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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.17 by jsr166, Thu Jul 23 23:07:57 2009 UTC vs.
Revision 1.148 by jsr166, Tue Nov 20 06:18:39 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	>	* block 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
322	>	* level).  These primary signals are buttressed by signals
323	>	* whenever other threads scan for work or do not have a task to
324	>	* process (including the case of leaving a hint to unparked
325	>	* threads to help signal others upon wakeup).  On most platforms,
326	>	* signalling (unpark) overhead time is noticeably long, and the
327	>	* time between signalling a thread and it actually making
328	>	* progress can be very noticeably long, so it is worth offloading
329	>	* these delays from critical paths as much as possible.
330	>	*
331	>	* Trimming workers. To release resources after periods of lack of
332	>	* use, a worker starting to wait when the pool is quiescent will
333	>	* time out and terminate if the pool has remained quiescent for a
334	>	* given period -- a short period if there are more threads than
335	>	* parallelism, longer as the number of threads decreases. This
336	>	* will slowly propagate, eventually terminating all workers after
337	>	* periods of non-use.
338	>	*
339	>	* Shutdown and Termination. A call to shutdownNow atomically sets
340	>	* a plock bit and then (non-atomically) sets each worker's
341	>	* qlock status, cancels all unprocessed tasks, and wakes up
342	>	* all waiting workers.  Detecting whether termination should
343	>	* commence after a non-abrupt shutdown() call requires more work
344	>	* and bookkeeping. We need consensus about quiescence (i.e., that
345	>	* there is no more work). The active count provides a primary
346	>	* indication but non-abrupt shutdown still requires a rechecking
347	>	* scan for any workers that are inactive but not queued.
348	>	*
349	>	* Joining Tasks
350	>	* =============
351	>	*
352	>	* Any of several actions may be taken when one worker is waiting
353	>	* to join a task stolen (or always held) by another.  Because we
354	>	* are multiplexing many tasks on to a pool of workers, we can't
355	>	* just let them block (as in Thread.join).  We also cannot just
356	>	* reassign the joiner's run-time stack with another and replace
357	>	* it later, which would be a form of "continuation", that even if
358	>	* possible is not necessarily a good idea since we sometimes need
359	>	* both an unblocked task and its continuation to progress.
360	>	* Instead we combine two tactics:
361	>	*
362	>	*   Helping: Arranging for the joiner to execute some task that it
363	>	*      would be running if the steal had not occurred.
364	>	*
365	>	*   Compensating: Unless there are already enough live threads,
366	>	*      method tryCompensate() may create or re-activate a spare
367	>	*      thread to compensate for blocked joiners until they unblock.
368	>	*
369	>	* A third form (implemented in tryRemoveAndExec) amounts to
370	>	* helping a hypothetical compensator: If we can readily tell that
371	>	* a possible action of a compensator is to steal and execute the
372	>	* task being joined, the joining thread can do so directly,
373	>	* without the need for a compensation thread (although at the
374	>	* expense of larger run-time stacks, but the tradeoff is
375	>	* typically worthwhile).
376	>	*
377	>	* The ManagedBlocker extension API can't use helping so relies
378	>	* only on compensation in method awaitBlocker.
379	>	*
380	>	* The algorithm in tryHelpStealer entails a form of "linear"
381	>	* helping: Each worker records (in field currentSteal) the most
382	>	* recent task it stole from some other worker. Plus, it records
383	>	* (in field currentJoin) the task it is currently actively
384	>	* joining. Method tryHelpStealer uses these markers to try to
385	>	* find a worker to help (i.e., steal back a task from and execute
386	>	* it) that could hasten completion of the actively joined task.
387	>	* In essence, the joiner executes a task that would be on its own
388	>	* local deque had the to-be-joined task not been stolen. This may
389	>	* be seen as a conservative variant of the approach in Wagner &
390	>	* Calder "Leapfrogging: a portable technique for implementing
391	>	* efficient futures" SIGPLAN Notices, 1993
392	>	* (http://portal.acm.org/citation.cfm?id=155354). It differs in
393	>	* that: (1) We only maintain dependency links across workers upon
394	>	* steals, rather than use per-task bookkeeping.  This sometimes
395	>	* requires a linear scan of workQueues array to locate stealers,
396	>	* but often doesn't because stealers leave hints (that may become
397	>	* stale/wrong) of where to locate them.  It is only a hint
398	>	* because a worker might have had multiple steals and the hint
399	>	* records only one of them (usually the most current).  Hinting
400	>	* isolates cost to when it is needed, rather than adding to
401	>	* per-task overhead.  (2) It is "shallow", ignoring nesting and
402	>	* potentially cyclic mutual steals.  (3) It is intentionally
403	>	* racy: field currentJoin is updated only while actively joining,
404	>	* which means that we miss links in the chain during long-lived
405	>	* tasks, GC stalls etc (which is OK since blocking in such cases
406	>	* is usually a good idea).  (4) We bound the number of attempts
407	>	* to find work (see MAX_HELP) and fall back to suspending the
408	>	* worker and if necessary replacing it with another.
409	>	*
410	>	* Helping actions for CountedCompleters are much simpler: Method
411	>	* helpComplete can take and execute any task with the same root
412	>	* as the task being waited on. However, this still entails some
413	>	* traversal of completer chains, so is less efficient than using
414	>	* CountedCompleters without explicit joins.
415	>	*
416	>	* It is impossible to keep exactly the target parallelism number
417	>	* of threads running at any given time.  Determining the
418	>	* existence of conservatively safe helping targets, the
419	>	* availability of already-created spares, and the apparent need
420	>	* to create new spares are all racy, so we rely on multiple
421	>	* retries of each.  Compensation in the apparent absence of
422	>	* helping opportunities is challenging to control on JVMs, where
423	>	* GC and other activities can stall progress of tasks that in
424	>	* turn stall out many other dependent tasks, without us being
425	>	* able to determine whether they will ever require compensation.
426	>	* Even though work-stealing otherwise encounters little
427	>	* degradation in the presence of more threads than cores,
428	>	* aggressively adding new threads in such cases entails risk of
429	>	* unwanted positive feedback control loops in which more threads
430	>	* cause more dependent stalls (as well as delayed progress of
431	>	* unblocked threads to the point that we know they are available)
432	>	* leading to more situations requiring more threads, and so
433	>	* on. This aspect of control can be seen as an (analytically
434	>	* intractable) game with an opponent that may choose the worst
435	>	* (for us) active thread to stall at any time.  We take several
436	>	* precautions to bound losses (and thus bound gains), mainly in
437	>	* methods tryCompensate and awaitJoin.
438	>	*
439	>	* Common Pool
440	>	* ===========
441	>	*
442	>	* The static commonPool always exists after static
443	>	* initialization.  Since it (or any other created pool) need
444	>	* never be used, we minimize initial construction overhead and
445	>	* footprint to the setup of about a dozen fields, with no nested
446	>	* allocation. Most bootstrapping occurs within method
447	>	* fullExternalPush during the first submission to the pool.
448	>	*
449	>	* When external threads submit to the common pool, they can
450	>	* perform some subtask processing (see externalHelpJoin and
451	>	* related methods).  We do not need to record whether these
452	>	* submissions are to the common pool -- if not, externalHelpJoin
453	>	* returns quickly (at the most helping to signal some common pool
454	>	* workers). These submitters would otherwise be blocked waiting
455	>	* for completion, so the extra effort (with liberally sprinkled
456	>	* task status checks) in inapplicable cases amounts to an odd
457	>	* form of limited spin-wait before blocking in ForkJoinTask.join.
458	>	*
459	>	* Style notes
460	>	* ===========
461	>	*
462	>	* There is a lot of representation-level coupling among classes
463	>	* ForkJoinPool, ForkJoinWorkerThread, and ForkJoinTask.  The
464	>	* fields of WorkQueue maintain data structures managed by
465	>	* ForkJoinPool, so are directly accessed.  There is little point
466	>	* trying to reduce this, since any associated future changes in
467	>	* representations will need to be accompanied by algorithmic
468	>	* changes anyway. Several methods intrinsically sprawl because
469	>	* they must accumulate sets of consistent reads of volatiles held
470	>	* in local variables.  Methods signalWork() and scan() are the
471	>	* main bottlenecks, so are especially heavily
472	>	* micro-optimized/mangled.  There are lots of inline assignments
473	>	* (of form "while ((local = field) != 0)") which are usually the
474	>	* simplest way to ensure the required read orderings (which are
475	>	* sometimes critical). This leads to a "C"-like style of listing
476	>	* declarations of these locals at the heads of methods or blocks.
477	>	* There are several occurrences of the unusual "do {} while
478	>	* (!cas...)"  which is the simplest way to force an update of a
479	>	* CAS'ed variable. There are also other coding oddities (including
480	>	* several unnecessary-looking hoisted null checks) that help
481	>	* some methods perform reasonably even when interpreted (not
482	>	* compiled).
483	>	*
484	>	* The order of declarations in this file is:
485	>	* (1) Static utility functions
486	>	* (2) Nested (static) classes
487	>	* (3) Static fields
488	>	* (4) Fields, along with constants used when unpacking some of them
489	>	* (5) Internal control methods
490	>	* (6) Callbacks and other support for ForkJoinTask methods
491	>	* (7) Exported methods
492	>	* (8) Static block initializing statics in minimally dependent order
493		*/
494
495	<	/** Mask for packing and unpacking shorts */
496	<	private static final int  shortMask = 0xffff;
495	>	// Static utilities
496	>
497	>	/**
498	>	* If there is a security manager, makes sure caller has
499	>	* permission to modify threads.
500	>	*/
501	>	private static void checkPermission() {
502	>	SecurityManager security = System.getSecurityManager();
503	>	if (security != null)
504	>	security.checkPermission(modifyThreadPermission);
505	>	}
506
507	<	/** Max pool size -- must be a power of two minus 1 */
74	<	private static final int MAX_THREADS =  0x7FFF;
507	>	// Nested classes
508
509		/**
510	<	* Factory for creating new ForkJoinWorkerThreads.  A
511	<	* ForkJoinWorkerThreadFactory must be defined and used for
512	<	* ForkJoinWorkerThread subclasses that extend base functionality
513	<	* or initialize threads with different contexts.
510	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
511	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
512	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
513	>	* functionality or initialize threads with different contexts.
514		*/
515		public static interface ForkJoinWorkerThreadFactory {
516		/**
517		* Returns a new worker thread operating in the given pool.
518		*
519		* @param pool the pool this thread works in
520	<	* @throws NullPointerException if pool is null
520	>	* @throws NullPointerException if the pool is null
521		*/
522		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
523		}
#	Line 93 | Line 526 | public class ForkJoinPool extends Abstra
526		* Default ForkJoinWorkerThreadFactory implementation; creates a
527		* new ForkJoinWorkerThread.
528		*/
529	<	static class  DefaultForkJoinWorkerThreadFactory
529	>	static final class DefaultForkJoinWorkerThreadFactory
530		implements ForkJoinWorkerThreadFactory {
531	<	public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
532	<	try {
533	<	return new ForkJoinWorkerThread(pool);
534	<	} catch (OutOfMemoryError oom)  {
531	>	public final ForkJoinWorkerThread newThread(ForkJoinPool pool) {
532	>	return new ForkJoinWorkerThread(pool);
533	>	}
534	>	}
535	>
536	>	/**
537	>	* Class for artificial tasks that are used to replace the target
538	>	* of local joins if they are removed from an interior queue slot
539	>	* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
540	>	* actually do anything beyond having a unique identity.
541	>	*/
542	>	static final class EmptyTask extends ForkJoinTask<Void> {
543	>	private static final long serialVersionUID = -7721805057305804111L;
544	>	EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
545	>	public final Void getRawResult() { return null; }
546	>	public final void setRawResult(Void x) {}
547	>	public final boolean exec() { return true; }
548	>	}
549	>
550	>	/**
551	>	* Queues supporting work-stealing as well as external task
552	>	* submission. See above for main rationale and algorithms.
553	>	* Implementation relies heavily on "Unsafe" intrinsics
554	>	* and selective use of "volatile":
555	>	*
556	>	* Field "base" is the index (mod array.length) of the least valid
557	>	* queue slot, which is always the next position to steal (poll)
558	>	* from if nonempty. Reads and writes require volatile orderings
559	>	* but not CAS, because updates are only performed after slot
560	>	* CASes.
561	>	*
562	>	* Field "top" is the index (mod array.length) of the next queue
563	>	* slot to push to or pop from. It is written only by owner thread
564	>	* for push, or under lock for external/shared push, and accessed
565	>	* by other threads only after reading (volatile) base.  Both top
566	>	* and base are allowed to wrap around on overflow, but (top -
567	>	* base) (or more commonly -(base - top) to force volatile read of
568	>	* base before top) still estimates size. The lock ("qlock") is
569	>	* forced to -1 on termination, causing all further lock attempts
570	>	* to fail. (Note: we don't need CAS for termination state because
571	>	* upon pool shutdown, all shared-queues will stop being used
572	>	* anyway.)  Nearly all lock bodies are set up so that exceptions
573	>	* within lock bodies are "impossible" (modulo JVM errors that
574	>	* would cause failure anyway.)
575	>	*
576	>	* The array slots are read and written using the emulation of
577	>	* volatiles/atomics provided by Unsafe. Insertions must in
578	>	* general use putOrderedObject as a form of releasing store to
579	>	* ensure that all writes to the task object are ordered before
580	>	* its publication in the queue.  All removals entail a CAS to
581	>	* null.  The array is always a power of two. To ensure safety of
582	>	* Unsafe array operations, all accesses perform explicit null
583	>	* checks and implicit bounds checks via power-of-two masking.
584	>	*
585	>	* In addition to basic queuing support, this class contains
586	>	* fields described elsewhere to control execution. It turns out
587	>	* to work better memory-layout-wise to include them in this class
588	>	* rather than a separate class.
589	>	*
590	>	* Performance on most platforms is very sensitive to placement of
591	>	* instances of both WorkQueues and their arrays -- we absolutely
592	>	* do not want multiple WorkQueue instances or multiple queue
593	>	* arrays sharing cache lines. (It would be best for queue objects
594	>	* and their arrays to share, but there is nothing available to
595	>	* help arrange that).  Unfortunately, because they are recorded
596	>	* in a common array, WorkQueue instances are often moved to be
597	>	* adjacent by garbage collectors. To reduce impact, we use field
598	>	* padding that works OK on common platforms; this effectively
599	>	* trades off slightly slower average field access for the sake of
600	>	* avoiding really bad worst-case access. (Until better JVM
601	>	* support is in place, this padding is dependent on transient
602	>	* properties of JVM field layout rules.)
603	>	*/
604	>	static final class WorkQueue {
605	>	/**
606	>	* Capacity of work-stealing queue array upon initialization.
607	>	* Must be a power of two; at least 4, but should be larger to
608	>	* reduce or eliminate cacheline sharing among queues.
609	>	* Currently, it is much larger, as a partial workaround for
610	>	* the fact that JVMs often place arrays in locations that
611	>	* share GC bookkeeping (especially cardmarks) such that
612	>	* per-write accesses encounter serious memory contention.
613	>	*/
614	>	static final int INITIAL_QUEUE_CAPACITY = 1 << 13;
615	>
616	>	/**
617	>	* Maximum size for queue arrays. Must be a power of two less
618	>	* than or equal to 1 << (31 - width of array entry) to ensure
619	>	* lack of wraparound of index calculations, but defined to a
620	>	* value a bit less than this to help users trap runaway
621	>	* programs before saturating systems.
622	>	*/
623	>	static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
624	>
625	>	int seed;                  // for random scanning; initialize nonzero
626	>	volatile int eventCount;   // encoded inactivation count; < 0 if inactive
627	>	int nextWait;              // encoded record of next event waiter
628	>	int hint;                  // steal or signal hint (index)
629	>	int poolIndex;             // index of this queue in pool (or 0)
630	>	final int mode;            // 0: lifo, > 0: fifo, < 0: shared
631	>	int nsteals;               // number of steals
632	>	volatile int qlock;        // 1: locked, -1: terminate; else 0
633	>	volatile int base;         // index of next slot for poll
634	>	int top;                   // index of next slot for push
635	>	ForkJoinTask<?>[] array;   // the elements (initially unallocated)
636	>	final ForkJoinPool pool;   // the containing pool (may be null)
637	>	final ForkJoinWorkerThread owner; // owning thread or null if shared
638	>	volatile Thread parker;    // == owner during call to park; else null
639	>	volatile ForkJoinTask<?> currentJoin;  // task being joined in awaitJoin
640	>	ForkJoinTask<?> currentSteal; // current non-local task being executed
641	>
642	>	// Heuristic padding to ameliorate unfortunate memory placements
643	>	Object p00, p01, p02, p03, p04, p05, p06, p07;
644	>	Object p08, p09, p0a, p0b, p0c;
645	>
646	>	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode,
647	>	int seed) {
648	>	this.array = new ForkJoinTask<?>[WorkQueue.INITIAL_QUEUE_CAPACITY];
649	>	this.pool = pool;
650	>	this.owner = owner;
651	>	this.mode = mode;
652	>	this.seed = seed;
653	>	// Place indices in the center of array
654	>	base = top = INITIAL_QUEUE_CAPACITY >>> 1;
655	>	}
656	>
657	>	/**
658	>	* Pushes a task. Call only by owner in unshared queues.
659	>	* Cases needing resizing or rejection are relayed to fullPush
660	>	* (that also handles shared queues).
661	>	*
662	>	* @param task the task. Caller must ensure non-null.
663	>	* @throw RejectedExecutionException if array cannot be resized
664	>	*/
665	>	final void push(ForkJoinTask<?> task) {
666	>	ForkJoinTask<?>[] a; ForkJoinPool p;
667	>	int s = top, m, n;
668	>	if ((a = array) != null) {    // ignore if queue removed
669	>	U.putOrderedObject
670	>	(a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task);
671	>	if ((n = (top = s + 1) - base) <= 1) {
672	>	if ((p = pool) != null)
673	>	p.signalWork(this, 0);
674	>	}
675	>	else if (n >= m)
676	>	growArray();
677	>	}
678	>	}
679	>
680	>	/**
681	>	* Pushes a task if lock is free and array is either big
682	>	* enough or can be resized to be big enough.
683	>	*
684	>	* @param task the task. Caller must ensure non-null.
685	>	* @return true if submitted
686	>	*/
687	>	final boolean trySharedPush(ForkJoinTask<?> task) {
688	>	boolean submitted = false;
689	>	if (qlock == 0 && U.compareAndSwapInt(this, QLOCK, 0, 1)) {
690	>	ForkJoinTask<?>[] a = array;  ForkJoinPool p;
691	>	int s = top;
692	>	try {
693	>	if ((a != null && a.length > s + 1 - base) ||
694	>	(a = growArray()) != null) {   // must presize
695	>	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
696	>	U.putOrderedObject(a, j, task);
697	>	top = s + 1;
698	>	submitted = true;
699	>	}
700	>	} finally {
701	>	qlock = 0;                         // unlock
702	>	}
703	>	if (submitted && (p = pool) != null)
704	>	p.signalWork(this, 0);
705	>	}
706	>	return submitted;
707	>	}
708	>
709	>	/**
710	>	* Initializes or doubles the capacity of array. Call either
711	>	* by owner or with lock held -- it is OK for base, but not
712	>	* top, to move while resizings are in progress.
713	>	*/
714	>	final ForkJoinTask<?>[] growArray() {
715	>	ForkJoinTask<?>[] oldA = array;
716	>	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
717	>	if (size > MAXIMUM_QUEUE_CAPACITY)
718	>	throw new RejectedExecutionException("Queue capacity exceeded");
719	>	int oldMask, t, b;
720	>	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
721	>	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
722	>	(t = top) - (b = base) > 0) {
723	>	int mask = size - 1;
724	>	do {
725	>	ForkJoinTask<?> x;
726	>	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
727	>	int j    = ((b &    mask) << ASHIFT) + ABASE;
728	>	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
729	>	if (x != null &&
730	>	U.compareAndSwapObject(oldA, oldj, x, null))
731	>	U.putObjectVolatile(a, j, x);
732	>	} while (++b != t);
733	>	}
734	>	return a;
735	>	}
736	>
737	>	/**
738	>	* Takes next task, if one exists, in LIFO order.  Call only
739	>	* by owner in unshared queues.
740	>	*/
741	>	final ForkJoinTask<?> pop() {
742	>	ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
743	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
744	>	for (int s; (s = top - 1) - base >= 0;) {
745	>	long j = ((m & s) << ASHIFT) + ABASE;
746	>	if ((t = (ForkJoinTask<?>)U.getObject(a, j)) == null)
747	>	break;
748	>	if (U.compareAndSwapObject(a, j, t, null)) {
749	>	top = s;
750	>	return t;
751	>	}
752	>	}
753	>	}
754	>	return null;
755	>	}
756	>
757	>	/**
758	>	* Takes a task in FIFO order if b is base of queue and a task
759	>	* can be claimed without contention. Specialized versions
760	>	* appear in ForkJoinPool methods scan and tryHelpStealer.
761	>	*/
762	>	final ForkJoinTask<?> pollAt(int b) {
763	>	ForkJoinTask<?> t; ForkJoinTask<?>[] a;
764	>	if ((a = array) != null) {
765	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
766	>	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
767	>	base == b &&
768	>	U.compareAndSwapObject(a, j, t, null)) {
769	>	base = b + 1;
770	>	return t;
771	>	}
772	>	}
773	>	return null;
774	>	}
775	>
776	>	/**
777	>	* Takes next task, if one exists, in FIFO order.
778	>	*/
779	>	final ForkJoinTask<?> poll() {
780	>	ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t;
781	>	while ((b = base) - top < 0 && (a = array) != null) {
782	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
783	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
784	>	if (t != null) {
785	>	if (base == b &&
786	>	U.compareAndSwapObject(a, j, t, null)) {
787	>	base = b + 1;
788	>	return t;
789	>	}
790	>	}
791	>	else if (base == b) {
792	>	if (b + 1 == top)
793	>	break;
794	>	Thread.yield(); // wait for lagging update (very rare)
795	>	}
796	>	}
797	>	return null;
798	>	}
799	>
800	>	/**
801	>	* Takes next task, if one exists, in order specified by mode.
802	>	*/
803	>	final ForkJoinTask<?> nextLocalTask() {
804	>	return mode == 0 ? pop() : poll();
805	>	}
806	>
807	>	/**
808	>	* Returns next task, if one exists, in order specified by mode.
809	>	*/
810	>	final ForkJoinTask<?> peek() {
811	>	ForkJoinTask<?>[] a = array; int m;
812	>	if (a == null || (m = a.length - 1) < 0)
813		return null;
814	+	int i = mode == 0 ? top - 1 : base;
815	+	int j = ((i & m) << ASHIFT) + ABASE;
816	+	return (ForkJoinTask<?>)U.getObjectVolatile(a, j);
817	+	}
818	+
819	+	/**
820	+	* Pops the given task only if it is at the current top.
821	+	* (A shared version is available only via FJP.tryExternalUnpush)
822	+	*/
823	+	final boolean tryUnpush(ForkJoinTask<?> t) {
824	+	ForkJoinTask<?>[] a; int s;
825	+	if ((a = array) != null && (s = top) != base &&
826	+	U.compareAndSwapObject
827	+	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
828	+	top = s;
829	+	return true;
830		}
831	+	return false;
832	+	}
833	+
834	+	/**
835	+	* Removes and cancels all known tasks, ignoring any exceptions.
836	+	*/
837	+	final void cancelAll() {
838	+	ForkJoinTask.cancelIgnoringExceptions(currentJoin);
839	+	ForkJoinTask.cancelIgnoringExceptions(currentSteal);
840	+	for (ForkJoinTask<?> t; (t = poll()) != null; )
841	+	ForkJoinTask.cancelIgnoringExceptions(t);
842	+	}
843	+
844	+	/**
845	+	* Computes next value for random probes.  Scans don't require
846	+	* a very high quality generator, but also not a crummy one.
847	+	* Marsaglia xor-shift is cheap and works well enough.  Note:
848	+	* This is manually inlined in its usages in ForkJoinPool to
849	+	* avoid writes inside busy scan loops.
850	+	*/
851	+	final int nextSeed() {
852	+	int r = seed;
853	+	r ^= r << 13;
854	+	r ^= r >>> 17;
855	+	return seed = r ^= r << 5;
856	+	}
857	+
858	+	/**
859	+	* Provides a more accurate estimate of size than (top - base)
860	+	* by ordering reads and checking whether a near-empty queue
861	+	* has at least one unclaimed task.
862	+	*/
863	+	final int queueSize() {
864	+	ForkJoinTask<?>[] a; int k, s, n;
865	+	return ((n = base - (s = top)) < 0 &&
866	+	(n != -1 ||
867	+	((a = array) != null && (k = a.length) > 0 &&
868	+	U.getObject
869	+	(a, (long)((((k - 1) & (s - 1)) << ASHIFT) + ABASE)) != null))) ?
870	+	-n : 0;
871	+	}
872	+
873	+	// Specialized execution methods
874	+
875	+	/**
876	+	* Pops and runs tasks until empty.
877	+	*/
878	+	private void popAndExecAll() {
879	+	// A bit faster than repeated pop calls
880	+	ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t;
881	+	while ((a = array) != null && (m = a.length - 1) >= 0 &&
882	+	(s = top - 1) - base >= 0 &&
883	+	(t = ((ForkJoinTask<?>)
884	+	U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
885	+	!= null) {
886	+	if (U.compareAndSwapObject(a, j, t, null)) {
887	+	top = s;
888	+	t.doExec();
889	+	}
890	+	}
891	+	}
892	+
893	+	/**
894	+	* Polls and runs tasks until empty.
895	+	*/
896	+	private void pollAndExecAll() {
897	+	for (ForkJoinTask<?> t; (t = poll()) != null;)
898	+	t.doExec();
899	+	}
900	+
901	+	/**
902	+	* If present, removes from queue and executes the given task,
903	+	* or any other cancelled task. Returns (true) on any CAS
904	+	* or consistency check failure so caller can retry.
905	+	*
906	+	* @return false if no progress can be made, else true;
907	+	*/
908	+	final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
909	+	boolean stat = true, removed = false, empty = true;
910	+	ForkJoinTask<?>[] a; int m, s, b, n;
911	+	if ((a = array) != null && (m = a.length - 1) >= 0 &&
912	+	(n = (s = top) - (b = base)) > 0) {
913	+	for (ForkJoinTask<?> t;;) {           // traverse from s to b
914	+	int j = ((--s & m) << ASHIFT) + ABASE;
915	+	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
916	+	if (t == null)                    // inconsistent length
917	+	break;
918	+	else if (t == task) {
919	+	if (s + 1 == top) {           // pop
920	+	if (!U.compareAndSwapObject(a, j, task, null))
921	+	break;
922	+	top = s;
923	+	removed = true;
924	+	}
925	+	else if (base == b)           // replace with proxy
926	+	removed = U.compareAndSwapObject(a, j, task,
927	+	new EmptyTask());
928	+	break;
929	+	}
930	+	else if (t.status >= 0)
931	+	empty = false;
932	+	else if (s + 1 == top) {          // pop and throw away
933	+	if (U.compareAndSwapObject(a, j, t, null))
934	+	top = s;
935	+	break;
936	+	}
937	+	if (--n == 0) {
938	+	if (!empty && base == b)
939	+	stat = false;
940	+	break;
941	+	}
942	+	}
943	+	}
944	+	if (removed)
945	+	task.doExec();
946	+	return stat;
947	+	}
948	+
949	+	/**
950	+	* Polls for and executes the given task or any other task in
951	+	* its CountedCompleter computation
952	+	*/
953	+	final boolean pollAndExecCC(ForkJoinTask<?> root) {
954	+	ForkJoinTask<?>[] a; int b; Object o;
955	+	outer: while ((b = base) - top < 0 && (a = array) != null) {
956	+	long j = (((a.length - 1) & b) << ASHIFT) + ABASE;
957	+	if ((o = U.getObject(a, j)) == null ||
958	+	!(o instanceof CountedCompleter))
959	+	break;
960	+	for (CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;;) {
961	+	if (r == root) {
962	+	if (base == b &&
963	+	U.compareAndSwapObject(a, j, t, null)) {
964	+	base = b + 1;
965	+	t.doExec();
966	+	return true;
967	+	}
968	+	else
969	+	break; // restart
970	+	}
971	+	if ((r = r.completer) == null)
972	+	break outer; // not part of root computation
973	+	}
974	+	}
975	+	return false;
976	+	}
977	+
978	+	/**
979	+	* Executes a top-level task and any local tasks remaining
980	+	* after execution.
981	+	*/
982	+	final void runTask(ForkJoinTask<?> t) {
983	+	if (t != null) {
984	+	(currentSteal = t).doExec();
985	+	currentSteal = null;
986	+	++nsteals;
987	+	if (top != base) {       // process remaining local tasks
988	+	if (mode == 0)
989	+	popAndExecAll();
990	+	else
991	+	pollAndExecAll();
992	+	}
993	+	}
994	+	}
995	+
996	+	/**
997	+	* Executes a non-top-level (stolen) task.
998	+	*/
999	+	final void runSubtask(ForkJoinTask<?> t) {
1000	+	if (t != null) {
1001	+	ForkJoinTask<?> ps = currentSteal;
1002	+	(currentSteal = t).doExec();
1003	+	currentSteal = ps;
1004	+	}
1005	+	}
1006	+
1007	+	/**
1008	+	* Returns true if owned and not known to be blocked.
1009	+	*/
1010	+	final boolean isApparentlyUnblocked() {
1011	+	Thread wt; Thread.State s;
1012	+	return (eventCount >= 0 &&
1013	+	(wt = owner) != null &&
1014	+	(s = wt.getState()) != Thread.State.BLOCKED &&
1015	+	s != Thread.State.WAITING &&
1016	+	s != Thread.State.TIMED_WAITING);
1017	+	}
1018	+
1019	+	/**
1020	+	* If this owned and is not already interrupted, try to
1021	+	* interrupt and/or unpark, ignoring exceptions.
1022	+	*/
1023	+	final void interruptOwner() {
1024	+	Thread wt, p;
1025	+	if ((wt = owner) != null && !wt.isInterrupted()) {
1026	+	try {
1027	+	wt.interrupt();
1028	+	} catch (SecurityException ignore) {
1029	+	}
1030	+	}
1031	+	if ((p = parker) != null)
1032	+	U.unpark(p);
1033	+	}
1034	+
1035	+	// Unsafe mechanics
1036	+	private static final sun.misc.Unsafe U;
1037	+	private static final long QLOCK;
1038	+	private static final int ABASE;
1039	+	private static final int ASHIFT;
1040	+	static {
1041	+	int s;
1042	+	try {
1043	+	U = getUnsafe();
1044	+	Class<?> k = WorkQueue.class;
1045	+	Class<?> ak = ForkJoinTask[].class;
1046	+	QLOCK = U.objectFieldOffset
1047	+	(k.getDeclaredField("qlock"));
1048	+	ABASE = U.arrayBaseOffset(ak);
1049	+	s = U.arrayIndexScale(ak);
1050	+	} catch (Exception e) {
1051	+	throw new Error(e);
1052	+	}
1053	+	if ((s & (s-1)) != 0)
1054	+	throw new Error("data type scale not a power of two");
1055	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
1056		}
1057		}
1058
1059	+	// static fields (initialized in static initializer below)
1060	+
1061		/**
1062		* Creates a new ForkJoinWorkerThread. This factory is used unless
1063		* overridden in ForkJoinPool constructors.
1064		*/
1065		public static final ForkJoinWorkerThreadFactory
1066	<	defaultForkJoinWorkerThreadFactory =
113	<	new DefaultForkJoinWorkerThreadFactory();
1066	>	defaultForkJoinWorkerThreadFactory;
1067
1068		/**
1069	<	* Permission required for callers of methods that may start or
1070	<	* kill threads.
1069	>	* Per-thread records for threads that submit to pools. Currently
1070	>	* holds only pseudo-random seed / index that is used to choose
1071	>	* submission queues in method externalPush. In the future, this may
1072	>	* also incorporate a means to implement different task rejection
1073	>	* and resubmission policies.
1074	>	*
1075	>	* Seeds for submitters and workers/workQueues work in basically
1076	>	* the same way but are initialized and updated using slightly
1077	>	* different mechanics. Both are initialized using the same
1078	>	* approach as in class ThreadLocal, where successive values are
1079	>	* unlikely to collide with previous values. Seeds are then
1080	>	* randomly modified upon collisions using xorshifts, which
1081	>	* requires a non-zero seed.
1082		*/
1083	<	private static final RuntimePermission modifyThreadPermission =
1084	<	new RuntimePermission("modifyThread");
1083	>	static final class Submitter {
1084	>	int seed;
1085	>	Submitter(int s) { seed = s; }
1086	>	}
1087
1088		/**
1089	<	* If there is a security manager, makes sure caller has
1090	<	* permission to modify threads.
1089	>	* Per-thread submission bookkeeping. Shared across all pools
1090	>	* to reduce ThreadLocal pollution and because random motion
1091	>	* to avoid contention in one pool is likely to hold for others.
1092	>	* Lazily initialized on first submission (but null-checked
1093	>	* in other contexts to avoid unnecessary initialization).
1094		*/
1095	<	private static void checkPermission() {
127	<	SecurityManager security = System.getSecurityManager();
128	<	if (security != null)
129	<	security.checkPermission(modifyThreadPermission);
130	<	}
1095	>	static final ThreadLocal<Submitter> submitters;
1096
1097		/**
1098	<	* Generator for assigning sequence numbers as pool names.
1098	>	* Common (static) pool. Non-null for public use unless a static
1099	>	* construction exception, but internal usages null-check on use
1100	>	* to paranoically avoid potential initialization circularities
1101	>	* as well as to simplify generated code.
1102		*/
1103	<	private static final AtomicInteger poolNumberGenerator =
136	<	new AtomicInteger();
1103	>	static final ForkJoinPool commonPool;
1104
1105		/**
1106	<	* Array holding all worker threads in the pool. Initialized upon
1107	<	* 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.
1106	>	* Permission required for callers of methods that may start or
1107	>	* kill threads.
1108		*/
1109	<	volatile ForkJoinWorkerThread[] workers;
1109	>	private static final RuntimePermission modifyThreadPermission;
1110
1111		/**
1112	<	* Lock protecting access to workers.
1112	>	* Common pool parallelism. Must equal commonPool.parallelism.
1113		*/
1114	<	private final ReentrantLock workerLock;
1114	>	static final int commonPoolParallelism;
1115
1116		/**
1117	<	* Condition for awaitTermination.
1117	>	* Sequence number for creating workerNamePrefix.
1118		*/
1119	<	private final Condition termination;
1119	>	private static int poolNumberSequence;
1120
1121		/**
1122	<	* The uncaught exception handler used when any worker
1123	<	* abruptly terminates
1122	>	* Return the next sequence number. We don't expect this to
1123	>	* ever contend so use simple builtin sync.
1124		*/
1125	<	private Thread.UncaughtExceptionHandler ueh;
1125	>	private static final synchronized int nextPoolId() {
1126	>	return ++poolNumberSequence;
1127	>	}
1128	>
1129	>	// static constants
1130
1131		/**
1132	<	* Creation factory for worker threads.
1132	>	* Initial timeout value (in nanoseconds) for the thread
1133	>	* triggering quiescence to park waiting for new work. On timeout,
1134	>	* the thread will instead try to shrink the number of
1135	>	* workers. The value should be large enough to avoid overly
1136	>	* aggressive shrinkage during most transient stalls (long GCs
1137	>	* etc).
1138		*/
1139	<	private final ForkJoinWorkerThreadFactory factory;
1139	>	private static final long IDLE_TIMEOUT      = 2000L * 1000L * 1000L; // 2sec
1140
1141		/**
1142	<	* Head of stack of threads that were created to maintain
170	<	* parallelism when other threads blocked, but have since
171	<	* suspended when the parallelism level rose.
1142	>	* Timeout value when there are more threads than parallelism level
1143		*/
1144	<	private volatile WaitQueueNode spareStack;
1144	>	private static final long FAST_IDLE_TIMEOUT =  200L * 1000L * 1000L;
1145
1146		/**
1147	<	* Sum of per-thread steal counts, updated only when threads are
1148	<	* idle or terminating.
1147	>	* The maximum stolen->joining link depth allowed in method
1148	>	* tryHelpStealer.  Must be a power of two.  Depths for legitimate
1149	>	* chains are unbounded, but we use a fixed constant to avoid
1150	>	* (otherwise unchecked) cycles and to bound staleness of
1151	>	* traversal parameters at the expense of sometimes blocking when
1152	>	* we could be helping.
1153		*/
1154	<	private final AtomicLong stealCount;
1154	>	private static final int MAX_HELP = 64;
1155
1156		/**
1157	<	* Queue for external submissions.
1157	>	* Increment for seed generators. See class ThreadLocal for
1158	>	* explanation.
1159		*/
1160	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
1160	>	private static final int SEED_INCREMENT = 0x61c88647;
1161
1162		/**
1163	<	* Head of Treiber stack for barrier sync. See below for explanation.
1163	>	* Bits and masks for control variables
1164	>	*
1165	>	* Field ctl is a long packed with:
1166	>	* AC: Number of active running workers minus target parallelism (16 bits)
1167	>	* TC: Number of total workers minus target parallelism (16 bits)
1168	>	* ST: true if pool is terminating (1 bit)
1169	>	* EC: the wait count of top waiting thread (15 bits)
1170	>	* ID: poolIndex of top of Treiber stack of waiters (16 bits)
1171	>	*
1172	>	* When convenient, we can extract the upper 32 bits of counts and
1173	>	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
1174	>	* (int)ctl.  The ec field is never accessed alone, but always
1175	>	* together with id and st. The offsets of counts by the target
1176	>	* parallelism and the positionings of fields makes it possible to
1177	>	* perform the most common checks via sign tests of fields: When
1178	>	* ac is negative, there are not enough active workers, when tc is
1179	>	* negative, there are not enough total workers, and when e is
1180	>	* negative, the pool is terminating.  To deal with these possibly
1181	>	* negative fields, we use casts in and out of "short" and/or
1182	>	* signed shifts to maintain signedness.
1183	>	*
1184	>	* When a thread is queued (inactivated), its eventCount field is
1185	>	* set negative, which is the only way to tell if a worker is
1186	>	* prevented from executing tasks, even though it must continue to
1187	>	* scan for them to avoid queuing races. Note however that
1188	>	* eventCount updates lag releases so usage requires care.
1189	>	*
1190	>	* Field plock is an int packed with:
1191	>	* SHUTDOWN: true if shutdown is enabled (1 bit)
1192	>	* SEQ:  a sequence lock, with PL_LOCK bit set if locked (30 bits)
1193	>	* SIGNAL: set when threads may be waiting on the lock (1 bit)
1194	>	*
1195	>	* The sequence number enables simple consistency checks:
1196	>	* Staleness of read-only operations on the workQueues array can
1197	>	* be checked by comparing plock before vs after the reads.
1198		*/
189	–	private volatile WaitQueueNode syncStack;
1199
1200	<	/**
1201	<	* The count for event barrier
1200	>	// bit positions/shifts for fields
1201	>	private static final int  AC_SHIFT   = 48;
1202	>	private static final int  TC_SHIFT   = 32;
1203	>	private static final int  ST_SHIFT   = 31;
1204	>	private static final int  EC_SHIFT   = 16;
1205	>
1206	>	// bounds
1207	>	private static final int  SMASK      = 0xffff;  // short bits
1208	>	private static final int  MAX_CAP    = 0x7fff;  // max #workers - 1
1209	>	private static final int  EVENMASK   = 0xfffe;  // even short bits
1210	>	private static final int  SQMASK     = 0x007e;  // max 64 (even) slots
1211	>	private static final int  SHORT_SIGN = 1 << 15;
1212	>	private static final int  INT_SIGN   = 1 << 31;
1213	>
1214	>	// masks
1215	>	private static final long STOP_BIT   = 0x0001L << ST_SHIFT;
1216	>	private static final long AC_MASK    = ((long)SMASK) << AC_SHIFT;
1217	>	private static final long TC_MASK    = ((long)SMASK) << TC_SHIFT;
1218	>
1219	>	// units for incrementing and decrementing
1220	>	private static final long TC_UNIT    = 1L << TC_SHIFT;
1221	>	private static final long AC_UNIT    = 1L << AC_SHIFT;
1222	>
1223	>	// masks and units for dealing with u = (int)(ctl >>> 32)
1224	>	private static final int  UAC_SHIFT  = AC_SHIFT - 32;
1225	>	private static final int  UTC_SHIFT  = TC_SHIFT - 32;
1226	>	private static final int  UAC_MASK   = SMASK << UAC_SHIFT;
1227	>	private static final int  UTC_MASK   = SMASK << UTC_SHIFT;
1228	>	private static final int  UAC_UNIT   = 1 << UAC_SHIFT;
1229	>	private static final int  UTC_UNIT   = 1 << UTC_SHIFT;
1230	>
1231	>	// masks and units for dealing with e = (int)ctl
1232	>	private static final int E_MASK      = 0x7fffffff; // no STOP_BIT
1233	>	private static final int E_SEQ       = 1 << EC_SHIFT;
1234	>
1235	>	// plock bits
1236	>	private static final int SHUTDOWN    = 1 << 31;
1237	>	private static final int PL_LOCK     = 2;
1238	>	private static final int PL_SIGNAL   = 1;
1239	>	private static final int PL_SPINS    = 1 << 8;
1240	>
1241	>	// access mode for WorkQueue
1242	>	static final int LIFO_QUEUE          =  0;
1243	>	static final int FIFO_QUEUE          =  1;
1244	>	static final int SHARED_QUEUE        = -1;
1245	>
1246	>	// bounds for #steps in scan loop -- must be power 2 minus 1
1247	>	private static final int MIN_SCAN    = 0x1ff;   // cover estimation slop
1248	>	private static final int MAX_SCAN    = 0x1ffff; // 4 * max workers
1249	>
1250	>	// Instance fields
1251	>
1252	>	/*
1253	>	* Field layout of this class tends to matter more than one would
1254	>	* like. Runtime layout order is only loosely related to
1255	>	* declaration order and may differ across JVMs, but the following
1256	>	* empirically works OK on current JVMs.
1257	>	*/
1258	>	volatile long stealCount;                  // collects worker counts
1259	>	volatile long ctl;                         // main pool control
1260	>	volatile int plock;                        // shutdown status and seqLock
1261	>	volatile int indexSeed;                    // worker/submitter index seed
1262	>	final int config;                          // mode and parallelism level
1263	>	WorkQueue[] workQueues;                    // main registry
1264	>	final ForkJoinWorkerThreadFactory factory;
1265	>	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1266	>	final String workerNamePrefix;             // to create worker name string
1267	>
1268	>	/*
1269	>	* Acquires the plock lock to protect worker array and related
1270	>	* updates. This method is called only if an initial CAS on plock
1271	>	* fails. This acts as a spinLock for normal cases, but falls back
1272	>	* to builtin monitor to block when (rarely) needed. This would be
1273	>	* a terrible idea for a highly contended lock, but works fine as
1274	>	* a more conservative alternative to a pure spinlock.  See
1275	>	* internal ConcurrentHashMap documentation for further
1276	>	* explanation of nearly the same construction.
1277		*/
1278	<	private volatile long eventCount;
1278	>	private int acquirePlock() {
1279	>	int spins = PL_SPINS, r = 0, ps, nps;
1280	>	for (;;) {
1281	>	if (((ps = plock) & PL_LOCK) == 0 &&
1282	>	U.compareAndSwapInt(this, PLOCK, ps, nps = ps + PL_LOCK))
1283	>	return nps;
1284	>	else if (r == 0) { // randomize spins if possible
1285	>	Thread t = Thread.currentThread(); WorkQueue w; Submitter z;
1286	>	if ((t instanceof ForkJoinWorkerThread) &&
1287	>	(w = ((ForkJoinWorkerThread)t).workQueue) != null)
1288	>	r = w.seed;
1289	>	else if ((z = submitters.get()) != null)
1290	>	r = z.seed;
1291	>	else
1292	>	r = 1;
1293	>	}
1294	>	else if (spins >= 0) {
1295	>	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1296	>	if (r >= 0)
1297	>	--spins;
1298	>	}
1299	>	else if (U.compareAndSwapInt(this, PLOCK, ps, ps | PL_SIGNAL)) {
1300	>	synchronized (this) {
1301	>	if ((plock & PL_SIGNAL) != 0) {
1302	>	try {
1303	>	wait();
1304	>	} catch (InterruptedException ie) {
1305	>	try {
1306	>	Thread.currentThread().interrupt();
1307	>	} catch (SecurityException ignore) {
1308	>	}
1309	>	}
1310	>	}
1311	>	else
1312	>	notifyAll();
1313	>	}
1314	>	}
1315	>	}
1316	>	}
1317
1318		/**
1319	<	* Pool number, just for assigning useful names to worker threads
1319	>	* Unlocks and signals any thread waiting for plock. Called only
1320	>	* when CAS of seq value for unlock fails.
1321		*/
1322	<	private final int poolNumber;
1322	>	private void releasePlock(int ps) {
1323	>	plock = ps;
1324	>	synchronized (this) { notifyAll(); }
1325	>	}
1326
1327		/**
1328	<	* The maximum allowed pool size
1328	>	* Tries to create and start a worker; adjusts counts etc on failure
1329		*/
1330	<	private volatile int maxPoolSize;
1330	>	private void addWorker() {
1331	>	ForkJoinWorkerThread wt = null;
1332	>	try {
1333	>	(wt = factory.newThread(this)).start();
1334	>	} catch (Throwable ex) {
1335	>	deregisterWorker(wt, ex); // adjust on failure
1336	>	}
1337	>	}
1338
1339		/**
1340	<	* The desired parallelism level, updated only under workerLock.
1340	>	* Performs secondary initialization, called when plock is zero.
1341	>	* Creates workQueue array and sets plock to a valid value.  The
1342	>	* lock body must be exception-free (so no try/finally) so we
1343	>	* optimistically allocate new array outside the lock and throw
1344	>	* away if (very rarely) not needed. (A similar tactic is used in
1345	>	* fullExternalPush.)  Because the plock seq value can eventually
1346	>	* wrap around zero, this method harmlessly fails to reinitialize
1347	>	* if workQueues exists, while still advancing plock.
1348	>	*/
1349	>	private void initWorkQueuesArray() {
1350	>	WorkQueue[] ws; int ps;
1351	>	int p = config & SMASK;        // find power of two table size
1352	>	int n = (p > 1) ? p - 1 : 1;   // ensure at least 2 slots
1353	>	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
1354	>	WorkQueue[] nws = new WorkQueue[(n + 1) << 1];
1355	>	if (((ps = plock) & PL_LOCK) != 0 ||
1356	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1357	>	ps = acquirePlock();
1358	>	if ((ws = workQueues) == null || ws.length == 0)
1359	>	workQueues = nws;
1360	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1361	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1362	>	releasePlock(nps);
1363	>	long c; int u;
1364	>	if ((u = (int)((c = ctl) >>> 32)) < 0 && (int)c == 0) {
1365	>	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) |
1366	>	((u + UAC_UNIT) & UAC_MASK)) << 32;
1367	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1368	>	addWorker();
1369	>	}
1370	>
1371	>	}
1372	>
1373	>	//  Registering and deregistering workers
1374	>
1375	>	/**
1376	>	* Callback from ForkJoinWorkerThread to establish and record its
1377	>	* WorkQueue. To avoid scanning bias due to packing entries in
1378	>	* front of the workQueues array, we treat the array as a simple
1379	>	* power-of-two hash table using per-thread seed as hash,
1380	>	* expanding as needed.
1381	>	*
1382	>	* @param wt the worker thread
1383	>	*/
1384	>	final void registerWorker(ForkJoinWorkerThread wt) {
1385	>	if (wt != null && wt.workQueue == null) {
1386	>	int s, ps;    // generate a rarely colliding candidate index seed
1387	>	do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed,
1388	>	s += SEED_INCREMENT) ||
1389	>	s == 0); // skip 0
1390	>	WorkQueue w = new WorkQueue(this, wt, config >>> 16, s);
1391	>	if (((ps = plock) & PL_LOCK) != 0 ||
1392	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1393	>	ps = acquirePlock();
1394	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1395	>	try {
1396	>	WorkQueue[] ws;
1397	>	if ((ws = workQueues) != null && wt.workQueue == null) {
1398	>	int n = ws.length, m = n - 1;
1399	>	int r = (s << 1) | 1;           // use odd-numbered indices
1400	>	if (ws[r &= m] != null) {       // collision
1401	>	int probes = 0;             // step by approx half size
1402	>	int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2;
1403	>	while (ws[r = (r + step) & m] != null) {
1404	>	if (++probes >= n) {
1405	>	workQueues = ws = Arrays.copyOf(ws, n <<= 1);
1406	>	m = n - 1;
1407	>	probes = 0;
1408	>	}
1409	>	}
1410	>	}
1411	>	w.eventCount = w.poolIndex = r; // volatile write orders
1412	>	wt.workQueue = ws[r] = w;
1413	>	}
1414	>	} finally {
1415	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1416	>	releasePlock(nps);
1417	>	}
1418	>	}
1419	>	}
1420	>
1421	>	/**
1422	>	* Final callback from terminating worker, as well as upon failure
1423	>	* to construct or start a worker.  Removes record of worker from
1424	>	* array, and adjusts counts. If pool is shutting down, tries to
1425	>	* complete termination.
1426	>	*
1427	>	* @param wt the worker thread or null if construction failed
1428	>	* @param ex the exception causing failure, or null if none
1429		*/
1430	<	private volatile int parallelism;
1430	>	final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1431	>	WorkQueue w = null;
1432	>	if (wt != null && (w = wt.workQueue) != null) {
1433	>	int ps;
1434	>	w.qlock = -1;                // ensure set
1435	>	long ns = w.nsteals, sc;     // collect steal count
1436	>	do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
1437	>	sc = stealCount, sc + ns));
1438	>	if (((ps = plock) & PL_LOCK) != 0 ||
1439	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1440	>	ps = acquirePlock();
1441	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1442	>	try {
1443	>	int idx = w.poolIndex;
1444	>	WorkQueue[] ws = workQueues;
1445	>	if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1446	>	ws[idx] = null;
1447	>	} finally {
1448	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1449	>	releasePlock(nps);
1450	>	}
1451	>	}
1452	>
1453	>	long c;                             // adjust ctl counts
1454	>	do {} while (!U.compareAndSwapLong
1455	>	(this, CTL, c = ctl, (((c - AC_UNIT) & AC_MASK) |
1456	>	((c - TC_UNIT) & TC_MASK) |
1457	>	(c & ~(AC_MASK|TC_MASK)))));
1458	>
1459	>	if (!tryTerminate(false, false) && w != null) {
1460	>	w.cancelAll();                  // cancel remaining tasks
1461	>	if (w.array != null)            // suppress signal if never ran
1462	>	helpSignal(null, 0);        // wake up or create replacement
1463	>	if (ex == null)                 // help clean refs on way out
1464	>	ForkJoinTask.helpExpungeStaleExceptions();
1465	>	}
1466	>
1467	>	if (ex != null)                     // rethrow
1468	>	ForkJoinTask.rethrow(ex);
1469	>	}
1470	>
1471	>	// Submissions
1472	>
1473	>	/**
1474	>	* Unless shutting down, adds the given task to a submission queue
1475	>	* at submitter's current queue index (modulo submission
1476	>	* range). Only the most common path is directly handled in this
1477	>	* method. All others are relayed to fullExternalPush.
1478	>	*
1479	>	* @param task the task. Caller must ensure non-null.
1480	>	*/
1481	>	final void externalPush(ForkJoinTask<?> task) {
1482	>	WorkQueue[] ws; WorkQueue q; Submitter z; int m; ForkJoinTask<?>[] a;
1483	>	if ((z = submitters.get()) != null && plock > 0 &&
1484	>	(ws = workQueues) != null && (m = (ws.length - 1)) >= 0 &&
1485	>	(q = ws[m & z.seed & SQMASK]) != null &&
1486	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock
1487	>	int b = q.base, s = q.top, n, an;
1488	>	if ((a = q.array) != null && (an = a.length) > (n = s + 1 - b)) {
1489	>	U.putObject(a, (long)(((an - 1) & s) << ASHIFT) + ABASE, task);
1490	>	q.top = s + 1;                     // push on to deque
1491	>	q.qlock = 0;
1492	>	if (n <= 2)
1493	>	signalWork(q, 0);
1494	>	return;
1495	>	}
1496	>	q.qlock = 0;
1497	>	}
1498	>	fullExternalPush(task);
1499	>	}
1500	>
1501	>	/**
1502	>	* Full version of externalPush. This method is called, among
1503	>	* other times, upon the first submission of the first task to the
1504	>	* pool, so must perform secondary initialization (via
1505	>	* initWorkQueuesArray). It also detects first submission by an
1506	>	* external thread by looking up its ThreadLocal, and creates a
1507	>	* new shared queue if the one at index if empty or contended. The
1508	>	* lock body must be exception-free (so no try/finally) so we
1509	>	* optimistically allocate new queues outside the lock and throw
1510	>	* them away if (very rarely) not needed.
1511	>	*/
1512	>	private void fullExternalPush(ForkJoinTask<?> task) {
1513	>	int r = 0;
1514	>	for (Submitter z = submitters.get();;) {
1515	>	WorkQueue[] ws; WorkQueue q; int ps, m, k;
1516	>	if (z == null) {
1517	>	if (U.compareAndSwapInt(this, INDEXSEED, r = indexSeed,
1518	>	r += SEED_INCREMENT) && r != 0)
1519	>	submitters.set(z = new Submitter(r));
1520	>	}
1521	>	else if (r == 0) {               // move to a different index
1522	>	r = z.seed;
1523	>	r ^= r << 13;                // same xorshift as WorkQueues
1524	>	r ^= r >>> 17;
1525	>	z.seed = r ^ (r << 5);
1526	>	}
1527	>	else if ((ps = plock) < 0)
1528	>	throw new RejectedExecutionException();
1529	>	else if (ps == 0 || (ws = workQueues) == null ||
1530	>	(m = ws.length - 1) < 0)
1531	>	initWorkQueuesArray();
1532	>	else if ((q = ws[k = r & m & SQMASK]) != null) {
1533	>	if (q.trySharedPush(task))
1534	>	return;
1535	>	else
1536	>	r = 0; // move on contention
1537	>	}
1538	>	else if (((ps = plock) & PL_LOCK) == 0) { // create new queue
1539	>	q = new WorkQueue(this, null, SHARED_QUEUE, r);
1540	>	if (((ps = plock) & PL_LOCK) != 0 ||
1541	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1542	>	ps = acquirePlock();
1543	>	if ((ws = workQueues) != null && k < ws.length && ws[k] == null)
1544	>	ws[k] = q;
1545	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1546	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1547	>	releasePlock(nps);
1548	>	}
1549	>	else
1550	>	r = 0; // try elsewhere while lock held
1551	>	}
1552	>	}
1553	>
1554	>	// Maintaining ctl counts
1555
1556		/**
1557	<	* True if use local fifo, not default lifo, for local polling
1557	>	* Increments active count; mainly called upon return from blocking.
1558		*/
1559	<	private volatile boolean locallyFifo;
1559	>	final void incrementActiveCount() {
1560	>	long c;
1561	>	do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
1562	>	}
1563
1564		/**
1565	<	* Holds number of total (i.e., created and not yet terminated)
1566	<	* and running (i.e., not blocked on joins or other managed sync)
1567	<	* threads, packed into one int to ensure consistent snapshot when
1568	<	* making decisions about creating and suspending spare
1569	<	* threads. Updated only by CAS.  Note: CASes in
1570	<	* updateRunningCount and preJoin assume that running active count
1571	<	* is in low word, so need to be modified if this changes.
1565	>	* Tries to create (at most one) or activate (possibly several)
1566	>	* workers if too few are active. On contention failure, continues
1567	>	* until at least one worker is signalled or the given queue is
1568	>	* empty or all workers are active.
1569	>	*
1570	>	* @param q if non-null, the queue holding tasks to be signalled
1571	>	* @param signals the target number of signals (at least one --
1572	>	* if argument is zero also sets signallee hint if parked).
1573	>	*/
1574	>	final void signalWork(WorkQueue q, int signals) {
1575	>	long c; int e, u, i, s; WorkQueue[] ws; WorkQueue w; Thread p;
1576	>	while ((u = (int)((c = ctl) >>> 32)) < 0) {
1577	>	if ((e = (int)c) > 0) {
1578	>	if ((ws = workQueues) != null && ws.length > (i = e & SMASK) &&
1579	>	(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
1580	>	long nc = (((long)(w.nextWait & E_MASK)) |
1581	>	((long)(u + UAC_UNIT) << 32));
1582	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1583	>	w.eventCount = (e + E_SEQ) & E_MASK;
1584	>	if ((p = w.parker) != null) {
1585	>	if (q != null && signals == 0)
1586	>	w.hint = q.poolIndex;
1587	>	U.unpark(p);
1588	>	}
1589	>	if (--signals <= 0)
1590	>	break;
1591	>	}
1592	>	if (q != null && (s = q.queueSize()) <= signals &&
1593	>	(signals = s) <= 0)
1594	>	break;
1595	>	}
1596	>	else
1597	>	break;
1598	>	}
1599	>	else if (e == 0 && (u & SHORT_SIGN) != 0) {
1600	>	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) |
1601	>	((u + UAC_UNIT) & UAC_MASK)) << 32;
1602	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1603	>	addWorker();
1604	>	break;
1605	>	}
1606	>	}
1607	>	else
1608	>	break;
1609	>	}
1610	>	}
1611	>
1612	>	// Scanning for tasks
1613	>
1614	>	/**
1615	>	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1616		*/
1617	<	private volatile int workerCounts;
1617	>	final void runWorker(WorkQueue w) {
1618	>	if (w != null) // skip on initialization failure
1619	>	do { w.runTask(scan(w)); } while (w.qlock >= 0);
1620	>	}
1621
1622	<	private static int totalCountOf(int s)           { return s >>> 16;  }
1623	<	private static int runningCountOf(int s)         { return s & shortMask; }
1624	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
1622	>	/**
1623	>	* Scans for and, if found, returns one task, else possibly
1624	>	* inactivates the worker. This method operates on single reads of
1625	>	* volatile state and is designed to be re-invoked continuously,
1626	>	* in part because it returns upon detecting inconsistencies,
1627	>	* contention, or state changes that indicate possible success on
1628	>	* re-invocation.
1629	>	*
1630	>	* The scan searches for tasks across queues (starting at a random
1631	>	* index, and relying on registerWorker to irregularly scatter
1632	>	* them within array to avoid bias), checking each at least twice.
1633	>	* The scan terminates upon either finding a non-empty queue, or
1634	>	* completing the sweep. If the worker is not inactivated, it
1635	>	* takes and returns a task from this queue. Otherwise, if not
1636	>	* activated, it signals workers (that may include itself) and
1637	>	* returns so caller can retry. Also returns for true if the
1638	>	* worker array may have changed during an empty scan.  On failure
1639	>	* to find a task, we take one of the following actions, after
1640	>	* which the caller will retry calling this method unless
1641	>	* terminated.
1642	>	*
1643	>	* * If pool is terminating, terminate the worker.
1644	>	*
1645	>	* * If not already enqueued, try to inactivate and enqueue the
1646	>	* worker on wait queue. Or, if inactivating has caused the pool
1647	>	* to be quiescent, relay to idleAwaitWork to check for
1648	>	* termination and possibly shrink pool.
1649	>	*
1650	>	* * If already enqueued and none of the above apply, possibly
1651	>	* (with 1/2 probability) park awaiting signal, else lingering to
1652	>	* help scan and signal.
1653	>	*
1654	>	* @param w the worker (via its WorkQueue)
1655	>	* @return a task or null if none found
1656	>	*/
1657	>	private final ForkJoinTask<?> scan(WorkQueue w) {
1658	>	WorkQueue[] ws; int m, hint;
1659	>	int ps = plock;                          // read plock before ws
1660	>	if (w != null && (ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1661	>	int ec = w.eventCount;               // ec is negative if inactive
1662	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1663	>	for (int j = ((m + m + 1) | MIN_SCAN) & MAX_SCAN; ; --j) {
1664	>	WorkQueue q; ForkJoinTask<?>[] a; int b;
1665	>	if ((q = ws[(r + j) & m]) != null && (b = q.base) - q.top < 0 &&
1666	>	(a = q.array) != null) {     // probably nonempty
1667	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1668	>	ForkJoinTask<?> t = (ForkJoinTask<?>)
1669	>	U.getObjectVolatile(a, i);
1670	>	if (q.base == b && ec >= 0 && t != null &&
1671	>	U.compareAndSwapObject(a, i, t, null)) {
1672	>	if ((q.base = b + 1) - q.top < 0)
1673	>	signalWork(q, 0);
1674	>	return t;                // taken
1675	>	}
1676	>	else if (ec < 0 || j < m) {  // cannot take or cannot rescan
1677	>	w.hint = q.poolIndex;    // use hint below
1678	>	break;                   // let caller retry after signal
1679	>	}
1680	>	}
1681	>	else if (j < 0) { // end of scan; in loop to simplify code
1682	>	long c, sc; int e, ns;
1683	>	if ((ns = w.nsteals) != 0) {
1684	>	if (U.compareAndSwapLong(this, STEALCOUNT,
1685	>	sc = stealCount, sc + ns))
1686	>	w.nsteals = 0;       // collect steals
1687	>	}
1688	>	else if (plock != ps)        // ws may have changed
1689	>	break;
1690	>	else if ((e = (int)(c = ctl)) < 0)
1691	>	w.qlock = -1;            // pool is terminating
1692	>	else if (ec >= 0) {          // try to enqueue/inactivate
1693	>	long nc = ((long)ec |
1694	>	((c - AC_UNIT) & (AC_MASK|TC_MASK)));
1695	>	w.nextWait = e;          // link and mark inactive
1696	>	w.hint = -1;             // use hint if set while parked
1697	>	w.eventCount = ec | INT_SIGN;
1698	>	if (ctl != c ||
1699	>	!U.compareAndSwapLong(this, CTL, c, nc))
1700	>	w.eventCount = ec;  // unmark on CAS failure
1701	>	else if ((int)(c >> AC_SHIFT) == 1 - (config & SMASK))
1702	>	idleAwaitWork(w, nc, c);
1703	>	}
1704	>	else if (w.eventCount < 0) { // block
1705	>	Thread wt = Thread.currentThread();
1706	>	Thread.interrupted();    // clear status
1707	>	U.putObject(wt, PARKBLOCKER, this);
1708	>	w.parker = wt;           // emulate LockSupport.park
1709	>	if (w.eventCount < 0)    // recheck
1710	>	U.park(false, 0L);
1711	>	w.parker = null;
1712	>	U.putObject(wt, PARKBLOCKER, null);
1713	>	}
1714	>	break;
1715	>	}
1716	>	}
1717	>	if ((hint = w.hint) >= 0) {          // help signal
1718	>	WorkQueue[] vs; WorkQueue v; int k;
1719	>	w.hint = -1;                     // suppress resignal
1720	>	if ((vs = workQueues) != null && hint < vs.length &&
1721	>	(v = vs[hint]) != null && (k = v.base - v.top) < -1)
1722	>	signalWork(v, 1 - k);
1723	>	}
1724	>	}
1725	>	return null;
1726	>	}
1727	>
1728	>	/**
1729	>	* If inactivating worker w has caused the pool to become
1730	>	* quiescent, checks for pool termination, and, so long as this is
1731	>	* not the only worker, waits for event for up to a given
1732	>	* duration.  On timeout, if ctl has not changed, terminates the
1733	>	* worker, which will in turn wake up another worker to possibly
1734	>	* repeat this process.
1735	>	*
1736	>	* @param w the calling worker
1737	>	* @param currentCtl the ctl value triggering possible quiescence
1738	>	* @param prevCtl the ctl value to restore if thread is terminated
1739	>	*/
1740	>	private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1741	>	if (w != null && w.eventCount < 0 &&
1742	>	!tryTerminate(false, false) && (int)prevCtl != 0) {
1743	>	int dc = -(short)(currentCtl >>> TC_SHIFT);
1744	>	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1745	>	long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop
1746	>	Thread wt = Thread.currentThread();
1747	>	while (ctl == currentCtl) {
1748	>	Thread.interrupted();  // timed variant of version in scan()
1749	>	U.putObject(wt, PARKBLOCKER, this);
1750	>	w.parker = wt;
1751	>	if (ctl == currentCtl)
1752	>	U.park(false, parkTime);
1753	>	w.parker = null;
1754	>	U.putObject(wt, PARKBLOCKER, null);
1755	>	if (ctl != currentCtl)
1756	>	break;
1757	>	if (deadline - System.nanoTime() <= 0L &&
1758	>	U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1759	>	w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
1760	>	w.qlock = -1;   // shrink
1761	>	w.hint = -1;    // suppress helping
1762	>	break;
1763	>	}
1764	>	}
1765	>	}
1766	>	}
1767	>
1768	>	/**
1769	>	* Scans through queues looking for work (optionally, while
1770	>	* joining a task); if any are present, signals. May return early
1771	>	* if more signalling is detectably unneeded.
1772	>	*
1773	>	* @param task if non-null, return early if done
1774	>	* @param origin an index to start scan
1775	>	*/
1776	>	final int helpSignal(ForkJoinTask<?> task, int origin) {
1777	>	WorkQueue[] ws; WorkQueue q; int m, n, s, u;
1778	>	if ((ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1779	>	for (int i = 0; i <= m; ++i) {
1780	>	if (task != null && (s = task.status) < 0)
1781	>	return s;
1782	>	if ((q = ws[(i + origin) & m]) != null &&
1783	>	(n = q.queueSize()) > 0) {
1784	>	signalWork(q, n);
1785	>	if ((u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0)
1786	>	break;
1787	>	}
1788	>	}
1789	>	}
1790	>	return 0;
1791	>	}
1792	>
1793	>	/**
1794	>	* Tries to locate and execute tasks for a stealer of the given
1795	>	* task, or in turn one of its stealers, Traces currentSteal ->
1796	>	* currentJoin links looking for a thread working on a descendant
1797	>	* of the given task and with a non-empty queue to steal back and
1798	>	* execute tasks from. The first call to this method upon a
1799	>	* waiting join will often entail scanning/search, (which is OK
1800	>	* because the joiner has nothing better to do), but this method
1801	>	* leaves hints in workers to speed up subsequent calls. The
1802	>	* implementation is very branchy to cope with potential
1803	>	* inconsistencies or loops encountering chains that are stale,
1804	>	* unknown, or so long that they are likely cyclic.
1805	>	*
1806	>	* @param joiner the joining worker
1807	>	* @param task the task to join
1808	>	* @return 0 if no progress can be made, negative if task
1809	>	* known complete, else positive
1810	>	*/
1811	>	private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1812	>	int stat = 0, steps = 0;                    // bound to avoid cycles
1813	>	if (joiner != null && task != null) {       // hoist null checks
1814	>	restart: for (;;) {
1815	>	ForkJoinTask<?> subtask = task;     // current target
1816	>	for (WorkQueue j = joiner, v;;) {   // v is stealer of subtask
1817	>	WorkQueue[] ws; int m, s, h;
1818	>	if ((s = task.status) < 0) {
1819	>	stat = s;
1820	>	break restart;
1821	>	}
1822	>	if ((ws = workQueues) == null || (m = ws.length - 1) <= 0)
1823	>	break restart;              // shutting down
1824	>	if ((v = ws[h = (j.hint | 1) & m]) == null ||
1825	>	v.currentSteal != subtask) {
1826	>	for (int origin = h;;) {    // find stealer
1827	>	if (((h = (h + 2) & m) & 15) == 1 &&
1828	>	(subtask.status < 0 || j.currentJoin != subtask))
1829	>	continue restart;   // occasional staleness check
1830	>	if ((v = ws[h]) != null &&
1831	>	v.currentSteal == subtask) {
1832	>	j.hint = h;        // save hint
1833	>	break;
1834	>	}
1835	>	if (h == origin)
1836	>	break restart;      // cannot find stealer
1837	>	}
1838	>	}
1839	>	for (;;) { // help stealer or descend to its stealer
1840	>	ForkJoinTask[] a;  int b;
1841	>	if (subtask.status < 0)     // surround probes with
1842	>	continue restart;       //   consistency checks
1843	>	if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
1844	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1845	>	ForkJoinTask<?> t =
1846	>	(ForkJoinTask<?>)U.getObjectVolatile(a, i);
1847	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1848	>	v.currentSteal != subtask)
1849	>	continue restart;   // stale
1850	>	stat = 1;               // apparent progress
1851	>	if (t != null && v.base == b &&
1852	>	U.compareAndSwapObject(a, i, t, null)) {
1853	>	v.base = b + 1;     // help stealer
1854	>	joiner.runSubtask(t);
1855	>	}
1856	>	else if (v.base == b && ++steps == MAX_HELP)
1857	>	break restart;      // v apparently stalled
1858	>	}
1859	>	else {                      // empty -- try to descend
1860	>	ForkJoinTask<?> next = v.currentJoin;
1861	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1862	>	v.currentSteal != subtask)
1863	>	continue restart;   // stale
1864	>	else if (next == null || ++steps == MAX_HELP)
1865	>	break restart;      // dead-end or maybe cyclic
1866	>	else {
1867	>	subtask = next;
1868	>	j = v;
1869	>	break;
1870	>	}
1871	>	}
1872	>	}
1873	>	}
1874	>	}
1875	>	}
1876	>	return stat;
1877	>	}
1878
1879		/**
1880	<	* Adds delta (which may be negative) to running count.  This must
1881	<	* be called before (with negative arg) and after (with positive)
234	<	* any managed synchronization (i.e., mainly, joins).
1880	>	* Analog of tryHelpStealer for CountedCompleters. Tries to steal
1881	>	* and run tasks within the target's computation.
1882		*
1883	<	* @param delta the number to add
1884	<	*/
1885	<	final void updateRunningCount(int delta) {
1886	<	int s;
1887	<	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
1883	>	* @param task the task to join
1884	>	* @param mode if shared, exit upon completing any task
1885	>	* if all workers are active
1886	>	*
1887	>	*/
1888	>	private int helpComplete(ForkJoinTask<?> task, int mode) {
1889	>	WorkQueue[] ws; WorkQueue q; int m, n, s, u;
1890	>	if (task != null && (ws = workQueues) != null &&
1891	>	(m = ws.length - 1) >= 0) {
1892	>	for (int j = 1, origin = j;;) {
1893	>	if ((s = task.status) < 0)
1894	>	return s;
1895	>	if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) {
1896	>	origin = j;
1897	>	if (mode == SHARED_QUEUE &&
1898	>	((u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0))
1899	>	break;
1900	>	}
1901	>	else if ((j = (j + 2) & m) == origin)
1902	>	break;
1903	>	}
1904	>	}
1905	>	return 0;
1906		}
1907
1908		/**
1909	<	* Adds delta (which may be negative) to both total and running
1910	<	* count.  This must be called upon creation and termination of
1911	<	* worker threads.
1909	>	* Tries to decrement active count (sometimes implicitly) and
1910	>	* possibly release or create a compensating worker in preparation
1911	>	* for blocking. Fails on contention or termination. Otherwise,
1912	>	* adds a new thread if no idle workers are available and pool
1913	>	* may become starved.
1914	>	*/
1915	>	final boolean tryCompensate() {
1916	>	int pc = config & SMASK, e, i, tc; long c;
1917	>	WorkQueue[] ws; WorkQueue w; Thread p;
1918	>	if ((ws = workQueues) != null && (e = (int)(c = ctl)) >= 0) {
1919	>	if (e != 0 && (i = e & SMASK) < ws.length &&
1920	>	(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
1921	>	long nc = ((long)(w.nextWait & E_MASK) |
1922	>	(c & (AC_MASK|TC_MASK)));
1923	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1924	>	w.eventCount = (e + E_SEQ) & E_MASK;
1925	>	if ((p = w.parker) != null)
1926	>	U.unpark(p);
1927	>	return true;   // replace with idle worker
1928	>	}
1929	>	}
1930	>	else if ((tc = (short)(c >>> TC_SHIFT)) >= 0 &&
1931	>	(int)(c >> AC_SHIFT) + pc > 1) {
1932	>	long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
1933	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1934	>	return true;   // no compensation
1935	>	}
1936	>	else if (tc + pc < MAX_CAP) {
1937	>	long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
1938	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1939	>	addWorker();
1940	>	return true;
1941	>	}
1942	>	}
1943	>	}
1944	>	return false;
1945	>	}
1946	>
1947	>	/**
1948	>	* Helps and/or blocks until the given task is done.
1949		*
1950	<	* @param delta the number to add
1950	>	* @param joiner the joining worker
1951	>	* @param task the task
1952	>	* @return task status on exit
1953		*/
1954	<	private void updateWorkerCount(int delta) {
1955	<	int d = delta + (delta << 16); // add to both lo and hi parts
1956	<	int s;
1957	<	do {} while (!casWorkerCounts(s = workerCounts, s + d));
1954	>	final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
1955	>	int s = 0;
1956	>	if (joiner != null && task != null && (s = task.status) >= 0) {
1957	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
1958	>	joiner.currentJoin = task;
1959	>	do {} while ((s = task.status) >= 0 &&
1960	>	joiner.queueSize() > 0 &&
1961	>	joiner.tryRemoveAndExec(task)); // process local tasks
1962	>	if (s >= 0 && (s = task.status) >= 0 &&
1963	>	(s = helpSignal(task, joiner.poolIndex)) >= 0 &&
1964	>	(task instanceof CountedCompleter))
1965	>	s = helpComplete(task, LIFO_QUEUE);
1966	>	int k = 0; // to perform pre-block yield for politeness
1967	>	while (s >= 0 && (s = task.status) >= 0) {
1968	>	if ((joiner.queueSize() > 0 ||           // try helping
1969	>	(s = tryHelpStealer(joiner, task)) == 0) &&
1970	>	(s = task.status) >= 0) {
1971	>	if (k < 3) {
1972	>	if (++k < 3)
1973	>	s = helpSignal(task, joiner.poolIndex);
1974	>	else
1975	>	Thread.yield();
1976	>	}
1977	>	else if (!tryCompensate())
1978	>	k = 0;
1979	>	else {
1980	>	if (task.trySetSignal() && (s = task.status) >= 0) {
1981	>	synchronized (task) {
1982	>	if (task.status >= 0) {
1983	>	try {                // see ForkJoinTask
1984	>	task.wait();     //  for explanation
1985	>	} catch (InterruptedException ie) {
1986	>	}
1987	>	}
1988	>	else
1989	>	task.notifyAll();
1990	>	}
1991	>	}
1992	>	long c;                          // re-activate
1993	>	do {} while (!U.compareAndSwapLong
1994	>	(this, CTL, c = ctl, c + AC_UNIT));
1995	>	}
1996	>	}
1997	>	}
1998	>	joiner.currentJoin = prevJoin;
1999	>	}
2000	>	return s;
2001		}
2002
2003		/**
2004	<	* Lifecycle control. High word contains runState, low word
2005	<	* contains the number of workers that are (probably) executing
2006	<	* tasks. This value is atomically incremented before a worker
2007	<	* gets a task to run, and decremented when worker has no tasks
2008	<	* and cannot find any. These two fields are bundled together to
2009	<	* support correct termination triggering.  Note: activeCount
263	<	* CAS'es cheat by assuming active count is in low word, so need
264	<	* to be modified if this changes
2004	>	* Stripped-down variant of awaitJoin used by timed joins. Tries
2005	>	* to help join only while there is continuous progress. (Caller
2006	>	* will then enter a timed wait.)
2007	>	*
2008	>	* @param joiner the joining worker
2009	>	* @param task the task
2010		*/
2011	<	private volatile int runControl;
2011	>	final void helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
2012	>	int s;
2013	>	if (joiner != null && task != null && (s = task.status) >= 0) {
2014	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2015	>	joiner.currentJoin = task;
2016	>	do {} while ((s = task.status) >= 0 &&
2017	>	joiner.queueSize() > 0 &&
2018	>	joiner.tryRemoveAndExec(task));
2019	>	if (s >= 0 && (s = task.status) >= 0 &&
2020	>	(s = helpSignal(task, joiner.poolIndex)) >= 0 &&
2021	>	(task instanceof CountedCompleter))
2022	>	s = helpComplete(task, LIFO_QUEUE);
2023	>	if (s >= 0 && joiner.queueSize() == 0) {
2024	>	do {} while (task.status >= 0 &&
2025	>	tryHelpStealer(joiner, task) > 0);
2026	>	}
2027	>	joiner.currentJoin = prevJoin;
2028	>	}
2029	>	}
2030
2031	<	// RunState values. Order among values matters
2032	<	private static final int RUNNING     = 0;
2033	<	private static final int SHUTDOWN    = 1;
2034	<	private static final int TERMINATING = 2;
2035	<	private static final int TERMINATED  = 3;
2031	>	/**
2032	>	* Returns a (probably) non-empty steal queue, if one is found
2033	>	* during a random, then cyclic scan, else null.  This method must
2034	>	* be retried by caller if, by the time it tries to use the queue,
2035	>	* it is empty.
2036	>	* @param r a (random) seed for scanning
2037	>	*/
2038	>	private WorkQueue findNonEmptyStealQueue(int r) {
2039	>	for (WorkQueue[] ws;;) {
2040	>	int ps = plock, m, n;
2041	>	if ((ws = workQueues) == null || (m = ws.length - 1) < 1)
2042	>	return null;
2043	>	for (int j = (m + 1) << 2; ;) {
2044	>	WorkQueue q = ws[(((r + j) << 1) | 1) & m];
2045	>	if (q != null && (n = q.queueSize()) > 0) {
2046	>	if (n > 1)
2047	>	signalWork(q, 0);
2048	>	return q;
2049	>	}
2050	>	else if (--j < 0) {
2051	>	if (plock == ps)
2052	>	return null;
2053	>	break;
2054	>	}
2055	>	}
2056	>	}
2057	>	}
2058
2059	<	private static int runStateOf(int c)             { return c >>> 16; }
2060	<	private static int activeCountOf(int c)          { return c & shortMask; }
2061	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
2059	>	/**
2060	>	* Runs tasks until {@code isQuiescent()}. We piggyback on
2061	>	* active count ctl maintenance, but rather than blocking
2062	>	* when tasks cannot be found, we rescan until all others cannot
2063	>	* find tasks either.
2064	>	*/
2065	>	final void helpQuiescePool(WorkQueue w) {
2066	>	for (boolean active = true;;) {
2067	>	ForkJoinTask<?> localTask; // exhaust local queue
2068	>	while ((localTask = w.nextLocalTask()) != null)
2069	>	localTask.doExec();
2070	>	// Similar to loop in scan(), but ignoring submissions
2071	>	WorkQueue q = findNonEmptyStealQueue(w.nextSeed());
2072	>	if (q != null) {
2073	>	ForkJoinTask<?> t; int b;
2074	>	if (!active) {      // re-establish active count
2075	>	long c;
2076	>	active = true;
2077	>	do {} while (!U.compareAndSwapLong
2078	>	(this, CTL, c = ctl, c + AC_UNIT));
2079	>	}
2080	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2081	>	w.runSubtask(t);
2082	>	}
2083	>	else {
2084	>	long c;
2085	>	if (active) {       // decrement active count without queuing
2086	>	active = false;
2087	>	do {} while (!U.compareAndSwapLong
2088	>	(this, CTL, c = ctl, c -= AC_UNIT));
2089	>	}
2090	>	else
2091	>	c = ctl;        // re-increment on exit
2092	>	if ((int)(c >> AC_SHIFT) + (config & SMASK) == 0) {
2093	>	do {} while (!U.compareAndSwapLong
2094	>	(this, CTL, c = ctl, c + AC_UNIT));
2095	>	break;
2096	>	}
2097	>	}
2098	>	}
2099	>	}
2100
2101		/**
2102	<	* Tries incrementing active count; fails on contention.
280	<	* Called by workers before/during executing tasks.
2102	>	* Gets and removes a local or stolen task for the given worker.
2103		*
2104	<	* @return true on success
2104	>	* @return a task, if available
2105		*/
2106	<	final boolean tryIncrementActiveCount() {
2107	<	int c = runControl;
2108	<	return casRunControl(c, c+1);
2106	>	final ForkJoinTask<?> nextTaskFor(WorkQueue w) {
2107	>	for (ForkJoinTask<?> t;;) {
2108	>	WorkQueue q; int b;
2109	>	if ((t = w.nextLocalTask()) != null)
2110	>	return t;
2111	>	if ((q = findNonEmptyStealQueue(w.nextSeed())) == null)
2112	>	return null;
2113	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2114	>	return t;
2115	>	}
2116		}
2117
2118		/**
2119	<	* Tries decrementing active count; fails on contention.
2120	<	* Possibly triggers termination on success.
2121	<	* Called by workers when they can't find tasks.
2122	<	*
2123	<	* @return true on success
2119	>	* Returns a cheap heuristic guide for task partitioning when
2120	>	* programmers, frameworks, tools, or languages have little or no
2121	>	* idea about task granularity.  In essence by offering this
2122	>	* method, we ask users only about tradeoffs in overhead vs
2123	>	* expected throughput and its variance, rather than how finely to
2124	>	* partition tasks.
2125	>	*
2126	>	* In a steady state strict (tree-structured) computation, each
2127	>	* thread makes available for stealing enough tasks for other
2128	>	* threads to remain active. Inductively, if all threads play by
2129	>	* the same rules, each thread should make available only a
2130	>	* constant number of tasks.
2131	>	*
2132	>	* The minimum useful constant is just 1. But using a value of 1
2133	>	* would require immediate replenishment upon each steal to
2134	>	* maintain enough tasks, which is infeasible.  Further,
2135	>	* partitionings/granularities of offered tasks should minimize
2136	>	* steal rates, which in general means that threads nearer the top
2137	>	* of computation tree should generate more than those nearer the
2138	>	* bottom. In perfect steady state, each thread is at
2139	>	* approximately the same level of computation tree. However,
2140	>	* producing extra tasks amortizes the uncertainty of progress and
2141	>	* diffusion assumptions.
2142	>	*
2143	>	* So, users will want to use values larger, but not much larger
2144	>	* than 1 to both smooth over transient shortages and hedge
2145	>	* against uneven progress; as traded off against the cost of
2146	>	* extra task overhead. We leave the user to pick a threshold
2147	>	* value to compare with the results of this call to guide
2148	>	* decisions, but recommend values such as 3.
2149	>	*
2150	>	* When all threads are active, it is on average OK to estimate
2151	>	* surplus strictly locally. In steady-state, if one thread is
2152	>	* maintaining say 2 surplus tasks, then so are others. So we can
2153	>	* just use estimated queue length.  However, this strategy alone
2154	>	* leads to serious mis-estimates in some non-steady-state
2155	>	* conditions (ramp-up, ramp-down, other stalls). We can detect
2156	>	* many of these by further considering the number of "idle"
2157	>	* threads, that are known to have zero queued tasks, so
2158	>	* compensate by a factor of (#idle/#active) threads.
2159	>	*
2160	>	* Note: The approximation of #busy workers as #active workers is
2161	>	* not very good under current signalling scheme, and should be
2162	>	* improved.
2163	>	*/
2164	>	static int getSurplusQueuedTaskCount() {
2165	>	Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q;
2166	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
2167	>	int p = (pool = (wt = (ForkJoinWorkerThread)t).pool).config & SMASK;
2168	>	int n = (q = wt.workQueue).top - q.base;
2169	>	int a = (int)(pool.ctl >> AC_SHIFT) + p;
2170	>	return n - (a > (p >>>= 1) ? 0 :
2171	>	a > (p >>>= 1) ? 1 :
2172	>	a > (p >>>= 1) ? 2 :
2173	>	a > (p >>>= 1) ? 4 :
2174	>	8);
2175	>	}
2176	>	return 0;
2177	>	}
2178	>
2179	>	//  Termination
2180	>
2181	>	/**
2182	>	* Possibly initiates and/or completes termination.  The caller
2183	>	* triggering termination runs three passes through workQueues:
2184	>	* (0) Setting termination status, followed by wakeups of queued
2185	>	* workers; (1) cancelling all tasks; (2) interrupting lagging
2186	>	* threads (likely in external tasks, but possibly also blocked in
2187	>	* joins).  Each pass repeats previous steps because of potential
2188	>	* lagging thread creation.
2189	>	*
2190	>	* @param now if true, unconditionally terminate, else only
2191	>	* if no work and no active workers
2192	>	* @param enable if true, enable shutdown when next possible
2193	>	* @return true if now terminating or terminated
2194		*/
2195	<	final boolean tryDecrementActiveCount() {
2196	<	int c = runControl;
298	<	int nextc = c - 1;
299	<	if (!casRunControl(c, nextc))
2195	>	private boolean tryTerminate(boolean now, boolean enable) {
2196	>	if (this == commonPool)                     // cannot shut down
2197		return false;
2198	<	if (canTerminateOnShutdown(nextc))
2199	<	terminateOnShutdown();
2200	<	return true;
2198	>	for (long c;;) {
2199	>	if (((c = ctl) & STOP_BIT) != 0) {      // already terminating
2200	>	if ((short)(c >>> TC_SHIFT) == -(config & SMASK)) {
2201	>	synchronized (this) {
2202	>	notifyAll();                // signal when 0 workers
2203	>	}
2204	>	}
2205	>	return true;
2206	>	}
2207	>	if (plock >= 0) {                       // not yet enabled
2208	>	int ps;
2209	>	if (!enable)
2210	>	return false;
2211	>	if (((ps = plock) & PL_LOCK) != 0 ||
2212	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
2213	>	ps = acquirePlock();
2214	>	int nps = SHUTDOWN;
2215	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
2216	>	releasePlock(nps);
2217	>	}
2218	>	if (!now) {                             // check if idle & no tasks
2219	>	if ((int)(c >> AC_SHIFT) != -(config & SMASK) ||
2220	>	hasQueuedSubmissions())
2221	>	return false;
2222	>	// Check for unqueued inactive workers. One pass suffices.
2223	>	WorkQueue[] ws = workQueues; WorkQueue w;
2224	>	if (ws != null) {
2225	>	for (int i = 1; i < ws.length; i += 2) {
2226	>	if ((w = ws[i]) != null && w.eventCount >= 0)
2227	>	return false;
2228	>	}
2229	>	}
2230	>	}
2231	>	if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT)) {
2232	>	for (int pass = 0; pass < 3; ++pass) {
2233	>	WorkQueue[] ws = workQueues;
2234	>	if (ws != null) {
2235	>	WorkQueue w;
2236	>	int n = ws.length;
2237	>	for (int i = 0; i < n; ++i) {
2238	>	if ((w = ws[i]) != null) {
2239	>	w.qlock = -1;
2240	>	if (pass > 0) {
2241	>	w.cancelAll();
2242	>	if (pass > 1)
2243	>	w.interruptOwner();
2244	>	}
2245	>	}
2246	>	}
2247	>	// Wake up workers parked on event queue
2248	>	int i, e; long cc; Thread p;
2249	>	while ((e = (int)(cc = ctl) & E_MASK) != 0 &&
2250	>	(i = e & SMASK) < n &&
2251	>	(w = ws[i]) != null) {
2252	>	long nc = ((long)(w.nextWait & E_MASK) |
2253	>	((cc + AC_UNIT) & AC_MASK) |
2254	>	(cc & (TC_MASK|STOP_BIT)));
2255	>	if (w.eventCount == (e | INT_SIGN) &&
2256	>	U.compareAndSwapLong(this, CTL, cc, nc)) {
2257	>	w.eventCount = (e + E_SEQ) & E_MASK;
2258	>	w.qlock = -1;
2259	>	if ((p = w.parker) != null)
2260	>	U.unpark(p);
2261	>	}
2262	>	}
2263	>	}
2264	>	}
2265	>	}
2266	>	}
2267		}
2268
2269	+	// external operations on common pool
2270	+
2271		/**
2272	<	* Returns true if argument represents zero active count and
2273	<	* nonzero runstate, which is the triggering condition for
309	<	* terminating on shutdown.
2272	>	* Returns common pool queue for a thread that has submitted at
2273	>	* least one task.
2274		*/
2275	<	private static boolean canTerminateOnShutdown(int c) {
2276	<	// i.e. least bit is nonzero runState bit
2277	<	return ((c & -c) >>> 16) != 0;
2275	>	static WorkQueue commonSubmitterQueue() {
2276	>	ForkJoinPool p; WorkQueue[] ws; int m; Submitter z;
2277	>	return ((z = submitters.get()) != null &&
2278	>	(p = commonPool) != null &&
2279	>	(ws = p.workQueues) != null &&
2280	>	(m = ws.length - 1) >= 0) ?
2281	>	ws[m & z.seed & SQMASK] : null;
2282		}
2283
2284		/**
2285	<	* Transition run state to at least the given state. Return true
2286	<	* if not already at least given state.
2287	<	*/
2288	<	private boolean transitionRunStateTo(int state) {
2289	<	for (;;) {
2290	<	int c = runControl;
2291	<	if (runStateOf(c) >= state)
2292	<	return false;
2293	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
2285	>	* Tries to pop the given task from submitter's queue in common pool.
2286	>	*/
2287	>	static boolean tryExternalUnpush(ForkJoinTask<?> t) {
2288	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q; Submitter z;
2289	>	ForkJoinTask<?>[] a;  int m, s; long j;
2290	>	if ((z = submitters.get()) != null &&
2291	>	(p = commonPool) != null &&
2292	>	(ws = p.workQueues) != null &&
2293	>	(m = ws.length - 1) >= 0 &&
2294	>	(q = ws[m & z.seed & SQMASK]) != null &&
2295	>	(s = q.top) != q.base &&
2296	>	(a = q.array) != null &&
2297	>	U.getObjectVolatile
2298	>	(a, j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE) == t &&
2299	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2300	>	if (q.array == a && q.top == s && // recheck
2301	>	U.compareAndSwapObject(a, j, t, null)) {
2302	>	q.top = s - 1;
2303	>	q.qlock = 0;
2304		return true;
2305	+	}
2306	+	q.qlock = 0;
2307		}
2308	+	return false;
2309		}
2310
2311		/**
2312	<	* Controls whether to add spares to maintain parallelism
2312	>	* Tries to pop and run local tasks within the same computation
2313	>	* as the given root. On failure, tries to help complete from
2314	>	* other queues via helpComplete.
2315	>	*/
2316	>	private void externalHelpComplete(WorkQueue q, ForkJoinTask<?> root) {
2317	>	ForkJoinTask<?>[] a; int m;
2318	>	if (q != null && (a = q.array) != null && (m = (a.length - 1)) >= 0 &&
2319	>	root != null && root.status >= 0) {
2320	>	for (;;) {
2321	>	int s, u; Object o; CountedCompleter<?> task = null;
2322	>	if ((s = q.top) - q.base > 0) {
2323	>	long j = ((m & (s - 1)) << ASHIFT) + ABASE;
2324	>	if ((o = U.getObject(a, j)) != null &&
2325	>	(o instanceof CountedCompleter)) {
2326	>	CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;
2327	>	do {
2328	>	if (r == root) {
2329	>	if (U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2330	>	if (q.array == a && q.top == s &&
2331	>	U.compareAndSwapObject(a, j, t, null)) {
2332	>	q.top = s - 1;
2333	>	task = t;
2334	>	}
2335	>	q.qlock = 0;
2336	>	}
2337	>	break;
2338	>	}
2339	>	} while ((r = r.completer) != null);
2340	>	}
2341	>	}
2342	>	if (task != null)
2343	>	task.doExec();
2344	>	if (root.status < 0 ||
2345	>	(u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0)
2346	>	break;
2347	>	if (task == null) {
2348	>	if (helpSignal(root, q.poolIndex) >= 0)
2349	>	helpComplete(root, SHARED_QUEUE);
2350	>	break;
2351	>	}
2352	>	}
2353	>	}
2354	>	}
2355	>
2356	>	/**
2357	>	* Tries to help execute or signal availability of the given task
2358	>	* from submitter's queue in common pool.
2359		*/
2360	<	private volatile boolean maintainsParallelism;
2360	>	static void externalHelpJoin(ForkJoinTask<?> t) {
2361	>	// Some hard-to-avoid overlap with tryExternalUnpush
2362	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; Submitter z;
2363	>	ForkJoinTask<?>[] a;  int m, s, n; long j;
2364	>	if (t != null &&
2365	>	(z = submitters.get()) != null &&
2366	>	(p = commonPool) != null &&
2367	>	(ws = p.workQueues) != null &&
2368	>	(m = ws.length - 1) >= 0 &&
2369	>	(q = ws[m & z.seed & SQMASK]) != null &&
2370	>	(a = q.array) != null &&
2371	>	t.status >= 0) {
2372	>	if ((s = q.top) != q.base &&
2373	>	U.getObjectVolatile
2374	>	(a, j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE) == t &&
2375	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2376	>	if (q.array == a && q.top == s &&
2377	>	U.compareAndSwapObject(a, j, t, null)) {
2378	>	q.top = s - 1;
2379	>	q.qlock = 0;
2380	>	t.doExec();
2381	>	}
2382	>	else
2383	>	q.qlock = 0;
2384	>	}
2385	>	if (t.status >= 0) {
2386	>	if (t instanceof CountedCompleter)
2387	>	p.externalHelpComplete(q, t);
2388	>	else
2389	>	p.helpSignal(t, q.poolIndex);
2390	>	}
2391	>	}
2392	>	}
2393	>
2394	>	/**
2395	>	* Restricted version of helpQuiescePool for external callers
2396	>	*/
2397	>	static void externalHelpQuiescePool() {
2398	>	ForkJoinPool p; ForkJoinTask<?> t; WorkQueue q; int b;
2399	>	if ((p = commonPool) != null &&
2400	>	(q = p.findNonEmptyStealQueue(1)) != null &&
2401	>	(b = q.base) - q.top < 0 &&
2402	>	(t = q.pollAt(b)) != null)
2403	>	t.doExec();
2404	>	}
2405	>
2406	>	// Exported methods
2407
2408		// Constructors
2409
2410		/**
2411	<	* Creates a ForkJoinPool with a pool size equal to the number of
2412	<	* processors available on the system, using the default
2413	<	* ForkJoinWorkerThreadFactory.
2411	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
2412	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
2413	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
2414	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
2415		*
2416		* @throws SecurityException if a security manager exists and
2417		*         the caller is not permitted to modify threads
#	Line 346 | Line 2420 | public class ForkJoinPool extends Abstra
2420		*/
2421		public ForkJoinPool() {
2422		this(Runtime.getRuntime().availableProcessors(),
2423	<	defaultForkJoinWorkerThreadFactory);
2423	>	defaultForkJoinWorkerThreadFactory, null, false);
2424		}
2425
2426		/**
2427	<	* Creates a ForkJoinPool with the indicated parallelism level
2428	<	* threads and using the default ForkJoinWorkerThreadFactory.
2427	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
2428	>	* level, the {@linkplain
2429	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
2430	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
2431		*
2432	<	* @param parallelism the number of worker threads
2432	>	* @param parallelism the parallelism level
2433		* @throws IllegalArgumentException if parallelism less than or
2434	<	* equal to zero
2434	>	*         equal to zero, or greater than implementation limit
2435		* @throws SecurityException if a security manager exists and
2436		*         the caller is not permitted to modify threads
2437		*         because it does not hold {@link
2438		*         java.lang.RuntimePermission}{@code ("modifyThread")}
2439		*/
2440		public ForkJoinPool(int parallelism) {
2441	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
366	<	}
367	<
368	<	/**
369	<	* Creates a ForkJoinPool with parallelism equal to the number of
370	<	* processors available on the system and using the given
371	<	* ForkJoinWorkerThreadFactory.
372	<	*
373	<	* @param factory the factory for creating new threads
374	<	* @throws NullPointerException if factory is null
375	<	* @throws SecurityException if a security manager exists and
376	<	*         the caller is not permitted to modify threads
377	<	*         because it does not hold {@link
378	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
379	<	*/
380	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
381	<	this(Runtime.getRuntime().availableProcessors(), factory);
2441	>	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
2442		}
2443
2444		/**
2445	<	* Creates a ForkJoinPool with the given parallelism and factory.
2445	>	* Creates a {@code ForkJoinPool} with the given parameters.
2446		*
2447	<	* @param parallelism the targeted number of worker threads
2448	<	* @param factory the factory for creating new threads
2447	>	* @param parallelism the parallelism level. For default value,
2448	>	* use {@link java.lang.Runtime#availableProcessors}.
2449	>	* @param factory the factory for creating new threads. For default value,
2450	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
2451	>	* @param handler the handler for internal worker threads that
2452	>	* terminate due to unrecoverable errors encountered while executing
2453	>	* tasks. For default value, use {@code null}.
2454	>	* @param asyncMode if true,
2455	>	* establishes local first-in-first-out scheduling mode for forked
2456	>	* tasks that are never joined. This mode may be more appropriate
2457	>	* than default locally stack-based mode in applications in which
2458	>	* worker threads only process event-style asynchronous tasks.
2459	>	* For default value, use {@code false}.
2460		* @throws IllegalArgumentException if parallelism less than or
2461	<	* equal to zero, or greater than implementation limit
2462	<	* @throws NullPointerException if factory is null
2461	>	*         equal to zero, or greater than implementation limit
2462	>	* @throws NullPointerException if the factory is null
2463		* @throws SecurityException if a security manager exists and
2464		*         the caller is not permitted to modify threads
2465		*         because it does not hold {@link
2466		*         java.lang.RuntimePermission}{@code ("modifyThread")}
2467		*/
2468	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
2469	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
2470	<	throw new IllegalArgumentException();
2468	>	public ForkJoinPool(int parallelism,
2469	>	ForkJoinWorkerThreadFactory factory,
2470	>	Thread.UncaughtExceptionHandler handler,
2471	>	boolean asyncMode) {
2472	>	checkPermission();
2473		if (factory == null)
2474		throw new NullPointerException();
2475	<	checkPermission();
2475	>	if (parallelism <= 0 || parallelism > MAX_CAP)
2476	>	throw new IllegalArgumentException();
2477		this.factory = factory;
2478	<	this.parallelism = parallelism;
2479	<	this.maxPoolSize = MAX_THREADS;
2480	<	this.maintainsParallelism = true;
2481	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
2482	<	this.workerLock = new ReentrantLock();
2483	<	this.termination = workerLock.newCondition();
2484	<	this.stealCount = new AtomicLong();
2485	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
2486	<	// worker array and workers are lazily constructed
2478	>	this.ueh = handler;
2479	>	this.config = parallelism | (asyncMode ? (FIFO_QUEUE << 16) : 0);
2480	>	long np = (long)(-parallelism); // offset ctl counts
2481	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
2482	>	int pn = nextPoolId();
2483	>	StringBuilder sb = new StringBuilder("ForkJoinPool-");
2484	>	sb.append(Integer.toString(pn));
2485	>	sb.append("-worker-");
2486	>	this.workerNamePrefix = sb.toString();
2487		}
2488
2489		/**
2490	<	* Creates a new worker thread using factory.
2491	<	*
2492	<	* @param index the index to assign worker
2493	<	* @return new worker, or null of factory failed
2494	<	*/
2495	<	private ForkJoinWorkerThread createWorker(int index) {
2496	<	Thread.UncaughtExceptionHandler h = ueh;
2497	<	ForkJoinWorkerThread w = factory.newThread(this);
2498	<	if (w != null) {
2499	<	w.poolIndex = index;
2500	<	w.setDaemon(true);
427	<	w.setAsyncMode(locallyFifo);
428	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
429	<	if (h != null)
430	<	w.setUncaughtExceptionHandler(h);
431	<	}
432	<	return w;
433	<	}
434	<
435	<	/**
436	<	* Returns a good size for worker array given pool size.
437	<	* Currently requires size to be a power of two.
438	<	*/
439	<	private static int arraySizeFor(int poolSize) {
440	<	return (poolSize <= 1) ? 1 :
441	<	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
2490	>	* Constructor for common pool, suitable only for static initialization.
2491	>	* Basically the same as above, but uses smallest possible initial footprint.
2492	>	*/
2493	>	ForkJoinPool(int parallelism, long ctl,
2494	>	ForkJoinWorkerThreadFactory factory,
2495	>	Thread.UncaughtExceptionHandler handler) {
2496	>	this.config = parallelism;
2497	>	this.ctl = ctl;
2498	>	this.factory = factory;
2499	>	this.ueh = handler;
2500	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2501		}
2502
2503		/**
2504	<	* Creates or resizes array if necessary to hold newLength.
446	<	* Call only under exclusion.
2504	>	* Returns the common pool instance.
2505		*
2506	<	* @return the array
449	<	*/
450	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
451	<	ForkJoinWorkerThread[] ws = workers;
452	<	if (ws == null)
453	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
454	<	else if (newLength > ws.length)
455	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
456	<	else
457	<	return ws;
458	<	}
459	<
460	<	/**
461	<	* Tries to shrink workers into smaller array after one or more terminate.
2506	>	* @return the common pool instance
2507		*/
2508	<	private void tryShrinkWorkerArray() {
2509	<	ForkJoinWorkerThread[] ws = workers;
2510	<	if (ws != null) {
466	<	int len = ws.length;
467	<	int last = len - 1;
468	<	while (last >= 0 && ws[last] == null)
469	<	--last;
470	<	int newLength = arraySizeFor(last+1);
471	<	if (newLength < len)
472	<	workers = Arrays.copyOf(ws, newLength);
473	<	}
474	<	}
475	<
476	<	/**
477	<	* Initializes workers if necessary.
478	<	*/
479	<	final void ensureWorkerInitialization() {
480	<	ForkJoinWorkerThread[] ws = workers;
481	<	if (ws == null) {
482	<	final ReentrantLock lock = this.workerLock;
483	<	lock.lock();
484	<	try {
485	<	ws = workers;
486	<	if (ws == null) {
487	<	int ps = parallelism;
488	<	ws = ensureWorkerArrayCapacity(ps);
489	<	for (int i = 0; i < ps; ++i) {
490	<	ForkJoinWorkerThread w = createWorker(i);
491	<	if (w != null) {
492	<	ws[i] = w;
493	<	w.start();
494	<	updateWorkerCount(1);
495	<	}
496	<	}
497	<	}
498	<	} finally {
499	<	lock.unlock();
500	<	}
501	<	}
502	<	}
503	<
504	<	/**
505	<	* Worker creation and startup for threads added via setParallelism.
506	<	*/
507	<	private void createAndStartAddedWorkers() {
508	<	resumeAllSpares();  // Allow spares to convert to nonspare
509	<	int ps = parallelism;
510	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
511	<	int len = ws.length;
512	<	// Sweep through slots, to keep lowest indices most populated
513	<	int k = 0;
514	<	while (k < len) {
515	<	if (ws[k] != null) {
516	<	++k;
517	<	continue;
518	<	}
519	<	int s = workerCounts;
520	<	int tc = totalCountOf(s);
521	<	int rc = runningCountOf(s);
522	<	if (rc >= ps || tc >= ps)
523	<	break;
524	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
525	<	ForkJoinWorkerThread w = createWorker(k);
526	<	if (w != null) {
527	<	ws[k++] = w;
528	<	w.start();
529	<	}
530	<	else {
531	<	updateWorkerCount(-1); // back out on failed creation
532	<	break;
533	<	}
534	<	}
535	<	}
2508	>	public static ForkJoinPool commonPool() {
2509	>	// assert commonPool != null : "static init error";
2510	>	return commonPool;
2511		}
2512
2513		// Execution methods
2514
2515		/**
541	–	* Common code for execute, invoke and submit
542	–	*/
543	–	private <T> void doSubmit(ForkJoinTask<T> task) {
544	–	if (isShutdown())
545	–	throw new RejectedExecutionException();
546	–	if (workers == null)
547	–	ensureWorkerInitialization();
548	–	submissionQueue.offer(task);
549	–	signalIdleWorkers();
550	–	}
551	–
552	–	/**
2516		* Performs the given task, returning its result upon completion.
2517	+	* If the computation encounters an unchecked Exception or Error,
2518	+	* it is rethrown as the outcome of this invocation.  Rethrown
2519	+	* exceptions behave in the same way as regular exceptions, but,
2520	+	* when possible, contain stack traces (as displayed for example
2521	+	* using {@code ex.printStackTrace()}) of both the current thread
2522	+	* as well as the thread actually encountering the exception;
2523	+	* minimally only the latter.
2524		*
2525		* @param task the task
2526		* @return the task's result
2527	<	* @throws NullPointerException if task is null
2528	<	* @throws RejectedExecutionException if pool is shut down
2527	>	* @throws NullPointerException if the task is null
2528	>	* @throws RejectedExecutionException if the task cannot be
2529	>	*         scheduled for execution
2530		*/
2531		public <T> T invoke(ForkJoinTask<T> task) {
2532	<	doSubmit(task);
2532	>	if (task == null)
2533	>	throw new NullPointerException();
2534	>	externalPush(task);
2535		return task.join();
2536		}
2537
#	Line 566 | Line 2539 | public class ForkJoinPool extends Abstra
2539		* Arranges for (asynchronous) execution of the given task.
2540		*
2541		* @param task the task
2542	<	* @throws NullPointerException if task is null
2543	<	* @throws RejectedExecutionException if pool is shut down
2542	>	* @throws NullPointerException if the task is null
2543	>	* @throws RejectedExecutionException if the task cannot be
2544	>	*         scheduled for execution
2545		*/
2546	<	public <T> void execute(ForkJoinTask<T> task) {
2547	<	doSubmit(task);
2546	>	public void execute(ForkJoinTask<?> task) {
2547	>	if (task == null)
2548	>	throw new NullPointerException();
2549	>	externalPush(task);
2550		}
2551
2552		// AbstractExecutorService methods
2553
2554	+	/**
2555	+	* @throws NullPointerException if the task is null
2556	+	* @throws RejectedExecutionException if the task cannot be
2557	+	*         scheduled for execution
2558	+	*/
2559		public void execute(Runnable task) {
2560	<	doSubmit(new AdaptedRunnable<Void>(task, null));
2560	>	if (task == null)
2561	>	throw new NullPointerException();
2562	>	ForkJoinTask<?> job;
2563	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2564	>	job = (ForkJoinTask<?>) task;
2565	>	else
2566	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2567	>	externalPush(job);
2568		}
2569
2570	<	public <T> ForkJoinTask<T> submit(Callable<T> task) {
2571	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
2572	<	doSubmit(job);
2573	<	return job;
2570	>	/**
2571	>	* Submits a ForkJoinTask for execution.
2572	>	*
2573	>	* @param task the task to submit
2574	>	* @return the task
2575	>	* @throws NullPointerException if the task is null
2576	>	* @throws RejectedExecutionException if the task cannot be
2577	>	*         scheduled for execution
2578	>	*/
2579	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2580	>	if (task == null)
2581	>	throw new NullPointerException();
2582	>	externalPush(task);
2583	>	return task;
2584		}
2585
2586	<	public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2587	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
2588	<	doSubmit(job);
2586	>	/**
2587	>	* @throws NullPointerException if the task is null
2588	>	* @throws RejectedExecutionException if the task cannot be
2589	>	*         scheduled for execution
2590	>	*/
2591	>	public <T> ForkJoinTask<T> submit(Callable<T> task) {
2592	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2593	>	externalPush(job);
2594		return job;
2595		}
2596
2597	<	public ForkJoinTask<?> submit(Runnable task) {
2598	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
2599	<	doSubmit(job);
2597	>	/**
2598	>	* @throws NullPointerException if the task is null
2599	>	* @throws RejectedExecutionException if the task cannot be
2600	>	*         scheduled for execution
2601	>	*/
2602	>	public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2603	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2604	>	externalPush(job);
2605		return job;
2606		}
2607
2608		/**
2609	<	* Adaptor for Runnables. This implements RunnableFuture
2610	<	* to be compliant with AbstractExecutorService constraints.
2609	>	* @throws NullPointerException if the task is null
2610	>	* @throws RejectedExecutionException if the task cannot be
2611	>	*         scheduled for execution
2612		*/
2613	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
2614	<	implements RunnableFuture<T> {
2615	<	final Runnable runnable;
2616	<	final T resultOnCompletion;
2617	<	T result;
2618	<	AdaptedRunnable(Runnable runnable, T result) {
2619	<	if (runnable == null) throw new NullPointerException();
2620	<	this.runnable = runnable;
2621	<	this.resultOnCompletion = result;
2622	<	}
614	<	public T getRawResult() { return result; }
615	<	public void setRawResult(T v) { result = v; }
616	<	public boolean exec() {
617	<	runnable.run();
618	<	result = resultOnCompletion;
619	<	return true;
620	<	}
621	<	public void run() { invoke(); }
2613	>	public ForkJoinTask<?> submit(Runnable task) {
2614	>	if (task == null)
2615	>	throw new NullPointerException();
2616	>	ForkJoinTask<?> job;
2617	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2618	>	job = (ForkJoinTask<?>) task;
2619	>	else
2620	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2621	>	externalPush(job);
2622	>	return job;
2623		}
2624
2625		/**
2626	<	* Adaptor for Callables
2626	>	* @throws NullPointerException       {@inheritDoc}
2627	>	* @throws RejectedExecutionException {@inheritDoc}
2628		*/
627	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
628	–	implements RunnableFuture<T> {
629	–	final Callable<T> callable;
630	–	T result;
631	–	AdaptedCallable(Callable<T> callable) {
632	–	if (callable == null) throw new NullPointerException();
633	–	this.callable = callable;
634	–	}
635	–	public T getRawResult() { return result; }
636	–	public void setRawResult(T v) { result = v; }
637	–	public boolean exec() {
638	–	try {
639	–	result = callable.call();
640	–	return true;
641	–	} catch (Error err) {
642	–	throw err;
643	–	} catch (RuntimeException rex) {
644	–	throw rex;
645	–	} catch (Exception ex) {
646	–	throw new RuntimeException(ex);
647	–	}
648	–	}
649	–	public void run() { invoke(); }
650	–	}
651	–
2629		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
2630	<	ArrayList<ForkJoinTask<T>> ts =
2631	<	new ArrayList<ForkJoinTask<T>>(tasks.size());
2632	<	for (Callable<T> c : tasks)
2633	<	ts.add(new AdaptedCallable<T>(c));
2634	<	invoke(new InvokeAll<T>(ts));
2635	<	return (List<Future<T>>) (List) ts;
2636	<	}
2630	>	// In previous versions of this class, this method constructed
2631	>	// a task to run ForkJoinTask.invokeAll, but now external
2632	>	// invocation of multiple tasks is at least as efficient.
2633	>	List<ForkJoinTask<T>> fs = new ArrayList<ForkJoinTask<T>>(tasks.size());
2634	>	// Workaround needed because method wasn't declared with
2635	>	// wildcards in return type but should have been.
2636	>	@SuppressWarnings({"unchecked", "rawtypes"})
2637	>	List<Future<T>> futures = (List<Future<T>>) (List) fs;
2638
2639	<	static final class InvokeAll<T> extends RecursiveAction {
2640	<	final ArrayList<ForkJoinTask<T>> tasks;
2641	<	InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
2642	<	public void compute() {
2643	<	try { invokeAll(tasks); }
2644	<	catch (Exception ignore) {}
2639	>	boolean done = false;
2640	>	try {
2641	>	for (Callable<T> t : tasks) {
2642	>	ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2643	>	externalPush(f);
2644	>	fs.add(f);
2645	>	}
2646	>	for (ForkJoinTask<T> f : fs)
2647	>	f.quietlyJoin();
2648	>	done = true;
2649	>	return futures;
2650	>	} finally {
2651	>	if (!done)
2652	>	for (ForkJoinTask<T> f : fs)
2653	>	f.cancel(false);
2654		}
2655		}
2656
670	–	// Configuration and status settings and queries
671	–
2657		/**
2658		* Returns the factory used for constructing new workers.
2659		*
#	Line 682 | Line 2667 | public class ForkJoinPool extends Abstra
2667		* Returns the handler for internal worker threads that terminate
2668		* due to unrecoverable errors encountered while executing tasks.
2669		*
2670	<	* @return the handler, or null if none
2670	>	* @return the handler, or {@code null} if none
2671		*/
2672		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
2673	<	Thread.UncaughtExceptionHandler h;
689	<	final ReentrantLock lock = this.workerLock;
690	<	lock.lock();
691	<	try {
692	<	h = ueh;
693	<	} finally {
694	<	lock.unlock();
695	<	}
696	<	return h;
2673	>	return ueh;
2674		}
2675
2676		/**
2677	<	* Sets the handler for internal worker threads that terminate due
701	<	* to unrecoverable errors encountered while executing tasks.
702	<	* Unless set, the current default or ThreadGroup handler is used
703	<	* as handler.
2677	>	* Returns the targeted parallelism level of this pool.
2678		*
2679	<	* @param h the new handler
706	<	* @return the old handler, or null if none
707	<	* @throws SecurityException if a security manager exists and
708	<	*         the caller is not permitted to modify threads
709	<	*         because it does not hold {@link
710	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
2679	>	* @return the targeted parallelism level of this pool
2680		*/
2681	<	public Thread.UncaughtExceptionHandler
2682	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
714	<	checkPermission();
715	<	Thread.UncaughtExceptionHandler old = null;
716	<	final ReentrantLock lock = this.workerLock;
717	<	lock.lock();
718	<	try {
719	<	old = ueh;
720	<	ueh = h;
721	<	ForkJoinWorkerThread[] ws = workers;
722	<	if (ws != null) {
723	<	for (int i = 0; i < ws.length; ++i) {
724	<	ForkJoinWorkerThread w = ws[i];
725	<	if (w != null)
726	<	w.setUncaughtExceptionHandler(h);
727	<	}
728	<	}
729	<	} finally {
730	<	lock.unlock();
731	<	}
732	<	return old;
733	<	}
734	<
735	<
736	<	/**
737	<	* Sets the target parallelism level of this pool.
738	<	*
739	<	* @param parallelism the target parallelism
740	<	* @throws IllegalArgumentException if parallelism less than or
741	<	* equal to zero or greater than maximum size bounds
742	<	* @throws SecurityException if a security manager exists and
743	<	*         the caller is not permitted to modify threads
744	<	*         because it does not hold {@link
745	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
746	<	*/
747	<	public void setParallelism(int parallelism) {
748	<	checkPermission();
749	<	if (parallelism <= 0 || parallelism > maxPoolSize)
750	<	throw new IllegalArgumentException();
751	<	final ReentrantLock lock = this.workerLock;
752	<	lock.lock();
753	<	try {
754	<	if (!isTerminating()) {
755	<	int p = this.parallelism;
756	<	this.parallelism = parallelism;
757	<	if (parallelism > p)
758	<	createAndStartAddedWorkers();
759	<	else
760	<	trimSpares();
761	<	}
762	<	} finally {
763	<	lock.unlock();
764	<	}
765	<	signalIdleWorkers();
2681	>	public int getParallelism() {
2682	>	return config & SMASK;
2683		}
2684
2685		/**
2686	<	* Returns the targeted number of worker threads in this pool.
2686	>	* Returns the targeted parallelism level of the common pool.
2687		*
2688	<	* @return the targeted number of worker threads in this pool
2688	>	* @return the targeted parallelism level of the common pool
2689		*/
2690	<	public int getParallelism() {
2691	<	return parallelism;
2690	>	public static int getCommonPoolParallelism() {
2691	>	return commonPoolParallelism;
2692		}
2693
2694		/**
2695		* Returns the number of worker threads that have started but not
2696	<	* yet terminated.  This result returned by this method may differ
2697	<	* from {@code getParallelism} when threads are created to
2696	>	* yet terminated.  The result returned by this method may differ
2697	>	* from {@link #getParallelism} when threads are created to
2698		* maintain parallelism when others are cooperatively blocked.
2699		*
2700		* @return the number of worker threads
2701		*/
2702		public int getPoolSize() {
2703	<	return totalCountOf(workerCounts);
787	<	}
788	<
789	<	/**
790	<	* Returns the maximum number of threads allowed to exist in the
791	<	* pool, even if there are insufficient unblocked running threads.
792	<	*
793	<	* @return the maximum
794	<	*/
795	<	public int getMaximumPoolSize() {
796	<	return maxPoolSize;
2703	>	return (config & SMASK) + (short)(ctl >>> TC_SHIFT);
2704		}
2705
2706		/**
2707	<	* Sets the maximum number of threads allowed to exist in the
801	<	* pool, even if there are insufficient unblocked running threads.
802	<	* Setting this value has no effect on current pool size. It
803	<	* controls construction of new threads.
804	<	*
805	<	* @throws IllegalArgumentException if negative or greater then
806	<	* internal implementation limit
807	<	*/
808	<	public void setMaximumPoolSize(int newMax) {
809	<	if (newMax < 0 || newMax > MAX_THREADS)
810	<	throw new IllegalArgumentException();
811	<	maxPoolSize = newMax;
812	<	}
813	<
814	<
815	<	/**
816	<	* Returns true if this pool dynamically maintains its target
817	<	* parallelism level. If false, new threads are added only to
818	<	* avoid possible starvation.
819	<	* This setting is by default true.
820	<	*
821	<	* @return true if maintains parallelism
822	<	*/
823	<	public boolean getMaintainsParallelism() {
824	<	return maintainsParallelism;
825	<	}
826	<
827	<	/**
828	<	* Sets whether this pool dynamically maintains its target
829	<	* parallelism level. If false, new threads are added only to
830	<	* avoid possible starvation.
831	<	*
832	<	* @param enable true to maintains parallelism
833	<	*/
834	<	public void setMaintainsParallelism(boolean enable) {
835	<	maintainsParallelism = enable;
836	<	}
837	<
838	<	/**
839	<	* Establishes local first-in-first-out scheduling mode for forked
840	<	* tasks that are never joined. This mode may be more appropriate
841	<	* than default locally stack-based mode in applications in which
842	<	* worker threads only process asynchronous tasks.  This method is
843	<	* designed to be invoked only when pool is quiescent, and
844	<	* typically only before any tasks are submitted. The effects of
845	<	* invocations at other times may be unpredictable.
846	<	*
847	<	* @param async if true, use locally FIFO scheduling
848	<	* @return the previous mode
849	<	*/
850	<	public boolean setAsyncMode(boolean async) {
851	<	boolean oldMode = locallyFifo;
852	<	locallyFifo = async;
853	<	ForkJoinWorkerThread[] ws = workers;
854	<	if (ws != null) {
855	<	for (int i = 0; i < ws.length; ++i) {
856	<	ForkJoinWorkerThread t = ws[i];
857	<	if (t != null)
858	<	t.setAsyncMode(async);
859	<	}
860	<	}
861	<	return oldMode;
862	<	}
863	<
864	<	/**
865	<	* Returns true if this pool uses local first-in-first-out
2707	>	* Returns {@code true} if this pool uses local first-in-first-out
2708		* scheduling mode for forked tasks that are never joined.
2709		*
2710	<	* @return true if this pool uses async mode
2710	>	* @return {@code true} if this pool uses async mode
2711		*/
2712		public boolean getAsyncMode() {
2713	<	return locallyFifo;
2713	>	return (config >>> 16) == FIFO_QUEUE;
2714		}
2715
2716		/**
2717		* Returns an estimate of the number of worker threads that are
2718		* not blocked waiting to join tasks or for other managed
2719	<	* synchronization.
2719	>	* synchronization. This method may overestimate the
2720	>	* number of running threads.
2721		*
2722		* @return the number of worker threads
2723		*/
2724		public int getRunningThreadCount() {
2725	<	return runningCountOf(workerCounts);
2725	>	int rc = 0;
2726	>	WorkQueue[] ws; WorkQueue w;
2727	>	if ((ws = workQueues) != null) {
2728	>	for (int i = 1; i < ws.length; i += 2) {
2729	>	if ((w = ws[i]) != null && w.isApparentlyUnblocked())
2730	>	++rc;
2731	>	}
2732	>	}
2733	>	return rc;
2734		}
2735
2736		/**
#	Line 890 | Line 2741 | public class ForkJoinPool extends Abstra
2741		* @return the number of active threads
2742		*/
2743		public int getActiveThreadCount() {
2744	<	return activeCountOf(runControl);
2745	<	}
895	<
896	<	/**
897	<	* Returns an estimate of the number of threads that are currently
898	<	* idle waiting for tasks. This method may underestimate the
899	<	* number of idle threads.
900	<	*
901	<	* @return the number of idle threads
902	<	*/
903	<	final int getIdleThreadCount() {
904	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
905	<	return (c <= 0) ? 0 : c;
2744	>	int r = (config & SMASK) + (int)(ctl >> AC_SHIFT);
2745	>	return (r <= 0) ? 0 : r; // suppress momentarily negative values
2746		}
2747
2748		/**
2749	<	* Returns true if all worker threads are currently idle. An idle
2750	<	* worker is one that cannot obtain a task to execute because none
2751	<	* are available to steal from other threads, and there are no
2752	<	* pending submissions to the pool. This method is conservative;
2753	<	* it might not return true immediately upon idleness of all
2754	<	* threads, but will eventually become true if threads remain
2755	<	* inactive.
2749	>	* Returns {@code true} if all worker threads are currently idle.
2750	>	* An idle worker is one that cannot obtain a task to execute
2751	>	* because none are available to steal from other threads, and
2752	>	* there are no pending submissions to the pool. This method is
2753	>	* conservative; it might not return {@code true} immediately upon
2754	>	* idleness of all threads, but will eventually become true if
2755	>	* threads remain inactive.
2756		*
2757	<	* @return true if all threads are currently idle
2757	>	* @return {@code true} if all threads are currently idle
2758		*/
2759		public boolean isQuiescent() {
2760	<	return activeCountOf(runControl) == 0;
2760	>	return (int)(ctl >> AC_SHIFT) + (config & SMASK) == 0;
2761		}
2762
2763		/**
#	Line 932 | Line 2772 | public class ForkJoinPool extends Abstra
2772		* @return the number of steals
2773		*/
2774		public long getStealCount() {
2775	<	return stealCount.get();
2776	<	}
2777	<
2778	<	/**
2779	<	* Accumulates steal count from a worker.
2780	<	* Call only when worker known to be idle.
2781	<	*/
2782	<	private void updateStealCount(ForkJoinWorkerThread w) {
2783	<	int sc = w.getAndClearStealCount();
944	<	if (sc != 0)
945	<	stealCount.addAndGet(sc);
2775	>	long count = stealCount;
2776	>	WorkQueue[] ws; WorkQueue w;
2777	>	if ((ws = workQueues) != null) {
2778	>	for (int i = 1; i < ws.length; i += 2) {
2779	>	if ((w = ws[i]) != null)
2780	>	count += w.nsteals;
2781	>	}
2782	>	}
2783	>	return count;
2784		}
2785
2786		/**
#	Line 957 | Line 2795 | public class ForkJoinPool extends Abstra
2795		*/
2796		public long getQueuedTaskCount() {
2797		long count = 0;
2798	<	ForkJoinWorkerThread[] ws = workers;
2799	<	if (ws != null) {
2800	<	for (int i = 0; i < ws.length; ++i) {
2801	<	ForkJoinWorkerThread t = ws[i];
2802	<	if (t != null)
965	<	count += t.getQueueSize();
2798	>	WorkQueue[] ws; WorkQueue w;
2799	>	if ((ws = workQueues) != null) {
2800	>	for (int i = 1; i < ws.length; i += 2) {
2801	>	if ((w = ws[i]) != null)
2802	>	count += w.queueSize();
2803		}
2804		}
2805		return count;
2806		}
2807
2808		/**
2809	<	* Returns an estimate of the number tasks submitted to this pool
2810	<	* that have not yet begun executing. This method takes time
2811	<	* proportional to the number of submissions.
2809	>	* Returns an estimate of the number of tasks submitted to this
2810	>	* pool that have not yet begun executing.  This method may take
2811	>	* time proportional to the number of submissions.
2812		*
2813		* @return the number of queued submissions
2814		*/
2815		public int getQueuedSubmissionCount() {
2816	<	return submissionQueue.size();
2816	>	int count = 0;
2817	>	WorkQueue[] ws; WorkQueue w;
2818	>	if ((ws = workQueues) != null) {
2819	>	for (int i = 0; i < ws.length; i += 2) {
2820	>	if ((w = ws[i]) != null)
2821	>	count += w.queueSize();
2822	>	}
2823	>	}
2824	>	return count;
2825		}
2826
2827		/**
2828	<	* Returns true if there are any tasks submitted to this pool
2829	<	* that have not yet begun executing.
2828	>	* Returns {@code true} if there are any tasks submitted to this
2829	>	* pool that have not yet begun executing.
2830		*
2831		* @return {@code true} if there are any queued submissions
2832		*/
2833		public boolean hasQueuedSubmissions() {
2834	<	return !submissionQueue.isEmpty();
2834	>	WorkQueue[] ws; WorkQueue w;
2835	>	if ((ws = workQueues) != null) {
2836	>	for (int i = 0; i < ws.length; i += 2) {
2837	>	if ((w = ws[i]) != null && w.queueSize() != 0)
2838	>	return true;
2839	>	}
2840	>	}
2841	>	return false;
2842		}
2843
2844		/**
#	Line 994 | Line 2846 | public class ForkJoinPool extends Abstra
2846		* available.  This method may be useful in extensions to this
2847		* class that re-assign work in systems with multiple pools.
2848		*
2849	<	* @return the next submission, or null if none
2849	>	* @return the next submission, or {@code null} if none
2850		*/
2851		protected ForkJoinTask<?> pollSubmission() {
2852	<	return submissionQueue.poll();
2852	>	WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2853	>	if ((ws = workQueues) != null) {
2854	>	for (int i = 0; i < ws.length; i += 2) {
2855	>	if ((w = ws[i]) != null && (t = w.poll()) != null)
2856	>	return t;
2857	>	}
2858	>	}
2859	>	return null;
2860		}
2861
2862		/**
2863		* Removes all available unexecuted submitted and forked tasks
2864		* from scheduling queues and adds them to the given collection,
2865		* without altering their execution status. These may include
2866	<	* artificially generated or wrapped tasks. This method is designed
2867	<	* to be invoked only when the pool is known to be
2866	>	* artificially generated or wrapped tasks. This method is
2867	>	* designed to be invoked only when the pool is known to be
2868		* quiescent. Invocations at other times may not remove all
2869		* tasks. A failure encountered while attempting to add elements
2870		* to collection {@code c} may result in elements being in
#	Line 1017 | Line 2876 | public class ForkJoinPool extends Abstra
2876		* @param c the collection to transfer elements into
2877		* @return the number of elements transferred
2878		*/
2879	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
2880	<	int n = submissionQueue.drainTo(c);
2881	<	ForkJoinWorkerThread[] ws = workers;
2882	<	if (ws != null) {
2879	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
2880	>	int count = 0;
2881	>	WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2882	>	if ((ws = workQueues) != null) {
2883		for (int i = 0; i < ws.length; ++i) {
2884	<	ForkJoinWorkerThread w = ws[i];
2885	<	if (w != null)
2886	<	n += w.drainTasksTo(c);
2884	>	if ((w = ws[i]) != null) {
2885	>	while ((t = w.poll()) != null) {
2886	>	c.add(t);
2887	>	++count;
2888	>	}
2889	>	}
2890		}
2891		}
2892	<	return n;
2892	>	return count;
2893		}
2894
2895		/**
#	Line 1038 | Line 2900 | public class ForkJoinPool extends Abstra
2900		* @return a string identifying this pool, as well as its state
2901		*/
2902		public String toString() {
2903	<	int ps = parallelism;
2904	<	int wc = workerCounts;
2905	<	int rc = runControl;
2906	<	long st = getStealCount();
2907	<	long qt = getQueuedTaskCount();
2908	<	long qs = getQueuedSubmissionCount();
2903	>	// Use a single pass through workQueues to collect counts
2904	>	long qt = 0L, qs = 0L; int rc = 0;
2905	>	long st = stealCount;
2906	>	long c = ctl;
2907	>	WorkQueue[] ws; WorkQueue w;
2908	>	if ((ws = workQueues) != null) {
2909	>	for (int i = 0; i < ws.length; ++i) {
2910	>	if ((w = ws[i]) != null) {
2911	>	int size = w.queueSize();
2912	>	if ((i & 1) == 0)
2913	>	qs += size;
2914	>	else {
2915	>	qt += size;
2916	>	st += w.nsteals;
2917	>	if (w.isApparentlyUnblocked())
2918	>	++rc;
2919	>	}
2920	>	}
2921	>	}
2922	>	}
2923	>	int pc = (config & SMASK);
2924	>	int tc = pc + (short)(c >>> TC_SHIFT);
2925	>	int ac = pc + (int)(c >> AC_SHIFT);
2926	>	if (ac < 0) // ignore transient negative
2927	>	ac = 0;
2928	>	String level;
2929	>	if ((c & STOP_BIT) != 0)
2930	>	level = (tc == 0) ? "Terminated" : "Terminating";
2931	>	else
2932	>	level = plock < 0 ? "Shutting down" : "Running";
2933		return super.toString() +
2934	<	"[" + runStateToString(runStateOf(rc)) +
2935	<	", parallelism = " + ps +
2936	<	", size = " + totalCountOf(wc) +
2937	<	", active = " + activeCountOf(rc) +
2938	<	", running = " + runningCountOf(wc) +
2934	>	"[" + level +
2935	>	", parallelism = " + pc +
2936	>	", size = " + tc +
2937	>	", active = " + ac +
2938	>	", running = " + rc +
2939		", steals = " + st +
2940		", tasks = " + qt +
2941		", submissions = " + qs +
2942		"]";
2943		}
2944
1059	–	private static String runStateToString(int rs) {
1060	–	switch(rs) {
1061	–	case RUNNING: return "Running";
1062	–	case SHUTDOWN: return "Shutting down";
1063	–	case TERMINATING: return "Terminating";
1064	–	case TERMINATED: return "Terminated";
1065	–	default: throw new Error("Unknown run state");
1066	–	}
1067	–	}
1068	–
1069	–	// lifecycle control
1070	–
2945		/**
2946	<	* Initiates an orderly shutdown in which previously submitted
2947	<	* tasks are executed, but no new tasks will be accepted.
2948	<	* Invocation has no additional effect if already shut down.
2949	<	* Tasks that are in the process of being submitted concurrently
2950	<	* during the course of this method may or may not be rejected.
2946	>	* Possibly initiates an orderly shutdown in which previously
2947	>	* submitted tasks are executed, but no new tasks will be
2948	>	* accepted. Invocation has no effect on execution state if this
2949	>	* is the {@link #commonPool}, and no additional effect if
2950	>	* already shut down.  Tasks that are in the process of being
2951	>	* submitted concurrently during the course of this method may or
2952	>	* may not be rejected.
2953		*
2954		* @throws SecurityException if a security manager exists and
2955		*         the caller is not permitted to modify threads
#	Line 1082 | Line 2958 | public class ForkJoinPool extends Abstra
2958		*/
2959		public void shutdown() {
2960		checkPermission();
2961	<	transitionRunStateTo(SHUTDOWN);
1086	<	if (canTerminateOnShutdown(runControl))
1087	<	terminateOnShutdown();
2961	>	tryTerminate(false, true);
2962		}
2963
2964		/**
2965	<	* Attempts to stop all actively executing tasks, and cancels all
2966	<	* waiting tasks.  Tasks that are in the process of being
2967	<	* submitted or executed concurrently during the course of this
2968	<	* method may or may not be rejected. Unlike some other executors,
2969	<	* this method cancels rather than collects non-executed tasks
2970	<	* upon termination, so always returns an empty list. However, you
2971	<	* can use method {@code drainTasksTo} before invoking this
2972	<	* method to transfer unexecuted tasks to another collection.
2965	>	* Possibly attempts to cancel and/or stop all tasks, and reject
2966	>	* all subsequently submitted tasks.  Invocation has no effect on
2967	>	* execution state if this is the {@link #commonPool}, and no
2968	>	* additional effect if already shut down. Otherwise, tasks that
2969	>	* are in the process of being submitted or executed concurrently
2970	>	* during the course of this method may or may not be
2971	>	* rejected. This method cancels both existing and unexecuted
2972	>	* tasks, in order to permit termination in the presence of task
2973	>	* dependencies. So the method always returns an empty list
2974	>	* (unlike the case for some other Executors).
2975		*
2976		* @return an empty list
2977		* @throws SecurityException if a security manager exists and
#	Line 1105 | Line 2981 | public class ForkJoinPool extends Abstra
2981		*/
2982		public List<Runnable> shutdownNow() {
2983		checkPermission();
2984	<	terminate();
2984	>	tryTerminate(true, true);
2985		return Collections.emptyList();
2986		}
2987
#	Line 1115 | Line 2991 | public class ForkJoinPool extends Abstra
2991		* @return {@code true} if all tasks have completed following shut down
2992		*/
2993		public boolean isTerminated() {
2994	<	return runStateOf(runControl) == TERMINATED;
2994	>	long c = ctl;
2995	>	return ((c & STOP_BIT) != 0L &&
2996	>	(short)(c >>> TC_SHIFT) == -(config & SMASK));
2997		}
2998
2999		/**
3000		* Returns {@code true} if the process of termination has
3001	<	* commenced but possibly not yet completed.
3001	>	* commenced but not yet completed.  This method may be useful for
3002	>	* debugging. A return of {@code true} reported a sufficient
3003	>	* period after shutdown may indicate that submitted tasks have
3004	>	* ignored or suppressed interruption, or are waiting for IO,
3005	>	* causing this executor not to properly terminate. (See the
3006	>	* advisory notes for class {@link ForkJoinTask} stating that
3007	>	* tasks should not normally entail blocking operations.  But if
3008	>	* they do, they must abort them on interrupt.)
3009		*
3010	<	* @return {@code true} if terminating
3010	>	* @return {@code true} if terminating but not yet terminated
3011		*/
3012		public boolean isTerminating() {
3013	<	return runStateOf(runControl) >= TERMINATING;
3013	>	long c = ctl;
3014	>	return ((c & STOP_BIT) != 0L &&
3015	>	(short)(c >>> TC_SHIFT) != -(config & SMASK));
3016		}
3017
3018		/**
#	Line 1134 | Line 3021 | public class ForkJoinPool extends Abstra
3021		* @return {@code true} if this pool has been shut down
3022		*/
3023		public boolean isShutdown() {
3024	<	return runStateOf(runControl) >= SHUTDOWN;
3024	>	return plock < 0;
3025		}
3026
3027		/**
3028	<	* Blocks until all tasks have completed execution after a shutdown
3029	<	* request, or the timeout occurs, or the current thread is
3030	<	* interrupted, whichever happens first.
3028	>	* Blocks until all tasks have completed execution after a
3029	>	* shutdown request, or the timeout occurs, or the current thread
3030	>	* is interrupted, whichever happens first. Note that the {@link
3031	>	* #commonPool()} never terminates until program shutdown so
3032	>	* this method will always time out.
3033		*
3034		* @param timeout the maximum time to wait
3035		* @param unit the time unit of the timeout argument
#	Line 1151 | Line 3040 | public class ForkJoinPool extends Abstra
3040		public boolean awaitTermination(long timeout, TimeUnit unit)
3041		throws InterruptedException {
3042		long nanos = unit.toNanos(timeout);
3043	<	final ReentrantLock lock = this.workerLock;
1155	<	lock.lock();
1156	<	try {
1157	<	for (;;) {
1158	<	if (isTerminated())
1159	<	return true;
1160	<	if (nanos <= 0)
1161	<	return false;
1162	<	nanos = termination.awaitNanos(nanos);
1163	<	}
1164	<	} finally {
1165	<	lock.unlock();
1166	<	}
1167	<	}
1168	<
1169	<	// Shutdown and termination support
1170	<
1171	<	/**
1172	<	* Callback from terminating worker. Nulls out the corresponding
1173	<	* workers slot, and if terminating, tries to terminate; else
1174	<	* tries to shrink workers array.
1175	<	*
1176	<	* @param w the worker
1177	<	*/
1178	<	final void workerTerminated(ForkJoinWorkerThread w) {
1179	<	updateStealCount(w);
1180	<	updateWorkerCount(-1);
1181	<	final ReentrantLock lock = this.workerLock;
1182	<	lock.lock();
1183	<	try {
1184	<	ForkJoinWorkerThread[] ws = workers;
1185	<	if (ws != null) {
1186	<	int idx = w.poolIndex;
1187	<	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1188	<	ws[idx] = null;
1189	<	if (totalCountOf(workerCounts) == 0) {
1190	<	terminate(); // no-op if already terminating
1191	<	transitionRunStateTo(TERMINATED);
1192	<	termination.signalAll();
1193	<	}
1194	<	else if (!isTerminating()) {
1195	<	tryShrinkWorkerArray();
1196	<	tryResumeSpare(true); // allow replacement
1197	<	}
1198	<	}
1199	<	} finally {
1200	<	lock.unlock();
1201	<	}
1202	<	signalIdleWorkers();
1203	<	}
1204	<
1205	<	/**
1206	<	* Initiates termination.
1207	<	*/
1208	<	private void terminate() {
1209	<	if (transitionRunStateTo(TERMINATING)) {
1210	<	stopAllWorkers();
1211	<	resumeAllSpares();
1212	<	signalIdleWorkers();
1213	<	cancelQueuedSubmissions();
1214	<	cancelQueuedWorkerTasks();
1215	<	interruptUnterminatedWorkers();
1216	<	signalIdleWorkers(); // resignal after interrupt
1217	<	}
1218	<	}
1219	<
1220	<	/**
1221	<	* Possibly terminates when on shutdown state.
1222	<	*/
1223	<	private void terminateOnShutdown() {
1224	<	if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
1225	<	terminate();
1226	<	}
1227	<
1228	<	/**
1229	<	* Clears out and cancels submissions.
1230	<	*/
1231	<	private void cancelQueuedSubmissions() {
1232	<	ForkJoinTask<?> task;
1233	<	while ((task = pollSubmission()) != null)
1234	<	task.cancel(false);
1235	<	}
1236	<
1237	<	/**
1238	<	* Cleans out worker queues.
1239	<	*/
1240	<	private void cancelQueuedWorkerTasks() {
1241	<	final ReentrantLock lock = this.workerLock;
1242	<	lock.lock();
1243	<	try {
1244	<	ForkJoinWorkerThread[] ws = workers;
1245	<	if (ws != null) {
1246	<	for (int i = 0; i < ws.length; ++i) {
1247	<	ForkJoinWorkerThread t = ws[i];
1248	<	if (t != null)
1249	<	t.cancelTasks();
1250	<	}
1251	<	}
1252	<	} finally {
1253	<	lock.unlock();
1254	<	}
1255	<	}
1256	<
1257	<	/**
1258	<	* Sets each worker's status to terminating. Requires lock to avoid
1259	<	* conflicts with add/remove.
1260	<	*/
1261	<	private void stopAllWorkers() {
1262	<	final ReentrantLock lock = this.workerLock;
1263	<	lock.lock();
1264	<	try {
1265	<	ForkJoinWorkerThread[] ws = workers;
1266	<	if (ws != null) {
1267	<	for (int i = 0; i < ws.length; ++i) {
1268	<	ForkJoinWorkerThread t = ws[i];
1269	<	if (t != null)
1270	<	t.shutdownNow();
1271	<	}
1272	<	}
1273	<	} finally {
1274	<	lock.unlock();
1275	<	}
1276	<	}
1277	<
1278	<	/**
1279	<	* Interrupts all unterminated workers.  This is not required for
1280	<	* sake of internal control, but may help unstick user code during
1281	<	* shutdown.
1282	<	*/
1283	<	private void interruptUnterminatedWorkers() {
1284	<	final ReentrantLock lock = this.workerLock;
1285	<	lock.lock();
1286	<	try {
1287	<	ForkJoinWorkerThread[] ws = workers;
1288	<	if (ws != null) {
1289	<	for (int i = 0; i < ws.length; ++i) {
1290	<	ForkJoinWorkerThread t = ws[i];
1291	<	if (t != null && !t.isTerminated()) {
1292	<	try {
1293	<	t.interrupt();
1294	<	} catch (SecurityException ignore) {
1295	<	}
1296	<	}
1297	<	}
1298	<	}
1299	<	} finally {
1300	<	lock.unlock();
1301	<	}
1302	<	}
1303	<
1304	<
1305	<	/*
1306	<	* Nodes for event barrier to manage idle threads.  Queue nodes
1307	<	* are basic Treiber stack nodes, also used for spare stack.
1308	<	*
1309	<	* The event barrier has an event count and a wait queue (actually
1310	<	* a Treiber stack).  Workers are enabled to look for work when
1311	<	* the eventCount is incremented. If they fail to find work, they
1312	<	* may wait for next count. Upon release, threads help others wake
1313	<	* up.
1314	<	*
1315	<	* Synchronization events occur only in enough contexts to
1316	<	* maintain overall liveness:
1317	<	*
1318	<	*   - Submission of a new task to the pool
1319	<	*   - Resizes or other changes to the workers array
1320	<	*   - pool termination
1321	<	*   - A worker pushing a task on an empty queue
1322	<	*
1323	<	* The case of pushing a task occurs often enough, and is heavy
1324	<	* enough compared to simple stack pushes, to require special
1325	<	* handling: Method signalWork returns without advancing count if
1326	<	* the queue appears to be empty.  This would ordinarily result in
1327	<	* races causing some queued waiters not to be woken up. To avoid
1328	<	* this, the first worker enqueued in method sync (see
1329	<	* syncIsReleasable) rescans for tasks after being enqueued, and
1330	<	* helps signal if any are found. This works well because the
1331	<	* worker has nothing better to do, and so might as well help
1332	<	* alleviate the overhead and contention on the threads actually
1333	<	* doing work.  Also, since event counts increments on task
1334	<	* availability exist to maintain liveness (rather than to force
1335	<	* refreshes etc), it is OK for callers to exit early if
1336	<	* contending with another signaller.
1337	<	*/
1338	<	static final class WaitQueueNode {
1339	<	WaitQueueNode next; // only written before enqueued
1340	<	volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1341	<	final long count; // unused for spare stack
1342	<
1343	<	WaitQueueNode(long c, ForkJoinWorkerThread w) {
1344	<	count = c;
1345	<	thread = w;
1346	<	}
1347	<
1348	<	/**
1349	<	* Wakes up waiter, returning false if known to already
1350	<	*/
1351	<	boolean signal() {
1352	<	ForkJoinWorkerThread t = thread;
1353	<	if (t == null)
1354	<	return false;
1355	<	thread = null;
1356	<	LockSupport.unpark(t);
3043	>	if (isTerminated())
3044		return true;
3045	<	}
3046	<
3047	<	/**
3048	<	* Awaits release on sync.
3049	<	*/
3050	<	void awaitSyncRelease(ForkJoinPool p) {
3051	<	while (thread != null && !p.syncIsReleasable(this))
1365	<	LockSupport.park(this);
1366	<	}
1367	<
1368	<	/**
1369	<	* Awaits resumption as spare.
1370	<	*/
1371	<	void awaitSpareRelease() {
1372	<	while (thread != null) {
1373	<	if (!Thread.interrupted())
1374	<	LockSupport.park(this);
1375	<	}
1376	<	}
1377	<	}
1378	<
1379	<	/**
1380	<	* Ensures that no thread is waiting for count to advance from the
1381	<	* current value of eventCount read on entry to this method, by
1382	<	* releasing waiting threads if necessary.
1383	<	*
1384	<	* @return the count
1385	<	*/
1386	<	final long ensureSync() {
1387	<	long c = eventCount;
1388	<	WaitQueueNode q;
1389	<	while ((q = syncStack) != null && q.count < c) {
1390	<	if (casBarrierStack(q, null)) {
1391	<	do {
1392	<	q.signal();
1393	<	} while ((q = q.next) != null);
1394	<	break;
1395	<	}
1396	<	}
1397	<	return c;
1398	<	}
1399	<
1400	<	/**
1401	<	* Increments event count and releases waiting threads.
1402	<	*/
1403	<	private void signalIdleWorkers() {
1404	<	long c;
1405	<	do {} while (!casEventCount(c = eventCount, c+1));
1406	<	ensureSync();
1407	<	}
1408	<
1409	<	/**
1410	<	* Signals threads waiting to poll a task. Because method sync
1411	<	* rechecks availability, it is OK to only proceed if queue
1412	<	* appears to be non-empty, and OK to skip under contention to
1413	<	* increment count (since some other thread succeeded).
1414	<	*/
1415	<	final void signalWork() {
1416	<	long c;
1417	<	WaitQueueNode q;
1418	<	if (syncStack != null &&
1419	<	casEventCount(c = eventCount, c+1) &&
1420	<	(((q = syncStack) != null && q.count <= c) &&
1421	<	(!casBarrierStack(q, q.next) || !q.signal())))
1422	<	ensureSync();
1423	<	}
1424	<
1425	<	/**
1426	<	* Waits until event count advances from last value held by
1427	<	* caller, or if excess threads, caller is resumed as spare, or
1428	<	* caller or pool is terminating. Updates caller's event on exit.
1429	<	*
1430	<	* @param w the calling worker thread
1431	<	*/
1432	<	final void sync(ForkJoinWorkerThread w) {
1433	<	updateStealCount(w); // Transfer w's count while it is idle
1434	<
1435	<	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1436	<	long prev = w.lastEventCount;
1437	<	WaitQueueNode node = null;
1438	<	WaitQueueNode h;
1439	<	while (eventCount == prev &&
1440	<	((h = syncStack) == null || h.count == prev)) {
1441	<	if (node == null)
1442	<	node = new WaitQueueNode(prev, w);
1443	<	if (casBarrierStack(node.next = h, node)) {
1444	<	node.awaitSyncRelease(this);
1445	<	break;
1446	<	}
1447	<	}
1448	<	long ec = ensureSync();
1449	<	if (ec != prev) {
1450	<	w.lastEventCount = ec;
1451	<	break;
1452	<	}
1453	<	}
1454	<	}
1455	<
1456	<	/**
1457	<	* Returns true if worker waiting on sync can proceed:
1458	<	*  - on signal (thread == null)
1459	<	*  - on event count advance (winning race to notify vs signaller)
1460	<	*  - on interrupt
1461	<	*  - if the first queued node, we find work available
1462	<	* If node was not signalled and event count not advanced on exit,
1463	<	* then we also help advance event count.
1464	<	*
1465	<	* @return true if node can be released
1466	<	*/
1467	<	final boolean syncIsReleasable(WaitQueueNode node) {
1468	<	long prev = node.count;
1469	<	if (!Thread.interrupted() && node.thread != null &&
1470	<	(node.next != null ||
1471	<	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1472	<	eventCount == prev)
1473	<	return false;
1474	<	if (node.thread != null) {
1475	<	node.thread = null;
1476	<	long ec = eventCount;
1477	<	if (prev <= ec) // help signal
1478	<	casEventCount(ec, ec+1);
1479	<	}
1480	<	return true;
1481	<	}
1482	<
1483	<	/**
1484	<	* Returns true if a new sync event occurred since last call to
1485	<	* sync or this method, if so, updating caller's count.
1486	<	*/
1487	<	final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1488	<	long lc = w.lastEventCount;
1489	<	long ec = ensureSync();
1490	<	if (ec == lc)
1491	<	return false;
1492	<	w.lastEventCount = ec;
1493	<	return true;
1494	<	}
1495	<
1496	<	//  Parallelism maintenance
1497	<
1498	<	/**
1499	<	* Decrements running count; if too low, adds spare.
1500	<	*
1501	<	* Conceptually, all we need to do here is add or resume a
1502	<	* spare thread when one is about to block (and remove or
1503	<	* suspend it later when unblocked -- see suspendIfSpare).
1504	<	* However, implementing this idea requires coping with
1505	<	* several problems: we have imperfect information about the
1506	<	* states of threads. Some count updates can and usually do
1507	<	* lag run state changes, despite arrangements to keep them
1508	<	* accurate (for example, when possible, updating counts
1509	<	* before signalling or resuming), especially when running on
1510	<	* dynamic JVMs that don't optimize the infrequent paths that
1511	<	* update counts. Generating too many threads can make these
1512	<	* problems become worse, because excess threads are more
1513	<	* likely to be context-switched with others, slowing them all
1514	<	* down, especially if there is no work available, so all are
1515	<	* busy scanning or idling.  Also, excess spare threads can
1516	<	* only be suspended or removed when they are idle, not
1517	<	* immediately when they aren't needed. So adding threads will
1518	<	* raise parallelism level for longer than necessary.  Also,
1519	<	* FJ applications often encounter highly transient peaks when
1520	<	* many threads are blocked joining, but for less time than it
1521	<	* takes to create or resume spares.
1522	<	*
1523	<	* @param joinMe if non-null, return early if done
1524	<	* @param maintainParallelism if true, try to stay within
1525	<	* target counts, else create only to avoid starvation
1526	<	* @return true if joinMe known to be done
1527	<	*/
1528	<	final boolean preJoin(ForkJoinTask<?> joinMe,
1529	<	boolean maintainParallelism) {
1530	<	maintainParallelism &= maintainsParallelism; // overrride
1531	<	boolean dec = false;  // true when running count decremented
1532	<	while (spareStack == null || !tryResumeSpare(dec)) {
1533	<	int counts = workerCounts;
1534	<	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1535	<	// CAS cheat
1536	<	if (!needSpare(counts, maintainParallelism))
1537	<	break;
1538	<	if (joinMe.status < 0)
1539	<	return true;
1540	<	if (tryAddSpare(counts))
1541	<	break;
1542	<	}
1543	<	}
1544	<	return false;
1545	<	}
1546	<
1547	<	/**
1548	<	* Same idea as preJoin
1549	<	*/
1550	<	final boolean preBlock(ManagedBlocker blocker,
1551	<	boolean maintainParallelism) {
1552	<	maintainParallelism &= maintainsParallelism;
1553	<	boolean dec = false;
1554	<	while (spareStack == null || !tryResumeSpare(dec)) {
1555	<	int counts = workerCounts;
1556	<	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1557	<	if (!needSpare(counts, maintainParallelism))
1558	<	break;
1559	<	if (blocker.isReleasable())
1560	<	return true;
1561	<	if (tryAddSpare(counts))
1562	<	break;
1563	<	}
1564	<	}
1565	<	return false;
1566	<	}
1567	<
1568	<	/**
1569	<	* Returns true if a spare thread appears to be needed.  If
1570	<	* maintaining parallelism, returns true when the deficit in
1571	<	* running threads is more than the surplus of total threads, and
1572	<	* there is apparently some work to do.  This self-limiting rule
1573	<	* means that the more threads that have already been added, the
1574	<	* less parallelism we will tolerate before adding another.
1575	<	*
1576	<	* @param counts current worker counts
1577	<	* @param maintainParallelism try to maintain parallelism
1578	<	*/
1579	<	private boolean needSpare(int counts, boolean maintainParallelism) {
1580	<	int ps = parallelism;
1581	<	int rc = runningCountOf(counts);
1582	<	int tc = totalCountOf(counts);
1583	<	int runningDeficit = ps - rc;
1584	<	int totalSurplus = tc - ps;
1585	<	return (tc < maxPoolSize &&
1586	<	(rc == 0 || totalSurplus < 0 ||
1587	<	(maintainParallelism &&
1588	<	runningDeficit > totalSurplus &&
1589	<	ForkJoinWorkerThread.hasQueuedTasks(workers))));
1590	<	}
1591	<
1592	<	/**
1593	<	* Adds a spare worker if lock available and no more than the
1594	<	* expected numbers of threads exist.
1595	<	*
1596	<	* @return true if successful
1597	<	*/
1598	<	private boolean tryAddSpare(int expectedCounts) {
1599	<	final ReentrantLock lock = this.workerLock;
1600	<	int expectedRunning = runningCountOf(expectedCounts);
1601	<	int expectedTotal = totalCountOf(expectedCounts);
1602	<	boolean success = false;
1603	<	boolean locked = false;
1604	<	// confirm counts while locking; CAS after obtaining lock
1605	<	try {
1606	<	for (;;) {
1607	<	int s = workerCounts;
1608	<	int tc = totalCountOf(s);
1609	<	int rc = runningCountOf(s);
1610	<	if (rc > expectedRunning || tc > expectedTotal)
1611	<	break;
1612	<	if (!locked && !(locked = lock.tryLock()))
3045	>	long startTime = System.nanoTime();
3046	>	boolean terminated = false;
3047	>	synchronized (this) {
3048	>	for (long waitTime = nanos, millis = 0L;;) {
3049	>	if (terminated = isTerminated() ||
3050	>	waitTime <= 0L ||
3051	>	(millis = unit.toMillis(waitTime)) <= 0L)
3052		break;
3053	<	if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) {
3054	<	createAndStartSpare(tc);
1616	<	success = true;
1617	<	break;
1618	<	}
1619	<	}
1620	<	} finally {
1621	<	if (locked)
1622	<	lock.unlock();
1623	<	}
1624	<	return success;
1625	<	}
1626	<
1627	<	/**
1628	<	* Adds the kth spare worker. On entry, pool counts are already
1629	<	* adjusted to reflect addition.
1630	<	*/
1631	<	private void createAndStartSpare(int k) {
1632	<	ForkJoinWorkerThread w = null;
1633	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1);
1634	<	int len = ws.length;
1635	<	// Probably, we can place at slot k. If not, find empty slot
1636	<	if (k < len && ws[k] != null) {
1637	<	for (k = 0; k < len && ws[k] != null; ++k)
1638	<	;
1639	<	}
1640	<	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1641	<	ws[k] = w;
1642	<	w.start();
1643	<	}
1644	<	else
1645	<	updateWorkerCount(-1); // adjust on failure
1646	<	signalIdleWorkers();
1647	<	}
1648	<
1649	<	/**
1650	<	* Suspends calling thread w if there are excess threads.  Called
1651	<	* only from sync.  Spares are enqueued in a Treiber stack using
1652	<	* the same WaitQueueNodes as barriers.  They are resumed mainly
1653	<	* in preJoin, but are also woken on pool events that require all
1654	<	* threads to check run state.
1655	<	*
1656	<	* @param w the caller
1657	<	*/
1658	<	private boolean suspendIfSpare(ForkJoinWorkerThread w) {
1659	<	WaitQueueNode node = null;
1660	<	int s;
1661	<	while (parallelism < runningCountOf(s = workerCounts)) {
1662	<	if (node == null)
1663	<	node = new WaitQueueNode(0, w);
1664	<	if (casWorkerCounts(s, s-1)) { // representation-dependent
1665	<	// push onto stack
1666	<	do {} while (!casSpareStack(node.next = spareStack, node));
1667	<	// block until released by resumeSpare
1668	<	node.awaitSpareRelease();
1669	<	return true;
1670	<	}
1671	<	}
1672	<	return false;
1673	<	}
1674	<
1675	<	/**
1676	<	* Tries to pop and resume a spare thread.
1677	<	*
1678	<	* @param updateCount if true, increment running count on success
1679	<	* @return true if successful
1680	<	*/
1681	<	private boolean tryResumeSpare(boolean updateCount) {
1682	<	WaitQueueNode q;
1683	<	while ((q = spareStack) != null) {
1684	<	if (casSpareStack(q, q.next)) {
1685	<	if (updateCount)
1686	<	updateRunningCount(1);
1687	<	q.signal();
1688	<	return true;
1689	<	}
1690	<	}
1691	<	return false;
1692	<	}
1693	<
1694	<	/**
1695	<	* Pops and resumes all spare threads. Same idea as ensureSync.
1696	<	*
1697	<	* @return true if any spares released
1698	<	*/
1699	<	private boolean resumeAllSpares() {
1700	<	WaitQueueNode q;
1701	<	while ( (q = spareStack) != null) {
1702	<	if (casSpareStack(q, null)) {
1703	<	do {
1704	<	updateRunningCount(1);
1705	<	q.signal();
1706	<	} while ((q = q.next) != null);
1707	<	return true;
1708	<	}
1709	<	}
1710	<	return false;
1711	<	}
1712	<
1713	<	/**
1714	<	* Pops and shuts down excessive spare threads. Call only while
1715	<	* holding lock. This is not guaranteed to eliminate all excess
1716	<	* threads, only those suspended as spares, which are the ones
1717	<	* unlikely to be needed in the future.
1718	<	*/
1719	<	private void trimSpares() {
1720	<	int surplus = totalCountOf(workerCounts) - parallelism;
1721	<	WaitQueueNode q;
1722	<	while (surplus > 0 && (q = spareStack) != null) {
1723	<	if (casSpareStack(q, null)) {
1724	<	do {
1725	<	updateRunningCount(1);
1726	<	ForkJoinWorkerThread w = q.thread;
1727	<	if (w != null && surplus > 0 &&
1728	<	runningCountOf(workerCounts) > 0 && w.shutdown())
1729	<	--surplus;
1730	<	q.signal();
1731	<	} while ((q = q.next) != null);
3053	>	wait(millis);
3054	>	waitTime = nanos - (System.nanoTime() - startTime);
3055		}
3056		}
3057	+	return terminated;
3058		}
3059
3060		/**
3061		* Interface for extending managed parallelism for tasks running
3062	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
3063	<	* Method {@code isReleasable} must return true if blocking is not
3064	<	* necessary. Method {@code block} blocks the current thread if
3065	<	* necessary (perhaps internally invoking {@code isReleasable}
3066	<	* before actually blocking.).
3062	>	* in {@link ForkJoinPool}s.
3063	>	*
3064	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
3065	>	* {@code isReleasable} must return {@code true} if blocking is
3066	>	* not necessary. Method {@code block} blocks the current thread
3067	>	* if necessary (perhaps internally invoking {@code isReleasable}
3068	>	* before actually blocking). These actions are performed by any
3069	>	* thread invoking {@link ForkJoinPool#managedBlock}.  The
3070	>	* unusual methods in this API accommodate synchronizers that may,
3071	>	* but don't usually, block for long periods. Similarly, they
3072	>	* allow more efficient internal handling of cases in which
3073	>	* additional workers may be, but usually are not, needed to
3074	>	* ensure sufficient parallelism.  Toward this end,
3075	>	* implementations of method {@code isReleasable} must be amenable
3076	>	* to repeated invocation.
3077		*
3078		* <p>For example, here is a ManagedBlocker based on a
3079		* ReentrantLock:
#	Line 1757 | Line 3091 | public class ForkJoinPool extends Abstra
3091		*     return hasLock || (hasLock = lock.tryLock());
3092		*   }
3093		* }}</pre>
3094	+	*
3095	+	* <p>Here is a class that possibly blocks waiting for an
3096	+	* item on a given queue:
3097	+	*  <pre> {@code
3098	+	* class QueueTaker<E> implements ManagedBlocker {
3099	+	*   final BlockingQueue<E> queue;
3100	+	*   volatile E item = null;
3101	+	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
3102	+	*   public boolean block() throws InterruptedException {
3103	+	*     if (item == null)
3104	+	*       item = queue.take();
3105	+	*     return true;
3106	+	*   }
3107	+	*   public boolean isReleasable() {
3108	+	*     return item != null || (item = queue.poll()) != null;
3109	+	*   }
3110	+	*   public E getItem() { // call after pool.managedBlock completes
3111	+	*     return item;
3112	+	*   }
3113	+	* }}</pre>
3114		*/
3115		public static interface ManagedBlocker {
3116		/**
3117		* Possibly blocks the current thread, for example waiting for
3118		* a lock or condition.
3119		*
3120	<	* @return true if no additional blocking is necessary (i.e.,
3121	<	* if isReleasable would return true)
3120	>	* @return {@code true} if no additional blocking is necessary
3121	>	* (i.e., if isReleasable would return true)
3122		* @throws InterruptedException if interrupted while waiting
3123		* (the method is not required to do so, but is allowed to)
3124		*/
3125		boolean block() throws InterruptedException;
3126
3127		/**
3128	<	* Returns true if blocking is unnecessary.
3128	>	* Returns {@code true} if blocking is unnecessary.
3129		*/
3130		boolean isReleasable();
3131		}
3132
3133		/**
3134		* Blocks in accord with the given blocker.  If the current thread
3135	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
3136	<	* spare thread to be activated if necessary to ensure parallelism
3137	<	* while the current thread is blocked.  If
1784	<	* {@code maintainParallelism} is true and the pool supports
1785	<	* it ({@link #getMaintainsParallelism}), this method attempts to
1786	<	* maintain the pool's nominal parallelism. Otherwise it activates
1787	<	* a thread only if necessary to avoid complete starvation. This
1788	<	* option may be preferable when blockages use timeouts, or are
1789	<	* almost always brief.
3135	>	* is a {@link ForkJoinWorkerThread}, this method possibly
3136	>	* arranges for a spare thread to be activated if necessary to
3137	>	* ensure sufficient parallelism while the current thread is blocked.
3138		*
3139	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
3140	<	* equivalent to
3139	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
3140	>	* behaviorally equivalent to
3141		*  <pre> {@code
3142		* while (!blocker.isReleasable())
3143		*   if (blocker.block())
3144		*     return;
3145		* }</pre>
3146	<	* If the caller is a ForkJoinTask, then the pool may first
3147	<	* be expanded to ensure parallelism, and later adjusted.
3146	>	*
3147	>	* If the caller is a {@code ForkJoinTask}, then the pool may
3148	>	* first be expanded to ensure parallelism, and later adjusted.
3149		*
3150		* @param blocker the blocker
1802	–	* @param maintainParallelism if true and supported by this pool,
1803	–	* attempt to maintain the pool's nominal parallelism; otherwise
1804	–	* activate a thread only if necessary to avoid complete
1805	–	* starvation.
3151		* @throws InterruptedException if blocker.block did so
3152		*/
3153	<	public static void managedBlock(ManagedBlocker blocker,
1809	<	boolean maintainParallelism)
3153	>	public static void managedBlock(ManagedBlocker blocker)
3154		throws InterruptedException {
3155		Thread t = Thread.currentThread();
3156	<	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
3157	<	((ForkJoinWorkerThread) t).pool : null);
3158	<	if (!blocker.isReleasable()) {
3159	<	try {
3160	<	if (pool == null ||
3161	<	!pool.preBlock(blocker, maintainParallelism))
3162	<	awaitBlocker(blocker);
3163	<	} finally {
3164	<	if (pool != null)
3165	<	pool.updateRunningCount(1);
3156	>	if (t instanceof ForkJoinWorkerThread) {
3157	>	ForkJoinPool p = ((ForkJoinWorkerThread)t).pool;
3158	>	while (!blocker.isReleasable()) { // variant of helpSignal
3159	>	WorkQueue[] ws; WorkQueue q; int m, n, u;
3160	>	if ((ws = p.workQueues) != null && (m = ws.length - 1) >= 0) {
3161	>	for (int i = 0; i <= m; ++i) {
3162	>	if (blocker.isReleasable())
3163	>	return;
3164	>	if ((q = ws[i]) != null && (n = q.queueSize()) > 0) {
3165	>	p.signalWork(q, n);
3166	>	if ((u = (int)(p.ctl >>> 32)) >= 0 ||
3167	>	(u >> UAC_SHIFT) >= 0)
3168	>	break;
3169	>	}
3170	>	}
3171	>	}
3172	>	if (p.tryCompensate()) {
3173	>	try {
3174	>	do {} while (!blocker.isReleasable() &&
3175	>	!blocker.block());
3176	>	} finally {
3177	>	p.incrementActiveCount();
3178	>	}
3179	>	break;
3180	>	}
3181		}
3182		}
3183	+	else {
3184	+	do {} while (!blocker.isReleasable() &&
3185	+	!blocker.block());
3186	+	}
3187		}
3188
3189	<	private static void awaitBlocker(ManagedBlocker blocker)
3190	<	throws InterruptedException {
3191	<	do {} while (!blocker.isReleasable() && !blocker.block());
1829	<	}
1830	<
1831	<	// AbstractExecutorService overrides
3189	>	// AbstractExecutorService overrides.  These rely on undocumented
3190	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
3191	>	// implement RunnableFuture.
3192
3193		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
3194	<	return new AdaptedRunnable(runnable, value);
3194	>	return new ForkJoinTask.AdaptedRunnable<T>(runnable, value);
3195		}
3196
3197		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
3198	<	return new AdaptedCallable(callable);
3198	>	return new ForkJoinTask.AdaptedCallable<T>(callable);
3199		}
3200
3201	+	// Unsafe mechanics
3202	+	private static final sun.misc.Unsafe U;
3203	+	private static final long CTL;
3204	+	private static final long PARKBLOCKER;
3205	+	private static final int ABASE;
3206	+	private static final int ASHIFT;
3207	+	private static final long STEALCOUNT;
3208	+	private static final long PLOCK;
3209	+	private static final long INDEXSEED;
3210	+	private static final long QLOCK;
3211
3212	<	// Temporary Unsafe mechanics for preliminary release
3213	<	private static Unsafe getUnsafe() throws Throwable {
3212	>	static {
3213	>	int s; // initialize field offsets for CAS etc
3214		try {
3215	<	return Unsafe.getUnsafe();
3215	>	U = getUnsafe();
3216	>	Class<?> k = ForkJoinPool.class;
3217	>	CTL = U.objectFieldOffset
3218	>	(k.getDeclaredField("ctl"));
3219	>	STEALCOUNT = U.objectFieldOffset
3220	>	(k.getDeclaredField("stealCount"));
3221	>	PLOCK = U.objectFieldOffset
3222	>	(k.getDeclaredField("plock"));
3223	>	INDEXSEED = U.objectFieldOffset
3224	>	(k.getDeclaredField("indexSeed"));
3225	>	Class<?> tk = Thread.class;
3226	>	PARKBLOCKER = U.objectFieldOffset
3227	>	(tk.getDeclaredField("parkBlocker"));
3228	>	Class<?> wk = WorkQueue.class;
3229	>	QLOCK = U.objectFieldOffset
3230	>	(wk.getDeclaredField("qlock"));
3231	>	Class<?> ak = ForkJoinTask[].class;
3232	>	ABASE = U.arrayBaseOffset(ak);
3233	>	s = U.arrayIndexScale(ak);
3234	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3235	>	} catch (Exception e) {
3236	>	throw new Error(e);
3237	>	}
3238	>	if ((s & (s-1)) != 0)
3239	>	throw new Error("data type scale not a power of two");
3240	>
3241	>	submitters = new ThreadLocal<Submitter>();
3242	>	ForkJoinWorkerThreadFactory fac = defaultForkJoinWorkerThreadFactory =
3243	>	new DefaultForkJoinWorkerThreadFactory();
3244	>	/*
3245	>	* Establish common pool parameters.  For extra caution,
3246	>	* computations to set up common pool state are here; the
3247	>	* constructor just assigns these values to fields.
3248	>	*/
3249	>
3250	>	int par = 0;
3251	>	Thread.UncaughtExceptionHandler handler = null;
3252	>	try {  // TBD: limit or report ignored exceptions?
3253	>	String pp = System.getProperty
3254	>	("java.util.concurrent.ForkJoinPool.common.parallelism");
3255	>	String hp = System.getProperty
3256	>	("java.util.concurrent.ForkJoinPool.common.exceptionHandler");
3257	>	String fp = System.getProperty
3258	>	("java.util.concurrent.ForkJoinPool.common.threadFactory");
3259	>	if (fp != null)
3260	>	fac = ((ForkJoinWorkerThreadFactory)ClassLoader.
3261	>	getSystemClassLoader().loadClass(fp).newInstance());
3262	>	if (hp != null)
3263	>	handler = ((Thread.UncaughtExceptionHandler)ClassLoader.
3264	>	getSystemClassLoader().loadClass(hp).newInstance());
3265	>	if (pp != null)
3266	>	par = Integer.parseInt(pp);
3267	>	} catch (Exception ignore) {
3268	>	}
3269	>
3270	>	if (par <= 0)
3271	>	par = Runtime.getRuntime().availableProcessors();
3272	>	if (par > MAX_CAP)
3273	>	par = MAX_CAP;
3274	>	commonPoolParallelism = par;
3275	>	long np = (long)(-par); // precompute initial ctl value
3276	>	long ct = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
3277	>
3278	>	commonPool = new ForkJoinPool(par, ct, fac, handler);
3279	>	modifyThreadPermission = new RuntimePermission("modifyThread");
3280	>	}
3281	>
3282	>	/**
3283	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
3284	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
3285	>	* into a jdk.
3286	>	*
3287	>	* @return a sun.misc.Unsafe
3288	>	*/
3289	>	private static sun.misc.Unsafe getUnsafe() {
3290	>	try {
3291	>	return sun.misc.Unsafe.getUnsafe();
3292		} catch (SecurityException se) {
3293		try {
3294		return java.security.AccessController.doPrivileged
3295	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
3296	<	public Unsafe run() throws Exception {
3297	<	return getUnsafePrivileged();
3295	>	(new java.security
3296	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
3297	>	public sun.misc.Unsafe run() throws Exception {
3298	>	java.lang.reflect.Field f = sun.misc
3299	>	.Unsafe.class.getDeclaredField("theUnsafe");
3300	>	f.setAccessible(true);
3301	>	return (sun.misc.Unsafe) f.get(null);
3302		}});
3303		} catch (java.security.PrivilegedActionException e) {
3304	<	throw e.getCause();
3304	>	throw new RuntimeException("Could not initialize intrinsics",
3305	>	e.getCause());
3306		}
3307		}
3308		}
3309
1859	–	private static Unsafe getUnsafePrivileged()
1860	–	throws NoSuchFieldException, IllegalAccessException {
1861	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1862	–	f.setAccessible(true);
1863	–	return (Unsafe) f.get(null);
1864	–	}
1865	–
1866	–	private static long fieldOffset(String fieldName)
1867	–	throws NoSuchFieldException {
1868	–	return UNSAFE.objectFieldOffset
1869	–	(ForkJoinPool.class.getDeclaredField(fieldName));
1870	–	}
1871	–
1872	–	static final Unsafe UNSAFE;
1873	–	static final long eventCountOffset;
1874	–	static final long workerCountsOffset;
1875	–	static final long runControlOffset;
1876	–	static final long syncStackOffset;
1877	–	static final long spareStackOffset;
1878	–
1879	–	static {
1880	–	try {
1881	–	UNSAFE = getUnsafe();
1882	–	eventCountOffset = fieldOffset("eventCount");
1883	–	workerCountsOffset = fieldOffset("workerCounts");
1884	–	runControlOffset = fieldOffset("runControl");
1885	–	syncStackOffset = fieldOffset("syncStack");
1886	–	spareStackOffset = fieldOffset("spareStack");
1887	–	} catch (Throwable e) {
1888	–	throw new RuntimeException("Could not initialize intrinsics", e);
1889	–	}
1890	–	}
1891	–
1892	–	private boolean casEventCount(long cmp, long val) {
1893	–	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1894	–	}
1895	–	private boolean casWorkerCounts(int cmp, int val) {
1896	–	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1897	–	}
1898	–	private boolean casRunControl(int cmp, int val) {
1899	–	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1900	–	}
1901	–	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1902	–	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1903	–	}
1904	–	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1905	–	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1906	–	}
3310		}

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