ViewVC Help

View File | Revision Log | Show Annotations | Download File | Root Listing

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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.16 by jsr166, Thu Jul 23 19:44:46 2009 UTC vs.
Revision 1.81 by jsr166, Mon Sep 20 20:42:36 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	<	* {@code setAsyncMode}, 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} interface enables extension of
48	<	* the kinds of synchronization accommodated.  The target parallelism
49	<	* level may also be changed dynamically ({@code setParallelism})
50	<	* and thread construction can be limited using methods
45	<	* {@code setMaximumPoolSize} and/or
46	<	* {@code setMaintainsParallelism}.
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}) 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} 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
#	Line 63 | Line 123 | import java.lang.reflect.*;
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 {
100	<	return new ForkJoinWorkerThread(pool);
101	<	} catch (OutOfMemoryError oom)  {
102	<	return null;
103	<	}
390	>	return new ForkJoinWorkerThread(pool);
391		}
392		}
393
#	Line 136 | 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
159	<	* abruptly 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 166 | Line 483 | public class ForkJoinPool extends Abstra
483		private final ForkJoinWorkerThreadFactory factory;
484
485		/**
169	–	* Head of stack of threads that were created to maintain
170	–	* parallelism when other threads blocked, but have since
171	–	* suspended when the parallelism level rose.
172	–	*/
173	–	private volatile WaitQueueNode spareStack;
174	–
175	–	/**
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
188	<	*/
189	<	private volatile WaitQueueNode syncStack;
499	>	private static final int  EVENT_COUNT_SHIFT = 32;
500	>	private static final long WAITER_ID_MASK    = (1L << 16) - 1L;
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
203	<	*/
204	<	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 assume that running active count
553	<	* is in low 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	<	* Adds delta (which may be negative) to running count.  This must
564	<	* be called before (with negative arg) and after (with positive)
234	<	* any managed synchronization (i.e., mainly, joins).
235	<	* @param delta the number to add
563	>	* The target parallelism level.
564	>	* Accessed directly by ForkJoinWorkerThreads.
565		*/
566	<	final void updateRunningCount(int delta) {
238	<	int s;
239	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
240	<	}
566	>	final int parallelism;
567
568		/**
569	<	* Adds delta (which may be negative) to both total and running
570	<	* count.  This must be called upon creation and termination of
245	<	* worker threads.
246	<	* @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) {
249	<	int d = delta + (delta << 16); // add to both lo and hi parts
250	<	int s;
251	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
252	<	}
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
257	<	* tasks. This value is atomically incremented before a worker
258	<	* gets a task to run, and decremented when worker has no tasks
259	<	* and cannot find any. These two fields are bundled together to
260	<	* support correct termination triggering.  Note: activeCount
261	<	* CAS'es cheat by assuming active count is in low word, so need
262	<	* 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;
270	<	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; }
274	<	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
278	<	* workers before/during executing tasks.
279	<	* @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	<	* Tries decrementing active count; fails on contention.
288	<	* Possibly triggers termination on success.
289	<	* Called by workers when they can't find tasks.
290	<	* @return true on success
599	>	* Tries to decrement running count unless already zero
600		*/
601	<	final boolean tryDecrementActiveCount() {
602	<	int c = runControl;
603	<	int nextc = c - 1;
295	<	if (!casRunControl(c, nextc))
601	>	final boolean tryDecrementRunningCount() {
602	>	int wc = workerCounts;
603	>	if ((wc & RUNNING_COUNT_MASK) == 0)
604		return false;
605	<	if (canTerminateOnShutdown(nextc))
606	<	terminateOnShutdown();
607	<	return true;
605	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
606	>	wc, wc - ONE_RUNNING);
607	>	}
608	>
609	>	/**
610	>	* Forces decrement of encoded workerCounts, awaiting nonzero if
611	>	* (rarely) necessary when other count updates lag.
612	>	*
613	>	* @param dr -- either zero or ONE_RUNNING
614	>	* @param dt -- either zero or ONE_TOTAL
615	>	*/
616	>	private void decrementWorkerCounts(int dr, int dt) {
617	>	for (;;) {
618	>	int wc = workerCounts;
619	>	if ((wc & RUNNING_COUNT_MASK)  - dr < 0 ||
620	>	(wc >>> TOTAL_COUNT_SHIFT) - dt < 0) {
621	>	if ((runState & TERMINATED) != 0)
622	>	return; // lagging termination on a backout
623	>	Thread.yield();
624	>	}
625	>	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
626	>	wc, wc - (dr + dt)))
627	>	return;
628	>	}
629		}
630
631		/**
632	<	* Returns true if argument represents zero active count and
633	<	* nonzero runstate, which is the triggering condition for
305	<	* terminating on shutdown.
632	>	* Tries decrementing active count; fails on contention.
633	>	* Called when workers cannot find tasks to run.
634		*/
635	<	private static boolean canTerminateOnShutdown(int c) {
636	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
635	>	final boolean tryDecrementActiveCount() {
636	>	int c;
637	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
638	>	c = runState, c - 1);
639		}
640
641		/**
642	<	* Transition run state to at least the given state. Return true
643	<	* if not already at least given state.
642	>	* Advances to at least the given level. Returns true if not
643	>	* already in at least the given level.
644		*/
645	<	private boolean transitionRunStateTo(int state) {
645	>	private boolean advanceRunLevel(int level) {
646		for (;;) {
647	<	int c = runControl;
648	<	if (runStateOf(c) >= state)
647	>	int s = runState;
648	>	if ((s & level) != 0)
649		return false;
650	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
650	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level))
651		return true;
652		}
653		}
654
655	+	// workers array maintenance
656	+
657		/**
658	<	* Controls whether to add spares to maintain parallelism
658	>	* Records and returns a workers array index for new worker.
659		*/
660	<	private volatile boolean maintainsParallelism;
660	>	private int recordWorker(ForkJoinWorkerThread w) {
661	>	// Try using slot totalCount-1. If not available, scan and/or resize
662	>	int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1;
663	>	final ReentrantLock lock = this.workerLock;
664	>	lock.lock();
665	>	try {
666	>	ForkJoinWorkerThread[] ws = workers;
667	>	int n = ws.length;
668	>	if (k < 0 || k >= n || ws[k] != null) {
669	>	for (k = 0; k < n && ws[k] != null; ++k)
670	>	;
671	>	if (k == n)
672	>	ws = Arrays.copyOf(ws, n << 1);
673	>	}
674	>	ws[k] = w;
675	>	workers = ws; // volatile array write ensures slot visibility
676	>	} finally {
677	>	lock.unlock();
678	>	}
679	>	return k;
680	>	}
681
682	<	// Constructors
682	>	/**
683	>	* Nulls out record of worker in workers array.
684	>	*/
685	>	private void forgetWorker(ForkJoinWorkerThread w) {
686	>	int idx = w.poolIndex;
687	>	// Locking helps method recordWorker avoid unnecessary expansion
688	>	final ReentrantLock lock = this.workerLock;
689	>	lock.lock();
690	>	try {
691	>	ForkJoinWorkerThread[] ws = workers;
692	>	if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify
693	>	ws[idx] = null;
694	>	} finally {
695	>	lock.unlock();
696	>	}
697	>	}
698
699		/**
700	<	* Creates a ForkJoinPool with a pool size equal to the number of
701	<	* processors available on the system and using the default
702	<	* ForkJoinWorkerThreadFactory,
703	<	* @throws SecurityException if a security manager exists and
704	<	*         the caller is not permitted to modify threads
338	<	*         because it does not hold {@link
339	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
700	>	* Final callback from terminating worker.  Removes record of
701	>	* worker from array, and adjusts counts. If pool is shutting
702	>	* down, tries to complete termination.
703	>	*
704	>	* @param w the worker
705		*/
706	<	public ForkJoinPool() {
707	<	this(Runtime.getRuntime().availableProcessors(),
708	<	defaultForkJoinWorkerThreadFactory);
706	>	final void workerTerminated(ForkJoinWorkerThread w) {
707	>	forgetWorker(w);
708	>	decrementWorkerCounts(w.isTrimmed()? 0 : ONE_RUNNING, ONE_TOTAL);
709	>	while (w.stealCount != 0) // collect final count
710	>	tryAccumulateStealCount(w);
711	>	tryTerminate(false);
712		}
713
714	+	// Waiting for and signalling events
715	+
716		/**
717	<	* Creates a ForkJoinPool with the indicated parallelism level
718	<	* threads, and using the default ForkJoinWorkerThreadFactory,
719	<	* @param parallelism the number of worker threads
720	<	* @throws IllegalArgumentException if parallelism less than or
351	<	* equal to zero
352	<	* @throws SecurityException if a security manager exists and
353	<	*         the caller is not permitted to modify threads
354	<	*         because it does not hold {@link
355	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
717	>	* Releases workers blocked on a count not equal to current count.
718	>	* Normally called after precheck that eventWaiters isn't zero to
719	>	* avoid wasted array checks. Gives up upon a change in count or
720	>	* upon releasing two workers, letting others take over.
721		*/
722	<	public ForkJoinPool(int parallelism) {
723	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
722	>	private void releaseEventWaiters() {
723	>	ForkJoinWorkerThread[] ws = workers;
724	>	int n = ws.length;
725	>	long h = eventWaiters;
726	>	int ec = eventCount;
727	>	boolean releasedOne = false;
728	>	ForkJoinWorkerThread w; int id;
729	>	while ((id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 &&
730	>	(int)(h >>> EVENT_COUNT_SHIFT) != ec &&
731	>	id < n && (w = ws[id]) != null) {
732	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
733	>	h,  w.nextWaiter)) {
734	>	LockSupport.unpark(w);
735	>	if (releasedOne) // exit on second release
736	>	break;
737	>	releasedOne = true;
738	>	}
739	>	if (eventCount != ec)
740	>	break;
741	>	h = eventWaiters;
742	>	}
743		}
744
745		/**
746	<	* Creates a ForkJoinPool with parallelism equal to the number of
747	<	* processors available on the system and using the given
364	<	* ForkJoinWorkerThreadFactory,
365	<	* @param factory the factory for creating new threads
366	<	* @throws NullPointerException if factory is null
367	<	* @throws SecurityException if a security manager exists and
368	<	*         the caller is not permitted to modify threads
369	<	*         because it does not hold {@link
370	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
746	>	* Tries to advance eventCount and releases waiters. Called only
747	>	* from workers.
748		*/
749	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
750	<	this(Runtime.getRuntime().availableProcessors(), factory);
749	>	final void signalWork() {
750	>	int c; // try to increment event count -- CAS failure OK
751	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
752	>	if (eventWaiters != 0L)
753	>	releaseEventWaiters();
754		}
755
756		/**
757	<	* Creates a ForkJoinPool with the given parallelism and factory.
757	>	* Adds the given worker to event queue and blocks until
758	>	* terminating or event count advances from the given value
759		*
760	<	* @param parallelism the targeted number of worker threads
761	<	* @param factory the factory for creating new threads
381	<	* @throws IllegalArgumentException if parallelism less than or
382	<	* equal to zero, or greater than implementation limit
383	<	* @throws NullPointerException if factory is null
384	<	* @throws SecurityException if a security manager exists and
385	<	*         the caller is not permitted to modify threads
386	<	*         because it does not hold {@link
387	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
760	>	* @param w the calling worker thread
761	>	* @param ec the count
762		*/
763	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
764	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
765	<	throw new IllegalArgumentException();
766	<	if (factory == null)
767	<	throw new NullPointerException();
768	<	checkPermission();
769	<	this.factory = factory;
770	<	this.parallelism = parallelism;
771	<	this.maxPoolSize = MAX_THREADS;
772	<	this.maintainsParallelism = true;
773	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
774	<	this.workerLock = new ReentrantLock();
775	<	this.termination = workerLock.newCondition();
402	<	this.stealCount = new AtomicLong();
403	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
404	<	// worker array and workers are lazily constructed
763	>	private void eventSync(ForkJoinWorkerThread w, int ec) {
764	>	long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1));
765	>	long h;
766	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
767	>	(((int)((h = eventWaiters) & WAITER_ID_MASK)) == 0 ||
768	>	(int)(h >>> EVENT_COUNT_SHIFT) == ec) &&
769	>	eventCount == ec) {
770	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
771	>	w.nextWaiter = h, nh)) {
772	>	awaitEvent(w, ec);
773	>	break;
774	>	}
775	>	}
776		}
777
778		/**
779	<	* Create new worker using factory.
780	<	* @param index the index to assign worker
781	<	* @return new worker, or null of factory failed
779	>	* Blocks the given worker (that has already been entered as an
780	>	* event waiter) until terminating or event count advances from
781	>	* the given value. The oldest (first) waiter uses a timed wait to
782	>	* occasionally one-by-one shrink the number of workers (to a
783	>	* minimum of one) if the pool has not been used for extended
784	>	* periods.
785	>	*
786	>	* @param w the calling worker thread
787	>	* @param ec the count
788		*/
789	<	private ForkJoinWorkerThread createWorker(int index) {
790	<	Thread.UncaughtExceptionHandler h = ueh;
791	<	ForkJoinWorkerThread w = factory.newThread(this);
792	<	if (w != null) {
793	<	w.poolIndex = index;
794	<	w.setDaemon(true);
795	<	w.setAsyncMode(locallyFifo);
796	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
797	<	if (h != null)
798	<	w.setUncaughtExceptionHandler(h);
789	>	private void awaitEvent(ForkJoinWorkerThread w, int ec) {
790	>	while (eventCount == ec) {
791	>	if (tryAccumulateStealCount(w)) { // transfer while idle
792	>	boolean untimed = (w.nextWaiter != 0L ||
793	>	(workerCounts & RUNNING_COUNT_MASK) <= 1);
794	>	long startTime = untimed? 0 : System.nanoTime();
795	>	Thread.interrupted();         // clear/ignore interrupt
796	>	if (eventCount != ec || w.isTerminating())
797	>	break;                    // recheck after clear
798	>	if (untimed)
799	>	LockSupport.park(w);
800	>	else {
801	>	LockSupport.parkNanos(w, SHRINK_RATE_NANOS);
802	>	if (eventCount != ec || w.isTerminating())
803	>	break;
804	>	if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS)
805	>	tryShutdownUnusedWorker(ec);
806	>	}
807	>	}
808		}
423	–	return w;
809		}
810
811	+	// Maintaining parallelism
812	+
813		/**
814	<	* Returns a good size for worker array given pool size.
428	<	* Currently requires size to be a power of two.
814	>	* Pushes worker onto the spare stack.
815		*/
816	<	private static int arraySizeFor(int ps) {
817	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
816	>	final void pushSpare(ForkJoinWorkerThread w) {
817	>	int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1);
818	>	do {} while (!UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
819	>	w.nextSpare = spareWaiters,ns));
820		}
821
822		/**
823	<	* Creates or resizes array if necessary to hold newLength.
824	<	* Call only under exclusion.
437	<	*
438	<	* @return the array
823	>	* Tries (once) to resume a spare if the number of running
824	>	* threads is less than target.
825		*/
826	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
826	>	private void tryResumeSpare() {
827	>	int sw, id;
828		ForkJoinWorkerThread[] ws = workers;
829	<	if (ws == null)
830	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
831	<	else if (newLength > ws.length)
832	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
833	<	else
834	<	return ws;
829	>	int n = ws.length;
830	>	ForkJoinWorkerThread w;
831	>	if ((sw = spareWaiters) != 0 &&
832	>	(id = (sw & SPARE_ID_MASK) - 1) >= 0 &&
833	>	id < n && (w = ws[id]) != null &&
834	>	(workerCounts & RUNNING_COUNT_MASK) < parallelism &&
835	>	spareWaiters == sw &&
836	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
837	>	sw, w.nextSpare)) {
838	>	int c; // increment running count before resume
839	>	do {} while (!UNSAFE.compareAndSwapInt
840	>	(this, workerCountsOffset,
841	>	c = workerCounts, c + ONE_RUNNING));
842	>	if (w.tryUnsuspend())
843	>	LockSupport.unpark(w);
844	>	else   // back out if w was shutdown
845	>	decrementWorkerCounts(ONE_RUNNING, 0);
846	>	}
847		}
848
849		/**
850	<	* Try to shrink workers into smaller array after one or more terminate
851	<	*/
852	<	private void tryShrinkWorkerArray() {
853	<	ForkJoinWorkerThread[] ws = workers;
854	<	if (ws != null) {
855	<	int len = ws.length;
856	<	int last = len - 1;
857	<	while (last >= 0 && ws[last] == null)
858	<	--last;
859	<	int newLength = arraySizeFor(last+1);
860	<	if (newLength < len)
861	<	workers = Arrays.copyOf(ws, newLength);
850	>	* Tries to increase the number of running workers if below target
851	>	* parallelism: If a spare exists tries to resume it via
852	>	* tryResumeSpare.  Otherwise, if not enough total workers or all
853	>	* existing workers are busy, adds a new worker. In all cases also
854	>	* helps wake up releasable workers waiting for work.
855	>	*/
856	>	private void helpMaintainParallelism() {
857	>	int pc = parallelism;
858	>	int wc, rs, tc;
859	>	while (((wc = workerCounts) & RUNNING_COUNT_MASK) < pc &&
860	>	(rs = runState) < TERMINATING) {
861	>	if (spareWaiters != 0)
862	>	tryResumeSpare();
863	>	else if ((tc = wc >>> TOTAL_COUNT_SHIFT) >= MAX_WORKERS ||
864	>	(tc >= pc && (rs & ACTIVE_COUNT_MASK) != tc))
865	>	break;   // enough total
866	>	else if (runState == rs && workerCounts == wc &&
867	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
868	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
869	>	ForkJoinWorkerThread w = null;
870	>	Throwable fail = null;
871	>	try {
872	>	w = factory.newThread(this);
873	>	} catch (Throwable ex) {
874	>	fail = ex;
875	>	}
876	>	if (w == null) { // null or exceptional factory return
877	>	decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL);
878	>	tryTerminate(false); // handle failure during shutdown
879	>	// If originating from an external caller,
880	>	// propagate exception, else ignore
881	>	if (fail != null && runState < TERMINATING &&
882	>	!(Thread.currentThread() instanceof
883	>	ForkJoinWorkerThread))
884	>	UNSAFE.throwException(fail);
885	>	break;
886	>	}
887	>	w.start(recordWorker(w), ueh);
888	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) >= pc) {
889	>	int c; // advance event count
890	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
891	>	c = eventCount, c+1);
892	>	break; // add at most one unless total below target
893	>	}
894	>	}
895		}
896	+	if (eventWaiters != 0L)
897	+	releaseEventWaiters();
898		}
899
900		/**
901	<	* Initialize workers if necessary
901	>	* Callback from the oldest waiter in awaitEvent waking up after a
902	>	* period of non-use. If all workers are idle, tries (once) to
903	>	* shutdown an event waiter or a spare, if one exists. Note that
904	>	* we don't need CAS or locks here because the method is called
905	>	* only from one thread occasionally waking (and even misfires are
906	>	* OK). Note that until the shutdown worker fully terminates,
907	>	* workerCounts will overestimate total count, which is tolerable.
908	>	*
909	>	* @param ec the event count waited on by caller (to abort
910	>	* attempt if count has since changed).
911		*/
912	<	final void ensureWorkerInitialization() {
913	<	ForkJoinWorkerThread[] ws = workers;
914	<	if (ws == null) {
915	<	final ReentrantLock lock = this.workerLock;
916	<	lock.lock();
917	<	try {
918	<	ws = workers;
919	<	if (ws == null) {
920	<	int ps = parallelism;
921	<	ws = ensureWorkerArrayCapacity(ps);
922	<	for (int i = 0; i < ps; ++i) {
923	<	ForkJoinWorkerThread w = createWorker(i);
924	<	if (w != null) {
925	<	ws[i] = w;
926	<	w.start();
927	<	updateWorkerCount(1);
928	<	}
929	<	}
912	>	private void tryShutdownUnusedWorker(int ec) {
913	>	if (runState == 0 && eventCount == ec) { // only trigger if all idle
914	>	ForkJoinWorkerThread[] ws = workers;
915	>	int n = ws.length;
916	>	ForkJoinWorkerThread w = null;
917	>	boolean shutdown = false;
918	>	int sw;
919	>	long h;
920	>	if ((sw = spareWaiters) != 0) { // prefer killing spares
921	>	int id = (sw & SPARE_ID_MASK) - 1;
922	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
923	>	UNSAFE.compareAndSwapInt(this, spareWaitersOffset,
924	>	sw, w.nextSpare))
925	>	shutdown = true;
926	>	}
927	>	else if ((h = eventWaiters) != 0L) {
928	>	long nh;
929	>	int id = ((int)(h & WAITER_ID_MASK)) - 1;
930	>	if (id >= 0 && id < n && (w = ws[id]) != null &&
931	>	(nh = w.nextWaiter) != 0L && // keep at least one worker
932	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh))
933	>	shutdown = true;
934	>	}
935	>	if (w != null && shutdown) {
936	>	w.shutdown();
937	>	LockSupport.unpark(w);
938	>	}
939	>	}
940	>	releaseEventWaiters(); // in case of interference
941	>	}
942	>
943	>	/**
944	>	* Callback from workers invoked upon each top-level action (i.e.,
945	>	* stealing a task or taking a submission and running it).
946	>	* Performs one or more of the following:
947	>	*
948	>	* 1. If the worker is active and either did not run a task
949	>	*    or there are too many workers, try to set its active status
950	>	*    to inactive and update activeCount. On contention, we may
951	>	*    try again in this or a subsequent call.
952	>	*
953	>	* 2. If not enough total workers, help create some.
954	>	*
955	>	* 3. If there are too many running workers, suspend this worker
956	>	*    (first forcing inactive if necessary).  If it is not needed,
957	>	*    it may be shutdown while suspended (via
958	>	*    tryShutdownUnusedWorker).  Otherwise, upon resume it
959	>	*    rechecks running thread count and need for event sync.
960	>	*
961	>	* 4. If worker did not run a task, await the next task event via
962	>	*    eventSync if necessary (first forcing inactivation), upon
963	>	*    which the worker may be shutdown via
964	>	*    tryShutdownUnusedWorker.  Otherwise, help release any
965	>	*    existing event waiters that are now releasable,
966	>	*
967	>	* @param w the worker
968	>	* @param ran true if worker ran a task since last call to this method
969	>	*/
970	>	final void preStep(ForkJoinWorkerThread w, boolean ran) {
971	>	int wec = w.lastEventCount;
972	>	boolean active = w.active;
973	>	boolean inactivate = false;
974	>	int pc = parallelism;
975	>	while (w.runState == 0) {
976	>	int rs = runState;
977	>	if (rs >= TERMINATING) { // propagate shutdown
978	>	w.shutdown();
979	>	break;
980	>	}
981	>	if ((inactivate || (active && (rs & ACTIVE_COUNT_MASK) >= pc)) &&
982	>	UNSAFE.compareAndSwapInt(this, runStateOffset, rs, rs - 1))
983	>	inactivate = active = w.active = false;
984	>	int wc = workerCounts;
985	>	if ((wc & RUNNING_COUNT_MASK) > pc) {
986	>	if (!(inactivate |= active) && // must inactivate to suspend
987	>	workerCounts == wc &&      // try to suspend as spare
988	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
989	>	wc, wc - ONE_RUNNING))
990	>	w.suspendAsSpare();
991	>	}
992	>	else if ((wc >>> TOTAL_COUNT_SHIFT) < pc)
993	>	helpMaintainParallelism();     // not enough workers
994	>	else if (!ran) {
995	>	long h = eventWaiters;
996	>	int ec = eventCount;
997	>	if (h != 0L && (int)(h >>> EVENT_COUNT_SHIFT) != ec)
998	>	releaseEventWaiters();     // release others before waiting
999	>	else if (ec != wec) {
1000	>	w.lastEventCount = ec;     // no need to wait
1001	>	break;
1002		}
1003	<	} finally {
1004	<	lock.unlock();
1003	>	else if (!(inactivate |= active))
1004	>	eventSync(w, wec);         // must inactivate before sync
1005		}
1006	+	else
1007	+	break;
1008		}
1009		}
1010
1011		/**
1012	<	* Worker creation and startup for threads added via setParallelism.
1012	>	* Helps and/or blocks awaiting join of the given task.
1013	>	* See above for explanation.
1014	>	*
1015	>	* @param joinMe the task to join
1016	>	* @param worker the current worker thread
1017		*/
1018	<	private void createAndStartAddedWorkers() {
1019	<	resumeAllSpares();  // Allow spares to convert to nonspare
1020	<	int ps = parallelism;
1021	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
1022	<	int len = ws.length;
1023	<	// Sweep through slots, to keep lowest indices most populated
1024	<	int k = 0;
1025	<	while (k < len) {
1026	<	if (ws[k] != null) {
1027	<	++k;
1028	<	continue;
1018	>	final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker) {
1019	>	int retries = 2 + (parallelism >> 2); // #helpJoins before blocking
1020	>	while (joinMe.status >= 0) {
1021	>	int wc;
1022	>	worker.helpJoinTask(joinMe);
1023	>	if (joinMe.status < 0)
1024	>	break;
1025	>	else if (retries > 0)
1026	>	--retries;
1027	>	else if (((wc = workerCounts) & RUNNING_COUNT_MASK) != 0 &&
1028	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1029	>	wc, wc - ONE_RUNNING)) {
1030	>	int stat, c; long h;
1031	>	while ((stat = joinMe.status) >= 0 &&
1032	>	(h = eventWaiters) != 0L && // help release others
1033	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1034	>	releaseEventWaiters();
1035	>	if (stat >= 0 &&
1036	>	((workerCounts & RUNNING_COUNT_MASK) == 0 ||
1037	>	(stat =
1038	>	joinMe.internalAwaitDone(JOIN_TIMEOUT_MILLIS)) >= 0))
1039	>	helpMaintainParallelism(); // timeout or no running workers
1040	>	do {} while (!UNSAFE.compareAndSwapInt
1041	>	(this, workerCountsOffset,
1042	>	c = workerCounts, c + ONE_RUNNING));
1043	>	if (stat < 0)
1044	>	break;   // else restart
1045		}
1046	<	int s = workerCounts;
1047	<	int tc = totalCountOf(s);
1048	<	int rc = runningCountOf(s);
1049	<	if (rc >= ps || tc >= ps)
1046	>	}
1047	>	}
1048	>
1049	>	/**
1050	>	* Same idea as awaitJoin, but no helping, retries, or timeouts.
1051	>	*/
1052	>	final void awaitBlocker(ManagedBlocker blocker)
1053	>	throws InterruptedException {
1054	>	while (!blocker.isReleasable()) {
1055	>	int wc = workerCounts;
1056	>	if ((wc & RUNNING_COUNT_MASK) != 0 &&
1057	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1058	>	wc, wc - ONE_RUNNING)) {
1059	>	try {
1060	>	while (!blocker.isReleasable()) {
1061	>	long h = eventWaiters;
1062	>	if (h != 0L &&
1063	>	(int)(h >>> EVENT_COUNT_SHIFT) != eventCount)
1064	>	releaseEventWaiters();
1065	>	else if ((workerCounts & RUNNING_COUNT_MASK) == 0 &&
1066	>	runState < TERMINATING)
1067	>	helpMaintainParallelism();
1068	>	else if (blocker.block())
1069	>	break;
1070	>	}
1071	>	} finally {
1072	>	int c;
1073	>	do {} while (!UNSAFE.compareAndSwapInt
1074	>	(this, workerCountsOffset,
1075	>	c = workerCounts, c + ONE_RUNNING));
1076	>	}
1077		break;
1078	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
1079	<	ForkJoinWorkerThread w = createWorker(k);
1078	>	}
1079	>	}
1080	>	}
1081	>
1082	>	/**
1083	>	* Possibly initiates and/or completes termination.
1084	>	*
1085	>	* @param now if true, unconditionally terminate, else only
1086	>	* if shutdown and empty queue and no active workers
1087	>	* @return true if now terminating or terminated
1088	>	*/
1089	>	private boolean tryTerminate(boolean now) {
1090	>	if (now)
1091	>	advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN
1092	>	else if (runState < SHUTDOWN ||
1093	>	!submissionQueue.isEmpty() ||
1094	>	(runState & ACTIVE_COUNT_MASK) != 0)
1095	>	return false;
1096	>
1097	>	if (advanceRunLevel(TERMINATING))
1098	>	startTerminating();
1099	>
1100	>	// Finish now if all threads terminated; else in some subsequent call
1101	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1102	>	advanceRunLevel(TERMINATED);
1103	>	termination.arrive();
1104	>	}
1105	>	return true;
1106	>	}
1107	>
1108	>
1109	>	/**
1110	>	* Actions on transition to TERMINATING
1111	>	*
1112	>	* Runs up to four passes through workers: (0) shutting down each
1113	>	* (without waking up if parked) to quickly spread notifications
1114	>	* without unnecessary bouncing around event queues etc (1) wake
1115	>	* up and help cancel tasks (2) interrupt (3) mop up races with
1116	>	* interrupted workers
1117	>	*/
1118	>	private void startTerminating() {
1119	>	cancelSubmissions();
1120	>	for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) {
1121	>	int c; // advance event count
1122	>	UNSAFE.compareAndSwapInt(this, eventCountOffset,
1123	>	c = eventCount, c+1);
1124	>	eventWaiters = 0L; // clobber lists
1125	>	spareWaiters = 0;
1126	>	for (ForkJoinWorkerThread w : workers) {
1127		if (w != null) {
1128	<	ws[k++] = w;
1129	<	w.start();
1130	<	}
1131	<	else {
1132	<	updateWorkerCount(-1); // back out on failed creation
1133	<	break;
1128	>	w.shutdown();
1129	>	if (passes > 0 && !w.isTerminated()) {
1130	>	w.cancelTasks();
1131	>	LockSupport.unpark(w);
1132	>	if (passes > 1 && !w.isInterrupted()) {
1133	>	try {
1134	>	w.interrupt();
1135	>	} catch (SecurityException ignore) {
1136	>	}
1137	>	}
1138	>	}
1139		}
1140		}
1141		}
1142		}
1143
1144	+	/**
1145	+	* Clears out and cancels submissions, ignoring exceptions.
1146	+	*/
1147	+	private void cancelSubmissions() {
1148	+	ForkJoinTask<?> task;
1149	+	while ((task = submissionQueue.poll()) != null) {
1150	+	try {
1151	+	task.cancel(false);
1152	+	} catch (Throwable ignore) {
1153	+	}
1154	+	}
1155	+	}
1156	+
1157	+	// misc support for ForkJoinWorkerThread
1158	+
1159	+	/**
1160	+	* Returns pool number.
1161	+	*/
1162	+	final int getPoolNumber() {
1163	+	return poolNumber;
1164	+	}
1165	+
1166	+	/**
1167	+	* Tries to accumulate steal count from a worker, clearing
1168	+	* the worker's value if successful.
1169	+	*
1170	+	* @return true if worker steal count now zero
1171	+	*/
1172	+	final boolean tryAccumulateStealCount(ForkJoinWorkerThread w) {
1173	+	int sc = w.stealCount;
1174	+	long c = stealCount;
1175	+	// CAS even if zero, for fence effects
1176	+	if (UNSAFE.compareAndSwapLong(this, stealCountOffset, c, c + sc)) {
1177	+	if (sc != 0)
1178	+	w.stealCount = 0;
1179	+	return true;
1180	+	}
1181	+	return sc == 0;
1182	+	}
1183	+
1184	+	/**
1185	+	* Returns the approximate (non-atomic) number of idle threads per
1186	+	* active thread.
1187	+	*/
1188	+	final int idlePerActive() {
1189	+	int pc = parallelism; // use parallelism, not rc
1190	+	int ac = runState;    // no mask -- artificially boosts during shutdown
1191	+	// Use exact results for small values, saturate past 4
1192	+	return ((pc <= ac) ? 0 :
1193	+	(pc >>> 1 <= ac) ? 1 :
1194	+	(pc >>> 2 <= ac) ? 3 :
1195	+	pc >>> 3);
1196	+	}
1197	+
1198	+	// Public and protected methods
1199	+
1200	+	// Constructors
1201	+
1202	+	/**
1203	+	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1204	+	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1205	+	* #defaultForkJoinWorkerThreadFactory default thread factory},
1206	+	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1207	+	*
1208	+	* @throws SecurityException if a security manager exists and
1209	+	*         the caller is not permitted to modify threads
1210	+	*         because it does not hold {@link
1211	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1212	+	*/
1213	+	public ForkJoinPool() {
1214	+	this(Runtime.getRuntime().availableProcessors(),
1215	+	defaultForkJoinWorkerThreadFactory, null, false);
1216	+	}
1217	+
1218	+	/**
1219	+	* Creates a {@code ForkJoinPool} with the indicated parallelism
1220	+	* level, the {@linkplain
1221	+	* #defaultForkJoinWorkerThreadFactory default thread factory},
1222	+	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1223	+	*
1224	+	* @param parallelism the parallelism level
1225	+	* @throws IllegalArgumentException if parallelism less than or
1226	+	*         equal to zero, or greater than implementation limit
1227	+	* @throws SecurityException if a security manager exists and
1228	+	*         the caller is not permitted to modify threads
1229	+	*         because it does not hold {@link
1230	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1231	+	*/
1232	+	public ForkJoinPool(int parallelism) {
1233	+	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1234	+	}
1235	+
1236	+	/**
1237	+	* Creates a {@code ForkJoinPool} with the given parameters.
1238	+	*
1239	+	* @param parallelism the parallelism level. For default value,
1240	+	* use {@link java.lang.Runtime#availableProcessors}.
1241	+	* @param factory the factory for creating new threads. For default value,
1242	+	* use {@link #defaultForkJoinWorkerThreadFactory}.
1243	+	* @param handler the handler for internal worker threads that
1244	+	* terminate due to unrecoverable errors encountered while executing
1245	+	* tasks. For default value, use {@code null}.
1246	+	* @param asyncMode if true,
1247	+	* establishes local first-in-first-out scheduling mode for forked
1248	+	* tasks that are never joined. This mode may be more appropriate
1249	+	* than default locally stack-based mode in applications in which
1250	+	* worker threads only process event-style asynchronous tasks.
1251	+	* For default value, use {@code false}.
1252	+	* @throws IllegalArgumentException if parallelism less than or
1253	+	*         equal to zero, or greater than implementation limit
1254	+	* @throws NullPointerException if the factory is null
1255	+	* @throws SecurityException if a security manager exists and
1256	+	*         the caller is not permitted to modify threads
1257	+	*         because it does not hold {@link
1258	+	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1259	+	*/
1260	+	public ForkJoinPool(int parallelism,
1261	+	ForkJoinWorkerThreadFactory factory,
1262	+	Thread.UncaughtExceptionHandler handler,
1263	+	boolean asyncMode) {
1264	+	checkPermission();
1265	+	if (factory == null)
1266	+	throw new NullPointerException();
1267	+	if (parallelism <= 0 || parallelism > MAX_WORKERS)
1268	+	throw new IllegalArgumentException();
1269	+	this.parallelism = parallelism;
1270	+	this.factory = factory;
1271	+	this.ueh = handler;
1272	+	this.locallyFifo = asyncMode;
1273	+	int arraySize = initialArraySizeFor(parallelism);
1274	+	this.workers = new ForkJoinWorkerThread[arraySize];
1275	+	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
1276	+	this.workerLock = new ReentrantLock();
1277	+	this.termination = new Phaser(1);
1278	+	this.poolNumber = poolNumberGenerator.incrementAndGet();
1279	+	}
1280	+
1281	+	/**
1282	+	* Returns initial power of two size for workers array.
1283	+	* @param pc the initial parallelism level
1284	+	*/
1285	+	private static int initialArraySizeFor(int pc) {
1286	+	// If possible, initially allocate enough space for one spare
1287	+	int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS;
1288	+	// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16)
1289	+	size |= size >>> 1;
1290	+	size |= size >>> 2;
1291	+	size |= size >>> 4;
1292	+	size |= size >>> 8;
1293	+	return size + 1;
1294	+	}
1295	+
1296		// Execution methods
1297
1298		/**
1299		* Common code for execute, invoke and submit
1300		*/
1301		private <T> void doSubmit(ForkJoinTask<T> task) {
1302	<	if (isShutdown())
1302	>	if (task == null)
1303	>	throw new NullPointerException();
1304	>	if (runState >= SHUTDOWN)
1305		throw new RejectedExecutionException();
536	–	if (workers == null)
537	–	ensureWorkerInitialization();
1306		submissionQueue.offer(task);
1307	<	signalIdleWorkers();
1307	>	int c; // try to increment event count -- CAS failure OK
1308	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
1309	>	helpMaintainParallelism(); // create, start, or resume some workers
1310		}
1311
1312		/**
1313	<	* Performs the given task; returning its result upon completion
1313	>	* Performs the given task, returning its result upon completion.
1314	>	*
1315		* @param task the task
1316		* @return the task's result
1317	<	* @throws NullPointerException if task is null
1318	<	* @throws RejectedExecutionException if pool is shut down
1317	>	* @throws NullPointerException if the task is null
1318	>	* @throws RejectedExecutionException if the task cannot be
1319	>	*         scheduled for execution
1320		*/
1321		public <T> T invoke(ForkJoinTask<T> task) {
1322		doSubmit(task);
#	Line 553 | Line 1325 | public class ForkJoinPool extends Abstra
1325
1326		/**
1327		* Arranges for (asynchronous) execution of the given task.
1328	+	*
1329		* @param task the task
1330	<	* @throws NullPointerException if task is null
1331	<	* @throws RejectedExecutionException if pool is shut down
1330	>	* @throws NullPointerException if the task is null
1331	>	* @throws RejectedExecutionException if the task cannot be
1332	>	*         scheduled for execution
1333		*/
1334	<	public <T> void execute(ForkJoinTask<T> task) {
1334	>	public void execute(ForkJoinTask<?> task) {
1335		doSubmit(task);
1336		}
1337
1338		// AbstractExecutorService methods
1339
1340	+	/**
1341	+	* @throws NullPointerException if the task is null
1342	+	* @throws RejectedExecutionException if the task cannot be
1343	+	*         scheduled for execution
1344	+	*/
1345		public void execute(Runnable task) {
1346	<	doSubmit(new AdaptedRunnable<Void>(task, null));
1346	>	ForkJoinTask<?> job;
1347	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1348	>	job = (ForkJoinTask<?>) task;
1349	>	else
1350	>	job = ForkJoinTask.adapt(task, null);
1351	>	doSubmit(job);
1352	>	}
1353	>
1354	>	/**
1355	>	* Submits a ForkJoinTask for execution.
1356	>	*
1357	>	* @param task the task to submit
1358	>	* @return the task
1359	>	* @throws NullPointerException if the task is null
1360	>	* @throws RejectedExecutionException if the task cannot be
1361	>	*         scheduled for execution
1362	>	*/
1363	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1364	>	doSubmit(task);
1365	>	return task;
1366		}
1367
1368	+	/**
1369	+	* @throws NullPointerException if the task is null
1370	+	* @throws RejectedExecutionException if the task cannot be
1371	+	*         scheduled for execution
1372	+	*/
1373		public <T> ForkJoinTask<T> submit(Callable<T> task) {
1374	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
1374	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1375		doSubmit(job);
1376		return job;
1377		}
1378
1379	+	/**
1380	+	* @throws NullPointerException if the task is null
1381	+	* @throws RejectedExecutionException if the task cannot be
1382	+	*         scheduled for execution
1383	+	*/
1384		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1385	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
1385	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1386		doSubmit(job);
1387		return job;
1388		}
1389
1390	+	/**
1391	+	* @throws NullPointerException if the task is null
1392	+	* @throws RejectedExecutionException if the task cannot be
1393	+	*         scheduled for execution
1394	+	*/
1395		public ForkJoinTask<?> submit(Runnable task) {
1396	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
1396	>	ForkJoinTask<?> job;
1397	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1398	>	job = (ForkJoinTask<?>) task;
1399	>	else
1400	>	job = ForkJoinTask.adapt(task, null);
1401		doSubmit(job);
1402		return job;
1403		}
1404
1405		/**
1406	<	* Adaptor for Runnables. This implements RunnableFuture
1407	<	* to be compliant with AbstractExecutorService constraints
591	<	*/
592	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
593	<	implements RunnableFuture<T> {
594	<	final Runnable runnable;
595	<	final T resultOnCompletion;
596	<	T result;
597	<	AdaptedRunnable(Runnable runnable, T result) {
598	<	if (runnable == null) throw new NullPointerException();
599	<	this.runnable = runnable;
600	<	this.resultOnCompletion = result;
601	<	}
602	<	public T getRawResult() { return result; }
603	<	public void setRawResult(T v) { result = v; }
604	<	public boolean exec() {
605	<	runnable.run();
606	<	result = resultOnCompletion;
607	<	return true;
608	<	}
609	<	public void run() { invoke(); }
610	<	}
611	<
612	<	/**
613	<	* Adaptor for Callables
1406	>	* @throws NullPointerException       {@inheritDoc}
1407	>	* @throws RejectedExecutionException {@inheritDoc}
1408		*/
615	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
616	–	implements RunnableFuture<T> {
617	–	final Callable<T> callable;
618	–	T result;
619	–	AdaptedCallable(Callable<T> callable) {
620	–	if (callable == null) throw new NullPointerException();
621	–	this.callable = callable;
622	–	}
623	–	public T getRawResult() { return result; }
624	–	public void setRawResult(T v) { result = v; }
625	–	public boolean exec() {
626	–	try {
627	–	result = callable.call();
628	–	return true;
629	–	} catch (Error err) {
630	–	throw err;
631	–	} catch (RuntimeException rex) {
632	–	throw rex;
633	–	} catch (Exception ex) {
634	–	throw new RuntimeException(ex);
635	–	}
636	–	}
637	–	public void run() { invoke(); }
638	–	}
639	–
1409		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
1410	<	ArrayList<ForkJoinTask<T>> ts =
1410	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
1411		new ArrayList<ForkJoinTask<T>>(tasks.size());
1412	<	for (Callable<T> c : tasks)
1413	<	ts.add(new AdaptedCallable<T>(c));
1414	<	invoke(new InvokeAll<T>(ts));
1415	<	return (List<Future<T>>)(List)ts;
1412	>	for (Callable<T> task : tasks)
1413	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
1414	>	invoke(new InvokeAll<T>(forkJoinTasks));
1415	>
1416	>	@SuppressWarnings({"unchecked", "rawtypes"})
1417	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1418	>	return futures;
1419		}
1420
1421		static final class InvokeAll<T> extends RecursiveAction {
1422		final ArrayList<ForkJoinTask<T>> tasks;
1423		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
1424		public void compute() {
1425	<	try { invokeAll(tasks); } catch(Exception ignore) {}
1425	>	try { invokeAll(tasks); }
1426	>	catch (Exception ignore) {}
1427		}
1428	+	private static final long serialVersionUID = -7914297376763021607L;
1429		}
1430
657	–	// Configuration and status settings and queries
658	–
1431		/**
1432	<	* Returns the factory used for constructing new workers
1432	>	* Returns the factory used for constructing new workers.
1433		*
1434		* @return the factory used for constructing new workers
1435		*/
#	Line 668 | Line 1440 | public class ForkJoinPool extends Abstra
1440		/**
1441		* Returns the handler for internal worker threads that terminate
1442		* due to unrecoverable errors encountered while executing tasks.
671	–	* @return the handler, or null if none
672	–	*/
673	–	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
674	–	Thread.UncaughtExceptionHandler h;
675	–	final ReentrantLock lock = this.workerLock;
676	–	lock.lock();
677	–	try {
678	–	h = ueh;
679	–	} finally {
680	–	lock.unlock();
681	–	}
682	–	return h;
683	–	}
684	–
685	–	/**
686	–	* Sets the handler for internal worker threads that terminate due
687	–	* to unrecoverable errors encountered while executing tasks.
688	–	* Unless set, the current default or ThreadGroup handler is used
689	–	* as handler.
1443		*
1444	<	* @param h the new handler
692	<	* @return the old handler, or null if none
693	<	* @throws SecurityException if a security manager exists and
694	<	*         the caller is not permitted to modify threads
695	<	*         because it does not hold {@link
696	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
697	<	*/
698	<	public Thread.UncaughtExceptionHandler
699	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
700	<	checkPermission();
701	<	Thread.UncaughtExceptionHandler old = null;
702	<	final ReentrantLock lock = this.workerLock;
703	<	lock.lock();
704	<	try {
705	<	old = ueh;
706	<	ueh = h;
707	<	ForkJoinWorkerThread[] ws = workers;
708	<	if (ws != null) {
709	<	for (int i = 0; i < ws.length; ++i) {
710	<	ForkJoinWorkerThread w = ws[i];
711	<	if (w != null)
712	<	w.setUncaughtExceptionHandler(h);
713	<	}
714	<	}
715	<	} finally {
716	<	lock.unlock();
717	<	}
718	<	return old;
719	<	}
720	<
721	<
722	<	/**
723	<	* Sets the target parallelism level of this pool.
724	<	* @param parallelism the target parallelism
725	<	* @throws IllegalArgumentException if parallelism less than or
726	<	* equal to zero or greater than maximum size bounds
727	<	* @throws SecurityException if a security manager exists and
728	<	*         the caller is not permitted to modify threads
729	<	*         because it does not hold {@link
730	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1444	>	* @return the handler, or {@code null} if none
1445		*/
1446	<	public void setParallelism(int parallelism) {
1447	<	checkPermission();
734	<	if (parallelism <= 0 || parallelism > maxPoolSize)
735	<	throw new IllegalArgumentException();
736	<	final ReentrantLock lock = this.workerLock;
737	<	lock.lock();
738	<	try {
739	<	if (!isTerminating()) {
740	<	int p = this.parallelism;
741	<	this.parallelism = parallelism;
742	<	if (parallelism > p)
743	<	createAndStartAddedWorkers();
744	<	else
745	<	trimSpares();
746	<	}
747	<	} finally {
748	<	lock.unlock();
749	<	}
750	<	signalIdleWorkers();
1446	>	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1447	>	return ueh;
1448		}
1449
1450		/**
1451	<	* Returns the targeted number of worker threads in this pool.
1451	>	* Returns the targeted parallelism level of this pool.
1452		*
1453	<	* @return the targeted number of worker threads in this pool
1453	>	* @return the targeted parallelism level of this pool
1454		*/
1455		public int getParallelism() {
1456		return parallelism;
#	Line 761 | Line 1458 | public class ForkJoinPool extends Abstra
1458
1459		/**
1460		* Returns the number of worker threads that have started but not
1461	<	* yet terminated.  This result returned by this method may differ
1462	<	* from {@code getParallelism} when threads are created to
1461	>	* yet terminated.  The result returned by this method may differ
1462	>	* from {@link #getParallelism} when threads are created to
1463		* maintain parallelism when others are cooperatively blocked.
1464		*
1465		* @return the number of worker threads
1466		*/
1467		public int getPoolSize() {
1468	<	return totalCountOf(workerCounts);
772	<	}
773	<
774	<	/**
775	<	* Returns the maximum number of threads allowed to exist in the
776	<	* pool, even if there are insufficient unblocked running threads.
777	<	* @return the maximum
778	<	*/
779	<	public int getMaximumPoolSize() {
780	<	return maxPoolSize;
781	<	}
782	<
783	<	/**
784	<	* Sets the maximum number of threads allowed to exist in the
785	<	* pool, even if there are insufficient unblocked running threads.
786	<	* Setting this value has no effect on current pool size. It
787	<	* controls construction of new threads.
788	<	* @throws IllegalArgumentException if negative or greater then
789	<	* internal implementation limit
790	<	*/
791	<	public void setMaximumPoolSize(int newMax) {
792	<	if (newMax < 0 || newMax > MAX_THREADS)
793	<	throw new IllegalArgumentException();
794	<	maxPoolSize = newMax;
795	<	}
796	<
797	<
798	<	/**
799	<	* Returns true if this pool dynamically maintains its target
800	<	* parallelism level. If false, new threads are added only to
801	<	* avoid possible starvation.
802	<	* This setting is by default true;
803	<	* @return true if maintains parallelism
804	<	*/
805	<	public boolean getMaintainsParallelism() {
806	<	return maintainsParallelism;
807	<	}
808	<
809	<	/**
810	<	* Sets whether this pool dynamically maintains its target
811	<	* parallelism level. If false, new threads are added only to
812	<	* avoid possible starvation.
813	<	* @param enable true to maintains parallelism
814	<	*/
815	<	public void setMaintainsParallelism(boolean enable) {
816	<	maintainsParallelism = enable;
817	<	}
818	<
819	<	/**
820	<	* Establishes local first-in-first-out scheduling mode for forked
821	<	* tasks that are never joined. This mode may be more appropriate
822	<	* than default locally stack-based mode in applications in which
823	<	* worker threads only process asynchronous tasks.  This method is
824	<	* designed to be invoked only when pool is quiescent, and
825	<	* typically only before any tasks are submitted. The effects of
826	<	* invocations at other times may be unpredictable.
827	<	*
828	<	* @param async if true, use locally FIFO scheduling
829	<	* @return the previous mode
830	<	*/
831	<	public boolean setAsyncMode(boolean async) {
832	<	boolean oldMode = locallyFifo;
833	<	locallyFifo = async;
834	<	ForkJoinWorkerThread[] ws = workers;
835	<	if (ws != null) {
836	<	for (int i = 0; i < ws.length; ++i) {
837	<	ForkJoinWorkerThread t = ws[i];
838	<	if (t != null)
839	<	t.setAsyncMode(async);
840	<	}
841	<	}
842	<	return oldMode;
1468	>	return workerCounts >>> TOTAL_COUNT_SHIFT;
1469		}
1470
1471		/**
1472	<	* Returns true if this pool uses local first-in-first-out
1472	>	* Returns {@code true} if this pool uses local first-in-first-out
1473		* scheduling mode for forked tasks that are never joined.
1474		*
1475	<	* @return true if this pool uses async mode
1475	>	* @return {@code true} if this pool uses async mode
1476		*/
1477		public boolean getAsyncMode() {
1478		return locallyFifo;
#	Line 855 | Line 1481 | public class ForkJoinPool extends Abstra
1481		/**
1482		* Returns an estimate of the number of worker threads that are
1483		* not blocked waiting to join tasks or for other managed
1484	<	* synchronization.
1484	>	* synchronization. This method may overestimate the
1485	>	* number of running threads.
1486		*
1487		* @return the number of worker threads
1488		*/
1489		public int getRunningThreadCount() {
1490	<	return runningCountOf(workerCounts);
1490	>	return workerCounts & RUNNING_COUNT_MASK;
1491		}
1492
1493		/**
1494		* Returns an estimate of the number of threads that are currently
1495		* stealing or executing tasks. This method may overestimate the
1496		* number of active threads.
1497	+	*
1498		* @return the number of active threads
1499		*/
1500		public int getActiveThreadCount() {
1501	<	return activeCountOf(runControl);
874	<	}
875	<
876	<	/**
877	<	* Returns an estimate of the number of threads that are currently
878	<	* idle waiting for tasks. This method may underestimate the
879	<	* number of idle threads.
880	<	* @return the number of idle threads
881	<	*/
882	<	final int getIdleThreadCount() {
883	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
884	<	return (c <= 0)? 0 : c;
1501	>	return runState & ACTIVE_COUNT_MASK;
1502		}
1503
1504		/**
1505	<	* Returns true if all worker threads are currently idle. An idle
1506	<	* worker is one that cannot obtain a task to execute because none
1507	<	* are available to steal from other threads, and there are no
1508	<	* pending submissions to the pool. This method is conservative:
1509	<	* It might not return true immediately upon idleness of all
1510	<	* threads, but will eventually become true if threads remain
1511	<	* inactive.
1512	<	* @return true if all threads are currently idle
1505	>	* Returns {@code true} if all worker threads are currently idle.
1506	>	* An idle worker is one that cannot obtain a task to execute
1507	>	* because none are available to steal from other threads, and
1508	>	* there are no pending submissions to the pool. This method is
1509	>	* conservative; it might not return {@code true} immediately upon
1510	>	* idleness of all threads, but will eventually become true if
1511	>	* threads remain inactive.
1512	>	*
1513	>	* @return {@code true} if all threads are currently idle
1514		*/
1515		public boolean isQuiescent() {
1516	<	return activeCountOf(runControl) == 0;
1516	>	return (runState & ACTIVE_COUNT_MASK) == 0;
1517		}
1518
1519		/**
#	Line 903 | Line 1521 | public class ForkJoinPool extends Abstra
1521		* one thread's work queue by another. The reported value
1522		* underestimates the actual total number of steals when the pool
1523		* is not quiescent. This value may be useful for monitoring and
1524	<	* tuning fork/join programs: In general, steal counts should be
1524	>	* tuning fork/join programs: in general, steal counts should be
1525		* high enough to keep threads busy, but low enough to avoid
1526		* overhead and contention across threads.
1527	+	*
1528		* @return the number of steals
1529		*/
1530		public long getStealCount() {
1531	<	return stealCount.get();
913	<	}
914	<
915	<	/**
916	<	* Accumulate steal count from a worker. Call only
917	<	* when worker known to be idle.
918	<	*/
919	<	private void updateStealCount(ForkJoinWorkerThread w) {
920	<	int sc = w.getAndClearStealCount();
921	<	if (sc != 0)
922	<	stealCount.addAndGet(sc);
1531	>	return stealCount;
1532		}
1533
1534		/**
#	Line 929 | Line 1538 | public class ForkJoinPool extends Abstra
1538		* an approximation, obtained by iterating across all threads in
1539		* the pool. This method may be useful for tuning task
1540		* granularities.
1541	+	*
1542		* @return the number of queued tasks
1543		*/
1544		public long getQueuedTaskCount() {
1545		long count = 0;
1546	<	ForkJoinWorkerThread[] ws = workers;
1547	<	if (ws != null) {
1548	<	for (int i = 0; i < ws.length; ++i) {
939	<	ForkJoinWorkerThread t = ws[i];
940	<	if (t != null)
941	<	count += t.getQueueSize();
942	<	}
943	<	}
1546	>	for (ForkJoinWorkerThread w : workers)
1547	>	if (w != null)
1548	>	count += w.getQueueSize();
1549		return count;
1550		}
1551
1552		/**
1553	<	* Returns an estimate of the number tasks submitted to this pool
1554	<	* that have not yet begun executing. This method takes time
1553	>	* Returns an estimate of the number of tasks submitted to this
1554	>	* pool that have not yet begun executing.  This method takes time
1555		* proportional to the number of submissions.
1556	+	*
1557		* @return the number of queued submissions
1558		*/
1559		public int getQueuedSubmissionCount() {
#	Line 955 | Line 1561 | public class ForkJoinPool extends Abstra
1561		}
1562
1563		/**
1564	<	* Returns true if there are any tasks submitted to this pool
1565	<	* that have not yet begun executing.
1564	>	* Returns {@code true} if there are any tasks submitted to this
1565	>	* pool that have not yet begun executing.
1566	>	*
1567		* @return {@code true} if there are any queued submissions
1568		*/
1569		public boolean hasQueuedSubmissions() {
#	Line 967 | Line 1574 | public class ForkJoinPool extends Abstra
1574		* Removes and returns the next unexecuted submission if one is
1575		* available.  This method may be useful in extensions to this
1576		* class that re-assign work in systems with multiple pools.
1577	<	* @return the next submission, or null if none
1577	>	*
1578	>	* @return the next submission, or {@code null} if none
1579		*/
1580		protected ForkJoinTask<?> pollSubmission() {
1581		return submissionQueue.poll();
#	Line 977 | Line 1585 | public class ForkJoinPool extends Abstra
1585		* Removes all available unexecuted submitted and forked tasks
1586		* from scheduling queues and adds them to the given collection,
1587		* without altering their execution status. These may include
1588	<	* artificially generated or wrapped tasks. This method is designed
1589	<	* to be invoked only when the pool is known to be
1588	>	* artificially generated or wrapped tasks. This method is
1589	>	* designed to be invoked only when the pool is known to be
1590		* quiescent. Invocations at other times may not remove all
1591		* tasks. A failure encountered while attempting to add elements
1592		* to collection {@code c} may result in elements being in
#	Line 986 | Line 1594 | public class ForkJoinPool extends Abstra
1594		* exception is thrown.  The behavior of this operation is
1595		* undefined if the specified collection is modified while the
1596		* operation is in progress.
1597	+	*
1598		* @param c the collection to transfer elements into
1599		* @return the number of elements transferred
1600		*/
1601	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1602	<	int n = submissionQueue.drainTo(c);
1603	<	ForkJoinWorkerThread[] ws = workers;
1604	<	if (ws != null) {
1605	<	for (int i = 0; i < ws.length; ++i) {
1606	<	ForkJoinWorkerThread w = ws[i];
998	<	if (w != null)
999	<	n += w.drainTasksTo(c);
1000	<	}
1001	<	}
1002	<	return n;
1601	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1602	>	int count = submissionQueue.drainTo(c);
1603	>	for (ForkJoinWorkerThread w : workers)
1604	>	if (w != null)
1605	>	count += w.drainTasksTo(c);
1606	>	return count;
1607		}
1608
1609		/**
#	Line 1010 | Line 1614 | public class ForkJoinPool extends Abstra
1614		* @return a string identifying this pool, as well as its state
1615		*/
1616		public String toString() {
1013	–	int ps = parallelism;
1014	–	int wc = workerCounts;
1015	–	int rc = runControl;
1617		long st = getStealCount();
1618		long qt = getQueuedTaskCount();
1619		long qs = getQueuedSubmissionCount();
1620	+	int wc = workerCounts;
1621	+	int tc = wc >>> TOTAL_COUNT_SHIFT;
1622	+	int rc = wc & RUNNING_COUNT_MASK;
1623	+	int pc = parallelism;
1624	+	int rs = runState;
1625	+	int ac = rs & ACTIVE_COUNT_MASK;
1626		return super.toString() +
1627	<	"[" + runStateToString(runStateOf(rc)) +
1628	<	", parallelism = " + ps +
1629	<	", size = " + totalCountOf(wc) +
1630	<	", active = " + activeCountOf(rc) +
1631	<	", running = " + runningCountOf(wc) +
1627	>	"[" + runLevelToString(rs) +
1628	>	", parallelism = " + pc +
1629	>	", size = " + tc +
1630	>	", active = " + ac +
1631	>	", running = " + rc +
1632		", steals = " + st +
1633		", tasks = " + qt +
1634		", submissions = " + qs +
1635		"]";
1636		}
1637
1638	<	private static String runStateToString(int rs) {
1639	<	switch(rs) {
1640	<	case RUNNING: return "Running";
1641	<	case SHUTDOWN: return "Shutting down";
1642	<	case TERMINATING: return "Terminating";
1036	<	case TERMINATED: return "Terminated";
1037	<	default: throw new Error("Unknown run state");
1038	<	}
1638	>	private static String runLevelToString(int s) {
1639	>	return ((s & TERMINATED) != 0 ? "Terminated" :
1640	>	((s & TERMINATING) != 0 ? "Terminating" :
1641	>	((s & SHUTDOWN) != 0 ? "Shutting down" :
1642	>	"Running")));
1643		}
1644
1041	–	// lifecycle control
1042	–
1645		/**
1646		* Initiates an orderly shutdown in which previously submitted
1647		* tasks are executed, but no new tasks will be accepted.
1648		* Invocation has no additional effect if already shut down.
1649		* Tasks that are in the process of being submitted concurrently
1650		* during the course of this method may or may not be rejected.
1651	+	*
1652		* @throws SecurityException if a security manager exists and
1653		*         the caller is not permitted to modify threads
1654		*         because it does not hold {@link
1655	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1655	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1656		*/
1657		public void shutdown() {
1658		checkPermission();
1659	<	transitionRunStateTo(SHUTDOWN);
1660	<	if (canTerminateOnShutdown(runControl))
1058	<	terminateOnShutdown();
1659	>	advanceRunLevel(SHUTDOWN);
1660	>	tryTerminate(false);
1661		}
1662
1663		/**
1664	<	* Attempts to stop all actively executing tasks, and cancels all
1665	<	* waiting tasks.  Tasks that are in the process of being
1666	<	* submitted or executed concurrently during the course of this
1667	<	* method may or may not be rejected. Unlike some other executors,
1668	<	* this method cancels rather than collects non-executed tasks
1669	<	* upon termination, so always returns an empty list. However, you
1670	<	* can use method {@code drainTasksTo} before invoking this
1671	<	* method to transfer unexecuted tasks to another collection.
1664	>	* Attempts to cancel and/or stop all tasks, and reject all
1665	>	* subsequently submitted tasks.  Tasks that are in the process of
1666	>	* being submitted or executed concurrently during the course of
1667	>	* this method may or may not be rejected. This method cancels
1668	>	* both existing and unexecuted tasks, in order to permit
1669	>	* termination in the presence of task dependencies. So the method
1670	>	* always returns an empty list (unlike the case for some other
1671	>	* Executors).
1672	>	*
1673		* @return an empty list
1674		* @throws SecurityException if a security manager exists and
1675		*         the caller is not permitted to modify threads
1676		*         because it does not hold {@link
1677	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1677	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1678		*/
1679		public List<Runnable> shutdownNow() {
1680		checkPermission();
1681	<	terminate();
1681	>	tryTerminate(true);
1682		return Collections.emptyList();
1683		}
1684
#	Line 1085 | Line 1688 | public class ForkJoinPool extends Abstra
1688		* @return {@code true} if all tasks have completed following shut down
1689		*/
1690		public boolean isTerminated() {
1691	<	return runStateOf(runControl) == TERMINATED;
1691	>	return runState >= TERMINATED;
1692		}
1693
1694		/**
1695		* Returns {@code true} if the process of termination has
1696	<	* commenced but possibly not yet completed.
1696	>	* commenced but not yet completed.  This method may be useful for
1697	>	* debugging. A return of {@code true} reported a sufficient
1698	>	* period after shutdown may indicate that submitted tasks have
1699	>	* ignored or suppressed interruption, causing this executor not
1700	>	* to properly terminate.
1701		*
1702	<	* @return {@code true} if terminating
1702	>	* @return {@code true} if terminating but not yet terminated
1703		*/
1704		public boolean isTerminating() {
1705	<	return runStateOf(runControl) >= TERMINATING;
1705	>	return (runState & (TERMINATING|TERMINATED)) == TERMINATING;
1706	>	}
1707	>
1708	>	/**
1709	>	* Returns true if terminating or terminated. Used by ForkJoinWorkerThread.
1710	>	*/
1711	>	final boolean isAtLeastTerminating() {
1712	>	return runState >= TERMINATING;
1713		}
1714
1715		/**
#	Line 1104 | Line 1718 | public class ForkJoinPool extends Abstra
1718		* @return {@code true} if this pool has been shut down
1719		*/
1720		public boolean isShutdown() {
1721	<	return runStateOf(runControl) >= SHUTDOWN;
1721	>	return runState >= SHUTDOWN;
1722		}
1723
1724		/**
#	Line 1120 | Line 1734 | public class ForkJoinPool extends Abstra
1734		*/
1735		public boolean awaitTermination(long timeout, TimeUnit unit)
1736		throws InterruptedException {
1123	–	long nanos = unit.toNanos(timeout);
1124	–	final ReentrantLock lock = this.workerLock;
1125	–	lock.lock();
1737		try {
1738	<	for (;;) {
1739	<	if (isTerminated())
1129	<	return true;
1130	<	if (nanos <= 0)
1131	<	return false;
1132	<	nanos = termination.awaitNanos(nanos);
1133	<	}
1134	<	} finally {
1135	<	lock.unlock();
1136	<	}
1137	<	}
1138	<
1139	<	// Shutdown and termination support
1140	<
1141	<	/**
1142	<	* Callback from terminating worker. Null out the corresponding
1143	<	* workers slot, and if terminating, try to terminate, else try to
1144	<	* shrink workers array.
1145	<	* @param w the worker
1146	<	*/
1147	<	final void workerTerminated(ForkJoinWorkerThread w) {
1148	<	updateStealCount(w);
1149	<	updateWorkerCount(-1);
1150	<	final ReentrantLock lock = this.workerLock;
1151	<	lock.lock();
1152	<	try {
1153	<	ForkJoinWorkerThread[] ws = workers;
1154	<	if (ws != null) {
1155	<	int idx = w.poolIndex;
1156	<	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1157	<	ws[idx] = null;
1158	<	if (totalCountOf(workerCounts) == 0) {
1159	<	terminate(); // no-op if already terminating
1160	<	transitionRunStateTo(TERMINATED);
1161	<	termination.signalAll();
1162	<	}
1163	<	else if (!isTerminating()) {
1164	<	tryShrinkWorkerArray();
1165	<	tryResumeSpare(true); // allow replacement
1166	<	}
1167	<	}
1168	<	} finally {
1169	<	lock.unlock();
1170	<	}
1171	<	signalIdleWorkers();
1172	<	}
1173	<
1174	<	/**
1175	<	* Initiate termination.
1176	<	*/
1177	<	private void terminate() {
1178	<	if (transitionRunStateTo(TERMINATING)) {
1179	<	stopAllWorkers();
1180	<	resumeAllSpares();
1181	<	signalIdleWorkers();
1182	<	cancelQueuedSubmissions();
1183	<	cancelQueuedWorkerTasks();
1184	<	interruptUnterminatedWorkers();
1185	<	signalIdleWorkers(); // resignal after interrupt
1186	<	}
1187	<	}
1188	<
1189	<	/**
1190	<	* Possibly terminates when on shutdown state.
1191	<	*/
1192	<	private void terminateOnShutdown() {
1193	<	if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
1194	<	terminate();
1195	<	}
1196	<
1197	<	/**
1198	<	* Clears out and cancels submissions.
1199	<	*/
1200	<	private void cancelQueuedSubmissions() {
1201	<	ForkJoinTask<?> task;
1202	<	while ((task = pollSubmission()) != null)
1203	<	task.cancel(false);
1204	<	}
1205	<
1206	<	/**
1207	<	* Cleans out worker queues.
1208	<	*/
1209	<	private void cancelQueuedWorkerTasks() {
1210	<	final ReentrantLock lock = this.workerLock;
1211	<	lock.lock();
1212	<	try {
1213	<	ForkJoinWorkerThread[] ws = workers;
1214	<	if (ws != null) {
1215	<	for (int i = 0; i < ws.length; ++i) {
1216	<	ForkJoinWorkerThread t = ws[i];
1217	<	if (t != null)
1218	<	t.cancelTasks();
1219	<	}
1220	<	}
1221	<	} finally {
1222	<	lock.unlock();
1223	<	}
1224	<	}
1225	<
1226	<	/**
1227	<	* Sets each worker's status to terminating. Requires lock to avoid
1228	<	* conflicts with add/remove.
1229	<	*/
1230	<	private void stopAllWorkers() {
1231	<	final ReentrantLock lock = this.workerLock;
1232	<	lock.lock();
1233	<	try {
1234	<	ForkJoinWorkerThread[] ws = workers;
1235	<	if (ws != null) {
1236	<	for (int i = 0; i < ws.length; ++i) {
1237	<	ForkJoinWorkerThread t = ws[i];
1238	<	if (t != null)
1239	<	t.shutdownNow();
1240	<	}
1241	<	}
1242	<	} finally {
1243	<	lock.unlock();
1244	<	}
1245	<	}
1246	<
1247	<	/**
1248	<	* Interrupts all unterminated workers.  This is not required for
1249	<	* sake of internal control, but may help unstick user code during
1250	<	* shutdown.
1251	<	*/
1252	<	private void interruptUnterminatedWorkers() {
1253	<	final ReentrantLock lock = this.workerLock;
1254	<	lock.lock();
1255	<	try {
1256	<	ForkJoinWorkerThread[] ws = workers;
1257	<	if (ws != null) {
1258	<	for (int i = 0; i < ws.length; ++i) {
1259	<	ForkJoinWorkerThread t = ws[i];
1260	<	if (t != null && !t.isTerminated()) {
1261	<	try {
1262	<	t.interrupt();
1263	<	} catch (SecurityException ignore) {
1264	<	}
1265	<	}
1266	<	}
1267	<	}
1268	<	} finally {
1269	<	lock.unlock();
1270	<	}
1271	<	}
1272	<
1273	<
1274	<	/*
1275	<	* Nodes for event barrier to manage idle threads.  Queue nodes
1276	<	* are basic Treiber stack nodes, also used for spare stack.
1277	<	*
1278	<	* The event barrier has an event count and a wait queue (actually
1279	<	* a Treiber stack).  Workers are enabled to look for work when
1280	<	* the eventCount is incremented. If they fail to find work, they
1281	<	* may wait for next count. Upon release, threads help others wake
1282	<	* up.
1283	<	*
1284	<	* Synchronization events occur only in enough contexts to
1285	<	* maintain overall liveness:
1286	<	*
1287	<	*   - Submission of a new task to the pool
1288	<	*   - Resizes or other changes to the workers array
1289	<	*   - pool termination
1290	<	*   - A worker pushing a task on an empty queue
1291	<	*
1292	<	* The case of pushing a task occurs often enough, and is heavy
1293	<	* enough compared to simple stack pushes, to require special
1294	<	* handling: Method signalWork returns without advancing count if
1295	<	* the queue appears to be empty.  This would ordinarily result in
1296	<	* races causing some queued waiters not to be woken up. To avoid
1297	<	* this, the first worker enqueued in method sync (see
1298	<	* syncIsReleasable) rescans for tasks after being enqueued, and
1299	<	* helps signal if any are found. This works well because the
1300	<	* worker has nothing better to do, and so might as well help
1301	<	* alleviate the overhead and contention on the threads actually
1302	<	* doing work.  Also, since event counts increments on task
1303	<	* availability exist to maintain liveness (rather than to force
1304	<	* refreshes etc), it is OK for callers to exit early if
1305	<	* contending with another signaller.
1306	<	*/
1307	<	static final class WaitQueueNode {
1308	<	WaitQueueNode next; // only written before enqueued
1309	<	volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1310	<	final long count; // unused for spare stack
1311	<
1312	<	WaitQueueNode(long c, ForkJoinWorkerThread w) {
1313	<	count = c;
1314	<	thread = w;
1315	<	}
1316	<
1317	<	/**
1318	<	* Wakes up waiter, returning false if known to already
1319	<	*/
1320	<	boolean signal() {
1321	<	ForkJoinWorkerThread t = thread;
1322	<	if (t == null)
1323	<	return false;
1324	<	thread = null;
1325	<	LockSupport.unpark(t);
1326	<	return true;
1327	<	}
1328	<
1329	<	/**
1330	<	* Awaits release on sync.
1331	<	*/
1332	<	void awaitSyncRelease(ForkJoinPool p) {
1333	<	while (thread != null && !p.syncIsReleasable(this))
1334	<	LockSupport.park(this);
1335	<	}
1336	<
1337	<	/**
1338	<	* Awaits resumption as spare.
1339	<	*/
1340	<	void awaitSpareRelease() {
1341	<	while (thread != null) {
1342	<	if (!Thread.interrupted())
1343	<	LockSupport.park(this);
1344	<	}
1345	<	}
1346	<	}
1347	<
1348	<	/**
1349	<	* Ensures that no thread is waiting for count to advance from the
1350	<	* current value of eventCount read on entry to this method, by
1351	<	* releasing waiting threads if necessary.
1352	<	* @return the count
1353	<	*/
1354	<	final long ensureSync() {
1355	<	long c = eventCount;
1356	<	WaitQueueNode q;
1357	<	while ((q = syncStack) != null && q.count < c) {
1358	<	if (casBarrierStack(q, null)) {
1359	<	do {
1360	<	q.signal();
1361	<	} while ((q = q.next) != null);
1362	<	break;
1363	<	}
1364	<	}
1365	<	return c;
1366	<	}
1367	<
1368	<	/**
1369	<	* Increments event count and releases waiting threads.
1370	<	*/
1371	<	private void signalIdleWorkers() {
1372	<	long c;
1373	<	do;while (!casEventCount(c = eventCount, c+1));
1374	<	ensureSync();
1375	<	}
1376	<
1377	<	/**
1378	<	* Signals threads waiting to poll a task. Because method sync
1379	<	* rechecks availability, it is OK to only proceed if queue
1380	<	* appears to be non-empty, and OK to skip under contention to
1381	<	* increment count (since some other thread succeeded).
1382	<	*/
1383	<	final void signalWork() {
1384	<	long c;
1385	<	WaitQueueNode q;
1386	<	if (syncStack != null &&
1387	<	casEventCount(c = eventCount, c+1) &&
1388	<	(((q = syncStack) != null && q.count <= c) &&
1389	<	(!casBarrierStack(q, q.next) || !q.signal())))
1390	<	ensureSync();
1391	<	}
1392	<
1393	<	/**
1394	<	* Waits until event count advances from last value held by
1395	<	* caller, or if excess threads, caller is resumed as spare, or
1396	<	* caller or pool is terminating. Updates caller's event on exit.
1397	<	* @param w the calling worker thread
1398	<	*/
1399	<	final void sync(ForkJoinWorkerThread w) {
1400	<	updateStealCount(w); // Transfer w's count while it is idle
1401	<
1402	<	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1403	<	long prev = w.lastEventCount;
1404	<	WaitQueueNode node = null;
1405	<	WaitQueueNode h;
1406	<	while (eventCount == prev &&
1407	<	((h = syncStack) == null || h.count == prev)) {
1408	<	if (node == null)
1409	<	node = new WaitQueueNode(prev, w);
1410	<	if (casBarrierStack(node.next = h, node)) {
1411	<	node.awaitSyncRelease(this);
1412	<	break;
1413	<	}
1414	<	}
1415	<	long ec = ensureSync();
1416	<	if (ec != prev) {
1417	<	w.lastEventCount = ec;
1418	<	break;
1419	<	}
1420	<	}
1421	<	}
1422	<
1423	<	/**
1424	<	* Returns true if worker waiting on sync can proceed:
1425	<	*  - on signal (thread == null)
1426	<	*  - on event count advance (winning race to notify vs signaller)
1427	<	*  - on Interrupt
1428	<	*  - if the first queued node, we find work available
1429	<	* If node was not signalled and event count not advanced on exit,
1430	<	* then we also help advance event count.
1431	<	* @return true if node can be released
1432	<	*/
1433	<	final boolean syncIsReleasable(WaitQueueNode node) {
1434	<	long prev = node.count;
1435	<	if (!Thread.interrupted() && node.thread != null &&
1436	<	(node.next != null ||
1437	<	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1438	<	eventCount == prev)
1738	>	return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1739	>	} catch (TimeoutException ex) {
1740		return false;
1440	–	if (node.thread != null) {
1441	–	node.thread = null;
1442	–	long ec = eventCount;
1443	–	if (prev <= ec) // help signal
1444	–	casEventCount(ec, ec+1);
1445	–	}
1446	–	return true;
1447	–	}
1448	–
1449	–	/**
1450	–	* Returns true if a new sync event occurred since last call to
1451	–	* sync or this method, if so, updating caller's count.
1452	–	*/
1453	–	final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1454	–	long lc = w.lastEventCount;
1455	–	long ec = ensureSync();
1456	–	if (ec == lc)
1457	–	return false;
1458	–	w.lastEventCount = ec;
1459	–	return true;
1460	–	}
1461	–
1462	–	//  Parallelism maintenance
1463	–
1464	–	/**
1465	–	* Decrements running count; if too low, adds spare.
1466	–	*
1467	–	* Conceptually, all we need to do here is add or resume a
1468	–	* spare thread when one is about to block (and remove or
1469	–	* suspend it later when unblocked -- see suspendIfSpare).
1470	–	* However, implementing this idea requires coping with
1471	–	* several problems: We have imperfect information about the
1472	–	* states of threads. Some count updates can and usually do
1473	–	* lag run state changes, despite arrangements to keep them
1474	–	* accurate (for example, when possible, updating counts
1475	–	* before signalling or resuming), especially when running on
1476	–	* dynamic JVMs that don't optimize the infrequent paths that
1477	–	* update counts. Generating too many threads can make these
1478	–	* problems become worse, because excess threads are more
1479	–	* likely to be context-switched with others, slowing them all
1480	–	* down, especially if there is no work available, so all are
1481	–	* busy scanning or idling.  Also, excess spare threads can
1482	–	* only be suspended or removed when they are idle, not
1483	–	* immediately when they aren't needed. So adding threads will
1484	–	* raise parallelism level for longer than necessary.  Also,
1485	–	* FJ applications often encounter highly transient peaks when
1486	–	* many threads are blocked joining, but for less time than it
1487	–	* takes to create or resume spares.
1488	–	*
1489	–	* @param joinMe if non-null, return early if done
1490	–	* @param maintainParallelism if true, try to stay within
1491	–	* target counts, else create only to avoid starvation
1492	–	* @return true if joinMe known to be done
1493	–	*/
1494	–	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1495	–	maintainParallelism &= maintainsParallelism; // overrride
1496	–	boolean dec = false;  // true when running count decremented
1497	–	while (spareStack == null || !tryResumeSpare(dec)) {
1498	–	int counts = workerCounts;
1499	–	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1500	–	if (!needSpare(counts, maintainParallelism))
1501	–	break;
1502	–	if (joinMe.status < 0)
1503	–	return true;
1504	–	if (tryAddSpare(counts))
1505	–	break;
1506	–	}
1507	–	}
1508	–	return false;
1509	–	}
1510	–
1511	–	/**
1512	–	* Same idea as preJoin
1513	–	*/
1514	–	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1515	–	maintainParallelism &= maintainsParallelism;
1516	–	boolean dec = false;
1517	–	while (spareStack == null || !tryResumeSpare(dec)) {
1518	–	int counts = workerCounts;
1519	–	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1520	–	if (!needSpare(counts, maintainParallelism))
1521	–	break;
1522	–	if (blocker.isReleasable())
1523	–	return true;
1524	–	if (tryAddSpare(counts))
1525	–	break;
1526	–	}
1527	–	}
1528	–	return false;
1529	–	}
1530	–
1531	–	/**
1532	–	* Returns true if a spare thread appears to be needed.  If
1533	–	* maintaining parallelism, returns true when the deficit in
1534	–	* running threads is more than the surplus of total threads, and
1535	–	* there is apparently some work to do.  This self-limiting rule
1536	–	* means that the more threads that have already been added, the
1537	–	* less parallelism we will tolerate before adding another.
1538	–	* @param counts current worker counts
1539	–	* @param maintainParallelism try to maintain parallelism
1540	–	*/
1541	–	private boolean needSpare(int counts, boolean maintainParallelism) {
1542	–	int ps = parallelism;
1543	–	int rc = runningCountOf(counts);
1544	–	int tc = totalCountOf(counts);
1545	–	int runningDeficit = ps - rc;
1546	–	int totalSurplus = tc - ps;
1547	–	return (tc < maxPoolSize &&
1548	–	(rc == 0 || totalSurplus < 0 ||
1549	–	(maintainParallelism &&
1550	–	runningDeficit > totalSurplus &&
1551	–	ForkJoinWorkerThread.hasQueuedTasks(workers))));
1552	–	}
1553	–
1554	–	/**
1555	–	* Adds a spare worker if lock available and no more than the
1556	–	* expected numbers of threads exist.
1557	–	* @return true if successful
1558	–	*/
1559	–	private boolean tryAddSpare(int expectedCounts) {
1560	–	final ReentrantLock lock = this.workerLock;
1561	–	int expectedRunning = runningCountOf(expectedCounts);
1562	–	int expectedTotal = totalCountOf(expectedCounts);
1563	–	boolean success = false;
1564	–	boolean locked = false;
1565	–	// confirm counts while locking; CAS after obtaining lock
1566	–	try {
1567	–	for (;;) {
1568	–	int s = workerCounts;
1569	–	int tc = totalCountOf(s);
1570	–	int rc = runningCountOf(s);
1571	–	if (rc > expectedRunning || tc > expectedTotal)
1572	–	break;
1573	–	if (!locked && !(locked = lock.tryLock()))
1574	–	break;
1575	–	if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) {
1576	–	createAndStartSpare(tc);
1577	–	success = true;
1578	–	break;
1579	–	}
1580	–	}
1581	–	} finally {
1582	–	if (locked)
1583	–	lock.unlock();
1584	–	}
1585	–	return success;
1586	–	}
1587	–
1588	–	/**
1589	–	* Adds the kth spare worker. On entry, pool counts are already
1590	–	* adjusted to reflect addition.
1591	–	*/
1592	–	private void createAndStartSpare(int k) {
1593	–	ForkJoinWorkerThread w = null;
1594	–	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1);
1595	–	int len = ws.length;
1596	–	// Probably, we can place at slot k. If not, find empty slot
1597	–	if (k < len && ws[k] != null) {
1598	–	for (k = 0; k < len && ws[k] != null; ++k)
1599	–	;
1600	–	}
1601	–	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1602	–	ws[k] = w;
1603	–	w.start();
1604	–	}
1605	–	else
1606	–	updateWorkerCount(-1); // adjust on failure
1607	–	signalIdleWorkers();
1608	–	}
1609	–
1610	–	/**
1611	–	* Suspends calling thread w if there are excess threads.  Called
1612	–	* only from sync.  Spares are enqueued in a Treiber stack using
1613	–	* the same WaitQueueNodes as barriers.  They are resumed mainly
1614	–	* in preJoin, but are also woken on pool events that require all
1615	–	* threads to check run state.
1616	–	* @param w the caller
1617	–	*/
1618	–	private boolean suspendIfSpare(ForkJoinWorkerThread w) {
1619	–	WaitQueueNode node = null;
1620	–	int s;
1621	–	while (parallelism < runningCountOf(s = workerCounts)) {
1622	–	if (node == null)
1623	–	node = new WaitQueueNode(0, w);
1624	–	if (casWorkerCounts(s, s-1)) { // representation-dependent
1625	–	// push onto stack
1626	–	do;while (!casSpareStack(node.next = spareStack, node));
1627	–	// block until released by resumeSpare
1628	–	node.awaitSpareRelease();
1629	–	return true;
1630	–	}
1631	–	}
1632	–	return false;
1633	–	}
1634	–
1635	–	/**
1636	–	* Tries to pop and resume a spare thread.
1637	–	* @param updateCount if true, increment running count on success
1638	–	* @return true if successful
1639	–	*/
1640	–	private boolean tryResumeSpare(boolean updateCount) {
1641	–	WaitQueueNode q;
1642	–	while ((q = spareStack) != null) {
1643	–	if (casSpareStack(q, q.next)) {
1644	–	if (updateCount)
1645	–	updateRunningCount(1);
1646	–	q.signal();
1647	–	return true;
1648	–	}
1649	–	}
1650	–	return false;
1651	–	}
1652	–
1653	–	/**
1654	–	* Pops and resumes all spare threads. Same idea as ensureSync.
1655	–	* @return true if any spares released
1656	–	*/
1657	–	private boolean resumeAllSpares() {
1658	–	WaitQueueNode q;
1659	–	while ( (q = spareStack) != null) {
1660	–	if (casSpareStack(q, null)) {
1661	–	do {
1662	–	updateRunningCount(1);
1663	–	q.signal();
1664	–	} while ((q = q.next) != null);
1665	–	return true;
1666	–	}
1667	–	}
1668	–	return false;
1669	–	}
1670	–
1671	–	/**
1672	–	* Pops and shuts down excessive spare threads. Call only while
1673	–	* holding lock. This is not guaranteed to eliminate all excess
1674	–	* threads, only those suspended as spares, which are the ones
1675	–	* unlikely to be needed in the future.
1676	–	*/
1677	–	private void trimSpares() {
1678	–	int surplus = totalCountOf(workerCounts) - parallelism;
1679	–	WaitQueueNode q;
1680	–	while (surplus > 0 && (q = spareStack) != null) {
1681	–	if (casSpareStack(q, null)) {
1682	–	do {
1683	–	updateRunningCount(1);
1684	–	ForkJoinWorkerThread w = q.thread;
1685	–	if (w != null && surplus > 0 &&
1686	–	runningCountOf(workerCounts) > 0 && w.shutdown())
1687	–	--surplus;
1688	–	q.signal();
1689	–	} while ((q = q.next) != null);
1690	–	}
1741		}
1742		}
1743
1744		/**
1745		* Interface for extending managed parallelism for tasks running
1746	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1747	<	* Method {@code isReleasable} must return true if blocking is not
1748	<	* necessary. Method {@code block} blocks the current thread
1749	<	* if necessary (perhaps internally invoking isReleasable before
1750	<	* actually blocking.).
1746	>	* in {@link ForkJoinPool}s.
1747	>	*
1748	>	* <p>A {@code ManagedBlocker} provides two methods.  Method
1749	>	* {@code isReleasable} must return {@code true} if blocking is
1750	>	* not necessary. Method {@code block} blocks the current thread
1751	>	* if necessary (perhaps internally invoking {@code isReleasable}
1752	>	* before actually blocking). The unusual methods in this API
1753	>	* accommodate synchronizers that may, but don't usually, block
1754	>	* for long periods. Similarly, they allow more efficient internal
1755	>	* handling of cases in which additional workers may be, but
1756	>	* usually are not, needed to ensure sufficient parallelism.
1757	>	* Toward this end, implementations of method {@code isReleasable}
1758	>	* must be amenable to repeated invocation.
1759	>	*
1760		* <p>For example, here is a ManagedBlocker based on a
1761		* ReentrantLock:
1762	<	* <pre>
1763	<	*   class ManagedLocker implements ManagedBlocker {
1764	<	*     final ReentrantLock lock;
1765	<	*     boolean hasLock = false;
1766	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1767	<	*     public boolean block() {
1768	<	*        if (!hasLock)
1769	<	*           lock.lock();
1770	<	*        return true;
1771	<	*     }
1772	<	*     public boolean isReleasable() {
1773	<	*        return hasLock || (hasLock = lock.tryLock());
1774	<	*     }
1762	>	*  <pre> {@code
1763	>	* class ManagedLocker implements ManagedBlocker {
1764	>	*   final ReentrantLock lock;
1765	>	*   boolean hasLock = false;
1766	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1767	>	*   public boolean block() {
1768	>	*     if (!hasLock)
1769	>	*       lock.lock();
1770	>	*     return true;
1771	>	*   }
1772	>	*   public boolean isReleasable() {
1773	>	*     return hasLock || (hasLock = lock.tryLock());
1774	>	*   }
1775	>	* }}</pre>
1776	>	*
1777	>	* <p>Here is a class that possibly blocks waiting for an
1778	>	* item on a given queue:
1779	>	*  <pre> {@code
1780	>	* class QueueTaker<E> implements ManagedBlocker {
1781	>	*   final BlockingQueue<E> queue;
1782	>	*   volatile E item = null;
1783	>	*   QueueTaker(BlockingQueue<E> q) { this.queue = q; }
1784	>	*   public boolean block() throws InterruptedException {
1785	>	*     if (item == null)
1786	>	*       item = queue.take();
1787	>	*     return true;
1788		*   }
1789	<	* </pre>
1789	>	*   public boolean isReleasable() {
1790	>	*     return item != null || (item = queue.poll()) != null;
1791	>	*   }
1792	>	*   public E getItem() { // call after pool.managedBlock completes
1793	>	*     return item;
1794	>	*   }
1795	>	* }}</pre>
1796		*/
1797		public static interface ManagedBlocker {
1798		/**
1799		* Possibly blocks the current thread, for example waiting for
1800		* a lock or condition.
1801	<	* @return true if no additional blocking is necessary (i.e.,
1802	<	* if isReleasable would return true)
1801	>	*
1802	>	* @return {@code true} if no additional blocking is necessary
1803	>	* (i.e., if isReleasable would return true)
1804		* @throws InterruptedException if interrupted while waiting
1805	<	* (the method is not required to do so, but is allowed to).
1805	>	* (the method is not required to do so, but is allowed to)
1806		*/
1807		boolean block() throws InterruptedException;
1808
1809		/**
1810	<	* Returns true if blocking is unnecessary.
1810	>	* Returns {@code true} if blocking is unnecessary.
1811		*/
1812		boolean isReleasable();
1813		}
1814
1815		/**
1816		* Blocks in accord with the given blocker.  If the current thread
1817	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1818	<	* spare thread to be activated if necessary to ensure parallelism
1819	<	* while the current thread is blocked.  If
1820	<	* {@code maintainParallelism} is true and the pool supports
1821	<	* it ({@link #getMaintainsParallelism}), this method attempts to
1822	<	* maintain the pool's nominal parallelism. Otherwise if activates
1823	<	* a thread only if necessary to avoid complete starvation. This
1824	<	* option may be preferable when blockages use timeouts, or are
1825	<	* almost always brief.
1826	<	*
1827	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1828	<	* equivalent to
1829	<	* <pre>
1830	<	*   while (!blocker.isReleasable())
1752	<	*      if (blocker.block())
1753	<	*         return;
1754	<	* </pre>
1755	<	* If the caller is a ForkJoinTask, then the pool may first
1756	<	* be expanded to ensure parallelism, and later adjusted.
1817	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1818	>	* arranges for a spare thread to be activated if necessary to
1819	>	* ensure sufficient parallelism while the current thread is blocked.
1820	>	*
1821	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1822	>	* behaviorally equivalent to
1823	>	*  <pre> {@code
1824	>	* while (!blocker.isReleasable())
1825	>	*   if (blocker.block())
1826	>	*     return;
1827	>	* }</pre>
1828	>	*
1829	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1830	>	* first be expanded to ensure parallelism, and later adjusted.
1831		*
1832		* @param blocker the blocker
1759	–	* @param maintainParallelism if true and supported by this pool,
1760	–	* attempt to maintain the pool's nominal parallelism; otherwise
1761	–	* activate a thread only if necessary to avoid complete
1762	–	* starvation.
1833		* @throws InterruptedException if blocker.block did so
1834		*/
1835	<	public static void managedBlock(ManagedBlocker blocker,
1766	<	boolean maintainParallelism)
1835	>	public static void managedBlock(ManagedBlocker blocker)
1836		throws InterruptedException {
1837		Thread t = Thread.currentThread();
1838	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1839	<	((ForkJoinWorkerThread)t).pool : null);
1840	<	if (!blocker.isReleasable()) {
1841	<	try {
1842	<	if (pool == null ||
1843	<	!pool.preBlock(blocker, maintainParallelism))
1775	<	awaitBlocker(blocker);
1776	<	} finally {
1777	<	if (pool != null)
1778	<	pool.updateRunningCount(1);
1779	<	}
1838	>	if (t instanceof ForkJoinWorkerThread) {
1839	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
1840	>	w.pool.awaitBlocker(blocker);
1841	>	}
1842	>	else {
1843	>	do {} while (!blocker.isReleasable() && !blocker.block());
1844		}
1845		}
1846
1847	<	private static void awaitBlocker(ManagedBlocker blocker)
1848	<	throws InterruptedException {
1849	<	do;while (!blocker.isReleasable() && !blocker.block());
1786	<	}
1787	<
1788	<	// AbstractExecutorService overrides
1847	>	// AbstractExecutorService overrides.  These rely on undocumented
1848	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1849	>	// implement RunnableFuture.
1850
1851		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1852	<	return new AdaptedRunnable(runnable, value);
1852	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1853		}
1854
1855		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1856	<	return new AdaptedCallable(callable);
1856	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1857		}
1858
1859	+	// Unsafe mechanics
1860
1861	<	// Temporary Unsafe mechanics for preliminary release
1862	<	private static Unsafe getUnsafe() throws Throwable {
1861	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1862	>	private static final long workerCountsOffset =
1863	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1864	>	private static final long runStateOffset =
1865	>	objectFieldOffset("runState", ForkJoinPool.class);
1866	>	private static final long eventCountOffset =
1867	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1868	>	private static final long eventWaitersOffset =
1869	>	objectFieldOffset("eventWaiters", ForkJoinPool.class);
1870	>	private static final long stealCountOffset =
1871	>	objectFieldOffset("stealCount", ForkJoinPool.class);
1872	>	private static final long spareWaitersOffset =
1873	>	objectFieldOffset("spareWaiters", ForkJoinPool.class);
1874	>
1875	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1876	>	try {
1877	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1878	>	} catch (NoSuchFieldException e) {
1879	>	// Convert Exception to corresponding Error
1880	>	NoSuchFieldError error = new NoSuchFieldError(field);
1881	>	error.initCause(e);
1882	>	throw error;
1883	>	}
1884	>	}
1885	>
1886	>	/**
1887	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1888	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1889	>	* into a jdk.
1890	>	*
1891	>	* @return a sun.misc.Unsafe
1892	>	*/
1893	>	private static sun.misc.Unsafe getUnsafe() {
1894		try {
1895	<	return Unsafe.getUnsafe();
1895	>	return sun.misc.Unsafe.getUnsafe();
1896		} catch (SecurityException se) {
1897		try {
1898		return java.security.AccessController.doPrivileged
1899	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1900	<	public Unsafe run() throws Exception {
1901	<	return getUnsafePrivileged();
1899	>	(new java.security
1900	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1901	>	public sun.misc.Unsafe run() throws Exception {
1902	>	java.lang.reflect.Field f = sun.misc
1903	>	.Unsafe.class.getDeclaredField("theUnsafe");
1904	>	f.setAccessible(true);
1905	>	return (sun.misc.Unsafe) f.get(null);
1906		}});
1907		} catch (java.security.PrivilegedActionException e) {
1908	<	throw e.getCause();
1908	>	throw new RuntimeException("Could not initialize intrinsics",
1909	>	e.getCause());
1910		}
1911		}
1912		}
1815	–
1816	–	private static Unsafe getUnsafePrivileged()
1817	–	throws NoSuchFieldException, IllegalAccessException {
1818	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1819	–	f.setAccessible(true);
1820	–	return (Unsafe) f.get(null);
1821	–	}
1822	–
1823	–	private static long fieldOffset(String fieldName)
1824	–	throws NoSuchFieldException {
1825	–	return UNSAFE.objectFieldOffset
1826	–	(ForkJoinPool.class.getDeclaredField(fieldName));
1827	–	}
1828	–
1829	–	static final Unsafe UNSAFE;
1830	–	static final long eventCountOffset;
1831	–	static final long workerCountsOffset;
1832	–	static final long runControlOffset;
1833	–	static final long syncStackOffset;
1834	–	static final long spareStackOffset;
1835	–
1836	–	static {
1837	–	try {
1838	–	UNSAFE = getUnsafe();
1839	–	eventCountOffset = fieldOffset("eventCount");
1840	–	workerCountsOffset = fieldOffset("workerCounts");
1841	–	runControlOffset = fieldOffset("runControl");
1842	–	syncStackOffset = fieldOffset("syncStack");
1843	–	spareStackOffset = fieldOffset("spareStack");
1844	–	} catch (Throwable e) {
1845	–	throw new RuntimeException("Could not initialize intrinsics", e);
1846	–	}
1847	–	}
1848	–
1849	–	private boolean casEventCount(long cmp, long val) {
1850	–	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1851	–	}
1852	–	private boolean casWorkerCounts(int cmp, int val) {
1853	–	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1854	–	}
1855	–	private boolean casRunControl(int cmp, int val) {
1856	–	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1857	–	}
1858	–	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1859	–	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1860	–	}
1861	–	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1862	–	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1863	–	}
1913		}

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines