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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 1.90 by jsr166, Mon Nov 29 20:58:06 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;
499	>	private static final int EVENT_COUNT_SHIFT = 32;
500	>	private static final int WAITER_ID_MASK    = (1 << 16) - 1;
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 543 | Line 596 | public class ForkJoinPool extends Abstra
596		}
597
598		/**
599	<	* Tries to decrement running count unless already zero
599	>	* Tries to increment running count part of workerCounts.
600		*/
601	<	final boolean tryDecrementRunningCount() {
602	<	int wc = workerCounts;
550	<	if ((wc & RUNNING_COUNT_MASK) == 0)
551	<	return false;
601	>	final boolean tryIncrementRunningCount() {
602	>	int c;
603		return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
604	<	wc, wc - ONE_RUNNING);
604	>	c = workerCounts,
605	>	c + ONE_RUNNING);
606		}
607
608		/**
609	<	* Tries to increment running count
609	>	* Tries to decrement running count unless already zero.
610		*/
611	<	final boolean tryIncrementRunningCount() {
612	<	int wc;
611	>	final boolean tryDecrementRunningCount() {
612	>	int wc = workerCounts;
613	>	if ((wc & RUNNING_COUNT_MASK) == 0)
614	>	return false;
615		return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
616	<	wc = workerCounts, wc + ONE_RUNNING);
616	>	wc, wc - ONE_RUNNING);
617		}
618
619		/**
620	<	* Tries incrementing active count; fails on contention.
621	<	* Called by workers before executing tasks.
620	>	* Forces decrement of encoded workerCounts, awaiting nonzero if
621	>	* (rarely) necessary when other count updates lag.
622		*
623	<	* @return true on success
623	>	* @param dr -- either zero or ONE_RUNNING
624	>	* @param dt -- either zero or ONE_TOTAL
625		*/
626	<	final boolean tryIncrementActiveCount() {
627	<	int c;
628	<	return UNSAFE.compareAndSwapInt(this, runStateOffset,
629	<	c = runState, c + ONE_ACTIVE);
626	>	private void decrementWorkerCounts(int dr, int dt) {
627	>	for (;;) {
628	>	int wc = workerCounts;
629	>	if ((wc & RUNNING_COUNT_MASK)  - dr < 0 ||
630	>	(wc >>> TOTAL_COUNT_SHIFT) - dt < 0) {
631	>	if ((runState & TERMINATED) != 0)
632	>	return; // lagging termination on a backout
633	>	Thread.yield();
634	>	}
635	>	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
636	>	wc, wc - (dr + dt)))
637	>	return;
638	>	}
639		}
640
641		/**
#	Line 581 | Line 645 | public class ForkJoinPool extends Abstra
645		final boolean tryDecrementActiveCount() {
646		int c;
647		return UNSAFE.compareAndSwapInt(this, runStateOffset,
648	<	c = runState, c - ONE_ACTIVE);
648	>	c = runState, c - 1);
649		}
650
651		/**
#	Line 610 | Line 674 | public class ForkJoinPool extends Abstra
674		lock.lock();
675		try {
676		ForkJoinWorkerThread[] ws = workers;
677	<	int nws = ws.length;
678	<	if (k < 0 || k >= nws || ws[k] != null) {
679	<	for (k = 0; k < nws && ws[k] != null; ++k)
677	>	int n = ws.length;
678	>	if (k < 0 || k >= n || ws[k] != null) {
679	>	for (k = 0; k < n && ws[k] != null; ++k)
680		;
681	<	if (k == nws)
682	<	ws = Arrays.copyOf(ws, nws << 1);
681	>	if (k == n)
682	>	ws = workers = Arrays.copyOf(ws, n << 1);
683		}
684		ws[k] = w;
685	<	workers = ws; // volatile array write ensures slot visibility
685	>	int c = eventCount; // advance event count to ensure visibility
686	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c, c+1);
687		} finally {
688		lock.unlock();
689		}
#	Line 626 | Line 691 | public class ForkJoinPool extends Abstra
691		}
692
693		/**
694	<	* Nulls out record of worker in workers array
694	>	* Nulls out record of worker in workers array.
695		*/
696		private void forgetWorker(ForkJoinWorkerThread w) {
697		int idx = w.poolIndex;
698	<	// Locking helps method recordWorker avoid unecessary expansion
698	>	// Locking helps method recordWorker avoid unnecessary expansion
699		final ReentrantLock lock = this.workerLock;
700		lock.lock();
701		try {
#	Line 642 | Line 707 | public class ForkJoinPool extends Abstra
707		}
708		}
709
645	–	// adding and removing workers
646	–
710		/**
711	<	* Tries to create and add new worker. Assumes that worker counts
712	<	* are already updated to accommodate the worker, so adjusts on
713	<	* failure.
711	>	* Final callback from terminating worker.  Removes record of
712	>	* worker from array, and adjusts counts. If pool is shutting
713	>	* down, tries to complete termination.
714		*
715	<	* @return new worker or null if creation failed
715	>	* @param w the worker
716		*/
717	<	private ForkJoinWorkerThread addWorker() {
718	<	ForkJoinWorkerThread w = null;
719	<	try {
720	<	w = factory.newThread(this);
721	<	} finally { // Adjust on either null or exceptional factory return
722	<	if (w == null)
660	<	onWorkerCreationFailure();
661	<	}
662	<	if (w != null)
663	<	w.start(recordWorker(w), ueh);
664	<	return w;
717	>	final void workerTerminated(ForkJoinWorkerThread w) {
718	>	forgetWorker(w);
719	>	decrementWorkerCounts(w.isTrimmed() ? 0 : ONE_RUNNING, ONE_TOTAL);
720	>	while (w.stealCount != 0) // collect final count
721	>	tryAccumulateStealCount(w);
722	>	tryTerminate(false);
723		}
724
725	+	// Waiting for and signalling events
726	+
727		/**
728	<	* Adjusts counts upon failure to create worker
728	>	* Releases workers blocked on a count not equal to current count.
729	>	* Normally called after precheck that eventWaiters isn't zero to
730	>	* avoid wasted array checks. Gives up upon a change in count or
731	>	* upon releasing four workers, letting others take over.
732		*/
733	<	private void onWorkerCreationFailure() {
734	<	for (;;) {
735	<	int wc = workerCounts;
736	<	int rc = wc & RUNNING_COUNT_MASK;
737	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
738	<	if (rc == 0 || wc == 0)
739	<	Thread.yield(); // must wait for other counts to settle
740	<	else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
741	<	wc - (ONE_RUNNING|ONE_TOTAL)))
733	>	private void releaseEventWaiters() {
734	>	ForkJoinWorkerThread[] ws = workers;
735	>	int n = ws.length;
736	>	long h = eventWaiters;
737	>	int ec = eventCount;
738	>	int releases = 4;
739	>	ForkJoinWorkerThread w; int id;
740	>	while ((id = (((int)h) & WAITER_ID_MASK) - 1) >= 0 &&
741	>	(int)(h >>> EVENT_COUNT_SHIFT) != ec &&
742	>	id < n && (w = ws[id]) != null) {
743	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
744	>	h,  w.nextWaiter)) {
745	>	LockSupport.unpark(w);
746	>	if (--releases == 0)
747	>	break;
748	>	}
749	>	if (eventCount != ec)
750		break;
751	+	h = eventWaiters;
752		}
681	–	tryTerminate(false); // in case of failure during shutdown
753		}
754
755		/**
756	<	* Creates enough total workers to establish target parallelism,
757	<	* giving up if terminating or addWorker fails
756	>	* Tries to advance eventCount and releases waiters. Called only
757	>	* from workers.
758		*/
759	<	private void ensureEnoughTotalWorkers() {
760	<	int wc;
761	<	while (((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < parallelism &&
762	<	runState < TERMINATING) {
763	<	if ((UNSAFE.compareAndSwapInt(this, workerCountsOffset,
693	<	wc, wc + (ONE_RUNNING|ONE_TOTAL)) &&
694	<	addWorker() == null))
695	<	break;
696	<	}
759	>	final void signalWork() {
760	>	int c; // try to increment event count -- CAS failure OK
761	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
762	>	if (eventWaiters != 0L)
763	>	releaseEventWaiters();
764		}
765
766		/**
767	<	* Final callback from terminating worker.  Removes record of
768	<	* worker from array, and adjusts counts. If pool is shutting
702	<	* down, tries to complete terminatation, else possibly replaces
703	<	* the worker.
767	>	* Adds the given worker to event queue and blocks until
768	>	* terminating or event count advances from the given value
769		*
770	<	* @param w the worker
770	>	* @param w the calling worker thread
771	>	* @param ec the count
772		*/
773	<	final void workerTerminated(ForkJoinWorkerThread w) {
774	<	if (w.active) { // force inactive
775	<	w.active = false;
776	<	do {} while (!tryDecrementActiveCount());
777	<	}
778	<	forgetWorker(w);
779	<
780	<	// Decrement total count, and if was running, running count
781	<	// Spin (waiting for other updates) if either would be negative
782	<	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))
773	>	private void eventSync(ForkJoinWorkerThread w, int ec) {
774	>	long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1));
775	>	long h;
776	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
777	>	(((int)(h = eventWaiters) & WAITER_ID_MASK) == 0 ||
778	>	(int)(h >>> EVENT_COUNT_SHIFT) == ec) &&
779	>	eventCount == ec) {
780	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
781	>	w.nextWaiter = h, nh)) {
782	>	awaitEvent(w, ec);
783		break;
784	+	}
785		}
728	–
729	–	accumulateStealCount(w); // collect final count
730	–	if (!tryTerminate(false))
731	–	ensureEnoughTotalWorkers();
786		}
787
734	–	// Waiting for and signalling events
735	–
788		/**
789	<	* Releases workers blocked on a count not equal to current count.
790	<	* @return true if any released
789	>	* Blocks the given worker (that has already been entered as an
790	>	* event waiter) until terminating or event count advances from
791	>	* the given value. The oldest (first) waiter uses a timed wait to
792	>	* occasionally one-by-one shrink the number of workers (to a
793	>	* minimum of one) if the pool has not been used for extended
794	>	* periods.
795	>	*
796	>	* @param w the calling worker thread
797	>	* @param ec the count
798		*/
799	<	private void releaseWaiters() {
800	<	long top;
801	<	while ((top = eventWaiters) != 0L) {
802	<	ForkJoinWorkerThread[] ws = workers;
803	<	int n = ws.length;
804	<	for (;;) {
805	<	int i = ((int)(top & WAITER_ID_MASK)) - 1;
806	<	int e = (int)(top >>> EVENT_COUNT_SHIFT);
807	<	if (i < 0 || e == eventCount)
808	<	return;
809	<	ForkJoinWorkerThread w;
810	<	if (i < n && (w = ws[i]) != null &&
811	<	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
812	<	top, w.nextWaiter)) {
813	<	LockSupport.unpark(w);
814	<	top = eventWaiters;
799	>	private void awaitEvent(ForkJoinWorkerThread w, int ec) {
800	>	while (eventCount == ec) {
801	>	if (tryAccumulateStealCount(w)) { // transfer while idle
802	>	boolean untimed = (w.nextWaiter != 0L ||
803	>	(workerCounts & RUNNING_COUNT_MASK) <= 1);
804	>	long startTime = untimed ? 0 : System.nanoTime();
805	>	Thread.interrupted();         // clear/ignore interrupt
806	>	if (w.isTerminating() || eventCount != ec)
807	>	break;                    // recheck after clear
808	>	if (untimed)
809	>	LockSupport.park(w);
810	>	else {
811	>	LockSupport.parkNanos(w, SHRINK_RATE_NANOS);
812	>	if (eventCount != ec || w.isTerminating())
813	>	break;
814	>	if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS)
815	>	tryShutdownUnusedWorker(ec);
816		}
757	–	else
758	–	break;      // possibly stale; reread
817		}
818		}
819		}
820
821	+	// Maintaining parallelism
822	+
823		/**
824	<	* Ensures eventCount on exit is different (mod 2^32) than on
765	<	* entry and wakes up all waiters
824	>	* Pushes worker onto the spare stack.
825		*/
826	<	private void signalEvent() {
827	<	int c;
828	<	do {} while (!UNSAFE.compareAndSwapInt(this, eventCountOffset,
829	<	c = eventCount, c+1));
771	<	releaseWaiters();
826	>	final void pushSpare(ForkJoinWorkerThread w) {
827	>	int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1);
828	>	do {} while (!UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
829	>	w.nextSpare = spareWaiters,ns));
830		}
831
832		/**
833	<	* Advances eventCount and releases waiters until interference by
834	<	* other releasing threads is detected.
833	>	* Tries (once) to resume a spare if the number of running
834	>	* threads is less than target.
835		*/
836	<	final void signalWork() {
837	<	int c;
838	<	UNSAFE.compareAndSwapInt(this, eventCountOffset, c=eventCount, c+1);
839	<	long top;
840	<	while ((top = eventWaiters) != 0L) {
841	<	int ec = eventCount;
842	<	ForkJoinWorkerThread[] ws = workers;
843	<	int n = ws.length;
844	<	for (;;) {
845	<	int i = ((int)(top & WAITER_ID_MASK)) - 1;
846	<	int e = (int)(top >>> EVENT_COUNT_SHIFT);
847	<	if (i < 0 || e == ec)
848	<	return;
849	<	ForkJoinWorkerThread w;
850	<	if (i < n && (w = ws[i]) != null &&
851	<	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
852	<	top, top = w.nextWaiter)) {
853	<	LockSupport.unpark(w);
854	<	if (top != eventWaiters) // let someone else take over
855	<	return;
836	>	private void tryResumeSpare() {
837	>	int sw, id;
838	>	ForkJoinWorkerThread[] ws = workers;
839	>	int n = ws.length;
840	>	ForkJoinWorkerThread w;
841	>	if ((sw = spareWaiters) != 0 &&
842	>	(id = (sw & SPARE_ID_MASK) - 1) >= 0 &&
843	>	id < n && (w = ws[id]) != null &&
844	>	(runState >= TERMINATING ||
845	>	(workerCounts & RUNNING_COUNT_MASK) < parallelism) &&
846	>	spareWaiters == sw &&
847	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
848	>	sw, w.nextSpare)) {
849	>	int c; // increment running count before resume
850	>	do {} while (!UNSAFE.compareAndSwapInt
851	>	(this, workerCountsOffset,
852	>	c = workerCounts, c + ONE_RUNNING));
853	>	if (w.tryUnsuspend())
854	>	LockSupport.unpark(w);
855	>	else   // back out if w was shutdown
856	>	decrementWorkerCounts(ONE_RUNNING, 0);
857	>	}
858	>	}
859	>
860	>	/**
861	>	* Tries to increase the number of running workers if below target
862	>	* parallelism: If a spare exists tries to resume it via
863	>	* tryResumeSpare.  Otherwise, if not enough total workers or all
864	>	* existing workers are busy, adds a new worker. In all cases also
865	>	* helps wake up releasable workers waiting for work.
866	>	*/
867	>	private void helpMaintainParallelism() {
868	>	int pc = parallelism;
869	>	int wc, rs, tc;
870	>	while (((wc = workerCounts) & RUNNING_COUNT_MASK) < pc &&
871	>	(rs = runState) < TERMINATING) {
872	>	if (spareWaiters != 0)
873	>	tryResumeSpare();
874	>	else if ((tc = wc >>> TOTAL_COUNT_SHIFT) >= MAX_WORKERS ||
875	>	(tc >= pc && (rs & ACTIVE_COUNT_MASK) != tc))
876	>	break;   // enough total
877	>	else if (runState == rs && workerCounts == wc &&
878	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
879	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
880	>	ForkJoinWorkerThread w = null;
881	>	Throwable fail = null;
882	>	try {
883	>	w = factory.newThread(this);
884	>	} catch (Throwable ex) {
885	>	fail = ex;
886	>	}
887	>	if (w == null) { // null or exceptional factory return
888	>	decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL);
889	>	tryTerminate(false); // handle failure during shutdown
890	>	// If originating from an external caller,
891	>	// propagate exception, else ignore
892	>	if (fail != null && runState < TERMINATING &&
893	>	!(Thread.currentThread() instanceof
894	>	ForkJoinWorkerThread))
895	>	UNSAFE.throwException(fail);
896	>	break;
897		}
898	<	else
899	<	break;      // possibly stale; reread
898	>	w.start(recordWorker(w), ueh);
899	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) >= pc)
900	>	break; // add at most one unless total below target
901		}
902		}
903	+	if (eventWaiters != 0L)
904	+	releaseEventWaiters();
905		}
906
907		/**
908	<	* Blockss worker until terminating or event count
909	<	* advances from last value held by worker
908	>	* Callback from the oldest waiter in awaitEvent waking up after a
909	>	* period of non-use. If all workers are idle, tries (once) to
910	>	* shutdown an event waiter or a spare, if one exists. Note that
911	>	* we don't need CAS or locks here because the method is called
912	>	* only from one thread occasionally waking (and even misfires are
913	>	* OK). Note that until the shutdown worker fully terminates,
914	>	* workerCounts will overestimate total count, which is tolerable.
915		*
916	<	* @param w the calling worker thread
916	>	* @param ec the event count waited on by caller (to abort
917	>	* attempt if count has since changed).
918		*/
919	<	private void eventSync(ForkJoinWorkerThread w) {
920	<	int wec = w.lastEventCount;
921	<	long nextTop = (((long)wec << EVENT_COUNT_SHIFT) |
922	<	((long)(w.poolIndex + 1)));
923	<	long top;
924	<	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
925	<	(((int)(top = eventWaiters) & WAITER_ID_MASK) == 0 ||
926	<	(int)(top >>> EVENT_COUNT_SHIFT) == wec) &&
927	<	eventCount == wec) {
928	<	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
929	<	w.nextWaiter = top, nextTop)) {
930	<	accumulateStealCount(w); // transfer steals while idle
931	<	Thread.interrupted();    // clear/ignore interrupt
932	<	while (eventCount == wec)
933	<	w.doPark();
934	<	break;
919	>	private void tryShutdownUnusedWorker(int ec) {
920	>	if (runState == 0 && eventCount == ec) { // only trigger if all idle
921	>	ForkJoinWorkerThread[] ws = workers;
922	>	int n = ws.length;
923	>	ForkJoinWorkerThread w = null;
924	>	boolean shutdown = false;
925	>	int sw;
926	>	long h;
927	>	if ((sw = spareWaiters) != 0) { // prefer killing spares
928	>	int id = (sw & SPARE_ID_MASK) - 1;
929	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
930	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
931	>	sw, w.nextSpare))
932	>	shutdown = true;
933	>	}
934	>	else if ((h = eventWaiters) != 0L) {
935	>	long nh;
936	>	int id = (((int)h) & WAITER_ID_MASK) - 1;
937	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
938	>	(nh = w.nextWaiter) != 0L && // keep at least one worker
939	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh))
940	>	shutdown = true;
941	>	}
942	>	if (w != null && shutdown) {
943	>	w.shutdown();
944	>	LockSupport.unpark(w);
945		}
946		}
947	<	w.lastEventCount = eventCount;
947	>	releaseEventWaiters(); // in case of interference
948		}
949
950		/**
951		* Callback from workers invoked upon each top-level action (i.e.,
952	<	* stealing a task or taking a submission and running
953	<	* it). Performs one or both of the following:
952	>	* stealing a task or taking a submission and running it).
953	>	* Performs one or more of the following:
954		*
955	<	* * If the worker cannot find work, updates its active status to
956	<	* inactive and updates activeCount unless there is contention, in
957	<	* which case it may try again (either in this or a subsequent
958	<	* call).  Additionally, awaits the next task event and/or helps
959	<	* wake up other releasable waiters.
960	<	*
961	<	* * If there are too many running threads, suspends this worker
962	<	* (first forcing inactivation if necessary).  If it is not
963	<	* resumed before a keepAlive elapses, the worker may be "trimmed"
964	<	* -- killed while suspended within suspendAsSpare. Otherwise,
965	<	* upon resume it rechecks to make sure that it is still needed.
955	>	* 1. If the worker is active and either did not run a task
956	>	*    or there are too many workers, try to set its active status
957	>	*    to inactive and update activeCount. On contention, we may
958	>	*    try again in this or a subsequent call.
959	>	*
960	>	* 2. If not enough total workers, help create some.
961	>	*
962	>	* 3. If there are too many running workers, suspend this worker
963	>	*    (first forcing inactive if necessary).  If it is not needed,
964	>	*    it may be shutdown while suspended (via
965	>	*    tryShutdownUnusedWorker).  Otherwise, upon resume it
966	>	*    rechecks running thread count and need for event sync.
967	>	*
968	>	* 4. If worker did not run a task, await the next task event via
969	>	*    eventSync if necessary (first forcing inactivation), upon
970	>	*    which the worker may be shutdown via
971	>	*    tryShutdownUnusedWorker.  Otherwise, help release any
972	>	*    existing event waiters that are now releasable,
973		*
974		* @param w the worker
975	<	* @param retries the number of scans by caller failing to find work
851	<	* find any (in which case it may block waiting for work).
975	>	* @param ran true if worker ran a task since last call to this method
976		*/
977	<	final void preStep(ForkJoinWorkerThread w, int retries) {
977	>	final void preStep(ForkJoinWorkerThread w, boolean ran) {
978	>	int wec = w.lastEventCount;
979		boolean active = w.active;
980	<	boolean inactivate = active && retries > 0;
981	<	for (;;) {
982	<	int rs, wc;
983	<	if (inactivate &&
984	<	UNSAFE.compareAndSwapInt(this, runStateOffset,
985	<	rs = runState, rs - ONE_ACTIVE))
980	>	boolean inactivate = false;
981	>	int pc = parallelism;
982	>	while (w.runState == 0) {
983	>	int rs = runState;
984	>	if (rs >= TERMINATING) {           // propagate shutdown
985	>	w.shutdown();
986	>	break;
987	>	}
988	>	if ((inactivate || (active && (rs & ACTIVE_COUNT_MASK) >= pc)) &&
989	>	UNSAFE.compareAndSwapInt(this, runStateOffset, rs, --rs)) {
990		inactivate = active = w.active = false;
991	<	if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= parallelism) {
992	<	if (retries > 0) {
993	<	if (retries > 1 && !active)
865	<	eventSync(w);
866	<	releaseWaiters();
991	>	if (rs == SHUTDOWN) {          // all inactive and shut down
992	>	tryTerminate(false);
993	>	continue;
994		}
868	–	break;
995		}
996	<	if (!(inactivate |= active) &&  // must inactivate to suspend
997	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
998	<	wc, wc - ONE_RUNNING) &&
999	<	!w.suspendAsSpare())             // false if trimmed
996	>	int wc = workerCounts;             // try to suspend as spare
997	>	if ((wc & RUNNING_COUNT_MASK) > pc) {
998	>	if (!(inactivate |= active) && // must inactivate to suspend
999	>	workerCounts == wc &&
1000	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1001	>	wc, wc - ONE_RUNNING))
1002	>	w.suspendAsSpare();
1003	>	}
1004	>	else if ((wc >>> TOTAL_COUNT_SHIFT) < pc)
1005	>	helpMaintainParallelism();     // not enough workers
1006	>	else if (ran)
1007		break;
1008	+	else {
1009	+	long h = eventWaiters;
1010	+	int ec = eventCount;
1011	+	if (h != 0L && (int)(h >>> EVENT_COUNT_SHIFT) != ec)
1012	+	releaseEventWaiters();     // release others before waiting
1013	+	else if (ec != wec) {
1014	+	w.lastEventCount = ec;     // no need to wait
1015	+	break;
1016	+	}
1017	+	else if (!(inactivate |= active))
1018	+	eventSync(w, wec);         // must inactivate before sync
1019	+	}
1020		}
1021		}
1022
1023		/**
1024	<	* Awaits join of the given task if enough threads, or can resume
1025	<	* 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.
1024	>	* Helps and/or blocks awaiting join of the given task.
1025	>	* See above for explanation.
1026		*
1027		* @param joinMe the task to join
1028	<	* @param retries the number of calls to this method for this join
1029	<	*/
1030	<	final void tryAwaitJoin(ForkJoinTask<?> joinMe, int retries) {
1031	<	int pc = parallelism;
1032	<	boolean running = true; // false when running count decremented
1033	<	outer:while (joinMe.status >= 0) {
1028	>	* @param worker the current worker thread
1029	>	* @param timed true if wait should time out
1030	>	* @param nanos timeout value if timed
1031	>	*/
1032	>	final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker,
1033	>	boolean timed, long nanos) {
1034	>	long startTime = timed ? System.nanoTime() : 0L;
1035	>	int retries = 2 + (parallelism >> 2); // #helpJoins before blocking
1036	>	boolean running = true;               // false when count decremented
1037	>	while (joinMe.status >= 0) {
1038	>	if (runState >= TERMINATING) {
1039	>	joinMe.cancelIgnoringExceptions();
1040	>	break;
1041	>	}
1042	>	running = worker.helpJoinTask(joinMe, running);
1043	>	if (joinMe.status < 0)
1044	>	break;
1045	>	if (retries > 0) {
1046	>	--retries;
1047	>	continue;
1048	>	}
1049		int wc = workerCounts;
1050	<	int rc = wc & RUNNING_COUNT_MASK;
1051	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
1052	<	if (running) { // replace with spare or decrement count
1053	<	if (rc <= pc && tc > pc &&
1054	<	(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) {
1055	<	ForkJoinWorkerThread[] ws = workers; // search for spare
1056	<	int nws = ws.length;
1057	<	for (int i = 0; i < nws; ++i) {
1058	<	ForkJoinWorkerThread w = ws[i];
1059	<	if (w != null && w.isSuspended()) {
1060	<	if ((workerCounts & RUNNING_COUNT_MASK) > pc)
1061	<	continue outer;
1062	<	if (joinMe.status < 0)
1063	<	break outer;
1064	<	if (w.tryResumeSpare()) {
1065	<	running = false;
1066	<	break outer;
1067	<	}
1068	<	continue outer; // rescan on failure to resume
1050	>	if ((wc & RUNNING_COUNT_MASK) != 0) {
1051	>	if (running) {
1052	>	if (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1053	>	wc, wc - ONE_RUNNING))
1054	>	continue;
1055	>	running = false;
1056	>	}
1057	>	long h = eventWaiters;
1058	>	if (h != 0L && (int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1059	>	releaseEventWaiters();
1060	>	if ((workerCounts & RUNNING_COUNT_MASK) != 0) {
1061	>	long ms; int ns;
1062	>	if (!timed) {
1063	>	ms = JOIN_TIMEOUT_MILLIS;
1064	>	ns = 0;
1065	>	}
1066	>	else { // at most JOIN_TIMEOUT_MILLIS per wait
1067	>	long nt = nanos - (System.nanoTime() - startTime);
1068	>	if (nt <= 0L)
1069	>	break;
1070	>	ms = nt / 1000000;
1071	>	if (ms > JOIN_TIMEOUT_MILLIS) {
1072	>	ms = JOIN_TIMEOUT_MILLIS;
1073	>	ns = 0;
1074		}
1075	+	else
1076	+	ns = (int) (nt % 1000000);
1077		}
1078	+	joinMe.internalAwaitDone(ms, ns);
1079		}
1080	<	if ((rc <= pc && (rc == 0 || --retries < 0)) || // no retry
936	<	joinMe.status < 0)
937	<	break;
938	<	if (workerCounts == wc &&
939	<	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
1080	>	if (joinMe.status < 0)
1081		break;
960	–	}
1082		}
1083	+	helpMaintainParallelism();
1084		}
1085	<	if (!running) { // can block
1086	<	int c;                      // to inline incrementRunningCount
965	<	joinMe.internalAwaitDone();
1085	>	if (!running) {
1086	>	int c;
1087		do {} while (!UNSAFE.compareAndSwapInt
1088		(this, workerCountsOffset,
1089		c = workerCounts, c + ONE_RUNNING));
#	Line 970 | Line 1091 | public class ForkJoinPool extends Abstra
1091		}
1092
1093		/**
1094	<	* 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.
1094	>	* Same idea as awaitJoin, but no helping, retries, or timeouts.
1095		*/
1096		final void awaitBlocker(ManagedBlocker blocker)
1097		throws InterruptedException {
1098	<	int pc = parallelism;
980	<	boolean running = true;
981	<	int retries = 0;
982	<	boolean done;
983	<	outer:while (!(done = blocker.isReleasable())) {
1098	>	while (!blocker.isReleasable()) {
1099		int wc = workerCounts;
1100	<	int rc = wc & RUNNING_COUNT_MASK;
1101	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
1102	<	if (running) {
1103	<	if (rc <= pc && tc > pc &&
1104	<	(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) {
1105	<	ForkJoinWorkerThread[] ws = workers;
1106	<	int nws = ws.length;
1107	<	for (int i = 0; i < nws; ++i) {
1108	<	ForkJoinWorkerThread w = ws[i];
1109	<	if (w != null && w.isSuspended()) {
1110	<	if ((workerCounts & RUNNING_COUNT_MASK) > pc)
1111	<	continue outer;
1112	<	if (done = blocker.isReleasable())
1113	<	break outer;
1114	<	if (w.tryResumeSpare()) {
1000	<	running = false;
1001	<	break outer;
1002	<	}
1003	<	continue outer;
1004	<	}
1100	>	if ((wc & RUNNING_COUNT_MASK) == 0)
1101	>	helpMaintainParallelism();
1102	>	else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1103	>	wc, wc - ONE_RUNNING)) {
1104	>	try {
1105	>	while (!blocker.isReleasable()) {
1106	>	long h = eventWaiters;
1107	>	if (h != 0L &&
1108	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1109	>	releaseEventWaiters();
1110	>	else if ((workerCounts & RUNNING_COUNT_MASK) == 0 &&
1111	>	runState < TERMINATING)
1112	>	helpMaintainParallelism();
1113	>	else if (blocker.block())
1114	>	break;
1115		}
1116	<	if (done = blocker.isReleasable())
1117	<	break;
1118	<	}
1119	<	if (rc > 0 && workerCounts == wc &&
1120	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1011	<	wc, wc - ONE_RUNNING)) {
1012	<	running = false;
1013	<	if (rc > pc)
1014	<	break;
1116	>	} finally {
1117	>	int c;
1118	>	do {} while (!UNSAFE.compareAndSwapInt
1119	>	(this, workerCountsOffset,
1120	>	c = workerCounts, c + ONE_RUNNING));
1121		}
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();
1122		break;
1123		}
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	–	}
1124		}
1125		}
1126
#	Line 1067 | Line 1145 | public class ForkJoinPool extends Abstra
1145		// Finish now if all threads terminated; else in some subsequent call
1146		if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1147		advanceRunLevel(TERMINATED);
1148	<	termination.arrive();
1148	>	termination.forceTermination();
1149		}
1150		return true;
1151		}
1152
1153		/**
1154		* Actions on transition to TERMINATING
1155	+	*
1156	+	* Runs up to four passes through workers: (0) shutting down each
1157	+	* (without waking up if parked) to quickly spread notifications
1158	+	* without unnecessary bouncing around event queues etc (1) wake
1159	+	* up and help cancel tasks (2) interrupt (3) mop up races with
1160	+	* interrupted workers
1161		*/
1162		private void startTerminating() {
1163	<	for (int i = 0; i < 2; ++i) { // twice to mop up newly created workers
1164	<	cancelSubmissions();
1165	<	shutdownWorkers();
1166	<	cancelWorkerTasks();
1167	<	signalEvent();
1168	<	interruptWorkers();
1163	>	cancelSubmissions();
1164	>	for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) {
1165	>	int c; // advance event count
1166	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
1167	>	c = eventCount, c+1);
1168	>	eventWaiters = 0L; // clobber lists
1169	>	spareWaiters = 0;
1170	>	for (ForkJoinWorkerThread w : workers) {
1171	>	if (w != null) {
1172	>	w.shutdown();
1173	>	if (passes > 0 && !w.isTerminated()) {
1174	>	w.cancelTasks();
1175	>	LockSupport.unpark(w);
1176	>	if (passes > 1 && !w.isInterrupted()) {
1177	>	try {
1178	>	w.interrupt();
1179	>	} catch (SecurityException ignore) {
1180	>	}
1181	>	}
1182	>	}
1183	>	}
1184	>	}
1185		}
1186		}
1187
1188		/**
1189	<	* Clear out and cancel submissions, ignoring exceptions
1189	>	* Clears out and cancels submissions, ignoring exceptions.
1190		*/
1191		private void cancelSubmissions() {
1192		ForkJoinTask<?> task;
#	Line 1098 | Line 1198 | public class ForkJoinPool extends Abstra
1198		}
1199		}
1200
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	–
1201		// misc support for ForkJoinWorkerThread
1202
1203		/**
1204	<	* Returns pool number
1204	>	* Returns pool number.
1205		*/
1206		final int getPoolNumber() {
1207		return poolNumber;
1208		}
1209
1210		/**
1211	<	* Accumulates steal count from a worker, clearing
1212	<	* the worker's value
1211	>	* Tries to accumulate steal count from a worker, clearing
1212	>	* the worker's value if successful.
1213	>	*
1214	>	* @return true if worker steal count now zero
1215		*/
1216	<	final void accumulateStealCount(ForkJoinWorkerThread w) {
1216	>	final boolean tryAccumulateStealCount(ForkJoinWorkerThread w) {
1217		int sc = w.stealCount;
1218	<	if (sc != 0) {
1219	<	long c;
1220	<	w.stealCount = 0;
1221	<	do {} while (!UNSAFE.compareAndSwapLong(this, stealCountOffset,
1222	<	c = stealCount, c + sc));
1218	>	long c = stealCount;
1219	>	// CAS even if zero, for fence effects
1220	>	if (UNSAFE.compareAndSwapLong(this, stealCountOffset, c, c + sc)) {
1221	>	if (sc != 0)
1222	>	w.stealCount = 0;
1223	>	return true;
1224		}
1225	+	return sc == 0;
1226		}
1227
1228		/**
#	Line 1171 | Line 1231 | public class ForkJoinPool extends Abstra
1231		*/
1232		final int idlePerActive() {
1233		int pc = parallelism; // use parallelism, not rc
1234	<	int ac = runState;    // no mask -- artifically boosts during shutdown
1234	>	int ac = runState;    // no mask -- artificially boosts during shutdown
1235		// Use exact results for small values, saturate past 4
1236	<	return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
1236	>	return ((pc <= ac) ? 0 :
1237	>	(pc >>> 1 <= ac) ? 1 :
1238	>	(pc >>> 2 <= ac) ? 3 :
1239	>	pc >>> 3);
1240		}
1241
1242		// Public and protected methods
#	Line 1223 | Line 1286 | public class ForkJoinPool extends Abstra
1286		* use {@link #defaultForkJoinWorkerThreadFactory}.
1287		* @param handler the handler for internal worker threads that
1288		* terminate due to unrecoverable errors encountered while executing
1289	<	* tasks. For default value, use <code>null</code>.
1289	>	* tasks. For default value, use {@code null}.
1290		* @param asyncMode if true,
1291		* establishes local first-in-first-out scheduling mode for forked
1292		* tasks that are never joined. This mode may be more appropriate
1293		* than default locally stack-based mode in applications in which
1294		* worker threads only process event-style asynchronous tasks.
1295	<	* For default value, use <code>false</code>.
1295	>	* For default value, use {@code false}.
1296		* @throws IllegalArgumentException if parallelism less than or
1297		*         equal to zero, or greater than implementation limit
1298		* @throws NullPointerException if the factory is null
#	Line 1245 | Line 1308 | public class ForkJoinPool extends Abstra
1308		checkPermission();
1309		if (factory == null)
1310		throw new NullPointerException();
1311	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
1311	>	if (parallelism <= 0 || parallelism > MAX_WORKERS)
1312		throw new IllegalArgumentException();
1313		this.parallelism = parallelism;
1314		this.factory = factory;
#	Line 1264 | Line 1327 | public class ForkJoinPool extends Abstra
1327		* @param pc the initial parallelism level
1328		*/
1329		private static int initialArraySizeFor(int pc) {
1330	<	// See Hackers Delight, sec 3.2. We know MAX_THREADS < (1 >>> 16)
1331	<	int size = pc < MAX_THREADS ? pc + 1 : MAX_THREADS;
1330	>	// If possible, initially allocate enough space for one spare
1331	>	int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS;
1332	>	// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16)
1333		size |= size >>> 1;
1334		size |= size >>> 2;
1335		size |= size >>> 4;
#	Line 1276 | Line 1340 | public class ForkJoinPool extends Abstra
1340		// Execution methods
1341
1342		/**
1343	<	* Common code for execute, invoke and submit
1343	>	* Submits task and creates, starts, or resumes some workers if necessary
1344		*/
1345		private <T> void doSubmit(ForkJoinTask<T> task) {
1282	–	if (task == null)
1283	–	throw new NullPointerException();
1284	–	if (runState >= SHUTDOWN)
1285	–	throw new RejectedExecutionException();
1346		submissionQueue.offer(task);
1347	<	signalEvent();
1348	<	ensureEnoughTotalWorkers();
1347	>	int c; // try to increment event count -- CAS failure OK
1348	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
1349	>	helpMaintainParallelism();
1350		}
1351
1352		/**
1353		* 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}.
1354		*
1355		* @param task the task
1356		* @return the task's result
#	Line 1301 | Line 1359 | public class ForkJoinPool extends Abstra
1359		*         scheduled for execution
1360		*/
1361		public <T> T invoke(ForkJoinTask<T> task) {
1362	<	doSubmit(task);
1363	<	return task.join();
1362	>	if (task == null)
1363	>	throw new NullPointerException();
1364	>	if (runState >= SHUTDOWN)
1365	>	throw new RejectedExecutionException();
1366	>	Thread t = Thread.currentThread();
1367	>	if ((t instanceof ForkJoinWorkerThread) &&
1368	>	((ForkJoinWorkerThread)t).pool == this)
1369	>	return task.invoke();  // bypass submit if in same pool
1370	>	else {
1371	>	doSubmit(task);
1372	>	return task.join();
1373	>	}
1374	>	}
1375	>
1376	>	/**
1377	>	* Unless terminating, forks task if within an ongoing FJ
1378	>	* computation in the current pool, else submits as external task.
1379	>	*/
1380	>	private <T> void forkOrSubmit(ForkJoinTask<T> task) {
1381	>	if (runState >= SHUTDOWN)
1382	>	throw new RejectedExecutionException();
1383	>	Thread t = Thread.currentThread();
1384	>	if ((t instanceof ForkJoinWorkerThread) &&
1385	>	((ForkJoinWorkerThread)t).pool == this)
1386	>	task.fork();
1387	>	else
1388	>	doSubmit(task);
1389		}
1390
1391		/**
1392		* 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}.
1393		*
1394		* @param task the task
1395		* @throws NullPointerException if the task is null
#	Line 1317 | Line 1397 | public class ForkJoinPool extends Abstra
1397		*         scheduled for execution
1398		*/
1399		public void execute(ForkJoinTask<?> task) {
1400	<	doSubmit(task);
1400	>	if (task == null)
1401	>	throw new NullPointerException();
1402	>	forkOrSubmit(task);
1403		}
1404
1405		// AbstractExecutorService methods
#	Line 1328 | Line 1410 | public class ForkJoinPool extends Abstra
1410		*         scheduled for execution
1411		*/
1412		public void execute(Runnable task) {
1413	+	if (task == null)
1414	+	throw new NullPointerException();
1415		ForkJoinTask<?> job;
1416		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1417		job = (ForkJoinTask<?>) task;
1418		else
1419		job = ForkJoinTask.adapt(task, null);
1420	<	doSubmit(job);
1420	>	forkOrSubmit(job);
1421		}
1422
1423		/**
1424		* 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}.
1425		*
1426		* @param task the task to submit
1427		* @return the task
#	Line 1349 | Line 1430 | public class ForkJoinPool extends Abstra
1430		*         scheduled for execution
1431		*/
1432		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1433	<	doSubmit(task);
1433	>	if (task == null)
1434	>	throw new NullPointerException();
1435	>	forkOrSubmit(task);
1436		return task;
1437		}
1438
#	Line 1359 | Line 1442 | public class ForkJoinPool extends Abstra
1442		*         scheduled for execution
1443		*/
1444		public <T> ForkJoinTask<T> submit(Callable<T> task) {
1445	+	if (task == null)
1446	+	throw new NullPointerException();
1447		ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1448	<	doSubmit(job);
1448	>	forkOrSubmit(job);
1449		return job;
1450		}
1451
#	Line 1370 | Line 1455 | public class ForkJoinPool extends Abstra
1455		*         scheduled for execution
1456		*/
1457		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1458	+	if (task == null)
1459	+	throw new NullPointerException();
1460		ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1461	<	doSubmit(job);
1461	>	forkOrSubmit(job);
1462		return job;
1463		}
1464
#	Line 1381 | Line 1468 | public class ForkJoinPool extends Abstra
1468		*         scheduled for execution
1469		*/
1470		public ForkJoinTask<?> submit(Runnable task) {
1471	+	if (task == null)
1472	+	throw new NullPointerException();
1473		ForkJoinTask<?> job;
1474		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1475		job = (ForkJoinTask<?>) task;
1476		else
1477		job = ForkJoinTask.adapt(task, null);
1478	<	doSubmit(job);
1478	>	forkOrSubmit(job);
1479		return job;
1480		}
1481
#	Line 1446 | Line 1535 | public class ForkJoinPool extends Abstra
1535
1536		/**
1537		* Returns the number of worker threads that have started but not
1538	<	* yet terminated.  This result returned by this method may differ
1538	>	* yet terminated.  The result returned by this method may differ
1539		* from {@link #getParallelism} when threads are created to
1540		* maintain parallelism when others are cooperatively blocked.
1541		*
#	Line 1531 | Line 1620 | public class ForkJoinPool extends Abstra
1620		*/
1621		public long getQueuedTaskCount() {
1622		long count = 0;
1623	<	ForkJoinWorkerThread[] ws = workers;
1535	<	int nws = ws.length;
1536	<	for (int i = 0; i < nws; ++i) {
1537	<	ForkJoinWorkerThread w = ws[i];
1623	>	for (ForkJoinWorkerThread w : workers)
1624		if (w != null)
1625		count += w.getQueueSize();
1540	–	}
1626		return count;
1627		}
1628
#	Line 1591 | Line 1676 | public class ForkJoinPool extends Abstra
1676		* @return the number of elements transferred
1677		*/
1678		protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1679	<	int n = submissionQueue.drainTo(c);
1680	<	ForkJoinWorkerThread[] ws = workers;
1596	<	int nws = ws.length;
1597	<	for (int i = 0; i < nws; ++i) {
1598	<	ForkJoinWorkerThread w = ws[i];
1599	<	if (w != null)
1600	<	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];
1679	>	int count = submissionQueue.drainTo(c);
1680	>	for (ForkJoinWorkerThread w : workers)
1681		if (w != null)
1682	<	count += w.parkCount;
1617	<	}
1682	>	count += w.drainTasksTo(c);
1683		return count;
1684		}
1685
#	Line 1635 | Line 1700 | public class ForkJoinPool extends Abstra
1700		int pc = parallelism;
1701		int rs = runState;
1702		int ac = rs & ACTIVE_COUNT_MASK;
1638	–	//        int pk = collectParkCount();
1703		return super.toString() +
1704		"[" + runLevelToString(rs) +
1705		", parallelism = " + pc +
#	Line 1645 | Line 1709 | public class ForkJoinPool extends Abstra
1709		", steals = " + st +
1710		", tasks = " + qt +
1711		", submissions = " + qs +
1648	–	//            ", parks = " + pk +
1712		"]";
1713		}
1714
#	Line 1710 | Line 1773 | public class ForkJoinPool extends Abstra
1773		* commenced but not yet completed.  This method may be useful for
1774		* debugging. A return of {@code true} reported a sufficient
1775		* period after shutdown may indicate that submitted tasks have
1776	<	* ignored or suppressed interruption, causing this executor not
1777	<	* to properly terminate.
1776	>	* ignored or suppressed interruption, or are waiting for IO,
1777	>	* causing this executor not to properly terminate. (See the
1778	>	* advisory notes for class {@link ForkJoinTask} stating that
1779	>	* tasks should not normally entail blocking operations.  But if
1780	>	* they do, they must abort them on interrupt.)
1781		*
1782		* @return {@code true} if terminating but not yet terminated
1783		*/
#	Line 1720 | Line 1786 | public class ForkJoinPool extends Abstra
1786		}
1787
1788		/**
1789	+	* Returns true if terminating or terminated. Used by ForkJoinWorkerThread.
1790	+	*/
1791	+	final boolean isAtLeastTerminating() {
1792	+	return runState >= TERMINATING;
1793	+	}
1794	+
1795	+	/**
1796		* Returns {@code true} if this pool has been shut down.
1797		*
1798		* @return {@code true} if this pool has been shut down
#	Line 1742 | Line 1815 | public class ForkJoinPool extends Abstra
1815		public boolean awaitTermination(long timeout, TimeUnit unit)
1816		throws InterruptedException {
1817		try {
1818	<	return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1819	<	} catch(TimeoutException ex) {
1818	>	termination.awaitAdvanceInterruptibly(0, timeout, unit);
1819	>	} catch (TimeoutException ex) {
1820		return false;
1821		}
1822	+	return true;
1823		}
1824
1825		/**
1826		* Interface for extending managed parallelism for tasks running
1827		* in {@link ForkJoinPool}s.
1828		*
1829	<	* <p>A {@code ManagedBlocker} provides two methods.
1830	<	* Method {@code isReleasable} must return {@code true} if
1831	<	* blocking is not necessary. Method {@code block} blocks the
1832	<	* current thread if necessary (perhaps internally invoking
1833	<	* {@code isReleasable} before actually blocking).
1829	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
1830	>	* {@code isReleasable} must return {@code true} if blocking is
1831	>	* not necessary. Method {@code block} blocks the current thread
1832	>	* if necessary (perhaps internally invoking {@code isReleasable}
1833	>	* before actually blocking). The unusual methods in this API
1834	>	* accommodate synchronizers that may, but don't usually, block
1835	>	* for long periods. Similarly, they allow more efficient internal
1836	>	* handling of cases in which additional workers may be, but
1837	>	* usually are not, needed to ensure sufficient parallelism.
1838	>	* Toward this end, implementations of method {@code isReleasable}
1839	>	* must be amenable to repeated invocation.
1840		*
1841		* <p>For example, here is a ManagedBlocker based on a
1842		* ReentrantLock:
#	Line 1774 | Line 1854 | public class ForkJoinPool extends Abstra
1854		*     return hasLock || (hasLock = lock.tryLock());
1855		*   }
1856		* }}</pre>
1857	+	*
1858	+	* <p>Here is a class that possibly blocks waiting for an
1859	+	* item on a given queue:
1860	+	*  <pre> {@code
1861	+	* class QueueTaker<E> implements ManagedBlocker {
1862	+	*   final BlockingQueue<E> queue;
1863	+	*   volatile E item = null;
1864	+	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
1865	+	*   public boolean block() throws InterruptedException {
1866	+	*     if (item == null)
1867	+	*       item = queue.take();
1868	+	*     return true;
1869	+	*   }
1870	+	*   public boolean isReleasable() {
1871	+	*     return item != null || (item = queue.poll()) != null;
1872	+	*   }
1873	+	*   public E getItem() { // call after pool.managedBlock completes
1874	+	*     return item;
1875	+	*   }
1876	+	* }}</pre>
1877		*/
1878		public static interface ManagedBlocker {
1879		/**
#	Line 1816 | Line 1916 | public class ForkJoinPool extends Abstra
1916		public static void managedBlock(ManagedBlocker blocker)
1917		throws InterruptedException {
1918		Thread t = Thread.currentThread();
1919	<	if (t instanceof ForkJoinWorkerThread)
1920	<	((ForkJoinWorkerThread) t).pool.awaitBlocker(blocker);
1919	>	if (t instanceof ForkJoinWorkerThread) {
1920	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
1921	>	w.pool.awaitBlocker(blocker);
1922	>	}
1923		else {
1924		do {} while (!blocker.isReleasable() && !blocker.block());
1925		}
#	Line 1845 | Line 1947 | public class ForkJoinPool extends Abstra
1947		private static final long eventCountOffset =
1948		objectFieldOffset("eventCount", ForkJoinPool.class);
1949		private static final long eventWaitersOffset =
1950	<	objectFieldOffset("eventWaiters",ForkJoinPool.class);
1950	>	objectFieldOffset("eventWaiters", ForkJoinPool.class);
1951		private static final long stealCountOffset =
1952	<	objectFieldOffset("stealCount",ForkJoinPool.class);
1952	>	objectFieldOffset("stealCount", ForkJoinPool.class);
1953	>	private static final long spareWaitersOffset =
1954	>	objectFieldOffset("spareWaiters", ForkJoinPool.class);
1955
1956		private static long objectFieldOffset(String field, Class<?> klazz) {
1957		try {

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