[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 1.158 by dl, Sat Dec 15 20:21:30 2012 UTC

#	Line 11 \| Line 11 \| import java.util.Arrays;
11		import java.util.Collection;
12		import java.util.Collections;
13		import java.util.List;
14	–	import java.util.Random;
14		import java.util.concurrent.AbstractExecutorService;
15		import java.util.concurrent.Callable;
16		import java.util.concurrent.ExecutorService;
#	Line 19 \| Line 18 \| import java.util.concurrent.Future;
18		import java.util.concurrent.RejectedExecutionException;
19		import java.util.concurrent.RunnableFuture;
20		import java.util.concurrent.TimeUnit;
22	–	import java.util.concurrent.atomic.AtomicInteger;
23	–	import java.util.concurrent.atomic.AtomicLong;
24	–	import java.util.concurrent.locks.ReentrantLock;
25	–	import java.util.concurrent.locks.Condition;
21
22		/**
23		* An {@link ExecutorService} for running {@link ForkJoinTask}s.
#	Line 42 \| Line 37 \| import java.util.concurrent.locks.Condit
37		* ForkJoinPool}s may also be appropriate for use with event-style
38		* tasks that are never joined.
39		*
40	<	* <p>A {@code ForkJoinPool} is constructed with a given target
41	<	* parallelism level; by default, equal to the number of available
42	<	* processors. The pool attempts to maintain enough active (or
43	<	* available) threads by dynamically adding, suspending, or resuming
44	<	* internal worker threads, even if some tasks are stalled waiting to
45	<	* join others. However, no such adjustments are guaranteed in the
46	<	* face of blocked IO or other unmanaged synchronization. The nested
47	<	* {@link ManagedBlocker} interface enables extension of the kinds of
40	>	* <p>A static {@link #commonPool()} is available and appropriate for
41	>	* most applications. The common pool is used by any ForkJoinTask that
42	>	* is not explicitly submitted to a specified pool. Using the common
43	>	* pool normally reduces resource usage (its threads are slowly
44	>	* reclaimed during periods of non-use, and reinstated upon subsequent
45	>	* use).
46	>	*
47	>	* <p>For applications that require separate or custom pools, a {@code
48	>	* ForkJoinPool} may be constructed with a given target parallelism
49	>	* level; by default, equal to the number of available processors. The
50	>	* pool attempts to maintain enough active (or available) threads by
51	>	* dynamically adding, suspending, or resuming internal worker
52	>	* threads, even if some tasks are stalled waiting to join
53	>	* others. However, no such adjustments are guaranteed in the face of
54	>	* blocked I/O or other unmanaged synchronization. The nested {@link
55	>	* ManagedBlocker} interface enables extension of the kinds of
56		* synchronization accommodated.
57		*
58		* <p>In addition to execution and lifecycle control methods, this
#	Line 59 \| Line 62 \| import java.util.concurrent.locks.Condit
62		* {@link #toString} returns indications of pool state in a
63		* convenient form for informal monitoring.
64		*
65	<	* <p> As is the case with other ExecutorServices, there are three
66	<	* main task execution methods summarized in the following
67	<	* table. These are designed to be used primarily by clients not
68	<	* already engaged in fork/join computations in the current pool. The
69	<	* main forms of these methods accept instances of {@code
70	<	* ForkJoinTask}, but overloaded forms also allow mixed execution of
71	<	* plain {@code Runnable}- or {@code Callable}- based activities as
72	<	* well. However, tasks that are already executing in a pool should
73	<	* normally instead use the within-computation forms listed in the
74	<	* table unless using async event-style tasks that are not usually
75	<	* joined, in which case there is little difference among choice of
73	<	* methods.
65	>	* <p>As is the case with other ExecutorServices, there are three
66	>	* main task execution methods summarized in the following table.
67	>	* These are designed to be used primarily by clients not already
68	>	* engaged in fork/join computations in the current pool. The main
69	>	* forms of these methods accept instances of {@code ForkJoinTask},
70	>	* but overloaded forms also allow mixed execution of plain {@code
71	>	* Runnable}- or {@code Callable}- based activities as well. However,
72	>	* tasks that are already executing in a pool should normally instead
73	>	* use the within-computation forms listed in the table unless using
74	>	* async event-style tasks that are not usually joined, in which case
75	>	* there is little difference among choice of methods.
76		*
77		* <table BORDER CELLPADDING=3 CELLSPACING=1>
78		* <tr>
#	Line 95 \| Line 97 \| import java.util.concurrent.locks.Condit
97		* </tr>
98		* </table>
99		*
100	<	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
101	<	* used for all parallel task execution in a program or subsystem.
102	<	* Otherwise, use would not usually outweigh the construction and
103	<	* bookkeeping overhead of creating a large set of threads. For
104	<	* example, a common pool could be used for the {@code SortTasks}
105	<	* illustrated in {@link RecursiveAction}. Because {@code
106	<	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
107	<	* daemon} mode, there is typically no need to explicitly {@link
108	<	* #shutdown} such a pool upon program exit.
109	<	*
108	<	* <pre> {@code
109	<	* static final ForkJoinPool mainPool = new ForkJoinPool();
110	<	* ...
111	<	* public void sort(long[] array) {
112	<	* mainPool.invoke(new SortTask(array, 0, array.length));
113	<	* }}</pre>
100	>	* <p>The common pool is by default constructed with default
101	>	* parameters, but these may be controlled by setting three {@link
102	>	* System#getProperty system properties} with prefix {@code
103	>	* java.util.concurrent.ForkJoinPool.common}: {@code parallelism} --
104	>	* an integer greater than zero, {@code threadFactory} -- the class
105	>	* name of a {@link ForkJoinWorkerThreadFactory}, and {@code
106	>	* exceptionHandler} -- the class name of a {@link
107	>	* java.lang.Thread.UncaughtExceptionHandler
108	>	* Thread.UncaughtExceptionHandler}. Upon any error in establishing
109	>	* these settings, default parameters are used.
110		*
111		* <p><b>Implementation notes</b>: This implementation restricts the
112		* maximum number of running threads to 32767. Attempts to create
#	Line 131 \| Line 127 \| public class ForkJoinPool extends Abstra
127		*
128		* This class and its nested classes provide the main
129		* functionality and control for a set of worker threads:
130	<	* Submissions from non-FJ threads enter into submission
131	<	* queues. Workers take these tasks and typically split them into
132	<	* subtasks that may be stolen by other workers. Preference rules
133	<	* give first priority to processing tasks from their own queues
134	<	* (LIFO or FIFO, depending on mode), then to randomized FIFO
135	<	* steals of tasks in other queues.
130	>	* Submissions from non-FJ threads enter into submission queues.
131	>	* Workers take these tasks and typically split them into subtasks
132	>	* that may be stolen by other workers. Preference rules give
133	>	* first priority to processing tasks from their own queues (LIFO
134	>	* or FIFO, depending on mode), then to randomized FIFO steals of
135	>	* tasks in other queues.
136		*
137	<	* WorkQueues.
137	>	* WorkQueues
138		* ==========
139		*
140		* Most operations occur within work-stealing queues (in nested
#	Line 156 \| Line 152 \| public class ForkJoinPool extends Abstra
152		* (http://research.sun.com/scalable/pubs/index.html) and
153		* "Idempotent work stealing" by Michael, Saraswat, and Vechev,
154		* PPoPP 2009 (http://portal.acm.org/citation.cfm?id=1504186).
155	<	* The main differences ultimately stem from gc requirements that
155	>	* The main differences ultimately stem from GC requirements that
156		* we null out taken slots as soon as we can, to maintain as small
157		* a footprint as possible even in programs generating huge
158		* numbers of tasks. To accomplish this, we shift the CAS
#	Line 178 \| Line 174 \| public class ForkJoinPool extends Abstra
174		* If an attempted steal fails, a thief always chooses a different
175		* random victim target to try next. So, in order for one thief to
176		* progress, it suffices for any in-progress poll or new push on
177	<	* any empty queue to complete.
177	>	* any empty queue to complete. (This is why we normally use
178	>	* method pollAt and its variants that try once at the apparent
179	>	* base index, else consider alternative actions, rather than
180	>	* method poll.)
181		*
182		* This approach also enables support of a user mode in which local
183		* task processing is in FIFO, not LIFO order, simply by using
#	Line 188 \| Line 187 \| public class ForkJoinPool extends Abstra
187		* rarely provide the best possible performance on a given
188		* machine, but portably provide good throughput by averaging over
189		* these factors. (Further, even if we did try to use such
190	<	* information, we do not usually have a basis for exploiting
191	<	* it. For example, some sets of tasks profit from cache
192	<	* affinities, but others are harmed by cache pollution effects.)
190	>	* information, we do not usually have a basis for exploiting it.
191	>	* For example, some sets of tasks profit from cache affinities,
192	>	* but others are harmed by cache pollution effects.)
193		*
194		* WorkQueues are also used in a similar way for tasks submitted
195		* to the pool. We cannot mix these tasks in the same queues used
196		* for work-stealing (this would contaminate lifo/fifo
197	<	* processing). Instead, we loosely associate (via hashing)
198	<	* submission queues with submitting threads, and randomly scan
199	<	* these queues as well when looking for work. In essence,
200	<	* submitters act like workers except that they never take tasks,
201	<	* and they are multiplexed on to a finite number of shared work
202	<	* queues. However, classes are set up so that future extensions
203	<	* could allow submitters to optionally help perform tasks as
204	<	* well. Pool submissions from internal workers are also allowed,
205	<	* but use randomized rather than thread-hashed queue indices to
206	<	* avoid imbalance. Insertion of tasks in shared mode requires a
207	<	* lock (mainly to protect in the case of resizing) but we use
208	<	* only a simple spinlock (using bits in field runState), because
209	<	* submitters encountering a busy queue try or create others so
210	<	* never block.
197	>	* processing). Instead, we randomly associate submission queues
198	>	* with submitting threads, using a form of hashing. The
199	>	* ThreadLocal Submitter class contains a value initially used as
200	>	* a hash code for choosing existing queues, but may be randomly
201	>	* repositioned upon contention with other submitters. In
202	>	* essence, submitters act like workers except that they are
203	>	* restricted to executing local tasks that they submitted (or in
204	>	* the case of CountedCompleters, others with the same root task).
205	>	* However, because most shared/external queue operations are more
206	>	* expensive than internal, and because, at steady state, external
207	>	* submitters will compete for CPU with workers, ForkJoinTask.join
208	>	* and related methods disable them from repeatedly helping to
209	>	* process tasks if all workers are active. Insertion of tasks in
210	>	* shared mode requires a lock (mainly to protect in the case of
211	>	* resizing) but we use only a simple spinlock (using bits in
212	>	* field qlock), because submitters encountering a busy queue move
213	>	* on to try or create other queues -- they block only when
214	>	* creating and registering new queues.
215		*
216	<	* Management.
216	>	* Management
217		* ==========
218		*
219		* The main throughput advantages of work-stealing stem from
#	Line 220 \| Line 223 \| public class ForkJoinPool extends Abstra
223		* tactic for avoiding bottlenecks is packing nearly all
224		* essentially atomic control state into two volatile variables
225		* that are by far most often read (not written) as status and
226	<	* consistency checks
226	>	* consistency checks.
227		*
228		* Field "ctl" contains 64 bits holding all the information needed
229		* to atomically decide to add, inactivate, enqueue (on an event
#	Line 230 \| Line 233 \| public class ForkJoinPool extends Abstra
233		* and their negations (used for thresholding) to fit into 16bit
234		* fields.
235		*
236	<	* Field "runState" contains 32 bits needed to register and
237	<	* deregister WorkQueues, as well as to enable shutdown. It is
238	<	* only modified under a lock (normally briefly held, but
239	<	* occasionally protecting allocations and resizings) but even
240	<	* when locked remains available to check consistency.
236	>	* Field "plock" is a form of sequence lock with a saturating
237	>	* shutdown bit (similarly for per-queue "qlocks"), mainly
238	>	* protecting updates to the workQueues array, as well as to
239	>	* enable shutdown. When used as a lock, it is normally only very
240	>	* briefly held, so is nearly always available after at most a
241	>	* brief spin, but we use a monitor-based backup strategy to
242	>	* block when needed.
243		*
244		* Recording WorkQueues. WorkQueues are recorded in the
245	<	* "workQueues" array that is created upon pool construction and
246	<	* expanded if necessary. Updates to the array while recording
247	<	* new workers and unrecording terminated ones are protected from
248	<	* each other by a lock but the array is otherwise concurrently
249	<	* readable, and accessed directly. To simplify index-based
250	<	* operations, the array size is always a power of two, and all
251	<	* readers must tolerate null slots. Shared (submission) queues
252	<	* are at even indices, worker queues at odd indices. Grouping
253	<	* them together in this way simplifies and speeds up task
254	<	* scanning. To avoid flailing during start-up, the array is
255	<	* presized to hold twice #parallelism workers (which is unlikely
256	<	* to need further resizing during execution). But to avoid
257	<	* dealing with so many null slots, variable runState includes a
258	<	* mask for the nearest power of two that contains all current
254	<	* workers. All worker thread creation is on-demand, triggered by
255	<	* task submissions, replacement of terminated workers, and/or
245	>	* "workQueues" array that is created upon first use and expanded
246	>	* if necessary. Updates to the array while recording new workers
247	>	* and unrecording terminated ones are protected from each other
248	>	* by a lock but the array is otherwise concurrently readable, and
249	>	* accessed directly. To simplify index-based operations, the
250	>	* array size is always a power of two, and all readers must
251	>	* tolerate null slots. Worker queues are at odd indices. Shared
252	>	* (submission) queues are at even indices, up to a maximum of 64
253	>	* slots, to limit growth even if array needs to expand to add
254	>	* more workers. Grouping them together in this way simplifies and
255	>	* speeds up task scanning.
256	>	*
257	>	* All worker thread creation is on-demand, triggered by task
258	>	* submissions, replacement of terminated workers, and/or
259		* compensation for blocked workers. However, all other support
260		* code is set up to work with other policies. To ensure that we
261		* do not hold on to worker references that would prevent GC, ALL
#	Line 265 \| Line 268 \| public class ForkJoinPool extends Abstra
268		* both index-check and null-check the IDs. All such accesses
269		* ignore bad IDs by returning out early from what they are doing,
270		* since this can only be associated with termination, in which
271	<	* case it is OK to give up.
272	<	*
273	<	* All uses of the workQueues array check that it is non-null
274	<	* (even if previously non-null). This allows nulling during
275	<	* termination, which is currently not necessary, but remains an
276	<	* option for resource-revocation-based shutdown schemes. It also
274	<	* helps reduce JIT issuance of uncommon-trap code, which tends to
271	>	* case it is OK to give up. All uses of the workQueues array
272	>	* also check that it is non-null (even if previously
273	>	* non-null). This allows nulling during termination, which is
274	>	* currently not necessary, but remains an option for
275	>	* resource-revocation-based shutdown schemes. It also helps
276	>	* reduce JIT issuance of uncommon-trap code, which tends to
277		* unnecessarily complicate control flow in some methods.
278		*
279		* Event Queuing. Unlike HPC work-stealing frameworks, we cannot
#	Line 299 \| Line 301 \| public class ForkJoinPool extends Abstra
301		* some other queued worker rather than itself, which has the same
302		* net effect. Because enqueued workers may actually be rescanning
303		* rather than waiting, we set and clear the "parker" field of
304	<	* Workqueues to reduce unnecessary calls to unpark. (This
304	>	* WorkQueues to reduce unnecessary calls to unpark. (This
305		* requires a secondary recheck to avoid missed signals.) Note
306		* the unusual conventions about Thread.interrupts surrounding
307		* parking and other blocking: Because interrupts are used solely
#	Line 311 \| Line 313 \| public class ForkJoinPool extends Abstra
313		*
314		* Signalling. We create or wake up workers only when there
315		* appears to be at least one task they might be able to find and
316	<	* execute. When a submission is added or another worker adds a
317	<	* task to a queue that previously had fewer than two tasks, they
318	<	* signal waiting workers (or trigger creation of new ones if
319	<	* fewer than the given parallelism level -- see signalWork).
320	<	* These primary signals are buttressed by signals during rescans;
321	<	* together these cover the signals needed in cases when more
322	<	* tasks are pushed but untaken, and improve performance compared
323	<	* to having one thread wake up all workers.
316	>	* execute. However, many other threads may notice the same task
317	>	* and each signal to wake up a thread that might take it. So in
318	>	* general, pools will be over-signalled. When a submission is
319	>	* added or another worker adds a task to a queue that has fewer
320	>	* than two tasks, they signal waiting workers (or trigger
321	>	* creation of new ones if fewer than the given parallelism level
322	>	* -- signalWork), and may leave a hint to the unparked worker to
323	>	* help signal others upon wakeup). These primary signals are
324	>	* buttressed by others (see method helpSignal) whenever other
325	>	* threads scan for work or do not have a task to process. On
326	>	* most platforms, signalling (unpark) overhead time is noticeably
327	>	* long, and the time between signalling a thread and it actually
328	>	* making progress can be very noticeably long, so it is worth
329	>	* offloading these delays from critical paths as much as
330	>	* possible.
331		*
332		* Trimming workers. To release resources after periods of lack of
333		* use, a worker starting to wait when the pool is quiescent will
334	<	* time out and terminate if the pool has remained quiescent for
335	<	* SHRINK_RATE nanosecs. This will slowly propagate, eventually
336	<	* terminating all workers after long periods of non-use.
334	>	* time out and terminate if the pool has remained quiescent for a
335	>	* given period -- a short period if there are more threads than
336	>	* parallelism, longer as the number of threads decreases. This
337	>	* will slowly propagate, eventually terminating all workers after
338	>	* periods of non-use.
339		*
340		* Shutdown and Termination. A call to shutdownNow atomically sets
341	<	* a runState bit and then (non-atomically) sets each workers
342	<	* runState status, cancels all unprocessed tasks, and wakes up
341	>	* a plock bit and then (non-atomically) sets each worker's
342	>	* qlock status, cancels all unprocessed tasks, and wakes up
343		* all waiting workers. Detecting whether termination should
344		* commence after a non-abrupt shutdown() call requires more work
345		* and bookkeeping. We need consensus about quiescence (i.e., that
#	Line 336 \| Line 347 \| public class ForkJoinPool extends Abstra
347		* indication but non-abrupt shutdown still requires a rechecking
348		* scan for any workers that are inactive but not queued.
349		*
350	<	* Joining Tasks.
351	<	* ==============
350	>	* Joining Tasks
351	>	* =============
352		*
353		* Any of several actions may be taken when one worker is waiting
354	<	* to join a task stolen (or always held by) another. Because we
354	>	* to join a task stolen (or always held) by another. Because we
355		* are multiplexing many tasks on to a pool of workers, we can't
356		* just let them block (as in Thread.join). We also cannot just
357		* reassign the joiner's run-time stack with another and replace
358		* it later, which would be a form of "continuation", that even if
359		* possible is not necessarily a good idea since we sometimes need
360	<	* both an unblocked task and its continuation to
361	<	* progress. Instead we combine two tactics:
360	>	* both an unblocked task and its continuation to progress.
361	>	* Instead we combine two tactics:
362		*
363		* Helping: Arranging for the joiner to execute some task that it
364		* would be running if the steal had not occurred.
#	Line 356 \| Line 367 \| public class ForkJoinPool extends Abstra
367		* method tryCompensate() may create or re-activate a spare
368		* thread to compensate for blocked joiners until they unblock.
369		*
370	<	* A third form (implemented in tryRemoveAndExec and
371	<	* tryPollForAndExec) amounts to helping a hypothetical
372	<	* compensator: If we can readily tell that a possible action of a
373	<	* compensator is to steal and execute the task being joined, the
374	<	* joining thread can do so directly, without the need for a
375	<	* compensation thread (although at the expense of larger run-time
376	<	* stacks, but the tradeoff is typically worthwhile).
370	>	* A third form (implemented in tryRemoveAndExec) amounts to
371	>	* helping a hypothetical compensator: If we can readily tell that
372	>	* a possible action of a compensator is to steal and execute the
373	>	* task being joined, the joining thread can do so directly,
374	>	* without the need for a compensation thread (although at the
375	>	* expense of larger run-time stacks, but the tradeoff is
376	>	* typically worthwhile).
377		*
378		* The ManagedBlocker extension API can't use helping so relies
379		* only on compensation in method awaitBlocker.
#	Line 382 \| Line 393 \| public class ForkJoinPool extends Abstra
393		* (http://portal.acm.org/citation.cfm?id=155354). It differs in
394		* that: (1) We only maintain dependency links across workers upon
395		* steals, rather than use per-task bookkeeping. This sometimes
396	<	* requires a linear scan of workers array to locate stealers, but
397	<	* often doesn't because stealers leave hints (that may become
398	<	* stale/wrong) of where to locate them. A stealHint is only a
399	<	* hint because a worker might have had multiple steals and the
400	<	* hint records only one of them (usually the most current).
401	<	* Hinting isolates cost to when it is needed, rather than adding
402	<	* to per-task overhead. (2) It is "shallow", ignoring nesting
403	<	* and potentially cyclic mutual steals. (3) It is intentionally
396	>	* requires a linear scan of workQueues array to locate stealers,
397	>	* but often doesn't because stealers leave hints (that may become
398	>	* stale/wrong) of where to locate them. It is only a hint
399	>	* because a worker might have had multiple steals and the hint
400	>	* records only one of them (usually the most current). Hinting
401	>	* isolates cost to when it is needed, rather than adding to
402	>	* per-task overhead. (2) It is "shallow", ignoring nesting and
403	>	* potentially cyclic mutual steals. (3) It is intentionally
404		* racy: field currentJoin is updated only while actively joining,
405		* which means that we miss links in the chain during long-lived
406		* tasks, GC stalls etc (which is OK since blocking in such cases
407		* is usually a good idea). (4) We bound the number of attempts
408	<	* to find work (see MAX_HELP_DEPTH) and fall back to suspending
409	<	* the worker and if necessary replacing it with another.
408	>	* to find work (see MAX_HELP) and fall back to suspending the
409	>	* worker and if necessary replacing it with another.
410	>	*
411	>	* Helping actions for CountedCompleters are much simpler: Method
412	>	* helpComplete can take and execute any task with the same root
413	>	* as the task being waited on. However, this still entails some
414	>	* traversal of completer chains, so is less efficient than using
415	>	* CountedCompleters without explicit joins.
416		*
417		* It is impossible to keep exactly the target parallelism number
418		* of threads running at any given time. Determining the
419		* existence of conservatively safe helping targets, the
420		* availability of already-created spares, and the apparent need
421		* to create new spares are all racy, so we rely on multiple
422	<	* retries of each. Currently, in keeping with on-demand
423	<	* signalling policy, we compensate only if blocking would leave
424	<	* less than one active (non-waiting, non-blocked) worker.
425	<	* Additionally, to avoid some false alarms due to GC, lagging
426	<	* counters, system activity, etc, compensated blocking for joins
427	<	* is only attempted after rechecks stabilize in
428	<	* ForkJoinTask.awaitJoin. (Retries are interspersed with
429	<	* Thread.yield, for good citizenship.)
430	<	*
431	<	* Style notes: There is a lot of representation-level coupling
432	<	* among classes ForkJoinPool, ForkJoinWorkerThread, and
433	<	* ForkJoinTask. The fields of WorkQueue maintain data structures
434	<	* managed by ForkJoinPool, so are directly accessed. There is
435	<	* little point trying to reduce this, since any associated future
436	<	* changes in representations will need to be accompanied by
437	<	* algorithmic changes anyway. All together, these low-level
438	<	* implementation choices produce as much as a factor of 4
439	<	* performance improvement compared to naive implementations, and
440	<	* enable the processing of billions of tasks per second, at the
441	<	* expense of some ugliness.
442	<	*
443	<	* Methods signalWork() and scan() are the main bottlenecks so are
444	<	* especially heavily micro-optimized/mangled. There are lots of
445	<	* inline assignments (of form "while ((local = field) != 0)")
446	<	* which are usually the simplest way to ensure the required read
447	<	* orderings (which are sometimes critical). This leads to a
448	<	* "C"-like style of listing declarations of these locals at the
449	<	* heads of methods or blocks. There are several occurrences of
450	<	* the unusual "do {} while (!cas...)" which is the simplest way
451	<	* to force an update of a CAS'ed variable. There are also other
452	<	* coding oddities that help some methods perform reasonably even
453	<	* when interpreted (not compiled).
454	<	*
455	<	* The order of declarations in this file is: (1) declarations of
456	<	* statics (2) fields (along with constants used when unpacking
457	<	* some of them), listed in an order that tends to reduce
458	<	* contention among them a bit under most JVMs; (3) nested
459	<	* classes; (4) internal control methods; (5) callbacks and other
460	<	* support for ForkJoinTask methods; (6) exported methods (plus a
461	<	* few little helpers); (7) static block initializing all statics
462	<	* in a minimally dependent order.
422	>	* retries of each. Compensation in the apparent absence of
423	>	* helping opportunities is challenging to control on JVMs, where
424	>	* GC and other activities can stall progress of tasks that in
425	>	* turn stall out many other dependent tasks, without us being
426	>	* able to determine whether they will ever require compensation.
427	>	* Even though work-stealing otherwise encounters little
428	>	* degradation in the presence of more threads than cores,
429	>	* aggressively adding new threads in such cases entails risk of
430	>	* unwanted positive feedback control loops in which more threads
431	>	* cause more dependent stalls (as well as delayed progress of
432	>	* unblocked threads to the point that we know they are available)
433	>	* leading to more situations requiring more threads, and so
434	>	* on. This aspect of control can be seen as an (analytically
435	>	* intractable) game with an opponent that may choose the worst
436	>	* (for us) active thread to stall at any time. We take several
437	>	* precautions to bound losses (and thus bound gains), mainly in
438	>	* methods tryCompensate and awaitJoin.
439	>	*
440	>	* Common Pool
441	>	* ===========
442	>	*
443	>	* The static commonPool always exists after static
444	>	* initialization. Since it (or any other created pool) need
445	>	* never be used, we minimize initial construction overhead and
446	>	* footprint to the setup of about a dozen fields, with no nested
447	>	* allocation. Most bootstrapping occurs within method
448	>	* fullExternalPush during the first submission to the pool.
449	>	*
450	>	* When external threads submit to the common pool, they can
451	>	* perform some subtask processing (see externalHelpJoin and
452	>	* related methods). We do not need to record whether these
453	>	* submissions are to the common pool -- if not, externalHelpJoin
454	>	* returns quickly (at the most helping to signal some common pool
455	>	* workers). These submitters would otherwise be blocked waiting
456	>	* for completion, so the extra effort (with liberally sprinkled
457	>	* task status checks) in inapplicable cases amounts to an odd
458	>	* form of limited spin-wait before blocking in ForkJoinTask.join.
459	>	*
460	>	* Style notes
461	>	* ===========
462	>	*
463	>	* There is a lot of representation-level coupling among classes
464	>	* ForkJoinPool, ForkJoinWorkerThread, and ForkJoinTask. The
465	>	* fields of WorkQueue maintain data structures managed by
466	>	* ForkJoinPool, so are directly accessed. There is little point
467	>	* trying to reduce this, since any associated future changes in
468	>	* representations will need to be accompanied by algorithmic
469	>	* changes anyway. Several methods intrinsically sprawl because
470	>	* they must accumulate sets of consistent reads of volatiles held
471	>	* in local variables. Methods signalWork() and scan() are the
472	>	* main bottlenecks, so are especially heavily
473	>	* micro-optimized/mangled. There are lots of inline assignments
474	>	* (of form "while ((local = field) != 0)") which are usually the
475	>	* simplest way to ensure the required read orderings (which are
476	>	* sometimes critical). This leads to a "C"-like style of listing
477	>	* declarations of these locals at the heads of methods or blocks.
478	>	* There are several occurrences of the unusual "do {} while
479	>	* (!cas...)" which is the simplest way to force an update of a
480	>	* CAS'ed variable. There are also other coding oddities (including
481	>	* several unnecessary-looking hoisted null checks) that help
482	>	* some methods perform reasonably even when interpreted (not
483	>	* compiled).
484	>	*
485	>	* The order of declarations in this file is:
486	>	* (1) Static utility functions
487	>	* (2) Nested (static) classes
488	>	* (3) Static fields
489	>	* (4) Fields, along with constants used when unpacking some of them
490	>	* (5) Internal control methods
491	>	* (6) Callbacks and other support for ForkJoinTask methods
492	>	* (7) Exported methods
493	>	* (8) Static block initializing statics in minimally dependent order
494		*/
495
496	+	// Static utilities
497	+
498	+	/**
499	+	* If there is a security manager, makes sure caller has
500	+	* permission to modify threads.
501	+	*/
502	+	private static void checkPermission() {
503	+	SecurityManager security = System.getSecurityManager();
504	+	if (security != null)
505	+	security.checkPermission(modifyThreadPermission);
506	+	}
507	+
508	+	// Nested classes
509	+
510		/**
511		* Factory for creating new {@link ForkJoinWorkerThread}s.
512		* A {@code ForkJoinWorkerThreadFactory} must be defined and used
#	Line 465 \| Line 527 \| public class ForkJoinPool extends Abstra
527		* Default ForkJoinWorkerThreadFactory implementation; creates a
528		* new ForkJoinWorkerThread.
529		*/
530	<	static class DefaultForkJoinWorkerThreadFactory
530	>	static final class DefaultForkJoinWorkerThreadFactory
531		implements ForkJoinWorkerThreadFactory {
532	<	public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
532	>	public final ForkJoinWorkerThread newThread(ForkJoinPool pool) {
533		return new ForkJoinWorkerThread(pool);
534		}
535		}
536
537		/**
538	<	* Creates a new ForkJoinWorkerThread. This factory is used unless
539	<	* overridden in ForkJoinPool constructors.
540	<	*/
541	<	public static final ForkJoinWorkerThreadFactory
542	<	defaultForkJoinWorkerThreadFactory;
543	<
544	<	/**
545	<	* Permission required for callers of methods that may start or
546	<	* kill threads.
547	<	*/
548	<	private static final RuntimePermission modifyThreadPermission;
549	<
550	<	/**
551	<	* If there is a security manager, makes sure caller has
552	<	* permission to modify threads.
553	<	*/
554	<	private static void checkPermission() {
493	<	SecurityManager security = System.getSecurityManager();
494	<	if (security != null)
495	<	security.checkPermission(modifyThreadPermission);
538	>	* Per-thread records for threads that submit to pools. Currently
539	>	* holds only pseudo-random seed / index that is used to choose
540	>	* submission queues in method externalPush. In the future, this may
541	>	* also incorporate a means to implement different task rejection
542	>	* and resubmission policies.
543	>	*
544	>	* Seeds for submitters and workers/workQueues work in basically
545	>	* the same way but are initialized and updated using slightly
546	>	* different mechanics. Both are initialized using the same
547	>	* approach as in class ThreadLocal, where successive values are
548	>	* unlikely to collide with previous values. Seeds are then
549	>	* randomly modified upon collisions using xorshifts, which
550	>	* requires a non-zero seed.
551	>	*/
552	>	static final class Submitter {
553	>	int seed;
554	>	Submitter(int s) { seed = s; }
555		}
556
557		/**
558	<	* Generator for assigning sequence numbers as pool names.
559	<	*/
560	<	private static final AtomicInteger poolNumberGenerator;
561	<
503	<	/**
504	<	* Bits and masks for control variables
505	<	*
506	<	* Field ctl is a long packed with:
507	<	* AC: Number of active running workers minus target parallelism (16 bits)
508	<	* TC: Number of total workers minus target parallelism (16 bits)
509	<	* ST: true if pool is terminating (1 bit)
510	<	* EC: the wait count of top waiting thread (15 bits)
511	<	* ID: ~(poolIndex >>> 1) of top of Treiber stack of waiters (16 bits)
512	<	*
513	<	* When convenient, we can extract the upper 32 bits of counts and
514	<	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
515	<	* (int)ctl. The ec field is never accessed alone, but always
516	<	* together with id and st. The offsets of counts by the target
517	<	* parallelism and the positionings of fields makes it possible to
518	<	* perform the most common checks via sign tests of fields: When
519	<	* ac is negative, there are not enough active workers, when tc is
520	<	* negative, there are not enough total workers, when id is
521	<	* negative, there is at least one waiting worker, and when e is
522	<	* negative, the pool is terminating. To deal with these possibly
523	<	* negative fields, we use casts in and out of "short" and/or
524	<	* signed shifts to maintain signedness.
525	<	*
526	<	* When a thread is queued (inactivated), its eventCount field is
527	<	* negative, which is the only way to tell if a worker is
528	<	* prevented from executing tasks, even though it must continue to
529	<	* scan for them to avoid queuing races.
530	<	*
531	<	* Field runState is an int packed with:
532	<	* SHUTDOWN: true if shutdown is enabled (1 bit)
533	<	* SEQ: a sequence number updated upon (de)registering workers (15 bits)
534	<	* MASK: mask (power of 2 - 1) covering all registered poolIndexes (16 bits)
535	<	*
536	<	* The combination of mask and sequence number enables simple
537	<	* consistency checks: Staleness of read-only operations on the
538	<	* workers and queues arrays can be checked by comparing runState
539	<	* before vs after the reads. The low 16 bits (i.e, anding with
540	<	* SMASK) hold (the smallest power of two covering all worker
541	<	* indices, minus one. The mask for queues (vs workers) is twice
542	<	* this value plus 1.
543	<	*/
544	<
545	<	// bit positions/shifts for fields
546	<	private static final int AC_SHIFT = 48;
547	<	private static final int TC_SHIFT = 32;
548	<	private static final int ST_SHIFT = 31;
549	<	private static final int EC_SHIFT = 16;
550	<
551	<	// bounds
552	<	private static final int MAX_ID = 0x7fff; // max poolIndex
553	<	private static final int SMASK = 0xffff; // mask short bits
554	<	private static final int SHORT_SIGN = 1 << 15;
555	<	private static final int INT_SIGN = 1 << 31;
556	<
557	<	// masks
558	<	private static final long STOP_BIT = 0x0001L << ST_SHIFT;
559	<	private static final long AC_MASK = ((long)SMASK) << AC_SHIFT;
560	<	private static final long TC_MASK = ((long)SMASK) << TC_SHIFT;
561	<
562	<	// units for incrementing and decrementing
563	<	private static final long TC_UNIT = 1L << TC_SHIFT;
564	<	private static final long AC_UNIT = 1L << AC_SHIFT;
565	<
566	<	// masks and units for dealing with u = (int)(ctl >>> 32)
567	<	private static final int UAC_SHIFT = AC_SHIFT - 32;
568	<	private static final int UTC_SHIFT = TC_SHIFT - 32;
569	<	private static final int UAC_MASK = SMASK << UAC_SHIFT;
570	<	private static final int UTC_MASK = SMASK << UTC_SHIFT;
571	<	private static final int UAC_UNIT = 1 << UAC_SHIFT;
572	<	private static final int UTC_UNIT = 1 << UTC_SHIFT;
573	<
574	<	// masks and units for dealing with e = (int)ctl
575	<	private static final int E_MASK = 0x7fffffff; // no STOP_BIT
576	<	private static final int E_SEQ = 1 << EC_SHIFT;
577	<
578	<	// runState bits
579	<	private static final int SHUTDOWN = 1 << 31;
580	<	private static final int RS_SEQ = 1 << 16;
581	<	private static final int RS_SEQ_MASK = 0x7fff0000;
582	<
583	<	// access mode for WorkQueue
584	<	static final int LIFO_QUEUE = 0;
585	<	static final int FIFO_QUEUE = 1;
586	<	static final int SHARED_QUEUE = -1;
587	<
588	<	/**
589	<	* The wakeup interval (in nanoseconds) for a worker waiting for a
590	<	* task when the pool is quiescent to instead try to shrink the
591	<	* number of workers. The exact value does not matter too
592	<	* much. It must be short enough to release resources during
593	<	* sustained periods of idleness, but not so short that threads
594	<	* are continually re-created.
595	<	*/
596	<	private static final long SHRINK_RATE =
597	<	4L * 1000L * 1000L * 1000L; // 4 seconds
598	<
599	<	/**
600	<	* The timeout value for attempted shrinkage, includes
601	<	* some slop to cope with system timer imprecision.
602	<	*/
603	<	private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
604	<
605	<	/**
606	<	* The maximum stolen->joining link depth allowed in tryHelpStealer.
607	<	* Depths for legitimate chains are unbounded, but we use a fixed
608	<	* constant to avoid (otherwise unchecked) cycles and to bound
609	<	* staleness of traversal parameters at the expense of sometimes
610	<	* blocking when we could be helping.
611	<	*/
612	<	private static final int MAX_HELP_DEPTH = 16;
613	<
614	<	/*
615	<	* Field layout order in this class tends to matter more than one
616	<	* would like. Runtime layout order is only loosely related to
617	<	* declaration order and may differ across JVMs, but the following
618	<	* empirically works OK on current JVMs.
558	>	* Class for artificial tasks that are used to replace the target
559	>	* of local joins if they are removed from an interior queue slot
560	>	* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
561	>	* actually do anything beyond having a unique identity.
562		*/
563	<
564	<	volatile long ctl; // main pool control
565	<	final int parallelism; // parallelism level
566	<	final int localMode; // per-worker scheduling mode
567	<	int nextPoolIndex; // hint used in registerWorker
568	<	volatile int runState; // shutdown status, seq, and mask
569	<	WorkQueue[] workQueues; // main registry
627	<	final ReentrantLock lock; // for registration
628	<	final Condition termination; // for awaitTermination
629	<	final ForkJoinWorkerThreadFactory factory; // factory for new workers
630	<	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
631	<	final AtomicLong stealCount; // collect counts when terminated
632	<	final AtomicInteger nextWorkerNumber; // to create worker name string
633	<	final String workerNamePrefix; // Prefix for assigning worker names
563	>	static final class EmptyTask extends ForkJoinTask<Void> {
564	>	private static final long serialVersionUID = -7721805057305804111L;
565	>	EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
566	>	public final Void getRawResult() { return null; }
567	>	public final void setRawResult(Void x) {}
568	>	public final boolean exec() { return true; }
569	>	}
570
571		/**
572		* Queues supporting work-stealing as well as external task
#	Line 646 \| Line 582 \| public class ForkJoinPool extends Abstra
582		*
583		* Field "top" is the index (mod array.length) of the next queue
584		* slot to push to or pop from. It is written only by owner thread
585	<	* for push, or under lock for trySharedPush, and accessed by
586	<	* other threads only after reading (volatile) base. Both top and
587	<	* base are allowed to wrap around on overflow, but (top - base)
588	<	* (or more comonly -(base - top) to force volatile read of base
589	<	* before top) still estimates size.
585	>	* for push, or under lock for external/shared push, and accessed
586	>	* by other threads only after reading (volatile) base. Both top
587	>	* and base are allowed to wrap around on overflow, but (top -
588	>	* base) (or more commonly -(base - top) to force volatile read of
589	>	* base before top) still estimates size. The lock ("qlock") is
590	>	* forced to -1 on termination, causing all further lock attempts
591	>	* to fail. (Note: we don't need CAS for termination state because
592	>	* upon pool shutdown, all shared-queues will stop being used
593	>	* anyway.) Nearly all lock bodies are set up so that exceptions
594	>	* within lock bodies are "impossible" (modulo JVM errors that
595	>	* would cause failure anyway.)
596		*
597		* The array slots are read and written using the emulation of
598		* volatiles/atomics provided by Unsafe. Insertions must in
599		* general use putOrderedObject as a form of releasing store to
600		* ensure that all writes to the task object are ordered before
601	<	* its publication in the queue. (Although we can avoid one case
602	<	* of this when locked in trySharedPush.) All removals entail a
603	<	* CAS to null. The array is always a power of two. To ensure
604	<	* safety of Unsafe array operations, all accesses perform
663	<	* explicit null checks and implicit bounds checks via
664	<	* power-of-two masking.
601	>	* its publication in the queue. All removals entail a CAS to
602	>	* null. The array is always a power of two. To ensure safety of
603	>	* Unsafe array operations, all accesses perform explicit null
604	>	* checks and implicit bounds checks via power-of-two masking.
605		*
606		* In addition to basic queuing support, this class contains
607		* fields described elsewhere to control execution. It turns out
608	<	* to work better memory-layout-wise to include them in this
609	<	* class rather than a separate class.
608	>	* to work better memory-layout-wise to include them in this class
609	>	* rather than a separate class.
610		*
611		* Performance on most platforms is very sensitive to placement of
612		* instances of both WorkQueues and their arrays -- we absolutely
#	Line 680 \| Line 620 \| public class ForkJoinPool extends Abstra
620		* trades off slightly slower average field access for the sake of
621		* avoiding really bad worst-case access. (Until better JVM
622		* support is in place, this padding is dependent on transient
623	<	* properties of JVM field layout rules.) We also take care in
624	<	* allocating and sizing and resizing the array. Non-shared queue
625	<	* arrays are initialized (via method growArray) by workers before
626	<	* use. Others are allocated on first use.
623	>	* properties of JVM field layout rules.) We also take care in
624	>	* allocating, sizing and resizing the array. Non-shared queue
625	>	* arrays are initialized by workers before use. Others are
626	>	* allocated on first use.
627		*/
628		static final class WorkQueue {
629		/**
630		* Capacity of work-stealing queue array upon initialization.
631	<	* Must be a power of two; at least 4, but set larger to
632	<	* reduce cacheline sharing among queues.
631	>	* Must be a power of two; at least 4, but should be larger to
632	>	* reduce or eliminate cacheline sharing among queues.
633	>	* Currently, it is much larger, as a partial workaround for
634	>	* the fact that JVMs often place arrays in locations that
635	>	* share GC bookkeeping (especially cardmarks) such that
636	>	* per-write accesses encounter serious memory contention.
637		*/
638	<	static final int INITIAL_QUEUE_CAPACITY = 1 << 8;
638	>	static final int INITIAL_QUEUE_CAPACITY = 1 << 13;
639
640		/**
641		* Maximum size for queue arrays. Must be a power of two less
#	Line 702 \| Line 646 \| public class ForkJoinPool extends Abstra
646		*/
647		static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
648
649	<	volatile long totalSteals; // cumulative number of steals
649	>	// Heuristic padding to ameliorate unfortunate memory placements
650	>	volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
651	>
652		int seed; // for random scanning; initialize nonzero
653		volatile int eventCount; // encoded inactivation count; < 0 if inactive
654		int nextWait; // encoded record of next event waiter
655	<	int rescans; // remaining scans until block
710	<	int nsteals; // top-level task executions since last idle
711	<	final int mode; // lifo, fifo, or shared
655	>	int hint; // steal or signal hint (index)
656		int poolIndex; // index of this queue in pool (or 0)
657	<	int stealHint; // index of most recent known stealer
658	<	volatile int runState; // 1: locked, -1: terminate; else 0
657	>	final int mode; // 0: lifo, > 0: fifo, < 0: shared
658	>	int nsteals; // number of steals
659	>	volatile int qlock; // 1: locked, -1: terminate; else 0
660		volatile int base; // index of next slot for poll
661		int top; // index of next slot for push
662		ForkJoinTask<?>[] array; // the elements (initially unallocated)
663	+	final ForkJoinPool pool; // the containing pool (may be null)
664		final ForkJoinWorkerThread owner; // owning thread or null if shared
665		volatile Thread parker; // == owner during call to park; else null
666	<	ForkJoinTask<?> currentJoin; // task being joined in awaitJoin
666	>	volatile ForkJoinTask<?> currentJoin; // task being joined in awaitJoin
667		ForkJoinTask<?> currentSteal; // current non-local task being executed
722	–	// Heuristic padding to ameliorate unfortunate memory placements
723	–	Object p00, p01, p02, p03, p04, p05, p06, p07, p08, p09, p0a;
668
669	<	WorkQueue(ForkJoinWorkerThread owner, int mode) {
669	>	volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
670	>	volatile Object pad18, pad19, pad1a, pad1b, pad1c, pad1d;
671	>
672	>	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode,
673	>	int seed) {
674	>	this.pool = pool;
675		this.owner = owner;
676		this.mode = mode;
677	+	this.seed = seed;
678		// Place indices in the center of array (that is not yet allocated)
679		base = top = INITIAL_QUEUE_CAPACITY >>> 1;
680		}
681
682		/**
683	<	* Returns number of tasks in the queue
683	>	* Returns the approximate number of tasks in the queue.
684		*/
685		final int queueSize() {
686	<	int n = base - top; // non-owner callers must read base first
687	<	return (n >= 0) ? 0 : -n;
686	>	int n = base - top; // non-owner callers must read base first
687	>	return (n >= 0) ? 0 : -n; // ignore transient negative
688	>	}
689	>
690	>	/**
691	>	* Provides a more accurate estimate of whether this queue has
692	>	* any tasks than does queueSize, by checking whether a
693	>	* near-empty queue has at least one unclaimed task.
694	>	*/
695	>	final boolean isEmpty() {
696	>	ForkJoinTask<?>[] a; int m, s;
697	>	int n = base - (s = top);
698	>	return (n >= 0 \|\|
699	>	(n == -1 &&
700	>	((a = array) == null \|\|
701	>	(m = a.length - 1) < 0 \|\|
702	>	U.getObject
703	>	(a, (long)((m & (s - 1)) << ASHIFT) + ABASE) == null)));
704		}
705
706		/**
707	<	* Pushes a task. Call only by owner in unshared queues.
707	>	* Pushes a task. Call only by owner in unshared queues. (The
708	>	* shared-queue version is embedded in method externalPush.)
709		*
710		* @param task the task. Caller must ensure non-null.
711	<	* @param p, if non-null, pool to signal if necessary
745	<	* @throw RejectedExecutionException if array cannot
746	<	* be resized
711	>	* @throw RejectedExecutionException if array cannot be resized
712		*/
713	<	final void push(ForkJoinTask<?> task, ForkJoinPool p) {
714	<	ForkJoinTask<?>[] a;
713	>	final void push(ForkJoinTask<?> task) {
714	>	ForkJoinTask<?>[] a; ForkJoinPool p;
715		int s = top, m, n;
716		if ((a = array) != null) { // ignore if queue removed
717	<	U.putOrderedObject
718	<	(a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task);
717	>	int j = (((m = a.length - 1) & s) << ASHIFT) + ABASE;
718	>	U.putOrderedObject(a, j, task);
719		if ((n = (top = s + 1) - base) <= 2) {
720	<	if (p != null)
721	<	p.signalWork();
720	>	if ((p = pool) != null)
721	>	p.signalWork(this);
722		}
723		else if (n >= m)
724	<	growArray(true);
724	>	growArray();
725	>	}
726	>	}
727	>
728	>	/**
729	>	* Initializes or doubles the capacity of array. Call either
730	>	* by owner or with lock held -- it is OK for base, but not
731	>	* top, to move while resizings are in progress.
732	>	*/
733	>	final ForkJoinTask<?>[] growArray() {
734	>	ForkJoinTask<?>[] oldA = array;
735	>	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
736	>	if (size > MAXIMUM_QUEUE_CAPACITY)
737	>	throw new RejectedExecutionException("Queue capacity exceeded");
738	>	int oldMask, t, b;
739	>	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
740	>	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
741	>	(t = top) - (b = base) > 0) {
742	>	int mask = size - 1;
743	>	do {
744	>	ForkJoinTask<?> x;
745	>	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
746	>	int j = ((b & mask) << ASHIFT) + ABASE;
747	>	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
748	>	if (x != null &&
749	>	U.compareAndSwapObject(oldA, oldj, x, null))
750	>	U.putObjectVolatile(a, j, x);
751	>	} while (++b != t);
752		}
753	+	return a;
754		}
755
756		/**
757	<	* Pushes a task if lock is free and array is either big
758	<	* enough or can be resized to be big enough.
766	<	*
767	<	* @param task the task. Caller must ensure non-null.
768	<	* @return true if submitted
757	>	* Takes next task, if one exists, in LIFO order. Call only
758	>	* by owner in unshared queues.
759		*/
760	<	final boolean trySharedPush(ForkJoinTask<?> task) {
761	<	boolean submitted = false;
762	<	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
763	<	ForkJoinTask<?>[] a = array;
764	<	int s = top, n = s - base;
765	<	try {
766	<	if ((a != null && n < a.length - 1) \|\|
767	<	(a = growArray(false)) != null) { // must presize
768	<	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
769	<	U.putObject(a, (long)j, task); // don't need "ordered"
780	<	top = s + 1;
781	<	submitted = true;
760	>	final ForkJoinTask<?> pop() {
761	>	ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
762	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
763	>	for (int s; (s = top - 1) - base >= 0;) {
764	>	long j = ((m & s) << ASHIFT) + ABASE;
765	>	if ((t = (ForkJoinTask<?>)U.getObject(a, j)) == null)
766	>	break;
767	>	if (U.compareAndSwapObject(a, j, t, null)) {
768	>	top = s;
769	>	return t;
770		}
783	–	} finally {
784	–	runState = 0; // unlock
771		}
772		}
773	<	return submitted;
773	>	return null;
774		}
775
776		/**
777	<	* Takes next task, if one exists, in FIFO order.
777	>	* Takes a task in FIFO order if b is base of queue and a task
778	>	* can be claimed without contention. Specialized versions
779	>	* appear in ForkJoinPool methods scan and tryHelpStealer.
780		*/
781	<	final ForkJoinTask<?> poll() {
782	<	ForkJoinTask<?>[] a; int b, i;
783	<	while ((b = base) - top < 0 && (a = array) != null &&
784	<	(i = (a.length - 1) & b) >= 0) {
785	<	int j = (i << ASHIFT) + ABASE;
786	<	ForkJoinTask<?> t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
799	<	if (t != null && base == b &&
781	>	final ForkJoinTask<?> pollAt(int b) {
782	>	ForkJoinTask<?> t; ForkJoinTask<?>[] a;
783	>	if ((a = array) != null) {
784	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
785	>	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
786	>	base == b &&
787		U.compareAndSwapObject(a, j, t, null)) {
788		base = b + 1;
789		return t;
#	Line 806 \| Line 793 \| public class ForkJoinPool extends Abstra
793		}
794
795		/**
796	<	* Takes next task, if one exists, in LIFO order.
810	<	* Call only by owner in unshared queues.
796	>	* Takes next task, if one exists, in FIFO order.
797		*/
798	<	final ForkJoinTask<?> pop() {
799	<	ForkJoinTask<?> t; int m;
800	<	ForkJoinTask<?>[] a = array;
801	<	if (a != null && (m = a.length - 1) >= 0) {
802	<	for (int s; (s = top - 1) - base >= 0;) {
803	<	int j = ((m & s) << ASHIFT) + ABASE;
804	<	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) == null)
805	<	break;
806	<	if (U.compareAndSwapObject(a, j, t, null)) {
821	<	top = s;
798	>	final ForkJoinTask<?> poll() {
799	>	ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t;
800	>	while ((b = base) - top < 0 && (a = array) != null) {
801	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
802	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
803	>	if (t != null) {
804	>	if (base == b &&
805	>	U.compareAndSwapObject(a, j, t, null)) {
806	>	base = b + 1;
807		return t;
808		}
809		}
810	+	else if (base == b) {
811	+	if (b + 1 == top)
812	+	break;
813	+	Thread.yield(); // wait for lagging update (very rare)
814	+	}
815		}
816		return null;
817		}
#	Line 846 \| Line 836 \| public class ForkJoinPool extends Abstra
836		}
837
838		/**
849	–	* Returns task at index b if b is current base of queue.
850	–	*/
851	–	final ForkJoinTask<?> pollAt(int b) {
852	–	ForkJoinTask<?>[] a; int i;
853	–	ForkJoinTask<?> task = null;
854	–	if ((a = array) != null && (i = ((a.length - 1) & b)) >= 0) {
855	–	int j = (i << ASHIFT) + ABASE;
856	–	ForkJoinTask<?> t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
857	–	if (t != null && base == b &&
858	–	U.compareAndSwapObject(a, j, t, null)) {
859	–	base = b + 1;
860	–	task = t;
861	–	}
862	–	}
863	–	return task;
864	–	}
865	–
866	–	/**
839		* Pops the given task only if it is at the current top.
840	+	* (A shared version is available only via FJP.tryExternalUnpush)
841		*/
842		final boolean tryUnpush(ForkJoinTask<?> t) {
843		ForkJoinTask<?>[] a; int s;
#	Line 878 \| Line 851 \| public class ForkJoinPool extends Abstra
851		}
852
853		/**
854	<	* Polls the given task only if it is at the current base.
854	>	* Removes and cancels all known tasks, ignoring any exceptions.
855		*/
856	<	final boolean pollFor(ForkJoinTask<?> task) {
857	<	ForkJoinTask<?>[] a; int b, i;
858	<	if ((b = base) - top < 0 && (a = array) != null &&
859	<	(i = (a.length - 1) & b) >= 0) {
860	<	int j = (i << ASHIFT) + ABASE;
861	<	if (U.getObjectVolatile(a, j) == task && base == b &&
862	<	U.compareAndSwapObject(a, j, task, null)) {
863	<	base = b + 1;
864	<	return true;
856	>	final void cancelAll() {
857	>	ForkJoinTask.cancelIgnoringExceptions(currentJoin);
858	>	ForkJoinTask.cancelIgnoringExceptions(currentSteal);
859	>	for (ForkJoinTask<?> t; (t = poll()) != null; )
860	>	ForkJoinTask.cancelIgnoringExceptions(t);
861	>	}
862	>
863	>	/**
864	>	* Computes next value for random probes. Scans don't require
865	>	* a very high quality generator, but also not a crummy one.
866	>	* Marsaglia xor-shift is cheap and works well enough. Note:
867	>	* This is manually inlined in its usages in ForkJoinPool to
868	>	* avoid writes inside busy scan loops.
869	>	*/
870	>	final int nextSeed() {
871	>	int r = seed;
872	>	r ^= r << 13;
873	>	r ^= r >>> 17;
874	>	return seed = r ^= r << 5;
875	>	}
876	>
877	>	// Specialized execution methods
878	>
879	>	/**
880	>	* Pops and runs tasks until empty.
881	>	*/
882	>	private void popAndExecAll() {
883	>	// A bit faster than repeated pop calls
884	>	ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t;
885	>	while ((a = array) != null && (m = a.length - 1) >= 0 &&
886	>	(s = top - 1) - base >= 0 &&
887	>	(t = ((ForkJoinTask<?>)
888	>	U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
889	>	!= null) {
890	>	if (U.compareAndSwapObject(a, j, t, null)) {
891	>	top = s;
892	>	t.doExec();
893		}
894		}
894	–	return false;
895		}
896
897		/**
898	<	* If present, removes from queue and executes the given task, or
899	<	* any other cancelled task. Returns (true) immediately on any CAS
898	>	* Polls and runs tasks until empty.
899	>	*/
900	>	private void pollAndExecAll() {
901	>	for (ForkJoinTask<?> t; (t = poll()) != null;)
902	>	t.doExec();
903	>	}
904	>
905	>	/**
906	>	* If present, removes from queue and executes the given task,
907	>	* or any other cancelled task. Returns (true) on any CAS
908		* or consistency check failure so caller can retry.
909		*
910	<	* @return false if no progress can be made
910	>	* @return false if no progress can be made, else true;
911		*/
912		final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
913	<	boolean removed = false, empty = true, progress = true;
913	>	boolean stat = true, removed = false, empty = true;
914		ForkJoinTask<?>[] a; int m, s, b, n;
915		if ((a = array) != null && (m = a.length - 1) >= 0 &&
916		(n = (s = top) - (b = base)) > 0) {
#	Line 932 \| Line 940 \| public class ForkJoinPool extends Abstra
940		}
941		if (--n == 0) {
942		if (!empty && base == b)
943	<	progress = false;
943	>	stat = false;
944		break;
945		}
946		}
947		}
948		if (removed)
949		task.doExec();
950	<	return progress;
950	>	return stat;
951		}
952
953		/**
954	<	* Initializes or doubles the capacity of array. Call either
955	<	* by owner or with lock held -- it is OK for base, but not
948	<	* top, to move while resizings are in progress.
949	<	*
950	<	* @param rejectOnFailure if true, throw exception if capacity
951	<	* exceeded (relayed ultimately to user); else return null.
954	>	* Polls for and executes the given task or any other task in
955	>	* its CountedCompleter computation
956		*/
957	<	final ForkJoinTask<?>[] growArray(boolean rejectOnFailure) {
958	<	ForkJoinTask<?>[] oldA = array;
959	<	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
960	<	if (size <= MAXIMUM_QUEUE_CAPACITY) {
961	<	int oldMask, t, b;
962	<	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
963	<	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
964	<	(t = top) - (b = base) > 0) {
965	<	int mask = size - 1;
966	<	do {
967	<	ForkJoinTask<?> x;
968	<	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
969	<	int j = ((b & mask) << ASHIFT) + ABASE;
970	<	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
971	<	if (x != null &&
972	<	U.compareAndSwapObject(oldA, oldj, x, null))
973	<	U.putObjectVolatile(a, j, x);
974	<	} while (++b != t);
957	>	final boolean pollAndExecCC(ForkJoinTask<?> root) {
958	>	ForkJoinTask<?>[] a; int b; Object o;
959	>	outer: while ((b = base) - top < 0 && (a = array) != null) {
960	>	long j = (((a.length - 1) & b) << ASHIFT) + ABASE;
961	>	if ((o = U.getObject(a, j)) == null \|\|
962	>	!(o instanceof CountedCompleter))
963	>	break;
964	>	for (CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;;) {
965	>	if (r == root) {
966	>	if (base == b &&
967	>	U.compareAndSwapObject(a, j, t, null)) {
968	>	base = b + 1;
969	>	t.doExec();
970	>	return true;
971	>	}
972	>	else
973	>	break; // restart
974	>	}
975	>	if ((r = r.completer) == null)
976	>	break outer; // not part of root computation
977		}
972	–	return a;
973	–	}
974	–	else if (!rejectOnFailure)
975	–	return null;
976	–	else
977	–	throw new RejectedExecutionException("Queue capacity exceeded");
978	–	}
979	–
980	–	/**
981	–	* Removes and cancels all known tasks, ignoring any exceptions
982	–	*/
983	–	final void cancelAll() {
984	–	ForkJoinTask.cancelIgnoringExceptions(currentJoin);
985	–	ForkJoinTask.cancelIgnoringExceptions(currentSteal);
986	–	for (ForkJoinTask<?> t; (t = poll()) != null; )
987	–	ForkJoinTask.cancelIgnoringExceptions(t);
988	–	}
989	–
990	–	// Execution methods
991	–
992	–	/**
993	–	* Removes and runs tasks until empty, using local mode
994	–	* ordering.
995	–	*/
996	–	final void runLocalTasks() {
997	–	if (base - top < 0) {
998	–	for (ForkJoinTask<?> t; (t = nextLocalTask()) != null; )
999	–	t.doExec();
978		}
979	+	return false;
980		}
981
982		/**
983		* Executes a top-level task and any local tasks remaining
984		* after execution.
1006	–	*
1007	–	* @return true unless terminating
985		*/
986	<	final boolean runTask(ForkJoinTask<?> t) {
1010	<	boolean alive = true;
986	>	final void runTask(ForkJoinTask<?> t) {
987		if (t != null) {
988	<	currentSteal = t;
1013	<	t.doExec();
1014	<	runLocalTasks();
1015	<	++nsteals;
988	>	(currentSteal = t).doExec();
989		currentSteal = null;
990	+	if (base - top < 0) { // process remaining local tasks
991	+	if (mode == 0)
992	+	popAndExecAll();
993	+	else
994	+	pollAndExecAll();
995	+	}
996	+	++nsteals;
997	+	hint = -1;
998		}
1018	–	else if (runState < 0) // terminating
1019	–	alive = false;
1020	–	return alive;
999		}
1000
1001		/**
1002	<	* Executes a non-top-level (stolen) task
1002	>	* Executes a non-top-level (stolen) task.
1003		*/
1004		final void runSubtask(ForkJoinTask<?> t) {
1005		if (t != null) {
1006		ForkJoinTask<?> ps = currentSteal;
1007	<	currentSteal = t;
1030	<	t.doExec();
1007	>	(currentSteal = t).doExec();
1008		currentSteal = ps;
1009		}
1010		}
1011
1012		/**
1013	<	* 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.
1013	>	* Returns true if owned and not known to be blocked.
1014		*/
1015	<	final int nextSeed() {
1016	<	int r = seed;
1017	<	r ^= r << 13;
1018	<	r ^= r >>> 17;
1019	<	r ^= r << 5;
1020	<	return seed = r;
1015	>	final boolean isApparentlyUnblocked() {
1016	>	Thread wt; Thread.State s;
1017	>	return (eventCount >= 0 &&
1018	>	(wt = owner) != null &&
1019	>	(s = wt.getState()) != Thread.State.BLOCKED &&
1020	>	s != Thread.State.WAITING &&
1021	>	s != Thread.State.TIMED_WAITING);
1022	>	}
1023	>
1024	>	/**
1025	>	* If this owned and is not already interrupted, try to
1026	>	* interrupt and/or unpark, ignoring exceptions.
1027	>	*/
1028	>	final void interruptOwner() {
1029	>	Thread wt, p;
1030	>	if ((wt = owner) != null && !wt.isInterrupted()) {
1031	>	try {
1032	>	wt.interrupt();
1033	>	} catch (SecurityException ignore) {
1034	>	}
1035	>	}
1036	>	if ((p = parker) != null)
1037	>	U.unpark(p);
1038		}
1039
1040		// Unsafe mechanics
1041		private static final sun.misc.Unsafe U;
1042	<	private static final long RUNSTATE;
1042	>	private static final long QLOCK;
1043		private static final int ABASE;
1044		private static final int ASHIFT;
1045		static {
#	Line 1058 \| Line 1048 \| public class ForkJoinPool extends Abstra
1048		U = getUnsafe();
1049		Class<?> k = WorkQueue.class;
1050		Class<?> ak = ForkJoinTask[].class;
1051	<	RUNSTATE = U.objectFieldOffset
1052	<	(k.getDeclaredField("runState"));
1051	>	QLOCK = U.objectFieldOffset
1052	>	(k.getDeclaredField("qlock"));
1053		ABASE = U.arrayBaseOffset(ak);
1054		s = U.arrayIndexScale(ak);
1055		} catch (Exception e) {
#	Line 1071 \| Line 1061 \| public class ForkJoinPool extends Abstra
1061		}
1062		}
1063
1064	+	// static fields (initialized in static initializer below)
1065	+
1066		/**
1067	<	* Class for artificial tasks that are used to replace the target
1068	<	* 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.
1067	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
1068	>	* overridden in ForkJoinPool constructors.
1069		*/
1070	<	static final class EmptyTask extends ForkJoinTask<Void> {
1071	<	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	<	}
1070	>	public static final ForkJoinWorkerThreadFactory
1071	>	defaultForkJoinWorkerThreadFactory;
1072
1073		/**
1074	<	* Computes a hash code for the given thread. This method is
1075	<	* expected to provide higher-quality hash codes than those using
1076	<	* method hashCode().
1074	>	* Per-thread submission bookkeeping. Shared across all pools
1075	>	* to reduce ThreadLocal pollution and because random motion
1076	>	* to avoid contention in one pool is likely to hold for others.
1077	>	* Lazily initialized on first submission (but null-checked
1078	>	* in other contexts to avoid unnecessary initialization).
1079		*/
1080	<	static final int hashThread(Thread t) {
1081	<	long id = (t == null)? 0L : t.getId(); // Use MurmurHash of thread id
1082	<	int h = (int)id ^ (int)(id >>> 32);
1083	<	h ^= h >>> 16;
1084	<	h *= 0x85ebca6b;
1085	<	h ^= h >>> 13;
1086	<	h *= 0xc2b2ae35;
1087	<	return h ^ (h >>> 16);
1088	<	}
1080	>	static final ThreadLocal<Submitter> submitters;
1081	>
1082	>	/**
1083	>	* Permission required for callers of methods that may start or
1084	>	* kill threads.
1085	>	*/
1086	>	private static final RuntimePermission modifyThreadPermission;
1087	>
1088	>	/**
1089	>	* Common (static) pool. Non-null for public use unless a static
1090	>	* construction exception, but internal usages null-check on use
1091	>	* to paranoically avoid potential initialization circularities
1092	>	* as well as to simplify generated code.
1093	>	*/
1094	>	static final ForkJoinPool commonPool;
1095	>
1096	>	/**
1097	>	* Common pool parallelism. Must equal commonPool.parallelism.
1098	>	*/
1099	>	static final int commonPoolParallelism;
1100
1101		/**
1102	<	* Top-level runloop for workers
1102	>	* Sequence number for creating workerNamePrefix.
1103		*/
1104	<	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
1104	>	private static int poolNumberSequence;
1105
1106	<	do {} while (w.runTask(scan(w)));
1106	>	/**
1107	>	* Return the next sequence number. We don't expect this to
1108	>	* ever contend so use simple builtin sync.
1109	>	*/
1110	>	private static final synchronized int nextPoolId() {
1111	>	return ++poolNumberSequence;
1112		}
1113
1114	<	// Creating, registering and deregistering workers
1114	>	// static constants
1115
1116		/**
1117	<	* Tries to create and start a worker
1117	>	* Initial timeout value (in nanoseconds) for the thread
1118	>	* triggering quiescence to park waiting for new work. On timeout,
1119	>	* the thread will instead try to shrink the number of
1120	>	* workers. The value should be large enough to avoid overly
1121	>	* aggressive shrinkage during most transient stalls (long GCs
1122	>	* etc).
1123		*/
1124	<	private void addWorker() {
1125	<	Throwable ex = null;
1126	<	ForkJoinWorkerThread w = null;
1127	<	try {
1128	<	if ((w = factory.newThread(this)) != null) {
1129	<	w.start();
1130	<	return;
1124	>	private static final long IDLE_TIMEOUT = 2000L * 1000L * 1000L; // 2sec
1125	>
1126	>	/**
1127	>	* Timeout value when there are more threads than parallelism level
1128	>	*/
1129	>	private static final long FAST_IDLE_TIMEOUT = 200L * 1000L * 1000L;
1130	>
1131	>	/**
1132	>	* Tolerance for idle timeouts, to cope with timer undershoots
1133	>	*/
1134	>	private static final long TIMEOUT_SLOP = 2000000L; // 20ms
1135	>
1136	>	/**
1137	>	* The maximum stolen->joining link depth allowed in method
1138	>	* tryHelpStealer. Must be a power of two. Depths for legitimate
1139	>	* chains are unbounded, but we use a fixed constant to avoid
1140	>	* (otherwise unchecked) cycles and to bound staleness of
1141	>	* traversal parameters at the expense of sometimes blocking when
1142	>	* we could be helping.
1143	>	*/
1144	>	private static final int MAX_HELP = 64;
1145	>
1146	>	/**
1147	>	* Increment for seed generators. See class ThreadLocal for
1148	>	* explanation.
1149	>	*/
1150	>	private static final int SEED_INCREMENT = 0x61c88647;
1151	>
1152	>	/**
1153	>	* Bits and masks for control variables
1154	>	*
1155	>	* Field ctl is a long packed with:
1156	>	* AC: Number of active running workers minus target parallelism (16 bits)
1157	>	* TC: Number of total workers minus target parallelism (16 bits)
1158	>	* ST: true if pool is terminating (1 bit)
1159	>	* EC: the wait count of top waiting thread (15 bits)
1160	>	* ID: poolIndex of top of Treiber stack of waiters (16 bits)
1161	>	*
1162	>	* When convenient, we can extract the upper 32 bits of counts and
1163	>	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
1164	>	* (int)ctl. The ec field is never accessed alone, but always
1165	>	* together with id and st. The offsets of counts by the target
1166	>	* parallelism and the positionings of fields makes it possible to
1167	>	* perform the most common checks via sign tests of fields: When
1168	>	* ac is negative, there are not enough active workers, when tc is
1169	>	* negative, there are not enough total workers, and when e is
1170	>	* negative, the pool is terminating. To deal with these possibly
1171	>	* negative fields, we use casts in and out of "short" and/or
1172	>	* signed shifts to maintain signedness.
1173	>	*
1174	>	* When a thread is queued (inactivated), its eventCount field is
1175	>	* set negative, which is the only way to tell if a worker is
1176	>	* prevented from executing tasks, even though it must continue to
1177	>	* scan for them to avoid queuing races. Note however that
1178	>	* eventCount updates lag releases so usage requires care.
1179	>	*
1180	>	* Field plock is an int packed with:
1181	>	* SHUTDOWN: true if shutdown is enabled (1 bit)
1182	>	* SEQ: a sequence lock, with PL_LOCK bit set if locked (30 bits)
1183	>	* SIGNAL: set when threads may be waiting on the lock (1 bit)
1184	>	*
1185	>	* The sequence number enables simple consistency checks:
1186	>	* Staleness of read-only operations on the workQueues array can
1187	>	* be checked by comparing plock before vs after the reads.
1188	>	*/
1189	>
1190	>	// bit positions/shifts for fields
1191	>	private static final int AC_SHIFT = 48;
1192	>	private static final int TC_SHIFT = 32;
1193	>	private static final int ST_SHIFT = 31;
1194	>	private static final int EC_SHIFT = 16;
1195	>
1196	>	// bounds
1197	>	private static final int SMASK = 0xffff; // short bits
1198	>	private static final int MAX_CAP = 0x7fff; // max #workers - 1
1199	>	private static final int EVENMASK = 0xfffe; // even short bits
1200	>	private static final int SQMASK = 0x007e; // max 64 (even) slots
1201	>	private static final int SHORT_SIGN = 1 << 15;
1202	>	private static final int INT_SIGN = 1 << 31;
1203	>
1204	>	// masks
1205	>	private static final long STOP_BIT = 0x0001L << ST_SHIFT;
1206	>	private static final long AC_MASK = ((long)SMASK) << AC_SHIFT;
1207	>	private static final long TC_MASK = ((long)SMASK) << TC_SHIFT;
1208	>
1209	>	// units for incrementing and decrementing
1210	>	private static final long TC_UNIT = 1L << TC_SHIFT;
1211	>	private static final long AC_UNIT = 1L << AC_SHIFT;
1212	>
1213	>	// masks and units for dealing with u = (int)(ctl >>> 32)
1214	>	private static final int UAC_SHIFT = AC_SHIFT - 32;
1215	>	private static final int UTC_SHIFT = TC_SHIFT - 32;
1216	>	private static final int UAC_MASK = SMASK << UAC_SHIFT;
1217	>	private static final int UTC_MASK = SMASK << UTC_SHIFT;
1218	>	private static final int UAC_UNIT = 1 << UAC_SHIFT;
1219	>	private static final int UTC_UNIT = 1 << UTC_SHIFT;
1220	>
1221	>	// masks and units for dealing with e = (int)ctl
1222	>	private static final int E_MASK = 0x7fffffff; // no STOP_BIT
1223	>	private static final int E_SEQ = 1 << EC_SHIFT;
1224	>
1225	>	// plock bits
1226	>	private static final int SHUTDOWN = 1 << 31;
1227	>	private static final int PL_LOCK = 2;
1228	>	private static final int PL_SIGNAL = 1;
1229	>	private static final int PL_SPINS = 1 << 8;
1230	>
1231	>	// access mode for WorkQueue
1232	>	static final int LIFO_QUEUE = 0;
1233	>	static final int FIFO_QUEUE = 1;
1234	>	static final int SHARED_QUEUE = -1;
1235	>
1236	>	// bounds for #steps in scan loop -- must be power 2 minus 1
1237	>	private static final int MIN_SCAN = 0x1ff; // cover estimation slop
1238	>	private static final int MAX_SCAN = 0x1ffff; // 4 * max workers
1239	>
1240	>	// Instance fields
1241	>
1242	>	/*
1243	>	* Field layout of this class tends to matter more than one would
1244	>	* like. Runtime layout order is only loosely related to
1245	>	* declaration order and may differ across JVMs, but the following
1246	>	* empirically works OK on current JVMs.
1247	>	*/
1248	>
1249	>	// Heuristic padding to ameliorate unfortunate memory placements
1250	>	volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
1251	>
1252	>	volatile long stealCount; // collects worker counts
1253	>	volatile long ctl; // main pool control
1254	>	volatile int plock; // shutdown status and seqLock
1255	>	volatile int indexSeed; // worker/submitter index seed
1256	>	final int config; // mode and parallelism level
1257	>	WorkQueue[] workQueues; // main registry
1258	>	final ForkJoinWorkerThreadFactory factory;
1259	>	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1260	>	final String workerNamePrefix; // to create worker name string
1261	>
1262	>	volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
1263	>	volatile Object pad18, pad19, pad1a, pad1b;
1264	>
1265	>	/*
1266	>	* Acquires the plock lock to protect worker array and related
1267	>	* updates. This method is called only if an initial CAS on plock
1268	>	* fails. This acts as a spinLock for normal cases, but falls back
1269	>	* to builtin monitor to block when (rarely) needed. This would be
1270	>	* a terrible idea for a highly contended lock, but works fine as
1271	>	* a more conservative alternative to a pure spinlock. See
1272	>	* internal ConcurrentHashMap documentation for further
1273	>	* explanation of nearly the same construction.
1274	>	*/
1275	>	private int acquirePlock() {
1276	>	int spins = PL_SPINS, r = 0, ps, nps;
1277	>	for (;;) {
1278	>	if (((ps = plock) & PL_LOCK) == 0 &&
1279	>	U.compareAndSwapInt(this, PLOCK, ps, nps = ps + PL_LOCK))
1280	>	return nps;
1281	>	else if (r == 0) { // randomize spins if possible
1282	>	Thread t = Thread.currentThread(); WorkQueue w; Submitter z;
1283	>	if ((t instanceof ForkJoinWorkerThread) &&
1284	>	(w = ((ForkJoinWorkerThread)t).workQueue) != null)
1285	>	r = w.seed;
1286	>	else if ((z = submitters.get()) != null)
1287	>	r = z.seed;
1288	>	else
1289	>	r = 1;
1290	>	}
1291	>	else if (spins >= 0) {
1292	>	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1293	>	if (r >= 0)
1294	>	--spins;
1295	>	}
1296	>	else if (U.compareAndSwapInt(this, PLOCK, ps, ps \| PL_SIGNAL)) {
1297	>	synchronized (this) {
1298	>	if ((plock & PL_SIGNAL) != 0) {
1299	>	try {
1300	>	wait();
1301	>	} catch (InterruptedException ie) {
1302	>	try {
1303	>	Thread.currentThread().interrupt();
1304	>	} catch (SecurityException ignore) {
1305	>	}
1306	>	}
1307	>	}
1308	>	else
1309	>	notifyAll();
1310	>	}
1311		}
1126	–	} catch (Throwable e) {
1127	–	ex = e;
1312		}
1129	–	deregisterWorker(w, ex);
1313		}
1314
1315		/**
1316	<	* Callback from ForkJoinWorkerThread constructor to assign a
1317	<	* public name. This must be separate from registerWorker because
1135	<	* it is called during the "super" constructor call in
1136	<	* ForkJoinWorkerThread.
1316	>	* Unlocks and signals any thread waiting for plock. Called only
1317	>	* when CAS of seq value for unlock fails.
1318		*/
1319	<	final String nextWorkerName() {
1320	<	return workerNamePrefix.concat
1321	<	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1319	>	private void releasePlock(int ps) {
1320	>	plock = ps;
1321	>	synchronized (this) { notifyAll(); }
1322	>	}
1323	>
1324	>	/**
1325	>	* Performs secondary initialization, called when plock is zero.
1326	>	* Creates workQueue array and sets plock to a valid value. The
1327	>	* lock body must be exception-free (so no try/finally) so we
1328	>	* optimistically allocate new array outside the lock and throw
1329	>	* away if (very rarely) not needed. (A similar tactic is used in
1330	>	* fullExternalPush.) Because the plock seq value can eventually
1331	>	* wrap around zero, this method harmlessly fails to reinitialize
1332	>	* if workQueues exists, while still advancing plock.
1333	>	*
1334	>	* Additionally tries to create the first worker.
1335	>	*/
1336	>	private void initWorkers() {
1337	>	WorkQueue[] ws, nws; int ps;
1338	>	int p = config & SMASK; // find power of two table size
1339	>	int n = (p > 1) ? p - 1 : 1; // ensure at least 2 slots
1340	>	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4; n \|= n >>> 8; n \|= n >>> 16;
1341	>	n = (n + 1) << 1;
1342	>	if ((ws = workQueues) == null \|\| ws.length == 0)
1343	>	nws = new WorkQueue[n];
1344	>	else
1345	>	nws = null;
1346	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1347	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1348	>	ps = acquirePlock();
1349	>	if (((ws = workQueues) == null \|\| ws.length == 0) && nws != null)
1350	>	workQueues = nws;
1351	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1352	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1353	>	releasePlock(nps);
1354	>	tryAddWorker();
1355	>	}
1356	>
1357	>	/**
1358	>	* Tries to create and start one worker if fewer than target
1359	>	* parallelism level exist. Adjusts counts etc on failure.
1360	>	*/
1361	>	private void tryAddWorker() {
1362	>	long c; int u;
1363	>	while ((u = (int)((c = ctl) >>> 32)) < 0 &&
1364	>	(u & SHORT_SIGN) != 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	>	ForkJoinWorkerThreadFactory fac;
1369	>	Throwable ex = null;
1370	>	ForkJoinWorkerThread wt = null;
1371	>	try {
1372	>	if ((fac = factory) != null &&
1373	>	(wt = fac.newThread(this)) != null) {
1374	>	wt.start();
1375	>	break;
1376	>	}
1377	>	} catch (Throwable e) {
1378	>	ex = e;
1379	>	}
1380	>	deregisterWorker(wt, ex);
1381	>	break;
1382	>	}
1383	>	}
1384		}
1385
1386	+	// Registering and deregistering workers
1387	+
1388		/**
1389	<	* Callback from ForkJoinWorkerThread constructor to establish and
1390	<	* record its WorkQueue
1389	>	* Callback from ForkJoinWorkerThread to establish and record its
1390	>	* WorkQueue. To avoid scanning bias due to packing entries in
1391	>	* front of the workQueues array, we treat the array as a simple
1392	>	* power-of-two hash table using per-thread seed as hash,
1393	>	* expanding as needed.
1394		*
1395		* @param wt the worker thread
1396	+	* @return the worker's queue
1397		*/
1398	<	final void registerWorker(ForkJoinWorkerThread wt) {
1399	<	WorkQueue w = wt.workQueue;
1400	<	ReentrantLock lock = this.lock;
1401	<	lock.lock();
1398	>	final WorkQueue registerWorker(ForkJoinWorkerThread wt) {
1399	>	Thread.UncaughtExceptionHandler handler; WorkQueue[] ws; int s, ps;
1400	>	wt.setDaemon(true);
1401	>	if ((handler = ueh) != null)
1402	>	wt.setUncaughtExceptionHandler(handler);
1403	>	do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed,
1404	>	s += SEED_INCREMENT) \|\|
1405	>	s == 0); // skip 0
1406	>	WorkQueue w = new WorkQueue(this, wt, config >>> 16, s);
1407	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1408	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1409	>	ps = acquirePlock();
1410	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1411		try {
1412	<	int k = nextPoolIndex;
1413	<	WorkQueue[] ws = workQueues;
1414	<	if (ws != null) { // ignore on shutdown
1415	<	int n = ws.length;
1416	<	if (k < 0 \|\| (k & 1) == 0 \|\| k >= n \|\| ws[k] != null) {
1417	<	for (k = 1; k < n && ws[k] != null; k += 2)
1418	<	; // workers are at odd indices
1419	<	if (k >= n) // resize
1420	<	workQueues = ws = Arrays.copyOf(ws, n << 1);
1421	<	}
1422	<	w.poolIndex = k;
1423	<	w.eventCount = ~(k >>> 1) & SMASK; // Set up wait count
1424	<	ws[k] = w; // record worker
1425	<	nextPoolIndex = k + 2;
1426	<	int rs = runState;
1427	<	int m = rs & SMASK; // recalculate runState mask
1170	<	if (k > m)
1171	<	m = (m << 1) + 1;
1172	<	runState = (rs & SHUTDOWN) \| ((rs + RS_SEQ) & RS_SEQ_MASK) \| m;
1412	>	if ((ws = workQueues) != null) { // skip if shutting down
1413	>	int n = ws.length, m = n - 1;
1414	>	int r = (s << 1) \| 1; // use odd-numbered indices
1415	>	if (ws[r &= m] != null) { // collision
1416	>	int probes = 0; // step by approx half size
1417	>	int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2;
1418	>	while (ws[r = (r + step) & m] != null) {
1419	>	if (++probes >= n) {
1420	>	workQueues = ws = Arrays.copyOf(ws, n <<= 1);
1421	>	m = n - 1;
1422	>	probes = 0;
1423	>	}
1424	>	}
1425	>	}
1426	>	w.eventCount = w.poolIndex = r; // volatile write orders
1427	>	ws[r] = w;
1428		}
1429		} finally {
1430	<	lock.unlock();
1430	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1431	>	releasePlock(nps);
1432		}
1433	+	wt.setName(workerNamePrefix.concat(Integer.toString(w.poolIndex)));
1434	+	return w;
1435		}
1436
1437		/**
1438	<	* Final callback from terminating worker, as well as failure to
1439	<	* construct or start a worker in addWorker. Removes record of
1440	<	* worker from array, and adjusts counts. If pool is shutting
1441	<	* down, tries to complete termination.
1438	>	* Final callback from terminating worker, as well as upon failure
1439	>	* to construct or start a worker. Removes record of worker from
1440	>	* array, and adjusts counts. If pool is shutting down, tries to
1441	>	* complete termination.
1442		*
1443	<	* @param wt the worker thread or null if addWorker failed
1443	>	* @param wt the worker thread or null if construction failed
1444		* @param ex the exception causing failure, or null if none
1445		*/
1446		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1447		WorkQueue w = null;
1448		if (wt != null && (w = wt.workQueue) != null) {
1449	<	w.runState = -1; // ensure runState is set
1450	<	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1451	<	int idx = w.poolIndex;
1452	<	ReentrantLock lock = this.lock;
1453	<	lock.lock();
1454	<	try { // remove record from array
1449	>	int ps;
1450	>	w.qlock = -1; // ensure set
1451	>	long ns = w.nsteals, sc; // collect steal count
1452	>	do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
1453	>	sc = stealCount, sc + ns));
1454	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1455	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1456	>	ps = acquirePlock();
1457	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1458	>	try {
1459	>	int idx = w.poolIndex;
1460		WorkQueue[] ws = workQueues;
1461		if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1462	<	ws[nextPoolIndex = idx] = null;
1462	>	ws[idx] = null;
1463		} finally {
1464	<	lock.unlock();
1464	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1465	>	releasePlock(nps);
1466		}
1467		}
1468
#	Line 1208 \| Line 1472 \| public class ForkJoinPool extends Abstra
1472		((c - TC_UNIT) & TC_MASK) \|
1473		(c & ~(AC_MASK\|TC_MASK)))));
1474
1475	<	if (!tryTerminate(false) && w != null) {
1475	>	if (!tryTerminate(false, false) && w != null && w.array != null) {
1476		w.cancelAll(); // cancel remaining tasks
1477	<	if (w.array != null) // suppress signal if never ran
1478	<	signalWork(); // wake up or create replacement
1477	>	int e, u, i, n; WorkQueue[] ws; WorkQueue v; Thread p;
1478	>	while ((u = (int)((c = ctl) >>> 32)) < 0) {
1479	>	if ((e = (int)c) > 0) { // activate or create replacement
1480	>	if ((ws = workQueues) != null &&
1481	>	ws.length > (i = e & SMASK) &&
1482	>	(v = ws[i]) != null && v.eventCount == (e \| INT_SIGN)) {
1483	>	long nc = (((long)(v.nextWait & E_MASK)) \|
1484	>	((long)(u + UAC_UNIT) << 32));
1485	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1486	>	v.eventCount = (e + E_SEQ) & E_MASK;
1487	>	if ((p = v.parker) != null)
1488	>	U.unpark(p);
1489	>	break;
1490	>	}
1491	>	}
1492	>	else
1493	>	break;
1494	>	}
1495	>	else {
1496	>	if ((short)u < 0)
1497	>	tryAddWorker();
1498	>	break;
1499	>	}
1500	>	}
1501		}
1502	<
1503	<	if (ex != null) // rethrow
1504	<	U.throwException(ex);
1502	>	if (ex == null) // help clean refs on way out
1503	>	ForkJoinTask.helpExpungeStaleExceptions();
1504	>	else // rethrow
1505	>	ForkJoinTask.rethrow(ex);
1506		}
1507
1508	<
1222	<	// Maintaining ctl counts
1223	<
1224	<	/**
1225	<	* Increments active count; mainly called upon return from blocking
1226	<	*/
1227	<	final void incrementActiveCount() {
1228	<	long c;
1229	<	do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
1230	<	}
1508	>	// Submissions
1509
1510		/**
1511	<	* Activates or creates a worker
1512	<	*/
1513	<	final void signalWork() {
1514	<	/*
1515	<	* The while condition is true if: (there is are too few total
1516	<	* workers OR there is at least one waiter) AND (there are too
1517	<	* few active workers OR the pool is terminating). The value
1518	<	* of e distinguishes the remaining cases: zero (no waiters)
1519	<	* for create, negative if terminating (in which case do
1520	<	* nothing), else release a waiter. The secondary checks for
1521	<	* release (non-null array etc) can fail if the pool begins
1522	<	* terminating after the test, and don't impose any added cost
1523	<	* because JVMs must perform null and bounds checks anyway.
1524	<	*/
1525	<	long c; int e, u;
1526	<	while ((((e = (int)(c = ctl)) \| (u = (int)(c >>> 32))) &
1527	<	(INT_SIGN\|SHORT_SIGN)) == (INT_SIGN\|SHORT_SIGN)) {
1528	<	WorkQueue[] ws = workQueues; int i; WorkQueue w; Thread p;
1529	<	if (e == 0) { // add a new worker
1530	<	if (U.compareAndSwapLong
1531	<	(this, CTL, c, (long)(((u + UTC_UNIT) & UTC_MASK) \|
1532	<	((u + UAC_UNIT) & UAC_MASK)) << 32)) {
1255	<	addWorker();
1256	<	break;
1257	<	}
1258	<	}
1259	<	else if (e > 0 && ws != null &&
1260	<	(i = ((~e << 1) \| 1) & SMASK) < ws.length &&
1261	<	(w = ws[i]) != null &&
1262	<	w.eventCount == (e \| INT_SIGN)) {
1263	<	if (U.compareAndSwapLong
1264	<	(this, CTL, c, (((long)(w.nextWait & E_MASK)) \|
1265	<	((long)(u + UAC_UNIT) << 32)))) {
1266	<	w.eventCount = (e + E_SEQ) & E_MASK;
1267	<	if ((p = w.parker) != null)
1268	<	U.unpark(p); // release a waiting worker
1269	<	break;
1270	<	}
1511	>	* Unless shutting down, adds the given task to a submission queue
1512	>	* at submitter's current queue index (modulo submission
1513	>	* range). Only the most common path is directly handled in this
1514	>	* method. All others are relayed to fullExternalPush.
1515	>	*
1516	>	* @param task the task. Caller must ensure non-null.
1517	>	*/
1518	>	final void externalPush(ForkJoinTask<?> task) {
1519	>	WorkQueue[] ws; WorkQueue q; Submitter z; int m; ForkJoinTask<?>[] a;
1520	>	if ((z = submitters.get()) != null && plock > 0 &&
1521	>	(ws = workQueues) != null && (m = (ws.length - 1)) >= 0 &&
1522	>	(q = ws[m & z.seed & SQMASK]) != null &&
1523	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock
1524	>	int b = q.base, s = q.top, n, an;
1525	>	if ((a = q.array) != null && (an = a.length) > (n = s + 1 - b)) {
1526	>	int j = (((an - 1) & s) << ASHIFT) + ABASE;
1527	>	U.putOrderedObject(a, j, task);
1528	>	q.top = s + 1; // push on to deque
1529	>	q.qlock = 0;
1530	>	if (n <= 2)
1531	>	signalWork(q);
1532	>	return;
1533		}
1534	<	else
1273	<	break;
1534	>	q.qlock = 0;
1535		}
1536	+	fullExternalPush(task);
1537		}
1538
1539		/**
1540	<	* Tries to decrement active count (sometimes implicitly) and
1541	<	* possibly release or create a compensating worker in preparation
1542	<	* for blocking. Fails on contention or termination.
1543	<	*
1544	<	* @return true if the caller can block, else should recheck and retry
1545	<	*/
1546	<	final boolean tryCompensate() {
1547	<	WorkQueue[] ws; WorkQueue w; Thread p;
1548	<	int pc = parallelism, e, u, ac, tc, i;
1549	<	long c = ctl;
1550	<
1551	<	if ((e = (int)c) >= 0) {
1552	<	if ((ac = ((u = (int)(c >>> 32)) >> UAC_SHIFT)) <= 0 &&
1553	<	e != 0 && (ws = workQueues) != null &&
1554	<	(i = ((~e << 1) \| 1) & SMASK) < ws.length &&
1555	<	(w = ws[i]) != null) {
1556	<	if (w.eventCount == (e \| INT_SIGN) &&
1557	<	U.compareAndSwapLong
1558	<	(this, CTL, c, ((long)(w.nextWait & E_MASK) \|
1559	<	(c & (AC_MASK\|TC_MASK))))) {
1560	<	w.eventCount = (e + E_SEQ) & E_MASK;
1561	<	if ((p = w.parker) != null)
1562	<	U.unpark(p);
1563	<	return true; // release an idle worker
1540	>	* Full version of externalPush. This method is called, among
1541	>	* other times, upon the first submission of the first task to the
1542	>	* pool, so must perform secondary initialization (via
1543	>	* initWorkers). It also detects first submission by an external
1544	>	* thread by looking up its ThreadLocal, and creates a new shared
1545	>	* queue if the one at index if empty or contended. The plock lock
1546	>	* body must be exception-free (so no try/finally) so we
1547	>	* optimistically allocate new queues outside the lock and throw
1548	>	* them away if (very rarely) not needed.
1549	>	*/
1550	>	private void fullExternalPush(ForkJoinTask<?> task) {
1551	>	int r = 0; // random index seed
1552	>	for (Submitter z = submitters.get();;) {
1553	>	WorkQueue[] ws; WorkQueue q; int ps, m, k;
1554	>	if (z == null) {
1555	>	if (U.compareAndSwapInt(this, INDEXSEED, r = indexSeed,
1556	>	r += SEED_INCREMENT) && r != 0)
1557	>	submitters.set(z = new Submitter(r));
1558	>	}
1559	>	else if (r == 0) { // move to a different index
1560	>	r = z.seed;
1561	>	r ^= r << 13; // same xorshift as WorkQueues
1562	>	r ^= r >>> 17;
1563	>	z.seed = r ^ (r << 5);
1564	>	}
1565	>	else if ((ps = plock) < 0)
1566	>	throw new RejectedExecutionException();
1567	>	else if (ps == 0 \|\| (ws = workQueues) == null \|\|
1568	>	(m = ws.length - 1) < 0)
1569	>	initWorkers();
1570	>	else if ((q = ws[k = r & m & SQMASK]) != null) {
1571	>	if (q.qlock == 0 && U.compareAndSwapInt(q, QLOCK, 0, 1)) {
1572	>	ForkJoinTask<?>[] a = q.array;
1573	>	int s = q.top;
1574	>	boolean submitted = false;
1575	>	try { // locked version of push
1576	>	if ((a != null && a.length > s + 1 - q.base) \|\|
1577	>	(a = q.growArray()) != null) { // must presize
1578	>	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
1579	>	U.putOrderedObject(a, j, task);
1580	>	q.top = s + 1;
1581	>	submitted = true;
1582	>	}
1583	>	} finally {
1584	>	q.qlock = 0; // unlock
1585	>	}
1586	>	if (submitted) {
1587	>	signalWork(q);
1588	>	return;
1589	>	}
1590		}
1591	+	r = 0; // move on failure
1592		}
1593	<	else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) {
1594	<	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
1595	<	if (U.compareAndSwapLong(this, CTL, c, nc))
1596	<	return true; // no compensation needed
1597	<	}
1598	<	else if (tc + pc < MAX_ID) {
1599	<	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
1600	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1601	<	addWorker();
1602	<	return true; // create replacement
1314	<	}
1593	>	else if (((ps = plock) & PL_LOCK) == 0) { // create new queue
1594	>	q = new WorkQueue(this, null, SHARED_QUEUE, r);
1595	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1596	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1597	>	ps = acquirePlock();
1598	>	if ((ws = workQueues) != null && k < ws.length && ws[k] == null)
1599	>	ws[k] = q;
1600	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1601	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1602	>	releasePlock(nps);
1603		}
1604	+	else
1605	+	r = 0; // try elsewhere while lock held
1606		}
1317	–	return false;
1607		}
1608
1609	<	// Submissions
1609	>	// Maintaining ctl counts
1610
1611		/**
1612	<	* 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.
1612	>	* Increments active count; mainly called upon return from blocking.
1613		*/
1614	<	private void doSubmit(ForkJoinTask<?> task) {
1615	<	if (task == null)
1616	<	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	<	}
1614	>	final void incrementActiveCount() {
1615	>	long c;
1616	>	do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
1617		}
1618
1619		/**
1620	<	* Tries to add and register a new queue at the given index.
1620	>	* Tries to create or activate a worker if too few are active.
1621		*
1622	<	* @param idx the workQueues array index to register the queue
1623	<	* @return the queue, or null if could not add because could
1624	<	* not acquire lock or idx is unusable
1625	<	*/
1626	<	private WorkQueue tryAddSharedQueue(int idx) {
1627	<	WorkQueue q = null;
1628	<	ReentrantLock lock = this.lock;
1629	<	if (idx >= 0 && (idx & 1) == 0 && !lock.isLocked()) {
1630	<	// create queue outside of lock but only if apparently free
1631	<	WorkQueue nq = new WorkQueue(null, SHARED_QUEUE);
1632	<	if (lock.tryLock()) {
1633	<	try {
1634	<	WorkQueue[] ws = workQueues;
1635	<	if (ws != null && idx < ws.length) {
1636	<	if ((q = ws[idx]) == null) {
1637	<	int rs; // update runState seq
1638	<	ws[idx] = q = nq;
1379	<	runState = (((rs = runState) & SHUTDOWN) \|
1380	<	((rs + RS_SEQ) & ~SHUTDOWN));
1381	<	}
1622	>	* @param q the (non-null) queue holding tasks to be signalled
1623	>	*/
1624	>	final void signalWork(WorkQueue q) {
1625	>	int hint = q.poolIndex;
1626	>	long c; int e, u, i, n; WorkQueue[] ws; WorkQueue w; Thread p;
1627	>	while ((u = (int)((c = ctl) >>> 32)) < 0) {
1628	>	if ((e = (int)c) > 0) {
1629	>	if ((ws = workQueues) != null && ws.length > (i = e & SMASK) &&
1630	>	(w = ws[i]) != null && w.eventCount == (e \| INT_SIGN)) {
1631	>	long nc = (((long)(w.nextWait & E_MASK)) \|
1632	>	((long)(u + UAC_UNIT) << 32));
1633	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1634	>	w.hint = hint;
1635	>	w.eventCount = (e + E_SEQ) & E_MASK;
1636	>	if ((p = w.parker) != null)
1637	>	U.unpark(p);
1638	>	break;
1639		}
1640	<	} finally {
1641	<	lock.unlock();
1640	>	if (q.top - q.base <= 0)
1641	>	break;
1642		}
1643	+	else
1644	+	break;
1645	+	}
1646	+	else {
1647	+	if ((short)u < 0)
1648	+	tryAddWorker();
1649	+	break;
1650		}
1651		}
1388	–	return q;
1652		}
1653
1654		// Scanning for tasks
1655
1656		/**
1657	+	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1658	+	*/
1659	+	final void runWorker(WorkQueue w) {
1660	+	w.growArray(); // allocate queue
1661	+	do { w.runTask(scan(w)); } while (w.qlock >= 0);
1662	+	}
1663	+
1664	+	/**
1665		* Scans for and, if found, returns one task, else possibly
1666		* inactivates the worker. This method operates on single reads of
1667	<	* volatile state and is designed to be re-invoked continuously in
1668	<	* part because it returns upon detecting inconsistencies,
1667	>	* volatile state and is designed to be re-invoked continuously,
1668	>	* in part because it returns upon detecting inconsistencies,
1669		* contention, or state changes that indicate possible success on
1670		* re-invocation.
1671		*
1672	<	* The scan searches for tasks across queues, randomly selecting
1673	<	* the first #queues probes, favoring steals 2:1 over submissions
1674	<	* (by exploiting even/odd indexing), and then performing a
1675	<	* circular sweep of all queues. The scan terminates upon either
1676	<	* finding a non-empty queue, or completing a full sweep. If the
1677	<	* worker is not inactivated, it takes and returns a task from
1678	<	* this queue. On failure to find a task, we take one of the
1679	<	* following actions, after which the caller will retry calling
1680	<	* this method unless terminated.
1681	<	*
1682	<	* * If not a complete sweep, try to release a waiting worker. If
1683	<	* 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.
1672	>	* The scan searches for tasks across queues (starting at a random
1673	>	* index, and relying on registerWorker to irregularly scatter
1674	>	* them within array to avoid bias), checking each at least twice.
1675	>	* The scan terminates upon either finding a non-empty queue, or
1676	>	* completing the sweep. If the worker is not inactivated, it
1677	>	* takes and returns a task from this queue. Otherwise, if not
1678	>	* activated, it signals workers (that may include itself) and
1679	>	* returns so caller can retry. Also returns for true if the
1680	>	* worker array may have changed during an empty scan. On failure
1681	>	* to find a task, we take one of the following actions, after
1682	>	* which the caller will retry calling this method unless
1683	>	* terminated.
1684		*
1685	<	* * If pool is terminating, terminate the worker
1685	>	* * If pool is terminating, terminate the worker.
1686		*
1687		* * If not already enqueued, try to inactivate and enqueue the
1688	<	* worker on wait queue.
1689	<	*
1690	<	* * If already enqueued and none of the above apply, either park
1691	<	* awaiting signal, or if this is the most recent waiter and pool
1692	<	* is quiescent, relay to idleAwaitWork to check for termination
1693	<	* and possibly shrink pool.
1688	>	* worker on wait queue. Or, if inactivating has caused the pool
1689	>	* to be quiescent, relay to idleAwaitWork to check for
1690	>	* termination and possibly shrink pool.
1691	>	*
1692	>	* * If already enqueued and none of the above apply, possibly
1693	>	* (with 1/2 probability) park awaiting signal, else lingering to
1694	>	* help scan and signal.
1695		*
1696		* @param w the worker (via its WorkQueue)
1697	<	* @return a task or null of none found
1697	>	* @return a task or null if none found
1698		*/
1699		private final ForkJoinTask<?> scan(WorkQueue w) {
1700	<	boolean swept = false; // true after full empty scan
1701	<	WorkQueue[] ws; // volatile read order matters
1702	<	int r = w.seed, ec = w.eventCount; // ec is negative if inactive
1703	<	int rs = runState, m = rs & SMASK;
1704	<	if ((ws = workQueues) != null && ws.length > m) {
1705	<	ForkJoinTask<?> task = null;
1706	<	for (int k = 0, j = -2 - m; ; ++j) {
1707	<	WorkQueue q; int b;
1708	<	if (j < 0) { // random probes while j negative
1709	<	r ^= r << 13; r ^= r >>> 17; k = (r ^= r << 5) \| (j & 1);
1710	<	} // worker (not submit) for odd j
1711	<	else // cyclic scan when j >= 0
1712	<	k += (m >>> 1) \| 1; // step by half to reduce bias
1713	<
1714	<	if ((q = ws[k & m]) != null && (b = q.base) - q.top < 0) {
1715	<	if (ec >= 0)
1716	<	task = q.pollAt(b); // steal
1717	<	break;
1700	>	WorkQueue[] ws; int m;
1701	>	int ps = plock; // read plock before ws
1702	>	if (w != null && (ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1703	>	int ec = w.eventCount; // ec is negative if inactive
1704	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1705	>	int j = ((m + m + 1) \| MIN_SCAN) & MAX_SCAN;
1706	>	do {
1707	>	WorkQueue q; ForkJoinTask<?>[] a; int b;
1708	>	if ((q = ws[(r + j) & m]) != null && (b = q.base) - q.top < 0 &&
1709	>	(a = q.array) != null) { // probably nonempty
1710	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1711	>	ForkJoinTask<?> t = (ForkJoinTask<?>)
1712	>	U.getObjectVolatile(a, i);
1713	>	if (q.base == b && ec >= 0 && t != null &&
1714	>	U.compareAndSwapObject(a, i, t, null)) {
1715	>	if ((q.base = b + 1) - q.top < 0)
1716	>	signalWork(q);
1717	>	return t; // taken
1718	>	}
1719	>	else if ((ec < 0 \|\| j < m) && (int)(ctl >> AC_SHIFT) <= 0) {
1720	>	w.hint = (r + j) & m; // help signal below
1721	>	break; // cannot take
1722	>	}
1723		}
1724	<	else if (j > m) {
1725	<	if (rs == runState) // staleness check
1726	<	swept = true;
1727	<	break;
1724	>	} while (--j >= 0);
1725	>
1726	>	long c, sc; int e, ns, h;
1727	>	if ((h = w.hint) < 0) {
1728	>	if ((ns = w.nsteals) != 0) {
1729	>	if (U.compareAndSwapLong(this, STEALCOUNT,
1730	>	sc = stealCount, sc + ns))
1731	>	w.nsteals = 0; // collect steals
1732	>	}
1733	>	else if (plock != ps) // consistency check
1734	>	; // skip
1735	>	else if ((e = (int)(c = ctl)) < 0)
1736	>	w.qlock = -1; // pool is terminating
1737	>	else if (ec >= 0) { // try to enqueue/inactivate
1738	>	long nc = ((long)ec \| ((c - AC_UNIT) & (AC_MASK\|TC_MASK)));
1739	>	w.nextWait = e; // link and mark inactive
1740	>	w.eventCount = ec \| INT_SIGN;
1741	>	if (ctl != c \|\| !U.compareAndSwapLong(this, CTL, c, nc))
1742	>	w.eventCount = ec; // unmark on CAS failure
1743	>	else if ((int)(c >> AC_SHIFT) == 1 - (config & SMASK))
1744	>	idleAwaitWork(w, nc, c);
1745	>	}
1746	>	else if (w.eventCount < 0) { // block
1747	>	Thread wt = Thread.currentThread();
1748	>	Thread.interrupted(); // clear status
1749	>	U.putObject(wt, PARKBLOCKER, this);
1750	>	w.parker = wt; // emulate LockSupport.park
1751	>	if (w.eventCount < 0) // recheck
1752	>	U.park(false, 0L);
1753	>	w.parker = null;
1754	>	U.putObject(wt, PARKBLOCKER, null);
1755		}
1756		}
1757	<	w.seed = r; // save seed for next scan
1758	<	if (task != null)
1466	<	return task;
1467	<	}
1468	<
1469	<	// Decode ctl on empty scan
1470	<	long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
1471	<	if (!swept) { // try to release a waiter
1472	<	WorkQueue v; Thread p;
1473	<	if (e > 0 && a < 0 && ws != null &&
1474	<	(v = ws[((~e << 1) \| 1) & m]) != null &&
1475	<	v.eventCount == (e \| INT_SIGN) && U.compareAndSwapLong
1476	<	(this, CTL, c, ((long)(v.nextWait & E_MASK) \|
1477	<	((c + AC_UNIT) & (AC_MASK\|TC_MASK))))) {
1478	<	v.eventCount = (e + E_SEQ) & E_MASK;
1479	<	if ((p = v.parker) != null)
1480	<	U.unpark(p);
1481	<	}
1482	<	}
1483	<	else if ((nr = w.rescans) > 0) { // continue rescanning
1484	<	int ac = a + parallelism;
1485	<	if ((w.rescans = (ac < nr) ? ac : nr - 1) > 0 && w.seed < 0 &&
1486	<	w.eventCount == ec)
1487	<	Thread.yield(); // 1 bit randomness for yield call
1488	<	}
1489	<	else if (e < 0) // pool is terminating
1490	<	w.runState = -1;
1491	<	else if (ec >= 0) { // try to enqueue
1492	<	long nc = (long)ec \| ((c - AC_UNIT) & (AC_MASK\|TC_MASK));
1493	<	w.nextWait = e;
1494	<	w.eventCount = ec \| INT_SIGN; // mark as inactive
1495	<	if (!U.compareAndSwapLong(this, CTL, c, nc))
1496	<	w.eventCount = ec; // back out on CAS failure
1497	<	else if ((ns = w.nsteals) != 0) { // set rescans if ran task
1498	<	if (a <= 0) // ... unless too many active
1499	<	w.rescans = a + parallelism;
1500	<	w.nsteals = 0;
1501	<	w.totalSteals += ns;
1502	<	}
1503	<	}
1504	<	else{ // already queued
1505	<	if (parallelism == -a)
1506	<	idleAwaitWork(w); // quiescent
1507	<	if (w.eventCount == ec) {
1508	<	Thread.interrupted(); // clear status
1509	<	ForkJoinWorkerThread wt = w.owner;
1510	<	U.putObject(wt, PARKBLOCKER, this);
1511	<	w.parker = wt; // emulate LockSupport.park
1512	<	if (w.eventCount == ec) // recheck
1513	<	U.park(false, 0L); // block
1514	<	w.parker = null;
1515	<	U.putObject(wt, PARKBLOCKER, null);
1516	<	}
1757	>	if (h >= 0 \|\| w.hint >= 0) // signal others before retry
1758	>	helpSignalHint(w);
1759		}
1760		return null;
1761		}
1762
1763		/**
1764	<	* If inactivating worker w has caused pool to become quiescent,
1765	<	* check for pool termination, and, so long as this is not the
1766	<	* only worker, wait for event for up to SHRINK_RATE nanosecs On
1767	<	* timeout, if ctl has not changed, terminate the worker, which
1768	<	* will in turn wake up another worker to possibly repeat this
1769	<	* process.
1764	>	* If inactivating worker w has caused the pool to become
1765	>	* quiescent, checks for pool termination, and, so long as this is
1766	>	* not the only worker, waits for event for up to a given
1767	>	* duration. On timeout, if ctl has not changed, terminates the
1768	>	* worker, which will in turn wake up another worker to possibly
1769	>	* repeat this process.
1770		*
1771		* @param w the calling worker
1772	+	* @param currentCtl the ctl value triggering possible quiescence
1773	+	* @param prevCtl the ctl value to restore if thread is terminated
1774		*/
1775	<	private void idleAwaitWork(WorkQueue w) {
1776	<	long c; int nw, ec;
1777	<	if (!tryTerminate(false) &&
1778	<	(int)((c = ctl) >> AC_SHIFT) + parallelism == 0 &&
1779	<	(ec = w.eventCount) == ((int)c \| INT_SIGN) &&
1780	<	(nw = w.nextWait) != 0) {
1781	<	long nc = ((long)(nw & E_MASK) \| // ctl to restore on timeout
1782	<	((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();
1775	>	private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1776	>	if (w != null && w.eventCount < 0 &&
1777	>	!tryTerminate(false, false) && (int)prevCtl != 0) {
1778	>	int dc = -(short)(currentCtl >>> TC_SHIFT);
1779	>	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1780	>	long deadline = System.nanoTime() + parkTime - TIMEOUT_SLOP;
1781	>	Thread wt = Thread.currentThread();
1782	>	while (ctl == currentCtl) {
1783		Thread.interrupted(); // timed variant of version in scan()
1784		U.putObject(wt, PARKBLOCKER, this);
1785		w.parker = wt;
1786	<	if (ctl == c)
1787	<	U.park(false, SHRINK_RATE);
1786	>	if (ctl == currentCtl)
1787	>	U.park(false, parkTime);
1788		w.parker = null;
1789		U.putObject(wt, PARKBLOCKER, null);
1790	<	if (ctl != c)
1790	>	if (ctl != currentCtl)
1791		break;
1792	<	if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
1793	<	U.compareAndSwapLong(this, CTL, c, nc)) {
1794	<	w.runState = -1; // shrink
1795	<	w.eventCount = (ec + E_SEQ) \| E_MASK;
1792	>	if (deadline - System.nanoTime() <= 0L &&
1793	>	U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1794	>	w.eventCount = (w.eventCount + E_SEQ) \| E_MASK;
1795	>	w.qlock = -1; // shrink
1796		break;
1797		}
1798		}
#	Line 1560 \| Line 1800 \| public class ForkJoinPool extends Abstra
1800		}
1801
1802		/**
1803	+	* Scans through queues looking for work while joining a task; if
1804	+	* any present, signals. May return early if more signalling is
1805	+	* detectably unneeded.
1806	+	*
1807	+	* @param task return early if done
1808	+	* @param origin an index to start scan
1809	+	*/
1810	+	private void helpSignal(ForkJoinTask<?> task, int origin) {
1811	+	WorkQueue[] ws; WorkQueue w; Thread p; long c; int m, u, e, i, s;
1812	+	if (task != null && task.status >= 0 &&
1813	+	(u = (int)(ctl >>> 32)) < 0 && (u >> UAC_SHIFT) < 0 &&
1814	+	(ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1815	+	outer: for (int k = origin, j = m; j >= 0; --j) {
1816	+	WorkQueue q = ws[k++ & m];
1817	+	for (int n = m;;) { // limit to at most m signals
1818	+	if (task.status < 0)
1819	+	break outer;
1820	+	if (q == null \|\|
1821	+	((s = -q.base + q.top) <= n && (n = s) <= 0))
1822	+	break;
1823	+	if ((u = (int)((c = ctl) >>> 32)) >= 0 \|\|
1824	+	(e = (int)c) <= 0 \|\| m < (i = e & SMASK) \|\|
1825	+	(w = ws[i]) == null)
1826	+	break outer;
1827	+	long nc = (((long)(w.nextWait & E_MASK)) \|
1828	+	((long)(u + UAC_UNIT) << 32));
1829	+	if (w.eventCount == (e \| INT_SIGN) &&
1830	+	U.compareAndSwapLong(this, CTL, c, nc)) {
1831	+	w.eventCount = (e + E_SEQ) & E_MASK;
1832	+	if ((p = w.parker) != null)
1833	+	U.unpark(p);
1834	+	if (--n <= 0)
1835	+	break;
1836	+	}
1837	+	}
1838	+	}
1839	+	}
1840	+	}
1841	+
1842	+	/**
1843	+	* Signals other workers if tasks are present in hinted queue.
1844	+	*
1845	+	* @param caller the worker with the hint
1846	+	*/
1847	+	private void helpSignalHint(WorkQueue caller) {
1848	+	WorkQueue[] ws; WorkQueue q, w; Thread p; long c; int h, m, u, e, i, s;
1849	+	if (caller != null && (h = caller.hint) >= 0) {
1850	+	caller.hint = -1;
1851	+	if ((u = (int)(ctl >>> 32)) < 0 && (u >> UAC_SHIFT) < 0 &&
1852	+	(ws = workQueues) != null && (m = ws.length - 1) >= 0 &&
1853	+	(q = ws[h & m]) != null) {
1854	+	for (int n = (m >>> 2) \| 1;;) { // limit signals
1855	+	int idleCount = (caller.eventCount < 0) ? 0 : -1;
1856	+	if (((s = idleCount - q.base + q.top) <= n &&
1857	+	(n = s) <= 0) \|\|
1858	+	(u = (int)((c = ctl) >>> 32)) >= 0 \|\|
1859	+	(e = (int)c) <= 0 \|\| m < (i = e & SMASK) \|\|
1860	+	(w = ws[i]) == null)
1861	+	break;
1862	+	long nc = (((long)(w.nextWait & E_MASK)) \|
1863	+	((long)(u + UAC_UNIT) << 32));
1864	+	if (w.eventCount == (e \| INT_SIGN) &&
1865	+	U.compareAndSwapLong(this, CTL, c, nc)) {
1866	+	w.hint = h;
1867	+	w.eventCount = (e + E_SEQ) & E_MASK;
1868	+	if ((p = w.parker) != null)
1869	+	U.unpark(p);
1870	+	if (--n <= 0)
1871	+	break;
1872	+	}
1873	+	}
1874	+	}
1875	+	}
1876	+	}
1877	+
1878	+	/**
1879		* Tries to locate and execute tasks for a stealer of the given
1880		* task, or in turn one of its stealers, Traces currentSteal ->
1881		* currentJoin links looking for a thread working on a descendant
#	Line 1570 \| Line 1886 \| public class ForkJoinPool extends Abstra
1886		* leaves hints in workers to speed up subsequent calls. The
1887		* implementation is very branchy to cope with potential
1888		* inconsistencies or loops encountering chains that are stale,
1889	<	* unknown, or of length greater than MAX_HELP_DEPTH links. All
1574	<	* of these cases are dealt with by just retrying by caller.
1889	>	* unknown, or so long that they are likely cyclic.
1890		*
1891		* @param joiner the joining worker
1892		* @param task the task to join
1893	<	* @return true if found or ran a task (and so is immediately retryable)
1893	>	* @return 0 if no progress can be made, negative if task
1894	>	* known complete, else positive
1895		*/
1896	<	final boolean tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1897	<	ForkJoinTask<?> subtask; // current target
1898	<	boolean progress = false;
1899	<	int depth = 0; // current chain depth
1900	<	int m = runState & SMASK;
1901	<	WorkQueue[] ws = workQueues;
1902	<
1903	<	if (ws != null && ws.length > m && (subtask = task).status >= 0) {
1904	<	outer:for (WorkQueue j = joiner;;) {
1905	<	// Try to find the stealer of subtask, by first using hint
1906	<	WorkQueue stealer = null;
1907	<	WorkQueue v = ws[j.stealHint & m];
1908	<	if (v != null && v.currentSteal == subtask)
1909	<	stealer = v;
1910	<	else {
1911	<	for (int i = 1; i <= m; i += 2) {
1912	<	if ((v = ws[i]) != null && v.currentSteal == subtask) {
1913	<	stealer = v;
1914	<	j.stealHint = i; // save hint
1915	<	break;
1896	>	private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1897	>	int stat = 0, steps = 0; // bound to avoid cycles
1898	>	if (joiner != null && task != null) { // hoist null checks
1899	>	restart: for (;;) {
1900	>	ForkJoinTask<?> subtask = task; // current target
1901	>	for (WorkQueue j = joiner, v;;) { // v is stealer of subtask
1902	>	WorkQueue[] ws; int m, s, h;
1903	>	if ((s = task.status) < 0) {
1904	>	stat = s;
1905	>	break restart;
1906	>	}
1907	>	if ((ws = workQueues) == null \|\| (m = ws.length - 1) <= 0)
1908	>	break restart; // shutting down
1909	>	if ((v = ws[h = (j.hint \| 1) & m]) == null \|\|
1910	>	v.currentSteal != subtask) {
1911	>	for (int origin = h;;) { // find stealer
1912	>	if (((h = (h + 2) & m) & 15) == 1 &&
1913	>	(subtask.status < 0 \|\| j.currentJoin != subtask))
1914	>	continue restart; // occasional staleness check
1915	>	if ((v = ws[h]) != null &&
1916	>	v.currentSteal == subtask) {
1917	>	j.hint = h; // save hint
1918	>	break;
1919	>	}
1920	>	if (h == origin)
1921	>	break restart; // cannot find stealer
1922		}
1923		}
1924	<	if (stealer == null)
1924	>	for (;;) { // help stealer or descend to its stealer
1925	>	ForkJoinTask[] a; int b;
1926	>	if (subtask.status < 0) // surround probes with
1927	>	continue restart; // consistency checks
1928	>	if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
1929	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1930	>	ForkJoinTask<?> t =
1931	>	(ForkJoinTask<?>)U.getObjectVolatile(a, i);
1932	>	if (subtask.status < 0 \|\| j.currentJoin != subtask \|\|
1933	>	v.currentSteal != subtask)
1934	>	continue restart; // stale
1935	>	stat = 1; // apparent progress
1936	>	if (t != null && v.base == b &&
1937	>	U.compareAndSwapObject(a, i, t, null)) {
1938	>	v.base = b + 1; // help stealer
1939	>	joiner.runSubtask(t);
1940	>	}
1941	>	else if (v.base == b && ++steps == MAX_HELP)
1942	>	break restart; // v apparently stalled
1943	>	}
1944	>	else { // empty -- try to descend
1945	>	ForkJoinTask<?> next = v.currentJoin;
1946	>	if (subtask.status < 0 \|\| j.currentJoin != subtask \|\|
1947	>	v.currentSteal != subtask)
1948	>	continue restart; // stale
1949	>	else if (next == null \|\| ++steps == MAX_HELP)
1950	>	break restart; // dead-end or maybe cyclic
1951	>	else {
1952	>	subtask = next;
1953	>	j = v;
1954	>	break;
1955	>	}
1956	>	}
1957	>	}
1958	>	}
1959	>	}
1960	>	}
1961	>	return stat;
1962	>	}
1963	>
1964	>	/**
1965	>	* Analog of tryHelpStealer for CountedCompleters. Tries to steal
1966	>	* and run tasks within the target's computation.
1967	>	*
1968	>	* @param task the task to join
1969	>	* @param mode if shared, exit upon completing any task
1970	>	* if all workers are active
1971	>	*
1972	>	*/
1973	>	private int helpComplete(ForkJoinTask<?> task, int mode) {
1974	>	WorkQueue[] ws; WorkQueue q; int m, n, s, u;
1975	>	if (task != null && (ws = workQueues) != null &&
1976	>	(m = ws.length - 1) >= 0) {
1977	>	for (int j = 1, origin = j;;) {
1978	>	if ((s = task.status) < 0)
1979	>	return s;
1980	>	if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) {
1981	>	origin = j;
1982	>	if (mode == SHARED_QUEUE &&
1983	>	((u = (int)(ctl >>> 32)) >= 0 \|\| (u >> UAC_SHIFT) >= 0))
1984		break;
1985		}
1986	+	else if ((j = (j + 2) & m) == origin)
1987	+	break;
1988	+	}
1989	+	}
1990	+	return 0;
1991	+	}
1992
1993	<	for (WorkQueue q = stealer;;) { // Try to help stealer
1994	<	ForkJoinTask<?> t; int b;
1995	<	if (task.status < 0)
1996	<	break outer;
1997	<	if ((b = q.base) - q.top < 0) {
1998	<	progress = true;
1999	<	if (subtask.status < 0)
2000	<	break outer; // stale
2001	<	if ((t = q.pollAt(b)) != null) {
2002	<	stealer.stealHint = joiner.poolIndex;
2003	<	joiner.runSubtask(t);
1993	>	/**
1994	>	* Tries to decrement active count (sometimes implicitly) and
1995	>	* possibly release or create a compensating worker in preparation
1996	>	* for blocking. Fails on contention or termination. Otherwise,
1997	>	* adds a new thread if no idle workers are available and pool
1998	>	* may become starved.
1999	>	*/
2000	>	final boolean tryCompensate() {
2001	>	int pc = config & SMASK, e, i, tc; long c;
2002	>	WorkQueue[] ws; WorkQueue w; Thread p;
2003	>	if ((ws = workQueues) != null && (e = (int)(c = ctl)) >= 0) {
2004	>	if (e != 0 && (i = e & SMASK) < ws.length &&
2005	>	(w = ws[i]) != null && w.eventCount == (e \| INT_SIGN)) {
2006	>	long nc = ((long)(w.nextWait & E_MASK) \|
2007	>	(c & (AC_MASK\|TC_MASK)));
2008	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
2009	>	w.eventCount = (e + E_SEQ) & E_MASK;
2010	>	if ((p = w.parker) != null)
2011	>	U.unpark(p);
2012	>	return true; // replace with idle worker
2013	>	}
2014	>	}
2015	>	else if ((tc = (short)(c >>> TC_SHIFT)) >= 0 &&
2016	>	(int)(c >> AC_SHIFT) + pc > 1) {
2017	>	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
2018	>	if (U.compareAndSwapLong(this, CTL, c, nc))
2019	>	return true; // no compensation
2020	>	}
2021	>	else if (tc + pc < MAX_CAP) {
2022	>	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
2023	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
2024	>	ForkJoinWorkerThreadFactory fac;
2025	>	Throwable ex = null;
2026	>	ForkJoinWorkerThread wt = null;
2027	>	try {
2028	>	if ((fac = factory) != null &&
2029	>	(wt = fac.newThread(this)) != null) {
2030	>	wt.start();
2031	>	return true;
2032		}
2033	+	} catch (Throwable rex) {
2034	+	ex = rex;
2035		}
2036	<	else { // empty - try to descend to find stealer's stealer
1620	<	ForkJoinTask<?> next = stealer.currentJoin;
1621	<	if (++depth == MAX_HELP_DEPTH \|\| subtask.status < 0 \|\|
1622	<	next == null \|\| next == subtask)
1623	<	break outer; // max depth, stale, dead-end, cyclic
1624	<	subtask = next;
1625	<	j = stealer;
1626	<	break;
1627	<	}
2036	>	deregisterWorker(wt, ex); // clean up and return false
2037		}
2038		}
2039		}
2040	<	return progress;
2040	>	return false;
2041		}
2042
2043		/**
2044	<	* If task is at base of some steal queue, steals and executes it.
2044	>	* Helps and/or blocks until the given task is done.
2045		*
2046		* @param joiner the joining worker
2047		* @param task the task
2048	+	* @return task status on exit
2049		*/
2050	<	final void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
2051	<	WorkQueue[] ws;
2052	<	int m = runState & SMASK;
2053	<	if ((ws = workQueues) != null && ws.length > m) {
2054	<	for (int j = 1; j <= m && task.status >= 0; j += 2) {
2055	<	WorkQueue q = ws[j];
2056	<	if (q != null && q.pollFor(task)) {
2057	<	joiner.runSubtask(task);
2058	<	break;
2050	>	final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
2051	>	int s = 0;
2052	>	if (joiner != null && task != null && (s = task.status) >= 0) {
2053	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2054	>	joiner.currentJoin = task;
2055	>	do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
2056	>	joiner.tryRemoveAndExec(task)); // process local tasks
2057	>	if (s >= 0 && (s = task.status) >= 0) {
2058	>	helpSignal(task, joiner.poolIndex);
2059	>	if ((s = task.status) >= 0 &&
2060	>	(task instanceof CountedCompleter))
2061	>	s = helpComplete(task, LIFO_QUEUE);
2062	>	}
2063	>	while (s >= 0 && (s = task.status) >= 0) {
2064	>	if ((!joiner.isEmpty() \|\| // try helping
2065	>	(s = tryHelpStealer(joiner, task)) == 0) &&
2066	>	(s = task.status) >= 0) {
2067	>	helpSignal(task, joiner.poolIndex);
2068	>	if ((s = task.status) >= 0 && tryCompensate()) {
2069	>	if (task.trySetSignal() && (s = task.status) >= 0) {
2070	>	synchronized (task) {
2071	>	if (task.status >= 0) {
2072	>	try { // see ForkJoinTask
2073	>	task.wait(); // for explanation
2074	>	} catch (InterruptedException ie) {
2075	>	}
2076	>	}
2077	>	else
2078	>	task.notifyAll();
2079	>	}
2080	>	}
2081	>	long c; // re-activate
2082	>	do {} while (!U.compareAndSwapLong
2083	>	(this, CTL, c = ctl, c + AC_UNIT));
2084	>	}
2085		}
2086		}
2087	+	joiner.currentJoin = prevJoin;
2088		}
2089	+	return s;
2090		}
2091
2092		/**
2093	<	* Returns a non-empty steal queue, if one is found during a random,
2094	<	* then cyclic scan, else null. This method must be retried by
2095	<	* caller if, by the time it tries to use the queue, it is empty.
2093	>	* Stripped-down variant of awaitJoin used by timed joins. Tries
2094	>	* to help join only while there is continuous progress. (Caller
2095	>	* will then enter a timed wait.)
2096	>	*
2097	>	* @param joiner the joining worker
2098	>	* @param task the task
2099		*/
2100	<	private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
2101	<	int r = w.seed; // Same idea as scan(), but ignoring submissions
2100	>	final void helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
2101	>	int s;
2102	>	if (joiner != null && task != null && (s = task.status) >= 0) {
2103	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2104	>	joiner.currentJoin = task;
2105	>	do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
2106	>	joiner.tryRemoveAndExec(task));
2107	>	if (s >= 0 && (s = task.status) >= 0) {
2108	>	helpSignal(task, joiner.poolIndex);
2109	>	if ((s = task.status) >= 0 &&
2110	>	(task instanceof CountedCompleter))
2111	>	s = helpComplete(task, LIFO_QUEUE);
2112	>	}
2113	>	if (s >= 0 && joiner.isEmpty()) {
2114	>	do {} while (task.status >= 0 &&
2115	>	tryHelpStealer(joiner, task) > 0);
2116	>	}
2117	>	joiner.currentJoin = prevJoin;
2118	>	}
2119	>	}
2120	>
2121	>	/**
2122	>	* Returns a (probably) non-empty steal queue, if one is found
2123	>	* during a random, then cyclic scan, else null. This method must
2124	>	* be retried by caller if, by the time it tries to use the queue,
2125	>	* it is empty.
2126	>	* @param r a (random) seed for scanning
2127	>	*/
2128	>	private WorkQueue findNonEmptyStealQueue(int r) {
2129		for (WorkQueue[] ws;;) {
2130	<	int m = runState & SMASK;
2131	<	if ((ws = workQueues) == null)
2130	>	int ps = plock, m, n;
2131	>	if ((ws = workQueues) == null \|\| (m = ws.length - 1) < 1)
2132		return null;
2133	<	if (ws.length > m) {
2134	<	WorkQueue q;
2135	<	for (int n = m << 2, k = r, j = -n;;) {
2136	<	r ^= r << 13; r ^= r >>> 17; r ^= r << 5;
2137	<	if ((q = ws[(k \| 1) & m]) != null && q.base - q.top < 0) {
2138	<	w.seed = r;
2139	<	return q;
2140	<	}
2141	<	else if (j > n)
2133	>	for (int j = (m + 1) << 2; ;) {
2134	>	WorkQueue q = ws[(((r + j) << 1) \| 1) & m];
2135	>	if (q != null && (n = q.base - q.top) < 0) {
2136	>	if (n < -1)
2137	>	signalWork(q);
2138	>	return q;
2139	>	}
2140	>	else if (--j < 0) {
2141	>	if (plock == ps)
2142		return null;
2143	<	else
1676	<	k = (j++ < 0) ? r : k + ((m >>> 1) \| 1);
1677	<
2143	>	break;
2144		}
2145		}
2146		}
#	Line 1688 \| Line 2154 \| public class ForkJoinPool extends Abstra
2154		*/
2155		final void helpQuiescePool(WorkQueue w) {
2156		for (boolean active = true;;) {
2157	<	w.runLocalTasks(); // exhaust local queue
2158	<	WorkQueue q = findNonEmptyStealQueue(w);
2157	>	ForkJoinTask<?> localTask; // exhaust local queue
2158	>	while ((localTask = w.nextLocalTask()) != null)
2159	>	localTask.doExec();
2160	>	// Similar to loop in scan(), but ignoring submissions
2161	>	WorkQueue q = findNonEmptyStealQueue(w.nextSeed());
2162		if (q != null) {
2163	<	ForkJoinTask<?> t;
2163	>	ForkJoinTask<?> t; int b;
2164		if (!active) { // re-establish active count
2165		long c;
2166		active = true;
2167		do {} while (!U.compareAndSwapLong
2168		(this, CTL, c = ctl, c + AC_UNIT));
2169		}
2170	<	if ((t = q.poll()) != null)
2170	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2171		w.runSubtask(t);
2172		}
2173		else {
#	Line 1710 \| Line 2179 \| public class ForkJoinPool extends Abstra
2179		}
2180		else
2181		c = ctl; // re-increment on exit
2182	<	if ((int)(c >> AC_SHIFT) + parallelism == 0) {
2182	>	if ((int)(c >> AC_SHIFT) + (config & SMASK) == 0) {
2183		do {} while (!U.compareAndSwapLong
2184		(this, CTL, c = ctl, c + AC_UNIT));
2185		break;
#	Line 1720 \| Line 2189 \| public class ForkJoinPool extends Abstra
2189		}
2190
2191		/**
2192	<	* Gets and removes a local or stolen task for the given worker
2192	>	* Gets and removes a local or stolen task for the given worker.
2193		*
2194		* @return a task, if available
2195		*/
2196		final ForkJoinTask<?> nextTaskFor(WorkQueue w) {
2197		for (ForkJoinTask<?> t;;) {
2198	<	WorkQueue q;
2198	>	WorkQueue q; int b;
2199		if ((t = w.nextLocalTask()) != null)
2200		return t;
2201	<	if ((q = findNonEmptyStealQueue(w)) == null)
2201	>	if ((q = findNonEmptyStealQueue(w.nextSeed())) == null)
2202		return null;
2203	<	if ((t = q.poll()) != null)
2203	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2204		return t;
2205		}
2206		}
2207
2208		/**
2209	<	* Returns the approximate (non-atomic) number of idle threads per
2210	<	* active thread to offset steal queue size for method
2211	<	* ForkJoinTask.getSurplusQueuedTaskCount().
2212	<	*/
2213	<	final int idlePerActive() {
2214	<	// Approximate at powers of two for small values, saturate past 4
2215	<	int p = parallelism;
2216	<	int a = p + (int)(ctl >> AC_SHIFT);
2217	<	return (a > (p >>>= 1) ? 0 :
2218	<	a > (p >>>= 1) ? 1 :
2219	<	a > (p >>>= 1) ? 2 :
2220	<	a > (p >>>= 1) ? 4 :
2221	<	8);
2222	<	}
2223	<
2224	<	// Termination
2225	<
2226	<	/**
2227	<	* Sets SHUTDOWN bit of runState under lock
2228	<	*/
2229	<	private void enableShutdown() {
2230	<	ReentrantLock lock = this.lock;
2231	<	if (runState >= 0) {
2232	<	lock.lock(); // don't need try/finally
2233	<	runState \|= SHUTDOWN;
2234	<	lock.unlock();
2209	>	* Returns a cheap heuristic guide for task partitioning when
2210	>	* programmers, frameworks, tools, or languages have little or no
2211	>	* idea about task granularity. In essence by offering this
2212	>	* method, we ask users only about tradeoffs in overhead vs
2213	>	* expected throughput and its variance, rather than how finely to
2214	>	* partition tasks.
2215	>	*
2216	>	* In a steady state strict (tree-structured) computation, each
2217	>	* thread makes available for stealing enough tasks for other
2218	>	* threads to remain active. Inductively, if all threads play by
2219	>	* the same rules, each thread should make available only a
2220	>	* constant number of tasks.
2221	>	*
2222	>	* The minimum useful constant is just 1. But using a value of 1
2223	>	* would require immediate replenishment upon each steal to
2224	>	* maintain enough tasks, which is infeasible. Further,
2225	>	* partitionings/granularities of offered tasks should minimize
2226	>	* steal rates, which in general means that threads nearer the top
2227	>	* of computation tree should generate more than those nearer the
2228	>	* bottom. In perfect steady state, each thread is at
2229	>	* approximately the same level of computation tree. However,
2230	>	* producing extra tasks amortizes the uncertainty of progress and
2231	>	* diffusion assumptions.
2232	>	*
2233	>	* So, users will want to use values larger, but not much larger
2234	>	* than 1 to both smooth over transient shortages and hedge
2235	>	* against uneven progress; as traded off against the cost of
2236	>	* extra task overhead. We leave the user to pick a threshold
2237	>	* value to compare with the results of this call to guide
2238	>	* decisions, but recommend values such as 3.
2239	>	*
2240	>	* When all threads are active, it is on average OK to estimate
2241	>	* surplus strictly locally. In steady-state, if one thread is
2242	>	* maintaining say 2 surplus tasks, then so are others. So we can
2243	>	* just use estimated queue length. However, this strategy alone
2244	>	* leads to serious mis-estimates in some non-steady-state
2245	>	* conditions (ramp-up, ramp-down, other stalls). We can detect
2246	>	* many of these by further considering the number of "idle"
2247	>	* threads, that are known to have zero queued tasks, so
2248	>	* compensate by a factor of (#idle/#active) threads.
2249	>	*
2250	>	* Note: The approximation of #busy workers as #active workers is
2251	>	* not very good under current signalling scheme, and should be
2252	>	* improved.
2253	>	*/
2254	>	static int getSurplusQueuedTaskCount() {
2255	>	Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q;
2256	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
2257	>	int p = (pool = (wt = (ForkJoinWorkerThread)t).pool).config & SMASK;
2258	>	int n = (q = wt.workQueue).top - q.base;
2259	>	int a = (int)(pool.ctl >> AC_SHIFT) + p;
2260	>	return n - (a > (p >>>= 1) ? 0 :
2261	>	a > (p >>>= 1) ? 1 :
2262	>	a > (p >>>= 1) ? 2 :
2263	>	a > (p >>>= 1) ? 4 :
2264	>	8);
2265		}
2266	+	return 0;
2267		}
2268
2269	+	// Termination
2270	+
2271		/**
2272	<	* Possibly initiates and/or completes termination. Upon
2273	<	* termination, cancels all queued tasks and then
2272	>	* Possibly initiates and/or completes termination. The caller
2273	>	* triggering termination runs three passes through workQueues:
2274	>	* (0) Setting termination status, followed by wakeups of queued
2275	>	* workers; (1) cancelling all tasks; (2) interrupting lagging
2276	>	* threads (likely in external tasks, but possibly also blocked in
2277	>	* joins). Each pass repeats previous steps because of potential
2278	>	* lagging thread creation.
2279		*
2280		* @param now if true, unconditionally terminate, else only
2281		* if no work and no active workers
2282	+	* @param enable if true, enable shutdown when next possible
2283		* @return true if now terminating or terminated
2284		*/
2285	<	private boolean tryTerminate(boolean now) {
2285	>	private boolean tryTerminate(boolean now, boolean enable) {
2286	>	if (this == commonPool) // cannot shut down
2287	>	return false;
2288		for (long c;;) {
2289		if (((c = ctl) & STOP_BIT) != 0) { // already terminating
2290	<	if ((short)(c >>> TC_SHIFT) == -parallelism) {
2291	<	ReentrantLock lock = this.lock; // signal when no workers
2292	<	lock.lock(); // don't need try/finally
2293	<	termination.signalAll(); // signal when 0 workers
1784	<	lock.unlock();
2290	>	if ((short)(c >>> TC_SHIFT) == -(config & SMASK)) {
2291	>	synchronized (this) {
2292	>	notifyAll(); // signal when 0 workers
2293	>	}
2294		}
2295		return true;
2296		}
2297	<	if (!now) {
2298	<	if ((int)(c >> AC_SHIFT) != -parallelism \|\| runState >= 0 \|\|
2297	>	if (plock >= 0) { // not yet enabled
2298	>	int ps;
2299	>	if (!enable)
2300	>	return false;
2301	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
2302	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
2303	>	ps = acquirePlock();
2304	>	int nps = SHUTDOWN;
2305	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
2306	>	releasePlock(nps);
2307	>	}
2308	>	if (!now) { // check if idle & no tasks
2309	>	if ((int)(c >> AC_SHIFT) != -(config & SMASK) \|\|
2310		hasQueuedSubmissions())
2311		return false;
2312		// Check for unqueued inactive workers. One pass suffices.
2313		WorkQueue[] ws = workQueues; WorkQueue w;
2314		if (ws != null) {
2315	<	int n = ws.length;
1796	<	for (int i = 1; i < n; i += 2) {
2315	>	for (int i = 1; i < ws.length; i += 2) {
2316		if ((w = ws[i]) != null && w.eventCount >= 0)
2317		return false;
2318		}
2319		}
2320		}
2321	<	if (U.compareAndSwapLong(this, CTL, c, c \| STOP_BIT))
2322	<	startTerminating();
2321	>	if (U.compareAndSwapLong(this, CTL, c, c \| STOP_BIT)) {
2322	>	for (int pass = 0; pass < 3; ++pass) {
2323	>	WorkQueue[] ws = workQueues;
2324	>	if (ws != null) {
2325	>	WorkQueue w;
2326	>	int n = ws.length;
2327	>	for (int i = 0; i < n; ++i) {
2328	>	if ((w = ws[i]) != null) {
2329	>	w.qlock = -1;
2330	>	if (pass > 0) {
2331	>	w.cancelAll();
2332	>	if (pass > 1)
2333	>	w.interruptOwner();
2334	>	}
2335	>	}
2336	>	}
2337	>	// Wake up workers parked on event queue
2338	>	int i, e; long cc; Thread p;
2339	>	while ((e = (int)(cc = ctl) & E_MASK) != 0 &&
2340	>	(i = e & SMASK) < n &&
2341	>	(w = ws[i]) != null) {
2342	>	long nc = ((long)(w.nextWait & E_MASK) \|
2343	>	((cc + AC_UNIT) & AC_MASK) \|
2344	>	(cc & (TC_MASK\|STOP_BIT)));
2345	>	if (w.eventCount == (e \| INT_SIGN) &&
2346	>	U.compareAndSwapLong(this, CTL, cc, nc)) {
2347	>	w.eventCount = (e + E_SEQ) & E_MASK;
2348	>	w.qlock = -1;
2349	>	if ((p = w.parker) != null)
2350	>	U.unpark(p);
2351	>	}
2352	>	}
2353	>	}
2354	>	}
2355	>	}
2356		}
2357		}
2358
2359	+	// external operations on common pool
2360	+
2361		/**
2362	<	* Initiates termination: Runs three passes through workQueues:
2363	<	* (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.
2362	>	* Returns common pool queue for a thread that has submitted at
2363	>	* least one task.
2364		*/
2365	<	private void startTerminating() {
2366	<	for (int pass = 0; pass < 3; ++pass) {
2367	<	WorkQueue[] ws = workQueues;
2368	<	if (ws != null) {
2369	<	WorkQueue w; Thread wt;
2370	<	int n = ws.length;
2371	<	for (int j = 0; j < n; ++j) {
2372	<	if ((w = ws[j]) != null) {
2373	<	w.runState = -1;
2374	<	if (pass > 0) {
2375	<	w.cancelAll();
2376	<	if (pass > 1 && (wt = w.owner) != null &&
2377	<	!wt.isInterrupted()) {
2378	<	try {
2379	<	wt.interrupt();
2380	<	} catch (SecurityException ignore) {
2365	>	static WorkQueue commonSubmitterQueue() {
2366	>	ForkJoinPool p; WorkQueue[] ws; int m; Submitter z;
2367	>	return ((z = submitters.get()) != null &&
2368	>	(p = commonPool) != null &&
2369	>	(ws = p.workQueues) != null &&
2370	>	(m = ws.length - 1) >= 0) ?
2371	>	ws[m & z.seed & SQMASK] : null;
2372	>	}
2373	>
2374	>	/**
2375	>	* Tries to pop the given task from submitter's queue in common pool.
2376	>	*/
2377	>	static boolean tryExternalUnpush(ForkJoinTask<?> t) {
2378	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q; Submitter z;
2379	>	ForkJoinTask<?>[] a; int m, s;
2380	>	if (t != null &&
2381	>	(z = submitters.get()) != null &&
2382	>	(p = commonPool) != null &&
2383	>	(ws = p.workQueues) != null &&
2384	>	(m = ws.length - 1) >= 0 &&
2385	>	(q = ws[m & z.seed & SQMASK]) != null &&
2386	>	(s = q.top) != q.base &&
2387	>	(a = q.array) != null) {
2388	>	long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE;
2389	>	if (U.getObject(a, j) == t &&
2390	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2391	>	if (q.array == a && q.top == s && // recheck
2392	>	U.compareAndSwapObject(a, j, t, null)) {
2393	>	q.top = s - 1;
2394	>	q.qlock = 0;
2395	>	return true;
2396	>	}
2397	>	q.qlock = 0;
2398	>	}
2399	>	}
2400	>	return false;
2401	>	}
2402	>
2403	>	/**
2404	>	* Tries to pop and run local tasks within the same computation
2405	>	* as the given root. On failure, tries to help complete from
2406	>	* other queues via helpComplete.
2407	>	*/
2408	>	private void externalHelpComplete(WorkQueue q, ForkJoinTask<?> root) {
2409	>	ForkJoinTask<?>[] a; int m;
2410	>	if (q != null && (a = q.array) != null && (m = (a.length - 1)) >= 0 &&
2411	>	root != null && root.status >= 0) {
2412	>	for (;;) {
2413	>	int s, u; Object o; CountedCompleter<?> task = null;
2414	>	if ((s = q.top) - q.base > 0) {
2415	>	long j = ((m & (s - 1)) << ASHIFT) + ABASE;
2416	>	if ((o = U.getObject(a, j)) != null &&
2417	>	(o instanceof CountedCompleter)) {
2418	>	CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;
2419	>	do {
2420	>	if (r == root) {
2421	>	if (U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2422	>	if (q.array == a && q.top == s &&
2423	>	U.compareAndSwapObject(a, j, t, null)) {
2424	>	q.top = s - 1;
2425	>	task = t;
2426	>	}
2427	>	q.qlock = 0;
2428		}
2429	+	break;
2430		}
2431	<	}
2431	>	} while ((r = r.completer) != null);
2432		}
2433		}
2434	<	// Wake up workers parked on event queue
2435	<	int i, e; long c; Thread p;
2436	<	while ((i = ((~(e = (int)(c = ctl)) << 1) \| 1) & SMASK) < n &&
2437	<	(w = ws[i]) != null &&
2438	<	w.eventCount == (e \| INT_SIGN)) {
2439	<	long nc = ((long)(w.nextWait & E_MASK) \|
2440	<	((c + AC_UNIT) & AC_MASK) \|
2441	<	(c & (TC_MASK\|STOP_BIT)));
2442	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
2443	<	w.eventCount = (e + E_SEQ) & E_MASK;
2444	<	if ((p = w.parker) != null)
2445	<	U.unpark(p);
2434	>	if (task != null)
2435	>	task.doExec();
2436	>	if (root.status < 0 \|\|
2437	>	(u = (int)(ctl >>> 32)) >= 0 \|\| (u >> UAC_SHIFT) >= 0)
2438	>	break;
2439	>	if (task == null) {
2440	>	helpSignal(root, q.poolIndex);
2441	>	if (root.status >= 0)
2442	>	helpComplete(root, SHARED_QUEUE);
2443	>	break;
2444	>	}
2445	>	}
2446	>	}
2447	>	}
2448	>
2449	>	/**
2450	>	* Tries to help execute or signal availability of the given task
2451	>	* from submitter's queue in common pool.
2452	>	*/
2453	>	static void externalHelpJoin(ForkJoinTask<?> t) {
2454	>	// Some hard-to-avoid overlap with tryExternalUnpush
2455	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; Submitter z;
2456	>	ForkJoinTask<?>[] a; int m, s, n;
2457	>	if (t != null &&
2458	>	(z = submitters.get()) != null &&
2459	>	(p = commonPool) != null &&
2460	>	(ws = p.workQueues) != null &&
2461	>	(m = ws.length - 1) >= 0 &&
2462	>	(q = ws[m & z.seed & SQMASK]) != null &&
2463	>	(a = q.array) != null) {
2464	>	int am = a.length - 1;
2465	>	if ((s = q.top) != q.base) {
2466	>	long j = ((am & (s - 1)) << ASHIFT) + ABASE;
2467	>	if (U.getObject(a, j) == t &&
2468	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2469	>	if (q.array == a && q.top == s &&
2470	>	U.compareAndSwapObject(a, j, t, null)) {
2471	>	q.top = s - 1;
2472	>	q.qlock = 0;
2473	>	t.doExec();
2474		}
2475	+	else
2476	+	q.qlock = 0;
2477		}
2478		}
2479	+	if (t.status >= 0) {
2480	+	if (t instanceof CountedCompleter)
2481	+	p.externalHelpComplete(q, t);
2482	+	else
2483	+	p.helpSignal(t, q.poolIndex);
2484	+	}
2485		}
2486		}
2487
2488	+	/**
2489	+	* Restricted version of helpQuiescePool for external callers
2490	+	*/
2491	+	static void externalHelpQuiescePool() {
2492	+	ForkJoinPool p; ForkJoinTask<?> t; WorkQueue q; int b;
2493	+	if ((p = commonPool) != null &&
2494	+	(q = p.findNonEmptyStealQueue(1)) != null &&
2495	+	(b = q.base) - q.top < 0 &&
2496	+	(t = q.pollAt(b)) != null)
2497	+	t.doExec();
2498	+	}
2499	+
2500		// Exported methods
2501
2502		// Constructors
#	Line 1920 \| Line 2566 \| public class ForkJoinPool extends Abstra
2566		checkPermission();
2567		if (factory == null)
2568		throw new NullPointerException();
2569	<	if (parallelism <= 0 \|\| parallelism > MAX_ID)
2569	>	if (parallelism <= 0 \|\| parallelism > MAX_CAP)
2570		throw new IllegalArgumentException();
1925	–	this.parallelism = parallelism;
2571		this.factory = factory;
2572		this.ueh = handler;
2573	<	this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE;
1929	<	this.nextPoolIndex = 1;
2573	>	this.config = parallelism \| (asyncMode ? (FIFO_QUEUE << 16) : 0);
2574		long np = (long)(-parallelism); // offset ctl counts
2575		this.ctl = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
2576	<	// 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();
2576	>	int pn = nextPoolId();
2577		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2578	<	sb.append(poolNumberGenerator.incrementAndGet());
2578	>	sb.append(Integer.toString(pn));
2579		sb.append("-worker-");
2580		this.workerNamePrefix = sb.toString();
2581	<	// Create initial submission queue
2582	<	WorkQueue sq = tryAddSharedQueue(0);
2583	<	if (sq != null)
2584	<	sq.growArray(false);
2581	>	}
2582	>
2583	>	/**
2584	>	* Constructor for common pool, suitable only for static initialization.
2585	>	* Basically the same as above, but uses smallest possible initial footprint.
2586	>	*/
2587	>	ForkJoinPool(int parallelism, long ctl,
2588	>	ForkJoinWorkerThreadFactory factory,
2589	>	Thread.UncaughtExceptionHandler handler) {
2590	>	this.config = parallelism;
2591	>	this.ctl = ctl;
2592	>	this.factory = factory;
2593	>	this.ueh = handler;
2594	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2595	>	}
2596	>
2597	>	/**
2598	>	* Returns the common pool instance.
2599	>	*
2600	>	* @return the common pool instance
2601	>	*/
2602	>	public static ForkJoinPool commonPool() {
2603	>	// assert commonPool != null : "static init error";
2604	>	return commonPool;
2605		}
2606
2607		// Execution methods
#	Line 1970 \| Line 2623 \| public class ForkJoinPool extends Abstra
2623		* scheduled for execution
2624		*/
2625		public <T> T invoke(ForkJoinTask<T> task) {
2626	<	doSubmit(task);
2626	>	if (task == null)
2627	>	throw new NullPointerException();
2628	>	externalPush(task);
2629		return task.join();
2630		}
2631
#	Line 1983 \| Line 2638 \| public class ForkJoinPool extends Abstra
2638		* scheduled for execution
2639		*/
2640		public void execute(ForkJoinTask<?> task) {
2641	<	doSubmit(task);
2641	>	if (task == null)
2642	>	throw new NullPointerException();
2643	>	externalPush(task);
2644		}
2645
2646		// AbstractExecutorService methods
#	Line 2000 \| Line 2657 \| public class ForkJoinPool extends Abstra
2657		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2658		job = (ForkJoinTask<?>) task;
2659		else
2660	<	job = ForkJoinTask.adapt(task, null);
2661	<	doSubmit(job);
2660	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2661	>	externalPush(job);
2662		}
2663
2664		/**
#	Line 2014 \| Line 2671 \| public class ForkJoinPool extends Abstra
2671		* scheduled for execution
2672		*/
2673		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2674	<	doSubmit(task);
2674	>	if (task == null)
2675	>	throw new NullPointerException();
2676	>	externalPush(task);
2677		return task;
2678		}
2679
#	Line 2024 \| Line 2683 \| public class ForkJoinPool extends Abstra
2683		* scheduled for execution
2684		*/
2685		public <T> ForkJoinTask<T> submit(Callable<T> task) {
2686	<	if (task == null)
2687	<	throw new NullPointerException();
2029	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
2030	<	doSubmit(job);
2686	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2687	>	externalPush(job);
2688		return job;
2689		}
2690
#	Line 2037 \| Line 2694 \| public class ForkJoinPool extends Abstra
2694		* scheduled for execution
2695		*/
2696		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2697	<	if (task == null)
2698	<	throw new NullPointerException();
2042	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
2043	<	doSubmit(job);
2697	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2698	>	externalPush(job);
2699		return job;
2700		}
2701
#	Line 2056 \| Line 2711 \| public class ForkJoinPool extends Abstra
2711		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2712		job = (ForkJoinTask<?>) task;
2713		else
2714	<	job = ForkJoinTask.adapt(task, null);
2715	<	doSubmit(job);
2714	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2715	>	externalPush(job);
2716		return job;
2717		}
2718
#	Line 2066 \| Line 2721 \| public class ForkJoinPool extends Abstra
2721		* @throws RejectedExecutionException {@inheritDoc}
2722		*/
2723		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
2724	<	ArrayList<ForkJoinTask<T>> forkJoinTasks =
2725	<	new ArrayList<ForkJoinTask<T>>(tasks.size());
2726	<	for (Callable<T> task : tasks)
2727	<	forkJoinTasks.add(ForkJoinTask.adapt(task));
2728	<	invoke(new InvokeAll<T>(forkJoinTasks));
2729	<
2724	>	// In previous versions of this class, this method constructed
2725	>	// a task to run ForkJoinTask.invokeAll, but now external
2726	>	// invocation of multiple tasks is at least as efficient.
2727	>	List<ForkJoinTask<T>> fs = new ArrayList<ForkJoinTask<T>>(tasks.size());
2728	>	// Workaround needed because method wasn't declared with
2729	>	// wildcards in return type but should have been.
2730		@SuppressWarnings({"unchecked", "rawtypes"})
2731	<	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
2077	<	return futures;
2078	<	}
2731	>	List<Future<T>> futures = (List<Future<T>>) (List) fs;
2732
2733	<	static final class InvokeAll<T> extends RecursiveAction {
2734	<	final ArrayList<ForkJoinTask<T>> tasks;
2735	<	InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
2736	<	public void compute() {
2737	<	try { invokeAll(tasks); }
2738	<	catch (Exception ignore) {}
2733	>	boolean done = false;
2734	>	try {
2735	>	for (Callable<T> t : tasks) {
2736	>	ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2737	>	externalPush(f);
2738	>	fs.add(f);
2739	>	}
2740	>	for (ForkJoinTask<T> f : fs)
2741	>	f.quietlyJoin();
2742	>	done = true;
2743	>	return futures;
2744	>	} finally {
2745	>	if (!done)
2746	>	for (ForkJoinTask<T> f : fs)
2747	>	f.cancel(false);
2748		}
2087	–	private static final long serialVersionUID = -7914297376763021607L;
2749		}
2750
2751		/**
#	Line 2112 \| Line 2773 \| public class ForkJoinPool extends Abstra
2773		* @return the targeted parallelism level of this pool
2774		*/
2775		public int getParallelism() {
2776	<	return parallelism;
2776	>	return config & SMASK;
2777	>	}
2778	>
2779	>	/**
2780	>	* Returns the targeted parallelism level of the common pool.
2781	>	*
2782	>	* @return the targeted parallelism level of the common pool
2783	>	*/
2784	>	public static int getCommonPoolParallelism() {
2785	>	return commonPoolParallelism;
2786		}
2787
2788		/**
#	Line 2124 \| Line 2794 \| public class ForkJoinPool extends Abstra
2794		* @return the number of worker threads
2795		*/
2796		public int getPoolSize() {
2797	<	return parallelism + (short)(ctl >>> TC_SHIFT);
2797	>	return (config & SMASK) + (short)(ctl >>> TC_SHIFT);
2798		}
2799
2800		/**
#	Line 2134 \| Line 2804 \| public class ForkJoinPool extends Abstra
2804		* @return {@code true} if this pool uses async mode
2805		*/
2806		public boolean getAsyncMode() {
2807	<	return localMode != 0;
2807	>	return (config >>> 16) == FIFO_QUEUE;
2808		}
2809
2810		/**
#	Line 2149 \| Line 2819 \| public class ForkJoinPool extends Abstra
2819		int rc = 0;
2820		WorkQueue[] ws; WorkQueue w;
2821		if ((ws = workQueues) != null) {
2822	<	int n = ws.length;
2823	<	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)
2822	>	for (int i = 1; i < ws.length; i += 2) {
2823	>	if ((w = ws[i]) != null && w.isApparentlyUnblocked())
2824		++rc;
2825		}
2826		}
#	Line 2171 \| Line 2835 \| public class ForkJoinPool extends Abstra
2835		* @return the number of active threads
2836		*/
2837		public int getActiveThreadCount() {
2838	<	int r = parallelism + (int)(ctl >> AC_SHIFT);
2838	>	int r = (config & SMASK) + (int)(ctl >> AC_SHIFT);
2839		return (r <= 0) ? 0 : r; // suppress momentarily negative values
2840		}
2841
#	Line 2187 \| Line 2851 \| public class ForkJoinPool extends Abstra
2851		* @return {@code true} if all threads are currently idle
2852		*/
2853		public boolean isQuiescent() {
2854	<	return (int)(ctl >> AC_SHIFT) + parallelism == 0;
2854	>	return (int)(ctl >> AC_SHIFT) + (config & SMASK) == 0;
2855		}
2856
2857		/**
#	Line 2202 \| Line 2866 \| public class ForkJoinPool extends Abstra
2866		* @return the number of steals
2867		*/
2868		public long getStealCount() {
2869	<	long count = stealCount.get();
2869	>	long count = stealCount;
2870		WorkQueue[] ws; WorkQueue w;
2871		if ((ws = workQueues) != null) {
2872	<	int n = ws.length;
2209	<	for (int i = 1; i < n; i += 2) {
2872	>	for (int i = 1; i < ws.length; i += 2) {
2873		if ((w = ws[i]) != null)
2874	<	count += w.totalSteals;
2874	>	count += w.nsteals;
2875		}
2876		}
2877		return count;
#	Line 2228 \| Line 2891 \| public class ForkJoinPool extends Abstra
2891		long count = 0;
2892		WorkQueue[] ws; WorkQueue w;
2893		if ((ws = workQueues) != null) {
2894	<	int n = ws.length;
2232	<	for (int i = 1; i < n; i += 2) {
2894	>	for (int i = 1; i < ws.length; i += 2) {
2895		if ((w = ws[i]) != null)
2896		count += w.queueSize();
2897		}
#	Line 2248 \| Line 2910 \| public class ForkJoinPool extends Abstra
2910		int count = 0;
2911		WorkQueue[] ws; WorkQueue w;
2912		if ((ws = workQueues) != null) {
2913	<	int n = ws.length;
2252	<	for (int i = 0; i < n; i += 2) {
2913	>	for (int i = 0; i < ws.length; i += 2) {
2914		if ((w = ws[i]) != null)
2915		count += w.queueSize();
2916		}
#	Line 2266 \| Line 2927 \| public class ForkJoinPool extends Abstra
2927		public boolean hasQueuedSubmissions() {
2928		WorkQueue[] ws; WorkQueue w;
2929		if ((ws = workQueues) != null) {
2930	<	int n = ws.length;
2931	<	for (int i = 0; i < n; i += 2) {
2271	<	if ((w = ws[i]) != null && w.queueSize() != 0)
2930	>	for (int i = 0; i < ws.length; i += 2) {
2931	>	if ((w = ws[i]) != null && !w.isEmpty())
2932		return true;
2933		}
2934		}
#	Line 2285 \| Line 2945 \| public class ForkJoinPool extends Abstra
2945		protected ForkJoinTask<?> pollSubmission() {
2946		WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2947		if ((ws = workQueues) != null) {
2948	<	int n = ws.length;
2289	<	for (int i = 0; i < n; i += 2) {
2948	>	for (int i = 0; i < ws.length; i += 2) {
2949		if ((w = ws[i]) != null && (t = w.poll()) != null)
2950		return t;
2951		}
#	Line 2315 \| Line 2974 \| public class ForkJoinPool extends Abstra
2974		int count = 0;
2975		WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2976		if ((ws = workQueues) != null) {
2977	<	int n = ws.length;
2319	<	for (int i = 0; i < n; ++i) {
2977	>	for (int i = 0; i < ws.length; ++i) {
2978		if ((w = ws[i]) != null) {
2979		while ((t = w.poll()) != null) {
2980		c.add(t);
#	Line 2336 \| Line 2994 \| public class ForkJoinPool extends Abstra
2994		* @return a string identifying this pool, as well as its state
2995		*/
2996		public String toString() {
2997	<	long st = getStealCount();
2998	<	long qt = getQueuedTaskCount();
2999	<	long qs = getQueuedSubmissionCount();
2342	<	int rc = getRunningThreadCount();
2343	<	int pc = parallelism;
2997	>	// Use a single pass through workQueues to collect counts
2998	>	long qt = 0L, qs = 0L; int rc = 0;
2999	>	long st = stealCount;
3000		long c = ctl;
3001	+	WorkQueue[] ws; WorkQueue w;
3002	+	if ((ws = workQueues) != null) {
3003	+	for (int i = 0; i < ws.length; ++i) {
3004	+	if ((w = ws[i]) != null) {
3005	+	int size = w.queueSize();
3006	+	if ((i & 1) == 0)
3007	+	qs += size;
3008	+	else {
3009	+	qt += size;
3010	+	st += w.nsteals;
3011	+	if (w.isApparentlyUnblocked())
3012	+	++rc;
3013	+	}
3014	+	}
3015	+	}
3016	+	}
3017	+	int pc = (config & SMASK);
3018		int tc = pc + (short)(c >>> TC_SHIFT);
3019		int ac = pc + (int)(c >> AC_SHIFT);
3020		if (ac < 0) // ignore transient negative
#	Line 2350 \| Line 3023 \| public class ForkJoinPool extends Abstra
3023		if ((c & STOP_BIT) != 0)
3024		level = (tc == 0) ? "Terminated" : "Terminating";
3025		else
3026	<	level = runState < 0 ? "Shutting down" : "Running";
3026	>	level = plock < 0 ? "Shutting down" : "Running";
3027		return super.toString() +
3028		"[" + level +
3029		", parallelism = " + pc +
#	Line 2364 \| Line 3037 \| public class ForkJoinPool extends Abstra
3037		}
3038
3039		/**
3040	<	* Initiates an orderly shutdown in which previously submitted
3041	<	* tasks are executed, but no new tasks will be accepted.
3042	<	* Invocation has no additional effect if already shut down.
3043	<	* Tasks that are in the process of being submitted concurrently
3044	<	* during the course of this method may or may not be rejected.
3040	>	* Possibly initiates an orderly shutdown in which previously
3041	>	* submitted tasks are executed, but no new tasks will be
3042	>	* accepted. Invocation has no effect on execution state if this
3043	>	* is the {@link #commonPool}, and no additional effect if
3044	>	* already shut down. Tasks that are in the process of being
3045	>	* submitted concurrently during the course of this method may or
3046	>	* may not be rejected.
3047		*
3048		* @throws SecurityException if a security manager exists and
3049		* the caller is not permitted to modify threads
#	Line 2377 \| Line 3052 \| public class ForkJoinPool extends Abstra
3052		*/
3053		public void shutdown() {
3054		checkPermission();
3055	<	enableShutdown();
2381	<	tryTerminate(false);
3055	>	tryTerminate(false, true);
3056		}
3057
3058		/**
3059	<	* Attempts to cancel and/or stop all tasks, and reject all
3060	<	* subsequently submitted tasks. Tasks that are in the process of
3061	<	* being submitted or executed concurrently during the course of
3062	<	* this method may or may not be rejected. This method cancels
3063	<	* both existing and unexecuted tasks, in order to permit
3064	<	* termination in the presence of task dependencies. So the method
3065	<	* always returns an empty list (unlike the case for some other
3066	<	* Executors).
3059	>	* Possibly attempts to cancel and/or stop all tasks, and reject
3060	>	* all subsequently submitted tasks. Invocation has no effect on
3061	>	* execution state if this is the {@link #commonPool}, and no
3062	>	* additional effect if already shut down. Otherwise, tasks that
3063	>	* are in the process of being submitted or executed concurrently
3064	>	* during the course of this method may or may not be
3065	>	* rejected. This method cancels both existing and unexecuted
3066	>	* tasks, in order to permit termination in the presence of task
3067	>	* dependencies. So the method always returns an empty list
3068	>	* (unlike the case for some other Executors).
3069		*
3070		* @return an empty list
3071		* @throws SecurityException if a security manager exists and
#	Line 2399 \| Line 3075 \| public class ForkJoinPool extends Abstra
3075		*/
3076		public List<Runnable> shutdownNow() {
3077		checkPermission();
3078	<	enableShutdown();
2403	<	tryTerminate(true);
3078	>	tryTerminate(true, true);
3079		return Collections.emptyList();
3080		}
3081
#	Line 2412 \| Line 3087 \| public class ForkJoinPool extends Abstra
3087		public boolean isTerminated() {
3088		long c = ctl;
3089		return ((c & STOP_BIT) != 0L &&
3090	<	(short)(c >>> TC_SHIFT) == -parallelism);
3090	>	(short)(c >>> TC_SHIFT) == -(config & SMASK));
3091		}
3092
3093		/**
#	Line 2420 \| Line 3095 \| public class ForkJoinPool extends Abstra
3095		* commenced but not yet completed. This method may be useful for
3096		* debugging. A return of {@code true} reported a sufficient
3097		* period after shutdown may indicate that submitted tasks have
3098	<	* ignored or suppressed interruption, or are waiting for IO,
3098	>	* ignored or suppressed interruption, or are waiting for I/O,
3099		* causing this executor not to properly terminate. (See the
3100		* advisory notes for class {@link ForkJoinTask} stating that
3101		* tasks should not normally entail blocking operations. But if
#	Line 2431 \| Line 3106 \| public class ForkJoinPool extends Abstra
3106		public boolean isTerminating() {
3107		long c = ctl;
3108		return ((c & STOP_BIT) != 0L &&
3109	<	(short)(c >>> TC_SHIFT) != -parallelism);
3109	>	(short)(c >>> TC_SHIFT) != -(config & SMASK));
3110		}
3111
3112		/**
#	Line 2440 \| Line 3115 \| public class ForkJoinPool extends Abstra
3115		* @return {@code true} if this pool has been shut down
3116		*/
3117		public boolean isShutdown() {
3118	<	return runState < 0;
3118	>	return plock < 0;
3119		}
3120
3121		/**
3122	<	* Blocks until all tasks have completed execution after a shutdown
3123	<	* request, or the timeout occurs, or the current thread is
3124	<	* interrupted, whichever happens first.
3122	>	* Blocks until all tasks have completed execution after a
3123	>	* shutdown request, or the timeout occurs, or the current thread
3124	>	* is interrupted, whichever happens first. Note that the {@link
3125	>	* #commonPool()} never terminates until program shutdown so
3126	>	* this method will always time out.
3127		*
3128		* @param timeout the maximum time to wait
3129		* @param unit the time unit of the timeout argument
#	Line 2457 \| Line 3134 \| public class ForkJoinPool extends Abstra
3134		public boolean awaitTermination(long timeout, TimeUnit unit)
3135		throws InterruptedException {
3136		long nanos = unit.toNanos(timeout);
3137	<	final ReentrantLock lock = this.lock;
3138	<	lock.lock();
3139	<	try {
3140	<	for (;;) {
3141	<	if (isTerminated())
3142	<	return true;
3143	<	if (nanos <= 0)
3144	<	return false;
3145	<	nanos = termination.awaitNanos(nanos);
3137	>	if (isTerminated())
3138	>	return true;
3139	>	long startTime = System.nanoTime();
3140	>	boolean terminated = false;
3141	>	synchronized (this) {
3142	>	for (long waitTime = nanos, millis = 0L;;) {
3143	>	if (terminated = isTerminated() \|\|
3144	>	waitTime <= 0L \|\|
3145	>	(millis = unit.toMillis(waitTime)) <= 0L)
3146	>	break;
3147	>	wait(millis);
3148	>	waitTime = nanos - (System.nanoTime() - startTime);
3149		}
2470	–	} finally {
2471	–	lock.unlock();
3150		}
3151	+	return terminated;
3152		}
3153
3154		/**
#	Line 2553 \| Line 3232 \| public class ForkJoinPool extends Abstra
3232		*
3233		* <p>If the caller is not a {@link ForkJoinTask}, this method is
3234		* behaviorally equivalent to
3235	<	a * <pre> {@code
3235	>	* <pre> {@code
3236		* while (!blocker.isReleasable())
3237		* if (blocker.block())
3238		* return;
#	Line 2568 \| Line 3247 \| *a <pre> {@code**
3247		public static void managedBlock(ManagedBlocker blocker)
3248		throws InterruptedException {
3249		Thread t = Thread.currentThread();
3250	<	ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ?
3251	<	((ForkJoinWorkerThread)t).pool : null);
3252	<	while (!blocker.isReleasable()) {
3253	<	if (p == null \|\| p.tryCompensate()) {
3254	<	try {
3255	<	do {} while (!blocker.isReleasable() && !blocker.block());
3256	<	} finally {
3257	<	if (p != null)
3250	>	if (t instanceof ForkJoinWorkerThread) {
3251	>	ForkJoinPool p = ((ForkJoinWorkerThread)t).pool;
3252	>	while (!blocker.isReleasable()) { // variant of helpSignal
3253	>	WorkQueue[] ws; WorkQueue q; int m, u;
3254	>	if ((ws = p.workQueues) != null && (m = ws.length - 1) >= 0) {
3255	>	for (int i = 0; i <= m; ++i) {
3256	>	if (blocker.isReleasable())
3257	>	return;
3258	>	if ((q = ws[i]) != null && q.base - q.top < 0) {
3259	>	p.signalWork(q);
3260	>	if ((u = (int)(p.ctl >>> 32)) >= 0 \|\|
3261	>	(u >> UAC_SHIFT) >= 0)
3262	>	break;
3263	>	}
3264	>	}
3265	>	}
3266	>	if (p.tryCompensate()) {
3267	>	try {
3268	>	do {} while (!blocker.isReleasable() &&
3269	>	!blocker.block());
3270	>	} finally {
3271		p.incrementActiveCount();
3272	+	}
3273	+	break;
3274		}
2581	–	break;
3275		}
3276		}
3277	+	else {
3278	+	do {} while (!blocker.isReleasable() &&
3279	+	!blocker.block());
3280	+	}
3281		}
3282
3283		// AbstractExecutorService overrides. These rely on undocumented
#	Line 2588 \| Line 3285 \| *a <pre> {@code**
3285		// implement RunnableFuture.
3286
3287		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
3288	<	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
3288	>	return new ForkJoinTask.AdaptedRunnable<T>(runnable, value);
3289		}
3290
3291		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
3292	<	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
3292	>	return new ForkJoinTask.AdaptedCallable<T>(callable);
3293		}
3294
3295		// Unsafe mechanics
3296		private static final sun.misc.Unsafe U;
3297		private static final long CTL;
2601	–	private static final long RUNSTATE;
3298		private static final long PARKBLOCKER;
3299	+	private static final int ABASE;
3300	+	private static final int ASHIFT;
3301	+	private static final long STEALCOUNT;
3302	+	private static final long PLOCK;
3303	+	private static final long INDEXSEED;
3304	+	private static final long QLOCK;
3305
3306		static {
3307	<	poolNumberGenerator = new AtomicInteger();
2606	<	modifyThreadPermission = new RuntimePermission("modifyThread");
2607	<	defaultForkJoinWorkerThreadFactory =
2608	<	new DefaultForkJoinWorkerThreadFactory();
2609	<	int s;
3307	>	int s; // initialize field offsets for CAS etc
3308		try {
3309		U = getUnsafe();
3310		Class<?> k = ForkJoinPool.class;
2613	–	Class<?> tk = Thread.class;
3311		CTL = U.objectFieldOffset
3312		(k.getDeclaredField("ctl"));
3313	<	RUNSTATE = U.objectFieldOffset
3314	<	(k.getDeclaredField("runState"));
3313	>	STEALCOUNT = U.objectFieldOffset
3314	>	(k.getDeclaredField("stealCount"));
3315	>	PLOCK = U.objectFieldOffset
3316	>	(k.getDeclaredField("plock"));
3317	>	INDEXSEED = U.objectFieldOffset
3318	>	(k.getDeclaredField("indexSeed"));
3319	>	Class<?> tk = Thread.class;
3320		PARKBLOCKER = U.objectFieldOffset
3321		(tk.getDeclaredField("parkBlocker"));
3322	+	Class<?> wk = WorkQueue.class;
3323	+	QLOCK = U.objectFieldOffset
3324	+	(wk.getDeclaredField("qlock"));
3325	+	Class<?> ak = ForkJoinTask[].class;
3326	+	ABASE = U.arrayBaseOffset(ak);
3327	+	s = U.arrayIndexScale(ak);
3328	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3329		} catch (Exception e) {
3330		throw new Error(e);
3331		}
3332	+	if ((s & (s-1)) != 0)
3333	+	throw new Error("data type scale not a power of two");
3334	+
3335	+	submitters = new ThreadLocal<Submitter>();
3336	+	ForkJoinWorkerThreadFactory fac = defaultForkJoinWorkerThreadFactory =
3337	+	new DefaultForkJoinWorkerThreadFactory();
3338	+	modifyThreadPermission = new RuntimePermission("modifyThread");
3339	+
3340	+	/*
3341	+	* Establish common pool parameters. For extra caution,
3342	+	* computations to set up common pool state are here; the
3343	+	* constructor just assigns these values to fields.
3344	+	*/
3345	+
3346	+	int par = 0;
3347	+	Thread.UncaughtExceptionHandler handler = null;
3348	+	try { // TBD: limit or report ignored exceptions?
3349	+	String pp = System.getProperty
3350	+	("java.util.concurrent.ForkJoinPool.common.parallelism");
3351	+	String hp = System.getProperty
3352	+	("java.util.concurrent.ForkJoinPool.common.exceptionHandler");
3353	+	String fp = System.getProperty
3354	+	("java.util.concurrent.ForkJoinPool.common.threadFactory");
3355	+	if (fp != null)
3356	+	fac = ((ForkJoinWorkerThreadFactory)ClassLoader.
3357	+	getSystemClassLoader().loadClass(fp).newInstance());
3358	+	if (hp != null)
3359	+	handler = ((Thread.UncaughtExceptionHandler)ClassLoader.
3360	+	getSystemClassLoader().loadClass(hp).newInstance());
3361	+	if (pp != null)
3362	+	par = Integer.parseInt(pp);
3363	+	} catch (Exception ignore) {
3364	+	}
3365	+
3366	+	if (par <= 0)
3367	+	par = Runtime.getRuntime().availableProcessors();
3368	+	if (par > MAX_CAP)
3369	+	par = MAX_CAP;
3370	+	commonPoolParallelism = par;
3371	+	long np = (long)(-par); // precompute initial ctl value
3372	+	long ct = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
3373	+
3374	+	commonPool = new ForkJoinPool(par, ct, fac, handler);
3375		}
3376
3377		/**

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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 1.158 by dl, Sat Dec 15 20:21:30 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 1.158 by dl, Sat Dec 15 20:21:30 2012 UTC