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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.1 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.57 by dl, Wed Jul 7 19:52:31 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.locks.*;
11	<	import java.util.concurrent.atomic.*;
12	<	import sun.misc.Unsafe;
13	<	import java.lang.reflect.*;
10	>
11	>	import java.util.ArrayList;
12	>	import java.util.Arrays;
13	>	import java.util.Collection;
14	>	import java.util.Collections;
15	>	import java.util.List;
16	>	import java.util.concurrent.locks.LockSupport;
17	>	import java.util.concurrent.locks.ReentrantLock;
18	>	import java.util.concurrent.atomic.AtomicInteger;
19	>	import java.util.concurrent.CountDownLatch;
20
21		/**
22	<	* Host for a group of ForkJoinWorkerThreads.  A ForkJoinPool provides
23	<	* the entry point for tasks submitted from non-ForkJoinTasks, as well
24	<	* as management and monitoring operations.  Normally a single
25	<	* ForkJoinPool is used for a large number of submitted
20	<	* tasks. Otherwise, use would not usually outweigh the construction
21	<	* and bookkeeping overhead of creating a large set of threads.
22	<	*
23	<	* <p>ForkJoinPools differ from other kinds of Executor mainly in that
24	<	* they provide <em>work-stealing</em>: all threads in the pool
25	<	* attempt to find and execute subtasks created by other active tasks
26	<	* (eventually blocking if none exist). This makes them efficient when
27	<	* most tasks spawn other subtasks (as do most ForkJoinTasks) but
28	<	* possibly less so otherwise. It is however fine to combine execution
29	<	* of some plain Runnable- or Callable- based activities with that of
30	<	* ForkJoinTasks.
22	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
23	>	* A {@code ForkJoinPool} provides the entry point for submissions
24	>	* from non-{@code ForkJoinTask} clients, as well as management and
25	>	* monitoring operations.
26		*
27	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
28	<	* (target pool size), which it attempts to maintain by dynamically
29	<	* adding, suspending, or resuming threads, even if some tasks have
30	<	* blocked waiting to join others. However, no such adjustments are
31	<	* performed in the face of blocked IO or other unmanaged
32	<	* synchronization. The nested ManagedBlocker interface enables
33	<	* extension of the kinds of synchronization accommodated.
27	>	* <p>A {@code ForkJoinPool} differs from other kinds of {@link
28	>	* ExecutorService} mainly by virtue of employing
29	>	* <em>work-stealing</em>: all threads in the pool attempt to find and
30	>	* execute subtasks created by other active tasks (eventually blocking
31	>	* waiting for work if none exist). This enables efficient processing
32	>	* when most tasks spawn other subtasks (as do most {@code
33	>	* ForkJoinTask}s). When setting <em>asyncMode</em> to true in
34	>	* constructors, {@code ForkJoinPool}s may also be appropriate for use
35	>	* with event-style tasks that are never joined.
36		*
37	<	* <p>The target parallelism level may also be set dynamically. You
38	<	* can limit the number of threads dynamically constructed using
39	<	* method <tt>setMaximumPoolSize</tt> and/or
40	<	* <tt>setMaintainParallelism</tt>.
37	>	* <p>A {@code ForkJoinPool} is constructed with a given target
38	>	* parallelism level; by default, equal to the number of available
39	>	* processors. The pool attempts to maintain enough active (or
40	>	* available) threads by dynamically adding, suspending, or resuming
41	>	* internal worker threads, even if some tasks are stalled waiting to
42	>	* join others. However, no such adjustments are guaranteed in the
43	>	* face of blocked IO or other unmanaged synchronization. The nested
44	>	* {@link ManagedBlocker} interface enables extension of the kinds of
45	>	* synchronization accommodated.
46		*
47		* <p>In addition to execution and lifecycle control methods, this
48		* class provides status check methods (for example
49	<	* <tt>getStealCount</tt>) that are intended to aid in developing,
49	>	* {@link #getStealCount}) that are intended to aid in developing,
50		* tuning, and monitoring fork/join applications. Also, method
51	<	* <tt>toString</tt> returns indications of pool state in a convenient
52	<	* form for informal monitoring.
51	>	* {@link #toString} returns indications of pool state in a
52	>	* convenient form for informal monitoring.
53	>	*
54	>	* <p> As is the case with other ExecutorServices, there are three
55	>	* main task execution methods summarized in the follwoing
56	>	* table. These are designed to be used by clients not already engaged
57	>	* in fork/join computations in the current pool.  The main forms of
58	>	* these methods accept instances of {@code ForkJoinTask}, but
59	>	* overloaded forms also allow mixed execution of plain {@code
60	>	* Runnable}- or {@code Callable}- based activities as well.  However,
61	>	* tasks that are already executing in a pool should normally
62	>	* <em>NOT</em> use these pool execution methods, but instead use the
63	>	* within-computation forms listed in the table. To avoid inadvertant
64	>	* cyclic task dependencies and to improve performance, task
65	>	* submissions to the current pool by an ongoing fork/join
66	>	* computations may be implicitly translated to the corresponding
67	>	* ForkJoinTask forms.
68	>	*
69	>	* <table BORDER CELLPADDING=3 CELLSPACING=1>
70	>	*  <tr>
71	>	*    <td></td>
72	>	*    <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
73	>	*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
74	>	*  </tr>
75	>	*  <tr>
76	>	*    <td> <b>Arange async execution</td>
77	>	*    <td> {@link #execute(ForkJoinTask)}</td>
78	>	*    <td> {@link ForkJoinTask#fork}</td>
79	>	*  </tr>
80	>	*  <tr>
81	>	*    <td> <b>Await and obtain result</td>
82	>	*    <td> {@link #invoke(ForkJoinTask)}</td>
83	>	*    <td> {@link ForkJoinTask#invoke}</td>
84	>	*  </tr>
85	>	*  <tr>
86	>	*    <td> <b>Arrange exec and obtain Future</td>
87	>	*    <td> {@link #submit(ForkJoinTask)}</td>
88	>	*    <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td>
89	>	*  </tr>
90	>	* </table>
91	>	*
92	>	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
93	>	* used for all parallel task execution in a program or subsystem.
94	>	* Otherwise, use would not usually outweigh the construction and
95	>	* bookkeeping overhead of creating a large set of threads. For
96	>	* example, a common pool could be used for the {@code SortTasks}
97	>	* illustrated in {@link RecursiveAction}. Because {@code
98	>	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
99	>	* daemon} mode, there is typically no need to explicitly {@link
100	>	* #shutdown} such a pool upon program exit.
101	>	*
102	>	* <pre>
103	>	* static final ForkJoinPool mainPool = new ForkJoinPool();
104	>	* ...
105	>	* public void sort(long[] array) {
106	>	*   mainPool.invoke(new SortTask(array, 0, array.length));
107	>	* }
108	>	* </pre>
109		*
110		* <p><b>Implementation notes</b>: This implementation restricts the
111	<	* maximum parallelism to 32767. Attempts to create pools with greater
112	<	* than the maximum result in IllegalArgumentExceptions.
111	>	* maximum number of running threads to 32767. Attempts to create
112	>	* pools with greater than the maximum number result in
113	>	* {@code IllegalArgumentException}.
114	>	*
115	>	* <p>This implementation rejects submitted tasks (that is, by throwing
116	>	* {@link RejectedExecutionException}) only when the pool is shut down.
117	>	*
118	>	* @since 1.7
119	>	* @author Doug Lea
120		*/
121	<	public class ForkJoinPool extends AbstractExecutorService
57	<	implements ExecutorService {
121	>	public class ForkJoinPool extends AbstractExecutorService {
122
123		/*
124	<	* See the extended comments interspersed below for design,
125	<	* rationale, and walkthroughs.
124	>	* Implementation Overview
125	>	*
126	>	* This class provides the central bookkeeping and control for a
127	>	* set of worker threads: Submissions from non-FJ threads enter
128	>	* into a submission queue. Workers take these tasks and typically
129	>	* split them into subtasks that may be stolen by other workers.
130	>	* The main work-stealing mechanics implemented in class
131	>	* ForkJoinWorkerThread give first priority to processing tasks
132	>	* from their own queues (LIFO or FIFO, depending on mode), then
133	>	* to randomized FIFO steals of tasks in other worker queues, and
134	>	* lastly to new submissions. These mechanics do not consider
135	>	* affinities, loads, cache localities, etc, so rarely provide the
136	>	* best possible performance on a given machine, but portably
137	>	* provide good throughput by averaging over these factors.
138	>	* (Further, even if we did try to use such information, we do not
139	>	* usually have a basis for exploiting it. For example, some sets
140	>	* of tasks profit from cache affinities, but others are harmed by
141	>	* cache pollution effects.)
142	>	*
143	>	* The main throughput advantages of work-stealing stem from
144	>	* decentralized control -- workers mostly steal tasks from each
145	>	* other. We do not want to negate this by creating bottlenecks
146	>	* implementing the management responsibilities of this class. So
147	>	* we use a collection of techniques that avoid, reduce, or cope
148	>	* well with contention. These entail several instances of
149	>	* bit-packing into CASable fields to maintain only the minimally
150	>	* required atomicity. To enable such packing, we restrict maximum
151	>	* parallelism to (1<<15)-1 (enabling twice this to fit into a 16
152	>	* bit field), which is far in excess of normal operating range.
153	>	* Even though updates to some of these bookkeeping fields do
154	>	* sometimes contend with each other, they don't normally
155	>	* cache-contend with updates to others enough to warrant memory
156	>	* padding or isolation. So they are all held as fields of
157	>	* ForkJoinPool objects.  The main capabilities are as follows:
158	>	*
159	>	* 1. Creating and removing workers. Workers are recorded in the
160	>	* "workers" array. This is an array as opposed to some other data
161	>	* structure to support index-based random steals by workers.
162	>	* Updates to the array recording new workers and unrecording
163	>	* terminated ones are protected from each other by a lock
164	>	* (workerLock) but the array is otherwise concurrently readable,
165	>	* and accessed directly by workers. To simplify index-based
166	>	* operations, the array size is always a power of two, and all
167	>	* readers must tolerate null slots. Currently, all worker thread
168	>	* creation is on-demand, triggered by task submissions,
169	>	* replacement of terminated workers, and/or compensation for
170	>	* blocked workers. However, all other support code is set up to
171	>	* work with other policies.
172	>	*
173	>	* 2. Bookkeeping for dynamically adding and removing workers. We
174	>	* aim to approximately maintain the given level of parallelism.
175	>	* When some workers are known to be blocked (on joins or via
176	>	* ManagedBlocker), we may create or resume others to take their
177	>	* place until they unblock (see below). Implementing this
178	>	* requires counts of the number of "running" threads (i.e., those
179	>	* that are neither blocked nor artifically suspended) as well as
180	>	* the total number.  These two values are packed into one field,
181	>	* "workerCounts" because we need accurate snapshots when deciding
182	>	* to create, resume or suspend.  To support these decisions,
183	>	* updates to spare counts must be prospective (not
184	>	* retrospective).  For example, the running count is decremented
185	>	* before blocking by a thread about to block as a spare, but
186	>	* incremented by the thread about to unblock it. Updates upon
187	>	* resumption ofr threads blocking in awaitJoin or awaitBlocker
188	>	* cannot usually be prospective, so the running count is in
189	>	* general an upper bound of the number of productively running
190	>	* threads Updates to the workerCounts field sometimes transiently
191	>	* encounter a fair amount of contention when join dependencies
192	>	* are such that many threads block or unblock at about the same
193	>	* time. We alleviate this by sometimes performing an alternative
194	>	* action on contention like releasing waiters or locating spares.
195	>	*
196	>	* 3. Maintaining global run state. The run state of the pool
197	>	* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to
198	>	* those in other Executor implementations, as well as a count of
199	>	* "active" workers -- those that are, or soon will be, or
200	>	* recently were executing tasks. The runLevel and active count
201	>	* are packed together in order to correctly trigger shutdown and
202	>	* termination. Without care, active counts can be subject to very
203	>	* high contention.  We substantially reduce this contention by
204	>	* relaxing update rules.  A worker must claim active status
205	>	* prospectively, by activating if it sees that a submitted or
206	>	* stealable task exists (it may find after activating that the
207	>	* task no longer exists). It stays active while processing this
208	>	* task (if it exists) and any other local subtasks it produces,
209	>	* until it cannot find any other tasks. It then tries
210	>	* inactivating (see method preStep), but upon update contention
211	>	* instead scans for more tasks, later retrying inactivation if it
212	>	* doesn't find any.
213	>	*
214	>	* 4. Managing idle workers waiting for tasks. We cannot let
215	>	* workers spin indefinitely scanning for tasks when none are
216	>	* available. On the other hand, we must quickly prod them into
217	>	* action when new tasks are submitted or generated.  We
218	>	* park/unpark these idle workers using an event-count scheme.
219	>	* Field eventCount is incremented upon events that may enable
220	>	* workers that previously could not find a task to now find one:
221	>	* Submission of a new task to the pool, or another worker pushing
222	>	* a task onto a previously empty queue.  (We also use this
223	>	* mechanism for termination and reconfiguration actions that
224	>	* require wakeups of idle workers).  Each worker maintains its
225	>	* last known event count, and blocks when a scan for work did not
226	>	* find a task AND its lastEventCount matches the current
227	>	* eventCount. Waiting idle workers are recorded in a variant of
228	>	* Treiber stack headed by field eventWaiters which, when nonzero,
229	>	* encodes the thread index and count awaited for by the worker
230	>	* thread most recently calling eventSync. This thread in turn has
231	>	* a record (field nextEventWaiter) for the next waiting worker.
232	>	* In addition to allowing simpler decisions about need for
233	>	* wakeup, the event count bits in eventWaiters serve the role of
234	>	* tags to avoid ABA errors in Treiber stacks.  To reduce delays
235	>	* in task diffusion, workers not otherwise occupied may invoke
236	>	* method releaseWaiters, that removes and signals (unparks)
237	>	* workers not waiting on current count. To minimize task
238	>	* production stalls associate with signalling, any worker pushing
239	>	* a task on an empty queue invokes the weaker method signalWork,
240	>	* that only releases idle workers until it detects interference
241	>	* by other threads trying to release, and lets them take
242	>	* over. The net effect is a tree-like diffusion of signals, where
243	>	* released threads (and possibly others) help with unparks.  To
244	>	* further reduce contention effects a bit, failed CASes to
245	>	* increment field eventCount are tolerated without retries.
246	>	* Conceptually they are merged into the same event, which is OK
247	>	* when their only purpose is to enable workers to scan for work.
248	>	*
249	>	* 5. Managing suspension of extra workers. When a worker is about
250	>	* to block waiting for a join (or via ManagedBlockers), we may
251	>	* create a new thread to maintain parallelism level, or at least
252	>	* avoid starvation (see below). Usually, extra threads are needed
253	>	* for only very short periods, yet join dependencies are such
254	>	* that we sometimes need them in bursts. Rather than create new
255	>	* threads each time this happens, we suspend no-longer-needed
256	>	* extra ones as "spares". For most purposes, we don't distinguish
257	>	* "extra" spare threads from normal "core" threads: On each call
258	>	* to preStep (the only point at which we can do this) a worker
259	>	* checks to see if there are now too many running workers, and if
260	>	* so, suspends itself.  Methods awaitJoin and awaitBlocker look
261	>	* for suspended threads to resume before considering creating a
262	>	* new replacement. We don't need a special data structure to
263	>	* maintain spares; simply scanning the workers array looking for
264	>	* worker.isSuspended() is fine because the calling thread is
265	>	* otherwise not doing anything useful anyway; we are at least as
266	>	* happy if after locating a spare, the caller doesn't actually
267	>	* block because the join is ready before we try to adjust and
268	>	* compensate.  Note that this is intrinsically racy.  One thread
269	>	* may become a spare at about the same time as another is
270	>	* needlessly being created. We counteract this and related slop
271	>	* in part by requiring resumed spares to immediately recheck (in
272	>	* preStep) to see whether they they should re-suspend. The only
273	>	* effective difference between "extra" and "core" threads is that
274	>	* we allow the "extra" ones to time out and die if they are not
275	>	* resumed within a keep-alive interval of a few seconds. This is
276	>	* implemented mainly within ForkJoinWorkerThread, but requires
277	>	* some coordination (isTrimmed() -- meaning killed while
278	>	* suspended) to correctly maintain pool counts.
279	>	*
280	>	* 6. Deciding when to create new workers. The main dynamic
281	>	* control in this class is deciding when to create extra threads,
282	>	* in methods awaitJoin and awaitBlocker. We always need to create
283	>	* one when the number of running threads becomes zero. But
284	>	* because blocked joins are typically dependent, we don't
285	>	* necessarily need or want one-to-one replacement. Instead, we
286	>	* use a combination of heuristics that adds threads only when the
287	>	* pool appears to be approaching starvation.  These effectively
288	>	* reduce churn at the price of systematically undershooting
289	>	* target parallelism when many threads are blocked.  However,
290	>	* biasing toward undeshooting partially compensates for the above
291	>	* mechanics to suspend extra threads, that normally lead to
292	>	* overshoot because we can only suspend workers in-between
293	>	* top-level actions. It also better copes with the fact that some
294	>	* of the methods in this class tend to never become compiled (but
295	>	* are interpreted), so some components of the entire set of
296	>	* controls might execute many times faster than others. And
297	>	* similarly for cases where the apparent lack of work is just due
298	>	* to GC stalls and other transient system activity.
299	>	*
300	>	* Beware that there is a lot of representation-level coupling
301	>	* among classes ForkJoinPool, ForkJoinWorkerThread, and
302	>	* ForkJoinTask.  For example, direct access to "workers" array by
303	>	* workers, and direct access to ForkJoinTask.status by both
304	>	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
305	>	* trying to reduce this, since any associated future changes in
306	>	* representations will need to be accompanied by algorithmic
307	>	* changes anyway.
308	>	*
309	>	* Style notes: There are lots of inline assignments (of form
310	>	* "while ((local = field) != 0)") which are usually the simplest
311	>	* way to ensure read orderings. Also several occurrences of the
312	>	* unusual "do {} while(!cas...)" which is the simplest way to
313	>	* force an update of a CAS'ed variable. There are also a few
314	>	* other coding oddities that help some methods perform reasonably
315	>	* even when interpreted (not compiled).
316	>	*
317	>	* The order of declarations in this file is: (1) statics (2)
318	>	* fields (along with constants used when unpacking some of them)
319	>	* (3) internal control methods (4) callbacks and other support
320	>	* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
321	>	* methods (plus a few little helpers).
322		*/
323
64	–	/** Mask for packing and unpacking shorts */
65	–	private static final int  shortMask = 0xffff;
66	–
67	–	/** Max pool size -- must be a power of two minus 1 */
68	–	private static final int MAX_THREADS =  0x7FFF;
69	–
324		/**
325	<	* Factory for creating new ForkJoinWorkerThreads.  A
326	<	* ForkJoinWorkerThreadFactory must be defined and used for
327	<	* ForkJoinWorkerThread subclasses that extend base functionality
328	<	* or initialize threads with different contexts.
325	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
326	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
327	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
328	>	* functionality or initialize threads with different contexts.
329		*/
330		public static interface ForkJoinWorkerThreadFactory {
331		/**
332		* Returns a new worker thread operating in the given pool.
333		*
334		* @param pool the pool this thread works in
335	<	* @throws NullPointerException if pool is null;
335	>	* @throws NullPointerException if the pool is null
336		*/
337		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
338		}
339
340		/**
341	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
341	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
342		* new ForkJoinWorkerThread.
343		*/
344	<	public static class  DefaultForkJoinWorkerThreadFactory
344	>	static class DefaultForkJoinWorkerThreadFactory
345		implements ForkJoinWorkerThreadFactory {
346		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
347	<	try {
94	<	return new ForkJoinWorkerThread(pool);
95	<	} catch (OutOfMemoryError oom)  {
96	<	return null;
97	<	}
347	>	return new ForkJoinWorkerThread(pool);
348		}
349		}
350
351		/**
352	<	* The default ForkJoinWorkerThreadFactory, used unless overridden
353	<	* in ForkJoinPool constructors.
352	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
353	>	* overridden in ForkJoinPool constructors.
354		*/
355	<	private static final DefaultForkJoinWorkerThreadFactory
355	>	public static final ForkJoinWorkerThreadFactory
356		defaultForkJoinWorkerThreadFactory =
357		new DefaultForkJoinWorkerThreadFactory();
358
109	–
359		/**
360		* Permission required for callers of methods that may start or
361		* kill threads.
#	Line 131 | Line 380 | public class ForkJoinPool extends Abstra
380		new AtomicInteger();
381
382		/**
383	<	* Array holding all worker threads in the pool. Array size must
383	>	* Absolute bound for parallelism level. Twice this number must
384	>	* fit into a 16bit field to enable word-packing for some counts.
385	>	*/
386	>	private static final int MAX_THREADS = 0x7fff;
387	>
388	>	/**
389	>	* Array holding all worker threads in the pool.  Array size must
390		* be a power of two.  Updates and replacements are protected by
391	<	* workerLock, but it is always kept in a consistent enough state
392	<	* to be randomly accessed without locking by workers performing
393	<	* work-stealing.
391	>	* workerLock, but the array is always kept in a consistent enough
392	>	* state to be randomly accessed without locking by workers
393	>	* performing work-stealing, as well as other traversal-based
394	>	* methods in this class. All readers must tolerate that some
395	>	* array slots may be null.
396		*/
397		volatile ForkJoinWorkerThread[] workers;
398
399		/**
400	<	* Lock protecting access to workers.
400	>	* Queue for external submissions.
401		*/
402	<	private final ReentrantLock workerLock;
402	>	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
403
404		/**
405	<	* Condition for awaitTermination.
405	>	* Lock protecting updates to workers array.
406		*/
407	<	private final Condition termination;
407	>	private final ReentrantLock workerLock;
408
409		/**
410	<	* The uncaught exception handler used when any worker
154	<	* abrupty terminates
410	>	* Latch released upon termination.
411		*/
412	<	private Thread.UncaughtExceptionHandler ueh;
412	>	private final Phaser termination;
413
414		/**
415		* Creation factory for worker threads.
#	Line 161 | Line 417 | public class ForkJoinPool extends Abstra
417		private final ForkJoinWorkerThreadFactory factory;
418
419		/**
164	–	* Head of stack of threads that were created to maintain
165	–	* parallelism when other threads blocked, but have since
166	–	* suspended when the parallelism level rose.
167	–	*/
168	–	private volatile WaitQueueNode spareStack;
169	–
170	–	/**
420		* Sum of per-thread steal counts, updated only when threads are
421		* idle or terminating.
422		*/
423	<	private final AtomicLong stealCount;
423	>	private volatile long stealCount;
424
425		/**
426	<	* Queue for external submissions.
426	>	* Encoded record of top of treiber stack of threads waiting for
427	>	* events. The top 32 bits contain the count being waited for. The
428	>	* bottom word contains one plus the pool index of waiting worker
429	>	* thread.
430		*/
431	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
431	>	private volatile long eventWaiters;
432	>
433	>	private static final int  EVENT_COUNT_SHIFT = 32;
434	>	private static final long WAITER_INDEX_MASK = (1L << EVENT_COUNT_SHIFT)-1L;
435
436		/**
437	<	* Head of Treiber stack for barrier sync. See below for explanation
437	>	* A counter for events that may wake up worker threads:
438	>	*   - Submission of a new task to the pool
439	>	*   - A worker pushing a task on an empty queue
440	>	*   - termination and reconfiguration
441		*/
442	<	private volatile WaitQueueNode barrierStack;
442	>	private volatile int eventCount;
443
444		/**
445	<	* The count for event barrier
445	>	* Lifecycle control. The low word contains the number of workers
446	>	* that are (probably) executing tasks. This value is atomically
447	>	* incremented before a worker gets a task to run, and decremented
448	>	* when worker has no tasks and cannot find any.  Bits 16-18
449	>	* contain runLevel value. When all are zero, the pool is
450	>	* running. Level transitions are monotonic (running -> shutdown
451	>	* -> terminating -> terminated) so each transition adds a bit.
452	>	* These are bundled together to ensure consistent read for
453	>	* termination checks (i.e., that runLevel is at least SHUTDOWN
454	>	* and active threads is zero).
455	>	*/
456	>	private volatile int runState;
457	>
458	>	// Note: The order among run level values matters.
459	>	private static final int RUNLEVEL_SHIFT     = 16;
460	>	private static final int SHUTDOWN           = 1 << RUNLEVEL_SHIFT;
461	>	private static final int TERMINATING        = 1 << (RUNLEVEL_SHIFT + 1);
462	>	private static final int TERMINATED         = 1 << (RUNLEVEL_SHIFT + 2);
463	>	private static final int ACTIVE_COUNT_MASK  = (1 << RUNLEVEL_SHIFT) - 1;
464	>	private static final int ONE_ACTIVE         = 1; // active update delta
465	>
466	>	/**
467	>	* Holds number of total (i.e., created and not yet terminated)
468	>	* and running (i.e., not blocked on joins or other managed sync)
469	>	* threads, packed together to ensure consistent snapshot when
470	>	* making decisions about creating and suspending spare
471	>	* threads. Updated only by CAS. Note that adding a new worker
472	>	* requires incrementing both counts, since workers start off in
473	>	* running state.  This field is also used for memory-fencing
474	>	* configuration parameters.
475		*/
476	<	private volatile long eventCount;
476	>	private volatile int workerCounts;
477	>
478	>	private static final int TOTAL_COUNT_SHIFT  = 16;
479	>	private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1;
480	>	private static final int ONE_RUNNING        = 1;
481	>	private static final int ONE_TOTAL          = 1 << TOTAL_COUNT_SHIFT;
482
483		/**
484	<	* Pool number, just for assigning useful names to worker threads
484	>	* The target parallelism level.
485	>	* Accessed directly by ForkJoinWorkerThreads.
486		*/
487	<	private final int poolNumber;
487	>	final int parallelism;
488
489		/**
490	<	* The maximum allowed pool size
490	>	* True if use local fifo, not default lifo, for local polling
491	>	* Read by, and replicated by ForkJoinWorkerThreads
492		*/
493	<	private volatile int maxPoolSize;
493	>	final boolean locallyFifo;
494
495		/**
496	<	* The desired parallelism level, updated only under workerLock.
496	>	* The uncaught exception handler used when any worker abruptly
497	>	* terminates.
498		*/
499	<	private volatile int parallelism;
499	>	private final Thread.UncaughtExceptionHandler ueh;
500
501		/**
502	<	* Holds number of total (i.e., created and not yet terminated)
208	<	* and running (i.e., not blocked on joins or other managed sync)
209	<	* threads, packed into one int to ensure consistent snapshot when
210	<	* making decisions about creating and suspending spare
211	<	* threads. Updated only by CAS.  Note: CASes in
212	<	* updateRunningCount and preJoin running active count is in low
213	<	* word, so need to be modified if this changes
502	>	* Pool number, just for assigning useful names to worker threads
503		*/
504	<	private volatile int workerCounts;
504	>	private final int poolNumber;
505
506	<	private static int totalCountOf(int s)           { return s >>> 16;  }
218	<	private static int runningCountOf(int s)         { return s & shortMask; }
219	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
506	>	// utilities for updating fields
507
508		/**
509	<	* Add delta (which may be negative) to running count.  This must
223	<	* be called before (with negative arg) and after (with positive)
224	<	* any managed synchronization (i.e., mainly, joins)
225	<	* @param delta the number to add
509	>	* Increments running count.  Also used by ForkJoinTask.
510		*/
511	<	final void updateRunningCount(int delta) {
512	<	int s;
513	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
511	>	final void incrementRunningCount() {
512	>	int c;
513	>	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
514	>	c = workerCounts,
515	>	c + ONE_RUNNING));
516	>	}
517	>
518	>	/**
519	>	* Tries to decrement running count unless already zero
520	>	*/
521	>	final boolean tryDecrementRunningCount() {
522	>	int wc = workerCounts;
523	>	if ((wc & RUNNING_COUNT_MASK) == 0)
524	>	return false;
525	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
526	>	wc, wc - ONE_RUNNING);
527		}
528
529		/**
530	<	* Add delta (which may be negative) to both total and running
531	<	* count.  This must be called upon creation and termination of
532	<	* worker threads.
533	<	* @param delta the number to add
530	>	* Tries incrementing active count; fails on contention.
531	>	* Called by workers before executing tasks.
532	>	*
533	>	* @return true on success
534		*/
535	<	private void updateWorkerCount(int delta) {
536	<	int d = delta + (delta << 16); // add to both lo and hi parts
537	<	int s;
538	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
535	>	final boolean tryIncrementActiveCount() {
536	>	int c;
537	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
538	>	c = runState, c + ONE_ACTIVE);
539		}
540
541		/**
542	<	* Lifecycle control. High word contains runState, low word
543	<	* contains the number of workers that are (probably) executing
247	<	* tasks. This value is atomically incremented before a worker
248	<	* gets a task to run, and decremented when worker has no tasks
249	<	* and cannot find any. These two fields are bundled together to
250	<	* support correct termination triggering.  Note: activeCount
251	<	* CAS'es cheat by assuming active count is in low word, so need
252	<	* to be modified if this changes
542	>	* Tries decrementing active count; fails on contention.
543	>	* Called when workers cannot find tasks to run.
544		*/
545	<	private volatile int runControl;
545	>	final boolean tryDecrementActiveCount() {
546	>	int c;
547	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
548	>	c = runState, c - ONE_ACTIVE);
549	>	}
550
551	<	// RunState values. Order among values matters
552	<	private static final int RUNNING     = 0;
553	<	private static final int SHUTDOWN    = 1;
554	<	private static final int TERMINATING = 2;
555	<	private static final int TERMINATED  = 3;
551	>	/**
552	>	* Advances to at least the given level. Returns true if not
553	>	* already in at least the given level.
554	>	*/
555	>	private boolean advanceRunLevel(int level) {
556	>	for (;;) {
557	>	int s = runState;
558	>	if ((s & level) != 0)
559	>	return false;
560	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level))
561	>	return true;
562	>	}
563	>	}
564
565	<	private static int runStateOf(int c)             { return c >>> 16; }
263	<	private static int activeCountOf(int c)          { return c & shortMask; }
264	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
565	>	// workers array maintenance
566
567		/**
568	<	* Increment active count. Called by workers before/during
268	<	* executing tasks.
568	>	* Records and returns a workers array index for new worker.
569		*/
570	<	final void incrementActiveCount() {
571	<	int c;
572	<	do;while (!casRunControl(c = runControl, c+1));
570	>	private int recordWorker(ForkJoinWorkerThread w) {
571	>	// Try using slot totalCount-1. If not available, scan and/or resize
572	>	int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1;
573	>	final ReentrantLock lock = this.workerLock;
574	>	lock.lock();
575	>	try {
576	>	ForkJoinWorkerThread[] ws = workers;
577	>	int nws = ws.length;
578	>	if (k < 0 || k >= nws || ws[k] != null) {
579	>	for (k = 0; k < nws && ws[k] != null; ++k)
580	>	;
581	>	if (k == nws)
582	>	ws = Arrays.copyOf(ws, nws << 1);
583	>	}
584	>	ws[k] = w;
585	>	workers = ws; // volatile array write ensures slot visibility
586	>	} finally {
587	>	lock.unlock();
588	>	}
589	>	return k;
590		}
591
592		/**
593	<	* Decrement active count; possibly trigger termination.
277	<	* Called by workers when they can't find tasks.
593	>	* Nulls out record of worker in workers array
594		*/
595	<	final void decrementActiveCount() {
596	<	int c, nextc;
597	<	do;while (!casRunControl(c = runControl, nextc = c-1));
598	<	if (canTerminateOnShutdown(nextc))
599	<	terminateOnShutdown();
595	>	private void forgetWorker(ForkJoinWorkerThread w) {
596	>	int idx = w.poolIndex;
597	>	// Locking helps method recordWorker avoid unecessary expansion
598	>	final ReentrantLock lock = this.workerLock;
599	>	lock.lock();
600	>	try {
601	>	ForkJoinWorkerThread[] ws = workers;
602	>	if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify
603	>	ws[idx] = null;
604	>	} finally {
605	>	lock.unlock();
606	>	}
607		}
608
609	+	// adding and removing workers
610	+
611		/**
612	<	* Return true if argument represents zero active count and
613	<	* nonzero runstate, which is the triggering condition for
614	<	* terminating on shutdown.
612	>	* Tries to create and add new worker. Assumes that worker counts
613	>	* are already updated to accommodate the worker, so adjusts on
614	>	* failure.
615	>	*
616	>	* @return new worker or null if creation failed
617		*/
618	<	private static boolean canTerminateOnShutdown(int c) {
619	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
618	>	private ForkJoinWorkerThread addWorker() {
619	>	ForkJoinWorkerThread w = null;
620	>	try {
621	>	w = factory.newThread(this);
622	>	} finally { // Adjust on either null or exceptional factory return
623	>	if (w == null) {
624	>	onWorkerCreationFailure();
625	>	return null;
626	>	}
627	>	}
628	>	w.start(recordWorker(w), ueh);
629	>	return w;
630		}
631
632		/**
633	<	* Transition run state to at least the given state. Return true
297	<	* if not already at least given state.
633	>	* Adjusts counts upon failure to create worker
634		*/
635	<	private boolean transitionRunStateTo(int state) {
635	>	private void onWorkerCreationFailure() {
636		for (;;) {
637	<	int c = runControl;
638	<	if (runStateOf(c) >= state)
639	<	return false;
640	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
641	<	return true;
637	>	int wc = workerCounts;
638	>	if ((wc >>> TOTAL_COUNT_SHIFT) > 0 &&
639	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
640	>	wc, wc - (ONE_RUNNING|ONE_TOTAL)))
641	>	break;
642		}
643	+	tryTerminate(false); // in case of failure during shutdown
644		}
645
646		/**
647	<	* Controls whether to add spares to maintain parallelism
647	>	* Create enough total workers to establish target parallelism,
648	>	* giving up if terminating or addWorker fails
649		*/
650	<	private volatile boolean maintainsParallelism;
650	>	private void ensureEnoughTotalWorkers() {
651	>	int wc;
652	>	while (((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < parallelism &&
653	>	runState < TERMINATING) {
654	>	if ((UNSAFE.compareAndSwapInt(this, workerCountsOffset,
655	>	wc, wc + (ONE_RUNNING|ONE_TOTAL)) &&
656	>	addWorker() == null))
657	>	break;
658	>	}
659	>	}
660
661	<	// Constructors
661	>	/**
662	>	* Final callback from terminating worker.  Removes record of
663	>	* worker from array, and adjusts counts. If pool is shutting
664	>	* down, tries to complete terminatation, else possibly replaces
665	>	* the worker.
666	>	*
667	>	* @param w the worker
668	>	*/
669	>	final void workerTerminated(ForkJoinWorkerThread w) {
670	>	if (w.active) { // force inactive
671	>	w.active = false;
672	>	do {} while (!tryDecrementActiveCount());
673	>	}
674	>	forgetWorker(w);
675	>
676	>	// Decrement total count, and if was running, running count
677	>	// Spin (waiting for other updates) if either would be negative
678	>	int nr = w.isTrimmed() ? 0 : ONE_RUNNING;
679	>	int unit = ONE_TOTAL + nr;
680	>	for (;;) {
681	>	int wc = workerCounts;
682	>	int rc = wc & RUNNING_COUNT_MASK;
683	>	if (rc - nr < 0 || (wc >>> TOTAL_COUNT_SHIFT) == 0)
684	>	Thread.yield(); // back off if waiting for other updates
685	>	else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
686	>	wc, wc - unit))
687	>	break;
688	>	}
689	>
690	>	accumulateStealCount(w); // collect final count
691	>	if (!tryTerminate(false))
692	>	ensureEnoughTotalWorkers();
693	>	}
694	>
695	>	// Waiting for and signalling events
696
697		/**
698	<	* Creates a ForkJoinPool with a pool size equal to the number of
318	<	* processors available on the system and using the default
319	<	* ForkJoinWorkerThreadFactory,
320	<	* @throws SecurityException if a security manager exists and
321	<	*         the caller is not permitted to modify threads
322	<	*         because it does not hold {@link
323	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
698	>	* Releases workers blocked on a count not equal to current count.
699		*/
700	<	public ForkJoinPool() {
701	<	this(Runtime.getRuntime().availableProcessors(),
702	<	defaultForkJoinWorkerThreadFactory);
700	>	private void releaseWaiters() {
701	>	long top;
702	>	int id;
703	>	while ((id = (int)((top = eventWaiters) & WAITER_INDEX_MASK)) > 0 &&
704	>	(int)(top >>> EVENT_COUNT_SHIFT) != eventCount) {
705	>	ForkJoinWorkerThread[] ws = workers;
706	>	ForkJoinWorkerThread w;
707	>	if (ws.length >= id && (w = ws[id - 1]) != null &&
708	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
709	>	top, w.nextWaiter))
710	>	LockSupport.unpark(w);
711	>	}
712		}
713
714		/**
715	<	* Creates a ForkJoinPool with the indicated parellelism level
716	<	* threads, and using the default ForkJoinWorkerThreadFactory,
333	<	* @param parallelism the number of worker threads
334	<	* @throws IllegalArgumentException if parallelism less than or
335	<	* equal to zero
336	<	* @throws SecurityException if a security manager exists and
337	<	*         the caller is not permitted to modify threads
338	<	*         because it does not hold {@link
339	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
715	>	* Ensures eventCount on exit is different (mod 2^32) than on
716	>	* entry and wakes up all waiters
717		*/
718	<	public ForkJoinPool(int parallelism) {
719	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
718	>	private void signalEvent() {
719	>	int c;
720	>	do {} while (!UNSAFE.compareAndSwapInt(this, eventCountOffset,
721	>	c = eventCount, c+1));
722	>	releaseWaiters();
723		}
724
725		/**
726	<	* Creates a ForkJoinPool with a pool size equal to the number of
727	<	* processors available on the system and using the given
728	<	* ForkJoinWorkerThreadFactory,
729	<	* @param factory the factory for creating new threads
730	<	* @throws NullPointerException if factory is null
731	<	* @throws SecurityException if a security manager exists and
732	<	*         the caller is not permitted to modify threads
733	<	*         because it does not hold {@link
734	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
726	>	* Advances eventCount and releases waiters until interference by
727	>	* other releasing threads is detected.
728	>	*/
729	>	final void signalWork() {
730	>	// EventCount CAS failures are OK -- any change in count suffices.
731	>	int ec;
732	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, ec=eventCount, ec+1);
733	>	outer:for (;;) {
734	>	long top = eventWaiters;
735	>	ec = eventCount;
736	>	for (;;) {
737	>	ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w;
738	>	int id = (int)(top & WAITER_INDEX_MASK);
739	>	if (id <= 0 || (int)(top >>> EVENT_COUNT_SHIFT) == ec)
740	>	return;
741	>	if ((ws = workers).length < id || (w = ws[id - 1]) == null ||
742	>	!UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
743	>	top, top = w.nextWaiter))
744	>	continue outer;      // possibly stale; reread
745	>	LockSupport.unpark(w);
746	>	if (top != eventWaiters) // let someone else take over
747	>	return;
748	>	}
749	>	}
750	>	}
751	>
752	>	/**
753	>	* If worker is inactive, blocks until terminating or event count
754	>	* advances from last value held by worker; in any case helps
755	>	* release others.
756	>	*
757	>	* @param w the calling worker thread
758		*/
759	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
760	<	this(Runtime.getRuntime().availableProcessors(), factory);
759	>	private void eventSync(ForkJoinWorkerThread w) {
760	>	if (!w.active) {
761	>	int prev = w.lastEventCount;
762	>	long nextTop = (((long)prev << EVENT_COUNT_SHIFT) |
763	>	((long)(w.poolIndex + 1)));
764	>	long top;
765	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
766	>	(((int)(top = eventWaiters) & WAITER_INDEX_MASK) == 0 ||
767	>	(int)(top >>> EVENT_COUNT_SHIFT) == prev) &&
768	>	eventCount == prev) {
769	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
770	>	w.nextWaiter = top, nextTop)) {
771	>	accumulateStealCount(w); // transfer steals while idle
772	>	Thread.interrupted();    // clear/ignore interrupt
773	>	while (eventCount == prev)
774	>	w.doPark();
775	>	break;
776	>	}
777	>	}
778	>	w.lastEventCount = eventCount;
779	>	}
780	>	releaseWaiters();
781		}
782
783		/**
784	<	* Creates a ForkJoinPool with the indicated target number of
785	<	* worker threads and the given factory.
784	>	* Callback from workers invoked upon each top-level action (i.e.,
785	>	* stealing a task or taking a submission and running
786	>	* it). Performs one or both of the following:
787		*
788	<	* @param parallelism the targeted number of worker threads
789	<	* @param factory the factory for creating new threads
790	<	* @throws IllegalArgumentException if parallelism less than or
791	<	* equal to zero, or greater than implementation limit.
792	<	* @throws NullPointerException if factory is null
793	<	* @throws SecurityException if a security manager exists and
794	<	*         the caller is not permitted to modify threads
795	<	*         because it does not hold {@link
796	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
788	>	* * If the worker cannot find work, updates its active status to
789	>	* inactive and updates activeCount unless there is contention, in
790	>	* which case it may try again (either in this or a subsequent
791	>	* call).  Additionally, awaits the next task event and/or helps
792	>	* wake up other releasable waiters.
793	>	*
794	>	* * If there are too many running threads, suspends this worker
795	>	* (first forcing inactivation if necessary).  If it is not
796	>	* resumed before a keepAlive elapses, the worker may be "trimmed"
797	>	* -- killed while suspended within suspendAsSpare. Otherwise,
798	>	* upon resume it rechecks to make sure that it is still needed.
799	>	*
800	>	* @param w the worker
801	>	* @param worked false if the worker scanned for work but didn't
802	>	* find any (in which case it may block waiting for work).
803		*/
804	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
805	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
806	<	throw new IllegalArgumentException();
807	<	if (factory == null)
808	<	throw new NullPointerException();
809	<	checkPermission();
810	<	this.factory = factory;
811	<	this.parallelism = parallelism;
812	<	this.maxPoolSize = MAX_THREADS;
813	<	this.maintainsParallelism = true;
814	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
815	<	this.workerLock = new ReentrantLock();
816	<	this.termination = workerLock.newCondition();
817	<	this.stealCount = new AtomicLong();
818	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
819	<	createAndStartInitialWorkers(parallelism);
804	>	final void preStep(ForkJoinWorkerThread w, boolean worked) {
805	>	boolean active = w.active;
806	>	boolean inactivate = !worked & active;
807	>	for (;;) {
808	>	if (inactivate) {
809	>	int rs = runState;
810	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset,
811	>	rs, rs - ONE_ACTIVE))
812	>	inactivate = active = w.active = false;
813	>	}
814	>	int wc = workerCounts;
815	>	if ((wc & RUNNING_COUNT_MASK) <= parallelism) {
816	>	if (!worked)
817	>	eventSync(w);
818	>	return;
819	>	}
820	>	if (!(inactivate |= active) &&  // must inactivate to suspend
821	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
822	>	wc, wc - ONE_RUNNING) &&
823	>	!w.suspendAsSpare())        // false if trimmed
824	>	return;
825	>	}
826		}
827
828		/**
829	<	* Create new worker using factory.
830	<	* @param index the index to assign worker
831	<	* @return new worker, or null of factory failed
832	<	*/
833	<	private ForkJoinWorkerThread createWorker(int index) {
834	<	Thread.UncaughtExceptionHandler h = ueh;
835	<	ForkJoinWorkerThread w = factory.newThread(this);
836	<	if (w != null) {
837	<	w.poolIndex = index;
838	<	w.setDaemon(true);
839	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
840	<	if (h != null)
841	<	w.setUncaughtExceptionHandler(h);
829	>	* Tries to decrement running count, and if so, possibly creates
830	>	* or resumes compensating threads before blocking on task joinMe.
831	>	* This code is sprawled out with manual inlining to evade some
832	>	* JIT oddities.
833	>	*
834	>	* @param joinMe the task to join
835	>	* @return task status on exit
836	>	*/
837	>	final int tryAwaitJoin(ForkJoinTask<?> joinMe) {
838	>	int cw = workerCounts; // read now to spoil CAS if counts change as ...
839	>	releaseWaiters();      // ... a byproduct of releaseWaiters
840	>	int stat = joinMe.status;
841	>	if (stat >= 0 && // inline variant of tryDecrementRunningCount
842	>	(cw & RUNNING_COUNT_MASK) > 0 &&
843	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
844	>	cw, cw - ONE_RUNNING)) {
845	>	int pc = parallelism;
846	>	int scans = 0;  // to require confirming passes to add threads
847	>	outer: while ((workerCounts & RUNNING_COUNT_MASK) < pc) {
848	>	if ((stat = joinMe.status) < 0)
849	>	break;
850	>	ForkJoinWorkerThread spare = null;
851	>	ForkJoinWorkerThread[] ws = workers;
852	>	int nws = ws.length;
853	>	for (int i = 0; i < nws; ++i) {
854	>	ForkJoinWorkerThread w = ws[i];
855	>	if (w != null && w.isSuspended()) {
856	>	spare = w;
857	>	break;
858	>	}
859	>	}
860	>	if ((stat = joinMe.status) < 0) // recheck to narrow race
861	>	break;
862	>	int wc = workerCounts;
863	>	int rc = wc & RUNNING_COUNT_MASK;
864	>	if (rc >= pc)
865	>	break;
866	>	if (spare != null) {
867	>	if (spare.tryUnsuspend()) {
868	>	int c; // inline incrementRunningCount
869	>	do {} while (!UNSAFE.compareAndSwapInt
870	>	(this, workerCountsOffset,
871	>	c = workerCounts, c + ONE_RUNNING));
872	>	LockSupport.unpark(spare);
873	>	break;
874	>	}
875	>	continue;
876	>	}
877	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
878	>	int sc = tc - pc;
879	>	if (rc > 0) {
880	>	int p = pc;
881	>	int s = sc;
882	>	while (s-- >= 0) { // try keeping 3/4 live
883	>	if (rc > (p -= (p >>> 2) + 1))
884	>	break outer;
885	>	}
886	>	}
887	>	if (scans++ > sc && tc < MAX_THREADS &&
888	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
889	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
890	>	addWorker();
891	>	break;
892	>	}
893	>	}
894	>	if (stat >= 0)
895	>	stat = joinMe.internalAwaitDone();
896	>	int c; // inline incrementRunningCount
897	>	do {} while (!UNSAFE.compareAndSwapInt
898	>	(this, workerCountsOffset,
899	>	c = workerCounts, c + ONE_RUNNING));
900		}
901	<	return w;
901	>	return stat;
902		}
903
904		/**
905	<	* Return a good size for worker array given pool size.
906	<	* Currently requires size to be a power of two.
905	>	* Same idea as (and mostly pasted from) tryAwaitJoin, but
906	>	* self-contained
907		*/
908	<	private static int arraySizeFor(int ps) {
909	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
908	>	final void awaitBlocker(ManagedBlocker blocker)
909	>	throws InterruptedException {
910	>	for (;;) {
911	>	if (blocker.isReleasable())
912	>	return;
913	>	int cw = workerCounts;
914	>	releaseWaiters();
915	>	if ((cw & RUNNING_COUNT_MASK) > 0 &&
916	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
917	>	cw, cw - ONE_RUNNING))
918	>	break;
919	>	}
920	>	boolean done = false;
921	>	int pc = parallelism;
922	>	int scans = 0;
923	>	outer: while ((workerCounts & RUNNING_COUNT_MASK) < pc) {
924	>	if (done = blocker.isReleasable())
925	>	break;
926	>	ForkJoinWorkerThread spare = null;
927	>	ForkJoinWorkerThread[] ws = workers;
928	>	int nws = ws.length;
929	>	for (int i = 0; i < nws; ++i) {
930	>	ForkJoinWorkerThread w = ws[i];
931	>	if (w != null && w.isSuspended()) {
932	>	spare = w;
933	>	break;
934	>	}
935	>	}
936	>	if (done = blocker.isReleasable())
937	>	break;
938	>	int wc = workerCounts;
939	>	int rc = wc & RUNNING_COUNT_MASK;
940	>	if (rc >= pc)
941	>	break;
942	>	if (spare != null) {
943	>	if (spare.tryUnsuspend()) {
944	>	int c;
945	>	do {} while (!UNSAFE.compareAndSwapInt
946	>	(this, workerCountsOffset,
947	>	c = workerCounts, c + ONE_RUNNING));
948	>	LockSupport.unpark(spare);
949	>	break;
950	>	}
951	>	continue;
952	>	}
953	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
954	>	int sc = tc - pc;
955	>	if (rc > 0) {
956	>	int p = pc;
957	>	int s = sc;
958	>	while (s-- >= 0) {
959	>	if (rc > (p -= (p >>> 2) + 1))
960	>	break outer;
961	>	}
962	>	}
963	>	if (scans++ > sc && tc < MAX_THREADS &&
964	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
965	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
966	>	addWorker();
967	>	break;
968	>	}
969	>	}
970	>	try {
971	>	if (!done)
972	>	do {} while (!blocker.isReleasable() &&
973	>	!blocker.block());
974	>	} finally {
975	>	int c;
976	>	do {} while (!UNSAFE.compareAndSwapInt
977	>	(this, workerCountsOffset,
978	>	c = workerCounts, c + ONE_RUNNING));
979	>	}
980	>	}
981	>
982	>	/**
983	>	* Possibly initiates and/or completes termination.
984	>	*
985	>	* @param now if true, unconditionally terminate, else only
986	>	* if shutdown and empty queue and no active workers
987	>	* @return true if now terminating or terminated
988	>	*/
989	>	private boolean tryTerminate(boolean now) {
990	>	if (now)
991	>	advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN
992	>	else if (runState < SHUTDOWN ||
993	>	!submissionQueue.isEmpty() ||
994	>	(runState & ACTIVE_COUNT_MASK) != 0)
995	>	return false;
996	>
997	>	if (advanceRunLevel(TERMINATING))
998	>	startTerminating();
999	>
1000	>	// Finish now if all threads terminated; else in some subsequent call
1001	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1002	>	advanceRunLevel(TERMINATED);
1003	>	termination.arrive();
1004	>	}
1005	>	return true;
1006	>	}
1007	>
1008	>	/**
1009	>	* Actions on transition to TERMINATING
1010	>	*/
1011	>	private void startTerminating() {
1012	>	for (int i = 0; i < 2; ++i) { // twice to mop up newly created workers
1013	>	cancelSubmissions();
1014	>	shutdownWorkers();
1015	>	cancelWorkerTasks();
1016	>	signalEvent();
1017	>	interruptWorkers();
1018	>	}
1019		}
1020
1021		/**
1022	<	* Create or resize array if necessary to hold newLength
420	<	* @return the array
1022	>	* Clear out and cancel submissions, ignoring exceptions
1023		*/
1024	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
1024	>	private void cancelSubmissions() {
1025	>	ForkJoinTask<?> task;
1026	>	while ((task = submissionQueue.poll()) != null) {
1027	>	try {
1028	>	task.cancel(false);
1029	>	} catch (Throwable ignore) {
1030	>	}
1031	>	}
1032	>	}
1033	>
1034	>	/**
1035	>	* Sets all worker run states to at least shutdown,
1036	>	* also resuming suspended workers
1037	>	*/
1038	>	private void shutdownWorkers() {
1039		ForkJoinWorkerThread[] ws = workers;
1040	<	if (ws == null)
1041	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
1042	<	else if (newLength > ws.length)
1043	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
1044	<	else
1045	<	return ws;
1040	>	int nws = ws.length;
1041	>	for (int i = 0; i < nws; ++i) {
1042	>	ForkJoinWorkerThread w = ws[i];
1043	>	if (w != null)
1044	>	w.shutdown();
1045	>	}
1046		}
1047
1048		/**
1049	<	* Try to shrink workers into smaller array after one or more terminate
1049	>	* Clears out and cancels all locally queued tasks
1050		*/
1051	<	private void tryShrinkWorkerArray() {
1051	>	private void cancelWorkerTasks() {
1052		ForkJoinWorkerThread[] ws = workers;
1053	<	int len = ws.length;
1054	<	int last = len - 1;
1055	<	while (last >= 0 && ws[last] == null)
1056	<	--last;
1057	<	int newLength = arraySizeFor(last+1);
1058	<	if (newLength < len)
443	<	workers = Arrays.copyOf(ws, newLength);
1053	>	int nws = ws.length;
1054	>	for (int i = 0; i < nws; ++i) {
1055	>	ForkJoinWorkerThread w = ws[i];
1056	>	if (w != null)
1057	>	w.cancelTasks();
1058	>	}
1059		}
1060
1061		/**
1062	<	* Initial worker array and worker creation and startup. (This
448	<	* must be done under lock to avoid interference by some of the
449	<	* newly started threads while creating others.)
1062	>	* Unsticks all workers blocked on joins etc
1063		*/
1064	<	private void createAndStartInitialWorkers(int ps) {
1065	<	final ReentrantLock lock = this.workerLock;
1066	<	lock.lock();
1067	<	try {
1068	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1069	<	for (int i = 0; i < ps; ++i) {
1070	<	ForkJoinWorkerThread w = createWorker(i);
1071	<	if (w != null) {
1072	<	ws[i] = w;
460	<	w.start();
461	<	updateWorkerCount(1);
1064	>	private void interruptWorkers() {
1065	>	ForkJoinWorkerThread[] ws = workers;
1066	>	int nws = ws.length;
1067	>	for (int i = 0; i < nws; ++i) {
1068	>	ForkJoinWorkerThread w = ws[i];
1069	>	if (w != null && !w.isTerminated()) {
1070	>	try {
1071	>	w.interrupt();
1072	>	} catch (SecurityException ignore) {
1073		}
1074		}
464	–	} finally {
465	–	lock.unlock();
1075		}
1076		}
1077
1078	+	// misc support for ForkJoinWorkerThread
1079	+
1080		/**
1081	<	* Worker creation and startup for threads added via setParallelism.
1081	>	* Returns pool number
1082		*/
1083	<	private void createAndStartAddedWorkers() {
1084	<	resumeAllSpares();  // Allow spares to convert to nonspare
1085	<	int ps = parallelism;
1086	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1087	<	int len = ws.length;
1088	<	// Sweep through slots, to keep lowest indices most populated
1089	<	int k = 0;
1090	<	while (k < len) {
1091	<	if (ws[k] != null) {
1092	<	++k;
1093	<	continue;
1094	<	}
1095	<	int s = workerCounts;
1096	<	int tc = totalCountOf(s);
1097	<	int rc = runningCountOf(s);
487	<	if (rc >= ps || tc >= ps)
488	<	break;
489	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
490	<	ForkJoinWorkerThread w = createWorker(k);
491	<	if (w != null) {
492	<	ws[k++] = w;
493	<	w.start();
494	<	}
495	<	else {
496	<	updateWorkerCount(-1); // back out on failed creation
497	<	break;
498	<	}
499	<	}
1083	>	final int getPoolNumber() {
1084	>	return poolNumber;
1085	>	}
1086	>
1087	>	/**
1088	>	* Accumulates steal count from a worker, clearing
1089	>	* the worker's value
1090	>	*/
1091	>	final void accumulateStealCount(ForkJoinWorkerThread w) {
1092	>	int sc = w.stealCount;
1093	>	if (sc != 0) {
1094	>	long c;
1095	>	w.stealCount = 0;
1096	>	do {} while (!UNSAFE.compareAndSwapLong(this, stealCountOffset,
1097	>	c = stealCount, c + sc));
1098		}
1099		}
1100
1101		/**
1102	<	* Sets the handler for internal worker threads that terminate due
1103	<	* to unrecoverable errors encountered while executing tasks.
1104	<	* Unless set, the current default or ThreadGroup handler is used
1105	<	* as handler.
1102	>	* Returns the approximate (non-atomic) number of idle threads per
1103	>	* active thread.
1104	>	*/
1105	>	final int idlePerActive() {
1106	>	int pc = parallelism; // use targeted parallelism, not rc
1107	>	int ac = runState;    // no mask -- artifically boosts during shutdown
1108	>	// Use exact results for small values, saturate past 4
1109	>	return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
1110	>	}
1111	>
1112	>	// Public and protected methods
1113	>
1114	>	// Constructors
1115	>
1116	>	/**
1117	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1118	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1119	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1120	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1121		*
509	–	* @param h the new handler
510	–	* @return the old handler, or null if none
1122		* @throws SecurityException if a security manager exists and
1123		*         the caller is not permitted to modify threads
1124		*         because it does not hold {@link
1125	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1125	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1126		*/
1127	<	public Thread.UncaughtExceptionHandler
1128	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
1127	>	public ForkJoinPool() {
1128	>	this(Runtime.getRuntime().availableProcessors(),
1129	>	defaultForkJoinWorkerThreadFactory, null, false);
1130	>	}
1131	>
1132	>	/**
1133	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
1134	>	* level, the {@linkplain
1135	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1136	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1137	>	*
1138	>	* @param parallelism the parallelism level
1139	>	* @throws IllegalArgumentException if parallelism less than or
1140	>	*         equal to zero, or greater than implementation limit
1141	>	* @throws SecurityException if a security manager exists and
1142	>	*         the caller is not permitted to modify threads
1143	>	*         because it does not hold {@link
1144	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1145	>	*/
1146	>	public ForkJoinPool(int parallelism) {
1147	>	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1148	>	}
1149	>
1150	>	/**
1151	>	* Creates a {@code ForkJoinPool} with the given parameters.
1152	>	*
1153	>	* @param parallelism the parallelism level. For default value,
1154	>	* use {@link java.lang.Runtime#availableProcessors}.
1155	>	* @param factory the factory for creating new threads. For default value,
1156	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
1157	>	* @param handler the handler for internal worker threads that
1158	>	* terminate due to unrecoverable errors encountered while executing
1159	>	* tasks. For default value, use <code>null</code>.
1160	>	* @param asyncMode if true,
1161	>	* establishes local first-in-first-out scheduling mode for forked
1162	>	* tasks that are never joined. This mode may be more appropriate
1163	>	* than default locally stack-based mode in applications in which
1164	>	* worker threads only process event-style asynchronous tasks.
1165	>	* For default value, use <code>false</code>.
1166	>	* @throws IllegalArgumentException if parallelism less than or
1167	>	*         equal to zero, or greater than implementation limit
1168	>	* @throws NullPointerException if the factory is null
1169	>	* @throws SecurityException if a security manager exists and
1170	>	*         the caller is not permitted to modify threads
1171	>	*         because it does not hold {@link
1172	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1173	>	*/
1174	>	public ForkJoinPool(int parallelism,
1175	>	ForkJoinWorkerThreadFactory factory,
1176	>	Thread.UncaughtExceptionHandler handler,
1177	>	boolean asyncMode) {
1178		checkPermission();
1179	<	Thread.UncaughtExceptionHandler old = null;
1180	<	final ReentrantLock lock = this.workerLock;
1181	<	lock.lock();
1182	<	try {
1183	<	old = ueh;
1184	<	ueh = h;
1185	<	ForkJoinWorkerThread[] ws = workers;
1186	<	for (int i = 0; i < ws.length; ++i) {
1187	<	ForkJoinWorkerThread w = ws[i];
1188	<	if (w != null)
1189	<	w.setUncaughtExceptionHandler(h);
1190	<	}
1191	<	} finally {
1192	<	lock.unlock();
533	<	}
534	<	return old;
1179	>	if (factory == null)
1180	>	throw new NullPointerException();
1181	>	if (parallelism <= 0 || parallelism > MAX_THREADS)
1182	>	throw new IllegalArgumentException();
1183	>	this.parallelism = parallelism;
1184	>	this.factory = factory;
1185	>	this.ueh = handler;
1186	>	this.locallyFifo = asyncMode;
1187	>	int arraySize = initialArraySizeFor(parallelism);
1188	>	this.workers = new ForkJoinWorkerThread[arraySize];
1189	>	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
1190	>	this.workerLock = new ReentrantLock();
1191	>	this.termination = new Phaser(1);
1192	>	this.poolNumber = poolNumberGenerator.incrementAndGet();
1193		}
1194
1195		/**
1196	<	* Returns the handler for internal worker threads that terminate
1197	<	* due to unrecoverable errors encountered while executing tasks.
540	<	* @return the handler, or null if none
1196	>	* Returns initial power of two size for workers array.
1197	>	* @param pc the initial parallelism level
1198		*/
1199	<	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1200	<	Thread.UncaughtExceptionHandler h;
1201	<	final ReentrantLock lock = this.workerLock;
1202	<	lock.lock();
1203	<	try {
1204	<	h = ueh;
1205	<	} finally {
1206	<	lock.unlock();
550	<	}
551	<	return h;
1199	>	private static int initialArraySizeFor(int pc) {
1200	>	// See Hackers Delight, sec 3.2. We know MAX_THREADS < (1 >>> 16)
1201	>	int size = pc < MAX_THREADS ? pc + 1 : MAX_THREADS;
1202	>	size |= size >>> 1;
1203	>	size |= size >>> 2;
1204	>	size |= size >>> 4;
1205	>	size |= size >>> 8;
1206	>	return size + 1;
1207		}
1208
1209		// Execution methods
#	Line 557 | Line 1212 | public class ForkJoinPool extends Abstra
1212		* Common code for execute, invoke and submit
1213		*/
1214		private <T> void doSubmit(ForkJoinTask<T> task) {
1215	<	if (isShutdown())
1215	>	if (task == null)
1216	>	throw new NullPointerException();
1217	>	if (runState >= SHUTDOWN)
1218		throw new RejectedExecutionException();
1219	<	submissionQueue.offer(task);
1220	<	signalIdleWorkers(true);
1219	>	// Convert submissions to current pool into forks
1220	>	Thread t = Thread.currentThread();
1221	>	ForkJoinWorkerThread w;
1222	>	if ((t instanceof ForkJoinWorkerThread) &&
1223	>	(w = (ForkJoinWorkerThread) t).pool == this)
1224	>	w.pushTask(task);
1225	>	else {
1226	>	submissionQueue.offer(task);
1227	>	signalEvent();
1228	>	ensureEnoughTotalWorkers();
1229	>	}
1230		}
1231
1232		/**
1233	<	* Performs the given task; returning its result upon completion
1233	>	* Performs the given task, returning its result upon completion.
1234	>	* If the caller is already engaged in a fork/join computation in
1235	>	* the current pool, this method is equivalent in effect to
1236	>	* {@link ForkJoinTask#invoke}.
1237	>	*
1238		* @param task the task
1239		* @return the task's result
1240	<	* @throws NullPointerException if task is null
1241	<	* @throws RejectedExecutionException if pool is shut down
1240	>	* @throws NullPointerException if the task is null
1241	>	* @throws RejectedExecutionException if the task cannot be
1242	>	*         scheduled for execution
1243		*/
1244		public <T> T invoke(ForkJoinTask<T> task) {
1245		doSubmit(task);
#	Line 577 | Line 1248 | public class ForkJoinPool extends Abstra
1248
1249		/**
1250		* Arranges for (asynchronous) execution of the given task.
1251	+	* If the caller is already engaged in a fork/join computation in
1252	+	* the current pool, this method is equivalent in effect to
1253	+	* {@link ForkJoinTask#fork}.
1254	+	*
1255		* @param task the task
1256	<	* @throws NullPointerException if task is null
1257	<	* @throws RejectedExecutionException if pool is shut down
1256	>	* @throws NullPointerException if the task is null
1257	>	* @throws RejectedExecutionException if the task cannot be
1258	>	*         scheduled for execution
1259		*/
1260	<	public <T> void execute(ForkJoinTask<T> task) {
1260	>	public void execute(ForkJoinTask<?> task) {
1261		doSubmit(task);
1262		}
1263
1264		// AbstractExecutorService methods
1265
1266	+	/**
1267	+	* @throws NullPointerException if the task is null
1268	+	* @throws RejectedExecutionException if the task cannot be
1269	+	*         scheduled for execution
1270	+	*/
1271		public void execute(Runnable task) {
1272	<	doSubmit(new AdaptedRunnable<Void>(task, null));
1272	>	ForkJoinTask<?> job;
1273	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1274	>	job = (ForkJoinTask<?>) task;
1275	>	else
1276	>	job = ForkJoinTask.adapt(task, null);
1277	>	doSubmit(job);
1278	>	}
1279	>
1280	>	/**
1281	>	* Submits a ForkJoinTask for execution.
1282	>	* If the caller is already engaged in a fork/join computation in
1283	>	* the current pool, this method is equivalent in effect to
1284	>	* {@link ForkJoinTask#fork}.
1285	>	*
1286	>	* @param task the task to submit
1287	>	* @return the task
1288	>	* @throws NullPointerException if the task is null
1289	>	* @throws RejectedExecutionException if the task cannot be
1290	>	*         scheduled for execution
1291	>	*/
1292	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1293	>	doSubmit(task);
1294	>	return task;
1295		}
1296
1297	+	/**
1298	+	* @throws NullPointerException if the task is null
1299	+	* @throws RejectedExecutionException if the task cannot be
1300	+	*         scheduled for execution
1301	+	*/
1302		public <T> ForkJoinTask<T> submit(Callable<T> task) {
1303	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
1303	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1304		doSubmit(job);
1305		return job;
1306		}
1307
1308	+	/**
1309	+	* @throws NullPointerException if the task is null
1310	+	* @throws RejectedExecutionException if the task cannot be
1311	+	*         scheduled for execution
1312	+	*/
1313		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1314	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
1314	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1315		doSubmit(job);
1316		return job;
1317		}
1318
1319	+	/**
1320	+	* @throws NullPointerException if the task is null
1321	+	* @throws RejectedExecutionException if the task cannot be
1322	+	*         scheduled for execution
1323	+	*/
1324		public ForkJoinTask<?> submit(Runnable task) {
1325	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
1325	>	ForkJoinTask<?> job;
1326	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1327	>	job = (ForkJoinTask<?>) task;
1328	>	else
1329	>	job = ForkJoinTask.adapt(task, null);
1330		doSubmit(job);
1331		return job;
1332		}
1333
612	–	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
613	–	return new AdaptedRunnable(runnable, value);
614	–	}
615	–
616	–	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
617	–	return new AdaptedCallable(callable);
618	–	}
619	–
620	–	/**
621	–	* Adaptor for Runnables. This implements RunnableFuture
622	–	* to be compliant with AbstractExecutorService constraints
623	–	*/
624	–	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
625	–	implements RunnableFuture<T> {
626	–	final Runnable runnable;
627	–	final T resultOnCompletion;
628	–	T result;
629	–	AdaptedRunnable(Runnable runnable, T result) {
630	–	if (runnable == null) throw new NullPointerException();
631	–	this.runnable = runnable;
632	–	this.resultOnCompletion = result;
633	–	}
634	–	public T getRawResult() { return result; }
635	–	public void setRawResult(T v) { result = v; }
636	–	public boolean exec() {
637	–	runnable.run();
638	–	result = resultOnCompletion;
639	–	return true;
640	–	}
641	–	public void run() { invoke(); }
642	–	}
643	–
1334		/**
1335	<	* Adaptor for Callables
1335	>	* @throws NullPointerException       {@inheritDoc}
1336	>	* @throws RejectedExecutionException {@inheritDoc}
1337		*/
647	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
648	–	implements RunnableFuture<T> {
649	–	final Callable<T> callable;
650	–	T result;
651	–	AdaptedCallable(Callable<T> callable) {
652	–	if (callable == null) throw new NullPointerException();
653	–	this.callable = callable;
654	–	}
655	–	public T getRawResult() { return result; }
656	–	public void setRawResult(T v) { result = v; }
657	–	public boolean exec() {
658	–	try {
659	–	result = callable.call();
660	–	return true;
661	–	} catch (Error err) {
662	–	throw err;
663	–	} catch (RuntimeException rex) {
664	–	throw rex;
665	–	} catch (Exception ex) {
666	–	throw new RuntimeException(ex);
667	–	}
668	–	}
669	–	public void run() { invoke(); }
670	–	}
671	–
1338		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
1339	<	ArrayList<ForkJoinTask<T>> ts =
1339	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
1340		new ArrayList<ForkJoinTask<T>>(tasks.size());
1341	<	for (Callable<T> c : tasks)
1342	<	ts.add(new AdaptedCallable<T>(c));
1343	<	invoke(new InvokeAll<T>(ts));
1344	<	return (List<Future<T>>)(List)ts;
1341	>	for (Callable<T> task : tasks)
1342	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
1343	>	invoke(new InvokeAll<T>(forkJoinTasks));
1344	>
1345	>	@SuppressWarnings({"unchecked", "rawtypes"})
1346	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1347	>	return futures;
1348		}
1349
1350		static final class InvokeAll<T> extends RecursiveAction {
1351		final ArrayList<ForkJoinTask<T>> tasks;
1352		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
1353		public void compute() {
1354	<	try { invokeAll(tasks); } catch(Exception ignore) {}
1354	>	try { invokeAll(tasks); }
1355	>	catch (Exception ignore) {}
1356		}
1357	+	private static final long serialVersionUID = -7914297376763021607L;
1358		}
1359
689	–	// Configuration and status settings and queries
690	–
1360		/**
1361	<	* Returns the factory used for constructing new workers
1361	>	* Returns the factory used for constructing new workers.
1362		*
1363		* @return the factory used for constructing new workers
1364		*/
#	Line 698 | Line 1367 | public class ForkJoinPool extends Abstra
1367		}
1368
1369		/**
1370	<	* Sets the target paralleism level of this pool.
1371	<	* @param parallelism the target parallelism
1372	<	* @throws IllegalArgumentException if parallelism less than or
1373	<	* equal to zero or greater than maximum size bounds.
705	<	* @throws SecurityException if a security manager exists and
706	<	*         the caller is not permitted to modify threads
707	<	*         because it does not hold {@link
708	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1370	>	* Returns the handler for internal worker threads that terminate
1371	>	* due to unrecoverable errors encountered while executing tasks.
1372	>	*
1373	>	* @return the handler, or {@code null} if none
1374		*/
1375	<	public void setParallelism(int parallelism) {
1376	<	checkPermission();
712	<	if (parallelism <= 0 || parallelism > maxPoolSize)
713	<	throw new IllegalArgumentException();
714	<	final ReentrantLock lock = this.workerLock;
715	<	lock.lock();
716	<	try {
717	<	if (!isTerminating()) {
718	<	int p = this.parallelism;
719	<	this.parallelism = parallelism;
720	<	if (parallelism > p)
721	<	createAndStartAddedWorkers();
722	<	else
723	<	trimSpares();
724	<	}
725	<	} finally {
726	<	lock.unlock();
727	<	}
728	<	signalIdleWorkers(false);
1375	>	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1376	>	return ueh;
1377		}
1378
1379		/**
1380	<	* Returns the targeted number of worker threads in this pool.
733	<	* This value does not necessarily reflect transient changes as
734	<	* threads are added, removed, or abruptly terminate.
1380	>	* Returns the targeted parallelism level of this pool.
1381		*
1382	<	* @return the targeted number of worker threads in this pool
1382	>	* @return the targeted parallelism level of this pool
1383		*/
1384		public int getParallelism() {
1385		return parallelism;
#	Line 742 | Line 1388 | public class ForkJoinPool extends Abstra
1388		/**
1389		* Returns the number of worker threads that have started but not
1390		* yet terminated.  This result returned by this method may differ
1391	<	* from <tt>getParallelism</tt> when threads are created to
1391	>	* from {@link #getParallelism} when threads are created to
1392		* maintain parallelism when others are cooperatively blocked.
1393		*
1394		* @return the number of worker threads
1395		*/
1396		public int getPoolSize() {
1397	<	return totalCountOf(workerCounts);
752	<	}
753	<
754	<	/**
755	<	* Returns the maximum number of threads allowed to exist in the
756	<	* pool, even if there are insufficient unblocked running threads.
757	<	* @return the maximum
758	<	*/
759	<	public int getMaximumPoolSize() {
760	<	return maxPoolSize;
761	<	}
762	<
763	<	/**
764	<	* Sets the maximum number of threads allowed to exist in the
765	<	* pool, even if there are insufficient unblocked running threads.
766	<	* Setting this value has no effect on current pool size. It
767	<	* controls construction of new threads.
768	<	* @throws IllegalArgumentException if negative or greater then
769	<	* internal implementation limit.
770	<	*/
771	<	public void setMaximumPoolSize(int newMax) {
772	<	if (newMax < 0 || newMax > MAX_THREADS)
773	<	throw new IllegalArgumentException();
774	<	maxPoolSize = newMax;
775	<	}
776	<
777	<
778	<	/**
779	<	* Returns true if this pool dynamically maintains its target
780	<	* parallelism level. If false, new threads are added only to
781	<	* avoid possible starvation.
782	<	* This setting is by default true;
783	<	* @return true if maintains parallelism
784	<	*/
785	<	public boolean getMaintainsParallelism() {
786	<	return maintainsParallelism;
1397	>	return workerCounts >>> TOTAL_COUNT_SHIFT;
1398		}
1399
1400		/**
1401	<	* Sets whether this pool dynamically maintains its target
1402	<	* parallelism level. If false, new threads are added only to
1403	<	* avoid possible starvation.
1404	<	* @param enable true to maintains parallelism
1401	>	* Returns {@code true} if this pool uses local first-in-first-out
1402	>	* scheduling mode for forked tasks that are never joined.
1403	>	*
1404	>	* @return {@code true} if this pool uses async mode
1405		*/
1406	<	public void setMaintainsParallelism(boolean enable) {
1407	<	maintainsParallelism = enable;
1406	>	public boolean getAsyncMode() {
1407	>	return locallyFifo;
1408		}
1409
1410		/**
1411	<	* Returns the approximate number of worker threads that are not
1412	<	* blocked waiting to join tasks or for other managed
1413	<	* synchronization.
1411	>	* Returns an estimate of the number of worker threads that are
1412	>	* not blocked waiting to join tasks or for other managed
1413	>	* synchronization. This method may overestimate the
1414	>	* number of running threads.
1415		*
1416		* @return the number of worker threads
1417		*/
1418		public int getRunningThreadCount() {
1419	<	return runningCountOf(workerCounts);
1419	>	return workerCounts & RUNNING_COUNT_MASK;
1420		}
1421
1422		/**
1423	<	* Returns the approximate number of threads that are currently
1423	>	* Returns an estimate of the number of threads that are currently
1424		* stealing or executing tasks. This method may overestimate the
1425		* number of active threads.
1426	<	* @return the number of active threads.
1426	>	*
1427	>	* @return the number of active threads
1428		*/
1429		public int getActiveThreadCount() {
1430	<	return activeCountOf(runControl);
1430	>	return runState & ACTIVE_COUNT_MASK;
1431		}
1432
1433		/**
1434	<	* Returns the approximate number of threads that are currently
1435	<	* idle waiting for tasks. This method may underestimate the
1436	<	* number of idle threads.
1437	<	* @return the number of idle threads.
1438	<	*/
1439	<	final int getIdleThreadCount() {
1440	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
1441	<	return (c <= 0)? 0 : c;
1442	<	}
830	<
831	<	/**
832	<	* Returns true if all worker threads are currently idle. An idle
833	<	* worker is one that cannot obtain a task to execute because none
834	<	* are available to steal from other threads, and there are no
835	<	* pending submissions to the pool. This method is conservative:
836	<	* It might not return true immediately upon idleness of all
837	<	* threads, but will eventually become true if threads remain
838	<	* inactive.
839	<	* @return true if all threads are currently idle
1434	>	* Returns {@code true} if all worker threads are currently idle.
1435	>	* An idle worker is one that cannot obtain a task to execute
1436	>	* because none are available to steal from other threads, and
1437	>	* there are no pending submissions to the pool. This method is
1438	>	* conservative; it might not return {@code true} immediately upon
1439	>	* idleness of all threads, but will eventually become true if
1440	>	* threads remain inactive.
1441	>	*
1442	>	* @return {@code true} if all threads are currently idle
1443		*/
1444		public boolean isQuiescent() {
1445	<	return activeCountOf(runControl) == 0;
1445	>	return (runState & ACTIVE_COUNT_MASK) == 0;
1446		}
1447
1448		/**
#	Line 847 | Line 1450 | public class ForkJoinPool extends Abstra
1450		* one thread's work queue by another. The reported value
1451		* underestimates the actual total number of steals when the pool
1452		* is not quiescent. This value may be useful for monitoring and
1453	<	* tuning fork/join programs: In general, steal counts should be
1453	>	* tuning fork/join programs: in general, steal counts should be
1454		* high enough to keep threads busy, but low enough to avoid
1455		* overhead and contention across threads.
1456	<	* @return the number of steals.
1456	>	*
1457	>	* @return the number of steals
1458		*/
1459		public long getStealCount() {
1460	<	return stealCount.get();
857	<	}
858	<
859	<	/**
860	<	* Accumulate steal count from a worker. Call only
861	<	* when worker known to be idle.
862	<	*/
863	<	private void updateStealCount(ForkJoinWorkerThread w) {
864	<	int sc = w.getAndClearStealCount();
865	<	if (sc != 0)
866	<	stealCount.addAndGet(sc);
1460	>	return stealCount;
1461		}
1462
1463		/**
1464	<	* Returns the total number of tasks currently held in queues by
1465	<	* worker threads (but not including tasks submitted to the pool
1466	<	* that have not begun executing). This value is only an
1467	<	* approximation, obtained by iterating across all threads in the
1468	<	* pool. This method may be useful for tuning task granularities.
1469	<	* @return the number of queued tasks.
1464	>	* Returns an estimate of the total number of tasks currently held
1465	>	* in queues by worker threads (but not including tasks submitted
1466	>	* to the pool that have not begun executing). This value is only
1467	>	* an approximation, obtained by iterating across all threads in
1468	>	* the pool. This method may be useful for tuning task
1469	>	* granularities.
1470	>	*
1471	>	* @return the number of queued tasks
1472		*/
1473		public long getQueuedTaskCount() {
1474		long count = 0;
1475		ForkJoinWorkerThread[] ws = workers;
1476	<	for (int i = 0; i < ws.length; ++i) {
1477	<	ForkJoinWorkerThread t = ws[i];
1478	<	if (t != null)
1479	<	count += t.getQueueSize();
1476	>	int nws = ws.length;
1477	>	for (int i = 0; i < nws; ++i) {
1478	>	ForkJoinWorkerThread w = ws[i];
1479	>	if (w != null)
1480	>	count += w.getQueueSize();
1481		}
1482		return count;
1483		}
1484
1485		/**
1486	<	* Returns the approximate number tasks submitted to this pool
1487	<	* that have not yet begun executing. This method takes time
1486	>	* Returns an estimate of the number of tasks submitted to this
1487	>	* pool that have not yet begun executing.  This method takes time
1488		* proportional to the number of submissions.
1489	<	* @return the number of queued submissions.
1489	>	*
1490	>	* @return the number of queued submissions
1491		*/
1492		public int getQueuedSubmissionCount() {
1493		return submissionQueue.size();
1494		}
1495
1496		/**
1497	<	* Returns true if there are any tasks submitted to this pool
1498	<	* that have not yet begun executing.
1499	<	* @return <tt>true</tt> if there are any queued submissions.
1497	>	* Returns {@code true} if there are any tasks submitted to this
1498	>	* pool that have not yet begun executing.
1499	>	*
1500	>	* @return {@code true} if there are any queued submissions
1501		*/
1502		public boolean hasQueuedSubmissions() {
1503		return !submissionQueue.isEmpty();
#	Line 908 | Line 1507 | public class ForkJoinPool extends Abstra
1507		* Removes and returns the next unexecuted submission if one is
1508		* available.  This method may be useful in extensions to this
1509		* class that re-assign work in systems with multiple pools.
1510	<	* @return the next submission, or null if none
1510	>	*
1511	>	* @return the next submission, or {@code null} if none
1512		*/
1513		protected ForkJoinTask<?> pollSubmission() {
1514		return submissionQueue.poll();
1515		}
1516
1517		/**
1518	+	* Removes all available unexecuted submitted and forked tasks
1519	+	* from scheduling queues and adds them to the given collection,
1520	+	* without altering their execution status. These may include
1521	+	* artificially generated or wrapped tasks. This method is
1522	+	* designed to be invoked only when the pool is known to be
1523	+	* quiescent. Invocations at other times may not remove all
1524	+	* tasks. A failure encountered while attempting to add elements
1525	+	* to collection {@code c} may result in elements being in
1526	+	* neither, either or both collections when the associated
1527	+	* exception is thrown.  The behavior of this operation is
1528	+	* undefined if the specified collection is modified while the
1529	+	* operation is in progress.
1530	+	*
1531	+	* @param c the collection to transfer elements into
1532	+	* @return the number of elements transferred
1533	+	*/
1534	+	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1535	+	int n = submissionQueue.drainTo(c);
1536	+	ForkJoinWorkerThread[] ws = workers;
1537	+	int nws = ws.length;
1538	+	for (int i = 0; i < nws; ++i) {
1539	+	ForkJoinWorkerThread w = ws[i];
1540	+	if (w != null)
1541	+	n += w.drainTasksTo(c);
1542	+	}
1543	+	return n;
1544	+	}
1545	+
1546	+	/**
1547	+	* Returns count of total parks by existing workers.
1548	+	* Used during development only since not meaningful to users.
1549	+	*/
1550	+	private int collectParkCount() {
1551	+	int count = 0;
1552	+	ForkJoinWorkerThread[] ws = workers;
1553	+	int nws = ws.length;
1554	+	for (int i = 0; i < nws; ++i) {
1555	+	ForkJoinWorkerThread w = ws[i];
1556	+	if (w != null)
1557	+	count += w.parkCount;
1558	+	}
1559	+	return count;
1560	+	}
1561	+
1562	+	/**
1563		* Returns a string identifying this pool, as well as its state,
1564		* including indications of run state, parallelism level, and
1565		* worker and task counts.
#	Line 922 | Line 1567 | public class ForkJoinPool extends Abstra
1567		* @return a string identifying this pool, as well as its state
1568		*/
1569		public String toString() {
925	–	int ps = parallelism;
926	–	int wc = workerCounts;
927	–	int rc = runControl;
1570		long st = getStealCount();
1571		long qt = getQueuedTaskCount();
1572		long qs = getQueuedSubmissionCount();
1573	+	int wc = workerCounts;
1574	+	int tc = wc >>> TOTAL_COUNT_SHIFT;
1575	+	int rc = wc & RUNNING_COUNT_MASK;
1576	+	int pc = parallelism;
1577	+	int rs = runState;
1578	+	int ac = rs & ACTIVE_COUNT_MASK;
1579	+	//        int pk = collectParkCount();
1580		return super.toString() +
1581	<	"[" + runStateToString(runStateOf(rc)) +
1582	<	", parallelism = " + ps +
1583	<	", size = " + totalCountOf(wc) +
1584	<	", active = " + activeCountOf(rc) +
1585	<	", running = " + runningCountOf(wc) +
1581	>	"[" + runLevelToString(rs) +
1582	>	", parallelism = " + pc +
1583	>	", size = " + tc +
1584	>	", active = " + ac +
1585	>	", running = " + rc +
1586		", steals = " + st +
1587		", tasks = " + qt +
1588		", submissions = " + qs +
1589	+	//            ", parks = " + pk +
1590		"]";
1591		}
1592
1593	<	private static String runStateToString(int rs) {
1594	<	switch(rs) {
1595	<	case RUNNING: return "Running";
1596	<	case SHUTDOWN: return "Shutting down";
1597	<	case TERMINATING: return "Terminating";
948	<	case TERMINATED: return "Terminated";
949	<	default: throw new Error("Unknown run state");
950	<	}
1593	>	private static String runLevelToString(int s) {
1594	>	return ((s & TERMINATED) != 0 ? "Terminated" :
1595	>	((s & TERMINATING) != 0 ? "Terminating" :
1596	>	((s & SHUTDOWN) != 0 ? "Shutting down" :
1597	>	"Running")));
1598		}
1599
953	–	// lifecycle control
954	–
1600		/**
1601		* Initiates an orderly shutdown in which previously submitted
1602		* tasks are executed, but no new tasks will be accepted.
1603		* Invocation has no additional effect if already shut down.
1604		* Tasks that are in the process of being submitted concurrently
1605		* during the course of this method may or may not be rejected.
1606	+	*
1607		* @throws SecurityException if a security manager exists and
1608		*         the caller is not permitted to modify threads
1609		*         because it does not hold {@link
1610	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1610	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1611		*/
1612		public void shutdown() {
1613		checkPermission();
1614	<	transitionRunStateTo(SHUTDOWN);
1615	<	if (canTerminateOnShutdown(runControl))
970	<	terminateOnShutdown();
1614	>	advanceRunLevel(SHUTDOWN);
1615	>	tryTerminate(false);
1616		}
1617
1618		/**
1619	<	* Attempts to stop all actively executing tasks, and cancels all
1620	<	* waiting tasks.  Tasks that are in the process of being
1621	<	* submitted or executed concurrently during the course of this
1622	<	* method may or may not be rejected. Unlike some other executors,
1623	<	* this method cancels rather than collects non-executed tasks,
1624	<	* so always returns an empty list.
1619	>	* Attempts to cancel and/or stop all tasks, and reject all
1620	>	* subsequently submitted tasks.  Tasks that are in the process of
1621	>	* being submitted or executed concurrently during the course of
1622	>	* this method may or may not be rejected. This method cancels
1623	>	* both existing and unexecuted tasks, in order to permit
1624	>	* termination in the presence of task dependencies. So the method
1625	>	* always returns an empty list (unlike the case for some other
1626	>	* Executors).
1627	>	*
1628		* @return an empty list
1629		* @throws SecurityException if a security manager exists and
1630		*         the caller is not permitted to modify threads
1631		*         because it does not hold {@link
1632	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1632	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1633		*/
1634		public List<Runnable> shutdownNow() {
1635		checkPermission();
1636	<	terminate();
1636	>	tryTerminate(true);
1637		return Collections.emptyList();
1638		}
1639
1640		/**
1641	<	* Returns <tt>true</tt> if all tasks have completed following shut down.
1641	>	* Returns {@code true} if all tasks have completed following shut down.
1642		*
1643	<	* @return <tt>true</tt> if all tasks have completed following shut down
1643	>	* @return {@code true} if all tasks have completed following shut down
1644		*/
1645		public boolean isTerminated() {
1646	<	return runStateOf(runControl) == TERMINATED;
1646	>	return runState >= TERMINATED;
1647		}
1648
1649		/**
1650	<	* Returns <tt>true</tt> if the process of termination has
1651	<	* commenced but possibly not yet completed.
1650	>	* Returns {@code true} if the process of termination has
1651	>	* commenced but not yet completed.  This method may be useful for
1652	>	* debugging. A return of {@code true} reported a sufficient
1653	>	* period after shutdown may indicate that submitted tasks have
1654	>	* ignored or suppressed interruption, causing this executor not
1655	>	* to properly terminate.
1656		*
1657	<	* @return <tt>true</tt> if terminating
1657	>	* @return {@code true} if terminating but not yet terminated
1658		*/
1659		public boolean isTerminating() {
1660	<	return runStateOf(runControl) >= TERMINATING;
1660	>	return (runState & (TERMINATING|TERMINATED)) == TERMINATING;
1661		}
1662
1663		/**
1664	<	* Returns <tt>true</tt> if this pool has been shut down.
1664	>	* Returns {@code true} if this pool has been shut down.
1665		*
1666	<	* @return <tt>true</tt> if this pool has been shut down
1666	>	* @return {@code true} if this pool has been shut down
1667		*/
1668		public boolean isShutdown() {
1669	<	return runStateOf(runControl) >= SHUTDOWN;
1669	>	return runState >= SHUTDOWN;
1670		}
1671
1672		/**
#	Line 1024 | Line 1676 | public class ForkJoinPool extends Abstra
1676		*
1677		* @param timeout the maximum time to wait
1678		* @param unit the time unit of the timeout argument
1679	<	* @return <tt>true</tt> if this executor terminated and
1680	<	*         <tt>false</tt> if the timeout elapsed before termination
1679	>	* @return {@code true} if this executor terminated and
1680	>	*         {@code false} if the timeout elapsed before termination
1681		* @throws InterruptedException if interrupted while waiting
1682		*/
1683		public boolean awaitTermination(long timeout, TimeUnit unit)
1684		throws InterruptedException {
1033	–	long nanos = unit.toNanos(timeout);
1034	–	final ReentrantLock lock = this.workerLock;
1035	–	lock.lock();
1036	–	try {
1037	–	for (;;) {
1038	–	if (isTerminated())
1039	–	return true;
1040	–	if (nanos <= 0)
1041	–	return false;
1042	–	nanos = termination.awaitNanos(nanos);
1043	–	}
1044	–	} finally {
1045	–	lock.unlock();
1046	–	}
1047	–	}
1048	–
1049	–	// Shutdown and termination support
1050	–
1051	–	/**
1052	–	* Callback from terminating worker. Null out the corresponding
1053	–	* workers slot, and if terminating, try to terminate, else try to
1054	–	* shrink workers array.
1055	–	* @param w the worker
1056	–	*/
1057	–	final void workerTerminated(ForkJoinWorkerThread w) {
1058	–	updateStealCount(w);
1059	–	updateWorkerCount(-1);
1060	–	final ReentrantLock lock = this.workerLock;
1061	–	lock.lock();
1685		try {
1686	<	ForkJoinWorkerThread[] ws = workers;
1687	<	int idx = w.poolIndex;
1065	<	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1066	<	ws[idx] = null;
1067	<	if (totalCountOf(workerCounts) == 0) {
1068	<	terminate(); // no-op if already terminating
1069	<	transitionRunStateTo(TERMINATED);
1070	<	termination.signalAll();
1071	<	}
1072	<	else if (!isTerminating()) {
1073	<	tryShrinkWorkerArray();
1074	<	tryResumeSpare(true); // allow replacement
1075	<	}
1076	<	} finally {
1077	<	lock.unlock();
1078	<	}
1079	<	signalIdleWorkers(false);
1080	<	}
1081	<
1082	<	/**
1083	<	* Initiate termination.
1084	<	*/
1085	<	private void terminate() {
1086	<	if (transitionRunStateTo(TERMINATING)) {
1087	<	stopAllWorkers();
1088	<	resumeAllSpares();
1089	<	signalIdleWorkers(true);
1090	<	cancelQueuedSubmissions();
1091	<	cancelQueuedWorkerTasks();
1092	<	interruptUnterminatedWorkers();
1093	<	signalIdleWorkers(true); // resignal after interrupt
1094	<	}
1095	<	}
1096	<
1097	<	/**
1098	<	* Possibly terminate when on shutdown state
1099	<	*/
1100	<	private void terminateOnShutdown() {
1101	<	if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
1102	<	terminate();
1103	<	}
1104	<
1105	<	/**
1106	<	* Clear out and cancel submissions
1107	<	*/
1108	<	private void cancelQueuedSubmissions() {
1109	<	ForkJoinTask<?> task;
1110	<	while ((task = pollSubmission()) != null)
1111	<	task.cancel(false);
1112	<	}
1113	<
1114	<	/**
1115	<	* Clean out worker queues.
1116	<	*/
1117	<	private void cancelQueuedWorkerTasks() {
1118	<	final ReentrantLock lock = this.workerLock;
1119	<	lock.lock();
1120	<	try {
1121	<	ForkJoinWorkerThread[] ws = workers;
1122	<	for (int i = 0; i < ws.length; ++i) {
1123	<	ForkJoinWorkerThread t = ws[i];
1124	<	if (t != null)
1125	<	t.cancelTasks();
1126	<	}
1127	<	} finally {
1128	<	lock.unlock();
1129	<	}
1130	<	}
1131	<
1132	<	/**
1133	<	* Set each worker's status to terminating. Requires lock to avoid
1134	<	* conflicts with add/remove
1135	<	*/
1136	<	private void stopAllWorkers() {
1137	<	final ReentrantLock lock = this.workerLock;
1138	<	lock.lock();
1139	<	try {
1140	<	ForkJoinWorkerThread[] ws = workers;
1141	<	for (int i = 0; i < ws.length; ++i) {
1142	<	ForkJoinWorkerThread t = ws[i];
1143	<	if (t != null)
1144	<	t.shutdownNow();
1145	<	}
1146	<	} finally {
1147	<	lock.unlock();
1148	<	}
1149	<	}
1150	<
1151	<	/**
1152	<	* Interrupt all unterminated workers.  This is not required for
1153	<	* sake of internal control, but may help unstick user code during
1154	<	* shutdown.
1155	<	*/
1156	<	private void interruptUnterminatedWorkers() {
1157	<	final ReentrantLock lock = this.workerLock;
1158	<	lock.lock();
1159	<	try {
1160	<	ForkJoinWorkerThread[] ws = workers;
1161	<	for (int i = 0; i < ws.length; ++i) {
1162	<	ForkJoinWorkerThread t = ws[i];
1163	<	if (t != null && !t.isTerminated()) {
1164	<	try {
1165	<	t.interrupt();
1166	<	} catch (SecurityException ignore) {
1167	<	}
1168	<	}
1169	<	}
1170	<	} finally {
1171	<	lock.unlock();
1172	<	}
1173	<	}
1174	<
1175	<
1176	<	/*
1177	<	* Nodes for event barrier to manage idle threads.
1178	<	*
1179	<	* The event barrier has an event count and a wait queue (actually
1180	<	* a Treiber stack).  Workers are enabled to look for work when
1181	<	* the eventCount is incremented. If they fail to find some,
1182	<	* they may wait for next count. Synchronization events occur only
1183	<	* in enough contexts to maintain overall liveness:
1184	<	*
1185	<	*   - Submission of a new task to the pool
1186	<	*   - Creation or termination of a worker
1187	<	*   - pool termination
1188	<	*   - A worker pushing a task on an empty queue
1189	<	*
1190	<	* The last case (pushing a task) occurs often enough, and is
1191	<	* heavy enough compared to simple stack pushes to require some
1192	<	* special handling: Method signalNonEmptyWorkerQueue returns
1193	<	* without advancing count if the queue appears to be empty.  This
1194	<	* would ordinarily result in races causing some queued waiters
1195	<	* not to be woken up. To avoid this, a worker in sync
1196	<	* rescans for tasks after being enqueued if it was the first to
1197	<	* enqueue, and aborts the wait if finding one, also helping to
1198	<	* signal others. This works well because the worker has nothing
1199	<	* better to do anyway, and so might as well help alleviate the
1200	<	* overhead and contention on the threads actually doing work.
1201	<	*
1202	<	* Queue nodes are basic Treiber stack nodes, also used for spare
1203	<	* stack.
1204	<	*/
1205	<	static final class WaitQueueNode {
1206	<	WaitQueueNode next; // only written before enqueued
1207	<	volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1208	<	final long count; // unused for spare stack
1209	<	WaitQueueNode(ForkJoinWorkerThread w, long c) {
1210	<	count = c;
1211	<	thread = w;
1212	<	}
1213	<	final boolean signal() {
1214	<	ForkJoinWorkerThread t = thread;
1215	<	thread = null;
1216	<	if (t != null) {
1217	<	LockSupport.unpark(t);
1218	<	return true;
1219	<	}
1686	>	return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1687	>	} catch(TimeoutException ex) {
1688		return false;
1689		}
1690		}
1691
1692		/**
1225	–	* Release at least one thread waiting for event count to advance,
1226	–	* if one exists. If initial attempt fails, release all threads.
1227	–	* @param all if false, at first try to only release one thread
1228	–	* @return current event
1229	–	*/
1230	–	private long releaseIdleWorkers(boolean all) {
1231	–	long c;
1232	–	for (;;) {
1233	–	WaitQueueNode q = barrierStack;
1234	–	c = eventCount;
1235	–	long qc;
1236	–	if (q == null || (qc = q.count) >= c)
1237	–	break;
1238	–	if (!all) {
1239	–	if (casBarrierStack(q, q.next) && q.signal())
1240	–	break;
1241	–	all = true;
1242	–	}
1243	–	else if (casBarrierStack(q, null)) {
1244	–	do {
1245	–	q.signal();
1246	–	} while ((q = q.next) != null);
1247	–	break;
1248	–	}
1249	–	}
1250	–	return c;
1251	–	}
1252	–
1253	–	/**
1254	–	* Returns current barrier event count
1255	–	* @return current barrier event count
1256	–	*/
1257	–	final long getEventCount() {
1258	–	long ec = eventCount;
1259	–	releaseIdleWorkers(true); // release to ensure accurate result
1260	–	return ec;
1261	–	}
1262	–
1263	–	/**
1264	–	* Increment event count and release at least one waiting thread,
1265	–	* if one exists (released threads will in turn wake up others).
1266	–	* @param all if true, try to wake up all
1267	–	*/
1268	–	final void signalIdleWorkers(boolean all) {
1269	–	long c;
1270	–	do;while (!casEventCount(c = eventCount, c+1));
1271	–	releaseIdleWorkers(all);
1272	–	}
1273	–
1274	–	/**
1275	–	* Wake up threads waiting to steal a task. Because method
1276	–	* sync rechecks availability, it is OK to only proceed if
1277	–	* queue appears to be non-empty.
1278	–	*/
1279	–	final void signalNonEmptyWorkerQueue() {
1280	–	// If CAS fails another signaller must have succeeded
1281	–	long c;
1282	–	if (barrierStack != null && casEventCount(c = eventCount, c+1))
1283	–	releaseIdleWorkers(false);
1284	–	}
1285	–
1286	–	/**
1287	–	* Waits until event count advances from count, or some thread is
1288	–	* waiting on a previous count, or there is stealable work
1289	–	* available. Help wake up others on release.
1290	–	* @param w the calling worker thread
1291	–	* @param prev previous value returned by sync (or 0)
1292	–	* @return current event count
1293	–	*/
1294	–	final long sync(ForkJoinWorkerThread w, long prev) {
1295	–	updateStealCount(w);
1296	–
1297	–	while (!w.isShutdown() && !isTerminating() &&
1298	–	(parallelism >= runningCountOf(workerCounts) ||
1299	–	!suspendIfSpare(w))) { // prefer suspend to waiting here
1300	–	WaitQueueNode node = null;
1301	–	boolean queued = false;
1302	–	for (;;) {
1303	–	if (!queued) {
1304	–	if (eventCount != prev)
1305	–	break;
1306	–	WaitQueueNode h = barrierStack;
1307	–	if (h != null && h.count != prev)
1308	–	break; // release below and maybe retry
1309	–	if (node == null)
1310	–	node = new WaitQueueNode(w, prev);
1311	–	queued = casBarrierStack(node.next = h, node);
1312	–	}
1313	–	else if (Thread.interrupted() ||
1314	–	node.thread == null ||
1315	–	(node.next == null && w.prescan()) ||
1316	–	eventCount != prev) {
1317	–	node.thread = null;
1318	–	if (eventCount == prev) // help trigger
1319	–	casEventCount(prev, prev+1);
1320	–	break;
1321	–	}
1322	–	else
1323	–	LockSupport.park(this);
1324	–	}
1325	–	long ec = eventCount;
1326	–	if (releaseIdleWorkers(false) != prev)
1327	–	return ec;
1328	–	}
1329	–	return prev; // return old count if aborted
1330	–	}
1331	–
1332	–	//  Parallelism maintenance
1333	–
1334	–	/**
1335	–	* Decrement running count; if too low, add spare.
1336	–	*
1337	–	* Conceptually, all we need to do here is add or resume a
1338	–	* spare thread when one is about to block (and remove or
1339	–	* suspend it later when unblocked -- see suspendIfSpare).
1340	–	* However, implementing this idea requires coping with
1341	–	* several problems: We have imperfect information about the
1342	–	* states of threads. Some count updates can and usually do
1343	–	* lag run state changes, despite arrangements to keep them
1344	–	* accurate (for example, when possible, updating counts
1345	–	* before signalling or resuming), especially when running on
1346	–	* dynamic JVMs that don't optimize the infrequent paths that
1347	–	* update counts. Generating too many threads can make these
1348	–	* problems become worse, because excess threads are more
1349	–	* likely to be context-switched with others, slowing them all
1350	–	* down, especially if there is no work available, so all are
1351	–	* busy scanning or idling.  Also, excess spare threads can
1352	–	* only be suspended or removed when they are idle, not
1353	–	* immediately when they aren't needed. So adding threads will
1354	–	* raise parallelism level for longer than necessary.  Also,
1355	–	* FJ applications often enounter highly transient peaks when
1356	–	* many threads are blocked joining, but for less time than it
1357	–	* takes to create or resume spares.
1358	–	*
1359	–	* @param joinMe if non-null, return early if done
1360	–	* @param maintainParallelism if true, try to stay within
1361	–	* target counts, else create only to avoid starvation
1362	–	* @return true if joinMe known to be done
1363	–	*/
1364	–	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1365	–	maintainParallelism &= maintainsParallelism; // overrride
1366	–	boolean dec = false;  // true when running count decremented
1367	–	while (spareStack == null || !tryResumeSpare(dec)) {
1368	–	int counts = workerCounts;
1369	–	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1370	–	if (!needSpare(counts, maintainParallelism))
1371	–	break;
1372	–	if (joinMe.status < 0)
1373	–	return true;
1374	–	if (tryAddSpare(counts))
1375	–	break;
1376	–	}
1377	–	}
1378	–	return false;
1379	–	}
1380	–
1381	–	/**
1382	–	* Same idea as preJoin
1383	–	*/
1384	–	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1385	–	maintainParallelism &= maintainsParallelism;
1386	–	boolean dec = false;
1387	–	while (spareStack == null || !tryResumeSpare(dec)) {
1388	–	int counts = workerCounts;
1389	–	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1390	–	if (!needSpare(counts, maintainParallelism))
1391	–	break;
1392	–	if (blocker.isReleasable())
1393	–	return true;
1394	–	if (tryAddSpare(counts))
1395	–	break;
1396	–	}
1397	–	}
1398	–	return false;
1399	–	}
1400	–
1401	–	/**
1402	–	* Returns true if a spare thread appears to be needed.  If
1403	–	* maintaining parallelism, returns true when the deficit in
1404	–	* running threads is more than the surplus of total threads, and
1405	–	* there is apparently some work to do.  This self-limiting rule
1406	–	* means that the more threads that have already been added, the
1407	–	* less parallelism we will tolerate before adding another.
1408	–	* @param counts current worker counts
1409	–	* @param maintainParallelism try to maintain parallelism
1410	–	*/
1411	–	private boolean needSpare(int counts, boolean maintainParallelism) {
1412	–	int ps = parallelism;
1413	–	int rc = runningCountOf(counts);
1414	–	int tc = totalCountOf(counts);
1415	–	int runningDeficit = ps - rc;
1416	–	int totalSurplus = tc - ps;
1417	–	return (tc < maxPoolSize &&
1418	–	(rc == 0 || totalSurplus < 0 ||
1419	–	(maintainParallelism &&
1420	–	runningDeficit > totalSurplus && mayHaveQueuedWork())));
1421	–	}
1422	–
1423	–	/**
1424	–	* Returns true if at least one worker queue appears to be
1425	–	* nonempty. This is expensive but not often called. It is not
1426	–	* critical that this be accurate, but if not, more or fewer
1427	–	* running threads than desired might be maintained.
1428	–	*/
1429	–	private boolean mayHaveQueuedWork() {
1430	–	ForkJoinWorkerThread[] ws = workers;
1431	–	int len = ws.length;
1432	–	ForkJoinWorkerThread v;
1433	–	for (int i = 0; i < len; ++i) {
1434	–	if ((v = ws[i]) != null && v.getRawQueueSize() > 0) {
1435	–	releaseIdleWorkers(false); // help wake up stragglers
1436	–	return true;
1437	–	}
1438	–	}
1439	–	return false;
1440	–	}
1441	–
1442	–	/**
1443	–	* Add a spare worker if lock available and no more than the
1444	–	* expected numbers of threads exist
1445	–	* @return true if successful
1446	–	*/
1447	–	private boolean tryAddSpare(int expectedCounts) {
1448	–	final ReentrantLock lock = this.workerLock;
1449	–	int expectedRunning = runningCountOf(expectedCounts);
1450	–	int expectedTotal = totalCountOf(expectedCounts);
1451	–	boolean success = false;
1452	–	boolean locked = false;
1453	–	// confirm counts while locking; CAS after obtaining lock
1454	–	try {
1455	–	for (;;) {
1456	–	int s = workerCounts;
1457	–	int tc = totalCountOf(s);
1458	–	int rc = runningCountOf(s);
1459	–	if (rc > expectedRunning || tc > expectedTotal)
1460	–	break;
1461	–	if (!locked && !(locked = lock.tryLock()))
1462	–	break;
1463	–	if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) {
1464	–	createAndStartSpare(tc);
1465	–	success = true;
1466	–	break;
1467	–	}
1468	–	}
1469	–	} finally {
1470	–	if (locked)
1471	–	lock.unlock();
1472	–	}
1473	–	return success;
1474	–	}
1475	–
1476	–	/**
1477	–	* Add the kth spare worker. On entry, pool coounts are already
1478	–	* adjusted to reflect addition.
1479	–	*/
1480	–	private void createAndStartSpare(int k) {
1481	–	ForkJoinWorkerThread w = null;
1482	–	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1);
1483	–	int len = ws.length;
1484	–	// Probably, we can place at slot k. If not, find empty slot
1485	–	if (k < len && ws[k] != null) {
1486	–	for (k = 0; k < len && ws[k] != null; ++k)
1487	–	;
1488	–	}
1489	–	if (k < len && (w = createWorker(k)) != null) {
1490	–	ws[k] = w;
1491	–	w.start();
1492	–	}
1493	–	else
1494	–	updateWorkerCount(-1); // adjust on failure
1495	–	signalIdleWorkers(false);
1496	–	}
1497	–
1498	–	/**
1499	–	* Suspend calling thread w if there are excess threads.  Called
1500	–	* only from sync.  Spares are enqueued in a Treiber stack
1501	–	* using the same WaitQueueNodes as barriers.  They are resumed
1502	–	* mainly in preJoin, but are also woken on pool events that
1503	–	* require all threads to check run state.
1504	–	* @param w the caller
1505	–	*/
1506	–	private boolean suspendIfSpare(ForkJoinWorkerThread w) {
1507	–	WaitQueueNode node = null;
1508	–	int s;
1509	–	while (parallelism < runningCountOf(s = workerCounts)) {
1510	–	if (node == null)
1511	–	node = new WaitQueueNode(w, 0);
1512	–	if (casWorkerCounts(s, s-1)) { // representation-dependent
1513	–	// push onto stack
1514	–	do;while (!casSpareStack(node.next = spareStack, node));
1515	–
1516	–	// block until released by resumeSpare
1517	–	while (node.thread != null) {
1518	–	if (!Thread.interrupted())
1519	–	LockSupport.park(this);
1520	–	}
1521	–	w.activate(); // help warm up
1522	–	return true;
1523	–	}
1524	–	}
1525	–	return false;
1526	–	}
1527	–
1528	–	/**
1529	–	* Try to pop and resume a spare thread.
1530	–	* @param updateCount if true, increment running count on success
1531	–	* @return true if successful
1532	–	*/
1533	–	private boolean tryResumeSpare(boolean updateCount) {
1534	–	WaitQueueNode q;
1535	–	while ((q = spareStack) != null) {
1536	–	if (casSpareStack(q, q.next)) {
1537	–	if (updateCount)
1538	–	updateRunningCount(1);
1539	–	q.signal();
1540	–	return true;
1541	–	}
1542	–	}
1543	–	return false;
1544	–	}
1545	–
1546	–	/**
1547	–	* Pop and resume all spare threads. Same idea as
1548	–	* releaseIdleWorkers.
1549	–	* @return true if any spares released
1550	–	*/
1551	–	private boolean resumeAllSpares() {
1552	–	WaitQueueNode q;
1553	–	while ( (q = spareStack) != null) {
1554	–	if (casSpareStack(q, null)) {
1555	–	do {
1556	–	updateRunningCount(1);
1557	–	q.signal();
1558	–	} while ((q = q.next) != null);
1559	–	return true;
1560	–	}
1561	–	}
1562	–	return false;
1563	–	}
1564	–
1565	–	/**
1566	–	* Pop and shutdown excessive spare threads. Call only while
1567	–	* holding lock. This is not guaranteed to eliminate all excess
1568	–	* threads, only those suspended as spares, which are the ones
1569	–	* unlikely to be needed in the future.
1570	–	*/
1571	–	private void trimSpares() {
1572	–	int surplus = totalCountOf(workerCounts) - parallelism;
1573	–	WaitQueueNode q;
1574	–	while (surplus > 0 && (q = spareStack) != null) {
1575	–	if (casSpareStack(q, null)) {
1576	–	do {
1577	–	updateRunningCount(1);
1578	–	ForkJoinWorkerThread w = q.thread;
1579	–	if (w != null && surplus > 0 &&
1580	–	runningCountOf(workerCounts) > 0 && w.shutdown())
1581	–	--surplus;
1582	–	q.signal();
1583	–	} while ((q = q.next) != null);
1584	–	}
1585	–	}
1586	–	}
1587	–
1588	–	/**
1589	–	* Returns approximate number of spares, just for diagnostics.
1590	–	*/
1591	–	private int countSpares() {
1592	–	int sum = 0;
1593	–	for (WaitQueueNode q = spareStack; q != null; q = q.next)
1594	–	++sum;
1595	–	return sum;
1596	–	}
1597	–
1598	–	/**
1693		* Interface for extending managed parallelism for tasks running
1694	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1695	<	* Method <tt>isReleasable</tt> must return true if blocking is not
1696	<	* necessary. Method <tt>block</tt> blocks the current thread
1697	<	* if necessary (perhaps internally invoking isReleasable before
1698	<	* actually blocking.).
1694	>	* in {@link ForkJoinPool}s.
1695	>	*
1696	>	* <p>A {@code ManagedBlocker} provides two methods.
1697	>	* Method {@code isReleasable} must return {@code true} if
1698	>	* blocking is not necessary. Method {@code block} blocks the
1699	>	* current thread if necessary (perhaps internally invoking
1700	>	* {@code isReleasable} before actually blocking).
1701	>	*
1702		* <p>For example, here is a ManagedBlocker based on a
1703		* ReentrantLock:
1704	<	* <pre>
1705	<	*   class ManagedLocker implements ManagedBlocker {
1706	<	*     final ReentrantLock lock;
1707	<	*     boolean hasLock = false;
1708	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1709	<	*     public boolean block() {
1710	<	*        if (!hasLock)
1711	<	*           lock.lock();
1712	<	*        return true;
1713	<	*     }
1714	<	*     public boolean isReleasable() {
1715	<	*        return hasLock || (hasLock = lock.tryLock());
1619	<	*     }
1704	>	*  <pre> {@code
1705	>	* class ManagedLocker implements ManagedBlocker {
1706	>	*   final ReentrantLock lock;
1707	>	*   boolean hasLock = false;
1708	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1709	>	*   public boolean block() {
1710	>	*     if (!hasLock)
1711	>	*       lock.lock();
1712	>	*     return true;
1713	>	*   }
1714	>	*   public boolean isReleasable() {
1715	>	*     return hasLock || (hasLock = lock.tryLock());
1716		*   }
1717	<	* </pre>
1717	>	* }}</pre>
1718		*/
1719		public static interface ManagedBlocker {
1720		/**
1721		* Possibly blocks the current thread, for example waiting for
1722		* a lock or condition.
1723	<	* @return true if no additional blocking is necessary (i.e.,
1724	<	* if isReleasable would return true).
1723	>	*
1724	>	* @return {@code true} if no additional blocking is necessary
1725	>	* (i.e., if isReleasable would return true)
1726		* @throws InterruptedException if interrupted while waiting
1727	<	* (the method is not required to do so, but is allowe to).
1727	>	* (the method is not required to do so, but is allowed to)
1728		*/
1729		boolean block() throws InterruptedException;
1730
1731		/**
1732	<	* Returns true if blocking is unnecessary.
1732	>	* Returns {@code true} if blocking is unnecessary.
1733		*/
1734		boolean isReleasable();
1735		}
1736
1737		/**
1738		* Blocks in accord with the given blocker.  If the current thread
1739	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1740	<	* spare thread to be activated if necessary to ensure parallelism
1741	<	* while the current thread is blocked.  If
1742	<	* <tt>maintainParallelism</tt> is true and the pool supports it
1743	<	* (see <tt>getMaintainsParallelism</tt>), this method attempts to
1744	<	* maintain the pool's nominal parallelism. Otherwise if activates
1745	<	* a thread only if necessary to avoid complete starvation. This
1746	<	* option may be preferable when blockages use timeouts, or are
1747	<	* almost always brief.
1748	<	*
1749	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1750	<	* equivalent to
1751	<	* <pre>
1752	<	*   while (!blocker.isReleasable())
1656	<	*      if (blocker.block())
1657	<	*         return;
1658	<	* </pre>
1659	<	* If the caller is a ForkJoinTask, then the pool may first
1660	<	* be expanded to ensure parallelism, and later adjusted.
1739	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1740	>	* arranges for a spare thread to be activated if necessary to
1741	>	* ensure sufficient parallelism while the current thread is blocked.
1742	>	*
1743	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1744	>	* behaviorally equivalent to
1745	>	*  <pre> {@code
1746	>	* while (!blocker.isReleasable())
1747	>	*   if (blocker.block())
1748	>	*     return;
1749	>	* }</pre>
1750	>	*
1751	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1752	>	* first be expanded to ensure parallelism, and later adjusted.
1753		*
1754		* @param blocker the blocker
1755	<	* @param maintainParallelism if true and supported by this pool,
1664	<	* attempt to maintain the pool's nominal parallelism; otherwise
1665	<	* activate a thread only if necessary to avoid complete
1666	<	* starvation.
1667	<	* @throws InterruptedException if blocker.block did so.
1755	>	* @throws InterruptedException if blocker.block did so
1756		*/
1757	<	public static void managedBlock(ManagedBlocker blocker,
1670	<	boolean maintainParallelism)
1757	>	public static void managedBlock(ManagedBlocker blocker)
1758		throws InterruptedException {
1759		Thread t = Thread.currentThread();
1760	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1761	<	((ForkJoinWorkerThread)t).pool : null);
1762	<	if (!blocker.isReleasable()) {
1763	<	try {
1677	<	if (pool == null ||
1678	<	!pool.preBlock(blocker, maintainParallelism))
1679	<	awaitBlocker(blocker);
1680	<	} finally {
1681	<	if (pool != null)
1682	<	pool.updateRunningCount(1);
1683	<	}
1760	>	if (t instanceof ForkJoinWorkerThread)
1761	>	((ForkJoinWorkerThread) t).pool.awaitBlocker(blocker);
1762	>	else {
1763	>	do {} while (!blocker.isReleasable() && !blocker.block());
1764		}
1765		}
1766
1767	<	private static void awaitBlocker(ManagedBlocker blocker)
1768	<	throws InterruptedException {
1769	<	do;while (!blocker.isReleasable() && !blocker.block());
1767	>	// AbstractExecutorService overrides.  These rely on undocumented
1768	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1769	>	// implement RunnableFuture.
1770	>
1771	>	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1772	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1773		}
1774
1775	+	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1776	+	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1777	+	}
1778
1779	<	// Temporary Unsafe mechanics for preliminary release
1779	>	// Unsafe mechanics
1780
1781	<	static final Unsafe _unsafe;
1782	<	static final long eventCountOffset;
1783	<	static final long workerCountsOffset;
1784	<	static final long runControlOffset;
1785	<	static final long barrierStackOffset;
1786	<	static final long spareStackOffset;
1781	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1782	>	private static final long workerCountsOffset =
1783	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1784	>	private static final long runStateOffset =
1785	>	objectFieldOffset("runState", ForkJoinPool.class);
1786	>	private static final long eventCountOffset =
1787	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1788	>	private static final long eventWaitersOffset =
1789	>	objectFieldOffset("eventWaiters",ForkJoinPool.class);
1790	>	private static final long stealCountOffset =
1791	>	objectFieldOffset("stealCount",ForkJoinPool.class);
1792
1793	<	static {
1793	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1794		try {
1795	<	if (ForkJoinPool.class.getClassLoader() != null) {
1796	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1797	<	f.setAccessible(true);
1798	<	_unsafe = (Unsafe)f.get(null);
1799	<	}
1800	<	else
1710	<	_unsafe = Unsafe.getUnsafe();
1711	<	eventCountOffset = _unsafe.objectFieldOffset
1712	<	(ForkJoinPool.class.getDeclaredField("eventCount"));
1713	<	workerCountsOffset = _unsafe.objectFieldOffset
1714	<	(ForkJoinPool.class.getDeclaredField("workerCounts"));
1715	<	runControlOffset = _unsafe.objectFieldOffset
1716	<	(ForkJoinPool.class.getDeclaredField("runControl"));
1717	<	barrierStackOffset = _unsafe.objectFieldOffset
1718	<	(ForkJoinPool.class.getDeclaredField("barrierStack"));
1719	<	spareStackOffset = _unsafe.objectFieldOffset
1720	<	(ForkJoinPool.class.getDeclaredField("spareStack"));
1721	<	} catch (Exception e) {
1722	<	throw new RuntimeException("Could not initialize intrinsics", e);
1795	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1796	>	} catch (NoSuchFieldException e) {
1797	>	// Convert Exception to corresponding Error
1798	>	NoSuchFieldError error = new NoSuchFieldError(field);
1799	>	error.initCause(e);
1800	>	throw error;
1801		}
1802		}
1803
1804	<	private boolean casEventCount(long cmp, long val) {
1805	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1806	<	}
1807	<	private boolean casWorkerCounts(int cmp, int val) {
1808	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1809	<	}
1810	<	private boolean casRunControl(int cmp, int val) {
1811	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1812	<	}
1813	<	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1814	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1815	<	}
1816	<	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1817	<	return _unsafe.compareAndSwapObject(this, barrierStackOffset, cmp, val);
1804	>	/**
1805	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1806	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1807	>	* into a jdk.
1808	>	*
1809	>	* @return a sun.misc.Unsafe
1810	>	*/
1811	>	private static sun.misc.Unsafe getUnsafe() {
1812	>	try {
1813	>	return sun.misc.Unsafe.getUnsafe();
1814	>	} catch (SecurityException se) {
1815	>	try {
1816	>	return java.security.AccessController.doPrivileged
1817	>	(new java.security
1818	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1819	>	public sun.misc.Unsafe run() throws Exception {
1820	>	java.lang.reflect.Field f = sun.misc
1821	>	.Unsafe.class.getDeclaredField("theUnsafe");
1822	>	f.setAccessible(true);
1823	>	return (sun.misc.Unsafe) f.get(null);
1824	>	}});
1825	>	} catch (java.security.PrivilegedActionException e) {
1826	>	throw new RuntimeException("Could not initialize intrinsics",
1827	>	e.getCause());
1828	>	}
1829	>	}
1830		}
1831		}

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