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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.56 by dl, Thu May 27 16:46:48 2010 UTC vs.
Revision 1.161 by dl, Mon Dec 17 12:09:36 2012 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
6
7		package jsr166y;
8
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 worker thread
244	<	* creation is on-demand, triggered by task submissions,
245	<	* replacement of terminated workers, and/or compensation for
246	<	* blocked workers. However, all other support code is set up to
247	<	* work with other policies.
248	<	*
249	<	* 2. Bookkeeping for dynamically adding and removing workers. We
250	<	* maintain a given level of parallelism (or, if
251	<	* maintainsParallelism is false, at least avoid starvation). When
252	<	* some workers are known to be blocked (on joins or via
253	<	* ManagedBlocker), we may create or resume others to take their
254	<	* place until they unblock (see below). Implementing this
255	<	* requires counts of the number of "running" threads (i.e., those
256	<	* that are neither blocked nor artifically suspended) as well as
257	<	* the total number.  These two values are packed into one field,
258	<	* "workerCounts" because we need accurate snapshots when deciding
259	<	* to create, resume or suspend.  To support these decisions,
260	<	* updates to spare counts must be prospective (not
261	<	* retrospective).  For example, the running count is decremented
262	<	* before blocking by a thread about to block as a spare, but
263	<	* incremented by the thread about to unblock it. Updates upon
264	<	* resumption ofr threads blocking in awaitJoin or awaitBlocker
265	<	* cannot usually be prospective, so the running count is in
266	<	* general an upper bound of the number of productively running
267	<	* threads Updates to the workerCounts field sometimes transiently
268	<	* encounter a fair amount of contention when join dependencies
269	<	* are such that many threads block or unblock at about the same
270	<	* time. We alleviate this by sometimes bundling updates (for
271	<	* example blocking one thread on join and resuming a spare cancel
272	<	* each other out), and in most other cases performing an
273	<	* alternative action like releasing waiters or locating spares.
274	<	*
275	<	* 3. Maintaining global run state. The run state of the pool
276	<	* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to
277	<	* those in other Executor implementations, as well as a count of
278	<	* "active" workers -- those that are, or soon will be, or
279	<	* recently were executing tasks. The runLevel and active count
280	<	* are packed together in order to correctly trigger shutdown and
281	<	* termination. Without care, active counts can be subject to very
282	<	* high contention.  We substantially reduce this contention by
283	<	* relaxing update rules.  A worker must claim active status
284	<	* prospectively, by activating if it sees that a submitted or
285	<	* stealable task exists (it may find after activating that the
286	<	* task no longer exists). It stays active while processing this
287	<	* task (if it exists) and any other local subtasks it produces,
288	<	* until it cannot find any other tasks. It then tries
289	<	* inactivating (see method preStep), but upon update contention
290	<	* instead scans for more tasks, later retrying inactivation if it
291	<	* doesn't find any.
292	<	*
293	<	* 4. Managing idle workers waiting for tasks. We cannot let
294	<	* workers spin indefinitely scanning for tasks when none are
295	<	* available. On the other hand, we must quickly prod them into
296	<	* action when new tasks are submitted or generated.  We
297	<	* park/unpark these idle workers using an event-count scheme.
298	<	* Field eventCount is incremented upon events that may enable
299	<	* workers that previously could not find a task to now find one:
300	<	* Submission of a new task to the pool, or another worker pushing
301	<	* a task onto a previously empty queue.  (We also use this
302	<	* mechanism for termination and reconfiguration actions that
303	<	* require wakeups of idle workers).  Each worker maintains its
304	<	* last known event count, and blocks when a scan for work did not
305	<	* find a task AND its lastEventCount matches the current
306	<	* eventCount. Waiting idle workers are recorded in a variant of
307	<	* Treiber stack headed by field eventWaiters which, when nonzero,
308	<	* encodes the thread index and count awaited for by the worker
309	<	* thread most recently calling eventSync. This thread in turn has
310	<	* a record (field nextEventWaiter) for the next waiting worker.
311	<	* In addition to allowing simpler decisions about need for
312	<	* wakeup, the event count bits in eventWaiters serve the role of
313	<	* tags to avoid ABA errors in Treiber stacks.  To reduce delays
314	<	* in task diffusion, workers not otherwise occupied may invoke
315	<	* method releaseWaiters, that removes and signals (unparks)
316	<	* workers not waiting on current count. To minimize task
317	<	* production stalls associate with signalling, any worker pushing
318	<	* a task on an empty queue invokes the weaker method signalWork,
319	<	* that only releases idle workers until it detects interference
320	<	* by other threads trying to release, and lets them take
321	<	* over. The net effect is a tree-like diffusion of signals, where
322	<	* released threads (and possibly others) help with unparks.  To
323	<	* further reduce contention effects a bit, failed CASes to
324	<	* increment field eventCount are tolerated without retries.
325	<	* Conceptually they are merged into the same event, which is OK
326	<	* when their only purpose is to enable workers to scan for work.
327	<	*
328	<	* 5. Managing suspension of extra workers. When a worker is about
329	<	* to block waiting for a join (or via ManagedBlockers), we may
330	<	* create a new thread to maintain parallelism level, or at least
331	<	* avoid starvation (see below). Usually, extra threads are needed
332	<	* for only very short periods, yet join dependencies are such
333	<	* that we sometimes need them in bursts. Rather than create new
334	<	* threads each time this happens, we suspend no-longer-needed
335	<	* extra ones as "spares". For most purposes, we don't distinguish
336	<	* "extra" spare threads from normal "core" threads: On each call
337	<	* to preStep (the only point at which we can do this) a worker
338	<	* checks to see if there are now too many running workers, and if
339	<	* so, suspends itself.  Methods awaitJoin and awaitBlocker look
340	<	* for suspended threads to resume before considering creating a
341	<	* new replacement. We don't need a special data structure to
342	<	* maintain spares; simply scanning the workers array looking for
343	<	* worker.isSuspended() is fine because the calling thread is
344	<	* otherwise not doing anything useful anyway; we are at least as
345	<	* happy if after locating a spare, the caller doesn't actually
346	<	* block because the join is ready before we try to adjust and
347	<	* compensate.  Note that this is intrinsically racy.  One thread
348	<	* may become a spare at about the same time as another is
349	<	* needlessly being created. We counteract this and related slop
350	<	* in part by requiring resumed spares to immediately recheck (in
351	<	* preStep) to see whether they they should re-suspend. The only
352	<	* effective difference between "extra" and "core" threads is that
353	<	* we allow the "extra" ones to time out and die if they are not
354	<	* resumed within a keep-alive interval of a few seconds. This is
355	<	* implemented mainly within ForkJoinWorkerThread, but requires
356	<	* some coordination (isTrimmed() -- meaning killed while
357	<	* suspended) to correctly maintain pool counts.
358	<	*
359	<	* 6. Deciding when to create new workers. The main dynamic
360	<	* control in this class is deciding when to create extra threads,
361	<	* in methods awaitJoin and awaitBlocker. We always
362	<	* need to create one when the number of running threads becomes
363	<	* zero. But because blocked joins are typically dependent, we
364	<	* don't necessarily need or want one-to-one replacement. Using a
365	<	* one-to-one compensation rule often leads to enough useless
366	<	* overhead creating, suspending, resuming, and/or killing threads
367	<	* to signficantly degrade throughput.  We use a rule reflecting
368	<	* the idea that, the more spare threads you already have, the
369	<	* more evidence you need to create another one. The "evidence"
370	<	* here takes two forms: (1) Using a creation threshold expressed
371	<	* in terms of the current deficit -- target minus running
372	<	* threads. To reduce flickering and drift around target values,
373	<	* the relation is quadratic: adding a spare if (dc*dc)>=(sc*pc)
374	<	* (where dc is deficit, sc is number of spare threads and pc is
375	<	* target parallelism.)  (2) Using a form of adaptive
376	<	* spionning. requiring a number of threshold checks proportional
377	<	* to the number of spare threads.  This effectively reduces churn
378	<	* at the price of systematically undershooting target parallelism
379	<	* when many threads are blocked.  However, biasing toward
380	<	* undeshooting partially compensates for the above mechanics to
381	<	* suspend extra threads, that normally lead to overshoot because
382	<	* we can only suspend workers in-between top-level actions. It
383	<	* also better copes with the fact that some of the methods in
384	<	* this class tend to never become compiled (but are interpreted),
385	<	* so some components of the entire set of controls might execute
386	<	* many times faster than others. And similarly for cases where
387	<	* the apparent lack of work is just due to GC stalls and other
388	<	* transient system activity.
389	<	*
390	<	* 7. Maintaining other configuration parameters and monitoring
391	<	* statistics. Updates to fields controlling parallelism level,
392	<	* max size, etc can only meaningfully take effect for individual
393	<	* threads upon their next top-level actions; i.e., between
394	<	* stealing/running tasks/submission, which are separated by calls
395	<	* to preStep.  Memory ordering for these (assumed infrequent)
396	<	* reconfiguration calls is ensured by using reads and writes to
397	<	* volatile field workerCounts (that must be read in preStep anyway)
398	<	* as "fences" -- user-level reads are preceded by reads of
399	<	* workCounts, and writes are followed by no-op CAS to
400	<	* workerCounts. The values reported by other management and
401	<	* monitoring methods are either computed on demand, or are kept
402	<	* in fields that are only updated when threads are otherwise
403	<	* idle.
404	<	*
405	<	* Beware that there is a lot of representation-level coupling
406	<	* among classes ForkJoinPool, ForkJoinWorkerThread, and
407	<	* ForkJoinTask.  For example, direct access to "workers" array by
408	<	* workers, and direct access to ForkJoinTask.status by both
409	<	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
220	>	* decentralized control -- workers mostly take tasks from
221	>	* themselves or each other. We cannot negate this in the
222	>	* implementation of other management responsibilities. The main
223	>	* tactic for avoiding bottlenecks is packing nearly all
224	>	* essentially atomic control state into two volatile variables
225	>	* that are by far most often read (not written) as status and
226	>	* consistency checks.
227	>	*
228	>	* Field "ctl" contains 64 bits holding all the information needed
229	>	* to atomically decide to add, inactivate, enqueue (on an event
230	>	* queue), dequeue, and/or re-activate workers.  To enable this
231	>	* packing, we restrict maximum parallelism to (1<<15)-1 (which is
232	>	* far in excess of normal operating range) to allow ids, counts,
233	>	* and their negations (used for thresholding) to fit into 16bit
234	>	* fields.
235	>	*
236	>	* Field "plock" is a form of sequence lock with a saturating
237	>	* shutdown bit (similarly for per-queue "qlocks"), mainly
238	>	* protecting updates to the workQueues array, as well as to
239	>	* enable shutdown.  When used as a lock, it is normally only very
240	>	* briefly held, so is nearly always available after at most a
241	>	* brief spin, but we use a monitor-based backup strategy to
242	>	* block when needed.
243	>	*
244	>	* Recording WorkQueues.  WorkQueues are recorded in the
245	>	* "workQueues" array that is created upon first use and expanded
246	>	* if necessary.  Updates to the array while recording new workers
247	>	* and unrecording terminated ones are protected from each other
248	>	* by a lock but the array is otherwise concurrently readable, and
249	>	* accessed directly.  To simplify index-based operations, the
250	>	* array size is always a power of two, and all readers must
251	>	* tolerate null slots. Worker queues are at odd indices. Shared
252	>	* (submission) queues are at even indices, up to a maximum of 64
253	>	* slots, to limit growth even if array needs to expand to add
254	>	* more workers. Grouping them together in this way simplifies and
255	>	* speeds up task scanning.
256	>	*
257	>	* All worker thread creation is on-demand, triggered by task
258	>	* submissions, replacement of terminated workers, and/or
259	>	* compensation for blocked workers. However, all other support
260	>	* code is set up to work with other policies.  To ensure that we
261	>	* do not hold on to worker references that would prevent GC, ALL
262	>	* accesses to workQueues are via indices into the workQueues
263	>	* array (which is one source of some of the messy code
264	>	* constructions here). In essence, the workQueues array serves as
265	>	* a weak reference mechanism. Thus for example the wait queue
266	>	* field of ctl stores indices, not references.  Access to the
267	>	* workQueues in associated methods (for example signalWork) must
268	>	* both index-check and null-check the IDs. All such accesses
269	>	* ignore bad IDs by returning out early from what they are doing,
270	>	* since this can only be associated with termination, in which
271	>	* case it is OK to give up.  All uses of the workQueues array
272	>	* also check that it is non-null (even if previously
273	>	* non-null). This allows nulling during termination, which is
274	>	* currently not necessary, but remains an option for
275	>	* resource-revocation-based shutdown schemes. It also helps
276	>	* reduce JIT issuance of uncommon-trap code, which tends to
277	>	* unnecessarily complicate control flow in some methods.
278	>	*
279	>	* Event Queuing. Unlike HPC work-stealing frameworks, we cannot
280	>	* let workers spin indefinitely scanning for tasks when none can
281	>	* be found immediately, and we cannot start/resume workers unless
282	>	* there appear to be tasks available.  On the other hand, we must
283	>	* quickly prod them into action when new tasks are submitted or
284	>	* generated. In many usages, ramp-up time to activate workers is
285	>	* the main limiting factor in overall performance (this is
286	>	* compounded at program start-up by JIT compilation and
287	>	* allocation). So we try to streamline this as much as possible.
288	>	* We park/unpark workers after placing in an event wait queue
289	>	* when they cannot find work. This "queue" is actually a simple
290	>	* Treiber stack, headed by the "id" field of ctl, plus a 15bit
291	>	* counter value (that reflects the number of times a worker has
292	>	* been inactivated) to avoid ABA effects (we need only as many
293	>	* version numbers as worker threads). Successors are held in
294	>	* field WorkQueue.nextWait.  Queuing deals with several intrinsic
295	>	* races, mainly that a task-producing thread can miss seeing (and
296	>	* signalling) another thread that gave up looking for work but
297	>	* has not yet entered the wait queue. We solve this by requiring
298	>	* a full sweep of all workers (via repeated calls to method
299	>	* scan()) both before and after a newly waiting worker is added
300	>	* to the wait queue. During a rescan, the worker might release
301	>	* some other queued worker rather than itself, which has the same
302	>	* net effect. Because enqueued workers may actually be rescanning
303	>	* rather than waiting, we set and clear the "parker" field of
304	>	* WorkQueues to reduce unnecessary calls to unpark.  (This
305	>	* requires a secondary recheck to avoid missed signals.)  Note
306	>	* the unusual conventions about Thread.interrupts surrounding
307	>	* parking and other blocking: Because interrupts are used solely
308	>	* to alert threads to check termination, which is checked anyway
309	>	* upon blocking, we clear status (using Thread.interrupted)
310	>	* before any call to park, so that park does not immediately
311	>	* return due to status being set via some other unrelated call to
312	>	* interrupt in user code.
313	>	*
314	>	* Signalling.  We create or wake up workers only when there
315	>	* appears to be at least one task they might be able to find and
316	>	* execute. However, many other threads may notice the same task
317	>	* and each signal to wake up a thread that might take it. So in
318	>	* general, pools will be over-signalled.  When a submission is
319	>	* added or another worker adds a task to a queue that 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 commonPool 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.
512		* A {@code ForkJoinWorkerThreadFactory} must be defined and used
#	Line 346 | 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
373	<	* permission to modify threads.
374	<	*/
375	<	private static void checkPermission() {
376	<	SecurityManager security = System.getSecurityManager();
377	<	if (security != null)
378	<	security.checkPermission(modifyThreadPermission);
379	<	}
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	>	* @throw 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	<	*/
436	<	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	<	private static final int  EVENT_COUNT_SHIFT = 32;
827	<	private static final long WAITER_INDEX_MASK = (1L << EVENT_COUNT_SHIFT)-1L;
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	<	/**
839	<	* A counter for events that may wake up worker threads:
840	<	*   - Submission of a new task to the pool
841	<	*   - A worker pushing a task on an empty queue
842	<	*   - termination and reconfiguration
843	<	*/
844	<	private volatile int eventCount;
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	<	* Lifecycle control. The low word contains the number of workers
855	<	* that are (probably) executing tasks. This value is atomically
856	<	* incremented before a worker gets a task to run, and decremented
857	<	* when worker has no tasks and cannot find any.  Bits 16-18
858	<	* contain runLevel value. When all are zero, the pool is
859	<	* running. Level transitions are monotonic (running -> shutdown
860	<	* -> terminating -> terminated) so each transition adds a bit.
861	<	* These are bundled together to ensure consistent read for
458	<	* termination checks (i.e., that runLevel is at least SHUTDOWN
459	<	* and active threads is zero).
460	<	*/
461	<	private volatile int runState;
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	<	// Note: The order among run level values matters.
864	<	private static final int RUNLEVEL_SHIFT     = 16;
865	<	private static final int SHUTDOWN           = 1 << RUNLEVEL_SHIFT;
866	<	private static final int TERMINATING        = 1 << (RUNLEVEL_SHIFT + 1);
867	<	private static final int TERMINATED         = 1 << (RUNLEVEL_SHIFT + 2);
868	<	private static final int ACTIVE_COUNT_MASK  = (1 << RUNLEVEL_SHIFT) - 1;
869	<	private static final int ONE_ACTIVE         = 1; // active update delta
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	<	/**
878	<	* Holds number of total (i.e., created and not yet terminated)
879	<	* and running (i.e., not blocked on joins or other managed sync)
880	<	* threads, packed together to ensure consistent snapshot when
881	<	* making decisions about creating and suspending spare
882	<	* threads. Updated only by CAS. Note that adding a new worker
883	<	* requires incrementing both counts, since workers start off in
884	<	* running state.  This field is also used for memory-fencing
885	<	* configuration parameters.
886	<	*/
887	<	private volatile int workerCounts;
877	>	// Specialized execution methods
878	>
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, and maintainsParallelism are
907	<	* non-volatile, but external reads/writes use workerCount fences
908	<	* to ensure visability.
909	<	*/
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	>	int s;
1030	>	try {
1031	>	U = getUnsafe();
1032	>	Class<?> k = WorkQueue.class;
1033	>	Class<?> ak = ForkJoinTask[].class;
1034	>	QLOCK = U.objectFieldOffset
1035	>	(k.getDeclaredField("qlock"));
1036	>	ABASE = U.arrayBaseOffset(ak);
1037	>	s = U.arrayIndexScale(ak);
1038	>	} catch (Exception e) {
1039	>	throw new Error(e);
1040	>	}
1041	>	if ((s & (s-1)) != 0)
1042	>	throw new Error("data type scale not a power of two");
1043	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
1044	>	}
1045	>	}
1046	>
1047	>	// static fields (initialized in static initializer below)
1048
1049		/**
1050	<	* The target parallelism level.
1050	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
1051	>	* overridden in ForkJoinPool constructors.
1052		*/
1053	<	private int parallelism;
1053	>	public static final ForkJoinWorkerThreadFactory
1054	>	defaultForkJoinWorkerThreadFactory;
1055
1056		/**
1057	<	* The maximum allowed pool size.
1057	>	* Per-thread submission bookkeeping. Shared across all pools
1058	>	* to reduce ThreadLocal pollution and because random motion
1059	>	* to avoid contention in one pool is likely to hold for others.
1060	>	* Lazily initialized on first submission (but null-checked
1061	>	* in other contexts to avoid unnecessary initialization).
1062		*/
1063	<	private int maxPoolSize;
1063	>	static final ThreadLocal<Submitter> submitters;
1064
1065		/**
1066	<	* True if use local fifo, not default lifo, for local polling
1067	<	* Replicated by ForkJoinWorkerThreads
1066	>	* Permission required for callers of methods that may start or
1067	>	* kill threads.
1068		*/
1069	<	private volatile boolean locallyFifo;
1069	>	private static final RuntimePermission modifyThreadPermission;
1070
1071		/**
1072	<	* Controls whether to add spares to maintain parallelism
1072	>	* Common (static) pool. Non-null for public use unless a static
1073	>	* construction exception, but internal usages null-check on use
1074	>	* to paranoically avoid potential initialization circularities
1075	>	* as well as to simplify generated code.
1076		*/
1077	<	private boolean maintainsParallelism;
1077	>	static final ForkJoinPool commonPool;
1078
1079		/**
1080	<	* The uncaught exception handler used when any worker
517	<	* abruptly terminates
1080	>	* Common pool parallelism. Must equal commonPool.parallelism.
1081		*/
1082	<	private volatile Thread.UncaughtExceptionHandler ueh;
1082	>	static final int commonPoolParallelism;
1083
1084		/**
1085	<	* Pool number, just for assigning useful names to worker threads
1085	>	* Sequence number for creating workerNamePrefix.
1086		*/
1087	<	private final int poolNumber;
525	<
526	<	// utilities for updating fields
1087	>	private static int poolNumberSequence;
1088
1089		/**
1090	<	* Adds delta to running count.  Used mainly by ForkJoinTask.
1090	>	* Return the next sequence number. We don't expect this to
1091	>	* ever contend so use simple builtin sync.
1092		*/
1093	<	final void updateRunningCount(int delta) {
1094	<	int wc;
533	<	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
534	<	wc = workerCounts,
535	<	wc + delta));
1093	>	private static final synchronized int nextPoolId() {
1094	>	return ++poolNumberSequence;
1095		}
1096
1097	+	// static constants
1098	+
1099		/**
1100	<	* Decrements running count unless already zero
1100	>	* Initial timeout value (in nanoseconds) for the thread
1101	>	* triggering quiescence to park waiting for new work. On timeout,
1102	>	* the thread will instead try to shrink the number of
1103	>	* workers. The value should be large enough to avoid overly
1104	>	* aggressive shrinkage during most transient stalls (long GCs
1105	>	* etc).
1106		*/
1107	<	final boolean tryDecrementRunningCount() {
542	<	int wc = workerCounts;
543	<	if ((wc & RUNNING_COUNT_MASK) == 0)
544	<	return false;
545	<	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
546	<	wc, wc - ONE_RUNNING);
547	<	}
1107	>	private static final long IDLE_TIMEOUT      = 2000L * 1000L * 1000L; // 2sec
1108
1109		/**
1110	<	* Write fence for user modifications of pool parameters
551	<	* (parallelism. etc).  Note that it doesn't matter if CAS fails.
1110	>	* Timeout value when there are more threads than parallelism level
1111		*/
1112	<	private void workerCountWriteFence() {
554	<	int wc;
555	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
556	<	wc = workerCounts, wc);
557	<	}
1112	>	private static final long FAST_IDLE_TIMEOUT =  200L * 1000L * 1000L;
1113
1114		/**
1115	<	* Read fence for external reads of pool parameters
561	<	* (parallelism. maxPoolSize, etc).
1115	>	* Tolerance for idle timeouts, to cope with timer undershoots
1116		*/
1117	<	private void workerCountReadFence() {
564	<	int ignore = workerCounts;
565	<	}
1117	>	private static final long TIMEOUT_SLOP = 2000000L;
1118
1119		/**
1120	<	* Tries incrementing active count; fails on contention.
1121	<	* Called by workers before executing tasks.
1122	<	*
1123	<	* @return true on success
1120	>	* The maximum stolen->joining link depth allowed in method
1121	>	* tryHelpStealer.  Must be a power of two.  Depths for legitimate
1122	>	* chains are unbounded, but we use a fixed constant to avoid
1123	>	* (otherwise unchecked) cycles and to bound staleness of
1124	>	* traversal parameters at the expense of sometimes blocking when
1125	>	* we could be helping.
1126		*/
1127	<	final boolean tryIncrementActiveCount() {
574	<	int c;
575	<	return UNSAFE.compareAndSwapInt(this, runStateOffset,
576	<	c = runState, c + ONE_ACTIVE);
577	<	}
1127	>	private static final int MAX_HELP = 64;
1128
1129		/**
1130	<	* Tries decrementing active count; fails on contention.
1131	<	* Called when workers cannot find tasks to run.
1130	>	* Increment for seed generators. See class ThreadLocal for
1131	>	* explanation.
1132		*/
1133	<	final boolean tryDecrementActiveCount() {
584	<	int c;
585	<	return UNSAFE.compareAndSwapInt(this, runStateOffset,
586	<	c = runState, c - ONE_ACTIVE);
587	<	}
1133	>	private static final int SEED_INCREMENT = 0x61c88647;
1134
1135		/**
1136	<	* Advances to at least the given level. Returns true if not
1137	<	* already in at least the given level.
1136	>	* Bits and masks for control variables
1137	>	*
1138	>	* Field ctl is a long packed with:
1139	>	* AC: Number of active running workers minus target parallelism (16 bits)
1140	>	* TC: Number of total workers minus target parallelism (16 bits)
1141	>	* ST: true if pool is terminating (1 bit)
1142	>	* EC: the wait count of top waiting thread (15 bits)
1143	>	* ID: poolIndex of top of Treiber stack of waiters (16 bits)
1144	>	*
1145	>	* When convenient, we can extract the upper 32 bits of counts and
1146	>	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
1147	>	* (int)ctl.  The ec field is never accessed alone, but always
1148	>	* together with id and st. The offsets of counts by the target
1149	>	* parallelism and the positionings of fields makes it possible to
1150	>	* perform the most common checks via sign tests of fields: When
1151	>	* ac is negative, there are not enough active workers, when tc is
1152	>	* negative, there are not enough total workers, and when e is
1153	>	* negative, the pool is terminating.  To deal with these possibly
1154	>	* negative fields, we use casts in and out of "short" and/or
1155	>	* signed shifts to maintain signedness.
1156	>	*
1157	>	* When a thread is queued (inactivated), its eventCount field is
1158	>	* set negative, which is the only way to tell if a worker is
1159	>	* prevented from executing tasks, even though it must continue to
1160	>	* scan for them to avoid queuing races. Note however that
1161	>	* eventCount updates lag releases so usage requires care.
1162	>	*
1163	>	* Field plock is an int packed with:
1164	>	* SHUTDOWN: true if shutdown is enabled (1 bit)
1165	>	* SEQ:  a sequence lock, with PL_LOCK bit set if locked (30 bits)
1166	>	* SIGNAL: set when threads may be waiting on the lock (1 bit)
1167	>	*
1168	>	* The sequence number enables simple consistency checks:
1169	>	* Staleness of read-only operations on the workQueues array can
1170	>	* be checked by comparing plock before vs after the reads.
1171		*/
593	–	private boolean advanceRunLevel(int level) {
594	–	for (;;) {
595	–	int s = runState;
596	–	if ((s & level) != 0)
597	–	return false;
598	–	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level))
599	–	return true;
600	–	}
601	–	}
1172
1173	<	// workers array maintenance
1173	>	// bit positions/shifts for fields
1174	>	private static final int  AC_SHIFT   = 48;
1175	>	private static final int  TC_SHIFT   = 32;
1176	>	private static final int  ST_SHIFT   = 31;
1177	>	private static final int  EC_SHIFT   = 16;
1178
1179	<	/**
1180	<	* Records and returns a workers array index for new worker.
1179	>	// bounds
1180	>	private static final int  SMASK      = 0xffff;  // short bits
1181	>	private static final int  MAX_CAP    = 0x7fff;  // max #workers - 1
1182	>	private static final int  EVENMASK   = 0xfffe;  // even short bits
1183	>	private static final int  SQMASK     = 0x007e;  // max 64 (even) slots
1184	>	private static final int  SHORT_SIGN = 1 << 15;
1185	>	private static final int  INT_SIGN   = 1 << 31;
1186	>
1187	>	// masks
1188	>	private static final long STOP_BIT   = 0x0001L << ST_SHIFT;
1189	>	private static final long AC_MASK    = ((long)SMASK) << AC_SHIFT;
1190	>	private static final long TC_MASK    = ((long)SMASK) << TC_SHIFT;
1191	>
1192	>	// units for incrementing and decrementing
1193	>	private static final long TC_UNIT    = 1L << TC_SHIFT;
1194	>	private static final long AC_UNIT    = 1L << AC_SHIFT;
1195	>
1196	>	// masks and units for dealing with u = (int)(ctl >>> 32)
1197	>	private static final int  UAC_SHIFT  = AC_SHIFT - 32;
1198	>	private static final int  UTC_SHIFT  = TC_SHIFT - 32;
1199	>	private static final int  UAC_MASK   = SMASK << UAC_SHIFT;
1200	>	private static final int  UTC_MASK   = SMASK << UTC_SHIFT;
1201	>	private static final int  UAC_UNIT   = 1 << UAC_SHIFT;
1202	>	private static final int  UTC_UNIT   = 1 << UTC_SHIFT;
1203	>
1204	>	// masks and units for dealing with e = (int)ctl
1205	>	private static final int E_MASK      = 0x7fffffff; // no STOP_BIT
1206	>	private static final int E_SEQ       = 1 << EC_SHIFT;
1207	>
1208	>	// plock bits
1209	>	private static final int SHUTDOWN    = 1 << 31;
1210	>	private static final int PL_LOCK     = 2;
1211	>	private static final int PL_SIGNAL   = 1;
1212	>	private static final int PL_SPINS    = 1 << 8;
1213	>
1214	>	// access mode for WorkQueue
1215	>	static final int LIFO_QUEUE          =  0;
1216	>	static final int FIFO_QUEUE          =  1;
1217	>	static final int SHARED_QUEUE        = -1;
1218	>
1219	>	// bounds for #steps in scan loop -- must be power 2 minus 1
1220	>	private static final int MIN_SCAN    = 0x1ff;   // cover estimation slop
1221	>	private static final int MAX_SCAN    = 0x1ffff; // 4 * max workers
1222	>
1223	>	// Instance fields
1224	>
1225	>	/*
1226	>	* Field layout of this class tends to matter more than one would
1227	>	* like. Runtime layout order is only loosely related to
1228	>	* declaration order and may differ across JVMs, but the following
1229	>	* empirically works OK on current JVMs.
1230	>	*/
1231	>
1232	>	// Heuristic padding to ameliorate unfortunate memory placements
1233	>	volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
1234	>
1235	>	volatile long stealCount;                  // collects worker counts
1236	>	volatile long ctl;                         // main pool control
1237	>	volatile int plock;                        // shutdown status and seqLock
1238	>	volatile int indexSeed;                    // worker/submitter index seed
1239	>	final int config;                          // mode and parallelism level
1240	>	WorkQueue[] workQueues;                    // main registry
1241	>	final ForkJoinWorkerThreadFactory factory;
1242	>	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1243	>	final String workerNamePrefix;             // to create worker name string
1244	>
1245	>	volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
1246	>	volatile Object pad18, pad19, pad1a, pad1b;
1247	>
1248	>	/*
1249	>	* Acquires the plock lock to protect worker array and related
1250	>	* updates. This method is called only if an initial CAS on plock
1251	>	* fails. This acts as a spinLock for normal cases, but falls back
1252	>	* to builtin monitor to block when (rarely) needed. This would be
1253	>	* a terrible idea for a highly contended lock, but works fine as
1254	>	* a more conservative alternative to a pure spinlock.
1255		*/
1256	<	private int recordWorker(ForkJoinWorkerThread w) {
1257	<	// Try using slot totalCount-1. If not available, scan and/or resize
1258	<	int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1;
1259	<	final ReentrantLock lock = this.workerLock;
1260	<	lock.lock();
1261	<	try {
1262	<	ForkJoinWorkerThread[] ws = workers;
1263	<	int nws = ws.length;
1264	<	if (k < 0 || k >= nws || ws[k] != null) {
1265	<	for (k = 0; k < nws && ws[k] != null; ++k)
1266	<	;
1267	<	if (k == nws)
1268	<	ws = Arrays.copyOf(ws, nws << 1);
1256	>	private int acquirePlock() {
1257	>	int spins = PL_SPINS, r = 0, ps, nps;
1258	>	for (;;) {
1259	>	if (((ps = plock) & PL_LOCK) == 0 &&
1260	>	U.compareAndSwapInt(this, PLOCK, ps, nps = ps + PL_LOCK))
1261	>	return nps;
1262	>	else if (r == 0) { // randomize spins if possible
1263	>	Thread t = Thread.currentThread(); WorkQueue w; Submitter z;
1264	>	if ((t instanceof ForkJoinWorkerThread) &&
1265	>	(w = ((ForkJoinWorkerThread)t).workQueue) != null)
1266	>	r = w.seed;
1267	>	else if ((z = submitters.get()) != null)
1268	>	r = z.seed;
1269	>	else
1270	>	r = 1;
1271	>	}
1272	>	else if (spins >= 0) {
1273	>	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1274	>	if (r >= 0)
1275	>	--spins;
1276	>	}
1277	>	else if (U.compareAndSwapInt(this, PLOCK, ps, ps | PL_SIGNAL)) {
1278	>	synchronized (this) {
1279	>	if ((plock & PL_SIGNAL) != 0) {
1280	>	try {
1281	>	wait();
1282	>	} catch (InterruptedException ie) {
1283	>	try {
1284	>	Thread.currentThread().interrupt();
1285	>	} catch (SecurityException ignore) {
1286	>	}
1287	>	}
1288	>	}
1289	>	else
1290	>	notifyAll();
1291	>	}
1292		}
622	–	ws[k] = w;
623	–	workers = ws; // volatile array write ensures slot visibility
624	–	} finally {
625	–	lock.unlock();
1293		}
627	–	return k;
1294		}
1295
1296		/**
1297	<	* Nulls out record of worker in workers array
1297	>	* Unlocks and signals any thread waiting for plock. Called only
1298	>	* when CAS of seq value for unlock fails.
1299		*/
1300	<	private void forgetWorker(ForkJoinWorkerThread w) {
1301	<	int idx = w.poolIndex;
1302	<	// Locking helps method recordWorker avoid unecessary expansion
1303	<	final ReentrantLock lock = this.workerLock;
1304	<	lock.lock();
1305	<	try {
1306	<	ForkJoinWorkerThread[] ws = workers;
1307	<	if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify
1308	<	ws[idx] = null;
1309	<	} finally {
1310	<	lock.unlock();
1300	>	private void releasePlock(int ps) {
1301	>	plock = ps;
1302	>	synchronized (this) { notifyAll(); }
1303	>	}
1304	>
1305	>	/**
1306	>	* Performs secondary initialization, called when plock is zero.
1307	>	* Creates workQueue array and sets plock to a valid value.  The
1308	>	* lock body must be exception-free (so no try/finally) so we
1309	>	* optimistically allocate new array outside the lock and throw
1310	>	* away if (very rarely) not needed. (A similar tactic is used in
1311	>	* fullExternalPush.)  Because the plock seq value can eventually
1312	>	* wrap around zero, this method harmlessly fails to reinitialize
1313	>	* if workQueues exists, while still advancing plock.
1314	>	*
1315	>	* Additionally tries to create the first worker.
1316	>	*/
1317	>	private void initWorkers() {
1318	>	WorkQueue[] ws, nws; int ps;
1319	>	int p = config & SMASK;        // find power of two table size
1320	>	int n = (p > 1) ? p - 1 : 1;   // ensure at least 2 slots
1321	>	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
1322	>	n = (n + 1) << 1;
1323	>	if ((ws = workQueues) == null || ws.length == 0)
1324	>	nws = new WorkQueue[n];
1325	>	else
1326	>	nws = null;
1327	>	if (((ps = plock) & PL_LOCK) != 0 ||
1328	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1329	>	ps = acquirePlock();
1330	>	if (((ws = workQueues) == null || ws.length == 0) && nws != null)
1331	>	workQueues = nws;
1332	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1333	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1334	>	releasePlock(nps);
1335	>	tryAddWorker();
1336	>	}
1337	>
1338	>	/**
1339	>	* Tries to create and start one worker if fewer than target
1340	>	* parallelism level exist. Adjusts counts etc on failure.
1341	>	*/
1342	>	private void tryAddWorker() {
1343	>	long c; int u;
1344	>	while ((u = (int)((c = ctl) >>> 32)) < 0 &&
1345	>	(u & SHORT_SIGN) != 0 && (int)c == 0) {
1346	>	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) |
1347	>	((u + UAC_UNIT) & UAC_MASK)) << 32;
1348	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1349	>	ForkJoinWorkerThreadFactory fac;
1350	>	Throwable ex = null;
1351	>	ForkJoinWorkerThread wt = null;
1352	>	try {
1353	>	if ((fac = factory) != null &&
1354	>	(wt = fac.newThread(this)) != null) {
1355	>	wt.start();
1356	>	break;
1357	>	}
1358	>	} catch (Throwable e) {
1359	>	ex = e;
1360	>	}
1361	>	deregisterWorker(wt, ex);
1362	>	break;
1363	>	}
1364		}
1365		}
1366
1367	<	// adding and removing workers
1367	>	//  Registering and deregistering workers
1368
1369		/**
1370	<	* Tries to create and add new worker. Assumes that worker counts
1371	<	* are already updated to accommodate the worker, so adjusts on
1372	<	* failure.
1373	<	*
1374	<	* @return new worker or null if creation failed
1375	<	*/
1376	<	private ForkJoinWorkerThread addWorker() {
1377	<	ForkJoinWorkerThread w = null;
1370	>	* Callback from ForkJoinWorkerThread to establish and record its
1371	>	* WorkQueue. To avoid scanning bias due to packing entries in
1372	>	* front of the workQueues array, we treat the array as a simple
1373	>	* power-of-two hash table using per-thread seed as hash,
1374	>	* expanding as needed.
1375	>	*
1376	>	* @param wt the worker thread
1377	>	* @return the worker's queue
1378	>	*/
1379	>	final WorkQueue registerWorker(ForkJoinWorkerThread wt) {
1380	>	Thread.UncaughtExceptionHandler handler; WorkQueue[] ws; int s, ps;
1381	>	wt.setDaemon(true);
1382	>	if ((handler = ueh) != null)
1383	>	wt.setUncaughtExceptionHandler(handler);
1384	>	do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed,
1385	>	s += SEED_INCREMENT) ||
1386	>	s == 0); // skip 0
1387	>	WorkQueue w = new WorkQueue(this, wt, config >>> 16, s);
1388	>	if (((ps = plock) & PL_LOCK) != 0 ||
1389	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1390	>	ps = acquirePlock();
1391	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1392		try {
1393	<	w = factory.newThread(this);
1394	<	} finally { // Adjust on either null or exceptional factory return
1395	<	if (w == null) {
1396	<	onWorkerCreationFailure();
1397	<	return null;
1393	>	if ((ws = workQueues) != null) {    // skip if shutting down
1394	>	int n = ws.length, m = n - 1;
1395	>	int r = (s << 1) | 1;           // use odd-numbered indices
1396	>	if (ws[r &= m] != null) {       // collision
1397	>	int probes = 0;             // step by approx half size
1398	>	int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2;
1399	>	while (ws[r = (r + step) & m] != null) {
1400	>	if (++probes >= n) {
1401	>	workQueues = ws = Arrays.copyOf(ws, n <<= 1);
1402	>	m = n - 1;
1403	>	probes = 0;
1404	>	}
1405	>	}
1406	>	}
1407	>	w.eventCount = w.poolIndex = r; // volatile write orders
1408	>	ws[r] = w;
1409		}
1410	+	} finally {
1411	+	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1412	+	releasePlock(nps);
1413		}
1414	<	w.start(recordWorker(w), locallyFifo, ueh);
1414	>	wt.setName(workerNamePrefix.concat(Integer.toString(w.poolIndex)));
1415		return w;
1416		}
1417
1418		/**
1419	<	* Adjusts counts upon failure to create worker
1420	<	*/
1421	<	private void onWorkerCreationFailure() {
1422	<	for (;;) {
1423	<	int wc = workerCounts;
1424	<	if ((wc >>> TOTAL_COUNT_SHIFT) > 0 &&
1425	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1426	<	wc, wc - (ONE_RUNNING|ONE_TOTAL)))
1427	<	break;
1419	>	* Final callback from terminating worker, as well as upon failure
1420	>	* to construct or start a worker.  Removes record of worker from
1421	>	* array, and adjusts counts. If pool is shutting down, tries to
1422	>	* complete termination.
1423	>	*
1424	>	* @param wt the worker thread or null if construction failed
1425	>	* @param ex the exception causing failure, or null if none
1426	>	*/
1427	>	final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1428	>	WorkQueue w = null;
1429	>	if (wt != null && (w = wt.workQueue) != null) {
1430	>	int ps;
1431	>	w.qlock = -1;                // ensure set
1432	>	long ns = w.nsteals, sc;     // collect steal count
1433	>	do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
1434	>	sc = stealCount, sc + ns));
1435	>	if (((ps = plock) & PL_LOCK) != 0 ||
1436	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1437	>	ps = acquirePlock();
1438	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1439	>	try {
1440	>	int idx = w.poolIndex;
1441	>	WorkQueue[] ws = workQueues;
1442	>	if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1443	>	ws[idx] = null;
1444	>	} finally {
1445	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1446	>	releasePlock(nps);
1447	>	}
1448		}
681	–	tryTerminate(false); // in case of failure during shutdown
682	–	}
1449
1450	<	/**
1451	<	* Create enough total workers to establish target parallelism,
1452	<	* giving up if terminating or addWorker fails
1453	<	*/
1454	<	private void ensureEnoughTotalWorkers() {
1455	<	int wc;
1456	<	while (((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < parallelism &&
1457	<	runState < TERMINATING) {
1458	<	if ((UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1459	<	wc, wc + (ONE_RUNNING|ONE_TOTAL)) &&
1460	<	addWorker() == null))
1461	<	break;
1450	>	long c;                          // adjust ctl counts
1451	>	do {} while (!U.compareAndSwapLong
1452	>	(this, CTL, c = ctl, (((c - AC_UNIT) & AC_MASK) |
1453	>	((c - TC_UNIT) & TC_MASK) |
1454	>	(c & ~(AC_MASK|TC_MASK)))));
1455	>
1456	>	if (!tryTerminate(false, false) && w != null && w.array != null) {
1457	>	w.cancelAll();               // cancel remaining tasks
1458	>	WorkQueue[] ws; WorkQueue v; Thread p; int u, i, e;
1459	>	while ((u = (int)((c = ctl) >>> 32)) < 0 && (e = (int)c) >= 0) {
1460	>	if (e > 0) {             // activate or create replacement
1461	>	if ((ws = workQueues) == null ||
1462	>	(i = e & SMASK) >= ws.length ||
1463	>	(v = ws[i]) != null)
1464	>	break;
1465	>	long nc = (((long)(v.nextWait & E_MASK)) |
1466	>	((long)(u + UAC_UNIT) << 32));
1467	>	if (v.eventCount != (e | INT_SIGN))
1468	>	break;
1469	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1470	>	v.eventCount = (e + E_SEQ) & E_MASK;
1471	>	if ((p = v.parker) != null)
1472	>	U.unpark(p);
1473	>	break;
1474	>	}
1475	>	}
1476	>	else {
1477	>	if ((short)u < 0)
1478	>	tryAddWorker();
1479	>	break;
1480	>	}
1481	>	}
1482		}
1483	+	if (ex == null)                     // help clean refs on way out
1484	+	ForkJoinTask.helpExpungeStaleExceptions();
1485	+	else                                // rethrow
1486	+	ForkJoinTask.rethrow(ex);
1487	+	}
1488	+
1489	+	// Submissions
1490	+
1491	+	/**
1492	+	* Unless shutting down, adds the given task to a submission queue
1493	+	* at submitter's current queue index (modulo submission
1494	+	* range). Only the most common path is directly handled in this
1495	+	* method. All others are relayed to fullExternalPush.
1496	+	*
1497	+	* @param task the task. Caller must ensure non-null.
1498	+	*/
1499	+	final void externalPush(ForkJoinTask<?> task) {
1500	+	WorkQueue[] ws; WorkQueue q; Submitter z; int m; ForkJoinTask<?>[] a;
1501	+	if ((z = submitters.get()) != null && plock > 0 &&
1502	+	(ws = workQueues) != null && (m = (ws.length - 1)) >= 0 &&
1503	+	(q = ws[m & z.seed & SQMASK]) != null &&
1504	+	U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock
1505	+	int b = q.base, s = q.top, n, an;
1506	+	if ((a = q.array) != null && (an = a.length) > (n = s + 1 - b)) {
1507	+	int j = (((an - 1) & s) << ASHIFT) + ABASE;
1508	+	U.putOrderedObject(a, j, task);
1509	+	q.top = s + 1;                     // push on to deque
1510	+	q.qlock = 0;
1511	+	if (n <= 2)
1512	+	signalWork(q);
1513	+	return;
1514	+	}
1515	+	q.qlock = 0;
1516	+	}
1517	+	fullExternalPush(task);
1518		}
1519
1520		/**
1521	<	* Final callback from terminating worker.  Removes record of
1522	<	* worker from array, and adjusts counts. If pool is shutting
1523	<	* down, tries to complete terminatation, else possibly replaces
1524	<	* the worker.
1525	<	*
1526	<	* @param w the worker
1527	<	*/
1528	<	final void workerTerminated(ForkJoinWorkerThread w) {
1529	<	if (w.active) { // force inactive
1530	<	w.active = false;
1531	<	do {} while (!tryDecrementActiveCount());
1532	<	}
1533	<	forgetWorker(w);
1534	<
1535	<	// Decrement total count, and if was running, running count
1536	<	// Spin (waiting for other updates) if either would be negative
1537	<	int nr = w.isTrimmed() ? 0 : ONE_RUNNING;
1538	<	int unit = ONE_TOTAL + nr;
1539	<	for (;;) {
1540	<	int wc = workerCounts;
1541	<	int rc = wc & RUNNING_COUNT_MASK;
1542	<	if (rc - nr < 0 || (wc >>> TOTAL_COUNT_SHIFT) == 0)
1543	<	Thread.yield(); // back off if waiting for other updates
1544	<	else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1545	<	wc, wc - unit))
1546	<	break;
1521	>	* Full version of externalPush. This method is called, among
1522	>	* other times, upon the first submission of the first task to the
1523	>	* pool, so must perform secondary initialization (via
1524	>	* initWorkers). It also detects first submission by an external
1525	>	* thread by looking up its ThreadLocal, and creates a new shared
1526	>	* queue if the one at index if empty or contended. The plock lock
1527	>	* body must be exception-free (so no try/finally) so we
1528	>	* optimistically allocate new queues outside the lock and throw
1529	>	* them away if (very rarely) not needed.
1530	>	*/
1531	>	private void fullExternalPush(ForkJoinTask<?> task) {
1532	>	int r = 0; // random index seed
1533	>	for (Submitter z = submitters.get();;) {
1534	>	WorkQueue[] ws; WorkQueue q; int ps, m, k;
1535	>	if (z == null) {
1536	>	if (U.compareAndSwapInt(this, INDEXSEED, r = indexSeed,
1537	>	r += SEED_INCREMENT) && r != 0)
1538	>	submitters.set(z = new Submitter(r));
1539	>	}
1540	>	else if (r == 0) {               // move to a different index
1541	>	r = z.seed;
1542	>	r ^= r << 13;                // same xorshift as WorkQueues
1543	>	r ^= r >>> 17;
1544	>	z.seed = r ^ (r << 5);
1545	>	}
1546	>	else if ((ps = plock) < 0)
1547	>	throw new RejectedExecutionException();
1548	>	else if (ps == 0 || (ws = workQueues) == null ||
1549	>	(m = ws.length - 1) < 0)
1550	>	initWorkers();
1551	>	else if ((q = ws[k = r & m & SQMASK]) != null) {
1552	>	if (q.qlock == 0 && U.compareAndSwapInt(q, QLOCK, 0, 1)) {
1553	>	ForkJoinTask<?>[] a = q.array;
1554	>	int s = q.top;
1555	>	boolean submitted = false;
1556	>	try {                      // locked version of push
1557	>	if ((a != null && a.length > s + 1 - q.base) ||
1558	>	(a = q.growArray()) != null) {   // must presize
1559	>	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
1560	>	U.putOrderedObject(a, j, task);
1561	>	q.top = s + 1;
1562	>	submitted = true;
1563	>	}
1564	>	} finally {
1565	>	q.qlock = 0;  // unlock
1566	>	}
1567	>	if (submitted) {
1568	>	signalWork(q);
1569	>	return;
1570	>	}
1571	>	}
1572	>	r = 0; // move on failure
1573	>	}
1574	>	else if (((ps = plock) & PL_LOCK) == 0) { // create new queue
1575	>	q = new WorkQueue(this, null, SHARED_QUEUE, r);
1576	>	if (((ps = plock) & PL_LOCK) != 0 ||
1577	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1578	>	ps = acquirePlock();
1579	>	if ((ws = workQueues) != null && k < ws.length && ws[k] == null)
1580	>	ws[k] = q;
1581	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1582	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1583	>	releasePlock(nps);
1584	>	}
1585	>	else
1586	>	r = 0; // try elsewhere while lock held
1587		}
727	–
728	–	accumulateStealCount(w); // collect final count
729	–	if (!tryTerminate(false))
730	–	ensureEnoughTotalWorkers();
1588		}
1589
1590	<	// Waiting for and signalling events
1590	>	// Maintaining ctl counts
1591
1592		/**
1593	<	* Ensures eventCount on exit is different (mod 2^32) than on
737	<	* entry.  CAS failures are OK -- any change in count suffices.
1593	>	* Increments active count; mainly called upon return from blocking.
1594		*/
1595	<	private void advanceEventCount() {
1596	<	int c;
1597	<	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
1595	>	final void incrementActiveCount() {
1596	>	long c;
1597	>	do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
1598		}
1599
1600		/**
1601	<	* Releases workers blocked on a count not equal to current count.
1601	>	* Tries to create or activate a worker if too few are active.
1602	>	*
1603	>	* @param q the (non-null) queue holding tasks to be signalled
1604		*/
1605	<	final void releaseWaiters() {
1606	<	long top;
1607	<	int id;
1608	<	while ((id = (int)((top = eventWaiters) & WAITER_INDEX_MASK)) > 0 &&
1609	<	(int)(top >>> EVENT_COUNT_SHIFT) != eventCount) {
1610	<	ForkJoinWorkerThread[] ws = workers;
1611	<	ForkJoinWorkerThread w;
1612	<	if (ws.length >= id && (w = ws[id - 1]) != null &&
1613	<	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
1614	<	top, w.nextWaiter))
1615	<	LockSupport.unpark(w);
1605	>	final void signalWork(WorkQueue q) {
1606	>	int hint = q.poolIndex;
1607	>	long c; int e, u, i, n; WorkQueue[] ws; WorkQueue w; Thread p;
1608	>	while ((u = (int)((c = ctl) >>> 32)) < 0) {
1609	>	if ((e = (int)c) > 0) {
1610	>	if ((ws = workQueues) != null && ws.length > (i = e & SMASK) &&
1611	>	(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
1612	>	long nc = (((long)(w.nextWait & E_MASK)) |
1613	>	((long)(u + UAC_UNIT) << 32));
1614	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1615	>	w.hint = hint;
1616	>	w.eventCount = (e + E_SEQ) & E_MASK;
1617	>	if ((p = w.parker) != null)
1618	>	U.unpark(p);
1619	>	break;
1620	>	}
1621	>	if (q.top - q.base <= 0)
1622	>	break;
1623	>	}
1624	>	else
1625	>	break;
1626	>	}
1627	>	else {
1628	>	if ((short)u < 0)
1629	>	tryAddWorker();
1630	>	break;
1631	>	}
1632		}
1633		}
1634
1635	+	// Scanning for tasks
1636	+
1637		/**
1638	<	* Advances eventCount and releases waiters until interference by
763	<	* other releasing threads is detected.
1638	>	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1639		*/
1640	<	final void signalWork() {
1641	<	int ec;
1642	<	UNSAFE.compareAndSwapInt(this, eventCountOffset, ec=eventCount, ec+1);
1643	<	outer:for (;;) {
1644	<	long top = eventWaiters;
1645	<	ec = eventCount;
1646	<	for (;;) {
1647	<	ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w;
1648	<	int id = (int)(top & WAITER_INDEX_MASK);
1649	<	if (id <= 0 || (int)(top >>> EVENT_COUNT_SHIFT) == ec)
1650	<	return;
1651	<	if ((ws = workers).length < id || (w = ws[id - 1]) == null ||
1652	<	!UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
1653	<	top, top = w.nextWaiter))
1654	<	continue outer;      // possibly stale; reread
1655	<	LockSupport.unpark(w);
1656	<	if (top != eventWaiters) // let someone else take over
1657	<	return;
1640	>	final void runWorker(WorkQueue w) {
1641	>	w.growArray(); // allocate queue
1642	>	do { w.runTask(scan(w)); } while (w.qlock >= 0);
1643	>	}
1644	>
1645	>	/**
1646	>	* Scans for and, if found, returns one task, else possibly
1647	>	* inactivates the worker. This method operates on single reads of
1648	>	* volatile state and is designed to be re-invoked continuously,
1649	>	* in part because it returns upon detecting inconsistencies,
1650	>	* contention, or state changes that indicate possible success on
1651	>	* re-invocation.
1652	>	*
1653	>	* The scan searches for tasks across queues (starting at a random
1654	>	* index, and relying on registerWorker to irregularly scatter
1655	>	* them within array to avoid bias), checking each at least twice.
1656	>	* The scan terminates upon either finding a non-empty queue, or
1657	>	* completing the sweep. If the worker is not inactivated, it
1658	>	* takes and returns a task from this queue. Otherwise, if not
1659	>	* activated, it signals workers (that may include itself) and
1660	>	* returns so caller can retry. Also returns for true if the
1661	>	* worker array may have changed during an empty scan.  On failure
1662	>	* to find a task, we take one of the following actions, after
1663	>	* which the caller will retry calling this method unless
1664	>	* terminated.
1665	>	*
1666	>	* * If pool is terminating, terminate the worker.
1667	>	*
1668	>	* * If not already enqueued, try to inactivate and enqueue the
1669	>	* worker on wait queue. Or, if inactivating has caused the pool
1670	>	* to be quiescent, relay to idleAwaitWork to possibly shrink
1671	>	* pool.
1672	>	*
1673	>	* * If already enqueued and none of the above apply, possibly
1674	>	* park awaiting signal, else lingering to help scan and signal.
1675	>	*
1676	>	* * If a non-empty queue discovered or left as a hint,
1677	>	* help wake up other workers before return
1678	>	*
1679	>	* @param w the worker (via its WorkQueue)
1680	>	* @return a task or null if none found
1681	>	*/
1682	>	private final ForkJoinTask<?> scan(WorkQueue w) {
1683	>	WorkQueue[] ws; int m;
1684	>	int ps = plock;                          // read plock before ws
1685	>	if (w != null && (ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1686	>	int ec = w.eventCount;               // ec is negative if inactive
1687	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1688	>	w.hint = -1;                         // update seed and clear hint
1689	>	int j = ((m + m + 1) | MIN_SCAN) & MAX_SCAN;
1690	>	do {
1691	>	WorkQueue q; ForkJoinTask<?>[] a; int b;
1692	>	if ((q = ws[(r + j) & m]) != null && (b = q.base) - q.top < 0 &&
1693	>	(a = q.array) != null) {     // probably nonempty
1694	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1695	>	ForkJoinTask<?> t = (ForkJoinTask<?>)
1696	>	U.getObjectVolatile(a, i);
1697	>	if (q.base == b && ec >= 0 && t != null &&
1698	>	U.compareAndSwapObject(a, i, t, null)) {
1699	>	if ((q.base = b + 1) - q.top < 0)
1700	>	signalWork(q);
1701	>	return t;                // taken
1702	>	}
1703	>	else if ((ec < 0 || j < m) && (int)(ctl >> AC_SHIFT) <= 0) {
1704	>	w.hint = (r + j) & m;    // help signal below
1705	>	break;                   // cannot take
1706	>	}
1707	>	}
1708	>	} while (--j >= 0);
1709	>
1710	>	int h, e, ns; long c, sc; WorkQueue q;
1711	>	if ((ns = w.nsteals) != 0) {
1712	>	if (U.compareAndSwapLong(this, STEALCOUNT,
1713	>	sc = stealCount, sc + ns))
1714	>	w.nsteals = 0;               // collect steals and rescan
1715	>	}
1716	>	else if (plock != ps)                // consistency check
1717	>	;                                // skip
1718	>	else if ((e = (int)(c = ctl)) < 0)
1719	>	w.qlock = -1;                    // pool is terminating
1720	>	else {
1721	>	if ((h = w.hint) < 0) {
1722	>	if (ec >= 0) {               // try to enqueue/inactivate
1723	>	long nc = (((long)ec |
1724	>	((c - AC_UNIT) & (AC_MASK|TC_MASK))));
1725	>	w.nextWait = e;          // link and mark inactive
1726	>	w.eventCount = ec | INT_SIGN;
1727	>	if (ctl != c || !U.compareAndSwapLong(this, CTL, c, nc))
1728	>	w.eventCount = ec;   // unmark on CAS failure
1729	>	else if ((int)(c >> AC_SHIFT) == 1 - (config & SMASK))
1730	>	idleAwaitWork(w, nc, c);
1731	>	}
1732	>	else if (w.eventCount < 0 && !tryTerminate(false, false) &&
1733	>	ctl == c) {         // block
1734	>	Thread wt = Thread.currentThread();
1735	>	Thread.interrupted();    // clear status
1736	>	U.putObject(wt, PARKBLOCKER, this);
1737	>	w.parker = wt;           // emulate LockSupport.park
1738	>	if (w.eventCount < 0)    // recheck
1739	>	U.park(false, 0L);
1740	>	w.parker = null;
1741	>	U.putObject(wt, PARKBLOCKER, null);
1742	>	}
1743	>	}
1744	>	if ((h >= 0 || (h = w.hint) >= 0) &&
1745	>	(ws = workQueues) != null && h < ws.length &&
1746	>	(q = ws[h]) != null) {      // signal others before retry
1747	>	WorkQueue v; Thread p; int u, i, s;
1748	>	for (int n = (config & SMASK) >>> 1;;) {
1749	>	int idleCount = (w.eventCount < 0) ? 0 : -1;
1750	>	if (((s = idleCount - q.base + q.top) <= n &&
1751	>	(n = s) <= 0) ||
1752	>	(u = (int)((c = ctl) >>> 32)) >= 0 ||
1753	>	(e = (int)c) <= 0 || m < (i = e & SMASK) ||
1754	>	(v = ws[i]) == null)
1755	>	break;
1756	>	long nc = (((long)(v.nextWait & E_MASK)) |
1757	>	((long)(u + UAC_UNIT) << 32));
1758	>	if (v.eventCount != (e | INT_SIGN) ||
1759	>	!U.compareAndSwapLong(this, CTL, c, nc))
1760	>	break;
1761	>	v.hint = h;
1762	>	v.eventCount = (e + E_SEQ) & E_MASK;
1763	>	if ((p = v.parker) != null)
1764	>	U.unpark(p);
1765	>	if (--n <= 0)
1766	>	break;
1767	>	}
1768	>	}
1769		}
1770		}
1771	+	return null;
1772		}
1773
1774		/**
1775	<	* If worker is inactive, blocks until terminating or event count
1776	<	* advances from last value held by worker; in any case helps
1777	<	* release others.
1778	<	*
1779	<	* @param w the calling worker thread
1780	<	*/
1781	<	private void eventSync(ForkJoinWorkerThread w) {
1782	<	if (!w.active) {
1783	<	int prev = w.lastEventCount;
1784	<	long nextTop = (((long)prev << EVENT_COUNT_SHIFT) |
1785	<	((long)(w.poolIndex + 1)));
1786	<	long top;
1787	<	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
1788	<	(((int)(top = eventWaiters) & WAITER_INDEX_MASK) == 0 ||
1789	<	(int)(top >>> EVENT_COUNT_SHIFT) == prev) &&
1790	<	eventCount == prev) {
1791	<	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
1792	<	w.nextWaiter = top, nextTop)) {
1793	<	accumulateStealCount(w); // transfer steals while idle
1794	<	Thread.interrupted();    // clear/ignore interrupt
1795	<	while (eventCount == prev)
1796	<	w.doPark();
1775	>	* If inactivating worker w has caused the pool to become
1776	>	* quiescent, checks for pool termination, and, so long as this is
1777	>	* not the only worker, waits for event for up to a given
1778	>	* duration.  On timeout, if ctl has not changed, terminates the
1779	>	* worker, which will in turn wake up another worker to possibly
1780	>	* repeat this process.
1781	>	*
1782	>	* @param w the calling worker
1783	>	* @param currentCtl the ctl value triggering possible quiescence
1784	>	* @param prevCtl the ctl value to restore if thread is terminated
1785	>	*/
1786	>	private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1787	>	if (w != null && w.eventCount < 0 &&
1788	>	!tryTerminate(false, false) && (int)prevCtl != 0) {
1789	>	int dc = -(short)(currentCtl >>> TC_SHIFT);
1790	>	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1791	>	long deadline = System.nanoTime() + parkTime - TIMEOUT_SLOP;
1792	>	Thread wt = Thread.currentThread();
1793	>	while (ctl == currentCtl) {
1794	>	Thread.interrupted();  // timed variant of version in scan()
1795	>	U.putObject(wt, PARKBLOCKER, this);
1796	>	w.parker = wt;
1797	>	if (ctl == currentCtl)
1798	>	U.park(false, parkTime);
1799	>	w.parker = null;
1800	>	U.putObject(wt, PARKBLOCKER, null);
1801	>	if (ctl != currentCtl)
1802	>	break;
1803	>	if (deadline - System.nanoTime() <= 0L &&
1804	>	U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1805	>	w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
1806	>	w.qlock = -1;   // shrink
1807		break;
1808		}
1809		}
813	–	w.lastEventCount = eventCount;
1810		}
815	–	releaseWaiters();
1811		}
1812
1813		/**
1814	<	* Callback from workers invoked upon each top-level action (i.e.,
1815	<	* stealing a task or taking a submission and running
1816	<	* it). Performs one or both of the following:
1817	<	*
1818	<	* * If the worker cannot find work, updates its active status to
1819	<	* inactive and updates activeCount unless there is contention, in
1820	<	* which case it may try again (either in this or a subsequent
1821	<	* call).  Additionally, awaits the next task event and/or helps
1822	<	* wake up other releasable waiters.
1823	<	*
1824	<	* * If there are too many running threads, suspends this worker
1825	<	* (first forcing inactivation if necessary).  If it is not
1826	<	* resumed before a keepAlive elapses, the worker may be "trimmed"
1827	<	* -- killed while suspended within suspendAsSpare. Otherwise,
1828	<	* upon resume it rechecks to make sure that it is still needed.
1829	<	*
1830	<	* @param w the worker
1831	<	* @param worked false if the worker scanned for work but didn't
1832	<	* find any (in which case it may block waiting for work).
1833	<	*/
1834	<	final void preStep(ForkJoinWorkerThread w, boolean worked) {
1835	<	boolean active = w.active;
1836	<	boolean inactivate = !worked & active;
1837	<	for (;;) {
1838	<	if (inactivate) {
1839	<	int c = runState;
1840	<	if (UNSAFE.compareAndSwapInt(this, runStateOffset,
1841	<	c, c - ONE_ACTIVE))
1842	<	inactivate = active = w.active = false;
1843	<	}
1844	<	int wc = workerCounts;
1845	<	if ((wc & RUNNING_COUNT_MASK) <= parallelism) {
1846	<	if (!worked)
1847	<	eventSync(w);
1848	<	return;
1814	>	* Scans through queues looking for work while joining a task; if
1815	>	* any present, signals. May return early if more signalling is
1816	>	* detectably unneeded.
1817	>	*
1818	>	* @param task return early if done
1819	>	* @param origin an index to start scan
1820	>	*/
1821	>	private void helpSignal(ForkJoinTask<?> task, int origin) {
1822	>	WorkQueue[] ws; WorkQueue w; Thread p; long c; int m, u, e, i, s;
1823	>	if (task != null && task.status >= 0 &&
1824	>	(u = (int)(ctl >>> 32)) < 0 && (u >> UAC_SHIFT) < 0 &&
1825	>	(ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1826	>	outer: for (int k = origin, j = m; j >= 0; --j) {
1827	>	WorkQueue q = ws[k++ & m];
1828	>	for (int n = m;;) { // limit to at most m signals
1829	>	if (task.status < 0)
1830	>	break outer;
1831	>	if (q == null ||
1832	>	((s = -q.base + q.top) <= n && (n = s) <= 0))
1833	>	break;
1834	>	if ((u = (int)((c = ctl) >>> 32)) >= 0 ||
1835	>	(e = (int)c) <= 0 || m < (i = e & SMASK) ||
1836	>	(w = ws[i]) == null)
1837	>	break outer;
1838	>	long nc = (((long)(w.nextWait & E_MASK)) |
1839	>	((long)(u + UAC_UNIT) << 32));
1840	>	if (w.eventCount != (e | INT_SIGN))
1841	>	break outer;
1842	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1843	>	w.eventCount = (e + E_SEQ) & E_MASK;
1844	>	if ((p = w.parker) != null)
1845	>	U.unpark(p);
1846	>	if (--n <= 0)
1847	>	break;
1848	>	}
1849	>	}
1850		}
855	–	if (!(inactivate |= active) &&  // must inactivate to suspend
856	–	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
857	–	wc, wc - ONE_RUNNING) &&
858	–	!w.suspendAsSpare())        // false if trimmed
859	–	return;
1851		}
1852		}
1853
1854		/**
1855	<	* Adjusts counts and creates or resumes compensating threads for
1856	<	* a worker blocking on task joinMe.  First tries resuming an
1857	<	* existing spare (which usually also avoids any count
1858	<	* adjustment), but must then decrement running count to determine
1859	<	* whether a new thread is needed. See above for fuller
1860	<	* explanation. This code is sprawled out non-modularly mainly
1861	<	* because adaptive spinning works best if the entire method is
1862	<	* either interpreted or compiled vs having only some pieces of it
1863	<	* compiled.
1864	<	*
1865	<	* @param joinMe the task to join
1866	<	* @return task status on exit (to simplify usage by callers)
1867	<	*/
1868	<	final int awaitJoin(ForkJoinTask<?> joinMe) {
1869	<	int pc = parallelism;
1870	<	boolean adj = false;        // true when running count adjusted
1871	<	int scans = 0;
1872	<
1873	<	while (joinMe.status >= 0) {
1874	<	ForkJoinWorkerThread spare = null;
1875	<	if ((workerCounts & RUNNING_COUNT_MASK) < pc) {
1876	<	ForkJoinWorkerThread[] ws = workers;
1877	<	int nws = ws.length;
1878	<	for (int i = 0; i < nws; ++i) {
1879	<	ForkJoinWorkerThread w = ws[i];
1880	<	if (w != null && w.isSuspended()) {
1881	<	spare = w;
891	<	break;
1855	>	* Tries to locate and execute tasks for a stealer of the given
1856	>	* task, or in turn one of its stealers, Traces currentSteal ->
1857	>	* currentJoin links looking for a thread working on a descendant
1858	>	* of the given task and with a non-empty queue to steal back and
1859	>	* execute tasks from. The first call to this method upon a
1860	>	* waiting join will often entail scanning/search, (which is OK
1861	>	* because the joiner has nothing better to do), but this method
1862	>	* leaves hints in workers to speed up subsequent calls. The
1863	>	* implementation is very branchy to cope with potential
1864	>	* inconsistencies or loops encountering chains that are stale,
1865	>	* unknown, or so long that they are likely cyclic.
1866	>	*
1867	>	* @param joiner the joining worker
1868	>	* @param task the task to join
1869	>	* @return 0 if no progress can be made, negative if task
1870	>	* known complete, else positive
1871	>	*/
1872	>	private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1873	>	int stat = 0, steps = 0;                    // bound to avoid cycles
1874	>	if (joiner != null && task != null) {       // hoist null checks
1875	>	restart: for (;;) {
1876	>	ForkJoinTask<?> subtask = task;     // current target
1877	>	for (WorkQueue j = joiner, v;;) {   // v is stealer of subtask
1878	>	WorkQueue[] ws; int m, s, h;
1879	>	if ((s = task.status) < 0) {
1880	>	stat = s;
1881	>	break restart;
1882		}
1883	<	}
1884	<	if (joinMe.status < 0)
1885	<	break;
1886	<	}
1887	<	int wc = workerCounts;
1888	<	int rc = wc & RUNNING_COUNT_MASK;
1889	<	int dc = pc - rc;
1890	<	if (dc > 0 && spare != null && spare.tryUnsuspend()) {
1891	<	if (adj) {
1892	<	int c;
1893	<	do {} while (!UNSAFE.compareAndSwapInt
1894	<	(this, workerCountsOffset,
1895	<	c = workerCounts, c + ONE_RUNNING));
1896	<	}
1897	<	adj = true;
1898	<	LockSupport.unpark(spare);
1899	<	}
1900	<	else if (adj) {
1901	<	if (dc <= 0)
1902	<	break;
1903	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
1904	<	if (scans > tc) {
1905	<	int ts = (tc - pc) * pc;
1906	<	if (rc != 0 &&  (dc * dc < ts || !maintainsParallelism))
1907	<	break;
1908	<	if (scans > ts && tc < maxPoolSize &&
1909	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
1910	<	wc+(ONE_RUNNING|ONE_TOTAL))){
1911	<	addWorker();
1912	<	break;
1883	>	if ((ws = workQueues) == null || (m = ws.length - 1) <= 0)
1884	>	break restart;              // shutting down
1885	>	if ((v = ws[h = (j.hint | 1) & m]) == null ||
1886	>	v.currentSteal != subtask) {
1887	>	for (int origin = h;;) {    // find stealer
1888	>	if (((h = (h + 2) & m) & 15) == 1 &&
1889	>	(subtask.status < 0 || j.currentJoin != subtask))
1890	>	continue restart;   // occasional staleness check
1891	>	if ((v = ws[h]) != null &&
1892	>	v.currentSteal == subtask) {
1893	>	j.hint = h;        // save hint
1894	>	break;
1895	>	}
1896	>	if (h == origin)
1897	>	break restart;      // cannot find stealer
1898	>	}
1899	>	}
1900	>	for (;;) { // help stealer or descend to its stealer
1901	>	ForkJoinTask[] a;  int b;
1902	>	if (subtask.status < 0)     // surround probes with
1903	>	continue restart;       //   consistency checks
1904	>	if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
1905	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1906	>	ForkJoinTask<?> t =
1907	>	(ForkJoinTask<?>)U.getObjectVolatile(a, i);
1908	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1909	>	v.currentSteal != subtask)
1910	>	continue restart;   // stale
1911	>	stat = 1;               // apparent progress
1912	>	if (t != null && v.base == b &&
1913	>	U.compareAndSwapObject(a, i, t, null)) {
1914	>	v.base = b + 1;     // help stealer
1915	>	joiner.runSubtask(t);
1916	>	}
1917	>	else if (v.base == b && ++steps == MAX_HELP)
1918	>	break restart;      // v apparently stalled
1919	>	}
1920	>	else {                      // empty -- try to descend
1921	>	ForkJoinTask<?> next = v.currentJoin;
1922	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1923	>	v.currentSteal != subtask)
1924	>	continue restart;   // stale
1925	>	else if (next == null || ++steps == MAX_HELP)
1926	>	break restart;      // dead-end or maybe cyclic
1927	>	else {
1928	>	subtask = next;
1929	>	j = v;
1930	>	break;
1931	>	}
1932	>	}
1933		}
1934		}
1935		}
926	–	else if (rc != 0)
927	–	adj = UNSAFE.compareAndSwapInt (this, workerCountsOffset,
928	–	wc, wc - ONE_RUNNING);
929	–	if ((scans++ & 1) == 0)
930	–	releaseWaiters();   // help others progress
931	–	else
932	–	Thread.yield();     // avoid starving productive threads
933	–	}
934	–
935	–	if (adj) {
936	–	joinMe.internalAwaitDone();
937	–	int c;
938	–	do {} while (!UNSAFE.compareAndSwapInt
939	–	(this, workerCountsOffset,
940	–	c = workerCounts, c + ONE_RUNNING));
1936		}
1937	<	return joinMe.status;
1937	>	return stat;
1938		}
1939
1940		/**
1941	<	* Same idea as awaitJoin
1941	>	* Analog of tryHelpStealer for CountedCompleters. Tries to steal
1942	>	* and run tasks within the target's computation.
1943	>	*
1944	>	* @param task the task to join
1945	>	* @param mode if shared, exit upon completing any task
1946	>	* if all workers are active
1947	>	*
1948		*/
1949	<	final void awaitBlocker(ManagedBlocker blocker, boolean maintainPar)
1950	<	throws InterruptedException {
1951	<	maintainPar &= maintainsParallelism;
1952	<	int pc = parallelism;
1953	<	boolean adj = false;        // true when running count adjusted
1954	<	int scans = 0;
1955	<	boolean done;
1956	<
1957	<	for (;;) {
1958	<	if (done = blocker.isReleasable())
1959	<	break;
959	<	ForkJoinWorkerThread spare = null;
960	<	if ((workerCounts & RUNNING_COUNT_MASK) < pc) {
961	<	ForkJoinWorkerThread[] ws = workers;
962	<	int nws = ws.length;
963	<	for (int i = 0; i < nws; ++i) {
964	<	ForkJoinWorkerThread w = ws[i];
965	<	if (w != null && w.isSuspended()) {
966	<	spare = w;
1949	>	private int helpComplete(ForkJoinTask<?> task, int mode) {
1950	>	WorkQueue[] ws; WorkQueue q; int m, n, s, u;
1951	>	if (task != null && (ws = workQueues) != null &&
1952	>	(m = ws.length - 1) >= 0) {
1953	>	for (int j = 1, origin = j;;) {
1954	>	if ((s = task.status) < 0)
1955	>	return s;
1956	>	if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) {
1957	>	origin = j;
1958	>	if (mode == SHARED_QUEUE &&
1959	>	((u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0))
1960		break;
968	–	}
1961		}
1962	<	if (done = blocker.isReleasable())
1962	>	else if ((j = (j + 2) & m) == origin)
1963		break;
1964		}
1965	<	int wc = workerCounts;
1966	<	int rc = wc & RUNNING_COUNT_MASK;
1967	<	int dc = pc - rc;
1968	<	if (dc > 0 && spare != null && spare.tryUnsuspend()) {
1969	<	if (adj) {
1970	<	int c;
1971	<	do {} while (!UNSAFE.compareAndSwapInt
1972	<	(this, workerCountsOffset,
1973	<	c = workerCounts, c + ONE_RUNNING));
1965	>	}
1966	>	return 0;
1967	>	}
1968	>
1969	>	/**
1970	>	* Tries to decrement active count (sometimes implicitly) and
1971	>	* possibly release or create a compensating worker in preparation
1972	>	* for blocking. Fails on contention or termination. Otherwise,
1973	>	* adds a new thread if no idle workers are available and pool
1974	>	* may become starved.
1975	>	*/
1976	>	final boolean tryCompensate() {
1977	>	int pc = config & SMASK, e, i, tc; long c;
1978	>	WorkQueue[] ws; WorkQueue w; Thread p;
1979	>	if ((ws = workQueues) != null && (e = (int)(c = ctl)) >= 0) {
1980	>	if (e != 0 && (i = e & SMASK) < ws.length &&
1981	>	(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
1982	>	long nc = ((long)(w.nextWait & E_MASK) |
1983	>	(c & (AC_MASK|TC_MASK)));
1984	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1985	>	w.eventCount = (e + E_SEQ) & E_MASK;
1986	>	if ((p = w.parker) != null)
1987	>	U.unpark(p);
1988	>	return true;   // replace with idle worker
1989		}
983	–	adj = true;
984	–	LockSupport.unpark(spare);
1990		}
1991	<	else if (adj) {
1992	<	if (dc <= 0)
1993	<	break;
1994	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
1995	<	if (scans > tc) {
1996	<	int ts = (tc - pc) * pc;
1997	<	if (rc != 0 &&  (dc * dc < ts || !maintainPar))
1998	<	break;
1999	<	if (scans > ts && tc < maxPoolSize &&
2000	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
2001	<	wc+(ONE_RUNNING|ONE_TOTAL))){
2002	<	addWorker();
2003	<	break;
1991	>	else if ((tc = (short)(c >>> TC_SHIFT)) >= 0 &&
1992	>	(int)(c >> AC_SHIFT) + pc > 1) {
1993	>	long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
1994	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1995	>	return true;   // no compensation
1996	>	}
1997	>	else if (tc + pc < MAX_CAP) {
1998	>	long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
1999	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
2000	>	ForkJoinWorkerThreadFactory fac;
2001	>	Throwable ex = null;
2002	>	ForkJoinWorkerThread wt = null;
2003	>	try {
2004	>	if ((fac = factory) != null &&
2005	>	(wt = fac.newThread(this)) != null) {
2006	>	wt.start();
2007	>	return true;
2008	>	}
2009	>	} catch (Throwable rex) {
2010	>	ex = rex;
2011		}
2012	+	deregisterWorker(wt, ex); // clean up and return false
2013		}
2014		}
1002	–	else if (rc != 0)
1003	–	adj = UNSAFE.compareAndSwapInt (this, workerCountsOffset,
1004	–	wc, wc - ONE_RUNNING);
1005	–	if ((++scans & 1) == 0)
1006	–	releaseWaiters();   // help others progress
1007	–	else
1008	–	Thread.yield();     // avoid starving productive threads
1009	–	}
1010	–
1011	–	try {
1012	–	if (!done)
1013	–	do {} while (!blocker.isReleasable() && !blocker.block());
1014	–	} finally {
1015	–	if (adj) {
1016	–	int c;
1017	–	do {} while (!UNSAFE.compareAndSwapInt
1018	–	(this, workerCountsOffset,
1019	–	c = workerCounts, c + ONE_RUNNING));
1020	–	}
2015		}
2016	+	return false;
2017		}
2018
2019		/**
2020	<	* Unless there are not enough other running threads, adjusts
1026	<	* counts and blocks a worker performing helpJoin that cannot find
1027	<	* any work.
2020	>	* Helps and/or blocks until the given task is done.
2021		*
2022	<	* @return true if joinMe now done
2022	>	* @param joiner the joining worker
2023	>	* @param task the task
2024	>	* @return task status on exit
2025		*/
2026	<	final boolean tryAwaitBusyJoin(ForkJoinTask<?> joinMe) {
2027	<	int pc = parallelism;
2028	<	outer:for (;;) {
2029	<	releaseWaiters();
2030	<	if ((workerCounts & RUNNING_COUNT_MASK) < pc) {
2031	<	ForkJoinWorkerThread[] ws = workers;
2032	<	int nws = ws.length;
2033	<	for (int i = 0; i < nws; ++i) {
2034	<	ForkJoinWorkerThread w = ws[i];
2035	<	if (w != null && w.isSuspended()) {
2036	<	if (joinMe.status < 0)
2037	<	return true;
2038	<	if ((workerCounts & RUNNING_COUNT_MASK) > pc)
2039	<	break;
2040	<	if (w.tryUnsuspend()) {
2041	<	LockSupport.unpark(w);
2042	<	break outer;
2026	>	final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
2027	>	int s = 0;
2028	>	if (joiner != null && task != null && (s = task.status) >= 0) {
2029	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2030	>	joiner.currentJoin = task;
2031	>	do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
2032	>	joiner.tryRemoveAndExec(task)); // process local tasks
2033	>	if (s >= 0 && (s = task.status) >= 0) {
2034	>	helpSignal(task, joiner.poolIndex);
2035	>	if ((s = task.status) >= 0 &&
2036	>	(task instanceof CountedCompleter))
2037	>	s = helpComplete(task, LIFO_QUEUE);
2038	>	}
2039	>	while (s >= 0 && (s = task.status) >= 0) {
2040	>	if ((!joiner.isEmpty() ||           // try helping
2041	>	(s = tryHelpStealer(joiner, task)) == 0) &&
2042	>	(s = task.status) >= 0) {
2043	>	helpSignal(task, joiner.poolIndex);
2044	>	if ((s = task.status) >= 0 && tryCompensate()) {
2045	>	if (task.trySetSignal() && (s = task.status) >= 0) {
2046	>	synchronized (task) {
2047	>	if (task.status >= 0) {
2048	>	try {                // see ForkJoinTask
2049	>	task.wait();     //  for explanation
2050	>	} catch (InterruptedException ie) {
2051	>	}
2052	>	}
2053	>	else
2054	>	task.notifyAll();
2055	>	}
2056		}
2057	<	continue outer;
2057	>	long c;                          // re-activate
2058	>	do {} while (!U.compareAndSwapLong
2059	>	(this, CTL, c = ctl, c + AC_UNIT));
2060		}
2061		}
2062		}
2063	<	if (joinMe.status < 0)
1054	<	return true;
1055	<	int wc = workerCounts;
1056	<	if ((wc & RUNNING_COUNT_MASK) <= 2 ||
1057	<	(wc >>> TOTAL_COUNT_SHIFT) < pc)
1058	<	return false;  // keep this thread alive
1059	<	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1060	<	wc, wc - ONE_RUNNING))
1061	<	break;
2063	>	joiner.currentJoin = prevJoin;
2064		}
2065	<
1064	<	joinMe.internalAwaitDone();
1065	<	int c;
1066	<	do {} while (!UNSAFE.compareAndSwapInt
1067	<	(this, workerCountsOffset,
1068	<	c = workerCounts, c + ONE_RUNNING));
1069	<	return true;
2065	>	return s;
2066		}
2067
2068		/**
2069	<	* Possibly initiates and/or completes termination.
2069	>	* Stripped-down variant of awaitJoin used by timed joins. Tries
2070	>	* to help join only while there is continuous progress. (Caller
2071	>	* will then enter a timed wait.)
2072		*
2073	<	* @param now if true, unconditionally terminate, else only
2074	<	* if shutdown and empty queue and no active workers
1077	<	* @return true if now terminating or terminated
2073	>	* @param joiner the joining worker
2074	>	* @param task the task
2075		*/
2076	<	private boolean tryTerminate(boolean now) {
2077	<	if (now)
2078	<	advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN
2079	<	else if (runState < SHUTDOWN ||
2080	<	!submissionQueue.isEmpty() ||
2081	<	(runState & ACTIVE_COUNT_MASK) != 0)
2082	<	return false;
2083	<
2084	<	if (advanceRunLevel(TERMINATING))
2085	<	startTerminating();
2086	<
2087	<	// Finish now if all threads terminated; else in some subsequent call
2088	<	if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
2089	<	advanceRunLevel(TERMINATED);
2090	<	terminationLatch.countDown();
2076	>	final void helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
2077	>	int s;
2078	>	if (joiner != null && task != null && (s = task.status) >= 0) {
2079	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2080	>	joiner.currentJoin = task;
2081	>	do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
2082	>	joiner.tryRemoveAndExec(task));
2083	>	if (s >= 0 && (s = task.status) >= 0) {
2084	>	helpSignal(task, joiner.poolIndex);
2085	>	if ((s = task.status) >= 0 &&
2086	>	(task instanceof CountedCompleter))
2087	>	s = helpComplete(task, LIFO_QUEUE);
2088	>	}
2089	>	if (s >= 0 && joiner.isEmpty()) {
2090	>	do {} while (task.status >= 0 &&
2091	>	tryHelpStealer(joiner, task) > 0);
2092	>	}
2093	>	joiner.currentJoin = prevJoin;
2094		}
1095	–	return true;
2095		}
2096
2097		/**
2098	<	* Actions on transition to TERMINATING
2098	>	* Returns a (probably) non-empty steal queue, if one is found
2099	>	* during a random, then cyclic scan, else null.  This method must
2100	>	* be retried by caller if, by the time it tries to use the queue,
2101	>	* it is empty.
2102	>	* @param r a (random) seed for scanning
2103		*/
2104	<	private void startTerminating() {
2105	<	for (int i = 0; i < 2; ++i) { // twice to mop up newly created workers
2106	<	cancelSubmissions();
2107	<	shutdownWorkers();
2108	<	cancelWorkerTasks();
2109	<	advanceEventCount();
2110	<	releaseWaiters();
2111	<	interruptWorkers();
2104	>	private WorkQueue findNonEmptyStealQueue(int r) {
2105	>	for (WorkQueue[] ws;;) {
2106	>	int ps = plock, m, n;
2107	>	if ((ws = workQueues) == null || (m = ws.length - 1) < 1)
2108	>	return null;
2109	>	for (int j = (m + 1) << 2; ;) {
2110	>	WorkQueue q = ws[(((r + j) << 1) | 1) & m];
2111	>	if (q != null && (n = q.base - q.top) < 0) {
2112	>	if (n < -1)
2113	>	signalWork(q);
2114	>	return q;
2115	>	}
2116	>	else if (--j < 0) {
2117	>	if (plock == ps)
2118	>	return null;
2119	>	break;
2120	>	}
2121	>	}
2122		}
2123		}
2124
2125		/**
2126	<	* Clear out and cancel submissions, ignoring exceptions
2127	<	*/
2128	<	private void cancelSubmissions() {
2129	<	ForkJoinTask<?> task;
2130	<	while ((task = submissionQueue.poll()) != null) {
2131	<	try {
2132	<	task.cancel(false);
2133	<	} catch (Throwable ignore) {
2126	>	* Runs tasks until {@code isQuiescent()}. We piggyback on
2127	>	* active count ctl maintenance, but rather than blocking
2128	>	* when tasks cannot be found, we rescan until all others cannot
2129	>	* find tasks either.
2130	>	*/
2131	>	final void helpQuiescePool(WorkQueue w) {
2132	>	for (boolean active = true;;) {
2133	>	ForkJoinTask<?> localTask; // exhaust local queue
2134	>	while ((localTask = w.nextLocalTask()) != null)
2135	>	localTask.doExec();
2136	>	// Similar to loop in scan(), but ignoring submissions
2137	>	WorkQueue q = findNonEmptyStealQueue(w.nextSeed());
2138	>	if (q != null) {
2139	>	ForkJoinTask<?> t; int b;
2140	>	if (!active) {      // re-establish active count
2141	>	long c;
2142	>	active = true;
2143	>	do {} while (!U.compareAndSwapLong
2144	>	(this, CTL, c = ctl, c + AC_UNIT));
2145	>	}
2146	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2147	>	w.runSubtask(t);
2148	>	}
2149	>	else {
2150	>	long c;
2151	>	if (active) {       // decrement active count without queuing
2152	>	active = false;
2153	>	do {} while (!U.compareAndSwapLong
2154	>	(this, CTL, c = ctl, c -= AC_UNIT));
2155	>	}
2156	>	else
2157	>	c = ctl;        // re-increment on exit
2158	>	if ((int)(c >> AC_SHIFT) + (config & SMASK) == 0) {
2159	>	do {} while (!U.compareAndSwapLong
2160	>	(this, CTL, c = ctl, c + AC_UNIT));
2161	>	break;
2162	>	}
2163		}
2164		}
2165		}
2166
2167		/**
2168	<	* Sets all worker run states to at least shutdown,
2169	<	* also resuming suspended workers
2168	>	* Gets and removes a local or stolen task for the given worker.
2169	>	*
2170	>	* @return a task, if available
2171		*/
2172	<	private void shutdownWorkers() {
2173	<	ForkJoinWorkerThread[] ws = workers;
2174	<	int nws = ws.length;
2175	<	for (int i = 0; i < nws; ++i) {
2176	<	ForkJoinWorkerThread w = ws[i];
2177	<	if (w != null)
2178	<	w.shutdown();
2172	>	final ForkJoinTask<?> nextTaskFor(WorkQueue w) {
2173	>	for (ForkJoinTask<?> t;;) {
2174	>	WorkQueue q; int b;
2175	>	if ((t = w.nextLocalTask()) != null)
2176	>	return t;
2177	>	if ((q = findNonEmptyStealQueue(w.nextSeed())) == null)
2178	>	return null;
2179	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2180	>	return t;
2181		}
2182		}
2183
2184		/**
2185	<	* Clears out and cancels all locally queued tasks
2185	>	* Returns a cheap heuristic guide for task partitioning when
2186	>	* programmers, frameworks, tools, or languages have little or no
2187	>	* idea about task granularity.  In essence by offering this
2188	>	* method, we ask users only about tradeoffs in overhead vs
2189	>	* expected throughput and its variance, rather than how finely to
2190	>	* partition tasks.
2191	>	*
2192	>	* In a steady state strict (tree-structured) computation, each
2193	>	* thread makes available for stealing enough tasks for other
2194	>	* threads to remain active. Inductively, if all threads play by
2195	>	* the same rules, each thread should make available only a
2196	>	* constant number of tasks.
2197	>	*
2198	>	* The minimum useful constant is just 1. But using a value of 1
2199	>	* would require immediate replenishment upon each steal to
2200	>	* maintain enough tasks, which is infeasible.  Further,
2201	>	* partitionings/granularities of offered tasks should minimize
2202	>	* steal rates, which in general means that threads nearer the top
2203	>	* of computation tree should generate more than those nearer the
2204	>	* bottom. In perfect steady state, each thread is at
2205	>	* approximately the same level of computation tree. However,
2206	>	* producing extra tasks amortizes the uncertainty of progress and
2207	>	* diffusion assumptions.
2208	>	*
2209	>	* So, users will want to use values larger, but not much larger
2210	>	* than 1 to both smooth over transient shortages and hedge
2211	>	* against uneven progress; as traded off against the cost of
2212	>	* extra task overhead. We leave the user to pick a threshold
2213	>	* value to compare with the results of this call to guide
2214	>	* decisions, but recommend values such as 3.
2215	>	*
2216	>	* When all threads are active, it is on average OK to estimate
2217	>	* surplus strictly locally. In steady-state, if one thread is
2218	>	* maintaining say 2 surplus tasks, then so are others. So we can
2219	>	* just use estimated queue length.  However, this strategy alone
2220	>	* leads to serious mis-estimates in some non-steady-state
2221	>	* conditions (ramp-up, ramp-down, other stalls). We can detect
2222	>	* many of these by further considering the number of "idle"
2223	>	* threads, that are known to have zero queued tasks, so
2224	>	* compensate by a factor of (#idle/#active) threads.
2225	>	*
2226	>	* Note: The approximation of #busy workers as #active workers is
2227	>	* not very good under current signalling scheme, and should be
2228	>	* improved.
2229	>	*/
2230	>	static int getSurplusQueuedTaskCount() {
2231	>	Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q;
2232	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
2233	>	int p = (pool = (wt = (ForkJoinWorkerThread)t).pool).config & SMASK;
2234	>	int n = (q = wt.workQueue).top - q.base;
2235	>	int a = (int)(pool.ctl >> AC_SHIFT) + p;
2236	>	return n - (a > (p >>>= 1) ? 0 :
2237	>	a > (p >>>= 1) ? 1 :
2238	>	a > (p >>>= 1) ? 2 :
2239	>	a > (p >>>= 1) ? 4 :
2240	>	8);
2241	>	}
2242	>	return 0;
2243	>	}
2244	>
2245	>	//  Termination
2246	>
2247	>	/**
2248	>	* Possibly initiates and/or completes termination.  The caller
2249	>	* triggering termination runs three passes through workQueues:
2250	>	* (0) Setting termination status, followed by wakeups of queued
2251	>	* workers; (1) cancelling all tasks; (2) interrupting lagging
2252	>	* threads (likely in external tasks, but possibly also blocked in
2253	>	* joins).  Each pass repeats previous steps because of potential
2254	>	* lagging thread creation.
2255	>	*
2256	>	* @param now if true, unconditionally terminate, else only
2257	>	* if no work and no active workers
2258	>	* @param enable if true, enable shutdown when next possible
2259	>	* @return true if now terminating or terminated
2260		*/
2261	<	private void cancelWorkerTasks() {
2262	<	ForkJoinWorkerThread[] ws = workers;
2263	<	int nws = ws.length;
2264	<	for (int i = 0; i < nws; ++i) {
2265	<	ForkJoinWorkerThread w = ws[i];
2266	<	if (w != null)
2267	<	w.cancelTasks();
2261	>	private boolean tryTerminate(boolean now, boolean enable) {
2262	>	if (this == commonPool)                     // cannot shut down
2263	>	return false;
2264	>	for (long c;;) {
2265	>	if (((c = ctl) & STOP_BIT) != 0) {      // already terminating
2266	>	if ((short)(c >>> TC_SHIFT) == -(config & SMASK)) {
2267	>	synchronized (this) {
2268	>	notifyAll();                // signal when 0 workers
2269	>	}
2270	>	}
2271	>	return true;
2272	>	}
2273	>	if (plock >= 0) {                       // not yet enabled
2274	>	int ps;
2275	>	if (!enable)
2276	>	return false;
2277	>	if (((ps = plock) & PL_LOCK) != 0 ||
2278	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
2279	>	ps = acquirePlock();
2280	>	if (!U.compareAndSwapInt(this, PLOCK, ps, SHUTDOWN))
2281	>	releasePlock(SHUTDOWN);
2282	>	}
2283	>	if (!now) {                             // check if idle & no tasks
2284	>	if ((int)(c >> AC_SHIFT) != -(config & SMASK) ||
2285	>	hasQueuedSubmissions())
2286	>	return false;
2287	>	// Check for unqueued inactive workers. One pass suffices.
2288	>	WorkQueue[] ws = workQueues; WorkQueue w;
2289	>	if (ws != null) {
2290	>	for (int i = 1; i < ws.length; i += 2) {
2291	>	if ((w = ws[i]) != null && w.eventCount >= 0)
2292	>	return false;
2293	>	}
2294	>	}
2295	>	}
2296	>	if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT)) {
2297	>	for (int pass = 0; pass < 3; ++pass) {
2298	>	WorkQueue[] ws = workQueues;
2299	>	if (ws != null) {
2300	>	WorkQueue w; Thread wt;
2301	>	int n = ws.length;
2302	>	for (int i = 0; i < n; ++i) {
2303	>	if ((w = ws[i]) != null) {
2304	>	w.qlock = -1;
2305	>	if (pass > 0) {
2306	>	w.cancelAll();
2307	>	if (pass > 1 && (wt = w.owner) != null) {
2308	>	if (!wt.isInterrupted()) {
2309	>	try {
2310	>	wt.interrupt();
2311	>	} catch (SecurityException ignore) {
2312	>	}
2313	>	}
2314	>	U.unpark(wt);
2315	>	}
2316	>	}
2317	>	}
2318	>	}
2319	>	// Wake up workers parked on event queue
2320	>	int i, e; long cc; Thread p;
2321	>	while ((e = (int)(cc = ctl) & E_MASK) != 0 &&
2322	>	(i = e & SMASK) < n &&
2323	>	(w = ws[i]) != null) {
2324	>	long nc = ((long)(w.nextWait & E_MASK) |
2325	>	((cc + AC_UNIT) & AC_MASK) |
2326	>	(cc & (TC_MASK|STOP_BIT)));
2327	>	if (w.eventCount == (e | INT_SIGN) &&
2328	>	U.compareAndSwapLong(this, CTL, cc, nc)) {
2329	>	w.eventCount = (e + E_SEQ) & E_MASK;
2330	>	w.qlock = -1;
2331	>	if ((p = w.parker) != null)
2332	>	U.unpark(p);
2333	>	}
2334	>	}
2335	>	}
2336	>	}
2337	>	}
2338		}
2339		}
2340
2341	+	// external operations on common pool
2342	+
2343		/**
2344	<	* Unsticks all workers blocked on joins etc
2344	>	* Returns common pool queue for a thread that has submitted at
2345	>	* least one task.
2346		*/
2347	<	private void interruptWorkers() {
2348	<	ForkJoinWorkerThread[] ws = workers;
2349	<	int nws = ws.length;
2350	<	for (int i = 0; i < nws; ++i) {
2351	<	ForkJoinWorkerThread w = ws[i];
2352	<	if (w != null && !w.isTerminated()) {
2353	<	try {
2354	<	w.interrupt();
2355	<	} catch (SecurityException ignore) {
2347	>	static WorkQueue commonSubmitterQueue() {
2348	>	ForkJoinPool p; WorkQueue[] ws; int m; Submitter z;
2349	>	return ((z = submitters.get()) != null &&
2350	>	(p = commonPool) != null &&
2351	>	(ws = p.workQueues) != null &&
2352	>	(m = ws.length - 1) >= 0) ?
2353	>	ws[m & z.seed & SQMASK] : null;
2354	>	}
2355	>
2356	>	/**
2357	>	* Tries to pop the given task from submitter's queue in common pool.
2358	>	*/
2359	>	static boolean tryExternalUnpush(ForkJoinTask<?> t) {
2360	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q; Submitter z;
2361	>	ForkJoinTask<?>[] a;  int m, s;
2362	>	if (t != null &&
2363	>	(z = submitters.get()) != null &&
2364	>	(p = commonPool) != null &&
2365	>	(ws = p.workQueues) != null &&
2366	>	(m = ws.length - 1) >= 0 &&
2367	>	(q = ws[m & z.seed & SQMASK]) != null &&
2368	>	(s = q.top) != q.base &&
2369	>	(a = q.array) != null) {
2370	>	long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE;
2371	>	if (U.getObject(a, j) == t &&
2372	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2373	>	if (q.array == a && q.top == s && // recheck
2374	>	U.compareAndSwapObject(a, j, t, null)) {
2375	>	q.top = s - 1;
2376	>	q.qlock = 0;
2377	>	return true;
2378		}
2379	+	q.qlock = 0;
2380		}
2381		}
2382	+	return false;
2383		}
2384
1169	–	// misc support for ForkJoinWorkerThread
1170	–
2385		/**
2386	<	* Returns pool number
2386	>	* Tries to pop and run local tasks within the same computation
2387	>	* as the given root. On failure, tries to help complete from
2388	>	* other queues via helpComplete.
2389		*/
2390	<	final int getPoolNumber() {
2391	<	return poolNumber;
2390	>	private void externalHelpComplete(WorkQueue q, ForkJoinTask<?> root) {
2391	>	ForkJoinTask<?>[] a; int m;
2392	>	if (q != null && (a = q.array) != null && (m = (a.length - 1)) >= 0 &&
2393	>	root != null && root.status >= 0) {
2394	>	for (;;) {
2395	>	int s, u; Object o; CountedCompleter<?> task = null;
2396	>	if ((s = q.top) - q.base > 0) {
2397	>	long j = ((m & (s - 1)) << ASHIFT) + ABASE;
2398	>	if ((o = U.getObject(a, j)) != null &&
2399	>	(o instanceof CountedCompleter)) {
2400	>	CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;
2401	>	do {
2402	>	if (r == root) {
2403	>	if (U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2404	>	if (q.array == a && q.top == s &&
2405	>	U.compareAndSwapObject(a, j, t, null)) {
2406	>	q.top = s - 1;
2407	>	task = t;
2408	>	}
2409	>	q.qlock = 0;
2410	>	}
2411	>	break;
2412	>	}
2413	>	} while ((r = r.completer) != null);
2414	>	}
2415	>	}
2416	>	if (task != null)
2417	>	task.doExec();
2418	>	if (root.status < 0 ||
2419	>	(u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0)
2420	>	break;
2421	>	if (task == null) {
2422	>	helpSignal(root, q.poolIndex);
2423	>	if (root.status >= 0)
2424	>	helpComplete(root, SHARED_QUEUE);
2425	>	break;
2426	>	}
2427	>	}
2428	>	}
2429		}
2430
2431		/**
2432	<	* Accumulates steal count from a worker, clearing
2433	<	* the worker's value
2432	>	* Tries to help execute or signal availability of the given task
2433	>	* from submitter's queue in common pool.
2434		*/
2435	<	final void accumulateStealCount(ForkJoinWorkerThread w) {
2436	<	int sc = w.stealCount;
2437	<	if (sc != 0) {
2438	<	long c;
2439	<	w.stealCount = 0;
2440	<	do {} while (!UNSAFE.compareAndSwapLong(this, stealCountOffset,
2441	<	c = stealCount, c + sc));
2435	>	static void externalHelpJoin(ForkJoinTask<?> t) {
2436	>	// Some hard-to-avoid overlap with tryExternalUnpush
2437	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; Submitter z;
2438	>	ForkJoinTask<?>[] a;  int m, s, n;
2439	>	if (t != null &&
2440	>	(z = submitters.get()) != null &&
2441	>	(p = commonPool) != null &&
2442	>	(ws = p.workQueues) != null &&
2443	>	(m = ws.length - 1) >= 0 &&
2444	>	(q = ws[m & z.seed & SQMASK]) != null &&
2445	>	(a = q.array) != null) {
2446	>	int am = a.length - 1;
2447	>	if ((s = q.top) != q.base) {
2448	>	long j = ((am & (s - 1)) << ASHIFT) + ABASE;
2449	>	if (U.getObject(a, j) == t &&
2450	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2451	>	if (q.array == a && q.top == s &&
2452	>	U.compareAndSwapObject(a, j, t, null)) {
2453	>	q.top = s - 1;
2454	>	q.qlock = 0;
2455	>	t.doExec();
2456	>	}
2457	>	else
2458	>	q.qlock = 0;
2459	>	}
2460	>	}
2461	>	if (t.status >= 0) {
2462	>	if (t instanceof CountedCompleter)
2463	>	p.externalHelpComplete(q, t);
2464	>	else
2465	>	p.helpSignal(t, q.poolIndex);
2466	>	}
2467		}
2468		}
2469
2470		/**
2471	<	* Returns the approximate (non-atomic) number of idle threads per
1194	<	* active thread.
2471	>	* Restricted version of helpQuiescePool for external callers
2472		*/
2473	<	final int idlePerActive() {
2474	<	int ac = runState;    // no mask -- artifically boosts during shutdown
2475	<	int pc = parallelism; // use targeted parallelism, not rc
2476	<	// Use exact results for small values, saturate past 4
2477	<	return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
2473	>	static void externalHelpQuiescePool() {
2474	>	ForkJoinPool p; ForkJoinTask<?> t; WorkQueue q; int b;
2475	>	if ((p = commonPool) != null &&
2476	>	(q = p.findNonEmptyStealQueue(1)) != null &&
2477	>	(b = q.base) - q.top < 0 &&
2478	>	(t = q.pollAt(b)) != null)
2479	>	t.doExec();
2480		}
2481
2482	<	// Public and protected methods
2482	>	// Exported methods
2483
2484		// Constructors
2485
2486		/**
2487		* Creates a {@code ForkJoinPool} with parallelism equal to {@link
2488	<	* java.lang.Runtime#availableProcessors}, and using the {@linkplain
2489	<	* #defaultForkJoinWorkerThreadFactory default thread factory}.
2488	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
2489	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
2490	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
2491		*
2492		* @throws SecurityException if a security manager exists and
2493		*         the caller is not permitted to modify threads
#	Line 1216 | Line 2496 | public class ForkJoinPool extends Abstra
2496		*/
2497		public ForkJoinPool() {
2498		this(Runtime.getRuntime().availableProcessors(),
2499	<	defaultForkJoinWorkerThreadFactory);
2499	>	defaultForkJoinWorkerThreadFactory, null, false);
2500		}
2501
2502		/**
2503		* Creates a {@code ForkJoinPool} with the indicated parallelism
2504	<	* level and using the {@linkplain
2505	<	* #defaultForkJoinWorkerThreadFactory default thread factory}.
2504	>	* level, the {@linkplain
2505	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
2506	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
2507		*
2508		* @param parallelism the parallelism level
2509		* @throws IllegalArgumentException if parallelism less than or
#	Line 1233 | Line 2514 | public class ForkJoinPool extends Abstra
2514		*         java.lang.RuntimePermission}{@code ("modifyThread")}
2515		*/
2516		public ForkJoinPool(int parallelism) {
2517	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
1237	<	}
1238	<
1239	<	/**
1240	<	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1241	<	* java.lang.Runtime#availableProcessors}, and using the given
1242	<	* thread factory.
1243	<	*
1244	<	* @param factory the factory for creating new threads
1245	<	* @throws NullPointerException if the factory is null
1246	<	* @throws SecurityException if a security manager exists and
1247	<	*         the caller is not permitted to modify threads
1248	<	*         because it does not hold {@link
1249	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1250	<	*/
1251	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
1252	<	this(Runtime.getRuntime().availableProcessors(), factory);
2517	>	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
2518		}
2519
2520		/**
2521	<	* Creates a {@code ForkJoinPool} with the given parallelism and
1257	<	* thread factory.
2521	>	* Creates a {@code ForkJoinPool} with the given parameters.
2522		*
2523	<	* @param parallelism the parallelism level
2524	<	* @param factory the factory for creating new threads
2523	>	* @param parallelism the parallelism level. For default value,
2524	>	* use {@link java.lang.Runtime#availableProcessors}.
2525	>	* @param factory the factory for creating new threads. For default value,
2526	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
2527	>	* @param handler the handler for internal worker threads that
2528	>	* terminate due to unrecoverable errors encountered while executing
2529	>	* tasks. For default value, use {@code null}.
2530	>	* @param asyncMode if true,
2531	>	* establishes local first-in-first-out scheduling mode for forked
2532	>	* tasks that are never joined. This mode may be more appropriate
2533	>	* than default locally stack-based mode in applications in which
2534	>	* worker threads only process event-style asynchronous tasks.
2535	>	* For default value, use {@code false}.
2536		* @throws IllegalArgumentException if parallelism less than or
2537		*         equal to zero, or greater than implementation limit
2538		* @throws NullPointerException if the factory is null
#	Line 1266 | Line 2541 | public class ForkJoinPool extends Abstra
2541		*         because it does not hold {@link
2542		*         java.lang.RuntimePermission}{@code ("modifyThread")}
2543		*/
2544	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
2544	>	public ForkJoinPool(int parallelism,
2545	>	ForkJoinWorkerThreadFactory factory,
2546	>	Thread.UncaughtExceptionHandler handler,
2547	>	boolean asyncMode) {
2548		checkPermission();
2549		if (factory == null)
2550		throw new NullPointerException();
2551	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
2551	>	if (parallelism <= 0 || parallelism > MAX_CAP)
2552		throw new IllegalArgumentException();
1275	–	this.poolNumber = poolNumberGenerator.incrementAndGet();
1276	–	int arraySize = initialArraySizeFor(parallelism);
1277	–	this.parallelism = parallelism;
2553		this.factory = factory;
2554	<	this.maxPoolSize = MAX_THREADS;
2555	<	this.maintainsParallelism = true;
2556	<	this.workers = new ForkJoinWorkerThread[arraySize];
2557	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
2558	<	this.workerLock = new ReentrantLock();
2559	<	this.terminationLatch = new CountDownLatch(1);
2554	>	this.ueh = handler;
2555	>	this.config = parallelism | (asyncMode ? (FIFO_QUEUE << 16) : 0);
2556	>	long np = (long)(-parallelism); // offset ctl counts
2557	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
2558	>	int pn = nextPoolId();
2559	>	StringBuilder sb = new StringBuilder("ForkJoinPool-");
2560	>	sb.append(Integer.toString(pn));
2561	>	sb.append("-worker-");
2562	>	this.workerNamePrefix = sb.toString();
2563		}
2564
2565		/**
2566	<	* Returns initial power of two size for workers array.
2567	<	* @param pc the initial parallelism level
2568	<	*/
2569	<	private static int initialArraySizeFor(int pc) {
2570	<	// See Hackers Delight, sec 3.2. We know MAX_THREADS < (1 >>> 16)
2571	<	int size = pc < MAX_THREADS ? pc + 1 : MAX_THREADS;
2572	<	size |= size >>> 1;
2573	<	size |= size >>> 2;
2574	<	size |= size >>> 4;
2575	<	size |= size >>> 8;
2576	<	return size + 1;
2566	>	* Constructor for common pool, suitable only for static initialization.
2567	>	* Basically the same as above, but uses smallest possible initial footprint.
2568	>	*/
2569	>	ForkJoinPool(int parallelism, long ctl,
2570	>	ForkJoinWorkerThreadFactory factory,
2571	>	Thread.UncaughtExceptionHandler handler) {
2572	>	this.config = parallelism;
2573	>	this.ctl = ctl;
2574	>	this.factory = factory;
2575	>	this.ueh = handler;
2576	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2577		}
2578
1301	–	// Execution methods
1302	–
2579		/**
2580	<	* Common code for execute, invoke and submit
2580	>	* Returns the common pool instance.
2581	>	*
2582	>	* @return the common pool instance
2583		*/
2584	<	private <T> void doSubmit(ForkJoinTask<T> task) {
2585	<	if (task == null)
2586	<	throw new NullPointerException();
1309	<	if (runState >= SHUTDOWN)
1310	<	throw new RejectedExecutionException();
1311	<	submissionQueue.offer(task);
1312	<	advanceEventCount();
1313	<	releaseWaiters();
1314	<	ensureEnoughTotalWorkers();
2584	>	public static ForkJoinPool commonPool() {
2585	>	// assert commonPool != null : "static init error";
2586	>	return commonPool;
2587		}
2588
2589	+	// Execution methods
2590	+
2591		/**
2592		* Performs the given task, returning its result upon completion.
2593	+	* If the computation encounters an unchecked Exception or Error,
2594	+	* it is rethrown as the outcome of this invocation.  Rethrown
2595	+	* exceptions behave in the same way as regular exceptions, but,
2596	+	* when possible, contain stack traces (as displayed for example
2597	+	* using {@code ex.printStackTrace()}) of both the current thread
2598	+	* as well as the thread actually encountering the exception;
2599	+	* minimally only the latter.
2600		*
2601		* @param task the task
2602		* @return the task's result
#	Line 1324 | Line 2605 | public class ForkJoinPool extends Abstra
2605		*         scheduled for execution
2606		*/
2607		public <T> T invoke(ForkJoinTask<T> task) {
2608	<	doSubmit(task);
2608	>	if (task == null)
2609	>	throw new NullPointerException();
2610	>	externalPush(task);
2611		return task.join();
2612		}
2613
#	Line 1337 | Line 2620 | public class ForkJoinPool extends Abstra
2620		*         scheduled for execution
2621		*/
2622		public void execute(ForkJoinTask<?> task) {
2623	<	doSubmit(task);
2623	>	if (task == null)
2624	>	throw new NullPointerException();
2625	>	externalPush(task);
2626		}
2627
2628		// AbstractExecutorService methods
#	Line 1348 | Line 2633 | public class ForkJoinPool extends Abstra
2633		*         scheduled for execution
2634		*/
2635		public void execute(Runnable task) {
2636	+	if (task == null)
2637	+	throw new NullPointerException();
2638		ForkJoinTask<?> job;
2639		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2640		job = (ForkJoinTask<?>) task;
2641		else
2642	<	job = ForkJoinTask.adapt(task, null);
2643	<	doSubmit(job);
2642	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2643	>	externalPush(job);
2644	>	}
2645	>
2646	>	/**
2647	>	* Submits a ForkJoinTask for execution.
2648	>	*
2649	>	* @param task the task to submit
2650	>	* @return the task
2651	>	* @throws NullPointerException if the task is null
2652	>	* @throws RejectedExecutionException if the task cannot be
2653	>	*         scheduled for execution
2654	>	*/
2655	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2656	>	if (task == null)
2657	>	throw new NullPointerException();
2658	>	externalPush(task);
2659	>	return task;
2660		}
2661
2662		/**
#	Line 1362 | Line 2665 | public class ForkJoinPool extends Abstra
2665		*         scheduled for execution
2666		*/
2667		public <T> ForkJoinTask<T> submit(Callable<T> task) {
2668	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
2669	<	doSubmit(job);
2668	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2669	>	externalPush(job);
2670		return job;
2671		}
2672
#	Line 1373 | Line 2676 | public class ForkJoinPool extends Abstra
2676		*         scheduled for execution
2677		*/
2678		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2679	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
2680	<	doSubmit(job);
2679	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2680	>	externalPush(job);
2681		return job;
2682		}
2683
#	Line 1384 | Line 2687 | public class ForkJoinPool extends Abstra
2687		*         scheduled for execution
2688		*/
2689		public ForkJoinTask<?> submit(Runnable task) {
2690	+	if (task == null)
2691	+	throw new NullPointerException();
2692		ForkJoinTask<?> job;
2693		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2694		job = (ForkJoinTask<?>) task;
2695		else
2696	<	job = ForkJoinTask.adapt(task, null);
2697	<	doSubmit(job);
2696	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2697	>	externalPush(job);
2698		return job;
2699		}
2700
2701		/**
1397	–	* Submits a ForkJoinTask for execution.
1398	–	*
1399	–	* @param task the task to submit
1400	–	* @return the task
1401	–	* @throws NullPointerException if the task is null
1402	–	* @throws RejectedExecutionException if the task cannot be
1403	–	*         scheduled for execution
1404	–	*/
1405	–	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1406	–	doSubmit(task);
1407	–	return task;
1408	–	}
1409	–
1410	–	/**
2702		* @throws NullPointerException       {@inheritDoc}
2703		* @throws RejectedExecutionException {@inheritDoc}
2704		*/
2705		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
2706	<	ArrayList<ForkJoinTask<T>> forkJoinTasks =
2707	<	new ArrayList<ForkJoinTask<T>>(tasks.size());
2708	<	for (Callable<T> task : tasks)
2709	<	forkJoinTasks.add(ForkJoinTask.adapt(task));
2710	<	invoke(new InvokeAll<T>(forkJoinTasks));
2711	<
2706	>	// In previous versions of this class, this method constructed
2707	>	// a task to run ForkJoinTask.invokeAll, but now external
2708	>	// invocation of multiple tasks is at least as efficient.
2709	>	List<ForkJoinTask<T>> fs = new ArrayList<ForkJoinTask<T>>(tasks.size());
2710	>	// Workaround needed because method wasn't declared with
2711	>	// wildcards in return type but should have been.
2712		@SuppressWarnings({"unchecked", "rawtypes"})
2713	<	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1423	<	return futures;
1424	<	}
2713	>	List<Future<T>> futures = (List<Future<T>>) (List) fs;
2714
2715	<	static final class InvokeAll<T> extends RecursiveAction {
2716	<	final ArrayList<ForkJoinTask<T>> tasks;
2717	<	InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
2718	<	public void compute() {
2719	<	try { invokeAll(tasks); }
2720	<	catch (Exception ignore) {}
2715	>	boolean done = false;
2716	>	try {
2717	>	for (Callable<T> t : tasks) {
2718	>	ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2719	>	externalPush(f);
2720	>	fs.add(f);
2721	>	}
2722	>	for (ForkJoinTask<T> f : fs)
2723	>	f.quietlyJoin();
2724	>	done = true;
2725	>	return futures;
2726	>	} finally {
2727	>	if (!done)
2728	>	for (ForkJoinTask<T> f : fs)
2729	>	f.cancel(false);
2730		}
1433	–	private static final long serialVersionUID = -7914297376763021607L;
2731		}
2732
2733		/**
#	Line 1449 | Line 2746 | public class ForkJoinPool extends Abstra
2746		* @return the handler, or {@code null} if none
2747		*/
2748		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1452	–	workerCountReadFence();
2749		return ueh;
2750		}
2751
2752		/**
2753	<	* Sets the handler for internal worker threads that terminate due
1458	<	* to unrecoverable errors encountered while executing tasks.
1459	<	* Unless set, the current default or ThreadGroup handler is used
1460	<	* as handler.
1461	<	*
1462	<	* @param h the new handler
1463	<	* @return the old handler, or {@code null} if none
1464	<	* @throws SecurityException if a security manager exists and
1465	<	*         the caller is not permitted to modify threads
1466	<	*         because it does not hold {@link
1467	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1468	<	*/
1469	<	public Thread.UncaughtExceptionHandler
1470	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
1471	<	checkPermission();
1472	<	Thread.UncaughtExceptionHandler old = ueh;
1473	<	if (h != old) {
1474	<	ueh = h;
1475	<	ForkJoinWorkerThread[] ws = workers;
1476	<	int nws = ws.length;
1477	<	for (int i = 0; i < nws; ++i) {
1478	<	ForkJoinWorkerThread w = ws[i];
1479	<	if (w != null)
1480	<	w.setUncaughtExceptionHandler(h);
1481	<	}
1482	<	}
1483	<	return old;
1484	<	}
1485	<
1486	<	/**
1487	<	* Sets the target parallelism level of this pool.
2753	>	* Returns the targeted parallelism level of this pool.
2754		*
2755	<	* @param parallelism the target parallelism
1490	<	* @throws IllegalArgumentException if parallelism less than or
1491	<	* equal to zero or greater than maximum size bounds
1492	<	* @throws SecurityException if a security manager exists and
1493	<	*         the caller is not permitted to modify threads
1494	<	*         because it does not hold {@link
1495	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
2755	>	* @return the targeted parallelism level of this pool
2756		*/
2757	<	public void setParallelism(int parallelism) {
2758	<	checkPermission();
1499	<	if (parallelism <= 0 || parallelism > maxPoolSize)
1500	<	throw new IllegalArgumentException();
1501	<	workerCountReadFence();
1502	<	int pc = this.parallelism;
1503	<	if (pc != parallelism) {
1504	<	this.parallelism = parallelism;
1505	<	workerCountWriteFence();
1506	<	// Release spares. If too many, some will die after re-suspend
1507	<	ForkJoinWorkerThread[] ws = workers;
1508	<	int nws = ws.length;
1509	<	for (int i = 0; i < nws; ++i) {
1510	<	ForkJoinWorkerThread w = ws[i];
1511	<	if (w != null && w.tryUnsuspend()) {
1512	<	int c;
1513	<	do {} while (!UNSAFE.compareAndSwapInt
1514	<	(this, workerCountsOffset,
1515	<	c = workerCounts, c + ONE_RUNNING));
1516	<	LockSupport.unpark(w);
1517	<	}
1518	<	}
1519	<	ensureEnoughTotalWorkers();
1520	<	advanceEventCount();
1521	<	releaseWaiters(); // force config recheck by existing workers
1522	<	}
2757	>	public int getParallelism() {
2758	>	return config & SMASK;
2759		}
2760
2761		/**
2762	<	* Returns the targeted parallelism level of this pool.
2762	>	* Returns the targeted parallelism level of the common pool.
2763		*
2764	<	* @return the targeted parallelism level of this pool
2764	>	* @return the targeted parallelism level of the common pool
2765		*/
2766	<	public int getParallelism() {
2767	<	//        workerCountReadFence(); // inlined below
1532	<	int ignore = workerCounts;
1533	<	return parallelism;
2766	>	public static int getCommonPoolParallelism() {
2767	>	return commonPoolParallelism;
2768		}
2769
2770		/**
2771		* Returns the number of worker threads that have started but not
2772	<	* yet terminated.  This result returned by this method may differ
2772	>	* yet terminated.  The result returned by this method may differ
2773		* from {@link #getParallelism} when threads are created to
2774		* maintain parallelism when others are cooperatively blocked.
2775		*
2776		* @return the number of worker threads
2777		*/
2778		public int getPoolSize() {
2779	<	return workerCounts >>> TOTAL_COUNT_SHIFT;
1546	<	}
1547	<
1548	<	/**
1549	<	* Returns the maximum number of threads allowed to exist in the
1550	<	* pool. Unless set using {@link #setMaximumPoolSize}, the
1551	<	* maximum is an implementation-defined value designed only to
1552	<	* prevent runaway growth.
1553	<	*
1554	<	* @return the maximum
1555	<	*/
1556	<	public int getMaximumPoolSize() {
1557	<	workerCountReadFence();
1558	<	return maxPoolSize;
1559	<	}
1560	<
1561	<	/**
1562	<	* Sets the maximum number of threads allowed to exist in the
1563	<	* pool. The given value should normally be greater than or equal
1564	<	* to the {@link #getParallelism parallelism} level. Setting this
1565	<	* value has no effect on current pool size. It controls
1566	<	* construction of new threads. The use of this method may cause
1567	<	* tasks that intrinsically require extra threads for dependent
1568	<	* computations to indefinitely stall. If you are instead trying
1569	<	* to minimize internal thread creation, consider setting {@link
1570	<	* #setMaintainsParallelism} as false.
1571	<	*
1572	<	* @throws IllegalArgumentException if negative or greater than
1573	<	* internal implementation limit
1574	<	*/
1575	<	public void setMaximumPoolSize(int newMax) {
1576	<	if (newMax < 0 || newMax > MAX_THREADS)
1577	<	throw new IllegalArgumentException();
1578	<	maxPoolSize = newMax;
1579	<	workerCountWriteFence();
1580	<	}
1581	<
1582	<	/**
1583	<	* Returns {@code true} if this pool dynamically maintains its
1584	<	* target parallelism level. If false, new threads are added only
1585	<	* to avoid possible starvation.  This setting is by default true.
1586	<	*
1587	<	* @return {@code true} if maintains parallelism
1588	<	*/
1589	<	public boolean getMaintainsParallelism() {
1590	<	workerCountReadFence();
1591	<	return maintainsParallelism;
1592	<	}
1593	<
1594	<	/**
1595	<	* Sets whether this pool dynamically maintains its target
1596	<	* parallelism level. If false, new threads are added only to
1597	<	* avoid possible starvation.
1598	<	*
1599	<	* @param enable {@code true} to maintain parallelism
1600	<	*/
1601	<	public void setMaintainsParallelism(boolean enable) {
1602	<	maintainsParallelism = enable;
1603	<	workerCountWriteFence();
1604	<	}
1605	<
1606	<	/**
1607	<	* Establishes local first-in-first-out scheduling mode for forked
1608	<	* tasks that are never joined. This mode may be more appropriate
1609	<	* than default locally stack-based mode in applications in which
1610	<	* worker threads only process asynchronous tasks.  This method is
1611	<	* designed to be invoked only when the pool is quiescent, and
1612	<	* typically only before any tasks are submitted. The effects of
1613	<	* invocations at other times may be unpredictable.
1614	<	*
1615	<	* @param async if {@code true}, use locally FIFO scheduling
1616	<	* @return the previous mode
1617	<	* @see #getAsyncMode
1618	<	*/
1619	<	public boolean setAsyncMode(boolean async) {
1620	<	workerCountReadFence();
1621	<	boolean oldMode = locallyFifo;
1622	<	if (oldMode != async) {
1623	<	locallyFifo = async;
1624	<	workerCountWriteFence();
1625	<	ForkJoinWorkerThread[] ws = workers;
1626	<	int nws = ws.length;
1627	<	for (int i = 0; i < nws; ++i) {
1628	<	ForkJoinWorkerThread w = ws[i];
1629	<	if (w != null)
1630	<	w.setAsyncMode(async);
1631	<	}
1632	<	}
1633	<	return oldMode;
2779	>	return (config & SMASK) + (short)(ctl >>> TC_SHIFT);
2780		}
2781
2782		/**
#	Line 1638 | Line 2784 | public class ForkJoinPool extends Abstra
2784		* scheduling mode for forked tasks that are never joined.
2785		*
2786		* @return {@code true} if this pool uses async mode
1641	–	* @see #setAsyncMode
2787		*/
2788		public boolean getAsyncMode() {
2789	<	workerCountReadFence();
1645	<	return locallyFifo;
2789	>	return (config >>> 16) == FIFO_QUEUE;
2790		}
2791
2792		/**
#	Line 1654 | Line 2798 | public class ForkJoinPool extends Abstra
2798		* @return the number of worker threads
2799		*/
2800		public int getRunningThreadCount() {
2801	<	return workerCounts & RUNNING_COUNT_MASK;
2801	>	int rc = 0;
2802	>	WorkQueue[] ws; WorkQueue w;
2803	>	if ((ws = workQueues) != null) {
2804	>	for (int i = 1; i < ws.length; i += 2) {
2805	>	if ((w = ws[i]) != null && w.isApparentlyUnblocked())
2806	>	++rc;
2807	>	}
2808	>	}
2809	>	return rc;
2810		}
2811
2812		/**
#	Line 1665 | Line 2817 | public class ForkJoinPool extends Abstra
2817		* @return the number of active threads
2818		*/
2819		public int getActiveThreadCount() {
2820	<	return runState & ACTIVE_COUNT_MASK;
2820	>	int r = (config & SMASK) + (int)(ctl >> AC_SHIFT);
2821	>	return (r <= 0) ? 0 : r; // suppress momentarily negative values
2822		}
2823
2824		/**
#	Line 1680 | Line 2833 | public class ForkJoinPool extends Abstra
2833		* @return {@code true} if all threads are currently idle
2834		*/
2835		public boolean isQuiescent() {
2836	<	return (runState & ACTIVE_COUNT_MASK) == 0;
2836	>	return (int)(ctl >> AC_SHIFT) + (config & SMASK) == 0;
2837		}
2838
2839		/**
#	Line 1695 | Line 2848 | public class ForkJoinPool extends Abstra
2848		* @return the number of steals
2849		*/
2850		public long getStealCount() {
2851	<	return stealCount;
2851	>	long count = stealCount;
2852	>	WorkQueue[] ws; WorkQueue w;
2853	>	if ((ws = workQueues) != null) {
2854	>	for (int i = 1; i < ws.length; i += 2) {
2855	>	if ((w = ws[i]) != null)
2856	>	count += w.nsteals;
2857	>	}
2858	>	}
2859	>	return count;
2860		}
2861
2862		/**
#	Line 1710 | Line 2871 | public class ForkJoinPool extends Abstra
2871		*/
2872		public long getQueuedTaskCount() {
2873		long count = 0;
2874	<	ForkJoinWorkerThread[] ws = workers;
2875	<	int nws = ws.length;
2876	<	for (int i = 0; i < nws; ++i) {
2877	<	ForkJoinWorkerThread w = ws[i];
2878	<	if (w != null)
2879	<	count += w.getQueueSize();
2874	>	WorkQueue[] ws; WorkQueue w;
2875	>	if ((ws = workQueues) != null) {
2876	>	for (int i = 1; i < ws.length; i += 2) {
2877	>	if ((w = ws[i]) != null)
2878	>	count += w.queueSize();
2879	>	}
2880		}
2881		return count;
2882		}
2883
2884		/**
2885		* Returns an estimate of the number of tasks submitted to this
2886	<	* pool that have not yet begun executing.  This method takes time
2887	<	* proportional to the number of submissions.
2886	>	* pool that have not yet begun executing.  This method may take
2887	>	* time proportional to the number of submissions.
2888		*
2889		* @return the number of queued submissions
2890		*/
2891		public int getQueuedSubmissionCount() {
2892	<	return submissionQueue.size();
2892	>	int count = 0;
2893	>	WorkQueue[] ws; WorkQueue w;
2894	>	if ((ws = workQueues) != null) {
2895	>	for (int i = 0; i < ws.length; i += 2) {
2896	>	if ((w = ws[i]) != null)
2897	>	count += w.queueSize();
2898	>	}
2899	>	}
2900	>	return count;
2901		}
2902
2903		/**
#	Line 1738 | Line 2907 | public class ForkJoinPool extends Abstra
2907		* @return {@code true} if there are any queued submissions
2908		*/
2909		public boolean hasQueuedSubmissions() {
2910	<	return !submissionQueue.isEmpty();
2910	>	WorkQueue[] ws; WorkQueue w;
2911	>	if ((ws = workQueues) != null) {
2912	>	for (int i = 0; i < ws.length; i += 2) {
2913	>	if ((w = ws[i]) != null && !w.isEmpty())
2914	>	return true;
2915	>	}
2916	>	}
2917	>	return false;
2918		}
2919
2920		/**
#	Line 1749 | Line 2925 | public class ForkJoinPool extends Abstra
2925		* @return the next submission, or {@code null} if none
2926		*/
2927		protected ForkJoinTask<?> pollSubmission() {
2928	<	return submissionQueue.poll();
2928	>	WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2929	>	if ((ws = workQueues) != null) {
2930	>	for (int i = 0; i < ws.length; i += 2) {
2931	>	if ((w = ws[i]) != null && (t = w.poll()) != null)
2932	>	return t;
2933	>	}
2934	>	}
2935	>	return null;
2936		}
2937
2938		/**
#	Line 1770 | Line 2953 | public class ForkJoinPool extends Abstra
2953		* @return the number of elements transferred
2954		*/
2955		protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
2956	<	int n = submissionQueue.drainTo(c);
2957	<	ForkJoinWorkerThread[] ws = workers;
2958	<	int nws = ws.length;
2959	<	for (int i = 0; i < nws; ++i) {
2960	<	ForkJoinWorkerThread w = ws[i];
2961	<	if (w != null)
2962	<	n += w.drainTasksTo(c);
2956	>	int count = 0;
2957	>	WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2958	>	if ((ws = workQueues) != null) {
2959	>	for (int i = 0; i < ws.length; ++i) {
2960	>	if ((w = ws[i]) != null) {
2961	>	while ((t = w.poll()) != null) {
2962	>	c.add(t);
2963	>	++count;
2964	>	}
2965	>	}
2966	>	}
2967		}
2968	<	return n;
2968	>	return count;
2969		}
2970
2971		/**
#	Line 1789 | Line 2976 | public class ForkJoinPool extends Abstra
2976		* @return a string identifying this pool, as well as its state
2977		*/
2978		public String toString() {
2979	<	long st = getStealCount();
2980	<	long qt = getQueuedTaskCount();
2981	<	long qs = getQueuedSubmissionCount();
2982	<	int wc = workerCounts;
2983	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
2984	<	int rc = wc & RUNNING_COUNT_MASK;
2985	<	int pc = parallelism;
2986	<	int rs = runState;
2987	<	int ac = rs & ACTIVE_COUNT_MASK;
2979	>	// Use a single pass through workQueues to collect counts
2980	>	long qt = 0L, qs = 0L; int rc = 0;
2981	>	long st = stealCount;
2982	>	long c = ctl;
2983	>	WorkQueue[] ws; WorkQueue w;
2984	>	if ((ws = workQueues) != null) {
2985	>	for (int i = 0; i < ws.length; ++i) {
2986	>	if ((w = ws[i]) != null) {
2987	>	int size = w.queueSize();
2988	>	if ((i & 1) == 0)
2989	>	qs += size;
2990	>	else {
2991	>	qt += size;
2992	>	st += w.nsteals;
2993	>	if (w.isApparentlyUnblocked())
2994	>	++rc;
2995	>	}
2996	>	}
2997	>	}
2998	>	}
2999	>	int pc = (config & SMASK);
3000	>	int tc = pc + (short)(c >>> TC_SHIFT);
3001	>	int ac = pc + (int)(c >> AC_SHIFT);
3002	>	if (ac < 0) // ignore transient negative
3003	>	ac = 0;
3004	>	String level;
3005	>	if ((c & STOP_BIT) != 0)
3006	>	level = (tc == 0) ? "Terminated" : "Terminating";
3007	>	else
3008	>	level = plock < 0 ? "Shutting down" : "Running";
3009		return super.toString() +
3010	<	"[" + runLevelToString(rs) +
3010	>	"[" + level +
3011		", parallelism = " + pc +
3012		", size = " + tc +
3013		", active = " + ac +
#	Line 1810 | Line 3018 | public class ForkJoinPool extends Abstra
3018		"]";
3019		}
3020
1813	–	private static String runLevelToString(int s) {
1814	–	return ((s & TERMINATED) != 0 ? "Terminated" :
1815	–	((s & TERMINATING) != 0 ? "Terminating" :
1816	–	((s & SHUTDOWN) != 0 ? "Shutting down" :
1817	–	"Running")));
1818	–	}
1819	–
3021		/**
3022	<	* Initiates an orderly shutdown in which previously submitted
3023	<	* tasks are executed, but no new tasks will be accepted.
3024	<	* Invocation has no additional effect if already shut down.
3025	<	* Tasks that are in the process of being submitted concurrently
3026	<	* during the course of this method may or may not be rejected.
3022	>	* Possibly initiates an orderly shutdown in which previously
3023	>	* submitted tasks are executed, but no new tasks will be
3024	>	* accepted. Invocation has no effect on execution state if this
3025	>	* is the {@link #commonPool}, and no additional effect if
3026	>	* already shut down.  Tasks that are in the process of being
3027	>	* submitted concurrently during the course of this method may or
3028	>	* may not be rejected.
3029		*
3030		* @throws SecurityException if a security manager exists and
3031		*         the caller is not permitted to modify threads
#	Line 1831 | Line 3034 | public class ForkJoinPool extends Abstra
3034		*/
3035		public void shutdown() {
3036		checkPermission();
3037	<	advanceRunLevel(SHUTDOWN);
1835	<	tryTerminate(false);
3037	>	tryTerminate(false, true);
3038		}
3039
3040		/**
3041	<	* Attempts to cancel and/or stop all tasks, and reject all
3042	<	* subsequently submitted tasks.  Tasks that are in the process of
3043	<	* being submitted or executed concurrently during the course of
3044	<	* this method may or may not be rejected. This method cancels
3045	<	* both existing and unexecuted tasks, in order to permit
3046	<	* termination in the presence of task dependencies. So the method
3047	<	* always returns an empty list (unlike the case for some other
3048	<	* Executors).
3041	>	* Possibly attempts to cancel and/or stop all tasks, and reject
3042	>	* all subsequently submitted tasks.  Invocation has no effect on
3043	>	* execution state if this is the {@link #commonPool}, and no
3044	>	* additional effect if already shut down. Otherwise, tasks that
3045	>	* are in the process of being submitted or executed concurrently
3046	>	* during the course of this method may or may not be
3047	>	* rejected. This method cancels both existing and unexecuted
3048	>	* tasks, in order to permit termination in the presence of task
3049	>	* dependencies. So the method always returns an empty list
3050	>	* (unlike the case for some other Executors).
3051		*
3052		* @return an empty list
3053		* @throws SecurityException if a security manager exists and
#	Line 1853 | Line 3057 | public class ForkJoinPool extends Abstra
3057		*/
3058		public List<Runnable> shutdownNow() {
3059		checkPermission();
3060	<	tryTerminate(true);
3060	>	tryTerminate(true, true);
3061		return Collections.emptyList();
3062		}
3063
#	Line 1863 | Line 3067 | public class ForkJoinPool extends Abstra
3067		* @return {@code true} if all tasks have completed following shut down
3068		*/
3069		public boolean isTerminated() {
3070	<	return runState >= TERMINATED;
3070	>	long c = ctl;
3071	>	return ((c & STOP_BIT) != 0L &&
3072	>	(short)(c >>> TC_SHIFT) == -(config & SMASK));
3073		}
3074
3075		/**
#	Line 1871 | Line 3077 | public class ForkJoinPool extends Abstra
3077		* commenced but not yet completed.  This method may be useful for
3078		* debugging. A return of {@code true} reported a sufficient
3079		* period after shutdown may indicate that submitted tasks have
3080	<	* ignored or suppressed interruption, causing this executor not
3081	<	* to properly terminate.
3080	>	* ignored or suppressed interruption, or are waiting for I/O,
3081	>	* causing this executor not to properly terminate. (See the
3082	>	* advisory notes for class {@link ForkJoinTask} stating that
3083	>	* tasks should not normally entail blocking operations.  But if
3084	>	* they do, they must abort them on interrupt.)
3085		*
3086		* @return {@code true} if terminating but not yet terminated
3087		*/
3088		public boolean isTerminating() {
3089	<	return (runState & (TERMINATING|TERMINATED)) == TERMINATING;
3089	>	long c = ctl;
3090	>	return ((c & STOP_BIT) != 0L &&
3091	>	(short)(c >>> TC_SHIFT) != -(config & SMASK));
3092		}
3093
3094		/**
#	Line 1886 | Line 3097 | public class ForkJoinPool extends Abstra
3097		* @return {@code true} if this pool has been shut down
3098		*/
3099		public boolean isShutdown() {
3100	<	return runState >= SHUTDOWN;
3100	>	return plock < 0;
3101		}
3102
3103		/**
3104	<	* Blocks until all tasks have completed execution after a shutdown
3105	<	* request, or the timeout occurs, or the current thread is
3106	<	* interrupted, whichever happens first.
3104	>	* Blocks until all tasks have completed execution after a
3105	>	* shutdown request, or the timeout occurs, or the current thread
3106	>	* is interrupted, whichever happens first. Note that the {@link
3107	>	* #commonPool()} never terminates until program shutdown so
3108	>	* this method will always time out.
3109		*
3110		* @param timeout the maximum time to wait
3111		* @param unit the time unit of the timeout argument
#	Line 1902 | Line 3115 | public class ForkJoinPool extends Abstra
3115		*/
3116		public boolean awaitTermination(long timeout, TimeUnit unit)
3117		throws InterruptedException {
3118	<	return terminationLatch.await(timeout, unit);
3118	>	long nanos = unit.toNanos(timeout);
3119	>	if (isTerminated())
3120	>	return true;
3121	>	long startTime = System.nanoTime();
3122	>	boolean terminated = false;
3123	>	synchronized (this) {
3124	>	for (long waitTime = nanos, millis = 0L;;) {
3125	>	if (terminated = isTerminated() ||
3126	>	waitTime <= 0L ||
3127	>	(millis = unit.toMillis(waitTime)) <= 0L)
3128	>	break;
3129	>	wait(millis);
3130	>	waitTime = nanos - (System.nanoTime() - startTime);
3131	>	}
3132	>	}
3133	>	return terminated;
3134		}
3135
3136		/**
3137		* Interface for extending managed parallelism for tasks running
3138		* in {@link ForkJoinPool}s.
3139		*
3140	<	* <p>A {@code ManagedBlocker} provides two methods.
3141	<	* Method {@code isReleasable} must return {@code true} if
3142	<	* blocking is not necessary. Method {@code block} blocks the
3143	<	* current thread if necessary (perhaps internally invoking
3144	<	* {@code isReleasable} before actually blocking).
3140	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
3141	>	* {@code isReleasable} must return {@code true} if blocking is
3142	>	* not necessary. Method {@code block} blocks the current thread
3143	>	* if necessary (perhaps internally invoking {@code isReleasable}
3144	>	* before actually blocking). These actions are performed by any
3145	>	* thread invoking {@link ForkJoinPool#managedBlock}.  The
3146	>	* unusual methods in this API accommodate synchronizers that may,
3147	>	* but don't usually, block for long periods. Similarly, they
3148	>	* allow more efficient internal handling of cases in which
3149	>	* additional workers may be, but usually are not, needed to
3150	>	* ensure sufficient parallelism.  Toward this end,
3151	>	* implementations of method {@code isReleasable} must be amenable
3152	>	* to repeated invocation.
3153		*
3154		* <p>For example, here is a ManagedBlocker based on a
3155		* ReentrantLock:
#	Line 1931 | Line 3167 | public class ForkJoinPool extends Abstra
3167		*     return hasLock || (hasLock = lock.tryLock());
3168		*   }
3169		* }}</pre>
3170	+	*
3171	+	* <p>Here is a class that possibly blocks waiting for an
3172	+	* item on a given queue:
3173	+	*  <pre> {@code
3174	+	* class QueueTaker<E> implements ManagedBlocker {
3175	+	*   final BlockingQueue<E> queue;
3176	+	*   volatile E item = null;
3177	+	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
3178	+	*   public boolean block() throws InterruptedException {
3179	+	*     if (item == null)
3180	+	*       item = queue.take();
3181	+	*     return true;
3182	+	*   }
3183	+	*   public boolean isReleasable() {
3184	+	*     return item != null || (item = queue.poll()) != null;
3185	+	*   }
3186	+	*   public E getItem() { // call after pool.managedBlock completes
3187	+	*     return item;
3188	+	*   }
3189	+	* }}</pre>
3190		*/
3191		public static interface ManagedBlocker {
3192		/**
#	Line 1954 | Line 3210 | public class ForkJoinPool extends Abstra
3210		* Blocks in accord with the given blocker.  If the current thread
3211		* is a {@link ForkJoinWorkerThread}, this method possibly
3212		* arranges for a spare thread to be activated if necessary to
3213	<	* ensure parallelism while the current thread is blocked.
1958	<	*
1959	<	* <p>If {@code maintainParallelism} is {@code true} and the pool
1960	<	* supports it ({@link #getMaintainsParallelism}), this method
1961	<	* attempts to maintain the pool's nominal parallelism. Otherwise
1962	<	* it activates a thread only if necessary to avoid complete
1963	<	* starvation. This option may be preferable when blockages use
1964	<	* timeouts, or are almost always brief.
3213	>	* ensure sufficient parallelism while the current thread is blocked.
3214		*
3215		* <p>If the caller is not a {@link ForkJoinTask}, this method is
3216		* behaviorally equivalent to
#	Line 1975 | Line 3224 | public class ForkJoinPool extends Abstra
3224		* first be expanded to ensure parallelism, and later adjusted.
3225		*
3226		* @param blocker the blocker
1978	–	* @param maintainParallelism if {@code true} and supported by
1979	–	* this pool, attempt to maintain the pool's nominal parallelism;
1980	–	* otherwise activate a thread only if necessary to avoid
1981	–	* complete starvation.
3227		* @throws InterruptedException if blocker.block did so
3228		*/
3229	<	public static void managedBlock(ManagedBlocker blocker,
1985	<	boolean maintainParallelism)
3229	>	public static void managedBlock(ManagedBlocker blocker)
3230		throws InterruptedException {
3231		Thread t = Thread.currentThread();
3232	<	if (t instanceof ForkJoinWorkerThread)
3233	<	((ForkJoinWorkerThread) t).pool.
3234	<	awaitBlocker(blocker, maintainParallelism);
3235	<	else
3236	<	awaitBlocker(blocker);
3237	<	}
3238	<
3239	<	/**
3240	<	* Performs Non-FJ blocking
3241	<	*/
3242	<	private static void awaitBlocker(ManagedBlocker blocker)
3243	<	throws InterruptedException {
3244	<	do {} while (!blocker.isReleasable() && !blocker.block());
3232	>	if (t instanceof ForkJoinWorkerThread) {
3233	>	ForkJoinPool p = ((ForkJoinWorkerThread)t).pool;
3234	>	while (!blocker.isReleasable()) { // variant of helpSignal
3235	>	WorkQueue[] ws; WorkQueue q; int m, u;
3236	>	if ((ws = p.workQueues) != null && (m = ws.length - 1) >= 0) {
3237	>	for (int i = 0; i <= m; ++i) {
3238	>	if (blocker.isReleasable())
3239	>	return;
3240	>	if ((q = ws[i]) != null && q.base - q.top < 0) {
3241	>	p.signalWork(q);
3242	>	if ((u = (int)(p.ctl >>> 32)) >= 0 ||
3243	>	(u >> UAC_SHIFT) >= 0)
3244	>	break;
3245	>	}
3246	>	}
3247	>	}
3248	>	if (p.tryCompensate()) {
3249	>	try {
3250	>	do {} while (!blocker.isReleasable() &&
3251	>	!blocker.block());
3252	>	} finally {
3253	>	p.incrementActiveCount();
3254	>	}
3255	>	break;
3256	>	}
3257	>	}
3258	>	}
3259	>	else {
3260	>	do {} while (!blocker.isReleasable() &&
3261	>	!blocker.block());
3262	>	}
3263		}
3264
3265		// AbstractExecutorService overrides.  These rely on undocumented
#	Line 2005 | Line 3267 | public class ForkJoinPool extends Abstra
3267		// implement RunnableFuture.
3268
3269		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
3270	<	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
3270	>	return new ForkJoinTask.AdaptedRunnable<T>(runnable, value);
3271		}
3272
3273		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
3274	<	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
3274	>	return new ForkJoinTask.AdaptedCallable<T>(callable);
3275		}
3276
3277		// Unsafe mechanics
3278	+	private static final sun.misc.Unsafe U;
3279	+	private static final long CTL;
3280	+	private static final long PARKBLOCKER;
3281	+	private static final int ABASE;
3282	+	private static final int ASHIFT;
3283	+	private static final long STEALCOUNT;
3284	+	private static final long PLOCK;
3285	+	private static final long INDEXSEED;
3286	+	private static final long QLOCK;
3287
3288	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
3289	<	private static final long workerCountsOffset =
3290	<	objectFieldOffset("workerCounts", ForkJoinPool.class);
3291	<	private static final long runStateOffset =
3292	<	objectFieldOffset("runState", ForkJoinPool.class);
3293	<	private static final long eventCountOffset =
3294	<	objectFieldOffset("eventCount", ForkJoinPool.class);
3295	<	private static final long eventWaitersOffset =
3296	<	objectFieldOffset("eventWaiters",ForkJoinPool.class);
3297	<	private static final long stealCountOffset =
3298	<	objectFieldOffset("stealCount",ForkJoinPool.class);
3288	>	static {
3289	>	int s; // initialize field offsets for CAS etc
3290	>	try {
3291	>	U = getUnsafe();
3292	>	Class<?> k = ForkJoinPool.class;
3293	>	CTL = U.objectFieldOffset
3294	>	(k.getDeclaredField("ctl"));
3295	>	STEALCOUNT = U.objectFieldOffset
3296	>	(k.getDeclaredField("stealCount"));
3297	>	PLOCK = U.objectFieldOffset
3298	>	(k.getDeclaredField("plock"));
3299	>	INDEXSEED = U.objectFieldOffset
3300	>	(k.getDeclaredField("indexSeed"));
3301	>	Class<?> tk = Thread.class;
3302	>	PARKBLOCKER = U.objectFieldOffset
3303	>	(tk.getDeclaredField("parkBlocker"));
3304	>	Class<?> wk = WorkQueue.class;
3305	>	QLOCK = U.objectFieldOffset
3306	>	(wk.getDeclaredField("qlock"));
3307	>	Class<?> ak = ForkJoinTask[].class;
3308	>	ABASE = U.arrayBaseOffset(ak);
3309	>	s = U.arrayIndexScale(ak);
3310	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3311	>	} catch (Exception e) {
3312	>	throw new Error(e);
3313	>	}
3314	>	if ((s & (s-1)) != 0)
3315	>	throw new Error("data type scale not a power of two");
3316	>
3317	>	submitters = new ThreadLocal<Submitter>();
3318	>	ForkJoinWorkerThreadFactory fac = defaultForkJoinWorkerThreadFactory =
3319	>	new DefaultForkJoinWorkerThreadFactory();
3320	>	modifyThreadPermission = new RuntimePermission("modifyThread");
3321	>
3322	>	/*
3323	>	* Establish common pool parameters.  For extra caution,
3324	>	* computations to set up common pool state are here; the
3325	>	* constructor just assigns these values to fields.
3326	>	*/
3327
3328	+	int par = 0;
3329	+	Thread.UncaughtExceptionHandler handler = null;
3330	+	try {  // TBD: limit or report ignored exceptions?
3331	+	String pp = System.getProperty
3332	+	("java.util.concurrent.ForkJoinPool.common.parallelism");
3333	+	String hp = System.getProperty
3334	+	("java.util.concurrent.ForkJoinPool.common.exceptionHandler");
3335	+	String fp = System.getProperty
3336	+	("java.util.concurrent.ForkJoinPool.common.threadFactory");
3337	+	if (fp != null)
3338	+	fac = ((ForkJoinWorkerThreadFactory)ClassLoader.
3339	+	getSystemClassLoader().loadClass(fp).newInstance());
3340	+	if (hp != null)
3341	+	handler = ((Thread.UncaughtExceptionHandler)ClassLoader.
3342	+	getSystemClassLoader().loadClass(hp).newInstance());
3343	+	if (pp != null)
3344	+	par = Integer.parseInt(pp);
3345	+	} catch (Exception ignore) {
3346	+	}
3347	+
3348	+	if (par <= 0)
3349	+	par = Runtime.getRuntime().availableProcessors();
3350	+	if (par > MAX_CAP)
3351	+	par = MAX_CAP;
3352	+	commonPoolParallelism = par;
3353	+	long np = (long)(-par); // precompute initial ctl value
3354	+	long ct = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
3355
3356	<	private static long objectFieldOffset(String field, Class<?> klazz) {
2031	<	try {
2032	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
2033	<	} catch (NoSuchFieldException e) {
2034	<	// Convert Exception to corresponding Error
2035	<	NoSuchFieldError error = new NoSuchFieldError(field);
2036	<	error.initCause(e);
2037	<	throw error;
2038	<	}
3356	>	commonPool = new ForkJoinPool(par, ct, fac, handler);
3357		}
3358
3359		/**
#	Line 2065 | Line 3383 | public class ForkJoinPool extends Abstra
3383		}
3384		}
3385		}
3386	+
3387		}

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