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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 1.60 by dl, Sat Jul 24 20:28:18 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 following
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 take actions when
142	+	* one worker is waiting to join a task stolen (or always held by)
143	+	* another.  Becauae we are multiplexing many tasks on to a pool
144	+	* of workers, we can't just let them block (as in Thread.join).
145	+	* We also cannot just reassign the joiner's run-time stack with
146	+	* another and replace it later, which would be a form of
147	+	* "continuation", that even if possible is not necessarily a good
148	+	* idea. Given that the creation costs of most threads on most
149	+	* systems mainly surrounds setting up runtime stacks, thread
150	+	* creation and switching is usually not much more expensive than
151	+	* stack creation and switching, and is more flexible). Instead we
152	+	* combine two tactics:
153	+	*
154	+	*   Helping: 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	+	*   Compensating: Unless there are already enough live threads,
160	+	*      creating or or re-activating a spare thread to compensate
161	+	*      for the (blocked) joiner until it unblocks.  Spares then
162	+	*      suspend at their next opportunity or eventually die if
163	+	*      unused for too long.  See below and the internal
164	+	*      documentation for tryAwaitJoin for more details about
165	+	*      compensation 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 helping so uses a
177	+	* special version of compensation 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 475 | Line 497 | public class ForkJoinPool extends Abstra
497		* making decisions about creating and suspending spare
498		* threads. Updated only by CAS. Note that adding a new worker
499		* requires incrementing both counts, since workers start off in
500	<	* running state.  This field is also used for memory-fencing
479	<	* configuration parameters.
500	>	* running state.
501		*/
502		private volatile int workerCounts;
503
#	Line 485 | Line 506 | public class ForkJoinPool extends Abstra
506		private static final int ONE_RUNNING        = 1;
507		private static final int ONE_TOTAL          = 1 << TOTAL_COUNT_SHIFT;
508
488	–	/*
489	–	* Fields parallelism. maxPoolSize, and maintainsParallelism are
490	–	* non-volatile, but external reads/writes use workerCount fences
491	–	* to ensure visability.
492	–	*/
493	–
509		/**
510		* The target parallelism level.
511	+	* Accessed directly by ForkJoinWorkerThreads.
512		*/
513	<	private int parallelism;
498	<
499	<	/**
500	<	* The maximum allowed pool size.
501	<	*/
502	<	private int maxPoolSize;
513	>	final int parallelism;
514
515		/**
516		* True if use local fifo, not default lifo, for local polling
517	<	* Replicated by ForkJoinWorkerThreads
517	>	* Read by, and replicated by ForkJoinWorkerThreads
518		*/
519	<	private volatile boolean locallyFifo;
519	>	final boolean locallyFifo;
520
521		/**
522	<	* Controls whether to add spares to maintain parallelism
522	>	* The uncaught exception handler used when any worker abruptly
523	>	* terminates.
524		*/
525	<	private boolean maintainsParallelism;
514	<
515	<	/**
516	<	* The uncaught exception handler used when any worker
517	<	* abruptly terminates
518	<	*/
519	<	private volatile Thread.UncaughtExceptionHandler ueh;
525	>	private final Thread.UncaughtExceptionHandler ueh;
526
527		/**
528		* Pool number, just for assigning useful names to worker threads
529		*/
530		private final int poolNumber;
531
532	<	// utilities for updating fields
532	>	// Utilities for CASing fields. Note that several of these
533	>	// are manually inlined by callers
534
535		/**
536	<	* Adds delta to running count.  Used mainly by ForkJoinTask.
536	>	* Increments running count.  Also used by ForkJoinTask.
537		*/
538	<	final void updateRunningCount(int delta) {
539	<	int wc;
538	>	final void incrementRunningCount() {
539	>	int c;
540		do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset,
541	<	wc = workerCounts,
542	<	wc + delta));
541	>	c = workerCounts,
542	>	c + ONE_RUNNING));
543		}
544
545		/**
546	<	* Decrements running count unless already zero
546	>	* Tries to decrement running count unless already zero
547		*/
548		final boolean tryDecrementRunningCount() {
549		int wc = workerCounts;
#	Line 547 | Line 554 | public class ForkJoinPool extends Abstra
554		}
555
556		/**
557	<	* Write fence for user modifications of pool parameters
551	<	* (parallelism. etc).  Note that it doesn't matter if CAS fails.
557	>	* Tries to increment running count
558		*/
559	<	private void workerCountWriteFence() {
559	>	final boolean tryIncrementRunningCount() {
560		int wc;
561	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
562	<	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;
561	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset,
562	>	wc = workerCounts, wc + ONE_RUNNING);
563		}
564
565		/**
#	Line 658 | Line 656 | public class ForkJoinPool extends Abstra
656		try {
657		w = factory.newThread(this);
658		} finally { // Adjust on either null or exceptional factory return
659	<	if (w == null) {
659	>	if (w == null)
660		onWorkerCreationFailure();
663	–	return null;
664	–	}
661		}
662	<	w.start(recordWorker(w), locallyFifo, ueh);
662	>	if (w != null)
663	>	w.start(recordWorker(w), ueh);
664		return w;
665		}
666
#	Line 673 | Line 670 | public class ForkJoinPool extends Abstra
670		private void onWorkerCreationFailure() {
671		for (;;) {
672		int wc = workerCounts;
673	<	if ((wc >>> TOTAL_COUNT_SHIFT) > 0 &&
674	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
675	<	wc, wc - (ONE_RUNNING|ONE_TOTAL)))
673	>	int rc = wc & RUNNING_COUNT_MASK;
674	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
675	>	if (rc == 0 || wc == 0)
676	>	Thread.yield(); // must 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,
685	>	* Creates enough total workers to establish target parallelism,
686		* giving up if terminating or addWorker fails
687		*/
688		private void ensureEnoughTotalWorkers() {
#	Line 718 | Line 718 | public class ForkJoinPool extends Abstra
718		for (;;) {
719		int wc = workerCounts;
720		int rc = wc & RUNNING_COUNT_MASK;
721	<	if (rc - nr < 0 || (wc >>> TOTAL_COUNT_SHIFT) == 0)
721	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
722	>	if (rc - nr < 0 || tc == 0)
723		Thread.yield(); // back off if waiting for other updates
724		else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset,
725		wc, wc - unit))
#	Line 733 | Line 734 | public class ForkJoinPool extends Abstra
734		// Waiting for and signalling events
735
736		/**
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	–	/**
737		* Releases workers blocked on a count not equal to current count.
738	+	* @return true if any released
739		*/
740	<	final void releaseWaiters() {
740	>	private void releaseWaiters() {
741		long top;
742	<	int id;
750	<	while ((id = (int)((top = eventWaiters) & WAITER_INDEX_MASK)) > 0 &&
751	<	(int)(top >>> EVENT_COUNT_SHIFT) != eventCount) {
742	>	while ((top = eventWaiters) != 0L) {
743		ForkJoinWorkerThread[] ws = workers;
744	<	ForkJoinWorkerThread w;
745	<	if (ws.length >= id && (w = ws[id - 1]) != null &&
746	<	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
747	<	top, w.nextWaiter))
748	<	LockSupport.unpark(w);
744	>	int n = ws.length;
745	>	for (;;) {
746	>	int i = ((int)(top & WAITER_ID_MASK)) - 1;
747	>	int e = (int)(top >>> EVENT_COUNT_SHIFT);
748	>	if (i < 0 || e == eventCount)
749	>	return;
750	>	ForkJoinWorkerThread w;
751	>	if (i < n && (w = ws[i]) != null &&
752	>	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
753	>	top, w.nextWaiter)) {
754	>	LockSupport.unpark(w);
755	>	top = eventWaiters;
756	>	}
757	>	else
758	>	break;      // possibly stale; reread
759	>	}
760		}
761		}
762
763		/**
764	+	* Ensures eventCount on exit is different (mod 2^32) than on
765	+	* entry and wakes up all waiters
766	+	*/
767	+	private void signalEvent() {
768	+	int c;
769	+	do {} while (!UNSAFE.compareAndSwapInt(this, eventCountOffset,
770	+	c = eventCount, c+1));
771	+	releaseWaiters();
772	+	}
773	+
774	+	/**
775		* Advances eventCount and releases waiters until interference by
776		* other releasing threads is detected.
777		*/
778		final void signalWork() {
779	<	int ec;
780	<	UNSAFE.compareAndSwapInt(this, eventCountOffset, ec=eventCount, ec+1);
781	<	outer:for (;;) {
782	<	long top = eventWaiters;
783	<	ec = eventCount;
779	>	int c;
780	>	UNSAFE.compareAndSwapInt(this, eventCountOffset, c=eventCount, c+1);
781	>	long top;
782	>	while ((top = eventWaiters) != 0L) {
783	>	int ec = eventCount;
784	>	ForkJoinWorkerThread[] ws = workers;
785	>	int n = ws.length;
786		for (;;) {
787	<	ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w;
788	<	int id = (int)(top & WAITER_INDEX_MASK);
789	<	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
787	>	int i = ((int)(top & WAITER_ID_MASK)) - 1;
788	>	int e = (int)(top >>> EVENT_COUNT_SHIFT);
789	>	if (i < 0 || e == ec)
790		return;
791	+	ForkJoinWorkerThread w;
792	+	if (i < n && (w = ws[i]) != null &&
793	+	UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
794	+	top, top = w.nextWaiter)) {
795	+	LockSupport.unpark(w);
796	+	if (top != eventWaiters) // let someone else take over
797	+	return;
798	+	}
799	+	else
800	+	break;      // possibly stale; reread
801		}
802		}
803		}
804
805		/**
806	<	* If worker is inactive, blocks until terminating or event count
807	<	* advances from last value held by worker; in any case helps
790	<	* release others.
806	>	* Blockss worker until terminating or event count
807	>	* advances from last value held by worker
808		*
809		* @param w the calling worker thread
810		*/
811		private void eventSync(ForkJoinWorkerThread w) {
812	<	if (!w.active) {
813	<	int prev = w.lastEventCount;
814	<	long nextTop = (((long)prev << EVENT_COUNT_SHIFT) |
815	<	((long)(w.poolIndex + 1)));
816	<	long top;
817	<	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
818	<	(((int)(top = eventWaiters) & WAITER_INDEX_MASK) == 0 ||
819	<	(int)(top >>> EVENT_COUNT_SHIFT) == prev) &&
820	<	eventCount == prev) {
821	<	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
822	<	w.nextWaiter = top, nextTop)) {
823	<	accumulateStealCount(w); // transfer steals while idle
824	<	Thread.interrupted();    // clear/ignore interrupt
825	<	while (eventCount == prev)
826	<	w.doPark();
810	<	break;
811	<	}
812	>	int wec = w.lastEventCount;
813	>	long nextTop = (((long)wec << EVENT_COUNT_SHIFT) |
814	>	((long)(w.poolIndex + 1)));
815	>	long top;
816	>	while ((runState < SHUTDOWN || !tryTerminate(false)) &&
817	>	(((int)(top = eventWaiters) & WAITER_ID_MASK) == 0 ||
818	>	(int)(top >>> EVENT_COUNT_SHIFT) == wec) &&
819	>	eventCount == wec) {
820	>	if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset,
821	>	w.nextWaiter = top, nextTop)) {
822	>	accumulateStealCount(w); // transfer steals while idle
823	>	Thread.interrupted();    // clear/ignore interrupt
824	>	while (eventCount == wec)
825	>	w.doPark();
826	>	break;
827		}
813	–	w.lastEventCount = eventCount;
828		}
829	<	releaseWaiters();
829	>	w.lastEventCount = eventCount;
830		}
831
832		/**
#	Line 833 | Line 847 | public class ForkJoinPool extends Abstra
847		* upon resume it rechecks to make sure that it is still needed.
848		*
849		* @param w the worker
850	<	* @param worked false if the worker scanned for work but didn't
850	>	* @param retries the number of scans by caller failing to find work
851		* find any (in which case it may block waiting for work).
852		*/
853	<	final void preStep(ForkJoinWorkerThread w, boolean worked) {
853	>	final void preStep(ForkJoinWorkerThread w, int retries) {
854		boolean active = w.active;
855	<	boolean inactivate = !worked & active;
855	>	boolean inactivate = active && retries > 0;
856		for (;;) {
857	<	if (inactivate) {
858	<	int c = runState;
859	<	if (UNSAFE.compareAndSwapInt(this, runStateOffset,
860	<	c, c - ONE_ACTIVE))
861	<	inactivate = active = w.active = false;
862	<	}
863	<	int wc = workerCounts;
864	<	if ((wc & RUNNING_COUNT_MASK) <= parallelism) {
865	<	if (!worked)
866	<	eventSync(w);
867	<	return;
857	>	int rs, wc;
858	>	if (inactivate &&
859	>	UNSAFE.compareAndSwapInt(this, runStateOffset,
860	>	rs = runState, rs - ONE_ACTIVE))
861	>	inactivate = active = w.active = false;
862	>	if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= parallelism) {
863	>	if (retries > 0) {
864	>	if (retries > 1 && !active)
865	>	eventSync(w);
866	>	releaseWaiters();
867	>	}
868	>	break;
869		}
870		if (!(inactivate |= active) &&  // must inactivate to suspend
871		UNSAFE.compareAndSwapInt(this, workerCountsOffset,
872		wc, wc - ONE_RUNNING) &&
873	<	!w.suspendAsSpare())        // false if trimmed
874	<	return;
873	>	!w.suspendAsSpare())             // false if trimmed
874	>	break;
875		}
876		}
877
878		/**
879	<	* Adjusts counts and creates or resumes compensating threads for
880	<	* a worker blocking on task joinMe.  First tries resuming an
881	<	* existing spare (which usually also avoids any count
882	<	* adjustment), but must then decrement running count to determine
883	<	* whether a new thread is needed. See above for fuller
884	<	* explanation. This code is sprawled out non-modularly mainly
885	<	* because adaptive spinning works best if the entire method is
886	<	* either interpreted or compiled vs having only some pieces of it
887	<	* compiled.
879	>	* Awaits join of the given task if enough threads, or can resume
880	>	* or create a spare. Fails (in which case the given task might
881	>	* not be done) upon contention or lack of decision about
882	>	* blocking.
883	>	*
884	>	* We allow blocking if:
885	>	*
886	>	* 1. There would still be at least as many running threads as
887	>	*    parallelism level if this thread blocks.
888	>	*
889	>	* 2. A spare is resumed to replace this worker. We tolerate
890	>	*    races in the decision to replace when a spare is found.
891	>	*    This may release too many, but if so, the superfluous ones
892	>	*    will re-suspend via preStep().
893	>	*
894	>	* 3. After #spares repeated retries, there are fewer than #spare
895	>	*    threads not running. We allow this slack to avoid hysteresis
896	>	*    and as a hedge against lag/uncertainty of running count
897	>	*    estimates when signalling or unblocking stalls.
898	>	*
899	>	* 4. All existing workers are busy (as rechecked via #spares
900	>	*    repeated retries by caller) and a new spare is created.
901	>	*
902	>	* If none of the above hold, we escape out by re-incrementing
903	>	* count and returning to caller, which can retry later.
904		*
905		* @param joinMe the task to join
906	<	* @return task status on exit (to simplify usage by callers)
906	>	* @param retries the number of calls to this method for this join
907		*/
908	<	final int awaitJoin(ForkJoinTask<?> joinMe) {
908	>	final void tryAwaitJoin(ForkJoinTask<?> joinMe, int retries) {
909		int pc = parallelism;
910	<	boolean adj = false;        // true when running count adjusted
911	<	int scans = 0;
912	<
913	<	while (joinMe.status >= 0) {
914	<	ForkJoinWorkerThread spare = null;
915	<	if ((workerCounts & RUNNING_COUNT_MASK) < pc) {
916	<	ForkJoinWorkerThread[] ws = workers;
917	<	int nws = ws.length;
918	<	for (int i = 0; i < nws; ++i) {
919	<	ForkJoinWorkerThread w = ws[i];
920	<	if (w != null && w.isSuspended()) {
921	<	spare = w;
922	<	break;
910	>	boolean running = true; // false when running count decremented
911	>	outer:while (joinMe.status >= 0) {
912	>	int wc = workerCounts;
913	>	int rc = wc & RUNNING_COUNT_MASK;
914	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
915	>	if (running) { // replace with spare or decrement count
916	>	if (rc <= pc && tc > pc &&
917	>	(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) {
918	>	ForkJoinWorkerThread[] ws = workers; // search for spare
919	>	int nws = ws.length;
920	>	for (int i = 0; i < nws; ++i) {
921	>	ForkJoinWorkerThread w = ws[i];
922	>	if (w != null && w.isSuspended()) {
923	>	if ((workerCounts & RUNNING_COUNT_MASK) > pc)
924	>	continue outer;
925	>	if (joinMe.status < 0)
926	>	break outer;
927	>	if (w.tryResumeSpare()) {
928	>	running = false;
929	>	break outer;
930	>	}
931	>	continue outer; // rescan on failure to resume
932	>	}
933		}
934		}
935	<	if (joinMe.status < 0)
935	>	if ((rc <= pc && (rc == 0 || --retries < 0)) || // no retry
936	>	joinMe.status < 0)
937		break;
938	+	if (workerCounts == wc &&
939	+	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
940	+	wc, wc - ONE_RUNNING))
941	+	running = false;
942		}
943	<	int wc = workerCounts;
944	<	int rc = wc & RUNNING_COUNT_MASK;
945	<	int dc = pc - rc;
946	<	if (dc > 0 && spare != null && spare.tryUnsuspend()) {
947	<	if (adj) {
948	<	int c;
949	<	do {} while (!UNSAFE.compareAndSwapInt
950	<	(this, workerCountsOffset,
951	<	c = workerCounts, c + ONE_RUNNING));
943	>	else { // allow blocking if enough threads
944	>	int sc = tc - pc + 1;          // = spares, plus the one to add
945	>	if (sc > 0 && rc > 0 && rc >= pc - sc && rc > pc - retries)
946	>	break;
947	>	if (--retries > sc && tc < MAX_THREADS &&
948	>	tc == (runState & ACTIVE_COUNT_MASK) &&
949	>	workerCounts == wc &&
950	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
951	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
952	>	addWorker();
953	>	break;
954		}
955	<	adj = true;
956	<	LockSupport.unpark(spare);
957	<	}
958	<	else if (adj) {
911	<	if (dc <= 0)
955	>	if (workerCounts == wc &&
956	>	UNSAFE.compareAndSwapInt (this, workerCountsOffset,
957	>	wc, wc + ONE_RUNNING)) {
958	>	running = true;            // back out; allow retry
959		break;
913	–	int tc = wc >>> TOTAL_COUNT_SHIFT;
914	–	if (scans > tc) {
915	–	int ts = (tc - pc) * pc;
916	–	if (rc != 0 &&  (dc * dc < ts || !maintainsParallelism))
917	–	break;
918	–	if (scans > ts && tc < maxPoolSize &&
919	–	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
920	–	wc+(ONE_RUNNING|ONE_TOTAL))){
921	–	addWorker();
922	–	break;
923	–	}
960		}
961		}
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
962		}
963	<
964	<	if (adj) {
963	>	if (!running) { // can block
964	>	int c;                      // to inline incrementRunningCount
965		joinMe.internalAwaitDone();
937	–	int c;
966		do {} while (!UNSAFE.compareAndSwapInt
967		(this, workerCountsOffset,
968		c = workerCounts, c + ONE_RUNNING));
969		}
942	–	return joinMe.status;
970		}
971
972		/**
973	<	* Same idea as awaitJoin
973	>	* Same idea as (and shares many code snippets with) tryAwaitJoin,
974	>	* but self-contained because there are no caller retries.
975	>	* TODO: Rework to use simpler API.
976		*/
977	<	final void awaitBlocker(ManagedBlocker blocker, boolean maintainPar)
977	>	final void awaitBlocker(ManagedBlocker blocker)
978		throws InterruptedException {
950	–	maintainPar &= maintainsParallelism;
979		int pc = parallelism;
980	<	boolean adj = false;        // true when running count adjusted
981	<	int scans = 0;
980	>	boolean running = true;
981	>	int retries = 0;
982		boolean done;
983	<
956	<	for (;;) {
957	<	if (done = blocker.isReleasable())
958	<	break;
959	<	ForkJoinWorkerThread spare = null;
960	<	if ((workerCounts & RUNNING_COUNT_MASK) < pc) {
961	<	ForkJoinWorkerThread[] ws = workers;
962	<	int nws = ws.length;
963	<	for (int i = 0; i < nws; ++i) {
964	<	ForkJoinWorkerThread w = ws[i];
965	<	if (w != null && w.isSuspended()) {
966	<	spare = w;
967	<	break;
968	<	}
969	<	}
970	<	if (done = blocker.isReleasable())
971	<	break;
972	<	}
983	>	outer:while (!(done = blocker.isReleasable())) {
984		int wc = workerCounts;
985		int rc = wc & RUNNING_COUNT_MASK;
986	<	int dc = pc - rc;
987	<	if (dc > 0 && spare != null && spare.tryUnsuspend()) {
988	<	if (adj) {
989	<	int c;
990	<	do {} while (!UNSAFE.compareAndSwapInt
991	<	(this, workerCountsOffset,
992	<	c = workerCounts, c + ONE_RUNNING));
993	<	}
994	<	adj = true;
995	<	LockSupport.unpark(spare);
996	<	}
997	<	else if (adj) {
998	<	if (dc <= 0)
999	<	break;
1000	<	int tc = wc >>> TOTAL_COUNT_SHIFT;
1001	<	if (scans > tc) {
1002	<	int ts = (tc - pc) * pc;
1003	<	if (rc != 0 &&  (dc * dc < ts || !maintainPar))
986	>	int tc = wc >>> TOTAL_COUNT_SHIFT;
987	>	if (running) {
988	>	if (rc <= pc && tc > pc &&
989	>	(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) {
990	>	ForkJoinWorkerThread[] ws = workers;
991	>	int nws = ws.length;
992	>	for (int i = 0; i < nws; ++i) {
993	>	ForkJoinWorkerThread w = ws[i];
994	>	if (w != null && w.isSuspended()) {
995	>	if ((workerCounts & RUNNING_COUNT_MASK) > pc)
996	>	continue outer;
997	>	if (done = blocker.isReleasable())
998	>	break outer;
999	>	if (w.tryResumeSpare()) {
1000	>	running = false;
1001	>	break outer;
1002	>	}
1003	>	continue outer;
1004	>	}
1005	>	}
1006	>	if (done = blocker.isReleasable())
1007		break;
1008	<	if (scans > ts && tc < maxPoolSize &&
1009	<	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
1010	<	wc+(ONE_RUNNING|ONE_TOTAL))){
1011	<	addWorker();
1008	>	}
1009	>	if (rc > 0 && workerCounts == wc &&
1010	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset,
1011	>	wc, wc - ONE_RUNNING)) {
1012	>	running = false;
1013	>	if (rc > pc)
1014		break;
999	–	}
1015		}
1016		}
1017	<	else if (rc != 0)
1018	<	adj = UNSAFE.compareAndSwapInt (this, workerCountsOffset,
1019	<	wc, wc - ONE_RUNNING);
1020	<	if ((++scans & 1) == 0)
1021	<	releaseWaiters();   // help others progress
1022	<	else
1023	<	Thread.yield();     // avoid starving productive threads
1017	>	else if (rc >= pc)
1018	>	break;
1019	>	else if (tc < MAX_THREADS &&
1020	>	tc == (runState & ACTIVE_COUNT_MASK) &&
1021	>	workerCounts == wc &&
1022	>	UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc,
1023	>	wc + (ONE_RUNNING|ONE_TOTAL))) {
1024	>	addWorker();
1025	>	break;
1026	>	}
1027	>	else if (workerCounts == wc &&
1028	>	UNSAFE.compareAndSwapInt (this, workerCountsOffset,
1029	>	wc, wc + ONE_RUNNING)) {
1030	>	Thread.yield();
1031	>	++retries;
1032	>	running = true;            // allow rescan
1033	>	}
1034		}
1035
1036		try {
1037		if (!done)
1038		do {} while (!blocker.isReleasable() && !blocker.block());
1039		} finally {
1040	<	if (adj) {
1040	>	if (!running) {
1041		int c;
1042		do {} while (!UNSAFE.compareAndSwapInt
1043		(this, workerCountsOffset,
#	Line 1022 | Line 1047 | public class ForkJoinPool extends Abstra
1047		}
1048
1049		/**
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	–	/**
1050		* Possibly initiates and/or completes termination.
1051		*
1052		* @param now if true, unconditionally terminate, else only
#	Line 1090 | Line 1067 | public class ForkJoinPool extends Abstra
1067		// Finish now if all threads terminated; else in some subsequent call
1068		if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) {
1069		advanceRunLevel(TERMINATED);
1070	<	terminationLatch.countDown();
1070	>	termination.arrive();
1071		}
1072		return true;
1073		}
#	Line 1103 | Line 1080 | public class ForkJoinPool extends Abstra
1080		cancelSubmissions();
1081		shutdownWorkers();
1082		cancelWorkerTasks();
1083	<	advanceEventCount();
1107	<	releaseWaiters();
1083	>	signalEvent();
1084		interruptWorkers();
1085		}
1086		}
#	Line 1194 | Line 1170 | public class ForkJoinPool extends Abstra
1170		* active thread.
1171		*/
1172		final int idlePerActive() {
1173	+	int pc = parallelism; // use parallelism, not rc
1174		int ac = runState;    // no mask -- artifically boosts during shutdown
1198	–	int pc = parallelism; // use targeted parallelism, not rc
1175		// Use exact results for small values, saturate past 4
1176		return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3;
1177		}
#	Line 1206 | Line 1182 | public class ForkJoinPool extends Abstra
1182
1183		/**
1184		* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1185	<	* java.lang.Runtime#availableProcessors}, and using the {@linkplain
1186	<	* #defaultForkJoinWorkerThreadFactory default thread factory}.
1185	>	* java.lang.Runtime#availableProcessors}, using the {@linkplain
1186	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1187	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1188		*
1189		* @throws SecurityException if a security manager exists and
1190		*         the caller is not permitted to modify threads
#	Line 1216 | Line 1193 | public class ForkJoinPool extends Abstra
1193		*/
1194		public ForkJoinPool() {
1195		this(Runtime.getRuntime().availableProcessors(),
1196	<	defaultForkJoinWorkerThreadFactory);
1196	>	defaultForkJoinWorkerThreadFactory, null, false);
1197		}
1198
1199		/**
1200		* Creates a {@code ForkJoinPool} with the indicated parallelism
1201	<	* level and using the {@linkplain
1202	<	* #defaultForkJoinWorkerThreadFactory default thread factory}.
1201	>	* level, the {@linkplain
1202	>	* #defaultForkJoinWorkerThreadFactory default thread factory},
1203	>	* no UncaughtExceptionHandler, and non-async LIFO processing mode.
1204		*
1205		* @param parallelism the parallelism level
1206		* @throws IllegalArgumentException if parallelism less than or
#	Line 1233 | Line 1211 | public class ForkJoinPool extends Abstra
1211		*         java.lang.RuntimePermission}{@code ("modifyThread")}
1212		*/
1213		public ForkJoinPool(int parallelism) {
1214	<	this(parallelism, defaultForkJoinWorkerThreadFactory);
1214	>	this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
1215		}
1216
1217		/**
1218	<	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
1241	<	* java.lang.Runtime#availableProcessors}, and using the given
1242	<	* thread factory.
1218	>	* Creates a {@code ForkJoinPool} with the given parameters.
1219		*
1220	<	* @param factory the factory for creating new threads
1221	<	* @throws NullPointerException if the factory is null
1222	<	* @throws SecurityException if a security manager exists and
1223	<	*         the caller is not permitted to modify threads
1224	<	*         because it does not hold {@link
1225	<	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1226	<	*/
1227	<	public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
1228	<	this(Runtime.getRuntime().availableProcessors(), factory);
1229	<	}
1230	<
1231	<	/**
1232	<	* Creates a {@code ForkJoinPool} with the given parallelism and
1257	<	* thread factory.
1258	<	*
1259	<	* @param parallelism the parallelism level
1260	<	* @param factory the factory for creating new threads
1220	>	* @param parallelism the parallelism level. For default value,
1221	>	* use {@link java.lang.Runtime#availableProcessors}.
1222	>	* @param factory the factory for creating new threads. For default value,
1223	>	* use {@link #defaultForkJoinWorkerThreadFactory}.
1224	>	* @param handler the handler for internal worker threads that
1225	>	* terminate due to unrecoverable errors encountered while executing
1226	>	* tasks. For default value, use <code>null</code>.
1227	>	* @param asyncMode if true,
1228	>	* establishes local first-in-first-out scheduling mode for forked
1229	>	* tasks that are never joined. This mode may be more appropriate
1230	>	* than default locally stack-based mode in applications in which
1231	>	* worker threads only process event-style asynchronous tasks.
1232	>	* For default value, use <code>false</code>.
1233		* @throws IllegalArgumentException if parallelism less than or
1234		*         equal to zero, or greater than implementation limit
1235		* @throws NullPointerException if the factory is null
#	Line 1266 | Line 1238 | public class ForkJoinPool extends Abstra
1238		*         because it does not hold {@link
1239		*         java.lang.RuntimePermission}{@code ("modifyThread")}
1240		*/
1241	<	public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
1241	>	public ForkJoinPool(int parallelism,
1242	>	ForkJoinWorkerThreadFactory factory,
1243	>	Thread.UncaughtExceptionHandler handler,
1244	>	boolean asyncMode) {
1245		checkPermission();
1246		if (factory == null)
1247		throw new NullPointerException();
1248		if (parallelism <= 0 || parallelism > MAX_THREADS)
1249		throw new IllegalArgumentException();
1275	–	this.poolNumber = poolNumberGenerator.incrementAndGet();
1276	–	int arraySize = initialArraySizeFor(parallelism);
1250		this.parallelism = parallelism;
1251		this.factory = factory;
1252	<	this.maxPoolSize = MAX_THREADS;
1253	<	this.maintainsParallelism = true;
1252	>	this.ueh = handler;
1253	>	this.locallyFifo = asyncMode;
1254	>	int arraySize = initialArraySizeFor(parallelism);
1255		this.workers = new ForkJoinWorkerThread[arraySize];
1256		this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
1257		this.workerLock = new ReentrantLock();
1258	<	this.terminationLatch = new CountDownLatch(1);
1258	>	this.termination = new Phaser(1);
1259	>	this.poolNumber = poolNumberGenerator.incrementAndGet();
1260		}
1261
1262		/**
#	Line 1309 | Line 1284 | public class ForkJoinPool extends Abstra
1284		if (runState >= SHUTDOWN)
1285		throw new RejectedExecutionException();
1286		submissionQueue.offer(task);
1287	<	advanceEventCount();
1313	<	releaseWaiters();
1287	>	signalEvent();
1288		ensureEnoughTotalWorkers();
1289		}
1290
1291		/**
1292		* Performs the given task, returning its result upon completion.
1293	+	* If the caller is already engaged in a fork/join computation in
1294	+	* the current pool, this method is equivalent in effect to
1295	+	* {@link ForkJoinTask#invoke}.
1296		*
1297		* @param task the task
1298		* @return the task's result
#	Line 1330 | Line 1307 | public class ForkJoinPool extends Abstra
1307
1308		/**
1309		* Arranges for (asynchronous) execution of the given task.
1310	+	* If the caller is already engaged in a fork/join computation in
1311	+	* the current pool, this method is equivalent in effect to
1312	+	* {@link ForkJoinTask#fork}.
1313		*
1314		* @param task the task
1315		* @throws NullPointerException if the task is null
#	Line 1357 | Line 1337 | public class ForkJoinPool extends Abstra
1337		}
1338
1339		/**
1340	+	* Submits a ForkJoinTask for execution.
1341	+	* If the caller is already engaged in a fork/join computation in
1342	+	* the current pool, this method is equivalent in effect to
1343	+	* {@link ForkJoinTask#fork}.
1344	+	*
1345	+	* @param task the task to submit
1346	+	* @return the task
1347	+	* @throws NullPointerException if the task is null
1348	+	* @throws RejectedExecutionException if the task cannot be
1349	+	*         scheduled for execution
1350	+	*/
1351	+	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
1352	+	doSubmit(task);
1353	+	return task;
1354	+	}
1355	+
1356	+	/**
1357		* @throws NullPointerException if the task is null
1358		* @throws RejectedExecutionException if the task cannot be
1359		*         scheduled for execution
#	Line 1394 | Line 1391 | public class ForkJoinPool extends Abstra
1391		}
1392
1393		/**
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	–	/**
1394		* @throws NullPointerException       {@inheritDoc}
1395		* @throws RejectedExecutionException {@inheritDoc}
1396		*/
#	Line 1449 | Line 1432 | public class ForkJoinPool extends Abstra
1432		* @return the handler, or {@code null} if none
1433		*/
1434		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
1452	–	workerCountReadFence();
1435		return ueh;
1436		}
1437
1438		/**
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	–	/**
1439		* Returns the targeted parallelism level of this pool.
1440		*
1441		* @return the targeted parallelism level of this pool
1442		*/
1443		public int getParallelism() {
1531	–	//        workerCountReadFence(); // inlined below
1532	–	int ignore = workerCounts;
1444		return parallelism;
1445		}
1446
#	Line 1546 | Line 1457 | public class ForkJoinPool extends Abstra
1457		}
1458
1459		/**
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	–	/**
1460		* Returns {@code true} if this pool uses local first-in-first-out
1461		* scheduling mode for forked tasks that are never joined.
1462		*
1463		* @return {@code true} if this pool uses async mode
1641	–	* @see #setAsyncMode
1464		*/
1465		public boolean getAsyncMode() {
1644	–	workerCountReadFence();
1466		return locallyFifo;
1467		}
1468
#	Line 1782 | Line 1603 | public class ForkJoinPool extends Abstra
1603		}
1604
1605		/**
1606	+	* Returns count of total parks by existing workers.
1607	+	* Used during development only since not meaningful to users.
1608	+	*/
1609	+	private int collectParkCount() {
1610	+	int count = 0;
1611	+	ForkJoinWorkerThread[] ws = workers;
1612	+	int nws = ws.length;
1613	+	for (int i = 0; i < nws; ++i) {
1614	+	ForkJoinWorkerThread w = ws[i];
1615	+	if (w != null)
1616	+	count += w.parkCount;
1617	+	}
1618	+	return count;
1619	+	}
1620	+
1621	+	/**
1622		* Returns a string identifying this pool, as well as its state,
1623		* including indications of run state, parallelism level, and
1624		* worker and task counts.
#	Line 1798 | Line 1635 | public class ForkJoinPool extends Abstra
1635		int pc = parallelism;
1636		int rs = runState;
1637		int ac = rs & ACTIVE_COUNT_MASK;
1638	+	//        int pk = collectParkCount();
1639		return super.toString() +
1640		"[" + runLevelToString(rs) +
1641		", parallelism = " + pc +
#	Line 1807 | Line 1645 | public class ForkJoinPool extends Abstra
1645		", steals = " + st +
1646		", tasks = " + qt +
1647		", submissions = " + qs +
1648	+	//            ", parks = " + pk +
1649		"]";
1650		}
1651
#	Line 1902 | Line 1741 | public class ForkJoinPool extends Abstra
1741		*/
1742		public boolean awaitTermination(long timeout, TimeUnit unit)
1743		throws InterruptedException {
1744	<	return terminationLatch.await(timeout, unit);
1744	>	try {
1745	>	return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0;
1746	>	} catch(TimeoutException ex) {
1747	>	return false;
1748	>	}
1749		}
1750
1751		/**
#	Line 1954 | Line 1797 | public class ForkJoinPool extends Abstra
1797		* Blocks in accord with the given blocker.  If the current thread
1798		* is a {@link ForkJoinWorkerThread}, this method possibly
1799		* arranges for a spare thread to be activated if necessary to
1800	<	* 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.
1800	>	* ensure sufficient parallelism while the current thread is blocked.
1801		*
1802		* <p>If the caller is not a {@link ForkJoinTask}, this method is
1803		* behaviorally equivalent to
#	Line 1975 | Line 1811 | public class ForkJoinPool extends Abstra
1811		* first be expanded to ensure parallelism, and later adjusted.
1812		*
1813		* @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.
1814		* @throws InterruptedException if blocker.block did so
1815		*/
1816	<	public static void managedBlock(ManagedBlocker blocker,
1985	<	boolean maintainParallelism)
1816	>	public static void managedBlock(ManagedBlocker blocker)
1817		throws InterruptedException {
1818		Thread t = Thread.currentThread();
1819		if (t instanceof ForkJoinWorkerThread)
1820	<	((ForkJoinWorkerThread) t).pool.
1821	<	awaitBlocker(blocker, maintainParallelism);
1822	<	else
1823	<	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());
1820	>	((ForkJoinWorkerThread) t).pool.awaitBlocker(blocker);
1821	>	else {
1822	>	do {} while (!blocker.isReleasable() && !blocker.block());
1823	>	}
1824		}
1825
1826		// AbstractExecutorService overrides.  These rely on undocumented
#	Line 2026 | Line 1849 | public class ForkJoinPool extends Abstra
1849		private static final long stealCountOffset =
1850		objectFieldOffset("stealCount",ForkJoinPool.class);
1851
2029	–
1852		private static long objectFieldOffset(String field, Class<?> klazz) {
1853		try {
1854		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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