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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 1.71 by jsr166, Mon Sep 6 21:36:43 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.locks.*;
11	<	import java.util.concurrent.atomic.*;
12	<	import sun.misc.Unsafe;
13	<	import java.lang.reflect.*;
10	>	import java.util.ArrayList;
11	>	import java.util.Arrays;
12	>	import java.util.Collection;
13	>	import java.util.Collections;
14	>	import java.util.List;
15	>	import java.util.concurrent.locks.LockSupport;
16	>	import java.util.concurrent.locks.ReentrantLock;
17	>	import java.util.concurrent.atomic.AtomicInteger;
18	>	import java.util.concurrent.CountDownLatch;
19
20		/**
21	<	* Host for a group of ForkJoinWorkerThreads.  A ForkJoinPool provides
22	<	* the entry point for tasks submitted from non-ForkJoinTasks, as well
23	<	* as management and monitoring operations.  Normally a single
24	<	* 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.
21	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
22	>	* A {@code ForkJoinPool} provides the entry point for submissions
23	>	* from non-{@code ForkJoinTask} clients, as well as management and
24	>	* monitoring operations.
25		*
26	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
27	<	* (target pool size), which it attempts to maintain by dynamically
28	<	* adding, suspending, or resuming threads, even if some tasks have
29	<	* blocked waiting to join others. However, no such adjustments are
30	<	* performed in the face of blocked IO or other unmanaged
31	<	* synchronization. The nested ManagedBlocker interface enables
32	<	* extension of the kinds of synchronization accommodated.
26	>	* <p>A {@code ForkJoinPool} differs from other kinds of {@link
27	>	* ExecutorService} mainly by virtue of employing
28	>	* <em>work-stealing</em>: all threads in the pool attempt to find and
29	>	* execute subtasks created by other active tasks (eventually blocking
30	>	* waiting for work if none exist). This enables efficient processing
31	>	* when most tasks spawn other subtasks (as do most {@code
32	>	* ForkJoinTask}s). When setting <em>asyncMode</em> to true in
33	>	* constructors, {@code ForkJoinPool}s may also be appropriate for use
34	>	* with event-style tasks that are never joined.
35		*
36	<	* <p>The target parallelism level may also be set dynamically. You
37	<	* can limit the number of threads dynamically constructed using
38	<	* method <tt>setMaximumPoolSize</tt> and/or
39	<	* <tt>setMaintainParallelism</tt>.
36	>	* <p>A {@code ForkJoinPool} is constructed with a given target
37	>	* parallelism level; by default, equal to the number of available
38	>	* processors. The pool attempts to maintain enough active (or
39	>	* available) threads by dynamically adding, suspending, or resuming
40	>	* internal worker threads, even if some tasks are stalled waiting to
41	>	* join others. However, no such adjustments are guaranteed in the
42	>	* face of blocked IO or other unmanaged synchronization. The nested
43	>	* {@link ManagedBlocker} interface enables extension of the kinds of
44	>	* synchronization accommodated.
45		*
46		* <p>In addition to execution and lifecycle control methods, this
47		* class provides status check methods (for example
48	<	* <tt>getStealCount</tt>) that are intended to aid in developing,
48	>	* {@link #getStealCount}) that are intended to aid in developing,
49		* tuning, and monitoring fork/join applications. Also, method
50	<	* <tt>toString</tt> returns indications of pool state in a convenient
51	<	* form for informal monitoring.
50	>	* {@link #toString} returns indications of pool state in a
51	>	* convenient form for informal monitoring.
52	>	*
53	>	* <p> As is the case with other ExecutorServices, there are three
54	>	* main task execution methods summarized in the following
55	>	* table. These are designed to be used by clients not already engaged
56	>	* in fork/join computations in the current pool.  The main forms of
57	>	* these methods accept instances of {@code ForkJoinTask}, but
58	>	* overloaded forms also allow mixed execution of plain {@code
59	>	* Runnable}- or {@code Callable}- based activities as well.  However,
60	>	* tasks that are already executing in a pool should normally
61	>	* <em>NOT</em> use these pool execution methods, but instead use the
62	>	* within-computation forms listed in the table.
63	>	*
64	>	* <table BORDER CELLPADDING=3 CELLSPACING=1>
65	>	*  <tr>
66	>	*    <td></td>
67	>	*    <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
68	>	*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
69	>	*  </tr>
70	>	*  <tr>
71	>	*    <td> <b>Arrange async execution</td>
72	>	*    <td> {@link #execute(ForkJoinTask)}</td>
73	>	*    <td> {@link ForkJoinTask#fork}</td>
74	>	*  </tr>
75	>	*  <tr>
76	>	*    <td> <b>Await and obtain result</td>
77	>	*    <td> {@link #invoke(ForkJoinTask)}</td>
78	>	*    <td> {@link ForkJoinTask#invoke}</td>
79	>	*  </tr>
80	>	*  <tr>
81	>	*    <td> <b>Arrange exec and obtain Future</td>
82	>	*    <td> {@link #submit(ForkJoinTask)}</td>
83	>	*    <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td>
84	>	*  </tr>
85	>	* </table>
86	>	*
87	>	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
88	>	* used for all parallel task execution in a program or subsystem.
89	>	* Otherwise, use would not usually outweigh the construction and
90	>	* bookkeeping overhead of creating a large set of threads. For
91	>	* example, a common pool could be used for the {@code SortTasks}
92	>	* illustrated in {@link RecursiveAction}. Because {@code
93	>	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
94	>	* daemon} mode, there is typically no need to explicitly {@link
95	>	* #shutdown} such a pool upon program exit.
96	>	*
97	>	* <pre>
98	>	* static final ForkJoinPool mainPool = new ForkJoinPool();
99	>	* ...
100	>	* public void sort(long[] array) {
101	>	*   mainPool.invoke(new SortTask(array, 0, array.length));
102	>	* }
103	>	* </pre>
104		*
105		* <p><b>Implementation notes</b>: This implementation restricts the
106	<	* maximum parallelism to 32767. Attempts to create pools with greater
107	<	* than the maximum result in IllegalArgumentExceptions.
106	>	* maximum number of running threads to 32767. Attempts to create
107	>	* pools with greater than the maximum number result in
108	>	* {@code IllegalArgumentException}.
109	>	*
110	>	* <p>This implementation rejects submitted tasks (that is, by throwing
111	>	* {@link RejectedExecutionException}) only when the pool is shut down
112	>	* or internal resources have been exhausted.
113	>	*
114	>	* @since 1.7
115	>	* @author Doug Lea
116		*/
117	<	public class ForkJoinPool extends AbstractExecutorService
57	<	implements ExecutorService {
117	>	public class ForkJoinPool extends AbstractExecutorService {
118
119		/*
120	<	* See the extended comments interspersed below for design,
121	<	* rationale, and walkthroughs.
120	>	* Implementation Overview
121	>	*
122	>	* This class provides the central bookkeeping and control for a
123	>	* set of worker threads: Submissions from non-FJ threads enter
124	>	* into a submission queue. Workers take these tasks and typically
125	>	* split them into subtasks that may be stolen by other workers.
126	>	* The main work-stealing mechanics implemented in class
127	>	* ForkJoinWorkerThread give first priority to processing tasks
128	>	* from their own queues (LIFO or FIFO, depending on mode), then
129	>	* to randomized FIFO steals of tasks in other worker queues, and
130	>	* lastly to new submissions. These mechanics do not consider
131	>	* affinities, loads, cache localities, etc, so rarely provide the
132	>	* best possible performance on a given machine, but portably
133	>	* provide good throughput by averaging over these factors.
134	>	* (Further, even if we did try to use such information, we do not
135	>	* usually have a basis for exploiting it. For example, some sets
136	>	* of tasks profit from cache affinities, but others are harmed by
137	>	* cache pollution effects.)
138	>	*
139	>	* Beyond work-stealing support and essential bookkeeping, the
140	>	* main responsibility of this framework is to take actions when
141	>	* one worker is waiting to join a task stolen (or always held by)
142	>	* another.  Because we are multiplexing many tasks on to a pool
143	>	* of workers, we can't just let them block (as in Thread.join).
144	>	* We also cannot just reassign the joiner's run-time stack with
145	>	* another and replace it later, which would be a form of
146	>	* "continuation", that even if possible is not necessarily a good
147	>	* idea. Given that the creation costs of most threads on most
148	>	* systems mainly surrounds setting up runtime stacks, thread
149	>	* creation and switching is usually not much more expensive than
150	>	* stack creation and switching, and is more flexible). Instead we
151	>	* combine two tactics:
152	>	*
153	>	*   Helping: Arranging for the joiner to execute some task that it
154	>	*      would be running if the steal had not occurred.  Method
155	>	*      ForkJoinWorkerThread.helpJoinTask tracks joining->stealing
156	>	*      links to try to find such a task.
157	>	*
158	>	*   Compensating: Unless there are already enough live threads,
159	>	*      method helpMaintainParallelism() may create or
160	>	*      re-activate a spare thread to compensate for blocked
161	>	*      joiners until they unblock.
162	>	*
163	>	* It is impossible to keep exactly the target (parallelism)
164	>	* number of threads running at any given time.  Determining
165	>	* existence of conservatively safe helping targets, the
166	>	* availability of already-created spares, and the apparent need
167	>	* to create new spares are all racy and require heuristic
168	>	* guidance, so we rely on multiple retries of each.  Compensation
169	>	* occurs in slow-motion. It is triggered only upon timeouts of
170	>	* Object.wait used for joins. This reduces poor decisions that
171	>	* would otherwise be made when threads are waiting for others
172	>	* that are stalled because of unrelated activities such as
173	>	* garbage collection.
174	>	*
175	>	* The ManagedBlocker extension API can't use helping so relies
176	>	* only on compensation in method awaitBlocker.
177	>	*
178	>	* The main throughput advantages of work-stealing stem from
179	>	* decentralized control -- workers mostly steal tasks from each
180	>	* other. We do not want to negate this by creating bottlenecks
181	>	* implementing other management responsibilities. So we use a
182	>	* collection of techniques that avoid, reduce, or cope well with
183	>	* contention. These entail several instances of bit-packing into
184	>	* CASable fields to maintain only the minimally required
185	>	* atomicity. To enable such packing, we restrict maximum
186	>	* parallelism to (1<<15)-1 (enabling twice this (to accommodate
187	>	* unbalanced increments and decrements) to fit into a 16 bit
188	>	* field, which is far in excess of normal operating range.  Even
189	>	* though updates to some of these bookkeeping fields do sometimes
190	>	* contend with each other, they don't normally cache-contend with
191	>	* updates to others enough to warrant memory padding or
192	>	* isolation. So they are all held as fields of ForkJoinPool
193	>	* objects.  The main capabilities are as follows:
194	>	*
195	>	* 1. Creating and removing workers. Workers are recorded in the
196	>	* "workers" array. This is an array as opposed to some other data
197	>	* structure to support index-based random steals by workers.
198	>	* Updates to the array recording new workers and unrecording
199	>	* terminated ones are protected from each other by a lock
200	>	* (workerLock) but the array is otherwise concurrently readable,
201	>	* and accessed directly by workers. To simplify index-based
202	>	* operations, the array size is always a power of two, and all
203	>	* readers must tolerate null slots. Currently, all worker thread
204	>	* creation is on-demand, triggered by task submissions,
205	>	* replacement of terminated workers, and/or compensation for
206	>	* blocked workers. However, all other support code is set up to
207	>	* work with other policies.
208	>	*
209	>	* To ensure that we do not hold on to worker references that
210	>	* would prevent GC, ALL accesses to workers are via indices into
211	>	* the workers array (which is one source of some of the unusual
212	>	* code constructions here). In essence, the workers array serves
213	>	* as a WeakReference mechanism. Thus for example the event queue
214	>	* stores worker indices, not worker references. Access to the
215	>	* workers in associated methods (for example releaseEventWaiters)
216	>	* must both index-check and null-check the IDs. All such accesses
217	>	* ignore bad IDs by returning out early from what they are doing,
218	>	* since this can only be associated with shutdown, in which case
219	>	* it is OK to give up. On termination, we just clobber these
220	>	* data structures without trying to use them.
221	>	*
222	>	* 2. Bookkeeping for dynamically adding and removing workers. We
223	>	* aim to approximately maintain the given level of parallelism.
224	>	* When some workers are known to be blocked (on joins or via
225	>	* ManagedBlocker), we may create or resume others to take their
226	>	* place until they unblock (see below). Implementing this
227	>	* requires counts of the number of "running" threads (i.e., those
228	>	* that are neither blocked nor artificially suspended) as well as
229	>	* the total number.  These two values are packed into one field,
230	>	* "workerCounts" because we need accurate snapshots when deciding
231	>	* to create, resume or suspend.  Note however that the
232	>	* correspondence of these counts to reality is not guaranteed. In
233	>	* particular updates for unblocked threads may lag until they
234	>	* actually wake up.
235	>	*
236	>	* 3. Maintaining global run state. The run state of the pool
237	>	* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to
238	>	* those in other Executor implementations, as well as a count of
239	>	* "active" workers -- those that are, or soon will be, or
240	>	* recently were executing tasks. The runLevel and active count
241	>	* are packed together in order to correctly trigger shutdown and
242	>	* termination. Without care, active counts can be subject to very
243	>	* high contention.  We substantially reduce this contention by
244	>	* relaxing update rules.  A worker must claim active status
245	>	* prospectively, by activating if it sees that a submitted or
246	>	* stealable task exists (it may find after activating that the
247	>	* task no longer exists). It stays active while processing this
248	>	* task (if it exists) and any other local subtasks it produces,
249	>	* until it cannot find any other tasks. It then tries
250	>	* inactivating (see method preStep), but upon update contention
251	>	* instead scans for more tasks, later retrying inactivation if it
252	>	* doesn't find any.
253	>	*
254	>	* 4. Managing idle workers waiting for tasks. We cannot let
255	>	* workers spin indefinitely scanning for tasks when none are
256	>	* available. On the other hand, we must quickly prod them into
257	>	* action when new tasks are submitted or generated.  We
258	>	* park/unpark these idle workers using an event-count scheme.
259	>	* Field eventCount is incremented upon events that may enable
260	>	* workers that previously could not find a task to now find one:
261	>	* Submission of a new task to the pool, or another worker pushing
262	>	* a task onto a previously empty queue.  (We also use this
263	>	* mechanism for configuration and termination actions that
264	>	* require wakeups of idle workers).  Each worker maintains its
265	>	* last known event count, and blocks when a scan for work did not
266	>	* find a task AND its lastEventCount matches the current
267	>	* eventCount. Waiting idle workers are recorded in a variant of
268	>	* Treiber stack headed by field eventWaiters which, when nonzero,
269	>	* encodes the thread index and count awaited for by the worker
270	>	* thread most recently calling eventSync. This thread in turn has
271	>	* a record (field nextEventWaiter) for the next waiting worker.
272	>	* In addition to allowing simpler decisions about need for
273	>	* wakeup, the event count bits in eventWaiters serve the role of
274	>	* tags to avoid ABA errors in Treiber stacks. Upon any wakeup,
275	>	* released threads also try to release at most two others.  The
276	>	* net effect is a tree-like diffusion of signals, where released
277	>	* threads (and possibly others) help with unparks.  To further
278	>	* reduce contention effects a bit, failed CASes to increment
279	>	* field eventCount are tolerated without retries in signalWork.
280	>	* Conceptually they are merged into the same event, which is OK
281	>	* when their only purpose is to enable workers to scan for work.
282	>	*
283	>	* 5. Managing suspension of extra workers. When a worker notices
284	>	* (usually upon timeout of a wait()) that there are too few
285	>	* running threads, we may create a new thread to maintain
286	>	* parallelism level, or at least avoid starvation. Usually, extra
287	>	* threads are needed for only very short periods, yet join
288	>	* dependencies are such that we sometimes need them in
289	>	* bursts. Rather than create new threads each time this happens,
290	>	* we suspend no-longer-needed extra ones as "spares". For most
291	>	* purposes, we don't distinguish "extra" spare threads from
292	>	* normal "core" threads: On each call to preStep (the only point
293	>	* at which we can do this) a worker checks to see if there are
294	>	* now too many running workers, and if so, suspends itself.
295	>	* Method helpMaintainParallelism looks for suspended threads to
296	>	* resume before considering creating a new replacement. The
297	>	* spares themselves are encoded on another variant of a Treiber
298	>	* Stack, headed at field "spareWaiters".  Note that the use of
299	>	* spares is intrinsically racy.  One thread may become a spare at
300	>	* about the same time as another is needlessly being created. We
301	>	* counteract this and related slop in part by requiring resumed
302	>	* spares to immediately recheck (in preStep) to see whether they
303	>	* they should re-suspend.
304	>	*
305	>	* 6. Killing off unneeded workers. A timeout mechanism is used to
306	>	* shed unused workers: The oldest (first) event queue waiter uses
307	>	* a timed rather than hard wait. When this wait times out without
308	>	* a normal wakeup, it tries to shutdown any one (for convenience
309	>	* the newest) other spare or event waiter via
310	>	* tryShutdownUnusedWorker. This eventually reduces the number of
311	>	* worker threads to a minimum of one after a long enough period
312	>	* without use.
313	>	*
314	>	* 7. Deciding when to create new workers. The main dynamic
315	>	* control in this class is deciding when to create extra threads
316	>	* in method helpMaintainParallelism. We would like to keep
317	>	* exactly #parallelism threads running, which is an impossible
318	>	* task. We always need to create one when the number of running
319	>	* threads would become zero and all workers are busy. Beyond
320	>	* this, we must rely on heuristics that work well in the
321	>	* presence of transient phenomena such as GC stalls, dynamic
322	>	* compilation, and wake-up lags. These transients are extremely
323	>	* common -- we are normally trying to fully saturate the CPUs on
324	>	* a machine, so almost any activity other than running tasks
325	>	* impedes accuracy. Our main defense is to allow parallelism to
326	>	* lapse for a while during joins, and use a timeout to see if,
327	>	* after the resulting settling, there is still a need for
328	>	* additional workers.  This also better copes with the fact that
329	>	* some of the methods in this class tend to never become compiled
330	>	* (but are interpreted), so some components of the entire set of
331	>	* controls might execute 100 times faster than others. And
332	>	* similarly for cases where the apparent lack of work is just due
333	>	* to GC stalls and other transient system activity.
334	>	*
335	>	* Beware that there is a lot of representation-level coupling
336	>	* among classes ForkJoinPool, ForkJoinWorkerThread, and
337	>	* ForkJoinTask.  For example, direct access to "workers" array by
338	>	* workers, and direct access to ForkJoinTask.status by both
339	>	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
340	>	* trying to reduce this, since any associated future changes in
341	>	* representations will need to be accompanied by algorithmic
342	>	* changes anyway.
343	>	*
344	>	* Style notes: There are lots of inline assignments (of form
345	>	* "while ((local = field) != 0)") which are usually the simplest
346	>	* way to ensure the required read orderings (which are sometimes
347	>	* critical). Also several occurrences of the unusual "do {}
348	>	* while (!cas...)" which is the simplest way to force an update of
349	>	* a CAS'ed variable. There are also other coding oddities that
350	>	* help some methods perform reasonably even when interpreted (not
351	>	* compiled), at the expense of some messy constructions that
352	>	* reduce byte code counts.
353	>	*
354	>	* The order of declarations in this file is: (1) statics (2)
355	>	* fields (along with constants used when unpacking some of them)
356	>	* (3) internal control methods (4) callbacks and other support
357	>	* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
358	>	* methods (plus a few little helpers).
359		*/
360
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	–
361		/**
362	<	* Factory for creating new ForkJoinWorkerThreads.  A
363	<	* ForkJoinWorkerThreadFactory must be defined and used for
364	<	* ForkJoinWorkerThread subclasses that extend base functionality
365	<	* or initialize threads with different contexts.
362	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
363	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
364	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
365	>	* functionality or initialize threads with different contexts.
366		*/
367		public static interface ForkJoinWorkerThreadFactory {
368		/**
369		* Returns a new worker thread operating in the given pool.
370		*
371		* @param pool the pool this thread works in
372	<	* @throws NullPointerException if pool is null;
372	>	* @throws NullPointerException if the pool is null
373		*/
374		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
375		}
376
377		/**
378	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
378	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
379		* new ForkJoinWorkerThread.
380		*/
381	<	public static class  DefaultForkJoinWorkerThreadFactory
381	>	static class DefaultForkJoinWorkerThreadFactory
382		implements ForkJoinWorkerThreadFactory {
383		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
384	<	try {
94	<	return new ForkJoinWorkerThread(pool);
95	<	} catch (OutOfMemoryError oom)  {
96	<	return null;
97	<	}
384	>	return new ForkJoinWorkerThread(pool);
385		}
386		}
387
388		/**
389	<	* The default ForkJoinWorkerThreadFactory, used unless overridden
390	<	* in ForkJoinPool constructors.
389	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
390	>	* overridden in ForkJoinPool constructors.
391		*/
392	<	private static final DefaultForkJoinWorkerThreadFactory
392	>	public static final ForkJoinWorkerThreadFactory
393		defaultForkJoinWorkerThreadFactory =
394		new DefaultForkJoinWorkerThreadFactory();
395
109	–
396		/**
397		* Permission required for callers of methods that may start or
398		* kill threads.
#	Line 131 | Line 417 | public class ForkJoinPool extends Abstra
417		new AtomicInteger();
418
419		/**
420	<	* Array holding all worker threads in the pool. Array size must
421	<	* be a power of two.  Updates and replacements are protected by
422	<	* workerLock, but it is always kept in a consistent enough state
423	<	* to be randomly accessed without locking by workers performing
424	<	* work-stealing.
420	>	* The time to block in a join (see awaitJoin) before checking if
421	>	* a new worker should be (re)started to maintain parallelism
422	>	* level. The value should be short enough to maintain global
423	>	* responsiveness and progress but long enough to avoid
424	>	* counterproductive firings during GC stalls or unrelated system
425	>	* activity, and to not bog down systems with continual re-firings
426	>	* on GCs or legitimately long waits.
427		*/
428	<	volatile ForkJoinWorkerThread[] workers;
428	>	private static final long JOIN_TIMEOUT_MILLIS = 250L; // 4 per second
429
430		/**
431	<	* Lock protecting access to workers.
431	>	* The wakeup interval (in nanoseconds) for the oldest worker
432	>	* worker waiting for an event invokes tryShutdownUnusedWorker to shrink
433	>	* the number of workers.  The exact value does not matter too
434	>	* much, but should be long enough to slowly release resources
435	>	* during long periods without use without disrupting normal use.
436		*/
437	<	private final ReentrantLock workerLock;
437	>	private static final long SHRINK_RATE_NANOS =
438	>	30L * 1000L * 1000L * 1000L; // 2 per minute
439
440		/**
441	<	* Condition for awaitTermination.
441	>	* Absolute bound for parallelism level. Twice this number plus
442	>	* one (i.e., 0xfff) must fit into a 16bit field to enable
443	>	* word-packing for some counts and indices.
444		*/
445	<	private final Condition termination;
445	>	private static final int MAX_WORKERS   = 0x7fff;
446
447		/**
448	<	* The uncaught exception handler used when any worker
449	<	* abrupty terminates
448	>	* Array holding all worker threads in the pool.  Array size must
449	>	* be a power of two.  Updates and replacements are protected by
450	>	* workerLock, but the array is always kept in a consistent enough
451	>	* state to be randomly accessed without locking by workers
452	>	* performing work-stealing, as well as other traversal-based
453	>	* methods in this class. All readers must tolerate that some
454	>	* array slots may be null.
455		*/
456	<	private Thread.UncaughtExceptionHandler ueh;
456	>	volatile ForkJoinWorkerThread[] workers;
457
458		/**
459	<	* Creation factory for worker threads.
459	>	* Queue for external submissions.
460		*/
461	<	private final ForkJoinWorkerThreadFactory factory;
461	>	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
462
463		/**
464	<	* 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.
464	>	* Lock protecting updates to workers array.
465		*/
466	<	private volatile WaitQueueNode spareStack;
466	>	private final ReentrantLock workerLock;
467
468		/**
469	<	* Sum of per-thread steal counts, updated only when threads are
172	<	* idle or terminating.
469	>	* Latch released upon termination.
470		*/
471	<	private final AtomicLong stealCount;
471	>	private final Phaser termination;
472
473		/**
474	<	* Queue for external submissions.
474	>	* Creation factory for worker threads.
475		*/
476	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
476	>	private final ForkJoinWorkerThreadFactory factory;
477
478		/**
479	<	* Head of Treiber stack for barrier sync. See below for explanation
479	>	* Sum of per-thread steal counts, updated only when threads are
480	>	* idle or terminating.
481		*/
482	<	private volatile WaitQueueNode barrierStack;
482	>	private volatile long stealCount;
483
484		/**
485	<	* The count for event barrier
485	>	* Encoded record of top of Treiber stack of threads waiting for
486	>	* events. The top 32 bits contain the count being waited for. The
487	>	* bottom 16 bits contains one plus the pool index of waiting
488	>	* worker thread. (Bits 16-31 are unused.)
489		*/
490	<	private volatile long eventCount;
490	>	private volatile long eventWaiters;
491	>
492	>	private static final int  EVENT_COUNT_SHIFT = 32;
493	>	private static final long WAITER_ID_MASK    = (1L << 16) - 1L;
494
495		/**
496	<	* Pool number, just for assigning useful names to worker threads
496	>	* A counter for events that may wake up worker threads:
497	>	*   - Submission of a new task to the pool
498	>	*   - A worker pushing a task on an empty queue
499	>	*   - termination
500		*/
501	<	private final int poolNumber;
501	>	private volatile int eventCount;
502
503		/**
504	<	* The maximum allowed pool size
504	>	* Encoded record of top of Treiber stack of spare threads waiting
505	>	* for resumption. The top 16 bits contain an arbitrary count to
506	>	* avoid ABA effects. The bottom 16bits contains one plus the pool
507	>	* index of waiting worker thread.
508		*/
509	<	private volatile int maxPoolSize;
509	>	private volatile int spareWaiters;
510	>
511	>	private static final int SPARE_COUNT_SHIFT = 16;
512	>	private static final int SPARE_ID_MASK     = (1 << 16) - 1;
513
514		/**
515	<	* The desired parallelism level, updated only under workerLock.
516	<	*/
517	<	private volatile int parallelism;
515	>	* Lifecycle control. The low word contains the number of workers
516	>	* that are (probably) executing tasks. This value is atomically
517	>	* incremented before a worker gets a task to run, and decremented
518	>	* when worker has no tasks and cannot find any.  Bits 16-18
519	>	* contain runLevel value. When all are zero, the pool is
520	>	* running. Level transitions are monotonic (running -> shutdown
521	>	* -> terminating -> terminated) so each transition adds a bit.
522	>	* These are bundled together to ensure consistent read for
523	>	* termination checks (i.e., that runLevel is at least SHUTDOWN
524	>	* and active threads is zero).
525	>	*
526	>	* Notes: Most direct CASes are dependent on these bitfield
527	>	* positions.  Also, this field is non-private to enable direct
528	>	* performance-sensitive CASes in ForkJoinWorkerThread.
529	>	*/
530	>	volatile int runState;
531	>
532	>	// Note: The order among run level values matters.
533	>	private static final int RUNLEVEL_SHIFT     = 16;
534	>	private static final int SHUTDOWN           = 1 << RUNLEVEL_SHIFT;
535	>	private static final int TERMINATING        = 1 << (RUNLEVEL_SHIFT + 1);
536	>	private static final int TERMINATED         = 1 << (RUNLEVEL_SHIFT + 2);
537	>	private static final int ACTIVE_COUNT_MASK  = (1 << RUNLEVEL_SHIFT) - 1;
538
539		/**
540		* Holds number of total (i.e., created and not yet terminated)
541		* and running (i.e., not blocked on joins or other managed sync)
542	<	* threads, packed into one int to ensure consistent snapshot when
542	>	* threads, packed together to ensure consistent snapshot when
543		* making decisions about creating and suspending spare
544	<	* threads. Updated only by CAS.  Note: CASes in
545	<	* updateRunningCount and preJoin running active count is in low
546	<	* word, so need to be modified if this changes
544	>	* threads. Updated only by CAS. Note that adding a new worker
545	>	* requires incrementing both counts, since workers start off in
546	>	* running state.
547		*/
548		private volatile int workerCounts;
549
550	<	private static int totalCountOf(int s)           { return s >>> 16;  }
551	<	private static int runningCountOf(int s)         { return s & shortMask; }
552	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
550	>	private static final int TOTAL_COUNT_SHIFT  = 16;
551	>	private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1;
552	>	private static final int ONE_RUNNING        = 1;
553	>	private static final int ONE_TOTAL          = 1 << TOTAL_COUNT_SHIFT;
554
555		/**
556	<	* Add delta (which may be negative) to running count.  This must
557	<	* 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
556	>	* The target parallelism level.
557	>	* Accessed directly by ForkJoinWorkerThreads.
558		*/
559	<	final void updateRunningCount(int delta) {
228	<	int s;
229	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
230	<	}
559	>	final int parallelism;
560
561		/**
562	<	* Add delta (which may be negative) to both total and running
563	<	* count.  This must be called upon creation and termination of
235	<	* worker threads.
236	<	* @param delta the number to add
562	>	* True if use local fifo, not default lifo, for local polling
563	>	* Read by, and replicated by ForkJoinWorkerThreads
564		*/
565	<	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	<	}
565	>	final boolean locallyFifo;
566
567		/**
568	<	* Lifecycle control. High word contains runState, low word
569	<	* 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
568	>	* The uncaught exception handler used when any worker abruptly
569	>	* terminates.
570		*/
571	<	private volatile int runControl;
571	>	private final Thread.UncaughtExceptionHandler ueh;
572
573	<	// RunState values. Order among values matters
574	<	private static final int RUNNING     = 0;
575	<	private static final int SHUTDOWN    = 1;
576	<	private static final int TERMINATING = 2;
260	<	private static final int TERMINATED  = 3;
573	>	/**
574	>	* Pool number, just for assigning useful names to worker threads
575	>	*/
576	>	private final int poolNumber;
577
578	<	private static int runStateOf(int c)             { return c >>> 16; }
579	<	private static int activeCountOf(int c)          { return c & shortMask; }
264	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
578	>	// Utilities for CASing fields. Note that most of these
579	>	// are usually manually inlined by callers
580
581		/**
582	<	* Increment active count. Called by workers before/during
268	<	* executing tasks.
582	>	* Increments running count part of workerCounts
583		*/
584	<	final void incrementActiveCount() {
584	>	final void incrementRunningCount() {
585		int c;
586	<	do;while (!casRunControl(c = runControl, c+1));
586	>	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
587	>	c = workerCounts,
588	>	c + ONE_RUNNING));
589	>	}
590	>
591	>	/**
592	>	* Tries to decrement running count unless already zero
593	>	*/
594	>	final boolean tryDecrementRunningCount() {
595	>	int wc = workerCounts;
596	>	if ((wc & RUNNING_COUNT_MASK) == 0)
597	>	return false;
598	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
599	>	wc, wc - ONE_RUNNING);
600		}
601
602		/**
603	<	* Decrement active count; possibly trigger termination.
604	<	* Called by workers when they can't find tasks.
603	>	* Forces decrement of encoded workerCounts, awaiting nonzero if
604	>	* (rarely) necessary when other count updates lag.
605	>	*
606	>	* @param dr -- either zero or ONE_RUNNING
607	>	* @param dt == either zero or ONE_TOTAL
608		*/
609	<	final void decrementActiveCount() {
610	<	int c, nextc;
611	<	do;while (!casRunControl(c = runControl, nextc = c-1));
612	<	if (canTerminateOnShutdown(nextc))
613	<	terminateOnShutdown();
609	>	private void decrementWorkerCounts(int dr, int dt) {
610	>	for (;;) {
611	>	int wc = workerCounts;
612	>	if ((wc & RUNNING_COUNT_MASK)  - dr < 0 ||
613	>	(wc >>> TOTAL_COUNT_SHIFT) - dt < 0) {
614	>	if ((runState & TERMINATED) != 0)
615	>	return; // lagging termination on a backout
616	>	Thread.yield();
617	>	}
618	>	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
619	>	wc, wc - (dr + dt)))
620	>	return;
621	>	}
622		}
623
624		/**
625	<	* Return true if argument represents zero active count and
626	<	* nonzero runstate, which is the triggering condition for
289	<	* terminating on shutdown.
625	>	* Tries decrementing active count; fails on contention.
626	>	* Called when workers cannot find tasks to run.
627		*/
628	<	private static boolean canTerminateOnShutdown(int c) {
629	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
628	>	final boolean tryDecrementActiveCount() {
629	>	int c;
630	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
631	>	c = runState, c - 1);
632		}
633
634		/**
635	<	* Transition run state to at least the given state. Return true
636	<	* if not already at least given state.
635	>	* Advances to at least the given level. Returns true if not
636	>	* already in at least the given level.
637		*/
638	<	private boolean transitionRunStateTo(int state) {
638	>	private boolean advanceRunLevel(int level) {
639		for (;;) {
640	<	int c = runControl;
641	<	if (runStateOf(c) >= state)
640	>	int s = runState;
641	>	if ((s & level) != 0)
642		return false;
643	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
643	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level))
644		return true;
645		}
646		}
647
648	+	// workers array maintenance
649	+
650		/**
651	<	* Controls whether to add spares to maintain parallelism
651	>	* Records and returns a workers array index for new worker.
652		*/
653	<	private volatile boolean maintainsParallelism;
653	>	private int recordWorker(ForkJoinWorkerThread w) {
654	>	// Try using slot totalCount-1. If not available, scan and/or resize
655	>	int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1;
656	>	final ReentrantLock lock = this.workerLock;
657	>	lock.lock();
658	>	try {
659	>	ForkJoinWorkerThread[] ws = workers;
660	>	int n = ws.length;
661	>	if (k < 0 || k >= n || ws[k] != null) {
662	>	for (k = 0; k < n && ws[k] != null; ++k)
663	>	;
664	>	if (k == n)
665	>	ws = Arrays.copyOf(ws, n << 1);
666	>	}
667	>	ws[k] = w;
668	>	workers = ws; // volatile array write ensures slot visibility
669	>	} finally {
670	>	lock.unlock();
671	>	}
672	>	return k;
673	>	}
674
675	<	// Constructors
675	>	/**
676	>	* Nulls out record of worker in workers array.
677	>	*/
678	>	private void forgetWorker(ForkJoinWorkerThread w) {
679	>	int idx = w.poolIndex;
680	>	// Locking helps method recordWorker avoid unnecessary expansion
681	>	final ReentrantLock lock = this.workerLock;
682	>	lock.lock();
683	>	try {
684	>	ForkJoinWorkerThread[] ws = workers;
685	>	if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify
686	>	ws[idx] = null;
687	>	} finally {
688	>	lock.unlock();
689	>	}
690	>	}
691
692		/**
693	<	* Creates a ForkJoinPool with a pool size equal to the number of
694	<	* processors available on the system and using the default
695	<	* ForkJoinWorkerThreadFactory,
696	<	* @throws SecurityException if a security manager exists and
697	<	*         the caller is not permitted to modify threads
322	<	*         because it does not hold {@link
323	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
693	>	* Final callback from terminating worker.  Removes record of
694	>	* worker from array, and adjusts counts. If pool is shutting
695	>	* down, tries to complete termination.
696	>	*
697	>	* @param w the worker
698		*/
699	<	public ForkJoinPool() {
700	<	this(Runtime.getRuntime().availableProcessors(),
701	<	defaultForkJoinWorkerThreadFactory);
699	>	final void workerTerminated(ForkJoinWorkerThread w) {
700	>	forgetWorker(w);
701	>	decrementWorkerCounts(w.isTrimmed()? 0 : ONE_RUNNING, ONE_TOTAL);
702	>	while (w.stealCount != 0) // collect final count
703	>	tryAccumulateStealCount(w);
704	>	tryTerminate(false);
705		}
706
707	+	// Waiting for and signalling events
708	+
709		/**
710	<	* Creates a ForkJoinPool with the indicated parellelism level
711	<	* threads, and using the default ForkJoinWorkerThreadFactory,
712	<	* @param parallelism the number of worker threads
713	<	* @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>,
710	>	* Releases workers blocked on a count not equal to current count.
711	>	* Normally called after precheck that eventWaiters isn't zero to
712	>	* avoid wasted array checks. Gives up upon a change in count or
713	>	* upon releasing two workers, letting others take over.
714		*/
715	<	public ForkJoinPool(int parallelism) {
716	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
715	>	private void releaseEventWaiters() {
716	>	ForkJoinWorkerThread[] ws = workers;
717	>	int n = ws.length;
718	>	long h = eventWaiters;
719	>	int ec = eventCount;
720	>	boolean releasedOne = false;
721	>	ForkJoinWorkerThread w; int id;
722	>	while ((id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 &&
723	>	(int)(h >>> EVENT_COUNT_SHIFT) != ec &&
724	>	id < n && (w = ws[id]) != null) {
725	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
726	>	h,  w.nextWaiter)) {
727	>	LockSupport.unpark(w);
728	>	if (releasedOne) // exit on second release
729	>	break;
730	>	releasedOne = true;
731	>	}
732	>	if (eventCount != ec)
733	>	break;
734	>	h = eventWaiters;
735	>	}
736		}
737
738		/**
739	<	* Creates a ForkJoinPool with a pool size equal to the number of
740	<	* 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>,
739	>	* Tries to advance eventCount and releases waiters. Called only
740	>	* from workers.
741		*/
742	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
743	<	this(Runtime.getRuntime().availableProcessors(), factory);
742	>	final void signalWork() {
743	>	int c; // try to increment event count -- CAS failure OK
744	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
745	>	if (eventWaiters != 0L)
746	>	releaseEventWaiters();
747		}
748
749		/**
750	<	* Creates a ForkJoinPool with the indicated target number of
751	<	* worker threads and the given factory.
750	>	* Adds the given worker to event queue and blocks until
751	>	* terminating or event count advances from the given value
752		*
753	<	* @param parallelism the targeted number of worker threads
754	<	* @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>,
753	>	* @param w the calling worker thread
754	>	* @param ec the count
755		*/
756	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
757	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
758	<	throw new IllegalArgumentException();
759	<	if (factory == null)
760	<	throw new NullPointerException();
761	<	checkPermission();
762	<	this.factory = factory;
763	<	this.parallelism = parallelism;
764	<	this.maxPoolSize = MAX_THREADS;
765	<	this.maintainsParallelism = true;
766	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
767	<	this.workerLock = new ReentrantLock();
768	<	this.termination = workerLock.newCondition();
387	<	this.stealCount = new AtomicLong();
388	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
389	<	createAndStartInitialWorkers(parallelism);
756	>	private void eventSync(ForkJoinWorkerThread w, int ec) {
757	>	long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1));
758	>	long h;
759	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
760	>	(((int)((h = eventWaiters) & WAITER_ID_MASK)) == 0 ||
761	>	(int)(h >>> EVENT_COUNT_SHIFT) == ec) &&
762	>	eventCount == ec) {
763	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
764	>	w.nextWaiter = h, nh)) {
765	>	awaitEvent(w, ec);
766	>	break;
767	>	}
768	>	}
769		}
770
771		/**
772	<	* Create new worker using factory.
773	<	* @param index the index to assign worker
774	<	* @return new worker, or null of factory failed
772	>	* Blocks the given worker (that has already been entered as an
773	>	* event waiter) until terminating or event count advances from
774	>	* the given value. The oldest (first) waiter uses a timed wait to
775	>	* occasionally one-by-one shrink the number of workers (to a
776	>	* minimum of one) if the pool has not been used for extended
777	>	* periods.
778	>	*
779	>	* @param w the calling worker thread
780	>	* @param ec the count
781		*/
782	<	private ForkJoinWorkerThread createWorker(int index) {
783	<	Thread.UncaughtExceptionHandler h = ueh;
784	<	ForkJoinWorkerThread w = factory.newThread(this);
785	<	if (w != null) {
786	<	w.poolIndex = index;
787	<	w.setDaemon(true);
788	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
789	<	if (h != null)
790	<	w.setUncaughtExceptionHandler(h);
782	>	private void awaitEvent(ForkJoinWorkerThread w, int ec) {
783	>	while (eventCount == ec) {
784	>	if (tryAccumulateStealCount(w)) { // transfer while idle
785	>	boolean untimed = (w.nextWaiter != 0L ||
786	>	(workerCounts & RUNNING_COUNT_MASK) <= 1);
787	>	long startTime = untimed? 0 : System.nanoTime();
788	>	Thread.interrupted();         // clear/ignore interrupt
789	>	if (eventCount != ec || w.runState != 0 ||
790	>	runState >= TERMINATING)  // recheck after clear
791	>	break;
792	>	if (untimed)
793	>	LockSupport.park(w);
794	>	else {
795	>	LockSupport.parkNanos(w, SHRINK_RATE_NANOS);
796	>	if (eventCount != ec || w.runState != 0 ||
797	>	runState >= TERMINATING)
798	>	break;
799	>	if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS)
800	>	tryShutdownUnusedWorker(ec);
801	>	}
802	>	}
803		}
407	–	return w;
804		}
805
806	+	// Maintaining parallelism
807	+
808		/**
809	<	* Return a good size for worker array given pool size.
412	<	* Currently requires size to be a power of two.
809	>	* Pushes worker onto the spare stack
810		*/
811	<	private static int arraySizeFor(int ps) {
812	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
811	>	final void pushSpare(ForkJoinWorkerThread w) {
812	>	int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1);
813	>	do {} while (!UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
814	>	w.nextSpare = spareWaiters,ns));
815		}
816
817		/**
818	<	* Create or resize array if necessary to hold newLength
819	<	* @return the array
818	>	* Tries (once) to resume a spare if the number of running
819	>	* threads is less than target.
820		*/
821	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
821	>	private void tryResumeSpare() {
822	>	int sw, id;
823		ForkJoinWorkerThread[] ws = workers;
824	<	if (ws == null)
825	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
826	<	else if (newLength > ws.length)
827	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
828	<	else
829	<	return ws;
824	>	int n = ws.length;
825	>	ForkJoinWorkerThread w;
826	>	if ((sw = spareWaiters) != 0 &&
827	>	(id = (sw & SPARE_ID_MASK) - 1) >= 0 &&
828	>	id < n && (w = ws[id]) != null &&
829	>	(workerCounts & RUNNING_COUNT_MASK) < parallelism &&
830	>	spareWaiters == sw &&
831	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
832	>	sw, w.nextSpare)) {
833	>	int c; // increment running count before resume
834	>	do {} while (!UNSAFE.compareAndSwapInt
835	>	(this, workerCountsOffset,
836	>	c = workerCounts, c + ONE_RUNNING));
837	>	if (w.tryUnsuspend())
838	>	LockSupport.unpark(w);
839	>	else   // back out if w was shutdown
840	>	decrementWorkerCounts(ONE_RUNNING, 0);
841	>	}
842		}
843
844		/**
845	<	* Try to shrink workers into smaller array after one or more terminate
845	>	* Tries to increase the number of running workers if below target
846	>	* parallelism: If a spare exists tries to resume it via
847	>	* tryResumeSpare.  Otherwise, if not enough total workers or all
848	>	* existing workers are busy, adds a new worker. In all cases also
849	>	* helps wake up releasable workers waiting for work.
850	>	*/
851	>	private void helpMaintainParallelism() {
852	>	int pc = parallelism;
853	>	int wc, rs, tc;
854	>	while (((wc = workerCounts) & RUNNING_COUNT_MASK) < pc &&
855	>	(rs = runState) < TERMINATING) {
856	>	if (spareWaiters != 0)
857	>	tryResumeSpare();
858	>	else if ((tc = wc >>> TOTAL_COUNT_SHIFT) >= MAX_WORKERS ||
859	>	(tc >= pc && (rs & ACTIVE_COUNT_MASK) != tc))
860	>	break;   // enough total
861	>	else if (runState == rs && workerCounts == wc &&
862	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
863	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
864	>	ForkJoinWorkerThread w = null;
865	>	try {
866	>	w = factory.newThread(this);
867	>	} finally { // adjust on null or exceptional factory return
868	>	if (w == null) {
869	>	decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL);
870	>	tryTerminate(false); // handle failure during shutdown
871	>	}
872	>	}
873	>	if (w == null)
874	>	break;
875	>	w.start(recordWorker(w), ueh);
876	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) >= pc) {
877	>	int c; // advance event count
878	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
879	>	c = eventCount, c+1);
880	>	break; // add at most one unless total below target
881	>	}
882	>	}
883	>	}
884	>	if (eventWaiters != 0L)
885	>	releaseEventWaiters();
886	>	}
887	>
888	>	/**
889	>	* Callback from the oldest waiter in awaitEvent waking up after a
890	>	* period of non-use. If all workers are idle, tries (once) to
891	>	* shutdown an event waiter or a spare, if one exists. Note that
892	>	* we don't need CAS or locks here because the method is called
893	>	* only from one thread occasionally waking (and even misfires are
894	>	* OK). Note that until the shutdown worker fully terminates,
895	>	* workerCounts will overestimate total count, which is tolerable.
896	>	*
897	>	* @param ec the event count waited on by caller (to abort
898	>	* attempt if count has since changed).
899		*/
900	<	private void tryShrinkWorkerArray() {
901	<	ForkJoinWorkerThread[] ws = workers;
902	<	int len = ws.length;
903	<	int last = len - 1;
904	<	while (last >= 0 && ws[last] == null)
905	<	--last;
906	<	int newLength = arraySizeFor(last+1);
907	<	if (newLength < len)
908	<	workers = Arrays.copyOf(ws, newLength);
900	>	private void tryShutdownUnusedWorker(int ec) {
901	>	if (runState == 0 && eventCount == ec) { // only trigger if all idle
902	>	ForkJoinWorkerThread[] ws = workers;
903	>	int n = ws.length;
904	>	ForkJoinWorkerThread w = null;
905	>	boolean shutdown = false;
906	>	int sw;
907	>	long h;
908	>	if ((sw = spareWaiters) != 0) { // prefer killing spares
909	>	int id = (sw & SPARE_ID_MASK) - 1;
910	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
911	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
912	>	sw, w.nextSpare))
913	>	shutdown = true;
914	>	}
915	>	else if ((h = eventWaiters) != 0L) {
916	>	long nh;
917	>	int id = ((int)(h & WAITER_ID_MASK)) - 1;
918	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
919	>	(nh = w.nextWaiter) != 0L && // keep at least one worker
920	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh))
921	>	shutdown = true;
922	>	}
923	>	if (w != null && shutdown) {
924	>	w.shutdown();
925	>	LockSupport.unpark(w);
926	>	}
927	>	}
928	>	releaseEventWaiters(); // in case of interference
929		}
930
931		/**
932	<	* Initial worker array and worker creation and startup. (This
933	<	* must be done under lock to avoid interference by some of the
934	<	* newly started threads while creating others.)
932	>	* Callback from workers invoked upon each top-level action (i.e.,
933	>	* stealing a task or taking a submission and running it).
934	>	* Performs one or more of the following:
935	>	*
936	>	* 1. If the worker is active and either did not run a task
937	>	*    or there are too many workers, try to set its active status
938	>	*    to inactive and update activeCount. On contention, we may
939	>	*    try again in this or a subsequent call.
940	>	*
941	>	* 2. If not enough total workers, help create some.
942	>	*
943	>	* 3. If there are too many running workers, suspend this worker
944	>	*    (first forcing inactive if necessary).  If it is not needed,
945	>	*    it may be shutdown while suspended (via
946	>	*    tryShutdownUnusedWorker).  Otherwise, upon resume it
947	>	*    rechecks running thread count and need for event sync.
948	>	*
949	>	* 4. If worker did not run a task, await the next task event via
950	>	*    eventSync if necessary (first forcing inactivation), upon
951	>	*    which the worker may be shutdown via
952	>	*    tryShutdownUnusedWorker.  Otherwise, help release any
953	>	*    existing event waiters that are now releasable,
954	>	*
955	>	* @param w the worker
956	>	* @param ran true if worker ran a task since last call to this method
957		*/
958	<	private void createAndStartInitialWorkers(int ps) {
959	<	final ReentrantLock lock = this.workerLock;
960	<	lock.lock();
961	<	try {
962	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
963	<	for (int i = 0; i < ps; ++i) {
964	<	ForkJoinWorkerThread w = createWorker(i);
965	<	if (w != null) {
966	<	ws[i] = w;
967	<	w.start();
968	<	updateWorkerCount(1);
958	>	final void preStep(ForkJoinWorkerThread w, boolean ran) {
959	>	int wec = w.lastEventCount;
960	>	boolean active = w.active;
961	>	boolean inactivate = false;
962	>	int pc = parallelism;
963	>	int rs;
964	>	while (w.runState == 0 && (rs = runState) < TERMINATING) {
965	>	if ((inactivate || (active && (rs & ACTIVE_COUNT_MASK) >= pc)) &&
966	>	UNSAFE.compareAndSwapInt(this, runStateOffset, rs, rs - 1))
967	>	inactivate = active = w.active = false;
968	>	int wc = workerCounts;
969	>	if ((wc & RUNNING_COUNT_MASK) > pc) {
970	>	if (!(inactivate |= active) && // must inactivate to suspend
971	>	workerCounts == wc &&      // try to suspend as spare
972	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
973	>	wc, wc - ONE_RUNNING))
974	>	w.suspendAsSpare();
975	>	}
976	>	else if ((wc >>> TOTAL_COUNT_SHIFT) < pc)
977	>	helpMaintainParallelism();     // not enough workers
978	>	else if (!ran) {
979	>	long h = eventWaiters;
980	>	int ec = eventCount;
981	>	if (h != 0L && (int)(h >>> EVENT_COUNT_SHIFT) != ec)
982	>	releaseEventWaiters();     // release others before waiting
983	>	else if (ec != wec) {
984	>	w.lastEventCount = ec;     // no need to wait
985	>	break;
986		}
987	+	else if (!(inactivate |= active))
988	+	eventSync(w, wec);         // must inactivate before sync
989		}
990	<	} finally {
991	<	lock.unlock();
990	>	else
991	>	break;
992		}
993		}
994
995		/**
996	<	* Worker creation and startup for threads added via setParallelism.
996	>	* Helps and/or blocks awaiting join of the given task.
997	>	* See above for explanation.
998	>	*
999	>	* @param joinMe the task to join
1000	>	* @param worker the current worker thread
1001		*/
1002	<	private void createAndStartAddedWorkers() {
1003	<	resumeAllSpares();  // Allow spares to convert to nonspare
1004	<	int ps = parallelism;
1005	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1006	<	int len = ws.length;
1007	<	// Sweep through slots, to keep lowest indices most populated
1008	<	int k = 0;
1009	<	while (k < len) {
1010	<	if (ws[k] != null) {
1011	<	++k;
1012	<	continue;
1002	>	final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker) {
1003	>	int retries = 2 + (parallelism >> 2); // #helpJoins before blocking
1004	>	while (joinMe.status >= 0) {
1005	>	int wc;
1006	>	worker.helpJoinTask(joinMe);
1007	>	if (joinMe.status < 0)
1008	>	break;
1009	>	else if (retries > 0)
1010	>	--retries;
1011	>	else if (((wc = workerCounts) & RUNNING_COUNT_MASK) != 0 &&
1012	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1013	>	wc, wc - ONE_RUNNING)) {
1014	>	int stat, c; long h;
1015	>	while ((stat = joinMe.status) >= 0 &&
1016	>	(h = eventWaiters) != 0L && // help release others
1017	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1018	>	releaseEventWaiters();
1019	>	if (stat >= 0 &&
1020	>	((workerCounts & RUNNING_COUNT_MASK) == 0 ||
1021	>	(stat =
1022	>	joinMe.internalAwaitDone(JOIN_TIMEOUT_MILLIS)) >= 0))
1023	>	helpMaintainParallelism(); // timeout or no running workers
1024	>	do {} while (!UNSAFE.compareAndSwapInt
1025	>	(this, workerCountsOffset,
1026	>	c = workerCounts, c + ONE_RUNNING));
1027	>	if (stat < 0)
1028	>	break;   // else restart
1029		}
1030	<	int s = workerCounts;
1031	<	int tc = totalCountOf(s);
1032	<	int rc = runningCountOf(s);
1033	<	if (rc >= ps || tc >= ps)
1030	>	}
1031	>	}
1032	>
1033	>	/**
1034	>	* Same idea as awaitJoin, but no helping, retries, or timeouts.
1035	>	*/
1036	>	final void awaitBlocker(ManagedBlocker blocker)
1037	>	throws InterruptedException {
1038	>	while (!blocker.isReleasable()) {
1039	>	int wc = workerCounts;
1040	>	if ((wc & RUNNING_COUNT_MASK) != 0 &&
1041	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1042	>	wc, wc - ONE_RUNNING)) {
1043	>	try {
1044	>	while (!blocker.isReleasable()) {
1045	>	long h = eventWaiters;
1046	>	if (h != 0L &&
1047	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1048	>	releaseEventWaiters();
1049	>	else if ((workerCounts & RUNNING_COUNT_MASK) == 0 &&
1050	>	runState < TERMINATING)
1051	>	helpMaintainParallelism();
1052	>	else if (blocker.block())
1053	>	break;
1054	>	}
1055	>	} finally {
1056	>	int c;
1057	>	do {} while (!UNSAFE.compareAndSwapInt
1058	>	(this, workerCountsOffset,
1059	>	c = workerCounts, c + ONE_RUNNING));
1060	>	}
1061		break;
1062	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
1063	<	ForkJoinWorkerThread w = createWorker(k);
1062	>	}
1063	>	}
1064	>	}
1065	>
1066	>	/**
1067	>	* Possibly initiates and/or completes termination.
1068	>	*
1069	>	* @param now if true, unconditionally terminate, else only
1070	>	* if shutdown and empty queue and no active workers
1071	>	* @return true if now terminating or terminated
1072	>	*/
1073	>	private boolean tryTerminate(boolean now) {
1074	>	if (now)
1075	>	advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN
1076	>	else if (runState < SHUTDOWN ||
1077	>	!submissionQueue.isEmpty() ||
1078	>	(runState & ACTIVE_COUNT_MASK) != 0)
1079	>	return false;
1080	>
1081	>	if (advanceRunLevel(TERMINATING))
1082	>	startTerminating();
1083	>
1084	>	// Finish now if all threads terminated; else in some subsequent call
1085	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1086	>	advanceRunLevel(TERMINATED);
1087	>	termination.arrive();
1088	>	}
1089	>	return true;
1090	>	}
1091	>
1092	>	/**
1093	>	* Actions on transition to TERMINATING
1094	>	*
1095	>	* Runs up to four passes through workers: (0) shutting down each
1096	>	* (without waking up if parked) to quickly spread notifications
1097	>	* without unnecessary bouncing around event queues etc (1) wake
1098	>	* up and help cancel tasks (2) interrupt (3) mop up races with
1099	>	* interrupted workers
1100	>	*/
1101	>	private void startTerminating() {
1102	>	cancelSubmissions();
1103	>	for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) {
1104	>	int c; // advance event count
1105	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
1106	>	c = eventCount, c+1);
1107	>	eventWaiters = 0L; // clobber lists
1108	>	spareWaiters = 0;
1109	>	for (ForkJoinWorkerThread w : workers) {
1110		if (w != null) {
1111	<	ws[k++] = w;
1112	<	w.start();
1113	<	}
1114	<	else {
1115	<	updateWorkerCount(-1); // back out on failed creation
1116	<	break;
1111	>	w.shutdown();
1112	>	if (passes > 0 && !w.isTerminated()) {
1113	>	w.cancelTasks();
1114	>	LockSupport.unpark(w);
1115	>	if (passes > 1) {
1116	>	try {
1117	>	w.interrupt();
1118	>	} catch (SecurityException ignore) {
1119	>	}
1120	>	}
1121	>	}
1122		}
1123		}
1124		}
1125		}
1126
1127		/**
1128	<	* Sets the handler for internal worker threads that terminate due
1129	<	* to unrecoverable errors encountered while executing tasks.
1130	<	* Unless set, the current default or ThreadGroup handler is used
1131	<	* as handler.
1128	>	* Clear out and cancel submissions, ignoring exceptions
1129	>	*/
1130	>	private void cancelSubmissions() {
1131	>	ForkJoinTask<?> task;
1132	>	while ((task = submissionQueue.poll()) != null) {
1133	>	try {
1134	>	task.cancel(false);
1135	>	} catch (Throwable ignore) {
1136	>	}
1137	>	}
1138	>	}
1139	>
1140	>	// misc support for ForkJoinWorkerThread
1141	>
1142	>	/**
1143	>	* Returns pool number
1144	>	*/
1145	>	final int getPoolNumber() {
1146	>	return poolNumber;
1147	>	}
1148	>
1149	>	/**
1150	>	* Tries to accumulates steal count from a worker, clearing
1151	>	* the worker's value.
1152	>	*
1153	>	* @return true if worker steal count now zero
1154	>	*/
1155	>	final boolean tryAccumulateStealCount(ForkJoinWorkerThread w) {
1156	>	int sc = w.stealCount;
1157	>	long c = stealCount;
1158	>	// CAS even if zero, for fence effects
1159	>	if (UNSAFE.compareAndSwapLong(this, stealCountOffset, c, c + sc)) {
1160	>	if (sc != 0)
1161	>	w.stealCount = 0;
1162	>	return true;
1163	>	}
1164	>	return sc == 0;
1165	>	}
1166	>
1167	>	/**
1168	>	* Returns the approximate (non-atomic) number of idle threads per
1169	>	* active thread.
1170	>	*/
1171	>	final int idlePerActive() {
1172	>	int pc = parallelism; // use parallelism, not rc
1173	>	int ac = runState;    // no mask -- artificially boosts during shutdown
1174	>	// Use exact results for small values, saturate past 4
1175	>	return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
1176	>	}
1177	>
1178	>	// Public and protected methods
1179	>
1180	>	// Constructors
1181	>
1182	>	/**
1183	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1184	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1185	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1186	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1187		*
509	–	* @param h the new handler
510	–	* @return the old handler, or null if none
1188		* @throws SecurityException if a security manager exists and
1189		*         the caller is not permitted to modify threads
1190		*         because it does not hold {@link
1191	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1191	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1192		*/
1193	<	public Thread.UncaughtExceptionHandler
1194	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
1193	>	public ForkJoinPool() {
1194	>	this(Runtime.getRuntime().availableProcessors(),
1195	>	defaultForkJoinWorkerThreadFactory, null, false);
1196	>	}
1197	>
1198	>	/**
1199	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
1200	>	* level, the {@linkplain
1201	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1202	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1203	>	*
1204	>	* @param parallelism the parallelism level
1205	>	* @throws IllegalArgumentException if parallelism less than or
1206	>	*         equal to zero, or greater than implementation limit
1207	>	* @throws SecurityException if a security manager exists and
1208	>	*         the caller is not permitted to modify threads
1209	>	*         because it does not hold {@link
1210	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1211	>	*/
1212	>	public ForkJoinPool(int parallelism) {
1213	>	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1214	>	}
1215	>
1216	>	/**
1217	>	* Creates a {@code ForkJoinPool} with the given parameters.
1218	>	*
1219	>	* @param parallelism the parallelism level. For default value,
1220	>	* use {@link java.lang.Runtime#availableProcessors}.
1221	>	* @param factory the factory for creating new threads. For default value,
1222	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
1223	>	* @param handler the handler for internal worker threads that
1224	>	* terminate due to unrecoverable errors encountered while executing
1225	>	* tasks. For default value, use <code>null</code>.
1226	>	* @param asyncMode if true,
1227	>	* establishes local first-in-first-out scheduling mode for forked
1228	>	* tasks that are never joined. This mode may be more appropriate
1229	>	* than default locally stack-based mode in applications in which
1230	>	* worker threads only process event-style asynchronous tasks.
1231	>	* For default value, use <code>false</code>.
1232	>	* @throws IllegalArgumentException if parallelism less than or
1233	>	*         equal to zero, or greater than implementation limit
1234	>	* @throws NullPointerException if the factory is null
1235	>	* @throws SecurityException if a security manager exists and
1236	>	*         the caller is not permitted to modify threads
1237	>	*         because it does not hold {@link
1238	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1239	>	*/
1240	>	public ForkJoinPool(int parallelism,
1241	>	ForkJoinWorkerThreadFactory factory,
1242	>	Thread.UncaughtExceptionHandler handler,
1243	>	boolean asyncMode) {
1244		checkPermission();
1245	<	Thread.UncaughtExceptionHandler old = null;
1246	<	final ReentrantLock lock = this.workerLock;
1247	<	lock.lock();
1248	<	try {
1249	<	old = ueh;
1250	<	ueh = h;
1251	<	ForkJoinWorkerThread[] ws = workers;
1252	<	for (int i = 0; i < ws.length; ++i) {
1253	<	ForkJoinWorkerThread w = ws[i];
1254	<	if (w != null)
1255	<	w.setUncaughtExceptionHandler(h);
1256	<	}
1257	<	} finally {
1258	<	lock.unlock();
533	<	}
534	<	return old;
1245	>	if (factory == null)
1246	>	throw new NullPointerException();
1247	>	if (parallelism <= 0 || parallelism > MAX_WORKERS)
1248	>	throw new IllegalArgumentException();
1249	>	this.parallelism = parallelism;
1250	>	this.factory = factory;
1251	>	this.ueh = handler;
1252	>	this.locallyFifo = asyncMode;
1253	>	int arraySize = initialArraySizeFor(parallelism);
1254	>	this.workers = new ForkJoinWorkerThread[arraySize];
1255	>	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
1256	>	this.workerLock = new ReentrantLock();
1257	>	this.termination = new Phaser(1);
1258	>	this.poolNumber = poolNumberGenerator.incrementAndGet();
1259		}
1260
1261		/**
1262	<	* Returns the handler for internal worker threads that terminate
1263	<	* due to unrecoverable errors encountered while executing tasks.
540	<	* @return the handler, or null if none
1262	>	* Returns initial power of two size for workers array.
1263	>	* @param pc the initial parallelism level
1264		*/
1265	<	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1266	<	Thread.UncaughtExceptionHandler h;
1267	<	final ReentrantLock lock = this.workerLock;
1268	<	lock.lock();
1269	<	try {
1270	<	h = ueh;
1271	<	} finally {
1272	<	lock.unlock();
1273	<	}
551	<	return h;
1265	>	private static int initialArraySizeFor(int pc) {
1266	>	// If possible, initially allocate enough space for one spare
1267	>	int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS;
1268	>	// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16)
1269	>	size |= size >>> 1;
1270	>	size |= size >>> 2;
1271	>	size |= size >>> 4;
1272	>	size |= size >>> 8;
1273	>	return size + 1;
1274		}
1275
1276		// Execution methods
#	Line 557 | Line 1279 | public class ForkJoinPool extends Abstra
1279		* Common code for execute, invoke and submit
1280		*/
1281		private <T> void doSubmit(ForkJoinTask<T> task) {
1282	<	if (isShutdown())
1282	>	if (task == null)
1283	>	throw new NullPointerException();
1284	>	if (runState >= SHUTDOWN)
1285		throw new RejectedExecutionException();
1286		submissionQueue.offer(task);
1287	<	signalIdleWorkers(true);
1287	>	int c; // try to increment event count -- CAS failure OK
1288	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
1289	>	helpMaintainParallelism(); // create, start, or resume some workers
1290		}
1291
1292		/**
1293	<	* Performs the given task; returning its result upon completion
1293	>	* Performs the given task, returning its result upon completion.
1294	>	*
1295		* @param task the task
1296		* @return the task's result
1297	<	* @throws NullPointerException if task is null
1298	<	* @throws RejectedExecutionException if pool is shut down
1297	>	* @throws NullPointerException if the task is null
1298	>	* @throws RejectedExecutionException if the task cannot be
1299	>	*         scheduled for execution
1300		*/
1301		public <T> T invoke(ForkJoinTask<T> task) {
1302		doSubmit(task);
#	Line 577 | Line 1305 | public class ForkJoinPool extends Abstra
1305
1306		/**
1307		* Arranges for (asynchronous) execution of the given task.
1308	+	*
1309		* @param task the task
1310	<	* @throws NullPointerException if task is null
1311	<	* @throws RejectedExecutionException if pool is shut down
1310	>	* @throws NullPointerException if the task is null
1311	>	* @throws RejectedExecutionException if the task cannot be
1312	>	*         scheduled for execution
1313		*/
1314	<	public <T> void execute(ForkJoinTask<T> task) {
1314	>	public void execute(ForkJoinTask<?> task) {
1315		doSubmit(task);
1316		}
1317
1318		// AbstractExecutorService methods
1319
1320	+	/**
1321	+	* @throws NullPointerException if the task is null
1322	+	* @throws RejectedExecutionException if the task cannot be
1323	+	*         scheduled for execution
1324	+	*/
1325		public void execute(Runnable task) {
1326	<	doSubmit(new AdaptedRunnable<Void>(task, null));
1326	>	ForkJoinTask<?> job;
1327	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1328	>	job = (ForkJoinTask<?>) task;
1329	>	else
1330	>	job = ForkJoinTask.adapt(task, null);
1331	>	doSubmit(job);
1332		}
1333
1334	+	/**
1335	+	* Submits a ForkJoinTask for execution.
1336	+	*
1337	+	* @param task the task to submit
1338	+	* @return the task
1339	+	* @throws NullPointerException if the task is null
1340	+	* @throws RejectedExecutionException if the task cannot be
1341	+	*         scheduled for execution
1342	+	*/
1343	+	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1344	+	doSubmit(task);
1345	+	return task;
1346	+	}
1347	+
1348	+	/**
1349	+	* @throws NullPointerException if the task is null
1350	+	* @throws RejectedExecutionException if the task cannot be
1351	+	*         scheduled for execution
1352	+	*/
1353		public <T> ForkJoinTask<T> submit(Callable<T> task) {
1354	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
1354	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1355		doSubmit(job);
1356		return job;
1357		}
1358
1359	+	/**
1360	+	* @throws NullPointerException if the task is null
1361	+	* @throws RejectedExecutionException if the task cannot be
1362	+	*         scheduled for execution
1363	+	*/
1364		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1365	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
1365	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1366		doSubmit(job);
1367		return job;
1368		}
1369
1370	+	/**
1371	+	* @throws NullPointerException if the task is null
1372	+	* @throws RejectedExecutionException if the task cannot be
1373	+	*         scheduled for execution
1374	+	*/
1375		public ForkJoinTask<?> submit(Runnable task) {
1376	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
1376	>	ForkJoinTask<?> job;
1377	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1378	>	job = (ForkJoinTask<?>) task;
1379	>	else
1380	>	job = ForkJoinTask.adapt(task, null);
1381		doSubmit(job);
1382		return job;
1383		}
1384
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	–
1385		/**
1386	<	* Adaptor for Callables
1386	>	* @throws NullPointerException       {@inheritDoc}
1387	>	* @throws RejectedExecutionException {@inheritDoc}
1388		*/
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	–
1389		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
1390	<	ArrayList<ForkJoinTask<T>> ts =
1390	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
1391		new ArrayList<ForkJoinTask<T>>(tasks.size());
1392	<	for (Callable<T> c : tasks)
1393	<	ts.add(new AdaptedCallable<T>(c));
1394	<	invoke(new InvokeAll<T>(ts));
1395	<	return (List<Future<T>>)(List)ts;
1392	>	for (Callable<T> task : tasks)
1393	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
1394	>	invoke(new InvokeAll<T>(forkJoinTasks));
1395	>
1396	>	@SuppressWarnings({"unchecked", "rawtypes"})
1397	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1398	>	return futures;
1399		}
1400
1401		static final class InvokeAll<T> extends RecursiveAction {
1402		final ArrayList<ForkJoinTask<T>> tasks;
1403		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
1404		public void compute() {
1405	<	try { invokeAll(tasks); } catch(Exception ignore) {}
1405	>	try { invokeAll(tasks); }
1406	>	catch (Exception ignore) {}
1407		}
1408	+	private static final long serialVersionUID = -7914297376763021607L;
1409		}
1410
689	–	// Configuration and status settings and queries
690	–
1411		/**
1412	<	* Returns the factory used for constructing new workers
1412	>	* Returns the factory used for constructing new workers.
1413		*
1414		* @return the factory used for constructing new workers
1415		*/
#	Line 698 | Line 1418 | public class ForkJoinPool extends Abstra
1418		}
1419
1420		/**
1421	<	* Sets the target paralleism level of this pool.
1422	<	* @param parallelism the target parallelism
1423	<	* @throws IllegalArgumentException if parallelism less than or
1424	<	* 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>,
1421	>	* Returns the handler for internal worker threads that terminate
1422	>	* due to unrecoverable errors encountered while executing tasks.
1423	>	*
1424	>	* @return the handler, or {@code null} if none
1425		*/
1426	<	public void setParallelism(int parallelism) {
1427	<	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);
1426	>	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1427	>	return ueh;
1428		}
1429
1430		/**
1431	<	* 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.
1431	>	* Returns the targeted parallelism level of this pool.
1432		*
1433	<	* @return the targeted number of worker threads in this pool
1433	>	* @return the targeted parallelism level of this pool
1434		*/
1435		public int getParallelism() {
1436		return parallelism;
#	Line 742 | Line 1439 | public class ForkJoinPool extends Abstra
1439		/**
1440		* Returns the number of worker threads that have started but not
1441		* yet terminated.  This result returned by this method may differ
1442	<	* from <tt>getParallelism</tt> when threads are created to
1442	>	* from {@link #getParallelism} when threads are created to
1443		* maintain parallelism when others are cooperatively blocked.
1444		*
1445		* @return the number of worker threads
1446		*/
1447		public int getPoolSize() {
1448	<	return totalCountOf(workerCounts);
1448	>	return workerCounts >>> TOTAL_COUNT_SHIFT;
1449		}
1450
1451		/**
1452	<	* Returns the maximum number of threads allowed to exist in the
1453	<	* pool, even if there are insufficient unblocked running threads.
1454	<	* @return the maximum
1455	<	*/
759	<	public int getMaximumPoolSize() {
760	<	return maxPoolSize;
761	<	}
762	<
763	<	/**
764	<	* Sets the maximum number of threads allowed to exist in the
765	<	* pool, even if there are insufficient unblocked running threads.
766	<	* Setting this value has no effect on current pool size. It
767	<	* controls construction of new threads.
768	<	* @throws IllegalArgumentException if negative or greater then
769	<	* internal implementation limit.
770	<	*/
771	<	public void setMaximumPoolSize(int newMax) {
772	<	if (newMax < 0 || newMax > MAX_THREADS)
773	<	throw new IllegalArgumentException();
774	<	maxPoolSize = newMax;
775	<	}
776	<
777	<
778	<	/**
779	<	* Returns true if this pool dynamically maintains its target
780	<	* parallelism level. If false, new threads are added only to
781	<	* avoid possible starvation.
782	<	* This setting is by default true;
783	<	* @return true if maintains parallelism
784	<	*/
785	<	public boolean getMaintainsParallelism() {
786	<	return maintainsParallelism;
787	<	}
788	<
789	<	/**
790	<	* Sets whether this pool dynamically maintains its target
791	<	* parallelism level. If false, new threads are added only to
792	<	* avoid possible starvation.
793	<	* @param enable true to maintains parallelism
1452	>	* Returns {@code true} if this pool uses local first-in-first-out
1453	>	* scheduling mode for forked tasks that are never joined.
1454	>	*
1455	>	* @return {@code true} if this pool uses async mode
1456		*/
1457	<	public void setMaintainsParallelism(boolean enable) {
1458	<	maintainsParallelism = enable;
1457	>	public boolean getAsyncMode() {
1458	>	return locallyFifo;
1459		}
1460
1461		/**
1462	<	* Returns the approximate number of worker threads that are not
1463	<	* blocked waiting to join tasks or for other managed
1464	<	* synchronization.
1462	>	* Returns an estimate of the number of worker threads that are
1463	>	* not blocked waiting to join tasks or for other managed
1464	>	* synchronization. This method may overestimate the
1465	>	* number of running threads.
1466		*
1467		* @return the number of worker threads
1468		*/
1469		public int getRunningThreadCount() {
1470	<	return runningCountOf(workerCounts);
1470	>	return workerCounts & RUNNING_COUNT_MASK;
1471		}
1472
1473		/**
1474	<	* Returns the approximate number of threads that are currently
1474	>	* Returns an estimate of the number of threads that are currently
1475		* stealing or executing tasks. This method may overestimate the
1476		* number of active threads.
1477	<	* @return the number of active threads.
1477	>	*
1478	>	* @return the number of active threads
1479		*/
1480		public int getActiveThreadCount() {
1481	<	return activeCountOf(runControl);
1481	>	return runState & ACTIVE_COUNT_MASK;
1482		}
1483
1484		/**
1485	<	* Returns the approximate number of threads that are currently
1486	<	* idle waiting for tasks. This method may underestimate the
1487	<	* number of idle threads.
1488	<	* @return the number of idle threads.
1489	<	*/
1490	<	final int getIdleThreadCount() {
1491	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
1492	<	return (c <= 0)? 0 : c;
1493	<	}
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
1485	>	* Returns {@code true} if all worker threads are currently idle.
1486	>	* An idle worker is one that cannot obtain a task to execute
1487	>	* because none are available to steal from other threads, and
1488	>	* there are no pending submissions to the pool. This method is
1489	>	* conservative; it might not return {@code true} immediately upon
1490	>	* idleness of all threads, but will eventually become true if
1491	>	* threads remain inactive.
1492	>	*
1493	>	* @return {@code true} if all threads are currently idle
1494		*/
1495		public boolean isQuiescent() {
1496	<	return activeCountOf(runControl) == 0;
1496	>	return (runState & ACTIVE_COUNT_MASK) == 0;
1497		}
1498
1499		/**
#	Line 847 | Line 1501 | public class ForkJoinPool extends Abstra
1501		* one thread's work queue by another. The reported value
1502		* underestimates the actual total number of steals when the pool
1503		* is not quiescent. This value may be useful for monitoring and
1504	<	* tuning fork/join programs: In general, steal counts should be
1504	>	* tuning fork/join programs: in general, steal counts should be
1505		* high enough to keep threads busy, but low enough to avoid
1506		* overhead and contention across threads.
1507	<	* @return the number of steals.
1507	>	*
1508	>	* @return the number of steals
1509		*/
1510		public long getStealCount() {
1511	<	return stealCount.get();
1511	>	return stealCount;
1512		}
1513
1514		/**
1515	<	* Accumulate steal count from a worker. Call only
1516	<	* when worker known to be idle.
1517	<	*/
1518	<	private void updateStealCount(ForkJoinWorkerThread w) {
1519	<	int sc = w.getAndClearStealCount();
1520	<	if (sc != 0)
1521	<	stealCount.addAndGet(sc);
1522	<	}
868	<
869	<	/**
870	<	* Returns the total number of tasks currently held in queues by
871	<	* worker threads (but not including tasks submitted to the pool
872	<	* that have not begun executing). This value is only an
873	<	* approximation, obtained by iterating across all threads in the
874	<	* pool. This method may be useful for tuning task granularities.
875	<	* @return the number of queued tasks.
1515	>	* Returns an estimate of the total number of tasks currently held
1516	>	* in queues by worker threads (but not including tasks submitted
1517	>	* to the pool that have not begun executing). This value is only
1518	>	* an approximation, obtained by iterating across all threads in
1519	>	* the pool. This method may be useful for tuning task
1520	>	* granularities.
1521	>	*
1522	>	* @return the number of queued tasks
1523		*/
1524		public long getQueuedTaskCount() {
1525		long count = 0;
1526	<	ForkJoinWorkerThread[] ws = workers;
1527	<	for (int i = 0; i < ws.length; ++i) {
1528	<	ForkJoinWorkerThread t = ws[i];
882	<	if (t != null)
883	<	count += t.getQueueSize();
884	<	}
1526	>	for (ForkJoinWorkerThread w : workers)
1527	>	if (w != null)
1528	>	count += w.getQueueSize();
1529		return count;
1530		}
1531
1532		/**
1533	<	* Returns the approximate number tasks submitted to this pool
1534	<	* that have not yet begun executing. This method takes time
1533	>	* Returns an estimate of the number of tasks submitted to this
1534	>	* pool that have not yet begun executing.  This method takes time
1535		* proportional to the number of submissions.
1536	<	* @return the number of queued submissions.
1536	>	*
1537	>	* @return the number of queued submissions
1538		*/
1539		public int getQueuedSubmissionCount() {
1540		return submissionQueue.size();
1541		}
1542
1543		/**
1544	<	* Returns true if there are any tasks submitted to this pool
1545	<	* that have not yet begun executing.
1546	<	* @return <tt>true</tt> if there are any queued submissions.
1544	>	* Returns {@code true} if there are any tasks submitted to this
1545	>	* pool that have not yet begun executing.
1546	>	*
1547	>	* @return {@code true} if there are any queued submissions
1548		*/
1549		public boolean hasQueuedSubmissions() {
1550		return !submissionQueue.isEmpty();
#	Line 908 | Line 1554 | public class ForkJoinPool extends Abstra
1554		* Removes and returns the next unexecuted submission if one is
1555		* available.  This method may be useful in extensions to this
1556		* class that re-assign work in systems with multiple pools.
1557	<	* @return the next submission, or null if none
1557	>	*
1558	>	* @return the next submission, or {@code null} if none
1559		*/
1560		protected ForkJoinTask<?> pollSubmission() {
1561		return submissionQueue.poll();
1562		}
1563
1564		/**
1565	+	* Removes all available unexecuted submitted and forked tasks
1566	+	* from scheduling queues and adds them to the given collection,
1567	+	* without altering their execution status. These may include
1568	+	* artificially generated or wrapped tasks. This method is
1569	+	* designed to be invoked only when the pool is known to be
1570	+	* quiescent. Invocations at other times may not remove all
1571	+	* tasks. A failure encountered while attempting to add elements
1572	+	* to collection {@code c} may result in elements being in
1573	+	* neither, either or both collections when the associated
1574	+	* exception is thrown.  The behavior of this operation is
1575	+	* undefined if the specified collection is modified while the
1576	+	* operation is in progress.
1577	+	*
1578	+	* @param c the collection to transfer elements into
1579	+	* @return the number of elements transferred
1580	+	*/
1581	+	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1582	+	int count = submissionQueue.drainTo(c);
1583	+	for (ForkJoinWorkerThread w : workers)
1584	+	if (w != null)
1585	+	count += w.drainTasksTo(c);
1586	+	return count;
1587	+	}
1588	+
1589	+	/**
1590		* Returns a string identifying this pool, as well as its state,
1591		* including indications of run state, parallelism level, and
1592		* worker and task counts.
#	Line 922 | Line 1594 | public class ForkJoinPool extends Abstra
1594		* @return a string identifying this pool, as well as its state
1595		*/
1596		public String toString() {
925	–	int ps = parallelism;
926	–	int wc = workerCounts;
927	–	int rc = runControl;
1597		long st = getStealCount();
1598		long qt = getQueuedTaskCount();
1599		long qs = getQueuedSubmissionCount();
1600	+	int wc = workerCounts;
1601	+	int tc = wc >>> TOTAL_COUNT_SHIFT;
1602	+	int rc = wc & RUNNING_COUNT_MASK;
1603	+	int pc = parallelism;
1604	+	int rs = runState;
1605	+	int ac = rs & ACTIVE_COUNT_MASK;
1606		return super.toString() +
1607	<	"[" + runStateToString(runStateOf(rc)) +
1608	<	", parallelism = " + ps +
1609	<	", size = " + totalCountOf(wc) +
1610	<	", active = " + activeCountOf(rc) +
1611	<	", running = " + runningCountOf(wc) +
1607	>	"[" + runLevelToString(rs) +
1608	>	", parallelism = " + pc +
1609	>	", size = " + tc +
1610	>	", active = " + ac +
1611	>	", running = " + rc +
1612		", steals = " + st +
1613		", tasks = " + qt +
1614		", submissions = " + qs +
1615		"]";
1616		}
1617
1618	<	private static String runStateToString(int rs) {
1619	<	switch(rs) {
1620	<	case RUNNING: return "Running";
1621	<	case SHUTDOWN: return "Shutting down";
1622	<	case TERMINATING: return "Terminating";
948	<	case TERMINATED: return "Terminated";
949	<	default: throw new Error("Unknown run state");
950	<	}
1618	>	private static String runLevelToString(int s) {
1619	>	return ((s & TERMINATED) != 0 ? "Terminated" :
1620	>	((s & TERMINATING) != 0 ? "Terminating" :
1621	>	((s & SHUTDOWN) != 0 ? "Shutting down" :
1622	>	"Running")));
1623		}
1624
953	–	// lifecycle control
954	–
1625		/**
1626		* Initiates an orderly shutdown in which previously submitted
1627		* tasks are executed, but no new tasks will be accepted.
1628		* Invocation has no additional effect if already shut down.
1629		* Tasks that are in the process of being submitted concurrently
1630		* during the course of this method may or may not be rejected.
1631	+	*
1632		* @throws SecurityException if a security manager exists and
1633		*         the caller is not permitted to modify threads
1634		*         because it does not hold {@link
1635	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1635	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1636		*/
1637		public void shutdown() {
1638		checkPermission();
1639	<	transitionRunStateTo(SHUTDOWN);
1640	<	if (canTerminateOnShutdown(runControl))
970	<	terminateOnShutdown();
1639	>	advanceRunLevel(SHUTDOWN);
1640	>	tryTerminate(false);
1641		}
1642
1643		/**
1644	<	* Attempts to stop all actively executing tasks, and cancels all
1645	<	* waiting tasks.  Tasks that are in the process of being
1646	<	* submitted or executed concurrently during the course of this
1647	<	* method may or may not be rejected. Unlike some other executors,
1648	<	* this method cancels rather than collects non-executed tasks,
1649	<	* so always returns an empty list.
1644	>	* Attempts to cancel and/or stop all tasks, and reject all
1645	>	* subsequently submitted tasks.  Tasks that are in the process of
1646	>	* being submitted or executed concurrently during the course of
1647	>	* this method may or may not be rejected. This method cancels
1648	>	* both existing and unexecuted tasks, in order to permit
1649	>	* termination in the presence of task dependencies. So the method
1650	>	* always returns an empty list (unlike the case for some other
1651	>	* Executors).
1652	>	*
1653		* @return an empty list
1654		* @throws SecurityException if a security manager exists and
1655		*         the caller is not permitted to modify threads
1656		*         because it does not hold {@link
1657	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1657	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1658		*/
1659		public List<Runnable> shutdownNow() {
1660		checkPermission();
1661	<	terminate();
1661	>	tryTerminate(true);
1662		return Collections.emptyList();
1663		}
1664
1665		/**
1666	<	* Returns <tt>true</tt> if all tasks have completed following shut down.
1666	>	* Returns {@code true} if all tasks have completed following shut down.
1667		*
1668	<	* @return <tt>true</tt> if all tasks have completed following shut down
1668	>	* @return {@code true} if all tasks have completed following shut down
1669		*/
1670		public boolean isTerminated() {
1671	<	return runStateOf(runControl) == TERMINATED;
1671	>	return runState >= TERMINATED;
1672		}
1673
1674		/**
1675	<	* Returns <tt>true</tt> if the process of termination has
1676	<	* commenced but possibly not yet completed.
1675	>	* Returns {@code true} if the process of termination has
1676	>	* commenced but not yet completed.  This method may be useful for
1677	>	* debugging. A return of {@code true} reported a sufficient
1678	>	* period after shutdown may indicate that submitted tasks have
1679	>	* ignored or suppressed interruption, causing this executor not
1680	>	* to properly terminate.
1681		*
1682	<	* @return <tt>true</tt> if terminating
1682	>	* @return {@code true} if terminating but not yet terminated
1683		*/
1684		public boolean isTerminating() {
1685	<	return runStateOf(runControl) >= TERMINATING;
1685	>	return (runState & (TERMINATING|TERMINATED)) == TERMINATING;
1686		}
1687
1688		/**
1689	<	* Returns <tt>true</tt> if this pool has been shut down.
1689	>	* Returns {@code true} if this pool has been shut down.
1690		*
1691	<	* @return <tt>true</tt> if this pool has been shut down
1691	>	* @return {@code true} if this pool has been shut down
1692		*/
1693		public boolean isShutdown() {
1694	<	return runStateOf(runControl) >= SHUTDOWN;
1694	>	return runState >= SHUTDOWN;
1695		}
1696
1697		/**
#	Line 1024 | Line 1701 | public class ForkJoinPool extends Abstra
1701		*
1702		* @param timeout the maximum time to wait
1703		* @param unit the time unit of the timeout argument
1704	<	* @return <tt>true</tt> if this executor terminated and
1705	<	*         <tt>false</tt> if the timeout elapsed before termination
1704	>	* @return {@code true} if this executor terminated and
1705	>	*         {@code false} if the timeout elapsed before termination
1706		* @throws InterruptedException if interrupted while waiting
1707		*/
1708		public boolean awaitTermination(long timeout, TimeUnit unit)
1709		throws InterruptedException {
1033	–	long nanos = unit.toNanos(timeout);
1034	–	final ReentrantLock lock = this.workerLock;
1035	–	lock.lock();
1710		try {
1711	<	for (;;) {
1712	<	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	<	}
1711	>	return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1712	>	} catch (TimeoutException ex) {
1713		return false;
1714		}
1715		}
1716
1717		/**
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	–	/**
1718		* Interface for extending managed parallelism for tasks running
1719	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1720	<	* Method <tt>isReleasable</tt> must return true if blocking is not
1721	<	* necessary. Method <tt>block</tt> blocks the current thread
1722	<	* if necessary (perhaps internally invoking isReleasable before
1723	<	* actually blocking.).
1719	>	* in {@link ForkJoinPool}s.
1720	>	*
1721	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
1722	>	* {@code isReleasable} must return {@code true} if blocking is
1723	>	* not necessary. Method {@code block} blocks the current thread
1724	>	* if necessary (perhaps internally invoking {@code isReleasable}
1725	>	* before actually blocking). The unusual methods in this API
1726	>	* accommodate synchronizers that may, but don't usually, block
1727	>	* for long periods. Similarly, they allow more efficient internal
1728	>	* handling of cases in which additional workers may be, but
1729	>	* usually are not, needed to ensure sufficient parallelism.
1730	>	* Toward this end, implementations of method {@code isReleasable}
1731	>	* must be amenable to repeated invocation.
1732	>	*
1733		* <p>For example, here is a ManagedBlocker based on a
1734		* ReentrantLock:
1735	<	* <pre>
1736	<	*   class ManagedLocker implements ManagedBlocker {
1737	<	*     final ReentrantLock lock;
1738	<	*     boolean hasLock = false;
1739	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1740	<	*     public boolean block() {
1741	<	*        if (!hasLock)
1742	<	*           lock.lock();
1743	<	*        return true;
1744	<	*     }
1745	<	*     public boolean isReleasable() {
1746	<	*        return hasLock || (hasLock = lock.tryLock());
1619	<	*     }
1735	>	*  <pre> {@code
1736	>	* class ManagedLocker implements ManagedBlocker {
1737	>	*   final ReentrantLock lock;
1738	>	*   boolean hasLock = false;
1739	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1740	>	*   public boolean block() {
1741	>	*     if (!hasLock)
1742	>	*       lock.lock();
1743	>	*     return true;
1744	>	*   }
1745	>	*   public boolean isReleasable() {
1746	>	*     return hasLock || (hasLock = lock.tryLock());
1747		*   }
1748	<	* </pre>
1748	>	* }}</pre>
1749	>	*
1750	>	* <p>Here is a class that possibly blocks waiting for an
1751	>	* item on a given queue:
1752	>	*  <pre> {@code
1753	>	* class QueueTaker<E> implements ManagedBlocker {
1754	>	*   final BlockingQueue<E> queue;
1755	>	*   volatile E item = null;
1756	>	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
1757	>	*   public boolean block() throws InterruptedException {
1758	>	*     if (item == null)
1759	>	*       item = queue.take();
1760	>	*     return true;
1761	>	*   }
1762	>	*   public boolean isReleasable() {
1763	>	*     return item != null || (item = queue.poll()) != null;
1764	>	*   }
1765	>	*   public E getItem() { // call after pool.managedBlock completes
1766	>	*     return item;
1767	>	*   }
1768	>	* }}</pre>
1769		*/
1770		public static interface ManagedBlocker {
1771		/**
1772		* Possibly blocks the current thread, for example waiting for
1773		* a lock or condition.
1774	<	* @return true if no additional blocking is necessary (i.e.,
1775	<	* if isReleasable would return true).
1774	>	*
1775	>	* @return {@code true} if no additional blocking is necessary
1776	>	* (i.e., if isReleasable would return true)
1777		* @throws InterruptedException if interrupted while waiting
1778	<	* (the method is not required to do so, but is allowe to).
1778	>	* (the method is not required to do so, but is allowed to)
1779		*/
1780		boolean block() throws InterruptedException;
1781
1782		/**
1783	<	* Returns true if blocking is unnecessary.
1783	>	* Returns {@code true} if blocking is unnecessary.
1784		*/
1785		boolean isReleasable();
1786		}
1787
1788		/**
1789		* Blocks in accord with the given blocker.  If the current thread
1790	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1791	<	* spare thread to be activated if necessary to ensure parallelism
1792	<	* while the current thread is blocked.  If
1793	<	* <tt>maintainParallelism</tt> is true and the pool supports it
1794	<	* (see <tt>getMaintainsParallelism</tt>), this method attempts to
1795	<	* maintain the pool's nominal parallelism. Otherwise if activates
1796	<	* a thread only if necessary to avoid complete starvation. This
1797	<	* option may be preferable when blockages use timeouts, or are
1798	<	* almost always brief.
1799	<	*
1800	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1801	<	* equivalent to
1802	<	* <pre>
1803	<	*   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.
1790	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1791	>	* arranges for a spare thread to be activated if necessary to
1792	>	* ensure sufficient parallelism while the current thread is blocked.
1793	>	*
1794	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1795	>	* behaviorally equivalent to
1796	>	*  <pre> {@code
1797	>	* while (!blocker.isReleasable())
1798	>	*   if (blocker.block())
1799	>	*     return;
1800	>	* }</pre>
1801	>	*
1802	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1803	>	* first be expanded to ensure parallelism, and later adjusted.
1804		*
1805		* @param blocker the blocker
1806	<	* @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.
1806	>	* @throws InterruptedException if blocker.block did so
1807		*/
1808	<	public static void managedBlock(ManagedBlocker blocker,
1670	<	boolean maintainParallelism)
1808	>	public static void managedBlock(ManagedBlocker blocker)
1809		throws InterruptedException {
1810		Thread t = Thread.currentThread();
1811	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1812	<	((ForkJoinWorkerThread)t).pool : null);
1813	<	if (!blocker.isReleasable()) {
1814	<	try {
1815	<	if (pool == null ||
1816	<	!pool.preBlock(blocker, maintainParallelism))
1679	<	awaitBlocker(blocker);
1680	<	} finally {
1681	<	if (pool != null)
1682	<	pool.updateRunningCount(1);
1683	<	}
1811	>	if (t instanceof ForkJoinWorkerThread) {
1812	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
1813	>	w.pool.awaitBlocker(blocker);
1814	>	}
1815	>	else {
1816	>	do {} while (!blocker.isReleasable() && !blocker.block());
1817		}
1818		}
1819
1820	<	private static void awaitBlocker(ManagedBlocker blocker)
1821	<	throws InterruptedException {
1822	<	do;while (!blocker.isReleasable() && !blocker.block());
1820	>	// AbstractExecutorService overrides.  These rely on undocumented
1821	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1822	>	// implement RunnableFuture.
1823	>
1824	>	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1825	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1826		}
1827
1828	+	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1829	+	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1830	+	}
1831
1832	<	// Temporary Unsafe mechanics for preliminary release
1832	>	// Unsafe mechanics
1833
1834	<	static final Unsafe _unsafe;
1835	<	static final long eventCountOffset;
1836	<	static final long workerCountsOffset;
1837	<	static final long runControlOffset;
1838	<	static final long barrierStackOffset;
1839	<	static final long spareStackOffset;
1834	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1835	>	private static final long workerCountsOffset =
1836	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1837	>	private static final long runStateOffset =
1838	>	objectFieldOffset("runState", ForkJoinPool.class);
1839	>	private static final long eventCountOffset =
1840	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1841	>	private static final long eventWaitersOffset =
1842	>	objectFieldOffset("eventWaiters",ForkJoinPool.class);
1843	>	private static final long stealCountOffset =
1844	>	objectFieldOffset("stealCount",ForkJoinPool.class);
1845	>	private static final long spareWaitersOffset =
1846	>	objectFieldOffset("spareWaiters",ForkJoinPool.class);
1847
1848	<	static {
1848	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1849		try {
1850	<	if (ForkJoinPool.class.getClassLoader() != null) {
1851	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1852	<	f.setAccessible(true);
1853	<	_unsafe = (Unsafe)f.get(null);
1854	<	}
1855	<	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);
1850	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1851	>	} catch (NoSuchFieldException e) {
1852	>	// Convert Exception to corresponding Error
1853	>	NoSuchFieldError error = new NoSuchFieldError(field);
1854	>	error.initCause(e);
1855	>	throw error;
1856		}
1857		}
1858
1859	<	private boolean casEventCount(long cmp, long val) {
1860	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1861	<	}
1862	<	private boolean casWorkerCounts(int cmp, int val) {
1863	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1864	<	}
1865	<	private boolean casRunControl(int cmp, int val) {
1866	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1867	<	}
1868	<	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1869	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1870	<	}
1871	<	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1872	<	return _unsafe.compareAndSwapObject(this, barrierStackOffset, cmp, val);
1859	>	/**
1860	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1861	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1862	>	* into a jdk.
1863	>	*
1864	>	* @return a sun.misc.Unsafe
1865	>	*/
1866	>	private static sun.misc.Unsafe getUnsafe() {
1867	>	try {
1868	>	return sun.misc.Unsafe.getUnsafe();
1869	>	} catch (SecurityException se) {
1870	>	try {
1871	>	return java.security.AccessController.doPrivileged
1872	>	(new java.security
1873	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1874	>	public sun.misc.Unsafe run() throws Exception {
1875	>	java.lang.reflect.Field f = sun.misc
1876	>	.Unsafe.class.getDeclaredField("theUnsafe");
1877	>	f.setAccessible(true);
1878	>	return (sun.misc.Unsafe) f.get(null);
1879	>	}});
1880	>	} catch (java.security.PrivilegedActionException e) {
1881	>	throw new RuntimeException("Could not initialize intrinsics",
1882	>	e.getCause());
1883	>	}
1884	>	}
1885		}
1886		}

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