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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.12 by jsr166, Tue Jul 21 18:11:44 2009 UTC vs.
Revision 1.116 by dl, Fri Jan 27 17:27:28 2012 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
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.*;
8	>
9	>	import java.util.ArrayList;
10	>	import java.util.Arrays;
11	>	import java.util.Collection;
12	>	import java.util.Collections;
13	>	import java.util.List;
14	>	import java.util.Random;
15	>	import java.util.concurrent.AbstractExecutorService;
16	>	import java.util.concurrent.Callable;
17	>	import java.util.concurrent.ExecutorService;
18	>	import java.util.concurrent.Future;
19	>	import java.util.concurrent.RejectedExecutionException;
20	>	import java.util.concurrent.RunnableFuture;
21	>	import java.util.concurrent.TimeUnit;
22	>	import java.util.concurrent.atomic.AtomicInteger;
23	>	import java.util.concurrent.atomic.AtomicLong;
24	>	import java.util.concurrent.locks.ReentrantLock;
25	>	import java.util.concurrent.locks.Condition;
26
27		/**
28	<	* An {@link ExecutorService} for running {@link ForkJoinTask}s.  A
29	<	* ForkJoinPool provides the entry point for submissions from
30	<	* non-ForkJoinTasks, as well as management and monitoring operations.
31	<	* Normally a single ForkJoinPool is used for a large number of
20	<	* submitted tasks. Otherwise, use would not usually outweigh the
21	<	* construction and bookkeeping overhead of creating a large set of
22	<	* threads.
28	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
29	>	* A {@code ForkJoinPool} provides the entry point for submissions
30	>	* from non-{@code ForkJoinTask} clients, as well as management and
31	>	* monitoring operations.
32		*
33	<	* <p>ForkJoinPools differ from other kinds of Executors mainly in
34	<	* that they provide <em>work-stealing</em>: all threads in the pool
35	<	* attempt to find and execute subtasks created by other active tasks
36	<	* (eventually blocking if none exist). This makes them efficient when
37	<	* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
38	<	* as the mixed execution of some plain Runnable- or Callable- based
39	<	* activities along with ForkJoinTasks. When setting
40	<	* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for
41	<	* use with fine-grained tasks that are never joined. Otherwise, other
42	<	* ExecutorService implementations are typically more appropriate
43	<	* choices.
33	>	* <p>A {@code ForkJoinPool} differs from other kinds of {@link
34	>	* ExecutorService} mainly by virtue of employing
35	>	* <em>work-stealing</em>: all threads in the pool attempt to find and
36	>	* execute tasks submitted to the pool and/or created by other active
37	>	* tasks (eventually blocking waiting for work if none exist). This
38	>	* enables efficient processing when most tasks spawn other subtasks
39	>	* (as do most {@code ForkJoinTask}s), as well as when many small
40	>	* tasks are submitted to the pool from external clients.  Especially
41	>	* when setting <em>asyncMode</em> to true in constructors, {@code
42	>	* ForkJoinPool}s may also be appropriate for use with event-style
43	>	* tasks that are never joined.
44		*
45	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
46	<	* (target pool size), which it attempts to maintain by dynamically
47	<	* adding, suspending, or resuming threads, even if some tasks are
48	<	* waiting to join others. However, no such adjustments are performed
49	<	* in the face of blocked IO or other unmanaged synchronization. The
50	<	* nested {@code ManagedBlocker} interface enables extension of
51	<	* the kinds of synchronization accommodated.  The target parallelism
52	<	* level may also be changed dynamically ({@code setParallelism})
53	<	* and thread construction can be limited using methods
45	<	* {@code setMaximumPoolSize} and/or
46	<	* {@code setMaintainsParallelism}.
45	>	* <p>A {@code ForkJoinPool} is constructed with a given target
46	>	* parallelism level; by default, equal to the number of available
47	>	* processors. The pool attempts to maintain enough active (or
48	>	* available) threads by dynamically adding, suspending, or resuming
49	>	* internal worker threads, even if some tasks are stalled waiting to
50	>	* join others. However, no such adjustments are guaranteed in the
51	>	* face of blocked IO or other unmanaged synchronization. The nested
52	>	* {@link ManagedBlocker} interface enables extension of the kinds of
53	>	* synchronization accommodated.
54		*
55		* <p>In addition to execution and lifecycle control methods, this
56		* class provides status check methods (for example
57	<	* {@code getStealCount}) that are intended to aid in developing,
57	>	* {@link #getStealCount}) that are intended to aid in developing,
58		* tuning, and monitoring fork/join applications. Also, method
59	<	* {@code toString} returns indications of pool state in a
59	>	* {@link #toString} returns indications of pool state in a
60		* convenient form for informal monitoring.
61		*
62	+	* <p> As is the case with other ExecutorServices, there are three
63	+	* main task execution methods summarized in the following
64	+	* table. These are designed to be used primarily by clients not
65	+	* already engaged in fork/join computations in the current pool.  The
66	+	* main forms of these methods accept instances of {@code
67	+	* ForkJoinTask}, but overloaded forms also allow mixed execution of
68	+	* plain {@code Runnable}- or {@code Callable}- based activities as
69	+	* well.  However, tasks that are already executing in a pool should
70	+	* normally instead use the within-computation forms listed in the
71	+	* table unless using async event-style tasks that are not usually
72	+	* joined, in which case there is little difference among choice of
73	+	* methods.
74	+	*
75	+	* <table BORDER CELLPADDING=3 CELLSPACING=1>
76	+	*  <tr>
77	+	*    <td></td>
78	+	*    <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
79	+	*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
80	+	*  </tr>
81	+	*  <tr>
82	+	*    <td> <b>Arrange async execution</td>
83	+	*    <td> {@link #execute(ForkJoinTask)}</td>
84	+	*    <td> {@link ForkJoinTask#fork}</td>
85	+	*  </tr>
86	+	*  <tr>
87	+	*    <td> <b>Await and obtain result</td>
88	+	*    <td> {@link #invoke(ForkJoinTask)}</td>
89	+	*    <td> {@link ForkJoinTask#invoke}</td>
90	+	*  </tr>
91	+	*  <tr>
92	+	*    <td> <b>Arrange exec and obtain Future</td>
93	+	*    <td> {@link #submit(ForkJoinTask)}</td>
94	+	*    <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td>
95	+	*  </tr>
96	+	* </table>
97	+	*
98	+	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
99	+	* used for all parallel task execution in a program or subsystem.
100	+	* Otherwise, use would not usually outweigh the construction and
101	+	* bookkeeping overhead of creating a large set of threads. For
102	+	* example, a common pool could be used for the {@code SortTasks}
103	+	* illustrated in {@link RecursiveAction}. Because {@code
104	+	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
105	+	* daemon} mode, there is typically no need to explicitly {@link
106	+	* #shutdown} such a pool upon program exit.
107	+	*
108	+	*  <pre> {@code
109	+	* static final ForkJoinPool mainPool = new ForkJoinPool();
110	+	* ...
111	+	* public void sort(long[] array) {
112	+	*   mainPool.invoke(new SortTask(array, 0, array.length));
113	+	* }}</pre>
114	+	*
115		* <p><b>Implementation notes</b>: This implementation restricts the
116		* maximum number of running threads to 32767. Attempts to create
117	<	* pools with greater than the maximum result in
118	<	* IllegalArgumentExceptions.
117	>	* pools with greater than the maximum number result in
118	>	* {@code IllegalArgumentException}.
119	>	*
120	>	* <p>This implementation rejects submitted tasks (that is, by throwing
121	>	* {@link RejectedExecutionException}) only when the pool is shut down
122	>	* or internal resources have been exhausted.
123	>	*
124	>	* @since 1.7
125	>	* @author Doug Lea
126		*/
127		public class ForkJoinPool extends AbstractExecutorService {
128
129		/*
130	<	* See the extended comments interspersed below for design,
131	<	* rationale, and walkthroughs.
132	<	*/
133	<
134	<	/** Mask for packing and unpacking shorts */
135	<	private static final int  shortMask = 0xffff;
136	<
137	<	/** Max pool size -- must be a power of two minus 1 */
138	<	private static final int MAX_THREADS =  0x7FFF;
139	<
140	<	/**
141	<	* Factory for creating new ForkJoinWorkerThreads.  A
142	<	* ForkJoinWorkerThreadFactory must be defined and used for
143	<	* ForkJoinWorkerThread subclasses that extend base functionality
144	<	* or initialize threads with different contexts.
130	>	* Implementation Overview
131	>	*
132	>	* This class and its nested classes provide the main
133	>	* functionality and control for a set of worker threads:
134	>	* Submissions from non-FJ threads enter into submission
135	>	* queues. Workers take these tasks and typically split them into
136	>	* subtasks that may be stolen by other workers.  Preference rules
137	>	* give first priority to processing tasks from their own queues
138	>	* (LIFO or FIFO, depending on mode), then to randomized FIFO
139	>	* steals of tasks in other queues.
140	>	*
141	>	* WorkQueues.
142	>	* ==========
143	>	*
144	>	* Most operations occur within work-stealing queues (in nested
145	>	* class WorkQueue).  These are special forms of Deques that
146	>	* support only three of the four possible end-operations -- push,
147	>	* pop, and poll (aka steal), under the further constraints that
148	>	* push and pop are called only from the owning thread (or, as
149	>	* extended here, under a lock), while poll may be called from
150	>	* other threads.  (If you are unfamiliar with them, you probably
151	>	* want to read Herlihy and Shavit's book "The Art of
152	>	* Multiprocessor programming", chapter 16 describing these in
153	>	* more detail before proceeding.)  The main work-stealing queue
154	>	* design is roughly similar to those in the papers "Dynamic
155	>	* Circular Work-Stealing Deque" by Chase and Lev, SPAA 2005
156	>	* (http://research.sun.com/scalable/pubs/index.html) and
157	>	* "Idempotent work stealing" by Michael, Saraswat, and Vechev,
158	>	* PPoPP 2009 (http://portal.acm.org/citation.cfm?id=1504186).
159	>	* The main differences ultimately stem from gc requirements that
160	>	* we null out taken slots as soon as we can, to maintain as small
161	>	* a footprint as possible even in programs generating huge
162	>	* numbers of tasks. To accomplish this, we shift the CAS
163	>	* arbitrating pop vs poll (steal) from being on the indices
164	>	* ("base" and "top") to the slots themselves.  So, both a
165	>	* successful pop and poll mainly entail a CAS of a slot from
166	>	* non-null to null.  Because we rely on CASes of references, we
167	>	* do not need tag bits on base or top.  They are simple ints as
168	>	* used in any circular array-based queue (see for example
169	>	* ArrayDeque).  Updates to the indices must still be ordered in a
170	>	* way that guarantees that top == base means the queue is empty,
171	>	* but otherwise may err on the side of possibly making the queue
172	>	* appear nonempty when a push, pop, or poll have not fully
173	>	* committed. Note that this means that the poll operation,
174	>	* considered individually, is not wait-free. One thief cannot
175	>	* successfully continue until another in-progress one (or, if
176	>	* previously empty, a push) completes.  However, in the
177	>	* aggregate, we ensure at least probabilistic non-blockingness.
178	>	* If an attempted steal fails, a thief always chooses a different
179	>	* random victim target to try next. So, in order for one thief to
180	>	* progress, it suffices for any in-progress poll or new push on
181	>	* any empty queue to complete.
182	>	*
183	>	* This approach also enables support of a user mode in which local
184	>	* task processing is in FIFO, not LIFO order, simply by using
185	>	* poll rather than pop.  This can be useful in message-passing
186	>	* frameworks in which tasks are never joined.  However neither
187	>	* mode considers affinities, loads, cache localities, etc, so
188	>	* rarely provide the best possible performance on a given
189	>	* machine, but portably provide good throughput by averaging over
190	>	* these factors.  (Further, even if we did try to use such
191	>	* information, we do not usually have a basis for exploiting
192	>	* it. For example, some sets of tasks profit from cache
193	>	* affinities, but others are harmed by cache pollution effects.)
194	>	*
195	>	* WorkQueues are also used in a similar way for tasks submitted
196	>	* to the pool. We cannot mix these tasks in the same queues used
197	>	* for work-stealing (this would contaminate lifo/fifo
198	>	* processing). Instead, we loosely associate submission queues
199	>	* with submitting threads, using a form of hashing.  The
200	>	* ThreadLocal Submitter class contains a value initially used as
201	>	* a hash code for choosing existing queues, but may be randomly
202	>	* repositioned upon contention with other submitters.  In
203	>	* essence, submitters act like workers except that they never
204	>	* take tasks, and they are multiplexed on to a finite number of
205	>	* shared work queues. However, classes are set up so that future
206	>	* extensions could allow submitters to optionally help perform
207	>	* tasks as well. Pool submissions from internal workers are also
208	>	* allowed, but use randomized rather than thread-hashed queue
209	>	* indices to avoid imbalance.  Insertion of tasks in shared mode
210	>	* requires a lock (mainly to protect in the case of resizing) but
211	>	* we use only a simple spinlock (using bits in field runState),
212	>	* because submitters encountering a busy queue try or create
213	>	* others so never block.
214	>	*
215	>	* Management.
216	>	* ==========
217	>	*
218	>	* The main throughput advantages of work-stealing stem from
219	>	* decentralized control -- workers mostly take tasks from
220	>	* themselves or each other. We cannot negate this in the
221	>	* implementation of other management responsibilities. The main
222	>	* tactic for avoiding bottlenecks is packing nearly all
223	>	* essentially atomic control state into two volatile variables
224	>	* that are by far most often read (not written) as status and
225	>	* consistency checks
226	>	*
227	>	* Field "ctl" contains 64 bits holding all the information needed
228	>	* to atomically decide to add, inactivate, enqueue (on an event
229	>	* queue), dequeue, and/or re-activate workers.  To enable this
230	>	* packing, we restrict maximum parallelism to (1<<15)-1 (which is
231	>	* far in excess of normal operating range) to allow ids, counts,
232	>	* and their negations (used for thresholding) to fit into 16bit
233	>	* fields.
234	>	*
235	>	* Field "runState" contains 32 bits needed to register and
236	>	* deregister WorkQueues, as well as to enable shutdown. It is
237	>	* only modified under a lock (normally briefly held, but
238	>	* occasionally protecting allocations and resizings) but even
239	>	* when locked remains available to check consistency.
240	>	*
241	>	* Recording WorkQueues.  WorkQueues are recorded in the
242	>	* "workQueues" array that is created upon pool construction and
243	>	* expanded if necessary.  Updates to the array while recording
244	>	* new workers and unrecording terminated ones are protected from
245	>	* each other by a lock but the array is otherwise concurrently
246	>	* readable, and accessed directly.  To simplify index-based
247	>	* operations, the array size is always a power of two, and all
248	>	* readers must tolerate null slots. Shared (submission) queues
249	>	* are at even indices, worker queues at odd indices. Grouping
250	>	* them together in this way simplifies and speeds up task
251	>	* scanning. To avoid flailing during start-up, the array is
252	>	* presized to hold twice #parallelism workers (which is unlikely
253	>	* to need further resizing during execution). But to avoid
254	>	* dealing with so many null slots, variable runState includes a
255	>	* mask for the nearest power of two that contains all current
256	>	* workers.  All worker thread creation is on-demand, triggered by
257	>	* task submissions, replacement of terminated workers, and/or
258	>	* compensation for blocked workers. However, all other support
259	>	* code is set up to work with other policies.  To ensure that we
260	>	* do not hold on to worker references that would prevent GC, ALL
261	>	* accesses to workQueues are via indices into the workQueues
262	>	* array (which is one source of some of the messy code
263	>	* constructions here). In essence, the workQueues array serves as
264	>	* a weak reference mechanism. Thus for example the wait queue
265	>	* field of ctl stores indices, not references.  Access to the
266	>	* workQueues in associated methods (for example signalWork) must
267	>	* both index-check and null-check the IDs. All such accesses
268	>	* ignore bad IDs by returning out early from what they are doing,
269	>	* since this can only be associated with termination, in which
270	>	* case it is OK to give up.
271	>	*
272	>	* All uses of the workQueues array check that it is non-null
273	>	* (even if previously non-null). This allows nulling during
274	>	* termination, which is currently not necessary, but remains an
275	>	* option for resource-revocation-based shutdown schemes. It also
276	>	* helps reduce JIT issuance of uncommon-trap code, which tends to
277	>	* unnecessarily complicate control flow in some methods.
278	>	*
279	>	* Event Queuing. Unlike HPC work-stealing frameworks, we cannot
280	>	* let workers spin indefinitely scanning for tasks when none can
281	>	* be found immediately, and we cannot start/resume workers unless
282	>	* there appear to be tasks available.  On the other hand, we must
283	>	* quickly prod them into action when new tasks are submitted or
284	>	* generated. In many usages, ramp-up time to activate workers is
285	>	* the main limiting factor in overall performance (this is
286	>	* compounded at program start-up by JIT compilation and
287	>	* allocation). So we try to streamline this as much as possible.
288	>	* We park/unpark workers after placing in an event wait queue
289	>	* when they cannot find work. This "queue" is actually a simple
290	>	* Treiber stack, headed by the "id" field of ctl, plus a 15bit
291	>	* counter value (that reflects the number of times a worker has
292	>	* been inactivated) to avoid ABA effects (we need only as many
293	>	* version numbers as worker threads). Successors are held in
294	>	* field WorkQueue.nextWait.  Queuing deals with several intrinsic
295	>	* races, mainly that a task-producing thread can miss seeing (and
296	>	* signalling) another thread that gave up looking for work but
297	>	* has not yet entered the wait queue. We solve this by requiring
298	>	* a full sweep of all workers (via repeated calls to method
299	>	* scan()) both before and after a newly waiting worker is added
300	>	* to the wait queue. During a rescan, the worker might release
301	>	* some other queued worker rather than itself, which has the same
302	>	* net effect. Because enqueued workers may actually be rescanning
303	>	* rather than waiting, we set and clear the "parker" field of
304	>	* Workqueues to reduce unnecessary calls to unpark.  (This
305	>	* requires a secondary recheck to avoid missed signals.)  Note
306	>	* the unusual conventions about Thread.interrupts surrounding
307	>	* parking and other blocking: Because interrupts are used solely
308	>	* to alert threads to check termination, which is checked anyway
309	>	* upon blocking, we clear status (using Thread.interrupted)
310	>	* before any call to park, so that park does not immediately
311	>	* return due to status being set via some other unrelated call to
312	>	* interrupt in user code.
313	>	*
314	>	* Signalling.  We create or wake up workers only when there
315	>	* appears to be at least one task they might be able to find and
316	>	* execute.  When a submission is added or another worker adds a
317	>	* task to a queue that previously had fewer than two tasks, they
318	>	* signal waiting workers (or trigger creation of new ones if
319	>	* fewer than the given parallelism level -- see signalWork).
320	>	* These primary signals are buttressed by signals during rescans;
321	>	* together these cover the signals needed in cases when more
322	>	* tasks are pushed but untaken, and improve performance compared
323	>	* to having one thread wake up all workers.
324	>	*
325	>	* Trimming workers. To release resources after periods of lack of
326	>	* use, a worker starting to wait when the pool is quiescent will
327	>	* time out and terminate if the pool has remained quiescent for
328	>	* SHRINK_RATE nanosecs. This will slowly propagate, eventually
329	>	* terminating all workers after long periods of non-use.
330	>	*
331	>	* Shutdown and Termination. A call to shutdownNow atomically sets
332	>	* a runState bit and then (non-atomically) sets each workers
333	>	* runState status, cancels all unprocessed tasks, and wakes up
334	>	* all waiting workers.  Detecting whether termination should
335	>	* commence after a non-abrupt shutdown() call requires more work
336	>	* and bookkeeping. We need consensus about quiescence (i.e., that
337	>	* there is no more work). The active count provides a primary
338	>	* indication but non-abrupt shutdown still requires a rechecking
339	>	* scan for any workers that are inactive but not queued.
340	>	*
341	>	* Joining Tasks.
342	>	* ==============
343	>	*
344	>	* Any of several actions may be taken when one worker is waiting
345	>	* to join a task stolen (or always held by) another.  Because we
346	>	* are multiplexing many tasks on to a pool of workers, we can't
347	>	* just let them block (as in Thread.join).  We also cannot just
348	>	* reassign the joiner's run-time stack with another and replace
349	>	* it later, which would be a form of "continuation", that even if
350	>	* possible is not necessarily a good idea since we sometimes need
351	>	* both an unblocked task and its continuation to
352	>	* progress. Instead we combine two tactics:
353	>	*
354	>	*   Helping: Arranging for the joiner to execute some task that it
355	>	*      would be running if the steal had not occurred.
356	>	*
357	>	*   Compensating: Unless there are already enough live threads,
358	>	*      method tryCompensate() may create or re-activate a spare
359	>	*      thread to compensate for blocked joiners until they unblock.
360	>	*
361	>	* A third form (implemented in tryRemoveAndExec and
362	>	* tryPollForAndExec) amounts to helping a hypothetical
363	>	* compensator: If we can readily tell that a possible action of a
364	>	* compensator is to steal and execute the task being joined, the
365	>	* joining thread can do so directly, without the need for a
366	>	* compensation thread (although at the expense of larger run-time
367	>	* stacks, but the tradeoff is typically worthwhile).
368	>	*
369	>	* The ManagedBlocker extension API can't use helping so relies
370	>	* only on compensation in method awaitBlocker.
371	>	*
372	>	* The algorithm in tryHelpStealer entails a form of "linear"
373	>	* helping: Each worker records (in field currentSteal) the most
374	>	* recent task it stole from some other worker. Plus, it records
375	>	* (in field currentJoin) the task it is currently actively
376	>	* joining. Method tryHelpStealer uses these markers to try to
377	>	* find a worker to help (i.e., steal back a task from and execute
378	>	* it) that could hasten completion of the actively joined task.
379	>	* In essence, the joiner executes a task that would be on its own
380	>	* local deque had the to-be-joined task not been stolen. This may
381	>	* be seen as a conservative variant of the approach in Wagner &
382	>	* Calder "Leapfrogging: a portable technique for implementing
383	>	* efficient futures" SIGPLAN Notices, 1993
384	>	* (http://portal.acm.org/citation.cfm?id=155354). It differs in
385	>	* that: (1) We only maintain dependency links across workers upon
386	>	* steals, rather than use per-task bookkeeping.  This sometimes
387	>	* requires a linear scan of workers array to locate stealers, but
388	>	* often doesn't because stealers leave hints (that may become
389	>	* stale/wrong) of where to locate them.  A stealHint is only a
390	>	* hint because a worker might have had multiple steals and the
391	>	* hint records only one of them (usually the most current).
392	>	* Hinting isolates cost to when it is needed, rather than adding
393	>	* to per-task overhead.  (2) It is "shallow", ignoring nesting
394	>	* and potentially cyclic mutual steals.  (3) It is intentionally
395	>	* racy: field currentJoin is updated only while actively joining,
396	>	* which means that we miss links in the chain during long-lived
397	>	* tasks, GC stalls etc (which is OK since blocking in such cases
398	>	* is usually a good idea).  (4) We bound the number of attempts
399	>	* to find work (see MAX_HELP_DEPTH) and fall back to suspending
400	>	* the worker and if necessary replacing it with another.
401	>	*
402	>	* It is impossible to keep exactly the target parallelism number
403	>	* of threads running at any given time.  Determining the
404	>	* existence of conservatively safe helping targets, the
405	>	* availability of already-created spares, and the apparent need
406	>	* to create new spares are all racy, so we rely on multiple
407	>	* retries of each.  Currently, in keeping with on-demand
408	>	* signalling policy, we compensate only if blocking would leave
409	>	* less than one active (non-waiting, non-blocked) worker.
410	>	* Additionally, to avoid some false alarms due to GC, lagging
411	>	* counters, system activity, etc, compensated blocking for joins
412	>	* is only attempted after rechecks stabilize in
413	>	* ForkJoinTask.awaitJoin. (Retries are interspersed with
414	>	* Thread.yield, for good citizenship.)
415	>	*
416	>	* Style notes: There is a lot of representation-level coupling
417	>	* among classes ForkJoinPool, ForkJoinWorkerThread, and
418	>	* ForkJoinTask.  The fields of WorkQueue maintain data structures
419	>	* managed by ForkJoinPool, so are directly accessed.  There is
420	>	* little point trying to reduce this, since any associated future
421	>	* changes in representations will need to be accompanied by
422	>	* algorithmic changes anyway. All together, these low-level
423	>	* implementation choices produce as much as a factor of 4
424	>	* performance improvement compared to naive implementations, and
425	>	* enable the processing of billions of tasks per second, at the
426	>	* expense of some ugliness.
427	>	*
428	>	* Methods signalWork() and scan() are the main bottlenecks so are
429	>	* especially heavily micro-optimized/mangled.  There are lots of
430	>	* inline assignments (of form "while ((local = field) != 0)")
431	>	* which are usually the simplest way to ensure the required read
432	>	* orderings (which are sometimes critical). This leads to a
433	>	* "C"-like style of listing declarations of these locals at the
434	>	* heads of methods or blocks.  There are several occurrences of
435	>	* the unusual "do {} while (!cas...)"  which is the simplest way
436	>	* to force an update of a CAS'ed variable. There are also other
437	>	* coding oddities that help some methods perform reasonably even
438	>	* when interpreted (not compiled).
439	>	*
440	>	* The order of declarations in this file is: (1) declarations of
441	>	* statics (2) fields (along with constants used when unpacking
442	>	* some of them), listed in an order that tends to reduce
443	>	* contention among them a bit under most JVMs; (3) nested
444	>	* classes; (4) internal control methods; (5) callbacks and other
445	>	* support for ForkJoinTask methods; (6) exported methods (plus a
446	>	* few little helpers); (7) static block initializing all statics
447	>	* in a minimally dependent order.
448	>	*/
449	>
450	>	/**
451	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
452	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
453	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
454	>	* functionality or initialize threads with different contexts.
455		*/
456		public static interface ForkJoinWorkerThreadFactory {
457		/**
458		* Returns a new worker thread operating in the given pool.
459		*
460		* @param pool the pool this thread works in
461	<	* @throws NullPointerException if pool is null
461	>	* @throws NullPointerException if the pool is null
462		*/
463		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
464		}
465
466		/**
467	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
467	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
468		* new ForkJoinWorkerThread.
469		*/
470	<	static class  DefaultForkJoinWorkerThreadFactory
470	>	static class DefaultForkJoinWorkerThreadFactory
471		implements ForkJoinWorkerThreadFactory {
472		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
473	<	try {
97	<	return new ForkJoinWorkerThread(pool);
98	<	} catch (OutOfMemoryError oom)  {
99	<	return null;
100	<	}
473	>	return new ForkJoinWorkerThread(pool);
474		}
475		}
476
#	Line 106 | Line 479 | public class ForkJoinPool extends Abstra
479		* overridden in ForkJoinPool constructors.
480		*/
481		public static final ForkJoinWorkerThreadFactory
482	<	defaultForkJoinWorkerThreadFactory =
110	<	new DefaultForkJoinWorkerThreadFactory();
482	>	defaultForkJoinWorkerThreadFactory;
483
484		/**
485		* Permission required for callers of methods that may start or
486		* kill threads.
487		*/
488	<	private static final RuntimePermission modifyThreadPermission =
117	<	new RuntimePermission("modifyThread");
488	>	private static final RuntimePermission modifyThreadPermission;
489
490		/**
491		* If there is a security manager, makes sure caller has
#	Line 129 | Line 500 | public class ForkJoinPool extends Abstra
500		/**
501		* Generator for assigning sequence numbers as pool names.
502		*/
503	<	private static final AtomicInteger poolNumberGenerator =
133	<	new AtomicInteger();
503	>	private static final AtomicInteger poolNumberGenerator;
504
505		/**
506	<	* Array holding all worker threads in the pool. Initialized upon
507	<	* first use. Array size must be a power of two.  Updates and
508	<	* replacements are protected by workerLock, but it is always kept
509	<	* in a consistent enough state to be randomly accessed without
510	<	* locking by workers performing work-stealing.
506	>	* Bits and masks for control variables
507	>	*
508	>	* Field ctl is a long packed with:
509	>	* AC: Number of active running workers minus target parallelism (16 bits)
510	>	* TC: Number of total workers minus target parallelism (16 bits)
511	>	* ST: true if pool is terminating (1 bit)
512	>	* EC: the wait count of top waiting thread (15 bits)
513	>	* ID: ~(poolIndex >>> 1) of top of Treiber stack of waiters (16 bits)
514	>	*
515	>	* When convenient, we can extract the upper 32 bits of counts and
516	>	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
517	>	* (int)ctl.  The ec field is never accessed alone, but always
518	>	* together with id and st. The offsets of counts by the target
519	>	* parallelism and the positionings of fields makes it possible to
520	>	* perform the most common checks via sign tests of fields: When
521	>	* ac is negative, there are not enough active workers, when tc is
522	>	* negative, there are not enough total workers, when id is
523	>	* negative, there is at least one waiting worker, and when e is
524	>	* negative, the pool is terminating.  To deal with these possibly
525	>	* negative fields, we use casts in and out of "short" and/or
526	>	* signed shifts to maintain signedness.
527	>	*
528	>	* When a thread is queued (inactivated), its eventCount field is
529	>	* negative, which is the only way to tell if a worker is
530	>	* prevented from executing tasks, even though it must continue to
531	>	* scan for them to avoid queuing races.
532	>	*
533	>	* Field runState is an int packed with:
534	>	* SHUTDOWN: true if shutdown is enabled (1 bit)
535	>	* SEQ:  a sequence number updated upon (de)registering workers (15 bits)
536	>	* MASK: mask (power of 2 - 1) covering all registered poolIndexes (16 bits)
537	>	*
538	>	* The combination of mask and sequence number enables simple
539	>	* consistency checks: Staleness of read-only operations on the
540	>	* workers and queues arrays can be checked by comparing runState
541	>	* before vs after the reads. The low 16 bits (i.e, anding with
542	>	* SMASK) hold (the smallest power of two covering all worker
543	>	* indices, minus one.  The mask for queues (vs workers) is twice
544	>	* this value plus 1.
545	>	*/
546	>
547	>	// bit positions/shifts for fields
548	>	private static final int  AC_SHIFT   = 48;
549	>	private static final int  TC_SHIFT   = 32;
550	>	private static final int  ST_SHIFT   = 31;
551	>	private static final int  EC_SHIFT   = 16;
552	>
553	>	// bounds
554	>	private static final int  MAX_ID     = 0x7fff;  // max poolIndex
555	>	private static final int  SMASK      = 0xffff;  // mask short bits
556	>	private static final int  SHORT_SIGN = 1 << 15;
557	>	private static final int  INT_SIGN   = 1 << 31;
558	>
559	>	// masks
560	>	private static final long STOP_BIT   = 0x0001L << ST_SHIFT;
561	>	private static final long AC_MASK    = ((long)SMASK) << AC_SHIFT;
562	>	private static final long TC_MASK    = ((long)SMASK) << TC_SHIFT;
563	>
564	>	// units for incrementing and decrementing
565	>	private static final long TC_UNIT    = 1L << TC_SHIFT;
566	>	private static final long AC_UNIT    = 1L << AC_SHIFT;
567	>
568	>	// masks and units for dealing with u = (int)(ctl >>> 32)
569	>	private static final int  UAC_SHIFT  = AC_SHIFT - 32;
570	>	private static final int  UTC_SHIFT  = TC_SHIFT - 32;
571	>	private static final int  UAC_MASK   = SMASK << UAC_SHIFT;
572	>	private static final int  UTC_MASK   = SMASK << UTC_SHIFT;
573	>	private static final int  UAC_UNIT   = 1 << UAC_SHIFT;
574	>	private static final int  UTC_UNIT   = 1 << UTC_SHIFT;
575	>
576	>	// masks and units for dealing with e = (int)ctl
577	>	private static final int E_MASK      = 0x7fffffff; // no STOP_BIT
578	>	private static final int E_SEQ       = 1 << EC_SHIFT;
579	>
580	>	// runState bits
581	>	private static final int SHUTDOWN    = 1 << 31;
582	>	private static final int RS_SEQ      = 1 << 16;
583	>	private static final int RS_SEQ_MASK = 0x7fff0000;
584	>
585	>	// access mode for WorkQueue
586	>	static final int LIFO_QUEUE          =  0;
587	>	static final int FIFO_QUEUE          =  1;
588	>	static final int SHARED_QUEUE        = -1;
589	>
590	>	/**
591	>	* The wakeup interval (in nanoseconds) for a worker waiting for a
592	>	* task when the pool is quiescent to instead try to shrink the
593	>	* number of workers.  The exact value does not matter too
594	>	* much. It must be short enough to release resources during
595	>	* sustained periods of idleness, but not so short that threads
596	>	* are continually re-created.
597	>	*/
598	>	private static final long SHRINK_RATE =
599	>	4L * 1000L * 1000L * 1000L; // 4 seconds
600	>
601	>	/**
602	>	* The timeout value for attempted shrinkage, includes
603	>	* some slop to cope with system timer imprecision.
604	>	*/
605	>	private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
606	>
607	>	/**
608	>	* The maximum stolen->joining link depth allowed in tryHelpStealer.
609	>	* Depths for legitimate chains are unbounded, but we use a fixed
610	>	* constant to avoid (otherwise unchecked) cycles and to bound
611	>	* staleness of traversal parameters at the expense of sometimes
612	>	* blocking when we could be helping.
613		*/
614	<	volatile ForkJoinWorkerThread[] workers;
614	>	private static final int MAX_HELP_DEPTH = 16;
615
616	<	/**
617	<	* Lock protecting access to workers.
616	>	/*
617	>	* Field layout order in this class tends to matter more than one
618	>	* would like. Runtime layout order is only loosely related to
619	>	* declaration order and may differ across JVMs, but the following
620	>	* empirically works OK on current JVMs.
621	>	*/
622	>
623	>	volatile long ctl;                       // main pool control
624	>	final int parallelism;                   // parallelism level
625	>	final int localMode;                     // per-worker scheduling mode
626	>	int nextPoolIndex;                       // hint used in registerWorker
627	>	volatile int runState;                   // shutdown status, seq, and mask
628	>	WorkQueue[] workQueues;                  // main registry
629	>	final ReentrantLock lock;                // for registration
630	>	final Condition termination;             // for awaitTermination
631	>	final ForkJoinWorkerThreadFactory factory; // factory for new workers
632	>	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
633	>	final AtomicLong stealCount;             // collect counts when terminated
634	>	final AtomicInteger nextWorkerNumber;    // to create worker name string
635	>	final String workerNamePrefix;           // Prefix for assigning worker names
636	>
637	>	/**
638	>	* Queues supporting work-stealing as well as external task
639	>	* submission. See above for main rationale and algorithms.
640	>	* Implementation relies heavily on "Unsafe" intrinsics
641	>	* and selective use of "volatile":
642	>	*
643	>	* Field "base" is the index (mod array.length) of the least valid
644	>	* queue slot, which is always the next position to steal (poll)
645	>	* from if nonempty. Reads and writes require volatile orderings
646	>	* but not CAS, because updates are only performed after slot
647	>	* CASes.
648	>	*
649	>	* Field "top" is the index (mod array.length) of the next queue
650	>	* slot to push to or pop from. It is written only by owner thread
651	>	* for push, or under lock for trySharedPush, and accessed by
652	>	* other threads only after reading (volatile) base.  Both top and
653	>	* base are allowed to wrap around on overflow, but (top - base)
654	>	* (or more commonly -(base - top) to force volatile read of base
655	>	* before top) still estimates size.
656	>	*
657	>	* The array slots are read and written using the emulation of
658	>	* volatiles/atomics provided by Unsafe. Insertions must in
659	>	* general use putOrderedObject as a form of releasing store to
660	>	* ensure that all writes to the task object are ordered before
661	>	* its publication in the queue. (Although we can avoid one case
662	>	* of this when locked in trySharedPush.) All removals entail a
663	>	* CAS to null.  The array is always a power of two. To ensure
664	>	* safety of Unsafe array operations, all accesses perform
665	>	* explicit null checks and implicit bounds checks via
666	>	* power-of-two masking.
667	>	*
668	>	* In addition to basic queuing support, this class contains
669	>	* fields described elsewhere to control execution. It turns out
670	>	* to work better memory-layout-wise to include them in this
671	>	* class rather than a separate class.
672	>	*
673	>	* Performance on most platforms is very sensitive to placement of
674	>	* instances of both WorkQueues and their arrays -- we absolutely
675	>	* do not want multiple WorkQueue instances or multiple queue
676	>	* arrays sharing cache lines. (It would be best for queue objects
677	>	* and their arrays to share, but there is nothing available to
678	>	* help arrange that).  Unfortunately, because they are recorded
679	>	* in a common array, WorkQueue instances are often moved to be
680	>	* adjacent by garbage collectors. To reduce impact, we use field
681	>	* padding that works OK on common platforms; this effectively
682	>	* trades off slightly slower average field access for the sake of
683	>	* avoiding really bad worst-case access. (Until better JVM
684	>	* support is in place, this padding is dependent on transient
685	>	* properties of JVM field layout rules.)  We also take care in
686	>	* allocating and sizing and resizing the array. Non-shared queue
687	>	* arrays are initialized (via method growArray) by workers before
688	>	* use. Others are allocated on first use.
689		*/
690	<	private final ReentrantLock workerLock;
690	>	static final class WorkQueue {
691	>	/**
692	>	* Capacity of work-stealing queue array upon initialization.
693	>	* Must be a power of two; at least 4, but set larger to
694	>	* reduce cacheline sharing among queues.
695	>	*/
696	>	static final int INITIAL_QUEUE_CAPACITY = 1 << 8;
697
698	<	/**
699	<	* Condition for awaitTermination.
700	<	*/
701	<	private final Condition termination;
698	>	/**
699	>	* Maximum size for queue arrays. Must be a power of two less
700	>	* than or equal to 1 << (31 - width of array entry) to ensure
701	>	* lack of wraparound of index calculations, but defined to a
702	>	* value a bit less than this to help users trap runaway
703	>	* programs before saturating systems.
704	>	*/
705	>	static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
706
707	<	/**
708	<	* The uncaught exception handler used when any worker
709	<	* abruptly terminates
710	<	*/
711	<	private Thread.UncaughtExceptionHandler ueh;
707	>	volatile long totalSteals; // cumulative number of steals
708	>	int seed;                  // for random scanning; initialize nonzero
709	>	volatile int eventCount;   // encoded inactivation count; < 0 if inactive
710	>	int nextWait;              // encoded record of next event waiter
711	>	int rescans;               // remaining scans until block
712	>	int nsteals;               // top-level task executions since last idle
713	>	final int mode;            // lifo, fifo, or shared
714	>	int poolIndex;             // index of this queue in pool (or 0)
715	>	int stealHint;             // index of most recent known stealer
716	>	volatile int runState;     // 1: locked, -1: terminate; else 0
717	>	volatile int base;         // index of next slot for poll
718	>	int top;                   // index of next slot for push
719	>	ForkJoinTask<?>[] array;   // the elements (initially unallocated)
720	>	final ForkJoinWorkerThread owner; // owning thread or null if shared
721	>	volatile Thread parker;    // == owner during call to park; else null
722	>	ForkJoinTask<?> currentJoin;  // task being joined in awaitJoin
723	>	ForkJoinTask<?> currentSteal; // current non-local task being executed
724	>	// Heuristic padding to ameliorate unfortunate memory placements
725	>	Object p00, p01, p02, p03, p04, p05, p06, p07, p08, p09, p0a;
726	>
727	>	WorkQueue(ForkJoinWorkerThread owner, int mode) {
728	>	this.owner = owner;
729	>	this.mode = mode;
730	>	// Place indices in the center of array (that is not yet allocated)
731	>	base = top = INITIAL_QUEUE_CAPACITY >>> 1;
732	>	}
733
734	<	/**
735	<	* Creation factory for worker threads.
736	<	*/
737	<	private final ForkJoinWorkerThreadFactory factory;
734	>	/**
735	>	* Returns number of tasks in the queue
736	>	*/
737	>	final int queueSize() {
738	>	int n = base - top; // non-owner callers must read base first
739	>	return (n >= 0) ? 0 : -n;
740	>	}
741
742	<	/**
743	<	* Head of stack of threads that were created to maintain
744	<	* parallelism when other threads blocked, but have since
745	<	* suspended when the parallelism level rose.
746	<	*/
747	<	private volatile WaitQueueNode spareStack;
742	>	/**
743	>	* Pushes a task. Call only by owner in unshared queues.
744	>	*
745	>	* @param task the task. Caller must ensure non-null.
746	>	* @param p, if non-null, pool to signal if necessary
747	>	* @throw RejectedExecutionException if array cannot
748	>	* be resized
749	>	*/
750	>	final void push(ForkJoinTask<?> task, ForkJoinPool p) {
751	>	ForkJoinTask<?>[] a;
752	>	int s = top, m, n;
753	>	if ((a = array) != null) {    // ignore if queue removed
754	>	U.putOrderedObject
755	>	(a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task);
756	>	if ((n = (top = s + 1) - base) <= 2) {
757	>	if (p != null)
758	>	p.signalWork();
759	>	}
760	>	else if (n >= m)
761	>	growArray(true);
762	>	}
763	>	}
764
765	<	/**
766	<	* Sum of per-thread steal counts, updated only when threads are
767	<	* idle or terminating.
768	<	*/
769	<	private final AtomicLong stealCount;
765	>	/**
766	>	* Pushes a task if lock is free and array is either big
767	>	* enough or can be resized to be big enough.
768	>	*
769	>	* @param task the task. Caller must ensure non-null.
770	>	* @return true if submitted
771	>	*/
772	>	final boolean trySharedPush(ForkJoinTask<?> task) {
773	>	boolean submitted = false;
774	>	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
775	>	ForkJoinTask<?>[] a = array;
776	>	int s = top, n = s - base;
777	>	try {
778	>	if ((a != null && n < a.length - 1) ||
779	>	(a = growArray(false)) != null) { // must presize
780	>	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
781	>	U.putObject(a, (long)j, task);    // don't need "ordered"
782	>	top = s + 1;
783	>	submitted = true;
784	>	}
785	>	} finally {
786	>	runState = 0;                         // unlock
787	>	}
788	>	}
789	>	return submitted;
790	>	}
791
792	<	/**
793	<	* Queue for external submissions.
794	<	*/
795	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
792	>	/**
793	>	* Takes next task, if one exists, in FIFO order.
794	>	*/
795	>	final ForkJoinTask<?> poll() {
796	>	ForkJoinTask<?>[] a; int b, i;
797	>	while ((b = base) - top < 0 && (a = array) != null &&
798	>	(i = (a.length - 1) & b) >= 0) {
799	>	int j = (i << ASHIFT) + ABASE;
800	>	ForkJoinTask<?> t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
801	>	if (t != null && base == b &&
802	>	U.compareAndSwapObject(a, j, t, null)) {
803	>	base = b + 1;
804	>	return t;
805	>	}
806	>	}
807	>	return null;
808	>	}
809
810	<	/**
811	<	* Head of Treiber stack for barrier sync. See below for explanation
812	<	*/
813	<	private volatile WaitQueueNode syncStack;
810	>	/**
811	>	* Takes next task, if one exists, in LIFO order.
812	>	* Call only by owner in unshared queues.
813	>	*/
814	>	final ForkJoinTask<?> pop() {
815	>	ForkJoinTask<?> t; int m;
816	>	ForkJoinTask<?>[] a = array;
817	>	if (a != null && (m = a.length - 1) >= 0) {
818	>	for (int s; (s = top - 1) - base >= 0;) {
819	>	int j = ((m & s) << ASHIFT) + ABASE;
820	>	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) == null)
821	>	break;
822	>	if (U.compareAndSwapObject(a, j, t, null)) {
823	>	top = s;
824	>	return t;
825	>	}
826	>	}
827	>	}
828	>	return null;
829	>	}
830
831	<	/**
832	<	* The count for event barrier
833	<	*/
834	<	private volatile long eventCount;
831	>	/**
832	>	* Takes next task, if one exists, in order specified by mode.
833	>	*/
834	>	final ForkJoinTask<?> nextLocalTask() {
835	>	return mode == 0 ? pop() : poll();
836	>	}
837
838	<	/**
839	<	* Pool number, just for assigning useful names to worker threads
840	<	*/
841	<	private final int poolNumber;
838	>	/**
839	>	* Returns next task, if one exists, in order specified by mode.
840	>	*/
841	>	final ForkJoinTask<?> peek() {
842	>	ForkJoinTask<?>[] a = array; int m;
843	>	if (a == null || (m = a.length - 1) < 0)
844	>	return null;
845	>	int i = mode == 0 ? top - 1 : base;
846	>	int j = ((i & m) << ASHIFT) + ABASE;
847	>	return (ForkJoinTask<?>)U.getObjectVolatile(a, j);
848	>	}
849	>
850	>	/**
851	>	* Returns task at index b if b is current base of queue.
852	>	*/
853	>	final ForkJoinTask<?> pollAt(int b) {
854	>	ForkJoinTask<?>[] a; int i;
855	>	ForkJoinTask<?> task = null;
856	>	if ((a = array) != null && (i = ((a.length - 1) & b)) >= 0) {
857	>	int j = (i << ASHIFT) + ABASE;
858	>	ForkJoinTask<?> t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
859	>	if (t != null && base == b &&
860	>	U.compareAndSwapObject(a, j, t, null)) {
861	>	base = b + 1;
862	>	task = t;
863	>	}
864	>	}
865	>	return task;
866	>	}
867	>
868	>	/**
869	>	* Pops the given task only if it is at the current top.
870	>	*/
871	>	final boolean tryUnpush(ForkJoinTask<?> t) {
872	>	ForkJoinTask<?>[] a; int s;
873	>	if ((a = array) != null && (s = top) != base &&
874	>	U.compareAndSwapObject
875	>	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
876	>	top = s;
877	>	return true;
878	>	}
879	>	return false;
880	>	}
881	>
882	>	/**
883	>	* Polls the given task only if it is at the current base.
884	>	*/
885	>	final boolean pollFor(ForkJoinTask<?> task) {
886	>	ForkJoinTask<?>[] a; int b, i;
887	>	if ((b = base) - top < 0 && (a = array) != null &&
888	>	(i = (a.length - 1) & b) >= 0) {
889	>	int j = (i << ASHIFT) + ABASE;
890	>	if (U.getObjectVolatile(a, j) == task && base == b &&
891	>	U.compareAndSwapObject(a, j, task, null)) {
892	>	base = b + 1;
893	>	return true;
894	>	}
895	>	}
896	>	return false;
897	>	}
898	>
899	>	/**
900	>	* If present, removes from queue and executes the given task, or
901	>	* any other cancelled task. Returns (true) immediately on any CAS
902	>	* or consistency check failure so caller can retry.
903	>	*
904	>	* @return false if no progress can be made
905	>	*/
906	>	final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
907	>	boolean removed = false, empty = true, progress = true;
908	>	ForkJoinTask<?>[] a; int m, s, b, n;
909	>	if ((a = array) != null && (m = a.length - 1) >= 0 &&
910	>	(n = (s = top) - (b = base)) > 0) {
911	>	for (ForkJoinTask<?> t;;) {           // traverse from s to b
912	>	int j = ((--s & m) << ASHIFT) + ABASE;
913	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
914	>	if (t == null)                    // inconsistent length
915	>	break;
916	>	else if (t == task) {
917	>	if (s + 1 == top) {           // pop
918	>	if (!U.compareAndSwapObject(a, j, task, null))
919	>	break;
920	>	top = s;
921	>	removed = true;
922	>	}
923	>	else if (base == b)           // replace with proxy
924	>	removed = U.compareAndSwapObject(a, j, task,
925	>	new EmptyTask());
926	>	break;
927	>	}
928	>	else if (t.status >= 0)
929	>	empty = false;
930	>	else if (s + 1 == top) {          // pop and throw away
931	>	if (U.compareAndSwapObject(a, j, t, null))
932	>	top = s;
933	>	break;
934	>	}
935	>	if (--n == 0) {
936	>	if (!empty && base == b)
937	>	progress = false;
938	>	break;
939	>	}
940	>	}
941	>	}
942	>	if (removed)
943	>	task.doExec();
944	>	return progress;
945	>	}
946	>
947	>	/**
948	>	* Initializes or doubles the capacity of array. Call either
949	>	* by owner or with lock held -- it is OK for base, but not
950	>	* top, to move while resizings are in progress.
951	>	*
952	>	* @param rejectOnFailure if true, throw exception if capacity
953	>	* exceeded (relayed ultimately to user); else return null.
954	>	*/
955	>	final ForkJoinTask<?>[] growArray(boolean rejectOnFailure) {
956	>	ForkJoinTask<?>[] oldA = array;
957	>	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
958	>	if (size <= MAXIMUM_QUEUE_CAPACITY) {
959	>	int oldMask, t, b;
960	>	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
961	>	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
962	>	(t = top) - (b = base) > 0) {
963	>	int mask = size - 1;
964	>	do {
965	>	ForkJoinTask<?> x;
966	>	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
967	>	int j    = ((b &    mask) << ASHIFT) + ABASE;
968	>	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
969	>	if (x != null &&
970	>	U.compareAndSwapObject(oldA, oldj, x, null))
971	>	U.putObjectVolatile(a, j, x);
972	>	} while (++b != t);
973	>	}
974	>	return a;
975	>	}
976	>	else if (!rejectOnFailure)
977	>	return null;
978	>	else
979	>	throw new RejectedExecutionException("Queue capacity exceeded");
980	>	}
981	>
982	>	/**
983	>	* Removes and cancels all known tasks, ignoring any exceptions
984	>	*/
985	>	final void cancelAll() {
986	>	ForkJoinTask.cancelIgnoringExceptions(currentJoin);
987	>	ForkJoinTask.cancelIgnoringExceptions(currentSteal);
988	>	for (ForkJoinTask<?> t; (t = poll()) != null; )
989	>	ForkJoinTask.cancelIgnoringExceptions(t);
990	>	}
991	>
992	>	// Execution methods
993	>
994	>	/**
995	>	* Removes and runs tasks until empty, using local mode
996	>	* ordering.
997	>	*/
998	>	final void runLocalTasks() {
999	>	if (base - top < 0) {
1000	>	for (ForkJoinTask<?> t; (t = nextLocalTask()) != null; )
1001	>	t.doExec();
1002	>	}
1003	>	}
1004	>
1005	>	/**
1006	>	* Executes a top-level task and any local tasks remaining
1007	>	* after execution.
1008	>	*
1009	>	* @return true unless terminating
1010	>	*/
1011	>	final boolean runTask(ForkJoinTask<?> t) {
1012	>	boolean alive = true;
1013	>	if (t != null) {
1014	>	currentSteal = t;
1015	>	t.doExec();
1016	>	runLocalTasks();
1017	>	++nsteals;
1018	>	currentSteal = null;
1019	>	}
1020	>	else if (runState < 0)            // terminating
1021	>	alive = false;
1022	>	return alive;
1023	>	}
1024	>
1025	>	/**
1026	>	* Executes a non-top-level (stolen) task
1027	>	*/
1028	>	final void runSubtask(ForkJoinTask<?> t) {
1029	>	if (t != null) {
1030	>	ForkJoinTask<?> ps = currentSteal;
1031	>	currentSteal = t;
1032	>	t.doExec();
1033	>	currentSteal = ps;
1034	>	}
1035	>	}
1036	>
1037	>	/**
1038	>	* Computes next value for random probes.  Scans don't require
1039	>	* a very high quality generator, but also not a crummy one.
1040	>	* Marsaglia xor-shift is cheap and works well enough.  Note:
1041	>	* This is manually inlined in several usages in ForkJoinPool
1042	>	* to avoid writes inside busy scan loops.
1043	>	*/
1044	>	final int nextSeed() {
1045	>	int r = seed;
1046	>	r ^= r << 13;
1047	>	r ^= r >>> 17;
1048	>	r ^= r << 5;
1049	>	return seed = r;
1050	>	}
1051	>
1052	>	// Unsafe mechanics
1053	>	private static final sun.misc.Unsafe U;
1054	>	private static final long RUNSTATE;
1055	>	private static final int ABASE;
1056	>	private static final int ASHIFT;
1057	>	static {
1058	>	int s;
1059	>	try {
1060	>	U = getUnsafe();
1061	>	Class<?> k = WorkQueue.class;
1062	>	Class<?> ak = ForkJoinTask[].class;
1063	>	RUNSTATE = U.objectFieldOffset
1064	>	(k.getDeclaredField("runState"));
1065	>	ABASE = U.arrayBaseOffset(ak);
1066	>	s = U.arrayIndexScale(ak);
1067	>	} catch (Exception e) {
1068	>	throw new Error(e);
1069	>	}
1070	>	if ((s & (s-1)) != 0)
1071	>	throw new Error("data type scale not a power of two");
1072	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
1073	>	}
1074	>	}
1075
1076		/**
1077	<	* The maximum allowed pool size
1077	>	* Class for artificial tasks that are used to replace the target
1078	>	* of local joins if they are removed from an interior queue slot
1079	>	* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
1080	>	* actually do anything beyond having a unique identity.
1081		*/
1082	<	private volatile int maxPoolSize;
1082	>	static final class EmptyTask extends ForkJoinTask<Void> {
1083	>	EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
1084	>	public Void getRawResult() { return null; }
1085	>	public void setRawResult(Void x) {}
1086	>	public boolean exec() { return true; }
1087	>	}
1088
1089		/**
1090	<	* The desired parallelism level, updated only under workerLock.
1090	>	<<<<<<< ForkJoinPool.java
1091	>	* Per-thread records for (typically non-FJ) threads that submit
1092	>	* to pools. Cureently holds only psuedo-random seed / index that
1093	>	* is used to chose submission queues in method doSubmit. In the
1094	>	* future, this may incorporate a means to implement different
1095	>	* task rejection and resubmission policies.
1096		*/
1097	<	private volatile int parallelism;
1097	>	static final class Submitter {
1098	>	int seed; // seed for random submission queue selection
1099	>
1100	>	// Heuristic padding to ameliorate unfortunate memory placements
1101	>	int p0, p1, p2, p3, p4, p5, p6, p7, p8, p9, pa, pb, pc, pd, pe;
1102	>
1103	>	Submitter() {
1104	>	// Use identityHashCode, forced negative, for seed
1105	>	seed = System.identityHashCode(Thread.currentThread()) | (1 << 31);
1106	>	}
1107	>
1108	>	/**
1109	>	* Computes next value for random probes.  Like method
1110	>	* WorkQueue.nextSeed, this is manually inlined in several
1111	>	* usages to avoid writes inside busy loops.
1112	>	*/
1113	>	final int nextSeed() {
1114	>	int r = seed;
1115	>	r ^= r << 13;
1116	>	r ^= r >>> 17;
1117	>	return seed = r ^= r << 5;
1118	>	}
1119	>	}
1120	>
1121	>	/** ThreadLocal class for Submitters */
1122	>	static final class ThreadSubmitter extends ThreadLocal<Submitter> {
1123	>	public Submitter initialValue() { return new Submitter(); }
1124	>	}
1125
1126		/**
1127	<	* True if use local fifo, not default lifo, for local polling
1127	>	* Per-thread submission bookeeping. Shared across all pools
1128	>	* to reduce ThreadLocal pollution and because random motion
1129	>	* to avoid contention in one pool is likely to hold for others.
1130		*/
1131	<	private volatile boolean locallyFifo;
1131	>	static final ThreadSubmitter submitters = new ThreadSubmitter();
1132
1133		/**
1134	<	* Holds number of total (i.e., created and not yet terminated)
215	<	* and running (i.e., not blocked on joins or other managed sync)
216	<	* threads, packed into one int to ensure consistent snapshot when
217	<	* making decisions about creating and suspending spare
218	<	* threads. Updated only by CAS.  Note: CASes in
219	<	* updateRunningCount and preJoin running active count is in low
220	<	* word, so need to be modified if this changes
1134	>	* Top-level runloop for workers
1135		*/
1136	<	private volatile int workerCounts;
1136	>	final void runWorker(ForkJoinWorkerThread wt) {
1137	>	// Initialize queue array and seed in this thread
1138	>	WorkQueue w = wt.workQueue;
1139	>	w.growArray(false);
1140	>	// Same initial hash as Submitters
1141	>	w.seed = System.identityHashCode(Thread.currentThread()) | (1 << 31);
1142	>
1143	>	do {} while (w.runTask(scan(w)));
1144	>	}
1145
1146	<	private static int totalCountOf(int s)           { return s >>> 16;  }
225	<	private static int runningCountOf(int s)         { return s & shortMask; }
226	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
1146	>	// Creating, registering and deregistering workers
1147
1148		/**
1149	<	* Adds delta (which may be negative) to running count.  This must
230	<	* be called before (with negative arg) and after (with positive)
231	<	* any managed synchronization (i.e., mainly, joins).
232	<	* @param delta the number to add
1149	>	* Tries to create and start a worker
1150		*/
1151	<	final void updateRunningCount(int delta) {
1152	<	int s;
1153	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
1151	>	private void addWorker() {
1152	>	Throwable ex = null;
1153	>	ForkJoinWorkerThread w = null;
1154	>	try {
1155	>	if ((w = factory.newThread(this)) != null) {
1156	>	w.start();
1157	>	return;
1158	>	}
1159	>	} catch (Throwable e) {
1160	>	ex = e;
1161	>	}
1162	>	deregisterWorker(w, ex);
1163		}
1164
1165		/**
1166	<	* Adds delta (which may be negative) to both total and running
1167	<	* count.  This must be called upon creation and termination of
1168	<	* worker threads.
1169	<	* @param delta the number to add
1166	>	* Callback from ForkJoinWorkerThread constructor to assign a
1167	>	* public name. This must be separate from registerWorker because
1168	>	* it is called during the "super" constructor call in
1169	>	* ForkJoinWorkerThread.
1170		*/
1171	<	private void updateWorkerCount(int delta) {
1172	<	int d = delta + (delta << 16); // add to both lo and hi parts
1173	<	int s;
248	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
1171	>	final String nextWorkerName() {
1172	>	return workerNamePrefix.concat
1173	>	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1174		}
1175
1176		/**
1177	<	* Lifecycle control. High word contains runState, low word
1178	<	* contains the number of workers that are (probably) executing
1179	<	* tasks. This value is atomically incremented before a worker
1180	<	* gets a task to run, and decremented when worker has no tasks
256	<	* and cannot find any. These two fields are bundled together to
257	<	* support correct termination triggering.  Note: activeCount
258	<	* CAS'es cheat by assuming active count is in low word, so need
259	<	* to be modified if this changes
1177	>	* Callback from ForkJoinWorkerThread constructor to establish and
1178	>	* record its WorkQueue
1179	>	*
1180	>	* @param wt the worker thread
1181		*/
1182	<	private volatile int runControl;
1183	<
1184	<	// RunState values. Order among values matters
1185	<	private static final int RUNNING     = 0;
1186	<	private static final int SHUTDOWN    = 1;
1187	<	private static final int TERMINATING = 2;
1188	<	private static final int TERMINATED  = 3;
1189	<
1190	<	private static int runStateOf(int c)             { return c >>> 16; }
1191	<	private static int activeCountOf(int c)          { return c & shortMask; }
1192	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
1182	>	final void registerWorker(ForkJoinWorkerThread wt) {
1183	>	WorkQueue w = wt.workQueue;
1184	>	ReentrantLock lock = this.lock;
1185	>	lock.lock();
1186	>	try {
1187	>	int k = nextPoolIndex;
1188	>	WorkQueue[] ws = workQueues;
1189	>	if (ws != null) {                       // ignore on shutdown
1190	>	int n = ws.length;
1191	>	if (k < 0 || (k & 1) == 0 || k >= n || ws[k] != null) {
1192	>	for (k = 1; k < n && ws[k] != null; k += 2)
1193	>	;                           // workers are at odd indices
1194	>	if (k >= n)                     // resize
1195	>	workQueues = ws = Arrays.copyOf(ws, n << 1);
1196	>	}
1197	>	w.poolIndex = k;
1198	>	w.eventCount = ~(k >>> 1) & SMASK;  // Set up wait count
1199	>	ws[k] = w;                          // record worker
1200	>	nextPoolIndex = k + 2;
1201	>	int rs = runState;
1202	>	int m = rs & SMASK;                 // recalculate runState mask
1203	>	if (k > m)
1204	>	m = (m << 1) + 1;
1205	>	runState = (rs & SHUTDOWN) | ((rs + RS_SEQ) & RS_SEQ_MASK) | m;
1206	>	}
1207	>	} finally {
1208	>	lock.unlock();
1209	>	}
1210	>	}
1211
1212		/**
1213	<	* Try incrementing active count; fail on contention. Called by
1214	<	* workers before/during executing tasks.
1215	<	* @return true on success
1216	<	*/
1217	<	final boolean tryIncrementActiveCount() {
1218	<	int c = runControl;
1219	<	return casRunControl(c, c+1);
1213	>	* Final callback from terminating worker, as well as failure to
1214	>	* construct or start a worker in addWorker.  Removes record of
1215	>	* worker from array, and adjusts counts. If pool is shutting
1216	>	* down, tries to complete termination.
1217	>	*
1218	>	* @param wt the worker thread or null if addWorker failed
1219	>	* @param ex the exception causing failure, or null if none
1220	>	*/
1221	>	final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1222	>	WorkQueue w = null;
1223	>	if (wt != null && (w = wt.workQueue) != null) {
1224	>	w.runState = -1;                // ensure runState is set
1225	>	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1226	>	int idx = w.poolIndex;
1227	>	ReentrantLock lock = this.lock;
1228	>	lock.lock();
1229	>	try {                           // remove record from array
1230	>	WorkQueue[] ws = workQueues;
1231	>	if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1232	>	ws[nextPoolIndex = idx] = null;
1233	>	} finally {
1234	>	lock.unlock();
1235	>	}
1236	>	}
1237	>
1238	>	long c;                             // adjust ctl counts
1239	>	do {} while (!U.compareAndSwapLong
1240	>	(this, CTL, c = ctl, (((c - AC_UNIT) & AC_MASK) |
1241	>	((c - TC_UNIT) & TC_MASK) |
1242	>	(c & ~(AC_MASK|TC_MASK)))));
1243	>
1244	>	if (!tryTerminate(false) && w != null) {
1245	>	w.cancelAll();                  // cancel remaining tasks
1246	>	if (w.array != null)            // suppress signal if never ran
1247	>	signalWork();               // wake up or create replacement
1248	>	}
1249	>
1250	>	if (ex != null)                     // rethrow
1251	>	U.throwException(ex);
1252		}
1253
1254		/**
1255	<	* Tries decrementing active count; fails on contention.
1256	<	* Possibly triggers termination on success.
1257	<	* Called by workers when they can't find tasks.
1258	<	* @return true on success
1259	<	*/
1260	<	final boolean tryDecrementActiveCount() {
1261	<	int c = runControl;
1262	<	int nextc = c - 1;
1263	<	if (!casRunControl(c, nextc))
1264	<	return false;
1265	<	if (canTerminateOnShutdown(nextc))
1266	<	terminateOnShutdown();
1267	<	return true;
1255	>	* Tries to add and register a new queue at the given index.
1256	>	*
1257	>	* @param idx the workQueues array index to register the queue
1258	>	* @return the queue, or null if could not add because could
1259	>	* not acquire lock or idx is unusable
1260	>	*/
1261	>	private WorkQueue tryAddSharedQueue(int idx) {
1262	>	WorkQueue q = null;
1263	>	ReentrantLock lock = this.lock;
1264	>	if (idx >= 0 && (idx & 1) == 0 && !lock.isLocked()) {
1265	>	// create queue outside of lock but only if apparently free
1266	>	WorkQueue nq = new WorkQueue(null, SHARED_QUEUE);
1267	>	if (lock.tryLock()) {
1268	>	try {
1269	>	WorkQueue[] ws = workQueues;
1270	>	if (ws != null && idx < ws.length) {
1271	>	if ((q = ws[idx]) == null) {
1272	>	int rs;         // update runState seq
1273	>	ws[idx] = q = nq;
1274	>	runState = (((rs = runState) & SHUTDOWN) |
1275	>	((rs + RS_SEQ) & ~SHUTDOWN));
1276	>	}
1277	>	}
1278	>	} finally {
1279	>	lock.unlock();
1280	>	}
1281	>	}
1282	>	}
1283	>	return q;
1284		}
1285
1286	+	// Maintaining ctl counts
1287	+
1288		/**
1289	<	* Returns true if argument represents zero active count and
301	<	* nonzero runstate, which is the triggering condition for
302	<	* terminating on shutdown.
1289	>	* Increments active count; mainly called upon return from blocking
1290		*/
1291	<	private static boolean canTerminateOnShutdown(int c) {
1292	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
1291	>	final void incrementActiveCount() {
1292	>	long c;
1293	>	do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
1294		}
1295
1296		/**
1297	<	* Transition run state to at least the given state. Return true
310	<	* if not already at least given state.
1297	>	* Activates or creates a worker
1298		*/
1299	<	private boolean transitionRunStateTo(int state) {
1300	<	for (;;) {
1301	<	int c = runControl;
1302	<	if (runStateOf(c) >= state)
1303	<	return false;
1304	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
1305	<	return true;
1299	>	final void signalWork() {
1300	>	/*
1301	>	* The while condition is true if: (there is are too few total
1302	>	* workers OR there is at least one waiter) AND (there are too
1303	>	* few active workers OR the pool is terminating).  The value
1304	>	* of e distinguishes the remaining cases: zero (no waiters)
1305	>	* for create, negative if terminating (in which case do
1306	>	* nothing), else release a waiter. The secondary checks for
1307	>	* release (non-null array etc) can fail if the pool begins
1308	>	* terminating after the test, and don't impose any added cost
1309	>	* because JVMs must perform null and bounds checks anyway.
1310	>	*/
1311	>	long c; int e, u;
1312	>	while ((((e = (int)(c = ctl)) | (u = (int)(c >>> 32))) &
1313	>	(INT_SIGN|SHORT_SIGN)) == (INT_SIGN|SHORT_SIGN)) {
1314	>	WorkQueue[] ws = workQueues; int i; WorkQueue w; Thread p;
1315	>	if (e == 0) {                    // add a new worker
1316	>	if (U.compareAndSwapLong
1317	>	(this, CTL, c, (long)(((u + UTC_UNIT) & UTC_MASK) |
1318	>	((u + UAC_UNIT) & UAC_MASK)) << 32)) {
1319	>	addWorker();
1320	>	break;
1321	>	}
1322	>	}
1323	>	else if (e > 0 && ws != null &&
1324	>	(i = ((~e << 1) | 1) & SMASK) < ws.length &&
1325	>	(w = ws[i]) != null &&
1326	>	w.eventCount == (e | INT_SIGN)) {
1327	>	if (U.compareAndSwapLong
1328	>	(this, CTL, c, (((long)(w.nextWait & E_MASK)) |
1329	>	((long)(u + UAC_UNIT) << 32)))) {
1330	>	w.eventCount = (e + E_SEQ) & E_MASK;
1331	>	if ((p = w.parker) != null)
1332	>	U.unpark(p);         // release a waiting worker
1333	>	break;
1334	>	}
1335	>	}
1336	>	else
1337	>	break;
1338		}
1339		}
1340
1341		/**
1342	<	* Controls whether to add spares to maintain parallelism
1343	<	*/
1344	<	private volatile boolean maintainsParallelism;
1342	>	* Tries to decrement active count (sometimes implicitly) and
1343	>	* possibly release or create a compensating worker in preparation
1344	>	* for blocking. Fails on contention or termination.
1345	>	*
1346	>	* @return true if the caller can block, else should recheck and retry
1347	>	*/
1348	>	final boolean tryCompensate() {
1349	>	WorkQueue[] ws; WorkQueue w; Thread p;
1350	>	int pc = parallelism, e, u, ac, tc, i;
1351	>	long c = ctl;
1352	>
1353	>	if ((e = (int)c) >= 0) {
1354	>	if ((ac = ((u = (int)(c >>> 32)) >> UAC_SHIFT)) <= 0 &&
1355	>	e != 0 && (ws = workQueues) != null &&
1356	>	(i = ((~e << 1) | 1) & SMASK) < ws.length &&
1357	>	(w = ws[i]) != null) {
1358	>	if (w.eventCount == (e | INT_SIGN) &&
1359	>	U.compareAndSwapLong
1360	>	(this, CTL, c, ((long)(w.nextWait & E_MASK) |
1361	>	(c & (AC_MASK|TC_MASK))))) {
1362	>	w.eventCount = (e + E_SEQ) & E_MASK;
1363	>	if ((p = w.parker) != null)
1364	>	U.unpark(p);
1365	>	return true;             // release an idle worker
1366	>	}
1367	>	}
1368	>	else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) {
1369	>	long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
1370	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1371	>	return true;             // no compensation needed
1372	>	}
1373	>	else if (tc + pc < MAX_ID) {
1374	>	long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
1375	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1376	>	addWorker();
1377	>	return true;             // create replacement
1378	>	}
1379	>	}
1380	>	}
1381	>	return false;
1382	>	}
1383
1384	<	// Constructors
1384	>	// Submissions
1385
1386		/**
1387	<	* Creates a ForkJoinPool with a pool size equal to the number of
1388	<	* processors available on the system and using the default
1389	<	* ForkJoinWorkerThreadFactory,
1390	<	* @throws SecurityException if a security manager exists and
334	<	*         the caller is not permitted to modify threads
335	<	*         because it does not hold {@link
336	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1387	>	* Unless shutting down, adds the given task to a submission queue
1388	>	* at submitter's current queue index. If no queue exists at the
1389	>	* index, one is created unless pool lock is busy.  If the queue
1390	>	* and/or lock are busy, another index is randomly chosen.
1391		*/
1392	<	public ForkJoinPool() {
1393	<	this(Runtime.getRuntime().availableProcessors(),
1394	<	defaultForkJoinWorkerThreadFactory);
1392	>	private void doSubmit(ForkJoinTask<?> task) {
1393	>	if (task == null)
1394	>	throw new NullPointerException();
1395	>	Submitter s = submitters.get();
1396	>	for (int r = s.seed;;) {
1397	>	WorkQueue q; int k;
1398	>	int rs = runState, m = rs & SMASK;
1399	>	WorkQueue[] ws = workQueues;
1400	>	if (rs < 0 || ws == null)   // shutting down
1401	>	throw new RejectedExecutionException();
1402	>	if (ws.length > m &&        // k must be at index
1403	>	((q = ws[k = (r << 1) & m]) != null ||
1404	>	(q = tryAddSharedQueue(k)) != null) &&
1405	>	q.trySharedPush(task)) {
1406	>	signalWork();
1407	>	return;
1408	>	}
1409	>	r ^= r << 13;               // xorshift seed to new position
1410	>	r ^= r >>> 17;
1411	>	if (((s.seed = r ^= r << 5) & m) == 0)
1412	>	Thread.yield();         // occasionally yield if busy
1413	>	}
1414	>	}
1415	>
1416	>
1417	>	// Scanning for tasks
1418	>
1419	>	/**
1420	>	* Scans for and, if found, returns one task, else possibly
1421	>	* inactivates the worker. This method operates on single reads of
1422	>	* volatile state and is designed to be re-invoked continuously in
1423	>	* part because it returns upon detecting inconsistencies,
1424	>	* contention, or state changes that indicate possible success on
1425	>	* re-invocation.
1426	>	*
1427	>	* The scan searches for tasks across queues, randomly selecting
1428	>	* the first #queues probes, favoring steals 2:1 over submissions
1429	>	* (by exploiting even/odd indexing), and then performing a
1430	>	* circular sweep of all queues.  The scan terminates upon either
1431	>	* finding a non-empty queue, or completing a full sweep. If the
1432	>	* worker is not inactivated, it takes and returns a task from
1433	>	* this queue.  On failure to find a task, we take one of the
1434	>	* following actions, after which the caller will retry calling
1435	>	* this method unless terminated.
1436	>	*
1437	>	* * If not a complete sweep, try to release a waiting worker.  If
1438	>	* the scan terminated because the worker is inactivated, then the
1439	>	* released worker will often be the calling worker, and it can
1440	>	* succeed obtaining a task on the next call. Or maybe it is
1441	>	* another worker, but with same net effect. Releasing in other
1442	>	* cases as well ensures that we have enough workers running.
1443	>	*
1444	>	* * If the caller has run a task since the the last empty scan,
1445	>	* return (to allow rescan) if other workers are not also yet
1446	>	* enqueued.  Field WorkQueue.rescans counts down on each scan to
1447	>	* ensure eventual inactivation, and occasional calls to
1448	>	* Thread.yield to help avoid interference with more useful
1449	>	* activities on the system.
1450	>	*
1451	>	* * If pool is terminating, terminate the worker
1452	>	*
1453	>	* * If not already enqueued, try to inactivate and enqueue the
1454	>	* worker on wait queue.
1455	>	*
1456	>	* * If already enqueued and none of the above apply, either park
1457	>	* awaiting signal, or if this is the most recent waiter and pool
1458	>	* is quiescent, relay to idleAwaitWork to check for termination
1459	>	* and possibly shrink pool.
1460	>	*
1461	>	* @param w the worker (via its WorkQueue)
1462	>	* @return a task or null of none found
1463	>	*/
1464	>	private final ForkJoinTask<?> scan(WorkQueue w) {
1465	>	boolean swept = false;                 // true after full empty scan
1466	>	WorkQueue[] ws;                        // volatile read order matters
1467	>	int r = w.seed, ec = w.eventCount;     // ec is negative if inactive
1468	>	int rs = runState, m = rs & SMASK;
1469	>	if ((ws = workQueues) != null && ws.length > m) {
1470	>	ForkJoinTask<?> task = null;
1471	>	for (int k = 0, j = -2 - m; ; ++j) {
1472	>	WorkQueue q; int b;
1473	>	if (j < 0) {                    // random probes while j negative
1474	>	r ^= r << 13; r ^= r >>> 17; k = (r ^= r << 5) | (j & 1);
1475	>	}                               // worker (not submit) for odd j
1476	>	else                            // cyclic scan when j >= 0
1477	>	k += (m >>> 1) | 1;         // step by half to reduce bias
1478	>
1479	>	if ((q = ws[k & m]) != null && (b = q.base) - q.top < 0) {
1480	>	if (ec >= 0)
1481	>	task = q.pollAt(b);     // steal
1482	>	break;
1483	>	}
1484	>	else if (j > m) {
1485	>	if (rs == runState)        // staleness check
1486	>	swept = true;
1487	>	break;
1488	>	}
1489	>	}
1490	>	w.seed = r;                        // save seed for next scan
1491	>	if (task != null)
1492	>	return task;
1493	>	}
1494	>
1495	>	// Decode ctl on empty scan
1496	>	long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
1497	>	if (!swept) {                          // try to release a waiter
1498	>	WorkQueue v; Thread p;
1499	>	if (e > 0 && a < 0 && ws != null &&
1500	>	(v = ws[((~e << 1) | 1) & m]) != null &&
1501	>	v.eventCount == (e | INT_SIGN) && U.compareAndSwapLong
1502	>	(this, CTL, c, ((long)(v.nextWait & E_MASK) |
1503	>	((c + AC_UNIT) & (AC_MASK|TC_MASK))))) {
1504	>	v.eventCount = (e + E_SEQ) & E_MASK;
1505	>	if ((p = v.parker) != null)
1506	>	U.unpark(p);
1507	>	}
1508	>	}
1509	>	else if ((nr = w.rescans) > 0) {       // continue rescanning
1510	>	int ac = a + parallelism;
1511	>	if ((w.rescans = (ac < nr) ? ac : nr - 1) > 0 && w.seed < 0 &&
1512	>	w.eventCount == ec)
1513	>	Thread.yield();                // 1 bit randomness for yield call
1514	>	}
1515	>	else if (e < 0)                        // pool is terminating
1516	>	w.runState = -1;
1517	>	else if (ec >= 0) {                    // try to enqueue
1518	>	long nc = (long)ec | ((c - AC_UNIT) & (AC_MASK|TC_MASK));
1519	>	w.nextWait = e;
1520	>	w.eventCount = ec | INT_SIGN;      // mark as inactive
1521	>	if (!U.compareAndSwapLong(this, CTL, c, nc))
1522	>	w.eventCount = ec;             // back out on CAS failure
1523	>	else if ((ns = w.nsteals) != 0) {  // set rescans if ran task
1524	>	if (a <= 0)                    // ... unless too many active
1525	>	w.rescans = a + parallelism;
1526	>	w.nsteals = 0;
1527	>	w.totalSteals += ns;
1528	>	}
1529	>	}
1530	>	else{                                  // already queued
1531	>	if (parallelism == -a)
1532	>	idleAwaitWork(w);              // quiescent
1533	>	if (w.eventCount == ec) {
1534	>	Thread.interrupted();          // clear status
1535	>	ForkJoinWorkerThread wt = w.owner;
1536	>	U.putObject(wt, PARKBLOCKER, this);
1537	>	w.parker = wt;                 // emulate LockSupport.park
1538	>	if (w.eventCount == ec)        // recheck
1539	>	U.park(false, 0L);         // block
1540	>	w.parker = null;
1541	>	U.putObject(wt, PARKBLOCKER, null);
1542	>	}
1543	>	}
1544	>	return null;
1545	>	}
1546	>
1547	>	/**
1548	>	* If inactivating worker w has caused pool to become quiescent,
1549	>	* check for pool termination, and, so long as this is not the
1550	>	* only worker, wait for event for up to SHRINK_RATE nanosecs On
1551	>	* timeout, if ctl has not changed, terminate the worker, which
1552	>	* will in turn wake up another worker to possibly repeat this
1553	>	* process.
1554	>	*
1555	>	* @param w the calling worker
1556	>	*/
1557	>	private void idleAwaitWork(WorkQueue w) {
1558	>	long c; int nw, ec;
1559	>	if (!tryTerminate(false) &&
1560	>	(int)((c = ctl) >> AC_SHIFT) + parallelism == 0 &&
1561	>	(ec = w.eventCount) == ((int)c | INT_SIGN) &&
1562	>	(nw = w.nextWait) != 0) {
1563	>	long nc = ((long)(nw & E_MASK) | // ctl to restore on timeout
1564	>	((c + AC_UNIT) & AC_MASK) | (c & TC_MASK));
1565	>	ForkJoinTask.helpExpungeStaleExceptions(); // help clean
1566	>	ForkJoinWorkerThread wt = w.owner;
1567	>	while (ctl == c) {
1568	>	long startTime = System.nanoTime();
1569	>	Thread.interrupted();  // timed variant of version in scan()
1570	>	U.putObject(wt, PARKBLOCKER, this);
1571	>	w.parker = wt;
1572	>	if (ctl == c)
1573	>	U.park(false, SHRINK_RATE);
1574	>	w.parker = null;
1575	>	U.putObject(wt, PARKBLOCKER, null);
1576	>	if (ctl != c)
1577	>	break;
1578	>	if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
1579	>	U.compareAndSwapLong(this, CTL, c, nc)) {
1580	>	w.runState = -1;          // shrink
1581	>	w.eventCount = (ec + E_SEQ) | E_MASK;
1582	>	break;
1583	>	}
1584	>	}
1585	>	}
1586		}
1587
1588		/**
1589	<	* Creates a ForkJoinPool with the indicated parallelism level
1590	<	* threads, and using the default ForkJoinWorkerThreadFactory,
1591	<	* @param parallelism the number of worker threads
1592	<	* @throws IllegalArgumentException if parallelism less than or
1593	<	* equal to zero
1594	<	* @throws SecurityException if a security manager exists and
1595	<	*         the caller is not permitted to modify threads
1596	<	*         because it does not hold {@link
1597	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1598	<	*/
1599	<	public ForkJoinPool(int parallelism) {
1600	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
1589	>	* Tries to locate and execute tasks for a stealer of the given
1590	>	* task, or in turn one of its stealers, Traces currentSteal ->
1591	>	* currentJoin links looking for a thread working on a descendant
1592	>	* of the given task and with a non-empty queue to steal back and
1593	>	* execute tasks from. The first call to this method upon a
1594	>	* waiting join will often entail scanning/search, (which is OK
1595	>	* because the joiner has nothing better to do), but this method
1596	>	* leaves hints in workers to speed up subsequent calls. The
1597	>	* implementation is very branchy to cope with potential
1598	>	* inconsistencies or loops encountering chains that are stale,
1599	>	* unknown, or of length greater than MAX_HELP_DEPTH links.  All
1600	>	* of these cases are dealt with by just retrying by caller.
1601	>	*
1602	>	* @param joiner the joining worker
1603	>	* @param task the task to join
1604	>	* @return true if found or ran a task (and so is immediately retryable)
1605	>	*/
1606	>	final boolean tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1607	>	ForkJoinTask<?> subtask;    // current target
1608	>	boolean progress = false;
1609	>	int depth = 0;              // current chain depth
1610	>	int m = runState & SMASK;
1611	>	WorkQueue[] ws = workQueues;
1612	>
1613	>	if (ws != null && ws.length > m && (subtask = task).status >= 0) {
1614	>	outer:for (WorkQueue j = joiner;;) {
1615	>	// Try to find the stealer of subtask, by first using hint
1616	>	WorkQueue stealer = null;
1617	>	WorkQueue v = ws[j.stealHint & m];
1618	>	if (v != null && v.currentSteal == subtask)
1619	>	stealer = v;
1620	>	else {
1621	>	for (int i = 1; i <= m; i += 2) {
1622	>	if ((v = ws[i]) != null && v.currentSteal == subtask) {
1623	>	stealer = v;
1624	>	j.stealHint = i; // save hint
1625	>	break;
1626	>	}
1627	>	}
1628	>	if (stealer == null)
1629	>	break;
1630	>	}
1631	>
1632	>	for (WorkQueue q = stealer;;) { // Try to help stealer
1633	>	ForkJoinTask<?> t; int b;
1634	>	if (task.status < 0)
1635	>	break outer;
1636	>	if ((b = q.base) - q.top < 0) {
1637	>	progress = true;
1638	>	if (subtask.status < 0)
1639	>	break outer;               // stale
1640	>	if ((t = q.pollAt(b)) != null) {
1641	>	stealer.stealHint = joiner.poolIndex;
1642	>	joiner.runSubtask(t);
1643	>	}
1644	>	}
1645	>	else { // empty - try to descend to find stealer's stealer
1646	>	ForkJoinTask<?> next = stealer.currentJoin;
1647	>	if (++depth == MAX_HELP_DEPTH || subtask.status < 0 ||
1648	>	next == null || next == subtask)
1649	>	break outer;  // max depth, stale, dead-end, cyclic
1650	>	subtask = next;
1651	>	j = stealer;
1652	>	break;
1653	>	}
1654	>	}
1655	>	}
1656	>	}
1657	>	return progress;
1658		}
1659
1660		/**
1661	<	* Creates a ForkJoinPool with parallelism equal to the number of
1662	<	* processors available on the system and using the given
1663	<	* ForkJoinWorkerThreadFactory,
1664	<	* @param factory the factory for creating new threads
363	<	* @throws NullPointerException if factory is null
364	<	* @throws SecurityException if a security manager exists and
365	<	*         the caller is not permitted to modify threads
366	<	*         because it does not hold {@link
367	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1661	>	* If task is at base of some steal queue, steals and executes it.
1662	>	*
1663	>	* @param joiner the joining worker
1664	>	* @param task the task
1665		*/
1666	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
1667	<	this(Runtime.getRuntime().availableProcessors(), factory);
1666	>	final void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
1667	>	WorkQueue[] ws;
1668	>	int m = runState & SMASK;
1669	>	if ((ws = workQueues) != null && ws.length > m) {
1670	>	for (int j = 1; j <= m && task.status >= 0; j += 2) {
1671	>	WorkQueue q = ws[j];
1672	>	if (q != null && q.pollFor(task)) {
1673	>	joiner.runSubtask(task);
1674	>	break;
1675	>	}
1676	>	}
1677	>	}
1678		}
1679
1680		/**
1681	<	* Creates a ForkJoinPool with the given parallelism and factory.
1682	<	*
1683	<	* @param parallelism the targeted number of worker threads
1684	<	* @param factory the factory for creating new threads
1685	<	* @throws IllegalArgumentException if parallelism less than or
1686	<	* equal to zero, or greater than implementation limit
1687	<	* @throws NullPointerException if factory is null
1688	<	* @throws SecurityException if a security manager exists and
1689	<	*         the caller is not permitted to modify threads
1690	<	*         because it does not hold {@link
1691	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1692	<	*/
1693	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
1694	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
1695	<	throw new IllegalArgumentException();
1696	<	if (factory == null)
1697	<	throw new NullPointerException();
1698	<	checkPermission();
1699	<	this.factory = factory;
1700	<	this.parallelism = parallelism;
1701	<	this.maxPoolSize = MAX_THREADS;
1702	<	this.maintainsParallelism = true;
1703	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
1704	<	this.workerLock = new ReentrantLock();
1705	<	this.termination = workerLock.newCondition();
1706	<	this.stealCount = new AtomicLong();
400	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
401	<	// worker array and workers are lazily constructed
1681	>	* Returns a non-empty steal queue, if one is found during a random,
1682	>	* then cyclic scan, else null.  This method must be retried by
1683	>	* caller if, by the time it tries to use the queue, it is empty.
1684	>	*/
1685	>	private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
1686	>	int r = w.seed;    // Same idea as scan(), but ignoring submissions
1687	>	for (WorkQueue[] ws;;) {
1688	>	int m = runState & SMASK;
1689	>	if ((ws = workQueues) == null)
1690	>	return null;
1691	>	if (ws.length > m) {
1692	>	WorkQueue q;
1693	>	for (int n = m << 2, k = r, j = -n;;) {
1694	>	r ^= r << 13; r ^= r >>> 17; r ^= r << 5;
1695	>	if ((q = ws[(k | 1) & m]) != null && q.base - q.top < 0) {
1696	>	w.seed = r;
1697	>	return q;
1698	>	}
1699	>	else if (j > n)
1700	>	return null;
1701	>	else
1702	>	k = (j++ < 0) ? r : k + ((m >>> 1) | 1);
1703	>
1704	>	}
1705	>	}
1706	>	}
1707		}
1708
1709		/**
1710	<	* Create new worker using factory.
1711	<	* @param index the index to assign worker
1712	<	* @return new worker, or null of factory failed
1713	<	*/
1714	<	private ForkJoinWorkerThread createWorker(int index) {
1715	<	Thread.UncaughtExceptionHandler h = ueh;
1716	<	ForkJoinWorkerThread w = factory.newThread(this);
1717	<	if (w != null) {
1718	<	w.poolIndex = index;
1719	<	w.setDaemon(true);
1720	<	w.setAsyncMode(locallyFifo);
1721	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
1722	<	if (h != null)
1723	<	w.setUncaughtExceptionHandler(h);
1710	>	* Runs tasks until {@code isQuiescent()}. We piggyback on
1711	>	* active count ctl maintenance, but rather than blocking
1712	>	* when tasks cannot be found, we rescan until all others cannot
1713	>	* find tasks either.
1714	>	*/
1715	>	final void helpQuiescePool(WorkQueue w) {
1716	>	for (boolean active = true;;) {
1717	>	w.runLocalTasks();      // exhaust local queue
1718	>	WorkQueue q = findNonEmptyStealQueue(w);
1719	>	if (q != null) {
1720	>	ForkJoinTask<?> t;
1721	>	if (!active) {      // re-establish active count
1722	>	long c;
1723	>	active = true;
1724	>	do {} while (!U.compareAndSwapLong
1725	>	(this, CTL, c = ctl, c + AC_UNIT));
1726	>	}
1727	>	if ((t = q.poll()) != null)
1728	>	w.runSubtask(t);
1729	>	}
1730	>	else {
1731	>	long c;
1732	>	if (active) {       // decrement active count without queuing
1733	>	active = false;
1734	>	do {} while (!U.compareAndSwapLong
1735	>	(this, CTL, c = ctl, c -= AC_UNIT));
1736	>	}
1737	>	else
1738	>	c = ctl;        // re-increment on exit
1739	>	if ((int)(c >> AC_SHIFT) + parallelism == 0) {
1740	>	do {} while (!U.compareAndSwapLong
1741	>	(this, CTL, c = ctl, c + AC_UNIT));
1742	>	break;
1743	>	}
1744	>	}
1745		}
420	–	return w;
1746		}
1747
1748		/**
1749	<	* Returns a good size for worker array given pool size.
1750	<	* Currently requires size to be a power of two.
1749	>	* Gets and removes a local or stolen task for the given worker
1750	>	*
1751	>	* @return a task, if available
1752		*/
1753	<	private static int arraySizeFor(int ps) {
1754	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
1753	>	final ForkJoinTask<?> nextTaskFor(WorkQueue w) {
1754	>	for (ForkJoinTask<?> t;;) {
1755	>	WorkQueue q;
1756	>	if ((t = w.nextLocalTask()) != null)
1757	>	return t;
1758	>	if ((q = findNonEmptyStealQueue(w)) == null)
1759	>	return null;
1760	>	if ((t = q.poll()) != null)
1761	>	return t;
1762	>	}
1763		}
1764
1765		/**
1766	<	* Creates or resizes array if necessary to hold newLength.
1767	<	* Call only under exclusion or lock.
1768	<	* @return the array
1766	>	* Returns the approximate (non-atomic) number of idle threads per
1767	>	* active thread to offset steal queue size for method
1768	>	* ForkJoinTask.getSurplusQueuedTaskCount().
1769		*/
1770	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
1771	<	ForkJoinWorkerThread[] ws = workers;
1772	<	if (ws == null)
1773	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
1774	<	else if (newLength > ws.length)
1775	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
1776	<	else
1777	<	return ws;
1770	>	final int idlePerActive() {
1771	>	// Approximate at powers of two for small values, saturate past 4
1772	>	int p = parallelism;
1773	>	int a = p + (int)(ctl >> AC_SHIFT);
1774	>	return (a > (p >>>= 1) ? 0 :
1775	>	a > (p >>>= 1) ? 1 :
1776	>	a > (p >>>= 1) ? 2 :
1777	>	a > (p >>>= 1) ? 4 :
1778	>	8);
1779		}
1780
1781	+	// Termination
1782	+
1783		/**
1784	<	* Try to shrink workers into smaller array after one or more terminate
1784	>	* Sets SHUTDOWN bit of runState under lock
1785		*/
1786	<	private void tryShrinkWorkerArray() {
1787	<	ForkJoinWorkerThread[] ws = workers;
1788	<	if (ws != null) {
1789	<	int len = ws.length;
1790	<	int last = len - 1;
1791	<	while (last >= 0 && ws[last] == null)
455	<	--last;
456	<	int newLength = arraySizeFor(last+1);
457	<	if (newLength < len)
458	<	workers = Arrays.copyOf(ws, newLength);
1786	>	private void enableShutdown() {
1787	>	ReentrantLock lock = this.lock;
1788	>	if (runState >= 0) {
1789	>	lock.lock();                       // don't need try/finally
1790	>	runState |= SHUTDOWN;
1791	>	lock.unlock();
1792		}
1793		}
1794
1795		/**
1796	<	* Initialize workers if necessary
1797	<	*/
1798	<	final void ensureWorkerInitialization() {
1799	<	ForkJoinWorkerThread[] ws = workers;
1800	<	if (ws == null) {
1801	<	final ReentrantLock lock = this.workerLock;
1802	<	lock.lock();
1803	<	try {
1804	<	ws = workers;
1805	<	if (ws == null) {
1806	<	int ps = parallelism;
1807	<	ws = ensureWorkerArrayCapacity(ps);
1808	<	for (int i = 0; i < ps; ++i) {
1809	<	ForkJoinWorkerThread w = createWorker(i);
1810	<	if (w != null) {
1811	<	ws[i] = w;
1812	<	w.start();
1813	<	updateWorkerCount(1);
1814	<	}
1796	>	* Possibly initiates and/or completes termination.  Upon
1797	>	* termination, cancels all queued tasks and then
1798	>	*
1799	>	* @param now if true, unconditionally terminate, else only
1800	>	* if no work and no active workers
1801	>	* @return true if now terminating or terminated
1802	>	*/
1803	>	private boolean tryTerminate(boolean now) {
1804	>	for (long c;;) {
1805	>	if (((c = ctl) & STOP_BIT) != 0) {      // already terminating
1806	>	if ((short)(c >>> TC_SHIFT) == -parallelism) {
1807	>	ReentrantLock lock = this.lock; // signal when no workers
1808	>	lock.lock();                    // don't need try/finally
1809	>	termination.signalAll();        // signal when 0 workers
1810	>	lock.unlock();
1811	>	}
1812	>	return true;
1813	>	}
1814	>	if (!now) {
1815	>	if ((int)(c >> AC_SHIFT) != -parallelism || runState >= 0 ||
1816	>	hasQueuedSubmissions())
1817	>	return false;
1818	>	// Check for unqueued inactive workers. One pass suffices.
1819	>	WorkQueue[] ws = workQueues; WorkQueue w;
1820	>	if (ws != null) {
1821	>	int n = ws.length;
1822	>	for (int i = 1; i < n; i += 2) {
1823	>	if ((w = ws[i]) != null && w.eventCount >= 0)
1824	>	return false;
1825		}
1826		}
484	–	} finally {
485	–	lock.unlock();
1827		}
1828	+	if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT))
1829	+	startTerminating();
1830		}
1831		}
1832
1833		/**
1834	<	* Worker creation and startup for threads added via setParallelism.
1834	>	* Initiates termination: Runs three passes through workQueues:
1835	>	* (0) Setting termination status, followed by wakeups of queued
1836	>	* workers; (1) cancelling all tasks; (2) interrupting lagging
1837	>	* threads (likely in external tasks, but possibly also blocked in
1838	>	* joins).  Each pass repeats previous steps because of potential
1839	>	* lagging thread creation.
1840		*/
1841	<	private void createAndStartAddedWorkers() {
1842	<	resumeAllSpares();  // Allow spares to convert to nonspare
1843	<	int ps = parallelism;
1844	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1845	<	int len = ws.length;
1846	<	// Sweep through slots, to keep lowest indices most populated
1847	<	int k = 0;
1848	<	while (k < len) {
1849	<	if (ws[k] != null) {
1850	<	++k;
1851	<	continue;
1852	<	}
1853	<	int s = workerCounts;
1854	<	int tc = totalCountOf(s);
1855	<	int rc = runningCountOf(s);
1856	<	if (rc >= ps || tc >= ps)
1857	<	break;
1858	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
1859	<	ForkJoinWorkerThread w = createWorker(k);
1860	<	if (w != null) {
513	<	ws[k++] = w;
514	<	w.start();
1841	>	private void startTerminating() {
1842	>	for (int pass = 0; pass < 3; ++pass) {
1843	>	WorkQueue[] ws = workQueues;
1844	>	if (ws != null) {
1845	>	WorkQueue w; Thread wt;
1846	>	int n = ws.length;
1847	>	for (int j = 0; j < n; ++j) {
1848	>	if ((w = ws[j]) != null) {
1849	>	w.runState = -1;
1850	>	if (pass > 0) {
1851	>	w.cancelAll();
1852	>	if (pass > 1 && (wt = w.owner) != null &&
1853	>	!wt.isInterrupted()) {
1854	>	try {
1855	>	wt.interrupt();
1856	>	} catch (SecurityException ignore) {
1857	>	}
1858	>	}
1859	>	}
1860	>	}
1861		}
1862	<	else {
1863	<	updateWorkerCount(-1); // back out on failed creation
1864	<	break;
1862	>	// Wake up workers parked on event queue
1863	>	int i, e; long c; Thread p;
1864	>	while ((i = ((~(e = (int)(c = ctl)) << 1) | 1) & SMASK) < n &&
1865	>	(w = ws[i]) != null &&
1866	>	w.eventCount == (e | INT_SIGN)) {
1867	>	long nc = ((long)(w.nextWait & E_MASK) |
1868	>	((c + AC_UNIT) & AC_MASK) |
1869	>	(c & (TC_MASK|STOP_BIT)));
1870	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1871	>	w.eventCount = (e + E_SEQ) & E_MASK;
1872	>	if ((p = w.parker) != null)
1873	>	U.unpark(p);
1874	>	}
1875		}
1876		}
1877		}
1878		}
1879
1880	<	// Execution methods
1880	>	// Exported methods
1881	>
1882	>	// Constructors
1883	>
1884	>	/**
1885	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1886	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1887	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1888	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1889	>	*
1890	>	* @throws SecurityException if a security manager exists and
1891	>	*         the caller is not permitted to modify threads
1892	>	*         because it does not hold {@link
1893	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1894	>	*/
1895	>	public ForkJoinPool() {
1896	>	this(Runtime.getRuntime().availableProcessors(),
1897	>	defaultForkJoinWorkerThreadFactory, null, false);
1898	>	}
1899
1900		/**
1901	<	* Common code for execute, invoke and submit
1901	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
1902	>	* level, the {@linkplain
1903	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1904	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1905	>	*
1906	>	* @param parallelism the parallelism level
1907	>	* @throws IllegalArgumentException if parallelism less than or
1908	>	*         equal to zero, or greater than implementation limit
1909	>	* @throws SecurityException if a security manager exists and
1910	>	*         the caller is not permitted to modify threads
1911	>	*         because it does not hold {@link
1912	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1913		*/
1914	<	private <T> void doSubmit(ForkJoinTask<T> task) {
1915	<	if (isShutdown())
531	<	throw new RejectedExecutionException();
532	<	if (workers == null)
533	<	ensureWorkerInitialization();
534	<	submissionQueue.offer(task);
535	<	signalIdleWorkers();
1914	>	public ForkJoinPool(int parallelism) {
1915	>	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1916		}
1917
1918		/**
1919	<	* Performs the given task; returning its result upon completion
1919	>	* Creates a {@code ForkJoinPool} with the given parameters.
1920	>	*
1921	>	* @param parallelism the parallelism level. For default value,
1922	>	* use {@link java.lang.Runtime#availableProcessors}.
1923	>	* @param factory the factory for creating new threads. For default value,
1924	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
1925	>	* @param handler the handler for internal worker threads that
1926	>	* terminate due to unrecoverable errors encountered while executing
1927	>	* tasks. For default value, use {@code null}.
1928	>	* @param asyncMode if true,
1929	>	* establishes local first-in-first-out scheduling mode for forked
1930	>	* tasks that are never joined. This mode may be more appropriate
1931	>	* than default locally stack-based mode in applications in which
1932	>	* worker threads only process event-style asynchronous tasks.
1933	>	* For default value, use {@code false}.
1934	>	* @throws IllegalArgumentException if parallelism less than or
1935	>	*         equal to zero, or greater than implementation limit
1936	>	* @throws NullPointerException if the factory is null
1937	>	* @throws SecurityException if a security manager exists and
1938	>	*         the caller is not permitted to modify threads
1939	>	*         because it does not hold {@link
1940	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1941	>	*/
1942	>	public ForkJoinPool(int parallelism,
1943	>	ForkJoinWorkerThreadFactory factory,
1944	>	Thread.UncaughtExceptionHandler handler,
1945	>	boolean asyncMode) {
1946	>	checkPermission();
1947	>	if (factory == null)
1948	>	throw new NullPointerException();
1949	>	if (parallelism <= 0 || parallelism > MAX_ID)
1950	>	throw new IllegalArgumentException();
1951	>	this.parallelism = parallelism;
1952	>	this.factory = factory;
1953	>	this.ueh = handler;
1954	>	this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE;
1955	>	this.nextPoolIndex = 1;
1956	>	long np = (long)(-parallelism); // offset ctl counts
1957	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
1958	>	// initialize workQueues array with room for 2*parallelism if possible
1959	>	int n = parallelism << 1;
1960	>	if (n >= MAX_ID)
1961	>	n = MAX_ID;
1962	>	else { // See Hackers Delight, sec 3.2, where n < (1 << 16)
1963	>	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8;
1964	>	}
1965	>	this.workQueues = new WorkQueue[(n + 1) << 1];
1966	>	ReentrantLock lck = this.lock = new ReentrantLock();
1967	>	this.termination = lck.newCondition();
1968	>	this.stealCount = new AtomicLong();
1969	>	this.nextWorkerNumber = new AtomicInteger();
1970	>	StringBuilder sb = new StringBuilder("ForkJoinPool-");
1971	>	sb.append(poolNumberGenerator.incrementAndGet());
1972	>	sb.append("-worker-");
1973	>	this.workerNamePrefix = sb.toString();
1974	>	// Create initial submission queue
1975	>	WorkQueue sq = tryAddSharedQueue(0);
1976	>	if (sq != null)
1977	>	sq.growArray(false);
1978	>	}
1979	>
1980	>	// Execution methods
1981	>
1982	>	/**
1983	>	* Performs the given task, returning its result upon completion.
1984	>	* If the computation encounters an unchecked Exception or Error,
1985	>	* it is rethrown as the outcome of this invocation.  Rethrown
1986	>	* exceptions behave in the same way as regular exceptions, but,
1987	>	* when possible, contain stack traces (as displayed for example
1988	>	* using {@code ex.printStackTrace()}) of both the current thread
1989	>	* as well as the thread actually encountering the exception;
1990	>	* minimally only the latter.
1991	>	*
1992		* @param task the task
1993		* @return the task's result
1994	<	* @throws NullPointerException if task is null
1995	<	* @throws RejectedExecutionException if pool is shut down
1994	>	* @throws NullPointerException if the task is null
1995	>	* @throws RejectedExecutionException if the task cannot be
1996	>	*         scheduled for execution
1997		*/
1998		public <T> T invoke(ForkJoinTask<T> task) {
1999		doSubmit(task);
#	Line 549 | Line 2002 | public class ForkJoinPool extends Abstra
2002
2003		/**
2004		* Arranges for (asynchronous) execution of the given task.
2005	+	*
2006		* @param task the task
2007	<	* @throws NullPointerException if task is null
2008	<	* @throws RejectedExecutionException if pool is shut down
2007	>	* @throws NullPointerException if the task is null
2008	>	* @throws RejectedExecutionException if the task cannot be
2009	>	*         scheduled for execution
2010		*/
2011	<	public <T> void execute(ForkJoinTask<T> task) {
2011	>	public void execute(ForkJoinTask<?> task) {
2012		doSubmit(task);
2013		}
2014
2015		// AbstractExecutorService methods
2016
2017	+	/**
2018	+	* @throws NullPointerException if the task is null
2019	+	* @throws RejectedExecutionException if the task cannot be
2020	+	*         scheduled for execution
2021	+	*/
2022		public void execute(Runnable task) {
2023	<	doSubmit(new AdaptedRunnable<Void>(task, null));
2023	>	if (task == null)
2024	>	throw new NullPointerException();
2025	>	ForkJoinTask<?> job;
2026	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2027	>	job = (ForkJoinTask<?>) task;
2028	>	else
2029	>	job = ForkJoinTask.adapt(task, null);
2030	>	doSubmit(job);
2031		}
2032
2033	+	/**
2034	+	* Submits a ForkJoinTask for execution.
2035	+	*
2036	+	* @param task the task to submit
2037	+	* @return the task
2038	+	* @throws NullPointerException if the task is null
2039	+	* @throws RejectedExecutionException if the task cannot be
2040	+	*         scheduled for execution
2041	+	*/
2042	+	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2043	+	doSubmit(task);
2044	+	return task;
2045	+	}
2046	+
2047	+	/**
2048	+	* @throws NullPointerException if the task is null
2049	+	* @throws RejectedExecutionException if the task cannot be
2050	+	*         scheduled for execution
2051	+	*/
2052		public <T> ForkJoinTask<T> submit(Callable<T> task) {
2053	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
2053	>	if (task == null)
2054	>	throw new NullPointerException();
2055	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
2056		doSubmit(job);
2057		return job;
2058		}
2059
2060	+	/**
2061	+	* @throws NullPointerException if the task is null
2062	+	* @throws RejectedExecutionException if the task cannot be
2063	+	*         scheduled for execution
2064	+	*/
2065		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2066	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
2066	>	if (task == null)
2067	>	throw new NullPointerException();
2068	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
2069		doSubmit(job);
2070		return job;
2071		}
2072
2073	+	/**
2074	+	* @throws NullPointerException if the task is null
2075	+	* @throws RejectedExecutionException if the task cannot be
2076	+	*         scheduled for execution
2077	+	*/
2078		public ForkJoinTask<?> submit(Runnable task) {
2079	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
2079	>	if (task == null)
2080	>	throw new NullPointerException();
2081	>	ForkJoinTask<?> job;
2082	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2083	>	job = (ForkJoinTask<?>) task;
2084	>	else
2085	>	job = ForkJoinTask.adapt(task, null);
2086		doSubmit(job);
2087		return job;
2088		}
2089
2090		/**
2091	<	* Adaptor for Runnables. This implements RunnableFuture
2092	<	* to be compliant with AbstractExecutorService constraints
2091	>	* @throws NullPointerException       {@inheritDoc}
2092	>	* @throws RejectedExecutionException {@inheritDoc}
2093		*/
588	–	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
589	–	implements RunnableFuture<T> {
590	–	final Runnable runnable;
591	–	final T resultOnCompletion;
592	–	T result;
593	–	AdaptedRunnable(Runnable runnable, T result) {
594	–	if (runnable == null) throw new NullPointerException();
595	–	this.runnable = runnable;
596	–	this.resultOnCompletion = result;
597	–	}
598	–	public T getRawResult() { return result; }
599	–	public void setRawResult(T v) { result = v; }
600	–	public boolean exec() {
601	–	runnable.run();
602	–	result = resultOnCompletion;
603	–	return true;
604	–	}
605	–	public void run() { invoke(); }
606	–	}
607	–
608	–	/**
609	–	* Adaptor for Callables
610	–	*/
611	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
612	–	implements RunnableFuture<T> {
613	–	final Callable<T> callable;
614	–	T result;
615	–	AdaptedCallable(Callable<T> callable) {
616	–	if (callable == null) throw new NullPointerException();
617	–	this.callable = callable;
618	–	}
619	–	public T getRawResult() { return result; }
620	–	public void setRawResult(T v) { result = v; }
621	–	public boolean exec() {
622	–	try {
623	–	result = callable.call();
624	–	return true;
625	–	} catch (Error err) {
626	–	throw err;
627	–	} catch (RuntimeException rex) {
628	–	throw rex;
629	–	} catch (Exception ex) {
630	–	throw new RuntimeException(ex);
631	–	}
632	–	}
633	–	public void run() { invoke(); }
634	–	}
635	–
2094		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
2095	<	ArrayList<ForkJoinTask<T>> ts =
2095	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
2096		new ArrayList<ForkJoinTask<T>>(tasks.size());
2097	<	for (Callable<T> c : tasks)
2098	<	ts.add(new AdaptedCallable<T>(c));
2099	<	invoke(new InvokeAll<T>(ts));
2100	<	return (List<Future<T>>)(List)ts;
2097	>	for (Callable<T> task : tasks)
2098	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
2099	>	invoke(new InvokeAll<T>(forkJoinTasks));
2100	>
2101	>	@SuppressWarnings({"unchecked", "rawtypes"})
2102	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
2103	>	return futures;
2104		}
2105
2106		static final class InvokeAll<T> extends RecursiveAction {
2107		final ArrayList<ForkJoinTask<T>> tasks;
2108		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
2109		public void compute() {
2110	<	try { invokeAll(tasks); } catch(Exception ignore) {}
2110	>	try { invokeAll(tasks); }
2111	>	catch (Exception ignore) {}
2112		}
2113	+	private static final long serialVersionUID = -7914297376763021607L;
2114		}
2115
653	–	// Configuration and status settings and queries
654	–
2116		/**
2117	<	* Returns the factory used for constructing new workers
2117	>	* Returns the factory used for constructing new workers.
2118		*
2119		* @return the factory used for constructing new workers
2120		*/
#	Line 664 | Line 2125 | public class ForkJoinPool extends Abstra
2125		/**
2126		* Returns the handler for internal worker threads that terminate
2127		* due to unrecoverable errors encountered while executing tasks.
667	–	* @return the handler, or null if none
668	–	*/
669	–	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
670	–	Thread.UncaughtExceptionHandler h;
671	–	final ReentrantLock lock = this.workerLock;
672	–	lock.lock();
673	–	try {
674	–	h = ueh;
675	–	} finally {
676	–	lock.unlock();
677	–	}
678	–	return h;
679	–	}
680	–
681	–	/**
682	–	* Sets the handler for internal worker threads that terminate due
683	–	* to unrecoverable errors encountered while executing tasks.
684	–	* Unless set, the current default or ThreadGroup handler is used
685	–	* as handler.
2128		*
2129	<	* @param h the new handler
688	<	* @return the old handler, or null if none
689	<	* @throws SecurityException if a security manager exists and
690	<	*         the caller is not permitted to modify threads
691	<	*         because it does not hold {@link
692	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
2129	>	* @return the handler, or {@code null} if none
2130		*/
2131	<	public Thread.UncaughtExceptionHandler
2132	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
696	<	checkPermission();
697	<	Thread.UncaughtExceptionHandler old = null;
698	<	final ReentrantLock lock = this.workerLock;
699	<	lock.lock();
700	<	try {
701	<	old = ueh;
702	<	ueh = h;
703	<	ForkJoinWorkerThread[] ws = workers;
704	<	if (ws != null) {
705	<	for (int i = 0; i < ws.length; ++i) {
706	<	ForkJoinWorkerThread w = ws[i];
707	<	if (w != null)
708	<	w.setUncaughtExceptionHandler(h);
709	<	}
710	<	}
711	<	} finally {
712	<	lock.unlock();
713	<	}
714	<	return old;
715	<	}
716	<
717	<
718	<	/**
719	<	* Sets the target parallelism level of this pool.
720	<	* @param parallelism the target parallelism
721	<	* @throws IllegalArgumentException if parallelism less than or
722	<	* equal to zero or greater than maximum size bounds
723	<	* @throws SecurityException if a security manager exists and
724	<	*         the caller is not permitted to modify threads
725	<	*         because it does not hold {@link
726	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
727	<	*/
728	<	public void setParallelism(int parallelism) {
729	<	checkPermission();
730	<	if (parallelism <= 0 || parallelism > maxPoolSize)
731	<	throw new IllegalArgumentException();
732	<	final ReentrantLock lock = this.workerLock;
733	<	lock.lock();
734	<	try {
735	<	if (!isTerminating()) {
736	<	int p = this.parallelism;
737	<	this.parallelism = parallelism;
738	<	if (parallelism > p)
739	<	createAndStartAddedWorkers();
740	<	else
741	<	trimSpares();
742	<	}
743	<	} finally {
744	<	lock.unlock();
745	<	}
746	<	signalIdleWorkers();
2131	>	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
2132	>	return ueh;
2133		}
2134
2135		/**
2136	<	* Returns the targeted number of worker threads in this pool.
2136	>	* Returns the targeted parallelism level of this pool.
2137		*
2138	<	* @return the targeted number of worker threads in this pool
2138	>	* @return the targeted parallelism level of this pool
2139		*/
2140		public int getParallelism() {
2141		return parallelism;
#	Line 757 | Line 2143 | public class ForkJoinPool extends Abstra
2143
2144		/**
2145		* Returns the number of worker threads that have started but not
2146	<	* yet terminated.  This result returned by this method may differ
2147	<	* from {@code getParallelism} when threads are created to
2146	>	* yet terminated.  The result returned by this method may differ
2147	>	* from {@link #getParallelism} when threads are created to
2148		* maintain parallelism when others are cooperatively blocked.
2149		*
2150		* @return the number of worker threads
2151		*/
2152		public int getPoolSize() {
2153	<	return totalCountOf(workerCounts);
2153	>	return parallelism + (short)(ctl >>> TC_SHIFT);
2154		}
2155
2156		/**
2157	<	* Returns the maximum number of threads allowed to exist in the
772	<	* pool, even if there are insufficient unblocked running threads.
773	<	* @return the maximum
774	<	*/
775	<	public int getMaximumPoolSize() {
776	<	return maxPoolSize;
777	<	}
778	<
779	<	/**
780	<	* Sets the maximum number of threads allowed to exist in the
781	<	* pool, even if there are insufficient unblocked running threads.
782	<	* Setting this value has no effect on current pool size. It
783	<	* controls construction of new threads.
784	<	* @throws IllegalArgumentException if negative or greater then
785	<	* internal implementation limit
786	<	*/
787	<	public void setMaximumPoolSize(int newMax) {
788	<	if (newMax < 0 || newMax > MAX_THREADS)
789	<	throw new IllegalArgumentException();
790	<	maxPoolSize = newMax;
791	<	}
792	<
793	<
794	<	/**
795	<	* Returns true if this pool dynamically maintains its target
796	<	* parallelism level. If false, new threads are added only to
797	<	* avoid possible starvation.
798	<	* This setting is by default true;
799	<	* @return true if maintains parallelism
800	<	*/
801	<	public boolean getMaintainsParallelism() {
802	<	return maintainsParallelism;
803	<	}
804	<
805	<	/**
806	<	* Sets whether this pool dynamically maintains its target
807	<	* parallelism level. If false, new threads are added only to
808	<	* avoid possible starvation.
809	<	* @param enable true to maintains parallelism
810	<	*/
811	<	public void setMaintainsParallelism(boolean enable) {
812	<	maintainsParallelism = enable;
813	<	}
814	<
815	<	/**
816	<	* Establishes local first-in-first-out scheduling mode for forked
817	<	* tasks that are never joined. This mode may be more appropriate
818	<	* than default locally stack-based mode in applications in which
819	<	* worker threads only process asynchronous tasks.  This method is
820	<	* designed to be invoked only when pool is quiescent, and
821	<	* typically only before any tasks are submitted. The effects of
822	<	* invocations at other times may be unpredictable.
823	<	*
824	<	* @param async if true, use locally FIFO scheduling
825	<	* @return the previous mode
826	<	*/
827	<	public boolean setAsyncMode(boolean async) {
828	<	boolean oldMode = locallyFifo;
829	<	locallyFifo = async;
830	<	ForkJoinWorkerThread[] ws = workers;
831	<	if (ws != null) {
832	<	for (int i = 0; i < ws.length; ++i) {
833	<	ForkJoinWorkerThread t = ws[i];
834	<	if (t != null)
835	<	t.setAsyncMode(async);
836	<	}
837	<	}
838	<	return oldMode;
839	<	}
840	<
841	<	/**
842	<	* Returns true if this pool uses local first-in-first-out
2157	>	* Returns {@code true} if this pool uses local first-in-first-out
2158		* scheduling mode for forked tasks that are never joined.
2159		*
2160	<	* @return true if this pool uses async mode
2160	>	* @return {@code true} if this pool uses async mode
2161		*/
2162		public boolean getAsyncMode() {
2163	<	return locallyFifo;
2163	>	return localMode != 0;
2164		}
2165
2166		/**
2167		* Returns an estimate of the number of worker threads that are
2168		* not blocked waiting to join tasks or for other managed
2169	<	* synchronization.
2169	>	* synchronization. This method may overestimate the
2170	>	* number of running threads.
2171		*
2172		* @return the number of worker threads
2173		*/
2174		public int getRunningThreadCount() {
2175	<	return runningCountOf(workerCounts);
2175	>	int rc = 0;
2176	>	WorkQueue[] ws; WorkQueue w;
2177	>	if ((ws = workQueues) != null) {
2178	>	int n = ws.length;
2179	>	for (int i = 1; i < n; i += 2) {
2180	>	Thread.State s; ForkJoinWorkerThread wt;
2181	>	if ((w = ws[i]) != null && (wt = w.owner) != null &&
2182	>	w.eventCount >= 0 &&
2183	>	(s = wt.getState()) != Thread.State.BLOCKED &&
2184	>	s != Thread.State.WAITING &&
2185	>	s != Thread.State.TIMED_WAITING)
2186	>	++rc;
2187	>	}
2188	>	}
2189	>	return rc;
2190		}
2191
2192		/**
2193		* Returns an estimate of the number of threads that are currently
2194		* stealing or executing tasks. This method may overestimate the
2195		* number of active threads.
2196	+	*
2197		* @return the number of active threads
2198		*/
2199		public int getActiveThreadCount() {
2200	<	return activeCountOf(runControl);
2201	<	}
871	<
872	<	/**
873	<	* Returns an estimate of the number of threads that are currently
874	<	* idle waiting for tasks. This method may underestimate the
875	<	* number of idle threads.
876	<	* @return the number of idle threads
877	<	*/
878	<	final int getIdleThreadCount() {
879	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
880	<	return (c <= 0)? 0 : c;
2200	>	int r = parallelism + (int)(ctl >> AC_SHIFT);
2201	>	return (r <= 0) ? 0 : r; // suppress momentarily negative values
2202		}
2203
2204		/**
2205	<	* Returns true if all worker threads are currently idle. An idle
2206	<	* worker is one that cannot obtain a task to execute because none
2207	<	* are available to steal from other threads, and there are no
2208	<	* pending submissions to the pool. This method is conservative:
2209	<	* It might not return true immediately upon idleness of all
2210	<	* threads, but will eventually become true if threads remain
2211	<	* inactive.
2212	<	* @return true if all threads are currently idle
2205	>	* Returns {@code true} if all worker threads are currently idle.
2206	>	* An idle worker is one that cannot obtain a task to execute
2207	>	* because none are available to steal from other threads, and
2208	>	* there are no pending submissions to the pool. This method is
2209	>	* conservative; it might not return {@code true} immediately upon
2210	>	* idleness of all threads, but will eventually become true if
2211	>	* threads remain inactive.
2212	>	*
2213	>	* @return {@code true} if all threads are currently idle
2214		*/
2215		public boolean isQuiescent() {
2216	<	return activeCountOf(runControl) == 0;
2216	>	return (int)(ctl >> AC_SHIFT) + parallelism == 0;
2217		}
2218
2219		/**
#	Line 899 | Line 2221 | public class ForkJoinPool extends Abstra
2221		* one thread's work queue by another. The reported value
2222		* underestimates the actual total number of steals when the pool
2223		* is not quiescent. This value may be useful for monitoring and
2224	<	* tuning fork/join programs: In general, steal counts should be
2224	>	* tuning fork/join programs: in general, steal counts should be
2225		* high enough to keep threads busy, but low enough to avoid
2226		* overhead and contention across threads.
2227	+	*
2228		* @return the number of steals
2229		*/
2230		public long getStealCount() {
2231	<	return stealCount.get();
2232	<	}
2233	<
2234	<	/**
2235	<	* Accumulate steal count from a worker. Call only
2236	<	* when worker known to be idle.
2237	<	*/
2238	<	private void updateStealCount(ForkJoinWorkerThread w) {
2239	<	int sc = w.getAndClearStealCount();
2240	<	if (sc != 0)
918	<	stealCount.addAndGet(sc);
2231	>	long count = stealCount.get();
2232	>	WorkQueue[] ws; WorkQueue w;
2233	>	if ((ws = workQueues) != null) {
2234	>	int n = ws.length;
2235	>	for (int i = 1; i < n; i += 2) {
2236	>	if ((w = ws[i]) != null)
2237	>	count += w.totalSteals;
2238	>	}
2239	>	}
2240	>	return count;
2241		}
2242
2243		/**
#	Line 925 | Line 2247 | public class ForkJoinPool extends Abstra
2247		* an approximation, obtained by iterating across all threads in
2248		* the pool. This method may be useful for tuning task
2249		* granularities.
2250	+	*
2251		* @return the number of queued tasks
2252		*/
2253		public long getQueuedTaskCount() {
2254		long count = 0;
2255	<	ForkJoinWorkerThread[] ws = workers;
2256	<	if (ws != null) {
2257	<	for (int i = 0; i < ws.length; ++i) {
2258	<	ForkJoinWorkerThread t = ws[i];
2259	<	if (t != null)
2260	<	count += t.getQueueSize();
2255	>	WorkQueue[] ws; WorkQueue w;
2256	>	if ((ws = workQueues) != null) {
2257	>	int n = ws.length;
2258	>	for (int i = 1; i < n; i += 2) {
2259	>	if ((w = ws[i]) != null)
2260	>	count += w.queueSize();
2261		}
2262		}
2263		return count;
2264		}
2265
2266		/**
2267	<	* Returns an estimate of the number tasks submitted to this pool
2268	<	* that have not yet begun executing. This method takes time
2269	<	* proportional to the number of submissions.
2267	>	* Returns an estimate of the number of tasks submitted to this
2268	>	* pool that have not yet begun executing.  This method may take
2269	>	* time proportional to the number of submissions.
2270	>	*
2271		* @return the number of queued submissions
2272		*/
2273		public int getQueuedSubmissionCount() {
2274	<	return submissionQueue.size();
2274	>	int count = 0;
2275	>	WorkQueue[] ws; WorkQueue w;
2276	>	if ((ws = workQueues) != null) {
2277	>	int n = ws.length;
2278	>	for (int i = 0; i < n; i += 2) {
2279	>	if ((w = ws[i]) != null)
2280	>	count += w.queueSize();
2281	>	}
2282	>	}
2283	>	return count;
2284		}
2285
2286		/**
2287	<	* Returns true if there are any tasks submitted to this pool
2288	<	* that have not yet begun executing.
2287	>	* Returns {@code true} if there are any tasks submitted to this
2288	>	* pool that have not yet begun executing.
2289	>	*
2290		* @return {@code true} if there are any queued submissions
2291		*/
2292		public boolean hasQueuedSubmissions() {
2293	<	return !submissionQueue.isEmpty();
2293	>	WorkQueue[] ws; WorkQueue w;
2294	>	if ((ws = workQueues) != null) {
2295	>	int n = ws.length;
2296	>	for (int i = 0; i < n; i += 2) {
2297	>	if ((w = ws[i]) != null && w.queueSize() != 0)
2298	>	return true;
2299	>	}
2300	>	}
2301	>	return false;
2302		}
2303
2304		/**
2305		* Removes and returns the next unexecuted submission if one is
2306		* available.  This method may be useful in extensions to this
2307		* class that re-assign work in systems with multiple pools.
2308	<	* @return the next submission, or null if none
2308	>	*
2309	>	* @return the next submission, or {@code null} if none
2310		*/
2311		protected ForkJoinTask<?> pollSubmission() {
2312	<	return submissionQueue.poll();
2312	>	WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2313	>	if ((ws = workQueues) != null) {
2314	>	int n = ws.length;
2315	>	for (int i = 0; i < n; i += 2) {
2316	>	if ((w = ws[i]) != null && (t = w.poll()) != null)
2317	>	return t;
2318	>	}
2319	>	}
2320	>	return null;
2321		}
2322
2323		/**
2324		* Removes all available unexecuted submitted and forked tasks
2325		* from scheduling queues and adds them to the given collection,
2326		* without altering their execution status. These may include
2327	<	* artificially generated or wrapped tasks. This method is designed
2328	<	* to be invoked only when the pool is known to be
2327	>	* artificially generated or wrapped tasks. This method is
2328	>	* designed to be invoked only when the pool is known to be
2329		* quiescent. Invocations at other times may not remove all
2330		* tasks. A failure encountered while attempting to add elements
2331		* to collection {@code c} may result in elements being in
#	Line 982 | Line 2333 | public class ForkJoinPool extends Abstra
2333		* exception is thrown.  The behavior of this operation is
2334		* undefined if the specified collection is modified while the
2335		* operation is in progress.
2336	+	*
2337		* @param c the collection to transfer elements into
2338		* @return the number of elements transferred
2339		*/
2340	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
2341	<	int n = submissionQueue.drainTo(c);
2342	<	ForkJoinWorkerThread[] ws = workers;
2343	<	if (ws != null) {
2344	<	for (int i = 0; i < ws.length; ++i) {
2345	<	ForkJoinWorkerThread w = ws[i];
2346	<	if (w != null)
2347	<	n += w.drainTasksTo(c);
2340	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
2341	>	int count = 0;
2342	>	WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2343	>	if ((ws = workQueues) != null) {
2344	>	int n = ws.length;
2345	>	for (int i = 0; i < n; ++i) {
2346	>	if ((w = ws[i]) != null) {
2347	>	while ((t = w.poll()) != null) {
2348	>	c.add(t);
2349	>	++count;
2350	>	}
2351	>	}
2352		}
2353		}
2354	<	return n;
2354	>	return count;
2355		}
2356
2357		/**
#	Line 1006 | Line 2362 | public class ForkJoinPool extends Abstra
2362		* @return a string identifying this pool, as well as its state
2363		*/
2364		public String toString() {
1009	–	int ps = parallelism;
1010	–	int wc = workerCounts;
1011	–	int rc = runControl;
2365		long st = getStealCount();
2366		long qt = getQueuedTaskCount();
2367		long qs = getQueuedSubmissionCount();
2368	+	int rc = getRunningThreadCount();
2369	+	int pc = parallelism;
2370	+	long c = ctl;
2371	+	int tc = pc + (short)(c >>> TC_SHIFT);
2372	+	int ac = pc + (int)(c >> AC_SHIFT);
2373	+	if (ac < 0) // ignore transient negative
2374	+	ac = 0;
2375	+	String level;
2376	+	if ((c & STOP_BIT) != 0)
2377	+	level = (tc == 0) ? "Terminated" : "Terminating";
2378	+	else
2379	+	level = runState < 0 ? "Shutting down" : "Running";
2380		return super.toString() +
2381	<	"[" + runStateToString(runStateOf(rc)) +
2382	<	", parallelism = " + ps +
2383	<	", size = " + totalCountOf(wc) +
2384	<	", active = " + activeCountOf(rc) +
2385	<	", running = " + runningCountOf(wc) +
2381	>	"[" + level +
2382	>	", parallelism = " + pc +
2383	>	", size = " + tc +
2384	>	", active = " + ac +
2385	>	", running = " + rc +
2386		", steals = " + st +
2387		", tasks = " + qt +
2388		", submissions = " + qs +
2389		"]";
2390		}
2391
1027	–	private static String runStateToString(int rs) {
1028	–	switch(rs) {
1029	–	case RUNNING: return "Running";
1030	–	case SHUTDOWN: return "Shutting down";
1031	–	case TERMINATING: return "Terminating";
1032	–	case TERMINATED: return "Terminated";
1033	–	default: throw new Error("Unknown run state");
1034	–	}
1035	–	}
1036	–
1037	–	// lifecycle control
1038	–
2392		/**
2393		* Initiates an orderly shutdown in which previously submitted
2394		* tasks are executed, but no new tasks will be accepted.
2395		* Invocation has no additional effect if already shut down.
2396		* Tasks that are in the process of being submitted concurrently
2397		* during the course of this method may or may not be rejected.
2398	+	*
2399		* @throws SecurityException if a security manager exists and
2400		*         the caller is not permitted to modify threads
2401		*         because it does not hold {@link
2402	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
2402	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
2403		*/
2404		public void shutdown() {
2405		checkPermission();
2406	<	transitionRunStateTo(SHUTDOWN);
2407	<	if (canTerminateOnShutdown(runControl))
1054	<	terminateOnShutdown();
2406	>	enableShutdown();
2407	>	tryTerminate(false);
2408		}
2409
2410		/**
2411	<	* Attempts to stop all actively executing tasks, and cancels all
2412	<	* waiting tasks.  Tasks that are in the process of being
2413	<	* submitted or executed concurrently during the course of this
2414	<	* method may or may not be rejected. Unlike some other executors,
2415	<	* this method cancels rather than collects non-executed tasks
2416	<	* upon termination, so always returns an empty list. However, you
2417	<	* can use method {@code drainTasksTo} before invoking this
2418	<	* method to transfer unexecuted tasks to another collection.
2411	>	* Attempts to cancel and/or stop all tasks, and reject all
2412	>	* subsequently submitted tasks.  Tasks that are in the process of
2413	>	* being submitted or executed concurrently during the course of
2414	>	* this method may or may not be rejected. This method cancels
2415	>	* both existing and unexecuted tasks, in order to permit
2416	>	* termination in the presence of task dependencies. So the method
2417	>	* always returns an empty list (unlike the case for some other
2418	>	* Executors).
2419	>	*
2420		* @return an empty list
2421		* @throws SecurityException if a security manager exists and
2422		*         the caller is not permitted to modify threads
2423		*         because it does not hold {@link
2424	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
2424	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
2425		*/
2426		public List<Runnable> shutdownNow() {
2427		checkPermission();
2428	<	terminate();
2428	>	enableShutdown();
2429	>	tryTerminate(true);
2430		return Collections.emptyList();
2431		}
2432
#	Line 1081 | Line 2436 | public class ForkJoinPool extends Abstra
2436		* @return {@code true} if all tasks have completed following shut down
2437		*/
2438		public boolean isTerminated() {
2439	<	return runStateOf(runControl) == TERMINATED;
2439	>	long c = ctl;
2440	>	return ((c & STOP_BIT) != 0L &&
2441	>	(short)(c >>> TC_SHIFT) == -parallelism);
2442		}
2443
2444		/**
2445		* Returns {@code true} if the process of termination has
2446	<	* commenced but possibly not yet completed.
2446	>	* commenced but not yet completed.  This method may be useful for
2447	>	* debugging. A return of {@code true} reported a sufficient
2448	>	* period after shutdown may indicate that submitted tasks have
2449	>	* ignored or suppressed interruption, or are waiting for IO,
2450	>	* causing this executor not to properly terminate. (See the
2451	>	* advisory notes for class {@link ForkJoinTask} stating that
2452	>	* tasks should not normally entail blocking operations.  But if
2453	>	* they do, they must abort them on interrupt.)
2454		*
2455	<	* @return {@code true} if terminating
2455	>	* @return {@code true} if terminating but not yet terminated
2456		*/
2457		public boolean isTerminating() {
2458	<	return runStateOf(runControl) >= TERMINATING;
2458	>	long c = ctl;
2459	>	return ((c & STOP_BIT) != 0L &&
2460	>	(short)(c >>> TC_SHIFT) != -parallelism);
2461		}
2462
2463		/**
#	Line 1100 | Line 2466 | public class ForkJoinPool extends Abstra
2466		* @return {@code true} if this pool has been shut down
2467		*/
2468		public boolean isShutdown() {
2469	<	return runStateOf(runControl) >= SHUTDOWN;
2469	>	return runState < 0;
2470		}
2471
2472		/**
#	Line 1117 | Line 2483 | public class ForkJoinPool extends Abstra
2483		public boolean awaitTermination(long timeout, TimeUnit unit)
2484		throws InterruptedException {
2485		long nanos = unit.toNanos(timeout);
2486	<	final ReentrantLock lock = this.workerLock;
2486	>	final ReentrantLock lock = this.lock;
2487		lock.lock();
2488		try {
2489		for (;;) {
#	Line 1132 | Line 2498 | public class ForkJoinPool extends Abstra
2498		}
2499		}
2500
1135	–	// Shutdown and termination support
1136	–
1137	–	/**
1138	–	* Callback from terminating worker. Null out the corresponding
1139	–	* workers slot, and if terminating, try to terminate, else try to
1140	–	* shrink workers array.
1141	–	* @param w the worker
1142	–	*/
1143	–	final void workerTerminated(ForkJoinWorkerThread w) {
1144	–	updateStealCount(w);
1145	–	updateWorkerCount(-1);
1146	–	final ReentrantLock lock = this.workerLock;
1147	–	lock.lock();
1148	–	try {
1149	–	ForkJoinWorkerThread[] ws = workers;
1150	–	if (ws != null) {
1151	–	int idx = w.poolIndex;
1152	–	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1153	–	ws[idx] = null;
1154	–	if (totalCountOf(workerCounts) == 0) {
1155	–	terminate(); // no-op if already terminating
1156	–	transitionRunStateTo(TERMINATED);
1157	–	termination.signalAll();
1158	–	}
1159	–	else if (!isTerminating()) {
1160	–	tryShrinkWorkerArray();
1161	–	tryResumeSpare(true); // allow replacement
1162	–	}
1163	–	}
1164	–	} finally {
1165	–	lock.unlock();
1166	–	}
1167	–	signalIdleWorkers();
1168	–	}
1169	–
2501		/**
2502	<	* Initiate termination.
2503	<	*/
1173	<	private void terminate() {
1174	<	if (transitionRunStateTo(TERMINATING)) {
1175	<	stopAllWorkers();
1176	<	resumeAllSpares();
1177	<	signalIdleWorkers();
1178	<	cancelQueuedSubmissions();
1179	<	cancelQueuedWorkerTasks();
1180	<	interruptUnterminatedWorkers();
1181	<	signalIdleWorkers(); // resignal after interrupt
1182	<	}
1183	<	}
1184	<
1185	<	/**
1186	<	* Possibly terminates when on shutdown state.
1187	<	*/
1188	<	private void terminateOnShutdown() {
1189	<	if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
1190	<	terminate();
1191	<	}
1192	<
1193	<	/**
1194	<	* Clears out and cancels submissions.
1195	<	*/
1196	<	private void cancelQueuedSubmissions() {
1197	<	ForkJoinTask<?> task;
1198	<	while ((task = pollSubmission()) != null)
1199	<	task.cancel(false);
1200	<	}
1201	<
1202	<	/**
1203	<	* Cleans out worker queues.
1204	<	*/
1205	<	private void cancelQueuedWorkerTasks() {
1206	<	final ReentrantLock lock = this.workerLock;
1207	<	lock.lock();
1208	<	try {
1209	<	ForkJoinWorkerThread[] ws = workers;
1210	<	if (ws != null) {
1211	<	for (int i = 0; i < ws.length; ++i) {
1212	<	ForkJoinWorkerThread t = ws[i];
1213	<	if (t != null)
1214	<	t.cancelTasks();
1215	<	}
1216	<	}
1217	<	} finally {
1218	<	lock.unlock();
1219	<	}
1220	<	}
1221	<
1222	<	/**
1223	<	* Sets each worker's status to terminating. Requires lock to avoid
1224	<	* conflicts with add/remove.
1225	<	*/
1226	<	private void stopAllWorkers() {
1227	<	final ReentrantLock lock = this.workerLock;
1228	<	lock.lock();
1229	<	try {
1230	<	ForkJoinWorkerThread[] ws = workers;
1231	<	if (ws != null) {
1232	<	for (int i = 0; i < ws.length; ++i) {
1233	<	ForkJoinWorkerThread t = ws[i];
1234	<	if (t != null)
1235	<	t.shutdownNow();
1236	<	}
1237	<	}
1238	<	} finally {
1239	<	lock.unlock();
1240	<	}
1241	<	}
1242	<
1243	<	/**
1244	<	* Interrupts all unterminated workers.  This is not required for
1245	<	* sake of internal control, but may help unstick user code during
1246	<	* shutdown.
1247	<	*/
1248	<	private void interruptUnterminatedWorkers() {
1249	<	final ReentrantLock lock = this.workerLock;
1250	<	lock.lock();
1251	<	try {
1252	<	ForkJoinWorkerThread[] ws = workers;
1253	<	if (ws != null) {
1254	<	for (int i = 0; i < ws.length; ++i) {
1255	<	ForkJoinWorkerThread t = ws[i];
1256	<	if (t != null && !t.isTerminated()) {
1257	<	try {
1258	<	t.interrupt();
1259	<	} catch (SecurityException ignore) {
1260	<	}
1261	<	}
1262	<	}
1263	<	}
1264	<	} finally {
1265	<	lock.unlock();
1266	<	}
1267	<	}
1268	<
1269	<
1270	<	/*
1271	<	* Nodes for event barrier to manage idle threads.  Queue nodes
1272	<	* are basic Treiber stack nodes, also used for spare stack.
1273	<	*
1274	<	* The event barrier has an event count and a wait queue (actually
1275	<	* a Treiber stack).  Workers are enabled to look for work when
1276	<	* the eventCount is incremented. If they fail to find work, they
1277	<	* may wait for next count. Upon release, threads help others wake
1278	<	* up.
1279	<	*
1280	<	* Synchronization events occur only in enough contexts to
1281	<	* maintain overall liveness:
1282	<	*
1283	<	*   - Submission of a new task to the pool
1284	<	*   - Resizes or other changes to the workers array
1285	<	*   - pool termination
1286	<	*   - A worker pushing a task on an empty queue
2502	>	* Interface for extending managed parallelism for tasks running
2503	>	* in {@link ForkJoinPool}s.
2504		*
2505	<	* The case of pushing a task occurs often enough, and is heavy
2506	<	* enough compared to simple stack pushes, to require special
2507	<	* handling: Method signalWork returns without advancing count if
2508	<	* the queue appears to be empty.  This would ordinarily result in
2509	<	* races causing some queued waiters not to be woken up. To avoid
2510	<	* this, the first worker enqueued in method sync (see
2511	<	* syncIsReleasable) rescans for tasks after being enqueued, and
2512	<	* helps signal if any are found. This works well because the
2513	<	* worker has nothing better to do, and so might as well help
2514	<	* alleviate the overhead and contention on the threads actually
2515	<	* doing work.  Also, since event counts increments on task
2516	<	* availability exist to maintain liveness (rather than to force
2517	<	* refreshes etc), it is OK for callers to exit early if
1301	<	* contending with another signaller.
1302	<	*/
1303	<	static final class WaitQueueNode {
1304	<	WaitQueueNode next; // only written before enqueued
1305	<	volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1306	<	final long count; // unused for spare stack
1307	<
1308	<	WaitQueueNode(long c, ForkJoinWorkerThread w) {
1309	<	count = c;
1310	<	thread = w;
1311	<	}
1312	<
1313	<	/**
1314	<	* Wakes up waiter, returning false if known to already
1315	<	*/
1316	<	boolean signal() {
1317	<	ForkJoinWorkerThread t = thread;
1318	<	if (t == null)
1319	<	return false;
1320	<	thread = null;
1321	<	LockSupport.unpark(t);
1322	<	return true;
1323	<	}
1324	<
1325	<	/**
1326	<	* Awaits release on sync.
1327	<	*/
1328	<	void awaitSyncRelease(ForkJoinPool p) {
1329	<	while (thread != null && !p.syncIsReleasable(this))
1330	<	LockSupport.park(this);
1331	<	}
1332	<
1333	<	/**
1334	<	* Awaits resumption as spare.
1335	<	*/
1336	<	void awaitSpareRelease() {
1337	<	while (thread != null) {
1338	<	if (!Thread.interrupted())
1339	<	LockSupport.park(this);
1340	<	}
1341	<	}
1342	<	}
1343	<
1344	<	/**
1345	<	* Ensures that no thread is waiting for count to advance from the
1346	<	* current value of eventCount read on entry to this method, by
1347	<	* releasing waiting threads if necessary.
1348	<	* @return the count
1349	<	*/
1350	<	final long ensureSync() {
1351	<	long c = eventCount;
1352	<	WaitQueueNode q;
1353	<	while ((q = syncStack) != null && q.count < c) {
1354	<	if (casBarrierStack(q, null)) {
1355	<	do {
1356	<	q.signal();
1357	<	} while ((q = q.next) != null);
1358	<	break;
1359	<	}
1360	<	}
1361	<	return c;
1362	<	}
1363	<
1364	<	/**
1365	<	* Increments event count and releases waiting threads.
1366	<	*/
1367	<	private void signalIdleWorkers() {
1368	<	long c;
1369	<	do;while (!casEventCount(c = eventCount, c+1));
1370	<	ensureSync();
1371	<	}
1372	<
1373	<	/**
1374	<	* Signals threads waiting to poll a task. Because method sync
1375	<	* rechecks availability, it is OK to only proceed if queue
1376	<	* appears to be non-empty, and OK to skip under contention to
1377	<	* increment count (since some other thread succeeded).
1378	<	*/
1379	<	final void signalWork() {
1380	<	long c;
1381	<	WaitQueueNode q;
1382	<	if (syncStack != null &&
1383	<	casEventCount(c = eventCount, c+1) &&
1384	<	(((q = syncStack) != null && q.count <= c) &&
1385	<	(!casBarrierStack(q, q.next) || !q.signal())))
1386	<	ensureSync();
1387	<	}
1388	<
1389	<	/**
1390	<	* Waits until event count advances from last value held by
1391	<	* caller, or if excess threads, caller is resumed as spare, or
1392	<	* caller or pool is terminating. Updates caller's event on exit.
1393	<	* @param w the calling worker thread
1394	<	*/
1395	<	final void sync(ForkJoinWorkerThread w) {
1396	<	updateStealCount(w); // Transfer w's count while it is idle
1397	<
1398	<	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1399	<	long prev = w.lastEventCount;
1400	<	WaitQueueNode node = null;
1401	<	WaitQueueNode h;
1402	<	while (eventCount == prev &&
1403	<	((h = syncStack) == null || h.count == prev)) {
1404	<	if (node == null)
1405	<	node = new WaitQueueNode(prev, w);
1406	<	if (casBarrierStack(node.next = h, node)) {
1407	<	node.awaitSyncRelease(this);
1408	<	break;
1409	<	}
1410	<	}
1411	<	long ec = ensureSync();
1412	<	if (ec != prev) {
1413	<	w.lastEventCount = ec;
1414	<	break;
1415	<	}
1416	<	}
1417	<	}
1418	<
1419	<	/**
1420	<	* Returns true if worker waiting on sync can proceed:
1421	<	*  - on signal (thread == null)
1422	<	*  - on event count advance (winning race to notify vs signaller)
1423	<	*  - on Interrupt
1424	<	*  - if the first queued node, we find work available
1425	<	* If node was not signalled and event count not advanced on exit,
1426	<	* then we also help advance event count.
1427	<	* @return true if node can be released
1428	<	*/
1429	<	final boolean syncIsReleasable(WaitQueueNode node) {
1430	<	long prev = node.count;
1431	<	if (!Thread.interrupted() && node.thread != null &&
1432	<	(node.next != null ||
1433	<	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1434	<	eventCount == prev)
1435	<	return false;
1436	<	if (node.thread != null) {
1437	<	node.thread = null;
1438	<	long ec = eventCount;
1439	<	if (prev <= ec) // help signal
1440	<	casEventCount(ec, ec+1);
1441	<	}
1442	<	return true;
1443	<	}
1444	<
1445	<	/**
1446	<	* Returns true if a new sync event occurred since last call to
1447	<	* sync or this method, if so, updating caller's count.
1448	<	*/
1449	<	final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1450	<	long lc = w.lastEventCount;
1451	<	long ec = ensureSync();
1452	<	if (ec == lc)
1453	<	return false;
1454	<	w.lastEventCount = ec;
1455	<	return true;
1456	<	}
1457	<
1458	<	//  Parallelism maintenance
1459	<
1460	<	/**
1461	<	* Decrements running count; if too low, adds spare.
2505	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
2506	>	* {@code isReleasable} must return {@code true} if blocking is
2507	>	* not necessary. Method {@code block} blocks the current thread
2508	>	* if necessary (perhaps internally invoking {@code isReleasable}
2509	>	* before actually blocking). These actions are performed by any
2510	>	* thread invoking {@link ForkJoinPool#managedBlock}.  The
2511	>	* unusual methods in this API accommodate synchronizers that may,
2512	>	* but don't usually, block for long periods. Similarly, they
2513	>	* allow more efficient internal handling of cases in which
2514	>	* additional workers may be, but usually are not, needed to
2515	>	* ensure sufficient parallelism.  Toward this end,
2516	>	* implementations of method {@code isReleasable} must be amenable
2517	>	* to repeated invocation.
2518		*
1463	–	* Conceptually, all we need to do here is add or resume a
1464	–	* spare thread when one is about to block (and remove or
1465	–	* suspend it later when unblocked -- see suspendIfSpare).
1466	–	* However, implementing this idea requires coping with
1467	–	* several problems: We have imperfect information about the
1468	–	* states of threads. Some count updates can and usually do
1469	–	* lag run state changes, despite arrangements to keep them
1470	–	* accurate (for example, when possible, updating counts
1471	–	* before signalling or resuming), especially when running on
1472	–	* dynamic JVMs that don't optimize the infrequent paths that
1473	–	* update counts. Generating too many threads can make these
1474	–	* problems become worse, because excess threads are more
1475	–	* likely to be context-switched with others, slowing them all
1476	–	* down, especially if there is no work available, so all are
1477	–	* busy scanning or idling.  Also, excess spare threads can
1478	–	* only be suspended or removed when they are idle, not
1479	–	* immediately when they aren't needed. So adding threads will
1480	–	* raise parallelism level for longer than necessary.  Also,
1481	–	* FJ applications often encounter highly transient peaks when
1482	–	* many threads are blocked joining, but for less time than it
1483	–	* takes to create or resume spares.
1484	–	*
1485	–	* @param joinMe if non-null, return early if done
1486	–	* @param maintainParallelism if true, try to stay within
1487	–	* target counts, else create only to avoid starvation
1488	–	* @return true if joinMe known to be done
1489	–	*/
1490	–	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1491	–	maintainParallelism &= maintainsParallelism; // overrride
1492	–	boolean dec = false;  // true when running count decremented
1493	–	while (spareStack == null || !tryResumeSpare(dec)) {
1494	–	int counts = workerCounts;
1495	–	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1496	–	if (!needSpare(counts, maintainParallelism))
1497	–	break;
1498	–	if (joinMe.status < 0)
1499	–	return true;
1500	–	if (tryAddSpare(counts))
1501	–	break;
1502	–	}
1503	–	}
1504	–	return false;
1505	–	}
1506	–
1507	–	/**
1508	–	* Same idea as preJoin
1509	–	*/
1510	–	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1511	–	maintainParallelism &= maintainsParallelism;
1512	–	boolean dec = false;
1513	–	while (spareStack == null || !tryResumeSpare(dec)) {
1514	–	int counts = workerCounts;
1515	–	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1516	–	if (!needSpare(counts, maintainParallelism))
1517	–	break;
1518	–	if (blocker.isReleasable())
1519	–	return true;
1520	–	if (tryAddSpare(counts))
1521	–	break;
1522	–	}
1523	–	}
1524	–	return false;
1525	–	}
1526	–
1527	–	/**
1528	–	* Returns true if a spare thread appears to be needed.  If
1529	–	* maintaining parallelism, returns true when the deficit in
1530	–	* running threads is more than the surplus of total threads, and
1531	–	* there is apparently some work to do.  This self-limiting rule
1532	–	* means that the more threads that have already been added, the
1533	–	* less parallelism we will tolerate before adding another.
1534	–	* @param counts current worker counts
1535	–	* @param maintainParallelism try to maintain parallelism
1536	–	*/
1537	–	private boolean needSpare(int counts, boolean maintainParallelism) {
1538	–	int ps = parallelism;
1539	–	int rc = runningCountOf(counts);
1540	–	int tc = totalCountOf(counts);
1541	–	int runningDeficit = ps - rc;
1542	–	int totalSurplus = tc - ps;
1543	–	return (tc < maxPoolSize &&
1544	–	(rc == 0 || totalSurplus < 0 ||
1545	–	(maintainParallelism &&
1546	–	runningDeficit > totalSurplus &&
1547	–	ForkJoinWorkerThread.hasQueuedTasks(workers))));
1548	–	}
1549	–
1550	–	/**
1551	–	* Adds a spare worker if lock available and no more than the
1552	–	* expected numbers of threads exist.
1553	–	* @return true if successful
1554	–	*/
1555	–	private boolean tryAddSpare(int expectedCounts) {
1556	–	final ReentrantLock lock = this.workerLock;
1557	–	int expectedRunning = runningCountOf(expectedCounts);
1558	–	int expectedTotal = totalCountOf(expectedCounts);
1559	–	boolean success = false;
1560	–	boolean locked = false;
1561	–	// confirm counts while locking; CAS after obtaining lock
1562	–	try {
1563	–	for (;;) {
1564	–	int s = workerCounts;
1565	–	int tc = totalCountOf(s);
1566	–	int rc = runningCountOf(s);
1567	–	if (rc > expectedRunning || tc > expectedTotal)
1568	–	break;
1569	–	if (!locked && !(locked = lock.tryLock()))
1570	–	break;
1571	–	if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) {
1572	–	createAndStartSpare(tc);
1573	–	success = true;
1574	–	break;
1575	–	}
1576	–	}
1577	–	} finally {
1578	–	if (locked)
1579	–	lock.unlock();
1580	–	}
1581	–	return success;
1582	–	}
1583	–
1584	–	/**
1585	–	* Adds the kth spare worker. On entry, pool counts are already
1586	–	* adjusted to reflect addition.
1587	–	*/
1588	–	private void createAndStartSpare(int k) {
1589	–	ForkJoinWorkerThread w = null;
1590	–	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1);
1591	–	int len = ws.length;
1592	–	// Probably, we can place at slot k. If not, find empty slot
1593	–	if (k < len && ws[k] != null) {
1594	–	for (k = 0; k < len && ws[k] != null; ++k)
1595	–	;
1596	–	}
1597	–	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1598	–	ws[k] = w;
1599	–	w.start();
1600	–	}
1601	–	else
1602	–	updateWorkerCount(-1); // adjust on failure
1603	–	signalIdleWorkers();
1604	–	}
1605	–
1606	–	/**
1607	–	* Suspends calling thread w if there are excess threads.  Called
1608	–	* only from sync.  Spares are enqueued in a Treiber stack using
1609	–	* the same WaitQueueNodes as barriers.  They are resumed mainly
1610	–	* in preJoin, but are also woken on pool events that require all
1611	–	* threads to check run state.
1612	–	* @param w the caller
1613	–	*/
1614	–	private boolean suspendIfSpare(ForkJoinWorkerThread w) {
1615	–	WaitQueueNode node = null;
1616	–	int s;
1617	–	while (parallelism < runningCountOf(s = workerCounts)) {
1618	–	if (node == null)
1619	–	node = new WaitQueueNode(0, w);
1620	–	if (casWorkerCounts(s, s-1)) { // representation-dependent
1621	–	// push onto stack
1622	–	do;while (!casSpareStack(node.next = spareStack, node));
1623	–	// block until released by resumeSpare
1624	–	node.awaitSpareRelease();
1625	–	return true;
1626	–	}
1627	–	}
1628	–	return false;
1629	–	}
1630	–
1631	–	/**
1632	–	* Tries to pop and resume a spare thread.
1633	–	* @param updateCount if true, increment running count on success
1634	–	* @return true if successful
1635	–	*/
1636	–	private boolean tryResumeSpare(boolean updateCount) {
1637	–	WaitQueueNode q;
1638	–	while ((q = spareStack) != null) {
1639	–	if (casSpareStack(q, q.next)) {
1640	–	if (updateCount)
1641	–	updateRunningCount(1);
1642	–	q.signal();
1643	–	return true;
1644	–	}
1645	–	}
1646	–	return false;
1647	–	}
1648	–
1649	–	/**
1650	–	* Pops and resumes all spare threads. Same idea as ensureSync.
1651	–	* @return true if any spares released
1652	–	*/
1653	–	private boolean resumeAllSpares() {
1654	–	WaitQueueNode q;
1655	–	while ( (q = spareStack) != null) {
1656	–	if (casSpareStack(q, null)) {
1657	–	do {
1658	–	updateRunningCount(1);
1659	–	q.signal();
1660	–	} while ((q = q.next) != null);
1661	–	return true;
1662	–	}
1663	–	}
1664	–	return false;
1665	–	}
1666	–
1667	–	/**
1668	–	* Pops and shuts down excessive spare threads. Call only while
1669	–	* holding lock. This is not guaranteed to eliminate all excess
1670	–	* threads, only those suspended as spares, which are the ones
1671	–	* unlikely to be needed in the future.
1672	–	*/
1673	–	private void trimSpares() {
1674	–	int surplus = totalCountOf(workerCounts) - parallelism;
1675	–	WaitQueueNode q;
1676	–	while (surplus > 0 && (q = spareStack) != null) {
1677	–	if (casSpareStack(q, null)) {
1678	–	do {
1679	–	updateRunningCount(1);
1680	–	ForkJoinWorkerThread w = q.thread;
1681	–	if (w != null && surplus > 0 &&
1682	–	runningCountOf(workerCounts) > 0 && w.shutdown())
1683	–	--surplus;
1684	–	q.signal();
1685	–	} while ((q = q.next) != null);
1686	–	}
1687	–	}
1688	–	}
1689	–
1690	–	/**
1691	–	* Interface for extending managed parallelism for tasks running
1692	–	* in ForkJoinPools. A ManagedBlocker provides two methods.
1693	–	* Method {@code isReleasable} must return true if blocking is not
1694	–	* necessary. Method {@code block} blocks the current thread
1695	–	* if necessary (perhaps internally invoking isReleasable before
1696	–	* actually blocking.).
2519		* <p>For example, here is a ManagedBlocker based on a
2520		* ReentrantLock:
2521	<	* <pre>
2522	<	*   class ManagedLocker implements ManagedBlocker {
2523	<	*     final ReentrantLock lock;
2524	<	*     boolean hasLock = false;
2525	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
2526	<	*     public boolean block() {
2527	<	*        if (!hasLock)
2528	<	*           lock.lock();
2529	<	*        return true;
2530	<	*     }
2531	<	*     public boolean isReleasable() {
2532	<	*        return hasLock || (hasLock = lock.tryLock());
1711	<	*     }
2521	>	*  <pre> {@code
2522	>	* class ManagedLocker implements ManagedBlocker {
2523	>	*   final ReentrantLock lock;
2524	>	*   boolean hasLock = false;
2525	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
2526	>	*   public boolean block() {
2527	>	*     if (!hasLock)
2528	>	*       lock.lock();
2529	>	*     return true;
2530	>	*   }
2531	>	*   public boolean isReleasable() {
2532	>	*     return hasLock || (hasLock = lock.tryLock());
2533		*   }
2534	<	* </pre>
2534	>	* }}</pre>
2535	>	*
2536	>	* <p>Here is a class that possibly blocks waiting for an
2537	>	* item on a given queue:
2538	>	*  <pre> {@code
2539	>	* class QueueTaker<E> implements ManagedBlocker {
2540	>	*   final BlockingQueue<E> queue;
2541	>	*   volatile E item = null;
2542	>	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
2543	>	*   public boolean block() throws InterruptedException {
2544	>	*     if (item == null)
2545	>	*       item = queue.take();
2546	>	*     return true;
2547	>	*   }
2548	>	*   public boolean isReleasable() {
2549	>	*     return item != null || (item = queue.poll()) != null;
2550	>	*   }
2551	>	*   public E getItem() { // call after pool.managedBlock completes
2552	>	*     return item;
2553	>	*   }
2554	>	* }}</pre>
2555		*/
2556		public static interface ManagedBlocker {
2557		/**
2558		* Possibly blocks the current thread, for example waiting for
2559		* a lock or condition.
2560	<	* @return true if no additional blocking is necessary (i.e.,
2561	<	* if isReleasable would return true)
2560	>	*
2561	>	* @return {@code true} if no additional blocking is necessary
2562	>	* (i.e., if isReleasable would return true)
2563		* @throws InterruptedException if interrupted while waiting
2564	<	* (the method is not required to do so, but is allowed to).
2564	>	* (the method is not required to do so, but is allowed to)
2565		*/
2566		boolean block() throws InterruptedException;
2567
2568		/**
2569	<	* Returns true if blocking is unnecessary.
2569	>	* Returns {@code true} if blocking is unnecessary.
2570		*/
2571		boolean isReleasable();
2572		}
2573
2574		/**
2575		* Blocks in accord with the given blocker.  If the current thread
2576	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
2577	<	* spare thread to be activated if necessary to ensure parallelism
2578	<	* while the current thread is blocked.  If
2579	<	* {@code maintainParallelism} is true and the pool supports
2580	<	* it ({@link #getMaintainsParallelism}), this method attempts to
2581	<	* maintain the pool's nominal parallelism. Otherwise if activates
2582	<	* a thread only if necessary to avoid complete starvation. This
2583	<	* option may be preferable when blockages use timeouts, or are
2584	<	* almost always brief.
2585	<	*
2586	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
2587	<	* equivalent to
2588	<	* <pre>
2589	<	*   while (!blocker.isReleasable())
1748	<	*      if (blocker.block())
1749	<	*         return;
1750	<	* </pre>
1751	<	* If the caller is a ForkJoinTask, then the pool may first
1752	<	* be expanded to ensure parallelism, and later adjusted.
2576	>	* is a {@link ForkJoinWorkerThread}, this method possibly
2577	>	* arranges for a spare thread to be activated if necessary to
2578	>	* ensure sufficient parallelism while the current thread is blocked.
2579	>	*
2580	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
2581	>	* behaviorally equivalent to
2582	>	*  <pre> {@code
2583	>	* while (!blocker.isReleasable())
2584	>	*   if (blocker.block())
2585	>	*     return;
2586	>	* }</pre>
2587	>	*
2588	>	* If the caller is a {@code ForkJoinTask}, then the pool may
2589	>	* first be expanded to ensure parallelism, and later adjusted.
2590		*
2591		* @param blocker the blocker
1755	–	* @param maintainParallelism if true and supported by this pool,
1756	–	* attempt to maintain the pool's nominal parallelism; otherwise
1757	–	* activate a thread only if necessary to avoid complete
1758	–	* starvation.
2592		* @throws InterruptedException if blocker.block did so
2593		*/
2594	<	public static void managedBlock(ManagedBlocker blocker,
1762	<	boolean maintainParallelism)
2594	>	public static void managedBlock(ManagedBlocker blocker)
2595		throws InterruptedException {
2596		Thread t = Thread.currentThread();
2597	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
2598	<	((ForkJoinWorkerThread)t).pool : null);
2599	<	if (!blocker.isReleasable()) {
2600	<	try {
2601	<	if (pool == null ||
2602	<	!pool.preBlock(blocker, maintainParallelism))
2603	<	awaitBlocker(blocker);
2604	<	} finally {
2605	<	if (pool != null)
2606	<	pool.updateRunningCount(1);
2597	>	ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ?
2598	>	((ForkJoinWorkerThread)t).pool : null);
2599	>	while (!blocker.isReleasable()) {
2600	>	if (p == null || p.tryCompensate()) {
2601	>	try {
2602	>	do {} while (!blocker.isReleasable() && !blocker.block());
2603	>	} finally {
2604	>	if (p != null)
2605	>	p.incrementActiveCount();
2606	>	}
2607	>	break;
2608		}
2609		}
2610		}
2611
2612	<	private static void awaitBlocker(ManagedBlocker blocker)
2613	<	throws InterruptedException {
2614	<	do;while (!blocker.isReleasable() && !blocker.block());
1782	<	}
1783	<
1784	<	// AbstractExecutorService overrides
2612	>	// AbstractExecutorService overrides.  These rely on undocumented
2613	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
2614	>	// implement RunnableFuture.
2615
2616		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
2617	<	return new AdaptedRunnable(runnable, value);
2617	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
2618		}
2619
2620		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
2621	<	return new AdaptedCallable(callable);
2621	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
2622		}
2623
2624	+	// Unsafe mechanics
2625	+	private static final sun.misc.Unsafe U;
2626	+	private static final long CTL;
2627	+	private static final long RUNSTATE;
2628	+	private static final long PARKBLOCKER;
2629
2630	<	// Temporary Unsafe mechanics for preliminary release
2631	<	private static Unsafe getUnsafe() throws Throwable {
2630	>	static {
2631	>	poolNumberGenerator = new AtomicInteger();
2632	>	modifyThreadPermission = new RuntimePermission("modifyThread");
2633	>	defaultForkJoinWorkerThreadFactory =
2634	>	new DefaultForkJoinWorkerThreadFactory();
2635	>	int s;
2636		try {
2637	<	return Unsafe.getUnsafe();
2637	>	U = getUnsafe();
2638	>	Class<?> k = ForkJoinPool.class;
2639	>	Class<?> tk = Thread.class;
2640	>	CTL = U.objectFieldOffset
2641	>	(k.getDeclaredField("ctl"));
2642	>	RUNSTATE = U.objectFieldOffset
2643	>	(k.getDeclaredField("runState"));
2644	>	PARKBLOCKER = U.objectFieldOffset
2645	>	(tk.getDeclaredField("parkBlocker"));
2646	>	} catch (Exception e) {
2647	>	throw new Error(e);
2648	>	}
2649	>	}
2650	>
2651	>	/**
2652	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
2653	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
2654	>	* into a jdk.
2655	>	*
2656	>	* @return a sun.misc.Unsafe
2657	>	*/
2658	>	private static sun.misc.Unsafe getUnsafe() {
2659	>	try {
2660	>	return sun.misc.Unsafe.getUnsafe();
2661		} catch (SecurityException se) {
2662		try {
2663		return java.security.AccessController.doPrivileged
2664	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
2665	<	public Unsafe run() throws Exception {
2666	<	return getUnsafePrivileged();
2664	>	(new java.security
2665	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
2666	>	public sun.misc.Unsafe run() throws Exception {
2667	>	java.lang.reflect.Field f = sun.misc
2668	>	.Unsafe.class.getDeclaredField("theUnsafe");
2669	>	f.setAccessible(true);
2670	>	return (sun.misc.Unsafe) f.get(null);
2671		}});
2672		} catch (java.security.PrivilegedActionException e) {
2673	<	throw e.getCause();
2673	>	throw new RuntimeException("Could not initialize intrinsics",
2674	>	e.getCause());
2675		}
2676		}
2677		}
2678
1812	–	private static Unsafe getUnsafePrivileged()
1813	–	throws NoSuchFieldException, IllegalAccessException {
1814	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1815	–	f.setAccessible(true);
1816	–	return (Unsafe) f.get(null);
1817	–	}
1818	–
1819	–	private static long fieldOffset(String fieldName)
1820	–	throws NoSuchFieldException {
1821	–	return UNSAFE.objectFieldOffset
1822	–	(ForkJoinPool.class.getDeclaredField(fieldName));
1823	–	}
1824	–
1825	–	static final Unsafe UNSAFE;
1826	–	static final long eventCountOffset;
1827	–	static final long workerCountsOffset;
1828	–	static final long runControlOffset;
1829	–	static final long syncStackOffset;
1830	–	static final long spareStackOffset;
1831	–
1832	–	static {
1833	–	try {
1834	–	UNSAFE = getUnsafe();
1835	–	eventCountOffset = fieldOffset("eventCount");
1836	–	workerCountsOffset = fieldOffset("workerCounts");
1837	–	runControlOffset = fieldOffset("runControl");
1838	–	syncStackOffset = fieldOffset("syncStack");
1839	–	spareStackOffset = fieldOffset("spareStack");
1840	–	} catch (Throwable e) {
1841	–	throw new RuntimeException("Could not initialize intrinsics", e);
1842	–	}
1843	–	}
1844	–
1845	–	private boolean casEventCount(long cmp, long val) {
1846	–	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1847	–	}
1848	–	private boolean casWorkerCounts(int cmp, int val) {
1849	–	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1850	–	}
1851	–	private boolean casRunControl(int cmp, int val) {
1852	–	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1853	–	}
1854	–	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1855	–	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1856	–	}
1857	–	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1858	–	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1859	–	}
2679		}

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