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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.91 by dl, Tue Feb 22 00:39:31 2011 UTC vs.
Revision 1.135 by dl, Sun Oct 28 22:36:01 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;
#	Line 19 | Line 19 | import java.util.concurrent.Future;
19		import java.util.concurrent.RejectedExecutionException;
20		import java.util.concurrent.RunnableFuture;
21		import java.util.concurrent.TimeUnit;
22	–	import java.util.concurrent.TimeoutException;
22		import java.util.concurrent.atomic.AtomicInteger;
23	<	import java.util.concurrent.locks.LockSupport;
24	<	import java.util.concurrent.locks.ReentrantLock;
23	>	import java.util.concurrent.atomic.AtomicLong;
24	>	import java.util.concurrent.locks.AbstractQueuedSynchronizer;
25		import java.util.concurrent.locks.Condition;
26
27		/**
#	Line 34 | Line 33 | import java.util.concurrent.locks.Condit
33		* <p>A {@code ForkJoinPool} differs from other kinds of {@link
34		* ExecutorService} mainly by virtue of employing
35		* <em>work-stealing</em>: all threads in the pool attempt to find and
36	<	* execute subtasks created by other active tasks (eventually blocking
37	<	* waiting for work if none exist). This enables efficient processing
38	<	* when most tasks spawn other subtasks (as do most {@code
39	<	* ForkJoinTask}s). When setting <em>asyncMode</em> to true in
40	<	* constructors, {@code ForkJoinPool}s may also be appropriate for use
41	<	* with event-style tasks that are never joined.
36	>	* execute tasks submitted to the pool and/or created by other active
37	>	* tasks (eventually blocking waiting for work if none exist). This
38	>	* enables efficient processing when most tasks spawn other subtasks
39	>	* (as do most {@code ForkJoinTask}s), as well as when many small
40	>	* tasks are submitted to the pool from external clients.  Especially
41	>	* when setting <em>asyncMode</em> to true in constructors, {@code
42	>	* ForkJoinPool}s may also be appropriate for use with event-style
43	>	* tasks that are never joined.
44		*
45	<	* <p>A {@code ForkJoinPool} is constructed with a given target
46	<	* parallelism level; by default, equal to the number of available
47	<	* processors. The pool attempts to maintain enough active (or
48	<	* available) threads by dynamically adding, suspending, or resuming
49	<	* internal worker threads, even if some tasks are stalled waiting to
50	<	* join others. However, no such adjustments are guaranteed in the
51	<	* face of blocked IO or other unmanaged synchronization. The nested
52	<	* {@link ManagedBlocker} interface enables extension of the kinds of
45	>	* <p>A static {@link #commonPool} is available and appropriate for
46	>	* most applications. The common pool is constructed upon first
47	>	* access, or upon usage by any ForkJoinTask that is not explictly
48	>	* submitted to a specified pool. Using the common pool normally
49	>	* reduces resource usage (its threads are slowly reclaimed during
50	>	* periods of non-use, and reinstated upon subsequent use).  The
51	>	* common pool is by default constructed with default parameters, but
52	>	* these may be controlled by setting any or all of the three
53	>	* properties {@code
54	>	* java.util.concurrent.ForkJoinPool.common.{parallelism,
55	>	* threadFactory, exceptionHandler}}.
56	>	*
57	>	* <p>For applications that require separate or custom pools, a {@code
58	>	* ForkJoinPool} may be constructed with a given target parallelism
59	>	* level; by default, equal to the number of available processors. The
60	>	* pool attempts to maintain enough active (or available) threads by
61	>	* dynamically adding, suspending, or resuming internal worker
62	>	* threads, even if some tasks are stalled waiting to join
63	>	* others. However, no such adjustments are guaranteed in the face of
64	>	* blocked IO or other unmanaged synchronization. The nested {@link
65	>	* ManagedBlocker} interface enables extension of the kinds of
66		* synchronization accommodated.
67		*
68		* <p>In addition to execution and lifecycle control methods, this
#	Line 59 | Line 73 | import java.util.concurrent.locks.Condit
73		* convenient form for informal monitoring.
74		*
75		* <p> As is the case with other ExecutorServices, there are three
76	<	* main task execution methods summarized in the following
77	<	* table. These are designed to be used by clients not already engaged
78	<	* in fork/join computations in the current pool.  The main forms of
79	<	* these methods accept instances of {@code ForkJoinTask}, but
80	<	* overloaded forms also allow mixed execution of plain {@code
76	>	* main task execution methods summarized in the following table.
77	>	* These are designed to be used primarily by clients not already
78	>	* engaged in fork/join computations in the current pool.  The main
79	>	* forms of these methods accept instances of {@code ForkJoinTask},
80	>	* but overloaded forms also allow mixed execution of plain {@code
81		* Runnable}- or {@code Callable}- based activities as well.  However,
82	<	* tasks that are already executing in a pool should normally
83	<	* <em>NOT</em> use these pool execution methods, but instead use the
84	<	* within-computation forms listed in the table.
82	>	* tasks that are already executing in a pool should normally instead
83	>	* use the within-computation forms listed in the table unless using
84	>	* async event-style tasks that are not usually joined, in which case
85	>	* there is little difference among choice of methods.
86		*
87		* <table BORDER CELLPADDING=3 CELLSPACING=1>
88		*  <tr>
#	Line 92 | Line 107 | import java.util.concurrent.locks.Condit
107		*  </tr>
108		* </table>
109		*
95	–	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
96	–	* used for all parallel task execution in a program or subsystem.
97	–	* Otherwise, use would not usually outweigh the construction and
98	–	* bookkeeping overhead of creating a large set of threads. For
99	–	* example, a common pool could be used for the {@code SortTasks}
100	–	* illustrated in {@link RecursiveAction}. Because {@code
101	–	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
102	–	* daemon} mode, there is typically no need to explicitly {@link
103	–	* #shutdown} such a pool upon program exit.
104	–	*
105	–	* <pre>
106	–	* static final ForkJoinPool mainPool = new ForkJoinPool();
107	–	* ...
108	–	* public void sort(long[] array) {
109	–	*   mainPool.invoke(new SortTask(array, 0, array.length));
110	–	* }
111	–	* </pre>
112	–	*
110		* <p><b>Implementation notes</b>: This implementation restricts the
111		* maximum number of running threads to 32767. Attempts to create
112		* pools with greater than the maximum number result in
#	Line 127 | Line 124 | public class ForkJoinPool extends Abstra
124		/*
125		* Implementation Overview
126		*
127	<	* This class provides the central bookkeeping and control for a
128	<	* set of worker threads: Submissions from non-FJ threads enter
129	<	* into a submission queue. Workers take these tasks and typically
130	<	* split them into subtasks that may be stolen by other workers.
131	<	* Preference rules give first priority to processing tasks from
132	<	* their own queues (LIFO or FIFO, depending on mode), then to
133	<	* randomized FIFO steals of tasks in other worker queues, and
134	<	* lastly to new submissions.
127	>	* This class and its nested classes provide the main
128	>	* functionality and control for a set of worker threads:
129	>	* Submissions from non-FJ threads enter into submission queues.
130	>	* Workers take these tasks and typically split them into subtasks
131	>	* that may be stolen by other workers.  Preference rules give
132	>	* first priority to processing tasks from their own queues (LIFO
133	>	* or FIFO, depending on mode), then to randomized FIFO steals of
134	>	* tasks in other queues.
135	>	*
136	>	* WorkQueues
137	>	* ==========
138	>	*
139	>	* Most operations occur within work-stealing queues (in nested
140	>	* class WorkQueue).  These are special forms of Deques that
141	>	* support only three of the four possible end-operations -- push,
142	>	* pop, and poll (aka steal), under the further constraints that
143	>	* push and pop are called only from the owning thread (or, as
144	>	* extended here, under a lock), while poll may be called from
145	>	* other threads.  (If you are unfamiliar with them, you probably
146	>	* want to read Herlihy and Shavit's book "The Art of
147	>	* Multiprocessor programming", chapter 16 describing these in
148	>	* more detail before proceeding.)  The main work-stealing queue
149	>	* design is roughly similar to those in the papers "Dynamic
150	>	* Circular Work-Stealing Deque" by Chase and Lev, SPAA 2005
151	>	* (http://research.sun.com/scalable/pubs/index.html) and
152	>	* "Idempotent work stealing" by Michael, Saraswat, and Vechev,
153	>	* PPoPP 2009 (http://portal.acm.org/citation.cfm?id=1504186).
154	>	* The main differences ultimately stem from GC requirements that
155	>	* we null out taken slots as soon as we can, to maintain as small
156	>	* a footprint as possible even in programs generating huge
157	>	* numbers of tasks. To accomplish this, we shift the CAS
158	>	* arbitrating pop vs poll (steal) from being on the indices
159	>	* ("base" and "top") to the slots themselves.  So, both a
160	>	* successful pop and poll mainly entail a CAS of a slot from
161	>	* non-null to null.  Because we rely on CASes of references, we
162	>	* do not need tag bits on base or top.  They are simple ints as
163	>	* used in any circular array-based queue (see for example
164	>	* ArrayDeque).  Updates to the indices must still be ordered in a
165	>	* way that guarantees that top == base means the queue is empty,
166	>	* but otherwise may err on the side of possibly making the queue
167	>	* appear nonempty when a push, pop, or poll have not fully
168	>	* committed. Note that this means that the poll operation,
169	>	* considered individually, is not wait-free. One thief cannot
170	>	* successfully continue until another in-progress one (or, if
171	>	* previously empty, a push) completes.  However, in the
172	>	* aggregate, we ensure at least probabilistic non-blockingness.
173	>	* If an attempted steal fails, a thief always chooses a different
174	>	* random victim target to try next. So, in order for one thief to
175	>	* progress, it suffices for any in-progress poll or new push on
176	>	* any empty queue to complete. (This is why we normally use
177	>	* method pollAt and its variants that try once at the apparent
178	>	* base index, else consider alternative actions, rather than
179	>	* method poll.)
180	>	*
181	>	* This approach also enables support of a user mode in which local
182	>	* task processing is in FIFO, not LIFO order, simply by using
183	>	* poll rather than pop.  This can be useful in message-passing
184	>	* frameworks in which tasks are never joined.  However neither
185	>	* mode considers affinities, loads, cache localities, etc, so
186	>	* rarely provide the best possible performance on a given
187	>	* machine, but portably provide good throughput by averaging over
188	>	* these factors.  (Further, even if we did try to use such
189	>	* information, we do not usually have a basis for exploiting it.
190	>	* For example, some sets of tasks profit from cache affinities,
191	>	* but others are harmed by cache pollution effects.)
192	>	*
193	>	* WorkQueues are also used in a similar way for tasks submitted
194	>	* to the pool. We cannot mix these tasks in the same queues used
195	>	* for work-stealing (this would contaminate lifo/fifo
196	>	* processing). Instead, we loosely associate submission queues
197	>	* with submitting threads, using a form of hashing.  The
198	>	* ThreadLocal Submitter class contains a value initially used as
199	>	* a hash code for choosing existing queues, but may be randomly
200	>	* repositioned upon contention with other submitters.  In
201	>	* essence, submitters act like workers except that they never
202	>	* take tasks, and they are multiplexed on to a finite number of
203	>	* shared work queues. However, classes are set up so that future
204	>	* extensions could allow submitters to optionally help perform
205	>	* tasks as well. Insertion of tasks in shared mode requires a
206	>	* lock (mainly to protect in the case of resizing) but we use
207	>	* only a simple spinlock (using bits in field runState), because
208	>	* submitters encountering a busy queue move on to try or create
209	>	* other queues -- they block only when creating and registering
210	>	* new queues.
211	>	*
212	>	* Management
213	>	* ==========
214		*
215		* The main throughput advantages of work-stealing stem from
216		* decentralized control -- workers mostly take tasks from
217		* themselves or each other. We cannot negate this in the
218		* implementation of other management responsibilities. The main
219		* tactic for avoiding bottlenecks is packing nearly all
220	<	* essentially atomic control state into a single 64bit volatile
221	<	* variable ("ctl"). This variable is read on the order of 10-100
222	<	* times as often as it is modified (always via CAS). (There is
223	<	* some additional control state, for example variable "shutdown"
224	<	* for which we can cope with uncoordinated updates.)  This
225	<	* streamlines synchronization and control at the expense of messy
226	<	* constructions needed to repack status bits upon updates.
227	<	* Updates tend not to contend with each other except during
228	<	* bursts while submitted tasks begin or end.  In some cases when
229	<	* they do contend, threads can instead do something else
230	<	* (usually, scan for tesks) until contention subsides.
231	<	*
232	<	* To enable packing, we restrict maximum parallelism to (1<<15)-1
233	<	* (which is far in excess of normal operating range) to allow
234	<	* ids, counts, and their negations (used for thresholding) to fit
235	<	* into 16bit fields.
236	<	*
237	<	* Recording Workers.  Workers are recorded in the "workers" array
238	<	* that is created upon pool construction and expanded if (rarely)
239	<	* necessary.  This is an array as opposed to some other data
240	<	* structure to support index-based random steals by workers.
241	<	* Updates to the array recording new workers and unrecording
242	<	* terminated ones are protected from each other by a seqLock
243	<	* (scanGuard) but the array is otherwise concurrently readable,
168	<	* and accessed directly by workers. To simplify index-based
220	>	* essentially atomic control state into two volatile variables
221	>	* that are by far most often read (not written) as status and
222	>	* consistency checks.
223	>	*
224	>	* Field "ctl" contains 64 bits holding all the information needed
225	>	* to atomically decide to add, inactivate, enqueue (on an event
226	>	* queue), dequeue, and/or re-activate workers.  To enable this
227	>	* packing, we restrict maximum parallelism to (1<<15)-1 (which is
228	>	* far in excess of normal operating range) to allow ids, counts,
229	>	* and their negations (used for thresholding) to fit into 16bit
230	>	* fields.
231	>	*
232	>	* Field "runState" contains 32 bits needed to register and
233	>	* deregister WorkQueues, as well as to enable shutdown. It is
234	>	* only modified under a lock (normally briefly held, but
235	>	* occasionally protecting allocations and resizings) but even
236	>	* when locked remains available to check consistency.
237	>	*
238	>	* Recording WorkQueues.  WorkQueues are recorded in the
239	>	* "workQueues" array that is created upon pool construction and
240	>	* expanded if necessary.  Updates to the array while recording
241	>	* new workers and unrecording terminated ones are protected from
242	>	* each other by a lock but the array is otherwise concurrently
243	>	* readable, and accessed directly.  To simplify index-based
244		* operations, the array size is always a power of two, and all
245	<	* readers must tolerate null slots. To avoid flailing during
246	<	* start-up, the array is presized to hold twice #parallelism
247	<	* workers (which is unlikely to need further resizing during
248	<	* execution). But to avoid dealing with so many null slots,
249	<	* variable scanGuard includes a mask for the nearest power of two
250	<	* that contains all current workers.  All worker thread creation
251	<	* is on-demand, triggered by task submissions, replacement of
252	<	* terminated workers, and/or compensation for blocked
253	<	* workers. However, all other support code is set up to work with
254	<	* other policies.  To ensure that we do not hold on to worker
255	<	* references that would prevent GC, ALL accesses to workers are
256	<	* via indices into the workers array (which is one source of some
257	<	* of the messy code constructions here). In essence, the workers
258	<	* array serves as a weak reference mechanism. Thus for example
259	<	* the wait queue field of ctl stores worker indices, not worker
260	<	* references.  Access to the workers in associated methods (for
261	<	* example signalWork) must both index-check and null-check the
262	<	* IDs. All such accesses ignore bad IDs by returning out early
263	<	* from what they are doing, since this can only be associated
264	<	* with termination, in which case it is OK to give up.
265	<	*
266	<	* All uses of the workers array, as well as queue arrays, check
267	<	* that the array is non-null (even if previously non-null). This
268	<	* allows nulling during termination, which is currently not
269	<	* necessary, but remains an option for resource-revocation-based
270	<	* shutdown schemes.
271	<	*
272	<	* Wait Queuing. Unlike HPC work-stealing frameworks, we cannot
273	<	* let workers spin indefinitely scanning for tasks when none are
274	<	* can be immediately found, and we cannot start/resume workers
275	<	* unless there appear to be tasks available.  On the other hand,
276	<	* we must quickly prod them into action when new tasks are
277	<	* submitted or generated.  We park/unpark workers after placing
278	<	* in an event wait queue when they cannot find work. This "queue"
279	<	* is actually a simple Treiber stack, headed by the "id" field of
280	<	* ctl, plus a 15bit counter value to both wake up waiters (by
281	<	* advancing their count) and avoid ABA effects. Successors are
282	<	* held in worker field "nextWait".  Queuing deals with several
283	<	* intrinsic races, mainly that a task-producing thread can miss
284	<	* seeing (and signalling) another thread that gave up looking for
285	<	* work but has not yet entered the wait queue. We solve this by
286	<	* requiring a full sweep of all workers both before (in scan())
287	<	* and after (in awaitWork()) a newly waiting worker is added to
288	<	* the wait queue. During a rescan, the worker might release some
289	<	* other queued worker rather than itself, which has the same net
290	<	* effect.
245	>	* readers must tolerate null slots. Shared (submission) queues
246	>	* are at even indices, worker queues at odd indices. Grouping
247	>	* them together in this way simplifies and speeds up task
248	>	* scanning.
249	>	*
250	>	* All worker thread creation is on-demand, triggered by task
251	>	* submissions, replacement of terminated workers, and/or
252	>	* compensation for blocked workers. However, all other support
253	>	* code is set up to work with other policies.  To ensure that we
254	>	* do not hold on to worker references that would prevent GC, ALL
255	>	* accesses to workQueues are via indices into the workQueues
256	>	* array (which is one source of some of the messy code
257	>	* constructions here). In essence, the workQueues array serves as
258	>	* a weak reference mechanism. Thus for example the wait queue
259	>	* field of ctl stores indices, not references.  Access to the
260	>	* workQueues in associated methods (for example signalWork) must
261	>	* both index-check and null-check the IDs. All such accesses
262	>	* ignore bad IDs by returning out early from what they are doing,
263	>	* since this can only be associated with termination, in which
264	>	* case it is OK to give up.  All uses of the workQueues array
265	>	* also check that it is non-null (even if previously
266	>	* non-null). This allows nulling during termination, which is
267	>	* currently not necessary, but remains an option for
268	>	* resource-revocation-based shutdown schemes. It also helps
269	>	* reduce JIT issuance of uncommon-trap code, which tends to
270	>	* unnecessarily complicate control flow in some methods.
271	>	*
272	>	* Event Queuing. Unlike HPC work-stealing frameworks, we cannot
273	>	* let workers spin indefinitely scanning for tasks when none can
274	>	* be found immediately, and we cannot start/resume workers unless
275	>	* there appear to be tasks available.  On the other hand, we must
276	>	* quickly prod them into action when new tasks are submitted or
277	>	* generated. In many usages, ramp-up time to activate workers is
278	>	* the main limiting factor in overall performance (this is
279	>	* compounded at program start-up by JIT compilation and
280	>	* allocation). So we try to streamline this as much as possible.
281	>	* We park/unpark workers after placing in an event wait queue
282	>	* when they cannot find work. This "queue" is actually a simple
283	>	* Treiber stack, headed by the "id" field of ctl, plus a 15bit
284	>	* counter value (that reflects the number of times a worker has
285	>	* been inactivated) to avoid ABA effects (we need only as many
286	>	* version numbers as worker threads). Successors are held in
287	>	* field WorkQueue.nextWait.  Queuing deals with several intrinsic
288	>	* races, mainly that a task-producing thread can miss seeing (and
289	>	* signalling) another thread that gave up looking for work but
290	>	* has not yet entered the wait queue. We solve this by requiring
291	>	* a full sweep of all workers (via repeated calls to method
292	>	* scan()) both before and after a newly waiting worker is added
293	>	* to the wait queue. During a rescan, the worker might release
294	>	* some other queued worker rather than itself, which has the same
295	>	* net effect. Because enqueued workers may actually be rescanning
296	>	* rather than waiting, we set and clear the "parker" field of
297	>	* WorkQueues to reduce unnecessary calls to unpark.  (This
298	>	* requires a secondary recheck to avoid missed signals.)  Note
299	>	* the unusual conventions about Thread.interrupts surrounding
300	>	* parking and other blocking: Because interrupts are used solely
301	>	* to alert threads to check termination, which is checked anyway
302	>	* upon blocking, we clear status (using Thread.interrupted)
303	>	* before any call to park, so that park does not immediately
304	>	* return due to status being set via some other unrelated call to
305	>	* interrupt in user code.
306		*
307		* Signalling.  We create or wake up workers only when there
308		* appears to be at least one task they might be able to find and
309		* execute.  When a submission is added or another worker adds a
310	<	* task to a queue that previously had two or fewer tasks, they
310	>	* task to a queue that previously had fewer than two tasks, they
311		* signal waiting workers (or trigger creation of new ones if
312		* fewer than the given parallelism level -- see signalWork).
313	<	* These primary signals are buttressed by signals during rescans
314	<	* as well as those performed when a worker steals a task and
315	<	* notices that there are more tasks too; together these cover the
316	<	* signals needed in cases when more than two tasks are pushed
227	<	* but untaken.
313	>	* These primary signals are buttressed by signals during rescans;
314	>	* together these cover the signals needed in cases when more
315	>	* tasks are pushed but untaken, and improve performance compared
316	>	* to having one thread wake up all workers.
317		*
318		* Trimming workers. To release resources after periods of lack of
319		* use, a worker starting to wait when the pool is quiescent will
320	<	* time out and terminate if the pool has remained quiescent for
321	<	* SHRINK_RATE nanosecs.
320	>	* time out and terminate if the pool has remained quiescent for a
321	>	* given period -- a short period if there are more threads than
322	>	* parallelism, longer as the number of threads decreases. This
323	>	* will slowly propagate, eventually terminating all workers after
324	>	* periods of non-use.
325		*
326	<	* Submissions. External submissions are maintained in an
327	<	* array-based queue that is structured identically to
328	<	* ForkJoinWorkerThread queues (which see) except for the use of
329	<	* submissionLock in method addSubmission. Unlike worker queues,
330	<	* multiple external threads can add new submissions.
331	<	*
332	<	* Compensation. Beyond work-stealing support and lifecycle
333	<	* control, the main responsibility of this framework is to take
334	<	* actions when one worker is waiting to join a task stolen (or
335	<	* always held by) another.  Because we are multiplexing many
336	<	* tasks on to a pool of workers, we can't just let them block (as
337	<	* in Thread.join).  We also cannot just reassign the joiner's
338	<	* run-time stack with another and replace it later, which would
339	<	* be a form of "continuation", that even if possible is not
340	<	* necessarily a good idea since we sometimes need both an
341	<	* unblocked task and its continuation to progress. Instead we
342	<	* combine two tactics:
326	>	* Shutdown and Termination. A call to shutdownNow atomically sets
327	>	* a runState bit and then (non-atomically) sets each worker's
328	>	* runState status, cancels all unprocessed tasks, and wakes up
329	>	* all waiting workers.  Detecting whether termination should
330	>	* commence after a non-abrupt shutdown() call requires more work
331	>	* and bookkeeping. We need consensus about quiescence (i.e., that
332	>	* there is no more work). The active count provides a primary
333	>	* indication but non-abrupt shutdown still requires a rechecking
334	>	* scan for any workers that are inactive but not queued.
335	>	*
336	>	* Joining Tasks
337	>	* =============
338	>	*
339	>	* Any of several actions may be taken when one worker is waiting
340	>	* to join a task stolen (or always held) by another.  Because we
341	>	* are multiplexing many tasks on to a pool of workers, we can't
342	>	* just let them block (as in Thread.join).  We also cannot just
343	>	* reassign the joiner's run-time stack with another and replace
344	>	* it later, which would be a form of "continuation", that even if
345	>	* possible is not necessarily a good idea since we sometimes need
346	>	* both an unblocked task and its continuation to progress.
347	>	* Instead we combine two tactics:
348		*
349		*   Helping: Arranging for the joiner to execute some task that it
350	<	*      would be running if the steal had not occurred.  Method
254	<	*      ForkJoinWorkerThread.joinTask tracks joining->stealing
255	<	*      links to try to find such a task.
350	>	*      would be running if the steal had not occurred.
351		*
352		*   Compensating: Unless there are already enough live threads,
353	<	*      method tryPreBlock() may create or re-activate a spare
354	<	*      thread to compensate for blocked joiners until they
355	<	*      unblock.
353	>	*      method tryCompensate() may create or re-activate a spare
354	>	*      thread to compensate for blocked joiners until they unblock.
355	>	*
356	>	* A third form (implemented in tryRemoveAndExec and
357	>	* tryPollForAndExec) amounts to helping a hypothetical
358	>	* compensator: If we can readily tell that a possible action of a
359	>	* compensator is to steal and execute the task being joined, the
360	>	* joining thread can do so directly, without the need for a
361	>	* compensation thread (although at the expense of larger run-time
362	>	* stacks, but the tradeoff is typically worthwhile).
363		*
364		* The ManagedBlocker extension API can't use helping so relies
365		* only on compensation in method awaitBlocker.
366		*
367	+	* The algorithm in tryHelpStealer entails a form of "linear"
368	+	* helping: Each worker records (in field currentSteal) the most
369	+	* recent task it stole from some other worker. Plus, it records
370	+	* (in field currentJoin) the task it is currently actively
371	+	* joining. Method tryHelpStealer uses these markers to try to
372	+	* find a worker to help (i.e., steal back a task from and execute
373	+	* it) that could hasten completion of the actively joined task.
374	+	* In essence, the joiner executes a task that would be on its own
375	+	* local deque had the to-be-joined task not been stolen. This may
376	+	* be seen as a conservative variant of the approach in Wagner &
377	+	* Calder "Leapfrogging: a portable technique for implementing
378	+	* efficient futures" SIGPLAN Notices, 1993
379	+	* (http://portal.acm.org/citation.cfm?id=155354). It differs in
380	+	* that: (1) We only maintain dependency links across workers upon
381	+	* steals, rather than use per-task bookkeeping.  This sometimes
382	+	* requires a linear scan of workQueues array to locate stealers,
383	+	* but often doesn't because stealers leave hints (that may become
384	+	* stale/wrong) of where to locate them.  A stealHint is only a
385	+	* hint because a worker might have had multiple steals and the
386	+	* hint records only one of them (usually the most current).
387	+	* Hinting isolates cost to when it is needed, rather than adding
388	+	* to per-task overhead.  (2) It is "shallow", ignoring nesting
389	+	* and potentially cyclic mutual steals.  (3) It is intentionally
390	+	* racy: field currentJoin is updated only while actively joining,
391	+	* which means that we miss links in the chain during long-lived
392	+	* tasks, GC stalls etc (which is OK since blocking in such cases
393	+	* is usually a good idea).  (4) We bound the number of attempts
394	+	* to find work (see MAX_HELP) and fall back to suspending the
395	+	* worker and if necessary replacing it with another.
396	+	*
397		* It is impossible to keep exactly the target parallelism number
398		* of threads running at any given time.  Determining the
399		* existence of conservatively safe helping targets, the
400		* availability of already-created spares, and the apparent need
401	<	* to create new spares are all racy and require heuristic
402	<	* guidance, so we rely on multiple retries of each.  Currently,
403	<	* in keeping with on-demand signalling policy, we compensate only
404	<	* if blocking would leave less than one active (non-waiting,
405	<	* non-blocked) worker. Additionally, to avoid some false alarms
406	<	* due to GC, lagging counters, system activity, etc, compensated
407	<	* blocking for joins is only attempted after a number of rechecks
408	<	* proportional to the current apparent deficit (where retries are
409	<	* interspersed with Thread.yield, for good citizenship).  The
410	<	* variable blockedCount, incremented before blocking and
411	<	* decremented after, is sometimes needed to distinguish cases of
412	<	* waiting for work vs blocking on joins or other managed sync,
413	<	* but both the cases are equivalent for most pool control, so we
414	<	* can update non-atomically. (Additionally, contention on
415	<	* blockedCount alleviates some contention on ctl).
416	<	*
417	<	* Shutdown and Termination. A call to shutdownNow atomically sets
418	<	* the ctl stop bit and then (non-atomically) sets each workers
419	<	* "terminate" status, cancels all unprocessed tasks, and wakes up
420	<	* all waiting workers.  Detecting whether termination should
421	<	* commence after a non-abrupt shutdown() call requires more work
422	<	* and bookkeeping. We need consensus about quiesence (i.e., that
423	<	* there is no more work) which is reflected in active counts so
424	<	* long as there are no current blockers, as well as possible
425	<	* re-evaluations during independent changes in blocking or
426	<	* quiescing workers.
401	>	* to create new spares are all racy, so we rely on multiple
402	>	* retries of each.  Compensation in the apparent absence of
403	>	* helping opportunities is challenging to control on JVMs, where
404	>	* GC and other activities can stall progress of tasks that in
405	>	* turn stall out many other dependent tasks, without us being
406	>	* able to determine whether they will ever require compensation.
407	>	* Even though work-stealing otherwise encounters little
408	>	* degradation in the presence of more threads than cores,
409	>	* aggressively adding new threads in such cases entails risk of
410	>	* unwanted positive feedback control loops in which more threads
411	>	* cause more dependent stalls (as well as delayed progress of
412	>	* unblocked threads to the point that we know they are available)
413	>	* leading to more situations requiring more threads, and so
414	>	* on. This aspect of control can be seen as an (analytically
415	>	* intractable) game with an opponent that may choose the worst
416	>	* (for us) active thread to stall at any time.  We take several
417	>	* precautions to bound losses (and thus bound gains), mainly in
418	>	* methods tryCompensate and awaitJoin: (1) We only try
419	>	* compensation after attempting enough helping steps (measured
420	>	* via counting and timing) that we have already consumed the
421	>	* estimated cost of creating and activating a new thread.  (2) We
422	>	* allow up to 50% of threads to be blocked before initially
423	>	* adding any others, and unless completely saturated, check that
424	>	* some work is available for a new worker before adding. Also, we
425	>	* create up to only 50% more threads until entering a mode that
426	>	* only adds a thread if all others are possibly blocked.  All
427	>	* together, this means that we might be half as fast to react,
428	>	* and create half as many threads as possible in the ideal case,
429	>	* but present vastly fewer anomalies in all other cases compared
430	>	* to both more aggressive and more conservative alternatives.
431		*
432		* Style notes: There is a lot of representation-level coupling
433		* among classes ForkJoinPool, ForkJoinWorkerThread, and
434	<	* ForkJoinTask.  Most fields of ForkJoinWorkerThread maintain
435	<	* data structures managed by ForkJoinPool, so are directly
436	<	* accessed.  Conversely we allow access to "workers" array by
437	<	* workers, and direct access to ForkJoinTask.status by both
438	<	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
439	<	* trying to reduce this, since any associated future changes in
440	<	* representations will need to be accompanied by algorithmic
441	<	* changes anyway. All together, these low-level implementation
442	<	* choices produce as much as a factor of 4 performance
443	<	* improvement compared to naive implementations, and enable the
444	<	* processing of billions of tasks per second, at the expense of
445	<	* some ugliness.
446	<	*
447	<	* Methods signalWork() and scan() are the main bottlenecks so are
448	<	* especially heavily micro-optimized/mangled.  There are lots of
449	<	* inline assignments (of form "while ((local = field) != 0)")
450	<	* which are usually the simplest way to ensure the required read
451	<	* orderings (which are sometimes critical). This leads to a
452	<	* "C"-like style of listing declarations of these locals at the
453	<	* heads of methods or blocks.  There are several occurrences of
454	<	* the unusual "do {} while (!cas...)"  which is the simplest way
455	<	* to force an update of a CAS'ed variable. There are also other
456	<	* coding oddities that help some methods perform reasonably even
457	<	* when interpreted (not compiled).
458	<	*
459	<	* The order of declarations in this file is: (1) declarations of
460	<	* statics (2) fields (along with constants used when unpacking
461	<	* some of them), listed in an order that tends to reduce
462	<	* contention among them a bit under most JVMs.  (3) internal
463	<	* control methods (4) callbacks and other support for
464	<	* ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
465	<	* methods (plus a few little helpers). (6) static block
466	<	* initializing all statics in a minimally dependent order.
434	>	* ForkJoinTask.  The fields of WorkQueue maintain data structures
435	>	* managed by ForkJoinPool, so are directly accessed.  There is
436	>	* little point trying to reduce this, since any associated future
437	>	* changes in representations will need to be accompanied by
438	>	* algorithmic changes anyway. Several methods intrinsically
439	>	* sprawl because they must accumulate sets of consistent reads of
440	>	* volatiles held in local variables.  Methods signalWork() and
441	>	* scan() are the main bottlenecks, so are especially heavily
442	>	* micro-optimized/mangled.  There are lots of inline assignments
443	>	* (of form "while ((local = field) != 0)") which are usually the
444	>	* simplest way to ensure the required read orderings (which are
445	>	* sometimes critical). This leads to a "C"-like style of listing
446	>	* declarations of these locals at the heads of methods or blocks.
447	>	* There are several occurrences of the unusual "do {} while
448	>	* (!cas...)"  which is the simplest way to force an update of a
449	>	* CAS'ed variable. There are also other coding oddities that help
450	>	* some methods perform reasonably even when interpreted (not
451	>	* compiled).
452	>	*
453	>	* The order of declarations in this file is:
454	>	* (1) Static utility functions
455	>	* (2) Nested (static) classes
456	>	* (3) Static fields
457	>	* (4) Fields, along with constants used when unpacking some of them
458	>	* (5) Internal control methods
459	>	* (6) Callbacks and other support for ForkJoinTask methods
460	>	* (7) Exported methods
461	>	* (8) Static block initializing statics in minimally dependent order
462	>	*/
463	>
464	>	// Static utilities
465	>
466	>	/**
467	>	* If there is a security manager, makes sure caller has
468	>	* permission to modify threads.
469		*/
470	+	private static void checkPermission() {
471	+	SecurityManager security = System.getSecurityManager();
472	+	if (security != null)
473	+	security.checkPermission(modifyThreadPermission);
474	+	}
475	+
476	+	// Nested classes
477
478		/**
479		* Factory for creating new {@link ForkJoinWorkerThread}s.
#	Line 358 | Line 503 | public class ForkJoinPool extends Abstra
503		}
504
505		/**
506	<	* Creates a new ForkJoinWorkerThread. This factory is used unless
507	<	* overridden in ForkJoinPool constructors.
506	>	* A simple non-reentrant lock used for exclusion when managing
507	>	* queues and workers. We use a custom lock so that we can readily
508	>	* probe lock state in constructions that check among alternative
509	>	* actions. The lock is normally only very briefly held, and
510	>	* sometimes treated as a spinlock, but other usages block to
511	>	* reduce overall contention in those cases where locked code
512	>	* bodies perform allocation/resizing.
513	>	*/
514	>	static final class Mutex extends AbstractQueuedSynchronizer {
515	>	public final boolean tryAcquire(int ignore) {
516	>	return compareAndSetState(0, 1);
517	>	}
518	>	public final boolean tryRelease(int ignore) {
519	>	setState(0);
520	>	return true;
521	>	}
522	>	public final void lock() { acquire(0); }
523	>	public final void unlock() { release(0); }
524	>	public final boolean isHeldExclusively() { return getState() == 1; }
525	>	public final Condition newCondition() { return new ConditionObject(); }
526	>	}
527	>
528	>	/**
529	>	* Class for artificial tasks that are used to replace the target
530	>	* of local joins if they are removed from an interior queue slot
531	>	* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
532	>	* actually do anything beyond having a unique identity.
533	>	*/
534	>	static final class EmptyTask extends ForkJoinTask<Void> {
535	>	EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
536	>	public final Void getRawResult() { return null; }
537	>	public final void setRawResult(Void x) {}
538	>	public final boolean exec() { return true; }
539	>	}
540	>
541	>	/**
542	>	* Queues supporting work-stealing as well as external task
543	>	* submission. See above for main rationale and algorithms.
544	>	* Implementation relies heavily on "Unsafe" intrinsics
545	>	* and selective use of "volatile":
546	>	*
547	>	* Field "base" is the index (mod array.length) of the least valid
548	>	* queue slot, which is always the next position to steal (poll)
549	>	* from if nonempty. Reads and writes require volatile orderings
550	>	* but not CAS, because updates are only performed after slot
551	>	* CASes.
552	>	*
553	>	* Field "top" is the index (mod array.length) of the next queue
554	>	* slot to push to or pop from. It is written only by owner thread
555	>	* for push, or under lock for trySharedPush, and accessed by
556	>	* other threads only after reading (volatile) base.  Both top and
557	>	* base are allowed to wrap around on overflow, but (top - base)
558	>	* (or more commonly -(base - top) to force volatile read of base
559	>	* before top) still estimates size.
560	>	*
561	>	* The array slots are read and written using the emulation of
562	>	* volatiles/atomics provided by Unsafe. Insertions must in
563	>	* general use putOrderedObject as a form of releasing store to
564	>	* ensure that all writes to the task object are ordered before
565	>	* its publication in the queue. (Although we can avoid one case
566	>	* of this when locked in trySharedPush.) All removals entail a
567	>	* CAS to null.  The array is always a power of two. To ensure
568	>	* safety of Unsafe array operations, all accesses perform
569	>	* explicit null checks and implicit bounds checks via
570	>	* power-of-two masking.
571	>	*
572	>	* In addition to basic queuing support, this class contains
573	>	* fields described elsewhere to control execution. It turns out
574	>	* to work better memory-layout-wise to include them in this
575	>	* class rather than a separate class.
576	>	*
577	>	* Performance on most platforms is very sensitive to placement of
578	>	* instances of both WorkQueues and their arrays -- we absolutely
579	>	* do not want multiple WorkQueue instances or multiple queue
580	>	* arrays sharing cache lines. (It would be best for queue objects
581	>	* and their arrays to share, but there is nothing available to
582	>	* help arrange that).  Unfortunately, because they are recorded
583	>	* in a common array, WorkQueue instances are often moved to be
584	>	* adjacent by garbage collectors. To reduce impact, we use field
585	>	* padding that works OK on common platforms; this effectively
586	>	* trades off slightly slower average field access for the sake of
587	>	* avoiding really bad worst-case access. (Until better JVM
588	>	* support is in place, this padding is dependent on transient
589	>	* properties of JVM field layout rules.)  We also take care in
590	>	* allocating, sizing and resizing the array. Non-shared queue
591	>	* arrays are initialized (via method growArray) by workers before
592	>	* use. Others are allocated on first use.
593		*/
594	<	public static final ForkJoinWorkerThreadFactory
595	<	defaultForkJoinWorkerThreadFactory;
594	>	static final class WorkQueue {
595	>	/**
596	>	* Capacity of work-stealing queue array upon initialization.
597	>	* Must be a power of two; at least 4, but should be larger to
598	>	* reduce or eliminate cacheline sharing among queues.
599	>	* Currently, it is much larger, as a partial workaround for
600	>	* the fact that JVMs often place arrays in locations that
601	>	* share GC bookkeeping (especially cardmarks) such that
602	>	* per-write accesses encounter serious memory contention.
603	>	*/
604	>	static final int INITIAL_QUEUE_CAPACITY = 1 << 13;
605	>
606	>	/**
607	>	* Maximum size for queue arrays. Must be a power of two less
608	>	* than or equal to 1 << (31 - width of array entry) to ensure
609	>	* lack of wraparound of index calculations, but defined to a
610	>	* value a bit less than this to help users trap runaway
611	>	* programs before saturating systems.
612	>	*/
613	>	static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
614	>
615	>	volatile long totalSteals; // cumulative number of steals
616	>	int seed;                  // for random scanning; initialize nonzero
617	>	volatile int eventCount;   // encoded inactivation count; < 0 if inactive
618	>	int nextWait;              // encoded record of next event waiter
619	>	int rescans;               // remaining scans until block
620	>	int nsteals;               // top-level task executions since last idle
621	>	final int mode;            // lifo, fifo, or shared
622	>	int poolIndex;             // index of this queue in pool (or 0)
623	>	int stealHint;             // index of most recent known stealer
624	>	volatile int runState;     // 1: locked, -1: terminate; else 0
625	>	volatile int base;         // index of next slot for poll
626	>	int top;                   // index of next slot for push
627	>	ForkJoinTask<?>[] array;   // the elements (initially unallocated)
628	>	final ForkJoinPool pool;   // the containing pool (may be null)
629	>	final ForkJoinWorkerThread owner; // owning thread or null if shared
630	>	volatile Thread parker;    // == owner during call to park; else null
631	>	volatile ForkJoinTask<?> currentJoin;  // task being joined in awaitJoin
632	>	ForkJoinTask<?> currentSteal; // current non-local task being executed
633	>	// Heuristic padding to ameliorate unfortunate memory placements
634	>	Object p00, p01, p02, p03, p04, p05, p06, p07;
635	>	Object p08, p09, p0a, p0b, p0c, p0d, p0e;
636	>
637	>	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode) {
638	>	this.mode = mode;
639	>	this.pool = pool;
640	>	this.owner = owner;
641	>	// Place indices in the center of array (that is not yet allocated)
642	>	base = top = INITIAL_QUEUE_CAPACITY >>> 1;
643	>	}
644	>
645	>	/**
646	>	* Returns the approximate number of tasks in the queue.
647	>	*/
648	>	final int queueSize() {
649	>	int n = base - top;       // non-owner callers must read base first
650	>	return (n >= 0) ? 0 : -n; // ignore transient negative
651	>	}
652	>
653	>	/**
654	>	* Provides a more accurate estimate of whether this queue has
655	>	* any tasks than does queueSize, by checking whether a
656	>	* near-empty queue has at least one unclaimed task.
657	>	*/
658	>	final boolean isEmpty() {
659	>	ForkJoinTask<?>[] a; int m, s;
660	>	int n = base - (s = top);
661	>	return (n >= 0 ||
662	>	(n == -1 &&
663	>	((a = array) == null ||
664	>	(m = a.length - 1) < 0 ||
665	>	U.getObjectVolatile
666	>	(a, ((m & (s - 1)) << ASHIFT) + ABASE) == null)));
667	>	}
668	>
669	>	/**
670	>	* Pushes a task. Call only by owner in unshared queues.
671	>	*
672	>	* @param task the task. Caller must ensure non-null.
673	>	* @throw RejectedExecutionException if array cannot be resized
674	>	*/
675	>	final void push(ForkJoinTask<?> task) {
676	>	ForkJoinTask<?>[] a; ForkJoinPool p;
677	>	int s = top, m, n;
678	>	if ((a = array) != null) {    // ignore if queue removed
679	>	U.putOrderedObject
680	>	(a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task);
681	>	if ((n = (top = s + 1) - base) <= 2) {
682	>	if ((p = pool) != null)
683	>	p.signalWork();
684	>	}
685	>	else if (n >= m)
686	>	growArray(true);
687	>	}
688	>	}
689	>
690	>	/**
691	>	* Pushes a task if lock is free and array is either big
692	>	* enough or can be resized to be big enough.
693	>	*
694	>	* @param task the task. Caller must ensure non-null.
695	>	* @return true if submitted
696	>	*/
697	>	final boolean trySharedPush(ForkJoinTask<?> task) {
698	>	boolean submitted = false;
699	>	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
700	>	ForkJoinTask<?>[] a = array;
701	>	int s = top;
702	>	try {
703	>	if ((a != null && a.length > s + 1 - base) ||
704	>	(a = growArray(false)) != null) { // must presize
705	>	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
706	>	U.putObject(a, (long)j, task);    // don't need "ordered"
707	>	top = s + 1;
708	>	submitted = true;
709	>	}
710	>	} finally {
711	>	runState = 0;                         // unlock
712	>	}
713	>	}
714	>	return submitted;
715	>	}
716	>
717	>	/**
718	>	* Takes next task, if one exists, in LIFO order.  Call only
719	>	* by owner in unshared queues. (We do not have a shared
720	>	* version of this method because it is never needed.)
721	>	*/
722	>	final ForkJoinTask<?> pop() {
723	>	ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
724	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
725	>	for (int s; (s = top - 1) - base >= 0;) {
726	>	long j = ((m & s) << ASHIFT) + ABASE;
727	>	if ((t = (ForkJoinTask<?>)U.getObject(a, j)) == null)
728	>	break;
729	>	if (U.compareAndSwapObject(a, j, t, null)) {
730	>	top = s;
731	>	return t;
732	>	}
733	>	}
734	>	}
735	>	return null;
736	>	}
737	>
738	>	/**
739	>	* Takes a task in FIFO order if b is base of queue and a task
740	>	* can be claimed without contention. Specialized versions
741	>	* appear in ForkJoinPool methods scan and tryHelpStealer.
742	>	*/
743	>	final ForkJoinTask<?> pollAt(int b) {
744	>	ForkJoinTask<?> t; ForkJoinTask<?>[] a;
745	>	if ((a = array) != null) {
746	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
747	>	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
748	>	base == b &&
749	>	U.compareAndSwapObject(a, j, t, null)) {
750	>	base = b + 1;
751	>	return t;
752	>	}
753	>	}
754	>	return null;
755	>	}
756	>
757	>	/**
758	>	* Takes next task, if one exists, in FIFO order.
759	>	*/
760	>	final ForkJoinTask<?> poll() {
761	>	ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t;
762	>	while ((b = base) - top < 0 && (a = array) != null) {
763	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
764	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
765	>	if (t != null) {
766	>	if (base == b &&
767	>	U.compareAndSwapObject(a, j, t, null)) {
768	>	base = b + 1;
769	>	return t;
770	>	}
771	>	}
772	>	else if (base == b) {
773	>	if (b + 1 == top)
774	>	break;
775	>	Thread.yield(); // wait for lagging update
776	>	}
777	>	}
778	>	return null;
779	>	}
780	>
781	>	/**
782	>	* Takes next task, if one exists, in order specified by mode.
783	>	*/
784	>	final ForkJoinTask<?> nextLocalTask() {
785	>	return mode == 0 ? pop() : poll();
786	>	}
787	>
788	>	/**
789	>	* Returns next task, if one exists, in order specified by mode.
790	>	*/
791	>	final ForkJoinTask<?> peek() {
792	>	ForkJoinTask<?>[] a = array; int m;
793	>	if (a == null || (m = a.length - 1) < 0)
794	>	return null;
795	>	int i = mode == 0 ? top - 1 : base;
796	>	int j = ((i & m) << ASHIFT) + ABASE;
797	>	return (ForkJoinTask<?>)U.getObjectVolatile(a, j);
798	>	}
799	>
800	>	/**
801	>	* Pops the given task only if it is at the current top.
802	>	*/
803	>	final boolean tryUnpush(ForkJoinTask<?> t) {
804	>	ForkJoinTask<?>[] a; int s;
805	>	if ((a = array) != null && (s = top) != base &&
806	>	U.compareAndSwapObject
807	>	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
808	>	top = s;
809	>	return true;
810	>	}
811	>	return false;
812	>	}
813	>
814	>	/**
815	>	* Version of tryUnpush for shared queues; called by non-FJ
816	>	* submitters. Conservatively fails to unpush if all workers
817	>	* are active unless there are multiple tasks in queue.
818	>	*/
819	>	final boolean trySharedUnpush(ForkJoinTask<?> task, ForkJoinPool p) {
820	>	boolean success = false;
821	>	if (task != null && top != base && runState == 0 &&
822	>	U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
823	>	try {
824	>	ForkJoinTask<?>[] a; int n, s;
825	>	if ((a = array) != null && (n = (s = top) - base) > 0 &&
826	>	(n > 1 || p == null || (int)(p.ctl >> AC_SHIFT) < 0)) {
827	>	int j = (((a.length - 1) & --s) << ASHIFT) + ABASE;
828	>	if (U.getObjectVolatile(a, j) == task &&
829	>	U.compareAndSwapObject(a, j, task, null)) {
830	>	top = s;
831	>	success = true;
832	>	}
833	>	}
834	>	} finally {
835	>	runState = 0;                         // unlock
836	>	}
837	>	}
838	>	return success;
839	>	}
840	>
841	>	/**
842	>	* Polls the given task only if it is at the current base.
843	>	*/
844	>	final boolean pollFor(ForkJoinTask<?> task) {
845	>	ForkJoinTask<?>[] a; int b;
846	>	if ((b = base) - top < 0 && (a = array) != null) {
847	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
848	>	if (U.getObjectVolatile(a, j) == task && base == b &&
849	>	U.compareAndSwapObject(a, j, task, null)) {
850	>	base = b + 1;
851	>	return true;
852	>	}
853	>	}
854	>	return false;
855	>	}
856	>
857	>	/**
858	>	* Initializes or doubles the capacity of array. Call either
859	>	* by owner or with lock held -- it is OK for base, but not
860	>	* top, to move while resizings are in progress.
861	>	*
862	>	* @param rejectOnFailure if true, throw exception if capacity
863	>	* exceeded (relayed ultimately to user); else return null.
864	>	*/
865	>	final ForkJoinTask<?>[] growArray(boolean rejectOnFailure) {
866	>	ForkJoinTask<?>[] oldA = array;
867	>	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
868	>	if (size <= MAXIMUM_QUEUE_CAPACITY) {
869	>	int oldMask, t, b;
870	>	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
871	>	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
872	>	(t = top) - (b = base) > 0) {
873	>	int mask = size - 1;
874	>	do {
875	>	ForkJoinTask<?> x;
876	>	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
877	>	int j    = ((b &    mask) << ASHIFT) + ABASE;
878	>	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
879	>	if (x != null &&
880	>	U.compareAndSwapObject(oldA, oldj, x, null))
881	>	U.putObjectVolatile(a, j, x);
882	>	} while (++b != t);
883	>	}
884	>	return a;
885	>	}
886	>	else if (!rejectOnFailure)
887	>	return null;
888	>	else
889	>	throw new RejectedExecutionException("Queue capacity exceeded");
890	>	}
891	>
892	>	/**
893	>	* Removes and cancels all known tasks, ignoring any exceptions.
894	>	*/
895	>	final void cancelAll() {
896	>	ForkJoinTask.cancelIgnoringExceptions(currentJoin);
897	>	ForkJoinTask.cancelIgnoringExceptions(currentSteal);
898	>	for (ForkJoinTask<?> t; (t = poll()) != null; )
899	>	ForkJoinTask.cancelIgnoringExceptions(t);
900	>	}
901	>
902	>	/**
903	>	* Computes next value for random probes.  Scans don't require
904	>	* a very high quality generator, but also not a crummy one.
905	>	* Marsaglia xor-shift is cheap and works well enough.  Note:
906	>	* This is manually inlined in its usages in ForkJoinPool to
907	>	* avoid writes inside busy scan loops.
908	>	*/
909	>	final int nextSeed() {
910	>	int r = seed;
911	>	r ^= r << 13;
912	>	r ^= r >>> 17;
913	>	return seed = r ^= r << 5;
914	>	}
915	>
916	>	// Execution methods
917	>
918	>	/**
919	>	* Pops and runs tasks until empty.
920	>	*/
921	>	private void popAndExecAll() {
922	>	// A bit faster than repeated pop calls
923	>	ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t;
924	>	while ((a = array) != null && (m = a.length - 1) >= 0 &&
925	>	(s = top - 1) - base >= 0 &&
926	>	(t = ((ForkJoinTask<?>)
927	>	U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
928	>	!= null) {
929	>	if (U.compareAndSwapObject(a, j, t, null)) {
930	>	top = s;
931	>	t.doExec();
932	>	}
933	>	}
934	>	}
935	>
936	>	/**
937	>	* Polls and runs tasks until empty.
938	>	*/
939	>	private void pollAndExecAll() {
940	>	for (ForkJoinTask<?> t; (t = poll()) != null;)
941	>	t.doExec();
942	>	}
943	>
944	>	/**
945	>	* If present, removes from queue and executes the given task, or
946	>	* any other cancelled task. Returns (true) immediately on any CAS
947	>	* or consistency check failure so caller can retry.
948	>	*
949	>	* @return 0 if no progress can be made, else positive
950	>	* (this unusual convention simplifies use with tryHelpStealer.)
951	>	*/
952	>	final int tryRemoveAndExec(ForkJoinTask<?> task) {
953	>	int stat = 1;
954	>	boolean removed = false, empty = true;
955	>	ForkJoinTask<?>[] a; int m, s, b, n;
956	>	if ((a = array) != null && (m = a.length - 1) >= 0 &&
957	>	(n = (s = top) - (b = base)) > 0) {
958	>	for (ForkJoinTask<?> t;;) {           // traverse from s to b
959	>	int j = ((--s & m) << ASHIFT) + ABASE;
960	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
961	>	if (t == null)                    // inconsistent length
962	>	break;
963	>	else if (t == task) {
964	>	if (s + 1 == top) {           // pop
965	>	if (!U.compareAndSwapObject(a, j, task, null))
966	>	break;
967	>	top = s;
968	>	removed = true;
969	>	}
970	>	else if (base == b)           // replace with proxy
971	>	removed = U.compareAndSwapObject(a, j, task,
972	>	new EmptyTask());
973	>	break;
974	>	}
975	>	else if (t.status >= 0)
976	>	empty = false;
977	>	else if (s + 1 == top) {          // pop and throw away
978	>	if (U.compareAndSwapObject(a, j, t, null))
979	>	top = s;
980	>	break;
981	>	}
982	>	if (--n == 0) {
983	>	if (!empty && base == b)
984	>	stat = 0;
985	>	break;
986	>	}
987	>	}
988	>	}
989	>	if (removed)
990	>	task.doExec();
991	>	return stat;
992	>	}
993	>
994	>	/**
995	>	* Executes a top-level task and any local tasks remaining
996	>	* after execution.
997	>	*/
998	>	final void runTask(ForkJoinTask<?> t) {
999	>	if (t != null) {
1000	>	currentSteal = t;
1001	>	t.doExec();
1002	>	if (top != base) {       // process remaining local tasks
1003	>	if (mode == 0)
1004	>	popAndExecAll();
1005	>	else
1006	>	pollAndExecAll();
1007	>	}
1008	>	++nsteals;
1009	>	currentSteal = null;
1010	>	}
1011	>	}
1012	>
1013	>	/**
1014	>	* Executes a non-top-level (stolen) task.
1015	>	*/
1016	>	final void runSubtask(ForkJoinTask<?> t) {
1017	>	if (t != null) {
1018	>	ForkJoinTask<?> ps = currentSteal;
1019	>	currentSteal = t;
1020	>	t.doExec();
1021	>	currentSteal = ps;
1022	>	}
1023	>	}
1024	>
1025	>	/**
1026	>	* Returns true if owned and not known to be blocked.
1027	>	*/
1028	>	final boolean isApparentlyUnblocked() {
1029	>	Thread wt; Thread.State s;
1030	>	return (eventCount >= 0 &&
1031	>	(wt = owner) != null &&
1032	>	(s = wt.getState()) != Thread.State.BLOCKED &&
1033	>	s != Thread.State.WAITING &&
1034	>	s != Thread.State.TIMED_WAITING);
1035	>	}
1036	>
1037	>	/**
1038	>	* If this owned and is not already interrupted, try to
1039	>	* interrupt and/or unpark, ignoring exceptions.
1040	>	*/
1041	>	final void interruptOwner() {
1042	>	Thread wt, p;
1043	>	if ((wt = owner) != null && !wt.isInterrupted()) {
1044	>	try {
1045	>	wt.interrupt();
1046	>	} catch (SecurityException ignore) {
1047	>	}
1048	>	}
1049	>	if ((p = parker) != null)
1050	>	U.unpark(p);
1051	>	}
1052	>
1053	>	// Unsafe mechanics
1054	>	private static final sun.misc.Unsafe U;
1055	>	private static final long RUNSTATE;
1056	>	private static final int ABASE;
1057	>	private static final int ASHIFT;
1058	>	static {
1059	>	int s;
1060	>	try {
1061	>	U = getUnsafe();
1062	>	Class<?> k = WorkQueue.class;
1063	>	Class<?> ak = ForkJoinTask[].class;
1064	>	RUNSTATE = U.objectFieldOffset
1065	>	(k.getDeclaredField("runState"));
1066	>	ABASE = U.arrayBaseOffset(ak);
1067	>	s = U.arrayIndexScale(ak);
1068	>	} catch (Exception e) {
1069	>	throw new Error(e);
1070	>	}
1071	>	if ((s & (s-1)) != 0)
1072	>	throw new Error("data type scale not a power of two");
1073	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
1074	>	}
1075	>	}
1076
1077		/**
1078	<	* Permission required for callers of methods that may start or
1079	<	* kill threads.
1078	>	* Per-thread records for threads that submit to pools. Currently
1079	>	* holds only pseudo-random seed / index that is used to choose
1080	>	* submission queues in method doSubmit. In the future, this may
1081	>	* also incorporate a means to implement different task rejection
1082	>	* and resubmission policies.
1083	>	*
1084	>	* Seeds for submitters and workers/workQueues work in basically
1085	>	* the same way but are initialized and updated using slightly
1086	>	* different mechanics. Both are initialized using the same
1087	>	* approach as in class ThreadLocal, where successive values are
1088	>	* unlikely to collide with previous values. This is done during
1089	>	* registration for workers, but requires a separate AtomicInteger
1090	>	* for submitters. Seeds are then randomly modified upon
1091	>	* collisions using xorshifts, which requires a non-zero seed.
1092		*/
1093	<	private static final RuntimePermission modifyThreadPermission;
1093	>	static final class Submitter {
1094	>	int seed;
1095	>	Submitter() {
1096	>	int s = nextSubmitterSeed.getAndAdd(SEED_INCREMENT);
1097	>	seed = (s == 0) ? 1 : s; // ensure non-zero
1098	>	}
1099	>	}
1100	>
1101	>	/** ThreadLocal class for Submitters */
1102	>	static final class ThreadSubmitter extends ThreadLocal<Submitter> {
1103	>	public Submitter initialValue() { return new Submitter(); }
1104	>	}
1105	>
1106	>	// static fields (initialized in static initializer below)
1107
1108		/**
1109	<	* If there is a security manager, makes sure caller has
1110	<	* permission to modify threads.
1109	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
1110	>	* overridden in ForkJoinPool constructors.
1111		*/
1112	<	private static void checkPermission() {
1113	<	SecurityManager security = System.getSecurityManager();
379	<	if (security != null)
380	<	security.checkPermission(modifyThreadPermission);
381	<	}
1112	>	public static final ForkJoinWorkerThreadFactory
1113	>	defaultForkJoinWorkerThreadFactory;
1114
1115		/**
1116		* Generator for assigning sequence numbers as pool names.
#	Line 386 | Line 1118 | public class ForkJoinPool extends Abstra
1118		private static final AtomicInteger poolNumberGenerator;
1119
1120		/**
1121	<	* Generator for initial random seeds for worker victim
1122	<	* selection. This is used only to create initial seeds. Random
391	<	* steals use a cheaper xorshift generator per steal attempt. We
392	<	* don't expect much contention on seedGenerator, so just use a
393	<	* plain Random.
1121	>	* Generator for initial hashes/seeds for submitters. Accessed by
1122	>	* Submitter class constructor.
1123		*/
1124	<	static final Random workerSeedGenerator;
1124	>	static final AtomicInteger nextSubmitterSeed;
1125
1126		/**
1127	<	* Array holding all worker threads in the pool.  Initialized upon
1128	<	* construction. Array size must be a power of two.  Updates and
400	<	* replacements are protected by scanGuard, but the array is
401	<	* always kept in a consistent enough state to be randomly
402	<	* accessed without locking by workers performing work-stealing,
403	<	* as well as other traversal-based methods in this class, so long
404	<	* as reads memory-acquire by first reading ctl. All readers must
405	<	* tolerate that some array slots may be null.
1127	>	* Permission required for callers of methods that may start or
1128	>	* kill threads.
1129		*/
1130	<	ForkJoinWorkerThread[] workers;
1130	>	private static final RuntimePermission modifyThreadPermission;
1131
1132		/**
1133	<	* Initial size for submission queue array. Must be a power of
1134	<	* two.  In many applications, these always stay small so we use a
1135	<	* small initial cap.
1133	>	* Per-thread submission bookkeeping. Shared across all pools
1134	>	* to reduce ThreadLocal pollution and because random motion
1135	>	* to avoid contention in one pool is likely to hold for others.
1136		*/
1137	<	private static final int INITIAL_QUEUE_CAPACITY = 8;
1137	>	private static final ThreadSubmitter submitters;
1138
1139	<	/**
1140	<	* Maximum size for submission queue array. Must be a power of two
418	<	* less than or equal to 1 << (31 - width of array entry) to
419	<	* ensure lack of index wraparound, but is capped at a lower
420	<	* value to help users trap runaway computations.
421	<	*/
422	<	private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 24; // 16M
1139	>	/** Common default pool */
1140	>	static volatile ForkJoinPool commonPool;
1141
1142	<	/**
1143	<	* Array serving as submission queue. Initialized upon construction.
1144	<	*/
1145	<	private ForkJoinTask<?>[] submissionQueue;
1142	>	// commonPool construction parameters
1143	>	private static final String propPrefix =
1144	>	"java.util.concurrent.ForkJoinPool.common.";
1145	>	private static final Thread.UncaughtExceptionHandler commonPoolUEH;
1146	>	private static final ForkJoinWorkerThreadFactory commonPoolFactory;
1147	>	static final int commonPoolParallelism;
1148
1149	<	/**
1150	<	* Lock protecting submissions array for addSubmission
1151	<	*/
1152	<	private final ReentrantLock submissionLock;
1149	>	/** Static initialization lock */
1150	>	private static final Mutex initializationLock;
1151	>
1152	>	// static constants
1153
1154		/**
1155	<	* Condition for awaitTermination, using submissionLock for
1156	<	* convenience.
1155	>	* Initial timeout value (in nanoseconds) for the tread triggering
1156	>	* quiescence to park waiting for new work. On timeout, the thread
1157	>	* will instead try to shrink the number of workers.
1158		*/
1159	<	private final Condition termination;
1159	>	private static final long IDLE_TIMEOUT      = 1000L * 1000L * 1000L; // 1sec
1160
1161		/**
1162	<	* Creation factory for worker threads.
1162	>	* Timeout value when there are more threads than parallelism level
1163		*/
1164	<	private final ForkJoinWorkerThreadFactory factory;
1164	>	private static final long FAST_IDLE_TIMEOUT =  100L * 1000L * 1000L;
1165
1166		/**
1167	<	* The uncaught exception handler used when any worker abruptly
1168	<	* terminates.
1167	>	* The maximum stolen->joining link depth allowed in method
1168	>	* tryHelpStealer.  Must be a power of two. This value also
1169	>	* controls the maximum number of times to try to help join a task
1170	>	* without any apparent progress or change in pool state before
1171	>	* giving up and blocking (see awaitJoin).  Depths for legitimate
1172	>	* chains are unbounded, but we use a fixed constant to avoid
1173	>	* (otherwise unchecked) cycles and to bound staleness of
1174	>	* traversal parameters at the expense of sometimes blocking when
1175	>	* we could be helping.
1176		*/
1177	<	final Thread.UncaughtExceptionHandler ueh;
1177	>	private static final int MAX_HELP = 64;
1178
1179		/**
1180	<	* Prefix for assigning names to worker threads
1180	>	* Secondary time-based bound (in nanosecs) for helping attempts
1181	>	* before trying compensated blocking in awaitJoin. Used in
1182	>	* conjunction with MAX_HELP to reduce variance due to different
1183	>	* polling rates associated with different helping options. The
1184	>	* value should roughly approximate the time required to create
1185	>	* and/or activate a worker thread.
1186		*/
1187	<	private final String workerNamePrefix;
1187	>	private static final long COMPENSATION_DELAY = 1L << 18; // ~0.25 millisec
1188
1189		/**
1190	<	* Sum of per-thread steal counts, updated only when threads are
1191	<	* idle or terminating.
1190	>	* Increment for seed generators. See class ThreadLocal for
1191	>	* explanation.
1192		*/
1193	<	private volatile long stealCount;
1193	>	private static final int SEED_INCREMENT = 0x61c88647;
1194
1195		/**
1196	<	* Main pool control -- a long packed with:
1196	>	* Bits and masks for control variables
1197	>	*
1198	>	* Field ctl is a long packed with:
1199		* AC: Number of active running workers minus target parallelism (16 bits)
1200	<	* TC: Number of total workers minus target parallelism (16bits)
1200	>	* TC: Number of total workers minus target parallelism (16 bits)
1201		* ST: true if pool is terminating (1 bit)
1202		* EC: the wait count of top waiting thread (15 bits)
1203	<	* ID: ~poolIndex of top of Treiber stack of waiting threads (16 bits)
1203	>	* ID: poolIndex of top of Treiber stack of waiters (16 bits)
1204		*
1205		* When convenient, we can extract the upper 32 bits of counts and
1206		* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
#	Line 474 | Line 1209 | public class ForkJoinPool extends Abstra
1209		* parallelism and the positionings of fields makes it possible to
1210		* perform the most common checks via sign tests of fields: When
1211		* ac is negative, there are not enough active workers, when tc is
1212	<	* negative, there are not enough total workers, when id is
478	<	* negative, there is at least one waiting worker, and when e is
1212	>	* negative, there are not enough total workers, and when e is
1213		* negative, the pool is terminating.  To deal with these possibly
1214		* negative fields, we use casts in and out of "short" and/or
1215	<	* signed shifts to maintain signedness.  Note: AC_SHIFT is
1216	<	* redundantly declared in ForkJoinWorkerThread in order to
1217	<	* integrate a surplus-threads check.
1215	>	* signed shifts to maintain signedness.
1216	>	*
1217	>	* When a thread is queued (inactivated), its eventCount field is
1218	>	* set negative, which is the only way to tell if a worker is
1219	>	* prevented from executing tasks, even though it must continue to
1220	>	* scan for them to avoid queuing races. Note however that
1221	>	* eventCount updates lag releases so usage requires care.
1222	>	*
1223	>	* Field runState is an int packed with:
1224	>	* SHUTDOWN: true if shutdown is enabled (1 bit)
1225	>	* SEQ:  a sequence number updated upon (de)registering workers (30 bits)
1226	>	* INIT: set true after workQueues array construction (1 bit)
1227	>	*
1228	>	* The sequence number enables simple consistency checks:
1229	>	* Staleness of read-only operations on the workQueues array can
1230	>	* be checked by comparing runState before vs after the reads.
1231		*/
485	–	volatile long ctl;
1232
1233		// bit positions/shifts for fields
1234		private static final int  AC_SHIFT   = 48;
#	Line 491 | Line 1237 | public class ForkJoinPool extends Abstra
1237		private static final int  EC_SHIFT   = 16;
1238
1239		// bounds
1240	<	private static final int  MAX_ID     = 0x7fff;  // max poolIndex
1241	<	private static final int  SMASK      = 0xffff;  // mask short bits
1240	>	private static final int  SMASK      = 0xffff;  // short bits
1241	>	private static final int  MAX_CAP    = 0x7fff;  // max #workers - 1
1242	>	private static final int  SQMASK     = 0xfffe;  // even short bits
1243		private static final int  SHORT_SIGN = 1 << 15;
1244		private static final int  INT_SIGN   = 1 << 31;
1245
#	Line 514 | Line 1261 | public class ForkJoinPool extends Abstra
1261		private static final int  UTC_UNIT   = 1 << UTC_SHIFT;
1262
1263		// masks and units for dealing with e = (int)ctl
1264	<	private static final int  E_MASK     = 0x7fffffff; // no STOP_BIT
1265	<	private static final int  EC_UNIT    = 1 << EC_SHIFT;
1264	>	private static final int E_MASK      = 0x7fffffff; // no STOP_BIT
1265	>	private static final int E_SEQ       = 1 << EC_SHIFT;
1266
1267	<	/**
1268	<	* The target parallelism level.
522	<	*/
523	<	final int parallelism;
1267	>	// runState bits
1268	>	private static final int SHUTDOWN    = 1 << 31;
1269
1270	<	/**
1271	<	* Index (mod submission queue length) of next element to take
1272	<	* from submission queue.
1273	<	*/
529	<	volatile int queueBase;
1270	>	// access mode for WorkQueue
1271	>	static final int LIFO_QUEUE          =  0;
1272	>	static final int FIFO_QUEUE          =  1;
1273	>	static final int SHARED_QUEUE        = -1;
1274
1275	<	/**
532	<	* Index (mod submission queue length) of next element to add
533	<	* in submission queue.
534	<	*/
535	<	int queueTop;
1275	>	// Instance fields
1276
1277	<	/**
1278	<	* True when shutdown() has been called.
1279	<	*/
1280	<	volatile boolean shutdown;
1277	>	/*
1278	>	* Field layout order in this class tends to matter more than one
1279	>	* would like. Runtime layout order is only loosely related to
1280	>	* declaration order and may differ across JVMs, but the following
1281	>	* empirically works OK on current JVMs.
1282	>	*/
1283	>
1284	>	volatile long ctl;                         // main pool control
1285	>	final int parallelism;                     // parallelism level
1286	>	final int localMode;                       // per-worker scheduling mode
1287	>	final int submitMask;                      // submit queue index bound
1288	>	int nextSeed;                              // for initializing worker seeds
1289	>	volatile int runState;                     // shutdown status and seq
1290	>	WorkQueue[] workQueues;                    // main registry
1291	>	final Mutex lock;                          // for registration
1292	>	final Condition termination;               // for awaitTermination
1293	>	final ForkJoinWorkerThreadFactory factory; // factory for new workers
1294	>	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1295	>	final AtomicLong stealCount;               // collect counts when terminated
1296	>	final AtomicInteger nextWorkerNumber;      // to create worker name string
1297	>	String workerNamePrefix;                   // to create worker name string
1298	>
1299	>	//  Creating, registering, and deregistering workers
1300
1301		/**
1302	<	* True if use local fifo, not default lifo, for local polling
544	<	* Read by, and replicated by ForkJoinWorkerThreads
1302	>	* Tries to create and start a worker
1303		*/
1304	<	final boolean locallyFifo;
1304	>	private void addWorker() {
1305	>	Throwable ex = null;
1306	>	ForkJoinWorkerThread wt = null;
1307	>	try {
1308	>	if ((wt = factory.newThread(this)) != null) {
1309	>	wt.start();
1310	>	return;
1311	>	}
1312	>	} catch (Throwable e) {
1313	>	ex = e;
1314	>	}
1315	>	deregisterWorker(wt, ex); // adjust counts etc on failure
1316	>	}
1317
1318		/**
1319	<	* The number of threads in ForkJoinWorkerThreads.helpQuiescePool.
1320	<	* When non-zero, suppresses automatic shutdown when active
1321	<	* counts become zero.
1319	>	* Callback from ForkJoinWorkerThread constructor to assign a
1320	>	* public name. This must be separate from registerWorker because
1321	>	* it is called during the "super" constructor call in
1322	>	* ForkJoinWorkerThread.
1323		*/
1324	<	volatile int quiescerCount;
1324	>	final String nextWorkerName() {
1325	>	return workerNamePrefix.concat
1326	>	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1327	>	}
1328
1329		/**
1330	<	* The number of threads blocked in join.
1330	>	* Callback from ForkJoinWorkerThread constructor to establish its
1331	>	* poolIndex and record its WorkQueue. To avoid scanning bias due
1332	>	* to packing entries in front of the workQueues array, we treat
1333	>	* the array as a simple power-of-two hash table using per-thread
1334	>	* seed as hash, expanding as needed.
1335	>	*
1336	>	* @param w the worker's queue
1337		*/
1338	<	volatile int blockedCount;
1338	>	final void registerWorker(WorkQueue w) {
1339	>	Mutex lock = this.lock;
1340	>	lock.lock();
1341	>	try {
1342	>	WorkQueue[] ws = workQueues;
1343	>	if (w != null && ws != null) {          // skip on shutdown/failure
1344	>	int rs, n = ws.length, m = n - 1;
1345	>	int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence
1346	>	w.seed = (s == 0) ? 1 : s;          // ensure non-zero seed
1347	>	int r = (s << 1) | 1;               // use odd-numbered indices
1348	>	if (ws[r &= m] != null) {           // collision
1349	>	int probes = 0;                 // step by approx half size
1350	>	int step = (n <= 4) ? 2 : ((n >>> 1) & SQMASK) + 2;
1351	>	while (ws[r = (r + step) & m] != null) {
1352	>	if (++probes >= n) {
1353	>	workQueues = ws = Arrays.copyOf(ws, n <<= 1);
1354	>	m = n - 1;
1355	>	probes = 0;
1356	>	}
1357	>	}
1358	>	}
1359	>	w.eventCount = w.poolIndex = r;     // establish before recording
1360	>	ws[r] = w;                          // also update seq
1361	>	runState = ((rs = runState) & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN);
1362	>	}
1363	>	} finally {
1364	>	lock.unlock();
1365	>	}
1366	>	}
1367
1368		/**
1369	<	* Counter for worker Thread names (unrelated to their poolIndex)
1369	>	* Final callback from terminating worker, as well as upon failure
1370	>	* to construct or start a worker in addWorker.  Removes record of
1371	>	* worker from array, and adjusts counts. If pool is shutting
1372	>	* down, tries to complete termination.
1373	>	*
1374	>	* @param wt the worker thread or null if addWorker failed
1375	>	* @param ex the exception causing failure, or null if none
1376		*/
1377	<	private volatile int nextWorkerNumber;
1377	>	final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1378	>	Mutex lock = this.lock;
1379	>	WorkQueue w = null;
1380	>	if (wt != null && (w = wt.workQueue) != null) {
1381	>	w.runState = -1;                // ensure runState is set
1382	>	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1383	>	int idx = w.poolIndex;
1384	>	lock.lock();
1385	>	try {                           // remove record from array
1386	>	WorkQueue[] ws = workQueues;
1387	>	if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1388	>	ws[idx] = null;
1389	>	} finally {
1390	>	lock.unlock();
1391	>	}
1392	>	}
1393	>
1394	>	long c;                             // adjust ctl counts
1395	>	do {} while (!U.compareAndSwapLong
1396	>	(this, CTL, c = ctl, (((c - AC_UNIT) & AC_MASK) |
1397	>	((c - TC_UNIT) & TC_MASK) |
1398	>	(c & ~(AC_MASK|TC_MASK)))));
1399	>
1400	>	if (!tryTerminate(false, false) && w != null) {
1401	>	w.cancelAll();                  // cancel remaining tasks
1402	>	if (w.array != null)            // suppress signal if never ran
1403	>	signalWork();               // wake up or create replacement
1404	>	if (ex == null)                 // help clean refs on way out
1405	>	ForkJoinTask.helpExpungeStaleExceptions();
1406	>	}
1407	>
1408	>	if (ex != null)                     // rethrow
1409	>	U.throwException(ex);
1410	>	}
1411	>
1412	>	// Submissions
1413
1414		/**
1415	<	* The index for the next created worker. Accessed under scanGuard.
1416	<	*/
1417	<	private int nextWorkerIndex;
1415	>	* Unless shutting down, adds the given task to a submission queue
1416	>	* at submitter's current queue index (modulo submission
1417	>	* range). If no queue exists at the index, one is created.  If
1418	>	* the queue is busy, another index is randomly chosen. The
1419	>	* submitMask bounds the effective number of queues to the
1420	>	* (nearest power of two for) parallelism level.
1421	>	*
1422	>	* @param task the task. Caller must ensure non-null.
1423	>	*/
1424	>	private void doSubmit(ForkJoinTask<?> task) {
1425	>	Submitter s = submitters.get();
1426	>	for (int r = s.seed, m = submitMask;;) {
1427	>	WorkQueue[] ws; WorkQueue q;
1428	>	int k = r & m & SQMASK;          // use only even indices
1429	>	if (runState < 0 || (ws = workQueues) == null || ws.length <= k)
1430	>	throw new RejectedExecutionException(); // shutting down
1431	>	else if ((q = ws[k]) == null) {  // create new queue
1432	>	WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE);
1433	>	Mutex lock = this.lock;      // construct outside lock
1434	>	lock.lock();
1435	>	try {                        // recheck under lock
1436	>	int rs = runState;       // to update seq
1437	>	if (ws == workQueues && ws[k] == null) {
1438	>	ws[k] = nq;
1439	>	runState = ((rs & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN));
1440	>	}
1441	>	} finally {
1442	>	lock.unlock();
1443	>	}
1444	>	}
1445	>	else if (q.trySharedPush(task)) {
1446	>	signalWork();
1447	>	return;
1448	>	}
1449	>	else if (m > 1) {                // move to a different index
1450	>	r ^= r << 13;                // same xorshift as WorkQueues
1451	>	r ^= r >>> 17;
1452	>	s.seed = r ^= r << 5;
1453	>	}
1454	>	else
1455	>	Thread.yield();              // yield if no alternatives
1456	>	}
1457	>	}
1458
1459		/**
1460	<	* SeqLock and index masking for for updates to workers array.
572	<	* Locked when SG_UNIT is set. Unlocking clears bit by adding
573	<	* SG_UNIT. Staleness of read-only operations can be checked by
574	<	* comparing scanGuard to value before the reads. The low 16 bits
575	<	* (i.e, anding with SMASK) hold (the smallest power of two
576	<	* covering all worker indices, minus one, and is used to avoid
577	<	* dealing with large numbers of null slots when the workers array
578	<	* is overallocated.
1460	>	* Submits the given (non-null) task to the common pool, if possible.
1461		*/
1462	<	volatile int scanGuard;
1463	<
1464	<	private static final int SG_UNIT = 1 << 16;
1462	>	static void submitToCommonPool(ForkJoinTask<?> task) {
1463	>	ForkJoinPool p;
1464	>	if ((p = commonPool) == null)
1465	>	p = ensureCommonPool();
1466	>	p.doSubmit(task);
1467	>	}
1468
1469		/**
1470	<	* The wakeup interval (in nanoseconds) for a worker waiting for a
1471	<	* task when the pool is quiescent to instead try to shrink the
1472	<	* number of workers.  The exact value does not matter too
1473	<	* much. It must be short enough to release resources during
1474	<	* sustained periods of idleness, but not so short that threads
1475	<	* are continually re-created.
1470	>	* Returns true if the given task was submitted to common pool
1471	>	* and has not yet commenced execution, and is available for
1472	>	* removal according to execution policies; if so removing the
1473	>	* submission from the pool.
1474	>	*
1475	>	* @param task the task
1476	>	* @return true if successful
1477		*/
1478	<	private static final long SHRINK_RATE =
1479	<	4L * 1000L * 1000L * 1000L; // 4 seconds
1478	>	static boolean tryUnsubmitFromCommonPool(ForkJoinTask<?> task) {
1479	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
1480	>	int k = submitters.get().seed & SQMASK;
1481	>	return ((p = commonPool) != null &&
1482	>	(ws = p.workQueues) != null &&
1483	>	ws.length > (k &= p.submitMask) &&
1484	>	(q = ws[k]) != null &&
1485	>	q.trySharedUnpush(task, p));
1486	>	}
1487	>
1488	>	// Maintaining ctl counts
1489
1490		/**
1491	<	* Top-level loop for worker threads: On each step: if the
597	<	* previous step swept through all queues and found no tasks, or
598	<	* there are excess threads, then possibly blocks. Otherwise,
599	<	* scans for and, if found, executes a task. Returns when pool
600	<	* and/or worker terminate.
601	<	*
602	<	* @param w the worker
1491	>	* Increments active count; mainly called upon return from blocking.
1492		*/
1493	<	final void work(ForkJoinWorkerThread w) {
605	<	boolean swept = false;                // true on empty scans
1493	>	final void incrementActiveCount() {
1494		long c;
1495	<	while (!w.terminate && (int)(c = ctl) >= 0) {
608	<	int a;                            // active count
609	<	if (!swept && (a = (int)(c >> AC_SHIFT)) <= 0)
610	<	swept = scan(w, a);
611	<	else if (tryAwaitWork(w, c))
612	<	swept = false;
613	<	}
1495	>	do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
1496		}
1497
616	–	// Signalling
617	–
1498		/**
1499	<	* Wakes up or creates a worker.
1499	>	* Tries to create one or activate one or more workers if too few are active.
1500		*/
1501		final void signalWork() {
1502	<	/*
1503	<	* The while condition is true if: (there is are too few total
1504	<	* workers OR there is at least one waiter) AND (there are too
1505	<	* few active workers OR the pool is terminating).  The value
1506	<	* of e distinguishes the remaining cases: zero (no waiters)
1507	<	* for create, negative if terminating (in which case do
1508	<	* nothing), else release a waiter. The secondary checks for
1509	<	* release (non-null array etc) can fail if the pool begins
1510	<	* terminating after the test, and don't impose any added cost
1511	<	* because JVMs must perform null and bounds checks anyway.
1512	<	*/
1513	<	long c; int e, u;
1514	<	while ((((e = (int)(c = ctl)) | (u = (int)(c >>> 32))) &
1515	<	(INT_SIGN|SHORT_SIGN)) == (INT_SIGN|SHORT_SIGN) && e >= 0) {
1516	<	if (e > 0) {                         // release a waiting worker
1517	<	int i; ForkJoinWorkerThread w; ForkJoinWorkerThread[] ws;
638	<	if ((ws = workers) == null ||
639	<	(i = ~e & SMASK) >= ws.length ||
640	<	(w = ws[i]) == null)
1502	>	long c; int u;
1503	>	while ((u = (int)((c = ctl) >>> 32)) < 0) {     // too few active
1504	>	WorkQueue[] ws = workQueues; int e, i; WorkQueue w; Thread p;
1505	>	if ((e = (int)c) > 0) {                     // at least one waiting
1506	>	if (ws != null && (i = e & SMASK) < ws.length &&
1507	>	(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
1508	>	long nc = (((long)(w.nextWait & E_MASK)) |
1509	>	((long)(u + UAC_UNIT) << 32));
1510	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1511	>	w.eventCount = (e + E_SEQ) & E_MASK;
1512	>	if ((p = w.parker) != null)
1513	>	U.unpark(p);                // activate and release
1514	>	break;
1515	>	}
1516	>	}
1517	>	else
1518		break;
1519	<	long nc = (((long)(w.nextWait & E_MASK)) |
1520	<	((long)(u + UAC_UNIT) << 32));
1521	<	if (w.eventCount == e &&
1522	<	UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
1523	<	w.eventCount = (e + EC_UNIT) & E_MASK;
1524	<	if (w.parked)
648	<	UNSAFE.unpark(w);
1519	>	}
1520	>	else if (e == 0 && (u & SHORT_SIGN) != 0) { // too few total
1521	>	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) |
1522	>	((u + UAC_UNIT) & UAC_MASK)) << 32;
1523	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1524	>	addWorker();
1525		break;
1526		}
1527		}
1528	<	else if (UNSAFE.compareAndSwapLong
653	<	(this, ctlOffset, c,
654	<	(long)(((u + UTC_UNIT) & UTC_MASK) |
655	<	((u + UAC_UNIT) & UAC_MASK)) << 32)) {
656	<	addWorker();
1528	>	else
1529		break;
658	–	}
659	–	}
660	–	}
661	–
662	–	/**
663	–	* Variant of signalWork to help release waiters on rescans.
664	–	* Tries once to release a waiter if active count < 0.
665	–	*
666	–	* @return false if failed due to contention, else true
667	–	*/
668	–	private boolean tryReleaseWaiter() {
669	–	long c; int e, i; ForkJoinWorkerThread w; ForkJoinWorkerThread[] ws;
670	–	if ((e = (int)(c = ctl)) > 0 &&
671	–	(int)(c >> AC_SHIFT) < 0 &&
672	–	(ws = workers) != null &&
673	–	(i = ~e & SMASK) < ws.length &&
674	–	(w = ws[i]) != null) {
675	–	long nc = ((long)(w.nextWait & E_MASK) |
676	–	((c + AC_UNIT) & (AC_MASK|TC_MASK)));
677	–	if (w.eventCount != e ||
678	–	!UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc))
679	–	return false;
680	–	w.eventCount = (e + EC_UNIT) & E_MASK;
681	–	if (w.parked)
682	–	UNSAFE.unpark(w);
1530		}
684	–	return true;
1531		}
1532
1533		// Scanning for tasks
1534
1535		/**
1536	<	* Scans for and, if found, executes one task. Scans start at a
1537	<	* random index of workers array, and randomly select the first
1538	<	* (2*#workers)-1 probes, and then, if all empty, resort to 2
1539	<	* circular sweeps, which is necessary to check quiescence. and
1540	<	* taking a submission only if no stealable tasks were found.  The
1541	<	* steal code inside the loop is a specialized form of
1542	<	* ForkJoinWorkerThread.deqTask, followed bookkeeping to support
1543	<	* helpJoinTask and signal propagation. The code for submission
1544	<	* queues is almost identical. On each steal, the worker completes
1545	<	* not only the task, but also all local tasks that this task may
1546	<	* have generated. On detecting staleness or contention when
1547	<	* trying to take a task, this method returns without finishing
1548	<	* sweep, which allows global state rechecks before retry.
1549	<	*
1550	<	* @param w the worker
1551	<	* @param a the number of active workers
1552	<	* @return true if swept all queues without finding a task
1553	<	*/
1554	<	private boolean scan(ForkJoinWorkerThread w, int a) {
1555	<	int g = scanGuard; // mask 0 avoids useless scans if only one active
1556	<	int m = parallelism == 1 - a? 0 : g & SMASK;
1557	<	ForkJoinWorkerThread[] ws = workers;
1558	<	if (ws == null || ws.length <= m)         // staleness check
1559	<	return false;
1560	<	for (int r = w.seed, k = r, j = -(m + m); j <= m + m; ++j) {
1561	<	ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i;
1562	<	ForkJoinWorkerThread v = ws[k & m];
1563	<	if (v != null && (b = v.queueBase) != v.queueTop &&
1564	<	(q = v.queue) != null && (i = (q.length - 1) & b) >= 0) {
1565	<	long u = (i << ASHIFT) + ABASE;
1566	<	if ((t = q[i]) != null && v.queueBase == b &&
1567	<	UNSAFE.compareAndSwapObject(q, u, t, null)) {
1568	<	int d = (v.queueBase = b + 1) - v.queueTop;
1569	<	v.stealHint = w.poolIndex;
1570	<	if (d != 0)
1571	<	signalWork();             // propagate if nonempty
1572	<	w.execTask(t);
1536	>	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1537	>	*/
1538	>	final void runWorker(WorkQueue w) {
1539	>	w.growArray(false);         // initialize queue array in this thread
1540	>	do { w.runTask(scan(w)); } while (w.runState >= 0);
1541	>	}
1542	>
1543	>	/**
1544	>	* Scans for and, if found, returns one task, else possibly
1545	>	* inactivates the worker. This method operates on single reads of
1546	>	* volatile state and is designed to be re-invoked continuously,
1547	>	* in part because it returns upon detecting inconsistencies,
1548	>	* contention, or state changes that indicate possible success on
1549	>	* re-invocation.
1550	>	*
1551	>	* The scan searches for tasks across a random permutation of
1552	>	* queues (starting at a random index and stepping by a random
1553	>	* relative prime, checking each at least once).  The scan
1554	>	* terminates upon either finding a non-empty queue, or completing
1555	>	* the sweep. If the worker is not inactivated, it takes and
1556	>	* returns a task from this queue.  On failure to find a task, we
1557	>	* take one of the following actions, after which the caller will
1558	>	* retry calling this method unless terminated.
1559	>	*
1560	>	* * If pool is terminating, terminate the worker.
1561	>	*
1562	>	* * If not a complete sweep, try to release a waiting worker.  If
1563	>	* the scan terminated because the worker is inactivated, then the
1564	>	* released worker will often be the calling worker, and it can
1565	>	* succeed obtaining a task on the next call. Or maybe it is
1566	>	* another worker, but with same net effect. Releasing in other
1567	>	* cases as well ensures that we have enough workers running.
1568	>	*
1569	>	* * If not already enqueued, try to inactivate and enqueue the
1570	>	* worker on wait queue. Or, if inactivating has caused the pool
1571	>	* to be quiescent, relay to idleAwaitWork to check for
1572	>	* termination and possibly shrink pool.
1573	>	*
1574	>	* * If already inactive, and the caller has run a task since the
1575	>	* last empty scan, return (to allow rescan) unless others are
1576	>	* also inactivated.  Field WorkQueue.rescans counts down on each
1577	>	* scan to ensure eventual inactivation and blocking.
1578	>	*
1579	>	* * If already enqueued and none of the above apply, park
1580	>	* awaiting signal,
1581	>	*
1582	>	* @param w the worker (via its WorkQueue)
1583	>	* @return a task or null if none found
1584	>	*/
1585	>	private final ForkJoinTask<?> scan(WorkQueue w) {
1586	>	WorkQueue[] ws;                       // first update random seed
1587	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1588	>	int rs = runState, m;                 // volatile read order matters
1589	>	if ((ws = workQueues) != null && (m = ws.length - 1) > 0) {
1590	>	int ec = w.eventCount;            // ec is negative if inactive
1591	>	int step = (r >>> 16) | 1;        // relative prime
1592	>	for (int j = (m + 1) << 2; ; r += step) {
1593	>	WorkQueue q; ForkJoinTask<?> t; ForkJoinTask<?>[] a; int b;
1594	>	if ((q = ws[r & m]) != null && (b = q.base) - q.top < 0 &&
1595	>	(a = q.array) != null) {  // probably nonempty
1596	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1597	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1598	>	if (q.base == b && ec >= 0 && t != null &&
1599	>	U.compareAndSwapObject(a, i, t, null)) {
1600	>	if (q.top - (q.base = b + 1) > 0)
1601	>	signalWork();    // help pushes signal
1602	>	return t;
1603	>	}
1604	>	else if (ec < 0 || j <= m) {
1605	>	rs = 0;               // mark scan as imcomplete
1606	>	break;                // caller can retry after release
1607	>	}
1608		}
1609	<	r ^= r << 13; r ^= r >>> 17; w.seed = r ^ (r << 5);
1610	<	return false;                     // store next seed
730	<	}
731	<	else if (j < 0) {                     // xorshift
732	<	r ^= r << 13; r ^= r >>> 17; k = r ^= r << 5;
1609	>	if (--j < 0)
1610	>	break;
1611		}
1612	<	else
1613	<	++k;
1614	<	}
1615	<	if (scanGuard != g)                       // staleness check
1616	<	return false;
1617	<	else {                                    // try to take submission
1618	<	ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i;
1619	<	if ((b = queueBase) != queueTop &&
1620	<	(q = submissionQueue) != null &&
1621	<	(i = (q.length - 1) & b) >= 0) {
1622	<	long u = (i << ASHIFT) + ABASE;
1623	<	if ((t = q[i]) != null && queueBase == b &&
1624	<	UNSAFE.compareAndSwapObject(q, u, t, null)) {
1625	<	queueBase = b + 1;
1626	<	w.execTask(t);
1612	>
1613	>	long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
1614	>	if (e < 0)                        // decode ctl on empty scan
1615	>	w.runState = -1;              // pool is terminating
1616	>	else if (rs == 0 || rs != runState) { // incomplete scan
1617	>	WorkQueue v; Thread p;        // try to release a waiter
1618	>	if (e > 0 && a < 0 && w.eventCount == ec &&
1619	>	(v = ws[e & m]) != null && v.eventCount == (e | INT_SIGN)) {
1620	>	long nc = ((long)(v.nextWait & E_MASK) |
1621	>	((c + AC_UNIT) & (AC_MASK|TC_MASK)));
1622	>	if (ctl == c && U.compareAndSwapLong(this, CTL, c, nc)) {
1623	>	v.eventCount = (e + E_SEQ) & E_MASK;
1624	>	if ((p = v.parker) != null)
1625	>	U.unpark(p);
1626	>	}
1627		}
750	–	return false;
1628		}
1629	<	return true;                         // all queues empty
1630	<	}
1631	<	}
1632	<
1633	<	/**
1634	<	* Tries to enqueue worker in wait queue and await change in
1635	<	* worker's eventCount.  Before blocking, rescans queues to avoid
1636	<	* missed signals.  If the pool is quiescent, possibly terminates
1637	<	* worker upon exit.
1638	<	*
1639	<	* @param w the calling worker
763	<	* @param c the ctl value on entry
764	<	* @return true if waited or another thread was released upon enq
765	<	*/
766	<	private boolean tryAwaitWork(ForkJoinWorkerThread w, long c) {
767	<	int v = w.eventCount;
768	<	w.nextWait = (int)c;                       // w's successor record
769	<	long nc = (long)(v & E_MASK) | ((c - AC_UNIT) & (AC_MASK|TC_MASK));
770	<	if (ctl != c || !UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
771	<	long d = ctl; // return true if lost to a deq, to force rescan
772	<	return (int)d != (int)c && ((d - c) & AC_MASK) >= 0L;
773	<	}
774	<	boolean rescanned = false;
775	<	for (int sc;;) {
776	<	if (w.eventCount != v)
777	<	return true;
778	<	if ((sc = w.stealCount) != 0) {
779	<	long s = stealCount;               // accumulate stealCount
780	<	if (UNSAFE.compareAndSwapLong(this, stealCountOffset, s, s+sc))
781	<	w.stealCount = 0;
782	<	}
783	<	else if (!rescanned) {
784	<	int g = scanGuard, m = g & SMASK;
785	<	ForkJoinWorkerThread[] ws = workers;
786	<	if (ws != null && m < ws.length) {
787	<	rescanned = true;
788	<	for (int i = 0; i <= m; ++i) {
789	<	ForkJoinWorkerThread u = ws[i];
790	<	if (u != null) {
791	<	if (u.queueBase != u.queueTop &&
792	<	!tryReleaseWaiter())
793	<	rescanned = false; // contended
794	<	if (w.eventCount != v)
795	<	return true;
796	<	}
1629	>	else if (ec >= 0) {               // try to enqueue/inactivate
1630	>	long nc = (long)ec | ((c - AC_UNIT) & (AC_MASK|TC_MASK));
1631	>	w.nextWait = e;
1632	>	w.eventCount = ec | INT_SIGN; // mark as inactive
1633	>	if (ctl != c || !U.compareAndSwapLong(this, CTL, c, nc))
1634	>	w.eventCount = ec;        // unmark on CAS failure
1635	>	else {
1636	>	if ((ns = w.nsteals) != 0) {
1637	>	w.nsteals = 0;        // set rescans if ran task
1638	>	w.rescans = (a > 0) ? 0 : a + parallelism;
1639	>	w.totalSteals += ns;
1640		}
1641	+	if (a == 1 - parallelism) // quiescent
1642	+	idleAwaitWork(w, nc, c);
1643		}
799	–	if (scanGuard != g ||              // stale
800	–	(queueBase != queueTop && !tryReleaseWaiter()))
801	–	rescanned = false;
802	–	if (!rescanned)
803	–	Thread.yield();                // reduce contention
804	–	else
805	–	Thread.interrupted();          // clear before park
1644		}
1645	<	else if (parallelism + (int)(ctl >> AC_SHIFT) == 0 &&
1646	<	blockedCount == 0 && quiescerCount == 0)
1647	<	idleAwaitWork(w, v);               // quiescent -- maybe shrink
1648	<	else {
1649	<	w.parked = true;                   // must recheck
1650	<	if (w.eventCount != v) {
1651	<	w.parked = false;
1652	<	return true;
1645	>	else if (w.eventCount < 0) {      // already queued
1646	>	int ac = a + parallelism;
1647	>	if ((nr = w.rescans) > 0)     // continue rescanning
1648	>	w.rescans = (ac < nr) ? ac : nr - 1;
1649	>	else if (((w.seed >>> 16) & ac) == 0) { // randomize park
1650	>	Thread.interrupted();     // clear status
1651	>	Thread wt = Thread.currentThread();
1652	>	U.putObject(wt, PARKBLOCKER, this);
1653	>	w.parker = wt;            // emulate LockSupport.park
1654	>	if (w.eventCount < 0)     // recheck
1655	>	U.park(false, 0L);
1656	>	w.parker = null;
1657	>	U.putObject(wt, PARKBLOCKER, null);
1658		}
816	–	LockSupport.park(this);
817	–	rescanned = w.parked = false;
1659		}
1660		}
1661	+	return null;
1662		}
1663
1664		/**
1665	<	* If pool is quiescent, checks for termination, and waits for
1666	<	* event signal for up to SHRINK_RATE nanosecs. On timeout, if ctl
1667	<	* has not changed, terminates the worker. Upon its termination
1668	<	* (see deregisterWorker), it may wake up another worker to
1669	<	* possibly repeat this process.
1665	>	* If inactivating worker w has caused the pool to become
1666	>	* quiescent, checks for pool termination, and, so long as this is
1667	>	* not the only worker, waits for event for up to a given
1668	>	* duration.  On timeout, if ctl has not changed, terminates the
1669	>	* worker, which will in turn wake up another worker to possibly
1670	>	* repeat this process.
1671		*
1672		* @param w the calling worker
1673	<	* @param v the eventCount w must wait until changed
1673	>	* @param currentCtl the ctl value triggering possible quiescence
1674	>	* @param prevCtl the ctl value to restore if thread is terminated
1675		*/
1676	<	private void idleAwaitWork(ForkJoinWorkerThread w, int v) {
1677	<	ForkJoinTask.helpExpungeStaleExceptions(); // help clean weak refs
1678	<	if (shutdown)
1679	<	tryTerminate(false);
1680	<	long c = ctl;
1681	<	long nc = (((c & (AC_MASK|TC_MASK)) + AC_UNIT) |
1682	<	(long)(w.nextWait & E_MASK)); // ctl value to release w
1683	<	if (w.eventCount == v &&
1684	<	parallelism + (int)(c >> AC_SHIFT) == 0 &&
1685	<	blockedCount == 0 && quiescerCount == 0) {
1686	<	long startTime = System.nanoTime();
1687	<	Thread.interrupted();
1688	<	if (w.eventCount == v) {
1689	<	w.parked = true;
1690	<	if (w.eventCount == v)
1691	<	LockSupport.parkNanos(this, SHRINK_RATE);
1692	<	w.parked = false;
1693	<	if (w.eventCount == v && ctl == c &&
1694	<	System.nanoTime() - startTime >= SHRINK_RATE &&
1695	<	UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
1696	<	w.terminate = true;
1697	<	w.eventCount = ((int)c + EC_UNIT) & E_MASK;
1676	>	private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1677	>	if (w.eventCount < 0 && !tryTerminate(false, false) &&
1678	>	(int)prevCtl != 0 && !hasQueuedSubmissions() && ctl == currentCtl) {
1679	>	int dc = -(short)(currentCtl >>> TC_SHIFT);
1680	>	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1681	>	long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop
1682	>	Thread wt = Thread.currentThread();
1683	>	while (ctl == currentCtl) {
1684	>	Thread.interrupted();  // timed variant of version in scan()
1685	>	U.putObject(wt, PARKBLOCKER, this);
1686	>	w.parker = wt;
1687	>	if (ctl == currentCtl)
1688	>	U.park(false, parkTime);
1689	>	w.parker = null;
1690	>	U.putObject(wt, PARKBLOCKER, null);
1691	>	if (ctl != currentCtl)
1692	>	break;
1693	>	if (deadline - System.nanoTime() <= 0L &&
1694	>	U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1695	>	w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
1696	>	w.runState = -1;   // shrink
1697	>	break;
1698		}
1699		}
1700		}
1701		}
1702
859	–	// Submissions
860	–
1703		/**
1704	<	* Enqueues the given task in the submissionQueue.  Same idea as
1705	<	* ForkJoinWorkerThread.pushTask except for use of submissionLock.
1706	<	*
1707	<	* @param t the task
1708	<	*/
1709	<	private void addSubmission(ForkJoinTask<?> t) {
1710	<	final ReentrantLock lock = this.submissionLock;
1711	<	lock.lock();
1712	<	try {
1713	<	ForkJoinTask<?>[] q; int s, m;
1714	<	if ((q = submissionQueue) != null) {    // ignore if queue removed
1715	<	long u = (((s = queueTop) & (m = q.length-1)) << ASHIFT)+ABASE;
1716	<	UNSAFE.putOrderedObject(q, u, t);
1717	<	queueTop = s + 1;
1718	<	if (s - queueBase == m)
1719	<	growSubmissionQueue();
1704	>	* Tries to locate and execute tasks for a stealer of the given
1705	>	* task, or in turn one of its stealers, Traces currentSteal ->
1706	>	* currentJoin links looking for a thread working on a descendant
1707	>	* of the given task and with a non-empty queue to steal back and
1708	>	* execute tasks from. The first call to this method upon a
1709	>	* waiting join will often entail scanning/search, (which is OK
1710	>	* because the joiner has nothing better to do), but this method
1711	>	* leaves hints in workers to speed up subsequent calls. The
1712	>	* implementation is very branchy to cope with potential
1713	>	* inconsistencies or loops encountering chains that are stale,
1714	>	* unknown, or so long that they are likely cyclic.
1715	>	*
1716	>	* @param joiner the joining worker
1717	>	* @param task the task to join
1718	>	* @return 0 if no progress can be made, negative if task
1719	>	* known complete, else positive
1720	>	*/
1721	>	private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1722	>	int stat = 0, steps = 0;                    // bound to avoid cycles
1723	>	if (joiner != null && task != null) {       // hoist null checks
1724	>	restart: for (;;) {
1725	>	ForkJoinTask<?> subtask = task;     // current target
1726	>	for (WorkQueue j = joiner, v;;) {   // v is stealer of subtask
1727	>	WorkQueue[] ws; int m, s, h;
1728	>	if ((s = task.status) < 0) {
1729	>	stat = s;
1730	>	break restart;
1731	>	}
1732	>	if ((ws = workQueues) == null || (m = ws.length - 1) <= 0)
1733	>	break restart;              // shutting down
1734	>	if ((v = ws[h = (j.stealHint | 1) & m]) == null ||
1735	>	v.currentSteal != subtask) {
1736	>	for (int origin = h;;) {    // find stealer
1737	>	if (((h = (h + 2) & m) & 15) == 1 &&
1738	>	(subtask.status < 0 || j.currentJoin != subtask))
1739	>	continue restart;   // occasional staleness check
1740	>	if ((v = ws[h]) != null &&
1741	>	v.currentSteal == subtask) {
1742	>	j.stealHint = h;    // save hint
1743	>	break;
1744	>	}
1745	>	if (h == origin)
1746	>	break restart;      // cannot find stealer
1747	>	}
1748	>	}
1749	>	for (;;) { // help stealer or descend to its stealer
1750	>	ForkJoinTask[] a;  int b;
1751	>	if (subtask.status < 0)     // surround probes with
1752	>	continue restart;       //   consistency checks
1753	>	if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
1754	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1755	>	ForkJoinTask<?> t =
1756	>	(ForkJoinTask<?>)U.getObjectVolatile(a, i);
1757	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1758	>	v.currentSteal != subtask)
1759	>	continue restart;   // stale
1760	>	stat = 1;               // apparent progress
1761	>	if (t != null && v.base == b &&
1762	>	U.compareAndSwapObject(a, i, t, null)) {
1763	>	v.base = b + 1;     // help stealer
1764	>	joiner.runSubtask(t);
1765	>	}
1766	>	else if (v.base == b && ++steps == MAX_HELP)
1767	>	break restart;      // v apparently stalled
1768	>	}
1769	>	else {                      // empty -- try to descend
1770	>	ForkJoinTask<?> next = v.currentJoin;
1771	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1772	>	v.currentSteal != subtask)
1773	>	continue restart;   // stale
1774	>	else if (next == null || ++steps == MAX_HELP)
1775	>	break restart;      // dead-end or maybe cyclic
1776	>	else {
1777	>	subtask = next;
1778	>	j = v;
1779	>	break;
1780	>	}
1781	>	}
1782	>	}
1783	>	}
1784		}
879	–	} finally {
880	–	lock.unlock();
1785		}
1786	<	signalWork();
1786	>	return stat;
1787		}
1788
885	–	//  (pollSubmission is defined below with exported methods)
886	–
1789		/**
1790	<	* Creates or doubles submissionQueue array.
1791	<	* Basically identical to ForkJoinWorkerThread version
1790	>	* If task is at base of some steal queue, steals and executes it.
1791	>	*
1792	>	* @param joiner the joining worker
1793	>	* @param task the task
1794		*/
1795	<	private void growSubmissionQueue() {
1796	<	ForkJoinTask<?>[] oldQ = submissionQueue;
1797	<	int size = oldQ != null ? oldQ.length << 1 : INITIAL_QUEUE_CAPACITY;
1798	<	if (size > MAXIMUM_QUEUE_CAPACITY)
1799	<	throw new RejectedExecutionException("Queue capacity exceeded");
1800	<	if (size < INITIAL_QUEUE_CAPACITY)
1801	<	size = INITIAL_QUEUE_CAPACITY;
1802	<	ForkJoinTask<?>[] q = submissionQueue = new ForkJoinTask<?>[size];
1803	<	int mask = size - 1;
900	<	int top = queueTop;
901	<	int oldMask;
902	<	if (oldQ != null && (oldMask = oldQ.length - 1) >= 0) {
903	<	for (int b = queueBase; b != top; ++b) {
904	<	long u = ((b & oldMask) << ASHIFT) + ABASE;
905	<	Object x = UNSAFE.getObjectVolatile(oldQ, u);
906	<	if (x != null && UNSAFE.compareAndSwapObject(oldQ, u, x, null))
907	<	UNSAFE.putObjectVolatile
908	<	(q, ((b & mask) << ASHIFT) + ABASE, x);
1795	>	private void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
1796	>	WorkQueue[] ws;
1797	>	if ((ws = workQueues) != null) {
1798	>	for (int j = 1; j < ws.length && task.status >= 0; j += 2) {
1799	>	WorkQueue q = ws[j];
1800	>	if (q != null && q.pollFor(task)) {
1801	>	joiner.runSubtask(task);
1802	>	break;
1803	>	}
1804		}
1805		}
1806		}
1807
913	–	// Blocking support
914	–
1808		/**
1809	<	* Tries to increment blockedCount, decrement active count
1810	<	* (sometimes implicitly) and possibly release or create a
1811	<	* compensating worker in preparation for blocking. Fails
1812	<	* on contention or termination.
1809	>	* Tries to decrement active count (sometimes implicitly) and
1810	>	* possibly release or create a compensating worker in preparation
1811	>	* for blocking. Fails on contention or termination. Otherwise,
1812	>	* adds a new thread if no idle workers are available and either
1813	>	* pool would become completely starved or: (at least half
1814	>	* starved, and fewer than 50% spares exist, and there is at least
1815	>	* one task apparently available). Even though the availability
1816	>	* check requires a full scan, it is worthwhile in reducing false
1817	>	* alarms.
1818		*
1819	+	* @param task if non-null, a task being waited for
1820	+	* @param blocker if non-null, a blocker being waited for
1821		* @return true if the caller can block, else should recheck and retry
1822		*/
1823	<	private boolean tryPreBlock() {
1824	<	int b = blockedCount;
1825	<	if (UNSAFE.compareAndSwapInt(this, blockedCountOffset, b, b + 1)) {
1826	<	int pc = parallelism;
1827	<	do {
1828	<	ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w;
1829	<	int e, ac, tc, rc, i;
1830	<	long c = ctl;
1831	<	int u = (int)(c >>> 32);
1832	<	if ((e = (int)c) < 0) {
1833	<	// skip -- terminating
1834	<	}
1835	<	else if ((ac = (u >> UAC_SHIFT)) <= 0 && e != 0 &&
1836	<	(ws = workers) != null &&
1837	<	(i = ~e & SMASK) < ws.length &&
1838	<	(w = ws[i]) != null) {
1839	<	long nc = ((long)(w.nextWait & E_MASK) |
1840	<	(c & (AC_MASK|TC_MASK)));
1841	<	if (w.eventCount == e &&
942	<	UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
943	<	w.eventCount = (e + EC_UNIT) & E_MASK;
944	<	if (w.parked)
945	<	UNSAFE.unpark(w);
946	<	return true;             // release an idle worker
1823	>	final boolean tryCompensate(ForkJoinTask<?> task, ManagedBlocker blocker) {
1824	>	int pc = parallelism, e;
1825	>	long c = ctl;
1826	>	WorkQueue[] ws = workQueues;
1827	>	if ((e = (int)c) >= 0 && ws != null) {
1828	>	int u, a, ac, hc;
1829	>	int tc = (short)((u = (int)(c >>> 32)) >>> UTC_SHIFT) + pc;
1830	>	boolean replace = false;
1831	>	if ((a = u >> UAC_SHIFT) <= 0) {
1832	>	if ((ac = a + pc) <= 1)
1833	>	replace = true;
1834	>	else if ((e > 0 || (task != null &&
1835	>	ac <= (hc = pc >>> 1) && tc < pc + hc))) {
1836	>	WorkQueue w;
1837	>	for (int j = 0; j < ws.length; ++j) {
1838	>	if ((w = ws[j]) != null && !w.isEmpty()) {
1839	>	replace = true;
1840	>	break;   // in compensation range and tasks available
1841	>	}
1842		}
1843		}
1844	<	else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) {
1844	>	}
1845	>	if ((task == null || task.status >= 0) && // recheck need to block
1846	>	(blocker == null || !blocker.isReleasable()) && ctl == c) {
1847	>	if (!replace) {          // no compensation
1848		long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
1849	<	if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc))
1850	<	return true;             // no compensation needed
1849	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1850	>	return true;
1851	>	}
1852	>	else if (e != 0) {       // release an idle worker
1853	>	WorkQueue w; Thread p; int i;
1854	>	if ((i = e & SMASK) < ws.length && (w = ws[i]) != null) {
1855	>	long nc = ((long)(w.nextWait & E_MASK) |
1856	>	(c & (AC_MASK|TC_MASK)));
1857	>	if (w.eventCount == (e | INT_SIGN) &&
1858	>	U.compareAndSwapLong(this, CTL, c, nc)) {
1859	>	w.eventCount = (e + E_SEQ) & E_MASK;
1860	>	if ((p = w.parker) != null)
1861	>	U.unpark(p);
1862	>	return true;
1863	>	}
1864	>	}
1865		}
1866	<	else if (tc + pc < MAX_ID) {
1866	>	else if (tc < MAX_CAP) { // create replacement
1867		long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
1868	<	if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
1868	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1869		addWorker();
1870	<	return true;            // create a replacement
1870	>	return true;
1871		}
1872		}
1873	<	// try to back out on any failure and let caller retry
962	<	} while (!UNSAFE.compareAndSwapInt(this, blockedCountOffset,
963	<	b = blockedCount, b - 1));
1873	>	}
1874		}
1875		return false;
1876		}
1877
1878		/**
1879	<	* Decrements blockedCount and increments active count
970	<	*/
971	<	private void postBlock() {
972	<	long c;
973	<	do {} while (!UNSAFE.compareAndSwapLong(this, ctlOffset,  // no mask
974	<	c = ctl, c + AC_UNIT));
975	<	int b;
976	<	do {} while(!UNSAFE.compareAndSwapInt(this, blockedCountOffset,
977	<	b = blockedCount, b - 1));
978	<	}
979	<
980	<	/**
981	<	* Possibly blocks waiting for the given task to complete, or
982	<	* cancels the task if terminating.  Fails to wait if contended.
1879	>	* Helps and/or blocks until the given task is done.
1880		*
1881	<	* @param joinMe the task
1881	>	* @param joiner the joining worker
1882	>	* @param task the task
1883	>	* @return task status on exit
1884		*/
1885	<	final void tryAwaitJoin(ForkJoinTask<?> joinMe) {
1885	>	final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
1886		int s;
1887	<	Thread.interrupted(); // clear interrupts before checking termination
1888	<	if (joinMe.status >= 0) {
1889	<	if (tryPreBlock()) {
1890	<	joinMe.tryAwaitDone(0L);
1891	<	postBlock();
1887	>	if ((s = task.status) >= 0) {
1888	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
1889	>	joiner.currentJoin = task;
1890	>	long startTime = 0L;
1891	>	for (int k = 0;;) {
1892	>	if ((s = (joiner.isEmpty() ?           // try to help
1893	>	tryHelpStealer(joiner, task) :
1894	>	joiner.tryRemoveAndExec(task))) == 0 &&
1895	>	(s = task.status) >= 0) {
1896	>	if (k == 0) {
1897	>	startTime = System.nanoTime();
1898	>	tryPollForAndExec(joiner, task); // check uncommon case
1899	>	}
1900	>	else if ((k & (MAX_HELP - 1)) == 0 &&
1901	>	System.nanoTime() - startTime >=
1902	>	COMPENSATION_DELAY &&
1903	>	tryCompensate(task, null)) {
1904	>	if (task.trySetSignal()) {
1905	>	synchronized (task) {
1906	>	if (task.status >= 0) {
1907	>	try {                // see ForkJoinTask
1908	>	task.wait();     //  for explanation
1909	>	} catch (InterruptedException ie) {
1910	>	}
1911	>	}
1912	>	else
1913	>	task.notifyAll();
1914	>	}
1915	>	}
1916	>	long c;                          // re-activate
1917	>	do {} while (!U.compareAndSwapLong
1918	>	(this, CTL, c = ctl, c + AC_UNIT));
1919	>	}
1920	>	}
1921	>	if (s < 0 || (s = task.status) < 0) {
1922	>	joiner.currentJoin = prevJoin;
1923	>	break;
1924	>	}
1925	>	else if ((k++ & (MAX_HELP - 1)) == MAX_HELP >>> 1)
1926	>	Thread.yield();                     // for politeness
1927		}
994	–	if ((ctl & STOP_BIT) != 0L)
995	–	joinMe.cancelIgnoringExceptions();
1928		}
1929	+	return s;
1930		}
1931
1932		/**
1933	<	* Possibly blocks the given worker waiting for joinMe to
1934	<	* complete or timeout
1933	>	* Stripped-down variant of awaitJoin used by timed joins. Tries
1934	>	* to help join only while there is continuous progress. (Caller
1935	>	* will then enter a timed wait.)
1936		*
1937	<	* @param joinMe the task
1938	<	* @param millis the wait time for underlying Object.wait
1937	>	* @param joiner the joining worker
1938	>	* @param task the task
1939	>	* @return task status on exit
1940		*/
1941	<	final void timedAwaitJoin(ForkJoinTask<?> joinMe, long nanos) {
1942	<	while (joinMe.status >= 0) {
1943	<	Thread.interrupted();
1944	<	if ((ctl & STOP_BIT) != 0L) {
1945	<	joinMe.cancelIgnoringExceptions();
1946	<	break;
1947	<	}
1948	<	if (tryPreBlock()) {
1014	<	long last = System.nanoTime();
1015	<	while (joinMe.status >= 0) {
1016	<	long millis = TimeUnit.NANOSECONDS.toMillis(nanos);
1017	<	if (millis <= 0)
1018	<	break;
1019	<	joinMe.tryAwaitDone(millis);
1020	<	if (joinMe.status < 0)
1021	<	break;
1022	<	if ((ctl & STOP_BIT) != 0L) {
1023	<	joinMe.cancelIgnoringExceptions();
1024	<	break;
1025	<	}
1026	<	long now = System.nanoTime();
1027	<	nanos -= now - last;
1028	<	last = now;
1029	<	}
1030	<	postBlock();
1031	<	break;
1032	<	}
1033	<	}
1941	>	final int helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
1942	>	int s;
1943	>	while ((s = task.status) >= 0 &&
1944	>	(joiner.isEmpty() ?
1945	>	tryHelpStealer(joiner, task) :
1946	>	joiner.tryRemoveAndExec(task)) != 0)
1947	>	;
1948	>	return s;
1949		}
1950
1951		/**
1952	<	* If necessary, compensates for blocker, and blocks
1953	<	*/
1954	<	private void awaitBlocker(ManagedBlocker blocker)
1955	<	throws InterruptedException {
1956	<	while (!blocker.isReleasable()) {
1957	<	if (tryPreBlock()) {
1958	<	try {
1959	<	do {} while (!blocker.isReleasable() && !blocker.block());
1960	<	} finally {
1961	<	postBlock();
1952	>	* Returns a (probably) non-empty steal queue, if one is found
1953	>	* during a random, then cyclic scan, else null.  This method must
1954	>	* be retried by caller if, by the time it tries to use the queue,
1955	>	* it is empty.
1956	>	*/
1957	>	private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
1958	>	// Similar to loop in scan(), but ignoring submissions
1959	>	int r;
1960	>	if (w == null) // allow external callers
1961	>	r = ThreadLocalRandom.current().nextInt();
1962	>	else {
1963	>	r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1964	>	}
1965	>	int step = (r >>> 16) | 1;
1966	>	for (WorkQueue[] ws;;) {
1967	>	int rs = runState, m;
1968	>	if ((ws = workQueues) == null || (m = ws.length - 1) < 1)
1969	>	return null;
1970	>	for (int j = (m + 1) << 2; ; r += step) {
1971	>	WorkQueue q = ws[((r << 1) | 1) & m];
1972	>	if (q != null && !q.isEmpty())
1973	>	return q;
1974	>	else if (--j < 0) {
1975	>	if (runState == rs)
1976	>	return null;
1977	>	break;
1978		}
1048	–	break;
1979		}
1980		}
1981		}
1982
1053	–	// Creating, registering and deregistring workers
1054	–
1983		/**
1984	<	* Tries to create and start a worker; minimally rolls back counts
1985	<	* on failure.
1986	<	*/
1987	<	private void addWorker() {
1988	<	Throwable ex = null;
1989	<	ForkJoinWorkerThread t = null;
1990	<	try {
1991	<	t = factory.newThread(this);
1992	<	} catch (Throwable e) {
1993	<	ex = e;
1994	<	}
1995	<	if (t == null) {  // null or exceptional factory return
1996	<	long c;       // adjust counts
1997	<	do {} while (!UNSAFE.compareAndSwapLong
1998	<	(this, ctlOffset, c = ctl,
1999	<	(((c - AC_UNIT) & AC_MASK) |
2000	<	((c - TC_UNIT) & TC_MASK) |
2001	<	(c & ~(AC_MASK|TC_MASK)))));
2002	<	// Propagate exception if originating from an external caller
2003	<	if (!tryTerminate(false) && ex != null &&
2004	<	!(Thread.currentThread() instanceof ForkJoinWorkerThread))
2005	<	UNSAFE.throwException(ex);
1984	>	* Runs tasks until {@code isQuiescent()}. We piggyback on
1985	>	* active count ctl maintenance, but rather than blocking
1986	>	* when tasks cannot be found, we rescan until all others cannot
1987	>	* find tasks either.
1988	>	*/
1989	>	final void helpQuiescePool(WorkQueue w) {
1990	>	for (boolean active = true;;) {
1991	>	ForkJoinTask<?> localTask; // exhaust local queue
1992	>	while ((localTask = w.nextLocalTask()) != null)
1993	>	localTask.doExec();
1994	>	WorkQueue q = findNonEmptyStealQueue(w);
1995	>	if (q != null) {
1996	>	ForkJoinTask<?> t; int b;
1997	>	if (!active) {      // re-establish active count
1998	>	long c;
1999	>	active = true;
2000	>	do {} while (!U.compareAndSwapLong
2001	>	(this, CTL, c = ctl, c + AC_UNIT));
2002	>	}
2003	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2004	>	w.runSubtask(t);
2005	>	}
2006	>	else {
2007	>	long c;
2008	>	if (active) {       // decrement active count without queuing
2009	>	active = false;
2010	>	do {} while (!U.compareAndSwapLong
2011	>	(this, CTL, c = ctl, c -= AC_UNIT));
2012	>	}
2013	>	else
2014	>	c = ctl;        // re-increment on exit
2015	>	if ((int)(c >> AC_SHIFT) + parallelism == 0) {
2016	>	do {} while (!U.compareAndSwapLong
2017	>	(this, CTL, c = ctl, c + AC_UNIT));
2018	>	break;
2019	>	}
2020	>	}
2021		}
1079	–	else
1080	–	t.start();
2022		}
2023
2024		/**
2025	<	* Callback from ForkJoinWorkerThread constructor to assign a
1085	<	* public name
2025	>	* Restricted version of helpQuiescePool for non-FJ callers
2026		*/
2027	<	final String nextWorkerName() {
2028	<	for (int n;;) {
2029	<	if (UNSAFE.compareAndSwapInt(this, nextWorkerNumberOffset,
2030	<	n = nextWorkerNumber, ++n))
2031	<	return workerNamePrefix + n;
2032	<	}
2027	>	static void externalHelpQuiescePool() {
2028	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q;
2029	>	ForkJoinTask<?> t; int b;
2030	>	int k = submitters.get().seed & SQMASK;
2031	>	if ((p = commonPool) != null &&
2032	>	(ws = p.workQueues) != null &&
2033	>	ws.length > (k &= p.submitMask) &&
2034	>	(w = ws[k]) != null &&
2035	>	(q = p.findNonEmptyStealQueue(w)) != null &&
2036	>	(b = q.base) - q.top < 0 &&
2037	>	(t = q.pollAt(b)) != null)
2038	>	t.doExec();
2039		}
2040
2041		/**
2042	<	* Callback from ForkJoinWorkerThread constructor to
2043	<	* determine its poolIndex and record in workers array.
2044	<	*
2045	<	* @param w the worker
2046	<	* @return the worker's pool index
2047	<	*/
2048	<	final int registerWorker(ForkJoinWorkerThread w) {
2049	<	/*
2050	<	* In the typical case, a new worker acquires the lock, uses
2051	<	* next available index and returns quickly.  Since we should
2052	<	* not block callers (ultimately from signalWork or
2053	<	* tryPreBlock) waiting for the lock needed to do this, we
2054	<	* instead help release other workers while waiting for the
1109	<	* lock.
1110	<	*/
1111	<	for (int g;;) {
1112	<	ForkJoinWorkerThread[] ws;
1113	<	if (((g = scanGuard) & SG_UNIT) == 0 &&
1114	<	UNSAFE.compareAndSwapInt(this, scanGuardOffset,
1115	<	g, g | SG_UNIT)) {
1116	<	int k = nextWorkerIndex;
1117	<	try {
1118	<	if ((ws = workers) != null) { // ignore on shutdown
1119	<	int n = ws.length;
1120	<	if (k < 0 || k >= n || ws[k] != null) {
1121	<	for (k = 0; k < n && ws[k] != null; ++k)
1122	<	;
1123	<	if (k == n)
1124	<	ws = workers = Arrays.copyOf(ws, n << 1);
1125	<	}
1126	<	ws[k] = w;
1127	<	nextWorkerIndex = k + 1;
1128	<	int m = g & SMASK;
1129	<	g = k >= m? ((m << 1) + 1) & SMASK : g + (SG_UNIT<<1);
1130	<	}
1131	<	} finally {
1132	<	scanGuard = g;
1133	<	}
1134	<	return k;
1135	<	}
1136	<	else if ((ws = workers) != null) { // help release others
1137	<	for (ForkJoinWorkerThread u : ws) {
1138	<	if (u != null && u.queueBase != u.queueTop) {
1139	<	if (tryReleaseWaiter())
1140	<	break;
1141	<	}
1142	<	}
1143	<	}
2042	>	* Gets and removes a local or stolen task for the given worker.
2043	>	*
2044	>	* @return a task, if available
2045	>	*/
2046	>	final ForkJoinTask<?> nextTaskFor(WorkQueue w) {
2047	>	for (ForkJoinTask<?> t;;) {
2048	>	WorkQueue q; int b;
2049	>	if ((t = w.nextLocalTask()) != null)
2050	>	return t;
2051	>	if ((q = findNonEmptyStealQueue(w)) == null)
2052	>	return null;
2053	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2054	>	return t;
2055		}
2056		}
2057
2058		/**
2059	<	* Final callback from terminating worker.  Removes record of
2060	<	* worker from array, and adjusts counts. If pool is shutting
2061	<	* down, tries to complete termination.
1151	<	*
1152	<	* @param w the worker
2059	>	* Returns the approximate (non-atomic) number of idle threads per
2060	>	* active thread to offset steal queue size for method
2061	>	* ForkJoinTask.getSurplusQueuedTaskCount().
2062		*/
2063	<	final void deregisterWorker(ForkJoinWorkerThread w, Throwable ex) {
2064	<	int idx = w.poolIndex;
2065	<	int sc = w.stealCount;
2066	<	int steps = 0;
2067	<	// Remove from array, adjust worker counts and collect steal count.
2068	<	// We can intermix failed removes or adjusts with steal updates
2069	<	do {
2070	<	long s, c;
2071	<	int g;
1163	<	if (steps == 0 && ((g = scanGuard) & SG_UNIT) == 0 &&
1164	<	UNSAFE.compareAndSwapInt(this, scanGuardOffset,
1165	<	g, g |= SG_UNIT)) {
1166	<	ForkJoinWorkerThread[] ws = workers;
1167	<	if (ws != null && idx >= 0 &&
1168	<	idx < ws.length && ws[idx] == w)
1169	<	ws[idx] = null;    // verify
1170	<	nextWorkerIndex = idx;
1171	<	scanGuard = g + SG_UNIT;
1172	<	steps = 1;
1173	<	}
1174	<	if (steps == 1 &&
1175	<	UNSAFE.compareAndSwapLong(this, ctlOffset, c = ctl,
1176	<	(((c - AC_UNIT) & AC_MASK) |
1177	<	((c - TC_UNIT) & TC_MASK) |
1178	<	(c & ~(AC_MASK|TC_MASK)))))
1179	<	steps = 2;
1180	<	if (sc != 0 &&
1181	<	UNSAFE.compareAndSwapLong(this, stealCountOffset,
1182	<	s = stealCount, s + sc))
1183	<	sc = 0;
1184	<	} while (steps != 2 || sc != 0);
1185	<	if (!tryTerminate(false)) {
1186	<	if (ex != null)   // possibly replace if died abnormally
1187	<	signalWork();
1188	<	else
1189	<	tryReleaseWaiter();
1190	<	}
2063	>	final int idlePerActive() {
2064	>	// Approximate at powers of two for small values, saturate past 4
2065	>	int p = parallelism;
2066	>	int a = p + (int)(ctl >> AC_SHIFT);
2067	>	return (a > (p >>>= 1) ? 0 :
2068	>	a > (p >>>= 1) ? 1 :
2069	>	a > (p >>>= 1) ? 2 :
2070	>	a > (p >>>= 1) ? 4 :
2071	>	8);
2072		}
2073
1193	–	// Shutdown and termination
1194	–
2074		/**
2075	<	* Possibly initiates and/or completes termination.
2075	>	* Returns approximate submission queue length for the given caller
2076	>	*/
2077	>	static int getEstimatedSubmitterQueueLength() {
2078	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
2079	>	int k = submitters.get().seed & SQMASK;
2080	>	return ((p = commonPool) != null &&
2081	>	p.runState >= 0 &&
2082	>	(ws = p.workQueues) != null &&
2083	>	ws.length > (k &= p.submitMask) &&
2084	>	(q = ws[k]) != null) ?
2085	>	q.queueSize() : 0;
2086	>	}
2087	>
2088	>	//  Termination
2089	>
2090	>	/**
2091	>	* Possibly initiates and/or completes termination.  The caller
2092	>	* triggering termination runs three passes through workQueues:
2093	>	* (0) Setting termination status, followed by wakeups of queued
2094	>	* workers; (1) cancelling all tasks; (2) interrupting lagging
2095	>	* threads (likely in external tasks, but possibly also blocked in
2096	>	* joins).  Each pass repeats previous steps because of potential
2097	>	* lagging thread creation.
2098		*
2099		* @param now if true, unconditionally terminate, else only
2100	<	* if shutdown and empty queue and no active workers
2100	>	* if no work and no active workers
2101	>	* @param enable if true, enable shutdown when next possible
2102		* @return true if now terminating or terminated
2103		*/
2104	<	private boolean tryTerminate(boolean now) {
2105	<	long c;
2106	<	while (((c = ctl) & STOP_BIT) == 0) {
2107	<	if (!now) {
2108	<	if ((int)(c >> AC_SHIFT) != -parallelism)
2104	>	private boolean tryTerminate(boolean now, boolean enable) {
2105	>	Mutex lock = this.lock;
2106	>	for (long c;;) {
2107	>	if (((c = ctl) & STOP_BIT) != 0) {      // already terminating
2108	>	if ((short)(c >>> TC_SHIFT) == -parallelism) {
2109	>	lock.lock();                    // don't need try/finally
2110	>	termination.signalAll();        // signal when 0 workers
2111	>	lock.unlock();
2112	>	}
2113	>	return true;
2114	>	}
2115	>	if (runState >= 0) {                    // not yet enabled
2116	>	if (!enable)
2117		return false;
2118	<	if (!shutdown || blockedCount != 0 || quiescerCount != 0 ||
2119	<	queueTop - queueBase > 0) {
2120	<	if (ctl == c) // staleness check
2121	<	return false;
2122	<	continue;
2123	<	}
2124	<	}
2125	<	if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, c | STOP_BIT))
2126	<	startTerminating();
2127	<	}
2128	<	if ((short)(c >>> TC_SHIFT) == -parallelism) {
2129	<	submissionLock.lock();
2130	<	termination.signalAll();
2131	<	submissionLock.unlock();
2132	<	}
2133	<	return true;
2134	<	}
2135	<
2136	<	/**
2137	<	* Runs up to three passes through workers: (0) Setting
2138	<	* termination status for each worker, followed by wakeups up
2139	<	* queued workers (1) helping cancel tasks (2) interrupting
2140	<	* lagging threads (likely in external tasks, but possibly also
2141	<	* blocked in joins).  Each pass repeats previous steps because of
2142	<	* potential lagging thread creation.
2143	<	*/
2144	<	private void startTerminating() {
2145	<	cancelSubmissions();
2146	<	for (int pass = 0; pass < 3; ++pass) {
2147	<	ForkJoinWorkerThread[] ws = workers;
1238	<	if (ws != null) {
1239	<	for (ForkJoinWorkerThread w : ws) {
1240	<	if (w != null) {
1241	<	w.terminate = true;
1242	<	if (pass > 0) {
1243	<	w.cancelTasks();
1244	<	if (pass > 1 && !w.isInterrupted()) {
1245	<	try {
1246	<	w.interrupt();
1247	<	} catch (SecurityException ignore) {
2118	>	lock.lock();
2119	>	runState |= SHUTDOWN;
2120	>	lock.unlock();
2121	>	}
2122	>	if (!now) {                             // check if idle & no tasks
2123	>	if ((int)(c >> AC_SHIFT) != -parallelism ||
2124	>	hasQueuedSubmissions())
2125	>	return false;
2126	>	// Check for unqueued inactive workers. One pass suffices.
2127	>	WorkQueue[] ws = workQueues; WorkQueue w;
2128	>	if (ws != null) {
2129	>	for (int i = 1; i < ws.length; i += 2) {
2130	>	if ((w = ws[i]) != null && w.eventCount >= 0)
2131	>	return false;
2132	>	}
2133	>	}
2134	>	}
2135	>	if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT)) {
2136	>	for (int pass = 0; pass < 3; ++pass) {
2137	>	WorkQueue[] ws = workQueues;
2138	>	if (ws != null) {
2139	>	WorkQueue w;
2140	>	int n = ws.length;
2141	>	for (int i = 0; i < n; ++i) {
2142	>	if ((w = ws[i]) != null) {
2143	>	w.runState = -1;
2144	>	if (pass > 0) {
2145	>	w.cancelAll();
2146	>	if (pass > 1)
2147	>	w.interruptOwner();
2148		}
2149		}
2150		}
2151	+	// Wake up workers parked on event queue
2152	+	int i, e; long cc; Thread p;
2153	+	while ((e = (int)(cc = ctl) & E_MASK) != 0 &&
2154	+	(i = e & SMASK) < n &&
2155	+	(w = ws[i]) != null) {
2156	+	long nc = ((long)(w.nextWait & E_MASK) |
2157	+	((cc + AC_UNIT) & AC_MASK) |
2158	+	(cc & (TC_MASK|STOP_BIT)));
2159	+	if (w.eventCount == (e | INT_SIGN) &&
2160	+	U.compareAndSwapLong(this, CTL, cc, nc)) {
2161	+	w.eventCount = (e + E_SEQ) & E_MASK;
2162	+	w.runState = -1;
2163	+	if ((p = w.parker) != null)
2164	+	U.unpark(p);
2165	+	}
2166	+	}
2167		}
2168		}
1253	–	terminateWaiters();
1254	–	}
1255	–	}
1256	–	}
1257	–
1258	–	/**
1259	–	* Polls and cancels all submissions. Called only during termination.
1260	–	*/
1261	–	private void cancelSubmissions() {
1262	–	while (queueBase != queueTop) {
1263	–	ForkJoinTask<?> task = pollSubmission();
1264	–	if (task != null) {
1265	–	try {
1266	–	task.cancel(false);
1267	–	} catch (Throwable ignore) {
1268	–	}
2169		}
2170		}
2171		}
2172
1273	–	/**
1274	–	* Tries to set the termination status of waiting workers, and
1275	–	* then wake them up (after which they will terminate).
1276	–	*/
1277	–	private void terminateWaiters() {
1278	–	ForkJoinWorkerThread[] ws = workers;
1279	–	if (ws != null) {
1280	–	ForkJoinWorkerThread w; long c; int i, e;
1281	–	int n = ws.length;
1282	–	while ((i = ~(e = (int)(c = ctl)) & SMASK) < n &&
1283	–	(w = ws[i]) != null && w.eventCount == (e & E_MASK)) {
1284	–	if (UNSAFE.compareAndSwapLong(this, ctlOffset, c,
1285	–	(long)(w.nextWait & E_MASK) |
1286	–	((c + AC_UNIT) & AC_MASK) |
1287	–	(c & (TC_MASK|STOP_BIT)))) {
1288	–	w.terminate = true;
1289	–	w.eventCount = e + EC_UNIT;
1290	–	if (w.parked)
1291	–	UNSAFE.unpark(w);
1292	–	}
1293	–	}
1294	–	}
1295	–	}
1296	–
1297	–	// misc ForkJoinWorkerThread support
1298	–
1299	–	/**
1300	–	* Increment or decrement quiescerCount. Needed only to prevent
1301	–	* triggering shutdown if a worker is transiently inactive while
1302	–	* checking quiescence.
1303	–	*
1304	–	* @param delta 1 for increment, -1 for decrement
1305	–	*/
1306	–	final void addQuiescerCount(int delta) {
1307	–	int c;
1308	–	do {} while(!UNSAFE.compareAndSwapInt(this, quiescerCountOffset,
1309	–	c = quiescerCount, c + delta));
1310	–	}
1311	–
1312	–	/**
1313	–	* Directly increment or decrement active count without
1314	–	* queuing. This method is used to transiently assert inactivation
1315	–	* while checking quiescence.
1316	–	*
1317	–	* @param delta 1 for increment, -1 for decrement
1318	–	*/
1319	–	final void addActiveCount(int delta) {
1320	–	long d = delta < 0 ? -AC_UNIT : AC_UNIT;
1321	–	long c;
1322	–	do {} while (!UNSAFE.compareAndSwapLong(this, ctlOffset, c = ctl,
1323	–	((c + d) & AC_MASK) |
1324	–	(c & ~AC_MASK)));
1325	–	}
1326	–
1327	–	/**
1328	–	* Returns the approximate (non-atomic) number of idle threads per
1329	–	* active thread.
1330	–	*/
1331	–	final int idlePerActive() {
1332	–	// Approximate at powers of two for small values, saturate past 4
1333	–	int p = parallelism;
1334	–	int a = p + (int)(ctl >> AC_SHIFT);
1335	–	return (a > (p >>>= 1) ? 0 :
1336	–	a > (p >>>= 1) ? 1 :
1337	–	a > (p >>>= 1) ? 2 :
1338	–	a > (p >>>= 1) ? 4 :
1339	–	8);
1340	–	}
1341	–
2173		// Exported methods
2174
2175		// Constructors
#	Line 1408 | Line 2239 | public class ForkJoinPool extends Abstra
2239		checkPermission();
2240		if (factory == null)
2241		throw new NullPointerException();
2242	<	if (parallelism <= 0 || parallelism > MAX_ID)
2242	>	if (parallelism <= 0 || parallelism > MAX_CAP)
2243		throw new IllegalArgumentException();
2244		this.parallelism = parallelism;
2245		this.factory = factory;
2246		this.ueh = handler;
2247	<	this.locallyFifo = asyncMode;
2247	>	this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE;
2248		long np = (long)(-parallelism); // offset ctl counts
2249		this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
2250	<	this.submissionQueue = new ForkJoinTask<?>[INITIAL_QUEUE_CAPACITY];
2251	<	// initialize workers array with room for 2*parallelism if possible
2252	<	int n = parallelism << 1;
2253	<	if (n >= MAX_ID)
2254	<	n = MAX_ID;
2255	<	else { // See Hackers Delight, sec 3.2, where n < (1 << 16)
2256	<	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8;
2257	<	}
2258	<	workers = new ForkJoinWorkerThread[n + 1];
2259	<	this.submissionLock = new ReentrantLock();
1429	<	this.termination = submissionLock.newCondition();
2250	>	// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2.
2251	>	int n = parallelism - 1;
2252	>	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
2253	>	int size = (n + 1) << 1;        // #slots = 2*#workers
2254	>	this.submitMask = size - 1;     // room for max # of submit queues
2255	>	this.workQueues = new WorkQueue[size];
2256	>	this.termination = (this.lock = new Mutex()).newCondition();
2257	>	this.stealCount = new AtomicLong();
2258	>	this.nextWorkerNumber = new AtomicInteger();
2259	>	int pn = poolNumberGenerator.incrementAndGet();
2260		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2261	<	sb.append(poolNumberGenerator.incrementAndGet());
2261	>	sb.append(Integer.toString(pn));
2262		sb.append("-worker-");
2263		this.workerNamePrefix = sb.toString();
2264	+	lock.lock();
2265	+	this.runState = 1;              // set init flag
2266	+	lock.unlock();
2267	+	}
2268	+
2269	+	/**
2270	+	* Returns the common pool instance
2271	+	*
2272	+	* @return the common pool instance
2273	+	*/
2274	+	public static ForkJoinPool commonPool() {
2275	+	ForkJoinPool p;
2276	+	return (p = commonPool) != null? p : ensureCommonPool();
2277	+	}
2278	+
2279	+	private static ForkJoinPool ensureCommonPool() {
2280	+	ForkJoinPool p;
2281	+	if ((p = commonPool) == null) {
2282	+	final Mutex lock = initializationLock;
2283	+	lock.lock();
2284	+	try {
2285	+	if ((p = commonPool) == null) {
2286	+	p = commonPool = new ForkJoinPool(commonPoolParallelism,
2287	+	commonPoolFactory,
2288	+	commonPoolUEH, false);
2289	+	// use a more informative name string for workers
2290	+	p.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2291	+	}
2292	+	} finally {
2293	+	lock.unlock();
2294	+	}
2295	+	}
2296	+	return p;
2297		}
2298
2299		// Execution methods
#	Line 1452 | Line 2315 | public class ForkJoinPool extends Abstra
2315		*         scheduled for execution
2316		*/
2317		public <T> T invoke(ForkJoinTask<T> task) {
1455	–	Thread t = Thread.currentThread();
2318		if (task == null)
2319		throw new NullPointerException();
2320	<	if (shutdown)
2321	<	throw new RejectedExecutionException();
1460	<	if ((t instanceof ForkJoinWorkerThread) &&
1461	<	((ForkJoinWorkerThread)t).pool == this)
1462	<	return task.invoke();  // bypass submit if in same pool
1463	<	else {
1464	<	addSubmission(task);
1465	<	return task.join();
1466	<	}
1467	<	}
1468	<
1469	<	/**
1470	<	* Unless terminating, forks task if within an ongoing FJ
1471	<	* computation in the current pool, else submits as external task.
1472	<	*/
1473	<	private <T> void forkOrSubmit(ForkJoinTask<T> task) {
1474	<	ForkJoinWorkerThread w;
1475	<	Thread t = Thread.currentThread();
1476	<	if (shutdown)
1477	<	throw new RejectedExecutionException();
1478	<	if ((t instanceof ForkJoinWorkerThread) &&
1479	<	(w = (ForkJoinWorkerThread)t).pool == this)
1480	<	w.pushTask(task);
1481	<	else
1482	<	addSubmission(task);
2320	>	doSubmit(task);
2321	>	return task.join();
2322		}
2323
2324		/**
#	Line 1493 | Line 2332 | public class ForkJoinPool extends Abstra
2332		public void execute(ForkJoinTask<?> task) {
2333		if (task == null)
2334		throw new NullPointerException();
2335	<	forkOrSubmit(task);
2335	>	doSubmit(task);
2336		}
2337
2338		// AbstractExecutorService methods
#	Line 1510 | Line 2349 | public class ForkJoinPool extends Abstra
2349		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2350		job = (ForkJoinTask<?>) task;
2351		else
2352	<	job = ForkJoinTask.adapt(task, null);
2353	<	forkOrSubmit(job);
2352	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2353	>	doSubmit(job);
2354		}
2355
2356		/**
#	Line 1526 | Line 2365 | public class ForkJoinPool extends Abstra
2365		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2366		if (task == null)
2367		throw new NullPointerException();
2368	<	forkOrSubmit(task);
2368	>	doSubmit(task);
2369		return task;
2370		}
2371
#	Line 1536 | Line 2375 | public class ForkJoinPool extends Abstra
2375		*         scheduled for execution
2376		*/
2377		public <T> ForkJoinTask<T> submit(Callable<T> task) {
2378	<	if (task == null)
2379	<	throw new NullPointerException();
1541	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1542	<	forkOrSubmit(job);
2378	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2379	>	doSubmit(job);
2380		return job;
2381		}
2382
#	Line 1549 | Line 2386 | public class ForkJoinPool extends Abstra
2386		*         scheduled for execution
2387		*/
2388		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2389	<	if (task == null)
2390	<	throw new NullPointerException();
1554	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1555	<	forkOrSubmit(job);
2389	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2390	>	doSubmit(job);
2391		return job;
2392		}
2393
#	Line 1568 | Line 2403 | public class ForkJoinPool extends Abstra
2403		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2404		job = (ForkJoinTask<?>) task;
2405		else
2406	<	job = ForkJoinTask.adapt(task, null);
2407	<	forkOrSubmit(job);
2406	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2407	>	doSubmit(job);
2408		return job;
2409		}
2410
#	Line 1578 | Line 2413 | public class ForkJoinPool extends Abstra
2413		* @throws RejectedExecutionException {@inheritDoc}
2414		*/
2415		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
2416	<	ArrayList<ForkJoinTask<T>> forkJoinTasks =
2417	<	new ArrayList<ForkJoinTask<T>>(tasks.size());
2418	<	for (Callable<T> task : tasks)
2419	<	forkJoinTasks.add(ForkJoinTask.adapt(task));
2420	<	invoke(new InvokeAll<T>(forkJoinTasks));
2421	<
2416	>	// In previous versions of this class, this method constructed
2417	>	// a task to run ForkJoinTask.invokeAll, but now external
2418	>	// invocation of multiple tasks is at least as efficient.
2419	>	List<ForkJoinTask<T>> fs = new ArrayList<ForkJoinTask<T>>(tasks.size());
2420	>	// Workaround needed because method wasn't declared with
2421	>	// wildcards in return type but should have been.
2422		@SuppressWarnings({"unchecked", "rawtypes"})
2423	<	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1589	<	return futures;
1590	<	}
2423	>	List<Future<T>> futures = (List<Future<T>>) (List) fs;
2424
2425	<	static final class InvokeAll<T> extends RecursiveAction {
2426	<	final ArrayList<ForkJoinTask<T>> tasks;
2427	<	InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
2428	<	public void compute() {
2429	<	try { invokeAll(tasks); }
2430	<	catch (Exception ignore) {}
2425	>	boolean done = false;
2426	>	try {
2427	>	for (Callable<T> t : tasks) {
2428	>	ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2429	>	doSubmit(f);
2430	>	fs.add(f);
2431	>	}
2432	>	for (ForkJoinTask<T> f : fs)
2433	>	f.quietlyJoin();
2434	>	done = true;
2435	>	return futures;
2436	>	} finally {
2437	>	if (!done)
2438	>	for (ForkJoinTask<T> f : fs)
2439	>	f.cancel(false);
2440		}
1599	–	private static final long serialVersionUID = -7914297376763021607L;
2441		}
2442
2443		/**
#	Line 1628 | Line 2469 | public class ForkJoinPool extends Abstra
2469		}
2470
2471		/**
2472	+	* Returns the targeted parallelism level of the common pool.
2473	+	*
2474	+	* @return the targeted parallelism level of the common pool
2475	+	*/
2476	+	public static int getCommonPoolParallelism() {
2477	+	return commonPoolParallelism;
2478	+	}
2479	+
2480	+	/**
2481		* Returns the number of worker threads that have started but not
2482		* yet terminated.  The result returned by this method may differ
2483		* from {@link #getParallelism} when threads are created to
#	Line 1646 | Line 2496 | public class ForkJoinPool extends Abstra
2496		* @return {@code true} if this pool uses async mode
2497		*/
2498		public boolean getAsyncMode() {
2499	<	return locallyFifo;
2499	>	return localMode != 0;
2500		}
2501
2502		/**
#	Line 1658 | Line 2508 | public class ForkJoinPool extends Abstra
2508		* @return the number of worker threads
2509		*/
2510		public int getRunningThreadCount() {
2511	<	int r = parallelism + (int)(ctl >> AC_SHIFT);
2512	<	return r <= 0? 0 : r; // suppress momentarily negative values
2511	>	int rc = 0;
2512	>	WorkQueue[] ws; WorkQueue w;
2513	>	if ((ws = workQueues) != null) {
2514	>	for (int i = 1; i < ws.length; i += 2) {
2515	>	if ((w = ws[i]) != null && w.isApparentlyUnblocked())
2516	>	++rc;
2517	>	}
2518	>	}
2519	>	return rc;
2520		}
2521
2522		/**
#	Line 1670 | Line 2527 | public class ForkJoinPool extends Abstra
2527		* @return the number of active threads
2528		*/
2529		public int getActiveThreadCount() {
2530	<	int r = parallelism + (int)(ctl >> AC_SHIFT) + blockedCount;
2531	<	return r <= 0? 0 : r; // suppress momentarily negative values
2530	>	int r = parallelism + (int)(ctl >> AC_SHIFT);
2531	>	return (r <= 0) ? 0 : r; // suppress momentarily negative values
2532		}
2533
2534		/**
#	Line 1686 | Line 2543 | public class ForkJoinPool extends Abstra
2543		* @return {@code true} if all threads are currently idle
2544		*/
2545		public boolean isQuiescent() {
2546	<	return parallelism + (int)(ctl >> AC_SHIFT) + blockedCount == 0;
2546	>	return (int)(ctl >> AC_SHIFT) + parallelism == 0;
2547		}
2548
2549		/**
#	Line 1701 | Line 2558 | public class ForkJoinPool extends Abstra
2558		* @return the number of steals
2559		*/
2560		public long getStealCount() {
2561	<	return stealCount;
2561	>	long count = stealCount.get();
2562	>	WorkQueue[] ws; WorkQueue w;
2563	>	if ((ws = workQueues) != null) {
2564	>	for (int i = 1; i < ws.length; i += 2) {
2565	>	if ((w = ws[i]) != null)
2566	>	count += w.totalSteals;
2567	>	}
2568	>	}
2569	>	return count;
2570		}
2571
2572		/**
#	Line 1716 | Line 2581 | public class ForkJoinPool extends Abstra
2581		*/
2582		public long getQueuedTaskCount() {
2583		long count = 0;
2584	<	ForkJoinWorkerThread[] ws;
2585	<	if ((short)(ctl >>> TC_SHIFT) > -parallelism &&
2586	<	(ws = workers) != null) {
2587	<	for (ForkJoinWorkerThread w : ws)
2588	<	if (w != null)
2589	<	count -= w.queueBase - w.queueTop; // must read base first
2584	>	WorkQueue[] ws; WorkQueue w;
2585	>	if ((ws = workQueues) != null) {
2586	>	for (int i = 1; i < ws.length; i += 2) {
2587	>	if ((w = ws[i]) != null)
2588	>	count += w.queueSize();
2589	>	}
2590		}
2591		return count;
2592		}
2593
2594		/**
2595		* Returns an estimate of the number of tasks submitted to this
2596	<	* pool that have not yet begun executing.  This meThod may take
2596	>	* pool that have not yet begun executing.  This method may take
2597		* time proportional to the number of submissions.
2598		*
2599		* @return the number of queued submissions
2600		*/
2601		public int getQueuedSubmissionCount() {
2602	<	return -queueBase + queueTop;
2602	>	int count = 0;
2603	>	WorkQueue[] ws; WorkQueue w;
2604	>	if ((ws = workQueues) != null) {
2605	>	for (int i = 0; i < ws.length; i += 2) {
2606	>	if ((w = ws[i]) != null)
2607	>	count += w.queueSize();
2608	>	}
2609	>	}
2610	>	return count;
2611		}
2612
2613		/**
#	Line 1744 | Line 2617 | public class ForkJoinPool extends Abstra
2617		* @return {@code true} if there are any queued submissions
2618		*/
2619		public boolean hasQueuedSubmissions() {
2620	<	return queueBase != queueTop;
2620	>	WorkQueue[] ws; WorkQueue w;
2621	>	if ((ws = workQueues) != null) {
2622	>	for (int i = 0; i < ws.length; i += 2) {
2623	>	if ((w = ws[i]) != null && !w.isEmpty())
2624	>	return true;
2625	>	}
2626	>	}
2627	>	return false;
2628		}
2629
2630		/**
#	Line 1755 | Line 2635 | public class ForkJoinPool extends Abstra
2635		* @return the next submission, or {@code null} if none
2636		*/
2637		protected ForkJoinTask<?> pollSubmission() {
2638	<	ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i;
2639	<	while ((b = queueBase) != queueTop &&
2640	<	(q = submissionQueue) != null &&
2641	<	(i = (q.length - 1) & b) >= 0) {
2642	<	long u = (i << ASHIFT) + ABASE;
1763	<	if ((t = q[i]) != null &&
1764	<	queueBase == b &&
1765	<	UNSAFE.compareAndSwapObject(q, u, t, null)) {
1766	<	queueBase = b + 1;
1767	<	return t;
2638	>	WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2639	>	if ((ws = workQueues) != null) {
2640	>	for (int i = 0; i < ws.length; i += 2) {
2641	>	if ((w = ws[i]) != null && (t = w.poll()) != null)
2642	>	return t;
2643		}
2644		}
2645		return null;
#	Line 1789 | Line 2664 | public class ForkJoinPool extends Abstra
2664		*/
2665		protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
2666		int count = 0;
2667	<	while (queueBase != queueTop) {
2668	<	ForkJoinTask<?> t = pollSubmission();
2669	<	if (t != null) {
2670	<	c.add(t);
2671	<	++count;
2667	>	WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2668	>	if ((ws = workQueues) != null) {
2669	>	for (int i = 0; i < ws.length; ++i) {
2670	>	if ((w = ws[i]) != null) {
2671	>	while ((t = w.poll()) != null) {
2672	>	c.add(t);
2673	>	++count;
2674	>	}
2675	>	}
2676		}
2677		}
1799	–	ForkJoinWorkerThread[] ws;
1800	–	if ((short)(ctl >>> TC_SHIFT) > -parallelism &&
1801	–	(ws = workers) != null) {
1802	–	for (ForkJoinWorkerThread w : ws)
1803	–	if (w != null)
1804	–	count += w.drainTasksTo(c);
1805	–	}
2678		return count;
2679		}
2680
#	Line 1814 | Line 2686 | public class ForkJoinPool extends Abstra
2686		* @return a string identifying this pool, as well as its state
2687		*/
2688		public String toString() {
2689	<	long st = getStealCount();
2690	<	long qt = getQueuedTaskCount();
2691	<	long qs = getQueuedSubmissionCount();
1820	<	int pc = parallelism;
2689	>	// Use a single pass through workQueues to collect counts
2690	>	long qt = 0L, qs = 0L; int rc = 0;
2691	>	long st = stealCount.get();
2692		long c = ctl;
2693	+	WorkQueue[] ws; WorkQueue w;
2694	+	if ((ws = workQueues) != null) {
2695	+	for (int i = 0; i < ws.length; ++i) {
2696	+	if ((w = ws[i]) != null) {
2697	+	int size = w.queueSize();
2698	+	if ((i & 1) == 0)
2699	+	qs += size;
2700	+	else {
2701	+	qt += size;
2702	+	st += w.totalSteals;
2703	+	if (w.isApparentlyUnblocked())
2704	+	++rc;
2705	+	}
2706	+	}
2707	+	}
2708	+	}
2709	+	int pc = parallelism;
2710		int tc = pc + (short)(c >>> TC_SHIFT);
2711	<	int rc = pc + (int)(c >> AC_SHIFT);
2712	<	if (rc < 0) // ignore transient negative
2713	<	rc = 0;
1826	<	int ac = rc + blockedCount;
2711	>	int ac = pc + (int)(c >> AC_SHIFT);
2712	>	if (ac < 0) // ignore transient negative
2713	>	ac = 0;
2714		String level;
2715		if ((c & STOP_BIT) != 0)
2716	<	level = (tc == 0)? "Terminated" : "Terminating";
2716	>	level = (tc == 0) ? "Terminated" : "Terminating";
2717		else
2718	<	level = shutdown? "Shutting down" : "Running";
2718	>	level = runState < 0 ? "Shutting down" : "Running";
2719		return super.toString() +
2720		"[" + level +
2721		", parallelism = " + pc +
#	Line 1842 | Line 2729 | public class ForkJoinPool extends Abstra
2729		}
2730
2731		/**
2732	<	* Initiates an orderly shutdown in which previously submitted
2733	<	* tasks are executed, but no new tasks will be accepted.
2734	<	* Invocation has no additional effect if already shut down.
2735	<	* Tasks that are in the process of being submitted concurrently
2736	<	* during the course of this method may or may not be rejected.
2732	>	* Possibly initiates an orderly shutdown in which previously
2733	>	* submitted tasks are executed, but no new tasks will be
2734	>	* accepted. Invocation has no effect on execution state if this
2735	>	* is the {@link #commonPool}, and no additional effect if
2736	>	* already shut down.  Tasks that are in the process of being
2737	>	* submitted concurrently during the course of this method may or
2738	>	* may not be rejected.
2739		*
2740		* @throws SecurityException if a security manager exists and
2741		*         the caller is not permitted to modify threads
#	Line 1855 | Line 2744 | public class ForkJoinPool extends Abstra
2744		*/
2745		public void shutdown() {
2746		checkPermission();
2747	<	shutdown = true;
2748	<	tryTerminate(false);
2747	>	if (this != commonPool)
2748	>	tryTerminate(false, true);
2749		}
2750
2751		/**
2752	<	* Attempts to cancel and/or stop all tasks, and reject all
2753	<	* subsequently submitted tasks.  Tasks that are in the process of
2754	<	* being submitted or executed concurrently during the course of
2755	<	* this method may or may not be rejected. This method cancels
2756	<	* both existing and unexecuted tasks, in order to permit
2757	<	* termination in the presence of task dependencies. So the method
2758	<	* always returns an empty list (unlike the case for some other
2759	<	* Executors).
2752	>	* Possibly attempts to cancel and/or stop all tasks, and reject
2753	>	* all subsequently submitted tasks.  Invocation has no effect on
2754	>	* execution state if this is the {@link #commonPool}, and no
2755	>	* additional effect if already shut down. Otherwise, tasks that
2756	>	* are in the process of being submitted or executed concurrently
2757	>	* during the course of this method may or may not be
2758	>	* rejected. This method cancels both existing and unexecuted
2759	>	* tasks, in order to permit termination in the presence of task
2760	>	* dependencies. So the method always returns an empty list
2761	>	* (unlike the case for some other Executors).
2762		*
2763		* @return an empty list
2764		* @throws SecurityException if a security manager exists and
#	Line 1877 | Line 2768 | public class ForkJoinPool extends Abstra
2768		*/
2769		public List<Runnable> shutdownNow() {
2770		checkPermission();
2771	<	shutdown = true;
2772	<	tryTerminate(true);
2771	>	if (this != commonPool)
2772	>	tryTerminate(true, true);
2773		return Collections.emptyList();
2774		}
2775
#	Line 1913 | Line 2804 | public class ForkJoinPool extends Abstra
2804		}
2805
2806		/**
1916	–	* Returns true if terminating or terminated. Used by ForkJoinWorkerThread.
1917	–	*/
1918	–	final boolean isAtLeastTerminating() {
1919	–	return (ctl & STOP_BIT) != 0L;
1920	–	}
1921	–
1922	–	/**
2807		* Returns {@code true} if this pool has been shut down.
2808		*
2809		* @return {@code true} if this pool has been shut down
2810		*/
2811		public boolean isShutdown() {
2812	<	return shutdown;
2812	>	return runState < 0;
2813		}
2814
2815		/**
#	Line 1942 | Line 2826 | public class ForkJoinPool extends Abstra
2826		public boolean awaitTermination(long timeout, TimeUnit unit)
2827		throws InterruptedException {
2828		long nanos = unit.toNanos(timeout);
2829	<	final ReentrantLock lock = this.submissionLock;
2829	>	final Mutex lock = this.lock;
2830		lock.lock();
2831		try {
2832		for (;;) {
#	Line 1965 | Line 2849 | public class ForkJoinPool extends Abstra
2849		* {@code isReleasable} must return {@code true} if blocking is
2850		* not necessary. Method {@code block} blocks the current thread
2851		* if necessary (perhaps internally invoking {@code isReleasable}
2852	<	* before actually blocking). The unusual methods in this API
2853	<	* accommodate synchronizers that may, but don't usually, block
2854	<	* for long periods. Similarly, they allow more efficient internal
2855	<	* handling of cases in which additional workers may be, but
2856	<	* usually are not, needed to ensure sufficient parallelism.
2857	<	* Toward this end, implementations of method {@code isReleasable}
2858	<	* must be amenable to repeated invocation.
2852	>	* before actually blocking). These actions are performed by any
2853	>	* thread invoking {@link ForkJoinPool#managedBlock}.  The
2854	>	* unusual methods in this API accommodate synchronizers that may,
2855	>	* but don't usually, block for long periods. Similarly, they
2856	>	* allow more efficient internal handling of cases in which
2857	>	* additional workers may be, but usually are not, needed to
2858	>	* ensure sufficient parallelism.  Toward this end,
2859	>	* implementations of method {@code isReleasable} must be amenable
2860	>	* to repeated invocation.
2861		*
2862		* <p>For example, here is a ManagedBlocker based on a
2863		* ReentrantLock:
#	Line 2051 | Line 2937 | public class ForkJoinPool extends Abstra
2937		public static void managedBlock(ManagedBlocker blocker)
2938		throws InterruptedException {
2939		Thread t = Thread.currentThread();
2940	<	if (t instanceof ForkJoinWorkerThread) {
2941	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
2942	<	w.pool.awaitBlocker(blocker);
2943	<	}
2944	<	else {
2945	<	do {} while (!blocker.isReleasable() && !blocker.block());
2940	>	ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ?
2941	>	((ForkJoinWorkerThread)t).pool : null);
2942	>	while (!blocker.isReleasable()) {
2943	>	if (p == null || p.tryCompensate(null, blocker)) {
2944	>	try {
2945	>	do {} while (!blocker.isReleasable() && !blocker.block());
2946	>	} finally {
2947	>	if (p != null)
2948	>	p.incrementActiveCount();
2949	>	}
2950	>	break;
2951	>	}
2952		}
2953		}
2954
#	Line 2065 | Line 2957 | public class ForkJoinPool extends Abstra
2957		// implement RunnableFuture.
2958
2959		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
2960	<	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
2960	>	return new ForkJoinTask.AdaptedRunnable<T>(runnable, value);
2961		}
2962
2963		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
2964	<	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
2964	>	return new ForkJoinTask.AdaptedCallable<T>(callable);
2965		}
2966
2967		// Unsafe mechanics
2968	<	private static final sun.misc.Unsafe UNSAFE;
2969	<	private static final long ctlOffset;
2970	<	private static final long stealCountOffset;
2971	<	private static final long blockedCountOffset;
2080	<	private static final long quiescerCountOffset;
2081	<	private static final long scanGuardOffset;
2082	<	private static final long nextWorkerNumberOffset;
2083	<	private static final long ABASE;
2968	>	private static final sun.misc.Unsafe U;
2969	>	private static final long CTL;
2970	>	private static final long PARKBLOCKER;
2971	>	private static final int ABASE;
2972		private static final int ASHIFT;
2973
2974		static {
2975		poolNumberGenerator = new AtomicInteger();
2976	<	workerSeedGenerator = new Random();
2976	>	nextSubmitterSeed = new AtomicInteger(0x55555555);
2977		modifyThreadPermission = new RuntimePermission("modifyThread");
2978		defaultForkJoinWorkerThreadFactory =
2979		new DefaultForkJoinWorkerThreadFactory();
2980	+	submitters = new ThreadSubmitter();
2981	+	initializationLock = new Mutex();
2982		int s;
2983		try {
2984	<	UNSAFE = getUnsafe();
2985	<	Class k = ForkJoinPool.class;
2986	<	ctlOffset = UNSAFE.objectFieldOffset
2984	>	U = getUnsafe();
2985	>	Class<?> k = ForkJoinPool.class;
2986	>	Class<?> ak = ForkJoinTask[].class;
2987	>	CTL = U.objectFieldOffset
2988		(k.getDeclaredField("ctl"));
2989	<	stealCountOffset = UNSAFE.objectFieldOffset
2990	<	(k.getDeclaredField("stealCount"));
2991	<	blockedCountOffset = UNSAFE.objectFieldOffset
2992	<	(k.getDeclaredField("blockedCount"));
2993	<	quiescerCountOffset = UNSAFE.objectFieldOffset
2103	<	(k.getDeclaredField("quiescerCount"));
2104	<	scanGuardOffset = UNSAFE.objectFieldOffset
2105	<	(k.getDeclaredField("scanGuard"));
2106	<	nextWorkerNumberOffset = UNSAFE.objectFieldOffset
2107	<	(k.getDeclaredField("nextWorkerNumber"));
2108	<	Class a = ForkJoinTask[].class;
2109	<	ABASE = UNSAFE.arrayBaseOffset(a);
2110	<	s = UNSAFE.arrayIndexScale(a);
2989	>	Class<?> tk = Thread.class;
2990	>	PARKBLOCKER = U.objectFieldOffset
2991	>	(tk.getDeclaredField("parkBlocker"));
2992	>	ABASE = U.arrayBaseOffset(ak);
2993	>	s = U.arrayIndexScale(ak);
2994		} catch (Exception e) {
2995		throw new Error(e);
2996		}
2997		if ((s & (s-1)) != 0)
2998		throw new Error("data type scale not a power of two");
2999		ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3000	+
3001	+	// Establish configuration for default pool
3002	+	try {
3003	+	String pp = System.getProperty(propPrefix + "parallelism");
3004	+	String fp = System.getProperty(propPrefix + "threadFactory");
3005	+	String up = System.getProperty(propPrefix + "exceptionHandler");
3006	+	int par;
3007	+	if ((pp == null || (par = Integer.parseInt(pp)) <= 0))
3008	+	par = Runtime.getRuntime().availableProcessors();
3009	+	commonPoolParallelism = par;
3010	+	if (fp != null)
3011	+	commonPoolFactory = (ForkJoinWorkerThreadFactory)
3012	+	ClassLoader.getSystemClassLoader().loadClass(fp).newInstance();
3013	+	else
3014	+	commonPoolFactory = defaultForkJoinWorkerThreadFactory;
3015	+	if (up != null)
3016	+	commonPoolUEH = (Thread.UncaughtExceptionHandler)
3017	+	ClassLoader.getSystemClassLoader().loadClass(up).newInstance();
3018	+	else
3019	+	commonPoolUEH = null;
3020	+	} catch (Exception e) {
3021	+	throw new Error(e);
3022	+	}
3023		}
3024
3025		/**
#	Line 2143 | Line 3049 | public class ForkJoinPool extends Abstra
3049		}
3050		}
3051		}
3052	+
3053		}

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