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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.1 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.58 by dl, Fri Jul 23 13:07:43 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.locks.*;
11	<	import java.util.concurrent.atomic.*;
12	<	import sun.misc.Unsafe;
13	<	import java.lang.reflect.*;
10	>
11	>	import java.util.ArrayList;
12	>	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.LockSupport;
17	>	import java.util.concurrent.locks.ReentrantLock;
18	>	import java.util.concurrent.atomic.AtomicInteger;
19	>	import java.util.concurrent.CountDownLatch;
20
21		/**
22	<	* Host for a group of ForkJoinWorkerThreads.  A ForkJoinPool provides
23	<	* the entry point for tasks submitted from non-ForkJoinTasks, as well
24	<	* as management and monitoring operations.  Normally a single
25	<	* ForkJoinPool is used for a large number of submitted
20	<	* tasks. Otherwise, use would not usually outweigh the construction
21	<	* and bookkeeping overhead of creating a large set of threads.
22	<	*
23	<	* <p>ForkJoinPools differ from other kinds of Executor mainly in that
24	<	* they provide <em>work-stealing</em>: all threads in the pool
25	<	* attempt to find and execute subtasks created by other active tasks
26	<	* (eventually blocking if none exist). This makes them efficient when
27	<	* most tasks spawn other subtasks (as do most ForkJoinTasks) but
28	<	* possibly less so otherwise. It is however fine to combine execution
29	<	* of some plain Runnable- or Callable- based activities with that of
30	<	* ForkJoinTasks.
22	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
23	>	* A {@code ForkJoinPool} provides the entry point for submissions
24	>	* from non-{@code ForkJoinTask} clients, as well as management and
25	>	* monitoring operations.
26		*
27	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
28	<	* (target pool size), which it attempts to maintain by dynamically
29	<	* adding, suspending, or resuming threads, even if some tasks have
30	<	* blocked waiting to join others. However, no such adjustments are
31	<	* performed in the face of blocked IO or other unmanaged
32	<	* synchronization. The nested ManagedBlocker interface enables
33	<	* extension of the kinds of synchronization accommodated.
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>The target parallelism level may also be set dynamically. You
38	<	* can limit the number of threads dynamically constructed using
39	<	* method <tt>setMaximumPoolSize</tt> and/or
40	<	* <tt>setMaintainParallelism</tt>.
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
49	<	* <tt>getStealCount</tt>) that are intended to aid in developing,
49	>	* {@link #getStealCount}) that are intended to aid in developing,
50		* tuning, and monitoring fork/join applications. Also, method
51	<	* <tt>toString</tt> returns indications of pool state in a convenient
52	<	* form for informal monitoring.
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 follwoing
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 parallelism to 32767. Attempts to create pools with greater
108	<	* than the maximum result in IllegalArgumentExceptions.
107	>	* maximum number of running threads to 32767. Attempts to create
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
57	<	implements ExecutorService {
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 arrange tactics for
142	>	* when one worker is waiting to join a task stolen (or always
143	>	* held by) another.  Becauae we are multiplexing many tasks on to
144	>	* a pool of workers, we can't just let them block (as in
145	>	* Thread.join).  We also cannot just reassign the joiner's
146	>	* run-time stack with another and replace it later, which would
147	>	* be a form of "continuation", that even if possible is not
148	>	* necessarily a good idea. Given that the creation costs of most
149	>	* threads on most systems mainly surrounds setting up runtime
150	>	* stacks, thread creation and switching is usually not much more
151	>	* expensive than stack creation and switching, and is more
152	>	* flexible). Instead we combine two tactics:
153	>	*
154	>	*   1. 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	>	*   2. Unless there are already enough live threads, creating or
160	>	*      or re-activating a spare thread to compensate for the
161	>	*      (blocked) joiner until it unblocks.  Spares then suspend
162	>	*      at their next opportunity or eventually die if unused for
163	>	*      too long.  See below and the internal documentation
164	>	*      for tryAwaitJoin for more details about compensation
165	>	*      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 option (1) so uses a
177	>	* special version of (2) 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
64	–	/** Mask for packing and unpacking shorts */
65	–	private static final int  shortMask = 0xffff;
66	–
67	–	/** Max pool size -- must be a power of two minus 1 */
68	–	private static final int MAX_THREADS =  0x7FFF;
69	–
351		/**
352	<	* Factory for creating new ForkJoinWorkerThreads.  A
353	<	* ForkJoinWorkerThreadFactory must be defined and used for
354	<	* ForkJoinWorkerThread subclasses that extend base functionality
355	<	* or initialize threads with different contexts.
352	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
353	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
354	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
355	>	* functionality or initialize threads with different contexts.
356		*/
357		public static interface ForkJoinWorkerThreadFactory {
358		/**
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		}
366
367		/**
368	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
368	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
369		* new ForkJoinWorkerThread.
370		*/
371	<	public static class  DefaultForkJoinWorkerThreadFactory
371	>	static class DefaultForkJoinWorkerThreadFactory
372		implements ForkJoinWorkerThreadFactory {
373		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
374	<	try {
94	<	return new ForkJoinWorkerThread(pool);
95	<	} catch (OutOfMemoryError oom)  {
96	<	return null;
97	<	}
374	>	return new ForkJoinWorkerThread(pool);
375		}
376		}
377
378		/**
379	<	* The default ForkJoinWorkerThreadFactory, used unless overridden
380	<	* in ForkJoinPool constructors.
379	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
380	>	* overridden in ForkJoinPool constructors.
381		*/
382	<	private static final DefaultForkJoinWorkerThreadFactory
382	>	public static final ForkJoinWorkerThreadFactory
383		defaultForkJoinWorkerThreadFactory =
384		new DefaultForkJoinWorkerThreadFactory();
385
109	–
386		/**
387		* Permission required for callers of methods that may start or
388		* kill threads.
#	Line 131 | Line 407 | public class ForkJoinPool extends Abstra
407		new AtomicInteger();
408
409		/**
410	<	* Array holding all worker threads in the pool. Array size must
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	>	private static final int MAX_THREADS = 0x7fff;
414	>
415	>	/**
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 it is always kept in a consistent enough state
419	<	* to be randomly accessed without locking by workers performing
420	<	* work-stealing.
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		volatile ForkJoinWorkerThread[] workers;
425
426		/**
427	<	* Lock protecting access to workers.
427	>	* Queue for external submissions.
428		*/
429	<	private final ReentrantLock workerLock;
429	>	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
430
431		/**
432	<	* Condition for awaitTermination.
432	>	* Lock protecting updates to workers array.
433		*/
434	<	private final Condition termination;
434	>	private final ReentrantLock workerLock;
435
436		/**
437	<	* The uncaught exception handler used when any worker
154	<	* abrupty terminates
437	>	* Latch released upon termination.
438		*/
439	<	private Thread.UncaughtExceptionHandler ueh;
439	>	private final Phaser termination;
440
441		/**
442		* Creation factory for worker threads.
#	Line 161 | Line 444 | public class ForkJoinPool extends Abstra
444		private final ForkJoinWorkerThreadFactory factory;
445
446		/**
447	<	* Head of stack of threads that were created to maintain
448	<	* parallelism when other threads blocked, but have since
166	<	* suspended when the parallelism level rose.
447	>	* Sum of per-thread steal counts, updated only when threads are
448	>	* idle or terminating.
449		*/
450	<	private volatile WaitQueueNode spareStack;
450	>	private volatile long stealCount;
451
452		/**
453	<	* Sum of per-thread steal counts, updated only when threads are
454	<	* idle or terminating.
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 AtomicLong stealCount;
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	<	* Queue for external submissions.
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 final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
469	>	private volatile int eventCount;
470	>
471	>	/**
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	<	* Head of Treiber stack for barrier sync. See below for explanation
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.  This field is also used for memory-fencing
501	>	* configuration parameters.
502		*/
503	<	private volatile WaitQueueNode barrierStack;
503	>	private volatile int workerCounts;
504	>
505	>	private static final int TOTAL_COUNT_SHIFT  = 16;
506	>	private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1;
507	>	private static final int ONE_RUNNING        = 1;
508	>	private static final int ONE_TOTAL          = 1 << TOTAL_COUNT_SHIFT;
509
510		/**
511	<	* The count for event barrier
511	>	* The target parallelism level.
512	>	* Accessed directly by ForkJoinWorkerThreads.
513		*/
514	<	private volatile long eventCount;
514	>	final int parallelism;
515	>
516	>	/**
517	>	* True if use local fifo, not default lifo, for local polling
518	>	* Read by, and replicated by ForkJoinWorkerThreads
519	>	*/
520	>	final boolean locallyFifo;
521	>
522	>	/**
523	>	* The uncaught exception handler used when any worker abruptly
524	>	* terminates.
525	>	*/
526	>	private final Thread.UncaughtExceptionHandler ueh;
527
528		/**
529		* Pool number, just for assigning useful names to worker threads
530		*/
531		private final int poolNumber;
532
533	+	// Utilities for CASing fields. Note that several of these
534	+	// are manually inlined by callers
535	+
536		/**
537	<	* The maximum allowed pool size
537	>	* Increments running count.  Also used by ForkJoinTask.
538		*/
539	<	private volatile int maxPoolSize;
539	>	final void incrementRunningCount() {
540	>	int c;
541	>	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
542	>	c = workerCounts,
543	>	c + ONE_RUNNING));
544	>	}
545
546		/**
547	<	* The desired parallelism level, updated only under workerLock.
547	>	* Tries to decrement running count unless already zero
548		*/
549	<	private volatile int parallelism;
549	>	final boolean tryDecrementRunningCount() {
550	>	int wc = workerCounts;
551	>	if ((wc & RUNNING_COUNT_MASK) == 0)
552	>	return false;
553	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
554	>	wc, wc - ONE_RUNNING);
555	>	}
556
557		/**
558	<	* Holds number of total (i.e., created and not yet terminated)
208	<	* and running (i.e., not blocked on joins or other managed sync)
209	<	* threads, packed into one int to ensure consistent snapshot when
210	<	* making decisions about creating and suspending spare
211	<	* threads. Updated only by CAS.  Note: CASes in
212	<	* updateRunningCount and preJoin running active count is in low
213	<	* word, so need to be modified if this changes
558	>	* Tries to increment running count
559		*/
560	<	private volatile int workerCounts;
560	>	final boolean tryIncrementRunningCount() {
561	>	int wc;
562	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
563	>	wc = workerCounts, wc + ONE_RUNNING);
564	>	}
565
566	<	private static int totalCountOf(int s)           { return s >>> 16;  }
567	<	private static int runningCountOf(int s)         { return s & shortMask; }
568	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
566	>	/**
567	>	* Tries incrementing active count; fails on contention.
568	>	* Called by workers before executing tasks.
569	>	*
570	>	* @return true on success
571	>	*/
572	>	final boolean tryIncrementActiveCount() {
573	>	int c;
574	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
575	>	c = runState, c + ONE_ACTIVE);
576	>	}
577
578		/**
579	<	* Add delta (which may be negative) to running count.  This must
580	<	* be called before (with negative arg) and after (with positive)
224	<	* any managed synchronization (i.e., mainly, joins)
225	<	* @param delta the number to add
579	>	* Tries decrementing active count; fails on contention.
580	>	* Called when workers cannot find tasks to run.
581		*/
582	<	final void updateRunningCount(int delta) {
583	<	int s;
584	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
582	>	final boolean tryDecrementActiveCount() {
583	>	int c;
584	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
585	>	c = runState, c - ONE_ACTIVE);
586		}
587
588		/**
589	<	* Add delta (which may be negative) to both total and running
590	<	* count.  This must be called upon creation and termination of
235	<	* worker threads.
236	<	* @param delta the number to add
589	>	* Advances to at least the given level. Returns true if not
590	>	* already in at least the given level.
591		*/
592	<	private void updateWorkerCount(int delta) {
593	<	int d = delta + (delta << 16); // add to both lo and hi parts
594	<	int s;
595	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
592	>	private boolean advanceRunLevel(int level) {
593	>	for (;;) {
594	>	int s = runState;
595	>	if ((s & level) != 0)
596	>	return false;
597	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level))
598	>	return true;
599	>	}
600		}
601
602	+	// workers array maintenance
603	+
604		/**
605	<	* Lifecycle control. High word contains runState, low word
246	<	* contains the number of workers that are (probably) executing
247	<	* tasks. This value is atomically incremented before a worker
248	<	* gets a task to run, and decremented when worker has no tasks
249	<	* and cannot find any. These two fields are bundled together to
250	<	* support correct termination triggering.  Note: activeCount
251	<	* CAS'es cheat by assuming active count is in low word, so need
252	<	* to be modified if this changes
605	>	* Records and returns a workers array index for new worker.
606		*/
607	<	private volatile int runControl;
607	>	private int recordWorker(ForkJoinWorkerThread w) {
608	>	// Try using slot totalCount-1. If not available, scan and/or resize
609	>	int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1;
610	>	final ReentrantLock lock = this.workerLock;
611	>	lock.lock();
612	>	try {
613	>	ForkJoinWorkerThread[] ws = workers;
614	>	int nws = ws.length;
615	>	if (k < 0 || k >= nws || ws[k] != null) {
616	>	for (k = 0; k < nws && ws[k] != null; ++k)
617	>	;
618	>	if (k == nws)
619	>	ws = Arrays.copyOf(ws, nws << 1);
620	>	}
621	>	ws[k] = w;
622	>	workers = ws; // volatile array write ensures slot visibility
623	>	} finally {
624	>	lock.unlock();
625	>	}
626	>	return k;
627	>	}
628
629	<	// RunState values. Order among values matters
630	<	private static final int RUNNING     = 0;
631	<	private static final int SHUTDOWN    = 1;
632	<	private static final int TERMINATING = 2;
633	<	private static final int TERMINATED  = 3;
629	>	/**
630	>	* Nulls out record of worker in workers array
631	>	*/
632	>	private void forgetWorker(ForkJoinWorkerThread w) {
633	>	int idx = w.poolIndex;
634	>	// Locking helps method recordWorker avoid unecessary expansion
635	>	final ReentrantLock lock = this.workerLock;
636	>	lock.lock();
637	>	try {
638	>	ForkJoinWorkerThread[] ws = workers;
639	>	if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify
640	>	ws[idx] = null;
641	>	} finally {
642	>	lock.unlock();
643	>	}
644	>	}
645
646	<	private static int runStateOf(int c)             { return c >>> 16; }
263	<	private static int activeCountOf(int c)          { return c & shortMask; }
264	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
646	>	// adding and removing workers
647
648		/**
649	<	* Increment active count. Called by workers before/during
650	<	* executing tasks.
649	>	* Tries to create and add new worker. Assumes that worker counts
650	>	* are already updated to accommodate the worker, so adjusts on
651	>	* failure.
652	>	*
653	>	* @return new worker or null if creation failed
654		*/
655	<	final void incrementActiveCount() {
656	<	int c;
657	<	do;while (!casRunControl(c = runControl, c+1));
655	>	private ForkJoinWorkerThread addWorker() {
656	>	ForkJoinWorkerThread w = null;
657	>	try {
658	>	w = factory.newThread(this);
659	>	} finally { // Adjust on either null or exceptional factory return
660	>	if (w == null) {
661	>	onWorkerCreationFailure();
662	>	return null;
663	>	}
664	>	}
665	>	w.start(recordWorker(w), ueh);
666	>	return w;
667		}
668
669		/**
670	<	* Decrement active count; possibly trigger termination.
277	<	* Called by workers when they can't find tasks.
670	>	* Adjusts counts upon failure to create worker
671		*/
672	<	final void decrementActiveCount() {
673	<	int c, nextc;
674	<	do;while (!casRunControl(c = runControl, nextc = c-1));
675	<	if (canTerminateOnShutdown(nextc))
676	<	terminateOnShutdown();
672	>	private void onWorkerCreationFailure() {
673	>	for (;;) {
674	>	int wc = workerCounts;
675	>	if ((wc >>> TOTAL_COUNT_SHIFT) == 0)
676	>	Thread.yield(); // 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	<	* Return true if argument represents zero active count and
686	<	* nonzero runstate, which is the triggering condition for
687	<	* terminating on shutdown.
685	>	* Creates and/or resumes enough workers to establish target
686	>	* parallelism, giving up if terminating or addWorker fails
687	>	*
688	>	* TODO: recast this to support lazier creation and automated
689	>	* parallelism maintenance
690		*/
691	<	private static boolean canTerminateOnShutdown(int c) {
692	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
691	>	private void ensureEnoughWorkers() {
692	>	for (;;) {
693	>	int pc = parallelism;
694	>	int wc = workerCounts;
695	>	int rc = wc & RUNNING_COUNT_MASK;
696	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
697	>	if (tc < pc) {
698	>	if (runState == TERMINATING ||
699	>	(UNSAFE.compareAndSwapInt
700	>	(this, workerCountsOffset,
701	>	wc, wc + (ONE_RUNNING|ONE_TOTAL)) &&
702	>	addWorker() == null))
703	>	break;
704	>	}
705	>	else if (tc > pc && rc < pc &&
706	>	tc > (runState & ACTIVE_COUNT_MASK)) {
707	>	ForkJoinWorkerThread spare = null;
708	>	ForkJoinWorkerThread[] ws = workers;
709	>	int nws = ws.length;
710	>	for (int i = 0; i < nws; ++i) {
711	>	ForkJoinWorkerThread w = ws[i];
712	>	if (w != null && w.isSuspended()) {
713	>	if ((workerCounts & RUNNING_COUNT_MASK) > pc ||
714	>	runState == TERMINATING)
715	>	return;
716	>	if (w.tryResumeSpare())
717	>	incrementRunningCount();
718	>	break;
719	>	}
720	>	}
721	>	}
722	>	else
723	>	break;
724	>	}
725		}
726
727		/**
728	<	* Transition run state to at least the given state. Return true
729	<	* if not already at least given state.
728	>	* Final callback from terminating worker.  Removes record of
729	>	* worker from array, and adjusts counts. If pool is shutting
730	>	* down, tries to complete terminatation, else possibly replaces
731	>	* the worker.
732	>	*
733	>	* @param w the worker
734		*/
735	<	private boolean transitionRunStateTo(int state) {
735	>	final void workerTerminated(ForkJoinWorkerThread w) {
736	>	if (w.active) { // force inactive
737	>	w.active = false;
738	>	do {} while (!tryDecrementActiveCount());
739	>	}
740	>	forgetWorker(w);
741	>
742	>	// Decrement total count, and if was running, running count
743	>	// Spin (waiting for other updates) if either would be negative
744	>	int nr = w.isTrimmed() ? 0 : ONE_RUNNING;
745	>	int unit = ONE_TOTAL + nr;
746		for (;;) {
747	<	int c = runControl;
748	<	if (runStateOf(c) >= state)
749	<	return false;
750	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
751	<	return true;
747	>	int wc = workerCounts;
748	>	int rc = wc & RUNNING_COUNT_MASK;
749	>	if (rc - nr < 0 || (wc >>> TOTAL_COUNT_SHIFT) == 0)
750	>	Thread.yield(); // back off if waiting for other updates
751	>	else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
752	>	wc, wc - unit))
753	>	break;
754		}
755	+
756	+	accumulateStealCount(w); // collect final count
757	+	if (!tryTerminate(false))
758	+	ensureEnoughWorkers();
759		}
760
761	+	// Waiting for and signalling events
762	+
763		/**
764	<	* Controls whether to add spares to maintain parallelism
764	>	* Releases workers blocked on a count not equal to current count.
765	>	* @return true if any released
766		*/
767	<	private volatile boolean maintainsParallelism;
767	>	private void releaseWaiters() {
768	>	long top;
769	>	while ((top = eventWaiters) != 0L) {
770	>	ForkJoinWorkerThread[] ws = workers;
771	>	int n = ws.length;
772	>	for (;;) {
773	>	int i = ((int)(top & WAITER_ID_MASK)) - 1;
774	>	if (i < 0 || (int)(top >>> EVENT_COUNT_SHIFT) == eventCount)
775	>	return;
776	>	ForkJoinWorkerThread w;
777	>	if (i < n && (w = ws[i]) != null &&
778	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
779	>	top, w.nextWaiter)) {
780	>	LockSupport.unpark(w);
781	>	top = eventWaiters;
782	>	}
783	>	else
784	>	break;      // possibly stale; reread
785	>	}
786	>	}
787	>	}
788
789	<	// Constructors
789	>	/**
790	>	* Ensures eventCount on exit is different (mod 2^32) than on
791	>	* entry and wakes up all waiters
792	>	*/
793	>	private void signalEvent() {
794	>	int c;
795	>	do {} while (!UNSAFE.compareAndSwapInt(this, eventCountOffset,
796	>	c = eventCount, c+1));
797	>	releaseWaiters();
798	>	}
799
800		/**
801	<	* Creates a ForkJoinPool with a pool size equal to the number of
802	<	* processors available on the system and using the default
319	<	* ForkJoinWorkerThreadFactory,
320	<	* @throws SecurityException if a security manager exists and
321	<	*         the caller is not permitted to modify threads
322	<	*         because it does not hold {@link
323	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
801	>	* Advances eventCount and releases waiters until interference by
802	>	* other releasing threads is detected.
803		*/
804	<	public ForkJoinPool() {
805	<	this(Runtime.getRuntime().availableProcessors(),
806	<	defaultForkJoinWorkerThreadFactory);
804	>	final void signalWork() {
805	>	int c;
806	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c=eventCount, c+1);
807	>	long top;
808	>	while ((top = eventWaiters) != 0L) {
809	>	int ec = eventCount;
810	>	ForkJoinWorkerThread[] ws = workers;
811	>	int n = ws.length;
812	>	for (;;) {
813	>	int i = ((int)(top & WAITER_ID_MASK)) - 1;
814	>	if (i < 0 || (int)(top >>> EVENT_COUNT_SHIFT) == ec)
815	>	return;
816	>	ForkJoinWorkerThread w;
817	>	if (i < n && (w = ws[i]) != null &&
818	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
819	>	top, top = w.nextWaiter)) {
820	>	LockSupport.unpark(w);
821	>	if (top != eventWaiters) // let someone else take over
822	>	return;
823	>	}
824	>	else
825	>	break;      // possibly stale; reread
826	>	}
827	>	}
828		}
829
830		/**
831	<	* Creates a ForkJoinPool with the indicated parellelism level
832	<	* threads, and using the default ForkJoinWorkerThreadFactory,
833	<	* @param parallelism the number of worker threads
834	<	* @throws IllegalArgumentException if parallelism less than or
835	<	* equal to zero
836	<	* @throws SecurityException if a security manager exists and
837	<	*         the caller is not permitted to modify threads
338	<	*         because it does not hold {@link
339	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
831	>	* If worker is inactive, blocks until terminating or event count
832	>	* advances from last value held by worker; in any case helps
833	>	* release others.
834	>	*
835	>	* @param w the calling worker thread
836	>	* @param retries the number of scans by caller failing to find work
837	>	* @return false if now too many threads running
838		*/
839	<	public ForkJoinPool(int parallelism) {
840	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
839	>	private boolean eventSync(ForkJoinWorkerThread w, int retries) {
840	>	int wec = w.lastEventCount;
841	>	if (retries > 1) { // can only block after 2nd miss
842	>	long nextTop = (((long)wec << EVENT_COUNT_SHIFT) |
843	>	((long)(w.poolIndex + 1)));
844	>	long top;
845	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
846	>	(((int)(top = eventWaiters) & WAITER_ID_MASK) == 0 ||
847	>	(int)(top >>> EVENT_COUNT_SHIFT) == wec) &&
848	>	eventCount == wec) {
849	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
850	>	w.nextWaiter = top, nextTop)) {
851	>	accumulateStealCount(w); // transfer steals while idle
852	>	Thread.interrupted();    // clear/ignore interrupt
853	>	while (eventCount == wec)
854	>	w.doPark();
855	>	break;
856	>	}
857	>	}
858	>	wec = eventCount;
859	>	}
860	>	releaseWaiters();
861	>	int wc = workerCounts;
862	>	if ((wc & RUNNING_COUNT_MASK) <= parallelism) {
863	>	w.lastEventCount = wec;
864	>	return true;
865	>	}
866	>	if (wec != w.lastEventCount) // back up if may re-wait
867	>	w.lastEventCount = wec - (wc >>> TOTAL_COUNT_SHIFT);
868	>	return false;
869		}
870
871		/**
872	<	* Creates a ForkJoinPool with a pool size equal to the number of
873	<	* processors available on the system and using the given
874	<	* ForkJoinWorkerThreadFactory,
875	<	* @param factory the factory for creating new threads
876	<	* @throws NullPointerException if factory is null
877	<	* @throws SecurityException if a security manager exists and
878	<	*         the caller is not permitted to modify threads
879	<	*         because it does not hold {@link
880	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
872	>	* Callback from workers invoked upon each top-level action (i.e.,
873	>	* stealing a task or taking a submission and running
874	>	* it). Performs one or both of the following:
875	>	*
876	>	* * If the worker cannot find work, updates its active status to
877	>	* inactive and updates activeCount unless there is contention, in
878	>	* which case it may try again (either in this or a subsequent
879	>	* call).  Additionally, awaits the next task event and/or helps
880	>	* wake up other releasable waiters.
881	>	*
882	>	* * If there are too many running threads, suspends this worker
883	>	* (first forcing inactivation if necessary).  If it is not
884	>	* resumed before a keepAlive elapses, the worker may be "trimmed"
885	>	* -- killed while suspended within suspendAsSpare. Otherwise,
886	>	* upon resume it rechecks to make sure that it is still needed.
887	>	*
888	>	* @param w the worker
889	>	* @param retries the number of scans by caller failing to find work
890	>	* find any (in which case it may block waiting for work).
891		*/
892	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
893	<	this(Runtime.getRuntime().availableProcessors(), factory);
892	>	final void preStep(ForkJoinWorkerThread w, int retries) {
893	>	boolean active = w.active;
894	>	boolean inactivate = active && retries != 0;
895	>	for (;;) {
896	>	int rs, wc;
897	>	if (inactivate &&
898	>	UNSAFE.compareAndSwapInt(this, runStateOffset,
899	>	rs = runState, rs - ONE_ACTIVE))
900	>	inactivate = active = w.active = false;
901	>	if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= parallelism) {
902	>	if (active || eventSync(w, retries))
903	>	break;
904	>	}
905	>	else if (!(inactivate |= active) &&  // must inactivate to suspend
906	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
907	>	wc, wc - ONE_RUNNING) &&
908	>	!w.suspendAsSpare())             // false if trimmed
909	>	break;
910	>	}
911		}
912
913		/**
914	<	* Creates a ForkJoinPool with the indicated target number of
915	<	* worker threads and the given factory.
914	>	* Awaits join of the given task if enough threads, or can resume
915	>	* or create a spare. Fails (in which case the given task might
916	>	* not be done) upon contention or lack of decision about
917	>	* blocking. Returns void because caller must check
918	>	* task status on return anyway.
919		*
920	<	* @param parallelism the targeted number of worker threads
921	<	* @param factory the factory for creating new threads
922	<	* @throws IllegalArgumentException if parallelism less than or
923	<	* equal to zero, or greater than implementation limit.
924	<	* @throws NullPointerException if factory is null
925	<	* @throws SecurityException if a security manager exists and
926	<	*         the caller is not permitted to modify threads
927	<	*         because it does not hold {@link
928	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
920	>	* We allow blocking if:
921	>	*
922	>	* 1. There would still be at least as many running threads as
923	>	*    parallelism level if this thread blocks.
924	>	*
925	>	* 2. A spare is resumed to replace this worker. We tolerate
926	>	*    slop in the decision to replace if a spare is found without
927	>	*    first decrementing run count.  This may release too many,
928	>	*    but if so, the superfluous ones will re-suspend via
929	>	*    preStep().
930	>	*
931	>	* 3. After #spares repeated checks, there are no fewer than #spare
932	>	*    threads not running. We allow this slack to avoid hysteresis
933	>	*    and as a hedge against lag/uncertainty of running count
934	>	*    estimates when signalling or unblocking stalls.
935	>	*
936	>	* 4. All existing workers are busy (as rechecked via repeated
937	>	*    retries by caller) and a new spare is created.
938	>	*
939	>	* If none of the above hold, we try to escape out by
940	>	* re-incrementing count and returning to caller, which can retry
941	>	* later.
942	>	*
943	>	* @param joinMe the task to join
944	>	* @param retries if negative, then serve only as a precheck
945	>	*   that the thread can be replaced by a spare. Otherwise,
946	>	*   the number of repeated calls to this method returning busy
947	>	* @return true if the call must be retried because there
948	>	*   none of the blocking checks hold
949		*/
950	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
951	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
952	<	throw new IllegalArgumentException();
953	<	if (factory == null)
954	<	throw new NullPointerException();
955	<	checkPermission();
956	<	this.factory = factory;
957	<	this.parallelism = parallelism;
958	<	this.maxPoolSize = MAX_THREADS;
959	<	this.maintainsParallelism = true;
960	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
961	<	this.workerLock = new ReentrantLock();
962	<	this.termination = workerLock.newCondition();
963	<	this.stealCount = new AtomicLong();
964	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
965	<	createAndStartInitialWorkers(parallelism);
950	>	final boolean tryAwaitJoin(ForkJoinTask<?> joinMe, int retries) {
951	>	if (joinMe.status < 0) // precheck to prime loop
952	>	return false;
953	>	int pc = parallelism;
954	>	boolean running = true; // false when running count decremented
955	>	outer:for (;;) {
956	>	int wc = workerCounts;
957	>	int rc = wc & RUNNING_COUNT_MASK;
958	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
959	>	if (running) { // replace with spare or decrement count
960	>	if (rc <= pc && tc > pc &&
961	>	(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) {
962	>	ForkJoinWorkerThread[] ws = workers;
963	>	int nws = ws.length;
964	>	for (int i = 0; i < nws; ++i) { // search for spare
965	>	ForkJoinWorkerThread w = ws[i];
966	>	if (w != null) {
967	>	if (joinMe.status < 0)
968	>	return false;
969	>	if (w.isSuspended()) {
970	>	if ((workerCounts & RUNNING_COUNT_MASK)>=pc &&
971	>	w.tryResumeSpare()) {
972	>	running = false;
973	>	break outer;
974	>	}
975	>	continue outer; // rescan
976	>	}
977	>	}
978	>	}
979	>	}
980	>	if (retries < 0 || // < 0 means replacement check only
981	>	rc == 0 || joinMe.status < 0 || workerCounts != wc ||
982	>	!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
983	>	wc, wc - ONE_RUNNING))
984	>	return false; // done or inconsistent or contended
985	>	running = false;
986	>	if (rc > pc)
987	>	break;
988	>	}
989	>	else { // allow blocking if enough threads
990	>	if (rc >= pc || joinMe.status < 0)
991	>	break;
992	>	int sc = tc - pc + 1; // = spare threads, plus the one to add
993	>	if (retries > sc) {
994	>	if (rc > 0 && rc >= pc - sc) // allow slack
995	>	break;
996	>	if (tc < MAX_THREADS &&
997	>	tc == (runState & ACTIVE_COUNT_MASK) &&
998	>	workerCounts == wc &&
999	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
1000	>	wc+(ONE_RUNNING|ONE_TOTAL))) {
1001	>	addWorker();
1002	>	break;
1003	>	}
1004	>	}
1005	>	if (workerCounts == wc &&        // back out to allow rescan
1006	>	UNSAFE.compareAndSwapInt (this, workerCountsOffset,
1007	>	wc, wc + ONE_RUNNING)) {
1008	>	releaseWaiters();            // help others progress
1009	>	return true;                 // let caller retry
1010	>	}
1011	>	}
1012	>	}
1013	>	// arrive here if can block
1014	>	joinMe.internalAwaitDone();
1015	>	int c;                      // to inline incrementRunningCount
1016	>	do {} while (!UNSAFE.compareAndSwapInt
1017	>	(this, workerCountsOffset,
1018	>	c = workerCounts, c + ONE_RUNNING));
1019	>	return false;
1020		}
1021
1022		/**
1023	<	* Create new worker using factory.
1024	<	* @param index the index to assign worker
1025	<	* @return new worker, or null of factory failed
1026	<	*/
1027	<	private ForkJoinWorkerThread createWorker(int index) {
1028	<	Thread.UncaughtExceptionHandler h = ueh;
1029	<	ForkJoinWorkerThread w = factory.newThread(this);
1030	<	if (w != null) {
1031	<	w.poolIndex = index;
1032	<	w.setDaemon(true);
1033	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
1034	<	if (h != null)
1035	<	w.setUncaughtExceptionHandler(h);
1023	>	* Same idea as (and shares many code snippets with) tryAwaitJoin,
1024	>	* but self-contained because there are no caller retries.
1025	>	* TODO: Rework to use simpler API.
1026	>	*/
1027	>	final void awaitBlocker(ManagedBlocker blocker)
1028	>	throws InterruptedException {
1029	>	boolean done;
1030	>	if (done = blocker.isReleasable())
1031	>	return;
1032	>	int pc = parallelism;
1033	>	int retries = 0;
1034	>	boolean running = true; // false when running count decremented
1035	>	outer:for (;;) {
1036	>	int wc = workerCounts;
1037	>	int rc = wc & RUNNING_COUNT_MASK;
1038	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
1039	>	if (running) {
1040	>	if (rc <= pc && tc > pc &&
1041	>	(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) {
1042	>	ForkJoinWorkerThread[] ws = workers;
1043	>	int nws = ws.length;
1044	>	for (int i = 0; i < nws; ++i) {
1045	>	ForkJoinWorkerThread w = ws[i];
1046	>	if (w != null) {
1047	>	if (done = blocker.isReleasable())
1048	>	return;
1049	>	if (w.isSuspended()) {
1050	>	if ((workerCounts & RUNNING_COUNT_MASK)>=pc &&
1051	>	w.tryResumeSpare()) {
1052	>	running = false;
1053	>	break outer;
1054	>	}
1055	>	continue outer; // rescan
1056	>	}
1057	>	}
1058	>	}
1059	>	}
1060	>	if (done = blocker.isReleasable())
1061	>	return;
1062	>	if (rc == 0 || workerCounts != wc ||
1063	>	!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1064	>	wc, wc - ONE_RUNNING))
1065	>	continue;
1066	>	running = false;
1067	>	if (rc > pc)
1068	>	break;
1069	>	}
1070	>	else {
1071	>	if (rc >= pc || (done = blocker.isReleasable()))
1072	>	break;
1073	>	int sc = tc - pc + 1;
1074	>	if (retries++ > sc) {
1075	>	if (rc > 0 && rc >= pc - sc)
1076	>	break;
1077	>	if (tc < MAX_THREADS &&
1078	>	tc == (runState & ACTIVE_COUNT_MASK) &&
1079	>	workerCounts == wc &&
1080	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
1081	>	wc+(ONE_RUNNING|ONE_TOTAL))) {
1082	>	addWorker();
1083	>	break;
1084	>	}
1085	>	}
1086	>	Thread.yield();
1087	>	}
1088		}
1089	<	return w;
1089	>
1090	>	try {
1091	>	if (!done)
1092	>	do {} while (!blocker.isReleasable() && !blocker.block());
1093	>	} finally {
1094	>	if (!running) {
1095	>	int c;
1096	>	do {} while (!UNSAFE.compareAndSwapInt
1097	>	(this, workerCountsOffset,
1098	>	c = workerCounts, c + ONE_RUNNING));
1099	>	}
1100	>	}
1101	>	}
1102	>
1103	>	/**
1104	>	* Possibly initiates and/or completes termination.
1105	>	*
1106	>	* @param now if true, unconditionally terminate, else only
1107	>	* if shutdown and empty queue and no active workers
1108	>	* @return true if now terminating or terminated
1109	>	*/
1110	>	private boolean tryTerminate(boolean now) {
1111	>	if (now)
1112	>	advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN
1113	>	else if (runState < SHUTDOWN ||
1114	>	!submissionQueue.isEmpty() ||
1115	>	(runState & ACTIVE_COUNT_MASK) != 0)
1116	>	return false;
1117	>
1118	>	if (advanceRunLevel(TERMINATING))
1119	>	startTerminating();
1120	>
1121	>	// Finish now if all threads terminated; else in some subsequent call
1122	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1123	>	advanceRunLevel(TERMINATED);
1124	>	termination.arrive();
1125	>	}
1126	>	return true;
1127		}
1128
1129		/**
1130	<	* Return a good size for worker array given pool size.
412	<	* Currently requires size to be a power of two.
1130	>	* Actions on transition to TERMINATING
1131		*/
1132	<	private static int arraySizeFor(int ps) {
1133	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
1132	>	private void startTerminating() {
1133	>	for (int i = 0; i < 2; ++i) { // twice to mop up newly created workers
1134	>	cancelSubmissions();
1135	>	shutdownWorkers();
1136	>	cancelWorkerTasks();
1137	>	signalEvent();
1138	>	interruptWorkers();
1139	>	}
1140		}
1141
1142		/**
1143	<	* Create or resize array if necessary to hold newLength
420	<	* @return the array
1143	>	* Clear out and cancel submissions, ignoring exceptions
1144		*/
1145	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
1145	>	private void cancelSubmissions() {
1146	>	ForkJoinTask<?> task;
1147	>	while ((task = submissionQueue.poll()) != null) {
1148	>	try {
1149	>	task.cancel(false);
1150	>	} catch (Throwable ignore) {
1151	>	}
1152	>	}
1153	>	}
1154	>
1155	>	/**
1156	>	* Sets all worker run states to at least shutdown,
1157	>	* also resuming suspended workers
1158	>	*/
1159	>	private void shutdownWorkers() {
1160		ForkJoinWorkerThread[] ws = workers;
1161	<	if (ws == null)
1162	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
1163	<	else if (newLength > ws.length)
1164	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
1165	<	else
1166	<	return ws;
1161	>	int nws = ws.length;
1162	>	for (int i = 0; i < nws; ++i) {
1163	>	ForkJoinWorkerThread w = ws[i];
1164	>	if (w != null)
1165	>	w.shutdown();
1166	>	}
1167		}
1168
1169		/**
1170	<	* Try to shrink workers into smaller array after one or more terminate
1170	>	* Clears out and cancels all locally queued tasks
1171		*/
1172	<	private void tryShrinkWorkerArray() {
1172	>	private void cancelWorkerTasks() {
1173		ForkJoinWorkerThread[] ws = workers;
1174	<	int len = ws.length;
1175	<	int last = len - 1;
1176	<	while (last >= 0 && ws[last] == null)
1177	<	--last;
1178	<	int newLength = arraySizeFor(last+1);
1179	<	if (newLength < len)
443	<	workers = Arrays.copyOf(ws, newLength);
1174	>	int nws = ws.length;
1175	>	for (int i = 0; i < nws; ++i) {
1176	>	ForkJoinWorkerThread w = ws[i];
1177	>	if (w != null)
1178	>	w.cancelTasks();
1179	>	}
1180		}
1181
1182		/**
1183	<	* Initial worker array and worker creation and startup. (This
448	<	* must be done under lock to avoid interference by some of the
449	<	* newly started threads while creating others.)
1183	>	* Unsticks all workers blocked on joins etc
1184		*/
1185	<	private void createAndStartInitialWorkers(int ps) {
1186	<	final ReentrantLock lock = this.workerLock;
1187	<	lock.lock();
1188	<	try {
1189	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1190	<	for (int i = 0; i < ps; ++i) {
1191	<	ForkJoinWorkerThread w = createWorker(i);
1192	<	if (w != null) {
1193	<	ws[i] = w;
460	<	w.start();
461	<	updateWorkerCount(1);
1185	>	private void interruptWorkers() {
1186	>	ForkJoinWorkerThread[] ws = workers;
1187	>	int nws = ws.length;
1188	>	for (int i = 0; i < nws; ++i) {
1189	>	ForkJoinWorkerThread w = ws[i];
1190	>	if (w != null && !w.isTerminated()) {
1191	>	try {
1192	>	w.interrupt();
1193	>	} catch (SecurityException ignore) {
1194		}
1195		}
464	–	} finally {
465	–	lock.unlock();
1196		}
1197		}
1198
1199	+	// misc support for ForkJoinWorkerThread
1200	+
1201		/**
1202	<	* Worker creation and startup for threads added via setParallelism.
1202	>	* Returns pool number
1203		*/
1204	<	private void createAndStartAddedWorkers() {
1205	<	resumeAllSpares();  // Allow spares to convert to nonspare
1206	<	int ps = parallelism;
1207	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1208	<	int len = ws.length;
1209	<	// Sweep through slots, to keep lowest indices most populated
1210	<	int k = 0;
1211	<	while (k < len) {
1212	<	if (ws[k] != null) {
1213	<	++k;
1214	<	continue;
1215	<	}
1216	<	int s = workerCounts;
1217	<	int tc = totalCountOf(s);
1218	<	int rc = runningCountOf(s);
487	<	if (rc >= ps || tc >= ps)
488	<	break;
489	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
490	<	ForkJoinWorkerThread w = createWorker(k);
491	<	if (w != null) {
492	<	ws[k++] = w;
493	<	w.start();
494	<	}
495	<	else {
496	<	updateWorkerCount(-1); // back out on failed creation
497	<	break;
498	<	}
499	<	}
1204	>	final int getPoolNumber() {
1205	>	return poolNumber;
1206	>	}
1207	>
1208	>	/**
1209	>	* Accumulates steal count from a worker, clearing
1210	>	* the worker's value
1211	>	*/
1212	>	final void accumulateStealCount(ForkJoinWorkerThread w) {
1213	>	int sc = w.stealCount;
1214	>	if (sc != 0) {
1215	>	long c;
1216	>	w.stealCount = 0;
1217	>	do {} while (!UNSAFE.compareAndSwapLong(this, stealCountOffset,
1218	>	c = stealCount, c + sc));
1219		}
1220		}
1221
1222		/**
1223	<	* Sets the handler for internal worker threads that terminate due
1224	<	* to unrecoverable errors encountered while executing tasks.
1225	<	* Unless set, the current default or ThreadGroup handler is used
1226	<	* as handler.
1223	>	* Returns the approximate (non-atomic) number of idle threads per
1224	>	* active thread.
1225	>	*/
1226	>	final int idlePerActive() {
1227	>	int pc = parallelism; // use parallelism, not rc
1228	>	int ac = runState;    // no mask -- artifically boosts during shutdown
1229	>	// Use exact results for small values, saturate past 4
1230	>	return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
1231	>	}
1232	>
1233	>	// Public and protected methods
1234	>
1235	>	// Constructors
1236	>
1237	>	/**
1238	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1239	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1240	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1241	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1242	>	*
1243	>	* @throws SecurityException if a security manager exists and
1244	>	*         the caller is not permitted to modify threads
1245	>	*         because it does not hold {@link
1246	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1247	>	*/
1248	>	public ForkJoinPool() {
1249	>	this(Runtime.getRuntime().availableProcessors(),
1250	>	defaultForkJoinWorkerThreadFactory, null, false);
1251	>	}
1252	>
1253	>	/**
1254	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
1255	>	* level, the {@linkplain
1256	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1257	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1258	>	*
1259	>	* @param parallelism the parallelism level
1260	>	* @throws IllegalArgumentException if parallelism less than or
1261	>	*         equal to zero, or greater than implementation limit
1262	>	* @throws SecurityException if a security manager exists and
1263	>	*         the caller is not permitted to modify threads
1264	>	*         because it does not hold {@link
1265	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1266	>	*/
1267	>	public ForkJoinPool(int parallelism) {
1268	>	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1269	>	}
1270	>
1271	>	/**
1272	>	* Creates a {@code ForkJoinPool} with the given parameters.
1273		*
1274	<	* @param h the new handler
1275	<	* @return the old handler, or null if none
1274	>	* @param parallelism the parallelism level. For default value,
1275	>	* use {@link java.lang.Runtime#availableProcessors}.
1276	>	* @param factory the factory for creating new threads. For default value,
1277	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
1278	>	* @param handler the handler for internal worker threads that
1279	>	* terminate due to unrecoverable errors encountered while executing
1280	>	* tasks. For default value, use <code>null</code>.
1281	>	* @param asyncMode if true,
1282	>	* establishes local first-in-first-out scheduling mode for forked
1283	>	* tasks that are never joined. This mode may be more appropriate
1284	>	* than default locally stack-based mode in applications in which
1285	>	* worker threads only process event-style asynchronous tasks.
1286	>	* For default value, use <code>false</code>.
1287	>	* @throws IllegalArgumentException if parallelism less than or
1288	>	*         equal to zero, or greater than implementation limit
1289	>	* @throws NullPointerException if the factory is null
1290		* @throws SecurityException if a security manager exists and
1291		*         the caller is not permitted to modify threads
1292		*         because it does not hold {@link
1293	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1293	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1294		*/
1295	<	public Thread.UncaughtExceptionHandler
1296	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
1295	>	public ForkJoinPool(int parallelism,
1296	>	ForkJoinWorkerThreadFactory factory,
1297	>	Thread.UncaughtExceptionHandler handler,
1298	>	boolean asyncMode) {
1299		checkPermission();
1300	<	Thread.UncaughtExceptionHandler old = null;
1301	<	final ReentrantLock lock = this.workerLock;
1302	<	lock.lock();
1303	<	try {
1304	<	old = ueh;
1305	<	ueh = h;
1306	<	ForkJoinWorkerThread[] ws = workers;
1307	<	for (int i = 0; i < ws.length; ++i) {
1308	<	ForkJoinWorkerThread w = ws[i];
1309	<	if (w != null)
1310	<	w.setUncaughtExceptionHandler(h);
1311	<	}
1312	<	} finally {
1313	<	lock.unlock();
533	<	}
534	<	return old;
1300	>	if (factory == null)
1301	>	throw new NullPointerException();
1302	>	if (parallelism <= 0 || parallelism > MAX_THREADS)
1303	>	throw new IllegalArgumentException();
1304	>	this.parallelism = parallelism;
1305	>	this.factory = factory;
1306	>	this.ueh = handler;
1307	>	this.locallyFifo = asyncMode;
1308	>	int arraySize = initialArraySizeFor(parallelism);
1309	>	this.workers = new ForkJoinWorkerThread[arraySize];
1310	>	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
1311	>	this.workerLock = new ReentrantLock();
1312	>	this.termination = new Phaser(1);
1313	>	this.poolNumber = poolNumberGenerator.incrementAndGet();
1314		}
1315
1316		/**
1317	<	* Returns the handler for internal worker threads that terminate
1318	<	* due to unrecoverable errors encountered while executing tasks.
540	<	* @return the handler, or null if none
1317	>	* Returns initial power of two size for workers array.
1318	>	* @param pc the initial parallelism level
1319		*/
1320	<	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1321	<	Thread.UncaughtExceptionHandler h;
1322	<	final ReentrantLock lock = this.workerLock;
1323	<	lock.lock();
1324	<	try {
1325	<	h = ueh;
1326	<	} finally {
1327	<	lock.unlock();
550	<	}
551	<	return h;
1320	>	private static int initialArraySizeFor(int pc) {
1321	>	// See Hackers Delight, sec 3.2. We know MAX_THREADS < (1 >>> 16)
1322	>	int size = pc < MAX_THREADS ? pc + 1 : MAX_THREADS;
1323	>	size |= size >>> 1;
1324	>	size |= size >>> 2;
1325	>	size |= size >>> 4;
1326	>	size |= size >>> 8;
1327	>	return size + 1;
1328		}
1329
1330		// Execution methods
#	Line 557 | Line 1333 | public class ForkJoinPool extends Abstra
1333		* Common code for execute, invoke and submit
1334		*/
1335		private <T> void doSubmit(ForkJoinTask<T> task) {
1336	<	if (isShutdown())
1336	>	if (task == null)
1337	>	throw new NullPointerException();
1338	>	if (runState >= SHUTDOWN)
1339		throw new RejectedExecutionException();
1340		submissionQueue.offer(task);
1341	<	signalIdleWorkers(true);
1341	>	signalEvent();
1342	>	ensureEnoughWorkers();
1343		}
1344
1345		/**
1346	<	* Performs the given task; returning its result upon completion
1346	>	* Performs the given task, returning its result upon completion.
1347	>	* If the caller is already engaged in a fork/join computation in
1348	>	* the current pool, this method is equivalent in effect to
1349	>	* {@link ForkJoinTask#invoke}.
1350	>	*
1351		* @param task the task
1352		* @return the task's result
1353	<	* @throws NullPointerException if task is null
1354	<	* @throws RejectedExecutionException if pool is shut down
1353	>	* @throws NullPointerException if the task is null
1354	>	* @throws RejectedExecutionException if the task cannot be
1355	>	*         scheduled for execution
1356		*/
1357		public <T> T invoke(ForkJoinTask<T> task) {
1358		doSubmit(task);
#	Line 577 | Line 1361 | public class ForkJoinPool extends Abstra
1361
1362		/**
1363		* Arranges for (asynchronous) execution of the given task.
1364	+	* If the caller is already engaged in a fork/join computation in
1365	+	* the current pool, this method is equivalent in effect to
1366	+	* {@link ForkJoinTask#fork}.
1367	+	*
1368		* @param task the task
1369	<	* @throws NullPointerException if task is null
1370	<	* @throws RejectedExecutionException if pool is shut down
1369	>	* @throws NullPointerException if the task is null
1370	>	* @throws RejectedExecutionException if the task cannot be
1371	>	*         scheduled for execution
1372		*/
1373	<	public <T> void execute(ForkJoinTask<T> task) {
1373	>	public void execute(ForkJoinTask<?> task) {
1374		doSubmit(task);
1375		}
1376
1377		// AbstractExecutorService methods
1378
1379	+	/**
1380	+	* @throws NullPointerException if the task is null
1381	+	* @throws RejectedExecutionException if the task cannot be
1382	+	*         scheduled for execution
1383	+	*/
1384		public void execute(Runnable task) {
1385	<	doSubmit(new AdaptedRunnable<Void>(task, null));
1385	>	ForkJoinTask<?> job;
1386	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1387	>	job = (ForkJoinTask<?>) task;
1388	>	else
1389	>	job = ForkJoinTask.adapt(task, null);
1390	>	doSubmit(job);
1391		}
1392
1393	+	/**
1394	+	* Submits a ForkJoinTask for execution.
1395	+	* If the caller is already engaged in a fork/join computation in
1396	+	* the current pool, this method is equivalent in effect to
1397	+	* {@link ForkJoinTask#fork}.
1398	+	*
1399	+	* @param task the task to submit
1400	+	* @return the task
1401	+	* @throws NullPointerException if the task is null
1402	+	* @throws RejectedExecutionException if the task cannot be
1403	+	*         scheduled for execution
1404	+	*/
1405	+	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1406	+	doSubmit(task);
1407	+	return task;
1408	+	}
1409	+
1410	+	/**
1411	+	* @throws NullPointerException if the task is null
1412	+	* @throws RejectedExecutionException if the task cannot be
1413	+	*         scheduled for execution
1414	+	*/
1415		public <T> ForkJoinTask<T> submit(Callable<T> task) {
1416	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
1416	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1417		doSubmit(job);
1418		return job;
1419		}
1420
1421	+	/**
1422	+	* @throws NullPointerException if the task is null
1423	+	* @throws RejectedExecutionException if the task cannot be
1424	+	*         scheduled for execution
1425	+	*/
1426		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1427	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
1427	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1428		doSubmit(job);
1429		return job;
1430		}
1431
1432	+	/**
1433	+	* @throws NullPointerException if the task is null
1434	+	* @throws RejectedExecutionException if the task cannot be
1435	+	*         scheduled for execution
1436	+	*/
1437		public ForkJoinTask<?> submit(Runnable task) {
1438	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
1438	>	ForkJoinTask<?> job;
1439	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1440	>	job = (ForkJoinTask<?>) task;
1441	>	else
1442	>	job = ForkJoinTask.adapt(task, null);
1443		doSubmit(job);
1444		return job;
1445		}
1446
612	–	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
613	–	return new AdaptedRunnable(runnable, value);
614	–	}
615	–
616	–	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
617	–	return new AdaptedCallable(callable);
618	–	}
619	–
620	–	/**
621	–	* Adaptor for Runnables. This implements RunnableFuture
622	–	* to be compliant with AbstractExecutorService constraints
623	–	*/
624	–	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
625	–	implements RunnableFuture<T> {
626	–	final Runnable runnable;
627	–	final T resultOnCompletion;
628	–	T result;
629	–	AdaptedRunnable(Runnable runnable, T result) {
630	–	if (runnable == null) throw new NullPointerException();
631	–	this.runnable = runnable;
632	–	this.resultOnCompletion = result;
633	–	}
634	–	public T getRawResult() { return result; }
635	–	public void setRawResult(T v) { result = v; }
636	–	public boolean exec() {
637	–	runnable.run();
638	–	result = resultOnCompletion;
639	–	return true;
640	–	}
641	–	public void run() { invoke(); }
642	–	}
643	–
1447		/**
1448	<	* Adaptor for Callables
1448	>	* @throws NullPointerException       {@inheritDoc}
1449	>	* @throws RejectedExecutionException {@inheritDoc}
1450		*/
647	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
648	–	implements RunnableFuture<T> {
649	–	final Callable<T> callable;
650	–	T result;
651	–	AdaptedCallable(Callable<T> callable) {
652	–	if (callable == null) throw new NullPointerException();
653	–	this.callable = callable;
654	–	}
655	–	public T getRawResult() { return result; }
656	–	public void setRawResult(T v) { result = v; }
657	–	public boolean exec() {
658	–	try {
659	–	result = callable.call();
660	–	return true;
661	–	} catch (Error err) {
662	–	throw err;
663	–	} catch (RuntimeException rex) {
664	–	throw rex;
665	–	} catch (Exception ex) {
666	–	throw new RuntimeException(ex);
667	–	}
668	–	}
669	–	public void run() { invoke(); }
670	–	}
671	–
1451		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
1452	<	ArrayList<ForkJoinTask<T>> ts =
1452	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
1453		new ArrayList<ForkJoinTask<T>>(tasks.size());
1454	<	for (Callable<T> c : tasks)
1455	<	ts.add(new AdaptedCallable<T>(c));
1456	<	invoke(new InvokeAll<T>(ts));
1457	<	return (List<Future<T>>)(List)ts;
1454	>	for (Callable<T> task : tasks)
1455	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
1456	>	invoke(new InvokeAll<T>(forkJoinTasks));
1457	>
1458	>	@SuppressWarnings({"unchecked", "rawtypes"})
1459	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1460	>	return futures;
1461		}
1462
1463		static final class InvokeAll<T> extends RecursiveAction {
1464		final ArrayList<ForkJoinTask<T>> tasks;
1465		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
1466		public void compute() {
1467	<	try { invokeAll(tasks); } catch(Exception ignore) {}
1467	>	try { invokeAll(tasks); }
1468	>	catch (Exception ignore) {}
1469		}
1470	+	private static final long serialVersionUID = -7914297376763021607L;
1471		}
1472
689	–	// Configuration and status settings and queries
690	–
1473		/**
1474	<	* Returns the factory used for constructing new workers
1474	>	* Returns the factory used for constructing new workers.
1475		*
1476		* @return the factory used for constructing new workers
1477		*/
#	Line 698 | Line 1480 | public class ForkJoinPool extends Abstra
1480		}
1481
1482		/**
1483	<	* Sets the target paralleism level of this pool.
1484	<	* @param parallelism the target parallelism
1485	<	* @throws IllegalArgumentException if parallelism less than or
1486	<	* equal to zero or greater than maximum size bounds.
705	<	* @throws SecurityException if a security manager exists and
706	<	*         the caller is not permitted to modify threads
707	<	*         because it does not hold {@link
708	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1483	>	* Returns the handler for internal worker threads that terminate
1484	>	* due to unrecoverable errors encountered while executing tasks.
1485	>	*
1486	>	* @return the handler, or {@code null} if none
1487		*/
1488	<	public void setParallelism(int parallelism) {
1489	<	checkPermission();
712	<	if (parallelism <= 0 || parallelism > maxPoolSize)
713	<	throw new IllegalArgumentException();
714	<	final ReentrantLock lock = this.workerLock;
715	<	lock.lock();
716	<	try {
717	<	if (!isTerminating()) {
718	<	int p = this.parallelism;
719	<	this.parallelism = parallelism;
720	<	if (parallelism > p)
721	<	createAndStartAddedWorkers();
722	<	else
723	<	trimSpares();
724	<	}
725	<	} finally {
726	<	lock.unlock();
727	<	}
728	<	signalIdleWorkers(false);
1488	>	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1489	>	return ueh;
1490		}
1491
1492		/**
1493	<	* Returns the targeted number of worker threads in this pool.
733	<	* This value does not necessarily reflect transient changes as
734	<	* threads are added, removed, or abruptly terminate.
1493	>	* Returns the targeted parallelism level of this pool.
1494		*
1495	<	* @return the targeted number of worker threads in this pool
1495	>	* @return the targeted parallelism level of this pool
1496		*/
1497		public int getParallelism() {
1498		return parallelism;
#	Line 742 | Line 1501 | public class ForkJoinPool extends Abstra
1501		/**
1502		* Returns the number of worker threads that have started but not
1503		* yet terminated.  This result returned by this method may differ
1504	<	* from <tt>getParallelism</tt> when threads are created to
1504	>	* from {@link #getParallelism} when threads are created to
1505		* maintain parallelism when others are cooperatively blocked.
1506		*
1507		* @return the number of worker threads
1508		*/
1509		public int getPoolSize() {
1510	<	return totalCountOf(workerCounts);
1510	>	return workerCounts >>> TOTAL_COUNT_SHIFT;
1511		}
1512
1513		/**
1514	<	* Returns the maximum number of threads allowed to exist in the
1515	<	* pool, even if there are insufficient unblocked running threads.
1516	<	* @return the maximum
1517	<	*/
759	<	public int getMaximumPoolSize() {
760	<	return maxPoolSize;
761	<	}
762	<
763	<	/**
764	<	* Sets the maximum number of threads allowed to exist in the
765	<	* pool, even if there are insufficient unblocked running threads.
766	<	* Setting this value has no effect on current pool size. It
767	<	* controls construction of new threads.
768	<	* @throws IllegalArgumentException if negative or greater then
769	<	* internal implementation limit.
770	<	*/
771	<	public void setMaximumPoolSize(int newMax) {
772	<	if (newMax < 0 || newMax > MAX_THREADS)
773	<	throw new IllegalArgumentException();
774	<	maxPoolSize = newMax;
775	<	}
776	<
777	<
778	<	/**
779	<	* Returns true if this pool dynamically maintains its target
780	<	* parallelism level. If false, new threads are added only to
781	<	* avoid possible starvation.
782	<	* This setting is by default true;
783	<	* @return true if maintains parallelism
784	<	*/
785	<	public boolean getMaintainsParallelism() {
786	<	return maintainsParallelism;
787	<	}
788	<
789	<	/**
790	<	* Sets whether this pool dynamically maintains its target
791	<	* parallelism level. If false, new threads are added only to
792	<	* avoid possible starvation.
793	<	* @param enable true to maintains parallelism
1514	>	* Returns {@code true} if this pool uses local first-in-first-out
1515	>	* scheduling mode for forked tasks that are never joined.
1516	>	*
1517	>	* @return {@code true} if this pool uses async mode
1518		*/
1519	<	public void setMaintainsParallelism(boolean enable) {
1520	<	maintainsParallelism = enable;
1519	>	public boolean getAsyncMode() {
1520	>	return locallyFifo;
1521		}
1522
1523		/**
1524	<	* Returns the approximate number of worker threads that are not
1525	<	* blocked waiting to join tasks or for other managed
1526	<	* synchronization.
1524	>	* Returns an estimate of the number of worker threads that are
1525	>	* not blocked waiting to join tasks or for other managed
1526	>	* synchronization. This method may overestimate the
1527	>	* number of running threads.
1528		*
1529		* @return the number of worker threads
1530		*/
1531		public int getRunningThreadCount() {
1532	<	return runningCountOf(workerCounts);
1532	>	return workerCounts & RUNNING_COUNT_MASK;
1533		}
1534
1535		/**
1536	<	* Returns the approximate number of threads that are currently
1536	>	* Returns an estimate of the number of threads that are currently
1537		* stealing or executing tasks. This method may overestimate the
1538		* number of active threads.
1539	<	* @return the number of active threads.
1539	>	*
1540	>	* @return the number of active threads
1541		*/
1542		public int getActiveThreadCount() {
1543	<	return activeCountOf(runControl);
818	<	}
819	<
820	<	/**
821	<	* Returns the approximate number of threads that are currently
822	<	* idle waiting for tasks. This method may underestimate the
823	<	* number of idle threads.
824	<	* @return the number of idle threads.
825	<	*/
826	<	final int getIdleThreadCount() {
827	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
828	<	return (c <= 0)? 0 : c;
1543	>	return runState & ACTIVE_COUNT_MASK;
1544		}
1545
1546		/**
1547	<	* Returns true if all worker threads are currently idle. An idle
1548	<	* worker is one that cannot obtain a task to execute because none
1549	<	* are available to steal from other threads, and there are no
1550	<	* pending submissions to the pool. This method is conservative:
1551	<	* It might not return true immediately upon idleness of all
1552	<	* threads, but will eventually become true if threads remain
1553	<	* inactive.
1554	<	* @return true if all threads are currently idle
1547	>	* Returns {@code true} if all worker threads are currently idle.
1548	>	* An idle worker is one that cannot obtain a task to execute
1549	>	* because none are available to steal from other threads, and
1550	>	* there are no pending submissions to the pool. This method is
1551	>	* conservative; it might not return {@code true} immediately upon
1552	>	* idleness of all threads, but will eventually become true if
1553	>	* threads remain inactive.
1554	>	*
1555	>	* @return {@code true} if all threads are currently idle
1556		*/
1557		public boolean isQuiescent() {
1558	<	return activeCountOf(runControl) == 0;
1558	>	return (runState & ACTIVE_COUNT_MASK) == 0;
1559		}
1560
1561		/**
#	Line 847 | Line 1563 | public class ForkJoinPool extends Abstra
1563		* one thread's work queue by another. The reported value
1564		* underestimates the actual total number of steals when the pool
1565		* is not quiescent. This value may be useful for monitoring and
1566	<	* tuning fork/join programs: In general, steal counts should be
1566	>	* tuning fork/join programs: in general, steal counts should be
1567		* high enough to keep threads busy, but low enough to avoid
1568		* overhead and contention across threads.
1569	<	* @return the number of steals.
1569	>	*
1570	>	* @return the number of steals
1571		*/
1572		public long getStealCount() {
1573	<	return stealCount.get();
1573	>	return stealCount;
1574		}
1575
1576		/**
1577	<	* Accumulate steal count from a worker. Call only
1578	<	* when worker known to be idle.
1579	<	*/
1580	<	private void updateStealCount(ForkJoinWorkerThread w) {
1581	<	int sc = w.getAndClearStealCount();
1582	<	if (sc != 0)
1583	<	stealCount.addAndGet(sc);
1584	<	}
868	<
869	<	/**
870	<	* Returns the total number of tasks currently held in queues by
871	<	* worker threads (but not including tasks submitted to the pool
872	<	* that have not begun executing). This value is only an
873	<	* approximation, obtained by iterating across all threads in the
874	<	* pool. This method may be useful for tuning task granularities.
875	<	* @return the number of queued tasks.
1577	>	* Returns an estimate of the total number of tasks currently held
1578	>	* in queues by worker threads (but not including tasks submitted
1579	>	* to the pool that have not begun executing). This value is only
1580	>	* an approximation, obtained by iterating across all threads in
1581	>	* the pool. This method may be useful for tuning task
1582	>	* granularities.
1583	>	*
1584	>	* @return the number of queued tasks
1585		*/
1586		public long getQueuedTaskCount() {
1587		long count = 0;
1588		ForkJoinWorkerThread[] ws = workers;
1589	<	for (int i = 0; i < ws.length; ++i) {
1590	<	ForkJoinWorkerThread t = ws[i];
1591	<	if (t != null)
1592	<	count += t.getQueueSize();
1589	>	int nws = ws.length;
1590	>	for (int i = 0; i < nws; ++i) {
1591	>	ForkJoinWorkerThread w = ws[i];
1592	>	if (w != null)
1593	>	count += w.getQueueSize();
1594		}
1595		return count;
1596		}
1597
1598		/**
1599	<	* Returns the approximate number tasks submitted to this pool
1600	<	* that have not yet begun executing. This method takes time
1599	>	* Returns an estimate of the number of tasks submitted to this
1600	>	* pool that have not yet begun executing.  This method takes time
1601		* proportional to the number of submissions.
1602	<	* @return the number of queued submissions.
1602	>	*
1603	>	* @return the number of queued submissions
1604		*/
1605		public int getQueuedSubmissionCount() {
1606		return submissionQueue.size();
1607		}
1608
1609		/**
1610	<	* Returns true if there are any tasks submitted to this pool
1611	<	* that have not yet begun executing.
1612	<	* @return <tt>true</tt> if there are any queued submissions.
1610	>	* Returns {@code true} if there are any tasks submitted to this
1611	>	* pool that have not yet begun executing.
1612	>	*
1613	>	* @return {@code true} if there are any queued submissions
1614		*/
1615		public boolean hasQueuedSubmissions() {
1616		return !submissionQueue.isEmpty();
#	Line 908 | Line 1620 | public class ForkJoinPool extends Abstra
1620		* Removes and returns the next unexecuted submission if one is
1621		* available.  This method may be useful in extensions to this
1622		* class that re-assign work in systems with multiple pools.
1623	<	* @return the next submission, or null if none
1623	>	*
1624	>	* @return the next submission, or {@code null} if none
1625		*/
1626		protected ForkJoinTask<?> pollSubmission() {
1627		return submissionQueue.poll();
1628		}
1629
1630		/**
1631	+	* Removes all available unexecuted submitted and forked tasks
1632	+	* from scheduling queues and adds them to the given collection,
1633	+	* without altering their execution status. These may include
1634	+	* artificially generated or wrapped tasks. This method is
1635	+	* designed to be invoked only when the pool is known to be
1636	+	* quiescent. Invocations at other times may not remove all
1637	+	* tasks. A failure encountered while attempting to add elements
1638	+	* to collection {@code c} may result in elements being in
1639	+	* neither, either or both collections when the associated
1640	+	* exception is thrown.  The behavior of this operation is
1641	+	* undefined if the specified collection is modified while the
1642	+	* operation is in progress.
1643	+	*
1644	+	* @param c the collection to transfer elements into
1645	+	* @return the number of elements transferred
1646	+	*/
1647	+	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1648	+	int n = submissionQueue.drainTo(c);
1649	+	ForkJoinWorkerThread[] ws = workers;
1650	+	int nws = ws.length;
1651	+	for (int i = 0; i < nws; ++i) {
1652	+	ForkJoinWorkerThread w = ws[i];
1653	+	if (w != null)
1654	+	n += w.drainTasksTo(c);
1655	+	}
1656	+	return n;
1657	+	}
1658	+
1659	+	/**
1660	+	* Returns count of total parks by existing workers.
1661	+	* Used during development only since not meaningful to users.
1662	+	*/
1663	+	private int collectParkCount() {
1664	+	int count = 0;
1665	+	ForkJoinWorkerThread[] ws = workers;
1666	+	int nws = ws.length;
1667	+	for (int i = 0; i < nws; ++i) {
1668	+	ForkJoinWorkerThread w = ws[i];
1669	+	if (w != null)
1670	+	count += w.parkCount;
1671	+	}
1672	+	return count;
1673	+	}
1674	+
1675	+	/**
1676		* Returns a string identifying this pool, as well as its state,
1677		* including indications of run state, parallelism level, and
1678		* worker and task counts.
#	Line 922 | Line 1680 | public class ForkJoinPool extends Abstra
1680		* @return a string identifying this pool, as well as its state
1681		*/
1682		public String toString() {
925	–	int ps = parallelism;
926	–	int wc = workerCounts;
927	–	int rc = runControl;
1683		long st = getStealCount();
1684		long qt = getQueuedTaskCount();
1685		long qs = getQueuedSubmissionCount();
1686	+	int wc = workerCounts;
1687	+	int tc = wc >>> TOTAL_COUNT_SHIFT;
1688	+	int rc = wc & RUNNING_COUNT_MASK;
1689	+	int pc = parallelism;
1690	+	int rs = runState;
1691	+	int ac = rs & ACTIVE_COUNT_MASK;
1692	+	//        int pk = collectParkCount();
1693		return super.toString() +
1694	<	"[" + runStateToString(runStateOf(rc)) +
1695	<	", parallelism = " + ps +
1696	<	", size = " + totalCountOf(wc) +
1697	<	", active = " + activeCountOf(rc) +
1698	<	", running = " + runningCountOf(wc) +
1694	>	"[" + runLevelToString(rs) +
1695	>	", parallelism = " + pc +
1696	>	", size = " + tc +
1697	>	", active = " + ac +
1698	>	", running = " + rc +
1699		", steals = " + st +
1700		", tasks = " + qt +
1701		", submissions = " + qs +
1702	+	//            ", parks = " + pk +
1703		"]";
1704		}
1705
1706	<	private static String runStateToString(int rs) {
1707	<	switch(rs) {
1708	<	case RUNNING: return "Running";
1709	<	case SHUTDOWN: return "Shutting down";
1710	<	case TERMINATING: return "Terminating";
948	<	case TERMINATED: return "Terminated";
949	<	default: throw new Error("Unknown run state");
950	<	}
1706	>	private static String runLevelToString(int s) {
1707	>	return ((s & TERMINATED) != 0 ? "Terminated" :
1708	>	((s & TERMINATING) != 0 ? "Terminating" :
1709	>	((s & SHUTDOWN) != 0 ? "Shutting down" :
1710	>	"Running")));
1711		}
1712
953	–	// lifecycle control
954	–
1713		/**
1714		* Initiates an orderly shutdown in which previously submitted
1715		* tasks are executed, but no new tasks will be accepted.
1716		* Invocation has no additional effect if already shut down.
1717		* Tasks that are in the process of being submitted concurrently
1718		* during the course of this method may or may not be rejected.
1719	+	*
1720		* @throws SecurityException if a security manager exists and
1721		*         the caller is not permitted to modify threads
1722		*         because it does not hold {@link
1723	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1723	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1724		*/
1725		public void shutdown() {
1726		checkPermission();
1727	<	transitionRunStateTo(SHUTDOWN);
1728	<	if (canTerminateOnShutdown(runControl))
970	<	terminateOnShutdown();
1727	>	advanceRunLevel(SHUTDOWN);
1728	>	tryTerminate(false);
1729		}
1730
1731		/**
1732	<	* Attempts to stop all actively executing tasks, and cancels all
1733	<	* waiting tasks.  Tasks that are in the process of being
1734	<	* submitted or executed concurrently during the course of this
1735	<	* method may or may not be rejected. Unlike some other executors,
1736	<	* this method cancels rather than collects non-executed tasks,
1737	<	* so always returns an empty list.
1732	>	* Attempts to cancel and/or stop all tasks, and reject all
1733	>	* subsequently submitted tasks.  Tasks that are in the process of
1734	>	* being submitted or executed concurrently during the course of
1735	>	* this method may or may not be rejected. This method cancels
1736	>	* both existing and unexecuted tasks, in order to permit
1737	>	* termination in the presence of task dependencies. So the method
1738	>	* always returns an empty list (unlike the case for some other
1739	>	* Executors).
1740	>	*
1741		* @return an empty list
1742		* @throws SecurityException if a security manager exists and
1743		*         the caller is not permitted to modify threads
1744		*         because it does not hold {@link
1745	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1745	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1746		*/
1747		public List<Runnable> shutdownNow() {
1748		checkPermission();
1749	<	terminate();
1749	>	tryTerminate(true);
1750		return Collections.emptyList();
1751		}
1752
1753		/**
1754	<	* Returns <tt>true</tt> if all tasks have completed following shut down.
1754	>	* Returns {@code true} if all tasks have completed following shut down.
1755		*
1756	<	* @return <tt>true</tt> if all tasks have completed following shut down
1756	>	* @return {@code true} if all tasks have completed following shut down
1757		*/
1758		public boolean isTerminated() {
1759	<	return runStateOf(runControl) == TERMINATED;
1759	>	return runState >= TERMINATED;
1760		}
1761
1762		/**
1763	<	* Returns <tt>true</tt> if the process of termination has
1764	<	* commenced but possibly not yet completed.
1763	>	* Returns {@code true} if the process of termination has
1764	>	* commenced but not yet completed.  This method may be useful for
1765	>	* debugging. A return of {@code true} reported a sufficient
1766	>	* period after shutdown may indicate that submitted tasks have
1767	>	* ignored or suppressed interruption, causing this executor not
1768	>	* to properly terminate.
1769		*
1770	<	* @return <tt>true</tt> if terminating
1770	>	* @return {@code true} if terminating but not yet terminated
1771		*/
1772		public boolean isTerminating() {
1773	<	return runStateOf(runControl) >= TERMINATING;
1773	>	return (runState & (TERMINATING|TERMINATED)) == TERMINATING;
1774		}
1775
1776		/**
1777	<	* Returns <tt>true</tt> if this pool has been shut down.
1777	>	* Returns {@code true} if this pool has been shut down.
1778		*
1779	<	* @return <tt>true</tt> if this pool has been shut down
1779	>	* @return {@code true} if this pool has been shut down
1780		*/
1781		public boolean isShutdown() {
1782	<	return runStateOf(runControl) >= SHUTDOWN;
1782	>	return runState >= SHUTDOWN;
1783		}
1784
1785		/**
#	Line 1024 | Line 1789 | public class ForkJoinPool extends Abstra
1789		*
1790		* @param timeout the maximum time to wait
1791		* @param unit the time unit of the timeout argument
1792	<	* @return <tt>true</tt> if this executor terminated and
1793	<	*         <tt>false</tt> if the timeout elapsed before termination
1792	>	* @return {@code true} if this executor terminated and
1793	>	*         {@code false} if the timeout elapsed before termination
1794		* @throws InterruptedException if interrupted while waiting
1795		*/
1796		public boolean awaitTermination(long timeout, TimeUnit unit)
1797		throws InterruptedException {
1033	–	long nanos = unit.toNanos(timeout);
1034	–	final ReentrantLock lock = this.workerLock;
1035	–	lock.lock();
1036	–	try {
1037	–	for (;;) {
1038	–	if (isTerminated())
1039	–	return true;
1040	–	if (nanos <= 0)
1041	–	return false;
1042	–	nanos = termination.awaitNanos(nanos);
1043	–	}
1044	–	} finally {
1045	–	lock.unlock();
1046	–	}
1047	–	}
1048	–
1049	–	// Shutdown and termination support
1050	–
1051	–	/**
1052	–	* Callback from terminating worker. Null out the corresponding
1053	–	* workers slot, and if terminating, try to terminate, else try to
1054	–	* shrink workers array.
1055	–	* @param w the worker
1056	–	*/
1057	–	final void workerTerminated(ForkJoinWorkerThread w) {
1058	–	updateStealCount(w);
1059	–	updateWorkerCount(-1);
1060	–	final ReentrantLock lock = this.workerLock;
1061	–	lock.lock();
1062	–	try {
1063	–	ForkJoinWorkerThread[] ws = workers;
1064	–	int idx = w.poolIndex;
1065	–	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1066	–	ws[idx] = null;
1067	–	if (totalCountOf(workerCounts) == 0) {
1068	–	terminate(); // no-op if already terminating
1069	–	transitionRunStateTo(TERMINATED);
1070	–	termination.signalAll();
1071	–	}
1072	–	else if (!isTerminating()) {
1073	–	tryShrinkWorkerArray();
1074	–	tryResumeSpare(true); // allow replacement
1075	–	}
1076	–	} finally {
1077	–	lock.unlock();
1078	–	}
1079	–	signalIdleWorkers(false);
1080	–	}
1081	–
1082	–	/**
1083	–	* Initiate termination.
1084	–	*/
1085	–	private void terminate() {
1086	–	if (transitionRunStateTo(TERMINATING)) {
1087	–	stopAllWorkers();
1088	–	resumeAllSpares();
1089	–	signalIdleWorkers(true);
1090	–	cancelQueuedSubmissions();
1091	–	cancelQueuedWorkerTasks();
1092	–	interruptUnterminatedWorkers();
1093	–	signalIdleWorkers(true); // resignal after interrupt
1094	–	}
1095	–	}
1096	–
1097	–	/**
1098	–	* Possibly terminate when on shutdown state
1099	–	*/
1100	–	private void terminateOnShutdown() {
1101	–	if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
1102	–	terminate();
1103	–	}
1104	–
1105	–	/**
1106	–	* Clear out and cancel submissions
1107	–	*/
1108	–	private void cancelQueuedSubmissions() {
1109	–	ForkJoinTask<?> task;
1110	–	while ((task = pollSubmission()) != null)
1111	–	task.cancel(false);
1112	–	}
1113	–
1114	–	/**
1115	–	* Clean out worker queues.
1116	–	*/
1117	–	private void cancelQueuedWorkerTasks() {
1118	–	final ReentrantLock lock = this.workerLock;
1119	–	lock.lock();
1120	–	try {
1121	–	ForkJoinWorkerThread[] ws = workers;
1122	–	for (int i = 0; i < ws.length; ++i) {
1123	–	ForkJoinWorkerThread t = ws[i];
1124	–	if (t != null)
1125	–	t.cancelTasks();
1126	–	}
1127	–	} finally {
1128	–	lock.unlock();
1129	–	}
1130	–	}
1131	–
1132	–	/**
1133	–	* Set each worker's status to terminating. Requires lock to avoid
1134	–	* conflicts with add/remove
1135	–	*/
1136	–	private void stopAllWorkers() {
1137	–	final ReentrantLock lock = this.workerLock;
1138	–	lock.lock();
1798		try {
1799	<	ForkJoinWorkerThread[] ws = workers;
1800	<	for (int i = 0; i < ws.length; ++i) {
1142	<	ForkJoinWorkerThread t = ws[i];
1143	<	if (t != null)
1144	<	t.shutdownNow();
1145	<	}
1146	<	} finally {
1147	<	lock.unlock();
1148	<	}
1149	<	}
1150	<
1151	<	/**
1152	<	* Interrupt all unterminated workers.  This is not required for
1153	<	* sake of internal control, but may help unstick user code during
1154	<	* shutdown.
1155	<	*/
1156	<	private void interruptUnterminatedWorkers() {
1157	<	final ReentrantLock lock = this.workerLock;
1158	<	lock.lock();
1159	<	try {
1160	<	ForkJoinWorkerThread[] ws = workers;
1161	<	for (int i = 0; i < ws.length; ++i) {
1162	<	ForkJoinWorkerThread t = ws[i];
1163	<	if (t != null && !t.isTerminated()) {
1164	<	try {
1165	<	t.interrupt();
1166	<	} catch (SecurityException ignore) {
1167	<	}
1168	<	}
1169	<	}
1170	<	} finally {
1171	<	lock.unlock();
1172	<	}
1173	<	}
1174	<
1175	<
1176	<	/*
1177	<	* Nodes for event barrier to manage idle threads.
1178	<	*
1179	<	* The event barrier has an event count and a wait queue (actually
1180	<	* a Treiber stack).  Workers are enabled to look for work when
1181	<	* the eventCount is incremented. If they fail to find some,
1182	<	* they may wait for next count. Synchronization events occur only
1183	<	* in enough contexts to maintain overall liveness:
1184	<	*
1185	<	*   - Submission of a new task to the pool
1186	<	*   - Creation or termination of a worker
1187	<	*   - pool termination
1188	<	*   - A worker pushing a task on an empty queue
1189	<	*
1190	<	* The last case (pushing a task) occurs often enough, and is
1191	<	* heavy enough compared to simple stack pushes to require some
1192	<	* special handling: Method signalNonEmptyWorkerQueue returns
1193	<	* without advancing count if the queue appears to be empty.  This
1194	<	* would ordinarily result in races causing some queued waiters
1195	<	* not to be woken up. To avoid this, a worker in sync
1196	<	* rescans for tasks after being enqueued if it was the first to
1197	<	* enqueue, and aborts the wait if finding one, also helping to
1198	<	* signal others. This works well because the worker has nothing
1199	<	* better to do anyway, and so might as well help alleviate the
1200	<	* overhead and contention on the threads actually doing work.
1201	<	*
1202	<	* Queue nodes are basic Treiber stack nodes, also used for spare
1203	<	* stack.
1204	<	*/
1205	<	static final class WaitQueueNode {
1206	<	WaitQueueNode next; // only written before enqueued
1207	<	volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1208	<	final long count; // unused for spare stack
1209	<	WaitQueueNode(ForkJoinWorkerThread w, long c) {
1210	<	count = c;
1211	<	thread = w;
1212	<	}
1213	<	final boolean signal() {
1214	<	ForkJoinWorkerThread t = thread;
1215	<	thread = null;
1216	<	if (t != null) {
1217	<	LockSupport.unpark(t);
1218	<	return true;
1219	<	}
1799	>	return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1800	>	} catch(TimeoutException ex) {
1801		return false;
1802		}
1803		}
1804
1805		/**
1225	–	* Release at least one thread waiting for event count to advance,
1226	–	* if one exists. If initial attempt fails, release all threads.
1227	–	* @param all if false, at first try to only release one thread
1228	–	* @return current event
1229	–	*/
1230	–	private long releaseIdleWorkers(boolean all) {
1231	–	long c;
1232	–	for (;;) {
1233	–	WaitQueueNode q = barrierStack;
1234	–	c = eventCount;
1235	–	long qc;
1236	–	if (q == null || (qc = q.count) >= c)
1237	–	break;
1238	–	if (!all) {
1239	–	if (casBarrierStack(q, q.next) && q.signal())
1240	–	break;
1241	–	all = true;
1242	–	}
1243	–	else if (casBarrierStack(q, null)) {
1244	–	do {
1245	–	q.signal();
1246	–	} while ((q = q.next) != null);
1247	–	break;
1248	–	}
1249	–	}
1250	–	return c;
1251	–	}
1252	–
1253	–	/**
1254	–	* Returns current barrier event count
1255	–	* @return current barrier event count
1256	–	*/
1257	–	final long getEventCount() {
1258	–	long ec = eventCount;
1259	–	releaseIdleWorkers(true); // release to ensure accurate result
1260	–	return ec;
1261	–	}
1262	–
1263	–	/**
1264	–	* Increment event count and release at least one waiting thread,
1265	–	* if one exists (released threads will in turn wake up others).
1266	–	* @param all if true, try to wake up all
1267	–	*/
1268	–	final void signalIdleWorkers(boolean all) {
1269	–	long c;
1270	–	do;while (!casEventCount(c = eventCount, c+1));
1271	–	releaseIdleWorkers(all);
1272	–	}
1273	–
1274	–	/**
1275	–	* Wake up threads waiting to steal a task. Because method
1276	–	* sync rechecks availability, it is OK to only proceed if
1277	–	* queue appears to be non-empty.
1278	–	*/
1279	–	final void signalNonEmptyWorkerQueue() {
1280	–	// If CAS fails another signaller must have succeeded
1281	–	long c;
1282	–	if (barrierStack != null && casEventCount(c = eventCount, c+1))
1283	–	releaseIdleWorkers(false);
1284	–	}
1285	–
1286	–	/**
1287	–	* Waits until event count advances from count, or some thread is
1288	–	* waiting on a previous count, or there is stealable work
1289	–	* available. Help wake up others on release.
1290	–	* @param w the calling worker thread
1291	–	* @param prev previous value returned by sync (or 0)
1292	–	* @return current event count
1293	–	*/
1294	–	final long sync(ForkJoinWorkerThread w, long prev) {
1295	–	updateStealCount(w);
1296	–
1297	–	while (!w.isShutdown() && !isTerminating() &&
1298	–	(parallelism >= runningCountOf(workerCounts) ||
1299	–	!suspendIfSpare(w))) { // prefer suspend to waiting here
1300	–	WaitQueueNode node = null;
1301	–	boolean queued = false;
1302	–	for (;;) {
1303	–	if (!queued) {
1304	–	if (eventCount != prev)
1305	–	break;
1306	–	WaitQueueNode h = barrierStack;
1307	–	if (h != null && h.count != prev)
1308	–	break; // release below and maybe retry
1309	–	if (node == null)
1310	–	node = new WaitQueueNode(w, prev);
1311	–	queued = casBarrierStack(node.next = h, node);
1312	–	}
1313	–	else if (Thread.interrupted() ||
1314	–	node.thread == null ||
1315	–	(node.next == null && w.prescan()) ||
1316	–	eventCount != prev) {
1317	–	node.thread = null;
1318	–	if (eventCount == prev) // help trigger
1319	–	casEventCount(prev, prev+1);
1320	–	break;
1321	–	}
1322	–	else
1323	–	LockSupport.park(this);
1324	–	}
1325	–	long ec = eventCount;
1326	–	if (releaseIdleWorkers(false) != prev)
1327	–	return ec;
1328	–	}
1329	–	return prev; // return old count if aborted
1330	–	}
1331	–
1332	–	//  Parallelism maintenance
1333	–
1334	–	/**
1335	–	* Decrement running count; if too low, add spare.
1336	–	*
1337	–	* Conceptually, all we need to do here is add or resume a
1338	–	* spare thread when one is about to block (and remove or
1339	–	* suspend it later when unblocked -- see suspendIfSpare).
1340	–	* However, implementing this idea requires coping with
1341	–	* several problems: We have imperfect information about the
1342	–	* states of threads. Some count updates can and usually do
1343	–	* lag run state changes, despite arrangements to keep them
1344	–	* accurate (for example, when possible, updating counts
1345	–	* before signalling or resuming), especially when running on
1346	–	* dynamic JVMs that don't optimize the infrequent paths that
1347	–	* update counts. Generating too many threads can make these
1348	–	* problems become worse, because excess threads are more
1349	–	* likely to be context-switched with others, slowing them all
1350	–	* down, especially if there is no work available, so all are
1351	–	* busy scanning or idling.  Also, excess spare threads can
1352	–	* only be suspended or removed when they are idle, not
1353	–	* immediately when they aren't needed. So adding threads will
1354	–	* raise parallelism level for longer than necessary.  Also,
1355	–	* FJ applications often enounter highly transient peaks when
1356	–	* many threads are blocked joining, but for less time than it
1357	–	* takes to create or resume spares.
1358	–	*
1359	–	* @param joinMe if non-null, return early if done
1360	–	* @param maintainParallelism if true, try to stay within
1361	–	* target counts, else create only to avoid starvation
1362	–	* @return true if joinMe known to be done
1363	–	*/
1364	–	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1365	–	maintainParallelism &= maintainsParallelism; // overrride
1366	–	boolean dec = false;  // true when running count decremented
1367	–	while (spareStack == null || !tryResumeSpare(dec)) {
1368	–	int counts = workerCounts;
1369	–	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1370	–	if (!needSpare(counts, maintainParallelism))
1371	–	break;
1372	–	if (joinMe.status < 0)
1373	–	return true;
1374	–	if (tryAddSpare(counts))
1375	–	break;
1376	–	}
1377	–	}
1378	–	return false;
1379	–	}
1380	–
1381	–	/**
1382	–	* Same idea as preJoin
1383	–	*/
1384	–	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1385	–	maintainParallelism &= maintainsParallelism;
1386	–	boolean dec = false;
1387	–	while (spareStack == null || !tryResumeSpare(dec)) {
1388	–	int counts = workerCounts;
1389	–	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1390	–	if (!needSpare(counts, maintainParallelism))
1391	–	break;
1392	–	if (blocker.isReleasable())
1393	–	return true;
1394	–	if (tryAddSpare(counts))
1395	–	break;
1396	–	}
1397	–	}
1398	–	return false;
1399	–	}
1400	–
1401	–	/**
1402	–	* Returns true if a spare thread appears to be needed.  If
1403	–	* maintaining parallelism, returns true when the deficit in
1404	–	* running threads is more than the surplus of total threads, and
1405	–	* there is apparently some work to do.  This self-limiting rule
1406	–	* means that the more threads that have already been added, the
1407	–	* less parallelism we will tolerate before adding another.
1408	–	* @param counts current worker counts
1409	–	* @param maintainParallelism try to maintain parallelism
1410	–	*/
1411	–	private boolean needSpare(int counts, boolean maintainParallelism) {
1412	–	int ps = parallelism;
1413	–	int rc = runningCountOf(counts);
1414	–	int tc = totalCountOf(counts);
1415	–	int runningDeficit = ps - rc;
1416	–	int totalSurplus = tc - ps;
1417	–	return (tc < maxPoolSize &&
1418	–	(rc == 0 || totalSurplus < 0 ||
1419	–	(maintainParallelism &&
1420	–	runningDeficit > totalSurplus && mayHaveQueuedWork())));
1421	–	}
1422	–
1423	–	/**
1424	–	* Returns true if at least one worker queue appears to be
1425	–	* nonempty. This is expensive but not often called. It is not
1426	–	* critical that this be accurate, but if not, more or fewer
1427	–	* running threads than desired might be maintained.
1428	–	*/
1429	–	private boolean mayHaveQueuedWork() {
1430	–	ForkJoinWorkerThread[] ws = workers;
1431	–	int len = ws.length;
1432	–	ForkJoinWorkerThread v;
1433	–	for (int i = 0; i < len; ++i) {
1434	–	if ((v = ws[i]) != null && v.getRawQueueSize() > 0) {
1435	–	releaseIdleWorkers(false); // help wake up stragglers
1436	–	return true;
1437	–	}
1438	–	}
1439	–	return false;
1440	–	}
1441	–
1442	–	/**
1443	–	* Add a spare worker if lock available and no more than the
1444	–	* expected numbers of threads exist
1445	–	* @return true if successful
1446	–	*/
1447	–	private boolean tryAddSpare(int expectedCounts) {
1448	–	final ReentrantLock lock = this.workerLock;
1449	–	int expectedRunning = runningCountOf(expectedCounts);
1450	–	int expectedTotal = totalCountOf(expectedCounts);
1451	–	boolean success = false;
1452	–	boolean locked = false;
1453	–	// confirm counts while locking; CAS after obtaining lock
1454	–	try {
1455	–	for (;;) {
1456	–	int s = workerCounts;
1457	–	int tc = totalCountOf(s);
1458	–	int rc = runningCountOf(s);
1459	–	if (rc > expectedRunning || tc > expectedTotal)
1460	–	break;
1461	–	if (!locked && !(locked = lock.tryLock()))
1462	–	break;
1463	–	if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) {
1464	–	createAndStartSpare(tc);
1465	–	success = true;
1466	–	break;
1467	–	}
1468	–	}
1469	–	} finally {
1470	–	if (locked)
1471	–	lock.unlock();
1472	–	}
1473	–	return success;
1474	–	}
1475	–
1476	–	/**
1477	–	* Add the kth spare worker. On entry, pool coounts are already
1478	–	* adjusted to reflect addition.
1479	–	*/
1480	–	private void createAndStartSpare(int k) {
1481	–	ForkJoinWorkerThread w = null;
1482	–	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1);
1483	–	int len = ws.length;
1484	–	// Probably, we can place at slot k. If not, find empty slot
1485	–	if (k < len && ws[k] != null) {
1486	–	for (k = 0; k < len && ws[k] != null; ++k)
1487	–	;
1488	–	}
1489	–	if (k < len && (w = createWorker(k)) != null) {
1490	–	ws[k] = w;
1491	–	w.start();
1492	–	}
1493	–	else
1494	–	updateWorkerCount(-1); // adjust on failure
1495	–	signalIdleWorkers(false);
1496	–	}
1497	–
1498	–	/**
1499	–	* Suspend calling thread w if there are excess threads.  Called
1500	–	* only from sync.  Spares are enqueued in a Treiber stack
1501	–	* using the same WaitQueueNodes as barriers.  They are resumed
1502	–	* mainly in preJoin, but are also woken on pool events that
1503	–	* require all threads to check run state.
1504	–	* @param w the caller
1505	–	*/
1506	–	private boolean suspendIfSpare(ForkJoinWorkerThread w) {
1507	–	WaitQueueNode node = null;
1508	–	int s;
1509	–	while (parallelism < runningCountOf(s = workerCounts)) {
1510	–	if (node == null)
1511	–	node = new WaitQueueNode(w, 0);
1512	–	if (casWorkerCounts(s, s-1)) { // representation-dependent
1513	–	// push onto stack
1514	–	do;while (!casSpareStack(node.next = spareStack, node));
1515	–
1516	–	// block until released by resumeSpare
1517	–	while (node.thread != null) {
1518	–	if (!Thread.interrupted())
1519	–	LockSupport.park(this);
1520	–	}
1521	–	w.activate(); // help warm up
1522	–	return true;
1523	–	}
1524	–	}
1525	–	return false;
1526	–	}
1527	–
1528	–	/**
1529	–	* Try to pop and resume a spare thread.
1530	–	* @param updateCount if true, increment running count on success
1531	–	* @return true if successful
1532	–	*/
1533	–	private boolean tryResumeSpare(boolean updateCount) {
1534	–	WaitQueueNode q;
1535	–	while ((q = spareStack) != null) {
1536	–	if (casSpareStack(q, q.next)) {
1537	–	if (updateCount)
1538	–	updateRunningCount(1);
1539	–	q.signal();
1540	–	return true;
1541	–	}
1542	–	}
1543	–	return false;
1544	–	}
1545	–
1546	–	/**
1547	–	* Pop and resume all spare threads. Same idea as
1548	–	* releaseIdleWorkers.
1549	–	* @return true if any spares released
1550	–	*/
1551	–	private boolean resumeAllSpares() {
1552	–	WaitQueueNode q;
1553	–	while ( (q = spareStack) != null) {
1554	–	if (casSpareStack(q, null)) {
1555	–	do {
1556	–	updateRunningCount(1);
1557	–	q.signal();
1558	–	} while ((q = q.next) != null);
1559	–	return true;
1560	–	}
1561	–	}
1562	–	return false;
1563	–	}
1564	–
1565	–	/**
1566	–	* Pop and shutdown excessive spare threads. Call only while
1567	–	* holding lock. This is not guaranteed to eliminate all excess
1568	–	* threads, only those suspended as spares, which are the ones
1569	–	* unlikely to be needed in the future.
1570	–	*/
1571	–	private void trimSpares() {
1572	–	int surplus = totalCountOf(workerCounts) - parallelism;
1573	–	WaitQueueNode q;
1574	–	while (surplus > 0 && (q = spareStack) != null) {
1575	–	if (casSpareStack(q, null)) {
1576	–	do {
1577	–	updateRunningCount(1);
1578	–	ForkJoinWorkerThread w = q.thread;
1579	–	if (w != null && surplus > 0 &&
1580	–	runningCountOf(workerCounts) > 0 && w.shutdown())
1581	–	--surplus;
1582	–	q.signal();
1583	–	} while ((q = q.next) != null);
1584	–	}
1585	–	}
1586	–	}
1587	–
1588	–	/**
1589	–	* Returns approximate number of spares, just for diagnostics.
1590	–	*/
1591	–	private int countSpares() {
1592	–	int sum = 0;
1593	–	for (WaitQueueNode q = spareStack; q != null; q = q.next)
1594	–	++sum;
1595	–	return sum;
1596	–	}
1597	–
1598	–	/**
1806		* Interface for extending managed parallelism for tasks running
1807	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1808	<	* Method <tt>isReleasable</tt> must return true if blocking is not
1809	<	* necessary. Method <tt>block</tt> blocks the current thread
1810	<	* if necessary (perhaps internally invoking isReleasable before
1811	<	* actually blocking.).
1807	>	* in {@link ForkJoinPool}s.
1808	>	*
1809	>	* <p>A {@code ManagedBlocker} provides two methods.
1810	>	* Method {@code isReleasable} must return {@code true} if
1811	>	* blocking is not necessary. Method {@code block} blocks the
1812	>	* current thread if necessary (perhaps internally invoking
1813	>	* {@code isReleasable} before actually blocking).
1814	>	*
1815		* <p>For example, here is a ManagedBlocker based on a
1816		* ReentrantLock:
1817	<	* <pre>
1818	<	*   class ManagedLocker implements ManagedBlocker {
1819	<	*     final ReentrantLock lock;
1820	<	*     boolean hasLock = false;
1821	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1822	<	*     public boolean block() {
1823	<	*        if (!hasLock)
1824	<	*           lock.lock();
1825	<	*        return true;
1826	<	*     }
1827	<	*     public boolean isReleasable() {
1828	<	*        return hasLock || (hasLock = lock.tryLock());
1619	<	*     }
1817	>	*  <pre> {@code
1818	>	* class ManagedLocker implements ManagedBlocker {
1819	>	*   final ReentrantLock lock;
1820	>	*   boolean hasLock = false;
1821	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1822	>	*   public boolean block() {
1823	>	*     if (!hasLock)
1824	>	*       lock.lock();
1825	>	*     return true;
1826	>	*   }
1827	>	*   public boolean isReleasable() {
1828	>	*     return hasLock || (hasLock = lock.tryLock());
1829		*   }
1830	<	* </pre>
1830	>	* }}</pre>
1831		*/
1832		public static interface ManagedBlocker {
1833		/**
1834		* Possibly blocks the current thread, for example waiting for
1835		* a lock or condition.
1836	<	* @return true if no additional blocking is necessary (i.e.,
1837	<	* if isReleasable would return true).
1836	>	*
1837	>	* @return {@code true} if no additional blocking is necessary
1838	>	* (i.e., if isReleasable would return true)
1839		* @throws InterruptedException if interrupted while waiting
1840	<	* (the method is not required to do so, but is allowe to).
1840	>	* (the method is not required to do so, but is allowed to)
1841		*/
1842		boolean block() throws InterruptedException;
1843
1844		/**
1845	<	* Returns true if blocking is unnecessary.
1845	>	* Returns {@code true} if blocking is unnecessary.
1846		*/
1847		boolean isReleasable();
1848		}
1849
1850		/**
1851		* Blocks in accord with the given blocker.  If the current thread
1852	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1853	<	* spare thread to be activated if necessary to ensure parallelism
1854	<	* while the current thread is blocked.  If
1855	<	* <tt>maintainParallelism</tt> is true and the pool supports it
1856	<	* (see <tt>getMaintainsParallelism</tt>), this method attempts to
1857	<	* maintain the pool's nominal parallelism. Otherwise if activates
1858	<	* a thread only if necessary to avoid complete starvation. This
1859	<	* option may be preferable when blockages use timeouts, or are
1860	<	* almost always brief.
1861	<	*
1862	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1863	<	* equivalent to
1864	<	* <pre>
1865	<	*   while (!blocker.isReleasable())
1656	<	*      if (blocker.block())
1657	<	*         return;
1658	<	* </pre>
1659	<	* If the caller is a ForkJoinTask, then the pool may first
1660	<	* be expanded to ensure parallelism, and later adjusted.
1852	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1853	>	* arranges for a spare thread to be activated if necessary to
1854	>	* ensure sufficient parallelism while the current thread is blocked.
1855	>	*
1856	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1857	>	* behaviorally equivalent to
1858	>	*  <pre> {@code
1859	>	* while (!blocker.isReleasable())
1860	>	*   if (blocker.block())
1861	>	*     return;
1862	>	* }</pre>
1863	>	*
1864	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1865	>	* first be expanded to ensure parallelism, and later adjusted.
1866		*
1867		* @param blocker the blocker
1868	<	* @param maintainParallelism if true and supported by this pool,
1664	<	* attempt to maintain the pool's nominal parallelism; otherwise
1665	<	* activate a thread only if necessary to avoid complete
1666	<	* starvation.
1667	<	* @throws InterruptedException if blocker.block did so.
1868	>	* @throws InterruptedException if blocker.block did so
1869		*/
1870	<	public static void managedBlock(ManagedBlocker blocker,
1670	<	boolean maintainParallelism)
1870	>	public static void managedBlock(ManagedBlocker blocker)
1871		throws InterruptedException {
1872		Thread t = Thread.currentThread();
1873	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1874	<	((ForkJoinWorkerThread)t).pool : null);
1875	<	if (!blocker.isReleasable()) {
1876	<	try {
1677	<	if (pool == null ||
1678	<	!pool.preBlock(blocker, maintainParallelism))
1679	<	awaitBlocker(blocker);
1680	<	} finally {
1681	<	if (pool != null)
1682	<	pool.updateRunningCount(1);
1683	<	}
1873	>	if (t instanceof ForkJoinWorkerThread)
1874	>	((ForkJoinWorkerThread) t).pool.awaitBlocker(blocker);
1875	>	else {
1876	>	do {} while (!blocker.isReleasable() && !blocker.block());
1877		}
1878		}
1879
1880	<	private static void awaitBlocker(ManagedBlocker blocker)
1881	<	throws InterruptedException {
1882	<	do;while (!blocker.isReleasable() && !blocker.block());
1880	>	// AbstractExecutorService overrides.  These rely on undocumented
1881	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1882	>	// implement RunnableFuture.
1883	>
1884	>	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1885	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1886		}
1887
1888	+	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1889	+	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1890	+	}
1891
1892	<	// Temporary Unsafe mechanics for preliminary release
1892	>	// Unsafe mechanics
1893
1894	<	static final Unsafe _unsafe;
1895	<	static final long eventCountOffset;
1896	<	static final long workerCountsOffset;
1897	<	static final long runControlOffset;
1898	<	static final long barrierStackOffset;
1899	<	static final long spareStackOffset;
1894	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1895	>	private static final long workerCountsOffset =
1896	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1897	>	private static final long runStateOffset =
1898	>	objectFieldOffset("runState", ForkJoinPool.class);
1899	>	private static final long eventCountOffset =
1900	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1901	>	private static final long eventWaitersOffset =
1902	>	objectFieldOffset("eventWaiters",ForkJoinPool.class);
1903	>	private static final long stealCountOffset =
1904	>	objectFieldOffset("stealCount",ForkJoinPool.class);
1905
1906	<	static {
1906	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1907		try {
1908	<	if (ForkJoinPool.class.getClassLoader() != null) {
1909	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1910	<	f.setAccessible(true);
1911	<	_unsafe = (Unsafe)f.get(null);
1912	<	}
1913	<	else
1710	<	_unsafe = Unsafe.getUnsafe();
1711	<	eventCountOffset = _unsafe.objectFieldOffset
1712	<	(ForkJoinPool.class.getDeclaredField("eventCount"));
1713	<	workerCountsOffset = _unsafe.objectFieldOffset
1714	<	(ForkJoinPool.class.getDeclaredField("workerCounts"));
1715	<	runControlOffset = _unsafe.objectFieldOffset
1716	<	(ForkJoinPool.class.getDeclaredField("runControl"));
1717	<	barrierStackOffset = _unsafe.objectFieldOffset
1718	<	(ForkJoinPool.class.getDeclaredField("barrierStack"));
1719	<	spareStackOffset = _unsafe.objectFieldOffset
1720	<	(ForkJoinPool.class.getDeclaredField("spareStack"));
1721	<	} catch (Exception e) {
1722	<	throw new RuntimeException("Could not initialize intrinsics", e);
1908	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1909	>	} catch (NoSuchFieldException e) {
1910	>	// Convert Exception to corresponding Error
1911	>	NoSuchFieldError error = new NoSuchFieldError(field);
1912	>	error.initCause(e);
1913	>	throw error;
1914		}
1915		}
1916
1917	<	private boolean casEventCount(long cmp, long val) {
1918	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1919	<	}
1920	<	private boolean casWorkerCounts(int cmp, int val) {
1921	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1922	<	}
1923	<	private boolean casRunControl(int cmp, int val) {
1924	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1925	<	}
1926	<	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1927	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1928	<	}
1929	<	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1930	<	return _unsafe.compareAndSwapObject(this, barrierStackOffset, cmp, val);
1917	>	/**
1918	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1919	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1920	>	* into a jdk.
1921	>	*
1922	>	* @return a sun.misc.Unsafe
1923	>	*/
1924	>	private static sun.misc.Unsafe getUnsafe() {
1925	>	try {
1926	>	return sun.misc.Unsafe.getUnsafe();
1927	>	} catch (SecurityException se) {
1928	>	try {
1929	>	return java.security.AccessController.doPrivileged
1930	>	(new java.security
1931	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1932	>	public sun.misc.Unsafe run() throws Exception {
1933	>	java.lang.reflect.Field f = sun.misc
1934	>	.Unsafe.class.getDeclaredField("theUnsafe");
1935	>	f.setAccessible(true);
1936	>	return (sun.misc.Unsafe) f.get(null);
1937	>	}});
1938	>	} catch (java.security.PrivilegedActionException e) {
1939	>	throw new RuntimeException("Could not initialize intrinsics",
1940	>	e.getCause());
1941	>	}
1942	>	}
1943		}
1944		}

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