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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 1.70 by dl, Sat Sep 4 11:33:53 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.locks.*;
11	<	import java.util.concurrent.atomic.*;
12	<	import sun.misc.Unsafe;
13	<	import java.lang.reflect.*;
10	>	import java.util.ArrayList;
11	>	import java.util.Arrays;
12	>	import java.util.Collection;
13	>	import java.util.Collections;
14	>	import java.util.List;
15	>	import java.util.concurrent.locks.LockSupport;
16	>	import java.util.concurrent.locks.ReentrantLock;
17	>	import java.util.concurrent.atomic.AtomicInteger;
18	>	import java.util.concurrent.CountDownLatch;
19
20		/**
21	<	* An {@link ExecutorService} for running {@link ForkJoinTask}s.  A
22	<	* ForkJoinPool provides the entry point for submissions from
23	<	* non-ForkJoinTasks, as well as management and monitoring operations.
24	<	* 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.
21	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
22	>	* A {@code ForkJoinPool} provides the entry point for submissions
23	>	* from non-{@code ForkJoinTask} clients, as well as management and
24	>	* monitoring operations.
25		*
26	<	* <p>ForkJoinPools differ from other kinds of Executors mainly in
27	<	* that they provide <em>work-stealing</em>: all threads in the pool
28	<	* attempt to find and execute subtasks created by other active tasks
29	<	* (eventually blocking if none exist). This makes them efficient when
30	<	* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
31	<	* as the mixed execution of some plain Runnable- or Callable- based
32	<	* activities along with ForkJoinTasks. Otherwise, other
33	<	* ExecutorService implementations are typically more appropriate
34	<	* choices.
26	>	* <p>A {@code ForkJoinPool} differs from other kinds of {@link
27	>	* ExecutorService} mainly by virtue of employing
28	>	* <em>work-stealing</em>: all threads in the pool attempt to find and
29	>	* execute subtasks created by other active tasks (eventually blocking
30	>	* waiting for work if none exist). This enables efficient processing
31	>	* when most tasks spawn other subtasks (as do most {@code
32	>	* ForkJoinTask}s). When setting <em>asyncMode</em> to true in
33	>	* constructors, {@code ForkJoinPool}s may also be appropriate for use
34	>	* with event-style tasks that are never joined.
35		*
36	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
37	<	* (target pool size), which it attempts to maintain by dynamically
38	<	* adding, suspending, or resuming threads, even if some tasks are
39	<	* waiting to join others. However, no such adjustments are performed
40	<	* in the face of blocked IO or other unmanaged synchronization. The
41	<	* nested <code>ManagedBlocker</code> interface enables extension of
42	<	* the kinds of synchronization accommodated.  The target parallelism
43	<	* level may also be changed dynamically (<code>setParallelism</code>)
44	<	* and dynamically thread construction can be limited using methods
43	<	* <code>setMaximumPoolSize</code> and/or
44	<	* <code>setMaintainsParallelism</code>.
36	>	* <p>A {@code ForkJoinPool} is constructed with a given target
37	>	* parallelism level; by default, equal to the number of available
38	>	* processors. The pool attempts to maintain enough active (or
39	>	* available) threads by dynamically adding, suspending, or resuming
40	>	* internal worker threads, even if some tasks are stalled waiting to
41	>	* join others. However, no such adjustments are guaranteed in the
42	>	* face of blocked IO or other unmanaged synchronization. The nested
43	>	* {@link ManagedBlocker} interface enables extension of the kinds of
44	>	* synchronization accommodated.
45		*
46		* <p>In addition to execution and lifecycle control methods, this
47		* class provides status check methods (for example
48	<	* <code>getStealCount</code>) that are intended to aid in developing,
48	>	* {@link #getStealCount}) that are intended to aid in developing,
49		* tuning, and monitoring fork/join applications. Also, method
50	<	* <code>toString</code> returns indications of pool state in a
50	>	* {@link #toString} returns indications of pool state in a
51		* convenient form for informal monitoring.
52		*
53	+	* <p> As is the case with other ExecutorServices, there are three
54	+	* main task execution methods summarized in the following
55	+	* table. These are designed to be used by clients not already engaged
56	+	* in fork/join computations in the current pool.  The main forms of
57	+	* these methods accept instances of {@code ForkJoinTask}, but
58	+	* overloaded forms also allow mixed execution of plain {@code
59	+	* Runnable}- or {@code Callable}- based activities as well.  However,
60	+	* tasks that are already executing in a pool should normally
61	+	* <em>NOT</em> use these pool execution methods, but instead use the
62	+	* within-computation forms listed in the table.
63	+	*
64	+	* <table BORDER CELLPADDING=3 CELLSPACING=1>
65	+	*  <tr>
66	+	*    <td></td>
67	+	*    <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
68	+	*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
69	+	*  </tr>
70	+	*  <tr>
71	+	*    <td> <b>Arrange async execution</td>
72	+	*    <td> {@link #execute(ForkJoinTask)}</td>
73	+	*    <td> {@link ForkJoinTask#fork}</td>
74	+	*  </tr>
75	+	*  <tr>
76	+	*    <td> <b>Await and obtain result</td>
77	+	*    <td> {@link #invoke(ForkJoinTask)}</td>
78	+	*    <td> {@link ForkJoinTask#invoke}</td>
79	+	*  </tr>
80	+	*  <tr>
81	+	*    <td> <b>Arrange exec and obtain Future</td>
82	+	*    <td> {@link #submit(ForkJoinTask)}</td>
83	+	*    <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td>
84	+	*  </tr>
85	+	* </table>
86	+	*
87	+	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
88	+	* used for all parallel task execution in a program or subsystem.
89	+	* Otherwise, use would not usually outweigh the construction and
90	+	* bookkeeping overhead of creating a large set of threads. For
91	+	* example, a common pool could be used for the {@code SortTasks}
92	+	* illustrated in {@link RecursiveAction}. Because {@code
93	+	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
94	+	* daemon} mode, there is typically no need to explicitly {@link
95	+	* #shutdown} such a pool upon program exit.
96	+	*
97	+	* <pre>
98	+	* static final ForkJoinPool mainPool = new ForkJoinPool();
99	+	* ...
100	+	* public void sort(long[] array) {
101	+	*   mainPool.invoke(new SortTask(array, 0, array.length));
102	+	* }
103	+	* </pre>
104	+	*
105		* <p><b>Implementation notes</b>: This implementation restricts the
106		* maximum number of running threads to 32767. Attempts to create
107	<	* pools with greater than the maximum result in
108	<	* IllegalArgumentExceptions.
107	>	* pools with greater than the maximum number result in
108	>	* {@code IllegalArgumentException}.
109	>	*
110	>	* <p>This implementation rejects submitted tasks (that is, by throwing
111	>	* {@link RejectedExecutionException}) only when the pool is shut down
112	>	* or internal resources have been exhausted.
113	>	*
114	>	* @since 1.7
115	>	* @author Doug Lea
116		*/
117		public class ForkJoinPool extends AbstractExecutorService {
118
119		/*
120	<	* See the extended comments interspersed below for design,
121	<	* rationale, and walkthroughs.
120	>	* Implementation Overview
121	>	*
122	>	* This class provides the central bookkeeping and control for a
123	>	* set of worker threads: Submissions from non-FJ threads enter
124	>	* into a submission queue. Workers take these tasks and typically
125	>	* split them into subtasks that may be stolen by other workers.
126	>	* The main work-stealing mechanics implemented in class
127	>	* ForkJoinWorkerThread give first priority to processing tasks
128	>	* from their own queues (LIFO or FIFO, depending on mode), then
129	>	* to randomized FIFO steals of tasks in other worker queues, and
130	>	* lastly to new submissions. These mechanics do not consider
131	>	* affinities, loads, cache localities, etc, so rarely provide the
132	>	* best possible performance on a given machine, but portably
133	>	* provide good throughput by averaging over these factors.
134	>	* (Further, even if we did try to use such information, we do not
135	>	* usually have a basis for exploiting it. For example, some sets
136	>	* of tasks profit from cache affinities, but others are harmed by
137	>	* cache pollution effects.)
138	>	*
139	>	* Beyond work-stealing support and essential bookkeeping, the
140	>	* main responsibility of this framework is to take actions when
141	>	* one worker is waiting to join a task stolen (or always held by)
142	>	* another.  Because we are multiplexing many tasks on to a pool
143	>	* of workers, we can't just let them block (as in Thread.join).
144	>	* We also cannot just reassign the joiner's run-time stack with
145	>	* another and replace it later, which would be a form of
146	>	* "continuation", that even if possible is not necessarily a good
147	>	* idea. Given that the creation costs of most threads on most
148	>	* systems mainly surrounds setting up runtime stacks, thread
149	>	* creation and switching is usually not much more expensive than
150	>	* stack creation and switching, and is more flexible). Instead we
151	>	* combine two tactics:
152	>	*
153	>	*   Helping: Arranging for the joiner to execute some task that it
154	>	*      would be running if the steal had not occurred.  Method
155	>	*      ForkJoinWorkerThread.helpJoinTask tracks joining->stealing
156	>	*      links to try to find such a task.
157	>	*
158	>	*   Compensating: Unless there are already enough live threads,
159	>	*      method helpMaintainParallelism() may create or
160	>	*      re-activate a spare thread to compensate for blocked
161	>	*      joiners until they unblock.
162	>	*
163	>	* It is impossible to keep exactly the target (parallelism)
164	>	* number of threads running at any given time.  Determining
165	>	* existence of conservatively safe helping targets, the
166	>	* availability of already-created spares, and the apparent need
167	>	* to create new spares are all racy and require heuristic
168	>	* guidance, so we rely on multiple retries of each.  Compensation
169	>	* occurs in slow-motion. It is triggered only upon timeouts of
170	>	* Object.wait used for joins. This reduces poor decisions that
171	>	* would otherwise be made when threads are waiting for others
172	>	* that are stalled because of unrelated activities such as
173	>	* garbage collection.
174	>	*
175	>	* The ManagedBlocker extension API can't use helping so relies
176	>	* only on compensation in method awaitBlocker.
177	>	*
178	>	* The main throughput advantages of work-stealing stem from
179	>	* decentralized control -- workers mostly steal tasks from each
180	>	* other. We do not want to negate this by creating bottlenecks
181	>	* implementing other management responsibilities. So we use a
182	>	* collection of techniques that avoid, reduce, or cope well with
183	>	* contention. These entail several instances of bit-packing into
184	>	* CASable fields to maintain only the minimally required
185	>	* atomicity. To enable such packing, we restrict maximum
186	>	* parallelism to (1<<15)-1 (enabling twice this (to accommodate
187	>	* unbalanced increments and decrements) to fit into a 16 bit
188	>	* field, which is far in excess of normal operating range.  Even
189	>	* though updates to some of these bookkeeping fields do sometimes
190	>	* contend with each other, they don't normally cache-contend with
191	>	* updates to others enough to warrant memory padding or
192	>	* isolation. So they are all held as fields of ForkJoinPool
193	>	* objects.  The main capabilities are as follows:
194	>	*
195	>	* 1. Creating and removing workers. Workers are recorded in the
196	>	* "workers" array. This is an array as opposed to some other data
197	>	* structure to support index-based random steals by workers.
198	>	* Updates to the array recording new workers and unrecording
199	>	* terminated ones are protected from each other by a lock
200	>	* (workerLock) but the array is otherwise concurrently readable,
201	>	* and accessed directly by workers. To simplify index-based
202	>	* operations, the array size is always a power of two, and all
203	>	* readers must tolerate null slots. Currently, all worker thread
204	>	* creation is on-demand, triggered by task submissions,
205	>	* replacement of terminated workers, and/or compensation for
206	>	* blocked workers. However, all other support code is set up to
207	>	* work with other policies.
208	>	*
209	>	* To ensure that we do not hold on to worker references that
210	>	* would prevent GC, ALL accesses to workers are via indices into
211	>	* the workers array (which is one source of some of the unusual
212	>	* code constructions here). In essence, the workers array serves
213	>	* as a WeakReference mechanism. Thus for example the event queue
214	>	* stores worker indices, not worker references. Access to the
215	>	* workers in associated methods (for example releaseEventWaiters)
216	>	* must both index-check and null-check the IDs. All such accesses
217	>	* ignore bad IDs by returning out early from what they are doing,
218	>	* since this can only be associated with shutdown, in which case
219	>	* it is OK to give up. On termination, we just clobber these
220	>	* data structures without trying to use them.
221	>	*
222	>	* 2. Bookkeeping for dynamically adding and removing workers. We
223	>	* aim to approximately maintain the given level of parallelism.
224	>	* When some workers are known to be blocked (on joins or via
225	>	* ManagedBlocker), we may create or resume others to take their
226	>	* place until they unblock (see below). Implementing this
227	>	* requires counts of the number of "running" threads (i.e., those
228	>	* that are neither blocked nor artificially suspended) as well as
229	>	* the total number.  These two values are packed into one field,
230	>	* "workerCounts" because we need accurate snapshots when deciding
231	>	* to create, resume or suspend.  Note however that the
232	>	* correspondence of these counts to reality is not guaranteed. In
233	>	* particular updates for unblocked threads may lag until they
234	>	* actually wake up.
235	>	*
236	>	* 3. Maintaining global run state. The run state of the pool
237	>	* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to
238	>	* those in other Executor implementations, as well as a count of
239	>	* "active" workers -- those that are, or soon will be, or
240	>	* recently were executing tasks. The runLevel and active count
241	>	* are packed together in order to correctly trigger shutdown and
242	>	* termination. Without care, active counts can be subject to very
243	>	* high contention.  We substantially reduce this contention by
244	>	* relaxing update rules.  A worker must claim active status
245	>	* prospectively, by activating if it sees that a submitted or
246	>	* stealable task exists (it may find after activating that the
247	>	* task no longer exists). It stays active while processing this
248	>	* task (if it exists) and any other local subtasks it produces,
249	>	* until it cannot find any other tasks. It then tries
250	>	* inactivating (see method preStep), but upon update contention
251	>	* instead scans for more tasks, later retrying inactivation if it
252	>	* doesn't find any.
253	>	*
254	>	* 4. Managing idle workers waiting for tasks. We cannot let
255	>	* workers spin indefinitely scanning for tasks when none are
256	>	* available. On the other hand, we must quickly prod them into
257	>	* action when new tasks are submitted or generated.  We
258	>	* park/unpark these idle workers using an event-count scheme.
259	>	* Field eventCount is incremented upon events that may enable
260	>	* workers that previously could not find a task to now find one:
261	>	* Submission of a new task to the pool, or another worker pushing
262	>	* a task onto a previously empty queue.  (We also use this
263	>	* mechanism for configuration and termination actions that
264	>	* require wakeups of idle workers).  Each worker maintains its
265	>	* last known event count, and blocks when a scan for work did not
266	>	* find a task AND its lastEventCount matches the current
267	>	* eventCount. Waiting idle workers are recorded in a variant of
268	>	* Treiber stack headed by field eventWaiters which, when nonzero,
269	>	* encodes the thread index and count awaited for by the worker
270	>	* thread most recently calling eventSync. This thread in turn has
271	>	* a record (field nextEventWaiter) for the next waiting worker.
272	>	* In addition to allowing simpler decisions about need for
273	>	* wakeup, the event count bits in eventWaiters serve the role of
274	>	* tags to avoid ABA errors in Treiber stacks. Upon any wakeup,
275	>	* released threads also try to release at most two others.  The
276	>	* net effect is a tree-like diffusion of signals, where released
277	>	* threads (and possibly others) help with unparks.  To further
278	>	* reduce contention effects a bit, failed CASes to increment
279	>	* field eventCount are tolerated without retries in signalWork.
280	>	* Conceptually they are merged into the same event, which is OK
281	>	* when their only purpose is to enable workers to scan for work.
282	>	*
283	>	* 5. Managing suspension of extra workers. When a worker notices
284	>	* (usually upon timeout of a wait()) that there are too few
285	>	* running threads, we may create a new thread to maintain
286	>	* parallelism level, or at least avoid starvation. Usually, extra
287	>	* threads are needed for only very short periods, yet join
288	>	* dependencies are such that we sometimes need them in
289	>	* bursts. Rather than create new threads each time this happens,
290	>	* we suspend no-longer-needed extra ones as "spares". For most
291	>	* purposes, we don't distinguish "extra" spare threads from
292	>	* normal "core" threads: On each call to preStep (the only point
293	>	* at which we can do this) a worker checks to see if there are
294	>	* now too many running workers, and if so, suspends itself.
295	>	* Method helpMaintainParallelism looks for suspended threads to
296	>	* resume before considering creating a new replacement. The
297	>	* spares themselves are encoded on another variant of a Treiber
298	>	* Stack, headed at field "spareWaiters".  Note that the use of
299	>	* spares is intrinsically racy.  One thread may become a spare at
300	>	* about the same time as another is needlessly being created. We
301	>	* counteract this and related slop in part by requiring resumed
302	>	* spares to immediately recheck (in preStep) to see whether they
303	>	* they should re-suspend.
304	>	*
305	>	* 6. Killing off unneeded workers. A timeout mechanism is used to
306	>	* shed unused workers: The oldest (first) event queue waiter uses
307	>	* a timed rather than hard wait. When this wait times out without
308	>	* a normal wakeup, it tries to shutdown any one (for convenience
309	>	* the newest) other spare or event waiter via
310	>	* tryShutdownUnusedWorker. This eventually reduces the number of
311	>	* worker threads to a minimum of one after a long enough period
312	>	* without use.
313	>	*
314	>	* 7. Deciding when to create new workers. The main dynamic
315	>	* control in this class is deciding when to create extra threads
316	>	* in method helpMaintainParallelism. We would like to keep
317	>	* exactly #parallelism threads running, which is an impossible
318	>	* task. We always need to create one when the number of running
319	>	* threads would become zero and all workers are busy. Beyond
320	>	* this, we must rely on heuristics that work well in the
321	>	* presence of transient phenomena such as GC stalls, dynamic
322	>	* compilation, and wake-up lags. These transients are extremely
323	>	* common -- we are normally trying to fully saturate the CPUs on
324	>	* a machine, so almost any activity other than running tasks
325	>	* impedes accuracy. Our main defense is to allow parallelism to
326	>	* lapse for a while during joins, and use a timeout to see if,
327	>	* after the resulting settling, there is still a need for
328	>	* additional workers.  This also better copes with the fact that
329	>	* some of the methods in this class tend to never become compiled
330	>	* (but are interpreted), so some components of the entire set of
331	>	* controls might execute 100 times faster than others. And
332	>	* similarly for cases where the apparent lack of work is just due
333	>	* to GC stalls and other transient system activity.
334	>	*
335	>	* Beware that there is a lot of representation-level coupling
336	>	* among classes ForkJoinPool, ForkJoinWorkerThread, and
337	>	* ForkJoinTask.  For example, direct access to "workers" array by
338	>	* workers, and direct access to ForkJoinTask.status by both
339	>	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
340	>	* trying to reduce this, since any associated future changes in
341	>	* representations will need to be accompanied by algorithmic
342	>	* changes anyway.
343	>	*
344	>	* Style notes: There are lots of inline assignments (of form
345	>	* "while ((local = field) != 0)") which are usually the simplest
346	>	* way to ensure the required read orderings (which are sometimes
347	>	* critical). Also several occurrences of the unusual "do {}
348	>	* while (!cas...)" which is the simplest way to force an update of
349	>	* a CAS'ed variable. There are also other coding oddities that
350	>	* help some methods perform reasonably even when interpreted (not
351	>	* compiled), at the expense of some messy constructions that
352	>	* reduce byte code counts.
353	>	*
354	>	* The order of declarations in this file is: (1) statics (2)
355	>	* fields (along with constants used when unpacking some of them)
356	>	* (3) internal control methods (4) callbacks and other support
357	>	* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
358	>	* methods (plus a few little helpers).
359		*/
360
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	–
361		/**
362	<	* Factory for creating new ForkJoinWorkerThreads.  A
363	<	* ForkJoinWorkerThreadFactory must be defined and used for
364	<	* ForkJoinWorkerThread subclasses that extend base functionality
365	<	* or initialize threads with different contexts.
362	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
363	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
364	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
365	>	* functionality or initialize threads with different contexts.
366		*/
367		public static interface ForkJoinWorkerThreadFactory {
368		/**
369		* Returns a new worker thread operating in the given pool.
370		*
371		* @param pool the pool this thread works in
372	<	* @throws NullPointerException if pool is null;
372	>	* @throws NullPointerException if the pool is null
373		*/
374		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
375		}
376
377		/**
378	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
378	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
379		* new ForkJoinWorkerThread.
380		*/
381	<	static class  DefaultForkJoinWorkerThreadFactory
381	>	static class DefaultForkJoinWorkerThreadFactory
382		implements ForkJoinWorkerThreadFactory {
383		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
384	<	try {
95	<	return new ForkJoinWorkerThread(pool);
96	<	} catch (OutOfMemoryError oom)  {
97	<	return null;
98	<	}
384	>	return new ForkJoinWorkerThread(pool);
385		}
386		}
387
#	Line 131 | Line 417 | public class ForkJoinPool extends Abstra
417		new AtomicInteger();
418
419		/**
420	<	* Array holding all worker threads in the pool. Array size must
421	<	* be a power of two.  Updates and replacements are protected by
422	<	* workerLock, but it is always kept in a consistent enough state
423	<	* to be randomly accessed without locking by workers performing
424	<	* work-stealing.
420	>	* The time to block in a join (see awaitJoin) before checking if
421	>	* a new worker should be (re)started to maintain parallelism
422	>	* level. The value should be short enough to maintain global
423	>	* responsiveness and progress but long enough to avoid
424	>	* counterproductive firings during GC stalls or unrelated system
425	>	* activity, and to not bog down systems with continual re-firings
426	>	* on GCs or legitimately long waits.
427		*/
428	<	volatile ForkJoinWorkerThread[] workers;
428	>	private static final long JOIN_TIMEOUT_MILLIS = 250L; // 4 per second
429
430		/**
431	<	* Lock protecting access to workers.
431	>	* The wakeup interval (in nanoseconds) for the oldest worker
432	>	* worker waiting for an event invokes tryShutdownUnusedWorker to shrink
433	>	* the number of workers.  The exact value does not matter too
434	>	* much, but should be long enough to slowly release resources
435	>	* during long periods without use without disrupting normal use.
436		*/
437	<	private final ReentrantLock workerLock;
437	>	private static final long SHRINK_RATE_NANOS =
438	>	30L * 1000L * 1000L * 1000L; // 2 per minute
439
440		/**
441	<	* Condition for awaitTermination.
441	>	* Absolute bound for parallelism level. Twice this number plus
442	>	* one (i.e., 0xfff) must fit into a 16bit field to enable
443	>	* word-packing for some counts and indices.
444		*/
445	<	private final Condition termination;
445	>	private static final int MAX_WORKERS   = 0x7fff;
446
447		/**
448	<	* The uncaught exception handler used when any worker
449	<	* abrupty terminates
448	>	* Array holding all worker threads in the pool.  Array size must
449	>	* be a power of two.  Updates and replacements are protected by
450	>	* workerLock, but the array is always kept in a consistent enough
451	>	* state to be randomly accessed without locking by workers
452	>	* performing work-stealing, as well as other traversal-based
453	>	* methods in this class. All readers must tolerate that some
454	>	* array slots may be null.
455		*/
456	<	private Thread.UncaughtExceptionHandler ueh;
456	>	volatile ForkJoinWorkerThread[] workers;
457
458		/**
459	<	* Creation factory for worker threads.
459	>	* Queue for external submissions.
460		*/
461	<	private final ForkJoinWorkerThreadFactory factory;
461	>	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
462
463		/**
464	<	* Head of stack of threads that were created to maintain
165	<	* parallelism when other threads blocked, but have since
166	<	* suspended when the parallelism level rose.
464	>	* Lock protecting updates to workers array.
465		*/
466	<	private volatile WaitQueueNode spareStack;
466	>	private final ReentrantLock workerLock;
467
468		/**
469	<	* Sum of per-thread steal counts, updated only when threads are
172	<	* idle or terminating.
469	>	* Latch released upon termination.
470		*/
471	<	private final AtomicLong stealCount;
471	>	private final Phaser termination;
472
473		/**
474	<	* Queue for external submissions.
474	>	* Creation factory for worker threads.
475		*/
476	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
476	>	private final ForkJoinWorkerThreadFactory factory;
477
478		/**
479	<	* Head of Treiber stack for barrier sync. See below for explanation
479	>	* Sum of per-thread steal counts, updated only when threads are
480	>	* idle or terminating.
481		*/
482	<	private volatile WaitQueueNode syncStack;
482	>	private volatile long stealCount;
483
484		/**
485	<	* The count for event barrier
485	>	* Encoded record of top of Treiber stack of threads waiting for
486	>	* events. The top 32 bits contain the count being waited for. The
487	>	* bottom 16 bits contains one plus the pool index of waiting
488	>	* worker thread. (Bits 16-31 are unused.)
489		*/
490	<	private volatile long eventCount;
490	>	private volatile long eventWaiters;
491	>
492	>	private static final int  EVENT_COUNT_SHIFT = 32;
493	>	private static final long WAITER_ID_MASK    = (1L << 16) - 1L;
494
495		/**
496	<	* Pool number, just for assigning useful names to worker threads
496	>	* A counter for events that may wake up worker threads:
497	>	*   - Submission of a new task to the pool
498	>	*   - A worker pushing a task on an empty queue
499	>	*   - termination
500		*/
501	<	private final int poolNumber;
501	>	private volatile int eventCount;
502
503		/**
504	<	* The maximum allowed pool size
504	>	* Encoded record of top of Treiber stack of spare threads waiting
505	>	* for resumption. The top 16 bits contain an arbitrary count to
506	>	* avoid ABA effects. The bottom 16bits contains one plus the pool
507	>	* index of waiting worker thread.
508		*/
509	<	private volatile int maxPoolSize;
509	>	private volatile int spareWaiters;
510	>
511	>	private static final int SPARE_COUNT_SHIFT = 16;
512	>	private static final int SPARE_ID_MASK     = (1 << 16) - 1;
513
514		/**
515	<	* The desired parallelism level, updated only under workerLock.
516	<	*/
517	<	private volatile int parallelism;
515	>	* Lifecycle control. The low word contains the number of workers
516	>	* that are (probably) executing tasks. This value is atomically
517	>	* incremented before a worker gets a task to run, and decremented
518	>	* when worker has no tasks and cannot find any.  Bits 16-18
519	>	* contain runLevel value. When all are zero, the pool is
520	>	* running. Level transitions are monotonic (running -> shutdown
521	>	* -> terminating -> terminated) so each transition adds a bit.
522	>	* These are bundled together to ensure consistent read for
523	>	* termination checks (i.e., that runLevel is at least SHUTDOWN
524	>	* and active threads is zero).
525	>	*
526	>	* Notes: Most direct CASes are dependent on these bitfield
527	>	* positions.  Also, this field is non-private to enable direct
528	>	* performance-sensitive CASes in ForkJoinWorkerThread.
529	>	*/
530	>	volatile int runState;
531	>
532	>	// Note: The order among run level values matters.
533	>	private static final int RUNLEVEL_SHIFT     = 16;
534	>	private static final int SHUTDOWN           = 1 << RUNLEVEL_SHIFT;
535	>	private static final int TERMINATING        = 1 << (RUNLEVEL_SHIFT + 1);
536	>	private static final int TERMINATED         = 1 << (RUNLEVEL_SHIFT + 2);
537	>	private static final int ACTIVE_COUNT_MASK  = (1 << RUNLEVEL_SHIFT) - 1;
538
539		/**
540		* Holds number of total (i.e., created and not yet terminated)
541		* and running (i.e., not blocked on joins or other managed sync)
542	<	* threads, packed into one int to ensure consistent snapshot when
542	>	* threads, packed together to ensure consistent snapshot when
543		* making decisions about creating and suspending spare
544	<	* threads. Updated only by CAS.  Note: CASes in
545	<	* updateRunningCount and preJoin running active count is in low
546	<	* word, so need to be modified if this changes
544	>	* threads. Updated only by CAS. Note that adding a new worker
545	>	* requires incrementing both counts, since workers start off in
546	>	* running state.
547		*/
548		private volatile int workerCounts;
549
550	<	private static int totalCountOf(int s)           { return s >>> 16;  }
551	<	private static int runningCountOf(int s)         { return s & shortMask; }
552	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
550	>	private static final int TOTAL_COUNT_SHIFT  = 16;
551	>	private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1;
552	>	private static final int ONE_RUNNING        = 1;
553	>	private static final int ONE_TOTAL          = 1 << TOTAL_COUNT_SHIFT;
554
555		/**
556	<	* Add delta (which may be negative) to running count.  This must
557	<	* be called before (with negative arg) and after (with positive)
224	<	* any managed synchronization (i.e., mainly, joins)
225	<	* @param delta the number to add
556	>	* The target parallelism level.
557	>	* Accessed directly by ForkJoinWorkerThreads.
558		*/
559	<	final void updateRunningCount(int delta) {
228	<	int s;
229	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
230	<	}
559	>	final int parallelism;
560
561		/**
562	<	* Add delta (which may be negative) to both total and running
563	<	* count.  This must be called upon creation and termination of
235	<	* worker threads.
236	<	* @param delta the number to add
562	>	* True if use local fifo, not default lifo, for local polling
563	>	* Read by, and replicated by ForkJoinWorkerThreads
564		*/
565	<	private void updateWorkerCount(int delta) {
239	<	int d = delta + (delta << 16); // add to both lo and hi parts
240	<	int s;
241	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
242	<	}
565	>	final boolean locallyFifo;
566
567		/**
568	<	* Lifecycle control. High word contains runState, low word
569	<	* contains the number of workers that are (probably) executing
247	<	* tasks. This value is atomically incremented before a worker
248	<	* gets a task to run, and decremented when worker has no tasks
249	<	* and cannot find any. These two fields are bundled together to
250	<	* support correct termination triggering.  Note: activeCount
251	<	* CAS'es cheat by assuming active count is in low word, so need
252	<	* to be modified if this changes
568	>	* The uncaught exception handler used when any worker abruptly
569	>	* terminates.
570		*/
571	<	private volatile int runControl;
571	>	private final Thread.UncaughtExceptionHandler ueh;
572
573	<	// RunState values. Order among values matters
574	<	private static final int RUNNING     = 0;
575	<	private static final int SHUTDOWN    = 1;
576	<	private static final int TERMINATING = 2;
260	<	private static final int TERMINATED  = 3;
573	>	/**
574	>	* Pool number, just for assigning useful names to worker threads
575	>	*/
576	>	private final int poolNumber;
577
578	<	private static int runStateOf(int c)             { return c >>> 16; }
579	<	private static int activeCountOf(int c)          { return c & shortMask; }
264	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
578	>	// Utilities for CASing fields. Note that most of these
579	>	// are usually manually inlined by callers
580
581		/**
582	<	* Try incrementing active count; fail on contention. Called by
268	<	* workers before/during executing tasks.
269	<	* @return true on success;
582	>	* Increments running count part of workerCounts
583		*/
584	<	final boolean tryIncrementActiveCount() {
585	<	int c = runControl;
586	<	return casRunControl(c, c+1);
584	>	final void incrementRunningCount() {
585	>	int c;
586	>	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
587	>	c = workerCounts,
588	>	c + ONE_RUNNING));
589		}
590
591		/**
592	<	* Try decrementing active count; fail on contention.
278	<	* Possibly trigger termination on success
279	<	* Called by workers when they can't find tasks.
280	<	* @return true on success
592	>	* Tries to decrement running count unless already zero
593		*/
594	<	final boolean tryDecrementActiveCount() {
595	<	int c = runControl;
596	<	int nextc = c - 1;
285	<	if (!casRunControl(c, nextc))
594	>	final boolean tryDecrementRunningCount() {
595	>	int wc = workerCounts;
596	>	if ((wc & RUNNING_COUNT_MASK) == 0)
597		return false;
598	<	if (canTerminateOnShutdown(nextc))
599	<	terminateOnShutdown();
289	<	return true;
598	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
599	>	wc, wc - ONE_RUNNING);
600		}
601
602		/**
603	<	* Return true if argument represents zero active count and
604	<	* nonzero runstate, which is the triggering condition for
605	<	* terminating on shutdown.
603	>	* Forces decrement of encoded workerCounts, awaiting nonzero if
604	>	* (rarely) necessary when other count updates lag.
605	>	*
606	>	* @param dr -- either zero or ONE_RUNNING
607	>	* @param dt == either zero or ONE_TOTAL
608		*/
609	<	private static boolean canTerminateOnShutdown(int c) {
610	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
609	>	private void decrementWorkerCounts(int dr, int dt) {
610	>	for (;;) {
611	>	int wc = workerCounts;
612	>	if ((wc & RUNNING_COUNT_MASK)  - dr < 0 ||
613	>	(wc >>> TOTAL_COUNT_SHIFT) - dt < 0) {
614	>	if ((runState & TERMINATED) != 0)
615	>	return; // lagging termination on a backout
616	>	Thread.yield();
617	>	}
618	>	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
619	>	wc, wc - (dr + dt)))
620	>	return;
621	>	}
622		}
623
624		/**
625	<	* Transition run state to at least the given state. Return true
626	<	* if not already at least given state.
625	>	* Tries decrementing active count; fails on contention.
626	>	* Called when workers cannot find tasks to run.
627		*/
628	<	private boolean transitionRunStateTo(int state) {
628	>	final boolean tryDecrementActiveCount() {
629	>	int c;
630	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
631	>	c = runState, c - 1);
632	>	}
633	>
634	>	/**
635	>	* Advances to at least the given level. Returns true if not
636	>	* already in at least the given level.
637	>	*/
638	>	private boolean advanceRunLevel(int level) {
639		for (;;) {
640	<	int c = runControl;
641	<	if (runStateOf(c) >= state)
640	>	int s = runState;
641	>	if ((s & level) != 0)
642		return false;
643	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
643	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level))
644		return true;
645		}
646		}
647
648	+	// workers array maintenance
649	+
650		/**
651	<	* Controls whether to add spares to maintain parallelism
651	>	* Records and returns a workers array index for new worker.
652		*/
653	<	private volatile boolean maintainsParallelism;
653	>	private int recordWorker(ForkJoinWorkerThread w) {
654	>	// Try using slot totalCount-1. If not available, scan and/or resize
655	>	int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1;
656	>	final ReentrantLock lock = this.workerLock;
657	>	lock.lock();
658	>	try {
659	>	ForkJoinWorkerThread[] ws = workers;
660	>	int n = ws.length;
661	>	if (k < 0 || k >= n || ws[k] != null) {
662	>	for (k = 0; k < n && ws[k] != null; ++k)
663	>	;
664	>	if (k == n)
665	>	ws = Arrays.copyOf(ws, n << 1);
666	>	}
667	>	ws[k] = w;
668	>	workers = ws; // volatile array write ensures slot visibility
669	>	} finally {
670	>	lock.unlock();
671	>	}
672	>	return k;
673	>	}
674
675	<	// Constructors
675	>	/**
676	>	* Nulls out record of worker in workers array
677	>	*/
678	>	private void forgetWorker(ForkJoinWorkerThread w) {
679	>	int idx = w.poolIndex;
680	>	// Locking helps method recordWorker avoid unnecessary expansion
681	>	final ReentrantLock lock = this.workerLock;
682	>	lock.lock();
683	>	try {
684	>	ForkJoinWorkerThread[] ws = workers;
685	>	if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify
686	>	ws[idx] = null;
687	>	} finally {
688	>	lock.unlock();
689	>	}
690	>	}
691
692		/**
693	<	* Creates a ForkJoinPool with a pool size equal to the number of
694	<	* processors available on the system and using the default
695	<	* ForkJoinWorkerThreadFactory,
696	<	* @throws SecurityException if a security manager exists and
697	<	*         the caller is not permitted to modify threads
328	<	*         because it does not hold {@link
329	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
693	>	* Final callback from terminating worker.  Removes record of
694	>	* worker from array, and adjusts counts. If pool is shutting
695	>	* down, tries to complete termination.
696	>	*
697	>	* @param w the worker
698		*/
699	<	public ForkJoinPool() {
700	<	this(Runtime.getRuntime().availableProcessors(),
701	<	defaultForkJoinWorkerThreadFactory);
699	>	final void workerTerminated(ForkJoinWorkerThread w) {
700	>	forgetWorker(w);
701	>	decrementWorkerCounts(w.isTrimmed()? 0 : ONE_RUNNING, ONE_TOTAL);
702	>	while (w.stealCount != 0) // collect final count
703	>	tryAccumulateStealCount(w);
704	>	tryTerminate(false);
705		}
706
707	+	// Waiting for and signalling events
708	+
709		/**
710	<	* Creates a ForkJoinPool with the indicated parellelism level
711	<	* threads, and using the default ForkJoinWorkerThreadFactory,
712	<	* @param parallelism the number of worker threads
713	<	* @throws IllegalArgumentException if parallelism less than or
341	<	* 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>,
710	>	* Releases workers blocked on a count not equal to current count.
711	>	* Normally called after precheck that eventWaiters isn't zero to
712	>	* avoid wasted array checks. Gives up upon a change in count or
713	>	* upon releasing two workers, letting others take over.
714		*/
715	<	public ForkJoinPool(int parallelism) {
716	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
715	>	private void releaseEventWaiters() {
716	>	ForkJoinWorkerThread[] ws = workers;
717	>	int n = ws.length;
718	>	long h = eventWaiters;
719	>	int ec = eventCount;
720	>	boolean releasedOne = false;
721	>	ForkJoinWorkerThread w; int id;
722	>	while ((id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 &&
723	>	(int)(h >>> EVENT_COUNT_SHIFT) != ec &&
724	>	id < n && (w = ws[id]) != null) {
725	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
726	>	h,  w.nextWaiter)) {
727	>	LockSupport.unpark(w);
728	>	if (releasedOne) // exit on second release
729	>	break;
730	>	releasedOne = true;
731	>	}
732	>	if (eventCount != ec)
733	>	break;
734	>	h = eventWaiters;
735	>	}
736		}
737
738		/**
739	<	* Creates a ForkJoinPool with parallelism equal to the number of
740	<	* 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>,
739	>	* Tries to advance eventCount and releases waiters. Called only
740	>	* from workers.
741		*/
742	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
743	<	this(Runtime.getRuntime().availableProcessors(), factory);
742	>	final void signalWork() {
743	>	int c; // try to increment event count -- CAS failure OK
744	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
745	>	if (eventWaiters != 0L)
746	>	releaseEventWaiters();
747		}
748
749		/**
750	<	* Creates a ForkJoinPool with the given parallelism and factory.
750	>	* Adds the given worker to event queue and blocks until
751	>	* terminating or event count advances from the given value
752		*
753	<	* @param parallelism the targeted number of worker threads
754	<	* @param factory the factory for creating new threads
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>,
753	>	* @param w the calling worker thread
754	>	* @param ec the count
755		*/
756	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
757	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
758	<	throw new IllegalArgumentException();
759	<	if (factory == null)
760	<	throw new NullPointerException();
761	<	checkPermission();
762	<	this.factory = factory;
763	<	this.parallelism = parallelism;
764	<	this.maxPoolSize = MAX_THREADS;
765	<	this.maintainsParallelism = true;
766	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
767	<	this.workerLock = new ReentrantLock();
768	<	this.termination = workerLock.newCondition();
392	<	this.stealCount = new AtomicLong();
393	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
394	<	createAndStartInitialWorkers(parallelism);
756	>	private void eventSync(ForkJoinWorkerThread w, int ec) {
757	>	long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1));
758	>	long h;
759	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
760	>	(((int)((h = eventWaiters) & WAITER_ID_MASK)) == 0 ||
761	>	(int)(h >>> EVENT_COUNT_SHIFT) == ec) &&
762	>	eventCount == ec) {
763	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
764	>	w.nextWaiter = h, nh)) {
765	>	awaitEvent(w, ec);
766	>	break;
767	>	}
768	>	}
769		}
770
771		/**
772	<	* Create new worker using factory.
773	<	* @param index the index to assign worker
774	<	* @return new worker, or null of factory failed
772	>	* Blocks the given worker (that has already been entered as an
773	>	* event waiter) until terminating or event count advances from
774	>	* the given value. The oldest (first) waiter uses a timed wait to
775	>	* occasionally one-by-one shrink the number of workers (to a
776	>	* minimum of one) if the pool has not been used for extended
777	>	* periods.
778	>	*
779	>	* @param w the calling worker thread
780	>	* @param ec the count
781		*/
782	<	private ForkJoinWorkerThread createWorker(int index) {
783	<	Thread.UncaughtExceptionHandler h = ueh;
784	<	ForkJoinWorkerThread w = factory.newThread(this);
785	<	if (w != null) {
786	<	w.poolIndex = index;
787	<	w.setDaemon(true);
788	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
789	<	if (h != null)
790	<	w.setUncaughtExceptionHandler(h);
782	>	private void awaitEvent(ForkJoinWorkerThread w, int ec) {
783	>	while (eventCount == ec) {
784	>	if (tryAccumulateStealCount(w)) { // transfer while idle
785	>	boolean untimed = (w.nextWaiter != 0L ||
786	>	(workerCounts & RUNNING_COUNT_MASK) <= 1);
787	>	long startTime = untimed? 0 : System.nanoTime();
788	>	Thread.interrupted();         // clear/ignore interrupt
789	>	if (eventCount != ec || w.runState != 0 ||
790	>	runState >= TERMINATING)  // recheck after clear
791	>	break;
792	>	if (untimed)
793	>	LockSupport.park(w);
794	>	else {
795	>	LockSupport.parkNanos(w, SHRINK_RATE_NANOS);
796	>	if (eventCount != ec || w.runState != 0 ||
797	>	runState >= TERMINATING)
798	>	break;
799	>	if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS)
800	>	tryShutdownUnusedWorker(ec);
801	>	}
802	>	}
803		}
412	–	return w;
804		}
805
806	+	// Maintaining parallelism
807	+
808		/**
809	<	* Return a good size for worker array given pool size.
417	<	* Currently requires size to be a power of two.
809	>	* Pushes worker onto the spare stack
810		*/
811	<	private static int arraySizeFor(int ps) {
812	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
811	>	final void pushSpare(ForkJoinWorkerThread w) {
812	>	int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1);
813	>	do {} while (!UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
814	>	w.nextSpare = spareWaiters,ns));
815		}
816
817		/**
818	<	* Create or resize array if necessary to hold newLength
819	<	* @return the array
818	>	* Tries (once) to resume a spare if the number of running
819	>	* threads is less than target.
820		*/
821	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
821	>	private void tryResumeSpare() {
822	>	int sw, id;
823		ForkJoinWorkerThread[] ws = workers;
824	<	if (ws == null)
825	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
826	<	else if (newLength > ws.length)
827	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
828	<	else
829	<	return ws;
824	>	int n = ws.length;
825	>	ForkJoinWorkerThread w;
826	>	if ((sw = spareWaiters) != 0 &&
827	>	(id = (sw & SPARE_ID_MASK) - 1) >= 0 &&
828	>	id < n && (w = ws[id]) != null &&
829	>	(workerCounts & RUNNING_COUNT_MASK) < parallelism &&
830	>	spareWaiters == sw &&
831	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
832	>	sw, w.nextSpare)) {
833	>	int c; // increment running count before resume
834	>	do {} while (!UNSAFE.compareAndSwapInt
835	>	(this, workerCountsOffset,
836	>	c = workerCounts, c + ONE_RUNNING));
837	>	if (w.tryUnsuspend())
838	>	LockSupport.unpark(w);
839	>	else   // back out if w was shutdown
840	>	decrementWorkerCounts(ONE_RUNNING, 0);
841	>	}
842		}
843
844		/**
845	<	* Try to shrink workers into smaller array after one or more terminate
845	>	* Tries to increase the number of running workers if below target
846	>	* parallelism: If a spare exists tries to resume it via
847	>	* tryResumeSpare.  Otherwise, if not enough total workers or all
848	>	* existing workers are busy, adds a new worker. In all cases also
849	>	* helps wake up releasable workers waiting for work.
850	>	*/
851	>	private void helpMaintainParallelism() {
852	>	int pc = parallelism;
853	>	int wc, rs, tc;
854	>	while (((wc = workerCounts) & RUNNING_COUNT_MASK) < pc &&
855	>	(rs = runState) < TERMINATING) {
856	>	if (spareWaiters != 0)
857	>	tryResumeSpare();
858	>	else if ((tc = wc >>> TOTAL_COUNT_SHIFT) >= MAX_WORKERS ||
859	>	(tc >= pc && (rs & ACTIVE_COUNT_MASK) != tc))
860	>	break;   // enough total
861	>	else if (runState == rs && workerCounts == wc &&
862	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
863	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
864	>	ForkJoinWorkerThread w = null;
865	>	try {
866	>	w = factory.newThread(this);
867	>	} finally { // adjust on null or exceptional factory return
868	>	if (w == null) {
869	>	decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL);
870	>	tryTerminate(false); // handle failure during shutdown
871	>	}
872	>	}
873	>	if (w == null)
874	>	break;
875	>	w.start(recordWorker(w), ueh);
876	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) >= pc) {
877	>	int c; // advance event count
878	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
879	>	c = eventCount, c+1);
880	>	break; // add at most one unless total below target
881	>	}
882	>	}
883	>	}
884	>	if (eventWaiters != 0L)
885	>	releaseEventWaiters();
886	>	}
887	>
888	>	/**
889	>	* Callback from the oldest waiter in awaitEvent waking up after a
890	>	* period of non-use. If all workers are idle, tries (once) to
891	>	* shutdown an event waiter or a spare, if one exists. Note that
892	>	* we don't need CAS or locks here because the method is called
893	>	* only from one thread occasionally waking (and even misfires are
894	>	* OK). Note that until the shutdown worker fully terminates,
895	>	* workerCounts will overestimate total count, which is tolerable.
896	>	*
897	>	* @param ec the event count waited on by caller (to abort
898	>	* attempt if count has since changed).
899		*/
900	<	private void tryShrinkWorkerArray() {
901	<	ForkJoinWorkerThread[] ws = workers;
902	<	int len = ws.length;
903	<	int last = len - 1;
904	<	while (last >= 0 && ws[last] == null)
905	<	--last;
906	<	int newLength = arraySizeFor(last+1);
907	<	if (newLength < len)
908	<	workers = Arrays.copyOf(ws, newLength);
900	>	private void tryShutdownUnusedWorker(int ec) {
901	>	if (runState == 0 && eventCount == ec) { // only trigger if all idle
902	>	ForkJoinWorkerThread[] ws = workers;
903	>	int n = ws.length;
904	>	ForkJoinWorkerThread w = null;
905	>	boolean shutdown = false;
906	>	int sw;
907	>	long h;
908	>	if ((sw = spareWaiters) != 0) { // prefer killing spares
909	>	int id = (sw & SPARE_ID_MASK) - 1;
910	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
911	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
912	>	sw, w.nextSpare))
913	>	shutdown = true;
914	>	}
915	>	else if ((h = eventWaiters) != 0L) {
916	>	long nh;
917	>	int id = ((int)(h & WAITER_ID_MASK)) - 1;
918	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
919	>	(nh = w.nextWaiter) != 0L && // keep at least one worker
920	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh))
921	>	shutdown = true;
922	>	}
923	>	if (w != null && shutdown) {
924	>	w.shutdown();
925	>	LockSupport.unpark(w);
926	>	}
927	>	}
928	>	releaseEventWaiters(); // in case of interference
929		}
930
931		/**
932	<	* Initial worker array and worker creation and startup. (This
933	<	* must be done under lock to avoid interference by some of the
934	<	* newly started threads while creating others.)
932	>	* Callback from workers invoked upon each top-level action (i.e.,
933	>	* stealing a task or taking a submission and running it).
934	>	* Performs one or more of the following:
935	>	*
936	>	* 1. If the worker is active and either did not run a task
937	>	*    or there are too many workers, try to set its active status
938	>	*    to inactive and update activeCount. On contention, we may
939	>	*    try again in this or a subsequent call.
940	>	*
941	>	* 2. If not enough total workers, help create some.
942	>	*
943	>	* 3. If there are too many running workers, suspend this worker
944	>	*    (first forcing inactive if necessary).  If it is not needed,
945	>	*    it may be shutdown while suspended (via
946	>	*    tryShutdownUnusedWorker).  Otherwise, upon resume it
947	>	*    rechecks running thread count and need for event sync.
948	>	*
949	>	* 4. If worker did not run a task, await the next task event via
950	>	*    eventSync if necessary (first forcing inactivation), upon
951	>	*    which the worker may be shutdown via
952	>	*    tryShutdownUnusedWorker.  Otherwise, help release any
953	>	*    existing event waiters that are now releasable,
954	>	*
955	>	* @param w the worker
956	>	* @param ran true if worker ran a task since last call to this method
957		*/
958	<	private void createAndStartInitialWorkers(int ps) {
959	<	final ReentrantLock lock = this.workerLock;
960	<	lock.lock();
961	<	try {
962	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
963	<	for (int i = 0; i < ps; ++i) {
964	<	ForkJoinWorkerThread w = createWorker(i);
965	<	if (w != null) {
966	<	ws[i] = w;
967	<	w.start();
968	<	updateWorkerCount(1);
958	>	final void preStep(ForkJoinWorkerThread w, boolean ran) {
959	>	int wec = w.lastEventCount;
960	>	boolean active = w.active;
961	>	boolean inactivate = false;
962	>	int pc = parallelism;
963	>	int rs;
964	>	while (w.runState == 0 && (rs = runState) < TERMINATING) {
965	>	if ((inactivate || (active && (rs & ACTIVE_COUNT_MASK) >= pc)) &&
966	>	UNSAFE.compareAndSwapInt(this, runStateOffset, rs, rs - 1))
967	>	inactivate = active = w.active = false;
968	>	int wc = workerCounts;
969	>	if ((wc & RUNNING_COUNT_MASK) > pc) {
970	>	if (!(inactivate |= active) && // must inactivate to suspend
971	>	workerCounts == wc &&      // try to suspend as spare
972	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
973	>	wc, wc - ONE_RUNNING))
974	>	w.suspendAsSpare();
975	>	}
976	>	else if ((wc >>> TOTAL_COUNT_SHIFT) < pc)
977	>	helpMaintainParallelism();     // not enough workers
978	>	else if (!ran) {
979	>	long h = eventWaiters;
980	>	int ec = eventCount;
981	>	if (h != 0L && (int)(h >>> EVENT_COUNT_SHIFT) != ec)
982	>	releaseEventWaiters();     // release others before waiting
983	>	else if (ec != wec) {
984	>	w.lastEventCount = ec;     // no need to wait
985	>	break;
986		}
987	+	else if (!(inactivate |= active))
988	+	eventSync(w, wec);         // must inactivate before sync
989		}
990	<	} finally {
991	<	lock.unlock();
990	>	else
991	>	break;
992		}
993		}
994
995		/**
996	<	* Worker creation and startup for threads added via setParallelism.
996	>	* Helps and/or blocks awaiting join of the given task.
997	>	* See above for explanation.
998	>	*
999	>	* @param joinMe the task to join
1000	>	* @param worker the current worker thread
1001		*/
1002	<	private void createAndStartAddedWorkers() {
1003	<	resumeAllSpares();  // Allow spares to convert to nonspare
1004	<	int ps = parallelism;
1005	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1006	<	int len = ws.length;
1007	<	// Sweep through slots, to keep lowest indices most populated
1008	<	int k = 0;
1009	<	while (k < len) {
1010	<	if (ws[k] != null) {
1011	<	++k;
1012	<	continue;
1002	>	final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker) {
1003	>	int retries = 2 + (parallelism >> 2); // #helpJoins before blocking
1004	>	while (joinMe.status >= 0) {
1005	>	int wc;
1006	>	worker.helpJoinTask(joinMe);
1007	>	if (joinMe.status < 0)
1008	>	break;
1009	>	else if (retries > 0)
1010	>	--retries;
1011	>	else if (((wc = workerCounts) & RUNNING_COUNT_MASK) != 0 &&
1012	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1013	>	wc, wc - ONE_RUNNING)) {
1014	>	int stat, c; long h;
1015	>	while ((stat = joinMe.status) >= 0 &&
1016	>	(h = eventWaiters) != 0L && // help release others
1017	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1018	>	releaseEventWaiters();
1019	>	if (stat >= 0 &&
1020	>	((workerCounts & RUNNING_COUNT_MASK) == 0 ||
1021	>	(stat =
1022	>	joinMe.internalAwaitDone(JOIN_TIMEOUT_MILLIS)) >= 0))
1023	>	helpMaintainParallelism(); // timeout or no running workers
1024	>	do {} while (!UNSAFE.compareAndSwapInt
1025	>	(this, workerCountsOffset,
1026	>	c = workerCounts, c + ONE_RUNNING));
1027	>	if (stat < 0)
1028	>	break;   // else restart
1029		}
1030	<	int s = workerCounts;
1031	<	int tc = totalCountOf(s);
1032	<	int rc = runningCountOf(s);
1033	<	if (rc >= ps || tc >= ps)
1030	>	}
1031	>	}
1032	>
1033	>	/**
1034	>	* Same idea as awaitJoin, but no helping, retries, or timeouts.
1035	>	*/
1036	>	final void awaitBlocker(ManagedBlocker blocker)
1037	>	throws InterruptedException {
1038	>	while (!blocker.isReleasable()) {
1039	>	int wc = workerCounts;
1040	>	if ((wc & RUNNING_COUNT_MASK) != 0 &&
1041	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1042	>	wc, wc - ONE_RUNNING)) {
1043	>	try {
1044	>	while (!blocker.isReleasable()) {
1045	>	long h = eventWaiters;
1046	>	if (h != 0L &&
1047	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1048	>	releaseEventWaiters();
1049	>	else if ((workerCounts & RUNNING_COUNT_MASK) == 0 &&
1050	>	runState < TERMINATING)
1051	>	helpMaintainParallelism();
1052	>	else if (blocker.block())
1053	>	break;
1054	>	}
1055	>	} finally {
1056	>	int c;
1057	>	do {} while (!UNSAFE.compareAndSwapInt
1058	>	(this, workerCountsOffset,
1059	>	c = workerCounts, c + ONE_RUNNING));
1060	>	}
1061		break;
1062	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
1063	<	ForkJoinWorkerThread w = createWorker(k);
1062	>	}
1063	>	}
1064	>	}
1065	>
1066	>	/**
1067	>	* Possibly initiates and/or completes termination.
1068	>	*
1069	>	* @param now if true, unconditionally terminate, else only
1070	>	* if shutdown and empty queue and no active workers
1071	>	* @return true if now terminating or terminated
1072	>	*/
1073	>	private boolean tryTerminate(boolean now) {
1074	>	if (now)
1075	>	advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN
1076	>	else if (runState < SHUTDOWN ||
1077	>	!submissionQueue.isEmpty() ||
1078	>	(runState & ACTIVE_COUNT_MASK) != 0)
1079	>	return false;
1080	>
1081	>	if (advanceRunLevel(TERMINATING))
1082	>	startTerminating();
1083	>
1084	>	// Finish now if all threads terminated; else in some subsequent call
1085	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1086	>	advanceRunLevel(TERMINATED);
1087	>	termination.arrive();
1088	>	}
1089	>	return true;
1090	>	}
1091	>
1092	>	/**
1093	>	* Actions on transition to TERMINATING
1094	>	*
1095	>	* Runs up to four passes through workers: (0) shutting down each
1096	>	* (without waking up if parked) to quickly spread notifications
1097	>	* without unnecessary bouncing around event queues etc (1) wake
1098	>	* up and help cancel tasks (2) interrupt (3) mop up races with
1099	>	* interrupted workers
1100	>	*/
1101	>	private void startTerminating() {
1102	>	cancelSubmissions();
1103	>	for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) {
1104	>	int c; // advance event count
1105	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
1106	>	c = eventCount, c+1);
1107	>	eventWaiters = 0L; // clobber lists
1108	>	spareWaiters = 0;
1109	>	ForkJoinWorkerThread[] ws = workers;
1110	>	int n = ws.length;
1111	>	for (int i = 0; i < n; ++i) {
1112	>	ForkJoinWorkerThread w = ws[i];
1113		if (w != null) {
1114	<	ws[k++] = w;
1115	<	w.start();
1116	<	}
1117	<	else {
1118	<	updateWorkerCount(-1); // back out on failed creation
1119	<	break;
1114	>	w.shutdown();
1115	>	if (passes > 0 && !w.isTerminated()) {
1116	>	w.cancelTasks();
1117	>	LockSupport.unpark(w);
1118	>	if (passes > 1) {
1119	>	try {
1120	>	w.interrupt();
1121	>	} catch (SecurityException ignore) {
1122	>	}
1123	>	}
1124	>	}
1125		}
1126		}
1127		}
1128		}
1129
1130	+	/**
1131	+	* Clear out and cancel submissions, ignoring exceptions
1132	+	*/
1133	+	private void cancelSubmissions() {
1134	+	ForkJoinTask<?> task;
1135	+	while ((task = submissionQueue.poll()) != null) {
1136	+	try {
1137	+	task.cancel(false);
1138	+	} catch (Throwable ignore) {
1139	+	}
1140	+	}
1141	+	}
1142	+
1143	+	// misc support for ForkJoinWorkerThread
1144	+
1145	+	/**
1146	+	* Returns pool number
1147	+	*/
1148	+	final int getPoolNumber() {
1149	+	return poolNumber;
1150	+	}
1151	+
1152	+	/**
1153	+	* Tries to accumulates steal count from a worker, clearing
1154	+	* the worker's value.
1155	+	*
1156	+	* @return true if worker steal count now zero
1157	+	*/
1158	+	final boolean tryAccumulateStealCount(ForkJoinWorkerThread w) {
1159	+	int sc = w.stealCount;
1160	+	long c = stealCount;
1161	+	// CAS even if zero, for fence effects
1162	+	if (UNSAFE.compareAndSwapLong(this, stealCountOffset, c, c + sc)) {
1163	+	if (sc != 0)
1164	+	w.stealCount = 0;
1165	+	return true;
1166	+	}
1167	+	return sc == 0;
1168	+	}
1169	+
1170	+	/**
1171	+	* Returns the approximate (non-atomic) number of idle threads per
1172	+	* active thread.
1173	+	*/
1174	+	final int idlePerActive() {
1175	+	int pc = parallelism; // use parallelism, not rc
1176	+	int ac = runState;    // no mask -- artificially boosts during shutdown
1177	+	// Use exact results for small values, saturate past 4
1178	+	return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
1179	+	}
1180	+
1181	+	// Public and protected methods
1182	+
1183	+	// Constructors
1184	+
1185	+	/**
1186	+	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1187	+	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1188	+	* #defaultForkJoinWorkerThreadFactory default thread factory},
1189	+	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1190	+	*
1191	+	* @throws SecurityException if a security manager exists and
1192	+	*         the caller is not permitted to modify threads
1193	+	*         because it does not hold {@link
1194	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1195	+	*/
1196	+	public ForkJoinPool() {
1197	+	this(Runtime.getRuntime().availableProcessors(),
1198	+	defaultForkJoinWorkerThreadFactory, null, false);
1199	+	}
1200	+
1201	+	/**
1202	+	* Creates a {@code ForkJoinPool} with the indicated parallelism
1203	+	* level, the {@linkplain
1204	+	* #defaultForkJoinWorkerThreadFactory default thread factory},
1205	+	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1206	+	*
1207	+	* @param parallelism the parallelism level
1208	+	* @throws IllegalArgumentException if parallelism less than or
1209	+	*         equal to zero, or greater than implementation limit
1210	+	* @throws SecurityException if a security manager exists and
1211	+	*         the caller is not permitted to modify threads
1212	+	*         because it does not hold {@link
1213	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1214	+	*/
1215	+	public ForkJoinPool(int parallelism) {
1216	+	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1217	+	}
1218	+
1219	+	/**
1220	+	* Creates a {@code ForkJoinPool} with the given parameters.
1221	+	*
1222	+	* @param parallelism the parallelism level. For default value,
1223	+	* use {@link java.lang.Runtime#availableProcessors}.
1224	+	* @param factory the factory for creating new threads. For default value,
1225	+	* use {@link #defaultForkJoinWorkerThreadFactory}.
1226	+	* @param handler the handler for internal worker threads that
1227	+	* terminate due to unrecoverable errors encountered while executing
1228	+	* tasks. For default value, use <code>null</code>.
1229	+	* @param asyncMode if true,
1230	+	* establishes local first-in-first-out scheduling mode for forked
1231	+	* tasks that are never joined. This mode may be more appropriate
1232	+	* than default locally stack-based mode in applications in which
1233	+	* worker threads only process event-style asynchronous tasks.
1234	+	* For default value, use <code>false</code>.
1235	+	* @throws IllegalArgumentException if parallelism less than or
1236	+	*         equal to zero, or greater than implementation limit
1237	+	* @throws NullPointerException if the factory is null
1238	+	* @throws SecurityException if a security manager exists and
1239	+	*         the caller is not permitted to modify threads
1240	+	*         because it does not hold {@link
1241	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1242	+	*/
1243	+	public ForkJoinPool(int parallelism,
1244	+	ForkJoinWorkerThreadFactory factory,
1245	+	Thread.UncaughtExceptionHandler handler,
1246	+	boolean asyncMode) {
1247	+	checkPermission();
1248	+	if (factory == null)
1249	+	throw new NullPointerException();
1250	+	if (parallelism <= 0 || parallelism > MAX_WORKERS)
1251	+	throw new IllegalArgumentException();
1252	+	this.parallelism = parallelism;
1253	+	this.factory = factory;
1254	+	this.ueh = handler;
1255	+	this.locallyFifo = asyncMode;
1256	+	int arraySize = initialArraySizeFor(parallelism);
1257	+	this.workers = new ForkJoinWorkerThread[arraySize];
1258	+	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
1259	+	this.workerLock = new ReentrantLock();
1260	+	this.termination = new Phaser(1);
1261	+	this.poolNumber = poolNumberGenerator.incrementAndGet();
1262	+	}
1263	+
1264	+	/**
1265	+	* Returns initial power of two size for workers array.
1266	+	* @param pc the initial parallelism level
1267	+	*/
1268	+	private static int initialArraySizeFor(int pc) {
1269	+	// If possible, initially allocate enough space for one spare
1270	+	int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS;
1271	+	// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16)
1272	+	size |= size >>> 1;
1273	+	size |= size >>> 2;
1274	+	size |= size >>> 4;
1275	+	size |= size >>> 8;
1276	+	return size + 1;
1277	+	}
1278	+
1279		// Execution methods
1280
1281		/**
1282		* Common code for execute, invoke and submit
1283		*/
1284		private <T> void doSubmit(ForkJoinTask<T> task) {
1285	<	if (isShutdown())
1285	>	if (task == null)
1286	>	throw new NullPointerException();
1287	>	if (runState >= SHUTDOWN)
1288		throw new RejectedExecutionException();
1289		submissionQueue.offer(task);
1290	<	signalIdleWorkers();
1290	>	int c; // try to increment event count -- CAS failure OK
1291	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
1292	>	helpMaintainParallelism(); // create, start, or resume some workers
1293		}
1294
1295		/**
1296	<	* Performs the given task; returning its result upon completion
1296	>	* Performs the given task, returning its result upon completion.
1297	>	*
1298		* @param task the task
1299		* @return the task's result
1300	<	* @throws NullPointerException if task is null
1301	<	* @throws RejectedExecutionException if pool is shut down
1300	>	* @throws NullPointerException if the task is null
1301	>	* @throws RejectedExecutionException if the task cannot be
1302	>	*         scheduled for execution
1303		*/
1304		public <T> T invoke(ForkJoinTask<T> task) {
1305		doSubmit(task);
#	Line 531 | Line 1308 | public class ForkJoinPool extends Abstra
1308
1309		/**
1310		* Arranges for (asynchronous) execution of the given task.
1311	+	*
1312		* @param task the task
1313	<	* @throws NullPointerException if task is null
1314	<	* @throws RejectedExecutionException if pool is shut down
1313	>	* @throws NullPointerException if the task is null
1314	>	* @throws RejectedExecutionException if the task cannot be
1315	>	*         scheduled for execution
1316		*/
1317	<	public <T> void execute(ForkJoinTask<T> task) {
1317	>	public void execute(ForkJoinTask<?> task) {
1318		doSubmit(task);
1319		}
1320
1321		// AbstractExecutorService methods
1322
1323	+	/**
1324	+	* @throws NullPointerException if the task is null
1325	+	* @throws RejectedExecutionException if the task cannot be
1326	+	*         scheduled for execution
1327	+	*/
1328		public void execute(Runnable task) {
1329	<	doSubmit(new AdaptedRunnable<Void>(task, null));
1329	>	ForkJoinTask<?> job;
1330	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1331	>	job = (ForkJoinTask<?>) task;
1332	>	else
1333	>	job = ForkJoinTask.adapt(task, null);
1334	>	doSubmit(job);
1335	>	}
1336	>
1337	>	/**
1338	>	* Submits a ForkJoinTask for execution.
1339	>	*
1340	>	* @param task the task to submit
1341	>	* @return the task
1342	>	* @throws NullPointerException if the task is null
1343	>	* @throws RejectedExecutionException if the task cannot be
1344	>	*         scheduled for execution
1345	>	*/
1346	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1347	>	doSubmit(task);
1348	>	return task;
1349		}
1350
1351	+	/**
1352	+	* @throws NullPointerException if the task is null
1353	+	* @throws RejectedExecutionException if the task cannot be
1354	+	*         scheduled for execution
1355	+	*/
1356		public <T> ForkJoinTask<T> submit(Callable<T> task) {
1357	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
1357	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1358		doSubmit(job);
1359		return job;
1360		}
1361
1362	+	/**
1363	+	* @throws NullPointerException if the task is null
1364	+	* @throws RejectedExecutionException if the task cannot be
1365	+	*         scheduled for execution
1366	+	*/
1367		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1368	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
1368	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1369		doSubmit(job);
1370		return job;
1371		}
1372
1373	+	/**
1374	+	* @throws NullPointerException if the task is null
1375	+	* @throws RejectedExecutionException if the task cannot be
1376	+	*         scheduled for execution
1377	+	*/
1378		public ForkJoinTask<?> submit(Runnable task) {
1379	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
1379	>	ForkJoinTask<?> job;
1380	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1381	>	job = (ForkJoinTask<?>) task;
1382	>	else
1383	>	job = ForkJoinTask.adapt(task, null);
1384		doSubmit(job);
1385		return job;
1386		}
1387
1388		/**
1389	<	* Adaptor for Runnables. This implements RunnableFuture
1390	<	* to be compliant with AbstractExecutorService constraints
569	<	*/
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
1389	>	* @throws NullPointerException       {@inheritDoc}
1390	>	* @throws RejectedExecutionException {@inheritDoc}
1391		*/
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	–
1392		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
1393	<	ArrayList<ForkJoinTask<T>> ts =
1393	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
1394		new ArrayList<ForkJoinTask<T>>(tasks.size());
1395	<	for (Callable<T> c : tasks)
1396	<	ts.add(new AdaptedCallable<T>(c));
1397	<	invoke(new InvokeAll<T>(ts));
1398	<	return (List<Future<T>>)(List)ts;
1395	>	for (Callable<T> task : tasks)
1396	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
1397	>	invoke(new InvokeAll<T>(forkJoinTasks));
1398	>
1399	>	@SuppressWarnings({"unchecked", "rawtypes"})
1400	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1401	>	return futures;
1402		}
1403
1404		static final class InvokeAll<T> extends RecursiveAction {
1405		final ArrayList<ForkJoinTask<T>> tasks;
1406		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
1407		public void compute() {
1408	<	try { invokeAll(tasks); } catch(Exception ignore) {}
1408	>	try { invokeAll(tasks); }
1409	>	catch (Exception ignore) {}
1410		}
1411	+	private static final long serialVersionUID = -7914297376763021607L;
1412		}
1413
635	–	// Configuration and status settings and queries
636	–
1414		/**
1415	<	* Returns the factory used for constructing new workers
1415	>	* Returns the factory used for constructing new workers.
1416		*
1417		* @return the factory used for constructing new workers
1418		*/
#	Line 646 | Line 1423 | public class ForkJoinPool extends Abstra
1423		/**
1424		* Returns the handler for internal worker threads that terminate
1425		* 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.
1426		*
1427	<	* @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>,
1427	>	* @return the handler, or {@code null} if none
1428		*/
1429	<	public void setParallelism(int parallelism) {
1430	<	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();
1429	>	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1430	>	return ueh;
1431		}
1432
1433		/**
1434	<	* Returns the targeted number of worker threads in this pool.
1434	>	* Returns the targeted parallelism level of this pool.
1435		*
1436	<	* @return the targeted number of worker threads in this pool
1436	>	* @return the targeted parallelism level of this pool
1437		*/
1438		public int getParallelism() {
1439		return parallelism;
#	Line 738 | Line 1442 | public class ForkJoinPool extends Abstra
1442		/**
1443		* Returns the number of worker threads that have started but not
1444		* yet terminated.  This result returned by this method may differ
1445	<	* from <code>getParallelism</code> when threads are created to
1445	>	* from {@link #getParallelism} when threads are created to
1446		* maintain parallelism when others are cooperatively blocked.
1447		*
1448		* @return the number of worker threads
1449		*/
1450		public int getPoolSize() {
1451	<	return totalCountOf(workerCounts);
748	<	}
749	<
750	<	/**
751	<	* Returns the maximum number of threads allowed to exist in the
752	<	* pool, even if there are insufficient unblocked running threads.
753	<	* @return the maximum
754	<	*/
755	<	public int getMaximumPoolSize() {
756	<	return maxPoolSize;
1451	>	return workerCounts >>> TOTAL_COUNT_SHIFT;
1452		}
1453
1454		/**
1455	<	* Sets the maximum number of threads allowed to exist in the
1456	<	* pool, even if there are insufficient unblocked running threads.
1457	<	* Setting this value has no effect on current pool size. It
1458	<	* 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
1455	>	* Returns {@code true} if this pool uses local first-in-first-out
1456	>	* scheduling mode for forked tasks that are never joined.
1457	>	*
1458	>	* @return {@code true} if this pool uses async mode
1459		*/
1460	<	public void setMaintainsParallelism(boolean enable) {
1461	<	maintainsParallelism = enable;
1460	>	public boolean getAsyncMode() {
1461	>	return locallyFifo;
1462		}
1463
1464		/**
1465		* Returns an estimate of the number of worker threads that are
1466		* not blocked waiting to join tasks or for other managed
1467	<	* synchronization.
1467	>	* synchronization. This method may overestimate the
1468	>	* number of running threads.
1469		*
1470		* @return the number of worker threads
1471		*/
1472		public int getRunningThreadCount() {
1473	<	return runningCountOf(workerCounts);
1473	>	return workerCounts & RUNNING_COUNT_MASK;
1474		}
1475
1476		/**
1477		* Returns an estimate of the number of threads that are currently
1478		* stealing or executing tasks. This method may overestimate the
1479		* number of active threads.
1480	<	* @return the number of active threads.
1480	>	*
1481	>	* @return the number of active threads
1482		*/
1483		public int getActiveThreadCount() {
1484	<	return activeCountOf(runControl);
814	<	}
815	<
816	<	/**
817	<	* Returns an estimate of the number of threads that are currently
818	<	* idle waiting for tasks. This method may underestimate the
819	<	* number of idle threads.
820	<	* @return the number of idle threads.
821	<	*/
822	<	final int getIdleThreadCount() {
823	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
824	<	return (c <= 0)? 0 : c;
1484	>	return runState & ACTIVE_COUNT_MASK;
1485		}
1486
1487		/**
1488	<	* Returns true if all worker threads are currently idle. An idle
1489	<	* worker is one that cannot obtain a task to execute because none
1490	<	* are available to steal from other threads, and there are no
1491	<	* pending submissions to the pool. This method is conservative:
1492	<	* It might not return true immediately upon idleness of all
1493	<	* threads, but will eventually become true if threads remain
1494	<	* inactive.
1495	<	* @return true if all threads are currently idle
1488	>	* Returns {@code true} if all worker threads are currently idle.
1489	>	* An idle worker is one that cannot obtain a task to execute
1490	>	* because none are available to steal from other threads, and
1491	>	* there are no pending submissions to the pool. This method is
1492	>	* conservative; it might not return {@code true} immediately upon
1493	>	* idleness of all threads, but will eventually become true if
1494	>	* threads remain inactive.
1495	>	*
1496	>	* @return {@code true} if all threads are currently idle
1497		*/
1498		public boolean isQuiescent() {
1499	<	return activeCountOf(runControl) == 0;
1499	>	return (runState & ACTIVE_COUNT_MASK) == 0;
1500		}
1501
1502		/**
#	Line 843 | Line 1504 | public class ForkJoinPool extends Abstra
1504		* one thread's work queue by another. The reported value
1505		* underestimates the actual total number of steals when the pool
1506		* is not quiescent. This value may be useful for monitoring and
1507	<	* tuning fork/join programs: In general, steal counts should be
1507	>	* tuning fork/join programs: in general, steal counts should be
1508		* high enough to keep threads busy, but low enough to avoid
1509		* overhead and contention across threads.
1510	<	* @return the number of steals.
1510	>	*
1511	>	* @return the number of steals
1512		*/
1513		public long getStealCount() {
1514	<	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);
1514	>	return stealCount;
1515		}
1516
1517		/**
#	Line 869 | Line 1521 | public class ForkJoinPool extends Abstra
1521		* an approximation, obtained by iterating across all threads in
1522		* the pool. This method may be useful for tuning task
1523		* granularities.
1524	<	* @return the number of queued tasks.
1524	>	*
1525	>	* @return the number of queued tasks
1526		*/
1527		public long getQueuedTaskCount() {
1528		long count = 0;
1529		ForkJoinWorkerThread[] ws = workers;
1530	<	for (int i = 0; i < ws.length; ++i) {
1531	<	ForkJoinWorkerThread t = ws[i];
1532	<	if (t != null)
1533	<	count += t.getQueueSize();
1530	>	int n = ws.length;
1531	>	for (int i = 0; i < n; ++i) {
1532	>	ForkJoinWorkerThread w = ws[i];
1533	>	if (w != null)
1534	>	count += w.getQueueSize();
1535		}
1536		return count;
1537		}
1538
1539		/**
1540	<	* Returns an estimate of the number tasks submitted to this pool
1541	<	* that have not yet begun executing. This method takes time
1540	>	* Returns an estimate of the number of tasks submitted to this
1541	>	* pool that have not yet begun executing.  This method takes time
1542		* proportional to the number of submissions.
1543	<	* @return the number of queued submissions.
1543	>	*
1544	>	* @return the number of queued submissions
1545		*/
1546		public int getQueuedSubmissionCount() {
1547		return submissionQueue.size();
1548		}
1549
1550		/**
1551	<	* Returns true if there are any tasks submitted to this pool
1552	<	* that have not yet begun executing.
1553	<	* @return <code>true</code> if there are any queued submissions.
1551	>	* Returns {@code true} if there are any tasks submitted to this
1552	>	* pool that have not yet begun executing.
1553	>	*
1554	>	* @return {@code true} if there are any queued submissions
1555		*/
1556		public boolean hasQueuedSubmissions() {
1557		return !submissionQueue.isEmpty();
#	Line 905 | Line 1561 | public class ForkJoinPool extends Abstra
1561		* Removes and returns the next unexecuted submission if one is
1562		* available.  This method may be useful in extensions to this
1563		* class that re-assign work in systems with multiple pools.
1564	<	* @return the next submission, or null if none
1564	>	*
1565	>	* @return the next submission, or {@code null} if none
1566		*/
1567		protected ForkJoinTask<?> pollSubmission() {
1568		return submissionQueue.poll();
1569		}
1570
1571		/**
1572	+	* Removes all available unexecuted submitted and forked tasks
1573	+	* from scheduling queues and adds them to the given collection,
1574	+	* without altering their execution status. These may include
1575	+	* artificially generated or wrapped tasks. This method is
1576	+	* designed to be invoked only when the pool is known to be
1577	+	* quiescent. Invocations at other times may not remove all
1578	+	* tasks. A failure encountered while attempting to add elements
1579	+	* to collection {@code c} may result in elements being in
1580	+	* neither, either or both collections when the associated
1581	+	* exception is thrown.  The behavior of this operation is
1582	+	* undefined if the specified collection is modified while the
1583	+	* operation is in progress.
1584	+	*
1585	+	* @param c the collection to transfer elements into
1586	+	* @return the number of elements transferred
1587	+	*/
1588	+	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1589	+	int count = submissionQueue.drainTo(c);
1590	+	ForkJoinWorkerThread[] ws = workers;
1591	+	int n = ws.length;
1592	+	for (int i = 0; i < n; ++i) {
1593	+	ForkJoinWorkerThread w = ws[i];
1594	+	if (w != null)
1595	+	count += w.drainTasksTo(c);
1596	+	}
1597	+	return count;
1598	+	}
1599	+
1600	+	/**
1601		* Returns a string identifying this pool, as well as its state,
1602		* including indications of run state, parallelism level, and
1603		* worker and task counts.
#	Line 919 | Line 1605 | public class ForkJoinPool extends Abstra
1605		* @return a string identifying this pool, as well as its state
1606		*/
1607		public String toString() {
922	–	int ps = parallelism;
923	–	int wc = workerCounts;
924	–	int rc = runControl;
1608		long st = getStealCount();
1609		long qt = getQueuedTaskCount();
1610		long qs = getQueuedSubmissionCount();
1611	+	int wc = workerCounts;
1612	+	int tc = wc >>> TOTAL_COUNT_SHIFT;
1613	+	int rc = wc & RUNNING_COUNT_MASK;
1614	+	int pc = parallelism;
1615	+	int rs = runState;
1616	+	int ac = rs & ACTIVE_COUNT_MASK;
1617		return super.toString() +
1618	<	"[" + runStateToString(runStateOf(rc)) +
1619	<	", parallelism = " + ps +
1620	<	", size = " + totalCountOf(wc) +
1621	<	", active = " + activeCountOf(rc) +
1622	<	", running = " + runningCountOf(wc) +
1618	>	"[" + runLevelToString(rs) +
1619	>	", parallelism = " + pc +
1620	>	", size = " + tc +
1621	>	", active = " + ac +
1622	>	", running = " + rc +
1623		", steals = " + st +
1624		", tasks = " + qt +
1625		", submissions = " + qs +
1626		"]";
1627		}
1628
1629	<	private static String runStateToString(int rs) {
1630	<	switch(rs) {
1631	<	case RUNNING: return "Running";
1632	<	case SHUTDOWN: return "Shutting down";
1633	<	case TERMINATING: return "Terminating";
945	<	case TERMINATED: return "Terminated";
946	<	default: throw new Error("Unknown run state");
947	<	}
1629	>	private static String runLevelToString(int s) {
1630	>	return ((s & TERMINATED) != 0 ? "Terminated" :
1631	>	((s & TERMINATING) != 0 ? "Terminating" :
1632	>	((s & SHUTDOWN) != 0 ? "Shutting down" :
1633	>	"Running")));
1634		}
1635
950	–	// lifecycle control
951	–
1636		/**
1637		* Initiates an orderly shutdown in which previously submitted
1638		* tasks are executed, but no new tasks will be accepted.
1639		* Invocation has no additional effect if already shut down.
1640		* Tasks that are in the process of being submitted concurrently
1641		* during the course of this method may or may not be rejected.
1642	+	*
1643		* @throws SecurityException if a security manager exists and
1644		*         the caller is not permitted to modify threads
1645		*         because it does not hold {@link
1646	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1646	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1647		*/
1648		public void shutdown() {
1649		checkPermission();
1650	<	transitionRunStateTo(SHUTDOWN);
1651	<	if (canTerminateOnShutdown(runControl))
967	<	terminateOnShutdown();
1650	>	advanceRunLevel(SHUTDOWN);
1651	>	tryTerminate(false);
1652		}
1653
1654		/**
1655	<	* Attempts to stop all actively executing tasks, and cancels all
1656	<	* waiting tasks.  Tasks that are in the process of being
1657	<	* submitted or executed concurrently during the course of this
1658	<	* method may or may not be rejected. Unlike some other executors,
1659	<	* this method cancels rather than collects non-executed tasks,
1660	<	* so always returns an empty list.
1655	>	* Attempts to cancel and/or stop all tasks, and reject all
1656	>	* subsequently submitted tasks.  Tasks that are in the process of
1657	>	* being submitted or executed concurrently during the course of
1658	>	* this method may or may not be rejected. This method cancels
1659	>	* both existing and unexecuted tasks, in order to permit
1660	>	* termination in the presence of task dependencies. So the method
1661	>	* always returns an empty list (unlike the case for some other
1662	>	* Executors).
1663	>	*
1664		* @return an empty list
1665		* @throws SecurityException if a security manager exists and
1666		*         the caller is not permitted to modify threads
1667		*         because it does not hold {@link
1668	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1668	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1669		*/
1670		public List<Runnable> shutdownNow() {
1671		checkPermission();
1672	<	terminate();
1672	>	tryTerminate(true);
1673		return Collections.emptyList();
1674		}
1675
1676		/**
1677	<	* Returns <code>true</code> if all tasks have completed following shut down.
1677	>	* Returns {@code true} if all tasks have completed following shut down.
1678		*
1679	<	* @return <code>true</code> if all tasks have completed following shut down
1679	>	* @return {@code true} if all tasks have completed following shut down
1680		*/
1681		public boolean isTerminated() {
1682	<	return runStateOf(runControl) == TERMINATED;
1682	>	return runState >= TERMINATED;
1683		}
1684
1685		/**
1686	<	* Returns <code>true</code> if the process of termination has
1687	<	* commenced but possibly not yet completed.
1686	>	* Returns {@code true} if the process of termination has
1687	>	* commenced but not yet completed.  This method may be useful for
1688	>	* debugging. A return of {@code true} reported a sufficient
1689	>	* period after shutdown may indicate that submitted tasks have
1690	>	* ignored or suppressed interruption, causing this executor not
1691	>	* to properly terminate.
1692		*
1693	<	* @return <code>true</code> if terminating
1693	>	* @return {@code true} if terminating but not yet terminated
1694		*/
1695		public boolean isTerminating() {
1696	<	return runStateOf(runControl) >= TERMINATING;
1696	>	return (runState & (TERMINATING|TERMINATED)) == TERMINATING;
1697		}
1698
1699		/**
1700	<	* Returns <code>true</code> if this pool has been shut down.
1700	>	* Returns {@code true} if this pool has been shut down.
1701		*
1702	<	* @return <code>true</code> if this pool has been shut down
1702	>	* @return {@code true} if this pool has been shut down
1703		*/
1704		public boolean isShutdown() {
1705	<	return runStateOf(runControl) >= SHUTDOWN;
1705	>	return runState >= SHUTDOWN;
1706		}
1707
1708		/**
#	Line 1021 | Line 1712 | public class ForkJoinPool extends Abstra
1712		*
1713		* @param timeout the maximum time to wait
1714		* @param unit the time unit of the timeout argument
1715	<	* @return <code>true</code> if this executor terminated and
1716	<	*         <code>false</code> if the timeout elapsed before termination
1715	>	* @return {@code true} if this executor terminated and
1716	>	*         {@code false} if the timeout elapsed before termination
1717		* @throws InterruptedException if interrupted while waiting
1718		*/
1719		public boolean awaitTermination(long timeout, TimeUnit unit)
1720		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();
1721		try {
1722	<	ForkJoinWorkerThread[] ws = workers;
1723	<	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();
1117	<	try {
1118	<	ForkJoinWorkerThread[] ws = workers;
1119	<	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)
1722	>	return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1723	>	} catch (TimeoutException ex) {
1724		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	–	}
1725		}
1726		}
1727
1728		/**
1729		* Interface for extending managed parallelism for tasks running
1730	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1731	<	* Method <code>isReleasable</code> must return true if blocking is not
1732	<	* necessary. Method <code>block</code> blocks the current thread
1733	<	* if necessary (perhaps internally invoking isReleasable before
1734	<	* actually blocking.).
1730	>	* in {@link ForkJoinPool}s.
1731	>	*
1732	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
1733	>	* {@code isReleasable} must return {@code true} if blocking is
1734	>	* not necessary. Method {@code block} blocks the current thread
1735	>	* if necessary (perhaps internally invoking {@code isReleasable}
1736	>	* before actually blocking). The unusual methods in this API
1737	>	* accommodate synchronizers that may, but don't usually, block
1738	>	* for long periods. Similarly, they allow more efficient internal
1739	>	* handling of cases in which additional workers may be, but
1740	>	* usually are not, needed to ensure sufficient parallelism.
1741	>	* Toward this end, implementations of method {@code isReleasable}
1742	>	* must be amenable to repeated invocation.
1743	>	*
1744		* <p>For example, here is a ManagedBlocker based on a
1745		* ReentrantLock:
1746	<	* <pre>
1747	<	*   class ManagedLocker implements ManagedBlocker {
1748	<	*     final ReentrantLock lock;
1749	<	*     boolean hasLock = false;
1750	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1751	<	*     public boolean block() {
1752	<	*        if (!hasLock)
1753	<	*           lock.lock();
1754	<	*        return true;
1755	<	*     }
1756	<	*     public boolean isReleasable() {
1757	<	*        return hasLock || (hasLock = lock.tryLock());
1758	<	*     }
1746	>	*  <pre> {@code
1747	>	* class ManagedLocker implements ManagedBlocker {
1748	>	*   final ReentrantLock lock;
1749	>	*   boolean hasLock = false;
1750	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1751	>	*   public boolean block() {
1752	>	*     if (!hasLock)
1753	>	*       lock.lock();
1754	>	*     return true;
1755	>	*   }
1756	>	*   public boolean isReleasable() {
1757	>	*     return hasLock || (hasLock = lock.tryLock());
1758	>	*   }
1759	>	* }}</pre>
1760	>	*
1761	>	* <p>Here is a class that possibly blocks waiting for an
1762	>	* item on a given queue:
1763	>	*  <pre> {@code
1764	>	* class QueueTaker<E> implements ManagedBlocker {
1765	>	*   final BlockingQueue<E> queue;
1766	>	*   volatile E item = null;
1767	>	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
1768	>	*   public boolean block() throws InterruptedException {
1769	>	*     if (item == null)
1770	>	*       item = queue.take();
1771	>	*     return true;
1772	>	*   }
1773	>	*   public boolean isReleasable() {
1774	>	*     return item != null || (item = queue.poll()) != null;
1775		*   }
1776	<	* </pre>
1776	>	*   public E getItem() { // call after pool.managedBlock completes
1777	>	*     return item;
1778	>	*   }
1779	>	* }}</pre>
1780		*/
1781		public static interface ManagedBlocker {
1782		/**
1783		* Possibly blocks the current thread, for example waiting for
1784		* a lock or condition.
1785	<	* @return true if no additional blocking is necessary (i.e.,
1786	<	* if isReleasable would return true).
1785	>	*
1786	>	* @return {@code true} if no additional blocking is necessary
1787	>	* (i.e., if isReleasable would return true)
1788		* @throws InterruptedException if interrupted while waiting
1789	<	* (the method is not required to do so, but is allowe to).
1789	>	* (the method is not required to do so, but is allowed to)
1790		*/
1791		boolean block() throws InterruptedException;
1792
1793		/**
1794	<	* Returns true if blocking is unnecessary.
1794	>	* Returns {@code true} if blocking is unnecessary.
1795		*/
1796		boolean isReleasable();
1797		}
1798
1799		/**
1800		* Blocks in accord with the given blocker.  If the current thread
1801	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1802	<	* spare thread to be activated if necessary to ensure parallelism
1803	<	* while the current thread is blocked.  If
1804	<	* <code>maintainParallelism</code> is true and the pool supports
1805	<	* it ({@link #getMaintainsParallelism}), this method attempts to
1806	<	* maintain the pool's nominal parallelism. Otherwise if activates
1807	<	* a thread only if necessary to avoid complete starvation. This
1808	<	* option may be preferable when blockages use timeouts, or are
1809	<	* almost always brief.
1810	<	*
1811	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1812	<	* equivalent to
1813	<	* <pre>
1814	<	*   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.
1801	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1802	>	* arranges for a spare thread to be activated if necessary to
1803	>	* ensure sufficient parallelism while the current thread is blocked.
1804	>	*
1805	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1806	>	* behaviorally equivalent to
1807	>	*  <pre> {@code
1808	>	* while (!blocker.isReleasable())
1809	>	*   if (blocker.block())
1810	>	*     return;
1811	>	* }</pre>
1812	>	*
1813	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1814	>	* first be expanded to ensure parallelism, and later adjusted.
1815		*
1816		* @param blocker the blocker
1817	<	* @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.
1817	>	* @throws InterruptedException if blocker.block did so
1818		*/
1819	<	public static void managedBlock(ManagedBlocker blocker,
1665	<	boolean maintainParallelism)
1819	>	public static void managedBlock(ManagedBlocker blocker)
1820		throws InterruptedException {
1821		Thread t = Thread.currentThread();
1822	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1823	<	((ForkJoinWorkerThread)t).pool : null);
1824	<	if (!blocker.isReleasable()) {
1825	<	try {
1826	<	if (pool == null ||
1827	<	!pool.preBlock(blocker, maintainParallelism))
1674	<	awaitBlocker(blocker);
1675	<	} finally {
1676	<	if (pool != null)
1677	<	pool.updateRunningCount(1);
1678	<	}
1822	>	if (t instanceof ForkJoinWorkerThread) {
1823	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
1824	>	w.pool.awaitBlocker(blocker);
1825	>	}
1826	>	else {
1827	>	do {} while (!blocker.isReleasable() && !blocker.block());
1828		}
1829		}
1830
1831	<	private static void awaitBlocker(ManagedBlocker blocker)
1832	<	throws InterruptedException {
1833	<	do;while (!blocker.isReleasable() && !blocker.block());
1685	<	}
1686	<
1687	<	// AbstractExecutorService overrides
1831	>	// AbstractExecutorService overrides.  These rely on undocumented
1832	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1833	>	// implement RunnableFuture.
1834
1835		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1836	<	return new AdaptedRunnable(runnable, value);
1836	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1837		}
1838
1839		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1840	<	return new AdaptedCallable(callable);
1840	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1841		}
1842
1843	+	// Unsafe mechanics
1844
1845	<	// Temporary Unsafe mechanics for preliminary release
1846	<	private static Unsafe getUnsafe() throws Throwable {
1845	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1846	>	private static final long workerCountsOffset =
1847	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1848	>	private static final long runStateOffset =
1849	>	objectFieldOffset("runState", ForkJoinPool.class);
1850	>	private static final long eventCountOffset =
1851	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1852	>	private static final long eventWaitersOffset =
1853	>	objectFieldOffset("eventWaiters",ForkJoinPool.class);
1854	>	private static final long stealCountOffset =
1855	>	objectFieldOffset("stealCount",ForkJoinPool.class);
1856	>	private static final long spareWaitersOffset =
1857	>	objectFieldOffset("spareWaiters",ForkJoinPool.class);
1858	>
1859	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1860	>	try {
1861	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1862	>	} catch (NoSuchFieldException e) {
1863	>	// Convert Exception to corresponding Error
1864	>	NoSuchFieldError error = new NoSuchFieldError(field);
1865	>	error.initCause(e);
1866	>	throw error;
1867	>	}
1868	>	}
1869	>
1870	>	/**
1871	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1872	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1873	>	* into a jdk.
1874	>	*
1875	>	* @return a sun.misc.Unsafe
1876	>	*/
1877	>	private static sun.misc.Unsafe getUnsafe() {
1878		try {
1879	<	return Unsafe.getUnsafe();
1879	>	return sun.misc.Unsafe.getUnsafe();
1880		} catch (SecurityException se) {
1881		try {
1882		return java.security.AccessController.doPrivileged
1883	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1884	<	public Unsafe run() throws Exception {
1885	<	return getUnsafePrivileged();
1883	>	(new java.security
1884	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1885	>	public sun.misc.Unsafe run() throws Exception {
1886	>	java.lang.reflect.Field f = sun.misc
1887	>	.Unsafe.class.getDeclaredField("theUnsafe");
1888	>	f.setAccessible(true);
1889	>	return (sun.misc.Unsafe) f.get(null);
1890		}});
1891		} catch (java.security.PrivilegedActionException e) {
1892	<	throw e.getCause();
1892	>	throw new RuntimeException("Could not initialize intrinsics",
1893	>	e.getCause());
1894		}
1895		}
1896		}
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	–	}
1897		}

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