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root/jsr166/jsr166/src/jsr166y/ForkJoinPool.java

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.28 by jsr166, Mon Jul 27 20:57:44 2009 UTC vs.
Revision 1.92 by dl, Tue Feb 22 10:50:51 2011 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	–	import java.util.concurrent.*;
10	–
9		import java.util.ArrayList;
10		import java.util.Arrays;
11		import java.util.Collection;
12		import java.util.Collections;
13		import java.util.List;
14	<	import java.util.concurrent.locks.Condition;
14	>	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.TimeUnit;
22	>	import java.util.concurrent.TimeoutException;
23	>	import java.util.concurrent.atomic.AtomicInteger;
24		import java.util.concurrent.locks.LockSupport;
25		import java.util.concurrent.locks.ReentrantLock;
26	<	import java.util.concurrent.atomic.AtomicInteger;
20	<	import java.util.concurrent.atomic.AtomicLong;
26	>	import java.util.concurrent.locks.Condition;
27
28		/**
29	<	* An {@link ExecutorService} for running {@link ForkJoinTask}s.  A
30	<	* ForkJoinPool provides the entry point for submissions from
31	<	* non-ForkJoinTasks, as well as management and monitoring operations.
32	<	* Normally a single ForkJoinPool is used for a large number of
27	<	* submitted tasks. Otherwise, use would not usually outweigh the
28	<	* construction and bookkeeping overhead of creating a large set of
29	<	* threads.
29	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
30	>	* A {@code ForkJoinPool} provides the entry point for submissions
31	>	* from non-{@code ForkJoinTask} clients, as well as management and
32	>	* monitoring operations.
33		*
34	<	* <p>ForkJoinPools differ from other kinds of Executors mainly in
35	<	* that they provide <em>work-stealing</em>: all threads in the pool
36	<	* attempt to find and execute subtasks created by other active tasks
37	<	* (eventually blocking if none exist). This makes them efficient when
38	<	* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
39	<	* as the mixed execution of some plain Runnable- or Callable- based
40	<	* activities along with ForkJoinTasks. When setting
41	<	* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for
42	<	* use with fine-grained tasks that are never joined. Otherwise, other
40	<	* ExecutorService implementations are typically more appropriate
41	<	* choices.
34	>	* <p>A {@code ForkJoinPool} differs from other kinds of {@link
35	>	* ExecutorService} mainly by virtue of employing
36	>	* <em>work-stealing</em>: all threads in the pool attempt to find and
37	>	* execute subtasks created by other active tasks (eventually blocking
38	>	* waiting for work if none exist). This enables efficient processing
39	>	* when most tasks spawn other subtasks (as do most {@code
40	>	* ForkJoinTask}s). When setting <em>asyncMode</em> to true in
41	>	* constructors, {@code ForkJoinPool}s may also be appropriate for use
42	>	* with event-style tasks that are never joined.
43		*
44	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
45	<	* (target pool size), which it attempts to maintain by dynamically
46	<	* adding, suspending, or resuming threads, even if some tasks are
47	<	* waiting to join others. However, no such adjustments are performed
48	<	* in the face of blocked IO or other unmanaged synchronization. The
49	<	* nested {@code ManagedBlocker} interface enables extension of
50	<	* the kinds of synchronization accommodated.  The target parallelism
51	<	* level may also be changed dynamically ({@code setParallelism})
52	<	* and thread construction can be limited using methods
52	<	* {@code setMaximumPoolSize} and/or
53	<	* {@code setMaintainsParallelism}.
44	>	* <p>A {@code ForkJoinPool} is constructed with a given target
45	>	* parallelism level; by default, equal to the number of available
46	>	* processors. The pool attempts to maintain enough active (or
47	>	* available) threads by dynamically adding, suspending, or resuming
48	>	* internal worker threads, even if some tasks are stalled waiting to
49	>	* join others. However, no such adjustments are guaranteed in the
50	>	* face of blocked IO or other unmanaged synchronization. The nested
51	>	* {@link ManagedBlocker} interface enables extension of the kinds of
52	>	* synchronization accommodated.
53		*
54		* <p>In addition to execution and lifecycle control methods, this
55		* class provides status check methods (for example
56	<	* {@code getStealCount}) that are intended to aid in developing,
56	>	* {@link #getStealCount}) that are intended to aid in developing,
57		* tuning, and monitoring fork/join applications. Also, method
58	<	* {@code toString} returns indications of pool state in a
58	>	* {@link #toString} returns indications of pool state in a
59		* convenient form for informal monitoring.
60		*
61	+	* <p> As is the case with other ExecutorServices, there are three
62	+	* main task execution methods summarized in the following
63	+	* table. These are designed to be used by clients not already engaged
64	+	* in fork/join computations in the current pool.  The main forms of
65	+	* these methods accept instances of {@code ForkJoinTask}, but
66	+	* overloaded forms also allow mixed execution of plain {@code
67	+	* Runnable}- or {@code Callable}- based activities as well.  However,
68	+	* tasks that are already executing in a pool should normally
69	+	* <em>NOT</em> use these pool execution methods, but instead use the
70	+	* within-computation forms listed in the table.
71	+	*
72	+	* <table BORDER CELLPADDING=3 CELLSPACING=1>
73	+	*  <tr>
74	+	*    <td></td>
75	+	*    <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
76	+	*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
77	+	*  </tr>
78	+	*  <tr>
79	+	*    <td> <b>Arrange async execution</td>
80	+	*    <td> {@link #execute(ForkJoinTask)}</td>
81	+	*    <td> {@link ForkJoinTask#fork}</td>
82	+	*  </tr>
83	+	*  <tr>
84	+	*    <td> <b>Await and obtain result</td>
85	+	*    <td> {@link #invoke(ForkJoinTask)}</td>
86	+	*    <td> {@link ForkJoinTask#invoke}</td>
87	+	*  </tr>
88	+	*  <tr>
89	+	*    <td> <b>Arrange exec and obtain Future</td>
90	+	*    <td> {@link #submit(ForkJoinTask)}</td>
91	+	*    <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td>
92	+	*  </tr>
93	+	* </table>
94	+	*
95	+	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
96	+	* used for all parallel task execution in a program or subsystem.
97	+	* Otherwise, use would not usually outweigh the construction and
98	+	* bookkeeping overhead of creating a large set of threads. For
99	+	* example, a common pool could be used for the {@code SortTasks}
100	+	* illustrated in {@link RecursiveAction}. Because {@code
101	+	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
102	+	* daemon} mode, there is typically no need to explicitly {@link
103	+	* #shutdown} such a pool upon program exit.
104	+	*
105	+	* <pre>
106	+	* static final ForkJoinPool mainPool = new ForkJoinPool();
107	+	* ...
108	+	* public void sort(long[] array) {
109	+	*   mainPool.invoke(new SortTask(array, 0, array.length));
110	+	* }
111	+	* </pre>
112	+	*
113		* <p><b>Implementation notes</b>: This implementation restricts the
114		* maximum number of running threads to 32767. Attempts to create
115	<	* pools with greater than the maximum result in
116	<	* IllegalArgumentExceptions.
115	>	* pools with greater than the maximum number result in
116	>	* {@code IllegalArgumentException}.
117	>	*
118	>	* <p>This implementation rejects submitted tasks (that is, by throwing
119	>	* {@link RejectedExecutionException}) only when the pool is shut down
120	>	* or internal resources have been exhausted.
121		*
122		* @since 1.7
123		* @author Doug Lea
#	Line 70 | Line 125 | import java.util.concurrent.atomic.Atomi
125		public class ForkJoinPool extends AbstractExecutorService {
126
127		/*
128	<	* See the extended comments interspersed below for design,
129	<	* rationale, and walkthroughs.
130	<	*/
131	<
132	<	/** Mask for packing and unpacking shorts */
133	<	private static final int  shortMask = 0xffff;
134	<
135	<	/** Max pool size -- must be a power of two minus 1 */
136	<	private static final int MAX_THREADS =  0x7FFF;
137	<
138	<	/**
139	<	* Factory for creating new ForkJoinWorkerThreads.  A
140	<	* ForkJoinWorkerThreadFactory must be defined and used for
141	<	* ForkJoinWorkerThread subclasses that extend base functionality
142	<	* or initialize threads with different contexts.
128	>	* Implementation Overview
129	>	*
130	>	* This class provides the central bookkeeping and control for a
131	>	* set of worker threads: Submissions from non-FJ threads enter
132	>	* into a submission queue. Workers take these tasks and typically
133	>	* split them into subtasks that may be stolen by other workers.
134	>	* Preference rules give first priority to processing tasks from
135	>	* their own queues (LIFO or FIFO, depending on mode), then to
136	>	* randomized FIFO steals of tasks in other worker queues, and
137	>	* lastly to new submissions.
138	>	*
139	>	* The main throughput advantages of work-stealing stem from
140	>	* decentralized control -- workers mostly take tasks from
141	>	* themselves or each other. We cannot negate this in the
142	>	* implementation of other management responsibilities. The main
143	>	* tactic for avoiding bottlenecks is packing nearly all
144	>	* essentially atomic control state into a single 64bit volatile
145	>	* variable ("ctl"). This variable is read on the order of 10-100
146	>	* times as often as it is modified (always via CAS). (There is
147	>	* some additional control state, for example variable "shutdown"
148	>	* for which we can cope with uncoordinated updates.)  This
149	>	* streamlines synchronization and control at the expense of messy
150	>	* constructions needed to repack status bits upon updates.
151	>	* Updates tend not to contend with each other except during
152	>	* bursts while submitted tasks begin or end.  In some cases when
153	>	* they do contend, threads can instead do something else
154	>	* (usually, scan for tesks) until contention subsides.
155	>	*
156	>	* To enable packing, we restrict maximum parallelism to (1<<15)-1
157	>	* (which is far in excess of normal operating range) to allow
158	>	* ids, counts, and their negations (used for thresholding) to fit
159	>	* into 16bit fields.
160	>	*
161	>	* Recording Workers.  Workers are recorded in the "workers" array
162	>	* that is created upon pool construction and expanded if (rarely)
163	>	* necessary.  This is an array as opposed to some other data
164	>	* structure to support index-based random steals by workers.
165	>	* Updates to the array recording new workers and unrecording
166	>	* terminated ones are protected from each other by a seqLock
167	>	* (scanGuard) but the array is otherwise concurrently readable,
168	>	* and accessed directly by workers. To simplify index-based
169	>	* operations, the array size is always a power of two, and all
170	>	* readers must tolerate null slots. To avoid flailing during
171	>	* start-up, the array is presized to hold twice #parallelism
172	>	* workers (which is unlikely to need further resizing during
173	>	* execution). But to avoid dealing with so many null slots,
174	>	* variable scanGuard includes a mask for the nearest power of two
175	>	* that contains all current workers.  All worker thread creation
176	>	* is on-demand, triggered by task submissions, replacement of
177	>	* terminated workers, and/or compensation for blocked
178	>	* workers. However, all other support code is set up to work with
179	>	* other policies.  To ensure that we do not hold on to worker
180	>	* references that would prevent GC, ALL accesses to workers are
181	>	* via indices into the workers array (which is one source of some
182	>	* of the messy code constructions here). In essence, the workers
183	>	* array serves as a weak reference mechanism. Thus for example
184	>	* the wait queue field of ctl stores worker indices, not worker
185	>	* references.  Access to the workers in associated methods (for
186	>	* example signalWork) must both index-check and null-check the
187	>	* IDs. All such accesses ignore bad IDs by returning out early
188	>	* from what they are doing, since this can only be associated
189	>	* with termination, in which case it is OK to give up.
190	>	*
191	>	* All uses of the workers array, as well as queue arrays, check
192	>	* that the array is non-null (even if previously non-null). This
193	>	* allows nulling during termination, which is currently not
194	>	* necessary, but remains an option for resource-revocation-based
195	>	* shutdown schemes.
196	>	*
197	>	* Wait Queuing. Unlike HPC work-stealing frameworks, we cannot
198	>	* let workers spin indefinitely scanning for tasks when none are
199	>	* can be immediately found, and we cannot start/resume workers
200	>	* unless there appear to be tasks available.  On the other hand,
201	>	* we must quickly prod them into action when new tasks are
202	>	* submitted or generated.  We park/unpark workers after placing
203	>	* in an event wait queue when they cannot find work. This "queue"
204	>	* is actually a simple Treiber stack, headed by the "id" field of
205	>	* ctl, plus a 15bit counter value to both wake up waiters (by
206	>	* advancing their count) and avoid ABA effects. Successors are
207	>	* held in worker field "nextWait".  Queuing deals with several
208	>	* intrinsic races, mainly that a task-producing thread can miss
209	>	* seeing (and signalling) another thread that gave up looking for
210	>	* work but has not yet entered the wait queue. We solve this by
211	>	* requiring a full sweep of all workers both before (in scan())
212	>	* and after (in awaitWork()) a newly waiting worker is added to
213	>	* the wait queue. During a rescan, the worker might release some
214	>	* other queued worker rather than itself, which has the same net
215	>	* effect.
216	>	*
217	>	* Signalling.  We create or wake up workers only when there
218	>	* appears to be at least one task they might be able to find and
219	>	* execute.  When a submission is added or another worker adds a
220	>	* task to a queue that previously had two or fewer tasks, they
221	>	* signal waiting workers (or trigger creation of new ones if
222	>	* fewer than the given parallelism level -- see signalWork).
223	>	* These primary signals are buttressed by signals during rescans
224	>	* as well as those performed when a worker steals a task and
225	>	* notices that there are more tasks too; together these cover the
226	>	* signals needed in cases when more than two tasks are pushed
227	>	* but untaken.
228	>	*
229	>	* Trimming workers. To release resources after periods of lack of
230	>	* use, a worker starting to wait when the pool is quiescent will
231	>	* time out and terminate if the pool has remained quiescent for
232	>	* SHRINK_RATE nanosecs.
233	>	*
234	>	* Submissions. External submissions are maintained in an
235	>	* array-based queue that is structured identically to
236	>	* ForkJoinWorkerThread queues (which see) except for the use of
237	>	* submissionLock in method addSubmission. Unlike worker queues,
238	>	* multiple external threads can add new submissions.
239	>	*
240	>	* Compensation. Beyond work-stealing support and lifecycle
241	>	* control, the main responsibility of this framework is to take
242	>	* actions when one worker is waiting to join a task stolen (or
243	>	* always held by) another.  Because we are multiplexing many
244	>	* tasks on to a pool of workers, we can't just let them block (as
245	>	* in Thread.join).  We also cannot just reassign the joiner's
246	>	* run-time stack with another and replace it later, which would
247	>	* be a form of "continuation", that even if possible is not
248	>	* necessarily a good idea since we sometimes need both an
249	>	* unblocked task and its continuation to progress. Instead we
250	>	* combine two tactics:
251	>	*
252	>	*   Helping: Arranging for the joiner to execute some task that it
253	>	*      would be running if the steal had not occurred.  Method
254	>	*      ForkJoinWorkerThread.joinTask tracks joining->stealing
255	>	*      links to try to find such a task.
256	>	*
257	>	*   Compensating: Unless there are already enough live threads,
258	>	*      method tryPreBlock() may create or re-activate a spare
259	>	*      thread to compensate for blocked joiners until they
260	>	*      unblock.
261	>	*
262	>	* The ManagedBlocker extension API can't use helping so relies
263	>	* only on compensation in method awaitBlocker.
264	>	*
265	>	* It is impossible to keep exactly the target parallelism number
266	>	* of threads running at any given time.  Determining the
267	>	* existence of conservatively safe helping targets, the
268	>	* availability of already-created spares, and the apparent need
269	>	* to create new spares are all racy and require heuristic
270	>	* guidance, so we rely on multiple retries of each.  Currently,
271	>	* in keeping with on-demand signalling policy, we compensate only
272	>	* if blocking would leave less than one active (non-waiting,
273	>	* non-blocked) worker. Additionally, to avoid some false alarms
274	>	* due to GC, lagging counters, system activity, etc, compensated
275	>	* blocking for joins is only attempted after a number of rechecks
276	>	* proportional to the current apparent deficit (where retries are
277	>	* interspersed with Thread.yield, for good citizenship).  The
278	>	* variable blockedCount, incremented before blocking and
279	>	* decremented after, is sometimes needed to distinguish cases of
280	>	* waiting for work vs blocking on joins or other managed sync,
281	>	* but both the cases are equivalent for most pool control, so we
282	>	* can update non-atomically. (Additionally, contention on
283	>	* blockedCount alleviates some contention on ctl).
284	>	*
285	>	* Shutdown and Termination. A call to shutdownNow atomically sets
286	>	* the ctl stop bit and then (non-atomically) sets each workers
287	>	* "terminate" status, cancels all unprocessed tasks, and wakes up
288	>	* all waiting workers.  Detecting whether termination should
289	>	* commence after a non-abrupt shutdown() call requires more work
290	>	* and bookkeeping. We need consensus about quiesence (i.e., that
291	>	* there is no more work) which is reflected in active counts so
292	>	* long as there are no current blockers, as well as possible
293	>	* re-evaluations during independent changes in blocking or
294	>	* quiescing workers.
295	>	*
296	>	* Style notes: There is a lot of representation-level coupling
297	>	* among classes ForkJoinPool, ForkJoinWorkerThread, and
298	>	* ForkJoinTask.  Most fields of ForkJoinWorkerThread maintain
299	>	* data structures managed by ForkJoinPool, so are directly
300	>	* accessed.  Conversely we allow access to "workers" array by
301	>	* workers, and direct access to ForkJoinTask.status by both
302	>	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
303	>	* trying to reduce this, since any associated future changes in
304	>	* representations will need to be accompanied by algorithmic
305	>	* changes anyway. All together, these low-level implementation
306	>	* choices produce as much as a factor of 4 performance
307	>	* improvement compared to naive implementations, and enable the
308	>	* processing of billions of tasks per second, at the expense of
309	>	* some ugliness.
310	>	*
311	>	* Methods signalWork() and scan() are the main bottlenecks so are
312	>	* especially heavily micro-optimized/mangled.  There are lots of
313	>	* inline assignments (of form "while ((local = field) != 0)")
314	>	* which are usually the simplest way to ensure the required read
315	>	* orderings (which are sometimes critical). This leads to a
316	>	* "C"-like style of listing declarations of these locals at the
317	>	* heads of methods or blocks.  There are several occurrences of
318	>	* the unusual "do {} while (!cas...)"  which is the simplest way
319	>	* to force an update of a CAS'ed variable. There are also other
320	>	* coding oddities that help some methods perform reasonably even
321	>	* when interpreted (not compiled).
322	>	*
323	>	* The order of declarations in this file is: (1) declarations of
324	>	* statics (2) fields (along with constants used when unpacking
325	>	* some of them), listed in an order that tends to reduce
326	>	* contention among them a bit under most JVMs.  (3) internal
327	>	* control methods (4) callbacks and other support for
328	>	* ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
329	>	* methods (plus a few little helpers). (6) static block
330	>	* initializing all statics in a minimally dependent order.
331	>	*/
332	>
333	>	/**
334	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
335	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
336	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
337	>	* functionality or initialize threads with different contexts.
338		*/
339		public static interface ForkJoinWorkerThreadFactory {
340		/**
341		* Returns a new worker thread operating in the given pool.
342		*
343		* @param pool the pool this thread works in
344	<	* @throws NullPointerException if pool is null
344	>	* @throws NullPointerException if the pool is null
345		*/
346		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
347		}
#	Line 100 | Line 350 | public class ForkJoinPool extends Abstra
350		* Default ForkJoinWorkerThreadFactory implementation; creates a
351		* new ForkJoinWorkerThread.
352		*/
353	<	static class  DefaultForkJoinWorkerThreadFactory
353	>	static class DefaultForkJoinWorkerThreadFactory
354		implements ForkJoinWorkerThreadFactory {
355		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
356	<	try {
107	<	return new ForkJoinWorkerThread(pool);
108	<	} catch (OutOfMemoryError oom)  {
109	<	return null;
110	<	}
356	>	return new ForkJoinWorkerThread(pool);
357		}
358		}
359
#	Line 116 | Line 362 | public class ForkJoinPool extends Abstra
362		* overridden in ForkJoinPool constructors.
363		*/
364		public static final ForkJoinWorkerThreadFactory
365	<	defaultForkJoinWorkerThreadFactory =
120	<	new DefaultForkJoinWorkerThreadFactory();
365	>	defaultForkJoinWorkerThreadFactory;
366
367		/**
368		* Permission required for callers of methods that may start or
369		* kill threads.
370		*/
371	<	private static final RuntimePermission modifyThreadPermission =
127	<	new RuntimePermission("modifyThread");
371	>	private static final RuntimePermission modifyThreadPermission;
372
373		/**
374		* If there is a security manager, makes sure caller has
#	Line 139 | Line 383 | public class ForkJoinPool extends Abstra
383		/**
384		* Generator for assigning sequence numbers as pool names.
385		*/
386	<	private static final AtomicInteger poolNumberGenerator =
143	<	new AtomicInteger();
386	>	private static final AtomicInteger poolNumberGenerator;
387
388		/**
389	<	* Array holding all worker threads in the pool. Initialized upon
390	<	* first use. Array size must be a power of two.  Updates and
391	<	* replacements are protected by workerLock, but it is always kept
392	<	* in a consistent enough state to be randomly accessed without
393	<	* locking by workers performing work-stealing.
389	>	* Generator for initial random seeds for worker victim
390	>	* selection. This is used only to create initial seeds. Random
391	>	* steals use a cheaper xorshift generator per steal attempt. We
392	>	* don't expect much contention on seedGenerator, so just use a
393	>	* plain Random.
394		*/
395	<	volatile ForkJoinWorkerThread[] workers;
395	>	static final Random workerSeedGenerator;
396
397		/**
398	<	* Lock protecting access to workers.
398	>	* Array holding all worker threads in the pool.  Initialized upon
399	>	* construction. Array size must be a power of two.  Updates and
400	>	* replacements are protected by scanGuard, but the array is
401	>	* always kept in a consistent enough state to be randomly
402	>	* accessed without locking by workers performing work-stealing,
403	>	* as well as other traversal-based methods in this class, so long
404	>	* as reads memory-acquire by first reading ctl. All readers must
405	>	* tolerate that some array slots may be null.
406		*/
407	<	private final ReentrantLock workerLock;
407	>	ForkJoinWorkerThread[] workers;
408
409		/**
410	<	* Condition for awaitTermination.
410	>	* Initial size for submission queue array. Must be a power of
411	>	* two.  In many applications, these always stay small so we use a
412	>	* small initial cap.
413		*/
414	<	private final Condition termination;
414	>	private static final int INITIAL_QUEUE_CAPACITY = 8;
415	>
416	>	/**
417	>	* Maximum size for submission queue array. Must be a power of two
418	>	* less than or equal to 1 << (31 - width of array entry) to
419	>	* ensure lack of index wraparound, but is capped at a lower
420	>	* value to help users trap runaway computations.
421	>	*/
422	>	private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 24; // 16M
423
424		/**
425	<	* The uncaught exception handler used when any worker
166	<	* abruptly terminates
425	>	* Array serving as submission queue. Initialized upon construction.
426		*/
427	<	private Thread.UncaughtExceptionHandler ueh;
427	>	private ForkJoinTask<?>[] submissionQueue;
428	>
429	>	/**
430	>	* Lock protecting submissions array for addSubmission
431	>	*/
432	>	private final ReentrantLock submissionLock;
433	>
434	>	/**
435	>	* Condition for awaitTermination, using submissionLock for
436	>	* convenience.
437	>	*/
438	>	private final Condition termination;
439
440		/**
441		* Creation factory for worker threads.
#	Line 173 | Line 443 | public class ForkJoinPool extends Abstra
443		private final ForkJoinWorkerThreadFactory factory;
444
445		/**
446	<	* Head of stack of threads that were created to maintain
447	<	* parallelism when other threads blocked, but have since
178	<	* suspended when the parallelism level rose.
446	>	* The uncaught exception handler used when any worker abruptly
447	>	* terminates.
448		*/
449	<	private volatile WaitQueueNode spareStack;
449	>	final Thread.UncaughtExceptionHandler ueh;
450
451		/**
452	<	* Sum of per-thread steal counts, updated only when threads are
184	<	* idle or terminating.
452	>	* Prefix for assigning names to worker threads
453		*/
454	<	private final AtomicLong stealCount;
454	>	private final String workerNamePrefix;
455
456		/**
457	<	* Queue for external submissions.
457	>	* Sum of per-thread steal counts, updated only when threads are
458	>	* idle or terminating.
459		*/
460	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
460	>	private volatile long stealCount;
461
462		/**
463	<	* Head of Treiber stack for barrier sync. See below for explanation.
463	>	* Main pool control -- a long packed with:
464	>	* AC: Number of active running workers minus target parallelism (16 bits)
465	>	* TC: Number of total workers minus target parallelism (16bits)
466	>	* ST: true if pool is terminating (1 bit)
467	>	* EC: the wait count of top waiting thread (15 bits)
468	>	* ID: ~poolIndex of top of Treiber stack of waiting threads (16 bits)
469	>	*
470	>	* When convenient, we can extract the upper 32 bits of counts and
471	>	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
472	>	* (int)ctl.  The ec field is never accessed alone, but always
473	>	* together with id and st. The offsets of counts by the target
474	>	* parallelism and the positionings of fields makes it possible to
475	>	* perform the most common checks via sign tests of fields: When
476	>	* ac is negative, there are not enough active workers, when tc is
477	>	* negative, there are not enough total workers, when id is
478	>	* negative, there is at least one waiting worker, and when e is
479	>	* negative, the pool is terminating.  To deal with these possibly
480	>	* negative fields, we use casts in and out of "short" and/or
481	>	* signed shifts to maintain signedness.  Note: AC_SHIFT is
482	>	* redundantly declared in ForkJoinWorkerThread in order to
483	>	* integrate a surplus-threads check.
484		*/
485	<	private volatile WaitQueueNode syncStack;
485	>	volatile long ctl;
486	>
487	>	// bit positions/shifts for fields
488	>	private static final int  AC_SHIFT   = 48;
489	>	private static final int  TC_SHIFT   = 32;
490	>	private static final int  ST_SHIFT   = 31;
491	>	private static final int  EC_SHIFT   = 16;
492	>
493	>	// bounds
494	>	private static final int  MAX_ID     = 0x7fff;  // max poolIndex
495	>	private static final int  SMASK      = 0xffff;  // mask short bits
496	>	private static final int  SHORT_SIGN = 1 << 15;
497	>	private static final int  INT_SIGN   = 1 << 31;
498	>
499	>	// masks
500	>	private static final long STOP_BIT   = 0x0001L << ST_SHIFT;
501	>	private static final long AC_MASK    = ((long)SMASK) << AC_SHIFT;
502	>	private static final long TC_MASK    = ((long)SMASK) << TC_SHIFT;
503	>
504	>	// units for incrementing and decrementing
505	>	private static final long TC_UNIT    = 1L << TC_SHIFT;
506	>	private static final long AC_UNIT    = 1L << AC_SHIFT;
507	>
508	>	// masks and units for dealing with u = (int)(ctl >>> 32)
509	>	private static final int  UAC_SHIFT  = AC_SHIFT - 32;
510	>	private static final int  UTC_SHIFT  = TC_SHIFT - 32;
511	>	private static final int  UAC_MASK   = SMASK << UAC_SHIFT;
512	>	private static final int  UTC_MASK   = SMASK << UTC_SHIFT;
513	>	private static final int  UAC_UNIT   = 1 << UAC_SHIFT;
514	>	private static final int  UTC_UNIT   = 1 << UTC_SHIFT;
515	>
516	>	// masks and units for dealing with e = (int)ctl
517	>	private static final int  E_MASK     = 0x7fffffff; // no STOP_BIT
518	>	private static final int  EC_UNIT    = 1 << EC_SHIFT;
519
520		/**
521	<	* The count for event barrier
521	>	* The target parallelism level.
522		*/
523	<	private volatile long eventCount;
523	>	final int parallelism;
524
525		/**
526	<	* Pool number, just for assigning useful names to worker threads
526	>	* Index (mod submission queue length) of next element to take
527	>	* from submission queue.
528		*/
529	<	private final int poolNumber;
529	>	volatile int queueBase;
530
531		/**
532	<	* The maximum allowed pool size
532	>	* Index (mod submission queue length) of next element to add
533	>	* in submission queue.
534		*/
535	<	private volatile int maxPoolSize;
535	>	int queueTop;
536
537		/**
538	<	* The desired parallelism level, updated only under workerLock.
538	>	* True when shutdown() has been called.
539		*/
540	<	private volatile int parallelism;
540	>	volatile boolean shutdown;
541
542		/**
543		* True if use local fifo, not default lifo, for local polling
544	+	* Read by, and replicated by ForkJoinWorkerThreads
545		*/
546	<	private volatile boolean locallyFifo;
546	>	final boolean locallyFifo;
547
548		/**
549	<	* Holds number of total (i.e., created and not yet terminated)
550	<	* and running (i.e., not blocked on joins or other managed sync)
551	<	* threads, packed into one int to ensure consistent snapshot when
227	<	* making decisions about creating and suspending spare
228	<	* threads. Updated only by CAS.  Note: CASes in
229	<	* updateRunningCount and preJoin assume that running active count
230	<	* is in low word, so need to be modified if this changes.
549	>	* The number of threads in ForkJoinWorkerThreads.helpQuiescePool.
550	>	* When non-zero, suppresses automatic shutdown when active
551	>	* counts become zero.
552		*/
553	<	private volatile int workerCounts;
553	>	volatile int quiescerCount;
554
555	<	private static int totalCountOf(int s)           { return s >>> 16;  }
556	<	private static int runningCountOf(int s)         { return s & shortMask; }
557	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
555	>	/**
556	>	* The number of threads blocked in join.
557	>	*/
558	>	volatile int blockedCount;
559
560		/**
561	<	* Adds delta (which may be negative) to running count.  This must
240	<	* be called before (with negative arg) and after (with positive)
241	<	* any managed synchronization (i.e., mainly, joins).
242	<	*
243	<	* @param delta the number to add
561	>	* Counter for worker Thread names (unrelated to their poolIndex)
562		*/
563	<	final void updateRunningCount(int delta) {
246	<	int s;
247	<	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
248	<	}
563	>	private volatile int nextWorkerNumber;
564
565		/**
566	<	* Adds delta (which may be negative) to both total and running
252	<	* count.  This must be called upon creation and termination of
253	<	* worker threads.
254	<	*
255	<	* @param delta the number to add
566	>	* The index for the next created worker. Accessed under scanGuard.
567		*/
568	<	private void updateWorkerCount(int delta) {
258	<	int d = delta + (delta << 16); // add to both lo and hi parts
259	<	int s;
260	<	do {} while (!casWorkerCounts(s = workerCounts, s + d));
261	<	}
568	>	private int nextWorkerIndex;
569
570		/**
571	<	* Lifecycle control. High word contains runState, low word
572	<	* contains the number of workers that are (probably) executing
573	<	* tasks. This value is atomically incremented before a worker
574	<	* gets a task to run, and decremented when worker has no tasks
575	<	* and cannot find any. These two fields are bundled together to
576	<	* support correct termination triggering.  Note: activeCount
577	<	* CAS'es cheat by assuming active count is in low word, so need
578	<	* to be modified if this changes
571	>	* SeqLock and index masking for for updates to workers array.
572	>	* Locked when SG_UNIT is set. Unlocking clears bit by adding
573	>	* SG_UNIT. Staleness of read-only operations can be checked by
574	>	* comparing scanGuard to value before the reads. The low 16 bits
575	>	* (i.e, anding with SMASK) hold (the smallest power of two
576	>	* covering all worker indices, minus one, and is used to avoid
577	>	* dealing with large numbers of null slots when the workers array
578	>	* is overallocated.
579		*/
580	<	private volatile int runControl;
580	>	volatile int scanGuard;
581
582	<	// RunState values. Order among values matters
276	<	private static final int RUNNING     = 0;
277	<	private static final int SHUTDOWN    = 1;
278	<	private static final int TERMINATING = 2;
279	<	private static final int TERMINATED  = 3;
582	>	private static final int SG_UNIT = 1 << 16;
583
584	<	private static int runStateOf(int c)             { return c >>> 16; }
585	<	private static int activeCountOf(int c)          { return c & shortMask; }
586	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
584	>	/**
585	>	* The wakeup interval (in nanoseconds) for a worker waiting for a
586	>	* task when the pool is quiescent to instead try to shrink the
587	>	* number of workers.  The exact value does not matter too
588	>	* much. It must be short enough to release resources during
589	>	* sustained periods of idleness, but not so short that threads
590	>	* are continually re-created.
591	>	*/
592	>	private static final long SHRINK_RATE =
593	>	4L * 1000L * 1000L * 1000L; // 4 seconds
594
595		/**
596	<	* Tries incrementing active count; fails on contention.
597	<	* Called by workers before/during executing tasks.
596	>	* Top-level loop for worker threads: On each step: if the
597	>	* previous step swept through all queues and found no tasks, or
598	>	* there are excess threads, then possibly blocks. Otherwise,
599	>	* scans for and, if found, executes a task. Returns when pool
600	>	* and/or worker terminate.
601		*
602	<	* @return true on success
602	>	* @param w the worker
603		*/
604	<	final boolean tryIncrementActiveCount() {
605	<	int c = runControl;
606	<	return casRunControl(c, c+1);
604	>	final void work(ForkJoinWorkerThread w) {
605	>	boolean swept = false;                // true on empty scans
606	>	long c;
607	>	while (!w.terminate && (int)(c = ctl) >= 0) {
608	>	int a;                            // active count
609	>	if (!swept && (a = (int)(c >> AC_SHIFT)) <= 0)
610	>	swept = scan(w, a);
611	>	else if (tryAwaitWork(w, c))
612	>	swept = false;
613	>	}
614		}
615
616	+	// Signalling
617	+
618		/**
619	<	* Tries decrementing active count; fails on contention.
620	<	* Possibly triggers termination on success.
621	<	* Called by workers when they can't find tasks.
619	>	* Wakes up or creates a worker.
620	>	*/
621	>	final void signalWork() {
622	>	/*
623	>	* The while condition is true if: (there is are too few total
624	>	* workers OR there is at least one waiter) AND (there are too
625	>	* few active workers OR the pool is terminating).  The value
626	>	* of e distinguishes the remaining cases: zero (no waiters)
627	>	* for create, negative if terminating (in which case do
628	>	* nothing), else release a waiter. The secondary checks for
629	>	* release (non-null array etc) can fail if the pool begins
630	>	* terminating after the test, and don't impose any added cost
631	>	* because JVMs must perform null and bounds checks anyway.
632	>	*/
633	>	long c; int e, u;
634	>	while ((((e = (int)(c = ctl)) | (u = (int)(c >>> 32))) &
635	>	(INT_SIGN|SHORT_SIGN)) == (INT_SIGN|SHORT_SIGN) && e >= 0) {
636	>	if (e > 0) {                         // release a waiting worker
637	>	int i; ForkJoinWorkerThread w; ForkJoinWorkerThread[] ws;
638	>	if ((ws = workers) == null ||
639	>	(i = ~e & SMASK) >= ws.length ||
640	>	(w = ws[i]) == null)
641	>	break;
642	>	long nc = (((long)(w.nextWait & E_MASK)) |
643	>	((long)(u + UAC_UNIT) << 32));
644	>	if (w.eventCount == e &&
645	>	UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
646	>	w.eventCount = (e + EC_UNIT) & E_MASK;
647	>	if (w.parked)
648	>	UNSAFE.unpark(w);
649	>	break;
650	>	}
651	>	}
652	>	else if (UNSAFE.compareAndSwapLong
653	>	(this, ctlOffset, c,
654	>	(long)(((u + UTC_UNIT) & UTC_MASK) |
655	>	((u + UAC_UNIT) & UAC_MASK)) << 32)) {
656	>	addWorker();
657	>	break;
658	>	}
659	>	}
660	>	}
661	>
662	>	/**
663	>	* Variant of signalWork to help release waiters on rescans.
664	>	* Tries once to release a waiter if active count < 0.
665		*
666	<	* @return true on success
666	>	* @return false if failed due to contention, else true
667		*/
668	<	final boolean tryDecrementActiveCount() {
669	<	int c = runControl;
670	<	int nextc = c - 1;
671	<	if (!casRunControl(c, nextc))
672	<	return false;
673	<	if (canTerminateOnShutdown(nextc))
674	<	terminateOnShutdown();
668	>	private boolean tryReleaseWaiter() {
669	>	long c; int e, i; ForkJoinWorkerThread w; ForkJoinWorkerThread[] ws;
670	>	if ((e = (int)(c = ctl)) > 0 &&
671	>	(int)(c >> AC_SHIFT) < 0 &&
672	>	(ws = workers) != null &&
673	>	(i = ~e & SMASK) < ws.length &&
674	>	(w = ws[i]) != null) {
675	>	long nc = ((long)(w.nextWait & E_MASK) |
676	>	((c + AC_UNIT) & (AC_MASK|TC_MASK)));
677	>	if (w.eventCount != e ||
678	>	!UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc))
679	>	return false;
680	>	w.eventCount = (e + EC_UNIT) & E_MASK;
681	>	if (w.parked)
682	>	UNSAFE.unpark(w);
683	>	}
684		return true;
685		}
686
687	+	// Scanning for tasks
688	+
689		/**
690	<	* Returns {@code true} if argument represents zero active count
691	<	* and nonzero runstate, which is the triggering condition for
692	<	* terminating on shutdown.
690	>	* Scans for and, if found, executes one task. Scans start at a
691	>	* random index of workers array, and randomly select the first
692	>	* (2*#workers)-1 probes, and then, if all empty, resort to 2
693	>	* circular sweeps, which is necessary to check quiescence. and
694	>	* taking a submission only if no stealable tasks were found.  The
695	>	* steal code inside the loop is a specialized form of
696	>	* ForkJoinWorkerThread.deqTask, followed bookkeeping to support
697	>	* helpJoinTask and signal propagation. The code for submission
698	>	* queues is almost identical. On each steal, the worker completes
699	>	* not only the task, but also all local tasks that this task may
700	>	* have generated. On detecting staleness or contention when
701	>	* trying to take a task, this method returns without finishing
702	>	* sweep, which allows global state rechecks before retry.
703	>	*
704	>	* @param w the worker
705	>	* @param a the number of active workers
706	>	* @return true if swept all queues without finding a task
707		*/
708	<	private static boolean canTerminateOnShutdown(int c) {
709	<	// i.e. least bit is nonzero runState bit
710	<	return ((c & -c) >>> 16) != 0;
708	>	private boolean scan(ForkJoinWorkerThread w, int a) {
709	>	int g = scanGuard; // mask 0 avoids useless scans if only one active
710	>	int m = parallelism == 1 - a? 0 : g & SMASK;
711	>	ForkJoinWorkerThread[] ws = workers;
712	>	if (ws == null || ws.length <= m)         // staleness check
713	>	return false;
714	>	for (int r = w.seed, k = r, j = -(m + m); j <= m + m; ++j) {
715	>	ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i;
716	>	ForkJoinWorkerThread v = ws[k & m];
717	>	if (v != null && (b = v.queueBase) != v.queueTop &&
718	>	(q = v.queue) != null && (i = (q.length - 1) & b) >= 0) {
719	>	long u = (i << ASHIFT) + ABASE;
720	>	if ((t = q[i]) != null && v.queueBase == b &&
721	>	UNSAFE.compareAndSwapObject(q, u, t, null)) {
722	>	int d = (v.queueBase = b + 1) - v.queueTop;
723	>	v.stealHint = w.poolIndex;
724	>	if (d != 0)
725	>	signalWork();             // propagate if nonempty
726	>	w.execTask(t);
727	>	}
728	>	r ^= r << 13; r ^= r >>> 17; w.seed = r ^ (r << 5);
729	>	return false;                     // store next seed
730	>	}
731	>	else if (j < 0) {                     // xorshift
732	>	r ^= r << 13; r ^= r >>> 17; k = r ^= r << 5;
733	>	}
734	>	else
735	>	++k;
736	>	}
737	>	if (scanGuard != g)                       // staleness check
738	>	return false;
739	>	else {                                    // try to take submission
740	>	ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i;
741	>	if ((b = queueBase) != queueTop &&
742	>	(q = submissionQueue) != null &&
743	>	(i = (q.length - 1) & b) >= 0) {
744	>	long u = (i << ASHIFT) + ABASE;
745	>	if ((t = q[i]) != null && queueBase == b &&
746	>	UNSAFE.compareAndSwapObject(q, u, t, null)) {
747	>	queueBase = b + 1;
748	>	w.execTask(t);
749	>	}
750	>	return false;
751	>	}
752	>	return true;                         // all queues empty
753	>	}
754		}
755
756		/**
757	<	* Transition run state to at least the given state. Return true
758	<	* if not already at least given state.
757	>	* Tries to enqueue worker in wait queue and await change in
758	>	* worker's eventCount.  Before blocking, rescans queues to avoid
759	>	* missed signals.  If the pool is quiescent, possibly terminates
760	>	* worker upon exit.
761	>	*
762	>	* @param w the calling worker
763	>	* @param c the ctl value on entry
764	>	* @return true if waited or another thread was released upon enq
765		*/
766	<	private boolean transitionRunStateTo(int state) {
767	<	for (;;) {
768	<	int c = runControl;
769	<	if (runStateOf(c) >= state)
770	<	return false;
771	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
766	>	private boolean tryAwaitWork(ForkJoinWorkerThread w, long c) {
767	>	int v = w.eventCount;
768	>	w.nextWait = (int)c;                       // w's successor record
769	>	long nc = (long)(v & E_MASK) | ((c - AC_UNIT) & (AC_MASK|TC_MASK));
770	>	if (ctl != c || !UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
771	>	long d = ctl; // return true if lost to a deq, to force rescan
772	>	return (int)d != (int)c && ((d - c) & AC_MASK) >= 0L;
773	>	}
774	>	if (parallelism + (int)(c >> AC_SHIFT) == 1 &&
775	>	blockedCount == 0 && quiescerCount == 0)
776	>	idleAwaitWork(w, v);               // quiescent -- maybe shrink
777	>
778	>	boolean rescanned = false;
779	>	for (int sc;;) {
780	>	if (w.eventCount != v)
781		return true;
782	+	if ((sc = w.stealCount) != 0) {
783	+	long s = stealCount;               // accumulate stealCount
784	+	if (UNSAFE.compareAndSwapLong(this, stealCountOffset, s, s+sc))
785	+	w.stealCount = 0;
786	+	}
787	+	else if (!rescanned) {
788	+	int g = scanGuard, m = g & SMASK;
789	+	ForkJoinWorkerThread[] ws = workers;
790	+	if (ws != null && m < ws.length) {
791	+	rescanned = true;
792	+	for (int i = 0; i <= m; ++i) {
793	+	ForkJoinWorkerThread u = ws[i];
794	+	if (u != null) {
795	+	if (u.queueBase != u.queueTop &&
796	+	!tryReleaseWaiter())
797	+	rescanned = false; // contended
798	+	if (w.eventCount != v)
799	+	return true;
800	+	}
801	+	}
802	+	}
803	+	if (scanGuard != g ||              // stale
804	+	(queueBase != queueTop && !tryReleaseWaiter()))
805	+	rescanned = false;
806	+	if (!rescanned)
807	+	Thread.yield();                // reduce contention
808	+	else
809	+	Thread.interrupted();          // clear before park
810	+	}
811	+	else {
812	+	w.parked = true;                   // must recheck
813	+	if (w.eventCount != v) {
814	+	w.parked = false;
815	+	return true;
816	+	}
817	+	LockSupport.park(this);
818	+	rescanned = w.parked = false;
819	+	}
820		}
821		}
822
823		/**
824	<	* Controls whether to add spares to maintain parallelism
825	<	*/
826	<	private volatile boolean maintainsParallelism;
824	>	* If pool is quiescent, checks for termination, and waits for
825	>	* event signal for up to SHRINK_RATE nanosecs. On timeout, if ctl
826	>	* has not changed, terminates the worker. Upon its termination
827	>	* (see deregisterWorker), it may wake up another worker to
828	>	* possibly repeat this process.
829	>	*
830	>	* @param w the calling worker
831	>	* @param v the eventCount w must wait until changed
832	>	*/
833	>	private void idleAwaitWork(ForkJoinWorkerThread w, int v) {
834	>	ForkJoinTask.helpExpungeStaleExceptions(); // help clean weak refs
835	>	if (shutdown)
836	>	tryTerminate(false);
837	>	long c = ctl;
838	>	long nc = (((c & (AC_MASK|TC_MASK)) + AC_UNIT) |
839	>	(long)(w.nextWait & E_MASK)); // ctl value to release w
840	>	if (w.eventCount == v &&
841	>	parallelism + (int)(c >> AC_SHIFT) == 0 &&
842	>	blockedCount == 0 && quiescerCount == 0) {
843	>	long startTime = System.nanoTime();
844	>	Thread.interrupted();
845	>	if (w.eventCount == v) {
846	>	w.parked = true;
847	>	if (w.eventCount == v)
848	>	LockSupport.parkNanos(this, SHRINK_RATE);
849	>	w.parked = false;
850	>	if (w.eventCount == v && ctl == c &&
851	>	System.nanoTime() - startTime >= SHRINK_RATE &&
852	>	UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
853	>	w.terminate = true;
854	>	w.eventCount = ((int)c + EC_UNIT) & E_MASK;
855	>	}
856	>	}
857	>	}
858	>	}
859
860	<	// Constructors
860	>	// Submissions
861
862		/**
863	<	* Creates a ForkJoinPool with a pool size equal to the number of
864	<	* processors available on the system, using the default
347	<	* ForkJoinWorkerThreadFactory.
863	>	* Enqueues the given task in the submissionQueue.  Same idea as
864	>	* ForkJoinWorkerThread.pushTask except for use of submissionLock.
865		*
866	<	* @throws SecurityException if a security manager exists and
350	<	*         the caller is not permitted to modify threads
351	<	*         because it does not hold {@link
352	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
866	>	* @param t the task
867		*/
868	<	public ForkJoinPool() {
869	<	this(Runtime.getRuntime().availableProcessors(),
870	<	defaultForkJoinWorkerThreadFactory);
868	>	private void addSubmission(ForkJoinTask<?> t) {
869	>	final ReentrantLock lock = this.submissionLock;
870	>	lock.lock();
871	>	try {
872	>	ForkJoinTask<?>[] q; int s, m;
873	>	if ((q = submissionQueue) != null) {    // ignore if queue removed
874	>	long u = (((s = queueTop) & (m = q.length-1)) << ASHIFT)+ABASE;
875	>	UNSAFE.putOrderedObject(q, u, t);
876	>	queueTop = s + 1;
877	>	if (s - queueBase == m)
878	>	growSubmissionQueue();
879	>	}
880	>	} finally {
881	>	lock.unlock();
882	>	}
883	>	signalWork();
884		}
885
886	+	//  (pollSubmission is defined below with exported methods)
887	+
888		/**
889	<	* Creates a ForkJoinPool with the indicated parallelism level
890	<	* threads and using the default ForkJoinWorkerThreadFactory.
362	<	*
363	<	* @param parallelism the number of worker threads
364	<	* @throws IllegalArgumentException if parallelism less than or
365	<	* equal to zero
366	<	* @throws SecurityException if a security manager exists and
367	<	*         the caller is not permitted to modify threads
368	<	*         because it does not hold {@link
369	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
889	>	* Creates or doubles submissionQueue array.
890	>	* Basically identical to ForkJoinWorkerThread version
891		*/
892	<	public ForkJoinPool(int parallelism) {
893	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
892	>	private void growSubmissionQueue() {
893	>	ForkJoinTask<?>[] oldQ = submissionQueue;
894	>	int size = oldQ != null ? oldQ.length << 1 : INITIAL_QUEUE_CAPACITY;
895	>	if (size > MAXIMUM_QUEUE_CAPACITY)
896	>	throw new RejectedExecutionException("Queue capacity exceeded");
897	>	if (size < INITIAL_QUEUE_CAPACITY)
898	>	size = INITIAL_QUEUE_CAPACITY;
899	>	ForkJoinTask<?>[] q = submissionQueue = new ForkJoinTask<?>[size];
900	>	int mask = size - 1;
901	>	int top = queueTop;
902	>	int oldMask;
903	>	if (oldQ != null && (oldMask = oldQ.length - 1) >= 0) {
904	>	for (int b = queueBase; b != top; ++b) {
905	>	long u = ((b & oldMask) << ASHIFT) + ABASE;
906	>	Object x = UNSAFE.getObjectVolatile(oldQ, u);
907	>	if (x != null && UNSAFE.compareAndSwapObject(oldQ, u, x, null))
908	>	UNSAFE.putObjectVolatile
909	>	(q, ((b & mask) << ASHIFT) + ABASE, x);
910	>	}
911	>	}
912	>	}
913	>
914	>	// Blocking support
915	>
916	>	/**
917	>	* Tries to increment blockedCount, decrement active count
918	>	* (sometimes implicitly) and possibly release or create a
919	>	* compensating worker in preparation for blocking. Fails
920	>	* on contention or termination.
921	>	*
922	>	* @return true if the caller can block, else should recheck and retry
923	>	*/
924	>	private boolean tryPreBlock() {
925	>	int b = blockedCount;
926	>	if (UNSAFE.compareAndSwapInt(this, blockedCountOffset, b, b + 1)) {
927	>	int pc = parallelism;
928	>	do {
929	>	ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w;
930	>	int e, ac, tc, rc, i;
931	>	long c = ctl;
932	>	int u = (int)(c >>> 32);
933	>	if ((e = (int)c) < 0) {
934	>	// skip -- terminating
935	>	}
936	>	else if ((ac = (u >> UAC_SHIFT)) <= 0 && e != 0 &&
937	>	(ws = workers) != null &&
938	>	(i = ~e & SMASK) < ws.length &&
939	>	(w = ws[i]) != null) {
940	>	long nc = ((long)(w.nextWait & E_MASK) |
941	>	(c & (AC_MASK|TC_MASK)));
942	>	if (w.eventCount == e &&
943	>	UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
944	>	w.eventCount = (e + EC_UNIT) & E_MASK;
945	>	if (w.parked)
946	>	UNSAFE.unpark(w);
947	>	return true;             // release an idle worker
948	>	}
949	>	}
950	>	else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) {
951	>	long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
952	>	if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc))
953	>	return true;             // no compensation needed
954	>	}
955	>	else if (tc + pc < MAX_ID) {
956	>	long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
957	>	if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
958	>	addWorker();
959	>	return true;            // create a replacement
960	>	}
961	>	}
962	>	// try to back out on any failure and let caller retry
963	>	} while (!UNSAFE.compareAndSwapInt(this, blockedCountOffset,
964	>	b = blockedCount, b - 1));
965	>	}
966	>	return false;
967		}
968
969		/**
970	<	* Creates a ForkJoinPool with parallelism equal to the number of
377	<	* processors available on the system and using the given
378	<	* ForkJoinWorkerThreadFactory.
379	<	*
380	<	* @param factory the factory for creating new threads
381	<	* @throws NullPointerException if factory is null
382	<	* @throws SecurityException if a security manager exists and
383	<	*         the caller is not permitted to modify threads
384	<	*         because it does not hold {@link
385	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
970	>	* Decrements blockedCount and increments active count
971		*/
972	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
973	<	this(Runtime.getRuntime().availableProcessors(), factory);
972	>	private void postBlock() {
973	>	long c;
974	>	do {} while (!UNSAFE.compareAndSwapLong(this, ctlOffset,  // no mask
975	>	c = ctl, c + AC_UNIT));
976	>	int b;
977	>	do {} while(!UNSAFE.compareAndSwapInt(this, blockedCountOffset,
978	>	b = blockedCount, b - 1));
979		}
980
981		/**
982	<	* Creates a ForkJoinPool with the given parallelism and factory.
982	>	* Possibly blocks waiting for the given task to complete, or
983	>	* cancels the task if terminating.  Fails to wait if contended.
984		*
985	<	* @param parallelism the targeted number of worker threads
395	<	* @param factory the factory for creating new threads
396	<	* @throws IllegalArgumentException if parallelism less than or
397	<	* equal to zero, or greater than implementation limit
398	<	* @throws NullPointerException if factory is null
399	<	* @throws SecurityException if a security manager exists and
400	<	*         the caller is not permitted to modify threads
401	<	*         because it does not hold {@link
402	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
985	>	* @param joinMe the task
986		*/
987	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
988	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
989	<	throw new IllegalArgumentException();
990	<	if (factory == null)
991	<	throw new NullPointerException();
992	<	checkPermission();
993	<	this.factory = factory;
994	<	this.parallelism = parallelism;
995	<	this.maxPoolSize = MAX_THREADS;
996	<	this.maintainsParallelism = true;
997	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
415	<	this.workerLock = new ReentrantLock();
416	<	this.termination = workerLock.newCondition();
417	<	this.stealCount = new AtomicLong();
418	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
419	<	// worker array and workers are lazily constructed
987	>	final void tryAwaitJoin(ForkJoinTask<?> joinMe) {
988	>	int s;
989	>	Thread.interrupted(); // clear interrupts before checking termination
990	>	if (joinMe.status >= 0) {
991	>	if (tryPreBlock()) {
992	>	joinMe.tryAwaitDone(0L);
993	>	postBlock();
994	>	}
995	>	if ((ctl & STOP_BIT) != 0L)
996	>	joinMe.cancelIgnoringExceptions();
997	>	}
998		}
999
1000		/**
1001	<	* Creates a new worker thread using factory.
1001	>	* Possibly blocks the given worker waiting for joinMe to
1002	>	* complete or timeout
1003		*
1004	<	* @param index the index to assign worker
1005	<	* @return new worker, or null of factory failed
1004	>	* @param joinMe the task
1005	>	* @param millis the wait time for underlying Object.wait
1006		*/
1007	<	private ForkJoinWorkerThread createWorker(int index) {
1008	<	Thread.UncaughtExceptionHandler h = ueh;
1009	<	ForkJoinWorkerThread w = factory.newThread(this);
1010	<	if (w != null) {
1011	<	w.poolIndex = index;
1012	<	w.setDaemon(true);
1013	<	w.setAsyncMode(locallyFifo);
1014	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
1015	<	if (h != null)
1016	<	w.setUncaughtExceptionHandler(h);
1007	>	final void timedAwaitJoin(ForkJoinTask<?> joinMe, long nanos) {
1008	>	while (joinMe.status >= 0) {
1009	>	Thread.interrupted();
1010	>	if ((ctl & STOP_BIT) != 0L) {
1011	>	joinMe.cancelIgnoringExceptions();
1012	>	break;
1013	>	}
1014	>	if (tryPreBlock()) {
1015	>	long last = System.nanoTime();
1016	>	while (joinMe.status >= 0) {
1017	>	long millis = TimeUnit.NANOSECONDS.toMillis(nanos);
1018	>	if (millis <= 0)
1019	>	break;
1020	>	joinMe.tryAwaitDone(millis);
1021	>	if (joinMe.status < 0)
1022	>	break;
1023	>	if ((ctl & STOP_BIT) != 0L) {
1024	>	joinMe.cancelIgnoringExceptions();
1025	>	break;
1026	>	}
1027	>	long now = System.nanoTime();
1028	>	nanos -= now - last;
1029	>	last = now;
1030	>	}
1031	>	postBlock();
1032	>	break;
1033	>	}
1034		}
439	–	return w;
1035		}
1036
1037		/**
1038	<	* Returns a good size for worker array given pool size.
444	<	* Currently requires size to be a power of two.
1038	>	* If necessary, compensates for blocker, and blocks
1039		*/
1040	<	private static int arraySizeFor(int poolSize) {
1041	<	return (poolSize <= 1) ? 1 :
1042	<	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
1040	>	private void awaitBlocker(ManagedBlocker blocker)
1041	>	throws InterruptedException {
1042	>	while (!blocker.isReleasable()) {
1043	>	if (tryPreBlock()) {
1044	>	try {
1045	>	do {} while (!blocker.isReleasable() && !blocker.block());
1046	>	} finally {
1047	>	postBlock();
1048	>	}
1049	>	break;
1050	>	}
1051	>	}
1052		}
1053
1054	+	// Creating, registering and deregistring workers
1055	+
1056		/**
1057	<	* Creates or resizes array if necessary to hold newLength.
1058	<	* Call only under exclusion.
454	<	*
455	<	* @return the array
1057	>	* Tries to create and start a worker; minimally rolls back counts
1058	>	* on failure.
1059		*/
1060	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
1061	<	ForkJoinWorkerThread[] ws = workers;
1062	<	if (ws == null)
1063	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
1064	<	else if (newLength > ws.length)
1065	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
1060	>	private void addWorker() {
1061	>	Throwable ex = null;
1062	>	ForkJoinWorkerThread t = null;
1063	>	try {
1064	>	t = factory.newThread(this);
1065	>	} catch (Throwable e) {
1066	>	ex = e;
1067	>	}
1068	>	if (t == null) {  // null or exceptional factory return
1069	>	long c;       // adjust counts
1070	>	do {} while (!UNSAFE.compareAndSwapLong
1071	>	(this, ctlOffset, c = ctl,
1072	>	(((c - AC_UNIT) & AC_MASK) |
1073	>	((c - TC_UNIT) & TC_MASK) |
1074	>	(c & ~(AC_MASK|TC_MASK)))));
1075	>	// Propagate exception if originating from an external caller
1076	>	if (!tryTerminate(false) && ex != null &&
1077	>	!(Thread.currentThread() instanceof ForkJoinWorkerThread))
1078	>	UNSAFE.throwException(ex);
1079	>	}
1080		else
1081	<	return ws;
1081	>	t.start();
1082		}
1083
1084		/**
1085	<	* Tries to shrink workers into smaller array after one or more terminate.
1085	>	* Callback from ForkJoinWorkerThread constructor to assign a
1086	>	* public name
1087		*/
1088	<	private void tryShrinkWorkerArray() {
1089	<	ForkJoinWorkerThread[] ws = workers;
1090	<	if (ws != null) {
1091	<	int len = ws.length;
1092	<	int last = len - 1;
475	<	while (last >= 0 && ws[last] == null)
476	<	--last;
477	<	int newLength = arraySizeFor(last+1);
478	<	if (newLength < len)
479	<	workers = Arrays.copyOf(ws, newLength);
1088	>	final String nextWorkerName() {
1089	>	for (int n;;) {
1090	>	if (UNSAFE.compareAndSwapInt(this, nextWorkerNumberOffset,
1091	>	n = nextWorkerNumber, ++n))
1092	>	return workerNamePrefix + n;
1093		}
1094		}
1095
1096		/**
1097	<	* Initializes workers if necessary.
1097	>	* Callback from ForkJoinWorkerThread constructor to
1098	>	* determine its poolIndex and record in workers array.
1099	>	*
1100	>	* @param w the worker
1101	>	* @return the worker's pool index
1102		*/
1103	<	final void ensureWorkerInitialization() {
1104	<	ForkJoinWorkerThread[] ws = workers;
1105	<	if (ws == null) {
1106	<	final ReentrantLock lock = this.workerLock;
1107	<	lock.lock();
1108	<	try {
1109	<	ws = workers;
1110	<	if (ws == null) {
1111	<	int ps = parallelism;
1112	<	ws = ensureWorkerArrayCapacity(ps);
1113	<	for (int i = 0; i < ps; ++i) {
1114	<	ForkJoinWorkerThread w = createWorker(i);
1115	<	if (w != null) {
1116	<	ws[i] = w;
1117	<	w.start();
1118	<	updateWorkerCount(1);
1103	>	final int registerWorker(ForkJoinWorkerThread w) {
1104	>	/*
1105	>	* In the typical case, a new worker acquires the lock, uses
1106	>	* next available index and returns quickly.  Since we should
1107	>	* not block callers (ultimately from signalWork or
1108	>	* tryPreBlock) waiting for the lock needed to do this, we
1109	>	* instead help release other workers while waiting for the
1110	>	* lock.
1111	>	*/
1112	>	for (int g;;) {
1113	>	ForkJoinWorkerThread[] ws;
1114	>	if (((g = scanGuard) & SG_UNIT) == 0 &&
1115	>	UNSAFE.compareAndSwapInt(this, scanGuardOffset,
1116	>	g, g | SG_UNIT)) {
1117	>	int k = nextWorkerIndex;
1118	>	try {
1119	>	if ((ws = workers) != null) { // ignore on shutdown
1120	>	int n = ws.length;
1121	>	if (k < 0 || k >= n || ws[k] != null) {
1122	>	for (k = 0; k < n && ws[k] != null; ++k)
1123	>	;
1124	>	if (k == n)
1125	>	ws = workers = Arrays.copyOf(ws, n << 1);
1126		}
1127	+	ws[k] = w;
1128	+	nextWorkerIndex = k + 1;
1129	+	int m = g & SMASK;
1130	+	g = k >= m? ((m << 1) + 1) & SMASK : g + (SG_UNIT<<1);
1131	+	}
1132	+	} finally {
1133	+	scanGuard = g;
1134	+	}
1135	+	return k;
1136	+	}
1137	+	else if ((ws = workers) != null) { // help release others
1138	+	for (ForkJoinWorkerThread u : ws) {
1139	+	if (u != null && u.queueBase != u.queueTop) {
1140	+	if (tryReleaseWaiter())
1141	+	break;
1142		}
1143		}
505	–	} finally {
506	–	lock.unlock();
1144		}
1145		}
1146		}
1147
1148		/**
1149	<	* Worker creation and startup for threads added via setParallelism.
1149	>	* Final callback from terminating worker.  Removes record of
1150	>	* worker from array, and adjusts counts. If pool is shutting
1151	>	* down, tries to complete termination.
1152	>	*
1153	>	* @param w the worker
1154		*/
1155	<	private void createAndStartAddedWorkers() {
1156	<	resumeAllSpares();  // Allow spares to convert to nonspare
1157	<	int ps = parallelism;
1158	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1159	<	int len = ws.length;
1160	<	// Sweep through slots, to keep lowest indices most populated
1161	<	int k = 0;
1162	<	while (k < len) {
1163	<	if (ws[k] != null) {
1164	<	++k;
1165	<	continue;
1155	>	final void deregisterWorker(ForkJoinWorkerThread w, Throwable ex) {
1156	>	int idx = w.poolIndex;
1157	>	int sc = w.stealCount;
1158	>	int steps = 0;
1159	>	// Remove from array, adjust worker counts and collect steal count.
1160	>	// We can intermix failed removes or adjusts with steal updates
1161	>	do {
1162	>	long s, c;
1163	>	int g;
1164	>	if (steps == 0 && ((g = scanGuard) & SG_UNIT) == 0 &&
1165	>	UNSAFE.compareAndSwapInt(this, scanGuardOffset,
1166	>	g, g |= SG_UNIT)) {
1167	>	ForkJoinWorkerThread[] ws = workers;
1168	>	if (ws != null && idx >= 0 &&
1169	>	idx < ws.length && ws[idx] == w)
1170	>	ws[idx] = null;    // verify
1171	>	nextWorkerIndex = idx;
1172	>	scanGuard = g + SG_UNIT;
1173	>	steps = 1;
1174	>	}
1175	>	if (steps == 1 &&
1176	>	UNSAFE.compareAndSwapLong(this, ctlOffset, c = ctl,
1177	>	(((c - AC_UNIT) & AC_MASK) |
1178	>	((c - TC_UNIT) & TC_MASK) |
1179	>	(c & ~(AC_MASK|TC_MASK)))))
1180	>	steps = 2;
1181	>	if (sc != 0 &&
1182	>	UNSAFE.compareAndSwapLong(this, stealCountOffset,
1183	>	s = stealCount, s + sc))
1184	>	sc = 0;
1185	>	} while (steps != 2 || sc != 0);
1186	>	if (!tryTerminate(false)) {
1187	>	if (ex != null)   // possibly replace if died abnormally
1188	>	signalWork();
1189	>	else
1190	>	tryReleaseWaiter();
1191	>	}
1192	>	}
1193	>
1194	>	// Shutdown and termination
1195	>
1196	>	/**
1197	>	* Possibly initiates and/or completes termination.
1198	>	*
1199	>	* @param now if true, unconditionally terminate, else only
1200	>	* if shutdown and empty queue and no active workers
1201	>	* @return true if now terminating or terminated
1202	>	*/
1203	>	private boolean tryTerminate(boolean now) {
1204	>	long c;
1205	>	while (((c = ctl) & STOP_BIT) == 0) {
1206	>	if (!now) {
1207	>	if ((int)(c >> AC_SHIFT) != -parallelism)
1208	>	return false;
1209	>	if (!shutdown || blockedCount != 0 || quiescerCount != 0 ||
1210	>	queueTop - queueBase > 0) {
1211	>	if (ctl == c) // staleness check
1212	>	return false;
1213	>	continue;
1214	>	}
1215		}
1216	<	int s = workerCounts;
1217	<	int tc = totalCountOf(s);
1218	<	int rc = runningCountOf(s);
1219	<	if (rc >= ps || tc >= ps)
1220	<	break;
1221	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
1222	<	ForkJoinWorkerThread w = createWorker(k);
1223	<	if (w != null) {
1224	<	ws[k++] = w;
1225	<	w.start();
1216	>	if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, c | STOP_BIT))
1217	>	startTerminating();
1218	>	}
1219	>	if ((short)(c >>> TC_SHIFT) == -parallelism) {
1220	>	submissionLock.lock();
1221	>	termination.signalAll();
1222	>	submissionLock.unlock();
1223	>	}
1224	>	return true;
1225	>	}
1226	>
1227	>	/**
1228	>	* Runs up to three passes through workers: (0) Setting
1229	>	* termination status for each worker, followed by wakeups up
1230	>	* queued workers (1) helping cancel tasks (2) interrupting
1231	>	* lagging threads (likely in external tasks, but possibly also
1232	>	* blocked in joins).  Each pass repeats previous steps because of
1233	>	* potential lagging thread creation.
1234	>	*/
1235	>	private void startTerminating() {
1236	>	cancelSubmissions();
1237	>	for (int pass = 0; pass < 3; ++pass) {
1238	>	ForkJoinWorkerThread[] ws = workers;
1239	>	if (ws != null) {
1240	>	for (ForkJoinWorkerThread w : ws) {
1241	>	if (w != null) {
1242	>	w.terminate = true;
1243	>	if (pass > 0) {
1244	>	w.cancelTasks();
1245	>	if (pass > 1 && !w.isInterrupted()) {
1246	>	try {
1247	>	w.interrupt();
1248	>	} catch (SecurityException ignore) {
1249	>	}
1250	>	}
1251	>	}
1252	>	}
1253		}
1254	<	else {
1255	<	updateWorkerCount(-1); // back out on failed creation
1256	<	break;
1254	>	terminateWaiters();
1255	>	}
1256	>	}
1257	>	}
1258	>
1259	>	/**
1260	>	* Polls and cancels all submissions. Called only during termination.
1261	>	*/
1262	>	private void cancelSubmissions() {
1263	>	while (queueBase != queueTop) {
1264	>	ForkJoinTask<?> task = pollSubmission();
1265	>	if (task != null) {
1266	>	try {
1267	>	task.cancel(false);
1268	>	} catch (Throwable ignore) {
1269		}
1270		}
1271		}
1272		}
1273
1274	<	// Execution methods
1274	>	/**
1275	>	* Tries to set the termination status of waiting workers, and
1276	>	* then wake them up (after which they will terminate).
1277	>	*/
1278	>	private void terminateWaiters() {
1279	>	ForkJoinWorkerThread[] ws = workers;
1280	>	if (ws != null) {
1281	>	ForkJoinWorkerThread w; long c; int i, e;
1282	>	int n = ws.length;
1283	>	while ((i = ~(e = (int)(c = ctl)) & SMASK) < n &&
1284	>	(w = ws[i]) != null && w.eventCount == (e & E_MASK)) {
1285	>	if (UNSAFE.compareAndSwapLong(this, ctlOffset, c,
1286	>	(long)(w.nextWait & E_MASK) |
1287	>	((c + AC_UNIT) & AC_MASK) |
1288	>	(c & (TC_MASK|STOP_BIT)))) {
1289	>	w.terminate = true;
1290	>	w.eventCount = e + EC_UNIT;
1291	>	if (w.parked)
1292	>	UNSAFE.unpark(w);
1293	>	}
1294	>	}
1295	>	}
1296	>	}
1297	>
1298	>	// misc ForkJoinWorkerThread support
1299
1300		/**
1301	<	* Common code for execute, invoke and submit
1301	>	* Increment or decrement quiescerCount. Needed only to prevent
1302	>	* triggering shutdown if a worker is transiently inactive while
1303	>	* checking quiescence.
1304	>	*
1305	>	* @param delta 1 for increment, -1 for decrement
1306		*/
1307	<	private <T> void doSubmit(ForkJoinTask<T> task) {
1308	<	if (task == null)
1307	>	final void addQuiescerCount(int delta) {
1308	>	int c;
1309	>	do {} while(!UNSAFE.compareAndSwapInt(this, quiescerCountOffset,
1310	>	c = quiescerCount, c + delta));
1311	>	}
1312	>
1313	>	/**
1314	>	* Directly increment or decrement active count without
1315	>	* queuing. This method is used to transiently assert inactivation
1316	>	* while checking quiescence.
1317	>	*
1318	>	* @param delta 1 for increment, -1 for decrement
1319	>	*/
1320	>	final void addActiveCount(int delta) {
1321	>	long d = delta < 0 ? -AC_UNIT : AC_UNIT;
1322	>	long c;
1323	>	do {} while (!UNSAFE.compareAndSwapLong(this, ctlOffset, c = ctl,
1324	>	((c + d) & AC_MASK) |
1325	>	(c & ~AC_MASK)));
1326	>	}
1327	>
1328	>	/**
1329	>	* Returns the approximate (non-atomic) number of idle threads per
1330	>	* active thread.
1331	>	*/
1332	>	final int idlePerActive() {
1333	>	// Approximate at powers of two for small values, saturate past 4
1334	>	int p = parallelism;
1335	>	int a = p + (int)(ctl >> AC_SHIFT);
1336	>	return (a > (p >>>= 1) ? 0 :
1337	>	a > (p >>>= 1) ? 1 :
1338	>	a > (p >>>= 1) ? 2 :
1339	>	a > (p >>>= 1) ? 4 :
1340	>	8);
1341	>	}
1342	>
1343	>	// Exported methods
1344	>
1345	>	// Constructors
1346	>
1347	>	/**
1348	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1349	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1350	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1351	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1352	>	*
1353	>	* @throws SecurityException if a security manager exists and
1354	>	*         the caller is not permitted to modify threads
1355	>	*         because it does not hold {@link
1356	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1357	>	*/
1358	>	public ForkJoinPool() {
1359	>	this(Runtime.getRuntime().availableProcessors(),
1360	>	defaultForkJoinWorkerThreadFactory, null, false);
1361	>	}
1362	>
1363	>	/**
1364	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
1365	>	* level, the {@linkplain
1366	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1367	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1368	>	*
1369	>	* @param parallelism the parallelism level
1370	>	* @throws IllegalArgumentException if parallelism less than or
1371	>	*         equal to zero, or greater than implementation limit
1372	>	* @throws SecurityException if a security manager exists and
1373	>	*         the caller is not permitted to modify threads
1374	>	*         because it does not hold {@link
1375	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1376	>	*/
1377	>	public ForkJoinPool(int parallelism) {
1378	>	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1379	>	}
1380	>
1381	>	/**
1382	>	* Creates a {@code ForkJoinPool} with the given parameters.
1383	>	*
1384	>	* @param parallelism the parallelism level. For default value,
1385	>	* use {@link java.lang.Runtime#availableProcessors}.
1386	>	* @param factory the factory for creating new threads. For default value,
1387	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
1388	>	* @param handler the handler for internal worker threads that
1389	>	* terminate due to unrecoverable errors encountered while executing
1390	>	* tasks. For default value, use {@code null}.
1391	>	* @param asyncMode if true,
1392	>	* establishes local first-in-first-out scheduling mode for forked
1393	>	* tasks that are never joined. This mode may be more appropriate
1394	>	* than default locally stack-based mode in applications in which
1395	>	* worker threads only process event-style asynchronous tasks.
1396	>	* For default value, use {@code false}.
1397	>	* @throws IllegalArgumentException if parallelism less than or
1398	>	*         equal to zero, or greater than implementation limit
1399	>	* @throws NullPointerException if the factory is null
1400	>	* @throws SecurityException if a security manager exists and
1401	>	*         the caller is not permitted to modify threads
1402	>	*         because it does not hold {@link
1403	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1404	>	*/
1405	>	public ForkJoinPool(int parallelism,
1406	>	ForkJoinWorkerThreadFactory factory,
1407	>	Thread.UncaughtExceptionHandler handler,
1408	>	boolean asyncMode) {
1409	>	checkPermission();
1410	>	if (factory == null)
1411		throw new NullPointerException();
1412	<	if (isShutdown())
1413	<	throw new RejectedExecutionException();
1414	<	if (workers == null)
1415	<	ensureWorkerInitialization();
1416	<	submissionQueue.offer(task);
1417	<	signalIdleWorkers();
1412	>	if (parallelism <= 0 || parallelism > MAX_ID)
1413	>	throw new IllegalArgumentException();
1414	>	this.parallelism = parallelism;
1415	>	this.factory = factory;
1416	>	this.ueh = handler;
1417	>	this.locallyFifo = asyncMode;
1418	>	long np = (long)(-parallelism); // offset ctl counts
1419	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
1420	>	this.submissionQueue = new ForkJoinTask<?>[INITIAL_QUEUE_CAPACITY];
1421	>	// initialize workers array with room for 2*parallelism if possible
1422	>	int n = parallelism << 1;
1423	>	if (n >= MAX_ID)
1424	>	n = MAX_ID;
1425	>	else { // See Hackers Delight, sec 3.2, where n < (1 << 16)
1426	>	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8;
1427	>	}
1428	>	workers = new ForkJoinWorkerThread[n + 1];
1429	>	this.submissionLock = new ReentrantLock();
1430	>	this.termination = submissionLock.newCondition();
1431	>	StringBuilder sb = new StringBuilder("ForkJoinPool-");
1432	>	sb.append(poolNumberGenerator.incrementAndGet());
1433	>	sb.append("-worker-");
1434	>	this.workerNamePrefix = sb.toString();
1435		}
1436
1437	+	// Execution methods
1438	+
1439		/**
1440		* Performs the given task, returning its result upon completion.
1441	+	* If the computation encounters an unchecked Exception or Error,
1442	+	* it is rethrown as the outcome of this invocation.  Rethrown
1443	+	* exceptions behave in the same way as regular exceptions, but,
1444	+	* when possible, contain stack traces (as displayed for example
1445	+	* using {@code ex.printStackTrace()}) of both the current thread
1446	+	* as well as the thread actually encountering the exception;
1447	+	* minimally only the latter.
1448		*
1449		* @param task the task
1450		* @return the task's result
1451	<	* @throws NullPointerException if task is null
1452	<	* @throws RejectedExecutionException if pool is shut down
1451	>	* @throws NullPointerException if the task is null
1452	>	* @throws RejectedExecutionException if the task cannot be
1453	>	*         scheduled for execution
1454		*/
1455		public <T> T invoke(ForkJoinTask<T> task) {
1456	<	doSubmit(task);
1457	<	return task.join();
1456	>	Thread t = Thread.currentThread();
1457	>	if (task == null)
1458	>	throw new NullPointerException();
1459	>	if (shutdown)
1460	>	throw new RejectedExecutionException();
1461	>	if ((t instanceof ForkJoinWorkerThread) &&
1462	>	((ForkJoinWorkerThread)t).pool == this)
1463	>	return task.invoke();  // bypass submit if in same pool
1464	>	else {
1465	>	addSubmission(task);
1466	>	return task.join();
1467	>	}
1468	>	}
1469	>
1470	>	/**
1471	>	* Unless terminating, forks task if within an ongoing FJ
1472	>	* computation in the current pool, else submits as external task.
1473	>	*/
1474	>	private <T> void forkOrSubmit(ForkJoinTask<T> task) {
1475	>	ForkJoinWorkerThread w;
1476	>	Thread t = Thread.currentThread();
1477	>	if (shutdown)
1478	>	throw new RejectedExecutionException();
1479	>	if ((t instanceof ForkJoinWorkerThread) &&
1480	>	(w = (ForkJoinWorkerThread)t).pool == this)
1481	>	w.pushTask(task);
1482	>	else
1483	>	addSubmission(task);
1484		}
1485
1486		/**
1487		* Arranges for (asynchronous) execution of the given task.
1488		*
1489		* @param task the task
1490	<	* @throws NullPointerException if task is null
1491	<	* @throws RejectedExecutionException if pool is shut down
1490	>	* @throws NullPointerException if the task is null
1491	>	* @throws RejectedExecutionException if the task cannot be
1492	>	*         scheduled for execution
1493		*/
1494	<	public <T> void execute(ForkJoinTask<T> task) {
1495	<	doSubmit(task);
1494	>	public void execute(ForkJoinTask<?> task) {
1495	>	if (task == null)
1496	>	throw new NullPointerException();
1497	>	forkOrSubmit(task);
1498		}
1499
1500		// AbstractExecutorService methods
1501
1502	+	/**
1503	+	* @throws NullPointerException if the task is null
1504	+	* @throws RejectedExecutionException if the task cannot be
1505	+	*         scheduled for execution
1506	+	*/
1507		public void execute(Runnable task) {
1508	+	if (task == null)
1509	+	throw new NullPointerException();
1510		ForkJoinTask<?> job;
1511		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1512		job = (ForkJoinTask<?>) task;
1513		else
1514	<	job = new AdaptedRunnable<Void>(task, null);
1515	<	doSubmit(job);
594	<	}
595	<
596	<	public <T> ForkJoinTask<T> submit(Callable<T> task) {
597	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
598	<	doSubmit(job);
599	<	return job;
600	<	}
601	<
602	<	public <T> ForkJoinTask<T> submit(Runnable task, T result) {
603	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
604	<	doSubmit(job);
605	<	return job;
606	<	}
607	<
608	<	public ForkJoinTask<?> submit(Runnable task) {
609	<	ForkJoinTask<?> job;
610	<	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
611	<	job = (ForkJoinTask<?>) task;
612	<	else
613	<	job = new AdaptedRunnable<Void>(task, null);
614	<	doSubmit(job);
615	<	return job;
1514	>	job = ForkJoinTask.adapt(task, null);
1515	>	forkOrSubmit(job);
1516		}
1517
1518		/**
#	Line 620 | Line 1520 | public class ForkJoinPool extends Abstra
1520		*
1521		* @param task the task to submit
1522		* @return the task
1523	+	* @throws NullPointerException if the task is null
1524		* @throws RejectedExecutionException if the task cannot be
1525		*         scheduled for execution
625	–	* @throws NullPointerException if the task is null
1526		*/
1527		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1528	<	doSubmit(task);
1528	>	if (task == null)
1529	>	throw new NullPointerException();
1530	>	forkOrSubmit(task);
1531		return task;
1532		}
1533
1534		/**
1535	<	* Adaptor for Runnables. This implements RunnableFuture
1536	<	* to be compliant with AbstractExecutorService constraints.
1535	>	* @throws NullPointerException if the task is null
1536	>	* @throws RejectedExecutionException if the task cannot be
1537	>	*         scheduled for execution
1538		*/
1539	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1540	<	implements RunnableFuture<T> {
1541	<	final Runnable runnable;
1542	<	final T resultOnCompletion;
1543	<	T result;
1544	<	AdaptedRunnable(Runnable runnable, T result) {
642	<	if (runnable == null) throw new NullPointerException();
643	<	this.runnable = runnable;
644	<	this.resultOnCompletion = result;
645	<	}
646	<	public T getRawResult() { return result; }
647	<	public void setRawResult(T v) { result = v; }
648	<	public boolean exec() {
649	<	runnable.run();
650	<	result = resultOnCompletion;
651	<	return true;
652	<	}
653	<	public void run() { invoke(); }
654	<	private static final long serialVersionUID = 5232453952276885070L;
1539	>	public <T> ForkJoinTask<T> submit(Callable<T> task) {
1540	>	if (task == null)
1541	>	throw new NullPointerException();
1542	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1543	>	forkOrSubmit(job);
1544	>	return job;
1545		}
1546
1547		/**
1548	<	* Adaptor for Callables
1549	<	*/
1550	<	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1551	<	implements RunnableFuture<T> {
1552	<	final Callable<T> callable;
1553	<	T result;
1554	<	AdaptedCallable(Callable<T> callable) {
1555	<	if (callable == null) throw new NullPointerException();
1556	<	this.callable = callable;
1557	<	}
1558	<	public T getRawResult() { return result; }
1559	<	public void setRawResult(T v) { result = v; }
1560	<	public boolean exec() {
1561	<	try {
1562	<	result = callable.call();
1563	<	return true;
1564	<	} catch (Error err) {
1565	<	throw err;
1566	<	} catch (RuntimeException rex) {
1567	<	throw rex;
1568	<	} catch (Exception ex) {
1569	<	throw new RuntimeException(ex);
1570	<	}
1571	<	}
1572	<	public void run() { invoke(); }
1573	<	private static final long serialVersionUID = 2838392045355241008L;
1548	>	* @throws NullPointerException if the task is null
1549	>	* @throws RejectedExecutionException if the task cannot be
1550	>	*         scheduled for execution
1551	>	*/
1552	>	public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1553	>	if (task == null)
1554	>	throw new NullPointerException();
1555	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1556	>	forkOrSubmit(job);
1557	>	return job;
1558	>	}
1559	>
1560	>	/**
1561	>	* @throws NullPointerException if the task is null
1562	>	* @throws RejectedExecutionException if the task cannot be
1563	>	*         scheduled for execution
1564	>	*/
1565	>	public ForkJoinTask<?> submit(Runnable task) {
1566	>	if (task == null)
1567	>	throw new NullPointerException();
1568	>	ForkJoinTask<?> job;
1569	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1570	>	job = (ForkJoinTask<?>) task;
1571	>	else
1572	>	job = ForkJoinTask.adapt(task, null);
1573	>	forkOrSubmit(job);
1574	>	return job;
1575		}
1576
1577	+	/**
1578	+	* @throws NullPointerException       {@inheritDoc}
1579	+	* @throws RejectedExecutionException {@inheritDoc}
1580	+	*/
1581		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
1582		ArrayList<ForkJoinTask<T>> forkJoinTasks =
1583		new ArrayList<ForkJoinTask<T>>(tasks.size());
1584		for (Callable<T> task : tasks)
1585	<	forkJoinTasks.add(new AdaptedCallable<T>(task));
1585	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
1586		invoke(new InvokeAll<T>(forkJoinTasks));
1587
1588		@SuppressWarnings({"unchecked", "rawtypes"})
1589	<	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1589	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1590		return futures;
1591		}
1592
#	Line 705 | Line 1600 | public class ForkJoinPool extends Abstra
1600		private static final long serialVersionUID = -7914297376763021607L;
1601		}
1602
708	–	// Configuration and status settings and queries
709	–
1603		/**
1604		* Returns the factory used for constructing new workers.
1605		*
#	Line 723 | Line 1616 | public class ForkJoinPool extends Abstra
1616		* @return the handler, or {@code null} if none
1617		*/
1618		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1619	<	Thread.UncaughtExceptionHandler h;
727	<	final ReentrantLock lock = this.workerLock;
728	<	lock.lock();
729	<	try {
730	<	h = ueh;
731	<	} finally {
732	<	lock.unlock();
733	<	}
734	<	return h;
735	<	}
736	<
737	<	/**
738	<	* Sets the handler for internal worker threads that terminate due
739	<	* to unrecoverable errors encountered while executing tasks.
740	<	* Unless set, the current default or ThreadGroup handler is used
741	<	* as handler.
742	<	*
743	<	* @param h the new handler
744	<	* @return the old handler, or {@code null} if none
745	<	* @throws SecurityException if a security manager exists and
746	<	*         the caller is not permitted to modify threads
747	<	*         because it does not hold {@link
748	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
749	<	*/
750	<	public Thread.UncaughtExceptionHandler
751	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
752	<	checkPermission();
753	<	Thread.UncaughtExceptionHandler old = null;
754	<	final ReentrantLock lock = this.workerLock;
755	<	lock.lock();
756	<	try {
757	<	old = ueh;
758	<	ueh = h;
759	<	ForkJoinWorkerThread[] ws = workers;
760	<	if (ws != null) {
761	<	for (int i = 0; i < ws.length; ++i) {
762	<	ForkJoinWorkerThread w = ws[i];
763	<	if (w != null)
764	<	w.setUncaughtExceptionHandler(h);
765	<	}
766	<	}
767	<	} finally {
768	<	lock.unlock();
769	<	}
770	<	return old;
1619	>	return ueh;
1620		}
1621
773	–
1622		/**
1623	<	* Sets the target parallelism level of this pool.
1623	>	* Returns the targeted parallelism level of this pool.
1624		*
1625	<	* @param parallelism the target parallelism
778	<	* @throws IllegalArgumentException if parallelism less than or
779	<	* equal to zero or greater than maximum size bounds
780	<	* @throws SecurityException if a security manager exists and
781	<	*         the caller is not permitted to modify threads
782	<	*         because it does not hold {@link
783	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
784	<	*/
785	<	public void setParallelism(int parallelism) {
786	<	checkPermission();
787	<	if (parallelism <= 0 || parallelism > maxPoolSize)
788	<	throw new IllegalArgumentException();
789	<	final ReentrantLock lock = this.workerLock;
790	<	lock.lock();
791	<	try {
792	<	if (!isTerminating()) {
793	<	int p = this.parallelism;
794	<	this.parallelism = parallelism;
795	<	if (parallelism > p)
796	<	createAndStartAddedWorkers();
797	<	else
798	<	trimSpares();
799	<	}
800	<	} finally {
801	<	lock.unlock();
802	<	}
803	<	signalIdleWorkers();
804	<	}
805	<
806	<	/**
807	<	* Returns the targeted number of worker threads in this pool.
808	<	*
809	<	* @return the targeted number of worker threads in this pool
1625	>	* @return the targeted parallelism level of this pool
1626		*/
1627		public int getParallelism() {
1628		return parallelism;
#	Line 814 | Line 1630 | public class ForkJoinPool extends Abstra
1630
1631		/**
1632		* Returns the number of worker threads that have started but not
1633	<	* yet terminated.  This result returned by this method may differ
1634	<	* from {@code getParallelism} when threads are created to
1633	>	* yet terminated.  The result returned by this method may differ
1634	>	* from {@link #getParallelism} when threads are created to
1635		* maintain parallelism when others are cooperatively blocked.
1636		*
1637		* @return the number of worker threads
1638		*/
1639		public int getPoolSize() {
1640	<	return totalCountOf(workerCounts);
825	<	}
826	<
827	<	/**
828	<	* Returns the maximum number of threads allowed to exist in the
829	<	* pool, even if there are insufficient unblocked running threads.
830	<	*
831	<	* @return the maximum
832	<	*/
833	<	public int getMaximumPoolSize() {
834	<	return maxPoolSize;
835	<	}
836	<
837	<	/**
838	<	* Sets the maximum number of threads allowed to exist in the
839	<	* pool, even if there are insufficient unblocked running threads.
840	<	* Setting this value has no effect on current pool size. It
841	<	* controls construction of new threads.
842	<	*
843	<	* @throws IllegalArgumentException if negative or greater then
844	<	* internal implementation limit
845	<	*/
846	<	public void setMaximumPoolSize(int newMax) {
847	<	if (newMax < 0 || newMax > MAX_THREADS)
848	<	throw new IllegalArgumentException();
849	<	maxPoolSize = newMax;
850	<	}
851	<
852	<
853	<	/**
854	<	* Returns {@code true} if this pool dynamically maintains its
855	<	* target parallelism level. If false, new threads are added only
856	<	* to avoid possible starvation.  This setting is by default true.
857	<	*
858	<	* @return {@code true} if maintains parallelism
859	<	*/
860	<	public boolean getMaintainsParallelism() {
861	<	return maintainsParallelism;
862	<	}
863	<
864	<	/**
865	<	* Sets whether this pool dynamically maintains its target
866	<	* parallelism level. If false, new threads are added only to
867	<	* avoid possible starvation.
868	<	*
869	<	* @param enable {@code true} to maintain parallelism
870	<	*/
871	<	public void setMaintainsParallelism(boolean enable) {
872	<	maintainsParallelism = enable;
873	<	}
874	<
875	<	/**
876	<	* Establishes local first-in-first-out scheduling mode for forked
877	<	* tasks that are never joined. This mode may be more appropriate
878	<	* than default locally stack-based mode in applications in which
879	<	* worker threads only process asynchronous tasks.  This method is
880	<	* designed to be invoked only when pool is quiescent, and
881	<	* typically only before any tasks are submitted. The effects of
882	<	* invocations at other times may be unpredictable.
883	<	*
884	<	* @param async if true, use locally FIFO scheduling
885	<	* @return the previous mode
886	<	*/
887	<	public boolean setAsyncMode(boolean async) {
888	<	boolean oldMode = locallyFifo;
889	<	locallyFifo = async;
890	<	ForkJoinWorkerThread[] ws = workers;
891	<	if (ws != null) {
892	<	for (int i = 0; i < ws.length; ++i) {
893	<	ForkJoinWorkerThread t = ws[i];
894	<	if (t != null)
895	<	t.setAsyncMode(async);
896	<	}
897	<	}
898	<	return oldMode;
1640	>	return parallelism + (short)(ctl >>> TC_SHIFT);
1641		}
1642
1643		/**
#	Line 911 | Line 1653 | public class ForkJoinPool extends Abstra
1653		/**
1654		* Returns an estimate of the number of worker threads that are
1655		* not blocked waiting to join tasks or for other managed
1656	<	* synchronization.
1656	>	* synchronization. This method may overestimate the
1657	>	* number of running threads.
1658		*
1659		* @return the number of worker threads
1660		*/
1661		public int getRunningThreadCount() {
1662	<	return runningCountOf(workerCounts);
1662	>	int r = parallelism + (int)(ctl >> AC_SHIFT);
1663	>	return r <= 0? 0 : r; // suppress momentarily negative values
1664		}
1665
1666		/**
#	Line 927 | Line 1671 | public class ForkJoinPool extends Abstra
1671		* @return the number of active threads
1672		*/
1673		public int getActiveThreadCount() {
1674	<	return activeCountOf(runControl);
1675	<	}
932	<
933	<	/**
934	<	* Returns an estimate of the number of threads that are currently
935	<	* idle waiting for tasks. This method may underestimate the
936	<	* number of idle threads.
937	<	*
938	<	* @return the number of idle threads
939	<	*/
940	<	final int getIdleThreadCount() {
941	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
942	<	return (c <= 0) ? 0 : c;
1674	>	int r = parallelism + (int)(ctl >> AC_SHIFT) + blockedCount;
1675	>	return r <= 0? 0 : r; // suppress momentarily negative values
1676		}
1677
1678		/**
#	Line 954 | Line 1687 | public class ForkJoinPool extends Abstra
1687		* @return {@code true} if all threads are currently idle
1688		*/
1689		public boolean isQuiescent() {
1690	<	return activeCountOf(runControl) == 0;
1690	>	return parallelism + (int)(ctl >> AC_SHIFT) + blockedCount == 0;
1691		}
1692
1693		/**
#	Line 969 | Line 1702 | public class ForkJoinPool extends Abstra
1702		* @return the number of steals
1703		*/
1704		public long getStealCount() {
1705	<	return stealCount.get();
973	<	}
974	<
975	<	/**
976	<	* Accumulates steal count from a worker.
977	<	* Call only when worker known to be idle.
978	<	*/
979	<	private void updateStealCount(ForkJoinWorkerThread w) {
980	<	int sc = w.getAndClearStealCount();
981	<	if (sc != 0)
982	<	stealCount.addAndGet(sc);
1705	>	return stealCount;
1706		}
1707
1708		/**
#	Line 994 | Line 1717 | public class ForkJoinPool extends Abstra
1717		*/
1718		public long getQueuedTaskCount() {
1719		long count = 0;
1720	<	ForkJoinWorkerThread[] ws = workers;
1721	<	if (ws != null) {
1722	<	for (int i = 0; i < ws.length; ++i) {
1723	<	ForkJoinWorkerThread t = ws[i];
1724	<	if (t != null)
1725	<	count += t.getQueueSize();
1003	<	}
1720	>	ForkJoinWorkerThread[] ws;
1721	>	if ((short)(ctl >>> TC_SHIFT) > -parallelism &&
1722	>	(ws = workers) != null) {
1723	>	for (ForkJoinWorkerThread w : ws)
1724	>	if (w != null)
1725	>	count -= w.queueBase - w.queueTop; // must read base first
1726		}
1727		return count;
1728		}
1729
1730		/**
1731	<	* Returns an estimate of the number tasks submitted to this pool
1732	<	* that have not yet begun executing. This method takes time
1733	<	* proportional to the number of submissions.
1731	>	* Returns an estimate of the number of tasks submitted to this
1732	>	* pool that have not yet begun executing.  This meThod may take
1733	>	* time proportional to the number of submissions.
1734		*
1735		* @return the number of queued submissions
1736		*/
1737		public int getQueuedSubmissionCount() {
1738	<	return submissionQueue.size();
1738	>	return -queueBase + queueTop;
1739		}
1740
1741		/**
#	Line 1023 | Line 1745 | public class ForkJoinPool extends Abstra
1745		* @return {@code true} if there are any queued submissions
1746		*/
1747		public boolean hasQueuedSubmissions() {
1748	<	return !submissionQueue.isEmpty();
1748	>	return queueBase != queueTop;
1749		}
1750
1751		/**
#	Line 1034 | Line 1756 | public class ForkJoinPool extends Abstra
1756		* @return the next submission, or {@code null} if none
1757		*/
1758		protected ForkJoinTask<?> pollSubmission() {
1759	<	return submissionQueue.poll();
1759	>	ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i;
1760	>	while ((b = queueBase) != queueTop &&
1761	>	(q = submissionQueue) != null &&
1762	>	(i = (q.length - 1) & b) >= 0) {
1763	>	long u = (i << ASHIFT) + ABASE;
1764	>	if ((t = q[i]) != null &&
1765	>	queueBase == b &&
1766	>	UNSAFE.compareAndSwapObject(q, u, t, null)) {
1767	>	queueBase = b + 1;
1768	>	return t;
1769	>	}
1770	>	}
1771	>	return null;
1772		}
1773
1774		/**
1775		* Removes all available unexecuted submitted and forked tasks
1776		* from scheduling queues and adds them to the given collection,
1777		* without altering their execution status. These may include
1778	<	* artificially generated or wrapped tasks. This method is designed
1779	<	* to be invoked only when the pool is known to be
1778	>	* artificially generated or wrapped tasks. This method is
1779	>	* designed to be invoked only when the pool is known to be
1780		* quiescent. Invocations at other times may not remove all
1781		* tasks. A failure encountered while attempting to add elements
1782		* to collection {@code c} may result in elements being in
#	Line 1054 | Line 1788 | public class ForkJoinPool extends Abstra
1788		* @param c the collection to transfer elements into
1789		* @return the number of elements transferred
1790		*/
1791	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1792	<	int n = submissionQueue.drainTo(c);
1793	<	ForkJoinWorkerThread[] ws = workers;
1794	<	if (ws != null) {
1795	<	for (int i = 0; i < ws.length; ++i) {
1796	<	ForkJoinWorkerThread w = ws[i];
1797	<	if (w != null)
1064	<	n += w.drainTasksTo(c);
1791	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1792	>	int count = 0;
1793	>	while (queueBase != queueTop) {
1794	>	ForkJoinTask<?> t = pollSubmission();
1795	>	if (t != null) {
1796	>	c.add(t);
1797	>	++count;
1798		}
1799		}
1800	<	return n;
1800	>	ForkJoinWorkerThread[] ws;
1801	>	if ((short)(ctl >>> TC_SHIFT) > -parallelism &&
1802	>	(ws = workers) != null) {
1803	>	for (ForkJoinWorkerThread w : ws)
1804	>	if (w != null)
1805	>	count += w.drainTasksTo(c);
1806	>	}
1807	>	return count;
1808		}
1809
1810		/**
#	Line 1075 | Line 1815 | public class ForkJoinPool extends Abstra
1815		* @return a string identifying this pool, as well as its state
1816		*/
1817		public String toString() {
1078	–	int ps = parallelism;
1079	–	int wc = workerCounts;
1080	–	int rc = runControl;
1818		long st = getStealCount();
1819		long qt = getQueuedTaskCount();
1820		long qs = getQueuedSubmissionCount();
1821	+	int pc = parallelism;
1822	+	long c = ctl;
1823	+	int tc = pc + (short)(c >>> TC_SHIFT);
1824	+	int rc = pc + (int)(c >> AC_SHIFT);
1825	+	if (rc < 0) // ignore transient negative
1826	+	rc = 0;
1827	+	int ac = rc + blockedCount;
1828	+	String level;
1829	+	if ((c & STOP_BIT) != 0)
1830	+	level = (tc == 0)? "Terminated" : "Terminating";
1831	+	else
1832	+	level = shutdown? "Shutting down" : "Running";
1833		return super.toString() +
1834	<	"[" + runStateToString(runStateOf(rc)) +
1835	<	", parallelism = " + ps +
1836	<	", size = " + totalCountOf(wc) +
1837	<	", active = " + activeCountOf(rc) +
1838	<	", running = " + runningCountOf(wc) +
1834	>	"[" + level +
1835	>	", parallelism = " + pc +
1836	>	", size = " + tc +
1837	>	", active = " + ac +
1838	>	", running = " + rc +
1839		", steals = " + st +
1840		", tasks = " + qt +
1841		", submissions = " + qs +
1842		"]";
1843		}
1844
1096	–	private static String runStateToString(int rs) {
1097	–	switch(rs) {
1098	–	case RUNNING: return "Running";
1099	–	case SHUTDOWN: return "Shutting down";
1100	–	case TERMINATING: return "Terminating";
1101	–	case TERMINATED: return "Terminated";
1102	–	default: throw new Error("Unknown run state");
1103	–	}
1104	–	}
1105	–
1106	–	// lifecycle control
1107	–
1845		/**
1846		* Initiates an orderly shutdown in which previously submitted
1847		* tasks are executed, but no new tasks will be accepted.
#	Line 1119 | Line 1856 | public class ForkJoinPool extends Abstra
1856		*/
1857		public void shutdown() {
1858		checkPermission();
1859	<	transitionRunStateTo(SHUTDOWN);
1860	<	if (canTerminateOnShutdown(runControl))
1124	<	terminateOnShutdown();
1859	>	shutdown = true;
1860	>	tryTerminate(false);
1861		}
1862
1863		/**
1864	<	* Attempts to stop all actively executing tasks, and cancels all
1865	<	* waiting tasks.  Tasks that are in the process of being
1866	<	* submitted or executed concurrently during the course of this
1867	<	* method may or may not be rejected. Unlike some other executors,
1868	<	* this method cancels rather than collects non-executed tasks
1869	<	* upon termination, so always returns an empty list. However, you
1870	<	* can use method {@code drainTasksTo} before invoking this
1871	<	* method to transfer unexecuted tasks to another collection.
1864	>	* Attempts to cancel and/or stop all tasks, and reject all
1865	>	* subsequently submitted tasks.  Tasks that are in the process of
1866	>	* being submitted or executed concurrently during the course of
1867	>	* this method may or may not be rejected. This method cancels
1868	>	* both existing and unexecuted tasks, in order to permit
1869	>	* termination in the presence of task dependencies. So the method
1870	>	* always returns an empty list (unlike the case for some other
1871	>	* Executors).
1872		*
1873		* @return an empty list
1874		* @throws SecurityException if a security manager exists and
#	Line 1142 | Line 1878 | public class ForkJoinPool extends Abstra
1878		*/
1879		public List<Runnable> shutdownNow() {
1880		checkPermission();
1881	<	terminate();
1881	>	shutdown = true;
1882	>	tryTerminate(true);
1883		return Collections.emptyList();
1884		}
1885
#	Line 1152 | Line 1889 | public class ForkJoinPool extends Abstra
1889		* @return {@code true} if all tasks have completed following shut down
1890		*/
1891		public boolean isTerminated() {
1892	<	return runStateOf(runControl) == TERMINATED;
1892	>	long c = ctl;
1893	>	return ((c & STOP_BIT) != 0L &&
1894	>	(short)(c >>> TC_SHIFT) == -parallelism);
1895		}
1896
1897		/**
1898		* Returns {@code true} if the process of termination has
1899	<	* commenced but possibly not yet completed.
1899	>	* commenced but not yet completed.  This method may be useful for
1900	>	* debugging. A return of {@code true} reported a sufficient
1901	>	* period after shutdown may indicate that submitted tasks have
1902	>	* ignored or suppressed interruption, or are waiting for IO,
1903	>	* causing this executor not to properly terminate. (See the
1904	>	* advisory notes for class {@link ForkJoinTask} stating that
1905	>	* tasks should not normally entail blocking operations.  But if
1906	>	* they do, they must abort them on interrupt.)
1907		*
1908	<	* @return {@code true} if terminating
1908	>	* @return {@code true} if terminating but not yet terminated
1909		*/
1910		public boolean isTerminating() {
1911	<	return runStateOf(runControl) >= TERMINATING;
1911	>	long c = ctl;
1912	>	return ((c & STOP_BIT) != 0L &&
1913	>	(short)(c >>> TC_SHIFT) != -parallelism);
1914	>	}
1915	>
1916	>	/**
1917	>	* Returns true if terminating or terminated. Used by ForkJoinWorkerThread.
1918	>	*/
1919	>	final boolean isAtLeastTerminating() {
1920	>	return (ctl & STOP_BIT) != 0L;
1921		}
1922
1923		/**
#	Line 1171 | Line 1926 | public class ForkJoinPool extends Abstra
1926		* @return {@code true} if this pool has been shut down
1927		*/
1928		public boolean isShutdown() {
1929	<	return runStateOf(runControl) >= SHUTDOWN;
1929	>	return shutdown;
1930		}
1931
1932		/**
#	Line 1188 | Line 1943 | public class ForkJoinPool extends Abstra
1943		public boolean awaitTermination(long timeout, TimeUnit unit)
1944		throws InterruptedException {
1945		long nanos = unit.toNanos(timeout);
1946	<	final ReentrantLock lock = this.workerLock;
1946	>	final ReentrantLock lock = this.submissionLock;
1947		lock.lock();
1948		try {
1949		for (;;) {
#	Line 1203 | Line 1958 | public class ForkJoinPool extends Abstra
1958		}
1959		}
1960
1206	–	// Shutdown and termination support
1207	–
1208	–	/**
1209	–	* Callback from terminating worker. Nulls out the corresponding
1210	–	* workers slot, and if terminating, tries to terminate; else
1211	–	* tries to shrink workers array.
1212	–	*
1213	–	* @param w the worker
1214	–	*/
1215	–	final void workerTerminated(ForkJoinWorkerThread w) {
1216	–	updateStealCount(w);
1217	–	updateWorkerCount(-1);
1218	–	final ReentrantLock lock = this.workerLock;
1219	–	lock.lock();
1220	–	try {
1221	–	ForkJoinWorkerThread[] ws = workers;
1222	–	if (ws != null) {
1223	–	int idx = w.poolIndex;
1224	–	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1225	–	ws[idx] = null;
1226	–	if (totalCountOf(workerCounts) == 0) {
1227	–	terminate(); // no-op if already terminating
1228	–	transitionRunStateTo(TERMINATED);
1229	–	termination.signalAll();
1230	–	}
1231	–	else if (!isTerminating()) {
1232	–	tryShrinkWorkerArray();
1233	–	tryResumeSpare(true); // allow replacement
1234	–	}
1235	–	}
1236	–	} finally {
1237	–	lock.unlock();
1238	–	}
1239	–	signalIdleWorkers();
1240	–	}
1241	–
1242	–	/**
1243	–	* Initiates termination.
1244	–	*/
1245	–	private void terminate() {
1246	–	if (transitionRunStateTo(TERMINATING)) {
1247	–	stopAllWorkers();
1248	–	resumeAllSpares();
1249	–	signalIdleWorkers();
1250	–	cancelQueuedSubmissions();
1251	–	cancelQueuedWorkerTasks();
1252	–	interruptUnterminatedWorkers();
1253	–	signalIdleWorkers(); // resignal after interrupt
1254	–	}
1255	–	}
1256	–
1257	–	/**
1258	–	* Possibly terminates when on shutdown state.
1259	–	*/
1260	–	private void terminateOnShutdown() {
1261	–	if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
1262	–	terminate();
1263	–	}
1264	–
1265	–	/**
1266	–	* Clears out and cancels submissions.
1267	–	*/
1268	–	private void cancelQueuedSubmissions() {
1269	–	ForkJoinTask<?> task;
1270	–	while ((task = pollSubmission()) != null)
1271	–	task.cancel(false);
1272	–	}
1273	–
1274	–	/**
1275	–	* Cleans out worker queues.
1276	–	*/
1277	–	private void cancelQueuedWorkerTasks() {
1278	–	final ReentrantLock lock = this.workerLock;
1279	–	lock.lock();
1280	–	try {
1281	–	ForkJoinWorkerThread[] ws = workers;
1282	–	if (ws != null) {
1283	–	for (int i = 0; i < ws.length; ++i) {
1284	–	ForkJoinWorkerThread t = ws[i];
1285	–	if (t != null)
1286	–	t.cancelTasks();
1287	–	}
1288	–	}
1289	–	} finally {
1290	–	lock.unlock();
1291	–	}
1292	–	}
1293	–
1294	–	/**
1295	–	* Sets each worker's status to terminating. Requires lock to avoid
1296	–	* conflicts with add/remove.
1297	–	*/
1298	–	private void stopAllWorkers() {
1299	–	final ReentrantLock lock = this.workerLock;
1300	–	lock.lock();
1301	–	try {
1302	–	ForkJoinWorkerThread[] ws = workers;
1303	–	if (ws != null) {
1304	–	for (int i = 0; i < ws.length; ++i) {
1305	–	ForkJoinWorkerThread t = ws[i];
1306	–	if (t != null)
1307	–	t.shutdownNow();
1308	–	}
1309	–	}
1310	–	} finally {
1311	–	lock.unlock();
1312	–	}
1313	–	}
1314	–
1315	–	/**
1316	–	* Interrupts all unterminated workers.  This is not required for
1317	–	* sake of internal control, but may help unstick user code during
1318	–	* shutdown.
1319	–	*/
1320	–	private void interruptUnterminatedWorkers() {
1321	–	final ReentrantLock lock = this.workerLock;
1322	–	lock.lock();
1323	–	try {
1324	–	ForkJoinWorkerThread[] ws = workers;
1325	–	if (ws != null) {
1326	–	for (int i = 0; i < ws.length; ++i) {
1327	–	ForkJoinWorkerThread t = ws[i];
1328	–	if (t != null && !t.isTerminated()) {
1329	–	try {
1330	–	t.interrupt();
1331	–	} catch (SecurityException ignore) {
1332	–	}
1333	–	}
1334	–	}
1335	–	}
1336	–	} finally {
1337	–	lock.unlock();
1338	–	}
1339	–	}
1340	–
1341	–
1342	–	/*
1343	–	* Nodes for event barrier to manage idle threads.  Queue nodes
1344	–	* are basic Treiber stack nodes, also used for spare stack.
1345	–	*
1346	–	* The event barrier has an event count and a wait queue (actually
1347	–	* a Treiber stack).  Workers are enabled to look for work when
1348	–	* the eventCount is incremented. If they fail to find work, they
1349	–	* may wait for next count. Upon release, threads help others wake
1350	–	* up.
1351	–	*
1352	–	* Synchronization events occur only in enough contexts to
1353	–	* maintain overall liveness:
1354	–	*
1355	–	*   - Submission of a new task to the pool
1356	–	*   - Resizes or other changes to the workers array
1357	–	*   - pool termination
1358	–	*   - A worker pushing a task on an empty queue
1359	–	*
1360	–	* The case of pushing a task occurs often enough, and is heavy
1361	–	* enough compared to simple stack pushes, to require special
1362	–	* handling: Method signalWork returns without advancing count if
1363	–	* the queue appears to be empty.  This would ordinarily result in
1364	–	* races causing some queued waiters not to be woken up. To avoid
1365	–	* this, the first worker enqueued in method sync (see
1366	–	* syncIsReleasable) rescans for tasks after being enqueued, and
1367	–	* helps signal if any are found. This works well because the
1368	–	* worker has nothing better to do, and so might as well help
1369	–	* alleviate the overhead and contention on the threads actually
1370	–	* doing work.  Also, since event counts increments on task
1371	–	* availability exist to maintain liveness (rather than to force
1372	–	* refreshes etc), it is OK for callers to exit early if
1373	–	* contending with another signaller.
1374	–	*/
1375	–	static final class WaitQueueNode {
1376	–	WaitQueueNode next; // only written before enqueued
1377	–	volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1378	–	final long count; // unused for spare stack
1379	–
1380	–	WaitQueueNode(long c, ForkJoinWorkerThread w) {
1381	–	count = c;
1382	–	thread = w;
1383	–	}
1384	–
1385	–	/**
1386	–	* Wakes up waiter, returning false if known to already
1387	–	*/
1388	–	boolean signal() {
1389	–	ForkJoinWorkerThread t = thread;
1390	–	if (t == null)
1391	–	return false;
1392	–	thread = null;
1393	–	LockSupport.unpark(t);
1394	–	return true;
1395	–	}
1396	–
1397	–	/**
1398	–	* Awaits release on sync.
1399	–	*/
1400	–	void awaitSyncRelease(ForkJoinPool p) {
1401	–	while (thread != null && !p.syncIsReleasable(this))
1402	–	LockSupport.park(this);
1403	–	}
1404	–
1405	–	/**
1406	–	* Awaits resumption as spare.
1407	–	*/
1408	–	void awaitSpareRelease() {
1409	–	while (thread != null) {
1410	–	if (!Thread.interrupted())
1411	–	LockSupport.park(this);
1412	–	}
1413	–	}
1414	–	}
1415	–
1416	–	/**
1417	–	* Ensures that no thread is waiting for count to advance from the
1418	–	* current value of eventCount read on entry to this method, by
1419	–	* releasing waiting threads if necessary.
1420	–	*
1421	–	* @return the count
1422	–	*/
1423	–	final long ensureSync() {
1424	–	long c = eventCount;
1425	–	WaitQueueNode q;
1426	–	while ((q = syncStack) != null && q.count < c) {
1427	–	if (casBarrierStack(q, null)) {
1428	–	do {
1429	–	q.signal();
1430	–	} while ((q = q.next) != null);
1431	–	break;
1432	–	}
1433	–	}
1434	–	return c;
1435	–	}
1436	–
1437	–	/**
1438	–	* Increments event count and releases waiting threads.
1439	–	*/
1440	–	private void signalIdleWorkers() {
1441	–	long c;
1442	–	do {} while (!casEventCount(c = eventCount, c+1));
1443	–	ensureSync();
1444	–	}
1445	–
1446	–	/**
1447	–	* Signals threads waiting to poll a task. Because method sync
1448	–	* rechecks availability, it is OK to only proceed if queue
1449	–	* appears to be non-empty, and OK to skip under contention to
1450	–	* increment count (since some other thread succeeded).
1451	–	*/
1452	–	final void signalWork() {
1453	–	long c;
1454	–	WaitQueueNode q;
1455	–	if (syncStack != null &&
1456	–	casEventCount(c = eventCount, c+1) &&
1457	–	(((q = syncStack) != null && q.count <= c) &&
1458	–	(!casBarrierStack(q, q.next) || !q.signal())))
1459	–	ensureSync();
1460	–	}
1461	–
1462	–	/**
1463	–	* Waits until event count advances from last value held by
1464	–	* caller, or if excess threads, caller is resumed as spare, or
1465	–	* caller or pool is terminating. Updates caller's event on exit.
1466	–	*
1467	–	* @param w the calling worker thread
1468	–	*/
1469	–	final void sync(ForkJoinWorkerThread w) {
1470	–	updateStealCount(w); // Transfer w's count while it is idle
1471	–
1472	–	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1473	–	long prev = w.lastEventCount;
1474	–	WaitQueueNode node = null;
1475	–	WaitQueueNode h;
1476	–	while (eventCount == prev &&
1477	–	((h = syncStack) == null || h.count == prev)) {
1478	–	if (node == null)
1479	–	node = new WaitQueueNode(prev, w);
1480	–	if (casBarrierStack(node.next = h, node)) {
1481	–	node.awaitSyncRelease(this);
1482	–	break;
1483	–	}
1484	–	}
1485	–	long ec = ensureSync();
1486	–	if (ec != prev) {
1487	–	w.lastEventCount = ec;
1488	–	break;
1489	–	}
1490	–	}
1491	–	}
1492	–
1493	–	/**
1494	–	* Returns {@code true} if worker waiting on sync can proceed:
1495	–	*  - on signal (thread == null)
1496	–	*  - on event count advance (winning race to notify vs signaller)
1497	–	*  - on interrupt
1498	–	*  - if the first queued node, we find work available
1499	–	* If node was not signalled and event count not advanced on exit,
1500	–	* then we also help advance event count.
1501	–	*
1502	–	* @return {@code true} if node can be released
1503	–	*/
1504	–	final boolean syncIsReleasable(WaitQueueNode node) {
1505	–	long prev = node.count;
1506	–	if (!Thread.interrupted() && node.thread != null &&
1507	–	(node.next != null ||
1508	–	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1509	–	eventCount == prev)
1510	–	return false;
1511	–	if (node.thread != null) {
1512	–	node.thread = null;
1513	–	long ec = eventCount;
1514	–	if (prev <= ec) // help signal
1515	–	casEventCount(ec, ec+1);
1516	–	}
1517	–	return true;
1518	–	}
1519	–
1520	–	/**
1521	–	* Returns {@code true} if a new sync event occurred since last
1522	–	* call to sync or this method, if so, updating caller's count.
1523	–	*/
1524	–	final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1525	–	long lc = w.lastEventCount;
1526	–	long ec = ensureSync();
1527	–	if (ec == lc)
1528	–	return false;
1529	–	w.lastEventCount = ec;
1530	–	return true;
1531	–	}
1532	–
1533	–	//  Parallelism maintenance
1534	–
1535	–	/**
1536	–	* Decrements running count; if too low, adds spare.
1537	–	*
1538	–	* Conceptually, all we need to do here is add or resume a
1539	–	* spare thread when one is about to block (and remove or
1540	–	* suspend it later when unblocked -- see suspendIfSpare).
1541	–	* However, implementing this idea requires coping with
1542	–	* several problems: we have imperfect information about the
1543	–	* states of threads. Some count updates can and usually do
1544	–	* lag run state changes, despite arrangements to keep them
1545	–	* accurate (for example, when possible, updating counts
1546	–	* before signalling or resuming), especially when running on
1547	–	* dynamic JVMs that don't optimize the infrequent paths that
1548	–	* update counts. Generating too many threads can make these
1549	–	* problems become worse, because excess threads are more
1550	–	* likely to be context-switched with others, slowing them all
1551	–	* down, especially if there is no work available, so all are
1552	–	* busy scanning or idling.  Also, excess spare threads can
1553	–	* only be suspended or removed when they are idle, not
1554	–	* immediately when they aren't needed. So adding threads will
1555	–	* raise parallelism level for longer than necessary.  Also,
1556	–	* FJ applications often encounter highly transient peaks when
1557	–	* many threads are blocked joining, but for less time than it
1558	–	* takes to create or resume spares.
1559	–	*
1560	–	* @param joinMe if non-null, return early if done
1561	–	* @param maintainParallelism if true, try to stay within
1562	–	* target counts, else create only to avoid starvation
1563	–	* @return true if joinMe known to be done
1564	–	*/
1565	–	final boolean preJoin(ForkJoinTask<?> joinMe,
1566	–	boolean maintainParallelism) {
1567	–	maintainParallelism &= maintainsParallelism; // overrride
1568	–	boolean dec = false;  // true when running count decremented
1569	–	while (spareStack == null || !tryResumeSpare(dec)) {
1570	–	int counts = workerCounts;
1571	–	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1572	–	// CAS cheat
1573	–	if (!needSpare(counts, maintainParallelism))
1574	–	break;
1575	–	if (joinMe.status < 0)
1576	–	return true;
1577	–	if (tryAddSpare(counts))
1578	–	break;
1579	–	}
1580	–	}
1581	–	return false;
1582	–	}
1583	–
1584	–	/**
1585	–	* Same idea as preJoin
1586	–	*/
1587	–	final boolean preBlock(ManagedBlocker blocker,
1588	–	boolean maintainParallelism) {
1589	–	maintainParallelism &= maintainsParallelism;
1590	–	boolean dec = false;
1591	–	while (spareStack == null || !tryResumeSpare(dec)) {
1592	–	int counts = workerCounts;
1593	–	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1594	–	if (!needSpare(counts, maintainParallelism))
1595	–	break;
1596	–	if (blocker.isReleasable())
1597	–	return true;
1598	–	if (tryAddSpare(counts))
1599	–	break;
1600	–	}
1601	–	}
1602	–	return false;
1603	–	}
1604	–
1605	–	/**
1606	–	* Returns {@code true} if a spare thread appears to be needed.
1607	–	* If maintaining parallelism, returns true when the deficit in
1608	–	* running threads is more than the surplus of total threads, and
1609	–	* there is apparently some work to do.  This self-limiting rule
1610	–	* means that the more threads that have already been added, the
1611	–	* less parallelism we will tolerate before adding another.
1612	–	*
1613	–	* @param counts current worker counts
1614	–	* @param maintainParallelism try to maintain parallelism
1615	–	*/
1616	–	private boolean needSpare(int counts, boolean maintainParallelism) {
1617	–	int ps = parallelism;
1618	–	int rc = runningCountOf(counts);
1619	–	int tc = totalCountOf(counts);
1620	–	int runningDeficit = ps - rc;
1621	–	int totalSurplus = tc - ps;
1622	–	return (tc < maxPoolSize &&
1623	–	(rc == 0 || totalSurplus < 0 ||
1624	–	(maintainParallelism &&
1625	–	runningDeficit > totalSurplus &&
1626	–	ForkJoinWorkerThread.hasQueuedTasks(workers))));
1627	–	}
1628	–
1629	–	/**
1630	–	* Adds a spare worker if lock available and no more than the
1631	–	* expected numbers of threads exist.
1632	–	*
1633	–	* @return true if successful
1634	–	*/
1635	–	private boolean tryAddSpare(int expectedCounts) {
1636	–	final ReentrantLock lock = this.workerLock;
1637	–	int expectedRunning = runningCountOf(expectedCounts);
1638	–	int expectedTotal = totalCountOf(expectedCounts);
1639	–	boolean success = false;
1640	–	boolean locked = false;
1641	–	// confirm counts while locking; CAS after obtaining lock
1642	–	try {
1643	–	for (;;) {
1644	–	int s = workerCounts;
1645	–	int tc = totalCountOf(s);
1646	–	int rc = runningCountOf(s);
1647	–	if (rc > expectedRunning || tc > expectedTotal)
1648	–	break;
1649	–	if (!locked && !(locked = lock.tryLock()))
1650	–	break;
1651	–	if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) {
1652	–	createAndStartSpare(tc);
1653	–	success = true;
1654	–	break;
1655	–	}
1656	–	}
1657	–	} finally {
1658	–	if (locked)
1659	–	lock.unlock();
1660	–	}
1661	–	return success;
1662	–	}
1663	–
1664	–	/**
1665	–	* Adds the kth spare worker. On entry, pool counts are already
1666	–	* adjusted to reflect addition.
1667	–	*/
1668	–	private void createAndStartSpare(int k) {
1669	–	ForkJoinWorkerThread w = null;
1670	–	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1);
1671	–	int len = ws.length;
1672	–	// Probably, we can place at slot k. If not, find empty slot
1673	–	if (k < len && ws[k] != null) {
1674	–	for (k = 0; k < len && ws[k] != null; ++k)
1675	–	;
1676	–	}
1677	–	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1678	–	ws[k] = w;
1679	–	w.start();
1680	–	}
1681	–	else
1682	–	updateWorkerCount(-1); // adjust on failure
1683	–	signalIdleWorkers();
1684	–	}
1685	–
1686	–	/**
1687	–	* Suspends calling thread w if there are excess threads.  Called
1688	–	* only from sync.  Spares are enqueued in a Treiber stack using
1689	–	* the same WaitQueueNodes as barriers.  They are resumed mainly
1690	–	* in preJoin, but are also woken on pool events that require all
1691	–	* threads to check run state.
1692	–	*
1693	–	* @param w the caller
1694	–	*/
1695	–	private boolean suspendIfSpare(ForkJoinWorkerThread w) {
1696	–	WaitQueueNode node = null;
1697	–	int s;
1698	–	while (parallelism < runningCountOf(s = workerCounts)) {
1699	–	if (node == null)
1700	–	node = new WaitQueueNode(0, w);
1701	–	if (casWorkerCounts(s, s-1)) { // representation-dependent
1702	–	// push onto stack
1703	–	do {} while (!casSpareStack(node.next = spareStack, node));
1704	–	// block until released by resumeSpare
1705	–	node.awaitSpareRelease();
1706	–	return true;
1707	–	}
1708	–	}
1709	–	return false;
1710	–	}
1711	–
1712	–	/**
1713	–	* Tries to pop and resume a spare thread.
1714	–	*
1715	–	* @param updateCount if true, increment running count on success
1716	–	* @return true if successful
1717	–	*/
1718	–	private boolean tryResumeSpare(boolean updateCount) {
1719	–	WaitQueueNode q;
1720	–	while ((q = spareStack) != null) {
1721	–	if (casSpareStack(q, q.next)) {
1722	–	if (updateCount)
1723	–	updateRunningCount(1);
1724	–	q.signal();
1725	–	return true;
1726	–	}
1727	–	}
1728	–	return false;
1729	–	}
1730	–
1731	–	/**
1732	–	* Pops and resumes all spare threads. Same idea as ensureSync.
1733	–	*
1734	–	* @return true if any spares released
1735	–	*/
1736	–	private boolean resumeAllSpares() {
1737	–	WaitQueueNode q;
1738	–	while ( (q = spareStack) != null) {
1739	–	if (casSpareStack(q, null)) {
1740	–	do {
1741	–	updateRunningCount(1);
1742	–	q.signal();
1743	–	} while ((q = q.next) != null);
1744	–	return true;
1745	–	}
1746	–	}
1747	–	return false;
1748	–	}
1749	–
1750	–	/**
1751	–	* Pops and shuts down excessive spare threads. Call only while
1752	–	* holding lock. This is not guaranteed to eliminate all excess
1753	–	* threads, only those suspended as spares, which are the ones
1754	–	* unlikely to be needed in the future.
1755	–	*/
1756	–	private void trimSpares() {
1757	–	int surplus = totalCountOf(workerCounts) - parallelism;
1758	–	WaitQueueNode q;
1759	–	while (surplus > 0 && (q = spareStack) != null) {
1760	–	if (casSpareStack(q, null)) {
1761	–	do {
1762	–	updateRunningCount(1);
1763	–	ForkJoinWorkerThread w = q.thread;
1764	–	if (w != null && surplus > 0 &&
1765	–	runningCountOf(workerCounts) > 0 && w.shutdown())
1766	–	--surplus;
1767	–	q.signal();
1768	–	} while ((q = q.next) != null);
1769	–	}
1770	–	}
1771	–	}
1772	–
1961		/**
1962		* Interface for extending managed parallelism for tasks running
1963	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1964	<	* Method {@code isReleasable} must return {@code true} if
1965	<	* blocking is not necessary. Method {@code block} blocks the
1966	<	* current thread if necessary (perhaps internally invoking
1967	<	* {@code isReleasable} before actually blocking.).
1963	>	* in {@link ForkJoinPool}s.
1964	>	*
1965	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
1966	>	* {@code isReleasable} must return {@code true} if blocking is
1967	>	* not necessary. Method {@code block} blocks the current thread
1968	>	* if necessary (perhaps internally invoking {@code isReleasable}
1969	>	* before actually blocking). The unusual methods in this API
1970	>	* accommodate synchronizers that may, but don't usually, block
1971	>	* for long periods. Similarly, they allow more efficient internal
1972	>	* handling of cases in which additional workers may be, but
1973	>	* usually are not, needed to ensure sufficient parallelism.
1974	>	* Toward this end, implementations of method {@code isReleasable}
1975	>	* must be amenable to repeated invocation.
1976		*
1977		* <p>For example, here is a ManagedBlocker based on a
1978		* ReentrantLock:
#	Line 1794 | Line 1990 | public class ForkJoinPool extends Abstra
1990		*     return hasLock || (hasLock = lock.tryLock());
1991		*   }
1992		* }}</pre>
1993	+	*
1994	+	* <p>Here is a class that possibly blocks waiting for an
1995	+	* item on a given queue:
1996	+	*  <pre> {@code
1997	+	* class QueueTaker<E> implements ManagedBlocker {
1998	+	*   final BlockingQueue<E> queue;
1999	+	*   volatile E item = null;
2000	+	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
2001	+	*   public boolean block() throws InterruptedException {
2002	+	*     if (item == null)
2003	+	*       item = queue.take();
2004	+	*     return true;
2005	+	*   }
2006	+	*   public boolean isReleasable() {
2007	+	*     return item != null || (item = queue.poll()) != null;
2008	+	*   }
2009	+	*   public E getItem() { // call after pool.managedBlock completes
2010	+	*     return item;
2011	+	*   }
2012	+	* }}</pre>
2013		*/
2014		public static interface ManagedBlocker {
2015		/**
#	Line 1815 | Line 2031 | public class ForkJoinPool extends Abstra
2031
2032		/**
2033		* Blocks in accord with the given blocker.  If the current thread
2034	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
2035	<	* spare thread to be activated if necessary to ensure parallelism
2036	<	* while the current thread is blocked.  If
1821	<	* {@code maintainParallelism} is {@code true} and the pool supports
1822	<	* it ({@link #getMaintainsParallelism}), this method attempts to
1823	<	* maintain the pool's nominal parallelism. Otherwise it activates
1824	<	* a thread only if necessary to avoid complete starvation. This
1825	<	* option may be preferable when blockages use timeouts, or are
1826	<	* almost always brief.
2034	>	* is a {@link ForkJoinWorkerThread}, this method possibly
2035	>	* arranges for a spare thread to be activated if necessary to
2036	>	* ensure sufficient parallelism while the current thread is blocked.
2037		*
2038	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
2039	<	* equivalent to
2038	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
2039	>	* behaviorally equivalent to
2040		*  <pre> {@code
2041		* while (!blocker.isReleasable())
2042		*   if (blocker.block())
2043		*     return;
2044		* }</pre>
2045	<	* If the caller is a ForkJoinTask, then the pool may first
2046	<	* be expanded to ensure parallelism, and later adjusted.
2045	>	*
2046	>	* If the caller is a {@code ForkJoinTask}, then the pool may
2047	>	* first be expanded to ensure parallelism, and later adjusted.
2048		*
2049		* @param blocker the blocker
1839	–	* @param maintainParallelism if {@code true} and supported by
1840	–	* this pool, attempt to maintain the pool's nominal parallelism;
1841	–	* otherwise activate a thread only if necessary to avoid
1842	–	* complete starvation.
2050		* @throws InterruptedException if blocker.block did so
2051		*/
2052	<	public static void managedBlock(ManagedBlocker blocker,
1846	<	boolean maintainParallelism)
2052	>	public static void managedBlock(ManagedBlocker blocker)
2053		throws InterruptedException {
2054		Thread t = Thread.currentThread();
2055	<	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
2056	<	((ForkJoinWorkerThread) t).pool : null);
2057	<	if (!blocker.isReleasable()) {
2058	<	try {
2059	<	if (pool == null ||
2060	<	!pool.preBlock(blocker, maintainParallelism))
1855	<	awaitBlocker(blocker);
1856	<	} finally {
1857	<	if (pool != null)
1858	<	pool.updateRunningCount(1);
1859	<	}
2055	>	if (t instanceof ForkJoinWorkerThread) {
2056	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
2057	>	w.pool.awaitBlocker(blocker);
2058	>	}
2059	>	else {
2060	>	do {} while (!blocker.isReleasable() && !blocker.block());
2061		}
2062		}
2063
2064	<	private static void awaitBlocker(ManagedBlocker blocker)
2065	<	throws InterruptedException {
2066	<	do {} while (!blocker.isReleasable() && !blocker.block());
1866	<	}
1867	<
1868	<	// AbstractExecutorService overrides
2064	>	// AbstractExecutorService overrides.  These rely on undocumented
2065	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
2066	>	// implement RunnableFuture.
2067
2068		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
2069	<	return new AdaptedRunnable<T>(runnable, value);
2069	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
2070		}
2071
2072		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
2073	<	return new AdaptedCallable<T>(callable);
2073	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
2074		}
2075
2076		// Unsafe mechanics
2077	<
2078	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
2079	<	private static final long eventCountOffset =
2080	<	objectFieldOffset("eventCount", ForkJoinPool.class);
2081	<	private static final long workerCountsOffset =
2082	<	objectFieldOffset("workerCounts", ForkJoinPool.class);
2083	<	private static final long runControlOffset =
2084	<	objectFieldOffset("runControl", ForkJoinPool.class);
2085	<	private static final long syncStackOffset =
2086	<	objectFieldOffset("syncStack",ForkJoinPool.class);
2087	<	private static final long spareStackOffset =
2088	<	objectFieldOffset("spareStack", ForkJoinPool.class);
2089	<
2090	<	private boolean casEventCount(long cmp, long val) {
2091	<	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
2092	<	}
2093	<	private boolean casWorkerCounts(int cmp, int val) {
1896	<	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1897	<	}
1898	<	private boolean casRunControl(int cmp, int val) {
1899	<	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1900	<	}
1901	<	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1902	<	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1903	<	}
1904	<	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1905	<	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1906	<	}
1907	<
1908	<	private static long objectFieldOffset(String field, Class<?> klazz) {
2077	>	private static final sun.misc.Unsafe UNSAFE;
2078	>	private static final long ctlOffset;
2079	>	private static final long stealCountOffset;
2080	>	private static final long blockedCountOffset;
2081	>	private static final long quiescerCountOffset;
2082	>	private static final long scanGuardOffset;
2083	>	private static final long nextWorkerNumberOffset;
2084	>	private static final long ABASE;
2085	>	private static final int ASHIFT;
2086	>
2087	>	static {
2088	>	poolNumberGenerator = new AtomicInteger();
2089	>	workerSeedGenerator = new Random();
2090	>	modifyThreadPermission = new RuntimePermission("modifyThread");
2091	>	defaultForkJoinWorkerThreadFactory =
2092	>	new DefaultForkJoinWorkerThreadFactory();
2093	>	int s;
2094		try {
2095	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
2096	<	} catch (NoSuchFieldException e) {
2097	<	// Convert Exception to corresponding Error
2098	<	NoSuchFieldError error = new NoSuchFieldError(field);
2099	<	error.initCause(e);
2100	<	throw error;
2101	<	}
2095	>	UNSAFE = getUnsafe();
2096	>	Class k = ForkJoinPool.class;
2097	>	ctlOffset = UNSAFE.objectFieldOffset
2098	>	(k.getDeclaredField("ctl"));
2099	>	stealCountOffset = UNSAFE.objectFieldOffset
2100	>	(k.getDeclaredField("stealCount"));
2101	>	blockedCountOffset = UNSAFE.objectFieldOffset
2102	>	(k.getDeclaredField("blockedCount"));
2103	>	quiescerCountOffset = UNSAFE.objectFieldOffset
2104	>	(k.getDeclaredField("quiescerCount"));
2105	>	scanGuardOffset = UNSAFE.objectFieldOffset
2106	>	(k.getDeclaredField("scanGuard"));
2107	>	nextWorkerNumberOffset = UNSAFE.objectFieldOffset
2108	>	(k.getDeclaredField("nextWorkerNumber"));
2109	>	Class a = ForkJoinTask[].class;
2110	>	ABASE = UNSAFE.arrayBaseOffset(a);
2111	>	s = UNSAFE.arrayIndexScale(a);
2112	>	} catch (Exception e) {
2113	>	throw new Error(e);
2114	>	}
2115	>	if ((s & (s-1)) != 0)
2116	>	throw new Error("data type scale not a power of two");
2117	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
2118		}
2119
2120		/**

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