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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 1.69 by jsr166, Wed Sep 1 20:12:39 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 following
56	>	* table. These are designed to be used by clients not already engaged
57	>	* in fork/join computations in the current pool.  The main forms of
58	>	* these methods accept instances of {@code ForkJoinTask}, but
59	>	* overloaded forms also allow mixed execution of plain {@code
60	>	* Runnable}- or {@code Callable}- based activities as well.  However,
61	>	* tasks that are already executing in a pool should normally
62	>	* <em>NOT</em> use these pool execution methods, but instead use the
63	>	* within-computation forms listed in the table.
64	>	*
65	>	* <table BORDER CELLPADDING=3 CELLSPACING=1>
66	>	*  <tr>
67	>	*    <td></td>
68	>	*    <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
69	>	*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
70	>	*  </tr>
71	>	*  <tr>
72	>	*    <td> <b>Arrange 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 exhausted.
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 take actions when
142	>	* one worker is waiting to join a task stolen (or always held by)
143	>	* another.  Because we are multiplexing many tasks on to a pool
144	>	* of workers, we can't just let them block (as in Thread.join).
145	>	* We also cannot just reassign the joiner's run-time stack with
146	>	* another and replace it later, which would be a form of
147	>	* "continuation", that even if possible is not necessarily a good
148	>	* idea. Given that the creation costs of most threads on most
149	>	* systems mainly surrounds setting up runtime stacks, thread
150	>	* creation and switching is usually not much more expensive than
151	>	* stack creation and switching, and is more flexible). Instead we
152	>	* combine two tactics:
153	>	*
154	>	*   Helping: Arranging for the joiner to execute some task that it
155	>	*      would be running if the steal had not occurred.  Method
156	>	*      ForkJoinWorkerThread.helpJoinTask tracks joining->stealing
157	>	*      links to try to find such a task.
158	>	*
159	>	*   Compensating: Unless there are already enough live threads,
160	>	*      method helpMaintainParallelism() may create or
161	>	*      re-activate a spare thread to compensate for blocked
162	>	*      joiners until they unblock.
163	>	*
164	>	* It is impossible to keep exactly the target (parallelism)
165	>	* number of threads running at any given time.  Determining
166	>	* existence of conservatively safe helping targets, the
167	>	* availability of already-created spares, and the apparent need
168	>	* to create new spares are all racy and require heuristic
169	>	* guidance, so we rely on multiple retries of each.  Compensation
170	>	* occurs in slow-motion. It is triggered only upon timeouts of
171	>	* Object.wait used for joins. This reduces poor decisions that
172	>	* would otherwise be made when threads are waiting for others
173	>	* that are stalled because of unrelated activities such as
174	>	* garbage collection.
175	>	*
176	>	* The ManagedBlocker extension API can't use helping so relies
177	>	* only on compensation in method awaitBlocker.
178	>	*
179	>	* The main throughput advantages of work-stealing stem from
180	>	* decentralized control -- workers mostly steal tasks from each
181	>	* other. We do not want to negate this by creating bottlenecks
182	>	* implementing other management responsibilities. So we use a
183	>	* collection of techniques that avoid, reduce, or cope well with
184	>	* contention. These entail several instances of bit-packing into
185	>	* CASable fields to maintain only the minimally required
186	>	* atomicity. To enable such packing, we restrict maximum
187	>	* parallelism to (1<<15)-1 (enabling twice this (to accommodate
188	>	* unbalanced increments and decrements) to fit into a 16 bit
189	>	* field, which is far in excess of normal operating range.  Even
190	>	* though updates to some of these bookkeeping fields do sometimes
191	>	* contend with each other, they don't normally cache-contend with
192	>	* updates to others enough to warrant memory padding or
193	>	* isolation. So they are all held as fields of ForkJoinPool
194	>	* objects.  The main capabilities are as follows:
195	>	*
196	>	* 1. Creating and removing workers. Workers are recorded in the
197	>	* "workers" array. This is an array as opposed to some other data
198	>	* structure to support index-based random steals by workers.
199	>	* Updates to the array recording new workers and unrecording
200	>	* terminated ones are protected from each other by a lock
201	>	* (workerLock) but the array is otherwise concurrently readable,
202	>	* and accessed directly by workers. To simplify index-based
203	>	* operations, the array size is always a power of two, and all
204	>	* readers must tolerate null slots. Currently, all worker thread
205	>	* creation is on-demand, triggered by task submissions,
206	>	* replacement of terminated workers, and/or compensation for
207	>	* blocked workers. However, all other support code is set up to
208	>	* work with other policies.
209	>	*
210	>	* To ensure that we do not hold on to worker references that
211	>	* would prevent GC, ALL accesses to workers are via indices into
212	>	* the workers array (which is one source of some of the unusual
213	>	* code constructions here). In essence, the workers array serves
214	>	* as a WeakReference mechanism. Thus for example the event queue
215	>	* stores worker indices, not worker references. Access to the
216	>	* workers in associated methods (for example releaseEventWaiters)
217	>	* must both index-check and null-check the IDs. All such accesses
218	>	* ignore bad IDs by returning out early from what they are doing,
219	>	* since this can only be associated with shutdown, in which case
220	>	* it is OK to give up. On termination, we just clobber these
221	>	* data structures without trying to use them.
222	>	*
223	>	* 2. Bookkeeping for dynamically adding and removing workers. We
224	>	* aim to approximately maintain the given level of parallelism.
225	>	* When some workers are known to be blocked (on joins or via
226	>	* ManagedBlocker), we may create or resume others to take their
227	>	* place until they unblock (see below). Implementing this
228	>	* requires counts of the number of "running" threads (i.e., those
229	>	* that are neither blocked nor artificially suspended) as well as
230	>	* the total number.  These two values are packed into one field,
231	>	* "workerCounts" because we need accurate snapshots when deciding
232	>	* to create, resume or suspend.  Note however that the
233	>	* correspondence of these counts to reality is not guaranteed. In
234	>	* particular updates for unblocked threads may lag until they
235	>	* actually wake up.
236	>	*
237	>	* 3. Maintaining global run state. The run state of the pool
238	>	* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to
239	>	* those in other Executor implementations, as well as a count of
240	>	* "active" workers -- those that are, or soon will be, or
241	>	* recently were executing tasks. The runLevel and active count
242	>	* are packed together in order to correctly trigger shutdown and
243	>	* termination. Without care, active counts can be subject to very
244	>	* high contention.  We substantially reduce this contention by
245	>	* relaxing update rules.  A worker must claim active status
246	>	* prospectively, by activating if it sees that a submitted or
247	>	* stealable task exists (it may find after activating that the
248	>	* task no longer exists). It stays active while processing this
249	>	* task (if it exists) and any other local subtasks it produces,
250	>	* until it cannot find any other tasks. It then tries
251	>	* inactivating (see method preStep), but upon update contention
252	>	* instead scans for more tasks, later retrying inactivation if it
253	>	* doesn't find any.
254	>	*
255	>	* 4. Managing idle workers waiting for tasks. We cannot let
256	>	* workers spin indefinitely scanning for tasks when none are
257	>	* available. On the other hand, we must quickly prod them into
258	>	* action when new tasks are submitted or generated.  We
259	>	* park/unpark these idle workers using an event-count scheme.
260	>	* Field eventCount is incremented upon events that may enable
261	>	* workers that previously could not find a task to now find one:
262	>	* Submission of a new task to the pool, or another worker pushing
263	>	* a task onto a previously empty queue.  (We also use this
264	>	* mechanism for configuration and termination actions that
265	>	* require wakeups of idle workers).  Each worker maintains its
266	>	* last known event count, and blocks when a scan for work did not
267	>	* find a task AND its lastEventCount matches the current
268	>	* eventCount. Waiting idle workers are recorded in a variant of
269	>	* Treiber stack headed by field eventWaiters which, when nonzero,
270	>	* encodes the thread index and count awaited for by the worker
271	>	* thread most recently calling eventSync. This thread in turn has
272	>	* a record (field nextEventWaiter) for the next waiting worker.
273	>	* In addition to allowing simpler decisions about need for
274	>	* wakeup, the event count bits in eventWaiters serve the role of
275	>	* tags to avoid ABA errors in Treiber stacks. Upon any wakeup,
276	>	* released threads also try to release at most two others.  The
277	>	* net effect is a tree-like diffusion of signals, where released
278	>	* threads (and possibly others) help with unparks.  To further
279	>	* reduce contention effects a bit, failed CASes to increment
280	>	* field eventCount are tolerated without retries in signalWork.
281	>	* Conceptually they are merged into the same event, which is OK
282	>	* when their only purpose is to enable workers to scan for work.
283	>	*
284	>	* 5. Managing suspension of extra workers. When a worker notices
285	>	* (usually upon timeout of a wait()) that there are too few
286	>	* running threads, we may create a new thread to maintain
287	>	* parallelism level, or at least avoid starvation. Usually, extra
288	>	* threads are needed for only very short periods, yet join
289	>	* dependencies are such that we sometimes need them in
290	>	* bursts. Rather than create new threads each time this happens,
291	>	* we suspend no-longer-needed extra ones as "spares". For most
292	>	* purposes, we don't distinguish "extra" spare threads from
293	>	* normal "core" threads: On each call to preStep (the only point
294	>	* at which we can do this) a worker checks to see if there are
295	>	* now too many running workers, and if so, suspends itself.
296	>	* Method helpMaintainParallelism looks for suspended threads to
297	>	* resume before considering creating a new replacement. The
298	>	* spares themselves are encoded on another variant of a Treiber
299	>	* Stack, headed at field "spareWaiters".  Note that the use of
300	>	* spares is intrinsically racy.  One thread may become a spare at
301	>	* about the same time as another is needlessly being created. We
302	>	* counteract this and related slop in part by requiring resumed
303	>	* spares to immediately recheck (in preStep) to see whether they
304	>	* they should re-suspend.
305	>	*
306	>	* 6. Killing off unneeded workers. A timeout mechanism is used to
307	>	* shed unused workers: The oldest (first) event queue waiter uses
308	>	* a timed rather than hard wait. When this wait times out without
309	>	* a normal wakeup, it tries to shutdown any one (for convenience
310	>	* the newest) other spare or event waiter via
311	>	* tryShutdownUnusedWorker. This eventually reduces the number of
312	>	* worker threads to a minimum of one after a long enough period
313	>	* without use.
314	>	*
315	>	* 7. Deciding when to create new workers. The main dynamic
316	>	* control in this class is deciding when to create extra threads
317	>	* in method helpMaintainParallelism. We would like to keep
318	>	* exactly #parallelism threads running, which is an impossible
319	>	* task. We always need to create one when the number of running
320	>	* threads would become zero and all workers are busy. Beyond
321	>	* this, we must rely on heuristics that work well in the
322	>	* presence of transient phenomena such as GC stalls, dynamic
323	>	* compilation, and wake-up lags. These transients are extremely
324	>	* common -- we are normally trying to fully saturate the CPUs on
325	>	* a machine, so almost any activity other than running tasks
326	>	* impedes accuracy. Our main defense is to allow parallelism to
327	>	* lapse for a while during joins, and use a timeout to see if,
328	>	* after the resulting settling, there is still a need for
329	>	* additional workers.  This also better copes with the fact that
330	>	* some of the methods in this class tend to never become compiled
331	>	* (but are interpreted), so some components of the entire set of
332	>	* controls might execute 100 times faster than others. And
333	>	* similarly for cases where the apparent lack of work is just due
334	>	* to GC stalls and other transient system activity.
335	>	*
336	>	* Beware that there is a lot of representation-level coupling
337	>	* among classes ForkJoinPool, ForkJoinWorkerThread, and
338	>	* ForkJoinTask.  For example, direct access to "workers" array by
339	>	* workers, and direct access to ForkJoinTask.status by both
340	>	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
341	>	* trying to reduce this, since any associated future changes in
342	>	* representations will need to be accompanied by algorithmic
343	>	* changes anyway.
344	>	*
345	>	* Style notes: There are lots of inline assignments (of form
346	>	* "while ((local = field) != 0)") which are usually the simplest
347	>	* way to ensure the required read orderings (which are sometimes
348	>	* critical). Also several occurrences of the unusual "do {}
349	>	* while (!cas...)" which is the simplest way to force an update of
350	>	* a CAS'ed variable. There are also other coding oddities that
351	>	* help some methods perform reasonably even when interpreted (not
352	>	* compiled), at the expense of some messy constructions that
353	>	* reduce byte code counts.
354	>	*
355	>	* The order of declarations in this file is: (1) statics (2)
356	>	* fields (along with constants used when unpacking some of them)
357	>	* (3) internal control methods (4) callbacks and other support
358	>	* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
359	>	* methods (plus a few little helpers).
360		*/
361
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	–
362		/**
363	<	* Factory for creating new ForkJoinWorkerThreads.  A
364	<	* ForkJoinWorkerThreadFactory must be defined and used for
365	<	* ForkJoinWorkerThread subclasses that extend base functionality
366	<	* or initialize threads with different contexts.
363	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
364	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
365	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
366	>	* functionality or initialize threads with different contexts.
367		*/
368		public static interface ForkJoinWorkerThreadFactory {
369		/**
370		* Returns a new worker thread operating in the given pool.
371		*
372		* @param pool the pool this thread works in
373	<	* @throws NullPointerException if pool is null;
373	>	* @throws NullPointerException if the pool is null
374		*/
375		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
376		}
377
378		/**
379	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
379	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
380		* new ForkJoinWorkerThread.
381		*/
382	<	public static class  DefaultForkJoinWorkerThreadFactory
382	>	static class DefaultForkJoinWorkerThreadFactory
383		implements ForkJoinWorkerThreadFactory {
384		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
385	<	try {
94	<	return new ForkJoinWorkerThread(pool);
95	<	} catch (OutOfMemoryError oom)  {
96	<	return null;
97	<	}
385	>	return new ForkJoinWorkerThread(pool);
386		}
387		}
388
389		/**
390	<	* The default ForkJoinWorkerThreadFactory, used unless overridden
391	<	* in ForkJoinPool constructors.
390	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
391	>	* overridden in ForkJoinPool constructors.
392		*/
393	<	private static final DefaultForkJoinWorkerThreadFactory
393	>	public static final ForkJoinWorkerThreadFactory
394		defaultForkJoinWorkerThreadFactory =
395		new DefaultForkJoinWorkerThreadFactory();
396
109	–
397		/**
398		* Permission required for callers of methods that may start or
399		* kill threads.
#	Line 131 | Line 418 | public class ForkJoinPool extends Abstra
418		new AtomicInteger();
419
420		/**
421	<	* Array holding all worker threads in the pool. Array size must
422	<	* be a power of two.  Updates and replacements are protected by
423	<	* workerLock, but it is always kept in a consistent enough state
424	<	* to be randomly accessed without locking by workers performing
425	<	* work-stealing.
421	>	* The time to block in a join (see awaitJoin) before checking if
422	>	* a new worker should be (re)started to maintain parallelism
423	>	* level. The value should be short enough to maintain global
424	>	* responsiveness and progress but long enough to avoid
425	>	* counterproductive firings during GC stalls or unrelated system
426	>	* activity, and to not bog down systems with continual re-firings
427	>	* on GCs or legitimately long waits.
428		*/
429	<	volatile ForkJoinWorkerThread[] workers;
429	>	private static final long JOIN_TIMEOUT_MILLIS = 250L; // 4 per second
430
431		/**
432	<	* Lock protecting access to workers.
432	>	* The wakeup interval (in nanoseconds) for the oldest worker
433	>	* worker waiting for an event invokes tryShutdownUnusedWorker to shrink
434	>	* the number of workers.  The exact value does not matter too
435	>	* much, but should be long enough to slowly release resources
436	>	* during long periods without use without disrupting normal use.
437		*/
438	<	private final ReentrantLock workerLock;
438	>	private static final long SHRINK_RATE_NANOS =
439	>	30L * 1000L * 1000L * 1000L; // 2 per minute
440
441		/**
442	<	* Condition for awaitTermination.
442	>	* Absolute bound for parallelism level. Twice this number plus
443	>	* one (i.e., 0xfff) must fit into a 16bit field to enable
444	>	* word-packing for some counts and indices.
445		*/
446	<	private final Condition termination;
446	>	private static final int MAX_WORKERS   = 0x7fff;
447
448		/**
449	<	* The uncaught exception handler used when any worker
450	<	* abrupty terminates
449	>	* Array holding all worker threads in the pool.  Array size must
450	>	* be a power of two.  Updates and replacements are protected by
451	>	* workerLock, but the array is always kept in a consistent enough
452	>	* state to be randomly accessed without locking by workers
453	>	* performing work-stealing, as well as other traversal-based
454	>	* methods in this class. All readers must tolerate that some
455	>	* array slots may be null.
456		*/
457	<	private Thread.UncaughtExceptionHandler ueh;
457	>	volatile ForkJoinWorkerThread[] workers;
458
459		/**
460	<	* Creation factory for worker threads.
460	>	* Queue for external submissions.
461		*/
462	<	private final ForkJoinWorkerThreadFactory factory;
462	>	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
463
464		/**
465	<	* Head of stack of threads that were created to maintain
165	<	* parallelism when other threads blocked, but have since
166	<	* suspended when the parallelism level rose.
465	>	* Lock protecting updates to workers array.
466		*/
467	<	private volatile WaitQueueNode spareStack;
467	>	private final ReentrantLock workerLock;
468
469		/**
470	<	* Sum of per-thread steal counts, updated only when threads are
172	<	* idle or terminating.
470	>	* Latch released upon termination.
471		*/
472	<	private final AtomicLong stealCount;
472	>	private final Phaser termination;
473
474		/**
475	<	* Queue for external submissions.
475	>	* Creation factory for worker threads.
476		*/
477	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
477	>	private final ForkJoinWorkerThreadFactory factory;
478
479		/**
480	<	* Head of Treiber stack for barrier sync. See below for explanation
480	>	* Sum of per-thread steal counts, updated only when threads are
481	>	* idle or terminating.
482		*/
483	<	private volatile WaitQueueNode barrierStack;
483	>	private volatile long stealCount;
484
485		/**
486	<	* The count for event barrier
486	>	* Encoded record of top of Treiber stack of threads waiting for
487	>	* events. The top 32 bits contain the count being waited for. The
488	>	* bottom 16 bits contains one plus the pool index of waiting
489	>	* worker thread. (Bits 16-31 are unused.)
490		*/
491	<	private volatile long eventCount;
491	>	private volatile long eventWaiters;
492	>
493	>	private static final int  EVENT_COUNT_SHIFT = 32;
494	>	private static final long WAITER_ID_MASK    = (1L << 16) - 1L;
495
496		/**
497	<	* Pool number, just for assigning useful names to worker threads
497	>	* A counter for events that may wake up worker threads:
498	>	*   - Submission of a new task to the pool
499	>	*   - A worker pushing a task on an empty queue
500	>	*   - termination
501		*/
502	<	private final int poolNumber;
502	>	private volatile int eventCount;
503
504		/**
505	<	* The maximum allowed pool size
505	>	* Encoded record of top of Treiber stack of spare threads waiting
506	>	* for resumption. The top 16 bits contain an arbitrary count to
507	>	* avoid ABA effects. The bottom 16bits contains one plus the pool
508	>	* index of waiting worker thread.
509		*/
510	<	private volatile int maxPoolSize;
510	>	private volatile int spareWaiters;
511	>
512	>	private static final int SPARE_COUNT_SHIFT = 16;
513	>	private static final int SPARE_ID_MASK     = (1 << 16) - 1;
514
515		/**
516	<	* The desired parallelism level, updated only under workerLock.
517	<	*/
518	<	private volatile int parallelism;
516	>	* Lifecycle control. The low word contains the number of workers
517	>	* that are (probably) executing tasks. This value is atomically
518	>	* incremented before a worker gets a task to run, and decremented
519	>	* when worker has no tasks and cannot find any.  Bits 16-18
520	>	* contain runLevel value. When all are zero, the pool is
521	>	* running. Level transitions are monotonic (running -> shutdown
522	>	* -> terminating -> terminated) so each transition adds a bit.
523	>	* These are bundled together to ensure consistent read for
524	>	* termination checks (i.e., that runLevel is at least SHUTDOWN
525	>	* and active threads is zero).
526	>	*
527	>	* Notes: Most direct CASes are dependent on these bitfield
528	>	* positions.  Also, this field is non-private to enable direct
529	>	* performance-sensitive CASes in ForkJoinWorkerThread.
530	>	*/
531	>	volatile int runState;
532	>
533	>	// Note: The order among run level values matters.
534	>	private static final int RUNLEVEL_SHIFT     = 16;
535	>	private static final int SHUTDOWN           = 1 << RUNLEVEL_SHIFT;
536	>	private static final int TERMINATING        = 1 << (RUNLEVEL_SHIFT + 1);
537	>	private static final int TERMINATED         = 1 << (RUNLEVEL_SHIFT + 2);
538	>	private static final int ACTIVE_COUNT_MASK  = (1 << RUNLEVEL_SHIFT) - 1;
539
540		/**
541		* Holds number of total (i.e., created and not yet terminated)
542		* and running (i.e., not blocked on joins or other managed sync)
543	<	* threads, packed into one int to ensure consistent snapshot when
543	>	* threads, packed together to ensure consistent snapshot when
544		* making decisions about creating and suspending spare
545	<	* threads. Updated only by CAS.  Note: CASes in
546	<	* updateRunningCount and preJoin running active count is in low
547	<	* word, so need to be modified if this changes
545	>	* threads. Updated only by CAS. Note that adding a new worker
546	>	* requires incrementing both counts, since workers start off in
547	>	* running state.
548		*/
549		private volatile int workerCounts;
550
551	<	private static int totalCountOf(int s)           { return s >>> 16;  }
552	<	private static int runningCountOf(int s)         { return s & shortMask; }
553	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
551	>	private static final int TOTAL_COUNT_SHIFT  = 16;
552	>	private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1;
553	>	private static final int ONE_RUNNING        = 1;
554	>	private static final int ONE_TOTAL          = 1 << TOTAL_COUNT_SHIFT;
555
556		/**
557	<	* Add delta (which may be negative) to running count.  This must
558	<	* 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
557	>	* The target parallelism level.
558	>	* Accessed directly by ForkJoinWorkerThreads.
559		*/
560	<	final void updateRunningCount(int delta) {
228	<	int s;
229	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
230	<	}
560	>	final int parallelism;
561
562		/**
563	<	* Add delta (which may be negative) to both total and running
564	<	* count.  This must be called upon creation and termination of
235	<	* worker threads.
236	<	* @param delta the number to add
563	>	* True if use local fifo, not default lifo, for local polling
564	>	* Read by, and replicated by ForkJoinWorkerThreads
565		*/
566	<	private void updateWorkerCount(int delta) {
239	<	int d = delta + (delta << 16); // add to both lo and hi parts
240	<	int s;
241	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
242	<	}
566	>	final boolean locallyFifo;
567
568		/**
569	<	* Lifecycle control. High word contains runState, low word
570	<	* 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
569	>	* The uncaught exception handler used when any worker abruptly
570	>	* terminates.
571		*/
572	<	private volatile int runControl;
572	>	private final Thread.UncaughtExceptionHandler ueh;
573
574	<	// RunState values. Order among values matters
575	<	private static final int RUNNING     = 0;
576	<	private static final int SHUTDOWN    = 1;
577	<	private static final int TERMINATING = 2;
260	<	private static final int TERMINATED  = 3;
574	>	/**
575	>	* Pool number, just for assigning useful names to worker threads
576	>	*/
577	>	private final int poolNumber;
578
579	<	private static int runStateOf(int c)             { return c >>> 16; }
580	<	private static int activeCountOf(int c)          { return c & shortMask; }
264	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
579	>	// Utilities for CASing fields. Note that most of these
580	>	// are usually manually inlined by callers
581
582		/**
583	<	* Increment active count. Called by workers before/during
268	<	* executing tasks.
583	>	* Increments running count part of workerCounts
584		*/
585	<	final void incrementActiveCount() {
585	>	final void incrementRunningCount() {
586		int c;
587	<	do;while (!casRunControl(c = runControl, c+1));
587	>	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
588	>	c = workerCounts,
589	>	c + ONE_RUNNING));
590		}
591
592		/**
593	<	* Decrement active count; possibly trigger termination.
277	<	* Called by workers when they can't find tasks.
593	>	* Tries to decrement running count unless already zero
594		*/
595	<	final void decrementActiveCount() {
596	<	int c, nextc;
597	<	do;while (!casRunControl(c = runControl, nextc = c-1));
598	<	if (canTerminateOnShutdown(nextc))
599	<	terminateOnShutdown();
595	>	final boolean tryDecrementRunningCount() {
596	>	int wc = workerCounts;
597	>	if ((wc & RUNNING_COUNT_MASK) == 0)
598	>	return false;
599	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
600	>	wc, wc - ONE_RUNNING);
601		}
602
603		/**
604	<	* Return true if argument represents zero active count and
605	<	* nonzero runstate, which is the triggering condition for
606	<	* terminating on shutdown.
604	>	* Forces decrement of encoded workerCounts, awaiting nonzero if
605	>	* (rarely) necessary when other count updates lag.
606	>	*
607	>	* @param dr -- either zero or ONE_RUNNING
608	>	* @param dt == either zero or ONE_TOTAL
609		*/
610	<	private static boolean canTerminateOnShutdown(int c) {
611	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
610	>	private void decrementWorkerCounts(int dr, int dt) {
611	>	for (;;) {
612	>	int wc = workerCounts;
613	>	if ((wc & RUNNING_COUNT_MASK)  - dr < 0 ||
614	>	(wc >>> TOTAL_COUNT_SHIFT) - dt < 0) {
615	>	if ((runState & TERMINATED) != 0)
616	>	return; // lagging termination on a backout
617	>	Thread.yield();
618	>	}
619	>	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
620	>	wc, wc - (dr + dt)))
621	>	return;
622	>	}
623		}
624
625		/**
626	<	* Transition run state to at least the given state. Return true
627	<	* if not already at least given state.
626	>	* Tries decrementing active count; fails on contention.
627	>	* Called when workers cannot find tasks to run.
628		*/
629	<	private boolean transitionRunStateTo(int state) {
629	>	final boolean tryDecrementActiveCount() {
630	>	int c;
631	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
632	>	c = runState, c - 1);
633	>	}
634	>
635	>	/**
636	>	* Advances to at least the given level. Returns true if not
637	>	* already in at least the given level.
638	>	*/
639	>	private boolean advanceRunLevel(int level) {
640		for (;;) {
641	<	int c = runControl;
642	<	if (runStateOf(c) >= state)
641	>	int s = runState;
642	>	if ((s & level) != 0)
643		return false;
644	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
644	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level))
645		return true;
646		}
647		}
648
649	+	// workers array maintenance
650	+
651		/**
652	<	* Controls whether to add spares to maintain parallelism
652	>	* Records and returns a workers array index for new worker.
653		*/
654	<	private volatile boolean maintainsParallelism;
654	>	private int recordWorker(ForkJoinWorkerThread w) {
655	>	// Try using slot totalCount-1. If not available, scan and/or resize
656	>	int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1;
657	>	final ReentrantLock lock = this.workerLock;
658	>	lock.lock();
659	>	try {
660	>	ForkJoinWorkerThread[] ws = workers;
661	>	int n = ws.length;
662	>	if (k < 0 || k >= n || ws[k] != null) {
663	>	for (k = 0; k < n && ws[k] != null; ++k)
664	>	;
665	>	if (k == n)
666	>	ws = Arrays.copyOf(ws, n << 1);
667	>	}
668	>	ws[k] = w;
669	>	workers = ws; // volatile array write ensures slot visibility
670	>	} finally {
671	>	lock.unlock();
672	>	}
673	>	return k;
674	>	}
675
676	<	// Constructors
676	>	/**
677	>	* Nulls out record of worker in workers array
678	>	*/
679	>	private void forgetWorker(ForkJoinWorkerThread w) {
680	>	int idx = w.poolIndex;
681	>	// Locking helps method recordWorker avoid unnecessary expansion
682	>	final ReentrantLock lock = this.workerLock;
683	>	lock.lock();
684	>	try {
685	>	ForkJoinWorkerThread[] ws = workers;
686	>	if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify
687	>	ws[idx] = null;
688	>	} finally {
689	>	lock.unlock();
690	>	}
691	>	}
692
693		/**
694	<	* Creates a ForkJoinPool with a pool size equal to the number of
695	<	* processors available on the system and using the default
696	<	* ForkJoinWorkerThreadFactory,
697	<	* @throws SecurityException if a security manager exists and
698	<	*         the caller is not permitted to modify threads
322	<	*         because it does not hold {@link
323	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
694	>	* Final callback from terminating worker.  Removes record of
695	>	* worker from array, and adjusts counts. If pool is shutting
696	>	* down, tries to complete termination.
697	>	*
698	>	* @param w the worker
699		*/
700	<	public ForkJoinPool() {
701	<	this(Runtime.getRuntime().availableProcessors(),
702	<	defaultForkJoinWorkerThreadFactory);
700	>	final void workerTerminated(ForkJoinWorkerThread w) {
701	>	forgetWorker(w);
702	>	decrementWorkerCounts(w.isTrimmed()? 0 : ONE_RUNNING, ONE_TOTAL);
703	>	while (w.stealCount != 0) // collect final count
704	>	tryAccumulateStealCount(w);
705	>	tryTerminate(false);
706		}
707
708	+	// Waiting for and signalling events
709	+
710		/**
711	<	* Creates a ForkJoinPool with the indicated parellelism level
712	<	* threads, and using the default ForkJoinWorkerThreadFactory,
713	<	* @param parallelism the number of worker threads
714	<	* @throws IllegalArgumentException if parallelism less than or
335	<	* equal to zero
336	<	* @throws SecurityException if a security manager exists and
337	<	*         the caller is not permitted to modify threads
338	<	*         because it does not hold {@link
339	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
711	>	* Releases workers blocked on a count not equal to current count.
712	>	* Normally called after precheck that eventWaiters isn't zero to
713	>	* avoid wasted array checks. Gives up upon a change in count or
714	>	* upon releasing two workers, letting others take over.
715		*/
716	<	public ForkJoinPool(int parallelism) {
717	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
716	>	private void releaseEventWaiters() {
717	>	ForkJoinWorkerThread[] ws = workers;
718	>	int n = ws.length;
719	>	long h = eventWaiters;
720	>	int ec = eventCount;
721	>	boolean releasedOne = false;
722	>	ForkJoinWorkerThread w; int id;
723	>	while ((id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 &&
724	>	(int)(h >>> EVENT_COUNT_SHIFT) != ec &&
725	>	id < n && (w = ws[id]) != null) {
726	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
727	>	h,  w.nextWaiter)) {
728	>	LockSupport.unpark(w);
729	>	if (releasedOne) // exit on second release
730	>	break;
731	>	releasedOne = true;
732	>	}
733	>	if (eventCount != ec)
734	>	break;
735	>	h = eventWaiters;
736	>	}
737		}
738
739		/**
740	<	* Creates a ForkJoinPool with a pool size equal to the number of
741	<	* processors available on the system and using the given
348	<	* ForkJoinWorkerThreadFactory,
349	<	* @param factory the factory for creating new threads
350	<	* @throws NullPointerException if factory is null
351	<	* @throws SecurityException if a security manager exists and
352	<	*         the caller is not permitted to modify threads
353	<	*         because it does not hold {@link
354	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
740	>	* Tries to advance eventCount and releases waiters. Called only
741	>	* from workers.
742		*/
743	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
744	<	this(Runtime.getRuntime().availableProcessors(), factory);
743	>	final void signalWork() {
744	>	int c; // try to increment event count -- CAS failure OK
745	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
746	>	if (eventWaiters != 0L)
747	>	releaseEventWaiters();
748		}
749
750		/**
751	<	* Creates a ForkJoinPool with the indicated target number of
752	<	* worker threads and the given factory.
751	>	* Adds the given worker to event queue and blocks until
752	>	* terminating or event count advances from the given value
753		*
754	<	* @param parallelism the targeted number of worker threads
755	<	* @param factory the factory for creating new threads
366	<	* @throws IllegalArgumentException if parallelism less than or
367	<	* equal to zero, or greater than implementation limit.
368	<	* @throws NullPointerException if factory is null
369	<	* @throws SecurityException if a security manager exists and
370	<	*         the caller is not permitted to modify threads
371	<	*         because it does not hold {@link
372	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
754	>	* @param w the calling worker thread
755	>	* @param ec the count
756		*/
757	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
758	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
759	<	throw new IllegalArgumentException();
760	<	if (factory == null)
761	<	throw new NullPointerException();
762	<	checkPermission();
763	<	this.factory = factory;
764	<	this.parallelism = parallelism;
765	<	this.maxPoolSize = MAX_THREADS;
766	<	this.maintainsParallelism = true;
767	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
768	<	this.workerLock = new ReentrantLock();
769	<	this.termination = workerLock.newCondition();
387	<	this.stealCount = new AtomicLong();
388	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
389	<	createAndStartInitialWorkers(parallelism);
757	>	private void eventSync(ForkJoinWorkerThread w, int ec) {
758	>	long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1));
759	>	long h;
760	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
761	>	(((int)((h = eventWaiters) & WAITER_ID_MASK)) == 0 ||
762	>	(int)(h >>> EVENT_COUNT_SHIFT) == ec) &&
763	>	eventCount == ec) {
764	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
765	>	w.nextWaiter = h, nh)) {
766	>	awaitEvent(w, ec);
767	>	break;
768	>	}
769	>	}
770		}
771
772		/**
773	<	* Create new worker using factory.
774	<	* @param index the index to assign worker
775	<	* @return new worker, or null of factory failed
773	>	* Blocks the given worker (that has already been entered as an
774	>	* event waiter) until terminating or event count advances from
775	>	* the given value. The oldest (first) waiter uses a timed wait to
776	>	* occasionally one-by-one shrink the number of workers (to a
777	>	* minimum of one) if the pool has not been used for extended
778	>	* periods.
779	>	*
780	>	* @param w the calling worker thread
781	>	* @param ec the count
782		*/
783	<	private ForkJoinWorkerThread createWorker(int index) {
784	<	Thread.UncaughtExceptionHandler h = ueh;
785	<	ForkJoinWorkerThread w = factory.newThread(this);
786	<	if (w != null) {
787	<	w.poolIndex = index;
788	<	w.setDaemon(true);
789	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
790	<	if (h != null)
791	<	w.setUncaughtExceptionHandler(h);
783	>	private void awaitEvent(ForkJoinWorkerThread w, int ec) {
784	>	while (eventCount == ec) {
785	>	if (tryAccumulateStealCount(w)) { // transfer while idle
786	>	boolean untimed = (w.nextWaiter != 0L ||
787	>	(workerCounts & RUNNING_COUNT_MASK) <= 1);
788	>	long startTime = untimed? 0 : System.nanoTime();
789	>	Thread.interrupted();         // clear/ignore interrupt
790	>	if (eventCount != ec || w.runState != 0 ||
791	>	runState >= TERMINATING)  // recheck after clear
792	>	break;
793	>	if (untimed)
794	>	LockSupport.park(w);
795	>	else {
796	>	LockSupport.parkNanos(w, SHRINK_RATE_NANOS);
797	>	if (eventCount != ec || w.runState != 0 ||
798	>	runState >= TERMINATING)
799	>	break;
800	>	if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS)
801	>	tryShutdownUnusedWorker(ec);
802	>	}
803	>	}
804		}
407	–	return w;
805		}
806
807	+	// Maintaining parallelism
808	+
809		/**
810	<	* Return a good size for worker array given pool size.
412	<	* Currently requires size to be a power of two.
810	>	* Pushes worker onto the spare stack
811		*/
812	<	private static int arraySizeFor(int ps) {
813	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
812	>	final void pushSpare(ForkJoinWorkerThread w) {
813	>	int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1);
814	>	do {} while (!UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
815	>	w.nextSpare = spareWaiters,ns));
816		}
817
818		/**
819	<	* Create or resize array if necessary to hold newLength
820	<	* @return the array
819	>	* Tries (once) to resume a spare if the number of running
820	>	* threads is less than target.
821		*/
822	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
822	>	private void tryResumeSpare() {
823	>	int sw, id;
824		ForkJoinWorkerThread[] ws = workers;
825	<	if (ws == null)
826	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
827	<	else if (newLength > ws.length)
828	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
829	<	else
830	<	return ws;
825	>	int n = ws.length;
826	>	ForkJoinWorkerThread w;
827	>	if ((sw = spareWaiters) != 0 &&
828	>	(id = (sw & SPARE_ID_MASK) - 1) >= 0 &&
829	>	id < n && (w = ws[id]) != null &&
830	>	(workerCounts & RUNNING_COUNT_MASK) < parallelism &&
831	>	spareWaiters == sw &&
832	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
833	>	sw, w.nextSpare)) {
834	>	int c; // increment running count before resume
835	>	do {} while (!UNSAFE.compareAndSwapInt
836	>	(this, workerCountsOffset,
837	>	c = workerCounts, c + ONE_RUNNING));
838	>	if (w.tryUnsuspend())
839	>	LockSupport.unpark(w);
840	>	else   // back out if w was shutdown
841	>	decrementWorkerCounts(ONE_RUNNING, 0);
842	>	}
843		}
844
845		/**
846	<	* Try to shrink workers into smaller array after one or more terminate
846	>	* Tries to increase the number of running workers if below target
847	>	* parallelism: If a spare exists tries to resume it via
848	>	* tryResumeSpare.  Otherwise, if not enough total workers or all
849	>	* existing workers are busy, adds a new worker. In all cases also
850	>	* helps wake up releasable workers waiting for work.
851	>	*/
852	>	private void helpMaintainParallelism() {
853	>	int pc = parallelism;
854	>	int wc, rs, tc;
855	>	while (((wc = workerCounts) & RUNNING_COUNT_MASK) < pc &&
856	>	(rs = runState) < TERMINATING) {
857	>	if (spareWaiters != 0)
858	>	tryResumeSpare();
859	>	else if ((tc = wc >>> TOTAL_COUNT_SHIFT) >= MAX_WORKERS ||
860	>	(tc >= pc && (rs & ACTIVE_COUNT_MASK) != tc))
861	>	break;   // enough total
862	>	else if (runState == rs && workerCounts == wc &&
863	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
864	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
865	>	ForkJoinWorkerThread w = null;
866	>	try {
867	>	w = factory.newThread(this);
868	>	} finally { // adjust on null or exceptional factory return
869	>	if (w == null) {
870	>	decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL);
871	>	tryTerminate(false); // handle failure during shutdown
872	>	}
873	>	}
874	>	if (w == null)
875	>	break;
876	>	w.start(recordWorker(w), ueh);
877	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) >= pc) {
878	>	int c; // advance event count
879	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
880	>	c = eventCount, c+1);
881	>	break; // add at most one unless total below target
882	>	}
883	>	}
884	>	}
885	>	if (eventWaiters != 0L)
886	>	releaseEventWaiters();
887	>	}
888	>
889	>	/**
890	>	* Callback from the oldest waiter in awaitEvent waking up after a
891	>	* period of non-use. If all workers are idle, tries (once) to
892	>	* shutdown an event waiter or a spare, if one exists. Note that
893	>	* we don't need CAS or locks here because the method is called
894	>	* only from one thread occasionally waking (and even misfires are
895	>	* OK). Note that until the shutdown worker fully terminates,
896	>	* workerCounts will overestimate total count, which is tolerable.
897	>	*
898	>	* @param ec the event count waited on by caller (to abort
899	>	* attempt if count has since changed).
900		*/
901	<	private void tryShrinkWorkerArray() {
902	<	ForkJoinWorkerThread[] ws = workers;
903	<	int len = ws.length;
904	<	int last = len - 1;
905	<	while (last >= 0 && ws[last] == null)
906	<	--last;
907	<	int newLength = arraySizeFor(last+1);
908	<	if (newLength < len)
909	<	workers = Arrays.copyOf(ws, newLength);
901	>	private void tryShutdownUnusedWorker(int ec) {
902	>	if (runState == 0 && eventCount == ec) { // only trigger if all idle
903	>	ForkJoinWorkerThread[] ws = workers;
904	>	int n = ws.length;
905	>	ForkJoinWorkerThread w = null;
906	>	boolean shutdown = false;
907	>	int sw;
908	>	long h;
909	>	if ((sw = spareWaiters) != 0) { // prefer killing spares
910	>	int id = (sw & SPARE_ID_MASK) - 1;
911	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
912	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
913	>	sw, w.nextSpare))
914	>	shutdown = true;
915	>	}
916	>	else if ((h = eventWaiters) != 0L) {
917	>	long nh;
918	>	int id = ((int)(h & WAITER_ID_MASK)) - 1;
919	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
920	>	(nh = w.nextWaiter) != 0L && // keep at least one worker
921	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh))
922	>	shutdown = true;
923	>	}
924	>	if (w != null && shutdown) {
925	>	w.shutdown();
926	>	LockSupport.unpark(w);
927	>	}
928	>	}
929	>	releaseEventWaiters(); // in case of interference
930		}
931
932		/**
933	<	* Initial worker array and worker creation and startup. (This
934	<	* must be done under lock to avoid interference by some of the
935	<	* newly started threads while creating others.)
933	>	* Callback from workers invoked upon each top-level action (i.e.,
934	>	* stealing a task or taking a submission and running it).
935	>	* Performs one or more of the following:
936	>	*
937	>	* 1. If the worker is active and either did not run a task
938	>	*    or there are too many workers, try to set its active status
939	>	*    to inactive and update activeCount. On contention, we may
940	>	*    try again in this or a subsequent call.
941	>	*
942	>	* 2. If not enough total workers, help create some.
943	>	*
944	>	* 3. If there are too many running workers, suspend this worker
945	>	*    (first forcing inactive if necessary).  If it is not needed,
946	>	*    it may be shutdown while suspended (via
947	>	*    tryShutdownUnusedWorker).  Otherwise, upon resume it
948	>	*    rechecks running thread count and need for event sync.
949	>	*
950	>	* 4. If worker did not run a task, await the next task event via
951	>	*    eventSync if necessary (first forcing inactivation), upon
952	>	*    which the worker may be shutdown via
953	>	*    tryShutdownUnusedWorker.  Otherwise, help release any
954	>	*    existing event waiters that are now releasable,
955	>	*
956	>	* @param w the worker
957	>	* @param ran true if worker ran a task since last call to this method
958		*/
959	<	private void createAndStartInitialWorkers(int ps) {
960	<	final ReentrantLock lock = this.workerLock;
961	<	lock.lock();
962	<	try {
963	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
964	<	for (int i = 0; i < ps; ++i) {
965	<	ForkJoinWorkerThread w = createWorker(i);
966	<	if (w != null) {
967	<	ws[i] = w;
968	<	w.start();
969	<	updateWorkerCount(1);
959	>	final void preStep(ForkJoinWorkerThread w, boolean ran) {
960	>	int wec = w.lastEventCount;
961	>	boolean active = w.active;
962	>	boolean inactivate = false;
963	>	int pc = parallelism;
964	>	int rs;
965	>	while (w.runState == 0 && (rs = runState) < TERMINATING) {
966	>	if ((inactivate || (active && (rs & ACTIVE_COUNT_MASK) >= pc)) &&
967	>	UNSAFE.compareAndSwapInt(this, runStateOffset, rs, rs - 1))
968	>	inactivate = active = w.active = false;
969	>	int wc = workerCounts;
970	>	if ((wc & RUNNING_COUNT_MASK) > pc) {
971	>	if (!(inactivate |= active) && // must inactivate to suspend
972	>	workerCounts == wc &&      // try to suspend as spare
973	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
974	>	wc, wc - ONE_RUNNING))
975	>	w.suspendAsSpare();
976	>	}
977	>	else if ((wc >>> TOTAL_COUNT_SHIFT) < pc)
978	>	helpMaintainParallelism();     // not enough workers
979	>	else if (!ran) {
980	>	long h = eventWaiters;
981	>	int ec = eventCount;
982	>	if (h != 0L && (int)(h >>> EVENT_COUNT_SHIFT) != ec)
983	>	releaseEventWaiters();     // release others before waiting
984	>	else if (ec != wec) {
985	>	w.lastEventCount = ec;     // no need to wait
986	>	break;
987		}
988	+	else if (!(inactivate |= active))
989	+	eventSync(w, wec);         // must inactivate before sync
990		}
991	<	} finally {
992	<	lock.unlock();
991	>	else
992	>	break;
993		}
994		}
995
996		/**
997	<	* Worker creation and startup for threads added via setParallelism.
997	>	* Helps and/or blocks awaiting join of the given task.
998	>	* See above for explanation.
999	>	*
1000	>	* @param joinMe the task to join
1001	>	* @param worker the current worker thread
1002		*/
1003	<	private void createAndStartAddedWorkers() {
1004	<	resumeAllSpares();  // Allow spares to convert to nonspare
1005	<	int ps = parallelism;
1006	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1007	<	int len = ws.length;
1008	<	// Sweep through slots, to keep lowest indices most populated
1009	<	int k = 0;
1010	<	while (k < len) {
1011	<	if (ws[k] != null) {
1012	<	++k;
1013	<	continue;
1003	>	final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker) {
1004	>	int retries = 2 + (parallelism >> 2); // #helpJoins before blocking
1005	>	while (joinMe.status >= 0) {
1006	>	int wc;
1007	>	worker.helpJoinTask(joinMe);
1008	>	if (joinMe.status < 0)
1009	>	break;
1010	>	else if (retries > 0)
1011	>	--retries;
1012	>	else if (((wc = workerCounts) & RUNNING_COUNT_MASK) != 0 &&
1013	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1014	>	wc, wc - ONE_RUNNING)) {
1015	>	int stat, c; long h;
1016	>	while ((stat = joinMe.status) >= 0 &&
1017	>	(h = eventWaiters) != 0L && // help release others
1018	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1019	>	releaseEventWaiters();
1020	>	if (stat >= 0 &&
1021	>	((workerCounts & RUNNING_COUNT_MASK) == 0 ||
1022	>	(stat =
1023	>	joinMe.internalAwaitDone(JOIN_TIMEOUT_MILLIS)) >= 0))
1024	>	helpMaintainParallelism(); // timeout or no running workers
1025	>	do {} while (!UNSAFE.compareAndSwapInt
1026	>	(this, workerCountsOffset,
1027	>	c = workerCounts, c + ONE_RUNNING));
1028	>	if (stat < 0)
1029	>	break;   // else restart
1030		}
1031	<	int s = workerCounts;
1032	<	int tc = totalCountOf(s);
1033	<	int rc = runningCountOf(s);
1034	<	if (rc >= ps || tc >= ps)
1031	>	}
1032	>	}
1033	>
1034	>	/**
1035	>	* Same idea as awaitJoin, but no helping, retries, or timeouts.
1036	>	*/
1037	>	final void awaitBlocker(ManagedBlocker blocker)
1038	>	throws InterruptedException {
1039	>	while (!blocker.isReleasable()) {
1040	>	int wc = workerCounts;
1041	>	if ((wc & RUNNING_COUNT_MASK) != 0 &&
1042	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1043	>	wc, wc - ONE_RUNNING)) {
1044	>	try {
1045	>	while (!blocker.isReleasable()) {
1046	>	long h = eventWaiters;
1047	>	if (h != 0L &&
1048	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1049	>	releaseEventWaiters();
1050	>	else if ((workerCounts & RUNNING_COUNT_MASK) == 0 &&
1051	>	runState < TERMINATING)
1052	>	helpMaintainParallelism();
1053	>	else if (blocker.block())
1054	>	break;
1055	>	}
1056	>	} finally {
1057	>	int c;
1058	>	do {} while (!UNSAFE.compareAndSwapInt
1059	>	(this, workerCountsOffset,
1060	>	c = workerCounts, c + ONE_RUNNING));
1061	>	}
1062		break;
1063	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
1064	<	ForkJoinWorkerThread w = createWorker(k);
1063	>	}
1064	>	}
1065	>	}
1066	>
1067	>	/**
1068	>	* Possibly initiates and/or completes termination.
1069	>	*
1070	>	* @param now if true, unconditionally terminate, else only
1071	>	* if shutdown and empty queue and no active workers
1072	>	* @return true if now terminating or terminated
1073	>	*/
1074	>	private boolean tryTerminate(boolean now) {
1075	>	if (now)
1076	>	advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN
1077	>	else if (runState < SHUTDOWN ||
1078	>	!submissionQueue.isEmpty() ||
1079	>	(runState & ACTIVE_COUNT_MASK) != 0)
1080	>	return false;
1081	>
1082	>	if (advanceRunLevel(TERMINATING))
1083	>	startTerminating();
1084	>
1085	>	// Finish now if all threads terminated; else in some subsequent call
1086	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1087	>	advanceRunLevel(TERMINATED);
1088	>	termination.arrive();
1089	>	}
1090	>	return true;
1091	>	}
1092	>
1093	>	/**
1094	>	* Actions on transition to TERMINATING
1095	>	*
1096	>	* Runs up to four passes through workers: (0) shutting down each
1097	>	* (without waking up if parked) to quickly spread notifications
1098	>	* without unnecessary bouncing around event queues etc (1) wake
1099	>	* up and help cancel tasks (2) interrupt (3) mop up races with
1100	>	* interrupted workers
1101	>	*/
1102	>	private void startTerminating() {
1103	>	cancelSubmissions();
1104	>	for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) {
1105	>	int c; // advance event count
1106	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
1107	>	c = eventCount, c+1);
1108	>	eventWaiters = 0L; // clobber lists
1109	>	spareWaiters = 0;
1110	>	ForkJoinWorkerThread[] ws = workers;
1111	>	int n = ws.length;
1112	>	for (int i = 0; i < n; ++i) {
1113	>	ForkJoinWorkerThread w = ws[i];
1114		if (w != null) {
1115	<	ws[k++] = w;
1116	<	w.start();
1117	<	}
1118	<	else {
1119	<	updateWorkerCount(-1); // back out on failed creation
1120	<	break;
1115	>	w.shutdown();
1116	>	if (passes > 0 && !w.isTerminated()) {
1117	>	w.cancelTasks();
1118	>	LockSupport.unpark(w);
1119	>	if (passes > 1) {
1120	>	try {
1121	>	w.interrupt();
1122	>	} catch (SecurityException ignore) {
1123	>	}
1124	>	}
1125	>	}
1126		}
1127		}
1128		}
1129		}
1130
1131		/**
1132	<	* Sets the handler for internal worker threads that terminate due
1133	<	* to unrecoverable errors encountered while executing tasks.
1134	<	* Unless set, the current default or ThreadGroup handler is used
1135	<	* as handler.
1132	>	* Clear out and cancel submissions, ignoring exceptions
1133	>	*/
1134	>	private void cancelSubmissions() {
1135	>	ForkJoinTask<?> task;
1136	>	while ((task = submissionQueue.poll()) != null) {
1137	>	try {
1138	>	task.cancel(false);
1139	>	} catch (Throwable ignore) {
1140	>	}
1141	>	}
1142	>	}
1143	>
1144	>	// misc support for ForkJoinWorkerThread
1145	>
1146	>	/**
1147	>	* Returns pool number
1148	>	*/
1149	>	final int getPoolNumber() {
1150	>	return poolNumber;
1151	>	}
1152	>
1153	>	/**
1154	>	* Tries to accumulates steal count from a worker, clearing
1155	>	* the worker's value.
1156	>	*
1157	>	* @return true if worker steal count now zero
1158	>	*/
1159	>	final boolean tryAccumulateStealCount(ForkJoinWorkerThread w) {
1160	>	int sc = w.stealCount;
1161	>	long c = stealCount;
1162	>	// CAS even if zero, for fence effects
1163	>	if (UNSAFE.compareAndSwapLong(this, stealCountOffset, c, c + sc)) {
1164	>	if (sc != 0)
1165	>	w.stealCount = 0;
1166	>	return true;
1167	>	}
1168	>	return sc == 0;
1169	>	}
1170	>
1171	>	/**
1172	>	* Returns the approximate (non-atomic) number of idle threads per
1173	>	* active thread.
1174	>	*/
1175	>	final int idlePerActive() {
1176	>	int pc = parallelism; // use parallelism, not rc
1177	>	int ac = runState;    // no mask -- artificially boosts during shutdown
1178	>	// Use exact results for small values, saturate past 4
1179	>	return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
1180	>	}
1181	>
1182	>	// Public and protected methods
1183	>
1184	>	// Constructors
1185	>
1186	>	/**
1187	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1188	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1189	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1190	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1191	>	*
1192	>	* @throws SecurityException if a security manager exists and
1193	>	*         the caller is not permitted to modify threads
1194	>	*         because it does not hold {@link
1195	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1196	>	*/
1197	>	public ForkJoinPool() {
1198	>	this(Runtime.getRuntime().availableProcessors(),
1199	>	defaultForkJoinWorkerThreadFactory, null, false);
1200	>	}
1201	>
1202	>	/**
1203	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
1204	>	* level, the {@linkplain
1205	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1206	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1207	>	*
1208	>	* @param parallelism the parallelism level
1209	>	* @throws IllegalArgumentException if parallelism less than or
1210	>	*         equal to zero, or greater than implementation limit
1211	>	* @throws SecurityException if a security manager exists and
1212	>	*         the caller is not permitted to modify threads
1213	>	*         because it does not hold {@link
1214	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1215	>	*/
1216	>	public ForkJoinPool(int parallelism) {
1217	>	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1218	>	}
1219	>
1220	>	/**
1221	>	* Creates a {@code ForkJoinPool} with the given parameters.
1222		*
1223	<	* @param h the new handler
1224	<	* @return the old handler, or null if none
1223	>	* @param parallelism the parallelism level. For default value,
1224	>	* use {@link java.lang.Runtime#availableProcessors}.
1225	>	* @param factory the factory for creating new threads. For default value,
1226	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
1227	>	* @param handler the handler for internal worker threads that
1228	>	* terminate due to unrecoverable errors encountered while executing
1229	>	* tasks. For default value, use <code>null</code>.
1230	>	* @param asyncMode if true,
1231	>	* establishes local first-in-first-out scheduling mode for forked
1232	>	* tasks that are never joined. This mode may be more appropriate
1233	>	* than default locally stack-based mode in applications in which
1234	>	* worker threads only process event-style asynchronous tasks.
1235	>	* For default value, use <code>false</code>.
1236	>	* @throws IllegalArgumentException if parallelism less than or
1237	>	*         equal to zero, or greater than implementation limit
1238	>	* @throws NullPointerException if the factory is null
1239		* @throws SecurityException if a security manager exists and
1240		*         the caller is not permitted to modify threads
1241		*         because it does not hold {@link
1242	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1242	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1243		*/
1244	<	public Thread.UncaughtExceptionHandler
1245	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
1244	>	public ForkJoinPool(int parallelism,
1245	>	ForkJoinWorkerThreadFactory factory,
1246	>	Thread.UncaughtExceptionHandler handler,
1247	>	boolean asyncMode) {
1248		checkPermission();
1249	<	Thread.UncaughtExceptionHandler old = null;
1250	<	final ReentrantLock lock = this.workerLock;
1251	<	lock.lock();
1252	<	try {
1253	<	old = ueh;
1254	<	ueh = h;
1255	<	ForkJoinWorkerThread[] ws = workers;
1256	<	for (int i = 0; i < ws.length; ++i) {
1257	<	ForkJoinWorkerThread w = ws[i];
1258	<	if (w != null)
1259	<	w.setUncaughtExceptionHandler(h);
1260	<	}
1261	<	} finally {
1262	<	lock.unlock();
533	<	}
534	<	return old;
1249	>	if (factory == null)
1250	>	throw new NullPointerException();
1251	>	if (parallelism <= 0 || parallelism > MAX_WORKERS)
1252	>	throw new IllegalArgumentException();
1253	>	this.parallelism = parallelism;
1254	>	this.factory = factory;
1255	>	this.ueh = handler;
1256	>	this.locallyFifo = asyncMode;
1257	>	int arraySize = initialArraySizeFor(parallelism);
1258	>	this.workers = new ForkJoinWorkerThread[arraySize];
1259	>	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
1260	>	this.workerLock = new ReentrantLock();
1261	>	this.termination = new Phaser(1);
1262	>	this.poolNumber = poolNumberGenerator.incrementAndGet();
1263		}
1264
1265		/**
1266	<	* Returns the handler for internal worker threads that terminate
1267	<	* due to unrecoverable errors encountered while executing tasks.
540	<	* @return the handler, or null if none
1266	>	* Returns initial power of two size for workers array.
1267	>	* @param pc the initial parallelism level
1268		*/
1269	<	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1270	<	Thread.UncaughtExceptionHandler h;
1271	<	final ReentrantLock lock = this.workerLock;
1272	<	lock.lock();
1273	<	try {
1274	<	h = ueh;
1275	<	} finally {
1276	<	lock.unlock();
1277	<	}
551	<	return h;
1269	>	private static int initialArraySizeFor(int pc) {
1270	>	// If possible, initially allocate enough space for one spare
1271	>	int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS;
1272	>	// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16)
1273	>	size |= size >>> 1;
1274	>	size |= size >>> 2;
1275	>	size |= size >>> 4;
1276	>	size |= size >>> 8;
1277	>	return size + 1;
1278		}
1279
1280		// Execution methods
#	Line 557 | Line 1283 | public class ForkJoinPool extends Abstra
1283		* Common code for execute, invoke and submit
1284		*/
1285		private <T> void doSubmit(ForkJoinTask<T> task) {
1286	<	if (isShutdown())
1286	>	if (task == null)
1287	>	throw new NullPointerException();
1288	>	if (runState >= SHUTDOWN)
1289		throw new RejectedExecutionException();
1290		submissionQueue.offer(task);
1291	<	signalIdleWorkers(true);
1291	>	int c; // try to increment event count -- CAS failure OK
1292	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
1293	>	helpMaintainParallelism(); // create, start, or resume some workers
1294		}
1295
1296		/**
1297	<	* Performs the given task; returning its result upon completion
1297	>	* Performs the given task, returning its result upon completion.
1298	>	*
1299		* @param task the task
1300		* @return the task's result
1301	<	* @throws NullPointerException if task is null
1302	<	* @throws RejectedExecutionException if pool is shut down
1301	>	* @throws NullPointerException if the task is null
1302	>	* @throws RejectedExecutionException if the task cannot be
1303	>	*         scheduled for execution
1304		*/
1305		public <T> T invoke(ForkJoinTask<T> task) {
1306		doSubmit(task);
#	Line 577 | Line 1309 | public class ForkJoinPool extends Abstra
1309
1310		/**
1311		* Arranges for (asynchronous) execution of the given task.
1312	+	*
1313		* @param task the task
1314	<	* @throws NullPointerException if task is null
1315	<	* @throws RejectedExecutionException if pool is shut down
1314	>	* @throws NullPointerException if the task is null
1315	>	* @throws RejectedExecutionException if the task cannot be
1316	>	*         scheduled for execution
1317		*/
1318	<	public <T> void execute(ForkJoinTask<T> task) {
1318	>	public void execute(ForkJoinTask<?> task) {
1319		doSubmit(task);
1320		}
1321
1322		// AbstractExecutorService methods
1323
1324	+	/**
1325	+	* @throws NullPointerException if the task is null
1326	+	* @throws RejectedExecutionException if the task cannot be
1327	+	*         scheduled for execution
1328	+	*/
1329		public void execute(Runnable task) {
1330	<	doSubmit(new AdaptedRunnable<Void>(task, null));
1330	>	ForkJoinTask<?> job;
1331	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1332	>	job = (ForkJoinTask<?>) task;
1333	>	else
1334	>	job = ForkJoinTask.adapt(task, null);
1335	>	doSubmit(job);
1336		}
1337
1338	+	/**
1339	+	* Submits a ForkJoinTask for execution.
1340	+	*
1341	+	* @param task the task to submit
1342	+	* @return the task
1343	+	* @throws NullPointerException if the task is null
1344	+	* @throws RejectedExecutionException if the task cannot be
1345	+	*         scheduled for execution
1346	+	*/
1347	+	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1348	+	doSubmit(task);
1349	+	return task;
1350	+	}
1351	+
1352	+	/**
1353	+	* @throws NullPointerException if the task is null
1354	+	* @throws RejectedExecutionException if the task cannot be
1355	+	*         scheduled for execution
1356	+	*/
1357		public <T> ForkJoinTask<T> submit(Callable<T> task) {
1358	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
1358	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1359		doSubmit(job);
1360		return job;
1361		}
1362
1363	+	/**
1364	+	* @throws NullPointerException if the task is null
1365	+	* @throws RejectedExecutionException if the task cannot be
1366	+	*         scheduled for execution
1367	+	*/
1368		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1369	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
1369	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1370		doSubmit(job);
1371		return job;
1372		}
1373
1374	+	/**
1375	+	* @throws NullPointerException if the task is null
1376	+	* @throws RejectedExecutionException if the task cannot be
1377	+	*         scheduled for execution
1378	+	*/
1379		public ForkJoinTask<?> submit(Runnable task) {
1380	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
1380	>	ForkJoinTask<?> job;
1381	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1382	>	job = (ForkJoinTask<?>) task;
1383	>	else
1384	>	job = ForkJoinTask.adapt(task, null);
1385		doSubmit(job);
1386		return job;
1387		}
1388
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	–
1389		/**
1390	<	* Adaptor for Callables
1390	>	* @throws NullPointerException       {@inheritDoc}
1391	>	* @throws RejectedExecutionException {@inheritDoc}
1392		*/
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	–
1393		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
1394	<	ArrayList<ForkJoinTask<T>> ts =
1394	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
1395		new ArrayList<ForkJoinTask<T>>(tasks.size());
1396	<	for (Callable<T> c : tasks)
1397	<	ts.add(new AdaptedCallable<T>(c));
1398	<	invoke(new InvokeAll<T>(ts));
1399	<	return (List<Future<T>>)(List)ts;
1396	>	for (Callable<T> task : tasks)
1397	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
1398	>	invoke(new InvokeAll<T>(forkJoinTasks));
1399	>
1400	>	@SuppressWarnings({"unchecked", "rawtypes"})
1401	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1402	>	return futures;
1403		}
1404
1405		static final class InvokeAll<T> extends RecursiveAction {
1406		final ArrayList<ForkJoinTask<T>> tasks;
1407		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
1408		public void compute() {
1409	<	try { invokeAll(tasks); } catch(Exception ignore) {}
1409	>	try { invokeAll(tasks); }
1410	>	catch (Exception ignore) {}
1411		}
1412	+	private static final long serialVersionUID = -7914297376763021607L;
1413		}
1414
689	–	// Configuration and status settings and queries
690	–
1415		/**
1416	<	* Returns the factory used for constructing new workers
1416	>	* Returns the factory used for constructing new workers.
1417		*
1418		* @return the factory used for constructing new workers
1419		*/
#	Line 698 | Line 1422 | public class ForkJoinPool extends Abstra
1422		}
1423
1424		/**
1425	<	* Sets the target paralleism level of this pool.
1426	<	* @param parallelism the target parallelism
1427	<	* @throws IllegalArgumentException if parallelism less than or
1428	<	* 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>,
1425	>	* Returns the handler for internal worker threads that terminate
1426	>	* due to unrecoverable errors encountered while executing tasks.
1427	>	*
1428	>	* @return the handler, or {@code null} if none
1429		*/
1430	<	public void setParallelism(int parallelism) {
1431	<	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);
1430	>	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1431	>	return ueh;
1432		}
1433
1434		/**
1435	<	* 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.
1435	>	* Returns the targeted parallelism level of this pool.
1436		*
1437	<	* @return the targeted number of worker threads in this pool
1437	>	* @return the targeted parallelism level of this pool
1438		*/
1439		public int getParallelism() {
1440		return parallelism;
#	Line 742 | Line 1443 | public class ForkJoinPool extends Abstra
1443		/**
1444		* Returns the number of worker threads that have started but not
1445		* yet terminated.  This result returned by this method may differ
1446	<	* from <tt>getParallelism</tt> when threads are created to
1446	>	* from {@link #getParallelism} when threads are created to
1447		* maintain parallelism when others are cooperatively blocked.
1448		*
1449		* @return the number of worker threads
1450		*/
1451		public int getPoolSize() {
1452	<	return totalCountOf(workerCounts);
752	<	}
753	<
754	<	/**
755	<	* Returns the maximum number of threads allowed to exist in the
756	<	* pool, even if there are insufficient unblocked running threads.
757	<	* @return the maximum
758	<	*/
759	<	public int getMaximumPoolSize() {
760	<	return maxPoolSize;
1452	>	return workerCounts >>> TOTAL_COUNT_SHIFT;
1453		}
1454
1455		/**
1456	<	* Sets the maximum number of threads allowed to exist in the
1457	<	* pool, even if there are insufficient unblocked running threads.
1458	<	* Setting this value has no effect on current pool size. It
1459	<	* 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
1456	>	* Returns {@code true} if this pool uses local first-in-first-out
1457	>	* scheduling mode for forked tasks that are never joined.
1458	>	*
1459	>	* @return {@code true} if this pool uses async mode
1460		*/
1461	<	public void setMaintainsParallelism(boolean enable) {
1462	<	maintainsParallelism = enable;
1461	>	public boolean getAsyncMode() {
1462	>	return locallyFifo;
1463		}
1464
1465		/**
1466	<	* Returns the approximate number of worker threads that are not
1467	<	* blocked waiting to join tasks or for other managed
1468	<	* synchronization.
1466	>	* Returns an estimate of the number of worker threads that are
1467	>	* not blocked waiting to join tasks or for other managed
1468	>	* synchronization. This method may overestimate the
1469	>	* number of running threads.
1470		*
1471		* @return the number of worker threads
1472		*/
1473		public int getRunningThreadCount() {
1474	<	return runningCountOf(workerCounts);
1474	>	return workerCounts & RUNNING_COUNT_MASK;
1475		}
1476
1477		/**
1478	<	* Returns the approximate number of threads that are currently
1478	>	* Returns an estimate of the number of threads that are currently
1479		* stealing or executing tasks. This method may overestimate the
1480		* number of active threads.
1481	<	* @return the number of active threads.
1481	>	*
1482	>	* @return the number of active threads
1483		*/
1484		public int getActiveThreadCount() {
1485	<	return activeCountOf(runControl);
1485	>	return runState & ACTIVE_COUNT_MASK;
1486		}
1487
1488		/**
1489	<	* Returns the approximate number of threads that are currently
1490	<	* idle waiting for tasks. This method may underestimate the
1491	<	* number of idle threads.
1492	<	* @return the number of idle threads.
1493	<	*/
1494	<	final int getIdleThreadCount() {
1495	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
1496	<	return (c <= 0)? 0 : c;
1497	<	}
830	<
831	<	/**
832	<	* Returns true if all worker threads are currently idle. An idle
833	<	* worker is one that cannot obtain a task to execute because none
834	<	* are available to steal from other threads, and there are no
835	<	* pending submissions to the pool. This method is conservative:
836	<	* It might not return true immediately upon idleness of all
837	<	* threads, but will eventually become true if threads remain
838	<	* inactive.
839	<	* @return true if all threads are currently idle
1489	>	* Returns {@code true} if all worker threads are currently idle.
1490	>	* An idle worker is one that cannot obtain a task to execute
1491	>	* because none are available to steal from other threads, and
1492	>	* there are no pending submissions to the pool. This method is
1493	>	* conservative; it might not return {@code true} immediately upon
1494	>	* idleness of all threads, but will eventually become true if
1495	>	* threads remain inactive.
1496	>	*
1497	>	* @return {@code true} if all threads are currently idle
1498		*/
1499		public boolean isQuiescent() {
1500	<	return activeCountOf(runControl) == 0;
1500	>	return (runState & ACTIVE_COUNT_MASK) == 0;
1501		}
1502
1503		/**
#	Line 847 | Line 1505 | public class ForkJoinPool extends Abstra
1505		* one thread's work queue by another. The reported value
1506		* underestimates the actual total number of steals when the pool
1507		* is not quiescent. This value may be useful for monitoring and
1508	<	* tuning fork/join programs: In general, steal counts should be
1508	>	* tuning fork/join programs: in general, steal counts should be
1509		* high enough to keep threads busy, but low enough to avoid
1510		* overhead and contention across threads.
1511	<	* @return the number of steals.
1511	>	*
1512	>	* @return the number of steals
1513		*/
1514		public long getStealCount() {
1515	<	return stealCount.get();
857	<	}
858	<
859	<	/**
860	<	* Accumulate steal count from a worker. Call only
861	<	* when worker known to be idle.
862	<	*/
863	<	private void updateStealCount(ForkJoinWorkerThread w) {
864	<	int sc = w.getAndClearStealCount();
865	<	if (sc != 0)
866	<	stealCount.addAndGet(sc);
1515	>	return stealCount;
1516		}
1517
1518		/**
1519	<	* Returns the total number of tasks currently held in queues by
1520	<	* worker threads (but not including tasks submitted to the pool
1521	<	* that have not begun executing). This value is only an
1522	<	* approximation, obtained by iterating across all threads in the
1523	<	* pool. This method may be useful for tuning task granularities.
1524	<	* @return the number of queued tasks.
1519	>	* Returns an estimate of the total number of tasks currently held
1520	>	* in queues by worker threads (but not including tasks submitted
1521	>	* to the pool that have not begun executing). This value is only
1522	>	* an approximation, obtained by iterating across all threads in
1523	>	* the pool. This method may be useful for tuning task
1524	>	* granularities.
1525	>	*
1526	>	* @return the number of queued tasks
1527		*/
1528		public long getQueuedTaskCount() {
1529		long count = 0;
1530		ForkJoinWorkerThread[] ws = workers;
1531	<	for (int i = 0; i < ws.length; ++i) {
1532	<	ForkJoinWorkerThread t = ws[i];
1533	<	if (t != null)
1534	<	count += t.getQueueSize();
1531	>	int n = ws.length;
1532	>	for (int i = 0; i < n; ++i) {
1533	>	ForkJoinWorkerThread w = ws[i];
1534	>	if (w != null)
1535	>	count += w.getQueueSize();
1536		}
1537		return count;
1538		}
1539
1540		/**
1541	<	* Returns the approximate number tasks submitted to this pool
1542	<	* that have not yet begun executing. This method takes time
1541	>	* Returns an estimate of the number of tasks submitted to this
1542	>	* pool that have not yet begun executing.  This method takes time
1543		* proportional to the number of submissions.
1544	<	* @return the number of queued submissions.
1544	>	*
1545	>	* @return the number of queued submissions
1546		*/
1547		public int getQueuedSubmissionCount() {
1548		return submissionQueue.size();
1549		}
1550
1551		/**
1552	<	* Returns true if there are any tasks submitted to this pool
1553	<	* that have not yet begun executing.
1554	<	* @return <tt>true</tt> if there are any queued submissions.
1552	>	* Returns {@code true} if there are any tasks submitted to this
1553	>	* pool that have not yet begun executing.
1554	>	*
1555	>	* @return {@code true} if there are any queued submissions
1556		*/
1557		public boolean hasQueuedSubmissions() {
1558		return !submissionQueue.isEmpty();
#	Line 908 | Line 1562 | public class ForkJoinPool extends Abstra
1562		* Removes and returns the next unexecuted submission if one is
1563		* available.  This method may be useful in extensions to this
1564		* class that re-assign work in systems with multiple pools.
1565	<	* @return the next submission, or null if none
1565	>	*
1566	>	* @return the next submission, or {@code null} if none
1567		*/
1568		protected ForkJoinTask<?> pollSubmission() {
1569		return submissionQueue.poll();
1570		}
1571
1572		/**
1573	+	* Removes all available unexecuted submitted and forked tasks
1574	+	* from scheduling queues and adds them to the given collection,
1575	+	* without altering their execution status. These may include
1576	+	* artificially generated or wrapped tasks. This method is
1577	+	* designed to be invoked only when the pool is known to be
1578	+	* quiescent. Invocations at other times may not remove all
1579	+	* tasks. A failure encountered while attempting to add elements
1580	+	* to collection {@code c} may result in elements being in
1581	+	* neither, either or both collections when the associated
1582	+	* exception is thrown.  The behavior of this operation is
1583	+	* undefined if the specified collection is modified while the
1584	+	* operation is in progress.
1585	+	*
1586	+	* @param c the collection to transfer elements into
1587	+	* @return the number of elements transferred
1588	+	*/
1589	+	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1590	+	int count = submissionQueue.drainTo(c);
1591	+	ForkJoinWorkerThread[] ws = workers;
1592	+	int n = ws.length;
1593	+	for (int i = 0; i < n; ++i) {
1594	+	ForkJoinWorkerThread w = ws[i];
1595	+	if (w != null)
1596	+	count += w.drainTasksTo(c);
1597	+	}
1598	+	return count;
1599	+	}
1600	+
1601	+	/**
1602		* Returns a string identifying this pool, as well as its state,
1603		* including indications of run state, parallelism level, and
1604		* worker and task counts.
#	Line 922 | Line 1606 | public class ForkJoinPool extends Abstra
1606		* @return a string identifying this pool, as well as its state
1607		*/
1608		public String toString() {
925	–	int ps = parallelism;
926	–	int wc = workerCounts;
927	–	int rc = runControl;
1609		long st = getStealCount();
1610		long qt = getQueuedTaskCount();
1611		long qs = getQueuedSubmissionCount();
1612	+	int wc = workerCounts;
1613	+	int tc = wc >>> TOTAL_COUNT_SHIFT;
1614	+	int rc = wc & RUNNING_COUNT_MASK;
1615	+	int pc = parallelism;
1616	+	int rs = runState;
1617	+	int ac = rs & ACTIVE_COUNT_MASK;
1618		return super.toString() +
1619	<	"[" + runStateToString(runStateOf(rc)) +
1620	<	", parallelism = " + ps +
1621	<	", size = " + totalCountOf(wc) +
1622	<	", active = " + activeCountOf(rc) +
1623	<	", running = " + runningCountOf(wc) +
1619	>	"[" + runLevelToString(rs) +
1620	>	", parallelism = " + pc +
1621	>	", size = " + tc +
1622	>	", active = " + ac +
1623	>	", running = " + rc +
1624		", steals = " + st +
1625		", tasks = " + qt +
1626		", submissions = " + qs +
1627		"]";
1628		}
1629
1630	<	private static String runStateToString(int rs) {
1631	<	switch(rs) {
1632	<	case RUNNING: return "Running";
1633	<	case SHUTDOWN: return "Shutting down";
1634	<	case TERMINATING: return "Terminating";
948	<	case TERMINATED: return "Terminated";
949	<	default: throw new Error("Unknown run state");
950	<	}
1630	>	private static String runLevelToString(int s) {
1631	>	return ((s & TERMINATED) != 0 ? "Terminated" :
1632	>	((s & TERMINATING) != 0 ? "Terminating" :
1633	>	((s & SHUTDOWN) != 0 ? "Shutting down" :
1634	>	"Running")));
1635		}
1636
953	–	// lifecycle control
954	–
1637		/**
1638		* Initiates an orderly shutdown in which previously submitted
1639		* tasks are executed, but no new tasks will be accepted.
1640		* Invocation has no additional effect if already shut down.
1641		* Tasks that are in the process of being submitted concurrently
1642		* during the course of this method may or may not be rejected.
1643	+	*
1644		* @throws SecurityException if a security manager exists and
1645		*         the caller is not permitted to modify threads
1646		*         because it does not hold {@link
1647	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1647	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1648		*/
1649		public void shutdown() {
1650		checkPermission();
1651	<	transitionRunStateTo(SHUTDOWN);
1652	<	if (canTerminateOnShutdown(runControl))
970	<	terminateOnShutdown();
1651	>	advanceRunLevel(SHUTDOWN);
1652	>	tryTerminate(false);
1653		}
1654
1655		/**
1656	<	* Attempts to stop all actively executing tasks, and cancels all
1657	<	* waiting tasks.  Tasks that are in the process of being
1658	<	* submitted or executed concurrently during the course of this
1659	<	* method may or may not be rejected. Unlike some other executors,
1660	<	* this method cancels rather than collects non-executed tasks,
1661	<	* so always returns an empty list.
1656	>	* Attempts to cancel and/or stop all tasks, and reject all
1657	>	* subsequently submitted tasks.  Tasks that are in the process of
1658	>	* being submitted or executed concurrently during the course of
1659	>	* this method may or may not be rejected. This method cancels
1660	>	* both existing and unexecuted tasks, in order to permit
1661	>	* termination in the presence of task dependencies. So the method
1662	>	* always returns an empty list (unlike the case for some other
1663	>	* Executors).
1664	>	*
1665		* @return an empty list
1666		* @throws SecurityException if a security manager exists and
1667		*         the caller is not permitted to modify threads
1668		*         because it does not hold {@link
1669	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1669	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1670		*/
1671		public List<Runnable> shutdownNow() {
1672		checkPermission();
1673	<	terminate();
1673	>	tryTerminate(true);
1674		return Collections.emptyList();
1675		}
1676
1677		/**
1678	<	* Returns <tt>true</tt> if all tasks have completed following shut down.
1678	>	* Returns {@code true} if all tasks have completed following shut down.
1679		*
1680	<	* @return <tt>true</tt> if all tasks have completed following shut down
1680	>	* @return {@code true} if all tasks have completed following shut down
1681		*/
1682		public boolean isTerminated() {
1683	<	return runStateOf(runControl) == TERMINATED;
1683	>	return runState >= TERMINATED;
1684		}
1685
1686		/**
1687	<	* Returns <tt>true</tt> if the process of termination has
1688	<	* commenced but possibly not yet completed.
1687	>	* Returns {@code true} if the process of termination has
1688	>	* commenced but not yet completed.  This method may be useful for
1689	>	* debugging. A return of {@code true} reported a sufficient
1690	>	* period after shutdown may indicate that submitted tasks have
1691	>	* ignored or suppressed interruption, causing this executor not
1692	>	* to properly terminate.
1693		*
1694	<	* @return <tt>true</tt> if terminating
1694	>	* @return {@code true} if terminating but not yet terminated
1695		*/
1696		public boolean isTerminating() {
1697	<	return runStateOf(runControl) >= TERMINATING;
1697	>	return (runState & (TERMINATING|TERMINATED)) == TERMINATING;
1698		}
1699
1700		/**
1701	<	* Returns <tt>true</tt> if this pool has been shut down.
1701	>	* Returns {@code true} if this pool has been shut down.
1702		*
1703	<	* @return <tt>true</tt> if this pool has been shut down
1703	>	* @return {@code true} if this pool has been shut down
1704		*/
1705		public boolean isShutdown() {
1706	<	return runStateOf(runControl) >= SHUTDOWN;
1706	>	return runState >= SHUTDOWN;
1707		}
1708
1709		/**
#	Line 1024 | Line 1713 | public class ForkJoinPool extends Abstra
1713		*
1714		* @param timeout the maximum time to wait
1715		* @param unit the time unit of the timeout argument
1716	<	* @return <tt>true</tt> if this executor terminated and
1717	<	*         <tt>false</tt> if the timeout elapsed before termination
1716	>	* @return {@code true} if this executor terminated and
1717	>	*         {@code false} if the timeout elapsed before termination
1718		* @throws InterruptedException if interrupted while waiting
1719		*/
1720		public boolean awaitTermination(long timeout, TimeUnit unit)
1721		throws InterruptedException {
1033	–	long nanos = unit.toNanos(timeout);
1034	–	final ReentrantLock lock = this.workerLock;
1035	–	lock.lock();
1722		try {
1723	<	for (;;) {
1724	<	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();
1139	<	try {
1140	<	ForkJoinWorkerThread[] ws = workers;
1141	<	for (int i = 0; i < ws.length; ++i) {
1142	<	ForkJoinWorkerThread t = ws[i];
1143	<	if (t != null)
1144	<	t.shutdownNow();
1145	<	}
1146	<	} finally {
1147	<	lock.unlock();
1148	<	}
1149	<	}
1150	<
1151	<	/**
1152	<	* Interrupt all unterminated workers.  This is not required for
1153	<	* sake of internal control, but may help unstick user code during
1154	<	* shutdown.
1155	<	*/
1156	<	private void interruptUnterminatedWorkers() {
1157	<	final ReentrantLock lock = this.workerLock;
1158	<	lock.lock();
1159	<	try {
1160	<	ForkJoinWorkerThread[] ws = workers;
1161	<	for (int i = 0; i < ws.length; ++i) {
1162	<	ForkJoinWorkerThread t = ws[i];
1163	<	if (t != null && !t.isTerminated()) {
1164	<	try {
1165	<	t.interrupt();
1166	<	} catch (SecurityException ignore) {
1167	<	}
1168	<	}
1169	<	}
1170	<	} finally {
1171	<	lock.unlock();
1172	<	}
1173	<	}
1174	<
1175	<
1176	<	/*
1177	<	* Nodes for event barrier to manage idle threads.
1178	<	*
1179	<	* The event barrier has an event count and a wait queue (actually
1180	<	* a Treiber stack).  Workers are enabled to look for work when
1181	<	* the eventCount is incremented. If they fail to find some,
1182	<	* they may wait for next count. Synchronization events occur only
1183	<	* in enough contexts to maintain overall liveness:
1184	<	*
1185	<	*   - Submission of a new task to the pool
1186	<	*   - Creation or termination of a worker
1187	<	*   - pool termination
1188	<	*   - A worker pushing a task on an empty queue
1189	<	*
1190	<	* The last case (pushing a task) occurs often enough, and is
1191	<	* heavy enough compared to simple stack pushes to require some
1192	<	* special handling: Method signalNonEmptyWorkerQueue returns
1193	<	* without advancing count if the queue appears to be empty.  This
1194	<	* would ordinarily result in races causing some queued waiters
1195	<	* not to be woken up. To avoid this, a worker in sync
1196	<	* rescans for tasks after being enqueued if it was the first to
1197	<	* enqueue, and aborts the wait if finding one, also helping to
1198	<	* signal others. This works well because the worker has nothing
1199	<	* better to do anyway, and so might as well help alleviate the
1200	<	* overhead and contention on the threads actually doing work.
1201	<	*
1202	<	* Queue nodes are basic Treiber stack nodes, also used for spare
1203	<	* stack.
1204	<	*/
1205	<	static final class WaitQueueNode {
1206	<	WaitQueueNode next; // only written before enqueued
1207	<	volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1208	<	final long count; // unused for spare stack
1209	<	WaitQueueNode(ForkJoinWorkerThread w, long c) {
1210	<	count = c;
1211	<	thread = w;
1212	<	}
1213	<	final boolean signal() {
1214	<	ForkJoinWorkerThread t = thread;
1215	<	thread = null;
1216	<	if (t != null) {
1217	<	LockSupport.unpark(t);
1218	<	return true;
1219	<	}
1723	>	return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1724	>	} catch (TimeoutException ex) {
1725		return false;
1726		}
1727		}
1728
1729		/**
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	–	/**
1730		* Interface for extending managed parallelism for tasks running
1731	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1732	<	* Method <tt>isReleasable</tt> must return true if blocking is not
1733	<	* necessary. Method <tt>block</tt> blocks the current thread
1734	<	* if necessary (perhaps internally invoking isReleasable before
1735	<	* actually blocking.).
1731	>	* in {@link ForkJoinPool}s.
1732	>	*
1733	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
1734	>	* {@code isReleasable} must return {@code true} if blocking is
1735	>	* not necessary. Method {@code block} blocks the current thread
1736	>	* if necessary (perhaps internally invoking {@code isReleasable}
1737	>	* before actually blocking). The unusual methods in this API
1738	>	* accommodate synchronizers that may, but don't usually, block
1739	>	* for long periods. Similarly, they allow more efficient internal
1740	>	* handling of cases in which additional workers may be, but
1741	>	* usually are not, needed to ensure sufficient parallelism.
1742	>	* Toward this end, implementations of method {@code isReleasable}
1743	>	* must be amenable to repeated invocation.
1744	>	*
1745		* <p>For example, here is a ManagedBlocker based on a
1746		* ReentrantLock:
1747	<	* <pre>
1748	<	*   class ManagedLocker implements ManagedBlocker {
1749	<	*     final ReentrantLock lock;
1750	<	*     boolean hasLock = false;
1751	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1752	<	*     public boolean block() {
1753	<	*        if (!hasLock)
1754	<	*           lock.lock();
1755	<	*        return true;
1756	<	*     }
1757	<	*     public boolean isReleasable() {
1758	<	*        return hasLock || (hasLock = lock.tryLock());
1619	<	*     }
1747	>	*  <pre> {@code
1748	>	* class ManagedLocker implements ManagedBlocker {
1749	>	*   final ReentrantLock lock;
1750	>	*   boolean hasLock = false;
1751	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1752	>	*   public boolean block() {
1753	>	*     if (!hasLock)
1754	>	*       lock.lock();
1755	>	*     return true;
1756	>	*   }
1757	>	*   public boolean isReleasable() {
1758	>	*     return hasLock || (hasLock = lock.tryLock());
1759		*   }
1760	<	* </pre>
1760	>	* }}</pre>
1761	>	*
1762	>	* <p>Here is a class that possibly blocks waiting for an
1763	>	* item on a given queue:
1764	>	*  <pre> {@code
1765	>	* class QueueTaker<E> implements ManagedBlocker {
1766	>	*   final BlockingQueue<E> queue;
1767	>	*   volatile E item = null;
1768	>	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
1769	>	*   public boolean block() throws InterruptedException {
1770	>	*     if (item == null)
1771	>	*       item = queue.take();
1772	>	*     return true;
1773	>	*   }
1774	>	*   public boolean isReleasable() {
1775	>	*     return item != null || (item = queue.poll()) != null;
1776	>	*   }
1777	>	*   public E getItem() { // call after pool.managedBlock completes
1778	>	*     return item;
1779	>	*   }
1780	>	* }}</pre>
1781		*/
1782		public static interface ManagedBlocker {
1783		/**
1784		* Possibly blocks the current thread, for example waiting for
1785		* a lock or condition.
1786	<	* @return true if no additional blocking is necessary (i.e.,
1787	<	* if isReleasable would return true).
1786	>	*
1787	>	* @return {@code true} if no additional blocking is necessary
1788	>	* (i.e., if isReleasable would return true)
1789		* @throws InterruptedException if interrupted while waiting
1790	<	* (the method is not required to do so, but is allowe to).
1790	>	* (the method is not required to do so, but is allowed to)
1791		*/
1792		boolean block() throws InterruptedException;
1793
1794		/**
1795	<	* Returns true if blocking is unnecessary.
1795	>	* Returns {@code true} if blocking is unnecessary.
1796		*/
1797		boolean isReleasable();
1798		}
1799
1800		/**
1801		* Blocks in accord with the given blocker.  If the current thread
1802	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1803	<	* spare thread to be activated if necessary to ensure parallelism
1804	<	* while the current thread is blocked.  If
1805	<	* <tt>maintainParallelism</tt> is true and the pool supports it
1806	<	* (see <tt>getMaintainsParallelism</tt>), this method attempts to
1807	<	* maintain the pool's nominal parallelism. Otherwise if activates
1808	<	* a thread only if necessary to avoid complete starvation. This
1809	<	* option may be preferable when blockages use timeouts, or are
1810	<	* almost always brief.
1811	<	*
1812	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1813	<	* equivalent to
1814	<	* <pre>
1815	<	*   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.
1802	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1803	>	* arranges for a spare thread to be activated if necessary to
1804	>	* ensure sufficient parallelism while the current thread is blocked.
1805	>	*
1806	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1807	>	* behaviorally equivalent to
1808	>	*  <pre> {@code
1809	>	* while (!blocker.isReleasable())
1810	>	*   if (blocker.block())
1811	>	*     return;
1812	>	* }</pre>
1813	>	*
1814	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1815	>	* first be expanded to ensure parallelism, and later adjusted.
1816		*
1817		* @param blocker the blocker
1818	<	* @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.
1818	>	* @throws InterruptedException if blocker.block did so
1819		*/
1820	<	public static void managedBlock(ManagedBlocker blocker,
1670	<	boolean maintainParallelism)
1820	>	public static void managedBlock(ManagedBlocker blocker)
1821		throws InterruptedException {
1822		Thread t = Thread.currentThread();
1823	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1824	<	((ForkJoinWorkerThread)t).pool : null);
1825	<	if (!blocker.isReleasable()) {
1826	<	try {
1827	<	if (pool == null ||
1828	<	!pool.preBlock(blocker, maintainParallelism))
1679	<	awaitBlocker(blocker);
1680	<	} finally {
1681	<	if (pool != null)
1682	<	pool.updateRunningCount(1);
1683	<	}
1823	>	if (t instanceof ForkJoinWorkerThread) {
1824	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
1825	>	w.pool.awaitBlocker(blocker);
1826	>	}
1827	>	else {
1828	>	do {} while (!blocker.isReleasable() && !blocker.block());
1829		}
1830		}
1831
1832	<	private static void awaitBlocker(ManagedBlocker blocker)
1833	<	throws InterruptedException {
1834	<	do;while (!blocker.isReleasable() && !blocker.block());
1832	>	// AbstractExecutorService overrides.  These rely on undocumented
1833	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1834	>	// implement RunnableFuture.
1835	>
1836	>	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1837	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1838		}
1839
1840	+	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1841	+	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1842	+	}
1843
1844	<	// Temporary Unsafe mechanics for preliminary release
1844	>	// Unsafe mechanics
1845
1846	<	static final Unsafe _unsafe;
1847	<	static final long eventCountOffset;
1848	<	static final long workerCountsOffset;
1849	<	static final long runControlOffset;
1850	<	static final long barrierStackOffset;
1851	<	static final long spareStackOffset;
1846	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1847	>	private static final long workerCountsOffset =
1848	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1849	>	private static final long runStateOffset =
1850	>	objectFieldOffset("runState", ForkJoinPool.class);
1851	>	private static final long eventCountOffset =
1852	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1853	>	private static final long eventWaitersOffset =
1854	>	objectFieldOffset("eventWaiters",ForkJoinPool.class);
1855	>	private static final long stealCountOffset =
1856	>	objectFieldOffset("stealCount",ForkJoinPool.class);
1857	>	private static final long spareWaitersOffset =
1858	>	objectFieldOffset("spareWaiters",ForkJoinPool.class);
1859
1860	<	static {
1860	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1861		try {
1862	<	if (ForkJoinPool.class.getClassLoader() != null) {
1863	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1864	<	f.setAccessible(true);
1865	<	_unsafe = (Unsafe)f.get(null);
1866	<	}
1867	<	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);
1862	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1863	>	} catch (NoSuchFieldException e) {
1864	>	// Convert Exception to corresponding Error
1865	>	NoSuchFieldError error = new NoSuchFieldError(field);
1866	>	error.initCause(e);
1867	>	throw error;
1868		}
1869		}
1870
1871	<	private boolean casEventCount(long cmp, long val) {
1872	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1873	<	}
1874	<	private boolean casWorkerCounts(int cmp, int val) {
1875	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1876	<	}
1877	<	private boolean casRunControl(int cmp, int val) {
1878	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1879	<	}
1880	<	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1881	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1882	<	}
1883	<	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1884	<	return _unsafe.compareAndSwapObject(this, barrierStackOffset, cmp, val);
1871	>	/**
1872	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1873	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1874	>	* into a jdk.
1875	>	*
1876	>	* @return a sun.misc.Unsafe
1877	>	*/
1878	>	private static sun.misc.Unsafe getUnsafe() {
1879	>	try {
1880	>	return sun.misc.Unsafe.getUnsafe();
1881	>	} catch (SecurityException se) {
1882	>	try {
1883	>	return java.security.AccessController.doPrivileged
1884	>	(new java.security
1885	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1886	>	public sun.misc.Unsafe run() throws Exception {
1887	>	java.lang.reflect.Field f = sun.misc
1888	>	.Unsafe.class.getDeclaredField("theUnsafe");
1889	>	f.setAccessible(true);
1890	>	return (sun.misc.Unsafe) f.get(null);
1891	>	}});
1892	>	} catch (java.security.PrivilegedActionException e) {
1893	>	throw new RuntimeException("Could not initialize intrinsics",
1894	>	e.getCause());
1895	>	}
1896	>	}
1897		}
1898		}

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