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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.13 by jsr166, Wed Jul 22 01:36:51 2009 UTC vs.
Revision 1.145 by jsr166, Mon Nov 19 01:04:24 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.concurrent.AbstractExecutorService;
15	>	import java.util.concurrent.Callable;
16	>	import java.util.concurrent.ExecutorService;
17	>	import java.util.concurrent.Future;
18	>	import java.util.concurrent.RejectedExecutionException;
19	>	import java.util.concurrent.RunnableFuture;
20	>	import java.util.concurrent.TimeUnit;
21
22		/**
23	<	* An {@link ExecutorService} for running {@link ForkJoinTask}s.  A
24	<	* ForkJoinPool provides the entry point for submissions from
25	<	* non-ForkJoinTasks, as well as management and monitoring operations.
26	<	* Normally a single ForkJoinPool is used for a large number of
27	<	* submitted tasks. Otherwise, use would not usually outweigh the
28	<	* construction and bookkeeping overhead of creating a large set of
29	<	* threads.
23	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
24	>	* A {@code ForkJoinPool} provides the entry point for submissions
25	>	* from non-{@code ForkJoinTask} clients, as well as management and
26	>	* monitoring operations.
27	>	*
28	>	* <p>A {@code ForkJoinPool} differs from other kinds of {@link
29	>	* ExecutorService} mainly by virtue of employing
30	>	* <em>work-stealing</em>: all threads in the pool attempt to find and
31	>	* execute tasks submitted to the pool and/or created by other active
32	>	* tasks (eventually blocking waiting for work if none exist). This
33	>	* enables efficient processing when most tasks spawn other subtasks
34	>	* (as do most {@code ForkJoinTask}s), as well as when many small
35	>	* tasks are submitted to the pool from external clients.  Especially
36	>	* when setting <em>asyncMode</em> to true in constructors, {@code
37	>	* ForkJoinPool}s may also be appropriate for use with event-style
38	>	* tasks that are never joined.
39		*
40	<	* <p>ForkJoinPools differ from other kinds of Executors mainly in
41	<	* that they provide <em>work-stealing</em>: all threads in the pool
42	<	* attempt to find and execute subtasks created by other active tasks
43	<	* (eventually blocking if none exist). This makes them efficient when
44	<	* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
45	<	* as the mixed execution of some plain Runnable- or Callable- based
30	<	* activities along with ForkJoinTasks. When setting
31	<	* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for
32	<	* use with fine-grained tasks that are never joined. Otherwise, other
33	<	* ExecutorService implementations are typically more appropriate
34	<	* choices.
40	>	* <p>A static {@link #commonPool} is available and appropriate for
41	>	* most applications. The common pool is used by any ForkJoinTask that
42	>	* is not explicitly submitted to a specified pool. Using the common
43	>	* pool normally reduces resource usage (its threads are slowly
44	>	* reclaimed during periods of non-use, and reinstated upon subsequent
45	>	* use).
46		*
47	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
48	<	* (target pool size), which it attempts to maintain by dynamically
49	<	* adding, suspending, or resuming threads, even if some tasks are
50	<	* waiting to join others. However, no such adjustments are performed
51	<	* in the face of blocked IO or other unmanaged synchronization. The
52	<	* nested {@code ManagedBlocker} interface enables extension of
53	<	* the kinds of synchronization accommodated.  The target parallelism
54	<	* level may also be changed dynamically ({@code setParallelism})
55	<	* and thread construction can be limited using methods
56	<	* {@code setMaximumPoolSize} and/or
46	<	* {@code setMaintainsParallelism}.
47	>	* <p>For applications that require separate or custom pools, a {@code
48	>	* ForkJoinPool} may be constructed with a given target parallelism
49	>	* level; by default, equal to the number of available processors. The
50	>	* pool attempts to maintain enough active (or available) threads by
51	>	* dynamically adding, suspending, or resuming internal worker
52	>	* threads, even if some tasks are stalled waiting to join
53	>	* others. However, no such adjustments are guaranteed in the face of
54	>	* blocked IO or other unmanaged synchronization. The nested {@link
55	>	* ManagedBlocker} interface enables extension of the kinds of
56	>	* synchronization accommodated.
57		*
58		* <p>In addition to execution and lifecycle control methods, this
59		* class provides status check methods (for example
60	<	* {@code getStealCount}) that are intended to aid in developing,
60	>	* {@link #getStealCount}) that are intended to aid in developing,
61		* tuning, and monitoring fork/join applications. Also, method
62	<	* {@code toString} returns indications of pool state in a
62	>	* {@link #toString} returns indications of pool state in a
63		* convenient form for informal monitoring.
64		*
65	+	* <p>As is the case with other ExecutorServices, there are three
66	+	* main task execution methods summarized in the following table.
67	+	* These are designed to be used primarily by clients not already
68	+	* engaged in fork/join computations in the current pool.  The main
69	+	* forms of these methods accept instances of {@code ForkJoinTask},
70	+	* but overloaded forms also allow mixed execution of plain {@code
71	+	* Runnable}- or {@code Callable}- based activities as well.  However,
72	+	* tasks that are already executing in a pool should normally instead
73	+	* use the within-computation forms listed in the table unless using
74	+	* async event-style tasks that are not usually joined, in which case
75	+	* there is little difference among choice of methods.
76	+	*
77	+	* <table BORDER CELLPADDING=3 CELLSPACING=1>
78	+	*  <tr>
79	+	*    <td></td>
80	+	*    <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
81	+	*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
82	+	*  </tr>
83	+	*  <tr>
84	+	*    <td> <b>Arrange async execution</td>
85	+	*    <td> {@link #execute(ForkJoinTask)}</td>
86	+	*    <td> {@link ForkJoinTask#fork}</td>
87	+	*  </tr>
88	+	*  <tr>
89	+	*    <td> <b>Await and obtain result</td>
90	+	*    <td> {@link #invoke(ForkJoinTask)}</td>
91	+	*    <td> {@link ForkJoinTask#invoke}</td>
92	+	*  </tr>
93	+	*  <tr>
94	+	*    <td> <b>Arrange exec and obtain Future</td>
95	+	*    <td> {@link #submit(ForkJoinTask)}</td>
96	+	*    <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td>
97	+	*  </tr>
98	+	* </table>
99	+	*
100	+	* <p>The common pool is by default constructed with default
101	+	* parameters, but these may be controlled by setting three {@link
102	+	* System#getProperty properties} with prefix {@code
103	+	* java.util.concurrent.ForkJoinPool.common}: {@code parallelism} --
104	+	* an integer greater than zero, {@code threadFactory} -- the class
105	+	* name of a {@link ForkJoinWorkerThreadFactory}, and {@code
106	+	* exceptionHandler} -- the class name of a {@link
107	+	* java.lang.Thread.UncaughtExceptionHandler
108	+	* Thread.UncaughtExceptionHandler}. Upon any error in establishing
109	+	* these settings, default parameters are used.
110	+	*
111		* <p><b>Implementation notes</b>: This implementation restricts the
112		* maximum number of running threads to 32767. Attempts to create
113	<	* pools with greater than the maximum result in
114	<	* IllegalArgumentExceptions.
113	>	* pools with greater than the maximum number result in
114	>	* {@code IllegalArgumentException}.
115	>	*
116	>	* <p>This implementation rejects submitted tasks (that is, by throwing
117	>	* {@link RejectedExecutionException}) only when the pool is shut down
118	>	* or internal resources have been exhausted.
119		*
120		* @since 1.7
121		* @author Doug Lea
#	Line 63 | Line 123 | import java.lang.reflect.*;
123		public class ForkJoinPool extends AbstractExecutorService {
124
125		/*
126	<	* See the extended comments interspersed below for design,
127	<	* rationale, and walkthroughs.
126	>	* Implementation Overview
127	>	*
128	>	* This class and its nested classes provide the main
129	>	* functionality and control for a set of worker threads:
130	>	* Submissions from non-FJ threads enter into submission queues.
131	>	* Workers take these tasks and typically split them into subtasks
132	>	* that may be stolen by other workers.  Preference rules give
133	>	* first priority to processing tasks from their own queues (LIFO
134	>	* or FIFO, depending on mode), then to randomized FIFO steals of
135	>	* tasks in other queues.
136	>	*
137	>	* WorkQueues
138	>	* ==========
139	>	*
140	>	* Most operations occur within work-stealing queues (in nested
141	>	* class WorkQueue).  These are special forms of Deques that
142	>	* support only three of the four possible end-operations -- push,
143	>	* pop, and poll (aka steal), under the further constraints that
144	>	* push and pop are called only from the owning thread (or, as
145	>	* extended here, under a lock), while poll may be called from
146	>	* other threads.  (If you are unfamiliar with them, you probably
147	>	* want to read Herlihy and Shavit's book "The Art of
148	>	* Multiprocessor programming", chapter 16 describing these in
149	>	* more detail before proceeding.)  The main work-stealing queue
150	>	* design is roughly similar to those in the papers "Dynamic
151	>	* Circular Work-Stealing Deque" by Chase and Lev, SPAA 2005
152	>	* (http://research.sun.com/scalable/pubs/index.html) and
153	>	* "Idempotent work stealing" by Michael, Saraswat, and Vechev,
154	>	* PPoPP 2009 (http://portal.acm.org/citation.cfm?id=1504186).
155	>	* The main differences ultimately stem from GC requirements that
156	>	* we null out taken slots as soon as we can, to maintain as small
157	>	* a footprint as possible even in programs generating huge
158	>	* numbers of tasks. To accomplish this, we shift the CAS
159	>	* arbitrating pop vs poll (steal) from being on the indices
160	>	* ("base" and "top") to the slots themselves.  So, both a
161	>	* successful pop and poll mainly entail a CAS of a slot from
162	>	* non-null to null.  Because we rely on CASes of references, we
163	>	* do not need tag bits on base or top.  They are simple ints as
164	>	* used in any circular array-based queue (see for example
165	>	* ArrayDeque).  Updates to the indices must still be ordered in a
166	>	* way that guarantees that top == base means the queue is empty,
167	>	* but otherwise may err on the side of possibly making the queue
168	>	* appear nonempty when a push, pop, or poll have not fully
169	>	* committed. Note that this means that the poll operation,
170	>	* considered individually, is not wait-free. One thief cannot
171	>	* successfully continue until another in-progress one (or, if
172	>	* previously empty, a push) completes.  However, in the
173	>	* aggregate, we ensure at least probabilistic non-blockingness.
174	>	* If an attempted steal fails, a thief always chooses a different
175	>	* random victim target to try next. So, in order for one thief to
176	>	* progress, it suffices for any in-progress poll or new push on
177	>	* any empty queue to complete. (This is why we normally use
178	>	* method pollAt and its variants that try once at the apparent
179	>	* base index, else consider alternative actions, rather than
180	>	* method poll.)
181	>	*
182	>	* This approach also enables support of a user mode in which local
183	>	* task processing is in FIFO, not LIFO order, simply by using
184	>	* poll rather than pop.  This can be useful in message-passing
185	>	* frameworks in which tasks are never joined.  However neither
186	>	* mode considers affinities, loads, cache localities, etc, so
187	>	* rarely provide the best possible performance on a given
188	>	* machine, but portably provide good throughput by averaging over
189	>	* these factors.  (Further, even if we did try to use such
190	>	* information, we do not usually have a basis for exploiting it.
191	>	* For example, some sets of tasks profit from cache affinities,
192	>	* but others are harmed by cache pollution effects.)
193	>	*
194	>	* WorkQueues are also used in a similar way for tasks submitted
195	>	* to the pool. We cannot mix these tasks in the same queues used
196	>	* for work-stealing (this would contaminate lifo/fifo
197	>	* processing). Instead, we randomly associate submission queues
198	>	* with submitting threads, using a form of hashing.  The
199	>	* ThreadLocal Submitter class contains a value initially used as
200	>	* a hash code for choosing existing queues, but may be randomly
201	>	* repositioned upon contention with other submitters.  In
202	>	* essence, submitters act like workers except that they are
203	>	* restricted to executing local tasks that they submitted (or in
204	>	* the case of CountedCompleters, others with the same root task).
205	>	* However, because most shared/external queue operations are more
206	>	* expensive than internal, and because, at steady state, external
207	>	* submitters will compete for CPU with workers, ForkJoinTask.join
208	>	* and related methods disable them from repeatedly helping to
209	>	* process tasks if all workers are active.  Insertion of tasks in
210	>	* shared mode requires a lock (mainly to protect in the case of
211	>	* resizing) but we use only a simple spinlock (using bits in
212	>	* field qlock), because submitters encountering a busy queue move
213	>	* on to try or create other queues -- they block only when
214	>	* creating and registering new queues.
215	>	*
216	>	* Management
217	>	* ==========
218	>	*
219	>	* The main throughput advantages of work-stealing stem from
220	>	* decentralized control -- workers mostly take tasks from
221	>	* themselves or each other. We cannot negate this in the
222	>	* implementation of other management responsibilities. The main
223	>	* tactic for avoiding bottlenecks is packing nearly all
224	>	* essentially atomic control state into two volatile variables
225	>	* that are by far most often read (not written) as status and
226	>	* consistency checks.
227	>	*
228	>	* Field "ctl" contains 64 bits holding all the information needed
229	>	* to atomically decide to add, inactivate, enqueue (on an event
230	>	* queue), dequeue, and/or re-activate workers.  To enable this
231	>	* packing, we restrict maximum parallelism to (1<<15)-1 (which is
232	>	* far in excess of normal operating range) to allow ids, counts,
233	>	* and their negations (used for thresholding) to fit into 16bit
234	>	* fields.
235	>	*
236	>	* Field "plock" is a form of sequence lock with a saturating
237	>	* shutdown bit (similarly for per-queue "qlocks"), mainly
238	>	* protecting updates to the workQueues array, as well as to
239	>	* enable shutdown.  When used as a lock, it is normally only very
240	>	* briefly held, so is nearly always available after at most a
241	>	* brief spin, but we use a monitor-based backup strategy to
242	>	* blocking when needed.
243	>	*
244	>	* Recording WorkQueues.  WorkQueues are recorded in the
245	>	* "workQueues" array that is created upon first use and expanded
246	>	* if necessary.  Updates to the array while recording new workers
247	>	* and unrecording terminated ones are protected from each other
248	>	* by a lock but the array is otherwise concurrently readable, and
249	>	* accessed directly.  To simplify index-based operations, the
250	>	* array size is always a power of two, and all readers must
251	>	* tolerate null slots. Worker queues are at odd indices Shared
252	>	* (submission) queues are at even indices, up to a maximum of 64
253	>	* slots, to limit growth even if array needs to expand to add
254	>	* more workers. Grouping them together in this way simplifies and
255	>	* speeds up task scanning.
256	>	*
257	>	* All worker thread creation is on-demand, triggered by task
258	>	* submissions, replacement of terminated workers, and/or
259	>	* compensation for blocked workers. However, all other support
260	>	* code is set up to work with other policies.  To ensure that we
261	>	* do not hold on to worker references that would prevent GC, ALL
262	>	* accesses to workQueues are via indices into the workQueues
263	>	* array (which is one source of some of the messy code
264	>	* constructions here). In essence, the workQueues array serves as
265	>	* a weak reference mechanism. Thus for example the wait queue
266	>	* field of ctl stores indices, not references.  Access to the
267	>	* workQueues in associated methods (for example signalWork) must
268	>	* both index-check and null-check the IDs. All such accesses
269	>	* ignore bad IDs by returning out early from what they are doing,
270	>	* since this can only be associated with termination, in which
271	>	* case it is OK to give up.  All uses of the workQueues array
272	>	* also check that it is non-null (even if previously
273	>	* non-null). This allows nulling during termination, which is
274	>	* currently not necessary, but remains an option for
275	>	* resource-revocation-based shutdown schemes. It also helps
276	>	* 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. However, many other threads may notice the same task
317	>	* and each signal to wake up a thread that might take it. So in
318	>	* general, pools will be over-signalled.  When a submission is
319	>	* added or another worker adds a task to a queue that is
320	>	* apparently empty, they signal waiting workers (or trigger
321	>	* creation of new ones if fewer than the given parallelism level
322	>	* -- see signalWork).  These primary signals are buttressed by
323	>	* signals whenever other threads scan for work or do not have a
324	>	* task to process. On most platforms, signalling (unpark)
325	>	* overhead time is noticeably long, and the time between
326	>	* signalling a thread and it actually making progress can be very
327	>	* noticeably long, so it is worth offloading these delays from
328	>	* critical paths as much as possible.
329	>	*
330	>	* Trimming workers. To release resources after periods of lack of
331	>	* use, a worker starting to wait when the pool is quiescent will
332	>	* time out and terminate if the pool has remained quiescent for a
333	>	* given period -- a short period if there are more threads than
334	>	* parallelism, longer as the number of threads decreases. This
335	>	* will slowly propagate, eventually terminating all workers after
336	>	* periods of non-use.
337	>	*
338	>	* Shutdown and Termination. A call to shutdownNow atomically sets
339	>	* a plock bit and then (non-atomically) sets each worker's
340	>	* qlock status, cancels all unprocessed tasks, and wakes up
341	>	* all waiting workers.  Detecting whether termination should
342	>	* commence after a non-abrupt shutdown() call requires more work
343	>	* and bookkeeping. We need consensus about quiescence (i.e., that
344	>	* there is no more work). The active count provides a primary
345	>	* indication but non-abrupt shutdown still requires a rechecking
346	>	* scan for any workers that are inactive but not queued.
347	>	*
348	>	* Joining Tasks
349	>	* =============
350	>	*
351	>	* Any of several actions may be taken when one worker is waiting
352	>	* to join a task stolen (or always held) by another.  Because we
353	>	* are multiplexing many tasks on to a pool of workers, we can't
354	>	* just let them block (as in Thread.join).  We also cannot just
355	>	* reassign the joiner's run-time stack with another and replace
356	>	* it later, which would be a form of "continuation", that even if
357	>	* possible is not necessarily a good idea since we sometimes need
358	>	* both an unblocked task and its continuation to progress.
359	>	* Instead we combine two tactics:
360	>	*
361	>	*   Helping: Arranging for the joiner to execute some task that it
362	>	*      would be running if the steal had not occurred.
363	>	*
364	>	*   Compensating: Unless there are already enough live threads,
365	>	*      method tryCompensate() may create or re-activate a spare
366	>	*      thread to compensate for blocked joiners until they unblock.
367	>	*
368	>	* A third form (implemented in tryRemoveAndExec) amounts to
369	>	* helping a hypothetical compensator: If we can readily tell that
370	>	* a possible action of a compensator is to steal and execute the
371	>	* task being joined, the joining thread can do so directly,
372	>	* without the need for a compensation thread (although at the
373	>	* expense of larger run-time stacks, but the tradeoff is
374	>	* typically worthwhile).
375	>	*
376	>	* The ManagedBlocker extension API can't use helping so relies
377	>	* only on compensation in method awaitBlocker.
378	>	*
379	>	* The algorithm in tryHelpStealer entails a form of "linear"
380	>	* helping: Each worker records (in field currentSteal) the most
381	>	* recent task it stole from some other worker. Plus, it records
382	>	* (in field currentJoin) the task it is currently actively
383	>	* joining. Method tryHelpStealer uses these markers to try to
384	>	* find a worker to help (i.e., steal back a task from and execute
385	>	* it) that could hasten completion of the actively joined task.
386	>	* In essence, the joiner executes a task that would be on its own
387	>	* local deque had the to-be-joined task not been stolen. This may
388	>	* be seen as a conservative variant of the approach in Wagner &
389	>	* Calder "Leapfrogging: a portable technique for implementing
390	>	* efficient futures" SIGPLAN Notices, 1993
391	>	* (http://portal.acm.org/citation.cfm?id=155354). It differs in
392	>	* that: (1) We only maintain dependency links across workers upon
393	>	* steals, rather than use per-task bookkeeping.  This sometimes
394	>	* requires a linear scan of workQueues array to locate stealers,
395	>	* but often doesn't because stealers leave hints (that may become
396	>	* stale/wrong) of where to locate them.  A stealHint is only a
397	>	* hint because a worker might have had multiple steals and the
398	>	* hint records only one of them (usually the most current).
399	>	* Hinting isolates cost to when it is needed, rather than adding
400	>	* to per-task overhead.  (2) It is "shallow", ignoring nesting
401	>	* and potentially cyclic mutual steals.  (3) It is intentionally
402	>	* racy: field currentJoin is updated only while actively joining,
403	>	* which means that we miss links in the chain during long-lived
404	>	* tasks, GC stalls etc (which is OK since blocking in such cases
405	>	* is usually a good idea).  (4) We bound the number of attempts
406	>	* to find work (see MAX_HELP) and fall back to suspending the
407	>	* worker and if necessary replacing it with another.
408	>	*
409	>	* Helping actions for CountedCompleters are much simpler: Method
410	>	* helpComplete can take and execute any task with the same root
411	>	* as the task being waited on. However, this still entails some
412	>	* traversal of completer chains, so is less efficient than using
413	>	* CountedCompleters without explicit joins.
414	>	*
415	>	* It is impossible to keep exactly the target parallelism number
416	>	* of threads running at any given time.  Determining the
417	>	* existence of conservatively safe helping targets, the
418	>	* availability of already-created spares, and the apparent need
419	>	* to create new spares are all racy, so we rely on multiple
420	>	* retries of each.  Compensation in the apparent absence of
421	>	* helping opportunities is challenging to control on JVMs, where
422	>	* GC and other activities can stall progress of tasks that in
423	>	* turn stall out many other dependent tasks, without us being
424	>	* able to determine whether they will ever require compensation.
425	>	* Even though work-stealing otherwise encounters little
426	>	* degradation in the presence of more threads than cores,
427	>	* aggressively adding new threads in such cases entails risk of
428	>	* unwanted positive feedback control loops in which more threads
429	>	* cause more dependent stalls (as well as delayed progress of
430	>	* unblocked threads to the point that we know they are available)
431	>	* leading to more situations requiring more threads, and so
432	>	* on. This aspect of control can be seen as an (analytically
433	>	* intractable) game with an opponent that may choose the worst
434	>	* (for us) active thread to stall at any time.  We take several
435	>	* precautions to bound losses (and thus bound gains), mainly in
436	>	* methods tryCompensate and awaitJoin.
437	>	*
438	>	* Common Pool
439	>	* ===========
440	>	*
441	>	* The static commonPool always exists after static
442	>	* initialization.  Since it (or any other created pool) need
443	>	* never be used, we minimize initial construction overhead and
444	>	* footprint to the setup of about a dozen fields, with no nested
445	>	* allocation. Most bootstrapping occurs within method
446	>	* fullExternalPush during the first submission to the pool.
447	>	*
448	>	* When external threads submit to the common pool, they can
449	>	* perform some subtask processing (see externalHelpJoin and
450	>	* related methods).  We do not need to record whether these
451	>	* submissions are to the common pool -- if not, externalHelpJoin
452	>	* returns quickly (at the most helping to signal some common pool
453	>	* workers). These submitters would otherwise be blocked waiting
454	>	* for completion, so the extra effort (with liberally sprinkled
455	>	* task status checks) in inapplicable cases amounts to an odd
456	>	* form of limited spin-wait before blocking in ForkJoinTask.join.
457	>	*
458	>	* Style notes
459	>	* ===========
460	>	*
461	>	* There is a lot of representation-level coupling among classes
462	>	* ForkJoinPool, ForkJoinWorkerThread, and ForkJoinTask.  The
463	>	* fields of WorkQueue maintain data structures managed by
464	>	* ForkJoinPool, so are directly accessed.  There is little point
465	>	* trying to reduce this, since any associated future changes in
466	>	* representations will need to be accompanied by algorithmic
467	>	* changes anyway. Several methods intrinsically sprawl because
468	>	* they must accumulate sets of consistent reads of volatiles held
469	>	* in local variables.  Methods signalWork() and scan() are the
470	>	* main bottlenecks, so are especially heavily
471	>	* micro-optimized/mangled.  There are lots of inline assignments
472	>	* (of form "while ((local = field) != 0)") which are usually the
473	>	* simplest way to ensure the required read orderings (which are
474	>	* sometimes critical). This leads to a "C"-like style of listing
475	>	* declarations of these locals at the heads of methods or blocks.
476	>	* There are several occurrences of the unusual "do {} while
477	>	* (!cas...)"  which is the simplest way to force an update of a
478	>	* CAS'ed variable. There are also other coding oddities (including
479	>	* several unnecessary-looking hoisted null checks) that help
480	>	* some methods perform reasonably even when interpreted (not
481	>	* compiled).
482	>	*
483	>	* The order of declarations in this file is:
484	>	* (1) Static utility functions
485	>	* (2) Nested (static) classes
486	>	* (3) Static fields
487	>	* (4) Fields, along with constants used when unpacking some of them
488	>	* (5) Internal control methods
489	>	* (6) Callbacks and other support for ForkJoinTask methods
490	>	* (7) Exported methods
491	>	* (8) Static block initializing statics in minimally dependent order
492		*/
493
494	<	/** Mask for packing and unpacking shorts */
495	<	private static final int  shortMask = 0xffff;
494	>	// Static utilities
495	>
496	>	/**
497	>	* If there is a security manager, makes sure caller has
498	>	* permission to modify threads.
499	>	*/
500	>	private static void checkPermission() {
501	>	SecurityManager security = System.getSecurityManager();
502	>	if (security != null)
503	>	security.checkPermission(modifyThreadPermission);
504	>	}
505
506	<	/** Max pool size -- must be a power of two minus 1 */
74	<	private static final int MAX_THREADS =  0x7FFF;
506	>	// Nested classes
507
508		/**
509	<	* Factory for creating new ForkJoinWorkerThreads.  A
510	<	* ForkJoinWorkerThreadFactory must be defined and used for
511	<	* ForkJoinWorkerThread subclasses that extend base functionality
512	<	* or initialize threads with different contexts.
509	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
510	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
511	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
512	>	* functionality or initialize threads with different contexts.
513		*/
514		public static interface ForkJoinWorkerThreadFactory {
515		/**
516		* Returns a new worker thread operating in the given pool.
517		*
518		* @param pool the pool this thread works in
519	<	* @throws NullPointerException if pool is null
519	>	* @throws NullPointerException if the pool is null
520		*/
521		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
522		}
523
524		/**
525	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
525	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
526		* new ForkJoinWorkerThread.
527		*/
528	<	static class  DefaultForkJoinWorkerThreadFactory
528	>	static class DefaultForkJoinWorkerThreadFactory
529		implements ForkJoinWorkerThreadFactory {
530		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
531	+	return new ForkJoinWorkerThread(pool);
532	+	}
533	+	}
534	+
535	+	/**
536	+	* Class for artificial tasks that are used to replace the target
537	+	* of local joins if they are removed from an interior queue slot
538	+	* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
539	+	* actually do anything beyond having a unique identity.
540	+	*/
541	+	static final class EmptyTask extends ForkJoinTask<Void> {
542	+	private static final long serialVersionUID = -7721805057305804111L;
543	+	EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
544	+	public final Void getRawResult() { return null; }
545	+	public final void setRawResult(Void x) {}
546	+	public final boolean exec() { return true; }
547	+	}
548	+
549	+	/**
550	+	* Queues supporting work-stealing as well as external task
551	+	* submission. See above for main rationale and algorithms.
552	+	* Implementation relies heavily on "Unsafe" intrinsics
553	+	* and selective use of "volatile":
554	+	*
555	+	* Field "base" is the index (mod array.length) of the least valid
556	+	* queue slot, which is always the next position to steal (poll)
557	+	* from if nonempty. Reads and writes require volatile orderings
558	+	* but not CAS, because updates are only performed after slot
559	+	* CASes.
560	+	*
561	+	* Field "top" is the index (mod array.length) of the next queue
562	+	* slot to push to or pop from. It is written only by owner thread
563	+	* for push, or under lock for external/shared push, and accessed
564	+	* by other threads only after reading (volatile) base.  Both top
565	+	* and base are allowed to wrap around on overflow, but (top -
566	+	* base) (or more commonly -(base - top) to force volatile read of
567	+	* base before top) still estimates size. The lock ("qlock") is
568	+	* forced to -1 on termination, causing all further lock attempts
569	+	* to fail. (Note: we don't need CAS for termination state because
570	+	* upon pool shutdown, all shared-queues will stop being used
571	+	* anyway.)  Nearly all lock bodies are set up so that exceptions
572	+	* within lock bodies are "impossible" (modulo JVM errors that
573	+	* would cause failure anyway.)
574	+	*
575	+	* The array slots are read and written using the emulation of
576	+	* volatiles/atomics provided by Unsafe. Insertions must in
577	+	* general use putOrderedObject as a form of releasing store to
578	+	* ensure that all writes to the task object are ordered before
579	+	* its publication in the queue.  All removals entail a CAS to
580	+	* null.  The array is always a power of two. To ensure safety of
581	+	* Unsafe array operations, all accesses perform explicit null
582	+	* checks and implicit bounds checks via power-of-two masking.
583	+	*
584	+	* In addition to basic queuing support, this class contains
585	+	* fields described elsewhere to control execution. It turns out
586	+	* to work better memory-layout-wise to include them in this class
587	+	* rather than a separate class.
588	+	*
589	+	* Performance on most platforms is very sensitive to placement of
590	+	* instances of both WorkQueues and their arrays -- we absolutely
591	+	* do not want multiple WorkQueue instances or multiple queue
592	+	* arrays sharing cache lines. (It would be best for queue objects
593	+	* and their arrays to share, but there is nothing available to
594	+	* help arrange that).  Unfortunately, because they are recorded
595	+	* in a common array, WorkQueue instances are often moved to be
596	+	* adjacent by garbage collectors. To reduce impact, we use field
597	+	* padding that works OK on common platforms; this effectively
598	+	* trades off slightly slower average field access for the sake of
599	+	* avoiding really bad worst-case access. (Until better JVM
600	+	* support is in place, this padding is dependent on transient
601	+	* properties of JVM field layout rules.)  We also take care in
602	+	* allocating, sizing and resizing the array. Non-shared queue
603	+	* arrays are initialized by workers before use. Others are
604	+	* allocated on first use.
605	+	*/
606	+	static final class WorkQueue {
607	+	/**
608	+	* Capacity of work-stealing queue array upon initialization.
609	+	* Must be a power of two; at least 4, but should be larger to
610	+	* reduce or eliminate cacheline sharing among queues.
611	+	* Currently, it is much larger, as a partial workaround for
612	+	* the fact that JVMs often place arrays in locations that
613	+	* share GC bookkeeping (especially cardmarks) such that
614	+	* per-write accesses encounter serious memory contention.
615	+	*/
616	+	static final int INITIAL_QUEUE_CAPACITY = 1 << 13;
617	+
618	+	/**
619	+	* Maximum size for queue arrays. Must be a power of two less
620	+	* than or equal to 1 << (31 - width of array entry) to ensure
621	+	* lack of wraparound of index calculations, but defined to a
622	+	* value a bit less than this to help users trap runaway
623	+	* programs before saturating systems.
624	+	*/
625	+	static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
626	+
627	+	int seed;                  // for random scanning; initialize nonzero
628	+	volatile int eventCount;   // encoded inactivation count; < 0 if inactive
629	+	int nextWait;              // encoded record of next event waiter
630	+	final int mode;            // lifo, fifo, or shared
631	+	int nsteals;               // cumulative number of steals
632	+	int poolIndex;             // index of this queue in pool (or 0)
633	+	int stealHint;             // index of most recent known stealer
634	+	volatile int qlock;        // 1: locked, -1: terminate; else 0
635	+	volatile int base;         // index of next slot for poll
636	+	int top;                   // index of next slot for push
637	+	ForkJoinTask<?>[] array;   // the elements (initially unallocated)
638	+	final ForkJoinPool pool;   // the containing pool (may be null)
639	+	final ForkJoinWorkerThread owner; // owning thread or null if shared
640	+	volatile Thread parker;    // == owner during call to park; else null
641	+	volatile ForkJoinTask<?> currentJoin;  // task being joined in awaitJoin
642	+	ForkJoinTask<?> currentSteal; // current non-local task being executed
643	+	// Heuristic padding to ameliorate unfortunate memory placements
644	+	Object p00, p01, p02, p03, p04, p05, p06, p07;
645	+	Object p08, p09, p0a, p0b, p0c, p0d, p0e;
646	+
647	+	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode) {
648	+	this.mode = mode;
649	+	this.pool = pool;
650	+	this.owner = owner;
651	+	// Place indices in the center of array (that is not yet allocated)
652	+	base = top = INITIAL_QUEUE_CAPACITY >>> 1;
653	+	}
654	+
655	+	/**
656	+	* Pushes a task. Call only by owner in unshared queues.
657	+	* Cases needing resizing or rejection are relayed to fullPush
658	+	* (that also handles shared queues).
659	+	*
660	+	* @param task the task. Caller must ensure non-null.
661	+	* @throw RejectedExecutionException if array cannot be resized
662	+	*/
663	+	final void push(ForkJoinTask<?> task) {
664	+	ForkJoinPool p; ForkJoinTask<?>[] a;
665	+	int s = top, n;
666	+	if ((a = array) != null && a.length > (n = s + 1 - base)) {
667	+	U.putOrderedObject
668	+	(a, (((a.length - 1) & s) << ASHIFT) + ABASE, task);
669	+	top = s + 1;
670	+	if (n <= 1 && (p = pool) != null)
671	+	p.signalWork(this, 1);
672	+	}
673	+	else
674	+	fullPush(task, true);
675	+	}
676	+
677	+	/**
678	+	* Pushes a task if lock is free and array is either big
679	+	* enough or can be resized to be big enough. Note: a
680	+	* specialization of a common fast path of this method is in
681	+	* ForkJoinPool.externalPush. When called from a FJWT queue,
682	+	* this can fail only if the pool has been shut down or
683	+	* an out of memory error.
684	+	*
685	+	* @param task the task. Caller must ensure non-null.
686	+	* @param owned if true, throw RJE on failure
687	+	*/
688	+	final boolean fullPush(ForkJoinTask<?> task, boolean owned) {
689	+	ForkJoinPool p; ForkJoinTask<?>[] a;
690	+	if (owned) {
691	+	if (qlock < 0) // must be shutting down
692	+	throw new RejectedExecutionException();
693	+	}
694	+	else if (!U.compareAndSwapInt(this, QLOCK, 0, 1))
695	+	return false;
696		try {
697	<	return new ForkJoinWorkerThread(pool);
698	<	} catch (OutOfMemoryError oom)  {
697	>	int s = top, oldLen, len;
698	>	if ((a = array) == null)
699	>	a = array = new ForkJoinTask<?>[len=INITIAL_QUEUE_CAPACITY];
700	>	else if ((oldLen = a.length) > s + 1 - base)
701	>	len = oldLen;
702	>	else if ((len = oldLen << 1) > MAXIMUM_QUEUE_CAPACITY)
703	>	throw new RejectedExecutionException("Capacity exceeded");
704	>	else {
705	>	int oldMask, b;
706	>	ForkJoinTask<?>[] oldA = a;
707	>	a = array = new ForkJoinTask<?>[len];
708	>	if ((oldMask = oldLen - 1) >= 0 && s - (b = base) > 0) {
709	>	int mask = len - 1;
710	>	do {
711	>	ForkJoinTask<?> x;
712	>	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
713	>	int j    = ((b &    mask) << ASHIFT) + ABASE;
714	>	x = (ForkJoinTask<?>)
715	>	U.getObjectVolatile(oldA, oldj);
716	>	if (x != null &&
717	>	U.compareAndSwapObject(oldA, oldj, x, null))
718	>	U.putObjectVolatile(a, j, x);
719	>	} while (++b != s);
720	>	}
721	>	}
722	>	U.putOrderedObject
723	>	(a, (((len - 1) & s) << ASHIFT) + ABASE, task);
724	>	top = s + 1;
725	>	} finally {
726	>	if (!owned)
727	>	qlock = 0;
728	>	}
729	>	if ((p = pool) != null)
730	>	p.signalWork(this, 1);
731	>	return true;
732	>	}
733	>
734	>	/**
735	>	* Takes next task, if one exists, in LIFO order.  Call only
736	>	* by owner in unshared queues.
737	>	*/
738	>	final ForkJoinTask<?> pop() {
739	>	ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
740	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
741	>	for (int s; (s = top - 1) - base >= 0;) {
742	>	long j = ((m & s) << ASHIFT) + ABASE;
743	>	if ((t = (ForkJoinTask<?>)U.getObject(a, j)) == null)
744	>	break;
745	>	if (U.compareAndSwapObject(a, j, t, null)) {
746	>	top = s;
747	>	return t;
748	>	}
749	>	}
750	>	}
751	>	return null;
752	>	}
753	>
754	>	/**
755	>	* Takes a task in FIFO order if b is base of queue and a task
756	>	* can be claimed without contention. Specialized versions
757	>	* appear in ForkJoinPool methods scan and tryHelpStealer.
758	>	*/
759	>	final ForkJoinTask<?> pollAt(int b) {
760	>	ForkJoinTask<?> t; ForkJoinTask<?>[] a;
761	>	if ((a = array) != null) {
762	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
763	>	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
764	>	base == b &&
765	>	U.compareAndSwapObject(a, j, t, null)) {
766	>	base = b + 1;
767	>	return t;
768	>	}
769	>	}
770	>	return null;
771	>	}
772	>
773	>	/**
774	>	* Takes next task, if one exists, in FIFO order.
775	>	*/
776	>	final ForkJoinTask<?> poll() {
777	>	ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t;
778	>	while ((b = base) - top < 0 && (a = array) != null) {
779	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
780	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
781	>	if (t != null) {
782	>	if (base == b &&
783	>	U.compareAndSwapObject(a, j, t, null)) {
784	>	base = b + 1;
785	>	return t;
786	>	}
787	>	}
788	>	else if (base == b) {
789	>	if (b + 1 == top)
790	>	break;
791	>	Thread.yield(); // wait for lagging update (very rare)
792	>	}
793	>	}
794	>	return null;
795	>	}
796	>
797	>	/**
798	>	* Takes next task, if one exists, in order specified by mode.
799	>	*/
800	>	final ForkJoinTask<?> nextLocalTask() {
801	>	return mode == 0 ? pop() : poll();
802	>	}
803	>
804	>	/**
805	>	* Returns next task, if one exists, in order specified by mode.
806	>	*/
807	>	final ForkJoinTask<?> peek() {
808	>	ForkJoinTask<?>[] a = array; int m;
809	>	if (a == null || (m = a.length - 1) < 0)
810		return null;
811	+	int i = mode == 0 ? top - 1 : base;
812	+	int j = ((i & m) << ASHIFT) + ABASE;
813	+	return (ForkJoinTask<?>)U.getObjectVolatile(a, j);
814	+	}
815	+
816	+	/**
817	+	* Pops the given task only if it is at the current top.
818	+	* (A shared version is available only via FJP.tryExternalUnpush)
819	+	*/
820	+	final boolean tryUnpush(ForkJoinTask<?> t) {
821	+	ForkJoinTask<?>[] a; int s;
822	+	if ((a = array) != null && (s = top) != base &&
823	+	U.compareAndSwapObject
824	+	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
825	+	top = s;
826	+	return true;
827	+	}
828	+	return false;
829	+	}
830	+
831	+	/**
832	+	* Removes and cancels all known tasks, ignoring any exceptions.
833	+	*/
834	+	final void cancelAll() {
835	+	ForkJoinTask.cancelIgnoringExceptions(currentJoin);
836	+	ForkJoinTask.cancelIgnoringExceptions(currentSteal);
837	+	for (ForkJoinTask<?> t; (t = poll()) != null; )
838	+	ForkJoinTask.cancelIgnoringExceptions(t);
839	+	}
840	+
841	+	/**
842	+	* Computes next value for random probes.  Scans don't require
843	+	* a very high quality generator, but also not a crummy one.
844	+	* Marsaglia xor-shift is cheap and works well enough.  Note:
845	+	* This is manually inlined in its usages in ForkJoinPool to
846	+	* avoid writes inside busy scan loops.
847	+	*/
848	+	final int nextSeed() {
849	+	int r = seed;
850	+	r ^= r << 13;
851	+	r ^= r >>> 17;
852	+	return seed = r ^= r << 5;
853	+	}
854	+
855	+	/**
856	+	* Provides a more accurate estimate of size than (top - base)
857	+	* by ordering reads and checking whether a near-empty queue
858	+	* has at least one unclaimed task.
859	+	*/
860	+	final int queueSize() {
861	+	ForkJoinTask<?>[] a; int k, s, n;
862	+	return ((n = base - (s = top)) < 0 &&
863	+	(n != -1 ||
864	+	((a = array) != null && (k = a.length) > 0 &&
865	+	U.getObject
866	+	(a, (long)((((k - 1) & (s - 1)) << ASHIFT) + ABASE)) != null))) ?
867	+	-n : 0;
868	+	}
869	+
870	+	// Specialized execution methods
871	+
872	+	/**
873	+	* Pops and runs tasks until empty.
874	+	*/
875	+	private void popAndExecAll() {
876	+	// A bit faster than repeated pop calls
877	+	ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t;
878	+	while ((a = array) != null && (m = a.length - 1) >= 0 &&
879	+	(s = top - 1) - base >= 0 &&
880	+	(t = ((ForkJoinTask<?>)
881	+	U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
882	+	!= null) {
883	+	if (U.compareAndSwapObject(a, j, t, null)) {
884	+	top = s;
885	+	t.doExec();
886	+	}
887		}
888		}
889	+
890	+	/**
891	+	* Polls and runs tasks until empty.
892	+	*/
893	+	private void pollAndExecAll() {
894	+	for (ForkJoinTask<?> t; (t = poll()) != null;)
895	+	t.doExec();
896	+	}
897	+
898	+	/**
899	+	* If present, removes from queue and executes the given task,
900	+	* or any other cancelled task. Returns (true) on any CAS
901	+	* or consistency check failure so caller can retry.
902	+	*
903	+	* @return false if no progress can be made, else true;
904	+	*/
905	+	final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
906	+	boolean stat = true, removed = false, empty = true;
907	+	ForkJoinTask<?>[] a; int m, s, b, n;
908	+	if ((a = array) != null && (m = a.length - 1) >= 0 &&
909	+	(n = (s = top) - (b = base)) > 0) {
910	+	for (ForkJoinTask<?> t;;) {           // traverse from s to b
911	+	int j = ((--s & m) << ASHIFT) + ABASE;
912	+	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
913	+	if (t == null)                    // inconsistent length
914	+	break;
915	+	else if (t == task) {
916	+	if (s + 1 == top) {           // pop
917	+	if (!U.compareAndSwapObject(a, j, task, null))
918	+	break;
919	+	top = s;
920	+	removed = true;
921	+	}
922	+	else if (base == b)           // replace with proxy
923	+	removed = U.compareAndSwapObject(a, j, task,
924	+	new EmptyTask());
925	+	break;
926	+	}
927	+	else if (t.status >= 0)
928	+	empty = false;
929	+	else if (s + 1 == top) {          // pop and throw away
930	+	if (U.compareAndSwapObject(a, j, t, null))
931	+	top = s;
932	+	break;
933	+	}
934	+	if (--n == 0) {
935	+	if (!empty && base == b)
936	+	stat = false;
937	+	break;
938	+	}
939	+	}
940	+	}
941	+	if (removed)
942	+	task.doExec();
943	+	return stat;
944	+	}
945	+
946	+	/**
947	+	* Polls for and executes the given task or any other task in
948	+	* its CountedCompleter computation
949	+	*/
950	+	final boolean pollAndExecCC(ForkJoinTask<?> root) {
951	+	ForkJoinTask<?>[] a; int b; Object o;
952	+	outer: while ((b = base) - top < 0 && (a = array) != null) {
953	+	long j = (((a.length - 1) & b) << ASHIFT) + ABASE;
954	+	if ((o = U.getObject(a, j)) == null ||
955	+	!(o instanceof CountedCompleter))
956	+	break;
957	+	for (CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;;) {
958	+	if (r == root) {
959	+	if (base == b &&
960	+	U.compareAndSwapObject(a, j, t, null)) {
961	+	base = b + 1;
962	+	t.doExec();
963	+	return true;
964	+	}
965	+	else
966	+	break; // restart
967	+	}
968	+	if ((r = r.completer) == null)
969	+	break outer; // not part of root computation
970	+	}
971	+	}
972	+	return false;
973	+	}
974	+
975	+	/**
976	+	* Executes a top-level task and any local tasks remaining
977	+	* after execution.
978	+	*/
979	+	final void runTask(ForkJoinTask<?> t) {
980	+	if (t != null) {
981	+	(currentSteal = t).doExec();
982	+	currentSteal = null;
983	+	if (++nsteals < 0) {     // spill on overflow
984	+	ForkJoinPool p;
985	+	if ((p = pool) != null)
986	+	p.collectStealCount(this);
987	+	}
988	+	if (top != base) {       // process remaining local tasks
989	+	if (mode == 0)
990	+	popAndExecAll();
991	+	else
992	+	pollAndExecAll();
993	+	}
994	+	}
995	+	}
996	+
997	+	/**
998	+	* Executes a non-top-level (stolen) task.
999	+	*/
1000	+	final void runSubtask(ForkJoinTask<?> t) {
1001	+	if (t != null) {
1002	+	ForkJoinTask<?> ps = currentSteal;
1003	+	(currentSteal = t).doExec();
1004	+	currentSteal = ps;
1005	+	}
1006	+	}
1007	+
1008	+	/**
1009	+	* Returns true if owned and not known to be blocked.
1010	+	*/
1011	+	final boolean isApparentlyUnblocked() {
1012	+	Thread wt; Thread.State s;
1013	+	return (eventCount >= 0 &&
1014	+	(wt = owner) != null &&
1015	+	(s = wt.getState()) != Thread.State.BLOCKED &&
1016	+	s != Thread.State.WAITING &&
1017	+	s != Thread.State.TIMED_WAITING);
1018	+	}
1019	+
1020	+	/**
1021	+	* If this owned and is not already interrupted, try to
1022	+	* interrupt and/or unpark, ignoring exceptions.
1023	+	*/
1024	+	final void interruptOwner() {
1025	+	Thread wt, p;
1026	+	if ((wt = owner) != null && !wt.isInterrupted()) {
1027	+	try {
1028	+	wt.interrupt();
1029	+	} catch (SecurityException ignore) {
1030	+	}
1031	+	}
1032	+	if ((p = parker) != null)
1033	+	U.unpark(p);
1034	+	}
1035	+
1036	+	// Unsafe mechanics
1037	+	private static final sun.misc.Unsafe U;
1038	+	private static final long QLOCK;
1039	+	private static final int ABASE;
1040	+	private static final int ASHIFT;
1041	+	static {
1042	+	int s;
1043	+	try {
1044	+	U = getUnsafe();
1045	+	Class<?> k = WorkQueue.class;
1046	+	Class<?> ak = ForkJoinTask[].class;
1047	+	QLOCK = U.objectFieldOffset
1048	+	(k.getDeclaredField("qlock"));
1049	+	ABASE = U.arrayBaseOffset(ak);
1050	+	s = U.arrayIndexScale(ak);
1051	+	} catch (Exception e) {
1052	+	throw new Error(e);
1053	+	}
1054	+	if ((s & (s-1)) != 0)
1055	+	throw new Error("data type scale not a power of two");
1056	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
1057	+	}
1058		}
1059
1060		/**
1061	+	* Per-thread records for threads that submit to pools. Currently
1062	+	* holds only pseudo-random seed / index that is used to choose
1063	+	* submission queues in method externalPush. In the future, this may
1064	+	* also incorporate a means to implement different task rejection
1065	+	* and resubmission policies.
1066	+	*
1067	+	* Seeds for submitters and workers/workQueues work in basically
1068	+	* the same way but are initialized and updated using slightly
1069	+	* different mechanics. Both are initialized using the same
1070	+	* approach as in class ThreadLocal, where successive values are
1071	+	* unlikely to collide with previous values. Seeds are then
1072	+	* randomly modified upon collisions using xorshifts, which
1073	+	* requires a non-zero seed.
1074	+	*/
1075	+	static final class Submitter {
1076	+	int seed;
1077	+	Submitter(int s) { seed = s; }
1078	+	}
1079	+
1080	+	/** Property prefix for constructing common pool */
1081	+	private static final String propPrefix =
1082	+	"java.util.concurrent.ForkJoinPool.common.";
1083	+
1084	+	// static fields (initialized in static initializer below)
1085	+
1086	+	/**
1087		* Creates a new ForkJoinWorkerThread. This factory is used unless
1088		* overridden in ForkJoinPool constructors.
1089		*/
1090		public static final ForkJoinWorkerThreadFactory
1091	<	defaultForkJoinWorkerThreadFactory =
1092	<	new DefaultForkJoinWorkerThreadFactory();
1091	>	defaultForkJoinWorkerThreadFactory;
1092	>
1093	>	/**
1094	>	* Common (static) pool. Non-null for public use unless a static
1095	>	* construction exception, but internal usages null-check on use
1096	>	* to paranoically avoid potential initialization circularities
1097	>	* as well as to simplify generated code.
1098	>	*/
1099	>	static final ForkJoinPool commonPool;
1100
1101		/**
1102		* Permission required for callers of methods that may start or
1103		* kill threads.
1104		*/
1105	<	private static final RuntimePermission modifyThreadPermission =
120	<	new RuntimePermission("modifyThread");
1105	>	private static final RuntimePermission modifyThreadPermission;
1106
1107		/**
1108	<	* If there is a security manager, makes sure caller has
1109	<	* permission to modify threads.
1108	>	* Per-thread submission bookkeeping. Shared across all pools
1109	>	* to reduce ThreadLocal pollution and because random motion
1110	>	* to avoid contention in one pool is likely to hold for others.
1111	>	* Lazily initialized on first submission (but null-checked
1112	>	* in other contexts to avoid unnecessary initialization).
1113		*/
1114	<	private static void checkPermission() {
127	<	SecurityManager security = System.getSecurityManager();
128	<	if (security != null)
129	<	security.checkPermission(modifyThreadPermission);
130	<	}
1114	>	static final ThreadLocal<Submitter> submitters;
1115
1116		/**
1117	<	* Generator for assigning sequence numbers as pool names.
1117	>	* Common pool parallelism. Must equal commonPool.parallelism.
1118		*/
1119	<	private static final AtomicInteger poolNumberGenerator =
136	<	new AtomicInteger();
1119	>	static final int commonPoolParallelism;
1120
1121		/**
1122	<	* Array holding all worker threads in the pool. Initialized upon
140	<	* first use. Array size must be a power of two.  Updates and
141	<	* replacements are protected by workerLock, but it is always kept
142	<	* in a consistent enough state to be randomly accessed without
143	<	* locking by workers performing work-stealing.
1122	>	* Sequence number for creating workerNamePrefix.
1123		*/
1124	<	volatile ForkJoinWorkerThread[] workers;
1124	>	private static int poolNumberSequence;
1125
1126		/**
1127	<	* Lock protecting access to workers.
1127	>	* Return the next sequence number. We don't expect this to
1128	>	* ever contend so use simple builtin sync.
1129		*/
1130	<	private final ReentrantLock workerLock;
1130	>	private static final synchronized int nextPoolId() {
1131	>	return ++poolNumberSequence;
1132	>	}
1133	>
1134	>	// static constants
1135
1136		/**
1137	<	* Condition for awaitTermination.
1137	>	* Initial timeout value (in nanoseconds) for the thread
1138	>	* triggering quiescence to park waiting for new work. On timeout,
1139	>	* the thread will instead try to shrink the number of
1140	>	* workers. The value should be large enough to avoid overly
1141	>	* aggressive shrinkage during most transient stalls (long GCs
1142	>	* etc).
1143		*/
1144	<	private final Condition termination;
1144	>	private static final long IDLE_TIMEOUT      = 2000L * 1000L * 1000L; // 2sec
1145
1146		/**
1147	<	* The uncaught exception handler used when any worker
159	<	* abruptly terminates
1147	>	* Timeout value when there are more threads than parallelism level
1148		*/
1149	<	private Thread.UncaughtExceptionHandler ueh;
1149	>	private static final long FAST_IDLE_TIMEOUT =  200L * 1000L * 1000L;
1150
1151		/**
1152	<	* Creation factory for worker threads.
1152	>	* The maximum stolen->joining link depth allowed in method
1153	>	* tryHelpStealer.  Must be a power of two.  Depths for legitimate
1154	>	* chains are unbounded, but we use a fixed constant to avoid
1155	>	* (otherwise unchecked) cycles and to bound staleness of
1156	>	* traversal parameters at the expense of sometimes blocking when
1157	>	* we could be helping.
1158		*/
1159	<	private final ForkJoinWorkerThreadFactory factory;
1159	>	private static final int MAX_HELP = 64;
1160
1161		/**
1162	<	* Head of stack of threads that were created to maintain
1163	<	* parallelism when other threads blocked, but have since
171	<	* suspended when the parallelism level rose.
1162	>	* Increment for seed generators. See class ThreadLocal for
1163	>	* explanation.
1164		*/
1165	<	private volatile WaitQueueNode spareStack;
1165	>	private static final int SEED_INCREMENT = 0x61c88647;
1166
1167		/**
1168	<	* Sum of per-thread steal counts, updated only when threads are
1169	<	* idle or terminating.
1168	>	* Bits and masks for control variables
1169	>	*
1170	>	* Field ctl is a long packed with:
1171	>	* AC: Number of active running workers minus target parallelism (16 bits)
1172	>	* TC: Number of total workers minus target parallelism (16 bits)
1173	>	* ST: true if pool is terminating (1 bit)
1174	>	* EC: the wait count of top waiting thread (15 bits)
1175	>	* ID: poolIndex of top of Treiber stack of waiters (16 bits)
1176	>	*
1177	>	* When convenient, we can extract the upper 32 bits of counts and
1178	>	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
1179	>	* (int)ctl.  The ec field is never accessed alone, but always
1180	>	* together with id and st. The offsets of counts by the target
1181	>	* parallelism and the positionings of fields makes it possible to
1182	>	* perform the most common checks via sign tests of fields: When
1183	>	* ac is negative, there are not enough active workers, when tc is
1184	>	* negative, there are not enough total workers, and when e is
1185	>	* negative, the pool is terminating.  To deal with these possibly
1186	>	* negative fields, we use casts in and out of "short" and/or
1187	>	* signed shifts to maintain signedness.
1188	>	*
1189	>	* When a thread is queued (inactivated), its eventCount field is
1190	>	* set negative, which is the only way to tell if a worker is
1191	>	* prevented from executing tasks, even though it must continue to
1192	>	* scan for them to avoid queuing races. Note however that
1193	>	* eventCount updates lag releases so usage requires care.
1194	>	*
1195	>	* Field plock is an int packed with:
1196	>	* SHUTDOWN: true if shutdown is enabled (1 bit)
1197	>	* SEQ:  a sequence lock, with PL_LOCK bit set if locked (30 bits)
1198	>	* SIGNAL: set when threads may be waiting on the lock (1 bit)
1199	>	*
1200	>	* The sequence number enables simple consistency checks:
1201	>	* Staleness of read-only operations on the workQueues array can
1202	>	* be checked by comparing plock before vs after the reads.
1203		*/
179	–	private final AtomicLong stealCount;
1204
1205	<	/**
1206	<	* Queue for external submissions.
1205	>	// bit positions/shifts for fields
1206	>	private static final int  AC_SHIFT   = 48;
1207	>	private static final int  TC_SHIFT   = 32;
1208	>	private static final int  ST_SHIFT   = 31;
1209	>	private static final int  EC_SHIFT   = 16;
1210	>
1211	>	// bounds
1212	>	private static final int  SMASK      = 0xffff;  // short bits
1213	>	private static final int  MAX_CAP    = 0x7fff;  // max #workers - 1
1214	>	private static final int  EVENMASK   = 0xfffe;  // even short bits
1215	>	private static final int  SQMASK     = 0x007e;  // max 64 (even) slots
1216	>	private static final int  SHORT_SIGN = 1 << 15;
1217	>	private static final int  INT_SIGN   = 1 << 31;
1218	>
1219	>	// masks
1220	>	private static final long STOP_BIT   = 0x0001L << ST_SHIFT;
1221	>	private static final long AC_MASK    = ((long)SMASK) << AC_SHIFT;
1222	>	private static final long TC_MASK    = ((long)SMASK) << TC_SHIFT;
1223	>
1224	>	// units for incrementing and decrementing
1225	>	private static final long TC_UNIT    = 1L << TC_SHIFT;
1226	>	private static final long AC_UNIT    = 1L << AC_SHIFT;
1227	>
1228	>	// masks and units for dealing with u = (int)(ctl >>> 32)
1229	>	private static final int  UAC_SHIFT  = AC_SHIFT - 32;
1230	>	private static final int  UTC_SHIFT  = TC_SHIFT - 32;
1231	>	private static final int  UAC_MASK   = SMASK << UAC_SHIFT;
1232	>	private static final int  UTC_MASK   = SMASK << UTC_SHIFT;
1233	>	private static final int  UAC_UNIT   = 1 << UAC_SHIFT;
1234	>	private static final int  UTC_UNIT   = 1 << UTC_SHIFT;
1235	>
1236	>	// masks and units for dealing with e = (int)ctl
1237	>	private static final int E_MASK      = 0x7fffffff; // no STOP_BIT
1238	>	private static final int E_SEQ       = 1 << EC_SHIFT;
1239	>
1240	>	// plock bits
1241	>	private static final int SHUTDOWN    = 1 << 31;
1242	>	private static final int PL_LOCK     = 2;
1243	>	private static final int PL_SIGNAL   = 1;
1244	>	private static final int PL_SPINS    = 1 << 8;
1245	>
1246	>	// access mode for WorkQueue
1247	>	static final int LIFO_QUEUE          =  0;
1248	>	static final int FIFO_QUEUE          =  1;
1249	>	static final int SHARED_QUEUE        = -1;
1250	>
1251	>	// Instance fields
1252	>
1253	>	/*
1254	>	* Field layout order in this class tends to matter more than one
1255	>	* would like. Runtime layout order is only loosely related to
1256	>	* declaration order and may differ across JVMs, but the following
1257	>	* empirically works OK on current JVMs.
1258	>	*/
1259	>	volatile long stealCount;                  // collects worker counts
1260	>	volatile long ctl;                         // main pool control
1261	>	final int parallelism;                     // parallelism level
1262	>	final int localMode;                       // per-worker scheduling mode
1263	>	volatile int indexSeed;                    // worker/submitter index seed
1264	>	volatile int plock;                        // shutdown status and seqLock
1265	>	WorkQueue[] workQueues;                    // main registry
1266	>	final ForkJoinWorkerThreadFactory factory; // factory for new workers
1267	>	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1268	>	final String workerNamePrefix;             // to create worker name string
1269	>
1270	>	/*
1271	>	* Acquires the plock lock to protect worker array and related
1272	>	* updates. This method is called only if an initial CAS on plock
1273	>	* fails. This acts as a spinLock for normal cases, but falls back
1274	>	* to builtin monitor to block when (rarely) needed. This would be
1275	>	* a terrible idea for a highly contended lock, but works fine as
1276	>	* a more conservative alternative to a pure spinlock.  See
1277	>	* internal ConcurrentHashMap documentation for further
1278	>	* explanation of nearly the same construction.
1279		*/
1280	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
1280	>	private int acquirePlock() {
1281	>	int spins = PL_SPINS, r = 0, ps, nps;
1282	>	for (;;) {
1283	>	if (((ps = plock) & PL_LOCK) == 0 &&
1284	>	U.compareAndSwapInt(this, PLOCK, ps, nps = ps + PL_LOCK))
1285	>	return nps;
1286	>	else if (r == 0)
1287	>	r = ThreadLocalRandom.current().nextInt(); // randomize spins
1288	>	else if (spins >= 0) {
1289	>	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1290	>	if (r >= 0)
1291	>	--spins;
1292	>	}
1293	>	else if (U.compareAndSwapInt(this, PLOCK, ps, ps | PL_SIGNAL)) {
1294	>	synchronized (this) {
1295	>	if ((plock & PL_SIGNAL) != 0) {
1296	>	try {
1297	>	wait();
1298	>	} catch (InterruptedException ie) {
1299	>	try {
1300	>	Thread.currentThread().interrupt();
1301	>	} catch (SecurityException ignore) {
1302	>	}
1303	>	}
1304	>	}
1305	>	else
1306	>	notifyAll();
1307	>	}
1308	>	}
1309	>	}
1310	>	}
1311
1312		/**
1313	<	* Head of Treiber stack for barrier sync. See below for explanation
1313	>	* Unlocks and signals any thread waiting for plock. Called only
1314	>	* when CAS of seq value for unlock fails.
1315		*/
1316	<	private volatile WaitQueueNode syncStack;
1316	>	private void releasePlock(int ps) {
1317	>	plock = ps;
1318	>	synchronized (this) { notifyAll(); }
1319	>	}
1320	>
1321	>	//  Registering and deregistering workers
1322	>
1323	>	/**
1324	>	* Callback from ForkJoinWorkerThread constructor to establish its
1325	>	* poolIndex and record its WorkQueue. To avoid scanning bias due
1326	>	* to packing entries in front of the workQueues array, we treat
1327	>	* the array as a simple power-of-two hash table using per-thread
1328	>	* seed as hash, expanding as needed.
1329	>	*
1330	>	* @param w the worker's queue
1331	>	*/
1332	>	final void registerWorker(WorkQueue w) {
1333	>	int s, ps; // generate a rarely colliding candidate index seed
1334	>	do {} while (!U.compareAndSwapInt(this, INDEXSEED,
1335	>	s = indexSeed, s += SEED_INCREMENT) ||
1336	>	s == 0); // skip 0
1337	>	if (((ps = plock) & PL_LOCK) != 0 ||
1338	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1339	>	ps = acquirePlock();
1340	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1341	>	try {
1342	>	WorkQueue[] ws;
1343	>	if (w != null && (ws = workQueues) != null) {
1344	>	w.seed = s;
1345	>	int n = ws.length, m = n - 1;
1346	>	int r = (s << 1) | 1;               // use odd-numbered indices
1347	>	if (ws[r &= m] != null) {           // collision
1348	>	int probes = 0;                 // step by approx half size
1349	>	int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2;
1350	>	while (ws[r = (r + step) & m] != null) {
1351	>	if (++probes >= n) {
1352	>	workQueues = ws = Arrays.copyOf(ws, n <<= 1);
1353	>	m = n - 1;
1354	>	probes = 0;
1355	>	}
1356	>	}
1357	>	}
1358	>	w.eventCount = w.poolIndex = r;     // establish before recording
1359	>	ws[r] = w;
1360	>	}
1361	>	} finally {
1362	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1363	>	releasePlock(nps);
1364	>	}
1365	>	}
1366
1367		/**
1368	<	* The count for event barrier
1369	<	*/
1370	<	private volatile long eventCount;
1368	>	* Final callback from terminating worker, as well as upon failure
1369	>	* to construct or start a worker.  Removes record of worker from
1370	>	* array, and adjusts counts. If pool is shutting down, tries to
1371	>	* complete termination.
1372	>	*
1373	>	* @param wt the worker thread or null if construction failed
1374	>	* @param ex the exception causing failure, or null if none
1375	>	*/
1376	>	final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1377	>	WorkQueue w = null;
1378	>	if (wt != null && (w = wt.workQueue) != null) {
1379	>	int ps;
1380	>	collectStealCount(w);
1381	>	w.qlock = -1;                // ensure set
1382	>	if (((ps = plock) & PL_LOCK) != 0 ||
1383	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1384	>	ps = acquirePlock();
1385	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1386	>	try {
1387	>	int idx = w.poolIndex;
1388	>	WorkQueue[] ws = workQueues;
1389	>	if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1390	>	ws[idx] = null;
1391	>	} finally {
1392	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1393	>	releasePlock(nps);
1394	>	}
1395	>	}
1396	>
1397	>	long c;                             // adjust ctl counts
1398	>	do {} while (!U.compareAndSwapLong
1399	>	(this, CTL, c = ctl, (((c - AC_UNIT) & AC_MASK) |
1400	>	((c - TC_UNIT) & TC_MASK) |
1401	>	(c & ~(AC_MASK|TC_MASK)))));
1402	>
1403	>	if (!tryTerminate(false, false) && w != null) {
1404	>	w.cancelAll();                  // cancel remaining tasks
1405	>	if (w.array != null)            // suppress signal if never ran
1406	>	signalWork(null, 1);        // wake up or create replacement
1407	>	if (ex == null)                 // help clean refs on way out
1408	>	ForkJoinTask.helpExpungeStaleExceptions();
1409	>	}
1410	>
1411	>	if (ex != null)                     // rethrow
1412	>	ForkJoinTask.rethrow(ex);
1413	>	}
1414
1415		/**
1416	<	* Pool number, just for assigning useful names to worker threads
1416	>	* Collect worker steal count into total. Called on termination
1417	>	* and upon int overflow of local count. (There is a possible race
1418	>	* in the latter case vs any caller of getStealCount, which can
1419	>	* make its results less accurate than usual.)
1420		*/
1421	<	private final int poolNumber;
1421	>	final void collectStealCount(WorkQueue w) {
1422	>	if (w != null) {
1423	>	long sc;
1424	>	int ns = w.nsteals;
1425	>	w.nsteals = 0; // handle overflow
1426	>	long steals = (ns >= 0) ? ns : 1L + (long)(Integer.MAX_VALUE);
1427	>	do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
1428	>	sc = stealCount, sc + steals));
1429	>	}
1430	>	}
1431	>
1432	>	// Submissions
1433	>
1434	>	/**
1435	>	* Unless shutting down, adds the given task to a submission queue
1436	>	* at submitter's current queue index (modulo submission
1437	>	* range). Only the most common path is directly handled in this
1438	>	* method. All others are relayed to fullExternalPush.
1439	>	*
1440	>	* @param task the task. Caller must ensure non-null.
1441	>	*/
1442	>	final void externalPush(ForkJoinTask<?> task) {
1443	>	WorkQueue[] ws; WorkQueue q; Submitter z; int m; ForkJoinTask<?>[] a;
1444	>	if ((z = submitters.get()) != null && plock > 0 &&
1445	>	(ws = workQueues) != null && (m = (ws.length - 1)) >= 0 &&
1446	>	(q = ws[m & z.seed & SQMASK]) != null &&
1447	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock
1448	>	int s = q.top, n;
1449	>	if ((a = q.array) != null && a.length > (n = s + 1 - q.base)) {
1450	>	U.putObject(a, (long)(((a.length - 1) & s) << ASHIFT) + ABASE,
1451	>	task);
1452	>	q.top = s + 1;                     // push on to deque
1453	>	q.qlock = 0;
1454	>	if (n <= 1)
1455	>	signalWork(q, 1);
1456	>	return;
1457	>	}
1458	>	q.qlock = 0;
1459	>	}
1460	>	fullExternalPush(task);
1461	>	}
1462	>
1463	>	/**
1464	>	* Full version of externalPush. This method is called, among
1465	>	* other times, upon the first submission of the first task to the
1466	>	* pool, so must perform secondary initialization: creating
1467	>	* workQueue array and setting plock to a valid value. It also
1468	>	* detects first submission by an external thread by looking up
1469	>	* its ThreadLocal, and creates a new shared queue if the one at
1470	>	* index if empty or contended. The lock bodies must be
1471	>	* exception-free (so no try/finally) so we optimistically
1472	>	* allocate new queues/arrays outside the locks and throw them
1473	>	* away if (very rarely) not needed. Note that the plock seq value
1474	>	* can eventually wrap around zero, but if so harmlessly fails to
1475	>	* reinitialize.
1476	>	*/
1477	>	private void fullExternalPush(ForkJoinTask<?> task) {
1478	>	for (Submitter z = null;;) {
1479	>	WorkQueue[] ws; WorkQueue q; int ps, m, r, s;
1480	>	if ((ps = plock) < 0)
1481	>	throw new RejectedExecutionException();
1482	>	else if ((ws = workQueues) == null || (m = ws.length - 1) < 0) {
1483	>	int n = parallelism - 1; n |= n >>> 1; n |= n >>> 2;
1484	>	n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
1485	>	WorkQueue[] nws = new WorkQueue[(n + 1) << 1]; // power of two
1486	>	if ((ps & PL_LOCK) != 0 ||
1487	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1488	>	ps = acquirePlock();
1489	>	if ((ws = workQueues) == null)
1490	>	workQueues = nws;
1491	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1492	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1493	>	releasePlock(nps);
1494	>	}
1495	>	else if (z == null && (z = submitters.get()) == null) {
1496	>	if (U.compareAndSwapInt(this, INDEXSEED,
1497	>	s = indexSeed, s += SEED_INCREMENT) &&
1498	>	s != 0) // skip 0
1499	>	submitters.set(z = new Submitter(s));
1500	>	}
1501	>	else {
1502	>	int k = (r = z.seed) & m & SQMASK;
1503	>	if ((q = ws[k]) == null && (ps & PL_LOCK) == 0) {
1504	>	(q = new WorkQueue(this, null, SHARED_QUEUE)).poolIndex = k;
1505	>	if (((ps = plock) & PL_LOCK) != 0 ||
1506	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1507	>	ps = acquirePlock();
1508	>	WorkQueue w = null;
1509	>	if ((ws = workQueues) != null && k < ws.length &&
1510	>	(w = ws[k]) == null)
1511	>	ws[k] = q;
1512	>	else
1513	>	q = w;
1514	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1515	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1516	>	releasePlock(nps);
1517	>	}
1518	>	if (q != null && q.qlock == 0 && q.fullPush(task, false))
1519	>	return;
1520	>	r ^= r << 13;                // same xorshift as WorkQueues
1521	>	r ^= r >>> 17;
1522	>	z.seed = r ^= r << 5;        // move to a different index
1523	>	}
1524	>	}
1525	>	}
1526	>
1527	>	// Maintaining ctl counts
1528
1529		/**
1530	<	* The maximum allowed pool size
1530	>	* Increments active count; mainly called upon return from blocking.
1531		*/
1532	<	private volatile int maxPoolSize;
1532	>	final void incrementActiveCount() {
1533	>	long c;
1534	>	do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
1535	>	}
1536
1537		/**
1538	<	* The desired parallelism level, updated only under workerLock.
1539	<	*/
1540	<	private volatile int parallelism;
1538	>	* Tries to create (at most one) or activate (possibly several)
1539	>	* workers if too few are active. On contention failure, continues
1540	>	* until at least one worker is signalled or the given queue is
1541	>	* empty or all workers are active.
1542	>	*
1543	>	* @param q if non-null, the queue holding tasks to be signalled
1544	>	* @param signals the target number of signals.
1545	>	*/
1546	>	final void signalWork(WorkQueue q, int signals) {
1547	>	long c; int e, u, i; WorkQueue[] ws; WorkQueue w; Thread p;
1548	>	while ((u = (int)((c = ctl) >>> 32)) < 0) {
1549	>	if ((e = (int)c) > 0) {
1550	>	if ((ws = workQueues) != null && ws.length > (i = e & SMASK) &&
1551	>	(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
1552	>	long nc = (((long)(w.nextWait & E_MASK)) |
1553	>	((long)(u + UAC_UNIT) << 32));
1554	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1555	>	w.eventCount = (e + E_SEQ) & E_MASK;
1556	>	if ((p = w.parker) != null)
1557	>	U.unpark(p);
1558	>	if (--signals <= 0)
1559	>	break;
1560	>	}
1561	>	else
1562	>	signals = 1;
1563	>	if ((q != null && q.queueSize() == 0))
1564	>	break;
1565	>	}
1566	>	else
1567	>	break;
1568	>	}
1569	>	else if (e == 0 && (u & SHORT_SIGN) != 0) {
1570	>	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) |
1571	>	((u + UAC_UNIT) & UAC_MASK)) << 32;
1572	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1573	>	ForkJoinWorkerThread wt = null;
1574	>	Throwable ex = null;
1575	>	boolean started = false;
1576	>	try {
1577	>	ForkJoinWorkerThreadFactory fac;
1578	>	if ((fac = factory) != null &&
1579	>	(wt = fac.newThread(this)) != null) {
1580	>	wt.start();
1581	>	started = true;
1582	>	}
1583	>	} catch (Throwable rex) {
1584	>	ex = rex;
1585	>	}
1586	>	if (!started)
1587	>	deregisterWorker(wt, ex); // adjust counts on failure
1588	>	break;
1589	>	}
1590	>	}
1591	>	else
1592	>	break;
1593	>	}
1594	>	}
1595	>
1596	>	// Scanning for tasks
1597
1598		/**
1599	<	* True if use local fifo, not default lifo, for local polling
1599	>	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1600		*/
1601	<	private volatile boolean locallyFifo;
1601	>	final void runWorker(WorkQueue w) {
1602	>	// initialize queue array in this thread
1603	>	w.array = new ForkJoinTask<?>[WorkQueue.INITIAL_QUEUE_CAPACITY];
1604	>	do { w.runTask(scan(w)); } while (w.qlock >= 0);
1605	>	}
1606
1607		/**
1608	<	* Holds number of total (i.e., created and not yet terminated)
1609	<	* and running (i.e., not blocked on joins or other managed sync)
1610	<	* threads, packed into one int to ensure consistent snapshot when
1611	<	* making decisions about creating and suspending spare
1612	<	* threads. Updated only by CAS.  Note: CASes in
1613	<	* updateRunningCount and preJoin running active count is in low
1614	<	* word, so need to be modified if this changes
1608	>	* Scans for and, if found, returns one task, else possibly
1609	>	* inactivates the worker. This method operates on single reads of
1610	>	* volatile state and is designed to be re-invoked continuously,
1611	>	* in part because it returns upon detecting inconsistencies,
1612	>	* contention, or state changes that indicate possible success on
1613	>	* re-invocation.
1614	>	*
1615	>	* The scan searches for tasks across a random permutation of
1616	>	* queues (starting at a random index and stepping by a random
1617	>	* relative prime, checking each at least once).  The scan
1618	>	* terminates upon either finding a non-empty queue, or completing
1619	>	* the sweep. If the worker is not inactivated, it takes and
1620	>	* returns a task from this queue. Otherwise, if not activated, it
1621	>	* signals workers (that may include itself) and returns so caller
1622	>	* can retry. Also returns for trtry if the worker array may have
1623	>	* changed during an empty scan.  On failure to find a task, we
1624	>	* take one of the following actions, after which the caller will
1625	>	* retry calling this method unless terminated.
1626	>	*
1627	>	* * If pool is terminating, terminate the worker.
1628	>	*
1629	>	* * If not already enqueued, try to inactivate and enqueue the
1630	>	* worker on wait queue. Or, if inactivating has caused the pool
1631	>	* to be quiescent, relay to idleAwaitWork to check for
1632	>	* termination and possibly shrink pool.
1633	>	*
1634	>	* * If already enqueued and none of the above apply, possibly
1635	>	* (with 1/2 probability) park awaiting signal, else lingering to
1636	>	* help scan and signal.
1637	>	*
1638	>	* @param w the worker (via its WorkQueue)
1639	>	* @return a task or null if none found
1640	>	*/
1641	>	private final ForkJoinTask<?> scan(WorkQueue w) {
1642	>	WorkQueue[] ws; WorkQueue q;           // first update random seed
1643	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1644	>	int ps = plock, m;                     // volatile read order matters
1645	>	if ((ws = workQueues) != null && (m = ws.length - 1) > 0) {
1646	>	int ec = w.eventCount;             // ec is negative if inactive
1647	>	int step = (r >>> 16) | 1;         // relatively prime
1648	>	for (int j = (m + 1) << 2;  ; --j, r += step) {
1649	>	ForkJoinTask<?> t; ForkJoinTask<?>[] a; int b, n;
1650	>	if ((q = ws[r & m]) != null && (b = q.base) - q.top < 0 &&
1651	>	(a = q.array) != null) {   // probably nonempty
1652	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1653	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1654	>	if (q.base == b && ec >= 0 && t != null &&
1655	>	U.compareAndSwapObject(a, i, t, null)) {
1656	>	if ((n = q.top - (q.base = b + 1)) > 0)
1657	>	signalWork(q, n);
1658	>	return t;              // taken
1659	>	}
1660	>	if (j < m || (ec < 0 && (ec = w.eventCount) < 0)) {
1661	>	if ((n = q.queueSize() - 1) > 0)
1662	>	signalWork(q, n);
1663	>	break;                 // let caller retry after signal
1664	>	}
1665	>	}
1666	>	else if (j < 0) {              // end of scan
1667	>	long c = ctl; int e;
1668	>	if (plock != ps)           // incomplete sweep
1669	>	break;
1670	>	if ((e = (int)c) < 0)      // pool is terminating
1671	>	w.qlock = -1;
1672	>	else if (ec >= 0) {        // try to enqueue/inactivate
1673	>	long nc = ((long)ec |
1674	>	((c - AC_UNIT) & (AC_MASK|TC_MASK)));
1675	>	w.nextWait = e;
1676	>	w.eventCount = ec | INT_SIGN; // mark as inactive
1677	>	if (ctl != c ||
1678	>	!U.compareAndSwapLong(this, CTL, c, nc))
1679	>	w.eventCount = ec; // unmark on CAS failure
1680	>	else if ((int)(c >> AC_SHIFT) == 1 - parallelism)
1681	>	idleAwaitWork(w, nc, c);  // quiescent
1682	>	}
1683	>	else if (w.seed >= 0 && w.eventCount < 0) {
1684	>	Thread wt = Thread.currentThread();
1685	>	Thread.interrupted();  // clear status
1686	>	U.putObject(wt, PARKBLOCKER, this);
1687	>	w.parker = wt;         // emulate LockSupport.park
1688	>	if (w.eventCount < 0)  // recheck
1689	>	U.park(false, 0L);
1690	>	w.parker = null;
1691	>	U.putObject(wt, PARKBLOCKER, null);
1692	>	}
1693	>	break;
1694	>	}
1695	>	}
1696	>	}
1697	>	return null;
1698	>	}
1699	>
1700	>	/**
1701	>	* If inactivating worker w has caused the pool to become
1702	>	* quiescent, checks for pool termination, and, so long as this is
1703	>	* not the only worker, waits for event for up to a given
1704	>	* duration.  On timeout, if ctl has not changed, terminates the
1705	>	* worker, which will in turn wake up another worker to possibly
1706	>	* repeat this process.
1707	>	*
1708	>	* @param w the calling worker
1709	>	* @param currentCtl the ctl value triggering possible quiescence
1710	>	* @param prevCtl the ctl value to restore if thread is terminated
1711	>	*/
1712	>	private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1713	>	if (w.eventCount < 0 &&
1714	>	(this == commonPool || !tryTerminate(false, false)) &&
1715	>	(int)prevCtl != 0) {
1716	>	int dc = -(short)(currentCtl >>> TC_SHIFT);
1717	>	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1718	>	long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop
1719	>	Thread wt = Thread.currentThread();
1720	>	while (ctl == currentCtl) {
1721	>	Thread.interrupted();  // timed variant of version in scan()
1722	>	U.putObject(wt, PARKBLOCKER, this);
1723	>	w.parker = wt;
1724	>	if (ctl == currentCtl)
1725	>	U.park(false, parkTime);
1726	>	w.parker = null;
1727	>	U.putObject(wt, PARKBLOCKER, null);
1728	>	if (ctl != currentCtl)
1729	>	break;
1730	>	if (deadline - System.nanoTime() <= 0L &&
1731	>	U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1732	>	w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
1733	>	w.qlock = -1;   // shrink
1734	>	break;
1735	>	}
1736	>	}
1737	>	}
1738	>	}
1739	>
1740	>	/**
1741	>	* Scans through queues looking for work while joining a task;
1742	>	* if any are present, signals.
1743	>	*
1744	>	* @param task to return early if done
1745	>	* @param origin an index to start scan
1746		*/
1747	<	private volatile int workerCounts;
1747	>	final int helpSignal(ForkJoinTask<?> task, int origin) {
1748	>	WorkQueue[] ws; WorkQueue q; int m, n, s;
1749	>	if (task != null && (ws = workQueues) != null &&
1750	>	(m = ws.length - 1) >= 0) {
1751	>	for (int i = 0; i <= m; ++i) {
1752	>	if ((s = task.status) < 0)
1753	>	return s;
1754	>	if ((q = ws[(i + origin) & m]) != null &&
1755	>	(n = q.queueSize()) > 0) {
1756	>	signalWork(q, n);
1757	>	if ((int)(ctl >> AC_SHIFT) >= 0)
1758	>	break;
1759	>	}
1760	>	}
1761	>	}
1762	>	return 0;
1763	>	}
1764
1765	<	private static int totalCountOf(int s)           { return s >>> 16;  }
1766	<	private static int runningCountOf(int s)         { return s & shortMask; }
1767	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
1765	>	/**
1766	>	* Tries to locate and execute tasks for a stealer of the given
1767	>	* task, or in turn one of its stealers, Traces currentSteal ->
1768	>	* currentJoin links looking for a thread working on a descendant
1769	>	* of the given task and with a non-empty queue to steal back and
1770	>	* execute tasks from. The first call to this method upon a
1771	>	* waiting join will often entail scanning/search, (which is OK
1772	>	* because the joiner has nothing better to do), but this method
1773	>	* leaves hints in workers to speed up subsequent calls. The
1774	>	* implementation is very branchy to cope with potential
1775	>	* inconsistencies or loops encountering chains that are stale,
1776	>	* unknown, or so long that they are likely cyclic.
1777	>	*
1778	>	* @param joiner the joining worker
1779	>	* @param task the task to join
1780	>	* @return 0 if no progress can be made, negative if task
1781	>	* known complete, else positive
1782	>	*/
1783	>	private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1784	>	int stat = 0, steps = 0;                    // bound to avoid cycles
1785	>	if (joiner != null && task != null) {       // hoist null checks
1786	>	restart: for (;;) {
1787	>	ForkJoinTask<?> subtask = task;     // current target
1788	>	for (WorkQueue j = joiner, v;;) {   // v is stealer of subtask
1789	>	WorkQueue[] ws; int m, s, h;
1790	>	if ((s = task.status) < 0) {
1791	>	stat = s;
1792	>	break restart;
1793	>	}
1794	>	if ((ws = workQueues) == null || (m = ws.length - 1) <= 0)
1795	>	break restart;              // shutting down
1796	>	if ((v = ws[h = (j.stealHint | 1) & m]) == null ||
1797	>	v.currentSteal != subtask) {
1798	>	for (int origin = h;;) {    // find stealer
1799	>	if (((h = (h + 2) & m) & 15) == 1 &&
1800	>	(subtask.status < 0 || j.currentJoin != subtask))
1801	>	continue restart;   // occasional staleness check
1802	>	if ((v = ws[h]) != null &&
1803	>	v.currentSteal == subtask) {
1804	>	j.stealHint = h;    // save hint
1805	>	break;
1806	>	}
1807	>	if (h == origin)
1808	>	break restart;      // cannot find stealer
1809	>	}
1810	>	}
1811	>	for (;;) { // help stealer or descend to its stealer
1812	>	ForkJoinTask[] a;  int b;
1813	>	if (subtask.status < 0)     // surround probes with
1814	>	continue restart;       //   consistency checks
1815	>	if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
1816	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1817	>	ForkJoinTask<?> t =
1818	>	(ForkJoinTask<?>)U.getObjectVolatile(a, i);
1819	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1820	>	v.currentSteal != subtask)
1821	>	continue restart;   // stale
1822	>	stat = 1;               // apparent progress
1823	>	if (t != null && v.base == b &&
1824	>	U.compareAndSwapObject(a, i, t, null)) {
1825	>	v.base = b + 1;     // help stealer
1826	>	joiner.runSubtask(t);
1827	>	}
1828	>	else if (v.base == b && ++steps == MAX_HELP)
1829	>	break restart;      // v apparently stalled
1830	>	}
1831	>	else {                      // empty -- try to descend
1832	>	ForkJoinTask<?> next = v.currentJoin;
1833	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1834	>	v.currentSteal != subtask)
1835	>	continue restart;   // stale
1836	>	else if (next == null || ++steps == MAX_HELP)
1837	>	break restart;      // dead-end or maybe cyclic
1838	>	else {
1839	>	subtask = next;
1840	>	j = v;
1841	>	break;
1842	>	}
1843	>	}
1844	>	}
1845	>	}
1846	>	}
1847	>	}
1848	>	return stat;
1849	>	}
1850
1851		/**
1852	<	* Adds delta (which may be negative) to running count.  This must
1853	<	* be called before (with negative arg) and after (with positive)
1854	<	* any managed synchronization (i.e., mainly, joins).
1855	<	* @param delta the number to add
1852	>	* Analog of tryHelpStealer for CountedCompleters. Tries to steal
1853	>	* and run tasks within the target's computation.
1854	>	*
1855	>	* @param task the task to join
1856	>	* @param mode if shared, exit upon completing any task
1857	>	* if all workers are active
1858	>	*
1859		*/
1860	<	final void updateRunningCount(int delta) {
1861	<	int s;
1862	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
1860	>	private int helpComplete(ForkJoinTask<?> task, int mode) {
1861	>	WorkQueue[] ws; WorkQueue q; int m, n, s;
1862	>	if (task != null && (ws = workQueues) != null &&
1863	>	(m = ws.length - 1) >= 0) {
1864	>	for (int j = 1, origin = j;;) {
1865	>	if ((s = task.status) < 0)
1866	>	return s;
1867	>	if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) {
1868	>	origin = j;
1869	>	if (mode == SHARED_QUEUE && (int)(ctl >> AC_SHIFT) >= 0)
1870	>	break;
1871	>	}
1872	>	else if ((j = (j + 2) & m) == origin)
1873	>	break;
1874	>	}
1875	>	}
1876	>	return 0;
1877	>	}
1878	>
1879	>	/**
1880	>	* Tries to decrement active count (sometimes implicitly) and
1881	>	* possibly release or create a compensating worker in preparation
1882	>	* for blocking. Fails on contention or termination. Otherwise,
1883	>	* adds a new thread if no idle workers are available and pool
1884	>	* may become starved.
1885	>	*/
1886	>	final boolean tryCompensate() {
1887	>	int pc = parallelism, e, u, i, tc; long c;
1888	>	WorkQueue[] ws; WorkQueue w; Thread p;
1889	>	if ((e = (int)(c = ctl)) >= 0 && (ws = workQueues) != null) {
1890	>	if (e != 0 && (i = e & SMASK) < ws.length &&
1891	>	(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
1892	>	long nc = ((long)(w.nextWait & E_MASK) |
1893	>	(c & (AC_MASK|TC_MASK)));
1894	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1895	>	w.eventCount = (e + E_SEQ) & E_MASK;
1896	>	if ((p = w.parker) != null)
1897	>	U.unpark(p);
1898	>	return true;   // replace with idle worker
1899	>	}
1900	>	}
1901	>	else if ((short)((u = (int)(c >>> 32)) >>> UTC_SHIFT) >= 0 &&
1902	>	(u >> UAC_SHIFT) + pc > 1) {
1903	>	long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
1904	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1905	>	return true;    // no compensation
1906	>	}
1907	>	else if ((tc = u + pc) < MAX_CAP) {
1908	>	long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
1909	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1910	>	Throwable ex = null;
1911	>	ForkJoinWorkerThread wt = null;
1912	>	try {
1913	>	ForkJoinWorkerThreadFactory fac;
1914	>	if ((fac = factory) != null &&
1915	>	(wt = fac.newThread(this)) != null) {
1916	>	wt.start();
1917	>	return true;
1918	>	}
1919	>	} catch (Throwable rex) {
1920	>	ex = rex;
1921	>	}
1922	>	deregisterWorker(wt, ex); // adjust counts etc
1923	>	}
1924	>	}
1925	>	}
1926	>	return false;
1927		}
1928
1929		/**
1930	<	* Adds delta (which may be negative) to both total and running
1931	<	* count.  This must be called upon creation and termination of
1932	<	* worker threads.
1933	<	* @param delta the number to add
1930	>	* Helps and/or blocks until the given task is done.
1931	>	*
1932	>	* @param joiner the joining worker
1933	>	* @param task the task
1934	>	* @return task status on exit
1935		*/
1936	<	private void updateWorkerCount(int delta) {
1937	<	int d = delta + (delta << 16); // add to both lo and hi parts
1938	<	int s;
1939	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
1936	>	final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
1937	>	int s = 0;
1938	>	if (joiner != null && task != null && (s = task.status) >= 0) {
1939	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
1940	>	joiner.currentJoin = task;
1941	>	do {} while ((s = task.status) >= 0 &&
1942	>	joiner.queueSize() > 0 &&
1943	>	joiner.tryRemoveAndExec(task)); // process local tasks
1944	>	if (s >= 0 && (s = task.status) >= 0 &&
1945	>	(s = helpSignal(task, joiner.poolIndex)) >= 0 &&
1946	>	(task instanceof CountedCompleter))
1947	>	s = helpComplete(task, LIFO_QUEUE);
1948	>	while (s >= 0 && (s = task.status) >= 0) {
1949	>	if ((joiner.queueSize() > 0 ||           // try helping
1950	>	(s = tryHelpStealer(joiner, task)) == 0) &&
1951	>	(s = task.status) >= 0 && tryCompensate()) {
1952	>	if (task.trySetSignal() && (s = task.status) >= 0) {
1953	>	synchronized (task) {
1954	>	if (task.status >= 0) {
1955	>	try {                // see ForkJoinTask
1956	>	task.wait();     //  for explanation
1957	>	} catch (InterruptedException ie) {
1958	>	}
1959	>	}
1960	>	else
1961	>	task.notifyAll();
1962	>	}
1963	>	}
1964	>	long c;                          // re-activate
1965	>	do {} while (!U.compareAndSwapLong
1966	>	(this, CTL, c = ctl, c + AC_UNIT));
1967	>	}
1968	>	}
1969	>	joiner.currentJoin = prevJoin;
1970	>	}
1971	>	return s;
1972		}
1973
1974		/**
1975	<	* Lifecycle control. High word contains runState, low word
1976	<	* contains the number of workers that are (probably) executing
1977	<	* tasks. This value is atomically incremented before a worker
1978	<	* gets a task to run, and decremented when worker has no tasks
1979	<	* and cannot find any. These two fields are bundled together to
1980	<	* support correct termination triggering.  Note: activeCount
261	<	* CAS'es cheat by assuming active count is in low word, so need
262	<	* to be modified if this changes
1975	>	* Stripped-down variant of awaitJoin used by timed joins. Tries
1976	>	* to help join only while there is continuous progress. (Caller
1977	>	* will then enter a timed wait.)
1978	>	*
1979	>	* @param joiner the joining worker
1980	>	* @param task the task
1981		*/
1982	<	private volatile int runControl;
1982	>	final void helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
1983	>	int s;
1984	>	if (joiner != null && task != null && (s = task.status) >= 0) {
1985	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
1986	>	joiner.currentJoin = task;
1987	>	do {} while ((s = task.status) >= 0 &&
1988	>	joiner.queueSize() > 0 &&
1989	>	joiner.tryRemoveAndExec(task));
1990	>	if (s >= 0 && (s = task.status) >= 0 &&
1991	>	(s = helpSignal(task, joiner.poolIndex)) >= 0 &&
1992	>	(task instanceof CountedCompleter))
1993	>	s = helpComplete(task, LIFO_QUEUE);
1994	>	if (s >= 0 && joiner.queueSize() == 0) {
1995	>	do {} while (task.status >= 0 &&
1996	>	tryHelpStealer(joiner, task) > 0);
1997	>	}
1998	>	joiner.currentJoin = prevJoin;
1999	>	}
2000	>	}
2001
2002	<	// RunState values. Order among values matters
2003	<	private static final int RUNNING     = 0;
2004	<	private static final int SHUTDOWN    = 1;
2005	<	private static final int TERMINATING = 2;
2006	<	private static final int TERMINATED  = 3;
2002	>	/**
2003	>	* Returns a (probably) non-empty steal queue, if one is found
2004	>	* during a random, then cyclic scan, else null.  This method must
2005	>	* be retried by caller if, by the time it tries to use the queue,
2006	>	* it is empty.
2007	>	* @param r a (random) seed for scanning
2008	>	*/
2009	>	private WorkQueue findNonEmptyStealQueue(int r) {
2010	>	int step = (r >>> 16) | 1;
2011	>	for (WorkQueue[] ws;;) {
2012	>	int ps = plock, m;
2013	>	if ((ws = workQueues) == null || (m = ws.length - 1) < 1)
2014	>	return null;
2015	>	for (int j = (m + 1) << 2; ; r += step) {
2016	>	WorkQueue q = ws[((r << 1) | 1) & m];
2017	>	if (q != null && q.queueSize() > 0)
2018	>	return q;
2019	>	else if (--j < 0) {
2020	>	if (plock == ps)
2021	>	return null;
2022	>	break;
2023	>	}
2024	>	}
2025	>	}
2026	>	}
2027
2028	<	private static int runStateOf(int c)             { return c >>> 16; }
2029	<	private static int activeCountOf(int c)          { return c & shortMask; }
2030	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
2028	>	/**
2029	>	* Runs tasks until {@code isQuiescent()}. We piggyback on
2030	>	* active count ctl maintenance, but rather than blocking
2031	>	* when tasks cannot be found, we rescan until all others cannot
2032	>	* find tasks either.
2033	>	*/
2034	>	final void helpQuiescePool(WorkQueue w) {
2035	>	for (boolean active = true;;) {
2036	>	ForkJoinTask<?> localTask; // exhaust local queue
2037	>	while ((localTask = w.nextLocalTask()) != null)
2038	>	localTask.doExec();
2039	>	// Similar to loop in scan(), but ignoring submissions
2040	>	WorkQueue q = findNonEmptyStealQueue(w.nextSeed());
2041	>	if (q != null) {
2042	>	ForkJoinTask<?> t; int b;
2043	>	if (!active) {      // re-establish active count
2044	>	long c;
2045	>	active = true;
2046	>	do {} while (!U.compareAndSwapLong
2047	>	(this, CTL, c = ctl, c + AC_UNIT));
2048	>	}
2049	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2050	>	w.runSubtask(t);
2051	>	}
2052	>	else {
2053	>	long c;
2054	>	if (active) {       // decrement active count without queuing
2055	>	active = false;
2056	>	do {} while (!U.compareAndSwapLong
2057	>	(this, CTL, c = ctl, c -= AC_UNIT));
2058	>	}
2059	>	else
2060	>	c = ctl;        // re-increment on exit
2061	>	if ((int)(c >> AC_SHIFT) + parallelism == 0) {
2062	>	do {} while (!U.compareAndSwapLong
2063	>	(this, CTL, c = ctl, c + AC_UNIT));
2064	>	break;
2065	>	}
2066	>	}
2067	>	}
2068	>	}
2069
2070		/**
2071	<	* Try incrementing active count; fail on contention. Called by
2072	<	* workers before/during executing tasks.
2073	<	* @return true on success
2071	>	* Gets and removes a local or stolen task for the given worker.
2072	>	*
2073	>	* @return a task, if available
2074		*/
2075	<	final boolean tryIncrementActiveCount() {
2076	<	int c = runControl;
2077	<	return casRunControl(c, c+1);
2075	>	final ForkJoinTask<?> nextTaskFor(WorkQueue w) {
2076	>	for (ForkJoinTask<?> t;;) {
2077	>	WorkQueue q; int b;
2078	>	if ((t = w.nextLocalTask()) != null)
2079	>	return t;
2080	>	if ((q = findNonEmptyStealQueue(w.nextSeed())) == null)
2081	>	return null;
2082	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2083	>	return t;
2084	>	}
2085		}
2086
2087		/**
2088	<	* Tries decrementing active count; fails on contention.
2089	<	* Possibly triggers termination on success.
2090	<	* Called by workers when they can't find tasks.
2091	<	* @return true on success
2088	>	* Returns a cheap heuristic guide for task partitioning when
2089	>	* programmers, frameworks, tools, or languages have little or no
2090	>	* idea about task granularity.  In essence by offering this
2091	>	* method, we ask users only about tradeoffs in overhead vs
2092	>	* expected throughput and its variance, rather than how finely to
2093	>	* partition tasks.
2094	>	*
2095	>	* In a steady state strict (tree-structured) computation, each
2096	>	* thread makes available for stealing enough tasks for other
2097	>	* threads to remain active. Inductively, if all threads play by
2098	>	* the same rules, each thread should make available only a
2099	>	* constant number of tasks.
2100	>	*
2101	>	* The minimum useful constant is just 1. But using a value of 1
2102	>	* would require immediate replenishment upon each steal to
2103	>	* maintain enough tasks, which is infeasible.  Further,
2104	>	* partitionings/granularities of offered tasks should minimize
2105	>	* steal rates, which in general means that threads nearer the top
2106	>	* of computation tree should generate more than those nearer the
2107	>	* bottom. In perfect steady state, each thread is at
2108	>	* approximately the same level of computation tree. However,
2109	>	* producing extra tasks amortizes the uncertainty of progress and
2110	>	* diffusion assumptions.
2111	>	*
2112	>	* So, users will want to use values larger, but not much larger
2113	>	* than 1 to both smooth over transient shortages and hedge
2114	>	* against uneven progress; as traded off against the cost of
2115	>	* extra task overhead. We leave the user to pick a threshold
2116	>	* value to compare with the results of this call to guide
2117	>	* decisions, but recommend values such as 3.
2118	>	*
2119	>	* When all threads are active, it is on average OK to estimate
2120	>	* surplus strictly locally. In steady-state, if one thread is
2121	>	* maintaining say 2 surplus tasks, then so are others. So we can
2122	>	* just use estimated queue length.  However, this strategy alone
2123	>	* leads to serious mis-estimates in some non-steady-state
2124	>	* conditions (ramp-up, ramp-down, other stalls). We can detect
2125	>	* many of these by further considering the number of "idle"
2126	>	* threads, that are known to have zero queued tasks, so
2127	>	* compensate by a factor of (#idle/#active) threads.
2128	>	*
2129	>	* Note: The approximation of #busy workers as #active workers is
2130	>	* not very good under current signalling scheme, and should be
2131	>	* improved.
2132	>	*/
2133	>	static int getSurplusQueuedTaskCount() {
2134	>	Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q;
2135	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
2136	>	int b = (q = (wt = (ForkJoinWorkerThread)t).workQueue).base;
2137	>	int p = (pool = wt.pool).parallelism;
2138	>	int a = (int)(pool.ctl >> AC_SHIFT) + p;
2139	>	return q.top - b - (a > (p >>>= 1) ? 0 :
2140	>	a > (p >>>= 1) ? 1 :
2141	>	a > (p >>>= 1) ? 2 :
2142	>	a > (p >>>= 1) ? 4 :
2143	>	8);
2144	>	}
2145	>	return 0;
2146	>	}
2147	>
2148	>	//  Termination
2149	>
2150	>	/**
2151	>	* Possibly initiates and/or completes termination.  The caller
2152	>	* triggering termination runs three passes through workQueues:
2153	>	* (0) Setting termination status, followed by wakeups of queued
2154	>	* workers; (1) cancelling all tasks; (2) interrupting lagging
2155	>	* threads (likely in external tasks, but possibly also blocked in
2156	>	* joins).  Each pass repeats previous steps because of potential
2157	>	* lagging thread creation.
2158	>	*
2159	>	* @param now if true, unconditionally terminate, else only
2160	>	* if no work and no active workers
2161	>	* @param enable if true, enable shutdown when next possible
2162	>	* @return true if now terminating or terminated
2163		*/
2164	<	final boolean tryDecrementActiveCount() {
2165	<	int c = runControl;
294	<	int nextc = c - 1;
295	<	if (!casRunControl(c, nextc))
2164	>	private boolean tryTerminate(boolean now, boolean enable) {
2165	>	if (this == commonPool)                     // cannot shut down
2166		return false;
2167	<	if (canTerminateOnShutdown(nextc))
2168	<	terminateOnShutdown();
2169	<	return true;
2167	>	for (long c;;) {
2168	>	if (((c = ctl) & STOP_BIT) != 0) {      // already terminating
2169	>	if ((short)(c >>> TC_SHIFT) == -parallelism) {
2170	>	synchronized (this) {
2171	>	notifyAll();                // signal when 0 workers
2172	>	}
2173	>	}
2174	>	return true;
2175	>	}
2176	>	if (plock >= 0) {                       // not yet enabled
2177	>	int ps;
2178	>	if (!enable)
2179	>	return false;
2180	>	if (((ps = plock) & PL_LOCK) != 0 ||
2181	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
2182	>	ps = acquirePlock();
2183	>	int nps = SHUTDOWN;
2184	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
2185	>	releasePlock(nps);
2186	>	}
2187	>	if (!now) {                             // check if idle & no tasks
2188	>	if ((int)(c >> AC_SHIFT) != -parallelism ||
2189	>	hasQueuedSubmissions())
2190	>	return false;
2191	>	// Check for unqueued inactive workers. One pass suffices.
2192	>	WorkQueue[] ws = workQueues; WorkQueue w;
2193	>	if (ws != null) {
2194	>	for (int i = 1; i < ws.length; i += 2) {
2195	>	if ((w = ws[i]) != null && w.eventCount >= 0)
2196	>	return false;
2197	>	}
2198	>	}
2199	>	}
2200	>	if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT)) {
2201	>	for (int pass = 0; pass < 3; ++pass) {
2202	>	WorkQueue[] ws = workQueues;
2203	>	if (ws != null) {
2204	>	WorkQueue w;
2205	>	int n = ws.length;
2206	>	for (int i = 0; i < n; ++i) {
2207	>	if ((w = ws[i]) != null) {
2208	>	w.qlock = -1;
2209	>	if (pass > 0) {
2210	>	w.cancelAll();
2211	>	if (pass > 1)
2212	>	w.interruptOwner();
2213	>	}
2214	>	}
2215	>	}
2216	>	// Wake up workers parked on event queue
2217	>	int i, e; long cc; Thread p;
2218	>	while ((e = (int)(cc = ctl) & E_MASK) != 0 &&
2219	>	(i = e & SMASK) < n &&
2220	>	(w = ws[i]) != null) {
2221	>	long nc = ((long)(w.nextWait & E_MASK) |
2222	>	((cc + AC_UNIT) & AC_MASK) |
2223	>	(cc & (TC_MASK|STOP_BIT)));
2224	>	if (w.eventCount == (e | INT_SIGN) &&
2225	>	U.compareAndSwapLong(this, CTL, cc, nc)) {
2226	>	w.eventCount = (e + E_SEQ) & E_MASK;
2227	>	w.qlock = -1;
2228	>	if ((p = w.parker) != null)
2229	>	U.unpark(p);
2230	>	}
2231	>	}
2232	>	}
2233	>	}
2234	>	}
2235	>	}
2236		}
2237
2238	+	// external operations on common pool
2239	+
2240		/**
2241	<	* Returns true if argument represents zero active count and
2242	<	* nonzero runstate, which is the triggering condition for
305	<	* terminating on shutdown.
2241	>	* Returns common pool queue for a thread that has submitted at
2242	>	* least one task.
2243		*/
2244	<	private static boolean canTerminateOnShutdown(int c) {
2245	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
2244	>	static WorkQueue commonSubmitterQueue() {
2245	>	ForkJoinPool p; WorkQueue[] ws; int m; Submitter z;
2246	>	return ((z = submitters.get()) != null &&
2247	>	(p = commonPool) != null &&
2248	>	(ws = p.workQueues) != null &&
2249	>	(m = ws.length - 1) >= 0) ?
2250	>	ws[m & z.seed & SQMASK] : null;
2251		}
2252
2253		/**
2254	<	* Transition run state to at least the given state. Return true
2255	<	* if not already at least given state.
2256	<	*/
2257	<	private boolean transitionRunStateTo(int state) {
2258	<	for (;;) {
2259	<	int c = runControl;
2260	<	if (runStateOf(c) >= state)
2261	<	return false;
2262	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
2254	>	* Tries to pop the given task from submitter's queue in common pool.
2255	>	*/
2256	>	static boolean tryExternalUnpush(ForkJoinTask<?> t) {
2257	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q; Submitter z;
2258	>	ForkJoinTask<?>[] a;  int m, s; long j;
2259	>	if ((z = submitters.get()) != null &&
2260	>	(p = commonPool) != null &&
2261	>	(ws = p.workQueues) != null &&
2262	>	(m = ws.length - 1) >= 0 &&
2263	>	(q = ws[m & z.seed & SQMASK]) != null &&
2264	>	(s = q.top) != q.base &&
2265	>	(a = q.array) != null &&
2266	>	U.getObjectVolatile
2267	>	(a, j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE) == t &&
2268	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2269	>	if (q.array == a && q.top == s && // recheck
2270	>	U.compareAndSwapObject(a, j, t, null)) {
2271	>	q.top = s - 1;
2272	>	q.qlock = 0;
2273		return true;
2274	+	}
2275	+	q.qlock = 0;
2276	+	}
2277	+	return false;
2278	+	}
2279	+
2280	+	/**
2281	+	* Tries to pop and run local tasks within the same computation
2282	+	* as the given root. On failure, tries to help complete from
2283	+	* other queues via helpComplete.
2284	+	*/
2285	+	private void externalHelpComplete(WorkQueue q, ForkJoinTask<?> root) {
2286	+	ForkJoinTask<?>[] a; int m;
2287	+	if (q != null && (a = q.array) != null && (m = (a.length - 1)) >= 0 &&
2288	+	root != null && root.status >= 0) {
2289	+	for (;;) {
2290	+	int s; Object o; CountedCompleter<?> task = null;
2291	+	if ((s = q.top) - q.base > 0) {
2292	+	long j = ((m & (s - 1)) << ASHIFT) + ABASE;
2293	+	if ((o = U.getObject(a, j)) != null &&
2294	+	(o instanceof CountedCompleter)) {
2295	+	CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;
2296	+	do {
2297	+	if (r == root) {
2298	+	if (U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2299	+	if (q.array == a && q.top == s &&
2300	+	U.compareAndSwapObject(a, j, t, null)) {
2301	+	q.top = s - 1;
2302	+	task = t;
2303	+	}
2304	+	q.qlock = 0;
2305	+	}
2306	+	break;
2307	+	}
2308	+	} while ((r = r.completer) != null);
2309	+	}
2310	+	}
2311	+	if (task != null)
2312	+	task.doExec();
2313	+	if (root.status < 0 || (int)(ctl >> AC_SHIFT) >= 0)
2314	+	break;
2315	+	if (task == null) {
2316	+	if (helpSignal(root, q.poolIndex) >= 0)
2317	+	helpComplete(root, SHARED_QUEUE);
2318	+	break;
2319	+	}
2320	+	}
2321		}
2322		}
2323
2324		/**
2325	<	* Controls whether to add spares to maintain parallelism
2325	>	* Tries to help execute or signal availability of the given task
2326	>	* from submitter's queue in common pool.
2327		*/
2328	<	private volatile boolean maintainsParallelism;
2328	>	static void externalHelpJoin(ForkJoinTask<?> t) {
2329	>	// Some hard-to-avoid overlap with tryExternalUnpush
2330	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; Submitter z;
2331	>	ForkJoinTask<?>[] a;  int m, s, n; long j;
2332	>	if (t != null && t.status >= 0 &&
2333	>	(z = submitters.get()) != null &&
2334	>	(p = commonPool) != null &&
2335	>	(ws = p.workQueues) != null &&
2336	>	(m = ws.length - 1) >= 0 &&
2337	>	(q = ws[m & z.seed & SQMASK]) != null &&
2338	>	(a = q.array) != null) {
2339	>	if ((s = q.top) != q.base &&
2340	>	U.getObjectVolatile
2341	>	(a, j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE) == t &&
2342	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2343	>	if (q.array == a && q.top == s &&
2344	>	U.compareAndSwapObject(a, j, t, null)) {
2345	>	q.top = s - 1;
2346	>	q.qlock = 0;
2347	>	t.doExec();
2348	>	}
2349	>	else
2350	>	q.qlock = 0;
2351	>	}
2352	>	if (t.status >= 0) {
2353	>	if (t instanceof CountedCompleter)
2354	>	p.externalHelpComplete(q, t);
2355	>	else
2356	>	p.helpSignal(t, q.poolIndex);
2357	>	}
2358	>	}
2359	>	}
2360	>
2361	>	/**
2362	>	* Restricted version of helpQuiescePool for external callers
2363	>	*/
2364	>	static void externalHelpQuiescePool() {
2365	>	ForkJoinPool p; ForkJoinTask<?> t; WorkQueue q; int b;
2366	>	int r = ThreadLocalRandom.current().nextInt();
2367	>	if ((p = commonPool) != null &&
2368	>	(q = p.findNonEmptyStealQueue(r)) != null &&
2369	>	(b = q.base) - q.top < 0 &&
2370	>	(t = q.pollAt(b)) != null)
2371	>	t.doExec();
2372	>	}
2373	>
2374	>	// Exported methods
2375
2376		// Constructors
2377
2378		/**
2379	<	* Creates a ForkJoinPool with a pool size equal to the number of
2380	<	* processors available on the system and using the default
2381	<	* ForkJoinWorkerThreadFactory,
2379	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
2380	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
2381	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
2382	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
2383	>	*
2384		* @throws SecurityException if a security manager exists and
2385		*         the caller is not permitted to modify threads
2386		*         because it does not hold {@link
2387	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
2387	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
2388		*/
2389		public ForkJoinPool() {
2390		this(Runtime.getRuntime().availableProcessors(),
2391	<	defaultForkJoinWorkerThreadFactory);
2391	>	defaultForkJoinWorkerThreadFactory, null, false);
2392		}
2393
2394		/**
2395	<	* Creates a ForkJoinPool with the indicated parallelism level
2396	<	* threads, and using the default ForkJoinWorkerThreadFactory,
2397	<	* @param parallelism the number of worker threads
2395	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
2396	>	* level, the {@linkplain
2397	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
2398	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
2399	>	*
2400	>	* @param parallelism the parallelism level
2401		* @throws IllegalArgumentException if parallelism less than or
2402	<	* equal to zero
2402	>	*         equal to zero, or greater than implementation limit
2403		* @throws SecurityException if a security manager exists and
2404		*         the caller is not permitted to modify threads
2405		*         because it does not hold {@link
2406	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
2406	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
2407		*/
2408		public ForkJoinPool(int parallelism) {
2409	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
359	<	}
360	<
361	<	/**
362	<	* Creates a ForkJoinPool with parallelism equal to the number of
363	<	* processors available on the system and using the given
364	<	* ForkJoinWorkerThreadFactory,
365	<	* @param factory the factory for creating new threads
366	<	* @throws NullPointerException if factory is null
367	<	* @throws SecurityException if a security manager exists and
368	<	*         the caller is not permitted to modify threads
369	<	*         because it does not hold {@link
370	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
371	<	*/
372	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
373	<	this(Runtime.getRuntime().availableProcessors(), factory);
2409	>	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
2410		}
2411
2412		/**
2413	<	* Creates a ForkJoinPool with the given parallelism and factory.
2413	>	* Creates a {@code ForkJoinPool} with the given parameters.
2414		*
2415	<	* @param parallelism the targeted number of worker threads
2416	<	* @param factory the factory for creating new threads
2415	>	* @param parallelism the parallelism level. For default value,
2416	>	* use {@link java.lang.Runtime#availableProcessors}.
2417	>	* @param factory the factory for creating new threads. For default value,
2418	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
2419	>	* @param handler the handler for internal worker threads that
2420	>	* terminate due to unrecoverable errors encountered while executing
2421	>	* tasks. For default value, use {@code null}.
2422	>	* @param asyncMode if true,
2423	>	* establishes local first-in-first-out scheduling mode for forked
2424	>	* tasks that are never joined. This mode may be more appropriate
2425	>	* than default locally stack-based mode in applications in which
2426	>	* worker threads only process event-style asynchronous tasks.
2427	>	* For default value, use {@code false}.
2428		* @throws IllegalArgumentException if parallelism less than or
2429	<	* equal to zero, or greater than implementation limit
2430	<	* @throws NullPointerException if factory is null
2429	>	*         equal to zero, or greater than implementation limit
2430	>	* @throws NullPointerException if the factory is null
2431		* @throws SecurityException if a security manager exists and
2432		*         the caller is not permitted to modify threads
2433		*         because it does not hold {@link
2434	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
2434	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
2435		*/
2436	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
2437	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
2438	<	throw new IllegalArgumentException();
2436	>	public ForkJoinPool(int parallelism,
2437	>	ForkJoinWorkerThreadFactory factory,
2438	>	Thread.UncaughtExceptionHandler handler,
2439	>	boolean asyncMode) {
2440	>	checkPermission();
2441		if (factory == null)
2442		throw new NullPointerException();
2443	<	checkPermission();
2444	<	this.factory = factory;
2443	>	if (parallelism <= 0 || parallelism > MAX_CAP)
2444	>	throw new IllegalArgumentException();
2445		this.parallelism = parallelism;
2446	<	this.maxPoolSize = MAX_THREADS;
2447	<	this.maintainsParallelism = true;
2448	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
2449	<	this.workerLock = new ReentrantLock();
2450	<	this.termination = workerLock.newCondition();
2451	<	this.stealCount = new AtomicLong();
2452	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
2453	<	// worker array and workers are lazily constructed
2454	<	}
2455	<
407	<	/**
408	<	* Create new worker using factory.
409	<	* @param index the index to assign worker
410	<	* @return new worker, or null of factory failed
411	<	*/
412	<	private ForkJoinWorkerThread createWorker(int index) {
413	<	Thread.UncaughtExceptionHandler h = ueh;
414	<	ForkJoinWorkerThread w = factory.newThread(this);
415	<	if (w != null) {
416	<	w.poolIndex = index;
417	<	w.setDaemon(true);
418	<	w.setAsyncMode(locallyFifo);
419	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
420	<	if (h != null)
421	<	w.setUncaughtExceptionHandler(h);
422	<	}
423	<	return w;
424	<	}
425	<
426	<	/**
427	<	* Returns a good size for worker array given pool size.
428	<	* Currently requires size to be a power of two.
429	<	*/
430	<	private static int arraySizeFor(int ps) {
431	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
432	<	}
433	<
434	<	/**
435	<	* Creates or resizes array if necessary to hold newLength.
436	<	* Call only under exclusion or lock.
437	<	* @return the array
438	<	*/
439	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
440	<	ForkJoinWorkerThread[] ws = workers;
441	<	if (ws == null)
442	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
443	<	else if (newLength > ws.length)
444	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
445	<	else
446	<	return ws;
447	<	}
448	<
449	<	/**
450	<	* Try to shrink workers into smaller array after one or more terminate
451	<	*/
452	<	private void tryShrinkWorkerArray() {
453	<	ForkJoinWorkerThread[] ws = workers;
454	<	if (ws != null) {
455	<	int len = ws.length;
456	<	int last = len - 1;
457	<	while (last >= 0 && ws[last] == null)
458	<	--last;
459	<	int newLength = arraySizeFor(last+1);
460	<	if (newLength < len)
461	<	workers = Arrays.copyOf(ws, newLength);
462	<	}
2446	>	this.factory = factory;
2447	>	this.ueh = handler;
2448	>	this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE;
2449	>	long np = (long)(-parallelism); // offset ctl counts
2450	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
2451	>	int pn = nextPoolId();
2452	>	StringBuilder sb = new StringBuilder("ForkJoinPool-");
2453	>	sb.append(Integer.toString(pn));
2454	>	sb.append("-worker-");
2455	>	this.workerNamePrefix = sb.toString();
2456		}
2457
2458		/**
2459	<	* Initialize workers if necessary
2460	<	*/
2461	<	final void ensureWorkerInitialization() {
2462	<	ForkJoinWorkerThread[] ws = workers;
2463	<	if (ws == null) {
2464	<	final ReentrantLock lock = this.workerLock;
2465	<	lock.lock();
2466	<	try {
2467	<	ws = workers;
2468	<	if (ws == null) {
2469	<	int ps = parallelism;
2470	<	ws = ensureWorkerArrayCapacity(ps);
478	<	for (int i = 0; i < ps; ++i) {
479	<	ForkJoinWorkerThread w = createWorker(i);
480	<	if (w != null) {
481	<	ws[i] = w;
482	<	w.start();
483	<	updateWorkerCount(1);
484	<	}
485	<	}
486	<	}
487	<	} finally {
488	<	lock.unlock();
489	<	}
490	<	}
2459	>	* Constructor for common pool, suitable only for static initialization.
2460	>	* Basically the same as above, but uses smallest possible initial footprint.
2461	>	*/
2462	>	ForkJoinPool(int parallelism, long ctl,
2463	>	ForkJoinWorkerThreadFactory factory,
2464	>	Thread.UncaughtExceptionHandler handler) {
2465	>	this.parallelism = parallelism;
2466	>	this.ctl = ctl;
2467	>	this.factory = factory;
2468	>	this.ueh = handler;
2469	>	this.localMode = LIFO_QUEUE;
2470	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2471		}
2472
2473		/**
2474	<	* Worker creation and startup for threads added via setParallelism.
2474	>	* Returns the common pool instance.
2475	>	*
2476	>	* @return the common pool instance
2477		*/
2478	<	private void createAndStartAddedWorkers() {
2479	<	resumeAllSpares();  // Allow spares to convert to nonspare
498	<	int ps = parallelism;
499	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
500	<	int len = ws.length;
501	<	// Sweep through slots, to keep lowest indices most populated
502	<	int k = 0;
503	<	while (k < len) {
504	<	if (ws[k] != null) {
505	<	++k;
506	<	continue;
507	<	}
508	<	int s = workerCounts;
509	<	int tc = totalCountOf(s);
510	<	int rc = runningCountOf(s);
511	<	if (rc >= ps || tc >= ps)
512	<	break;
513	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
514	<	ForkJoinWorkerThread w = createWorker(k);
515	<	if (w != null) {
516	<	ws[k++] = w;
517	<	w.start();
518	<	}
519	<	else {
520	<	updateWorkerCount(-1); // back out on failed creation
521	<	break;
522	<	}
523	<	}
524	<	}
2478	>	public static ForkJoinPool commonPool() {
2479	>	return commonPool; // cannot be null (if so, a static init error)
2480		}
2481
2482		// Execution methods
2483
2484		/**
2485	<	* Common code for execute, invoke and submit
2486	<	*/
2487	<	private <T> void doSubmit(ForkJoinTask<T> task) {
2488	<	if (isShutdown())
2489	<	throw new RejectedExecutionException();
2490	<	if (workers == null)
2491	<	ensureWorkerInitialization();
2492	<	submissionQueue.offer(task);
2493	<	signalIdleWorkers();
539	<	}
540	<
541	<	/**
542	<	* Performs the given task; returning its result upon completion
2485	>	* Performs the given task, returning its result upon completion.
2486	>	* If the computation encounters an unchecked Exception or Error,
2487	>	* it is rethrown as the outcome of this invocation.  Rethrown
2488	>	* exceptions behave in the same way as regular exceptions, but,
2489	>	* when possible, contain stack traces (as displayed for example
2490	>	* using {@code ex.printStackTrace()}) of both the current thread
2491	>	* as well as the thread actually encountering the exception;
2492	>	* minimally only the latter.
2493	>	*
2494		* @param task the task
2495		* @return the task's result
2496	<	* @throws NullPointerException if task is null
2497	<	* @throws RejectedExecutionException if pool is shut down
2496	>	* @throws NullPointerException if the task is null
2497	>	* @throws RejectedExecutionException if the task cannot be
2498	>	*         scheduled for execution
2499		*/
2500		public <T> T invoke(ForkJoinTask<T> task) {
2501	<	doSubmit(task);
2501	>	if (task == null)
2502	>	throw new NullPointerException();
2503	>	externalPush(task);
2504		return task.join();
2505		}
2506
2507		/**
2508		* Arranges for (asynchronous) execution of the given task.
2509	+	*
2510		* @param task the task
2511	<	* @throws NullPointerException if task is null
2512	<	* @throws RejectedExecutionException if pool is shut down
2511	>	* @throws NullPointerException if the task is null
2512	>	* @throws RejectedExecutionException if the task cannot be
2513	>	*         scheduled for execution
2514		*/
2515	<	public <T> void execute(ForkJoinTask<T> task) {
2516	<	doSubmit(task);
2515	>	public void execute(ForkJoinTask<?> task) {
2516	>	if (task == null)
2517	>	throw new NullPointerException();
2518	>	externalPush(task);
2519		}
2520
2521		// AbstractExecutorService methods
2522
2523	+	/**
2524	+	* @throws NullPointerException if the task is null
2525	+	* @throws RejectedExecutionException if the task cannot be
2526	+	*         scheduled for execution
2527	+	*/
2528		public void execute(Runnable task) {
2529	<	doSubmit(new AdaptedRunnable<Void>(task, null));
2529	>	if (task == null)
2530	>	throw new NullPointerException();
2531	>	ForkJoinTask<?> job;
2532	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2533	>	job = (ForkJoinTask<?>) task;
2534	>	else
2535	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2536	>	externalPush(job);
2537		}
2538
2539	<	public <T> ForkJoinTask<T> submit(Callable<T> task) {
2540	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
2541	<	doSubmit(job);
2542	<	return job;
2539	>	/**
2540	>	* Submits a ForkJoinTask for execution.
2541	>	*
2542	>	* @param task the task to submit
2543	>	* @return the task
2544	>	* @throws NullPointerException if the task is null
2545	>	* @throws RejectedExecutionException if the task cannot be
2546	>	*         scheduled for execution
2547	>	*/
2548	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2549	>	if (task == null)
2550	>	throw new NullPointerException();
2551	>	externalPush(task);
2552	>	return task;
2553		}
2554
2555	<	public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2556	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
2557	<	doSubmit(job);
2555	>	/**
2556	>	* @throws NullPointerException if the task is null
2557	>	* @throws RejectedExecutionException if the task cannot be
2558	>	*         scheduled for execution
2559	>	*/
2560	>	public <T> ForkJoinTask<T> submit(Callable<T> task) {
2561	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2562	>	externalPush(job);
2563		return job;
2564		}
2565
2566	<	public ForkJoinTask<?> submit(Runnable task) {
2567	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
2568	<	doSubmit(job);
2566	>	/**
2567	>	* @throws NullPointerException if the task is null
2568	>	* @throws RejectedExecutionException if the task cannot be
2569	>	*         scheduled for execution
2570	>	*/
2571	>	public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2572	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2573	>	externalPush(job);
2574		return job;
2575		}
2576
2577		/**
2578	<	* Adaptor for Runnables. This implements RunnableFuture
2579	<	* to be compliant with AbstractExecutorService constraints
2578	>	* @throws NullPointerException if the task is null
2579	>	* @throws RejectedExecutionException if the task cannot be
2580	>	*         scheduled for execution
2581		*/
2582	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
2583	<	implements RunnableFuture<T> {
2584	<	final Runnable runnable;
2585	<	final T resultOnCompletion;
2586	<	T result;
2587	<	AdaptedRunnable(Runnable runnable, T result) {
2588	<	if (runnable == null) throw new NullPointerException();
2589	<	this.runnable = runnable;
2590	<	this.resultOnCompletion = result;
2591	<	}
601	<	public T getRawResult() { return result; }
602	<	public void setRawResult(T v) { result = v; }
603	<	public boolean exec() {
604	<	runnable.run();
605	<	result = resultOnCompletion;
606	<	return true;
607	<	}
608	<	public void run() { invoke(); }
2582	>	public ForkJoinTask<?> submit(Runnable task) {
2583	>	if (task == null)
2584	>	throw new NullPointerException();
2585	>	ForkJoinTask<?> job;
2586	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2587	>	job = (ForkJoinTask<?>) task;
2588	>	else
2589	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2590	>	externalPush(job);
2591	>	return job;
2592		}
2593
2594		/**
2595	<	* Adaptor for Callables
2595	>	* @throws NullPointerException       {@inheritDoc}
2596	>	* @throws RejectedExecutionException {@inheritDoc}
2597		*/
614	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
615	–	implements RunnableFuture<T> {
616	–	final Callable<T> callable;
617	–	T result;
618	–	AdaptedCallable(Callable<T> callable) {
619	–	if (callable == null) throw new NullPointerException();
620	–	this.callable = callable;
621	–	}
622	–	public T getRawResult() { return result; }
623	–	public void setRawResult(T v) { result = v; }
624	–	public boolean exec() {
625	–	try {
626	–	result = callable.call();
627	–	return true;
628	–	} catch (Error err) {
629	–	throw err;
630	–	} catch (RuntimeException rex) {
631	–	throw rex;
632	–	} catch (Exception ex) {
633	–	throw new RuntimeException(ex);
634	–	}
635	–	}
636	–	public void run() { invoke(); }
637	–	}
638	–
2598		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
2599	<	ArrayList<ForkJoinTask<T>> ts =
2600	<	new ArrayList<ForkJoinTask<T>>(tasks.size());
2601	<	for (Callable<T> c : tasks)
2602	<	ts.add(new AdaptedCallable<T>(c));
2603	<	invoke(new InvokeAll<T>(ts));
2604	<	return (List<Future<T>>)(List)ts;
2605	<	}
2599	>	// In previous versions of this class, this method constructed
2600	>	// a task to run ForkJoinTask.invokeAll, but now external
2601	>	// invocation of multiple tasks is at least as efficient.
2602	>	List<ForkJoinTask<T>> fs = new ArrayList<ForkJoinTask<T>>(tasks.size());
2603	>	// Workaround needed because method wasn't declared with
2604	>	// wildcards in return type but should have been.
2605	>	@SuppressWarnings({"unchecked", "rawtypes"})
2606	>	List<Future<T>> futures = (List<Future<T>>) (List) fs;
2607
2608	<	static final class InvokeAll<T> extends RecursiveAction {
2609	<	final ArrayList<ForkJoinTask<T>> tasks;
2610	<	InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
2611	<	public void compute() {
2612	<	try { invokeAll(tasks); } catch(Exception ignore) {}
2608	>	boolean done = false;
2609	>	try {
2610	>	for (Callable<T> t : tasks) {
2611	>	ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2612	>	externalPush(f);
2613	>	fs.add(f);
2614	>	}
2615	>	for (ForkJoinTask<T> f : fs)
2616	>	f.quietlyJoin();
2617	>	done = true;
2618	>	return futures;
2619	>	} finally {
2620	>	if (!done)
2621	>	for (ForkJoinTask<T> f : fs)
2622	>	f.cancel(false);
2623		}
2624		}
2625
656	–	// Configuration and status settings and queries
657	–
2626		/**
2627	<	* Returns the factory used for constructing new workers
2627	>	* Returns the factory used for constructing new workers.
2628		*
2629		* @return the factory used for constructing new workers
2630		*/
#	Line 667 | Line 2635 | public class ForkJoinPool extends Abstra
2635		/**
2636		* Returns the handler for internal worker threads that terminate
2637		* due to unrecoverable errors encountered while executing tasks.
2638	<	* @return the handler, or null if none
2638	>	*
2639	>	* @return the handler, or {@code null} if none
2640		*/
2641		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
2642	<	Thread.UncaughtExceptionHandler h;
674	<	final ReentrantLock lock = this.workerLock;
675	<	lock.lock();
676	<	try {
677	<	h = ueh;
678	<	} finally {
679	<	lock.unlock();
680	<	}
681	<	return h;
2642	>	return ueh;
2643		}
2644
2645		/**
2646	<	* Sets the handler for internal worker threads that terminate due
686	<	* to unrecoverable errors encountered while executing tasks.
687	<	* Unless set, the current default or ThreadGroup handler is used
688	<	* as handler.
2646	>	* Returns the targeted parallelism level of this pool.
2647		*
2648	<	* @param h the new handler
691	<	* @return the old handler, or null if none
692	<	* @throws SecurityException if a security manager exists and
693	<	*         the caller is not permitted to modify threads
694	<	*         because it does not hold {@link
695	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
696	<	*/
697	<	public Thread.UncaughtExceptionHandler
698	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
699	<	checkPermission();
700	<	Thread.UncaughtExceptionHandler old = null;
701	<	final ReentrantLock lock = this.workerLock;
702	<	lock.lock();
703	<	try {
704	<	old = ueh;
705	<	ueh = h;
706	<	ForkJoinWorkerThread[] ws = workers;
707	<	if (ws != null) {
708	<	for (int i = 0; i < ws.length; ++i) {
709	<	ForkJoinWorkerThread w = ws[i];
710	<	if (w != null)
711	<	w.setUncaughtExceptionHandler(h);
712	<	}
713	<	}
714	<	} finally {
715	<	lock.unlock();
716	<	}
717	<	return old;
718	<	}
719	<
720	<
721	<	/**
722	<	* Sets the target parallelism level of this pool.
723	<	* @param parallelism the target parallelism
724	<	* @throws IllegalArgumentException if parallelism less than or
725	<	* equal to zero or greater than maximum size bounds
726	<	* @throws SecurityException if a security manager exists and
727	<	*         the caller is not permitted to modify threads
728	<	*         because it does not hold {@link
729	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
2648	>	* @return the targeted parallelism level of this pool
2649		*/
2650	<	public void setParallelism(int parallelism) {
2651	<	checkPermission();
733	<	if (parallelism <= 0 || parallelism > maxPoolSize)
734	<	throw new IllegalArgumentException();
735	<	final ReentrantLock lock = this.workerLock;
736	<	lock.lock();
737	<	try {
738	<	if (!isTerminating()) {
739	<	int p = this.parallelism;
740	<	this.parallelism = parallelism;
741	<	if (parallelism > p)
742	<	createAndStartAddedWorkers();
743	<	else
744	<	trimSpares();
745	<	}
746	<	} finally {
747	<	lock.unlock();
748	<	}
749	<	signalIdleWorkers();
2650	>	public int getParallelism() {
2651	>	return parallelism;
2652		}
2653
2654		/**
2655	<	* Returns the targeted number of worker threads in this pool.
2655	>	* Returns the targeted parallelism level of the common pool.
2656		*
2657	<	* @return the targeted number of worker threads in this pool
2657	>	* @return the targeted parallelism level of the common pool
2658		*/
2659	<	public int getParallelism() {
2660	<	return parallelism;
2659	>	public static int getCommonPoolParallelism() {
2660	>	return commonPoolParallelism;
2661		}
2662
2663		/**
2664		* Returns the number of worker threads that have started but not
2665	<	* yet terminated.  This result returned by this method may differ
2666	<	* from {@code getParallelism} when threads are created to
2665	>	* yet terminated.  The result returned by this method may differ
2666	>	* from {@link #getParallelism} when threads are created to
2667		* maintain parallelism when others are cooperatively blocked.
2668		*
2669		* @return the number of worker threads
2670		*/
2671		public int getPoolSize() {
2672	<	return totalCountOf(workerCounts);
771	<	}
772	<
773	<	/**
774	<	* Returns the maximum number of threads allowed to exist in the
775	<	* pool, even if there are insufficient unblocked running threads.
776	<	* @return the maximum
777	<	*/
778	<	public int getMaximumPoolSize() {
779	<	return maxPoolSize;
2672	>	return parallelism + (short)(ctl >>> TC_SHIFT);
2673		}
2674
2675		/**
2676	<	* Sets the maximum number of threads allowed to exist in the
784	<	* pool, even if there are insufficient unblocked running threads.
785	<	* Setting this value has no effect on current pool size. It
786	<	* controls construction of new threads.
787	<	* @throws IllegalArgumentException if negative or greater then
788	<	* internal implementation limit
789	<	*/
790	<	public void setMaximumPoolSize(int newMax) {
791	<	if (newMax < 0 || newMax > MAX_THREADS)
792	<	throw new IllegalArgumentException();
793	<	maxPoolSize = newMax;
794	<	}
795	<
796	<
797	<	/**
798	<	* Returns true if this pool dynamically maintains its target
799	<	* parallelism level. If false, new threads are added only to
800	<	* avoid possible starvation.
801	<	* This setting is by default true;
802	<	* @return true if maintains parallelism
803	<	*/
804	<	public boolean getMaintainsParallelism() {
805	<	return maintainsParallelism;
806	<	}
807	<
808	<	/**
809	<	* Sets whether this pool dynamically maintains its target
810	<	* parallelism level. If false, new threads are added only to
811	<	* avoid possible starvation.
812	<	* @param enable true to maintains parallelism
813	<	*/
814	<	public void setMaintainsParallelism(boolean enable) {
815	<	maintainsParallelism = enable;
816	<	}
817	<
818	<	/**
819	<	* Establishes local first-in-first-out scheduling mode for forked
820	<	* tasks that are never joined. This mode may be more appropriate
821	<	* than default locally stack-based mode in applications in which
822	<	* worker threads only process asynchronous tasks.  This method is
823	<	* designed to be invoked only when pool is quiescent, and
824	<	* typically only before any tasks are submitted. The effects of
825	<	* invocations at other times may be unpredictable.
826	<	*
827	<	* @param async if true, use locally FIFO scheduling
828	<	* @return the previous mode
829	<	*/
830	<	public boolean setAsyncMode(boolean async) {
831	<	boolean oldMode = locallyFifo;
832	<	locallyFifo = async;
833	<	ForkJoinWorkerThread[] ws = workers;
834	<	if (ws != null) {
835	<	for (int i = 0; i < ws.length; ++i) {
836	<	ForkJoinWorkerThread t = ws[i];
837	<	if (t != null)
838	<	t.setAsyncMode(async);
839	<	}
840	<	}
841	<	return oldMode;
842	<	}
843	<
844	<	/**
845	<	* Returns true if this pool uses local first-in-first-out
2676	>	* Returns {@code true} if this pool uses local first-in-first-out
2677		* scheduling mode for forked tasks that are never joined.
2678		*
2679	<	* @return true if this pool uses async mode
2679	>	* @return {@code true} if this pool uses async mode
2680		*/
2681		public boolean getAsyncMode() {
2682	<	return locallyFifo;
2682	>	return localMode != 0;
2683		}
2684
2685		/**
2686		* Returns an estimate of the number of worker threads that are
2687		* not blocked waiting to join tasks or for other managed
2688	<	* synchronization.
2688	>	* synchronization. This method may overestimate the
2689	>	* number of running threads.
2690		*
2691		* @return the number of worker threads
2692		*/
2693		public int getRunningThreadCount() {
2694	<	return runningCountOf(workerCounts);
2694	>	int rc = 0;
2695	>	WorkQueue[] ws; WorkQueue w;
2696	>	if ((ws = workQueues) != null) {
2697	>	for (int i = 1; i < ws.length; i += 2) {
2698	>	if ((w = ws[i]) != null && w.isApparentlyUnblocked())
2699	>	++rc;
2700	>	}
2701	>	}
2702	>	return rc;
2703		}
2704
2705		/**
2706		* Returns an estimate of the number of threads that are currently
2707		* stealing or executing tasks. This method may overestimate the
2708		* number of active threads.
2709	+	*
2710		* @return the number of active threads
2711		*/
2712		public int getActiveThreadCount() {
2713	<	return activeCountOf(runControl);
2714	<	}
874	<
875	<	/**
876	<	* Returns an estimate of the number of threads that are currently
877	<	* idle waiting for tasks. This method may underestimate the
878	<	* number of idle threads.
879	<	* @return the number of idle threads
880	<	*/
881	<	final int getIdleThreadCount() {
882	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
883	<	return (c <= 0)? 0 : c;
2713	>	int r = parallelism + (int)(ctl >> AC_SHIFT);
2714	>	return (r <= 0) ? 0 : r; // suppress momentarily negative values
2715		}
2716
2717		/**
2718	<	* Returns true if all worker threads are currently idle. An idle
2719	<	* worker is one that cannot obtain a task to execute because none
2720	<	* are available to steal from other threads, and there are no
2721	<	* pending submissions to the pool. This method is conservative:
2722	<	* It might not return true immediately upon idleness of all
2723	<	* threads, but will eventually become true if threads remain
2724	<	* inactive.
2725	<	* @return true if all threads are currently idle
2718	>	* Returns {@code true} if all worker threads are currently idle.
2719	>	* An idle worker is one that cannot obtain a task to execute
2720	>	* because none are available to steal from other threads, and
2721	>	* there are no pending submissions to the pool. This method is
2722	>	* conservative; it might not return {@code true} immediately upon
2723	>	* idleness of all threads, but will eventually become true if
2724	>	* threads remain inactive.
2725	>	*
2726	>	* @return {@code true} if all threads are currently idle
2727		*/
2728		public boolean isQuiescent() {
2729	<	return activeCountOf(runControl) == 0;
2729	>	return (int)(ctl >> AC_SHIFT) + parallelism == 0;
2730		}
2731
2732		/**
#	Line 902 | Line 2734 | public class ForkJoinPool extends Abstra
2734		* one thread's work queue by another. The reported value
2735		* underestimates the actual total number of steals when the pool
2736		* is not quiescent. This value may be useful for monitoring and
2737	<	* tuning fork/join programs: In general, steal counts should be
2737	>	* tuning fork/join programs: in general, steal counts should be
2738		* high enough to keep threads busy, but low enough to avoid
2739		* overhead and contention across threads.
2740	+	*
2741		* @return the number of steals
2742		*/
2743		public long getStealCount() {
2744	<	return stealCount.get();
2745	<	}
2746	<
2747	<	/**
2748	<	* Accumulate steal count from a worker. Call only
2749	<	* when worker known to be idle.
2750	<	*/
2751	<	private void updateStealCount(ForkJoinWorkerThread w) {
2752	<	int sc = w.getAndClearStealCount();
920	<	if (sc != 0)
921	<	stealCount.addAndGet(sc);
2744	>	long count = stealCount;
2745	>	WorkQueue[] ws; WorkQueue w;
2746	>	if ((ws = workQueues) != null) {
2747	>	for (int i = 1; i < ws.length; i += 2) {
2748	>	if ((w = ws[i]) != null)
2749	>	count += w.nsteals;
2750	>	}
2751	>	}
2752	>	return count;
2753		}
2754
2755		/**
#	Line 928 | Line 2759 | public class ForkJoinPool extends Abstra
2759		* an approximation, obtained by iterating across all threads in
2760		* the pool. This method may be useful for tuning task
2761		* granularities.
2762	+	*
2763		* @return the number of queued tasks
2764		*/
2765		public long getQueuedTaskCount() {
2766		long count = 0;
2767	<	ForkJoinWorkerThread[] ws = workers;
2768	<	if (ws != null) {
2769	<	for (int i = 0; i < ws.length; ++i) {
2770	<	ForkJoinWorkerThread t = ws[i];
2771	<	if (t != null)
940	<	count += t.getQueueSize();
2767	>	WorkQueue[] ws; WorkQueue w;
2768	>	if ((ws = workQueues) != null) {
2769	>	for (int i = 1; i < ws.length; i += 2) {
2770	>	if ((w = ws[i]) != null)
2771	>	count += w.queueSize();
2772		}
2773		}
2774		return count;
2775		}
2776
2777		/**
2778	<	* Returns an estimate of the number tasks submitted to this pool
2779	<	* that have not yet begun executing. This method takes time
2780	<	* proportional to the number of submissions.
2778	>	* Returns an estimate of the number of tasks submitted to this
2779	>	* pool that have not yet begun executing.  This method may take
2780	>	* time proportional to the number of submissions.
2781	>	*
2782		* @return the number of queued submissions
2783		*/
2784		public int getQueuedSubmissionCount() {
2785	<	return submissionQueue.size();
2785	>	int count = 0;
2786	>	WorkQueue[] ws; WorkQueue w;
2787	>	if ((ws = workQueues) != null) {
2788	>	for (int i = 0; i < ws.length; i += 2) {
2789	>	if ((w = ws[i]) != null)
2790	>	count += w.queueSize();
2791	>	}
2792	>	}
2793	>	return count;
2794		}
2795
2796		/**
2797	<	* Returns true if there are any tasks submitted to this pool
2798	<	* that have not yet begun executing.
2797	>	* Returns {@code true} if there are any tasks submitted to this
2798	>	* pool that have not yet begun executing.
2799	>	*
2800		* @return {@code true} if there are any queued submissions
2801		*/
2802		public boolean hasQueuedSubmissions() {
2803	<	return !submissionQueue.isEmpty();
2803	>	WorkQueue[] ws; WorkQueue w;
2804	>	if ((ws = workQueues) != null) {
2805	>	for (int i = 0; i < ws.length; i += 2) {
2806	>	if ((w = ws[i]) != null && w.queueSize() != 0)
2807	>	return true;
2808	>	}
2809	>	}
2810	>	return false;
2811		}
2812
2813		/**
2814		* Removes and returns the next unexecuted submission if one is
2815		* available.  This method may be useful in extensions to this
2816		* class that re-assign work in systems with multiple pools.
2817	<	* @return the next submission, or null if none
2817	>	*
2818	>	* @return the next submission, or {@code null} if none
2819		*/
2820		protected ForkJoinTask<?> pollSubmission() {
2821	<	return submissionQueue.poll();
2821	>	WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2822	>	if ((ws = workQueues) != null) {
2823	>	for (int i = 0; i < ws.length; i += 2) {
2824	>	if ((w = ws[i]) != null && (t = w.poll()) != null)
2825	>	return t;
2826	>	}
2827	>	}
2828	>	return null;
2829		}
2830
2831		/**
2832		* Removes all available unexecuted submitted and forked tasks
2833		* from scheduling queues and adds them to the given collection,
2834		* without altering their execution status. These may include
2835	<	* artificially generated or wrapped tasks. This method is designed
2836	<	* to be invoked only when the pool is known to be
2835	>	* artificially generated or wrapped tasks. This method is
2836	>	* designed to be invoked only when the pool is known to be
2837		* quiescent. Invocations at other times may not remove all
2838		* tasks. A failure encountered while attempting to add elements
2839		* to collection {@code c} may result in elements being in
#	Line 985 | Line 2841 | public class ForkJoinPool extends Abstra
2841		* exception is thrown.  The behavior of this operation is
2842		* undefined if the specified collection is modified while the
2843		* operation is in progress.
2844	+	*
2845		* @param c the collection to transfer elements into
2846		* @return the number of elements transferred
2847		*/
2848	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
2849	<	int n = submissionQueue.drainTo(c);
2850	<	ForkJoinWorkerThread[] ws = workers;
2851	<	if (ws != null) {
2848	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
2849	>	int count = 0;
2850	>	WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2851	>	if ((ws = workQueues) != null) {
2852		for (int i = 0; i < ws.length; ++i) {
2853	<	ForkJoinWorkerThread w = ws[i];
2854	<	if (w != null)
2855	<	n += w.drainTasksTo(c);
2853	>	if ((w = ws[i]) != null) {
2854	>	while ((t = w.poll()) != null) {
2855	>	c.add(t);
2856	>	++count;
2857	>	}
2858	>	}
2859		}
2860		}
2861	<	return n;
2861	>	return count;
2862		}
2863
2864		/**
#	Line 1009 | Line 2869 | public class ForkJoinPool extends Abstra
2869		* @return a string identifying this pool, as well as its state
2870		*/
2871		public String toString() {
2872	<	int ps = parallelism;
2873	<	int wc = workerCounts;
2874	<	int rc = runControl;
2875	<	long st = getStealCount();
2876	<	long qt = getQueuedTaskCount();
2877	<	long qs = getQueuedSubmissionCount();
2872	>	// Use a single pass through workQueues to collect counts
2873	>	long qt = 0L, qs = 0L; int rc = 0;
2874	>	long st = stealCount;
2875	>	long c = ctl;
2876	>	WorkQueue[] ws; WorkQueue w;
2877	>	if ((ws = workQueues) != null) {
2878	>	for (int i = 0; i < ws.length; ++i) {
2879	>	if ((w = ws[i]) != null) {
2880	>	int size = w.queueSize();
2881	>	if ((i & 1) == 0)
2882	>	qs += size;
2883	>	else {
2884	>	qt += size;
2885	>	st += w.nsteals;
2886	>	if (w.isApparentlyUnblocked())
2887	>	++rc;
2888	>	}
2889	>	}
2890	>	}
2891	>	}
2892	>	int pc = parallelism;
2893	>	int tc = pc + (short)(c >>> TC_SHIFT);
2894	>	int ac = pc + (int)(c >> AC_SHIFT);
2895	>	if (ac < 0) // ignore transient negative
2896	>	ac = 0;
2897	>	String level;
2898	>	if ((c & STOP_BIT) != 0)
2899	>	level = (tc == 0) ? "Terminated" : "Terminating";
2900	>	else
2901	>	level = plock < 0 ? "Shutting down" : "Running";
2902		return super.toString() +
2903	<	"[" + runStateToString(runStateOf(rc)) +
2904	<	", parallelism = " + ps +
2905	<	", size = " + totalCountOf(wc) +
2906	<	", active = " + activeCountOf(rc) +
2907	<	", running = " + runningCountOf(wc) +
2903	>	"[" + level +
2904	>	", parallelism = " + pc +
2905	>	", size = " + tc +
2906	>	", active = " + ac +
2907	>	", running = " + rc +
2908		", steals = " + st +
2909		", tasks = " + qt +
2910		", submissions = " + qs +
2911		"]";
2912		}
2913
1030	–	private static String runStateToString(int rs) {
1031	–	switch(rs) {
1032	–	case RUNNING: return "Running";
1033	–	case SHUTDOWN: return "Shutting down";
1034	–	case TERMINATING: return "Terminating";
1035	–	case TERMINATED: return "Terminated";
1036	–	default: throw new Error("Unknown run state");
1037	–	}
1038	–	}
1039	–
1040	–	// lifecycle control
1041	–
2914		/**
2915	<	* Initiates an orderly shutdown in which previously submitted
2916	<	* tasks are executed, but no new tasks will be accepted.
2917	<	* Invocation has no additional effect if already shut down.
2918	<	* Tasks that are in the process of being submitted concurrently
2919	<	* during the course of this method may or may not be rejected.
2915	>	* Possibly initiates an orderly shutdown in which previously
2916	>	* submitted tasks are executed, but no new tasks will be
2917	>	* accepted. Invocation has no effect on execution state if this
2918	>	* is the {@link #commonPool}, and no additional effect if
2919	>	* already shut down.  Tasks that are in the process of being
2920	>	* submitted concurrently during the course of this method may or
2921	>	* may not be rejected.
2922	>	*
2923		* @throws SecurityException if a security manager exists and
2924		*         the caller is not permitted to modify threads
2925		*         because it does not hold {@link
2926	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
2926	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
2927		*/
2928		public void shutdown() {
2929		checkPermission();
2930	<	transitionRunStateTo(SHUTDOWN);
1056	<	if (canTerminateOnShutdown(runControl))
1057	<	terminateOnShutdown();
2930	>	tryTerminate(false, true);
2931		}
2932
2933		/**
2934	<	* Attempts to stop all actively executing tasks, and cancels all
2935	<	* waiting tasks.  Tasks that are in the process of being
2936	<	* submitted or executed concurrently during the course of this
2937	<	* method may or may not be rejected. Unlike some other executors,
2938	<	* this method cancels rather than collects non-executed tasks
2939	<	* upon termination, so always returns an empty list. However, you
2940	<	* can use method {@code drainTasksTo} before invoking this
2941	<	* method to transfer unexecuted tasks to another collection.
2934	>	* Possibly attempts to cancel and/or stop all tasks, and reject
2935	>	* all subsequently submitted tasks.  Invocation has no effect on
2936	>	* execution state if this is the {@link #commonPool}, and no
2937	>	* additional effect if already shut down. Otherwise, tasks that
2938	>	* are in the process of being submitted or executed concurrently
2939	>	* during the course of this method may or may not be
2940	>	* rejected. This method cancels both existing and unexecuted
2941	>	* tasks, in order to permit termination in the presence of task
2942	>	* dependencies. So the method always returns an empty list
2943	>	* (unlike the case for some other Executors).
2944	>	*
2945		* @return an empty list
2946		* @throws SecurityException if a security manager exists and
2947		*         the caller is not permitted to modify threads
2948		*         because it does not hold {@link
2949	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
2949	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
2950		*/
2951		public List<Runnable> shutdownNow() {
2952		checkPermission();
2953	<	terminate();
2953	>	tryTerminate(true, true);
2954		return Collections.emptyList();
2955		}
2956
#	Line 1084 | Line 2960 | public class ForkJoinPool extends Abstra
2960		* @return {@code true} if all tasks have completed following shut down
2961		*/
2962		public boolean isTerminated() {
2963	<	return runStateOf(runControl) == TERMINATED;
2963	>	long c = ctl;
2964	>	return ((c & STOP_BIT) != 0L &&
2965	>	(short)(c >>> TC_SHIFT) == -parallelism);
2966		}
2967
2968		/**
2969		* Returns {@code true} if the process of termination has
2970	<	* commenced but possibly not yet completed.
2970	>	* commenced but not yet completed.  This method may be useful for
2971	>	* debugging. A return of {@code true} reported a sufficient
2972	>	* period after shutdown may indicate that submitted tasks have
2973	>	* ignored or suppressed interruption, or are waiting for IO,
2974	>	* causing this executor not to properly terminate. (See the
2975	>	* advisory notes for class {@link ForkJoinTask} stating that
2976	>	* tasks should not normally entail blocking operations.  But if
2977	>	* they do, they must abort them on interrupt.)
2978		*
2979	<	* @return {@code true} if terminating
2979	>	* @return {@code true} if terminating but not yet terminated
2980		*/
2981		public boolean isTerminating() {
2982	<	return runStateOf(runControl) >= TERMINATING;
2982	>	long c = ctl;
2983	>	return ((c & STOP_BIT) != 0L &&
2984	>	(short)(c >>> TC_SHIFT) != -parallelism);
2985		}
2986
2987		/**
#	Line 1103 | Line 2990 | public class ForkJoinPool extends Abstra
2990		* @return {@code true} if this pool has been shut down
2991		*/
2992		public boolean isShutdown() {
2993	<	return runStateOf(runControl) >= SHUTDOWN;
2993	>	return plock < 0;
2994		}
2995
2996		/**
2997	<	* Blocks until all tasks have completed execution after a shutdown
2998	<	* request, or the timeout occurs, or the current thread is
2999	<	* interrupted, whichever happens first.
2997	>	* Blocks until all tasks have completed execution after a
2998	>	* shutdown request, or the timeout occurs, or the current thread
2999	>	* is interrupted, whichever happens first. Note that the {@link
3000	>	* #commonPool()} never terminates until program shutdown so
3001	>	* this method will always time out.
3002		*
3003		* @param timeout the maximum time to wait
3004		* @param unit the time unit of the timeout argument
#	Line 1120 | Line 3009 | public class ForkJoinPool extends Abstra
3009		public boolean awaitTermination(long timeout, TimeUnit unit)
3010		throws InterruptedException {
3011		long nanos = unit.toNanos(timeout);
3012	<	final ReentrantLock lock = this.workerLock;
1124	<	lock.lock();
1125	<	try {
1126	<	for (;;) {
1127	<	if (isTerminated())
1128	<	return true;
1129	<	if (nanos <= 0)
1130	<	return false;
1131	<	nanos = termination.awaitNanos(nanos);
1132	<	}
1133	<	} finally {
1134	<	lock.unlock();
1135	<	}
1136	<	}
1137	<
1138	<	// Shutdown and termination support
1139	<
1140	<	/**
1141	<	* Callback from terminating worker. Null out the corresponding
1142	<	* workers slot, and if terminating, try to terminate, else try to
1143	<	* shrink workers array.
1144	<	* @param w the worker
1145	<	*/
1146	<	final void workerTerminated(ForkJoinWorkerThread w) {
1147	<	updateStealCount(w);
1148	<	updateWorkerCount(-1);
1149	<	final ReentrantLock lock = this.workerLock;
1150	<	lock.lock();
1151	<	try {
1152	<	ForkJoinWorkerThread[] ws = workers;
1153	<	if (ws != null) {
1154	<	int idx = w.poolIndex;
1155	<	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1156	<	ws[idx] = null;
1157	<	if (totalCountOf(workerCounts) == 0) {
1158	<	terminate(); // no-op if already terminating
1159	<	transitionRunStateTo(TERMINATED);
1160	<	termination.signalAll();
1161	<	}
1162	<	else if (!isTerminating()) {
1163	<	tryShrinkWorkerArray();
1164	<	tryResumeSpare(true); // allow replacement
1165	<	}
1166	<	}
1167	<	} finally {
1168	<	lock.unlock();
1169	<	}
1170	<	signalIdleWorkers();
1171	<	}
1172	<
1173	<	/**
1174	<	* Initiate termination.
1175	<	*/
1176	<	private void terminate() {
1177	<	if (transitionRunStateTo(TERMINATING)) {
1178	<	stopAllWorkers();
1179	<	resumeAllSpares();
1180	<	signalIdleWorkers();
1181	<	cancelQueuedSubmissions();
1182	<	cancelQueuedWorkerTasks();
1183	<	interruptUnterminatedWorkers();
1184	<	signalIdleWorkers(); // resignal after interrupt
1185	<	}
1186	<	}
1187	<
1188	<	/**
1189	<	* Possibly terminates when on shutdown state.
1190	<	*/
1191	<	private void terminateOnShutdown() {
1192	<	if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
1193	<	terminate();
1194	<	}
1195	<
1196	<	/**
1197	<	* Clears out and cancels submissions.
1198	<	*/
1199	<	private void cancelQueuedSubmissions() {
1200	<	ForkJoinTask<?> task;
1201	<	while ((task = pollSubmission()) != null)
1202	<	task.cancel(false);
1203	<	}
1204	<
1205	<	/**
1206	<	* Cleans out worker queues.
1207	<	*/
1208	<	private void cancelQueuedWorkerTasks() {
1209	<	final ReentrantLock lock = this.workerLock;
1210	<	lock.lock();
1211	<	try {
1212	<	ForkJoinWorkerThread[] ws = workers;
1213	<	if (ws != null) {
1214	<	for (int i = 0; i < ws.length; ++i) {
1215	<	ForkJoinWorkerThread t = ws[i];
1216	<	if (t != null)
1217	<	t.cancelTasks();
1218	<	}
1219	<	}
1220	<	} finally {
1221	<	lock.unlock();
1222	<	}
1223	<	}
1224	<
1225	<	/**
1226	<	* Sets each worker's status to terminating. Requires lock to avoid
1227	<	* conflicts with add/remove.
1228	<	*/
1229	<	private void stopAllWorkers() {
1230	<	final ReentrantLock lock = this.workerLock;
1231	<	lock.lock();
1232	<	try {
1233	<	ForkJoinWorkerThread[] ws = workers;
1234	<	if (ws != null) {
1235	<	for (int i = 0; i < ws.length; ++i) {
1236	<	ForkJoinWorkerThread t = ws[i];
1237	<	if (t != null)
1238	<	t.shutdownNow();
1239	<	}
1240	<	}
1241	<	} finally {
1242	<	lock.unlock();
1243	<	}
1244	<	}
1245	<
1246	<	/**
1247	<	* Interrupts all unterminated workers.  This is not required for
1248	<	* sake of internal control, but may help unstick user code during
1249	<	* shutdown.
1250	<	*/
1251	<	private void interruptUnterminatedWorkers() {
1252	<	final ReentrantLock lock = this.workerLock;
1253	<	lock.lock();
1254	<	try {
1255	<	ForkJoinWorkerThread[] ws = workers;
1256	<	if (ws != null) {
1257	<	for (int i = 0; i < ws.length; ++i) {
1258	<	ForkJoinWorkerThread t = ws[i];
1259	<	if (t != null && !t.isTerminated()) {
1260	<	try {
1261	<	t.interrupt();
1262	<	} catch (SecurityException ignore) {
1263	<	}
1264	<	}
1265	<	}
1266	<	}
1267	<	} finally {
1268	<	lock.unlock();
1269	<	}
1270	<	}
1271	<
1272	<
1273	<	/*
1274	<	* Nodes for event barrier to manage idle threads.  Queue nodes
1275	<	* are basic Treiber stack nodes, also used for spare stack.
1276	<	*
1277	<	* The event barrier has an event count and a wait queue (actually
1278	<	* a Treiber stack).  Workers are enabled to look for work when
1279	<	* the eventCount is incremented. If they fail to find work, they
1280	<	* may wait for next count. Upon release, threads help others wake
1281	<	* up.
1282	<	*
1283	<	* Synchronization events occur only in enough contexts to
1284	<	* maintain overall liveness:
1285	<	*
1286	<	*   - Submission of a new task to the pool
1287	<	*   - Resizes or other changes to the workers array
1288	<	*   - pool termination
1289	<	*   - A worker pushing a task on an empty queue
1290	<	*
1291	<	* The case of pushing a task occurs often enough, and is heavy
1292	<	* enough compared to simple stack pushes, to require special
1293	<	* handling: Method signalWork returns without advancing count if
1294	<	* the queue appears to be empty.  This would ordinarily result in
1295	<	* races causing some queued waiters not to be woken up. To avoid
1296	<	* this, the first worker enqueued in method sync (see
1297	<	* syncIsReleasable) rescans for tasks after being enqueued, and
1298	<	* helps signal if any are found. This works well because the
1299	<	* worker has nothing better to do, and so might as well help
1300	<	* alleviate the overhead and contention on the threads actually
1301	<	* doing work.  Also, since event counts increments on task
1302	<	* availability exist to maintain liveness (rather than to force
1303	<	* refreshes etc), it is OK for callers to exit early if
1304	<	* contending with another signaller.
1305	<	*/
1306	<	static final class WaitQueueNode {
1307	<	WaitQueueNode next; // only written before enqueued
1308	<	volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1309	<	final long count; // unused for spare stack
1310	<
1311	<	WaitQueueNode(long c, ForkJoinWorkerThread w) {
1312	<	count = c;
1313	<	thread = w;
1314	<	}
1315	<
1316	<	/**
1317	<	* Wakes up waiter, returning false if known to already
1318	<	*/
1319	<	boolean signal() {
1320	<	ForkJoinWorkerThread t = thread;
1321	<	if (t == null)
1322	<	return false;
1323	<	thread = null;
1324	<	LockSupport.unpark(t);
3012	>	if (isTerminated())
3013		return true;
3014	<	}
3015	<
3016	<	/**
3017	<	* Awaits release on sync.
3018	<	*/
3019	<	void awaitSyncRelease(ForkJoinPool p) {
3020	<	while (thread != null && !p.syncIsReleasable(this))
1333	<	LockSupport.park(this);
1334	<	}
1335	<
1336	<	/**
1337	<	* Awaits resumption as spare.
1338	<	*/
1339	<	void awaitSpareRelease() {
1340	<	while (thread != null) {
1341	<	if (!Thread.interrupted())
1342	<	LockSupport.park(this);
1343	<	}
1344	<	}
1345	<	}
1346	<
1347	<	/**
1348	<	* Ensures that no thread is waiting for count to advance from the
1349	<	* current value of eventCount read on entry to this method, by
1350	<	* releasing waiting threads if necessary.
1351	<	* @return the count
1352	<	*/
1353	<	final long ensureSync() {
1354	<	long c = eventCount;
1355	<	WaitQueueNode q;
1356	<	while ((q = syncStack) != null && q.count < c) {
1357	<	if (casBarrierStack(q, null)) {
1358	<	do {
1359	<	q.signal();
1360	<	} while ((q = q.next) != null);
1361	<	break;
1362	<	}
1363	<	}
1364	<	return c;
1365	<	}
1366	<
1367	<	/**
1368	<	* Increments event count and releases waiting threads.
1369	<	*/
1370	<	private void signalIdleWorkers() {
1371	<	long c;
1372	<	do;while (!casEventCount(c = eventCount, c+1));
1373	<	ensureSync();
1374	<	}
1375	<
1376	<	/**
1377	<	* Signals threads waiting to poll a task. Because method sync
1378	<	* rechecks availability, it is OK to only proceed if queue
1379	<	* appears to be non-empty, and OK to skip under contention to
1380	<	* increment count (since some other thread succeeded).
1381	<	*/
1382	<	final void signalWork() {
1383	<	long c;
1384	<	WaitQueueNode q;
1385	<	if (syncStack != null &&
1386	<	casEventCount(c = eventCount, c+1) &&
1387	<	(((q = syncStack) != null && q.count <= c) &&
1388	<	(!casBarrierStack(q, q.next) || !q.signal())))
1389	<	ensureSync();
1390	<	}
1391	<
1392	<	/**
1393	<	* Waits until event count advances from last value held by
1394	<	* caller, or if excess threads, caller is resumed as spare, or
1395	<	* caller or pool is terminating. Updates caller's event on exit.
1396	<	* @param w the calling worker thread
1397	<	*/
1398	<	final void sync(ForkJoinWorkerThread w) {
1399	<	updateStealCount(w); // Transfer w's count while it is idle
1400	<
1401	<	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1402	<	long prev = w.lastEventCount;
1403	<	WaitQueueNode node = null;
1404	<	WaitQueueNode h;
1405	<	while (eventCount == prev &&
1406	<	((h = syncStack) == null || h.count == prev)) {
1407	<	if (node == null)
1408	<	node = new WaitQueueNode(prev, w);
1409	<	if (casBarrierStack(node.next = h, node)) {
1410	<	node.awaitSyncRelease(this);
1411	<	break;
1412	<	}
1413	<	}
1414	<	long ec = ensureSync();
1415	<	if (ec != prev) {
1416	<	w.lastEventCount = ec;
1417	<	break;
1418	<	}
1419	<	}
1420	<	}
1421	<
1422	<	/**
1423	<	* Returns true if worker waiting on sync can proceed:
1424	<	*  - on signal (thread == null)
1425	<	*  - on event count advance (winning race to notify vs signaller)
1426	<	*  - on Interrupt
1427	<	*  - if the first queued node, we find work available
1428	<	* If node was not signalled and event count not advanced on exit,
1429	<	* then we also help advance event count.
1430	<	* @return true if node can be released
1431	<	*/
1432	<	final boolean syncIsReleasable(WaitQueueNode node) {
1433	<	long prev = node.count;
1434	<	if (!Thread.interrupted() && node.thread != null &&
1435	<	(node.next != null ||
1436	<	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1437	<	eventCount == prev)
1438	<	return false;
1439	<	if (node.thread != null) {
1440	<	node.thread = null;
1441	<	long ec = eventCount;
1442	<	if (prev <= ec) // help signal
1443	<	casEventCount(ec, ec+1);
1444	<	}
1445	<	return true;
1446	<	}
1447	<
1448	<	/**
1449	<	* Returns true if a new sync event occurred since last call to
1450	<	* sync or this method, if so, updating caller's count.
1451	<	*/
1452	<	final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1453	<	long lc = w.lastEventCount;
1454	<	long ec = ensureSync();
1455	<	if (ec == lc)
1456	<	return false;
1457	<	w.lastEventCount = ec;
1458	<	return true;
1459	<	}
1460	<
1461	<	//  Parallelism maintenance
1462	<
1463	<	/**
1464	<	* Decrements running count; if too low, adds spare.
1465	<	*
1466	<	* Conceptually, all we need to do here is add or resume a
1467	<	* spare thread when one is about to block (and remove or
1468	<	* suspend it later when unblocked -- see suspendIfSpare).
1469	<	* However, implementing this idea requires coping with
1470	<	* several problems: We have imperfect information about the
1471	<	* states of threads. Some count updates can and usually do
1472	<	* lag run state changes, despite arrangements to keep them
1473	<	* accurate (for example, when possible, updating counts
1474	<	* before signalling or resuming), especially when running on
1475	<	* dynamic JVMs that don't optimize the infrequent paths that
1476	<	* update counts. Generating too many threads can make these
1477	<	* problems become worse, because excess threads are more
1478	<	* likely to be context-switched with others, slowing them all
1479	<	* down, especially if there is no work available, so all are
1480	<	* busy scanning or idling.  Also, excess spare threads can
1481	<	* only be suspended or removed when they are idle, not
1482	<	* immediately when they aren't needed. So adding threads will
1483	<	* raise parallelism level for longer than necessary.  Also,
1484	<	* FJ applications often encounter highly transient peaks when
1485	<	* many threads are blocked joining, but for less time than it
1486	<	* takes to create or resume spares.
1487	<	*
1488	<	* @param joinMe if non-null, return early if done
1489	<	* @param maintainParallelism if true, try to stay within
1490	<	* target counts, else create only to avoid starvation
1491	<	* @return true if joinMe known to be done
1492	<	*/
1493	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1494	<	maintainParallelism &= maintainsParallelism; // overrride
1495	<	boolean dec = false;  // true when running count decremented
1496	<	while (spareStack == null || !tryResumeSpare(dec)) {
1497	<	int counts = workerCounts;
1498	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1499	<	if (!needSpare(counts, maintainParallelism))
1500	<	break;
1501	<	if (joinMe.status < 0)
1502	<	return true;
1503	<	if (tryAddSpare(counts))
3014	>	long startTime = System.nanoTime();
3015	>	boolean terminated = false;
3016	>	synchronized (this) {
3017	>	for (long waitTime = nanos, millis = 0L;;) {
3018	>	if (terminated = isTerminated() ||
3019	>	waitTime <= 0L ||
3020	>	(millis = unit.toMillis(waitTime)) <= 0L)
3021		break;
3022	+	wait(millis);
3023	+	waitTime = nanos - (System.nanoTime() - startTime);
3024		}
3025		}
3026	<	return false;
1508	<	}
1509	<
1510	<	/**
1511	<	* Same idea as preJoin
1512	<	*/
1513	<	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1514	<	maintainParallelism &= maintainsParallelism;
1515	<	boolean dec = false;
1516	<	while (spareStack == null || !tryResumeSpare(dec)) {
1517	<	int counts = workerCounts;
1518	<	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1519	<	if (!needSpare(counts, maintainParallelism))
1520	<	break;
1521	<	if (blocker.isReleasable())
1522	<	return true;
1523	<	if (tryAddSpare(counts))
1524	<	break;
1525	<	}
1526	<	}
1527	<	return false;
1528	<	}
1529	<
1530	<	/**
1531	<	* Returns true if a spare thread appears to be needed.  If
1532	<	* maintaining parallelism, returns true when the deficit in
1533	<	* running threads is more than the surplus of total threads, and
1534	<	* there is apparently some work to do.  This self-limiting rule
1535	<	* means that the more threads that have already been added, the
1536	<	* less parallelism we will tolerate before adding another.
1537	<	* @param counts current worker counts
1538	<	* @param maintainParallelism try to maintain parallelism
1539	<	*/
1540	<	private boolean needSpare(int counts, boolean maintainParallelism) {
1541	<	int ps = parallelism;
1542	<	int rc = runningCountOf(counts);
1543	<	int tc = totalCountOf(counts);
1544	<	int runningDeficit = ps - rc;
1545	<	int totalSurplus = tc - ps;
1546	<	return (tc < maxPoolSize &&
1547	<	(rc == 0 || totalSurplus < 0 ||
1548	<	(maintainParallelism &&
1549	<	runningDeficit > totalSurplus &&
1550	<	ForkJoinWorkerThread.hasQueuedTasks(workers))));
1551	<	}
1552	<
1553	<	/**
1554	<	* Adds a spare worker if lock available and no more than the
1555	<	* expected numbers of threads exist.
1556	<	* @return true if successful
1557	<	*/
1558	<	private boolean tryAddSpare(int expectedCounts) {
1559	<	final ReentrantLock lock = this.workerLock;
1560	<	int expectedRunning = runningCountOf(expectedCounts);
1561	<	int expectedTotal = totalCountOf(expectedCounts);
1562	<	boolean success = false;
1563	<	boolean locked = false;
1564	<	// confirm counts while locking; CAS after obtaining lock
1565	<	try {
1566	<	for (;;) {
1567	<	int s = workerCounts;
1568	<	int tc = totalCountOf(s);
1569	<	int rc = runningCountOf(s);
1570	<	if (rc > expectedRunning || tc > expectedTotal)
1571	<	break;
1572	<	if (!locked && !(locked = lock.tryLock()))
1573	<	break;
1574	<	if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) {
1575	<	createAndStartSpare(tc);
1576	<	success = true;
1577	<	break;
1578	<	}
1579	<	}
1580	<	} finally {
1581	<	if (locked)
1582	<	lock.unlock();
1583	<	}
1584	<	return success;
1585	<	}
1586	<
1587	<	/**
1588	<	* Adds the kth spare worker. On entry, pool counts are already
1589	<	* adjusted to reflect addition.
1590	<	*/
1591	<	private void createAndStartSpare(int k) {
1592	<	ForkJoinWorkerThread w = null;
1593	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1);
1594	<	int len = ws.length;
1595	<	// Probably, we can place at slot k. If not, find empty slot
1596	<	if (k < len && ws[k] != null) {
1597	<	for (k = 0; k < len && ws[k] != null; ++k)
1598	<	;
1599	<	}
1600	<	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1601	<	ws[k] = w;
1602	<	w.start();
1603	<	}
1604	<	else
1605	<	updateWorkerCount(-1); // adjust on failure
1606	<	signalIdleWorkers();
1607	<	}
1608	<
1609	<	/**
1610	<	* Suspends calling thread w if there are excess threads.  Called
1611	<	* only from sync.  Spares are enqueued in a Treiber stack using
1612	<	* the same WaitQueueNodes as barriers.  They are resumed mainly
1613	<	* in preJoin, but are also woken on pool events that require all
1614	<	* threads to check run state.
1615	<	* @param w the caller
1616	<	*/
1617	<	private boolean suspendIfSpare(ForkJoinWorkerThread w) {
1618	<	WaitQueueNode node = null;
1619	<	int s;
1620	<	while (parallelism < runningCountOf(s = workerCounts)) {
1621	<	if (node == null)
1622	<	node = new WaitQueueNode(0, w);
1623	<	if (casWorkerCounts(s, s-1)) { // representation-dependent
1624	<	// push onto stack
1625	<	do;while (!casSpareStack(node.next = spareStack, node));
1626	<	// block until released by resumeSpare
1627	<	node.awaitSpareRelease();
1628	<	return true;
1629	<	}
1630	<	}
1631	<	return false;
1632	<	}
1633	<
1634	<	/**
1635	<	* Tries to pop and resume a spare thread.
1636	<	* @param updateCount if true, increment running count on success
1637	<	* @return true if successful
1638	<	*/
1639	<	private boolean tryResumeSpare(boolean updateCount) {
1640	<	WaitQueueNode q;
1641	<	while ((q = spareStack) != null) {
1642	<	if (casSpareStack(q, q.next)) {
1643	<	if (updateCount)
1644	<	updateRunningCount(1);
1645	<	q.signal();
1646	<	return true;
1647	<	}
1648	<	}
1649	<	return false;
1650	<	}
1651	<
1652	<	/**
1653	<	* Pops and resumes all spare threads. Same idea as ensureSync.
1654	<	* @return true if any spares released
1655	<	*/
1656	<	private boolean resumeAllSpares() {
1657	<	WaitQueueNode q;
1658	<	while ( (q = spareStack) != null) {
1659	<	if (casSpareStack(q, null)) {
1660	<	do {
1661	<	updateRunningCount(1);
1662	<	q.signal();
1663	<	} while ((q = q.next) != null);
1664	<	return true;
1665	<	}
1666	<	}
1667	<	return false;
1668	<	}
1669	<
1670	<	/**
1671	<	* Pops and shuts down excessive spare threads. Call only while
1672	<	* holding lock. This is not guaranteed to eliminate all excess
1673	<	* threads, only those suspended as spares, which are the ones
1674	<	* unlikely to be needed in the future.
1675	<	*/
1676	<	private void trimSpares() {
1677	<	int surplus = totalCountOf(workerCounts) - parallelism;
1678	<	WaitQueueNode q;
1679	<	while (surplus > 0 && (q = spareStack) != null) {
1680	<	if (casSpareStack(q, null)) {
1681	<	do {
1682	<	updateRunningCount(1);
1683	<	ForkJoinWorkerThread w = q.thread;
1684	<	if (w != null && surplus > 0 &&
1685	<	runningCountOf(workerCounts) > 0 && w.shutdown())
1686	<	--surplus;
1687	<	q.signal();
1688	<	} while ((q = q.next) != null);
1689	<	}
1690	<	}
3026	>	return terminated;
3027		}
3028
3029		/**
3030		* Interface for extending managed parallelism for tasks running
3031	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
3032	<	* Method {@code isReleasable} must return true if blocking is not
3033	<	* necessary. Method {@code block} blocks the current thread
3034	<	* if necessary (perhaps internally invoking isReleasable before
3035	<	* actually blocking.).
3031	>	* in {@link ForkJoinPool}s.
3032	>	*
3033	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
3034	>	* {@code isReleasable} must return {@code true} if blocking is
3035	>	* not necessary. Method {@code block} blocks the current thread
3036	>	* if necessary (perhaps internally invoking {@code isReleasable}
3037	>	* before actually blocking). These actions are performed by any
3038	>	* thread invoking {@link ForkJoinPool#managedBlock}.  The
3039	>	* unusual methods in this API accommodate synchronizers that may,
3040	>	* but don't usually, block for long periods. Similarly, they
3041	>	* allow more efficient internal handling of cases in which
3042	>	* additional workers may be, but usually are not, needed to
3043	>	* ensure sufficient parallelism.  Toward this end,
3044	>	* implementations of method {@code isReleasable} must be amenable
3045	>	* to repeated invocation.
3046	>	*
3047		* <p>For example, here is a ManagedBlocker based on a
3048		* ReentrantLock:
3049	<	* <pre>
3050	<	*   class ManagedLocker implements ManagedBlocker {
3051	<	*     final ReentrantLock lock;
3052	<	*     boolean hasLock = false;
3053	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
3054	<	*     public boolean block() {
3055	<	*        if (!hasLock)
3056	<	*           lock.lock();
3057	<	*        return true;
3058	<	*     }
3059	<	*     public boolean isReleasable() {
3060	<	*        return hasLock || (hasLock = lock.tryLock());
3061	<	*     }
3049	>	*  <pre> {@code
3050	>	* class ManagedLocker implements ManagedBlocker {
3051	>	*   final ReentrantLock lock;
3052	>	*   boolean hasLock = false;
3053	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
3054	>	*   public boolean block() {
3055	>	*     if (!hasLock)
3056	>	*       lock.lock();
3057	>	*     return true;
3058	>	*   }
3059	>	*   public boolean isReleasable() {
3060	>	*     return hasLock || (hasLock = lock.tryLock());
3061	>	*   }
3062	>	* }}</pre>
3063	>	*
3064	>	* <p>Here is a class that possibly blocks waiting for an
3065	>	* item on a given queue:
3066	>	*  <pre> {@code
3067	>	* class QueueTaker<E> implements ManagedBlocker {
3068	>	*   final BlockingQueue<E> queue;
3069	>	*   volatile E item = null;
3070	>	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
3071	>	*   public boolean block() throws InterruptedException {
3072	>	*     if (item == null)
3073	>	*       item = queue.take();
3074	>	*     return true;
3075		*   }
3076	<	* </pre>
3076	>	*   public boolean isReleasable() {
3077	>	*     return item != null || (item = queue.poll()) != null;
3078	>	*   }
3079	>	*   public E getItem() { // call after pool.managedBlock completes
3080	>	*     return item;
3081	>	*   }
3082	>	* }}</pre>
3083		*/
3084		public static interface ManagedBlocker {
3085		/**
3086		* Possibly blocks the current thread, for example waiting for
3087		* a lock or condition.
3088	<	* @return true if no additional blocking is necessary (i.e.,
3089	<	* if isReleasable would return true)
3088	>	*
3089	>	* @return {@code true} if no additional blocking is necessary
3090	>	* (i.e., if isReleasable would return true)
3091		* @throws InterruptedException if interrupted while waiting
3092	<	* (the method is not required to do so, but is allowed to).
3092	>	* (the method is not required to do so, but is allowed to)
3093		*/
3094		boolean block() throws InterruptedException;
3095
3096		/**
3097	<	* Returns true if blocking is unnecessary.
3097	>	* Returns {@code true} if blocking is unnecessary.
3098		*/
3099		boolean isReleasable();
3100		}
3101
3102		/**
3103		* Blocks in accord with the given blocker.  If the current thread
3104	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
3105	<	* spare thread to be activated if necessary to ensure parallelism
3106	<	* while the current thread is blocked.  If
3107	<	* {@code maintainParallelism} is true and the pool supports
3108	<	* it ({@link #getMaintainsParallelism}), this method attempts to
3109	<	* maintain the pool's nominal parallelism. Otherwise if activates
3110	<	* a thread only if necessary to avoid complete starvation. This
3111	<	* option may be preferable when blockages use timeouts, or are
3112	<	* almost always brief.
3113	<	*
3114	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
3115	<	* equivalent to
3116	<	* <pre>
3117	<	*   while (!blocker.isReleasable())
1751	<	*      if (blocker.block())
1752	<	*         return;
1753	<	* </pre>
1754	<	* If the caller is a ForkJoinTask, then the pool may first
1755	<	* be expanded to ensure parallelism, and later adjusted.
3104	>	* is a {@link ForkJoinWorkerThread}, this method possibly
3105	>	* arranges for a spare thread to be activated if necessary to
3106	>	* ensure sufficient parallelism while the current thread is blocked.
3107	>	*
3108	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
3109	>	* behaviorally equivalent to
3110	>	*  <pre> {@code
3111	>	* while (!blocker.isReleasable())
3112	>	*   if (blocker.block())
3113	>	*     return;
3114	>	* }</pre>
3115	>	*
3116	>	* If the caller is a {@code ForkJoinTask}, then the pool may
3117	>	* first be expanded to ensure parallelism, and later adjusted.
3118		*
3119		* @param blocker the blocker
1758	–	* @param maintainParallelism if true and supported by this pool,
1759	–	* attempt to maintain the pool's nominal parallelism; otherwise
1760	–	* activate a thread only if necessary to avoid complete
1761	–	* starvation.
3120		* @throws InterruptedException if blocker.block did so
3121		*/
3122	<	public static void managedBlock(ManagedBlocker blocker,
1765	<	boolean maintainParallelism)
3122	>	public static void managedBlock(ManagedBlocker blocker)
3123		throws InterruptedException {
3124		Thread t = Thread.currentThread();
3125	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
3126	<	((ForkJoinWorkerThread)t).pool : null);
3127	<	if (!blocker.isReleasable()) {
3128	<	try {
3129	<	if (pool == null ||
3130	<	!pool.preBlock(blocker, maintainParallelism))
3131	<	awaitBlocker(blocker);
3132	<	} finally {
3133	<	if (pool != null)
3134	<	pool.updateRunningCount(1);
3125	>	if (t instanceof ForkJoinWorkerThread) {
3126	>	ForkJoinPool p = ((ForkJoinWorkerThread)t).pool;
3127	>	while (!blocker.isReleasable()) { // variant of helpSignal
3128	>	WorkQueue[] ws; WorkQueue q; int m, n;
3129	>	if ((ws = p.workQueues) != null && (m = ws.length - 1) >= 0) {
3130	>	for (int i = 0; i <= m; ++i) {
3131	>	if (blocker.isReleasable())
3132	>	return;
3133	>	if ((q = ws[i]) != null && (n = q.queueSize()) > 0) {
3134	>	p.signalWork(q, n);
3135	>	if ((int)(p.ctl >> AC_SHIFT) >= 0)
3136	>	break;
3137	>	}
3138	>	}
3139	>	}
3140	>	if (p.tryCompensate()) {
3141	>	try {
3142	>	do {} while (!blocker.isReleasable() &&
3143	>	!blocker.block());
3144	>	} finally {
3145	>	p.incrementActiveCount();
3146	>	}
3147	>	break;
3148	>	}
3149		}
3150		}
3151	+	else {
3152	+	do {} while (!blocker.isReleasable() &&
3153	+	!blocker.block());
3154	+	}
3155		}
3156
3157	<	private static void awaitBlocker(ManagedBlocker blocker)
3158	<	throws InterruptedException {
3159	<	do;while (!blocker.isReleasable() && !blocker.block());
1785	<	}
1786	<
1787	<	// AbstractExecutorService overrides
3157	>	// AbstractExecutorService overrides.  These rely on undocumented
3158	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
3159	>	// implement RunnableFuture.
3160
3161		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
3162	<	return new AdaptedRunnable(runnable, value);
3162	>	return new ForkJoinTask.AdaptedRunnable<T>(runnable, value);
3163		}
3164
3165		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
3166	<	return new AdaptedCallable(callable);
3166	>	return new ForkJoinTask.AdaptedCallable<T>(callable);
3167		}
3168
3169	+	// Unsafe mechanics
3170	+	private static final sun.misc.Unsafe U;
3171	+	private static final long CTL;
3172	+	private static final long PARKBLOCKER;
3173	+	private static final int ABASE;
3174	+	private static final int ASHIFT;
3175	+	private static final long STEALCOUNT;
3176	+	private static final long PLOCK;
3177	+	private static final long INDEXSEED;
3178	+	private static final long QLOCK;
3179	+
3180	+	static {
3181	+	// Establish common pool parameters
3182	+	// TBD: limit or report ignored exceptions?
3183	+
3184	+	int par = 0;
3185	+	ForkJoinWorkerThreadFactory fac = null;
3186	+	Thread.UncaughtExceptionHandler handler = null;
3187	+	try {
3188	+	String pp = System.getProperty(propPrefix + "parallelism");
3189	+	String hp = System.getProperty(propPrefix + "exceptionHandler");
3190	+	String fp = System.getProperty(propPrefix + "threadFactory");
3191	+	if (fp != null)
3192	+	fac = ((ForkJoinWorkerThreadFactory)ClassLoader.
3193	+	getSystemClassLoader().loadClass(fp).newInstance());
3194	+	if (hp != null)
3195	+	handler = ((Thread.UncaughtExceptionHandler)ClassLoader.
3196	+	getSystemClassLoader().loadClass(hp).newInstance());
3197	+	if (pp != null)
3198	+	par = Integer.parseInt(pp);
3199	+	} catch (Exception ignore) {
3200	+	}
3201
3202	<	// Temporary Unsafe mechanics for preliminary release
1799	<	private static Unsafe getUnsafe() throws Throwable {
3202	>	int s; // initialize field offsets for CAS etc
3203		try {
3204	<	return Unsafe.getUnsafe();
3204	>	U = getUnsafe();
3205	>	Class<?> k = ForkJoinPool.class;
3206	>	CTL = U.objectFieldOffset
3207	>	(k.getDeclaredField("ctl"));
3208	>	STEALCOUNT = U.objectFieldOffset
3209	>	(k.getDeclaredField("stealCount"));
3210	>	PLOCK = U.objectFieldOffset
3211	>	(k.getDeclaredField("plock"));
3212	>	INDEXSEED = U.objectFieldOffset
3213	>	(k.getDeclaredField("indexSeed"));
3214	>	Class<?> tk = Thread.class;
3215	>	PARKBLOCKER = U.objectFieldOffset
3216	>	(tk.getDeclaredField("parkBlocker"));
3217	>	Class<?> wk = WorkQueue.class;
3218	>	QLOCK = U.objectFieldOffset
3219	>	(wk.getDeclaredField("qlock"));
3220	>	Class<?> ak = ForkJoinTask[].class;
3221	>	ABASE = U.arrayBaseOffset(ak);
3222	>	s = U.arrayIndexScale(ak);
3223	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3224	>	} catch (Exception e) {
3225	>	throw new Error(e);
3226	>	}
3227	>	if ((s & (s-1)) != 0)
3228	>	throw new Error("data type scale not a power of two");
3229	>
3230	>	/*
3231	>	* For extra caution, computations to set up pool state are
3232	>	* here; the constructor just assigns these values to fields.
3233	>	*/
3234	>	ForkJoinWorkerThreadFactory defaultFac =
3235	>	defaultForkJoinWorkerThreadFactory =
3236	>	new DefaultForkJoinWorkerThreadFactory();
3237	>	if (fac == null)
3238	>	fac = defaultFac;
3239	>	if (par <= 0)
3240	>	par = Runtime.getRuntime().availableProcessors();
3241	>	if (par > MAX_CAP)
3242	>	par = MAX_CAP;
3243	>	long np = (long)(-par); // precompute initial ctl value
3244	>	long ct = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
3245	>
3246	>	commonPoolParallelism = par;
3247	>	commonPool = new ForkJoinPool(par, ct, fac, handler);
3248	>	modifyThreadPermission = new RuntimePermission("modifyThread");
3249	>	submitters = new ThreadLocal<Submitter>();
3250	>	}
3251	>
3252	>	/**
3253	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
3254	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
3255	>	* into a jdk.
3256	>	*
3257	>	* @return a sun.misc.Unsafe
3258	>	*/
3259	>	private static sun.misc.Unsafe getUnsafe() {
3260	>	try {
3261	>	return sun.misc.Unsafe.getUnsafe();
3262		} catch (SecurityException se) {
3263		try {
3264		return java.security.AccessController.doPrivileged
3265	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
3266	<	public Unsafe run() throws Exception {
3267	<	return getUnsafePrivileged();
3265	>	(new java.security
3266	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
3267	>	public sun.misc.Unsafe run() throws Exception {
3268	>	java.lang.reflect.Field f = sun.misc
3269	>	.Unsafe.class.getDeclaredField("theUnsafe");
3270	>	f.setAccessible(true);
3271	>	return (sun.misc.Unsafe) f.get(null);
3272		}});
3273		} catch (java.security.PrivilegedActionException e) {
3274	<	throw e.getCause();
3274	>	throw new RuntimeException("Could not initialize intrinsics",
3275	>	e.getCause());
3276		}
3277		}
3278		}
3279
1815	–	private static Unsafe getUnsafePrivileged()
1816	–	throws NoSuchFieldException, IllegalAccessException {
1817	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1818	–	f.setAccessible(true);
1819	–	return (Unsafe) f.get(null);
1820	–	}
1821	–
1822	–	private static long fieldOffset(String fieldName)
1823	–	throws NoSuchFieldException {
1824	–	return UNSAFE.objectFieldOffset
1825	–	(ForkJoinPool.class.getDeclaredField(fieldName));
1826	–	}
1827	–
1828	–	static final Unsafe UNSAFE;
1829	–	static final long eventCountOffset;
1830	–	static final long workerCountsOffset;
1831	–	static final long runControlOffset;
1832	–	static final long syncStackOffset;
1833	–	static final long spareStackOffset;
1834	–
1835	–	static {
1836	–	try {
1837	–	UNSAFE = getUnsafe();
1838	–	eventCountOffset = fieldOffset("eventCount");
1839	–	workerCountsOffset = fieldOffset("workerCounts");
1840	–	runControlOffset = fieldOffset("runControl");
1841	–	syncStackOffset = fieldOffset("syncStack");
1842	–	spareStackOffset = fieldOffset("spareStack");
1843	–	} catch (Throwable e) {
1844	–	throw new RuntimeException("Could not initialize intrinsics", e);
1845	–	}
1846	–	}
1847	–
1848	–	private boolean casEventCount(long cmp, long val) {
1849	–	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1850	–	}
1851	–	private boolean casWorkerCounts(int cmp, int val) {
1852	–	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1853	–	}
1854	–	private boolean casRunControl(int cmp, int val) {
1855	–	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1856	–	}
1857	–	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1858	–	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1859	–	}
1860	–	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1861	–	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1862	–	}
3280		}

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