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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.56 by dl, Thu May 27 16:46:48 2010 UTC vs.
Revision 1.59 by dl, Fri Jul 23 14:09:17 2010 UTC

#	Line 21 | Line 21 | import java.util.concurrent.CountDownLat
21		/**
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
24	>	* from non-{@code ForkJoinTask} clients, as well as management and
25		* monitoring operations.
26		*
27		* <p>A {@code ForkJoinPool} differs from other kinds of {@link
#	Line 30 | Line 30 | import java.util.concurrent.CountDownLat
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.
33	>	* ForkJoinTask}s). When setting <em>asyncMode</em> to true in
34	>	* constructors, {@code ForkJoinPool}s may also be appropriate for use
35	>	* with event-style tasks that are never joined.
36		*
37		* <p>A {@code ForkJoinPool} is constructed with a given target
38		* parallelism level; by default, equal to the number of available
39	<	* processors. Unless configured otherwise via {@link
40	<	* #setMaintainsParallelism}, the pool attempts to maintain this
41	<	* number of active (or available) threads by dynamically adding,
42	<	* suspending, or resuming internal worker threads, even if some tasks
43	<	* are stalled waiting to join others. However, no such adjustments
44	<	* are performed in the face of blocked IO or other unmanaged
45	<	* 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.
39	>	* processors. The pool attempts to maintain enough active (or
40	>	* available) threads by dynamically adding, suspending, or resuming
41	>	* internal worker threads, even if some tasks are stalled waiting to
42	>	* join others. However, no such adjustments are guaranteed in the
43	>	* face of blocked IO or other unmanaged synchronization. The nested
44	>	* {@link ManagedBlocker} interface enables extension of the kinds of
45	>	* synchronization accommodated.
46		*
47		* <p>In addition to execution and lifecycle control methods, this
48		* class provides status check methods (for example
#	Line 65 | Line 51 | import java.util.concurrent.CountDownLat
51		* {@link #toString} returns indications of pool state in a
52		* convenient form for informal monitoring.
53		*
54	+	* <p> As is the case with other ExecutorServices, there are three
55	+	* main task execution methods summarized in the follwoing
56	+	* table. These are designed to be used by clients not already engaged
57	+	* in fork/join computations in the current pool.  The main forms of
58	+	* these methods accept instances of {@code ForkJoinTask}, but
59	+	* overloaded forms also allow mixed execution of plain {@code
60	+	* Runnable}- or {@code Callable}- based activities as well.  However,
61	+	* tasks that are already executing in a pool should normally
62	+	* <em>NOT</em> use these pool execution methods, but instead use the
63	+	* within-computation forms listed in the table.
64	+	*
65	+	* <table BORDER CELLPADDING=3 CELLSPACING=1>
66	+	*  <tr>
67	+	*    <td></td>
68	+	*    <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
69	+	*    <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
70	+	*  </tr>
71	+	*  <tr>
72	+	*    <td> <b>Arange async execution</td>
73	+	*    <td> {@link #execute(ForkJoinTask)}</td>
74	+	*    <td> {@link ForkJoinTask#fork}</td>
75	+	*  </tr>
76	+	*  <tr>
77	+	*    <td> <b>Await and obtain result</td>
78	+	*    <td> {@link #invoke(ForkJoinTask)}</td>
79	+	*    <td> {@link ForkJoinTask#invoke}</td>
80	+	*  </tr>
81	+	*  <tr>
82	+	*    <td> <b>Arrange exec and obtain Future</td>
83	+	*    <td> {@link #submit(ForkJoinTask)}</td>
84	+	*    <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td>
85	+	*  </tr>
86	+	* </table>
87	+	*
88		* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
89		* used for all parallel task execution in a program or subsystem.
90		* Otherwise, use would not usually outweigh the construction and
#	Line 89 | Line 109 | import java.util.concurrent.CountDownLat
109		* {@code IllegalArgumentException}.
110		*
111		* <p>This implementation rejects submitted tasks (that is, by throwing
112	<	* {@link RejectedExecutionException}) only when the pool is shut down.
112	>	* {@link RejectedExecutionException}) only when the pool is shut down
113	>	* or internal resources have been exhuasted.
114		*
115		* @since 1.7
116		* @author Doug Lea
#	Line 116 | Line 137 | public class ForkJoinPool extends Abstra
137		* of tasks profit from cache affinities, but others are harmed by
138		* cache pollution effects.)
139		*
140	+	* Beyond work-stealing support and essential bookkeeping, the
141	+	* main responsibility of this framework is to arrange tactics for
142	+	* when one worker is waiting to join a task stolen (or always
143	+	* held by) another.  Becauae we are multiplexing many tasks on to
144	+	* a pool of workers, we can't just let them block (as in
145	+	* Thread.join).  We also cannot just reassign the joiner's
146	+	* run-time stack with another and replace it later, which would
147	+	* be a form of "continuation", that even if possible is not
148	+	* necessarily a good idea. Given that the creation costs of most
149	+	* threads on most systems mainly surrounds setting up runtime
150	+	* stacks, thread creation and switching is usually not much more
151	+	* expensive than stack creation and switching, and is more
152	+	* flexible). Instead we combine two tactics:
153	+	*
154	+	*   1. Arranging for the joiner to execute some task that it
155	+	*      would be running if the steal had not occurred.  Method
156	+	*      ForkJoinWorkerThread.helpJoinTask tracks joining->stealing
157	+	*      links to try to find such a task.
158	+	*
159	+	*   2. Unless there are already enough live threads, creating or
160	+	*      or re-activating a spare thread to compensate for the
161	+	*      (blocked) joiner until it unblocks.  Spares then suspend
162	+	*      at their next opportunity or eventually die if unused for
163	+	*      too long.  See below and the internal documentation
164	+	*      for tryAwaitJoin for more details about compensation
165	+	*      rules.
166	+	*
167	+	* Because the determining existence of conservatively safe
168	+	* helping targets, the availability of already-created spares,
169	+	* and the apparent need to create new spares are all racy and
170	+	* require heuristic guidance, joins (in
171	+	* ForkJoinWorkerThread.joinTask) interleave these options until
172	+	* successful.  Creating a new spare always succeeds, but also
173	+	* increases application footprint, so we try to avoid it, within
174	+	* reason.
175	+	*
176	+	* The ManagedBlocker extension API can't use option (1) so uses a
177	+	* special version of (2) in method awaitBlocker.
178	+	*
179		* The main throughput advantages of work-stealing stem from
180		* decentralized control -- workers mostly steal tasks from each
181		* other. We do not want to negate this by creating bottlenecks
182	<	* implementing the management responsibilities of this class. So
183	<	* we use a collection of techniques that avoid, reduce, or cope
184	<	* well with contention. These entail several instances of
185	<	* bit-packing into CASable fields to maintain only the minimally
186	<	* required atomicity. To enable such packing, we restrict maximum
187	<	* parallelism to (1<<15)-1 (enabling twice this to fit into a 16
188	<	* bit field), which is far in excess of normal operating range.
189	<	* Even though updates to some of these bookkeeping fields do
190	<	* sometimes contend with each other, they don't normally
191	<	* cache-contend with updates to others enough to warrant memory
192	<	* padding or isolation. So they are all held as fields of
193	<	* ForkJoinPool objects.  The main capabilities are as follows:
182	>	* implementing other management responsibilities. So we use a
183	>	* collection of techniques that avoid, reduce, or cope well with
184	>	* contention. These entail several instances of bit-packing into
185	>	* CASable fields to maintain only the minimally required
186	>	* atomicity. To enable such packing, we restrict maximum
187	>	* parallelism to (1<<15)-1 (enabling twice this (to accommodate
188	>	* unbalanced increments and decrements) to fit into a 16 bit
189	>	* field, which is far in excess of normal operating range.  Even
190	>	* though updates to some of these bookkeeping fields do sometimes
191	>	* contend with each other, they don't normally cache-contend with
192	>	* updates to others enough to warrant memory padding or
193	>	* isolation. So they are all held as fields of ForkJoinPool
194	>	* objects.  The main capabilities are as follows:
195		*
196		* 1. Creating and removing workers. Workers are recorded in the
197		* "workers" array. This is an array as opposed to some other data
#	Line 147 | Line 208 | public class ForkJoinPool extends Abstra
208		* work with other policies.
209		*
210		* 2. Bookkeeping for dynamically adding and removing workers. We
211	<	* maintain a given level of parallelism (or, if
212	<	* maintainsParallelism is false, at least avoid starvation). When
152	<	* some workers are known to be blocked (on joins or via
211	>	* aim to approximately maintain the given level of parallelism.
212	>	* When some workers are known to be blocked (on joins or via
213		* ManagedBlocker), we may create or resume others to take their
214		* place until they unblock (see below). Implementing this
215		* requires counts of the number of "running" threads (i.e., those
216		* that are neither blocked nor artifically suspended) as well as
217		* the total number.  These two values are packed into one field,
218		* "workerCounts" because we need accurate snapshots when deciding
219	<	* to create, resume or suspend.  To support these decisions,
220	<	* updates to spare counts must be prospective (not
221	<	* retrospective).  For example, the running count is decremented
222	<	* before blocking by a thread about to block as a spare, but
163	<	* incremented by the thread about to unblock it. Updates upon
164	<	* resumption ofr threads blocking in awaitJoin or awaitBlocker
165	<	* cannot usually be prospective, so the running count is in
166	<	* general an upper bound of the number of productively running
167	<	* threads Updates to the workerCounts field sometimes transiently
168	<	* encounter a fair amount of contention when join dependencies
169	<	* are such that many threads block or unblock at about the same
170	<	* time. We alleviate this by sometimes bundling updates (for
171	<	* example blocking one thread on join and resuming a spare cancel
172	<	* each other out), and in most other cases performing an
173	<	* alternative action like releasing waiters or locating spares.
219	>	* to create, resume or suspend.  Note however that the
220	>	* correspondance of these counts to reality is not guaranteed. In
221	>	* particular updates for unblocked threads may lag until they
222	>	* actually wake up.
223		*
224		* 3. Maintaining global run state. The run state of the pool
225		* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to
#	Line 228 | Line 277 | public class ForkJoinPool extends Abstra
277		* 5. Managing suspension of extra workers. When a worker is about
278		* to block waiting for a join (or via ManagedBlockers), we may
279		* create a new thread to maintain parallelism level, or at least
280	<	* avoid starvation (see below). Usually, extra threads are needed
281	<	* for only very short periods, yet join dependencies are such
282	<	* that we sometimes need them in bursts. Rather than create new
283	<	* threads each time this happens, we suspend no-longer-needed
284	<	* extra ones as "spares". For most purposes, we don't distinguish
285	<	* "extra" spare threads from normal "core" threads: On each call
286	<	* to preStep (the only point at which we can do this) a worker
280	>	* avoid starvation. Usually, extra threads are needed for only
281	>	* very short periods, yet join dependencies are such that we
282	>	* sometimes need them in bursts. Rather than create new threads
283	>	* each time this happens, we suspend no-longer-needed extra ones
284	>	* as "spares". For most purposes, we don't distinguish "extra"
285	>	* spare threads from normal "core" threads: On each call to
286	>	* preStep (the only point at which we can do this) a worker
287		* checks to see if there are now too many running workers, and if
288	<	* so, suspends itself.  Methods awaitJoin and awaitBlocker look
289	<	* for suspended threads to resume before considering creating a
290	<	* new replacement. We don't need a special data structure to
291	<	* maintain spares; simply scanning the workers array looking for
292	<	* worker.isSuspended() is fine because the calling thread is
293	<	* otherwise not doing anything useful anyway; we are at least as
294	<	* happy if after locating a spare, the caller doesn't actually
295	<	* block because the join is ready before we try to adjust and
296	<	* compensate.  Note that this is intrinsically racy.  One thread
297	<	* may become a spare at about the same time as another is
298	<	* needlessly being created. We counteract this and related slop
299	<	* in part by requiring resumed spares to immediately recheck (in
300	<	* preStep) to see whether they they should re-suspend. The only
301	<	* effective difference between "extra" and "core" threads is that
302	<	* we allow the "extra" ones to time out and die if they are not
303	<	* resumed within a keep-alive interval of a few seconds. This is
304	<	* implemented mainly within ForkJoinWorkerThread, but requires
288	>	* so, suspends itself.  Methods tryAwaitJoin and awaitBlocker
289	>	* look for suspended threads to resume before considering
290	>	* creating a new replacement. We don't need a special data
291	>	* structure to maintain spares; simply scanning the workers array
292	>	* looking for worker.isSuspended() is fine because the calling
293	>	* thread is otherwise not doing anything useful anyway; we are at
294	>	* least as happy if after locating a spare, the caller doesn't
295	>	* actually block because the join is ready before we try to
296	>	* adjust and compensate.  Note that this is intrinsically racy.
297	>	* One thread may become a spare at about the same time as another
298	>	* is needlessly being created. We counteract this and related
299	>	* slop in part by requiring resumed spares to immediately recheck
300	>	* (in preStep) to see whether they they should re-suspend. The
301	>	* only effective difference between "extra" and "core" threads is
302	>	* that we allow the "extra" ones to time out and die if they are
303	>	* not resumed within a keep-alive interval of a few seconds. This
304	>	* is implemented mainly within ForkJoinWorkerThread, but requires
305		* some coordination (isTrimmed() -- meaning killed while
306		* suspended) to correctly maintain pool counts.
307		*
308		* 6. Deciding when to create new workers. The main dynamic
309		* control in this class is deciding when to create extra threads,
310	<	* in methods awaitJoin and awaitBlocker. We always
311	<	* need to create one when the number of running threads becomes
312	<	* zero. But because blocked joins are typically dependent, we
313	<	* don't necessarily need or want one-to-one replacement. Using a
314	<	* one-to-one compensation rule often leads to enough useless
315	<	* overhead creating, suspending, resuming, and/or killing threads
316	<	* to signficantly degrade throughput.  We use a rule reflecting
317	<	* the idea that, the more spare threads you already have, the
318	<	* more evidence you need to create another one. The "evidence"
319	<	* here takes two forms: (1) Using a creation threshold expressed
320	<	* in terms of the current deficit -- target minus running
321	<	* threads. To reduce flickering and drift around target values,
322	<	* the relation is quadratic: adding a spare if (dc*dc)>=(sc*pc)
323	<	* (where dc is deficit, sc is number of spare threads and pc is
324	<	* target parallelism.)  (2) Using a form of adaptive
325	<	* spionning. requiring a number of threshold checks proportional
277	<	* to the number of spare threads.  This effectively reduces churn
278	<	* at the price of systematically undershooting target parallelism
279	<	* when many threads are blocked.  However, biasing toward
280	<	* undeshooting partially compensates for the above mechanics to
281	<	* suspend extra threads, that normally lead to overshoot because
282	<	* we can only suspend workers in-between top-level actions. It
283	<	* also better copes with the fact that some of the methods in
284	<	* this class tend to never become compiled (but are interpreted),
285	<	* so some components of the entire set of controls might execute
286	<	* many times faster than others. And similarly for cases where
287	<	* the apparent lack of work is just due to GC stalls and other
288	<	* transient system activity.
289	<	*
290	<	* 7. Maintaining other configuration parameters and monitoring
291	<	* statistics. Updates to fields controlling parallelism level,
292	<	* max size, etc can only meaningfully take effect for individual
293	<	* threads upon their next top-level actions; i.e., between
294	<	* stealing/running tasks/submission, which are separated by calls
295	<	* to preStep.  Memory ordering for these (assumed infrequent)
296	<	* reconfiguration calls is ensured by using reads and writes to
297	<	* volatile field workerCounts (that must be read in preStep anyway)
298	<	* as "fences" -- user-level reads are preceded by reads of
299	<	* workCounts, and writes are followed by no-op CAS to
300	<	* workerCounts. The values reported by other management and
301	<	* monitoring methods are either computed on demand, or are kept
302	<	* in fields that are only updated when threads are otherwise
303	<	* idle.
310	>	* in methods awaitJoin and awaitBlocker. We always need to create
311	>	* one when the number of running threads would become zero and
312	>	* all workers are busy. However, this is not easy to detect
313	>	* reliably in the presence of transients so we use retries and
314	>	* allow slack (in tryAwaitJoin) to reduce false alarms.  These
315	>	* effectively reduce churn at the price of systematically
316	>	* undershooting target parallelism when many threads are blocked.
317	>	* However, biasing toward undeshooting partially compensates for
318	>	* the above mechanics to suspend extra threads, that normally
319	>	* lead to overshoot because we can only suspend workers
320	>	* in-between top-level actions. It also better copes with the
321	>	* fact that some of the methods in this class tend to never
322	>	* become compiled (but are interpreted), so some components of
323	>	* the entire set of controls might execute many times faster than
324	>	* others. And similarly for cases where the apparent lack of work
325	>	* is just due to GC stalls and other transient system activity.
326		*
327		* Beware that there is a lot of representation-level coupling
328		* among classes ForkJoinPool, ForkJoinWorkerThread, and
#	Line 315 | Line 337 | public class ForkJoinPool extends Abstra
337		* "while ((local = field) != 0)") which are usually the simplest
338		* way to ensure read orderings. Also several occurrences of the
339		* unusual "do {} while(!cas...)" which is the simplest way to
340	<	* force an update of a CAS'ed variable. There are also a few
341	<	* other coding oddities that help some methods perform reasonably
342	<	* even when interpreted (not compiled).
340	>	* force an update of a CAS'ed variable. There are also other
341	>	* coding oddities that help some methods perform reasonably even
342	>	* when interpreted (not compiled), at the expense of messiness.
343		*
344		* The order of declarations in this file is: (1) statics (2)
345		* fields (along with constants used when unpacking some of them)
#	Line 346 | Line 368 | public class ForkJoinPool extends Abstra
368		* Default ForkJoinWorkerThreadFactory implementation; creates a
369		* new ForkJoinWorkerThread.
370		*/
371	<	static class  DefaultForkJoinWorkerThreadFactory
371	>	static class DefaultForkJoinWorkerThreadFactory
372		implements ForkJoinWorkerThreadFactory {
373		public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
374		return new ForkJoinWorkerThread(pool);
#	Line 414 | Line 436 | public class ForkJoinPool extends Abstra
436		/**
437		* Latch released upon termination.
438		*/
439	<	private final CountDownLatch terminationLatch;
439	>	private final Phaser termination;
440
441		/**
442		* Creation factory for worker threads.
#	Line 436 | Line 458 | public class ForkJoinPool extends Abstra
458		private volatile long eventWaiters;
459
460		private static final int  EVENT_COUNT_SHIFT = 32;
461	<	private static final long WAITER_INDEX_MASK = (1L << EVENT_COUNT_SHIFT)-1L;
461	>	private static final long WAITER_ID_MASK = (1L << EVENT_COUNT_SHIFT)-1L;
462
463		/**
464		* A counter for events that may wake up worker threads:
#	Line 485 | Line 507 | public class ForkJoinPool extends Abstra
507		private static final int ONE_RUNNING        = 1;
508		private static final int ONE_TOTAL          = 1 << TOTAL_COUNT_SHIFT;
509
488	–	/*
489	–	* Fields parallelism. maxPoolSize, and maintainsParallelism are
490	–	* non-volatile, but external reads/writes use workerCount fences
491	–	* to ensure visability.
492	–	*/
493	–
510		/**
511		* The target parallelism level.
512	+	* Accessed directly by ForkJoinWorkerThreads.
513		*/
514	<	private int parallelism;
498	<
499	<	/**
500	<	* The maximum allowed pool size.
501	<	*/
502	<	private int maxPoolSize;
514	>	final int parallelism;
515
516		/**
517		* True if use local fifo, not default lifo, for local polling
518	<	* Replicated by ForkJoinWorkerThreads
518	>	* Read by, and replicated by ForkJoinWorkerThreads
519		*/
520	<	private volatile boolean locallyFifo;
520	>	final boolean locallyFifo;
521
522		/**
523	<	* Controls whether to add spares to maintain parallelism
523	>	* The uncaught exception handler used when any worker abruptly
524	>	* terminates.
525		*/
526	<	private boolean maintainsParallelism;
514	<
515	<	/**
516	<	* The uncaught exception handler used when any worker
517	<	* abruptly terminates
518	<	*/
519	<	private volatile Thread.UncaughtExceptionHandler ueh;
526	>	private final Thread.UncaughtExceptionHandler ueh;
527
528		/**
529		* Pool number, just for assigning useful names to worker threads
530		*/
531		private final int poolNumber;
532
533	<	// utilities for updating fields
533	>	// Utilities for CASing fields. Note that several of these
534	>	// are manually inlined by callers
535
536		/**
537	<	* Adds delta to running count.  Used mainly by ForkJoinTask.
537	>	* Increments running count.  Also used by ForkJoinTask.
538		*/
539	<	final void updateRunningCount(int delta) {
540	<	int wc;
539	>	final void incrementRunningCount() {
540	>	int c;
541		do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
542	<	wc = workerCounts,
543	<	wc + delta));
542	>	c = workerCounts,
543	>	c + ONE_RUNNING));
544		}
545
546		/**
547	<	* Decrements running count unless already zero
547	>	* Tries to decrement running count unless already zero
548		*/
549		final boolean tryDecrementRunningCount() {
550		int wc = workerCounts;
#	Line 547 | Line 555 | public class ForkJoinPool extends Abstra
555		}
556
557		/**
558	<	* Write fence for user modifications of pool parameters
551	<	* (parallelism. etc).  Note that it doesn't matter if CAS fails.
558	>	* Tries to increment running count
559		*/
560	<	private void workerCountWriteFence() {
560	>	final boolean tryIncrementRunningCount() {
561		int wc;
562	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
563	<	wc = workerCounts, wc);
557	<	}
558	<
559	<	/**
560	<	* Read fence for external reads of pool parameters
561	<	* (parallelism. maxPoolSize, etc).
562	<	*/
563	<	private void workerCountReadFence() {
564	<	int ignore = workerCounts;
562	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
563	>	wc = workerCounts, wc + ONE_RUNNING);
564		}
565
566		/**
#	Line 663 | Line 662 | public class ForkJoinPool extends Abstra
662		return null;
663		}
664		}
665	<	w.start(recordWorker(w), locallyFifo, ueh);
665	>	w.start(recordWorker(w), ueh);
666		return w;
667		}
668
#	Line 673 | Line 672 | public class ForkJoinPool extends Abstra
672		private void onWorkerCreationFailure() {
673		for (;;) {
674		int wc = workerCounts;
675	<	if ((wc >>> TOTAL_COUNT_SHIFT) > 0 &&
676	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
677	<	wc, wc - (ONE_RUNNING|ONE_TOTAL)))
675	>	if ((wc >>> TOTAL_COUNT_SHIFT) == 0)
676	>	Thread.yield(); // wait for other counts to settle
677	>	else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
678	>	wc - (ONE_RUNNING|ONE_TOTAL)))
679		break;
680		}
681		tryTerminate(false); // in case of failure during shutdown
682		}
683
684		/**
685	<	* Create enough total workers to establish target parallelism,
686	<	* giving up if terminating or addWorker fails
685	>	* Creates and/or resumes enough workers to establish target
686	>	* parallelism, giving up if terminating or addWorker fails
687	>	*
688	>	* TODO: recast this to support lazier creation and automated
689	>	* parallelism maintenance
690		*/
691	<	private void ensureEnoughTotalWorkers() {
692	<	int wc;
693	<	while (((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < parallelism &&
694	<	runState < TERMINATING) {
695	<	if ((UNSAFE.compareAndSwapInt(this, workerCountsOffset,
696	<	wc, wc + (ONE_RUNNING|ONE_TOTAL)) &&
697	<	addWorker() == null))
691	>	private void ensureEnoughWorkers() {
692	>	while ((runState & TERMINATING) == 0) {
693	>	int pc = parallelism;
694	>	int wc = workerCounts;
695	>	int rc = wc & RUNNING_COUNT_MASK;
696	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
697	>	if (tc < pc) {
698	>	if (UNSAFE.compareAndSwapInt
699	>	(this, workerCountsOffset,
700	>	wc, wc + (ONE_RUNNING|ONE_TOTAL)) &&
701	>	addWorker() == null)
702	>	break;
703	>	}
704	>	else if (tc > pc && rc < pc &&
705	>	tc > (runState & ACTIVE_COUNT_MASK)) {
706	>	ForkJoinWorkerThread spare = null;
707	>	ForkJoinWorkerThread[] ws = workers;
708	>	int nws = ws.length;
709	>	for (int i = 0; i < nws; ++i) {
710	>	ForkJoinWorkerThread w = ws[i];
711	>	if (w != null && w.isSuspended()) {
712	>	if ((workerCounts & RUNNING_COUNT_MASK) > pc)
713	>	return;
714	>	if (w.tryResumeSpare())
715	>	incrementRunningCount();
716	>	break;
717	>	}
718	>	}
719	>	}
720	>	else
721		break;
722		}
723		}
#	Line 727 | Line 753 | public class ForkJoinPool extends Abstra
753
754		accumulateStealCount(w); // collect final count
755		if (!tryTerminate(false))
756	<	ensureEnoughTotalWorkers();
756	>	ensureEnoughWorkers();
757		}
758
759		// Waiting for and signalling events
760
761		/**
736	–	* Ensures eventCount on exit is different (mod 2^32) than on
737	–	* entry.  CAS failures are OK -- any change in count suffices.
738	–	*/
739	–	private void advanceEventCount() {
740	–	int c;
741	–	UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1);
742	–	}
743	–
744	–	/**
762		* Releases workers blocked on a count not equal to current count.
763	+	* @return true if any released
764		*/
765	<	final void releaseWaiters() {
765	>	private void releaseWaiters() {
766		long top;
767	<	int id;
750	<	while ((id = (int)((top = eventWaiters) & WAITER_INDEX_MASK)) > 0 &&
751	<	(int)(top >>> EVENT_COUNT_SHIFT) != eventCount) {
767	>	while ((top = eventWaiters) != 0L) {
768		ForkJoinWorkerThread[] ws = workers;
769	<	ForkJoinWorkerThread w;
770	<	if (ws.length >= id && (w = ws[id - 1]) != null &&
771	<	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
772	<	top, w.nextWaiter))
773	<	LockSupport.unpark(w);
769	>	int n = ws.length;
770	>	for (;;) {
771	>	int i = ((int)(top & WAITER_ID_MASK)) - 1;
772	>	if (i < 0 || (int)(top >>> EVENT_COUNT_SHIFT) == eventCount)
773	>	return;
774	>	ForkJoinWorkerThread w;
775	>	if (i < n && (w = ws[i]) != null &&
776	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
777	>	top, w.nextWaiter)) {
778	>	LockSupport.unpark(w);
779	>	top = eventWaiters;
780	>	}
781	>	else
782	>	break;      // possibly stale; reread
783	>	}
784		}
785		}
786
787		/**
788	+	* Ensures eventCount on exit is different (mod 2^32) than on
789	+	* entry and wakes up all waiters
790	+	*/
791	+	private void signalEvent() {
792	+	int c;
793	+	do {} while (!UNSAFE.compareAndSwapInt(this, eventCountOffset,
794	+	c = eventCount, c+1));
795	+	releaseWaiters();
796	+	}
797	+
798	+	/**
799		* Advances eventCount and releases waiters until interference by
800		* other releasing threads is detected.
801		*/
802		final void signalWork() {
803	<	int ec;
804	<	UNSAFE.compareAndSwapInt(this, eventCountOffset, ec=eventCount, ec+1);
805	<	outer:for (;;) {
806	<	long top = eventWaiters;
807	<	ec = eventCount;
803	>	int c;
804	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c=eventCount, c+1);
805	>	long top;
806	>	while ((top = eventWaiters) != 0L) {
807	>	int ec = eventCount;
808	>	ForkJoinWorkerThread[] ws = workers;
809	>	int n = ws.length;
810		for (;;) {
811	<	ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w;
812	<	int id = (int)(top & WAITER_INDEX_MASK);
774	<	if (id <= 0 || (int)(top >>> EVENT_COUNT_SHIFT) == ec)
775	<	return;
776	<	if ((ws = workers).length < id || (w = ws[id - 1]) == null ||
777	<	!UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
778	<	top, top = w.nextWaiter))
779	<	continue outer;      // possibly stale; reread
780	<	LockSupport.unpark(w);
781	<	if (top != eventWaiters) // let someone else take over
811	>	int i = ((int)(top & WAITER_ID_MASK)) - 1;
812	>	if (i < 0 || (int)(top >>> EVENT_COUNT_SHIFT) == ec)
813		return;
814	+	ForkJoinWorkerThread w;
815	+	if (i < n && (w = ws[i]) != null &&
816	+	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
817	+	top, top = w.nextWaiter)) {
818	+	LockSupport.unpark(w);
819	+	if (top != eventWaiters) // let someone else take over
820	+	return;
821	+	}
822	+	else
823	+	break;      // possibly stale; reread
824		}
825		}
826		}
#	Line 790 | Line 831 | public class ForkJoinPool extends Abstra
831		* release others.
832		*
833		* @param w the calling worker thread
834	+	* @param retries the number of scans by caller failing to find work
835	+	* @return false if now too many threads running
836		*/
837	<	private void eventSync(ForkJoinWorkerThread w) {
838	<	if (!w.active) {
839	<	int prev = w.lastEventCount;
840	<	long nextTop = (((long)prev << EVENT_COUNT_SHIFT) |
837	>	private boolean eventSync(ForkJoinWorkerThread w, int retries) {
838	>	int wec = w.lastEventCount;
839	>	if (retries > 1) { // can only block after 2nd miss
840	>	long nextTop = (((long)wec << EVENT_COUNT_SHIFT) |
841		((long)(w.poolIndex + 1)));
842		long top;
843		while ((runState < SHUTDOWN || !tryTerminate(false)) &&
844	<	(((int)(top = eventWaiters) & WAITER_INDEX_MASK) == 0 ||
845	<	(int)(top >>> EVENT_COUNT_SHIFT) == prev) &&
846	<	eventCount == prev) {
844	>	(((int)(top = eventWaiters) & WAITER_ID_MASK) == 0 ||
845	>	(int)(top >>> EVENT_COUNT_SHIFT) == wec) &&
846	>	eventCount == wec) {
847		if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
848		w.nextWaiter = top, nextTop)) {
849		accumulateStealCount(w); // transfer steals while idle
850		Thread.interrupted();    // clear/ignore interrupt
851	<	while (eventCount == prev)
851	>	while (eventCount == wec)
852		w.doPark();
853		break;
854		}
855		}
856	<	w.lastEventCount = eventCount;
856	>	wec = eventCount;
857		}
858		releaseWaiters();
859	+	int wc = workerCounts;
860	+	if ((wc & RUNNING_COUNT_MASK) <= parallelism) {
861	+	w.lastEventCount = wec;
862	+	return true;
863	+	}
864	+	if (wec != w.lastEventCount) // back up if may re-wait
865	+	w.lastEventCount = wec - (wc >>> TOTAL_COUNT_SHIFT);
866	+	return false;
867		}
868
869		/**
#	Line 833 | Line 884 | public class ForkJoinPool extends Abstra
884		* upon resume it rechecks to make sure that it is still needed.
885		*
886		* @param w the worker
887	<	* @param worked false if the worker scanned for work but didn't
887	>	* @param retries the number of scans by caller failing to find work
888		* find any (in which case it may block waiting for work).
889		*/
890	<	final void preStep(ForkJoinWorkerThread w, boolean worked) {
890	>	final void preStep(ForkJoinWorkerThread w, int retries) {
891		boolean active = w.active;
892	<	boolean inactivate = !worked & active;
892	>	boolean inactivate = active && retries != 0;
893		for (;;) {
894	<	if (inactivate) {
895	<	int c = runState;
896	<	if (UNSAFE.compareAndSwapInt(this, runStateOffset,
897	<	c, c - ONE_ACTIVE))
898	<	inactivate = active = w.active = false;
899	<	}
900	<	int wc = workerCounts;
901	<	if ((wc & RUNNING_COUNT_MASK) <= parallelism) {
851	<	if (!worked)
852	<	eventSync(w);
853	<	return;
894	>	int rs, wc;
895	>	if (inactivate &&
896	>	UNSAFE.compareAndSwapInt(this, runStateOffset,
897	>	rs = runState, rs - ONE_ACTIVE))
898	>	inactivate = active = w.active = false;
899	>	if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= parallelism) {
900	>	if (active || eventSync(w, retries))
901	>	break;
902		}
903	<	if (!(inactivate |= active) &&  // must inactivate to suspend
903	>	else if (!(inactivate |= active) &&  // must inactivate to suspend
904		UNSAFE.compareAndSwapInt(this, workerCountsOffset,
905		wc, wc - ONE_RUNNING) &&
906	<	!w.suspendAsSpare())        // false if trimmed
907	<	return;
906	>	!w.suspendAsSpare())             // false if trimmed
907	>	break;
908		}
909		}
910
911		/**
912	<	* Adjusts counts and creates or resumes compensating threads for
913	<	* a worker blocking on task joinMe.  First tries resuming an
914	<	* existing spare (which usually also avoids any count
915	<	* adjustment), but must then decrement running count to determine
916	<	* whether a new thread is needed. See above for fuller
917	<	* explanation. This code is sprawled out non-modularly mainly
918	<	* because adaptive spinning works best if the entire method is
919	<	* either interpreted or compiled vs having only some pieces of it
920	<	* compiled.
912	>	* Awaits join of the given task if enough threads, or can resume
913	>	* or create a spare. Fails (in which case the given task might
914	>	* not be done) upon contention or lack of decision about
915	>	* blocking. Returns void because caller must check
916	>	* task status on return anyway.
917	>	*
918	>	* We allow blocking if:
919	>	*
920	>	* 1. There would still be at least as many running threads as
921	>	*    parallelism level if this thread blocks.
922	>	*
923	>	* 2. A spare is resumed to replace this worker. We tolerate
924	>	*    slop in the decision to replace if a spare is found without
925	>	*    first decrementing run count.  This may release too many,
926	>	*    but if so, the superfluous ones will re-suspend via
927	>	*    preStep().
928	>	*
929	>	* 3. After #spares repeated checks, there are no fewer than #spare
930	>	*    threads not running. We allow this slack to avoid hysteresis
931	>	*    and as a hedge against lag/uncertainty of running count
932	>	*    estimates when signalling or unblocking stalls.
933	>	*
934	>	* 4. All existing workers are busy (as rechecked via repeated
935	>	*    retries by caller) and a new spare is created.
936	>	*
937	>	* If none of the above hold, we try to escape out by
938	>	* re-incrementing count and returning to caller, which can retry
939	>	* later.
940		*
941		* @param joinMe the task to join
942	<	* @return task status on exit (to simplify usage by callers)
942	>	* @param retries if negative, then serve only as a precheck
943	>	*   that the thread can be replaced by a spare. Otherwise,
944	>	*   the number of repeated calls to this method returning busy
945	>	* @return true if the call must be retried because there
946	>	*   none of the blocking checks hold
947		*/
948	<	final int awaitJoin(ForkJoinTask<?> joinMe) {
949	<	int pc = parallelism;
950	<	boolean adj = false;        // true when running count adjusted
951	<	int scans = 0;
948	>	final boolean tryAwaitJoin(ForkJoinTask<?> joinMe, int retries) {
949	>	if (joinMe.status < 0) // precheck for cancellation
950	>	return false;
951	>	if ((runState & TERMINATING) != 0) { // shutting down
952	>	joinMe.cancelIgnoringExceptions();
953	>	return false;
954	>	}
955
956	<	while (joinMe.status >= 0) {
957	<	ForkJoinWorkerThread spare = null;
958	<	if ((workerCounts & RUNNING_COUNT_MASK) < pc) {
885	<	ForkJoinWorkerThread[] ws = workers;
886	<	int nws = ws.length;
887	<	for (int i = 0; i < nws; ++i) {
888	<	ForkJoinWorkerThread w = ws[i];
889	<	if (w != null && w.isSuspended()) {
890	<	spare = w;
891	<	break;
892	<	}
893	<	}
894	<	if (joinMe.status < 0)
895	<	break;
896	<	}
956	>	int pc = parallelism;
957	>	boolean running = true; // false when running count decremented
958	>	outer:for (;;) {
959		int wc = workerCounts;
960		int rc = wc & RUNNING_COUNT_MASK;
961	<	int dc = pc - rc;
962	<	if (dc > 0 && spare != null && spare.tryUnsuspend()) {
963	<	if (adj) {
964	<	int c;
965	<	do {} while (!UNSAFE.compareAndSwapInt
966	<	(this, workerCountsOffset,
967	<	c = workerCounts, c + ONE_RUNNING));
961	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
962	>	if (running) { // replace with spare or decrement count
963	>	if (rc <= pc && tc > pc &&
964	>	(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) {
965	>	ForkJoinWorkerThread[] ws = workers;
966	>	int nws = ws.length;
967	>	for (int i = 0; i < nws; ++i) { // search for spare
968	>	ForkJoinWorkerThread w = ws[i];
969	>	if (w != null) {
970	>	if (joinMe.status < 0)
971	>	return false;
972	>	if (w.isSuspended()) {
973	>	if ((workerCounts & RUNNING_COUNT_MASK)>=pc &&
974	>	w.tryResumeSpare()) {
975	>	running = false;
976	>	break outer;
977	>	}
978	>	continue outer; // rescan
979	>	}
980	>	}
981	>	}
982		}
983	<	adj = true;
984	<	LockSupport.unpark(spare);
983	>	if (retries < 0 || // < 0 means replacement check only
984	>	rc == 0 || joinMe.status < 0 || workerCounts != wc ||
985	>	!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
986	>	wc, wc - ONE_RUNNING))
987	>	return false; // done or inconsistent or contended
988	>	running = false;
989	>	if (rc > pc)
990	>	break;
991		}
992	<	else if (adj) {
993	<	if (dc <= 0)
992	>	else { // allow blocking if enough threads
993	>	if (rc >= pc || joinMe.status < 0)
994		break;
995	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
996	<	if (scans > tc) {
997	<	int ts = (tc - pc) * pc;
916	<	if (rc != 0 &&  (dc * dc < ts || !maintainsParallelism))
995	>	int sc = tc - pc + 1; // = spare threads, plus the one to add
996	>	if (retries > sc) {
997	>	if (rc > 0 && rc >= pc - sc) // allow slack
998		break;
999	<	if (scans > ts && tc < maxPoolSize &&
999	>	if (tc < MAX_THREADS &&
1000	>	tc == (runState & ACTIVE_COUNT_MASK) &&
1001	>	workerCounts == wc &&
1002		UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
1003	<	wc+(ONE_RUNNING|ONE_TOTAL))){
1003	>	wc+(ONE_RUNNING|ONE_TOTAL))) {
1004		addWorker();
1005		break;
1006		}
1007		}
1008	+	if (workerCounts == wc &&        // back out to allow rescan
1009	+	UNSAFE.compareAndSwapInt (this, workerCountsOffset,
1010	+	wc, wc + ONE_RUNNING)) {
1011	+	releaseWaiters();            // help others progress
1012	+	return true;                 // let caller retry
1013	+	}
1014		}
926	–	else if (rc != 0)
927	–	adj = UNSAFE.compareAndSwapInt (this, workerCountsOffset,
928	–	wc, wc - ONE_RUNNING);
929	–	if ((scans++ & 1) == 0)
930	–	releaseWaiters();   // help others progress
931	–	else
932	–	Thread.yield();     // avoid starving productive threads
933	–	}
934	–
935	–	if (adj) {
936	–	joinMe.internalAwaitDone();
937	–	int c;
938	–	do {} while (!UNSAFE.compareAndSwapInt
939	–	(this, workerCountsOffset,
940	–	c = workerCounts, c + ONE_RUNNING));
1015		}
1016	<	return joinMe.status;
1016	>	// arrive here if can block
1017	>	joinMe.internalAwaitDone();
1018	>	int c;                      // to inline incrementRunningCount
1019	>	do {} while (!UNSAFE.compareAndSwapInt
1020	>	(this, workerCountsOffset,
1021	>	c = workerCounts, c + ONE_RUNNING));
1022	>	return false;
1023		}
1024
1025		/**
1026	<	* Same idea as awaitJoin
1026	>	* Same idea as (and shares many code snippets with) tryAwaitJoin,
1027	>	* but self-contained because there are no caller retries.
1028	>	* TODO: Rework to use simpler API.
1029		*/
1030	<	final void awaitBlocker(ManagedBlocker blocker, boolean maintainPar)
1030	>	final void awaitBlocker(ManagedBlocker blocker)
1031		throws InterruptedException {
950	–	maintainPar &= maintainsParallelism;
951	–	int pc = parallelism;
952	–	boolean adj = false;        // true when running count adjusted
953	–	int scans = 0;
1032		boolean done;
1033	<
1034	<	for (;;) {
1035	<	if (done = blocker.isReleasable())
1036	<	break;
1037	<	ForkJoinWorkerThread spare = null;
1038	<	if ((workerCounts & RUNNING_COUNT_MASK) < pc) {
1039	<	ForkJoinWorkerThread[] ws = workers;
1040	<	int nws = ws.length;
1041	<	for (int i = 0; i < nws; ++i) {
1042	<	ForkJoinWorkerThread w = ws[i];
1043	<	if (w != null && w.isSuspended()) {
1044	<	spare = w;
1045	<	break;
1033	>	if (done = blocker.isReleasable())
1034	>	return;
1035	>	int pc = parallelism;
1036	>	int retries = 0;
1037	>	boolean running = true; // false when running count decremented
1038	>	outer:for (;;) {
1039	>	int wc = workerCounts;
1040	>	int rc = wc & RUNNING_COUNT_MASK;
1041	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
1042	>	if (running) {
1043	>	if (rc <= pc && tc > pc &&
1044	>	(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) {
1045	>	ForkJoinWorkerThread[] ws = workers;
1046	>	int nws = ws.length;
1047	>	for (int i = 0; i < nws; ++i) {
1048	>	ForkJoinWorkerThread w = ws[i];
1049	>	if (w != null) {
1050	>	if (done = blocker.isReleasable())
1051	>	return;
1052	>	if (w.isSuspended()) {
1053	>	if ((workerCounts & RUNNING_COUNT_MASK)>=pc &&
1054	>	w.tryResumeSpare()) {
1055	>	running = false;
1056	>	break outer;
1057	>	}
1058	>	continue outer; // rescan
1059	>	}
1060	>	}
1061		}
1062		}
1063		if (done = blocker.isReleasable())
1064	+	return;
1065	+	if (rc == 0 || workerCounts != wc ||
1066	+	!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1067	+	wc, wc - ONE_RUNNING))
1068	+	continue;
1069	+	running = false;
1070	+	if (rc > pc)
1071		break;
1072		}
1073	<	int wc = workerCounts;
1074	<	int rc = wc & RUNNING_COUNT_MASK;
975	<	int dc = pc - rc;
976	<	if (dc > 0 && spare != null && spare.tryUnsuspend()) {
977	<	if (adj) {
978	<	int c;
979	<	do {} while (!UNSAFE.compareAndSwapInt
980	<	(this, workerCountsOffset,
981	<	c = workerCounts, c + ONE_RUNNING));
982	<	}
983	<	adj = true;
984	<	LockSupport.unpark(spare);
985	<	}
986	<	else if (adj) {
987	<	if (dc <= 0)
1073	>	else {
1074	>	if (rc >= pc || (done = blocker.isReleasable()))
1075		break;
1076	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
1077	<	if (scans > tc) {
1078	<	int ts = (tc - pc) * pc;
992	<	if (rc != 0 &&  (dc * dc < ts || !maintainPar))
1076	>	int sc = tc - pc + 1;
1077	>	if (retries++ > sc) {
1078	>	if (rc > 0 && rc >= pc - sc)
1079		break;
1080	<	if (scans > ts && tc < maxPoolSize &&
1080	>	if (tc < MAX_THREADS &&
1081	>	tc == (runState & ACTIVE_COUNT_MASK) &&
1082	>	workerCounts == wc &&
1083		UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
1084	<	wc+(ONE_RUNNING|ONE_TOTAL))){
1084	>	wc+(ONE_RUNNING|ONE_TOTAL))) {
1085		addWorker();
1086		break;
1087		}
1088		}
1089	+	Thread.yield();
1090		}
1002	–	else if (rc != 0)
1003	–	adj = UNSAFE.compareAndSwapInt (this, workerCountsOffset,
1004	–	wc, wc - ONE_RUNNING);
1005	–	if ((++scans & 1) == 0)
1006	–	releaseWaiters();   // help others progress
1007	–	else
1008	–	Thread.yield();     // avoid starving productive threads
1091		}
1092
1093		try {
1094		if (!done)
1095		do {} while (!blocker.isReleasable() && !blocker.block());
1096		} finally {
1097	<	if (adj) {
1097	>	if (!running) {
1098		int c;
1099		do {} while (!UNSAFE.compareAndSwapInt
1100		(this, workerCountsOffset,
#	Line 1022 | Line 1104 | public class ForkJoinPool extends Abstra
1104		}
1105
1106		/**
1025	–	* Unless there are not enough other running threads, adjusts
1026	–	* counts and blocks a worker performing helpJoin that cannot find
1027	–	* any work.
1028	–	*
1029	–	* @return true if joinMe now done
1030	–	*/
1031	–	final boolean tryAwaitBusyJoin(ForkJoinTask<?> joinMe) {
1032	–	int pc = parallelism;
1033	–	outer:for (;;) {
1034	–	releaseWaiters();
1035	–	if ((workerCounts & RUNNING_COUNT_MASK) < pc) {
1036	–	ForkJoinWorkerThread[] ws = workers;
1037	–	int nws = ws.length;
1038	–	for (int i = 0; i < nws; ++i) {
1039	–	ForkJoinWorkerThread w = ws[i];
1040	–	if (w != null && w.isSuspended()) {
1041	–	if (joinMe.status < 0)
1042	–	return true;
1043	–	if ((workerCounts & RUNNING_COUNT_MASK) > pc)
1044	–	break;
1045	–	if (w.tryUnsuspend()) {
1046	–	LockSupport.unpark(w);
1047	–	break outer;
1048	–	}
1049	–	continue outer;
1050	–	}
1051	–	}
1052	–	}
1053	–	if (joinMe.status < 0)
1054	–	return true;
1055	–	int wc = workerCounts;
1056	–	if ((wc & RUNNING_COUNT_MASK) <= 2 ||
1057	–	(wc >>> TOTAL_COUNT_SHIFT) < pc)
1058	–	return false;  // keep this thread alive
1059	–	if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1060	–	wc, wc - ONE_RUNNING))
1061	–	break;
1062	–	}
1063	–
1064	–	joinMe.internalAwaitDone();
1065	–	int c;
1066	–	do {} while (!UNSAFE.compareAndSwapInt
1067	–	(this, workerCountsOffset,
1068	–	c = workerCounts, c + ONE_RUNNING));
1069	–	return true;
1070	–	}
1071	–
1072	–	/**
1107		* Possibly initiates and/or completes termination.
1108		*
1109		* @param now if true, unconditionally terminate, else only
#	Line 1090 | Line 1124 | public class ForkJoinPool extends Abstra
1124		// Finish now if all threads terminated; else in some subsequent call
1125		if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1126		advanceRunLevel(TERMINATED);
1127	<	terminationLatch.countDown();
1127	>	termination.arrive();
1128		}
1129		return true;
1130		}
#	Line 1103 | Line 1137 | public class ForkJoinPool extends Abstra
1137		cancelSubmissions();
1138		shutdownWorkers();
1139		cancelWorkerTasks();
1140	<	advanceEventCount();
1107	<	releaseWaiters();
1140	>	signalEvent();
1141		interruptWorkers();
1142		}
1143		}
#	Line 1194 | Line 1227 | public class ForkJoinPool extends Abstra
1227		* active thread.
1228		*/
1229		final int idlePerActive() {
1230	+	int pc = parallelism; // use parallelism, not rc
1231		int ac = runState;    // no mask -- artifically boosts during shutdown
1198	–	int pc = parallelism; // use targeted parallelism, not rc
1232		// Use exact results for small values, saturate past 4
1233		return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
1234		}
#	Line 1206 | Line 1239 | public class ForkJoinPool extends Abstra
1239
1240		/**
1241		* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1242	<	* java.lang.Runtime#availableProcessors}, and using the {@linkplain
1243	<	* #defaultForkJoinWorkerThreadFactory default thread factory}.
1242	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1243	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1244	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1245		*
1246		* @throws SecurityException if a security manager exists and
1247		*         the caller is not permitted to modify threads
#	Line 1216 | Line 1250 | public class ForkJoinPool extends Abstra
1250		*/
1251		public ForkJoinPool() {
1252		this(Runtime.getRuntime().availableProcessors(),
1253	<	defaultForkJoinWorkerThreadFactory);
1253	>	defaultForkJoinWorkerThreadFactory, null, false);
1254		}
1255
1256		/**
1257		* Creates a {@code ForkJoinPool} with the indicated parallelism
1258	<	* level and using the {@linkplain
1259	<	* #defaultForkJoinWorkerThreadFactory default thread factory}.
1258	>	* level, the {@linkplain
1259	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1260	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1261		*
1262		* @param parallelism the parallelism level
1263		* @throws IllegalArgumentException if parallelism less than or
#	Line 1233 | Line 1268 | public class ForkJoinPool extends Abstra
1268		*         java.lang.RuntimePermission}{@code ("modifyThread")}
1269		*/
1270		public ForkJoinPool(int parallelism) {
1271	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
1237	<	}
1238	<
1239	<	/**
1240	<	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1241	<	* java.lang.Runtime#availableProcessors}, and using the given
1242	<	* thread factory.
1243	<	*
1244	<	* @param factory the factory for creating new threads
1245	<	* @throws NullPointerException if the factory is null
1246	<	* @throws SecurityException if a security manager exists and
1247	<	*         the caller is not permitted to modify threads
1248	<	*         because it does not hold {@link
1249	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1250	<	*/
1251	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
1252	<	this(Runtime.getRuntime().availableProcessors(), factory);
1271	>	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1272		}
1273
1274		/**
1275	<	* Creates a {@code ForkJoinPool} with the given parallelism and
1257	<	* thread factory.
1275	>	* Creates a {@code ForkJoinPool} with the given parameters.
1276		*
1277	<	* @param parallelism the parallelism level
1278	<	* @param factory the factory for creating new threads
1277	>	* @param parallelism the parallelism level. For default value,
1278	>	* use {@link java.lang.Runtime#availableProcessors}.
1279	>	* @param factory the factory for creating new threads. For default value,
1280	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
1281	>	* @param handler the handler for internal worker threads that
1282	>	* terminate due to unrecoverable errors encountered while executing
1283	>	* tasks. For default value, use <code>null</code>.
1284	>	* @param asyncMode if true,
1285	>	* establishes local first-in-first-out scheduling mode for forked
1286	>	* tasks that are never joined. This mode may be more appropriate
1287	>	* than default locally stack-based mode in applications in which
1288	>	* worker threads only process event-style asynchronous tasks.
1289	>	* For default value, use <code>false</code>.
1290		* @throws IllegalArgumentException if parallelism less than or
1291		*         equal to zero, or greater than implementation limit
1292		* @throws NullPointerException if the factory is null
#	Line 1266 | Line 1295 | public class ForkJoinPool extends Abstra
1295		*         because it does not hold {@link
1296		*         java.lang.RuntimePermission}{@code ("modifyThread")}
1297		*/
1298	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
1298	>	public ForkJoinPool(int parallelism,
1299	>	ForkJoinWorkerThreadFactory factory,
1300	>	Thread.UncaughtExceptionHandler handler,
1301	>	boolean asyncMode) {
1302		checkPermission();
1303		if (factory == null)
1304		throw new NullPointerException();
1305		if (parallelism <= 0 || parallelism > MAX_THREADS)
1306		throw new IllegalArgumentException();
1275	–	this.poolNumber = poolNumberGenerator.incrementAndGet();
1276	–	int arraySize = initialArraySizeFor(parallelism);
1307		this.parallelism = parallelism;
1308		this.factory = factory;
1309	<	this.maxPoolSize = MAX_THREADS;
1310	<	this.maintainsParallelism = true;
1309	>	this.ueh = handler;
1310	>	this.locallyFifo = asyncMode;
1311	>	int arraySize = initialArraySizeFor(parallelism);
1312		this.workers = new ForkJoinWorkerThread[arraySize];
1313		this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
1314		this.workerLock = new ReentrantLock();
1315	<	this.terminationLatch = new CountDownLatch(1);
1315	>	this.termination = new Phaser(1);
1316	>	this.poolNumber = poolNumberGenerator.incrementAndGet();
1317		}
1318
1319		/**
#	Line 1309 | Line 1341 | public class ForkJoinPool extends Abstra
1341		if (runState >= SHUTDOWN)
1342		throw new RejectedExecutionException();
1343		submissionQueue.offer(task);
1344	<	advanceEventCount();
1345	<	releaseWaiters();
1314	<	ensureEnoughTotalWorkers();
1344	>	signalEvent();
1345	>	ensureEnoughWorkers();
1346		}
1347
1348		/**
1349		* Performs the given task, returning its result upon completion.
1350	+	* If the caller is already engaged in a fork/join computation in
1351	+	* the current pool, this method is equivalent in effect to
1352	+	* {@link ForkJoinTask#invoke}.
1353		*
1354		* @param task the task
1355		* @return the task's result
#	Line 1330 | Line 1364 | public class ForkJoinPool extends Abstra
1364
1365		/**
1366		* Arranges for (asynchronous) execution of the given task.
1367	+	* If the caller is already engaged in a fork/join computation in
1368	+	* the current pool, this method is equivalent in effect to
1369	+	* {@link ForkJoinTask#fork}.
1370		*
1371		* @param task the task
1372		* @throws NullPointerException if the task is null
#	Line 1357 | Line 1394 | public class ForkJoinPool extends Abstra
1394		}
1395
1396		/**
1397	+	* Submits a ForkJoinTask for execution.
1398	+	* If the caller is already engaged in a fork/join computation in
1399	+	* the current pool, this method is equivalent in effect to
1400	+	* {@link ForkJoinTask#fork}.
1401	+	*
1402	+	* @param task the task to submit
1403	+	* @return the task
1404	+	* @throws NullPointerException if the task is null
1405	+	* @throws RejectedExecutionException if the task cannot be
1406	+	*         scheduled for execution
1407	+	*/
1408	+	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1409	+	doSubmit(task);
1410	+	return task;
1411	+	}
1412	+
1413	+	/**
1414		* @throws NullPointerException if the task is null
1415		* @throws RejectedExecutionException if the task cannot be
1416		*         scheduled for execution
#	Line 1394 | Line 1448 | public class ForkJoinPool extends Abstra
1448		}
1449
1450		/**
1397	–	* Submits a ForkJoinTask for execution.
1398	–	*
1399	–	* @param task the task to submit
1400	–	* @return the task
1401	–	* @throws NullPointerException if the task is null
1402	–	* @throws RejectedExecutionException if the task cannot be
1403	–	*         scheduled for execution
1404	–	*/
1405	–	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1406	–	doSubmit(task);
1407	–	return task;
1408	–	}
1409	–
1410	–	/**
1451		* @throws NullPointerException       {@inheritDoc}
1452		* @throws RejectedExecutionException {@inheritDoc}
1453		*/
#	Line 1449 | Line 1489 | public class ForkJoinPool extends Abstra
1489		* @return the handler, or {@code null} if none
1490		*/
1491		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1452	–	workerCountReadFence();
1492		return ueh;
1493		}
1494
1495		/**
1457	–	* Sets the handler for internal worker threads that terminate due
1458	–	* to unrecoverable errors encountered while executing tasks.
1459	–	* Unless set, the current default or ThreadGroup handler is used
1460	–	* as handler.
1461	–	*
1462	–	* @param h the new handler
1463	–	* @return the old handler, or {@code null} if none
1464	–	* @throws SecurityException if a security manager exists and
1465	–	*         the caller is not permitted to modify threads
1466	–	*         because it does not hold {@link
1467	–	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1468	–	*/
1469	–	public Thread.UncaughtExceptionHandler
1470	–	setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
1471	–	checkPermission();
1472	–	Thread.UncaughtExceptionHandler old = ueh;
1473	–	if (h != old) {
1474	–	ueh = h;
1475	–	ForkJoinWorkerThread[] ws = workers;
1476	–	int nws = ws.length;
1477	–	for (int i = 0; i < nws; ++i) {
1478	–	ForkJoinWorkerThread w = ws[i];
1479	–	if (w != null)
1480	–	w.setUncaughtExceptionHandler(h);
1481	–	}
1482	–	}
1483	–	return old;
1484	–	}
1485	–
1486	–	/**
1487	–	* Sets the target parallelism level of this pool.
1488	–	*
1489	–	* @param parallelism the target parallelism
1490	–	* @throws IllegalArgumentException if parallelism less than or
1491	–	* equal to zero or greater than maximum size bounds
1492	–	* @throws SecurityException if a security manager exists and
1493	–	*         the caller is not permitted to modify threads
1494	–	*         because it does not hold {@link
1495	–	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1496	–	*/
1497	–	public void setParallelism(int parallelism) {
1498	–	checkPermission();
1499	–	if (parallelism <= 0 || parallelism > maxPoolSize)
1500	–	throw new IllegalArgumentException();
1501	–	workerCountReadFence();
1502	–	int pc = this.parallelism;
1503	–	if (pc != parallelism) {
1504	–	this.parallelism = parallelism;
1505	–	workerCountWriteFence();
1506	–	// Release spares. If too many, some will die after re-suspend
1507	–	ForkJoinWorkerThread[] ws = workers;
1508	–	int nws = ws.length;
1509	–	for (int i = 0; i < nws; ++i) {
1510	–	ForkJoinWorkerThread w = ws[i];
1511	–	if (w != null && w.tryUnsuspend()) {
1512	–	int c;
1513	–	do {} while (!UNSAFE.compareAndSwapInt
1514	–	(this, workerCountsOffset,
1515	–	c = workerCounts, c + ONE_RUNNING));
1516	–	LockSupport.unpark(w);
1517	–	}
1518	–	}
1519	–	ensureEnoughTotalWorkers();
1520	–	advanceEventCount();
1521	–	releaseWaiters(); // force config recheck by existing workers
1522	–	}
1523	–	}
1524	–
1525	–	/**
1496		* Returns the targeted parallelism level of this pool.
1497		*
1498		* @return the targeted parallelism level of this pool
1499		*/
1500		public int getParallelism() {
1531	–	//        workerCountReadFence(); // inlined below
1532	–	int ignore = workerCounts;
1501		return parallelism;
1502		}
1503
#	Line 1546 | Line 1514 | public class ForkJoinPool extends Abstra
1514		}
1515
1516		/**
1549	–	* Returns the maximum number of threads allowed to exist in the
1550	–	* pool. Unless set using {@link #setMaximumPoolSize}, the
1551	–	* maximum is an implementation-defined value designed only to
1552	–	* prevent runaway growth.
1553	–	*
1554	–	* @return the maximum
1555	–	*/
1556	–	public int getMaximumPoolSize() {
1557	–	workerCountReadFence();
1558	–	return maxPoolSize;
1559	–	}
1560	–
1561	–	/**
1562	–	* Sets the maximum number of threads allowed to exist in the
1563	–	* pool. The given value should normally be greater than or equal
1564	–	* to the {@link #getParallelism parallelism} level. Setting this
1565	–	* value has no effect on current pool size. It controls
1566	–	* construction of new threads. The use of this method may cause
1567	–	* tasks that intrinsically require extra threads for dependent
1568	–	* computations to indefinitely stall. If you are instead trying
1569	–	* to minimize internal thread creation, consider setting {@link
1570	–	* #setMaintainsParallelism} as false.
1571	–	*
1572	–	* @throws IllegalArgumentException if negative or greater than
1573	–	* internal implementation limit
1574	–	*/
1575	–	public void setMaximumPoolSize(int newMax) {
1576	–	if (newMax < 0 || newMax > MAX_THREADS)
1577	–	throw new IllegalArgumentException();
1578	–	maxPoolSize = newMax;
1579	–	workerCountWriteFence();
1580	–	}
1581	–
1582	–	/**
1583	–	* Returns {@code true} if this pool dynamically maintains its
1584	–	* target parallelism level. If false, new threads are added only
1585	–	* to avoid possible starvation.  This setting is by default true.
1586	–	*
1587	–	* @return {@code true} if maintains parallelism
1588	–	*/
1589	–	public boolean getMaintainsParallelism() {
1590	–	workerCountReadFence();
1591	–	return maintainsParallelism;
1592	–	}
1593	–
1594	–	/**
1595	–	* Sets whether this pool dynamically maintains its target
1596	–	* parallelism level. If false, new threads are added only to
1597	–	* avoid possible starvation.
1598	–	*
1599	–	* @param enable {@code true} to maintain parallelism
1600	–	*/
1601	–	public void setMaintainsParallelism(boolean enable) {
1602	–	maintainsParallelism = enable;
1603	–	workerCountWriteFence();
1604	–	}
1605	–
1606	–	/**
1607	–	* Establishes local first-in-first-out scheduling mode for forked
1608	–	* tasks that are never joined. This mode may be more appropriate
1609	–	* than default locally stack-based mode in applications in which
1610	–	* worker threads only process asynchronous tasks.  This method is
1611	–	* designed to be invoked only when the pool is quiescent, and
1612	–	* typically only before any tasks are submitted. The effects of
1613	–	* invocations at other times may be unpredictable.
1614	–	*
1615	–	* @param async if {@code true}, use locally FIFO scheduling
1616	–	* @return the previous mode
1617	–	* @see #getAsyncMode
1618	–	*/
1619	–	public boolean setAsyncMode(boolean async) {
1620	–	workerCountReadFence();
1621	–	boolean oldMode = locallyFifo;
1622	–	if (oldMode != async) {
1623	–	locallyFifo = async;
1624	–	workerCountWriteFence();
1625	–	ForkJoinWorkerThread[] ws = workers;
1626	–	int nws = ws.length;
1627	–	for (int i = 0; i < nws; ++i) {
1628	–	ForkJoinWorkerThread w = ws[i];
1629	–	if (w != null)
1630	–	w.setAsyncMode(async);
1631	–	}
1632	–	}
1633	–	return oldMode;
1634	–	}
1635	–
1636	–	/**
1517		* Returns {@code true} if this pool uses local first-in-first-out
1518		* scheduling mode for forked tasks that are never joined.
1519		*
1520		* @return {@code true} if this pool uses async mode
1641	–	* @see #setAsyncMode
1521		*/
1522		public boolean getAsyncMode() {
1644	–	workerCountReadFence();
1523		return locallyFifo;
1524		}
1525
#	Line 1782 | Line 1660 | public class ForkJoinPool extends Abstra
1660		}
1661
1662		/**
1663	+	* Returns count of total parks by existing workers.
1664	+	* Used during development only since not meaningful to users.
1665	+	*/
1666	+	private int collectParkCount() {
1667	+	int count = 0;
1668	+	ForkJoinWorkerThread[] ws = workers;
1669	+	int nws = ws.length;
1670	+	for (int i = 0; i < nws; ++i) {
1671	+	ForkJoinWorkerThread w = ws[i];
1672	+	if (w != null)
1673	+	count += w.parkCount;
1674	+	}
1675	+	return count;
1676	+	}
1677	+
1678	+	/**
1679		* Returns a string identifying this pool, as well as its state,
1680		* including indications of run state, parallelism level, and
1681		* worker and task counts.
#	Line 1798 | Line 1692 | public class ForkJoinPool extends Abstra
1692		int pc = parallelism;
1693		int rs = runState;
1694		int ac = rs & ACTIVE_COUNT_MASK;
1695	+	//        int pk = collectParkCount();
1696		return super.toString() +
1697		"[" + runLevelToString(rs) +
1698		", parallelism = " + pc +
#	Line 1807 | Line 1702 | public class ForkJoinPool extends Abstra
1702		", steals = " + st +
1703		", tasks = " + qt +
1704		", submissions = " + qs +
1705	+	//            ", parks = " + pk +
1706		"]";
1707		}
1708
#	Line 1902 | Line 1798 | public class ForkJoinPool extends Abstra
1798		*/
1799		public boolean awaitTermination(long timeout, TimeUnit unit)
1800		throws InterruptedException {
1801	<	return terminationLatch.await(timeout, unit);
1801	>	try {
1802	>	return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1803	>	} catch(TimeoutException ex) {
1804	>	return false;
1805	>	}
1806		}
1807
1808		/**
#	Line 1954 | Line 1854 | public class ForkJoinPool extends Abstra
1854		* Blocks in accord with the given blocker.  If the current thread
1855		* is a {@link ForkJoinWorkerThread}, this method possibly
1856		* arranges for a spare thread to be activated if necessary to
1857	<	* ensure parallelism while the current thread is blocked.
1958	<	*
1959	<	* <p>If {@code maintainParallelism} is {@code true} and the pool
1960	<	* supports it ({@link #getMaintainsParallelism}), this method
1961	<	* attempts to maintain the pool's nominal parallelism. Otherwise
1962	<	* it activates a thread only if necessary to avoid complete
1963	<	* starvation. This option may be preferable when blockages use
1964	<	* timeouts, or are almost always brief.
1857	>	* ensure sufficient parallelism while the current thread is blocked.
1858		*
1859		* <p>If the caller is not a {@link ForkJoinTask}, this method is
1860		* behaviorally equivalent to
#	Line 1975 | Line 1868 | public class ForkJoinPool extends Abstra
1868		* first be expanded to ensure parallelism, and later adjusted.
1869		*
1870		* @param blocker the blocker
1978	–	* @param maintainParallelism if {@code true} and supported by
1979	–	* this pool, attempt to maintain the pool's nominal parallelism;
1980	–	* otherwise activate a thread only if necessary to avoid
1981	–	* complete starvation.
1871		* @throws InterruptedException if blocker.block did so
1872		*/
1873	<	public static void managedBlock(ManagedBlocker blocker,
1985	<	boolean maintainParallelism)
1873	>	public static void managedBlock(ManagedBlocker blocker)
1874		throws InterruptedException {
1875		Thread t = Thread.currentThread();
1876		if (t instanceof ForkJoinWorkerThread)
1877	<	((ForkJoinWorkerThread) t).pool.
1878	<	awaitBlocker(blocker, maintainParallelism);
1879	<	else
1880	<	awaitBlocker(blocker);
1993	<	}
1994	<
1995	<	/**
1996	<	* Performs Non-FJ blocking
1997	<	*/
1998	<	private static void awaitBlocker(ManagedBlocker blocker)
1999	<	throws InterruptedException {
2000	<	do {} while (!blocker.isReleasable() && !blocker.block());
1877	>	((ForkJoinWorkerThread) t).pool.awaitBlocker(blocker);
1878	>	else {
1879	>	do {} while (!blocker.isReleasable() && !blocker.block());
1880	>	}
1881		}
1882
1883		// AbstractExecutorService overrides.  These rely on undocumented
#	Line 2026 | Line 1906 | public class ForkJoinPool extends Abstra
1906		private static final long stealCountOffset =
1907		objectFieldOffset("stealCount",ForkJoinPool.class);
1908
2029	–
1909		private static long objectFieldOffset(String field, Class<?> klazz) {
1910		try {
1911		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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