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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.7 by jsr166, Mon Jul 20 21:45:06 2009 UTC vs.
Revision 1.88 by dl, Tue Nov 23 01:06:00 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
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.*;
8	>
9	>	import java.util.ArrayList;
10	>	import java.util.Arrays;
11	>	import java.util.Collection;
12	>	import java.util.Collections;
13	>	import java.util.List;
14	>	import java.util.concurrent.AbstractExecutorService;
15	>	import java.util.concurrent.Callable;
16	>	import java.util.concurrent.ExecutorService;
17	>	import java.util.concurrent.Future;
18	>	import java.util.concurrent.RejectedExecutionException;
19	>	import java.util.concurrent.RunnableFuture;
20	>	import java.util.concurrent.TimeUnit;
21	>	import java.util.concurrent.TimeoutException;
22	>	import java.util.concurrent.atomic.AtomicInteger;
23	>	import java.util.concurrent.locks.LockSupport;
24	>	import java.util.concurrent.locks.ReentrantLock;
25
26		/**
27	<	* An {@link ExecutorService} for running {@link ForkJoinTask}s.  A
28	<	* ForkJoinPool provides the entry point for submissions from
29	<	* non-ForkJoinTasks, as well as management and monitoring operations.
30	<	* 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.
27	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
28	>	* A {@code ForkJoinPool} provides the entry point for submissions
29	>	* from non-{@code ForkJoinTask} clients, as well as management and
30	>	* monitoring operations.
31		*
32	<	* <p>ForkJoinPools differ from other kinds of Executors mainly in
33	<	* that they provide <em>work-stealing</em>: all threads in the pool
34	<	* attempt to find and execute subtasks created by other active tasks
35	<	* (eventually blocking if none exist). This makes them efficient when
36	<	* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
37	<	* as the mixed execution of some plain Runnable- or Callable- based
38	<	* activities along with ForkJoinTasks. When setting
39	<	* <tt>setAsyncMode</tt>, a ForkJoinPools may also be appropriate for
40	<	* use with fine-grained tasks that are never joined. Otherwise, other
33	<	* ExecutorService implementations are typically more appropriate
34	<	* choices.
32	>	* <p>A {@code ForkJoinPool} differs from other kinds of {@link
33	>	* ExecutorService} mainly by virtue of employing
34	>	* <em>work-stealing</em>: all threads in the pool attempt to find and
35	>	* execute subtasks created by other active tasks (eventually blocking
36	>	* waiting for work if none exist). This enables efficient processing
37	>	* when most tasks spawn other subtasks (as do most {@code
38	>	* ForkJoinTask}s). When setting <em>asyncMode</em> to true in
39	>	* constructors, {@code ForkJoinPool}s may also be appropriate for use
40	>	* with event-style tasks that are never joined.
41		*
42	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
43	<	* (target pool size), which it attempts to maintain by dynamically
44	<	* adding, suspending, or resuming threads, even if some tasks are
45	<	* waiting to join others. However, no such adjustments are performed
46	<	* in the face of blocked IO or other unmanaged synchronization. The
47	<	* nested <code>ManagedBlocker</code> interface enables extension of
48	<	* the kinds of synchronization accommodated.  The target parallelism
49	<	* level may also be changed dynamically (<code>setParallelism</code>)
50	<	* and thread construction can be limited using methods
45	<	* <code>setMaximumPoolSize</code> and/or
46	<	* <code>setMaintainsParallelism</code>.
42	>	* <p>A {@code ForkJoinPool} is constructed with a given target
43	>	* parallelism level; by default, equal to the number of available
44	>	* processors. The pool attempts to maintain enough active (or
45	>	* available) threads by dynamically adding, suspending, or resuming
46	>	* internal worker threads, even if some tasks are stalled waiting to
47	>	* join others. However, no such adjustments are guaranteed in the
48	>	* face of blocked IO or other unmanaged synchronization. The nested
49	>	* {@link ManagedBlocker} interface enables extension of the kinds of
50	>	* synchronization accommodated.
51		*
52		* <p>In addition to execution and lifecycle control methods, this
53		* class provides status check methods (for example
54	<	* <code>getStealCount</code>) that are intended to aid in developing,
54	>	* {@link #getStealCount}) that are intended to aid in developing,
55		* tuning, and monitoring fork/join applications. Also, method
56	<	* <code>toString</code> returns indications of pool state in a
56	>	* {@link #toString} returns indications of pool state in a
57		* convenient form for informal monitoring.
58		*
59	+	* <p> As is the case with other ExecutorServices, there are three
60	+	* main task execution methods summarized in the following
61	+	* table. These are designed to be used by clients not already engaged
62	+	* in fork/join computations in the current pool.  The main forms of
63	+	* these methods accept instances of {@code ForkJoinTask}, but
64	+	* overloaded forms also allow mixed execution of plain {@code
65	+	* Runnable}- or {@code Callable}- based activities as well.  However,
66	+	* tasks that are already executing in a pool should normally
67	+	* <em>NOT</em> use these pool execution methods, but instead use the
68	+	* within-computation forms listed in the table.
69	+	*
70	+	* <table BORDER CELLPADDING=3 CELLSPACING=1>
71	+	*  <tr>
72	+	*    <td></td>
73	+	*    <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
74	+	*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
75	+	*  </tr>
76	+	*  <tr>
77	+	*    <td> <b>Arrange async execution</td>
78	+	*    <td> {@link #execute(ForkJoinTask)}</td>
79	+	*    <td> {@link ForkJoinTask#fork}</td>
80	+	*  </tr>
81	+	*  <tr>
82	+	*    <td> <b>Await and obtain result</td>
83	+	*    <td> {@link #invoke(ForkJoinTask)}</td>
84	+	*    <td> {@link ForkJoinTask#invoke}</td>
85	+	*  </tr>
86	+	*  <tr>
87	+	*    <td> <b>Arrange exec and obtain Future</td>
88	+	*    <td> {@link #submit(ForkJoinTask)}</td>
89	+	*    <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td>
90	+	*  </tr>
91	+	* </table>
92	+	*
93	+	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
94	+	* used for all parallel task execution in a program or subsystem.
95	+	* Otherwise, use would not usually outweigh the construction and
96	+	* bookkeeping overhead of creating a large set of threads. For
97	+	* example, a common pool could be used for the {@code SortTasks}
98	+	* illustrated in {@link RecursiveAction}. Because {@code
99	+	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
100	+	* daemon} mode, there is typically no need to explicitly {@link
101	+	* #shutdown} such a pool upon program exit.
102	+	*
103	+	* <pre>
104	+	* static final ForkJoinPool mainPool = new ForkJoinPool();
105	+	* ...
106	+	* public void sort(long[] array) {
107	+	*   mainPool.invoke(new SortTask(array, 0, array.length));
108	+	* }
109	+	* </pre>
110	+	*
111		* <p><b>Implementation notes</b>: This implementation restricts the
112		* maximum number of running threads to 32767. Attempts to create
113	<	* pools with greater than the maximum result in
114	<	* IllegalArgumentExceptions.
113	>	* pools with greater than the maximum number result in
114	>	* {@code IllegalArgumentException}.
115	>	*
116	>	* <p>This implementation rejects submitted tasks (that is, by throwing
117	>	* {@link RejectedExecutionException}) only when the pool is shut down
118	>	* or internal resources have been exhausted.
119	>	*
120	>	* @since 1.7
121	>	* @author Doug Lea
122		*/
123		public class ForkJoinPool extends AbstractExecutorService {
124
125		/*
126	<	* See the extended comments interspersed below for design,
127	<	* rationale, and walkthroughs.
128	<	*/
129	<
130	<	/** Mask for packing and unpacking shorts */
131	<	private static final int  shortMask = 0xffff;
132	<
133	<	/** Max pool size -- must be a power of two minus 1 */
134	<	private static final int MAX_THREADS =  0x7FFF;
135	<
136	<	/**
137	<	* Factory for creating new ForkJoinWorkerThreads.  A
138	<	* ForkJoinWorkerThreadFactory must be defined and used for
139	<	* ForkJoinWorkerThread subclasses that extend base functionality
140	<	* or initialize threads with different contexts.
126	>	* Implementation Overview
127	>	*
128	>	* This class provides the central bookkeeping and control for a
129	>	* set of worker threads: Submissions from non-FJ threads enter
130	>	* into a submission queue. Workers take these tasks and typically
131	>	* split them into subtasks that may be stolen by other workers.
132	>	* The main work-stealing mechanics implemented in class
133	>	* ForkJoinWorkerThread give first priority to processing tasks
134	>	* from their own queues (LIFO or FIFO, depending on mode), then
135	>	* to randomized FIFO steals of tasks in other worker queues, and
136	>	* lastly to new submissions. These mechanics do not consider
137	>	* affinities, loads, cache localities, etc, so rarely provide the
138	>	* best possible performance on a given machine, but portably
139	>	* provide good throughput by averaging over these factors.
140	>	* (Further, even if we did try to use such information, we do not
141	>	* usually have a basis for exploiting it. For example, some sets
142	>	* of tasks profit from cache affinities, but others are harmed by
143	>	* cache pollution effects.)
144	>	*
145	>	* Beyond work-stealing support and essential bookkeeping, the
146	>	* main responsibility of this framework is to take actions when
147	>	* one worker is waiting to join a task stolen (or always held by)
148	>	* another.  Because we are multiplexing many tasks on to a pool
149	>	* of workers, we can't just let them block (as in Thread.join).
150	>	* We also cannot just reassign the joiner's run-time stack with
151	>	* another and replace it later, which would be a form of
152	>	* "continuation", that even if possible is not necessarily a good
153	>	* idea. Given that the creation costs of most threads on most
154	>	* systems mainly surrounds setting up runtime stacks, thread
155	>	* creation and switching is usually not much more expensive than
156	>	* stack creation and switching, and is more flexible). Instead we
157	>	* combine two tactics:
158	>	*
159	>	*   Helping: Arranging for the joiner to execute some task that it
160	>	*      would be running if the steal had not occurred.  Method
161	>	*      ForkJoinWorkerThread.helpJoinTask tracks joining->stealing
162	>	*      links to try to find such a task.
163	>	*
164	>	*   Compensating: Unless there are already enough live threads,
165	>	*      method helpMaintainParallelism() may create or
166	>	*      re-activate a spare thread to compensate for blocked
167	>	*      joiners until they unblock.
168	>	*
169	>	* It is impossible to keep exactly the target (parallelism)
170	>	* number of threads running at any given time.  Determining
171	>	* existence of conservatively safe helping targets, the
172	>	* availability of already-created spares, and the apparent need
173	>	* to create new spares are all racy and require heuristic
174	>	* guidance, so we rely on multiple retries of each.  Compensation
175	>	* occurs in slow-motion. It is triggered only upon timeouts of
176	>	* Object.wait used for joins. This reduces poor decisions that
177	>	* would otherwise be made when threads are waiting for others
178	>	* that are stalled because of unrelated activities such as
179	>	* garbage collection.
180	>	*
181	>	* The ManagedBlocker extension API can't use helping so relies
182	>	* only on compensation in method awaitBlocker.
183	>	*
184	>	* The main throughput advantages of work-stealing stem from
185	>	* decentralized control -- workers mostly steal tasks from each
186	>	* other. We do not want to negate this by creating bottlenecks
187	>	* implementing other management responsibilities. So we use a
188	>	* collection of techniques that avoid, reduce, or cope well with
189	>	* contention. These entail several instances of bit-packing into
190	>	* CASable fields to maintain only the minimally required
191	>	* atomicity. To enable such packing, we restrict maximum
192	>	* parallelism to (1<<15)-1 (enabling twice this (to accommodate
193	>	* unbalanced increments and decrements) to fit into a 16 bit
194	>	* field, which is far in excess of normal operating range.  Even
195	>	* though updates to some of these bookkeeping fields do sometimes
196	>	* contend with each other, they don't normally cache-contend with
197	>	* updates to others enough to warrant memory padding or
198	>	* isolation. So they are all held as fields of ForkJoinPool
199	>	* objects.  The main capabilities are as follows:
200	>	*
201	>	* 1. Creating and removing workers. Workers are recorded in the
202	>	* "workers" array. This is an array as opposed to some other data
203	>	* structure to support index-based random steals by workers.
204	>	* Updates to the array recording new workers and unrecording
205	>	* terminated ones are protected from each other by a lock
206	>	* (workerLock) but the array is otherwise concurrently readable,
207	>	* and accessed directly by workers. To simplify index-based
208	>	* operations, the array size is always a power of two, and all
209	>	* readers must tolerate null slots. Currently, all worker thread
210	>	* creation is on-demand, triggered by task submissions,
211	>	* replacement of terminated workers, and/or compensation for
212	>	* blocked workers. However, all other support code is set up to
213	>	* work with other policies.
214	>	*
215	>	* To ensure that we do not hold on to worker references that
216	>	* would prevent GC, ALL accesses to workers are via indices into
217	>	* the workers array (which is one source of some of the unusual
218	>	* code constructions here). In essence, the workers array serves
219	>	* as a WeakReference mechanism. Thus for example the event queue
220	>	* stores worker indices, not worker references. Access to the
221	>	* workers in associated methods (for example releaseEventWaiters)
222	>	* must both index-check and null-check the IDs. All such accesses
223	>	* ignore bad IDs by returning out early from what they are doing,
224	>	* since this can only be associated with shutdown, in which case
225	>	* it is OK to give up. On termination, we just clobber these
226	>	* data structures without trying to use them.
227	>	*
228	>	* 2. Bookkeeping for dynamically adding and removing workers. We
229	>	* aim to approximately maintain the given level of parallelism.
230	>	* When some workers are known to be blocked (on joins or via
231	>	* ManagedBlocker), we may create or resume others to take their
232	>	* place until they unblock (see below). Implementing this
233	>	* requires counts of the number of "running" threads (i.e., those
234	>	* that are neither blocked nor artificially suspended) as well as
235	>	* the total number.  These two values are packed into one field,
236	>	* "workerCounts" because we need accurate snapshots when deciding
237	>	* to create, resume or suspend.  Note however that the
238	>	* correspondence of these counts to reality is not guaranteed. In
239	>	* particular updates for unblocked threads may lag until they
240	>	* actually wake up.
241	>	*
242	>	* 3. Maintaining global run state. The run state of the pool
243	>	* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to
244	>	* those in other Executor implementations, as well as a count of
245	>	* "active" workers -- those that are, or soon will be, or
246	>	* recently were executing tasks. The runLevel and active count
247	>	* are packed together in order to correctly trigger shutdown and
248	>	* termination. Without care, active counts can be subject to very
249	>	* high contention.  We substantially reduce this contention by
250	>	* relaxing update rules.  A worker must claim active status
251	>	* prospectively, by activating if it sees that a submitted or
252	>	* stealable task exists (it may find after activating that the
253	>	* task no longer exists). It stays active while processing this
254	>	* task (if it exists) and any other local subtasks it produces,
255	>	* until it cannot find any other tasks. It then tries
256	>	* inactivating (see method preStep), but upon update contention
257	>	* instead scans for more tasks, later retrying inactivation if it
258	>	* doesn't find any.
259	>	*
260	>	* 4. Managing idle workers waiting for tasks. We cannot let
261	>	* workers spin indefinitely scanning for tasks when none are
262	>	* available. On the other hand, we must quickly prod them into
263	>	* action when new tasks are submitted or generated.  We
264	>	* park/unpark these idle workers using an event-count scheme.
265	>	* Field eventCount is incremented upon events that may enable
266	>	* workers that previously could not find a task to now find one:
267	>	* Submission of a new task to the pool, or another worker pushing
268	>	* a task onto a previously empty queue.  (We also use this
269	>	* mechanism for configuration and termination actions that
270	>	* require wakeups of idle workers).  Each worker maintains its
271	>	* last known event count, and blocks when a scan for work did not
272	>	* find a task AND its lastEventCount matches the current
273	>	* eventCount. Waiting idle workers are recorded in a variant of
274	>	* Treiber stack headed by field eventWaiters which, when nonzero,
275	>	* encodes the thread index and count awaited for by the worker
276	>	* thread most recently calling eventSync. This thread in turn has
277	>	* a record (field nextEventWaiter) for the next waiting worker.
278	>	* In addition to allowing simpler decisions about need for
279	>	* wakeup, the event count bits in eventWaiters serve the role of
280	>	* tags to avoid ABA errors in Treiber stacks. Upon any wakeup,
281	>	* released threads also try to release at most two others.  The
282	>	* net effect is a tree-like diffusion of signals, where released
283	>	* threads (and possibly others) help with unparks.  To further
284	>	* reduce contention effects a bit, failed CASes to increment
285	>	* field eventCount are tolerated without retries in signalWork.
286	>	* Conceptually they are merged into the same event, which is OK
287	>	* when their only purpose is to enable workers to scan for work.
288	>	*
289	>	* 5. Managing suspension of extra workers. When a worker notices
290	>	* (usually upon timeout of a wait()) that there are too few
291	>	* running threads, we may create a new thread to maintain
292	>	* parallelism level, or at least avoid starvation. Usually, extra
293	>	* threads are needed for only very short periods, yet join
294	>	* dependencies are such that we sometimes need them in
295	>	* bursts. Rather than create new threads each time this happens,
296	>	* we suspend no-longer-needed extra ones as "spares". For most
297	>	* purposes, we don't distinguish "extra" spare threads from
298	>	* normal "core" threads: On each call to preStep (the only point
299	>	* at which we can do this) a worker checks to see if there are
300	>	* now too many running workers, and if so, suspends itself.
301	>	* Method helpMaintainParallelism looks for suspended threads to
302	>	* resume before considering creating a new replacement. The
303	>	* spares themselves are encoded on another variant of a Treiber
304	>	* Stack, headed at field "spareWaiters".  Note that the use of
305	>	* spares is intrinsically racy.  One thread may become a spare at
306	>	* about the same time as another is needlessly being created. We
307	>	* counteract this and related slop in part by requiring resumed
308	>	* spares to immediately recheck (in preStep) to see whether they
309	>	* should re-suspend.
310	>	*
311	>	* 6. Killing off unneeded workers. A timeout mechanism is used to
312	>	* shed unused workers: The oldest (first) event queue waiter uses
313	>	* a timed rather than hard wait. When this wait times out without
314	>	* a normal wakeup, it tries to shutdown any one (for convenience
315	>	* the newest) other spare or event waiter via
316	>	* tryShutdownUnusedWorker. This eventually reduces the number of
317	>	* worker threads to a minimum of one after a long enough period
318	>	* without use.
319	>	*
320	>	* 7. Deciding when to create new workers. The main dynamic
321	>	* control in this class is deciding when to create extra threads
322	>	* in method helpMaintainParallelism. We would like to keep
323	>	* exactly #parallelism threads running, which is an impossible
324	>	* task. We always need to create one when the number of running
325	>	* threads would become zero and all workers are busy. Beyond
326	>	* this, we must rely on heuristics that work well in the
327	>	* presence of transient phenomena such as GC stalls, dynamic
328	>	* compilation, and wake-up lags. These transients are extremely
329	>	* common -- we are normally trying to fully saturate the CPUs on
330	>	* a machine, so almost any activity other than running tasks
331	>	* impedes accuracy. Our main defense is to allow parallelism to
332	>	* lapse for a while during joins, and use a timeout to see if,
333	>	* after the resulting settling, there is still a need for
334	>	* additional workers.  This also better copes with the fact that
335	>	* some of the methods in this class tend to never become compiled
336	>	* (but are interpreted), so some components of the entire set of
337	>	* controls might execute 100 times faster than others. And
338	>	* similarly for cases where the apparent lack of work is just due
339	>	* to GC stalls and other transient system activity.
340	>	*
341	>	* Beware that there is a lot of representation-level coupling
342	>	* among classes ForkJoinPool, ForkJoinWorkerThread, and
343	>	* ForkJoinTask.  For example, direct access to "workers" array by
344	>	* workers, and direct access to ForkJoinTask.status by both
345	>	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
346	>	* trying to reduce this, since any associated future changes in
347	>	* representations will need to be accompanied by algorithmic
348	>	* changes anyway.
349	>	*
350	>	* Style notes: There are lots of inline assignments (of form
351	>	* "while ((local = field) != 0)") which are usually the simplest
352	>	* way to ensure the required read orderings (which are sometimes
353	>	* critical). Also several occurrences of the unusual "do {}
354	>	* while (!cas...)" which is the simplest way to force an update of
355	>	* a CAS'ed variable. There are also other coding oddities that
356	>	* help some methods perform reasonably even when interpreted (not
357	>	* compiled), at the expense of some messy constructions that
358	>	* reduce byte code counts.
359	>	*
360	>	* The order of declarations in this file is: (1) statics (2)
361	>	* fields (along with constants used when unpacking some of them)
362	>	* (3) internal control methods (4) callbacks and other support
363	>	* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
364	>	* methods (plus a few little helpers).
365	>	*/
366	>
367	>	/**
368	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
369	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
370	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
371	>	* functionality or initialize threads with different contexts.
372		*/
373		public static interface ForkJoinWorkerThreadFactory {
374		/**
375		* Returns a new worker thread operating in the given pool.
376		*
377		* @param pool the pool this thread works in
378	<	* @throws NullPointerException if pool is null;
378	>	* @throws NullPointerException if the pool is null
379		*/
380		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
381		}
382
383		/**
384	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
384	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
385		* new ForkJoinWorkerThread.
386		*/
387	<	static class  DefaultForkJoinWorkerThreadFactory
387	>	static class DefaultForkJoinWorkerThreadFactory
388		implements ForkJoinWorkerThreadFactory {
389		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
390	<	try {
97	<	return new ForkJoinWorkerThread(pool);
98	<	} catch (OutOfMemoryError oom)  {
99	<	return null;
100	<	}
390	>	return new ForkJoinWorkerThread(pool);
391		}
392		}
393
#	Line 133 | Line 423 | public class ForkJoinPool extends Abstra
423		new AtomicInteger();
424
425		/**
426	<	* Array holding all worker threads in the pool. Initialized upon
427	<	* first use. Array size must be a power of two.  Updates and
428	<	* replacements are protected by workerLock, but it is always kept
429	<	* in a consistent enough state to be randomly accessed without
430	<	* locking by workers performing work-stealing.
426	>	* The time to block in a join (see awaitJoin) before checking if
427	>	* a new worker should be (re)started to maintain parallelism
428	>	* level. The value should be short enough to maintain global
429	>	* responsiveness and progress but long enough to avoid
430	>	* counterproductive firings during GC stalls or unrelated system
431	>	* activity, and to not bog down systems with continual re-firings
432	>	* on GCs or legitimately long waits.
433	>	*/
434	>	private static final long JOIN_TIMEOUT_MILLIS = 250L; // 4 per second
435	>
436	>	/**
437	>	* The wakeup interval (in nanoseconds) for the oldest worker
438	>	* waiting for an event to invoke tryShutdownUnusedWorker to
439	>	* shrink the number of workers.  The exact value does not matter
440	>	* too much. It must be short enough to release resources during
441	>	* sustained periods of idleness, but not so short that threads
442	>	* are continually re-created.
443	>	*/
444	>	private static final long SHRINK_RATE_NANOS =
445	>	30L * 1000L * 1000L * 1000L; // 2 per minute
446	>
447	>	/**
448	>	* Absolute bound for parallelism level. Twice this number plus
449	>	* one (i.e., 0xfff) must fit into a 16bit field to enable
450	>	* word-packing for some counts and indices.
451	>	*/
452	>	private static final int MAX_WORKERS   = 0x7fff;
453	>
454	>	/**
455	>	* Array holding all worker threads in the pool.  Array size must
456	>	* be a power of two.  Updates and replacements are protected by
457	>	* workerLock, but the array is always kept in a consistent enough
458	>	* state to be randomly accessed without locking by workers
459	>	* performing work-stealing, as well as other traversal-based
460	>	* methods in this class. All readers must tolerate that some
461	>	* array slots may be null.
462		*/
463		volatile ForkJoinWorkerThread[] workers;
464
465		/**
466	<	* Lock protecting access to workers.
466	>	* Queue for external submissions.
467		*/
468	<	private final ReentrantLock workerLock;
468	>	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
469
470		/**
471	<	* Condition for awaitTermination.
471	>	* Lock protecting updates to workers array.
472		*/
473	<	private final Condition termination;
473	>	private final ReentrantLock workerLock;
474
475		/**
476	<	* The uncaught exception handler used when any worker
156	<	* abrupty terminates
476	>	* Latch released upon termination.
477		*/
478	<	private Thread.UncaughtExceptionHandler ueh;
478	>	private final Phaser termination;
479
480		/**
481		* Creation factory for worker threads.
#	Line 163 | Line 483 | public class ForkJoinPool extends Abstra
483		private final ForkJoinWorkerThreadFactory factory;
484
485		/**
166	–	* Head of stack of threads that were created to maintain
167	–	* parallelism when other threads blocked, but have since
168	–	* suspended when the parallelism level rose.
169	–	*/
170	–	private volatile WaitQueueNode spareStack;
171	–
172	–	/**
486		* Sum of per-thread steal counts, updated only when threads are
487		* idle or terminating.
488		*/
489	<	private final AtomicLong stealCount;
489	>	private volatile long stealCount;
490
491		/**
492	<	* Queue for external submissions.
492	>	* Encoded record of top of Treiber stack of threads waiting for
493	>	* events. The top 32 bits contain the count being waited for. The
494	>	* bottom 16 bits contains one plus the pool index of waiting
495	>	* worker thread. (Bits 16-31 are unused.)
496		*/
497	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
497	>	private volatile long eventWaiters;
498
499	<	/**
500	<	* Head of Treiber stack for barrier sync. See below for explanation
185	<	*/
186	<	private volatile WaitQueueNode syncStack;
499	>	private static final int EVENT_COUNT_SHIFT = 32;
500	>	private static final int WAITER_ID_MASK    = (1 << 16) - 1;
501
502		/**
503	<	* The count for event barrier
503	>	* A counter for events that may wake up worker threads:
504	>	*   - Submission of a new task to the pool
505	>	*   - A worker pushing a task on an empty queue
506	>	*   - termination
507		*/
508	<	private volatile long eventCount;
508	>	private volatile int eventCount;
509
510		/**
511	<	* Pool number, just for assigning useful names to worker threads
511	>	* Encoded record of top of Treiber stack of spare threads waiting
512	>	* for resumption. The top 16 bits contain an arbitrary count to
513	>	* avoid ABA effects. The bottom 16bits contains one plus the pool
514	>	* index of waiting worker thread.
515		*/
516	<	private final int poolNumber;
516	>	private volatile int spareWaiters;
517
518	<	/**
519	<	* The maximum allowed pool size
200	<	*/
201	<	private volatile int maxPoolSize;
518	>	private static final int SPARE_COUNT_SHIFT = 16;
519	>	private static final int SPARE_ID_MASK     = (1 << 16) - 1;
520
521		/**
522	<	* The desired parallelism level, updated only under workerLock.
522	>	* Lifecycle control. The low word contains the number of workers
523	>	* that are (probably) executing tasks. This value is atomically
524	>	* incremented before a worker gets a task to run, and decremented
525	>	* when a worker has no tasks and cannot find any.  Bits 16-18
526	>	* contain runLevel value. When all are zero, the pool is
527	>	* running. Level transitions are monotonic (running -> shutdown
528	>	* -> terminating -> terminated) so each transition adds a bit.
529	>	* These are bundled together to ensure consistent read for
530	>	* termination checks (i.e., that runLevel is at least SHUTDOWN
531	>	* and active threads is zero).
532	>	*
533	>	* Notes: Most direct CASes are dependent on these bitfield
534	>	* positions.  Also, this field is non-private to enable direct
535	>	* performance-sensitive CASes in ForkJoinWorkerThread.
536		*/
537	<	private volatile int parallelism;
537	>	volatile int runState;
538
539	<	/**
540	<	* True if use local fifo, not default lifo, for local polling
541	<	*/
542	<	private volatile boolean locallyFifo;
539	>	// Note: The order among run level values matters.
540	>	private static final int RUNLEVEL_SHIFT     = 16;
541	>	private static final int SHUTDOWN           = 1 << RUNLEVEL_SHIFT;
542	>	private static final int TERMINATING        = 1 << (RUNLEVEL_SHIFT + 1);
543	>	private static final int TERMINATED         = 1 << (RUNLEVEL_SHIFT + 2);
544	>	private static final int ACTIVE_COUNT_MASK  = (1 << RUNLEVEL_SHIFT) - 1;
545
546		/**
547		* Holds number of total (i.e., created and not yet terminated)
548		* and running (i.e., not blocked on joins or other managed sync)
549	<	* threads, packed into one int to ensure consistent snapshot when
549	>	* threads, packed together to ensure consistent snapshot when
550		* making decisions about creating and suspending spare
551	<	* threads. Updated only by CAS.  Note: CASes in
552	<	* updateRunningCount and preJoin running active count is in low
553	<	* word, so need to be modified if this changes
551	>	* threads. Updated only by CAS. Note that adding a new worker
552	>	* requires incrementing both counts, since workers start off in
553	>	* running state.
554		*/
555		private volatile int workerCounts;
556
557	<	private static int totalCountOf(int s)           { return s >>> 16;  }
558	<	private static int runningCountOf(int s)         { return s & shortMask; }
559	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
557	>	private static final int TOTAL_COUNT_SHIFT  = 16;
558	>	private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1;
559	>	private static final int ONE_RUNNING        = 1;
560	>	private static final int ONE_TOTAL          = 1 << TOTAL_COUNT_SHIFT;
561
562		/**
563	<	* Add delta (which may be negative) to running count.  This must
564	<	* be called before (with negative arg) and after (with positive)
231	<	* any managed synchronization (i.e., mainly, joins)
232	<	* @param delta the number to add
563	>	* The target parallelism level.
564	>	* Accessed directly by ForkJoinWorkerThreads.
565		*/
566	<	final void updateRunningCount(int delta) {
235	<	int s;
236	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
237	<	}
566	>	final int parallelism;
567
568		/**
569	<	* Add delta (which may be negative) to both total and running
570	<	* count.  This must be called upon creation and termination of
242	<	* worker threads.
243	<	* @param delta the number to add
569	>	* True if use local fifo, not default lifo, for local polling
570	>	* Read by, and replicated by ForkJoinWorkerThreads
571		*/
572	<	private void updateWorkerCount(int delta) {
246	<	int d = delta + (delta << 16); // add to both lo and hi parts
247	<	int s;
248	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
249	<	}
572	>	final boolean locallyFifo;
573
574		/**
575	<	* Lifecycle control. High word contains runState, low word
576	<	* contains the number of workers that are (probably) executing
254	<	* tasks. This value is atomically incremented before a worker
255	<	* gets a task to run, and decremented when worker has no tasks
256	<	* and cannot find any. These two fields are bundled together to
257	<	* support correct termination triggering.  Note: activeCount
258	<	* CAS'es cheat by assuming active count is in low word, so need
259	<	* to be modified if this changes
575	>	* The uncaught exception handler used when any worker abruptly
576	>	* terminates.
577		*/
578	<	private volatile int runControl;
578	>	private final Thread.UncaughtExceptionHandler ueh;
579
580	<	// RunState values. Order among values matters
581	<	private static final int RUNNING     = 0;
582	<	private static final int SHUTDOWN    = 1;
583	<	private static final int TERMINATING = 2;
267	<	private static final int TERMINATED  = 3;
580	>	/**
581	>	* Pool number, just for assigning useful names to worker threads
582	>	*/
583	>	private final int poolNumber;
584
585	<	private static int runStateOf(int c)             { return c >>> 16; }
586	<	private static int activeCountOf(int c)          { return c & shortMask; }
271	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
585	>	// Utilities for CASing fields. Note that most of these
586	>	// are usually manually inlined by callers
587
588		/**
589	<	* Try incrementing active count; fail on contention. Called by
275	<	* workers before/during executing tasks.
276	<	* @return true on success;
589	>	* Increments running count part of workerCounts.
590		*/
591	<	final boolean tryIncrementActiveCount() {
592	<	int c = runControl;
593	<	return casRunControl(c, c+1);
591	>	final void incrementRunningCount() {
592	>	int c;
593	>	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
594	>	c = workerCounts,
595	>	c + ONE_RUNNING));
596		}
597
598		/**
599	<	* Try decrementing active count; fail on contention.
285	<	* Possibly trigger termination on success
286	<	* Called by workers when they can't find tasks.
287	<	* @return true on success
599	>	* Tries to increment running count part of workerCounts.
600		*/
601	<	final boolean tryDecrementActiveCount() {
602	<	int c = runControl;
603	<	int nextc = c - 1;
604	<	if (!casRunControl(c, nextc))
605	<	return false;
294	<	if (canTerminateOnShutdown(nextc))
295	<	terminateOnShutdown();
296	<	return true;
601	>	final boolean tryIncrementRunningCount() {
602	>	int c;
603	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
604	>	c = workerCounts,
605	>	c + ONE_RUNNING);
606		}
607
608		/**
609	<	* Return true if argument represents zero active count and
301	<	* nonzero runstate, which is the triggering condition for
302	<	* terminating on shutdown.
609	>	* Tries to decrement running count unless already zero.
610		*/
611	<	private static boolean canTerminateOnShutdown(int c) {
612	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
611	>	final boolean tryDecrementRunningCount() {
612	>	int wc = workerCounts;
613	>	if ((wc & RUNNING_COUNT_MASK) == 0)
614	>	return false;
615	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
616	>	wc, wc - ONE_RUNNING);
617		}
618
619		/**
620	<	* Transition run state to at least the given state. Return true
621	<	* if not already at least given state.
620	>	* Forces decrement of encoded workerCounts, awaiting nonzero if
621	>	* (rarely) necessary when other count updates lag.
622	>	*
623	>	* @param dr -- either zero or ONE_RUNNING
624	>	* @param dt -- either zero or ONE_TOTAL
625		*/
626	<	private boolean transitionRunStateTo(int state) {
626	>	private void decrementWorkerCounts(int dr, int dt) {
627		for (;;) {
628	<	int c = runControl;
629	<	if (runStateOf(c) >= state)
630	<	return false;
631	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
632	<	return true;
628	>	int wc = workerCounts;
629	>	if ((wc & RUNNING_COUNT_MASK)  - dr < 0 ||
630	>	(wc >>> TOTAL_COUNT_SHIFT) - dt < 0) {
631	>	if ((runState & TERMINATED) != 0)
632	>	return; // lagging termination on a backout
633	>	Thread.yield();
634	>	}
635	>	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
636	>	wc, wc - (dr + dt)))
637	>	return;
638		}
639		}
640
641		/**
642	<	* Controls whether to add spares to maintain parallelism
642	>	* Tries decrementing active count; fails on contention.
643	>	* Called when workers cannot find tasks to run.
644		*/
645	<	private volatile boolean maintainsParallelism;
646	<
647	<	// Constructors
645	>	final boolean tryDecrementActiveCount() {
646	>	int c;
647	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
648	>	c = runState, c - 1);
649	>	}
650
651		/**
652	<	* Creates a ForkJoinPool with a pool size equal to the number of
653	<	* processors available on the system and using the default
332	<	* ForkJoinWorkerThreadFactory,
333	<	* @throws SecurityException if a security manager exists and
334	<	*         the caller is not permitted to modify threads
335	<	*         because it does not hold {@link
336	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
652	>	* Advances to at least the given level. Returns true if not
653	>	* already in at least the given level.
654		*/
655	<	public ForkJoinPool() {
656	<	this(Runtime.getRuntime().availableProcessors(),
657	<	defaultForkJoinWorkerThreadFactory);
655	>	private boolean advanceRunLevel(int level) {
656	>	for (;;) {
657	>	int s = runState;
658	>	if ((s & level) != 0)
659	>	return false;
660	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level))
661	>	return true;
662	>	}
663		}
664
665	+	// workers array maintenance
666	+
667		/**
668	<	* Creates a ForkJoinPool with the indicated parellelism level
345	<	* threads, and using the default ForkJoinWorkerThreadFactory,
346	<	* @param parallelism the number of worker threads
347	<	* @throws IllegalArgumentException if parallelism less than or
348	<	* equal to zero
349	<	* @throws SecurityException if a security manager exists and
350	<	*         the caller is not permitted to modify threads
351	<	*         because it does not hold {@link
352	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
668	>	* Records and returns a workers array index for new worker.
669		*/
670	<	public ForkJoinPool(int parallelism) {
671	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
670	>	private int recordWorker(ForkJoinWorkerThread w) {
671	>	// Try using slot totalCount-1. If not available, scan and/or resize
672	>	int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1;
673	>	final ReentrantLock lock = this.workerLock;
674	>	lock.lock();
675	>	try {
676	>	ForkJoinWorkerThread[] ws = workers;
677	>	int n = ws.length;
678	>	if (k < 0 || k >= n || ws[k] != null) {
679	>	for (k = 0; k < n && ws[k] != null; ++k)
680	>	;
681	>	if (k == n)
682	>	ws = workers = Arrays.copyOf(ws, n << 1);
683	>	}
684	>	ws[k] = w;
685	>	int c = eventCount; // advance event count to ensure visibility
686	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c, c+1);
687	>	} finally {
688	>	lock.unlock();
689	>	}
690	>	return k;
691		}
692
693		/**
694	<	* Creates a ForkJoinPool with parallelism equal to the number of
360	<	* processors available on the system and using the given
361	<	* ForkJoinWorkerThreadFactory,
362	<	* @param factory the factory for creating new threads
363	<	* @throws NullPointerException if factory is null
364	<	* @throws SecurityException if a security manager exists and
365	<	*         the caller is not permitted to modify threads
366	<	*         because it does not hold {@link
367	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
694	>	* Nulls out record of worker in workers array.
695		*/
696	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
697	<	this(Runtime.getRuntime().availableProcessors(), factory);
696	>	private void forgetWorker(ForkJoinWorkerThread w) {
697	>	int idx = w.poolIndex;
698	>	// Locking helps method recordWorker avoid unnecessary expansion
699	>	final ReentrantLock lock = this.workerLock;
700	>	lock.lock();
701	>	try {
702	>	ForkJoinWorkerThread[] ws = workers;
703	>	if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify
704	>	ws[idx] = null;
705	>	} finally {
706	>	lock.unlock();
707	>	}
708		}
709
710		/**
711	<	* Creates a ForkJoinPool with the given parallelism and factory.
711	>	* Final callback from terminating worker.  Removes record of
712	>	* worker from array, and adjusts counts. If pool is shutting
713	>	* down, tries to complete termination.
714		*
715	<	* @param parallelism the targeted number of worker threads
377	<	* @param factory the factory for creating new threads
378	<	* @throws IllegalArgumentException if parallelism less than or
379	<	* equal to zero, or greater than implementation limit.
380	<	* @throws NullPointerException if factory is null
381	<	* @throws SecurityException if a security manager exists and
382	<	*         the caller is not permitted to modify threads
383	<	*         because it does not hold {@link
384	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
715	>	* @param w the worker
716		*/
717	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
718	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
719	<	throw new IllegalArgumentException();
720	<	if (factory == null)
721	<	throw new NullPointerException();
722	<	checkPermission();
392	<	this.factory = factory;
393	<	this.parallelism = parallelism;
394	<	this.maxPoolSize = MAX_THREADS;
395	<	this.maintainsParallelism = true;
396	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
397	<	this.workerLock = new ReentrantLock();
398	<	this.termination = workerLock.newCondition();
399	<	this.stealCount = new AtomicLong();
400	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
401	<	// worker array and workers are lazily constructed
717	>	final void workerTerminated(ForkJoinWorkerThread w) {
718	>	forgetWorker(w);
719	>	decrementWorkerCounts(w.isTrimmed() ? 0 : ONE_RUNNING, ONE_TOTAL);
720	>	while (w.stealCount != 0) // collect final count
721	>	tryAccumulateStealCount(w);
722	>	tryTerminate(false);
723		}
724
725	+	// Waiting for and signalling events
726	+
727		/**
728	<	* Create new worker using factory.
729	<	* @param index the index to assign worker
730	<	* @return new worker, or null of factory failed
728	>	* Releases workers blocked on a count not equal to current count.
729	>	* Normally called after precheck that eventWaiters isn't zero to
730	>	* avoid wasted array checks. Gives up upon a change in count or
731	>	* upon releasing two workers, letting others take over.
732		*/
733	<	private ForkJoinWorkerThread createWorker(int index) {
734	<	Thread.UncaughtExceptionHandler h = ueh;
735	<	ForkJoinWorkerThread w = factory.newThread(this);
736	<	if (w != null) {
737	<	w.poolIndex = index;
738	<	w.setDaemon(true);
739	<	w.setAsyncMode(locallyFifo);
740	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
741	<	if (h != null)
742	<	w.setUncaughtExceptionHandler(h);
733	>	private void releaseEventWaiters() {
734	>	ForkJoinWorkerThread[] ws = workers;
735	>	int n = ws.length;
736	>	long h = eventWaiters;
737	>	int ec = eventCount;
738	>	boolean releasedOne = false;
739	>	ForkJoinWorkerThread w; int id;
740	>	while ((id = (((int)h) & WAITER_ID_MASK) - 1) >= 0 &&
741	>	(int)(h >>> EVENT_COUNT_SHIFT) != ec &&
742	>	id < n && (w = ws[id]) != null) {
743	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
744	>	h,  w.nextWaiter)) {
745	>	LockSupport.unpark(w);
746	>	if (releasedOne) // exit on second release
747	>	break;
748	>	releasedOne = true;
749	>	}
750	>	if (eventCount != ec)
751	>	break;
752	>	h = eventWaiters;
753		}
420	–	return w;
754		}
755
756		/**
757	<	* Return a good size for worker array given pool size.
758	<	* Currently requires size to be a power of two.
757	>	* Tries to advance eventCount and releases waiters. Called only
758	>	* from workers.
759		*/
760	<	private static int arraySizeFor(int ps) {
761	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
760	>	final void signalWork() {
761	>	int c; // try to increment event count -- CAS failure OK
762	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
763	>	if (eventWaiters != 0L)
764	>	releaseEventWaiters();
765		}
766
767		/**
768	<	* Create or resize array if necessary to hold newLength.
769	<	* Call only under exlusion or lock
770	<	* @return the array
768	>	* Adds the given worker to event queue and blocks until
769	>	* terminating or event count advances from the given value
770	>	*
771	>	* @param w the calling worker thread
772	>	* @param ec the count
773		*/
774	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
775	<	ForkJoinWorkerThread[] ws = workers;
776	<	if (ws == null)
777	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
778	<	else if (newLength > ws.length)
779	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
780	<	else
781	<	return ws;
774	>	private void eventSync(ForkJoinWorkerThread w, int ec) {
775	>	long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1));
776	>	long h;
777	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
778	>	(((int)(h = eventWaiters) & WAITER_ID_MASK) == 0 ||
779	>	(int)(h >>> EVENT_COUNT_SHIFT) == ec) &&
780	>	eventCount == ec) {
781	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
782	>	w.nextWaiter = h, nh)) {
783	>	awaitEvent(w, ec);
784	>	break;
785	>	}
786	>	}
787		}
788
789		/**
790	<	* Try to shrink workers into smaller array after one or more terminate
790	>	* Blocks the given worker (that has already been entered as an
791	>	* event waiter) until terminating or event count advances from
792	>	* the given value. The oldest (first) waiter uses a timed wait to
793	>	* occasionally one-by-one shrink the number of workers (to a
794	>	* minimum of one) if the pool has not been used for extended
795	>	* periods.
796	>	*
797	>	* @param w the calling worker thread
798	>	* @param ec the count
799		*/
800	<	private void tryShrinkWorkerArray() {
801	<	ForkJoinWorkerThread[] ws = workers;
802	<	if (ws != null) {
803	<	int len = ws.length;
804	<	int last = len - 1;
805	<	while (last >= 0 && ws[last] == null)
806	<	--last;
807	<	int newLength = arraySizeFor(last+1);
808	<	if (newLength < len)
809	<	workers = Arrays.copyOf(ws, newLength);
800	>	private void awaitEvent(ForkJoinWorkerThread w, int ec) {
801	>	while (eventCount == ec) {
802	>	if (tryAccumulateStealCount(w)) { // transfer while idle
803	>	boolean untimed = (w.nextWaiter != 0L ||
804	>	(workerCounts & RUNNING_COUNT_MASK) <= 1);
805	>	long startTime = untimed ? 0 : System.nanoTime();
806	>	Thread.interrupted();         // clear/ignore interrupt
807	>	if (w.isTerminating() || eventCount != ec)
808	>	break;                    // recheck after clear
809	>	if (untimed)
810	>	LockSupport.park(w);
811	>	else {
812	>	LockSupport.parkNanos(w, SHRINK_RATE_NANOS);
813	>	if (eventCount != ec || w.isTerminating())
814	>	break;
815	>	if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS)
816	>	tryShutdownUnusedWorker(ec);
817	>	}
818	>	}
819		}
820		}
821
822	+	// Maintaining parallelism
823	+
824	+	/**
825	+	* Pushes worker onto the spare stack.
826	+	*/
827	+	final void pushSpare(ForkJoinWorkerThread w) {
828	+	int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1);
829	+	do {} while (!UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
830	+	w.nextSpare = spareWaiters,ns));
831	+	}
832	+
833		/**
834	<	* Initialize workers if necessary
834	>	* Tries (once) to resume a spare if the number of running
835	>	* threads is less than target.
836		*/
837	<	final void ensureWorkerInitialization() {
837	>	private void tryResumeSpare() {
838	>	int sw, id;
839		ForkJoinWorkerThread[] ws = workers;
840	<	if (ws == null) {
841	<	final ReentrantLock lock = this.workerLock;
842	<	lock.lock();
843	<	try {
844	<	ws = workers;
845	<	if (ws == null) {
846	<	int ps = parallelism;
847	<	ws = ensureWorkerArrayCapacity(ps);
848	<	for (int i = 0; i < ps; ++i) {
849	<	ForkJoinWorkerThread w = createWorker(i);
850	<	if (w != null) {
851	<	ws[i] = w;
852	<	w.start();
853	<	updateWorkerCount(1);
854	<	}
855	<	}
856	<	}
857	<	} finally {
485	<	lock.unlock();
486	<	}
840	>	int n = ws.length;
841	>	ForkJoinWorkerThread w;
842	>	if ((sw = spareWaiters) != 0 &&
843	>	(id = (sw & SPARE_ID_MASK) - 1) >= 0 &&
844	>	id < n && (w = ws[id]) != null &&
845	>	(runState >= TERMINATING ||
846	>	(workerCounts & RUNNING_COUNT_MASK) < parallelism) &&
847	>	spareWaiters == sw &&
848	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
849	>	sw, w.nextSpare)) {
850	>	int c; // increment running count before resume
851	>	do {} while (!UNSAFE.compareAndSwapInt
852	>	(this, workerCountsOffset,
853	>	c = workerCounts, c + ONE_RUNNING));
854	>	if (w.tryUnsuspend())
855	>	LockSupport.unpark(w);
856	>	else   // back out if w was shutdown
857	>	decrementWorkerCounts(ONE_RUNNING, 0);
858		}
859		}
860
861		/**
862	<	* Worker creation and startup for threads added via setParallelism.
863	<	*/
864	<	private void createAndStartAddedWorkers() {
865	<	resumeAllSpares();  // Allow spares to convert to nonspare
866	<	int ps = parallelism;
867	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
868	<	int len = ws.length;
869	<	// Sweep through slots, to keep lowest indices most populated
870	<	int k = 0;
871	<	while (k < len) {
872	<	if (ws[k] != null) {
873	<	++k;
874	<	continue;
875	<	}
876	<	int s = workerCounts;
877	<	int tc = totalCountOf(s);
878	<	int rc = runningCountOf(s);
879	<	if (rc >= ps || tc >= ps)
880	<	break;
881	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
882	<	ForkJoinWorkerThread w = createWorker(k);
883	<	if (w != null) {
884	<	ws[k++] = w;
885	<	w.start();
862	>	* Tries to increase the number of running workers if below target
863	>	* parallelism: If a spare exists tries to resume it via
864	>	* tryResumeSpare.  Otherwise, if not enough total workers or all
865	>	* existing workers are busy, adds a new worker. In all cases also
866	>	* helps wake up releasable workers waiting for work.
867	>	*/
868	>	private void helpMaintainParallelism() {
869	>	int pc = parallelism;
870	>	int wc, rs, tc;
871	>	while (((wc = workerCounts) & RUNNING_COUNT_MASK) < pc &&
872	>	(rs = runState) < TERMINATING) {
873	>	if (spareWaiters != 0)
874	>	tryResumeSpare();
875	>	else if ((tc = wc >>> TOTAL_COUNT_SHIFT) >= MAX_WORKERS ||
876	>	(tc >= pc && (rs & ACTIVE_COUNT_MASK) != tc))
877	>	break;   // enough total
878	>	else if (runState == rs && workerCounts == wc &&
879	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
880	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
881	>	ForkJoinWorkerThread w = null;
882	>	Throwable fail = null;
883	>	try {
884	>	w = factory.newThread(this);
885	>	} catch (Throwable ex) {
886	>	fail = ex;
887		}
888	<	else {
889	<	updateWorkerCount(-1); // back out on failed creation
888	>	if (w == null) { // null or exceptional factory return
889	>	decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL);
890	>	tryTerminate(false); // handle failure during shutdown
891	>	// If originating from an external caller,
892	>	// propagate exception, else ignore
893	>	if (fail != null && runState < TERMINATING &&
894	>	!(Thread.currentThread() instanceof
895	>	ForkJoinWorkerThread))
896	>	UNSAFE.throwException(fail);
897		break;
898		}
899	+	w.start(recordWorker(w), ueh);
900	+	if ((workerCounts >>> TOTAL_COUNT_SHIFT) >= pc)
901	+	break; // add at most one unless total below target
902		}
903		}
904	+	if (eventWaiters != 0L)
905	+	releaseEventWaiters();
906		}
907
524	–	// Execution methods
525	–
908		/**
909	<	* Common code for execute, invoke and submit
909	>	* Callback from the oldest waiter in awaitEvent waking up after a
910	>	* period of non-use. If all workers are idle, tries (once) to
911	>	* shutdown an event waiter or a spare, if one exists. Note that
912	>	* we don't need CAS or locks here because the method is called
913	>	* only from one thread occasionally waking (and even misfires are
914	>	* OK). Note that until the shutdown worker fully terminates,
915	>	* workerCounts will overestimate total count, which is tolerable.
916	>	*
917	>	* @param ec the event count waited on by caller (to abort
918	>	* attempt if count has since changed).
919		*/
920	<	private <T> void doSubmit(ForkJoinTask<T> task) {
921	<	if (isShutdown())
922	<	throw new RejectedExecutionException();
923	<	if (workers == null)
924	<	ensureWorkerInitialization();
925	<	submissionQueue.offer(task);
926	<	signalIdleWorkers();
920	>	private void tryShutdownUnusedWorker(int ec) {
921	>	if (runState == 0 && eventCount == ec) { // only trigger if all idle
922	>	ForkJoinWorkerThread[] ws = workers;
923	>	int n = ws.length;
924	>	ForkJoinWorkerThread w = null;
925	>	boolean shutdown = false;
926	>	int sw;
927	>	long h;
928	>	if ((sw = spareWaiters) != 0) { // prefer killing spares
929	>	int id = (sw & SPARE_ID_MASK) - 1;
930	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
931	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
932	>	sw, w.nextSpare))
933	>	shutdown = true;
934	>	}
935	>	else if ((h = eventWaiters) != 0L) {
936	>	long nh;
937	>	int id = (((int)h) & WAITER_ID_MASK) - 1;
938	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
939	>	(nh = w.nextWaiter) != 0L && // keep at least one worker
940	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh))
941	>	shutdown = true;
942	>	}
943	>	if (w != null && shutdown) {
944	>	w.shutdown();
945	>	LockSupport.unpark(w);
946	>	}
947	>	}
948	>	releaseEventWaiters(); // in case of interference
949		}
950
951		/**
952	<	* Performs the given task; returning its result upon completion
953	<	* @param task the task
954	<	* @return the task's result
955	<	* @throws NullPointerException if task is null
956	<	* @throws RejectedExecutionException if pool is shut down
952	>	* Callback from workers invoked upon each top-level action (i.e.,
953	>	* stealing a task or taking a submission and running it).
954	>	* Performs one or more of the following:
955	>	*
956	>	* 1. If the worker is active and either did not run a task
957	>	*    or there are too many workers, try to set its active status
958	>	*    to inactive and update activeCount. On contention, we may
959	>	*    try again in this or a subsequent call.
960	>	*
961	>	* 2. If not enough total workers, help create some.
962	>	*
963	>	* 3. If there are too many running workers, suspend this worker
964	>	*    (first forcing inactive if necessary).  If it is not needed,
965	>	*    it may be shutdown while suspended (via
966	>	*    tryShutdownUnusedWorker).  Otherwise, upon resume it
967	>	*    rechecks running thread count and need for event sync.
968	>	*
969	>	* 4. If worker did not run a task, await the next task event via
970	>	*    eventSync if necessary (first forcing inactivation), upon
971	>	*    which the worker may be shutdown via
972	>	*    tryShutdownUnusedWorker.  Otherwise, help release any
973	>	*    existing event waiters that are now releasable,
974	>	*
975	>	* @param w the worker
976	>	* @param ran true if worker ran a task since last call to this method
977		*/
978	<	public <T> T invoke(ForkJoinTask<T> task) {
979	<	doSubmit(task);
980	<	return task.join();
978	>	final void preStep(ForkJoinWorkerThread w, boolean ran) {
979	>	int wec = w.lastEventCount;
980	>	boolean active = w.active;
981	>	boolean inactivate = false;
982	>	int pc = parallelism;
983	>	while (w.runState == 0) {
984	>	int rs = runState;
985	>	if (rs >= TERMINATING) {           // propagate shutdown
986	>	w.shutdown();
987	>	break;
988	>	}
989	>	if ((inactivate || (active && (rs & ACTIVE_COUNT_MASK) >= pc)) &&
990	>	UNSAFE.compareAndSwapInt(this, runStateOffset, rs, --rs)) {
991	>	inactivate = active = w.active = false;
992	>	if (rs == SHUTDOWN) {          // all inactive and shut down
993	>	tryTerminate(false);
994	>	continue;
995	>	}
996	>	}
997	>	int wc = workerCounts;             // try to suspend as spare
998	>	if ((wc & RUNNING_COUNT_MASK) > pc) {
999	>	if (!(inactivate |= active) && // must inactivate to suspend
1000	>	workerCounts == wc &&
1001	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1002	>	wc, wc - ONE_RUNNING))
1003	>	w.suspendAsSpare();
1004	>	}
1005	>	else if ((wc >>> TOTAL_COUNT_SHIFT) < pc)
1006	>	helpMaintainParallelism();     // not enough workers
1007	>	else if (ran)
1008	>	break;
1009	>	else {
1010	>	long h = eventWaiters;
1011	>	int ec = eventCount;
1012	>	if (h != 0L && (int)(h >>> EVENT_COUNT_SHIFT) != ec)
1013	>	releaseEventWaiters();     // release others before waiting
1014	>	else if (ec != wec) {
1015	>	w.lastEventCount = ec;     // no need to wait
1016	>	break;
1017	>	}
1018	>	else if (!(inactivate |= active))
1019	>	eventSync(w, wec);         // must inactivate before sync
1020	>	}
1021	>	}
1022		}
1023
1024		/**
1025	<	* Arranges for (asynchronous) execution of the given task.
1026	<	* @param task the task
1027	<	* @throws NullPointerException if task is null
1028	<	* @throws RejectedExecutionException if pool is shut down
1025	>	* Helps and/or blocks awaiting join of the given task.
1026	>	* See above for explanation.
1027	>	*
1028	>	* @param joinMe the task to join
1029	>	* @param worker the current worker thread
1030	>	* @param timed true if wait should time out
1031	>	* @param nanos timeout value if timed
1032		*/
1033	<	public <T> void execute(ForkJoinTask<T> task) {
1034	<	doSubmit(task);
1033	>	final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker,
1034	>	boolean timed, long nanos) {
1035	>	long startTime = timed? System.nanoTime() : 0L;
1036	>	int retries = 2 + (parallelism >> 2); // #helpJoins before blocking
1037	>	boolean running = true;               // false when count decremented
1038	>	while (joinMe.status >= 0) {
1039	>	if (runState >= TERMINATING) {
1040	>	joinMe.cancelIgnoringExceptions();
1041	>	break;
1042	>	}
1043	>	running = worker.helpJoinTask(joinMe, running);
1044	>	if (joinMe.status < 0)
1045	>	break;
1046	>	if (retries > 0) {
1047	>	--retries;
1048	>	continue;
1049	>	}
1050	>	int wc = workerCounts;
1051	>	if ((wc & RUNNING_COUNT_MASK) != 0) {
1052	>	if (running) {
1053	>	if (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1054	>	wc, wc - ONE_RUNNING))
1055	>	continue;
1056	>	running = false;
1057	>	}
1058	>	long h = eventWaiters;
1059	>	if (h != 0L && (int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1060	>	releaseEventWaiters();
1061	>	if ((workerCounts & RUNNING_COUNT_MASK) != 0) {
1062	>	long ms; int ns;
1063	>	if (!timed) {
1064	>	ms = JOIN_TIMEOUT_MILLIS;
1065	>	ns = 0;
1066	>	}
1067	>	else { // at most JOIN_TIMEOUT_MILLIS per wait
1068	>	long nt = nanos - (System.nanoTime() - startTime);
1069	>	if (nt <= 0L)
1070	>	break;
1071	>	ms = nt / 1000000;
1072	>	if (ms > JOIN_TIMEOUT_MILLIS) {
1073	>	ms = JOIN_TIMEOUT_MILLIS;
1074	>	ns = 0;
1075	>	}
1076	>	else
1077	>	ns = (int) (nt % 1000000);
1078	>	}
1079	>	joinMe.internalAwaitDone(ms, ns);
1080	>	}
1081	>	if (joinMe.status < 0)
1082	>	break;
1083	>	}
1084	>	helpMaintainParallelism();
1085	>	}
1086	>	if (!running) {
1087	>	int c;
1088	>	do {} while (!UNSAFE.compareAndSwapInt
1089	>	(this, workerCountsOffset,
1090	>	c = workerCounts, c + ONE_RUNNING));
1091	>	}
1092		}
1093
1094	<	// AbstractExecutorService methods
1095	<
1096	<	public void execute(Runnable task) {
1097	<	doSubmit(new AdaptedRunnable<Void>(task, null));
1094	>	/**
1095	>	* Same idea as awaitJoin, but no helping, retries, or timeouts.
1096	>	*/
1097	>	final void awaitBlocker(ManagedBlocker blocker)
1098	>	throws InterruptedException {
1099	>	while (!blocker.isReleasable()) {
1100	>	int wc = workerCounts;
1101	>	if ((wc & RUNNING_COUNT_MASK) == 0)
1102	>	helpMaintainParallelism();
1103	>	else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1104	>	wc, wc - ONE_RUNNING)) {
1105	>	try {
1106	>	while (!blocker.isReleasable()) {
1107	>	long h = eventWaiters;
1108	>	if (h != 0L &&
1109	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1110	>	releaseEventWaiters();
1111	>	else if ((workerCounts & RUNNING_COUNT_MASK) == 0 &&
1112	>	runState < TERMINATING)
1113	>	helpMaintainParallelism();
1114	>	else if (blocker.block())
1115	>	break;
1116	>	}
1117	>	} finally {
1118	>	int c;
1119	>	do {} while (!UNSAFE.compareAndSwapInt
1120	>	(this, workerCountsOffset,
1121	>	c = workerCounts, c + ONE_RUNNING));
1122	>	}
1123	>	break;
1124	>	}
1125	>	}
1126		}
1127
1128	<	public <T> ForkJoinTask<T> submit(Callable<T> task) {
1129	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
1130	<	doSubmit(job);
1131	<	return job;
1132	<	}
1128	>	/**
1129	>	* Possibly initiates and/or completes termination.
1130	>	*
1131	>	* @param now if true, unconditionally terminate, else only
1132	>	* if shutdown and empty queue and no active workers
1133	>	* @return true if now terminating or terminated
1134	>	*/
1135	>	private boolean tryTerminate(boolean now) {
1136	>	if (now)
1137	>	advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN
1138	>	else if (runState < SHUTDOWN ||
1139	>	!submissionQueue.isEmpty() ||
1140	>	(runState & ACTIVE_COUNT_MASK) != 0)
1141	>	return false;
1142
1143	<	public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1144	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
574	<	doSubmit(job);
575	<	return job;
576	<	}
1143	>	if (advanceRunLevel(TERMINATING))
1144	>	startTerminating();
1145
1146	<	public ForkJoinTask<?> submit(Runnable task) {
1147	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
1148	<	doSubmit(job);
1149	<	return job;
1146	>	// Finish now if all threads terminated; else in some subsequent call
1147	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1148	>	advanceRunLevel(TERMINATED);
1149	>	termination.forceTermination();
1150	>	}
1151	>	return true;
1152		}
1153
1154		/**
1155	<	* Adaptor for Runnables. This implements RunnableFuture
1156	<	* to be compliant with AbstractExecutorService constraints
1157	<	*/
1158	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1159	<	implements RunnableFuture<T> {
1160	<	final Runnable runnable;
1161	<	final T resultOnCompletion;
1162	<	T result;
1163	<	AdaptedRunnable(Runnable runnable, T result) {
1164	<	if (runnable == null) throw new NullPointerException();
1165	<	this.runnable = runnable;
1166	<	this.resultOnCompletion = result;
1167	<	}
1168	<	public T getRawResult() { return result; }
1169	<	public void setRawResult(T v) { result = v; }
1170	<	public boolean exec() {
1171	<	runnable.run();
1172	<	result = resultOnCompletion;
1173	<	return true;
1155	>	* Actions on transition to TERMINATING
1156	>	*
1157	>	* Runs up to four passes through workers: (0) shutting down each
1158	>	* (without waking up if parked) to quickly spread notifications
1159	>	* without unnecessary bouncing around event queues etc (1) wake
1160	>	* up and help cancel tasks (2) interrupt (3) mop up races with
1161	>	* interrupted workers
1162	>	*/
1163	>	private void startTerminating() {
1164	>	cancelSubmissions();
1165	>	for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) {
1166	>	int c; // advance event count
1167	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
1168	>	c = eventCount, c+1);
1169	>	eventWaiters = 0L; // clobber lists
1170	>	spareWaiters = 0;
1171	>	for (ForkJoinWorkerThread w : workers) {
1172	>	if (w != null) {
1173	>	w.shutdown();
1174	>	if (passes > 0 && !w.isTerminated()) {
1175	>	w.cancelTasks();
1176	>	LockSupport.unpark(w);
1177	>	if (passes > 1 && !w.isInterrupted()) {
1178	>	try {
1179	>	w.interrupt();
1180	>	} catch (SecurityException ignore) {
1181	>	}
1182	>	}
1183	>	}
1184	>	}
1185	>	}
1186		}
605	–	public void run() { invoke(); }
1187		}
1188
1189		/**
1190	<	* Adaptor for Callables
1190	>	* Clears out and cancels submissions, ignoring exceptions.
1191		*/
1192	<	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1193	<	implements RunnableFuture<T> {
1194	<	final Callable<T> callable;
614	<	T result;
615	<	AdaptedCallable(Callable<T> callable) {
616	<	if (callable == null) throw new NullPointerException();
617	<	this.callable = callable;
618	<	}
619	<	public T getRawResult() { return result; }
620	<	public void setRawResult(T v) { result = v; }
621	<	public boolean exec() {
1192	>	private void cancelSubmissions() {
1193	>	ForkJoinTask<?> task;
1194	>	while ((task = submissionQueue.poll()) != null) {
1195		try {
1196	<	result = callable.call();
1197	<	return true;
625	<	} catch (Error err) {
626	<	throw err;
627	<	} catch (RuntimeException rex) {
628	<	throw rex;
629	<	} catch (Exception ex) {
630	<	throw new RuntimeException(ex);
1196	>	task.cancel(false);
1197	>	} catch (Throwable ignore) {
1198		}
1199		}
633	–	public void run() { invoke(); }
1200		}
1201
1202	<	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
637	<	ArrayList<ForkJoinTask<T>> ts =
638	<	new ArrayList<ForkJoinTask<T>>(tasks.size());
639	<	for (Callable<T> c : tasks)
640	<	ts.add(new AdaptedCallable<T>(c));
641	<	invoke(new InvokeAll<T>(ts));
642	<	return (List<Future<T>>)(List)ts;
643	<	}
1202	>	// misc support for ForkJoinWorkerThread
1203
1204	<	static final class InvokeAll<T> extends RecursiveAction {
1205	<	final ArrayList<ForkJoinTask<T>> tasks;
1206	<	InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
1207	<	public void compute() {
1208	<	try { invokeAll(tasks); } catch(Exception ignore) {}
650	<	}
1204	>	/**
1205	>	* Returns pool number.
1206	>	*/
1207	>	final int getPoolNumber() {
1208	>	return poolNumber;
1209		}
1210
653	–	// Configuration and status settings and queries
654	–
1211		/**
1212	<	* Returns the factory used for constructing new workers
1212	>	* Tries to accumulate steal count from a worker, clearing
1213	>	* the worker's value if successful.
1214		*
1215	<	* @return the factory used for constructing new workers
1215	>	* @return true if worker steal count now zero
1216		*/
1217	<	public ForkJoinWorkerThreadFactory getFactory() {
1218	<	return factory;
1217	>	final boolean tryAccumulateStealCount(ForkJoinWorkerThread w) {
1218	>	int sc = w.stealCount;
1219	>	long c = stealCount;
1220	>	// CAS even if zero, for fence effects
1221	>	if (UNSAFE.compareAndSwapLong(this, stealCountOffset, c, c + sc)) {
1222	>	if (sc != 0)
1223	>	w.stealCount = 0;
1224	>	return true;
1225	>	}
1226	>	return sc == 0;
1227		}
1228
1229		/**
1230	<	* Returns the handler for internal worker threads that terminate
1231	<	* due to unrecoverable errors encountered while executing tasks.
667	<	* @return the handler, or null if none
1230	>	* Returns the approximate (non-atomic) number of idle threads per
1231	>	* active thread.
1232		*/
1233	<	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1234	<	Thread.UncaughtExceptionHandler h;
1235	<	final ReentrantLock lock = this.workerLock;
1236	<	lock.lock();
1237	<	try {
1238	<	h = ueh;
1239	<	} finally {
1240	<	lock.unlock();
677	<	}
678	<	return h;
1233	>	final int idlePerActive() {
1234	>	int pc = parallelism; // use parallelism, not rc
1235	>	int ac = runState;    // no mask -- artificially boosts during shutdown
1236	>	// Use exact results for small values, saturate past 4
1237	>	return ((pc <= ac) ? 0 :
1238	>	(pc >>> 1 <= ac) ? 1 :
1239	>	(pc >>> 2 <= ac) ? 3 :
1240	>	pc >>> 3);
1241		}
1242
1243	+	// Public and protected methods
1244	+
1245	+	// Constructors
1246	+
1247		/**
1248	<	* Sets the handler for internal worker threads that terminate due
1249	<	* to unrecoverable errors encountered while executing tasks.
1250	<	* Unless set, the current default or ThreadGroup handler is used
1251	<	* as handler.
1248	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1249	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1250	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1251	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1252		*
687	–	* @param h the new handler
688	–	* @return the old handler, or null if none
1253		* @throws SecurityException if a security manager exists and
1254		*         the caller is not permitted to modify threads
1255		*         because it does not hold {@link
1256	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1256	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1257		*/
1258	<	public Thread.UncaughtExceptionHandler
1259	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
1260	<	checkPermission();
697	<	Thread.UncaughtExceptionHandler old = null;
698	<	final ReentrantLock lock = this.workerLock;
699	<	lock.lock();
700	<	try {
701	<	old = ueh;
702	<	ueh = h;
703	<	ForkJoinWorkerThread[] ws = workers;
704	<	if (ws != null) {
705	<	for (int i = 0; i < ws.length; ++i) {
706	<	ForkJoinWorkerThread w = ws[i];
707	<	if (w != null)
708	<	w.setUncaughtExceptionHandler(h);
709	<	}
710	<	}
711	<	} finally {
712	<	lock.unlock();
713	<	}
714	<	return old;
1258	>	public ForkJoinPool() {
1259	>	this(Runtime.getRuntime().availableProcessors(),
1260	>	defaultForkJoinWorkerThreadFactory, null, false);
1261		}
1262
1263	+	/**
1264	+	* Creates a {@code ForkJoinPool} with the indicated parallelism
1265	+	* level, the {@linkplain
1266	+	* #defaultForkJoinWorkerThreadFactory default thread factory},
1267	+	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1268	+	*
1269	+	* @param parallelism the parallelism level
1270	+	* @throws IllegalArgumentException if parallelism less than or
1271	+	*         equal to zero, or greater than implementation limit
1272	+	* @throws SecurityException if a security manager exists and
1273	+	*         the caller is not permitted to modify threads
1274	+	*         because it does not hold {@link
1275	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1276	+	*/
1277	+	public ForkJoinPool(int parallelism) {
1278	+	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1279	+	}
1280
1281		/**
1282	<	* Sets the target paralleism level of this pool.
1283	<	* @param parallelism the target parallelism
1282	>	* Creates a {@code ForkJoinPool} with the given parameters.
1283	>	*
1284	>	* @param parallelism the parallelism level. For default value,
1285	>	* use {@link java.lang.Runtime#availableProcessors}.
1286	>	* @param factory the factory for creating new threads. For default value,
1287	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
1288	>	* @param handler the handler for internal worker threads that
1289	>	* terminate due to unrecoverable errors encountered while executing
1290	>	* tasks. For default value, use {@code null}.
1291	>	* @param asyncMode if true,
1292	>	* establishes local first-in-first-out scheduling mode for forked
1293	>	* tasks that are never joined. This mode may be more appropriate
1294	>	* than default locally stack-based mode in applications in which
1295	>	* worker threads only process event-style asynchronous tasks.
1296	>	* For default value, use {@code false}.
1297		* @throws IllegalArgumentException if parallelism less than or
1298	<	* equal to zero or greater than maximum size bounds.
1298	>	*         equal to zero, or greater than implementation limit
1299	>	* @throws NullPointerException if the factory is null
1300		* @throws SecurityException if a security manager exists and
1301		*         the caller is not permitted to modify threads
1302		*         because it does not hold {@link
1303	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1303	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1304		*/
1305	<	public void setParallelism(int parallelism) {
1305	>	public ForkJoinPool(int parallelism,
1306	>	ForkJoinWorkerThreadFactory factory,
1307	>	Thread.UncaughtExceptionHandler handler,
1308	>	boolean asyncMode) {
1309		checkPermission();
1310	<	if (parallelism <= 0 || parallelism > maxPoolSize)
1310	>	if (factory == null)
1311	>	throw new NullPointerException();
1312	>	if (parallelism <= 0 || parallelism > MAX_WORKERS)
1313		throw new IllegalArgumentException();
1314	<	final ReentrantLock lock = this.workerLock;
1315	<	lock.lock();
1316	<	try {
1317	<	if (!isTerminating()) {
1318	<	int p = this.parallelism;
1319	<	this.parallelism = parallelism;
1320	<	if (parallelism > p)
1321	<	createAndStartAddedWorkers();
1322	<	else
1323	<	trimSpares();
1324	<	}
1325	<	} finally {
1326	<	lock.unlock();
1327	<	}
1328	<	signalIdleWorkers();
1314	>	this.parallelism = parallelism;
1315	>	this.factory = factory;
1316	>	this.ueh = handler;
1317	>	this.locallyFifo = asyncMode;
1318	>	int arraySize = initialArraySizeFor(parallelism);
1319	>	this.workers = new ForkJoinWorkerThread[arraySize];
1320	>	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
1321	>	this.workerLock = new ReentrantLock();
1322	>	this.termination = new Phaser(1);
1323	>	this.poolNumber = poolNumberGenerator.incrementAndGet();
1324	>	}
1325	>
1326	>	/**
1327	>	* Returns initial power of two size for workers array.
1328	>	* @param pc the initial parallelism level
1329	>	*/
1330	>	private static int initialArraySizeFor(int pc) {
1331	>	// If possible, initially allocate enough space for one spare
1332	>	int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS;
1333	>	// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16)
1334	>	size |= size >>> 1;
1335	>	size |= size >>> 2;
1336	>	size |= size >>> 4;
1337	>	size |= size >>> 8;
1338	>	return size + 1;
1339	>	}
1340	>
1341	>	// Execution methods
1342	>
1343	>	/**
1344	>	* Submits task and creates, starts, or resumes some workers if necessary
1345	>	*/
1346	>	private <T> void doSubmit(ForkJoinTask<T> task) {
1347	>	submissionQueue.offer(task);
1348	>	int c; // try to increment event count -- CAS failure OK
1349	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
1350	>	helpMaintainParallelism();
1351		}
1352
1353		/**
1354	<	* Returns the targeted number of worker threads in this pool.
1354	>	* Performs the given task, returning its result upon completion.
1355		*
1356	<	* @return the targeted number of worker threads in this pool
1356	>	* @param task the task
1357	>	* @return the task's result
1358	>	* @throws NullPointerException if the task is null
1359	>	* @throws RejectedExecutionException if the task cannot be
1360	>	*         scheduled for execution
1361		*/
1362	<	public int getParallelism() {
1363	<	return parallelism;
1362	>	public <T> T invoke(ForkJoinTask<T> task) {
1363	>	if (task == null)
1364	>	throw new NullPointerException();
1365	>	if (runState >= SHUTDOWN)
1366	>	throw new RejectedExecutionException();
1367	>	Thread t = Thread.currentThread();
1368	>	if ((t instanceof ForkJoinWorkerThread) &&
1369	>	((ForkJoinWorkerThread)t).pool == this)
1370	>	return task.invoke();  // bypass submit if in same pool
1371	>	else {
1372	>	doSubmit(task);
1373	>	return task.join();
1374	>	}
1375		}
1376
1377		/**
1378	<	* Returns the number of worker threads that have started but not
1379	<	* yet terminated.  This result returned by this method may differ
1380	<	* from <code>getParallelism</code> when threads are created to
1381	<	* maintain parallelism when others are cooperatively blocked.
1378	>	* Unless terminating, forks task if within an ongoing FJ
1379	>	* computation in the current pool, else submits as external task.
1380	>	*/
1381	>	private <T> void forkOrSubmit(ForkJoinTask<T> task) {
1382	>	if (runState >= SHUTDOWN)
1383	>	throw new RejectedExecutionException();
1384	>	Thread t = Thread.currentThread();
1385	>	if ((t instanceof ForkJoinWorkerThread) &&
1386	>	((ForkJoinWorkerThread)t).pool == this)
1387	>	task.fork();
1388	>	else
1389	>	doSubmit(task);
1390	>	}
1391	>
1392	>	/**
1393	>	* Arranges for (asynchronous) execution of the given task.
1394		*
1395	<	* @return the number of worker threads
1395	>	* @param task the task
1396	>	* @throws NullPointerException if the task is null
1397	>	* @throws RejectedExecutionException if the task cannot be
1398	>	*         scheduled for execution
1399		*/
1400	<	public int getPoolSize() {
1401	<	return totalCountOf(workerCounts);
1400	>	public void execute(ForkJoinTask<?> task) {
1401	>	if (task == null)
1402	>	throw new NullPointerException();
1403	>	forkOrSubmit(task);
1404		}
1405
1406	+	// AbstractExecutorService methods
1407	+
1408		/**
1409	<	* Returns the maximum number of threads allowed to exist in the
1410	<	* pool, even if there are insufficient unblocked running threads.
1411	<	* @return the maximum
1409	>	* @throws NullPointerException if the task is null
1410	>	* @throws RejectedExecutionException if the task cannot be
1411	>	*         scheduled for execution
1412		*/
1413	<	public int getMaximumPoolSize() {
1414	<	return maxPoolSize;
1413	>	public void execute(Runnable task) {
1414	>	if (task == null)
1415	>	throw new NullPointerException();
1416	>	ForkJoinTask<?> job;
1417	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1418	>	job = (ForkJoinTask<?>) task;
1419	>	else
1420	>	job = ForkJoinTask.adapt(task, null);
1421	>	forkOrSubmit(job);
1422		}
1423
1424		/**
1425	<	* Sets the maximum number of threads allowed to exist in the
1426	<	* pool, even if there are insufficient unblocked running threads.
1427	<	* Setting this value has no effect on current pool size. It
1428	<	* controls construction of new threads.
1429	<	* @throws IllegalArgumentException if negative or greater then
1430	<	* internal implementation limit.
1425	>	* Submits a ForkJoinTask for execution.
1426	>	*
1427	>	* @param task the task to submit
1428	>	* @return the task
1429	>	* @throws NullPointerException if the task is null
1430	>	* @throws RejectedExecutionException if the task cannot be
1431	>	*         scheduled for execution
1432		*/
1433	<	public void setMaximumPoolSize(int newMax) {
1434	<	if (newMax < 0 || newMax > MAX_THREADS)
1435	<	throw new IllegalArgumentException();
1436	<	maxPoolSize = newMax;
1433	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1434	>	if (task == null)
1435	>	throw new NullPointerException();
1436	>	forkOrSubmit(task);
1437	>	return task;
1438		}
1439
1440	+	/**
1441	+	* @throws NullPointerException if the task is null
1442	+	* @throws RejectedExecutionException if the task cannot be
1443	+	*         scheduled for execution
1444	+	*/
1445	+	public <T> ForkJoinTask<T> submit(Callable<T> task) {
1446	+	if (task == null)
1447	+	throw new NullPointerException();
1448	+	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1449	+	forkOrSubmit(job);
1450	+	return job;
1451	+	}
1452
1453		/**
1454	<	* Returns true if this pool dynamically maintains its target
1455	<	* parallelism level. If false, new threads are added only to
1456	<	* avoid possible starvation.
798	<	* This setting is by default true;
799	<	* @return true if maintains parallelism
1454	>	* @throws NullPointerException if the task is null
1455	>	* @throws RejectedExecutionException if the task cannot be
1456	>	*         scheduled for execution
1457		*/
1458	<	public boolean getMaintainsParallelism() {
1459	<	return maintainsParallelism;
1458	>	public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1459	>	if (task == null)
1460	>	throw new NullPointerException();
1461	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1462	>	forkOrSubmit(job);
1463	>	return job;
1464		}
1465
1466		/**
1467	<	* Sets whether this pool dynamically maintains its target
1468	<	* parallelism level. If false, new threads are added only to
1469	<	* avoid possible starvation.
809	<	* @param enable true to maintains parallelism
1467	>	* @throws NullPointerException if the task is null
1468	>	* @throws RejectedExecutionException if the task cannot be
1469	>	*         scheduled for execution
1470		*/
1471	<	public void setMaintainsParallelism(boolean enable) {
1472	<	maintainsParallelism = enable;
1471	>	public ForkJoinTask<?> submit(Runnable task) {
1472	>	if (task == null)
1473	>	throw new NullPointerException();
1474	>	ForkJoinTask<?> job;
1475	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1476	>	job = (ForkJoinTask<?>) task;
1477	>	else
1478	>	job = ForkJoinTask.adapt(task, null);
1479	>	forkOrSubmit(job);
1480	>	return job;
1481		}
1482
1483		/**
1484	<	* Establishes local first-in-first-out scheduling mode for forked
1485	<	* tasks that are never joined. This mode may be more appropriate
1486	<	* than default locally stack-based mode in applications in which
1487	<	* worker threads only process asynchronous tasks.  This method is
1488	<	* designed to be invoked only when pool is quiescent, and
1489	<	* typically only before any tasks are submitted. The effects of
1490	<	* invocations at ather times may be unpredictable.
1491	<	*
1492	<	* @param async if true, use locally FIFO scheduling
1493	<	* @return the previous mode.
1494	<	*/
1495	<	public boolean setAsyncMode(boolean async) {
1496	<	boolean oldMode = locallyFifo;
1497	<	locallyFifo = async;
1498	<	ForkJoinWorkerThread[] ws = workers;
1499	<	if (ws != null) {
1500	<	for (int i = 0; i < ws.length; ++i) {
1501	<	ForkJoinWorkerThread t = ws[i];
1502	<	if (t != null)
1503	<	t.setAsyncMode(async);
1504	<	}
1484	>	* @throws NullPointerException       {@inheritDoc}
1485	>	* @throws RejectedExecutionException {@inheritDoc}
1486	>	*/
1487	>	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
1488	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
1489	>	new ArrayList<ForkJoinTask<T>>(tasks.size());
1490	>	for (Callable<T> task : tasks)
1491	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
1492	>	invoke(new InvokeAll<T>(forkJoinTasks));
1493	>
1494	>	@SuppressWarnings({"unchecked", "rawtypes"})
1495	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1496	>	return futures;
1497	>	}
1498	>
1499	>	static final class InvokeAll<T> extends RecursiveAction {
1500	>	final ArrayList<ForkJoinTask<T>> tasks;
1501	>	InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
1502	>	public void compute() {
1503	>	try { invokeAll(tasks); }
1504	>	catch (Exception ignore) {}
1505		}
1506	<	return oldMode;
1506	>	private static final long serialVersionUID = -7914297376763021607L;
1507	>	}
1508	>
1509	>	/**
1510	>	* Returns the factory used for constructing new workers.
1511	>	*
1512	>	* @return the factory used for constructing new workers
1513	>	*/
1514	>	public ForkJoinWorkerThreadFactory getFactory() {
1515	>	return factory;
1516	>	}
1517	>
1518	>	/**
1519	>	* Returns the handler for internal worker threads that terminate
1520	>	* due to unrecoverable errors encountered while executing tasks.
1521	>	*
1522	>	* @return the handler, or {@code null} if none
1523	>	*/
1524	>	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1525	>	return ueh;
1526	>	}
1527	>
1528	>	/**
1529	>	* Returns the targeted parallelism level of this pool.
1530	>	*
1531	>	* @return the targeted parallelism level of this pool
1532	>	*/
1533	>	public int getParallelism() {
1534	>	return parallelism;
1535		}
1536
1537		/**
1538	<	* Returns true if this pool uses local first-in-first-out
1538	>	* Returns the number of worker threads that have started but not
1539	>	* yet terminated.  The result returned by this method may differ
1540	>	* from {@link #getParallelism} when threads are created to
1541	>	* maintain parallelism when others are cooperatively blocked.
1542	>	*
1543	>	* @return the number of worker threads
1544	>	*/
1545	>	public int getPoolSize() {
1546	>	return workerCounts >>> TOTAL_COUNT_SHIFT;
1547	>	}
1548	>
1549	>	/**
1550	>	* Returns {@code true} if this pool uses local first-in-first-out
1551		* scheduling mode for forked tasks that are never joined.
1552		*
1553	<	* @return true if this pool uses async mode.
1553	>	* @return {@code true} if this pool uses async mode
1554		*/
1555		public boolean getAsyncMode() {
1556		return locallyFifo;
#	Line 851 | Line 1559 | public class ForkJoinPool extends Abstra
1559		/**
1560		* Returns an estimate of the number of worker threads that are
1561		* not blocked waiting to join tasks or for other managed
1562	<	* synchronization.
1562	>	* synchronization. This method may overestimate the
1563	>	* number of running threads.
1564		*
1565		* @return the number of worker threads
1566		*/
1567		public int getRunningThreadCount() {
1568	<	return runningCountOf(workerCounts);
1568	>	return workerCounts & RUNNING_COUNT_MASK;
1569		}
1570
1571		/**
1572		* Returns an estimate of the number of threads that are currently
1573		* stealing or executing tasks. This method may overestimate the
1574		* number of active threads.
1575	<	* @return the number of active threads.
1575	>	*
1576	>	* @return the number of active threads
1577		*/
1578		public int getActiveThreadCount() {
1579	<	return activeCountOf(runControl);
870	<	}
871	<
872	<	/**
873	<	* Returns an estimate of the number of threads that are currently
874	<	* idle waiting for tasks. This method may underestimate the
875	<	* number of idle threads.
876	<	* @return the number of idle threads.
877	<	*/
878	<	final int getIdleThreadCount() {
879	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
880	<	return (c <= 0)? 0 : c;
1579	>	return runState & ACTIVE_COUNT_MASK;
1580		}
1581
1582		/**
1583	<	* Returns true if all worker threads are currently idle. An idle
1584	<	* worker is one that cannot obtain a task to execute because none
1585	<	* are available to steal from other threads, and there are no
1586	<	* pending submissions to the pool. This method is conservative:
1587	<	* It might not return true immediately upon idleness of all
1588	<	* threads, but will eventually become true if threads remain
1589	<	* inactive.
1590	<	* @return true if all threads are currently idle
1583	>	* Returns {@code true} if all worker threads are currently idle.
1584	>	* An idle worker is one that cannot obtain a task to execute
1585	>	* because none are available to steal from other threads, and
1586	>	* there are no pending submissions to the pool. This method is
1587	>	* conservative; it might not return {@code true} immediately upon
1588	>	* idleness of all threads, but will eventually become true if
1589	>	* threads remain inactive.
1590	>	*
1591	>	* @return {@code true} if all threads are currently idle
1592		*/
1593		public boolean isQuiescent() {
1594	<	return activeCountOf(runControl) == 0;
1594	>	return (runState & ACTIVE_COUNT_MASK) == 0;
1595		}
1596
1597		/**
#	Line 899 | Line 1599 | public class ForkJoinPool extends Abstra
1599		* one thread's work queue by another. The reported value
1600		* underestimates the actual total number of steals when the pool
1601		* is not quiescent. This value may be useful for monitoring and
1602	<	* tuning fork/join programs: In general, steal counts should be
1602	>	* tuning fork/join programs: in general, steal counts should be
1603		* high enough to keep threads busy, but low enough to avoid
1604		* overhead and contention across threads.
1605	<	* @return the number of steals.
1605	>	*
1606	>	* @return the number of steals
1607		*/
1608		public long getStealCount() {
1609	<	return stealCount.get();
909	<	}
910	<
911	<	/**
912	<	* Accumulate steal count from a worker. Call only
913	<	* when worker known to be idle.
914	<	*/
915	<	private void updateStealCount(ForkJoinWorkerThread w) {
916	<	int sc = w.getAndClearStealCount();
917	<	if (sc != 0)
918	<	stealCount.addAndGet(sc);
1609	>	return stealCount;
1610		}
1611
1612		/**
#	Line 925 | Line 1616 | public class ForkJoinPool extends Abstra
1616		* an approximation, obtained by iterating across all threads in
1617		* the pool. This method may be useful for tuning task
1618		* granularities.
1619	<	* @return the number of queued tasks.
1619	>	*
1620	>	* @return the number of queued tasks
1621		*/
1622		public long getQueuedTaskCount() {
1623		long count = 0;
1624	<	ForkJoinWorkerThread[] ws = workers;
1625	<	if (ws != null) {
1626	<	for (int i = 0; i < ws.length; ++i) {
935	<	ForkJoinWorkerThread t = ws[i];
936	<	if (t != null)
937	<	count += t.getQueueSize();
938	<	}
939	<	}
1624	>	for (ForkJoinWorkerThread w : workers)
1625	>	if (w != null)
1626	>	count += w.getQueueSize();
1627		return count;
1628		}
1629
1630		/**
1631	<	* Returns an estimate of the number tasks submitted to this pool
1632	<	* that have not yet begun executing. This method takes time
1631	>	* Returns an estimate of the number of tasks submitted to this
1632	>	* pool that have not yet begun executing.  This method takes time
1633		* proportional to the number of submissions.
1634	<	* @return the number of queued submissions.
1634	>	*
1635	>	* @return the number of queued submissions
1636		*/
1637		public int getQueuedSubmissionCount() {
1638		return submissionQueue.size();
1639		}
1640
1641		/**
1642	<	* Returns true if there are any tasks submitted to this pool
1643	<	* that have not yet begun executing.
1644	<	* @return <code>true</code> if there are any queued submissions.
1642	>	* Returns {@code true} if there are any tasks submitted to this
1643	>	* pool that have not yet begun executing.
1644	>	*
1645	>	* @return {@code true} if there are any queued submissions
1646		*/
1647		public boolean hasQueuedSubmissions() {
1648		return !submissionQueue.isEmpty();
#	Line 963 | Line 1652 | public class ForkJoinPool extends Abstra
1652		* Removes and returns the next unexecuted submission if one is
1653		* available.  This method may be useful in extensions to this
1654		* class that re-assign work in systems with multiple pools.
1655	<	* @return the next submission, or null if none
1655	>	*
1656	>	* @return the next submission, or {@code null} if none
1657		*/
1658		protected ForkJoinTask<?> pollSubmission() {
1659		return submissionQueue.poll();
#	Line 973 | Line 1663 | public class ForkJoinPool extends Abstra
1663		* Removes all available unexecuted submitted and forked tasks
1664		* from scheduling queues and adds them to the given collection,
1665		* without altering their execution status. These may include
1666	<	* artifically generated or wrapped tasks. This method id designed
1667	<	* to be invoked only when the pool is known to be
1666	>	* artificially generated or wrapped tasks. This method is
1667	>	* designed to be invoked only when the pool is known to be
1668		* quiescent. Invocations at other times may not remove all
1669		* tasks. A failure encountered while attempting to add elements
1670	<	* to collection <tt>c</tt> may result in elements being in
1670	>	* to collection {@code c} may result in elements being in
1671		* neither, either or both collections when the associated
1672		* exception is thrown.  The behavior of this operation is
1673		* undefined if the specified collection is modified while the
1674		* operation is in progress.
1675	+	*
1676		* @param c the collection to transfer elements into
1677		* @return the number of elements transferred
1678		*/
1679	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1680	<	int n = submissionQueue.drainTo(c);
1681	<	ForkJoinWorkerThread[] ws = workers;
1682	<	if (ws != null) {
1683	<	for (int i = 0; i < ws.length; ++i) {
1684	<	ForkJoinWorkerThread w = ws[i];
994	<	if (w != null)
995	<	n += w.drainTasksTo(c);
996	<	}
997	<	}
998	<	return n;
1679	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1680	>	int count = submissionQueue.drainTo(c);
1681	>	for (ForkJoinWorkerThread w : workers)
1682	>	if (w != null)
1683	>	count += w.drainTasksTo(c);
1684	>	return count;
1685		}
1686
1687		/**
#	Line 1006 | Line 1692 | public class ForkJoinPool extends Abstra
1692		* @return a string identifying this pool, as well as its state
1693		*/
1694		public String toString() {
1009	–	int ps = parallelism;
1010	–	int wc = workerCounts;
1011	–	int rc = runControl;
1695		long st = getStealCount();
1696		long qt = getQueuedTaskCount();
1697		long qs = getQueuedSubmissionCount();
1698	+	int wc = workerCounts;
1699	+	int tc = wc >>> TOTAL_COUNT_SHIFT;
1700	+	int rc = wc & RUNNING_COUNT_MASK;
1701	+	int pc = parallelism;
1702	+	int rs = runState;
1703	+	int ac = rs & ACTIVE_COUNT_MASK;
1704		return super.toString() +
1705	<	"[" + runStateToString(runStateOf(rc)) +
1706	<	", parallelism = " + ps +
1707	<	", size = " + totalCountOf(wc) +
1708	<	", active = " + activeCountOf(rc) +
1709	<	", running = " + runningCountOf(wc) +
1705	>	"[" + runLevelToString(rs) +
1706	>	", parallelism = " + pc +
1707	>	", size = " + tc +
1708	>	", active = " + ac +
1709	>	", running = " + rc +
1710		", steals = " + st +
1711		", tasks = " + qt +
1712		", submissions = " + qs +
1713		"]";
1714		}
1715
1716	<	private static String runStateToString(int rs) {
1717	<	switch(rs) {
1718	<	case RUNNING: return "Running";
1719	<	case SHUTDOWN: return "Shutting down";
1720	<	case TERMINATING: return "Terminating";
1032	<	case TERMINATED: return "Terminated";
1033	<	default: throw new Error("Unknown run state");
1034	<	}
1716	>	private static String runLevelToString(int s) {
1717	>	return ((s & TERMINATED) != 0 ? "Terminated" :
1718	>	((s & TERMINATING) != 0 ? "Terminating" :
1719	>	((s & SHUTDOWN) != 0 ? "Shutting down" :
1720	>	"Running")));
1721		}
1722
1037	–	// lifecycle control
1038	–
1723		/**
1724		* Initiates an orderly shutdown in which previously submitted
1725		* tasks are executed, but no new tasks will be accepted.
1726		* Invocation has no additional effect if already shut down.
1727		* Tasks that are in the process of being submitted concurrently
1728		* during the course of this method may or may not be rejected.
1729	+	*
1730		* @throws SecurityException if a security manager exists and
1731		*         the caller is not permitted to modify threads
1732		*         because it does not hold {@link
1733	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1733	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1734		*/
1735		public void shutdown() {
1736		checkPermission();
1737	<	transitionRunStateTo(SHUTDOWN);
1738	<	if (canTerminateOnShutdown(runControl))
1054	<	terminateOnShutdown();
1737	>	advanceRunLevel(SHUTDOWN);
1738	>	tryTerminate(false);
1739		}
1740
1741		/**
1742	<	* Attempts to stop all actively executing tasks, and cancels all
1743	<	* waiting tasks.  Tasks that are in the process of being
1744	<	* submitted or executed concurrently during the course of this
1745	<	* method may or may not be rejected. Unlike some other executors,
1746	<	* this method cancels rather than collects non-executed tasks
1747	<	* upon termination, so always returns an empty list. However, you
1748	<	* can use method <code>drainTasksTo</code> before invoking this
1749	<	* method to transfer unexecuted tasks to another collection.
1742	>	* Attempts to cancel and/or stop all tasks, and reject all
1743	>	* subsequently submitted tasks.  Tasks that are in the process of
1744	>	* being submitted or executed concurrently during the course of
1745	>	* this method may or may not be rejected. This method cancels
1746	>	* both existing and unexecuted tasks, in order to permit
1747	>	* termination in the presence of task dependencies. So the method
1748	>	* always returns an empty list (unlike the case for some other
1749	>	* Executors).
1750	>	*
1751		* @return an empty list
1752		* @throws SecurityException if a security manager exists and
1753		*         the caller is not permitted to modify threads
1754		*         because it does not hold {@link
1755	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1755	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1756		*/
1757		public List<Runnable> shutdownNow() {
1758		checkPermission();
1759	<	terminate();
1759	>	tryTerminate(true);
1760		return Collections.emptyList();
1761		}
1762
1763		/**
1764	<	* Returns <code>true</code> if all tasks have completed following shut down.
1764	>	* Returns {@code true} if all tasks have completed following shut down.
1765		*
1766	<	* @return <code>true</code> if all tasks have completed following shut down
1766	>	* @return {@code true} if all tasks have completed following shut down
1767		*/
1768		public boolean isTerminated() {
1769	<	return runStateOf(runControl) == TERMINATED;
1769	>	return runState >= TERMINATED;
1770		}
1771
1772		/**
1773	<	* Returns <code>true</code> if the process of termination has
1774	<	* commenced but possibly not yet completed.
1773	>	* Returns {@code true} if the process of termination has
1774	>	* commenced but not yet completed.  This method may be useful for
1775	>	* debugging. A return of {@code true} reported a sufficient
1776	>	* period after shutdown may indicate that submitted tasks have
1777	>	* ignored or suppressed interruption, or are waiting for IO,
1778	>	* causing this executor not to properly terminate. (See the
1779	>	* advisory notes for class {@link ForkJoinTask} stating that
1780	>	* tasks should not normally entail blocking operations.  But if
1781	>	* they do, they must abort them on interrupt.)
1782		*
1783	<	* @return <code>true</code> if terminating
1783	>	* @return {@code true} if terminating but not yet terminated
1784		*/
1785		public boolean isTerminating() {
1786	<	return runStateOf(runControl) >= TERMINATING;
1786	>	return (runState & (TERMINATING|TERMINATED)) == TERMINATING;
1787		}
1788
1789		/**
1790	<	* Returns <code>true</code> if this pool has been shut down.
1790	>	* Returns true if terminating or terminated. Used by ForkJoinWorkerThread.
1791	>	*/
1792	>	final boolean isAtLeastTerminating() {
1793	>	return runState >= TERMINATING;
1794	>	}
1795	>
1796	>	/**
1797	>	* Returns {@code true} if this pool has been shut down.
1798		*
1799	<	* @return <code>true</code> if this pool has been shut down
1799	>	* @return {@code true} if this pool has been shut down
1800		*/
1801		public boolean isShutdown() {
1802	<	return runStateOf(runControl) >= SHUTDOWN;
1802	>	return runState >= SHUTDOWN;
1803		}
1804
1805		/**
#	Line 1110 | Line 1809 | public class ForkJoinPool extends Abstra
1809		*
1810		* @param timeout the maximum time to wait
1811		* @param unit the time unit of the timeout argument
1812	<	* @return <code>true</code> if this executor terminated and
1813	<	*         <code>false</code> if the timeout elapsed before termination
1812	>	* @return {@code true} if this executor terminated and
1813	>	*         {@code false} if the timeout elapsed before termination
1814		* @throws InterruptedException if interrupted while waiting
1815		*/
1816		public boolean awaitTermination(long timeout, TimeUnit unit)
1817		throws InterruptedException {
1119	–	long nanos = unit.toNanos(timeout);
1120	–	final ReentrantLock lock = this.workerLock;
1121	–	lock.lock();
1122	–	try {
1123	–	for (;;) {
1124	–	if (isTerminated())
1125	–	return true;
1126	–	if (nanos <= 0)
1127	–	return false;
1128	–	nanos = termination.awaitNanos(nanos);
1129	–	}
1130	–	} finally {
1131	–	lock.unlock();
1132	–	}
1133	–	}
1134	–
1135	–	// Shutdown and termination support
1136	–
1137	–	/**
1138	–	* Callback from terminating worker. Null out the corresponding
1139	–	* workers slot, and if terminating, try to terminate, else try to
1140	–	* shrink workers array.
1141	–	* @param w the worker
1142	–	*/
1143	–	final void workerTerminated(ForkJoinWorkerThread w) {
1144	–	updateStealCount(w);
1145	–	updateWorkerCount(-1);
1146	–	final ReentrantLock lock = this.workerLock;
1147	–	lock.lock();
1148	–	try {
1149	–	ForkJoinWorkerThread[] ws = workers;
1150	–	if (ws != null) {
1151	–	int idx = w.poolIndex;
1152	–	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1153	–	ws[idx] = null;
1154	–	if (totalCountOf(workerCounts) == 0) {
1155	–	terminate(); // no-op if already terminating
1156	–	transitionRunStateTo(TERMINATED);
1157	–	termination.signalAll();
1158	–	}
1159	–	else if (!isTerminating()) {
1160	–	tryShrinkWorkerArray();
1161	–	tryResumeSpare(true); // allow replacement
1162	–	}
1163	–	}
1164	–	} finally {
1165	–	lock.unlock();
1166	–	}
1167	–	signalIdleWorkers();
1168	–	}
1169	–
1170	–	/**
1171	–	* Initiate termination.
1172	–	*/
1173	–	private void terminate() {
1174	–	if (transitionRunStateTo(TERMINATING)) {
1175	–	stopAllWorkers();
1176	–	resumeAllSpares();
1177	–	signalIdleWorkers();
1178	–	cancelQueuedSubmissions();
1179	–	cancelQueuedWorkerTasks();
1180	–	interruptUnterminatedWorkers();
1181	–	signalIdleWorkers(); // resignal after interrupt
1182	–	}
1183	–	}
1184	–
1185	–	/**
1186	–	* Possibly terminate when on shutdown state
1187	–	*/
1188	–	private void terminateOnShutdown() {
1189	–	if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
1190	–	terminate();
1191	–	}
1192	–
1193	–	/**
1194	–	* Clear out and cancel submissions
1195	–	*/
1196	–	private void cancelQueuedSubmissions() {
1197	–	ForkJoinTask<?> task;
1198	–	while ((task = pollSubmission()) != null)
1199	–	task.cancel(false);
1200	–	}
1201	–
1202	–	/**
1203	–	* Clean out worker queues.
1204	–	*/
1205	–	private void cancelQueuedWorkerTasks() {
1206	–	final ReentrantLock lock = this.workerLock;
1207	–	lock.lock();
1818		try {
1819	<	ForkJoinWorkerThread[] ws = workers;
1820	<	if (ws != null) {
1211	<	for (int i = 0; i < ws.length; ++i) {
1212	<	ForkJoinWorkerThread t = ws[i];
1213	<	if (t != null)
1214	<	t.cancelTasks();
1215	<	}
1216	<	}
1217	<	} finally {
1218	<	lock.unlock();
1219	<	}
1220	<	}
1221	<
1222	<	/**
1223	<	* Set each worker's status to terminating. Requires lock to avoid
1224	<	* conflicts with add/remove
1225	<	*/
1226	<	private void stopAllWorkers() {
1227	<	final ReentrantLock lock = this.workerLock;
1228	<	lock.lock();
1229	<	try {
1230	<	ForkJoinWorkerThread[] ws = workers;
1231	<	if (ws != null) {
1232	<	for (int i = 0; i < ws.length; ++i) {
1233	<	ForkJoinWorkerThread t = ws[i];
1234	<	if (t != null)
1235	<	t.shutdownNow();
1236	<	}
1237	<	}
1238	<	} finally {
1239	<	lock.unlock();
1240	<	}
1241	<	}
1242	<
1243	<	/**
1244	<	* Interrupt all unterminated workers.  This is not required for
1245	<	* sake of internal control, but may help unstick user code during
1246	<	* shutdown.
1247	<	*/
1248	<	private void interruptUnterminatedWorkers() {
1249	<	final ReentrantLock lock = this.workerLock;
1250	<	lock.lock();
1251	<	try {
1252	<	ForkJoinWorkerThread[] ws = workers;
1253	<	if (ws != null) {
1254	<	for (int i = 0; i < ws.length; ++i) {
1255	<	ForkJoinWorkerThread t = ws[i];
1256	<	if (t != null && !t.isTerminated()) {
1257	<	try {
1258	<	t.interrupt();
1259	<	} catch (SecurityException ignore) {
1260	<	}
1261	<	}
1262	<	}
1263	<	}
1264	<	} finally {
1265	<	lock.unlock();
1266	<	}
1267	<	}
1268	<
1269	<
1270	<	/*
1271	<	* Nodes for event barrier to manage idle threads.  Queue nodes
1272	<	* are basic Treiber stack nodes, also used for spare stack.
1273	<	*
1274	<	* The event barrier has an event count and a wait queue (actually
1275	<	* a Treiber stack).  Workers are enabled to look for work when
1276	<	* the eventCount is incremented. If they fail to find work, they
1277	<	* may wait for next count. Upon release, threads help others wake
1278	<	* up.
1279	<	*
1280	<	* Synchronization events occur only in enough contexts to
1281	<	* maintain overall liveness:
1282	<	*
1283	<	*   - Submission of a new task to the pool
1284	<	*   - Resizes or other changes to the workers array
1285	<	*   - pool termination
1286	<	*   - A worker pushing a task on an empty queue
1287	<	*
1288	<	* The case of pushing a task occurs often enough, and is heavy
1289	<	* enough compared to simple stack pushes, to require special
1290	<	* handling: Method signalWork returns without advancing count if
1291	<	* the queue appears to be empty.  This would ordinarily result in
1292	<	* races causing some queued waiters not to be woken up. To avoid
1293	<	* this, the first worker enqueued in method sync (see
1294	<	* syncIsReleasable) rescans for tasks after being enqueued, and
1295	<	* helps signal if any are found. This works well because the
1296	<	* worker has nothing better to do, and so might as well help
1297	<	* alleviate the overhead and contention on the threads actually
1298	<	* doing work.  Also, since event counts increments on task
1299	<	* availability exist to maintain liveness (rather than to force
1300	<	* refreshes etc), it is OK for callers to exit early if
1301	<	* contending with another signaller.
1302	<	*/
1303	<	static final class WaitQueueNode {
1304	<	WaitQueueNode next; // only written before enqueued
1305	<	volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1306	<	final long count; // unused for spare stack
1307	<
1308	<	WaitQueueNode(long c, ForkJoinWorkerThread w) {
1309	<	count = c;
1310	<	thread = w;
1311	<	}
1312	<
1313	<	/**
1314	<	* Wake up waiter, returning false if known to already
1315	<	*/
1316	<	boolean signal() {
1317	<	ForkJoinWorkerThread t = thread;
1318	<	if (t == null)
1319	<	return false;
1320	<	thread = null;
1321	<	LockSupport.unpark(t);
1322	<	return true;
1323	<	}
1324	<
1325	<	/**
1326	<	* Await release on sync
1327	<	*/
1328	<	void awaitSyncRelease(ForkJoinPool p) {
1329	<	while (thread != null && !p.syncIsReleasable(this))
1330	<	LockSupport.park(this);
1331	<	}
1332	<
1333	<	/**
1334	<	* Await resumption as spare
1335	<	*/
1336	<	void awaitSpareRelease() {
1337	<	while (thread != null) {
1338	<	if (!Thread.interrupted())
1339	<	LockSupport.park(this);
1340	<	}
1341	<	}
1342	<	}
1343	<
1344	<	/**
1345	<	* Ensures that no thread is waiting for count to advance from the
1346	<	* current value of eventCount read on entry to this method, by
1347	<	* releasing waiting threads if necessary.
1348	<	* @return the count
1349	<	*/
1350	<	final long ensureSync() {
1351	<	long c = eventCount;
1352	<	WaitQueueNode q;
1353	<	while ((q = syncStack) != null && q.count < c) {
1354	<	if (casBarrierStack(q, null)) {
1355	<	do {
1356	<	q.signal();
1357	<	} while ((q = q.next) != null);
1358	<	break;
1359	<	}
1360	<	}
1361	<	return c;
1362	<	}
1363	<
1364	<	/**
1365	<	* Increments event count and releases waiting threads.
1366	<	*/
1367	<	private void signalIdleWorkers() {
1368	<	long c;
1369	<	do;while (!casEventCount(c = eventCount, c+1));
1370	<	ensureSync();
1371	<	}
1372	<
1373	<	/**
1374	<	* Signal threads waiting to poll a task. Because method sync
1375	<	* rechecks availability, it is OK to only proceed if queue
1376	<	* appears to be non-empty, and OK to skip under contention to
1377	<	* increment count (since some other thread succeeded).
1378	<	*/
1379	<	final void signalWork() {
1380	<	long c;
1381	<	WaitQueueNode q;
1382	<	if (syncStack != null &&
1383	<	casEventCount(c = eventCount, c+1) &&
1384	<	(((q = syncStack) != null && q.count <= c) &&
1385	<	(!casBarrierStack(q, q.next) || !q.signal())))
1386	<	ensureSync();
1387	<	}
1388	<
1389	<	/**
1390	<	* Waits until event count advances from last value held by
1391	<	* caller, or if excess threads, caller is resumed as spare, or
1392	<	* caller or pool is terminating. Updates caller's event on exit.
1393	<	* @param w the calling worker thread
1394	<	*/
1395	<	final void sync(ForkJoinWorkerThread w) {
1396	<	updateStealCount(w); // Transfer w's count while it is idle
1397	<
1398	<	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1399	<	long prev = w.lastEventCount;
1400	<	WaitQueueNode node = null;
1401	<	WaitQueueNode h;
1402	<	while (eventCount == prev &&
1403	<	((h = syncStack) == null || h.count == prev)) {
1404	<	if (node == null)
1405	<	node = new WaitQueueNode(prev, w);
1406	<	if (casBarrierStack(node.next = h, node)) {
1407	<	node.awaitSyncRelease(this);
1408	<	break;
1409	<	}
1410	<	}
1411	<	long ec = ensureSync();
1412	<	if (ec != prev) {
1413	<	w.lastEventCount = ec;
1414	<	break;
1415	<	}
1416	<	}
1417	<	}
1418	<
1419	<	/**
1420	<	* Returns true if worker waiting on sync can proceed:
1421	<	*  - on signal (thread == null)
1422	<	*  - on event count advance (winning race to notify vs signaller)
1423	<	*  - on Interrupt
1424	<	*  - if the first queued node, we find work available
1425	<	* If node was not signalled and event count not advanced on exit,
1426	<	* then we also help advance event count.
1427	<	* @return true if node can be released
1428	<	*/
1429	<	final boolean syncIsReleasable(WaitQueueNode node) {
1430	<	long prev = node.count;
1431	<	if (!Thread.interrupted() && node.thread != null &&
1432	<	(node.next != null ||
1433	<	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1434	<	eventCount == prev)
1819	>	termination.awaitAdvanceInterruptibly(0, timeout, unit);
1820	>	} catch (TimeoutException ex) {
1821		return false;
1436	–	if (node.thread != null) {
1437	–	node.thread = null;
1438	–	long ec = eventCount;
1439	–	if (prev <= ec) // help signal
1440	–	casEventCount(ec, ec+1);
1822		}
1823		return true;
1824		}
1825
1826		/**
1446	–	* Returns true if a new sync event occurred since last call to
1447	–	* sync or this method, if so, updating caller's count.
1448	–	*/
1449	–	final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1450	–	long lc = w.lastEventCount;
1451	–	long ec = ensureSync();
1452	–	if (ec == lc)
1453	–	return false;
1454	–	w.lastEventCount = ec;
1455	–	return true;
1456	–	}
1457	–
1458	–	//  Parallelism maintenance
1459	–
1460	–	/**
1461	–	* Decrement running count; if too low, add spare.
1462	–	*
1463	–	* Conceptually, all we need to do here is add or resume a
1464	–	* spare thread when one is about to block (and remove or
1465	–	* suspend it later when unblocked -- see suspendIfSpare).
1466	–	* However, implementing this idea requires coping with
1467	–	* several problems: We have imperfect information about the
1468	–	* states of threads. Some count updates can and usually do
1469	–	* lag run state changes, despite arrangements to keep them
1470	–	* accurate (for example, when possible, updating counts
1471	–	* before signalling or resuming), especially when running on
1472	–	* dynamic JVMs that don't optimize the infrequent paths that
1473	–	* update counts. Generating too many threads can make these
1474	–	* problems become worse, because excess threads are more
1475	–	* likely to be context-switched with others, slowing them all
1476	–	* down, especially if there is no work available, so all are
1477	–	* busy scanning or idling.  Also, excess spare threads can
1478	–	* only be suspended or removed when they are idle, not
1479	–	* immediately when they aren't needed. So adding threads will
1480	–	* raise parallelism level for longer than necessary.  Also,
1481	–	* FJ applications often enounter highly transient peaks when
1482	–	* many threads are blocked joining, but for less time than it
1483	–	* takes to create or resume spares.
1484	–	*
1485	–	* @param joinMe if non-null, return early if done
1486	–	* @param maintainParallelism if true, try to stay within
1487	–	* target counts, else create only to avoid starvation
1488	–	* @return true if joinMe known to be done
1489	–	*/
1490	–	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1491	–	maintainParallelism &= maintainsParallelism; // overrride
1492	–	boolean dec = false;  // true when running count decremented
1493	–	while (spareStack == null || !tryResumeSpare(dec)) {
1494	–	int counts = workerCounts;
1495	–	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1496	–	if (!needSpare(counts, maintainParallelism))
1497	–	break;
1498	–	if (joinMe.status < 0)
1499	–	return true;
1500	–	if (tryAddSpare(counts))
1501	–	break;
1502	–	}
1503	–	}
1504	–	return false;
1505	–	}
1506	–
1507	–	/**
1508	–	* Same idea as preJoin
1509	–	*/
1510	–	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1511	–	maintainParallelism &= maintainsParallelism;
1512	–	boolean dec = false;
1513	–	while (spareStack == null || !tryResumeSpare(dec)) {
1514	–	int counts = workerCounts;
1515	–	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1516	–	if (!needSpare(counts, maintainParallelism))
1517	–	break;
1518	–	if (blocker.isReleasable())
1519	–	return true;
1520	–	if (tryAddSpare(counts))
1521	–	break;
1522	–	}
1523	–	}
1524	–	return false;
1525	–	}
1526	–
1527	–	/**
1528	–	* Returns true if a spare thread appears to be needed.  If
1529	–	* maintaining parallelism, returns true when the deficit in
1530	–	* running threads is more than the surplus of total threads, and
1531	–	* there is apparently some work to do.  This self-limiting rule
1532	–	* means that the more threads that have already been added, the
1533	–	* less parallelism we will tolerate before adding another.
1534	–	* @param counts current worker counts
1535	–	* @param maintainParallelism try to maintain parallelism
1536	–	*/
1537	–	private boolean needSpare(int counts, boolean maintainParallelism) {
1538	–	int ps = parallelism;
1539	–	int rc = runningCountOf(counts);
1540	–	int tc = totalCountOf(counts);
1541	–	int runningDeficit = ps - rc;
1542	–	int totalSurplus = tc - ps;
1543	–	return (tc < maxPoolSize &&
1544	–	(rc == 0 || totalSurplus < 0 ||
1545	–	(maintainParallelism &&
1546	–	runningDeficit > totalSurplus &&
1547	–	ForkJoinWorkerThread.hasQueuedTasks(workers))));
1548	–	}
1549	–
1550	–	/**
1551	–	* Add a spare worker if lock available and no more than the
1552	–	* expected numbers of threads exist
1553	–	* @return true if successful
1554	–	*/
1555	–	private boolean tryAddSpare(int expectedCounts) {
1556	–	final ReentrantLock lock = this.workerLock;
1557	–	int expectedRunning = runningCountOf(expectedCounts);
1558	–	int expectedTotal = totalCountOf(expectedCounts);
1559	–	boolean success = false;
1560	–	boolean locked = false;
1561	–	// confirm counts while locking; CAS after obtaining lock
1562	–	try {
1563	–	for (;;) {
1564	–	int s = workerCounts;
1565	–	int tc = totalCountOf(s);
1566	–	int rc = runningCountOf(s);
1567	–	if (rc > expectedRunning || tc > expectedTotal)
1568	–	break;
1569	–	if (!locked && !(locked = lock.tryLock()))
1570	–	break;
1571	–	if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) {
1572	–	createAndStartSpare(tc);
1573	–	success = true;
1574	–	break;
1575	–	}
1576	–	}
1577	–	} finally {
1578	–	if (locked)
1579	–	lock.unlock();
1580	–	}
1581	–	return success;
1582	–	}
1583	–
1584	–	/**
1585	–	* Add the kth spare worker. On entry, pool coounts are already
1586	–	* adjusted to reflect addition.
1587	–	*/
1588	–	private void createAndStartSpare(int k) {
1589	–	ForkJoinWorkerThread w = null;
1590	–	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1);
1591	–	int len = ws.length;
1592	–	// Probably, we can place at slot k. If not, find empty slot
1593	–	if (k < len && ws[k] != null) {
1594	–	for (k = 0; k < len && ws[k] != null; ++k)
1595	–	;
1596	–	}
1597	–	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1598	–	ws[k] = w;
1599	–	w.start();
1600	–	}
1601	–	else
1602	–	updateWorkerCount(-1); // adjust on failure
1603	–	signalIdleWorkers();
1604	–	}
1605	–
1606	–	/**
1607	–	* Suspend calling thread w if there are excess threads.  Called
1608	–	* only from sync.  Spares are enqueued in a Treiber stack
1609	–	* using the same WaitQueueNodes as barriers.  They are resumed
1610	–	* mainly in preJoin, but are also woken on pool events that
1611	–	* require all threads to check run state.
1612	–	* @param w the caller
1613	–	*/
1614	–	private boolean suspendIfSpare(ForkJoinWorkerThread w) {
1615	–	WaitQueueNode node = null;
1616	–	int s;
1617	–	while (parallelism < runningCountOf(s = workerCounts)) {
1618	–	if (node == null)
1619	–	node = new WaitQueueNode(0, w);
1620	–	if (casWorkerCounts(s, s-1)) { // representation-dependent
1621	–	// push onto stack
1622	–	do;while (!casSpareStack(node.next = spareStack, node));
1623	–	// block until released by resumeSpare
1624	–	node.awaitSpareRelease();
1625	–	return true;
1626	–	}
1627	–	}
1628	–	return false;
1629	–	}
1630	–
1631	–	/**
1632	–	* Try to pop and resume a spare thread.
1633	–	* @param updateCount if true, increment running count on success
1634	–	* @return true if successful
1635	–	*/
1636	–	private boolean tryResumeSpare(boolean updateCount) {
1637	–	WaitQueueNode q;
1638	–	while ((q = spareStack) != null) {
1639	–	if (casSpareStack(q, q.next)) {
1640	–	if (updateCount)
1641	–	updateRunningCount(1);
1642	–	q.signal();
1643	–	return true;
1644	–	}
1645	–	}
1646	–	return false;
1647	–	}
1648	–
1649	–	/**
1650	–	* Pop and resume all spare threads. Same idea as ensureSync.
1651	–	* @return true if any spares released
1652	–	*/
1653	–	private boolean resumeAllSpares() {
1654	–	WaitQueueNode q;
1655	–	while ( (q = spareStack) != null) {
1656	–	if (casSpareStack(q, null)) {
1657	–	do {
1658	–	updateRunningCount(1);
1659	–	q.signal();
1660	–	} while ((q = q.next) != null);
1661	–	return true;
1662	–	}
1663	–	}
1664	–	return false;
1665	–	}
1666	–
1667	–	/**
1668	–	* Pop and shutdown excessive spare threads. Call only while
1669	–	* holding lock. This is not guaranteed to eliminate all excess
1670	–	* threads, only those suspended as spares, which are the ones
1671	–	* unlikely to be needed in the future.
1672	–	*/
1673	–	private void trimSpares() {
1674	–	int surplus = totalCountOf(workerCounts) - parallelism;
1675	–	WaitQueueNode q;
1676	–	while (surplus > 0 && (q = spareStack) != null) {
1677	–	if (casSpareStack(q, null)) {
1678	–	do {
1679	–	updateRunningCount(1);
1680	–	ForkJoinWorkerThread w = q.thread;
1681	–	if (w != null && surplus > 0 &&
1682	–	runningCountOf(workerCounts) > 0 && w.shutdown())
1683	–	--surplus;
1684	–	q.signal();
1685	–	} while ((q = q.next) != null);
1686	–	}
1687	–	}
1688	–	}
1689	–
1690	–	/**
1827		* Interface for extending managed parallelism for tasks running
1828	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1829	<	* Method <code>isReleasable</code> must return true if blocking is not
1830	<	* necessary. Method <code>block</code> blocks the current thread
1831	<	* if necessary (perhaps internally invoking isReleasable before
1832	<	* actually blocking.).
1828	>	* in {@link ForkJoinPool}s.
1829	>	*
1830	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
1831	>	* {@code isReleasable} must return {@code true} if blocking is
1832	>	* not necessary. Method {@code block} blocks the current thread
1833	>	* if necessary (perhaps internally invoking {@code isReleasable}
1834	>	* before actually blocking). The unusual methods in this API
1835	>	* accommodate synchronizers that may, but don't usually, block
1836	>	* for long periods. Similarly, they allow more efficient internal
1837	>	* handling of cases in which additional workers may be, but
1838	>	* usually are not, needed to ensure sufficient parallelism.
1839	>	* Toward this end, implementations of method {@code isReleasable}
1840	>	* must be amenable to repeated invocation.
1841	>	*
1842		* <p>For example, here is a ManagedBlocker based on a
1843		* ReentrantLock:
1844	<	* <pre>
1845	<	*   class ManagedLocker implements ManagedBlocker {
1846	<	*     final ReentrantLock lock;
1847	<	*     boolean hasLock = false;
1848	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1849	<	*     public boolean block() {
1850	<	*        if (!hasLock)
1851	<	*           lock.lock();
1852	<	*        return true;
1853	<	*     }
1854	<	*     public boolean isReleasable() {
1855	<	*        return hasLock || (hasLock = lock.tryLock());
1856	<	*     }
1844	>	*  <pre> {@code
1845	>	* class ManagedLocker implements ManagedBlocker {
1846	>	*   final ReentrantLock lock;
1847	>	*   boolean hasLock = false;
1848	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1849	>	*   public boolean block() {
1850	>	*     if (!hasLock)
1851	>	*       lock.lock();
1852	>	*     return true;
1853	>	*   }
1854	>	*   public boolean isReleasable() {
1855	>	*     return hasLock || (hasLock = lock.tryLock());
1856	>	*   }
1857	>	* }}</pre>
1858	>	*
1859	>	* <p>Here is a class that possibly blocks waiting for an
1860	>	* item on a given queue:
1861	>	*  <pre> {@code
1862	>	* class QueueTaker<E> implements ManagedBlocker {
1863	>	*   final BlockingQueue<E> queue;
1864	>	*   volatile E item = null;
1865	>	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
1866	>	*   public boolean block() throws InterruptedException {
1867	>	*     if (item == null)
1868	>	*       item = queue.take();
1869	>	*     return true;
1870	>	*   }
1871	>	*   public boolean isReleasable() {
1872	>	*     return item != null || (item = queue.poll()) != null;
1873	>	*   }
1874	>	*   public E getItem() { // call after pool.managedBlock completes
1875	>	*     return item;
1876		*   }
1877	<	* </pre>
1877	>	* }}</pre>
1878		*/
1879		public static interface ManagedBlocker {
1880		/**
1881		* Possibly blocks the current thread, for example waiting for
1882		* a lock or condition.
1883	<	* @return true if no additional blocking is necessary (i.e.,
1884	<	* if isReleasable would return true).
1883	>	*
1884	>	* @return {@code true} if no additional blocking is necessary
1885	>	* (i.e., if isReleasable would return true)
1886		* @throws InterruptedException if interrupted while waiting
1887	<	* (the method is not required to do so, but is allowe to).
1887	>	* (the method is not required to do so, but is allowed to)
1888		*/
1889		boolean block() throws InterruptedException;
1890
1891		/**
1892	<	* Returns true if blocking is unnecessary.
1892	>	* Returns {@code true} if blocking is unnecessary.
1893		*/
1894		boolean isReleasable();
1895		}
1896
1897		/**
1898		* Blocks in accord with the given blocker.  If the current thread
1899	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1900	<	* spare thread to be activated if necessary to ensure parallelism
1901	<	* while the current thread is blocked.  If
1902	<	* <code>maintainParallelism</code> is true and the pool supports
1903	<	* it ({@link #getMaintainsParallelism}), this method attempts to
1904	<	* maintain the pool's nominal parallelism. Otherwise if activates
1905	<	* a thread only if necessary to avoid complete starvation. This
1906	<	* option may be preferable when blockages use timeouts, or are
1907	<	* almost always brief.
1908	<	*
1909	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1910	<	* equivalent to
1911	<	* <pre>
1912	<	*   while (!blocker.isReleasable())
1748	<	*      if (blocker.block())
1749	<	*         return;
1750	<	* </pre>
1751	<	* If the caller is a ForkJoinTask, then the pool may first
1752	<	* be expanded to ensure parallelism, and later adjusted.
1899	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1900	>	* arranges for a spare thread to be activated if necessary to
1901	>	* ensure sufficient parallelism while the current thread is blocked.
1902	>	*
1903	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1904	>	* behaviorally equivalent to
1905	>	*  <pre> {@code
1906	>	* while (!blocker.isReleasable())
1907	>	*   if (blocker.block())
1908	>	*     return;
1909	>	* }</pre>
1910	>	*
1911	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1912	>	* first be expanded to ensure parallelism, and later adjusted.
1913		*
1914		* @param blocker the blocker
1915	<	* @param maintainParallelism if true and supported by this pool,
1756	<	* attempt to maintain the pool's nominal parallelism; otherwise
1757	<	* activate a thread only if necessary to avoid complete
1758	<	* starvation.
1759	<	* @throws InterruptedException if blocker.block did so.
1915	>	* @throws InterruptedException if blocker.block did so
1916		*/
1917	<	public static void managedBlock(ManagedBlocker blocker,
1762	<	boolean maintainParallelism)
1917	>	public static void managedBlock(ManagedBlocker blocker)
1918		throws InterruptedException {
1919		Thread t = Thread.currentThread();
1920	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1921	<	((ForkJoinWorkerThread)t).pool : null);
1922	<	if (!blocker.isReleasable()) {
1923	<	try {
1924	<	if (pool == null ||
1925	<	!pool.preBlock(blocker, maintainParallelism))
1771	<	awaitBlocker(blocker);
1772	<	} finally {
1773	<	if (pool != null)
1774	<	pool.updateRunningCount(1);
1775	<	}
1920	>	if (t instanceof ForkJoinWorkerThread) {
1921	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
1922	>	w.pool.awaitBlocker(blocker);
1923	>	}
1924	>	else {
1925	>	do {} while (!blocker.isReleasable() && !blocker.block());
1926		}
1927		}
1928
1929	<	private static void awaitBlocker(ManagedBlocker blocker)
1930	<	throws InterruptedException {
1931	<	do;while (!blocker.isReleasable() && !blocker.block());
1782	<	}
1783	<
1784	<	// AbstractExecutorService overrides
1929	>	// AbstractExecutorService overrides.  These rely on undocumented
1930	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1931	>	// implement RunnableFuture.
1932
1933		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1934	<	return new AdaptedRunnable(runnable, value);
1934	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1935		}
1936
1937		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1938	<	return new AdaptedCallable(callable);
1938	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1939		}
1940
1941	+	// Unsafe mechanics
1942	+
1943	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1944	+	private static final long workerCountsOffset =
1945	+	objectFieldOffset("workerCounts", ForkJoinPool.class);
1946	+	private static final long runStateOffset =
1947	+	objectFieldOffset("runState", ForkJoinPool.class);
1948	+	private static final long eventCountOffset =
1949	+	objectFieldOffset("eventCount", ForkJoinPool.class);
1950	+	private static final long eventWaitersOffset =
1951	+	objectFieldOffset("eventWaiters", ForkJoinPool.class);
1952	+	private static final long stealCountOffset =
1953	+	objectFieldOffset("stealCount", ForkJoinPool.class);
1954	+	private static final long spareWaitersOffset =
1955	+	objectFieldOffset("spareWaiters", ForkJoinPool.class);
1956	+
1957	+	private static long objectFieldOffset(String field, Class<?> klazz) {
1958	+	try {
1959	+	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1960	+	} catch (NoSuchFieldException e) {
1961	+	// Convert Exception to corresponding Error
1962	+	NoSuchFieldError error = new NoSuchFieldError(field);
1963	+	error.initCause(e);
1964	+	throw error;
1965	+	}
1966	+	}
1967
1968	<	// Temporary Unsafe mechanics for preliminary release
1969	<	private static Unsafe getUnsafe() throws Throwable {
1968	>	/**
1969	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1970	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1971	>	* into a jdk.
1972	>	*
1973	>	* @return a sun.misc.Unsafe
1974	>	*/
1975	>	private static sun.misc.Unsafe getUnsafe() {
1976		try {
1977	<	return Unsafe.getUnsafe();
1977	>	return sun.misc.Unsafe.getUnsafe();
1978		} catch (SecurityException se) {
1979		try {
1980		return java.security.AccessController.doPrivileged
1981	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1982	<	public Unsafe run() throws Exception {
1983	<	return getUnsafePrivileged();
1981	>	(new java.security
1982	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1983	>	public sun.misc.Unsafe run() throws Exception {
1984	>	java.lang.reflect.Field f = sun.misc
1985	>	.Unsafe.class.getDeclaredField("theUnsafe");
1986	>	f.setAccessible(true);
1987	>	return (sun.misc.Unsafe) f.get(null);
1988		}});
1989		} catch (java.security.PrivilegedActionException e) {
1990	<	throw e.getCause();
1990	>	throw new RuntimeException("Could not initialize intrinsics",
1991	>	e.getCause());
1992		}
1993		}
1994		}
1811	–
1812	–	private static Unsafe getUnsafePrivileged()
1813	–	throws NoSuchFieldException, IllegalAccessException {
1814	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1815	–	f.setAccessible(true);
1816	–	return (Unsafe) f.get(null);
1817	–	}
1818	–
1819	–	private static long fieldOffset(String fieldName)
1820	–	throws NoSuchFieldException {
1821	–	return _unsafe.objectFieldOffset
1822	–	(ForkJoinPool.class.getDeclaredField(fieldName));
1823	–	}
1824	–
1825	–	static final Unsafe _unsafe;
1826	–	static final long eventCountOffset;
1827	–	static final long workerCountsOffset;
1828	–	static final long runControlOffset;
1829	–	static final long syncStackOffset;
1830	–	static final long spareStackOffset;
1831	–
1832	–	static {
1833	–	try {
1834	–	_unsafe = getUnsafe();
1835	–	eventCountOffset = fieldOffset("eventCount");
1836	–	workerCountsOffset = fieldOffset("workerCounts");
1837	–	runControlOffset = fieldOffset("runControl");
1838	–	syncStackOffset = fieldOffset("syncStack");
1839	–	spareStackOffset = fieldOffset("spareStack");
1840	–	} catch (Throwable e) {
1841	–	throw new RuntimeException("Could not initialize intrinsics", e);
1842	–	}
1843	–	}
1844	–
1845	–	private boolean casEventCount(long cmp, long val) {
1846	–	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1847	–	}
1848	–	private boolean casWorkerCounts(int cmp, int val) {
1849	–	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1850	–	}
1851	–	private boolean casRunControl(int cmp, int val) {
1852	–	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1853	–	}
1854	–	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1855	–	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1856	–	}
1857	–	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1858	–	return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val);
1859	–	}
1995		}

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