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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 1.60 by dl, Sat Jul 24 20:28:18 2010 UTC

#	Line 13 | Line 13 | import java.util.Arrays;
13		import java.util.Collection;
14		import java.util.Collections;
15		import java.util.List;
16	–	import java.util.concurrent.locks.Condition;
16		import java.util.concurrent.locks.LockSupport;
17		import java.util.concurrent.locks.ReentrantLock;
18		import java.util.concurrent.atomic.AtomicInteger;
19	<	import java.util.concurrent.atomic.AtomicLong;
19	>	import java.util.concurrent.CountDownLatch;
20
21		/**
22		* An {@link ExecutorService} for running {@link ForkJoinTask}s.
23		* A {@code ForkJoinPool} provides the entry point for submissions
24	<	* from non-{@code ForkJoinTask}s, as well as management and
25	<	* 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.
24	>	* from non-{@code ForkJoinTask} clients, as well as management and
25	>	* monitoring operations.
26		*
27	<	* <p>{@code ForkJoinPool}s differ from other kinds of {@link
28	<	* Executor}s mainly in that they provide <em>work-stealing</em>: all
29	<	* threads in the pool attempt to find and execute subtasks created by
30	<	* other active tasks (eventually blocking if none exist). This makes
31	<	* them efficient when most tasks spawn other subtasks (as do most
32	<	* {@code ForkJoinTask}s), as well as the mixed execution of some
33	<	* plain {@code Runnable}- or {@code Callable}- based activities along
34	<	* with {@code ForkJoinTask}s. When setting {@linkplain #setAsyncMode
35	<	* 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.
27	>	* <p>A {@code ForkJoinPool} differs from other kinds of {@link
28	>	* ExecutorService} mainly by virtue of employing
29	>	* <em>work-stealing</em>: all threads in the pool attempt to find and
30	>	* execute subtasks created by other active tasks (eventually blocking
31	>	* waiting for work if none exist). This enables efficient processing
32	>	* when most tasks spawn other subtasks (as do most {@code
33	>	* ForkJoinTask}s). When setting <em>asyncMode</em> to true in
34	>	* constructors, {@code ForkJoinPool}s may also be appropriate for use
35	>	* with event-style tasks that are never joined.
36		*
37	<	* <p>A {@code ForkJoinPool} may be constructed with a given
38	<	* parallelism level (target pool size), which it attempts to maintain
39	<	* by dynamically adding, suspending, or resuming threads, even if
40	<	* some tasks are waiting to join others. However, no such adjustments
41	<	* are performed in the face of blocked IO or other unmanaged
42	<	* synchronization. The nested {@link ManagedBlocker} interface
43	<	* enables extension of the kinds of synchronization accommodated.
44	<	* The target parallelism level may also be changed dynamically
45	<	* ({@link #setParallelism}) and thread construction can be limited
53	<	* using methods {@link #setMaximumPoolSize} and/or {@link
54	<	* #setMaintainsParallelism}.
37	>	* <p>A {@code ForkJoinPool} is constructed with a given target
38	>	* parallelism level; by default, equal to the number of available
39	>	* processors. The pool attempts to maintain enough active (or
40	>	* available) threads by dynamically adding, suspending, or resuming
41	>	* internal worker threads, even if some tasks are stalled waiting to
42	>	* join others. However, no such adjustments are guaranteed in the
43	>	* face of blocked IO or other unmanaged synchronization. The nested
44	>	* {@link ManagedBlocker} interface enables extension of the kinds of
45	>	* synchronization accommodated.
46		*
47		* <p>In addition to execution and lifecycle control methods, this
48		* class provides status check methods (for example
#	Line 60 | Line 51 | import java.util.concurrent.atomic.Atomi
51		* {@link #toString} returns indications of pool state in a
52		* convenient form for informal monitoring.
53		*
54	+	* <p> As is the case with other ExecutorServices, there are three
55	+	* main task execution methods summarized in the following
56	+	* table. These are designed to be used by clients not already engaged
57	+	* in fork/join computations in the current pool.  The main forms of
58	+	* these methods accept instances of {@code ForkJoinTask}, but
59	+	* overloaded forms also allow mixed execution of plain {@code
60	+	* Runnable}- or {@code Callable}- based activities as well.  However,
61	+	* tasks that are already executing in a pool should normally
62	+	* <em>NOT</em> use these pool execution methods, but instead use the
63	+	* within-computation forms listed in the table.
64	+	*
65	+	* <table BORDER CELLPADDING=3 CELLSPACING=1>
66	+	*  <tr>
67	+	*    <td></td>
68	+	*    <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
69	+	*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
70	+	*  </tr>
71	+	*  <tr>
72	+	*    <td> <b>Arange async execution</td>
73	+	*    <td> {@link #execute(ForkJoinTask)}</td>
74	+	*    <td> {@link ForkJoinTask#fork}</td>
75	+	*  </tr>
76	+	*  <tr>
77	+	*    <td> <b>Await and obtain result</td>
78	+	*    <td> {@link #invoke(ForkJoinTask)}</td>
79	+	*    <td> {@link ForkJoinTask#invoke}</td>
80	+	*  </tr>
81	+	*  <tr>
82	+	*    <td> <b>Arrange exec and obtain Future</td>
83	+	*    <td> {@link #submit(ForkJoinTask)}</td>
84	+	*    <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td>
85	+	*  </tr>
86	+	* </table>
87	+	*
88	+	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
89	+	* used for all parallel task execution in a program or subsystem.
90	+	* Otherwise, use would not usually outweigh the construction and
91	+	* bookkeeping overhead of creating a large set of threads. For
92	+	* example, a common pool could be used for the {@code SortTasks}
93	+	* illustrated in {@link RecursiveAction}. Because {@code
94	+	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
95	+	* daemon} mode, there is typically no need to explicitly {@link
96	+	* #shutdown} such a pool upon program exit.
97	+	*
98	+	* <pre>
99	+	* static final ForkJoinPool mainPool = new ForkJoinPool();
100	+	* ...
101	+	* public void sort(long[] array) {
102	+	*   mainPool.invoke(new SortTask(array, 0, array.length));
103	+	* }
104	+	* </pre>
105	+	*
106		* <p><b>Implementation notes</b>: This implementation restricts the
107		* maximum number of running threads to 32767. Attempts to create
108	<	* pools with greater than the maximum result in
108	>	* pools with greater than the maximum number result in
109		* {@code IllegalArgumentException}.
110		*
111	+	* <p>This implementation rejects submitted tasks (that is, by throwing
112	+	* {@link RejectedExecutionException}) only when the pool is shut down
113	+	* or internal resources have been exhuasted.
114	+	*
115		* @since 1.7
116		* @author Doug Lea
117		*/
118		public class ForkJoinPool extends AbstractExecutorService {
119
120		/*
121	<	* See the extended comments interspersed below for design,
122	<	* rationale, and walkthroughs.
121	>	* Implementation Overview
122	>	*
123	>	* This class provides the central bookkeeping and control for a
124	>	* set of worker threads: Submissions from non-FJ threads enter
125	>	* into a submission queue. Workers take these tasks and typically
126	>	* split them into subtasks that may be stolen by other workers.
127	>	* The main work-stealing mechanics implemented in class
128	>	* ForkJoinWorkerThread give first priority to processing tasks
129	>	* from their own queues (LIFO or FIFO, depending on mode), then
130	>	* to randomized FIFO steals of tasks in other worker queues, and
131	>	* lastly to new submissions. These mechanics do not consider
132	>	* affinities, loads, cache localities, etc, so rarely provide the
133	>	* best possible performance on a given machine, but portably
134	>	* provide good throughput by averaging over these factors.
135	>	* (Further, even if we did try to use such information, we do not
136	>	* usually have a basis for exploiting it. For example, some sets
137	>	* of tasks profit from cache affinities, but others are harmed by
138	>	* cache pollution effects.)
139	>	*
140	>	* Beyond work-stealing support and essential bookkeeping, the
141	>	* main responsibility of this framework is to take actions when
142	>	* one worker is waiting to join a task stolen (or always held by)
143	>	* another.  Becauae we are multiplexing many tasks on to a pool
144	>	* of workers, we can't just let them block (as in Thread.join).
145	>	* We also cannot just reassign the joiner's run-time stack with
146	>	* another and replace it later, which would be a form of
147	>	* "continuation", that even if possible is not necessarily a good
148	>	* idea. Given that the creation costs of most threads on most
149	>	* systems mainly surrounds setting up runtime stacks, thread
150	>	* creation and switching is usually not much more expensive than
151	>	* stack creation and switching, and is more flexible). Instead we
152	>	* combine two tactics:
153	>	*
154	>	*   Helping: Arranging for the joiner to execute some task that it
155	>	*      would be running if the steal had not occurred.  Method
156	>	*      ForkJoinWorkerThread.helpJoinTask tracks joining->stealing
157	>	*      links to try to find such a task.
158	>	*
159	>	*   Compensating: Unless there are already enough live threads,
160	>	*      creating or or re-activating a spare thread to compensate
161	>	*      for the (blocked) joiner until it unblocks.  Spares then
162	>	*      suspend at their next opportunity or eventually die if
163	>	*      unused for too long.  See below and the internal
164	>	*      documentation for tryAwaitJoin for more details about
165	>	*      compensation rules.
166	>	*
167	>	* Because the determining existence of conservatively safe
168	>	* helping targets, the availability of already-created spares,
169	>	* and the apparent need to create new spares are all racy and
170	>	* require heuristic guidance, joins (in
171	>	* ForkJoinWorkerThread.joinTask) interleave these options until
172	>	* successful.  Creating a new spare always succeeds, but also
173	>	* increases application footprint, so we try to avoid it, within
174	>	* reason.
175	>	*
176	>	* The ManagedBlocker extension API can't use helping so uses a
177	>	* special version of compensation in method awaitBlocker.
178	>	*
179	>	* The main throughput advantages of work-stealing stem from
180	>	* decentralized control -- workers mostly steal tasks from each
181	>	* other. We do not want to negate this by creating bottlenecks
182	>	* implementing other management responsibilities. So we use a
183	>	* collection of techniques that avoid, reduce, or cope well with
184	>	* contention. These entail several instances of bit-packing into
185	>	* CASable fields to maintain only the minimally required
186	>	* atomicity. To enable such packing, we restrict maximum
187	>	* parallelism to (1<<15)-1 (enabling twice this (to accommodate
188	>	* unbalanced increments and decrements) to fit into a 16 bit
189	>	* field, which is far in excess of normal operating range.  Even
190	>	* though updates to some of these bookkeeping fields do sometimes
191	>	* contend with each other, they don't normally cache-contend with
192	>	* updates to others enough to warrant memory padding or
193	>	* isolation. So they are all held as fields of ForkJoinPool
194	>	* objects.  The main capabilities are as follows:
195	>	*
196	>	* 1. Creating and removing workers. Workers are recorded in the
197	>	* "workers" array. This is an array as opposed to some other data
198	>	* structure to support index-based random steals by workers.
199	>	* Updates to the array recording new workers and unrecording
200	>	* terminated ones are protected from each other by a lock
201	>	* (workerLock) but the array is otherwise concurrently readable,
202	>	* and accessed directly by workers. To simplify index-based
203	>	* operations, the array size is always a power of two, and all
204	>	* readers must tolerate null slots. Currently, all worker thread
205	>	* creation is on-demand, triggered by task submissions,
206	>	* replacement of terminated workers, and/or compensation for
207	>	* blocked workers. However, all other support code is set up to
208	>	* work with other policies.
209	>	*
210	>	* 2. Bookkeeping for dynamically adding and removing workers. We
211	>	* aim to approximately maintain the given level of parallelism.
212	>	* When some workers are known to be blocked (on joins or via
213	>	* ManagedBlocker), we may create or resume others to take their
214	>	* place until they unblock (see below). Implementing this
215	>	* requires counts of the number of "running" threads (i.e., those
216	>	* that are neither blocked nor artifically suspended) as well as
217	>	* the total number.  These two values are packed into one field,
218	>	* "workerCounts" because we need accurate snapshots when deciding
219	>	* to create, resume or suspend.  Note however that the
220	>	* correspondance of these counts to reality is not guaranteed. In
221	>	* particular updates for unblocked threads may lag until they
222	>	* actually wake up.
223	>	*
224	>	* 3. Maintaining global run state. The run state of the pool
225	>	* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to
226	>	* those in other Executor implementations, as well as a count of
227	>	* "active" workers -- those that are, or soon will be, or
228	>	* recently were executing tasks. The runLevel and active count
229	>	* are packed together in order to correctly trigger shutdown and
230	>	* termination. Without care, active counts can be subject to very
231	>	* high contention.  We substantially reduce this contention by
232	>	* relaxing update rules.  A worker must claim active status
233	>	* prospectively, by activating if it sees that a submitted or
234	>	* stealable task exists (it may find after activating that the
235	>	* task no longer exists). It stays active while processing this
236	>	* task (if it exists) and any other local subtasks it produces,
237	>	* until it cannot find any other tasks. It then tries
238	>	* inactivating (see method preStep), but upon update contention
239	>	* instead scans for more tasks, later retrying inactivation if it
240	>	* doesn't find any.
241	>	*
242	>	* 4. Managing idle workers waiting for tasks. We cannot let
243	>	* workers spin indefinitely scanning for tasks when none are
244	>	* available. On the other hand, we must quickly prod them into
245	>	* action when new tasks are submitted or generated.  We
246	>	* park/unpark these idle workers using an event-count scheme.
247	>	* Field eventCount is incremented upon events that may enable
248	>	* workers that previously could not find a task to now find one:
249	>	* Submission of a new task to the pool, or another worker pushing
250	>	* a task onto a previously empty queue.  (We also use this
251	>	* mechanism for termination and reconfiguration actions that
252	>	* require wakeups of idle workers).  Each worker maintains its
253	>	* last known event count, and blocks when a scan for work did not
254	>	* find a task AND its lastEventCount matches the current
255	>	* eventCount. Waiting idle workers are recorded in a variant of
256	>	* Treiber stack headed by field eventWaiters which, when nonzero,
257	>	* encodes the thread index and count awaited for by the worker
258	>	* thread most recently calling eventSync. This thread in turn has
259	>	* a record (field nextEventWaiter) for the next waiting worker.
260	>	* In addition to allowing simpler decisions about need for
261	>	* wakeup, the event count bits in eventWaiters serve the role of
262	>	* tags to avoid ABA errors in Treiber stacks.  To reduce delays
263	>	* in task diffusion, workers not otherwise occupied may invoke
264	>	* method releaseWaiters, that removes and signals (unparks)
265	>	* workers not waiting on current count. To minimize task
266	>	* production stalls associate with signalling, any worker pushing
267	>	* a task on an empty queue invokes the weaker method signalWork,
268	>	* that only releases idle workers until it detects interference
269	>	* by other threads trying to release, and lets them take
270	>	* over. The net effect is a tree-like diffusion of signals, where
271	>	* released threads (and possibly others) help with unparks.  To
272	>	* further reduce contention effects a bit, failed CASes to
273	>	* increment field eventCount are tolerated without retries.
274	>	* Conceptually they are merged into the same event, which is OK
275	>	* when their only purpose is to enable workers to scan for work.
276	>	*
277	>	* 5. Managing suspension of extra workers. When a worker is about
278	>	* to block waiting for a join (or via ManagedBlockers), we may
279	>	* create a new thread to maintain parallelism level, or at least
280	>	* avoid starvation. Usually, extra threads are needed for only
281	>	* very short periods, yet join dependencies are such that we
282	>	* sometimes need them in bursts. Rather than create new threads
283	>	* each time this happens, we suspend no-longer-needed extra ones
284	>	* as "spares". For most purposes, we don't distinguish "extra"
285	>	* spare threads from normal "core" threads: On each call to
286	>	* preStep (the only point at which we can do this) a worker
287	>	* checks to see if there are now too many running workers, and if
288	>	* so, suspends itself.  Methods tryAwaitJoin and awaitBlocker
289	>	* look for suspended threads to resume before considering
290	>	* creating a new replacement. We don't need a special data
291	>	* structure to maintain spares; simply scanning the workers array
292	>	* looking for worker.isSuspended() is fine because the calling
293	>	* thread is otherwise not doing anything useful anyway; we are at
294	>	* least as happy if after locating a spare, the caller doesn't
295	>	* actually block because the join is ready before we try to
296	>	* adjust and compensate.  Note that this is intrinsically racy.
297	>	* One thread may become a spare at about the same time as another
298	>	* is needlessly being created. We counteract this and related
299	>	* slop in part by requiring resumed spares to immediately recheck
300	>	* (in preStep) to see whether they they should re-suspend. The
301	>	* only effective difference between "extra" and "core" threads is
302	>	* that we allow the "extra" ones to time out and die if they are
303	>	* not resumed within a keep-alive interval of a few seconds. This
304	>	* is implemented mainly within ForkJoinWorkerThread, but requires
305	>	* some coordination (isTrimmed() -- meaning killed while
306	>	* suspended) to correctly maintain pool counts.
307	>	*
308	>	* 6. Deciding when to create new workers. The main dynamic
309	>	* control in this class is deciding when to create extra threads,
310	>	* in methods awaitJoin and awaitBlocker. We always need to create
311	>	* one when the number of running threads would become zero and
312	>	* all workers are busy. However, this is not easy to detect
313	>	* reliably in the presence of transients so we use retries and
314	>	* allow slack (in tryAwaitJoin) to reduce false alarms.  These
315	>	* effectively reduce churn at the price of systematically
316	>	* undershooting target parallelism when many threads are blocked.
317	>	* However, biasing toward undeshooting partially compensates for
318	>	* the above mechanics to suspend extra threads, that normally
319	>	* lead to overshoot because we can only suspend workers
320	>	* in-between top-level actions. It also better copes with the
321	>	* fact that some of the methods in this class tend to never
322	>	* become compiled (but are interpreted), so some components of
323	>	* the entire set of controls might execute many times faster than
324	>	* others. And similarly for cases where the apparent lack of work
325	>	* is just due to GC stalls and other transient system activity.
326	>	*
327	>	* Beware that there is a lot of representation-level coupling
328	>	* among classes ForkJoinPool, ForkJoinWorkerThread, and
329	>	* ForkJoinTask.  For example, direct access to "workers" array by
330	>	* workers, and direct access to ForkJoinTask.status by both
331	>	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
332	>	* trying to reduce this, since any associated future changes in
333	>	* representations will need to be accompanied by algorithmic
334	>	* changes anyway.
335	>	*
336	>	* Style notes: There are lots of inline assignments (of form
337	>	* "while ((local = field) != 0)") which are usually the simplest
338	>	* way to ensure read orderings. Also several occurrences of the
339	>	* unusual "do {} while(!cas...)" which is the simplest way to
340	>	* force an update of a CAS'ed variable. There are also other
341	>	* coding oddities that help some methods perform reasonably even
342	>	* when interpreted (not compiled), at the expense of messiness.
343	>	*
344	>	* The order of declarations in this file is: (1) statics (2)
345	>	* fields (along with constants used when unpacking some of them)
346	>	* (3) internal control methods (4) callbacks and other support
347	>	* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
348	>	* methods (plus a few little helpers).
349		*/
350
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	–
351		/**
352		* Factory for creating new {@link ForkJoinWorkerThread}s.
353		* A {@code ForkJoinWorkerThreadFactory} must be defined and used
#	Line 92 | Line 359 | public class ForkJoinPool extends Abstra
359		* Returns a new worker thread operating in the given pool.
360		*
361		* @param pool the pool this thread works in
362	<	* @throws NullPointerException if pool is null
362	>	* @throws NullPointerException if the pool is null
363		*/
364		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
365		}
#	Line 101 | Line 368 | public class ForkJoinPool extends Abstra
368		* Default ForkJoinWorkerThreadFactory implementation; creates a
369		* new ForkJoinWorkerThread.
370		*/
371	<	static class  DefaultForkJoinWorkerThreadFactory
371	>	static class DefaultForkJoinWorkerThreadFactory
372		implements ForkJoinWorkerThreadFactory {
373		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
374	<	try {
108	<	return new ForkJoinWorkerThread(pool);
109	<	} catch (OutOfMemoryError oom)  {
110	<	return null;
111	<	}
374	>	return new ForkJoinWorkerThread(pool);
375		}
376		}
377
#	Line 144 | Line 407 | public class ForkJoinPool extends Abstra
407		new AtomicInteger();
408
409		/**
410	<	* Array holding all worker threads in the pool. Initialized upon
411	<	* first use. Array size must be a power of two.  Updates and
149	<	* replacements are protected by workerLock, but it is always kept
150	<	* in a consistent enough state to be randomly accessed without
151	<	* locking by workers performing work-stealing.
410	>	* Absolute bound for parallelism level. Twice this number must
411	>	* fit into a 16bit field to enable word-packing for some counts.
412		*/
413	<	volatile ForkJoinWorkerThread[] workers;
413	>	private static final int MAX_THREADS = 0x7fff;
414
415		/**
416	<	* Lock protecting access to workers.
416	>	* Array holding all worker threads in the pool.  Array size must
417	>	* be a power of two.  Updates and replacements are protected by
418	>	* workerLock, but the array is always kept in a consistent enough
419	>	* state to be randomly accessed without locking by workers
420	>	* performing work-stealing, as well as other traversal-based
421	>	* methods in this class. All readers must tolerate that some
422	>	* array slots may be null.
423		*/
424	<	private final ReentrantLock workerLock;
424	>	volatile ForkJoinWorkerThread[] workers;
425
426		/**
427	<	* Condition for awaitTermination.
427	>	* Queue for external submissions.
428		*/
429	<	private final Condition termination;
429	>	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
430
431		/**
432	<	* The uncaught exception handler used when any worker
167	<	* abruptly terminates
432	>	* Lock protecting updates to workers array.
433		*/
434	<	private Thread.UncaughtExceptionHandler ueh;
434	>	private final ReentrantLock workerLock;
435
436		/**
437	<	* Creation factory for worker threads.
437	>	* Latch released upon termination.
438		*/
439	<	private final ForkJoinWorkerThreadFactory factory;
439	>	private final Phaser termination;
440
441		/**
442	<	* 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.
442	>	* Creation factory for worker threads.
443		*/
444	<	private volatile WaitQueueNode spareStack;
444	>	private final ForkJoinWorkerThreadFactory factory;
445
446		/**
447		* Sum of per-thread steal counts, updated only when threads are
448		* idle or terminating.
449		*/
450	<	private final AtomicLong stealCount;
450	>	private volatile long stealCount;
451
452		/**
453	<	* Queue for external submissions.
453	>	* Encoded record of top of treiber stack of threads waiting for
454	>	* events. The top 32 bits contain the count being waited for. The
455	>	* bottom word contains one plus the pool index of waiting worker
456	>	* thread.
457		*/
458	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
458	>	private volatile long eventWaiters;
459	>
460	>	private static final int  EVENT_COUNT_SHIFT = 32;
461	>	private static final long WAITER_ID_MASK = (1L << EVENT_COUNT_SHIFT)-1L;
462
463		/**
464	<	* Head of Treiber stack for barrier sync. See below for explanation.
464	>	* A counter for events that may wake up worker threads:
465	>	*   - Submission of a new task to the pool
466	>	*   - A worker pushing a task on an empty queue
467	>	*   - termination and reconfiguration
468		*/
469	<	private volatile WaitQueueNode syncStack;
469	>	private volatile int eventCount;
470
471		/**
472	<	* The count for event barrier
473	<	*/
474	<	private volatile long eventCount;
472	>	* Lifecycle control. The low word contains the number of workers
473	>	* that are (probably) executing tasks. This value is atomically
474	>	* incremented before a worker gets a task to run, and decremented
475	>	* when worker has no tasks and cannot find any.  Bits 16-18
476	>	* contain runLevel value. When all are zero, the pool is
477	>	* running. Level transitions are monotonic (running -> shutdown
478	>	* -> terminating -> terminated) so each transition adds a bit.
479	>	* These are bundled together to ensure consistent read for
480	>	* termination checks (i.e., that runLevel is at least SHUTDOWN
481	>	* and active threads is zero).
482	>	*/
483	>	private volatile int runState;
484	>
485	>	// Note: The order among run level values matters.
486	>	private static final int RUNLEVEL_SHIFT     = 16;
487	>	private static final int SHUTDOWN           = 1 << RUNLEVEL_SHIFT;
488	>	private static final int TERMINATING        = 1 << (RUNLEVEL_SHIFT + 1);
489	>	private static final int TERMINATED         = 1 << (RUNLEVEL_SHIFT + 2);
490	>	private static final int ACTIVE_COUNT_MASK  = (1 << RUNLEVEL_SHIFT) - 1;
491	>	private static final int ONE_ACTIVE         = 1; // active update delta
492
493		/**
494	<	* Pool number, just for assigning useful names to worker threads
494	>	* Holds number of total (i.e., created and not yet terminated)
495	>	* and running (i.e., not blocked on joins or other managed sync)
496	>	* threads, packed together to ensure consistent snapshot when
497	>	* making decisions about creating and suspending spare
498	>	* threads. Updated only by CAS. Note that adding a new worker
499	>	* requires incrementing both counts, since workers start off in
500	>	* running state.
501		*/
502	<	private final int poolNumber;
502	>	private volatile int workerCounts;
503	>
504	>	private static final int TOTAL_COUNT_SHIFT  = 16;
505	>	private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1;
506	>	private static final int ONE_RUNNING        = 1;
507	>	private static final int ONE_TOTAL          = 1 << TOTAL_COUNT_SHIFT;
508
509		/**
510	<	* The maximum allowed pool size
510	>	* The target parallelism level.
511	>	* Accessed directly by ForkJoinWorkerThreads.
512		*/
513	<	private volatile int maxPoolSize;
513	>	final int parallelism;
514
515		/**
516	<	* The desired parallelism level, updated only under workerLock.
516	>	* True if use local fifo, not default lifo, for local polling
517	>	* Read by, and replicated by ForkJoinWorkerThreads
518		*/
519	<	private volatile int parallelism;
519	>	final boolean locallyFifo;
520
521		/**
522	<	* True if use local fifo, not default lifo, for local polling
522	>	* The uncaught exception handler used when any worker abruptly
523	>	* terminates.
524		*/
525	<	private volatile boolean locallyFifo;
525	>	private final Thread.UncaughtExceptionHandler ueh;
526
527		/**
528	<	* Holds number of total (i.e., created and not yet terminated)
226	<	* and running (i.e., not blocked on joins or other managed sync)
227	<	* threads, packed into one int to ensure consistent snapshot when
228	<	* making decisions about creating and suspending spare
229	<	* threads. Updated only by CAS.  Note: CASes in
230	<	* updateRunningCount and preJoin assume that running active count
231	<	* is in low word, so need to be modified if this changes.
528	>	* Pool number, just for assigning useful names to worker threads
529		*/
530	<	private volatile int workerCounts;
530	>	private final int poolNumber;
531
532	<	private static int totalCountOf(int s)           { return s >>> 16;  }
533	<	private static int runningCountOf(int s)         { return s & shortMask; }
237	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
532	>	// Utilities for CASing fields. Note that several of these
533	>	// are manually inlined by callers
534
535		/**
536	<	* Adds delta (which may be negative) to running count.  This must
241	<	* 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
536	>	* Increments running count.  Also used by ForkJoinTask.
537		*/
538	<	final void updateRunningCount(int delta) {
539	<	int s;
540	<	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
538	>	final void incrementRunningCount() {
539	>	int c;
540	>	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
541	>	c = workerCounts,
542	>	c + ONE_RUNNING));
543		}
544
545		/**
546	<	* Adds delta (which may be negative) to both total and running
253	<	* count.  This must be called upon creation and termination of
254	<	* worker threads.
255	<	*
256	<	* @param delta the number to add
546	>	* Tries to decrement running count unless already zero
547		*/
548	<	private void updateWorkerCount(int delta) {
549	<	int d = delta + (delta << 16); // add to both lo and hi parts
550	<	int s;
551	<	do {} while (!casWorkerCounts(s = workerCounts, s + d));
548	>	final boolean tryDecrementRunningCount() {
549	>	int wc = workerCounts;
550	>	if ((wc & RUNNING_COUNT_MASK) == 0)
551	>	return false;
552	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
553	>	wc, wc - ONE_RUNNING);
554		}
555
556		/**
557	<	* Lifecycle control. High word contains runState, low word
266	<	* 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
557	>	* Tries to increment running count
558		*/
559	<	private volatile int runControl;
560	<
561	<	// RunState values. Order among values matters
562	<	private static final int RUNNING     = 0;
563	<	private static final int SHUTDOWN    = 1;
279	<	private static final int TERMINATING = 2;
280	<	private static final int TERMINATED  = 3;
281	<
282	<	private static int runStateOf(int c)             { return c >>> 16; }
283	<	private static int activeCountOf(int c)          { return c & shortMask; }
284	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
559	>	final boolean tryIncrementRunningCount() {
560	>	int wc;
561	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
562	>	wc = workerCounts, wc + ONE_RUNNING);
563	>	}
564
565		/**
566		* Tries incrementing active count; fails on contention.
567	<	* Called by workers before/during executing tasks.
567	>	* Called by workers before executing tasks.
568		*
569		* @return true on success
570		*/
571		final boolean tryIncrementActiveCount() {
572	<	int c = runControl;
573	<	return casRunControl(c, c+1);
572	>	int c;
573	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
574	>	c = runState, c + ONE_ACTIVE);
575		}
576
577		/**
578		* Tries decrementing active count; fails on contention.
579	<	* Possibly triggers termination on success.
300	<	* Called by workers when they can't find tasks.
301	<	*
302	<	* @return true on success
579	>	* Called when workers cannot find tasks to run.
580		*/
581		final boolean tryDecrementActiveCount() {
582	<	int c = runControl;
583	<	int nextc = c - 1;
584	<	if (!casRunControl(c, nextc))
308	<	return false;
309	<	if (canTerminateOnShutdown(nextc))
310	<	terminateOnShutdown();
311	<	return true;
582	>	int c;
583	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
584	>	c = runState, c - ONE_ACTIVE);
585		}
586
587		/**
588	<	* Returns {@code true} if argument represents zero active count
589	<	* and nonzero runstate, which is the triggering condition for
317	<	* terminating on shutdown.
588	>	* Advances to at least the given level. Returns true if not
589	>	* already in at least the given level.
590		*/
591	<	private static boolean canTerminateOnShutdown(int c) {
592	<	// i.e. least bit is nonzero runState bit
593	<	return ((c & -c) >>> 16) != 0;
591	>	private boolean advanceRunLevel(int level) {
592	>	for (;;) {
593	>	int s = runState;
594	>	if ((s & level) != 0)
595	>	return false;
596	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level))
597	>	return true;
598	>	}
599		}
600
601	+	// workers array maintenance
602	+
603		/**
604	<	* Transition run state to at least the given state. Return true
326	<	* if not already at least given state.
604	>	* Records and returns a workers array index for new worker.
605		*/
606	<	private boolean transitionRunStateTo(int state) {
607	<	for (;;) {
608	<	int c = runControl;
609	<	if (runStateOf(c) >= state)
610	<	return false;
611	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
612	<	return true;
606	>	private int recordWorker(ForkJoinWorkerThread w) {
607	>	// Try using slot totalCount-1. If not available, scan and/or resize
608	>	int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1;
609	>	final ReentrantLock lock = this.workerLock;
610	>	lock.lock();
611	>	try {
612	>	ForkJoinWorkerThread[] ws = workers;
613	>	int nws = ws.length;
614	>	if (k < 0 || k >= nws || ws[k] != null) {
615	>	for (k = 0; k < nws && ws[k] != null; ++k)
616	>	;
617	>	if (k == nws)
618	>	ws = Arrays.copyOf(ws, nws << 1);
619	>	}
620	>	ws[k] = w;
621	>	workers = ws; // volatile array write ensures slot visibility
622	>	} finally {
623	>	lock.unlock();
624		}
625	+	return k;
626		}
627
628		/**
629	<	* Controls whether to add spares to maintain parallelism
629	>	* Nulls out record of worker in workers array
630		*/
631	<	private volatile boolean maintainsParallelism;
631	>	private void forgetWorker(ForkJoinWorkerThread w) {
632	>	int idx = w.poolIndex;
633	>	// Locking helps method recordWorker avoid unecessary expansion
634	>	final ReentrantLock lock = this.workerLock;
635	>	lock.lock();
636	>	try {
637	>	ForkJoinWorkerThread[] ws = workers;
638	>	if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify
639	>	ws[idx] = null;
640	>	} finally {
641	>	lock.unlock();
642	>	}
643	>	}
644
645	<	// Constructors
645	>	// adding and removing workers
646
647		/**
648	<	* Creates a {@code ForkJoinPool} with a pool size equal to the
649	<	* number of processors available on the system, using the
650	<	* {@linkplain #defaultForkJoinWorkerThreadFactory default thread factory}.
648	>	* Tries to create and add new worker. Assumes that worker counts
649	>	* are already updated to accommodate the worker, so adjusts on
650	>	* failure.
651		*
652	<	* @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")}
652	>	* @return new worker or null if creation failed
653		*/
654	<	public ForkJoinPool() {
655	<	this(Runtime.getRuntime().availableProcessors(),
656	<	defaultForkJoinWorkerThreadFactory);
654	>	private ForkJoinWorkerThread addWorker() {
655	>	ForkJoinWorkerThread w = null;
656	>	try {
657	>	w = factory.newThread(this);
658	>	} finally { // Adjust on either null or exceptional factory return
659	>	if (w == null)
660	>	onWorkerCreationFailure();
661	>	}
662	>	if (w != null)
663	>	w.start(recordWorker(w), ueh);
664	>	return w;
665		}
666
667		/**
668	<	* Creates a {@code ForkJoinPool} with the indicated parallelism level
362	<	* threads and using the
363	<	* {@linkplain #defaultForkJoinWorkerThreadFactory default thread factory}.
364	<	*
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")}
668	>	* Adjusts counts upon failure to create worker
669		*/
670	<	public ForkJoinPool(int parallelism) {
671	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
670	>	private void onWorkerCreationFailure() {
671	>	for (;;) {
672	>	int wc = workerCounts;
673	>	int rc = wc & RUNNING_COUNT_MASK;
674	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
675	>	if (rc == 0 || wc == 0)
676	>	Thread.yield(); // must wait for other counts to settle
677	>	else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
678	>	wc - (ONE_RUNNING|ONE_TOTAL)))
679	>	break;
680	>	}
681	>	tryTerminate(false); // in case of failure during shutdown
682		}
683
684		/**
685	<	* Creates a {@code ForkJoinPool} with parallelism equal to the
686	<	* 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")}
685	>	* Creates enough total workers to establish target parallelism,
686	>	* giving up if terminating or addWorker fails
687		*/
688	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
689	<	this(Runtime.getRuntime().availableProcessors(), factory);
688	>	private void ensureEnoughTotalWorkers() {
689	>	int wc;
690	>	while (((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < parallelism &&
691	>	runState < TERMINATING) {
692	>	if ((UNSAFE.compareAndSwapInt(this, workerCountsOffset,
693	>	wc, wc + (ONE_RUNNING|ONE_TOTAL)) &&
694	>	addWorker() == null))
695	>	break;
696	>	}
697		}
698
699		/**
700	<	* Creates a {@code ForkJoinPool} with the given parallelism and
701	<	* 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 terminatation, else possibly replaces
703	>	* the worker.
704		*
705	<	* @param parallelism the targeted number of worker threads
398	<	* @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")}
705	>	* @param w the worker
706		*/
707	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
708	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
709	<	throw new IllegalArgumentException();
710	<	if (factory == null)
711	<	throw new NullPointerException();
712	<	checkPermission();
713	<	this.factory = factory;
714	<	this.parallelism = parallelism;
715	<	this.maxPoolSize = MAX_THREADS;
716	<	this.maintainsParallelism = true;
717	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
718	<	this.workerLock = new ReentrantLock();
719	<	this.termination = workerLock.newCondition();
720	<	this.stealCount = new AtomicLong();
721	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
722	<	// worker array and workers are lazily constructed
707	>	final void workerTerminated(ForkJoinWorkerThread w) {
708	>	if (w.active) { // force inactive
709	>	w.active = false;
710	>	do {} while (!tryDecrementActiveCount());
711	>	}
712	>	forgetWorker(w);
713	>
714	>	// Decrement total count, and if was running, running count
715	>	// Spin (waiting for other updates) if either would be negative
716	>	int nr = w.isTrimmed() ? 0 : ONE_RUNNING;
717	>	int unit = ONE_TOTAL + nr;
718	>	for (;;) {
719	>	int wc = workerCounts;
720	>	int rc = wc & RUNNING_COUNT_MASK;
721	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
722	>	if (rc - nr < 0 || tc == 0)
723	>	Thread.yield(); // back off if waiting for other updates
724	>	else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
725	>	wc, wc - unit))
726	>	break;
727	>	}
728	>
729	>	accumulateStealCount(w); // collect final count
730	>	if (!tryTerminate(false))
731	>	ensureEnoughTotalWorkers();
732		}
733
734	+	// Waiting for and signalling events
735	+
736		/**
737	<	* Creates a new worker thread using factory.
738	<	*
428	<	* @param index the index to assign worker
429	<	* @return new worker, or null if factory failed
737	>	* Releases workers blocked on a count not equal to current count.
738	>	* @return true if any released
739		*/
740	<	private ForkJoinWorkerThread createWorker(int index) {
741	<	Thread.UncaughtExceptionHandler h = ueh;
742	<	ForkJoinWorkerThread w = factory.newThread(this);
743	<	if (w != null) {
744	<	w.poolIndex = index;
745	<	w.setDaemon(true);
746	<	w.setAsyncMode(locallyFifo);
747	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
748	<	if (h != null)
749	<	w.setUncaughtExceptionHandler(h);
740	>	private void releaseWaiters() {
741	>	long top;
742	>	while ((top = eventWaiters) != 0L) {
743	>	ForkJoinWorkerThread[] ws = workers;
744	>	int n = ws.length;
745	>	for (;;) {
746	>	int i = ((int)(top & WAITER_ID_MASK)) - 1;
747	>	int e = (int)(top >>> EVENT_COUNT_SHIFT);
748	>	if (i < 0 || e == eventCount)
749	>	return;
750	>	ForkJoinWorkerThread w;
751	>	if (i < n && (w = ws[i]) != null &&
752	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
753	>	top, w.nextWaiter)) {
754	>	LockSupport.unpark(w);
755	>	top = eventWaiters;
756	>	}
757	>	else
758	>	break;      // possibly stale; reread
759	>	}
760		}
442	–	return w;
761		}
762
763		/**
764	<	* Returns a good size for worker array given pool size.
765	<	* Currently requires size to be a power of two.
764	>	* Ensures eventCount on exit is different (mod 2^32) than on
765	>	* entry and wakes up all waiters
766		*/
767	<	private static int arraySizeFor(int poolSize) {
768	<	return (poolSize <= 1) ? 1 :
769	<	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
767	>	private void signalEvent() {
768	>	int c;
769	>	do {} while (!UNSAFE.compareAndSwapInt(this, eventCountOffset,
770	>	c = eventCount, c+1));
771	>	releaseWaiters();
772		}
773
774		/**
775	<	* Creates or resizes array if necessary to hold newLength.
776	<	* Call only under exclusion.
457	<	*
458	<	* @return the array
775	>	* Advances eventCount and releases waiters until interference by
776	>	* other releasing threads is detected.
777		*/
778	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
779	<	ForkJoinWorkerThread[] ws = workers;
780	<	if (ws == null)
781	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
782	<	else if (newLength > ws.length)
783	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
784	<	else
785	<	return ws;
778	>	final void signalWork() {
779	>	int c;
780	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c=eventCount, c+1);
781	>	long top;
782	>	while ((top = eventWaiters) != 0L) {
783	>	int ec = eventCount;
784	>	ForkJoinWorkerThread[] ws = workers;
785	>	int n = ws.length;
786	>	for (;;) {
787	>	int i = ((int)(top & WAITER_ID_MASK)) - 1;
788	>	int e = (int)(top >>> EVENT_COUNT_SHIFT);
789	>	if (i < 0 || e == ec)
790	>	return;
791	>	ForkJoinWorkerThread w;
792	>	if (i < n && (w = ws[i]) != null &&
793	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
794	>	top, top = w.nextWaiter)) {
795	>	LockSupport.unpark(w);
796	>	if (top != eventWaiters) // let someone else take over
797	>	return;
798	>	}
799	>	else
800	>	break;      // possibly stale; reread
801	>	}
802	>	}
803		}
804
805		/**
806	<	* Tries to shrink workers into smaller array after one or more terminate.
806	>	* Blockss worker until terminating or event count
807	>	* advances from last value held by worker
808	>	*
809	>	* @param w the calling worker thread
810		*/
811	<	private void tryShrinkWorkerArray() {
812	<	ForkJoinWorkerThread[] ws = workers;
813	<	if (ws != null) {
814	<	int len = ws.length;
815	<	int last = len - 1;
816	<	while (last >= 0 && ws[last] == null)
817	<	--last;
818	<	int newLength = arraySizeFor(last+1);
819	<	if (newLength < len)
820	<	workers = Arrays.copyOf(ws, newLength);
811	>	private void eventSync(ForkJoinWorkerThread w) {
812	>	int wec = w.lastEventCount;
813	>	long nextTop = (((long)wec << EVENT_COUNT_SHIFT) |
814	>	((long)(w.poolIndex + 1)));
815	>	long top;
816	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
817	>	(((int)(top = eventWaiters) & WAITER_ID_MASK) == 0 ||
818	>	(int)(top >>> EVENT_COUNT_SHIFT) == wec) &&
819	>	eventCount == wec) {
820	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
821	>	w.nextWaiter = top, nextTop)) {
822	>	accumulateStealCount(w); // transfer steals while idle
823	>	Thread.interrupted();    // clear/ignore interrupt
824	>	while (eventCount == wec)
825	>	w.doPark();
826	>	break;
827	>	}
828		}
829	+	w.lastEventCount = eventCount;
830		}
831
832		/**
833	<	* Initializes workers if necessary.
833	>	* Callback from workers invoked upon each top-level action (i.e.,
834	>	* stealing a task or taking a submission and running
835	>	* it). Performs one or both of the following:
836	>	*
837	>	* * If the worker cannot find work, updates its active status to
838	>	* inactive and updates activeCount unless there is contention, in
839	>	* which case it may try again (either in this or a subsequent
840	>	* call).  Additionally, awaits the next task event and/or helps
841	>	* wake up other releasable waiters.
842	>	*
843	>	* * If there are too many running threads, suspends this worker
844	>	* (first forcing inactivation if necessary).  If it is not
845	>	* resumed before a keepAlive elapses, the worker may be "trimmed"
846	>	* -- killed while suspended within suspendAsSpare. Otherwise,
847	>	* upon resume it rechecks to make sure that it is still needed.
848	>	*
849	>	* @param w the worker
850	>	* @param retries the number of scans by caller failing to find work
851	>	* find any (in which case it may block waiting for work).
852		*/
853	<	final void ensureWorkerInitialization() {
854	<	ForkJoinWorkerThread[] ws = workers;
855	<	if (ws == null) {
856	<	final ReentrantLock lock = this.workerLock;
857	<	lock.lock();
858	<	try {
859	<	ws = workers;
860	<	if (ws == null) {
861	<	int ps = parallelism;
862	<	ws = ensureWorkerArrayCapacity(ps);
863	<	for (int i = 0; i < ps; ++i) {
864	<	ForkJoinWorkerThread w = createWorker(i);
865	<	if (w != null) {
866	<	ws[i] = w;
867	<	w.start();
868	<	updateWorkerCount(1);
853	>	final void preStep(ForkJoinWorkerThread w, int retries) {
854	>	boolean active = w.active;
855	>	boolean inactivate = active && retries > 0;
856	>	for (;;) {
857	>	int rs, wc;
858	>	if (inactivate &&
859	>	UNSAFE.compareAndSwapInt(this, runStateOffset,
860	>	rs = runState, rs - ONE_ACTIVE))
861	>	inactivate = active = w.active = false;
862	>	if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= parallelism) {
863	>	if (retries > 0) {
864	>	if (retries > 1 && !active)
865	>	eventSync(w);
866	>	releaseWaiters();
867	>	}
868	>	break;
869	>	}
870	>	if (!(inactivate |= active) &&  // must inactivate to suspend
871	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
872	>	wc, wc - ONE_RUNNING) &&
873	>	!w.suspendAsSpare())             // false if trimmed
874	>	break;
875	>	}
876	>	}
877	>
878	>	/**
879	>	* Awaits join of the given task if enough threads, or can resume
880	>	* or create a spare. Fails (in which case the given task might
881	>	* not be done) upon contention or lack of decision about
882	>	* blocking.
883	>	*
884	>	* We allow blocking if:
885	>	*
886	>	* 1. There would still be at least as many running threads as
887	>	*    parallelism level if this thread blocks.
888	>	*
889	>	* 2. A spare is resumed to replace this worker. We tolerate
890	>	*    races in the decision to replace when a spare is found.
891	>	*    This may release too many, but if so, the superfluous ones
892	>	*    will re-suspend via preStep().
893	>	*
894	>	* 3. After #spares repeated retries, there are fewer than #spare
895	>	*    threads not running. We allow this slack to avoid hysteresis
896	>	*    and as a hedge against lag/uncertainty of running count
897	>	*    estimates when signalling or unblocking stalls.
898	>	*
899	>	* 4. All existing workers are busy (as rechecked via #spares
900	>	*    repeated retries by caller) and a new spare is created.
901	>	*
902	>	* If none of the above hold, we escape out by re-incrementing
903	>	* count and returning to caller, which can retry later.
904	>	*
905	>	* @param joinMe the task to join
906	>	* @param retries the number of calls to this method for this join
907	>	*/
908	>	final void tryAwaitJoin(ForkJoinTask<?> joinMe, int retries) {
909	>	int pc = parallelism;
910	>	boolean running = true; // false when running count decremented
911	>	outer:while (joinMe.status >= 0) {
912	>	int wc = workerCounts;
913	>	int rc = wc & RUNNING_COUNT_MASK;
914	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
915	>	if (running) { // replace with spare or decrement count
916	>	if (rc <= pc && tc > pc &&
917	>	(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) {
918	>	ForkJoinWorkerThread[] ws = workers; // search for spare
919	>	int nws = ws.length;
920	>	for (int i = 0; i < nws; ++i) {
921	>	ForkJoinWorkerThread w = ws[i];
922	>	if (w != null && w.isSuspended()) {
923	>	if ((workerCounts & RUNNING_COUNT_MASK) > pc)
924	>	continue outer;
925	>	if (joinMe.status < 0)
926	>	break outer;
927	>	if (w.tryResumeSpare()) {
928	>	running = false;
929	>	break outer;
930	>	}
931	>	continue outer; // rescan on failure to resume
932		}
933		}
934		}
935	<	} finally {
936	<	lock.unlock();
935	>	if ((rc <= pc && (rc == 0 || --retries < 0)) || // no retry
936	>	joinMe.status < 0)
937	>	break;
938	>	if (workerCounts == wc &&
939	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
940	>	wc, wc - ONE_RUNNING))
941	>	running = false;
942	>	}
943	>	else { // allow blocking if enough threads
944	>	int sc = tc - pc + 1;          // = spares, plus the one to add
945	>	if (sc > 0 && rc > 0 && rc >= pc - sc && rc > pc - retries)
946	>	break;
947	>	if (--retries > sc && tc < MAX_THREADS &&
948	>	tc == (runState & ACTIVE_COUNT_MASK) &&
949	>	workerCounts == wc &&
950	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
951	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
952	>	addWorker();
953	>	break;
954	>	}
955	>	if (workerCounts == wc &&
956	>	UNSAFE.compareAndSwapInt (this, workerCountsOffset,
957	>	wc, wc + ONE_RUNNING)) {
958	>	running = true;            // back out; allow retry
959	>	break;
960	>	}
961		}
962		}
963	+	if (!running) { // can block
964	+	int c;                      // to inline incrementRunningCount
965	+	joinMe.internalAwaitDone();
966	+	do {} while (!UNSAFE.compareAndSwapInt
967	+	(this, workerCountsOffset,
968	+	c = workerCounts, c + ONE_RUNNING));
969	+	}
970		}
971
972		/**
973	<	* Worker creation and startup for threads added via setParallelism.
973	>	* Same idea as (and shares many code snippets with) tryAwaitJoin,
974	>	* but self-contained because there are no caller retries.
975	>	* TODO: Rework to use simpler API.
976		*/
977	<	private void createAndStartAddedWorkers() {
978	<	resumeAllSpares();  // Allow spares to convert to nonspare
979	<	int ps = parallelism;
980	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
981	<	int len = ws.length;
982	<	// Sweep through slots, to keep lowest indices most populated
983	<	int k = 0;
984	<	while (k < len) {
985	<	if (ws[k] != null) {
986	<	++k;
987	<	continue;
977	>	final void awaitBlocker(ManagedBlocker blocker)
978	>	throws InterruptedException {
979	>	int pc = parallelism;
980	>	boolean running = true;
981	>	int retries = 0;
982	>	boolean done;
983	>	outer:while (!(done = blocker.isReleasable())) {
984	>	int wc = workerCounts;
985	>	int rc = wc & RUNNING_COUNT_MASK;
986	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
987	>	if (running) {
988	>	if (rc <= pc && tc > pc &&
989	>	(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) {
990	>	ForkJoinWorkerThread[] ws = workers;
991	>	int nws = ws.length;
992	>	for (int i = 0; i < nws; ++i) {
993	>	ForkJoinWorkerThread w = ws[i];
994	>	if (w != null && w.isSuspended()) {
995	>	if ((workerCounts & RUNNING_COUNT_MASK) > pc)
996	>	continue outer;
997	>	if (done = blocker.isReleasable())
998	>	break outer;
999	>	if (w.tryResumeSpare()) {
1000	>	running = false;
1001	>	break outer;
1002	>	}
1003	>	continue outer;
1004	>	}
1005	>	}
1006	>	if (done = blocker.isReleasable())
1007	>	break;
1008	>	}
1009	>	if (rc > 0 && workerCounts == wc &&
1010	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1011	>	wc, wc - ONE_RUNNING)) {
1012	>	running = false;
1013	>	if (rc > pc)
1014	>	break;
1015	>	}
1016		}
1017	<	int s = workerCounts;
530	<	int tc = totalCountOf(s);
531	<	int rc = runningCountOf(s);
532	<	if (rc >= ps || tc >= ps)
1017	>	else if (rc >= pc)
1018		break;
1019	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
1020	<	ForkJoinWorkerThread w = createWorker(k);
1021	<	if (w != null) {
1022	<	ws[k++] = w;
1023	<	w.start();
1024	<	}
1025	<	else {
1026	<	updateWorkerCount(-1); // back out on failed creation
1027	<	break;
1019	>	else if (tc < MAX_THREADS &&
1020	>	tc == (runState & ACTIVE_COUNT_MASK) &&
1021	>	workerCounts == wc &&
1022	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
1023	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
1024	>	addWorker();
1025	>	break;
1026	>	}
1027	>	else if (workerCounts == wc &&
1028	>	UNSAFE.compareAndSwapInt (this, workerCountsOffset,
1029	>	wc, wc + ONE_RUNNING)) {
1030	>	Thread.yield();
1031	>	++retries;
1032	>	running = true;            // allow rescan
1033	>	}
1034	>	}
1035	>
1036	>	try {
1037	>	if (!done)
1038	>	do {} while (!blocker.isReleasable() && !blocker.block());
1039	>	} finally {
1040	>	if (!running) {
1041	>	int c;
1042	>	do {} while (!UNSAFE.compareAndSwapInt
1043	>	(this, workerCountsOffset,
1044	>	c = workerCounts, c + ONE_RUNNING));
1045	>	}
1046	>	}
1047	>	}
1048	>
1049	>	/**
1050	>	* Possibly initiates and/or completes termination.
1051	>	*
1052	>	* @param now if true, unconditionally terminate, else only
1053	>	* if shutdown and empty queue and no active workers
1054	>	* @return true if now terminating or terminated
1055	>	*/
1056	>	private boolean tryTerminate(boolean now) {
1057	>	if (now)
1058	>	advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN
1059	>	else if (runState < SHUTDOWN ||
1060	>	!submissionQueue.isEmpty() ||
1061	>	(runState & ACTIVE_COUNT_MASK) != 0)
1062	>	return false;
1063	>
1064	>	if (advanceRunLevel(TERMINATING))
1065	>	startTerminating();
1066	>
1067	>	// Finish now if all threads terminated; else in some subsequent call
1068	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1069	>	advanceRunLevel(TERMINATED);
1070	>	termination.arrive();
1071	>	}
1072	>	return true;
1073	>	}
1074	>
1075	>	/**
1076	>	* Actions on transition to TERMINATING
1077	>	*/
1078	>	private void startTerminating() {
1079	>	for (int i = 0; i < 2; ++i) { // twice to mop up newly created workers
1080	>	cancelSubmissions();
1081	>	shutdownWorkers();
1082	>	cancelWorkerTasks();
1083	>	signalEvent();
1084	>	interruptWorkers();
1085	>	}
1086	>	}
1087	>
1088	>	/**
1089	>	* Clear out and cancel submissions, ignoring exceptions
1090	>	*/
1091	>	private void cancelSubmissions() {
1092	>	ForkJoinTask<?> task;
1093	>	while ((task = submissionQueue.poll()) != null) {
1094	>	try {
1095	>	task.cancel(false);
1096	>	} catch (Throwable ignore) {
1097	>	}
1098	>	}
1099	>	}
1100	>
1101	>	/**
1102	>	* Sets all worker run states to at least shutdown,
1103	>	* also resuming suspended workers
1104	>	*/
1105	>	private void shutdownWorkers() {
1106	>	ForkJoinWorkerThread[] ws = workers;
1107	>	int nws = ws.length;
1108	>	for (int i = 0; i < nws; ++i) {
1109	>	ForkJoinWorkerThread w = ws[i];
1110	>	if (w != null)
1111	>	w.shutdown();
1112	>	}
1113	>	}
1114	>
1115	>	/**
1116	>	* Clears out and cancels all locally queued tasks
1117	>	*/
1118	>	private void cancelWorkerTasks() {
1119	>	ForkJoinWorkerThread[] ws = workers;
1120	>	int nws = ws.length;
1121	>	for (int i = 0; i < nws; ++i) {
1122	>	ForkJoinWorkerThread w = ws[i];
1123	>	if (w != null)
1124	>	w.cancelTasks();
1125	>	}
1126	>	}
1127	>
1128	>	/**
1129	>	* Unsticks all workers blocked on joins etc
1130	>	*/
1131	>	private void interruptWorkers() {
1132	>	ForkJoinWorkerThread[] ws = workers;
1133	>	int nws = ws.length;
1134	>	for (int i = 0; i < nws; ++i) {
1135	>	ForkJoinWorkerThread w = ws[i];
1136	>	if (w != null && !w.isTerminated()) {
1137	>	try {
1138	>	w.interrupt();
1139	>	} catch (SecurityException ignore) {
1140		}
1141		}
1142		}
1143		}
1144
1145	+	// misc support for ForkJoinWorkerThread
1146	+
1147	+	/**
1148	+	* Returns pool number
1149	+	*/
1150	+	final int getPoolNumber() {
1151	+	return poolNumber;
1152	+	}
1153	+
1154	+	/**
1155	+	* Accumulates steal count from a worker, clearing
1156	+	* the worker's value
1157	+	*/
1158	+	final void accumulateStealCount(ForkJoinWorkerThread w) {
1159	+	int sc = w.stealCount;
1160	+	if (sc != 0) {
1161	+	long c;
1162	+	w.stealCount = 0;
1163	+	do {} while (!UNSAFE.compareAndSwapLong(this, stealCountOffset,
1164	+	c = stealCount, c + sc));
1165	+	}
1166	+	}
1167	+
1168	+	/**
1169	+	* Returns the approximate (non-atomic) number of idle threads per
1170	+	* active thread.
1171	+	*/
1172	+	final int idlePerActive() {
1173	+	int pc = parallelism; // use parallelism, not rc
1174	+	int ac = runState;    // no mask -- artifically boosts during shutdown
1175	+	// Use exact results for small values, saturate past 4
1176	+	return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
1177	+	}
1178	+
1179	+	// Public and protected methods
1180	+
1181	+	// Constructors
1182	+
1183	+	/**
1184	+	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1185	+	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1186	+	* #defaultForkJoinWorkerThreadFactory default thread factory},
1187	+	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1188	+	*
1189	+	* @throws SecurityException if a security manager exists and
1190	+	*         the caller is not permitted to modify threads
1191	+	*         because it does not hold {@link
1192	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1193	+	*/
1194	+	public ForkJoinPool() {
1195	+	this(Runtime.getRuntime().availableProcessors(),
1196	+	defaultForkJoinWorkerThreadFactory, null, false);
1197	+	}
1198	+
1199	+	/**
1200	+	* Creates a {@code ForkJoinPool} with the indicated parallelism
1201	+	* level, the {@linkplain
1202	+	* #defaultForkJoinWorkerThreadFactory default thread factory},
1203	+	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1204	+	*
1205	+	* @param parallelism the parallelism level
1206	+	* @throws IllegalArgumentException if parallelism less than or
1207	+	*         equal to zero, or greater than implementation limit
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(int parallelism) {
1214	+	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1215	+	}
1216	+
1217	+	/**
1218	+	* Creates a {@code ForkJoinPool} with the given parameters.
1219	+	*
1220	+	* @param parallelism the parallelism level. For default value,
1221	+	* use {@link java.lang.Runtime#availableProcessors}.
1222	+	* @param factory the factory for creating new threads. For default value,
1223	+	* use {@link #defaultForkJoinWorkerThreadFactory}.
1224	+	* @param handler the handler for internal worker threads that
1225	+	* terminate due to unrecoverable errors encountered while executing
1226	+	* tasks. For default value, use <code>null</code>.
1227	+	* @param asyncMode if true,
1228	+	* establishes local first-in-first-out scheduling mode for forked
1229	+	* tasks that are never joined. This mode may be more appropriate
1230	+	* than default locally stack-based mode in applications in which
1231	+	* worker threads only process event-style asynchronous tasks.
1232	+	* For default value, use <code>false</code>.
1233	+	* @throws IllegalArgumentException if parallelism less than or
1234	+	*         equal to zero, or greater than implementation limit
1235	+	* @throws NullPointerException if the factory is null
1236	+	* @throws SecurityException if a security manager exists and
1237	+	*         the caller is not permitted to modify threads
1238	+	*         because it does not hold {@link
1239	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1240	+	*/
1241	+	public ForkJoinPool(int parallelism,
1242	+	ForkJoinWorkerThreadFactory factory,
1243	+	Thread.UncaughtExceptionHandler handler,
1244	+	boolean asyncMode) {
1245	+	checkPermission();
1246	+	if (factory == null)
1247	+	throw new NullPointerException();
1248	+	if (parallelism <= 0 || parallelism > MAX_THREADS)
1249	+	throw new IllegalArgumentException();
1250	+	this.parallelism = parallelism;
1251	+	this.factory = factory;
1252	+	this.ueh = handler;
1253	+	this.locallyFifo = asyncMode;
1254	+	int arraySize = initialArraySizeFor(parallelism);
1255	+	this.workers = new ForkJoinWorkerThread[arraySize];
1256	+	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
1257	+	this.workerLock = new ReentrantLock();
1258	+	this.termination = new Phaser(1);
1259	+	this.poolNumber = poolNumberGenerator.incrementAndGet();
1260	+	}
1261	+
1262	+	/**
1263	+	* Returns initial power of two size for workers array.
1264	+	* @param pc the initial parallelism level
1265	+	*/
1266	+	private static int initialArraySizeFor(int pc) {
1267	+	// See Hackers Delight, sec 3.2. We know MAX_THREADS < (1 >>> 16)
1268	+	int size = pc < MAX_THREADS ? pc + 1 : MAX_THREADS;
1269	+	size |= size >>> 1;
1270	+	size |= size >>> 2;
1271	+	size |= size >>> 4;
1272	+	size |= size >>> 8;
1273	+	return size + 1;
1274	+	}
1275	+
1276		// Execution methods
1277
1278		/**
#	Line 553 | Line 1281 | public class ForkJoinPool extends Abstra
1281		private <T> void doSubmit(ForkJoinTask<T> task) {
1282		if (task == null)
1283		throw new NullPointerException();
1284	<	if (isShutdown())
1284	>	if (runState >= SHUTDOWN)
1285		throw new RejectedExecutionException();
558	–	if (workers == null)
559	–	ensureWorkerInitialization();
1286		submissionQueue.offer(task);
1287	<	signalIdleWorkers();
1287	>	signalEvent();
1288	>	ensureEnoughTotalWorkers();
1289		}
1290
1291		/**
1292		* Performs the given task, returning its result upon completion.
1293	+	* If the caller is already engaged in a fork/join computation in
1294	+	* the current pool, this method is equivalent in effect to
1295	+	* {@link ForkJoinTask#invoke}.
1296		*
1297		* @param task the task
1298		* @return the task's result
1299	<	* @throws NullPointerException if task is null
1300	<	* @throws RejectedExecutionException if pool is shut down
1299	>	* @throws NullPointerException if the task is null
1300	>	* @throws RejectedExecutionException if the task cannot be
1301	>	*         scheduled for execution
1302		*/
1303		public <T> T invoke(ForkJoinTask<T> task) {
1304		doSubmit(task);
#	Line 576 | Line 1307 | public class ForkJoinPool extends Abstra
1307
1308		/**
1309		* Arranges for (asynchronous) execution of the given task.
1310	+	* If the caller is already engaged in a fork/join computation in
1311	+	* the current pool, this method is equivalent in effect to
1312	+	* {@link ForkJoinTask#fork}.
1313		*
1314		* @param task the task
1315	<	* @throws NullPointerException if task is null
1316	<	* @throws RejectedExecutionException if pool is shut down
1315	>	* @throws NullPointerException if the task is null
1316	>	* @throws RejectedExecutionException if the task cannot be
1317	>	*         scheduled for execution
1318		*/
1319		public void execute(ForkJoinTask<?> task) {
1320		doSubmit(task);
#	Line 587 | Line 1322 | public class ForkJoinPool extends Abstra
1322
1323		// AbstractExecutorService methods
1324
1325	+	/**
1326	+	* @throws NullPointerException if the task is null
1327	+	* @throws RejectedExecutionException if the task cannot be
1328	+	*         scheduled for execution
1329	+	*/
1330		public void execute(Runnable task) {
1331		ForkJoinTask<?> job;
1332		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
#	Line 596 | Line 1336 | public class ForkJoinPool extends Abstra
1336		doSubmit(job);
1337		}
1338
1339	+	/**
1340	+	* Submits a ForkJoinTask for execution.
1341	+	* If the caller is already engaged in a fork/join computation in
1342	+	* the current pool, this method is equivalent in effect to
1343	+	* {@link ForkJoinTask#fork}.
1344	+	*
1345	+	* @param task the task to submit
1346	+	* @return the task
1347	+	* @throws NullPointerException if the task is null
1348	+	* @throws RejectedExecutionException if the task cannot be
1349	+	*         scheduled for execution
1350	+	*/
1351	+	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1352	+	doSubmit(task);
1353	+	return task;
1354	+	}
1355	+
1356	+	/**
1357	+	* @throws NullPointerException if the task is null
1358	+	* @throws RejectedExecutionException if the task cannot be
1359	+	*         scheduled for execution
1360	+	*/
1361		public <T> ForkJoinTask<T> submit(Callable<T> task) {
1362		ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1363		doSubmit(job);
1364		return job;
1365		}
1366
1367	+	/**
1368	+	* @throws NullPointerException if the task is null
1369	+	* @throws RejectedExecutionException if the task cannot be
1370	+	*         scheduled for execution
1371	+	*/
1372		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1373		ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1374		doSubmit(job);
1375		return job;
1376		}
1377
1378	+	/**
1379	+	* @throws NullPointerException if the task is null
1380	+	* @throws RejectedExecutionException if the task cannot be
1381	+	*         scheduled for execution
1382	+	*/
1383		public ForkJoinTask<?> submit(Runnable task) {
1384		ForkJoinTask<?> job;
1385		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
#	Line 619 | Line 1391 | public class ForkJoinPool extends Abstra
1391		}
1392
1393		/**
1394	<	* Submits a ForkJoinTask for execution.
1395	<	*
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
1394	>	* @throws NullPointerException       {@inheritDoc}
1395	>	* @throws RejectedExecutionException {@inheritDoc}
1396		*/
630	–	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
631	–	doSubmit(task);
632	–	return task;
633	–	}
634	–
635	–
1397		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
1398		ArrayList<ForkJoinTask<T>> forkJoinTasks =
1399		new ArrayList<ForkJoinTask<T>>(tasks.size());
#	Line 641 | Line 1402 | public class ForkJoinPool extends Abstra
1402		invoke(new InvokeAll<T>(forkJoinTasks));
1403
1404		@SuppressWarnings({"unchecked", "rawtypes"})
1405	<	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1405	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1406		return futures;
1407		}
1408
#	Line 655 | Line 1416 | public class ForkJoinPool extends Abstra
1416		private static final long serialVersionUID = -7914297376763021607L;
1417		}
1418
658	–	// Configuration and status settings and queries
659	–
1419		/**
1420		* Returns the factory used for constructing new workers.
1421		*
#	Line 673 | Line 1432 | public class ForkJoinPool extends Abstra
1432		* @return the handler, or {@code null} if none
1433		*/
1434		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1435	<	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;
1435	>	return ueh;
1436		}
1437
1438		/**
1439	<	* 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.
1439	>	* Returns the targeted parallelism level of this pool.
1440		*
1441	<	* @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();
754	<	}
755	<
756	<	/**
757	<	* Returns the targeted number of worker threads in this pool.
758	<	*
759	<	* @return the targeted number of worker threads in this pool
1441	>	* @return the targeted parallelism level of this pool
1442		*/
1443		public int getParallelism() {
1444		return parallelism;
#	Line 771 | Line 1453 | public class ForkJoinPool extends Abstra
1453		* @return the number of worker threads
1454		*/
1455		public int getPoolSize() {
1456	<	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;
1456	>	return workerCounts >>> TOTAL_COUNT_SHIFT;
1457		}
1458
1459		/**
#	Line 854 | Line 1461 | public class ForkJoinPool extends Abstra
1461		* scheduling mode for forked tasks that are never joined.
1462		*
1463		* @return {@code true} if this pool uses async mode
857	–	* @see #setAsyncMode
1464		*/
1465		public boolean getAsyncMode() {
1466		return locallyFifo;
#	Line 863 | Line 1469 | public class ForkJoinPool extends Abstra
1469		/**
1470		* Returns an estimate of the number of worker threads that are
1471		* not blocked waiting to join tasks or for other managed
1472	<	* synchronization.
1472	>	* synchronization. This method may overestimate the
1473	>	* number of running threads.
1474		*
1475		* @return the number of worker threads
1476		*/
1477		public int getRunningThreadCount() {
1478	<	return runningCountOf(workerCounts);
1478	>	return workerCounts & RUNNING_COUNT_MASK;
1479		}
1480
1481		/**
#	Line 879 | Line 1486 | public class ForkJoinPool extends Abstra
1486		* @return the number of active threads
1487		*/
1488		public int getActiveThreadCount() {
1489	<	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;
1489	>	return runState & ACTIVE_COUNT_MASK;
1490		}
1491
1492		/**
#	Line 906 | Line 1501 | public class ForkJoinPool extends Abstra
1501		* @return {@code true} if all threads are currently idle
1502		*/
1503		public boolean isQuiescent() {
1504	<	return activeCountOf(runControl) == 0;
1504	>	return (runState & ACTIVE_COUNT_MASK) == 0;
1505		}
1506
1507		/**
#	Line 921 | Line 1516 | public class ForkJoinPool extends Abstra
1516		* @return the number of steals
1517		*/
1518		public long getStealCount() {
1519	<	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);
1519	>	return stealCount;
1520		}
1521
1522		/**
#	Line 947 | Line 1532 | public class ForkJoinPool extends Abstra
1532		public long getQueuedTaskCount() {
1533		long count = 0;
1534		ForkJoinWorkerThread[] ws = workers;
1535	<	if (ws != null) {
1536	<	for (int i = 0; i < ws.length; ++i) {
1537	<	ForkJoinWorkerThread t = ws[i];
1538	<	if (t != null)
1539	<	count += t.getQueueSize();
955	<	}
1535	>	int nws = ws.length;
1536	>	for (int i = 0; i < nws; ++i) {
1537	>	ForkJoinWorkerThread w = ws[i];
1538	>	if (w != null)
1539	>	count += w.getQueueSize();
1540		}
1541		return count;
1542		}
#	Line 1009 | Line 1593 | public class ForkJoinPool extends Abstra
1593		protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1594		int n = submissionQueue.drainTo(c);
1595		ForkJoinWorkerThread[] ws = workers;
1596	<	if (ws != null) {
1597	<	for (int i = 0; i < ws.length; ++i) {
1598	<	ForkJoinWorkerThread w = ws[i];
1599	<	if (w != null)
1600	<	n += w.drainTasksTo(c);
1017	<	}
1596	>	int nws = ws.length;
1597	>	for (int i = 0; i < nws; ++i) {
1598	>	ForkJoinWorkerThread w = ws[i];
1599	>	if (w != null)
1600	>	n += w.drainTasksTo(c);
1601		}
1602		return n;
1603		}
1604
1605		/**
1606	+	* Returns count of total parks by existing workers.
1607	+	* Used during development only since not meaningful to users.
1608	+	*/
1609	+	private int collectParkCount() {
1610	+	int count = 0;
1611	+	ForkJoinWorkerThread[] ws = workers;
1612	+	int nws = ws.length;
1613	+	for (int i = 0; i < nws; ++i) {
1614	+	ForkJoinWorkerThread w = ws[i];
1615	+	if (w != null)
1616	+	count += w.parkCount;
1617	+	}
1618	+	return count;
1619	+	}
1620	+
1621	+	/**
1622		* Returns a string identifying this pool, as well as its state,
1623		* including indications of run state, parallelism level, and
1624		* worker and task counts.
#	Line 1027 | Line 1626 | public class ForkJoinPool extends Abstra
1626		* @return a string identifying this pool, as well as its state
1627		*/
1628		public String toString() {
1030	–	int ps = parallelism;
1031	–	int wc = workerCounts;
1032	–	int rc = runControl;
1629		long st = getStealCount();
1630		long qt = getQueuedTaskCount();
1631		long qs = getQueuedSubmissionCount();
1632	+	int wc = workerCounts;
1633	+	int tc = wc >>> TOTAL_COUNT_SHIFT;
1634	+	int rc = wc & RUNNING_COUNT_MASK;
1635	+	int pc = parallelism;
1636	+	int rs = runState;
1637	+	int ac = rs & ACTIVE_COUNT_MASK;
1638	+	//        int pk = collectParkCount();
1639		return super.toString() +
1640	<	"[" + runStateToString(runStateOf(rc)) +
1641	<	", parallelism = " + ps +
1642	<	", size = " + totalCountOf(wc) +
1643	<	", active = " + activeCountOf(rc) +
1644	<	", running = " + runningCountOf(wc) +
1640	>	"[" + runLevelToString(rs) +
1641	>	", parallelism = " + pc +
1642	>	", size = " + tc +
1643	>	", active = " + ac +
1644	>	", running = " + rc +
1645		", steals = " + st +
1646		", tasks = " + qt +
1647		", submissions = " + qs +
1648	+	//            ", parks = " + pk +
1649		"]";
1650		}
1651
1652	<	private static String runStateToString(int rs) {
1653	<	switch(rs) {
1654	<	case RUNNING: return "Running";
1655	<	case SHUTDOWN: return "Shutting down";
1656	<	case TERMINATING: return "Terminating";
1053	<	case TERMINATED: return "Terminated";
1054	<	default: throw new Error("Unknown run state");
1055	<	}
1652	>	private static String runLevelToString(int s) {
1653	>	return ((s & TERMINATED) != 0 ? "Terminated" :
1654	>	((s & TERMINATING) != 0 ? "Terminating" :
1655	>	((s & SHUTDOWN) != 0 ? "Shutting down" :
1656	>	"Running")));
1657		}
1658
1058	–	// lifecycle control
1059	–
1659		/**
1660		* Initiates an orderly shutdown in which previously submitted
1661		* tasks are executed, but no new tasks will be accepted.
#	Line 1071 | Line 1670 | public class ForkJoinPool extends Abstra
1670		*/
1671		public void shutdown() {
1672		checkPermission();
1673	<	transitionRunStateTo(SHUTDOWN);
1674	<	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	<	}
1673	>	advanceRunLevel(SHUTDOWN);
1674	>	tryTerminate(false);
1675		}
1676
1677		/**
1678	<	* Attempts to stop all actively executing tasks, and cancels all
1679	<	* waiting tasks.  Tasks that are in the process of being
1680	<	* submitted or executed concurrently during the course of this
1681	<	* method may or may not be rejected. Unlike some other executors,
1682	<	* this method cancels rather than collects non-executed tasks
1683	<	* upon termination, so always returns an empty list. However, you
1684	<	* can use method {@link #drainTasksTo} before invoking this
1685	<	* method to transfer unexecuted tasks to another collection.
1678	>	* Attempts to cancel and/or stop all tasks, and reject all
1679	>	* subsequently submitted tasks.  Tasks that are in the process of
1680	>	* being submitted or executed concurrently during the course of
1681	>	* this method may or may not be rejected. This method cancels
1682	>	* both existing and unexecuted tasks, in order to permit
1683	>	* termination in the presence of task dependencies. So the method
1684	>	* always returns an empty list (unlike the case for some other
1685	>	* Executors).
1686		*
1687		* @return an empty list
1688		* @throws SecurityException if a security manager exists and
#	Line 1108 | Line 1692 | public class ForkJoinPool extends Abstra
1692		*/
1693		public List<Runnable> shutdownNow() {
1694		checkPermission();
1695	<	terminate();
1695	>	tryTerminate(true);
1696		return Collections.emptyList();
1697		}
1698
#	Line 1118 | Line 1702 | public class ForkJoinPool extends Abstra
1702		* @return {@code true} if all tasks have completed following shut down
1703		*/
1704		public boolean isTerminated() {
1705	<	return runStateOf(runControl) == TERMINATED;
1705	>	return runState >= TERMINATED;
1706		}
1707
1708		/**
1709		* Returns {@code true} if the process of termination has
1710	<	* commenced but possibly not yet completed.
1710	>	* commenced but not yet completed.  This method may be useful for
1711	>	* debugging. A return of {@code true} reported a sufficient
1712	>	* period after shutdown may indicate that submitted tasks have
1713	>	* ignored or suppressed interruption, causing this executor not
1714	>	* to properly terminate.
1715		*
1716	<	* @return {@code true} if terminating
1716	>	* @return {@code true} if terminating but not yet terminated
1717		*/
1718		public boolean isTerminating() {
1719	<	return runStateOf(runControl) >= TERMINATING;
1719	>	return (runState & (TERMINATING|TERMINATED)) == TERMINATING;
1720		}
1721
1722		/**
#	Line 1137 | Line 1725 | public class ForkJoinPool extends Abstra
1725		* @return {@code true} if this pool has been shut down
1726		*/
1727		public boolean isShutdown() {
1728	<	return runStateOf(runControl) >= SHUTDOWN;
1728	>	return runState >= SHUTDOWN;
1729		}
1730
1731		/**
#	Line 1153 | Line 1741 | public class ForkJoinPool extends Abstra
1741		*/
1742		public boolean awaitTermination(long timeout, TimeUnit unit)
1743		throws InterruptedException {
1156	–	long nanos = unit.toNanos(timeout);
1157	–	final ReentrantLock lock = this.workerLock;
1158	–	lock.lock();
1744		try {
1745	<	for (;;) {
1746	<	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();
1246	<	try {
1247	<	ForkJoinWorkerThread[] ws = workers;
1248	<	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)
1745	>	return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1746	>	} catch(TimeoutException ex) {
1747		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)
1494	–	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	–	}
1748		}
1749		}
1750
#	Line 1785 | Line 1797 | public class ForkJoinPool extends Abstra
1797		* Blocks in accord with the given blocker.  If the current thread
1798		* is a {@link ForkJoinWorkerThread}, this method possibly
1799		* arranges for a spare thread to be activated if necessary to
1800	<	* 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.
1800	>	* ensure sufficient parallelism while the current thread is blocked.
1801		*
1802		* <p>If the caller is not a {@link ForkJoinTask}, this method is
1803		* behaviorally equivalent to
#	Line 1806 | Line 1811 | public class ForkJoinPool extends Abstra
1811		* first be expanded to ensure parallelism, and later adjusted.
1812		*
1813		* @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.
1814		* @throws InterruptedException if blocker.block did so
1815		*/
1816	<	public static void managedBlock(ManagedBlocker blocker,
1816	<	boolean maintainParallelism)
1816	>	public static void managedBlock(ManagedBlocker blocker)
1817		throws InterruptedException {
1818		Thread t = Thread.currentThread();
1819	<	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1820	<	((ForkJoinWorkerThread) t).pool : null);
1821	<	if (!blocker.isReleasable()) {
1822	<	try {
1823	<	if (pool == null ||
1824	<	!pool.preBlock(blocker, maintainParallelism))
1825	<	awaitBlocker(blocker);
1826	<	} finally {
1827	<	if (pool != null)
1828	<	pool.updateRunningCount(1);
1829	<	}
1819	>	if (t instanceof ForkJoinWorkerThread)
1820	>	((ForkJoinWorkerThread) t).pool.awaitBlocker(blocker);
1821	>	else {
1822	>	do {} while (!blocker.isReleasable() && !blocker.block());
1823		}
1824		}
1825
1833	–	private static void awaitBlocker(ManagedBlocker blocker)
1834	–	throws InterruptedException {
1835	–	do {} while (!blocker.isReleasable() && !blocker.block());
1836	–	}
1837	–
1826		// AbstractExecutorService overrides.  These rely on undocumented
1827		// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1828		// implement RunnableFuture.
#	Line 1850 | Line 1838 | public class ForkJoinPool extends Abstra
1838		// Unsafe mechanics
1839
1840		private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1853	–	private static final long eventCountOffset =
1854	–	objectFieldOffset("eventCount", ForkJoinPool.class);
1841		private static final long workerCountsOffset =
1842		objectFieldOffset("workerCounts", ForkJoinPool.class);
1843	<	private static final long runControlOffset =
1844	<	objectFieldOffset("runControl", ForkJoinPool.class);
1845	<	private static final long syncStackOffset =
1846	<	objectFieldOffset("syncStack",ForkJoinPool.class);
1847	<	private static final long spareStackOffset =
1848	<	objectFieldOffset("spareStack", ForkJoinPool.class);
1849	<
1850	<	private boolean casEventCount(long cmp, long val) {
1865	<	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1866	<	}
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	<	}
1843	>	private static final long runStateOffset =
1844	>	objectFieldOffset("runState", ForkJoinPool.class);
1845	>	private static final long eventCountOffset =
1846	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1847	>	private static final long eventWaitersOffset =
1848	>	objectFieldOffset("eventWaiters",ForkJoinPool.class);
1849	>	private static final long stealCountOffset =
1850	>	objectFieldOffset("stealCount",ForkJoinPool.class);
1851
1852		private static long objectFieldOffset(String field, Class<?> klazz) {
1853		try {

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