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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.55 by dl, Sun Apr 18 13:59:57 2010 UTC vs.
Revision 1.180 by jsr166, Tue Feb 5 01:20:56 2013 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
9	–	import java.util.concurrent.*;
10	–
9		import java.util.ArrayList;
10		import java.util.Arrays;
11		import java.util.Collection;
12		import java.util.Collections;
13		import java.util.List;
14	<	import java.util.concurrent.locks.LockSupport;
15	<	import java.util.concurrent.locks.ReentrantLock;
16	<	import java.util.concurrent.atomic.AtomicInteger;
17	<	import java.util.concurrent.CountDownLatch;
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.
24		* A {@code ForkJoinPool} provides the entry point for submissions
25	<	* from non-{@code ForkJoinTask}s, as well as management and
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 subtasks created by other active tasks (eventually blocking
32	<	* waiting for work if none exist). This enables efficient processing
33	<	* when most tasks spawn other subtasks (as do most {@code
34	<	* ForkJoinTask}s). A {@code ForkJoinPool} may also be used for mixed
35	<	* execution of some plain {@code Runnable}- or {@code Callable}-
36	<	* based activities along with {@code ForkJoinTask}s. When setting
37	<	* {@linkplain #setAsyncMode async mode}, a {@code ForkJoinPool} may
38	<	* also be appropriate for use with fine-grained tasks of any form
39	<	* that are never joined. Otherwise, other {@code ExecutorService}
40	<	* implementations are typically more appropriate choices.
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>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 {@code ForkJoinPool} is constructed with a given target
48	<	* parallelism level; by default, equal to the number of available
49	<	* processors. Unless configured otherwise via {@link
50	<	* #setMaintainsParallelism}, the pool attempts to maintain this
51	<	* number of active (or available) threads by dynamically adding,
52	<	* suspending, or resuming internal worker threads, even if some tasks
53	<	* are stalled waiting to join others. However, no such adjustments
54	<	* are performed in the face of blocked IO or other unmanaged
55	<	* synchronization. The nested {@link ManagedBlocker} interface
56	<	* enables extension of the kinds of synchronization accommodated.
51	<	* The target parallelism level may also be changed dynamically
52	<	* ({@link #setParallelism}). The total number of threads may be
53	<	* limited using method {@link #setMaximumPoolSize}, in which case it
54	<	* may become possible for the activities of a pool to stall due to
55	<	* the lack of available threads to process new tasks. When the pool
56	<	* is executing tasks, these and other configuration setting methods
57	<	* may only gradually affect actual pool sizes. It is normally best
58	<	* practice to invoke these methods only when the pool is known to be
59	<	* quiescent.
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 I/O 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
#	Line 65 | Line 62 | import java.util.concurrent.CountDownLat
62		* {@link #toString} returns indications of pool state in a
63		* convenient form for informal monitoring.
64		*
65	<	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
66	<	* used for all parallel task execution in a program or subsystem.
67	<	* Otherwise, use would not usually outweigh the construction and
68	<	* bookkeeping overhead of creating a large set of threads. For
69	<	* example, a common pool could be used for the {@code SortTasks}
70	<	* illustrated in {@link RecursiveAction}. Because {@code
71	<	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
72	<	* daemon} mode, there is typically no need to explicitly {@link
73	<	* #shutdown} such a pool upon program exit.
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	<	* <pre>
101	<	* static final ForkJoinPool mainPool = new ForkJoinPool();
102	<	* ...
103	<	* public void sort(long[] array) {
104	<	*   mainPool.invoke(new SortTask(array, 0, array.length));
105	<	* }
106	<	* </pre>
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 system 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
#	Line 89 | Line 114 | import java.util.concurrent.CountDownLat
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.
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 99 | Line 125 | public class ForkJoinPool extends Abstra
125		/*
126		* Implementation Overview
127		*
128	<	* This class provides the central bookkeeping and control for a
129	<	* set of worker threads: Submissions from non-FJ threads enter
130	<	* into a submission queue. Workers take these tasks and typically
131	<	* split them into subtasks that may be stolen by other workers.
132	<	* The main work-stealing mechanics implemented in class
133	<	* ForkJoinWorkerThread give first priority to processing tasks
134	<	* from their own queues (LIFO or FIFO, depending on mode), then
135	<	* to randomized FIFO steals of tasks in other worker queues, and
136	<	* lastly to new submissions. These mechanics do not consider
137	<	* affinities, loads, cache localities, etc, so rarely provide the
138	<	* best possible performance on a given machine, but portably
139	<	* provide good throughput by averaging over these factors.
140	<	* (Further, even if we did try to use such information, we do not
141	<	* usually have a basis for exploiting it. For example, some sets
142	<	* of tasks profit from cache affinities, but others are harmed by
143	<	* cache pollution effects.)
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 steal tasks from each
221	<	* other. We do not want to negate this by creating bottlenecks
222	<	* implementing the management responsibilities of this class. So
223	<	* we use a collection of techniques that avoid, reduce, or cope
224	<	* well with contention. These entail several instances of
225	<	* bit-packing into CASable fields to maintain only the minimally
226	<	* required atomicity. To enable such packing, we restrict maximum
227	<	* parallelism to (1<<15)-1 (enabling twice this to fit into a 16
228	<	* bit field), which is far in excess of normal operating range.
229	<	* Even though updates to some of these bookkeeping fields do
230	<	* sometimes contend with each other, they don't normally
231	<	* cache-contend with updates to others enough to warrant memory
232	<	* padding or isolation. So they are all held as fields of
233	<	* ForkJoinPool objects.  The main capabilities are as follows:
234	<	*
235	<	* 1. Creating and removing workers. Workers are recorded in the
236	<	* "workers" array. This is an array as opposed to some other data
237	<	* structure to support index-based random steals by workers.
238	<	* Updates to the array recording new workers and unrecording
239	<	* terminated ones are protected from each other by a lock
240	<	* (workerLock) but the array is otherwise concurrently readable,
241	<	* and accessed directly by workers. To simplify index-based
242	<	* operations, the array size is always a power of two, and all
243	<	* readers must tolerate null slots. Currently, all but the first
244	<	* worker thread creation is on-demand, triggered by task
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.
261	<	*
262	<	* 2. Bookkeeping for dynamically adding and removing workers. We
263	<	* maintain a given level of parallelism (or, if
264	<	* maintainsParallelism is false, at least avoid starvation). When
265	<	* some workers are known to be blocked (on joins or via
266	<	* ManagedBlocker), we may create or resume others to take their
267	<	* place until they unblock (see below). Implementing this
268	<	* requires counts of the number of "running" threads (i.e., those
269	<	* that are neither blocked nor artifically suspended) as well as
270	<	* the total number.  These two values are packed into one field,
271	<	* "workerCounts" because we need accurate snapshots when deciding
272	<	* to create, resume or suspend.  To support these decisions,
273	<	* updates must be prospective (not retrospective).  For example,
274	<	* the running count is decremented before blocking by a thread
275	<	* about to block, but incremented by the thread about to unblock
276	<	* it. (In a few cases, these prospective updates may need to be
277	<	* rolled back, for example when deciding to create a new worker
278	<	* but the thread factory fails or returns null. In these cases,
279	<	* we are no worse off wrt other decisions than we would be
280	<	* otherwise.)  Updates to the workerCounts field sometimes
281	<	* transiently encounter a fair amount of contention when join
282	<	* dependencies are such that many threads block or unblock at
283	<	* about the same time. We alleviate this by sometimes bundling
284	<	* updates (for example blocking one thread on join and resuming a
285	<	* spare cancel each other out), and in most other cases
286	<	* performing an alternative action (like releasing waiters and
287	<	* finding spares; see below) as a more productive form of
288	<	* backoff.
289	<	*
290	<	* 3. Maintaining global run state. The run state of the pool
291	<	* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to
292	<	* those in other Executor implementations, as well as a count of
293	<	* "active" workers -- those that are, or soon will be, or
294	<	* recently were executing tasks. The runLevel and active count
295	<	* are packed together in order to correctly trigger shutdown and
296	<	* termination. Without care, active counts can be subject to very
297	<	* high contention.  We substantially reduce this contention by
298	<	* relaxing update rules.  A worker must claim active status
299	<	* prospectively, by activating if it sees that a submitted or
300	<	* stealable task exists (it may find after activating that the
301	<	* task no longer exists). It stays active while processing this
302	<	* task (if it exists) and any other local subtasks it produces,
303	<	* until it cannot find any other tasks. It then tries
304	<	* inactivating (see method preStep), but upon update contention
305	<	* instead scans for more tasks, later retrying inactivation if it
306	<	* doesn't find any.
307	<	*
308	<	* 4. Managing idle workers waiting for tasks. We cannot let
309	<	* workers spin indefinitely scanning for tasks when none are
310	<	* available. On the other hand, we must quickly prod them into
311	<	* action when new tasks are submitted or generated.  We
312	<	* park/unpark these idle workers using an event-count scheme.
313	<	* Field eventCount is incremented upon events that may enable
314	<	* workers that previously could not find a task to now find one:
315	<	* Submission of a new task to the pool, or another worker pushing
316	<	* a task onto a previously empty queue.  (We also use this
317	<	* mechanism for termination and reconfiguration actions that
318	<	* require wakeups of idle workers).  Each worker maintains its
319	<	* last known event count, and blocks when a scan for work did not
320	<	* find a task AND its lastEventCount matches the current
321	<	* eventCount. Waiting idle workers are recorded in a variant of
322	<	* Treiber stack headed by field eventWaiters which, when nonzero,
323	<	* encodes the thread index and count awaited for by the worker
324	<	* thread most recently calling eventSync. This thread in turn has
325	<	* a record (field nextEventWaiter) for the next waiting worker.
326	<	* In addition to allowing simpler decisions about need for
327	<	* wakeup, the event count bits in eventWaiters serve the role of
328	<	* tags to avoid ABA errors in Treiber stacks.  To reduce delays
329	<	* in task diffusion, workers not otherwise occupied may invoke
330	<	* method releaseWaiters, that removes and signals (unparks)
331	<	* workers not waiting on current count. To minimize task
332	<	* production stalls associate with signalling, any worker pushing
333	<	* a task on an empty queue invokes the weaker method signalWork,
334	<	* that only releases idle workers until it detects interference
335	<	* by other threads trying to release, and lets them take
336	<	* over. The net effect is a tree-like diffusion of signals, where
337	<	* released threads and possibly others) help with unparks.  To
338	<	* further reduce contention effects a bit, failed CASes to
339	<	* increment field eventCount are tolerated without retries.
340	<	* Conceptually they are merged into the same event, which is OK
341	<	* when their only purpose is to enable workers to scan for work.
342	<	*
343	<	* 5. Managing suspension of extra workers. When a worker is about
344	<	* to block waiting for a join (or via ManagedBlockers), we may
345	<	* create a new thread to maintain parallelism level, or at least
346	<	* avoid starvation (see below). Usually, extra threads are needed
347	<	* for only very short periods, yet join dependencies are such
348	<	* that we sometimes need them in bursts. Rather than create new
349	<	* threads each time this happens, we suspend no-longer-needed
350	<	* extra ones as "spares". For most purposes, we don't distinguish
351	<	* "extra" spare threads from normal "core" threads: On each call
352	<	* to preStep (the only point at which we can do this) a worker
353	<	* checks to see if there are now too many running workers, and if
354	<	* so, suspends itself.  Methods preJoin and doBlock look for
355	<	* suspended threads to resume before considering creating a new
356	<	* replacement. We don't need a special data structure to maintain
357	<	* spares; simply scanning the workers array looking for
358	<	* worker.isSuspended() is fine because the calling thread is
359	<	* otherwise not doing anything useful anyway; we are at least as
360	<	* happy if after locating a spare, the caller doesn't actually
361	<	* block because the join is ready before we try to adjust and
362	<	* compensate.  Note that this is intrinsically racy.  One thread
363	<	* may become a spare at about the same time as another is
364	<	* needlessly being created. We counteract this and related slop
365	<	* in part by requiring resumed spares to immediately recheck (in
366	<	* preStep) to see whether they they should re-suspend. The only
367	<	* effective difference between "extra" and "core" threads is that
368	<	* we allow the "extra" ones to time out and die if they are not
369	<	* resumed within a keep-alive interval of a few seconds. This is
370	<	* implemented mainly within ForkJoinWorkerThread, but requires
371	<	* some coordination (isTrimmed() -- meaning killed while
372	<	* suspended) to correctly maintain pool counts.
373	<	*
374	<	* 6. Deciding when to create new workers. The main dynamic
375	<	* control in this class is deciding when to create extra threads,
376	<	* in methods preJoin and doBlock. We always need to create one
377	<	* when the number of running threads becomes zero. But because
378	<	* blocked joins are typically dependent, we don't necessarily
379	<	* need or want one-to-one replacement. Using a one-to-one
380	<	* compensation rule often leads to enough useless overhead
381	<	* creating, suspending, resuming, and/or killing threads to
382	<	* signficantly degrade throughput.  We use a rule reflecting the
383	<	* idea that, the more spare threads you already have, the more
384	<	* evidence you need to create another one; where "evidence" is
385	<	* expressed as the current deficit -- target minus running
386	<	* threads. To reduce flickering and drift around target values,
387	<	* the relation is quadratic: adding a spare if (dc*dc)>=(sc*pc)
388	<	* (where dc is deficit, sc is number of spare threads and pc is
389	<	* target parallelism.)  This effectively reduces churn at the
390	<	* price of systematically undershooting target parallelism when
391	<	* many threads are blocked.  However, biasing toward undeshooting
392	<	* partially compensates for the above mechanics to suspend extra
393	<	* threads, that normally lead to overshoot because we can only
394	<	* suspend workers in-between top-level actions. It also better
395	<	* copes with the fact that some of the methods in this class tend
396	<	* to never become compiled (but are interpreted), so some
397	<	* components of the entire set of controls might execute many
398	<	* times faster than others. And similarly for cases where the
399	<	* apparent lack of work is just due to GC stalls and other
400	<	* transient system activity.
401	<	*
402	<	* 7. Maintaining other configuration parameters and monitoring
403	<	* statistics. Updates to fields controlling parallelism level,
404	<	* max size, etc can only meaningfully take effect for individual
405	<	* threads upon their next top-level actions; i.e., between
406	<	* stealing/running tasks/submission, which are separated by calls
407	<	* to preStep.  Memory ordering for these (assumed infrequent)
408	<	* reconfiguration calls is ensured by using reads and writes to
409	<	* volatile field workerCounts (that must be read in preStep anyway)
410	<	* as "fences" -- user-level reads are preceded by reads of
411	<	* workCounts, and writes are followed by no-op CAS to
412	<	* workerCounts. The values reported by other management and
413	<	* monitoring methods are either computed on demand, or are kept
414	<	* in fields that are only updated when threads are otherwise
415	<	* idle.
416	<	*
417	<	* Beware that there is a lot of representation-level coupling
418	<	* among classes ForkJoinPool, ForkJoinWorkerThread, and
419	<	* ForkJoinTask.  For example, direct access to "workers" array by
420	<	* workers, and direct access to ForkJoinTask.status by both
421	<	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
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 has fewer
320	>	* than two tasks, they signal waiting workers (or trigger
321	>	* creation of new ones if fewer than the given parallelism level
322	>	* -- signalWork), and may leave a hint to the unparked worker to
323	>	* help signal others upon wakeup).  These primary signals are
324	>	* buttressed by others (see method helpSignal) whenever other
325	>	* threads scan for work or do not have a task to process.  On
326	>	* most platforms, signalling (unpark) overhead time is noticeably
327	>	* long, and the time between signalling a thread and it actually
328	>	* making progress can be very noticeably long, so it is worth
329	>	* offloading these delays from critical paths as much as
330	>	* possible.
331	>	*
332	>	* Trimming workers. To release resources after periods of lack of
333	>	* use, a worker starting to wait when the pool is quiescent will
334	>	* time out and terminate if the pool has remained quiescent for a
335	>	* given period -- a short period if there are more threads than
336	>	* parallelism, longer as the number of threads decreases. This
337	>	* will slowly propagate, eventually terminating all workers after
338	>	* periods of non-use.
339	>	*
340	>	* Shutdown and Termination. A call to shutdownNow atomically sets
341	>	* a plock bit and then (non-atomically) sets each worker's
342	>	* qlock status, cancels all unprocessed tasks, and wakes up
343	>	* all waiting workers.  Detecting whether termination should
344	>	* commence after a non-abrupt shutdown() call requires more work
345	>	* and bookkeeping. We need consensus about quiescence (i.e., that
346	>	* there is no more work). The active count provides a primary
347	>	* indication but non-abrupt shutdown still requires a rechecking
348	>	* scan for any workers that are inactive but not queued.
349	>	*
350	>	* Joining Tasks
351	>	* =============
352	>	*
353	>	* Any of several actions may be taken when one worker is waiting
354	>	* to join a task stolen (or always held) by another.  Because we
355	>	* are multiplexing many tasks on to a pool of workers, we can't
356	>	* just let them block (as in Thread.join).  We also cannot just
357	>	* reassign the joiner's run-time stack with another and replace
358	>	* it later, which would be a form of "continuation", that even if
359	>	* possible is not necessarily a good idea since we sometimes need
360	>	* both an unblocked task and its continuation to progress.
361	>	* Instead we combine two tactics:
362	>	*
363	>	*   Helping: Arranging for the joiner to execute some task that it
364	>	*      would be running if the steal had not occurred.
365	>	*
366	>	*   Compensating: Unless there are already enough live threads,
367	>	*      method tryCompensate() may create or re-activate a spare
368	>	*      thread to compensate for blocked joiners until they unblock.
369	>	*
370	>	* A third form (implemented in tryRemoveAndExec) amounts to
371	>	* helping a hypothetical compensator: If we can readily tell that
372	>	* a possible action of a compensator is to steal and execute the
373	>	* task being joined, the joining thread can do so directly,
374	>	* without the need for a compensation thread (although at the
375	>	* expense of larger run-time stacks, but the tradeoff is
376	>	* typically worthwhile).
377	>	*
378	>	* The ManagedBlocker extension API can't use helping so relies
379	>	* only on compensation in method awaitBlocker.
380	>	*
381	>	* The algorithm in tryHelpStealer entails a form of "linear"
382	>	* helping: Each worker records (in field currentSteal) the most
383	>	* recent task it stole from some other worker. Plus, it records
384	>	* (in field currentJoin) the task it is currently actively
385	>	* joining. Method tryHelpStealer uses these markers to try to
386	>	* find a worker to help (i.e., steal back a task from and execute
387	>	* it) that could hasten completion of the actively joined task.
388	>	* In essence, the joiner executes a task that would be on its own
389	>	* local deque had the to-be-joined task not been stolen. This may
390	>	* be seen as a conservative variant of the approach in Wagner &
391	>	* Calder "Leapfrogging: a portable technique for implementing
392	>	* efficient futures" SIGPLAN Notices, 1993
393	>	* (http://portal.acm.org/citation.cfm?id=155354). It differs in
394	>	* that: (1) We only maintain dependency links across workers upon
395	>	* steals, rather than use per-task bookkeeping.  This sometimes
396	>	* requires a linear scan of workQueues array to locate stealers,
397	>	* but often doesn't because stealers leave hints (that may become
398	>	* stale/wrong) of where to locate them.  It is only a hint
399	>	* because a worker might have had multiple steals and the hint
400	>	* records only one of them (usually the most current).  Hinting
401	>	* isolates cost to when it is needed, rather than adding to
402	>	* per-task overhead.  (2) It is "shallow", ignoring nesting and
403	>	* potentially cyclic mutual steals.  (3) It is intentionally
404	>	* racy: field currentJoin is updated only while actively joining,
405	>	* which means that we miss links in the chain during long-lived
406	>	* tasks, GC stalls etc (which is OK since blocking in such cases
407	>	* is usually a good idea).  (4) We bound the number of attempts
408	>	* to find work (see MAX_HELP) and fall back to suspending the
409	>	* worker and if necessary replacing it with another.
410	>	*
411	>	* Helping actions for CountedCompleters are much simpler: Method
412	>	* helpComplete can take and execute any task with the same root
413	>	* as the task being waited on. However, this still entails some
414	>	* traversal of completer chains, so is less efficient than using
415	>	* CountedCompleters without explicit joins.
416	>	*
417	>	* It is impossible to keep exactly the target parallelism number
418	>	* of threads running at any given time.  Determining the
419	>	* existence of conservatively safe helping targets, the
420	>	* availability of already-created spares, and the apparent need
421	>	* to create new spares are all racy, so we rely on multiple
422	>	* retries of each.  Compensation in the apparent absence of
423	>	* helping opportunities is challenging to control on JVMs, where
424	>	* GC and other activities can stall progress of tasks that in
425	>	* turn stall out many other dependent tasks, without us being
426	>	* able to determine whether they will ever require compensation.
427	>	* Even though work-stealing otherwise encounters little
428	>	* degradation in the presence of more threads than cores,
429	>	* aggressively adding new threads in such cases entails risk of
430	>	* unwanted positive feedback control loops in which more threads
431	>	* cause more dependent stalls (as well as delayed progress of
432	>	* unblocked threads to the point that we know they are available)
433	>	* leading to more situations requiring more threads, and so
434	>	* on. This aspect of control can be seen as an (analytically
435	>	* intractable) game with an opponent that may choose the worst
436	>	* (for us) active thread to stall at any time.  We take several
437	>	* precautions to bound losses (and thus bound gains), mainly in
438	>	* methods tryCompensate and awaitJoin.
439	>	*
440	>	* Common Pool
441	>	* ===========
442	>	*
443	>	* The static common Pool always exists after static
444	>	* initialization.  Since it (or any other created pool) need
445	>	* never be used, we minimize initial construction overhead and
446	>	* footprint to the setup of about a dozen fields, with no nested
447	>	* allocation. Most bootstrapping occurs within method
448	>	* fullExternalPush during the first submission to the pool.
449	>	*
450	>	* When external threads submit to the common pool, they can
451	>	* perform some subtask processing (see externalHelpJoin and
452	>	* related methods).  We do not need to record whether these
453	>	* submissions are to the common pool -- if not, externalHelpJoin
454	>	* returns quickly (at the most helping to signal some common pool
455	>	* workers). These submitters would otherwise be blocked waiting
456	>	* for completion, so the extra effort (with liberally sprinkled
457	>	* task status checks) in inapplicable cases amounts to an odd
458	>	* form of limited spin-wait before blocking in ForkJoinTask.join.
459	>	*
460	>	* Style notes
461	>	* ===========
462	>	*
463	>	* There is a lot of representation-level coupling among classes
464	>	* ForkJoinPool, ForkJoinWorkerThread, and ForkJoinTask.  The
465	>	* fields of WorkQueue maintain data structures managed by
466	>	* ForkJoinPool, so are directly accessed.  There is little point
467		* trying to reduce this, since any associated future changes in
468		* representations will need to be accompanied by algorithmic
469	<	* changes anyway.
470	<	*
471	<	* Style notes: There are lots of inline assignments (of form
472	<	* "while ((local = field) != 0)") which are usually the simplest
473	<	* way to ensure read orderings. Also several occurrences of the
474	<	* unusual "do {} while(!cas...)" which is the simplest way to
475	<	* force an update of a CAS'ed variable. There are also a few
476	<	* other coding oddities that help some methods perform reasonably
477	<	* even when interpreted (not compiled).
478	<	*
479	<	* The order of declarations in this file is: (1) statics (2)
480	<	* fields (along with constants used when unpacking some of them)
481	<	* (3) internal control methods (4) callbacks and other support
482	<	* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
483	<	* methods (plus a few little helpers).
469	>	* changes anyway. Several methods intrinsically sprawl because
470	>	* they must accumulate sets of consistent reads of volatiles held
471	>	* in local variables.  Methods signalWork() and scan() are the
472	>	* main bottlenecks, so are especially heavily
473	>	* micro-optimized/mangled.  There are lots of inline assignments
474	>	* (of form "while ((local = field) != 0)") which are usually the
475	>	* simplest way to ensure the required read orderings (which are
476	>	* sometimes critical). This leads to a "C"-like style of listing
477	>	* declarations of these locals at the heads of methods or blocks.
478	>	* There are several occurrences of the unusual "do {} while
479	>	* (!cas...)"  which is the simplest way to force an update of a
480	>	* CAS'ed variable. There are also other coding oddities (including
481	>	* several unnecessary-looking hoisted null checks) that help
482	>	* some methods perform reasonably even when interpreted (not
483	>	* compiled).
484	>	*
485	>	* The order of declarations in this file is:
486	>	* (1) Static utility functions
487	>	* (2) Nested (static) classes
488	>	* (3) Static fields
489	>	* (4) Fields, along with constants used when unpacking some of them
490	>	* (5) Internal control methods
491	>	* (6) Callbacks and other support for ForkJoinTask methods
492	>	* (7) Exported methods
493	>	* (8) Static block initializing statics in minimally dependent order
494	>	*/
495	>
496	>	// Static utilities
497	>
498	>	/**
499	>	* If there is a security manager, makes sure caller has
500	>	* permission to modify threads.
501		*/
502	+	private static void checkPermission() {
503	+	SecurityManager security = System.getSecurityManager();
504	+	if (security != null)
505	+	security.checkPermission(modifyThreadPermission);
506	+	}
507	+
508	+	// Nested classes
509
510		/**
511		* Factory for creating new {@link ForkJoinWorkerThread}s.
#	Line 345 | Line 527 | public class ForkJoinPool extends Abstra
527		* Default ForkJoinWorkerThreadFactory implementation; creates a
528		* new ForkJoinWorkerThread.
529		*/
530	<	static class  DefaultForkJoinWorkerThreadFactory
530	>	static final class DefaultForkJoinWorkerThreadFactory
531		implements ForkJoinWorkerThreadFactory {
532	<	public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
532	>	public final ForkJoinWorkerThread newThread(ForkJoinPool pool) {
533		return new ForkJoinWorkerThread(pool);
534		}
535		}
536
537		/**
538	<	* Creates a new ForkJoinWorkerThread. This factory is used unless
539	<	* overridden in ForkJoinPool constructors.
538	>	* Per-thread records for threads that submit to pools. Currently
539	>	* holds only pseudo-random seed / index that is used to choose
540	>	* submission queues in method externalPush. In the future, this may
541	>	* also incorporate a means to implement different task rejection
542	>	* and resubmission policies.
543	>	*
544	>	* Seeds for submitters and workers/workQueues work in basically
545	>	* the same way but are initialized and updated using slightly
546	>	* different mechanics. Both are initialized using the same
547	>	* approach as in class ThreadLocal, where successive values are
548	>	* unlikely to collide with previous values. Seeds are then
549	>	* randomly modified upon collisions using xorshifts, which
550	>	* requires a non-zero seed.
551	>	*/
552	>	static final class Submitter {
553	>	int seed;
554	>	Submitter(int s) { seed = s; }
555	>	}
556	>
557	>	/**
558	>	* Class for artificial tasks that are used to replace the target
559	>	* of local joins if they are removed from an interior queue slot
560	>	* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
561	>	* actually do anything beyond having a unique identity.
562	>	*/
563	>	static final class EmptyTask extends ForkJoinTask<Void> {
564	>	private static final long serialVersionUID = -7721805057305804111L;
565	>	EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
566	>	public final Void getRawResult() { return null; }
567	>	public final void setRawResult(Void x) {}
568	>	public final boolean exec() { return true; }
569	>	}
570	>
571	>	/**
572	>	* Queues supporting work-stealing as well as external task
573	>	* submission. See above for main rationale and algorithms.
574	>	* Implementation relies heavily on "Unsafe" intrinsics
575	>	* and selective use of "volatile":
576	>	*
577	>	* Field "base" is the index (mod array.length) of the least valid
578	>	* queue slot, which is always the next position to steal (poll)
579	>	* from if nonempty. Reads and writes require volatile orderings
580	>	* but not CAS, because updates are only performed after slot
581	>	* CASes.
582	>	*
583	>	* Field "top" is the index (mod array.length) of the next queue
584	>	* slot to push to or pop from. It is written only by owner thread
585	>	* for push, or under lock for external/shared push, and accessed
586	>	* by other threads only after reading (volatile) base.  Both top
587	>	* and base are allowed to wrap around on overflow, but (top -
588	>	* base) (or more commonly -(base - top) to force volatile read of
589	>	* base before top) still estimates size. The lock ("qlock") is
590	>	* forced to -1 on termination, causing all further lock attempts
591	>	* to fail. (Note: we don't need CAS for termination state because
592	>	* upon pool shutdown, all shared-queues will stop being used
593	>	* anyway.)  Nearly all lock bodies are set up so that exceptions
594	>	* within lock bodies are "impossible" (modulo JVM errors that
595	>	* would cause failure anyway.)
596	>	*
597	>	* The array slots are read and written using the emulation of
598	>	* volatiles/atomics provided by Unsafe. Insertions must in
599	>	* general use putOrderedObject as a form of releasing store to
600	>	* ensure that all writes to the task object are ordered before
601	>	* its publication in the queue.  All removals entail a CAS to
602	>	* null.  The array is always a power of two. To ensure safety of
603	>	* Unsafe array operations, all accesses perform explicit null
604	>	* checks and implicit bounds checks via power-of-two masking.
605	>	*
606	>	* In addition to basic queuing support, this class contains
607	>	* fields described elsewhere to control execution. It turns out
608	>	* to work better memory-layout-wise to include them in this class
609	>	* rather than a separate class.
610	>	*
611	>	* Performance on most platforms is very sensitive to placement of
612	>	* instances of both WorkQueues and their arrays -- we absolutely
613	>	* do not want multiple WorkQueue instances or multiple queue
614	>	* arrays sharing cache lines. (It would be best for queue objects
615	>	* and their arrays to share, but there is nothing available to
616	>	* help arrange that).  Unfortunately, because they are recorded
617	>	* in a common array, WorkQueue instances are often moved to be
618	>	* adjacent by garbage collectors. To reduce impact, we use field
619	>	* padding that works OK on common platforms; this effectively
620	>	* trades off slightly slower average field access for the sake of
621	>	* avoiding really bad worst-case access. (Until better JVM
622	>	* support is in place, this padding is dependent on transient
623	>	* properties of JVM field layout rules.) We also take care in
624	>	* allocating, sizing and resizing the array. Non-shared queue
625	>	* arrays are initialized by workers before use. Others are
626	>	* allocated on first use.
627		*/
628	<	public static final ForkJoinWorkerThreadFactory
629	<	defaultForkJoinWorkerThreadFactory =
630	<	new DefaultForkJoinWorkerThreadFactory();
628	>	static final class WorkQueue {
629	>	/**
630	>	* Capacity of work-stealing queue array upon initialization.
631	>	* Must be a power of two; at least 4, but should be larger to
632	>	* reduce or eliminate cacheline sharing among queues.
633	>	* Currently, it is much larger, as a partial workaround for
634	>	* the fact that JVMs often place arrays in locations that
635	>	* share GC bookkeeping (especially cardmarks) such that
636	>	* per-write accesses encounter serious memory contention.
637	>	*/
638	>	static final int INITIAL_QUEUE_CAPACITY = 1 << 13;
639
640	<	/**
641	<	* Permission required for callers of methods that may start or
642	<	* kill threads.
643	<	*/
644	<	private static final RuntimePermission modifyThreadPermission =
645	<	new RuntimePermission("modifyThread");
640	>	/**
641	>	* Maximum size for queue arrays. Must be a power of two less
642	>	* than or equal to 1 << (31 - width of array entry) to ensure
643	>	* lack of wraparound of index calculations, but defined to a
644	>	* value a bit less than this to help users trap runaway
645	>	* programs before saturating systems.
646	>	*/
647	>	static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
648
649	<	/**
650	<	* If there is a security manager, makes sure caller has
372	<	* permission to modify threads.
373	<	*/
374	<	private static void checkPermission() {
375	<	SecurityManager security = System.getSecurityManager();
376	<	if (security != null)
377	<	security.checkPermission(modifyThreadPermission);
378	<	}
649	>	// Heuristic padding to ameliorate unfortunate memory placements
650	>	volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
651
652	<	/**
653	<	* Generator for assigning sequence numbers as pool names.
654	<	*/
655	<	private static final AtomicInteger poolNumberGenerator =
656	<	new AtomicInteger();
652	>	int seed;                  // for random scanning; initialize nonzero
653	>	volatile int eventCount;   // encoded inactivation count; < 0 if inactive
654	>	int nextWait;              // encoded record of next event waiter
655	>	int hint;                  // steal or signal hint (index)
656	>	int poolIndex;             // index of this queue in pool (or 0)
657	>	final int mode;            // 0: lifo, > 0: fifo, < 0: shared
658	>	int nsteals;               // number of steals
659	>	volatile int qlock;        // 1: locked, -1: terminate; else 0
660	>	volatile int base;         // index of next slot for poll
661	>	int top;                   // index of next slot for push
662	>	ForkJoinTask<?>[] array;   // the elements (initially unallocated)
663	>	final ForkJoinPool pool;   // the containing pool (may be null)
664	>	final ForkJoinWorkerThread owner; // owning thread or null if shared
665	>	volatile Thread parker;    // == owner during call to park; else null
666	>	volatile ForkJoinTask<?> currentJoin;  // task being joined in awaitJoin
667	>	ForkJoinTask<?> currentSteal; // current non-local task being executed
668	>
669	>	volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
670	>	volatile Object pad18, pad19, pad1a, pad1b, pad1c, pad1d;
671	>
672	>	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode,
673	>	int seed) {
674	>	this.pool = pool;
675	>	this.owner = owner;
676	>	this.mode = mode;
677	>	this.seed = seed;
678	>	// Place indices in the center of array (that is not yet allocated)
679	>	base = top = INITIAL_QUEUE_CAPACITY >>> 1;
680	>	}
681
682	<	/**
683	<	* Absolute bound for parallelism level. Twice this number must
684	<	* fit into a 16bit field to enable word-packing for some counts.
685	<	*/
686	<	private static final int MAX_THREADS = 0x7fff;
682	>	/**
683	>	* Returns the approximate number of tasks in the queue.
684	>	*/
685	>	final int queueSize() {
686	>	int n = base - top;       // non-owner callers must read base first
687	>	return (n >= 0) ? 0 : -n; // ignore transient negative
688	>	}
689
690	<	/**
691	<	* Array holding all worker threads in the pool.  Array size must
692	<	* be a power of two.  Updates and replacements are protected by
693	<	* workerLock, but the array is always kept in a consistent enough
694	<	* state to be randomly accessed without locking by workers
695	<	* performing work-stealing, as well as other traversal-based
696	<	* methods in this class. All readers must tolerate that some
697	<	* array slots may be null.
698	<	*/
699	<	volatile ForkJoinWorkerThread[] workers;
690	>	/**
691	>	* Provides a more accurate estimate of whether this queue has
692	>	* any tasks than does queueSize, by checking whether a
693	>	* near-empty queue has at least one unclaimed task.
694	>	*/
695	>	final boolean isEmpty() {
696	>	ForkJoinTask<?>[] a; int m, s;
697	>	int n = base - (s = top);
698	>	return (n >= 0 ||
699	>	(n == -1 &&
700	>	((a = array) == null ||
701	>	(m = a.length - 1) < 0 ||
702	>	U.getObject
703	>	(a, (long)((m & (s - 1)) << ASHIFT) + ABASE) == null)));
704	>	}
705
706	<	/**
707	<	* Queue for external submissions.
708	<	*/
709	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
706	>	/**
707	>	* Pushes a task. Call only by owner in unshared queues.  (The
708	>	* shared-queue version is embedded in method externalPush.)
709	>	*
710	>	* @param task the task. Caller must ensure non-null.
711	>	* @throws RejectedExecutionException if array cannot be resized
712	>	*/
713	>	final void push(ForkJoinTask<?> task) {
714	>	ForkJoinTask<?>[] a; ForkJoinPool p;
715	>	int s = top, m, n;
716	>	if ((a = array) != null) {    // ignore if queue removed
717	>	int j = (((m = a.length - 1) & s) << ASHIFT) + ABASE;
718	>	U.putOrderedObject(a, j, task);
719	>	if ((n = (top = s + 1) - base) <= 2) {
720	>	if ((p = pool) != null)
721	>	p.signalWork(this);
722	>	}
723	>	else if (n >= m)
724	>	growArray();
725	>	}
726	>	}
727
728	<	/**
729	<	* Lock protecting updates to workers array.
730	<	*/
731	<	private final ReentrantLock workerLock;
728	>	/**
729	>	* Initializes or doubles the capacity of array. Call either
730	>	* by owner or with lock held -- it is OK for base, but not
731	>	* top, to move while resizings are in progress.
732	>	*/
733	>	final ForkJoinTask<?>[] growArray() {
734	>	ForkJoinTask<?>[] oldA = array;
735	>	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
736	>	if (size > MAXIMUM_QUEUE_CAPACITY)
737	>	throw new RejectedExecutionException("Queue capacity exceeded");
738	>	int oldMask, t, b;
739	>	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
740	>	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
741	>	(t = top) - (b = base) > 0) {
742	>	int mask = size - 1;
743	>	do {
744	>	ForkJoinTask<?> x;
745	>	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
746	>	int j    = ((b &    mask) << ASHIFT) + ABASE;
747	>	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
748	>	if (x != null &&
749	>	U.compareAndSwapObject(oldA, oldj, x, null))
750	>	U.putObjectVolatile(a, j, x);
751	>	} while (++b != t);
752	>	}
753	>	return a;
754	>	}
755
756	<	/**
757	<	* Latch released upon termination.
758	<	*/
759	<	private final CountDownLatch terminationLatch;
756	>	/**
757	>	* Takes next task, if one exists, in LIFO order.  Call only
758	>	* by owner in unshared queues.
759	>	*/
760	>	final ForkJoinTask<?> pop() {
761	>	ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
762	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
763	>	for (int s; (s = top - 1) - base >= 0;) {
764	>	long j = ((m & s) << ASHIFT) + ABASE;
765	>	if ((t = (ForkJoinTask<?>)U.getObject(a, j)) == null)
766	>	break;
767	>	if (U.compareAndSwapObject(a, j, t, null)) {
768	>	top = s;
769	>	return t;
770	>	}
771	>	}
772	>	}
773	>	return null;
774	>	}
775
776	<	/**
777	<	* Creation factory for worker threads.
778	<	*/
779	<	private final ForkJoinWorkerThreadFactory factory;
776	>	/**
777	>	* Takes a task in FIFO order if b is base of queue and a task
778	>	* can be claimed without contention. Specialized versions
779	>	* appear in ForkJoinPool methods scan and tryHelpStealer.
780	>	*/
781	>	final ForkJoinTask<?> pollAt(int b) {
782	>	ForkJoinTask<?> t; ForkJoinTask<?>[] a;
783	>	if ((a = array) != null) {
784	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
785	>	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
786	>	base == b &&
787	>	U.compareAndSwapObject(a, j, t, null)) {
788	>	base = b + 1;
789	>	return t;
790	>	}
791	>	}
792	>	return null;
793	>	}
794
795	<	/**
796	<	* Sum of per-thread steal counts, updated only when threads are
797	<	* idle or terminating.
798	<	*/
799	<	private volatile long stealCount;
795	>	/**
796	>	* Takes next task, if one exists, in FIFO order.
797	>	*/
798	>	final ForkJoinTask<?> poll() {
799	>	ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t;
800	>	while ((b = base) - top < 0 && (a = array) != null) {
801	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
802	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
803	>	if (t != null) {
804	>	if (base == b &&
805	>	U.compareAndSwapObject(a, j, t, null)) {
806	>	base = b + 1;
807	>	return t;
808	>	}
809	>	}
810	>	else if (base == b) {
811	>	if (b + 1 == top)
812	>	break;
813	>	Thread.yield(); // wait for lagging update (very rare)
814	>	}
815	>	}
816	>	return null;
817	>	}
818
819	<	/**
820	<	* Encoded record of top of treiber stack of threads waiting for
821	<	* events. The top 32 bits contain the count being waited for. The
822	<	* bottom word contains one plus the pool index of waiting worker
823	<	* thread.
824	<	*/
825	<	private volatile long eventWaiters;
819	>	/**
820	>	* Takes next task, if one exists, in order specified by mode.
821	>	*/
822	>	final ForkJoinTask<?> nextLocalTask() {
823	>	return mode == 0 ? pop() : poll();
824	>	}
825	>
826	>	/**
827	>	* Returns next task, if one exists, in order specified by mode.
828	>	*/
829	>	final ForkJoinTask<?> peek() {
830	>	ForkJoinTask<?>[] a = array; int m;
831	>	if (a == null || (m = a.length - 1) < 0)
832	>	return null;
833	>	int i = mode == 0 ? top - 1 : base;
834	>	int j = ((i & m) << ASHIFT) + ABASE;
835	>	return (ForkJoinTask<?>)U.getObjectVolatile(a, j);
836	>	}
837
838	<	private static final int  EVENT_COUNT_SHIFT = 32;
839	<	private static final long WAITER_INDEX_MASK = (1L << EVENT_COUNT_SHIFT)-1L;
838	>	/**
839	>	* Pops the given task only if it is at the current top.
840	>	* (A shared version is available only via FJP.tryExternalUnpush)
841	>	*/
842	>	final boolean tryUnpush(ForkJoinTask<?> t) {
843	>	ForkJoinTask<?>[] a; int s;
844	>	if ((a = array) != null && (s = top) != base &&
845	>	U.compareAndSwapObject
846	>	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
847	>	top = s;
848	>	return true;
849	>	}
850	>	return false;
851	>	}
852
853	<	/**
854	<	* A counter for events that may wake up worker threads:
855	<	*   - Submission of a new task to the pool
856	<	*   - A worker pushing a task on an empty queue
857	<	*   - termination and reconfiguration
858	<	*/
859	<	private volatile int eventCount;
853	>	/**
854	>	* Removes and cancels all known tasks, ignoring any exceptions.
855	>	*/
856	>	final void cancelAll() {
857	>	ForkJoinTask.cancelIgnoringExceptions(currentJoin);
858	>	ForkJoinTask.cancelIgnoringExceptions(currentSteal);
859	>	for (ForkJoinTask<?> t; (t = poll()) != null; )
860	>	ForkJoinTask.cancelIgnoringExceptions(t);
861	>	}
862
863	<	/**
864	<	* Lifecycle control. The low word contains the number of workers
865	<	* that are (probably) executing tasks. This value is atomically
866	<	* incremented before a worker gets a task to run, and decremented
867	<	* when worker has no tasks and cannot find any.  Bits 16-18
868	<	* contain runLevel value. When all are zero, the pool is
869	<	* running. Level transitions are monotonic (running -> shutdown
870	<	* -> terminating -> terminated) so each transition adds a bit.
871	<	* These are bundled together to ensure consistent read for
872	<	* termination checks (i.e., that runLevel is at least SHUTDOWN
873	<	* and active threads is zero).
874	<	*/
875	<	private volatile int runState;
863	>	/**
864	>	* Computes next value for random probes.  Scans don't require
865	>	* a very high quality generator, but also not a crummy one.
866	>	* Marsaglia xor-shift is cheap and works well enough.  Note:
867	>	* This is manually inlined in its usages in ForkJoinPool to
868	>	* avoid writes inside busy scan loops.
869	>	*/
870	>	final int nextSeed() {
871	>	int r = seed;
872	>	r ^= r << 13;
873	>	r ^= r >>> 17;
874	>	return seed = r ^= r << 5;
875	>	}
876
877	<	// Note: The order among run level values matters.
463	<	private static final int RUNLEVEL_SHIFT     = 16;
464	<	private static final int SHUTDOWN           = 1 << RUNLEVEL_SHIFT;
465	<	private static final int TERMINATING        = 1 << (RUNLEVEL_SHIFT + 1);
466	<	private static final int TERMINATED         = 1 << (RUNLEVEL_SHIFT + 2);
467	<	private static final int ACTIVE_COUNT_MASK  = (1 << RUNLEVEL_SHIFT) - 1;
468	<	private static final int ONE_ACTIVE         = 1; // active update delta
877	>	// Specialized execution methods
878
879	<	/**
880	<	* Holds number of total (i.e., created and not yet terminated)
881	<	* and running (i.e., not blocked on joins or other managed sync)
882	<	* threads, packed together to ensure consistent snapshot when
883	<	* making decisions about creating and suspending spare
884	<	* threads. Updated only by CAS. Note that adding a new worker
885	<	* requires incrementing both counts, since workers start off in
886	<	* running state.  This field is also used for memory-fencing
887	<	* configuration parameters.
888	<	*/
889	<	private volatile int workerCounts;
879	>	/**
880	>	* Pops and runs tasks until empty.
881	>	*/
882	>	private void popAndExecAll() {
883	>	// A bit faster than repeated pop calls
884	>	ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t;
885	>	while ((a = array) != null && (m = a.length - 1) >= 0 &&
886	>	(s = top - 1) - base >= 0 &&
887	>	(t = ((ForkJoinTask<?>)
888	>	U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
889	>	!= null) {
890	>	if (U.compareAndSwapObject(a, j, t, null)) {
891	>	top = s;
892	>	t.doExec();
893	>	}
894	>	}
895	>	}
896
897	<	private static final int TOTAL_COUNT_SHIFT  = 16;
898	<	private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1;
899	<	private static final int ONE_RUNNING        = 1;
900	<	private static final int ONE_TOTAL          = 1 << TOTAL_COUNT_SHIFT;
897	>	/**
898	>	* Polls and runs tasks until empty.
899	>	*/
900	>	private void pollAndExecAll() {
901	>	for (ForkJoinTask<?> t; (t = poll()) != null;)
902	>	t.doExec();
903	>	}
904
905	<	/*
906	<	* Fields parallelism. maxPoolSize, locallyFifo,
907	<	* maintainsParallelism, and ueh are non-volatile, but external
908	<	* reads/writes use workerCount fences to ensure visability.
905	>	/**
906	>	* If present, removes from queue and executes the given task,
907	>	* or any other cancelled task. Returns (true) on any CAS
908	>	* or consistency check failure so caller can retry.
909	>	*
910	>	* @return false if no progress can be made, else true;
911	>	*/
912	>	final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
913	>	boolean stat = true, removed = false, empty = true;
914	>	ForkJoinTask<?>[] a; int m, s, b, n;
915	>	if ((a = array) != null && (m = a.length - 1) >= 0 &&
916	>	(n = (s = top) - (b = base)) > 0) {
917	>	for (ForkJoinTask<?> t;;) {           // traverse from s to b
918	>	int j = ((--s & m) << ASHIFT) + ABASE;
919	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
920	>	if (t == null)                    // inconsistent length
921	>	break;
922	>	else if (t == task) {
923	>	if (s + 1 == top) {           // pop
924	>	if (!U.compareAndSwapObject(a, j, task, null))
925	>	break;
926	>	top = s;
927	>	removed = true;
928	>	}
929	>	else if (base == b)           // replace with proxy
930	>	removed = U.compareAndSwapObject(a, j, task,
931	>	new EmptyTask());
932	>	break;
933	>	}
934	>	else if (t.status >= 0)
935	>	empty = false;
936	>	else if (s + 1 == top) {          // pop and throw away
937	>	if (U.compareAndSwapObject(a, j, t, null))
938	>	top = s;
939	>	break;
940	>	}
941	>	if (--n == 0) {
942	>	if (!empty && base == b)
943	>	stat = false;
944	>	break;
945	>	}
946	>	}
947	>	}
948	>	if (removed)
949	>	task.doExec();
950	>	return stat;
951	>	}
952	>
953	>	/**
954	>	* Polls for and executes the given task or any other task in
955	>	* its CountedCompleter computation
956	>	*/
957	>	final boolean pollAndExecCC(ForkJoinTask<?> root) {
958	>	ForkJoinTask<?>[] a; int b; Object o;
959	>	outer: while ((b = base) - top < 0 && (a = array) != null) {
960	>	long j = (((a.length - 1) & b) << ASHIFT) + ABASE;
961	>	if ((o = U.getObject(a, j)) == null ||
962	>	!(o instanceof CountedCompleter))
963	>	break;
964	>	for (CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;;) {
965	>	if (r == root) {
966	>	if (base == b &&
967	>	U.compareAndSwapObject(a, j, t, null)) {
968	>	base = b + 1;
969	>	t.doExec();
970	>	return true;
971	>	}
972	>	else
973	>	break; // restart
974	>	}
975	>	if ((r = r.completer) == null)
976	>	break outer; // not part of root computation
977	>	}
978	>	}
979	>	return false;
980	>	}
981	>
982	>	/**
983	>	* Executes a top-level task and any local tasks remaining
984	>	* after execution.
985	>	*/
986	>	final void runTask(ForkJoinTask<?> t) {
987	>	if (t != null) {
988	>	(currentSteal = t).doExec();
989	>	currentSteal = null;
990	>	++nsteals;
991	>	if (base - top < 0) {       // process remaining local tasks
992	>	if (mode == 0)
993	>	popAndExecAll();
994	>	else
995	>	pollAndExecAll();
996	>	}
997	>	}
998	>	}
999	>
1000	>	/**
1001	>	* Executes a non-top-level (stolen) task.
1002	>	*/
1003	>	final void runSubtask(ForkJoinTask<?> t) {
1004	>	if (t != null) {
1005	>	ForkJoinTask<?> ps = currentSteal;
1006	>	(currentSteal = t).doExec();
1007	>	currentSteal = ps;
1008	>	}
1009	>	}
1010	>
1011	>	/**
1012	>	* Returns true if owned and not known to be blocked.
1013	>	*/
1014	>	final boolean isApparentlyUnblocked() {
1015	>	Thread wt; Thread.State s;
1016	>	return (eventCount >= 0 &&
1017	>	(wt = owner) != null &&
1018	>	(s = wt.getState()) != Thread.State.BLOCKED &&
1019	>	s != Thread.State.WAITING &&
1020	>	s != Thread.State.TIMED_WAITING);
1021	>	}
1022	>
1023	>	// Unsafe mechanics
1024	>	private static final sun.misc.Unsafe U;
1025	>	private static final long QLOCK;
1026	>	private static final int ABASE;
1027	>	private static final int ASHIFT;
1028	>	static {
1029	>	try {
1030	>	U = getUnsafe();
1031	>	Class<?> k = WorkQueue.class;
1032	>	Class<?> ak = ForkJoinTask[].class;
1033	>	QLOCK = U.objectFieldOffset
1034	>	(k.getDeclaredField("qlock"));
1035	>	ABASE = U.arrayBaseOffset(ak);
1036	>	int scale = U.arrayIndexScale(ak);
1037	>	if ((scale & (scale - 1)) != 0)
1038	>	throw new Error("data type scale not a power of two");
1039	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
1040	>	} catch (Exception e) {
1041	>	throw new Error(e);
1042	>	}
1043	>	}
1044	>	}
1045	>
1046	>	// static fields (initialized in static initializer below)
1047	>
1048	>	/**
1049	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
1050	>	* overridden in ForkJoinPool constructors.
1051		*/
1052	+	public static final ForkJoinWorkerThreadFactory
1053	+	defaultForkJoinWorkerThreadFactory;
1054
1055		/**
1056	<	* The target parallelism level.
1056	>	* Per-thread submission bookkeeping. Shared across all pools
1057	>	* to reduce ThreadLocal pollution and because random motion
1058	>	* to avoid contention in one pool is likely to hold for others.
1059	>	* Lazily initialized on first submission (but null-checked
1060	>	* in other contexts to avoid unnecessary initialization).
1061		*/
1062	<	private int parallelism;
1062	>	static final ThreadLocal<Submitter> submitters;
1063
1064		/**
1065	<	* The maximum allowed pool size.
1065	>	* Permission required for callers of methods that may start or
1066	>	* kill threads.
1067		*/
1068	<	private int maxPoolSize;
1068	>	private static final RuntimePermission modifyThreadPermission;
1069
1070		/**
1071	<	* True if use local fifo, not default lifo, for local polling
1072	<	* Replicated by ForkJoinWorkerThreads
1071	>	* Common (static) pool. Non-null for public use unless a static
1072	>	* construction exception, but internal usages null-check on use
1073	>	* to paranoically avoid potential initialization circularities
1074	>	* as well as to simplify generated code.
1075		*/
1076	<	private boolean locallyFifo;
1076	>	static final ForkJoinPool common;
1077
1078		/**
1079	<	* Controls whether to add spares to maintain parallelism
1079	>	* Common pool parallelism. Must equal common.parallelism.
1080		*/
1081	<	private boolean maintainsParallelism;
1081	>	static final int commonParallelism;
1082
1083		/**
1084	<	* The uncaught exception handler used when any worker
516	<	* abruptly terminates
1084	>	* Sequence number for creating workerNamePrefix.
1085		*/
1086	<	private Thread.UncaughtExceptionHandler ueh;
1086	>	private static int poolNumberSequence;
1087
1088		/**
1089	<	* Pool number, just for assigning useful names to worker threads
1089	>	* Returns the next sequence number. We don't expect this to
1090	>	* ever contend, so use simple builtin sync.
1091		*/
1092	<	private final int poolNumber;
1092	>	private static final synchronized int nextPoolId() {
1093	>	return ++poolNumberSequence;
1094	>	}
1095
1096	<	// utilities for updating fields
1096	>	// static constants
1097
1098		/**
1099	<	* Adds delta to running count.  Used mainly by ForkJoinTask.
1100	<	*
1101	<	* @param delta the number to add
1099	>	* Initial timeout value (in nanoseconds) for the thread
1100	>	* triggering quiescence to park waiting for new work. On timeout,
1101	>	* the thread will instead try to shrink the number of
1102	>	* workers. The value should be large enough to avoid overly
1103	>	* aggressive shrinkage during most transient stalls (long GCs
1104	>	* etc).
1105		*/
1106	<	final void updateRunningCount(int delta) {
533	<	int wc;
534	<	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
535	<	wc = workerCounts,
536	<	wc + delta));
537	<	}
1106	>	private static final long IDLE_TIMEOUT      = 2000L * 1000L * 1000L; // 2sec
1107
1108		/**
1109	<	* Write fence for user modifications of pool parameters
541	<	* (parallelism. etc).  Note that it doesn't matter if CAS fails.
1109	>	* Timeout value when there are more threads than parallelism level
1110		*/
1111	<	private void workerCountWriteFence() {
544	<	int wc;
545	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
546	<	wc = workerCounts, wc);
547	<	}
1111	>	private static final long FAST_IDLE_TIMEOUT =  200L * 1000L * 1000L;
1112
1113		/**
1114	<	* Read fence for external reads of pool parameters
551	<	* (parallelism. maxPoolSize, etc).
1114	>	* Tolerance for idle timeouts, to cope with timer undershoots
1115		*/
1116	<	private void workerCountReadFence() {
554	<	int ignore = workerCounts;
555	<	}
1116	>	private static final long TIMEOUT_SLOP = 2000000L;
1117
1118		/**
1119	<	* Tries incrementing active count; fails on contention.
1120	<	* Called by workers before executing tasks.
1121	<	*
1122	<	* @return true on success
1119	>	* The maximum stolen->joining link depth allowed in method
1120	>	* tryHelpStealer.  Must be a power of two.  Depths for legitimate
1121	>	* chains are unbounded, but we use a fixed constant to avoid
1122	>	* (otherwise unchecked) cycles and to bound staleness of
1123	>	* traversal parameters at the expense of sometimes blocking when
1124	>	* we could be helping.
1125		*/
1126	<	final boolean tryIncrementActiveCount() {
564	<	int c;
565	<	return UNSAFE.compareAndSwapInt(this, runStateOffset,
566	<	c = runState, c + ONE_ACTIVE);
567	<	}
1126	>	private static final int MAX_HELP = 64;
1127
1128		/**
1129	<	* Tries decrementing active count; fails on contention.
1130	<	* Called when workers cannot find tasks to run.
1129	>	* Increment for seed generators. See class ThreadLocal for
1130	>	* explanation.
1131		*/
1132	<	final boolean tryDecrementActiveCount() {
574	<	int c;
575	<	return UNSAFE.compareAndSwapInt(this, runStateOffset,
576	<	c = runState, c - ONE_ACTIVE);
577	<	}
1132	>	private static final int SEED_INCREMENT = 0x61c88647;
1133
1134		/**
1135	<	* Advances to at least the given level. Returns true if not
1136	<	* already in at least the given level.
1135	>	* Bits and masks for control variables
1136	>	*
1137	>	* Field ctl is a long packed with:
1138	>	* AC: Number of active running workers minus target parallelism (16 bits)
1139	>	* TC: Number of total workers minus target parallelism (16 bits)
1140	>	* ST: true if pool is terminating (1 bit)
1141	>	* EC: the wait count of top waiting thread (15 bits)
1142	>	* ID: poolIndex of top of Treiber stack of waiters (16 bits)
1143	>	*
1144	>	* When convenient, we can extract the upper 32 bits of counts and
1145	>	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
1146	>	* (int)ctl.  The ec field is never accessed alone, but always
1147	>	* together with id and st. The offsets of counts by the target
1148	>	* parallelism and the positionings of fields makes it possible to
1149	>	* perform the most common checks via sign tests of fields: When
1150	>	* ac is negative, there are not enough active workers, when tc is
1151	>	* negative, there are not enough total workers, and when e is
1152	>	* negative, the pool is terminating.  To deal with these possibly
1153	>	* negative fields, we use casts in and out of "short" and/or
1154	>	* signed shifts to maintain signedness.
1155	>	*
1156	>	* When a thread is queued (inactivated), its eventCount field is
1157	>	* set negative, which is the only way to tell if a worker is
1158	>	* prevented from executing tasks, even though it must continue to
1159	>	* scan for them to avoid queuing races. Note however that
1160	>	* eventCount updates lag releases so usage requires care.
1161	>	*
1162	>	* Field plock is an int packed with:
1163	>	* SHUTDOWN: true if shutdown is enabled (1 bit)
1164	>	* SEQ:  a sequence lock, with PL_LOCK bit set if locked (30 bits)
1165	>	* SIGNAL: set when threads may be waiting on the lock (1 bit)
1166	>	*
1167	>	* The sequence number enables simple consistency checks:
1168	>	* Staleness of read-only operations on the workQueues array can
1169	>	* be checked by comparing plock before vs after the reads.
1170		*/
583	–	private boolean advanceRunLevel(int level) {
584	–	for (;;) {
585	–	int s = runState;
586	–	if ((s & level) != 0)
587	–	return false;
588	–	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level))
589	–	return true;
590	–	}
591	–	}
1171
1172	<	// workers array maintenance
1172	>	// bit positions/shifts for fields
1173	>	private static final int  AC_SHIFT   = 48;
1174	>	private static final int  TC_SHIFT   = 32;
1175	>	private static final int  ST_SHIFT   = 31;
1176	>	private static final int  EC_SHIFT   = 16;
1177
1178	<	/**
1179	<	* Records and returns a workers array index for new worker.
1178	>	// bounds
1179	>	private static final int  SMASK      = 0xffff;  // short bits
1180	>	private static final int  MAX_CAP    = 0x7fff;  // max #workers - 1
1181	>	private static final int  EVENMASK   = 0xfffe;  // even short bits
1182	>	private static final int  SQMASK     = 0x007e;  // max 64 (even) slots
1183	>	private static final int  SHORT_SIGN = 1 << 15;
1184	>	private static final int  INT_SIGN   = 1 << 31;
1185	>
1186	>	// masks
1187	>	private static final long STOP_BIT   = 0x0001L << ST_SHIFT;
1188	>	private static final long AC_MASK    = ((long)SMASK) << AC_SHIFT;
1189	>	private static final long TC_MASK    = ((long)SMASK) << TC_SHIFT;
1190	>
1191	>	// units for incrementing and decrementing
1192	>	private static final long TC_UNIT    = 1L << TC_SHIFT;
1193	>	private static final long AC_UNIT    = 1L << AC_SHIFT;
1194	>
1195	>	// masks and units for dealing with u = (int)(ctl >>> 32)
1196	>	private static final int  UAC_SHIFT  = AC_SHIFT - 32;
1197	>	private static final int  UTC_SHIFT  = TC_SHIFT - 32;
1198	>	private static final int  UAC_MASK   = SMASK << UAC_SHIFT;
1199	>	private static final int  UTC_MASK   = SMASK << UTC_SHIFT;
1200	>	private static final int  UAC_UNIT   = 1 << UAC_SHIFT;
1201	>	private static final int  UTC_UNIT   = 1 << UTC_SHIFT;
1202	>
1203	>	// masks and units for dealing with e = (int)ctl
1204	>	private static final int E_MASK      = 0x7fffffff; // no STOP_BIT
1205	>	private static final int E_SEQ       = 1 << EC_SHIFT;
1206	>
1207	>	// plock bits
1208	>	private static final int SHUTDOWN    = 1 << 31;
1209	>	private static final int PL_LOCK     = 2;
1210	>	private static final int PL_SIGNAL   = 1;
1211	>	private static final int PL_SPINS    = 1 << 8;
1212	>
1213	>	// access mode for WorkQueue
1214	>	static final int LIFO_QUEUE          =  0;
1215	>	static final int FIFO_QUEUE          =  1;
1216	>	static final int SHARED_QUEUE        = -1;
1217	>
1218	>	// bounds for #steps in scan loop -- must be power 2 minus 1
1219	>	private static final int MIN_SCAN    = 0x1ff;   // cover estimation slop
1220	>	private static final int MAX_SCAN    = 0x1ffff; // 4 * max workers
1221	>
1222	>	// Instance fields
1223	>
1224	>	/*
1225	>	* Field layout of this class tends to matter more than one would
1226	>	* like. Runtime layout order is only loosely related to
1227	>	* declaration order and may differ across JVMs, but the following
1228	>	* empirically works OK on current JVMs.
1229	>	*/
1230	>
1231	>	// Heuristic padding to ameliorate unfortunate memory placements
1232	>	volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
1233	>
1234	>	volatile long stealCount;                  // collects worker counts
1235	>	volatile long ctl;                         // main pool control
1236	>	volatile int plock;                        // shutdown status and seqLock
1237	>	volatile int indexSeed;                    // worker/submitter index seed
1238	>	final int config;                          // mode and parallelism level
1239	>	WorkQueue[] workQueues;                    // main registry
1240	>	final ForkJoinWorkerThreadFactory factory;
1241	>	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1242	>	final String workerNamePrefix;             // to create worker name string
1243	>
1244	>	volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
1245	>	volatile Object pad18, pad19, pad1a, pad1b;
1246	>
1247	>	/**
1248	>	* Acquires the plock lock to protect worker array and related
1249	>	* updates. This method is called only if an initial CAS on plock
1250	>	* fails. This acts as a spinlock for normal cases, but falls back
1251	>	* to builtin monitor to block when (rarely) needed. This would be
1252	>	* a terrible idea for a highly contended lock, but works fine as
1253	>	* a more conservative alternative to a pure spinlock.
1254		*/
1255	<	private int recordWorker(ForkJoinWorkerThread w) {
1256	<	// Try using slot totalCount-1. If not available, scan and/or resize
1257	<	int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1;
1258	<	final ReentrantLock lock = this.workerLock;
1259	<	lock.lock();
1260	<	try {
1261	<	ForkJoinWorkerThread[] ws = workers;
1262	<	int len = ws.length;
1263	<	if (k < 0 || k >= len || ws[k] != null) {
1264	<	for (k = 0; k < len && ws[k] != null; ++k)
1265	<	;
1266	<	if (k == len)
1267	<	ws = Arrays.copyOf(ws, len << 1);
1255	>	private int acquirePlock() {
1256	>	int spins = PL_SPINS, r = 0, ps, nps;
1257	>	for (;;) {
1258	>	if (((ps = plock) & PL_LOCK) == 0 &&
1259	>	U.compareAndSwapInt(this, PLOCK, ps, nps = ps + PL_LOCK))
1260	>	return nps;
1261	>	else if (r == 0) { // randomize spins if possible
1262	>	Thread t = Thread.currentThread(); WorkQueue w; Submitter z;
1263	>	if ((t instanceof ForkJoinWorkerThread) &&
1264	>	(w = ((ForkJoinWorkerThread)t).workQueue) != null)
1265	>	r = w.seed;
1266	>	else if ((z = submitters.get()) != null)
1267	>	r = z.seed;
1268	>	else
1269	>	r = 1;
1270	>	}
1271	>	else if (spins >= 0) {
1272	>	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1273	>	if (r >= 0)
1274	>	--spins;
1275	>	}
1276	>	else if (U.compareAndSwapInt(this, PLOCK, ps, ps | PL_SIGNAL)) {
1277	>	synchronized (this) {
1278	>	if ((plock & PL_SIGNAL) != 0) {
1279	>	try {
1280	>	wait();
1281	>	} catch (InterruptedException ie) {
1282	>	try {
1283	>	Thread.currentThread().interrupt();
1284	>	} catch (SecurityException ignore) {
1285	>	}
1286	>	}
1287	>	}
1288	>	else
1289	>	notifyAll();
1290	>	}
1291		}
612	–	ws[k] = w;
613	–	workers = ws; // volatile array write ensures slot visibility
614	–	} finally {
615	–	lock.unlock();
1292		}
617	–	return k;
1293		}
1294
1295		/**
1296	<	* Nulls out record of worker in workers array
1296	>	* Unlocks and signals any thread waiting for plock. Called only
1297	>	* when CAS of seq value for unlock fails.
1298		*/
1299	<	private void forgetWorker(ForkJoinWorkerThread w) {
1300	<	int idx = w.poolIndex;
1301	<	// Locking helps method recordWorker avoid unecessary expansion
1302	<	final ReentrantLock lock = this.workerLock;
1303	<	lock.lock();
1304	<	try {
1305	<	ForkJoinWorkerThread[] ws = workers;
1306	<	if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify
1307	<	ws[idx] = null;
1308	<	} finally {
1309	<	lock.unlock();
1299	>	private void releasePlock(int ps) {
1300	>	plock = ps;
1301	>	synchronized (this) { notifyAll(); }
1302	>	}
1303	>
1304	>	/**
1305	>	* Tries to create and start one worker if fewer than target
1306	>	* parallelism level exist. Adjusts counts etc on failure.
1307	>	*/
1308	>	private void tryAddWorker() {
1309	>	long c; int u;
1310	>	while ((u = (int)((c = ctl) >>> 32)) < 0 &&
1311	>	(u & SHORT_SIGN) != 0 && (int)c == 0) {
1312	>	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) |
1313	>	((u + UAC_UNIT) & UAC_MASK)) << 32;
1314	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1315	>	ForkJoinWorkerThreadFactory fac;
1316	>	Throwable ex = null;
1317	>	ForkJoinWorkerThread wt = null;
1318	>	try {
1319	>	if ((fac = factory) != null &&
1320	>	(wt = fac.newThread(this)) != null) {
1321	>	wt.start();
1322	>	break;
1323	>	}
1324	>	} catch (Throwable e) {
1325	>	ex = e;
1326	>	}
1327	>	deregisterWorker(wt, ex);
1328	>	break;
1329	>	}
1330		}
1331		}
1332
1333	<	// adding and removing workers
1333	>	//  Registering and deregistering workers
1334
1335		/**
1336	<	* Tries to create and add new worker. Assumes that worker counts
1337	<	* are already updated to accommodate the worker, so adjusts on
1338	<	* failure.
1339	<	*
1340	<	* @return new worker or null if creation failed
1341	<	*/
1342	<	private ForkJoinWorkerThread addWorker() {
1343	<	ForkJoinWorkerThread w = null;
1336	>	* Callback from ForkJoinWorkerThread to establish and record its
1337	>	* WorkQueue. To avoid scanning bias due to packing entries in
1338	>	* front of the workQueues array, we treat the array as a simple
1339	>	* power-of-two hash table using per-thread seed as hash,
1340	>	* expanding as needed.
1341	>	*
1342	>	* @param wt the worker thread
1343	>	* @return the worker's queue
1344	>	*/
1345	>	final WorkQueue registerWorker(ForkJoinWorkerThread wt) {
1346	>	Thread.UncaughtExceptionHandler handler; WorkQueue[] ws; int s, ps;
1347	>	wt.setDaemon(true);
1348	>	if ((handler = ueh) != null)
1349	>	wt.setUncaughtExceptionHandler(handler);
1350	>	do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed,
1351	>	s += SEED_INCREMENT) ||
1352	>	s == 0); // skip 0
1353	>	WorkQueue w = new WorkQueue(this, wt, config >>> 16, s);
1354	>	if (((ps = plock) & PL_LOCK) != 0 ||
1355	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1356	>	ps = acquirePlock();
1357	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1358		try {
1359	<	w = factory.newThread(this);
1360	<	} finally { // Adjust on either null or exceptional factory return
1361	<	if (w == null) {
1362	<	onWorkerCreationFailure();
1363	<	return null;
1359	>	if ((ws = workQueues) != null) {    // skip if shutting down
1360	>	int n = ws.length, m = n - 1;
1361	>	int r = (s << 1) | 1;           // use odd-numbered indices
1362	>	if (ws[r &= m] != null) {       // collision
1363	>	int probes = 0;             // step by approx half size
1364	>	int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2;
1365	>	while (ws[r = (r + step) & m] != null) {
1366	>	if (++probes >= n) {
1367	>	workQueues = ws = Arrays.copyOf(ws, n <<= 1);
1368	>	m = n - 1;
1369	>	probes = 0;
1370	>	}
1371	>	}
1372	>	}
1373	>	w.eventCount = w.poolIndex = r; // volatile write orders
1374	>	ws[r] = w;
1375		}
1376	+	} finally {
1377	+	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1378	+	releasePlock(nps);
1379		}
1380	<	w.start(recordWorker(w), locallyFifo, ueh);
1380	>	wt.setName(workerNamePrefix.concat(Integer.toString(w.poolIndex)));
1381		return w;
1382		}
1383
1384		/**
1385	<	* Adjusts counts upon failure to create worker
1386	<	*/
1387	<	private void onWorkerCreationFailure() {
1388	<	int c;
1389	<	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1390	<	c = workerCounts,
1391	<	c - (ONE_RUNNING|ONE_TOTAL)));
1392	<	tryTerminate(false); // in case of failure during shutdown
1393	<	}
1385	>	* Final callback from terminating worker, as well as upon failure
1386	>	* to construct or start a worker.  Removes record of worker from
1387	>	* array, and adjusts counts. If pool is shutting down, tries to
1388	>	* complete termination.
1389	>	*
1390	>	* @param wt the worker thread or null if construction failed
1391	>	* @param ex the exception causing failure, or null if none
1392	>	*/
1393	>	final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1394	>	WorkQueue w = null;
1395	>	if (wt != null && (w = wt.workQueue) != null) {
1396	>	int ps;
1397	>	w.qlock = -1;                // ensure set
1398	>	long ns = w.nsteals, sc;     // collect steal count
1399	>	do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
1400	>	sc = stealCount, sc + ns));
1401	>	if (((ps = plock) & PL_LOCK) != 0 ||
1402	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1403	>	ps = acquirePlock();
1404	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1405	>	try {
1406	>	int idx = w.poolIndex;
1407	>	WorkQueue[] ws = workQueues;
1408	>	if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1409	>	ws[idx] = null;
1410	>	} finally {
1411	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1412	>	releasePlock(nps);
1413	>	}
1414	>	}
1415
1416	<	/**
1417	<	* Create enough total workers to establish target parallelism,
1418	<	* giving up if terminating or addWorker fails
1419	<	*/
1420	<	private void ensureEnoughTotalWorkers() {
1421	<	int wc;
1422	<	while (runState < TERMINATING &&
1423	<	((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < parallelism) {
1424	<	if ((UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1425	<	wc, wc + (ONE_RUNNING|ONE_TOTAL)) &&
1426	<	addWorker() == null))
1427	<	break;
1416	>	long c;                          // adjust ctl counts
1417	>	do {} while (!U.compareAndSwapLong
1418	>	(this, CTL, c = ctl, (((c - AC_UNIT) & AC_MASK) |
1419	>	((c - TC_UNIT) & TC_MASK) |
1420	>	(c & ~(AC_MASK|TC_MASK)))));
1421	>
1422	>	if (!tryTerminate(false, false) && w != null && w.array != null) {
1423	>	w.cancelAll();               // cancel remaining tasks
1424	>	WorkQueue[] ws; WorkQueue v; Thread p; int u, i, e;
1425	>	while ((u = (int)((c = ctl) >>> 32)) < 0 && (e = (int)c) >= 0) {
1426	>	if (e > 0) {             // activate or create replacement
1427	>	if ((ws = workQueues) == null ||
1428	>	(i = e & SMASK) >= ws.length ||
1429	>	(v = ws[i]) == null)
1430	>	break;
1431	>	long nc = (((long)(v.nextWait & E_MASK)) |
1432	>	((long)(u + UAC_UNIT) << 32));
1433	>	if (v.eventCount != (e | INT_SIGN))
1434	>	break;
1435	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1436	>	v.eventCount = (e + E_SEQ) & E_MASK;
1437	>	if ((p = v.parker) != null)
1438	>	U.unpark(p);
1439	>	break;
1440	>	}
1441	>	}
1442	>	else {
1443	>	if ((short)u < 0)
1444	>	tryAddWorker();
1445	>	break;
1446	>	}
1447	>	}
1448	>	}
1449	>	if (ex == null)                     // help clean refs on way out
1450	>	ForkJoinTask.helpExpungeStaleExceptions();
1451	>	else                                // rethrow
1452	>	ForkJoinTask.rethrow(ex);
1453	>	}
1454	>
1455	>	// Submissions
1456	>
1457	>	/**
1458	>	* Unless shutting down, adds the given task to a submission queue
1459	>	* at submitter's current queue index (modulo submission
1460	>	* range). Only the most common path is directly handled in this
1461	>	* method. All others are relayed to fullExternalPush.
1462	>	*
1463	>	* @param task the task. Caller must ensure non-null.
1464	>	*/
1465	>	final void externalPush(ForkJoinTask<?> task) {
1466	>	WorkQueue[] ws; WorkQueue q; Submitter z; int m; ForkJoinTask<?>[] a;
1467	>	if ((z = submitters.get()) != null && plock > 0 &&
1468	>	(ws = workQueues) != null && (m = (ws.length - 1)) >= 0 &&
1469	>	(q = ws[m & z.seed & SQMASK]) != null &&
1470	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock
1471	>	int b = q.base, s = q.top, n, an;
1472	>	if ((a = q.array) != null && (an = a.length) > (n = s + 1 - b)) {
1473	>	int j = (((an - 1) & s) << ASHIFT) + ABASE;
1474	>	U.putOrderedObject(a, j, task);
1475	>	q.top = s + 1;                     // push on to deque
1476	>	q.qlock = 0;
1477	>	if (n <= 2)
1478	>	signalWork(q);
1479	>	return;
1480	>	}
1481	>	q.qlock = 0;
1482		}
1483	+	fullExternalPush(task);
1484		}
1485
1486		/**
1487	<	* Final callback from terminating worker.  Removes record of
1488	<	* worker from array, and adjusts counts. If pool is shutting
1489	<	* down, tries to complete terminatation, else possibly replaces
1490	<	* the worker.
1491	<	*
1492	<	* @param w the worker
1493	<	*/
1494	<	final void workerTerminated(ForkJoinWorkerThread w) {
1495	<	if (w.active) { // force inactive
1496	<	w.active = false;
1497	<	do {} while (!tryDecrementActiveCount());
1487	>	* Full version of externalPush. This method is called, among
1488	>	* other times, upon the first submission of the first task to the
1489	>	* pool, so must perform secondary initialization.  It also
1490	>	* detects first submission by an external thread by looking up
1491	>	* its ThreadLocal, and creates a new shared queue if the one at
1492	>	* index if empty or contended. The plock lock body must be
1493	>	* exception-free (so no try/finally) so we optimistically
1494	>	* allocate new queues outside the lock and throw them away if
1495	>	* (very rarely) not needed.
1496	>	*
1497	>	* Secondary initialization occurs when plock is zero, to create
1498	>	* workQueue array and set plock to a valid value.  This lock body
1499	>	* must also be exception-free. Because the plock seq value can
1500	>	* eventually wrap around zero, this method harmlessly fails to
1501	>	* reinitialize if workQueues exists, while still advancing plock.
1502	>	*/
1503	>	private void fullExternalPush(ForkJoinTask<?> task) {
1504	>	int r = 0; // random index seed
1505	>	for (Submitter z = submitters.get();;) {
1506	>	WorkQueue[] ws; WorkQueue q; int ps, m, k;
1507	>	if (z == null) {
1508	>	if (U.compareAndSwapInt(this, INDEXSEED, r = indexSeed,
1509	>	r += SEED_INCREMENT) && r != 0)
1510	>	submitters.set(z = new Submitter(r));
1511	>	}
1512	>	else if (r == 0) {                  // move to a different index
1513	>	r = z.seed;
1514	>	r ^= r << 13;                   // same xorshift as WorkQueues
1515	>	r ^= r >>> 17;
1516	>	z.seed = r ^ (r << 5);
1517	>	}
1518	>	else if ((ps = plock) < 0)
1519	>	throw new RejectedExecutionException();
1520	>	else if (ps == 0 || (ws = workQueues) == null ||
1521	>	(m = ws.length - 1) < 0) { // initialize workQueues
1522	>	int p = config & SMASK;         // find power of two table size
1523	>	int n = (p > 1) ? p - 1 : 1;    // ensure at least 2 slots
1524	>	n |= n >>> 1; n |= n >>> 2;  n |= n >>> 4;
1525	>	n |= n >>> 8; n |= n >>> 16; n = (n + 1) << 1;
1526	>	WorkQueue[] nws = ((ws = workQueues) == null || ws.length == 0 ?
1527	>	new WorkQueue[n] : null);
1528	>	if (((ps = plock) & PL_LOCK) != 0 ||
1529	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1530	>	ps = acquirePlock();
1531	>	if (((ws = workQueues) == null || ws.length == 0) && nws != null)
1532	>	workQueues = nws;
1533	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1534	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1535	>	releasePlock(nps);
1536	>	}
1537	>	else if ((q = ws[k = r & m & SQMASK]) != null) {
1538	>	if (q.qlock == 0 && U.compareAndSwapInt(q, QLOCK, 0, 1)) {
1539	>	ForkJoinTask<?>[] a = q.array;
1540	>	int s = q.top;
1541	>	boolean submitted = false;
1542	>	try {                      // locked version of push
1543	>	if ((a != null && a.length > s + 1 - q.base) ||
1544	>	(a = q.growArray()) != null) {   // must presize
1545	>	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
1546	>	U.putOrderedObject(a, j, task);
1547	>	q.top = s + 1;
1548	>	submitted = true;
1549	>	}
1550	>	} finally {
1551	>	q.qlock = 0;  // unlock
1552	>	}
1553	>	if (submitted) {
1554	>	signalWork(q);
1555	>	return;
1556	>	}
1557	>	}
1558	>	r = 0; // move on failure
1559	>	}
1560	>	else if (((ps = plock) & PL_LOCK) == 0) { // create new queue
1561	>	q = new WorkQueue(this, null, SHARED_QUEUE, r);
1562	>	if (((ps = plock) & PL_LOCK) != 0 ||
1563	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1564	>	ps = acquirePlock();
1565	>	if ((ws = workQueues) != null && k < ws.length && ws[k] == null)
1566	>	ws[k] = q;
1567	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1568	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1569	>	releasePlock(nps);
1570	>	}
1571	>	else
1572	>	r = 0; // try elsewhere while lock held
1573		}
699	–	forgetWorker(w);
700	–
701	–	// decrement total count, and if was running, running count
702	–	int unit = w.isTrimmed()? ONE_TOTAL : (ONE_RUNNING|ONE_TOTAL);
703	–	int wc;
704	–	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
705	–	wc = workerCounts, wc - unit));
706	–
707	–	accumulateStealCount(w); // collect final count
708	–	if (!tryTerminate(false))
709	–	ensureEnoughTotalWorkers();
1574		}
1575
1576	<	// Waiting for and signalling events
1576	>	// Maintaining ctl counts
1577
1578		/**
1579	<	* Ensures eventCount on exit is different (mod 2^32) than on
716	<	* entry.  CAS failures are OK -- any change in count suffices.
1579	>	* Increments active count; mainly called upon return from blocking.
1580		*/
1581	<	private void advanceEventCount() {
1582	<	int c;
1583	<	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
1581	>	final void incrementActiveCount() {
1582	>	long c;
1583	>	do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
1584		}
1585
1586		/**
1587	<	* Releases workers blocked on a count not equal to current count.
1587	>	* Tries to create or activate a worker if too few are active.
1588	>	*
1589	>	* @param q the (non-null) queue holding tasks to be signalled
1590		*/
1591	<	final void releaseWaiters() {
1592	<	long top;
1593	<	int id;
1594	<	while ((id = (int)((top = eventWaiters) & WAITER_INDEX_MASK)) > 0 &&
1595	<	(int)(top >>> EVENT_COUNT_SHIFT) != eventCount) {
1596	<	ForkJoinWorkerThread[] ws = workers;
1597	<	ForkJoinWorkerThread w;
1598	<	if (ws.length >= id && (w = ws[id - 1]) != null &&
1599	<	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
1600	<	top, w.nextWaiter))
1601	<	LockSupport.unpark(w);
1591	>	final void signalWork(WorkQueue q) {
1592	>	int hint = q.poolIndex;
1593	>	long c; int e, u, i, n; WorkQueue[] ws; WorkQueue w; Thread p;
1594	>	while ((u = (int)((c = ctl) >>> 32)) < 0) {
1595	>	if ((e = (int)c) > 0) {
1596	>	if ((ws = workQueues) != null && ws.length > (i = e & SMASK) &&
1597	>	(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
1598	>	long nc = (((long)(w.nextWait & E_MASK)) |
1599	>	((long)(u + UAC_UNIT) << 32));
1600	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1601	>	w.hint = hint;
1602	>	w.eventCount = (e + E_SEQ) & E_MASK;
1603	>	if ((p = w.parker) != null)
1604	>	U.unpark(p);
1605	>	break;
1606	>	}
1607	>	if (q.top - q.base <= 0)
1608	>	break;
1609	>	}
1610	>	else
1611	>	break;
1612	>	}
1613	>	else {
1614	>	if ((short)u < 0)
1615	>	tryAddWorker();
1616	>	break;
1617	>	}
1618		}
1619		}
1620
1621	+	// Scanning for tasks
1622	+
1623		/**
1624	<	* Advances eventCount and releases waiters until interference by
742	<	* other releasing threads is detected.
1624	>	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1625		*/
1626	<	final void signalWork() {
1627	<	int ec;
1628	<	UNSAFE.compareAndSwapInt(this, eventCountOffset, ec=eventCount, ec+1);
1629	<	outer:for (;;) {
1630	<	long top = eventWaiters;
1631	<	ec = eventCount;
1632	<	for (;;) {
1633	<	ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w;
1634	<	int id = (int)(top & WAITER_INDEX_MASK);
1635	<	if (id <= 0 || (int)(top >>> EVENT_COUNT_SHIFT) == ec)
1636	<	return;
1637	<	if ((ws = workers).length < id || (w = ws[id - 1]) == null ||
1638	<	!UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
1639	<	top, top = w.nextWaiter))
1640	<	continue outer;      // possibly stale; reread
1641	<	LockSupport.unpark(w);
1642	<	if (top != eventWaiters) // let someone else take over
1643	<	return;
1626	>	final void runWorker(WorkQueue w) {
1627	>	w.growArray(); // allocate queue
1628	>	do { w.runTask(scan(w)); } while (w.qlock >= 0);
1629	>	}
1630	>
1631	>	/**
1632	>	* Scans for and, if found, returns one task, else possibly
1633	>	* inactivates the worker. This method operates on single reads of
1634	>	* volatile state and is designed to be re-invoked continuously,
1635	>	* in part because it returns upon detecting inconsistencies,
1636	>	* contention, or state changes that indicate possible success on
1637	>	* re-invocation.
1638	>	*
1639	>	* The scan searches for tasks across queues (starting at a random
1640	>	* index, and relying on registerWorker to irregularly scatter
1641	>	* them within array to avoid bias), checking each at least twice.
1642	>	* The scan terminates upon either finding a non-empty queue, or
1643	>	* completing the sweep. If the worker is not inactivated, it
1644	>	* takes and returns a task from this queue. Otherwise, if not
1645	>	* activated, it signals workers (that may include itself) and
1646	>	* returns so caller can retry. Also returns for true if the
1647	>	* worker array may have changed during an empty scan.  On failure
1648	>	* to find a task, we take one of the following actions, after
1649	>	* which the caller will retry calling this method unless
1650	>	* terminated.
1651	>	*
1652	>	* * If pool is terminating, terminate the worker.
1653	>	*
1654	>	* * If not already enqueued, try to inactivate and enqueue the
1655	>	* worker on wait queue. Or, if inactivating has caused the pool
1656	>	* to be quiescent, relay to idleAwaitWork to possibly shrink
1657	>	* pool.
1658	>	*
1659	>	* * If already enqueued and none of the above apply, possibly
1660	>	* park awaiting signal, else lingering to help scan and signal.
1661	>	*
1662	>	* * If a non-empty queue discovered or left as a hint,
1663	>	* help wake up other workers before return.
1664	>	*
1665	>	* @param w the worker (via its WorkQueue)
1666	>	* @return a task or null if none found
1667	>	*/
1668	>	private final ForkJoinTask<?> scan(WorkQueue w) {
1669	>	WorkQueue[] ws; int m;
1670	>	int ps = plock;                          // read plock before ws
1671	>	if (w != null && (ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1672	>	int ec = w.eventCount;               // ec is negative if inactive
1673	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1674	>	w.hint = -1;                         // update seed and clear hint
1675	>	int j = ((m + m + 1) | MIN_SCAN) & MAX_SCAN;
1676	>	do {
1677	>	WorkQueue q; ForkJoinTask<?>[] a; int b;
1678	>	if ((q = ws[(r + j) & m]) != null && (b = q.base) - q.top < 0 &&
1679	>	(a = q.array) != null) {     // probably nonempty
1680	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1681	>	ForkJoinTask<?> t = (ForkJoinTask<?>)
1682	>	U.getObjectVolatile(a, i);
1683	>	if (q.base == b && ec >= 0 && t != null &&
1684	>	U.compareAndSwapObject(a, i, t, null)) {
1685	>	if ((q.base = b + 1) - q.top < 0)
1686	>	signalWork(q);
1687	>	return t;                // taken
1688	>	}
1689	>	else if ((ec < 0 || j < m) && (int)(ctl >> AC_SHIFT) <= 0) {
1690	>	w.hint = (r + j) & m;    // help signal below
1691	>	break;                   // cannot take
1692	>	}
1693	>	}
1694	>	} while (--j >= 0);
1695	>
1696	>	int h, e, ns; long c, sc; WorkQueue q;
1697	>	if ((ns = w.nsteals) != 0) {
1698	>	if (U.compareAndSwapLong(this, STEALCOUNT,
1699	>	sc = stealCount, sc + ns))
1700	>	w.nsteals = 0;               // collect steals and rescan
1701	>	}
1702	>	else if (plock != ps)                // consistency check
1703	>	;                                // skip
1704	>	else if ((e = (int)(c = ctl)) < 0)
1705	>	w.qlock = -1;                    // pool is terminating
1706	>	else {
1707	>	if ((h = w.hint) < 0) {
1708	>	if (ec >= 0) {               // try to enqueue/inactivate
1709	>	long nc = (((long)ec |
1710	>	((c - AC_UNIT) & (AC_MASK|TC_MASK))));
1711	>	w.nextWait = e;          // link and mark inactive
1712	>	w.eventCount = ec | INT_SIGN;
1713	>	if (ctl != c || !U.compareAndSwapLong(this, CTL, c, nc))
1714	>	w.eventCount = ec;   // unmark on CAS failure
1715	>	else if ((int)(c >> AC_SHIFT) == 1 - (config & SMASK))
1716	>	idleAwaitWork(w, nc, c);
1717	>	}
1718	>	else if (w.eventCount < 0 && ctl == c) {
1719	>	Thread wt = Thread.currentThread();
1720	>	Thread.interrupted();    // clear status
1721	>	U.putObject(wt, PARKBLOCKER, this);
1722	>	w.parker = wt;           // emulate LockSupport.park
1723	>	if (w.eventCount < 0)    // recheck
1724	>	U.park(false, 0L);   // block
1725	>	w.parker = null;
1726	>	U.putObject(wt, PARKBLOCKER, null);
1727	>	}
1728	>	}
1729	>	if ((h >= 0 || (h = w.hint) >= 0) &&
1730	>	(ws = workQueues) != null && h < ws.length &&
1731	>	(q = ws[h]) != null) {      // signal others before retry
1732	>	WorkQueue v; Thread p; int u, i, s;
1733	>	for (int n = (config & SMASK) - 1;;) {
1734	>	int idleCount = (w.eventCount < 0) ? 0 : -1;
1735	>	if (((s = idleCount - q.base + q.top) <= n &&
1736	>	(n = s) <= 0) ||
1737	>	(u = (int)((c = ctl) >>> 32)) >= 0 ||
1738	>	(e = (int)c) <= 0 || m < (i = e & SMASK) ||
1739	>	(v = ws[i]) == null)
1740	>	break;
1741	>	long nc = (((long)(v.nextWait & E_MASK)) |
1742	>	((long)(u + UAC_UNIT) << 32));
1743	>	if (v.eventCount != (e | INT_SIGN) ||
1744	>	!U.compareAndSwapLong(this, CTL, c, nc))
1745	>	break;
1746	>	v.hint = h;
1747	>	v.eventCount = (e + E_SEQ) & E_MASK;
1748	>	if ((p = v.parker) != null)
1749	>	U.unpark(p);
1750	>	if (--n <= 0)
1751	>	break;
1752	>	}
1753	>	}
1754		}
1755		}
1756	+	return null;
1757		}
1758
1759		/**
1760	<	* If worker is inactive, blocks until terminating or event count
1761	<	* advances from last value held by worker; in any case helps
1762	<	* release others.
1763	<	*
1764	<	* @param w the calling worker thread
1765	<	*/
1766	<	private void eventSync(ForkJoinWorkerThread w) {
1767	<	if (!w.active) {
1768	<	int prev = w.lastEventCount;
1769	<	long nextTop = (((long)prev << EVENT_COUNT_SHIFT) |
1770	<	((long)(w.poolIndex + 1)));
1771	<	long top;
1772	<	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
1773	<	(((int)(top = eventWaiters) & WAITER_INDEX_MASK) == 0 ||
1774	<	(int)(top >>> EVENT_COUNT_SHIFT) == prev) &&
1775	<	eventCount == prev) {
1776	<	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
1777	<	w.nextWaiter = top, nextTop)) {
1778	<	accumulateStealCount(w); // transfer steals while idle
1779	<	Thread.interrupted();    // clear/ignore interrupt
1780	<	while (eventCount == prev)
1781	<	w.doPark();
1760	>	* If inactivating worker w has caused the pool to become
1761	>	* quiescent, checks for pool termination, and, so long as this is
1762	>	* not the only worker, waits for event for up to a given
1763	>	* duration.  On timeout, if ctl has not changed, terminates the
1764	>	* worker, which will in turn wake up another worker to possibly
1765	>	* repeat this process.
1766	>	*
1767	>	* @param w the calling worker
1768	>	* @param currentCtl the ctl value triggering possible quiescence
1769	>	* @param prevCtl the ctl value to restore if thread is terminated
1770	>	*/
1771	>	private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1772	>	if (w != null && w.eventCount < 0 &&
1773	>	!tryTerminate(false, false) && (int)prevCtl != 0 &&
1774	>	ctl == currentCtl) {
1775	>	int dc = -(short)(currentCtl >>> TC_SHIFT);
1776	>	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1777	>	long deadline = System.nanoTime() + parkTime - TIMEOUT_SLOP;
1778	>	Thread wt = Thread.currentThread();
1779	>	while (ctl == currentCtl) {
1780	>	Thread.interrupted();  // timed variant of version in scan()
1781	>	U.putObject(wt, PARKBLOCKER, this);
1782	>	w.parker = wt;
1783	>	if (ctl == currentCtl)
1784	>	U.park(false, parkTime);
1785	>	w.parker = null;
1786	>	U.putObject(wt, PARKBLOCKER, null);
1787	>	if (ctl != currentCtl)
1788	>	break;
1789	>	if (deadline - System.nanoTime() <= 0L &&
1790	>	U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1791	>	w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
1792	>	w.hint = -1;
1793	>	w.qlock = -1;   // shrink
1794		break;
1795		}
1796		}
792	–	w.lastEventCount = eventCount;
1797		}
794	–	releaseWaiters();
1798		}
1799
1800		/**
1801	<	* Callback from workers invoked upon each top-level action (i.e.,
1802	<	* stealing a task or taking a submission and running
1803	<	* it). Performs one or both of the following:
1804	<	*
1805	<	* * If the worker cannot find work, updates its active status to
1806	<	* inactive and updates activeCount unless there is contention, in
1807	<	* which case it may try again (either in this or a subsequent
1808	<	* call).  Additionally, awaits the next task event and/or helps
1809	<	* wake up other releasable waiters.
1810	<	*
1811	<	* * If there are too many running threads, suspends this worker
1812	<	* (first forcing inactivation if necessary).  If it is not
1813	<	* resumed before a keepAlive elapses, the worker may be "trimmed"
1814	<	* -- killed while suspended within suspendAsSpare. Otherwise,
1815	<	* upon resume it rechecks to make sure that it is still needed.
1816	<	*
1817	<	* @param w the worker
1818	<	* @param worked false if the worker scanned for work but didn't
1819	<	* find any (in which case it may block waiting for work).
1820	<	*/
1821	<	final void preStep(ForkJoinWorkerThread w, boolean worked) {
1822	<	boolean active = w.active;
1823	<	boolean inactivate = !worked & active;
1824	<	for (;;) {
1825	<	if (inactivate) {
1826	<	int c = runState;
1827	<	if (UNSAFE.compareAndSwapInt(this, runStateOffset,
1828	<	c, c - ONE_ACTIVE))
1829	<	inactivate = active = w.active = false;
1830	<	}
1831	<	int wc = workerCounts;
1832	<	if ((wc & RUNNING_COUNT_MASK) <= parallelism) {
1833	<	if (!worked)
1834	<	eventSync(w);
1835	<	return;
1801	>	* Scans through queues looking for work while joining a task; if
1802	>	* any present, signals. May return early if more signalling is
1803	>	* detectably unneeded.
1804	>	*
1805	>	* @param task return early if done
1806	>	* @param origin an index to start scan
1807	>	*/
1808	>	private void helpSignal(ForkJoinTask<?> task, int origin) {
1809	>	WorkQueue[] ws; WorkQueue w; Thread p; long c; int m, u, e, i, s;
1810	>	if (task != null && task.status >= 0 &&
1811	>	(u = (int)(ctl >>> 32)) < 0 && (u >> UAC_SHIFT) < 0 &&
1812	>	(ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1813	>	outer: for (int k = origin, j = m; j >= 0; --j) {
1814	>	WorkQueue q = ws[k++ & m];
1815	>	for (int n = m;;) { // limit to at most m signals
1816	>	if (task.status < 0)
1817	>	break outer;
1818	>	if (q == null ||
1819	>	((s = -q.base + q.top) <= n && (n = s) <= 0))
1820	>	break;
1821	>	if ((u = (int)((c = ctl) >>> 32)) >= 0 ||
1822	>	(e = (int)c) <= 0 || m < (i = e & SMASK) ||
1823	>	(w = ws[i]) == null)
1824	>	break outer;
1825	>	long nc = (((long)(w.nextWait & E_MASK)) |
1826	>	((long)(u + UAC_UNIT) << 32));
1827	>	if (w.eventCount != (e | INT_SIGN))
1828	>	break outer;
1829	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1830	>	w.eventCount = (e + E_SEQ) & E_MASK;
1831	>	if ((p = w.parker) != null)
1832	>	U.unpark(p);
1833	>	if (--n <= 0)
1834	>	break;
1835	>	}
1836	>	}
1837		}
834	–	if (!(inactivate |= active) &&  // must inactivate to suspend
835	–	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
836	–	wc, wc - ONE_RUNNING) &&
837	–	!w.suspendAsSpare())        // false if trimmed
838	–	return;
1838		}
1839		}
1840
1841		/**
1842	<	* Adjusts counts and creates or resumes compensating threads for
1843	<	* a worker about to block on task joinMe, returning early if
1844	<	* joinMe becomes ready. First tries resuming an existing spare
1845	<	* (which usually also avoids any count adjustment), but must then
1846	<	* decrement running count to determine whether a new thread is
1847	<	* needed. See above for fuller explanation.
1848	<	*/
1849	<	final void preJoin(ForkJoinTask<?> joinMe) {
1850	<	boolean dec = false;       // true when running count decremented
1851	<	for (;;) {
1852	<	releaseWaiters();      // help other threads progress
1853	<
1854	<	if (joinMe.status < 0) // surround spare search with done checks
1855	<	return;
1856	<	ForkJoinWorkerThread spare = null;
1857	<	for (ForkJoinWorkerThread w : workers) {
1858	<	if (w != null && w.isSuspended()) {
1859	<	spare = w;
1860	<	break;
1842	>	* Tries to locate and execute tasks for a stealer of the given
1843	>	* task, or in turn one of its stealers, Traces currentSteal ->
1844	>	* currentJoin links looking for a thread working on a descendant
1845	>	* of the given task and with a non-empty queue to steal back and
1846	>	* execute tasks from. The first call to this method upon a
1847	>	* waiting join will often entail scanning/search, (which is OK
1848	>	* because the joiner has nothing better to do), but this method
1849	>	* leaves hints in workers to speed up subsequent calls. The
1850	>	* implementation is very branchy to cope with potential
1851	>	* inconsistencies or loops encountering chains that are stale,
1852	>	* unknown, or so long that they are likely cyclic.
1853	>	*
1854	>	* @param joiner the joining worker
1855	>	* @param task the task to join
1856	>	* @return 0 if no progress can be made, negative if task
1857	>	* known complete, else positive
1858	>	*/
1859	>	private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1860	>	int stat = 0, steps = 0;                    // bound to avoid cycles
1861	>	if (joiner != null && task != null) {       // hoist null checks
1862	>	restart: for (;;) {
1863	>	ForkJoinTask<?> subtask = task;     // current target
1864	>	for (WorkQueue j = joiner, v;;) {   // v is stealer of subtask
1865	>	WorkQueue[] ws; int m, s, h;
1866	>	if ((s = task.status) < 0) {
1867	>	stat = s;
1868	>	break restart;
1869	>	}
1870	>	if ((ws = workQueues) == null || (m = ws.length - 1) <= 0)
1871	>	break restart;              // shutting down
1872	>	if ((v = ws[h = (j.hint | 1) & m]) == null ||
1873	>	v.currentSteal != subtask) {
1874	>	for (int origin = h;;) {    // find stealer
1875	>	if (((h = (h + 2) & m) & 15) == 1 &&
1876	>	(subtask.status < 0 || j.currentJoin != subtask))
1877	>	continue restart;   // occasional staleness check
1878	>	if ((v = ws[h]) != null &&
1879	>	v.currentSteal == subtask) {
1880	>	j.hint = h;        // save hint
1881	>	break;
1882	>	}
1883	>	if (h == origin)
1884	>	break restart;      // cannot find stealer
1885	>	}
1886	>	}
1887	>	for (;;) { // help stealer or descend to its stealer
1888	>	ForkJoinTask[] a;  int b;
1889	>	if (subtask.status < 0)     // surround probes with
1890	>	continue restart;       //   consistency checks
1891	>	if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
1892	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1893	>	ForkJoinTask<?> t =
1894	>	(ForkJoinTask<?>)U.getObjectVolatile(a, i);
1895	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1896	>	v.currentSteal != subtask)
1897	>	continue restart;   // stale
1898	>	stat = 1;               // apparent progress
1899	>	if (t != null && v.base == b &&
1900	>	U.compareAndSwapObject(a, i, t, null)) {
1901	>	v.base = b + 1;     // help stealer
1902	>	joiner.runSubtask(t);
1903	>	}
1904	>	else if (v.base == b && ++steps == MAX_HELP)
1905	>	break restart;      // v apparently stalled
1906	>	}
1907	>	else {                      // empty -- try to descend
1908	>	ForkJoinTask<?> next = v.currentJoin;
1909	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1910	>	v.currentSteal != subtask)
1911	>	continue restart;   // stale
1912	>	else if (next == null || ++steps == MAX_HELP)
1913	>	break restart;      // dead-end or maybe cyclic
1914	>	else {
1915	>	subtask = next;
1916	>	j = v;
1917	>	break;
1918	>	}
1919	>	}
1920	>	}
1921		}
1922		}
1923	<	if (joinMe.status < 0)
1924	<	return;
1925	<
867	<	if (spare != null && spare.tryUnsuspend()) {
868	<	if (dec || joinMe.requestSignal() < 0) {
869	<	int c;
870	<	do {} while (!UNSAFE.compareAndSwapInt(this,
871	<	workerCountsOffset,
872	<	c = workerCounts,
873	<	c + ONE_RUNNING));
874	<	} // else no net count change
875	<	LockSupport.unpark(spare);
876	<	return;
877	<	}
878	<
879	<	int wc = workerCounts; // decrement running count
880	<	if (!dec && (wc & RUNNING_COUNT_MASK) != 0 &&
881	<	(dec = UNSAFE.compareAndSwapInt(this, workerCountsOffset,
882	<	wc, wc -= ONE_RUNNING)) &&
883	<	joinMe.requestSignal() < 0) { // cannot block
884	<	int c;                        // back out
885	<	do {} while (!UNSAFE.compareAndSwapInt(this,
886	<	workerCountsOffset,
887	<	c = workerCounts,
888	<	c + ONE_RUNNING));
889	<	return;
890	<	}
1923	>	}
1924	>	return stat;
1925	>	}
1926
1927	<	if (dec) {
1928	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
1929	<	int pc = parallelism;
1930	<	int dc = pc - (wc & RUNNING_COUNT_MASK); // deficit count
1931	<	if ((dc < pc && (dc <= 0 || (dc * dc < (tc - pc) * pc) ||
1932	<	!maintainsParallelism)) ||
1933	<	tc >= maxPoolSize) // cannot add
1934	<	return;
1935	<	if (spare == null &&
1936	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
1937	<	wc + (ONE_RUNNING|ONE_TOTAL))) {
1938	<	addWorker();
1939	<	return;
1927	>	/**
1928	>	* Analog of tryHelpStealer for CountedCompleters. Tries to steal
1929	>	* and run tasks within the target's computation.
1930	>	*
1931	>	* @param task the task to join
1932	>	* @param mode if shared, exit upon completing any task
1933	>	* if all workers are active
1934	>	*/
1935	>	private int helpComplete(ForkJoinTask<?> task, int mode) {
1936	>	WorkQueue[] ws; WorkQueue q; int m, n, s, u;
1937	>	if (task != null && (ws = workQueues) != null &&
1938	>	(m = ws.length - 1) >= 0) {
1939	>	for (int j = 1, origin = j;;) {
1940	>	if ((s = task.status) < 0)
1941	>	return s;
1942	>	if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) {
1943	>	origin = j;
1944	>	if (mode == SHARED_QUEUE &&
1945	>	((u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0))
1946	>	break;
1947		}
1948	+	else if ((j = (j + 2) & m) == origin)
1949	+	break;
1950		}
1951		}
1952	+	return 0;
1953		}
1954
1955		/**
1956	<	* Same idea as preJoin but with too many differing details to
1957	<	* integrate: There are no task-based signal counts, and only one
1958	<	* way to do the actual blocking. So for simplicity it is directly
1959	<	* incorporated into this method.
1960	<	*/
1961	<	final void doBlock(ManagedBlocker blocker, boolean maintainPar)
1962	<	throws InterruptedException {
1963	<	maintainPar &= maintainsParallelism; // override
1964	<	boolean dec = false;
1965	<	boolean done = false;
1966	<	for (;;) {
1967	<	releaseWaiters();
1968	<	if (done = blocker.isReleasable())
1969	<	break;
1970	<	ForkJoinWorkerThread spare = null;
1971	<	for (ForkJoinWorkerThread w : workers) {
1972	<	if (w != null && w.isSuspended()) {
1973	<	spare = w;
1974	<	break;
1956	>	* Tries to decrement active count (sometimes implicitly) and
1957	>	* possibly release or create a compensating worker in preparation
1958	>	* for blocking. Fails on contention or termination. Otherwise,
1959	>	* adds a new thread if no idle workers are available and pool
1960	>	* may become starved.
1961	>	*/
1962	>	final boolean tryCompensate() {
1963	>	int pc = config & SMASK, e, i, tc; long c;
1964	>	WorkQueue[] ws; WorkQueue w; Thread p;
1965	>	if ((ws = workQueues) != null && (e = (int)(c = ctl)) >= 0) {
1966	>	if (e != 0 && (i = e & SMASK) < ws.length &&
1967	>	(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
1968	>	long nc = ((long)(w.nextWait & E_MASK) |
1969	>	(c & (AC_MASK|TC_MASK)));
1970	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1971	>	w.eventCount = (e + E_SEQ) & E_MASK;
1972	>	if ((p = w.parker) != null)
1973	>	U.unpark(p);
1974	>	return true;   // replace with idle worker
1975		}
1976		}
1977	<	if (done = blocker.isReleasable())
1978	<	break;
1979	<	if (spare != null && spare.tryUnsuspend()) {
1980	<	if (dec) {
1981	<	int c;
1982	<	do {} while (!UNSAFE.compareAndSwapInt(this,
1983	<	workerCountsOffset,
1984	<	c = workerCounts,
1985	<	c + ONE_RUNNING));
1986	<	}
1987	<	LockSupport.unpark(spare);
1988	<	break;
1989	<	}
1990	<	int wc = workerCounts;
1991	<	if (!dec && (wc & RUNNING_COUNT_MASK) != 0)
1992	<	dec = UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1993	<	wc, wc -= ONE_RUNNING);
1994	<	if (dec) {
1995	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
1996	<	int pc = parallelism;
1997	<	int dc = pc - (wc & RUNNING_COUNT_MASK);
1998	<	if ((dc < pc && (dc <= 0 || (dc * dc < (tc - pc) * pc) ||
954	<	!maintainPar)) ||
955	<	tc >= maxPoolSize)
956	<	break;
957	<	if (spare == null &&
958	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
959	<	wc + (ONE_RUNNING|ONE_TOTAL))){
960	<	addWorker();
961	<	break;
1977	>	else if ((tc = (short)(c >>> TC_SHIFT)) >= 0 &&
1978	>	(int)(c >> AC_SHIFT) + pc > 1) {
1979	>	long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
1980	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1981	>	return true;   // no compensation
1982	>	}
1983	>	else if (tc + pc < MAX_CAP) {
1984	>	long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
1985	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1986	>	ForkJoinWorkerThreadFactory fac;
1987	>	Throwable ex = null;
1988	>	ForkJoinWorkerThread wt = null;
1989	>	try {
1990	>	if ((fac = factory) != null &&
1991	>	(wt = fac.newThread(this)) != null) {
1992	>	wt.start();
1993	>	return true;
1994	>	}
1995	>	} catch (Throwable rex) {
1996	>	ex = rex;
1997	>	}
1998	>	deregisterWorker(wt, ex); // clean up and return false
1999		}
2000		}
2001		}
2002	+	return false;
2003	+	}
2004
2005	<	try {
2006	<	if (!done)
2007	<	do {} while (!blocker.isReleasable() && !blocker.block());
2008	<	} finally {
2009	<	if (dec) {
2010	<	int c;
2011	<	do {} while (!UNSAFE.compareAndSwapInt(this,
2012	<	workerCountsOffset,
2013	<	c = workerCounts,
2014	<	c + ONE_RUNNING));
2005	>	/**
2006	>	* Helps and/or blocks until the given task is done.
2007	>	*
2008	>	* @param joiner the joining worker
2009	>	* @param task the task
2010	>	* @return task status on exit
2011	>	*/
2012	>	final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
2013	>	int s = 0;
2014	>	if (joiner != null && task != null && (s = task.status) >= 0) {
2015	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2016	>	joiner.currentJoin = task;
2017	>	do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
2018	>	joiner.tryRemoveAndExec(task)); // process local tasks
2019	>	if (s >= 0 && (s = task.status) >= 0) {
2020	>	helpSignal(task, joiner.poolIndex);
2021	>	if ((s = task.status) >= 0 &&
2022	>	(task instanceof CountedCompleter))
2023	>	s = helpComplete(task, LIFO_QUEUE);
2024	>	}
2025	>	while (s >= 0 && (s = task.status) >= 0) {
2026	>	if ((!joiner.isEmpty() ||           // try helping
2027	>	(s = tryHelpStealer(joiner, task)) == 0) &&
2028	>	(s = task.status) >= 0) {
2029	>	helpSignal(task, joiner.poolIndex);
2030	>	if ((s = task.status) >= 0 && tryCompensate()) {
2031	>	if (task.trySetSignal() && (s = task.status) >= 0) {
2032	>	synchronized (task) {
2033	>	if (task.status >= 0) {
2034	>	try {                // see ForkJoinTask
2035	>	task.wait();     //  for explanation
2036	>	} catch (InterruptedException ie) {
2037	>	}
2038	>	}
2039	>	else
2040	>	task.notifyAll();
2041	>	}
2042	>	}
2043	>	long c;                          // re-activate
2044	>	do {} while (!U.compareAndSwapLong
2045	>	(this, CTL, c = ctl, c + AC_UNIT));
2046	>	}
2047	>	}
2048		}
2049	+	joiner.currentJoin = prevJoin;
2050		}
2051	+	return s;
2052		}
2053
2054		/**
2055	<	* Unless there are not enough other running threads, adjusts
2056	<	* counts for a a worker in performing helpJoin that cannot find
2057	<	* any work, so that this worker can now block.
2055	>	* Stripped-down variant of awaitJoin used by timed joins. Tries
2056	>	* to help join only while there is continuous progress. (Caller
2057	>	* will then enter a timed wait.)
2058		*
2059	<	* @return true if worker may block
2059	>	* @param joiner the joining worker
2060	>	* @param task the task
2061		*/
2062	<	final boolean preBlockHelpingJoin(ForkJoinTask<?> joinMe) {
2063	<	while (joinMe.status >= 0) {
2064	<	releaseWaiters(); // help other threads progress
2062	>	final void helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
2063	>	int s;
2064	>	if (joiner != null && task != null && (s = task.status) >= 0) {
2065	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2066	>	joiner.currentJoin = task;
2067	>	do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
2068	>	joiner.tryRemoveAndExec(task));
2069	>	if (s >= 0 && (s = task.status) >= 0) {
2070	>	helpSignal(task, joiner.poolIndex);
2071	>	if ((s = task.status) >= 0 &&
2072	>	(task instanceof CountedCompleter))
2073	>	s = helpComplete(task, LIFO_QUEUE);
2074	>	}
2075	>	if (s >= 0 && joiner.isEmpty()) {
2076	>	do {} while (task.status >= 0 &&
2077	>	tryHelpStealer(joiner, task) > 0);
2078	>	}
2079	>	joiner.currentJoin = prevJoin;
2080	>	}
2081	>	}
2082
2083	<	// if a spare exists, resume it to maintain parallelism level
2084	<	if ((workerCounts & RUNNING_COUNT_MASK) <= parallelism) {
2085	<	ForkJoinWorkerThread spare = null;
2086	<	for (ForkJoinWorkerThread w : workers) {
2087	<	if (w != null && w.isSuspended()) {
2088	<	spare = w;
2089	<	break;
2090	<	}
2091	<	}
2092	<	if (joinMe.status < 0)
2093	<	break;
2094	<	if (spare != null) {
2095	<	if (spare.tryUnsuspend()) {
2096	<	boolean canBlock = true;
1005	<	if (joinMe.requestSignal() < 0) {
1006	<	canBlock = false; // already done
1007	<	int c;
1008	<	do {} while (!UNSAFE.compareAndSwapInt
1009	<	(this, workerCountsOffset,
1010	<	c = workerCounts, c + ONE_RUNNING));
1011	<	}
1012	<	LockSupport.unpark(spare);
1013	<	return canBlock;
1014	<	}
1015	<	continue; // recheck -- another spare may exist
2083	>	/**
2084	>	* Returns a (probably) non-empty steal queue, if one is found
2085	>	* during a scan, else null.  This method must be retried by
2086	>	* caller if, by the time it tries to use the queue, it is empty.
2087	>	* @param r a (random) seed for scanning
2088	>	*/
2089	>	private WorkQueue findNonEmptyStealQueue(int r) {
2090	>	for (;;) {
2091	>	int ps = plock, m; WorkQueue[] ws; WorkQueue q;
2092	>	if ((ws = workQueues) != null && (m = ws.length - 1) >= 0) {
2093	>	for (int j = (m + 1) << 2; j >= 0; --j) {
2094	>	if ((q = ws[(((r + j) << 1) | 1) & m]) != null &&
2095	>	q.base - q.top < 0)
2096	>	return q;
2097		}
2098		}
2099	+	if (plock == ps)
2100	+	return null;
2101	+	}
2102	+	}
2103
2104	<	int wc = workerCounts; // reread to shorten CAS window
2105	<	int rc = wc & RUNNING_COUNT_MASK;
2106	<	if (rc <= 2) // keep this and at most one other thread alive
2107	<	break;
2108	<
2109	<	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
2110	<	wc, wc - ONE_RUNNING)) {
2111	<	if (joinMe.requestSignal() >= 0)
2112	<	return true;
2113	<	int c;                        // back out
2114	<	do {} while (!UNSAFE.compareAndSwapInt
2115	<	(this, workerCountsOffset,
2116	<	c = workerCounts, c + ONE_RUNNING));
2117	<	break;
2104	>	/**
2105	>	* Runs tasks until {@code isQuiescent()}. We piggyback on
2106	>	* active count ctl maintenance, but rather than blocking
2107	>	* when tasks cannot be found, we rescan until all others cannot
2108	>	* find tasks either.
2109	>	*/
2110	>	final void helpQuiescePool(WorkQueue w) {
2111	>	for (boolean active = true;;) {
2112	>	long c; WorkQueue q; ForkJoinTask<?> t; int b;
2113	>	while ((t = w.nextLocalTask()) != null) {
2114	>	if (w.base - w.top < 0)
2115	>	signalWork(w);
2116	>	t.doExec();
2117	>	}
2118	>	if ((q = findNonEmptyStealQueue(w.nextSeed())) != null) {
2119	>	if (!active) {      // re-establish active count
2120	>	active = true;
2121	>	do {} while (!U.compareAndSwapLong
2122	>	(this, CTL, c = ctl, c + AC_UNIT));
2123	>	}
2124	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) {
2125	>	if (q.base - q.top < 0)
2126	>	signalWork(q);
2127	>	w.runSubtask(t);
2128	>	}
2129	>	}
2130	>	else if (active) {       // decrement active count without queuing
2131	>	long nc = (c = ctl) - AC_UNIT;
2132	>	if ((int)(nc >> AC_SHIFT) + (config & SMASK) == 0)
2133	>	return;          // bypass decrement-then-increment
2134	>	if (U.compareAndSwapLong(this, CTL, c, nc))
2135	>	active = false;
2136		}
2137	+	else if ((int)((c = ctl) >> AC_SHIFT) + (config & SMASK) == 0 &&
2138	+	U.compareAndSwapLong(this, CTL, c, c + AC_UNIT))
2139	+	return;
2140		}
1035	–	return false;
2141		}
2142
2143		/**
2144	<	* Possibly initiates and/or completes termination.
2144	>	* Gets and removes a local or stolen task for the given worker.
2145		*
2146	<	* @param now if true, unconditionally terminate, else only
1042	<	* if shutdown and empty queue and no active workers
1043	<	* @return true if now terminating or terminated
2146	>	* @return a task, if available
2147		*/
2148	<	private boolean tryTerminate(boolean now) {
2149	<	if (now)
2150	<	advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN
2151	<	else if (runState < SHUTDOWN ||
2152	<	!submissionQueue.isEmpty() ||
2153	<	(runState & ACTIVE_COUNT_MASK) != 0)
2154	<	return false;
2155	<
2156	<	if (advanceRunLevel(TERMINATING))
2157	<	startTerminating();
2158	<
2159	<	// Finish now if all threads terminated; else in some subsequent call
1057	<	if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1058	<	advanceRunLevel(TERMINATED);
1059	<	terminationLatch.countDown();
2148	>	final ForkJoinTask<?> nextTaskFor(WorkQueue w) {
2149	>	for (ForkJoinTask<?> t;;) {
2150	>	WorkQueue q; int b;
2151	>	if ((t = w.nextLocalTask()) != null)
2152	>	return t;
2153	>	if ((q = findNonEmptyStealQueue(w.nextSeed())) == null)
2154	>	return null;
2155	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) {
2156	>	if (q.base - q.top < 0)
2157	>	signalWork(q);
2158	>	return t;
2159	>	}
2160		}
1061	–	return true;
2161		}
2162
2163		/**
2164	<	* Actions on transition to TERMINATING
2164	>	* Returns a cheap heuristic guide for task partitioning when
2165	>	* programmers, frameworks, tools, or languages have little or no
2166	>	* idea about task granularity.  In essence by offering this
2167	>	* method, we ask users only about tradeoffs in overhead vs
2168	>	* expected throughput and its variance, rather than how finely to
2169	>	* partition tasks.
2170	>	*
2171	>	* In a steady state strict (tree-structured) computation, each
2172	>	* thread makes available for stealing enough tasks for other
2173	>	* threads to remain active. Inductively, if all threads play by
2174	>	* the same rules, each thread should make available only a
2175	>	* constant number of tasks.
2176	>	*
2177	>	* The minimum useful constant is just 1. But using a value of 1
2178	>	* would require immediate replenishment upon each steal to
2179	>	* maintain enough tasks, which is infeasible.  Further,
2180	>	* partitionings/granularities of offered tasks should minimize
2181	>	* steal rates, which in general means that threads nearer the top
2182	>	* of computation tree should generate more than those nearer the
2183	>	* bottom. In perfect steady state, each thread is at
2184	>	* approximately the same level of computation tree. However,
2185	>	* producing extra tasks amortizes the uncertainty of progress and
2186	>	* diffusion assumptions.
2187	>	*
2188	>	* So, users will want to use values larger, but not much larger
2189	>	* than 1 to both smooth over transient shortages and hedge
2190	>	* against uneven progress; as traded off against the cost of
2191	>	* extra task overhead. We leave the user to pick a threshold
2192	>	* value to compare with the results of this call to guide
2193	>	* decisions, but recommend values such as 3.
2194	>	*
2195	>	* When all threads are active, it is on average OK to estimate
2196	>	* surplus strictly locally. In steady-state, if one thread is
2197	>	* maintaining say 2 surplus tasks, then so are others. So we can
2198	>	* just use estimated queue length.  However, this strategy alone
2199	>	* leads to serious mis-estimates in some non-steady-state
2200	>	* conditions (ramp-up, ramp-down, other stalls). We can detect
2201	>	* many of these by further considering the number of "idle"
2202	>	* threads, that are known to have zero queued tasks, so
2203	>	* compensate by a factor of (#idle/#active) threads.
2204	>	*
2205	>	* Note: The approximation of #busy workers as #active workers is
2206	>	* not very good under current signalling scheme, and should be
2207	>	* improved.
2208	>	*/
2209	>	static int getSurplusQueuedTaskCount() {
2210	>	Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q;
2211	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
2212	>	int p = (pool = (wt = (ForkJoinWorkerThread)t).pool).config & SMASK;
2213	>	int n = (q = wt.workQueue).top - q.base;
2214	>	int a = (int)(pool.ctl >> AC_SHIFT) + p;
2215	>	return n - (a > (p >>>= 1) ? 0 :
2216	>	a > (p >>>= 1) ? 1 :
2217	>	a > (p >>>= 1) ? 2 :
2218	>	a > (p >>>= 1) ? 4 :
2219	>	8);
2220	>	}
2221	>	return 0;
2222	>	}
2223	>
2224	>	//  Termination
2225	>
2226	>	/**
2227	>	* Possibly initiates and/or completes termination.  The caller
2228	>	* triggering termination runs three passes through workQueues:
2229	>	* (0) Setting termination status, followed by wakeups of queued
2230	>	* workers; (1) cancelling all tasks; (2) interrupting lagging
2231	>	* threads (likely in external tasks, but possibly also blocked in
2232	>	* joins).  Each pass repeats previous steps because of potential
2233	>	* lagging thread creation.
2234	>	*
2235	>	* @param now if true, unconditionally terminate, else only
2236	>	* if no work and no active workers
2237	>	* @param enable if true, enable shutdown when next possible
2238	>	* @return true if now terminating or terminated
2239		*/
2240	<	private void startTerminating() {
2241	<	// Clear out and cancel submissions, ignoring exceptions
2242	<	ForkJoinTask<?> task;
2243	<	while ((task = submissionQueue.poll()) != null) {
2244	<	try {
2245	<	task.cancel(false);
2246	<	} catch (Throwable ignore) {
2240	>	private boolean tryTerminate(boolean now, boolean enable) {
2241	>	int ps;
2242	>	if (this == common)                    // cannot shut down
2243	>	return false;
2244	>	if ((ps = plock) >= 0) {                   // enable by setting plock
2245	>	if (!enable)
2246	>	return false;
2247	>	if ((ps & PL_LOCK) != 0 ||
2248	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
2249	>	ps = acquirePlock();
2250	>	int nps = ((ps + PL_LOCK) & ~SHUTDOWN) | SHUTDOWN;
2251	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
2252	>	releasePlock(nps);
2253	>	}
2254	>	for (long c;;) {
2255	>	if (((c = ctl) & STOP_BIT) != 0) {     // already terminating
2256	>	if ((short)(c >>> TC_SHIFT) == -(config & SMASK)) {
2257	>	synchronized (this) {
2258	>	notifyAll();               // signal when 0 workers
2259	>	}
2260	>	}
2261	>	return true;
2262		}
2263	<	}
2264	<	// Propagate run level
2265	<	for (ForkJoinWorkerThread w : workers) {
2266	<	if (w != null)
2267	<	w.shutdown();    // also resumes suspended workers
2268	<	}
2269	<	// Ensure no straggling local tasks
2270	<	for (ForkJoinWorkerThread w : workers) {
2271	<	if (w != null)
2272	<	w.cancelTasks();
2273	<	}
2274	<	// Wake up idle workers
2275	<	advanceEventCount();
2276	<	releaseWaiters();
2277	<	// Unstick pending joins
2278	<	for (ForkJoinWorkerThread w : workers) {
2279	<	if (w != null && !w.isTerminated()) {
2280	<	try {
2281	<	w.interrupt();
2282	<	} catch (SecurityException ignore) {
2263	>	if (!now) {                            // check if idle & no tasks
2264	>	WorkQueue[] ws; WorkQueue w;
2265	>	if ((int)(c >> AC_SHIFT) != -(config & SMASK))
2266	>	return false;
2267	>	if ((ws = workQueues) != null) {
2268	>	for (int i = 0; i < ws.length; ++i) {
2269	>	if ((w = ws[i]) != null) {
2270	>	if (!w.isEmpty()) {    // signal unprocessed tasks
2271	>	signalWork(w);
2272	>	return false;
2273	>	}
2274	>	if ((i & 1) != 0 && w.eventCount >= 0)
2275	>	return false;      // unqueued inactive worker
2276	>	}
2277	>	}
2278	>	}
2279	>	}
2280	>	if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT)) {
2281	>	for (int pass = 0; pass < 3; ++pass) {
2282	>	WorkQueue[] ws; WorkQueue w; Thread wt;
2283	>	if ((ws = workQueues) != null) {
2284	>	int n = ws.length;
2285	>	for (int i = 0; i < n; ++i) {
2286	>	if ((w = ws[i]) != null) {
2287	>	w.qlock = -1;
2288	>	if (pass > 0) {
2289	>	w.cancelAll();
2290	>	if (pass > 1 && (wt = w.owner) != null) {
2291	>	if (!wt.isInterrupted()) {
2292	>	try {
2293	>	wt.interrupt();
2294	>	} catch (Throwable ignore) {
2295	>	}
2296	>	}
2297	>	U.unpark(wt);
2298	>	}
2299	>	}
2300	>	}
2301	>	}
2302	>	// Wake up workers parked on event queue
2303	>	int i, e; long cc; Thread p;
2304	>	while ((e = (int)(cc = ctl) & E_MASK) != 0 &&
2305	>	(i = e & SMASK) < n && i >= 0 &&
2306	>	(w = ws[i]) != null) {
2307	>	long nc = ((long)(w.nextWait & E_MASK) |
2308	>	((cc + AC_UNIT) & AC_MASK) |
2309	>	(cc & (TC_MASK|STOP_BIT)));
2310	>	if (w.eventCount == (e | INT_SIGN) &&
2311	>	U.compareAndSwapLong(this, CTL, cc, nc)) {
2312	>	w.eventCount = (e + E_SEQ) & E_MASK;
2313	>	w.qlock = -1;
2314	>	if ((p = w.parker) != null)
2315	>	U.unpark(p);
2316	>	}
2317	>	}
2318	>	}
2319		}
2320		}
2321		}
2322		}
2323
2324	<	// misc support for ForkJoinWorkerThread
2324	>	// external operations on common pool
2325
2326		/**
2327	<	* Returns pool number
2327	>	* Returns common pool queue for a thread that has submitted at
2328	>	* least one task.
2329		*/
2330	<	final int getPoolNumber() {
2331	<	return poolNumber;
2330	>	static WorkQueue commonSubmitterQueue() {
2331	>	ForkJoinPool p; WorkQueue[] ws; int m; Submitter z;
2332	>	return ((z = submitters.get()) != null &&
2333	>	(p = common) != null &&
2334	>	(ws = p.workQueues) != null &&
2335	>	(m = ws.length - 1) >= 0) ?
2336	>	ws[m & z.seed & SQMASK] : null;
2337		}
2338
2339		/**
2340	<	* Accumulates steal count from a worker, clearing
2341	<	* the worker's value
2342	<	*/
2343	<	final void accumulateStealCount(ForkJoinWorkerThread w) {
2344	<	int sc = w.stealCount;
2345	<	if (sc != 0) {
2346	<	long c;
2347	<	w.stealCount = 0;
2348	<	do {} while (!UNSAFE.compareAndSwapLong(this, stealCountOffset,
2349	<	c = stealCount, c + sc));
2340	>	* Tries to pop the given task from submitter's queue in common pool.
2341	>	*/
2342	>	static boolean tryExternalUnpush(ForkJoinTask<?> t) {
2343	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q; Submitter z;
2344	>	ForkJoinTask<?>[] a;  int m, s;
2345	>	if (t != null &&
2346	>	(z = submitters.get()) != null &&
2347	>	(p = common) != null &&
2348	>	(ws = p.workQueues) != null &&
2349	>	(m = ws.length - 1) >= 0 &&
2350	>	(q = ws[m & z.seed & SQMASK]) != null &&
2351	>	(s = q.top) != q.base &&
2352	>	(a = q.array) != null) {
2353	>	long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE;
2354	>	if (U.getObject(a, j) == t &&
2355	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2356	>	if (q.array == a && q.top == s && // recheck
2357	>	U.compareAndSwapObject(a, j, t, null)) {
2358	>	q.top = s - 1;
2359	>	q.qlock = 0;
2360	>	return true;
2361	>	}
2362	>	q.qlock = 0;
2363	>	}
2364	>	}
2365	>	return false;
2366	>	}
2367	>
2368	>	/**
2369	>	* Tries to pop and run local tasks within the same computation
2370	>	* as the given root. On failure, tries to help complete from
2371	>	* other queues via helpComplete.
2372	>	*/
2373	>	private void externalHelpComplete(WorkQueue q, ForkJoinTask<?> root) {
2374	>	ForkJoinTask<?>[] a; int m;
2375	>	if (q != null && (a = q.array) != null && (m = (a.length - 1)) >= 0 &&
2376	>	root != null && root.status >= 0) {
2377	>	for (;;) {
2378	>	int s, u; Object o; CountedCompleter<?> task = null;
2379	>	if ((s = q.top) - q.base > 0) {
2380	>	long j = ((m & (s - 1)) << ASHIFT) + ABASE;
2381	>	if ((o = U.getObject(a, j)) != null &&
2382	>	(o instanceof CountedCompleter)) {
2383	>	CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;
2384	>	do {
2385	>	if (r == root) {
2386	>	if (U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2387	>	if (q.array == a && q.top == s &&
2388	>	U.compareAndSwapObject(a, j, t, null)) {
2389	>	q.top = s - 1;
2390	>	task = t;
2391	>	}
2392	>	q.qlock = 0;
2393	>	}
2394	>	break;
2395	>	}
2396	>	} while ((r = r.completer) != null);
2397	>	}
2398	>	}
2399	>	if (task != null)
2400	>	task.doExec();
2401	>	if (root.status < 0 ||
2402	>	(u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0)
2403	>	break;
2404	>	if (task == null) {
2405	>	helpSignal(root, q.poolIndex);
2406	>	if (root.status >= 0)
2407	>	helpComplete(root, SHARED_QUEUE);
2408	>	break;
2409	>	}
2410	>	}
2411		}
2412		}
2413
2414		/**
2415	<	* Returns the approximate (non-atomic) number of idle threads per
2416	<	* active thread.
2415	>	* Tries to help execute or signal availability of the given task
2416	>	* from submitter's queue in common pool.
2417		*/
2418	<	final int idlePerActive() {
2419	<	int ac = runState;    // no mask -- artifically boosts during shutdown
2420	<	int pc = parallelism; // use targeted parallelism, not rc
2421	<	// Use exact results for small values, saturate past 4
2422	<	return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
2418	>	static void externalHelpJoin(ForkJoinTask<?> t) {
2419	>	// Some hard-to-avoid overlap with tryExternalUnpush
2420	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; Submitter z;
2421	>	ForkJoinTask<?>[] a;  int m, s, n;
2422	>	if (t != null &&
2423	>	(z = submitters.get()) != null &&
2424	>	(p = common) != null &&
2425	>	(ws = p.workQueues) != null &&
2426	>	(m = ws.length - 1) >= 0 &&
2427	>	(q = ws[m & z.seed & SQMASK]) != null &&
2428	>	(a = q.array) != null) {
2429	>	int am = a.length - 1;
2430	>	if ((s = q.top) != q.base) {
2431	>	long j = ((am & (s - 1)) << ASHIFT) + ABASE;
2432	>	if (U.getObject(a, j) == t &&
2433	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2434	>	if (q.array == a && q.top == s &&
2435	>	U.compareAndSwapObject(a, j, t, null)) {
2436	>	q.top = s - 1;
2437	>	q.qlock = 0;
2438	>	t.doExec();
2439	>	}
2440	>	else
2441	>	q.qlock = 0;
2442	>	}
2443	>	}
2444	>	if (t.status >= 0) {
2445	>	if (t instanceof CountedCompleter)
2446	>	p.externalHelpComplete(q, t);
2447	>	else
2448	>	p.helpSignal(t, q.poolIndex);
2449	>	}
2450	>	}
2451		}
2452
2453	<	// Public and protected methods
2453	>	// Exported methods
2454
2455		// Constructors
2456
2457		/**
2458		* Creates a {@code ForkJoinPool} with parallelism equal to {@link
2459	<	* java.lang.Runtime#availableProcessors}, and using the {@linkplain
2460	<	* #defaultForkJoinWorkerThreadFactory default thread factory}.
2459	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
2460	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
2461	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
2462		*
2463		* @throws SecurityException if a security manager exists and
2464		*         the caller is not permitted to modify threads
#	Line 1146 | Line 2466 | public class ForkJoinPool extends Abstra
2466		*         java.lang.RuntimePermission}{@code ("modifyThread")}
2467		*/
2468		public ForkJoinPool() {
2469	<	this(Runtime.getRuntime().availableProcessors(),
2470	<	defaultForkJoinWorkerThreadFactory);
2469	>	this(Math.min(MAX_CAP, Runtime.getRuntime().availableProcessors()),
2470	>	defaultForkJoinWorkerThreadFactory, null, false);
2471		}
2472
2473		/**
2474		* Creates a {@code ForkJoinPool} with the indicated parallelism
2475	<	* level and using the {@linkplain
2476	<	* #defaultForkJoinWorkerThreadFactory default thread factory}.
2475	>	* level, the {@linkplain
2476	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
2477	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
2478		*
2479		* @param parallelism the parallelism level
2480		* @throws IllegalArgumentException if parallelism less than or
#	Line 1164 | Line 2485 | public class ForkJoinPool extends Abstra
2485		*         java.lang.RuntimePermission}{@code ("modifyThread")}
2486		*/
2487		public ForkJoinPool(int parallelism) {
2488	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
1168	<	}
1169	<
1170	<	/**
1171	<	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1172	<	* java.lang.Runtime#availableProcessors}, and using the given
1173	<	* thread factory.
1174	<	*
1175	<	* @param factory the factory for creating new threads
1176	<	* @throws NullPointerException if the factory is null
1177	<	* @throws SecurityException if a security manager exists and
1178	<	*         the caller is not permitted to modify threads
1179	<	*         because it does not hold {@link
1180	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1181	<	*/
1182	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
1183	<	this(Runtime.getRuntime().availableProcessors(), factory);
2488	>	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
2489		}
2490
2491		/**
2492	<	* Creates a {@code ForkJoinPool} with the given parallelism and
1188	<	* thread factory.
2492	>	* Creates a {@code ForkJoinPool} with the given parameters.
2493		*
2494	<	* @param parallelism the parallelism level
2495	<	* @param factory the factory for creating new threads
2494	>	* @param parallelism the parallelism level. For default value,
2495	>	* use {@link java.lang.Runtime#availableProcessors}.
2496	>	* @param factory the factory for creating new threads. For default value,
2497	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
2498	>	* @param handler the handler for internal worker threads that
2499	>	* terminate due to unrecoverable errors encountered while executing
2500	>	* tasks. For default value, use {@code null}.
2501	>	* @param asyncMode if true,
2502	>	* establishes local first-in-first-out scheduling mode for forked
2503	>	* tasks that are never joined. This mode may be more appropriate
2504	>	* than default locally stack-based mode in applications in which
2505	>	* worker threads only process event-style asynchronous tasks.
2506	>	* For default value, use {@code false}.
2507		* @throws IllegalArgumentException if parallelism less than or
2508		*         equal to zero, or greater than implementation limit
2509		* @throws NullPointerException if the factory is null
#	Line 1197 | Line 2512 | public class ForkJoinPool extends Abstra
2512		*         because it does not hold {@link
2513		*         java.lang.RuntimePermission}{@code ("modifyThread")}
2514		*/
2515	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
2515	>	public ForkJoinPool(int parallelism,
2516	>	ForkJoinWorkerThreadFactory factory,
2517	>	Thread.UncaughtExceptionHandler handler,
2518	>	boolean asyncMode) {
2519		checkPermission();
2520		if (factory == null)
2521		throw new NullPointerException();
2522	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
2522	>	if (parallelism <= 0 || parallelism > MAX_CAP)
2523		throw new IllegalArgumentException();
1206	–	this.poolNumber = poolNumberGenerator.incrementAndGet();
1207	–	int arraySize = initialArraySizeFor(parallelism);
1208	–	this.parallelism = parallelism;
2524		this.factory = factory;
2525	<	this.maxPoolSize = MAX_THREADS;
2526	<	this.maintainsParallelism = true;
2527	<	this.workers = new ForkJoinWorkerThread[arraySize];
2528	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
2529	<	this.workerLock = new ReentrantLock();
2530	<	this.terminationLatch = new CountDownLatch(1);
2531	<	// Start first worker; remaining workers added upon first submission
2532	<	workerCounts = ONE_RUNNING | ONE_TOTAL;
2533	<	addWorker();
2525	>	this.ueh = handler;
2526	>	this.config = parallelism | (asyncMode ? (FIFO_QUEUE << 16) : 0);
2527	>	long np = (long)(-parallelism); // offset ctl counts
2528	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
2529	>	int pn = nextPoolId();
2530	>	StringBuilder sb = new StringBuilder("ForkJoinPool-");
2531	>	sb.append(Integer.toString(pn));
2532	>	sb.append("-worker-");
2533	>	this.workerNamePrefix = sb.toString();
2534		}
2535
2536		/**
2537	<	* Returns initial power of two size for workers array.
2538	<	* @param pc the initial parallelism level
2539	<	*/
2540	<	private static int initialArraySizeFor(int pc) {
2541	<	// See Hackers Delight, sec 3.2. We know MAX_THREADS < (1 >>> 16)
2542	<	int size = pc < MAX_THREADS ? pc + 1 : MAX_THREADS;
2543	<	size |= size >>> 1;
2544	<	size |= size >>> 2;
2545	<	size |= size >>> 4;
2546	<	size |= size >>> 8;
2547	<	return size + 1;
2537	>	* Constructor for common pool, suitable only for static initialization.
2538	>	* Basically the same as above, but uses smallest possible initial footprint.
2539	>	*/
2540	>	ForkJoinPool(int parallelism, long ctl,
2541	>	ForkJoinWorkerThreadFactory factory,
2542	>	Thread.UncaughtExceptionHandler handler) {
2543	>	this.config = parallelism;
2544	>	this.ctl = ctl;
2545	>	this.factory = factory;
2546	>	this.ueh = handler;
2547	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2548		}
2549
1235	–	// Execution methods
1236	–
2550		/**
2551	<	* Common code for execute, invoke and submit
2552	<	*/
2553	<	private <T> void doSubmit(ForkJoinTask<T> task) {
2554	<	if (task == null)
2555	<	throw new NullPointerException();
2556	<	if (runState >= SHUTDOWN)
2557	<	throw new RejectedExecutionException();
2558	<	submissionQueue.offer(task);
2559	<	advanceEventCount();
2560	<	releaseWaiters();
2561	<	if ((workerCounts >>> TOTAL_COUNT_SHIFT) < parallelism)
2562	<	ensureEnoughTotalWorkers();
2551	>	* Returns the common pool instance. This pool is statically
2552	>	* constructed; its run state is unaffected by attempts to {@link
2553	>	* #shutdown} or {@link #shutdownNow}. However this pool and any
2554	>	* ongoing processing are automatically terminated upon program
2555	>	* {@link System#exit}.  Any program that relies on asynchronous
2556	>	* task processing to complete before program termination should
2557	>	* invoke {@code commonPool().}{@link #awaitQuiescence}, before
2558	>	* exit.
2559	>	*
2560	>	* @return the common pool instance
2561	>	* @since 1.8
2562	>	*/
2563	>	public static ForkJoinPool commonPool() {
2564	>	// assert common != null : "static init error";
2565	>	return common;
2566		}
2567
2568	+	// Execution methods
2569	+
2570		/**
2571		* Performs the given task, returning its result upon completion.
2572	+	* If the computation encounters an unchecked Exception or Error,
2573	+	* it is rethrown as the outcome of this invocation.  Rethrown
2574	+	* exceptions behave in the same way as regular exceptions, but,
2575	+	* when possible, contain stack traces (as displayed for example
2576	+	* using {@code ex.printStackTrace()}) of both the current thread
2577	+	* as well as the thread actually encountering the exception;
2578	+	* minimally only the latter.
2579		*
2580		* @param task the task
2581		* @return the task's result
#	Line 1259 | Line 2584 | public class ForkJoinPool extends Abstra
2584		*         scheduled for execution
2585		*/
2586		public <T> T invoke(ForkJoinTask<T> task) {
2587	<	doSubmit(task);
2587	>	if (task == null)
2588	>	throw new NullPointerException();
2589	>	externalPush(task);
2590		return task.join();
2591		}
2592
#	Line 1272 | Line 2599 | public class ForkJoinPool extends Abstra
2599		*         scheduled for execution
2600		*/
2601		public void execute(ForkJoinTask<?> task) {
2602	<	doSubmit(task);
2602	>	if (task == null)
2603	>	throw new NullPointerException();
2604	>	externalPush(task);
2605		}
2606
2607		// AbstractExecutorService methods
#	Line 1283 | Line 2612 | public class ForkJoinPool extends Abstra
2612		*         scheduled for execution
2613		*/
2614		public void execute(Runnable task) {
2615	+	if (task == null)
2616	+	throw new NullPointerException();
2617		ForkJoinTask<?> job;
2618		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2619		job = (ForkJoinTask<?>) task;
2620		else
2621	<	job = ForkJoinTask.adapt(task, null);
2622	<	doSubmit(job);
2621	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2622	>	externalPush(job);
2623	>	}
2624	>
2625	>	/**
2626	>	* Submits a ForkJoinTask for execution.
2627	>	*
2628	>	* @param task the task to submit
2629	>	* @return the task
2630	>	* @throws NullPointerException if the task is null
2631	>	* @throws RejectedExecutionException if the task cannot be
2632	>	*         scheduled for execution
2633	>	*/
2634	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2635	>	if (task == null)
2636	>	throw new NullPointerException();
2637	>	externalPush(task);
2638	>	return task;
2639		}
2640
2641		/**
#	Line 1297 | Line 2644 | public class ForkJoinPool extends Abstra
2644		*         scheduled for execution
2645		*/
2646		public <T> ForkJoinTask<T> submit(Callable<T> task) {
2647	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
2648	<	doSubmit(job);
2647	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2648	>	externalPush(job);
2649		return job;
2650		}
2651
#	Line 1308 | Line 2655 | public class ForkJoinPool extends Abstra
2655		*         scheduled for execution
2656		*/
2657		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2658	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
2659	<	doSubmit(job);
2658	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2659	>	externalPush(job);
2660		return job;
2661		}
2662
#	Line 1319 | Line 2666 | public class ForkJoinPool extends Abstra
2666		*         scheduled for execution
2667		*/
2668		public ForkJoinTask<?> submit(Runnable task) {
2669	+	if (task == null)
2670	+	throw new NullPointerException();
2671		ForkJoinTask<?> job;
2672		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2673		job = (ForkJoinTask<?>) task;
2674		else
2675	<	job = ForkJoinTask.adapt(task, null);
2676	<	doSubmit(job);
2675	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2676	>	externalPush(job);
2677		return job;
2678		}
2679
2680		/**
1332	–	* Submits a ForkJoinTask for execution.
1333	–	*
1334	–	* @param task the task to submit
1335	–	* @return the task
1336	–	* @throws NullPointerException if the task is null
1337	–	* @throws RejectedExecutionException if the task cannot be
1338	–	*         scheduled for execution
1339	–	*/
1340	–	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1341	–	doSubmit(task);
1342	–	return task;
1343	–	}
1344	–
1345	–	/**
2681		* @throws NullPointerException       {@inheritDoc}
2682		* @throws RejectedExecutionException {@inheritDoc}
2683		*/
2684		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
2685	<	ArrayList<ForkJoinTask<T>> forkJoinTasks =
2686	<	new ArrayList<ForkJoinTask<T>>(tasks.size());
2687	<	for (Callable<T> task : tasks)
2688	<	forkJoinTasks.add(ForkJoinTask.adapt(task));
2689	<	invoke(new InvokeAll<T>(forkJoinTasks));
2690	<
2691	<	@SuppressWarnings({"unchecked", "rawtypes"})
2692	<	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
2693	<	return futures;
2694	<	}
2695	<
2696	<	static final class InvokeAll<T> extends RecursiveAction {
2697	<	final ArrayList<ForkJoinTask<T>> tasks;
2698	<	InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
2699	<	public void compute() {
2700	<	try { invokeAll(tasks); }
2701	<	catch (Exception ignore) {}
2685	>	// In previous versions of this class, this method constructed
2686	>	// a task to run ForkJoinTask.invokeAll, but now external
2687	>	// invocation of multiple tasks is at least as efficient.
2688	>	ArrayList<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
2689	>
2690	>	boolean done = false;
2691	>	try {
2692	>	for (Callable<T> t : tasks) {
2693	>	ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2694	>	futures.add(f);
2695	>	externalPush(f);
2696	>	}
2697	>	for (int i = 0, size = futures.size(); i < size; i++)
2698	>	((ForkJoinTask<?>)futures.get(i)).quietlyJoin();
2699	>	done = true;
2700	>	return futures;
2701	>	} finally {
2702	>	if (!done)
2703	>	for (int i = 0, size = futures.size(); i < size; i++)
2704	>	futures.get(i).cancel(false);
2705		}
1368	–	private static final long serialVersionUID = -7914297376763021607L;
2706		}
2707
2708		/**
#	Line 1384 | Line 2721 | public class ForkJoinPool extends Abstra
2721		* @return the handler, or {@code null} if none
2722		*/
2723		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1387	–	workerCountReadFence();
2724		return ueh;
2725		}
2726
2727		/**
2728	<	* Sets the handler for internal worker threads that terminate due
1393	<	* to unrecoverable errors encountered while executing tasks.
1394	<	* Unless set, the current default or ThreadGroup handler is used
1395	<	* as handler.
1396	<	*
1397	<	* @param h the new handler
1398	<	* @return the old handler, or {@code null} if none
1399	<	* @throws SecurityException if a security manager exists and
1400	<	*         the caller is not permitted to modify threads
1401	<	*         because it does not hold {@link
1402	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1403	<	*/
1404	<	public Thread.UncaughtExceptionHandler
1405	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
1406	<	checkPermission();
1407	<	workerCountReadFence();
1408	<	Thread.UncaughtExceptionHandler old = ueh;
1409	<	if (h != old) {
1410	<	ueh = h;
1411	<	workerCountWriteFence();
1412	<	for (ForkJoinWorkerThread w : workers) {
1413	<	if (w != null)
1414	<	w.setUncaughtExceptionHandler(h);
1415	<	}
1416	<	}
1417	<	return old;
1418	<	}
1419	<
1420	<	/**
1421	<	* Sets the target parallelism level of this pool.
2728	>	* Returns the targeted parallelism level of this pool.
2729		*
2730	<	* @param parallelism the target parallelism
1424	<	* @throws IllegalArgumentException if parallelism less than or
1425	<	* equal to zero or greater than maximum size bounds
1426	<	* @throws SecurityException if a security manager exists and
1427	<	*         the caller is not permitted to modify threads
1428	<	*         because it does not hold {@link
1429	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
2730	>	* @return the targeted parallelism level of this pool
2731		*/
2732	<	public void setParallelism(int parallelism) {
2733	<	checkPermission();
1433	<	if (parallelism <= 0 || parallelism > maxPoolSize)
1434	<	throw new IllegalArgumentException();
1435	<	workerCountReadFence();
1436	<	int pc = this.parallelism;
1437	<	if (pc != parallelism) {
1438	<	this.parallelism = parallelism;
1439	<	workerCountWriteFence();
1440	<	// Release spares. If too many, some will die after re-suspend
1441	<	for (ForkJoinWorkerThread w : workers) {
1442	<	if (w != null && w.tryUnsuspend()) {
1443	<	updateRunningCount(1);
1444	<	LockSupport.unpark(w);
1445	<	}
1446	<	}
1447	<	ensureEnoughTotalWorkers();
1448	<	advanceEventCount();
1449	<	releaseWaiters(); // force config recheck by existing workers
1450	<	}
2732	>	public int getParallelism() {
2733	>	return config & SMASK;
2734		}
2735
2736		/**
2737	<	* Returns the targeted parallelism level of this pool.
2737	>	* Returns the targeted parallelism level of the common pool.
2738		*
2739	<	* @return the targeted parallelism level of this pool
2739	>	* @return the targeted parallelism level of the common pool
2740	>	* @since 1.8
2741		*/
2742	<	public int getParallelism() {
2743	<	//        workerCountReadFence(); // inlined below
1460	<	int ignore = workerCounts;
1461	<	return parallelism;
2742	>	public static int getCommonPoolParallelism() {
2743	>	return commonParallelism;
2744		}
2745
2746		/**
2747		* Returns the number of worker threads that have started but not
2748	<	* yet terminated.  This result returned by this method may differ
2748	>	* yet terminated.  The result returned by this method may differ
2749		* from {@link #getParallelism} when threads are created to
2750		* maintain parallelism when others are cooperatively blocked.
2751		*
2752		* @return the number of worker threads
2753		*/
2754		public int getPoolSize() {
2755	<	return workerCounts >>> TOTAL_COUNT_SHIFT;
1474	<	}
1475	<
1476	<	/**
1477	<	* Returns the maximum number of threads allowed to exist in the
1478	<	* pool. Unless set using {@link #setMaximumPoolSize}, the
1479	<	* maximum is an implementation-defined value designed only to
1480	<	* prevent runaway growth.
1481	<	*
1482	<	* @return the maximum
1483	<	*/
1484	<	public int getMaximumPoolSize() {
1485	<	workerCountReadFence();
1486	<	return maxPoolSize;
1487	<	}
1488	<
1489	<	/**
1490	<	* Sets the maximum number of threads allowed to exist in the
1491	<	* pool. The given value should normally be greater than or equal
1492	<	* to the {@link #getParallelism parallelism} level. Setting this
1493	<	* value has no effect on current pool size. It controls
1494	<	* construction of new threads. The use of this method may cause
1495	<	* tasks that intrinsically require extra threads for dependent
1496	<	* computations to indefinitely stall. If you are instead trying
1497	<	* to minimize internal thread creation, consider setting {@link
1498	<	* #setMaintainsParallelism} as false.
1499	<	*
1500	<	* @throws IllegalArgumentException if negative or greater than
1501	<	* internal implementation limit
1502	<	*/
1503	<	public void setMaximumPoolSize(int newMax) {
1504	<	if (newMax < 0 || newMax > MAX_THREADS)
1505	<	throw new IllegalArgumentException();
1506	<	maxPoolSize = newMax;
1507	<	workerCountWriteFence();
1508	<	}
1509	<
1510	<	/**
1511	<	* Returns {@code true} if this pool dynamically maintains its
1512	<	* target parallelism level. If false, new threads are added only
1513	<	* to avoid possible starvation.  This setting is by default true.
1514	<	*
1515	<	* @return {@code true} if maintains parallelism
1516	<	*/
1517	<	public boolean getMaintainsParallelism() {
1518	<	workerCountReadFence();
1519	<	return maintainsParallelism;
1520	<	}
1521	<
1522	<	/**
1523	<	* Sets whether this pool dynamically maintains its target
1524	<	* parallelism level. If false, new threads are added only to
1525	<	* avoid possible starvation.
1526	<	*
1527	<	* @param enable {@code true} to maintain parallelism
1528	<	*/
1529	<	public void setMaintainsParallelism(boolean enable) {
1530	<	maintainsParallelism = enable;
1531	<	workerCountWriteFence();
1532	<	}
1533	<
1534	<	/**
1535	<	* Establishes local first-in-first-out scheduling mode for forked
1536	<	* tasks that are never joined. This mode may be more appropriate
1537	<	* than default locally stack-based mode in applications in which
1538	<	* worker threads only process asynchronous tasks.  This method is
1539	<	* designed to be invoked only when the pool is quiescent, and
1540	<	* typically only before any tasks are submitted. The effects of
1541	<	* invocations at other times may be unpredictable.
1542	<	*
1543	<	* @param async if {@code true}, use locally FIFO scheduling
1544	<	* @return the previous mode
1545	<	* @see #getAsyncMode
1546	<	*/
1547	<	public boolean setAsyncMode(boolean async) {
1548	<	workerCountReadFence();
1549	<	boolean oldMode = locallyFifo;
1550	<	if (oldMode != async) {
1551	<	locallyFifo = async;
1552	<	workerCountWriteFence();
1553	<	for (ForkJoinWorkerThread w : workers) {
1554	<	if (w != null)
1555	<	w.setAsyncMode(async);
1556	<	}
1557	<	}
1558	<	return oldMode;
2755	>	return (config & SMASK) + (short)(ctl >>> TC_SHIFT);
2756		}
2757
2758		/**
#	Line 1563 | Line 2760 | public class ForkJoinPool extends Abstra
2760		* scheduling mode for forked tasks that are never joined.
2761		*
2762		* @return {@code true} if this pool uses async mode
1566	–	* @see #setAsyncMode
2763		*/
2764		public boolean getAsyncMode() {
2765	<	workerCountReadFence();
1570	<	return locallyFifo;
2765	>	return (config >>> 16) == FIFO_QUEUE;
2766		}
2767
2768		/**
#	Line 1579 | Line 2774 | public class ForkJoinPool extends Abstra
2774		* @return the number of worker threads
2775		*/
2776		public int getRunningThreadCount() {
2777	<	return workerCounts & RUNNING_COUNT_MASK;
2777	>	int rc = 0;
2778	>	WorkQueue[] ws; WorkQueue w;
2779	>	if ((ws = workQueues) != null) {
2780	>	for (int i = 1; i < ws.length; i += 2) {
2781	>	if ((w = ws[i]) != null && w.isApparentlyUnblocked())
2782	>	++rc;
2783	>	}
2784	>	}
2785	>	return rc;
2786		}
2787
2788		/**
#	Line 1590 | Line 2793 | public class ForkJoinPool extends Abstra
2793		* @return the number of active threads
2794		*/
2795		public int getActiveThreadCount() {
2796	<	return runState & ACTIVE_COUNT_MASK;
2796	>	int r = (config & SMASK) + (int)(ctl >> AC_SHIFT);
2797	>	return (r <= 0) ? 0 : r; // suppress momentarily negative values
2798		}
2799
2800		/**
#	Line 1605 | Line 2809 | public class ForkJoinPool extends Abstra
2809		* @return {@code true} if all threads are currently idle
2810		*/
2811		public boolean isQuiescent() {
2812	<	return (runState & ACTIVE_COUNT_MASK) == 0;
2812	>	return (int)(ctl >> AC_SHIFT) + (config & SMASK) == 0;
2813		}
2814
2815		/**
#	Line 1620 | Line 2824 | public class ForkJoinPool extends Abstra
2824		* @return the number of steals
2825		*/
2826		public long getStealCount() {
2827	<	return stealCount;
2827	>	long count = stealCount;
2828	>	WorkQueue[] ws; WorkQueue w;
2829	>	if ((ws = workQueues) != null) {
2830	>	for (int i = 1; i < ws.length; i += 2) {
2831	>	if ((w = ws[i]) != null)
2832	>	count += w.nsteals;
2833	>	}
2834	>	}
2835	>	return count;
2836		}
2837
2838		/**
#	Line 1635 | Line 2847 | public class ForkJoinPool extends Abstra
2847		*/
2848		public long getQueuedTaskCount() {
2849		long count = 0;
2850	<	for (ForkJoinWorkerThread w : workers) {
2851	<	if (w != null)
2852	<	count += w.getQueueSize();
2850	>	WorkQueue[] ws; WorkQueue w;
2851	>	if ((ws = workQueues) != null) {
2852	>	for (int i = 1; i < ws.length; i += 2) {
2853	>	if ((w = ws[i]) != null)
2854	>	count += w.queueSize();
2855	>	}
2856		}
2857		return count;
2858		}
2859
2860		/**
2861		* Returns an estimate of the number of tasks submitted to this
2862	<	* pool that have not yet begun executing.  This method takes time
2863	<	* proportional to the number of submissions.
2862	>	* pool that have not yet begun executing.  This method may take
2863	>	* time proportional to the number of submissions.
2864		*
2865		* @return the number of queued submissions
2866		*/
2867		public int getQueuedSubmissionCount() {
2868	<	return submissionQueue.size();
2868	>	int count = 0;
2869	>	WorkQueue[] ws; WorkQueue w;
2870	>	if ((ws = workQueues) != null) {
2871	>	for (int i = 0; i < ws.length; i += 2) {
2872	>	if ((w = ws[i]) != null)
2873	>	count += w.queueSize();
2874	>	}
2875	>	}
2876	>	return count;
2877		}
2878
2879		/**
#	Line 1660 | Line 2883 | public class ForkJoinPool extends Abstra
2883		* @return {@code true} if there are any queued submissions
2884		*/
2885		public boolean hasQueuedSubmissions() {
2886	<	return !submissionQueue.isEmpty();
2886	>	WorkQueue[] ws; WorkQueue w;
2887	>	if ((ws = workQueues) != null) {
2888	>	for (int i = 0; i < ws.length; i += 2) {
2889	>	if ((w = ws[i]) != null && !w.isEmpty())
2890	>	return true;
2891	>	}
2892	>	}
2893	>	return false;
2894		}
2895
2896		/**
#	Line 1671 | Line 2901 | public class ForkJoinPool extends Abstra
2901		* @return the next submission, or {@code null} if none
2902		*/
2903		protected ForkJoinTask<?> pollSubmission() {
2904	<	return submissionQueue.poll();
2904	>	WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2905	>	if ((ws = workQueues) != null) {
2906	>	for (int i = 0; i < ws.length; i += 2) {
2907	>	if ((w = ws[i]) != null && (t = w.poll()) != null)
2908	>	return t;
2909	>	}
2910	>	}
2911	>	return null;
2912		}
2913
2914		/**
#	Line 1692 | Line 2929 | public class ForkJoinPool extends Abstra
2929		* @return the number of elements transferred
2930		*/
2931		protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
2932	<	int n = submissionQueue.drainTo(c);
2933	<	for (ForkJoinWorkerThread w : workers) {
2934	<	if (w != null)
2935	<	n += w.drainTasksTo(c);
2932	>	int count = 0;
2933	>	WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2934	>	if ((ws = workQueues) != null) {
2935	>	for (int i = 0; i < ws.length; ++i) {
2936	>	if ((w = ws[i]) != null) {
2937	>	while ((t = w.poll()) != null) {
2938	>	c.add(t);
2939	>	++count;
2940	>	}
2941	>	}
2942	>	}
2943		}
2944	<	return n;
2944	>	return count;
2945		}
2946
2947		/**
#	Line 1708 | Line 2952 | public class ForkJoinPool extends Abstra
2952		* @return a string identifying this pool, as well as its state
2953		*/
2954		public String toString() {
2955	<	long st = getStealCount();
2956	<	long qt = getQueuedTaskCount();
2957	<	long qs = getQueuedSubmissionCount();
2958	<	int wc = workerCounts;
2959	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
2960	<	int rc = wc & RUNNING_COUNT_MASK;
2961	<	int pc = parallelism;
2962	<	int rs = runState;
2963	<	int ac = rs & ACTIVE_COUNT_MASK;
2955	>	// Use a single pass through workQueues to collect counts
2956	>	long qt = 0L, qs = 0L; int rc = 0;
2957	>	long st = stealCount;
2958	>	long c = ctl;
2959	>	WorkQueue[] ws; WorkQueue w;
2960	>	if ((ws = workQueues) != null) {
2961	>	for (int i = 0; i < ws.length; ++i) {
2962	>	if ((w = ws[i]) != null) {
2963	>	int size = w.queueSize();
2964	>	if ((i & 1) == 0)
2965	>	qs += size;
2966	>	else {
2967	>	qt += size;
2968	>	st += w.nsteals;
2969	>	if (w.isApparentlyUnblocked())
2970	>	++rc;
2971	>	}
2972	>	}
2973	>	}
2974	>	}
2975	>	int pc = (config & SMASK);
2976	>	int tc = pc + (short)(c >>> TC_SHIFT);
2977	>	int ac = pc + (int)(c >> AC_SHIFT);
2978	>	if (ac < 0) // ignore transient negative
2979	>	ac = 0;
2980	>	String level;
2981	>	if ((c & STOP_BIT) != 0)
2982	>	level = (tc == 0) ? "Terminated" : "Terminating";
2983	>	else
2984	>	level = plock < 0 ? "Shutting down" : "Running";
2985		return super.toString() +
2986	<	"[" + runLevelToString(rs) +
2986	>	"[" + level +
2987		", parallelism = " + pc +
2988		", size = " + tc +
2989		", active = " + ac +
#	Line 1729 | Line 2994 | public class ForkJoinPool extends Abstra
2994		"]";
2995		}
2996
1732	–	private static String runLevelToString(int s) {
1733	–	return ((s & TERMINATED) != 0 ? "Terminated" :
1734	–	((s & TERMINATING) != 0 ? "Terminating" :
1735	–	((s & SHUTDOWN) != 0 ? "Shutting down" :
1736	–	"Running")));
1737	–	}
1738	–
2997		/**
2998	<	* Initiates an orderly shutdown in which previously submitted
2999	<	* tasks are executed, but no new tasks will be accepted.
3000	<	* Invocation has no additional effect if already shut down.
3001	<	* Tasks that are in the process of being submitted concurrently
3002	<	* during the course of this method may or may not be rejected.
2998	>	* Possibly initiates an orderly shutdown in which previously
2999	>	* submitted tasks are executed, but no new tasks will be
3000	>	* accepted. Invocation has no effect on execution state if this
3001	>	* is the {@link #commonPool()}, and no additional effect if
3002	>	* already shut down.  Tasks that are in the process of being
3003	>	* submitted concurrently during the course of this method may or
3004	>	* may not be rejected.
3005		*
3006		* @throws SecurityException if a security manager exists and
3007		*         the caller is not permitted to modify threads
#	Line 1750 | Line 3010 | public class ForkJoinPool extends Abstra
3010		*/
3011		public void shutdown() {
3012		checkPermission();
3013	<	advanceRunLevel(SHUTDOWN);
1754	<	tryTerminate(false);
3013	>	tryTerminate(false, true);
3014		}
3015
3016		/**
3017	<	* Attempts to cancel and/or stop all tasks, and reject all
3018	<	* subsequently submitted tasks.  Tasks that are in the process of
3019	<	* being submitted or executed concurrently during the course of
3020	<	* this method may or may not be rejected. This method cancels
3021	<	* both existing and unexecuted tasks, in order to permit
3022	<	* termination in the presence of task dependencies. So the method
3023	<	* always returns an empty list (unlike the case for some other
3024	<	* Executors).
3017	>	* Possibly attempts to cancel and/or stop all tasks, and reject
3018	>	* all subsequently submitted tasks.  Invocation has no effect on
3019	>	* execution state if this is the {@link #commonPool()}, and no
3020	>	* additional effect if already shut down. Otherwise, tasks that
3021	>	* are in the process of being submitted or executed concurrently
3022	>	* during the course of this method may or may not be
3023	>	* rejected. This method cancels both existing and unexecuted
3024	>	* tasks, in order to permit termination in the presence of task
3025	>	* dependencies. So the method always returns an empty list
3026	>	* (unlike the case for some other Executors).
3027		*
3028		* @return an empty list
3029		* @throws SecurityException if a security manager exists and
#	Line 1772 | Line 3033 | public class ForkJoinPool extends Abstra
3033		*/
3034		public List<Runnable> shutdownNow() {
3035		checkPermission();
3036	<	tryTerminate(true);
3036	>	tryTerminate(true, true);
3037		return Collections.emptyList();
3038		}
3039
#	Line 1782 | Line 3043 | public class ForkJoinPool extends Abstra
3043		* @return {@code true} if all tasks have completed following shut down
3044		*/
3045		public boolean isTerminated() {
3046	<	return runState >= TERMINATED;
3046	>	long c = ctl;
3047	>	return ((c & STOP_BIT) != 0L &&
3048	>	(short)(c >>> TC_SHIFT) == -(config & SMASK));
3049		}
3050
3051		/**
#	Line 1790 | Line 3053 | public class ForkJoinPool extends Abstra
3053		* commenced but not yet completed.  This method may be useful for
3054		* debugging. A return of {@code true} reported a sufficient
3055		* period after shutdown may indicate that submitted tasks have
3056	<	* ignored or suppressed interruption, causing this executor not
3057	<	* to properly terminate.
3056	>	* ignored or suppressed interruption, or are waiting for I/O,
3057	>	* causing this executor not to properly terminate. (See the
3058	>	* advisory notes for class {@link ForkJoinTask} stating that
3059	>	* tasks should not normally entail blocking operations.  But if
3060	>	* they do, they must abort them on interrupt.)
3061		*
3062		* @return {@code true} if terminating but not yet terminated
3063		*/
3064		public boolean isTerminating() {
3065	<	return (runState & (TERMINATING|TERMINATED)) == TERMINATING;
3065	>	long c = ctl;
3066	>	return ((c & STOP_BIT) != 0L &&
3067	>	(short)(c >>> TC_SHIFT) != -(config & SMASK));
3068		}
3069
3070		/**
#	Line 1805 | Line 3073 | public class ForkJoinPool extends Abstra
3073		* @return {@code true} if this pool has been shut down
3074		*/
3075		public boolean isShutdown() {
3076	<	return runState >= SHUTDOWN;
3076	>	return plock < 0;
3077		}
3078
3079		/**
3080	<	* Blocks until all tasks have completed execution after a shutdown
3081	<	* request, or the timeout occurs, or the current thread is
3082	<	* interrupted, whichever happens first.
3080	>	* Blocks until all tasks have completed execution after a
3081	>	* shutdown request, or the timeout occurs, or the current thread
3082	>	* is interrupted, whichever happens first. Because the {@link
3083	>	* #commonPool()} never terminates until program shutdown, when
3084	>	* applied to the common pool, this method is equivalent to {@link
3085	>	* #awaitQuiescence} but always returns {@code false}.
3086		*
3087		* @param timeout the maximum time to wait
3088		* @param unit the time unit of the timeout argument
#	Line 1821 | Line 3092 | public class ForkJoinPool extends Abstra
3092		*/
3093		public boolean awaitTermination(long timeout, TimeUnit unit)
3094		throws InterruptedException {
3095	<	return terminationLatch.await(timeout, unit);
3095	>	if (Thread.interrupted())
3096	>	throw new InterruptedException();
3097	>	if (this == common) {
3098	>	awaitQuiescence(timeout, unit);
3099	>	return false;
3100	>	}
3101	>	long nanos = unit.toNanos(timeout);
3102	>	if (isTerminated())
3103	>	return true;
3104	>	long startTime = System.nanoTime();
3105	>	boolean terminated = false;
3106	>	synchronized (this) {
3107	>	for (long waitTime = nanos, millis = 0L;;) {
3108	>	if (terminated = isTerminated() ||
3109	>	waitTime <= 0L ||
3110	>	(millis = unit.toMillis(waitTime)) <= 0L)
3111	>	break;
3112	>	wait(millis);
3113	>	waitTime = nanos - (System.nanoTime() - startTime);
3114	>	}
3115	>	}
3116	>	return terminated;
3117	>	}
3118	>
3119	>	/**
3120	>	* If called by a ForkJoinTask operating in this pool, equivalent
3121	>	* in effect to {@link ForkJoinTask#helpQuiesce}. Otherwise,
3122	>	* waits and/or attempts to assist performing tasks until this
3123	>	* pool {@link #isQuiescent} or the indicated timeout elapses.
3124	>	*
3125	>	* @param timeout the maximum time to wait
3126	>	* @param unit the time unit of the timeout argument
3127	>	* @return {@code true} if quiescent; {@code false} if the
3128	>	* timeout elapsed.
3129	>	*/
3130	>	public boolean awaitQuiescence(long timeout, TimeUnit unit) {
3131	>	long nanos = unit.toNanos(timeout);
3132	>	ForkJoinWorkerThread wt;
3133	>	Thread thread = Thread.currentThread();
3134	>	if ((thread instanceof ForkJoinWorkerThread) &&
3135	>	(wt = (ForkJoinWorkerThread)thread).pool == this) {
3136	>	helpQuiescePool(wt.workQueue);
3137	>	return true;
3138	>	}
3139	>	long startTime = System.nanoTime();
3140	>	WorkQueue[] ws;
3141	>	int r = 0, m;
3142	>	boolean found = true;
3143	>	while (!isQuiescent() && (ws = workQueues) != null &&
3144	>	(m = ws.length - 1) >= 0) {
3145	>	if (!found) {
3146	>	if ((System.nanoTime() - startTime) > nanos)
3147	>	return false;
3148	>	Thread.yield(); // cannot block
3149	>	}
3150	>	found = false;
3151	>	for (int j = (m + 1) << 2; j >= 0; --j) {
3152	>	ForkJoinTask<?> t; WorkQueue q; int b;
3153	>	if ((q = ws[r++ & m]) != null && (b = q.base) - q.top < 0) {
3154	>	found = true;
3155	>	if ((t = q.pollAt(b)) != null) {
3156	>	if (q.base - q.top < 0)
3157	>	signalWork(q);
3158	>	t.doExec();
3159	>	}
3160	>	break;
3161	>	}
3162	>	}
3163	>	}
3164	>	return true;
3165	>	}
3166	>
3167	>	/**
3168	>	* Waits and/or attempts to assist performing tasks indefinitely
3169	>	* until the {@link #commonPool()} {@link #isQuiescent}
3170	>	*/
3171	>	static void quiesceCommonPool() {
3172	>	common.awaitQuiescence(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
3173		}
3174
3175		/**
3176		* Interface for extending managed parallelism for tasks running
3177		* in {@link ForkJoinPool}s.
3178		*
3179	<	* <p>A {@code ManagedBlocker} provides two methods.
3180	<	* Method {@code isReleasable} must return {@code true} if
3181	<	* blocking is not necessary. Method {@code block} blocks the
3182	<	* current thread if necessary (perhaps internally invoking
3183	<	* {@code isReleasable} before actually blocking).
3179	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
3180	>	* {@code isReleasable} must return {@code true} if blocking is
3181	>	* not necessary. Method {@code block} blocks the current thread
3182	>	* if necessary (perhaps internally invoking {@code isReleasable}
3183	>	* before actually blocking). These actions are performed by any
3184	>	* thread invoking {@link ForkJoinPool#managedBlock}.  The
3185	>	* unusual methods in this API accommodate synchronizers that may,
3186	>	* but don't usually, block for long periods. Similarly, they
3187	>	* allow more efficient internal handling of cases in which
3188	>	* additional workers may be, but usually are not, needed to
3189	>	* ensure sufficient parallelism.  Toward this end,
3190	>	* implementations of method {@code isReleasable} must be amenable
3191	>	* to repeated invocation.
3192		*
3193		* <p>For example, here is a ManagedBlocker based on a
3194		* ReentrantLock:
#	Line 1850 | Line 3206 | public class ForkJoinPool extends Abstra
3206		*     return hasLock || (hasLock = lock.tryLock());
3207		*   }
3208		* }}</pre>
3209	+	*
3210	+	* <p>Here is a class that possibly blocks waiting for an
3211	+	* item on a given queue:
3212	+	*  <pre> {@code
3213	+	* class QueueTaker<E> implements ManagedBlocker {
3214	+	*   final BlockingQueue<E> queue;
3215	+	*   volatile E item = null;
3216	+	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
3217	+	*   public boolean block() throws InterruptedException {
3218	+	*     if (item == null)
3219	+	*       item = queue.take();
3220	+	*     return true;
3221	+	*   }
3222	+	*   public boolean isReleasable() {
3223	+	*     return item != null || (item = queue.poll()) != null;
3224	+	*   }
3225	+	*   public E getItem() { // call after pool.managedBlock completes
3226	+	*     return item;
3227	+	*   }
3228	+	* }}</pre>
3229		*/
3230		public static interface ManagedBlocker {
3231		/**
#	Line 1873 | Line 3249 | public class ForkJoinPool extends Abstra
3249		* Blocks in accord with the given blocker.  If the current thread
3250		* is a {@link ForkJoinWorkerThread}, this method possibly
3251		* arranges for a spare thread to be activated if necessary to
3252	<	* ensure parallelism while the current thread is blocked.
1877	<	*
1878	<	* <p>If {@code maintainParallelism} is {@code true} and the pool
1879	<	* supports it ({@link #getMaintainsParallelism}), this method
1880	<	* attempts to maintain the pool's nominal parallelism. Otherwise
1881	<	* it activates a thread only if necessary to avoid complete
1882	<	* starvation. This option may be preferable when blockages use
1883	<	* timeouts, or are almost always brief.
3252	>	* ensure sufficient parallelism while the current thread is blocked.
3253		*
3254		* <p>If the caller is not a {@link ForkJoinTask}, this method is
3255		* behaviorally equivalent to
#	Line 1894 | Line 3263 | public class ForkJoinPool extends Abstra
3263		* first be expanded to ensure parallelism, and later adjusted.
3264		*
3265		* @param blocker the blocker
1897	–	* @param maintainParallelism if {@code true} and supported by
1898	–	* this pool, attempt to maintain the pool's nominal parallelism;
1899	–	* otherwise activate a thread only if necessary to avoid
1900	–	* complete starvation.
3266		* @throws InterruptedException if blocker.block did so
3267		*/
3268	<	public static void managedBlock(ManagedBlocker blocker,
1904	<	boolean maintainParallelism)
3268	>	public static void managedBlock(ManagedBlocker blocker)
3269		throws InterruptedException {
3270		Thread t = Thread.currentThread();
3271	<	if (t instanceof ForkJoinWorkerThread)
3272	<	((ForkJoinWorkerThread) t).pool.
3273	<	doBlock(blocker, maintainParallelism);
3274	<	else
3275	<	awaitBlocker(blocker);
3276	<	}
3277	<
3278	<	/**
3279	<	* Performs Non-FJ blocking
3280	<	*/
3281	<	private static void awaitBlocker(ManagedBlocker blocker)
3282	<	throws InterruptedException {
3283	<	do {} while (!blocker.isReleasable() && !blocker.block());
3271	>	if (t instanceof ForkJoinWorkerThread) {
3272	>	ForkJoinPool p = ((ForkJoinWorkerThread)t).pool;
3273	>	while (!blocker.isReleasable()) { // variant of helpSignal
3274	>	WorkQueue[] ws; WorkQueue q; int m, u;
3275	>	if ((ws = p.workQueues) != null && (m = ws.length - 1) >= 0) {
3276	>	for (int i = 0; i <= m; ++i) {
3277	>	if (blocker.isReleasable())
3278	>	return;
3279	>	if ((q = ws[i]) != null && q.base - q.top < 0) {
3280	>	p.signalWork(q);
3281	>	if ((u = (int)(p.ctl >>> 32)) >= 0 ||
3282	>	(u >> UAC_SHIFT) >= 0)
3283	>	break;
3284	>	}
3285	>	}
3286	>	}
3287	>	if (p.tryCompensate()) {
3288	>	try {
3289	>	do {} while (!blocker.isReleasable() &&
3290	>	!blocker.block());
3291	>	} finally {
3292	>	p.incrementActiveCount();
3293	>	}
3294	>	break;
3295	>	}
3296	>	}
3297	>	}
3298	>	else {
3299	>	do {} while (!blocker.isReleasable() &&
3300	>	!blocker.block());
3301	>	}
3302		}
3303
3304		// AbstractExecutorService overrides.  These rely on undocumented
#	Line 1924 | Line 3306 | public class ForkJoinPool extends Abstra
3306		// implement RunnableFuture.
3307
3308		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
3309	<	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
3309	>	return new ForkJoinTask.AdaptedRunnable<T>(runnable, value);
3310		}
3311
3312		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
3313	<	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
3313	>	return new ForkJoinTask.AdaptedCallable<T>(callable);
3314		}
3315
3316		// Unsafe mechanics
3317	+	private static final sun.misc.Unsafe U;
3318	+	private static final long CTL;
3319	+	private static final long PARKBLOCKER;
3320	+	private static final int ABASE;
3321	+	private static final int ASHIFT;
3322	+	private static final long STEALCOUNT;
3323	+	private static final long PLOCK;
3324	+	private static final long INDEXSEED;
3325	+	private static final long QLOCK;
3326
3327	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
3328	<	private static final long workerCountsOffset =
3329	<	objectFieldOffset("workerCounts", ForkJoinPool.class);
3330	<	private static final long runStateOffset =
3331	<	objectFieldOffset("runState", ForkJoinPool.class);
3332	<	private static final long eventCountOffset =
3333	<	objectFieldOffset("eventCount", ForkJoinPool.class);
3334	<	private static final long eventWaitersOffset =
3335	<	objectFieldOffset("eventWaiters",ForkJoinPool.class);
3336	<	private static final long stealCountOffset =
3337	<	objectFieldOffset("stealCount",ForkJoinPool.class);
3327	>	static {
3328	>	// initialize field offsets for CAS etc
3329	>	try {
3330	>	U = getUnsafe();
3331	>	Class<?> k = ForkJoinPool.class;
3332	>	CTL = U.objectFieldOffset
3333	>	(k.getDeclaredField("ctl"));
3334	>	STEALCOUNT = U.objectFieldOffset
3335	>	(k.getDeclaredField("stealCount"));
3336	>	PLOCK = U.objectFieldOffset
3337	>	(k.getDeclaredField("plock"));
3338	>	INDEXSEED = U.objectFieldOffset
3339	>	(k.getDeclaredField("indexSeed"));
3340	>	Class<?> tk = Thread.class;
3341	>	PARKBLOCKER = U.objectFieldOffset
3342	>	(tk.getDeclaredField("parkBlocker"));
3343	>	Class<?> wk = WorkQueue.class;
3344	>	QLOCK = U.objectFieldOffset
3345	>	(wk.getDeclaredField("qlock"));
3346	>	Class<?> ak = ForkJoinTask[].class;
3347	>	ABASE = U.arrayBaseOffset(ak);
3348	>	int scale = U.arrayIndexScale(ak);
3349	>	if ((scale & (scale - 1)) != 0)
3350	>	throw new Error("data type scale not a power of two");
3351	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
3352	>	} catch (Exception e) {
3353	>	throw new Error(e);
3354	>	}
3355	>
3356	>	submitters = new ThreadLocal<Submitter>();
3357	>	ForkJoinWorkerThreadFactory fac = defaultForkJoinWorkerThreadFactory =
3358	>	new DefaultForkJoinWorkerThreadFactory();
3359	>	modifyThreadPermission = new RuntimePermission("modifyThread");
3360	>
3361	>	/*
3362	>	* Establish common pool parameters.  For extra caution,
3363	>	* computations to set up common pool state are here; the
3364	>	* constructor just assigns these values to fields.
3365	>	*/
3366
3367	+	int par = 0;
3368	+	Thread.UncaughtExceptionHandler handler = null;
3369	+	try {  // TBD: limit or report ignored exceptions?
3370	+	String pp = System.getProperty
3371	+	("java.util.concurrent.ForkJoinPool.common.parallelism");
3372	+	String hp = System.getProperty
3373	+	("java.util.concurrent.ForkJoinPool.common.exceptionHandler");
3374	+	String fp = System.getProperty
3375	+	("java.util.concurrent.ForkJoinPool.common.threadFactory");
3376	+	if (fp != null)
3377	+	fac = ((ForkJoinWorkerThreadFactory)ClassLoader.
3378	+	getSystemClassLoader().loadClass(fp).newInstance());
3379	+	if (hp != null)
3380	+	handler = ((Thread.UncaughtExceptionHandler)ClassLoader.
3381	+	getSystemClassLoader().loadClass(hp).newInstance());
3382	+	if (pp != null)
3383	+	par = Integer.parseInt(pp);
3384	+	} catch (Exception ignore) {
3385	+	}
3386	+
3387	+	if (par <= 0)
3388	+	par = Runtime.getRuntime().availableProcessors();
3389	+	if (par > MAX_CAP)
3390	+	par = MAX_CAP;
3391	+	commonParallelism = par;
3392	+	long np = (long)(-par); // precompute initial ctl value
3393	+	long ct = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
3394
3395	<	private static long objectFieldOffset(String field, Class<?> klazz) {
1950	<	try {
1951	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1952	<	} catch (NoSuchFieldException e) {
1953	<	// Convert Exception to corresponding Error
1954	<	NoSuchFieldError error = new NoSuchFieldError(field);
1955	<	error.initCause(e);
1956	<	throw error;
1957	<	}
3395	>	common = new ForkJoinPool(par, ct, fac, handler);
3396		}
3397
3398		/**
#	Line 1967 | Line 3405 | public class ForkJoinPool extends Abstra
3405		private static sun.misc.Unsafe getUnsafe() {
3406		try {
3407		return sun.misc.Unsafe.getUnsafe();
3408	<	} catch (SecurityException se) {
3409	<	try {
3410	<	return java.security.AccessController.doPrivileged
3411	<	(new java.security
3412	<	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
3413	<	public sun.misc.Unsafe run() throws Exception {
3414	<	java.lang.reflect.Field f = sun.misc
3415	<	.Unsafe.class.getDeclaredField("theUnsafe");
3416	<	f.setAccessible(true);
3417	<	return (sun.misc.Unsafe) f.get(null);
3418	<	}});
3419	<	} catch (java.security.PrivilegedActionException e) {
3420	<	throw new RuntimeException("Could not initialize intrinsics",
3421	<	e.getCause());
3422	<	}
3408	>	} catch (SecurityException tryReflectionInstead) {}
3409	>	try {
3410	>	return java.security.AccessController.doPrivileged
3411	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
3412	>	public sun.misc.Unsafe run() throws Exception {
3413	>	Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class;
3414	>	for (java.lang.reflect.Field f : k.getDeclaredFields()) {
3415	>	f.setAccessible(true);
3416	>	Object x = f.get(null);
3417	>	if (k.isInstance(x))
3418	>	return k.cast(x);
3419	>	}
3420	>	throw new NoSuchFieldError("the Unsafe");
3421	>	}});
3422	>	} catch (java.security.PrivilegedActionException e) {
3423	>	throw new RuntimeException("Could not initialize intrinsics",
3424	>	e.getCause());
3425		}
3426		}
3427		}

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