pushing a task on an empty queue
506	<	*   - termination and reconfiguration
506	>	*   - termination
507		*/
508		private volatile int eventCount;
509
510		/**
511	+	* Encoded record of top of Treiber stack of spare threads waiting
512	+	* for resumption. The top 16 bits contain an arbitrary count to
513	+	* avoid ABA effects. The bottom 16bits contains one plus the pool
514	+	* index of waiting worker thread.
515	+	*/
516	+	private volatile int spareWaiters;
517	+
518	+	private static final int SPARE_COUNT_SHIFT = 16;
519	+	private static final int SPARE_ID_MASK     = (1 << 16) - 1;
520	+
521	+	/**
522		* Lifecycle control. The low word contains the number of workers
523		* that are (probably) executing tasks. This value is atomically
524		* incremented before a worker gets a task to run, and decremented
525	<	* when worker has no tasks and cannot find any.  Bits 16-18
525	>	* when a worker has no tasks and cannot find any.  Bits 16-18
526		* contain runLevel value. When all are zero, the pool is
527		* running. Level transitions are monotonic (running -> shutdown
528		* -> terminating -> terminated) so each transition adds a bit.
529		* These are bundled together to ensure consistent read for
530		* termination checks (i.e., that runLevel is at least SHUTDOWN
531		* and active threads is zero).
532	+	*
533	+	* Notes: Most direct CASes are dependent on these bitfield
534	+	* positions.  Also, this field is non-private to enable direct
535	+	* performance-sensitive CASes in ForkJoinWorkerThread.
536		*/
537	<	private volatile int runState;
537	>	volatile int runState;
538
539		// Note: The order among run level values matters.
540		private static final int RUNLEVEL_SHIFT     = 16;
#	Line 488 | Line 542 | public class ForkJoinPool extends Abstra
542		private static final int TERMINATING        = 1 << (RUNLEVEL_SHIFT + 1);
543		private static final int TERMINATED         = 1 << (RUNLEVEL_SHIFT + 2);
544		private static final int ACTIVE_COUNT_MASK  = (1 << RUNLEVEL_SHIFT) - 1;
491	–	private static final int ONE_ACTIVE         = 1; // active update delta
545
546		/**
547		* Holds number of total (i.e., created and not yet terminated)
#	Line 529 | Line 582 | public class ForkJoinPool extends Abstra
582		*/
583		private final int poolNumber;
584
585	<	// Utilities for CASing fields. Note that several of these
586	<	// are manually inlined by callers
585	>	// Utilities for CASing fields. Note that most of these
586	>	// are usually manually inlined by callers
587
588		/**
589	<	* Increments running count.  Also used by ForkJoinTask.
589	>	* Increments running count part of workerCounts
590		*/
591		final void incrementRunningCount() {
592		int c;
#	Line 554 | Line 607 | public class ForkJoinPool extends Abstra
607		}
608
609		/**
610	<	* Tries to increment running count
611	<	*/
559	<	final boolean tryIncrementRunningCount() {
560	<	int wc;
561	<	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
562	<	wc = workerCounts, wc + ONE_RUNNING);
563	<	}
564	<
565	<	/**
566	<	* Tries incrementing active count; fails on contention.
567	<	* Called by workers before executing tasks.
610	>	* Forces decrement of encoded workerCounts, awaiting nonzero if
611	>	* (rarely) necessary when other count updates lag.
612		*
613	<	* @return true on success
613	>	* @param dr -- either zero or ONE_RUNNING
614	>	* @param dt -- either zero or ONE_TOTAL
615		*/
616	<	final boolean tryIncrementActiveCount() {
617	<	int c;
618	<	return UNSAFE.compareAndSwapInt(this, runStateOffset,
619	<	c = runState, c + ONE_ACTIVE);
616	>	private void decrementWorkerCounts(int dr, int dt) {
617	>	for (;;) {
618	>	int wc = workerCounts;
619	>	if ((wc & RUNNING_COUNT_MASK)  - dr < 0 ||
620	>	(wc >>> TOTAL_COUNT_SHIFT) - dt < 0) {
621	>	if ((runState & TERMINATED) != 0)
622	>	return; // lagging termination on a backout
623	>	Thread.yield();
624	>	}
625	>	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
626	>	wc, wc - (dr + dt)))
627	>	return;
628	>	}
629		}
630
631		/**
#	Line 581 | Line 635 | public class ForkJoinPool extends Abstra
635		final boolean tryDecrementActiveCount() {
636		int c;
637		return UNSAFE.compareAndSwapInt(this, runStateOffset,
638	<	c = runState, c - ONE_ACTIVE);
638	>	c = runState, c - 1);
639		}
640
641		/**
#	Line 610 | Line 664 | public class ForkJoinPool extends Abstra
664		lock.lock();
665		try {
666		ForkJoinWorkerThread[] ws = workers;
667	<	int nws = ws.length;
668	<	if (k < 0 || k >= nws || ws[k] != null) {
669	<	for (k = 0; k < nws && ws[k] != null; ++k)
667	>	int n = ws.length;
668	>	if (k < 0 || k >= n || ws[k] != null) {
669	>	for (k = 0; k < n && ws[k] != null; ++k)
670		;
671	<	if (k == nws)
672	<	ws = Arrays.copyOf(ws, nws << 1);
671	>	if (k == n)
672	>	ws = Arrays.copyOf(ws, n << 1);
673		}
674		ws[k] = w;
675		workers = ws; // volatile array write ensures slot visibility
#	Line 626 | Line 680 | public class ForkJoinPool extends Abstra
680		}
681
682		/**
683	<	* Nulls out record of worker in workers array
683	>	* Nulls out record of worker in workers array.
684		*/
685		private void forgetWorker(ForkJoinWorkerThread w) {
686		int idx = w.poolIndex;
687	<	// Locking helps method recordWorker avoid unecessary expansion
687	>	// Locking helps method recordWorker avoid unnecessary expansion
688		final ReentrantLock lock = this.workerLock;
689		lock.lock();
690		try {
#	Line 642 | Line 696 | public class ForkJoinPool extends Abstra
696		}
697		}
698
645	–	// adding and removing workers
646	–
699		/**
700	<	* Tries to create and add new worker. Assumes that worker counts
701	<	* are already updated to accommodate the worker, so adjusts on
702	<	* failure.
700	>	* Final callback from terminating worker.  Removes record of
701	>	* worker from array, and adjusts counts. If pool is shutting
702	>	* down, tries to complete termination.
703		*
704	<	* @return new worker or null if creation failed
704	>	* @param w the worker
705		*/
706	<	private ForkJoinWorkerThread addWorker() {
707	<	ForkJoinWorkerThread w = null;
708	<	try {
709	<	w = factory.newThread(this);
710	<	} finally { // Adjust on either null or exceptional factory return
711	<	if (w == null)
660	<	onWorkerCreationFailure();
661	<	}
662	<	if (w != null)
663	<	w.start(recordWorker(w), ueh);
664	<	return w;
706	>	final void workerTerminated(ForkJoinWorkerThread w) {
707	>	forgetWorker(w);
708	>	decrementWorkerCounts(w.isTrimmed() ? 0 : ONE_RUNNING, ONE_TOTAL);
709	>	while (w.stealCount != 0) // collect final count
710	>	tryAccumulateStealCount(w);
711	>	tryTerminate(false);
712		}
713
714	+	// Waiting for and signalling events
715	+
716		/**
717	<	* Adjusts counts upon failure to create worker
717	>	* Releases workers blocked on a count not equal to current count.
718	>	* Normally called after precheck that eventWaiters isn't zero to
719	>	* avoid wasted array checks. Gives up upon a change in count or
720	>	* upon releasing two workers, letting others take over.
721		*/
722	<	private void onWorkerCreationFailure() {
723	<	for (;;) {
724	<	int wc = workerCounts;
725	<	int rc = wc & RUNNING_COUNT_MASK;
726	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
727	<	if (rc == 0 || wc == 0)
728	<	Thread.yield(); // must wait for other counts to settle
729	<	else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
730	<	wc - (ONE_RUNNING|ONE_TOTAL)))
722	>	private void releaseEventWaiters() {
723	>	ForkJoinWorkerThread[] ws = workers;
724	>	int n = ws.length;
725	>	long h = eventWaiters;
726	>	int ec = eventCount;
727	>	boolean releasedOne = false;
728	>	ForkJoinWorkerThread w; int id;
729	>	while ((id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 &&
730	>	(int)(h >>> EVENT_COUNT_SHIFT) != ec &&
731	>	id < n && (w = ws[id]) != null) {
732	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
733	>	h,  w.nextWaiter)) {
734	>	LockSupport.unpark(w);
735	>	if (releasedOne) // exit on second release
736	>	break;
737	>	releasedOne = true;
738	>	}
739	>	if (eventCount != ec)
740		break;
741	+	h = eventWaiters;
742		}
681	–	tryTerminate(false); // in case of failure during shutdown
743		}
744
745		/**
746	<	* Creates enough total workers to establish target parallelism,
747	<	* giving up if terminating or addWorker fails
746	>	* Tries to advance eventCount and releases waiters. Called only
747	>	* from workers.
748		*/
749	<	private void ensureEnoughTotalWorkers() {
750	<	int wc;
751	<	while (((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < parallelism &&
752	<	runState < TERMINATING) {
753	<	if ((UNSAFE.compareAndSwapInt(this, workerCountsOffset,
693	<	wc, wc + (ONE_RUNNING|ONE_TOTAL)) &&
694	<	addWorker() == null))
695	<	break;
696	<	}
749	>	final void signalWork() {
750	>	int c; // try to increment event count -- CAS failure OK
751	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
752	>	if (eventWaiters != 0L)
753	>	releaseEventWaiters();
754		}
755
756		/**
757	<	* Final callback from terminating worker.  Removes record of
758	<	* worker from array, and adjusts counts. If pool is shutting
702	<	* down, tries to complete terminatation, else possibly replaces
703	<	* the worker.
757	>	* Adds the given worker to event queue and blocks until
758	>	* terminating or event count advances from the given value
759		*
760	<	* @param w the worker
760	>	* @param w the calling worker thread
761	>	* @param ec the count
762		*/
763	<	final void workerTerminated(ForkJoinWorkerThread w) {
764	<	if (w.active) { // force inactive
765	<	w.active = false;
766	<	do {} while (!tryDecrementActiveCount());
767	<	}
768	<	forgetWorker(w);
769	<
770	<	// Decrement total count, and if was running, running count
771	<	// Spin (waiting for other updates) if either would be negative
772	<	int nr = w.isTrimmed() ? 0 : ONE_RUNNING;
717	<	int unit = ONE_TOTAL + nr;
718	<	for (;;) {
719	<	int wc = workerCounts;
720	<	int rc = wc & RUNNING_COUNT_MASK;
721	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
722	<	if (rc - nr < 0 || tc == 0)
723	<	Thread.yield(); // back off if waiting for other updates
724	<	else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
725	<	wc, wc - unit))
763	>	private void eventSync(ForkJoinWorkerThread w, int ec) {
764	>	long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1));
765	>	long h;
766	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
767	>	(((int)((h = eventWaiters) & WAITER_ID_MASK)) == 0 ||
768	>	(int)(h >>> EVENT_COUNT_SHIFT) == ec) &&
769	>	eventCount == ec) {
770	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
771	>	w.nextWaiter = h, nh)) {
772	>	awaitEvent(w, ec);
773		break;
774	+	}
775		}
728	–
729	–	accumulateStealCount(w); // collect final count
730	–	if (!tryTerminate(false))
731	–	ensureEnoughTotalWorkers();
776		}
777
734	–	// Waiting for and signalling events
735	–
778		/**
779	<	* Releases workers blocked on a count not equal to current count.
780	<	* @return true if any released
779	>	* Blocks the given worker (that has already been entered as an
780	>	* event waiter) until terminating or event count advances from
781	>	* the given value. The oldest (first) waiter uses a timed wait to
782	>	* occasionally one-by-one shrink the number of workers (to a
783	>	* minimum of one) if the pool has not been used for extended
784	>	* periods.
785	>	*
786	>	* @param w the calling worker thread
787	>	* @param ec the count
788		*/
789	<	private void releaseWaiters() {
790	<	long top;
791	<	while ((top = eventWaiters) != 0L) {
792	<	ForkJoinWorkerThread[] ws = workers;
793	<	int n = ws.length;
794	<	for (;;) {
795	<	int i = ((int)(top & WAITER_ID_MASK)) - 1;
796	<	int e = (int)(top >>> EVENT_COUNT_SHIFT);
797	<	if (i < 0 || e == eventCount)
798	<	return;
799	<	ForkJoinWorkerThread w;
800	<	if (i < n && (w = ws[i]) != null &&
801	<	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
802	<	top, w.nextWaiter)) {
803	<	LockSupport.unpark(w);
804	<	top = eventWaiters;
789	>	private void awaitEvent(ForkJoinWorkerThread w, int ec) {
790	>	while (eventCount == ec) {
791	>	if (tryAccumulateStealCount(w)) { // transfer while idle
792	>	boolean untimed = (w.nextWaiter != 0L ||
793	>	(workerCounts & RUNNING_COUNT_MASK) <= 1);
794	>	long startTime = untimed ? 0 : System.nanoTime();
795	>	Thread.interrupted();         // clear/ignore interrupt
796	>	if (eventCount != ec || w.isTerminating())
797	>	break;                    // recheck after clear
798	>	if (untimed)
799	>	LockSupport.park(w);
800	>	else {
801	>	LockSupport.parkNanos(w, SHRINK_RATE_NANOS);
802	>	if (eventCount != ec || w.isTerminating())
803	>	break;
804	>	if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS)
805	>	tryShutdownUnusedWorker(ec);
806		}
757	–	else
758	–	break;      // possibly stale; reread
807		}
808		}
809		}
810
811	+	// Maintaining parallelism
812	+
813		/**
814	<	* Ensures eventCount on exit is different (mod 2^32) than on
765	<	* entry and wakes up all waiters
814	>	* Pushes worker onto the spare stack.
815		*/
816	<	private void signalEvent() {
817	<	int c;
818	<	do {} while (!UNSAFE.compareAndSwapInt(this, eventCountOffset,
819	<	c = eventCount, c+1));
771	<	releaseWaiters();
816	>	final void pushSpare(ForkJoinWorkerThread w) {
817	>	int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1);
818	>	do {} while (!UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
819	>	w.nextSpare = spareWaiters,ns));
820		}
821
822		/**
823	<	* Advances eventCount and releases waiters until interference by
824	<	* other releasing threads is detected.
823	>	* Tries (once) to resume a spare if the number of running
824	>	* threads is less than target.
825		*/
826	<	final void signalWork() {
827	<	int c;
828	<	UNSAFE.compareAndSwapInt(this, eventCountOffset, c=eventCount, c+1);
829	<	long top;
830	<	while ((top = eventWaiters) != 0L) {
831	<	int ec = eventCount;
832	<	ForkJoinWorkerThread[] ws = workers;
833	<	int n = ws.length;
834	<	for (;;) {
835	<	int i = ((int)(top & WAITER_ID_MASK)) - 1;
836	<	int e = (int)(top >>> EVENT_COUNT_SHIFT);
837	<	if (i < 0 || e == ec)
838	<	return;
839	<	ForkJoinWorkerThread w;
840	<	if (i < n && (w = ws[i]) != null &&
841	<	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
842	<	top, top = w.nextWaiter)) {
843	<	LockSupport.unpark(w);
844	<	if (top != eventWaiters) // let someone else take over
845	<	return;
826	>	private void tryResumeSpare() {
827	>	int sw, id;
828	>	ForkJoinWorkerThread[] ws = workers;
829	>	int n = ws.length;
830	>	ForkJoinWorkerThread w;
831	>	if ((sw = spareWaiters) != 0 &&
832	>	(id = (sw & SPARE_ID_MASK) - 1) >= 0 &&
833	>	id < n && (w = ws[id]) != null &&
834	>	(workerCounts & RUNNING_COUNT_MASK) < parallelism &&
835	>	spareWaiters == sw &&
836	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
837	>	sw, w.nextSpare)) {
838	>	int c; // increment running count before resume
839	>	do {} while (!UNSAFE.compareAndSwapInt
840	>	(this, workerCountsOffset,
841	>	c = workerCounts, c + ONE_RUNNING));
842	>	if (w.tryUnsuspend())
843	>	LockSupport.unpark(w);
844	>	else   // back out if w was shutdown
845	>	decrementWorkerCounts(ONE_RUNNING, 0);
846	>	}
847	>	}
848	>
849	>	/**
850	>	* Tries to increase the number of running workers if below target
851	>	* parallelism: If a spare exists tries to resume it via
852	>	* tryResumeSpare.  Otherwise, if not enough total workers or all
853	>	* existing workers are busy, adds a new worker. In all cases also
854	>	* helps wake up releasable workers waiting for work.
855	>	*/
856	>	private void helpMaintainParallelism() {
857	>	int pc = parallelism;
858	>	int wc, rs, tc;
859	>	while (((wc = workerCounts) & RUNNING_COUNT_MASK) < pc &&
860	>	(rs = runState) < TERMINATING) {
861	>	if (spareWaiters != 0)
862	>	tryResumeSpare();
863	>	else if ((tc = wc >>> TOTAL_COUNT_SHIFT) >= MAX_WORKERS ||
864	>	(tc >= pc && (rs & ACTIVE_COUNT_MASK) != tc))
865	>	break;   // enough total
866	>	else if (runState == rs && workerCounts == wc &&
867	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
868	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
869	>	ForkJoinWorkerThread w = null;
870	>	Throwable fail = null;
871	>	try {
872	>	w = factory.newThread(this);
873	>	} catch (Throwable ex) {
874	>	fail = ex;
875	>	}
876	>	if (w == null) { // null or exceptional factory return
877	>	decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL);
878	>	tryTerminate(false); // handle failure during shutdown
879	>	// If originating from an external caller,
880	>	// propagate exception, else ignore
881	>	if (fail != null && runState < TERMINATING &&
882	>	!(Thread.currentThread() instanceof
883	>	ForkJoinWorkerThread))
884	>	UNSAFE.throwException(fail);
885	>	break;
886	>	}
887	>	w.start(recordWorker(w), ueh);
888	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) >= pc) {
889	>	int c; // advance event count
890	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
891	>	c = eventCount, c+1);
892	>	break; // add at most one unless total below target
893		}
799	–	else
800	–	break;      // possibly stale; reread
894		}
895		}
896	+	if (eventWaiters != 0L)
897	+	releaseEventWaiters();
898		}
899
900		/**
901	<	* Blockss worker until terminating or event count
902	<	* advances from last value held by worker
901	>	* Callback from the oldest waiter in awaitEvent waking up after a
902	>	* period of non-use. If all workers are idle, tries (once) to
903	>	* shutdown an event waiter or a spare, if one exists. Note that
904	>	* we don't need CAS or locks here because the method is called
905	>	* only from one thread occasionally waking (and even misfires are
906	>	* OK). Note that until the shutdown worker fully terminates,
907	>	* workerCounts will overestimate total count, which is tolerable.
908		*
909	<	* @param w the calling worker thread
909	>	* @param ec the event count waited on by caller (to abort
910	>	* attempt if count has since changed).
911		*/
912	<	private void eventSync(ForkJoinWorkerThread w) {
913	<	int wec = w.lastEventCount;
914	<	long nextTop = (((long)wec << EVENT_COUNT_SHIFT) |
915	<	((long)(w.poolIndex + 1)));
916	<	long top;
917	<	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
918	<	(((int)(top = eventWaiters) & WAITER_ID_MASK) == 0 ||
919	<	(int)(top >>> EVENT_COUNT_SHIFT) == wec) &&
920	<	eventCount == wec) {
921	<	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
922	<	w.nextWaiter = top, nextTop)) {
923	<	accumulateStealCount(w); // transfer steals while idle
924	<	Thread.interrupted();    // clear/ignore interrupt
925	<	while (eventCount == wec)
926	<	w.doPark();
927	<	break;
912	>	private void tryShutdownUnusedWorker(int ec) {
913	>	if (runState == 0 && eventCount == ec) { // only trigger if all idle
914	>	ForkJoinWorkerThread[] ws = workers;
915	>	int n = ws.length;
916	>	ForkJoinWorkerThread w = null;
917	>	boolean shutdown = false;
918	>	int sw;
919	>	long h;
920	>	if ((sw = spareWaiters) != 0) { // prefer killing spares
921	>	int id = (sw & SPARE_ID_MASK) - 1;
922	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
923	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
924	>	sw, w.nextSpare))
925	>	shutdown = true;
926	>	}
927	>	else if ((h = eventWaiters) != 0L) {
928	>	long nh;
929	>	int id = ((int)(h & WAITER_ID_MASK)) - 1;
930	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
931	>	(nh = w.nextWaiter) != 0L && // keep at least one worker
932	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh))
933	>	shutdown = true;
934	>	}
935	>	if (w != null && shutdown) {
936	>	w.shutdown();
937	>	LockSupport.unpark(w);
938		}
939		}
940	<	w.lastEventCount = eventCount;
940	>	releaseEventWaiters(); // in case of interference
941		}
942
943		/**
944		* Callback from workers invoked upon each top-level action (i.e.,
945	<	* stealing a task or taking a submission and running
946	<	* it). Performs one or both of the following:
945	>	* stealing a task or taking a submission and running it).
946	>	* Performs one or more of the following:
947		*
948	<	* * If the worker cannot find work, updates its active status to
949	<	* inactive and updates activeCount unless there is contention, in
950	<	* which case it may try again (either in this or a subsequent
951	<	* call).  Additionally, awaits the next task event and/or helps
952	<	* wake up other releasable waiters.
953	<	*
954	<	* * If there are too many running threads, suspends this worker
955	<	* (first forcing inactivation if necessary).  If it is not
956	<	* resumed before a keepAlive elapses, the worker may be "trimmed"
957	<	* -- killed while suspended within suspendAsSpare. Otherwise,
958	<	* upon resume it rechecks to make sure that it is still needed.
948	>	* 1. If the worker is active and either did not run a task
949	>	*    or there are too many workers, try to set its active status
950	>	*    to inactive and update activeCount. On contention, we may
951	>	*    try again in this or a subsequent call.
952	>	*
953	>	* 2. If not enough total workers, help create some.
954	>	*
955	>	* 3. If there are too many running workers, suspend this worker
956	>	*    (first forcing inactive if necessary).  If it is not needed,
957	>	*    it may be shutdown while suspended (via
958	>	*    tryShutdownUnusedWorker).  Otherwise, upon resume it
959	>	*    rechecks running thread count and need for event sync.
960	>	*
961	>	* 4. If worker did not run a task, await the next task event via
962	>	*    eventSync if necessary (first forcing inactivation), upon
963	>	*    which the worker may be shutdown via
964	>	*    tryShutdownUnusedWorker.  Otherwise, help release any
965	>	*    existing event waiters that are now releasable,
966		*
967		* @param w the worker
968	<	* @param retries the number of scans by caller failing to find work
851	<	* find any (in which case it may block waiting for work).
968	>	* @param ran true if worker ran a task since last call to this method
969		*/
970	<	final void preStep(ForkJoinWorkerThread w, int retries) {
970	>	final void preStep(ForkJoinWorkerThread w, boolean ran) {
971	>	int wec = w.lastEventCount;
972		boolean active = w.active;
973	<	boolean inactivate = active && retries > 0;
974	<	for (;;) {
975	<	int rs, wc;
976	<	if (inactivate &&
977	<	UNSAFE.compareAndSwapInt(this, runStateOffset,
978	<	rs = runState, rs - ONE_ACTIVE))
973	>	boolean inactivate = false;
974	>	int pc = parallelism;
975	>	while (w.runState == 0) {
976	>	int rs = runState;
977	>	if (rs >= TERMINATING) { // propagate shutdown
978	>	w.shutdown();
979	>	break;
980	>	}
981	>	if ((inactivate || (active && (rs & ACTIVE_COUNT_MASK) >= pc)) &&
982	>	UNSAFE.compareAndSwapInt(this, runStateOffset, rs, rs - 1))
983		inactivate = active = w.active = false;
984	<	if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= parallelism) {
985	<	if (retries > 0) {
986	<	if (retries > 1 && !active)
987	<	eventSync(w);
988	<	releaseWaiters();
984	>	int wc = workerCounts;
985	>	if ((wc & RUNNING_COUNT_MASK) > pc) {
986	>	if (!(inactivate |= active) && // must inactivate to suspend
987	>	workerCounts == wc &&      // try to suspend as spare
988	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
989	>	wc, wc - ONE_RUNNING))
990	>	w.suspendAsSpare();
991	>	}
992	>	else if ((wc >>> TOTAL_COUNT_SHIFT) < pc)
993	>	helpMaintainParallelism();     // not enough workers
994	>	else if (!ran) {
995	>	long h = eventWaiters;
996	>	int ec = eventCount;
997	>	if (h != 0L && (int)(h >>> EVENT_COUNT_SHIFT) != ec)
998	>	releaseEventWaiters();     // release others before waiting
999	>	else if (ec != wec) {
1000	>	w.lastEventCount = ec;     // no need to wait
1001	>	break;
1002		}
1003	<	break;
1003	>	else if (!(inactivate |= active))
1004	>	eventSync(w, wec);         // must inactivate before sync
1005		}
1006	<	if (!(inactivate |= active) &&  // must inactivate to suspend
871	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
872	<	wc, wc - ONE_RUNNING) &&
873	<	!w.suspendAsSpare())             // false if trimmed
1006	>	else
1007		break;
1008		}
1009		}
1010
1011		/**
1012	<	* Awaits join of the given task if enough threads, or can resume
1013	<	* or create a spare. Fails (in which case the given task might
881	<	* not be done) upon contention or lack of decision about
882	<	* blocking.
883	<	*
884	<	* We allow blocking if:
885	<	*
886	<	* 1. There would still be at least as many running threads as
887	<	*    parallelism level if this thread blocks.
888	<	*
889	<	* 2. A spare is resumed to replace this worker. We tolerate
890	<	*    races in the decision to replace when a spare is found.
891	<	*    This may release too many, but if so, the superfluous ones
892	<	*    will re-suspend via preStep().
893	<	*
894	<	* 3. After #spares repeated retries, there are fewer than #spare
895	<	*    threads not running. We allow this slack to avoid hysteresis
896	<	*    and as a hedge against lag/uncertainty of running count
897	<	*    estimates when signalling or unblocking stalls.
898	<	*
899	<	* 4. All existing workers are busy (as rechecked via #spares
900	<	*    repeated retries by caller) and a new spare is created.
901	<	*
902	<	* If none of the above hold, we escape out by re-incrementing
903	<	* count and returning to caller, which can retry later.
1012	>	* Helps and/or blocks awaiting join of the given task.
1013	>	* See above for explanation.
1014		*
1015		* @param joinMe the task to join
1016	<	* @param retries the number of calls to this method for this join
1017	<	*/
1018	<	final void tryAwaitJoin(ForkJoinTask<?> joinMe, int retries) {
1019	<	int pc = parallelism;
1020	<	boolean running = true; // false when running count decremented
1021	<	outer:while (joinMe.status >= 0) {
1022	<	int wc = workerCounts;
1023	<	int rc = wc & RUNNING_COUNT_MASK;
1024	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
1025	<	if (running) { // replace with spare or decrement count
1026	<	if (rc <= pc && tc > pc &&
1027	<	(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) {
1028	<	ForkJoinWorkerThread[] ws = workers; // search for spare
1029	<	int nws = ws.length;
1030	<	for (int i = 0; i < nws; ++i) {
1031	<	ForkJoinWorkerThread w = ws[i];
1032	<	if (w != null && w.isSuspended()) {
1033	<	if ((workerCounts & RUNNING_COUNT_MASK) > pc)
1034	<	continue outer;
1035	<	if (joinMe.status < 0)
1036	<	break outer;
1037	<	if (w.tryResumeSpare()) {
1038	<	running = false;
1039	<	break outer;
1016	>	* @param worker the current worker thread
1017	>	* @param timed true if wait should time out
1018	>	* @param nanos timeout value if timed
1019	>	*/
1020	>	final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker,
1021	>	boolean timed, long nanos) {
1022	>	long startTime = timed? System.nanoTime() : 0L;
1023	>	int retries = 2 + (parallelism >> 2); // #helpJoins before blocking
1024	>	while (joinMe.status >= 0) {
1025	>	int wc;
1026	>	long nt = 0L;
1027	>	if (runState >= TERMINATING) {
1028	>	joinMe.cancelIgnoringExceptions();
1029	>	break;
1030	>	}
1031	>	worker.helpJoinTask(joinMe);
1032	>	if (joinMe.status < 0)
1033	>	break;
1034	>	else if (retries > 0)
1035	>	--retries;
1036	>	else if (timed &&
1037	>	(nt = nanos - (System.nanoTime() - startTime)) <= 0L)
1038	>	break;
1039	>	else if (((wc = workerCounts) & RUNNING_COUNT_MASK) != 0 &&
1040	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1041	>	wc, wc - ONE_RUNNING)) {
1042	>	int stat, c; long h;
1043	>	while ((stat = joinMe.status) >= 0 &&
1044	>	(h = eventWaiters) != 0L && // help release others
1045	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1046	>	releaseEventWaiters();
1047	>	if (stat >= 0) {
1048	>	if ((workerCounts & RUNNING_COUNT_MASK) != 0) {
1049	>	long ms; int ns;
1050	>	if (!timed) {
1051	>	ms = JOIN_TIMEOUT_MILLIS;
1052	>	ns = 0;
1053	>	}
1054	>	else { // at most JOIN_TIMEOUT_MILLIS per wait
1055	>	ms = nt / 1000000;
1056	>	if (ms > JOIN_TIMEOUT_MILLIS) {
1057	>	ms = JOIN_TIMEOUT_MILLIS;
1058	>	ns = 0;
1059		}
1060	<	continue outer; // rescan on failure to resume
1060	>	else
1061	>	ns = (int) (nt % 1000000);
1062		}
1063	+	stat = joinMe.internalAwaitDone(ms, ns);
1064		}
1065	+	if (stat >= 0) // timeout or no running workers
1066	+	helpMaintainParallelism();
1067		}
1068	<	if ((rc <= pc && (rc == 0 || --retries < 0)) || // no retry
1069	<	joinMe.status < 0)
1070	<	break;
1071	<	if (workerCounts == wc &&
1072	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
940	<	wc, wc - ONE_RUNNING))
941	<	running = false;
942	<	}
943	<	else { // allow blocking if enough threads
944	<	int sc = tc - pc + 1;          // = spares, plus the one to add
945	<	if (sc > 0 && rc > 0 && rc >= pc - sc && rc > pc - retries)
946	<	break;
947	<	if (--retries > sc && tc < MAX_THREADS &&
948	<	tc == (runState & ACTIVE_COUNT_MASK) &&
949	<	workerCounts == wc &&
950	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
951	<	wc + (ONE_RUNNING|ONE_TOTAL))) {
952	<	addWorker();
953	<	break;
954	<	}
955	<	if (workerCounts == wc &&
956	<	UNSAFE.compareAndSwapInt (this, workerCountsOffset,
957	<	wc, wc + ONE_RUNNING)) {
958	<	running = true;            // back out; allow retry
959	<	break;
960	<	}
1068	>	do {} while (!UNSAFE.compareAndSwapInt
1069	>	(this, workerCountsOffset,
1070	>	c = workerCounts, c + ONE_RUNNING));
1071	>	if (stat < 0)
1072	>	break;   // else restart
1073		}
1074		}
963	–	if (!running) { // can block
964	–	int c;                      // to inline incrementRunningCount
965	–	joinMe.internalAwaitDone();
966	–	do {} while (!UNSAFE.compareAndSwapInt
967	–	(this, workerCountsOffset,
968	–	c = workerCounts, c + ONE_RUNNING));
969	–	}
1075		}
1076
1077		/**
1078	<	* Same idea as (and shares many code snippets with) tryAwaitJoin,
974	<	* but self-contained because there are no caller retries.
975	<	* TODO: Rework to use simpler API.
1078	>	* Same idea as awaitJoin, but no helping, retries, or timeouts.
1079		*/
1080		final void awaitBlocker(ManagedBlocker blocker)
1081		throws InterruptedException {
1082	<	int pc = parallelism;
980	<	boolean running = true;
981	<	int retries = 0;
982	<	boolean done;
983	<	outer:while (!(done = blocker.isReleasable())) {
1082	>	while (!blocker.isReleasable()) {
1083		int wc = workerCounts;
1084	<	int rc = wc & RUNNING_COUNT_MASK;
1085	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
1086	<	if (running) {
1087	<	if (rc <= pc && tc > pc &&
1088	<	(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) {
1089	<	ForkJoinWorkerThread[] ws = workers;
1090	<	int nws = ws.length;
1091	<	for (int i = 0; i < nws; ++i) {
1092	<	ForkJoinWorkerThread w = ws[i];
1093	<	if (w != null && w.isSuspended()) {
1094	<	if ((workerCounts & RUNNING_COUNT_MASK) > pc)
1095	<	continue outer;
1096	<	if (done = blocker.isReleasable())
1097	<	break outer;
999	<	if (w.tryResumeSpare()) {
1000	<	running = false;
1001	<	break outer;
1002	<	}
1003	<	continue outer;
1004	<	}
1084	>	if ((wc & RUNNING_COUNT_MASK) != 0 &&
1085	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1086	>	wc, wc - ONE_RUNNING)) {
1087	>	try {
1088	>	while (!blocker.isReleasable()) {
1089	>	long h = eventWaiters;
1090	>	if (h != 0L &&
1091	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1092	>	releaseEventWaiters();
1093	>	else if ((workerCounts & RUNNING_COUNT_MASK) == 0 &&
1094	>	runState < TERMINATING)
1095	>	helpMaintainParallelism();
1096	>	else if (blocker.block())
1097	>	break;
1098		}
1099	<	if (done = blocker.isReleasable())
1100	<	break;
1101	<	}
1102	<	if (rc > 0 && workerCounts == wc &&
1103	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1011	<	wc, wc - ONE_RUNNING)) {
1012	<	running = false;
1013	<	if (rc > pc)
1014	<	break;
1099	>	} finally {
1100	>	int c;
1101	>	do {} while (!UNSAFE.compareAndSwapInt
1102	>	(this, workerCountsOffset,
1103	>	c = workerCounts, c + ONE_RUNNING));
1104		}
1016	–	}
1017	–	else if (rc >= pc)
1018	–	break;
1019	–	else if (tc < MAX_THREADS &&
1020	–	tc == (runState & ACTIVE_COUNT_MASK) &&
1021	–	workerCounts == wc &&
1022	–	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
1023	–	wc + (ONE_RUNNING|ONE_TOTAL))) {
1024	–	addWorker();
1105		break;
1106		}
1027	–	else if (workerCounts == wc &&
1028	–	UNSAFE.compareAndSwapInt (this, workerCountsOffset,
1029	–	wc, wc + ONE_RUNNING)) {
1030	–	Thread.yield();
1031	–	++retries;
1032	–	running = true;            // allow rescan
1033	–	}
1034	–	}
1035	–
1036	–	try {
1037	–	if (!done)
1038	–	do {} while (!blocker.isReleasable() && !blocker.block());
1039	–	} finally {
1040	–	if (!running) {
1041	–	int c;
1042	–	do {} while (!UNSAFE.compareAndSwapInt
1043	–	(this, workerCountsOffset,
1044	–	c = workerCounts, c + ONE_RUNNING));
1045	–	}
1107		}
1108		}
1109
#	Line 1072 | Line 1133 | public class ForkJoinPool extends Abstra
1133		return true;
1134		}
1135
1136	+
1137		/**
1138		* Actions on transition to TERMINATING
1139	+	*
1140	+	* Runs up to four passes through workers: (0) shutting down each
1141	+	* (without waking up if parked) to quickly spread notifications
1142	+	* without unnecessary bouncing around event queues etc (1) wake
1143	+	* up and help cancel tasks (2) interrupt (3) mop up races with
1144	+	* interrupted workers
1145		*/
1146		private void startTerminating() {
1147	<	for (int i = 0; i < 2; ++i) { // twice to mop up newly created workers
1148	<	cancelSubmissions();
1149	<	shutdownWorkers();
1150	<	cancelWorkerTasks();
1151	<	signalEvent();
1152	<	interruptWorkers();
1147	>	cancelSubmissions();
1148	>	for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) {
1149	>	int c; // advance event count
1150	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
1151	>	c = eventCount, c+1);
1152	>	eventWaiters = 0L; // clobber lists
1153	>	spareWaiters = 0;
1154	>	for (ForkJoinWorkerThread w : workers) {
1155	>	if (w != null) {
1156	>	w.shutdown();
1157	>	if (passes > 0 && !w.isTerminated()) {
1158	>	w.cancelTasks();
1159	>	LockSupport.unpark(w);
1160	>	if (passes > 1 && !w.isInterrupted()) {
1161	>	try {
1162	>	w.interrupt();
1163	>	} catch (SecurityException ignore) {
1164	>	}
1165	>	}
1166	>	}
1167	>	}
1168	>	}
1169		}
1170		}
1171
1172		/**
1173	<	* Clear out and cancel submissions, ignoring exceptions
1173	>	* Clears out and cancels submissions, ignoring exceptions.
1174		*/
1175		private void cancelSubmissions() {
1176		ForkJoinTask<?> task;
#	Line 1098 | Line 1182 | public class ForkJoinPool extends Abstra
1182		}
1183		}
1184
1101	–	/**
1102	–	* Sets all worker run states to at least shutdown,
1103	–	* also resuming suspended workers
1104	–	*/
1105	–	private void shutdownWorkers() {
1106	–	ForkJoinWorkerThread[] ws = workers;
1107	–	int nws = ws.length;
1108	–	for (int i = 0; i < nws; ++i) {
1109	–	ForkJoinWorkerThread w = ws[i];
1110	–	if (w != null)
1111	–	w.shutdown();
1112	–	}
1113	–	}
1114	–
1115	–	/**
1116	–	* Clears out and cancels all locally queued tasks
1117	–	*/
1118	–	private void cancelWorkerTasks() {
1119	–	ForkJoinWorkerThread[] ws = workers;
1120	–	int nws = ws.length;
1121	–	for (int i = 0; i < nws; ++i) {
1122	–	ForkJoinWorkerThread w = ws[i];
1123	–	if (w != null)
1124	–	w.cancelTasks();
1125	–	}
1126	–	}
1127	–
1128	–	/**
1129	–	* Unsticks all workers blocked on joins etc
1130	–	*/
1131	–	private void interruptWorkers() {
1132	–	ForkJoinWorkerThread[] ws = workers;
1133	–	int nws = ws.length;
1134	–	for (int i = 0; i < nws; ++i) {
1135	–	ForkJoinWorkerThread w = ws[i];
1136	–	if (w != null && !w.isTerminated()) {
1137	–	try {
1138	–	w.interrupt();
1139	–	} catch (SecurityException ignore) {
1140	–	}
1141	–	}
1142	–	}
1143	–	}
1144	–
1185		// misc support for ForkJoinWorkerThread
1186
1187		/**
1188	<	* Returns pool number
1188	>	* Returns pool number.
1189		*/
1190		final int getPoolNumber() {
1191		return poolNumber;
1192		}
1193
1194		/**
1195	<	* Accumulates steal count from a worker, clearing
1196	<	* the worker's value
1195	>	* Tries to accumulate steal count from a worker, clearing
1196	>	* the worker's value if successful.
1197	>	*
1198	>	* @return true if worker steal count now zero
1199		*/
1200	<	final void accumulateStealCount(ForkJoinWorkerThread w) {
1200	>	final boolean tryAccumulateStealCount(ForkJoinWorkerThread w) {
1201		int sc = w.stealCount;
1202	<	if (sc != 0) {
1203	<	long c;
1204	<	w.stealCount = 0;
1205	<	do {} while (!UNSAFE.compareAndSwapLong(this, stealCountOffset,
1206	<	c = stealCount, c + sc));
1202	>	long c = stealCount;
1203	>	// CAS even if zero, for fence effects
1204	>	if (UNSAFE.compareAndSwapLong(this, stealCountOffset, c, c + sc)) {
1205	>	if (sc != 0)
1206	>	w.stealCount = 0;
1207	>	return true;
1208		}
1209	+	return sc == 0;
1210		}
1211
1212		/**
#	Line 1171 | Line 1215 | public class ForkJoinPool extends Abstra
1215		*/
1216		final int idlePerActive() {
1217		int pc = parallelism; // use parallelism, not rc
1218	<	int ac = runState;    // no mask -- artifically boosts during shutdown
1218	>	int ac = runState;    // no mask -- artificially boosts during shutdown
1219		// Use exact results for small values, saturate past 4
1220	<	return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
1220	>	return ((pc <= ac) ? 0 :
1221	>	(pc >>> 1 <= ac) ? 1 :
1222	>	(pc >>> 2 <= ac) ? 3 :
1223	>	pc >>> 3);
1224		}
1225
1226		// Public and protected methods
#	Line 1223 | Line 1270 | public class ForkJoinPool extends Abstra
1270		* use {@link #defaultForkJoinWorkerThreadFactory}.
1271		* @param handler the handler for internal worker threads that
1272		* terminate due to unrecoverable errors encountered while executing
1273	<	* tasks. For default value, use <code>null</code>.
1273	>	* tasks. For default value, use {@code null}.
1274		* @param asyncMode if true,
1275		* establishes local first-in-first-out scheduling mode for forked
1276		* tasks that are never joined. This mode may be more appropriate
1277		* than default locally stack-based mode in applications in which
1278		* worker threads only process event-style asynchronous tasks.
1279	<	* For default value, use <code>false</code>.
1279	>	* For default value, use {@code false}.
1280		* @throws IllegalArgumentException if parallelism less than or
1281		*         equal to zero, or greater than implementation limit
1282		* @throws NullPointerException if the factory is null
#	Line 1245 | Line 1292 | public class ForkJoinPool extends Abstra
1292		checkPermission();
1293		if (factory == null)
1294		throw new NullPointerException();
1295	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
1295	>	if (parallelism <= 0 || parallelism > MAX_WORKERS)
1296		throw new IllegalArgumentException();
1297		this.parallelism = parallelism;
1298		this.factory = factory;
#	Line 1264 | Line 1311 | public class ForkJoinPool extends Abstra
1311		* @param pc the initial parallelism level
1312		*/
1313		private static int initialArraySizeFor(int pc) {
1314	<	// See Hackers Delight, sec 3.2. We know MAX_THREADS < (1 >>> 16)
1315	<	int size = pc < MAX_THREADS ? pc + 1 : MAX_THREADS;
1314	>	// If possible, initially allocate enough space for one spare
1315	>	int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS;
1316	>	// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16)
1317		size |= size >>> 1;
1318		size |= size >>> 2;
1319		size |= size >>> 4;
#	Line 1276 | Line 1324 | public class ForkJoinPool extends Abstra
1324		// Execution methods
1325
1326		/**
1327	<	* Common code for execute, invoke and submit
1327	>	* Submits task and creates, starts, or resumes some workers if necessary
1328		*/
1329		private <T> void doSubmit(ForkJoinTask<T> task) {
1282	–	if (task == null)
1283	–	throw new NullPointerException();
1284	–	if (runState >= SHUTDOWN)
1285	–	throw new RejectedExecutionException();
1330		submissionQueue.offer(task);
1331	<	signalEvent();
1332	<	ensureEnoughTotalWorkers();
1331	>	int c; // try to increment event count -- CAS failure OK
1332	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
1333	>	helpMaintainParallelism();
1334		}
1335
1336		/**
1337		* Performs the given task, returning its result upon completion.
1293	–	* If the caller is already engaged in a fork/join computation in
1294	–	* the current pool, this method is equivalent in effect to
1295	–	* {@link ForkJoinTask#invoke}.
1338		*
1339		* @param task the task
1340		* @return the task's result
#	Line 1301 | Line 1343 | public class ForkJoinPool extends Abstra
1343		*         scheduled for execution
1344		*/
1345		public <T> T invoke(ForkJoinTask<T> task) {
1346	<	doSubmit(task);
1347	<	return task.join();
1346	>	if (task == null)
1347	>	throw new NullPointerException();
1348	>	if (runState >= SHUTDOWN)
1349	>	throw new RejectedExecutionException();
1350	>	Thread t = Thread.currentThread();
1351	>	if ((t instanceof ForkJoinWorkerThread) &&
1352	>	((ForkJoinWorkerThread)t).pool == this)
1353	>	return task.invoke();  // bypass submit if in same pool
1354	>	else {
1355	>	doSubmit(task);
1356	>	return task.join();
1357	>	}
1358	>	}
1359	>
1360	>	/**
1361	>	* Unless terminating, forks task if within an ongoing FJ
1362	>	* computation in the current pool, else submits as external task.
1363	>	*/
1364	>	private <T> void forkOrSubmit(ForkJoinTask<T> task) {
1365	>	if (runState >= SHUTDOWN)
1366	>	throw new RejectedExecutionException();
1367	>	Thread t = Thread.currentThread();
1368	>	if ((t instanceof ForkJoinWorkerThread) &&
1369	>	((ForkJoinWorkerThread)t).pool == this)
1370	>	task.fork();
1371	>	else
1372	>	doSubmit(task);
1373		}
1374
1375		/**
1376		* Arranges for (asynchronous) execution of the given task.
1310	–	* If the caller is already engaged in a fork/join computation in
1311	–	* the current pool, this method is equivalent in effect to
1312	–	* {@link ForkJoinTask#fork}.
1377		*
1378		* @param task the task
1379		* @throws NullPointerException if the task is null
#	Line 1317 | Line 1381 | public class ForkJoinPool extends Abstra
1381		*         scheduled for execution
1382		*/
1383		public void execute(ForkJoinTask<?> task) {
1384	<	doSubmit(task);
1384	>	if (task == null)
1385	>	throw new NullPointerException();
1386	>	forkOrSubmit(task);
1387		}
1388
1389		// AbstractExecutorService methods
#	Line 1328 | Line 1394 | public class ForkJoinPool extends Abstra
1394		*         scheduled for execution
1395		*/
1396		public void execute(Runnable task) {
1397	+	if (task == null)
1398	+	throw new NullPointerException();
1399		ForkJoinTask<?> job;
1400		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1401		job = (ForkJoinTask<?>) task;
1402		else
1403		job = ForkJoinTask.adapt(task, null);
1404	<	doSubmit(job);
1404	>	forkOrSubmit(job);
1405		}
1406
1407		/**
1408		* Submits a ForkJoinTask for execution.
1341	–	* If the caller is already engaged in a fork/join computation in
1342	–	* the current pool, this method is equivalent in effect to
1343	–	* {@link ForkJoinTask#fork}.
1409		*
1410		* @param task the task to submit
1411		* @return the task
#	Line 1349 | Line 1414 | public class ForkJoinPool extends Abstra
1414		*         scheduled for execution
1415		*/
1416		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1417	<	doSubmit(task);
1417	>	if (task == null)
1418	>	throw new NullPointerException();
1419	>	forkOrSubmit(task);
1420		return task;
1421		}
1422
#	Line 1359 | Line 1426 | public class ForkJoinPool extends Abstra
1426		*         scheduled for execution
1427		*/
1428		public <T> ForkJoinTask<T> submit(Callable<T> task) {
1429	+	if (task == null)
1430	+	throw new NullPointerException();
1431		ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1432	<	doSubmit(job);
1432	>	forkOrSubmit(job);
1433		return job;
1434		}
1435
#	Line 1370 | Line 1439 | public class ForkJoinPool extends Abstra
1439		*         scheduled for execution
1440		*/
1441		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1442	+	if (task == null)
1443	+	throw new NullPointerException();
1444		ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1445	<	doSubmit(job);
1445	>	forkOrSubmit(job);
1446		return job;
1447		}
1448
#	Line 1381 | Line 1452 | public class ForkJoinPool extends Abstra
1452		*         scheduled for execution
1453		*/
1454		public ForkJoinTask<?> submit(Runnable task) {
1455	+	if (task == null)
1456	+	throw new NullPointerException();
1457		ForkJoinTask<?> job;
1458		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1459		job = (ForkJoinTask<?>) task;
1460		else
1461		job = ForkJoinTask.adapt(task, null);
1462	<	doSubmit(job);
1462	>	forkOrSubmit(job);
1463		return job;
1464		}
1465
#	Line 1446 | Line 1519 | public class ForkJoinPool extends Abstra
1519
1520		/**
1521		* Returns the number of worker threads that have started but not
1522	<	* yet terminated.  This result returned by this method may differ
1522	>	* yet terminated.  The result returned by this method may differ
1523		* from {@link #getParallelism} when threads are created to
1524		* maintain parallelism when others are cooperatively blocked.
1525		*
#	Line 1531 | Line 1604 | public class ForkJoinPool extends Abstra
1604		*/
1605		public long getQueuedTaskCount() {
1606		long count = 0;
1607	<	ForkJoinWorkerThread[] ws = workers;
1535	<	int nws = ws.length;
1536	<	for (int i = 0; i < nws; ++i) {
1537	<	ForkJoinWorkerThread w = ws[i];
1607	>	for (ForkJoinWorkerThread w : workers)
1608		if (w != null)
1609		count += w.getQueueSize();
1540	–	}
1610		return count;
1611		}
1612
#	Line 1591 | Line 1660 | public class ForkJoinPool extends Abstra
1660		* @return the number of elements transferred
1661		*/
1662		protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1663	<	int n = submissionQueue.drainTo(c);
1664	<	ForkJoinWorkerThread[] ws = workers;
1596	<	int nws = ws.length;
1597	<	for (int i = 0; i < nws; ++i) {
1598	<	ForkJoinWorkerThread w = ws[i];
1663	>	int count = submissionQueue.drainTo(c);
1664	>	for (ForkJoinWorkerThread w : workers)
1665		if (w != null)
1666	<	n += w.drainTasksTo(c);
1601	<	}
1602	<	return n;
1603	<	}
1604	<
1605	<	/**
1606	<	* Returns count of total parks by existing workers.
1607	<	* Used during development only since not meaningful to users.
1608	<	*/
1609	<	private int collectParkCount() {
1610	<	int count = 0;
1611	<	ForkJoinWorkerThread[] ws = workers;
1612	<	int nws = ws.length;
1613	<	for (int i = 0; i < nws; ++i) {
1614	<	ForkJoinWorkerThread w = ws[i];
1615	<	if (w != null)
1616	<	count += w.parkCount;
1617	<	}
1666	>	count += w.drainTasksTo(c);
1667		return count;
1668		}
1669
#	Line 1635 | Line 1684 | public class ForkJoinPool extends Abstra
1684		int pc = parallelism;
1685		int rs = runState;
1686		int ac = rs & ACTIVE_COUNT_MASK;
1638	–	//        int pk = collectParkCount();
1687		return super.toString() +
1688		"[" + runLevelToString(rs) +
1689		", parallelism = " + pc +
#	Line 1645 | Line 1693 | public class ForkJoinPool extends Abstra
1693		", steals = " + st +
1694		", tasks = " + qt +
1695		", submissions = " + qs +
1648	–	//            ", parks = " + pk +
1696		"]";
1697		}
1698
#	Line 1720 | Line 1767 | public class ForkJoinPool extends Abstra
1767		}
1768
1769		/**
1770	+	* Returns true if terminating or terminated. Used by ForkJoinWorkerThread.
1771	+	*/
1772	+	final boolean isAtLeastTerminating() {
1773	+	return runState >= TERMINATING;
1774	+	}
1775	+
1776	+	/**
1777		* Returns {@code true} if this pool has been shut down.
1778		*
1779		* @return {@code true} if this pool has been shut down
#	Line 1743 | Line 1797 | public class ForkJoinPool extends Abstra
1797		throws InterruptedException {
1798		try {
1799		return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1800	<	} catch(TimeoutException ex) {
1800	>	} catch (TimeoutException ex) {
1801		return false;
1802		}
1803		}
#	Line 1752 | Line 1806 | public class ForkJoinPool extends Abstra
1806		* Interface for extending managed parallelism for tasks running
1807		* in {@link ForkJoinPool}s.
1808		*
1809	<	* <p>A {@code ManagedBlocker} provides two methods.
1810	<	* Method {@code isReleasable} must return {@code true} if
1811	<	* blocking is not necessary. Method {@code block} blocks the
1812	<	* current thread if necessary (perhaps internally invoking
1813	<	* {@code isReleasable} before actually blocking).
1809	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
1810	>	* {@code isReleasable} must return {@code true} if blocking is
1811	>	* not necessary. Method {@code block} blocks the current thread
1812	>	* if necessary (perhaps internally invoking {@code isReleasable}
1813	>	* before actually blocking). The unusual methods in this API
1814	>	* accommodate synchronizers that may, but don't usually, block
1815	>	* for long periods. Similarly, they allow more efficient internal
1816	>	* handling of cases in which additional workers may be, but
1817	>	* usually are not, needed to ensure sufficient parallelism.
1818	>	* Toward this end, implementations of method {@code isReleasable}
1819	>	* must be amenable to repeated invocation.
1820		*
1821		* <p>For example, here is a ManagedBlocker based on a
1822		* ReentrantLock:
#	Line 1774 | Line 1834 | public class ForkJoinPool extends Abstra
1834		*     return hasLock || (hasLock = lock.tryLock());
1835		*   }
1836		* }}</pre>
1837	+	*
1838	+	* <p>Here is a class that possibly blocks waiting for an
1839	+	* item on a given queue:
1840	+	*  <pre> {@code
1841	+	* class QueueTaker<E> implements ManagedBlocker {
1842	+	*   final BlockingQueue<E> queue;
1843	+	*   volatile E item = null;
1844	+	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
1845	+	*   public boolean block() throws InterruptedException {
1846	+	*     if (item == null)
1847	+	*       item = queue.take();
1848	+	*     return true;
1849	+	*   }
1850	+	*   public boolean isReleasable() {
1851	+	*     return item != null || (item = queue.poll()) != null;
1852	+	*   }
1853	+	*   public E getItem() { // call after pool.managedBlock completes
1854	+	*     return item;
1855	+	*   }
1856	+	* }}</pre>
1857		*/
1858		public static interface ManagedBlocker {
1859		/**
#	Line 1816 | Line 1896 | public class ForkJoinPool extends Abstra
1896		public static void managedBlock(ManagedBlocker blocker)
1897		throws InterruptedException {
1898		Thread t = Thread.currentThread();
1899	<	if (t instanceof ForkJoinWorkerThread)
1900	<	((ForkJoinWorkerThread) t).pool.awaitBlocker(blocker);
1899	>	if (t instanceof ForkJoinWorkerThread) {
1900	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
1901	>	w.pool.awaitBlocker(blocker);
1902	>	}
1903		else {
1904		do {} while (!blocker.isReleasable() && !blocker.block());
1905		}
#	Line 1845 | Line 1927 | public class ForkJoinPool extends Abstra
1927		private static final long eventCountOffset =
1928		objectFieldOffset("eventCount", ForkJoinPool.class);
1929		private static final long eventWaitersOffset =
1930	<	objectFieldOffset("eventWaiters",ForkJoinPool.class);
1930	>	objectFieldOffset("eventWaiters", ForkJoinPool.class);
1931		private static final long stealCountOffset =
1932	<	objectFieldOffset("stealCount",ForkJoinPool.class);
1932	>	objectFieldOffset("stealCount", ForkJoinPool.class);
1933	>	private static final long spareWaitersOffset =
1934	>	objectFieldOffset("spareWaiters", ForkJoinPool.class);
1935
1936		private static long objectFieldOffset(String field, Class<?> klazz) {
1937		try {

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