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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.112 by dl, Thu Jan 26 18:15:12 2012 UTC vs.
Revision 1.148 by jsr166, Tue Nov 20 06:18:39 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 IO or other unmanaged synchronization. The nested {@link
55	>	* ManagedBlocker} interface enables extension of the kinds of
56		* synchronization accommodated.
57		*
58		* <p>In addition to execution and lifecycle control methods, this
#	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 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 is
320	>	* apparently empty, they signal waiting workers (or trigger
321	>	* creation of new ones if fewer than the given parallelism
322	>	* level). These primary signals are buttressed by signals
323	>	* whenever other threads scan for work or do not have a task to
324	>	* process (including the case of leaving a hint to unparked
325	>	* threads to help signal others upon wakeup). On most platforms,
326	>	* signalling (unpark) overhead time is noticeably long, and the
327	>	* time between signalling a thread and it actually making
328	>	* progress can be very noticeably long, so it is worth offloading
329	>	* these delays from critical paths as much as possible.
330		*
331		* Trimming workers. To release resources after periods of lack of
332		* use, a worker starting to wait when the pool is quiescent will
333	<	* time out and terminate if the pool has remained quiescent for
334	<	* SHRINK_RATE nanosecs. This will slowly propagate, eventually
335	<	* terminating all workers after long periods of non-use.
333	>	* time out and terminate if the pool has remained quiescent for a
334	>	* given period -- a short period if there are more threads than
335	>	* parallelism, longer as the number of threads decreases. This
336	>	* will slowly propagate, eventually terminating all workers after
337	>	* periods of non-use.
338		*
339		* Shutdown and Termination. A call to shutdownNow atomically sets
340	<	* a runState bit and then (non-atomically) sets each workers
341	<	* runState status, cancels all unprocessed tasks, and wakes up
340	>	* a plock bit and then (non-atomically) sets each worker's
341	>	* qlock status, cancels all unprocessed tasks, and wakes up
342		* all waiting workers. Detecting whether termination should
343		* commence after a non-abrupt shutdown() call requires more work
344		* and bookkeeping. We need consensus about quiescence (i.e., that
#	Line 336 \| Line 346 \| public class ForkJoinPool extends Abstra
346		* indication but non-abrupt shutdown still requires a rechecking
347		* scan for any workers that are inactive but not queued.
348		*
349	<	* Joining Tasks.
350	<	* ==============
349	>	* Joining Tasks
350	>	* =============
351		*
352		* Any of several actions may be taken when one worker is waiting
353	<	* to join a task stolen (or always held by) another. Because we
353	>	* to join a task stolen (or always held) by another. Because we
354		* are multiplexing many tasks on to a pool of workers, we can't
355		* just let them block (as in Thread.join). We also cannot just
356		* reassign the joiner's run-time stack with another and replace
357		* it later, which would be a form of "continuation", that even if
358		* possible is not necessarily a good idea since we sometimes need
359	<	* both an unblocked task and its continuation to
360	<	* progress. Instead we combine two tactics:
359	>	* both an unblocked task and its continuation to progress.
360	>	* Instead we combine two tactics:
361		*
362		* Helping: Arranging for the joiner to execute some task that it
363		* would be running if the steal had not occurred.
#	Line 356 \| Line 366 \| public class ForkJoinPool extends Abstra
366		* method tryCompensate() may create or re-activate a spare
367		* thread to compensate for blocked joiners until they unblock.
368		*
369	<	* A third form (implemented in tryRemoveAndExec and
370	<	* tryPollForAndExec) amounts to helping a hypothetical
371	<	* compensator: If we can readily tell that a possible action of a
372	<	* compensator is to steal and execute the task being joined, the
373	<	* joining thread can do so directly, without the need for a
374	<	* compensation thread (although at the expense of larger run-time
375	<	* stacks, but the tradeoff is typically worthwhile).
369	>	* A third form (implemented in tryRemoveAndExec) amounts to
370	>	* helping a hypothetical compensator: If we can readily tell that
371	>	* a possible action of a compensator is to steal and execute the
372	>	* task being joined, the joining thread can do so directly,
373	>	* without the need for a compensation thread (although at the
374	>	* expense of larger run-time stacks, but the tradeoff is
375	>	* typically worthwhile).
376		*
377		* The ManagedBlocker extension API can't use helping so relies
378		* only on compensation in method awaitBlocker.
#	Line 382 \| Line 392 \| public class ForkJoinPool extends Abstra
392		* (http://portal.acm.org/citation.cfm?id=155354). It differs in
393		* that: (1) We only maintain dependency links across workers upon
394		* steals, rather than use per-task bookkeeping. This sometimes
395	<	* requires a linear scan of workers array to locate stealers, but
396	<	* often doesn't because stealers leave hints (that may become
397	<	* stale/wrong) of where to locate them. A stealHint is only a
398	<	* hint because a worker might have had multiple steals and the
399	<	* hint records only one of them (usually the most current).
400	<	* Hinting isolates cost to when it is needed, rather than adding
401	<	* to per-task overhead. (2) It is "shallow", ignoring nesting
402	<	* and potentially cyclic mutual steals. (3) It is intentionally
395	>	* requires a linear scan of workQueues array to locate stealers,
396	>	* but often doesn't because stealers leave hints (that may become
397	>	* stale/wrong) of where to locate them. It is only a hint
398	>	* because a worker might have had multiple steals and the hint
399	>	* records only one of them (usually the most current). Hinting
400	>	* isolates cost to when it is needed, rather than adding to
401	>	* per-task overhead. (2) It is "shallow", ignoring nesting and
402	>	* potentially cyclic mutual steals. (3) It is intentionally
403		* racy: field currentJoin is updated only while actively joining,
404		* which means that we miss links in the chain during long-lived
405		* tasks, GC stalls etc (which is OK since blocking in such cases
406		* is usually a good idea). (4) We bound the number of attempts
407	<	* to find work (see MAX_HELP_DEPTH) and fall back to suspending
408	<	* the worker and if necessary replacing it with another.
407	>	* to find work (see MAX_HELP) and fall back to suspending the
408	>	* worker and if necessary replacing it with another.
409	>	*
410	>	* Helping actions for CountedCompleters are much simpler: Method
411	>	* helpComplete can take and execute any task with the same root
412	>	* as the task being waited on. However, this still entails some
413	>	* traversal of completer chains, so is less efficient than using
414	>	* CountedCompleters without explicit joins.
415		*
416		* It is impossible to keep exactly the target parallelism number
417		* of threads running at any given time. Determining the
418		* existence of conservatively safe helping targets, the
419		* availability of already-created spares, and the apparent need
420		* to create new spares are all racy, so we rely on multiple
421	<	* retries of each. Currently, in keeping with on-demand
422	<	* signalling policy, we compensate only if blocking would leave
423	<	* less than one active (non-waiting, non-blocked) worker.
424	<	* Additionally, to avoid some false alarms due to GC, lagging
425	<	* counters, system activity, etc, compensated blocking for joins
426	<	* is only attempted after rechecks stabilize in
427	<	* ForkJoinTask.awaitJoin. (Retries are interspersed with
428	<	* Thread.yield, for good citizenship.)
429	<	*
430	<	* Style notes: There is a lot of representation-level coupling
431	<	* among classes ForkJoinPool, ForkJoinWorkerThread, and
432	<	* ForkJoinTask. The fields of WorkQueue maintain data structures
433	<	* managed by ForkJoinPool, so are directly accessed. There is
434	<	* little point trying to reduce this, since any associated future
435	<	* changes in representations will need to be accompanied by
436	<	* algorithmic changes anyway. All together, these low-level
437	<	* implementation choices produce as much as a factor of 4
438	<	* performance improvement compared to naive implementations, and
439	<	* enable the processing of billions of tasks per second, at the
440	<	* expense of some ugliness.
441	<	*
442	<	* Methods signalWork() and scan() are the main bottlenecks so are
443	<	* especially heavily micro-optimized/mangled. There are lots of
444	<	* inline assignments (of form "while ((local = field) != 0)")
445	<	* which are usually the simplest way to ensure the required read
446	<	* orderings (which are sometimes critical). This leads to a
447	<	* "C"-like style of listing declarations of these locals at the
448	<	* heads of methods or blocks. There are several occurrences of
449	<	* the unusual "do {} while (!cas...)" which is the simplest way
450	<	* to force an update of a CAS'ed variable. There are also other
451	<	* coding oddities that help some methods perform reasonably even
452	<	* when interpreted (not compiled).
453	<	*
454	<	* The order of declarations in this file is: (1) declarations of
455	<	* statics (2) fields (along with constants used when unpacking
456	<	* some of them), listed in an order that tends to reduce
457	<	* contention among them a bit under most JVMs; (3) nested
458	<	* classes; (4) internal control methods; (5) callbacks and other
459	<	* support for ForkJoinTask methods; (6) exported methods (plus a
460	<	* few little helpers); (7) static block initializing all statics
461	<	* in a minimally dependent order.
421	>	* retries of each. Compensation in the apparent absence of
422	>	* helping opportunities is challenging to control on JVMs, where
423	>	* GC and other activities can stall progress of tasks that in
424	>	* turn stall out many other dependent tasks, without us being
425	>	* able to determine whether they will ever require compensation.
426	>	* Even though work-stealing otherwise encounters little
427	>	* degradation in the presence of more threads than cores,
428	>	* aggressively adding new threads in such cases entails risk of
429	>	* unwanted positive feedback control loops in which more threads
430	>	* cause more dependent stalls (as well as delayed progress of
431	>	* unblocked threads to the point that we know they are available)
432	>	* leading to more situations requiring more threads, and so
433	>	* on. This aspect of control can be seen as an (analytically
434	>	* intractable) game with an opponent that may choose the worst
435	>	* (for us) active thread to stall at any time. We take several
436	>	* precautions to bound losses (and thus bound gains), mainly in
437	>	* methods tryCompensate and awaitJoin.
438	>	*
439	>	* Common Pool
440	>	* ===========
441	>	*
442	>	* The static commonPool always exists after static
443	>	* initialization. Since it (or any other created pool) need
444	>	* never be used, we minimize initial construction overhead and
445	>	* footprint to the setup of about a dozen fields, with no nested
446	>	* allocation. Most bootstrapping occurs within method
447	>	* fullExternalPush during the first submission to the pool.
448	>	*
449	>	* When external threads submit to the common pool, they can
450	>	* perform some subtask processing (see externalHelpJoin and
451	>	* related methods). We do not need to record whether these
452	>	* submissions are to the common pool -- if not, externalHelpJoin
453	>	* returns quickly (at the most helping to signal some common pool
454	>	* workers). These submitters would otherwise be blocked waiting
455	>	* for completion, so the extra effort (with liberally sprinkled
456	>	* task status checks) in inapplicable cases amounts to an odd
457	>	* form of limited spin-wait before blocking in ForkJoinTask.join.
458	>	*
459	>	* Style notes
460	>	* ===========
461	>	*
462	>	* There is a lot of representation-level coupling among classes
463	>	* ForkJoinPool, ForkJoinWorkerThread, and ForkJoinTask. The
464	>	* fields of WorkQueue maintain data structures managed by
465	>	* ForkJoinPool, so are directly accessed. There is little point
466	>	* trying to reduce this, since any associated future changes in
467	>	* representations will need to be accompanied by algorithmic
468	>	* changes anyway. Several methods intrinsically sprawl because
469	>	* they must accumulate sets of consistent reads of volatiles held
470	>	* in local variables. Methods signalWork() and scan() are the
471	>	* main bottlenecks, so are especially heavily
472	>	* micro-optimized/mangled. There are lots of inline assignments
473	>	* (of form "while ((local = field) != 0)") which are usually the
474	>	* simplest way to ensure the required read orderings (which are
475	>	* sometimes critical). This leads to a "C"-like style of listing
476	>	* declarations of these locals at the heads of methods or blocks.
477	>	* There are several occurrences of the unusual "do {} while
478	>	* (!cas...)" which is the simplest way to force an update of a
479	>	* CAS'ed variable. There are also other coding oddities (including
480	>	* several unnecessary-looking hoisted null checks) that help
481	>	* some methods perform reasonably even when interpreted (not
482	>	* compiled).
483	>	*
484	>	* The order of declarations in this file is:
485	>	* (1) Static utility functions
486	>	* (2) Nested (static) classes
487	>	* (3) Static fields
488	>	* (4) Fields, along with constants used when unpacking some of them
489	>	* (5) Internal control methods
490	>	* (6) Callbacks and other support for ForkJoinTask methods
491	>	* (7) Exported methods
492	>	* (8) Static block initializing statics in minimally dependent order
493	>	*/
494	>
495	>	// Static utilities
496	>
497	>	/**
498	>	* If there is a security manager, makes sure caller has
499	>	* permission to modify threads.
500		*/
501	+	private static void checkPermission() {
502	+	SecurityManager security = System.getSecurityManager();
503	+	if (security != null)
504	+	security.checkPermission(modifyThreadPermission);
505	+	}
506	+
507	+	// Nested classes
508
509		/**
510		* Factory for creating new {@link ForkJoinWorkerThread}s.
#	Line 465 \| Line 526 \| public class ForkJoinPool extends Abstra
526		* Default ForkJoinWorkerThreadFactory implementation; creates a
527		* new ForkJoinWorkerThread.
528		*/
529	<	static class DefaultForkJoinWorkerThreadFactory
529	>	static final class DefaultForkJoinWorkerThreadFactory
530		implements ForkJoinWorkerThreadFactory {
531	<	public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
531	>	public final ForkJoinWorkerThread newThread(ForkJoinPool pool) {
532		return new ForkJoinWorkerThread(pool);
533		}
534		}
535
536		/**
537	<	* Creates a new ForkJoinWorkerThread. This factory is used unless
538	<	* overridden in ForkJoinPool constructors.
539	<	*/
540	<	public static final ForkJoinWorkerThreadFactory
480	<	defaultForkJoinWorkerThreadFactory;
481	<
482	<	/**
483	<	* Permission required for callers of methods that may start or
484	<	* kill threads.
485	<	*/
486	<	private static final RuntimePermission modifyThreadPermission;
487	<
488	<	/**
489	<	* If there is a security manager, makes sure caller has
490	<	* permission to modify threads.
537	>	* Class for artificial tasks that are used to replace the target
538	>	* of local joins if they are removed from an interior queue slot
539	>	* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
540	>	* actually do anything beyond having a unique identity.
541		*/
542	<	private static void checkPermission() {
543	<	SecurityManager security = System.getSecurityManager();
544	<	if (security != null)
545	<	security.checkPermission(modifyThreadPermission);
542	>	static final class EmptyTask extends ForkJoinTask<Void> {
543	>	private static final long serialVersionUID = -7721805057305804111L;
544	>	EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
545	>	public final Void getRawResult() { return null; }
546	>	public final void setRawResult(Void x) {}
547	>	public final boolean exec() { return true; }
548		}
549
550		/**
499	–	* Generator for assigning sequence numbers as pool names.
500	–	*/
501	–	private static final AtomicInteger poolNumberGenerator;
502	–
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.
619	–	*/
620	–
621	–	volatile long ctl; // main pool control
622	–	final int parallelism; // parallelism level
623	–	final int localMode; // per-worker scheduling mode
624	–	int nextPoolIndex; // hint used in registerWorker
625	–	volatile int runState; // shutdown status, seq, and mask
626	–	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
634	–
635	–	/**
551		* Queues supporting work-stealing as well as external task
552		* submission. See above for main rationale and algorithms.
553		* Implementation relies heavily on "Unsafe" intrinsics
#	Line 646 \| Line 561 \| public class ForkJoinPool extends Abstra
561		*
562		* Field "top" is the index (mod array.length) of the next queue
563		* slot to push to or pop from. It is written only by owner thread
564	<	* for push, or under lock for trySharedPush, and accessed by
565	<	* other threads only after reading (volatile) base. Both top and
566	<	* base are allowed to wrap around on overflow, but (top - base)
567	<	* (or more comonly -(base - top) to force volatile read of base
568	<	* before top) still estimates size.
564	>	* for push, or under lock for external/shared push, and accessed
565	>	* by other threads only after reading (volatile) base. Both top
566	>	* and base are allowed to wrap around on overflow, but (top -
567	>	* base) (or more commonly -(base - top) to force volatile read of
568	>	* base before top) still estimates size. The lock ("qlock") is
569	>	* forced to -1 on termination, causing all further lock attempts
570	>	* to fail. (Note: we don't need CAS for termination state because
571	>	* upon pool shutdown, all shared-queues will stop being used
572	>	* anyway.) Nearly all lock bodies are set up so that exceptions
573	>	* within lock bodies are "impossible" (modulo JVM errors that
574	>	* would cause failure anyway.)
575		*
576		* The array slots are read and written using the emulation of
577		* volatiles/atomics provided by Unsafe. Insertions must in
578		* general use putOrderedObject as a form of releasing store to
579		* ensure that all writes to the task object are ordered before
580	<	* its publication in the queue. (Although we can avoid one case
581	<	* of this when locked in trySharedPush.) All removals entail a
582	<	* CAS to null. The array is always a power of two. To ensure
583	<	* safety of Unsafe array operations, all accesses perform
663	<	* explicit null checks and implicit bounds checks via
664	<	* power-of-two masking.
580	>	* its publication in the queue. All removals entail a CAS to
581	>	* null. The array is always a power of two. To ensure safety of
582	>	* Unsafe array operations, all accesses perform explicit null
583	>	* checks and implicit bounds checks via power-of-two masking.
584		*
585		* In addition to basic queuing support, this class contains
586		* fields described elsewhere to control execution. It turns out
587	<	* to work better memory-layout-wise to include them in this
588	<	* class rather than a separate class.
587	>	* to work better memory-layout-wise to include them in this class
588	>	* rather than a separate class.
589		*
590		* Performance on most platforms is very sensitive to placement of
591		* instances of both WorkQueues and their arrays -- we absolutely
#	Line 680 \| Line 599 \| public class ForkJoinPool extends Abstra
599		* trades off slightly slower average field access for the sake of
600		* avoiding really bad worst-case access. (Until better JVM
601		* support is in place, this padding is dependent on transient
602	<	* properties of JVM field layout rules.) We also take care in
684	<	* allocating and sizing and resizing the array. Non-shared queue
685	<	* arrays are initialized (via method growArray) by workers before
686	<	* use. Others are allocated on first use.
602	>	* properties of JVM field layout rules.)
603		*/
604		static final class WorkQueue {
605		/**
606		* Capacity of work-stealing queue array upon initialization.
607	<	* Must be a power of two; at least 4, but set larger to
608	<	* reduce cacheline sharing among queues.
607	>	* Must be a power of two; at least 4, but should be larger to
608	>	* reduce or eliminate cacheline sharing among queues.
609	>	* Currently, it is much larger, as a partial workaround for
610	>	* the fact that JVMs often place arrays in locations that
611	>	* share GC bookkeeping (especially cardmarks) such that
612	>	* per-write accesses encounter serious memory contention.
613		*/
614	<	static final int INITIAL_QUEUE_CAPACITY = 1 << 8;
614	>	static final int INITIAL_QUEUE_CAPACITY = 1 << 13;
615
616		/**
617		* Maximum size for queue arrays. Must be a power of two less
#	Line 702 \| Line 622 \| public class ForkJoinPool extends Abstra
622		*/
623		static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
624
705	–	volatile long totalSteals; // cumulative number of steals
625		int seed; // for random scanning; initialize nonzero
626		volatile int eventCount; // encoded inactivation count; < 0 if inactive
627		int nextWait; // encoded record of next event waiter
628	<	int rescans; // remaining scans until block
710	<	int nsteals; // top-level task executions since last idle
711	<	final int mode; // lifo, fifo, or shared
628	>	int hint; // steal or signal hint (index)
629		int poolIndex; // index of this queue in pool (or 0)
630	<	int stealHint; // index of most recent known stealer
631	<	volatile int runState; // 1: locked, -1: terminate; else 0
630	>	final int mode; // 0: lifo, > 0: fifo, < 0: shared
631	>	int nsteals; // number of steals
632	>	volatile int qlock; // 1: locked, -1: terminate; else 0
633		volatile int base; // index of next slot for poll
634		int top; // index of next slot for push
635		ForkJoinTask<?>[] array; // the elements (initially unallocated)
636	+	final ForkJoinPool pool; // the containing pool (may be null)
637		final ForkJoinWorkerThread owner; // owning thread or null if shared
638		volatile Thread parker; // == owner during call to park; else null
639	<	ForkJoinTask<?> currentJoin; // task being joined in awaitJoin
639	>	volatile ForkJoinTask<?> currentJoin; // task being joined in awaitJoin
640		ForkJoinTask<?> currentSteal; // current non-local task being executed
641	+
642		// Heuristic padding to ameliorate unfortunate memory placements
643	<	Object p00, p01, p02, p03, p04, p05, p06, p07, p08, p09, p0a;
643	>	Object p00, p01, p02, p03, p04, p05, p06, p07;
644	>	Object p08, p09, p0a, p0b, p0c;
645
646	<	WorkQueue(ForkJoinWorkerThread owner, int mode) {
646	>	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode,
647	>	int seed) {
648	>	this.array = new ForkJoinTask<?>[WorkQueue.INITIAL_QUEUE_CAPACITY];
649	>	this.pool = pool;
650		this.owner = owner;
651		this.mode = mode;
652	<	// Place indices in the center of array (that is not yet allocated)
652	>	this.seed = seed;
653	>	// Place indices in the center of array
654		base = top = INITIAL_QUEUE_CAPACITY >>> 1;
655		}
656
657		/**
733	–	* Returns number of tasks in the queue
734	–	*/
735	–	final int queueSize() {
736	–	int n = base - top; // non-owner callers must read base first
737	–	return (n >= 0) ? 0 : -n;
738	–	}
739	–
740	–	/**
658		* Pushes a task. Call only by owner in unshared queues.
659	+	* Cases needing resizing or rejection are relayed to fullPush
660	+	* (that also handles shared queues).
661		*
662		* @param task the task. Caller must ensure non-null.
663	<	* @param p, if non-null, pool to signal if necessary
745	<	* @throw RejectedExecutionException if array cannot
746	<	* be resized
663	>	* @throw RejectedExecutionException if array cannot be resized
664		*/
665	<	final void push(ForkJoinTask<?> task, ForkJoinPool p) {
666	<	ForkJoinTask<?>[] a;
665	>	final void push(ForkJoinTask<?> task) {
666	>	ForkJoinTask<?>[] a; ForkJoinPool p;
667		int s = top, m, n;
668		if ((a = array) != null) { // ignore if queue removed
669		U.putOrderedObject
670		(a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task);
671	<	if ((n = (top = s + 1) - base) <= 2) {
672	<	if (p != null)
673	<	p.signalWork();
671	>	if ((n = (top = s + 1) - base) <= 1) {
672	>	if ((p = pool) != null)
673	>	p.signalWork(this, 0);
674		}
675		else if (n >= m)
676	<	growArray(true);
676	>	growArray();
677		}
678		}
679
#	Line 769 \| Line 686 \| public class ForkJoinPool extends Abstra
686		*/
687		final boolean trySharedPush(ForkJoinTask<?> task) {
688		boolean submitted = false;
689	<	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
690	<	ForkJoinTask<?>[] a = array;
691	<	int s = top, n = s - base;
689	>	if (qlock == 0 && U.compareAndSwapInt(this, QLOCK, 0, 1)) {
690	>	ForkJoinTask<?>[] a = array; ForkJoinPool p;
691	>	int s = top;
692		try {
693	<	if ((a != null && n < a.length - 1) \|\|
694	<	(a = growArray(false)) != null) { // must presize
693	>	if ((a != null && a.length > s + 1 - base) \|\|
694	>	(a = growArray()) != null) { // must presize
695		int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
696	<	U.putObject(a, (long)j, task); // don't need "ordered"
696	>	U.putOrderedObject(a, j, task);
697		top = s + 1;
698		submitted = true;
699		}
700		} finally {
701	<	runState = 0; // unlock
701	>	qlock = 0; // unlock
702		}
703	+	if (submitted && (p = pool) != null)
704	+	p.signalWork(this, 0);
705		}
706		return submitted;
707		}
708
709	+	/**
710	+	* Initializes or doubles the capacity of array. Call either
711	+	* by owner or with lock held -- it is OK for base, but not
712	+	* top, to move while resizings are in progress.
713	+	*/
714	+	final ForkJoinTask<?>[] growArray() {
715	+	ForkJoinTask<?>[] oldA = array;
716	+	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
717	+	if (size > MAXIMUM_QUEUE_CAPACITY)
718	+	throw new RejectedExecutionException("Queue capacity exceeded");
719	+	int oldMask, t, b;
720	+	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
721	+	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
722	+	(t = top) - (b = base) > 0) {
723	+	int mask = size - 1;
724	+	do {
725	+	ForkJoinTask<?> x;
726	+	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
727	+	int j = ((b & mask) << ASHIFT) + ABASE;
728	+	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
729	+	if (x != null &&
730	+	U.compareAndSwapObject(oldA, oldj, x, null))
731	+	U.putObjectVolatile(a, j, x);
732	+	} while (++b != t);
733	+	}
734	+	return a;
735	+	}
736	+
737		/**
738	<	* Takes next task, if one exists, in FIFO order.
738	>	* Takes next task, if one exists, in LIFO order. Call only
739	>	* by owner in unshared queues.
740		*/
741	<	final ForkJoinTask<?> poll() {
742	<	ForkJoinTask<?>[] a; int b, i;
743	<	while ((b = base) - top < 0 && (a = array) != null &&
744	<	(i = (a.length - 1) & b) >= 0) {
745	<	int j = (i << ASHIFT) + ABASE;
746	<	ForkJoinTask<?> t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
747	<	if (t != null && base == b &&
741	>	final ForkJoinTask<?> pop() {
742	>	ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
743	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
744	>	for (int s; (s = top - 1) - base >= 0;) {
745	>	long j = ((m & s) << ASHIFT) + ABASE;
746	>	if ((t = (ForkJoinTask<?>)U.getObject(a, j)) == null)
747	>	break;
748	>	if (U.compareAndSwapObject(a, j, t, null)) {
749	>	top = s;
750	>	return t;
751	>	}
752	>	}
753	>	}
754	>	return null;
755	>	}
756	>
757	>	/**
758	>	* Takes a task in FIFO order if b is base of queue and a task
759	>	* can be claimed without contention. Specialized versions
760	>	* appear in ForkJoinPool methods scan and tryHelpStealer.
761	>	*/
762	>	final ForkJoinTask<?> pollAt(int b) {
763	>	ForkJoinTask<?> t; ForkJoinTask<?>[] a;
764	>	if ((a = array) != null) {
765	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
766	>	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
767	>	base == b &&
768		U.compareAndSwapObject(a, j, t, null)) {
769		base = b + 1;
770		return t;
#	Line 806 \| Line 774 \| public class ForkJoinPool extends Abstra
774		}
775
776		/**
777	<	* Takes next task, if one exists, in LIFO order.
810	<	* Call only by owner in unshared queues.
777	>	* Takes next task, if one exists, in FIFO order.
778		*/
779	<	final ForkJoinTask<?> pop() {
780	<	ForkJoinTask<?> t; int m;
781	<	ForkJoinTask<?>[] a = array;
782	<	if (a != null && (m = a.length - 1) >= 0) {
783	<	for (int s; (s = top - 1) - base >= 0;) {
784	<	int j = ((m & s) << ASHIFT) + ABASE;
785	<	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) == null)
786	<	break;
787	<	if (U.compareAndSwapObject(a, j, t, null)) {
821	<	top = s;
779	>	final ForkJoinTask<?> poll() {
780	>	ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t;
781	>	while ((b = base) - top < 0 && (a = array) != null) {
782	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
783	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
784	>	if (t != null) {
785	>	if (base == b &&
786	>	U.compareAndSwapObject(a, j, t, null)) {
787	>	base = b + 1;
788		return t;
789		}
790		}
791	+	else if (base == b) {
792	+	if (b + 1 == top)
793	+	break;
794	+	Thread.yield(); // wait for lagging update (very rare)
795	+	}
796		}
797		return null;
798		}
#	Line 846 \| Line 817 \| public class ForkJoinPool extends Abstra
817		}
818
819		/**
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	–	/**
820		* Pops the given task only if it is at the current top.
821	+	* (A shared version is available only via FJP.tryExternalUnpush)
822		*/
823		final boolean tryUnpush(ForkJoinTask<?> t) {
824		ForkJoinTask<?>[] a; int s;
#	Line 878 \| Line 832 \| public class ForkJoinPool extends Abstra
832		}
833
834		/**
835	<	* Polls the given task only if it is at the current base.
835	>	* Removes and cancels all known tasks, ignoring any exceptions.
836		*/
837	<	final boolean pollFor(ForkJoinTask<?> task) {
838	<	ForkJoinTask<?>[] a; int b, i;
839	<	if ((b = base) - top < 0 && (a = array) != null &&
840	<	(i = (a.length - 1) & b) >= 0) {
841	<	int j = (i << ASHIFT) + ABASE;
842	<	if (U.getObjectVolatile(a, j) == task && base == b &&
843	<	U.compareAndSwapObject(a, j, task, null)) {
844	<	base = b + 1;
845	<	return true;
837	>	final void cancelAll() {
838	>	ForkJoinTask.cancelIgnoringExceptions(currentJoin);
839	>	ForkJoinTask.cancelIgnoringExceptions(currentSteal);
840	>	for (ForkJoinTask<?> t; (t = poll()) != null; )
841	>	ForkJoinTask.cancelIgnoringExceptions(t);
842	>	}
843	>
844	>	/**
845	>	* Computes next value for random probes. Scans don't require
846	>	* a very high quality generator, but also not a crummy one.
847	>	* Marsaglia xor-shift is cheap and works well enough. Note:
848	>	* This is manually inlined in its usages in ForkJoinPool to
849	>	* avoid writes inside busy scan loops.
850	>	*/
851	>	final int nextSeed() {
852	>	int r = seed;
853	>	r ^= r << 13;
854	>	r ^= r >>> 17;
855	>	return seed = r ^= r << 5;
856	>	}
857	>
858	>	/**
859	>	* Provides a more accurate estimate of size than (top - base)
860	>	* by ordering reads and checking whether a near-empty queue
861	>	* has at least one unclaimed task.
862	>	*/
863	>	final int queueSize() {
864	>	ForkJoinTask<?>[] a; int k, s, n;
865	>	return ((n = base - (s = top)) < 0 &&
866	>	(n != -1 \|\|
867	>	((a = array) != null && (k = a.length) > 0 &&
868	>	U.getObject
869	>	(a, (long)((((k - 1) & (s - 1)) << ASHIFT) + ABASE)) != null))) ?
870	>	-n : 0;
871	>	}
872	>
873	>	// Specialized execution methods
874	>
875	>	/**
876	>	* Pops and runs tasks until empty.
877	>	*/
878	>	private void popAndExecAll() {
879	>	// A bit faster than repeated pop calls
880	>	ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t;
881	>	while ((a = array) != null && (m = a.length - 1) >= 0 &&
882	>	(s = top - 1) - base >= 0 &&
883	>	(t = ((ForkJoinTask<?>)
884	>	U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
885	>	!= null) {
886	>	if (U.compareAndSwapObject(a, j, t, null)) {
887	>	top = s;
888	>	t.doExec();
889		}
890		}
894	–	return false;
891		}
892
893		/**
894	<	* If present, removes from queue and executes the given task, or
895	<	* any other cancelled task. Returns (true) immediately on any CAS
894	>	* Polls and runs tasks until empty.
895	>	*/
896	>	private void pollAndExecAll() {
897	>	for (ForkJoinTask<?> t; (t = poll()) != null;)
898	>	t.doExec();
899	>	}
900	>
901	>	/**
902	>	* If present, removes from queue and executes the given task,
903	>	* or any other cancelled task. Returns (true) on any CAS
904		* or consistency check failure so caller can retry.
905		*
906	<	* @return false if no progress can be made
906	>	* @return false if no progress can be made, else true;
907		*/
908		final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
909	<	boolean removed = false, empty = true, progress = true;
909	>	boolean stat = true, removed = false, empty = true;
910		ForkJoinTask<?>[] a; int m, s, b, n;
911		if ((a = array) != null && (m = a.length - 1) >= 0 &&
912		(n = (s = top) - (b = base)) > 0) {
#	Line 932 \| Line 936 \| public class ForkJoinPool extends Abstra
936		}
937		if (--n == 0) {
938		if (!empty && base == b)
939	<	progress = false;
939	>	stat = false;
940		break;
941		}
942		}
943		}
944		if (removed)
945		task.doExec();
946	<	return progress;
946	>	return stat;
947		}
948
949		/**
950	<	* Initializes or doubles the capacity of array. Call either
951	<	* 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.
950	>	* Polls for and executes the given task or any other task in
951	>	* its CountedCompleter computation
952		*/
953	<	final ForkJoinTask<?>[] growArray(boolean rejectOnFailure) {
954	<	ForkJoinTask<?>[] oldA = array;
955	<	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
956	<	if (size <= MAXIMUM_QUEUE_CAPACITY) {
957	<	int oldMask, t, b;
958	<	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
959	<	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
960	<	(t = top) - (b = base) > 0) {
961	<	int mask = size - 1;
962	<	do {
963	<	ForkJoinTask<?> x;
964	<	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
965	<	int j = ((b & mask) << ASHIFT) + ABASE;
966	<	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
967	<	if (x != null &&
968	<	U.compareAndSwapObject(oldA, oldj, x, null))
969	<	U.putObjectVolatile(a, j, x);
970	<	} while (++b != t);
953	>	final boolean pollAndExecCC(ForkJoinTask<?> root) {
954	>	ForkJoinTask<?>[] a; int b; Object o;
955	>	outer: while ((b = base) - top < 0 && (a = array) != null) {
956	>	long j = (((a.length - 1) & b) << ASHIFT) + ABASE;
957	>	if ((o = U.getObject(a, j)) == null \|\|
958	>	!(o instanceof CountedCompleter))
959	>	break;
960	>	for (CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;;) {
961	>	if (r == root) {
962	>	if (base == b &&
963	>	U.compareAndSwapObject(a, j, t, null)) {
964	>	base = b + 1;
965	>	t.doExec();
966	>	return true;
967	>	}
968	>	else
969	>	break; // restart
970	>	}
971	>	if ((r = r.completer) == null)
972	>	break outer; // not part of root computation
973		}
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();
974		}
975	+	return false;
976		}
977
978		/**
979		* Executes a top-level task and any local tasks remaining
980		* after execution.
1006	–	*
1007	–	* @return true unless terminating
981		*/
982	<	final boolean runTask(ForkJoinTask<?> t) {
1010	<	boolean alive = true;
982	>	final void runTask(ForkJoinTask<?> t) {
983		if (t != null) {
984	<	currentSteal = t;
1013	<	t.doExec();
1014	<	runLocalTasks();
1015	<	++nsteals;
984	>	(currentSteal = t).doExec();
985		currentSteal = null;
986	+	++nsteals;
987	+	if (top != base) { // process remaining local tasks
988	+	if (mode == 0)
989	+	popAndExecAll();
990	+	else
991	+	pollAndExecAll();
992	+	}
993		}
1018	–	else if (runState < 0) // terminating
1019	–	alive = false;
1020	–	return alive;
994		}
995
996		/**
997	<	* Executes a non-top-level (stolen) task
997	>	* Executes a non-top-level (stolen) task.
998		*/
999		final void runSubtask(ForkJoinTask<?> t) {
1000		if (t != null) {
1001		ForkJoinTask<?> ps = currentSteal;
1002	<	currentSteal = t;
1030	<	t.doExec();
1002	>	(currentSteal = t).doExec();
1003		currentSteal = ps;
1004		}
1005		}
1006
1007		/**
1008	<	* 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.
1008	>	* Returns true if owned and not known to be blocked.
1009		*/
1010	<	final int nextSeed() {
1011	<	int r = seed;
1012	<	r ^= r << 13;
1013	<	r ^= r >>> 17;
1014	<	r ^= r << 5;
1015	<	return seed = r;
1010	>	final boolean isApparentlyUnblocked() {
1011	>	Thread wt; Thread.State s;
1012	>	return (eventCount >= 0 &&
1013	>	(wt = owner) != null &&
1014	>	(s = wt.getState()) != Thread.State.BLOCKED &&
1015	>	s != Thread.State.WAITING &&
1016	>	s != Thread.State.TIMED_WAITING);
1017	>	}
1018	>
1019	>	/**
1020	>	* If this owned and is not already interrupted, try to
1021	>	* interrupt and/or unpark, ignoring exceptions.
1022	>	*/
1023	>	final void interruptOwner() {
1024	>	Thread wt, p;
1025	>	if ((wt = owner) != null && !wt.isInterrupted()) {
1026	>	try {
1027	>	wt.interrupt();
1028	>	} catch (SecurityException ignore) {
1029	>	}
1030	>	}
1031	>	if ((p = parker) != null)
1032	>	U.unpark(p);
1033		}
1034
1035		// Unsafe mechanics
1036		private static final sun.misc.Unsafe U;
1037	<	private static final long RUNSTATE;
1037	>	private static final long QLOCK;
1038		private static final int ABASE;
1039		private static final int ASHIFT;
1040		static {
#	Line 1058 \| Line 1043 \| public class ForkJoinPool extends Abstra
1043		U = getUnsafe();
1044		Class<?> k = WorkQueue.class;
1045		Class<?> ak = ForkJoinTask[].class;
1046	<	RUNSTATE = U.objectFieldOffset
1047	<	(k.getDeclaredField("runState"));
1046	>	QLOCK = U.objectFieldOffset
1047	>	(k.getDeclaredField("qlock"));
1048		ABASE = U.arrayBaseOffset(ak);
1049		s = U.arrayIndexScale(ak);
1050		} catch (Exception e) {
#	Line 1071 \| Line 1056 \| public class ForkJoinPool extends Abstra
1056		}
1057		}
1058
1059	+	// static fields (initialized in static initializer below)
1060	+
1061		/**
1062	<	* Class for artificial tasks that are used to replace the target
1063	<	* 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.
1062	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
1063	>	* overridden in ForkJoinPool constructors.
1064		*/
1065	<	static final class EmptyTask extends ForkJoinTask<Void> {
1066	<	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	<	}
1065	>	public static final ForkJoinWorkerThreadFactory
1066	>	defaultForkJoinWorkerThreadFactory;
1067
1068		/**
1069	<	* Computes a hash code for the given thread. This method is
1070	<	* expected to provide higher-quality hash codes than those using
1071	<	* method hashCode().
1069	>	* Per-thread records for threads that submit to pools. Currently
1070	>	* holds only pseudo-random seed / index that is used to choose
1071	>	* submission queues in method externalPush. In the future, this may
1072	>	* also incorporate a means to implement different task rejection
1073	>	* and resubmission policies.
1074	>	*
1075	>	* Seeds for submitters and workers/workQueues work in basically
1076	>	* the same way but are initialized and updated using slightly
1077	>	* different mechanics. Both are initialized using the same
1078	>	* approach as in class ThreadLocal, where successive values are
1079	>	* unlikely to collide with previous values. Seeds are then
1080	>	* randomly modified upon collisions using xorshifts, which
1081	>	* requires a non-zero seed.
1082		*/
1083	<	static final int hashThread(Thread t) {
1084	<	long id = (t == null)? 0L : t.getId(); // Use MurmurHash of thread id
1085	<	int h = (int)id ^ (int)(id >>> 32);
1095	<	h ^= h >>> 16;
1096	<	h *= 0x85ebca6b;
1097	<	h ^= h >>> 13;
1098	<	h *= 0xc2b2ae35;
1099	<	return h ^ (h >>> 16);
1083	>	static final class Submitter {
1084	>	int seed;
1085	>	Submitter(int s) { seed = s; }
1086		}
1087
1088		/**
1089	<	* Top-level runloop for workers
1089	>	* Per-thread submission bookkeeping. Shared across all pools
1090	>	* to reduce ThreadLocal pollution and because random motion
1091	>	* to avoid contention in one pool is likely to hold for others.
1092	>	* Lazily initialized on first submission (but null-checked
1093	>	* in other contexts to avoid unnecessary initialization).
1094	>	*/
1095	>	static final ThreadLocal<Submitter> submitters;
1096	>
1097	>	/**
1098	>	* Common (static) pool. Non-null for public use unless a static
1099	>	* construction exception, but internal usages null-check on use
1100	>	* to paranoically avoid potential initialization circularities
1101	>	* as well as to simplify generated code.
1102	>	*/
1103	>	static final ForkJoinPool commonPool;
1104	>
1105	>	/**
1106	>	* Permission required for callers of methods that may start or
1107	>	* kill threads.
1108	>	*/
1109	>	private static final RuntimePermission modifyThreadPermission;
1110	>
1111	>	/**
1112	>	* Common pool parallelism. Must equal commonPool.parallelism.
1113	>	*/
1114	>	static final int commonPoolParallelism;
1115	>
1116	>	/**
1117	>	* Sequence number for creating workerNamePrefix.
1118		*/
1119	<	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
1119	>	private static int poolNumberSequence;
1120
1121	<	do {} while (w.runTask(scan(w)));
1121	>	/**
1122	>	* Return the next sequence number. We don't expect this to
1123	>	* ever contend so use simple builtin sync.
1124	>	*/
1125	>	private static final synchronized int nextPoolId() {
1126	>	return ++poolNumberSequence;
1127		}
1128
1129	<	// Creating, registering and deregistering workers
1129	>	// static constants
1130
1131		/**
1132	<	* Tries to create and start a worker
1132	>	* Initial timeout value (in nanoseconds) for the thread
1133	>	* triggering quiescence to park waiting for new work. On timeout,
1134	>	* the thread will instead try to shrink the number of
1135	>	* workers. The value should be large enough to avoid overly
1136	>	* aggressive shrinkage during most transient stalls (long GCs
1137	>	* etc).
1138		*/
1139	<	private void addWorker() {
1140	<	Throwable ex = null;
1141	<	ForkJoinWorkerThread w = null;
1142	<	try {
1143	<	if ((w = factory.newThread(this)) != null) {
1144	<	w.start();
1145	<	return;
1139	>	private static final long IDLE_TIMEOUT = 2000L * 1000L * 1000L; // 2sec
1140	>
1141	>	/**
1142	>	* Timeout value when there are more threads than parallelism level
1143	>	*/
1144	>	private static final long FAST_IDLE_TIMEOUT = 200L * 1000L * 1000L;
1145	>
1146	>	/**
1147	>	* The maximum stolen->joining link depth allowed in method
1148	>	* tryHelpStealer. Must be a power of two. Depths for legitimate
1149	>	* chains are unbounded, but we use a fixed constant to avoid
1150	>	* (otherwise unchecked) cycles and to bound staleness of
1151	>	* traversal parameters at the expense of sometimes blocking when
1152	>	* we could be helping.
1153	>	*/
1154	>	private static final int MAX_HELP = 64;
1155	>
1156	>	/**
1157	>	* Increment for seed generators. See class ThreadLocal for
1158	>	* explanation.
1159	>	*/
1160	>	private static final int SEED_INCREMENT = 0x61c88647;
1161	>
1162	>	/**
1163	>	* Bits and masks for control variables
1164	>	*
1165	>	* Field ctl is a long packed with:
1166	>	* AC: Number of active running workers minus target parallelism (16 bits)
1167	>	* TC: Number of total workers minus target parallelism (16 bits)
1168	>	* ST: true if pool is terminating (1 bit)
1169	>	* EC: the wait count of top waiting thread (15 bits)
1170	>	* ID: poolIndex of top of Treiber stack of waiters (16 bits)
1171	>	*
1172	>	* When convenient, we can extract the upper 32 bits of counts and
1173	>	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
1174	>	* (int)ctl. The ec field is never accessed alone, but always
1175	>	* together with id and st. The offsets of counts by the target
1176	>	* parallelism and the positionings of fields makes it possible to
1177	>	* perform the most common checks via sign tests of fields: When
1178	>	* ac is negative, there are not enough active workers, when tc is
1179	>	* negative, there are not enough total workers, and when e is
1180	>	* negative, the pool is terminating. To deal with these possibly
1181	>	* negative fields, we use casts in and out of "short" and/or
1182	>	* signed shifts to maintain signedness.
1183	>	*
1184	>	* When a thread is queued (inactivated), its eventCount field is
1185	>	* set negative, which is the only way to tell if a worker is
1186	>	* prevented from executing tasks, even though it must continue to
1187	>	* scan for them to avoid queuing races. Note however that
1188	>	* eventCount updates lag releases so usage requires care.
1189	>	*
1190	>	* Field plock is an int packed with:
1191	>	* SHUTDOWN: true if shutdown is enabled (1 bit)
1192	>	* SEQ: a sequence lock, with PL_LOCK bit set if locked (30 bits)
1193	>	* SIGNAL: set when threads may be waiting on the lock (1 bit)
1194	>	*
1195	>	* The sequence number enables simple consistency checks:
1196	>	* Staleness of read-only operations on the workQueues array can
1197	>	* be checked by comparing plock before vs after the reads.
1198	>	*/
1199	>
1200	>	// bit positions/shifts for fields
1201	>	private static final int AC_SHIFT = 48;
1202	>	private static final int TC_SHIFT = 32;
1203	>	private static final int ST_SHIFT = 31;
1204	>	private static final int EC_SHIFT = 16;
1205	>
1206	>	// bounds
1207	>	private static final int SMASK = 0xffff; // short bits
1208	>	private static final int MAX_CAP = 0x7fff; // max #workers - 1
1209	>	private static final int EVENMASK = 0xfffe; // even short bits
1210	>	private static final int SQMASK = 0x007e; // max 64 (even) slots
1211	>	private static final int SHORT_SIGN = 1 << 15;
1212	>	private static final int INT_SIGN = 1 << 31;
1213	>
1214	>	// masks
1215	>	private static final long STOP_BIT = 0x0001L << ST_SHIFT;
1216	>	private static final long AC_MASK = ((long)SMASK) << AC_SHIFT;
1217	>	private static final long TC_MASK = ((long)SMASK) << TC_SHIFT;
1218	>
1219	>	// units for incrementing and decrementing
1220	>	private static final long TC_UNIT = 1L << TC_SHIFT;
1221	>	private static final long AC_UNIT = 1L << AC_SHIFT;
1222	>
1223	>	// masks and units for dealing with u = (int)(ctl >>> 32)
1224	>	private static final int UAC_SHIFT = AC_SHIFT - 32;
1225	>	private static final int UTC_SHIFT = TC_SHIFT - 32;
1226	>	private static final int UAC_MASK = SMASK << UAC_SHIFT;
1227	>	private static final int UTC_MASK = SMASK << UTC_SHIFT;
1228	>	private static final int UAC_UNIT = 1 << UAC_SHIFT;
1229	>	private static final int UTC_UNIT = 1 << UTC_SHIFT;
1230	>
1231	>	// masks and units for dealing with e = (int)ctl
1232	>	private static final int E_MASK = 0x7fffffff; // no STOP_BIT
1233	>	private static final int E_SEQ = 1 << EC_SHIFT;
1234	>
1235	>	// plock bits
1236	>	private static final int SHUTDOWN = 1 << 31;
1237	>	private static final int PL_LOCK = 2;
1238	>	private static final int PL_SIGNAL = 1;
1239	>	private static final int PL_SPINS = 1 << 8;
1240	>
1241	>	// access mode for WorkQueue
1242	>	static final int LIFO_QUEUE = 0;
1243	>	static final int FIFO_QUEUE = 1;
1244	>	static final int SHARED_QUEUE = -1;
1245	>
1246	>	// bounds for #steps in scan loop -- must be power 2 minus 1
1247	>	private static final int MIN_SCAN = 0x1ff; // cover estimation slop
1248	>	private static final int MAX_SCAN = 0x1ffff; // 4 * max workers
1249	>
1250	>	// Instance fields
1251	>
1252	>	/*
1253	>	* Field layout of this class tends to matter more than one would
1254	>	* like. Runtime layout order is only loosely related to
1255	>	* declaration order and may differ across JVMs, but the following
1256	>	* empirically works OK on current JVMs.
1257	>	*/
1258	>	volatile long stealCount; // collects worker counts
1259	>	volatile long ctl; // main pool control
1260	>	volatile int plock; // shutdown status and seqLock
1261	>	volatile int indexSeed; // worker/submitter index seed
1262	>	final int config; // mode and parallelism level
1263	>	WorkQueue[] workQueues; // main registry
1264	>	final ForkJoinWorkerThreadFactory factory;
1265	>	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1266	>	final String workerNamePrefix; // to create worker name string
1267	>
1268	>	/*
1269	>	* Acquires the plock lock to protect worker array and related
1270	>	* updates. This method is called only if an initial CAS on plock
1271	>	* fails. This acts as a spinLock for normal cases, but falls back
1272	>	* to builtin monitor to block when (rarely) needed. This would be
1273	>	* a terrible idea for a highly contended lock, but works fine as
1274	>	* a more conservative alternative to a pure spinlock. See
1275	>	* internal ConcurrentHashMap documentation for further
1276	>	* explanation of nearly the same construction.
1277	>	*/
1278	>	private int acquirePlock() {
1279	>	int spins = PL_SPINS, r = 0, ps, nps;
1280	>	for (;;) {
1281	>	if (((ps = plock) & PL_LOCK) == 0 &&
1282	>	U.compareAndSwapInt(this, PLOCK, ps, nps = ps + PL_LOCK))
1283	>	return nps;
1284	>	else if (r == 0) { // randomize spins if possible
1285	>	Thread t = Thread.currentThread(); WorkQueue w; Submitter z;
1286	>	if ((t instanceof ForkJoinWorkerThread) &&
1287	>	(w = ((ForkJoinWorkerThread)t).workQueue) != null)
1288	>	r = w.seed;
1289	>	else if ((z = submitters.get()) != null)
1290	>	r = z.seed;
1291	>	else
1292	>	r = 1;
1293	>	}
1294	>	else if (spins >= 0) {
1295	>	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1296	>	if (r >= 0)
1297	>	--spins;
1298	>	}
1299	>	else if (U.compareAndSwapInt(this, PLOCK, ps, ps \| PL_SIGNAL)) {
1300	>	synchronized (this) {
1301	>	if ((plock & PL_SIGNAL) != 0) {
1302	>	try {
1303	>	wait();
1304	>	} catch (InterruptedException ie) {
1305	>	try {
1306	>	Thread.currentThread().interrupt();
1307	>	} catch (SecurityException ignore) {
1308	>	}
1309	>	}
1310	>	}
1311	>	else
1312	>	notifyAll();
1313	>	}
1314		}
1126	–	} catch (Throwable e) {
1127	–	ex = e;
1315		}
1129	–	deregisterWorker(w, ex);
1316		}
1317
1318		/**
1319	<	* Callback from ForkJoinWorkerThread constructor to assign a
1320	<	* public name. This must be separate from registerWorker because
1135	<	* it is called during the "super" constructor call in
1136	<	* ForkJoinWorkerThread.
1319	>	* Unlocks and signals any thread waiting for plock. Called only
1320	>	* when CAS of seq value for unlock fails.
1321		*/
1322	<	final String nextWorkerName() {
1323	<	return workerNamePrefix.concat
1324	<	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1322	>	private void releasePlock(int ps) {
1323	>	plock = ps;
1324	>	synchronized (this) { notifyAll(); }
1325		}
1326
1327		/**
1328	<	* Callback from ForkJoinWorkerThread constructor to establish and
1329	<	* record its WorkQueue
1328	>	* Tries to create and start a worker; adjusts counts etc on failure
1329	>	*/
1330	>	private void addWorker() {
1331	>	ForkJoinWorkerThread wt = null;
1332	>	try {
1333	>	(wt = factory.newThread(this)).start();
1334	>	} catch (Throwable ex) {
1335	>	deregisterWorker(wt, ex); // adjust on failure
1336	>	}
1337	>	}
1338	>
1339	>	/**
1340	>	* Performs secondary initialization, called when plock is zero.
1341	>	* Creates workQueue array and sets plock to a valid value. The
1342	>	* lock body must be exception-free (so no try/finally) so we
1343	>	* optimistically allocate new array outside the lock and throw
1344	>	* away if (very rarely) not needed. (A similar tactic is used in
1345	>	* fullExternalPush.) Because the plock seq value can eventually
1346	>	* wrap around zero, this method harmlessly fails to reinitialize
1347	>	* if workQueues exists, while still advancing plock.
1348	>	*/
1349	>	private void initWorkQueuesArray() {
1350	>	WorkQueue[] ws; int ps;
1351	>	int p = config & SMASK; // find power of two table size
1352	>	int n = (p > 1) ? p - 1 : 1; // ensure at least 2 slots
1353	>	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4; n \|= n >>> 8; n \|= n >>> 16;
1354	>	WorkQueue[] nws = new WorkQueue[(n + 1) << 1];
1355	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1356	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1357	>	ps = acquirePlock();
1358	>	if ((ws = workQueues) == null \|\| ws.length == 0)
1359	>	workQueues = nws;
1360	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1361	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1362	>	releasePlock(nps);
1363	>	long c; int u;
1364	>	if ((u = (int)((c = ctl) >>> 32)) < 0 && (int)c == 0) {
1365	>	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) \|
1366	>	((u + UAC_UNIT) & UAC_MASK)) << 32;
1367	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1368	>	addWorker();
1369	>	}
1370	>
1371	>	}
1372	>
1373	>	// Registering and deregistering workers
1374	>
1375	>	/**
1376	>	* Callback from ForkJoinWorkerThread to establish and record its
1377	>	* WorkQueue. To avoid scanning bias due to packing entries in
1378	>	* front of the workQueues array, we treat the array as a simple
1379	>	* power-of-two hash table using per-thread seed as hash,
1380	>	* expanding as needed.
1381		*
1382		* @param wt the worker thread
1383		*/
1384		final void registerWorker(ForkJoinWorkerThread wt) {
1385	<	WorkQueue w = wt.workQueue;
1386	<	ReentrantLock lock = this.lock;
1387	<	lock.lock();
1388	<	try {
1389	<	int k = nextPoolIndex;
1390	<	WorkQueue[] ws = workQueues;
1391	<	if (ws != null) { // ignore on shutdown
1392	<	int n = ws.length;
1393	<	if (k < 0 \|\| (k & 1) == 0 \|\| k >= n \|\| ws[k] != null) {
1394	<	for (k = 1; k < n && ws[k] != null; k += 2)
1395	<	; // workers are at odd indices
1396	<	if (k >= n) // resize
1397	<	workQueues = ws = Arrays.copyOf(ws, n << 1);
1398	<	}
1399	<	w.poolIndex = k;
1400	<	w.eventCount = ~(k >>> 1) & SMASK; // Set up wait count
1401	<	ws[k] = w; // record worker
1402	<	nextPoolIndex = k + 2;
1403	<	int rs = runState;
1404	<	int m = rs & SMASK; // recalculate runState mask
1405	<	if (k > m)
1406	<	m = (m << 1) + 1;
1407	<	runState = (rs & SHUTDOWN) \| ((rs + RS_SEQ) & RS_SEQ_MASK) \| m;
1385	>	if (wt != null && wt.workQueue == null) {
1386	>	int s, ps; // generate a rarely colliding candidate index seed
1387	>	do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed,
1388	>	s += SEED_INCREMENT) \|\|
1389	>	s == 0); // skip 0
1390	>	WorkQueue w = new WorkQueue(this, wt, config >>> 16, s);
1391	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1392	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1393	>	ps = acquirePlock();
1394	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1395	>	try {
1396	>	WorkQueue[] ws;
1397	>	if ((ws = workQueues) != null && wt.workQueue == null) {
1398	>	int n = ws.length, m = n - 1;
1399	>	int r = (s << 1) \| 1; // use odd-numbered indices
1400	>	if (ws[r &= m] != null) { // collision
1401	>	int probes = 0; // step by approx half size
1402	>	int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2;
1403	>	while (ws[r = (r + step) & m] != null) {
1404	>	if (++probes >= n) {
1405	>	workQueues = ws = Arrays.copyOf(ws, n <<= 1);
1406	>	m = n - 1;
1407	>	probes = 0;
1408	>	}
1409	>	}
1410	>	}
1411	>	w.eventCount = w.poolIndex = r; // volatile write orders
1412	>	wt.workQueue = ws[r] = w;
1413	>	}
1414	>	} finally {
1415	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1416	>	releasePlock(nps);
1417		}
1174	–	} finally {
1175	–	lock.unlock();
1418		}
1419		}
1420
1421		/**
1422	<	* Final callback from terminating worker, as well as failure to
1423	<	* construct or start a worker in addWorker. Removes record of
1424	<	* worker from array, and adjusts counts. If pool is shutting
1425	<	* down, tries to complete termination.
1422	>	* Final callback from terminating worker, as well as upon failure
1423	>	* to construct or start a worker. Removes record of worker from
1424	>	* array, and adjusts counts. If pool is shutting down, tries to
1425	>	* complete termination.
1426		*
1427	<	* @param wt the worker thread or null if addWorker failed
1427	>	* @param wt the worker thread or null if construction failed
1428		* @param ex the exception causing failure, or null if none
1429		*/
1430		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1431		WorkQueue w = null;
1432		if (wt != null && (w = wt.workQueue) != null) {
1433	<	w.runState = -1; // ensure runState is set
1434	<	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1435	<	int idx = w.poolIndex;
1436	<	ReentrantLock lock = this.lock;
1437	<	lock.lock();
1438	<	try { // remove record from array
1433	>	int ps;
1434	>	w.qlock = -1; // ensure set
1435	>	long ns = w.nsteals, sc; // collect steal count
1436	>	do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
1437	>	sc = stealCount, sc + ns));
1438	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1439	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1440	>	ps = acquirePlock();
1441	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1442	>	try {
1443	>	int idx = w.poolIndex;
1444		WorkQueue[] ws = workQueues;
1445		if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1446	<	ws[nextPoolIndex = idx] = null;
1446	>	ws[idx] = null;
1447		} finally {
1448	<	lock.unlock();
1448	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1449	>	releasePlock(nps);
1450		}
1451		}
1452
#	Line 1208 \| Line 1456 \| public class ForkJoinPool extends Abstra
1456		((c - TC_UNIT) & TC_MASK) \|
1457		(c & ~(AC_MASK\|TC_MASK)))));
1458
1459	<	if (!tryTerminate(false) && w != null) {
1459	>	if (!tryTerminate(false, false) && w != null) {
1460		w.cancelAll(); // cancel remaining tasks
1461		if (w.array != null) // suppress signal if never ran
1462	<	signalWork(); // wake up or create replacement
1462	>	helpSignal(null, 0); // wake up or create replacement
1463	>	if (ex == null) // help clean refs on way out
1464	>	ForkJoinTask.helpExpungeStaleExceptions();
1465		}
1466
1467		if (ex != null) // rethrow
1468	<	U.throwException(ex);
1468	>	ForkJoinTask.rethrow(ex);
1469		}
1470
1471	<
1222	<	// Maintaining ctl counts
1471	>	// Submissions
1472
1473		/**
1474	<	* Increments active count; mainly called upon return from blocking
1475	<	*/
1476	<	final void incrementActiveCount() {
1477	<	long c;
1478	<	do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
1474	>	* Unless shutting down, adds the given task to a submission queue
1475	>	* at submitter's current queue index (modulo submission
1476	>	* range). Only the most common path is directly handled in this
1477	>	* method. All others are relayed to fullExternalPush.
1478	>	*
1479	>	* @param task the task. Caller must ensure non-null.
1480	>	*/
1481	>	final void externalPush(ForkJoinTask<?> task) {
1482	>	WorkQueue[] ws; WorkQueue q; Submitter z; int m; ForkJoinTask<?>[] a;
1483	>	if ((z = submitters.get()) != null && plock > 0 &&
1484	>	(ws = workQueues) != null && (m = (ws.length - 1)) >= 0 &&
1485	>	(q = ws[m & z.seed & SQMASK]) != null &&
1486	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock
1487	>	int b = q.base, s = q.top, n, an;
1488	>	if ((a = q.array) != null && (an = a.length) > (n = s + 1 - b)) {
1489	>	U.putObject(a, (long)(((an - 1) & s) << ASHIFT) + ABASE, task);
1490	>	q.top = s + 1; // push on to deque
1491	>	q.qlock = 0;
1492	>	if (n <= 2)
1493	>	signalWork(q, 0);
1494	>	return;
1495	>	}
1496	>	q.qlock = 0;
1497	>	}
1498	>	fullExternalPush(task);
1499		}
1500
1501		/**
1502	<	* Activates or creates a worker
1503	<	*/
1504	<	final void signalWork() {
1505	<	/*
1506	<	* The while condition is true if: (there is are too few total
1507	<	* workers OR there is at least one waiter) AND (there are too
1508	<	* few active workers OR the pool is terminating). The value
1509	<	* of e distinguishes the remaining cases: zero (no waiters)
1510	<	* for create, negative if terminating (in which case do
1511	<	* nothing), else release a waiter. The secondary checks for
1512	<	* release (non-null array etc) can fail if the pool begins
1513	<	* terminating after the test, and don't impose any added cost
1514	<	* because JVMs must perform null and bounds checks anyway.
1515	<	*/
1516	<	long c; int e, u;
1517	<	while ((((e = (int)(c = ctl)) \| (u = (int)(c >>> 32))) &
1518	<	(INT_SIGN\|SHORT_SIGN)) == (INT_SIGN\|SHORT_SIGN)) {
1519	<	WorkQueue[] ws = workQueues; int i; WorkQueue w; Thread p;
1520	<	if (e == 0) { // add a new worker
1521	<	if (U.compareAndSwapLong
1522	<	(this, CTL, c, (long)(((u + UTC_UNIT) & UTC_MASK) \|
1523	<	((u + UAC_UNIT) & UAC_MASK)) << 32)) {
1524	<	addWorker();
1525	<	break;
1526	<	}
1502	>	* Full version of externalPush. This method is called, among
1503	>	* other times, upon the first submission of the first task to the
1504	>	* pool, so must perform secondary initialization (via
1505	>	* initWorkQueuesArray). It also detects first submission by an
1506	>	* external thread by looking up its ThreadLocal, and creates a
1507	>	* new shared queue if the one at index if empty or contended. The
1508	>	* lock body must be exception-free (so no try/finally) so we
1509	>	* optimistically allocate new queues outside the lock and throw
1510	>	* them away if (very rarely) not needed.
1511	>	*/
1512	>	private void fullExternalPush(ForkJoinTask<?> task) {
1513	>	int r = 0;
1514	>	for (Submitter z = submitters.get();;) {
1515	>	WorkQueue[] ws; WorkQueue q; int ps, m, k;
1516	>	if (z == null) {
1517	>	if (U.compareAndSwapInt(this, INDEXSEED, r = indexSeed,
1518	>	r += SEED_INCREMENT) && r != 0)
1519	>	submitters.set(z = new Submitter(r));
1520	>	}
1521	>	else if (r == 0) { // move to a different index
1522	>	r = z.seed;
1523	>	r ^= r << 13; // same xorshift as WorkQueues
1524	>	r ^= r >>> 17;
1525	>	z.seed = r ^ (r << 5);
1526	>	}
1527	>	else if ((ps = plock) < 0)
1528	>	throw new RejectedExecutionException();
1529	>	else if (ps == 0 \|\| (ws = workQueues) == null \|\|
1530	>	(m = ws.length - 1) < 0)
1531	>	initWorkQueuesArray();
1532	>	else if ((q = ws[k = r & m & SQMASK]) != null) {
1533	>	if (q.trySharedPush(task))
1534	>	return;
1535	>	else
1536	>	r = 0; // move on contention
1537		}
1538	<	else if (e > 0 && ws != null &&
1539	<	(i = ((~e << 1) \| 1) & SMASK) < ws.length &&
1540	<	(w = ws[i]) != null &&
1541	<	w.eventCount == (e \| INT_SIGN)) {
1542	<	if (U.compareAndSwapLong
1543	<	(this, CTL, c, (((long)(w.nextWait & E_MASK)) \|
1544	<	((long)(u + UAC_UNIT) << 32)))) {
1545	<	w.eventCount = (e + E_SEQ) & E_MASK;
1546	<	if ((p = w.parker) != null)
1547	<	U.unpark(p); // release a waiting worker
1269	<	break;
1270	<	}
1538	>	else if (((ps = plock) & PL_LOCK) == 0) { // create new queue
1539	>	q = new WorkQueue(this, null, SHARED_QUEUE, r);
1540	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1541	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1542	>	ps = acquirePlock();
1543	>	if ((ws = workQueues) != null && k < ws.length && ws[k] == null)
1544	>	ws[k] = q;
1545	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1546	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1547	>	releasePlock(nps);
1548		}
1549		else
1550	<	break;
1550	>	r = 0; // try elsewhere while lock held
1551		}
1552		}
1553
1554	+	// Maintaining ctl counts
1555	+
1556		/**
1557	<	* Tries to decrement active count (sometimes implicitly) and
1279	<	* possibly release or create a compensating worker in preparation
1280	<	* for blocking. Fails on contention or termination.
1281	<	*
1282	<	* @return true if the caller can block, else should recheck and retry
1557	>	* Increments active count; mainly called upon return from blocking.
1558		*/
1559	<	final boolean tryCompensate() {
1560	<	WorkQueue[] ws; WorkQueue w; Thread p;
1561	<	int pc = parallelism, e, u, ac, tc, i;
1562	<	long c = ctl;
1559	>	final void incrementActiveCount() {
1560	>	long c;
1561	>	do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
1562	>	}
1563
1564	<	if ((e = (int)c) >= 0) {
1565	<	if ((ac = ((u = (int)(c >>> 32)) >> UAC_SHIFT)) <= 0 &&
1566	<	e != 0 && (ws = workQueues) != null &&
1567	<	(i = ((~e << 1) \| 1) & SMASK) < ws.length &&
1568	<	(w = ws[i]) != null) {
1569	<	if (w.eventCount == (e \| INT_SIGN) &&
1570	<	U.compareAndSwapLong
1571	<	(this, CTL, c, ((long)(w.nextWait & E_MASK) \|
1572	<	(c & (AC_MASK\|TC_MASK))))) {
1573	<	w.eventCount = (e + E_SEQ) & E_MASK;
1574	<	if ((p = w.parker) != null)
1575	<	U.unpark(p);
1576	<	return true; // release an idle worker
1564	>	/**
1565	>	* Tries to create (at most one) or activate (possibly several)
1566	>	* workers if too few are active. On contention failure, continues
1567	>	* until at least one worker is signalled or the given queue is
1568	>	* empty or all workers are active.
1569	>	*
1570	>	* @param q if non-null, the queue holding tasks to be signalled
1571	>	* @param signals the target number of signals (at least one --
1572	>	* if argument is zero also sets signallee hint if parked).
1573	>	*/
1574	>	final void signalWork(WorkQueue q, int signals) {
1575	>	long c; int e, u, i, s; WorkQueue[] ws; WorkQueue w; Thread p;
1576	>	while ((u = (int)((c = ctl) >>> 32)) < 0) {
1577	>	if ((e = (int)c) > 0) {
1578	>	if ((ws = workQueues) != null && ws.length > (i = e & SMASK) &&
1579	>	(w = ws[i]) != null && w.eventCount == (e \| INT_SIGN)) {
1580	>	long nc = (((long)(w.nextWait & E_MASK)) \|
1581	>	((long)(u + UAC_UNIT) << 32));
1582	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1583	>	w.eventCount = (e + E_SEQ) & E_MASK;
1584	>	if ((p = w.parker) != null) {
1585	>	if (q != null && signals == 0)
1586	>	w.hint = q.poolIndex;
1587	>	U.unpark(p);
1588	>	}
1589	>	if (--signals <= 0)
1590	>	break;
1591	>	}
1592	>	if (q != null && (s = q.queueSize()) <= signals &&
1593	>	(signals = s) <= 0)
1594	>	break;
1595		}
1596	+	else
1597	+	break;
1598		}
1599	<	else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) {
1600	<	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
1601	<	if (U.compareAndSwapLong(this, CTL, c, nc))
1307	<	return true; // no compensation needed
1308	<	}
1309	<	else if (tc + pc < MAX_ID) {
1310	<	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
1599	>	else if (e == 0 && (u & SHORT_SIGN) != 0) {
1600	>	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) \|
1601	>	((u + UAC_UNIT) & UAC_MASK)) << 32;
1602		if (U.compareAndSwapLong(this, CTL, c, nc)) {
1603		addWorker();
1604	<	return true; // create replacement
1604	>	break;
1605		}
1606		}
1607	+	else
1608	+	break;
1609		}
1317	–	return false;
1610		}
1611
1612	<	// Submissions
1612	>	// Scanning for tasks
1613
1614		/**
1615	<	* 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.
1615	>	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1616		*/
1617	<	private void doSubmit(ForkJoinTask<?> task) {
1618	<	if (task == null)
1619	<	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	<	}
1357	<	}
1358	<
1359	<	/**
1360	<	* Tries to add and register a new queue at the given index.
1361	<	*
1362	<	* @param idx the workQueues array index to register the queue
1363	<	* @return the queue, or null if could not add because could
1364	<	* not acquire lock or idx is unusable
1365	<	*/
1366	<	private WorkQueue tryAddSharedQueue(int idx) {
1367	<	WorkQueue q = null;
1368	<	ReentrantLock lock = this.lock;
1369	<	if (idx >= 0 && (idx & 1) == 0 && !lock.isLocked()) {
1370	<	// create queue outside of lock but only if apparently free
1371	<	WorkQueue nq = new WorkQueue(null, SHARED_QUEUE);
1372	<	if (lock.tryLock()) {
1373	<	try {
1374	<	WorkQueue[] ws = workQueues;
1375	<	if (ws != null && idx < ws.length) {
1376	<	if ((q = ws[idx]) == null) {
1377	<	int rs; // update runState seq
1378	<	ws[idx] = q = nq;
1379	<	runState = (((rs = runState) & SHUTDOWN) \|
1380	<	((rs + RS_SEQ) & ~SHUTDOWN));
1381	<	}
1382	<	}
1383	<	} finally {
1384	<	lock.unlock();
1385	<	}
1386	<	}
1387	<	}
1388	<	return q;
1617	>	final void runWorker(WorkQueue w) {
1618	>	if (w != null) // skip on initialization failure
1619	>	do { w.runTask(scan(w)); } while (w.qlock >= 0);
1620		}
1621
1391	–	// Scanning for tasks
1392	–
1622		/**
1623		* Scans for and, if found, returns one task, else possibly
1624		* inactivates the worker. This method operates on single reads of
1625	<	* volatile state and is designed to be re-invoked continuously in
1626	<	* part because it returns upon detecting inconsistencies,
1625	>	* volatile state and is designed to be re-invoked continuously,
1626	>	* in part because it returns upon detecting inconsistencies,
1627		* contention, or state changes that indicate possible success on
1628		* re-invocation.
1629		*
1630	<	* The scan searches for tasks across queues, randomly selecting
1631	<	* the first #queues probes, favoring steals 2:1 over submissions
1632	<	* (by exploiting even/odd indexing), and then performing a
1633	<	* circular sweep of all queues. The scan terminates upon either
1634	<	* finding a non-empty queue, or completing a full sweep. If the
1635	<	* worker is not inactivated, it takes and returns a task from
1636	<	* this queue. On failure to find a task, we take one of the
1637	<	* following actions, after which the caller will retry calling
1638	<	* this method unless terminated.
1639	<	*
1640	<	* * If not a complete sweep, try to release a waiting worker. If
1641	<	* 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.
1630	>	* The scan searches for tasks across queues (starting at a random
1631	>	* index, and relying on registerWorker to irregularly scatter
1632	>	* them within array to avoid bias), checking each at least twice.
1633	>	* The scan terminates upon either finding a non-empty queue, or
1634	>	* completing the sweep. If the worker is not inactivated, it
1635	>	* takes and returns a task from this queue. Otherwise, if not
1636	>	* activated, it signals workers (that may include itself) and
1637	>	* returns so caller can retry. Also returns for true if the
1638	>	* worker array may have changed during an empty scan. On failure
1639	>	* to find a task, we take one of the following actions, after
1640	>	* which the caller will retry calling this method unless
1641	>	* terminated.
1642		*
1643	<	* * If pool is terminating, terminate the worker
1643	>	* * If pool is terminating, terminate the worker.
1644		*
1645		* * If not already enqueued, try to inactivate and enqueue the
1646	<	* worker on wait queue.
1647	<	*
1648	<	* * If already enqueued and none of the above apply, either park
1649	<	* awaiting signal, or if this is the most recent waiter and pool
1650	<	* is quiescent, relay to idleAwaitWork to check for termination
1651	<	* and possibly shrink pool.
1646	>	* worker on wait queue. Or, if inactivating has caused the pool
1647	>	* to be quiescent, relay to idleAwaitWork to check for
1648	>	* termination and possibly shrink pool.
1649	>	*
1650	>	* * If already enqueued and none of the above apply, possibly
1651	>	* (with 1/2 probability) park awaiting signal, else lingering to
1652	>	* help scan and signal.
1653		*
1654		* @param w the worker (via its WorkQueue)
1655	<	* @return a task or null of none found
1655	>	* @return a task or null if none found
1656		*/
1657		private final ForkJoinTask<?> scan(WorkQueue w) {
1658	<	boolean swept = false; // true after full empty scan
1659	<	WorkQueue[] ws; // volatile read order matters
1660	<	int r = w.seed, ec = w.eventCount; // ec is negative if inactive
1661	<	int rs = runState, m = rs & SMASK;
1662	<	if ((ws = workQueues) != null && ws.length > m) {
1663	<	ForkJoinTask<?> task = null;
1664	<	for (int k = 0, j = -2 - m; ; ++j) {
1665	<	WorkQueue q; int b;
1666	<	if (j < 0) { // random probes while j negative
1667	<	r ^= r << 13; r ^= r >>> 17; k = (r ^= r << 5) \| (j & 1);
1668	<	} // worker (not submit) for odd j
1669	<	else // cyclic scan when j >= 0
1670	<	k += (m >>> 1) \| 1; // step by half to reduce bias
1671	<
1672	<	if ((q = ws[k & m]) != null && (b = q.base) - q.top < 0) {
1673	<	if (ec >= 0)
1674	<	task = q.pollAt(b); // steal
1675	<	break;
1658	>	WorkQueue[] ws; int m, hint;
1659	>	int ps = plock; // read plock before ws
1660	>	if (w != null && (ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1661	>	int ec = w.eventCount; // ec is negative if inactive
1662	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1663	>	for (int j = ((m + m + 1) \| MIN_SCAN) & MAX_SCAN; ; --j) {
1664	>	WorkQueue q; ForkJoinTask<?>[] a; int b;
1665	>	if ((q = ws[(r + j) & m]) != null && (b = q.base) - q.top < 0 &&
1666	>	(a = q.array) != null) { // probably nonempty
1667	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1668	>	ForkJoinTask<?> t = (ForkJoinTask<?>)
1669	>	U.getObjectVolatile(a, i);
1670	>	if (q.base == b && ec >= 0 && t != null &&
1671	>	U.compareAndSwapObject(a, i, t, null)) {
1672	>	if ((q.base = b + 1) - q.top < 0)
1673	>	signalWork(q, 0);
1674	>	return t; // taken
1675	>	}
1676	>	else if (ec < 0 \|\| j < m) { // cannot take or cannot rescan
1677	>	w.hint = q.poolIndex; // use hint below
1678	>	break; // let caller retry after signal
1679	>	}
1680		}
1681	<	else if (j > m) {
1682	<	if (rs == runState) // staleness check
1683	<	swept = true;
1681	>	else if (j < 0) { // end of scan; in loop to simplify code
1682	>	long c, sc; int e, ns;
1683	>	if ((ns = w.nsteals) != 0) {
1684	>	if (U.compareAndSwapLong(this, STEALCOUNT,
1685	>	sc = stealCount, sc + ns))
1686	>	w.nsteals = 0; // collect steals
1687	>	}
1688	>	else if (plock != ps) // ws may have changed
1689	>	break;
1690	>	else if ((e = (int)(c = ctl)) < 0)
1691	>	w.qlock = -1; // pool is terminating
1692	>	else if (ec >= 0) { // try to enqueue/inactivate
1693	>	long nc = ((long)ec \|
1694	>	((c - AC_UNIT) & (AC_MASK\|TC_MASK)));
1695	>	w.nextWait = e; // link and mark inactive
1696	>	w.hint = -1; // use hint if set while parked
1697	>	w.eventCount = ec \| INT_SIGN;
1698	>	if (ctl != c \|\|
1699	>	!U.compareAndSwapLong(this, CTL, c, nc))
1700	>	w.eventCount = ec; // unmark on CAS failure
1701	>	else if ((int)(c >> AC_SHIFT) == 1 - (config & SMASK))
1702	>	idleAwaitWork(w, nc, c);
1703	>	}
1704	>	else if (w.eventCount < 0) { // block
1705	>	Thread wt = Thread.currentThread();
1706	>	Thread.interrupted(); // clear status
1707	>	U.putObject(wt, PARKBLOCKER, this);
1708	>	w.parker = wt; // emulate LockSupport.park
1709	>	if (w.eventCount < 0) // recheck
1710	>	U.park(false, 0L);
1711	>	w.parker = null;
1712	>	U.putObject(wt, PARKBLOCKER, null);
1713	>	}
1714		break;
1715		}
1716		}
1717	<	w.seed = r; // save seed for next scan
1718	<	if (task != null)
1719	<	return task;
1720	<	}
1721	<
1722	<	// 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);
1717	>	if ((hint = w.hint) >= 0) { // help signal
1718	>	WorkQueue[] vs; WorkQueue v; int k;
1719	>	w.hint = -1; // suppress resignal
1720	>	if ((vs = workQueues) != null && hint < vs.length &&
1721	>	(v = vs[hint]) != null && (k = v.base - v.top) < -1)
1722	>	signalWork(v, 1 - k);
1723		}
1724		}
1725		return null;
1726		}
1727
1728		/**
1729	<	* If inactivating worker w has caused pool to become quiescent,
1730	<	* check for pool termination, and, so long as this is not the
1731	<	* only worker, wait for event for up to SHRINK_RATE nanosecs On
1732	<	* timeout, if ctl has not changed, terminate the worker, which
1733	<	* will in turn wake up another worker to possibly repeat this
1734	<	* process.
1729	>	* If inactivating worker w has caused the pool to become
1730	>	* quiescent, checks for pool termination, and, so long as this is
1731	>	* not the only worker, waits for event for up to a given
1732	>	* duration. On timeout, if ctl has not changed, terminates the
1733	>	* worker, which will in turn wake up another worker to possibly
1734	>	* repeat this process.
1735		*
1736		* @param w the calling worker
1737	+	* @param currentCtl the ctl value triggering possible quiescence
1738	+	* @param prevCtl the ctl value to restore if thread is terminated
1739		*/
1740	<	private void idleAwaitWork(WorkQueue w) {
1741	<	long c; int nw, ec;
1742	<	if (!tryTerminate(false) &&
1743	<	(int)((c = ctl) >> AC_SHIFT) + parallelism == 0 &&
1744	<	(ec = w.eventCount) == ((int)c \| INT_SIGN) &&
1745	<	(nw = w.nextWait) != 0) {
1746	<	long nc = ((long)(nw & E_MASK) \| // ctl to restore on timeout
1747	<	((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();
1740	>	private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1741	>	if (w != null && w.eventCount < 0 &&
1742	>	!tryTerminate(false, false) && (int)prevCtl != 0) {
1743	>	int dc = -(short)(currentCtl >>> TC_SHIFT);
1744	>	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1745	>	long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop
1746	>	Thread wt = Thread.currentThread();
1747	>	while (ctl == currentCtl) {
1748		Thread.interrupted(); // timed variant of version in scan()
1749		U.putObject(wt, PARKBLOCKER, this);
1750		w.parker = wt;
1751	<	if (ctl == c)
1752	<	U.park(false, SHRINK_RATE);
1751	>	if (ctl == currentCtl)
1752	>	U.park(false, parkTime);
1753		w.parker = null;
1754		U.putObject(wt, PARKBLOCKER, null);
1755	<	if (ctl != c)
1755	>	if (ctl != currentCtl)
1756		break;
1757	<	if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
1758	<	U.compareAndSwapLong(this, CTL, c, nc)) {
1759	<	w.runState = -1; // shrink
1760	<	w.eventCount = (ec + E_SEQ) \| E_MASK;
1757	>	if (deadline - System.nanoTime() <= 0L &&
1758	>	U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1759	>	w.eventCount = (w.eventCount + E_SEQ) \| E_MASK;
1760	>	w.qlock = -1; // shrink
1761	>	w.hint = -1; // suppress helping
1762		break;
1763		}
1764		}
#	Line 1560 \| Line 1766 \| public class ForkJoinPool extends Abstra
1766		}
1767
1768		/**
1769	+	* Scans through queues looking for work (optionally, while
1770	+	* joining a task); if any are present, signals. May return early
1771	+	* if more signalling is detectably unneeded.
1772	+	*
1773	+	* @param task if non-null, return early if done
1774	+	* @param origin an index to start scan
1775	+	*/
1776	+	final int helpSignal(ForkJoinTask<?> task, int origin) {
1777	+	WorkQueue[] ws; WorkQueue q; int m, n, s, u;
1778	+	if ((ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1779	+	for (int i = 0; i <= m; ++i) {
1780	+	if (task != null && (s = task.status) < 0)
1781	+	return s;
1782	+	if ((q = ws[(i + origin) & m]) != null &&
1783	+	(n = q.queueSize()) > 0) {
1784	+	signalWork(q, n);
1785	+	if ((u = (int)(ctl >>> 32)) >= 0 \|\| (u >> UAC_SHIFT) >= 0)
1786	+	break;
1787	+	}
1788	+	}
1789	+	}
1790	+	return 0;
1791	+	}
1792	+
1793	+	/**
1794		* Tries to locate and execute tasks for a stealer of the given
1795		* task, or in turn one of its stealers, Traces currentSteal ->
1796		* currentJoin links looking for a thread working on a descendant
#	Line 1570 \| Line 1801 \| public class ForkJoinPool extends Abstra
1801		* leaves hints in workers to speed up subsequent calls. The
1802		* implementation is very branchy to cope with potential
1803		* inconsistencies or loops encountering chains that are stale,
1804	<	* unknown, or of length greater than MAX_HELP_DEPTH links. All
1574	<	* of these cases are dealt with by just retrying by caller.
1804	>	* unknown, or so long that they are likely cyclic.
1805		*
1806		* @param joiner the joining worker
1807		* @param task the task to join
1808	<	* @return true if found or ran a task (and so is immediately retryable)
1808	>	* @return 0 if no progress can be made, negative if task
1809	>	* known complete, else positive
1810		*/
1811	<	final boolean tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1812	<	ForkJoinTask<?> subtask; // current target
1813	<	boolean progress = false;
1814	<	int depth = 0; // current chain depth
1815	<	int m = runState & SMASK;
1816	<	WorkQueue[] ws = workQueues;
1817	<
1818	<	if (ws != null && ws.length > m && (subtask = task).status >= 0) {
1819	<	outer:for (WorkQueue j = joiner;;) {
1820	<	// Try to find the stealer of subtask, by first using hint
1821	<	WorkQueue stealer = null;
1822	<	WorkQueue v = ws[j.stealHint & m];
1823	<	if (v != null && v.currentSteal == subtask)
1824	<	stealer = v;
1825	<	else {
1826	<	for (int i = 1; i <= m; i += 2) {
1827	<	if ((v = ws[i]) != null && v.currentSteal == subtask) {
1828	<	stealer = v;
1829	<	j.stealHint = i; // save hint
1830	<	break;
1811	>	private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1812	>	int stat = 0, steps = 0; // bound to avoid cycles
1813	>	if (joiner != null && task != null) { // hoist null checks
1814	>	restart: for (;;) {
1815	>	ForkJoinTask<?> subtask = task; // current target
1816	>	for (WorkQueue j = joiner, v;;) { // v is stealer of subtask
1817	>	WorkQueue[] ws; int m, s, h;
1818	>	if ((s = task.status) < 0) {
1819	>	stat = s;
1820	>	break restart;
1821	>	}
1822	>	if ((ws = workQueues) == null \|\| (m = ws.length - 1) <= 0)
1823	>	break restart; // shutting down
1824	>	if ((v = ws[h = (j.hint \| 1) & m]) == null \|\|
1825	>	v.currentSteal != subtask) {
1826	>	for (int origin = h;;) { // find stealer
1827	>	if (((h = (h + 2) & m) & 15) == 1 &&
1828	>	(subtask.status < 0 \|\| j.currentJoin != subtask))
1829	>	continue restart; // occasional staleness check
1830	>	if ((v = ws[h]) != null &&
1831	>	v.currentSteal == subtask) {
1832	>	j.hint = h; // save hint
1833	>	break;
1834	>	}
1835	>	if (h == origin)
1836	>	break restart; // cannot find stealer
1837		}
1838		}
1839	<	if (stealer == null)
1840	<	break;
1841	<	}
1842	<
1843	<	for (WorkQueue q = stealer;;) { // Try to help stealer
1844	<	ForkJoinTask<?> t; int b;
1845	<	if (task.status < 0)
1846	<	break outer;
1847	<	if ((b = q.base) - q.top < 0) {
1848	<	progress = true;
1849	<	if (subtask.status < 0)
1850	<	break outer; // stale
1851	<	if ((t = q.pollAt(b)) != null) {
1852	<	stealer.stealHint = joiner.poolIndex;
1853	<	joiner.runSubtask(t);
1839	>	for (;;) { // help stealer or descend to its stealer
1840	>	ForkJoinTask[] a; int b;
1841	>	if (subtask.status < 0) // surround probes with
1842	>	continue restart; // consistency checks
1843	>	if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
1844	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1845	>	ForkJoinTask<?> t =
1846	>	(ForkJoinTask<?>)U.getObjectVolatile(a, i);
1847	>	if (subtask.status < 0 \|\| j.currentJoin != subtask \|\|
1848	>	v.currentSteal != subtask)
1849	>	continue restart; // stale
1850	>	stat = 1; // apparent progress
1851	>	if (t != null && v.base == b &&
1852	>	U.compareAndSwapObject(a, i, t, null)) {
1853	>	v.base = b + 1; // help stealer
1854	>	joiner.runSubtask(t);
1855	>	}
1856	>	else if (v.base == b && ++steps == MAX_HELP)
1857	>	break restart; // v apparently stalled
1858	>	}
1859	>	else { // empty -- try to descend
1860	>	ForkJoinTask<?> next = v.currentJoin;
1861	>	if (subtask.status < 0 \|\| j.currentJoin != subtask \|\|
1862	>	v.currentSteal != subtask)
1863	>	continue restart; // stale
1864	>	else if (next == null \|\| ++steps == MAX_HELP)
1865	>	break restart; // dead-end or maybe cyclic
1866	>	else {
1867	>	subtask = next;
1868	>	j = v;
1869	>	break;
1870	>	}
1871		}
1872		}
1873	<	else { // empty - try to descend to find stealer's stealer
1874	<	ForkJoinTask<?> next = stealer.currentJoin;
1875	<	if (++depth == MAX_HELP_DEPTH \|\| subtask.status < 0 \|\|
1876	<	next == null \|\| next == subtask)
1877	<	break outer; // max depth, stale, dead-end, cyclic
1878	<	subtask = next;
1879	<	j = stealer;
1873	>	}
1874	>	}
1875	>	}
1876	>	return stat;
1877	>	}
1878	>
1879	>	/**
1880	>	* Analog of tryHelpStealer for CountedCompleters. Tries to steal
1881	>	* and run tasks within the target's computation.
1882	>	*
1883	>	* @param task the task to join
1884	>	* @param mode if shared, exit upon completing any task
1885	>	* if all workers are active
1886	>	*
1887	>	*/
1888	>	private int helpComplete(ForkJoinTask<?> task, int mode) {
1889	>	WorkQueue[] ws; WorkQueue q; int m, n, s, u;
1890	>	if (task != null && (ws = workQueues) != null &&
1891	>	(m = ws.length - 1) >= 0) {
1892	>	for (int j = 1, origin = j;;) {
1893	>	if ((s = task.status) < 0)
1894	>	return s;
1895	>	if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) {
1896	>	origin = j;
1897	>	if (mode == SHARED_QUEUE &&
1898	>	((u = (int)(ctl >>> 32)) >= 0 \|\| (u >> UAC_SHIFT) >= 0))
1899		break;
1900	<	}
1900	>	}
1901	>	else if ((j = (j + 2) & m) == origin)
1902	>	break;
1903	>	}
1904	>	}
1905	>	return 0;
1906	>	}
1907	>
1908	>	/**
1909	>	* Tries to decrement active count (sometimes implicitly) and
1910	>	* possibly release or create a compensating worker in preparation
1911	>	* for blocking. Fails on contention or termination. Otherwise,
1912	>	* adds a new thread if no idle workers are available and pool
1913	>	* may become starved.
1914	>	*/
1915	>	final boolean tryCompensate() {
1916	>	int pc = config & SMASK, e, i, tc; long c;
1917	>	WorkQueue[] ws; WorkQueue w; Thread p;
1918	>	if ((ws = workQueues) != null && (e = (int)(c = ctl)) >= 0) {
1919	>	if (e != 0 && (i = e & SMASK) < ws.length &&
1920	>	(w = ws[i]) != null && w.eventCount == (e \| INT_SIGN)) {
1921	>	long nc = ((long)(w.nextWait & E_MASK) \|
1922	>	(c & (AC_MASK\|TC_MASK)));
1923	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1924	>	w.eventCount = (e + E_SEQ) & E_MASK;
1925	>	if ((p = w.parker) != null)
1926	>	U.unpark(p);
1927	>	return true; // replace with idle worker
1928	>	}
1929	>	}
1930	>	else if ((tc = (short)(c >>> TC_SHIFT)) >= 0 &&
1931	>	(int)(c >> AC_SHIFT) + pc > 1) {
1932	>	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
1933	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1934	>	return true; // no compensation
1935	>	}
1936	>	else if (tc + pc < MAX_CAP) {
1937	>	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
1938	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1939	>	addWorker();
1940	>	return true;
1941		}
1942		}
1943		}
1944	<	return progress;
1944	>	return false;
1945		}
1946
1947		/**
1948	<	* If task is at base of some steal queue, steals and executes it.
1948	>	* Helps and/or blocks until the given task is done.
1949		*
1950		* @param joiner the joining worker
1951		* @param task the task
1952	+	* @return task status on exit
1953		*/
1954	<	final void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
1955	<	WorkQueue[] ws;
1956	<	int m = runState & SMASK;
1957	<	if ((ws = workQueues) != null && ws.length > m) {
1958	<	for (int j = 1; j <= m && task.status >= 0; j += 2) {
1959	<	WorkQueue q = ws[j];
1960	<	if (q != null && q.pollFor(task)) {
1961	<	joiner.runSubtask(task);
1962	<	break;
1954	>	final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
1955	>	int s = 0;
1956	>	if (joiner != null && task != null && (s = task.status) >= 0) {
1957	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
1958	>	joiner.currentJoin = task;
1959	>	do {} while ((s = task.status) >= 0 &&
1960	>	joiner.queueSize() > 0 &&
1961	>	joiner.tryRemoveAndExec(task)); // process local tasks
1962	>	if (s >= 0 && (s = task.status) >= 0 &&
1963	>	(s = helpSignal(task, joiner.poolIndex)) >= 0 &&
1964	>	(task instanceof CountedCompleter))
1965	>	s = helpComplete(task, LIFO_QUEUE);
1966	>	int k = 0; // to perform pre-block yield for politeness
1967	>	while (s >= 0 && (s = task.status) >= 0) {
1968	>	if ((joiner.queueSize() > 0 \|\| // try helping
1969	>	(s = tryHelpStealer(joiner, task)) == 0) &&
1970	>	(s = task.status) >= 0) {
1971	>	if (k < 3) {
1972	>	if (++k < 3)
1973	>	s = helpSignal(task, joiner.poolIndex);
1974	>	else
1975	>	Thread.yield();
1976	>	}
1977	>	else if (!tryCompensate())
1978	>	k = 0;
1979	>	else {
1980	>	if (task.trySetSignal() && (s = task.status) >= 0) {
1981	>	synchronized (task) {
1982	>	if (task.status >= 0) {
1983	>	try { // see ForkJoinTask
1984	>	task.wait(); // for explanation
1985	>	} catch (InterruptedException ie) {
1986	>	}
1987	>	}
1988	>	else
1989	>	task.notifyAll();
1990	>	}
1991	>	}
1992	>	long c; // re-activate
1993	>	do {} while (!U.compareAndSwapLong
1994	>	(this, CTL, c = ctl, c + AC_UNIT));
1995	>	}
1996		}
1997		}
1998	+	joiner.currentJoin = prevJoin;
1999	+	}
2000	+	return s;
2001	+	}
2002	+
2003	+	/**
2004	+	* Stripped-down variant of awaitJoin used by timed joins. Tries
2005	+	* to help join only while there is continuous progress. (Caller
2006	+	* will then enter a timed wait.)
2007	+	*
2008	+	* @param joiner the joining worker
2009	+	* @param task the task
2010	+	*/
2011	+	final void helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
2012	+	int s;
2013	+	if (joiner != null && task != null && (s = task.status) >= 0) {
2014	+	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2015	+	joiner.currentJoin = task;
2016	+	do {} while ((s = task.status) >= 0 &&
2017	+	joiner.queueSize() > 0 &&
2018	+	joiner.tryRemoveAndExec(task));
2019	+	if (s >= 0 && (s = task.status) >= 0 &&
2020	+	(s = helpSignal(task, joiner.poolIndex)) >= 0 &&
2021	+	(task instanceof CountedCompleter))
2022	+	s = helpComplete(task, LIFO_QUEUE);
2023	+	if (s >= 0 && joiner.queueSize() == 0) {
2024	+	do {} while (task.status >= 0 &&
2025	+	tryHelpStealer(joiner, task) > 0);
2026	+	}
2027	+	joiner.currentJoin = prevJoin;
2028		}
2029		}
2030
2031		/**
2032	<	* Returns a non-empty steal queue, if one is found during a random,
2033	<	* then cyclic scan, else null. This method must be retried by
2034	<	* caller if, by the time it tries to use the queue, it is empty.
2032	>	* Returns a (probably) non-empty steal queue, if one is found
2033	>	* during a random, then cyclic scan, else null. This method must
2034	>	* be retried by caller if, by the time it tries to use the queue,
2035	>	* it is empty.
2036	>	* @param r a (random) seed for scanning
2037		*/
2038	<	private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
1660	<	int r = w.seed; // Same idea as scan(), but ignoring submissions
2038	>	private WorkQueue findNonEmptyStealQueue(int r) {
2039		for (WorkQueue[] ws;;) {
2040	<	int m = runState & SMASK;
2041	<	if ((ws = workQueues) == null)
2040	>	int ps = plock, m, n;
2041	>	if ((ws = workQueues) == null \|\| (m = ws.length - 1) < 1)
2042		return null;
2043	<	if (ws.length > m) {
2044	<	WorkQueue q;
2045	<	for (int n = m << 2, k = r, j = -n;;) {
2046	<	r ^= r << 13; r ^= r >>> 17; r ^= r << 5;
2047	<	if ((q = ws[(k \| 1) & m]) != null && q.base - q.top < 0) {
2048	<	w.seed = r;
2049	<	return q;
2050	<	}
2051	<	else if (j > n)
2043	>	for (int j = (m + 1) << 2; ;) {
2044	>	WorkQueue q = ws[(((r + j) << 1) \| 1) & m];
2045	>	if (q != null && (n = q.queueSize()) > 0) {
2046	>	if (n > 1)
2047	>	signalWork(q, 0);
2048	>	return q;
2049	>	}
2050	>	else if (--j < 0) {
2051	>	if (plock == ps)
2052		return null;
2053	<	else
1676	<	k = (j++ < 0) ? r : k + ((m >>> 1) \| 1);
1677	<
2053	>	break;
2054		}
2055		}
2056		}
#	Line 1688 \| Line 2064 \| public class ForkJoinPool extends Abstra
2064		*/
2065		final void helpQuiescePool(WorkQueue w) {
2066		for (boolean active = true;;) {
2067	<	w.runLocalTasks(); // exhaust local queue
2068	<	WorkQueue q = findNonEmptyStealQueue(w);
2067	>	ForkJoinTask<?> localTask; // exhaust local queue
2068	>	while ((localTask = w.nextLocalTask()) != null)
2069	>	localTask.doExec();
2070	>	// Similar to loop in scan(), but ignoring submissions
2071	>	WorkQueue q = findNonEmptyStealQueue(w.nextSeed());
2072		if (q != null) {
2073	<	ForkJoinTask<?> t;
2073	>	ForkJoinTask<?> t; int b;
2074		if (!active) { // re-establish active count
2075		long c;
2076		active = true;
2077		do {} while (!U.compareAndSwapLong
2078		(this, CTL, c = ctl, c + AC_UNIT));
2079		}
2080	<	if ((t = q.poll()) != null)
2080	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2081		w.runSubtask(t);
2082		}
2083		else {
#	Line 1710 \| Line 2089 \| public class ForkJoinPool extends Abstra
2089		}
2090		else
2091		c = ctl; // re-increment on exit
2092	<	if ((int)(c >> AC_SHIFT) + parallelism == 0) {
2092	>	if ((int)(c >> AC_SHIFT) + (config & SMASK) == 0) {
2093		do {} while (!U.compareAndSwapLong
2094		(this, CTL, c = ctl, c + AC_UNIT));
2095		break;
#	Line 1720 \| Line 2099 \| public class ForkJoinPool extends Abstra
2099		}
2100
2101		/**
2102	<	* Gets and removes a local or stolen task for the given worker
2102	>	* Gets and removes a local or stolen task for the given worker.
2103		*
2104		* @return a task, if available
2105		*/
2106		final ForkJoinTask<?> nextTaskFor(WorkQueue w) {
2107		for (ForkJoinTask<?> t;;) {
2108	<	WorkQueue q;
2108	>	WorkQueue q; int b;
2109		if ((t = w.nextLocalTask()) != null)
2110		return t;
2111	<	if ((q = findNonEmptyStealQueue(w)) == null)
2111	>	if ((q = findNonEmptyStealQueue(w.nextSeed())) == null)
2112		return null;
2113	<	if ((t = q.poll()) != null)
2113	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2114		return t;
2115		}
2116		}
2117
2118		/**
2119	<	* Returns the approximate (non-atomic) number of idle threads per
2120	<	* active thread to offset steal queue size for method
2121	<	* ForkJoinTask.getSurplusQueuedTaskCount().
2122	<	*/
2123	<	final int idlePerActive() {
2124	<	// Approximate at powers of two for small values, saturate past 4
2125	<	int p = parallelism;
2126	<	int a = p + (int)(ctl >> AC_SHIFT);
2127	<	return (a > (p >>>= 1) ? 0 :
2128	<	a > (p >>>= 1) ? 1 :
2129	<	a > (p >>>= 1) ? 2 :
2130	<	a > (p >>>= 1) ? 4 :
2131	<	8);
2132	<	}
2133	<
2134	<	// Termination
2135	<
2136	<	/**
2137	<	* Sets SHUTDOWN bit of runState under lock
2138	<	*/
2139	<	private void enableShutdown() {
2140	<	ReentrantLock lock = this.lock;
2141	<	if (runState >= 0) {
2142	<	lock.lock(); // don't need try/finally
2143	<	runState \|= SHUTDOWN;
2144	<	lock.unlock();
2119	>	* Returns a cheap heuristic guide for task partitioning when
2120	>	* programmers, frameworks, tools, or languages have little or no
2121	>	* idea about task granularity. In essence by offering this
2122	>	* method, we ask users only about tradeoffs in overhead vs
2123	>	* expected throughput and its variance, rather than how finely to
2124	>	* partition tasks.
2125	>	*
2126	>	* In a steady state strict (tree-structured) computation, each
2127	>	* thread makes available for stealing enough tasks for other
2128	>	* threads to remain active. Inductively, if all threads play by
2129	>	* the same rules, each thread should make available only a
2130	>	* constant number of tasks.
2131	>	*
2132	>	* The minimum useful constant is just 1. But using a value of 1
2133	>	* would require immediate replenishment upon each steal to
2134	>	* maintain enough tasks, which is infeasible. Further,
2135	>	* partitionings/granularities of offered tasks should minimize
2136	>	* steal rates, which in general means that threads nearer the top
2137	>	* of computation tree should generate more than those nearer the
2138	>	* bottom. In perfect steady state, each thread is at
2139	>	* approximately the same level of computation tree. However,
2140	>	* producing extra tasks amortizes the uncertainty of progress and
2141	>	* diffusion assumptions.
2142	>	*
2143	>	* So, users will want to use values larger, but not much larger
2144	>	* than 1 to both smooth over transient shortages and hedge
2145	>	* against uneven progress; as traded off against the cost of
2146	>	* extra task overhead. We leave the user to pick a threshold
2147	>	* value to compare with the results of this call to guide
2148	>	* decisions, but recommend values such as 3.
2149	>	*
2150	>	* When all threads are active, it is on average OK to estimate
2151	>	* surplus strictly locally. In steady-state, if one thread is
2152	>	* maintaining say 2 surplus tasks, then so are others. So we can
2153	>	* just use estimated queue length. However, this strategy alone
2154	>	* leads to serious mis-estimates in some non-steady-state
2155	>	* conditions (ramp-up, ramp-down, other stalls). We can detect
2156	>	* many of these by further considering the number of "idle"
2157	>	* threads, that are known to have zero queued tasks, so
2158	>	* compensate by a factor of (#idle/#active) threads.
2159	>	*
2160	>	* Note: The approximation of #busy workers as #active workers is
2161	>	* not very good under current signalling scheme, and should be
2162	>	* improved.
2163	>	*/
2164	>	static int getSurplusQueuedTaskCount() {
2165	>	Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q;
2166	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
2167	>	int p = (pool = (wt = (ForkJoinWorkerThread)t).pool).config & SMASK;
2168	>	int n = (q = wt.workQueue).top - q.base;
2169	>	int a = (int)(pool.ctl >> AC_SHIFT) + p;
2170	>	return n - (a > (p >>>= 1) ? 0 :
2171	>	a > (p >>>= 1) ? 1 :
2172	>	a > (p >>>= 1) ? 2 :
2173	>	a > (p >>>= 1) ? 4 :
2174	>	8);
2175		}
2176	+	return 0;
2177		}
2178
2179	+	// Termination
2180	+
2181		/**
2182	<	* Possibly initiates and/or completes termination. Upon
2183	<	* termination, cancels all queued tasks and then
2182	>	* Possibly initiates and/or completes termination. The caller
2183	>	* triggering termination runs three passes through workQueues:
2184	>	* (0) Setting termination status, followed by wakeups of queued
2185	>	* workers; (1) cancelling all tasks; (2) interrupting lagging
2186	>	* threads (likely in external tasks, but possibly also blocked in
2187	>	* joins). Each pass repeats previous steps because of potential
2188	>	* lagging thread creation.
2189		*
2190		* @param now if true, unconditionally terminate, else only
2191		* if no work and no active workers
2192	+	* @param enable if true, enable shutdown when next possible
2193		* @return true if now terminating or terminated
2194		*/
2195	<	private boolean tryTerminate(boolean now) {
2195	>	private boolean tryTerminate(boolean now, boolean enable) {
2196	>	if (this == commonPool) // cannot shut down
2197	>	return false;
2198		for (long c;;) {
2199		if (((c = ctl) & STOP_BIT) != 0) { // already terminating
2200	<	if ((short)(c >>> TC_SHIFT) == -parallelism) {
2201	<	ReentrantLock lock = this.lock; // signal when no workers
2202	<	lock.lock(); // don't need try/finally
2203	<	termination.signalAll(); // signal when 0 workers
1784	<	lock.unlock();
2200	>	if ((short)(c >>> TC_SHIFT) == -(config & SMASK)) {
2201	>	synchronized (this) {
2202	>	notifyAll(); // signal when 0 workers
2203	>	}
2204		}
2205		return true;
2206		}
2207	<	if (!now) {
2208	<	if ((int)(c >> AC_SHIFT) != -parallelism \|\| runState >= 0 \|\|
2207	>	if (plock >= 0) { // not yet enabled
2208	>	int ps;
2209	>	if (!enable)
2210	>	return false;
2211	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
2212	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
2213	>	ps = acquirePlock();
2214	>	int nps = SHUTDOWN;
2215	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
2216	>	releasePlock(nps);
2217	>	}
2218	>	if (!now) { // check if idle & no tasks
2219	>	if ((int)(c >> AC_SHIFT) != -(config & SMASK) \|\|
2220		hasQueuedSubmissions())
2221		return false;
2222		// Check for unqueued inactive workers. One pass suffices.
2223		WorkQueue[] ws = workQueues; WorkQueue w;
2224		if (ws != null) {
2225	<	int n = ws.length;
1796	<	for (int i = 1; i < n; i += 2) {
2225	>	for (int i = 1; i < ws.length; i += 2) {
2226		if ((w = ws[i]) != null && w.eventCount >= 0)
2227		return false;
2228		}
2229		}
2230		}
2231	<	if (U.compareAndSwapLong(this, CTL, c, c \| STOP_BIT))
2232	<	startTerminating();
2231	>	if (U.compareAndSwapLong(this, CTL, c, c \| STOP_BIT)) {
2232	>	for (int pass = 0; pass < 3; ++pass) {
2233	>	WorkQueue[] ws = workQueues;
2234	>	if (ws != null) {
2235	>	WorkQueue w;
2236	>	int n = ws.length;
2237	>	for (int i = 0; i < n; ++i) {
2238	>	if ((w = ws[i]) != null) {
2239	>	w.qlock = -1;
2240	>	if (pass > 0) {
2241	>	w.cancelAll();
2242	>	if (pass > 1)
2243	>	w.interruptOwner();
2244	>	}
2245	>	}
2246	>	}
2247	>	// Wake up workers parked on event queue
2248	>	int i, e; long cc; Thread p;
2249	>	while ((e = (int)(cc = ctl) & E_MASK) != 0 &&
2250	>	(i = e & SMASK) < n &&
2251	>	(w = ws[i]) != null) {
2252	>	long nc = ((long)(w.nextWait & E_MASK) \|
2253	>	((cc + AC_UNIT) & AC_MASK) \|
2254	>	(cc & (TC_MASK\|STOP_BIT)));
2255	>	if (w.eventCount == (e \| INT_SIGN) &&
2256	>	U.compareAndSwapLong(this, CTL, cc, nc)) {
2257	>	w.eventCount = (e + E_SEQ) & E_MASK;
2258	>	w.qlock = -1;
2259	>	if ((p = w.parker) != null)
2260	>	U.unpark(p);
2261	>	}
2262	>	}
2263	>	}
2264	>	}
2265	>	}
2266		}
2267		}
2268
2269	+	// external operations on common pool
2270	+
2271		/**
2272	<	* Initiates termination: Runs three passes through workQueues:
2273	<	* (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.
2272	>	* Returns common pool queue for a thread that has submitted at
2273	>	* least one task.
2274		*/
2275	<	private void startTerminating() {
2276	<	for (int pass = 0; pass < 3; ++pass) {
2277	<	WorkQueue[] ws = workQueues;
2278	<	if (ws != null) {
2279	<	WorkQueue w; Thread wt;
2280	<	int n = ws.length;
2281	<	for (int j = 0; j < n; ++j) {
2282	<	if ((w = ws[j]) != null) {
2283	<	w.runState = -1;
2284	<	if (pass > 0) {
2285	<	w.cancelAll();
2286	<	if (pass > 1 && (wt = w.owner) != null &&
2287	<	!wt.isInterrupted()) {
2288	<	try {
2289	<	wt.interrupt();
2290	<	} catch (SecurityException ignore) {
2275	>	static WorkQueue commonSubmitterQueue() {
2276	>	ForkJoinPool p; WorkQueue[] ws; int m; Submitter z;
2277	>	return ((z = submitters.get()) != null &&
2278	>	(p = commonPool) != null &&
2279	>	(ws = p.workQueues) != null &&
2280	>	(m = ws.length - 1) >= 0) ?
2281	>	ws[m & z.seed & SQMASK] : null;
2282	>	}
2283	>
2284	>	/**
2285	>	* Tries to pop the given task from submitter's queue in common pool.
2286	>	*/
2287	>	static boolean tryExternalUnpush(ForkJoinTask<?> t) {
2288	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q; Submitter z;
2289	>	ForkJoinTask<?>[] a; int m, s; long j;
2290	>	if ((z = submitters.get()) != null &&
2291	>	(p = commonPool) != null &&
2292	>	(ws = p.workQueues) != null &&
2293	>	(m = ws.length - 1) >= 0 &&
2294	>	(q = ws[m & z.seed & SQMASK]) != null &&
2295	>	(s = q.top) != q.base &&
2296	>	(a = q.array) != null &&
2297	>	U.getObjectVolatile
2298	>	(a, j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE) == t &&
2299	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2300	>	if (q.array == a && q.top == s && // recheck
2301	>	U.compareAndSwapObject(a, j, t, null)) {
2302	>	q.top = s - 1;
2303	>	q.qlock = 0;
2304	>	return true;
2305	>	}
2306	>	q.qlock = 0;
2307	>	}
2308	>	return false;
2309	>	}
2310	>
2311	>	/**
2312	>	* Tries to pop and run local tasks within the same computation
2313	>	* as the given root. On failure, tries to help complete from
2314	>	* other queues via helpComplete.
2315	>	*/
2316	>	private void externalHelpComplete(WorkQueue q, ForkJoinTask<?> root) {
2317	>	ForkJoinTask<?>[] a; int m;
2318	>	if (q != null && (a = q.array) != null && (m = (a.length - 1)) >= 0 &&
2319	>	root != null && root.status >= 0) {
2320	>	for (;;) {
2321	>	int s, u; Object o; CountedCompleter<?> task = null;
2322	>	if ((s = q.top) - q.base > 0) {
2323	>	long j = ((m & (s - 1)) << ASHIFT) + ABASE;
2324	>	if ((o = U.getObject(a, j)) != null &&
2325	>	(o instanceof CountedCompleter)) {
2326	>	CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;
2327	>	do {
2328	>	if (r == root) {
2329	>	if (U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2330	>	if (q.array == a && q.top == s &&
2331	>	U.compareAndSwapObject(a, j, t, null)) {
2332	>	q.top = s - 1;
2333	>	task = t;
2334	>	}
2335	>	q.qlock = 0;
2336		}
2337	+	break;
2338		}
2339	<	}
2339	>	} while ((r = r.completer) != null);
2340		}
2341		}
2342	<	// Wake up workers parked on event queue
2343	<	int i, e; long c; Thread p;
2344	<	while ((i = ((~(e = (int)(c = ctl)) << 1) \| 1) & SMASK) < n &&
2345	<	(w = ws[i]) != null &&
2346	<	w.eventCount == (e \| INT_SIGN)) {
2347	<	long nc = ((long)(w.nextWait & E_MASK) \|
2348	<	((c + AC_UNIT) & AC_MASK) \|
2349	<	(c & (TC_MASK\|STOP_BIT)));
2350	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
2351	<	w.eventCount = (e + E_SEQ) & E_MASK;
2352	<	if ((p = w.parker) != null)
2353	<	U.unpark(p);
2354	<	}
2342	>	if (task != null)
2343	>	task.doExec();
2344	>	if (root.status < 0 \|\|
2345	>	(u = (int)(ctl >>> 32)) >= 0 \|\| (u >> UAC_SHIFT) >= 0)
2346	>	break;
2347	>	if (task == null) {
2348	>	if (helpSignal(root, q.poolIndex) >= 0)
2349	>	helpComplete(root, SHARED_QUEUE);
2350	>	break;
2351	>	}
2352	>	}
2353	>	}
2354	>	}
2355	>
2356	>	/**
2357	>	* Tries to help execute or signal availability of the given task
2358	>	* from submitter's queue in common pool.
2359	>	*/
2360	>	static void externalHelpJoin(ForkJoinTask<?> t) {
2361	>	// Some hard-to-avoid overlap with tryExternalUnpush
2362	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; Submitter z;
2363	>	ForkJoinTask<?>[] a; int m, s, n; long j;
2364	>	if (t != null &&
2365	>	(z = submitters.get()) != null &&
2366	>	(p = commonPool) != null &&
2367	>	(ws = p.workQueues) != null &&
2368	>	(m = ws.length - 1) >= 0 &&
2369	>	(q = ws[m & z.seed & SQMASK]) != null &&
2370	>	(a = q.array) != null &&
2371	>	t.status >= 0) {
2372	>	if ((s = q.top) != q.base &&
2373	>	U.getObjectVolatile
2374	>	(a, j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE) == t &&
2375	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2376	>	if (q.array == a && q.top == s &&
2377	>	U.compareAndSwapObject(a, j, t, null)) {
2378	>	q.top = s - 1;
2379	>	q.qlock = 0;
2380	>	t.doExec();
2381		}
2382	+	else
2383	+	q.qlock = 0;
2384	+	}
2385	+	if (t.status >= 0) {
2386	+	if (t instanceof CountedCompleter)
2387	+	p.externalHelpComplete(q, t);
2388	+	else
2389	+	p.helpSignal(t, q.poolIndex);
2390		}
2391		}
2392		}
2393
2394	+	/**
2395	+	* Restricted version of helpQuiescePool for external callers
2396	+	*/
2397	+	static void externalHelpQuiescePool() {
2398	+	ForkJoinPool p; ForkJoinTask<?> t; WorkQueue q; int b;
2399	+	if ((p = commonPool) != null &&
2400	+	(q = p.findNonEmptyStealQueue(1)) != null &&
2401	+	(b = q.base) - q.top < 0 &&
2402	+	(t = q.pollAt(b)) != null)
2403	+	t.doExec();
2404	+	}
2405	+
2406		// Exported methods
2407
2408		// Constructors
#	Line 1920 \| Line 2472 \| public class ForkJoinPool extends Abstra
2472		checkPermission();
2473		if (factory == null)
2474		throw new NullPointerException();
2475	<	if (parallelism <= 0 \|\| parallelism > MAX_ID)
2475	>	if (parallelism <= 0 \|\| parallelism > MAX_CAP)
2476		throw new IllegalArgumentException();
1925	–	this.parallelism = parallelism;
2477		this.factory = factory;
2478		this.ueh = handler;
2479	<	this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE;
1929	<	this.nextPoolIndex = 1;
2479	>	this.config = parallelism \| (asyncMode ? (FIFO_QUEUE << 16) : 0);
2480		long np = (long)(-parallelism); // offset ctl counts
2481		this.ctl = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
2482	<	// 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();
2482	>	int pn = nextPoolId();
2483		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2484	<	sb.append(poolNumberGenerator.incrementAndGet());
2484	>	sb.append(Integer.toString(pn));
2485		sb.append("-worker-");
2486		this.workerNamePrefix = sb.toString();
2487	<	// Create initial submission queue
2488	<	WorkQueue sq = tryAddSharedQueue(0);
2489	<	if (sq != null)
2490	<	sq.growArray(false);
2487	>	}
2488	>
2489	>	/**
2490	>	* Constructor for common pool, suitable only for static initialization.
2491	>	* Basically the same as above, but uses smallest possible initial footprint.
2492	>	*/
2493	>	ForkJoinPool(int parallelism, long ctl,
2494	>	ForkJoinWorkerThreadFactory factory,
2495	>	Thread.UncaughtExceptionHandler handler) {
2496	>	this.config = parallelism;
2497	>	this.ctl = ctl;
2498	>	this.factory = factory;
2499	>	this.ueh = handler;
2500	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2501	>	}
2502	>
2503	>	/**
2504	>	* Returns the common pool instance.
2505	>	*
2506	>	* @return the common pool instance
2507	>	*/
2508	>	public static ForkJoinPool commonPool() {
2509	>	// assert commonPool != null : "static init error";
2510	>	return commonPool;
2511		}
2512
2513		// Execution methods
#	Line 1970 \| Line 2529 \| public class ForkJoinPool extends Abstra
2529		* scheduled for execution
2530		*/
2531		public <T> T invoke(ForkJoinTask<T> task) {
2532	<	doSubmit(task);
2532	>	if (task == null)
2533	>	throw new NullPointerException();
2534	>	externalPush(task);
2535		return task.join();
2536		}
2537
#	Line 1983 \| Line 2544 \| public class ForkJoinPool extends Abstra
2544		* scheduled for execution
2545		*/
2546		public void execute(ForkJoinTask<?> task) {
2547	<	doSubmit(task);
2547	>	if (task == null)
2548	>	throw new NullPointerException();
2549	>	externalPush(task);
2550		}
2551
2552		// AbstractExecutorService methods
#	Line 2000 \| Line 2563 \| public class ForkJoinPool extends Abstra
2563		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2564		job = (ForkJoinTask<?>) task;
2565		else
2566	<	job = ForkJoinTask.adapt(task, null);
2567	<	doSubmit(job);
2566	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2567	>	externalPush(job);
2568		}
2569
2570		/**
#	Line 2014 \| Line 2577 \| public class ForkJoinPool extends Abstra
2577		* scheduled for execution
2578		*/
2579		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2580	<	doSubmit(task);
2580	>	if (task == null)
2581	>	throw new NullPointerException();
2582	>	externalPush(task);
2583		return task;
2584		}
2585
#	Line 2024 \| Line 2589 \| public class ForkJoinPool extends Abstra
2589		* scheduled for execution
2590		*/
2591		public <T> ForkJoinTask<T> submit(Callable<T> task) {
2592	<	if (task == null)
2593	<	throw new NullPointerException();
2029	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
2030	<	doSubmit(job);
2592	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2593	>	externalPush(job);
2594		return job;
2595		}
2596
#	Line 2037 \| Line 2600 \| public class ForkJoinPool extends Abstra
2600		* scheduled for execution
2601		*/
2602		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2603	<	if (task == null)
2604	<	throw new NullPointerException();
2042	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
2043	<	doSubmit(job);
2603	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2604	>	externalPush(job);
2605		return job;
2606		}
2607
#	Line 2056 \| Line 2617 \| public class ForkJoinPool extends Abstra
2617		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2618		job = (ForkJoinTask<?>) task;
2619		else
2620	<	job = ForkJoinTask.adapt(task, null);
2621	<	doSubmit(job);
2620	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2621	>	externalPush(job);
2622		return job;
2623		}
2624
#	Line 2066 \| Line 2627 \| public class ForkJoinPool extends Abstra
2627		* @throws RejectedExecutionException {@inheritDoc}
2628		*/
2629		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
2630	<	ArrayList<ForkJoinTask<T>> forkJoinTasks =
2631	<	new ArrayList<ForkJoinTask<T>>(tasks.size());
2632	<	for (Callable<T> task : tasks)
2633	<	forkJoinTasks.add(ForkJoinTask.adapt(task));
2634	<	invoke(new InvokeAll<T>(forkJoinTasks));
2635	<
2630	>	// In previous versions of this class, this method constructed
2631	>	// a task to run ForkJoinTask.invokeAll, but now external
2632	>	// invocation of multiple tasks is at least as efficient.
2633	>	List<ForkJoinTask<T>> fs = new ArrayList<ForkJoinTask<T>>(tasks.size());
2634	>	// Workaround needed because method wasn't declared with
2635	>	// wildcards in return type but should have been.
2636		@SuppressWarnings({"unchecked", "rawtypes"})
2637	<	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
2077	<	return futures;
2078	<	}
2637	>	List<Future<T>> futures = (List<Future<T>>) (List) fs;
2638
2639	<	static final class InvokeAll<T> extends RecursiveAction {
2640	<	final ArrayList<ForkJoinTask<T>> tasks;
2641	<	InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
2642	<	public void compute() {
2643	<	try { invokeAll(tasks); }
2644	<	catch (Exception ignore) {}
2639	>	boolean done = false;
2640	>	try {
2641	>	for (Callable<T> t : tasks) {
2642	>	ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2643	>	externalPush(f);
2644	>	fs.add(f);
2645	>	}
2646	>	for (ForkJoinTask<T> f : fs)
2647	>	f.quietlyJoin();
2648	>	done = true;
2649	>	return futures;
2650	>	} finally {
2651	>	if (!done)
2652	>	for (ForkJoinTask<T> f : fs)
2653	>	f.cancel(false);
2654		}
2087	–	private static final long serialVersionUID = -7914297376763021607L;
2655		}
2656
2657		/**
#	Line 2112 \| Line 2679 \| public class ForkJoinPool extends Abstra
2679		* @return the targeted parallelism level of this pool
2680		*/
2681		public int getParallelism() {
2682	<	return parallelism;
2682	>	return config & SMASK;
2683	>	}
2684	>
2685	>	/**
2686	>	* Returns the targeted parallelism level of the common pool.
2687	>	*
2688	>	* @return the targeted parallelism level of the common pool
2689	>	*/
2690	>	public static int getCommonPoolParallelism() {
2691	>	return commonPoolParallelism;
2692		}
2693
2694		/**
#	Line 2124 \| Line 2700 \| public class ForkJoinPool extends Abstra
2700		* @return the number of worker threads
2701		*/
2702		public int getPoolSize() {
2703	<	return parallelism + (short)(ctl >>> TC_SHIFT);
2703	>	return (config & SMASK) + (short)(ctl >>> TC_SHIFT);
2704		}
2705
2706		/**
#	Line 2134 \| Line 2710 \| public class ForkJoinPool extends Abstra
2710		* @return {@code true} if this pool uses async mode
2711		*/
2712		public boolean getAsyncMode() {
2713	<	return localMode != 0;
2713	>	return (config >>> 16) == FIFO_QUEUE;
2714		}
2715
2716		/**
#	Line 2149 \| Line 2725 \| public class ForkJoinPool extends Abstra
2725		int rc = 0;
2726		WorkQueue[] ws; WorkQueue w;
2727		if ((ws = workQueues) != null) {
2728	<	int n = ws.length;
2729	<	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)
2728	>	for (int i = 1; i < ws.length; i += 2) {
2729	>	if ((w = ws[i]) != null && w.isApparentlyUnblocked())
2730		++rc;
2731		}
2732		}
#	Line 2171 \| Line 2741 \| public class ForkJoinPool extends Abstra
2741		* @return the number of active threads
2742		*/
2743		public int getActiveThreadCount() {
2744	<	int r = parallelism + (int)(ctl >> AC_SHIFT);
2744	>	int r = (config & SMASK) + (int)(ctl >> AC_SHIFT);
2745		return (r <= 0) ? 0 : r; // suppress momentarily negative values
2746		}
2747
#	Line 2187 \| Line 2757 \| public class ForkJoinPool extends Abstra
2757		* @return {@code true} if all threads are currently idle
2758		*/
2759		public boolean isQuiescent() {
2760	<	return (int)(ctl >> AC_SHIFT) + parallelism == 0;
2760	>	return (int)(ctl >> AC_SHIFT) + (config & SMASK) == 0;
2761		}
2762
2763		/**
#	Line 2202 \| Line 2772 \| public class ForkJoinPool extends Abstra
2772		* @return the number of steals
2773		*/
2774		public long getStealCount() {
2775	<	long count = stealCount.get();
2775	>	long count = stealCount;
2776		WorkQueue[] ws; WorkQueue w;
2777		if ((ws = workQueues) != null) {
2778	<	int n = ws.length;
2209	<	for (int i = 1; i < n; i += 2) {
2778	>	for (int i = 1; i < ws.length; i += 2) {
2779		if ((w = ws[i]) != null)
2780	<	count += w.totalSteals;
2780	>	count += w.nsteals;
2781		}
2782		}
2783		return count;
#	Line 2228 \| Line 2797 \| public class ForkJoinPool extends Abstra
2797		long count = 0;
2798		WorkQueue[] ws; WorkQueue w;
2799		if ((ws = workQueues) != null) {
2800	<	int n = ws.length;
2232	<	for (int i = 1; i < n; i += 2) {
2800	>	for (int i = 1; i < ws.length; i += 2) {
2801		if ((w = ws[i]) != null)
2802		count += w.queueSize();
2803		}
#	Line 2248 \| Line 2816 \| public class ForkJoinPool extends Abstra
2816		int count = 0;
2817		WorkQueue[] ws; WorkQueue w;
2818		if ((ws = workQueues) != null) {
2819	<	int n = ws.length;
2252	<	for (int i = 0; i < n; i += 2) {
2819	>	for (int i = 0; i < ws.length; i += 2) {
2820		if ((w = ws[i]) != null)
2821		count += w.queueSize();
2822		}
#	Line 2266 \| Line 2833 \| public class ForkJoinPool extends Abstra
2833		public boolean hasQueuedSubmissions() {
2834		WorkQueue[] ws; WorkQueue w;
2835		if ((ws = workQueues) != null) {
2836	<	int n = ws.length;
2270	<	for (int i = 0; i < n; i += 2) {
2836	>	for (int i = 0; i < ws.length; i += 2) {
2837		if ((w = ws[i]) != null && w.queueSize() != 0)
2838		return true;
2839		}
#	Line 2285 \| Line 2851 \| public class ForkJoinPool extends Abstra
2851		protected ForkJoinTask<?> pollSubmission() {
2852		WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2853		if ((ws = workQueues) != null) {
2854	<	int n = ws.length;
2289	<	for (int i = 0; i < n; i += 2) {
2854	>	for (int i = 0; i < ws.length; i += 2) {
2855		if ((w = ws[i]) != null && (t = w.poll()) != null)
2856		return t;
2857		}
#	Line 2315 \| Line 2880 \| public class ForkJoinPool extends Abstra
2880		int count = 0;
2881		WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2882		if ((ws = workQueues) != null) {
2883	<	int n = ws.length;
2319	<	for (int i = 0; i < n; ++i) {
2883	>	for (int i = 0; i < ws.length; ++i) {
2884		if ((w = ws[i]) != null) {
2885		while ((t = w.poll()) != null) {
2886		c.add(t);
#	Line 2336 \| Line 2900 \| public class ForkJoinPool extends Abstra
2900		* @return a string identifying this pool, as well as its state
2901		*/
2902		public String toString() {
2903	<	long st = getStealCount();
2904	<	long qt = getQueuedTaskCount();
2905	<	long qs = getQueuedSubmissionCount();
2342	<	int rc = getRunningThreadCount();
2343	<	int pc = parallelism;
2903	>	// Use a single pass through workQueues to collect counts
2904	>	long qt = 0L, qs = 0L; int rc = 0;
2905	>	long st = stealCount;
2906		long c = ctl;
2907	+	WorkQueue[] ws; WorkQueue w;
2908	+	if ((ws = workQueues) != null) {
2909	+	for (int i = 0; i < ws.length; ++i) {
2910	+	if ((w = ws[i]) != null) {
2911	+	int size = w.queueSize();
2912	+	if ((i & 1) == 0)
2913	+	qs += size;
2914	+	else {
2915	+	qt += size;
2916	+	st += w.nsteals;
2917	+	if (w.isApparentlyUnblocked())
2918	+	++rc;
2919	+	}
2920	+	}
2921	+	}
2922	+	}
2923	+	int pc = (config & SMASK);
2924		int tc = pc + (short)(c >>> TC_SHIFT);
2925		int ac = pc + (int)(c >> AC_SHIFT);
2926		if (ac < 0) // ignore transient negative
#	Line 2350 \| Line 2929 \| public class ForkJoinPool extends Abstra
2929		if ((c & STOP_BIT) != 0)
2930		level = (tc == 0) ? "Terminated" : "Terminating";
2931		else
2932	<	level = runState < 0 ? "Shutting down" : "Running";
2932	>	level = plock < 0 ? "Shutting down" : "Running";
2933		return super.toString() +
2934		"[" + level +
2935		", parallelism = " + pc +
#	Line 2364 \| Line 2943 \| public class ForkJoinPool extends Abstra
2943		}
2944
2945		/**
2946	<	* Initiates an orderly shutdown in which previously submitted
2947	<	* tasks are executed, but no new tasks will be accepted.
2948	<	* Invocation has no additional effect if already shut down.
2949	<	* Tasks that are in the process of being submitted concurrently
2950	<	* during the course of this method may or may not be rejected.
2946	>	* Possibly initiates an orderly shutdown in which previously
2947	>	* submitted tasks are executed, but no new tasks will be
2948	>	* accepted. Invocation has no effect on execution state if this
2949	>	* is the {@link #commonPool}, and no additional effect if
2950	>	* already shut down. Tasks that are in the process of being
2951	>	* submitted concurrently during the course of this method may or
2952	>	* may not be rejected.
2953		*
2954		* @throws SecurityException if a security manager exists and
2955		* the caller is not permitted to modify threads
#	Line 2377 \| Line 2958 \| public class ForkJoinPool extends Abstra
2958		*/
2959		public void shutdown() {
2960		checkPermission();
2961	<	enableShutdown();
2381	<	tryTerminate(false);
2961	>	tryTerminate(false, true);
2962		}
2963
2964		/**
2965	<	* Attempts to cancel and/or stop all tasks, and reject all
2966	<	* subsequently submitted tasks. Tasks that are in the process of
2967	<	* being submitted or executed concurrently during the course of
2968	<	* this method may or may not be rejected. This method cancels
2969	<	* both existing and unexecuted tasks, in order to permit
2970	<	* termination in the presence of task dependencies. So the method
2971	<	* always returns an empty list (unlike the case for some other
2972	<	* Executors).
2965	>	* Possibly attempts to cancel and/or stop all tasks, and reject
2966	>	* all subsequently submitted tasks. Invocation has no effect on
2967	>	* execution state if this is the {@link #commonPool}, and no
2968	>	* additional effect if already shut down. Otherwise, tasks that
2969	>	* are in the process of being submitted or executed concurrently
2970	>	* during the course of this method may or may not be
2971	>	* rejected. This method cancels both existing and unexecuted
2972	>	* tasks, in order to permit termination in the presence of task
2973	>	* dependencies. So the method always returns an empty list
2974	>	* (unlike the case for some other Executors).
2975		*
2976		* @return an empty list
2977		* @throws SecurityException if a security manager exists and
#	Line 2399 \| Line 2981 \| public class ForkJoinPool extends Abstra
2981		*/
2982		public List<Runnable> shutdownNow() {
2983		checkPermission();
2984	<	enableShutdown();
2403	<	tryTerminate(true);
2984	>	tryTerminate(true, true);
2985		return Collections.emptyList();
2986		}
2987
#	Line 2412 \| Line 2993 \| public class ForkJoinPool extends Abstra
2993		public boolean isTerminated() {
2994		long c = ctl;
2995		return ((c & STOP_BIT) != 0L &&
2996	<	(short)(c >>> TC_SHIFT) == -parallelism);
2996	>	(short)(c >>> TC_SHIFT) == -(config & SMASK));
2997		}
2998
2999		/**
#	Line 2431 \| Line 3012 \| public class ForkJoinPool extends Abstra
3012		public boolean isTerminating() {
3013		long c = ctl;
3014		return ((c & STOP_BIT) != 0L &&
3015	<	(short)(c >>> TC_SHIFT) != -parallelism);
3015	>	(short)(c >>> TC_SHIFT) != -(config & SMASK));
3016		}
3017
3018		/**
#	Line 2440 \| Line 3021 \| public class ForkJoinPool extends Abstra
3021		* @return {@code true} if this pool has been shut down
3022		*/
3023		public boolean isShutdown() {
3024	<	return runState < 0;
3024	>	return plock < 0;
3025		}
3026
3027		/**
3028	<	* Blocks until all tasks have completed execution after a shutdown
3029	<	* request, or the timeout occurs, or the current thread is
3030	<	* interrupted, whichever happens first.
3028	>	* Blocks until all tasks have completed execution after a
3029	>	* shutdown request, or the timeout occurs, or the current thread
3030	>	* is interrupted, whichever happens first. Note that the {@link
3031	>	* #commonPool()} never terminates until program shutdown so
3032	>	* this method will always time out.
3033		*
3034		* @param timeout the maximum time to wait
3035		* @param unit the time unit of the timeout argument
#	Line 2457 \| Line 3040 \| public class ForkJoinPool extends Abstra
3040		public boolean awaitTermination(long timeout, TimeUnit unit)
3041		throws InterruptedException {
3042		long nanos = unit.toNanos(timeout);
3043	<	final ReentrantLock lock = this.lock;
3044	<	lock.lock();
3045	<	try {
3046	<	for (;;) {
3047	<	if (isTerminated())
3048	<	return true;
3049	<	if (nanos <= 0)
3050	<	return false;
3051	<	nanos = termination.awaitNanos(nanos);
3043	>	if (isTerminated())
3044	>	return true;
3045	>	long startTime = System.nanoTime();
3046	>	boolean terminated = false;
3047	>	synchronized (this) {
3048	>	for (long waitTime = nanos, millis = 0L;;) {
3049	>	if (terminated = isTerminated() \|\|
3050	>	waitTime <= 0L \|\|
3051	>	(millis = unit.toMillis(waitTime)) <= 0L)
3052	>	break;
3053	>	wait(millis);
3054	>	waitTime = nanos - (System.nanoTime() - startTime);
3055		}
2470	–	} finally {
2471	–	lock.unlock();
3056		}
3057	+	return terminated;
3058		}
3059
3060		/**
#	Line 2553 \| Line 3138 \| public class ForkJoinPool extends Abstra
3138		*
3139		* <p>If the caller is not a {@link ForkJoinTask}, this method is
3140		* behaviorally equivalent to
3141	<	a * <pre> {@code
3141	>	* <pre> {@code
3142		* while (!blocker.isReleasable())
3143		* if (blocker.block())
3144		* return;
#	Line 2568 \| Line 3153 \| *a <pre> {@code**
3153		public static void managedBlock(ManagedBlocker blocker)
3154		throws InterruptedException {
3155		Thread t = Thread.currentThread();
3156	<	ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ?
3157	<	((ForkJoinWorkerThread)t).pool : null);
3158	<	while (!blocker.isReleasable()) {
3159	<	if (p == null \|\| p.tryCompensate()) {
3160	<	try {
3161	<	do {} while (!blocker.isReleasable() && !blocker.block());
3162	<	} finally {
3163	<	if (p != null)
3156	>	if (t instanceof ForkJoinWorkerThread) {
3157	>	ForkJoinPool p = ((ForkJoinWorkerThread)t).pool;
3158	>	while (!blocker.isReleasable()) { // variant of helpSignal
3159	>	WorkQueue[] ws; WorkQueue q; int m, n, u;
3160	>	if ((ws = p.workQueues) != null && (m = ws.length - 1) >= 0) {
3161	>	for (int i = 0; i <= m; ++i) {
3162	>	if (blocker.isReleasable())
3163	>	return;
3164	>	if ((q = ws[i]) != null && (n = q.queueSize()) > 0) {
3165	>	p.signalWork(q, n);
3166	>	if ((u = (int)(p.ctl >>> 32)) >= 0 \|\|
3167	>	(u >> UAC_SHIFT) >= 0)
3168	>	break;
3169	>	}
3170	>	}
3171	>	}
3172	>	if (p.tryCompensate()) {
3173	>	try {
3174	>	do {} while (!blocker.isReleasable() &&
3175	>	!blocker.block());
3176	>	} finally {
3177		p.incrementActiveCount();
3178	+	}
3179	+	break;
3180		}
2581	–	break;
3181		}
3182		}
3183	+	else {
3184	+	do {} while (!blocker.isReleasable() &&
3185	+	!blocker.block());
3186	+	}
3187		}
3188
3189		// AbstractExecutorService overrides. These rely on undocumented
#	Line 2588 \| Line 3191 \| *a <pre> {@code**
3191		// implement RunnableFuture.
3192
3193		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
3194	<	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
3194	>	return new ForkJoinTask.AdaptedRunnable<T>(runnable, value);
3195		}
3196
3197		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
3198	<	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
3198	>	return new ForkJoinTask.AdaptedCallable<T>(callable);
3199		}
3200
3201		// Unsafe mechanics
3202		private static final sun.misc.Unsafe U;
3203		private static final long CTL;
2601	–	private static final long RUNSTATE;
3204		private static final long PARKBLOCKER;
3205	+	private static final int ABASE;
3206	+	private static final int ASHIFT;
3207	+	private static final long STEALCOUNT;
3208	+	private static final long PLOCK;
3209	+	private static final long INDEXSEED;
3210	+	private static final long QLOCK;
3211
3212		static {
3213	<	poolNumberGenerator = new AtomicInteger();
2606	<	modifyThreadPermission = new RuntimePermission("modifyThread");
2607	<	defaultForkJoinWorkerThreadFactory =
2608	<	new DefaultForkJoinWorkerThreadFactory();
2609	<	int s;
3213	>	int s; // initialize field offsets for CAS etc
3214		try {
3215		U = getUnsafe();
3216		Class<?> k = ForkJoinPool.class;
2613	–	Class<?> tk = Thread.class;
3217		CTL = U.objectFieldOffset
3218		(k.getDeclaredField("ctl"));
3219	<	RUNSTATE = U.objectFieldOffset
3220	<	(k.getDeclaredField("runState"));
3219	>	STEALCOUNT = U.objectFieldOffset
3220	>	(k.getDeclaredField("stealCount"));
3221	>	PLOCK = U.objectFieldOffset
3222	>	(k.getDeclaredField("plock"));
3223	>	INDEXSEED = U.objectFieldOffset
3224	>	(k.getDeclaredField("indexSeed"));
3225	>	Class<?> tk = Thread.class;
3226		PARKBLOCKER = U.objectFieldOffset
3227		(tk.getDeclaredField("parkBlocker"));
3228	+	Class<?> wk = WorkQueue.class;
3229	+	QLOCK = U.objectFieldOffset
3230	+	(wk.getDeclaredField("qlock"));
3231	+	Class<?> ak = ForkJoinTask[].class;
3232	+	ABASE = U.arrayBaseOffset(ak);
3233	+	s = U.arrayIndexScale(ak);
3234	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3235		} catch (Exception e) {
3236		throw new Error(e);
3237		}
3238	+	if ((s & (s-1)) != 0)
3239	+	throw new Error("data type scale not a power of two");
3240	+
3241	+	submitters = new ThreadLocal<Submitter>();
3242	+	ForkJoinWorkerThreadFactory fac = defaultForkJoinWorkerThreadFactory =
3243	+	new DefaultForkJoinWorkerThreadFactory();
3244	+	/*
3245	+	* Establish common pool parameters. For extra caution,
3246	+	* computations to set up common pool state are here; the
3247	+	* constructor just assigns these values to fields.
3248	+	*/
3249	+
3250	+	int par = 0;
3251	+	Thread.UncaughtExceptionHandler handler = null;
3252	+	try { // TBD: limit or report ignored exceptions?
3253	+	String pp = System.getProperty
3254	+	("java.util.concurrent.ForkJoinPool.common.parallelism");
3255	+	String hp = System.getProperty
3256	+	("java.util.concurrent.ForkJoinPool.common.exceptionHandler");
3257	+	String fp = System.getProperty
3258	+	("java.util.concurrent.ForkJoinPool.common.threadFactory");
3259	+	if (fp != null)
3260	+	fac = ((ForkJoinWorkerThreadFactory)ClassLoader.
3261	+	getSystemClassLoader().loadClass(fp).newInstance());
3262	+	if (hp != null)
3263	+	handler = ((Thread.UncaughtExceptionHandler)ClassLoader.
3264	+	getSystemClassLoader().loadClass(hp).newInstance());
3265	+	if (pp != null)
3266	+	par = Integer.parseInt(pp);
3267	+	} catch (Exception ignore) {
3268	+	}
3269	+
3270	+	if (par <= 0)
3271	+	par = Runtime.getRuntime().availableProcessors();
3272	+	if (par > MAX_CAP)
3273	+	par = MAX_CAP;
3274	+	commonPoolParallelism = par;
3275	+	long np = (long)(-par); // precompute initial ctl value
3276	+	long ct = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
3277	+
3278	+	commonPool = new ForkJoinPool(par, ct, fac, handler);
3279	+	modifyThreadPermission = new RuntimePermission("modifyThread");
3280		}
3281
3282		/**

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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents): Revision 1.112 by dl, Thu Jan 26 18:15:12 2012 UTC vs. Revision 1.148 by jsr166, Tue Nov 20 06:18:39 2012 UTC

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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.112 by dl, Thu Jan 26 18:15:12 2012 UTC vs.
Revision 1.148 by jsr166, Tue Nov 20 06:18:39 2012 UTC