[ViewVC] Diff of: jsr166/jsr166/src/jsr166e/ForkJoinPool.java

Comparing jsr166/src/jsr166e/ForkJoinPool.java (file contents):
Revision 1.5 by jsr166, Sun Oct 21 04:14:31 2012 UTC vs.
Revision 1.58 by dl, Wed Jun 19 14:55:40 2013 UTC

#	Line 5 \| Line 5
5		*/
6
7		package jsr166e;
8	+
9	+	import java.lang.Thread.UncaughtExceptionHandler;
10		import java.util.ArrayList;
11		import java.util.Arrays;
12		import java.util.Collection;
13		import java.util.Collections;
14		import java.util.List;
13	–	import java.util.Random;
15		import java.util.concurrent.AbstractExecutorService;
16		import java.util.concurrent.Callable;
17		import java.util.concurrent.ExecutorService;
18		import java.util.concurrent.Future;
19		import java.util.concurrent.RejectedExecutionException;
20		import java.util.concurrent.RunnableFuture;
21	+	import java.util.concurrent.ThreadLocalRandom;
22		import java.util.concurrent.TimeUnit;
21	–	import java.util.concurrent.atomic.AtomicInteger;
22	–	import java.util.concurrent.atomic.AtomicLong;
23	–	import java.util.concurrent.locks.AbstractQueuedSynchronizer;
24	–	import java.util.concurrent.locks.Condition;
23
24		/**
25		* An {@link ExecutorService} for running {@link ForkJoinTask}s.
#	Line 41 \| Line 39 \| import java.util.concurrent.locks.Condit
39		* ForkJoinPool}s may also be appropriate for use with event-style
40		* tasks that are never joined.
41		*
42	<	* <p>A {@code ForkJoinPool} is constructed with a given target
43	<	* parallelism level; by default, equal to the number of available
44	<	* processors. The pool attempts to maintain enough active (or
45	<	* available) threads by dynamically adding, suspending, or resuming
46	<	* internal worker threads, even if some tasks are stalled waiting to
47	<	* join others. However, no such adjustments are guaranteed in the
48	<	* face of blocked IO or other unmanaged synchronization. The nested
49	<	* {@link ManagedBlocker} interface enables extension of the kinds of
42	>	* <p>A static {@link #commonPool()} is available and appropriate for
43	>	* most applications. The common pool is used by any ForkJoinTask that
44	>	* is not explicitly submitted to a specified pool. Using the common
45	>	* pool normally reduces resource usage (its threads are slowly
46	>	* reclaimed during periods of non-use, and reinstated upon subsequent
47	>	* use).
48	>	*
49	>	* <p>For applications that require separate or custom pools, a {@code
50	>	* ForkJoinPool} may be constructed with a given target parallelism
51	>	* level; by default, equal to the number of available processors. The
52	>	* pool attempts to maintain enough active (or available) threads by
53	>	* dynamically adding, suspending, or resuming internal worker
54	>	* threads, even if some tasks are stalled waiting to join others.
55	>	* However, no such adjustments are guaranteed in the face of blocked
56	>	* I/O or other unmanaged synchronization. The nested {@link
57	>	* ManagedBlocker} interface enables extension of the kinds of
58		* synchronization accommodated.
59		*
60		* <p>In addition to execution and lifecycle control methods, this
#	Line 58 \| Line 64 \| import java.util.concurrent.locks.Condit
64		* {@link #toString} returns indications of pool state in a
65		* convenient form for informal monitoring.
66		*
67	<	* <p> As is the case with other ExecutorServices, there are three
67	>	* <p>As is the case with other ExecutorServices, there are three
68		* main task execution methods summarized in the following table.
69		* These are designed to be used primarily by clients not already
70		* engaged in fork/join computations in the current pool. The main
#	Line 71 \| Line 77 \| import java.util.concurrent.locks.Condit
77		* there is little difference among choice of methods.
78		*
79		* <table BORDER CELLPADDING=3 CELLSPACING=1>
80	+	* <caption>Summary of task execution methods</caption>
81		* <tr>
82		* <td></td>
83		* <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
84		* <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
85		* </tr>
86		* <tr>
87	<	* <td> <b>Arrange async execution</td>
87	>	* <td> <b>Arrange async execution</b></td>
88		* <td> {@link #execute(ForkJoinTask)}</td>
89		* <td> {@link ForkJoinTask#fork}</td>
90		* </tr>
91		* <tr>
92	<	* <td> <b>Await and obtain result</td>
92	>	* <td> <b>Await and obtain result</b></td>
93		* <td> {@link #invoke(ForkJoinTask)}</td>
94		* <td> {@link ForkJoinTask#invoke}</td>
95		* </tr>
96		* <tr>
97	<	* <td> <b>Arrange exec and obtain Future</td>
97	>	* <td> <b>Arrange exec and obtain Future</b></td>
98		* <td> {@link #submit(ForkJoinTask)}</td>
99		* <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td>
100		* </tr>
101		* </table>
102		*
103	<	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
104	<	* used for all parallel task execution in a program or subsystem.
105	<	* Otherwise, use would not usually outweigh the construction and
106	<	* bookkeeping overhead of creating a large set of threads. For
107	<	* example, a common pool could be used for the {@code SortTasks}
108	<	* illustrated in {@link RecursiveAction}. Because {@code
109	<	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
110	<	* daemon} mode, there is typically no need to explicitly {@link
111	<	* #shutdown} such a pool upon program exit.
112	<	*
113	<	* <pre> {@code
114	<	* static final ForkJoinPool mainPool = new ForkJoinPool();
115	<	* ...
116	<	* public void sort(long[] array) {
117	<	* mainPool.invoke(new SortTask(array, 0, array.length));
118	<	* }}</pre>
103	>	* <p>The common pool is by default constructed with default
104	>	* parameters, but these may be controlled by setting three
105	>	* {@linkplain System#getProperty system properties}:
106	>	* <ul>
107	>	* <li>{@code java.util.concurrent.ForkJoinPool.common.parallelism}
108	>	* - the parallelism level, a non-negative integer
109	>	* <li>{@code java.util.concurrent.ForkJoinPool.common.threadFactory}
110	>	* - the class name of a {@link ForkJoinWorkerThreadFactory}
111	>	* <li>{@code java.util.concurrent.ForkJoinPool.common.exceptionHandler}
112	>	* - the class name of a {@link UncaughtExceptionHandler}
113	>	* </ul>
114	>	* The system class loader is used to load these classes.
115	>	* Upon any error in establishing these settings, default parameters
116	>	* are used. It is possible to disable or limit the use of threads in
117	>	* the common pool by setting the parallelism property to zero, and/or
118	>	* using a factory that may return {@code null}.
119		*
120		* <p><b>Implementation notes</b>: This implementation restricts the
121		* maximum number of running threads to 32767. Attempts to create
#	Line 154 \| Line 161 \| public class ForkJoinPool extends Abstra
161		* (http://research.sun.com/scalable/pubs/index.html) and
162		* "Idempotent work stealing" by Michael, Saraswat, and Vechev,
163		* PPoPP 2009 (http://portal.acm.org/citation.cfm?id=1504186).
164	<	* The main differences ultimately stem from GC requirements that
165	<	* we null out taken slots as soon as we can, to maintain as small
166	<	* a footprint as possible even in programs generating huge
167	<	* numbers of tasks. To accomplish this, we shift the CAS
168	<	* arbitrating pop vs poll (steal) from being on the indices
169	<	* ("base" and "top") to the slots themselves. So, both a
170	<	* successful pop and poll mainly entail a CAS of a slot from
171	<	* non-null to null. Because we rely on CASes of references, we
172	<	* do not need tag bits on base or top. They are simple ints as
173	<	* used in any circular array-based queue (see for example
174	<	* ArrayDeque). Updates to the indices must still be ordered in a
175	<	* way that guarantees that top == base means the queue is empty,
176	<	* but otherwise may err on the side of possibly making the queue
177	<	* appear nonempty when a push, pop, or poll have not fully
178	<	* committed. Note that this means that the poll operation,
179	<	* considered individually, is not wait-free. One thief cannot
180	<	* successfully continue until another in-progress one (or, if
181	<	* previously empty, a push) completes. However, in the
182	<	* aggregate, we ensure at least probabilistic non-blockingness.
183	<	* If an attempted steal fails, a thief always chooses a different
184	<	* random victim target to try next. So, in order for one thief to
185	<	* progress, it suffices for any in-progress poll or new push on
186	<	* any empty queue to complete. (This is why we normally use
187	<	* method pollAt and its variants that try once at the apparent
188	<	* base index, else consider alternative actions, rather than
189	<	* method poll.)
164	>	* See also "Correct and Efficient Work-Stealing for Weak Memory
165	>	* Models" by Le, Pop, Cohen, and Nardelli, PPoPP 2013
166	>	* (http://www.di.ens.fr/~zappa/readings/ppopp13.pdf) for an
167	>	* analysis of memory ordering (atomic, volatile etc) issues. The
168	>	* main differences ultimately stem from GC requirements that we
169	>	* null out taken slots as soon as we can, to maintain as small a
170	>	* footprint as possible even in programs generating huge numbers
171	>	* of tasks. To accomplish this, we shift the CAS arbitrating pop
172	>	* vs poll (steal) from being on the indices ("base" and "top") to
173	>	* the slots themselves. So, both a successful pop and poll
174	>	* mainly entail a CAS of a slot from non-null to null. Because
175	>	* we rely on CASes of references, we do not need tag bits on base
176	>	* or top. They are simple ints as used in any circular
177	>	* array-based queue (see for example ArrayDeque). Updates to the
178	>	* indices must still be ordered in a way that guarantees that top
179	>	* == base means the queue is empty, but otherwise may err on the
180	>	* side of possibly making the queue appear nonempty when a push,
181	>	* pop, or poll have not fully committed. Note that this means
182	>	* that the poll operation, considered individually, is not
183	>	* wait-free. One thief cannot successfully continue until another
184	>	* in-progress one (or, if previously empty, a push) completes.
185	>	* However, in the aggregate, we ensure at least probabilistic
186	>	* non-blockingness. If an attempted steal fails, a thief always
187	>	* chooses a different random victim target to try next. So, in
188	>	* order for one thief to progress, it suffices for any
189	>	* in-progress poll or new push on any empty queue to
190	>	* complete. (This is why we normally use method pollAt and its
191	>	* variants that try once at the apparent base index, else
192	>	* consider alternative actions, rather than method poll.)
193		*
194		* This approach also enables support of a user mode in which local
195		* task processing is in FIFO, not LIFO order, simply by using
#	Line 196 \| Line 206 \| public class ForkJoinPool extends Abstra
206		* WorkQueues are also used in a similar way for tasks submitted
207		* to the pool. We cannot mix these tasks in the same queues used
208		* for work-stealing (this would contaminate lifo/fifo
209	<	* processing). Instead, we loosely associate submission queues
209	>	* processing). Instead, we randomly associate submission queues
210		* with submitting threads, using a form of hashing. The
211	<	* ThreadLocal Submitter class contains a value initially used as
212	<	* a hash code for choosing existing queues, but may be randomly
213	<	* repositioned upon contention with other submitters. In
214	<	* essence, submitters act like workers except that they never
215	<	* take tasks, and they are multiplexed on to a finite number of
216	<	* shared work queues. However, classes are set up so that future
217	<	* extensions could allow submitters to optionally help perform
218	<	* tasks as well. Insertion of tasks in shared mode requires a
219	<	* lock (mainly to protect in the case of resizing) but we use
220	<	* only a simple spinlock (using bits in field runState), because
221	<	* submitters encountering a busy queue move on to try or create
222	<	* other queues -- they block only when creating and registering
223	<	* new queues.
211	>	* Submitter probe value serves as a hash code for
212	>	* choosing existing queues, and may be randomly repositioned upon
213	>	* contention with other submitters. In essence, submitters act
214	>	* like workers except that they are restricted to executing local
215	>	* tasks that they submitted (or in the case of CountedCompleters,
216	>	* others with the same root task). However, because most
217	>	* shared/external queue operations are more expensive than
218	>	* internal, and because, at steady state, external submitters
219	>	* will compete for CPU with workers, ForkJoinTask.join and
220	>	* related methods disable them from repeatedly helping to process
221	>	* tasks if all workers are active. Insertion of tasks in shared
222	>	* mode requires a lock (mainly to protect in the case of
223	>	* resizing) but we use only a simple spinlock (using bits in
224	>	* field qlock), because submitters encountering a busy queue move
225	>	* on to try or create other queues -- they block only when
226	>	* creating and registering new queues.
227		*
228		* Management
229		* ==========
#	Line 232 \| Line 245 \| public class ForkJoinPool extends Abstra
245		* and their negations (used for thresholding) to fit into 16bit
246		* fields.
247		*
248	<	* Field "runState" contains 32 bits needed to register and
249	<	* deregister WorkQueues, as well as to enable shutdown. It is
250	<	* only modified under a lock (normally briefly held, but
251	<	* occasionally protecting allocations and resizings) but even
252	<	* when locked remains available to check consistency.
248	>	* Field "plock" is a form of sequence lock with a saturating
249	>	* shutdown bit (similarly for per-queue "qlocks"), mainly
250	>	* protecting updates to the workQueues array, as well as to
251	>	* enable shutdown. When used as a lock, it is normally only very
252	>	* briefly held, so is nearly always available after at most a
253	>	* brief spin, but we use a monitor-based backup strategy to
254	>	* block when needed.
255		*
256		* Recording WorkQueues. WorkQueues are recorded in the
257	<	* "workQueues" array that is created upon pool construction and
258	<	* expanded if necessary. Updates to the array while recording
259	<	* new workers and unrecording terminated ones are protected from
260	<	* each other by a lock but the array is otherwise concurrently
261	<	* readable, and accessed directly. To simplify index-based
262	<	* operations, the array size is always a power of two, and all
263	<	* readers must tolerate null slots. Shared (submission) queues
264	<	* are at even indices, worker queues at odd indices. Grouping
265	<	* them together in this way simplifies and speeds up task
266	<	* scanning.
257	>	* "workQueues" array that is created upon first use and expanded
258	>	* if necessary. Updates to the array while recording new workers
259	>	* and unrecording terminated ones are protected from each other
260	>	* by a lock but the array is otherwise concurrently readable, and
261	>	* accessed directly. To simplify index-based operations, the
262	>	* array size is always a power of two, and all readers must
263	>	* tolerate null slots. Worker queues are at odd indices. Shared
264	>	* (submission) queues are at even indices, up to a maximum of 64
265	>	* slots, to limit growth even if array needs to expand to add
266	>	* more workers. Grouping them together in this way simplifies and
267	>	* speeds up task scanning.
268		*
269		* All worker thread creation is on-demand, triggered by task
270		* submissions, replacement of terminated workers, and/or
#	Line 293 \| Line 309 \| public class ForkJoinPool extends Abstra
309		* has not yet entered the wait queue. We solve this by requiring
310		* a full sweep of all workers (via repeated calls to method
311		* scan()) both before and after a newly waiting worker is added
312	<	* to the wait queue. During a rescan, the worker might release
313	<	* some other queued worker rather than itself, which has the same
314	<	* net effect. Because enqueued workers may actually be rescanning
315	<	* rather than waiting, we set and clear the "parker" field of
316	<	* WorkQueues to reduce unnecessary calls to unpark. (This
317	<	* requires a secondary recheck to avoid missed signals.) Note
318	<	* the unusual conventions about Thread.interrupts surrounding
319	<	* parking and other blocking: Because interrupts are used solely
320	<	* to alert threads to check termination, which is checked anyway
321	<	* upon blocking, we clear status (using Thread.interrupted)
322	<	* before any call to park, so that park does not immediately
307	<	* return due to status being set via some other unrelated call to
308	<	* interrupt in user code.
312	>	* to the wait queue. Because enqueued workers may actually be
313	>	* rescanning rather than waiting, we set and clear the "parker"
314	>	* field of WorkQueues to reduce unnecessary calls to unpark.
315	>	* (This requires a secondary recheck to avoid missed signals.)
316	>	* Note the unusual conventions about Thread.interrupts
317	>	* surrounding parking and other blocking: Because interrupts are
318	>	* used solely to alert threads to check termination, which is
319	>	* checked anyway upon blocking, we clear status (using
320	>	* Thread.interrupted) before any call to park, so that park does
321	>	* not immediately return due to status being set via some other
322	>	* unrelated call to interrupt in user code.
323		*
324		* Signalling. We create or wake up workers only when there
325		* appears to be at least one task they might be able to find and
326		* execute. When a submission is added or another worker adds a
327	<	* task to a queue that previously had fewer than two tasks, they
328	<	* signal waiting workers (or trigger creation of new ones if
329	<	* fewer than the given parallelism level -- see signalWork).
330	<	* These primary signals are buttressed by signals during rescans;
331	<	* together these cover the signals needed in cases when more
332	<	* tasks are pushed but untaken, and improve performance compared
333	<	* to having one thread wake up all workers.
327	>	* task to a queue that has fewer than two tasks, they signal
328	>	* waiting workers (or trigger creation of new ones if fewer than
329	>	* the given parallelism level -- signalWork). These primary
330	>	* signals are buttressed by others whenever other threads remove
331	>	* a task from a queue and notice that there are other tasks there
332	>	* as well. So in general, pools will be over-signalled. On most
333	>	* platforms, signalling (unpark) overhead time is noticeably
334	>	* long, and the time between signalling a thread and it actually
335	>	* making progress can be very noticeably long, so it is worth
336	>	* offloading these delays from critical paths as much as
337	>	* possible. Additionally, workers spin-down gradually, by staying
338	>	* alive so long as they see the ctl state changing. Similar
339	>	* stability-sensing techniques are also used before blocking in
340	>	* awaitJoin and helpComplete.
341		*
342		* Trimming workers. To release resources after periods of lack of
343		* use, a worker starting to wait when the pool is quiescent will
344	<	* time out and terminate if the pool has remained quiescent for
345	<	* SHRINK_RATE nanosecs. This will slowly propagate, eventually
346	<	* terminating all workers after long periods of non-use.
344	>	* time out and terminate if the pool has remained quiescent for a
345	>	* given period -- a short period if there are more threads than
346	>	* parallelism, longer as the number of threads decreases. This
347	>	* will slowly propagate, eventually terminating all workers after
348	>	* periods of non-use.
349		*
350		* Shutdown and Termination. A call to shutdownNow atomically sets
351	<	* a runState bit and then (non-atomically) sets each worker's
352	<	* runState status, cancels all unprocessed tasks, and wakes up
351	>	* a plock bit and then (non-atomically) sets each worker's
352	>	* qlock status, cancels all unprocessed tasks, and wakes up
353		* all waiting workers. Detecting whether termination should
354		* commence after a non-abrupt shutdown() call requires more work
355		* and bookkeeping. We need consensus about quiescence (i.e., that
#	Line 354 \| Line 377 \| public class ForkJoinPool extends Abstra
377		* method tryCompensate() may create or re-activate a spare
378		* thread to compensate for blocked joiners until they unblock.
379		*
380	<	* A third form (implemented in tryRemoveAndExec and
381	<	* tryPollForAndExec) amounts to helping a hypothetical
382	<	* compensator: If we can readily tell that a possible action of a
383	<	* compensator is to steal and execute the task being joined, the
384	<	* joining thread can do so directly, without the need for a
385	<	* compensation thread (although at the expense of larger run-time
386	<	* stacks, but the tradeoff is typically worthwhile).
380	>	* A third form (implemented in tryRemoveAndExec) amounts to
381	>	* helping a hypothetical compensator: If we can readily tell that
382	>	* a possible action of a compensator is to steal and execute the
383	>	* task being joined, the joining thread can do so directly,
384	>	* without the need for a compensation thread (although at the
385	>	* expense of larger run-time stacks, but the tradeoff is
386	>	* typically worthwhile).
387		*
388		* The ManagedBlocker extension API can't use helping so relies
389		* only on compensation in method awaitBlocker.
#	Line 382 \| Line 405 \| public class ForkJoinPool extends Abstra
405		* steals, rather than use per-task bookkeeping. This sometimes
406		* requires a linear scan of workQueues array to locate stealers,
407		* but often doesn't because stealers leave hints (that may become
408	<	* stale/wrong) of where to locate them. A stealHint is only a
409	<	* hint because a worker might have had multiple steals and the
410	<	* hint records only one of them (usually the most current).
411	<	* Hinting isolates cost to when it is needed, rather than adding
412	<	* to per-task overhead. (2) It is "shallow", ignoring nesting
413	<	* and potentially cyclic mutual steals. (3) It is intentionally
408	>	* stale/wrong) of where to locate them. It is only a hint
409	>	* because a worker might have had multiple steals and the hint
410	>	* records only one of them (usually the most current). Hinting
411	>	* isolates cost to when it is needed, rather than adding to
412	>	* per-task overhead. (2) It is "shallow", ignoring nesting and
413	>	* potentially cyclic mutual steals. (3) It is intentionally
414		* racy: field currentJoin is updated only while actively joining,
415		* which means that we miss links in the chain during long-lived
416		* tasks, GC stalls etc (which is OK since blocking in such cases
#	Line 395 \| Line 418 \| public class ForkJoinPool extends Abstra
418		* to find work (see MAX_HELP) and fall back to suspending the
419		* worker and if necessary replacing it with another.
420		*
421	+	* Helping actions for CountedCompleters are much simpler: Method
422	+	* helpComplete can take and execute any task with the same root
423	+	* as the task being waited on. However, this still entails some
424	+	* traversal of completer chains, so is less efficient than using
425	+	* CountedCompleters without explicit joins.
426	+	*
427		* It is impossible to keep exactly the target parallelism number
428		* of threads running at any given time. Determining the
429		* existence of conservatively safe helping targets, the
#	Line 416 \| Line 445 \| public class ForkJoinPool extends Abstra
445		* intractable) game with an opponent that may choose the worst
446		* (for us) active thread to stall at any time. We take several
447		* precautions to bound losses (and thus bound gains), mainly in
448	<	* methods tryCompensate and awaitJoin: (1) We only try
449	<	* compensation after attempting enough helping steps (measured
450	<	* via counting and timing) that we have already consumed the
451	<	* estimated cost of creating and activating a new thread. (2) We
452	<	* allow up to 50% of threads to be blocked before initially
453	<	* adding any others, and unless completely saturated, check that
454	<	* some work is available for a new worker before adding. Also, we
455	<	* create up to only 50% more threads until entering a mode that
456	<	* only adds a thread if all others are possibly blocked. All
457	<	* together, this means that we might be half as fast to react,
458	<	* and create half as many threads as possible in the ideal case,
459	<	* but present vastly fewer anomalies in all other cases compared
460	<	* to both more aggressive and more conservative alternatives.
461	<	*
462	<	* Style notes: There is a lot of representation-level coupling
463	<	* among classes ForkJoinPool, ForkJoinWorkerThread, and
464	<	* ForkJoinTask. The fields of WorkQueue maintain data structures
465	<	* managed by ForkJoinPool, so are directly accessed. There is
466	<	* little point trying to reduce this, since any associated future
467	<	* changes in representations will need to be accompanied by
468	<	* algorithmic changes anyway. Several methods intrinsically
469	<	* sprawl because they must accumulate sets of consistent reads of
470	<	* volatiles held in local variables. Methods signalWork() and
471	<	* scan() are the main bottlenecks, so are especially heavily
448	>	* methods tryCompensate and awaitJoin.
449	>	*
450	>	* Common Pool
451	>	* ===========
452	>	*
453	>	* The static common pool always exists after static
454	>	* initialization. Since it (or any other created pool) need
455	>	* never be used, we minimize initial construction overhead and
456	>	* footprint to the setup of about a dozen fields, with no nested
457	>	* allocation. Most bootstrapping occurs within method
458	>	* fullExternalPush during the first submission to the pool.
459	>	*
460	>	* When external threads submit to the common pool, they can
461	>	* perform subtask processing (see externalHelpJoin and related
462	>	* methods). This caller-helps policy makes it sensible to set
463	>	* common pool parallelism level to one (or more) less than the
464	>	* total number of available cores, or even zero for pure
465	>	* caller-runs. We do not need to record whether external
466	>	* submissions are to the common pool -- if not, externalHelpJoin
467	>	* returns quickly (at the most helping to signal some common pool
468	>	* workers). These submitters would otherwise be blocked waiting
469	>	* for completion, so the extra effort (with liberally sprinkled
470	>	* task status checks) in inapplicable cases amounts to an odd
471	>	* form of limited spin-wait before blocking in ForkJoinTask.join.
472	>	*
473	>	* Style notes
474	>	* ===========
475	>	*
476	>	* There is a lot of representation-level coupling among classes
477	>	* ForkJoinPool, ForkJoinWorkerThread, and ForkJoinTask. The
478	>	* fields of WorkQueue maintain data structures managed by
479	>	* ForkJoinPool, so are directly accessed. There is little point
480	>	* trying to reduce this, since any associated future changes in
481	>	* representations will need to be accompanied by algorithmic
482	>	* changes anyway. Several methods intrinsically sprawl because
483	>	* they must accumulate sets of consistent reads of volatiles held
484	>	* in local variables. Methods signalWork() and scan() are the
485	>	* main bottlenecks, so are especially heavily
486		* micro-optimized/mangled. There are lots of inline assignments
487		* (of form "while ((local = field) != 0)") which are usually the
488		* simplest way to ensure the required read orderings (which are
#	Line 447 \| Line 490 \| public class ForkJoinPool extends Abstra
490		* declarations of these locals at the heads of methods or blocks.
491		* There are several occurrences of the unusual "do {} while
492		* (!cas...)" which is the simplest way to force an update of a
493	<	* CAS'ed variable. There are also other coding oddities that help
493	>	* CAS'ed variable. There are also other coding oddities (including
494	>	* several unnecessary-looking hoisted null checks) that help
495		* some methods perform reasonably even when interpreted (not
496		* compiled).
497		*
#	Line 488 \| Line 532 \| public class ForkJoinPool extends Abstra
532		*
533		* @param pool the pool this thread works in
534		* @throws NullPointerException if the pool is null
535	+	* @return the new worker thread
536		*/
537		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
538		}
#	Line 496 \| Line 541 \| public class ForkJoinPool extends Abstra
541		* Default ForkJoinWorkerThreadFactory implementation; creates a
542		* new ForkJoinWorkerThread.
543		*/
544	<	static class DefaultForkJoinWorkerThreadFactory
544	>	static final class DefaultForkJoinWorkerThreadFactory
545		implements ForkJoinWorkerThreadFactory {
546	<	public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
546	>	public final ForkJoinWorkerThread newThread(ForkJoinPool pool) {
547		return new ForkJoinWorkerThread(pool);
548		}
549		}
550
551		/**
507	–	* A simple non-reentrant lock used for exclusion when managing
508	–	* queues and workers. We use a custom lock so that we can readily
509	–	* probe lock state in constructions that check among alternative
510	–	* actions. The lock is normally only very briefly held, and
511	–	* sometimes treated as a spinlock, but other usages block to
512	–	* reduce overall contention in those cases where locked code
513	–	* bodies perform allocation/resizing.
514	–	*/
515	–	static final class Mutex extends AbstractQueuedSynchronizer {
516	–	public final boolean tryAcquire(int ignore) {
517	–	return compareAndSetState(0, 1);
518	–	}
519	–	public final boolean tryRelease(int ignore) {
520	–	setState(0);
521	–	return true;
522	–	}
523	–	public final void lock() { acquire(0); }
524	–	public final void unlock() { release(0); }
525	–	public final boolean isHeldExclusively() { return getState() == 1; }
526	–	public final Condition newCondition() { return new ConditionObject(); }
527	–	}
528	–
529	–	/**
552		* Class for artificial tasks that are used to replace the target
553		* of local joins if they are removed from an interior queue slot
554		* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
555		* actually do anything beyond having a unique identity.
556		*/
557		static final class EmptyTask extends ForkJoinTask<Void> {
558	+	private static final long serialVersionUID = -7721805057305804111L;
559		EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
560		public final Void getRawResult() { return null; }
561		public final void setRawResult(Void x) {}
#	Line 553 \| Line 576 \| public class ForkJoinPool extends Abstra
576		*
577		* Field "top" is the index (mod array.length) of the next queue
578		* slot to push to or pop from. It is written only by owner thread
579	<	* for push, or under lock for trySharedPush, and accessed by
580	<	* other threads only after reading (volatile) base. Both top and
581	<	* base are allowed to wrap around on overflow, but (top - base)
582	<	* (or more commonly -(base - top) to force volatile read of base
583	<	* before top) still estimates size.
579	>	* for push, or under lock for external/shared push, and accessed
580	>	* by other threads only after reading (volatile) base. Both top
581	>	* and base are allowed to wrap around on overflow, but (top -
582	>	* base) (or more commonly -(base - top) to force volatile read of
583	>	* base before top) still estimates size. The lock ("qlock") is
584	>	* forced to -1 on termination, causing all further lock attempts
585	>	* to fail. (Note: we don't need CAS for termination state because
586	>	* upon pool shutdown, all shared-queues will stop being used
587	>	* anyway.) Nearly all lock bodies are set up so that exceptions
588	>	* within lock bodies are "impossible" (modulo JVM errors that
589	>	* would cause failure anyway.)
590		*
591		* The array slots are read and written using the emulation of
592		* volatiles/atomics provided by Unsafe. Insertions must in
593		* general use putOrderedObject as a form of releasing store to
594		* ensure that all writes to the task object are ordered before
595	<	* its publication in the queue. (Although we can avoid one case
596	<	* of this when locked in trySharedPush.) All removals entail a
597	<	* CAS to null. The array is always a power of two. To ensure
598	<	* safety of Unsafe array operations, all accesses perform
570	<	* explicit null checks and implicit bounds checks via
571	<	* power-of-two masking.
595	>	* its publication in the queue. All removals entail a CAS to
596	>	* null. The array is always a power of two. To ensure safety of
597	>	* Unsafe array operations, all accesses perform explicit null
598	>	* checks and implicit bounds checks via power-of-two masking.
599		*
600		* In addition to basic queuing support, this class contains
601		* fields described elsewhere to control execution. It turns out
602	<	* to work better memory-layout-wise to include them in this
603	<	* class rather than a separate class.
602	>	* to work better memory-layout-wise to include them in this class
603	>	* rather than a separate class.
604		*
605		* Performance on most platforms is very sensitive to placement of
606		* instances of both WorkQueues and their arrays -- we absolutely
607		* do not want multiple WorkQueue instances or multiple queue
608		* arrays sharing cache lines. (It would be best for queue objects
609		* and their arrays to share, but there is nothing available to
610	<	* help arrange that). Unfortunately, because they are recorded
611	<	* in a common array, WorkQueue instances are often moved to be
585	<	* adjacent by garbage collectors. To reduce impact, we use field
586	<	* padding that works OK on common platforms; this effectively
587	<	* trades off slightly slower average field access for the sake of
588	<	* avoiding really bad worst-case access. (Until better JVM
589	<	* support is in place, this padding is dependent on transient
590	<	* properties of JVM field layout rules.) We also take care in
591	<	* allocating, sizing and resizing the array. Non-shared queue
592	<	* arrays are initialized (via method growArray) by workers before
593	<	* use. Others are allocated on first use.
610	>	* help arrange that). The @Contended annotation alerts JVMs to
611	>	* try to keep instances apart.
612		*/
613		static final class WorkQueue {
614		/**
#	Line 613 \| Line 631 \| public class ForkJoinPool extends Abstra
631		*/
632		static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
633
634	<	volatile long totalSteals; // cumulative number of steals
635	<	int seed; // for random scanning; initialize nonzero
634	>	// Heuristic padding to ameliorate unfortunate memory placements
635	>	volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
636	>
637		volatile int eventCount; // encoded inactivation count; < 0 if inactive
638		int nextWait; // encoded record of next event waiter
639	<	int rescans; // remaining scans until block
640	<	int nsteals; // top-level task executions since last idle
641	<	final int mode; // lifo, fifo, or shared
642	<	int poolIndex; // index of this queue in pool (or 0)
643	<	int stealHint; // index of most recent known stealer
625	<	volatile int runState; // 1: locked, -1: terminate; else 0
639	>	int nsteals; // number of steals
640	>	int hint; // steal index hint
641	>	short poolIndex; // index of this queue in pool
642	>	final short mode; // 0: lifo, > 0: fifo, < 0: shared
643	>	volatile int qlock; // 1: locked, -1: terminate; else 0
644		volatile int base; // index of next slot for poll
645		int top; // index of next slot for push
646		ForkJoinTask<?>[] array; // the elements (initially unallocated)
#	Line 631 \| Line 649 \| public class ForkJoinPool extends Abstra
649		volatile Thread parker; // == owner during call to park; else null
650		volatile ForkJoinTask<?> currentJoin; // task being joined in awaitJoin
651		ForkJoinTask<?> currentSteal; // current non-local task being executed
634	–	// Heuristic padding to ameliorate unfortunate memory placements
635	–	Object p00, p01, p02, p03, p04, p05, p06, p07;
636	–	Object p08, p09, p0a, p0b, p0c, p0d, p0e;
652
653	<	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode) {
654	<	this.mode = mode;
653	>	volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
654	>	volatile Object pad18, pad19, pad1a, pad1b, pad1c, pad1d;
655	>
656	>	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode,
657	>	int seed) {
658		this.pool = pool;
659		this.owner = owner;
660	+	this.mode = (short)mode;
661	+	this.hint = seed; // store initial seed for runWorker
662		// Place indices in the center of array (that is not yet allocated)
663		base = top = INITIAL_QUEUE_CAPACITY >>> 1;
664		}
#	Line 663 \| Line 683 \| public class ForkJoinPool extends Abstra
683		(n == -1 &&
684		((a = array) == null \|\|
685		(m = a.length - 1) < 0 \|\|
686	<	U.getObjectVolatile
687	<	(a, ((m & (s - 1)) << ASHIFT) + ABASE) == null)));
686	>	U.getObject
687	>	(a, (long)((m & (s - 1)) << ASHIFT) + ABASE) == null)));
688		}
689
690		/**
691	<	* Pushes a task. Call only by owner in unshared queues.
691	>	* Pushes a task. Call only by owner in unshared queues. (The
692	>	* shared-queue version is embedded in method externalPush.)
693		*
694		* @param task the task. Caller must ensure non-null.
695	<	* @throw RejectedExecutionException if array cannot be resized
695	>	* @throws RejectedExecutionException if array cannot be resized
696		*/
697		final void push(ForkJoinTask<?> task) {
698		ForkJoinTask<?>[] a; ForkJoinPool p;
699	<	int s = top, m, n;
699	>	int s = top, n;
700		if ((a = array) != null) { // ignore if queue removed
701	<	U.putOrderedObject
702	<	(a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task);
703	<	if ((n = (top = s + 1) - base) <= 2) {
704	<	if ((p = pool) != null)
684	<	p.signalWork();
685	<	}
701	>	int m = a.length - 1;
702	>	U.putOrderedObject(a, ((m & s) << ASHIFT) + ABASE, task);
703	>	if ((n = (top = s + 1) - base) <= 2)
704	>	(p = pool).signalWork(p.workQueues, this);
705		else if (n >= m)
706	<	growArray(true);
706	>	growArray();
707		}
708		}
709
710		/**
711	<	* Pushes a task if lock is free and array is either big
712	<	* enough or can be resized to be big enough.
713	<	*
695	<	* @param task the task. Caller must ensure non-null.
696	<	* @return true if submitted
711	>	* Initializes or doubles the capacity of array. Call either
712	>	* by owner or with lock held -- it is OK for base, but not
713	>	* top, to move while resizings are in progress.
714		*/
715	<	final boolean trySharedPush(ForkJoinTask<?> task) {
716	<	boolean submitted = false;
717	<	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
718	<	ForkJoinTask<?>[] a = array;
719	<	int s = top;
720	<	try {
721	<	if ((a != null && a.length > s + 1 - base) \|\|
722	<	(a = growArray(false)) != null) { // must presize
723	<	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
724	<	U.putObject(a, (long)j, task); // don't need "ordered"
725	<	top = s + 1;
726	<	submitted = true;
727	<	}
728	<	} finally {
729	<	runState = 0; // unlock
730	<	}
715	>	final ForkJoinTask<?>[] growArray() {
716	>	ForkJoinTask<?>[] oldA = array;
717	>	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
718	>	if (size > MAXIMUM_QUEUE_CAPACITY)
719	>	throw new RejectedExecutionException("Queue capacity exceeded");
720	>	int oldMask, t, b;
721	>	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
722	>	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
723	>	(t = top) - (b = base) > 0) {
724	>	int mask = size - 1;
725	>	do {
726	>	ForkJoinTask<?> x;
727	>	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
728	>	int j = ((b & mask) << ASHIFT) + ABASE;
729	>	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
730	>	if (x != null &&
731	>	U.compareAndSwapObject(oldA, oldj, x, null))
732	>	U.putObjectVolatile(a, j, x);
733	>	} while (++b != t);
734		}
735	<	return submitted;
735	>	return a;
736		}
737
738		/**
739		* Takes next task, if one exists, in LIFO order. Call only
740	<	* by owner in unshared queues. (We do not have a shared
721	<	* version of this method because it is never needed.)
740	>	* by owner in unshared queues.
741		*/
742		final ForkJoinTask<?> pop() {
743		ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
#	Line 746 \| Line 765 \| public class ForkJoinPool extends Abstra
765		if ((a = array) != null) {
766		int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
767		if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
768	<	base == b &&
769	<	U.compareAndSwapObject(a, j, t, null)) {
751	<	base = b + 1;
768	>	base == b && U.compareAndSwapObject(a, j, t, null)) {
769	>	U.putOrderedInt(this, QBASE, b + 1);
770		return t;
771		}
772		}
#	Line 764 \| Line 782 \| public class ForkJoinPool extends Abstra
782		int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
783		t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
784		if (t != null) {
785	<	if (base == b &&
786	<	U.compareAndSwapObject(a, j, t, null)) {
769	<	base = b + 1;
785	>	if (U.compareAndSwapObject(a, j, t, null)) {
786	>	U.putOrderedInt(this, QBASE, b + 1);
787		return t;
788		}
789		}
790		else if (base == b) {
791		if (b + 1 == top)
792		break;
793	<	Thread.yield(); // wait for lagging update
793	>	Thread.yield(); // wait for lagging update (very rare)
794		}
795		}
796		return null;
#	Line 800 \| Line 817 \| public class ForkJoinPool extends Abstra
817
818		/**
819		* Pops the given task only if it is at the current top.
820	+	* (A shared version is available only via FJP.tryExternalUnpush)
821		*/
822		final boolean tryUnpush(ForkJoinTask<?> t) {
823		ForkJoinTask<?>[] a; int s;
#	Line 813 \| Line 831 \| public class ForkJoinPool extends Abstra
831		}
832
833		/**
816	–	* Polls the given task only if it is at the current base.
817	–	*/
818	–	final boolean pollFor(ForkJoinTask<?> task) {
819	–	ForkJoinTask<?>[] a; int b;
820	–	if ((b = base) - top < 0 && (a = array) != null) {
821	–	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
822	–	if (U.getObjectVolatile(a, j) == task && base == b &&
823	–	U.compareAndSwapObject(a, j, task, null)) {
824	–	base = b + 1;
825	–	return true;
826	–	}
827	–	}
828	–	return false;
829	–	}
830	–
831	–	/**
832	–	* Initializes or doubles the capacity of array. Call either
833	–	* by owner or with lock held -- it is OK for base, but not
834	–	* top, to move while resizings are in progress.
835	–	*
836	–	* @param rejectOnFailure if true, throw exception if capacity
837	–	* exceeded (relayed ultimately to user); else return null.
838	–	*/
839	–	final ForkJoinTask<?>[] growArray(boolean rejectOnFailure) {
840	–	ForkJoinTask<?>[] oldA = array;
841	–	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
842	–	if (size <= MAXIMUM_QUEUE_CAPACITY) {
843	–	int oldMask, t, b;
844	–	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
845	–	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
846	–	(t = top) - (b = base) > 0) {
847	–	int mask = size - 1;
848	–	do {
849	–	ForkJoinTask<?> x;
850	–	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
851	–	int j = ((b & mask) << ASHIFT) + ABASE;
852	–	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
853	–	if (x != null &&
854	–	U.compareAndSwapObject(oldA, oldj, x, null))
855	–	U.putObjectVolatile(a, j, x);
856	–	} while (++b != t);
857	–	}
858	–	return a;
859	–	}
860	–	else if (!rejectOnFailure)
861	–	return null;
862	–	else
863	–	throw new RejectedExecutionException("Queue capacity exceeded");
864	–	}
865	–
866	–	/**
834		* Removes and cancels all known tasks, ignoring any exceptions.
835		*/
836		final void cancelAll() {
#	Line 873 \| Line 840 \| public class ForkJoinPool extends Abstra
840		ForkJoinTask.cancelIgnoringExceptions(t);
841		}
842
843	<	/**
877	<	* Computes next value for random probes. Scans don't require
878	<	* a very high quality generator, but also not a crummy one.
879	<	* Marsaglia xor-shift is cheap and works well enough. Note:
880	<	* This is manually inlined in its usages in ForkJoinPool to
881	<	* avoid writes inside busy scan loops.
882	<	*/
883	<	final int nextSeed() {
884	<	int r = seed;
885	<	r ^= r << 13;
886	<	r ^= r >>> 17;
887	<	return seed = r ^= r << 5;
888	<	}
889	<
890	<	// Execution methods
891	<
892	<	/**
893	<	* Pops and runs tasks until empty.
894	<	*/
895	<	private void popAndExecAll() {
896	<	// A bit faster than repeated pop calls
897	<	ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t;
898	<	while ((a = array) != null && (m = a.length - 1) >= 0 &&
899	<	(s = top - 1) - base >= 0 &&
900	<	(t = ((ForkJoinTask<?>)
901	<	U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
902	<	!= null) {
903	<	if (U.compareAndSwapObject(a, j, t, null)) {
904	<	top = s;
905	<	t.doExec();
906	<	}
907	<	}
908	<	}
843	>	// Specialized execution methods
844
845		/**
846		* Polls and runs tasks until empty.
847		*/
848	<	private void pollAndExecAll() {
848	>	final void pollAndExecAll() {
849		for (ForkJoinTask<?> t; (t = poll()) != null;)
850		t.doExec();
851		}
852
853		/**
854	<	* If present, removes from queue and executes the given task, or
855	<	* any other cancelled task. Returns (true) immediately on any CAS
854	>	* Executes a top-level task and any local tasks remaining
855	>	* after execution.
856	>	*/
857	>	final void runTask(ForkJoinTask<?> task) {
858	>	if ((currentSteal = task) != null) {
859	>	task.doExec();
860	>	ForkJoinTask<?>[] a = array;
861	>	int md = mode;
862	>	++nsteals;
863	>	currentSteal = null;
864	>	if (md != 0)
865	>	pollAndExecAll();
866	>	else if (a != null) {
867	>	int s, m = a.length - 1;
868	>	while ((s = top - 1) - base >= 0) {
869	>	long i = ((m & s) << ASHIFT) + ABASE;
870	>	ForkJoinTask<?> t = (ForkJoinTask<?>)U.getObject(a, i);
871	>	if (t == null)
872	>	break;
873	>	if (U.compareAndSwapObject(a, i, t, null)) {
874	>	top = s;
875	>	t.doExec();
876	>	}
877	>	}
878	>	}
879	>	}
880	>	}
881	>
882	>	/**
883	>	* If present, removes from queue and executes the given task,
884	>	* or any other cancelled task. Returns (true) on any CAS
885		* or consistency check failure so caller can retry.
886		*
887	<	* @return 0 if no progress can be made, else positive
924	<	* (this unusual convention simplifies use with tryHelpStealer.)
887	>	* @return false if no progress can be made, else true
888		*/
889	<	final int tryRemoveAndExec(ForkJoinTask<?> task) {
890	<	int stat = 1;
928	<	boolean removed = false, empty = true;
889	>	final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
890	>	boolean stat;
891		ForkJoinTask<?>[] a; int m, s, b, n;
892	<	if ((a = array) != null && (m = a.length - 1) >= 0 &&
892	>	if (task != null && (a = array) != null && (m = a.length - 1) >= 0 &&
893		(n = (s = top) - (b = base)) > 0) {
894	+	boolean removed = false, empty = true;
895	+	stat = true;
896		for (ForkJoinTask<?> t;;) { // traverse from s to b
897	<	int j = ((--s & m) << ASHIFT) + ABASE;
898	<	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
897	>	long j = ((--s & m) << ASHIFT) + ABASE;
898	>	t = (ForkJoinTask<?>)U.getObject(a, j);
899		if (t == null) // inconsistent length
900		break;
901		else if (t == task) {
#	Line 955 \| Line 919 \| public class ForkJoinPool extends Abstra
919		}
920		if (--n == 0) {
921		if (!empty && base == b)
922	<	stat = 0;
922	>	stat = false;
923		break;
924		}
925		}
926	+	if (removed)
927	+	task.doExec();
928		}
929	<	if (removed)
930	<	task.doExec();
929	>	else
930	>	stat = false;
931		return stat;
932		}
933
934		/**
935	<	* Executes a top-level task and any local tasks remaining
936	<	* after execution.
935	>	* Tries to poll for and execute the given task or any other
936	>	* task in its CountedCompleter computation.
937		*/
938	<	final void runTask(ForkJoinTask<?> t) {
939	<	if (t != null) {
940	<	currentSteal = t;
941	<	t.doExec();
942	<	if (top != base) { // process remaining local tasks
943	<	if (mode == 0)
944	<	popAndExecAll();
945	<	else
946	<	pollAndExecAll();
938	>	final boolean pollAndExecCC(CountedCompleter<?> root) {
939	>	ForkJoinTask<?>[] a; int b; Object o; CountedCompleter<?> t, r;
940	>	if ((b = base) - top < 0 && (a = array) != null) {
941	>	long j = (((a.length - 1) & b) << ASHIFT) + ABASE;
942	>	if ((o = U.getObjectVolatile(a, j)) == null)
943	>	return true; // retry
944	>	if (o instanceof CountedCompleter) {
945	>	for (t = (CountedCompleter<?>)o, r = t;;) {
946	>	if (r == root) {
947	>	if (base == b &&
948	>	U.compareAndSwapObject(a, j, t, null)) {
949	>	U.putOrderedInt(this, QBASE, b + 1);
950	>	t.doExec();
951	>	}
952	>	return true;
953	>	}
954	>	else if ((r = r.completer) == null)
955	>	break; // not part of root computation
956	>	}
957		}
982	–	++nsteals;
983	–	currentSteal = null;
958		}
959	+	return false;
960		}
961
962		/**
963	<	* Executes a non-top-level (stolen) task.
963	>	* Tries to pop and execute the given task or any other task
964	>	* in its CountedCompleter computation.
965		*/
966	<	final void runSubtask(ForkJoinTask<?> t) {
967	<	if (t != null) {
968	<	ForkJoinTask<?> ps = currentSteal;
969	<	currentSteal = t;
970	<	t.doExec();
971	<	currentSteal = ps;
966	>	final boolean externalPopAndExecCC(CountedCompleter<?> root) {
967	>	ForkJoinTask<?>[] a; int s; Object o; CountedCompleter<?> t, r;
968	>	if (base - (s = top) < 0 && (a = array) != null) {
969	>	long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE;
970	>	if ((o = U.getObject(a, j)) instanceof CountedCompleter) {
971	>	for (t = (CountedCompleter<?>)o, r = t;;) {
972	>	if (r == root) {
973	>	if (U.compareAndSwapInt(this, QLOCK, 0, 1)) {
974	>	if (top == s && array == a &&
975	>	U.compareAndSwapObject(a, j, t, null)) {
976	>	top = s - 1;
977	>	qlock = 0;
978	>	t.doExec();
979	>	}
980	>	else
981	>	qlock = 0;
982	>	}
983	>	return true;
984	>	}
985	>	else if ((r = r.completer) == null)
986	>	break;
987	>	}
988	>	}
989		}
990	+	return false;
991	+	}
992	+
993	+	/**
994	+	* Internal version
995	+	*/
996	+	final boolean internalPopAndExecCC(CountedCompleter<?> root) {
997	+	ForkJoinTask<?>[] a; int s; Object o; CountedCompleter<?> t, r;
998	+	if (base - (s = top) < 0 && (a = array) != null) {
999	+	long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE;
1000	+	if ((o = U.getObject(a, j)) instanceof CountedCompleter) {
1001	+	for (t = (CountedCompleter<?>)o, r = t;;) {
1002	+	if (r == root) {
1003	+	if (U.compareAndSwapObject(a, j, t, null)) {
1004	+	top = s - 1;
1005	+	t.doExec();
1006	+	}
1007	+	return true;
1008	+	}
1009	+	else if ((r = r.completer) == null)
1010	+	break;
1011	+	}
1012	+	}
1013	+	}
1014	+	return false;
1015		}
1016
1017		/**
#	Line 1008 \| Line 1026 \| public class ForkJoinPool extends Abstra
1026		s != Thread.State.TIMED_WAITING);
1027		}
1028
1011	–	/**
1012	–	* If this owned and is not already interrupted, try to
1013	–	* interrupt and/or unpark, ignoring exceptions.
1014	–	*/
1015	–	final void interruptOwner() {
1016	–	Thread wt, p;
1017	–	if ((wt = owner) != null && !wt.isInterrupted()) {
1018	–	try {
1019	–	wt.interrupt();
1020	–	} catch (SecurityException ignore) {
1021	–	}
1022	–	}
1023	–	if ((p = parker) != null)
1024	–	U.unpark(p);
1025	–	}
1026	–
1029		// Unsafe mechanics
1030		private static final sun.misc.Unsafe U;
1031	<	private static final long RUNSTATE;
1031	>	private static final long QBASE;
1032	>	private static final long QLOCK;
1033		private static final int ABASE;
1034		private static final int ASHIFT;
1035		static {
1033	–	int s;
1036		try {
1037		U = getUnsafe();
1038		Class<?> k = WorkQueue.class;
1039		Class<?> ak = ForkJoinTask[].class;
1040	<	RUNSTATE = U.objectFieldOffset
1041	<	(k.getDeclaredField("runState"));
1040	>	QBASE = U.objectFieldOffset
1041	>	(k.getDeclaredField("base"));
1042	>	QLOCK = U.objectFieldOffset
1043	>	(k.getDeclaredField("qlock"));
1044		ABASE = U.arrayBaseOffset(ak);
1045	<	s = U.arrayIndexScale(ak);
1045	>	int scale = U.arrayIndexScale(ak);
1046	>	if ((scale & (scale - 1)) != 0)
1047	>	throw new Error("data type scale not a power of two");
1048	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
1049		} catch (Exception e) {
1050		throw new Error(e);
1051		}
1045	–	if ((s & (s-1)) != 0)
1046	–	throw new Error("data type scale not a power of two");
1047	–	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
1052		}
1053		}
1054
1055	+	// static fields (initialized in static initializer below)
1056	+
1057		/**
1058	<	* Per-thread records for threads that submit to pools. Currently
1059	<	* holds only pseudo-random seed / index that is used to choose
1060	<	* submission queues in method doSubmit. In the future, this may
1061	<	* also incorporate a means to implement different task rejection
1062	<	* and resubmission policies.
1057	<	*
1058	<	* Seeds for submitters and workers/workQueues work in basically
1059	<	* the same way but are initialized and updated using slightly
1060	<	* different mechanics. Both are initialized using the same
1061	<	* approach as in class ThreadLocal, where successive values are
1062	<	* unlikely to collide with previous values. This is done during
1063	<	* registration for workers, but requires a separate AtomicInteger
1064	<	* for submitters. Seeds are then randomly modified upon
1065	<	* collisions using xorshifts, which requires a non-zero seed.
1058	>	* Per-thread submission bookkeeping. Shared across all pools
1059	>	* to reduce ThreadLocal pollution and because random motion
1060	>	* to avoid contention in one pool is likely to hold for others.
1061	>	* Lazily initialized on first submission (but null-checked
1062	>	* in other contexts to avoid unnecessary initialization).
1063		*/
1064	<	static final class Submitter {
1068	<	int seed;
1069	<	Submitter() {
1070	<	int s = nextSubmitterSeed.getAndAdd(SEED_INCREMENT);
1071	<	seed = (s == 0) ? 1 : s; // ensure non-zero
1072	<	}
1073	<	}
1074	<
1075	<	/** ThreadLocal class for Submitters */
1076	<	static final class ThreadSubmitter extends ThreadLocal<Submitter> {
1077	<	public Submitter initialValue() { return new Submitter(); }
1078	<	}
1079	<
1080	<	// static fields (initialized in static initializer below)
1064	>	static final ThreadLocal<Submitter> submitters;
1065
1066		/**
1067		* Creates a new ForkJoinWorkerThread. This factory is used unless
#	Line 1087 \| Line 1071 \| public class ForkJoinPool extends Abstra
1071		defaultForkJoinWorkerThreadFactory;
1072
1073		/**
1074	<	* Generator for assigning sequence numbers as pool names.
1074	>	* Permission required for callers of methods that may start or
1075	>	* kill threads.
1076		*/
1077	<	private static final AtomicInteger poolNumberGenerator;
1077	>	private static final RuntimePermission modifyThreadPermission;
1078
1079		/**
1080	<	* Generator for initial hashes/seeds for submitters. Accessed by
1081	<	* Submitter class constructor.
1080	>	* Common (static) pool. Non-null for public use unless a static
1081	>	* construction exception, but internal usages null-check on use
1082	>	* to paranoically avoid potential initialization circularities
1083	>	* as well as to simplify generated code.
1084		*/
1085	<	static final AtomicInteger nextSubmitterSeed;
1085	>	static final ForkJoinPool common;
1086
1087		/**
1088	<	* Permission required for callers of methods that may start or
1089	<	* kill threads.
1088	>	* Common pool parallelism. To allow simpler use and management
1089	>	* when common pool threads are disabled, we allow the underlying
1090	>	* common.parallelism field to be zero, but in that case still report
1091	>	* parallelism as 1 to reflect resulting caller-runs mechanics.
1092		*/
1093	<	private static final RuntimePermission modifyThreadPermission;
1093	>	static final int commonParallelism;
1094
1095		/**
1096	<	* Per-thread submission bookkeeping. Shared across all pools
1108	<	* to reduce ThreadLocal pollution and because random motion
1109	<	* to avoid contention in one pool is likely to hold for others.
1096	>	* Sequence number for creating workerNamePrefix.
1097		*/
1098	<	private static final ThreadSubmitter submitters;
1098	>	private static int poolNumberSequence;
1099	>
1100	>	/**
1101	>	* Returns the next sequence number. We don't expect this to
1102	>	* ever contend, so use simple builtin sync.
1103	>	*/
1104	>	private static final synchronized int nextPoolId() {
1105	>	return ++poolNumberSequence;
1106	>	}
1107
1108		// static constants
1109
1110		/**
1111	<	* The wakeup interval (in nanoseconds) for a worker waiting for a
1112	<	* task when the pool is quiescent to instead try to shrink the
1113	<	* number of workers. The exact value does not matter too
1114	<	* much. It must be short enough to release resources during
1115	<	* sustained periods of idleness, but not so short that threads
1116	<	* are continually re-created.
1111	>	* Initial timeout value (in nanoseconds) for the thread
1112	>	* triggering quiescence to park waiting for new work. On timeout,
1113	>	* the thread will instead try to shrink the number of
1114	>	* workers. The value should be large enough to avoid overly
1115	>	* aggressive shrinkage during most transient stalls (long GCs
1116	>	* etc).
1117	>	*/
1118	>	private static final long IDLE_TIMEOUT = 2000L * 1000L * 1000L; // 2sec
1119	>
1120	>	/**
1121	>	* Timeout value when there are more threads than parallelism level
1122		*/
1123	<	private static final long SHRINK_RATE =
1124	<	4L * 1000L * 1000L * 1000L; // 4 seconds
1123	>	private static final long FAST_IDLE_TIMEOUT = 200L * 1000L * 1000L;
1124
1125		/**
1126	<	* The timeout value for attempted shrinkage, includes
1128	<	* some slop to cope with system timer imprecision.
1126	>	* Tolerance for idle timeouts, to cope with timer undershoots
1127		*/
1128	<	private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
1128	>	private static final long TIMEOUT_SLOP = 2000000L;
1129
1130		/**
1131		* The maximum stolen->joining link depth allowed in method
1132	<	* tryHelpStealer. Must be a power of two. This value also
1135	<	* controls the maximum number of times to try to help join a task
1136	<	* without any apparent progress or change in pool state before
1137	<	* giving up and blocking (see awaitJoin). Depths for legitimate
1132	>	* tryHelpStealer. Must be a power of two. Depths for legitimate
1133		* chains are unbounded, but we use a fixed constant to avoid
1134		* (otherwise unchecked) cycles and to bound staleness of
1135		* traversal parameters at the expense of sometimes blocking when
#	Line 1143 \| Line 1138 \| public class ForkJoinPool extends Abstra
1138		private static final int MAX_HELP = 64;
1139
1140		/**
1146	–	* Secondary time-based bound (in nanosecs) for helping attempts
1147	–	* before trying compensated blocking in awaitJoin. Used in
1148	–	* conjunction with MAX_HELP to reduce variance due to different
1149	–	* polling rates associated with different helping options. The
1150	–	* value should roughly approximate the time required to create
1151	–	* and/or activate a worker thread.
1152	–	*/
1153	–	private static final long COMPENSATION_DELAY = 1L << 18; // ~0.25 millisec
1154	–
1155	–	/**
1141		* Increment for seed generators. See class ThreadLocal for
1142		* explanation.
1143		*/
1144		private static final int SEED_INCREMENT = 0x61c88647;
1145
1146	<	/**
1146	>	/*
1147		* Bits and masks for control variables
1148		*
1149		* Field ctl is a long packed with:
#	Line 1186 \| Line 1171 \| public class ForkJoinPool extends Abstra
1171		* scan for them to avoid queuing races. Note however that
1172		* eventCount updates lag releases so usage requires care.
1173		*
1174	<	* Field runState is an int packed with:
1174	>	* Field plock is an int packed with:
1175		* SHUTDOWN: true if shutdown is enabled (1 bit)
1176	<	* SEQ: a sequence number updated upon (de)registering workers (30 bits)
1177	<	* INIT: set true after workQueues array construction (1 bit)
1176	>	* SEQ: a sequence lock, with PL_LOCK bit set if locked (30 bits)
1177	>	* SIGNAL: set when threads may be waiting on the lock (1 bit)
1178		*
1179		* The sequence number enables simple consistency checks:
1180		* Staleness of read-only operations on the workQueues array can
1181	<	* be checked by comparing runState before vs after the reads.
1181	>	* be checked by comparing plock before vs after the reads.
1182		*/
1183
1184		// bit positions/shifts for fields
#	Line 1205 \| Line 1190 \| public class ForkJoinPool extends Abstra
1190		// bounds
1191		private static final int SMASK = 0xffff; // short bits
1192		private static final int MAX_CAP = 0x7fff; // max #workers - 1
1193	<	private static final int SQMASK = 0xfffe; // even short bits
1193	>	private static final int EVENMASK = 0xfffe; // even short bits
1194	>	private static final int SQMASK = 0x007e; // max 64 (even) slots
1195		private static final int SHORT_SIGN = 1 << 15;
1196		private static final int INT_SIGN = 1 << 31;
1197
#	Line 1230 \| Line 1216 \| public class ForkJoinPool extends Abstra
1216		private static final int E_MASK = 0x7fffffff; // no STOP_BIT
1217		private static final int E_SEQ = 1 << EC_SHIFT;
1218
1219	<	// runState bits
1219	>	// plock bits
1220		private static final int SHUTDOWN = 1 << 31;
1221	+	private static final int PL_LOCK = 2;
1222	+	private static final int PL_SIGNAL = 1;
1223	+	private static final int PL_SPINS = 1 << 8;
1224
1225		// access mode for WorkQueue
1226		static final int LIFO_QUEUE = 0;
1227		static final int FIFO_QUEUE = 1;
1228		static final int SHARED_QUEUE = -1;
1229
1230	<	// Instance fields
1231	<
1243	<	/*
1244	<	* Field layout order in this class tends to matter more than one
1245	<	* would like. Runtime layout order is only loosely related to
1246	<	* declaration order and may differ across JVMs, but the following
1247	<	* empirically works OK on current JVMs.
1248	<	*/
1230	>	// Heuristic padding to ameliorate unfortunate memory placements
1231	>	volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
1232
1233	+	// Instance fields
1234	+	volatile long stealCount; // collects worker counts
1235		volatile long ctl; // main pool control
1236	<	final int parallelism; // parallelism level
1237	<	final int localMode; // per-worker scheduling mode
1238	<	final int submitMask; // submit queue index bound
1239	<	int nextSeed; // for initializing worker seeds
1255	<	volatile int runState; // shutdown status and seq
1236	>	volatile int plock; // shutdown status and seqLock
1237	>	volatile int indexSeed; // worker/submitter index seed
1238	>	final short parallelism; // parallelism level
1239	>	final short mode; // LIFO/FIFO
1240		WorkQueue[] workQueues; // main registry
1241	<	final Mutex lock; // for registration
1242	<	final Condition termination; // for awaitTermination
1259	<	final ForkJoinWorkerThreadFactory factory; // factory for new workers
1260	<	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1261	<	final AtomicLong stealCount; // collect counts when terminated
1262	<	final AtomicInteger nextWorkerNumber; // to create worker name string
1241	>	final ForkJoinWorkerThreadFactory factory;
1242	>	final UncaughtExceptionHandler ueh; // per-worker UEH
1243		final String workerNamePrefix; // to create worker name string
1244
1245	<	// Creating, registering, and deregistering workers
1245	>	volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
1246	>	volatile Object pad18, pad19, pad1a, pad1b;
1247
1248		/**
1249	<	* Tries to create and start a worker
1250	<	*/
1251	<	private void addWorker() {
1252	<	Throwable ex = null;
1253	<	ForkJoinWorkerThread wt = null;
1254	<	try {
1255	<	if ((wt = factory.newThread(this)) != null) {
1256	<	wt.start();
1257	<	return;
1249	>	* Acquires the plock lock to protect worker array and related
1250	>	* updates. This method is called only if an initial CAS on plock
1251	>	* fails. This acts as a spinlock for normal cases, but falls back
1252	>	* to builtin monitor to block when (rarely) needed. This would be
1253	>	* a terrible idea for a highly contended lock, but works fine as
1254	>	* a more conservative alternative to a pure spinlock.
1255	>	*/
1256	>	private int acquirePlock() {
1257	>	int spins = PL_SPINS, ps, nps;
1258	>	for (;;) {
1259	>	if (((ps = plock) & PL_LOCK) == 0 &&
1260	>	U.compareAndSwapInt(this, PLOCK, ps, nps = ps + PL_LOCK))
1261	>	return nps;
1262	>	else if (spins >= 0) {
1263	>	if (ThreadLocalRandom.current().nextInt() >= 0)
1264	>	--spins;
1265	>	}
1266	>	else if (U.compareAndSwapInt(this, PLOCK, ps, ps \| PL_SIGNAL)) {
1267	>	synchronized (this) {
1268	>	if ((plock & PL_SIGNAL) != 0) {
1269	>	try {
1270	>	wait();
1271	>	} catch (InterruptedException ie) {
1272	>	try {
1273	>	Thread.currentThread().interrupt();
1274	>	} catch (SecurityException ignore) {
1275	>	}
1276	>	}
1277	>	}
1278	>	else
1279	>	notifyAll();
1280	>	}
1281		}
1278	–	} catch (Throwable e) {
1279	–	ex = e;
1282		}
1281	–	deregisterWorker(wt, ex); // adjust counts etc on failure
1283		}
1284
1285		/**
1286	<	* Callback from ForkJoinWorkerThread constructor to assign a
1287	<	* public name. This must be separate from registerWorker because
1287	<	* it is called during the "super" constructor call in
1288	<	* ForkJoinWorkerThread.
1286	>	* Unlocks and signals any thread waiting for plock. Called only
1287	>	* when CAS of seq value for unlock fails.
1288		*/
1289	<	final String nextWorkerName() {
1290	<	return workerNamePrefix.concat
1291	<	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1289	>	private void releasePlock(int ps) {
1290	>	plock = ps;
1291	>	synchronized (this) { notifyAll(); }
1292		}
1293
1294		/**
1295	<	* Callback from ForkJoinWorkerThread constructor to establish its
1296	<	* poolIndex and record its WorkQueue. To avoid scanning bias due
1298	<	* to packing entries in front of the workQueues array, we treat
1299	<	* the array as a simple power-of-two hash table using per-thread
1300	<	* seed as hash, expanding as needed.
1301	<	*
1302	<	* @param w the worker's queue
1295	>	* Tries to create and start one worker if fewer than target
1296	>	* parallelism level exist. Adjusts counts etc on failure.
1297		*/
1298	+	private void tryAddWorker() {
1299	+	long c; int u, e;
1300	+	while ((u = (int)((c = ctl) >>> 32)) < 0 &&
1301	+	(u & SHORT_SIGN) != 0 && (e = (int)c) >= 0) {
1302	+	long nc = ((long)(((u + UTC_UNIT) & UTC_MASK) \|
1303	+	((u + UAC_UNIT) & UAC_MASK)) << 32) \| (long)e;
1304	+	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1305	+	ForkJoinWorkerThreadFactory fac;
1306	+	Throwable ex = null;
1307	+	ForkJoinWorkerThread wt = null;
1308	+	try {
1309	+	if ((fac = factory) != null &&
1310	+	(wt = fac.newThread(this)) != null) {
1311	+	wt.start();
1312	+	break;
1313	+	}
1314	+	} catch (Throwable rex) {
1315	+	ex = rex;
1316	+	}
1317	+	deregisterWorker(wt, ex);
1318	+	break;
1319	+	}
1320	+	}
1321	+	}
1322
1323	<	final void registerWorker(WorkQueue w) {
1324	<	Mutex lock = this.lock;
1325	<	lock.lock();
1323	>	// Registering and deregistering workers
1324	>
1325	>	/**
1326	>	* Callback from ForkJoinWorkerThread to establish and record its
1327	>	* WorkQueue. To avoid scanning bias due to packing entries in
1328	>	* front of the workQueues array, we treat the array as a simple
1329	>	* power-of-two hash table using per-thread seed as hash,
1330	>	* expanding as needed.
1331	>	*
1332	>	* @param wt the worker thread
1333	>	* @return the worker's queue
1334	>	*/
1335	>	final WorkQueue registerWorker(ForkJoinWorkerThread wt) {
1336	>	UncaughtExceptionHandler handler; WorkQueue[] ws; int s, ps;
1337	>	wt.setDaemon(true);
1338	>	if ((handler = ueh) != null)
1339	>	wt.setUncaughtExceptionHandler(handler);
1340	>	do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed,
1341	>	s += SEED_INCREMENT) \|\|
1342	>	s == 0); // skip 0
1343	>	WorkQueue w = new WorkQueue(this, wt, mode, s);
1344	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1345	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1346	>	ps = acquirePlock();
1347	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1348		try {
1349	<	WorkQueue[] ws = workQueues;
1350	<	if (w != null && ws != null) { // skip on shutdown/failure
1351	<	int rs, n = ws.length, m = n - 1;
1352	<	int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence
1353	<	w.seed = (s == 0) ? 1 : s; // ensure non-zero seed
1354	<	int r = (s << 1) \| 1; // use odd-numbered indices
1315	<	if (ws[r &= m] != null) { // collision
1316	<	int probes = 0; // step by approx half size
1317	<	int step = (n <= 4) ? 2 : ((n >>> 1) & SQMASK) + 2;
1349	>	if ((ws = workQueues) != null) { // skip if shutting down
1350	>	int n = ws.length, m = n - 1;
1351	>	int r = (s << 1) \| 1; // use odd-numbered indices
1352	>	if (ws[r &= m] != null) { // collision
1353	>	int probes = 0; // step by approx half size
1354	>	int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2;
1355		while (ws[r = (r + step) & m] != null) {
1356		if (++probes >= n) {
1357		workQueues = ws = Arrays.copyOf(ws, n <<= 1);
#	Line 1323 \| Line 1360 \| public class ForkJoinPool extends Abstra
1360		}
1361		}
1362		}
1363	<	w.eventCount = w.poolIndex = r; // establish before recording
1364	<	ws[r] = w; // also update seq
1365	<	runState = ((rs = runState) & SHUTDOWN) \| ((rs + 2) & ~SHUTDOWN);
1363	>	w.poolIndex = (short)r;
1364	>	w.eventCount = r; // volatile write orders
1365	>	ws[r] = w;
1366		}
1367		} finally {
1368	<	lock.unlock();
1368	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1369	>	releasePlock(nps);
1370		}
1371	+	wt.setName(workerNamePrefix.concat(Integer.toString(w.poolIndex >>> 1)));
1372	+	return w;
1373		}
1374
1375		/**
1376		* Final callback from terminating worker, as well as upon failure
1377	<	* to construct or start a worker in addWorker. Removes record of
1378	<	* worker from array, and adjusts counts. If pool is shutting
1379	<	* down, tries to complete termination.
1377	>	* to construct or start a worker. Removes record of worker from
1378	>	* array, and adjusts counts. If pool is shutting down, tries to
1379	>	* complete termination.
1380		*
1381	<	* @param wt the worker thread or null if addWorker failed
1381	>	* @param wt the worker thread, or null if construction failed
1382		* @param ex the exception causing failure, or null if none
1383		*/
1384		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1345	–	Mutex lock = this.lock;
1385		WorkQueue w = null;
1386		if (wt != null && (w = wt.workQueue) != null) {
1387	<	w.runState = -1; // ensure runState is set
1388	<	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1389	<	int idx = w.poolIndex;
1390	<	lock.lock();
1391	<	try { // remove record from array
1387	>	int ps; long sc;
1388	>	w.qlock = -1; // ensure set
1389	>	do {} while(!U.compareAndSwapLong(this, STEALCOUNT, sc = stealCount,
1390	>	sc + w.nsteals));
1391	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1392	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1393	>	ps = acquirePlock();
1394	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1395	>	try {
1396	>	int idx = w.poolIndex;
1397		WorkQueue[] ws = workQueues;
1398		if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1399		ws[idx] = null;
1400		} finally {
1401	<	lock.unlock();
1401	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1402	>	releasePlock(nps);
1403		}
1404		}
1405
1406	<	long c; // adjust ctl counts
1406	>	long c; // adjust ctl counts
1407		do {} while (!U.compareAndSwapLong
1408		(this, CTL, c = ctl, (((c - AC_UNIT) & AC_MASK) \|
1409		((c - TC_UNIT) & TC_MASK) \|
1410		(c & ~(AC_MASK\|TC_MASK)))));
1411
1412	<	if (!tryTerminate(false, false) && w != null) {
1413	<	w.cancelAll(); // cancel remaining tasks
1414	<	if (w.array != null) // suppress signal if never ran
1415	<	signalWork(); // wake up or create replacement
1416	<	if (ex == null) // help clean refs on way out
1417	<	ForkJoinTask.helpExpungeStaleExceptions();
1412	>	if (!tryTerminate(false, false) && w != null && w.array != null) {
1413	>	w.cancelAll(); // cancel remaining tasks
1414	>	WorkQueue[] ws; WorkQueue v; Thread p; int u, i, e;
1415	>	while ((u = (int)((c = ctl) >>> 32)) < 0 && (e = (int)c) >= 0) {
1416	>	if (e > 0) { // activate or create replacement
1417	>	if ((ws = workQueues) == null \|\|
1418	>	(i = e & SMASK) >= ws.length \|\|
1419	>	(v = ws[i]) == null)
1420	>	break;
1421	>	long nc = (((long)(v.nextWait & E_MASK)) \|
1422	>	((long)(u + UAC_UNIT) << 32));
1423	>	if (v.eventCount != (e \| INT_SIGN))
1424	>	break;
1425	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1426	>	v.eventCount = (e + E_SEQ) & E_MASK;
1427	>	if ((p = v.parker) != null)
1428	>	U.unpark(p);
1429	>	break;
1430	>	}
1431	>	}
1432	>	else {
1433	>	if ((short)u < 0)
1434	>	tryAddWorker();
1435	>	break;
1436	>	}
1437	>	}
1438		}
1439	<
1440	<	if (ex != null) // rethrow
1441	<	U.throwException(ex);
1439	>	if (ex == null) // help clean refs on way out
1440	>	ForkJoinTask.helpExpungeStaleExceptions();
1441	>	else // rethrow
1442	>	ForkJoinTask.rethrow(ex);
1443		}
1444
1379	–
1445		// Submissions
1446
1447		/**
1448	+	* Per-thread records for threads that submit to pools. Currently
1449	+	* holds only pseudo-random seed / index that is used to choose
1450	+	* submission queues in method externalPush. In the future, this may
1451	+	* also incorporate a means to implement different task rejection
1452	+	* and resubmission policies.
1453	+	*
1454	+	* Seeds for submitters and workers/workQueues work in basically
1455	+	* the same way but are initialized and updated using slightly
1456	+	* different mechanics. Both are initialized using the same
1457	+	* approach as in class ThreadLocal, where successive values are
1458	+	* unlikely to collide with previous values. Seeds are then
1459	+	* randomly modified upon collisions using xorshifts, which
1460	+	* requires a non-zero seed.
1461	+	*/
1462	+	static final class Submitter {
1463	+	int seed;
1464	+	Submitter(int s) { seed = s; }
1465	+	}
1466	+
1467	+	/**
1468		* Unless shutting down, adds the given task to a submission queue
1469		* at submitter's current queue index (modulo submission
1470	<	* range). If no queue exists at the index, one is created. If
1471	<	* the queue is busy, another index is randomly chosen. The
1387	<	* submitMask bounds the effective number of queues to the
1388	<	* (nearest power of two for) parallelism level.
1470	>	* range). Only the most common path is directly handled in this
1471	>	* method. All others are relayed to fullExternalPush.
1472		*
1473		* @param task the task. Caller must ensure non-null.
1474		*/
1475	<	private void doSubmit(ForkJoinTask<?> task) {
1476	<	Submitter s = submitters.get();
1477	<	for (int r = s.seed, m = submitMask;;) {
1478	<	WorkQueue[] ws; WorkQueue q;
1479	<	int k = r & m & SQMASK; // use only even indices
1480	<	if (runState < 0 \|\| (ws = workQueues) == null \|\| ws.length <= k)
1481	<	throw new RejectedExecutionException(); // shutting down
1482	<	else if ((q = ws[k]) == null) { // create new queue
1483	<	WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE);
1484	<	Mutex lock = this.lock; // construct outside lock
1485	<	lock.lock();
1486	<	try { // recheck under lock
1487	<	int rs = runState; // to update seq
1488	<	if (ws == workQueues && ws[k] == null) {
1489	<	ws[k] = nq;
1490	<	runState = ((rs & SHUTDOWN) \| ((rs + 2) & ~SHUTDOWN));
1408	<	}
1409	<	} finally {
1410	<	lock.unlock();
1411	<	}
1412	<	}
1413	<	else if (q.trySharedPush(task)) {
1414	<	signalWork();
1475	>	final void externalPush(ForkJoinTask<?> task) {
1476	>	Submitter z = submitters.get();
1477	>	WorkQueue q; int r, m, s, n, am; ForkJoinTask<?>[] a;
1478	>	int ps = plock;
1479	>	WorkQueue[] ws = workQueues;
1480	>	if (z != null && ps > 0 && ws != null && (m = (ws.length - 1)) >= 0 &&
1481	>	(q = ws[m & (r = z.seed) & SQMASK]) != null && r != 0 &&
1482	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock
1483	>	if ((a = q.array) != null &&
1484	>	(am = a.length - 1) > (n = (s = q.top) - q.base)) {
1485	>	int j = ((am & s) << ASHIFT) + ABASE;
1486	>	U.putOrderedObject(a, j, task);
1487	>	q.top = s + 1; // push on to deque
1488	>	q.qlock = 0;
1489	>	if (n <= 1)
1490	>	signalWork(ws, q);
1491		return;
1492		}
1493	<	else if (m > 1) { // move to a different index
1494	<	r ^= r << 13; // same xorshift as WorkQueues
1493	>	q.qlock = 0;
1494	>	}
1495	>	fullExternalPush(task);
1496	>	}
1497	>
1498	>	/**
1499	>	* Full version of externalPush. This method is called, among
1500	>	* other times, upon the first submission of the first task to the
1501	>	* pool, so must perform secondary initialization. It also
1502	>	* detects first submission by an external thread by looking up
1503	>	* its ThreadLocal, and creates a new shared queue if the one at
1504	>	* index if empty or contended. The plock lock body must be
1505	>	* exception-free (so no try/finally) so we optimistically
1506	>	* allocate new queues outside the lock and throw them away if
1507	>	* (very rarely) not needed.
1508	>	*
1509	>	* Secondary initialization occurs when plock is zero, to create
1510	>	* workQueue array and set plock to a valid value. This lock body
1511	>	* must also be exception-free. Because the plock seq value can
1512	>	* eventually wrap around zero, this method harmlessly fails to
1513	>	* reinitialize if workQueues exists, while still advancing plock.
1514	>	*/
1515	>	private void fullExternalPush(ForkJoinTask<?> task) {
1516	>	int r = 0; // random index seed
1517	>	for (Submitter z = submitters.get();;) {
1518	>	WorkQueue[] ws; WorkQueue q; int ps, m, k;
1519	>	if (z == null) {
1520	>	if (U.compareAndSwapInt(this, INDEXSEED, r = indexSeed,
1521	>	r += SEED_INCREMENT) && r != 0)
1522	>	submitters.set(z = new Submitter(r));
1523	>	}
1524	>	else if (r == 0) { // move to a different index
1525	>	r = z.seed;
1526	>	r ^= r << 13; // same xorshift as WorkQueues
1527		r ^= r >>> 17;
1528	<	s.seed = r ^= r << 5;
1528	>	z.seed = r ^= (r << 5);
1529	>	}
1530	>	if ((ps = plock) < 0)
1531	>	throw new RejectedExecutionException();
1532	>	else if (ps == 0 \|\| (ws = workQueues) == null \|\|
1533	>	(m = ws.length - 1) < 0) { // initialize workQueues
1534	>	int p = parallelism; // find power of two table size
1535	>	int n = (p > 1) ? p - 1 : 1; // ensure at least 2 slots
1536	>	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4;
1537	>	n \|= n >>> 8; n \|= n >>> 16; n = (n + 1) << 1;
1538	>	WorkQueue[] nws = ((ws = workQueues) == null \|\| ws.length == 0 ?
1539	>	new WorkQueue[n] : null);
1540	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1541	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1542	>	ps = acquirePlock();
1543	>	if (((ws = workQueues) == null \|\| ws.length == 0) && nws != null)
1544	>	workQueues = nws;
1545	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1546	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1547	>	releasePlock(nps);
1548	>	}
1549	>	else if ((q = ws[k = r & m & SQMASK]) != null) {
1550	>	if (q.qlock == 0 && U.compareAndSwapInt(q, QLOCK, 0, 1)) {
1551	>	ForkJoinTask<?>[] a = q.array;
1552	>	int s = q.top;
1553	>	boolean submitted = false;
1554	>	try { // locked version of push
1555	>	if ((a != null && a.length > s + 1 - q.base) \|\|
1556	>	(a = q.growArray()) != null) { // must presize
1557	>	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
1558	>	U.putOrderedObject(a, j, task);
1559	>	q.top = s + 1;
1560	>	submitted = true;
1561	>	}
1562	>	} finally {
1563	>	q.qlock = 0; // unlock
1564	>	}
1565	>	if (submitted) {
1566	>	signalWork(ws, q);
1567	>	return;
1568	>	}
1569	>	}
1570	>	r = 0; // move on failure
1571	>	}
1572	>	else if (((ps = plock) & PL_LOCK) == 0) { // create new queue
1573	>	q = new WorkQueue(this, null, SHARED_QUEUE, r);
1574	>	q.poolIndex = (short)k;
1575	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1576	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1577	>	ps = acquirePlock();
1578	>	if ((ws = workQueues) != null && k < ws.length && ws[k] == null)
1579	>	ws[k] = q;
1580	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1581	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1582	>	releasePlock(nps);
1583		}
1584		else
1585	<	Thread.yield(); // yield if no alternatives
1585	>	r = 0;
1586		}
1587		}
1588
#	Line 1431 \| Line 1593 \| public class ForkJoinPool extends Abstra
1593		*/
1594		final void incrementActiveCount() {
1595		long c;
1596	<	do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
1596	>	do {} while (!U.compareAndSwapLong
1597	>	(this, CTL, c = ctl, ((c & ~AC_MASK) \|
1598	>	((c & AC_MASK) + AC_UNIT))));
1599		}
1600
1601		/**
1602	<	* Tries to activate or create a worker if too few are active.
1602	>	* Tries to create or activate a worker if too few are active.
1603	>	*
1604	>	* @param ws the worker array to use to find signallees
1605	>	* @param q if non-null, the queue holding tasks to be processed
1606		*/
1607	<	final void signalWork() {
1608	<	long c; int u;
1609	<	while ((u = (int)((c = ctl) >>> 32)) < 0) { // too few active
1610	<	WorkQueue[] ws = workQueues; int e, i; WorkQueue w; Thread p;
1611	<	if ((e = (int)c) > 0) { // at least one waiting
1612	<	if (ws != null && (i = e & SMASK) < ws.length &&
1613	<	(w = ws[i]) != null && w.eventCount == (e \| INT_SIGN)) {
1614	<	long nc = (((long)(w.nextWait & E_MASK)) \|
1615	<	((long)(u + UAC_UNIT) << 32));
1449	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1450	<	w.eventCount = (e + E_SEQ) & E_MASK;
1451	<	if ((p = w.parker) != null)
1452	<	U.unpark(p); // activate and release
1453	<	break;
1454	<	}
1455	<	}
1456	<	else
1457	<	break;
1607	>	final void signalWork(WorkQueue[] ws, WorkQueue q) {
1608	>	for (;;) {
1609	>	long c; int e, u, i; WorkQueue w; Thread p;
1610	>	if ((u = (int)((c = ctl) >>> 32)) >= 0)
1611	>	break;
1612	>	if ((e = (int)c) <= 0) {
1613	>	if ((short)u < 0)
1614	>	tryAddWorker();
1615	>	break;
1616		}
1617	<	else if (e == 0 && (u & SHORT_SIGN) != 0) { // too few total
1618	<	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) \|
1619	<	((u + UAC_UNIT) & UAC_MASK)) << 32;
1620	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1621	<	addWorker();
1622	<	break;
1623	<	}
1617	>	if (ws == null \|\| ws.length <= (i = e & SMASK) \|\|
1618	>	(w = ws[i]) == null)
1619	>	break;
1620	>	long nc = (((long)(w.nextWait & E_MASK)) \|
1621	>	((long)(u + UAC_UNIT)) << 32);
1622	>	int ne = (e + E_SEQ) & E_MASK;
1623	>	if (w.eventCount == (e \| INT_SIGN) &&
1624	>	U.compareAndSwapLong(this, CTL, c, nc)) {
1625	>	w.eventCount = ne;
1626	>	if ((p = w.parker) != null)
1627	>	U.unpark(p);
1628	>	break;
1629		}
1630	<	else
1630	>	if (q != null && q.base >= q.top)
1631		break;
1632		}
1633		}
#	Line 1475 \| Line 1638 \| public class ForkJoinPool extends Abstra
1638		* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1639		*/
1640		final void runWorker(WorkQueue w) {
1641	<	w.growArray(false); // initialize queue array in this thread
1642	<	do { w.runTask(scan(w)); } while (w.runState >= 0);
1641	>	w.growArray(); // allocate queue
1642	>	for (int r = w.hint; scan(w, r) == 0; ) {
1643	>	r ^= r << 13; r ^= r >>> 17; r ^= r << 5; // xorshift
1644	>	}
1645		}
1646
1647		/**
1648	<	* Scans for and, if found, returns one task, else possibly
1648	>	* Scans for and, if found, runs one task, else possibly
1649		* inactivates the worker. This method operates on single reads of
1650		* volatile state and is designed to be re-invoked continuously,
1651		* in part because it returns upon detecting inconsistencies,
1652		* contention, or state changes that indicate possible success on
1653		* re-invocation.
1654		*
1655	<	* The scan searches for tasks across a random permutation of
1656	<	* queues (starting at a random index and stepping by a random
1657	<	* relative prime, checking each at least once). The scan
1658	<	* terminates upon either finding a non-empty queue, or completing
1659	<	* the sweep. If the worker is not inactivated, it takes and
1660	<	* returns a task from this queue. On failure to find a task, we
1661	<	* take one of the following actions, after which the caller will
1662	<	* retry calling this method unless terminated.
1663	<	*
1499	<	* * If pool is terminating, terminate the worker.
1500	<	*
1501	<	* * If not a complete sweep, try to release a waiting worker. If
1502	<	* the scan terminated because the worker is inactivated, then the
1503	<	* released worker will often be the calling worker, and it can
1504	<	* succeed obtaining a task on the next call. Or maybe it is
1505	<	* another worker, but with same net effect. Releasing in other
1506	<	* cases as well ensures that we have enough workers running.
1507	<	*
1508	<	* * If not already enqueued, try to inactivate and enqueue the
1509	<	* worker on wait queue. Or, if inactivating has caused the pool
1510	<	* to be quiescent, relay to idleAwaitWork to check for
1511	<	* termination and possibly shrink pool.
1512	<	*
1513	<	* * If already inactive, and the caller has run a task since the
1514	<	* last empty scan, return (to allow rescan) unless others are
1515	<	* also inactivated. Field WorkQueue.rescans counts down on each
1516	<	* scan to ensure eventual inactivation and blocking.
1517	<	*
1518	<	* * If already enqueued and none of the above apply, park
1519	<	* awaiting signal,
1655	>	* The scan searches for tasks across queues starting at a random
1656	>	* index, checking each at least twice. The scan terminates upon
1657	>	* either finding a non-empty queue, or completing the sweep. If
1658	>	* the worker is not inactivated, it takes and runs a task from
1659	>	* this queue. Otherwise, if not activated, it tries to activate
1660	>	* itself or some other worker by signalling. On failure to find a
1661	>	* task, returns (for retry) if pool state may have changed during
1662	>	* an empty scan, or tries to inactivate if active, else possibly
1663	>	* blocks or terminates via method awaitWork.
1664		*
1665		* @param w the worker (via its WorkQueue)
1666	<	* @return a task or null if none found
1666	>	* @param r a random seed
1667	>	* @return worker qlock status if would have waited, else 0
1668		*/
1669	<	private final ForkJoinTask<?> scan(WorkQueue w) {
1670	<	WorkQueue[] ws; // first update random seed
1671	<	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1672	<	int rs = runState, m; // volatile read order matters
1673	<	if ((ws = workQueues) != null && (m = ws.length - 1) > 0) {
1674	<	int ec = w.eventCount; // ec is negative if inactive
1675	<	int step = (r >>> 16) \| 1; // relative prime
1676	<	for (int j = (m + 1) << 2; ; r += step) {
1677	<	WorkQueue q; ForkJoinTask<?> t; ForkJoinTask<?>[] a; int b;
1678	<	if ((q = ws[r & m]) != null && (b = q.base) - q.top < 0 &&
1679	<	(a = q.array) != null) { // probably nonempty
1680	<	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1681	<	t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1682	<	if (q.base == b && ec >= 0 && t != null &&
1683	<	U.compareAndSwapObject(a, i, t, null)) {
1684	<	if (q.top - (q.base = b + 1) > 1)
1685	<	signalWork(); // help pushes signal
1686	<	return t;
1687	<	}
1688	<	else if (ec < 0 \|\| j <= m) {
1544	<	rs = 0; // mark scan as imcomplete
1545	<	break; // caller can retry after release
1669	>	private final int scan(WorkQueue w, int r) {
1670	>	WorkQueue[] ws; int m;
1671	>	long c = ctl; // for consistency check
1672	>	if ((ws = workQueues) != null && (m = ws.length - 1) >= 0 && w != null) {
1673	>	for (int j = m + m + 1, ec = w.eventCount;;) {
1674	>	WorkQueue q; int b, e; ForkJoinTask<?>[] a; ForkJoinTask<?> t;
1675	>	if ((q = ws[(r - j) & m]) != null &&
1676	>	(b = q.base) - q.top < 0 && (a = q.array) != null) {
1677	>	long i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1678	>	if ((t = ((ForkJoinTask<?>)
1679	>	U.getObjectVolatile(a, i))) != null) {
1680	>	if (ec < 0)
1681	>	helpRelease(c, ws, w, q, b);
1682	>	else if (q.base == b &&
1683	>	U.compareAndSwapObject(a, i, t, null)) {
1684	>	U.putOrderedInt(q, QBASE, b + 1);
1685	>	if ((b + 1) - q.top < 0)
1686	>	signalWork(ws, q);
1687	>	w.runTask(t);
1688	>	}
1689		}
1547	–	}
1548	–	if (--j < 0)
1690		break;
1691	<	}
1692	<
1693	<	long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
1694	<	if (e < 0) // decode ctl on empty scan
1695	<	w.runState = -1; // pool is terminating
1696	<	else if (rs == 0 \|\| rs != runState) { // incomplete scan
1697	<	WorkQueue v; Thread p; // try to release a waiter
1698	<	if (e > 0 && a < 0 && w.eventCount == ec &&
1699	<	(v = ws[e & m]) != null && v.eventCount == (e \| INT_SIGN)) {
1700	<	long nc = ((long)(v.nextWait & E_MASK) \|
1560	<	((c + AC_UNIT) & (AC_MASK\|TC_MASK)));
1561	<	if (ctl == c && U.compareAndSwapLong(this, CTL, c, nc)) {
1562	<	v.eventCount = (e + E_SEQ) & E_MASK;
1563	<	if ((p = v.parker) != null)
1564	<	U.unpark(p);
1691	>	}
1692	>	else if (--j < 0) {
1693	>	if ((ec \| (e = (int)c)) < 0) // inactive or terminating
1694	>	return awaitWork(w, c, ec);
1695	>	else if (ctl == c) { // try to inactivate and enqueue
1696	>	long nc = (long)ec \| ((c - AC_UNIT) & (AC_MASK\|TC_MASK));
1697	>	w.nextWait = e;
1698	>	w.eventCount = ec \| INT_SIGN;
1699	>	if (!U.compareAndSwapLong(this, CTL, c, nc))
1700	>	w.eventCount = ec; // back out
1701		}
1702	+	break;
1703		}
1704		}
1705	<	else if (ec >= 0) { // try to enqueue/inactivate
1706	<	long nc = (long)ec \| ((c - AC_UNIT) & (AC_MASK\|TC_MASK));
1707	<	w.nextWait = e;
1708	<	w.eventCount = ec \| INT_SIGN; // mark as inactive
1709	<	if (ctl != c \|\| !U.compareAndSwapLong(this, CTL, c, nc))
1710	<	w.eventCount = ec; // unmark on CAS failure
1711	<	else {
1712	<	if ((ns = w.nsteals) != 0) {
1713	<	w.nsteals = 0; // set rescans if ran task
1714	<	w.rescans = (a > 0) ? 0 : a + parallelism;
1715	<	w.totalSteals += ns;
1716	<	}
1717	<	if (a == 1 - parallelism) // quiescent
1718	<	idleAwaitWork(w, nc, c);
1719	<	}
1705	>	}
1706	>	return 0;
1707	>	}
1708	>
1709	>	/**
1710	>	* A continuation of scan(), possibly blocking or terminating
1711	>	* worker w. Returns without blocking if pool state has apparently
1712	>	* changed since last invocation. Also, if inactivating w has
1713	>	* caused the pool to become quiescent, checks for pool
1714	>	* termination, and, so long as this is not the only worker, waits
1715	>	* for event for up to a given duration. On timeout, if ctl has
1716	>	* not changed, terminates the worker, which will in turn wake up
1717	>	* another worker to possibly repeat this process.
1718	>	*
1719	>	* @param w the calling worker
1720	>	* @param c the ctl value on entry to scan
1721	>	* @param ec the worker's eventCount on entry to scan
1722	>	*/
1723	>	private final int awaitWork(WorkQueue w, long c, int ec) {
1724	>	int stat, ns; long parkTime, deadline;
1725	>	if ((stat = w.qlock) >= 0 && w.eventCount == ec && ctl == c &&
1726	>	!Thread.interrupted()) {
1727	>	int e = (int)c;
1728	>	int u = (int)(c >>> 32);
1729	>	int d = (u >> UAC_SHIFT) + parallelism; // active count
1730	>
1731	>	if (e < 0 \|\| (d <= 0 && tryTerminate(false, false)))
1732	>	stat = w.qlock = -1; // pool is terminating
1733	>	else if ((ns = w.nsteals) != 0) { // collect steals and retry
1734	>	long sc;
1735	>	w.nsteals = 0;
1736	>	do {} while(!U.compareAndSwapLong(this, STEALCOUNT,
1737	>	sc = stealCount, sc + ns));
1738		}
1739	<	else if (w.eventCount < 0) { // already queued
1740	<	if ((nr = w.rescans) > 0) { // continue rescanning
1741	<	int ac = a + parallelism;
1742	<	if (((w.rescans = (ac < nr) ? ac : nr - 1) & 3) == 0)
1743	<	Thread.yield(); // yield before block
1739	>	else {
1740	>	long pc = ((d > 0 \|\| ec != (e \| INT_SIGN)) ? 0L :
1741	>	((long)(w.nextWait & E_MASK)) \| // ctl to restore
1742	>	((long)(u + UAC_UNIT)) << 32);
1743	>	if (pc != 0L) { // timed wait if last waiter
1744	>	int dc = -(short)(c >>> TC_SHIFT);
1745	>	parkTime = (dc < 0 ? FAST_IDLE_TIMEOUT:
1746	>	(dc + 1) * IDLE_TIMEOUT);
1747	>	deadline = System.nanoTime() + parkTime - TIMEOUT_SLOP;
1748		}
1749	<	else {
1750	<	Thread.interrupted(); // clear status
1749	>	else
1750	>	parkTime = deadline = 0L;
1751	>	if (w.eventCount == ec && ctl == c) {
1752		Thread wt = Thread.currentThread();
1753		U.putObject(wt, PARKBLOCKER, this);
1754		w.parker = wt; // emulate LockSupport.park
1755	<	if (w.eventCount < 0) // recheck
1756	<	U.park(false, 0L);
1755	>	if (w.eventCount == ec && ctl == c)
1756	>	U.park(false, parkTime); // must recheck before park
1757		w.parker = null;
1758		U.putObject(wt, PARKBLOCKER, null);
1759	+	if (parkTime != 0L && ctl == c &&
1760	+	deadline - System.nanoTime() <= 0L &&
1761	+	U.compareAndSwapLong(this, CTL, c, pc))
1762	+	stat = w.qlock = -1; // shrink pool
1763		}
1764		}
1765		}
1766	<	return null;
1766	>	return stat;
1767		}
1768
1769		/**
1770	<	* If inactivating worker w has caused the pool to become
1771	<	* quiescent, checks for pool termination, and, so long as this is
1772	<	* not the only worker, waits for event for up to SHRINK_RATE
1773	<	* nanosecs. On timeout, if ctl has not changed, terminates the
1774	<	* worker, which will in turn wake up another worker to possibly
1775	<	* repeat this process.
1776	<	*
1777	<	* @param w the calling worker
1778	<	* @param currentCtl the ctl value triggering possible quiescence
1779	<	* @param prevCtl the ctl value to restore if thread is terminated
1780	<	*/
1781	<	private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1782	<	if (w.eventCount < 0 && !tryTerminate(false, false) &&
1783	<	(int)prevCtl != 0 && !hasQueuedSubmissions() && ctl == currentCtl) {
1784	<	Thread wt = Thread.currentThread();
1785	<	Thread.yield(); // yield before block
1786	<	while (ctl == currentCtl) {
1787	<	long startTime = System.nanoTime();
1788	<	Thread.interrupted(); // timed variant of version in scan()
1789	<	U.putObject(wt, PARKBLOCKER, this);
1626	<	w.parker = wt;
1627	<	if (ctl == currentCtl)
1628	<	U.park(false, SHRINK_RATE);
1629	<	w.parker = null;
1630	<	U.putObject(wt, PARKBLOCKER, null);
1631	<	if (ctl != currentCtl)
1632	<	break;
1633	<	if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
1634	<	U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1635	<	w.eventCount = (w.eventCount + E_SEQ) \| E_MASK;
1636	<	w.runState = -1; // shrink
1637	<	break;
1638	<	}
1770	>	* Possibly releases (signals) a worker. Called only from scan()
1771	>	* when a worker with apparently inactive status finds a non-empty
1772	>	* queue. This requires revalidating all of the associated state
1773	>	* from caller.
1774	>	*/
1775	>	private final void helpRelease(long c, WorkQueue[] ws, WorkQueue w,
1776	>	WorkQueue q, int b) {
1777	>	WorkQueue v; int e, i; Thread p;
1778	>	if (w != null && w.eventCount < 0 && (e = (int)c) > 0 &&
1779	>	ws != null && ws.length > (i = e & SMASK) &&
1780	>	(v = ws[i]) != null && ctl == c) {
1781	>	long nc = (((long)(v.nextWait & E_MASK)) \|
1782	>	((long)((int)(c >>> 32) + UAC_UNIT)) << 32);
1783	>	int ne = (e + E_SEQ) & E_MASK;
1784	>	if (q != null && q.base == b && w.eventCount < 0 &&
1785	>	v.eventCount == (e \| INT_SIGN) &&
1786	>	U.compareAndSwapLong(this, CTL, c, nc)) {
1787	>	v.eventCount = ne;
1788	>	if ((p = v.parker) != null)
1789	>	U.unpark(p);
1790		}
1791		}
1792		}
#	Line 1660 \| Line 1811 \| public class ForkJoinPool extends Abstra
1811		*/
1812		private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1813		int stat = 0, steps = 0; // bound to avoid cycles
1814	<	if (joiner != null && task != null) { // hoist null checks
1814	>	if (task != null && joiner != null &&
1815	>	joiner.base - joiner.top >= 0) { // hoist checks
1816		restart: for (;;) {
1817		ForkJoinTask<?> subtask = task; // current target
1818		for (WorkQueue j = joiner, v;;) { // v is stealer of subtask
#	Line 1671 \| Line 1823 \| public class ForkJoinPool extends Abstra
1823		}
1824		if ((ws = workQueues) == null \|\| (m = ws.length - 1) <= 0)
1825		break restart; // shutting down
1826	<	if ((v = ws[h = (j.stealHint \| 1) & m]) == null \|\|
1826	>	if ((v = ws[h = (j.hint \| 1) & m]) == null \|\|
1827		v.currentSteal != subtask) {
1828		for (int origin = h;;) { // find stealer
1829		if (((h = (h + 2) & m) & 15) == 1 &&
#	Line 1679 \| Line 1831 \| public class ForkJoinPool extends Abstra
1831		continue restart; // occasional staleness check
1832		if ((v = ws[h]) != null &&
1833		v.currentSteal == subtask) {
1834	<	j.stealHint = h; // save hint
1834	>	j.hint = h; // save hint
1835		break;
1836		}
1837		if (h == origin)
#	Line 1687 \| Line 1839 \| public class ForkJoinPool extends Abstra
1839		}
1840		}
1841		for (;;) { // help stealer or descend to its stealer
1842	<	ForkJoinTask[] a; int b;
1842	>	ForkJoinTask[] a; int b;
1843		if (subtask.status < 0) // surround probes with
1844		continue restart; // consistency checks
1845		if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
#	Line 1698 \| Line 1850 \| public class ForkJoinPool extends Abstra
1850		v.currentSteal != subtask)
1851		continue restart; // stale
1852		stat = 1; // apparent progress
1853	<	if (t != null && v.base == b &&
1854	<	U.compareAndSwapObject(a, i, t, null)) {
1855	<	v.base = b + 1; // help stealer
1856	<	joiner.runSubtask(t);
1853	>	if (v.base == b) {
1854	>	if (t == null)
1855	>	break restart;
1856	>	if (U.compareAndSwapObject(a, i, t, null)) {
1857	>	U.putOrderedInt(v, QBASE, b + 1);
1858	>	ForkJoinTask<?> ps = joiner.currentSteal;
1859	>	int jt = joiner.top;
1860	>	do {
1861	>	joiner.currentSteal = t;
1862	>	t.doExec(); // clear local tasks too
1863	>	} while (task.status >= 0 &&
1864	>	joiner.top != jt &&
1865	>	(t = joiner.pop()) != null);
1866	>	joiner.currentSteal = ps;
1867	>	break restart;
1868	>	}
1869		}
1706	–	else if (v.base == b && ++steps == MAX_HELP)
1707	–	break restart; // v apparently stalled
1870		}
1871		else { // empty -- try to descend
1872		ForkJoinTask<?> next = v.currentJoin;
#	Line 1727 \| Line 1889 \| public class ForkJoinPool extends Abstra
1889		}
1890
1891		/**
1892	<	* If task is at base of some steal queue, steals and executes it.
1892	>	* Analog of tryHelpStealer for CountedCompleters. Tries to steal
1893	>	* and run tasks within the target's computation.
1894		*
1895	<	* @param joiner the joining worker
1733	<	* @param task the task
1895	>	* @param task the task to join
1896		*/
1897	<	private void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
1898	<	WorkQueue[] ws;
1899	<	if ((ws = workQueues) != null) {
1900	<	for (int j = 1; j < ws.length && task.status >= 0; j += 2) {
1901	<	WorkQueue q = ws[j];
1902	<	if (q != null && q.pollFor(task)) {
1903	<	joiner.runSubtask(task);
1897	>	private int helpComplete(WorkQueue joiner, CountedCompleter<?> task) {
1898	>	WorkQueue[] ws; int m;
1899	>	int s = 0;
1900	>	if ((ws = workQueues) != null && (m = ws.length - 1) >= 0 &&
1901	>	joiner != null && task != null) {
1902	>	int j = joiner.poolIndex;
1903	>	int scans = m + m + 1;
1904	>	long c = 0L; // for stability check
1905	>	for (int k = scans; ; j += 2) {
1906	>	WorkQueue q;
1907	>	if ((s = task.status) < 0)
1908	>	break;
1909	>	else if (joiner.internalPopAndExecCC(task))
1910	>	k = scans;
1911	>	else if ((s = task.status) < 0)
1912		break;
1913	+	else if ((q = ws[j & m]) != null && q.pollAndExecCC(task))
1914	+	k = scans;
1915	+	else if (--k < 0) {
1916	+	if (c == (c = ctl))
1917	+	break;
1918	+	k = scans;
1919		}
1920		}
1921		}
1922	+	return s;
1923		}
1924
1925		/**
1926		* Tries to decrement active count (sometimes implicitly) and
1927		* possibly release or create a compensating worker in preparation
1928		* for blocking. Fails on contention or termination. Otherwise,
1929	<	* adds a new thread if no idle workers are available and either
1930	<	* pool would become completely starved or: (at least half
1931	<	* starved, and fewer than 50% spares exist, and there is at least
1932	<	* one task apparently available). Even though the availability
1756	<	* check requires a full scan, it is worthwhile in reducing false
1757	<	* alarms.
1758	<	*
1759	<	* @param task if non-null, a task being waited for
1760	<	* @param blocker if non-null, a blocker being waited for
1761	<	* @return true if the caller can block, else should recheck and retry
1929	>	* adds a new thread if no idle workers are available and pool
1930	>	* may become starved.
1931	>	*
1932	>	* @param c the assumed ctl value
1933		*/
1934	<	final boolean tryCompensate(ForkJoinTask<?> task, ManagedBlocker blocker) {
1764	<	int pc = parallelism, e;
1765	<	long c = ctl;
1934	>	final boolean tryCompensate(long c) {
1935		WorkQueue[] ws = workQueues;
1936	<	if ((e = (int)c) >= 0 && ws != null) {
1937	<	int u, a, ac, hc;
1938	<	int tc = (short)((u = (int)(c >>> 32)) >>> UTC_SHIFT) + pc;
1939	<	boolean replace = false;
1940	<	if ((a = u >> UAC_SHIFT) <= 0) {
1941	<	if ((ac = a + pc) <= 1)
1942	<	replace = true;
1943	<	else if ((e > 0 \|\| (task != null &&
1944	<	ac <= (hc = pc >>> 1) && tc < pc + hc))) {
1945	<	WorkQueue w;
1946	<	for (int j = 0; j < ws.length; ++j) {
1947	<	if ((w = ws[j]) != null && !w.isEmpty()) {
1948	<	replace = true;
1949	<	break; // in compensation range and tasks available
1950	<	}
1951	<	}
1952	<	}
1936	>	int pc = parallelism, e = (int)c, m, tc;
1937	>	if (ws != null && (m = ws.length - 1) >= 0 && e >= 0 && ctl == c) {
1938	>	WorkQueue w = ws[e & m];
1939	>	if (e != 0 && w != null) {
1940	>	Thread p;
1941	>	long nc = ((long)(w.nextWait & E_MASK) \|
1942	>	(c & (AC_MASK\|TC_MASK)));
1943	>	int ne = (e + E_SEQ) & E_MASK;
1944	>	if (w.eventCount == (e \| INT_SIGN) &&
1945	>	U.compareAndSwapLong(this, CTL, c, nc)) {
1946	>	w.eventCount = ne;
1947	>	if ((p = w.parker) != null)
1948	>	U.unpark(p);
1949	>	return true; // replace with idle worker
1950	>	}
1951	>	}
1952	>	else if ((tc = (short)(c >>> TC_SHIFT)) >= 0 &&
1953	>	(int)(c >> AC_SHIFT) + pc > 1) {
1954	>	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
1955	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1956	>	return true; // no compensation
1957		}
1958	<	if ((task == null \|\| task.status >= 0) && // recheck need to block
1959	<	(blocker == null \|\| !blocker.isReleasable()) && ctl == c) {
1960	<	if (!replace) { // no compensation
1961	<	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
1962	<	if (U.compareAndSwapLong(this, CTL, c, nc))
1963	<	return true;
1964	<	}
1965	<	else if (e != 0) { // release an idle worker
1966	<	WorkQueue w; Thread p; int i;
1967	<	if ((i = e & SMASK) < ws.length && (w = ws[i]) != null) {
1795	<	long nc = ((long)(w.nextWait & E_MASK) \|
1796	<	(c & (AC_MASK\|TC_MASK)));
1797	<	if (w.eventCount == (e \| INT_SIGN) &&
1798	<	U.compareAndSwapLong(this, CTL, c, nc)) {
1799	<	w.eventCount = (e + E_SEQ) & E_MASK;
1800	<	if ((p = w.parker) != null)
1801	<	U.unpark(p);
1958	>	else if (tc + pc < MAX_CAP) {
1959	>	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
1960	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1961	>	ForkJoinWorkerThreadFactory fac;
1962	>	Throwable ex = null;
1963	>	ForkJoinWorkerThread wt = null;
1964	>	try {
1965	>	if ((fac = factory) != null &&
1966	>	(wt = fac.newThread(this)) != null) {
1967	>	wt.start();
1968		return true;
1969		}
1970	+	} catch (Throwable rex) {
1971	+	ex = rex;
1972		}
1973	<	}
1806	<	else if (tc < MAX_CAP) { // create replacement
1807	<	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
1808	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1809	<	addWorker();
1810	<	return true;
1811	<	}
1973	>	deregisterWorker(wt, ex); // clean up and return false
1974		}
1975		}
1976		}
#	Line 1823 \| Line 1985 \| public class ForkJoinPool extends Abstra
1985		* @return task status on exit
1986		*/
1987		final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
1988	<	int s;
1989	<	if ((s = task.status) >= 0) {
1988	>	int s = 0;
1989	>	if (task != null && (s = task.status) >= 0 && joiner != null) {
1990		ForkJoinTask<?> prevJoin = joiner.currentJoin;
1991		joiner.currentJoin = task;
1992	<	long startTime = 0L;
1993	<	for (int k = 0;;) {
1994	<	if ((s = (joiner.isEmpty() ? // try to help
1995	<	tryHelpStealer(joiner, task) :
1996	<	joiner.tryRemoveAndExec(task))) == 0 &&
1992	>	do {} while (joiner.tryRemoveAndExec(task) && // process local tasks
1993	>	(s = task.status) >= 0);
1994	>	if (s >= 0 && (task instanceof CountedCompleter))
1995	>	s = helpComplete(joiner, (CountedCompleter<?>)task);
1996	>	long cc = 0; // for stability checks
1997	>	while (s >= 0 && (s = task.status) >= 0) {
1998	>	if ((s = tryHelpStealer(joiner, task)) == 0 &&
1999		(s = task.status) >= 0) {
2000	<	if (k == 0) {
2001	<	startTime = System.nanoTime();
2002	<	tryPollForAndExec(joiner, task); // check uncommon case
2003	<	}
1840	<	else if ((k & (MAX_HELP - 1)) == 0 &&
1841	<	System.nanoTime() - startTime >=
1842	<	COMPENSATION_DELAY &&
1843	<	tryCompensate(task, null)) {
1844	<	if (task.trySetSignal()) {
2000	>	if (!tryCompensate(cc))
2001	>	cc = ctl;
2002	>	else {
2003	>	if (task.trySetSignal() && (s = task.status) >= 0) {
2004		synchronized (task) {
2005		if (task.status >= 0) {
2006		try { // see ForkJoinTask
#	Line 1853 \| Line 2012 \| public class ForkJoinPool extends Abstra
2012		task.notifyAll();
2013		}
2014		}
2015	<	long c; // re-activate
2015	>	long c; // reactivate
2016		do {} while (!U.compareAndSwapLong
2017	<	(this, CTL, c = ctl, c + AC_UNIT));
2017	>	(this, CTL, c = ctl,
2018	>	((c & ~AC_MASK) \|
2019	>	((c & AC_MASK) + AC_UNIT))));
2020		}
2021		}
1861	–	if (s < 0 \|\| (s = task.status) < 0) {
1862	–	joiner.currentJoin = prevJoin;
1863	–	break;
1864	–	}
1865	–	else if ((k++ & (MAX_HELP - 1)) == MAX_HELP >>> 1)
1866	–	Thread.yield(); // for politeness
2022		}
2023	+	joiner.currentJoin = prevJoin;
2024		}
2025		return s;
2026		}
#	Line 1876 \| Line 2032 \| public class ForkJoinPool extends Abstra
2032		*
2033		* @param joiner the joining worker
2034		* @param task the task
1879	–	* @return task status on exit
2035		*/
2036	<	final int helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
2036	>	final void helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
2037		int s;
2038	<	while ((s = task.status) >= 0 &&
2039	<	(joiner.isEmpty() ?
2040	<	tryHelpStealer(joiner, task) :
2041	<	joiner.tryRemoveAndExec(task)) != 0)
2042	<	;
2043	<	return s;
2038	>	if (joiner != null && task != null && (s = task.status) >= 0) {
2039	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2040	>	joiner.currentJoin = task;
2041	>	do {} while (joiner.tryRemoveAndExec(task) && // process local tasks
2042	>	(s = task.status) >= 0);
2043	>	if (s >= 0) {
2044	>	if (task instanceof CountedCompleter)
2045	>	helpComplete(joiner, (CountedCompleter<?>)task);
2046	>	do {} while (task.status >= 0 &&
2047	>	tryHelpStealer(joiner, task) > 0);
2048	>	}
2049	>	joiner.currentJoin = prevJoin;
2050	>	}
2051		}
2052
2053		/**
2054		* Returns a (probably) non-empty steal queue, if one is found
2055	<	* during a random, then cyclic scan, else null. This method must
2056	<	* be retried by caller if, by the time it tries to use the queue,
2057	<	* it is empty.
2058	<	*/
2059	<	private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
2060	<	// Similar to loop in scan(), but ignoring submissions
2061	<	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
2062	<	int step = (r >>> 16) \| 1;
2063	<	for (WorkQueue[] ws;;) {
2064	<	int rs = runState, m;
2065	<	if ((ws = workQueues) == null \|\| (m = ws.length - 1) < 1)
2066	<	return null;
1905	<	for (int j = (m + 1) << 2; ; r += step) {
1906	<	WorkQueue q = ws[((r << 1) \| 1) & m];
1907	<	if (q != null && !q.isEmpty())
1908	<	return q;
1909	<	else if (--j < 0) {
1910	<	if (runState == rs)
1911	<	return null;
1912	<	break;
2055	>	* during a scan, else null. This method must be retried by
2056	>	* caller if, by the time it tries to use the queue, it is empty.
2057	>	*/
2058	>	private WorkQueue findNonEmptyStealQueue() {
2059	>	int r = ThreadLocalRandom.current().nextInt();
2060	>	for (;;) {
2061	>	int ps = plock, m; WorkQueue[] ws; WorkQueue q;
2062	>	if ((ws = workQueues) != null && (m = ws.length - 1) >= 0) {
2063	>	for (int j = (m + 1) << 2; j >= 0; --j) {
2064	>	if ((q = ws[(((r - j) << 1) \| 1) & m]) != null &&
2065	>	q.base - q.top < 0)
2066	>	return q;
2067		}
2068		}
2069	+	if (plock == ps)
2070	+	return null;
2071		}
2072		}
2073
1918	–
2074		/**
2075		* Runs tasks until {@code isQuiescent()}. We piggyback on
2076		* active count ctl maintenance, but rather than blocking
#	Line 1923 \| Line 2078 \| public class ForkJoinPool extends Abstra
2078		* find tasks either.
2079		*/
2080		final void helpQuiescePool(WorkQueue w) {
2081	+	ForkJoinTask<?> ps = w.currentSteal;
2082		for (boolean active = true;;) {
2083	<	ForkJoinTask<?> localTask; // exhaust local queue
2084	<	while ((localTask = w.nextLocalTask()) != null)
2085	<	localTask.doExec();
2086	<	WorkQueue q = findNonEmptyStealQueue(w);
1931	<	if (q != null) {
1932	<	ForkJoinTask<?> t; int b;
2083	>	long c; WorkQueue q; ForkJoinTask<?> t; int b;
2084	>	while ((t = w.nextLocalTask()) != null)
2085	>	t.doExec();
2086	>	if ((q = findNonEmptyStealQueue()) != null) {
2087		if (!active) { // re-establish active count
1934	–	long c;
2088		active = true;
2089		do {} while (!U.compareAndSwapLong
2090	<	(this, CTL, c = ctl, c + AC_UNIT));
2090	>	(this, CTL, c = ctl,
2091	>	((c & ~AC_MASK) \|
2092	>	((c & AC_MASK) + AC_UNIT))));
2093	>	}
2094	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) {
2095	>	(w.currentSteal = t).doExec();
2096	>	w.currentSteal = ps;
2097		}
1939	–	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
1940	–	w.runSubtask(t);
2098		}
2099	<	else {
2100	<	long c;
2101	<	if (active) { // decrement active count without queuing
2099	>	else if (active) { // decrement active count without queuing
2100	>	long nc = ((c = ctl) & ~AC_MASK) \| ((c & AC_MASK) - AC_UNIT);
2101	>	if ((int)(nc >> AC_SHIFT) + parallelism == 0)
2102	>	break; // bypass decrement-then-increment
2103	>	if (U.compareAndSwapLong(this, CTL, c, nc))
2104		active = false;
1946	–	do {} while (!U.compareAndSwapLong
1947	–	(this, CTL, c = ctl, c -= AC_UNIT));
1948	–	}
1949	–	else
1950	–	c = ctl; // re-increment on exit
1951	–	if ((int)(c >> AC_SHIFT) + parallelism == 0) {
1952	–	do {} while (!U.compareAndSwapLong
1953	–	(this, CTL, c = ctl, c + AC_UNIT));
1954	–	break;
1955	–	}
2105		}
2106	+	else if ((int)((c = ctl) >> AC_SHIFT) + parallelism <= 0 &&
2107	+	U.compareAndSwapLong
2108	+	(this, CTL, c, ((c & ~AC_MASK) \|
2109	+	((c & AC_MASK) + AC_UNIT))))
2110	+	break;
2111		}
2112		}
2113
#	Line 1967 \| Line 2121 \| public class ForkJoinPool extends Abstra
2121		WorkQueue q; int b;
2122		if ((t = w.nextLocalTask()) != null)
2123		return t;
2124	<	if ((q = findNonEmptyStealQueue(w)) == null)
2124	>	if ((q = findNonEmptyStealQueue()) == null)
2125		return null;
2126		if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2127		return t;
#	Line 1975 \| Line 2129 \| public class ForkJoinPool extends Abstra
2129		}
2130
2131		/**
2132	<	* Returns the approximate (non-atomic) number of idle threads per
2133	<	* active thread to offset steal queue size for method
2134	<	* ForkJoinTask.getSurplusQueuedTaskCount().
2135	<	*/
2136	<	final int idlePerActive() {
2137	<	// Approximate at powers of two for small values, saturate past 4
2138	<	int p = parallelism;
2139	<	int a = p + (int)(ctl >> AC_SHIFT);
2140	<	return (a > (p >>>= 1) ? 0 :
2141	<	a > (p >>>= 1) ? 1 :
2142	<	a > (p >>>= 1) ? 2 :
2143	<	a > (p >>>= 1) ? 4 :
2144	<	8);
2132	>	* Returns a cheap heuristic guide for task partitioning when
2133	>	* programmers, frameworks, tools, or languages have little or no
2134	>	* idea about task granularity. In essence by offering this
2135	>	* method, we ask users only about tradeoffs in overhead vs
2136	>	* expected throughput and its variance, rather than how finely to
2137	>	* partition tasks.
2138	>	*
2139	>	* In a steady state strict (tree-structured) computation, each
2140	>	* thread makes available for stealing enough tasks for other
2141	>	* threads to remain active. Inductively, if all threads play by
2142	>	* the same rules, each thread should make available only a
2143	>	* constant number of tasks.
2144	>	*
2145	>	* The minimum useful constant is just 1. But using a value of 1
2146	>	* would require immediate replenishment upon each steal to
2147	>	* maintain enough tasks, which is infeasible. Further,
2148	>	* partitionings/granularities of offered tasks should minimize
2149	>	* steal rates, which in general means that threads nearer the top
2150	>	* of computation tree should generate more than those nearer the
2151	>	* bottom. In perfect steady state, each thread is at
2152	>	* approximately the same level of computation tree. However,
2153	>	* producing extra tasks amortizes the uncertainty of progress and
2154	>	* diffusion assumptions.
2155	>	*
2156	>	* So, users will want to use values larger (but not much larger)
2157	>	* than 1 to both smooth over transient shortages and hedge
2158	>	* against uneven progress; as traded off against the cost of
2159	>	* extra task overhead. We leave the user to pick a threshold
2160	>	* value to compare with the results of this call to guide
2161	>	* decisions, but recommend values such as 3.
2162	>	*
2163	>	* When all threads are active, it is on average OK to estimate
2164	>	* surplus strictly locally. In steady-state, if one thread is
2165	>	* maintaining say 2 surplus tasks, then so are others. So we can
2166	>	* just use estimated queue length. However, this strategy alone
2167	>	* leads to serious mis-estimates in some non-steady-state
2168	>	* conditions (ramp-up, ramp-down, other stalls). We can detect
2169	>	* many of these by further considering the number of "idle"
2170	>	* threads, that are known to have zero queued tasks, so
2171	>	* compensate by a factor of (#idle/#active) threads.
2172	>	*
2173	>	* Note: The approximation of #busy workers as #active workers is
2174	>	* not very good under current signalling scheme, and should be
2175	>	* improved.
2176	>	*/
2177	>	static int getSurplusQueuedTaskCount() {
2178	>	Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q;
2179	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
2180	>	int p = (pool = (wt = (ForkJoinWorkerThread)t).pool).parallelism;
2181	>	int n = (q = wt.workQueue).top - q.base;
2182	>	int a = (int)(pool.ctl >> AC_SHIFT) + p;
2183	>	return n - (a > (p >>>= 1) ? 0 :
2184	>	a > (p >>>= 1) ? 1 :
2185	>	a > (p >>>= 1) ? 2 :
2186	>	a > (p >>>= 1) ? 4 :
2187	>	8);
2188	>	}
2189	>	return 0;
2190		}
2191
2192		// Termination
#	Line 2007 \| Line 2206 \| public class ForkJoinPool extends Abstra
2206		* @return true if now terminating or terminated
2207		*/
2208		private boolean tryTerminate(boolean now, boolean enable) {
2209	<	Mutex lock = this.lock;
2209	>	int ps;
2210	>	if (this == common) // cannot shut down
2211	>	return false;
2212	>	if ((ps = plock) >= 0) { // enable by setting plock
2213	>	if (!enable)
2214	>	return false;
2215	>	if ((ps & PL_LOCK) != 0 \|\|
2216	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
2217	>	ps = acquirePlock();
2218	>	int nps = ((ps + PL_LOCK) & ~SHUTDOWN) \| SHUTDOWN;
2219	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
2220	>	releasePlock(nps);
2221	>	}
2222		for (long c;;) {
2223	<	if (((c = ctl) & STOP_BIT) != 0) { // already terminating
2224	<	if ((short)(c >>> TC_SHIFT) == -parallelism) {
2225	<	lock.lock(); // don't need try/finally
2226	<	termination.signalAll(); // signal when 0 workers
2227	<	lock.unlock();
2223	>	if (((c = ctl) & STOP_BIT) != 0) { // already terminating
2224	>	if ((short)(c >>> TC_SHIFT) + parallelism <= 0) {
2225	>	synchronized (this) {
2226	>	notifyAll(); // signal when 0 workers
2227	>	}
2228		}
2229		return true;
2230		}
2231	<	if (runState >= 0) { // not yet enabled
2232	<	if (!enable)
2233	<	return false;
2023	<	lock.lock();
2024	<	runState \|= SHUTDOWN;
2025	<	lock.unlock();
2026	<	}
2027	<	if (!now) { // check if idle & no tasks
2028	<	if ((int)(c >> AC_SHIFT) != -parallelism \|\|
2029	<	hasQueuedSubmissions())
2231	>	if (!now) { // check if idle & no tasks
2232	>	WorkQueue[] ws; WorkQueue w;
2233	>	if ((int)(c >> AC_SHIFT) + parallelism > 0)
2234		return false;
2235	<	// Check for unqueued inactive workers. One pass suffices.
2236	<	WorkQueue[] ws = workQueues; WorkQueue w;
2237	<	if (ws != null) {
2238	<	for (int i = 1; i < ws.length; i += 2) {
2239	<	if ((w = ws[i]) != null && w.eventCount >= 0)
2235	>	if ((ws = workQueues) != null) {
2236	>	for (int i = 0; i < ws.length; ++i) {
2237	>	if ((w = ws[i]) != null &&
2238	>	(!w.isEmpty() \|\|
2239	>	((i & 1) != 0 && w.eventCount >= 0))) {
2240	>	signalWork(ws, w);
2241		return false;
2242	+	}
2243		}
2244		}
2245		}
2246		if (U.compareAndSwapLong(this, CTL, c, c \| STOP_BIT)) {
2247		for (int pass = 0; pass < 3; ++pass) {
2248	<	WorkQueue[] ws = workQueues;
2249	<	if (ws != null) {
2044	<	WorkQueue w;
2248	>	WorkQueue[] ws; WorkQueue w; Thread wt;
2249	>	if ((ws = workQueues) != null) {
2250		int n = ws.length;
2251		for (int i = 0; i < n; ++i) {
2252		if ((w = ws[i]) != null) {
2253	<	w.runState = -1;
2253	>	w.qlock = -1;
2254		if (pass > 0) {
2255		w.cancelAll();
2256	<	if (pass > 1)
2257	<	w.interruptOwner();
2256	>	if (pass > 1 && (wt = w.owner) != null) {
2257	>	if (!wt.isInterrupted()) {
2258	>	try {
2259	>	wt.interrupt();
2260	>	} catch (Throwable ignore) {
2261	>	}
2262	>	}
2263	>	U.unpark(wt);
2264	>	}
2265		}
2266		}
2267		}
2268		// Wake up workers parked on event queue
2269		int i, e; long cc; Thread p;
2270		while ((e = (int)(cc = ctl) & E_MASK) != 0 &&
2271	<	(i = e & SMASK) < n &&
2271	>	(i = e & SMASK) < n && i >= 0 &&
2272		(w = ws[i]) != null) {
2273		long nc = ((long)(w.nextWait & E_MASK) \|
2274		((cc + AC_UNIT) & AC_MASK) \|
#	Line 2064 \| Line 2276 \| public class ForkJoinPool extends Abstra
2276		if (w.eventCount == (e \| INT_SIGN) &&
2277		U.compareAndSwapLong(this, CTL, cc, nc)) {
2278		w.eventCount = (e + E_SEQ) & E_MASK;
2279	<	w.runState = -1;
2279	>	w.qlock = -1;
2280		if ((p = w.parker) != null)
2281		U.unpark(p);
2282		}
#	Line 2075 \| Line 2287 \| public class ForkJoinPool extends Abstra
2287		}
2288		}
2289
2290	+	// external operations on common pool
2291	+
2292	+	/**
2293	+	* Returns common pool queue for a thread that has submitted at
2294	+	* least one task.
2295	+	*/
2296	+	static WorkQueue commonSubmitterQueue() {
2297	+	Submitter z; ForkJoinPool p; WorkQueue[] ws; int m, r;
2298	+	return ((z = submitters.get()) != null &&
2299	+	(p = common) != null &&
2300	+	(ws = p.workQueues) != null &&
2301	+	(m = ws.length - 1) >= 0) ?
2302	+	ws[m & z.seed & SQMASK] : null;
2303	+	}
2304	+
2305	+	/**
2306	+	* Tries to pop the given task from submitter's queue in common pool.
2307	+	*/
2308	+	final boolean tryExternalUnpush(ForkJoinTask<?> task) {
2309	+	WorkQueue joiner; ForkJoinTask<?>[] a; int m, s;
2310	+	Submitter z = submitters.get();
2311	+	WorkQueue[] ws = workQueues;
2312	+	boolean popped = false;
2313	+	if (z != null && ws != null && (m = ws.length - 1) >= 0 &&
2314	+	(joiner = ws[z.seed & m & SQMASK]) != null &&
2315	+	joiner.base != (s = joiner.top) &&
2316	+	(a = joiner.array) != null) {
2317	+	long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE;
2318	+	if (U.getObject(a, j) == task &&
2319	+	U.compareAndSwapInt(joiner, QLOCK, 0, 1)) {
2320	+	if (joiner.top == s && joiner.array == a &&
2321	+	U.compareAndSwapObject(a, j, task, null)) {
2322	+	joiner.top = s - 1;
2323	+	popped = true;
2324	+	}
2325	+	joiner.qlock = 0;
2326	+	}
2327	+	}
2328	+	return popped;
2329	+	}
2330	+
2331	+	final int externalHelpComplete(CountedCompleter<?> task) {
2332	+	WorkQueue joiner; int m, j;
2333	+	Submitter z = submitters.get();
2334	+	WorkQueue[] ws = workQueues;
2335	+	int s = 0;
2336	+	if (z != null && ws != null && (m = ws.length - 1) >= 0 &&
2337	+	(joiner = ws[(j = z.seed) & m & SQMASK]) != null && task != null) {
2338	+	int scans = m + m + 1;
2339	+	long c = 0L; // for stability check
2340	+	j \|= 1; // poll odd queues
2341	+	for (int k = scans; ; j += 2) {
2342	+	WorkQueue q;
2343	+	if ((s = task.status) < 0)
2344	+	break;
2345	+	else if (joiner.externalPopAndExecCC(task))
2346	+	k = scans;
2347	+	else if ((s = task.status) < 0)
2348	+	break;
2349	+	else if ((q = ws[j & m]) != null && q.pollAndExecCC(task))
2350	+	k = scans;
2351	+	else if (--k < 0) {
2352	+	if (c == (c = ctl))
2353	+	break;
2354	+	k = scans;
2355	+	}
2356	+	}
2357	+	}
2358	+	return s;
2359	+	}
2360	+
2361		// Exported methods
2362
2363		// Constructors
#	Line 2091 \| Line 2374 \| public class ForkJoinPool extends Abstra
2374		* java.lang.RuntimePermission}{@code ("modifyThread")}
2375		*/
2376		public ForkJoinPool() {
2377	<	this(Runtime.getRuntime().availableProcessors(),
2377	>	this(Math.min(MAX_CAP, Runtime.getRuntime().availableProcessors()),
2378		defaultForkJoinWorkerThreadFactory, null, false);
2379		}
2380
#	Line 2139 \| Line 2422 \| public class ForkJoinPool extends Abstra
2422		*/
2423		public ForkJoinPool(int parallelism,
2424		ForkJoinWorkerThreadFactory factory,
2425	<	Thread.UncaughtExceptionHandler handler,
2425	>	UncaughtExceptionHandler handler,
2426		boolean asyncMode) {
2427	+	this(checkParallelism(parallelism),
2428	+	checkFactory(factory),
2429	+	handler,
2430	+	(asyncMode ? FIFO_QUEUE : LIFO_QUEUE),
2431	+	"ForkJoinPool-" + nextPoolId() + "-worker-");
2432		checkPermission();
2433	<	if (factory == null)
2434	<	throw new NullPointerException();
2433	>	}
2434	>
2435	>	private static int checkParallelism(int parallelism) {
2436		if (parallelism <= 0 \|\| parallelism > MAX_CAP)
2437		throw new IllegalArgumentException();
2438	<	this.parallelism = parallelism;
2438	>	return parallelism;
2439	>	}
2440	>
2441	>	private static ForkJoinWorkerThreadFactory checkFactory
2442	>	(ForkJoinWorkerThreadFactory factory) {
2443	>	if (factory == null)
2444	>	throw new NullPointerException();
2445	>	return factory;
2446	>	}
2447	>
2448	>	/**
2449	>	* Creates a {@code ForkJoinPool} with the given parameters, without
2450	>	* any security checks or parameter validation. Invoked directly by
2451	>	* makeCommonPool.
2452	>	*/
2453	>	private ForkJoinPool(int parallelism,
2454	>	ForkJoinWorkerThreadFactory factory,
2455	>	UncaughtExceptionHandler handler,
2456	>	int mode,
2457	>	String workerNamePrefix) {
2458	>	this.workerNamePrefix = workerNamePrefix;
2459		this.factory = factory;
2460		this.ueh = handler;
2461	<	this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE;
2461	>	this.mode = (short)mode;
2462	>	this.parallelism = (short)parallelism;
2463		long np = (long)(-parallelism); // offset ctl counts
2464		this.ctl = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
2465	<	// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2.
2466	<	int n = parallelism - 1;
2467	<	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4; n \|= n >>> 8; n \|= n >>> 16;
2468	<	int size = (n + 1) << 1; // #slots = 2*#workers
2469	<	this.submitMask = size - 1; // room for max # of submit queues
2470	<	this.workQueues = new WorkQueue[size];
2471	<	this.termination = (this.lock = new Mutex()).newCondition();
2472	<	this.stealCount = new AtomicLong();
2473	<	this.nextWorkerNumber = new AtomicInteger();
2474	<	int pn = poolNumberGenerator.incrementAndGet();
2475	<	StringBuilder sb = new StringBuilder("ForkJoinPool-");
2476	<	sb.append(Integer.toString(pn));
2477	<	sb.append("-worker-");
2478	<	this.workerNamePrefix = sb.toString();
2479	<	lock.lock();
2480	<	this.runState = 1; // set init flag
2481	<	lock.unlock();
2465	>	}
2466	>
2467	>	/**
2468	>	* Returns the common pool instance. This pool is statically
2469	>	* constructed; its run state is unaffected by attempts to {@link
2470	>	* #shutdown} or {@link #shutdownNow}. However this pool and any
2471	>	* ongoing processing are automatically terminated upon program
2472	>	* {@link System#exit}. Any program that relies on asynchronous
2473	>	* task processing to complete before program termination should
2474	>	* invoke {@code commonPool().}{@link #awaitQuiescence awaitQuiescence},
2475	>	* before exit.
2476	>	*
2477	>	* @return the common pool instance
2478	>	* @since 1.8
2479	>	*/
2480	>	public static ForkJoinPool commonPool() {
2481	>	// assert common != null : "static init error";
2482	>	return common;
2483		}
2484
2485		// Execution methods
#	Line 2192 \| Line 2503 \| public class ForkJoinPool extends Abstra
2503		public <T> T invoke(ForkJoinTask<T> task) {
2504		if (task == null)
2505		throw new NullPointerException();
2506	<	doSubmit(task);
2506	>	externalPush(task);
2507		return task.join();
2508		}
2509
#	Line 2207 \| Line 2518 \| public class ForkJoinPool extends Abstra
2518		public void execute(ForkJoinTask<?> task) {
2519		if (task == null)
2520		throw new NullPointerException();
2521	<	doSubmit(task);
2521	>	externalPush(task);
2522		}
2523
2524		// AbstractExecutorService methods
#	Line 2224 \| Line 2535 \| public class ForkJoinPool extends Abstra
2535		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2536		job = (ForkJoinTask<?>) task;
2537		else
2538	<	job = new ForkJoinTask.AdaptedRunnableAction(task);
2539	<	doSubmit(job);
2538	>	job = new ForkJoinTask.RunnableExecuteAction(task);
2539	>	externalPush(job);
2540		}
2541
2542		/**
#	Line 2240 \| Line 2551 \| public class ForkJoinPool extends Abstra
2551		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2552		if (task == null)
2553		throw new NullPointerException();
2554	<	doSubmit(task);
2554	>	externalPush(task);
2555		return task;
2556		}
2557
#	Line 2251 \| Line 2562 \| public class ForkJoinPool extends Abstra
2562		*/
2563		public <T> ForkJoinTask<T> submit(Callable<T> task) {
2564		ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2565	<	doSubmit(job);
2565	>	externalPush(job);
2566		return job;
2567		}
2568
#	Line 2262 \| Line 2573 \| public class ForkJoinPool extends Abstra
2573		*/
2574		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2575		ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2576	<	doSubmit(job);
2576	>	externalPush(job);
2577		return job;
2578		}
2579
#	Line 2279 \| Line 2590 \| public class ForkJoinPool extends Abstra
2590		job = (ForkJoinTask<?>) task;
2591		else
2592		job = new ForkJoinTask.AdaptedRunnableAction(task);
2593	<	doSubmit(job);
2593	>	externalPush(job);
2594		return job;
2595		}
2596
#	Line 2291 \| Line 2602 \| public class ForkJoinPool extends Abstra
2602		// In previous versions of this class, this method constructed
2603		// a task to run ForkJoinTask.invokeAll, but now external
2604		// invocation of multiple tasks is at least as efficient.
2605	<	List<ForkJoinTask<T>> fs = new ArrayList<ForkJoinTask<T>>(tasks.size());
2295	<	// Workaround needed because method wasn't declared with
2296	<	// wildcards in return type but should have been.
2297	<	@SuppressWarnings({"unchecked", "rawtypes"})
2298	<	List<Future<T>> futures = (List<Future<T>>) (List) fs;
2605	>	ArrayList<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
2606
2607		boolean done = false;
2608		try {
2609		for (Callable<T> t : tasks) {
2610		ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2611	<	doSubmit(f);
2612	<	fs.add(f);
2611	>	futures.add(f);
2612	>	externalPush(f);
2613		}
2614	<	for (ForkJoinTask<T> f : fs)
2615	<	f.quietlyJoin();
2614	>	for (int i = 0, size = futures.size(); i < size; i++)
2615	>	((ForkJoinTask<?>)futures.get(i)).quietlyJoin();
2616		done = true;
2617		return futures;
2618		} finally {
2619		if (!done)
2620	<	for (ForkJoinTask<T> f : fs)
2621	<	f.cancel(false);
2620	>	for (int i = 0, size = futures.size(); i < size; i++)
2621	>	futures.get(i).cancel(false);
2622		}
2623		}
2624
#	Line 2330 \| Line 2637 \| public class ForkJoinPool extends Abstra
2637		*
2638		* @return the handler, or {@code null} if none
2639		*/
2640	<	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
2640	>	public UncaughtExceptionHandler getUncaughtExceptionHandler() {
2641		return ueh;
2642		}
2643
#	Line 2340 \| Line 2647 \| public class ForkJoinPool extends Abstra
2647		* @return the targeted parallelism level of this pool
2648		*/
2649		public int getParallelism() {
2650	<	return parallelism;
2650	>	int par;
2651	>	return ((par = parallelism) > 0) ? par : 1;
2652	>	}
2653	>
2654	>	/**
2655	>	* Returns the targeted parallelism level of the common pool.
2656	>	*
2657	>	* @return the targeted parallelism level of the common pool
2658	>	* @since 1.8
2659	>	*/
2660	>	public static int getCommonPoolParallelism() {
2661	>	return commonParallelism;
2662		}
2663
2664		/**
#	Line 2362 \| Line 2680 \| public class ForkJoinPool extends Abstra
2680		* @return {@code true} if this pool uses async mode
2681		*/
2682		public boolean getAsyncMode() {
2683	<	return localMode != 0;
2683	>	return mode == FIFO_QUEUE;
2684		}
2685
2686		/**
#	Line 2409 \| Line 2727 \| public class ForkJoinPool extends Abstra
2727		* @return {@code true} if all threads are currently idle
2728		*/
2729		public boolean isQuiescent() {
2730	<	return (int)(ctl >> AC_SHIFT) + parallelism == 0;
2730	>	return parallelism + (int)(ctl >> AC_SHIFT) <= 0;
2731		}
2732
2733		/**
#	Line 2424 \| Line 2742 \| public class ForkJoinPool extends Abstra
2742		* @return the number of steals
2743		*/
2744		public long getStealCount() {
2745	<	long count = stealCount.get();
2745	>	long count = stealCount;
2746		WorkQueue[] ws; WorkQueue w;
2747		if ((ws = workQueues) != null) {
2748		for (int i = 1; i < ws.length; i += 2) {
2749		if ((w = ws[i]) != null)
2750	<	count += w.totalSteals;
2750	>	count += w.nsteals;
2751		}
2752		}
2753		return count;
#	Line 2554 \| Line 2872 \| public class ForkJoinPool extends Abstra
2872		public String toString() {
2873		// Use a single pass through workQueues to collect counts
2874		long qt = 0L, qs = 0L; int rc = 0;
2875	<	long st = stealCount.get();
2875	>	long st = stealCount;
2876		long c = ctl;
2877		WorkQueue[] ws; WorkQueue w;
2878		if ((ws = workQueues) != null) {
#	Line 2565 \| Line 2883 \| public class ForkJoinPool extends Abstra
2883		qs += size;
2884		else {
2885		qt += size;
2886	<	st += w.totalSteals;
2886	>	st += w.nsteals;
2887		if (w.isApparentlyUnblocked())
2888		++rc;
2889		}
#	Line 2581 \| Line 2899 \| public class ForkJoinPool extends Abstra
2899		if ((c & STOP_BIT) != 0)
2900		level = (tc == 0) ? "Terminated" : "Terminating";
2901		else
2902	<	level = runState < 0 ? "Shutting down" : "Running";
2902	>	level = plock < 0 ? "Shutting down" : "Running";
2903		return super.toString() +
2904		"[" + level +
2905		", parallelism = " + pc +
#	Line 2595 \| Line 2913 \| public class ForkJoinPool extends Abstra
2913		}
2914
2915		/**
2916	<	* Initiates an orderly shutdown in which previously submitted
2917	<	* tasks are executed, but no new tasks will be accepted.
2918	<	* Invocation has no additional effect if already shut down.
2919	<	* Tasks that are in the process of being submitted concurrently
2920	<	* during the course of this method may or may not be rejected.
2916	>	* Possibly initiates an orderly shutdown in which previously
2917	>	* submitted tasks are executed, but no new tasks will be
2918	>	* accepted. Invocation has no effect on execution state if this
2919	>	* is the {@link #commonPool()}, and no additional effect if
2920	>	* already shut down. Tasks that are in the process of being
2921	>	* submitted concurrently during the course of this method may or
2922	>	* may not be rejected.
2923		*
2924		* @throws SecurityException if a security manager exists and
2925		* the caller is not permitted to modify threads
#	Line 2612 \| Line 2932 \| public class ForkJoinPool extends Abstra
2932		}
2933
2934		/**
2935	<	* Attempts to cancel and/or stop all tasks, and reject all
2936	<	* subsequently submitted tasks. Tasks that are in the process of
2937	<	* being submitted or executed concurrently during the course of
2938	<	* this method may or may not be rejected. This method cancels
2939	<	* both existing and unexecuted tasks, in order to permit
2940	<	* termination in the presence of task dependencies. So the method
2941	<	* always returns an empty list (unlike the case for some other
2942	<	* Executors).
2935	>	* Possibly attempts to cancel and/or stop all tasks, and reject
2936	>	* all subsequently submitted tasks. Invocation has no effect on
2937	>	* execution state if this is the {@link #commonPool()}, and no
2938	>	* additional effect if already shut down. Otherwise, tasks that
2939	>	* are in the process of being submitted or executed concurrently
2940	>	* during the course of this method may or may not be
2941	>	* rejected. This method cancels both existing and unexecuted
2942	>	* tasks, in order to permit termination in the presence of task
2943	>	* dependencies. So the method always returns an empty list
2944	>	* (unlike the case for some other Executors).
2945		*
2946		* @return an empty list
2947		* @throws SecurityException if a security manager exists and
#	Line 2641 \| Line 2963 \| public class ForkJoinPool extends Abstra
2963		public boolean isTerminated() {
2964		long c = ctl;
2965		return ((c & STOP_BIT) != 0L &&
2966	<	(short)(c >>> TC_SHIFT) == -parallelism);
2966	>	(short)(c >>> TC_SHIFT) + parallelism <= 0);
2967		}
2968
2969		/**
#	Line 2649 \| Line 2971 \| public class ForkJoinPool extends Abstra
2971		* commenced but not yet completed. This method may be useful for
2972		* debugging. A return of {@code true} reported a sufficient
2973		* period after shutdown may indicate that submitted tasks have
2974	<	* ignored or suppressed interruption, or are waiting for IO,
2974	>	* ignored or suppressed interruption, or are waiting for I/O,
2975		* causing this executor not to properly terminate. (See the
2976		* advisory notes for class {@link ForkJoinTask} stating that
2977		* tasks should not normally entail blocking operations. But if
#	Line 2660 \| Line 2982 \| public class ForkJoinPool extends Abstra
2982		public boolean isTerminating() {
2983		long c = ctl;
2984		return ((c & STOP_BIT) != 0L &&
2985	<	(short)(c >>> TC_SHIFT) != -parallelism);
2985	>	(short)(c >>> TC_SHIFT) + parallelism > 0);
2986		}
2987
2988		/**
#	Line 2669 \| Line 2991 \| public class ForkJoinPool extends Abstra
2991		* @return {@code true} if this pool has been shut down
2992		*/
2993		public boolean isShutdown() {
2994	<	return runState < 0;
2994	>	return plock < 0;
2995		}
2996
2997		/**
2998	<	* Blocks until all tasks have completed execution after a shutdown
2999	<	* request, or the timeout occurs, or the current thread is
3000	<	* interrupted, whichever happens first.
2998	>	* Blocks until all tasks have completed execution after a
2999	>	* shutdown request, or the timeout occurs, or the current thread
3000	>	* is interrupted, whichever happens first. Because the {@link
3001	>	* #commonPool()} never terminates until program shutdown, when
3002	>	* applied to the common pool, this method is equivalent to {@link
3003	>	* #awaitQuiescence(long, TimeUnit)} but always returns {@code false}.
3004		*
3005		* @param timeout the maximum time to wait
3006		* @param unit the time unit of the timeout argument
#	Line 2685 \| Line 3010 \| public class ForkJoinPool extends Abstra
3010		*/
3011		public boolean awaitTermination(long timeout, TimeUnit unit)
3012		throws InterruptedException {
3013	+	if (Thread.interrupted())
3014	+	throw new InterruptedException();
3015	+	if (this == common) {
3016	+	awaitQuiescence(timeout, unit);
3017	+	return false;
3018	+	}
3019		long nanos = unit.toNanos(timeout);
3020	<	final Mutex lock = this.lock;
3021	<	lock.lock();
3022	<	try {
3020	>	if (isTerminated())
3021	>	return true;
3022	>	if (nanos <= 0L)
3023	>	return false;
3024	>	long deadline = System.nanoTime() + nanos;
3025	>	synchronized (this) {
3026		for (;;) {
3027		if (isTerminated())
3028		return true;
3029	<	if (nanos <= 0)
3029	>	if (nanos <= 0L)
3030		return false;
3031	<	nanos = termination.awaitNanos(nanos);
3031	>	long millis = TimeUnit.NANOSECONDS.toMillis(nanos);
3032	>	wait(millis > 0L ? millis : 1L);
3033	>	nanos = deadline - System.nanoTime();
3034		}
2699	–	} finally {
2700	–	lock.unlock();
3035		}
3036		}
3037
3038		/**
3039	+	* If called by a ForkJoinTask operating in this pool, equivalent
3040	+	* in effect to {@link ForkJoinTask#helpQuiesce}. Otherwise,
3041	+	* waits and/or attempts to assist performing tasks until this
3042	+	* pool {@link #isQuiescent} or the indicated timeout elapses.
3043	+	*
3044	+	* @param timeout the maximum time to wait
3045	+	* @param unit the time unit of the timeout argument
3046	+	* @return {@code true} if quiescent; {@code false} if the
3047	+	* timeout elapsed.
3048	+	*/
3049	+	public boolean awaitQuiescence(long timeout, TimeUnit unit) {
3050	+	long nanos = unit.toNanos(timeout);
3051	+	ForkJoinWorkerThread wt;
3052	+	Thread thread = Thread.currentThread();
3053	+	if ((thread instanceof ForkJoinWorkerThread) &&
3054	+	(wt = (ForkJoinWorkerThread)thread).pool == this) {
3055	+	helpQuiescePool(wt.workQueue);
3056	+	return true;
3057	+	}
3058	+	long startTime = System.nanoTime();
3059	+	WorkQueue[] ws;
3060	+	int r = 0, m;
3061	+	boolean found = true;
3062	+	while (!isQuiescent() && (ws = workQueues) != null &&
3063	+	(m = ws.length - 1) >= 0) {
3064	+	if (!found) {
3065	+	if ((System.nanoTime() - startTime) > nanos)
3066	+	return false;
3067	+	Thread.yield(); // cannot block
3068	+	}
3069	+	found = false;
3070	+	for (int j = (m + 1) << 2; j >= 0; --j) {
3071	+	ForkJoinTask<?> t; WorkQueue q; int b;
3072	+	if ((q = ws[r++ & m]) != null && (b = q.base) - q.top < 0) {
3073	+	found = true;
3074	+	if ((t = q.pollAt(b)) != null)
3075	+	t.doExec();
3076	+	break;
3077	+	}
3078	+	}
3079	+	}
3080	+	return true;
3081	+	}
3082	+
3083	+	/**
3084	+	* Waits and/or attempts to assist performing tasks indefinitely
3085	+	* until the {@link #commonPool()} {@link #isQuiescent}.
3086	+	*/
3087	+	static void quiesceCommonPool() {
3088	+	common.awaitQuiescence(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
3089	+	}
3090	+
3091	+	/**
3092		* Interface for extending managed parallelism for tasks running
3093		* in {@link ForkJoinPool}s.
3094		*
#	Line 2710 \| Line 3097 \| public class ForkJoinPool extends Abstra
3097		* not necessary. Method {@code block} blocks the current thread
3098		* if necessary (perhaps internally invoking {@code isReleasable}
3099		* before actually blocking). These actions are performed by any
3100	<	* thread invoking {@link ForkJoinPool#managedBlock}. The
3101	<	* unusual methods in this API accommodate synchronizers that may,
3102	<	* but don't usually, block for long periods. Similarly, they
3100	>	* thread invoking {@link ForkJoinPool#managedBlock(ManagedBlocker)}.
3101	>	* The unusual methods in this API accommodate synchronizers that
3102	>	* may, but don't usually, block for long periods. Similarly, they
3103		* allow more efficient internal handling of cases in which
3104		* additional workers may be, but usually are not, needed to
3105		* ensure sufficient parallelism. Toward this end,
#	Line 2770 \| Line 3157 \| public class ForkJoinPool extends Abstra
3157
3158		/**
3159		* Returns {@code true} if blocking is unnecessary.
3160	+	* @return {@code true} if blocking is unnecessary
3161		*/
3162		boolean isReleasable();
3163		}
#	Line 2797 \| Line 3185 \| public class ForkJoinPool extends Abstra
3185		public static void managedBlock(ManagedBlocker blocker)
3186		throws InterruptedException {
3187		Thread t = Thread.currentThread();
3188	<	ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ?
3189	<	((ForkJoinWorkerThread)t).pool : null);
3190	<	while (!blocker.isReleasable()) {
3191	<	if (p == null \|\| p.tryCompensate(null, blocker)) {
3192	<	try {
3193	<	do {} while (!blocker.isReleasable() && !blocker.block());
3194	<	} finally {
3195	<	if (p != null)
3188	>	if (t instanceof ForkJoinWorkerThread) {
3189	>	ForkJoinPool p = ((ForkJoinWorkerThread)t).pool;
3190	>	while (!blocker.isReleasable()) {
3191	>	if (p.tryCompensate(p.ctl)) {
3192	>	try {
3193	>	do {} while (!blocker.isReleasable() &&
3194	>	!blocker.block());
3195	>	} finally {
3196		p.incrementActiveCount();
3197	+	}
3198	+	break;
3199		}
2810	–	break;
3200		}
3201		}
3202	+	else {
3203	+	do {} while (!blocker.isReleasable() &&
3204	+	!blocker.block());
3205	+	}
3206		}
3207
3208		// AbstractExecutorService overrides. These rely on undocumented
#	Line 2830 \| Line 3223 \| public class ForkJoinPool extends Abstra
3223		private static final long PARKBLOCKER;
3224		private static final int ABASE;
3225		private static final int ASHIFT;
3226	+	private static final long STEALCOUNT;
3227	+	private static final long PLOCK;
3228	+	private static final long INDEXSEED;
3229	+	private static final long QBASE;
3230	+	private static final long QLOCK;
3231
3232		static {
3233	<	poolNumberGenerator = new AtomicInteger();
2836	<	nextSubmitterSeed = new AtomicInteger(0x55555555);
2837	<	modifyThreadPermission = new RuntimePermission("modifyThread");
2838	<	defaultForkJoinWorkerThreadFactory =
2839	<	new DefaultForkJoinWorkerThreadFactory();
2840	<	submitters = new ThreadSubmitter();
2841	<	int s;
3233	>	// initialize field offsets for CAS etc
3234		try {
3235		U = getUnsafe();
3236		Class<?> k = ForkJoinPool.class;
2845	–	Class<?> ak = ForkJoinTask[].class;
3237		CTL = U.objectFieldOffset
3238		(k.getDeclaredField("ctl"));
3239	+	STEALCOUNT = U.objectFieldOffset
3240	+	(k.getDeclaredField("stealCount"));
3241	+	PLOCK = U.objectFieldOffset
3242	+	(k.getDeclaredField("plock"));
3243	+	INDEXSEED = U.objectFieldOffset
3244	+	(k.getDeclaredField("indexSeed"));
3245		Class<?> tk = Thread.class;
3246		PARKBLOCKER = U.objectFieldOffset
3247		(tk.getDeclaredField("parkBlocker"));
3248	+	Class<?> wk = WorkQueue.class;
3249	+	QBASE = U.objectFieldOffset
3250	+	(wk.getDeclaredField("base"));
3251	+	QLOCK = U.objectFieldOffset
3252	+	(wk.getDeclaredField("qlock"));
3253	+	Class<?> ak = ForkJoinTask[].class;
3254		ABASE = U.arrayBaseOffset(ak);
3255	<	s = U.arrayIndexScale(ak);
3255	>	int scale = U.arrayIndexScale(ak);
3256	>	if ((scale & (scale - 1)) != 0)
3257	>	throw new Error("data type scale not a power of two");
3258	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
3259		} catch (Exception e) {
3260		throw new Error(e);
3261		}
3262	<	if ((s & (s-1)) != 0)
3263	<	throw new Error("data type scale not a power of two");
3264	<	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3262	>
3263	>	submitters = new ThreadLocal<Submitter>();
3264	>	defaultForkJoinWorkerThreadFactory =
3265	>	new DefaultForkJoinWorkerThreadFactory();
3266	>	modifyThreadPermission = new RuntimePermission("modifyThread");
3267	>
3268	>	common = java.security.AccessController.doPrivileged
3269	>	(new java.security.PrivilegedAction<ForkJoinPool>() {
3270	>	public ForkJoinPool run() { return makeCommonPool(); }});
3271	>	int par = common.parallelism; // report 1 even if threads disabled
3272	>	commonParallelism = par > 0 ? par : 1;
3273	>	}
3274	>
3275	>	/**
3276	>	* Creates and returns the common pool, respecting user settings
3277	>	* specified via system properties.
3278	>	*/
3279	>	private static ForkJoinPool makeCommonPool() {
3280	>	int parallelism = -1;
3281	>	ForkJoinWorkerThreadFactory factory
3282	>	= defaultForkJoinWorkerThreadFactory;
3283	>	UncaughtExceptionHandler handler = null;
3284	>	try { // ignore exceptions in accesing/parsing properties
3285	>	String pp = System.getProperty
3286	>	("java.util.concurrent.ForkJoinPool.common.parallelism");
3287	>	String fp = System.getProperty
3288	>	("java.util.concurrent.ForkJoinPool.common.threadFactory");
3289	>	String hp = System.getProperty
3290	>	("java.util.concurrent.ForkJoinPool.common.exceptionHandler");
3291	>	if (pp != null)
3292	>	parallelism = Integer.parseInt(pp);
3293	>	if (fp != null)
3294	>	factory = ((ForkJoinWorkerThreadFactory)ClassLoader.
3295	>	getSystemClassLoader().loadClass(fp).newInstance());
3296	>	if (hp != null)
3297	>	handler = ((UncaughtExceptionHandler)ClassLoader.
3298	>	getSystemClassLoader().loadClass(hp).newInstance());
3299	>	} catch (Exception ignore) {
3300	>	}
3301	>
3302	>	if (parallelism < 0 && // default 1 less than #cores
3303	>	(parallelism = Runtime.getRuntime().availableProcessors() - 1) < 0)
3304	>	parallelism = 0;
3305	>	if (parallelism > MAX_CAP)
3306	>	parallelism = MAX_CAP;
3307	>	return new ForkJoinPool(parallelism, factory, handler, LIFO_QUEUE,
3308	>	"ForkJoinPool.commonPool-worker-");
3309		}
3310
3311		/**
#	Line 2868 \| Line 3318 \| public class ForkJoinPool extends Abstra
3318		private static sun.misc.Unsafe getUnsafe() {
3319		try {
3320		return sun.misc.Unsafe.getUnsafe();
3321	<	} catch (SecurityException se) {
3322	<	try {
3323	<	return java.security.AccessController.doPrivileged
3324	<	(new java.security
3325	<	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
3326	<	public sun.misc.Unsafe run() throws Exception {
3327	<	java.lang.reflect.Field f = sun.misc
3328	<	.Unsafe.class.getDeclaredField("theUnsafe");
3329	<	f.setAccessible(true);
3330	<	return (sun.misc.Unsafe) f.get(null);
3331	<	}});
3332	<	} catch (java.security.PrivilegedActionException e) {
3333	<	throw new RuntimeException("Could not initialize intrinsics",
3334	<	e.getCause());
3335	<	}
3321	>	} catch (SecurityException tryReflectionInstead) {}
3322	>	try {
3323	>	return java.security.AccessController.doPrivileged
3324	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
3325	>	public sun.misc.Unsafe run() throws Exception {
3326	>	Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class;
3327	>	for (java.lang.reflect.Field f : k.getDeclaredFields()) {
3328	>	f.setAccessible(true);
3329	>	Object x = f.get(null);
3330	>	if (k.isInstance(x))
3331	>	return k.cast(x);
3332	>	}
3333	>	throw new NoSuchFieldError("the Unsafe");
3334	>	}});
3335	>	} catch (java.security.PrivilegedActionException e) {
3336	>	throw new RuntimeException("Could not initialize intrinsics",
3337	>	e.getCause());
3338		}
3339		}
2888	–
3340		}

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Comparing jsr166/src/jsr166e/ForkJoinPool.java (file contents): Revision 1.5 by jsr166, Sun Oct 21 04:14:31 2012 UTC vs. Revision 1.58 by dl, Wed Jun 19 14:55:40 2013 UTC

Diff Legend

Comparing jsr166/src/jsr166e/ForkJoinPool.java (file contents):
Revision 1.5 by jsr166, Sun Oct 21 04:14:31 2012 UTC vs.
Revision 1.58 by dl, Wed Jun 19 14:55:40 2013 UTC