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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.1 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.100 by dl, Fri Apr 1 20:20:37 2011 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
9	<	import java.util.concurrent.*;
10	<	import java.util.concurrent.locks.*;
11	<	import java.util.concurrent.atomic.*;
12	<	import sun.misc.Unsafe;
13	<	import java.lang.reflect.*;
8	>
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.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.locks.Condition;
27
28		/**
29	<	* Host for a group of ForkJoinWorkerThreads.  A ForkJoinPool provides
30	<	* the entry point for tasks submitted from non-ForkJoinTasks, as well
31	<	* as management and monitoring operations.  Normally a single
32	<	* ForkJoinPool is used for a large number of submitted
20	<	* tasks. Otherwise, use would not usually outweigh the construction
21	<	* and bookkeeping overhead of creating a large set of threads.
22	<	*
23	<	* <p>ForkJoinPools differ from other kinds of Executor mainly in that
24	<	* they provide <em>work-stealing</em>: all threads in the pool
25	<	* attempt to find and execute subtasks created by other active tasks
26	<	* (eventually blocking if none exist). This makes them efficient when
27	<	* most tasks spawn other subtasks (as do most ForkJoinTasks) but
28	<	* possibly less so otherwise. It is however fine to combine execution
29	<	* of some plain Runnable- or Callable- based activities with that of
30	<	* ForkJoinTasks.
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>A ForkJoinPool may be constructed with a given parallelism level
35	<	* (target pool size), which it attempts to maintain by dynamically
36	<	* adding, suspending, or resuming threads, even if some tasks have
37	<	* blocked waiting to join others. However, no such adjustments are
38	<	* performed in the face of blocked IO or other unmanaged
39	<	* synchronization. The nested ManagedBlocker interface enables
40	<	* extension of the kinds of synchronization accommodated.
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>The target parallelism level may also be set dynamically. You
45	<	* can limit the number of threads dynamically constructed using
46	<	* method <tt>setMaximumPoolSize</tt> and/or
47	<	* <tt>setMaintainParallelism</tt>.
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	<	* <tt>getStealCount</tt>) 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	<	* <tt>toString</tt> returns indications of pool state in a convenient
59	<	* form for informal monitoring.
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 parallelism to 32767. Attempts to create pools with greater
115	<	* than the maximum result in IllegalArgumentExceptions.
114	>	* maximum number of running threads to 32767. Attempts to create
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
124		*/
125	<	public class ForkJoinPool extends AbstractExecutorService
57	<	implements ExecutorService {
125	>	public class ForkJoinPool extends AbstractExecutorService {
126
127		/*
128	<	* See the extended comments interspersed below for design,
129	<	* rationale, and walkthroughs.
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 tasks) 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 can
199	>	* be found immediately, and we cannot start/resume workers unless
200	>	* there appear to be tasks available.  On the other hand, we must
201	>	* quickly prod them into action when new tasks are submitted or
202	>	* generated.  We park/unpark workers after placing in an event
203	>	* wait queue when they cannot find work. This "queue" is actually
204	>	* a simple Treiber stack, headed by the "id" field of ctl, plus a
205	>	* 15bit counter value to both wake up waiters (by advancing their
206	>	* count) and avoid ABA effects. Successors are held in worker
207	>	* field "nextWait".  Queuing deals with several intrinsic races,
208	>	* mainly that a task-producing thread can miss seeing (and
209	>	* signalling) another thread that gave up looking for work but
210	>	* has not yet entered the wait queue. We solve this by requiring
211	>	* a full sweep of all workers both before (in scan()) and after
212	>	* (in tryAwaitWork()) a newly waiting worker is added to the wait
213	>	* queue. During a rescan, the worker might release some other
214	>	* queued worker rather than itself, which has the same net
215	>	* effect. Because enqueued workers may actually be rescanning
216	>	* rather than waiting, we set and clear the "parked" field of
217	>	* ForkJoinWorkerThread to reduce unnecessary calls to unpark.
218	>	* (Use of the parked field requires a secondary recheck to avoid
219	>	* missed signals.)
220	>	*
221	>	* Signalling.  We create or wake up workers only when there
222	>	* appears to be at least one task they might be able to find and
223	>	* execute.  When a submission is added or another worker adds a
224	>	* task to a queue that previously had two or fewer tasks, they
225	>	* signal waiting workers (or trigger creation of new ones if
226	>	* fewer than the given parallelism level -- see signalWork).
227	>	* These primary signals are buttressed by signals during rescans
228	>	* as well as those performed when a worker steals a task and
229	>	* notices that there are more tasks too; together these cover the
230	>	* signals needed in cases when more than two tasks are pushed
231	>	* but untaken.
232	>	*
233	>	* Trimming workers. To release resources after periods of lack of
234	>	* use, a worker starting to wait when the pool is quiescent will
235	>	* time out and terminate if the pool has remained quiescent for
236	>	* SHRINK_RATE nanosecs. This will slowly propagate, eventually
237	>	* terminating all workers after long periods of non-use.
238	>	*
239	>	* Submissions. External submissions are maintained in an
240	>	* array-based queue that is structured identically to
241	>	* ForkJoinWorkerThread queues except for the use of
242	>	* submissionLock in method addSubmission. Unlike the case for
243	>	* worker queues, multiple external threads can add new
244	>	* submissions, so adding requires a lock.
245	>	*
246	>	* Compensation. Beyond work-stealing support and lifecycle
247	>	* control, the main responsibility of this framework is to take
248	>	* actions when one worker is waiting to join a task stolen (or
249	>	* always held by) another.  Because we are multiplexing many
250	>	* tasks on to a pool of workers, we can't just let them block (as
251	>	* in Thread.join).  We also cannot just reassign the joiner's
252	>	* run-time stack with another and replace it later, which would
253	>	* be a form of "continuation", that even if possible is not
254	>	* necessarily a good idea since we sometimes need both an
255	>	* unblocked task and its continuation to progress. Instead we
256	>	* combine two tactics:
257	>	*
258	>	*   Helping: Arranging for the joiner to execute some task that it
259	>	*      would be running if the steal had not occurred.  Method
260	>	*      ForkJoinWorkerThread.joinTask tracks joining->stealing
261	>	*      links to try to find such a task.
262	>	*
263	>	*   Compensating: Unless there are already enough live threads,
264	>	*      method tryPreBlock() may create or re-activate a spare
265	>	*      thread to compensate for blocked joiners until they
266	>	*      unblock.
267	>	*
268	>	* The ManagedBlocker extension API can't use helping so relies
269	>	* only on compensation in method awaitBlocker.
270	>	*
271	>	* It is impossible to keep exactly the target parallelism number
272	>	* of threads running at any given time.  Determining the
273	>	* existence of conservatively safe helping targets, the
274	>	* availability of already-created spares, and the apparent need
275	>	* to create new spares are all racy and require heuristic
276	>	* guidance, so we rely on multiple retries of each.  Currently,
277	>	* in keeping with on-demand signalling policy, we compensate only
278	>	* if blocking would leave less than one active (non-waiting,
279	>	* non-blocked) worker. Additionally, to avoid some false alarms
280	>	* due to GC, lagging counters, system activity, etc, compensated
281	>	* blocking for joins is only attempted after rechecks stabilize
282	>	* (retries are interspersed with Thread.yield, for good
283	>	* citizenship).  The variable blockedCount, incremented before
284	>	* blocking and decremented after, is sometimes needed to
285	>	* distinguish cases of waiting for work vs blocking on joins or
286	>	* other managed sync. Both cases are equivalent for most pool
287	>	* control, so we can update non-atomically. (Additionally,
288	>	* contention on blockedCount alleviates some contention on ctl).
289	>	*
290	>	* Shutdown and Termination. A call to shutdownNow atomically sets
291	>	* the ctl stop bit and then (non-atomically) sets each workers
292	>	* "terminate" status, cancels all unprocessed tasks, and wakes up
293	>	* all waiting workers.  Detecting whether termination should
294	>	* commence after a non-abrupt shutdown() call requires more work
295	>	* and bookkeeping. We need consensus about quiesence (i.e., that
296	>	* there is no more work) which is reflected in active counts so
297	>	* long as there are no current blockers, as well as possible
298	>	* re-evaluations during independent changes in blocking or
299	>	* quiescing workers.
300	>	*
301	>	* Style notes: There is a lot of representation-level coupling
302	>	* among classes ForkJoinPool, ForkJoinWorkerThread, and
303	>	* ForkJoinTask.  Most fields of ForkJoinWorkerThread maintain
304	>	* data structures managed by ForkJoinPool, so are directly
305	>	* accessed.  Conversely we allow access to "workers" array by
306	>	* workers, and direct access to ForkJoinTask.status by both
307	>	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
308	>	* trying to reduce this, since any associated future changes in
309	>	* representations will need to be accompanied by algorithmic
310	>	* changes anyway. All together, these low-level implementation
311	>	* choices produce as much as a factor of 4 performance
312	>	* improvement compared to naive implementations, and enable the
313	>	* processing of billions of tasks per second, at the expense of
314	>	* some ugliness.
315	>	*
316	>	* Methods signalWork() and scan() are the main bottlenecks so are
317	>	* especially heavily micro-optimized/mangled.  There are lots of
318	>	* inline assignments (of form "while ((local = field) != 0)")
319	>	* which are usually the simplest way to ensure the required read
320	>	* orderings (which are sometimes critical). This leads to a
321	>	* "C"-like style of listing declarations of these locals at the
322	>	* heads of methods or blocks.  There are several occurrences of
323	>	* the unusual "do {} while (!cas...)"  which is the simplest way
324	>	* to force an update of a CAS'ed variable. There are also other
325	>	* coding oddities that help some methods perform reasonably even
326	>	* when interpreted (not compiled).
327	>	*
328	>	* The order of declarations in this file is: (1) declarations of
329	>	* statics (2) fields (along with constants used when unpacking
330	>	* some of them), listed in an order that tends to reduce
331	>	* contention among them a bit under most JVMs.  (3) internal
332	>	* control methods (4) callbacks and other support for
333	>	* ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
334	>	* methods (plus a few little helpers). (6) static block
335	>	* initializing all statics in a minimally dependent order.
336		*/
337
64	–	/** Mask for packing and unpacking shorts */
65	–	private static final int  shortMask = 0xffff;
66	–
67	–	/** Max pool size -- must be a power of two minus 1 */
68	–	private static final int MAX_THREADS =  0x7FFF;
69	–
338		/**
339	<	* Factory for creating new ForkJoinWorkerThreads.  A
340	<	* ForkJoinWorkerThreadFactory must be defined and used for
341	<	* ForkJoinWorkerThread subclasses that extend base functionality
342	<	* or initialize threads with different contexts.
339	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
340	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
341	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
342	>	* functionality or initialize threads with different contexts.
343		*/
344		public static interface ForkJoinWorkerThreadFactory {
345		/**
346		* Returns a new worker thread operating in the given pool.
347		*
348		* @param pool the pool this thread works in
349	<	* @throws NullPointerException if pool is null;
349	>	* @throws NullPointerException if the pool is null
350		*/
351		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
352		}
353
354		/**
355	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
355	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
356		* new ForkJoinWorkerThread.
357		*/
358	<	public static class  DefaultForkJoinWorkerThreadFactory
358	>	static class DefaultForkJoinWorkerThreadFactory
359		implements ForkJoinWorkerThreadFactory {
360		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
361	<	try {
94	<	return new ForkJoinWorkerThread(pool);
95	<	} catch (OutOfMemoryError oom)  {
96	<	return null;
97	<	}
361	>	return new ForkJoinWorkerThread(pool);
362		}
363		}
364
365		/**
366	<	* The default ForkJoinWorkerThreadFactory, used unless overridden
367	<	* in ForkJoinPool constructors.
366	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
367	>	* overridden in ForkJoinPool constructors.
368		*/
369	<	private static final DefaultForkJoinWorkerThreadFactory
370	<	defaultForkJoinWorkerThreadFactory =
107	<	new DefaultForkJoinWorkerThreadFactory();
108	<
369	>	public static final ForkJoinWorkerThreadFactory
370	>	defaultForkJoinWorkerThreadFactory;
371
372		/**
373		* Permission required for callers of methods that may start or
374		* kill threads.
375		*/
376	<	private static final RuntimePermission modifyThreadPermission =
115	<	new RuntimePermission("modifyThread");
376	>	private static final RuntimePermission modifyThreadPermission;
377
378		/**
379		* If there is a security manager, makes sure caller has
#	Line 127 | Line 388 | public class ForkJoinPool extends Abstra
388		/**
389		* Generator for assigning sequence numbers as pool names.
390		*/
391	<	private static final AtomicInteger poolNumberGenerator =
131	<	new AtomicInteger();
391	>	private static final AtomicInteger poolNumberGenerator;
392
393		/**
394	<	* Array holding all worker threads in the pool. Array size must
395	<	* be a power of two.  Updates and replacements are protected by
396	<	* workerLock, but it is always kept in a consistent enough state
397	<	* to be randomly accessed without locking by workers performing
398	<	* work-stealing.
394	>	* Generator for initial random seeds for worker victim
395	>	* selection. This is used only to create initial seeds. Random
396	>	* steals use a cheaper xorshift generator per steal attempt. We
397	>	* don't expect much contention on seedGenerator, so just use a
398	>	* plain Random.
399		*/
400	<	volatile ForkJoinWorkerThread[] workers;
400	>	static final Random workerSeedGenerator;
401
402		/**
403	<	* Lock protecting access to workers.
403	>	* Array holding all worker threads in the pool.  Initialized upon
404	>	* construction. Array size must be a power of two.  Updates and
405	>	* replacements are protected by scanGuard, but the array is
406	>	* always kept in a consistent enough state to be randomly
407	>	* accessed without locking by workers performing work-stealing,
408	>	* as well as other traversal-based methods in this class, so long
409	>	* as reads memory-acquire by first reading ctl. All readers must
410	>	* tolerate that some array slots may be null.
411		*/
412	<	private final ReentrantLock workerLock;
412	>	ForkJoinWorkerThread[] workers;
413
414		/**
415	<	* Condition for awaitTermination.
415	>	* Initial size for submission queue array. Must be a power of
416	>	* two.  In many applications, these always stay small so we use a
417	>	* small initial cap.
418		*/
419	<	private final Condition termination;
419	>	private static final int INITIAL_QUEUE_CAPACITY = 8;
420	>
421	>	/**
422	>	* Maximum size for submission queue array. Must be a power of two
423	>	* less than or equal to 1 << (31 - width of array entry) to
424	>	* ensure lack of index wraparound, but is capped at a lower
425	>	* value to help users trap runaway computations.
426	>	*/
427	>	private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 24; // 16M
428
429		/**
430	<	* The uncaught exception handler used when any worker
154	<	* abrupty terminates
430	>	* Array serving as submission queue. Initialized upon construction.
431		*/
432	<	private Thread.UncaughtExceptionHandler ueh;
432	>	private ForkJoinTask<?>[] submissionQueue;
433	>
434	>	/**
435	>	* Lock protecting submissions array for addSubmission
436	>	*/
437	>	private final ReentrantLock submissionLock;
438	>
439	>	/**
440	>	* Condition for awaitTermination, using submissionLock for
441	>	* convenience.
442	>	*/
443	>	private final Condition termination;
444
445		/**
446		* Creation factory for worker threads.
#	Line 161 | Line 448 | public class ForkJoinPool extends Abstra
448		private final ForkJoinWorkerThreadFactory factory;
449
450		/**
451	<	* Head of stack of threads that were created to maintain
452	<	* parallelism when other threads blocked, but have since
453	<	* suspended when the parallelism level rose.
451	>	* The uncaught exception handler used when any worker abruptly
452	>	* terminates.
453	>	*/
454	>	final Thread.UncaughtExceptionHandler ueh;
455	>
456	>	/**
457	>	* Prefix for assigning names to worker threads
458		*/
459	<	private volatile WaitQueueNode spareStack;
459	>	private final String workerNamePrefix;
460
461		/**
462		* Sum of per-thread steal counts, updated only when threads are
463		* idle or terminating.
464		*/
465	<	private final AtomicLong stealCount;
465	>	private volatile long stealCount;
466
467		/**
468	<	* Queue for external submissions.
468	>	* Main pool control -- a long packed with:
469	>	* AC: Number of active running workers minus target parallelism (16 bits)
470	>	* TC: Number of total workers minus target parallelism (16bits)
471	>	* ST: true if pool is terminating (1 bit)
472	>	* EC: the wait count of top waiting thread (15 bits)
473	>	* ID: ~poolIndex of top of Treiber stack of waiting threads (16 bits)
474	>	*
475	>	* When convenient, we can extract the upper 32 bits of counts and
476	>	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
477	>	* (int)ctl.  The ec field is never accessed alone, but always
478	>	* together with id and st. The offsets of counts by the target
479	>	* parallelism and the positionings of fields makes it possible to
480	>	* perform the most common checks via sign tests of fields: When
481	>	* ac is negative, there are not enough active workers, when tc is
482	>	* negative, there are not enough total workers, when id is
483	>	* negative, there is at least one waiting worker, and when e is
484	>	* negative, the pool is terminating.  To deal with these possibly
485	>	* negative fields, we use casts in and out of "short" and/or
486	>	* signed shifts to maintain signedness.
487		*/
488	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
488	>	volatile long ctl;
489	>
490	>	// bit positions/shifts for fields
491	>	private static final int  AC_SHIFT   = 48;
492	>	private static final int  TC_SHIFT   = 32;
493	>	private static final int  ST_SHIFT   = 31;
494	>	private static final int  EC_SHIFT   = 16;
495	>
496	>	// bounds
497	>	private static final int  MAX_ID     = 0x7fff;  // max poolIndex
498	>	private static final int  SMASK      = 0xffff;  // mask short bits
499	>	private static final int  SHORT_SIGN = 1 << 15;
500	>	private static final int  INT_SIGN   = 1 << 31;
501	>
502	>	// masks
503	>	private static final long STOP_BIT   = 0x0001L << ST_SHIFT;
504	>	private static final long AC_MASK    = ((long)SMASK) << AC_SHIFT;
505	>	private static final long TC_MASK    = ((long)SMASK) << TC_SHIFT;
506	>
507	>	// units for incrementing and decrementing
508	>	private static final long TC_UNIT    = 1L << TC_SHIFT;
509	>	private static final long AC_UNIT    = 1L << AC_SHIFT;
510	>
511	>	// masks and units for dealing with u = (int)(ctl >>> 32)
512	>	private static final int  UAC_SHIFT  = AC_SHIFT - 32;
513	>	private static final int  UTC_SHIFT  = TC_SHIFT - 32;
514	>	private static final int  UAC_MASK   = SMASK << UAC_SHIFT;
515	>	private static final int  UTC_MASK   = SMASK << UTC_SHIFT;
516	>	private static final int  UAC_UNIT   = 1 << UAC_SHIFT;
517	>	private static final int  UTC_UNIT   = 1 << UTC_SHIFT;
518	>
519	>	// masks and units for dealing with e = (int)ctl
520	>	private static final int  E_MASK     = 0x7fffffff; // no STOP_BIT
521	>	private static final int  EC_UNIT    = 1 << EC_SHIFT;
522
523		/**
524	<	* Head of Treiber stack for barrier sync. See below for explanation
524	>	* The target parallelism level.
525		*/
526	<	private volatile WaitQueueNode barrierStack;
526	>	final int parallelism;
527
528		/**
529	<	* The count for event barrier
529	>	* Index (mod submission queue length) of next element to take
530	>	* from submission queue. Usage is identical to that for
531	>	* per-worker queues -- see ForkJoinWorkerThread internal
532	>	* documentation.
533		*/
534	<	private volatile long eventCount;
534	>	volatile int queueBase;
535
536		/**
537	<	* Pool number, just for assigning useful names to worker threads
537	>	* Index (mod submission queue length) of next element to add
538	>	* in submission queue. Usage is identical to that for
539	>	* per-worker queues -- see ForkJoinWorkerThread internal
540	>	* documentation.
541		*/
542	<	private final int poolNumber;
542	>	int queueTop;
543
544		/**
545	<	* The maximum allowed pool size
545	>	* True when shutdown() has been called.
546		*/
547	<	private volatile int maxPoolSize;
547	>	volatile boolean shutdown;
548
549		/**
550	<	* The desired parallelism level, updated only under workerLock.
550	>	* True if use local fifo, not default lifo, for local polling
551	>	* Read by, and replicated by ForkJoinWorkerThreads
552		*/
553	<	private volatile int parallelism;
553	>	final boolean locallyFifo;
554
555		/**
556	<	* Holds number of total (i.e., created and not yet terminated)
557	<	* and running (i.e., not blocked on joins or other managed sync)
558	<	* threads, packed into one int to ensure consistent snapshot when
210	<	* making decisions about creating and suspending spare
211	<	* threads. Updated only by CAS.  Note: CASes in
212	<	* updateRunningCount and preJoin running active count is in low
213	<	* word, so need to be modified if this changes
556	>	* The number of threads in ForkJoinWorkerThreads.helpQuiescePool.
557	>	* When non-zero, suppresses automatic shutdown when active
558	>	* counts become zero.
559		*/
560	<	private volatile int workerCounts;
216	<
217	<	private static int totalCountOf(int s)           { return s >>> 16;  }
218	<	private static int runningCountOf(int s)         { return s & shortMask; }
219	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
560	>	volatile int quiescerCount;
561
562		/**
563	<	* Add delta (which may be negative) to running count.  This must
223	<	* be called before (with negative arg) and after (with positive)
224	<	* any managed synchronization (i.e., mainly, joins)
225	<	* @param delta the number to add
563	>	* The number of threads blocked in join.
564		*/
565	<	final void updateRunningCount(int delta) {
228	<	int s;
229	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
230	<	}
565	>	volatile int blockedCount;
566
567		/**
568	<	* Add delta (which may be negative) to both total and running
234	<	* count.  This must be called upon creation and termination of
235	<	* worker threads.
236	<	* @param delta the number to add
568	>	* Counter for worker Thread names (unrelated to their poolIndex)
569		*/
570	<	private void updateWorkerCount(int delta) {
239	<	int d = delta + (delta << 16); // add to both lo and hi parts
240	<	int s;
241	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
242	<	}
570	>	private volatile int nextWorkerNumber;
571
572		/**
573	<	* Lifecycle control. High word contains runState, low word
246	<	* contains the number of workers that are (probably) executing
247	<	* tasks. This value is atomically incremented before a worker
248	<	* gets a task to run, and decremented when worker has no tasks
249	<	* and cannot find any. These two fields are bundled together to
250	<	* support correct termination triggering.  Note: activeCount
251	<	* CAS'es cheat by assuming active count is in low word, so need
252	<	* to be modified if this changes
573	>	* The index for the next created worker. Accessed under scanGuard.
574		*/
575	<	private volatile int runControl;
575	>	private int nextWorkerIndex;
576
577	<	// RunState values. Order among values matters
578	<	private static final int RUNNING     = 0;
579	<	private static final int SHUTDOWN    = 1;
580	<	private static final int TERMINATING = 2;
581	<	private static final int TERMINATED  = 3;
577	>	/**
578	>	* SeqLock and index masking for updates to workers array.  Locked
579	>	* when SG_UNIT is set. Unlocking clears bit by adding
580	>	* SG_UNIT. Staleness of read-only operations can be checked by
581	>	* comparing scanGuard to value before the reads. The low 16 bits
582	>	* (i.e, anding with SMASK) hold (the smallest power of two
583	>	* covering all worker indices, minus one, and is used to avoid
584	>	* dealing with large numbers of null slots when the workers array
585	>	* is overallocated.
586	>	*/
587	>	volatile int scanGuard;
588
589	<	private static int runStateOf(int c)             { return c >>> 16; }
263	<	private static int activeCountOf(int c)          { return c & shortMask; }
264	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
589	>	private static final int SG_UNIT = 1 << 16;
590
591		/**
592	<	* Increment active count. Called by workers before/during
593	<	* executing tasks.
592	>	* The wakeup interval (in nanoseconds) for a worker waiting for a
593	>	* task when the pool is quiescent to instead try to shrink the
594	>	* number of workers.  The exact value does not matter too
595	>	* much. It must be short enough to release resources during
596	>	* sustained periods of idleness, but not so short that threads
597	>	* are continually re-created.
598		*/
599	<	final void incrementActiveCount() {
600	<	int c;
272	<	do;while (!casRunControl(c = runControl, c+1));
273	<	}
599	>	private static final long SHRINK_RATE =
600	>	4L * 1000L * 1000L * 1000L; // 4 seconds
601
602		/**
603	<	* Decrement active count; possibly trigger termination.
604	<	* Called by workers when they can't find tasks.
603	>	* Top-level loop for worker threads: On each step: if the
604	>	* previous step swept through all queues and found no tasks, or
605	>	* there are excess threads, then possibly blocks. Otherwise,
606	>	* scans for and, if found, executes a task. Returns when pool
607	>	* and/or worker terminate.
608	>	*
609	>	* @param w the worker
610		*/
611	<	final void decrementActiveCount() {
612	<	int c, nextc;
613	<	do;while (!casRunControl(c = runControl, nextc = c-1));
614	<	if (canTerminateOnShutdown(nextc))
615	<	terminateOnShutdown();
611	>	final void work(ForkJoinWorkerThread w) {
612	>	boolean swept = false;                // true on empty scans
613	>	long c;
614	>	while (!w.terminate && (int)(c = ctl) >= 0) {
615	>	int a;                            // active count
616	>	if (!swept && (a = (int)(c >> AC_SHIFT)) <= 0)
617	>	swept = scan(w, a);
618	>	else if (tryAwaitWork(w, c))
619	>	swept = false;
620	>	}
621		}
622
623	<	/**
624	<	* Return true if argument represents zero active count and
625	<	* nonzero runstate, which is the triggering condition for
626	<	* terminating on shutdown.
627	<	*/
628	<	private static boolean canTerminateOnShutdown(int c) {
629	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
623	>	// Signalling
624	>
625	>	/**
626	>	* Wakes up or creates a worker.
627	>	*/
628	>	final void signalWork() {
629	>	/*
630	>	* The while condition is true if: (there is are too few total
631	>	* workers OR there is at least one waiter) AND (there are too
632	>	* few active workers OR the pool is terminating).  The value
633	>	* of e distinguishes the remaining cases: zero (no waiters)
634	>	* for create, negative if terminating (in which case do
635	>	* nothing), else release a waiter. The secondary checks for
636	>	* release (non-null array etc) can fail if the pool begins
637	>	* terminating after the test, and don't impose any added cost
638	>	* because JVMs must perform null and bounds checks anyway.
639	>	*/
640	>	long c; int e, u;
641	>	while ((((e = (int)(c = ctl)) | (u = (int)(c >>> 32))) &
642	>	(INT_SIGN|SHORT_SIGN)) == (INT_SIGN|SHORT_SIGN) && e >= 0) {
643	>	if (e > 0) {                         // release a waiting worker
644	>	int i; ForkJoinWorkerThread w; ForkJoinWorkerThread[] ws;
645	>	if ((ws = workers) == null ||
646	>	(i = ~e & SMASK) >= ws.length ||
647	>	(w = ws[i]) == null)
648	>	break;
649	>	long nc = (((long)(w.nextWait & E_MASK)) |
650	>	((long)(u + UAC_UNIT) << 32));
651	>	if (w.eventCount == e &&
652	>	UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
653	>	w.eventCount = (e + EC_UNIT) & E_MASK;
654	>	if (w.parked)
655	>	UNSAFE.unpark(w);
656	>	break;
657	>	}
658	>	}
659	>	else if (UNSAFE.compareAndSwapLong
660	>	(this, ctlOffset, c,
661	>	(long)(((u + UTC_UNIT) & UTC_MASK) |
662	>	((u + UAC_UNIT) & UAC_MASK)) << 32)) {
663	>	addWorker();
664	>	break;
665	>	}
666	>	}
667		}
668
669		/**
670	<	* Transition run state to at least the given state. Return true
671	<	* if not already at least given state.
670	>	* Variant of signalWork to help release waiters on rescans.
671	>	* Tries once to release a waiter if active count < 0.
672	>	*
673	>	* @return false if failed due to contention, else true
674	>	*/
675	>	private boolean tryReleaseWaiter() {
676	>	long c; int e, i; ForkJoinWorkerThread w; ForkJoinWorkerThread[] ws;
677	>	if ((e = (int)(c = ctl)) > 0 &&
678	>	(int)(c >> AC_SHIFT) < 0 &&
679	>	(ws = workers) != null &&
680	>	(i = ~e & SMASK) < ws.length &&
681	>	(w = ws[i]) != null) {
682	>	long nc = ((long)(w.nextWait & E_MASK) |
683	>	((c + AC_UNIT) & (AC_MASK|TC_MASK)));
684	>	if (w.eventCount != e ||
685	>	!UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc))
686	>	return false;
687	>	w.eventCount = (e + EC_UNIT) & E_MASK;
688	>	if (w.parked)
689	>	UNSAFE.unpark(w);
690	>	}
691	>	return true;
692	>	}
693	>
694	>	// Scanning for tasks
695	>
696	>	/**
697	>	* Scans for and, if found, executes one task. Scans start at a
698	>	* random index of workers array, and randomly select the first
699	>	* (2*#workers)-1 probes, and then, if all empty, resort to 2
700	>	* circular sweeps, which is necessary to check quiescence. and
701	>	* taking a submission only if no stealable tasks were found.  The
702	>	* steal code inside the loop is a specialized form of
703	>	* ForkJoinWorkerThread.deqTask, followed bookkeeping to support
704	>	* helpJoinTask and signal propagation. The code for submission
705	>	* queues is almost identical. On each steal, the worker completes
706	>	* not only the task, but also all local tasks that this task may
707	>	* have generated. On detecting staleness or contention when
708	>	* trying to take a task, this method returns without finishing
709	>	* sweep, which allows global state rechecks before retry.
710	>	*
711	>	* @param w the worker
712	>	* @param a the number of active workers
713	>	* @return true if swept all queues without finding a task
714		*/
715	<	private boolean transitionRunStateTo(int state) {
716	<	for (;;) {
717	<	int c = runControl;
718	<	if (runStateOf(c) >= state)
715	>	private boolean scan(ForkJoinWorkerThread w, int a) {
716	>	int g = scanGuard; // mask 0 avoids useless scans if only one active
717	>	int m = (parallelism == 1 - a && blockedCount == 0) ? 0 : g & SMASK;
718	>	ForkJoinWorkerThread[] ws = workers;
719	>	if (ws == null || ws.length <= m)         // staleness check
720	>	return false;
721	>	for (int r = w.seed, k = r, j = -(m + m); j <= m + m; ++j) {
722	>	ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i;
723	>	ForkJoinWorkerThread v = ws[k & m];
724	>	if (v != null && (b = v.queueBase) != v.queueTop &&
725	>	(q = v.queue) != null && (i = (q.length - 1) & b) >= 0) {
726	>	long u = (i << ASHIFT) + ABASE;
727	>	if ((t = q[i]) != null && v.queueBase == b &&
728	>	UNSAFE.compareAndSwapObject(q, u, t, null)) {
729	>	int d = (v.queueBase = b + 1) - v.queueTop;
730	>	v.stealHint = w.poolIndex;
731	>	if (d != 0)
732	>	signalWork();             // propagate if nonempty
733	>	w.execTask(t);
734	>	}
735	>	r ^= r << 13; r ^= r >>> 17; w.seed = r ^ (r << 5);
736	>	return false;                     // store next seed
737	>	}
738	>	else if (j < 0) {                     // xorshift
739	>	r ^= r << 13; r ^= r >>> 17; k = r ^= r << 5;
740	>	}
741	>	else
742	>	++k;
743	>	}
744	>	if (scanGuard != g)                       // staleness check
745	>	return false;
746	>	else {                                    // try to take submission
747	>	ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i;
748	>	if ((b = queueBase) != queueTop &&
749	>	(q = submissionQueue) != null &&
750	>	(i = (q.length - 1) & b) >= 0) {
751	>	long u = (i << ASHIFT) + ABASE;
752	>	if ((t = q[i]) != null && queueBase == b &&
753	>	UNSAFE.compareAndSwapObject(q, u, t, null)) {
754	>	queueBase = b + 1;
755	>	w.execTask(t);
756	>	}
757		return false;
758	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
758	>	}
759	>	return true;                         // all queues empty
760	>	}
761	>	}
762	>
763	>	/**
764	>	* Tries to enqueue worker w in wait queue and await change in
765	>	* worker's eventCount.  If the pool is quiescent and there is
766	>	* more than one worker, possibly terminates worker upon exit.
767	>	* Otherwise, before blocking, rescans queues to avoid missed
768	>	* signals.  Upon finding work, releases at least one worker
769	>	* (which may be the current worker). Rescans restart upon
770	>	* detected staleness or failure to release due to
771	>	* contention. Note the unusual conventions about Thread.interrupt
772	>	* here and elsewhere: Because interrupts are used solely to alert
773	>	* threads to check termination, which is checked here anyway, we
774	>	* clear status (using Thread.interrupted) before any call to
775	>	* park, so that park does not immediately return due to status
776	>	* being set via some other unrelated call to interrupt in user
777	>	* code.
778	>	*
779	>	* @param w the calling worker
780	>	* @param c the ctl value on entry
781	>	* @return true if waited or another thread was released upon enq
782	>	*/
783	>	private boolean tryAwaitWork(ForkJoinWorkerThread w, long c) {
784	>	int v = w.eventCount;
785	>	w.nextWait = (int)c;                      // w's successor record
786	>	long nc = (long)(v & E_MASK) | ((c - AC_UNIT) & (AC_MASK|TC_MASK));
787	>	if (ctl != c || !UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
788	>	long d = ctl; // return true if lost to a deq, to force scan
789	>	return (int)d != (int)c && ((d - c) & AC_MASK) >= 0L;
790	>	}
791	>	for (int sc = w.stealCount; sc != 0;) {   // accumulate stealCount
792	>	long s = stealCount;
793	>	if (UNSAFE.compareAndSwapLong(this, stealCountOffset, s, s + sc))
794	>	sc = w.stealCount = 0;
795	>	else if (w.eventCount != v)
796	>	return true;                      // update next time
797	>	}
798	>	if ((int)c != 0 && parallelism + (int)(nc >> AC_SHIFT) == 0 &&
799	>	blockedCount == 0 && quiescerCount == 0)
800	>	idleAwaitWork(w, nc, c, v);           // quiescent
801	>	for (boolean rescanned = false;;) {
802	>	if (w.eventCount != v)
803		return true;
804	+	if (!rescanned) {
805	+	int g = scanGuard, m = g & SMASK;
806	+	ForkJoinWorkerThread[] ws = workers;
807	+	if (ws != null && m < ws.length) {
808	+	rescanned = true;
809	+	for (int i = 0; i <= m; ++i) {
810	+	ForkJoinWorkerThread u = ws[i];
811	+	if (u != null) {
812	+	if (u.queueBase != u.queueTop &&
813	+	!tryReleaseWaiter())
814	+	rescanned = false; // contended
815	+	if (w.eventCount != v)
816	+	return true;
817	+	}
818	+	}
819	+	}
820	+	if (scanGuard != g ||              // stale
821	+	(queueBase != queueTop && !tryReleaseWaiter()))
822	+	rescanned = false;
823	+	if (!rescanned)
824	+	Thread.yield();                // reduce contention
825	+	else
826	+	Thread.interrupted();          // clear before park
827	+	}
828	+	else {
829	+	w.parked = true;                   // must recheck
830	+	if (w.eventCount != v) {
831	+	w.parked = false;
832	+	return true;
833	+	}
834	+	LockSupport.park(this);
835	+	rescanned = w.parked = false;
836	+	}
837	+	}
838	+	}
839	+
840	+	/**
841	+	* If inactivating worker w has caused pool to become
842	+	* quiescent, check for pool termination, and wait for event
843	+	* for up to SHRINK_RATE nanosecs (rescans are unnecessary in
844	+	* this case because quiescence reflects consensus about lack
845	+	* of work). On timeout, if ctl has not changed, terminate the
846	+	* worker. Upon its termination (see deregisterWorker), it may
847	+	* wake up another worker to possibly repeat this process.
848	+	*
849	+	* @param w the calling worker
850	+	* @param currentCtl the ctl value after enqueuing w
851	+	* @param prevCtl the ctl value if w terminated
852	+	* @param v the eventCount w awaits change
853	+	*/
854	+	private void idleAwaitWork(ForkJoinWorkerThread w, long currentCtl,
855	+	long prevCtl, int v) {
856	+	if (w.eventCount == v) {
857	+	if (shutdown)
858	+	tryTerminate(false);
859	+	ForkJoinTask.helpExpungeStaleExceptions(); // help clean weak refs
860	+	while (ctl == currentCtl) {
861	+	long startTime = System.nanoTime();
862	+	w.parked = true;
863	+	if (w.eventCount == v)             // must recheck
864	+	LockSupport.parkNanos(this, SHRINK_RATE);
865	+	w.parked = false;
866	+	if (w.eventCount != v)
867	+	break;
868	+	else if (System.nanoTime() - startTime <
869	+	SHRINK_RATE - (SHRINK_RATE / 10)) // timing slop
870	+	Thread.interrupted();          // spurious wakeup
871	+	else if (UNSAFE.compareAndSwapLong(this, ctlOffset,
872	+	currentCtl, prevCtl)) {
873	+	w.terminate = true;            // restore previous
874	+	w.eventCount = ((int)currentCtl + EC_UNIT) & E_MASK;
875	+	break;
876	+	}
877	+	}
878		}
879		}
880
881	+	// Submissions
882	+
883		/**
884	<	* Controls whether to add spares to maintain parallelism
884	>	* Enqueues the given task in the submissionQueue.  Same idea as
885	>	* ForkJoinWorkerThread.pushTask except for use of submissionLock.
886	>	*
887	>	* @param t the task
888		*/
889	<	private volatile boolean maintainsParallelism;
889	>	private void addSubmission(ForkJoinTask<?> t) {
890	>	final ReentrantLock lock = this.submissionLock;
891	>	lock.lock();
892	>	try {
893	>	ForkJoinTask<?>[] q; int s, m;
894	>	if ((q = submissionQueue) != null) {    // ignore if queue removed
895	>	long u = (((s = queueTop) & (m = q.length-1)) << ASHIFT)+ABASE;
896	>	UNSAFE.putOrderedObject(q, u, t);
897	>	queueTop = s + 1;
898	>	if (s - queueBase == m)
899	>	growSubmissionQueue();
900	>	}
901	>	} finally {
902	>	lock.unlock();
903	>	}
904	>	signalWork();
905	>	}
906
907	<	// Constructors
907	>	//  (pollSubmission is defined below with exported methods)
908
909		/**
910	<	* Creates a ForkJoinPool with a pool size equal to the number of
911	<	* processors available on the system and using the default
319	<	* ForkJoinWorkerThreadFactory,
320	<	* @throws SecurityException if a security manager exists and
321	<	*         the caller is not permitted to modify threads
322	<	*         because it does not hold {@link
323	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
910	>	* Creates or doubles submissionQueue array.
911	>	* Basically identical to ForkJoinWorkerThread version.
912		*/
913	<	public ForkJoinPool() {
914	<	this(Runtime.getRuntime().availableProcessors(),
915	<	defaultForkJoinWorkerThreadFactory);
913	>	private void growSubmissionQueue() {
914	>	ForkJoinTask<?>[] oldQ = submissionQueue;
915	>	int size = oldQ != null ? oldQ.length << 1 : INITIAL_QUEUE_CAPACITY;
916	>	if (size > MAXIMUM_QUEUE_CAPACITY)
917	>	throw new RejectedExecutionException("Queue capacity exceeded");
918	>	if (size < INITIAL_QUEUE_CAPACITY)
919	>	size = INITIAL_QUEUE_CAPACITY;
920	>	ForkJoinTask<?>[] q = submissionQueue = new ForkJoinTask<?>[size];
921	>	int mask = size - 1;
922	>	int top = queueTop;
923	>	int oldMask;
924	>	if (oldQ != null && (oldMask = oldQ.length - 1) >= 0) {
925	>	for (int b = queueBase; b != top; ++b) {
926	>	long u = ((b & oldMask) << ASHIFT) + ABASE;
927	>	Object x = UNSAFE.getObjectVolatile(oldQ, u);
928	>	if (x != null && UNSAFE.compareAndSwapObject(oldQ, u, x, null))
929	>	UNSAFE.putObjectVolatile
930	>	(q, ((b & mask) << ASHIFT) + ABASE, x);
931	>	}
932	>	}
933		}
934
935	+	// Blocking support
936	+
937		/**
938	<	* Creates a ForkJoinPool with the indicated parellelism level
939	<	* threads, and using the default ForkJoinWorkerThreadFactory,
940	<	* @param parallelism the number of worker threads
941	<	* @throws IllegalArgumentException if parallelism less than or
942	<	* equal to zero
943	<	* @throws SecurityException if a security manager exists and
337	<	*         the caller is not permitted to modify threads
338	<	*         because it does not hold {@link
339	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
938	>	* Tries to increment blockedCount, decrement active count
939	>	* (sometimes implicitly) and possibly release or create a
940	>	* compensating worker in preparation for blocking. Fails
941	>	* on contention or termination.
942	>	*
943	>	* @return true if the caller can block, else should recheck and retry
944		*/
945	<	public ForkJoinPool(int parallelism) {
946	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
945	>	private boolean tryPreBlock() {
946	>	int b = blockedCount;
947	>	if (UNSAFE.compareAndSwapInt(this, blockedCountOffset, b, b + 1)) {
948	>	int pc = parallelism;
949	>	do {
950	>	ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w;
951	>	int e, ac, tc, rc, i;
952	>	long c = ctl;
953	>	int u = (int)(c >>> 32);
954	>	if ((e = (int)c) < 0) {
955	>	// skip -- terminating
956	>	}
957	>	else if ((ac = (u >> UAC_SHIFT)) <= 0 && e != 0 &&
958	>	(ws = workers) != null &&
959	>	(i = ~e & SMASK) < ws.length &&
960	>	(w = ws[i]) != null) {
961	>	long nc = ((long)(w.nextWait & E_MASK) |
962	>	(c & (AC_MASK|TC_MASK)));
963	>	if (w.eventCount == e &&
964	>	UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
965	>	w.eventCount = (e + EC_UNIT) & E_MASK;
966	>	if (w.parked)
967	>	UNSAFE.unpark(w);
968	>	return true;             // release an idle worker
969	>	}
970	>	}
971	>	else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) {
972	>	long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
973	>	if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc))
974	>	return true;             // no compensation needed
975	>	}
976	>	else if (tc + pc < MAX_ID) {
977	>	long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
978	>	if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
979	>	addWorker();
980	>	return true;            // create a replacement
981	>	}
982	>	}
983	>	// try to back out on any failure and let caller retry
984	>	} while (!UNSAFE.compareAndSwapInt(this, blockedCountOffset,
985	>	b = blockedCount, b - 1));
986	>	}
987	>	return false;
988		}
989
990		/**
991	<	* Creates a ForkJoinPool with a pool size equal to the number of
347	<	* processors available on the system and using the given
348	<	* ForkJoinWorkerThreadFactory,
349	<	* @param factory the factory for creating new threads
350	<	* @throws NullPointerException if factory is null
351	<	* @throws SecurityException if a security manager exists and
352	<	*         the caller is not permitted to modify threads
353	<	*         because it does not hold {@link
354	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
991	>	* Decrements blockedCount and increments active count
992		*/
993	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
994	<	this(Runtime.getRuntime().availableProcessors(), factory);
993	>	private void postBlock() {
994	>	long c;
995	>	do {} while (!UNSAFE.compareAndSwapLong(this, ctlOffset,  // no mask
996	>	c = ctl, c + AC_UNIT));
997	>	int b;
998	>	do {} while(!UNSAFE.compareAndSwapInt(this, blockedCountOffset,
999	>	b = blockedCount, b - 1));
1000		}
1001
1002		/**
1003	<	* Creates a ForkJoinPool with the indicated target number of
1004	<	* worker threads and the given factory.
1003	>	* Possibly blocks waiting for the given task to complete, or
1004	>	* cancels the task if terminating.  Fails to wait if contended.
1005		*
1006	<	* @param parallelism the targeted number of worker threads
365	<	* @param factory the factory for creating new threads
366	<	* @throws IllegalArgumentException if parallelism less than or
367	<	* equal to zero, or greater than implementation limit.
368	<	* @throws NullPointerException if factory is null
369	<	* @throws SecurityException if a security manager exists and
370	<	*         the caller is not permitted to modify threads
371	<	*         because it does not hold {@link
372	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1006	>	* @param joinMe the task
1007		*/
1008	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
1009	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
1010	<	throw new IllegalArgumentException();
1011	<	if (factory == null)
1012	<	throw new NullPointerException();
1013	<	checkPermission();
1014	<	this.factory = factory;
1015	<	this.parallelism = parallelism;
1016	<	this.maxPoolSize = MAX_THREADS;
1017	<	this.maintainsParallelism = true;
1018	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
385	<	this.workerLock = new ReentrantLock();
386	<	this.termination = workerLock.newCondition();
387	<	this.stealCount = new AtomicLong();
388	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
389	<	createAndStartInitialWorkers(parallelism);
1008	>	final void tryAwaitJoin(ForkJoinTask<?> joinMe) {
1009	>	int s;
1010	>	Thread.interrupted(); // clear interrupts before checking termination
1011	>	if (joinMe.status >= 0) {
1012	>	if (tryPreBlock()) {
1013	>	joinMe.tryAwaitDone(0L);
1014	>	postBlock();
1015	>	}
1016	>	else if ((ctl & STOP_BIT) != 0L)
1017	>	joinMe.cancelIgnoringExceptions();
1018	>	}
1019		}
1020
1021		/**
1022	<	* Create new worker using factory.
1023	<	* @param index the index to assign worker
1024	<	* @return new worker, or null of factory failed
1022	>	* Possibly blocks the given worker waiting for joinMe to
1023	>	* complete or timeout
1024	>	*
1025	>	* @param joinMe the task
1026	>	* @param millis the wait time for underlying Object.wait
1027		*/
1028	<	private ForkJoinWorkerThread createWorker(int index) {
1029	<	Thread.UncaughtExceptionHandler h = ueh;
1030	<	ForkJoinWorkerThread w = factory.newThread(this);
1031	<	if (w != null) {
1032	<	w.poolIndex = index;
1033	<	w.setDaemon(true);
1034	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
1035	<	if (h != null)
1036	<	w.setUncaughtExceptionHandler(h);
1028	>	final void timedAwaitJoin(ForkJoinTask<?> joinMe, long nanos) {
1029	>	while (joinMe.status >= 0) {
1030	>	Thread.interrupted();
1031	>	if ((ctl & STOP_BIT) != 0L) {
1032	>	joinMe.cancelIgnoringExceptions();
1033	>	break;
1034	>	}
1035	>	if (tryPreBlock()) {
1036	>	long last = System.nanoTime();
1037	>	while (joinMe.status >= 0) {
1038	>	long millis = TimeUnit.NANOSECONDS.toMillis(nanos);
1039	>	if (millis <= 0)
1040	>	break;
1041	>	joinMe.tryAwaitDone(millis);
1042	>	if (joinMe.status < 0)
1043	>	break;
1044	>	if ((ctl & STOP_BIT) != 0L) {
1045	>	joinMe.cancelIgnoringExceptions();
1046	>	break;
1047	>	}
1048	>	long now = System.nanoTime();
1049	>	nanos -= now - last;
1050	>	last = now;
1051	>	}
1052	>	postBlock();
1053	>	break;
1054	>	}
1055		}
407	–	return w;
1056		}
1057
1058		/**
1059	<	* Return a good size for worker array given pool size.
412	<	* Currently requires size to be a power of two.
1059	>	* If necessary, compensates for blocker, and blocks
1060		*/
1061	<	private static int arraySizeFor(int ps) {
1062	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
1061	>	private void awaitBlocker(ManagedBlocker blocker)
1062	>	throws InterruptedException {
1063	>	while (!blocker.isReleasable()) {
1064	>	if (tryPreBlock()) {
1065	>	try {
1066	>	do {} while (!blocker.isReleasable() && !blocker.block());
1067	>	} finally {
1068	>	postBlock();
1069	>	}
1070	>	break;
1071	>	}
1072	>	}
1073		}
1074
1075	+	// Creating, registering and deregistring workers
1076	+
1077		/**
1078	<	* Create or resize array if necessary to hold newLength
1079	<	* @return the array
1078	>	* Tries to create and start a worker; minimally rolls back counts
1079	>	* on failure.
1080		*/
1081	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
1082	<	ForkJoinWorkerThread[] ws = workers;
1083	<	if (ws == null)
1084	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
1085	<	else if (newLength > ws.length)
1086	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
1081	>	private void addWorker() {
1082	>	Throwable ex = null;
1083	>	ForkJoinWorkerThread t = null;
1084	>	try {
1085	>	t = factory.newThread(this);
1086	>	} catch (Throwable e) {
1087	>	ex = e;
1088	>	}
1089	>	if (t == null) {  // null or exceptional factory return
1090	>	long c;       // adjust counts
1091	>	do {} while (!UNSAFE.compareAndSwapLong
1092	>	(this, ctlOffset, c = ctl,
1093	>	(((c - AC_UNIT) & AC_MASK) |
1094	>	((c - TC_UNIT) & TC_MASK) |
1095	>	(c & ~(AC_MASK|TC_MASK)))));
1096	>	// Propagate exception if originating from an external caller
1097	>	if (!tryTerminate(false) && ex != null &&
1098	>	!(Thread.currentThread() instanceof ForkJoinWorkerThread))
1099	>	UNSAFE.throwException(ex);
1100	>	}
1101		else
1102	<	return ws;
1102	>	t.start();
1103		}
1104
1105		/**
1106	<	* Try to shrink workers into smaller array after one or more terminate
1106	>	* Callback from ForkJoinWorkerThread constructor to assign a
1107	>	* public name
1108		*/
1109	<	private void tryShrinkWorkerArray() {
1110	<	ForkJoinWorkerThread[] ws = workers;
1111	<	int len = ws.length;
1112	<	int last = len - 1;
1113	<	while (last >= 0 && ws[last] == null)
1114	<	--last;
441	<	int newLength = arraySizeFor(last+1);
442	<	if (newLength < len)
443	<	workers = Arrays.copyOf(ws, newLength);
1109	>	final String nextWorkerName() {
1110	>	for (int n;;) {
1111	>	if (UNSAFE.compareAndSwapInt(this, nextWorkerNumberOffset,
1112	>	n = nextWorkerNumber, ++n))
1113	>	return workerNamePrefix + n;
1114	>	}
1115		}
1116
1117		/**
1118	<	* Initial worker array and worker creation and startup. (This
1119	<	* must be done under lock to avoid interference by some of the
1120	<	* newly started threads while creating others.)
1118	>	* Callback from ForkJoinWorkerThread constructor to
1119	>	* determine its poolIndex and record in workers array.
1120	>	*
1121	>	* @param w the worker
1122	>	* @return the worker's pool index
1123		*/
1124	<	private void createAndStartInitialWorkers(int ps) {
1125	<	final ReentrantLock lock = this.workerLock;
1126	<	lock.lock();
1127	<	try {
1128	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1129	<	for (int i = 0; i < ps; ++i) {
1130	<	ForkJoinWorkerThread w = createWorker(i);
1131	<	if (w != null) {
1132	<	ws[i] = w;
1133	<	w.start();
1134	<	updateWorkerCount(1);
1124	>	final int registerWorker(ForkJoinWorkerThread w) {
1125	>	/*
1126	>	* In the typical case, a new worker acquires the lock, uses
1127	>	* next available index and returns quickly.  Since we should
1128	>	* not block callers (ultimately from signalWork or
1129	>	* tryPreBlock) waiting for the lock needed to do this, we
1130	>	* instead help release other workers while waiting for the
1131	>	* lock.
1132	>	*/
1133	>	for (int g;;) {
1134	>	ForkJoinWorkerThread[] ws;
1135	>	if (((g = scanGuard) & SG_UNIT) == 0 &&
1136	>	UNSAFE.compareAndSwapInt(this, scanGuardOffset,
1137	>	g, g | SG_UNIT)) {
1138	>	int k = nextWorkerIndex;
1139	>	try {
1140	>	if ((ws = workers) != null) { // ignore on shutdown
1141	>	int n = ws.length;
1142	>	if (k < 0 || k >= n || ws[k] != null) {
1143	>	for (k = 0; k < n && ws[k] != null; ++k)
1144	>	;
1145	>	if (k == n)
1146	>	ws = workers = Arrays.copyOf(ws, n << 1);
1147	>	}
1148	>	ws[k] = w;
1149	>	nextWorkerIndex = k + 1;
1150	>	int m = g & SMASK;
1151	>	g = k > m? ((m << 1) + 1) & SMASK : g + (SG_UNIT<<1);
1152	>	}
1153	>	} finally {
1154	>	scanGuard = g;
1155	>	}
1156	>	return k;
1157	>	}
1158	>	else if ((ws = workers) != null) { // help release others
1159	>	for (ForkJoinWorkerThread u : ws) {
1160	>	if (u != null && u.queueBase != u.queueTop) {
1161	>	if (tryReleaseWaiter())
1162	>	break;
1163	>	}
1164		}
1165		}
464	–	} finally {
465	–	lock.unlock();
1166		}
1167		}
1168
1169		/**
1170	<	* Worker creation and startup for threads added via setParallelism.
1170	>	* Final callback from terminating worker.  Removes record of
1171	>	* worker from array, and adjusts counts. If pool is shutting
1172	>	* down, tries to complete termination.
1173	>	*
1174	>	* @param w the worker
1175		*/
1176	<	private void createAndStartAddedWorkers() {
1177	<	resumeAllSpares();  // Allow spares to convert to nonspare
1178	<	int ps = parallelism;
1179	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1180	<	int len = ws.length;
1181	<	// Sweep through slots, to keep lowest indices most populated
1182	<	int k = 0;
1183	<	while (k < len) {
1184	<	if (ws[k] != null) {
1185	<	++k;
1186	<	continue;
1176	>	final void deregisterWorker(ForkJoinWorkerThread w, Throwable ex) {
1177	>	int idx = w.poolIndex;
1178	>	int sc = w.stealCount;
1179	>	int steps = 0;
1180	>	// Remove from array, adjust worker counts and collect steal count.
1181	>	// We can intermix failed removes or adjusts with steal updates
1182	>	do {
1183	>	long s, c;
1184	>	int g;
1185	>	if (steps == 0 && ((g = scanGuard) & SG_UNIT) == 0 &&
1186	>	UNSAFE.compareAndSwapInt(this, scanGuardOffset,
1187	>	g, g |= SG_UNIT)) {
1188	>	ForkJoinWorkerThread[] ws = workers;
1189	>	if (ws != null && idx >= 0 &&
1190	>	idx < ws.length && ws[idx] == w)
1191	>	ws[idx] = null;    // verify
1192	>	nextWorkerIndex = idx;
1193	>	scanGuard = g + SG_UNIT;
1194	>	steps = 1;
1195	>	}
1196	>	if (steps == 1 &&
1197	>	UNSAFE.compareAndSwapLong(this, ctlOffset, c = ctl,
1198	>	(((c - AC_UNIT) & AC_MASK) |
1199	>	((c - TC_UNIT) & TC_MASK) |
1200	>	(c & ~(AC_MASK|TC_MASK)))))
1201	>	steps = 2;
1202	>	if (sc != 0 &&
1203	>	UNSAFE.compareAndSwapLong(this, stealCountOffset,
1204	>	s = stealCount, s + sc))
1205	>	sc = 0;
1206	>	} while (steps != 2 || sc != 0);
1207	>	if (!tryTerminate(false)) {
1208	>	if (ex != null)   // possibly replace if died abnormally
1209	>	signalWork();
1210	>	else
1211	>	tryReleaseWaiter();
1212	>	}
1213	>	}
1214	>
1215	>	// Shutdown and termination
1216	>
1217	>	/**
1218	>	* Possibly initiates and/or completes termination.
1219	>	*
1220	>	* @param now if true, unconditionally terminate, else only
1221	>	* if shutdown and empty queue and no active workers
1222	>	* @return true if now terminating or terminated
1223	>	*/
1224	>	private boolean tryTerminate(boolean now) {
1225	>	long c;
1226	>	while (((c = ctl) & STOP_BIT) == 0) {
1227	>	if (!now) {
1228	>	if ((int)(c >> AC_SHIFT) != -parallelism)
1229	>	return false;
1230	>	if (!shutdown || blockedCount != 0 || quiescerCount != 0 ||
1231	>	queueBase != queueTop) {
1232	>	if (ctl == c) // staleness check
1233	>	return false;
1234	>	continue;
1235	>	}
1236		}
1237	<	int s = workerCounts;
1238	<	int tc = totalCountOf(s);
1239	<	int rc = runningCountOf(s);
1240	<	if (rc >= ps || tc >= ps)
1241	<	break;
1242	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
1243	<	ForkJoinWorkerThread w = createWorker(k);
1244	<	if (w != null) {
1245	<	ws[k++] = w;
1246	<	w.start();
1237	>	if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, c | STOP_BIT))
1238	>	startTerminating();
1239	>	}
1240	>	if ((short)(c >>> TC_SHIFT) == -parallelism) { // signal when 0 workers
1241	>	final ReentrantLock lock = this.submissionLock;
1242	>	lock.lock();
1243	>	try {
1244	>	termination.signalAll();
1245	>	} finally {
1246	>	lock.unlock();
1247	>	}
1248	>	}
1249	>	return true;
1250	>	}
1251	>
1252	>	/**
1253	>	* Runs up to three passes through workers: (0) Setting
1254	>	* termination status for each worker, followed by wakeups up to
1255	>	* queued workers; (1) helping cancel tasks; (2) interrupting
1256	>	* lagging threads (likely in external tasks, but possibly also
1257	>	* blocked in joins).  Each pass repeats previous steps because of
1258	>	* potential lagging thread creation.
1259	>	*/
1260	>	private void startTerminating() {
1261	>	cancelSubmissions();
1262	>	for (int pass = 0; pass < 3; ++pass) {
1263	>	ForkJoinWorkerThread[] ws = workers;
1264	>	if (ws != null) {
1265	>	for (ForkJoinWorkerThread w : ws) {
1266	>	if (w != null) {
1267	>	w.terminate = true;
1268	>	if (pass > 0) {
1269	>	w.cancelTasks();
1270	>	if (pass > 1 && !w.isInterrupted()) {
1271	>	try {
1272	>	w.interrupt();
1273	>	} catch (SecurityException ignore) {
1274	>	}
1275	>	}
1276	>	}
1277	>	}
1278		}
1279	<	else {
1280	<	updateWorkerCount(-1); // back out on failed creation
1281	<	break;
1279	>	terminateWaiters();
1280	>	}
1281	>	}
1282	>	}
1283	>
1284	>	/**
1285	>	* Polls and cancels all submissions. Called only during termination.
1286	>	*/
1287	>	private void cancelSubmissions() {
1288	>	while (queueBase != queueTop) {
1289	>	ForkJoinTask<?> task = pollSubmission();
1290	>	if (task != null) {
1291	>	try {
1292	>	task.cancel(false);
1293	>	} catch (Throwable ignore) {
1294	>	}
1295	>	}
1296	>	}
1297	>	}
1298	>
1299	>	/**
1300	>	* Tries to set the termination status of waiting workers, and
1301	>	* then wakes them up (after which they will terminate).
1302	>	*/
1303	>	private void terminateWaiters() {
1304	>	ForkJoinWorkerThread[] ws = workers;
1305	>	if (ws != null) {
1306	>	ForkJoinWorkerThread w; long c; int i, e;
1307	>	int n = ws.length;
1308	>	while ((i = ~(e = (int)(c = ctl)) & SMASK) < n &&
1309	>	(w = ws[i]) != null && w.eventCount == (e & E_MASK)) {
1310	>	if (UNSAFE.compareAndSwapLong(this, ctlOffset, c,
1311	>	(long)(w.nextWait & E_MASK) |
1312	>	((c + AC_UNIT) & AC_MASK) |
1313	>	(c & (TC_MASK|STOP_BIT)))) {
1314	>	w.terminate = true;
1315	>	w.eventCount = e + EC_UNIT;
1316	>	if (w.parked)
1317	>	UNSAFE.unpark(w);
1318		}
1319		}
1320		}
1321		}
1322
1323	+	// misc ForkJoinWorkerThread support
1324	+
1325		/**
1326	<	* Sets the handler for internal worker threads that terminate due
1327	<	* to unrecoverable errors encountered while executing tasks.
1328	<	* Unless set, the current default or ThreadGroup handler is used
1329	<	* as handler.
1326	>	* Increment or decrement quiescerCount. Needed only to prevent
1327	>	* triggering shutdown if a worker is transiently inactive while
1328	>	* checking quiescence.
1329	>	*
1330	>	* @param delta 1 for increment, -1 for decrement
1331	>	*/
1332	>	final void addQuiescerCount(int delta) {
1333	>	int c;
1334	>	do {} while(!UNSAFE.compareAndSwapInt(this, quiescerCountOffset,
1335	>	c = quiescerCount, c + delta));
1336	>	}
1337	>
1338	>	/**
1339	>	* Directly increment or decrement active count without
1340	>	* queuing. This method is used to transiently assert inactivation
1341	>	* while checking quiescence.
1342	>	*
1343	>	* @param delta 1 for increment, -1 for decrement
1344	>	*/
1345	>	final void addActiveCount(int delta) {
1346	>	long d = delta < 0 ? -AC_UNIT : AC_UNIT;
1347	>	long c;
1348	>	do {} while (!UNSAFE.compareAndSwapLong(this, ctlOffset, c = ctl,
1349	>	((c + d) & AC_MASK) |
1350	>	(c & ~AC_MASK)));
1351	>	}
1352	>
1353	>	/**
1354	>	* Returns the approximate (non-atomic) number of idle threads per
1355	>	* active thread.
1356	>	*/
1357	>	final int idlePerActive() {
1358	>	// Approximate at powers of two for small values, saturate past 4
1359	>	int p = parallelism;
1360	>	int a = p + (int)(ctl >> AC_SHIFT);
1361	>	return (a > (p >>>= 1) ? 0 :
1362	>	a > (p >>>= 1) ? 1 :
1363	>	a > (p >>>= 1) ? 2 :
1364	>	a > (p >>>= 1) ? 4 :
1365	>	8);
1366	>	}
1367	>
1368	>	// Exported methods
1369	>
1370	>	// Constructors
1371	>
1372	>	/**
1373	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1374	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1375	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1376	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1377		*
509	–	* @param h the new handler
510	–	* @return the old handler, or null if none
1378		* @throws SecurityException if a security manager exists and
1379		*         the caller is not permitted to modify threads
1380		*         because it does not hold {@link
1381	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1381	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1382		*/
1383	<	public Thread.UncaughtExceptionHandler
1384	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
1385	<	checkPermission();
519	<	Thread.UncaughtExceptionHandler old = null;
520	<	final ReentrantLock lock = this.workerLock;
521	<	lock.lock();
522	<	try {
523	<	old = ueh;
524	<	ueh = h;
525	<	ForkJoinWorkerThread[] ws = workers;
526	<	for (int i = 0; i < ws.length; ++i) {
527	<	ForkJoinWorkerThread w = ws[i];
528	<	if (w != null)
529	<	w.setUncaughtExceptionHandler(h);
530	<	}
531	<	} finally {
532	<	lock.unlock();
533	<	}
534	<	return old;
1383	>	public ForkJoinPool() {
1384	>	this(Runtime.getRuntime().availableProcessors(),
1385	>	defaultForkJoinWorkerThreadFactory, null, false);
1386		}
1387
1388		/**
1389	<	* Returns the handler for internal worker threads that terminate
1390	<	* due to unrecoverable errors encountered while executing tasks.
1391	<	* @return the handler, or null if none
1389	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
1390	>	* level, the {@linkplain
1391	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1392	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1393	>	*
1394	>	* @param parallelism the parallelism level
1395	>	* @throws IllegalArgumentException if parallelism less than or
1396	>	*         equal to zero, or greater than implementation limit
1397	>	* @throws SecurityException if a security manager exists and
1398	>	*         the caller is not permitted to modify threads
1399	>	*         because it does not hold {@link
1400	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1401		*/
1402	<	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1403	<	Thread.UncaughtExceptionHandler h;
544	<	final ReentrantLock lock = this.workerLock;
545	<	lock.lock();
546	<	try {
547	<	h = ueh;
548	<	} finally {
549	<	lock.unlock();
550	<	}
551	<	return h;
1402	>	public ForkJoinPool(int parallelism) {
1403	>	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1404		}
1405
554	–	// Execution methods
555	–
1406		/**
1407	<	* Common code for execute, invoke and submit
1407	>	* Creates a {@code ForkJoinPool} with the given parameters.
1408	>	*
1409	>	* @param parallelism the parallelism level. For default value,
1410	>	* use {@link java.lang.Runtime#availableProcessors}.
1411	>	* @param factory the factory for creating new threads. For default value,
1412	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
1413	>	* @param handler the handler for internal worker threads that
1414	>	* terminate due to unrecoverable errors encountered while executing
1415	>	* tasks. For default value, use {@code null}.
1416	>	* @param asyncMode if true,
1417	>	* establishes local first-in-first-out scheduling mode for forked
1418	>	* tasks that are never joined. This mode may be more appropriate
1419	>	* than default locally stack-based mode in applications in which
1420	>	* worker threads only process event-style asynchronous tasks.
1421	>	* For default value, use {@code false}.
1422	>	* @throws IllegalArgumentException if parallelism less than or
1423	>	*         equal to zero, or greater than implementation limit
1424	>	* @throws NullPointerException if the factory is null
1425	>	* @throws SecurityException if a security manager exists and
1426	>	*         the caller is not permitted to modify threads
1427	>	*         because it does not hold {@link
1428	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1429		*/
1430	<	private <T> void doSubmit(ForkJoinTask<T> task) {
1431	<	if (isShutdown())
1432	<	throw new RejectedExecutionException();
1433	<	submissionQueue.offer(task);
1434	<	signalIdleWorkers(true);
1430	>	public ForkJoinPool(int parallelism,
1431	>	ForkJoinWorkerThreadFactory factory,
1432	>	Thread.UncaughtExceptionHandler handler,
1433	>	boolean asyncMode) {
1434	>	checkPermission();
1435	>	if (factory == null)
1436	>	throw new NullPointerException();
1437	>	if (parallelism <= 0 || parallelism > MAX_ID)
1438	>	throw new IllegalArgumentException();
1439	>	this.parallelism = parallelism;
1440	>	this.factory = factory;
1441	>	this.ueh = handler;
1442	>	this.locallyFifo = asyncMode;
1443	>	long np = (long)(-parallelism); // offset ctl counts
1444	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
1445	>	this.submissionQueue = new ForkJoinTask<?>[INITIAL_QUEUE_CAPACITY];
1446	>	// initialize workers array with room for 2*parallelism if possible
1447	>	int n = parallelism << 1;
1448	>	if (n >= MAX_ID)
1449	>	n = MAX_ID;
1450	>	else { // See Hackers Delight, sec 3.2, where n < (1 << 16)
1451	>	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8;
1452	>	}
1453	>	workers = new ForkJoinWorkerThread[n + 1];
1454	>	this.submissionLock = new ReentrantLock();
1455	>	this.termination = submissionLock.newCondition();
1456	>	StringBuilder sb = new StringBuilder("ForkJoinPool-");
1457	>	sb.append(poolNumberGenerator.incrementAndGet());
1458	>	sb.append("-worker-");
1459	>	this.workerNamePrefix = sb.toString();
1460		}
1461
1462	+	// Execution methods
1463	+
1464		/**
1465	<	* Performs the given task; returning its result upon completion
1465	>	* Performs the given task, returning its result upon completion.
1466	>	* If the computation encounters an unchecked Exception or Error,
1467	>	* it is rethrown as the outcome of this invocation.  Rethrown
1468	>	* exceptions behave in the same way as regular exceptions, but,
1469	>	* when possible, contain stack traces (as displayed for example
1470	>	* using {@code ex.printStackTrace()}) of both the current thread
1471	>	* as well as the thread actually encountering the exception;
1472	>	* minimally only the latter.
1473	>	*
1474		* @param task the task
1475		* @return the task's result
1476	<	* @throws NullPointerException if task is null
1477	<	* @throws RejectedExecutionException if pool is shut down
1476	>	* @throws NullPointerException if the task is null
1477	>	* @throws RejectedExecutionException if the task cannot be
1478	>	*         scheduled for execution
1479		*/
1480		public <T> T invoke(ForkJoinTask<T> task) {
1481	<	doSubmit(task);
1482	<	return task.join();
1481	>	Thread t = Thread.currentThread();
1482	>	if (task == null)
1483	>	throw new NullPointerException();
1484	>	if (shutdown)
1485	>	throw new RejectedExecutionException();
1486	>	if ((t instanceof ForkJoinWorkerThread) &&
1487	>	((ForkJoinWorkerThread)t).pool == this)
1488	>	return task.invoke();  // bypass submit if in same pool
1489	>	else {
1490	>	addSubmission(task);
1491	>	return task.join();
1492	>	}
1493	>	}
1494	>
1495	>	/**
1496	>	* Unless terminating, forks task if within an ongoing FJ
1497	>	* computation in the current pool, else submits as external task.
1498	>	*/
1499	>	private <T> void forkOrSubmit(ForkJoinTask<T> task) {
1500	>	ForkJoinWorkerThread w;
1501	>	Thread t = Thread.currentThread();
1502	>	if (shutdown)
1503	>	throw new RejectedExecutionException();
1504	>	if ((t instanceof ForkJoinWorkerThread) &&
1505	>	(w = (ForkJoinWorkerThread)t).pool == this)
1506	>	w.pushTask(task);
1507	>	else
1508	>	addSubmission(task);
1509		}
1510
1511		/**
1512		* Arranges for (asynchronous) execution of the given task.
1513	+	*
1514		* @param task the task
1515	<	* @throws NullPointerException if task is null
1516	<	* @throws RejectedExecutionException if pool is shut down
1515	>	* @throws NullPointerException if the task is null
1516	>	* @throws RejectedExecutionException if the task cannot be
1517	>	*         scheduled for execution
1518		*/
1519	<	public <T> void execute(ForkJoinTask<T> task) {
1520	<	doSubmit(task);
1519	>	public void execute(ForkJoinTask<?> task) {
1520	>	if (task == null)
1521	>	throw new NullPointerException();
1522	>	forkOrSubmit(task);
1523		}
1524
1525		// AbstractExecutorService methods
1526
1527	+	/**
1528	+	* @throws NullPointerException if the task is null
1529	+	* @throws RejectedExecutionException if the task cannot be
1530	+	*         scheduled for execution
1531	+	*/
1532		public void execute(Runnable task) {
1533	<	doSubmit(new AdaptedRunnable<Void>(task, null));
1533	>	if (task == null)
1534	>	throw new NullPointerException();
1535	>	ForkJoinTask<?> job;
1536	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1537	>	job = (ForkJoinTask<?>) task;
1538	>	else
1539	>	job = ForkJoinTask.adapt(task, null);
1540	>	forkOrSubmit(job);
1541		}
1542
1543	<	public <T> ForkJoinTask<T> submit(Callable<T> task) {
1544	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
1545	<	doSubmit(job);
1546	<	return job;
1543	>	/**
1544	>	* Submits a ForkJoinTask for execution.
1545	>	*
1546	>	* @param task the task to submit
1547	>	* @return the task
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(ForkJoinTask<T> task) {
1553	>	if (task == null)
1554	>	throw new NullPointerException();
1555	>	forkOrSubmit(task);
1556	>	return task;
1557		}
1558
1559	<	public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1560	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
1561	<	doSubmit(job);
1559	>	/**
1560	>	* @throws NullPointerException if the task is null
1561	>	* @throws RejectedExecutionException if the task cannot be
1562	>	*         scheduled for execution
1563	>	*/
1564	>	public <T> ForkJoinTask<T> submit(Callable<T> task) {
1565	>	if (task == null)
1566	>	throw new NullPointerException();
1567	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1568	>	forkOrSubmit(job);
1569		return job;
1570		}
1571
1572	<	public ForkJoinTask<?> submit(Runnable task) {
1573	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
1574	<	doSubmit(job);
1572	>	/**
1573	>	* @throws NullPointerException if the task is null
1574	>	* @throws RejectedExecutionException if the task cannot be
1575	>	*         scheduled for execution
1576	>	*/
1577	>	public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1578	>	if (task == null)
1579	>	throw new NullPointerException();
1580	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1581	>	forkOrSubmit(job);
1582		return job;
1583		}
1584
612	–	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
613	–	return new AdaptedRunnable(runnable, value);
614	–	}
615	–
616	–	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
617	–	return new AdaptedCallable(callable);
618	–	}
619	–
1585		/**
1586	<	* Adaptor for Runnables. This implements RunnableFuture
1587	<	* to be compliant with AbstractExecutorService constraints
1586	>	* @throws NullPointerException if the task is null
1587	>	* @throws RejectedExecutionException if the task cannot be
1588	>	*         scheduled for execution
1589		*/
1590	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1591	<	implements RunnableFuture<T> {
1592	<	final Runnable runnable;
1593	<	final T resultOnCompletion;
1594	<	T result;
1595	<	AdaptedRunnable(Runnable runnable, T result) {
1596	<	if (runnable == null) throw new NullPointerException();
1597	<	this.runnable = runnable;
1598	<	this.resultOnCompletion = result;
1599	<	}
634	<	public T getRawResult() { return result; }
635	<	public void setRawResult(T v) { result = v; }
636	<	public boolean exec() {
637	<	runnable.run();
638	<	result = resultOnCompletion;
639	<	return true;
640	<	}
641	<	public void run() { invoke(); }
1590	>	public ForkJoinTask<?> submit(Runnable task) {
1591	>	if (task == null)
1592	>	throw new NullPointerException();
1593	>	ForkJoinTask<?> job;
1594	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1595	>	job = (ForkJoinTask<?>) task;
1596	>	else
1597	>	job = ForkJoinTask.adapt(task, null);
1598	>	forkOrSubmit(job);
1599	>	return job;
1600		}
1601
1602		/**
1603	<	* Adaptor for Callables
1603	>	* @throws NullPointerException       {@inheritDoc}
1604	>	* @throws RejectedExecutionException {@inheritDoc}
1605		*/
647	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
648	–	implements RunnableFuture<T> {
649	–	final Callable<T> callable;
650	–	T result;
651	–	AdaptedCallable(Callable<T> callable) {
652	–	if (callable == null) throw new NullPointerException();
653	–	this.callable = callable;
654	–	}
655	–	public T getRawResult() { return result; }
656	–	public void setRawResult(T v) { result = v; }
657	–	public boolean exec() {
658	–	try {
659	–	result = callable.call();
660	–	return true;
661	–	} catch (Error err) {
662	–	throw err;
663	–	} catch (RuntimeException rex) {
664	–	throw rex;
665	–	} catch (Exception ex) {
666	–	throw new RuntimeException(ex);
667	–	}
668	–	}
669	–	public void run() { invoke(); }
670	–	}
671	–
1606		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
1607	<	ArrayList<ForkJoinTask<T>> ts =
1607	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
1608		new ArrayList<ForkJoinTask<T>>(tasks.size());
1609	<	for (Callable<T> c : tasks)
1610	<	ts.add(new AdaptedCallable<T>(c));
1611	<	invoke(new InvokeAll<T>(ts));
1612	<	return (List<Future<T>>)(List)ts;
1609	>	for (Callable<T> task : tasks)
1610	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
1611	>	invoke(new InvokeAll<T>(forkJoinTasks));
1612	>
1613	>	@SuppressWarnings({"unchecked", "rawtypes"})
1614	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1615	>	return futures;
1616		}
1617
1618		static final class InvokeAll<T> extends RecursiveAction {
1619		final ArrayList<ForkJoinTask<T>> tasks;
1620		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
1621		public void compute() {
1622	<	try { invokeAll(tasks); } catch(Exception ignore) {}
1622	>	try { invokeAll(tasks); }
1623	>	catch (Exception ignore) {}
1624		}
1625	+	private static final long serialVersionUID = -7914297376763021607L;
1626		}
1627
689	–	// Configuration and status settings and queries
690	–
1628		/**
1629	<	* Returns the factory used for constructing new workers
1629	>	* Returns the factory used for constructing new workers.
1630		*
1631		* @return the factory used for constructing new workers
1632		*/
#	Line 698 | Line 1635 | public class ForkJoinPool extends Abstra
1635		}
1636
1637		/**
1638	<	* Sets the target paralleism level of this pool.
1639	<	* @param parallelism the target parallelism
1640	<	* @throws IllegalArgumentException if parallelism less than or
1641	<	* equal to zero or greater than maximum size bounds.
705	<	* @throws SecurityException if a security manager exists and
706	<	*         the caller is not permitted to modify threads
707	<	*         because it does not hold {@link
708	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1638	>	* Returns the handler for internal worker threads that terminate
1639	>	* due to unrecoverable errors encountered while executing tasks.
1640	>	*
1641	>	* @return the handler, or {@code null} if none
1642		*/
1643	<	public void setParallelism(int parallelism) {
1644	<	checkPermission();
712	<	if (parallelism <= 0 || parallelism > maxPoolSize)
713	<	throw new IllegalArgumentException();
714	<	final ReentrantLock lock = this.workerLock;
715	<	lock.lock();
716	<	try {
717	<	if (!isTerminating()) {
718	<	int p = this.parallelism;
719	<	this.parallelism = parallelism;
720	<	if (parallelism > p)
721	<	createAndStartAddedWorkers();
722	<	else
723	<	trimSpares();
724	<	}
725	<	} finally {
726	<	lock.unlock();
727	<	}
728	<	signalIdleWorkers(false);
1643	>	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1644	>	return ueh;
1645		}
1646
1647		/**
1648	<	* Returns the targeted number of worker threads in this pool.
733	<	* This value does not necessarily reflect transient changes as
734	<	* threads are added, removed, or abruptly terminate.
1648	>	* Returns the targeted parallelism level of this pool.
1649		*
1650	<	* @return the targeted number of worker threads in this pool
1650	>	* @return the targeted parallelism level of this pool
1651		*/
1652		public int getParallelism() {
1653		return parallelism;
#	Line 741 | Line 1655 | public class ForkJoinPool extends Abstra
1655
1656		/**
1657		* Returns the number of worker threads that have started but not
1658	<	* yet terminated.  This result returned by this method may differ
1659	<	* from <tt>getParallelism</tt> when threads are created to
1658	>	* yet terminated.  The result returned by this method may differ
1659	>	* from {@link #getParallelism} when threads are created to
1660		* maintain parallelism when others are cooperatively blocked.
1661		*
1662		* @return the number of worker threads
1663		*/
1664		public int getPoolSize() {
1665	<	return totalCountOf(workerCounts);
752	<	}
753	<
754	<	/**
755	<	* Returns the maximum number of threads allowed to exist in the
756	<	* pool, even if there are insufficient unblocked running threads.
757	<	* @return the maximum
758	<	*/
759	<	public int getMaximumPoolSize() {
760	<	return maxPoolSize;
761	<	}
762	<
763	<	/**
764	<	* Sets the maximum number of threads allowed to exist in the
765	<	* pool, even if there are insufficient unblocked running threads.
766	<	* Setting this value has no effect on current pool size. It
767	<	* controls construction of new threads.
768	<	* @throws IllegalArgumentException if negative or greater then
769	<	* internal implementation limit.
770	<	*/
771	<	public void setMaximumPoolSize(int newMax) {
772	<	if (newMax < 0 || newMax > MAX_THREADS)
773	<	throw new IllegalArgumentException();
774	<	maxPoolSize = newMax;
775	<	}
776	<
777	<
778	<	/**
779	<	* Returns true if this pool dynamically maintains its target
780	<	* parallelism level. If false, new threads are added only to
781	<	* avoid possible starvation.
782	<	* This setting is by default true;
783	<	* @return true if maintains parallelism
784	<	*/
785	<	public boolean getMaintainsParallelism() {
786	<	return maintainsParallelism;
1665	>	return parallelism + (short)(ctl >>> TC_SHIFT);
1666		}
1667
1668		/**
1669	<	* Sets whether this pool dynamically maintains its target
1670	<	* parallelism level. If false, new threads are added only to
1671	<	* avoid possible starvation.
1672	<	* @param enable true to maintains parallelism
1669	>	* Returns {@code true} if this pool uses local first-in-first-out
1670	>	* scheduling mode for forked tasks that are never joined.
1671	>	*
1672	>	* @return {@code true} if this pool uses async mode
1673		*/
1674	<	public void setMaintainsParallelism(boolean enable) {
1675	<	maintainsParallelism = enable;
1674	>	public boolean getAsyncMode() {
1675	>	return locallyFifo;
1676		}
1677
1678		/**
1679	<	* Returns the approximate number of worker threads that are not
1680	<	* blocked waiting to join tasks or for other managed
1681	<	* synchronization.
1679	>	* Returns an estimate of the number of worker threads that are
1680	>	* not blocked waiting to join tasks or for other managed
1681	>	* synchronization. This method may overestimate the
1682	>	* number of running threads.
1683		*
1684		* @return the number of worker threads
1685		*/
1686		public int getRunningThreadCount() {
1687	<	return runningCountOf(workerCounts);
1687	>	int r = parallelism + (int)(ctl >> AC_SHIFT);
1688	>	return r <= 0? 0 : r; // suppress momentarily negative values
1689		}
1690
1691		/**
1692	<	* Returns the approximate number of threads that are currently
1692	>	* Returns an estimate of the number of threads that are currently
1693		* stealing or executing tasks. This method may overestimate the
1694		* number of active threads.
1695	<	* @return the number of active threads.
1695	>	*
1696	>	* @return the number of active threads
1697		*/
1698		public int getActiveThreadCount() {
1699	<	return activeCountOf(runControl);
1700	<	}
819	<
820	<	/**
821	<	* Returns the approximate number of threads that are currently
822	<	* idle waiting for tasks. This method may underestimate the
823	<	* number of idle threads.
824	<	* @return the number of idle threads.
825	<	*/
826	<	final int getIdleThreadCount() {
827	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
828	<	return (c <= 0)? 0 : c;
1699	>	int r = parallelism + (int)(ctl >> AC_SHIFT) + blockedCount;
1700	>	return r <= 0? 0 : r; // suppress momentarily negative values
1701		}
1702
1703		/**
1704	<	* Returns true if all worker threads are currently idle. An idle
1705	<	* worker is one that cannot obtain a task to execute because none
1706	<	* are available to steal from other threads, and there are no
1707	<	* pending submissions to the pool. This method is conservative:
1708	<	* It might not return true immediately upon idleness of all
1709	<	* threads, but will eventually become true if threads remain
1710	<	* inactive.
1711	<	* @return true if all threads are currently idle
1704	>	* Returns {@code true} if all worker threads are currently idle.
1705	>	* An idle worker is one that cannot obtain a task to execute
1706	>	* because none are available to steal from other threads, and
1707	>	* there are no pending submissions to the pool. This method is
1708	>	* conservative; it might not return {@code true} immediately upon
1709	>	* idleness of all threads, but will eventually become true if
1710	>	* threads remain inactive.
1711	>	*
1712	>	* @return {@code true} if all threads are currently idle
1713		*/
1714		public boolean isQuiescent() {
1715	<	return activeCountOf(runControl) == 0;
1715	>	return parallelism + (int)(ctl >> AC_SHIFT) + blockedCount == 0;
1716		}
1717
1718		/**
#	Line 847 | Line 1720 | public class ForkJoinPool extends Abstra
1720		* one thread's work queue by another. The reported value
1721		* underestimates the actual total number of steals when the pool
1722		* is not quiescent. This value may be useful for monitoring and
1723	<	* tuning fork/join programs: In general, steal counts should be
1723	>	* tuning fork/join programs: in general, steal counts should be
1724		* high enough to keep threads busy, but low enough to avoid
1725		* overhead and contention across threads.
1726	<	* @return the number of steals.
1726	>	*
1727	>	* @return the number of steals
1728		*/
1729		public long getStealCount() {
1730	<	return stealCount.get();
857	<	}
858	<
859	<	/**
860	<	* Accumulate steal count from a worker. Call only
861	<	* when worker known to be idle.
862	<	*/
863	<	private void updateStealCount(ForkJoinWorkerThread w) {
864	<	int sc = w.getAndClearStealCount();
865	<	if (sc != 0)
866	<	stealCount.addAndGet(sc);
1730	>	return stealCount;
1731		}
1732
1733		/**
1734	<	* Returns the total number of tasks currently held in queues by
1735	<	* worker threads (but not including tasks submitted to the pool
1736	<	* that have not begun executing). This value is only an
1737	<	* approximation, obtained by iterating across all threads in the
1738	<	* pool. This method may be useful for tuning task granularities.
1739	<	* @return the number of queued tasks.
1734	>	* Returns an estimate of the total number of tasks currently held
1735	>	* in queues by worker threads (but not including tasks submitted
1736	>	* to the pool that have not begun executing). This value is only
1737	>	* an approximation, obtained by iterating across all threads in
1738	>	* the pool. This method may be useful for tuning task
1739	>	* granularities.
1740	>	*
1741	>	* @return the number of queued tasks
1742		*/
1743		public long getQueuedTaskCount() {
1744		long count = 0;
1745	<	ForkJoinWorkerThread[] ws = workers;
1746	<	for (int i = 0; i < ws.length; ++i) {
1747	<	ForkJoinWorkerThread t = ws[i];
1748	<	if (t != null)
1749	<	count += t.getQueueSize();
1745	>	ForkJoinWorkerThread[] ws;
1746	>	if ((short)(ctl >>> TC_SHIFT) > -parallelism &&
1747	>	(ws = workers) != null) {
1748	>	for (ForkJoinWorkerThread w : ws)
1749	>	if (w != null)
1750	>	count -= w.queueBase - w.queueTop; // must read base first
1751		}
1752		return count;
1753		}
1754
1755		/**
1756	<	* Returns the approximate number tasks submitted to this pool
1757	<	* that have not yet begun executing. This method takes time
1758	<	* proportional to the number of submissions.
1759	<	* @return the number of queued submissions.
1756	>	* Returns an estimate of the number of tasks submitted to this
1757	>	* pool that have not yet begun executing.  This method may take
1758	>	* time proportional to the number of submissions.
1759	>	*
1760	>	* @return the number of queued submissions
1761		*/
1762		public int getQueuedSubmissionCount() {
1763	<	return submissionQueue.size();
1763	>	return -queueBase + queueTop;
1764		}
1765
1766		/**
1767	<	* Returns true if there are any tasks submitted to this pool
1768	<	* that have not yet begun executing.
1769	<	* @return <tt>true</tt> if there are any queued submissions.
1767	>	* Returns {@code true} if there are any tasks submitted to this
1768	>	* pool that have not yet begun executing.
1769	>	*
1770	>	* @return {@code true} if there are any queued submissions
1771		*/
1772		public boolean hasQueuedSubmissions() {
1773	<	return !submissionQueue.isEmpty();
1773	>	return queueBase != queueTop;
1774		}
1775
1776		/**
1777		* Removes and returns the next unexecuted submission if one is
1778		* available.  This method may be useful in extensions to this
1779		* class that re-assign work in systems with multiple pools.
1780	<	* @return the next submission, or null if none
1780	>	*
1781	>	* @return the next submission, or {@code null} if none
1782		*/
1783		protected ForkJoinTask<?> pollSubmission() {
1784	<	return submissionQueue.poll();
1784	>	ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i;
1785	>	while ((b = queueBase) != queueTop &&
1786	>	(q = submissionQueue) != null &&
1787	>	(i = (q.length - 1) & b) >= 0) {
1788	>	long u = (i << ASHIFT) + ABASE;
1789	>	if ((t = q[i]) != null &&
1790	>	queueBase == b &&
1791	>	UNSAFE.compareAndSwapObject(q, u, t, null)) {
1792	>	queueBase = b + 1;
1793	>	return t;
1794	>	}
1795	>	}
1796	>	return null;
1797	>	}
1798	>
1799	>	/**
1800	>	* Removes all available unexecuted submitted and forked tasks
1801	>	* from scheduling queues and adds them to the given collection,
1802	>	* without altering their execution status. These may include
1803	>	* artificially generated or wrapped tasks. This method is
1804	>	* designed to be invoked only when the pool is known to be
1805	>	* quiescent. Invocations at other times may not remove all
1806	>	* tasks. A failure encountered while attempting to add elements
1807	>	* to collection {@code c} may result in elements being in
1808	>	* neither, either or both collections when the associated
1809	>	* exception is thrown.  The behavior of this operation is
1810	>	* undefined if the specified collection is modified while the
1811	>	* operation is in progress.
1812	>	*
1813	>	* @param c the collection to transfer elements into
1814	>	* @return the number of elements transferred
1815	>	*/
1816	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1817	>	int count = 0;
1818	>	while (queueBase != queueTop) {
1819	>	ForkJoinTask<?> t = pollSubmission();
1820	>	if (t != null) {
1821	>	c.add(t);
1822	>	++count;
1823	>	}
1824	>	}
1825	>	ForkJoinWorkerThread[] ws;
1826	>	if ((short)(ctl >>> TC_SHIFT) > -parallelism &&
1827	>	(ws = workers) != null) {
1828	>	for (ForkJoinWorkerThread w : ws)
1829	>	if (w != null)
1830	>	count += w.drainTasksTo(c);
1831	>	}
1832	>	return count;
1833		}
1834
1835		/**
#	Line 922 | Line 1840 | public class ForkJoinPool extends Abstra
1840		* @return a string identifying this pool, as well as its state
1841		*/
1842		public String toString() {
925	–	int ps = parallelism;
926	–	int wc = workerCounts;
927	–	int rc = runControl;
1843		long st = getStealCount();
1844		long qt = getQueuedTaskCount();
1845		long qs = getQueuedSubmissionCount();
1846	+	int pc = parallelism;
1847	+	long c = ctl;
1848	+	int tc = pc + (short)(c >>> TC_SHIFT);
1849	+	int rc = pc + (int)(c >> AC_SHIFT);
1850	+	if (rc < 0) // ignore transient negative
1851	+	rc = 0;
1852	+	int ac = rc + blockedCount;
1853	+	String level;
1854	+	if ((c & STOP_BIT) != 0)
1855	+	level = (tc == 0)? "Terminated" : "Terminating";
1856	+	else
1857	+	level = shutdown? "Shutting down" : "Running";
1858		return super.toString() +
1859	<	"[" + runStateToString(runStateOf(rc)) +
1860	<	", parallelism = " + ps +
1861	<	", size = " + totalCountOf(wc) +
1862	<	", active = " + activeCountOf(rc) +
1863	<	", running = " + runningCountOf(wc) +
1859	>	"[" + level +
1860	>	", parallelism = " + pc +
1861	>	", size = " + tc +
1862	>	", active = " + ac +
1863	>	", running = " + rc +
1864		", steals = " + st +
1865		", tasks = " + qt +
1866		", submissions = " + qs +
1867		"]";
1868		}
1869
943	–	private static String runStateToString(int rs) {
944	–	switch(rs) {
945	–	case RUNNING: return "Running";
946	–	case SHUTDOWN: return "Shutting down";
947	–	case TERMINATING: return "Terminating";
948	–	case TERMINATED: return "Terminated";
949	–	default: throw new Error("Unknown run state");
950	–	}
951	–	}
952	–
953	–	// lifecycle control
954	–
1870		/**
1871		* Initiates an orderly shutdown in which previously submitted
1872		* tasks are executed, but no new tasks will be accepted.
1873		* Invocation has no additional effect if already shut down.
1874		* Tasks that are in the process of being submitted concurrently
1875		* during the course of this method may or may not be rejected.
1876	+	*
1877		* @throws SecurityException if a security manager exists and
1878		*         the caller is not permitted to modify threads
1879		*         because it does not hold {@link
1880	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1880	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1881		*/
1882		public void shutdown() {
1883		checkPermission();
1884	<	transitionRunStateTo(SHUTDOWN);
1885	<	if (canTerminateOnShutdown(runControl))
970	<	terminateOnShutdown();
1884	>	shutdown = true;
1885	>	tryTerminate(false);
1886		}
1887
1888		/**
1889	<	* Attempts to stop all actively executing tasks, and cancels all
1890	<	* waiting tasks.  Tasks that are in the process of being
1891	<	* submitted or executed concurrently during the course of this
1892	<	* method may or may not be rejected. Unlike some other executors,
1893	<	* this method cancels rather than collects non-executed tasks,
1894	<	* so always returns an empty list.
1889	>	* Attempts to cancel and/or stop all tasks, and reject all
1890	>	* subsequently submitted tasks.  Tasks that are in the process of
1891	>	* being submitted or executed concurrently during the course of
1892	>	* this method may or may not be rejected. This method cancels
1893	>	* both existing and unexecuted tasks, in order to permit
1894	>	* termination in the presence of task dependencies. So the method
1895	>	* always returns an empty list (unlike the case for some other
1896	>	* Executors).
1897	>	*
1898		* @return an empty list
1899		* @throws SecurityException if a security manager exists and
1900		*         the caller is not permitted to modify threads
1901		*         because it does not hold {@link
1902	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1902	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1903		*/
1904		public List<Runnable> shutdownNow() {
1905		checkPermission();
1906	<	terminate();
1906	>	shutdown = true;
1907	>	tryTerminate(true);
1908		return Collections.emptyList();
1909		}
1910
1911		/**
1912	<	* Returns <tt>true</tt> if all tasks have completed following shut down.
1912	>	* Returns {@code true} if all tasks have completed following shut down.
1913		*
1914	<	* @return <tt>true</tt> if all tasks have completed following shut down
1914	>	* @return {@code true} if all tasks have completed following shut down
1915		*/
1916		public boolean isTerminated() {
1917	<	return runStateOf(runControl) == TERMINATED;
1917	>	long c = ctl;
1918	>	return ((c & STOP_BIT) != 0L &&
1919	>	(short)(c >>> TC_SHIFT) == -parallelism);
1920		}
1921
1922		/**
1923	<	* Returns <tt>true</tt> if the process of termination has
1924	<	* commenced but possibly not yet completed.
1923	>	* Returns {@code true} if the process of termination has
1924	>	* commenced but not yet completed.  This method may be useful for
1925	>	* debugging. A return of {@code true} reported a sufficient
1926	>	* period after shutdown may indicate that submitted tasks have
1927	>	* ignored or suppressed interruption, or are waiting for IO,
1928	>	* causing this executor not to properly terminate. (See the
1929	>	* advisory notes for class {@link ForkJoinTask} stating that
1930	>	* tasks should not normally entail blocking operations.  But if
1931	>	* they do, they must abort them on interrupt.)
1932		*
1933	<	* @return <tt>true</tt> if terminating
1933	>	* @return {@code true} if terminating but not yet terminated
1934		*/
1935		public boolean isTerminating() {
1936	<	return runStateOf(runControl) >= TERMINATING;
1936	>	long c = ctl;
1937	>	return ((c & STOP_BIT) != 0L &&
1938	>	(short)(c >>> TC_SHIFT) != -parallelism);
1939	>	}
1940	>
1941	>	/**
1942	>	* Returns true if terminating or terminated. Used by ForkJoinWorkerThread.
1943	>	*/
1944	>	final boolean isAtLeastTerminating() {
1945	>	return (ctl & STOP_BIT) != 0L;
1946		}
1947
1948		/**
1949	<	* Returns <tt>true</tt> if this pool has been shut down.
1949	>	* Returns {@code true} if this pool has been shut down.
1950		*
1951	<	* @return <tt>true</tt> if this pool has been shut down
1951	>	* @return {@code true} if this pool has been shut down
1952		*/
1953		public boolean isShutdown() {
1954	<	return runStateOf(runControl) >= SHUTDOWN;
1954	>	return shutdown;
1955		}
1956
1957		/**
#	Line 1024 | Line 1961 | public class ForkJoinPool extends Abstra
1961		*
1962		* @param timeout the maximum time to wait
1963		* @param unit the time unit of the timeout argument
1964	<	* @return <tt>true</tt> if this executor terminated and
1965	<	*         <tt>false</tt> if the timeout elapsed before termination
1964	>	* @return {@code true} if this executor terminated and
1965	>	*         {@code false} if the timeout elapsed before termination
1966		* @throws InterruptedException if interrupted while waiting
1967		*/
1968		public boolean awaitTermination(long timeout, TimeUnit unit)
1969		throws InterruptedException {
1970		long nanos = unit.toNanos(timeout);
1971	<	final ReentrantLock lock = this.workerLock;
1971	>	final ReentrantLock lock = this.submissionLock;
1972		lock.lock();
1973		try {
1974		for (;;) {
#	Line 1046 | Line 1983 | public class ForkJoinPool extends Abstra
1983		}
1984		}
1985
1049	–	// Shutdown and termination support
1050	–
1051	–	/**
1052	–	* Callback from terminating worker. Null out the corresponding
1053	–	* workers slot, and if terminating, try to terminate, else try to
1054	–	* shrink workers array.
1055	–	* @param w the worker
1056	–	*/
1057	–	final void workerTerminated(ForkJoinWorkerThread w) {
1058	–	updateStealCount(w);
1059	–	updateWorkerCount(-1);
1060	–	final ReentrantLock lock = this.workerLock;
1061	–	lock.lock();
1062	–	try {
1063	–	ForkJoinWorkerThread[] ws = workers;
1064	–	int idx = w.poolIndex;
1065	–	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1066	–	ws[idx] = null;
1067	–	if (totalCountOf(workerCounts) == 0) {
1068	–	terminate(); // no-op if already terminating
1069	–	transitionRunStateTo(TERMINATED);
1070	–	termination.signalAll();
1071	–	}
1072	–	else if (!isTerminating()) {
1073	–	tryShrinkWorkerArray();
1074	–	tryResumeSpare(true); // allow replacement
1075	–	}
1076	–	} finally {
1077	–	lock.unlock();
1078	–	}
1079	–	signalIdleWorkers(false);
1080	–	}
1081	–
1082	–	/**
1083	–	* Initiate termination.
1084	–	*/
1085	–	private void terminate() {
1086	–	if (transitionRunStateTo(TERMINATING)) {
1087	–	stopAllWorkers();
1088	–	resumeAllSpares();
1089	–	signalIdleWorkers(true);
1090	–	cancelQueuedSubmissions();
1091	–	cancelQueuedWorkerTasks();
1092	–	interruptUnterminatedWorkers();
1093	–	signalIdleWorkers(true); // resignal after interrupt
1094	–	}
1095	–	}
1096	–
1097	–	/**
1098	–	* Possibly terminate when on shutdown state
1099	–	*/
1100	–	private void terminateOnShutdown() {
1101	–	if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
1102	–	terminate();
1103	–	}
1104	–
1105	–	/**
1106	–	* Clear out and cancel submissions
1107	–	*/
1108	–	private void cancelQueuedSubmissions() {
1109	–	ForkJoinTask<?> task;
1110	–	while ((task = pollSubmission()) != null)
1111	–	task.cancel(false);
1112	–	}
1113	–
1114	–	/**
1115	–	* Clean out worker queues.
1116	–	*/
1117	–	private void cancelQueuedWorkerTasks() {
1118	–	final ReentrantLock lock = this.workerLock;
1119	–	lock.lock();
1120	–	try {
1121	–	ForkJoinWorkerThread[] ws = workers;
1122	–	for (int i = 0; i < ws.length; ++i) {
1123	–	ForkJoinWorkerThread t = ws[i];
1124	–	if (t != null)
1125	–	t.cancelTasks();
1126	–	}
1127	–	} finally {
1128	–	lock.unlock();
1129	–	}
1130	–	}
1131	–
1132	–	/**
1133	–	* Set each worker's status to terminating. Requires lock to avoid
1134	–	* conflicts with add/remove
1135	–	*/
1136	–	private void stopAllWorkers() {
1137	–	final ReentrantLock lock = this.workerLock;
1138	–	lock.lock();
1139	–	try {
1140	–	ForkJoinWorkerThread[] ws = workers;
1141	–	for (int i = 0; i < ws.length; ++i) {
1142	–	ForkJoinWorkerThread t = ws[i];
1143	–	if (t != null)
1144	–	t.shutdownNow();
1145	–	}
1146	–	} finally {
1147	–	lock.unlock();
1148	–	}
1149	–	}
1150	–
1151	–	/**
1152	–	* Interrupt all unterminated workers.  This is not required for
1153	–	* sake of internal control, but may help unstick user code during
1154	–	* shutdown.
1155	–	*/
1156	–	private void interruptUnterminatedWorkers() {
1157	–	final ReentrantLock lock = this.workerLock;
1158	–	lock.lock();
1159	–	try {
1160	–	ForkJoinWorkerThread[] ws = workers;
1161	–	for (int i = 0; i < ws.length; ++i) {
1162	–	ForkJoinWorkerThread t = ws[i];
1163	–	if (t != null && !t.isTerminated()) {
1164	–	try {
1165	–	t.interrupt();
1166	–	} catch (SecurityException ignore) {
1167	–	}
1168	–	}
1169	–	}
1170	–	} finally {
1171	–	lock.unlock();
1172	–	}
1173	–	}
1174	–
1175	–
1176	–	/*
1177	–	* Nodes for event barrier to manage idle threads.
1178	–	*
1179	–	* The event barrier has an event count and a wait queue (actually
1180	–	* a Treiber stack).  Workers are enabled to look for work when
1181	–	* the eventCount is incremented. If they fail to find some,
1182	–	* they may wait for next count. Synchronization events occur only
1183	–	* in enough contexts to maintain overall liveness:
1184	–	*
1185	–	*   - Submission of a new task to the pool
1186	–	*   - Creation or termination of a worker
1187	–	*   - pool termination
1188	–	*   - A worker pushing a task on an empty queue
1189	–	*
1190	–	* The last case (pushing a task) occurs often enough, and is
1191	–	* heavy enough compared to simple stack pushes to require some
1192	–	* special handling: Method signalNonEmptyWorkerQueue returns
1193	–	* without advancing count if the queue appears to be empty.  This
1194	–	* would ordinarily result in races causing some queued waiters
1195	–	* not to be woken up. To avoid this, a worker in sync
1196	–	* rescans for tasks after being enqueued if it was the first to
1197	–	* enqueue, and aborts the wait if finding one, also helping to
1198	–	* signal others. This works well because the worker has nothing
1199	–	* better to do anyway, and so might as well help alleviate the
1200	–	* overhead and contention on the threads actually doing work.
1201	–	*
1202	–	* Queue nodes are basic Treiber stack nodes, also used for spare
1203	–	* stack.
1204	–	*/
1205	–	static final class WaitQueueNode {
1206	–	WaitQueueNode next; // only written before enqueued
1207	–	volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1208	–	final long count; // unused for spare stack
1209	–	WaitQueueNode(ForkJoinWorkerThread w, long c) {
1210	–	count = c;
1211	–	thread = w;
1212	–	}
1213	–	final boolean signal() {
1214	–	ForkJoinWorkerThread t = thread;
1215	–	thread = null;
1216	–	if (t != null) {
1217	–	LockSupport.unpark(t);
1218	–	return true;
1219	–	}
1220	–	return false;
1221	–	}
1222	–	}
1223	–
1224	–	/**
1225	–	* Release at least one thread waiting for event count to advance,
1226	–	* if one exists. If initial attempt fails, release all threads.
1227	–	* @param all if false, at first try to only release one thread
1228	–	* @return current event
1229	–	*/
1230	–	private long releaseIdleWorkers(boolean all) {
1231	–	long c;
1232	–	for (;;) {
1233	–	WaitQueueNode q = barrierStack;
1234	–	c = eventCount;
1235	–	long qc;
1236	–	if (q == null || (qc = q.count) >= c)
1237	–	break;
1238	–	if (!all) {
1239	–	if (casBarrierStack(q, q.next) && q.signal())
1240	–	break;
1241	–	all = true;
1242	–	}
1243	–	else if (casBarrierStack(q, null)) {
1244	–	do {
1245	–	q.signal();
1246	–	} while ((q = q.next) != null);
1247	–	break;
1248	–	}
1249	–	}
1250	–	return c;
1251	–	}
1252	–
1253	–	/**
1254	–	* Returns current barrier event count
1255	–	* @return current barrier event count
1256	–	*/
1257	–	final long getEventCount() {
1258	–	long ec = eventCount;
1259	–	releaseIdleWorkers(true); // release to ensure accurate result
1260	–	return ec;
1261	–	}
1262	–
1263	–	/**
1264	–	* Increment event count and release at least one waiting thread,
1265	–	* if one exists (released threads will in turn wake up others).
1266	–	* @param all if true, try to wake up all
1267	–	*/
1268	–	final void signalIdleWorkers(boolean all) {
1269	–	long c;
1270	–	do;while (!casEventCount(c = eventCount, c+1));
1271	–	releaseIdleWorkers(all);
1272	–	}
1273	–
1274	–	/**
1275	–	* Wake up threads waiting to steal a task. Because method
1276	–	* sync rechecks availability, it is OK to only proceed if
1277	–	* queue appears to be non-empty.
1278	–	*/
1279	–	final void signalNonEmptyWorkerQueue() {
1280	–	// If CAS fails another signaller must have succeeded
1281	–	long c;
1282	–	if (barrierStack != null && casEventCount(c = eventCount, c+1))
1283	–	releaseIdleWorkers(false);
1284	–	}
1285	–
1286	–	/**
1287	–	* Waits until event count advances from count, or some thread is
1288	–	* waiting on a previous count, or there is stealable work
1289	–	* available. Help wake up others on release.
1290	–	* @param w the calling worker thread
1291	–	* @param prev previous value returned by sync (or 0)
1292	–	* @return current event count
1293	–	*/
1294	–	final long sync(ForkJoinWorkerThread w, long prev) {
1295	–	updateStealCount(w);
1296	–
1297	–	while (!w.isShutdown() && !isTerminating() &&
1298	–	(parallelism >= runningCountOf(workerCounts) ||
1299	–	!suspendIfSpare(w))) { // prefer suspend to waiting here
1300	–	WaitQueueNode node = null;
1301	–	boolean queued = false;
1302	–	for (;;) {
1303	–	if (!queued) {
1304	–	if (eventCount != prev)
1305	–	break;
1306	–	WaitQueueNode h = barrierStack;
1307	–	if (h != null && h.count != prev)
1308	–	break; // release below and maybe retry
1309	–	if (node == null)
1310	–	node = new WaitQueueNode(w, prev);
1311	–	queued = casBarrierStack(node.next = h, node);
1312	–	}
1313	–	else if (Thread.interrupted() ||
1314	–	node.thread == null ||
1315	–	(node.next == null && w.prescan()) ||
1316	–	eventCount != prev) {
1317	–	node.thread = null;
1318	–	if (eventCount == prev) // help trigger
1319	–	casEventCount(prev, prev+1);
1320	–	break;
1321	–	}
1322	–	else
1323	–	LockSupport.park(this);
1324	–	}
1325	–	long ec = eventCount;
1326	–	if (releaseIdleWorkers(false) != prev)
1327	–	return ec;
1328	–	}
1329	–	return prev; // return old count if aborted
1330	–	}
1331	–
1332	–	//  Parallelism maintenance
1333	–
1334	–	/**
1335	–	* Decrement running count; if too low, add spare.
1336	–	*
1337	–	* Conceptually, all we need to do here is add or resume a
1338	–	* spare thread when one is about to block (and remove or
1339	–	* suspend it later when unblocked -- see suspendIfSpare).
1340	–	* However, implementing this idea requires coping with
1341	–	* several problems: We have imperfect information about the
1342	–	* states of threads. Some count updates can and usually do
1343	–	* lag run state changes, despite arrangements to keep them
1344	–	* accurate (for example, when possible, updating counts
1345	–	* before signalling or resuming), especially when running on
1346	–	* dynamic JVMs that don't optimize the infrequent paths that
1347	–	* update counts. Generating too many threads can make these
1348	–	* problems become worse, because excess threads are more
1349	–	* likely to be context-switched with others, slowing them all
1350	–	* down, especially if there is no work available, so all are
1351	–	* busy scanning or idling.  Also, excess spare threads can
1352	–	* only be suspended or removed when they are idle, not
1353	–	* immediately when they aren't needed. So adding threads will
1354	–	* raise parallelism level for longer than necessary.  Also,
1355	–	* FJ applications often enounter highly transient peaks when
1356	–	* many threads are blocked joining, but for less time than it
1357	–	* takes to create or resume spares.
1358	–	*
1359	–	* @param joinMe if non-null, return early if done
1360	–	* @param maintainParallelism if true, try to stay within
1361	–	* target counts, else create only to avoid starvation
1362	–	* @return true if joinMe known to be done
1363	–	*/
1364	–	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1365	–	maintainParallelism &= maintainsParallelism; // overrride
1366	–	boolean dec = false;  // true when running count decremented
1367	–	while (spareStack == null || !tryResumeSpare(dec)) {
1368	–	int counts = workerCounts;
1369	–	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1370	–	if (!needSpare(counts, maintainParallelism))
1371	–	break;
1372	–	if (joinMe.status < 0)
1373	–	return true;
1374	–	if (tryAddSpare(counts))
1375	–	break;
1376	–	}
1377	–	}
1378	–	return false;
1379	–	}
1380	–
1381	–	/**
1382	–	* Same idea as preJoin
1383	–	*/
1384	–	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1385	–	maintainParallelism &= maintainsParallelism;
1386	–	boolean dec = false;
1387	–	while (spareStack == null || !tryResumeSpare(dec)) {
1388	–	int counts = workerCounts;
1389	–	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1390	–	if (!needSpare(counts, maintainParallelism))
1391	–	break;
1392	–	if (blocker.isReleasable())
1393	–	return true;
1394	–	if (tryAddSpare(counts))
1395	–	break;
1396	–	}
1397	–	}
1398	–	return false;
1399	–	}
1400	–
1401	–	/**
1402	–	* Returns true if a spare thread appears to be needed.  If
1403	–	* maintaining parallelism, returns true when the deficit in
1404	–	* running threads is more than the surplus of total threads, and
1405	–	* there is apparently some work to do.  This self-limiting rule
1406	–	* means that the more threads that have already been added, the
1407	–	* less parallelism we will tolerate before adding another.
1408	–	* @param counts current worker counts
1409	–	* @param maintainParallelism try to maintain parallelism
1410	–	*/
1411	–	private boolean needSpare(int counts, boolean maintainParallelism) {
1412	–	int ps = parallelism;
1413	–	int rc = runningCountOf(counts);
1414	–	int tc = totalCountOf(counts);
1415	–	int runningDeficit = ps - rc;
1416	–	int totalSurplus = tc - ps;
1417	–	return (tc < maxPoolSize &&
1418	–	(rc == 0 || totalSurplus < 0 ||
1419	–	(maintainParallelism &&
1420	–	runningDeficit > totalSurplus && mayHaveQueuedWork())));
1421	–	}
1422	–
1423	–	/**
1424	–	* Returns true if at least one worker queue appears to be
1425	–	* nonempty. This is expensive but not often called. It is not
1426	–	* critical that this be accurate, but if not, more or fewer
1427	–	* running threads than desired might be maintained.
1428	–	*/
1429	–	private boolean mayHaveQueuedWork() {
1430	–	ForkJoinWorkerThread[] ws = workers;
1431	–	int len = ws.length;
1432	–	ForkJoinWorkerThread v;
1433	–	for (int i = 0; i < len; ++i) {
1434	–	if ((v = ws[i]) != null && v.getRawQueueSize() > 0) {
1435	–	releaseIdleWorkers(false); // help wake up stragglers
1436	–	return true;
1437	–	}
1438	–	}
1439	–	return false;
1440	–	}
1441	–
1442	–	/**
1443	–	* Add a spare worker if lock available and no more than the
1444	–	* expected numbers of threads exist
1445	–	* @return true if successful
1446	–	*/
1447	–	private boolean tryAddSpare(int expectedCounts) {
1448	–	final ReentrantLock lock = this.workerLock;
1449	–	int expectedRunning = runningCountOf(expectedCounts);
1450	–	int expectedTotal = totalCountOf(expectedCounts);
1451	–	boolean success = false;
1452	–	boolean locked = false;
1453	–	// confirm counts while locking; CAS after obtaining lock
1454	–	try {
1455	–	for (;;) {
1456	–	int s = workerCounts;
1457	–	int tc = totalCountOf(s);
1458	–	int rc = runningCountOf(s);
1459	–	if (rc > expectedRunning || tc > expectedTotal)
1460	–	break;
1461	–	if (!locked && !(locked = lock.tryLock()))
1462	–	break;
1463	–	if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) {
1464	–	createAndStartSpare(tc);
1465	–	success = true;
1466	–	break;
1467	–	}
1468	–	}
1469	–	} finally {
1470	–	if (locked)
1471	–	lock.unlock();
1472	–	}
1473	–	return success;
1474	–	}
1475	–
1476	–	/**
1477	–	* Add the kth spare worker. On entry, pool coounts are already
1478	–	* adjusted to reflect addition.
1479	–	*/
1480	–	private void createAndStartSpare(int k) {
1481	–	ForkJoinWorkerThread w = null;
1482	–	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1);
1483	–	int len = ws.length;
1484	–	// Probably, we can place at slot k. If not, find empty slot
1485	–	if (k < len && ws[k] != null) {
1486	–	for (k = 0; k < len && ws[k] != null; ++k)
1487	–	;
1488	–	}
1489	–	if (k < len && (w = createWorker(k)) != null) {
1490	–	ws[k] = w;
1491	–	w.start();
1492	–	}
1493	–	else
1494	–	updateWorkerCount(-1); // adjust on failure
1495	–	signalIdleWorkers(false);
1496	–	}
1497	–
1498	–	/**
1499	–	* Suspend calling thread w if there are excess threads.  Called
1500	–	* only from sync.  Spares are enqueued in a Treiber stack
1501	–	* using the same WaitQueueNodes as barriers.  They are resumed
1502	–	* mainly in preJoin, but are also woken on pool events that
1503	–	* require all threads to check run state.
1504	–	* @param w the caller
1505	–	*/
1506	–	private boolean suspendIfSpare(ForkJoinWorkerThread w) {
1507	–	WaitQueueNode node = null;
1508	–	int s;
1509	–	while (parallelism < runningCountOf(s = workerCounts)) {
1510	–	if (node == null)
1511	–	node = new WaitQueueNode(w, 0);
1512	–	if (casWorkerCounts(s, s-1)) { // representation-dependent
1513	–	// push onto stack
1514	–	do;while (!casSpareStack(node.next = spareStack, node));
1515	–
1516	–	// block until released by resumeSpare
1517	–	while (node.thread != null) {
1518	–	if (!Thread.interrupted())
1519	–	LockSupport.park(this);
1520	–	}
1521	–	w.activate(); // help warm up
1522	–	return true;
1523	–	}
1524	–	}
1525	–	return false;
1526	–	}
1527	–
1528	–	/**
1529	–	* Try to pop and resume a spare thread.
1530	–	* @param updateCount if true, increment running count on success
1531	–	* @return true if successful
1532	–	*/
1533	–	private boolean tryResumeSpare(boolean updateCount) {
1534	–	WaitQueueNode q;
1535	–	while ((q = spareStack) != null) {
1536	–	if (casSpareStack(q, q.next)) {
1537	–	if (updateCount)
1538	–	updateRunningCount(1);
1539	–	q.signal();
1540	–	return true;
1541	–	}
1542	–	}
1543	–	return false;
1544	–	}
1545	–
1546	–	/**
1547	–	* Pop and resume all spare threads. Same idea as
1548	–	* releaseIdleWorkers.
1549	–	* @return true if any spares released
1550	–	*/
1551	–	private boolean resumeAllSpares() {
1552	–	WaitQueueNode q;
1553	–	while ( (q = spareStack) != null) {
1554	–	if (casSpareStack(q, null)) {
1555	–	do {
1556	–	updateRunningCount(1);
1557	–	q.signal();
1558	–	} while ((q = q.next) != null);
1559	–	return true;
1560	–	}
1561	–	}
1562	–	return false;
1563	–	}
1564	–
1565	–	/**
1566	–	* Pop and shutdown excessive spare threads. Call only while
1567	–	* holding lock. This is not guaranteed to eliminate all excess
1568	–	* threads, only those suspended as spares, which are the ones
1569	–	* unlikely to be needed in the future.
1570	–	*/
1571	–	private void trimSpares() {
1572	–	int surplus = totalCountOf(workerCounts) - parallelism;
1573	–	WaitQueueNode q;
1574	–	while (surplus > 0 && (q = spareStack) != null) {
1575	–	if (casSpareStack(q, null)) {
1576	–	do {
1577	–	updateRunningCount(1);
1578	–	ForkJoinWorkerThread w = q.thread;
1579	–	if (w != null && surplus > 0 &&
1580	–	runningCountOf(workerCounts) > 0 && w.shutdown())
1581	–	--surplus;
1582	–	q.signal();
1583	–	} while ((q = q.next) != null);
1584	–	}
1585	–	}
1586	–	}
1587	–
1588	–	/**
1589	–	* Returns approximate number of spares, just for diagnostics.
1590	–	*/
1591	–	private int countSpares() {
1592	–	int sum = 0;
1593	–	for (WaitQueueNode q = spareStack; q != null; q = q.next)
1594	–	++sum;
1595	–	return sum;
1596	–	}
1597	–
1986		/**
1987		* Interface for extending managed parallelism for tasks running
1988	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1989	<	* Method <tt>isReleasable</tt> must return true if blocking is not
1990	<	* necessary. Method <tt>block</tt> blocks the current thread
1991	<	* if necessary (perhaps internally invoking isReleasable before
1992	<	* actually blocking.).
1988	>	* in {@link ForkJoinPool}s.
1989	>	*
1990	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
1991	>	* {@code isReleasable} must return {@code true} if blocking is
1992	>	* not necessary. Method {@code block} blocks the current thread
1993	>	* if necessary (perhaps internally invoking {@code isReleasable}
1994	>	* before actually blocking). These actions are performed by any
1995	>	* thread invoking {@link ForkJoinPool#managedBlock}.  The
1996	>	* unusual methods in this API accommodate synchronizers that may,
1997	>	* but don't usually, block for long periods. Similarly, they
1998	>	* allow more efficient internal handling of cases in which
1999	>	* additional workers may be, but usually are not, needed to
2000	>	* ensure sufficient parallelism.  Toward this end,
2001	>	* implementations of method {@code isReleasable} must be amenable
2002	>	* to repeated invocation.
2003	>	*
2004		* <p>For example, here is a ManagedBlocker based on a
2005		* ReentrantLock:
2006	<	* <pre>
2007	<	*   class ManagedLocker implements ManagedBlocker {
2008	<	*     final ReentrantLock lock;
2009	<	*     boolean hasLock = false;
2010	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
2011	<	*     public boolean block() {
2012	<	*        if (!hasLock)
2013	<	*           lock.lock();
2014	<	*        return true;
2015	<	*     }
2016	<	*     public boolean isReleasable() {
2017	<	*        return hasLock || (hasLock = lock.tryLock());
2018	<	*     }
2006	>	*  <pre> {@code
2007	>	* class ManagedLocker implements ManagedBlocker {
2008	>	*   final ReentrantLock lock;
2009	>	*   boolean hasLock = false;
2010	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
2011	>	*   public boolean block() {
2012	>	*     if (!hasLock)
2013	>	*       lock.lock();
2014	>	*     return true;
2015	>	*   }
2016	>	*   public boolean isReleasable() {
2017	>	*     return hasLock || (hasLock = lock.tryLock());
2018	>	*   }
2019	>	* }}</pre>
2020	>	*
2021	>	* <p>Here is a class that possibly blocks waiting for an
2022	>	* item on a given queue:
2023	>	*  <pre> {@code
2024	>	* class QueueTaker<E> implements ManagedBlocker {
2025	>	*   final BlockingQueue<E> queue;
2026	>	*   volatile E item = null;
2027	>	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
2028	>	*   public boolean block() throws InterruptedException {
2029	>	*     if (item == null)
2030	>	*       item = queue.take();
2031	>	*     return true;
2032		*   }
2033	<	* </pre>
2033	>	*   public boolean isReleasable() {
2034	>	*     return item != null || (item = queue.poll()) != null;
2035	>	*   }
2036	>	*   public E getItem() { // call after pool.managedBlock completes
2037	>	*     return item;
2038	>	*   }
2039	>	* }}</pre>
2040		*/
2041		public static interface ManagedBlocker {
2042		/**
2043		* Possibly blocks the current thread, for example waiting for
2044		* a lock or condition.
2045	<	* @return true if no additional blocking is necessary (i.e.,
2046	<	* if isReleasable would return true).
2045	>	*
2046	>	* @return {@code true} if no additional blocking is necessary
2047	>	* (i.e., if isReleasable would return true)
2048		* @throws InterruptedException if interrupted while waiting
2049	<	* (the method is not required to do so, but is allowe to).
2049	>	* (the method is not required to do so, but is allowed to)
2050		*/
2051		boolean block() throws InterruptedException;
2052
2053		/**
2054	<	* Returns true if blocking is unnecessary.
2054	>	* Returns {@code true} if blocking is unnecessary.
2055		*/
2056		boolean isReleasable();
2057		}
2058
2059		/**
2060		* Blocks in accord with the given blocker.  If the current thread
2061	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
2062	<	* spare thread to be activated if necessary to ensure parallelism
2063	<	* while the current thread is blocked.  If
2064	<	* <tt>maintainParallelism</tt> is true and the pool supports it
2065	<	* (see <tt>getMaintainsParallelism</tt>), this method attempts to
2066	<	* maintain the pool's nominal parallelism. Otherwise if activates
2067	<	* a thread only if necessary to avoid complete starvation. This
2068	<	* option may be preferable when blockages use timeouts, or are
2069	<	* almost always brief.
2070	<	*
2071	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
2072	<	* equivalent to
2073	<	* <pre>
2074	<	*   while (!blocker.isReleasable())
1656	<	*      if (blocker.block())
1657	<	*         return;
1658	<	* </pre>
1659	<	* If the caller is a ForkJoinTask, then the pool may first
1660	<	* be expanded to ensure parallelism, and later adjusted.
2061	>	* is a {@link ForkJoinWorkerThread}, this method possibly
2062	>	* arranges for a spare thread to be activated if necessary to
2063	>	* ensure sufficient parallelism while the current thread is blocked.
2064	>	*
2065	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
2066	>	* behaviorally equivalent to
2067	>	*  <pre> {@code
2068	>	* while (!blocker.isReleasable())
2069	>	*   if (blocker.block())
2070	>	*     return;
2071	>	* }</pre>
2072	>	*
2073	>	* If the caller is a {@code ForkJoinTask}, then the pool may
2074	>	* first be expanded to ensure parallelism, and later adjusted.
2075		*
2076		* @param blocker the blocker
2077	<	* @param maintainParallelism if true and supported by this pool,
1664	<	* attempt to maintain the pool's nominal parallelism; otherwise
1665	<	* activate a thread only if necessary to avoid complete
1666	<	* starvation.
1667	<	* @throws InterruptedException if blocker.block did so.
2077	>	* @throws InterruptedException if blocker.block did so
2078		*/
2079	<	public static void managedBlock(ManagedBlocker blocker,
1670	<	boolean maintainParallelism)
2079	>	public static void managedBlock(ManagedBlocker blocker)
2080		throws InterruptedException {
2081		Thread t = Thread.currentThread();
2082	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
2083	<	((ForkJoinWorkerThread)t).pool : null);
2084	<	if (!blocker.isReleasable()) {
2085	<	try {
2086	<	if (pool == null ||
2087	<	!pool.preBlock(blocker, maintainParallelism))
1679	<	awaitBlocker(blocker);
1680	<	} finally {
1681	<	if (pool != null)
1682	<	pool.updateRunningCount(1);
1683	<	}
2082	>	if (t instanceof ForkJoinWorkerThread) {
2083	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
2084	>	w.pool.awaitBlocker(blocker);
2085	>	}
2086	>	else {
2087	>	do {} while (!blocker.isReleasable() && !blocker.block());
2088		}
2089		}
2090
2091	<	private static void awaitBlocker(ManagedBlocker blocker)
2092	<	throws InterruptedException {
2093	<	do;while (!blocker.isReleasable() && !blocker.block());
1690	<	}
2091	>	// AbstractExecutorService overrides.  These rely on undocumented
2092	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
2093	>	// implement RunnableFuture.
2094
2095	+	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
2096	+	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
2097	+	}
2098
2099	<	// Temporary Unsafe mechanics for preliminary release
2099	>	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
2100	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
2101	>	}
2102
2103	<	static final Unsafe _unsafe;
2104	<	static final long eventCountOffset;
2105	<	static final long workerCountsOffset;
2106	<	static final long runControlOffset;
2107	<	static final long barrierStackOffset;
2108	<	static final long spareStackOffset;
2103	>	// Unsafe mechanics
2104	>	private static final sun.misc.Unsafe UNSAFE;
2105	>	private static final long ctlOffset;
2106	>	private static final long stealCountOffset;
2107	>	private static final long blockedCountOffset;
2108	>	private static final long quiescerCountOffset;
2109	>	private static final long scanGuardOffset;
2110	>	private static final long nextWorkerNumberOffset;
2111	>	private static final long ABASE;
2112	>	private static final int ASHIFT;
2113
2114		static {
2115	+	poolNumberGenerator = new AtomicInteger();
2116	+	workerSeedGenerator = new Random();
2117	+	modifyThreadPermission = new RuntimePermission("modifyThread");
2118	+	defaultForkJoinWorkerThreadFactory =
2119	+	new DefaultForkJoinWorkerThreadFactory();
2120	+	int s;
2121		try {
2122	<	if (ForkJoinPool.class.getClassLoader() != null) {
2123	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
2124	<	f.setAccessible(true);
2125	<	_unsafe = (Unsafe)f.get(null);
2126	<	}
2127	<	else
2128	<	_unsafe = Unsafe.getUnsafe();
2129	<	eventCountOffset = _unsafe.objectFieldOffset
2130	<	(ForkJoinPool.class.getDeclaredField("eventCount"));
2131	<	workerCountsOffset = _unsafe.objectFieldOffset
2132	<	(ForkJoinPool.class.getDeclaredField("workerCounts"));
2133	<	runControlOffset = _unsafe.objectFieldOffset
2134	<	(ForkJoinPool.class.getDeclaredField("runControl"));
2135	<	barrierStackOffset = _unsafe.objectFieldOffset
2136	<	(ForkJoinPool.class.getDeclaredField("barrierStack"));
2137	<	spareStackOffset = _unsafe.objectFieldOffset
2138	<	(ForkJoinPool.class.getDeclaredField("spareStack"));
2122	>	UNSAFE = getUnsafe();
2123	>	Class k = ForkJoinPool.class;
2124	>	ctlOffset = UNSAFE.objectFieldOffset
2125	>	(k.getDeclaredField("ctl"));
2126	>	stealCountOffset = UNSAFE.objectFieldOffset
2127	>	(k.getDeclaredField("stealCount"));
2128	>	blockedCountOffset = UNSAFE.objectFieldOffset
2129	>	(k.getDeclaredField("blockedCount"));
2130	>	quiescerCountOffset = UNSAFE.objectFieldOffset
2131	>	(k.getDeclaredField("quiescerCount"));
2132	>	scanGuardOffset = UNSAFE.objectFieldOffset
2133	>	(k.getDeclaredField("scanGuard"));
2134	>	nextWorkerNumberOffset = UNSAFE.objectFieldOffset
2135	>	(k.getDeclaredField("nextWorkerNumber"));
2136	>	Class a = ForkJoinTask[].class;
2137	>	ABASE = UNSAFE.arrayBaseOffset(a);
2138	>	s = UNSAFE.arrayIndexScale(a);
2139		} catch (Exception e) {
2140	<	throw new RuntimeException("Could not initialize intrinsics", e);
2140	>	throw new Error(e);
2141		}
2142	+	if ((s & (s-1)) != 0)
2143	+	throw new Error("data type scale not a power of two");
2144	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
2145		}
2146
2147	<	private boolean casEventCount(long cmp, long val) {
2148	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
2149	<	}
2150	<	private boolean casWorkerCounts(int cmp, int val) {
2151	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
2152	<	}
2153	<	private boolean casRunControl(int cmp, int val) {
2154	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
2155	<	}
2156	<	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
2157	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
2158	<	}
2159	<	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
2160	<	return _unsafe.compareAndSwapObject(this, barrierStackOffset, cmp, val);
2147	>	/**
2148	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
2149	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
2150	>	* into a jdk.
2151	>	*
2152	>	* @return a sun.misc.Unsafe
2153	>	*/
2154	>	private static sun.misc.Unsafe getUnsafe() {
2155	>	try {
2156	>	return sun.misc.Unsafe.getUnsafe();
2157	>	} catch (SecurityException se) {
2158	>	try {
2159	>	return java.security.AccessController.doPrivileged
2160	>	(new java.security
2161	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
2162	>	public sun.misc.Unsafe run() throws Exception {
2163	>	java.lang.reflect.Field f = sun.misc
2164	>	.Unsafe.class.getDeclaredField("theUnsafe");
2165	>	f.setAccessible(true);
2166	>	return (sun.misc.Unsafe) f.get(null);
2167	>	}});
2168	>	} catch (java.security.PrivilegedActionException e) {
2169	>	throw new RuntimeException("Could not initialize intrinsics",
2170	>	e.getCause());
2171	>	}
2172	>	}
2173		}
2174		}

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