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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.41 by jsr166, Mon Aug 3 01:11:58 2009 UTC vs.
Revision 1.80 by dl, Fri Sep 17 14:24:56 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	–	import java.util.concurrent.*;
10	–
9		import java.util.ArrayList;
10		import java.util.Arrays;
11		import java.util.Collection;
12		import java.util.Collections;
13		import java.util.List;
14	<	import java.util.concurrent.locks.Condition;
14	>	import java.util.concurrent.AbstractExecutorService;
15	>	import java.util.concurrent.Callable;
16	>	import java.util.concurrent.ExecutorService;
17	>	import java.util.concurrent.Future;
18	>	import java.util.concurrent.RejectedExecutionException;
19	>	import java.util.concurrent.RunnableFuture;
20	>	import java.util.concurrent.TimeUnit;
21	>	import java.util.concurrent.TimeoutException;
22	>	import java.util.concurrent.atomic.AtomicInteger;
23		import java.util.concurrent.locks.LockSupport;
24		import java.util.concurrent.locks.ReentrantLock;
19	–	import java.util.concurrent.atomic.AtomicInteger;
20	–	import java.util.concurrent.atomic.AtomicLong;
25
26		/**
27		* An {@link ExecutorService} for running {@link ForkJoinTask}s.
28		* A {@code ForkJoinPool} provides the entry point for submissions
29	<	* from non-{@code ForkJoinTask}s, as well as management and
30	<	* monitoring operations.  Normally a single {@code ForkJoinPool} is
27	<	* used for a large number of submitted tasks. Otherwise, use would
28	<	* not usually outweigh the construction and bookkeeping overhead of
29	<	* creating a large set of threads.
29	>	* from non-{@code ForkJoinTask} clients, as well as management and
30	>	* monitoring operations.
31		*
32	<	* <p>{@code ForkJoinPool}s differ from other kinds of {@link
33	<	* Executor}s mainly in that they provide <em>work-stealing</em>: all
34	<	* threads in the pool attempt to find and execute subtasks created by
35	<	* other active tasks (eventually blocking if none exist). This makes
36	<	* them efficient when most tasks spawn other subtasks (as do most
37	<	* {@code ForkJoinTask}s), as well as the mixed execution of some
38	<	* plain {@code Runnable}- or {@code Callable}- based activities along
39	<	* with {@code ForkJoinTask}s. When setting {@linkplain #setAsyncMode
40	<	* async mode}, a {@code ForkJoinPool} may also be appropriate for use
40	<	* with fine-grained tasks that are never joined. Otherwise, other
41	<	* {@code ExecutorService} implementations are typically more
42	<	* appropriate choices.
32	>	* <p>A {@code ForkJoinPool} differs from other kinds of {@link
33	>	* ExecutorService} mainly by virtue of employing
34	>	* <em>work-stealing</em>: all threads in the pool attempt to find and
35	>	* execute subtasks created by other active tasks (eventually blocking
36	>	* waiting for work if none exist). This enables efficient processing
37	>	* when most tasks spawn other subtasks (as do most {@code
38	>	* ForkJoinTask}s). When setting <em>asyncMode</em> to true in
39	>	* constructors, {@code ForkJoinPool}s may also be appropriate for use
40	>	* with event-style tasks that are never joined.
41		*
42	<	* <p>A {@code ForkJoinPool} may be constructed with a given
43	<	* parallelism level (target pool size), which it attempts to maintain
44	<	* by dynamically adding, suspending, or resuming threads, even if
45	<	* some tasks are waiting to join others. However, no such adjustments
46	<	* are performed in the face of blocked IO or other unmanaged
47	<	* synchronization. The nested {@link ManagedBlocker} interface
48	<	* enables extension of the kinds of synchronization accommodated.
49	<	* The target parallelism level may also be changed dynamically
50	<	* ({@link #setParallelism}) and thread construction can be limited
53	<	* using methods {@link #setMaximumPoolSize} and/or {@link
54	<	* #setMaintainsParallelism}.
42	>	* <p>A {@code ForkJoinPool} is constructed with a given target
43	>	* parallelism level; by default, equal to the number of available
44	>	* processors. The pool attempts to maintain enough active (or
45	>	* available) threads by dynamically adding, suspending, or resuming
46	>	* internal worker threads, even if some tasks are stalled waiting to
47	>	* join others. However, no such adjustments are guaranteed in the
48	>	* face of blocked IO or other unmanaged synchronization. The nested
49	>	* {@link ManagedBlocker} interface enables extension of the kinds of
50	>	* synchronization accommodated.
51		*
52		* <p>In addition to execution and lifecycle control methods, this
53		* class provides status check methods (for example
#	Line 60 | Line 56 | import java.util.concurrent.atomic.Atomi
56		* {@link #toString} returns indications of pool state in a
57		* convenient form for informal monitoring.
58		*
59	+	* <p> As is the case with other ExecutorServices, there are three
60	+	* main task execution methods summarized in the following
61	+	* table. These are designed to be used by clients not already engaged
62	+	* in fork/join computations in the current pool.  The main forms of
63	+	* these methods accept instances of {@code ForkJoinTask}, but
64	+	* overloaded forms also allow mixed execution of plain {@code
65	+	* Runnable}- or {@code Callable}- based activities as well.  However,
66	+	* tasks that are already executing in a pool should normally
67	+	* <em>NOT</em> use these pool execution methods, but instead use the
68	+	* within-computation forms listed in the table.
69	+	*
70	+	* <table BORDER CELLPADDING=3 CELLSPACING=1>
71	+	*  <tr>
72	+	*    <td></td>
73	+	*    <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
74	+	*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
75	+	*  </tr>
76	+	*  <tr>
77	+	*    <td> <b>Arrange async execution</td>
78	+	*    <td> {@link #execute(ForkJoinTask)}</td>
79	+	*    <td> {@link ForkJoinTask#fork}</td>
80	+	*  </tr>
81	+	*  <tr>
82	+	*    <td> <b>Await and obtain result</td>
83	+	*    <td> {@link #invoke(ForkJoinTask)}</td>
84	+	*    <td> {@link ForkJoinTask#invoke}</td>
85	+	*  </tr>
86	+	*  <tr>
87	+	*    <td> <b>Arrange exec and obtain Future</td>
88	+	*    <td> {@link #submit(ForkJoinTask)}</td>
89	+	*    <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td>
90	+	*  </tr>
91	+	* </table>
92	+	*
93	+	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
94	+	* used for all parallel task execution in a program or subsystem.
95	+	* Otherwise, use would not usually outweigh the construction and
96	+	* bookkeeping overhead of creating a large set of threads. For
97	+	* example, a common pool could be used for the {@code SortTasks}
98	+	* illustrated in {@link RecursiveAction}. Because {@code
99	+	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
100	+	* daemon} mode, there is typically no need to explicitly {@link
101	+	* #shutdown} such a pool upon program exit.
102	+	*
103	+	* <pre>
104	+	* static final ForkJoinPool mainPool = new ForkJoinPool();
105	+	* ...
106	+	* public void sort(long[] array) {
107	+	*   mainPool.invoke(new SortTask(array, 0, array.length));
108	+	* }
109	+	* </pre>
110	+	*
111		* <p><b>Implementation notes</b>: This implementation restricts the
112		* maximum number of running threads to 32767. Attempts to create
113	<	* pools with greater than the maximum result in
113	>	* pools with greater than the maximum number result in
114		* {@code IllegalArgumentException}.
115		*
116	+	* <p>This implementation rejects submitted tasks (that is, by throwing
117	+	* {@link RejectedExecutionException}) only when the pool is shut down
118	+	* or internal resources have been exhausted.
119	+	*
120		* @since 1.7
121		* @author Doug Lea
122		*/
123		public class ForkJoinPool extends AbstractExecutorService {
124
125		/*
126	<	* See the extended comments interspersed below for design,
127	<	* rationale, and walkthroughs.
126	>	* Implementation Overview
127	>	*
128	>	* This class provides the central bookkeeping and control for a
129	>	* set of worker threads: Submissions from non-FJ threads enter
130	>	* into a submission queue. Workers take these tasks and typically
131	>	* split them into subtasks that may be stolen by other workers.
132	>	* The main work-stealing mechanics implemented in class
133	>	* ForkJoinWorkerThread give first priority to processing tasks
134	>	* from their own queues (LIFO or FIFO, depending on mode), then
135	>	* to randomized FIFO steals of tasks in other worker queues, and
136	>	* lastly to new submissions. These mechanics do not consider
137	>	* affinities, loads, cache localities, etc, so rarely provide the
138	>	* best possible performance on a given machine, but portably
139	>	* provide good throughput by averaging over these factors.
140	>	* (Further, even if we did try to use such information, we do not
141	>	* usually have a basis for exploiting it. For example, some sets
142	>	* of tasks profit from cache affinities, but others are harmed by
143	>	* cache pollution effects.)
144	>	*
145	>	* Beyond work-stealing support and essential bookkeeping, the
146	>	* main responsibility of this framework is to take actions when
147	>	* one worker is waiting to join a task stolen (or always held by)
148	>	* another.  Because we are multiplexing many tasks on to a pool
149	>	* of workers, we can't just let them block (as in Thread.join).
150	>	* We also cannot just reassign the joiner's run-time stack with
151	>	* another and replace it later, which would be a form of
152	>	* "continuation", that even if possible is not necessarily a good
153	>	* idea. Given that the creation costs of most threads on most
154	>	* systems mainly surrounds setting up runtime stacks, thread
155	>	* creation and switching is usually not much more expensive than
156	>	* stack creation and switching, and is more flexible). Instead we
157	>	* combine two tactics:
158	>	*
159	>	*   Helping: Arranging for the joiner to execute some task that it
160	>	*      would be running if the steal had not occurred.  Method
161	>	*      ForkJoinWorkerThread.helpJoinTask tracks joining->stealing
162	>	*      links to try to find such a task.
163	>	*
164	>	*   Compensating: Unless there are already enough live threads,
165	>	*      method helpMaintainParallelism() may create or
166	>	*      re-activate a spare thread to compensate for blocked
167	>	*      joiners until they unblock.
168	>	*
169	>	* It is impossible to keep exactly the target (parallelism)
170	>	* number of threads running at any given time.  Determining
171	>	* existence of conservatively safe helping targets, the
172	>	* availability of already-created spares, and the apparent need
173	>	* to create new spares are all racy and require heuristic
174	>	* guidance, so we rely on multiple retries of each.  Compensation
175	>	* occurs in slow-motion. It is triggered only upon timeouts of
176	>	* Object.wait used for joins. This reduces poor decisions that
177	>	* would otherwise be made when threads are waiting for others
178	>	* that are stalled because of unrelated activities such as
179	>	* garbage collection.
180	>	*
181	>	* The ManagedBlocker extension API can't use helping so relies
182	>	* only on compensation in method awaitBlocker.
183	>	*
184	>	* The main throughput advantages of work-stealing stem from
185	>	* decentralized control -- workers mostly steal tasks from each
186	>	* other. We do not want to negate this by creating bottlenecks
187	>	* implementing other management responsibilities. So we use a
188	>	* collection of techniques that avoid, reduce, or cope well with
189	>	* contention. These entail several instances of bit-packing into
190	>	* CASable fields to maintain only the minimally required
191	>	* atomicity. To enable such packing, we restrict maximum
192	>	* parallelism to (1<<15)-1 (enabling twice this (to accommodate
193	>	* unbalanced increments and decrements) to fit into a 16 bit
194	>	* field, which is far in excess of normal operating range.  Even
195	>	* though updates to some of these bookkeeping fields do sometimes
196	>	* contend with each other, they don't normally cache-contend with
197	>	* updates to others enough to warrant memory padding or
198	>	* isolation. So they are all held as fields of ForkJoinPool
199	>	* objects.  The main capabilities are as follows:
200	>	*
201	>	* 1. Creating and removing workers. Workers are recorded in the
202	>	* "workers" array. This is an array as opposed to some other data
203	>	* structure to support index-based random steals by workers.
204	>	* Updates to the array recording new workers and unrecording
205	>	* terminated ones are protected from each other by a lock
206	>	* (workerLock) but the array is otherwise concurrently readable,
207	>	* and accessed directly by workers. To simplify index-based
208	>	* operations, the array size is always a power of two, and all
209	>	* readers must tolerate null slots. Currently, all worker thread
210	>	* creation is on-demand, triggered by task submissions,
211	>	* replacement of terminated workers, and/or compensation for
212	>	* blocked workers. However, all other support code is set up to
213	>	* work with other policies.
214	>	*
215	>	* To ensure that we do not hold on to worker references that
216	>	* would prevent GC, ALL accesses to workers are via indices into
217	>	* the workers array (which is one source of some of the unusual
218	>	* code constructions here). In essence, the workers array serves
219	>	* as a WeakReference mechanism. Thus for example the event queue
220	>	* stores worker indices, not worker references. Access to the
221	>	* workers in associated methods (for example releaseEventWaiters)
222	>	* must both index-check and null-check the IDs. All such accesses
223	>	* ignore bad IDs by returning out early from what they are doing,
224	>	* since this can only be associated with shutdown, in which case
225	>	* it is OK to give up. On termination, we just clobber these
226	>	* data structures without trying to use them.
227	>	*
228	>	* 2. Bookkeeping for dynamically adding and removing workers. We
229	>	* aim to approximately maintain the given level of parallelism.
230	>	* When some workers are known to be blocked (on joins or via
231	>	* ManagedBlocker), we may create or resume others to take their
232	>	* place until they unblock (see below). Implementing this
233	>	* requires counts of the number of "running" threads (i.e., those
234	>	* that are neither blocked nor artificially suspended) as well as
235	>	* the total number.  These two values are packed into one field,
236	>	* "workerCounts" because we need accurate snapshots when deciding
237	>	* to create, resume or suspend.  Note however that the
238	>	* correspondence of these counts to reality is not guaranteed. In
239	>	* particular updates for unblocked threads may lag until they
240	>	* actually wake up.
241	>	*
242	>	* 3. Maintaining global run state. The run state of the pool
243	>	* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to
244	>	* those in other Executor implementations, as well as a count of
245	>	* "active" workers -- those that are, or soon will be, or
246	>	* recently were executing tasks. The runLevel and active count
247	>	* are packed together in order to correctly trigger shutdown and
248	>	* termination. Without care, active counts can be subject to very
249	>	* high contention.  We substantially reduce this contention by
250	>	* relaxing update rules.  A worker must claim active status
251	>	* prospectively, by activating if it sees that a submitted or
252	>	* stealable task exists (it may find after activating that the
253	>	* task no longer exists). It stays active while processing this
254	>	* task (if it exists) and any other local subtasks it produces,
255	>	* until it cannot find any other tasks. It then tries
256	>	* inactivating (see method preStep), but upon update contention
257	>	* instead scans for more tasks, later retrying inactivation if it
258	>	* doesn't find any.
259	>	*
260	>	* 4. Managing idle workers waiting for tasks. We cannot let
261	>	* workers spin indefinitely scanning for tasks when none are
262	>	* available. On the other hand, we must quickly prod them into
263	>	* action when new tasks are submitted or generated.  We
264	>	* park/unpark these idle workers using an event-count scheme.
265	>	* Field eventCount is incremented upon events that may enable
266	>	* workers that previously could not find a task to now find one:
267	>	* Submission of a new task to the pool, or another worker pushing
268	>	* a task onto a previously empty queue.  (We also use this
269	>	* mechanism for configuration and termination actions that
270	>	* require wakeups of idle workers).  Each worker maintains its
271	>	* last known event count, and blocks when a scan for work did not
272	>	* find a task AND its lastEventCount matches the current
273	>	* eventCount. Waiting idle workers are recorded in a variant of
274	>	* Treiber stack headed by field eventWaiters which, when nonzero,
275	>	* encodes the thread index and count awaited for by the worker
276	>	* thread most recently calling eventSync. This thread in turn has
277	>	* a record (field nextEventWaiter) for the next waiting worker.
278	>	* In addition to allowing simpler decisions about need for
279	>	* wakeup, the event count bits in eventWaiters serve the role of
280	>	* tags to avoid ABA errors in Treiber stacks. Upon any wakeup,
281	>	* released threads also try to release at most two others.  The
282	>	* net effect is a tree-like diffusion of signals, where released
283	>	* threads (and possibly others) help with unparks.  To further
284	>	* reduce contention effects a bit, failed CASes to increment
285	>	* field eventCount are tolerated without retries in signalWork.
286	>	* Conceptually they are merged into the same event, which is OK
287	>	* when their only purpose is to enable workers to scan for work.
288	>	*
289	>	* 5. Managing suspension of extra workers. When a worker notices
290	>	* (usually upon timeout of a wait()) that there are too few
291	>	* running threads, we may create a new thread to maintain
292	>	* parallelism level, or at least avoid starvation. Usually, extra
293	>	* threads are needed for only very short periods, yet join
294	>	* dependencies are such that we sometimes need them in
295	>	* bursts. Rather than create new threads each time this happens,
296	>	* we suspend no-longer-needed extra ones as "spares". For most
297	>	* purposes, we don't distinguish "extra" spare threads from
298	>	* normal "core" threads: On each call to preStep (the only point
299	>	* at which we can do this) a worker checks to see if there are
300	>	* now too many running workers, and if so, suspends itself.
301	>	* Method helpMaintainParallelism looks for suspended threads to
302	>	* resume before considering creating a new replacement. The
303	>	* spares themselves are encoded on another variant of a Treiber
304	>	* Stack, headed at field "spareWaiters".  Note that the use of
305	>	* spares is intrinsically racy.  One thread may become a spare at
306	>	* about the same time as another is needlessly being created. We
307	>	* counteract this and related slop in part by requiring resumed
308	>	* spares to immediately recheck (in preStep) to see whether they
309	>	* should re-suspend.
310	>	*
311	>	* 6. Killing off unneeded workers. A timeout mechanism is used to
312	>	* shed unused workers: The oldest (first) event queue waiter uses
313	>	* a timed rather than hard wait. When this wait times out without
314	>	* a normal wakeup, it tries to shutdown any one (for convenience
315	>	* the newest) other spare or event waiter via
316	>	* tryShutdownUnusedWorker. This eventually reduces the number of
317	>	* worker threads to a minimum of one after a long enough period
318	>	* without use.
319	>	*
320	>	* 7. Deciding when to create new workers. The main dynamic
321	>	* control in this class is deciding when to create extra threads
322	>	* in method helpMaintainParallelism. We would like to keep
323	>	* exactly #parallelism threads running, which is an impossible
324	>	* task. We always need to create one when the number of running
325	>	* threads would become zero and all workers are busy. Beyond
326	>	* this, we must rely on heuristics that work well in the
327	>	* presence of transient phenomena such as GC stalls, dynamic
328	>	* compilation, and wake-up lags. These transients are extremely
329	>	* common -- we are normally trying to fully saturate the CPUs on
330	>	* a machine, so almost any activity other than running tasks
331	>	* impedes accuracy. Our main defense is to allow parallelism to
332	>	* lapse for a while during joins, and use a timeout to see if,
333	>	* after the resulting settling, there is still a need for
334	>	* additional workers.  This also better copes with the fact that
335	>	* some of the methods in this class tend to never become compiled
336	>	* (but are interpreted), so some components of the entire set of
337	>	* controls might execute 100 times faster than others. And
338	>	* similarly for cases where the apparent lack of work is just due
339	>	* to GC stalls and other transient system activity.
340	>	*
341	>	* Beware that there is a lot of representation-level coupling
342	>	* among classes ForkJoinPool, ForkJoinWorkerThread, and
343	>	* ForkJoinTask.  For example, direct access to "workers" array by
344	>	* workers, and direct access to ForkJoinTask.status by both
345	>	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
346	>	* trying to reduce this, since any associated future changes in
347	>	* representations will need to be accompanied by algorithmic
348	>	* changes anyway.
349	>	*
350	>	* Style notes: There are lots of inline assignments (of form
351	>	* "while ((local = field) != 0)") which are usually the simplest
352	>	* way to ensure the required read orderings (which are sometimes
353	>	* critical). Also several occurrences of the unusual "do {}
354	>	* while (!cas...)" which is the simplest way to force an update of
355	>	* a CAS'ed variable. There are also other coding oddities that
356	>	* help some methods perform reasonably even when interpreted (not
357	>	* compiled), at the expense of some messy constructions that
358	>	* reduce byte code counts.
359	>	*
360	>	* The order of declarations in this file is: (1) statics (2)
361	>	* fields (along with constants used when unpacking some of them)
362	>	* (3) internal control methods (4) callbacks and other support
363	>	* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
364	>	* methods (plus a few little helpers).
365		*/
366
78	–	/** Mask for packing and unpacking shorts */
79	–	private static final int  shortMask = 0xffff;
80	–
81	–	/** Max pool size -- must be a power of two minus 1 */
82	–	private static final int MAX_THREADS =  0x7FFF;
83	–
367		/**
368		* Factory for creating new {@link ForkJoinWorkerThread}s.
369		* A {@code ForkJoinWorkerThreadFactory} must be defined and used
#	Line 92 | Line 375 | public class ForkJoinPool extends Abstra
375		* Returns a new worker thread operating in the given pool.
376		*
377		* @param pool the pool this thread works in
378	<	* @throws NullPointerException if pool is null
378	>	* @throws NullPointerException if the pool is null
379		*/
380		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
381		}
#	Line 101 | Line 384 | public class ForkJoinPool extends Abstra
384		* Default ForkJoinWorkerThreadFactory implementation; creates a
385		* new ForkJoinWorkerThread.
386		*/
387	<	static class  DefaultForkJoinWorkerThreadFactory
387	>	static class DefaultForkJoinWorkerThreadFactory
388		implements ForkJoinWorkerThreadFactory {
389		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
390	<	try {
108	<	return new ForkJoinWorkerThread(pool);
109	<	} catch (OutOfMemoryError oom)  {
110	<	return null;
111	<	}
390	>	return new ForkJoinWorkerThread(pool);
391		}
392		}
393
#	Line 144 | Line 423 | public class ForkJoinPool extends Abstra
423		new AtomicInteger();
424
425		/**
426	<	* Array holding all worker threads in the pool. Initialized upon
427	<	* first use. Array size must be a power of two.  Updates and
428	<	* replacements are protected by workerLock, but it is always kept
429	<	* in a consistent enough state to be randomly accessed without
430	<	* locking by workers performing work-stealing.
426	>	* The time to block in a join (see awaitJoin) before checking if
427	>	* a new worker should be (re)started to maintain parallelism
428	>	* level. The value should be short enough to maintain global
429	>	* responsiveness and progress but long enough to avoid
430	>	* counterproductive firings during GC stalls or unrelated system
431	>	* activity, and to not bog down systems with continual re-firings
432	>	* on GCs or legitimately long waits.
433	>	*/
434	>	private static final long JOIN_TIMEOUT_MILLIS = 250L; // 4 per second
435	>
436	>	/**
437	>	* The wakeup interval (in nanoseconds) for the oldest worker
438	>	* waiting for an event to invoke tryShutdownUnusedWorker to
439	>	* shrink the number of workers.  The exact value does not matter
440	>	* too much. It must be short enough to release resources during
441	>	* sustained periods of idleness, but not so short that threads
442	>	* are continually re-created.
443	>	*/
444	>	private static final long SHRINK_RATE_NANOS =
445	>	30L * 1000L * 1000L * 1000L; // 2 per minute
446	>
447	>	/**
448	>	* Absolute bound for parallelism level. Twice this number plus
449	>	* one (i.e., 0xfff) must fit into a 16bit field to enable
450	>	* word-packing for some counts and indices.
451	>	*/
452	>	private static final int MAX_WORKERS   = 0x7fff;
453	>
454	>	/**
455	>	* Array holding all worker threads in the pool.  Array size must
456	>	* be a power of two.  Updates and replacements are protected by
457	>	* workerLock, but the array is always kept in a consistent enough
458	>	* state to be randomly accessed without locking by workers
459	>	* performing work-stealing, as well as other traversal-based
460	>	* methods in this class. All readers must tolerate that some
461	>	* array slots may be null.
462		*/
463		volatile ForkJoinWorkerThread[] workers;
464
465		/**
466	<	* Lock protecting access to workers.
466	>	* Queue for external submissions.
467		*/
468	<	private final ReentrantLock workerLock;
468	>	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
469
470		/**
471	<	* Condition for awaitTermination.
471	>	* Lock protecting updates to workers array.
472		*/
473	<	private final Condition termination;
473	>	private final ReentrantLock workerLock;
474
475		/**
476	<	* The uncaught exception handler used when any worker
167	<	* abruptly terminates
476	>	* Latch released upon termination.
477		*/
478	<	private Thread.UncaughtExceptionHandler ueh;
478	>	private final Phaser termination;
479
480		/**
481		* Creation factory for worker threads.
#	Line 174 | Line 483 | public class ForkJoinPool extends Abstra
483		private final ForkJoinWorkerThreadFactory factory;
484
485		/**
177	–	* Head of stack of threads that were created to maintain
178	–	* parallelism when other threads blocked, but have since
179	–	* suspended when the parallelism level rose.
180	–	*/
181	–	private volatile WaitQueueNode spareStack;
182	–
183	–	/**
486		* Sum of per-thread steal counts, updated only when threads are
487		* idle or terminating.
488		*/
489	<	private final AtomicLong stealCount;
489	>	private volatile long stealCount;
490
491		/**
492	<	* Queue for external submissions.
492	>	* Encoded record of top of Treiber stack of threads waiting for
493	>	* events. The top 32 bits contain the count being waited for. The
494	>	* bottom 16 bits contains one plus the pool index of waiting
495	>	* worker thread. (Bits 16-31 are unused.)
496		*/
497	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
497	>	private volatile long eventWaiters;
498
499	<	/**
500	<	* Head of Treiber stack for barrier sync. See below for explanation.
196	<	*/
197	<	private volatile WaitQueueNode syncStack;
499	>	private static final int  EVENT_COUNT_SHIFT = 32;
500	>	private static final long WAITER_ID_MASK    = (1L << 16) - 1L;
501
502		/**
503	<	* The count for event barrier
503	>	* A counter for events that may wake up worker threads:
504	>	*   - Submission of a new task to the pool
505	>	*   - A worker pushing a task on an empty queue
506	>	*   - termination
507		*/
508	<	private volatile long eventCount;
508	>	private volatile int eventCount;
509
510		/**
511	<	* Pool number, just for assigning useful names to worker threads
511	>	* Encoded record of top of Treiber stack of spare threads waiting
512	>	* for resumption. The top 16 bits contain an arbitrary count to
513	>	* avoid ABA effects. The bottom 16bits contains one plus the pool
514	>	* index of waiting worker thread.
515		*/
516	<	private final int poolNumber;
516	>	private volatile int spareWaiters;
517
518	<	/**
519	<	* The maximum allowed pool size
211	<	*/
212	<	private volatile int maxPoolSize;
518	>	private static final int SPARE_COUNT_SHIFT = 16;
519	>	private static final int SPARE_ID_MASK     = (1 << 16) - 1;
520
521		/**
522	<	* The desired parallelism level, updated only under workerLock.
522	>	* Lifecycle control. The low word contains the number of workers
523	>	* that are (probably) executing tasks. This value is atomically
524	>	* incremented before a worker gets a task to run, and decremented
525	>	* when a worker has no tasks and cannot find any.  Bits 16-18
526	>	* contain runLevel value. When all are zero, the pool is
527	>	* running. Level transitions are monotonic (running -> shutdown
528	>	* -> terminating -> terminated) so each transition adds a bit.
529	>	* These are bundled together to ensure consistent read for
530	>	* termination checks (i.e., that runLevel is at least SHUTDOWN
531	>	* and active threads is zero).
532	>	*
533	>	* Notes: Most direct CASes are dependent on these bitfield
534	>	* positions.  Also, this field is non-private to enable direct
535	>	* performance-sensitive CASes in ForkJoinWorkerThread.
536		*/
537	<	private volatile int parallelism;
537	>	volatile int runState;
538
539	<	/**
540	<	* True if use local fifo, not default lifo, for local polling
541	<	*/
542	<	private volatile boolean locallyFifo;
539	>	// Note: The order among run level values matters.
540	>	private static final int RUNLEVEL_SHIFT     = 16;
541	>	private static final int SHUTDOWN           = 1 << RUNLEVEL_SHIFT;
542	>	private static final int TERMINATING        = 1 << (RUNLEVEL_SHIFT + 1);
543	>	private static final int TERMINATED         = 1 << (RUNLEVEL_SHIFT + 2);
544	>	private static final int ACTIVE_COUNT_MASK  = (1 << RUNLEVEL_SHIFT) - 1;
545
546		/**
547		* Holds number of total (i.e., created and not yet terminated)
548		* and running (i.e., not blocked on joins or other managed sync)
549	<	* threads, packed into one int to ensure consistent snapshot when
549	>	* threads, packed together to ensure consistent snapshot when
550		* making decisions about creating and suspending spare
551	<	* threads. Updated only by CAS.  Note: CASes in
552	<	* updateRunningCount and preJoin assume that running active count
553	<	* is in low word, so need to be modified if this changes.
551	>	* threads. Updated only by CAS. Note that adding a new worker
552	>	* requires incrementing both counts, since workers start off in
553	>	* running state.
554		*/
555		private volatile int workerCounts;
556
557	<	private static int totalCountOf(int s)           { return s >>> 16;  }
558	<	private static int runningCountOf(int s)         { return s & shortMask; }
559	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
557	>	private static final int TOTAL_COUNT_SHIFT  = 16;
558	>	private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1;
559	>	private static final int ONE_RUNNING        = 1;
560	>	private static final int ONE_TOTAL          = 1 << TOTAL_COUNT_SHIFT;
561
562		/**
563	<	* Adds delta (which may be negative) to running count.  This must
564	<	* be called before (with negative arg) and after (with positive)
242	<	* any managed synchronization (i.e., mainly, joins).
243	<	*
244	<	* @param delta the number to add
563	>	* The target parallelism level.
564	>	* Accessed directly by ForkJoinWorkerThreads.
565		*/
566	<	final void updateRunningCount(int delta) {
247	<	int s;
248	<	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
249	<	}
566	>	final int parallelism;
567
568		/**
569	<	* Adds delta (which may be negative) to both total and running
570	<	* count.  This must be called upon creation and termination of
254	<	* worker threads.
255	<	*
256	<	* @param delta the number to add
569	>	* True if use local fifo, not default lifo, for local polling
570	>	* Read by, and replicated by ForkJoinWorkerThreads
571		*/
572	<	private void updateWorkerCount(int delta) {
259	<	int d = delta + (delta << 16); // add to both lo and hi parts
260	<	int s;
261	<	do {} while (!casWorkerCounts(s = workerCounts, s + d));
262	<	}
572	>	final boolean locallyFifo;
573
574		/**
575	<	* Lifecycle control. High word contains runState, low word
576	<	* contains the number of workers that are (probably) executing
267	<	* tasks. This value is atomically incremented before a worker
268	<	* gets a task to run, and decremented when worker has no tasks
269	<	* and cannot find any. These two fields are bundled together to
270	<	* support correct termination triggering.  Note: activeCount
271	<	* CAS'es cheat by assuming active count is in low word, so need
272	<	* to be modified if this changes
575	>	* The uncaught exception handler used when any worker abruptly
576	>	* terminates.
577		*/
578	<	private volatile int runControl;
578	>	private final Thread.UncaughtExceptionHandler ueh;
579
580	<	// RunState values. Order among values matters
581	<	private static final int RUNNING     = 0;
582	<	private static final int SHUTDOWN    = 1;
583	<	private static final int TERMINATING = 2;
280	<	private static final int TERMINATED  = 3;
580	>	/**
581	>	* Pool number, just for assigning useful names to worker threads
582	>	*/
583	>	private final int poolNumber;
584
585	<	private static int runStateOf(int c)             { return c >>> 16; }
586	<	private static int activeCountOf(int c)          { return c & shortMask; }
284	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
585	>	// Utilities for CASing fields. Note that most of these
586	>	// are usually manually inlined by callers
587
588		/**
589	<	* Tries incrementing active count; fails on contention.
288	<	* Called by workers before/during executing tasks.
289	<	*
290	<	* @return true on success
589	>	* Increments running count part of workerCounts
590		*/
591	<	final boolean tryIncrementActiveCount() {
592	<	int c = runControl;
593	<	return casRunControl(c, c+1);
591	>	final void incrementRunningCount() {
592	>	int c;
593	>	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
594	>	c = workerCounts,
595	>	c + ONE_RUNNING));
596		}
597
598		/**
599	<	* Tries decrementing active count; fails on contention.
299	<	* Possibly triggers termination on success.
300	<	* Called by workers when they can't find tasks.
301	<	*
302	<	* @return true on success
599	>	* Tries to decrement running count unless already zero
600		*/
601	<	final boolean tryDecrementActiveCount() {
602	<	int c = runControl;
603	<	int nextc = c - 1;
307	<	if (!casRunControl(c, nextc))
601	>	final boolean tryDecrementRunningCount() {
602	>	int wc = workerCounts;
603	>	if ((wc & RUNNING_COUNT_MASK) == 0)
604		return false;
605	<	if (canTerminateOnShutdown(nextc))
606	<	terminateOnShutdown();
311	<	return true;
605	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
606	>	wc, wc - ONE_RUNNING);
607		}
608
609		/**
610	<	* Returns {@code true} if argument represents zero active count
611	<	* and nonzero runstate, which is the triggering condition for
612	<	* terminating on shutdown.
610	>	* Forces decrement of encoded workerCounts, awaiting nonzero if
611	>	* (rarely) necessary when other count updates lag.
612	>	*
613	>	* @param dr -- either zero or ONE_RUNNING
614	>	* @param dt -- either zero or ONE_TOTAL
615		*/
616	<	private static boolean canTerminateOnShutdown(int c) {
617	<	// i.e. least bit is nonzero runState bit
618	<	return ((c & -c) >>> 16) != 0;
616	>	private void decrementWorkerCounts(int dr, int dt) {
617	>	for (;;) {
618	>	int wc = workerCounts;
619	>	if ((wc & RUNNING_COUNT_MASK)  - dr < 0 ||
620	>	(wc >>> TOTAL_COUNT_SHIFT) - dt < 0) {
621	>	if ((runState & TERMINATED) != 0)
622	>	return; // lagging termination on a backout
623	>	Thread.yield();
624	>	}
625	>	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
626	>	wc, wc - (dr + dt)))
627	>	return;
628	>	}
629		}
630
631		/**
632	<	* Transition run state to at least the given state. Return true
633	<	* if not already at least given state.
632	>	* Tries decrementing active count; fails on contention.
633	>	* Called when workers cannot find tasks to run.
634		*/
635	<	private boolean transitionRunStateTo(int state) {
635	>	final boolean tryDecrementActiveCount() {
636	>	int c;
637	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
638	>	c = runState, c - 1);
639	>	}
640	>
641	>	/**
642	>	* Advances to at least the given level. Returns true if not
643	>	* already in at least the given level.
644	>	*/
645	>	private boolean advanceRunLevel(int level) {
646		for (;;) {
647	<	int c = runControl;
648	<	if (runStateOf(c) >= state)
647	>	int s = runState;
648	>	if ((s & level) != 0)
649		return false;
650	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
650	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level))
651		return true;
652		}
653		}
654
655	+	// workers array maintenance
656	+
657		/**
658	<	* Controls whether to add spares to maintain parallelism
658	>	* Records and returns a workers array index for new worker.
659		*/
660	<	private volatile boolean maintainsParallelism;
660	>	private int recordWorker(ForkJoinWorkerThread w) {
661	>	// Try using slot totalCount-1. If not available, scan and/or resize
662	>	int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1;
663	>	final ReentrantLock lock = this.workerLock;
664	>	lock.lock();
665	>	try {
666	>	ForkJoinWorkerThread[] ws = workers;
667	>	int n = ws.length;
668	>	if (k < 0 || k >= n || ws[k] != null) {
669	>	for (k = 0; k < n && ws[k] != null; ++k)
670	>	;
671	>	if (k == n)
672	>	ws = Arrays.copyOf(ws, n << 1);
673	>	}
674	>	ws[k] = w;
675	>	workers = ws; // volatile array write ensures slot visibility
676	>	} finally {
677	>	lock.unlock();
678	>	}
679	>	return k;
680	>	}
681
682	<	// Constructors
682	>	/**
683	>	* Nulls out record of worker in workers array.
684	>	*/
685	>	private void forgetWorker(ForkJoinWorkerThread w) {
686	>	int idx = w.poolIndex;
687	>	// Locking helps method recordWorker avoid unnecessary expansion
688	>	final ReentrantLock lock = this.workerLock;
689	>	lock.lock();
690	>	try {
691	>	ForkJoinWorkerThread[] ws = workers;
692	>	if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify
693	>	ws[idx] = null;
694	>	} finally {
695	>	lock.unlock();
696	>	}
697	>	}
698
699		/**
700	<	* Creates a {@code ForkJoinPool} with a pool size equal to the
701	<	* number of processors available on the system, using the
702	<	* {@linkplain #defaultForkJoinWorkerThreadFactory default thread factory}.
700	>	* Final callback from terminating worker.  Removes record of
701	>	* worker from array, and adjusts counts. If pool is shutting
702	>	* down, tries to complete termination.
703		*
704	<	* @throws SecurityException if a security manager exists and
351	<	*         the caller is not permitted to modify threads
352	<	*         because it does not hold {@link
353	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
704	>	* @param w the worker
705		*/
706	<	public ForkJoinPool() {
707	<	this(Runtime.getRuntime().availableProcessors(),
708	<	defaultForkJoinWorkerThreadFactory);
706	>	final void workerTerminated(ForkJoinWorkerThread w) {
707	>	forgetWorker(w);
708	>	decrementWorkerCounts(w.isTrimmed()? 0 : ONE_RUNNING, ONE_TOTAL);
709	>	while (w.stealCount != 0) // collect final count
710	>	tryAccumulateStealCount(w);
711	>	tryTerminate(false);
712		}
713
714	+	// Waiting for and signalling events
715	+
716		/**
717	<	* Creates a {@code ForkJoinPool} with the indicated parallelism level
718	<	* threads and using the
719	<	* {@linkplain #defaultForkJoinWorkerThreadFactory default thread factory}.
720	<	*
365	<	* @param parallelism the number of worker threads
366	<	* @throws IllegalArgumentException if parallelism less than or
367	<	* equal to zero
368	<	* @throws SecurityException if a security manager exists and
369	<	*         the caller is not permitted to modify threads
370	<	*         because it does not hold {@link
371	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
717	>	* Releases workers blocked on a count not equal to current count.
718	>	* Normally called after precheck that eventWaiters isn't zero to
719	>	* avoid wasted array checks. Gives up upon a change in count or
720	>	* upon releasing two workers, letting others take over.
721		*/
722	<	public ForkJoinPool(int parallelism) {
723	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
722	>	private void releaseEventWaiters() {
723	>	ForkJoinWorkerThread[] ws = workers;
724	>	int n = ws.length;
725	>	long h = eventWaiters;
726	>	int ec = eventCount;
727	>	boolean releasedOne = false;
728	>	ForkJoinWorkerThread w; int id;
729	>	while ((id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 &&
730	>	(int)(h >>> EVENT_COUNT_SHIFT) != ec &&
731	>	id < n && (w = ws[id]) != null) {
732	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
733	>	h,  w.nextWaiter)) {
734	>	LockSupport.unpark(w);
735	>	if (releasedOne) // exit on second release
736	>	break;
737	>	releasedOne = true;
738	>	}
739	>	if (eventCount != ec)
740	>	break;
741	>	h = eventWaiters;
742	>	}
743		}
744
745		/**
746	<	* Creates a {@code ForkJoinPool} with parallelism equal to the
747	<	* number of processors available on the system and using the
380	<	* given thread factory.
381	<	*
382	<	* @param factory the factory for creating new threads
383	<	* @throws NullPointerException if factory is null
384	<	* @throws SecurityException if a security manager exists and
385	<	*         the caller is not permitted to modify threads
386	<	*         because it does not hold {@link
387	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
746	>	* Tries to advance eventCount and releases waiters. Called only
747	>	* from workers.
748		*/
749	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
750	<	this(Runtime.getRuntime().availableProcessors(), factory);
749	>	final void signalWork() {
750	>	int c; // try to increment event count -- CAS failure OK
751	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
752	>	if (eventWaiters != 0L)
753	>	releaseEventWaiters();
754		}
755
756		/**
757	<	* Creates a {@code ForkJoinPool} with the given parallelism and
758	<	* thread factory.
757	>	* Adds the given worker to event queue and blocks until
758	>	* terminating or event count advances from the given value
759		*
760	<	* @param parallelism the targeted number of worker threads
761	<	* @param factory the factory for creating new threads
399	<	* @throws IllegalArgumentException if parallelism less than or
400	<	* equal to zero, or greater than implementation limit
401	<	* @throws NullPointerException if factory is null
402	<	* @throws SecurityException if a security manager exists and
403	<	*         the caller is not permitted to modify threads
404	<	*         because it does not hold {@link
405	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
760	>	* @param w the calling worker thread
761	>	* @param ec the count
762		*/
763	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
764	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
765	<	throw new IllegalArgumentException();
766	<	if (factory == null)
767	<	throw new NullPointerException();
768	<	checkPermission();
769	<	this.factory = factory;
770	<	this.parallelism = parallelism;
771	<	this.maxPoolSize = MAX_THREADS;
772	<	this.maintainsParallelism = true;
773	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
774	<	this.workerLock = new ReentrantLock();
775	<	this.termination = workerLock.newCondition();
420	<	this.stealCount = new AtomicLong();
421	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
422	<	// worker array and workers are lazily constructed
763	>	private void eventSync(ForkJoinWorkerThread w, int ec) {
764	>	long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1));
765	>	long h;
766	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
767	>	(((int)((h = eventWaiters) & WAITER_ID_MASK)) == 0 ||
768	>	(int)(h >>> EVENT_COUNT_SHIFT) == ec) &&
769	>	eventCount == ec) {
770	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
771	>	w.nextWaiter = h, nh)) {
772	>	awaitEvent(w, ec);
773	>	break;
774	>	}
775	>	}
776		}
777
778		/**
779	<	* Creates a new worker thread using factory.
779	>	* Blocks the given worker (that has already been entered as an
780	>	* event waiter) until terminating or event count advances from
781	>	* the given value. The oldest (first) waiter uses a timed wait to
782	>	* occasionally one-by-one shrink the number of workers (to a
783	>	* minimum of one) if the pool has not been used for extended
784	>	* periods.
785		*
786	<	* @param index the index to assign worker
787	<	* @return new worker, or null if factory failed
786	>	* @param w the calling worker thread
787	>	* @param ec the count
788		*/
789	<	private ForkJoinWorkerThread createWorker(int index) {
790	<	Thread.UncaughtExceptionHandler h = ueh;
791	<	ForkJoinWorkerThread w = factory.newThread(this);
792	<	if (w != null) {
793	<	w.poolIndex = index;
794	<	w.setDaemon(true);
795	<	w.setAsyncMode(locallyFifo);
796	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
797	<	if (h != null)
798	<	w.setUncaughtExceptionHandler(h);
789	>	private void awaitEvent(ForkJoinWorkerThread w, int ec) {
790	>	while (eventCount == ec) {
791	>	if (tryAccumulateStealCount(w)) { // transfer while idle
792	>	boolean untimed = (w.nextWaiter != 0L ||
793	>	(workerCounts & RUNNING_COUNT_MASK) <= 1);
794	>	long startTime = untimed? 0 : System.nanoTime();
795	>	Thread.interrupted();         // clear/ignore interrupt
796	>	if (eventCount != ec || w.isTerminating())
797	>	break;                    // recheck after clear
798	>	if (untimed)
799	>	LockSupport.park(w);
800	>	else {
801	>	LockSupport.parkNanos(w, SHRINK_RATE_NANOS);
802	>	if (eventCount != ec || w.isTerminating())
803	>	break;
804	>	if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS)
805	>	tryShutdownUnusedWorker(ec);
806	>	}
807	>	}
808		}
442	–	return w;
809		}
810
811	+	// Maintaining parallelism
812	+
813		/**
814	<	* Returns a good size for worker array given pool size.
447	<	* Currently requires size to be a power of two.
814	>	* Pushes worker onto the spare stack.
815		*/
816	<	private static int arraySizeFor(int poolSize) {
817	<	return (poolSize <= 1) ? 1 :
818	<	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
816	>	final void pushSpare(ForkJoinWorkerThread w) {
817	>	int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1);
818	>	do {} while (!UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
819	>	w.nextSpare = spareWaiters,ns));
820		}
821
822		/**
823	<	* Creates or resizes array if necessary to hold newLength.
824	<	* Call only under exclusion.
457	<	*
458	<	* @return the array
823	>	* Tries (once) to resume a spare if the number of running
824	>	* threads is less than target.
825		*/
826	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
826	>	private void tryResumeSpare() {
827	>	int sw, id;
828		ForkJoinWorkerThread[] ws = workers;
829	<	if (ws == null)
830	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
831	<	else if (newLength > ws.length)
832	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
833	<	else
834	<	return ws;
829	>	int n = ws.length;
830	>	ForkJoinWorkerThread w;
831	>	if ((sw = spareWaiters) != 0 &&
832	>	(id = (sw & SPARE_ID_MASK) - 1) >= 0 &&
833	>	id < n && (w = ws[id]) != null &&
834	>	(workerCounts & RUNNING_COUNT_MASK) < parallelism &&
835	>	spareWaiters == sw &&
836	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
837	>	sw, w.nextSpare)) {
838	>	int c; // increment running count before resume
839	>	do {} while (!UNSAFE.compareAndSwapInt
840	>	(this, workerCountsOffset,
841	>	c = workerCounts, c + ONE_RUNNING));
842	>	if (w.tryUnsuspend())
843	>	LockSupport.unpark(w);
844	>	else   // back out if w was shutdown
845	>	decrementWorkerCounts(ONE_RUNNING, 0);
846	>	}
847		}
848
849		/**
850	<	* Tries to shrink workers into smaller array after one or more terminate.
851	<	*/
852	<	private void tryShrinkWorkerArray() {
853	<	ForkJoinWorkerThread[] ws = workers;
854	<	if (ws != null) {
855	<	int len = ws.length;
856	<	int last = len - 1;
857	<	while (last >= 0 && ws[last] == null)
858	<	--last;
859	<	int newLength = arraySizeFor(last+1);
860	<	if (newLength < len)
861	<	workers = Arrays.copyOf(ws, newLength);
850	>	* Tries to increase the number of running workers if below target
851	>	* parallelism: If a spare exists tries to resume it via
852	>	* tryResumeSpare.  Otherwise, if not enough total workers or all
853	>	* existing workers are busy, adds a new worker. In all cases also
854	>	* helps wake up releasable workers waiting for work.
855	>	*/
856	>	private void helpMaintainParallelism() {
857	>	int pc = parallelism;
858	>	int wc, rs, tc;
859	>	while (((wc = workerCounts) & RUNNING_COUNT_MASK) < pc &&
860	>	(rs = runState) < TERMINATING) {
861	>	if (spareWaiters != 0)
862	>	tryResumeSpare();
863	>	else if ((tc = wc >>> TOTAL_COUNT_SHIFT) >= MAX_WORKERS ||
864	>	(tc >= pc && (rs & ACTIVE_COUNT_MASK) != tc))
865	>	break;   // enough total
866	>	else if (runState == rs && workerCounts == wc &&
867	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
868	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
869	>	ForkJoinWorkerThread w = null;
870	>	Throwable fail = null;
871	>	try {
872	>	w = factory.newThread(this);
873	>	} catch (Throwable ex) {
874	>	fail = ex;
875	>	}
876	>	if (w == null) { // null or exceptional factory return
877	>	decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL);
878	>	tryTerminate(false); // handle failure during shutdown
879	>	// If originating from an external caller,
880	>	// propagate exception, else ignore
881	>	if (fail != null && runState < TERMINATING &&
882	>	!(Thread.currentThread() instanceof
883	>	ForkJoinWorkerThread))
884	>	UNSAFE.throwException(fail);
885	>	break;
886	>	}
887	>	w.start(recordWorker(w), ueh);
888	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) >= pc) {
889	>	int c; // advance event count
890	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
891	>	c = eventCount, c+1);
892	>	break; // add at most one unless total below target
893	>	}
894	>	}
895		}
896	+	if (eventWaiters != 0L)
897	+	releaseEventWaiters();
898		}
899
900		/**
901	<	* Initializes workers if necessary.
901	>	* Callback from the oldest waiter in awaitEvent waking up after a
902	>	* period of non-use. If all workers are idle, tries (once) to
903	>	* shutdown an event waiter or a spare, if one exists. Note that
904	>	* we don't need CAS or locks here because the method is called
905	>	* only from one thread occasionally waking (and even misfires are
906	>	* OK). Note that until the shutdown worker fully terminates,
907	>	* workerCounts will overestimate total count, which is tolerable.
908	>	*
909	>	* @param ec the event count waited on by caller (to abort
910	>	* attempt if count has since changed).
911		*/
912	<	final void ensureWorkerInitialization() {
913	<	ForkJoinWorkerThread[] ws = workers;
914	<	if (ws == null) {
915	<	final ReentrantLock lock = this.workerLock;
916	<	lock.lock();
917	<	try {
918	<	ws = workers;
919	<	if (ws == null) {
920	<	int ps = parallelism;
921	<	ws = ensureWorkerArrayCapacity(ps);
922	<	for (int i = 0; i < ps; ++i) {
923	<	ForkJoinWorkerThread w = createWorker(i);
924	<	if (w != null) {
925	<	ws[i] = w;
926	<	w.start();
927	<	updateWorkerCount(1);
928	<	}
929	<	}
912	>	private void tryShutdownUnusedWorker(int ec) {
913	>	if (runState == 0 && eventCount == ec) { // only trigger if all idle
914	>	ForkJoinWorkerThread[] ws = workers;
915	>	int n = ws.length;
916	>	ForkJoinWorkerThread w = null;
917	>	boolean shutdown = false;
918	>	int sw;
919	>	long h;
920	>	if ((sw = spareWaiters) != 0) { // prefer killing spares
921	>	int id = (sw & SPARE_ID_MASK) - 1;
922	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
923	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
924	>	sw, w.nextSpare))
925	>	shutdown = true;
926	>	}
927	>	else if ((h = eventWaiters) != 0L) {
928	>	long nh;
929	>	int id = ((int)(h & WAITER_ID_MASK)) - 1;
930	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
931	>	(nh = w.nextWaiter) != 0L && // keep at least one worker
932	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh))
933	>	shutdown = true;
934	>	}
935	>	if (w != null && shutdown) {
936	>	w.shutdown();
937	>	LockSupport.unpark(w);
938	>	}
939	>	}
940	>	releaseEventWaiters(); // in case of interference
941	>	}
942	>
943	>	/**
944	>	* Callback from workers invoked upon each top-level action (i.e.,
945	>	* stealing a task or taking a submission and running it).
946	>	* Performs one or more of the following:
947	>	*
948	>	* 1. If the worker is active and either did not run a task
949	>	*    or there are too many workers, try to set its active status
950	>	*    to inactive and update activeCount. On contention, we may
951	>	*    try again in this or a subsequent call.
952	>	*
953	>	* 2. If not enough total workers, help create some.
954	>	*
955	>	* 3. If there are too many running workers, suspend this worker
956	>	*    (first forcing inactive if necessary).  If it is not needed,
957	>	*    it may be shutdown while suspended (via
958	>	*    tryShutdownUnusedWorker).  Otherwise, upon resume it
959	>	*    rechecks running thread count and need for event sync.
960	>	*
961	>	* 4. If worker did not run a task, await the next task event via
962	>	*    eventSync if necessary (first forcing inactivation), upon
963	>	*    which the worker may be shutdown via
964	>	*    tryShutdownUnusedWorker.  Otherwise, help release any
965	>	*    existing event waiters that are now releasable,
966	>	*
967	>	* @param w the worker
968	>	* @param ran true if worker ran a task since last call to this method
969	>	*/
970	>	final void preStep(ForkJoinWorkerThread w, boolean ran) {
971	>	int wec = w.lastEventCount;
972	>	boolean active = w.active;
973	>	boolean inactivate = false;
974	>	int pc = parallelism;
975	>	while (w.runState == 0) {
976	>	int rs = runState;
977	>	if (rs >= TERMINATING) { // propagate shutdown
978	>	w.shutdown();
979	>	break;
980	>	}
981	>	if ((inactivate || (active && (rs & ACTIVE_COUNT_MASK) >= pc)) &&
982	>	UNSAFE.compareAndSwapInt(this, runStateOffset, rs, rs - 1))
983	>	inactivate = active = w.active = false;
984	>	int wc = workerCounts;
985	>	if ((wc & RUNNING_COUNT_MASK) > pc) {
986	>	if (!(inactivate |= active) && // must inactivate to suspend
987	>	workerCounts == wc &&      // try to suspend as spare
988	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
989	>	wc, wc - ONE_RUNNING))
990	>	w.suspendAsSpare();
991	>	}
992	>	else if ((wc >>> TOTAL_COUNT_SHIFT) < pc)
993	>	helpMaintainParallelism();     // not enough workers
994	>	else if (!ran) {
995	>	long h = eventWaiters;
996	>	int ec = eventCount;
997	>	if (h != 0L && (int)(h >>> EVENT_COUNT_SHIFT) != ec)
998	>	releaseEventWaiters();     // release others before waiting
999	>	else if (ec != wec) {
1000	>	w.lastEventCount = ec;     // no need to wait
1001	>	break;
1002		}
1003	<	} finally {
1004	<	lock.unlock();
1003	>	else if (!(inactivate |= active))
1004	>	eventSync(w, wec);         // must inactivate before sync
1005		}
1006	+	else
1007	+	break;
1008		}
1009		}
1010
1011		/**
1012	<	* Worker creation and startup for threads added via setParallelism.
1012	>	* Helps and/or blocks awaiting join of the given task.
1013	>	* See above for explanation.
1014	>	*
1015	>	* @param joinMe the task to join
1016	>	* @param worker the current worker thread
1017		*/
1018	<	private void createAndStartAddedWorkers() {
1019	<	resumeAllSpares();  // Allow spares to convert to nonspare
1020	<	int ps = parallelism;
1021	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1022	<	int len = ws.length;
1023	<	// Sweep through slots, to keep lowest indices most populated
1024	<	int k = 0;
1025	<	while (k < len) {
1026	<	if (ws[k] != null) {
1027	<	++k;
1028	<	continue;
1018	>	final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker) {
1019	>	int retries = 2 + (parallelism >> 2); // #helpJoins before blocking
1020	>	while (joinMe.status >= 0) {
1021	>	int wc;
1022	>	worker.helpJoinTask(joinMe);
1023	>	if (joinMe.status < 0)
1024	>	break;
1025	>	else if (retries > 0)
1026	>	--retries;
1027	>	else if (((wc = workerCounts) & RUNNING_COUNT_MASK) != 0 &&
1028	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1029	>	wc, wc - ONE_RUNNING)) {
1030	>	int stat, c; long h;
1031	>	while ((stat = joinMe.status) >= 0 &&
1032	>	(h = eventWaiters) != 0L && // help release others
1033	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1034	>	releaseEventWaiters();
1035	>	if (stat >= 0 &&
1036	>	((workerCounts & RUNNING_COUNT_MASK) == 0 ||
1037	>	(stat =
1038	>	joinMe.internalAwaitDone(JOIN_TIMEOUT_MILLIS)) >= 0))
1039	>	helpMaintainParallelism(); // timeout or no running workers
1040	>	do {} while (!UNSAFE.compareAndSwapInt
1041	>	(this, workerCountsOffset,
1042	>	c = workerCounts, c + ONE_RUNNING));
1043	>	if (stat < 0)
1044	>	break;   // else restart
1045		}
1046	<	int s = workerCounts;
1047	<	int tc = totalCountOf(s);
1048	<	int rc = runningCountOf(s);
1049	<	if (rc >= ps || tc >= ps)
1046	>	}
1047	>	}
1048	>
1049	>	/**
1050	>	* Same idea as awaitJoin, but no helping, retries, or timeouts.
1051	>	*/
1052	>	final void awaitBlocker(ManagedBlocker blocker)
1053	>	throws InterruptedException {
1054	>	while (!blocker.isReleasable()) {
1055	>	int wc = workerCounts;
1056	>	if ((wc & RUNNING_COUNT_MASK) != 0 &&
1057	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1058	>	wc, wc - ONE_RUNNING)) {
1059	>	try {
1060	>	while (!blocker.isReleasable()) {
1061	>	long h = eventWaiters;
1062	>	if (h != 0L &&
1063	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1064	>	releaseEventWaiters();
1065	>	else if ((workerCounts & RUNNING_COUNT_MASK) == 0 &&
1066	>	runState < TERMINATING)
1067	>	helpMaintainParallelism();
1068	>	else if (blocker.block())
1069	>	break;
1070	>	}
1071	>	} finally {
1072	>	int c;
1073	>	do {} while (!UNSAFE.compareAndSwapInt
1074	>	(this, workerCountsOffset,
1075	>	c = workerCounts, c + ONE_RUNNING));
1076	>	}
1077		break;
1078	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
1079	<	ForkJoinWorkerThread w = createWorker(k);
1078	>	}
1079	>	}
1080	>	}
1081	>
1082	>	/**
1083	>	* Possibly initiates and/or completes termination.
1084	>	*
1085	>	* @param now if true, unconditionally terminate, else only
1086	>	* if shutdown and empty queue and no active workers
1087	>	* @return true if now terminating or terminated
1088	>	*/
1089	>	private boolean tryTerminate(boolean now) {
1090	>	if (now)
1091	>	advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN
1092	>	else if (runState < SHUTDOWN ||
1093	>	!submissionQueue.isEmpty() ||
1094	>	(runState & ACTIVE_COUNT_MASK) != 0)
1095	>	return false;
1096	>
1097	>	if (advanceRunLevel(TERMINATING))
1098	>	startTerminating();
1099	>
1100	>	// Finish now if all threads terminated; else in some subsequent call
1101	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1102	>	advanceRunLevel(TERMINATED);
1103	>	termination.arrive();
1104	>	}
1105	>	return true;
1106	>	}
1107	>
1108	>
1109	>	/**
1110	>	* Actions on transition to TERMINATING
1111	>	*
1112	>	* Runs up to four passes through workers: (0) shutting down each
1113	>	* (without waking up if parked) to quickly spread notifications
1114	>	* without unnecessary bouncing around event queues etc (1) wake
1115	>	* up and help cancel tasks (2) interrupt (3) mop up races with
1116	>	* interrupted workers
1117	>	*/
1118	>	private void startTerminating() {
1119	>	cancelSubmissions();
1120	>	for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) {
1121	>	int c; // advance event count
1122	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
1123	>	c = eventCount, c+1);
1124	>	eventWaiters = 0L; // clobber lists
1125	>	spareWaiters = 0;
1126	>	for (ForkJoinWorkerThread w : workers) {
1127		if (w != null) {
1128	<	ws[k++] = w;
1129	<	w.start();
1130	<	}
1131	<	else {
1132	<	updateWorkerCount(-1); // back out on failed creation
1133	<	break;
1128	>	w.shutdown();
1129	>	if (passes > 0 && !w.isTerminated()) {
1130	>	w.cancelTasks();
1131	>	LockSupport.unpark(w);
1132	>	if (passes > 1 && !w.isInterrupted()) {
1133	>	try {
1134	>	w.interrupt();
1135	>	} catch (SecurityException ignore) {
1136	>	}
1137	>	}
1138	>	}
1139		}
1140		}
1141		}
1142		}
1143
1144	+	/**
1145	+	* Clears out and cancels submissions, ignoring exceptions.
1146	+	*/
1147	+	private void cancelSubmissions() {
1148	+	ForkJoinTask<?> task;
1149	+	while ((task = submissionQueue.poll()) != null) {
1150	+	try {
1151	+	task.cancel(false);
1152	+	} catch (Throwable ignore) {
1153	+	}
1154	+	}
1155	+	}
1156	+
1157	+	// misc support for ForkJoinWorkerThread
1158	+
1159	+	/**
1160	+	* Returns pool number.
1161	+	*/
1162	+	final int getPoolNumber() {
1163	+	return poolNumber;
1164	+	}
1165	+
1166	+	/**
1167	+	* Tries to accumulate steal count from a worker, clearing
1168	+	* the worker's value if successful.
1169	+	*
1170	+	* @return true if worker steal count now zero
1171	+	*/
1172	+	final boolean tryAccumulateStealCount(ForkJoinWorkerThread w) {
1173	+	int sc = w.stealCount;
1174	+	long c = stealCount;
1175	+	// CAS even if zero, for fence effects
1176	+	if (UNSAFE.compareAndSwapLong(this, stealCountOffset, c, c + sc)) {
1177	+	if (sc != 0)
1178	+	w.stealCount = 0;
1179	+	return true;
1180	+	}
1181	+	return sc == 0;
1182	+	}
1183	+
1184	+	/**
1185	+	* Returns the approximate (non-atomic) number of idle threads per
1186	+	* active thread.
1187	+	*/
1188	+	final int idlePerActive() {
1189	+	int pc = parallelism; // use parallelism, not rc
1190	+	int ac = runState;    // no mask -- artificially boosts during shutdown
1191	+	// Use exact results for small values, saturate past 4
1192	+	return ((pc <= ac) ? 0 :
1193	+	(pc >>> 1 <= ac) ? 1 :
1194	+	(pc >>> 2 <= ac) ? 3 :
1195	+	pc >>> 3);
1196	+	}
1197	+
1198	+	// Public and protected methods
1199	+
1200	+	// Constructors
1201	+
1202	+	/**
1203	+	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1204	+	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1205	+	* #defaultForkJoinWorkerThreadFactory default thread factory},
1206	+	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1207	+	*
1208	+	* @throws SecurityException if a security manager exists and
1209	+	*         the caller is not permitted to modify threads
1210	+	*         because it does not hold {@link
1211	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1212	+	*/
1213	+	public ForkJoinPool() {
1214	+	this(Runtime.getRuntime().availableProcessors(),
1215	+	defaultForkJoinWorkerThreadFactory, null, false);
1216	+	}
1217	+
1218	+	/**
1219	+	* Creates a {@code ForkJoinPool} with the indicated parallelism
1220	+	* level, the {@linkplain
1221	+	* #defaultForkJoinWorkerThreadFactory default thread factory},
1222	+	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1223	+	*
1224	+	* @param parallelism the parallelism level
1225	+	* @throws IllegalArgumentException if parallelism less than or
1226	+	*         equal to zero, or greater than implementation limit
1227	+	* @throws SecurityException if a security manager exists and
1228	+	*         the caller is not permitted to modify threads
1229	+	*         because it does not hold {@link
1230	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1231	+	*/
1232	+	public ForkJoinPool(int parallelism) {
1233	+	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1234	+	}
1235	+
1236	+	/**
1237	+	* Creates a {@code ForkJoinPool} with the given parameters.
1238	+	*
1239	+	* @param parallelism the parallelism level. For default value,
1240	+	* use {@link java.lang.Runtime#availableProcessors}.
1241	+	* @param factory the factory for creating new threads. For default value,
1242	+	* use {@link #defaultForkJoinWorkerThreadFactory}.
1243	+	* @param handler the handler for internal worker threads that
1244	+	* terminate due to unrecoverable errors encountered while executing
1245	+	* tasks. For default value, use {@code null}.
1246	+	* @param asyncMode if true,
1247	+	* establishes local first-in-first-out scheduling mode for forked
1248	+	* tasks that are never joined. This mode may be more appropriate
1249	+	* than default locally stack-based mode in applications in which
1250	+	* worker threads only process event-style asynchronous tasks.
1251	+	* For default value, use {@code false}.
1252	+	* @throws IllegalArgumentException if parallelism less than or
1253	+	*         equal to zero, or greater than implementation limit
1254	+	* @throws NullPointerException if the factory is null
1255	+	* @throws SecurityException if a security manager exists and
1256	+	*         the caller is not permitted to modify threads
1257	+	*         because it does not hold {@link
1258	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1259	+	*/
1260	+	public ForkJoinPool(int parallelism,
1261	+	ForkJoinWorkerThreadFactory factory,
1262	+	Thread.UncaughtExceptionHandler handler,
1263	+	boolean asyncMode) {
1264	+	checkPermission();
1265	+	if (factory == null)
1266	+	throw new NullPointerException();
1267	+	if (parallelism <= 0 || parallelism > MAX_WORKERS)
1268	+	throw new IllegalArgumentException();
1269	+	this.parallelism = parallelism;
1270	+	this.factory = factory;
1271	+	this.ueh = handler;
1272	+	this.locallyFifo = asyncMode;
1273	+	int arraySize = initialArraySizeFor(parallelism);
1274	+	this.workers = new ForkJoinWorkerThread[arraySize];
1275	+	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
1276	+	this.workerLock = new ReentrantLock();
1277	+	this.termination = new Phaser(1);
1278	+	this.poolNumber = poolNumberGenerator.incrementAndGet();
1279	+	}
1280	+
1281	+	/**
1282	+	* Returns initial power of two size for workers array.
1283	+	* @param pc the initial parallelism level
1284	+	*/
1285	+	private static int initialArraySizeFor(int pc) {
1286	+	// If possible, initially allocate enough space for one spare
1287	+	int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS;
1288	+	// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16)
1289	+	size |= size >>> 1;
1290	+	size |= size >>> 2;
1291	+	size |= size >>> 4;
1292	+	size |= size >>> 8;
1293	+	return size + 1;
1294	+	}
1295	+
1296		// Execution methods
1297
1298		/**
#	Line 553 | Line 1301 | public class ForkJoinPool extends Abstra
1301		private <T> void doSubmit(ForkJoinTask<T> task) {
1302		if (task == null)
1303		throw new NullPointerException();
1304	<	if (isShutdown())
1304	>	if (runState >= SHUTDOWN)
1305		throw new RejectedExecutionException();
558	–	if (workers == null)
559	–	ensureWorkerInitialization();
1306		submissionQueue.offer(task);
1307	<	signalIdleWorkers();
1307	>	int c; // try to increment event count -- CAS failure OK
1308	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
1309	>	helpMaintainParallelism(); // create, start, or resume some workers
1310		}
1311
1312		/**
#	Line 566 | Line 1314 | public class ForkJoinPool extends Abstra
1314		*
1315		* @param task the task
1316		* @return the task's result
1317	<	* @throws NullPointerException if task is null
1318	<	* @throws RejectedExecutionException if pool is shut down
1317	>	* @throws NullPointerException if the task is null
1318	>	* @throws RejectedExecutionException if the task cannot be
1319	>	*         scheduled for execution
1320		*/
1321		public <T> T invoke(ForkJoinTask<T> task) {
1322		doSubmit(task);
#	Line 578 | Line 1327 | public class ForkJoinPool extends Abstra
1327		* Arranges for (asynchronous) execution of the given task.
1328		*
1329		* @param task the task
1330	<	* @throws NullPointerException if task is null
1331	<	* @throws RejectedExecutionException if pool is shut down
1330	>	* @throws NullPointerException if the task is null
1331	>	* @throws RejectedExecutionException if the task cannot be
1332	>	*         scheduled for execution
1333		*/
1334		public void execute(ForkJoinTask<?> task) {
1335		doSubmit(task);
#	Line 587 | Line 1337 | public class ForkJoinPool extends Abstra
1337
1338		// AbstractExecutorService methods
1339
1340	+	/**
1341	+	* @throws NullPointerException if the task is null
1342	+	* @throws RejectedExecutionException if the task cannot be
1343	+	*         scheduled for execution
1344	+	*/
1345		public void execute(Runnable task) {
1346		ForkJoinTask<?> job;
1347		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
#	Line 596 | Line 1351 | public class ForkJoinPool extends Abstra
1351		doSubmit(job);
1352		}
1353
1354	+	/**
1355	+	* Submits a ForkJoinTask for execution.
1356	+	*
1357	+	* @param task the task to submit
1358	+	* @return the task
1359	+	* @throws NullPointerException if the task is null
1360	+	* @throws RejectedExecutionException if the task cannot be
1361	+	*         scheduled for execution
1362	+	*/
1363	+	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1364	+	doSubmit(task);
1365	+	return task;
1366	+	}
1367	+
1368	+	/**
1369	+	* @throws NullPointerException if the task is null
1370	+	* @throws RejectedExecutionException if the task cannot be
1371	+	*         scheduled for execution
1372	+	*/
1373		public <T> ForkJoinTask<T> submit(Callable<T> task) {
1374		ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1375		doSubmit(job);
1376		return job;
1377		}
1378
1379	+	/**
1380	+	* @throws NullPointerException if the task is null
1381	+	* @throws RejectedExecutionException if the task cannot be
1382	+	*         scheduled for execution
1383	+	*/
1384		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1385		ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1386		doSubmit(job);
1387		return job;
1388		}
1389
1390	+	/**
1391	+	* @throws NullPointerException if the task is null
1392	+	* @throws RejectedExecutionException if the task cannot be
1393	+	*         scheduled for execution
1394	+	*/
1395		public ForkJoinTask<?> submit(Runnable task) {
1396		ForkJoinTask<?> job;
1397		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
#	Line 619 | Line 1403 | public class ForkJoinPool extends Abstra
1403		}
1404
1405		/**
1406	<	* Submits a ForkJoinTask for execution.
1407	<	*
624	<	* @param task the task to submit
625	<	* @return the task
626	<	* @throws RejectedExecutionException if the task cannot be
627	<	*         scheduled for execution
628	<	* @throws NullPointerException if the task is null
1406	>	* @throws NullPointerException       {@inheritDoc}
1407	>	* @throws RejectedExecutionException {@inheritDoc}
1408		*/
630	–	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
631	–	doSubmit(task);
632	–	return task;
633	–	}
634	–
635	–
1409		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
1410		ArrayList<ForkJoinTask<T>> forkJoinTasks =
1411		new ArrayList<ForkJoinTask<T>>(tasks.size());
#	Line 641 | Line 1414 | public class ForkJoinPool extends Abstra
1414		invoke(new InvokeAll<T>(forkJoinTasks));
1415
1416		@SuppressWarnings({"unchecked", "rawtypes"})
1417	<	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1417	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1418		return futures;
1419		}
1420
#	Line 655 | Line 1428 | public class ForkJoinPool extends Abstra
1428		private static final long serialVersionUID = -7914297376763021607L;
1429		}
1430
658	–	// Configuration and status settings and queries
659	–
1431		/**
1432		* Returns the factory used for constructing new workers.
1433		*
#	Line 673 | Line 1444 | public class ForkJoinPool extends Abstra
1444		* @return the handler, or {@code null} if none
1445		*/
1446		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1447	<	Thread.UncaughtExceptionHandler h;
677	<	final ReentrantLock lock = this.workerLock;
678	<	lock.lock();
679	<	try {
680	<	h = ueh;
681	<	} finally {
682	<	lock.unlock();
683	<	}
684	<	return h;
685	<	}
686	<
687	<	/**
688	<	* Sets the handler for internal worker threads that terminate due
689	<	* to unrecoverable errors encountered while executing tasks.
690	<	* Unless set, the current default or ThreadGroup handler is used
691	<	* as handler.
692	<	*
693	<	* @param h the new handler
694	<	* @return the old handler, or {@code null} if none
695	<	* @throws SecurityException if a security manager exists and
696	<	*         the caller is not permitted to modify threads
697	<	*         because it does not hold {@link
698	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
699	<	*/
700	<	public Thread.UncaughtExceptionHandler
701	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
702	<	checkPermission();
703	<	Thread.UncaughtExceptionHandler old = null;
704	<	final ReentrantLock lock = this.workerLock;
705	<	lock.lock();
706	<	try {
707	<	old = ueh;
708	<	ueh = h;
709	<	ForkJoinWorkerThread[] ws = workers;
710	<	if (ws != null) {
711	<	for (int i = 0; i < ws.length; ++i) {
712	<	ForkJoinWorkerThread w = ws[i];
713	<	if (w != null)
714	<	w.setUncaughtExceptionHandler(h);
715	<	}
716	<	}
717	<	} finally {
718	<	lock.unlock();
719	<	}
720	<	return old;
721	<	}
722	<
723	<
724	<	/**
725	<	* Sets the target parallelism level of this pool.
726	<	*
727	<	* @param parallelism the target parallelism
728	<	* @throws IllegalArgumentException if parallelism less than or
729	<	* equal to zero or greater than maximum size bounds
730	<	* @throws SecurityException if a security manager exists and
731	<	*         the caller is not permitted to modify threads
732	<	*         because it does not hold {@link
733	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
734	<	*/
735	<	public void setParallelism(int parallelism) {
736	<	checkPermission();
737	<	if (parallelism <= 0 || parallelism > maxPoolSize)
738	<	throw new IllegalArgumentException();
739	<	final ReentrantLock lock = this.workerLock;
740	<	lock.lock();
741	<	try {
742	<	if (!isTerminating()) {
743	<	int p = this.parallelism;
744	<	this.parallelism = parallelism;
745	<	if (parallelism > p)
746	<	createAndStartAddedWorkers();
747	<	else
748	<	trimSpares();
749	<	}
750	<	} finally {
751	<	lock.unlock();
752	<	}
753	<	signalIdleWorkers();
1447	>	return ueh;
1448		}
1449
1450		/**
1451	<	* Returns the targeted number of worker threads in this pool.
1451	>	* Returns the targeted parallelism level of this pool.
1452		*
1453	<	* @return the targeted number of worker threads in this pool
1453	>	* @return the targeted parallelism level of this pool
1454		*/
1455		public int getParallelism() {
1456		return parallelism;
#	Line 764 | Line 1458 | public class ForkJoinPool extends Abstra
1458
1459		/**
1460		* Returns the number of worker threads that have started but not
1461	<	* yet terminated.  This result returned by this method may differ
1461	>	* yet terminated.  The result returned by this method may differ
1462		* from {@link #getParallelism} when threads are created to
1463		* maintain parallelism when others are cooperatively blocked.
1464		*
1465		* @return the number of worker threads
1466		*/
1467		public int getPoolSize() {
1468	<	return totalCountOf(workerCounts);
775	<	}
776	<
777	<	/**
778	<	* Returns the maximum number of threads allowed to exist in the
779	<	* pool, even if there are insufficient unblocked running threads.
780	<	*
781	<	* @return the maximum
782	<	*/
783	<	public int getMaximumPoolSize() {
784	<	return maxPoolSize;
785	<	}
786	<
787	<	/**
788	<	* Sets the maximum number of threads allowed to exist in the
789	<	* pool, even if there are insufficient unblocked running threads.
790	<	* Setting this value has no effect on current pool size. It
791	<	* controls construction of new threads.
792	<	*
793	<	* @throws IllegalArgumentException if negative or greater than
794	<	* internal implementation limit
795	<	*/
796	<	public void setMaximumPoolSize(int newMax) {
797	<	if (newMax < 0 || newMax > MAX_THREADS)
798	<	throw new IllegalArgumentException();
799	<	maxPoolSize = newMax;
800	<	}
801	<
802	<
803	<	/**
804	<	* Returns {@code true} if this pool dynamically maintains its
805	<	* target parallelism level. If false, new threads are added only
806	<	* to avoid possible starvation.  This setting is by default true.
807	<	*
808	<	* @return {@code true} if maintains parallelism
809	<	*/
810	<	public boolean getMaintainsParallelism() {
811	<	return maintainsParallelism;
812	<	}
813	<
814	<	/**
815	<	* Sets whether this pool dynamically maintains its target
816	<	* parallelism level. If false, new threads are added only to
817	<	* avoid possible starvation.
818	<	*
819	<	* @param enable {@code true} to maintain parallelism
820	<	*/
821	<	public void setMaintainsParallelism(boolean enable) {
822	<	maintainsParallelism = enable;
823	<	}
824	<
825	<	/**
826	<	* Establishes local first-in-first-out scheduling mode for forked
827	<	* tasks that are never joined. This mode may be more appropriate
828	<	* than default locally stack-based mode in applications in which
829	<	* worker threads only process asynchronous tasks.  This method is
830	<	* designed to be invoked only when the pool is quiescent, and
831	<	* typically only before any tasks are submitted. The effects of
832	<	* invocations at other times may be unpredictable.
833	<	*
834	<	* @param async if {@code true}, use locally FIFO scheduling
835	<	* @return the previous mode
836	<	* @see #getAsyncMode
837	<	*/
838	<	public boolean setAsyncMode(boolean async) {
839	<	boolean oldMode = locallyFifo;
840	<	locallyFifo = async;
841	<	ForkJoinWorkerThread[] ws = workers;
842	<	if (ws != null) {
843	<	for (int i = 0; i < ws.length; ++i) {
844	<	ForkJoinWorkerThread t = ws[i];
845	<	if (t != null)
846	<	t.setAsyncMode(async);
847	<	}
848	<	}
849	<	return oldMode;
1468	>	return workerCounts >>> TOTAL_COUNT_SHIFT;
1469		}
1470
1471		/**
#	Line 854 | Line 1473 | public class ForkJoinPool extends Abstra
1473		* scheduling mode for forked tasks that are never joined.
1474		*
1475		* @return {@code true} if this pool uses async mode
857	–	* @see #setAsyncMode
1476		*/
1477		public boolean getAsyncMode() {
1478		return locallyFifo;
#	Line 863 | Line 1481 | public class ForkJoinPool extends Abstra
1481		/**
1482		* Returns an estimate of the number of worker threads that are
1483		* not blocked waiting to join tasks or for other managed
1484	<	* synchronization.
1484	>	* synchronization. This method may overestimate the
1485	>	* number of running threads.
1486		*
1487		* @return the number of worker threads
1488		*/
1489		public int getRunningThreadCount() {
1490	<	return runningCountOf(workerCounts);
1490	>	return workerCounts & RUNNING_COUNT_MASK;
1491		}
1492
1493		/**
#	Line 879 | Line 1498 | public class ForkJoinPool extends Abstra
1498		* @return the number of active threads
1499		*/
1500		public int getActiveThreadCount() {
1501	<	return activeCountOf(runControl);
883	<	}
884	<
885	<	/**
886	<	* Returns an estimate of the number of threads that are currently
887	<	* idle waiting for tasks. This method may underestimate the
888	<	* number of idle threads.
889	<	*
890	<	* @return the number of idle threads
891	<	*/
892	<	final int getIdleThreadCount() {
893	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
894	<	return (c <= 0) ? 0 : c;
1501	>	return runState & ACTIVE_COUNT_MASK;
1502		}
1503
1504		/**
#	Line 906 | Line 1513 | public class ForkJoinPool extends Abstra
1513		* @return {@code true} if all threads are currently idle
1514		*/
1515		public boolean isQuiescent() {
1516	<	return activeCountOf(runControl) == 0;
1516	>	return (runState & ACTIVE_COUNT_MASK) == 0;
1517		}
1518
1519		/**
#	Line 921 | Line 1528 | public class ForkJoinPool extends Abstra
1528		* @return the number of steals
1529		*/
1530		public long getStealCount() {
1531	<	return stealCount.get();
925	<	}
926	<
927	<	/**
928	<	* Accumulates steal count from a worker.
929	<	* Call only when worker known to be idle.
930	<	*/
931	<	private void updateStealCount(ForkJoinWorkerThread w) {
932	<	int sc = w.getAndClearStealCount();
933	<	if (sc != 0)
934	<	stealCount.addAndGet(sc);
1531	>	return stealCount;
1532		}
1533
1534		/**
#	Line 946 | Line 1543 | public class ForkJoinPool extends Abstra
1543		*/
1544		public long getQueuedTaskCount() {
1545		long count = 0;
1546	<	ForkJoinWorkerThread[] ws = workers;
1547	<	if (ws != null) {
1548	<	for (int i = 0; i < ws.length; ++i) {
952	<	ForkJoinWorkerThread t = ws[i];
953	<	if (t != null)
954	<	count += t.getQueueSize();
955	<	}
956	<	}
1546	>	for (ForkJoinWorkerThread w : workers)
1547	>	if (w != null)
1548	>	count += w.getQueueSize();
1549		return count;
1550		}
1551
#	Line 1007 | Line 1599 | public class ForkJoinPool extends Abstra
1599		* @return the number of elements transferred
1600		*/
1601		protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1602	<	int n = submissionQueue.drainTo(c);
1603	<	ForkJoinWorkerThread[] ws = workers;
1604	<	if (ws != null) {
1605	<	for (int i = 0; i < ws.length; ++i) {
1606	<	ForkJoinWorkerThread w = ws[i];
1015	<	if (w != null)
1016	<	n += w.drainTasksTo(c);
1017	<	}
1018	<	}
1019	<	return n;
1602	>	int count = submissionQueue.drainTo(c);
1603	>	for (ForkJoinWorkerThread w : workers)
1604	>	if (w != null)
1605	>	count += w.drainTasksTo(c);
1606	>	return count;
1607		}
1608
1609		/**
#	Line 1027 | Line 1614 | public class ForkJoinPool extends Abstra
1614		* @return a string identifying this pool, as well as its state
1615		*/
1616		public String toString() {
1030	–	int ps = parallelism;
1031	–	int wc = workerCounts;
1032	–	int rc = runControl;
1617		long st = getStealCount();
1618		long qt = getQueuedTaskCount();
1619		long qs = getQueuedSubmissionCount();
1620	+	int wc = workerCounts;
1621	+	int tc = wc >>> TOTAL_COUNT_SHIFT;
1622	+	int rc = wc & RUNNING_COUNT_MASK;
1623	+	int pc = parallelism;
1624	+	int rs = runState;
1625	+	int ac = rs & ACTIVE_COUNT_MASK;
1626		return super.toString() +
1627	<	"[" + runStateToString(runStateOf(rc)) +
1628	<	", parallelism = " + ps +
1629	<	", size = " + totalCountOf(wc) +
1630	<	", active = " + activeCountOf(rc) +
1631	<	", running = " + runningCountOf(wc) +
1627	>	"[" + runLevelToString(rs) +
1628	>	", parallelism = " + pc +
1629	>	", size = " + tc +
1630	>	", active = " + ac +
1631	>	", running = " + rc +
1632		", steals = " + st +
1633		", tasks = " + qt +
1634		", submissions = " + qs +
1635		"]";
1636		}
1637
1638	<	private static String runStateToString(int rs) {
1639	<	switch(rs) {
1640	<	case RUNNING: return "Running";
1641	<	case SHUTDOWN: return "Shutting down";
1642	<	case TERMINATING: return "Terminating";
1053	<	case TERMINATED: return "Terminated";
1054	<	default: throw new Error("Unknown run state");
1055	<	}
1638	>	private static String runLevelToString(int s) {
1639	>	return ((s & TERMINATED) != 0 ? "Terminated" :
1640	>	((s & TERMINATING) != 0 ? "Terminating" :
1641	>	((s & SHUTDOWN) != 0 ? "Shutting down" :
1642	>	"Running")));
1643		}
1644
1058	–	// lifecycle control
1059	–
1645		/**
1646		* Initiates an orderly shutdown in which previously submitted
1647		* tasks are executed, but no new tasks will be accepted.
#	Line 1071 | Line 1656 | public class ForkJoinPool extends Abstra
1656		*/
1657		public void shutdown() {
1658		checkPermission();
1659	<	transitionRunStateTo(SHUTDOWN);
1660	<	if (canTerminateOnShutdown(runControl)) {
1076	<	if (workers == null) { // shutting down before workers created
1077	<	final ReentrantLock lock = this.workerLock;
1078	<	lock.lock();
1079	<	try {
1080	<	if (workers == null) {
1081	<	terminate();
1082	<	transitionRunStateTo(TERMINATED);
1083	<	termination.signalAll();
1084	<	}
1085	<	} finally {
1086	<	lock.unlock();
1087	<	}
1088	<	}
1089	<	terminateOnShutdown();
1090	<	}
1659	>	advanceRunLevel(SHUTDOWN);
1660	>	tryTerminate(false);
1661		}
1662
1663		/**
1664	<	* Attempts to stop all actively executing tasks, and cancels all
1665	<	* waiting tasks.  Tasks that are in the process of being
1666	<	* submitted or executed concurrently during the course of this
1667	<	* method may or may not be rejected. Unlike some other executors,
1668	<	* this method cancels rather than collects non-executed tasks
1669	<	* upon termination, so always returns an empty list. However, you
1670	<	* can use method {@link #drainTasksTo} before invoking this
1671	<	* method to transfer unexecuted tasks to another collection.
1664	>	* Attempts to cancel and/or stop all tasks, and reject all
1665	>	* subsequently submitted tasks.  Tasks that are in the process of
1666	>	* being submitted or executed concurrently during the course of
1667	>	* this method may or may not be rejected. This method cancels
1668	>	* both existing and unexecuted tasks, in order to permit
1669	>	* termination in the presence of task dependencies. So the method
1670	>	* always returns an empty list (unlike the case for some other
1671	>	* Executors).
1672		*
1673		* @return an empty list
1674		* @throws SecurityException if a security manager exists and
#	Line 1108 | Line 1678 | public class ForkJoinPool extends Abstra
1678		*/
1679		public List<Runnable> shutdownNow() {
1680		checkPermission();
1681	<	terminate();
1681	>	tryTerminate(true);
1682		return Collections.emptyList();
1683		}
1684
#	Line 1118 | Line 1688 | public class ForkJoinPool extends Abstra
1688		* @return {@code true} if all tasks have completed following shut down
1689		*/
1690		public boolean isTerminated() {
1691	<	return runStateOf(runControl) == TERMINATED;
1691	>	return runState >= TERMINATED;
1692		}
1693
1694		/**
1695		* Returns {@code true} if the process of termination has
1696	<	* commenced but possibly not yet completed.
1696	>	* commenced but not yet completed.  This method may be useful for
1697	>	* debugging. A return of {@code true} reported a sufficient
1698	>	* period after shutdown may indicate that submitted tasks have
1699	>	* ignored or suppressed interruption, causing this executor not
1700	>	* to properly terminate.
1701		*
1702	<	* @return {@code true} if terminating
1702	>	* @return {@code true} if terminating but not yet terminated
1703		*/
1704		public boolean isTerminating() {
1705	<	return runStateOf(runControl) >= TERMINATING;
1705	>	return (runState & (TERMINATING|TERMINATED)) == TERMINATING;
1706		}
1707
1708		/**
1709	+	* Returns true if terminating or terminated. Used by ForkJoinWorkerThread.
1710	+	*/
1711	+	final boolean isAtLeastTerminating() {
1712	+	return runState >= TERMINATING;
1713	+	}
1714	+
1715	+	/**
1716		* Returns {@code true} if this pool has been shut down.
1717		*
1718		* @return {@code true} if this pool has been shut down
1719		*/
1720		public boolean isShutdown() {
1721	<	return runStateOf(runControl) >= SHUTDOWN;
1721	>	return runState >= SHUTDOWN;
1722		}
1723
1724		/**
#	Line 1153 | Line 1734 | public class ForkJoinPool extends Abstra
1734		*/
1735		public boolean awaitTermination(long timeout, TimeUnit unit)
1736		throws InterruptedException {
1156	–	long nanos = unit.toNanos(timeout);
1157	–	final ReentrantLock lock = this.workerLock;
1158	–	lock.lock();
1159	–	try {
1160	–	for (;;) {
1161	–	if (isTerminated())
1162	–	return true;
1163	–	if (nanos <= 0)
1164	–	return false;
1165	–	nanos = termination.awaitNanos(nanos);
1166	–	}
1167	–	} finally {
1168	–	lock.unlock();
1169	–	}
1170	–	}
1171	–
1172	–	// Shutdown and termination support
1173	–
1174	–	/**
1175	–	* Callback from terminating worker. Nulls out the corresponding
1176	–	* workers slot, and if terminating, tries to terminate; else
1177	–	* tries to shrink workers array.
1178	–	*
1179	–	* @param w the worker
1180	–	*/
1181	–	final void workerTerminated(ForkJoinWorkerThread w) {
1182	–	updateStealCount(w);
1183	–	updateWorkerCount(-1);
1184	–	final ReentrantLock lock = this.workerLock;
1185	–	lock.lock();
1186	–	try {
1187	–	ForkJoinWorkerThread[] ws = workers;
1188	–	if (ws != null) {
1189	–	int idx = w.poolIndex;
1190	–	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1191	–	ws[idx] = null;
1192	–	if (totalCountOf(workerCounts) == 0) {
1193	–	terminate(); // no-op if already terminating
1194	–	transitionRunStateTo(TERMINATED);
1195	–	termination.signalAll();
1196	–	}
1197	–	else if (!isTerminating()) {
1198	–	tryShrinkWorkerArray();
1199	–	tryResumeSpare(true); // allow replacement
1200	–	}
1201	–	}
1202	–	} finally {
1203	–	lock.unlock();
1204	–	}
1205	–	signalIdleWorkers();
1206	–	}
1207	–
1208	–	/**
1209	–	* Initiates termination.
1210	–	*/
1211	–	private void terminate() {
1212	–	if (transitionRunStateTo(TERMINATING)) {
1213	–	stopAllWorkers();
1214	–	resumeAllSpares();
1215	–	signalIdleWorkers();
1216	–	cancelQueuedSubmissions();
1217	–	cancelQueuedWorkerTasks();
1218	–	interruptUnterminatedWorkers();
1219	–	signalIdleWorkers(); // resignal after interrupt
1220	–	}
1221	–	}
1222	–
1223	–	/**
1224	–	* Possibly terminates when on shutdown state.
1225	–	*/
1226	–	private void terminateOnShutdown() {
1227	–	if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
1228	–	terminate();
1229	–	}
1230	–
1231	–	/**
1232	–	* Clears out and cancels submissions.
1233	–	*/
1234	–	private void cancelQueuedSubmissions() {
1235	–	ForkJoinTask<?> task;
1236	–	while ((task = pollSubmission()) != null)
1237	–	task.cancel(false);
1238	–	}
1239	–
1240	–	/**
1241	–	* Cleans out worker queues.
1242	–	*/
1243	–	private void cancelQueuedWorkerTasks() {
1244	–	final ReentrantLock lock = this.workerLock;
1245	–	lock.lock();
1737		try {
1738	<	ForkJoinWorkerThread[] ws = workers;
1739	<	if (ws != null) {
1249	<	for (int i = 0; i < ws.length; ++i) {
1250	<	ForkJoinWorkerThread t = ws[i];
1251	<	if (t != null)
1252	<	t.cancelTasks();
1253	<	}
1254	<	}
1255	<	} finally {
1256	<	lock.unlock();
1257	<	}
1258	<	}
1259	<
1260	<	/**
1261	<	* Sets each worker's status to terminating. Requires lock to avoid
1262	<	* conflicts with add/remove.
1263	<	*/
1264	<	private void stopAllWorkers() {
1265	<	final ReentrantLock lock = this.workerLock;
1266	<	lock.lock();
1267	<	try {
1268	<	ForkJoinWorkerThread[] ws = workers;
1269	<	if (ws != null) {
1270	<	for (int i = 0; i < ws.length; ++i) {
1271	<	ForkJoinWorkerThread t = ws[i];
1272	<	if (t != null)
1273	<	t.shutdownNow();
1274	<	}
1275	<	}
1276	<	} finally {
1277	<	lock.unlock();
1278	<	}
1279	<	}
1280	<
1281	<	/**
1282	<	* Interrupts all unterminated workers.  This is not required for
1283	<	* sake of internal control, but may help unstick user code during
1284	<	* shutdown.
1285	<	*/
1286	<	private void interruptUnterminatedWorkers() {
1287	<	final ReentrantLock lock = this.workerLock;
1288	<	lock.lock();
1289	<	try {
1290	<	ForkJoinWorkerThread[] ws = workers;
1291	<	if (ws != null) {
1292	<	for (int i = 0; i < ws.length; ++i) {
1293	<	ForkJoinWorkerThread t = ws[i];
1294	<	if (t != null && !t.isTerminated()) {
1295	<	try {
1296	<	t.interrupt();
1297	<	} catch (SecurityException ignore) {
1298	<	}
1299	<	}
1300	<	}
1301	<	}
1302	<	} finally {
1303	<	lock.unlock();
1304	<	}
1305	<	}
1306	<
1307	<
1308	<	/*
1309	<	* Nodes for event barrier to manage idle threads.  Queue nodes
1310	<	* are basic Treiber stack nodes, also used for spare stack.
1311	<	*
1312	<	* The event barrier has an event count and a wait queue (actually
1313	<	* a Treiber stack).  Workers are enabled to look for work when
1314	<	* the eventCount is incremented. If they fail to find work, they
1315	<	* may wait for next count. Upon release, threads help others wake
1316	<	* up.
1317	<	*
1318	<	* Synchronization events occur only in enough contexts to
1319	<	* maintain overall liveness:
1320	<	*
1321	<	*   - Submission of a new task to the pool
1322	<	*   - Resizes or other changes to the workers array
1323	<	*   - pool termination
1324	<	*   - A worker pushing a task on an empty queue
1325	<	*
1326	<	* The case of pushing a task occurs often enough, and is heavy
1327	<	* enough compared to simple stack pushes, to require special
1328	<	* handling: Method signalWork returns without advancing count if
1329	<	* the queue appears to be empty.  This would ordinarily result in
1330	<	* races causing some queued waiters not to be woken up. To avoid
1331	<	* this, the first worker enqueued in method sync (see
1332	<	* syncIsReleasable) rescans for tasks after being enqueued, and
1333	<	* helps signal if any are found. This works well because the
1334	<	* worker has nothing better to do, and so might as well help
1335	<	* alleviate the overhead and contention on the threads actually
1336	<	* doing work.  Also, since event counts increments on task
1337	<	* availability exist to maintain liveness (rather than to force
1338	<	* refreshes etc), it is OK for callers to exit early if
1339	<	* contending with another signaller.
1340	<	*/
1341	<	static final class WaitQueueNode {
1342	<	WaitQueueNode next; // only written before enqueued
1343	<	volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1344	<	final long count; // unused for spare stack
1345	<
1346	<	WaitQueueNode(long c, ForkJoinWorkerThread w) {
1347	<	count = c;
1348	<	thread = w;
1349	<	}
1350	<
1351	<	/**
1352	<	* Wakes up waiter, returning false if known to already
1353	<	*/
1354	<	boolean signal() {
1355	<	ForkJoinWorkerThread t = thread;
1356	<	if (t == null)
1357	<	return false;
1358	<	thread = null;
1359	<	LockSupport.unpark(t);
1360	<	return true;
1361	<	}
1362	<
1363	<	/**
1364	<	* Awaits release on sync.
1365	<	*/
1366	<	void awaitSyncRelease(ForkJoinPool p) {
1367	<	while (thread != null && !p.syncIsReleasable(this))
1368	<	LockSupport.park(this);
1369	<	}
1370	<
1371	<	/**
1372	<	* Awaits resumption as spare.
1373	<	*/
1374	<	void awaitSpareRelease() {
1375	<	while (thread != null) {
1376	<	if (!Thread.interrupted())
1377	<	LockSupport.park(this);
1378	<	}
1379	<	}
1380	<	}
1381	<
1382	<	/**
1383	<	* Ensures that no thread is waiting for count to advance from the
1384	<	* current value of eventCount read on entry to this method, by
1385	<	* releasing waiting threads if necessary.
1386	<	*
1387	<	* @return the count
1388	<	*/
1389	<	final long ensureSync() {
1390	<	long c = eventCount;
1391	<	WaitQueueNode q;
1392	<	while ((q = syncStack) != null && q.count < c) {
1393	<	if (casBarrierStack(q, null)) {
1394	<	do {
1395	<	q.signal();
1396	<	} while ((q = q.next) != null);
1397	<	break;
1398	<	}
1399	<	}
1400	<	return c;
1401	<	}
1402	<
1403	<	/**
1404	<	* Increments event count and releases waiting threads.
1405	<	*/
1406	<	private void signalIdleWorkers() {
1407	<	long c;
1408	<	do {} while (!casEventCount(c = eventCount, c+1));
1409	<	ensureSync();
1410	<	}
1411	<
1412	<	/**
1413	<	* Signals threads waiting to poll a task. Because method sync
1414	<	* rechecks availability, it is OK to only proceed if queue
1415	<	* appears to be non-empty, and OK to skip under contention to
1416	<	* increment count (since some other thread succeeded).
1417	<	*/
1418	<	final void signalWork() {
1419	<	long c;
1420	<	WaitQueueNode q;
1421	<	if (syncStack != null &&
1422	<	casEventCount(c = eventCount, c+1) &&
1423	<	(((q = syncStack) != null && q.count <= c) &&
1424	<	(!casBarrierStack(q, q.next) || !q.signal())))
1425	<	ensureSync();
1426	<	}
1427	<
1428	<	/**
1429	<	* Waits until event count advances from last value held by
1430	<	* caller, or if excess threads, caller is resumed as spare, or
1431	<	* caller or pool is terminating. Updates caller's event on exit.
1432	<	*
1433	<	* @param w the calling worker thread
1434	<	*/
1435	<	final void sync(ForkJoinWorkerThread w) {
1436	<	updateStealCount(w); // Transfer w's count while it is idle
1437	<
1438	<	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1439	<	long prev = w.lastEventCount;
1440	<	WaitQueueNode node = null;
1441	<	WaitQueueNode h;
1442	<	while (eventCount == prev &&
1443	<	((h = syncStack) == null || h.count == prev)) {
1444	<	if (node == null)
1445	<	node = new WaitQueueNode(prev, w);
1446	<	if (casBarrierStack(node.next = h, node)) {
1447	<	node.awaitSyncRelease(this);
1448	<	break;
1449	<	}
1450	<	}
1451	<	long ec = ensureSync();
1452	<	if (ec != prev) {
1453	<	w.lastEventCount = ec;
1454	<	break;
1455	<	}
1456	<	}
1457	<	}
1458	<
1459	<	/**
1460	<	* Returns {@code true} if worker waiting on sync can proceed:
1461	<	*  - on signal (thread == null)
1462	<	*  - on event count advance (winning race to notify vs signaller)
1463	<	*  - on interrupt
1464	<	*  - if the first queued node, we find work available
1465	<	* If node was not signalled and event count not advanced on exit,
1466	<	* then we also help advance event count.
1467	<	*
1468	<	* @return {@code true} if node can be released
1469	<	*/
1470	<	final boolean syncIsReleasable(WaitQueueNode node) {
1471	<	long prev = node.count;
1472	<	if (!Thread.interrupted() && node.thread != null &&
1473	<	(node.next != null ||
1474	<	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1475	<	eventCount == prev)
1476	<	return false;
1477	<	if (node.thread != null) {
1478	<	node.thread = null;
1479	<	long ec = eventCount;
1480	<	if (prev <= ec) // help signal
1481	<	casEventCount(ec, ec+1);
1482	<	}
1483	<	return true;
1484	<	}
1485	<
1486	<	/**
1487	<	* Returns {@code true} if a new sync event occurred since last
1488	<	* call to sync or this method, if so, updating caller's count.
1489	<	*/
1490	<	final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1491	<	long lc = w.lastEventCount;
1492	<	long ec = ensureSync();
1493	<	if (ec == lc)
1738	>	return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1739	>	} catch (TimeoutException ex) {
1740		return false;
1495	–	w.lastEventCount = ec;
1496	–	return true;
1497	–	}
1498	–
1499	–	//  Parallelism maintenance
1500	–
1501	–	/**
1502	–	* Decrements running count; if too low, adds spare.
1503	–	*
1504	–	* Conceptually, all we need to do here is add or resume a
1505	–	* spare thread when one is about to block (and remove or
1506	–	* suspend it later when unblocked -- see suspendIfSpare).
1507	–	* However, implementing this idea requires coping with
1508	–	* several problems: we have imperfect information about the
1509	–	* states of threads. Some count updates can and usually do
1510	–	* lag run state changes, despite arrangements to keep them
1511	–	* accurate (for example, when possible, updating counts
1512	–	* before signalling or resuming), especially when running on
1513	–	* dynamic JVMs that don't optimize the infrequent paths that
1514	–	* update counts. Generating too many threads can make these
1515	–	* problems become worse, because excess threads are more
1516	–	* likely to be context-switched with others, slowing them all
1517	–	* down, especially if there is no work available, so all are
1518	–	* busy scanning or idling.  Also, excess spare threads can
1519	–	* only be suspended or removed when they are idle, not
1520	–	* immediately when they aren't needed. So adding threads will
1521	–	* raise parallelism level for longer than necessary.  Also,
1522	–	* FJ applications often encounter highly transient peaks when
1523	–	* many threads are blocked joining, but for less time than it
1524	–	* takes to create or resume spares.
1525	–	*
1526	–	* @param joinMe if non-null, return early if done
1527	–	* @param maintainParallelism if true, try to stay within
1528	–	* target counts, else create only to avoid starvation
1529	–	* @return true if joinMe known to be done
1530	–	*/
1531	–	final boolean preJoin(ForkJoinTask<?> joinMe,
1532	–	boolean maintainParallelism) {
1533	–	maintainParallelism &= maintainsParallelism; // overrride
1534	–	boolean dec = false;  // true when running count decremented
1535	–	while (spareStack == null || !tryResumeSpare(dec)) {
1536	–	int counts = workerCounts;
1537	–	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1538	–	// CAS cheat
1539	–	if (!needSpare(counts, maintainParallelism))
1540	–	break;
1541	–	if (joinMe.status < 0)
1542	–	return true;
1543	–	if (tryAddSpare(counts))
1544	–	break;
1545	–	}
1546	–	}
1547	–	return false;
1548	–	}
1549	–
1550	–	/**
1551	–	* Same idea as preJoin
1552	–	*/
1553	–	final boolean preBlock(ManagedBlocker blocker,
1554	–	boolean maintainParallelism) {
1555	–	maintainParallelism &= maintainsParallelism;
1556	–	boolean dec = false;
1557	–	while (spareStack == null || !tryResumeSpare(dec)) {
1558	–	int counts = workerCounts;
1559	–	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1560	–	if (!needSpare(counts, maintainParallelism))
1561	–	break;
1562	–	if (blocker.isReleasable())
1563	–	return true;
1564	–	if (tryAddSpare(counts))
1565	–	break;
1566	–	}
1567	–	}
1568	–	return false;
1569	–	}
1570	–
1571	–	/**
1572	–	* Returns {@code true} if a spare thread appears to be needed.
1573	–	* If maintaining parallelism, returns true when the deficit in
1574	–	* running threads is more than the surplus of total threads, and
1575	–	* there is apparently some work to do.  This self-limiting rule
1576	–	* means that the more threads that have already been added, the
1577	–	* less parallelism we will tolerate before adding another.
1578	–	*
1579	–	* @param counts current worker counts
1580	–	* @param maintainParallelism try to maintain parallelism
1581	–	*/
1582	–	private boolean needSpare(int counts, boolean maintainParallelism) {
1583	–	int ps = parallelism;
1584	–	int rc = runningCountOf(counts);
1585	–	int tc = totalCountOf(counts);
1586	–	int runningDeficit = ps - rc;
1587	–	int totalSurplus = tc - ps;
1588	–	return (tc < maxPoolSize &&
1589	–	(rc == 0 || totalSurplus < 0 ||
1590	–	(maintainParallelism &&
1591	–	runningDeficit > totalSurplus &&
1592	–	ForkJoinWorkerThread.hasQueuedTasks(workers))));
1593	–	}
1594	–
1595	–	/**
1596	–	* Adds a spare worker if lock available and no more than the
1597	–	* expected numbers of threads exist.
1598	–	*
1599	–	* @return true if successful
1600	–	*/
1601	–	private boolean tryAddSpare(int expectedCounts) {
1602	–	final ReentrantLock lock = this.workerLock;
1603	–	int expectedRunning = runningCountOf(expectedCounts);
1604	–	int expectedTotal = totalCountOf(expectedCounts);
1605	–	boolean success = false;
1606	–	boolean locked = false;
1607	–	// confirm counts while locking; CAS after obtaining lock
1608	–	try {
1609	–	for (;;) {
1610	–	int s = workerCounts;
1611	–	int tc = totalCountOf(s);
1612	–	int rc = runningCountOf(s);
1613	–	if (rc > expectedRunning || tc > expectedTotal)
1614	–	break;
1615	–	if (!locked && !(locked = lock.tryLock()))
1616	–	break;
1617	–	if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) {
1618	–	createAndStartSpare(tc);
1619	–	success = true;
1620	–	break;
1621	–	}
1622	–	}
1623	–	} finally {
1624	–	if (locked)
1625	–	lock.unlock();
1626	–	}
1627	–	return success;
1628	–	}
1629	–
1630	–	/**
1631	–	* Adds the kth spare worker. On entry, pool counts are already
1632	–	* adjusted to reflect addition.
1633	–	*/
1634	–	private void createAndStartSpare(int k) {
1635	–	ForkJoinWorkerThread w = null;
1636	–	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1);
1637	–	int len = ws.length;
1638	–	// Probably, we can place at slot k. If not, find empty slot
1639	–	if (k < len && ws[k] != null) {
1640	–	for (k = 0; k < len && ws[k] != null; ++k)
1641	–	;
1642	–	}
1643	–	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1644	–	ws[k] = w;
1645	–	w.start();
1646	–	}
1647	–	else
1648	–	updateWorkerCount(-1); // adjust on failure
1649	–	signalIdleWorkers();
1650	–	}
1651	–
1652	–	/**
1653	–	* Suspends calling thread w if there are excess threads.  Called
1654	–	* only from sync.  Spares are enqueued in a Treiber stack using
1655	–	* the same WaitQueueNodes as barriers.  They are resumed mainly
1656	–	* in preJoin, but are also woken on pool events that require all
1657	–	* threads to check run state.
1658	–	*
1659	–	* @param w the caller
1660	–	*/
1661	–	private boolean suspendIfSpare(ForkJoinWorkerThread w) {
1662	–	WaitQueueNode node = null;
1663	–	int s;
1664	–	while (parallelism < runningCountOf(s = workerCounts)) {
1665	–	if (node == null)
1666	–	node = new WaitQueueNode(0, w);
1667	–	if (casWorkerCounts(s, s-1)) { // representation-dependent
1668	–	// push onto stack
1669	–	do {} while (!casSpareStack(node.next = spareStack, node));
1670	–	// block until released by resumeSpare
1671	–	node.awaitSpareRelease();
1672	–	return true;
1673	–	}
1674	–	}
1675	–	return false;
1676	–	}
1677	–
1678	–	/**
1679	–	* Tries to pop and resume a spare thread.
1680	–	*
1681	–	* @param updateCount if true, increment running count on success
1682	–	* @return true if successful
1683	–	*/
1684	–	private boolean tryResumeSpare(boolean updateCount) {
1685	–	WaitQueueNode q;
1686	–	while ((q = spareStack) != null) {
1687	–	if (casSpareStack(q, q.next)) {
1688	–	if (updateCount)
1689	–	updateRunningCount(1);
1690	–	q.signal();
1691	–	return true;
1692	–	}
1693	–	}
1694	–	return false;
1695	–	}
1696	–
1697	–	/**
1698	–	* Pops and resumes all spare threads. Same idea as ensureSync.
1699	–	*
1700	–	* @return true if any spares released
1701	–	*/
1702	–	private boolean resumeAllSpares() {
1703	–	WaitQueueNode q;
1704	–	while ( (q = spareStack) != null) {
1705	–	if (casSpareStack(q, null)) {
1706	–	do {
1707	–	updateRunningCount(1);
1708	–	q.signal();
1709	–	} while ((q = q.next) != null);
1710	–	return true;
1711	–	}
1712	–	}
1713	–	return false;
1714	–	}
1715	–
1716	–	/**
1717	–	* Pops and shuts down excessive spare threads. Call only while
1718	–	* holding lock. This is not guaranteed to eliminate all excess
1719	–	* threads, only those suspended as spares, which are the ones
1720	–	* unlikely to be needed in the future.
1721	–	*/
1722	–	private void trimSpares() {
1723	–	int surplus = totalCountOf(workerCounts) - parallelism;
1724	–	WaitQueueNode q;
1725	–	while (surplus > 0 && (q = spareStack) != null) {
1726	–	if (casSpareStack(q, null)) {
1727	–	do {
1728	–	updateRunningCount(1);
1729	–	ForkJoinWorkerThread w = q.thread;
1730	–	if (w != null && surplus > 0 &&
1731	–	runningCountOf(workerCounts) > 0 && w.shutdown())
1732	–	--surplus;
1733	–	q.signal();
1734	–	} while ((q = q.next) != null);
1735	–	}
1741		}
1742		}
1743
#	Line 1740 | Line 1745 | public class ForkJoinPool extends Abstra
1745		* Interface for extending managed parallelism for tasks running
1746		* in {@link ForkJoinPool}s.
1747		*
1748	<	* <p>A {@code ManagedBlocker} provides two methods.
1749	<	* Method {@code isReleasable} must return {@code true} if
1750	<	* blocking is not necessary. Method {@code block} blocks the
1751	<	* current thread if necessary (perhaps internally invoking
1752	<	* {@code isReleasable} before actually blocking).
1748	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
1749	>	* {@code isReleasable} must return {@code true} if blocking is
1750	>	* not necessary. Method {@code block} blocks the current thread
1751	>	* if necessary (perhaps internally invoking {@code isReleasable}
1752	>	* before actually blocking). The unusual methods in this API
1753	>	* accommodate synchronizers that may, but don't usually, block
1754	>	* for long periods. Similarly, they allow more efficient internal
1755	>	* handling of cases in which additional workers may be, but
1756	>	* usually are not, needed to ensure sufficient parallelism.
1757	>	* Toward this end, implementations of method {@code isReleasable}
1758	>	* must be amenable to repeated invocation.
1759		*
1760		* <p>For example, here is a ManagedBlocker based on a
1761		* ReentrantLock:
#	Line 1762 | Line 1773 | public class ForkJoinPool extends Abstra
1773		*     return hasLock || (hasLock = lock.tryLock());
1774		*   }
1775		* }}</pre>
1776	+	*
1777	+	* <p>Here is a class that possibly blocks waiting for an
1778	+	* item on a given queue:
1779	+	*  <pre> {@code
1780	+	* class QueueTaker<E> implements ManagedBlocker {
1781	+	*   final BlockingQueue<E> queue;
1782	+	*   volatile E item = null;
1783	+	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
1784	+	*   public boolean block() throws InterruptedException {
1785	+	*     if (item == null)
1786	+	*       item = queue.take();
1787	+	*     return true;
1788	+	*   }
1789	+	*   public boolean isReleasable() {
1790	+	*     return item != null || (item = queue.poll()) != null;
1791	+	*   }
1792	+	*   public E getItem() { // call after pool.managedBlock completes
1793	+	*     return item;
1794	+	*   }
1795	+	* }}</pre>
1796		*/
1797		public static interface ManagedBlocker {
1798		/**
#	Line 1785 | Line 1816 | public class ForkJoinPool extends Abstra
1816		* Blocks in accord with the given blocker.  If the current thread
1817		* is a {@link ForkJoinWorkerThread}, this method possibly
1818		* arranges for a spare thread to be activated if necessary to
1819	<	* ensure parallelism while the current thread is blocked.
1789	<	*
1790	<	* <p>If {@code maintainParallelism} is {@code true} and the pool
1791	<	* supports it ({@link #getMaintainsParallelism}), this method
1792	<	* attempts to maintain the pool's nominal parallelism. Otherwise
1793	<	* it activates a thread only if necessary to avoid complete
1794	<	* starvation. This option may be preferable when blockages use
1795	<	* timeouts, or are almost always brief.
1819	>	* ensure sufficient parallelism while the current thread is blocked.
1820		*
1821		* <p>If the caller is not a {@link ForkJoinTask}, this method is
1822		* behaviorally equivalent to
#	Line 1806 | Line 1830 | public class ForkJoinPool extends Abstra
1830		* first be expanded to ensure parallelism, and later adjusted.
1831		*
1832		* @param blocker the blocker
1809	–	* @param maintainParallelism if {@code true} and supported by
1810	–	* this pool, attempt to maintain the pool's nominal parallelism;
1811	–	* otherwise activate a thread only if necessary to avoid
1812	–	* complete starvation.
1833		* @throws InterruptedException if blocker.block did so
1834		*/
1835	<	public static void managedBlock(ManagedBlocker blocker,
1816	<	boolean maintainParallelism)
1835	>	public static void managedBlock(ManagedBlocker blocker)
1836		throws InterruptedException {
1837		Thread t = Thread.currentThread();
1838	<	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1839	<	((ForkJoinWorkerThread) t).pool : null);
1840	<	if (!blocker.isReleasable()) {
1841	<	try {
1842	<	if (pool == null ||
1843	<	!pool.preBlock(blocker, maintainParallelism))
1825	<	awaitBlocker(blocker);
1826	<	} finally {
1827	<	if (pool != null)
1828	<	pool.updateRunningCount(1);
1829	<	}
1838	>	if (t instanceof ForkJoinWorkerThread) {
1839	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
1840	>	w.pool.awaitBlocker(blocker);
1841	>	}
1842	>	else {
1843	>	do {} while (!blocker.isReleasable() && !blocker.block());
1844		}
1831	–	}
1832	–
1833	–	private static void awaitBlocker(ManagedBlocker blocker)
1834	–	throws InterruptedException {
1835	–	do {} while (!blocker.isReleasable() && !blocker.block());
1845		}
1846
1847		// AbstractExecutorService overrides.  These rely on undocumented
#	Line 1850 | Line 1859 | public class ForkJoinPool extends Abstra
1859		// Unsafe mechanics
1860
1861		private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1853	–	private static final long eventCountOffset =
1854	–	objectFieldOffset("eventCount", ForkJoinPool.class);
1862		private static final long workerCountsOffset =
1863		objectFieldOffset("workerCounts", ForkJoinPool.class);
1864	<	private static final long runControlOffset =
1865	<	objectFieldOffset("runControl", ForkJoinPool.class);
1866	<	private static final long syncStackOffset =
1867	<	objectFieldOffset("syncStack",ForkJoinPool.class);
1868	<	private static final long spareStackOffset =
1869	<	objectFieldOffset("spareStack", ForkJoinPool.class);
1870	<
1871	<	private boolean casEventCount(long cmp, long val) {
1872	<	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1873	<	}
1867	<	private boolean casWorkerCounts(int cmp, int val) {
1868	<	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1869	<	}
1870	<	private boolean casRunControl(int cmp, int val) {
1871	<	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1872	<	}
1873	<	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1874	<	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1875	<	}
1876	<	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1877	<	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1878	<	}
1864	>	private static final long runStateOffset =
1865	>	objectFieldOffset("runState", ForkJoinPool.class);
1866	>	private static final long eventCountOffset =
1867	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1868	>	private static final long eventWaitersOffset =
1869	>	objectFieldOffset("eventWaiters", ForkJoinPool.class);
1870	>	private static final long stealCountOffset =
1871	>	objectFieldOffset("stealCount", ForkJoinPool.class);
1872	>	private static final long spareWaitersOffset =
1873	>	objectFieldOffset("spareWaiters", ForkJoinPool.class);
1874
1875		private static long objectFieldOffset(String field, Class<?> klazz) {
1876		try {

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