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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.5 by jsr166, Thu Mar 19 05:10:42 2009 UTC vs.
Revision 1.65 by dl, Wed Aug 18 14:05:27 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.locks.*;
11	<	import java.util.concurrent.atomic.*;
12	<	import sun.misc.Unsafe;
13	<	import java.lang.reflect.*;
10	>
11	>	import java.util.ArrayList;
12	>	import java.util.Arrays;
13	>	import java.util.Collection;
14	>	import java.util.Collections;
15	>	import java.util.List;
16	>	import java.util.concurrent.locks.LockSupport;
17	>	import java.util.concurrent.locks.ReentrantLock;
18	>	import java.util.concurrent.atomic.AtomicInteger;
19	>	import java.util.concurrent.CountDownLatch;
20
21		/**
22	<	* An {@link ExecutorService} for running {@link ForkJoinTask}s.  A
23	<	* ForkJoinPool provides the entry point for submissions from
24	<	* non-ForkJoinTasks, as well as management and monitoring operations.
25	<	* Normally a single ForkJoinPool is used for a large number of
20	<	* submitted tasks. Otherwise, use would not usually outweigh the
21	<	* construction and bookkeeping overhead of creating a large set of
22	<	* threads.
22	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
23	>	* A {@code ForkJoinPool} provides the entry point for submissions
24	>	* from non-{@code ForkJoinTask} clients, as well as management and
25	>	* monitoring operations.
26		*
27	<	* <p>ForkJoinPools differ from other kinds of Executors mainly in
28	<	* that they provide <em>work-stealing</em>: all threads in the pool
29	<	* attempt to find and execute subtasks created by other active tasks
30	<	* (eventually blocking if none exist). This makes them efficient when
31	<	* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
32	<	* as the mixed execution of some plain Runnable- or Callable- based
33	<	* activities along with ForkJoinTasks. Otherwise, other
34	<	* ExecutorService implementations are typically more appropriate
35	<	* choices.
27	>	* <p>A {@code ForkJoinPool} differs from other kinds of {@link
28	>	* ExecutorService} mainly by virtue of employing
29	>	* <em>work-stealing</em>: all threads in the pool attempt to find and
30	>	* execute subtasks created by other active tasks (eventually blocking
31	>	* waiting for work if none exist). This enables efficient processing
32	>	* when most tasks spawn other subtasks (as do most {@code
33	>	* ForkJoinTask}s). When setting <em>asyncMode</em> to true in
34	>	* constructors, {@code ForkJoinPool}s may also be appropriate for use
35	>	* with event-style tasks that are never joined.
36		*
37	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
38	<	* (target pool size), which it attempts to maintain by dynamically
39	<	* adding, suspending, or resuming threads, even if some tasks are
40	<	* waiting to join others. However, no such adjustments are performed
41	<	* in the face of blocked IO or other unmanaged synchronization. The
42	<	* nested <code>ManagedBlocker</code> interface enables extension of
43	<	* the kinds of synchronization accommodated.  The target parallelism
44	<	* level may also be changed dynamically (<code>setParallelism</code>)
45	<	* and dynamically thread construction can be limited using methods
43	<	* <code>setMaximumPoolSize</code> and/or
44	<	* <code>setMaintainsParallelism</code>.
37	>	* <p>A {@code ForkJoinPool} is constructed with a given target
38	>	* parallelism level; by default, equal to the number of available
39	>	* processors. The pool attempts to maintain enough active (or
40	>	* available) threads by dynamically adding, suspending, or resuming
41	>	* internal worker threads, even if some tasks are stalled waiting to
42	>	* join others. However, no such adjustments are guaranteed in the
43	>	* face of blocked IO or other unmanaged synchronization. The nested
44	>	* {@link ManagedBlocker} interface enables extension of the kinds of
45	>	* synchronization accommodated.
46		*
47		* <p>In addition to execution and lifecycle control methods, this
48		* class provides status check methods (for example
49	<	* <code>getStealCount</code>) that are intended to aid in developing,
49	>	* {@link #getStealCount}) that are intended to aid in developing,
50		* tuning, and monitoring fork/join applications. Also, method
51	<	* <code>toString</code> returns indications of pool state in a
51	>	* {@link #toString} returns indications of pool state in a
52		* convenient form for informal monitoring.
53		*
54	+	* <p> As is the case with other ExecutorServices, there are three
55	+	* main task execution methods summarized in the following
56	+	* table. These are designed to be used by clients not already engaged
57	+	* in fork/join computations in the current pool.  The main forms of
58	+	* these methods accept instances of {@code ForkJoinTask}, but
59	+	* overloaded forms also allow mixed execution of plain {@code
60	+	* Runnable}- or {@code Callable}- based activities as well.  However,
61	+	* tasks that are already executing in a pool should normally
62	+	* <em>NOT</em> use these pool execution methods, but instead use the
63	+	* within-computation forms listed in the table.
64	+	*
65	+	* <table BORDER CELLPADDING=3 CELLSPACING=1>
66	+	*  <tr>
67	+	*    <td></td>
68	+	*    <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
69	+	*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
70	+	*  </tr>
71	+	*  <tr>
72	+	*    <td> <b>Arange async execution</td>
73	+	*    <td> {@link #execute(ForkJoinTask)}</td>
74	+	*    <td> {@link ForkJoinTask#fork}</td>
75	+	*  </tr>
76	+	*  <tr>
77	+	*    <td> <b>Await and obtain result</td>
78	+	*    <td> {@link #invoke(ForkJoinTask)}</td>
79	+	*    <td> {@link ForkJoinTask#invoke}</td>
80	+	*  </tr>
81	+	*  <tr>
82	+	*    <td> <b>Arrange exec and obtain Future</td>
83	+	*    <td> {@link #submit(ForkJoinTask)}</td>
84	+	*    <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td>
85	+	*  </tr>
86	+	* </table>
87	+	*
88	+	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
89	+	* used for all parallel task execution in a program or subsystem.
90	+	* Otherwise, use would not usually outweigh the construction and
91	+	* bookkeeping overhead of creating a large set of threads. For
92	+	* example, a common pool could be used for the {@code SortTasks}
93	+	* illustrated in {@link RecursiveAction}. Because {@code
94	+	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
95	+	* daemon} mode, there is typically no need to explicitly {@link
96	+	* #shutdown} such a pool upon program exit.
97	+	*
98	+	* <pre>
99	+	* static final ForkJoinPool mainPool = new ForkJoinPool();
100	+	* ...
101	+	* public void sort(long[] array) {
102	+	*   mainPool.invoke(new SortTask(array, 0, array.length));
103	+	* }
104	+	* </pre>
105	+	*
106		* <p><b>Implementation notes</b>: This implementation restricts the
107		* maximum number of running threads to 32767. Attempts to create
108	<	* pools with greater than the maximum result in
109	<	* IllegalArgumentExceptions.
108	>	* pools with greater than the maximum number result in
109	>	* {@code IllegalArgumentException}.
110	>	*
111	>	* <p>This implementation rejects submitted tasks (that is, by throwing
112	>	* {@link RejectedExecutionException}) only when the pool is shut down
113	>	* or internal resources have been exhausted.
114	>	*
115	>	* @since 1.7
116	>	* @author Doug Lea
117		*/
118		public class ForkJoinPool extends AbstractExecutorService {
119
120		/*
121	<	* See the extended comments interspersed below for design,
122	<	* rationale, and walkthroughs.
121	>	* Implementation Overview
122	>	*
123	>	* This class provides the central bookkeeping and control for a
124	>	* set of worker threads: Submissions from non-FJ threads enter
125	>	* into a submission queue. Workers take these tasks and typically
126	>	* split them into subtasks that may be stolen by other workers.
127	>	* The main work-stealing mechanics implemented in class
128	>	* ForkJoinWorkerThread give first priority to processing tasks
129	>	* from their own queues (LIFO or FIFO, depending on mode), then
130	>	* to randomized FIFO steals of tasks in other worker queues, and
131	>	* lastly to new submissions. These mechanics do not consider
132	>	* affinities, loads, cache localities, etc, so rarely provide the
133	>	* best possible performance on a given machine, but portably
134	>	* provide good throughput by averaging over these factors.
135	>	* (Further, even if we did try to use such information, we do not
136	>	* usually have a basis for exploiting it. For example, some sets
137	>	* of tasks profit from cache affinities, but others are harmed by
138	>	* cache pollution effects.)
139	>	*
140	>	* Beyond work-stealing support and essential bookkeeping, the
141	>	* main responsibility of this framework is to take actions when
142	>	* one worker is waiting to join a task stolen (or always held by)
143	>	* another.  Becauae we are multiplexing many tasks on to a pool
144	>	* of workers, we can't just let them block (as in Thread.join).
145	>	* We also cannot just reassign the joiner's run-time stack with
146	>	* another and replace it later, which would be a form of
147	>	* "continuation", that even if possible is not necessarily a good
148	>	* idea. Given that the creation costs of most threads on most
149	>	* systems mainly surrounds setting up runtime stacks, thread
150	>	* creation and switching is usually not much more expensive than
151	>	* stack creation and switching, and is more flexible). Instead we
152	>	* combine two tactics:
153	>	*
154	>	*   Helping: Arranging for the joiner to execute some task that it
155	>	*      would be running if the steal had not occurred.  Method
156	>	*      ForkJoinWorkerThread.helpJoinTask tracks joining->stealing
157	>	*      links to try to find such a task.
158	>	*
159	>	*   Compensating: Unless there are already enough live threads,
160	>	*      method helpMaintainParallelism() may create or or
161	>	*      re-activate a spare thread to compensate for blocked
162	>	*      joiners until they unblock.
163	>	*
164	>	* Because the determining existence of conservatively safe
165	>	* helping targets, the availability of already-created spares,
166	>	* and the apparent need to create new spares are all racy and
167	>	* require heuristic guidance, we rely on multiple retries of
168	>	* each. Further, because it is impossible to keep exactly the
169	>	* target (parallelism) number of threads running at any given
170	>	* time, we allow compensation during joins to fail, and enlist
171	>	* all other threads to help out whenever they are not otherwise
172	>	* occupied (i.e., mainly in method preStep).
173	>	*
174	>	* The ManagedBlocker extension API can't use helping so relies
175	>	* only on compensation in method awaitBlocker.
176	>	*
177	>	* The main throughput advantages of work-stealing stem from
178	>	* decentralized control -- workers mostly steal tasks from each
179	>	* other. We do not want to negate this by creating bottlenecks
180	>	* implementing other management responsibilities. So we use a
181	>	* collection of techniques that avoid, reduce, or cope well with
182	>	* contention. These entail several instances of bit-packing into
183	>	* CASable fields to maintain only the minimally required
184	>	* atomicity. To enable such packing, we restrict maximum
185	>	* parallelism to (1<<15)-1 (enabling twice this (to accommodate
186	>	* unbalanced increments and decrements) to fit into a 16 bit
187	>	* field, which is far in excess of normal operating range.  Even
188	>	* though updates to some of these bookkeeping fields do sometimes
189	>	* contend with each other, they don't normally cache-contend with
190	>	* updates to others enough to warrant memory padding or
191	>	* isolation. So they are all held as fields of ForkJoinPool
192	>	* objects.  The main capabilities are as follows:
193	>	*
194	>	* 1. Creating and removing workers. Workers are recorded in the
195	>	* "workers" array. This is an array as opposed to some other data
196	>	* structure to support index-based random steals by workers.
197	>	* Updates to the array recording new workers and unrecording
198	>	* terminated ones are protected from each other by a lock
199	>	* (workerLock) but the array is otherwise concurrently readable,
200	>	* and accessed directly by workers. To simplify index-based
201	>	* operations, the array size is always a power of two, and all
202	>	* readers must tolerate null slots. Currently, all worker thread
203	>	* creation is on-demand, triggered by task submissions,
204	>	* replacement of terminated workers, and/or compensation for
205	>	* blocked workers. However, all other support code is set up to
206	>	* work with other policies.
207	>	*
208	>	* To ensure that we do not hold on to worker references that
209	>	* would prevent GC, ALL accesses to workers are via indices into
210	>	* the workers array (which is one source of some of the unusual
211	>	* code constructions here). In essence, the workers array serves
212	>	* as a WeakReference mechanism. Thus for example the event queue
213	>	* stores worker indices, not worker references. Access to the
214	>	* workers in associated methods (for example releaseEventWaiters)
215	>	* must both index-check and null-check the IDs. All such accesses
216	>	* ignore bad IDs by returning out early from what they are doing,
217	>	* since this can only be associated with shutdown, in which case
218	>	* it is OK to give up. On termination, we just clobber these
219	>	* data structures without trying to use them.
220	>	*
221	>	* 2. Bookkeeping for dynamically adding and removing workers. We
222	>	* aim to approximately maintain the given level of parallelism.
223	>	* When some workers are known to be blocked (on joins or via
224	>	* ManagedBlocker), we may create or resume others to take their
225	>	* place until they unblock (see below). Implementing this
226	>	* requires counts of the number of "running" threads (i.e., those
227	>	* that are neither blocked nor artifically suspended) as well as
228	>	* the total number.  These two values are packed into one field,
229	>	* "workerCounts" because we need accurate snapshots when deciding
230	>	* to create, resume or suspend.  Note however that the
231	>	* correspondance of these counts to reality is not guaranteed. In
232	>	* particular updates for unblocked threads may lag until they
233	>	* actually wake up.
234	>	*
235	>	* 3. Maintaining global run state. The run state of the pool
236	>	* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to
237	>	* those in other Executor implementations, as well as a count of
238	>	* "active" workers -- those that are, or soon will be, or
239	>	* recently were executing tasks. The runLevel and active count
240	>	* are packed together in order to correctly trigger shutdown and
241	>	* termination. Without care, active counts can be subject to very
242	>	* high contention.  We substantially reduce this contention by
243	>	* relaxing update rules.  A worker must claim active status
244	>	* prospectively, by activating if it sees that a submitted or
245	>	* stealable task exists (it may find after activating that the
246	>	* task no longer exists). It stays active while processing this
247	>	* task (if it exists) and any other local subtasks it produces,
248	>	* until it cannot find any other tasks. It then tries
249	>	* inactivating (see method preStep), but upon update contention
250	>	* instead scans for more tasks, later retrying inactivation if it
251	>	* doesn't find any.
252	>	*
253	>	* 4. Managing idle workers waiting for tasks. We cannot let
254	>	* workers spin indefinitely scanning for tasks when none are
255	>	* available. On the other hand, we must quickly prod them into
256	>	* action when new tasks are submitted or generated.  We
257	>	* park/unpark these idle workers using an event-count scheme.
258	>	* Field eventCount is incremented upon events that may enable
259	>	* workers that previously could not find a task to now find one:
260	>	* Submission of a new task to the pool, or another worker pushing
261	>	* a task onto a previously empty queue.  (We also use this
262	>	* mechanism for configuration and termination actions that
263	>	* require wakeups of idle workers).  Each worker maintains its
264	>	* last known event count, and blocks when a scan for work did not
265	>	* find a task AND its lastEventCount matches the current
266	>	* eventCount. Waiting idle workers are recorded in a variant of
267	>	* Treiber stack headed by field eventWaiters which, when nonzero,
268	>	* encodes the thread index and count awaited for by the worker
269	>	* thread most recently calling eventSync. This thread in turn has
270	>	* a record (field nextEventWaiter) for the next waiting worker.
271	>	* In addition to allowing simpler decisions about need for
272	>	* wakeup, the event count bits in eventWaiters serve the role of
273	>	* tags to avoid ABA errors in Treiber stacks. Upon any wakeup,
274	>	* released threads also try to release others (but give up upon
275	>	* contention to reduce useless flailing).  The net effect is a
276	>	* tree-like diffusion of signals, where released threads (and
277	>	* possibly others) help with unparks.  To further reduce
278	>	* contention effects a bit, failed CASes to increment field
279	>	* 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 is about
284	>	* to block waiting for a join (or via ManagedBlockers), we may
285	>	* create a new thread to maintain parallelism level, or at least
286	>	* avoid starvation. Usually, extra threads are needed for only
287	>	* very short periods, yet join dependencies are such that we
288	>	* sometimes need them in bursts. Rather than create new threads
289	>	* each time this happens, we suspend no-longer-needed extra ones
290	>	* as "spares". For most purposes, we don't distinguish "extra"
291	>	* spare threads from normal "core" threads: On each call to
292	>	* preStep (the only point at which we can do this) a worker
293	>	* checks to see if there are now too many running workers, and if
294	>	* so, suspends itself.  Method helpMaintainParallelism looks for
295	>	* suspended threads to resume before considering creating a new
296	>	* replacement. The spares themselves are encoded on another
297	>	* variant of a Treiber Stack, headed at field "spareWaiters".
298	>	* Note that the use of spares is intrinsically racy.  One thread
299	>	* may become a spare at about the same time as another is
300	>	* needlessly being created. We counteract this and related slop
301	>	* in part by requiring resumed spares to immediately recheck (in
302	>	* preStep) to see whether they they should re-suspend.
303	>	*
304	>	* 6. Killing off unneeded workers. The Spare and Event queues use
305	>	* similar mechanisms to shed unused workers: The oldest (first)
306	>	* waiter uses a timed rather than hard wait. When this wait times
307	>	* out without a normal wakeup, it tries to shutdown any one (for
308	>	* convenience the newest) other waiter via tryShutdownSpare or
309	>	* tryShutdownWaiter, respectively. The wakeup rates for spares
310	>	* are much shorter than for waiters. Together, they will
311	>	* eventually reduce the number of worker threads to a minimum of
312	>	* one after a long enough period 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 impossble
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 the
321	>	* presence of transients 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 some slack in
326	>	* creation thresholds, using rules that reflect the fact that the
327	>	* more threads we have running, the more likely that we are
328	>	* underestimating the number running threads. (We also include
329	>	* some heuristic use of Thread.yield when all workers appear to
330	>	* be busy, to improve likelihood of counts settling.) The rules
331	>	* also better cope with the fact that some of the methods in this
332	>	* class tend to never become compiled (but are interpreted), so
333	>	* some components of the entire set of controls might execute 100
334	>	* times faster than others. And similarly for cases where the
335	>	* apparent lack of work is just due to GC stalls and other
336	>	* transient system activity.
337	>	*
338	>	* Beware that there is a lot of representation-level coupling
339	>	* among classes ForkJoinPool, ForkJoinWorkerThread, and
340	>	* ForkJoinTask.  For example, direct access to "workers" array by
341	>	* workers, and direct access to ForkJoinTask.status by both
342	>	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
343	>	* trying to reduce this, since any associated future changes in
344	>	* representations will need to be accompanied by algorithmic
345	>	* changes anyway.
346	>	*
347	>	* Style notes: There are lots of inline assignments (of form
348	>	* "while ((local = field) != 0)") which are usually the simplest
349	>	* way to ensure the required read orderings (which are sometimes
350	>	* critical). Also several occurrences of the unusual "do {}
351	>	* while(!cas...)" which is the simplest way to force an update of
352	>	* a CAS'ed variable. There are also other coding oddities that
353	>	* help some methods perform reasonably even when interpreted (not
354	>	* compiled), at the expense of some messy constructions that
355	>	* reduce byte code counts.
356	>	*
357	>	* The order of declarations in this file is: (1) statics (2)
358	>	* fields (along with constants used when unpacking some of them)
359	>	* (3) internal control methods (4) callbacks and other support
360	>	* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
361	>	* methods (plus a few little helpers).
362		*/
363
65	–	/** Mask for packing and unpacking shorts */
66	–	private static final int  shortMask = 0xffff;
67	–
68	–	/** Max pool size -- must be a power of two minus 1 */
69	–	private static final int MAX_THREADS =  0x7FFF;
70	–
364		/**
365	<	* Factory for creating new ForkJoinWorkerThreads.  A
366	<	* ForkJoinWorkerThreadFactory must be defined and used for
367	<	* ForkJoinWorkerThread subclasses that extend base functionality
368	<	* or initialize threads with different contexts.
365	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
366	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
367	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
368	>	* functionality or initialize threads with different contexts.
369		*/
370		public static interface ForkJoinWorkerThreadFactory {
371		/**
372		* Returns a new worker thread operating in the given pool.
373		*
374		* @param pool the pool this thread works in
375	<	* @throws NullPointerException if pool is null;
375	>	* @throws NullPointerException if the pool is null
376		*/
377		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
378		}
379
380		/**
381	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
381	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
382		* new ForkJoinWorkerThread.
383		*/
384	<	static class  DefaultForkJoinWorkerThreadFactory
384	>	static class DefaultForkJoinWorkerThreadFactory
385		implements ForkJoinWorkerThreadFactory {
386		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
387	<	try {
95	<	return new ForkJoinWorkerThread(pool);
96	<	} catch (OutOfMemoryError oom)  {
97	<	return null;
98	<	}
387	>	return new ForkJoinWorkerThread(pool);
388		}
389		}
390
#	Line 131 | Line 420 | public class ForkJoinPool extends Abstra
420		new AtomicInteger();
421
422		/**
423	<	* Array holding all worker threads in the pool. Array size must
423	>	* The wakeup interval (in nanoseconds) for the oldest worker
424	>	* worker waiting for an event invokes tryShutdownWaiter to shrink
425	>	* the number of workers.  The exact value does not matter too
426	>	* much, but should be long enough to slowly release resources
427	>	* during long periods without use without disrupting normal use.
428	>	*/
429	>	private static final long SHRINK_RATE_NANOS =
430	>	60L * 1000L * 1000L * 1000L; // one minute
431	>
432	>	/**
433	>	* Absolute bound for parallelism level. Twice this number plus
434	>	* one (i.e., 0xfff) must fit into a 16bit field to enable
435	>	* word-packing for some counts and indices.
436	>	*/
437	>	private static final int MAX_WORKERS   = 0x7fff;
438	>
439	>	/**
440	>	* Array holding all worker threads in the pool.  Array size must
441		* be a power of two.  Updates and replacements are protected by
442	<	* workerLock, but it is always kept in a consistent enough state
443	<	* to be randomly accessed without locking by workers performing
444	<	* work-stealing.
442	>	* workerLock, but the array is always kept in a consistent enough
443	>	* state to be randomly accessed without locking by workers
444	>	* performing work-stealing, as well as other traversal-based
445	>	* methods in this class. All readers must tolerate that some
446	>	* array slots may be null.
447		*/
448		volatile ForkJoinWorkerThread[] workers;
449
450		/**
451	<	* Lock protecting access to workers.
451	>	* Queue for external submissions.
452		*/
453	<	private final ReentrantLock workerLock;
453	>	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
454
455		/**
456	<	* Condition for awaitTermination.
456	>	* Lock protecting updates to workers array.
457		*/
458	<	private final Condition termination;
458	>	private final ReentrantLock workerLock;
459
460		/**
461	<	* The uncaught exception handler used when any worker
154	<	* abrupty terminates
461	>	* Latch released upon termination.
462		*/
463	<	private Thread.UncaughtExceptionHandler ueh;
463	>	private final Phaser termination;
464
465		/**
466		* Creation factory for worker threads.
#	Line 161 | Line 468 | public class ForkJoinPool extends Abstra
468		private final ForkJoinWorkerThreadFactory factory;
469
470		/**
471	<	* Head of stack of threads that were created to maintain
472	<	* parallelism when other threads blocked, but have since
166	<	* suspended when the parallelism level rose.
471	>	* Sum of per-thread steal counts, updated only when threads are
472	>	* idle or terminating.
473		*/
474	<	private volatile WaitQueueNode spareStack;
474	>	private volatile long stealCount;
475
476		/**
477	<	* Sum of per-thread steal counts, updated only when threads are
478	<	* idle or terminating.
477	>	* Encoded record of top of treiber stack of threads waiting for
478	>	* events. The top 32 bits contain the count being waited for. The
479	>	* bottom 16 bits contains one plus the pool index of waiting
480	>	* worker thread. (Bits 16-31 are unused.)
481		*/
482	<	private final AtomicLong stealCount;
482	>	private volatile long eventWaiters;
483	>
484	>	private static final int  EVENT_COUNT_SHIFT = 32;
485	>	private static final long WAITER_ID_MASK    = (1L << 16) - 1L;
486
487		/**
488	<	* Queue for external submissions.
488	>	* A counter for events that may wake up worker threads:
489	>	*   - Submission of a new task to the pool
490	>	*   - A worker pushing a task on an empty queue
491	>	*   - termination
492		*/
493	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
493	>	private volatile int eventCount;
494
495		/**
496	<	* Head of Treiber stack for barrier sync. See below for explanation
496	>	* Encoded record of top of treiber stack of spare threads waiting
497	>	* for resumption. The top 16 bits contain an arbitrary count to
498	>	* avoid ABA effects. The bottom 16bits contains one plus the pool
499	>	* index of waiting worker thread.
500		*/
501	<	private volatile WaitQueueNode syncStack;
501	>	private volatile int spareWaiters;
502	>
503	>	private static final int SPARE_COUNT_SHIFT = 16;
504	>	private static final int SPARE_ID_MASK     = (1 << 16) - 1;
505
506		/**
507	<	* The count for event barrier
507	>	* Lifecycle control. The low word contains the number of workers
508	>	* that are (probably) executing tasks. This value is atomically
509	>	* incremented before a worker gets a task to run, and decremented
510	>	* when worker has no tasks and cannot find any.  Bits 16-18
511	>	* contain runLevel value. When all are zero, the pool is
512	>	* running. Level transitions are monotonic (running -> shutdown
513	>	* -> terminating -> terminated) so each transition adds a bit.
514	>	* These are bundled together to ensure consistent read for
515	>	* termination checks (i.e., that runLevel is at least SHUTDOWN
516	>	* and active threads is zero).
517	>	*
518	>	* Notes: Most direct CASes are dependent on these bitfield
519	>	* positions.  Also, this field is non-private to enable direct
520	>	* performance-sensitive CASes in ForkJoinWorkerThread.
521	>	*/
522	>	volatile int runState;
523	>
524	>	// Note: The order among run level values matters.
525	>	private static final int RUNLEVEL_SHIFT     = 16;
526	>	private static final int SHUTDOWN           = 1 << RUNLEVEL_SHIFT;
527	>	private static final int TERMINATING        = 1 << (RUNLEVEL_SHIFT + 1);
528	>	private static final int TERMINATED         = 1 << (RUNLEVEL_SHIFT + 2);
529	>	private static final int ACTIVE_COUNT_MASK  = (1 << RUNLEVEL_SHIFT) - 1;
530	>
531	>	/**
532	>	* Holds number of total (i.e., created and not yet terminated)
533	>	* and running (i.e., not blocked on joins or other managed sync)
534	>	* threads, packed together to ensure consistent snapshot when
535	>	* making decisions about creating and suspending spare
536	>	* threads. Updated only by CAS. Note that adding a new worker
537	>	* requires incrementing both counts, since workers start off in
538	>	* running state.
539		*/
540	<	private volatile long eventCount;
540	>	private volatile int workerCounts;
541	>
542	>	private static final int TOTAL_COUNT_SHIFT  = 16;
543	>	private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1;
544	>	private static final int ONE_RUNNING        = 1;
545	>	private static final int ONE_TOTAL          = 1 << TOTAL_COUNT_SHIFT;
546
547		/**
548	<	* Pool number, just for assigning useful names to worker threads
548	>	* The target parallelism level.
549	>	* Accessed directly by ForkJoinWorkerThreads.
550		*/
551	<	private final int poolNumber;
551	>	final int parallelism;
552
553		/**
554	<	* The maximum allowed pool size
554	>	* True if use local fifo, not default lifo, for local polling
555	>	* Read by, and replicated by ForkJoinWorkerThreads
556		*/
557	<	private volatile int maxPoolSize;
557	>	final boolean locallyFifo;
558
559		/**
560	<	* The desired parallelism level, updated only under workerLock.
560	>	* The uncaught exception handler used when any worker abruptly
561	>	* terminates.
562		*/
563	<	private volatile int parallelism;
563	>	private final Thread.UncaughtExceptionHandler ueh;
564
565		/**
566	<	* Holds number of total (i.e., created and not yet terminated)
208	<	* and running (i.e., not blocked on joins or other managed sync)
209	<	* threads, packed into one int to ensure consistent snapshot when
210	<	* making decisions about creating and suspending spare
211	<	* threads. Updated only by CAS.  Note: CASes in
212	<	* updateRunningCount and preJoin running active count is in low
213	<	* word, so need to be modified if this changes
566	>	* Pool number, just for assigning useful names to worker threads
567		*/
568	<	private volatile int workerCounts;
568	>	private final int poolNumber;
569	>
570
571	<	private static int totalCountOf(int s)           { return s >>> 16;  }
572	<	private static int runningCountOf(int s)         { return s & shortMask; }
219	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
571	>	// Utilities for CASing fields. Note that most of these
572	>	// are usually manually inlined by callers
573
574		/**
575	<	* Add delta (which may be negative) to running count.  This must
223	<	* 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
575	>	* Increments running count part of workerCounts
576		*/
577	<	final void updateRunningCount(int delta) {
578	<	int s;
579	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
577	>	final void incrementRunningCount() {
578	>	int c;
579	>	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
580	>	c = workerCounts,
581	>	c + ONE_RUNNING));
582		}
583
584		/**
585	<	* Add delta (which may be negative) to both total and running
234	<	* count.  This must be called upon creation and termination of
235	<	* worker threads.
236	<	* @param delta the number to add
585	>	* Tries to decrement running count unless already zero
586		*/
587	<	private void updateWorkerCount(int delta) {
588	<	int d = delta + (delta << 16); // add to both lo and hi parts
589	<	int s;
590	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
587	>	final boolean tryDecrementRunningCount() {
588	>	int wc = workerCounts;
589	>	if ((wc & RUNNING_COUNT_MASK) == 0)
590	>	return false;
591	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
592	>	wc, wc - ONE_RUNNING);
593		}
594
595		/**
596	<	* Lifecycle control. High word contains runState, low word
597	<	* contains the number of workers that are (probably) executing
598	<	* tasks. This value is atomically incremented before a worker
599	<	* gets a task to run, and decremented when worker has no tasks
600	<	* 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
596	>	* Forces decrement of encoded workerCounts, awaiting nonzero if
597	>	* (rarely) necessary when other count updates lag.
598	>	*
599	>	* @param dr -- either zero or ONE_RUNNING
600	>	* @param dt == either zero or ONE_TOTAL
601		*/
602	<	private volatile int runControl;
603	<
604	<	// RunState values. Order among values matters
605	<	private static final int RUNNING     = 0;
606	<	private static final int SHUTDOWN    = 1;
607	<	private static final int TERMINATING = 2;
608	<	private static final int TERMINATED  = 3;
609	<
610	<	private static int runStateOf(int c)             { return c >>> 16; }
611	<	private static int activeCountOf(int c)          { return c & shortMask; }
612	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
602	>	private void decrementWorkerCounts(int dr, int dt) {
603	>	for (;;) {
604	>	int wc = workerCounts;
605	>	if ((wc & RUNNING_COUNT_MASK)  - dr < 0 ||
606	>	(wc >>> TOTAL_COUNT_SHIFT) - dt < 0) {
607	>	if ((runState & TERMINATED) != 0)
608	>	return; // lagging termination on a backout
609	>	Thread.yield();
610	>	}
611	>	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
612	>	wc, wc - (dr + dt)))
613	>	return;
614	>	}
615	>	}
616
617		/**
618	<	* Try incrementing active count; fail on contention. Called by
268	<	* workers before/during executing tasks.
269	<	* @return true on success;
618	>	* Increments event count
619		*/
620	<	final boolean tryIncrementActiveCount() {
621	<	int c = runControl;
622	<	return casRunControl(c, c+1);
620	>	private void advanceEventCount() {
621	>	int c;
622	>	do {} while(!UNSAFE.compareAndSwapInt(this, eventCountOffset,
623	>	c = eventCount, c+1));
624		}
625
626		/**
627	<	* Try decrementing active count; fail on contention.
628	<	* Possibly trigger termination on success
629	<	* Called by workers when they can't find tasks.
627	>	* Tries incrementing active count; fails on contention.
628	>	* Called by workers before executing tasks.
629	>	*
630		* @return true on success
631		*/
632	<	final boolean tryDecrementActiveCount() {
633	<	int c = runControl;
634	<	int nextc = c - 1;
635	<	if (!casRunControl(c, nextc))
286	<	return false;
287	<	if (canTerminateOnShutdown(nextc))
288	<	terminateOnShutdown();
289	<	return true;
632	>	final boolean tryIncrementActiveCount() {
633	>	int c;
634	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
635	>	c = runState, c + 1);
636		}
637
638		/**
639	<	* Return true if argument represents zero active count and
640	<	* nonzero runstate, which is the triggering condition for
295	<	* terminating on shutdown.
639	>	* Tries decrementing active count; fails on contention.
640	>	* Called when workers cannot find tasks to run.
641		*/
642	<	private static boolean canTerminateOnShutdown(int c) {
643	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
642	>	final boolean tryDecrementActiveCount() {
643	>	int c;
644	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
645	>	c = runState, c - 1);
646		}
647
648		/**
649	<	* Transition run state to at least the given state. Return true
650	<	* if not already at least given state.
649	>	* Advances to at least the given level. Returns true if not
650	>	* already in at least the given level.
651		*/
652	<	private boolean transitionRunStateTo(int state) {
652	>	private boolean advanceRunLevel(int level) {
653		for (;;) {
654	<	int c = runControl;
655	<	if (runStateOf(c) >= state)
654	>	int s = runState;
655	>	if ((s & level) != 0)
656		return false;
657	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
657	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level))
658		return true;
659		}
660		}
661
662	+	// workers array maintenance
663	+
664	+	/**
665	+	* Records and returns a workers array index for new worker.
666	+	*/
667	+	private int recordWorker(ForkJoinWorkerThread w) {
668	+	// Try using slot totalCount-1. If not available, scan and/or resize
669	+	int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1;
670	+	final ReentrantLock lock = this.workerLock;
671	+	lock.lock();
672	+	try {
673	+	ForkJoinWorkerThread[] ws = workers;
674	+	int n = ws.length;
675	+	if (k < 0 || k >= n || ws[k] != null) {
676	+	for (k = 0; k < n && ws[k] != null; ++k)
677	+	;
678	+	if (k == n)
679	+	ws = Arrays.copyOf(ws, n << 1);
680	+	}
681	+	ws[k] = w;
682	+	workers = ws; // volatile array write ensures slot visibility
683	+	} finally {
684	+	lock.unlock();
685	+	}
686	+	return k;
687	+	}
688	+
689		/**
690	<	* Controls whether to add spares to maintain parallelism
690	>	* Nulls out record of worker in workers array
691		*/
692	<	private volatile boolean maintainsParallelism;
692	>	private void forgetWorker(ForkJoinWorkerThread w) {
693	>	int idx = w.poolIndex;
694	>	// Locking helps method recordWorker avoid unecessary expansion
695	>	final ReentrantLock lock = this.workerLock;
696	>	lock.lock();
697	>	try {
698	>	ForkJoinWorkerThread[] ws = workers;
699	>	if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify
700	>	ws[idx] = null;
701	>	} finally {
702	>	lock.unlock();
703	>	}
704	>	}
705
706	<	// Constructors
706	>	// adding and removing workers
707
708		/**
709	<	* Creates a ForkJoinPool with a pool size equal to the number of
710	<	* processors available on the system and using the default
711	<	* ForkJoinWorkerThreadFactory,
712	<	* @throws SecurityException if a security manager exists and
713	<	*         the caller is not permitted to modify threads
328	<	*         because it does not hold {@link
329	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
709	>	* Tries to create and add new worker. Assumes that worker counts
710	>	* are already updated to accommodate the worker, so adjusts on
711	>	* failure.
712	>	*
713	>	* @return the worker, or null on failure
714		*/
715	<	public ForkJoinPool() {
716	<	this(Runtime.getRuntime().availableProcessors(),
717	<	defaultForkJoinWorkerThreadFactory);
715	>	private ForkJoinWorkerThread addWorker() {
716	>	ForkJoinWorkerThread w = null;
717	>	try {
718	>	w = factory.newThread(this);
719	>	} finally { // Adjust on either null or exceptional factory return
720	>	if (w == null) {
721	>	decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL);
722	>	tryTerminate(false); // in case of failure during shutdown
723	>	}
724	>	}
725	>	if (w != null) {
726	>	w.start(recordWorker(w), ueh);
727	>	advanceEventCount();
728	>	}
729	>	return w;
730		}
731
732		/**
733	<	* Creates a ForkJoinPool with the indicated parellelism level
734	<	* threads, and using the default ForkJoinWorkerThreadFactory,
735	<	* @param parallelism the number of worker threads
736	<	* @throws IllegalArgumentException if parallelism less than or
737	<	* equal to zero
342	<	* @throws SecurityException if a security manager exists and
343	<	*         the caller is not permitted to modify threads
344	<	*         because it does not hold {@link
345	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
733	>	* Final callback from terminating worker.  Removes record of
734	>	* worker from array, and adjusts counts. If pool is shutting
735	>	* down, tries to complete terminatation.
736	>	*
737	>	* @param w the worker
738		*/
739	<	public ForkJoinPool(int parallelism) {
740	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
739	>	final void workerTerminated(ForkJoinWorkerThread w) {
740	>	forgetWorker(w);
741	>	decrementWorkerCounts(w.isTrimmed()? 0 : ONE_RUNNING, ONE_TOTAL);
742	>	while (w.stealCount != 0) // collect final count
743	>	tryAccumulateStealCount(w);
744	>	tryTerminate(false);
745	>	}
746	>
747	>	// Waiting for and signalling events
748	>
749	>	/**
750	>	* Releases workers blocked on a count not equal to current count.
751	>	* Normally called after precheck that eventWaiters isn't zero to
752	>	* avoid wasted array checks. Gives up upon a change in count or
753	>	* contention, letting other workers take over.
754	>	*/
755	>	private void releaseEventWaiters() {
756	>	ForkJoinWorkerThread[] ws = workers;
757	>	int n = ws.length;
758	>	long h = eventWaiters;
759	>	int ec = eventCount;
760	>	ForkJoinWorkerThread w; int id;
761	>	while ((int)(h >>> EVENT_COUNT_SHIFT) != ec &&
762	>	(id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 &&
763	>	id < n && (w = ws[id]) != null &&
764	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
765	>	h,  h = w.nextWaiter)) {
766	>	LockSupport.unpark(w);
767	>	if (eventWaiters != h || eventCount != ec)
768	>	break;
769	>	}
770		}
771
772		/**
773	<	* Creates a ForkJoinPool with parallelism equal to the number of
774	<	* processors available on the system and using the given
354	<	* ForkJoinWorkerThreadFactory,
355	<	* @param factory the factory for creating new threads
356	<	* @throws NullPointerException if factory is null
357	<	* @throws SecurityException if a security manager exists and
358	<	*         the caller is not permitted to modify threads
359	<	*         because it does not hold {@link
360	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
773	>	* Tries to advance eventCount and releases waiters. Called only
774	>	* from workers.
775		*/
776	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
777	<	this(Runtime.getRuntime().availableProcessors(), factory);
776	>	final void signalWork() {
777	>	int c; // try to increment event count -- CAS failure OK
778	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
779	>	if (eventWaiters != 0L)
780	>	releaseEventWaiters();
781		}
782
783		/**
784	<	* Creates a ForkJoinPool with the given parallelism and factory.
784	>	* Adds the given worker to event queue and blocks until
785	>	* terminating or event count advances from the workers
786	>	* lastEventCount value
787		*
788	<	* @param parallelism the targeted number of worker threads
370	<	* @param factory the factory for creating new threads
371	<	* @throws IllegalArgumentException if parallelism less than or
372	<	* equal to zero, or greater than implementation limit.
373	<	* @throws NullPointerException if factory is null
374	<	* @throws SecurityException if a security manager exists and
375	<	*         the caller is not permitted to modify threads
376	<	*         because it does not hold {@link
377	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
788	>	* @param w the calling worker thread
789		*/
790	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
791	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
792	<	throw new IllegalArgumentException();
793	<	if (factory == null)
794	<	throw new NullPointerException();
795	<	checkPermission();
796	<	this.factory = factory;
797	<	this.parallelism = parallelism;
798	<	this.maxPoolSize = MAX_THREADS;
799	<	this.maintainsParallelism = true;
800	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
801	<	this.workerLock = new ReentrantLock();
802	<	this.termination = workerLock.newCondition();
803	<	this.stealCount = new AtomicLong();
393	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
394	<	createAndStartInitialWorkers(parallelism);
790	>	private void eventSync(ForkJoinWorkerThread w) {
791	>	int ec = w.lastEventCount;
792	>	long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1));
793	>	long h;
794	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
795	>	(((int)((h = eventWaiters) & WAITER_ID_MASK)) == 0 ||
796	>	(int)(h >>> EVENT_COUNT_SHIFT) == ec) &&
797	>	eventCount == ec) {
798	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
799	>	w.nextWaiter = h, nh)) {
800	>	awaitEvent(w, ec);
801	>	break;
802	>	}
803	>	}
804		}
805
806		/**
807	<	* Create new worker using factory.
808	<	* @param index the index to assign worker
809	<	* @return new worker, or null of factory failed
807	>	* Blocks the given worker (that has already been entered as an
808	>	* event waiter) until terminating or event count advances from
809	>	* the given value. The oldest (first) waiter uses a timed wait to
810	>	* occasionally one-by-one shrink the number of workers (to a
811	>	* minumum of one) if the pool has not been used for extended
812	>	* periods.
813	>	*
814	>	* @param w the calling worker thread
815	>	* @param ec the count
816		*/
817	<	private ForkJoinWorkerThread createWorker(int index) {
818	<	Thread.UncaughtExceptionHandler h = ueh;
819	<	ForkJoinWorkerThread w = factory.newThread(this);
820	<	if (w != null) {
821	<	w.poolIndex = index;
822	<	w.setDaemon(true);
823	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
824	<	if (h != null)
825	<	w.setUncaughtExceptionHandler(h);
817	>	private void awaitEvent(ForkJoinWorkerThread w, int ec) {
818	>	while (eventCount == ec) {
819	>	if (tryAccumulateStealCount(w)) { // transfer while idle
820	>	boolean untimed = (w.nextWaiter != 0L ||
821	>	(workerCounts & RUNNING_COUNT_MASK) <= 1);
822	>	long startTime = untimed? 0 : System.nanoTime();
823	>	Thread.interrupted();         // clear/ignore interrupt
824	>	if (eventCount != ec || !w.isRunning() ||
825	>	runState >= TERMINATING)  // recheck after clear
826	>	break;
827	>	if (untimed)
828	>	LockSupport.park(w);
829	>	else {
830	>	LockSupport.parkNanos(w, SHRINK_RATE_NANOS);
831	>	if (eventCount != ec || !w.isRunning() ||
832	>	runState >= TERMINATING)
833	>	break;
834	>	if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS)
835	>	tryShutdownWaiter(ec);
836	>	}
837	>	}
838		}
412	–	return w;
839		}
840
841		/**
842	<	* Return a good size for worker array given pool size.
843	<	* Currently requires size to be a power of two.
842	>	* Callback from the oldest waiter in awaitEvent waking up after a
843	>	* period of non-use. Tries (once) to shutdown an event waiter (or
844	>	* a spare, if one exists). Note that we don't need CAS or locks
845	>	* here because the method is called only from one thread
846	>	* occasionally waking (and even misfires are OK). Note that
847	>	* until the shutdown worker fully terminates, workerCounts
848	>	* will overestimate total count, which is tolerable.
849	>	*
850	>	* @param ec the event count waited on by caller (to abort
851	>	* attempt if count has since changed).
852		*/
853	<	private static int arraySizeFor(int ps) {
854	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
853	>	private void tryShutdownWaiter(int ec) {
854	>	if (spareWaiters != 0) { // prefer killing spares
855	>	tryShutdownSpare();
856	>	return;
857	>	}
858	>	ForkJoinWorkerThread[] ws = workers;
859	>	int n = ws.length;
860	>	long h = eventWaiters;
861	>	ForkJoinWorkerThread w; int id; long nh;
862	>	if (runState == 0 &&
863	>	submissionQueue.isEmpty() &&
864	>	eventCount == ec &&
865	>	(id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 &&
866	>	id < n && (w = ws[id]) != null &&
867	>	(nh = w.nextWaiter) != 0L && // keep at least one worker
868	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh)) {
869	>	w.shutdown();
870	>	LockSupport.unpark(w);
871	>	}
872	>	releaseEventWaiters();
873		}
874
875	+	// Maintaining spares
876	+
877		/**
878	<	* Create or resize array if necessary to hold newLength
425	<	* @return the array
878	>	* Pushes worker onto the spare stack
879		*/
880	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
881	<	ForkJoinWorkerThread[] ws = workers;
882	<	if (ws == null)
883	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
431	<	else if (newLength > ws.length)
432	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
433	<	else
434	<	return ws;
880	>	final void pushSpare(ForkJoinWorkerThread w) {
881	>	int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1);
882	>	do {} while (!UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
883	>	w.nextSpare = spareWaiters,ns));
884		}
885
886		/**
887	<	* Try to shrink workers into smaller array after one or more terminate
887	>	* Callback from oldest spare occasionally waking up.  Tries
888	>	* (once) to shutdown a spare. Same idea as tryShutdownWaiter.
889		*/
890	<	private void tryShrinkWorkerArray() {
890	>	final void tryShutdownSpare() {
891	>	int sw, id;
892	>	ForkJoinWorkerThread w;
893	>	ForkJoinWorkerThread[] ws;
894	>	if ((id = ((sw = spareWaiters) & SPARE_ID_MASK) - 1) >= 0 &&
895	>	id < (ws = workers).length && (w = ws[id]) != null &&
896	>	(workerCounts & RUNNING_COUNT_MASK) >= parallelism &&
897	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
898	>	sw, w.nextSpare)) {
899	>	w.shutdown();
900	>	LockSupport.unpark(w);
901	>	advanceEventCount();
902	>	}
903	>	}
904	>
905	>	/**
906	>	* Tries (once) to resume a spare if worker counts match
907	>	* the given count.
908	>	*
909	>	* @param wc workerCounts value on invocation of this method
910	>	*/
911	>	private void tryResumeSpare(int wc) {
912		ForkJoinWorkerThread[] ws = workers;
913	<	int len = ws.length;
914	<	int last = len - 1;
915	<	while (last >= 0 && ws[last] == null)
916	<	--last;
917	<	int newLength = arraySizeFor(last+1);
918	<	if (newLength < len)
919	<	workers = Arrays.copyOf(ws, newLength);
913	>	int n = ws.length;
914	>	int sw, id, rs;  ForkJoinWorkerThread w;
915	>	if ((id = ((sw = spareWaiters) & SPARE_ID_MASK) - 1) >= 0 &&
916	>	id < n && (w = ws[id]) != null &&
917	>	(rs = runState) < TERMINATING &&
918	>	eventWaiters == 0L && workerCounts == wc) {
919	>	// In case all workers busy, heuristically back off to let settle
920	>	Thread.yield();
921	>	if (eventWaiters == 0L && runState == rs && // recheck
922	>	workerCounts == wc && spareWaiters == sw &&
923	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
924	>	sw, w.nextSpare)) {
925	>	int c;              // increment running count before resume
926	>	do {} while(!UNSAFE.compareAndSwapInt
927	>	(this, workerCountsOffset,
928	>	c = workerCounts, c + ONE_RUNNING));
929	>	if (w.tryUnsuspend())
930	>	LockSupport.unpark(w);
931	>	else               // back out if w was shutdown
932	>	decrementWorkerCounts(ONE_RUNNING, 0);
933	>	}
934	>	}
935	>	}
936	>
937	>	// adding workers on demand
938	>
939	>	/**
940	>	* Adds one or more workers if needed to establish target parallelism.
941	>	* Retries upon contention.
942	>	*/
943	>	private void addWorkerIfBelowTarget() {
944	>	int pc = parallelism;
945	>	int wc;
946	>	while (((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < pc &&
947	>	runState < TERMINATING) {
948	>	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
949	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
950	>	if (addWorker() == null)
951	>	break;
952	>	}
953	>	}
954		}
955
956		/**
957	<	* Initial worker array and worker creation and startup. (This
958	<	* must be done under lock to avoid interference by some of the
959	<	* newly started threads while creating others.)
957	>	* Tries (once) to add a new worker if all existing workers are
958	>	* busy, and there are either no running workers or the deficit is
959	>	* at least twice the surplus.
960	>	*
961	>	* @param wc workerCounts value on invocation of this method
962		*/
963	<	private void createAndStartInitialWorkers(int ps) {
964	<	final ReentrantLock lock = this.workerLock;
965	<	lock.lock();
966	<	try {
967	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
968	<	for (int i = 0; i < ps; ++i) {
969	<	ForkJoinWorkerThread w = createWorker(i);
970	<	if (w != null) {
971	<	ws[i] = w;
972	<	w.start();
973	<	updateWorkerCount(1);
963	>	private void tryAddWorkerIfBusy(int wc) {
964	>	int tc, rc, rs;
965	>	int pc = parallelism;
966	>	if ((tc = wc >>> TOTAL_COUNT_SHIFT) < MAX_WORKERS &&
967	>	((rc = wc & RUNNING_COUNT_MASK) == 0 ||
968	>	rc < pc - ((tc - pc) << 1)) &&
969	>	(rs = runState) < TERMINATING &&
970	>	(rs & ACTIVE_COUNT_MASK) == tc) {
971	>	// Since all workers busy, heuristically back off to let settle
972	>	Thread.yield();
973	>	if (eventWaiters == 0L && spareWaiters == 0 && // recheck
974	>	runState == rs && workerCounts == wc &&
975	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
976	>	wc + (ONE_RUNNING|ONE_TOTAL)))
977	>	addWorker();
978	>	}
979	>	}
980	>
981	>	/**
982	>	* Does at most one of:
983	>	*
984	>	* 1. Help wake up existing workers waiting for work via
985	>	*    releaseEventWaiters. (If any exist, then it doesn't
986	>	*    matter right now if under target parallelism level.)
987	>	*
988	>	* 2. If a spare exists, try (once) to resume it via tryResumeSpare.
989	>	*
990	>	* 3. If there are not enough total workers, add some
991	>	*    via addWorkerIfBelowTarget;
992	>	*
993	>	* 4. Try (once) to add a new worker if all existing workers
994	>	*     are busy, via tryAddWorkerIfBusy
995	>	*/
996	>	private void helpMaintainParallelism() {
997	>	long h; int pc, wc;
998	>	if (((int)((h = eventWaiters) & WAITER_ID_MASK)) != 0) {
999	>	if ((int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1000	>	releaseEventWaiters(); // avoid useless call
1001	>	}
1002	>	else if ((pc = parallelism) >
1003	>	((wc = workerCounts) & RUNNING_COUNT_MASK)) {
1004	>	if (spareWaiters != 0)
1005	>	tryResumeSpare(wc);
1006	>	else if ((wc >>> TOTAL_COUNT_SHIFT) < pc)
1007	>	addWorkerIfBelowTarget();
1008	>	else
1009	>	tryAddWorkerIfBusy(wc);
1010	>	}
1011	>	}
1012	>
1013	>	/**
1014	>	* Callback from workers invoked upon each top-level action (i.e.,
1015	>	* stealing a task or taking a submission and running it).
1016	>	* Performs one or more of the following:
1017	>	*
1018	>	* 1. If the worker is active, try to set its active status to
1019	>	*    inactive and update activeCount. On contention, we may try
1020	>	*    again on this or subsequent call.
1021	>	*
1022	>	* 2. Release any existing event waiters that are now relesable
1023	>	*
1024	>	* 3. If there are too many running threads, suspend this worker
1025	>	*    (first forcing inactive if necessary).  If it is not
1026	>	*    needed, it may be killed while suspended via
1027	>	*    tryShutdownSpare. Otherwise, upon resume it rechecks to make
1028	>	*    sure that it is still needed.
1029	>	*
1030	>	* 4. If more than 1 miss, await the next task event via
1031	>	*    eventSync (first forcing inactivation if necessary), upon
1032	>	*    which worker may also be killed, via tryShutdownWaiter.
1033	>	*
1034	>	* 5. Help reactivate other workers via helpMaintainParallelism
1035	>	*
1036	>	* @param w the worker
1037	>	* @param misses the number of scans by caller failing to find work
1038	>	* (saturating at 2 to avoid wraparound)
1039	>	*/
1040	>	final void preStep(ForkJoinWorkerThread w, int misses) {
1041	>	boolean active = w.active;
1042	>	int pc = parallelism;
1043	>	for (;;) {
1044	>	int rs, wc, rc, ec; long h;
1045	>	if (active && UNSAFE.compareAndSwapInt(this, runStateOffset,
1046	>	rs = runState, rs - 1))
1047	>	active = w.active = false;
1048	>	if (((int)((h = eventWaiters) & WAITER_ID_MASK)) != 0 &&
1049	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount) {
1050	>	releaseEventWaiters();
1051	>	if (misses > 1)
1052	>	continue;                  // clear before sync below
1053	>	}
1054	>	if ((rc = ((wc = workerCounts) & RUNNING_COUNT_MASK)) > pc) {
1055	>	if (!active &&                 // must inactivate to suspend
1056	>	workerCounts == wc &&      // try to suspend as spare
1057	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1058	>	wc, wc - ONE_RUNNING)) {
1059	>	w.suspendAsSpare();
1060	>	if (!w.isRunning())
1061	>	break;                 // was killed while spare
1062		}
1063	+	continue;
1064		}
1065	<	} finally {
1066	<	lock.unlock();
1065	>	if (misses > 0) {
1066	>	if ((ec = eventCount) == w.lastEventCount && misses > 1) {
1067	>	if (!active) {             // must inactivate to sync
1068	>	eventSync(w);
1069	>	if (w.isRunning())
1070	>	misses = 1;        // don't re-sync
1071	>	else
1072	>	break;             // was killed while waiting
1073	>	}
1074	>	continue;
1075	>	}
1076	>	w.lastEventCount = ec;
1077	>	}
1078	>	if (rc < pc)
1079	>	helpMaintainParallelism();
1080	>	break;
1081		}
1082		}
1083
1084		/**
1085	<	* Worker creation and startup for threads added via setParallelism.
1085	>	* Helps and/or blocks awaiting join of the given task.
1086	>	* Alternates between helpJoinTask() and helpMaintainParallelism()
1087	>	* as many times as there is a deficit in running count (or longer
1088	>	* if running count would become zero), then blocks if task still
1089	>	* not done.
1090	>	*
1091	>	* @param joinMe the task to join
1092		*/
1093	<	private void createAndStartAddedWorkers() {
1094	<	resumeAllSpares();  // Allow spares to convert to nonspare
1095	<	int ps = parallelism;
1096	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1097	<	int len = ws.length;
1098	<	// Sweep through slots, to keep lowest indices most populated
1099	<	int k = 0;
1100	<	while (k < len) {
1101	<	if (ws[k] != null) {
1102	<	++k;
1103	<	continue;
1093	>	final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker) {
1094	>	int threshold = parallelism;         // descend blocking thresholds
1095	>	while (joinMe.status >= 0) {
1096	>	boolean block; int wc;
1097	>	worker.helpJoinTask(joinMe);
1098	>	if (joinMe.status < 0)
1099	>	break;
1100	>	if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= threshold) {
1101	>	if (threshold > 0)
1102	>	--threshold;
1103	>	else
1104	>	advanceEventCount(); // force release
1105	>	block = false;
1106		}
1107	<	int s = workerCounts;
1108	<	int tc = totalCountOf(s);
1109	<	int rc = runningCountOf(s);
1110	<	if (rc >= ps || tc >= ps)
1107	>	else
1108	>	block = UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1109	>	wc, wc - ONE_RUNNING);
1110	>	helpMaintainParallelism();
1111	>	if (block) {
1112	>	int c;
1113	>	joinMe.internalAwaitDone();
1114	>	do {} while (!UNSAFE.compareAndSwapInt
1115	>	(this, workerCountsOffset,
1116	>	c = workerCounts, c + ONE_RUNNING));
1117		break;
1118	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
1119	<	ForkJoinWorkerThread w = createWorker(k);
1120	<	if (w != null) {
1121	<	ws[k++] = w;
1122	<	w.start();
1118	>	}
1119	>	}
1120	>	}
1121	>
1122	>	/**
1123	>	* Same idea as awaitJoin, but no helping
1124	>	*/
1125	>	final void awaitBlocker(ManagedBlocker blocker)
1126	>	throws InterruptedException {
1127	>	int threshold = parallelism;
1128	>	while (!blocker.isReleasable()) {
1129	>	boolean block; int wc;
1130	>	if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= threshold) {
1131	>	if (threshold > 0)
1132	>	--threshold;
1133	>	else
1134	>	advanceEventCount();
1135	>	block = false;
1136	>	}
1137	>	else
1138	>	block = UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1139	>	wc, wc - ONE_RUNNING);
1140	>	helpMaintainParallelism();
1141	>	if (block) {
1142	>	try {
1143	>	do {} while (!blocker.isReleasable() && !blocker.block());
1144	>	} finally {
1145	>	int c;
1146	>	do {} while (!UNSAFE.compareAndSwapInt
1147	>	(this, workerCountsOffset,
1148	>	c = workerCounts, c + ONE_RUNNING));
1149		}
1150	<	else {
1151	<	updateWorkerCount(-1); // back out on failed creation
1152	<	break;
1150	>	break;
1151	>	}
1152	>	}
1153	>	}
1154	>
1155	>	/**
1156	>	* Possibly initiates and/or completes termination.
1157	>	*
1158	>	* @param now if true, unconditionally terminate, else only
1159	>	* if shutdown and empty queue and no active workers
1160	>	* @return true if now terminating or terminated
1161	>	*/
1162	>	private boolean tryTerminate(boolean now) {
1163	>	if (now)
1164	>	advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN
1165	>	else if (runState < SHUTDOWN ||
1166	>	!submissionQueue.isEmpty() ||
1167	>	(runState & ACTIVE_COUNT_MASK) != 0)
1168	>	return false;
1169	>
1170	>	if (advanceRunLevel(TERMINATING))
1171	>	startTerminating();
1172	>
1173	>	// Finish now if all threads terminated; else in some subsequent call
1174	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1175	>	advanceRunLevel(TERMINATED);
1176	>	termination.arrive();
1177	>	}
1178	>	return true;
1179	>	}
1180	>
1181	>	/**
1182	>	* Actions on transition to TERMINATING
1183	>	*
1184	>	* Runs up to four passes through workers: (0) shutting down each
1185	>	* (without waking up if parked) to quickly spread notifications
1186	>	* without unnecessary bouncing around event queues etc (1) wake
1187	>	* up and help cancel tasks (2) interrupt (3) mop up races with
1188	>	* interrupted workers
1189	>	*/
1190	>	private void startTerminating() {
1191	>	cancelSubmissions();
1192	>	for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) {
1193	>	advanceEventCount();
1194	>	eventWaiters = 0L; // clobber lists
1195	>	spareWaiters = 0;
1196	>	ForkJoinWorkerThread[] ws = workers;
1197	>	int n = ws.length;
1198	>	for (int i = 0; i < n; ++i) {
1199	>	ForkJoinWorkerThread w = ws[i];
1200	>	if (w != null) {
1201	>	w.shutdown();
1202	>	if (passes > 0 && !w.isTerminated()) {
1203	>	w.cancelTasks();
1204	>	LockSupport.unpark(w);
1205	>	if (passes > 1) {
1206	>	try {
1207	>	w.interrupt();
1208	>	} catch (SecurityException ignore) {
1209	>	}
1210	>	}
1211	>	}
1212		}
1213		}
1214		}
1215		}
1216
1217	+	/**
1218	+	* Clear out and cancel submissions, ignoring exceptions
1219	+	*/
1220	+	private void cancelSubmissions() {
1221	+	ForkJoinTask<?> task;
1222	+	while ((task = submissionQueue.poll()) != null) {
1223	+	try {
1224	+	task.cancel(false);
1225	+	} catch (Throwable ignore) {
1226	+	}
1227	+	}
1228	+	}
1229	+
1230	+	// misc support for ForkJoinWorkerThread
1231	+
1232	+	/**
1233	+	* Returns pool number
1234	+	*/
1235	+	final int getPoolNumber() {
1236	+	return poolNumber;
1237	+	}
1238	+
1239	+	/**
1240	+	* Tries to accumulates steal count from a worker, clearing
1241	+	* the worker's value.
1242	+	*
1243	+	* @return true if worker steal count now zero
1244	+	*/
1245	+	final boolean tryAccumulateStealCount(ForkJoinWorkerThread w) {
1246	+	int sc = w.stealCount;
1247	+	long c = stealCount;
1248	+	// CAS even if zero, for fence effects
1249	+	if (UNSAFE.compareAndSwapLong(this, stealCountOffset, c, c + sc)) {
1250	+	if (sc != 0)
1251	+	w.stealCount = 0;
1252	+	return true;
1253	+	}
1254	+	return sc == 0;
1255	+	}
1256	+
1257	+	/**
1258	+	* Returns the approximate (non-atomic) number of idle threads per
1259	+	* active thread.
1260	+	*/
1261	+	final int idlePerActive() {
1262	+	int pc = parallelism; // use parallelism, not rc
1263	+	int ac = runState;    // no mask -- artifically boosts during shutdown
1264	+	// Use exact results for small values, saturate past 4
1265	+	return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
1266	+	}
1267	+
1268	+	// Public and protected methods
1269	+
1270	+	// Constructors
1271	+
1272	+	/**
1273	+	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1274	+	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1275	+	* #defaultForkJoinWorkerThreadFactory default thread factory},
1276	+	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1277	+	*
1278	+	* @throws SecurityException if a security manager exists and
1279	+	*         the caller is not permitted to modify threads
1280	+	*         because it does not hold {@link
1281	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1282	+	*/
1283	+	public ForkJoinPool() {
1284	+	this(Runtime.getRuntime().availableProcessors(),
1285	+	defaultForkJoinWorkerThreadFactory, null, false);
1286	+	}
1287	+
1288	+	/**
1289	+	* Creates a {@code ForkJoinPool} with the indicated parallelism
1290	+	* level, the {@linkplain
1291	+	* #defaultForkJoinWorkerThreadFactory default thread factory},
1292	+	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1293	+	*
1294	+	* @param parallelism the parallelism level
1295	+	* @throws IllegalArgumentException if parallelism less than or
1296	+	*         equal to zero, or greater than implementation limit
1297	+	* @throws SecurityException if a security manager exists and
1298	+	*         the caller is not permitted to modify threads
1299	+	*         because it does not hold {@link
1300	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1301	+	*/
1302	+	public ForkJoinPool(int parallelism) {
1303	+	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1304	+	}
1305	+
1306	+	/**
1307	+	* Creates a {@code ForkJoinPool} with the given parameters.
1308	+	*
1309	+	* @param parallelism the parallelism level. For default value,
1310	+	* use {@link java.lang.Runtime#availableProcessors}.
1311	+	* @param factory the factory for creating new threads. For default value,
1312	+	* use {@link #defaultForkJoinWorkerThreadFactory}.
1313	+	* @param handler the handler for internal worker threads that
1314	+	* terminate due to unrecoverable errors encountered while executing
1315	+	* tasks. For default value, use <code>null</code>.
1316	+	* @param asyncMode if true,
1317	+	* establishes local first-in-first-out scheduling mode for forked
1318	+	* tasks that are never joined. This mode may be more appropriate
1319	+	* than default locally stack-based mode in applications in which
1320	+	* worker threads only process event-style asynchronous tasks.
1321	+	* For default value, use <code>false</code>.
1322	+	* @throws IllegalArgumentException if parallelism less than or
1323	+	*         equal to zero, or greater than implementation limit
1324	+	* @throws NullPointerException if the factory is null
1325	+	* @throws SecurityException if a security manager exists and
1326	+	*         the caller is not permitted to modify threads
1327	+	*         because it does not hold {@link
1328	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1329	+	*/
1330	+	public ForkJoinPool(int parallelism,
1331	+	ForkJoinWorkerThreadFactory factory,
1332	+	Thread.UncaughtExceptionHandler handler,
1333	+	boolean asyncMode) {
1334	+	checkPermission();
1335	+	if (factory == null)
1336	+	throw new NullPointerException();
1337	+	if (parallelism <= 0 || parallelism > MAX_WORKERS)
1338	+	throw new IllegalArgumentException();
1339	+	this.parallelism = parallelism;
1340	+	this.factory = factory;
1341	+	this.ueh = handler;
1342	+	this.locallyFifo = asyncMode;
1343	+	int arraySize = initialArraySizeFor(parallelism);
1344	+	this.workers = new ForkJoinWorkerThread[arraySize];
1345	+	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
1346	+	this.workerLock = new ReentrantLock();
1347	+	this.termination = new Phaser(1);
1348	+	this.poolNumber = poolNumberGenerator.incrementAndGet();
1349	+	}
1350	+
1351	+	/**
1352	+	* Returns initial power of two size for workers array.
1353	+	* @param pc the initial parallelism level
1354	+	*/
1355	+	private static int initialArraySizeFor(int pc) {
1356	+	// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16)
1357	+	int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS;
1358	+	size |= size >>> 1;
1359	+	size |= size >>> 2;
1360	+	size |= size >>> 4;
1361	+	size |= size >>> 8;
1362	+	return size + 1;
1363	+	}
1364	+
1365		// Execution methods
1366
1367		/**
1368		* Common code for execute, invoke and submit
1369		*/
1370		private <T> void doSubmit(ForkJoinTask<T> task) {
1371	<	if (isShutdown())
1371	>	if (task == null)
1372	>	throw new NullPointerException();
1373	>	if (runState >= SHUTDOWN)
1374		throw new RejectedExecutionException();
1375		submissionQueue.offer(task);
1376	<	signalIdleWorkers();
1376	>	advanceEventCount();
1377	>	if (eventWaiters != 0L)
1378	>	releaseEventWaiters();
1379	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) < parallelism)
1380	>	addWorkerIfBelowTarget();
1381		}
1382
1383		/**
1384	<	* Performs the given task; returning its result upon completion
1384	>	* Performs the given task, returning its result upon completion.
1385	>	*
1386		* @param task the task
1387		* @return the task's result
1388	<	* @throws NullPointerException if task is null
1389	<	* @throws RejectedExecutionException if pool is shut down
1388	>	* @throws NullPointerException if the task is null
1389	>	* @throws RejectedExecutionException if the task cannot be
1390	>	*         scheduled for execution
1391		*/
1392		public <T> T invoke(ForkJoinTask<T> task) {
1393		doSubmit(task);
#	Line 531 | Line 1396 | public class ForkJoinPool extends Abstra
1396
1397		/**
1398		* Arranges for (asynchronous) execution of the given task.
1399	+	*
1400		* @param task the task
1401	<	* @throws NullPointerException if task is null
1402	<	* @throws RejectedExecutionException if pool is shut down
1401	>	* @throws NullPointerException if the task is null
1402	>	* @throws RejectedExecutionException if the task cannot be
1403	>	*         scheduled for execution
1404		*/
1405	<	public <T> void execute(ForkJoinTask<T> task) {
1405	>	public void execute(ForkJoinTask<?> task) {
1406		doSubmit(task);
1407		}
1408
1409		// AbstractExecutorService methods
1410
1411	+	/**
1412	+	* @throws NullPointerException if the task is null
1413	+	* @throws RejectedExecutionException if the task cannot be
1414	+	*         scheduled for execution
1415	+	*/
1416		public void execute(Runnable task) {
1417	<	doSubmit(new AdaptedRunnable<Void>(task, null));
1417	>	ForkJoinTask<?> job;
1418	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1419	>	job = (ForkJoinTask<?>) task;
1420	>	else
1421	>	job = ForkJoinTask.adapt(task, null);
1422	>	doSubmit(job);
1423		}
1424
1425	+	/**
1426	+	* Submits a ForkJoinTask for execution.
1427	+	*
1428	+	* @param task the task to submit
1429	+	* @return the task
1430	+	* @throws NullPointerException if the task is null
1431	+	* @throws RejectedExecutionException if the task cannot be
1432	+	*         scheduled for execution
1433	+	*/
1434	+	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1435	+	doSubmit(task);
1436	+	return task;
1437	+	}
1438	+
1439	+	/**
1440	+	* @throws NullPointerException if the task is null
1441	+	* @throws RejectedExecutionException if the task cannot be
1442	+	*         scheduled for execution
1443	+	*/
1444		public <T> ForkJoinTask<T> submit(Callable<T> task) {
1445	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
1445	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1446		doSubmit(job);
1447		return job;
1448		}
1449
1450	+	/**
1451	+	* @throws NullPointerException if the task is null
1452	+	* @throws RejectedExecutionException if the task cannot be
1453	+	*         scheduled for execution
1454	+	*/
1455		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1456	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
1456	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1457		doSubmit(job);
1458		return job;
1459		}
1460
1461	+	/**
1462	+	* @throws NullPointerException if the task is null
1463	+	* @throws RejectedExecutionException if the task cannot be
1464	+	*         scheduled for execution
1465	+	*/
1466		public ForkJoinTask<?> submit(Runnable task) {
1467	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
1467	>	ForkJoinTask<?> job;
1468	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1469	>	job = (ForkJoinTask<?>) task;
1470	>	else
1471	>	job = ForkJoinTask.adapt(task, null);
1472		doSubmit(job);
1473		return job;
1474		}
1475
1476		/**
1477	<	* Adaptor for Runnables. This implements RunnableFuture
1478	<	* to be compliant with AbstractExecutorService constraints
1477	>	* @throws NullPointerException       {@inheritDoc}
1478	>	* @throws RejectedExecutionException {@inheritDoc}
1479		*/
570	–	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
571	–	implements RunnableFuture<T> {
572	–	final Runnable runnable;
573	–	final T resultOnCompletion;
574	–	T result;
575	–	AdaptedRunnable(Runnable runnable, T result) {
576	–	if (runnable == null) throw new NullPointerException();
577	–	this.runnable = runnable;
578	–	this.resultOnCompletion = result;
579	–	}
580	–	public T getRawResult() { return result; }
581	–	public void setRawResult(T v) { result = v; }
582	–	public boolean exec() {
583	–	runnable.run();
584	–	result = resultOnCompletion;
585	–	return true;
586	–	}
587	–	public void run() { invoke(); }
588	–	}
589	–
590	–	/**
591	–	* Adaptor for Callables
592	–	*/
593	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
594	–	implements RunnableFuture<T> {
595	–	final Callable<T> callable;
596	–	T result;
597	–	AdaptedCallable(Callable<T> callable) {
598	–	if (callable == null) throw new NullPointerException();
599	–	this.callable = callable;
600	–	}
601	–	public T getRawResult() { return result; }
602	–	public void setRawResult(T v) { result = v; }
603	–	public boolean exec() {
604	–	try {
605	–	result = callable.call();
606	–	return true;
607	–	} catch (Error err) {
608	–	throw err;
609	–	} catch (RuntimeException rex) {
610	–	throw rex;
611	–	} catch (Exception ex) {
612	–	throw new RuntimeException(ex);
613	–	}
614	–	}
615	–	public void run() { invoke(); }
616	–	}
617	–
1480		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
1481	<	ArrayList<ForkJoinTask<T>> ts =
1481	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
1482		new ArrayList<ForkJoinTask<T>>(tasks.size());
1483	<	for (Callable<T> c : tasks)
1484	<	ts.add(new AdaptedCallable<T>(c));
1485	<	invoke(new InvokeAll<T>(ts));
1486	<	return (List<Future<T>>)(List)ts;
1483	>	for (Callable<T> task : tasks)
1484	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
1485	>	invoke(new InvokeAll<T>(forkJoinTasks));
1486	>
1487	>	@SuppressWarnings({"unchecked", "rawtypes"})
1488	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1489	>	return futures;
1490		}
1491
1492		static final class InvokeAll<T> extends RecursiveAction {
1493		final ArrayList<ForkJoinTask<T>> tasks;
1494		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
1495		public void compute() {
1496	<	try { invokeAll(tasks); } catch(Exception ignore) {}
1496	>	try { invokeAll(tasks); }
1497	>	catch (Exception ignore) {}
1498		}
1499	+	private static final long serialVersionUID = -7914297376763021607L;
1500		}
1501
635	–	// Configuration and status settings and queries
636	–
1502		/**
1503	<	* Returns the factory used for constructing new workers
1503	>	* Returns the factory used for constructing new workers.
1504		*
1505		* @return the factory used for constructing new workers
1506		*/
#	Line 646 | Line 1511 | public class ForkJoinPool extends Abstra
1511		/**
1512		* Returns the handler for internal worker threads that terminate
1513		* due to unrecoverable errors encountered while executing tasks.
649	–	* @return the handler, or null if none
650	–	*/
651	–	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
652	–	Thread.UncaughtExceptionHandler h;
653	–	final ReentrantLock lock = this.workerLock;
654	–	lock.lock();
655	–	try {
656	–	h = ueh;
657	–	} finally {
658	–	lock.unlock();
659	–	}
660	–	return h;
661	–	}
662	–
663	–	/**
664	–	* Sets the handler for internal worker threads that terminate due
665	–	* to unrecoverable errors encountered while executing tasks.
666	–	* Unless set, the current default or ThreadGroup handler is used
667	–	* as handler.
1514		*
1515	<	* @param h the new handler
670	<	* @return the old handler, or null if none
671	<	* @throws SecurityException if a security manager exists and
672	<	*         the caller is not permitted to modify threads
673	<	*         because it does not hold {@link
674	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
675	<	*/
676	<	public Thread.UncaughtExceptionHandler
677	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
678	<	checkPermission();
679	<	Thread.UncaughtExceptionHandler old = null;
680	<	final ReentrantLock lock = this.workerLock;
681	<	lock.lock();
682	<	try {
683	<	old = ueh;
684	<	ueh = h;
685	<	ForkJoinWorkerThread[] ws = workers;
686	<	for (int i = 0; i < ws.length; ++i) {
687	<	ForkJoinWorkerThread w = ws[i];
688	<	if (w != null)
689	<	w.setUncaughtExceptionHandler(h);
690	<	}
691	<	} finally {
692	<	lock.unlock();
693	<	}
694	<	return old;
695	<	}
696	<
697	<
698	<	/**
699	<	* Sets the target paralleism level of this pool.
700	<	* @param parallelism the target parallelism
701	<	* @throws IllegalArgumentException if parallelism less than or
702	<	* equal to zero or greater than maximum size bounds.
703	<	* @throws SecurityException if a security manager exists and
704	<	*         the caller is not permitted to modify threads
705	<	*         because it does not hold {@link
706	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1515	>	* @return the handler, or {@code null} if none
1516		*/
1517	<	public void setParallelism(int parallelism) {
1518	<	checkPermission();
710	<	if (parallelism <= 0 || parallelism > maxPoolSize)
711	<	throw new IllegalArgumentException();
712	<	final ReentrantLock lock = this.workerLock;
713	<	lock.lock();
714	<	try {
715	<	if (!isTerminating()) {
716	<	int p = this.parallelism;
717	<	this.parallelism = parallelism;
718	<	if (parallelism > p)
719	<	createAndStartAddedWorkers();
720	<	else
721	<	trimSpares();
722	<	}
723	<	} finally {
724	<	lock.unlock();
725	<	}
726	<	signalIdleWorkers();
1517	>	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1518	>	return ueh;
1519		}
1520
1521		/**
1522	<	* Returns the targeted number of worker threads in this pool.
1522	>	* Returns the targeted parallelism level of this pool.
1523		*
1524	<	* @return the targeted number of worker threads in this pool
1524	>	* @return the targeted parallelism level of this pool
1525		*/
1526		public int getParallelism() {
1527		return parallelism;
#	Line 738 | Line 1530 | public class ForkJoinPool extends Abstra
1530		/**
1531		* Returns the number of worker threads that have started but not
1532		* yet terminated.  This result returned by this method may differ
1533	<	* from <code>getParallelism</code> when threads are created to
1533	>	* from {@link #getParallelism} when threads are created to
1534		* maintain parallelism when others are cooperatively blocked.
1535		*
1536		* @return the number of worker threads
1537		*/
1538		public int getPoolSize() {
1539	<	return totalCountOf(workerCounts);
1539	>	return workerCounts >>> TOTAL_COUNT_SHIFT;
1540		}
1541
1542		/**
1543	<	* Returns the maximum number of threads allowed to exist in the
1544	<	* pool, even if there are insufficient unblocked running threads.
1545	<	* @return the maximum
1546	<	*/
755	<	public int getMaximumPoolSize() {
756	<	return maxPoolSize;
757	<	}
758	<
759	<	/**
760	<	* Sets the maximum number of threads allowed to exist in the
761	<	* pool, even if there are insufficient unblocked running threads.
762	<	* Setting this value has no effect on current pool size. It
763	<	* controls construction of new threads.
764	<	* @throws IllegalArgumentException if negative or greater then
765	<	* internal implementation limit.
766	<	*/
767	<	public void setMaximumPoolSize(int newMax) {
768	<	if (newMax < 0 || newMax > MAX_THREADS)
769	<	throw new IllegalArgumentException();
770	<	maxPoolSize = newMax;
771	<	}
772	<
773	<
774	<	/**
775	<	* Returns true if this pool dynamically maintains its target
776	<	* parallelism level. If false, new threads are added only to
777	<	* avoid possible starvation.
778	<	* This setting is by default true;
779	<	* @return true if maintains parallelism
780	<	*/
781	<	public boolean getMaintainsParallelism() {
782	<	return maintainsParallelism;
783	<	}
784	<
785	<	/**
786	<	* Sets whether this pool dynamically maintains its target
787	<	* parallelism level. If false, new threads are added only to
788	<	* avoid possible starvation.
789	<	* @param enable true to maintains parallelism
1543	>	* Returns {@code true} if this pool uses local first-in-first-out
1544	>	* scheduling mode for forked tasks that are never joined.
1545	>	*
1546	>	* @return {@code true} if this pool uses async mode
1547		*/
1548	<	public void setMaintainsParallelism(boolean enable) {
1549	<	maintainsParallelism = enable;
1548	>	public boolean getAsyncMode() {
1549	>	return locallyFifo;
1550		}
1551
1552		/**
1553		* Returns an estimate of the number of worker threads that are
1554		* not blocked waiting to join tasks or for other managed
1555	<	* synchronization.
1555	>	* synchronization. This method may overestimate the
1556	>	* number of running threads.
1557		*
1558		* @return the number of worker threads
1559		*/
1560		public int getRunningThreadCount() {
1561	<	return runningCountOf(workerCounts);
1561	>	return workerCounts & RUNNING_COUNT_MASK;
1562		}
1563
1564		/**
1565		* Returns an estimate of the number of threads that are currently
1566		* stealing or executing tasks. This method may overestimate the
1567		* number of active threads.
1568	<	* @return the number of active threads.
1568	>	*
1569	>	* @return the number of active threads
1570		*/
1571		public int getActiveThreadCount() {
1572	<	return activeCountOf(runControl);
1572	>	return runState & ACTIVE_COUNT_MASK;
1573		}
1574
1575		/**
1576	<	* Returns an estimate of the number of threads that are currently
1577	<	* idle waiting for tasks. This method may underestimate the
1578	<	* number of idle threads.
1579	<	* @return the number of idle threads.
1580	<	*/
1581	<	final int getIdleThreadCount() {
1582	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
1583	<	return (c <= 0)? 0 : c;
1584	<	}
826	<
827	<	/**
828	<	* Returns true if all worker threads are currently idle. An idle
829	<	* worker is one that cannot obtain a task to execute because none
830	<	* are available to steal from other threads, and there are no
831	<	* pending submissions to the pool. This method is conservative:
832	<	* It might not return true immediately upon idleness of all
833	<	* threads, but will eventually become true if threads remain
834	<	* inactive.
835	<	* @return true if all threads are currently idle
1576	>	* Returns {@code true} if all worker threads are currently idle.
1577	>	* An idle worker is one that cannot obtain a task to execute
1578	>	* because none are available to steal from other threads, and
1579	>	* there are no pending submissions to the pool. This method is
1580	>	* conservative; it might not return {@code true} immediately upon
1581	>	* idleness of all threads, but will eventually become true if
1582	>	* threads remain inactive.
1583	>	*
1584	>	* @return {@code true} if all threads are currently idle
1585		*/
1586		public boolean isQuiescent() {
1587	<	return activeCountOf(runControl) == 0;
1587	>	return (runState & ACTIVE_COUNT_MASK) == 0;
1588		}
1589
1590		/**
#	Line 843 | Line 1592 | public class ForkJoinPool extends Abstra
1592		* one thread's work queue by another. The reported value
1593		* underestimates the actual total number of steals when the pool
1594		* is not quiescent. This value may be useful for monitoring and
1595	<	* tuning fork/join programs: In general, steal counts should be
1595	>	* tuning fork/join programs: in general, steal counts should be
1596		* high enough to keep threads busy, but low enough to avoid
1597		* overhead and contention across threads.
1598	<	* @return the number of steals.
1598	>	*
1599	>	* @return the number of steals
1600		*/
1601		public long getStealCount() {
1602	<	return stealCount.get();
853	<	}
854	<
855	<	/**
856	<	* Accumulate steal count from a worker. Call only
857	<	* when worker known to be idle.
858	<	*/
859	<	private void updateStealCount(ForkJoinWorkerThread w) {
860	<	int sc = w.getAndClearStealCount();
861	<	if (sc != 0)
862	<	stealCount.addAndGet(sc);
1602	>	return stealCount;
1603		}
1604
1605		/**
#	Line 869 | Line 1609 | public class ForkJoinPool extends Abstra
1609		* an approximation, obtained by iterating across all threads in
1610		* the pool. This method may be useful for tuning task
1611		* granularities.
1612	<	* @return the number of queued tasks.
1612	>	*
1613	>	* @return the number of queued tasks
1614		*/
1615		public long getQueuedTaskCount() {
1616		long count = 0;
1617		ForkJoinWorkerThread[] ws = workers;
1618	<	for (int i = 0; i < ws.length; ++i) {
1619	<	ForkJoinWorkerThread t = ws[i];
1620	<	if (t != null)
1621	<	count += t.getQueueSize();
1618	>	int n = ws.length;
1619	>	for (int i = 0; i < n; ++i) {
1620	>	ForkJoinWorkerThread w = ws[i];
1621	>	if (w != null)
1622	>	count += w.getQueueSize();
1623		}
1624		return count;
1625		}
1626
1627		/**
1628	<	* Returns an estimate of the number tasks submitted to this pool
1629	<	* that have not yet begun executing. This method takes time
1628	>	* Returns an estimate of the number of tasks submitted to this
1629	>	* pool that have not yet begun executing.  This method takes time
1630		* proportional to the number of submissions.
1631	<	* @return the number of queued submissions.
1631	>	*
1632	>	* @return the number of queued submissions
1633		*/
1634		public int getQueuedSubmissionCount() {
1635		return submissionQueue.size();
1636		}
1637
1638		/**
1639	<	* Returns true if there are any tasks submitted to this pool
1640	<	* that have not yet begun executing.
1641	<	* @return <code>true</code> if there are any queued submissions.
1639	>	* Returns {@code true} if there are any tasks submitted to this
1640	>	* pool that have not yet begun executing.
1641	>	*
1642	>	* @return {@code true} if there are any queued submissions
1643		*/
1644		public boolean hasQueuedSubmissions() {
1645		return !submissionQueue.isEmpty();
#	Line 905 | Line 1649 | public class ForkJoinPool extends Abstra
1649		* Removes and returns the next unexecuted submission if one is
1650		* available.  This method may be useful in extensions to this
1651		* class that re-assign work in systems with multiple pools.
1652	<	* @return the next submission, or null if none
1652	>	*
1653	>	* @return the next submission, or {@code null} if none
1654		*/
1655		protected ForkJoinTask<?> pollSubmission() {
1656		return submissionQueue.poll();
1657		}
1658
1659		/**
1660	+	* Removes all available unexecuted submitted and forked tasks
1661	+	* from scheduling queues and adds them to the given collection,
1662	+	* without altering their execution status. These may include
1663	+	* artificially generated or wrapped tasks. This method is
1664	+	* designed to be invoked only when the pool is known to be
1665	+	* quiescent. Invocations at other times may not remove all
1666	+	* tasks. A failure encountered while attempting to add elements
1667	+	* to collection {@code c} may result in elements being in
1668	+	* neither, either or both collections when the associated
1669	+	* exception is thrown.  The behavior of this operation is
1670	+	* undefined if the specified collection is modified while the
1671	+	* operation is in progress.
1672	+	*
1673	+	* @param c the collection to transfer elements into
1674	+	* @return the number of elements transferred
1675	+	*/
1676	+	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1677	+	int count = submissionQueue.drainTo(c);
1678	+	ForkJoinWorkerThread[] ws = workers;
1679	+	int n = ws.length;
1680	+	for (int i = 0; i < n; ++i) {
1681	+	ForkJoinWorkerThread w = ws[i];
1682	+	if (w != null)
1683	+	count += w.drainTasksTo(c);
1684	+	}
1685	+	return count;
1686	+	}
1687	+
1688	+	/**
1689		* Returns a string identifying this pool, as well as its state,
1690		* including indications of run state, parallelism level, and
1691		* worker and task counts.
#	Line 919 | Line 1693 | public class ForkJoinPool extends Abstra
1693		* @return a string identifying this pool, as well as its state
1694		*/
1695		public String toString() {
922	–	int ps = parallelism;
923	–	int wc = workerCounts;
924	–	int rc = runControl;
1696		long st = getStealCount();
1697		long qt = getQueuedTaskCount();
1698		long qs = getQueuedSubmissionCount();
1699	+	int wc = workerCounts;
1700	+	int tc = wc >>> TOTAL_COUNT_SHIFT;
1701	+	int rc = wc & RUNNING_COUNT_MASK;
1702	+	int pc = parallelism;
1703	+	int rs = runState;
1704	+	int ac = rs & ACTIVE_COUNT_MASK;
1705		return super.toString() +
1706	<	"[" + runStateToString(runStateOf(rc)) +
1707	<	", parallelism = " + ps +
1708	<	", size = " + totalCountOf(wc) +
1709	<	", active = " + activeCountOf(rc) +
1710	<	", running = " + runningCountOf(wc) +
1706	>	"[" + runLevelToString(rs) +
1707	>	", parallelism = " + pc +
1708	>	", size = " + tc +
1709	>	", active = " + ac +
1710	>	", running = " + rc +
1711		", steals = " + st +
1712		", tasks = " + qt +
1713		", submissions = " + qs +
1714		"]";
1715		}
1716
1717	<	private static String runStateToString(int rs) {
1718	<	switch(rs) {
1719	<	case RUNNING: return "Running";
1720	<	case SHUTDOWN: return "Shutting down";
1721	<	case TERMINATING: return "Terminating";
945	<	case TERMINATED: return "Terminated";
946	<	default: throw new Error("Unknown run state");
947	<	}
1717	>	private static String runLevelToString(int s) {
1718	>	return ((s & TERMINATED) != 0 ? "Terminated" :
1719	>	((s & TERMINATING) != 0 ? "Terminating" :
1720	>	((s & SHUTDOWN) != 0 ? "Shutting down" :
1721	>	"Running")));
1722		}
1723
950	–	// lifecycle control
951	–
1724		/**
1725		* Initiates an orderly shutdown in which previously submitted
1726		* tasks are executed, but no new tasks will be accepted.
1727		* Invocation has no additional effect if already shut down.
1728		* Tasks that are in the process of being submitted concurrently
1729		* during the course of this method may or may not be rejected.
1730	+	*
1731		* @throws SecurityException if a security manager exists and
1732		*         the caller is not permitted to modify threads
1733		*         because it does not hold {@link
1734	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1734	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1735		*/
1736		public void shutdown() {
1737		checkPermission();
1738	<	transitionRunStateTo(SHUTDOWN);
1739	<	if (canTerminateOnShutdown(runControl))
967	<	terminateOnShutdown();
1738	>	advanceRunLevel(SHUTDOWN);
1739	>	tryTerminate(false);
1740		}
1741
1742		/**
1743	<	* Attempts to stop all actively executing tasks, and cancels all
1744	<	* waiting tasks.  Tasks that are in the process of being
1745	<	* submitted or executed concurrently during the course of this
1746	<	* method may or may not be rejected. Unlike some other executors,
1747	<	* this method cancels rather than collects non-executed tasks,
1748	<	* so always returns an empty list.
1743	>	* Attempts to cancel and/or stop all tasks, and reject all
1744	>	* subsequently submitted tasks.  Tasks that are in the process of
1745	>	* being submitted or executed concurrently during the course of
1746	>	* this method may or may not be rejected. This method cancels
1747	>	* both existing and unexecuted tasks, in order to permit
1748	>	* termination in the presence of task dependencies. So the method
1749	>	* always returns an empty list (unlike the case for some other
1750	>	* Executors).
1751	>	*
1752		* @return an empty list
1753		* @throws SecurityException if a security manager exists and
1754		*         the caller is not permitted to modify threads
1755		*         because it does not hold {@link
1756	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1756	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1757		*/
1758		public List<Runnable> shutdownNow() {
1759		checkPermission();
1760	<	terminate();
1760	>	tryTerminate(true);
1761		return Collections.emptyList();
1762		}
1763
1764		/**
1765	<	* Returns <code>true</code> if all tasks have completed following shut down.
1765	>	* Returns {@code true} if all tasks have completed following shut down.
1766		*
1767	<	* @return <code>true</code> if all tasks have completed following shut down
1767	>	* @return {@code true} if all tasks have completed following shut down
1768		*/
1769		public boolean isTerminated() {
1770	<	return runStateOf(runControl) == TERMINATED;
1770	>	return runState >= TERMINATED;
1771		}
1772
1773		/**
1774	<	* Returns <code>true</code> if the process of termination has
1775	<	* commenced but possibly not yet completed.
1774	>	* Returns {@code true} if the process of termination has
1775	>	* commenced but not yet completed.  This method may be useful for
1776	>	* debugging. A return of {@code true} reported a sufficient
1777	>	* period after shutdown may indicate that submitted tasks have
1778	>	* ignored or suppressed interruption, causing this executor not
1779	>	* to properly terminate.
1780		*
1781	<	* @return <code>true</code> if terminating
1781	>	* @return {@code true} if terminating but not yet terminated
1782		*/
1783		public boolean isTerminating() {
1784	<	return runStateOf(runControl) >= TERMINATING;
1784	>	return (runState & (TERMINATING|TERMINATED)) == TERMINATING;
1785		}
1786
1787		/**
1788	<	* Returns <code>true</code> if this pool has been shut down.
1788	>	* Returns {@code true} if this pool has been shut down.
1789		*
1790	<	* @return <code>true</code> if this pool has been shut down
1790	>	* @return {@code true} if this pool has been shut down
1791		*/
1792		public boolean isShutdown() {
1793	<	return runStateOf(runControl) >= SHUTDOWN;
1793	>	return runState >= SHUTDOWN;
1794		}
1795
1796		/**
#	Line 1021 | Line 1800 | public class ForkJoinPool extends Abstra
1800		*
1801		* @param timeout the maximum time to wait
1802		* @param unit the time unit of the timeout argument
1803	<	* @return <code>true</code> if this executor terminated and
1804	<	*         <code>false</code> if the timeout elapsed before termination
1803	>	* @return {@code true} if this executor terminated and
1804	>	*         {@code false} if the timeout elapsed before termination
1805		* @throws InterruptedException if interrupted while waiting
1806		*/
1807		public boolean awaitTermination(long timeout, TimeUnit unit)
1808		throws InterruptedException {
1030	–	long nanos = unit.toNanos(timeout);
1031	–	final ReentrantLock lock = this.workerLock;
1032	–	lock.lock();
1033	–	try {
1034	–	for (;;) {
1035	–	if (isTerminated())
1036	–	return true;
1037	–	if (nanos <= 0)
1038	–	return false;
1039	–	nanos = termination.awaitNanos(nanos);
1040	–	}
1041	–	} finally {
1042	–	lock.unlock();
1043	–	}
1044	–	}
1045	–
1046	–	// Shutdown and termination support
1047	–
1048	–	/**
1049	–	* Callback from terminating worker. Null out the corresponding
1050	–	* workers slot, and if terminating, try to terminate, else try to
1051	–	* shrink workers array.
1052	–	* @param w the worker
1053	–	*/
1054	–	final void workerTerminated(ForkJoinWorkerThread w) {
1055	–	updateStealCount(w);
1056	–	updateWorkerCount(-1);
1057	–	final ReentrantLock lock = this.workerLock;
1058	–	lock.lock();
1059	–	try {
1060	–	ForkJoinWorkerThread[] ws = workers;
1061	–	int idx = w.poolIndex;
1062	–	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1063	–	ws[idx] = null;
1064	–	if (totalCountOf(workerCounts) == 0) {
1065	–	terminate(); // no-op if already terminating
1066	–	transitionRunStateTo(TERMINATED);
1067	–	termination.signalAll();
1068	–	}
1069	–	else if (!isTerminating()) {
1070	–	tryShrinkWorkerArray();
1071	–	tryResumeSpare(true); // allow replacement
1072	–	}
1073	–	} finally {
1074	–	lock.unlock();
1075	–	}
1076	–	signalIdleWorkers();
1077	–	}
1078	–
1079	–	/**
1080	–	* Initiate termination.
1081	–	*/
1082	–	private void terminate() {
1083	–	if (transitionRunStateTo(TERMINATING)) {
1084	–	stopAllWorkers();
1085	–	resumeAllSpares();
1086	–	signalIdleWorkers();
1087	–	cancelQueuedSubmissions();
1088	–	cancelQueuedWorkerTasks();
1089	–	interruptUnterminatedWorkers();
1090	–	signalIdleWorkers(); // resignal after interrupt
1091	–	}
1092	–	}
1093	–
1094	–	/**
1095	–	* Possibly terminate when on shutdown state
1096	–	*/
1097	–	private void terminateOnShutdown() {
1098	–	if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
1099	–	terminate();
1100	–	}
1101	–
1102	–	/**
1103	–	* Clear out and cancel submissions
1104	–	*/
1105	–	private void cancelQueuedSubmissions() {
1106	–	ForkJoinTask<?> task;
1107	–	while ((task = pollSubmission()) != null)
1108	–	task.cancel(false);
1109	–	}
1110	–
1111	–	/**
1112	–	* Clean out worker queues.
1113	–	*/
1114	–	private void cancelQueuedWorkerTasks() {
1115	–	final ReentrantLock lock = this.workerLock;
1116	–	lock.lock();
1809		try {
1810	<	ForkJoinWorkerThread[] ws = workers;
1811	<	for (int i = 0; i < ws.length; ++i) {
1120	<	ForkJoinWorkerThread t = ws[i];
1121	<	if (t != null)
1122	<	t.cancelTasks();
1123	<	}
1124	<	} finally {
1125	<	lock.unlock();
1126	<	}
1127	<	}
1128	<
1129	<	/**
1130	<	* Set each worker's status to terminating. Requires lock to avoid
1131	<	* conflicts with add/remove
1132	<	*/
1133	<	private void stopAllWorkers() {
1134	<	final ReentrantLock lock = this.workerLock;
1135	<	lock.lock();
1136	<	try {
1137	<	ForkJoinWorkerThread[] ws = workers;
1138	<	for (int i = 0; i < ws.length; ++i) {
1139	<	ForkJoinWorkerThread t = ws[i];
1140	<	if (t != null)
1141	<	t.shutdownNow();
1142	<	}
1143	<	} finally {
1144	<	lock.unlock();
1145	<	}
1146	<	}
1147	<
1148	<	/**
1149	<	* Interrupt all unterminated workers.  This is not required for
1150	<	* sake of internal control, but may help unstick user code during
1151	<	* shutdown.
1152	<	*/
1153	<	private void interruptUnterminatedWorkers() {
1154	<	final ReentrantLock lock = this.workerLock;
1155	<	lock.lock();
1156	<	try {
1157	<	ForkJoinWorkerThread[] ws = workers;
1158	<	for (int i = 0; i < ws.length; ++i) {
1159	<	ForkJoinWorkerThread t = ws[i];
1160	<	if (t != null && !t.isTerminated()) {
1161	<	try {
1162	<	t.interrupt();
1163	<	} catch (SecurityException ignore) {
1164	<	}
1165	<	}
1166	<	}
1167	<	} finally {
1168	<	lock.unlock();
1169	<	}
1170	<	}
1171	<
1172	<
1173	<	/*
1174	<	* Nodes for event barrier to manage idle threads.  Queue nodes
1175	<	* are basic Treiber stack nodes, also used for spare stack.
1176	<	*
1177	<	* The event barrier has an event count and a wait queue (actually
1178	<	* a Treiber stack).  Workers are enabled to look for work when
1179	<	* the eventCount is incremented. If they fail to find work, they
1180	<	* may wait for next count. Upon release, threads help others wake
1181	<	* up.
1182	<	*
1183	<	* Synchronization events occur only in enough contexts to
1184	<	* maintain overall liveness:
1185	<	*
1186	<	*   - Submission of a new task to the pool
1187	<	*   - Resizes or other changes to the workers array
1188	<	*   - pool termination
1189	<	*   - A worker pushing a task on an empty queue
1190	<	*
1191	<	* The case of pushing a task occurs often enough, and is heavy
1192	<	* enough compared to simple stack pushes, to require special
1193	<	* handling: Method signalWork returns without advancing count if
1194	<	* the queue appears to be empty.  This would ordinarily result in
1195	<	* races causing some queued waiters not to be woken up. To avoid
1196	<	* this, the first worker enqueued in method sync (see
1197	<	* syncIsReleasable) rescans for tasks after being enqueued, and
1198	<	* helps signal if any are found. This works well because the
1199	<	* worker has nothing better to do, and so might as well help
1200	<	* alleviate the overhead and contention on the threads actually
1201	<	* doing work.  Also, since event counts increments on task
1202	<	* availability exist to maintain liveness (rather than to force
1203	<	* refreshes etc), it is OK for callers to exit early if
1204	<	* contending with another signaller.
1205	<	*/
1206	<	static final class WaitQueueNode {
1207	<	WaitQueueNode next; // only written before enqueued
1208	<	volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1209	<	final long count; // unused for spare stack
1210	<
1211	<	WaitQueueNode(long c, ForkJoinWorkerThread w) {
1212	<	count = c;
1213	<	thread = w;
1214	<	}
1215	<
1216	<	/**
1217	<	* Wake up waiter, returning false if known to already
1218	<	*/
1219	<	boolean signal() {
1220	<	ForkJoinWorkerThread t = thread;
1221	<	if (t == null)
1222	<	return false;
1223	<	thread = null;
1224	<	LockSupport.unpark(t);
1225	<	return true;
1226	<	}
1227	<
1228	<	/**
1229	<	* Await release on sync
1230	<	*/
1231	<	void awaitSyncRelease(ForkJoinPool p) {
1232	<	while (thread != null && !p.syncIsReleasable(this))
1233	<	LockSupport.park(this);
1234	<	}
1235	<
1236	<	/**
1237	<	* Await resumption as spare
1238	<	*/
1239	<	void awaitSpareRelease() {
1240	<	while (thread != null) {
1241	<	if (!Thread.interrupted())
1242	<	LockSupport.park(this);
1243	<	}
1244	<	}
1245	<	}
1246	<
1247	<	/**
1248	<	* Ensures that no thread is waiting for count to advance from the
1249	<	* current value of eventCount read on entry to this method, by
1250	<	* releasing waiting threads if necessary.
1251	<	* @return the count
1252	<	*/
1253	<	final long ensureSync() {
1254	<	long c = eventCount;
1255	<	WaitQueueNode q;
1256	<	while ((q = syncStack) != null && q.count < c) {
1257	<	if (casBarrierStack(q, null)) {
1258	<	do {
1259	<	q.signal();
1260	<	} while ((q = q.next) != null);
1261	<	break;
1262	<	}
1263	<	}
1264	<	return c;
1265	<	}
1266	<
1267	<	/**
1268	<	* Increments event count and releases waiting threads.
1269	<	*/
1270	<	private void signalIdleWorkers() {
1271	<	long c;
1272	<	do;while (!casEventCount(c = eventCount, c+1));
1273	<	ensureSync();
1274	<	}
1275	<
1276	<	/**
1277	<	* Signal threads waiting to poll a task. Because method sync
1278	<	* rechecks availability, it is OK to only proceed if queue
1279	<	* appears to be non-empty, and OK to skip under contention to
1280	<	* increment count (since some other thread succeeded).
1281	<	*/
1282	<	final void signalWork() {
1283	<	long c;
1284	<	WaitQueueNode q;
1285	<	if (syncStack != null &&
1286	<	casEventCount(c = eventCount, c+1) &&
1287	<	(((q = syncStack) != null && q.count <= c) &&
1288	<	(!casBarrierStack(q, q.next) || !q.signal())))
1289	<	ensureSync();
1290	<	}
1291	<
1292	<	/**
1293	<	* Waits until event count advances from last value held by
1294	<	* caller, or if excess threads, caller is resumed as spare, or
1295	<	* caller or pool is terminating. Updates caller's event on exit.
1296	<	* @param w the calling worker thread
1297	<	*/
1298	<	final void sync(ForkJoinWorkerThread w) {
1299	<	updateStealCount(w); // Transfer w's count while it is idle
1300	<
1301	<	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1302	<	long prev = w.lastEventCount;
1303	<	WaitQueueNode node = null;
1304	<	WaitQueueNode h;
1305	<	while (eventCount == prev &&
1306	<	((h = syncStack) == null || h.count == prev)) {
1307	<	if (node == null)
1308	<	node = new WaitQueueNode(prev, w);
1309	<	if (casBarrierStack(node.next = h, node)) {
1310	<	node.awaitSyncRelease(this);
1311	<	break;
1312	<	}
1313	<	}
1314	<	long ec = ensureSync();
1315	<	if (ec != prev) {
1316	<	w.lastEventCount = ec;
1317	<	break;
1318	<	}
1319	<	}
1320	<	}
1321	<
1322	<	/**
1323	<	* Returns true if worker waiting on sync can proceed:
1324	<	*  - on signal (thread == null)
1325	<	*  - on event count advance (winning race to notify vs signaller)
1326	<	*  - on Interrupt
1327	<	*  - if the first queued node, we find work available
1328	<	* If node was not signalled and event count not advanced on exit,
1329	<	* then we also help advance event count.
1330	<	* @return true if node can be released
1331	<	*/
1332	<	final boolean syncIsReleasable(WaitQueueNode node) {
1333	<	long prev = node.count;
1334	<	if (!Thread.interrupted() && node.thread != null &&
1335	<	(node.next != null ||
1336	<	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1337	<	eventCount == prev)
1810	>	return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1811	>	} catch(TimeoutException ex) {
1812		return false;
1339	–	if (node.thread != null) {
1340	–	node.thread = null;
1341	–	long ec = eventCount;
1342	–	if (prev <= ec) // help signal
1343	–	casEventCount(ec, ec+1);
1344	–	}
1345	–	return true;
1346	–	}
1347	–
1348	–	/**
1349	–	* Returns true if a new sync event occurred since last call to
1350	–	* sync or this method, if so, updating caller's count.
1351	–	*/
1352	–	final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1353	–	long lc = w.lastEventCount;
1354	–	long ec = ensureSync();
1355	–	if (ec == lc)
1356	–	return false;
1357	–	w.lastEventCount = ec;
1358	–	return true;
1359	–	}
1360	–
1361	–	//  Parallelism maintenance
1362	–
1363	–	/**
1364	–	* Decrement running count; if too low, add spare.
1365	–	*
1366	–	* Conceptually, all we need to do here is add or resume a
1367	–	* spare thread when one is about to block (and remove or
1368	–	* suspend it later when unblocked -- see suspendIfSpare).
1369	–	* However, implementing this idea requires coping with
1370	–	* several problems: We have imperfect information about the
1371	–	* states of threads. Some count updates can and usually do
1372	–	* lag run state changes, despite arrangements to keep them
1373	–	* accurate (for example, when possible, updating counts
1374	–	* before signalling or resuming), especially when running on
1375	–	* dynamic JVMs that don't optimize the infrequent paths that
1376	–	* update counts. Generating too many threads can make these
1377	–	* problems become worse, because excess threads are more
1378	–	* likely to be context-switched with others, slowing them all
1379	–	* down, especially if there is no work available, so all are
1380	–	* busy scanning or idling.  Also, excess spare threads can
1381	–	* only be suspended or removed when they are idle, not
1382	–	* immediately when they aren't needed. So adding threads will
1383	–	* raise parallelism level for longer than necessary.  Also,
1384	–	* FJ applications often enounter highly transient peaks when
1385	–	* many threads are blocked joining, but for less time than it
1386	–	* takes to create or resume spares.
1387	–	*
1388	–	* @param joinMe if non-null, return early if done
1389	–	* @param maintainParallelism if true, try to stay within
1390	–	* target counts, else create only to avoid starvation
1391	–	* @return true if joinMe known to be done
1392	–	*/
1393	–	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1394	–	maintainParallelism &= maintainsParallelism; // overrride
1395	–	boolean dec = false;  // true when running count decremented
1396	–	while (spareStack == null || !tryResumeSpare(dec)) {
1397	–	int counts = workerCounts;
1398	–	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1399	–	if (!needSpare(counts, maintainParallelism))
1400	–	break;
1401	–	if (joinMe.status < 0)
1402	–	return true;
1403	–	if (tryAddSpare(counts))
1404	–	break;
1405	–	}
1406	–	}
1407	–	return false;
1408	–	}
1409	–
1410	–	/**
1411	–	* Same idea as preJoin
1412	–	*/
1413	–	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1414	–	maintainParallelism &= maintainsParallelism;
1415	–	boolean dec = false;
1416	–	while (spareStack == null || !tryResumeSpare(dec)) {
1417	–	int counts = workerCounts;
1418	–	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1419	–	if (!needSpare(counts, maintainParallelism))
1420	–	break;
1421	–	if (blocker.isReleasable())
1422	–	return true;
1423	–	if (tryAddSpare(counts))
1424	–	break;
1425	–	}
1426	–	}
1427	–	return false;
1428	–	}
1429	–
1430	–	/**
1431	–	* Returns true if a spare thread appears to be needed.  If
1432	–	* maintaining parallelism, returns true when the deficit in
1433	–	* running threads is more than the surplus of total threads, and
1434	–	* there is apparently some work to do.  This self-limiting rule
1435	–	* means that the more threads that have already been added, the
1436	–	* less parallelism we will tolerate before adding another.
1437	–	* @param counts current worker counts
1438	–	* @param maintainParallelism try to maintain parallelism
1439	–	*/
1440	–	private boolean needSpare(int counts, boolean maintainParallelism) {
1441	–	int ps = parallelism;
1442	–	int rc = runningCountOf(counts);
1443	–	int tc = totalCountOf(counts);
1444	–	int runningDeficit = ps - rc;
1445	–	int totalSurplus = tc - ps;
1446	–	return (tc < maxPoolSize &&
1447	–	(rc == 0 || totalSurplus < 0 ||
1448	–	(maintainParallelism &&
1449	–	runningDeficit > totalSurplus &&
1450	–	ForkJoinWorkerThread.hasQueuedTasks(workers))));
1451	–	}
1452	–
1453	–	/**
1454	–	* Add a spare worker if lock available and no more than the
1455	–	* expected numbers of threads exist
1456	–	* @return true if successful
1457	–	*/
1458	–	private boolean tryAddSpare(int expectedCounts) {
1459	–	final ReentrantLock lock = this.workerLock;
1460	–	int expectedRunning = runningCountOf(expectedCounts);
1461	–	int expectedTotal = totalCountOf(expectedCounts);
1462	–	boolean success = false;
1463	–	boolean locked = false;
1464	–	// confirm counts while locking; CAS after obtaining lock
1465	–	try {
1466	–	for (;;) {
1467	–	int s = workerCounts;
1468	–	int tc = totalCountOf(s);
1469	–	int rc = runningCountOf(s);
1470	–	if (rc > expectedRunning || tc > expectedTotal)
1471	–	break;
1472	–	if (!locked && !(locked = lock.tryLock()))
1473	–	break;
1474	–	if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) {
1475	–	createAndStartSpare(tc);
1476	–	success = true;
1477	–	break;
1478	–	}
1479	–	}
1480	–	} finally {
1481	–	if (locked)
1482	–	lock.unlock();
1483	–	}
1484	–	return success;
1485	–	}
1486	–
1487	–	/**
1488	–	* Add the kth spare worker. On entry, pool coounts are already
1489	–	* adjusted to reflect addition.
1490	–	*/
1491	–	private void createAndStartSpare(int k) {
1492	–	ForkJoinWorkerThread w = null;
1493	–	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1);
1494	–	int len = ws.length;
1495	–	// Probably, we can place at slot k. If not, find empty slot
1496	–	if (k < len && ws[k] != null) {
1497	–	for (k = 0; k < len && ws[k] != null; ++k)
1498	–	;
1499	–	}
1500	–	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1501	–	ws[k] = w;
1502	–	w.start();
1503	–	}
1504	–	else
1505	–	updateWorkerCount(-1); // adjust on failure
1506	–	signalIdleWorkers();
1507	–	}
1508	–
1509	–	/**
1510	–	* Suspend calling thread w if there are excess threads.  Called
1511	–	* only from sync.  Spares are enqueued in a Treiber stack
1512	–	* using the same WaitQueueNodes as barriers.  They are resumed
1513	–	* mainly in preJoin, but are also woken on pool events that
1514	–	* require all threads to check run state.
1515	–	* @param w the caller
1516	–	*/
1517	–	private boolean suspendIfSpare(ForkJoinWorkerThread w) {
1518	–	WaitQueueNode node = null;
1519	–	int s;
1520	–	while (parallelism < runningCountOf(s = workerCounts)) {
1521	–	if (node == null)
1522	–	node = new WaitQueueNode(0, w);
1523	–	if (casWorkerCounts(s, s-1)) { // representation-dependent
1524	–	// push onto stack
1525	–	do;while (!casSpareStack(node.next = spareStack, node));
1526	–	// block until released by resumeSpare
1527	–	node.awaitSpareRelease();
1528	–	return true;
1529	–	}
1530	–	}
1531	–	return false;
1532	–	}
1533	–
1534	–	/**
1535	–	* Try to pop and resume a spare thread.
1536	–	* @param updateCount if true, increment running count on success
1537	–	* @return true if successful
1538	–	*/
1539	–	private boolean tryResumeSpare(boolean updateCount) {
1540	–	WaitQueueNode q;
1541	–	while ((q = spareStack) != null) {
1542	–	if (casSpareStack(q, q.next)) {
1543	–	if (updateCount)
1544	–	updateRunningCount(1);
1545	–	q.signal();
1546	–	return true;
1547	–	}
1548	–	}
1549	–	return false;
1550	–	}
1551	–
1552	–	/**
1553	–	* Pop and resume all spare threads. Same idea as ensureSync.
1554	–	* @return true if any spares released
1555	–	*/
1556	–	private boolean resumeAllSpares() {
1557	–	WaitQueueNode q;
1558	–	while ( (q = spareStack) != null) {
1559	–	if (casSpareStack(q, null)) {
1560	–	do {
1561	–	updateRunningCount(1);
1562	–	q.signal();
1563	–	} while ((q = q.next) != null);
1564	–	return true;
1565	–	}
1566	–	}
1567	–	return false;
1568	–	}
1569	–
1570	–	/**
1571	–	* Pop and shutdown excessive spare threads. Call only while
1572	–	* holding lock. This is not guaranteed to eliminate all excess
1573	–	* threads, only those suspended as spares, which are the ones
1574	–	* unlikely to be needed in the future.
1575	–	*/
1576	–	private void trimSpares() {
1577	–	int surplus = totalCountOf(workerCounts) - parallelism;
1578	–	WaitQueueNode q;
1579	–	while (surplus > 0 && (q = spareStack) != null) {
1580	–	if (casSpareStack(q, null)) {
1581	–	do {
1582	–	updateRunningCount(1);
1583	–	ForkJoinWorkerThread w = q.thread;
1584	–	if (w != null && surplus > 0 &&
1585	–	runningCountOf(workerCounts) > 0 && w.shutdown())
1586	–	--surplus;
1587	–	q.signal();
1588	–	} while ((q = q.next) != null);
1589	–	}
1813		}
1814		}
1815
1816		/**
1817		* Interface for extending managed parallelism for tasks running
1818	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1819	<	* Method <code>isReleasable</code> must return true if blocking is not
1820	<	* necessary. Method <code>block</code> blocks the current thread
1821	<	* if necessary (perhaps internally invoking isReleasable before
1822	<	* actually blocking.).
1818	>	* in {@link ForkJoinPool}s.
1819	>	*
1820	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
1821	>	* {@code isReleasable} must return {@code true} if blocking is
1822	>	* not necessary. Method {@code block} blocks the current thread
1823	>	* if necessary (perhaps internally invoking {@code isReleasable}
1824	>	* before actually blocking). The unusual methods in this API
1825	>	* accommodate synchronizers that may, but don't usually, block
1826	>	* for long periods. Similarly, they allow more efficient internal
1827	>	* handling of cases in which additional workers may be, but
1828	>	* usually are not, needed to ensure sufficient parallelism.
1829	>	* Toward this end, implementations of method {@code isReleasable}
1830	>	* must be amenable to repeated invocation.
1831	>	*
1832		* <p>For example, here is a ManagedBlocker based on a
1833		* ReentrantLock:
1834	<	* <pre>
1835	<	*   class ManagedLocker implements ManagedBlocker {
1836	<	*     final ReentrantLock lock;
1837	<	*     boolean hasLock = false;
1838	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1839	<	*     public boolean block() {
1840	<	*        if (!hasLock)
1841	<	*           lock.lock();
1842	<	*        return true;
1611	<	*     }
1612	<	*     public boolean isReleasable() {
1613	<	*        return hasLock || (hasLock = lock.tryLock());
1614	<	*     }
1834	>	*  <pre> {@code
1835	>	* class ManagedLocker implements ManagedBlocker {
1836	>	*   final ReentrantLock lock;
1837	>	*   boolean hasLock = false;
1838	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1839	>	*   public boolean block() {
1840	>	*     if (!hasLock)
1841	>	*       lock.lock();
1842	>	*     return true;
1843		*   }
1844	<	* </pre>
1844	>	*   public boolean isReleasable() {
1845	>	*     return hasLock || (hasLock = lock.tryLock());
1846	>	*   }
1847	>	* }}</pre>
1848	>	*
1849	>	* <p>Here is a class that possibly blocks waiting for an
1850	>	* item on a given queue:
1851	>	*  <pre> {@code
1852	>	* class QueueTaker<E> implements ManagedBlocker {
1853	>	*   final BlockingQueue<E> queue;
1854	>	*   volatile E item = null;
1855	>	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
1856	>	*   public boolean block() throws InterruptedException {
1857	>	*     if (item == null)
1858	>	*       item = queue.take();
1859	>	*     return true;
1860	>	*   }
1861	>	*   public boolean isReleasable() {
1862	>	*     return item != null || (item = queue.poll()) != null;
1863	>	*   }
1864	>	*   public E getItem() { // call after pool.managedBlock completes
1865	>	*     return item;
1866	>	*   }
1867	>	* }}</pre>
1868		*/
1869		public static interface ManagedBlocker {
1870		/**
1871		* Possibly blocks the current thread, for example waiting for
1872		* a lock or condition.
1873	<	* @return true if no additional blocking is necessary (i.e.,
1874	<	* if isReleasable would return true).
1873	>	*
1874	>	* @return {@code true} if no additional blocking is necessary
1875	>	* (i.e., if isReleasable would return true)
1876		* @throws InterruptedException if interrupted while waiting
1877	<	* (the method is not required to do so, but is allowe to).
1877	>	* (the method is not required to do so, but is allowed to)
1878		*/
1879		boolean block() throws InterruptedException;
1880
1881		/**
1882	<	* Returns true if blocking is unnecessary.
1882	>	* Returns {@code true} if blocking is unnecessary.
1883		*/
1884		boolean isReleasable();
1885		}
1886
1887		/**
1888		* Blocks in accord with the given blocker.  If the current thread
1889	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1890	<	* spare thread to be activated if necessary to ensure parallelism
1891	<	* while the current thread is blocked.  If
1892	<	* <code>maintainParallelism</code> is true and the pool supports
1893	<	* it ({@link #getMaintainsParallelism}), this method attempts to
1894	<	* maintain the pool's nominal parallelism. Otherwise if activates
1895	<	* a thread only if necessary to avoid complete starvation. This
1896	<	* option may be preferable when blockages use timeouts, or are
1897	<	* almost always brief.
1898	<	*
1899	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1900	<	* equivalent to
1901	<	* <pre>
1902	<	*   while (!blocker.isReleasable())
1651	<	*      if (blocker.block())
1652	<	*         return;
1653	<	* </pre>
1654	<	* If the caller is a ForkJoinTask, then the pool may first
1655	<	* be expanded to ensure parallelism, and later adjusted.
1889	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1890	>	* arranges for a spare thread to be activated if necessary to
1891	>	* ensure sufficient parallelism while the current thread is blocked.
1892	>	*
1893	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1894	>	* behaviorally equivalent to
1895	>	*  <pre> {@code
1896	>	* while (!blocker.isReleasable())
1897	>	*   if (blocker.block())
1898	>	*     return;
1899	>	* }</pre>
1900	>	*
1901	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1902	>	* first be expanded to ensure parallelism, and later adjusted.
1903		*
1904		* @param blocker the blocker
1905	<	* @param maintainParallelism if true and supported by this pool,
1659	<	* attempt to maintain the pool's nominal parallelism; otherwise
1660	<	* activate a thread only if necessary to avoid complete
1661	<	* starvation.
1662	<	* @throws InterruptedException if blocker.block did so.
1905	>	* @throws InterruptedException if blocker.block did so
1906		*/
1907	<	public static void managedBlock(ManagedBlocker blocker,
1665	<	boolean maintainParallelism)
1907	>	public static void managedBlock(ManagedBlocker blocker)
1908		throws InterruptedException {
1909		Thread t = Thread.currentThread();
1910	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1911	<	((ForkJoinWorkerThread)t).pool : null);
1912	<	if (!blocker.isReleasable()) {
1913	<	try {
1914	<	if (pool == null ||
1915	<	!pool.preBlock(blocker, maintainParallelism))
1674	<	awaitBlocker(blocker);
1675	<	} finally {
1676	<	if (pool != null)
1677	<	pool.updateRunningCount(1);
1678	<	}
1910	>	if (t instanceof ForkJoinWorkerThread) {
1911	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
1912	>	w.pool.awaitBlocker(blocker);
1913	>	}
1914	>	else {
1915	>	do {} while (!blocker.isReleasable() && !blocker.block());
1916		}
1917		}
1918
1919	<	private static void awaitBlocker(ManagedBlocker blocker)
1920	<	throws InterruptedException {
1921	<	do;while (!blocker.isReleasable() && !blocker.block());
1685	<	}
1686	<
1687	<	// AbstractExecutorService overrides
1919	>	// AbstractExecutorService overrides.  These rely on undocumented
1920	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1921	>	// implement RunnableFuture.
1922
1923		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1924	<	return new AdaptedRunnable(runnable, value);
1924	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1925		}
1926
1927		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1928	<	return new AdaptedCallable(callable);
1928	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1929		}
1930
1931	+	// Unsafe mechanics
1932	+
1933	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1934	+	private static final long workerCountsOffset =
1935	+	objectFieldOffset("workerCounts", ForkJoinPool.class);
1936	+	private static final long runStateOffset =
1937	+	objectFieldOffset("runState", ForkJoinPool.class);
1938	+	private static final long eventCountOffset =
1939	+	objectFieldOffset("eventCount", ForkJoinPool.class);
1940	+	private static final long eventWaitersOffset =
1941	+	objectFieldOffset("eventWaiters",ForkJoinPool.class);
1942	+	private static final long stealCountOffset =
1943	+	objectFieldOffset("stealCount",ForkJoinPool.class);
1944	+	private static final long spareWaitersOffset =
1945	+	objectFieldOffset("spareWaiters",ForkJoinPool.class);
1946
1947	<	// Temporary Unsafe mechanics for preliminary release
1699	<	private static Unsafe getUnsafe() throws Throwable {
1947	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1948		try {
1949	<	return Unsafe.getUnsafe();
1949	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1950	>	} catch (NoSuchFieldException e) {
1951	>	// Convert Exception to corresponding Error
1952	>	NoSuchFieldError error = new NoSuchFieldError(field);
1953	>	error.initCause(e);
1954	>	throw error;
1955	>	}
1956	>	}
1957	>
1958	>	/**
1959	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1960	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1961	>	* into a jdk.
1962	>	*
1963	>	* @return a sun.misc.Unsafe
1964	>	*/
1965	>	private static sun.misc.Unsafe getUnsafe() {
1966	>	try {
1967	>	return sun.misc.Unsafe.getUnsafe();
1968		} catch (SecurityException se) {
1969		try {
1970		return java.security.AccessController.doPrivileged
1971	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1972	<	public Unsafe run() throws Exception {
1973	<	return getUnsafePrivileged();
1971	>	(new java.security
1972	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1973	>	public sun.misc.Unsafe run() throws Exception {
1974	>	java.lang.reflect.Field f = sun.misc
1975	>	.Unsafe.class.getDeclaredField("theUnsafe");
1976	>	f.setAccessible(true);
1977	>	return (sun.misc.Unsafe) f.get(null);
1978		}});
1979		} catch (java.security.PrivilegedActionException e) {
1980	<	throw e.getCause();
1980	>	throw new RuntimeException("Could not initialize intrinsics",
1981	>	e.getCause());
1982		}
1983		}
1984		}
1714	–
1715	–	private static Unsafe getUnsafePrivileged()
1716	–	throws NoSuchFieldException, IllegalAccessException {
1717	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1718	–	f.setAccessible(true);
1719	–	return (Unsafe) f.get(null);
1720	–	}
1721	–
1722	–	private static long fieldOffset(String fieldName)
1723	–	throws NoSuchFieldException {
1724	–	return _unsafe.objectFieldOffset
1725	–	(ForkJoinPool.class.getDeclaredField(fieldName));
1726	–	}
1727	–
1728	–	static final Unsafe _unsafe;
1729	–	static final long eventCountOffset;
1730	–	static final long workerCountsOffset;
1731	–	static final long runControlOffset;
1732	–	static final long syncStackOffset;
1733	–	static final long spareStackOffset;
1734	–
1735	–	static {
1736	–	try {
1737	–	_unsafe = getUnsafe();
1738	–	eventCountOffset = fieldOffset("eventCount");
1739	–	workerCountsOffset = fieldOffset("workerCounts");
1740	–	runControlOffset = fieldOffset("runControl");
1741	–	syncStackOffset = fieldOffset("syncStack");
1742	–	spareStackOffset = fieldOffset("spareStack");
1743	–	} catch (Throwable e) {
1744	–	throw new RuntimeException("Could not initialize intrinsics", e);
1745	–	}
1746	–	}
1747	–
1748	–	private boolean casEventCount(long cmp, long val) {
1749	–	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1750	–	}
1751	–	private boolean casWorkerCounts(int cmp, int val) {
1752	–	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1753	–	}
1754	–	private boolean casRunControl(int cmp, int val) {
1755	–	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1756	–	}
1757	–	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1758	–	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1759	–	}
1760	–	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1761	–	return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val);
1762	–	}
1985		}

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