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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.1 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.53 by dl, Mon Apr 5 15:52:26 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.locks.*;
11	<	import java.util.concurrent.atomic.*;
12	<	import sun.misc.Unsafe;
13	<	import java.lang.reflect.*;
10	>
11	>	import java.util.ArrayList;
12	>	import java.util.Arrays;
13	>	import java.util.Collection;
14	>	import java.util.Collections;
15	>	import java.util.List;
16	>	import java.util.concurrent.locks.LockSupport;
17	>	import java.util.concurrent.locks.ReentrantLock;
18	>	import java.util.concurrent.atomic.AtomicInteger;
19	>	import java.util.concurrent.CountDownLatch;
20
21		/**
22	<	* Host for a group of ForkJoinWorkerThreads.  A ForkJoinPool provides
23	<	* the entry point for tasks submitted from non-ForkJoinTasks, as well
24	<	* as management and monitoring operations.  Normally a single
25	<	* ForkJoinPool is used for a large number of submitted
20	<	* tasks. Otherwise, use would not usually outweigh the construction
21	<	* and bookkeeping overhead of creating a large set of threads.
22	<	*
23	<	* <p>ForkJoinPools differ from other kinds of Executor mainly in that
24	<	* they provide <em>work-stealing</em>: all threads in the pool
25	<	* attempt to find and execute subtasks created by other active tasks
26	<	* (eventually blocking if none exist). This makes them efficient when
27	<	* most tasks spawn other subtasks (as do most ForkJoinTasks) but
28	<	* possibly less so otherwise. It is however fine to combine execution
29	<	* of some plain Runnable- or Callable- based activities with that of
30	<	* ForkJoinTasks.
22	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
23	>	* A {@code ForkJoinPool} provides the entry point for submissions
24	>	* from non-{@code ForkJoinTask}s, as well as management and
25	>	* monitoring operations.
26		*
27	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
28	<	* (target pool size), which it attempts to maintain by dynamically
29	<	* adding, suspending, or resuming threads, even if some tasks have
30	<	* blocked waiting to join others. However, no such adjustments are
31	<	* performed in the face of blocked IO or other unmanaged
32	<	* synchronization. The nested ManagedBlocker interface enables
33	<	* extension of the kinds of synchronization accommodated.
27	>	* <p>A {@code ForkJoinPool} differs from other kinds of {@link
28	>	* ExecutorService} mainly by virtue of employing
29	>	* <em>work-stealing</em>: all threads in the pool attempt to find and
30	>	* execute subtasks created by other active tasks (eventually blocking
31	>	* waiting for work if none exist). This enables efficient processing
32	>	* when most tasks spawn other subtasks (as do most {@code
33	>	* ForkJoinTask}s). A {@code ForkJoinPool} may also be used for mixed
34	>	* execution of some plain {@code Runnable}- or {@code Callable}-
35	>	* based activities along with {@code ForkJoinTask}s. When setting
36	>	* {@linkplain #setAsyncMode async mode}, a {@code ForkJoinPool} may
37	>	* also be appropriate for use with fine-grained tasks of any form
38	>	* that are never joined. Otherwise, other {@code ExecutorService}
39	>	* implementations are typically more appropriate choices.
40		*
41	<	* <p>The target parallelism level may also be set dynamically. You
42	<	* can limit the number of threads dynamically constructed using
43	<	* method <tt>setMaximumPoolSize</tt> and/or
44	<	* <tt>setMaintainParallelism</tt>.
41	>	* <p>A {@code ForkJoinPool} is constructed with a given target
42	>	* parallelism level; by default, equal to the number of available
43	>	* processors. Unless configured otherwise via {@link
44	>	* #setMaintainsParallelism}, the pool attempts to maintain this
45	>	* number of active (or available) threads by dynamically adding,
46	>	* suspending, or resuming internal worker threads, even if some tasks
47	>	* are stalled waiting to join others. However, no such adjustments
48	>	* are performed in the face of blocked IO or other unmanaged
49	>	* synchronization. The nested {@link ManagedBlocker} interface
50	>	* enables extension of the kinds of synchronization accommodated.
51	>	* The target parallelism level may also be changed dynamically
52	>	* ({@link #setParallelism}). The total number of threads may be
53	>	* limited using method {@link #setMaximumPoolSize}, in which case it
54	>	* may become possible for the activities of a pool to stall due to
55	>	* the lack of available threads to process new tasks. When the pool
56	>	* is executing tasks, these and other configuration setting methods
57	>	* may only gradually affect actual pool sizes. It is normally best
58	>	* practice to invoke these methods only when the pool is known to be
59	>	* quiescent.
60		*
61		* <p>In addition to execution and lifecycle control methods, this
62		* class provides status check methods (for example
63	<	* <tt>getStealCount</tt>) that are intended to aid in developing,
63	>	* {@link #getStealCount}) that are intended to aid in developing,
64		* tuning, and monitoring fork/join applications. Also, method
65	<	* <tt>toString</tt> returns indications of pool state in a convenient
66	<	* form for informal monitoring.
65	>	* {@link #toString} returns indications of pool state in a
66	>	* convenient form for informal monitoring.
67	>	*
68	>	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
69	>	* used for all parallel task execution in a program or subsystem.
70	>	* Otherwise, use would not usually outweigh the construction and
71	>	* bookkeeping overhead of creating a large set of threads. For
72	>	* example, a common pool could be used for the {@code SortTasks}
73	>	* illustrated in {@link RecursiveAction}. Because {@code
74	>	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
75	>	* daemon} mode, there is typically no need to explicitly {@link
76	>	* #shutdown} such a pool upon program exit.
77	>	*
78	>	* <pre>
79	>	* static final ForkJoinPool mainPool = new ForkJoinPool();
80	>	* ...
81	>	* public void sort(long[] array) {
82	>	*   mainPool.invoke(new SortTask(array, 0, array.length));
83	>	* }
84	>	* </pre>
85		*
86		* <p><b>Implementation notes</b>: This implementation restricts the
87	<	* maximum parallelism to 32767. Attempts to create pools with greater
88	<	* than the maximum result in IllegalArgumentExceptions.
87	>	* maximum number of running threads to 32767. Attempts to create
88	>	* pools with greater than the maximum number result in
89	>	* {@code IllegalArgumentException}.
90	>	*
91	>	* <p>This implementation rejects submitted tasks (that is, by throwing
92	>	* {@link RejectedExecutionException}) only when the pool is shut down.
93	>	*
94	>	* @since 1.7
95	>	* @author Doug Lea
96		*/
97	<	public class ForkJoinPool extends AbstractExecutorService
57	<	implements ExecutorService {
97	>	public class ForkJoinPool extends AbstractExecutorService {
98
99		/*
100	<	* See the extended comments interspersed below for design,
101	<	* rationale, and walkthroughs.
100	>	* Implementation Overview
101	>	*
102	>	* This class provides the central bookkeeping and control for a
103	>	* set of worker threads: Submissions from non-FJ threads enter
104	>	* into a submission queue. Workers take these tasks and typically
105	>	* split them into subtasks that may be stolen by other workers.
106	>	* The main work-stealing mechanics implemented in class
107	>	* ForkJoinWorkerThread give first priority to processing tasks
108	>	* from their own queues (LIFO or FIFO, depending on mode), then
109	>	* to randomized FIFO steals of tasks in other worker queues, and
110	>	* lastly to new submissions. These mechanics do not consider
111	>	* affinities, loads, cache localities, etc, so rarely provide the
112	>	* best possible performance on a given machine, but portably
113	>	* provide good throughput by averaging over these factors.
114	>	* (Further, even if we did try to use such information, we do not
115	>	* usually have a basis for exploiting it. For example, some sets
116	>	* of tasks profit from cache affinities, but others are harmed by
117	>	* cache pollution effects.)
118	>	*
119	>	* The main throughput advantages of work-stealing stem from
120	>	* decentralized control -- workers mostly steal tasks from each
121	>	* other. We do not want to negate this by creating bottlenecks
122	>	* implementing the management responsibilities of this class. So
123	>	* we use a collection of techniques that avoid, reduce, or cope
124	>	* well with contention. These entail several instances of
125	>	* bit-packing into CASable fields to maintain only the minimally
126	>	* required atomicity. To enable such packing, we restrict maximum
127	>	* parallelism to (1<<15)-1 (enabling twice this to fit into a 16
128	>	* bit field), which is far in excess of normal operating range.
129	>	* Even though updates to some of these bookkeeping fields do
130	>	* sometimes contend with each other, they don't normally
131	>	* cache-contend with updates to others enough to warrant memory
132	>	* padding or isolation. So they are all held as fields of
133	>	* ForkJoinPool objects.  The main capabilities are as follows:
134	>	*
135	>	* 1. Creating and removing workers. Workers are recorded in the
136	>	* "workers" array. This is an array as opposed to some other data
137	>	* structure to support index-based random steals by workers.
138	>	* Updates to the array recording new workers and unrecording
139	>	* terminated ones are protected from each other by a lock
140	>	* (workerLock) but the array is otherwise concurrently readable,
141	>	* and accessed directly by workers. To simplify index-based
142	>	* operations, the array size is always a power of two, and all
143	>	* readers must tolerate null slots. Currently, all but the first
144	>	* worker thread creation is on-demand, triggered by task
145	>	* submissions, replacement of terminated workers, and/or
146	>	* compensation for blocked workers. However, all other support
147	>	* code is set up to work with other policies.
148	>	*
149	>	* 2. Bookkeeping for dynamically adding and removing workers. We
150	>	* maintain a given level of parallelism (or, if
151	>	* maintainsParallelism is false, at least avoid starvation). When
152	>	* some workers are known to be blocked (on joins or via
153	>	* ManagedBlocker), we may create or resume others to take their
154	>	* place until they unblock (see below). Implementing this
155	>	* requires counts of the number of "running" threads (i.e., those
156	>	* that are neither blocked nor artifically suspended) as well as
157	>	* the total number.  These two values are packed into one field,
158	>	* "workerCounts" because we need accurate snapshots when deciding
159	>	* to create, resume or suspend.  To support these decisions,
160	>	* updates must be prospective (not retrospective).  For example,
161	>	* the running count is decremented before blocking by a thread
162	>	* about to block, but incremented by the thread about to unblock
163	>	* it. (In a few cases, these prospective updates may need to be
164	>	* rolled back, for example when deciding to create a new worker
165	>	* but the thread factory fails or returns null. In these cases,
166	>	* we are no worse off wrt other decisions than we would be
167	>	* otherwise.)  Updates to the workerCounts field sometimes
168	>	* transiently encounter a fair amount of contention when join
169	>	* dependencies are such that many threads block or unblock at
170	>	* about the same time. We alleviate this by sometimes bundling
171	>	* updates (for example blocking one thread on join and resuming a
172	>	* spare cancel each other out), and in most other cases
173	>	* performing an alternative action (like releasing waiters and
174	>	* finding spares; see below) as a more productive form of
175	>	* backoff.
176	>	*
177	>	* 3. Maintaining global run state. The run state of the pool
178	>	* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to
179	>	* those in other Executor implementations, as well as a count of
180	>	* "active" workers -- those that are, or soon will be, or
181	>	* recently were executing tasks. The runLevel and active count
182	>	* are packed together in order to correctly trigger shutdown and
183	>	* termination. Without care, active counts can be subject to very
184	>	* high contention.  We substantially reduce this contention by
185	>	* relaxing update rules.  A worker must claim active status
186	>	* prospectively, by activating if it sees that a submitted or
187	>	* stealable task exists (it may find after activating that the
188	>	* task no longer exists). It stays active while processing this
189	>	* task (if it exists) and any other local subtasks it produces,
190	>	* until it cannot find any other tasks. It then tries
191	>	* inactivating (see method preStep), but upon update contention
192	>	* instead scans for more tasks, later retrying inactivation if it
193	>	* doesn't find any.
194	>	*
195	>	* 4. Managing idle workers waiting for tasks. We cannot let
196	>	* workers spin indefinitely scanning for tasks when none are
197	>	* available. On the other hand, we must quickly prod them into
198	>	* action when new tasks are submitted or generated.  We
199	>	* park/unpark these idle workers using an event-count scheme.
200	>	* Field eventCount is incremented upon events that may enable
201	>	* workers that previously could not find a task to now find one:
202	>	* Submission of a new task to the pool, or another worker pushing
203	>	* a task onto a previously empty queue.  (We also use this
204	>	* mechanism for termination and reconfiguration actions that
205	>	* require wakeups of idle workers).  Each worker maintains its
206	>	* last known event count, and blocks when a scan for work did not
207	>	* find a task AND its lastEventCount matches the current
208	>	* eventCount. Waiting idle workers are recorded in a variant of
209	>	* Treiber stack headed by field eventWaiters which, when nonzero,
210	>	* encodes the thread index and count awaited for by the worker
211	>	* thread most recently calling eventSync. This thread in turn has
212	>	* a record (field nextEventWaiter) for the next waiting worker.
213	>	* In addition to allowing simpler decisions about need for
214	>	* wakeup, the event count bits in eventWaiters serve the role of
215	>	* tags to avoid ABA errors in Treiber stacks.  To reduce delays
216	>	* in task diffusion, workers not otherwise occupied may invoke
217	>	* method releaseWaiters, that removes and signals (unparks)
218	>	* workers not waiting on current count. To minimize task
219	>	* production stalls associate with signalling, any worker pushing
220	>	* a task on an empty queue invokes the weaker method signalWork,
221	>	* that only releases idle workers until it detects interference
222	>	* by other threads trying to release, and lets them take
223	>	* over. The net effect is a tree-like diffusion of signals, where
224	>	* released threads and possibly others) help with unparks.  To
225	>	* further reduce contention effects a bit, failed CASes to
226	>	* increment field eventCount are tolerated without retries.
227	>	* Conceptually they are merged into the same event, which is OK
228	>	* when their only purpose is to enable workers to scan for work.
229	>	*
230	>	* 5. Managing suspension of extra workers. When a worker is about
231	>	* to block waiting for a join (or via ManagedBlockers), we may
232	>	* create a new thread to maintain parallelism level, or at least
233	>	* avoid starvation (see below). Usually, extra threads are needed
234	>	* for only very short periods, yet join dependencies are such
235	>	* that we sometimes need them in bursts. Rather than create new
236	>	* threads each time this happens, we suspend no-longer-needed
237	>	* extra ones as "spares". For most purposes, we don't distinguish
238	>	* "extra" spare threads from normal "core" threads: On each call
239	>	* to preStep (the only point at which we can do this) a worker
240	>	* checks to see if there are now too many running workers, and if
241	>	* so, suspends itself.  Methods preJoin and doBlock look for
242	>	* suspended threads to resume before considering creating a new
243	>	* replacement. We don't need a special data structure to maintain
244	>	* spares; simply scanning the workers array looking for
245	>	* worker.isSuspended() is fine because the calling thread is
246	>	* otherwise not doing anything useful anyway; we are at least as
247	>	* happy if after locating a spare, the caller doesn't actually
248	>	* block because the join is ready before we try to adjust and
249	>	* compensate.  Note that this is intrinsically racy.  One thread
250	>	* may become a spare at about the same time as another is
251	>	* needlessly being created. We counteract this and related slop
252	>	* in part by requiring resumed spares to immediately recheck (in
253	>	* preStep) to see whether they they should re-suspend. The only
254	>	* effective difference between "extra" and "core" threads is that
255	>	* we allow the "extra" ones to time out and die if they are not
256	>	* resumed within a keep-alive interval of a few seconds. This is
257	>	* implemented mainly within ForkJoinWorkerThread, but requires
258	>	* some coordination (isTrimmed() -- meaning killed while
259	>	* suspended) to correctly maintain pool counts.
260	>	*
261	>	* 6. Deciding when to create new workers. The main dynamic
262	>	* control in this class is deciding when to create extra threads,
263	>	* in methods preJoin and doBlock. We always need to create one
264	>	* when the number of running threads becomes zero. But because
265	>	* blocked joins are typically dependent, we don't necessarily
266	>	* need or want one-to-one replacement. Using a one-to-one
267	>	* compensation rule often leads to enough useless overhead
268	>	* creating, suspending, resuming, and/or killing threads to
269	>	* signficantly degrade throughput.  We use a rule reflecting the
270	>	* idea that, the more spare threads you already have, the more
271	>	* evidence you need to create another one; where "evidence" is
272	>	* expressed as the current deficit -- target minus running
273	>	* threads. To reduce flickering and drift around target values,
274	>	* the relation is quadratic: adding a spare if (dc*dc)>=(sc*pc)
275	>	* (where dc is deficit, sc is number of spare threads and pc is
276	>	* target parallelism.)  This effectively reduces churn at the
277	>	* price of systematically undershooting target parallelism when
278	>	* many threads are blocked.  However, biasing toward undeshooting
279	>	* partially compensates for the above mechanics to suspend extra
280	>	* threads, that normally lead to overshoot because we can only
281	>	* suspend workers in-between top-level actions. It also better
282	>	* copes with the fact that some of the methods in this class tend
283	>	* to never become compiled (but are interpreted), so some
284	>	* components of the entire set of controls might execute many
285	>	* times faster than others. And similarly for cases where the
286	>	* apparent lack of work is just due to GC stalls and other
287	>	* transient system activity.
288	>	*
289	>	* 7. Maintaining other configuration parameters and monitoring
290	>	* statistics. Updates to fields controlling parallelism level,
291	>	* max size, etc can only meaningfully take effect for individual
292	>	* threads upon their next top-level actions; i.e., between
293	>	* stealing/running tasks/submission, which are separated by calls
294	>	* to preStep.  Memory ordering for these (assumed infrequent)
295	>	* reconfiguration calls is ensured by using reads and writes to
296	>	* volatile field workerCounts (that must be read in preStep anyway)
297	>	* as "fences" -- user-level reads are preceded by reads of
298	>	* workCounts, and writes are followed by no-op CAS to
299	>	* workerCounts. The values reported by other management and
300	>	* monitoring methods are either computed on demand, or are kept
301	>	* in fields that are only updated when threads are otherwise
302	>	* idle.
303	>	*
304	>	* Beware that there is a lot of representation-level coupling
305	>	* among classes ForkJoinPool, ForkJoinWorkerThread, and
306	>	* ForkJoinTask.  For example, direct access to "workers" array by
307	>	* workers, and direct access to ForkJoinTask.status by both
308	>	* ForkJoinPool and ForkJoinWorkerThread.  There is little point
309	>	* trying to reduce this, since any associated future changes in
310	>	* representations will need to be accompanied by algorithmic
311	>	* changes anyway.
312	>	*
313	>	* Style notes: There are lots of inline assignments (of form
314	>	* "while ((local = field) != 0)") which are usually the simplest
315	>	* way to ensure read orderings. Also several occurrences of the
316	>	* unusual "do {} while(!cas...)" which is the simplest way to
317	>	* force an update of a CAS'ed variable. There are also a few
318	>	* other coding oddities that help some methods perform reasonably
319	>	* even when interpreted (not compiled).
320	>	*
321	>	* The order of declarations in this file is: (1) statics (2)
322	>	* fields (along with constants used when unpacking some of them)
323	>	* (3) internal control methods (4) callbacks and other support
324	>	* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
325	>	* methods (plus a few little helpers).
326		*/
327
64	–	/** Mask for packing and unpacking shorts */
65	–	private static final int  shortMask = 0xffff;
66	–
67	–	/** Max pool size -- must be a power of two minus 1 */
68	–	private static final int MAX_THREADS =  0x7FFF;
69	–
328		/**
329	<	* Factory for creating new ForkJoinWorkerThreads.  A
330	<	* ForkJoinWorkerThreadFactory must be defined and used for
331	<	* ForkJoinWorkerThread subclasses that extend base functionality
332	<	* or initialize threads with different contexts.
329	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
330	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
331	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
332	>	* functionality or initialize threads with different contexts.
333		*/
334		public static interface ForkJoinWorkerThreadFactory {
335		/**
336		* Returns a new worker thread operating in the given pool.
337		*
338		* @param pool the pool this thread works in
339	<	* @throws NullPointerException if pool is null;
339	>	* @throws NullPointerException if the pool is null
340		*/
341		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
342		}
343
344		/**
345	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
345	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
346		* new ForkJoinWorkerThread.
347		*/
348	<	public static class  DefaultForkJoinWorkerThreadFactory
348	>	static class  DefaultForkJoinWorkerThreadFactory
349		implements ForkJoinWorkerThreadFactory {
350		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
351	<	try {
94	<	return new ForkJoinWorkerThread(pool);
95	<	} catch (OutOfMemoryError oom)  {
96	<	return null;
97	<	}
351	>	return new ForkJoinWorkerThread(pool);
352		}
353		}
354
355		/**
356	<	* The default ForkJoinWorkerThreadFactory, used unless overridden
357	<	* in ForkJoinPool constructors.
356	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
357	>	* overridden in ForkJoinPool constructors.
358		*/
359	<	private static final DefaultForkJoinWorkerThreadFactory
359	>	public static final ForkJoinWorkerThreadFactory
360		defaultForkJoinWorkerThreadFactory =
361		new DefaultForkJoinWorkerThreadFactory();
362
109	–
363		/**
364		* Permission required for callers of methods that may start or
365		* kill threads.
#	Line 131 | Line 384 | public class ForkJoinPool extends Abstra
384		new AtomicInteger();
385
386		/**
387	<	* Array holding all worker threads in the pool. Array size must
387	>	* Absolute bound for parallelism level. Twice this number must
388	>	* fit into a 16bit field to enable word-packing for some counts.
389	>	*/
390	>	private static final int MAX_THREADS = 0x7fff;
391	>
392	>	/**
393	>	* Array holding all worker threads in the pool.  Array size must
394		* be a power of two.  Updates and replacements are protected by
395	<	* workerLock, but it is always kept in a consistent enough state
396	<	* to be randomly accessed without locking by workers performing
397	<	* work-stealing.
395	>	* workerLock, but the array is always kept in a consistent enough
396	>	* state to be randomly accessed without locking by workers
397	>	* performing work-stealing, as well as other traversal-based
398	>	* methods in this class. All readers must tolerate that some
399	>	* array slots may be null.
400		*/
401		volatile ForkJoinWorkerThread[] workers;
402
403		/**
404	<	* Lock protecting access to workers.
404	>	* Queue for external submissions.
405		*/
406	<	private final ReentrantLock workerLock;
406	>	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
407
408		/**
409	<	* Condition for awaitTermination.
409	>	* Lock protecting updates to workers array.
410		*/
411	<	private final Condition termination;
411	>	private final ReentrantLock workerLock;
412
413		/**
414	<	* The uncaught exception handler used when any worker
154	<	* abrupty terminates
414	>	* Latch released upon termination.
415		*/
416	<	private Thread.UncaughtExceptionHandler ueh;
416	>	private final CountDownLatch terminationLatch;
417
418		/**
419		* Creation factory for worker threads.
#	Line 161 | Line 421 | public class ForkJoinPool extends Abstra
421		private final ForkJoinWorkerThreadFactory factory;
422
423		/**
424	<	* Head of stack of threads that were created to maintain
425	<	* parallelism when other threads blocked, but have since
166	<	* suspended when the parallelism level rose.
424	>	* Sum of per-thread steal counts, updated only when threads are
425	>	* idle or terminating.
426		*/
427	<	private volatile WaitQueueNode spareStack;
427	>	private volatile long stealCount;
428
429		/**
430	<	* Sum of per-thread steal counts, updated only when threads are
431	<	* idle or terminating.
430	>	* Encoded record of top of treiber stack of threads waiting for
431	>	* events. The top 32 bits contain the count being waited for. The
432	>	* bottom word contains one plus the pool index of waiting worker
433	>	* thread.
434		*/
435	<	private final AtomicLong stealCount;
435	>	private volatile long eventWaiters;
436	>
437	>	private static final int  EVENT_COUNT_SHIFT = 32;
438	>	private static final long WAITER_INDEX_MASK = (1L << EVENT_COUNT_SHIFT)-1L;
439
440		/**
441	<	* Queue for external submissions.
441	>	* A counter for events that may wake up worker threads:
442	>	*   - Submission of a new task to the pool
443	>	*   - A worker pushing a task on an empty queue
444	>	*   - termination and reconfiguration
445		*/
446	<	private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
446	>	private volatile int eventCount;
447	>
448	>	/**
449	>	* Lifecycle control. The low word contains the number of workers
450	>	* that are (probably) executing tasks. This value is atomically
451	>	* incremented before a worker gets a task to run, and decremented
452	>	* when worker has no tasks and cannot find any.  Bits 16-18
453	>	* contain runLevel value. When all are zero, the pool is
454	>	* running. Level transitions are monotonic (running -> shutdown
455	>	* -> terminating -> terminated) so each transition adds a bit.
456	>	* These are bundled together to ensure consistent read for
457	>	* termination checks (i.e., that runLevel is at least SHUTDOWN
458	>	* and active threads is zero).
459	>	*/
460	>	private volatile int runState;
461	>
462	>	// Note: The order among run level values matters.
463	>	private static final int RUNLEVEL_SHIFT     = 16;
464	>	private static final int SHUTDOWN           = 1 << RUNLEVEL_SHIFT;
465	>	private static final int TERMINATING        = 1 << (RUNLEVEL_SHIFT + 1);
466	>	private static final int TERMINATED         = 1 << (RUNLEVEL_SHIFT + 2);
467	>	private static final int ACTIVE_COUNT_MASK  = (1 << RUNLEVEL_SHIFT) - 1;
468	>	private static final int ONE_ACTIVE         = 1; // active update delta
469
470		/**
471	<	* Head of Treiber stack for barrier sync. See below for explanation
471	>	* Holds number of total (i.e., created and not yet terminated)
472	>	* and running (i.e., not blocked on joins or other managed sync)
473	>	* threads, packed together to ensure consistent snapshot when
474	>	* making decisions about creating and suspending spare
475	>	* threads. Updated only by CAS. Note that adding a new worker
476	>	* requires incrementing both counts, since workers start off in
477	>	* running state.  This field is also used for memory-fencing
478	>	* configuration parameters.
479	>	*/
480	>	private volatile int workerCounts;
481	>
482	>	private static final int TOTAL_COUNT_SHIFT  = 16;
483	>	private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1;
484	>	private static final int ONE_RUNNING        = 1;
485	>	private static final int ONE_TOTAL          = 1 << TOTAL_COUNT_SHIFT;
486	>
487	>	/*
488	>	* Fields parallelism. maxPoolSize, locallyFifo,
489	>	* maintainsParallelism, and ueh are non-volatile, but external
490	>	* reads/writes use workerCount fences to ensure visability.
491		*/
184	–	private volatile WaitQueueNode barrierStack;
492
493		/**
494	<	* The count for event barrier
494	>	* The target parallelism level.
495		*/
496	<	private volatile long eventCount;
496	>	private int parallelism;
497
498		/**
499	<	* Pool number, just for assigning useful names to worker threads
499	>	* The maximum allowed pool size.
500		*/
501	<	private final int poolNumber;
501	>	private int maxPoolSize;
502
503		/**
504	<	* The maximum allowed pool size
504	>	* True if use local fifo, not default lifo, for local polling
505	>	* Replicated by ForkJoinWorkerThreads
506		*/
507	<	private volatile int maxPoolSize;
507	>	private boolean locallyFifo;
508
509		/**
510	<	* The desired parallelism level, updated only under workerLock.
510	>	* Controls whether to add spares to maintain parallelism
511		*/
512	<	private volatile int parallelism;
512	>	private boolean maintainsParallelism;
513
514		/**
515	<	* Holds number of total (i.e., created and not yet terminated)
516	<	* and running (i.e., not blocked on joins or other managed sync)
209	<	* threads, packed into one int to ensure consistent snapshot when
210	<	* making decisions about creating and suspending spare
211	<	* threads. Updated only by CAS.  Note: CASes in
212	<	* updateRunningCount and preJoin running active count is in low
213	<	* word, so need to be modified if this changes
515	>	* The uncaught exception handler used when any worker
516	>	* abruptly terminates
517		*/
518	<	private volatile int workerCounts;
518	>	private Thread.UncaughtExceptionHandler ueh;
519	>
520	>	/**
521	>	* Pool number, just for assigning useful names to worker threads
522	>	*/
523	>	private final int poolNumber;
524
525	<	private static int totalCountOf(int s)           { return s >>> 16;  }
218	<	private static int runningCountOf(int s)         { return s & shortMask; }
219	<	private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
525	>	// utilities for updating fields
526
527		/**
528	<	* Add delta (which may be negative) to running count.  This must
529	<	* be called before (with negative arg) and after (with positive)
224	<	* any managed synchronization (i.e., mainly, joins)
528	>	* Adds delta to running count.  Used mainly by ForkJoinTask.
529	>	*
530		* @param delta the number to add
531		*/
532		final void updateRunningCount(int delta) {
533	<	int s;
534	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
533	>	int wc;
534	>	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
535	>	wc = workerCounts,
536	>	wc + delta));
537		}
538
539		/**
540	<	* Add delta (which may be negative) to both total and running
541	<	* count.  This must be called upon creation and termination of
235	<	* worker threads.
236	<	* @param delta the number to add
540	>	* Write fence for user modifications of pool parameters
541	>	* (parallelism. etc).  Note that it doesn't matter if CAS fails.
542		*/
543	<	private void updateWorkerCount(int delta) {
544	<	int d = delta + (delta << 16); // add to both lo and hi parts
545	<	int s;
546	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
543	>	private void workerCountWriteFence() {
544	>	int wc;
545	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
546	>	wc = workerCounts, wc);
547		}
548
549		/**
550	<	* Lifecycle control. High word contains runState, low word
551	<	* contains the number of workers that are (probably) executing
247	<	* tasks. This value is atomically incremented before a worker
248	<	* gets a task to run, and decremented when worker has no tasks
249	<	* and cannot find any. These two fields are bundled together to
250	<	* support correct termination triggering.  Note: activeCount
251	<	* CAS'es cheat by assuming active count is in low word, so need
252	<	* to be modified if this changes
550	>	* Read fence for external reads of pool parameters
551	>	* (parallelism. maxPoolSize, etc).
552		*/
553	<	private volatile int runControl;
554	<
555	<	// RunState values. Order among values matters
257	<	private static final int RUNNING     = 0;
258	<	private static final int SHUTDOWN    = 1;
259	<	private static final int TERMINATING = 2;
260	<	private static final int TERMINATED  = 3;
261	<
262	<	private static int runStateOf(int c)             { return c >>> 16; }
263	<	private static int activeCountOf(int c)          { return c & shortMask; }
264	<	private static int runControlFor(int r, int a)   { return (r << 16) + a; }
553	>	private void workerCountReadFence() {
554	>	int ignore = workerCounts;
555	>	}
556
557		/**
558	<	* Increment active count. Called by workers before/during
559	<	* executing tasks.
558	>	* Tries incrementing active count; fails on contention.
559	>	* Called by workers before executing tasks.
560	>	*
561	>	* @return true on success
562		*/
563	<	final void incrementActiveCount() {
563	>	final boolean tryIncrementActiveCount() {
564		int c;
565	<	do;while (!casRunControl(c = runControl, c+1));
565	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
566	>	c = runState, c + ONE_ACTIVE);
567		}
568
569		/**
570	<	* Decrement active count; possibly trigger termination.
571	<	* Called by workers when they can't find tasks.
570	>	* Tries decrementing active count; fails on contention.
571	>	* Called when workers cannot find tasks to run.
572		*/
573	<	final void decrementActiveCount() {
574	<	int c, nextc;
575	<	do;while (!casRunControl(c = runControl, nextc = c-1));
576	<	if (canTerminateOnShutdown(nextc))
283	<	terminateOnShutdown();
573	>	final boolean tryDecrementActiveCount() {
574	>	int c;
575	>	return UNSAFE.compareAndSwapInt(this, runStateOffset,
576	>	c = runState, c - ONE_ACTIVE);
577		}
578
579		/**
580	<	* Return true if argument represents zero active count and
581	<	* nonzero runstate, which is the triggering condition for
289	<	* terminating on shutdown.
580	>	* Advances to at least the given level. Returns true if not
581	>	* already in at least the given level.
582		*/
583	<	private static boolean canTerminateOnShutdown(int c) {
584	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
583	>	private boolean advanceRunLevel(int level) {
584	>	for (;;) {
585	>	int s = runState;
586	>	if ((s & level) != 0)
587	>	return false;
588	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level))
589	>	return true;
590	>	}
591		}
592
593	+	// workers array maintenance
594	+
595		/**
596	<	* Transition run state to at least the given state. Return true
297	<	* if not already at least given state.
596	>	* Records and returns a workers array index for new worker.
597		*/
598	<	private boolean transitionRunStateTo(int state) {
599	<	for (;;) {
600	<	int c = runControl;
601	<	if (runStateOf(c) >= state)
602	<	return false;
603	<	if (casRunControl(c, runControlFor(state, activeCountOf(c))))
604	<	return true;
598	>	private int recordWorker(ForkJoinWorkerThread w) {
599	>	// Try using slot totalCount-1. If not available, scan and/or resize
600	>	int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1;
601	>	final ReentrantLock lock = this.workerLock;
602	>	lock.lock();
603	>	try {
604	>	ForkJoinWorkerThread[] ws = workers;
605	>	int len = ws.length;
606	>	if (k < 0 || k >= len || ws[k] != null) {
607	>	for (k = 0; k < len && ws[k] != null; ++k)
608	>	;
609	>	if (k == len)
610	>	ws = Arrays.copyOf(ws, len << 1);
611	>	}
612	>	ws[k] = w;
613	>	workers = ws; // volatile array write ensures slot visibility
614	>	} finally {
615	>	lock.unlock();
616		}
617	+	return k;
618		}
619
620		/**
621	<	* Controls whether to add spares to maintain parallelism
621	>	* Nulls out record of worker in workers array
622		*/
623	<	private volatile boolean maintainsParallelism;
623	>	private void forgetWorker(ForkJoinWorkerThread w) {
624	>	int idx = w.poolIndex;
625	>	// Locking helps method recordWorker avoid unecessary expansion
626	>	final ReentrantLock lock = this.workerLock;
627	>	lock.lock();
628	>	try {
629	>	ForkJoinWorkerThread[] ws = workers;
630	>	if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify
631	>	ws[idx] = null;
632	>	} finally {
633	>	lock.unlock();
634	>	}
635	>	}
636
637	<	// Constructors
637	>	// adding and removing workers
638
639		/**
640	<	* Creates a ForkJoinPool with a pool size equal to the number of
641	<	* processors available on the system and using the default
642	<	* ForkJoinWorkerThreadFactory,
643	<	* @throws SecurityException if a security manager exists and
644	<	*         the caller is not permitted to modify threads
322	<	*         because it does not hold {@link
323	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
640	>	* Tries to create and add new worker. Assumes that worker counts
641	>	* are already updated to accommodate the worker, so adjusts on
642	>	* failure.
643	>	*
644	>	* @return new worker or null if creation failed
645		*/
646	<	public ForkJoinPool() {
647	<	this(Runtime.getRuntime().availableProcessors(),
648	<	defaultForkJoinWorkerThreadFactory);
646	>	private ForkJoinWorkerThread addWorker() {
647	>	ForkJoinWorkerThread w = null;
648	>	try {
649	>	w = factory.newThread(this);
650	>	} finally { // Adjust on either null or exceptional factory return
651	>	if (w == null) {
652	>	onWorkerCreationFailure();
653	>	return null;
654	>	}
655	>	}
656	>	w.start(recordWorker(w), locallyFifo, ueh);
657	>	return w;
658		}
659
660		/**
661	<	* Creates a ForkJoinPool with the indicated parellelism level
332	<	* threads, and using the default ForkJoinWorkerThreadFactory,
333	<	* @param parallelism the number of worker threads
334	<	* @throws IllegalArgumentException if parallelism less than or
335	<	* equal to zero
336	<	* @throws SecurityException if a security manager exists and
337	<	*         the caller is not permitted to modify threads
338	<	*         because it does not hold {@link
339	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
661	>	* Adjusts counts upon failure to create worker
662		*/
663	<	public ForkJoinPool(int parallelism) {
664	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
663	>	private void onWorkerCreationFailure() {
664	>	int c;
665	>	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
666	>	c = workerCounts,
667	>	c - (ONE_RUNNING|ONE_TOTAL)));
668	>	tryTerminate(false); // in case of failure during shutdown
669		}
670
671		/**
672	<	* Creates a ForkJoinPool with a pool size equal to the number of
673	<	* processors available on the system and using the given
674	<	* ForkJoinWorkerThreadFactory,
675	<	* @param factory the factory for creating new threads
676	<	* @throws NullPointerException if factory is null
677	<	* @throws SecurityException if a security manager exists and
678	<	*         the caller is not permitted to modify threads
679	<	*         because it does not hold {@link
680	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
681	<	*/
682	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
683	<	this(Runtime.getRuntime().availableProcessors(), factory);
672	>	* Create enough total workers to establish target parallelism,
673	>	* giving up if terminating or addWorker fails
674	>	*/
675	>	private void ensureEnoughTotalWorkers() {
676	>	int wc;
677	>	while (runState < TERMINATING &&
678	>	((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < parallelism) {
679	>	if ((UNSAFE.compareAndSwapInt(this, workerCountsOffset,
680	>	wc, wc + (ONE_RUNNING|ONE_TOTAL)) &&
681	>	addWorker() == null))
682	>	break;
683	>	}
684		}
685
686		/**
687	<	* Creates a ForkJoinPool with the indicated target number of
688	<	* worker threads and the given factory.
687	>	* Final callback from terminating worker.  Removes record of
688	>	* worker from array, and adjusts counts. If pool is shutting
689	>	* down, tries to complete terminatation, else possibly replaces
690	>	* the worker.
691		*
692	<	* @param parallelism the targeted number of worker threads
365	<	* @param factory the factory for creating new threads
366	<	* @throws IllegalArgumentException if parallelism less than or
367	<	* equal to zero, or greater than implementation limit.
368	<	* @throws NullPointerException if factory is null
369	<	* @throws SecurityException if a security manager exists and
370	<	*         the caller is not permitted to modify threads
371	<	*         because it does not hold {@link
372	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
692	>	* @param w the worker
693		*/
694	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
695	<	if (parallelism <= 0 || parallelism > MAX_THREADS)
696	<	throw new IllegalArgumentException();
697	<	if (factory == null)
698	<	throw new NullPointerException();
699	<	checkPermission();
700	<	this.factory = factory;
701	<	this.parallelism = parallelism;
702	<	this.maxPoolSize = MAX_THREADS;
703	<	this.maintainsParallelism = true;
704	<	this.poolNumber = poolNumberGenerator.incrementAndGet();
705	<	this.workerLock = new ReentrantLock();
706	<	this.termination = workerLock.newCondition();
707	<	this.stealCount = new AtomicLong();
708	<	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
709	<	createAndStartInitialWorkers(parallelism);
694	>	final void workerTerminated(ForkJoinWorkerThread w) {
695	>	if (w.active) { // force inactive
696	>	w.active = false;
697	>	do {} while (!tryDecrementActiveCount());
698	>	}
699	>	forgetWorker(w);
700	>
701	>	// decrement total count, and if was running, running count
702	>	int unit = w.isTrimmed()? ONE_TOTAL : (ONE_RUNNING|ONE_TOTAL);
703	>	int wc;
704	>	do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
705	>	wc = workerCounts, wc - unit));
706	>
707	>	accumulateStealCount(w); // collect final count
708	>	if (!tryTerminate(false))
709	>	ensureEnoughTotalWorkers();
710	>	}
711	>
712	>	// Waiting for and signalling events
713	>
714	>	/**
715	>	* Ensures eventCount on exit is different (mod 2^32) than on
716	>	* entry.  CAS failures are OK -- any change in count suffices.
717	>	*/
718	>	private void advanceEventCount() {
719	>	int c;
720	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
721		}
722
723		/**
724	<	* Create new worker using factory.
725	<	* @param index the index to assign worker
726	<	* @return new worker, or null of factory failed
727	<	*/
728	<	private ForkJoinWorkerThread createWorker(int index) {
729	<	Thread.UncaughtExceptionHandler h = ueh;
730	<	ForkJoinWorkerThread w = factory.newThread(this);
731	<	if (w != null) {
732	<	w.poolIndex = index;
733	<	w.setDaemon(true);
734	<	w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
735	<	if (h != null)
736	<	w.setUncaughtExceptionHandler(h);
724	>	* Releases workers blocked on a count not equal to current count.
725	>	*/
726	>	final void releaseWaiters() {
727	>	long top;
728	>	int id;
729	>	while ((id = (int)((top = eventWaiters) & WAITER_INDEX_MASK)) > 0 &&
730	>	(int)(top >>> EVENT_COUNT_SHIFT) != eventCount) {
731	>	ForkJoinWorkerThread[] ws = workers;
732	>	ForkJoinWorkerThread w;
733	>	if (ws.length >= id && (w = ws[id - 1]) != null &&
734	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
735	>	top, w.nextWaiter))
736	>	LockSupport.unpark(w);
737		}
407	–	return w;
738		}
739
740		/**
741	<	* Return a good size for worker array given pool size.
742	<	* Currently requires size to be a power of two.
741	>	* Advances eventCount and releases waiters until interference by
742	>	* other releasing threads is detected.
743		*/
744	<	private static int arraySizeFor(int ps) {
745	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
744	>	final void signalWork() {
745	>	int ec;
746	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, ec=eventCount, ec+1);
747	>	outer:for (;;) {
748	>	long top = eventWaiters;
749	>	ec = eventCount;
750	>	for (;;) {
751	>	ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w;
752	>	int id = (int)(top & WAITER_INDEX_MASK);
753	>	if (id <= 0 || (int)(top >>> EVENT_COUNT_SHIFT) == ec)
754	>	return;
755	>	if ((ws = workers).length < id || (w = ws[id - 1]) == null ||
756	>	!UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
757	>	top, top = w.nextWaiter))
758	>	continue outer;      // possibly stale; reread
759	>	LockSupport.unpark(w);
760	>	if (top != eventWaiters) // let someone else take over
761	>	return;
762	>	}
763	>	}
764		}
765
766		/**
767	<	* Create or resize array if necessary to hold newLength
768	<	* @return the array
767	>	* If worker is inactive, blocks until terminating or event count
768	>	* advances from last value held by worker; in any case helps
769	>	* release others.
770	>	*
771	>	* @param w the calling worker thread
772		*/
773	<	private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
774	<	ForkJoinWorkerThread[] ws = workers;
775	<	if (ws == null)
776	<	return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)];
777	<	else if (newLength > ws.length)
778	<	return workers = Arrays.copyOf(ws, arraySizeFor(newLength));
779	<	else
780	<	return ws;
773	>	private void eventSync(ForkJoinWorkerThread w) {
774	>	if (!w.active) {
775	>	int prev = w.lastEventCount;
776	>	long nextTop = (((long)prev << EVENT_COUNT_SHIFT) |
777	>	((long)(w.poolIndex + 1)));
778	>	long top;
779	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
780	>	(((int)(top = eventWaiters) & WAITER_INDEX_MASK) == 0 ||
781	>	(int)(top >>> EVENT_COUNT_SHIFT) == prev) &&
782	>	eventCount == prev) {
783	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
784	>	w.nextWaiter = top, nextTop)) {
785	>	accumulateStealCount(w); // transfer steals while idle
786	>	Thread.interrupted();    // clear/ignore interrupt
787	>	while (eventCount == prev)
788	>	w.doPark();
789	>	break;
790	>	}
791	>	}
792	>	w.lastEventCount = eventCount;
793	>	}
794	>	releaseWaiters();
795		}
796
797		/**
798	<	* Try to shrink workers into smaller array after one or more terminate
798	>	* Callback from workers invoked upon each top-level action (i.e.,
799	>	* stealing a task or taking a submission and running
800	>	* it). Performs one or both of the following:
801	>	*
802	>	* * If the worker cannot find work, updates its active status to
803	>	* inactive and updates activeCount unless there is contention, in
804	>	* which case it may try again (either in this or a subsequent
805	>	* call).  Additionally, awaits the next task event and/or helps
806	>	* wake up other releasable waiters.
807	>	*
808	>	* * If there are too many running threads, suspends this worker
809	>	* (first forcing inactivation if necessary).  If it is not
810	>	* resumed before a keepAlive elapses, the worker may be "trimmed"
811	>	* -- killed while suspended within suspendAsSpare. Otherwise,
812	>	* upon resume it rechecks to make sure that it is still needed.
813	>	*
814	>	* @param w the worker
815	>	* @param worked false if the worker scanned for work but didn't
816	>	* find any (in which case it may block waiting for work).
817		*/
818	<	private void tryShrinkWorkerArray() {
819	<	ForkJoinWorkerThread[] ws = workers;
820	<	int len = ws.length;
821	<	int last = len - 1;
822	<	while (last >= 0 && ws[last] == null)
823	<	--last;
824	<	int newLength = arraySizeFor(last+1);
825	<	if (newLength < len)
826	<	workers = Arrays.copyOf(ws, newLength);
818	>	final void preStep(ForkJoinWorkerThread w, boolean worked) {
819	>	boolean active = w.active;
820	>	boolean inactivate = !worked & active;
821	>	for (;;) {
822	>	if (inactivate) {
823	>	int c = runState;
824	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset,
825	>	c, c - ONE_ACTIVE))
826	>	inactivate = active = w.active = false;
827	>	}
828	>	int wc = workerCounts;
829	>	if ((wc & RUNNING_COUNT_MASK) <= parallelism) {
830	>	if (!worked)
831	>	eventSync(w);
832	>	return;
833	>	}
834	>	if (!(inactivate |= active) &&  // must inactivate to suspend
835	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
836	>	wc, wc - ONE_RUNNING) &&
837	>	!w.suspendAsSpare())        // false if trimmed
838	>	return;
839	>	}
840		}
841
842		/**
843	<	* Initial worker array and worker creation and startup. (This
844	<	* must be done under lock to avoid interference by some of the
845	<	* newly started threads while creating others.)
843	>	* Adjusts counts and creates or resumes compensating threads for
844	>	* a worker about to block on task joinMe, returning early if
845	>	* joinMe becomes ready. First tries resuming an existing spare
846	>	* (which usually also avoids any count adjustment), but must then
847	>	* decrement running count to determine whether a new thread is
848	>	* needed. See above for fuller explanation.
849		*/
850	<	private void createAndStartInitialWorkers(int ps) {
851	<	final ReentrantLock lock = this.workerLock;
852	<	lock.lock();
853	<	try {
854	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
855	<	for (int i = 0; i < ps; ++i) {
856	<	ForkJoinWorkerThread w = createWorker(i);
857	<	if (w != null) {
858	<	ws[i] = w;
859	<	w.start();
860	<	updateWorkerCount(1);
850	>	final void preJoin(ForkJoinTask<?> joinMe) {
851	>	boolean dec = false;       // true when running count decremented
852	>	for (;;) {
853	>	releaseWaiters();      // help other threads progress
854	>
855	>	if (joinMe.status < 0) // surround spare search with done checks
856	>	return;
857	>	ForkJoinWorkerThread spare = null;
858	>	for (ForkJoinWorkerThread w : workers) {
859	>	if (w != null && w.isSuspended()) {
860	>	spare = w;
861	>	break;
862	>	}
863	>	}
864	>	if (joinMe.status < 0)
865	>	return;
866	>
867	>	if (spare != null && spare.tryUnsuspend()) {
868	>	if (dec || joinMe.requestSignal() < 0) {
869	>	int c;
870	>	do {} while (!UNSAFE.compareAndSwapInt(this,
871	>	workerCountsOffset,
872	>	c = workerCounts,
873	>	c + ONE_RUNNING));
874	>	} // else no net count change
875	>	LockSupport.unpark(spare);
876	>	return;
877	>	}
878	>
879	>	int wc = workerCounts; // decrement running count
880	>	if (!dec && (wc & RUNNING_COUNT_MASK) != 0 &&
881	>	(dec = UNSAFE.compareAndSwapInt(this, workerCountsOffset,
882	>	wc, wc -= ONE_RUNNING)) &&
883	>	joinMe.requestSignal() < 0) { // cannot block
884	>	int c;                        // back out
885	>	do {} while (!UNSAFE.compareAndSwapInt(this,
886	>	workerCountsOffset,
887	>	c = workerCounts,
888	>	c + ONE_RUNNING));
889	>	return;
890	>	}
891	>
892	>	if (dec) {
893	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
894	>	int pc = parallelism;
895	>	int dc = pc - (wc & RUNNING_COUNT_MASK); // deficit count
896	>	if ((dc < pc && (dc <= 0 || (dc * dc < (tc - pc) * pc) ||
897	>	!maintainsParallelism)) ||
898	>	tc >= maxPoolSize) // cannot add
899	>	return;
900	>	if (spare == null &&
901	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
902	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
903	>	addWorker();
904	>	return;
905		}
906		}
464	–	} finally {
465	–	lock.unlock();
907		}
908		}
909
910		/**
911	<	* Worker creation and startup for threads added via setParallelism.
911	>	* Same idea as preJoin but with too many differing details to
912	>	* integrate: There are no task-based signal counts, and only one
913	>	* way to do the actual blocking. So for simplicity it is directly
914	>	* incorporated into this method.
915		*/
916	<	private void createAndStartAddedWorkers() {
917	<	resumeAllSpares();  // Allow spares to convert to nonspare
918	<	int ps = parallelism;
919	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
920	<	int len = ws.length;
921	<	// Sweep through slots, to keep lowest indices most populated
922	<	int k = 0;
923	<	while (k < len) {
924	<	if (ws[k] != null) {
925	<	++k;
926	<	continue;
916	>	final void doBlock(ManagedBlocker blocker, boolean maintainPar)
917	>	throws InterruptedException {
918	>	maintainPar &= maintainsParallelism; // override
919	>	boolean dec = false;
920	>	boolean done = false;
921	>	for (;;) {
922	>	releaseWaiters();
923	>	if (done = blocker.isReleasable())
924	>	break;
925	>	ForkJoinWorkerThread spare = null;
926	>	for (ForkJoinWorkerThread w : workers) {
927	>	if (w != null && w.isSuspended()) {
928	>	spare = w;
929	>	break;
930	>	}
931		}
932	<	int s = workerCounts;
485	<	int tc = totalCountOf(s);
486	<	int rc = runningCountOf(s);
487	<	if (rc >= ps || tc >= ps)
932	>	if (done = blocker.isReleasable())
933		break;
934	<	if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) {
935	<	ForkJoinWorkerThread w = createWorker(k);
936	<	if (w != null) {
937	<	ws[k++] = w;
938	<	w.start();
934	>	if (spare != null && spare.tryUnsuspend()) {
935	>	if (dec) {
936	>	int c;
937	>	do {} while (!UNSAFE.compareAndSwapInt(this,
938	>	workerCountsOffset,
939	>	c = workerCounts,
940	>	c + ONE_RUNNING));
941		}
942	<	else {
943	<	updateWorkerCount(-1); // back out on failed creation
942	>	LockSupport.unpark(spare);
943	>	break;
944	>	}
945	>	int wc = workerCounts;
946	>	if (!dec && (wc & RUNNING_COUNT_MASK) != 0)
947	>	dec = UNSAFE.compareAndSwapInt(this, workerCountsOffset,
948	>	wc, wc -= ONE_RUNNING);
949	>	if (dec) {
950	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
951	>	int pc = parallelism;
952	>	int dc = pc - (wc & RUNNING_COUNT_MASK);
953	>	if ((dc < pc && (dc <= 0 || (dc * dc < (tc - pc) * pc) ||
954	>	!maintainPar)) ||
955	>	tc >= maxPoolSize)
956	>	break;
957	>	if (spare == null &&
958	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
959	>	wc + (ONE_RUNNING|ONE_TOTAL))){
960	>	addWorker();
961		break;
962		}
963		}
964		}
965	+
966	+	try {
967	+	if (!done)
968	+	do {} while (!blocker.isReleasable() && !blocker.block());
969	+	} finally {
970	+	if (dec) {
971	+	int c;
972	+	do {} while (!UNSAFE.compareAndSwapInt(this,
973	+	workerCountsOffset,
974	+	c = workerCounts,
975	+	c + ONE_RUNNING));
976	+	}
977	+	}
978		}
979
980		/**
981	<	* Sets the handler for internal worker threads that terminate due
505	<	* to unrecoverable errors encountered while executing tasks.
506	<	* Unless set, the current default or ThreadGroup handler is used
507	<	* as handler.
981	>	* Possibly initiates and/or completes termination.
982		*
983	<	* @param h the new handler
984	<	* @return the old handler, or null if none
985	<	* @throws SecurityException if a security manager exists and
986	<	*         the caller is not permitted to modify threads
987	<	*         because it does not hold {@link
988	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
983	>	* @param now if true, unconditionally terminate, else only
984	>	* if shutdown and empty queue and no active workers
985	>	* @return true if now terminating or terminated
986	>	*/
987	>	private boolean tryTerminate(boolean now) {
988	>	if (now)
989	>	advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN
990	>	else if (runState < SHUTDOWN ||
991	>	!submissionQueue.isEmpty() ||
992	>	(runState & ACTIVE_COUNT_MASK) != 0)
993	>	return false;
994	>
995	>	if (advanceRunLevel(TERMINATING))
996	>	startTerminating();
997	>
998	>	// Finish now if all threads terminated; else in some subsequent call
999	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1000	>	advanceRunLevel(TERMINATED);
1001	>	terminationLatch.countDown();
1002	>	}
1003	>	return true;
1004	>	}
1005	>
1006	>	/**
1007	>	* Actions on transition to TERMINATING
1008		*/
1009	<	public Thread.UncaughtExceptionHandler
1010	<	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
1011	<	checkPermission();
1012	<	Thread.UncaughtExceptionHandler old = null;
1013	<	final ReentrantLock lock = this.workerLock;
1014	<	lock.lock();
1015	<	try {
1016	<	old = ueh;
1017	<	ueh = h;
1018	<	ForkJoinWorkerThread[] ws = workers;
1019	<	for (int i = 0; i < ws.length; ++i) {
1020	<	ForkJoinWorkerThread w = ws[i];
1021	<	if (w != null)
1022	<	w.setUncaughtExceptionHandler(h);
1009	>	private void startTerminating() {
1010	>	// Clear out and cancel submissions, ignoring exceptions
1011	>	ForkJoinTask<?> task;
1012	>	while ((task = submissionQueue.poll()) != null) {
1013	>	try {
1014	>	task.cancel(false);
1015	>	} catch (Throwable ignore) {
1016	>	}
1017	>	}
1018	>	// Propagate run level
1019	>	for (ForkJoinWorkerThread w : workers) {
1020	>	if (w != null)
1021	>	w.shutdown();    // also resumes suspended workers
1022	>	}
1023	>	// Ensure no straggling local tasks
1024	>	for (ForkJoinWorkerThread w : workers) {
1025	>	if (w != null)
1026	>	w.cancelTasks();
1027	>	}
1028	>	// Wake up idle workers
1029	>	advanceEventCount();
1030	>	releaseWaiters();
1031	>	// Unstick pending joins
1032	>	for (ForkJoinWorkerThread w : workers) {
1033	>	if (w != null && !w.isTerminated()) {
1034	>	try {
1035	>	w.interrupt();
1036	>	} catch (SecurityException ignore) {
1037	>	}
1038		}
531	–	} finally {
532	–	lock.unlock();
1039		}
534	–	return old;
1040		}
1041
1042	+	// misc support for ForkJoinWorkerThread
1043	+
1044		/**
1045	<	* Returns the handler for internal worker threads that terminate
539	<	* due to unrecoverable errors encountered while executing tasks.
540	<	* @return the handler, or null if none
1045	>	* Returns pool number
1046		*/
1047	<	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1048	<	Thread.UncaughtExceptionHandler h;
1049	<	final ReentrantLock lock = this.workerLock;
1050	<	lock.lock();
1051	<	try {
1052	<	h = ueh;
1053	<	} finally {
1054	<	lock.unlock();
1047	>	final int getPoolNumber() {
1048	>	return poolNumber;
1049	>	}
1050	>
1051	>	/**
1052	>	* Accumulates steal count from a worker, clearing
1053	>	* the worker's value
1054	>	*/
1055	>	final void accumulateStealCount(ForkJoinWorkerThread w) {
1056	>	int sc = w.stealCount;
1057	>	if (sc != 0) {
1058	>	long c;
1059	>	w.stealCount = 0;
1060	>	do {} while (!UNSAFE.compareAndSwapLong(this, stealCountOffset,
1061	>	c = stealCount, c + sc));
1062		}
1063	<	return h;
1063	>	}
1064	>
1065	>	/**
1066	>	* Returns the approximate (non-atomic) number of idle threads per
1067	>	* active thread.
1068	>	*/
1069	>	final int idlePerActive() {
1070	>	int ac = runState;    // no mask -- artifically boosts during shutdown
1071	>	int pc = parallelism; // use targeted parallelism, not rc
1072	>	// Use exact results for small values, saturate past 4
1073	>	return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
1074	>	}
1075	>
1076	>	/**
1077	>	* Returns the approximate (non-atomic) difference between running
1078	>	* and active counts.
1079	>	*/
1080	>	final int inactiveCount() {
1081	>	return (workerCounts & RUNNING_COUNT_MASK) -
1082	>	(runState & ACTIVE_COUNT_MASK);
1083	>	}
1084	>
1085	>	// Public and protected methods
1086	>
1087	>	// Constructors
1088	>
1089	>	/**
1090	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1091	>	* java.lang.Runtime#availableProcessors}, and using the {@linkplain
1092	>	* #defaultForkJoinWorkerThreadFactory default thread factory}.
1093	>	*
1094	>	* @throws SecurityException if a security manager exists and
1095	>	*         the caller is not permitted to modify threads
1096	>	*         because it does not hold {@link
1097	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1098	>	*/
1099	>	public ForkJoinPool() {
1100	>	this(Runtime.getRuntime().availableProcessors(),
1101	>	defaultForkJoinWorkerThreadFactory);
1102	>	}
1103	>
1104	>	/**
1105	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
1106	>	* level and using the {@linkplain
1107	>	* #defaultForkJoinWorkerThreadFactory default thread factory}.
1108	>	*
1109	>	* @param parallelism the parallelism level
1110	>	* @throws IllegalArgumentException if parallelism less than or
1111	>	*         equal to zero, or greater than implementation limit
1112	>	* @throws SecurityException if a security manager exists and
1113	>	*         the caller is not permitted to modify threads
1114	>	*         because it does not hold {@link
1115	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1116	>	*/
1117	>	public ForkJoinPool(int parallelism) {
1118	>	this(parallelism, defaultForkJoinWorkerThreadFactory);
1119	>	}
1120	>
1121	>	/**
1122	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1123	>	* java.lang.Runtime#availableProcessors}, and using the given
1124	>	* thread factory.
1125	>	*
1126	>	* @param factory the factory for creating new threads
1127	>	* @throws NullPointerException if the factory is null
1128	>	* @throws SecurityException if a security manager exists and
1129	>	*         the caller is not permitted to modify threads
1130	>	*         because it does not hold {@link
1131	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1132	>	*/
1133	>	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
1134	>	this(Runtime.getRuntime().availableProcessors(), factory);
1135	>	}
1136	>
1137	>	/**
1138	>	* Creates a {@code ForkJoinPool} with the given parallelism and
1139	>	* thread factory.
1140	>	*
1141	>	* @param parallelism the parallelism level
1142	>	* @param factory the factory for creating new threads
1143	>	* @throws IllegalArgumentException if parallelism less than or
1144	>	*         equal to zero, or greater than implementation limit
1145	>	* @throws NullPointerException if the factory is null
1146	>	* @throws SecurityException if a security manager exists and
1147	>	*         the caller is not permitted to modify threads
1148	>	*         because it does not hold {@link
1149	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1150	>	*/
1151	>	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
1152	>	checkPermission();
1153	>	if (factory == null)
1154	>	throw new NullPointerException();
1155	>	if (parallelism <= 0 || parallelism > MAX_THREADS)
1156	>	throw new IllegalArgumentException();
1157	>	this.poolNumber = poolNumberGenerator.incrementAndGet();
1158	>	int arraySize = initialArraySizeFor(parallelism);
1159	>	this.parallelism = parallelism;
1160	>	this.factory = factory;
1161	>	this.maxPoolSize = MAX_THREADS;
1162	>	this.maintainsParallelism = true;
1163	>	this.workers = new ForkJoinWorkerThread[arraySize];
1164	>	this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
1165	>	this.workerLock = new ReentrantLock();
1166	>	this.terminationLatch = new CountDownLatch(1);
1167	>	// Start first worker; remaining workers added upon first submission
1168	>	workerCounts = ONE_RUNNING | ONE_TOTAL;
1169	>	addWorker();
1170	>	}
1171	>
1172	>	/**
1173	>	* Returns initial power of two size for workers array.
1174	>	* @param pc the initial parallelism level
1175	>	*/
1176	>	private static int initialArraySizeFor(int pc) {
1177	>	// See Hackers Delight, sec 3.2. We know MAX_THREADS < (1 >>> 16)
1178	>	int size = pc < MAX_THREADS ? pc + 1 : MAX_THREADS;
1179	>	size |= size >>> 1;
1180	>	size |= size >>> 2;
1181	>	size |= size >>> 4;
1182	>	size |= size >>> 8;
1183	>	return size + 1;
1184		}
1185
1186		// Execution methods
#	Line 557 | Line 1189 | public class ForkJoinPool extends Abstra
1189		* Common code for execute, invoke and submit
1190		*/
1191		private <T> void doSubmit(ForkJoinTask<T> task) {
1192	<	if (isShutdown())
1192	>	if (task == null)
1193	>	throw new NullPointerException();
1194	>	if (runState >= SHUTDOWN)
1195		throw new RejectedExecutionException();
1196		submissionQueue.offer(task);
1197	<	signalIdleWorkers(true);
1197	>	advanceEventCount();
1198	>	releaseWaiters();
1199	>	if ((workerCounts >>> TOTAL_COUNT_SHIFT) < parallelism)
1200	>	ensureEnoughTotalWorkers();
1201		}
1202
1203		/**
1204	<	* Performs the given task; returning its result upon completion
1204	>	* Performs the given task, returning its result upon completion.
1205	>	*
1206		* @param task the task
1207		* @return the task's result
1208	<	* @throws NullPointerException if task is null
1209	<	* @throws RejectedExecutionException if pool is shut down
1208	>	* @throws NullPointerException if the task is null
1209	>	* @throws RejectedExecutionException if the task cannot be
1210	>	*         scheduled for execution
1211		*/
1212		public <T> T invoke(ForkJoinTask<T> task) {
1213		doSubmit(task);
#	Line 577 | Line 1216 | public class ForkJoinPool extends Abstra
1216
1217		/**
1218		* Arranges for (asynchronous) execution of the given task.
1219	+	*
1220		* @param task the task
1221	<	* @throws NullPointerException if task is null
1222	<	* @throws RejectedExecutionException if pool is shut down
1221	>	* @throws NullPointerException if the task is null
1222	>	* @throws RejectedExecutionException if the task cannot be
1223	>	*         scheduled for execution
1224		*/
1225	<	public <T> void execute(ForkJoinTask<T> task) {
1225	>	public void execute(ForkJoinTask<?> task) {
1226		doSubmit(task);
1227		}
1228
1229		// AbstractExecutorService methods
1230
1231	+	/**
1232	+	* @throws NullPointerException if the task is null
1233	+	* @throws RejectedExecutionException if the task cannot be
1234	+	*         scheduled for execution
1235	+	*/
1236		public void execute(Runnable task) {
1237	<	doSubmit(new AdaptedRunnable<Void>(task, null));
1237	>	ForkJoinTask<?> job;
1238	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1239	>	job = (ForkJoinTask<?>) task;
1240	>	else
1241	>	job = ForkJoinTask.adapt(task, null);
1242	>	doSubmit(job);
1243		}
1244
1245	+	/**
1246	+	* @throws NullPointerException if the task is null
1247	+	* @throws RejectedExecutionException if the task cannot be
1248	+	*         scheduled for execution
1249	+	*/
1250		public <T> ForkJoinTask<T> submit(Callable<T> task) {
1251	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
1251	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
1252		doSubmit(job);
1253		return job;
1254		}
1255
1256	+	/**
1257	+	* @throws NullPointerException if the task is null
1258	+	* @throws RejectedExecutionException if the task cannot be
1259	+	*         scheduled for execution
1260	+	*/
1261		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
1262	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
1262	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
1263		doSubmit(job);
1264		return job;
1265		}
1266
1267	+	/**
1268	+	* @throws NullPointerException if the task is null
1269	+	* @throws RejectedExecutionException if the task cannot be
1270	+	*         scheduled for execution
1271	+	*/
1272		public ForkJoinTask<?> submit(Runnable task) {
1273	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
1273	>	ForkJoinTask<?> job;
1274	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
1275	>	job = (ForkJoinTask<?>) task;
1276	>	else
1277	>	job = ForkJoinTask.adapt(task, null);
1278		doSubmit(job);
1279		return job;
1280		}
1281
612	–	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
613	–	return new AdaptedRunnable(runnable, value);
614	–	}
615	–
616	–	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
617	–	return new AdaptedCallable(callable);
618	–	}
619	–
1282		/**
1283	<	* Adaptor for Runnables. This implements RunnableFuture
1284	<	* to be compliant with AbstractExecutorService constraints
1283	>	* Submits a ForkJoinTask for execution.
1284	>	*
1285	>	* @param task the task to submit
1286	>	* @return the task
1287	>	* @throws NullPointerException if the task is null
1288	>	* @throws RejectedExecutionException if the task cannot be
1289	>	*         scheduled for execution
1290		*/
1291	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1292	<	implements RunnableFuture<T> {
1293	<	final Runnable runnable;
627	<	final T resultOnCompletion;
628	<	T result;
629	<	AdaptedRunnable(Runnable runnable, T result) {
630	<	if (runnable == null) throw new NullPointerException();
631	<	this.runnable = runnable;
632	<	this.resultOnCompletion = result;
633	<	}
634	<	public T getRawResult() { return result; }
635	<	public void setRawResult(T v) { result = v; }
636	<	public boolean exec() {
637	<	runnable.run();
638	<	result = resultOnCompletion;
639	<	return true;
640	<	}
641	<	public void run() { invoke(); }
1291	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1292	>	doSubmit(task);
1293	>	return task;
1294		}
1295
1296		/**
1297	<	* Adaptor for Callables
1297	>	* @throws NullPointerException       {@inheritDoc}
1298	>	* @throws RejectedExecutionException {@inheritDoc}
1299		*/
647	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
648	–	implements RunnableFuture<T> {
649	–	final Callable<T> callable;
650	–	T result;
651	–	AdaptedCallable(Callable<T> callable) {
652	–	if (callable == null) throw new NullPointerException();
653	–	this.callable = callable;
654	–	}
655	–	public T getRawResult() { return result; }
656	–	public void setRawResult(T v) { result = v; }
657	–	public boolean exec() {
658	–	try {
659	–	result = callable.call();
660	–	return true;
661	–	} catch (Error err) {
662	–	throw err;
663	–	} catch (RuntimeException rex) {
664	–	throw rex;
665	–	} catch (Exception ex) {
666	–	throw new RuntimeException(ex);
667	–	}
668	–	}
669	–	public void run() { invoke(); }
670	–	}
671	–
1300		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
1301	<	ArrayList<ForkJoinTask<T>> ts =
1301	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
1302		new ArrayList<ForkJoinTask<T>>(tasks.size());
1303	<	for (Callable<T> c : tasks)
1304	<	ts.add(new AdaptedCallable<T>(c));
1305	<	invoke(new InvokeAll<T>(ts));
1306	<	return (List<Future<T>>)(List)ts;
1303	>	for (Callable<T> task : tasks)
1304	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
1305	>	invoke(new InvokeAll<T>(forkJoinTasks));
1306	>
1307	>	@SuppressWarnings({"unchecked", "rawtypes"})
1308	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
1309	>	return futures;
1310		}
1311
1312		static final class InvokeAll<T> extends RecursiveAction {
1313		final ArrayList<ForkJoinTask<T>> tasks;
1314		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
1315		public void compute() {
1316	<	try { invokeAll(tasks); } catch(Exception ignore) {}
1316	>	try { invokeAll(tasks); }
1317	>	catch (Exception ignore) {}
1318		}
1319	+	private static final long serialVersionUID = -7914297376763021607L;
1320		}
1321
689	–	// Configuration and status settings and queries
690	–
1322		/**
1323	<	* Returns the factory used for constructing new workers
1323	>	* Returns the factory used for constructing new workers.
1324		*
1325		* @return the factory used for constructing new workers
1326		*/
#	Line 698 | Line 1329 | public class ForkJoinPool extends Abstra
1329		}
1330
1331		/**
1332	<	* Sets the target paralleism level of this pool.
1332	>	* Returns the handler for internal worker threads that terminate
1333	>	* due to unrecoverable errors encountered while executing tasks.
1334	>	*
1335	>	* @return the handler, or {@code null} if none
1336	>	*/
1337	>	public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1338	>	workerCountReadFence();
1339	>	return ueh;
1340	>	}
1341	>
1342	>	/**
1343	>	* Sets the handler for internal worker threads that terminate due
1344	>	* to unrecoverable errors encountered while executing tasks.
1345	>	* Unless set, the current default or ThreadGroup handler is used
1346	>	* as handler.
1347	>	*
1348	>	* @param h the new handler
1349	>	* @return the old handler, or {@code null} if none
1350	>	* @throws SecurityException if a security manager exists and
1351	>	*         the caller is not permitted to modify threads
1352	>	*         because it does not hold {@link
1353	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1354	>	*/
1355	>	public Thread.UncaughtExceptionHandler
1356	>	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
1357	>	checkPermission();
1358	>	workerCountReadFence();
1359	>	Thread.UncaughtExceptionHandler old = ueh;
1360	>	if (h != old) {
1361	>	ueh = h;
1362	>	workerCountWriteFence();
1363	>	for (ForkJoinWorkerThread w : workers) {
1364	>	if (w != null)
1365	>	w.setUncaughtExceptionHandler(h);
1366	>	}
1367	>	}
1368	>	return old;
1369	>	}
1370	>
1371	>	/**
1372	>	* Sets the target parallelism level of this pool.
1373	>	*
1374		* @param parallelism the target parallelism
1375		* @throws IllegalArgumentException if parallelism less than or
1376	<	* equal to zero or greater than maximum size bounds.
1376	>	* equal to zero or greater than maximum size bounds
1377		* @throws SecurityException if a security manager exists and
1378		*         the caller is not permitted to modify threads
1379		*         because it does not hold {@link
1380	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1380	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1381		*/
1382		public void setParallelism(int parallelism) {
1383		checkPermission();
1384		if (parallelism <= 0 || parallelism > maxPoolSize)
1385		throw new IllegalArgumentException();
1386	<	final ReentrantLock lock = this.workerLock;
1387	<	lock.lock();
1388	<	try {
1389	<	if (!isTerminating()) {
1390	<	int p = this.parallelism;
1391	<	this.parallelism = parallelism;
1392	<	if (parallelism > p)
1393	<	createAndStartAddedWorkers();
1394	<	else
1395	<	trimSpares();
1386	>	workerCountReadFence();
1387	>	int pc = this.parallelism;
1388	>	if (pc != parallelism) {
1389	>	this.parallelism = parallelism;
1390	>	workerCountWriteFence();
1391	>	// Release spares. If too many, some will die after re-suspend
1392	>	for (ForkJoinWorkerThread w : workers) {
1393	>	if (w != null && w.tryUnsuspend()) {
1394	>	updateRunningCount(1);
1395	>	LockSupport.unpark(w);
1396	>	}
1397		}
1398	<	} finally {
1399	<	lock.unlock();
1398	>	ensureEnoughTotalWorkers();
1399	>	advanceEventCount();
1400	>	releaseWaiters(); // force config recheck by existing workers
1401		}
728	–	signalIdleWorkers(false);
1402		}
1403
1404		/**
1405	<	* Returns the targeted number of worker threads in this pool.
733	<	* This value does not necessarily reflect transient changes as
734	<	* threads are added, removed, or abruptly terminate.
1405	>	* Returns the targeted parallelism level of this pool.
1406		*
1407	<	* @return the targeted number of worker threads in this pool
1407	>	* @return the targeted parallelism level of this pool
1408		*/
1409		public int getParallelism() {
1410	+	//        workerCountReadFence(); // inlined below
1411	+	int ignore = workerCounts;
1412		return parallelism;
1413		}
1414
1415		/**
1416		* Returns the number of worker threads that have started but not
1417		* yet terminated.  This result returned by this method may differ
1418	<	* from <tt>getParallelism</tt> when threads are created to
1418	>	* from {@link #getParallelism} when threads are created to
1419		* maintain parallelism when others are cooperatively blocked.
1420		*
1421		* @return the number of worker threads
1422		*/
1423		public int getPoolSize() {
1424	<	return totalCountOf(workerCounts);
1424	>	return workerCounts >>> TOTAL_COUNT_SHIFT;
1425		}
1426
1427		/**
1428		* Returns the maximum number of threads allowed to exist in the
1429	<	* pool, even if there are insufficient unblocked running threads.
1429	>	* pool. Unless set using {@link #setMaximumPoolSize}, the
1430	>	* maximum is an implementation-defined value designed only to
1431	>	* prevent runaway growth.
1432	>	*
1433		* @return the maximum
1434		*/
1435		public int getMaximumPoolSize() {
1436	+	workerCountReadFence();
1437		return maxPoolSize;
1438		}
1439
1440		/**
1441		* Sets the maximum number of threads allowed to exist in the
1442	<	* pool, even if there are insufficient unblocked running threads.
1443	<	* Setting this value has no effect on current pool size. It
1444	<	* controls construction of new threads.
1445	<	* @throws IllegalArgumentException if negative or greater then
1446	<	* internal implementation limit.
1442	>	* pool. The given value should normally be greater than or equal
1443	>	* to the {@link #getParallelism parallelism} level. Setting this
1444	>	* value has no effect on current pool size. It controls
1445	>	* construction of new threads.
1446	>	*
1447	>	* @throws IllegalArgumentException if negative or greater than
1448	>	* internal implementation limit
1449		*/
1450		public void setMaximumPoolSize(int newMax) {
1451		if (newMax < 0 || newMax > MAX_THREADS)
1452		throw new IllegalArgumentException();
1453		maxPoolSize = newMax;
1454	+	workerCountWriteFence();
1455		}
1456
777	–
1457		/**
1458	<	* Returns true if this pool dynamically maintains its target
1459	<	* parallelism level. If false, new threads are added only to
1460	<	* avoid possible starvation.
1461	<	* This setting is by default true;
1462	<	* @return true if maintains parallelism
1458	>	* Returns {@code true} if this pool dynamically maintains its
1459	>	* target parallelism level. If false, new threads are added only
1460	>	* to avoid possible starvation.  This setting is by default true.
1461	>	*
1462	>	* @return {@code true} if maintains parallelism
1463		*/
1464		public boolean getMaintainsParallelism() {
1465	+	workerCountReadFence();
1466		return maintainsParallelism;
1467		}
1468
#	Line 790 | Line 1470 | public class ForkJoinPool extends Abstra
1470		* Sets whether this pool dynamically maintains its target
1471		* parallelism level. If false, new threads are added only to
1472		* avoid possible starvation.
1473	<	* @param enable true to maintains parallelism
1473	>	*
1474	>	* @param enable {@code true} to maintain parallelism
1475		*/
1476		public void setMaintainsParallelism(boolean enable) {
1477		maintainsParallelism = enable;
1478	+	workerCountWriteFence();
1479		}
1480
1481		/**
1482	<	* Returns the approximate number of worker threads that are not
1483	<	* blocked waiting to join tasks or for other managed
1484	<	* synchronization.
1482	>	* Establishes local first-in-first-out scheduling mode for forked
1483	>	* tasks that are never joined. This mode may be more appropriate
1484	>	* than default locally stack-based mode in applications in which
1485	>	* worker threads only process asynchronous tasks.  This method is
1486	>	* designed to be invoked only when the pool is quiescent, and
1487	>	* typically only before any tasks are submitted. The effects of
1488	>	* invocations at other times may be unpredictable.
1489	>	*
1490	>	* @param async if {@code true}, use locally FIFO scheduling
1491	>	* @return the previous mode
1492	>	* @see #getAsyncMode
1493	>	*/
1494	>	public boolean setAsyncMode(boolean async) {
1495	>	workerCountReadFence();
1496	>	boolean oldMode = locallyFifo;
1497	>	if (oldMode != async) {
1498	>	locallyFifo = async;
1499	>	workerCountWriteFence();
1500	>	for (ForkJoinWorkerThread w : workers) {
1501	>	if (w != null)
1502	>	w.setAsyncMode(async);
1503	>	}
1504	>	}
1505	>	return oldMode;
1506	>	}
1507	>
1508	>	/**
1509	>	* Returns {@code true} if this pool uses local first-in-first-out
1510	>	* scheduling mode for forked tasks that are never joined.
1511	>	*
1512	>	* @return {@code true} if this pool uses async mode
1513	>	* @see #setAsyncMode
1514	>	*/
1515	>	public boolean getAsyncMode() {
1516	>	workerCountReadFence();
1517	>	return locallyFifo;
1518	>	}
1519	>
1520	>	/**
1521	>	* Returns an estimate of the number of worker threads that are
1522	>	* not blocked waiting to join tasks or for other managed
1523	>	* synchronization. This method may overestimate the
1524	>	* number of running threads.
1525		*
1526		* @return the number of worker threads
1527		*/
1528		public int getRunningThreadCount() {
1529	<	return runningCountOf(workerCounts);
1529	>	return workerCounts & RUNNING_COUNT_MASK;
1530		}
1531
1532		/**
1533	<	* Returns the approximate number of threads that are currently
1533	>	* Returns an estimate of the number of threads that are currently
1534		* stealing or executing tasks. This method may overestimate the
1535		* number of active threads.
1536	<	* @return the number of active threads.
1536	>	*
1537	>	* @return the number of active threads
1538		*/
1539		public int getActiveThreadCount() {
1540	<	return activeCountOf(runControl);
818	<	}
819	<
820	<	/**
821	<	* Returns the approximate number of threads that are currently
822	<	* idle waiting for tasks. This method may underestimate the
823	<	* number of idle threads.
824	<	* @return the number of idle threads.
825	<	*/
826	<	final int getIdleThreadCount() {
827	<	int c = runningCountOf(workerCounts) - activeCountOf(runControl);
828	<	return (c <= 0)? 0 : c;
1540	>	return runState & ACTIVE_COUNT_MASK;
1541		}
1542
1543		/**
1544	<	* Returns true if all worker threads are currently idle. An idle
1545	<	* worker is one that cannot obtain a task to execute because none
1546	<	* are available to steal from other threads, and there are no
1547	<	* pending submissions to the pool. This method is conservative:
1548	<	* It might not return true immediately upon idleness of all
1549	<	* threads, but will eventually become true if threads remain
1550	<	* inactive.
1551	<	* @return true if all threads are currently idle
1544	>	* Returns {@code true} if all worker threads are currently idle.
1545	>	* An idle worker is one that cannot obtain a task to execute
1546	>	* because none are available to steal from other threads, and
1547	>	* there are no pending submissions to the pool. This method is
1548	>	* conservative; it might not return {@code true} immediately upon
1549	>	* idleness of all threads, but will eventually become true if
1550	>	* threads remain inactive.
1551	>	*
1552	>	* @return {@code true} if all threads are currently idle
1553		*/
1554		public boolean isQuiescent() {
1555	<	return activeCountOf(runControl) == 0;
1555	>	return (runState & ACTIVE_COUNT_MASK) == 0;
1556		}
1557
1558		/**
#	Line 847 | Line 1560 | public class ForkJoinPool extends Abstra
1560		* one thread's work queue by another. The reported value
1561		* underestimates the actual total number of steals when the pool
1562		* is not quiescent. This value may be useful for monitoring and
1563	<	* tuning fork/join programs: In general, steal counts should be
1563	>	* tuning fork/join programs: in general, steal counts should be
1564		* high enough to keep threads busy, but low enough to avoid
1565		* overhead and contention across threads.
1566	<	* @return the number of steals.
1566	>	*
1567	>	* @return the number of steals
1568		*/
1569		public long getStealCount() {
1570	<	return stealCount.get();
1570	>	return stealCount;
1571		}
1572
1573		/**
1574	<	* Accumulate steal count from a worker. Call only
1575	<	* when worker known to be idle.
1576	<	*/
1577	<	private void updateStealCount(ForkJoinWorkerThread w) {
1578	<	int sc = w.getAndClearStealCount();
1579	<	if (sc != 0)
1580	<	stealCount.addAndGet(sc);
1581	<	}
868	<
869	<	/**
870	<	* Returns the total number of tasks currently held in queues by
871	<	* worker threads (but not including tasks submitted to the pool
872	<	* that have not begun executing). This value is only an
873	<	* approximation, obtained by iterating across all threads in the
874	<	* pool. This method may be useful for tuning task granularities.
875	<	* @return the number of queued tasks.
1574	>	* Returns an estimate of the total number of tasks currently held
1575	>	* in queues by worker threads (but not including tasks submitted
1576	>	* to the pool that have not begun executing). This value is only
1577	>	* an approximation, obtained by iterating across all threads in
1578	>	* the pool. This method may be useful for tuning task
1579	>	* granularities.
1580	>	*
1581	>	* @return the number of queued tasks
1582		*/
1583		public long getQueuedTaskCount() {
1584		long count = 0;
1585	<	ForkJoinWorkerThread[] ws = workers;
1586	<	for (int i = 0; i < ws.length; ++i) {
1587	<	ForkJoinWorkerThread t = ws[i];
882	<	if (t != null)
883	<	count += t.getQueueSize();
1585	>	for (ForkJoinWorkerThread w : workers) {
1586	>	if (w != null)
1587	>	count += w.getQueueSize();
1588		}
1589		return count;
1590		}
1591
1592		/**
1593	<	* Returns the approximate number tasks submitted to this pool
1594	<	* that have not yet begun executing. This method takes time
1593	>	* Returns an estimate of the number of tasks submitted to this
1594	>	* pool that have not yet begun executing.  This method takes time
1595		* proportional to the number of submissions.
1596	<	* @return the number of queued submissions.
1596	>	*
1597	>	* @return the number of queued submissions
1598		*/
1599		public int getQueuedSubmissionCount() {
1600		return submissionQueue.size();
1601		}
1602
1603		/**
1604	<	* Returns true if there are any tasks submitted to this pool
1605	<	* that have not yet begun executing.
1606	<	* @return <tt>true</tt> if there are any queued submissions.
1604	>	* Returns {@code true} if there are any tasks submitted to this
1605	>	* pool that have not yet begun executing.
1606	>	*
1607	>	* @return {@code true} if there are any queued submissions
1608		*/
1609		public boolean hasQueuedSubmissions() {
1610		return !submissionQueue.isEmpty();
#	Line 908 | Line 1614 | public class ForkJoinPool extends Abstra
1614		* Removes and returns the next unexecuted submission if one is
1615		* available.  This method may be useful in extensions to this
1616		* class that re-assign work in systems with multiple pools.
1617	<	* @return the next submission, or null if none
1617	>	*
1618	>	* @return the next submission, or {@code null} if none
1619		*/
1620		protected ForkJoinTask<?> pollSubmission() {
1621		return submissionQueue.poll();
1622		}
1623
1624		/**
1625	+	* Removes all available unexecuted submitted and forked tasks
1626	+	* from scheduling queues and adds them to the given collection,
1627	+	* without altering their execution status. These may include
1628	+	* artificially generated or wrapped tasks. This method is
1629	+	* designed to be invoked only when the pool is known to be
1630	+	* quiescent. Invocations at other times may not remove all
1631	+	* tasks. A failure encountered while attempting to add elements
1632	+	* to collection {@code c} may result in elements being in
1633	+	* neither, either or both collections when the associated
1634	+	* exception is thrown.  The behavior of this operation is
1635	+	* undefined if the specified collection is modified while the
1636	+	* operation is in progress.
1637	+	*
1638	+	* @param c the collection to transfer elements into
1639	+	* @return the number of elements transferred
1640	+	*/
1641	+	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1642	+	int n = submissionQueue.drainTo(c);
1643	+	for (ForkJoinWorkerThread w : workers) {
1644	+	if (w != null)
1645	+	n += w.drainTasksTo(c);
1646	+	}
1647	+	return n;
1648	+	}
1649	+
1650	+	/**
1651		* Returns a string identifying this pool, as well as its state,
1652		* including indications of run state, parallelism level, and
1653		* worker and task counts.
#	Line 922 | Line 1655 | public class ForkJoinPool extends Abstra
1655		* @return a string identifying this pool, as well as its state
1656		*/
1657		public String toString() {
925	–	int ps = parallelism;
926	–	int wc = workerCounts;
927	–	int rc = runControl;
1658		long st = getStealCount();
1659		long qt = getQueuedTaskCount();
1660		long qs = getQueuedSubmissionCount();
1661	+	int wc = workerCounts;
1662	+	int tc = wc >>> TOTAL_COUNT_SHIFT;
1663	+	int rc = wc & RUNNING_COUNT_MASK;
1664	+	int pc = parallelism;
1665	+	int rs = runState;
1666	+	int ac = rs & ACTIVE_COUNT_MASK;
1667		return super.toString() +
1668	<	"[" + runStateToString(runStateOf(rc)) +
1669	<	", parallelism = " + ps +
1670	<	", size = " + totalCountOf(wc) +
1671	<	", active = " + activeCountOf(rc) +
1672	<	", running = " + runningCountOf(wc) +
1668	>	"[" + runLevelToString(rs) +
1669	>	", parallelism = " + pc +
1670	>	", size = " + tc +
1671	>	", active = " + ac +
1672	>	", running = " + rc +
1673		", steals = " + st +
1674		", tasks = " + qt +
1675		", submissions = " + qs +
1676		"]";
1677		}
1678
1679	<	private static String runStateToString(int rs) {
1680	<	switch(rs) {
1681	<	case RUNNING: return "Running";
1682	<	case SHUTDOWN: return "Shutting down";
1683	<	case TERMINATING: return "Terminating";
948	<	case TERMINATED: return "Terminated";
949	<	default: throw new Error("Unknown run state");
950	<	}
1679	>	private static String runLevelToString(int s) {
1680	>	return ((s & TERMINATED) != 0 ? "Terminated" :
1681	>	((s & TERMINATING) != 0 ? "Terminating" :
1682	>	((s & SHUTDOWN) != 0 ? "Shutting down" :
1683	>	"Running")));
1684		}
1685
953	–	// lifecycle control
954	–
1686		/**
1687		* Initiates an orderly shutdown in which previously submitted
1688		* tasks are executed, but no new tasks will be accepted.
1689		* Invocation has no additional effect if already shut down.
1690		* Tasks that are in the process of being submitted concurrently
1691		* during the course of this method may or may not be rejected.
1692	+	*
1693		* @throws SecurityException if a security manager exists and
1694		*         the caller is not permitted to modify threads
1695		*         because it does not hold {@link
1696	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1696	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1697		*/
1698		public void shutdown() {
1699		checkPermission();
1700	<	transitionRunStateTo(SHUTDOWN);
1701	<	if (canTerminateOnShutdown(runControl))
970	<	terminateOnShutdown();
1700	>	advanceRunLevel(SHUTDOWN);
1701	>	tryTerminate(false);
1702		}
1703
1704		/**
1705	<	* Attempts to stop all actively executing tasks, and cancels all
1706	<	* waiting tasks.  Tasks that are in the process of being
1707	<	* submitted or executed concurrently during the course of this
1708	<	* method may or may not be rejected. Unlike some other executors,
1709	<	* this method cancels rather than collects non-executed tasks,
1710	<	* so always returns an empty list.
1705	>	* Attempts to cancel and/or stop all tasks, and reject all
1706	>	* subsequently submitted tasks.  Tasks that are in the process of
1707	>	* being submitted or executed concurrently during the course of
1708	>	* this method may or may not be rejected. This method cancels
1709	>	* both existing and unexecuted tasks, in order to permit
1710	>	* termination in the presence of task dependencies. So the method
1711	>	* always returns an empty list (unlike the case for some other
1712	>	* Executors).
1713	>	*
1714		* @return an empty list
1715		* @throws SecurityException if a security manager exists and
1716		*         the caller is not permitted to modify threads
1717		*         because it does not hold {@link
1718	<	*         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
1718	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1719		*/
1720		public List<Runnable> shutdownNow() {
1721		checkPermission();
1722	<	terminate();
1722	>	tryTerminate(true);
1723		return Collections.emptyList();
1724		}
1725
1726		/**
1727	<	* Returns <tt>true</tt> if all tasks have completed following shut down.
1727	>	* Returns {@code true} if all tasks have completed following shut down.
1728		*
1729	<	* @return <tt>true</tt> if all tasks have completed following shut down
1729	>	* @return {@code true} if all tasks have completed following shut down
1730		*/
1731		public boolean isTerminated() {
1732	<	return runStateOf(runControl) == TERMINATED;
1732	>	return runState >= TERMINATED;
1733		}
1734
1735		/**
1736	<	* Returns <tt>true</tt> if the process of termination has
1737	<	* commenced but possibly not yet completed.
1736	>	* Returns {@code true} if the process of termination has
1737	>	* commenced but not yet completed.  This method may be useful for
1738	>	* debugging. A return of {@code true} reported a sufficient
1739	>	* period after shutdown may indicate that submitted tasks have
1740	>	* ignored or suppressed interruption, causing this executor not
1741	>	* to properly terminate.
1742		*
1743	<	* @return <tt>true</tt> if terminating
1743	>	* @return {@code true} if terminating but not yet terminated
1744		*/
1745		public boolean isTerminating() {
1746	<	return runStateOf(runControl) >= TERMINATING;
1746	>	return (runState & (TERMINATING|TERMINATED)) == TERMINATING;
1747		}
1748
1749		/**
1750	<	* Returns <tt>true</tt> if this pool has been shut down.
1750	>	* Returns {@code true} if this pool has been shut down.
1751		*
1752	<	* @return <tt>true</tt> if this pool has been shut down
1752	>	* @return {@code true} if this pool has been shut down
1753		*/
1754		public boolean isShutdown() {
1755	<	return runStateOf(runControl) >= SHUTDOWN;
1755	>	return runState >= SHUTDOWN;
1756		}
1757
1758		/**
#	Line 1024 | Line 1762 | public class ForkJoinPool extends Abstra
1762		*
1763		* @param timeout the maximum time to wait
1764		* @param unit the time unit of the timeout argument
1765	<	* @return <tt>true</tt> if this executor terminated and
1766	<	*         <tt>false</tt> if the timeout elapsed before termination
1765	>	* @return {@code true} if this executor terminated and
1766	>	*         {@code false} if the timeout elapsed before termination
1767		* @throws InterruptedException if interrupted while waiting
1768		*/
1769		public boolean awaitTermination(long timeout, TimeUnit unit)
1770		throws InterruptedException {
1771	<	long nanos = unit.toNanos(timeout);
1034	<	final ReentrantLock lock = this.workerLock;
1035	<	lock.lock();
1036	<	try {
1037	<	for (;;) {
1038	<	if (isTerminated())
1039	<	return true;
1040	<	if (nanos <= 0)
1041	<	return false;
1042	<	nanos = termination.awaitNanos(nanos);
1043	<	}
1044	<	} finally {
1045	<	lock.unlock();
1046	<	}
1771	>	return terminationLatch.await(timeout, unit);
1772		}
1773
1049	–	// Shutdown and termination support
1050	–
1774		/**
1775	<	* Callback from terminating worker. Null out the corresponding
1776	<	* workers slot, and if terminating, try to terminate, else try to
1054	<	* shrink workers array.
1055	<	* @param w the worker
1056	<	*/
1057	<	final void workerTerminated(ForkJoinWorkerThread w) {
1058	<	updateStealCount(w);
1059	<	updateWorkerCount(-1);
1060	<	final ReentrantLock lock = this.workerLock;
1061	<	lock.lock();
1062	<	try {
1063	<	ForkJoinWorkerThread[] ws = workers;
1064	<	int idx = w.poolIndex;
1065	<	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1066	<	ws[idx] = null;
1067	<	if (totalCountOf(workerCounts) == 0) {
1068	<	terminate(); // no-op if already terminating
1069	<	transitionRunStateTo(TERMINATED);
1070	<	termination.signalAll();
1071	<	}
1072	<	else if (!isTerminating()) {
1073	<	tryShrinkWorkerArray();
1074	<	tryResumeSpare(true); // allow replacement
1075	<	}
1076	<	} finally {
1077	<	lock.unlock();
1078	<	}
1079	<	signalIdleWorkers(false);
1080	<	}
1081	<
1082	<	/**
1083	<	* Initiate termination.
1084	<	*/
1085	<	private void terminate() {
1086	<	if (transitionRunStateTo(TERMINATING)) {
1087	<	stopAllWorkers();
1088	<	resumeAllSpares();
1089	<	signalIdleWorkers(true);
1090	<	cancelQueuedSubmissions();
1091	<	cancelQueuedWorkerTasks();
1092	<	interruptUnterminatedWorkers();
1093	<	signalIdleWorkers(true); // resignal after interrupt
1094	<	}
1095	<	}
1096	<
1097	<	/**
1098	<	* Possibly terminate when on shutdown state
1099	<	*/
1100	<	private void terminateOnShutdown() {
1101	<	if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
1102	<	terminate();
1103	<	}
1104	<
1105	<	/**
1106	<	* Clear out and cancel submissions
1107	<	*/
1108	<	private void cancelQueuedSubmissions() {
1109	<	ForkJoinTask<?> task;
1110	<	while ((task = pollSubmission()) != null)
1111	<	task.cancel(false);
1112	<	}
1113	<
1114	<	/**
1115	<	* Clean out worker queues.
1116	<	*/
1117	<	private void cancelQueuedWorkerTasks() {
1118	<	final ReentrantLock lock = this.workerLock;
1119	<	lock.lock();
1120	<	try {
1121	<	ForkJoinWorkerThread[] ws = workers;
1122	<	for (int i = 0; i < ws.length; ++i) {
1123	<	ForkJoinWorkerThread t = ws[i];
1124	<	if (t != null)
1125	<	t.cancelTasks();
1126	<	}
1127	<	} finally {
1128	<	lock.unlock();
1129	<	}
1130	<	}
1131	<
1132	<	/**
1133	<	* Set each worker's status to terminating. Requires lock to avoid
1134	<	* conflicts with add/remove
1135	<	*/
1136	<	private void stopAllWorkers() {
1137	<	final ReentrantLock lock = this.workerLock;
1138	<	lock.lock();
1139	<	try {
1140	<	ForkJoinWorkerThread[] ws = workers;
1141	<	for (int i = 0; i < ws.length; ++i) {
1142	<	ForkJoinWorkerThread t = ws[i];
1143	<	if (t != null)
1144	<	t.shutdownNow();
1145	<	}
1146	<	} finally {
1147	<	lock.unlock();
1148	<	}
1149	<	}
1150	<
1151	<	/**
1152	<	* Interrupt all unterminated workers.  This is not required for
1153	<	* sake of internal control, but may help unstick user code during
1154	<	* shutdown.
1155	<	*/
1156	<	private void interruptUnterminatedWorkers() {
1157	<	final ReentrantLock lock = this.workerLock;
1158	<	lock.lock();
1159	<	try {
1160	<	ForkJoinWorkerThread[] ws = workers;
1161	<	for (int i = 0; i < ws.length; ++i) {
1162	<	ForkJoinWorkerThread t = ws[i];
1163	<	if (t != null && !t.isTerminated()) {
1164	<	try {
1165	<	t.interrupt();
1166	<	} catch (SecurityException ignore) {
1167	<	}
1168	<	}
1169	<	}
1170	<	} finally {
1171	<	lock.unlock();
1172	<	}
1173	<	}
1174	<
1175	<
1176	<	/*
1177	<	* Nodes for event barrier to manage idle threads.
1178	<	*
1179	<	* The event barrier has an event count and a wait queue (actually
1180	<	* a Treiber stack).  Workers are enabled to look for work when
1181	<	* the eventCount is incremented. If they fail to find some,
1182	<	* they may wait for next count. Synchronization events occur only
1183	<	* in enough contexts to maintain overall liveness:
1775	>	* Interface for extending managed parallelism for tasks running
1776	>	* in {@link ForkJoinPool}s.
1777		*
1778	<	*   - Submission of a new task to the pool
1779	<	*   - Creation or termination of a worker
1780	<	*   - pool termination
1781	<	*   - A worker pushing a task on an empty queue
1778	>	* <p>A {@code ManagedBlocker} provides two methods.
1779	>	* Method {@code isReleasable} must return {@code true} if
1780	>	* blocking is not necessary. Method {@code block} blocks the
1781	>	* current thread if necessary (perhaps internally invoking
1782	>	* {@code isReleasable} before actually blocking).
1783		*
1190	–	* The last case (pushing a task) occurs often enough, and is
1191	–	* heavy enough compared to simple stack pushes to require some
1192	–	* special handling: Method signalNonEmptyWorkerQueue returns
1193	–	* without advancing count if the queue appears to be empty.  This
1194	–	* would ordinarily result in races causing some queued waiters
1195	–	* not to be woken up. To avoid this, a worker in sync
1196	–	* rescans for tasks after being enqueued if it was the first to
1197	–	* enqueue, and aborts the wait if finding one, also helping to
1198	–	* signal others. This works well because the worker has nothing
1199	–	* better to do anyway, and so might as well help alleviate the
1200	–	* overhead and contention on the threads actually doing work.
1201	–	*
1202	–	* Queue nodes are basic Treiber stack nodes, also used for spare
1203	–	* stack.
1204	–	*/
1205	–	static final class WaitQueueNode {
1206	–	WaitQueueNode next; // only written before enqueued
1207	–	volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1208	–	final long count; // unused for spare stack
1209	–	WaitQueueNode(ForkJoinWorkerThread w, long c) {
1210	–	count = c;
1211	–	thread = w;
1212	–	}
1213	–	final boolean signal() {
1214	–	ForkJoinWorkerThread t = thread;
1215	–	thread = null;
1216	–	if (t != null) {
1217	–	LockSupport.unpark(t);
1218	–	return true;
1219	–	}
1220	–	return false;
1221	–	}
1222	–	}
1223	–
1224	–	/**
1225	–	* Release at least one thread waiting for event count to advance,
1226	–	* if one exists. If initial attempt fails, release all threads.
1227	–	* @param all if false, at first try to only release one thread
1228	–	* @return current event
1229	–	*/
1230	–	private long releaseIdleWorkers(boolean all) {
1231	–	long c;
1232	–	for (;;) {
1233	–	WaitQueueNode q = barrierStack;
1234	–	c = eventCount;
1235	–	long qc;
1236	–	if (q == null || (qc = q.count) >= c)
1237	–	break;
1238	–	if (!all) {
1239	–	if (casBarrierStack(q, q.next) && q.signal())
1240	–	break;
1241	–	all = true;
1242	–	}
1243	–	else if (casBarrierStack(q, null)) {
1244	–	do {
1245	–	q.signal();
1246	–	} while ((q = q.next) != null);
1247	–	break;
1248	–	}
1249	–	}
1250	–	return c;
1251	–	}
1252	–
1253	–	/**
1254	–	* Returns current barrier event count
1255	–	* @return current barrier event count
1256	–	*/
1257	–	final long getEventCount() {
1258	–	long ec = eventCount;
1259	–	releaseIdleWorkers(true); // release to ensure accurate result
1260	–	return ec;
1261	–	}
1262	–
1263	–	/**
1264	–	* Increment event count and release at least one waiting thread,
1265	–	* if one exists (released threads will in turn wake up others).
1266	–	* @param all if true, try to wake up all
1267	–	*/
1268	–	final void signalIdleWorkers(boolean all) {
1269	–	long c;
1270	–	do;while (!casEventCount(c = eventCount, c+1));
1271	–	releaseIdleWorkers(all);
1272	–	}
1273	–
1274	–	/**
1275	–	* Wake up threads waiting to steal a task. Because method
1276	–	* sync rechecks availability, it is OK to only proceed if
1277	–	* queue appears to be non-empty.
1278	–	*/
1279	–	final void signalNonEmptyWorkerQueue() {
1280	–	// If CAS fails another signaller must have succeeded
1281	–	long c;
1282	–	if (barrierStack != null && casEventCount(c = eventCount, c+1))
1283	–	releaseIdleWorkers(false);
1284	–	}
1285	–
1286	–	/**
1287	–	* Waits until event count advances from count, or some thread is
1288	–	* waiting on a previous count, or there is stealable work
1289	–	* available. Help wake up others on release.
1290	–	* @param w the calling worker thread
1291	–	* @param prev previous value returned by sync (or 0)
1292	–	* @return current event count
1293	–	*/
1294	–	final long sync(ForkJoinWorkerThread w, long prev) {
1295	–	updateStealCount(w);
1296	–
1297	–	while (!w.isShutdown() && !isTerminating() &&
1298	–	(parallelism >= runningCountOf(workerCounts) ||
1299	–	!suspendIfSpare(w))) { // prefer suspend to waiting here
1300	–	WaitQueueNode node = null;
1301	–	boolean queued = false;
1302	–	for (;;) {
1303	–	if (!queued) {
1304	–	if (eventCount != prev)
1305	–	break;
1306	–	WaitQueueNode h = barrierStack;
1307	–	if (h != null && h.count != prev)
1308	–	break; // release below and maybe retry
1309	–	if (node == null)
1310	–	node = new WaitQueueNode(w, prev);
1311	–	queued = casBarrierStack(node.next = h, node);
1312	–	}
1313	–	else if (Thread.interrupted() ||
1314	–	node.thread == null ||
1315	–	(node.next == null && w.prescan()) ||
1316	–	eventCount != prev) {
1317	–	node.thread = null;
1318	–	if (eventCount == prev) // help trigger
1319	–	casEventCount(prev, prev+1);
1320	–	break;
1321	–	}
1322	–	else
1323	–	LockSupport.park(this);
1324	–	}
1325	–	long ec = eventCount;
1326	–	if (releaseIdleWorkers(false) != prev)
1327	–	return ec;
1328	–	}
1329	–	return prev; // return old count if aborted
1330	–	}
1331	–
1332	–	//  Parallelism maintenance
1333	–
1334	–	/**
1335	–	* Decrement running count; if too low, add spare.
1336	–	*
1337	–	* Conceptually, all we need to do here is add or resume a
1338	–	* spare thread when one is about to block (and remove or
1339	–	* suspend it later when unblocked -- see suspendIfSpare).
1340	–	* However, implementing this idea requires coping with
1341	–	* several problems: We have imperfect information about the
1342	–	* states of threads. Some count updates can and usually do
1343	–	* lag run state changes, despite arrangements to keep them
1344	–	* accurate (for example, when possible, updating counts
1345	–	* before signalling or resuming), especially when running on
1346	–	* dynamic JVMs that don't optimize the infrequent paths that
1347	–	* update counts. Generating too many threads can make these
1348	–	* problems become worse, because excess threads are more
1349	–	* likely to be context-switched with others, slowing them all
1350	–	* down, especially if there is no work available, so all are
1351	–	* busy scanning or idling.  Also, excess spare threads can
1352	–	* only be suspended or removed when they are idle, not
1353	–	* immediately when they aren't needed. So adding threads will
1354	–	* raise parallelism level for longer than necessary.  Also,
1355	–	* FJ applications often enounter highly transient peaks when
1356	–	* many threads are blocked joining, but for less time than it
1357	–	* takes to create or resume spares.
1358	–	*
1359	–	* @param joinMe if non-null, return early if done
1360	–	* @param maintainParallelism if true, try to stay within
1361	–	* target counts, else create only to avoid starvation
1362	–	* @return true if joinMe known to be done
1363	–	*/
1364	–	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1365	–	maintainParallelism &= maintainsParallelism; // overrride
1366	–	boolean dec = false;  // true when running count decremented
1367	–	while (spareStack == null || !tryResumeSpare(dec)) {
1368	–	int counts = workerCounts;
1369	–	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1370	–	if (!needSpare(counts, maintainParallelism))
1371	–	break;
1372	–	if (joinMe.status < 0)
1373	–	return true;
1374	–	if (tryAddSpare(counts))
1375	–	break;
1376	–	}
1377	–	}
1378	–	return false;
1379	–	}
1380	–
1381	–	/**
1382	–	* Same idea as preJoin
1383	–	*/
1384	–	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1385	–	maintainParallelism &= maintainsParallelism;
1386	–	boolean dec = false;
1387	–	while (spareStack == null || !tryResumeSpare(dec)) {
1388	–	int counts = workerCounts;
1389	–	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1390	–	if (!needSpare(counts, maintainParallelism))
1391	–	break;
1392	–	if (blocker.isReleasable())
1393	–	return true;
1394	–	if (tryAddSpare(counts))
1395	–	break;
1396	–	}
1397	–	}
1398	–	return false;
1399	–	}
1400	–
1401	–	/**
1402	–	* Returns true if a spare thread appears to be needed.  If
1403	–	* maintaining parallelism, returns true when the deficit in
1404	–	* running threads is more than the surplus of total threads, and
1405	–	* there is apparently some work to do.  This self-limiting rule
1406	–	* means that the more threads that have already been added, the
1407	–	* less parallelism we will tolerate before adding another.
1408	–	* @param counts current worker counts
1409	–	* @param maintainParallelism try to maintain parallelism
1410	–	*/
1411	–	private boolean needSpare(int counts, boolean maintainParallelism) {
1412	–	int ps = parallelism;
1413	–	int rc = runningCountOf(counts);
1414	–	int tc = totalCountOf(counts);
1415	–	int runningDeficit = ps - rc;
1416	–	int totalSurplus = tc - ps;
1417	–	return (tc < maxPoolSize &&
1418	–	(rc == 0 || totalSurplus < 0 ||
1419	–	(maintainParallelism &&
1420	–	runningDeficit > totalSurplus && mayHaveQueuedWork())));
1421	–	}
1422	–
1423	–	/**
1424	–	* Returns true if at least one worker queue appears to be
1425	–	* nonempty. This is expensive but not often called. It is not
1426	–	* critical that this be accurate, but if not, more or fewer
1427	–	* running threads than desired might be maintained.
1428	–	*/
1429	–	private boolean mayHaveQueuedWork() {
1430	–	ForkJoinWorkerThread[] ws = workers;
1431	–	int len = ws.length;
1432	–	ForkJoinWorkerThread v;
1433	–	for (int i = 0; i < len; ++i) {
1434	–	if ((v = ws[i]) != null && v.getRawQueueSize() > 0) {
1435	–	releaseIdleWorkers(false); // help wake up stragglers
1436	–	return true;
1437	–	}
1438	–	}
1439	–	return false;
1440	–	}
1441	–
1442	–	/**
1443	–	* Add a spare worker if lock available and no more than the
1444	–	* expected numbers of threads exist
1445	–	* @return true if successful
1446	–	*/
1447	–	private boolean tryAddSpare(int expectedCounts) {
1448	–	final ReentrantLock lock = this.workerLock;
1449	–	int expectedRunning = runningCountOf(expectedCounts);
1450	–	int expectedTotal = totalCountOf(expectedCounts);
1451	–	boolean success = false;
1452	–	boolean locked = false;
1453	–	// confirm counts while locking; CAS after obtaining lock
1454	–	try {
1455	–	for (;;) {
1456	–	int s = workerCounts;
1457	–	int tc = totalCountOf(s);
1458	–	int rc = runningCountOf(s);
1459	–	if (rc > expectedRunning || tc > expectedTotal)
1460	–	break;
1461	–	if (!locked && !(locked = lock.tryLock()))
1462	–	break;
1463	–	if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) {
1464	–	createAndStartSpare(tc);
1465	–	success = true;
1466	–	break;
1467	–	}
1468	–	}
1469	–	} finally {
1470	–	if (locked)
1471	–	lock.unlock();
1472	–	}
1473	–	return success;
1474	–	}
1475	–
1476	–	/**
1477	–	* Add the kth spare worker. On entry, pool coounts are already
1478	–	* adjusted to reflect addition.
1479	–	*/
1480	–	private void createAndStartSpare(int k) {
1481	–	ForkJoinWorkerThread w = null;
1482	–	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1);
1483	–	int len = ws.length;
1484	–	// Probably, we can place at slot k. If not, find empty slot
1485	–	if (k < len && ws[k] != null) {
1486	–	for (k = 0; k < len && ws[k] != null; ++k)
1487	–	;
1488	–	}
1489	–	if (k < len && (w = createWorker(k)) != null) {
1490	–	ws[k] = w;
1491	–	w.start();
1492	–	}
1493	–	else
1494	–	updateWorkerCount(-1); // adjust on failure
1495	–	signalIdleWorkers(false);
1496	–	}
1497	–
1498	–	/**
1499	–	* Suspend calling thread w if there are excess threads.  Called
1500	–	* only from sync.  Spares are enqueued in a Treiber stack
1501	–	* using the same WaitQueueNodes as barriers.  They are resumed
1502	–	* mainly in preJoin, but are also woken on pool events that
1503	–	* require all threads to check run state.
1504	–	* @param w the caller
1505	–	*/
1506	–	private boolean suspendIfSpare(ForkJoinWorkerThread w) {
1507	–	WaitQueueNode node = null;
1508	–	int s;
1509	–	while (parallelism < runningCountOf(s = workerCounts)) {
1510	–	if (node == null)
1511	–	node = new WaitQueueNode(w, 0);
1512	–	if (casWorkerCounts(s, s-1)) { // representation-dependent
1513	–	// push onto stack
1514	–	do;while (!casSpareStack(node.next = spareStack, node));
1515	–
1516	–	// block until released by resumeSpare
1517	–	while (node.thread != null) {
1518	–	if (!Thread.interrupted())
1519	–	LockSupport.park(this);
1520	–	}
1521	–	w.activate(); // help warm up
1522	–	return true;
1523	–	}
1524	–	}
1525	–	return false;
1526	–	}
1527	–
1528	–	/**
1529	–	* Try to pop and resume a spare thread.
1530	–	* @param updateCount if true, increment running count on success
1531	–	* @return true if successful
1532	–	*/
1533	–	private boolean tryResumeSpare(boolean updateCount) {
1534	–	WaitQueueNode q;
1535	–	while ((q = spareStack) != null) {
1536	–	if (casSpareStack(q, q.next)) {
1537	–	if (updateCount)
1538	–	updateRunningCount(1);
1539	–	q.signal();
1540	–	return true;
1541	–	}
1542	–	}
1543	–	return false;
1544	–	}
1545	–
1546	–	/**
1547	–	* Pop and resume all spare threads. Same idea as
1548	–	* releaseIdleWorkers.
1549	–	* @return true if any spares released
1550	–	*/
1551	–	private boolean resumeAllSpares() {
1552	–	WaitQueueNode q;
1553	–	while ( (q = spareStack) != null) {
1554	–	if (casSpareStack(q, null)) {
1555	–	do {
1556	–	updateRunningCount(1);
1557	–	q.signal();
1558	–	} while ((q = q.next) != null);
1559	–	return true;
1560	–	}
1561	–	}
1562	–	return false;
1563	–	}
1564	–
1565	–	/**
1566	–	* Pop and shutdown excessive spare threads. Call only while
1567	–	* holding lock. This is not guaranteed to eliminate all excess
1568	–	* threads, only those suspended as spares, which are the ones
1569	–	* unlikely to be needed in the future.
1570	–	*/
1571	–	private void trimSpares() {
1572	–	int surplus = totalCountOf(workerCounts) - parallelism;
1573	–	WaitQueueNode q;
1574	–	while (surplus > 0 && (q = spareStack) != null) {
1575	–	if (casSpareStack(q, null)) {
1576	–	do {
1577	–	updateRunningCount(1);
1578	–	ForkJoinWorkerThread w = q.thread;
1579	–	if (w != null && surplus > 0 &&
1580	–	runningCountOf(workerCounts) > 0 && w.shutdown())
1581	–	--surplus;
1582	–	q.signal();
1583	–	} while ((q = q.next) != null);
1584	–	}
1585	–	}
1586	–	}
1587	–
1588	–	/**
1589	–	* Returns approximate number of spares, just for diagnostics.
1590	–	*/
1591	–	private int countSpares() {
1592	–	int sum = 0;
1593	–	for (WaitQueueNode q = spareStack; q != null; q = q.next)
1594	–	++sum;
1595	–	return sum;
1596	–	}
1597	–
1598	–	/**
1599	–	* Interface for extending managed parallelism for tasks running
1600	–	* in ForkJoinPools. A ManagedBlocker provides two methods.
1601	–	* Method <tt>isReleasable</tt> must return true if blocking is not
1602	–	* necessary. Method <tt>block</tt> blocks the current thread
1603	–	* if necessary (perhaps internally invoking isReleasable before
1604	–	* actually blocking.).
1784		* <p>For example, here is a ManagedBlocker based on a
1785		* ReentrantLock:
1786	<	* <pre>
1787	<	*   class ManagedLocker implements ManagedBlocker {
1788	<	*     final ReentrantLock lock;
1789	<	*     boolean hasLock = false;
1790	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1791	<	*     public boolean block() {
1792	<	*        if (!hasLock)
1793	<	*           lock.lock();
1794	<	*        return true;
1795	<	*     }
1796	<	*     public boolean isReleasable() {
1797	<	*        return hasLock || (hasLock = lock.tryLock());
1619	<	*     }
1786	>	*  <pre> {@code
1787	>	* class ManagedLocker implements ManagedBlocker {
1788	>	*   final ReentrantLock lock;
1789	>	*   boolean hasLock = false;
1790	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1791	>	*   public boolean block() {
1792	>	*     if (!hasLock)
1793	>	*       lock.lock();
1794	>	*     return true;
1795	>	*   }
1796	>	*   public boolean isReleasable() {
1797	>	*     return hasLock || (hasLock = lock.tryLock());
1798		*   }
1799	<	* </pre>
1799	>	* }}</pre>
1800		*/
1801		public static interface ManagedBlocker {
1802		/**
1803		* Possibly blocks the current thread, for example waiting for
1804		* a lock or condition.
1805	<	* @return true if no additional blocking is necessary (i.e.,
1806	<	* if isReleasable would return true).
1805	>	*
1806	>	* @return {@code true} if no additional blocking is necessary
1807	>	* (i.e., if isReleasable would return true)
1808		* @throws InterruptedException if interrupted while waiting
1809	<	* (the method is not required to do so, but is allowe to).
1809	>	* (the method is not required to do so, but is allowed to)
1810		*/
1811		boolean block() throws InterruptedException;
1812
1813		/**
1814	<	* Returns true if blocking is unnecessary.
1814	>	* Returns {@code true} if blocking is unnecessary.
1815		*/
1816		boolean isReleasable();
1817		}
1818
1819		/**
1820		* Blocks in accord with the given blocker.  If the current thread
1821	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1822	<	* spare thread to be activated if necessary to ensure parallelism
1823	<	* while the current thread is blocked.  If
1824	<	* <tt>maintainParallelism</tt> is true and the pool supports it
1825	<	* (see <tt>getMaintainsParallelism</tt>), this method attempts to
1826	<	* maintain the pool's nominal parallelism. Otherwise if activates
1827	<	* a thread only if necessary to avoid complete starvation. This
1828	<	* option may be preferable when blockages use timeouts, or are
1829	<	* almost always brief.
1830	<	*
1831	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1832	<	* equivalent to
1833	<	* <pre>
1834	<	*   while (!blocker.isReleasable())
1835	<	*      if (blocker.block())
1836	<	*         return;
1837	<	* </pre>
1838	<	* If the caller is a ForkJoinTask, then the pool may first
1839	<	* be expanded to ensure parallelism, and later adjusted.
1821	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1822	>	* arranges for a spare thread to be activated if necessary to
1823	>	* ensure parallelism while the current thread is blocked.
1824	>	*
1825	>	* <p>If {@code maintainParallelism} is {@code true} and the pool
1826	>	* supports it ({@link #getMaintainsParallelism}), this method
1827	>	* attempts to maintain the pool's nominal parallelism. Otherwise
1828	>	* it activates a thread only if necessary to avoid complete
1829	>	* starvation. This option may be preferable when blockages use
1830	>	* timeouts, or are almost always brief.
1831	>	*
1832	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1833	>	* behaviorally equivalent to
1834	>	*  <pre> {@code
1835	>	* while (!blocker.isReleasable())
1836	>	*   if (blocker.block())
1837	>	*     return;
1838	>	* }</pre>
1839	>	*
1840	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1841	>	* first be expanded to ensure parallelism, and later adjusted.
1842		*
1843		* @param blocker the blocker
1844	<	* @param maintainParallelism if true and supported by this pool,
1845	<	* attempt to maintain the pool's nominal parallelism; otherwise
1846	<	* activate a thread only if necessary to avoid complete
1847	<	* starvation.
1848	<	* @throws InterruptedException if blocker.block did so.
1844	>	* @param maintainParallelism if {@code true} and supported by
1845	>	* this pool, attempt to maintain the pool's nominal parallelism;
1846	>	* otherwise activate a thread only if necessary to avoid
1847	>	* complete starvation.
1848	>	* @throws InterruptedException if blocker.block did so
1849		*/
1850		public static void managedBlock(ManagedBlocker blocker,
1851		boolean maintainParallelism)
1852		throws InterruptedException {
1853		Thread t = Thread.currentThread();
1854	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1855	<	((ForkJoinWorkerThread)t).pool : null);
1856	<	if (!blocker.isReleasable()) {
1857	<	try {
1858	<	if (pool == null ||
1678	<	!pool.preBlock(blocker, maintainParallelism))
1679	<	awaitBlocker(blocker);
1680	<	} finally {
1681	<	if (pool != null)
1682	<	pool.updateRunningCount(1);
1683	<	}
1684	<	}
1854	>	if (t instanceof ForkJoinWorkerThread)
1855	>	((ForkJoinWorkerThread) t).pool.
1856	>	doBlock(blocker, maintainParallelism);
1857	>	else
1858	>	awaitBlocker(blocker);
1859		}
1860
1861	+	/**
1862	+	* Performs Non-FJ blocking
1863	+	*/
1864		private static void awaitBlocker(ManagedBlocker blocker)
1865		throws InterruptedException {
1866	<	do;while (!blocker.isReleasable() && !blocker.block());
1866	>	do {} while (!blocker.isReleasable() && !blocker.block());
1867	>	}
1868	>
1869	>	// AbstractExecutorService overrides.  These rely on undocumented
1870	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1871	>	// implement RunnableFuture.
1872	>
1873	>	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1874	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1875		}
1876
1877	+	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1878	+	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1879	+	}
1880
1881	<	// Temporary Unsafe mechanics for preliminary release
1881	>	// Unsafe mechanics
1882
1883	<	static final Unsafe _unsafe;
1884	<	static final long eventCountOffset;
1885	<	static final long workerCountsOffset;
1886	<	static final long runControlOffset;
1887	<	static final long barrierStackOffset;
1888	<	static final long spareStackOffset;
1883	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1884	>	private static final long workerCountsOffset =
1885	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1886	>	private static final long runStateOffset =
1887	>	objectFieldOffset("runState", ForkJoinPool.class);
1888	>	private static final long eventCountOffset =
1889	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1890	>	private static final long eventWaitersOffset =
1891	>	objectFieldOffset("eventWaiters",ForkJoinPool.class);
1892	>	private static final long stealCountOffset =
1893	>	objectFieldOffset("stealCount",ForkJoinPool.class);
1894
1895	<	static {
1895	>
1896	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1897		try {
1898	<	if (ForkJoinPool.class.getClassLoader() != null) {
1899	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1900	<	f.setAccessible(true);
1901	<	_unsafe = (Unsafe)f.get(null);
1902	<	}
1903	<	else
1710	<	_unsafe = Unsafe.getUnsafe();
1711	<	eventCountOffset = _unsafe.objectFieldOffset
1712	<	(ForkJoinPool.class.getDeclaredField("eventCount"));
1713	<	workerCountsOffset = _unsafe.objectFieldOffset
1714	<	(ForkJoinPool.class.getDeclaredField("workerCounts"));
1715	<	runControlOffset = _unsafe.objectFieldOffset
1716	<	(ForkJoinPool.class.getDeclaredField("runControl"));
1717	<	barrierStackOffset = _unsafe.objectFieldOffset
1718	<	(ForkJoinPool.class.getDeclaredField("barrierStack"));
1719	<	spareStackOffset = _unsafe.objectFieldOffset
1720	<	(ForkJoinPool.class.getDeclaredField("spareStack"));
1721	<	} catch (Exception e) {
1722	<	throw new RuntimeException("Could not initialize intrinsics", e);
1898	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1899	>	} catch (NoSuchFieldException e) {
1900	>	// Convert Exception to corresponding Error
1901	>	NoSuchFieldError error = new NoSuchFieldError(field);
1902	>	error.initCause(e);
1903	>	throw error;
1904		}
1905		}
1906
1907	<	private boolean casEventCount(long cmp, long val) {
1908	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1909	<	}
1910	<	private boolean casWorkerCounts(int cmp, int val) {
1911	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1912	<	}
1913	<	private boolean casRunControl(int cmp, int val) {
1914	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1915	<	}
1916	<	private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1917	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1918	<	}
1919	<	private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1920	<	return _unsafe.compareAndSwapObject(this, barrierStackOffset, cmp, val);
1907	>	/**
1908	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1909	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1910	>	* into a jdk.
1911	>	*
1912	>	* @return a sun.misc.Unsafe
1913	>	*/
1914	>	private static sun.misc.Unsafe getUnsafe() {
1915	>	try {
1916	>	return sun.misc.Unsafe.getUnsafe();
1917	>	} catch (SecurityException se) {
1918	>	try {
1919	>	return java.security.AccessController.doPrivileged
1920	>	(new java.security
1921	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1922	>	public sun.misc.Unsafe run() throws Exception {
1923	>	java.lang.reflect.Field f = sun.misc
1924	>	.Unsafe.class.getDeclaredField("theUnsafe");
1925	>	f.setAccessible(true);
1926	>	return (sun.misc.Unsafe) f.get(null);
1927	>	}});
1928	>	} catch (java.security.PrivilegedActionException e) {
1929	>	throw new RuntimeException("Could not initialize intrinsics",
1930	>	e.getCause());
1931	>	}
1932	>	}
1933		}
1934		}

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