[ViewVC] Diff of: jsr166/jsr166/src/jsr166y/ForkJoinPool.java

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.115 by jsr166, Thu Jan 26 19:10:27 2012 UTC vs.
Revision 1.164 by dl, Tue Dec 18 21:46:16 2012 UTC

#	Line 11 \| Line 11 \| import java.util.Arrays;
11		import java.util.Collection;
12		import java.util.Collections;
13		import java.util.List;
14	–	import java.util.Random;
14		import java.util.concurrent.AbstractExecutorService;
15		import java.util.concurrent.Callable;
16		import java.util.concurrent.ExecutorService;
#	Line 19 \| Line 18 \| import java.util.concurrent.Future;
18		import java.util.concurrent.RejectedExecutionException;
19		import java.util.concurrent.RunnableFuture;
20		import java.util.concurrent.TimeUnit;
22	–	import java.util.concurrent.atomic.AtomicInteger;
23	–	import java.util.concurrent.atomic.AtomicLong;
24	–	import java.util.concurrent.locks.ReentrantLock;
25	–	import java.util.concurrent.locks.Condition;
21
22		/**
23		* An {@link ExecutorService} for running {@link ForkJoinTask}s.
#	Line 42 \| Line 37 \| import java.util.concurrent.locks.Condit
37		* ForkJoinPool}s may also be appropriate for use with event-style
38		* tasks that are never joined.
39		*
40	<	* <p>A {@code ForkJoinPool} is constructed with a given target
41	<	* parallelism level; by default, equal to the number of available
42	<	* processors. The pool attempts to maintain enough active (or
43	<	* available) threads by dynamically adding, suspending, or resuming
44	<	* internal worker threads, even if some tasks are stalled waiting to
45	<	* join others. However, no such adjustments are guaranteed in the
46	<	* face of blocked IO or other unmanaged synchronization. The nested
47	<	* {@link ManagedBlocker} interface enables extension of the kinds of
40	>	* <p>A static {@link #commonPool()} is available and appropriate for
41	>	* most applications. The common pool is used by any ForkJoinTask that
42	>	* is not explicitly submitted to a specified pool. Using the common
43	>	* pool normally reduces resource usage (its threads are slowly
44	>	* reclaimed during periods of non-use, and reinstated upon subsequent
45	>	* use).
46	>	*
47	>	* <p>For applications that require separate or custom pools, a {@code
48	>	* ForkJoinPool} may be constructed with a given target parallelism
49	>	* level; by default, equal to the number of available processors. The
50	>	* pool attempts to maintain enough active (or available) threads by
51	>	* dynamically adding, suspending, or resuming internal worker
52	>	* threads, even if some tasks are stalled waiting to join
53	>	* others. However, no such adjustments are guaranteed in the face of
54	>	* blocked I/O or other unmanaged synchronization. The nested {@link
55	>	* ManagedBlocker} interface enables extension of the kinds of
56		* synchronization accommodated.
57		*
58		* <p>In addition to execution and lifecycle control methods, this
#	Line 59 \| Line 62 \| import java.util.concurrent.locks.Condit
62		* {@link #toString} returns indications of pool state in a
63		* convenient form for informal monitoring.
64		*
65	<	* <p> As is the case with other ExecutorServices, there are three
66	<	* main task execution methods summarized in the following
67	<	* table. These are designed to be used primarily by clients not
68	<	* already engaged in fork/join computations in the current pool. The
69	<	* main forms of these methods accept instances of {@code
70	<	* ForkJoinTask}, but overloaded forms also allow mixed execution of
71	<	* plain {@code Runnable}- or {@code Callable}- based activities as
72	<	* well. However, tasks that are already executing in a pool should
73	<	* normally instead use the within-computation forms listed in the
74	<	* table unless using async event-style tasks that are not usually
75	<	* joined, in which case there is little difference among choice of
73	<	* methods.
65	>	* <p>As is the case with other ExecutorServices, there are three
66	>	* main task execution methods summarized in the following table.
67	>	* These are designed to be used primarily by clients not already
68	>	* engaged in fork/join computations in the current pool. The main
69	>	* forms of these methods accept instances of {@code ForkJoinTask},
70	>	* but overloaded forms also allow mixed execution of plain {@code
71	>	* Runnable}- or {@code Callable}- based activities as well. However,
72	>	* tasks that are already executing in a pool should normally instead
73	>	* use the within-computation forms listed in the table unless using
74	>	* async event-style tasks that are not usually joined, in which case
75	>	* there is little difference among choice of methods.
76		*
77		* <table BORDER CELLPADDING=3 CELLSPACING=1>
78		* <tr>
#	Line 95 \| Line 97 \| import java.util.concurrent.locks.Condit
97		* </tr>
98		* </table>
99		*
100	<	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
101	<	* used for all parallel task execution in a program or subsystem.
102	<	* Otherwise, use would not usually outweigh the construction and
103	<	* bookkeeping overhead of creating a large set of threads. For
104	<	* example, a common pool could be used for the {@code SortTasks}
105	<	* illustrated in {@link RecursiveAction}. Because {@code
106	<	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
107	<	* daemon} mode, there is typically no need to explicitly {@link
108	<	* #shutdown} such a pool upon program exit.
109	<	*
108	<	* <pre> {@code
109	<	* static final ForkJoinPool mainPool = new ForkJoinPool();
110	<	* ...
111	<	* public void sort(long[] array) {
112	<	* mainPool.invoke(new SortTask(array, 0, array.length));
113	<	* }}</pre>
100	>	* <p>The common pool is by default constructed with default
101	>	* parameters, but these may be controlled by setting three {@link
102	>	* System#getProperty system properties} with prefix {@code
103	>	* java.util.concurrent.ForkJoinPool.common}: {@code parallelism} --
104	>	* an integer greater than zero, {@code threadFactory} -- the class
105	>	* name of a {@link ForkJoinWorkerThreadFactory}, and {@code
106	>	* exceptionHandler} -- the class name of a {@link
107	>	* java.lang.Thread.UncaughtExceptionHandler
108	>	* Thread.UncaughtExceptionHandler}. Upon any error in establishing
109	>	* these settings, default parameters are used.
110		*
111		* <p><b>Implementation notes</b>: This implementation restricts the
112		* maximum number of running threads to 32767. Attempts to create
#	Line 131 \| Line 127 \| public class ForkJoinPool extends Abstra
127		*
128		* This class and its nested classes provide the main
129		* functionality and control for a set of worker threads:
130	<	* Submissions from non-FJ threads enter into submission
131	<	* queues. Workers take these tasks and typically split them into
132	<	* subtasks that may be stolen by other workers. Preference rules
133	<	* give first priority to processing tasks from their own queues
134	<	* (LIFO or FIFO, depending on mode), then to randomized FIFO
135	<	* steals of tasks in other queues.
130	>	* Submissions from non-FJ threads enter into submission queues.
131	>	* Workers take these tasks and typically split them into subtasks
132	>	* that may be stolen by other workers. Preference rules give
133	>	* first priority to processing tasks from their own queues (LIFO
134	>	* or FIFO, depending on mode), then to randomized FIFO steals of
135	>	* tasks in other queues.
136		*
137	<	* WorkQueues.
137	>	* WorkQueues
138		* ==========
139		*
140		* Most operations occur within work-stealing queues (in nested
#	Line 156 \| Line 152 \| public class ForkJoinPool extends Abstra
152		* (http://research.sun.com/scalable/pubs/index.html) and
153		* "Idempotent work stealing" by Michael, Saraswat, and Vechev,
154		* PPoPP 2009 (http://portal.acm.org/citation.cfm?id=1504186).
155	<	* The main differences ultimately stem from gc requirements that
155	>	* The main differences ultimately stem from GC requirements that
156		* we null out taken slots as soon as we can, to maintain as small
157		* a footprint as possible even in programs generating huge
158		* numbers of tasks. To accomplish this, we shift the CAS
#	Line 178 \| Line 174 \| public class ForkJoinPool extends Abstra
174		* If an attempted steal fails, a thief always chooses a different
175		* random victim target to try next. So, in order for one thief to
176		* progress, it suffices for any in-progress poll or new push on
177	<	* any empty queue to complete.
177	>	* any empty queue to complete. (This is why we normally use
178	>	* method pollAt and its variants that try once at the apparent
179	>	* base index, else consider alternative actions, rather than
180	>	* method poll.)
181		*
182		* This approach also enables support of a user mode in which local
183		* task processing is in FIFO, not LIFO order, simply by using
#	Line 188 \| Line 187 \| public class ForkJoinPool extends Abstra
187		* rarely provide the best possible performance on a given
188		* machine, but portably provide good throughput by averaging over
189		* these factors. (Further, even if we did try to use such
190	<	* information, we do not usually have a basis for exploiting
191	<	* it. For example, some sets of tasks profit from cache
192	<	* affinities, but others are harmed by cache pollution effects.)
190	>	* information, we do not usually have a basis for exploiting it.
191	>	* For example, some sets of tasks profit from cache affinities,
192	>	* but others are harmed by cache pollution effects.)
193		*
194		* WorkQueues are also used in a similar way for tasks submitted
195		* to the pool. We cannot mix these tasks in the same queues used
196		* for work-stealing (this would contaminate lifo/fifo
197	<	* processing). Instead, we loosely associate (via hashing)
198	<	* submission queues with submitting threads, and randomly scan
199	<	* these queues as well when looking for work. In essence,
200	<	* submitters act like workers except that they never take tasks,
201	<	* and they are multiplexed on to a finite number of shared work
202	<	* queues. However, classes are set up so that future extensions
203	<	* could allow submitters to optionally help perform tasks as
204	<	* well. Pool submissions from internal workers are also allowed,
205	<	* but use randomized rather than thread-hashed queue indices to
206	<	* avoid imbalance. Insertion of tasks in shared mode requires a
207	<	* lock (mainly to protect in the case of resizing) but we use
208	<	* only a simple spinlock (using bits in field runState), because
209	<	* submitters encountering a busy queue try or create others so
210	<	* never block.
197	>	* processing). Instead, we randomly associate submission queues
198	>	* with submitting threads, using a form of hashing. The
199	>	* ThreadLocal Submitter class contains a value initially used as
200	>	* a hash code for choosing existing queues, but may be randomly
201	>	* repositioned upon contention with other submitters. In
202	>	* essence, submitters act like workers except that they are
203	>	* restricted to executing local tasks that they submitted (or in
204	>	* the case of CountedCompleters, others with the same root task).
205	>	* However, because most shared/external queue operations are more
206	>	* expensive than internal, and because, at steady state, external
207	>	* submitters will compete for CPU with workers, ForkJoinTask.join
208	>	* and related methods disable them from repeatedly helping to
209	>	* process tasks if all workers are active. Insertion of tasks in
210	>	* shared mode requires a lock (mainly to protect in the case of
211	>	* resizing) but we use only a simple spinlock (using bits in
212	>	* field qlock), because submitters encountering a busy queue move
213	>	* on to try or create other queues -- they block only when
214	>	* creating and registering new queues.
215		*
216	<	* Management.
216	>	* Management
217		* ==========
218		*
219		* The main throughput advantages of work-stealing stem from
#	Line 220 \| Line 223 \| public class ForkJoinPool extends Abstra
223		* tactic for avoiding bottlenecks is packing nearly all
224		* essentially atomic control state into two volatile variables
225		* that are by far most often read (not written) as status and
226	<	* consistency checks
226	>	* consistency checks.
227		*
228		* Field "ctl" contains 64 bits holding all the information needed
229		* to atomically decide to add, inactivate, enqueue (on an event
#	Line 230 \| Line 233 \| public class ForkJoinPool extends Abstra
233		* and their negations (used for thresholding) to fit into 16bit
234		* fields.
235		*
236	<	* Field "runState" contains 32 bits needed to register and
237	<	* deregister WorkQueues, as well as to enable shutdown. It is
238	<	* only modified under a lock (normally briefly held, but
239	<	* occasionally protecting allocations and resizings) but even
240	<	* when locked remains available to check consistency.
236	>	* Field "plock" is a form of sequence lock with a saturating
237	>	* shutdown bit (similarly for per-queue "qlocks"), mainly
238	>	* protecting updates to the workQueues array, as well as to
239	>	* enable shutdown. When used as a lock, it is normally only very
240	>	* briefly held, so is nearly always available after at most a
241	>	* brief spin, but we use a monitor-based backup strategy to
242	>	* block when needed.
243		*
244		* Recording WorkQueues. WorkQueues are recorded in the
245	<	* "workQueues" array that is created upon pool construction and
246	<	* expanded if necessary. Updates to the array while recording
247	<	* new workers and unrecording terminated ones are protected from
248	<	* each other by a lock but the array is otherwise concurrently
249	<	* readable, and accessed directly. To simplify index-based
250	<	* operations, the array size is always a power of two, and all
251	<	* readers must tolerate null slots. Shared (submission) queues
252	<	* are at even indices, worker queues at odd indices. Grouping
253	<	* them together in this way simplifies and speeds up task
254	<	* scanning. To avoid flailing during start-up, the array is
255	<	* presized to hold twice #parallelism workers (which is unlikely
256	<	* to need further resizing during execution). But to avoid
257	<	* dealing with so many null slots, variable runState includes a
258	<	* mask for the nearest power of two that contains all current
254	<	* workers. All worker thread creation is on-demand, triggered by
255	<	* task submissions, replacement of terminated workers, and/or
245	>	* "workQueues" array that is created upon first use and expanded
246	>	* if necessary. Updates to the array while recording new workers
247	>	* and unrecording terminated ones are protected from each other
248	>	* by a lock but the array is otherwise concurrently readable, and
249	>	* accessed directly. To simplify index-based operations, the
250	>	* array size is always a power of two, and all readers must
251	>	* tolerate null slots. Worker queues are at odd indices. Shared
252	>	* (submission) queues are at even indices, up to a maximum of 64
253	>	* slots, to limit growth even if array needs to expand to add
254	>	* more workers. Grouping them together in this way simplifies and
255	>	* speeds up task scanning.
256	>	*
257	>	* All worker thread creation is on-demand, triggered by task
258	>	* submissions, replacement of terminated workers, and/or
259		* compensation for blocked workers. However, all other support
260		* code is set up to work with other policies. To ensure that we
261		* do not hold on to worker references that would prevent GC, ALL
#	Line 265 \| Line 268 \| public class ForkJoinPool extends Abstra
268		* both index-check and null-check the IDs. All such accesses
269		* ignore bad IDs by returning out early from what they are doing,
270		* since this can only be associated with termination, in which
271	<	* case it is OK to give up.
272	<	*
273	<	* All uses of the workQueues array check that it is non-null
274	<	* (even if previously non-null). This allows nulling during
275	<	* termination, which is currently not necessary, but remains an
276	<	* option for resource-revocation-based shutdown schemes. It also
274	<	* helps reduce JIT issuance of uncommon-trap code, which tends to
271	>	* case it is OK to give up. All uses of the workQueues array
272	>	* also check that it is non-null (even if previously
273	>	* non-null). This allows nulling during termination, which is
274	>	* currently not necessary, but remains an option for
275	>	* resource-revocation-based shutdown schemes. It also helps
276	>	* reduce JIT issuance of uncommon-trap code, which tends to
277		* unnecessarily complicate control flow in some methods.
278		*
279		* Event Queuing. Unlike HPC work-stealing frameworks, we cannot
#	Line 299 \| Line 301 \| public class ForkJoinPool extends Abstra
301		* some other queued worker rather than itself, which has the same
302		* net effect. Because enqueued workers may actually be rescanning
303		* rather than waiting, we set and clear the "parker" field of
304	<	* Workqueues to reduce unnecessary calls to unpark. (This
304	>	* WorkQueues to reduce unnecessary calls to unpark. (This
305		* requires a secondary recheck to avoid missed signals.) Note
306		* the unusual conventions about Thread.interrupts surrounding
307		* parking and other blocking: Because interrupts are used solely
#	Line 311 \| Line 313 \| public class ForkJoinPool extends Abstra
313		*
314		* Signalling. We create or wake up workers only when there
315		* appears to be at least one task they might be able to find and
316	<	* execute. When a submission is added or another worker adds a
317	<	* task to a queue that previously had fewer than two tasks, they
318	<	* signal waiting workers (or trigger creation of new ones if
319	<	* fewer than the given parallelism level -- see signalWork).
320	<	* These primary signals are buttressed by signals during rescans;
321	<	* together these cover the signals needed in cases when more
322	<	* tasks are pushed but untaken, and improve performance compared
323	<	* to having one thread wake up all workers.
316	>	* execute. However, many other threads may notice the same task
317	>	* and each signal to wake up a thread that might take it. So in
318	>	* general, pools will be over-signalled. When a submission is
319	>	* added or another worker adds a task to a queue that has fewer
320	>	* than two tasks, they signal waiting workers (or trigger
321	>	* creation of new ones if fewer than the given parallelism level
322	>	* -- signalWork), and may leave a hint to the unparked worker to
323	>	* help signal others upon wakeup). These primary signals are
324	>	* buttressed by others (see method helpSignal) whenever other
325	>	* threads scan for work or do not have a task to process. On
326	>	* most platforms, signalling (unpark) overhead time is noticeably
327	>	* long, and the time between signalling a thread and it actually
328	>	* making progress can be very noticeably long, so it is worth
329	>	* offloading these delays from critical paths as much as
330	>	* possible.
331		*
332		* Trimming workers. To release resources after periods of lack of
333		* use, a worker starting to wait when the pool is quiescent will
334	<	* time out and terminate if the pool has remained quiescent for
335	<	* SHRINK_RATE nanosecs. This will slowly propagate, eventually
336	<	* terminating all workers after long periods of non-use.
334	>	* time out and terminate if the pool has remained quiescent for a
335	>	* given period -- a short period if there are more threads than
336	>	* parallelism, longer as the number of threads decreases. This
337	>	* will slowly propagate, eventually terminating all workers after
338	>	* periods of non-use.
339		*
340		* Shutdown and Termination. A call to shutdownNow atomically sets
341	<	* a runState bit and then (non-atomically) sets each workers
342	<	* runState status, cancels all unprocessed tasks, and wakes up
341	>	* a plock bit and then (non-atomically) sets each worker's
342	>	* qlock status, cancels all unprocessed tasks, and wakes up
343		* all waiting workers. Detecting whether termination should
344		* commence after a non-abrupt shutdown() call requires more work
345		* and bookkeeping. We need consensus about quiescence (i.e., that
#	Line 336 \| Line 347 \| public class ForkJoinPool extends Abstra
347		* indication but non-abrupt shutdown still requires a rechecking
348		* scan for any workers that are inactive but not queued.
349		*
350	<	* Joining Tasks.
351	<	* ==============
350	>	* Joining Tasks
351	>	* =============
352		*
353		* Any of several actions may be taken when one worker is waiting
354	<	* to join a task stolen (or always held by) another. Because we
354	>	* to join a task stolen (or always held) by another. Because we
355		* are multiplexing many tasks on to a pool of workers, we can't
356		* just let them block (as in Thread.join). We also cannot just
357		* reassign the joiner's run-time stack with another and replace
358		* it later, which would be a form of "continuation", that even if
359		* possible is not necessarily a good idea since we sometimes need
360	<	* both an unblocked task and its continuation to
361	<	* progress. Instead we combine two tactics:
360	>	* both an unblocked task and its continuation to progress.
361	>	* Instead we combine two tactics:
362		*
363		* Helping: Arranging for the joiner to execute some task that it
364		* would be running if the steal had not occurred.
#	Line 356 \| Line 367 \| public class ForkJoinPool extends Abstra
367		* method tryCompensate() may create or re-activate a spare
368		* thread to compensate for blocked joiners until they unblock.
369		*
370	<	* A third form (implemented in tryRemoveAndExec and
371	<	* tryPollForAndExec) amounts to helping a hypothetical
372	<	* compensator: If we can readily tell that a possible action of a
373	<	* compensator is to steal and execute the task being joined, the
374	<	* joining thread can do so directly, without the need for a
375	<	* compensation thread (although at the expense of larger run-time
376	<	* stacks, but the tradeoff is typically worthwhile).
370	>	* A third form (implemented in tryRemoveAndExec) amounts to
371	>	* helping a hypothetical compensator: If we can readily tell that
372	>	* a possible action of a compensator is to steal and execute the
373	>	* task being joined, the joining thread can do so directly,
374	>	* without the need for a compensation thread (although at the
375	>	* expense of larger run-time stacks, but the tradeoff is
376	>	* typically worthwhile).
377		*
378		* The ManagedBlocker extension API can't use helping so relies
379		* only on compensation in method awaitBlocker.
#	Line 382 \| Line 393 \| public class ForkJoinPool extends Abstra
393		* (http://portal.acm.org/citation.cfm?id=155354). It differs in
394		* that: (1) We only maintain dependency links across workers upon
395		* steals, rather than use per-task bookkeeping. This sometimes
396	<	* requires a linear scan of workers array to locate stealers, but
397	<	* often doesn't because stealers leave hints (that may become
398	<	* stale/wrong) of where to locate them. A stealHint is only a
399	<	* hint because a worker might have had multiple steals and the
400	<	* hint records only one of them (usually the most current).
401	<	* Hinting isolates cost to when it is needed, rather than adding
402	<	* to per-task overhead. (2) It is "shallow", ignoring nesting
403	<	* and potentially cyclic mutual steals. (3) It is intentionally
396	>	* requires a linear scan of workQueues array to locate stealers,
397	>	* but often doesn't because stealers leave hints (that may become
398	>	* stale/wrong) of where to locate them. It is only a hint
399	>	* because a worker might have had multiple steals and the hint
400	>	* records only one of them (usually the most current). Hinting
401	>	* isolates cost to when it is needed, rather than adding to
402	>	* per-task overhead. (2) It is "shallow", ignoring nesting and
403	>	* potentially cyclic mutual steals. (3) It is intentionally
404		* racy: field currentJoin is updated only while actively joining,
405		* which means that we miss links in the chain during long-lived
406		* tasks, GC stalls etc (which is OK since blocking in such cases
407		* is usually a good idea). (4) We bound the number of attempts
408	<	* to find work (see MAX_HELP_DEPTH) and fall back to suspending
409	<	* the worker and if necessary replacing it with another.
408	>	* to find work (see MAX_HELP) and fall back to suspending the
409	>	* worker and if necessary replacing it with another.
410	>	*
411	>	* Helping actions for CountedCompleters are much simpler: Method
412	>	* helpComplete can take and execute any task with the same root
413	>	* as the task being waited on. However, this still entails some
414	>	* traversal of completer chains, so is less efficient than using
415	>	* CountedCompleters without explicit joins.
416		*
417		* It is impossible to keep exactly the target parallelism number
418		* of threads running at any given time. Determining the
419		* existence of conservatively safe helping targets, the
420		* availability of already-created spares, and the apparent need
421		* to create new spares are all racy, so we rely on multiple
422	<	* retries of each. Currently, in keeping with on-demand
423	<	* signalling policy, we compensate only if blocking would leave
424	<	* less than one active (non-waiting, non-blocked) worker.
425	<	* Additionally, to avoid some false alarms due to GC, lagging
426	<	* counters, system activity, etc, compensated blocking for joins
427	<	* is only attempted after rechecks stabilize in
428	<	* ForkJoinTask.awaitJoin. (Retries are interspersed with
429	<	* Thread.yield, for good citizenship.)
430	<	*
431	<	* Style notes: There is a lot of representation-level coupling
432	<	* among classes ForkJoinPool, ForkJoinWorkerThread, and
433	<	* ForkJoinTask. The fields of WorkQueue maintain data structures
434	<	* managed by ForkJoinPool, so are directly accessed. There is
435	<	* little point trying to reduce this, since any associated future
436	<	* changes in representations will need to be accompanied by
437	<	* algorithmic changes anyway. All together, these low-level
438	<	* implementation choices produce as much as a factor of 4
439	<	* performance improvement compared to naive implementations, and
440	<	* enable the processing of billions of tasks per second, at the
441	<	* expense of some ugliness.
442	<	*
443	<	* Methods signalWork() and scan() are the main bottlenecks so are
444	<	* especially heavily micro-optimized/mangled. There are lots of
445	<	* inline assignments (of form "while ((local = field) != 0)")
446	<	* which are usually the simplest way to ensure the required read
447	<	* orderings (which are sometimes critical). This leads to a
448	<	* "C"-like style of listing declarations of these locals at the
449	<	* heads of methods or blocks. There are several occurrences of
450	<	* the unusual "do {} while (!cas...)" which is the simplest way
451	<	* to force an update of a CAS'ed variable. There are also other
452	<	* coding oddities that help some methods perform reasonably even
453	<	* when interpreted (not compiled).
454	<	*
455	<	* The order of declarations in this file is: (1) declarations of
456	<	* statics (2) fields (along with constants used when unpacking
457	<	* some of them), listed in an order that tends to reduce
458	<	* contention among them a bit under most JVMs; (3) nested
459	<	* classes; (4) internal control methods; (5) callbacks and other
460	<	* support for ForkJoinTask methods; (6) exported methods (plus a
461	<	* few little helpers); (7) static block initializing all statics
462	<	* in a minimally dependent order.
422	>	* retries of each. Compensation in the apparent absence of
423	>	* helping opportunities is challenging to control on JVMs, where
424	>	* GC and other activities can stall progress of tasks that in
425	>	* turn stall out many other dependent tasks, without us being
426	>	* able to determine whether they will ever require compensation.
427	>	* Even though work-stealing otherwise encounters little
428	>	* degradation in the presence of more threads than cores,
429	>	* aggressively adding new threads in such cases entails risk of
430	>	* unwanted positive feedback control loops in which more threads
431	>	* cause more dependent stalls (as well as delayed progress of
432	>	* unblocked threads to the point that we know they are available)
433	>	* leading to more situations requiring more threads, and so
434	>	* on. This aspect of control can be seen as an (analytically
435	>	* intractable) game with an opponent that may choose the worst
436	>	* (for us) active thread to stall at any time. We take several
437	>	* precautions to bound losses (and thus bound gains), mainly in
438	>	* methods tryCompensate and awaitJoin.
439	>	*
440	>	* Common Pool
441	>	* ===========
442	>	*
443	>	* The static commonPool always exists after static
444	>	* initialization. Since it (or any other created pool) need
445	>	* never be used, we minimize initial construction overhead and
446	>	* footprint to the setup of about a dozen fields, with no nested
447	>	* allocation. Most bootstrapping occurs within method
448	>	* fullExternalPush during the first submission to the pool.
449	>	*
450	>	* When external threads submit to the common pool, they can
451	>	* perform some subtask processing (see externalHelpJoin and
452	>	* related methods). We do not need to record whether these
453	>	* submissions are to the common pool -- if not, externalHelpJoin
454	>	* returns quickly (at the most helping to signal some common pool
455	>	* workers). These submitters would otherwise be blocked waiting
456	>	* for completion, so the extra effort (with liberally sprinkled
457	>	* task status checks) in inapplicable cases amounts to an odd
458	>	* form of limited spin-wait before blocking in ForkJoinTask.join.
459	>	*
460	>	* Style notes
461	>	* ===========
462	>	*
463	>	* There is a lot of representation-level coupling among classes
464	>	* ForkJoinPool, ForkJoinWorkerThread, and ForkJoinTask. The
465	>	* fields of WorkQueue maintain data structures managed by
466	>	* ForkJoinPool, so are directly accessed. There is little point
467	>	* trying to reduce this, since any associated future changes in
468	>	* representations will need to be accompanied by algorithmic
469	>	* changes anyway. Several methods intrinsically sprawl because
470	>	* they must accumulate sets of consistent reads of volatiles held
471	>	* in local variables. Methods signalWork() and scan() are the
472	>	* main bottlenecks, so are especially heavily
473	>	* micro-optimized/mangled. There are lots of inline assignments
474	>	* (of form "while ((local = field) != 0)") which are usually the
475	>	* simplest way to ensure the required read orderings (which are
476	>	* sometimes critical). This leads to a "C"-like style of listing
477	>	* declarations of these locals at the heads of methods or blocks.
478	>	* There are several occurrences of the unusual "do {} while
479	>	* (!cas...)" which is the simplest way to force an update of a
480	>	* CAS'ed variable. There are also other coding oddities (including
481	>	* several unnecessary-looking hoisted null checks) that help
482	>	* some methods perform reasonably even when interpreted (not
483	>	* compiled).
484	>	*
485	>	* The order of declarations in this file is:
486	>	* (1) Static utility functions
487	>	* (2) Nested (static) classes
488	>	* (3) Static fields
489	>	* (4) Fields, along with constants used when unpacking some of them
490	>	* (5) Internal control methods
491	>	* (6) Callbacks and other support for ForkJoinTask methods
492	>	* (7) Exported methods
493	>	* (8) Static block initializing statics in minimally dependent order
494		*/
495
496	+	// Static utilities
497	+
498	+	/**
499	+	* If there is a security manager, makes sure caller has
500	+	* permission to modify threads.
501	+	*/
502	+	private static void checkPermission() {
503	+	SecurityManager security = System.getSecurityManager();
504	+	if (security != null)
505	+	security.checkPermission(modifyThreadPermission);
506	+	}
507	+
508	+	// Nested classes
509	+
510		/**
511		* Factory for creating new {@link ForkJoinWorkerThread}s.
512		* A {@code ForkJoinWorkerThreadFactory} must be defined and used
#	Line 465 \| Line 527 \| public class ForkJoinPool extends Abstra
527		* Default ForkJoinWorkerThreadFactory implementation; creates a
528		* new ForkJoinWorkerThread.
529		*/
530	<	static class DefaultForkJoinWorkerThreadFactory
530	>	static final class DefaultForkJoinWorkerThreadFactory
531		implements ForkJoinWorkerThreadFactory {
532	<	public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
532	>	public final ForkJoinWorkerThread newThread(ForkJoinPool pool) {
533		return new ForkJoinWorkerThread(pool);
534		}
535		}
536
537		/**
538	<	* Creates a new ForkJoinWorkerThread. This factory is used unless
539	<	* overridden in ForkJoinPool constructors.
540	<	*/
541	<	public static final ForkJoinWorkerThreadFactory
542	<	defaultForkJoinWorkerThreadFactory;
543	<
544	<	/**
545	<	* Permission required for callers of methods that may start or
546	<	* kill threads.
547	<	*/
548	<	private static final RuntimePermission modifyThreadPermission;
549	<
550	<	/**
551	<	* If there is a security manager, makes sure caller has
552	<	* permission to modify threads.
553	<	*/
554	<	private static void checkPermission() {
493	<	SecurityManager security = System.getSecurityManager();
494	<	if (security != null)
495	<	security.checkPermission(modifyThreadPermission);
538	>	* Per-thread records for threads that submit to pools. Currently
539	>	* holds only pseudo-random seed / index that is used to choose
540	>	* submission queues in method externalPush. In the future, this may
541	>	* also incorporate a means to implement different task rejection
542	>	* and resubmission policies.
543	>	*
544	>	* Seeds for submitters and workers/workQueues work in basically
545	>	* the same way but are initialized and updated using slightly
546	>	* different mechanics. Both are initialized using the same
547	>	* approach as in class ThreadLocal, where successive values are
548	>	* unlikely to collide with previous values. Seeds are then
549	>	* randomly modified upon collisions using xorshifts, which
550	>	* requires a non-zero seed.
551	>	*/
552	>	static final class Submitter {
553	>	int seed;
554	>	Submitter(int s) { seed = s; }
555		}
556
557		/**
558	<	* Generator for assigning sequence numbers as pool names.
559	<	*/
560	<	private static final AtomicInteger poolNumberGenerator;
561	<
503	<	/**
504	<	* Bits and masks for control variables
505	<	*
506	<	* Field ctl is a long packed with:
507	<	* AC: Number of active running workers minus target parallelism (16 bits)
508	<	* TC: Number of total workers minus target parallelism (16 bits)
509	<	* ST: true if pool is terminating (1 bit)
510	<	* EC: the wait count of top waiting thread (15 bits)
511	<	* ID: ~(poolIndex >>> 1) of top of Treiber stack of waiters (16 bits)
512	<	*
513	<	* When convenient, we can extract the upper 32 bits of counts and
514	<	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
515	<	* (int)ctl. The ec field is never accessed alone, but always
516	<	* together with id and st. The offsets of counts by the target
517	<	* parallelism and the positionings of fields makes it possible to
518	<	* perform the most common checks via sign tests of fields: When
519	<	* ac is negative, there are not enough active workers, when tc is
520	<	* negative, there are not enough total workers, when id is
521	<	* negative, there is at least one waiting worker, and when e is
522	<	* negative, the pool is terminating. To deal with these possibly
523	<	* negative fields, we use casts in and out of "short" and/or
524	<	* signed shifts to maintain signedness.
525	<	*
526	<	* When a thread is queued (inactivated), its eventCount field is
527	<	* negative, which is the only way to tell if a worker is
528	<	* prevented from executing tasks, even though it must continue to
529	<	* scan for them to avoid queuing races.
530	<	*
531	<	* Field runState is an int packed with:
532	<	* SHUTDOWN: true if shutdown is enabled (1 bit)
533	<	* SEQ: a sequence number updated upon (de)registering workers (15 bits)
534	<	* MASK: mask (power of 2 - 1) covering all registered poolIndexes (16 bits)
535	<	*
536	<	* The combination of mask and sequence number enables simple
537	<	* consistency checks: Staleness of read-only operations on the
538	<	* workers and queues arrays can be checked by comparing runState
539	<	* before vs after the reads. The low 16 bits (i.e, anding with
540	<	* SMASK) hold (the smallest power of two covering all worker
541	<	* indices, minus one. The mask for queues (vs workers) is twice
542	<	* this value plus 1.
543	<	*/
544	<
545	<	// bit positions/shifts for fields
546	<	private static final int AC_SHIFT = 48;
547	<	private static final int TC_SHIFT = 32;
548	<	private static final int ST_SHIFT = 31;
549	<	private static final int EC_SHIFT = 16;
550	<
551	<	// bounds
552	<	private static final int MAX_ID = 0x7fff; // max poolIndex
553	<	private static final int SMASK = 0xffff; // mask short bits
554	<	private static final int SHORT_SIGN = 1 << 15;
555	<	private static final int INT_SIGN = 1 << 31;
556	<
557	<	// masks
558	<	private static final long STOP_BIT = 0x0001L << ST_SHIFT;
559	<	private static final long AC_MASK = ((long)SMASK) << AC_SHIFT;
560	<	private static final long TC_MASK = ((long)SMASK) << TC_SHIFT;
561	<
562	<	// units for incrementing and decrementing
563	<	private static final long TC_UNIT = 1L << TC_SHIFT;
564	<	private static final long AC_UNIT = 1L << AC_SHIFT;
565	<
566	<	// masks and units for dealing with u = (int)(ctl >>> 32)
567	<	private static final int UAC_SHIFT = AC_SHIFT - 32;
568	<	private static final int UTC_SHIFT = TC_SHIFT - 32;
569	<	private static final int UAC_MASK = SMASK << UAC_SHIFT;
570	<	private static final int UTC_MASK = SMASK << UTC_SHIFT;
571	<	private static final int UAC_UNIT = 1 << UAC_SHIFT;
572	<	private static final int UTC_UNIT = 1 << UTC_SHIFT;
573	<
574	<	// masks and units for dealing with e = (int)ctl
575	<	private static final int E_MASK = 0x7fffffff; // no STOP_BIT
576	<	private static final int E_SEQ = 1 << EC_SHIFT;
577	<
578	<	// runState bits
579	<	private static final int SHUTDOWN = 1 << 31;
580	<	private static final int RS_SEQ = 1 << 16;
581	<	private static final int RS_SEQ_MASK = 0x7fff0000;
582	<
583	<	// access mode for WorkQueue
584	<	static final int LIFO_QUEUE = 0;
585	<	static final int FIFO_QUEUE = 1;
586	<	static final int SHARED_QUEUE = -1;
587	<
588	<	/**
589	<	* The wakeup interval (in nanoseconds) for a worker waiting for a
590	<	* task when the pool is quiescent to instead try to shrink the
591	<	* number of workers. The exact value does not matter too
592	<	* much. It must be short enough to release resources during
593	<	* sustained periods of idleness, but not so short that threads
594	<	* are continually re-created.
595	<	*/
596	<	private static final long SHRINK_RATE =
597	<	4L * 1000L * 1000L * 1000L; // 4 seconds
598	<
599	<	/**
600	<	* The timeout value for attempted shrinkage, includes
601	<	* some slop to cope with system timer imprecision.
602	<	*/
603	<	private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
604	<
605	<	/**
606	<	* The maximum stolen->joining link depth allowed in tryHelpStealer.
607	<	* Depths for legitimate chains are unbounded, but we use a fixed
608	<	* constant to avoid (otherwise unchecked) cycles and to bound
609	<	* staleness of traversal parameters at the expense of sometimes
610	<	* blocking when we could be helping.
611	<	*/
612	<	private static final int MAX_HELP_DEPTH = 16;
613	<
614	<	/*
615	<	* Field layout order in this class tends to matter more than one
616	<	* would like. Runtime layout order is only loosely related to
617	<	* declaration order and may differ across JVMs, but the following
618	<	* empirically works OK on current JVMs.
558	>	* Class for artificial tasks that are used to replace the target
559	>	* of local joins if they are removed from an interior queue slot
560	>	* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
561	>	* actually do anything beyond having a unique identity.
562		*/
563	<
564	<	volatile long ctl; // main pool control
565	<	final int parallelism; // parallelism level
566	<	final int localMode; // per-worker scheduling mode
567	<	int nextPoolIndex; // hint used in registerWorker
568	<	volatile int runState; // shutdown status, seq, and mask
569	<	WorkQueue[] workQueues; // main registry
627	<	final ReentrantLock lock; // for registration
628	<	final Condition termination; // for awaitTermination
629	<	final ForkJoinWorkerThreadFactory factory; // factory for new workers
630	<	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
631	<	final AtomicLong stealCount; // collect counts when terminated
632	<	final AtomicInteger nextWorkerNumber; // to create worker name string
633	<	final String workerNamePrefix; // Prefix for assigning worker names
563	>	static final class EmptyTask extends ForkJoinTask<Void> {
564	>	private static final long serialVersionUID = -7721805057305804111L;
565	>	EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
566	>	public final Void getRawResult() { return null; }
567	>	public final void setRawResult(Void x) {}
568	>	public final boolean exec() { return true; }
569	>	}
570
571		/**
572		* Queues supporting work-stealing as well as external task
#	Line 646 \| Line 582 \| public class ForkJoinPool extends Abstra
582		*
583		* Field "top" is the index (mod array.length) of the next queue
584		* slot to push to or pop from. It is written only by owner thread
585	<	* for push, or under lock for trySharedPush, and accessed by
586	<	* other threads only after reading (volatile) base. Both top and
587	<	* base are allowed to wrap around on overflow, but (top - base)
588	<	* (or more commonly -(base - top) to force volatile read of base
589	<	* before top) still estimates size.
585	>	* for push, or under lock for external/shared push, and accessed
586	>	* by other threads only after reading (volatile) base. Both top
587	>	* and base are allowed to wrap around on overflow, but (top -
588	>	* base) (or more commonly -(base - top) to force volatile read of
589	>	* base before top) still estimates size. The lock ("qlock") is
590	>	* forced to -1 on termination, causing all further lock attempts
591	>	* to fail. (Note: we don't need CAS for termination state because
592	>	* upon pool shutdown, all shared-queues will stop being used
593	>	* anyway.) Nearly all lock bodies are set up so that exceptions
594	>	* within lock bodies are "impossible" (modulo JVM errors that
595	>	* would cause failure anyway.)
596		*
597		* The array slots are read and written using the emulation of
598		* volatiles/atomics provided by Unsafe. Insertions must in
599		* general use putOrderedObject as a form of releasing store to
600		* ensure that all writes to the task object are ordered before
601	<	* its publication in the queue. (Although we can avoid one case
602	<	* of this when locked in trySharedPush.) All removals entail a
603	<	* CAS to null. The array is always a power of two. To ensure
604	<	* safety of Unsafe array operations, all accesses perform
663	<	* explicit null checks and implicit bounds checks via
664	<	* power-of-two masking.
601	>	* its publication in the queue. All removals entail a CAS to
602	>	* null. The array is always a power of two. To ensure safety of
603	>	* Unsafe array operations, all accesses perform explicit null
604	>	* checks and implicit bounds checks via power-of-two masking.
605		*
606		* In addition to basic queuing support, this class contains
607		* fields described elsewhere to control execution. It turns out
608	<	* to work better memory-layout-wise to include them in this
609	<	* class rather than a separate class.
608	>	* to work better memory-layout-wise to include them in this class
609	>	* rather than a separate class.
610		*
611		* Performance on most platforms is very sensitive to placement of
612		* instances of both WorkQueues and their arrays -- we absolutely
#	Line 680 \| Line 620 \| public class ForkJoinPool extends Abstra
620		* trades off slightly slower average field access for the sake of
621		* avoiding really bad worst-case access. (Until better JVM
622		* support is in place, this padding is dependent on transient
623	<	* properties of JVM field layout rules.) We also take care in
624	<	* allocating and sizing and resizing the array. Non-shared queue
625	<	* arrays are initialized (via method growArray) by workers before
626	<	* use. Others are allocated on first use.
623	>	* properties of JVM field layout rules.) We also take care in
624	>	* allocating, sizing and resizing the array. Non-shared queue
625	>	* arrays are initialized by workers before use. Others are
626	>	* allocated on first use.
627		*/
628		static final class WorkQueue {
629		/**
630		* Capacity of work-stealing queue array upon initialization.
631	<	* Must be a power of two; at least 4, but set larger to
632	<	* reduce cacheline sharing among queues.
631	>	* Must be a power of two; at least 4, but should be larger to
632	>	* reduce or eliminate cacheline sharing among queues.
633	>	* Currently, it is much larger, as a partial workaround for
634	>	* the fact that JVMs often place arrays in locations that
635	>	* share GC bookkeeping (especially cardmarks) such that
636	>	* per-write accesses encounter serious memory contention.
637		*/
638	<	static final int INITIAL_QUEUE_CAPACITY = 1 << 8;
638	>	static final int INITIAL_QUEUE_CAPACITY = 1 << 13;
639
640		/**
641		* Maximum size for queue arrays. Must be a power of two less
#	Line 702 \| Line 646 \| public class ForkJoinPool extends Abstra
646		*/
647		static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
648
649	<	volatile long totalSteals; // cumulative number of steals
649	>	// Heuristic padding to ameliorate unfortunate memory placements
650	>	volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
651	>
652		int seed; // for random scanning; initialize nonzero
653		volatile int eventCount; // encoded inactivation count; < 0 if inactive
654		int nextWait; // encoded record of next event waiter
655	<	int rescans; // remaining scans until block
710	<	int nsteals; // top-level task executions since last idle
711	<	final int mode; // lifo, fifo, or shared
655	>	int hint; // steal or signal hint (index)
656		int poolIndex; // index of this queue in pool (or 0)
657	<	int stealHint; // index of most recent known stealer
658	<	volatile int runState; // 1: locked, -1: terminate; else 0
657	>	final int mode; // 0: lifo, > 0: fifo, < 0: shared
658	>	int nsteals; // number of steals
659	>	volatile int qlock; // 1: locked, -1: terminate; else 0
660		volatile int base; // index of next slot for poll
661		int top; // index of next slot for push
662		ForkJoinTask<?>[] array; // the elements (initially unallocated)
663	+	final ForkJoinPool pool; // the containing pool (may be null)
664		final ForkJoinWorkerThread owner; // owning thread or null if shared
665		volatile Thread parker; // == owner during call to park; else null
666	<	ForkJoinTask<?> currentJoin; // task being joined in awaitJoin
666	>	volatile ForkJoinTask<?> currentJoin; // task being joined in awaitJoin
667		ForkJoinTask<?> currentSteal; // current non-local task being executed
722	–	// Heuristic padding to ameliorate unfortunate memory placements
723	–	Object p00, p01, p02, p03, p04, p05, p06, p07, p08, p09, p0a;
668
669	<	WorkQueue(ForkJoinWorkerThread owner, int mode) {
669	>	volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
670	>	volatile Object pad18, pad19, pad1a, pad1b, pad1c, pad1d;
671	>
672	>	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode,
673	>	int seed) {
674	>	this.pool = pool;
675		this.owner = owner;
676		this.mode = mode;
677	+	this.seed = seed;
678		// Place indices in the center of array (that is not yet allocated)
679		base = top = INITIAL_QUEUE_CAPACITY >>> 1;
680		}
681
682		/**
683	<	* Returns number of tasks in the queue
683	>	* Returns the approximate number of tasks in the queue.
684		*/
685		final int queueSize() {
686	<	int n = base - top; // non-owner callers must read base first
687	<	return (n >= 0) ? 0 : -n;
686	>	int n = base - top; // non-owner callers must read base first
687	>	return (n >= 0) ? 0 : -n; // ignore transient negative
688	>	}
689	>
690	>	/**
691	>	* Provides a more accurate estimate of whether this queue has
692	>	* any tasks than does queueSize, by checking whether a
693	>	* near-empty queue has at least one unclaimed task.
694	>	*/
695	>	final boolean isEmpty() {
696	>	ForkJoinTask<?>[] a; int m, s;
697	>	int n = base - (s = top);
698	>	return (n >= 0 \|\|
699	>	(n == -1 &&
700	>	((a = array) == null \|\|
701	>	(m = a.length - 1) < 0 \|\|
702	>	U.getObject
703	>	(a, (long)((m & (s - 1)) << ASHIFT) + ABASE) == null)));
704		}
705
706		/**
707	<	* Pushes a task. Call only by owner in unshared queues.
707	>	* Pushes a task. Call only by owner in unshared queues. (The
708	>	* shared-queue version is embedded in method externalPush.)
709		*
710		* @param task the task. Caller must ensure non-null.
711	<	* @param p, if non-null, pool to signal if necessary
745	<	* @throw RejectedExecutionException if array cannot
746	<	* be resized
711	>	* @throw RejectedExecutionException if array cannot be resized
712		*/
713	<	final void push(ForkJoinTask<?> task, ForkJoinPool p) {
714	<	ForkJoinTask<?>[] a;
713	>	final void push(ForkJoinTask<?> task) {
714	>	ForkJoinTask<?>[] a; ForkJoinPool p;
715		int s = top, m, n;
716		if ((a = array) != null) { // ignore if queue removed
717	<	U.putOrderedObject
718	<	(a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task);
717	>	int j = (((m = a.length - 1) & s) << ASHIFT) + ABASE;
718	>	U.putOrderedObject(a, j, task);
719		if ((n = (top = s + 1) - base) <= 2) {
720	<	if (p != null)
721	<	p.signalWork();
720	>	if ((p = pool) != null)
721	>	p.signalWork(this);
722		}
723		else if (n >= m)
724	<	growArray(true);
724	>	growArray();
725		}
726		}
727
728	+	/**
729	+	* Initializes or doubles the capacity of array. Call either
730	+	* by owner or with lock held -- it is OK for base, but not
731	+	* top, to move while resizings are in progress.
732	+	*/
733	+	final ForkJoinTask<?>[] growArray() {
734	+	ForkJoinTask<?>[] oldA = array;
735	+	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
736	+	if (size > MAXIMUM_QUEUE_CAPACITY)
737	+	throw new RejectedExecutionException("Queue capacity exceeded");
738	+	int oldMask, t, b;
739	+	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
740	+	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
741	+	(t = top) - (b = base) > 0) {
742	+	int mask = size - 1;
743	+	do {
744	+	ForkJoinTask<?> x;
745	+	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
746	+	int j = ((b & mask) << ASHIFT) + ABASE;
747	+	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
748	+	if (x != null &&
749	+	U.compareAndSwapObject(oldA, oldj, x, null))
750	+	U.putObjectVolatile(a, j, x);
751	+	} while (++b != t);
752	+	}
753	+	return a;
754	+	}
755	+
756		/**
757	<	* Pushes a task if lock is free and array is either big
758	<	* enough or can be resized to be big enough.
766	<	*
767	<	* @param task the task. Caller must ensure non-null.
768	<	* @return true if submitted
757	>	* Takes next task, if one exists, in LIFO order. Call only
758	>	* by owner in unshared queues.
759		*/
760	<	final boolean trySharedPush(ForkJoinTask<?> task) {
761	<	boolean submitted = false;
762	<	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
763	<	ForkJoinTask<?>[] a = array;
764	<	int s = top, n = s - base;
765	<	try {
766	<	if ((a != null && n < a.length - 1) \|\|
767	<	(a = growArray(false)) != null) { // must presize
768	<	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
769	<	U.putObject(a, (long)j, task); // don't need "ordered"
780	<	top = s + 1;
781	<	submitted = true;
760	>	final ForkJoinTask<?> pop() {
761	>	ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
762	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
763	>	for (int s; (s = top - 1) - base >= 0;) {
764	>	long j = ((m & s) << ASHIFT) + ABASE;
765	>	if ((t = (ForkJoinTask<?>)U.getObject(a, j)) == null)
766	>	break;
767	>	if (U.compareAndSwapObject(a, j, t, null)) {
768	>	top = s;
769	>	return t;
770		}
783	–	} finally {
784	–	runState = 0; // unlock
771		}
772		}
773	<	return submitted;
773	>	return null;
774		}
775
776		/**
777	<	* Takes next task, if one exists, in FIFO order.
777	>	* Takes a task in FIFO order if b is base of queue and a task
778	>	* can be claimed without contention. Specialized versions
779	>	* appear in ForkJoinPool methods scan and tryHelpStealer.
780		*/
781	<	final ForkJoinTask<?> poll() {
782	<	ForkJoinTask<?>[] a; int b, i;
783	<	while ((b = base) - top < 0 && (a = array) != null &&
784	<	(i = (a.length - 1) & b) >= 0) {
785	<	int j = (i << ASHIFT) + ABASE;
786	<	ForkJoinTask<?> t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
799	<	if (t != null && base == b &&
781	>	final ForkJoinTask<?> pollAt(int b) {
782	>	ForkJoinTask<?> t; ForkJoinTask<?>[] a;
783	>	if ((a = array) != null) {
784	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
785	>	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
786	>	base == b &&
787		U.compareAndSwapObject(a, j, t, null)) {
788		base = b + 1;
789		return t;
#	Line 806 \| Line 793 \| public class ForkJoinPool extends Abstra
793		}
794
795		/**
796	<	* Takes next task, if one exists, in LIFO order.
810	<	* Call only by owner in unshared queues.
796	>	* Takes next task, if one exists, in FIFO order.
797		*/
798	<	final ForkJoinTask<?> pop() {
799	<	ForkJoinTask<?> t; int m;
800	<	ForkJoinTask<?>[] a = array;
801	<	if (a != null && (m = a.length - 1) >= 0) {
802	<	for (int s; (s = top - 1) - base >= 0;) {
803	<	int j = ((m & s) << ASHIFT) + ABASE;
804	<	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) == null)
805	<	break;
806	<	if (U.compareAndSwapObject(a, j, t, null)) {
821	<	top = s;
798	>	final ForkJoinTask<?> poll() {
799	>	ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t;
800	>	while ((b = base) - top < 0 && (a = array) != null) {
801	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
802	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
803	>	if (t != null) {
804	>	if (base == b &&
805	>	U.compareAndSwapObject(a, j, t, null)) {
806	>	base = b + 1;
807		return t;
808		}
809		}
810	+	else if (base == b) {
811	+	if (b + 1 == top)
812	+	break;
813	+	Thread.yield(); // wait for lagging update (very rare)
814	+	}
815		}
816		return null;
817		}
#	Line 846 \| Line 836 \| public class ForkJoinPool extends Abstra
836		}
837
838		/**
849	–	* Returns task at index b if b is current base of queue.
850	–	*/
851	–	final ForkJoinTask<?> pollAt(int b) {
852	–	ForkJoinTask<?>[] a; int i;
853	–	ForkJoinTask<?> task = null;
854	–	if ((a = array) != null && (i = ((a.length - 1) & b)) >= 0) {
855	–	int j = (i << ASHIFT) + ABASE;
856	–	ForkJoinTask<?> t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
857	–	if (t != null && base == b &&
858	–	U.compareAndSwapObject(a, j, t, null)) {
859	–	base = b + 1;
860	–	task = t;
861	–	}
862	–	}
863	–	return task;
864	–	}
865	–
866	–	/**
839		* Pops the given task only if it is at the current top.
840	+	* (A shared version is available only via FJP.tryExternalUnpush)
841		*/
842		final boolean tryUnpush(ForkJoinTask<?> t) {
843		ForkJoinTask<?>[] a; int s;
#	Line 878 \| Line 851 \| public class ForkJoinPool extends Abstra
851		}
852
853		/**
854	<	* Polls the given task only if it is at the current base.
854	>	* Removes and cancels all known tasks, ignoring any exceptions.
855		*/
856	<	final boolean pollFor(ForkJoinTask<?> task) {
857	<	ForkJoinTask<?>[] a; int b, i;
858	<	if ((b = base) - top < 0 && (a = array) != null &&
859	<	(i = (a.length - 1) & b) >= 0) {
860	<	int j = (i << ASHIFT) + ABASE;
861	<	if (U.getObjectVolatile(a, j) == task && base == b &&
862	<	U.compareAndSwapObject(a, j, task, null)) {
863	<	base = b + 1;
864	<	return true;
856	>	final void cancelAll() {
857	>	ForkJoinTask.cancelIgnoringExceptions(currentJoin);
858	>	ForkJoinTask.cancelIgnoringExceptions(currentSteal);
859	>	for (ForkJoinTask<?> t; (t = poll()) != null; )
860	>	ForkJoinTask.cancelIgnoringExceptions(t);
861	>	}
862	>
863	>	/**
864	>	* Computes next value for random probes. Scans don't require
865	>	* a very high quality generator, but also not a crummy one.
866	>	* Marsaglia xor-shift is cheap and works well enough. Note:
867	>	* This is manually inlined in its usages in ForkJoinPool to
868	>	* avoid writes inside busy scan loops.
869	>	*/
870	>	final int nextSeed() {
871	>	int r = seed;
872	>	r ^= r << 13;
873	>	r ^= r >>> 17;
874	>	return seed = r ^= r << 5;
875	>	}
876	>
877	>	// Specialized execution methods
878	>
879	>	/**
880	>	* Pops and runs tasks until empty.
881	>	*/
882	>	private void popAndExecAll() {
883	>	// A bit faster than repeated pop calls
884	>	ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t;
885	>	while ((a = array) != null && (m = a.length - 1) >= 0 &&
886	>	(s = top - 1) - base >= 0 &&
887	>	(t = ((ForkJoinTask<?>)
888	>	U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
889	>	!= null) {
890	>	if (U.compareAndSwapObject(a, j, t, null)) {
891	>	top = s;
892	>	t.doExec();
893		}
894		}
894	–	return false;
895		}
896
897		/**
898	<	* If present, removes from queue and executes the given task, or
899	<	* any other cancelled task. Returns (true) immediately on any CAS
898	>	* Polls and runs tasks until empty.
899	>	*/
900	>	private void pollAndExecAll() {
901	>	for (ForkJoinTask<?> t; (t = poll()) != null;)
902	>	t.doExec();
903	>	}
904	>
905	>	/**
906	>	* If present, removes from queue and executes the given task,
907	>	* or any other cancelled task. Returns (true) on any CAS
908		* or consistency check failure so caller can retry.
909		*
910	<	* @return false if no progress can be made
910	>	* @return false if no progress can be made, else true;
911		*/
912		final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
913	<	boolean removed = false, empty = true, progress = true;
913	>	boolean stat = true, removed = false, empty = true;
914		ForkJoinTask<?>[] a; int m, s, b, n;
915		if ((a = array) != null && (m = a.length - 1) >= 0 &&
916		(n = (s = top) - (b = base)) > 0) {
#	Line 932 \| Line 940 \| public class ForkJoinPool extends Abstra
940		}
941		if (--n == 0) {
942		if (!empty && base == b)
943	<	progress = false;
943	>	stat = false;
944		break;
945		}
946		}
947		}
948		if (removed)
949		task.doExec();
950	<	return progress;
950	>	return stat;
951		}
952
953		/**
954	<	* Initializes or doubles the capacity of array. Call either
955	<	* by owner or with lock held -- it is OK for base, but not
948	<	* top, to move while resizings are in progress.
949	<	*
950	<	* @param rejectOnFailure if true, throw exception if capacity
951	<	* exceeded (relayed ultimately to user); else return null.
954	>	* Polls for and executes the given task or any other task in
955	>	* its CountedCompleter computation
956		*/
957	<	final ForkJoinTask<?>[] growArray(boolean rejectOnFailure) {
958	<	ForkJoinTask<?>[] oldA = array;
959	<	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
960	<	if (size <= MAXIMUM_QUEUE_CAPACITY) {
961	<	int oldMask, t, b;
962	<	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
963	<	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
964	<	(t = top) - (b = base) > 0) {
965	<	int mask = size - 1;
966	<	do {
967	<	ForkJoinTask<?> x;
968	<	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
969	<	int j = ((b & mask) << ASHIFT) + ABASE;
970	<	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
971	<	if (x != null &&
972	<	U.compareAndSwapObject(oldA, oldj, x, null))
973	<	U.putObjectVolatile(a, j, x);
974	<	} while (++b != t);
957	>	final boolean pollAndExecCC(ForkJoinTask<?> root) {
958	>	ForkJoinTask<?>[] a; int b; Object o;
959	>	outer: while ((b = base) - top < 0 && (a = array) != null) {
960	>	long j = (((a.length - 1) & b) << ASHIFT) + ABASE;
961	>	if ((o = U.getObject(a, j)) == null \|\|
962	>	!(o instanceof CountedCompleter))
963	>	break;
964	>	for (CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;;) {
965	>	if (r == root) {
966	>	if (base == b &&
967	>	U.compareAndSwapObject(a, j, t, null)) {
968	>	base = b + 1;
969	>	t.doExec();
970	>	return true;
971	>	}
972	>	else
973	>	break; // restart
974	>	}
975	>	if ((r = r.completer) == null)
976	>	break outer; // not part of root computation
977		}
972	–	return a;
973	–	}
974	–	else if (!rejectOnFailure)
975	–	return null;
976	–	else
977	–	throw new RejectedExecutionException("Queue capacity exceeded");
978	–	}
979	–
980	–	/**
981	–	* Removes and cancels all known tasks, ignoring any exceptions
982	–	*/
983	–	final void cancelAll() {
984	–	ForkJoinTask.cancelIgnoringExceptions(currentJoin);
985	–	ForkJoinTask.cancelIgnoringExceptions(currentSteal);
986	–	for (ForkJoinTask<?> t; (t = poll()) != null; )
987	–	ForkJoinTask.cancelIgnoringExceptions(t);
988	–	}
989	–
990	–	// Execution methods
991	–
992	–	/**
993	–	* Removes and runs tasks until empty, using local mode
994	–	* ordering.
995	–	*/
996	–	final void runLocalTasks() {
997	–	if (base - top < 0) {
998	–	for (ForkJoinTask<?> t; (t = nextLocalTask()) != null; )
999	–	t.doExec();
978		}
979	+	return false;
980		}
981
982		/**
983		* Executes a top-level task and any local tasks remaining
984		* after execution.
1006	–	*
1007	–	* @return true unless terminating
985		*/
986	<	final boolean runTask(ForkJoinTask<?> t) {
1010	<	boolean alive = true;
986	>	final void runTask(ForkJoinTask<?> t) {
987		if (t != null) {
988	<	currentSteal = t;
1013	<	t.doExec();
1014	<	runLocalTasks();
1015	<	++nsteals;
988	>	(currentSteal = t).doExec();
989		currentSteal = null;
990	+	++nsteals;
991	+	if (base - top < 0) { // process remaining local tasks
992	+	if (mode == 0)
993	+	popAndExecAll();
994	+	else
995	+	pollAndExecAll();
996	+	}
997		}
1018	–	else if (runState < 0) // terminating
1019	–	alive = false;
1020	–	return alive;
998		}
999
1000		/**
1001	<	* Executes a non-top-level (stolen) task
1001	>	* Executes a non-top-level (stolen) task.
1002		*/
1003		final void runSubtask(ForkJoinTask<?> t) {
1004		if (t != null) {
1005		ForkJoinTask<?> ps = currentSteal;
1006	<	currentSteal = t;
1030	<	t.doExec();
1006	>	(currentSteal = t).doExec();
1007		currentSteal = ps;
1008		}
1009		}
1010
1011		/**
1012	<	* Computes next value for random probes. Scans don't require
1037	<	* a very high quality generator, but also not a crummy one.
1038	<	* Marsaglia xor-shift is cheap and works well enough. Note:
1039	<	* This is manually inlined in several usages in ForkJoinPool
1040	<	* to avoid writes inside busy scan loops.
1012	>	* Returns true if owned and not known to be blocked.
1013		*/
1014	<	final int nextSeed() {
1015	<	int r = seed;
1016	<	r ^= r << 13;
1017	<	r ^= r >>> 17;
1018	<	r ^= r << 5;
1019	<	return seed = r;
1014	>	final boolean isApparentlyUnblocked() {
1015	>	Thread wt; Thread.State s;
1016	>	return (eventCount >= 0 &&
1017	>	(wt = owner) != null &&
1018	>	(s = wt.getState()) != Thread.State.BLOCKED &&
1019	>	s != Thread.State.WAITING &&
1020	>	s != Thread.State.TIMED_WAITING);
1021		}
1022
1023		// Unsafe mechanics
1024		private static final sun.misc.Unsafe U;
1025	<	private static final long RUNSTATE;
1025	>	private static final long QLOCK;
1026		private static final int ABASE;
1027		private static final int ASHIFT;
1028		static {
#	Line 1058 \| Line 1031 \| public class ForkJoinPool extends Abstra
1031		U = getUnsafe();
1032		Class<?> k = WorkQueue.class;
1033		Class<?> ak = ForkJoinTask[].class;
1034	<	RUNSTATE = U.objectFieldOffset
1035	<	(k.getDeclaredField("runState"));
1034	>	QLOCK = U.objectFieldOffset
1035	>	(k.getDeclaredField("qlock"));
1036		ABASE = U.arrayBaseOffset(ak);
1037		s = U.arrayIndexScale(ak);
1038		} catch (Exception e) {
#	Line 1071 \| Line 1044 \| public class ForkJoinPool extends Abstra
1044		}
1045		}
1046
1047	+	// static fields (initialized in static initializer below)
1048	+
1049		/**
1050	<	* Class for artificial tasks that are used to replace the target
1051	<	* of local joins if they are removed from an interior queue slot
1077	<	* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
1078	<	* actually do anything beyond having a unique identity.
1050	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
1051	>	* overridden in ForkJoinPool constructors.
1052		*/
1053	<	static final class EmptyTask extends ForkJoinTask<Void> {
1054	<	EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
1082	<	public Void getRawResult() { return null; }
1083	<	public void setRawResult(Void x) {}
1084	<	public boolean exec() { return true; }
1085	<	}
1053	>	public static final ForkJoinWorkerThreadFactory
1054	>	defaultForkJoinWorkerThreadFactory;
1055
1056		/**
1057	<	* Computes a hash code for the given thread. This method is
1058	<	* expected to provide higher-quality hash codes than those using
1059	<	* method hashCode().
1057	>	* Per-thread submission bookkeeping. Shared across all pools
1058	>	* to reduce ThreadLocal pollution and because random motion
1059	>	* to avoid contention in one pool is likely to hold for others.
1060	>	* Lazily initialized on first submission (but null-checked
1061	>	* in other contexts to avoid unnecessary initialization).
1062		*/
1063	<	static final int hashThread(Thread t) {
1064	<	long id = (t == null) ? 0L : t.getId(); // Use MurmurHash of thread id
1065	<	int h = (int)id ^ (int)(id >>> 32);
1066	<	h ^= h >>> 16;
1067	<	h *= 0x85ebca6b;
1068	<	h ^= h >>> 13;
1069	<	h *= 0xc2b2ae35;
1070	<	return h ^ (h >>> 16);
1071	<	}
1063	>	static final ThreadLocal<Submitter> submitters;
1064	>
1065	>	/**
1066	>	* Permission required for callers of methods that may start or
1067	>	* kill threads.
1068	>	*/
1069	>	private static final RuntimePermission modifyThreadPermission;
1070	>
1071	>	/**
1072	>	* Common (static) pool. Non-null for public use unless a static
1073	>	* construction exception, but internal usages null-check on use
1074	>	* to paranoically avoid potential initialization circularities
1075	>	* as well as to simplify generated code.
1076	>	*/
1077	>	static final ForkJoinPool commonPool;
1078	>
1079	>	/**
1080	>	* Common pool parallelism. Must equal commonPool.parallelism.
1081	>	*/
1082	>	static final int commonPoolParallelism;
1083
1084		/**
1085	<	* Top-level runloop for workers
1085	>	* Sequence number for creating workerNamePrefix.
1086		*/
1087	<	final void runWorker(ForkJoinWorkerThread wt) {
1106	<	WorkQueue w = wt.workQueue;
1107	<	w.growArray(false); // Initialize queue array and seed in this thread
1108	<	w.seed = hashThread(Thread.currentThread()) \| (1 << 31); // force < 0
1087	>	private static int poolNumberSequence;
1088
1089	<	do {} while (w.runTask(scan(w)));
1089	>	/**
1090	>	* Return the next sequence number. We don't expect this to
1091	>	* ever contend so use simple builtin sync.
1092	>	*/
1093	>	private static final synchronized int nextPoolId() {
1094	>	return ++poolNumberSequence;
1095		}
1096
1097	<	// Creating, registering and deregistering workers
1097	>	// static constants
1098
1099		/**
1100	<	* Tries to create and start a worker
1100	>	* Initial timeout value (in nanoseconds) for the thread
1101	>	* triggering quiescence to park waiting for new work. On timeout,
1102	>	* the thread will instead try to shrink the number of
1103	>	* workers. The value should be large enough to avoid overly
1104	>	* aggressive shrinkage during most transient stalls (long GCs
1105	>	* etc).
1106		*/
1107	<	private void addWorker() {
1108	<	Throwable ex = null;
1109	<	ForkJoinWorkerThread w = null;
1110	<	try {
1111	<	if ((w = factory.newThread(this)) != null) {
1112	<	w.start();
1113	<	return;
1107	>	private static final long IDLE_TIMEOUT = 2000L * 1000L * 1000L; // 2sec
1108	>
1109	>	/**
1110	>	* Timeout value when there are more threads than parallelism level
1111	>	*/
1112	>	private static final long FAST_IDLE_TIMEOUT = 200L * 1000L * 1000L;
1113	>
1114	>	/**
1115	>	* Tolerance for idle timeouts, to cope with timer undershoots
1116	>	*/
1117	>	private static final long TIMEOUT_SLOP = 2000000L;
1118	>
1119	>	/**
1120	>	* The maximum stolen->joining link depth allowed in method
1121	>	* tryHelpStealer. Must be a power of two. Depths for legitimate
1122	>	* chains are unbounded, but we use a fixed constant to avoid
1123	>	* (otherwise unchecked) cycles and to bound staleness of
1124	>	* traversal parameters at the expense of sometimes blocking when
1125	>	* we could be helping.
1126	>	*/
1127	>	private static final int MAX_HELP = 64;
1128	>
1129	>	/**
1130	>	* Increment for seed generators. See class ThreadLocal for
1131	>	* explanation.
1132	>	*/
1133	>	private static final int SEED_INCREMENT = 0x61c88647;
1134	>
1135	>	/**
1136	>	* Bits and masks for control variables
1137	>	*
1138	>	* Field ctl is a long packed with:
1139	>	* AC: Number of active running workers minus target parallelism (16 bits)
1140	>	* TC: Number of total workers minus target parallelism (16 bits)
1141	>	* ST: true if pool is terminating (1 bit)
1142	>	* EC: the wait count of top waiting thread (15 bits)
1143	>	* ID: poolIndex of top of Treiber stack of waiters (16 bits)
1144	>	*
1145	>	* When convenient, we can extract the upper 32 bits of counts and
1146	>	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
1147	>	* (int)ctl. The ec field is never accessed alone, but always
1148	>	* together with id and st. The offsets of counts by the target
1149	>	* parallelism and the positionings of fields makes it possible to
1150	>	* perform the most common checks via sign tests of fields: When
1151	>	* ac is negative, there are not enough active workers, when tc is
1152	>	* negative, there are not enough total workers, and when e is
1153	>	* negative, the pool is terminating. To deal with these possibly
1154	>	* negative fields, we use casts in and out of "short" and/or
1155	>	* signed shifts to maintain signedness.
1156	>	*
1157	>	* When a thread is queued (inactivated), its eventCount field is
1158	>	* set negative, which is the only way to tell if a worker is
1159	>	* prevented from executing tasks, even though it must continue to
1160	>	* scan for them to avoid queuing races. Note however that
1161	>	* eventCount updates lag releases so usage requires care.
1162	>	*
1163	>	* Field plock is an int packed with:
1164	>	* SHUTDOWN: true if shutdown is enabled (1 bit)
1165	>	* SEQ: a sequence lock, with PL_LOCK bit set if locked (30 bits)
1166	>	* SIGNAL: set when threads may be waiting on the lock (1 bit)
1167	>	*
1168	>	* The sequence number enables simple consistency checks:
1169	>	* Staleness of read-only operations on the workQueues array can
1170	>	* be checked by comparing plock before vs after the reads.
1171	>	*/
1172	>
1173	>	// bit positions/shifts for fields
1174	>	private static final int AC_SHIFT = 48;
1175	>	private static final int TC_SHIFT = 32;
1176	>	private static final int ST_SHIFT = 31;
1177	>	private static final int EC_SHIFT = 16;
1178	>
1179	>	// bounds
1180	>	private static final int SMASK = 0xffff; // short bits
1181	>	private static final int MAX_CAP = 0x7fff; // max #workers - 1
1182	>	private static final int EVENMASK = 0xfffe; // even short bits
1183	>	private static final int SQMASK = 0x007e; // max 64 (even) slots
1184	>	private static final int SHORT_SIGN = 1 << 15;
1185	>	private static final int INT_SIGN = 1 << 31;
1186	>
1187	>	// masks
1188	>	private static final long STOP_BIT = 0x0001L << ST_SHIFT;
1189	>	private static final long AC_MASK = ((long)SMASK) << AC_SHIFT;
1190	>	private static final long TC_MASK = ((long)SMASK) << TC_SHIFT;
1191	>
1192	>	// units for incrementing and decrementing
1193	>	private static final long TC_UNIT = 1L << TC_SHIFT;
1194	>	private static final long AC_UNIT = 1L << AC_SHIFT;
1195	>
1196	>	// masks and units for dealing with u = (int)(ctl >>> 32)
1197	>	private static final int UAC_SHIFT = AC_SHIFT - 32;
1198	>	private static final int UTC_SHIFT = TC_SHIFT - 32;
1199	>	private static final int UAC_MASK = SMASK << UAC_SHIFT;
1200	>	private static final int UTC_MASK = SMASK << UTC_SHIFT;
1201	>	private static final int UAC_UNIT = 1 << UAC_SHIFT;
1202	>	private static final int UTC_UNIT = 1 << UTC_SHIFT;
1203	>
1204	>	// masks and units for dealing with e = (int)ctl
1205	>	private static final int E_MASK = 0x7fffffff; // no STOP_BIT
1206	>	private static final int E_SEQ = 1 << EC_SHIFT;
1207	>
1208	>	// plock bits
1209	>	private static final int SHUTDOWN = 1 << 31;
1210	>	private static final int PL_LOCK = 2;
1211	>	private static final int PL_SIGNAL = 1;
1212	>	private static final int PL_SPINS = 1 << 8;
1213	>
1214	>	// access mode for WorkQueue
1215	>	static final int LIFO_QUEUE = 0;
1216	>	static final int FIFO_QUEUE = 1;
1217	>	static final int SHARED_QUEUE = -1;
1218	>
1219	>	// bounds for #steps in scan loop -- must be power 2 minus 1
1220	>	private static final int MIN_SCAN = 0x1ff; // cover estimation slop
1221	>	private static final int MAX_SCAN = 0x1ffff; // 4 * max workers
1222	>
1223	>	// Instance fields
1224	>
1225	>	/*
1226	>	* Field layout of this class tends to matter more than one would
1227	>	* like. Runtime layout order is only loosely related to
1228	>	* declaration order and may differ across JVMs, but the following
1229	>	* empirically works OK on current JVMs.
1230	>	*/
1231	>
1232	>	// Heuristic padding to ameliorate unfortunate memory placements
1233	>	volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
1234	>
1235	>	volatile long stealCount; // collects worker counts
1236	>	volatile long ctl; // main pool control
1237	>	volatile int plock; // shutdown status and seqLock
1238	>	volatile int indexSeed; // worker/submitter index seed
1239	>	final int config; // mode and parallelism level
1240	>	WorkQueue[] workQueues; // main registry
1241	>	final ForkJoinWorkerThreadFactory factory;
1242	>	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1243	>	final String workerNamePrefix; // to create worker name string
1244	>
1245	>	volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
1246	>	volatile Object pad18, pad19, pad1a, pad1b;
1247	>
1248	>	/*
1249	>	* Acquires the plock lock to protect worker array and related
1250	>	* updates. This method is called only if an initial CAS on plock
1251	>	* fails. This acts as a spinLock for normal cases, but falls back
1252	>	* to builtin monitor to block when (rarely) needed. This would be
1253	>	* a terrible idea for a highly contended lock, but works fine as
1254	>	* a more conservative alternative to a pure spinlock.
1255	>	*/
1256	>	private int acquirePlock() {
1257	>	int spins = PL_SPINS, r = 0, ps, nps;
1258	>	for (;;) {
1259	>	if (((ps = plock) & PL_LOCK) == 0 &&
1260	>	U.compareAndSwapInt(this, PLOCK, ps, nps = ps + PL_LOCK))
1261	>	return nps;
1262	>	else if (r == 0) { // randomize spins if possible
1263	>	Thread t = Thread.currentThread(); WorkQueue w; Submitter z;
1264	>	if ((t instanceof ForkJoinWorkerThread) &&
1265	>	(w = ((ForkJoinWorkerThread)t).workQueue) != null)
1266	>	r = w.seed;
1267	>	else if ((z = submitters.get()) != null)
1268	>	r = z.seed;
1269	>	else
1270	>	r = 1;
1271	>	}
1272	>	else if (spins >= 0) {
1273	>	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1274	>	if (r >= 0)
1275	>	--spins;
1276	>	}
1277	>	else if (U.compareAndSwapInt(this, PLOCK, ps, ps \| PL_SIGNAL)) {
1278	>	synchronized (this) {
1279	>	if ((plock & PL_SIGNAL) != 0) {
1280	>	try {
1281	>	wait();
1282	>	} catch (InterruptedException ie) {
1283	>	try {
1284	>	Thread.currentThread().interrupt();
1285	>	} catch (SecurityException ignore) {
1286	>	}
1287	>	}
1288	>	}
1289	>	else
1290	>	notifyAll();
1291	>	}
1292		}
1126	–	} catch (Throwable e) {
1127	–	ex = e;
1293		}
1129	–	deregisterWorker(w, ex);
1294		}
1295
1296		/**
1297	<	* Callback from ForkJoinWorkerThread constructor to assign a
1298	<	* public name. This must be separate from registerWorker because
1135	<	* it is called during the "super" constructor call in
1136	<	* ForkJoinWorkerThread.
1297	>	* Unlocks and signals any thread waiting for plock. Called only
1298	>	* when CAS of seq value for unlock fails.
1299		*/
1300	<	final String nextWorkerName() {
1301	<	return workerNamePrefix.concat
1302	<	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1300	>	private void releasePlock(int ps) {
1301	>	plock = ps;
1302	>	synchronized (this) { notifyAll(); }
1303	>	}
1304	>
1305	>	/**
1306	>	* Performs secondary initialization, called when plock is zero.
1307	>	* Creates workQueue array and sets plock to a valid value. The
1308	>	* lock body must be exception-free (so no try/finally) so we
1309	>	* optimistically allocate new array outside the lock and throw
1310	>	* away if (very rarely) not needed. (A similar tactic is used in
1311	>	* fullExternalPush.) Because the plock seq value can eventually
1312	>	* wrap around zero, this method harmlessly fails to reinitialize
1313	>	* if workQueues exists, while still advancing plock.
1314	>	*
1315	>	* Additionally tries to create the first worker.
1316	>	*/
1317	>	private void initWorkers() {
1318	>	WorkQueue[] ws, nws; int ps;
1319	>	int p = config & SMASK; // find power of two table size
1320	>	int n = (p > 1) ? p - 1 : 1; // ensure at least 2 slots
1321	>	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4; n \|= n >>> 8; n \|= n >>> 16;
1322	>	n = (n + 1) << 1;
1323	>	if ((ws = workQueues) == null \|\| ws.length == 0)
1324	>	nws = new WorkQueue[n];
1325	>	else
1326	>	nws = null;
1327	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1328	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1329	>	ps = acquirePlock();
1330	>	if (((ws = workQueues) == null \|\| ws.length == 0) && nws != null)
1331	>	workQueues = nws;
1332	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1333	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1334	>	releasePlock(nps);
1335	>	tryAddWorker();
1336	>	}
1337	>
1338	>	/**
1339	>	* Tries to create and start one worker if fewer than target
1340	>	* parallelism level exist. Adjusts counts etc on failure.
1341	>	*/
1342	>	private void tryAddWorker() {
1343	>	long c; int u;
1344	>	while ((u = (int)((c = ctl) >>> 32)) < 0 &&
1345	>	(u & SHORT_SIGN) != 0 && (int)c == 0) {
1346	>	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) \|
1347	>	((u + UAC_UNIT) & UAC_MASK)) << 32;
1348	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1349	>	ForkJoinWorkerThreadFactory fac;
1350	>	Throwable ex = null;
1351	>	ForkJoinWorkerThread wt = null;
1352	>	try {
1353	>	if ((fac = factory) != null &&
1354	>	(wt = fac.newThread(this)) != null) {
1355	>	wt.start();
1356	>	break;
1357	>	}
1358	>	} catch (Throwable e) {
1359	>	ex = e;
1360	>	}
1361	>	deregisterWorker(wt, ex);
1362	>	break;
1363	>	}
1364	>	}
1365		}
1366
1367	+	// Registering and deregistering workers
1368	+
1369		/**
1370	<	* Callback from ForkJoinWorkerThread constructor to establish and
1371	<	* record its WorkQueue
1370	>	* Callback from ForkJoinWorkerThread to establish and record its
1371	>	* WorkQueue. To avoid scanning bias due to packing entries in
1372	>	* front of the workQueues array, we treat the array as a simple
1373	>	* power-of-two hash table using per-thread seed as hash,
1374	>	* expanding as needed.
1375		*
1376		* @param wt the worker thread
1377	+	* @return the worker's queue
1378		*/
1379	<	final void registerWorker(ForkJoinWorkerThread wt) {
1380	<	WorkQueue w = wt.workQueue;
1381	<	ReentrantLock lock = this.lock;
1382	<	lock.lock();
1379	>	final WorkQueue registerWorker(ForkJoinWorkerThread wt) {
1380	>	Thread.UncaughtExceptionHandler handler; WorkQueue[] ws; int s, ps;
1381	>	wt.setDaemon(true);
1382	>	if ((handler = ueh) != null)
1383	>	wt.setUncaughtExceptionHandler(handler);
1384	>	do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed,
1385	>	s += SEED_INCREMENT) \|\|
1386	>	s == 0); // skip 0
1387	>	WorkQueue w = new WorkQueue(this, wt, config >>> 16, s);
1388	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1389	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1390	>	ps = acquirePlock();
1391	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1392		try {
1393	<	int k = nextPoolIndex;
1394	<	WorkQueue[] ws = workQueues;
1395	<	if (ws != null) { // ignore on shutdown
1396	<	int n = ws.length;
1397	<	if (k < 0 \|\| (k & 1) == 0 \|\| k >= n \|\| ws[k] != null) {
1398	<	for (k = 1; k < n && ws[k] != null; k += 2)
1399	<	; // workers are at odd indices
1400	<	if (k >= n) // resize
1401	<	workQueues = ws = Arrays.copyOf(ws, n << 1);
1402	<	}
1403	<	w.poolIndex = k;
1404	<	w.eventCount = ~(k >>> 1) & SMASK; // Set up wait count
1405	<	ws[k] = w; // record worker
1406	<	nextPoolIndex = k + 2;
1407	<	int rs = runState;
1408	<	int m = rs & SMASK; // recalculate runState mask
1170	<	if (k > m)
1171	<	m = (m << 1) + 1;
1172	<	runState = (rs & SHUTDOWN) \| ((rs + RS_SEQ) & RS_SEQ_MASK) \| m;
1393	>	if ((ws = workQueues) != null) { // skip if shutting down
1394	>	int n = ws.length, m = n - 1;
1395	>	int r = (s << 1) \| 1; // use odd-numbered indices
1396	>	if (ws[r &= m] != null) { // collision
1397	>	int probes = 0; // step by approx half size
1398	>	int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2;
1399	>	while (ws[r = (r + step) & m] != null) {
1400	>	if (++probes >= n) {
1401	>	workQueues = ws = Arrays.copyOf(ws, n <<= 1);
1402	>	m = n - 1;
1403	>	probes = 0;
1404	>	}
1405	>	}
1406	>	}
1407	>	w.eventCount = w.poolIndex = r; // volatile write orders
1408	>	ws[r] = w;
1409		}
1410		} finally {
1411	<	lock.unlock();
1411	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1412	>	releasePlock(nps);
1413		}
1414	+	wt.setName(workerNamePrefix.concat(Integer.toString(w.poolIndex)));
1415	+	return w;
1416		}
1417
1418		/**
1419	<	* Final callback from terminating worker, as well as failure to
1420	<	* construct or start a worker in addWorker. Removes record of
1421	<	* worker from array, and adjusts counts. If pool is shutting
1422	<	* down, tries to complete termination.
1419	>	* Final callback from terminating worker, as well as upon failure
1420	>	* to construct or start a worker. Removes record of worker from
1421	>	* array, and adjusts counts. If pool is shutting down, tries to
1422	>	* complete termination.
1423		*
1424	<	* @param wt the worker thread or null if addWorker failed
1424	>	* @param wt the worker thread or null if construction failed
1425		* @param ex the exception causing failure, or null if none
1426		*/
1427		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1428		WorkQueue w = null;
1429		if (wt != null && (w = wt.workQueue) != null) {
1430	<	w.runState = -1; // ensure runState is set
1431	<	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1432	<	int idx = w.poolIndex;
1433	<	ReentrantLock lock = this.lock;
1434	<	lock.lock();
1435	<	try { // remove record from array
1430	>	int ps;
1431	>	w.qlock = -1; // ensure set
1432	>	long ns = w.nsteals, sc; // collect steal count
1433	>	do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
1434	>	sc = stealCount, sc + ns));
1435	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1436	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1437	>	ps = acquirePlock();
1438	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1439	>	try {
1440	>	int idx = w.poolIndex;
1441		WorkQueue[] ws = workQueues;
1442		if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1443	<	ws[nextPoolIndex = idx] = null;
1443	>	ws[idx] = null;
1444		} finally {
1445	<	lock.unlock();
1445	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1446	>	releasePlock(nps);
1447		}
1448		}
1449
1450	<	long c; // adjust ctl counts
1450	>	long c; // adjust ctl counts
1451		do {} while (!U.compareAndSwapLong
1452		(this, CTL, c = ctl, (((c - AC_UNIT) & AC_MASK) \|
1453		((c - TC_UNIT) & TC_MASK) \|
1454		(c & ~(AC_MASK\|TC_MASK)))));
1455
1456	<	if (!tryTerminate(false) && w != null) {
1457	<	w.cancelAll(); // cancel remaining tasks
1458	<	if (w.array != null) // suppress signal if never ran
1459	<	signalWork(); // wake up or create replacement
1456	>	if (!tryTerminate(false, false) && w != null && w.array != null) {
1457	>	w.cancelAll(); // cancel remaining tasks
1458	>	WorkQueue[] ws; WorkQueue v; Thread p; int u, i, e;
1459	>	while ((u = (int)((c = ctl) >>> 32)) < 0 && (e = (int)c) >= 0) {
1460	>	if (e > 0) { // activate or create replacement
1461	>	if ((ws = workQueues) == null \|\|
1462	>	(i = e & SMASK) >= ws.length \|\|
1463	>	(v = ws[i]) == null)
1464	>	break;
1465	>	long nc = (((long)(v.nextWait & E_MASK)) \|
1466	>	((long)(u + UAC_UNIT) << 32));
1467	>	if (v.eventCount != (e \| INT_SIGN))
1468	>	break;
1469	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1470	>	v.eventCount = (e + E_SEQ) & E_MASK;
1471	>	if ((p = v.parker) != null)
1472	>	U.unpark(p);
1473	>	break;
1474	>	}
1475	>	}
1476	>	else {
1477	>	if ((short)u < 0)
1478	>	tryAddWorker();
1479	>	break;
1480	>	}
1481	>	}
1482		}
1483	<
1484	<	if (ex != null) // rethrow
1485	<	U.throwException(ex);
1483	>	if (ex == null) // help clean refs on way out
1484	>	ForkJoinTask.helpExpungeStaleExceptions();
1485	>	else // rethrow
1486	>	ForkJoinTask.rethrow(ex);
1487		}
1488
1489	<
1222	<	// Maintaining ctl counts
1223	<
1224	<	/**
1225	<	* Increments active count; mainly called upon return from blocking
1226	<	*/
1227	<	final void incrementActiveCount() {
1228	<	long c;
1229	<	do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
1230	<	}
1489	>	// Submissions
1490
1491		/**
1492	<	* Activates or creates a worker
1493	<	*/
1494	<	final void signalWork() {
1495	<	/*
1496	<	* The while condition is true if: (there is are too few total
1497	<	* workers OR there is at least one waiter) AND (there are too
1498	<	* few active workers OR the pool is terminating). The value
1499	<	* of e distinguishes the remaining cases: zero (no waiters)
1500	<	* for create, negative if terminating (in which case do
1501	<	* nothing), else release a waiter. The secondary checks for
1502	<	* release (non-null array etc) can fail if the pool begins
1503	<	* terminating after the test, and don't impose any added cost
1504	<	* because JVMs must perform null and bounds checks anyway.
1505	<	*/
1506	<	long c; int e, u;
1507	<	while ((((e = (int)(c = ctl)) \| (u = (int)(c >>> 32))) &
1508	<	(INT_SIGN\|SHORT_SIGN)) == (INT_SIGN\|SHORT_SIGN)) {
1509	<	WorkQueue[] ws = workQueues; int i; WorkQueue w; Thread p;
1510	<	if (e == 0) { // add a new worker
1511	<	if (U.compareAndSwapLong
1512	<	(this, CTL, c, (long)(((u + UTC_UNIT) & UTC_MASK) \|
1513	<	((u + UAC_UNIT) & UAC_MASK)) << 32)) {
1255	<	addWorker();
1256	<	break;
1257	<	}
1258	<	}
1259	<	else if (e > 0 && ws != null &&
1260	<	(i = ((~e << 1) \| 1) & SMASK) < ws.length &&
1261	<	(w = ws[i]) != null &&
1262	<	w.eventCount == (e \| INT_SIGN)) {
1263	<	if (U.compareAndSwapLong
1264	<	(this, CTL, c, (((long)(w.nextWait & E_MASK)) \|
1265	<	((long)(u + UAC_UNIT) << 32)))) {
1266	<	w.eventCount = (e + E_SEQ) & E_MASK;
1267	<	if ((p = w.parker) != null)
1268	<	U.unpark(p); // release a waiting worker
1269	<	break;
1270	<	}
1492	>	* Unless shutting down, adds the given task to a submission queue
1493	>	* at submitter's current queue index (modulo submission
1494	>	* range). Only the most common path is directly handled in this
1495	>	* method. All others are relayed to fullExternalPush.
1496	>	*
1497	>	* @param task the task. Caller must ensure non-null.
1498	>	*/
1499	>	final void externalPush(ForkJoinTask<?> task) {
1500	>	WorkQueue[] ws; WorkQueue q; Submitter z; int m; ForkJoinTask<?>[] a;
1501	>	if ((z = submitters.get()) != null && plock > 0 &&
1502	>	(ws = workQueues) != null && (m = (ws.length - 1)) >= 0 &&
1503	>	(q = ws[m & z.seed & SQMASK]) != null &&
1504	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock
1505	>	int b = q.base, s = q.top, n, an;
1506	>	if ((a = q.array) != null && (an = a.length) > (n = s + 1 - b)) {
1507	>	int j = (((an - 1) & s) << ASHIFT) + ABASE;
1508	>	U.putOrderedObject(a, j, task);
1509	>	q.top = s + 1; // push on to deque
1510	>	q.qlock = 0;
1511	>	if (n <= 2)
1512	>	signalWork(q);
1513	>	return;
1514		}
1515	<	else
1273	<	break;
1515	>	q.qlock = 0;
1516		}
1517	+	fullExternalPush(task);
1518		}
1519
1520		/**
1521	<	* Tries to decrement active count (sometimes implicitly) and
1522	<	* possibly release or create a compensating worker in preparation
1523	<	* for blocking. Fails on contention or termination.
1524	<	*
1525	<	* @return true if the caller can block, else should recheck and retry
1526	<	*/
1527	<	final boolean tryCompensate() {
1528	<	WorkQueue[] ws; WorkQueue w; Thread p;
1529	<	int pc = parallelism, e, u, ac, tc, i;
1530	<	long c = ctl;
1531	<
1532	<	if ((e = (int)c) >= 0) {
1533	<	if ((ac = ((u = (int)(c >>> 32)) >> UAC_SHIFT)) <= 0 &&
1534	<	e != 0 && (ws = workQueues) != null &&
1535	<	(i = ((~e << 1) \| 1) & SMASK) < ws.length &&
1536	<	(w = ws[i]) != null) {
1537	<	if (w.eventCount == (e \| INT_SIGN) &&
1538	<	U.compareAndSwapLong
1539	<	(this, CTL, c, ((long)(w.nextWait & E_MASK) \|
1540	<	(c & (AC_MASK\|TC_MASK))))) {
1541	<	w.eventCount = (e + E_SEQ) & E_MASK;
1542	<	if ((p = w.parker) != null)
1543	<	U.unpark(p);
1544	<	return true; // release an idle worker
1521	>	* Full version of externalPush. This method is called, among
1522	>	* other times, upon the first submission of the first task to the
1523	>	* pool, so must perform secondary initialization (via
1524	>	* initWorkers). It also detects first submission by an external
1525	>	* thread by looking up its ThreadLocal, and creates a new shared
1526	>	* queue if the one at index if empty or contended. The plock lock
1527	>	* body must be exception-free (so no try/finally) so we
1528	>	* optimistically allocate new queues outside the lock and throw
1529	>	* them away if (very rarely) not needed.
1530	>	*/
1531	>	private void fullExternalPush(ForkJoinTask<?> task) {
1532	>	int r = 0; // random index seed
1533	>	for (Submitter z = submitters.get();;) {
1534	>	WorkQueue[] ws; WorkQueue q; int ps, m, k;
1535	>	if (z == null) {
1536	>	if (U.compareAndSwapInt(this, INDEXSEED, r = indexSeed,
1537	>	r += SEED_INCREMENT) && r != 0)
1538	>	submitters.set(z = new Submitter(r));
1539	>	}
1540	>	else if (r == 0) { // move to a different index
1541	>	r = z.seed;
1542	>	r ^= r << 13; // same xorshift as WorkQueues
1543	>	r ^= r >>> 17;
1544	>	z.seed = r ^ (r << 5);
1545	>	}
1546	>	else if ((ps = plock) < 0)
1547	>	throw new RejectedExecutionException();
1548	>	else if (ps == 0 \|\| (ws = workQueues) == null \|\|
1549	>	(m = ws.length - 1) < 0)
1550	>	initWorkers();
1551	>	else if ((q = ws[k = r & m & SQMASK]) != null) {
1552	>	if (q.qlock == 0 && U.compareAndSwapInt(q, QLOCK, 0, 1)) {
1553	>	ForkJoinTask<?>[] a = q.array;
1554	>	int s = q.top;
1555	>	boolean submitted = false;
1556	>	try { // locked version of push
1557	>	if ((a != null && a.length > s + 1 - q.base) \|\|
1558	>	(a = q.growArray()) != null) { // must presize
1559	>	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
1560	>	U.putOrderedObject(a, j, task);
1561	>	q.top = s + 1;
1562	>	submitted = true;
1563	>	}
1564	>	} finally {
1565	>	q.qlock = 0; // unlock
1566	>	}
1567	>	if (submitted) {
1568	>	signalWork(q);
1569	>	return;
1570	>	}
1571		}
1572	+	r = 0; // move on failure
1573		}
1574	<	else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) {
1575	<	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
1576	<	if (U.compareAndSwapLong(this, CTL, c, nc))
1577	<	return true; // no compensation needed
1578	<	}
1579	<	else if (tc + pc < MAX_ID) {
1580	<	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
1581	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1582	<	addWorker();
1583	<	return true; // create replacement
1314	<	}
1574	>	else if (((ps = plock) & PL_LOCK) == 0) { // create new queue
1575	>	q = new WorkQueue(this, null, SHARED_QUEUE, r);
1576	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1577	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1578	>	ps = acquirePlock();
1579	>	if ((ws = workQueues) != null && k < ws.length && ws[k] == null)
1580	>	ws[k] = q;
1581	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1582	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1583	>	releasePlock(nps);
1584		}
1585	+	else
1586	+	r = 0; // try elsewhere while lock held
1587		}
1317	–	return false;
1588		}
1589
1590	<	// Submissions
1590	>	// Maintaining ctl counts
1591
1592		/**
1593	<	* Unless shutting down, adds the given task to some submission
1324	<	* queue; using a randomly chosen queue index if the caller is a
1325	<	* ForkJoinWorkerThread, else one based on caller thread's hash
1326	<	* code. If no queue exists at the index, one is created. If the
1327	<	* queue is busy, another is chosen by sweeping through the queues
1328	<	* array.
1593	>	* Increments active count; mainly called upon return from blocking.
1594		*/
1595	<	private void doSubmit(ForkJoinTask<?> task) {
1596	<	if (task == null)
1597	<	throw new NullPointerException();
1333	<	Thread t = Thread.currentThread();
1334	<	int r = ((t instanceof ForkJoinWorkerThread) ?
1335	<	((ForkJoinWorkerThread)t).workQueue.nextSeed() : hashThread(t));
1336	<	for (;;) {
1337	<	int rs = runState, m = rs & SMASK;
1338	<	int j = r &= (m & ~1); // even numbered queues
1339	<	WorkQueue[] ws = workQueues;
1340	<	if (rs < 0 \|\| ws == null)
1341	<	throw new RejectedExecutionException(); // shutting down
1342	<	if (ws.length > m) { // consistency check
1343	<	for (WorkQueue q;;) { // circular sweep
1344	<	if (((q = ws[j]) != null \|\|
1345	<	(q = tryAddSharedQueue(j)) != null) &&
1346	<	q.trySharedPush(task)) {
1347	<	signalWork();
1348	<	return;
1349	<	}
1350	<	if ((j = (j + 2) & m) == r) {
1351	<	Thread.yield(); // all queues busy
1352	<	break;
1353	<	}
1354	<	}
1355	<	}
1356	<	}
1595	>	final void incrementActiveCount() {
1596	>	long c;
1597	>	do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
1598		}
1599
1600		/**
1601	<	* Tries to add and register a new queue at the given index.
1601	>	* Tries to create or activate a worker if too few are active.
1602		*
1603	<	* @param idx the workQueues array index to register the queue
1604	<	* @return the queue, or null if could not add because could
1605	<	* not acquire lock or idx is unusable
1606	<	*/
1607	<	private WorkQueue tryAddSharedQueue(int idx) {
1608	<	WorkQueue q = null;
1609	<	ReentrantLock lock = this.lock;
1610	<	if (idx >= 0 && (idx & 1) == 0 && !lock.isLocked()) {
1611	<	// create queue outside of lock but only if apparently free
1612	<	WorkQueue nq = new WorkQueue(null, SHARED_QUEUE);
1613	<	if (lock.tryLock()) {
1614	<	try {
1615	<	WorkQueue[] ws = workQueues;
1616	<	if (ws != null && idx < ws.length) {
1617	<	if ((q = ws[idx]) == null) {
1618	<	int rs; // update runState seq
1619	<	ws[idx] = q = nq;
1379	<	runState = (((rs = runState) & SHUTDOWN) \|
1380	<	((rs + RS_SEQ) & ~SHUTDOWN));
1381	<	}
1603	>	* @param q the (non-null) queue holding tasks to be signalled
1604	>	*/
1605	>	final void signalWork(WorkQueue q) {
1606	>	int hint = q.poolIndex;
1607	>	long c; int e, u, i, n; WorkQueue[] ws; WorkQueue w; Thread p;
1608	>	while ((u = (int)((c = ctl) >>> 32)) < 0) {
1609	>	if ((e = (int)c) > 0) {
1610	>	if ((ws = workQueues) != null && ws.length > (i = e & SMASK) &&
1611	>	(w = ws[i]) != null && w.eventCount == (e \| INT_SIGN)) {
1612	>	long nc = (((long)(w.nextWait & E_MASK)) \|
1613	>	((long)(u + UAC_UNIT) << 32));
1614	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1615	>	w.hint = hint;
1616	>	w.eventCount = (e + E_SEQ) & E_MASK;
1617	>	if ((p = w.parker) != null)
1618	>	U.unpark(p);
1619	>	break;
1620		}
1621	<	} finally {
1622	<	lock.unlock();
1621	>	if (q.top - q.base <= 0)
1622	>	break;
1623		}
1624	+	else
1625	+	break;
1626	+	}
1627	+	else {
1628	+	if ((short)u < 0)
1629	+	tryAddWorker();
1630	+	break;
1631		}
1632		}
1388	–	return q;
1633		}
1634
1635		// Scanning for tasks
1636
1637		/**
1638	+	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1639	+	*/
1640	+	final void runWorker(WorkQueue w) {
1641	+	w.growArray(); // allocate queue
1642	+	do { w.runTask(scan(w)); } while (w.qlock >= 0);
1643	+	}
1644	+
1645	+	/**
1646		* Scans for and, if found, returns one task, else possibly
1647		* inactivates the worker. This method operates on single reads of
1648	<	* volatile state and is designed to be re-invoked continuously in
1649	<	* part because it returns upon detecting inconsistencies,
1648	>	* volatile state and is designed to be re-invoked continuously,
1649	>	* in part because it returns upon detecting inconsistencies,
1650		* contention, or state changes that indicate possible success on
1651		* re-invocation.
1652		*
1653	<	* The scan searches for tasks across queues, randomly selecting
1654	<	* the first #queues probes, favoring steals 2:1 over submissions
1655	<	* (by exploiting even/odd indexing), and then performing a
1656	<	* circular sweep of all queues. The scan terminates upon either
1657	<	* finding a non-empty queue, or completing a full sweep. If the
1658	<	* worker is not inactivated, it takes and returns a task from
1659	<	* this queue. On failure to find a task, we take one of the
1660	<	* following actions, after which the caller will retry calling
1661	<	* this method unless terminated.
1662	<	*
1663	<	* * If not a complete sweep, try to release a waiting worker. If
1664	<	* the scan terminated because the worker is inactivated, then the
1413	<	* released worker will often be the calling worker, and it can
1414	<	* succeed obtaining a task on the next call. Or maybe it is
1415	<	* another worker, but with same net effect. Releasing in other
1416	<	* cases as well ensures that we have enough workers running.
1417	<	*
1418	<	* * If the caller has run a task since the the last empty scan,
1419	<	* return (to allow rescan) if other workers are not also yet
1420	<	* enqueued. Field WorkQueue.rescans counts down on each scan to
1421	<	* ensure eventual inactivation, and occasional calls to
1422	<	* Thread.yield to help avoid interference with more useful
1423	<	* activities on the system.
1653	>	* The scan searches for tasks across queues (starting at a random
1654	>	* index, and relying on registerWorker to irregularly scatter
1655	>	* them within array to avoid bias), checking each at least twice.
1656	>	* The scan terminates upon either finding a non-empty queue, or
1657	>	* completing the sweep. If the worker is not inactivated, it
1658	>	* takes and returns a task from this queue. Otherwise, if not
1659	>	* activated, it signals workers (that may include itself) and
1660	>	* returns so caller can retry. Also returns for true if the
1661	>	* worker array may have changed during an empty scan. On failure
1662	>	* to find a task, we take one of the following actions, after
1663	>	* which the caller will retry calling this method unless
1664	>	* terminated.
1665		*
1666	<	* * If pool is terminating, terminate the worker
1666	>	* * If pool is terminating, terminate the worker.
1667		*
1668		* * If not already enqueued, try to inactivate and enqueue the
1669	<	* worker on wait queue.
1669	>	* worker on wait queue. Or, if inactivating has caused the pool
1670	>	* to be quiescent, relay to idleAwaitWork to possibly shrink
1671	>	* pool.
1672	>	*
1673	>	* * If already enqueued and none of the above apply, possibly
1674	>	* park awaiting signal, else lingering to help scan and signal.
1675		*
1676	<	* * If already enqueued and none of the above apply, either park
1677	<	* awaiting signal, or if this is the most recent waiter and pool
1432	<	* is quiescent, relay to idleAwaitWork to check for termination
1433	<	* and possibly shrink pool.
1676	>	* * If a non-empty queue discovered or left as a hint,
1677	>	* help wake up other workers before return
1678		*
1679		* @param w the worker (via its WorkQueue)
1680	<	* @return a task or null of none found
1680	>	* @return a task or null if none found
1681		*/
1682		private final ForkJoinTask<?> scan(WorkQueue w) {
1683	<	boolean swept = false; // true after full empty scan
1684	<	WorkQueue[] ws; // volatile read order matters
1685	<	int r = w.seed, ec = w.eventCount; // ec is negative if inactive
1686	<	int rs = runState, m = rs & SMASK;
1687	<	if ((ws = workQueues) != null && ws.length > m) {
1688	<	ForkJoinTask<?> task = null;
1689	<	for (int k = 0, j = -2 - m; ; ++j) {
1690	<	WorkQueue q; int b;
1691	<	if (j < 0) { // random probes while j negative
1692	<	r ^= r << 13; r ^= r >>> 17; k = (r ^= r << 5) \| (j & 1);
1693	<	} // worker (not submit) for odd j
1694	<	else // cyclic scan when j >= 0
1695	<	k += (m >>> 1) \| 1; // step by half to reduce bias
1696	<
1697	<	if ((q = ws[k & m]) != null && (b = q.base) - q.top < 0) {
1698	<	if (ec >= 0)
1699	<	task = q.pollAt(b); // steal
1700	<	break;
1683	>	WorkQueue[] ws; int m;
1684	>	int ps = plock; // read plock before ws
1685	>	if (w != null && (ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1686	>	int ec = w.eventCount; // ec is negative if inactive
1687	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1688	>	w.hint = -1; // update seed and clear hint
1689	>	int j = ((m + m + 1) \| MIN_SCAN) & MAX_SCAN;
1690	>	do {
1691	>	WorkQueue q; ForkJoinTask<?>[] a; int b;
1692	>	if ((q = ws[(r + j) & m]) != null && (b = q.base) - q.top < 0 &&
1693	>	(a = q.array) != null) { // probably nonempty
1694	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1695	>	ForkJoinTask<?> t = (ForkJoinTask<?>)
1696	>	U.getObjectVolatile(a, i);
1697	>	if (q.base == b && ec >= 0 && t != null &&
1698	>	U.compareAndSwapObject(a, i, t, null)) {
1699	>	if ((q.base = b + 1) - q.top < 0)
1700	>	signalWork(q);
1701	>	return t; // taken
1702	>	}
1703	>	else if ((ec < 0 \|\| j < m) && (int)(ctl >> AC_SHIFT) <= 0) {
1704	>	w.hint = (r + j) & m; // help signal below
1705	>	break; // cannot take
1706	>	}
1707		}
1708	<	else if (j > m) {
1709	<	if (rs == runState) // staleness check
1710	<	swept = true;
1711	<	break;
1708	>	} while (--j >= 0);
1709	>
1710	>	int h, e, ns; long c, sc; WorkQueue q;
1711	>	if ((ns = w.nsteals) != 0) {
1712	>	if (U.compareAndSwapLong(this, STEALCOUNT,
1713	>	sc = stealCount, sc + ns))
1714	>	w.nsteals = 0; // collect steals and rescan
1715	>	}
1716	>	else if (plock != ps) // consistency check
1717	>	; // skip
1718	>	else if ((e = (int)(c = ctl)) < 0)
1719	>	w.qlock = -1; // pool is terminating
1720	>	else {
1721	>	if ((h = w.hint) < 0) {
1722	>	if (ec >= 0) { // try to enqueue/inactivate
1723	>	long nc = (((long)ec \|
1724	>	((c - AC_UNIT) & (AC_MASK\|TC_MASK))));
1725	>	w.nextWait = e; // link and mark inactive
1726	>	w.eventCount = ec \| INT_SIGN;
1727	>	if (ctl != c \|\| !U.compareAndSwapLong(this, CTL, c, nc))
1728	>	w.eventCount = ec; // unmark on CAS failure
1729	>	else if ((int)(c >> AC_SHIFT) == 1 - (config & SMASK))
1730	>	idleAwaitWork(w, nc, c);
1731	>	}
1732	>	else if (w.eventCount < 0 && !tryTerminate(false, false) &&
1733	>	ctl == c) { // block
1734	>	Thread wt = Thread.currentThread();
1735	>	Thread.interrupted(); // clear status
1736	>	U.putObject(wt, PARKBLOCKER, this);
1737	>	w.parker = wt; // emulate LockSupport.park
1738	>	if (w.eventCount < 0) // recheck
1739	>	U.park(false, 0L);
1740	>	w.parker = null;
1741	>	U.putObject(wt, PARKBLOCKER, null);
1742	>	}
1743	>	}
1744	>	if ((h >= 0 \|\| (h = w.hint) >= 0) &&
1745	>	(ws = workQueues) != null && h < ws.length &&
1746	>	(q = ws[h]) != null) { // signal others before retry
1747	>	WorkQueue v; Thread p; int u, i, s;
1748	>	for (int n = (config & SMASK) >>> 1;;) {
1749	>	int idleCount = (w.eventCount < 0) ? 0 : -1;
1750	>	if (((s = idleCount - q.base + q.top) <= n &&
1751	>	(n = s) <= 0) \|\|
1752	>	(u = (int)((c = ctl) >>> 32)) >= 0 \|\|
1753	>	(e = (int)c) <= 0 \|\| m < (i = e & SMASK) \|\|
1754	>	(v = ws[i]) == null)
1755	>	break;
1756	>	long nc = (((long)(v.nextWait & E_MASK)) \|
1757	>	((long)(u + UAC_UNIT) << 32));
1758	>	if (v.eventCount != (e \| INT_SIGN) \|\|
1759	>	!U.compareAndSwapLong(this, CTL, c, nc))
1760	>	break;
1761	>	v.hint = h;
1762	>	v.eventCount = (e + E_SEQ) & E_MASK;
1763	>	if ((p = v.parker) != null)
1764	>	U.unpark(p);
1765	>	if (--n <= 0)
1766	>	break;
1767	>	}
1768		}
1463	–	}
1464	–	w.seed = r; // save seed for next scan
1465	–	if (task != null)
1466	–	return task;
1467	–	}
1468	–
1469	–	// Decode ctl on empty scan
1470	–	long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
1471	–	if (!swept) { // try to release a waiter
1472	–	WorkQueue v; Thread p;
1473	–	if (e > 0 && a < 0 && ws != null &&
1474	–	(v = ws[((~e << 1) \| 1) & m]) != null &&
1475	–	v.eventCount == (e \| INT_SIGN) && U.compareAndSwapLong
1476	–	(this, CTL, c, ((long)(v.nextWait & E_MASK) \|
1477	–	((c + AC_UNIT) & (AC_MASK\|TC_MASK))))) {
1478	–	v.eventCount = (e + E_SEQ) & E_MASK;
1479	–	if ((p = v.parker) != null)
1480	–	U.unpark(p);
1481	–	}
1482	–	}
1483	–	else if ((nr = w.rescans) > 0) { // continue rescanning
1484	–	int ac = a + parallelism;
1485	–	if ((w.rescans = (ac < nr) ? ac : nr - 1) > 0 && w.seed < 0 &&
1486	–	w.eventCount == ec)
1487	–	Thread.yield(); // 1 bit randomness for yield call
1488	–	}
1489	–	else if (e < 0) // pool is terminating
1490	–	w.runState = -1;
1491	–	else if (ec >= 0) { // try to enqueue
1492	–	long nc = (long)ec \| ((c - AC_UNIT) & (AC_MASK\|TC_MASK));
1493	–	w.nextWait = e;
1494	–	w.eventCount = ec \| INT_SIGN; // mark as inactive
1495	–	if (!U.compareAndSwapLong(this, CTL, c, nc))
1496	–	w.eventCount = ec; // back out on CAS failure
1497	–	else if ((ns = w.nsteals) != 0) { // set rescans if ran task
1498	–	if (a <= 0) // ... unless too many active
1499	–	w.rescans = a + parallelism;
1500	–	w.nsteals = 0;
1501	–	w.totalSteals += ns;
1502	–	}
1503	–	}
1504	–	else{ // already queued
1505	–	if (parallelism == -a)
1506	–	idleAwaitWork(w); // quiescent
1507	–	if (w.eventCount == ec) {
1508	–	Thread.interrupted(); // clear status
1509	–	ForkJoinWorkerThread wt = w.owner;
1510	–	U.putObject(wt, PARKBLOCKER, this);
1511	–	w.parker = wt; // emulate LockSupport.park
1512	–	if (w.eventCount == ec) // recheck
1513	–	U.park(false, 0L); // block
1514	–	w.parker = null;
1515	–	U.putObject(wt, PARKBLOCKER, null);
1769		}
1770		}
1771		return null;
1772		}
1773
1774		/**
1775	<	* If inactivating worker w has caused pool to become quiescent,
1776	<	* check for pool termination, and, so long as this is not the
1777	<	* only worker, wait for event for up to SHRINK_RATE nanosecs On
1778	<	* timeout, if ctl has not changed, terminate the worker, which
1779	<	* will in turn wake up another worker to possibly repeat this
1780	<	* process.
1775	>	* If inactivating worker w has caused the pool to become
1776	>	* quiescent, checks for pool termination, and, so long as this is
1777	>	* not the only worker, waits for event for up to a given
1778	>	* duration. On timeout, if ctl has not changed, terminates the
1779	>	* worker, which will in turn wake up another worker to possibly
1780	>	* repeat this process.
1781		*
1782		* @param w the calling worker
1783	+	* @param currentCtl the ctl value triggering possible quiescence
1784	+	* @param prevCtl the ctl value to restore if thread is terminated
1785		*/
1786	<	private void idleAwaitWork(WorkQueue w) {
1787	<	long c; int nw, ec;
1788	<	if (!tryTerminate(false) &&
1789	<	(int)((c = ctl) >> AC_SHIFT) + parallelism == 0 &&
1790	<	(ec = w.eventCount) == ((int)c \| INT_SIGN) &&
1791	<	(nw = w.nextWait) != 0) {
1792	<	long nc = ((long)(nw & E_MASK) \| // ctl to restore on timeout
1793	<	((c + AC_UNIT) & AC_MASK) \| (c & TC_MASK));
1539	<	ForkJoinTask.helpExpungeStaleExceptions(); // help clean
1540	<	ForkJoinWorkerThread wt = w.owner;
1541	<	while (ctl == c) {
1542	<	long startTime = System.nanoTime();
1786	>	private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1787	>	if (w != null && w.eventCount < 0 &&
1788	>	!tryTerminate(false, false) && (int)prevCtl != 0) {
1789	>	int dc = -(short)(currentCtl >>> TC_SHIFT);
1790	>	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1791	>	long deadline = System.nanoTime() + parkTime - TIMEOUT_SLOP;
1792	>	Thread wt = Thread.currentThread();
1793	>	while (ctl == currentCtl) {
1794		Thread.interrupted(); // timed variant of version in scan()
1795		U.putObject(wt, PARKBLOCKER, this);
1796		w.parker = wt;
1797	<	if (ctl == c)
1798	<	U.park(false, SHRINK_RATE);
1797	>	if (ctl == currentCtl)
1798	>	U.park(false, parkTime);
1799		w.parker = null;
1800		U.putObject(wt, PARKBLOCKER, null);
1801	<	if (ctl != c)
1801	>	if (ctl != currentCtl)
1802		break;
1803	<	if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
1804	<	U.compareAndSwapLong(this, CTL, c, nc)) {
1805	<	w.runState = -1; // shrink
1806	<	w.eventCount = (ec + E_SEQ) \| E_MASK;
1803	>	if (deadline - System.nanoTime() <= 0L &&
1804	>	U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1805	>	w.eventCount = (w.eventCount + E_SEQ) \| E_MASK;
1806	>	w.qlock = -1; // shrink
1807		break;
1808		}
1809		}
#	Line 1560 \| Line 1811 \| public class ForkJoinPool extends Abstra
1811		}
1812
1813		/**
1814	+	* Scans through queues looking for work while joining a task; if
1815	+	* any present, signals. May return early if more signalling is
1816	+	* detectably unneeded.
1817	+	*
1818	+	* @param task return early if done
1819	+	* @param origin an index to start scan
1820	+	*/
1821	+	private void helpSignal(ForkJoinTask<?> task, int origin) {
1822	+	WorkQueue[] ws; WorkQueue w; Thread p; long c; int m, u, e, i, s;
1823	+	if (task != null && task.status >= 0 &&
1824	+	(u = (int)(ctl >>> 32)) < 0 && (u >> UAC_SHIFT) < 0 &&
1825	+	(ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1826	+	outer: for (int k = origin, j = m; j >= 0; --j) {
1827	+	WorkQueue q = ws[k++ & m];
1828	+	for (int n = m;;) { // limit to at most m signals
1829	+	if (task.status < 0)
1830	+	break outer;
1831	+	if (q == null \|\|
1832	+	((s = -q.base + q.top) <= n && (n = s) <= 0))
1833	+	break;
1834	+	if ((u = (int)((c = ctl) >>> 32)) >= 0 \|\|
1835	+	(e = (int)c) <= 0 \|\| m < (i = e & SMASK) \|\|
1836	+	(w = ws[i]) == null)
1837	+	break outer;
1838	+	long nc = (((long)(w.nextWait & E_MASK)) \|
1839	+	((long)(u + UAC_UNIT) << 32));
1840	+	if (w.eventCount != (e \| INT_SIGN))
1841	+	break outer;
1842	+	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1843	+	w.eventCount = (e + E_SEQ) & E_MASK;
1844	+	if ((p = w.parker) != null)
1845	+	U.unpark(p);
1846	+	if (--n <= 0)
1847	+	break;
1848	+	}
1849	+	}
1850	+	}
1851	+	}
1852	+	}
1853	+
1854	+	/**
1855		* Tries to locate and execute tasks for a stealer of the given
1856		* task, or in turn one of its stealers, Traces currentSteal ->
1857		* currentJoin links looking for a thread working on a descendant
#	Line 1570 \| Line 1862 \| public class ForkJoinPool extends Abstra
1862		* leaves hints in workers to speed up subsequent calls. The
1863		* implementation is very branchy to cope with potential
1864		* inconsistencies or loops encountering chains that are stale,
1865	<	* unknown, or of length greater than MAX_HELP_DEPTH links. All
1574	<	* of these cases are dealt with by just retrying by caller.
1865	>	* unknown, or so long that they are likely cyclic.
1866		*
1867		* @param joiner the joining worker
1868		* @param task the task to join
1869	<	* @return true if found or ran a task (and so is immediately retryable)
1869	>	* @return 0 if no progress can be made, negative if task
1870	>	* known complete, else positive
1871		*/
1872	<	final boolean tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1873	<	ForkJoinTask<?> subtask; // current target
1874	<	boolean progress = false;
1875	<	int depth = 0; // current chain depth
1876	<	int m = runState & SMASK;
1877	<	WorkQueue[] ws = workQueues;
1878	<
1879	<	if (ws != null && ws.length > m && (subtask = task).status >= 0) {
1880	<	outer:for (WorkQueue j = joiner;;) {
1881	<	// Try to find the stealer of subtask, by first using hint
1882	<	WorkQueue stealer = null;
1883	<	WorkQueue v = ws[j.stealHint & m];
1884	<	if (v != null && v.currentSteal == subtask)
1885	<	stealer = v;
1886	<	else {
1887	<	for (int i = 1; i <= m; i += 2) {
1888	<	if ((v = ws[i]) != null && v.currentSteal == subtask) {
1889	<	stealer = v;
1890	<	j.stealHint = i; // save hint
1891	<	break;
1872	>	private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1873	>	int stat = 0, steps = 0; // bound to avoid cycles
1874	>	if (joiner != null && task != null) { // hoist null checks
1875	>	restart: for (;;) {
1876	>	ForkJoinTask<?> subtask = task; // current target
1877	>	for (WorkQueue j = joiner, v;;) { // v is stealer of subtask
1878	>	WorkQueue[] ws; int m, s, h;
1879	>	if ((s = task.status) < 0) {
1880	>	stat = s;
1881	>	break restart;
1882	>	}
1883	>	if ((ws = workQueues) == null \|\| (m = ws.length - 1) <= 0)
1884	>	break restart; // shutting down
1885	>	if ((v = ws[h = (j.hint \| 1) & m]) == null \|\|
1886	>	v.currentSteal != subtask) {
1887	>	for (int origin = h;;) { // find stealer
1888	>	if (((h = (h + 2) & m) & 15) == 1 &&
1889	>	(subtask.status < 0 \|\| j.currentJoin != subtask))
1890	>	continue restart; // occasional staleness check
1891	>	if ((v = ws[h]) != null &&
1892	>	v.currentSteal == subtask) {
1893	>	j.hint = h; // save hint
1894	>	break;
1895	>	}
1896	>	if (h == origin)
1897	>	break restart; // cannot find stealer
1898	>	}
1899	>	}
1900	>	for (;;) { // help stealer or descend to its stealer
1901	>	ForkJoinTask[] a; int b;
1902	>	if (subtask.status < 0) // surround probes with
1903	>	continue restart; // consistency checks
1904	>	if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
1905	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1906	>	ForkJoinTask<?> t =
1907	>	(ForkJoinTask<?>)U.getObjectVolatile(a, i);
1908	>	if (subtask.status < 0 \|\| j.currentJoin != subtask \|\|
1909	>	v.currentSteal != subtask)
1910	>	continue restart; // stale
1911	>	stat = 1; // apparent progress
1912	>	if (t != null && v.base == b &&
1913	>	U.compareAndSwapObject(a, i, t, null)) {
1914	>	v.base = b + 1; // help stealer
1915	>	joiner.runSubtask(t);
1916	>	}
1917	>	else if (v.base == b && ++steps == MAX_HELP)
1918	>	break restart; // v apparently stalled
1919	>	}
1920	>	else { // empty -- try to descend
1921	>	ForkJoinTask<?> next = v.currentJoin;
1922	>	if (subtask.status < 0 \|\| j.currentJoin != subtask \|\|
1923	>	v.currentSteal != subtask)
1924	>	continue restart; // stale
1925	>	else if (next == null \|\| ++steps == MAX_HELP)
1926	>	break restart; // dead-end or maybe cyclic
1927	>	else {
1928	>	subtask = next;
1929	>	j = v;
1930	>	break;
1931	>	}
1932		}
1933		}
1934	<	if (stealer == null)
1934	>	}
1935	>	}
1936	>	}
1937	>	return stat;
1938	>	}
1939	>
1940	>	/**
1941	>	* Analog of tryHelpStealer for CountedCompleters. Tries to steal
1942	>	* and run tasks within the target's computation.
1943	>	*
1944	>	* @param task the task to join
1945	>	* @param mode if shared, exit upon completing any task
1946	>	* if all workers are active
1947	>	*
1948	>	*/
1949	>	private int helpComplete(ForkJoinTask<?> task, int mode) {
1950	>	WorkQueue[] ws; WorkQueue q; int m, n, s, u;
1951	>	if (task != null && (ws = workQueues) != null &&
1952	>	(m = ws.length - 1) >= 0) {
1953	>	for (int j = 1, origin = j;;) {
1954	>	if ((s = task.status) < 0)
1955	>	return s;
1956	>	if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) {
1957	>	origin = j;
1958	>	if (mode == SHARED_QUEUE &&
1959	>	((u = (int)(ctl >>> 32)) >= 0 \|\| (u >> UAC_SHIFT) >= 0))
1960		break;
1961		}
1962	+	else if ((j = (j + 2) & m) == origin)
1963	+	break;
1964	+	}
1965	+	}
1966	+	return 0;
1967	+	}
1968
1969	<	for (WorkQueue q = stealer;;) { // Try to help stealer
1970	<	ForkJoinTask<?> t; int b;
1971	<	if (task.status < 0)
1972	<	break outer;
1973	<	if ((b = q.base) - q.top < 0) {
1974	<	progress = true;
1975	<	if (subtask.status < 0)
1976	<	break outer; // stale
1977	<	if ((t = q.pollAt(b)) != null) {
1978	<	stealer.stealHint = joiner.poolIndex;
1979	<	joiner.runSubtask(t);
1969	>	/**
1970	>	* Tries to decrement active count (sometimes implicitly) and
1971	>	* possibly release or create a compensating worker in preparation
1972	>	* for blocking. Fails on contention or termination. Otherwise,
1973	>	* adds a new thread if no idle workers are available and pool
1974	>	* may become starved.
1975	>	*/
1976	>	final boolean tryCompensate() {
1977	>	int pc = config & SMASK, e, i, tc; long c;
1978	>	WorkQueue[] ws; WorkQueue w; Thread p;
1979	>	if ((ws = workQueues) != null && (e = (int)(c = ctl)) >= 0) {
1980	>	if (e != 0 && (i = e & SMASK) < ws.length &&
1981	>	(w = ws[i]) != null && w.eventCount == (e \| INT_SIGN)) {
1982	>	long nc = ((long)(w.nextWait & E_MASK) \|
1983	>	(c & (AC_MASK\|TC_MASK)));
1984	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1985	>	w.eventCount = (e + E_SEQ) & E_MASK;
1986	>	if ((p = w.parker) != null)
1987	>	U.unpark(p);
1988	>	return true; // replace with idle worker
1989	>	}
1990	>	}
1991	>	else if ((tc = (short)(c >>> TC_SHIFT)) >= 0 &&
1992	>	(int)(c >> AC_SHIFT) + pc > 1) {
1993	>	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
1994	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1995	>	return true; // no compensation
1996	>	}
1997	>	else if (tc + pc < MAX_CAP) {
1998	>	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
1999	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
2000	>	ForkJoinWorkerThreadFactory fac;
2001	>	Throwable ex = null;
2002	>	ForkJoinWorkerThread wt = null;
2003	>	try {
2004	>	if ((fac = factory) != null &&
2005	>	(wt = fac.newThread(this)) != null) {
2006	>	wt.start();
2007	>	return true;
2008		}
2009	+	} catch (Throwable rex) {
2010	+	ex = rex;
2011		}
2012	<	else { // empty - try to descend to find stealer's stealer
1620	<	ForkJoinTask<?> next = stealer.currentJoin;
1621	<	if (++depth == MAX_HELP_DEPTH \|\| subtask.status < 0 \|\|
1622	<	next == null \|\| next == subtask)
1623	<	break outer; // max depth, stale, dead-end, cyclic
1624	<	subtask = next;
1625	<	j = stealer;
1626	<	break;
1627	<	}
2012	>	deregisterWorker(wt, ex); // clean up and return false
2013		}
2014		}
2015		}
2016	<	return progress;
2016	>	return false;
2017		}
2018
2019		/**
2020	<	* If task is at base of some steal queue, steals and executes it.
2020	>	* Helps and/or blocks until the given task is done.
2021		*
2022		* @param joiner the joining worker
2023		* @param task the task
2024	+	* @return task status on exit
2025		*/
2026	<	final void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
2027	<	WorkQueue[] ws;
2028	<	int m = runState & SMASK;
2029	<	if ((ws = workQueues) != null && ws.length > m) {
2030	<	for (int j = 1; j <= m && task.status >= 0; j += 2) {
2031	<	WorkQueue q = ws[j];
2032	<	if (q != null && q.pollFor(task)) {
2033	<	joiner.runSubtask(task);
2034	<	break;
2026	>	final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
2027	>	int s = 0;
2028	>	if (joiner != null && task != null && (s = task.status) >= 0) {
2029	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2030	>	joiner.currentJoin = task;
2031	>	do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
2032	>	joiner.tryRemoveAndExec(task)); // process local tasks
2033	>	if (s >= 0 && (s = task.status) >= 0) {
2034	>	helpSignal(task, joiner.poolIndex);
2035	>	if ((s = task.status) >= 0 &&
2036	>	(task instanceof CountedCompleter))
2037	>	s = helpComplete(task, LIFO_QUEUE);
2038	>	}
2039	>	while (s >= 0 && (s = task.status) >= 0) {
2040	>	if ((!joiner.isEmpty() \|\| // try helping
2041	>	(s = tryHelpStealer(joiner, task)) == 0) &&
2042	>	(s = task.status) >= 0) {
2043	>	helpSignal(task, joiner.poolIndex);
2044	>	if ((s = task.status) >= 0 && tryCompensate()) {
2045	>	if (task.trySetSignal() && (s = task.status) >= 0) {
2046	>	synchronized (task) {
2047	>	if (task.status >= 0) {
2048	>	try { // see ForkJoinTask
2049	>	task.wait(); // for explanation
2050	>	} catch (InterruptedException ie) {
2051	>	}
2052	>	}
2053	>	else
2054	>	task.notifyAll();
2055	>	}
2056	>	}
2057	>	long c; // re-activate
2058	>	do {} while (!U.compareAndSwapLong
2059	>	(this, CTL, c = ctl, c + AC_UNIT));
2060	>	}
2061		}
2062		}
2063	+	joiner.currentJoin = prevJoin;
2064		}
2065	+	return s;
2066		}
2067
2068		/**
2069	<	* Returns a non-empty steal queue, if one is found during a random,
2070	<	* then cyclic scan, else null. This method must be retried by
2071	<	* caller if, by the time it tries to use the queue, it is empty.
2069	>	* Stripped-down variant of awaitJoin used by timed joins. Tries
2070	>	* to help join only while there is continuous progress. (Caller
2071	>	* will then enter a timed wait.)
2072	>	*
2073	>	* @param joiner the joining worker
2074	>	* @param task the task
2075		*/
2076	<	private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
2077	<	int r = w.seed; // Same idea as scan(), but ignoring submissions
2076	>	final void helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
2077	>	int s;
2078	>	if (joiner != null && task != null && (s = task.status) >= 0) {
2079	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2080	>	joiner.currentJoin = task;
2081	>	do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
2082	>	joiner.tryRemoveAndExec(task));
2083	>	if (s >= 0 && (s = task.status) >= 0) {
2084	>	helpSignal(task, joiner.poolIndex);
2085	>	if ((s = task.status) >= 0 &&
2086	>	(task instanceof CountedCompleter))
2087	>	s = helpComplete(task, LIFO_QUEUE);
2088	>	}
2089	>	if (s >= 0 && joiner.isEmpty()) {
2090	>	do {} while (task.status >= 0 &&
2091	>	tryHelpStealer(joiner, task) > 0);
2092	>	}
2093	>	joiner.currentJoin = prevJoin;
2094	>	}
2095	>	}
2096	>
2097	>	/**
2098	>	* Returns a (probably) non-empty steal queue, if one is found
2099	>	* during a random, then cyclic scan, else null. This method must
2100	>	* be retried by caller if, by the time it tries to use the queue,
2101	>	* it is empty.
2102	>	* @param r a (random) seed for scanning
2103	>	*/
2104	>	private WorkQueue findNonEmptyStealQueue(int r) {
2105		for (WorkQueue[] ws;;) {
2106	<	int m = runState & SMASK;
2107	<	if ((ws = workQueues) == null)
2106	>	int ps = plock, m;
2107	>	if ((ws = workQueues) == null \|\| (m = ws.length - 1) < 1)
2108		return null;
2109	<	if (ws.length > m) {
2110	<	WorkQueue q;
2111	<	for (int n = m << 2, k = r, j = -n;;) {
2112	<	r ^= r << 13; r ^= r >>> 17; r ^= r << 5;
2113	<	if ((q = ws[(k \| 1) & m]) != null && q.base - q.top < 0) {
2114	<	w.seed = r;
1671	<	return q;
1672	<	}
1673	<	else if (j > n)
2109	>	for (int j = (m + 1) << 2; ;) {
2110	>	WorkQueue q = ws[(((r + j) << 1) \| 1) & m];
2111	>	if (q != null && q.base - q.top < 0)
2112	>	return q;
2113	>	else if (--j < 0) {
2114	>	if (plock == ps)
2115		return null;
2116	<	else
1676	<	k = (j++ < 0) ? r : k + ((m >>> 1) \| 1);
1677	<
2116	>	break;
2117		}
2118		}
2119		}
#	Line 1688 \| Line 2127 \| public class ForkJoinPool extends Abstra
2127		*/
2128		final void helpQuiescePool(WorkQueue w) {
2129		for (boolean active = true;;) {
2130	<	w.runLocalTasks(); // exhaust local queue
2131	<	WorkQueue q = findNonEmptyStealQueue(w);
2130	>	ForkJoinTask<?> localTask; // exhaust local queue
2131	>	while ((localTask = w.nextLocalTask()) != null)
2132	>	localTask.doExec();
2133	>	// Similar to loop in scan(), but ignoring submissions
2134	>	WorkQueue q = findNonEmptyStealQueue(w.nextSeed());
2135		if (q != null) {
2136	<	ForkJoinTask<?> t;
2136	>	ForkJoinTask<?> t; int b;
2137		if (!active) { // re-establish active count
2138		long c;
2139		active = true;
2140		do {} while (!U.compareAndSwapLong
2141		(this, CTL, c = ctl, c + AC_UNIT));
2142		}
2143	<	if ((t = q.poll()) != null)
2143	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) {
2144	>	if (q.base - q.top < 0)
2145	>	signalWork(q);
2146		w.runSubtask(t);
2147	+	}
2148		}
2149		else {
2150		long c;
#	Line 1710 \| Line 2155 \| public class ForkJoinPool extends Abstra
2155		}
2156		else
2157		c = ctl; // re-increment on exit
2158	<	if ((int)(c >> AC_SHIFT) + parallelism == 0) {
2158	>	if ((int)(c >> AC_SHIFT) + (config & SMASK) == 0) {
2159		do {} while (!U.compareAndSwapLong
2160		(this, CTL, c = ctl, c + AC_UNIT));
2161		break;
#	Line 1720 \| Line 2165 \| public class ForkJoinPool extends Abstra
2165		}
2166
2167		/**
2168	<	* Gets and removes a local or stolen task for the given worker
2168	>	* Gets and removes a local or stolen task for the given worker.
2169		*
2170		* @return a task, if available
2171		*/
2172		final ForkJoinTask<?> nextTaskFor(WorkQueue w) {
2173		for (ForkJoinTask<?> t;;) {
2174	<	WorkQueue q;
2174	>	WorkQueue q; int b;
2175		if ((t = w.nextLocalTask()) != null)
2176		return t;
2177	<	if ((q = findNonEmptyStealQueue(w)) == null)
2177	>	if ((q = findNonEmptyStealQueue(w.nextSeed())) == null)
2178		return null;
2179	<	if ((t = q.poll()) != null)
2179	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) {
2180	>	if (q.base - q.top < 0)
2181	>	signalWork(q);
2182		return t;
2183	+	}
2184		}
2185		}
2186
2187		/**
2188	<	* Returns the approximate (non-atomic) number of idle threads per
2189	<	* active thread to offset steal queue size for method
2190	<	* ForkJoinTask.getSurplusQueuedTaskCount().
2191	<	*/
2192	<	final int idlePerActive() {
2193	<	// Approximate at powers of two for small values, saturate past 4
2194	<	int p = parallelism;
2195	<	int a = p + (int)(ctl >> AC_SHIFT);
2196	<	return (a > (p >>>= 1) ? 0 :
2197	<	a > (p >>>= 1) ? 1 :
2198	<	a > (p >>>= 1) ? 2 :
2199	<	a > (p >>>= 1) ? 4 :
2200	<	8);
2201	<	}
2202	<
2203	<	// Termination
2204	<
2205	<	/**
2206	<	* Sets SHUTDOWN bit of runState under lock
2207	<	*/
2208	<	private void enableShutdown() {
2209	<	ReentrantLock lock = this.lock;
2210	<	if (runState >= 0) {
2211	<	lock.lock(); // don't need try/finally
2212	<	runState \|= SHUTDOWN;
2213	<	lock.unlock();
2188	>	* Returns a cheap heuristic guide for task partitioning when
2189	>	* programmers, frameworks, tools, or languages have little or no
2190	>	* idea about task granularity. In essence by offering this
2191	>	* method, we ask users only about tradeoffs in overhead vs
2192	>	* expected throughput and its variance, rather than how finely to
2193	>	* partition tasks.
2194	>	*
2195	>	* In a steady state strict (tree-structured) computation, each
2196	>	* thread makes available for stealing enough tasks for other
2197	>	* threads to remain active. Inductively, if all threads play by
2198	>	* the same rules, each thread should make available only a
2199	>	* constant number of tasks.
2200	>	*
2201	>	* The minimum useful constant is just 1. But using a value of 1
2202	>	* would require immediate replenishment upon each steal to
2203	>	* maintain enough tasks, which is infeasible. Further,
2204	>	* partitionings/granularities of offered tasks should minimize
2205	>	* steal rates, which in general means that threads nearer the top
2206	>	* of computation tree should generate more than those nearer the
2207	>	* bottom. In perfect steady state, each thread is at
2208	>	* approximately the same level of computation tree. However,
2209	>	* producing extra tasks amortizes the uncertainty of progress and
2210	>	* diffusion assumptions.
2211	>	*
2212	>	* So, users will want to use values larger, but not much larger
2213	>	* than 1 to both smooth over transient shortages and hedge
2214	>	* against uneven progress; as traded off against the cost of
2215	>	* extra task overhead. We leave the user to pick a threshold
2216	>	* value to compare with the results of this call to guide
2217	>	* decisions, but recommend values such as 3.
2218	>	*
2219	>	* When all threads are active, it is on average OK to estimate
2220	>	* surplus strictly locally. In steady-state, if one thread is
2221	>	* maintaining say 2 surplus tasks, then so are others. So we can
2222	>	* just use estimated queue length. However, this strategy alone
2223	>	* leads to serious mis-estimates in some non-steady-state
2224	>	* conditions (ramp-up, ramp-down, other stalls). We can detect
2225	>	* many of these by further considering the number of "idle"
2226	>	* threads, that are known to have zero queued tasks, so
2227	>	* compensate by a factor of (#idle/#active) threads.
2228	>	*
2229	>	* Note: The approximation of #busy workers as #active workers is
2230	>	* not very good under current signalling scheme, and should be
2231	>	* improved.
2232	>	*/
2233	>	static int getSurplusQueuedTaskCount() {
2234	>	Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q;
2235	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
2236	>	int p = (pool = (wt = (ForkJoinWorkerThread)t).pool).config & SMASK;
2237	>	int n = (q = wt.workQueue).top - q.base;
2238	>	int a = (int)(pool.ctl >> AC_SHIFT) + p;
2239	>	return n - (a > (p >>>= 1) ? 0 :
2240	>	a > (p >>>= 1) ? 1 :
2241	>	a > (p >>>= 1) ? 2 :
2242	>	a > (p >>>= 1) ? 4 :
2243	>	8);
2244		}
2245	+	return 0;
2246		}
2247
2248	+	// Termination
2249	+
2250		/**
2251	<	* Possibly initiates and/or completes termination. Upon
2252	<	* termination, cancels all queued tasks and then
2251	>	* Possibly initiates and/or completes termination. The caller
2252	>	* triggering termination runs three passes through workQueues:
2253	>	* (0) Setting termination status, followed by wakeups of queued
2254	>	* workers; (1) cancelling all tasks; (2) interrupting lagging
2255	>	* threads (likely in external tasks, but possibly also blocked in
2256	>	* joins). Each pass repeats previous steps because of potential
2257	>	* lagging thread creation.
2258		*
2259		* @param now if true, unconditionally terminate, else only
2260		* if no work and no active workers
2261	+	* @param enable if true, enable shutdown when next possible
2262		* @return true if now terminating or terminated
2263		*/
2264	<	private boolean tryTerminate(boolean now) {
2264	>	private boolean tryTerminate(boolean now, boolean enable) {
2265	>	if (this == commonPool) // cannot shut down
2266	>	return false;
2267		for (long c;;) {
2268		if (((c = ctl) & STOP_BIT) != 0) { // already terminating
2269	<	if ((short)(c >>> TC_SHIFT) == -parallelism) {
2270	<	ReentrantLock lock = this.lock; // signal when no workers
2271	<	lock.lock(); // don't need try/finally
2272	<	termination.signalAll(); // signal when 0 workers
1784	<	lock.unlock();
2269	>	if ((short)(c >>> TC_SHIFT) == -(config & SMASK)) {
2270	>	synchronized (this) {
2271	>	notifyAll(); // signal when 0 workers
2272	>	}
2273		}
2274		return true;
2275		}
2276	<	if (!now) {
2277	<	if ((int)(c >> AC_SHIFT) != -parallelism \|\| runState >= 0 \|\|
2276	>	if (plock >= 0) { // not yet enabled
2277	>	int ps;
2278	>	if (!enable)
2279	>	return false;
2280	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
2281	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
2282	>	ps = acquirePlock();
2283	>	if (!U.compareAndSwapInt(this, PLOCK, ps, SHUTDOWN))
2284	>	releasePlock(SHUTDOWN);
2285	>	}
2286	>	if (!now) { // check if idle & no tasks
2287	>	if ((int)(c >> AC_SHIFT) != -(config & SMASK) \|\|
2288		hasQueuedSubmissions())
2289		return false;
2290		// Check for unqueued inactive workers. One pass suffices.
2291		WorkQueue[] ws = workQueues; WorkQueue w;
2292		if (ws != null) {
2293	<	int n = ws.length;
1796	<	for (int i = 1; i < n; i += 2) {
2293	>	for (int i = 1; i < ws.length; i += 2) {
2294		if ((w = ws[i]) != null && w.eventCount >= 0)
2295		return false;
2296		}
2297		}
2298		}
2299	<	if (U.compareAndSwapLong(this, CTL, c, c \| STOP_BIT))
2300	<	startTerminating();
2299	>	if (U.compareAndSwapLong(this, CTL, c, c \| STOP_BIT)) {
2300	>	for (int pass = 0; pass < 3; ++pass) {
2301	>	WorkQueue[] ws = workQueues;
2302	>	if (ws != null) {
2303	>	WorkQueue w; Thread wt;
2304	>	int n = ws.length;
2305	>	for (int i = 0; i < n; ++i) {
2306	>	if ((w = ws[i]) != null) {
2307	>	w.qlock = -1;
2308	>	if (pass > 0) {
2309	>	w.cancelAll();
2310	>	if (pass > 1 && (wt = w.owner) != null) {
2311	>	if (!wt.isInterrupted()) {
2312	>	try {
2313	>	wt.interrupt();
2314	>	} catch (SecurityException ignore) {
2315	>	}
2316	>	}
2317	>	U.unpark(wt);
2318	>	}
2319	>	}
2320	>	}
2321	>	}
2322	>	// Wake up workers parked on event queue
2323	>	int i, e; long cc; Thread p;
2324	>	while ((e = (int)(cc = ctl) & E_MASK) != 0 &&
2325	>	(i = e & SMASK) < n &&
2326	>	(w = ws[i]) != null) {
2327	>	long nc = ((long)(w.nextWait & E_MASK) \|
2328	>	((cc + AC_UNIT) & AC_MASK) \|
2329	>	(cc & (TC_MASK\|STOP_BIT)));
2330	>	if (w.eventCount == (e \| INT_SIGN) &&
2331	>	U.compareAndSwapLong(this, CTL, cc, nc)) {
2332	>	w.eventCount = (e + E_SEQ) & E_MASK;
2333	>	w.qlock = -1;
2334	>	if ((p = w.parker) != null)
2335	>	U.unpark(p);
2336	>	}
2337	>	}
2338	>	}
2339	>	}
2340	>	}
2341		}
2342		}
2343
2344	+	// external operations on common pool
2345	+
2346		/**
2347	<	* Initiates termination: Runs three passes through workQueues:
2348	<	* (0) Setting termination status, followed by wakeups of queued
1810	<	* workers; (1) cancelling all tasks; (2) interrupting lagging
1811	<	* threads (likely in external tasks, but possibly also blocked in
1812	<	* joins). Each pass repeats previous steps because of potential
1813	<	* lagging thread creation.
2347	>	* Returns common pool queue for a thread that has submitted at
2348	>	* least one task.
2349		*/
2350	<	private void startTerminating() {
2351	<	for (int pass = 0; pass < 3; ++pass) {
2352	<	WorkQueue[] ws = workQueues;
2353	<	if (ws != null) {
2354	<	WorkQueue w; Thread wt;
2355	<	int n = ws.length;
2356	<	for (int j = 0; j < n; ++j) {
2357	<	if ((w = ws[j]) != null) {
2358	<	w.runState = -1;
2359	<	if (pass > 0) {
2360	<	w.cancelAll();
2361	<	if (pass > 1 && (wt = w.owner) != null &&
2362	<	!wt.isInterrupted()) {
2363	<	try {
2364	<	wt.interrupt();
2365	<	} catch (SecurityException ignore) {
2350	>	static WorkQueue commonSubmitterQueue() {
2351	>	ForkJoinPool p; WorkQueue[] ws; int m; Submitter z;
2352	>	return ((z = submitters.get()) != null &&
2353	>	(p = commonPool) != null &&
2354	>	(ws = p.workQueues) != null &&
2355	>	(m = ws.length - 1) >= 0) ?
2356	>	ws[m & z.seed & SQMASK] : null;
2357	>	}
2358	>
2359	>	/**
2360	>	* Tries to pop the given task from submitter's queue in common pool.
2361	>	*/
2362	>	static boolean tryExternalUnpush(ForkJoinTask<?> t) {
2363	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q; Submitter z;
2364	>	ForkJoinTask<?>[] a; int m, s;
2365	>	if (t != null &&
2366	>	(z = submitters.get()) != null &&
2367	>	(p = commonPool) != null &&
2368	>	(ws = p.workQueues) != null &&
2369	>	(m = ws.length - 1) >= 0 &&
2370	>	(q = ws[m & z.seed & SQMASK]) != null &&
2371	>	(s = q.top) != q.base &&
2372	>	(a = q.array) != null) {
2373	>	long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE;
2374	>	if (U.getObject(a, j) == t &&
2375	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2376	>	if (q.array == a && q.top == s && // recheck
2377	>	U.compareAndSwapObject(a, j, t, null)) {
2378	>	q.top = s - 1;
2379	>	q.qlock = 0;
2380	>	return true;
2381	>	}
2382	>	q.qlock = 0;
2383	>	}
2384	>	}
2385	>	return false;
2386	>	}
2387	>
2388	>	/**
2389	>	* Tries to pop and run local tasks within the same computation
2390	>	* as the given root. On failure, tries to help complete from
2391	>	* other queues via helpComplete.
2392	>	*/
2393	>	private void externalHelpComplete(WorkQueue q, ForkJoinTask<?> root) {
2394	>	ForkJoinTask<?>[] a; int m;
2395	>	if (q != null && (a = q.array) != null && (m = (a.length - 1)) >= 0 &&
2396	>	root != null && root.status >= 0) {
2397	>	for (;;) {
2398	>	int s, u; Object o; CountedCompleter<?> task = null;
2399	>	if ((s = q.top) - q.base > 0) {
2400	>	long j = ((m & (s - 1)) << ASHIFT) + ABASE;
2401	>	if ((o = U.getObject(a, j)) != null &&
2402	>	(o instanceof CountedCompleter)) {
2403	>	CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;
2404	>	do {
2405	>	if (r == root) {
2406	>	if (U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2407	>	if (q.array == a && q.top == s &&
2408	>	U.compareAndSwapObject(a, j, t, null)) {
2409	>	q.top = s - 1;
2410	>	task = t;
2411	>	}
2412	>	q.qlock = 0;
2413		}
2414	+	break;
2415		}
2416	<	}
2416	>	} while ((r = r.completer) != null);
2417		}
2418		}
2419	<	// Wake up workers parked on event queue
2420	<	int i, e; long c; Thread p;
2421	<	while ((i = ((~(e = (int)(c = ctl)) << 1) \| 1) & SMASK) < n &&
2422	<	(w = ws[i]) != null &&
2423	<	w.eventCount == (e \| INT_SIGN)) {
2424	<	long nc = ((long)(w.nextWait & E_MASK) \|
2425	<	((c + AC_UNIT) & AC_MASK) \|
2426	<	(c & (TC_MASK\|STOP_BIT)));
2427	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
2428	<	w.eventCount = (e + E_SEQ) & E_MASK;
2429	<	if ((p = w.parker) != null)
2430	<	U.unpark(p);
2419	>	if (task != null)
2420	>	task.doExec();
2421	>	if (root.status < 0 \|\|
2422	>	(u = (int)(ctl >>> 32)) >= 0 \|\| (u >> UAC_SHIFT) >= 0)
2423	>	break;
2424	>	if (task == null) {
2425	>	helpSignal(root, q.poolIndex);
2426	>	if (root.status >= 0)
2427	>	helpComplete(root, SHARED_QUEUE);
2428	>	break;
2429	>	}
2430	>	}
2431	>	}
2432	>	}
2433	>
2434	>	/**
2435	>	* Tries to help execute or signal availability of the given task
2436	>	* from submitter's queue in common pool.
2437	>	*/
2438	>	static void externalHelpJoin(ForkJoinTask<?> t) {
2439	>	// Some hard-to-avoid overlap with tryExternalUnpush
2440	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; Submitter z;
2441	>	ForkJoinTask<?>[] a; int m, s, n;
2442	>	if (t != null &&
2443	>	(z = submitters.get()) != null &&
2444	>	(p = commonPool) != null &&
2445	>	(ws = p.workQueues) != null &&
2446	>	(m = ws.length - 1) >= 0 &&
2447	>	(q = ws[m & z.seed & SQMASK]) != null &&
2448	>	(a = q.array) != null) {
2449	>	int am = a.length - 1;
2450	>	if ((s = q.top) != q.base) {
2451	>	long j = ((am & (s - 1)) << ASHIFT) + ABASE;
2452	>	if (U.getObject(a, j) == t &&
2453	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2454	>	if (q.array == a && q.top == s &&
2455	>	U.compareAndSwapObject(a, j, t, null)) {
2456	>	q.top = s - 1;
2457	>	q.qlock = 0;
2458	>	t.doExec();
2459		}
2460	+	else
2461	+	q.qlock = 0;
2462		}
2463		}
2464	+	if (t.status >= 0) {
2465	+	if (t instanceof CountedCompleter)
2466	+	p.externalHelpComplete(q, t);
2467	+	else
2468	+	p.helpSignal(t, q.poolIndex);
2469	+	}
2470	+	}
2471	+	}
2472	+
2473	+	/**
2474	+	* Restricted version of helpQuiescePool for external callers
2475	+	*/
2476	+	static void externalHelpQuiescePool() {
2477	+	ForkJoinPool p; ForkJoinTask<?> t; WorkQueue q; int b;
2478	+	if ((p = commonPool) != null &&
2479	+	(q = p.findNonEmptyStealQueue(1)) != null &&
2480	+	(b = q.base) - q.top < 0 &&
2481	+	(t = q.pollAt(b)) != null) {
2482	+	if (q.base - q.top < 0)
2483	+	p.signalWork(q);
2484	+	t.doExec();
2485		}
2486		}
2487
#	Line 1920 \| Line 2554 \| public class ForkJoinPool extends Abstra
2554		checkPermission();
2555		if (factory == null)
2556		throw new NullPointerException();
2557	<	if (parallelism <= 0 \|\| parallelism > MAX_ID)
2557	>	if (parallelism <= 0 \|\| parallelism > MAX_CAP)
2558		throw new IllegalArgumentException();
1925	–	this.parallelism = parallelism;
2559		this.factory = factory;
2560		this.ueh = handler;
2561	<	this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE;
1929	<	this.nextPoolIndex = 1;
2561	>	this.config = parallelism \| (asyncMode ? (FIFO_QUEUE << 16) : 0);
2562		long np = (long)(-parallelism); // offset ctl counts
2563		this.ctl = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
2564	<	// initialize workQueues array with room for 2*parallelism if possible
1933	<	int n = parallelism << 1;
1934	<	if (n >= MAX_ID)
1935	<	n = MAX_ID;
1936	<	else { // See Hackers Delight, sec 3.2, where n < (1 << 16)
1937	<	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4; n \|= n >>> 8;
1938	<	}
1939	<	this.workQueues = new WorkQueue[(n + 1) << 1];
1940	<	ReentrantLock lck = this.lock = new ReentrantLock();
1941	<	this.termination = lck.newCondition();
1942	<	this.stealCount = new AtomicLong();
1943	<	this.nextWorkerNumber = new AtomicInteger();
2564	>	int pn = nextPoolId();
2565		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2566	<	sb.append(poolNumberGenerator.incrementAndGet());
2566	>	sb.append(Integer.toString(pn));
2567		sb.append("-worker-");
2568		this.workerNamePrefix = sb.toString();
2569	<	// Create initial submission queue
2570	<	WorkQueue sq = tryAddSharedQueue(0);
2571	<	if (sq != null)
2572	<	sq.growArray(false);
2569	>	}
2570	>
2571	>	/**
2572	>	* Constructor for common pool, suitable only for static initialization.
2573	>	* Basically the same as above, but uses smallest possible initial footprint.
2574	>	*/
2575	>	ForkJoinPool(int parallelism, long ctl,
2576	>	ForkJoinWorkerThreadFactory factory,
2577	>	Thread.UncaughtExceptionHandler handler) {
2578	>	this.config = parallelism;
2579	>	this.ctl = ctl;
2580	>	this.factory = factory;
2581	>	this.ueh = handler;
2582	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2583	>	}
2584	>
2585	>	/**
2586	>	* Returns the common pool instance. This pool is statically
2587	>	* constructed; its run state is unaffected by attempts to
2588	>	* {@link #shutdown} or {@link #shutdownNow}.
2589	>	*
2590	>	* @return the common pool instance
2591	>	*/
2592	>	public static ForkJoinPool commonPool() {
2593	>	// assert commonPool != null : "static init error";
2594	>	return commonPool;
2595		}
2596
2597		// Execution methods
#	Line 1970 \| Line 2613 \| public class ForkJoinPool extends Abstra
2613		* scheduled for execution
2614		*/
2615		public <T> T invoke(ForkJoinTask<T> task) {
2616	<	doSubmit(task);
2616	>	if (task == null)
2617	>	throw new NullPointerException();
2618	>	externalPush(task);
2619		return task.join();
2620		}
2621
#	Line 1983 \| Line 2628 \| public class ForkJoinPool extends Abstra
2628		* scheduled for execution
2629		*/
2630		public void execute(ForkJoinTask<?> task) {
2631	<	doSubmit(task);
2631	>	if (task == null)
2632	>	throw new NullPointerException();
2633	>	externalPush(task);
2634		}
2635
2636		// AbstractExecutorService methods
#	Line 2000 \| Line 2647 \| public class ForkJoinPool extends Abstra
2647		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2648		job = (ForkJoinTask<?>) task;
2649		else
2650	<	job = ForkJoinTask.adapt(task, null);
2651	<	doSubmit(job);
2650	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2651	>	externalPush(job);
2652		}
2653
2654		/**
#	Line 2014 \| Line 2661 \| public class ForkJoinPool extends Abstra
2661		* scheduled for execution
2662		*/
2663		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2664	<	doSubmit(task);
2664	>	if (task == null)
2665	>	throw new NullPointerException();
2666	>	externalPush(task);
2667		return task;
2668		}
2669
#	Line 2024 \| Line 2673 \| public class ForkJoinPool extends Abstra
2673		* scheduled for execution
2674		*/
2675		public <T> ForkJoinTask<T> submit(Callable<T> task) {
2676	<	if (task == null)
2677	<	throw new NullPointerException();
2029	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
2030	<	doSubmit(job);
2676	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2677	>	externalPush(job);
2678		return job;
2679		}
2680
#	Line 2037 \| Line 2684 \| public class ForkJoinPool extends Abstra
2684		* scheduled for execution
2685		*/
2686		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2687	<	if (task == null)
2688	<	throw new NullPointerException();
2042	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
2043	<	doSubmit(job);
2687	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2688	>	externalPush(job);
2689		return job;
2690		}
2691
#	Line 2056 \| Line 2701 \| public class ForkJoinPool extends Abstra
2701		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2702		job = (ForkJoinTask<?>) task;
2703		else
2704	<	job = ForkJoinTask.adapt(task, null);
2705	<	doSubmit(job);
2704	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2705	>	externalPush(job);
2706		return job;
2707		}
2708
#	Line 2066 \| Line 2711 \| public class ForkJoinPool extends Abstra
2711		* @throws RejectedExecutionException {@inheritDoc}
2712		*/
2713		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
2714	<	ArrayList<ForkJoinTask<T>> forkJoinTasks =
2715	<	new ArrayList<ForkJoinTask<T>>(tasks.size());
2716	<	for (Callable<T> task : tasks)
2717	<	forkJoinTasks.add(ForkJoinTask.adapt(task));
2718	<	invoke(new InvokeAll<T>(forkJoinTasks));
2719	<
2714	>	// In previous versions of this class, this method constructed
2715	>	// a task to run ForkJoinTask.invokeAll, but now external
2716	>	// invocation of multiple tasks is at least as efficient.
2717	>	List<ForkJoinTask<T>> fs = new ArrayList<ForkJoinTask<T>>(tasks.size());
2718	>	// Workaround needed because method wasn't declared with
2719	>	// wildcards in return type but should have been.
2720		@SuppressWarnings({"unchecked", "rawtypes"})
2721	<	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
2077	<	return futures;
2078	<	}
2721	>	List<Future<T>> futures = (List<Future<T>>) (List) fs;
2722
2723	<	static final class InvokeAll<T> extends RecursiveAction {
2724	<	final ArrayList<ForkJoinTask<T>> tasks;
2725	<	InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
2726	<	public void compute() {
2727	<	try { invokeAll(tasks); }
2728	<	catch (Exception ignore) {}
2723	>	boolean done = false;
2724	>	try {
2725	>	for (Callable<T> t : tasks) {
2726	>	ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2727	>	externalPush(f);
2728	>	fs.add(f);
2729	>	}
2730	>	for (ForkJoinTask<T> f : fs)
2731	>	f.quietlyJoin();
2732	>	done = true;
2733	>	return futures;
2734	>	} finally {
2735	>	if (!done)
2736	>	for (ForkJoinTask<T> f : fs)
2737	>	f.cancel(false);
2738		}
2087	–	private static final long serialVersionUID = -7914297376763021607L;
2739		}
2740
2741		/**
#	Line 2112 \| Line 2763 \| public class ForkJoinPool extends Abstra
2763		* @return the targeted parallelism level of this pool
2764		*/
2765		public int getParallelism() {
2766	<	return parallelism;
2766	>	return config & SMASK;
2767	>	}
2768	>
2769	>	/**
2770	>	* Returns the targeted parallelism level of the common pool.
2771	>	*
2772	>	* @return the targeted parallelism level of the common pool
2773	>	*/
2774	>	public static int getCommonPoolParallelism() {
2775	>	return commonPoolParallelism;
2776		}
2777
2778		/**
#	Line 2124 \| Line 2784 \| public class ForkJoinPool extends Abstra
2784		* @return the number of worker threads
2785		*/
2786		public int getPoolSize() {
2787	<	return parallelism + (short)(ctl >>> TC_SHIFT);
2787	>	return (config & SMASK) + (short)(ctl >>> TC_SHIFT);
2788		}
2789
2790		/**
#	Line 2134 \| Line 2794 \| public class ForkJoinPool extends Abstra
2794		* @return {@code true} if this pool uses async mode
2795		*/
2796		public boolean getAsyncMode() {
2797	<	return localMode != 0;
2797	>	return (config >>> 16) == FIFO_QUEUE;
2798		}
2799
2800		/**
#	Line 2149 \| Line 2809 \| public class ForkJoinPool extends Abstra
2809		int rc = 0;
2810		WorkQueue[] ws; WorkQueue w;
2811		if ((ws = workQueues) != null) {
2812	<	int n = ws.length;
2813	<	for (int i = 1; i < n; i += 2) {
2154	<	Thread.State s; ForkJoinWorkerThread wt;
2155	<	if ((w = ws[i]) != null && (wt = w.owner) != null &&
2156	<	w.eventCount >= 0 &&
2157	<	(s = wt.getState()) != Thread.State.BLOCKED &&
2158	<	s != Thread.State.WAITING &&
2159	<	s != Thread.State.TIMED_WAITING)
2812	>	for (int i = 1; i < ws.length; i += 2) {
2813	>	if ((w = ws[i]) != null && w.isApparentlyUnblocked())
2814		++rc;
2815		}
2816		}
#	Line 2171 \| Line 2825 \| public class ForkJoinPool extends Abstra
2825		* @return the number of active threads
2826		*/
2827		public int getActiveThreadCount() {
2828	<	int r = parallelism + (int)(ctl >> AC_SHIFT);
2828	>	int r = (config & SMASK) + (int)(ctl >> AC_SHIFT);
2829		return (r <= 0) ? 0 : r; // suppress momentarily negative values
2830		}
2831
#	Line 2187 \| Line 2841 \| public class ForkJoinPool extends Abstra
2841		* @return {@code true} if all threads are currently idle
2842		*/
2843		public boolean isQuiescent() {
2844	<	return (int)(ctl >> AC_SHIFT) + parallelism == 0;
2844	>	return (int)(ctl >> AC_SHIFT) + (config & SMASK) == 0;
2845		}
2846
2847		/**
#	Line 2202 \| Line 2856 \| public class ForkJoinPool extends Abstra
2856		* @return the number of steals
2857		*/
2858		public long getStealCount() {
2859	<	long count = stealCount.get();
2859	>	long count = stealCount;
2860		WorkQueue[] ws; WorkQueue w;
2861		if ((ws = workQueues) != null) {
2862	<	int n = ws.length;
2209	<	for (int i = 1; i < n; i += 2) {
2862	>	for (int i = 1; i < ws.length; i += 2) {
2863		if ((w = ws[i]) != null)
2864	<	count += w.totalSteals;
2864	>	count += w.nsteals;
2865		}
2866		}
2867		return count;
#	Line 2228 \| Line 2881 \| public class ForkJoinPool extends Abstra
2881		long count = 0;
2882		WorkQueue[] ws; WorkQueue w;
2883		if ((ws = workQueues) != null) {
2884	<	int n = ws.length;
2232	<	for (int i = 1; i < n; i += 2) {
2884	>	for (int i = 1; i < ws.length; i += 2) {
2885		if ((w = ws[i]) != null)
2886		count += w.queueSize();
2887		}
#	Line 2248 \| Line 2900 \| public class ForkJoinPool extends Abstra
2900		int count = 0;
2901		WorkQueue[] ws; WorkQueue w;
2902		if ((ws = workQueues) != null) {
2903	<	int n = ws.length;
2252	<	for (int i = 0; i < n; i += 2) {
2903	>	for (int i = 0; i < ws.length; i += 2) {
2904		if ((w = ws[i]) != null)
2905		count += w.queueSize();
2906		}
#	Line 2266 \| Line 2917 \| public class ForkJoinPool extends Abstra
2917		public boolean hasQueuedSubmissions() {
2918		WorkQueue[] ws; WorkQueue w;
2919		if ((ws = workQueues) != null) {
2920	<	int n = ws.length;
2921	<	for (int i = 0; i < n; i += 2) {
2271	<	if ((w = ws[i]) != null && w.queueSize() != 0)
2920	>	for (int i = 0; i < ws.length; i += 2) {
2921	>	if ((w = ws[i]) != null && !w.isEmpty())
2922		return true;
2923		}
2924		}
#	Line 2285 \| Line 2935 \| public class ForkJoinPool extends Abstra
2935		protected ForkJoinTask<?> pollSubmission() {
2936		WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2937		if ((ws = workQueues) != null) {
2938	<	int n = ws.length;
2289	<	for (int i = 0; i < n; i += 2) {
2938	>	for (int i = 0; i < ws.length; i += 2) {
2939		if ((w = ws[i]) != null && (t = w.poll()) != null)
2940		return t;
2941		}
#	Line 2315 \| Line 2964 \| public class ForkJoinPool extends Abstra
2964		int count = 0;
2965		WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2966		if ((ws = workQueues) != null) {
2967	<	int n = ws.length;
2319	<	for (int i = 0; i < n; ++i) {
2967	>	for (int i = 0; i < ws.length; ++i) {
2968		if ((w = ws[i]) != null) {
2969		while ((t = w.poll()) != null) {
2970		c.add(t);
#	Line 2336 \| Line 2984 \| public class ForkJoinPool extends Abstra
2984		* @return a string identifying this pool, as well as its state
2985		*/
2986		public String toString() {
2987	<	long st = getStealCount();
2988	<	long qt = getQueuedTaskCount();
2989	<	long qs = getQueuedSubmissionCount();
2342	<	int rc = getRunningThreadCount();
2343	<	int pc = parallelism;
2987	>	// Use a single pass through workQueues to collect counts
2988	>	long qt = 0L, qs = 0L; int rc = 0;
2989	>	long st = stealCount;
2990		long c = ctl;
2991	+	WorkQueue[] ws; WorkQueue w;
2992	+	if ((ws = workQueues) != null) {
2993	+	for (int i = 0; i < ws.length; ++i) {
2994	+	if ((w = ws[i]) != null) {
2995	+	int size = w.queueSize();
2996	+	if ((i & 1) == 0)
2997	+	qs += size;
2998	+	else {
2999	+	qt += size;
3000	+	st += w.nsteals;
3001	+	if (w.isApparentlyUnblocked())
3002	+	++rc;
3003	+	}
3004	+	}
3005	+	}
3006	+	}
3007	+	int pc = (config & SMASK);
3008		int tc = pc + (short)(c >>> TC_SHIFT);
3009		int ac = pc + (int)(c >> AC_SHIFT);
3010		if (ac < 0) // ignore transient negative
#	Line 2350 \| Line 3013 \| public class ForkJoinPool extends Abstra
3013		if ((c & STOP_BIT) != 0)
3014		level = (tc == 0) ? "Terminated" : "Terminating";
3015		else
3016	<	level = runState < 0 ? "Shutting down" : "Running";
3016	>	level = plock < 0 ? "Shutting down" : "Running";
3017		return super.toString() +
3018		"[" + level +
3019		", parallelism = " + pc +
#	Line 2364 \| Line 3027 \| public class ForkJoinPool extends Abstra
3027		}
3028
3029		/**
3030	<	* Initiates an orderly shutdown in which previously submitted
3031	<	* tasks are executed, but no new tasks will be accepted.
3032	<	* Invocation has no additional effect if already shut down.
3033	<	* Tasks that are in the process of being submitted concurrently
3034	<	* during the course of this method may or may not be rejected.
3030	>	* Possibly initiates an orderly shutdown in which previously
3031	>	* submitted tasks are executed, but no new tasks will be
3032	>	* accepted. Invocation has no effect on execution state if this
3033	>	* is the {@link #commonPool}, and no additional effect if
3034	>	* already shut down. Tasks that are in the process of being
3035	>	* submitted concurrently during the course of this method may or
3036	>	* may not be rejected.
3037		*
3038		* @throws SecurityException if a security manager exists and
3039		* the caller is not permitted to modify threads
#	Line 2377 \| Line 3042 \| public class ForkJoinPool extends Abstra
3042		*/
3043		public void shutdown() {
3044		checkPermission();
3045	<	enableShutdown();
2381	<	tryTerminate(false);
3045	>	tryTerminate(false, true);
3046		}
3047
3048		/**
3049	<	* Attempts to cancel and/or stop all tasks, and reject all
3050	<	* subsequently submitted tasks. Tasks that are in the process of
3051	<	* being submitted or executed concurrently during the course of
3052	<	* this method may or may not be rejected. This method cancels
3053	<	* both existing and unexecuted tasks, in order to permit
3054	<	* termination in the presence of task dependencies. So the method
3055	<	* always returns an empty list (unlike the case for some other
3056	<	* Executors).
3049	>	* Possibly attempts to cancel and/or stop all tasks, and reject
3050	>	* all subsequently submitted tasks. Invocation has no effect on
3051	>	* execution state if this is the {@link #commonPool}, and no
3052	>	* additional effect if already shut down. Otherwise, tasks that
3053	>	* are in the process of being submitted or executed concurrently
3054	>	* during the course of this method may or may not be
3055	>	* rejected. This method cancels both existing and unexecuted
3056	>	* tasks, in order to permit termination in the presence of task
3057	>	* dependencies. So the method always returns an empty list
3058	>	* (unlike the case for some other Executors).
3059		*
3060		* @return an empty list
3061		* @throws SecurityException if a security manager exists and
#	Line 2399 \| Line 3065 \| public class ForkJoinPool extends Abstra
3065		*/
3066		public List<Runnable> shutdownNow() {
3067		checkPermission();
3068	<	enableShutdown();
2403	<	tryTerminate(true);
3068	>	tryTerminate(true, true);
3069		return Collections.emptyList();
3070		}
3071
#	Line 2412 \| Line 3077 \| public class ForkJoinPool extends Abstra
3077		public boolean isTerminated() {
3078		long c = ctl;
3079		return ((c & STOP_BIT) != 0L &&
3080	<	(short)(c >>> TC_SHIFT) == -parallelism);
3080	>	(short)(c >>> TC_SHIFT) == -(config & SMASK));
3081		}
3082
3083		/**
#	Line 2420 \| Line 3085 \| public class ForkJoinPool extends Abstra
3085		* commenced but not yet completed. This method may be useful for
3086		* debugging. A return of {@code true} reported a sufficient
3087		* period after shutdown may indicate that submitted tasks have
3088	<	* ignored or suppressed interruption, or are waiting for IO,
3088	>	* ignored or suppressed interruption, or are waiting for I/O,
3089		* causing this executor not to properly terminate. (See the
3090		* advisory notes for class {@link ForkJoinTask} stating that
3091		* tasks should not normally entail blocking operations. But if
#	Line 2431 \| Line 3096 \| public class ForkJoinPool extends Abstra
3096		public boolean isTerminating() {
3097		long c = ctl;
3098		return ((c & STOP_BIT) != 0L &&
3099	<	(short)(c >>> TC_SHIFT) != -parallelism);
3099	>	(short)(c >>> TC_SHIFT) != -(config & SMASK));
3100		}
3101
3102		/**
#	Line 2440 \| Line 3105 \| public class ForkJoinPool extends Abstra
3105		* @return {@code true} if this pool has been shut down
3106		*/
3107		public boolean isShutdown() {
3108	<	return runState < 0;
3108	>	return plock < 0;
3109		}
3110
3111		/**
3112	<	* Blocks until all tasks have completed execution after a shutdown
3113	<	* request, or the timeout occurs, or the current thread is
3114	<	* interrupted, whichever happens first.
3112	>	* Blocks until all tasks have completed execution after a
3113	>	* shutdown request, or the timeout occurs, or the current thread
3114	>	* is interrupted, whichever happens first. Note that the {@link
3115	>	* #commonPool()} never terminates until program shutdown so
3116	>	* this method will always time out.
3117		*
3118		* @param timeout the maximum time to wait
3119		* @param unit the time unit of the timeout argument
#	Line 2457 \| Line 3124 \| public class ForkJoinPool extends Abstra
3124		public boolean awaitTermination(long timeout, TimeUnit unit)
3125		throws InterruptedException {
3126		long nanos = unit.toNanos(timeout);
3127	<	final ReentrantLock lock = this.lock;
3128	<	lock.lock();
3129	<	try {
3130	<	for (;;) {
3131	<	if (isTerminated())
3132	<	return true;
3133	<	if (nanos <= 0)
3134	<	return false;
3135	<	nanos = termination.awaitNanos(nanos);
3127	>	if (isTerminated())
3128	>	return true;
3129	>	long startTime = System.nanoTime();
3130	>	boolean terminated = false;
3131	>	synchronized (this) {
3132	>	for (long waitTime = nanos, millis = 0L;;) {
3133	>	if (terminated = isTerminated() \|\|
3134	>	waitTime <= 0L \|\|
3135	>	(millis = unit.toMillis(waitTime)) <= 0L)
3136	>	break;
3137	>	wait(millis);
3138	>	waitTime = nanos - (System.nanoTime() - startTime);
3139		}
2470	–	} finally {
2471	–	lock.unlock();
3140		}
3141	+	return terminated;
3142		}
3143
3144		/**
#	Line 2568 \| Line 3237 \| public class ForkJoinPool extends Abstra
3237		public static void managedBlock(ManagedBlocker blocker)
3238		throws InterruptedException {
3239		Thread t = Thread.currentThread();
3240	<	ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ?
3241	<	((ForkJoinWorkerThread)t).pool : null);
3242	<	while (!blocker.isReleasable()) {
3243	<	if (p == null \|\| p.tryCompensate()) {
3244	<	try {
3245	<	do {} while (!blocker.isReleasable() && !blocker.block());
3246	<	} finally {
3247	<	if (p != null)
3240	>	if (t instanceof ForkJoinWorkerThread) {
3241	>	ForkJoinPool p = ((ForkJoinWorkerThread)t).pool;
3242	>	while (!blocker.isReleasable()) { // variant of helpSignal
3243	>	WorkQueue[] ws; WorkQueue q; int m, u;
3244	>	if ((ws = p.workQueues) != null && (m = ws.length - 1) >= 0) {
3245	>	for (int i = 0; i <= m; ++i) {
3246	>	if (blocker.isReleasable())
3247	>	return;
3248	>	if ((q = ws[i]) != null && q.base - q.top < 0) {
3249	>	p.signalWork(q);
3250	>	if ((u = (int)(p.ctl >>> 32)) >= 0 \|\|
3251	>	(u >> UAC_SHIFT) >= 0)
3252	>	break;
3253	>	}
3254	>	}
3255	>	}
3256	>	if (p.tryCompensate()) {
3257	>	try {
3258	>	do {} while (!blocker.isReleasable() &&
3259	>	!blocker.block());
3260	>	} finally {
3261		p.incrementActiveCount();
3262	+	}
3263	+	break;
3264		}
2581	–	break;
3265		}
3266		}
3267	+	else {
3268	+	do {} while (!blocker.isReleasable() &&
3269	+	!blocker.block());
3270	+	}
3271		}
3272
3273		// AbstractExecutorService overrides. These rely on undocumented
#	Line 2588 \| Line 3275 \| public class ForkJoinPool extends Abstra
3275		// implement RunnableFuture.
3276
3277		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
3278	<	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
3278	>	return new ForkJoinTask.AdaptedRunnable<T>(runnable, value);
3279		}
3280
3281		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
3282	<	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
3282	>	return new ForkJoinTask.AdaptedCallable<T>(callable);
3283		}
3284
3285		// Unsafe mechanics
3286		private static final sun.misc.Unsafe U;
3287		private static final long CTL;
2601	–	private static final long RUNSTATE;
3288		private static final long PARKBLOCKER;
3289	+	private static final int ABASE;
3290	+	private static final int ASHIFT;
3291	+	private static final long STEALCOUNT;
3292	+	private static final long PLOCK;
3293	+	private static final long INDEXSEED;
3294	+	private static final long QLOCK;
3295
3296		static {
3297	<	poolNumberGenerator = new AtomicInteger();
2606	<	modifyThreadPermission = new RuntimePermission("modifyThread");
2607	<	defaultForkJoinWorkerThreadFactory =
2608	<	new DefaultForkJoinWorkerThreadFactory();
2609	<	int s;
3297	>	int s; // initialize field offsets for CAS etc
3298		try {
3299		U = getUnsafe();
3300		Class<?> k = ForkJoinPool.class;
2613	–	Class<?> tk = Thread.class;
3301		CTL = U.objectFieldOffset
3302		(k.getDeclaredField("ctl"));
3303	<	RUNSTATE = U.objectFieldOffset
3304	<	(k.getDeclaredField("runState"));
3303	>	STEALCOUNT = U.objectFieldOffset
3304	>	(k.getDeclaredField("stealCount"));
3305	>	PLOCK = U.objectFieldOffset
3306	>	(k.getDeclaredField("plock"));
3307	>	INDEXSEED = U.objectFieldOffset
3308	>	(k.getDeclaredField("indexSeed"));
3309	>	Class<?> tk = Thread.class;
3310		PARKBLOCKER = U.objectFieldOffset
3311		(tk.getDeclaredField("parkBlocker"));
3312	+	Class<?> wk = WorkQueue.class;
3313	+	QLOCK = U.objectFieldOffset
3314	+	(wk.getDeclaredField("qlock"));
3315	+	Class<?> ak = ForkJoinTask[].class;
3316	+	ABASE = U.arrayBaseOffset(ak);
3317	+	s = U.arrayIndexScale(ak);
3318	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3319		} catch (Exception e) {
3320		throw new Error(e);
3321		}
3322	+	if ((s & (s-1)) != 0)
3323	+	throw new Error("data type scale not a power of two");
3324	+
3325	+	submitters = new ThreadLocal<Submitter>();
3326	+	ForkJoinWorkerThreadFactory fac = defaultForkJoinWorkerThreadFactory =
3327	+	new DefaultForkJoinWorkerThreadFactory();
3328	+	modifyThreadPermission = new RuntimePermission("modifyThread");
3329	+
3330	+	/*
3331	+	* Establish common pool parameters. For extra caution,
3332	+	* computations to set up common pool state are here; the
3333	+	* constructor just assigns these values to fields.
3334	+	*/
3335	+
3336	+	int par = 0;
3337	+	Thread.UncaughtExceptionHandler handler = null;
3338	+	try { // TBD: limit or report ignored exceptions?
3339	+	String pp = System.getProperty
3340	+	("java.util.concurrent.ForkJoinPool.common.parallelism");
3341	+	String hp = System.getProperty
3342	+	("java.util.concurrent.ForkJoinPool.common.exceptionHandler");
3343	+	String fp = System.getProperty
3344	+	("java.util.concurrent.ForkJoinPool.common.threadFactory");
3345	+	if (fp != null)
3346	+	fac = ((ForkJoinWorkerThreadFactory)ClassLoader.
3347	+	getSystemClassLoader().loadClass(fp).newInstance());
3348	+	if (hp != null)
3349	+	handler = ((Thread.UncaughtExceptionHandler)ClassLoader.
3350	+	getSystemClassLoader().loadClass(hp).newInstance());
3351	+	if (pp != null)
3352	+	par = Integer.parseInt(pp);
3353	+	} catch (Exception ignore) {
3354	+	}
3355	+
3356	+	if (par <= 0)
3357	+	par = Runtime.getRuntime().availableProcessors();
3358	+	if (par > MAX_CAP)
3359	+	par = MAX_CAP;
3360	+	commonPoolParallelism = par;
3361	+	long np = (long)(-par); // precompute initial ctl value
3362	+	long ct = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
3363	+
3364	+	commonPool = new ForkJoinPool(par, ct, fac, handler);
3365		}
3366
3367		/**

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents): Revision 1.115 by jsr166, Thu Jan 26 19:10:27 2012 UTC vs. Revision 1.164 by dl, Tue Dec 18 21:46:16 2012 UTC

Diff Legend

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.115 by jsr166, Thu Jan 26 19:10:27 2012 UTC vs.
Revision 1.164 by dl, Tue Dec 18 21:46:16 2012 UTC