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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.115 by jsr166, Thu Jan 26 19:10:27 2012 UTC vs.
Revision 1.123 by dl, Mon Feb 20 18:20:06 2012 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	–
8		import java.util.ArrayList;
9		import java.util.Arrays;
10		import java.util.Collection;
#	Line 21 | Line 20 | import java.util.concurrent.RunnableFutu
20		import java.util.concurrent.TimeUnit;
21		import java.util.concurrent.atomic.AtomicInteger;
22		import java.util.concurrent.atomic.AtomicLong;
23	<	import java.util.concurrent.locks.ReentrantLock;
23	>	import java.util.concurrent.locks.AbstractQueuedSynchronizer;
24		import java.util.concurrent.locks.Condition;
25
26		/**
#	Line 60 | Line 59 | import java.util.concurrent.locks.Condit
59		* convenient form for informal monitoring.
60		*
61		* <p> As is the case with other ExecutorServices, there are three
62	<	* main task execution methods summarized in the following
63	<	* table. These are designed to be used primarily by clients not
64	<	* already engaged in fork/join computations in the current pool.  The
65	<	* main forms of these methods accept instances of {@code
66	<	* ForkJoinTask}, but overloaded forms also allow mixed execution of
67	<	* plain {@code Runnable}- or {@code Callable}- based activities as
68	<	* well.  However, tasks that are already executing in a pool should
69	<	* normally instead use the within-computation forms listed in the
70	<	* table unless using async event-style tasks that are not usually
71	<	* joined, in which case there is little difference among choice of
73	<	* methods.
62	>	* main task execution methods summarized in the following table.
63	>	* These are designed to be used primarily by clients not already
64	>	* engaged in fork/join computations in the current pool.  The main
65	>	* forms of these methods accept instances of {@code ForkJoinTask},
66	>	* but overloaded forms also allow mixed execution of plain {@code
67	>	* Runnable}- or {@code Callable}- based activities as well.  However,
68	>	* tasks that are already executing in a pool should normally instead
69	>	* use the within-computation forms listed in the table unless using
70	>	* async event-style tasks that are not usually joined, in which case
71	>	* there is little difference among choice of methods.
72		*
73		* <table BORDER CELLPADDING=3 CELLSPACING=1>
74		*  <tr>
#	Line 131 | Line 129 | public class ForkJoinPool extends Abstra
129		*
130		* This class and its nested classes provide the main
131		* functionality and control for a set of worker threads:
132	<	* Submissions from non-FJ threads enter into submission
133	<	* queues. Workers take these tasks and typically split them into
134	<	* subtasks that may be stolen by other workers.  Preference rules
135	<	* give first priority to processing tasks from their own queues
136	<	* (LIFO or FIFO, depending on mode), then to randomized FIFO
137	<	* steals of tasks in other queues.
132	>	* Submissions from non-FJ threads enter into submission queues.
133	>	* Workers take these tasks and typically split them into subtasks
134	>	* that may be stolen by other workers.  Preference rules give
135	>	* first priority to processing tasks from their own queues (LIFO
136	>	* or FIFO, depending on mode), then to randomized FIFO steals of
137	>	* tasks in other queues.
138		*
139	<	* WorkQueues.
139	>	* WorkQueues
140		* ==========
141		*
142		* Most operations occur within work-stealing queues (in nested
#	Line 156 | Line 154 | public class ForkJoinPool extends Abstra
154		* (http://research.sun.com/scalable/pubs/index.html) and
155		* "Idempotent work stealing" by Michael, Saraswat, and Vechev,
156		* PPoPP 2009 (http://portal.acm.org/citation.cfm?id=1504186).
157	<	* The main differences ultimately stem from gc requirements that
157	>	* The main differences ultimately stem from GC requirements that
158		* we null out taken slots as soon as we can, to maintain as small
159		* a footprint as possible even in programs generating huge
160		* numbers of tasks. To accomplish this, we shift the CAS
#	Line 178 | Line 176 | public class ForkJoinPool extends Abstra
176		* If an attempted steal fails, a thief always chooses a different
177		* random victim target to try next. So, in order for one thief to
178		* progress, it suffices for any in-progress poll or new push on
179	<	* any empty queue to complete.
179	>	* any empty queue to complete. (This is why we normally use
180	>	* method pollAt and its variants that try once at the apparent
181	>	* base index, else consider alternative actions, rather than
182	>	* method poll.)
183		*
184		* This approach also enables support of a user mode in which local
185		* task processing is in FIFO, not LIFO order, simply by using
#	Line 188 | Line 189 | public class ForkJoinPool extends Abstra
189		* rarely provide the best possible performance on a given
190		* machine, but portably provide good throughput by averaging over
191		* these factors.  (Further, even if we did try to use such
192	<	* information, we do not usually have a basis for exploiting
193	<	* it. For example, some sets of tasks profit from cache
194	<	* affinities, but others are harmed by cache pollution effects.)
192	>	* information, we do not usually have a basis for exploiting it.
193	>	* For example, some sets of tasks profit from cache affinities,
194	>	* but others are harmed by cache pollution effects.)
195		*
196		* WorkQueues are also used in a similar way for tasks submitted
197		* to the pool. We cannot mix these tasks in the same queues used
198		* for work-stealing (this would contaminate lifo/fifo
199	<	* processing). Instead, we loosely associate (via hashing)
200	<	* submission queues with submitting threads, and randomly scan
201	<	* these queues as well when looking for work. In essence,
202	<	* submitters act like workers except that they never take tasks,
203	<	* and they are multiplexed on to a finite number of shared work
204	<	* queues. However, classes are set up so that future extensions
205	<	* could allow submitters to optionally help perform tasks as
206	<	* well. Pool submissions from internal workers are also allowed,
207	<	* but use randomized rather than thread-hashed queue indices to
208	<	* avoid imbalance.  Insertion of tasks in shared mode requires a
199	>	* processing). Instead, we loosely associate submission queues
200	>	* with submitting threads, using a form of hashing.  The
201	>	* ThreadLocal Submitter class contains a value initially used as
202	>	* a hash code for choosing existing queues, but may be randomly
203	>	* repositioned upon contention with other submitters.  In
204	>	* essence, submitters act like workers except that they never
205	>	* take tasks, and they are multiplexed on to a finite number of
206	>	* shared work queues. However, classes are set up so that future
207	>	* extensions could allow submitters to optionally help perform
208	>	* tasks as well. Insertion of tasks in shared mode requires a
209		* lock (mainly to protect in the case of resizing) but we use
210		* only a simple spinlock (using bits in field runState), because
211	<	* submitters encountering a busy queue try or create others so
212	<	* never block.
211	>	* submitters encountering a busy queue move on to try or create
212	>	* other queues -- they block only when creating and registering
213	>	* new queues.
214		*
215	<	* Management.
215	>	* Management
216		* ==========
217		*
218		* The main throughput advantages of work-stealing stem from
#	Line 220 | Line 222 | public class ForkJoinPool extends Abstra
222		* tactic for avoiding bottlenecks is packing nearly all
223		* essentially atomic control state into two volatile variables
224		* that are by far most often read (not written) as status and
225	<	* consistency checks
225	>	* consistency checks.
226		*
227		* Field "ctl" contains 64 bits holding all the information needed
228		* to atomically decide to add, inactivate, enqueue (on an event
#	Line 246 | Line 248 | public class ForkJoinPool extends Abstra
248		* readers must tolerate null slots. Shared (submission) queues
249		* are at even indices, worker queues at odd indices. Grouping
250		* them together in this way simplifies and speeds up task
251	<	* scanning. To avoid flailing during start-up, the array is
252	<	* presized to hold twice #parallelism workers (which is unlikely
253	<	* to need further resizing during execution). But to avoid
254	<	* dealing with so many null slots, variable runState includes a
253	<	* mask for the nearest power of two that contains all current
254	<	* workers.  All worker thread creation is on-demand, triggered by
255	<	* task submissions, replacement of terminated workers, and/or
251	>	* scanning.
252	>	*
253	>	* All worker thread creation is on-demand, triggered by task
254	>	* submissions, replacement of terminated workers, and/or
255		* compensation for blocked workers. However, all other support
256		* code is set up to work with other policies.  To ensure that we
257		* do not hold on to worker references that would prevent GC, ALL
#	Line 265 | Line 264 | public class ForkJoinPool extends Abstra
264		* both index-check and null-check the IDs. All such accesses
265		* ignore bad IDs by returning out early from what they are doing,
266		* since this can only be associated with termination, in which
267	<	* case it is OK to give up.
268	<	*
269	<	* All uses of the workQueues array check that it is non-null
270	<	* (even if previously non-null). This allows nulling during
271	<	* termination, which is currently not necessary, but remains an
272	<	* option for resource-revocation-based shutdown schemes. It also
274	<	* helps reduce JIT issuance of uncommon-trap code, which tends to
267	>	* case it is OK to give up.  All uses of the workQueues array
268	>	* also check that it is non-null (even if previously
269	>	* non-null). This allows nulling during termination, which is
270	>	* currently not necessary, but remains an option for
271	>	* resource-revocation-based shutdown schemes. It also helps
272	>	* reduce JIT issuance of uncommon-trap code, which tends to
273		* unnecessarily complicate control flow in some methods.
274		*
275		* Event Queuing. Unlike HPC work-stealing frameworks, we cannot
#	Line 299 | Line 297 | public class ForkJoinPool extends Abstra
297		* some other queued worker rather than itself, which has the same
298		* net effect. Because enqueued workers may actually be rescanning
299		* rather than waiting, we set and clear the "parker" field of
300	<	* Workqueues to reduce unnecessary calls to unpark.  (This
300	>	* WorkQueues to reduce unnecessary calls to unpark.  (This
301		* requires a secondary recheck to avoid missed signals.)  Note
302		* the unusual conventions about Thread.interrupts surrounding
303		* parking and other blocking: Because interrupts are used solely
#	Line 327 | Line 325 | public class ForkJoinPool extends Abstra
325		* terminating all workers after long periods of non-use.
326		*
327		* Shutdown and Termination. A call to shutdownNow atomically sets
328	<	* a runState bit and then (non-atomically) sets each workers
328	>	* a runState bit and then (non-atomically) sets each worker's
329		* runState status, cancels all unprocessed tasks, and wakes up
330		* all waiting workers.  Detecting whether termination should
331		* commence after a non-abrupt shutdown() call requires more work
#	Line 336 | Line 334 | public class ForkJoinPool extends Abstra
334		* indication but non-abrupt shutdown still requires a rechecking
335		* scan for any workers that are inactive but not queued.
336		*
337	<	* Joining Tasks.
338	<	* ==============
337	>	* Joining Tasks
338	>	* =============
339		*
340		* Any of several actions may be taken when one worker is waiting
341	<	* to join a task stolen (or always held by) another.  Because we
341	>	* to join a task stolen (or always held) by another.  Because we
342		* are multiplexing many tasks on to a pool of workers, we can't
343		* just let them block (as in Thread.join).  We also cannot just
344		* reassign the joiner's run-time stack with another and replace
345		* it later, which would be a form of "continuation", that even if
346		* possible is not necessarily a good idea since we sometimes need
347	<	* both an unblocked task and its continuation to
348	<	* progress. Instead we combine two tactics:
347	>	* both an unblocked task and its continuation to progress.
348	>	* Instead we combine two tactics:
349		*
350		*   Helping: Arranging for the joiner to execute some task that it
351		*      would be running if the steal had not occurred.
#	Line 382 | Line 380 | public class ForkJoinPool extends Abstra
380		* (http://portal.acm.org/citation.cfm?id=155354). It differs in
381		* that: (1) We only maintain dependency links across workers upon
382		* steals, rather than use per-task bookkeeping.  This sometimes
383	<	* requires a linear scan of workers array to locate stealers, but
384	<	* often doesn't because stealers leave hints (that may become
383	>	* requires a linear scan of workQueues array to locate stealers,
384	>	* but often doesn't because stealers leave hints (that may become
385		* stale/wrong) of where to locate them.  A stealHint is only a
386		* hint because a worker might have had multiple steals and the
387		* hint records only one of them (usually the most current).
#	Line 394 | Line 392 | public class ForkJoinPool extends Abstra
392		* which means that we miss links in the chain during long-lived
393		* tasks, GC stalls etc (which is OK since blocking in such cases
394		* is usually a good idea).  (4) We bound the number of attempts
395	<	* to find work (see MAX_HELP_DEPTH) and fall back to suspending
396	<	* the worker and if necessary replacing it with another.
395	>	* to find work (see MAX_HELP) and fall back to suspending the
396	>	* worker and if necessary replacing it with another.
397		*
398		* It is impossible to keep exactly the target parallelism number
399		* of threads running at any given time.  Determining the
400		* existence of conservatively safe helping targets, the
401		* availability of already-created spares, and the apparent need
402		* to create new spares are all racy, so we rely on multiple
403	<	* retries of each.  Currently, in keeping with on-demand
404	<	* signalling policy, we compensate only if blocking would leave
405	<	* less than one active (non-waiting, non-blocked) worker.
406	<	* Additionally, to avoid some false alarms due to GC, lagging
407	<	* counters, system activity, etc, compensated blocking for joins
408	<	* is only attempted after rechecks stabilize in
409	<	* ForkJoinTask.awaitJoin. (Retries are interspersed with
410	<	* Thread.yield, for good citizenship.)
403	>	* retries of each.  Compensation in the apparent absence of
404	>	* helping opportunities is challenging to control on JVMs, where
405	>	* GC and other activities can stall progress of tasks that in
406	>	* turn stall out many other dependent tasks, without us being
407	>	* able to determine whether they will ever require compensation.
408	>	* Even though work-stealing otherwise encounters little
409	>	* degradation in the presence of more threads than cores,
410	>	* aggressively adding new threads in such cases entails risk of
411	>	* unwanted positive feedback control loops in which more threads
412	>	* cause more dependent stalls (as well as delayed progress of
413	>	* unblocked threads to the point that we know they are available)
414	>	* leading to more situations requiring more threads, and so
415	>	* on. This aspect of control can be seen as an (analytically
416	>	* intractible) game with an opponent that may choose the worst
417	>	* (for us) active thread to stall at any time.  We take several
418	>	* precautions to bound losses (and thus bound gains), mainly in
419	>	* methods tryCompensate and awaitJoin: (1) We only try
420	>	* compensation after attempting enough helping steps (measured
421	>	* via counting and timing) that we have already consumed the
422	>	* estimated cost of creating and activating a new thread.  (2) We
423	>	* allow up to 50% of threads to be blocked before initially
424	>	* adding any others, and unless completely saturated, check that
425	>	* some work is available for a new worker before adding. Also, we
426	>	* create up to only 50% more threads until entering a mode that
427	>	* only adds a thread if all others are possibly blocked.  All
428	>	* together, this means that we might be half as fast to react,
429	>	* and create half as many threads as possible in the ideal case,
430	>	* but present vastly fewer anomalies in all other cases compared
431	>	* to both more aggressive and more conservative alternatives.
432		*
433		* Style notes: There is a lot of representation-level coupling
434		* among classes ForkJoinPool, ForkJoinWorkerThread, and
#	Line 417 | Line 436 | public class ForkJoinPool extends Abstra
436		* managed by ForkJoinPool, so are directly accessed.  There is
437		* little point trying to reduce this, since any associated future
438		* changes in representations will need to be accompanied by
439	<	* algorithmic changes anyway. All together, these low-level
440	<	* implementation choices produce as much as a factor of 4
441	<	* performance improvement compared to naive implementations, and
442	<	* enable the processing of billions of tasks per second, at the
443	<	* expense of some ugliness.
444	<	*
445	<	* Methods signalWork() and scan() are the main bottlenecks so are
446	<	* especially heavily micro-optimized/mangled.  There are lots of
447	<	* inline assignments (of form "while ((local = field) != 0)")
448	<	* which are usually the simplest way to ensure the required read
449	<	* orderings (which are sometimes critical). This leads to a
450	<	* "C"-like style of listing declarations of these locals at the
451	<	* heads of methods or blocks.  There are several occurrences of
452	<	* the unusual "do {} while (!cas...)"  which is the simplest way
453	<	* to force an update of a CAS'ed variable. There are also other
454	<	* coding oddities that help some methods perform reasonably even
455	<	* when interpreted (not compiled).
456	<	*
457	<	* The order of declarations in this file is: (1) declarations of
458	<	* statics (2) fields (along with constants used when unpacking
459	<	* some of them), listed in an order that tends to reduce
460	<	* contention among them a bit under most JVMs; (3) nested
461	<	* classes; (4) internal control methods; (5) callbacks and other
462	<	* support for ForkJoinTask methods; (6) exported methods (plus a
444	<	* few little helpers); (7) static block initializing all statics
445	<	* in a minimally dependent order.
439	>	* algorithmic changes anyway. Several methods intrinsically
440	>	* sprawl because they must accumulate sets of consistent reads of
441	>	* volatiles held in local variables.  Methods signalWork() and
442	>	* scan() are the main bottlenecks, so are especially heavily
443	>	* micro-optimized/mangled.  There are lots of inline assignments
444	>	* (of form "while ((local = field) != 0)") which are usually the
445	>	* simplest way to ensure the required read orderings (which are
446	>	* sometimes critical). This leads to a "C"-like style of listing
447	>	* declarations of these locals at the heads of methods or blocks.
448	>	* There are several occurrences of the unusual "do {} while
449	>	* (!cas...)"  which is the simplest way to force an update of a
450	>	* CAS'ed variable. There are also other coding oddities that help
451	>	* some methods perform reasonably even when interpreted (not
452	>	* compiled).
453	>	*
454	>	* The order of declarations in this file is:
455	>	* (1) Static utility functions
456	>	* (2) Nested (static) classes
457	>	* (3) Static fields
458	>	* (4) Fields, along with constants used when unpacking some of them
459	>	* (5) Internal control methods
460	>	* (6) Callbacks and other support for ForkJoinTask methods
461	>	* (7) Exported methods
462	>	* (8) Static block initializing statics in minimally dependent order
463		*/
464
465	+	// Static utilities
466	+
467	+	/**
468	+	* If there is a security manager, makes sure caller has
469	+	* permission to modify threads.
470	+	*/
471	+	private static void checkPermission() {
472	+	SecurityManager security = System.getSecurityManager();
473	+	if (security != null)
474	+	security.checkPermission(modifyThreadPermission);
475	+	}
476	+
477	+	// Nested classes
478	+
479		/**
480		* Factory for creating new {@link ForkJoinWorkerThread}s.
481		* A {@code ForkJoinWorkerThreadFactory} must be defined and used
#	Line 473 | Line 504 | public class ForkJoinPool extends Abstra
504		}
505
506		/**
507	<	* Creates a new ForkJoinWorkerThread. This factory is used unless
508	<	* overridden in ForkJoinPool constructors.
509	<	*/
510	<	public static final ForkJoinWorkerThreadFactory
511	<	defaultForkJoinWorkerThreadFactory;
512	<
513	<	/**
514	<	* Permission required for callers of methods that may start or
515	<	* kill threads.
516	<	*/
517	<	private static final RuntimePermission modifyThreadPermission;
518	<
519	<	/**
520	<	* If there is a security manager, makes sure caller has
521	<	* permission to modify threads.
522	<	*/
523	<	private static void checkPermission() {
524	<	SecurityManager security = System.getSecurityManager();
525	<	if (security != null)
526	<	security.checkPermission(modifyThreadPermission);
507	>	* A simple non-reentrant lock used for exclusion when managing
508	>	* queues and workers. We use a custom lock so that we can readily
509	>	* probe lock state in constructions that check among alternative
510	>	* actions. The lock is normally only very briefly held, and
511	>	* sometimes treated as a spinlock, but other usages block to
512	>	* reduce overall contention in those cases where locked code
513	>	* bodies perform allocation/resizing.
514	>	*/
515	>	static final class Mutex extends AbstractQueuedSynchronizer {
516	>	public final boolean tryAcquire(int ignore) {
517	>	return compareAndSetState(0, 1);
518	>	}
519	>	public final boolean tryRelease(int ignore) {
520	>	setState(0);
521	>	return true;
522	>	}
523	>	public final void lock() { acquire(0); }
524	>	public final void unlock() { release(0); }
525	>	public final boolean isHeldExclusively() { return getState() == 1; }
526	>	public final Condition newCondition() { return new ConditionObject(); }
527		}
528
529		/**
530	<	* Generator for assigning sequence numbers as pool names.
531	<	*/
532	<	private static final AtomicInteger poolNumberGenerator;
533	<
503	<	/**
504	<	* Bits and masks for control variables
505	<	*
506	<	* Field ctl is a long packed with:
507	<	* AC: Number of active running workers minus target parallelism (16 bits)
508	<	* TC: Number of total workers minus target parallelism (16 bits)
509	<	* ST: true if pool is terminating (1 bit)
510	<	* EC: the wait count of top waiting thread (15 bits)
511	<	* ID: ~(poolIndex >>> 1) of top of Treiber stack of waiters (16 bits)
512	<	*
513	<	* When convenient, we can extract the upper 32 bits of counts and
514	<	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
515	<	* (int)ctl.  The ec field is never accessed alone, but always
516	<	* together with id and st. The offsets of counts by the target
517	<	* parallelism and the positionings of fields makes it possible to
518	<	* perform the most common checks via sign tests of fields: When
519	<	* ac is negative, there are not enough active workers, when tc is
520	<	* negative, there are not enough total workers, when id is
521	<	* negative, there is at least one waiting worker, and when e is
522	<	* negative, the pool is terminating.  To deal with these possibly
523	<	* negative fields, we use casts in and out of "short" and/or
524	<	* signed shifts to maintain signedness.
525	<	*
526	<	* When a thread is queued (inactivated), its eventCount field is
527	<	* negative, which is the only way to tell if a worker is
528	<	* prevented from executing tasks, even though it must continue to
529	<	* scan for them to avoid queuing races.
530	<	*
531	<	* Field runState is an int packed with:
532	<	* SHUTDOWN: true if shutdown is enabled (1 bit)
533	<	* SEQ:  a sequence number updated upon (de)registering workers (15 bits)
534	<	* MASK: mask (power of 2 - 1) covering all registered poolIndexes (16 bits)
535	<	*
536	<	* The combination of mask and sequence number enables simple
537	<	* consistency checks: Staleness of read-only operations on the
538	<	* workers and queues arrays can be checked by comparing runState
539	<	* before vs after the reads. The low 16 bits (i.e, anding with
540	<	* SMASK) hold (the smallest power of two covering all worker
541	<	* indices, minus one.  The mask for queues (vs workers) is twice
542	<	* this value plus 1.
543	<	*/
544	<
545	<	// bit positions/shifts for fields
546	<	private static final int  AC_SHIFT   = 48;
547	<	private static final int  TC_SHIFT   = 32;
548	<	private static final int  ST_SHIFT   = 31;
549	<	private static final int  EC_SHIFT   = 16;
550	<
551	<	// bounds
552	<	private static final int  MAX_ID     = 0x7fff;  // max poolIndex
553	<	private static final int  SMASK      = 0xffff;  // mask short bits
554	<	private static final int  SHORT_SIGN = 1 << 15;
555	<	private static final int  INT_SIGN   = 1 << 31;
556	<
557	<	// masks
558	<	private static final long STOP_BIT   = 0x0001L << ST_SHIFT;
559	<	private static final long AC_MASK    = ((long)SMASK) << AC_SHIFT;
560	<	private static final long TC_MASK    = ((long)SMASK) << TC_SHIFT;
561	<
562	<	// units for incrementing and decrementing
563	<	private static final long TC_UNIT    = 1L << TC_SHIFT;
564	<	private static final long AC_UNIT    = 1L << AC_SHIFT;
565	<
566	<	// masks and units for dealing with u = (int)(ctl >>> 32)
567	<	private static final int  UAC_SHIFT  = AC_SHIFT - 32;
568	<	private static final int  UTC_SHIFT  = TC_SHIFT - 32;
569	<	private static final int  UAC_MASK   = SMASK << UAC_SHIFT;
570	<	private static final int  UTC_MASK   = SMASK << UTC_SHIFT;
571	<	private static final int  UAC_UNIT   = 1 << UAC_SHIFT;
572	<	private static final int  UTC_UNIT   = 1 << UTC_SHIFT;
573	<
574	<	// masks and units for dealing with e = (int)ctl
575	<	private static final int E_MASK      = 0x7fffffff; // no STOP_BIT
576	<	private static final int E_SEQ       = 1 << EC_SHIFT;
577	<
578	<	// runState bits
579	<	private static final int SHUTDOWN    = 1 << 31;
580	<	private static final int RS_SEQ      = 1 << 16;
581	<	private static final int RS_SEQ_MASK = 0x7fff0000;
582	<
583	<	// access mode for WorkQueue
584	<	static final int LIFO_QUEUE          =  0;
585	<	static final int FIFO_QUEUE          =  1;
586	<	static final int SHARED_QUEUE        = -1;
587	<
588	<	/**
589	<	* The wakeup interval (in nanoseconds) for a worker waiting for a
590	<	* task when the pool is quiescent to instead try to shrink the
591	<	* number of workers.  The exact value does not matter too
592	<	* much. It must be short enough to release resources during
593	<	* sustained periods of idleness, but not so short that threads
594	<	* are continually re-created.
595	<	*/
596	<	private static final long SHRINK_RATE =
597	<	4L * 1000L * 1000L * 1000L; // 4 seconds
598	<
599	<	/**
600	<	* The timeout value for attempted shrinkage, includes
601	<	* some slop to cope with system timer imprecision.
602	<	*/
603	<	private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
604	<
605	<	/**
606	<	* The maximum stolen->joining link depth allowed in tryHelpStealer.
607	<	* Depths for legitimate chains are unbounded, but we use a fixed
608	<	* constant to avoid (otherwise unchecked) cycles and to bound
609	<	* staleness of traversal parameters at the expense of sometimes
610	<	* blocking when we could be helping.
611	<	*/
612	<	private static final int MAX_HELP_DEPTH = 16;
613	<
614	<	/*
615	<	* Field layout order in this class tends to matter more than one
616	<	* would like. Runtime layout order is only loosely related to
617	<	* declaration order and may differ across JVMs, but the following
618	<	* empirically works OK on current JVMs.
530	>	* Class for artificial tasks that are used to replace the target
531	>	* of local joins if they are removed from an interior queue slot
532	>	* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
533	>	* actually do anything beyond having a unique identity.
534		*/
535	<
536	<	volatile long ctl;                       // main pool control
537	<	final int parallelism;                   // parallelism level
538	<	final int localMode;                     // per-worker scheduling mode
539	<	int nextPoolIndex;                       // hint used in registerWorker
540	<	volatile int runState;                   // shutdown status, seq, and mask
626	<	WorkQueue[] workQueues;                  // main registry
627	<	final ReentrantLock lock;                // for registration
628	<	final Condition termination;             // for awaitTermination
629	<	final ForkJoinWorkerThreadFactory factory; // factory for new workers
630	<	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
631	<	final AtomicLong stealCount;             // collect counts when terminated
632	<	final AtomicInteger nextWorkerNumber;    // to create worker name string
633	<	final String workerNamePrefix;           // Prefix for assigning worker names
535	>	static final class EmptyTask extends ForkJoinTask<Void> {
536	>	EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
537	>	public final Void getRawResult() { return null; }
538	>	public final void setRawResult(Void x) {}
539	>	public final boolean exec() { return true; }
540	>	}
541
542		/**
543		* Queues supporting work-stealing as well as external task
#	Line 681 | Line 588 | public class ForkJoinPool extends Abstra
588		* avoiding really bad worst-case access. (Until better JVM
589		* support is in place, this padding is dependent on transient
590		* properties of JVM field layout rules.)  We also take care in
591	<	* allocating and sizing and resizing the array. Non-shared queue
591	>	* allocating, sizing and resizing the array. Non-shared queue
592		* arrays are initialized (via method growArray) by workers before
593		* use. Others are allocated on first use.
594		*/
595		static final class WorkQueue {
596		/**
597		* Capacity of work-stealing queue array upon initialization.
598	<	* Must be a power of two; at least 4, but set larger to
599	<	* reduce cacheline sharing among queues.
598	>	* Must be a power of two; at least 4, but should be larger to
599	>	* reduce or eliminate cacheline sharing among queues.
600	>	* Currently, it is much larger, as a partial workaround for
601	>	* the fact that JVMs often place arrays in locations that
602	>	* share GC bookkeeping (especially cardmarks) such that
603	>	* per-write accesses encounter serious memory contention.
604		*/
605	<	static final int INITIAL_QUEUE_CAPACITY = 1 << 8;
605	>	static final int INITIAL_QUEUE_CAPACITY = 1 << 13;
606
607		/**
608		* Maximum size for queue arrays. Must be a power of two less
#	Line 715 | Line 626 | public class ForkJoinPool extends Abstra
626		volatile int base;         // index of next slot for poll
627		int top;                   // index of next slot for push
628		ForkJoinTask<?>[] array;   // the elements (initially unallocated)
629	+	final ForkJoinPool pool;   // the containing pool (may be null)
630		final ForkJoinWorkerThread owner; // owning thread or null if shared
631		volatile Thread parker;    // == owner during call to park; else null
632		ForkJoinTask<?> currentJoin;  // task being joined in awaitJoin
633		ForkJoinTask<?> currentSteal; // current non-local task being executed
634		// Heuristic padding to ameliorate unfortunate memory placements
635	<	Object p00, p01, p02, p03, p04, p05, p06, p07, p08, p09, p0a;
635	>	Object p00, p01, p02, p03, p04, p05, p06, p07;
636	>	Object p08, p09, p0a, p0b, p0c, p0d, p0e;
637
638	<	WorkQueue(ForkJoinWorkerThread owner, int mode) {
726	<	this.owner = owner;
638	>	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode) {
639		this.mode = mode;
640	+	this.pool = pool;
641	+	this.owner = owner;
642		// Place indices in the center of array (that is not yet allocated)
643		base = top = INITIAL_QUEUE_CAPACITY >>> 1;
644		}
645
646		/**
647	<	* Returns number of tasks in the queue
647	>	* Returns the approximate number of tasks in the queue.
648		*/
649		final int queueSize() {
650	<	int n = base - top; // non-owner callers must read base first
651	<	return (n >= 0) ? 0 : -n;
650	>	int n = base - top;       // non-owner callers must read base first
651	>	return (n >= 0) ? 0 : -n; // ignore transient negative
652	>	}
653	>
654	>	/**
655	>	* Provides a more accurate estimate of whether this queue has
656	>	* any tasks than does queueSize, by checking whether a
657	>	* near-empty queue has at least one unclaimed task.
658	>	*/
659	>	final boolean isEmpty() {
660	>	ForkJoinTask<?>[] a; int m, s;
661	>	int n = base - (s = top);
662	>	return (n >= 0 ||
663	>	(n == -1 &&
664	>	((a = array) == null ||
665	>	(m = a.length - 1) < 0 ||
666	>	U.getObjectVolatile
667	>	(a, ((m & (s - 1)) << ASHIFT) + ABASE) == null)));
668		}
669
670		/**
671		* Pushes a task. Call only by owner in unshared queues.
672		*
673		* @param task the task. Caller must ensure non-null.
674	<	* @param p, if non-null, pool to signal if necessary
745	<	* @throw RejectedExecutionException if array cannot
746	<	* be resized
674	>	* @throw RejectedExecutionException if array cannot be resized
675		*/
676	<	final void push(ForkJoinTask<?> task, ForkJoinPool p) {
677	<	ForkJoinTask<?>[] a;
676	>	final void push(ForkJoinTask<?> task) {
677	>	ForkJoinTask<?>[] a; ForkJoinPool p;
678		int s = top, m, n;
679		if ((a = array) != null) {    // ignore if queue removed
680		U.putOrderedObject
681		(a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task);
682		if ((n = (top = s + 1) - base) <= 2) {
683	<	if (p != null)
683	>	if ((p = pool) != null)
684		p.signalWork();
685		}
686		else if (n >= m)
#	Line 771 | Line 699 | public class ForkJoinPool extends Abstra
699		boolean submitted = false;
700		if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
701		ForkJoinTask<?>[] a = array;
702	<	int s = top, n = s - base;
702	>	int s = top;
703		try {
704	<	if ((a != null && n < a.length - 1) ||
704	>	if ((a != null && a.length > s + 1 - base) ||
705		(a = growArray(false)) != null) { // must presize
706		int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
707		U.putObject(a, (long)j, task);    // don't need "ordered"
#	Line 788 | Line 716 | public class ForkJoinPool extends Abstra
716		}
717
718		/**
719	<	* Takes next task, if one exists, in FIFO order.
720	<	*/
721	<	final ForkJoinTask<?> poll() {
794	<	ForkJoinTask<?>[] a; int b, i;
795	<	while ((b = base) - top < 0 && (a = array) != null &&
796	<	(i = (a.length - 1) & b) >= 0) {
797	<	int j = (i << ASHIFT) + ABASE;
798	<	ForkJoinTask<?> t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
799	<	if (t != null && base == b &&
800	<	U.compareAndSwapObject(a, j, t, null)) {
801	<	base = b + 1;
802	<	return t;
803	<	}
804	<	}
805	<	return null;
806	<	}
807	<
808	<	/**
809	<	* Takes next task, if one exists, in LIFO order.
810	<	* Call only by owner in unshared queues.
719	>	* Takes next task, if one exists, in LIFO order.  Call only
720	>	* by owner in unshared queues. (We do not have a shared
721	>	* version of this method because it is never needed.)
722		*/
723		final ForkJoinTask<?> pop() {
724		ForkJoinTask<?> t; int m;
#	Line 827 | Line 738 | public class ForkJoinPool extends Abstra
738		}
739
740		/**
741	+	* Takes a task in FIFO order if b is base of queue and a task
742	+	* can be claimed without contention. Specialized versions
743	+	* appear in ForkJoinPool methods scan and tryHelpStealer.
744	+	*/
745	+	final ForkJoinTask<?> pollAt(int b) {
746	+	ForkJoinTask<?> t; ForkJoinTask<?>[] a;
747	+	if ((a = array) != null) {
748	+	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
749	+	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
750	+	base == b &&
751	+	U.compareAndSwapObject(a, j, t, null)) {
752	+	base = b + 1;
753	+	return t;
754	+	}
755	+	}
756	+	return null;
757	+	}
758	+
759	+	/**
760	+	* Takes next task, if one exists, in FIFO order.
761	+	*/
762	+	final ForkJoinTask<?> poll() {
763	+	ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t;
764	+	while ((b = base) - top < 0 && (a = array) != null) {
765	+	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
766	+	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
767	+	if (t != null) {
768	+	if (base == b &&
769	+	U.compareAndSwapObject(a, j, t, null)) {
770	+	base = b + 1;
771	+	return t;
772	+	}
773	+	}
774	+	else if (base == b) {
775	+	if (b + 1 == top)
776	+	break;
777	+	Thread.yield(); // wait for lagging update
778	+	}
779	+	}
780	+	return null;
781	+	}
782	+
783	+	/**
784		* Takes next task, if one exists, in order specified by mode.
785		*/
786		final ForkJoinTask<?> nextLocalTask() {
#	Line 846 | Line 800 | public class ForkJoinPool extends Abstra
800		}
801
802		/**
849	–	* Returns task at index b if b is current base of queue.
850	–	*/
851	–	final ForkJoinTask<?> pollAt(int b) {
852	–	ForkJoinTask<?>[] a; int i;
853	–	ForkJoinTask<?> task = null;
854	–	if ((a = array) != null && (i = ((a.length - 1) & b)) >= 0) {
855	–	int j = (i << ASHIFT) + ABASE;
856	–	ForkJoinTask<?> t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
857	–	if (t != null && base == b &&
858	–	U.compareAndSwapObject(a, j, t, null)) {
859	–	base = b + 1;
860	–	task = t;
861	–	}
862	–	}
863	–	return task;
864	–	}
865	–
866	–	/**
803		* Pops the given task only if it is at the current top.
804		*/
805		final boolean tryUnpush(ForkJoinTask<?> t) {
#	Line 881 | Line 817 | public class ForkJoinPool extends Abstra
817		* Polls the given task only if it is at the current base.
818		*/
819		final boolean pollFor(ForkJoinTask<?> task) {
820	<	ForkJoinTask<?>[] a; int b, i;
821	<	if ((b = base) - top < 0 && (a = array) != null &&
822	<	(i = (a.length - 1) & b) >= 0) {
887	<	int j = (i << ASHIFT) + ABASE;
820	>	ForkJoinTask<?>[] a; int b;
821	>	if ((b = base) - top < 0 && (a = array) != null) {
822	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
823		if (U.getObjectVolatile(a, j) == task && base == b &&
824		U.compareAndSwapObject(a, j, task, null)) {
825		base = b + 1;
#	Line 978 | Line 913 | public class ForkJoinPool extends Abstra
913		}
914
915		/**
916	<	* Removes and cancels all known tasks, ignoring any exceptions
916	>	* Removes and cancels all known tasks, ignoring any exceptions.
917		*/
918		final void cancelAll() {
919		ForkJoinTask.cancelIgnoringExceptions(currentJoin);
#	Line 987 | Line 922 | public class ForkJoinPool extends Abstra
922		ForkJoinTask.cancelIgnoringExceptions(t);
923		}
924
925	+	/**
926	+	* Computes next value for random probes.  Scans don't require
927	+	* a very high quality generator, but also not a crummy one.
928	+	* Marsaglia xor-shift is cheap and works well enough.  Note:
929	+	* This is manually inlined in its usages in ForkJoinPool to
930	+	* avoid writes inside busy scan loops.
931	+	*/
932	+	final int nextSeed() {
933	+	int r = seed;
934	+	r ^= r << 13;
935	+	r ^= r >>> 17;
936	+	return seed = r ^= r << 5;
937	+	}
938	+
939		// Execution methods
940
941		/**
942		* Removes and runs tasks until empty, using local mode
943	<	* ordering.
943	>	* ordering. Normally called only after checking for apparent
944	>	* non-emptiness.
945		*/
946		final void runLocalTasks() {
947	<	if (base - top < 0) {
948	<	for (ForkJoinTask<?> t; (t = nextLocalTask()) != null; )
949	<	t.doExec();
947	>	// hoist checks from repeated pop/poll
948	>	ForkJoinTask<?>[] a; int m;
949	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
950	>	if (mode == 0) {
951	>	for (int s; (s = top - 1) - base >= 0;) {
952	>	int j = ((m & s) << ASHIFT) + ABASE;
953	>	ForkJoinTask<?> t =
954	>	(ForkJoinTask<?>)U.getObjectVolatile(a, j);
955	>	if (t != null) {
956	>	if (U.compareAndSwapObject(a, j, t, null)) {
957	>	top = s;
958	>	t.doExec();
959	>	}
960	>	}
961	>	else
962	>	break;
963	>	}
964	>	}
965	>	else {
966	>	for (int b; (b = base) - top < 0;) {
967	>	int j = ((m & b) << ASHIFT) + ABASE;
968	>	ForkJoinTask<?> t =
969	>	(ForkJoinTask<?>)U.getObjectVolatile(a, j);
970	>	if (t != null) {
971	>	if (base == b &&
972	>	U.compareAndSwapObject(a, j, t, null)) {
973	>	base = b + 1;
974	>	t.doExec();
975	>	}
976	>	} else if (base == b) {
977	>	if (b + 1 == top)
978	>	break;
979	>	Thread.yield(); // wait for lagging update
980	>	}
981	>	}
982	>	}
983		}
984		}
985
#	Line 1011 | Line 994 | public class ForkJoinPool extends Abstra
994		if (t != null) {
995		currentSteal = t;
996		t.doExec();
997	<	runLocalTasks();
997	>	if (top != base)        // conservative guard
998	>	runLocalTasks();
999		++nsteals;
1000		currentSteal = null;
1001		}
1002	<	else if (runState < 0)            // terminating
1002	>	else if (runState < 0)      // terminating
1003		alive = false;
1004		return alive;
1005		}
1006
1007		/**
1008	<	* Executes a non-top-level (stolen) task
1008	>	* Executes a non-top-level (stolen) task.
1009		*/
1010		final void runSubtask(ForkJoinTask<?> t) {
1011		if (t != null) {
#	Line 1033 | Line 1017 | public class ForkJoinPool extends Abstra
1017		}
1018
1019		/**
1020	<	* Computes next value for random probes.  Scans don't require
1037	<	* a very high quality generator, but also not a crummy one.
1038	<	* Marsaglia xor-shift is cheap and works well enough.  Note:
1039	<	* This is manually inlined in several usages in ForkJoinPool
1040	<	* to avoid writes inside busy scan loops.
1020	>	* Returns true if owned and not known to be blocked.
1021		*/
1022	<	final int nextSeed() {
1023	<	int r = seed;
1024	<	r ^= r << 13;
1025	<	r ^= r >>> 17;
1026	<	r ^= r << 5;
1027	<	return seed = r;
1022	>	final boolean isApparentlyUnblocked() {
1023	>	Thread wt; Thread.State s;
1024	>	return (eventCount >= 0 &&
1025	>	(wt = owner) != null &&
1026	>	(s = wt.getState()) != Thread.State.BLOCKED &&
1027	>	s != Thread.State.WAITING &&
1028	>	s != Thread.State.TIMED_WAITING);
1029	>	}
1030	>
1031	>	/**
1032	>	* If this owned and is not already interrupted, try to
1033	>	* interrupt and/or unpark, ignoring exceptions.
1034	>	*/
1035	>	final void interruptOwner() {
1036	>	Thread wt, p;
1037	>	if ((wt = owner) != null && !wt.isInterrupted()) {
1038	>	try {
1039	>	wt.interrupt();
1040	>	} catch (SecurityException ignore) {
1041	>	}
1042	>	}
1043	>	if ((p = parker) != null)
1044	>	U.unpark(p);
1045		}
1046
1047		// Unsafe mechanics
#	Line 1072 | Line 1069 | public class ForkJoinPool extends Abstra
1069		}
1070
1071		/**
1072	<	* Class for artificial tasks that are used to replace the target
1073	<	* of local joins if they are removed from an interior queue slot
1074	<	* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
1075	<	* actually do anything beyond having a unique identity.
1076	<	*/
1077	<	static final class EmptyTask extends ForkJoinTask<Void> {
1078	<	EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
1079	<	public Void getRawResult() { return null; }
1080	<	public void setRawResult(Void x) {}
1081	<	public boolean exec() { return true; }
1072	>	* Per-thread records for threads that submit to pools. Currently
1073	>	* holds only pseudo-random seed / index that is used to choose
1074	>	* submission queues in method doSubmit. In the future, this may
1075	>	* also incorporate a means to implement different task rejection
1076	>	* and resubmission policies.
1077	>	*
1078	>	* Seeds for submitters and workers/workQueues work in basically
1079	>	* the same way but are initialized and updated using slightly
1080	>	* different mechanics. Both are initialized using the same
1081	>	* approach as in class ThreadLocal, where successive values are
1082	>	* unlikely to collide with previous values. This is done during
1083	>	* registration for workers, but requires a separate AtomicInteger
1084	>	* for submitters. Seeds are then randomly modified upon
1085	>	* collisions using xorshifts, which requires a non-zero seed.
1086	>	*/
1087	>	static final class Submitter {
1088	>	int seed;
1089	>	Submitter() {
1090	>	int s = nextSubmitterSeed.getAndAdd(SEED_INCREMENT);
1091	>	seed = (s == 0) ? 1 : s; // ensure non-zero
1092	>	}
1093		}
1094
1095	+	/** ThreadLocal class for Submitters */
1096	+	static final class ThreadSubmitter extends ThreadLocal<Submitter> {
1097	+	public Submitter initialValue() { return new Submitter(); }
1098	+	}
1099	+
1100	+	// static fields (initialized in static initializer below)
1101	+
1102		/**
1103	<	* Computes a hash code for the given thread. This method is
1104	<	* expected to provide higher-quality hash codes than those using
1090	<	* method hashCode().
1103	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
1104	>	* overridden in ForkJoinPool constructors.
1105		*/
1106	<	static final int hashThread(Thread t) {
1107	<	long id = (t == null) ? 0L : t.getId(); // Use MurmurHash of thread id
1094	<	int h = (int)id ^ (int)(id >>> 32);
1095	<	h ^= h >>> 16;
1096	<	h *= 0x85ebca6b;
1097	<	h ^= h >>> 13;
1098	<	h *= 0xc2b2ae35;
1099	<	return h ^ (h >>> 16);
1100	<	}
1106	>	public static final ForkJoinWorkerThreadFactory
1107	>	defaultForkJoinWorkerThreadFactory;
1108
1109		/**
1110	<	* Top-level runloop for workers
1110	>	* Generator for assigning sequence numbers as pool names.
1111		*/
1112	<	final void runWorker(ForkJoinWorkerThread wt) {
1106	<	WorkQueue w = wt.workQueue;
1107	<	w.growArray(false);     // Initialize queue array and seed in this thread
1108	<	w.seed = hashThread(Thread.currentThread()) | (1 << 31); // force < 0
1112	>	private static final AtomicInteger poolNumberGenerator;
1113
1114	<	do {} while (w.runTask(scan(w)));
1115	<	}
1114	>	/**
1115	>	* Generator for initial hashes/seeds for submitters. Accessed by
1116	>	* Submitter class constructor.
1117	>	*/
1118	>	static final AtomicInteger nextSubmitterSeed;
1119	>
1120	>	/**
1121	>	* Permission required for callers of methods that may start or
1122	>	* kill threads.
1123	>	*/
1124	>	private static final RuntimePermission modifyThreadPermission;
1125	>
1126	>	/**
1127	>	* Per-thread submission bookeeping. Shared across all pools
1128	>	* to reduce ThreadLocal pollution and because random motion
1129	>	* to avoid contention in one pool is likely to hold for others.
1130	>	*/
1131	>	private static final ThreadSubmitter submitters;
1132	>
1133	>	// static constants
1134	>
1135	>	/**
1136	>	* The wakeup interval (in nanoseconds) for a worker waiting for a
1137	>	* task when the pool is quiescent to instead try to shrink the
1138	>	* number of workers.  The exact value does not matter too
1139	>	* much. It must be short enough to release resources during
1140	>	* sustained periods of idleness, but not so short that threads
1141	>	* are continually re-created.
1142	>	*/
1143	>	private static final long SHRINK_RATE =
1144	>	4L * 1000L * 1000L * 1000L; // 4 seconds
1145	>
1146	>	/**
1147	>	* The timeout value for attempted shrinkage, includes
1148	>	* some slop to cope with system timer imprecision.
1149	>	*/
1150	>	private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
1151	>
1152	>	/**
1153	>	* The maximum stolen->joining link depth allowed in method
1154	>	* tryHelpStealer.  Must be a power of two. This value also
1155	>	* controls the maximum number of times to try to help join a task
1156	>	* without any apparent progress or change in pool state before
1157	>	* giving up and blocking (see awaitJoin).  Depths for legitimate
1158	>	* chains are unbounded, but we use a fixed constant to avoid
1159	>	* (otherwise unchecked) cycles and to bound staleness of
1160	>	* traversal parameters at the expense of sometimes blocking when
1161	>	* we could be helping.
1162	>	*/
1163	>	private static final int MAX_HELP = 32;
1164	>
1165	>	/**
1166	>	* Secondary time-based bound (in nanosecs) for helping attempts
1167	>	* before trying compensated blocking in awaitJoin. Used in
1168	>	* conjunction with MAX_HELP to reduce variance due to different
1169	>	* polling rates associated with different helping options. The
1170	>	* value should roughly approximate the time required to create
1171	>	* and/or activate a worker thread.
1172	>	*/
1173	>	private static final long COMPENSATION_DELAY = 100L * 1000L; // 0.1 millisec
1174	>
1175	>	/**
1176	>	* Increment for seed generators. See class ThreadLocal for
1177	>	* explanation.
1178	>	*/
1179	>	private static final int SEED_INCREMENT = 0x61c88647;
1180	>
1181	>	/**
1182	>	* Bits and masks for control variables
1183	>	*
1184	>	* Field ctl is a long packed with:
1185	>	* AC: Number of active running workers minus target parallelism (16 bits)
1186	>	* TC: Number of total workers minus target parallelism (16 bits)
1187	>	* ST: true if pool is terminating (1 bit)
1188	>	* EC: the wait count of top waiting thread (15 bits)
1189	>	* ID: poolIndex of top of Treiber stack of waiters (16 bits)
1190	>	*
1191	>	* When convenient, we can extract the upper 32 bits of counts and
1192	>	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
1193	>	* (int)ctl.  The ec field is never accessed alone, but always
1194	>	* together with id and st. The offsets of counts by the target
1195	>	* parallelism and the positionings of fields makes it possible to
1196	>	* perform the most common checks via sign tests of fields: When
1197	>	* ac is negative, there are not enough active workers, when tc is
1198	>	* negative, there are not enough total workers, and when e is
1199	>	* negative, the pool is terminating.  To deal with these possibly
1200	>	* negative fields, we use casts in and out of "short" and/or
1201	>	* signed shifts to maintain signedness.
1202	>	*
1203	>	* When a thread is queued (inactivated), its eventCount field is
1204	>	* set negative, which is the only way to tell if a worker is
1205	>	* prevented from executing tasks, even though it must continue to
1206	>	* scan for them to avoid queuing races. Note however that
1207	>	* eventCount updates lag releases so usage requires care.
1208	>	*
1209	>	* Field runState is an int packed with:
1210	>	* SHUTDOWN: true if shutdown is enabled (1 bit)
1211	>	* SEQ:  a sequence number updated upon (de)registering workers (30 bits)
1212	>	* INIT: set true after workQueues array construction (1 bit)
1213	>	*
1214	>	* The sequence number enables simple consistency checks:
1215	>	* Staleness of read-only operations on the workQueues array can
1216	>	* be checked by comparing runState before vs after the reads.
1217	>	*/
1218	>
1219	>	// bit positions/shifts for fields
1220	>	private static final int  AC_SHIFT   = 48;
1221	>	private static final int  TC_SHIFT   = 32;
1222	>	private static final int  ST_SHIFT   = 31;
1223	>	private static final int  EC_SHIFT   = 16;
1224
1225	<	// Creating, registering and deregistering workers
1225	>	// bounds
1226	>	private static final int  SMASK      = 0xffff;  // short bits
1227	>	private static final int  MAX_CAP    = 0x7fff;  // max #workers - 1
1228	>	private static final int  SQMASK     = 0xfffe;  // even short bits
1229	>	private static final int  SHORT_SIGN = 1 << 15;
1230	>	private static final int  INT_SIGN   = 1 << 31;
1231	>
1232	>	// masks
1233	>	private static final long STOP_BIT   = 0x0001L << ST_SHIFT;
1234	>	private static final long AC_MASK    = ((long)SMASK) << AC_SHIFT;
1235	>	private static final long TC_MASK    = ((long)SMASK) << TC_SHIFT;
1236	>
1237	>	// units for incrementing and decrementing
1238	>	private static final long TC_UNIT    = 1L << TC_SHIFT;
1239	>	private static final long AC_UNIT    = 1L << AC_SHIFT;
1240	>
1241	>	// masks and units for dealing with u = (int)(ctl >>> 32)
1242	>	private static final int  UAC_SHIFT  = AC_SHIFT - 32;
1243	>	private static final int  UTC_SHIFT  = TC_SHIFT - 32;
1244	>	private static final int  UAC_MASK   = SMASK << UAC_SHIFT;
1245	>	private static final int  UTC_MASK   = SMASK << UTC_SHIFT;
1246	>	private static final int  UAC_UNIT   = 1 << UAC_SHIFT;
1247	>	private static final int  UTC_UNIT   = 1 << UTC_SHIFT;
1248	>
1249	>	// masks and units for dealing with e = (int)ctl
1250	>	private static final int E_MASK      = 0x7fffffff; // no STOP_BIT
1251	>	private static final int E_SEQ       = 1 << EC_SHIFT;
1252	>
1253	>	// runState bits
1254	>	private static final int SHUTDOWN    = 1 << 31;
1255	>
1256	>	// access mode for WorkQueue
1257	>	static final int LIFO_QUEUE          =  0;
1258	>	static final int FIFO_QUEUE          =  1;
1259	>	static final int SHARED_QUEUE        = -1;
1260	>
1261	>	// Instance fields
1262	>
1263	>	/*
1264	>	* Field layout order in this class tends to matter more than one
1265	>	* would like. Runtime layout order is only loosely related to
1266	>	* declaration order and may differ across JVMs, but the following
1267	>	* empirically works OK on current JVMs.
1268	>	*/
1269	>
1270	>	volatile long ctl;                         // main pool control
1271	>	final int parallelism;                     // parallelism level
1272	>	final int localMode;                       // per-worker scheduling mode
1273	>	final int submitMask;                      // submit queue index bound
1274	>	int nextSeed;                              // for initializing worker seeds
1275	>	volatile int runState;                     // shutdown status and seq
1276	>	WorkQueue[] workQueues;                    // main registry
1277	>	final Mutex lock;                          // for registration
1278	>	final Condition termination;               // for awaitTermination
1279	>	final ForkJoinWorkerThreadFactory factory; // factory for new workers
1280	>	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1281	>	final AtomicLong stealCount;               // collect counts when terminated
1282	>	final AtomicInteger nextWorkerNumber;      // to create worker name string
1283	>	final String workerNamePrefix;             // to create worker name string
1284	>
1285	>	//  Creating, registering, and deregistering workers
1286
1287		/**
1288		* Tries to create and start a worker
1289		*/
1290		private void addWorker() {
1291		Throwable ex = null;
1292	<	ForkJoinWorkerThread w = null;
1292	>	ForkJoinWorkerThread wt = null;
1293		try {
1294	<	if ((w = factory.newThread(this)) != null) {
1295	<	w.start();
1294	>	if ((wt = factory.newThread(this)) != null) {
1295	>	wt.start();
1296		return;
1297		}
1298		} catch (Throwable e) {
1299		ex = e;
1300		}
1301	<	deregisterWorker(w, ex);
1301	>	deregisterWorker(wt, ex); // adjust counts etc on failure
1302		}
1303
1304		/**
#	Line 1141 | Line 1313 | public class ForkJoinPool extends Abstra
1313		}
1314
1315		/**
1316	<	* Callback from ForkJoinWorkerThread constructor to establish and
1317	<	* record its WorkQueue
1316	>	* Callback from ForkJoinWorkerThread constructor to establish its
1317	>	* poolIndex and record its WorkQueue. To avoid scanning bias due
1318	>	* to packing entries in front of the workQueues array, we treat
1319	>	* the array as a simple power-of-two hash table using per-thread
1320	>	* seed as hash, expanding as needed.
1321		*
1322	<	* @param wt the worker thread
1322	>	* @param w the worker's queue
1323		*/
1324	<	final void registerWorker(ForkJoinWorkerThread wt) {
1325	<	WorkQueue w = wt.workQueue;
1151	<	ReentrantLock lock = this.lock;
1324	>	final void registerWorker(WorkQueue w) {
1325	>	Mutex lock = this.lock;
1326		lock.lock();
1327		try {
1154	–	int k = nextPoolIndex;
1328		WorkQueue[] ws = workQueues;
1329	<	if (ws != null) {                       // ignore on shutdown
1330	<	int n = ws.length;
1331	<	if (k < 0 || (k & 1) == 0 || k >= n || ws[k] != null) {
1332	<	for (k = 1; k < n && ws[k] != null; k += 2)
1333	<	;                           // workers are at odd indices
1334	<	if (k >= n)                     // resize
1335	<	workQueues = ws = Arrays.copyOf(ws, n << 1);
1336	<	}
1337	<	w.poolIndex = k;
1338	<	w.eventCount = ~(k >>> 1) & SMASK;  // Set up wait count
1339	<	ws[k] = w;                          // record worker
1340	<	nextPoolIndex = k + 2;
1341	<	int rs = runState;
1342	<	int m = rs & SMASK;                 // recalculate runState mask
1170	<	if (k > m)
1171	<	m = (m << 1) + 1;
1172	<	runState = (rs & SHUTDOWN) | ((rs + RS_SEQ) & RS_SEQ_MASK) | m;
1329	>	if (w != null && ws != null) {          // skip on shutdown/failure
1330	>	int rs, n;
1331	>	while ((n = ws.length) <            // ensure can hold total
1332	>	(parallelism + (short)(ctl >>> TC_SHIFT) << 1))
1333	>	workQueues = ws = Arrays.copyOf(ws, n << 1);
1334	>	int m = n - 1;
1335	>	int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence
1336	>	w.seed = (s == 0) ? 1 : s;          // ensure non-zero seed
1337	>	int r = (s << 1) | 1;               // use odd-numbered indices
1338	>	while (ws[r &= m] != null)          // step by approx half size
1339	>	r += ((n >>> 1) & SQMASK) + 2;
1340	>	w.eventCount = w.poolIndex = r;     // establish before recording
1341	>	ws[r] = w;                          // also update seq
1342	>	runState = ((rs = runState) & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN);
1343		}
1344		} finally {
1345		lock.unlock();
#	Line 1177 | Line 1347 | public class ForkJoinPool extends Abstra
1347		}
1348
1349		/**
1350	<	* Final callback from terminating worker, as well as failure to
1351	<	* construct or start a worker in addWorker.  Removes record of
1350	>	* Final callback from terminating worker, as well as upon failure
1351	>	* to construct or start a worker in addWorker.  Removes record of
1352		* worker from array, and adjusts counts. If pool is shutting
1353		* down, tries to complete termination.
1354		*
#	Line 1186 | Line 1356 | public class ForkJoinPool extends Abstra
1356		* @param ex the exception causing failure, or null if none
1357		*/
1358		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1359	+	Mutex lock = this.lock;
1360		WorkQueue w = null;
1361		if (wt != null && (w = wt.workQueue) != null) {
1362		w.runState = -1;                // ensure runState is set
1363		stealCount.getAndAdd(w.totalSteals + w.nsteals);
1364		int idx = w.poolIndex;
1194	–	ReentrantLock lock = this.lock;
1365		lock.lock();
1366		try {                           // remove record from array
1367		WorkQueue[] ws = workQueues;
1368		if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1369	<	ws[nextPoolIndex = idx] = null;
1369	>	ws[idx] = null;
1370		} finally {
1371		lock.unlock();
1372		}
#	Line 1208 | Line 1378 | public class ForkJoinPool extends Abstra
1378		((c - TC_UNIT) & TC_MASK) |
1379		(c & ~(AC_MASK|TC_MASK)))));
1380
1381	<	if (!tryTerminate(false) && w != null) {
1381	>	if (!tryTerminate(false, false) && w != null) {
1382		w.cancelAll();                  // cancel remaining tasks
1383		if (w.array != null)            // suppress signal if never ran
1384		signalWork();               // wake up or create replacement
1385	+	if (ex == null)                 // help clean refs on way out
1386	+	ForkJoinTask.helpExpungeStaleExceptions();
1387		}
1388
1389		if (ex != null)                     // rethrow
#	Line 1219 | Line 1391 | public class ForkJoinPool extends Abstra
1391		}
1392
1393
1394	+	// Submissions
1395	+
1396	+	/**
1397	+	* Unless shutting down, adds the given task to a submission queue
1398	+	* at submitter's current queue index (modulo submission
1399	+	* range). If no queue exists at the index, one is created.  If
1400	+	* the queue is busy, another index is randomly chosen. The
1401	+	* submitMask bounds the effective number of queues to the
1402	+	* (nearest poswer of two for) parallelism level.
1403	+	*
1404	+	* @param task the task. Caller must ensure non-null.
1405	+	*/
1406	+	private void doSubmit(ForkJoinTask<?> task) {
1407	+	Submitter s = submitters.get();
1408	+	for (int r = s.seed, m = submitMask;;) {
1409	+	WorkQueue[] ws; WorkQueue q;
1410	+	int k = r & m & SQMASK;          // use only even indices
1411	+	if (runState < 0 || (ws = workQueues) == null || ws.length <= k)
1412	+	throw new RejectedExecutionException(); // shutting down
1413	+	else if ((q = ws[k]) == null) {  // create new queue
1414	+	WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE);
1415	+	Mutex lock = this.lock;      // construct outside lock
1416	+	lock.lock();
1417	+	try {                        // recheck under lock
1418	+	int rs = runState;       // to update seq
1419	+	if (ws == workQueues && ws[k] == null) {
1420	+	ws[k] = nq;
1421	+	runState = ((rs & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN));
1422	+	}
1423	+	} finally {
1424	+	lock.unlock();
1425	+	}
1426	+	}
1427	+	else if (q.trySharedPush(task)) {
1428	+	signalWork();
1429	+	return;
1430	+	}
1431	+	else if (m > 1) {                // move to a different index
1432	+	r ^= r << 13;                // same xorshift as WorkQueues
1433	+	r ^= r >>> 17;
1434	+	s.seed = r ^= r << 5;
1435	+	}
1436	+	else
1437	+	Thread.yield();              // yield if no alternatives
1438	+	}
1439	+	}
1440	+
1441		// Maintaining ctl counts
1442
1443		/**
1444	<	* Increments active count; mainly called upon return from blocking
1444	>	* Increments active count; mainly called upon return from blocking.
1445		*/
1446		final void incrementActiveCount() {
1447		long c;
#	Line 1230 | Line 1449 | public class ForkJoinPool extends Abstra
1449		}
1450
1451		/**
1452	<	* Activates or creates a worker
1452	>	* Tries to activate or create a worker if too few are active.
1453		*/
1454		final void signalWork() {
1455	<	/*
1456	<	* The while condition is true if: (there is are too few total
1457	<	* workers OR there is at least one waiter) AND (there are too
1458	<	* few active workers OR the pool is terminating).  The value
1459	<	* of e distinguishes the remaining cases: zero (no waiters)
1460	<	* for create, negative if terminating (in which case do
1461	<	* nothing), else release a waiter. The secondary checks for
1462	<	* release (non-null array etc) can fail if the pool begins
1463	<	* terminating after the test, and don't impose any added cost
1464	<	* because JVMs must perform null and bounds checks anyway.
1465	<	*/
1466	<	long c; int e, u;
1467	<	while ((((e = (int)(c = ctl)) | (u = (int)(c >>> 32))) &
1468	<	(INT_SIGN|SHORT_SIGN)) == (INT_SIGN|SHORT_SIGN)) {
1250	<	WorkQueue[] ws = workQueues; int i; WorkQueue w; Thread p;
1251	<	if (e == 0) {                    // add a new worker
1252	<	if (U.compareAndSwapLong
1253	<	(this, CTL, c, (long)(((u + UTC_UNIT) & UTC_MASK) |
1254	<	((u + UAC_UNIT) & UAC_MASK)) << 32)) {
1255	<	addWorker();
1256	<	break;
1455	>	long c; int u;
1456	>	while ((u = (int)((c = ctl) >>> 32)) < 0) {     // too few active
1457	>	WorkQueue[] ws = workQueues; int e, i; WorkQueue w; Thread p;
1458	>	if ((e = (int)c) > 0) {                     // at least one waiting
1459	>	if (ws != null && (i = e & SMASK) < ws.length &&
1460	>	(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
1461	>	long nc = (((long)(w.nextWait & E_MASK)) |
1462	>	((long)(u + UAC_UNIT) << 32));
1463	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1464	>	w.eventCount = (e + E_SEQ) & E_MASK;
1465	>	if ((p = w.parker) != null)
1466	>	U.unpark(p);                // activate and release
1467	>	break;
1468	>	}
1469		}
1470	+	else
1471	+	break;
1472		}
1473	<	else if (e > 0 && ws != null &&
1474	<	(i = ((~e << 1) | 1) & SMASK) < ws.length &&
1475	<	(w = ws[i]) != null &&
1476	<	w.eventCount == (e | INT_SIGN)) {
1477	<	if (U.compareAndSwapLong
1264	<	(this, CTL, c, (((long)(w.nextWait & E_MASK)) |
1265	<	((long)(u + UAC_UNIT) << 32)))) {
1266	<	w.eventCount = (e + E_SEQ) & E_MASK;
1267	<	if ((p = w.parker) != null)
1268	<	U.unpark(p);         // release a waiting worker
1473	>	else if (e == 0 && (u & SHORT_SIGN) != 0) { // too few total
1474	>	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) |
1475	>	((u + UAC_UNIT) & UAC_MASK)) << 32;
1476	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1477	>	addWorker();
1478		break;
1479		}
1480		}
#	Line 1274 | Line 1483 | public class ForkJoinPool extends Abstra
1483		}
1484		}
1485
1277	–	/**
1278	–	* Tries to decrement active count (sometimes implicitly) and
1279	–	* possibly release or create a compensating worker in preparation
1280	–	* for blocking. Fails on contention or termination.
1281	–	*
1282	–	* @return true if the caller can block, else should recheck and retry
1283	–	*/
1284	–	final boolean tryCompensate() {
1285	–	WorkQueue[] ws; WorkQueue w; Thread p;
1286	–	int pc = parallelism, e, u, ac, tc, i;
1287	–	long c = ctl;
1288	–
1289	–	if ((e = (int)c) >= 0) {
1290	–	if ((ac = ((u = (int)(c >>> 32)) >> UAC_SHIFT)) <= 0 &&
1291	–	e != 0 && (ws = workQueues) != null &&
1292	–	(i = ((~e << 1) | 1) & SMASK) < ws.length &&
1293	–	(w = ws[i]) != null) {
1294	–	if (w.eventCount == (e | INT_SIGN) &&
1295	–	U.compareAndSwapLong
1296	–	(this, CTL, c, ((long)(w.nextWait & E_MASK) |
1297	–	(c & (AC_MASK|TC_MASK))))) {
1298	–	w.eventCount = (e + E_SEQ) & E_MASK;
1299	–	if ((p = w.parker) != null)
1300	–	U.unpark(p);
1301	–	return true;             // release an idle worker
1302	–	}
1303	–	}
1304	–	else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) {
1305	–	long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
1306	–	if (U.compareAndSwapLong(this, CTL, c, nc))
1307	–	return true;             // no compensation needed
1308	–	}
1309	–	else if (tc + pc < MAX_ID) {
1310	–	long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
1311	–	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1312	–	addWorker();
1313	–	return true;             // create replacement
1314	–	}
1315	–	}
1316	–	}
1317	–	return false;
1318	–	}
1486
1487	<	// Submissions
1487	>	// Scanning for tasks
1488
1489		/**
1490	<	* Unless shutting down, adds the given task to some submission
1324	<	* queue; using a randomly chosen queue index if the caller is a
1325	<	* ForkJoinWorkerThread, else one based on caller thread's hash
1326	<	* code. If no queue exists at the index, one is created.  If the
1327	<	* queue is busy, another is chosen by sweeping through the queues
1328	<	* array.
1490	>	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1491		*/
1492	<	private void doSubmit(ForkJoinTask<?> task) {
1493	<	if (task == null)
1494	<	throw new NullPointerException();
1333	<	Thread t = Thread.currentThread();
1334	<	int r = ((t instanceof ForkJoinWorkerThread) ?
1335	<	((ForkJoinWorkerThread)t).workQueue.nextSeed() : hashThread(t));
1336	<	for (;;) {
1337	<	int rs = runState, m = rs & SMASK;
1338	<	int j = r &= (m & ~1);                      // even numbered queues
1339	<	WorkQueue[] ws = workQueues;
1340	<	if (rs < 0 || ws == null)
1341	<	throw new RejectedExecutionException(); // shutting down
1342	<	if (ws.length > m) {                        // consistency check
1343	<	for (WorkQueue q;;) {                   // circular sweep
1344	<	if (((q = ws[j]) != null ||
1345	<	(q = tryAddSharedQueue(j)) != null) &&
1346	<	q.trySharedPush(task)) {
1347	<	signalWork();
1348	<	return;
1349	<	}
1350	<	if ((j = (j + 2) & m) == r) {
1351	<	Thread.yield();                 // all queues busy
1352	<	break;
1353	<	}
1354	<	}
1355	<	}
1356	<	}
1357	<	}
1358	<
1359	<	/**
1360	<	* Tries to add and register a new queue at the given index.
1361	<	*
1362	<	* @param idx the workQueues array index to register the queue
1363	<	* @return the queue, or null if could not add because could
1364	<	* not acquire lock or idx is unusable
1365	<	*/
1366	<	private WorkQueue tryAddSharedQueue(int idx) {
1367	<	WorkQueue q = null;
1368	<	ReentrantLock lock = this.lock;
1369	<	if (idx >= 0 && (idx & 1) == 0 && !lock.isLocked()) {
1370	<	// create queue outside of lock but only if apparently free
1371	<	WorkQueue nq = new WorkQueue(null, SHARED_QUEUE);
1372	<	if (lock.tryLock()) {
1373	<	try {
1374	<	WorkQueue[] ws = workQueues;
1375	<	if (ws != null && idx < ws.length) {
1376	<	if ((q = ws[idx]) == null) {
1377	<	int rs;         // update runState seq
1378	<	ws[idx] = q = nq;
1379	<	runState = (((rs = runState) & SHUTDOWN) |
1380	<	((rs + RS_SEQ) & ~SHUTDOWN));
1381	<	}
1382	<	}
1383	<	} finally {
1384	<	lock.unlock();
1385	<	}
1386	<	}
1387	<	}
1388	<	return q;
1492	>	final void runWorker(WorkQueue w) {
1493	>	w.growArray(false);         // initialize queue array in this thread
1494	>	do {} while (w.runTask(scan(w)));
1495		}
1496
1391	–	// Scanning for tasks
1392	–
1497		/**
1498		* Scans for and, if found, returns one task, else possibly
1499		* inactivates the worker. This method operates on single reads of
1500	<	* volatile state and is designed to be re-invoked continuously in
1501	<	* part because it returns upon detecting inconsistencies,
1500	>	* volatile state and is designed to be re-invoked continuously,
1501	>	* in part because it returns upon detecting inconsistencies,
1502		* contention, or state changes that indicate possible success on
1503		* re-invocation.
1504		*
1505	<	* The scan searches for tasks across queues, randomly selecting
1506	<	* the first #queues probes, favoring steals 2:1 over submissions
1507	<	* (by exploiting even/odd indexing), and then performing a
1508	<	* circular sweep of all queues.  The scan terminates upon either
1509	<	* finding a non-empty queue, or completing a full sweep. If the
1510	<	* worker is not inactivated, it takes and returns a task from
1511	<	* this queue.  On failure to find a task, we take one of the
1512	<	* following actions, after which the caller will retry calling
1513	<	* this method unless terminated.
1505	>	* The scan searches for tasks across a random permutation of
1506	>	* queues (starting at a random index and stepping by a random
1507	>	* relative prime, checking each at least once).  The scan
1508	>	* terminates upon either finding a non-empty queue, or completing
1509	>	* the sweep. If the worker is not inactivated, it takes and
1510	>	* returns a task from this queue.  On failure to find a task, we
1511	>	* take one of the following actions, after which the caller will
1512	>	* retry calling this method unless terminated.
1513	>	*
1514	>	* * If pool is terminating, terminate the worker.
1515		*
1516		* * If not a complete sweep, try to release a waiting worker.  If
1517		* the scan terminated because the worker is inactivated, then the
#	Line 1415 | Line 1520 | public class ForkJoinPool extends Abstra
1520		* another worker, but with same net effect. Releasing in other
1521		* cases as well ensures that we have enough workers running.
1522		*
1418	–	* * If the caller has run a task since the the last empty scan,
1419	–	* return (to allow rescan) if other workers are not also yet
1420	–	* enqueued.  Field WorkQueue.rescans counts down on each scan to
1421	–	* ensure eventual inactivation, and occasional calls to
1422	–	* Thread.yield to help avoid interference with more useful
1423	–	* activities on the system.
1424	–	*
1425	–	* * If pool is terminating, terminate the worker
1426	–	*
1523		* * If not already enqueued, try to inactivate and enqueue the
1524	<	* worker on wait queue.
1524	>	* worker on wait queue. Or, if inactivating has caused the pool
1525	>	* to be quiescent, relay to idleAwaitWork to check for
1526	>	* termination and possibly shrink pool.
1527	>	*
1528	>	* * If already inactive, and the caller has run a task since the
1529	>	* last empty scan, return (to allow rescan) unless others are
1530	>	* also inactivated.  Field WorkQueue.rescans counts down on each
1531	>	* scan to ensure eventual inactivation and blocking.
1532		*
1533	<	* * If already enqueued and none of the above apply, either park
1534	<	* awaiting signal, or if this is the most recent waiter and pool
1432	<	* is quiescent, relay to idleAwaitWork to check for termination
1433	<	* and possibly shrink pool.
1533	>	* * If already enqueued and none of the above apply, park
1534	>	* awaiting signal,
1535		*
1536		* @param w the worker (via its WorkQueue)
1537		* @return a task or null of none found
1538		*/
1539		private final ForkJoinTask<?> scan(WorkQueue w) {
1540	<	boolean swept = false;                 // true after full empty scan
1541	<	WorkQueue[] ws;                        // volatile read order matters
1542	<	int r = w.seed, ec = w.eventCount;     // ec is negative if inactive
1543	<	int rs = runState, m = rs & SMASK;
1544	<	if ((ws = workQueues) != null && ws.length > m) {
1545	<	ForkJoinTask<?> task = null;
1546	<	for (int k = 0, j = -2 - m; ; ++j) {
1547	<	WorkQueue q; int b;
1548	<	if (j < 0) {                    // random probes while j negative
1549	<	r ^= r << 13; r ^= r >>> 17; k = (r ^= r << 5) | (j & 1);
1550	<	}                               // worker (not submit) for odd j
1551	<	else                            // cyclic scan when j >= 0
1552	<	k += (m >>> 1) | 1;         // step by half to reduce bias
1553	<
1554	<	if ((q = ws[k & m]) != null && (b = q.base) - q.top < 0) {
1555	<	if (ec >= 0)
1556	<	task = q.pollAt(b);     // steal
1557	<	break;
1540	>	WorkQueue[] ws;                       // first update random seed
1541	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1542	>	int rs = runState, m;                 // volatile read order matters
1543	>	if ((ws = workQueues) != null && (m = ws.length - 1) > 0) {
1544	>	int ec = w.eventCount;            // ec is negative if inactive
1545	>	int step = (r >>> 16) | 1;        // relative prime
1546	>	for (int j = (m + 1) << 2; ; r += step) {
1547	>	WorkQueue q; ForkJoinTask<?> t; ForkJoinTask<?>[] a; int b;
1548	>	if ((q = ws[r & m]) != null && (b = q.base) - q.top < 0 &&
1549	>	(a = q.array) != null) {  // probably nonempty
1550	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1551	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1552	>	if (q.base == b && ec >= 0 && t != null &&
1553	>	U.compareAndSwapObject(a, i, t, null)) {
1554	>	q.base = b + 1;       // specialization of pollAt
1555	>	return t;
1556	>	}
1557	>	else if ((t != null || b + 1 != q.top) &&
1558	>	(ec < 0 || j <= m)) {
1559	>	rs = 0;               // mark scan as imcomplete
1560	>	break;                // caller can retry after release
1561	>	}
1562		}
1563	<	else if (j > m) {
1459	<	if (rs == runState)        // staleness check
1460	<	swept = true;
1563	>	if (--j < 0)
1564		break;
1565	+	}
1566	+	long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
1567	+	if (e < 0)                        // decode ctl on empty scan
1568	+	w.runState = -1;              // pool is terminating
1569	+	else if (rs == 0 || rs != runState) { // incomplete scan
1570	+	WorkQueue v; Thread p;        // try to release a waiter
1571	+	if (e > 0 && a < 0 && w.eventCount == ec &&
1572	+	(v = ws[e & m]) != null && v.eventCount == (e | INT_SIGN)) {
1573	+	long nc = ((long)(v.nextWait & E_MASK) |
1574	+	((c + AC_UNIT) & (AC_MASK|TC_MASK)));
1575	+	if (ctl == c && U.compareAndSwapLong(this, CTL, c, nc)) {
1576	+	v.eventCount = (e + E_SEQ) & E_MASK;
1577	+	if ((p = v.parker) != null)
1578	+	U.unpark(p);
1579	+	}
1580		}
1581		}
1582	<	w.seed = r;                        // save seed for next scan
1583	<	if (task != null)
1584	<	return task;
1585	<	}
1586	<
1587	<	// Decode ctl on empty scan
1588	<	long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
1589	<	if (!swept) {                          // try to release a waiter
1590	<	WorkQueue v; Thread p;
1591	<	if (e > 0 && a < 0 && ws != null &&
1592	<	(v = ws[((~e << 1) | 1) & m]) != null &&
1593	<	v.eventCount == (e | INT_SIGN) && U.compareAndSwapLong
1594	<	(this, CTL, c, ((long)(v.nextWait & E_MASK) |
1595	<	((c + AC_UNIT) & (AC_MASK|TC_MASK))))) {
1596	<	v.eventCount = (e + E_SEQ) & E_MASK;
1597	<	if ((p = v.parker) != null)
1598	<	U.unpark(p);
1599	<	}
1600	<	}
1601	<	else if ((nr = w.rescans) > 0) {       // continue rescanning
1602	<	int ac = a + parallelism;
1603	<	if ((w.rescans = (ac < nr) ? ac : nr - 1) > 0 && w.seed < 0 &&
1604	<	w.eventCount == ec)
1605	<	Thread.yield();                // 1 bit randomness for yield call
1606	<	}
1607	<	else if (e < 0)                        // pool is terminating
1608	<	w.runState = -1;
1609	<	else if (ec >= 0) {                    // try to enqueue
1610	<	long nc = (long)ec | ((c - AC_UNIT) & (AC_MASK|TC_MASK));
1611	<	w.nextWait = e;
1612	<	w.eventCount = ec | INT_SIGN;      // mark as inactive
1613	<	if (!U.compareAndSwapLong(this, CTL, c, nc))
1496	<	w.eventCount = ec;             // back out on CAS failure
1497	<	else if ((ns = w.nsteals) != 0) {  // set rescans if ran task
1498	<	if (a <= 0)                    // ... unless too many active
1499	<	w.rescans = a + parallelism;
1500	<	w.nsteals = 0;
1501	<	w.totalSteals += ns;
1502	<	}
1503	<	}
1504	<	else{                                  // already queued
1505	<	if (parallelism == -a)
1506	<	idleAwaitWork(w);              // quiescent
1507	<	if (w.eventCount == ec) {
1508	<	Thread.interrupted();          // clear status
1509	<	ForkJoinWorkerThread wt = w.owner;
1510	<	U.putObject(wt, PARKBLOCKER, this);
1511	<	w.parker = wt;                 // emulate LockSupport.park
1512	<	if (w.eventCount == ec)        // recheck
1513	<	U.park(false, 0L);         // block
1514	<	w.parker = null;
1515	<	U.putObject(wt, PARKBLOCKER, null);
1582	>	else if (ec >= 0) {               // try to enqueue/inactivate
1583	>	long nc = (long)ec | ((c - AC_UNIT) & (AC_MASK|TC_MASK));
1584	>	w.nextWait = e;
1585	>	w.eventCount = ec | INT_SIGN; // mark as inactive
1586	>	if (ctl != c || !U.compareAndSwapLong(this, CTL, c, nc))
1587	>	w.eventCount = ec;        // unmark on CAS failure
1588	>	else {
1589	>	if ((ns = w.nsteals) != 0) {
1590	>	w.nsteals = 0;        // set rescans if ran task
1591	>	w.rescans = (a > 0)? 0 : a + parallelism;
1592	>	w.totalSteals += ns;
1593	>	}
1594	>	if (a == 1 - parallelism) // quiescent
1595	>	idleAwaitWork(w, nc, c);
1596	>	}
1597	>	}
1598	>	else if (w.eventCount < 0) {      // already queued
1599	>	if ((nr = w.rescans) > 0) {   // continue rescanning
1600	>	int ac = a + parallelism;
1601	>	if (((w.rescans = (ac < nr) ? ac : nr - 1) & 3) == 0)
1602	>	Thread.yield();       // yield before block
1603	>	}
1604	>	else {
1605	>	Thread.interrupted();     // clear status
1606	>	Thread wt = Thread.currentThread();
1607	>	U.putObject(wt, PARKBLOCKER, this);
1608	>	w.parker = wt;            // emulate LockSupport.park
1609	>	if (w.eventCount < 0)     // recheck
1610	>	U.park(false, 0L);
1611	>	w.parker = null;
1612	>	U.putObject(wt, PARKBLOCKER, null);
1613	>	}
1614		}
1615		}
1616		return null;
1617		}
1618
1619		/**
1620	<	* If inactivating worker w has caused pool to become quiescent,
1621	<	* check for pool termination, and, so long as this is not the
1622	<	* only worker, wait for event for up to SHRINK_RATE nanosecs On
1623	<	* timeout, if ctl has not changed, terminate the worker, which
1624	<	* will in turn wake up another worker to possibly repeat this
1625	<	* process.
1620	>	* If inactivating worker w has caused the pool to become
1621	>	* quiescent, checks for pool termination, and, so long as this is
1622	>	* not the only worker, waits for event for up to SHRINK_RATE
1623	>	* nanosecs.  On timeout, if ctl has not changed, terminates the
1624	>	* worker, which will in turn wake up another worker to possibly
1625	>	* repeat this process.
1626		*
1627		* @param w the calling worker
1628	+	* @param currentCtl the ctl value triggering possible quiescence
1629	+	* @param prevCtl the ctl value to restore if thread is terminated
1630		*/
1631	<	private void idleAwaitWork(WorkQueue w) {
1632	<	long c; int nw, ec;
1633	<	if (!tryTerminate(false) &&
1634	<	(int)((c = ctl) >> AC_SHIFT) + parallelism == 0 &&
1635	<	(ec = w.eventCount) == ((int)c | INT_SIGN) &&
1636	<	(nw = w.nextWait) != 0) {
1537	<	long nc = ((long)(nw & E_MASK) | // ctl to restore on timeout
1538	<	((c + AC_UNIT) & AC_MASK) | (c & TC_MASK));
1539	<	ForkJoinTask.helpExpungeStaleExceptions(); // help clean
1540	<	ForkJoinWorkerThread wt = w.owner;
1541	<	while (ctl == c) {
1631	>	private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1632	>	if (w.eventCount < 0 && !tryTerminate(false, false) &&
1633	>	(int)prevCtl != 0 && ctl == currentCtl) {
1634	>	Thread wt = Thread.currentThread();
1635	>	Thread.yield();            // yield before block
1636	>	while (ctl == currentCtl) {
1637		long startTime = System.nanoTime();
1638		Thread.interrupted();  // timed variant of version in scan()
1639		U.putObject(wt, PARKBLOCKER, this);
1640		w.parker = wt;
1641	<	if (ctl == c)
1641	>	if (ctl == currentCtl)
1642		U.park(false, SHRINK_RATE);
1643		w.parker = null;
1644		U.putObject(wt, PARKBLOCKER, null);
1645	<	if (ctl != c)
1645	>	if (ctl != currentCtl)
1646		break;
1647		if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
1648	<	U.compareAndSwapLong(this, CTL, c, nc)) {
1649	<	w.runState = -1;          // shrink
1650	<	w.eventCount = (ec + E_SEQ) | E_MASK;
1648	>	U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1649	>	w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
1650	>	w.runState = -1;   // shrink
1651		break;
1652		}
1653		}
#	Line 1570 | Line 1665 | public class ForkJoinPool extends Abstra
1665		* leaves hints in workers to speed up subsequent calls. The
1666		* implementation is very branchy to cope with potential
1667		* inconsistencies or loops encountering chains that are stale,
1668	<	* unknown, or of length greater than MAX_HELP_DEPTH links.  All
1669	<	* of these cases are dealt with by just retrying by caller.
1668	>	* unknown, or so long that they are likely cyclic.  All of these
1669	>	* cases are dealt with by just retrying by caller.
1670		*
1671		* @param joiner the joining worker
1672		* @param task the task to join
1673		* @return true if found or ran a task (and so is immediately retryable)
1674		*/
1675	<	final boolean tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1676	<	ForkJoinTask<?> subtask;    // current target
1675	>	private boolean tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1676	>	WorkQueue[] ws;
1677	>	int m, depth = MAX_HELP;                // remaining chain depth
1678		boolean progress = false;
1679	<	int depth = 0;              // current chain depth
1680	<	int m = runState & SMASK;
1681	<	WorkQueue[] ws = workQueues;
1682	<
1683	<	if (ws != null && ws.length > m && (subtask = task).status >= 0) {
1684	<	outer:for (WorkQueue j = joiner;;) {
1589	<	// Try to find the stealer of subtask, by first using hint
1590	<	WorkQueue stealer = null;
1591	<	WorkQueue v = ws[j.stealHint & m];
1679	>	if ((ws = workQueues) != null && (m = ws.length - 1) > 0 &&
1680	>	task.status >= 0) {
1681	>	ForkJoinTask<?> subtask = task;     // current target
1682	>	outer: for (WorkQueue j = joiner;;) {
1683	>	WorkQueue stealer = null;       // find stealer of subtask
1684	>	WorkQueue v = ws[j.stealHint & m]; // try hint
1685		if (v != null && v.currentSteal == subtask)
1686		stealer = v;
1687	<	else {
1687	>	else {                          // scan
1688		for (int i = 1; i <= m; i += 2) {
1689	<	if ((v = ws[i]) != null && v.currentSteal == subtask) {
1689	>	if ((v = ws[i]) != null && v.currentSteal == subtask &&
1690	>	v != joiner) {
1691		stealer = v;
1692	<	j.stealHint = i; // save hint
1692	>	j.stealHint = i;    // save hint
1693		break;
1694		}
1695		}
#	Line 1603 | Line 1697 | public class ForkJoinPool extends Abstra
1697		break;
1698		}
1699
1700	<	for (WorkQueue q = stealer;;) { // Try to help stealer
1701	<	ForkJoinTask<?> t; int b;
1700	>	for (WorkQueue q = stealer;;) { // try to help stealer
1701	>	ForkJoinTask[] a; ForkJoinTask<?> t; int b;
1702		if (task.status < 0)
1703		break outer;
1704	<	if ((b = q.base) - q.top < 0) {
1704	>	if ((b = q.base) - q.top < 0 && (a = q.array) != null) {
1705		progress = true;
1706	<	if (subtask.status < 0)
1707	<	break outer;               // stale
1708	<	if ((t = q.pollAt(b)) != null) {
1709	<	stealer.stealHint = joiner.poolIndex;
1706	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1707	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1708	>	if (subtask.status < 0) // must recheck before taking
1709	>	break outer;
1710	>	if (t != null &&
1711	>	q.base == b &&
1712	>	U.compareAndSwapObject(a, i, t, null)) {
1713	>	q.base = b + 1;
1714		joiner.runSubtask(t);
1715		}
1716	+	else if (q.base == b)
1717	+	break outer;        // possibly stalled
1718		}
1719	<	else { // empty - try to descend to find stealer's stealer
1719	>	else {                      // descend
1720		ForkJoinTask<?> next = stealer.currentJoin;
1721	<	if (++depth == MAX_HELP_DEPTH || subtask.status < 0 ||
1721	>	if (--depth <= 0 || subtask.status < 0 ||
1722		next == null || next == subtask)
1723	<	break outer;  // max depth, stale, dead-end, cyclic
1723	>	break outer;        // stale, dead-end, or cyclic
1724		subtask = next;
1725		j = stealer;
1726		break;
#	Line 1637 | Line 1737 | public class ForkJoinPool extends Abstra
1737		* @param joiner the joining worker
1738		* @param task the task
1739		*/
1740	<	final void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
1740	>	private void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
1741		WorkQueue[] ws;
1742	<	int m = runState & SMASK;
1743	<	if ((ws = workQueues) != null && ws.length > m) {
1644	<	for (int j = 1; j <= m && task.status >= 0; j += 2) {
1742	>	if ((ws = workQueues) != null) {
1743	>	for (int j = 1; j < ws.length && task.status >= 0; j += 2) {
1744		WorkQueue q = ws[j];
1745		if (q != null && q.pollFor(task)) {
1746		joiner.runSubtask(task);
#	Line 1652 | Line 1751 | public class ForkJoinPool extends Abstra
1751		}
1752
1753		/**
1754	<	* Returns a non-empty steal queue, if one is found during a random,
1755	<	* then cyclic scan, else null.  This method must be retried by
1756	<	* caller if, by the time it tries to use the queue, it is empty.
1754	>	* Tries to decrement active count (sometimes implicitly) and
1755	>	* possibly release or create a compensating worker in preparation
1756	>	* for blocking. Fails on contention or termination. Otherwise,
1757	>	* adds a new thread if no idle workers are available and either
1758	>	* pool would become completely starved or: (at least half
1759	>	* starved, and fewer than 50% spares exist, and there is at least
1760	>	* one task apparently available). Even though the availablity
1761	>	* check requires a full scan, it is worthwhile in reducing false
1762	>	* alarms.
1763	>	*
1764	>	* @param task if nonnull, a task being waited for
1765	>	* @param blocker if nonnull, a blocker being waited for
1766	>	* @return true if the caller can block, else should recheck and retry
1767	>	*/
1768	>	final boolean tryCompensate(ForkJoinTask<?> task, ManagedBlocker blocker) {
1769	>	int pc = parallelism, e;
1770	>	long c = ctl;
1771	>	WorkQueue[] ws = workQueues;
1772	>	if ((e = (int)c) >= 0 && ws != null) {
1773	>	int u, a, ac, hc;
1774	>	int tc = (short)((u = (int)(c >>> 32)) >>> UTC_SHIFT) + pc;
1775	>	boolean replace = false;
1776	>	if ((a = u >> UAC_SHIFT) <= 0) {
1777	>	if ((ac = a + pc) <= 1)
1778	>	replace = true;
1779	>	else if ((e > 0 || (task != null &&
1780	>	ac <= (hc = pc >>> 1) && tc < pc + hc))) {
1781	>	WorkQueue w;
1782	>	for (int j = 0; j < ws.length; ++j) {
1783	>	if ((w = ws[j]) != null && !w.isEmpty()) {
1784	>	replace = true;
1785	>	break;   // in compensation range and tasks available
1786	>	}
1787	>	}
1788	>	}
1789	>	}
1790	>	if ((task == null || task.status >= 0) && // recheck need to block
1791	>	(blocker == null || !blocker.isReleasable()) && ctl == c) {
1792	>	if (!replace) {          // no compensation
1793	>	long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
1794	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1795	>	return true;
1796	>	}
1797	>	else if (e != 0) {       // release an idle worker
1798	>	WorkQueue w; Thread p; int i;
1799	>	if ((i = e & SMASK) < ws.length && (w = ws[i]) != null) {
1800	>	long nc = ((long)(w.nextWait & E_MASK) |
1801	>	(c & (AC_MASK|TC_MASK)));
1802	>	if (w.eventCount == (e | INT_SIGN) &&
1803	>	U.compareAndSwapLong(this, CTL, c, nc)) {
1804	>	w.eventCount = (e + E_SEQ) & E_MASK;
1805	>	if ((p = w.parker) != null)
1806	>	U.unpark(p);
1807	>	return true;
1808	>	}
1809	>	}
1810	>	}
1811	>	else if (tc < MAX_CAP) { // create replacement
1812	>	long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
1813	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1814	>	addWorker();
1815	>	return true;
1816	>	}
1817	>	}
1818	>	}
1819	>	}
1820	>	return false;
1821	>	}
1822	>
1823	>	/**
1824	>	* Helps and/or blocks until the given task is done
1825	>	*
1826	>	* @param joiner the joining worker
1827	>	* @param task the task
1828	>	* @return task status on exit
1829	>	*/
1830	>	final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
1831	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
1832	>	joiner.currentJoin = task;
1833	>	long startTime = 0L;
1834	>	for (int k = 0, s; ; ++k) {
1835	>	if ((joiner.isEmpty() ?                  // try to help
1836	>	!tryHelpStealer(joiner, task) :
1837	>	!joiner.tryRemoveAndExec(task))) {
1838	>	if (k == 0) {
1839	>	startTime = System.nanoTime();
1840	>	tryPollForAndExec(joiner, task); // check uncommon case
1841	>	}
1842	>	else if ((k & (MAX_HELP - 1)) == 0 &&
1843	>	System.nanoTime() - startTime >= COMPENSATION_DELAY &&
1844	>	tryCompensate(task, null)) {
1845	>	if (task.trySetSignal() && task.status >= 0) {
1846	>	synchronized (task) {
1847	>	if (task.status >= 0) {
1848	>	try {                // see ForkJoinTask
1849	>	task.wait();     //  for explanation
1850	>	} catch (InterruptedException ie) {
1851	>	}
1852	>	}
1853	>	else
1854	>	task.notifyAll();
1855	>	}
1856	>	}
1857	>	long c;                          // re-activate
1858	>	do {} while (!U.compareAndSwapLong
1859	>	(this, CTL, c = ctl, c + AC_UNIT));
1860	>	}
1861	>	}
1862	>	if ((s = task.status) < 0) {
1863	>	joiner.currentJoin = prevJoin;
1864	>	return s;
1865	>	}
1866	>	else if ((k & (MAX_HELP - 1)) == MAX_HELP >>> 1)
1867	>	Thread.yield();                     // for politeness
1868	>	}
1869	>	}
1870	>
1871	>	/**
1872	>	* Stripped-down variant of awaitJoin used by timed joins. Tries
1873	>	* to help join only while there is continuous progress. (Caller
1874	>	* will then enter a timed wait.)
1875	>	*
1876	>	* @param joiner the joining worker
1877	>	* @param task the task
1878	>	* @return task status on exit
1879	>	*/
1880	>	final int helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
1881	>	int s;
1882	>	while ((s = task.status) >= 0 &&
1883	>	(joiner.isEmpty() ?
1884	>	tryHelpStealer(joiner, task) :
1885	>	joiner.tryRemoveAndExec(task)))
1886	>	;
1887	>	return s;
1888	>	}
1889	>
1890	>	/**
1891	>	* Returns a (probably) non-empty steal queue, if one is found
1892	>	* during a random, then cyclic scan, else null.  This method must
1893	>	* be retried by caller if, by the time it tries to use the queue,
1894	>	* it is empty.
1895		*/
1896		private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
1897	<	int r = w.seed;    // Same idea as scan(), but ignoring submissions
1897	>	// Similar to loop in scan(), but ignoring submissions
1898	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1899	>	int step = (r >>> 16) | 1;
1900		for (WorkQueue[] ws;;) {
1901	<	int m = runState & SMASK;
1902	<	if ((ws = workQueues) == null)
1901	>	int rs = runState, m;
1902	>	if ((ws = workQueues) == null || (m = ws.length - 1) < 1)
1903		return null;
1904	<	if (ws.length > m) {
1905	<	WorkQueue q;
1906	<	for (int n = m << 2, k = r, j = -n;;) {
1907	<	r ^= r << 13; r ^= r >>> 17; r ^= r << 5;
1908	<	if ((q = ws[(k | 1) & m]) != null && q.base - q.top < 0) {
1909	<	w.seed = r;
1671	<	return q;
1672	<	}
1673	<	else if (j > n)
1904	>	for (int j = (m + 1) << 2; ; r += step) {
1905	>	WorkQueue q = ws[((r << 1) | 1) & m];
1906	>	if (q != null && !q.isEmpty())
1907	>	return q;
1908	>	else if (--j < 0) {
1909	>	if (runState == rs)
1910		return null;
1911	<	else
1676	<	k = (j++ < 0) ? r : k + ((m >>> 1) | 1);
1677	<
1911	>	break;
1912		}
1913		}
1914		}
#	Line 1688 | Line 1922 | public class ForkJoinPool extends Abstra
1922		*/
1923		final void helpQuiescePool(WorkQueue w) {
1924		for (boolean active = true;;) {
1925	<	w.runLocalTasks();      // exhaust local queue
1925	>	if (w.base - w.top < 0)
1926	>	w.runLocalTasks();  // exhaust local queue
1927		WorkQueue q = findNonEmptyStealQueue(w);
1928		if (q != null) {
1929	<	ForkJoinTask<?> t;
1929	>	ForkJoinTask<?> t; int b;
1930		if (!active) {      // re-establish active count
1931		long c;
1932		active = true;
1933		do {} while (!U.compareAndSwapLong
1934		(this, CTL, c = ctl, c + AC_UNIT));
1935		}
1936	<	if ((t = q.poll()) != null)
1936	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
1937		w.runSubtask(t);
1938		}
1939		else {
#	Line 1720 | Line 1955 | public class ForkJoinPool extends Abstra
1955		}
1956
1957		/**
1958	<	* Gets and removes a local or stolen task for the given worker
1958	>	* Gets and removes a local or stolen task for the given worker.
1959		*
1960		* @return a task, if available
1961		*/
1962		final ForkJoinTask<?> nextTaskFor(WorkQueue w) {
1963		for (ForkJoinTask<?> t;;) {
1964	<	WorkQueue q;
1964	>	WorkQueue q; int b;
1965		if ((t = w.nextLocalTask()) != null)
1966		return t;
1967		if ((q = findNonEmptyStealQueue(w)) == null)
1968		return null;
1969	<	if ((t = q.poll()) != null)
1969	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
1970		return t;
1971		}
1972		}
#	Line 1752 | Line 1987 | public class ForkJoinPool extends Abstra
1987		8);
1988		}
1989
1990	<	// Termination
1990	>	//  Termination
1991
1992		/**
1993	<	* Sets SHUTDOWN bit of runState under lock
1994	<	*/
1995	<	private void enableShutdown() {
1996	<	ReentrantLock lock = this.lock;
1997	<	if (runState >= 0) {
1998	<	lock.lock();                       // don't need try/finally
1999	<	runState |= SHUTDOWN;
1765	<	lock.unlock();
1766	<	}
1767	<	}
1768	<
1769	<	/**
1770	<	* Possibly initiates and/or completes termination.  Upon
1771	<	* termination, cancels all queued tasks and then
1993	>	* Possibly initiates and/or completes termination.  The caller
1994	>	* triggering termination runs three passes through workQueues:
1995	>	* (0) Setting termination status, followed by wakeups of queued
1996	>	* workers; (1) cancelling all tasks; (2) interrupting lagging
1997	>	* threads (likely in external tasks, but possibly also blocked in
1998	>	* joins).  Each pass repeats previous steps because of potential
1999	>	* lagging thread creation.
2000		*
2001		* @param now if true, unconditionally terminate, else only
2002		* if no work and no active workers
2003	+	* @param enable if true, enable shutdown when next possible
2004		* @return true if now terminating or terminated
2005		*/
2006	<	private boolean tryTerminate(boolean now) {
2006	>	private boolean tryTerminate(boolean now, boolean enable) {
2007	>	Mutex lock = this.lock;
2008		for (long c;;) {
2009		if (((c = ctl) & STOP_BIT) != 0) {      // already terminating
2010		if ((short)(c >>> TC_SHIFT) == -parallelism) {
1781	–	ReentrantLock lock = this.lock; // signal when no workers
2011		lock.lock();                    // don't need try/finally
2012		termination.signalAll();        // signal when 0 workers
2013		lock.unlock();
2014		}
2015		return true;
2016		}
2017	<	if (!now) {
2018	<	if ((int)(c >> AC_SHIFT) != -parallelism || runState >= 0 ||
2017	>	if (runState >= 0) {                    // not yet enabled
2018	>	if (!enable)
2019	>	return false;
2020	>	lock.lock();
2021	>	runState |= SHUTDOWN;
2022	>	lock.unlock();
2023	>	}
2024	>	if (!now) {                             // check if idle & no tasks
2025	>	if ((int)(c >> AC_SHIFT) != -parallelism ||
2026		hasQueuedSubmissions())
2027		return false;
2028		// Check for unqueued inactive workers. One pass suffices.
2029		WorkQueue[] ws = workQueues; WorkQueue w;
2030		if (ws != null) {
2031	<	int n = ws.length;
1796	<	for (int i = 1; i < n; i += 2) {
2031	>	for (int i = 1; i < ws.length; i += 2) {
2032		if ((w = ws[i]) != null && w.eventCount >= 0)
2033		return false;
2034		}
2035		}
2036		}
2037	<	if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT))
2038	<	startTerminating();
2039	<	}
2040	<	}
2041	<
2042	<	/**
2043	<	* Initiates termination: Runs three passes through workQueues:
2044	<	* (0) Setting termination status, followed by wakeups of queued
2045	<	* workers; (1) cancelling all tasks; (2) interrupting lagging
2046	<	* threads (likely in external tasks, but possibly also blocked in
2047	<	* joins).  Each pass repeats previous steps because of potential
2048	<	* lagging thread creation.
2049	<	*/
1815	<	private void startTerminating() {
1816	<	for (int pass = 0; pass < 3; ++pass) {
1817	<	WorkQueue[] ws = workQueues;
1818	<	if (ws != null) {
1819	<	WorkQueue w; Thread wt;
1820	<	int n = ws.length;
1821	<	for (int j = 0; j < n; ++j) {
1822	<	if ((w = ws[j]) != null) {
1823	<	w.runState = -1;
1824	<	if (pass > 0) {
1825	<	w.cancelAll();
1826	<	if (pass > 1 && (wt = w.owner) != null &&
1827	<	!wt.isInterrupted()) {
1828	<	try {
1829	<	wt.interrupt();
1830	<	} catch (SecurityException ignore) {
2037	>	if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT)) {
2038	>	for (int pass = 0; pass < 3; ++pass) {
2039	>	WorkQueue[] ws = workQueues;
2040	>	if (ws != null) {
2041	>	WorkQueue w;
2042	>	int n = ws.length;
2043	>	for (int i = 0; i < n; ++i) {
2044	>	if ((w = ws[i]) != null) {
2045	>	w.runState = -1;
2046	>	if (pass > 0) {
2047	>	w.cancelAll();
2048	>	if (pass > 1)
2049	>	w.interruptOwner();
2050		}
2051		}
2052		}
2053	<	}
2054	<	}
2055	<	// Wake up workers parked on event queue
2056	<	int i, e; long c; Thread p;
2057	<	while ((i = ((~(e = (int)(c = ctl)) << 1) | 1) & SMASK) < n &&
2058	<	(w = ws[i]) != null &&
2059	<	w.eventCount == (e | INT_SIGN)) {
2060	<	long nc = ((long)(w.nextWait & E_MASK) |
2061	<	((c + AC_UNIT) & AC_MASK) |
2062	<	(c & (TC_MASK|STOP_BIT)));
2063	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
2064	<	w.eventCount = (e + E_SEQ) & E_MASK;
2065	<	if ((p = w.parker) != null)
2066	<	U.unpark(p);
2053	>	// Wake up workers parked on event queue
2054	>	int i, e; long cc; Thread p;
2055	>	while ((e = (int)(cc = ctl) & E_MASK) != 0 &&
2056	>	(i = e & SMASK) < n &&
2057	>	(w = ws[i]) != null) {
2058	>	long nc = ((long)(w.nextWait & E_MASK) |
2059	>	((cc + AC_UNIT) & AC_MASK) |
2060	>	(cc & (TC_MASK|STOP_BIT)));
2061	>	if (w.eventCount == (e | INT_SIGN) &&
2062	>	U.compareAndSwapLong(this, CTL, cc, nc)) {
2063	>	w.eventCount = (e + E_SEQ) & E_MASK;
2064	>	w.runState = -1;
2065	>	if ((p = w.parker) != null)
2066	>	U.unpark(p);
2067	>	}
2068	>	}
2069		}
2070		}
2071		}
#	Line 1920 | Line 2141 | public class ForkJoinPool extends Abstra
2141		checkPermission();
2142		if (factory == null)
2143		throw new NullPointerException();
2144	<	if (parallelism <= 0 || parallelism > MAX_ID)
2144	>	if (parallelism <= 0 || parallelism > MAX_CAP)
2145		throw new IllegalArgumentException();
2146		this.parallelism = parallelism;
2147		this.factory = factory;
2148		this.ueh = handler;
2149		this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE;
1929	–	this.nextPoolIndex = 1;
2150		long np = (long)(-parallelism); // offset ctl counts
2151		this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
2152	<	// initialize workQueues array with room for 2*parallelism if possible
2153	<	int n = parallelism << 1;
2154	<	if (n >= MAX_ID)
2155	<	n = MAX_ID;
2156	<	else { // See Hackers Delight, sec 3.2, where n < (1 << 16)
2157	<	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8;
2158	<	}
1939	<	this.workQueues = new WorkQueue[(n + 1) << 1];
1940	<	ReentrantLock lck = this.lock = new ReentrantLock();
1941	<	this.termination = lck.newCondition();
2152	>	// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2.
2153	>	int n = parallelism - 1;
2154	>	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
2155	>	int size = (n + 1) << 1;        // #slots = 2*#workers
2156	>	this.submitMask = size - 1;     // room for max # of submit queues
2157	>	this.workQueues = new WorkQueue[size];
2158	>	this.termination = (this.lock = new Mutex()).newCondition();
2159		this.stealCount = new AtomicLong();
2160		this.nextWorkerNumber = new AtomicInteger();
2161	+	int pn = poolNumberGenerator.incrementAndGet();
2162		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2163	<	sb.append(poolNumberGenerator.incrementAndGet());
2163	>	sb.append(Integer.toString(pn));
2164		sb.append("-worker-");
2165		this.workerNamePrefix = sb.toString();
2166	<	// Create initial submission queue
2167	<	WorkQueue sq = tryAddSharedQueue(0);
2168	<	if (sq != null)
1951	<	sq.growArray(false);
2166	>	lock.lock();
2167	>	this.runState = 1;              // set init flag
2168	>	lock.unlock();
2169		}
2170
2171		// Execution methods
#	Line 1970 | Line 2187 | public class ForkJoinPool extends Abstra
2187		*         scheduled for execution
2188		*/
2189		public <T> T invoke(ForkJoinTask<T> task) {
2190	+	if (task == null)
2191	+	throw new NullPointerException();
2192		doSubmit(task);
2193		return task.join();
2194		}
#	Line 1983 | Line 2202 | public class ForkJoinPool extends Abstra
2202		*         scheduled for execution
2203		*/
2204		public void execute(ForkJoinTask<?> task) {
2205	+	if (task == null)
2206	+	throw new NullPointerException();
2207		doSubmit(task);
2208		}
2209
#	Line 2000 | Line 2221 | public class ForkJoinPool extends Abstra
2221		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2222		job = (ForkJoinTask<?>) task;
2223		else
2224	<	job = ForkJoinTask.adapt(task, null);
2224	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2225		doSubmit(job);
2226		}
2227
#	Line 2014 | Line 2235 | public class ForkJoinPool extends Abstra
2235		*         scheduled for execution
2236		*/
2237		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2238	+	if (task == null)
2239	+	throw new NullPointerException();
2240		doSubmit(task);
2241		return task;
2242		}
#	Line 2024 | Line 2247 | public class ForkJoinPool extends Abstra
2247		*         scheduled for execution
2248		*/
2249		public <T> ForkJoinTask<T> submit(Callable<T> task) {
2250	<	if (task == null)
2028	<	throw new NullPointerException();
2029	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
2250	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2251		doSubmit(job);
2252		return job;
2253		}
#	Line 2037 | Line 2258 | public class ForkJoinPool extends Abstra
2258		*         scheduled for execution
2259		*/
2260		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2261	<	if (task == null)
2041	<	throw new NullPointerException();
2042	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
2261	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2262		doSubmit(job);
2263		return job;
2264		}
#	Line 2056 | Line 2275 | public class ForkJoinPool extends Abstra
2275		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2276		job = (ForkJoinTask<?>) task;
2277		else
2278	<	job = ForkJoinTask.adapt(task, null);
2278	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2279		doSubmit(job);
2280		return job;
2281		}
#	Line 2066 | Line 2285 | public class ForkJoinPool extends Abstra
2285		* @throws RejectedExecutionException {@inheritDoc}
2286		*/
2287		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
2288	<	ArrayList<ForkJoinTask<T>> forkJoinTasks =
2289	<	new ArrayList<ForkJoinTask<T>>(tasks.size());
2290	<	for (Callable<T> task : tasks)
2291	<	forkJoinTasks.add(ForkJoinTask.adapt(task));
2292	<	invoke(new InvokeAll<T>(forkJoinTasks));
2293	<
2288	>	// In previous versions of this class, this method constructed
2289	>	// a task to run ForkJoinTask.invokeAll, but now external
2290	>	// invocation of multiple tasks is at least as efficient.
2291	>	List<ForkJoinTask<T>> fs = new ArrayList<ForkJoinTask<T>>(tasks.size());
2292	>	// Workaround needed because method wasn't declared with
2293	>	// wildcards in return type but should have been.
2294		@SuppressWarnings({"unchecked", "rawtypes"})
2295	<	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
2077	<	return futures;
2078	<	}
2295	>	List<Future<T>> futures = (List<Future<T>>) (List) fs;
2296
2297	<	static final class InvokeAll<T> extends RecursiveAction {
2298	<	final ArrayList<ForkJoinTask<T>> tasks;
2299	<	InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
2300	<	public void compute() {
2301	<	try { invokeAll(tasks); }
2302	<	catch (Exception ignore) {}
2297	>	boolean done = false;
2298	>	try {
2299	>	for (Callable<T> t : tasks) {
2300	>	ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2301	>	doSubmit(f);
2302	>	fs.add(f);
2303	>	}
2304	>	for (ForkJoinTask<T> f : fs)
2305	>	f.quietlyJoin();
2306	>	done = true;
2307	>	return futures;
2308	>	} finally {
2309	>	if (!done)
2310	>	for (ForkJoinTask<T> f : fs)
2311	>	f.cancel(false);
2312		}
2087	–	private static final long serialVersionUID = -7914297376763021607L;
2313		}
2314
2315		/**
#	Line 2149 | Line 2374 | public class ForkJoinPool extends Abstra
2374		int rc = 0;
2375		WorkQueue[] ws; WorkQueue w;
2376		if ((ws = workQueues) != null) {
2377	<	int n = ws.length;
2378	<	for (int i = 1; i < n; i += 2) {
2154	<	Thread.State s; ForkJoinWorkerThread wt;
2155	<	if ((w = ws[i]) != null && (wt = w.owner) != null &&
2156	<	w.eventCount >= 0 &&
2157	<	(s = wt.getState()) != Thread.State.BLOCKED &&
2158	<	s != Thread.State.WAITING &&
2159	<	s != Thread.State.TIMED_WAITING)
2377	>	for (int i = 1; i < ws.length; i += 2) {
2378	>	if ((w = ws[i]) != null && w.isApparentlyUnblocked())
2379		++rc;
2380		}
2381		}
#	Line 2205 | Line 2424 | public class ForkJoinPool extends Abstra
2424		long count = stealCount.get();
2425		WorkQueue[] ws; WorkQueue w;
2426		if ((ws = workQueues) != null) {
2427	<	int n = ws.length;
2209	<	for (int i = 1; i < n; i += 2) {
2427	>	for (int i = 1; i < ws.length; i += 2) {
2428		if ((w = ws[i]) != null)
2429		count += w.totalSteals;
2430		}
#	Line 2228 | Line 2446 | public class ForkJoinPool extends Abstra
2446		long count = 0;
2447		WorkQueue[] ws; WorkQueue w;
2448		if ((ws = workQueues) != null) {
2449	<	int n = ws.length;
2232	<	for (int i = 1; i < n; i += 2) {
2449	>	for (int i = 1; i < ws.length; i += 2) {
2450		if ((w = ws[i]) != null)
2451		count += w.queueSize();
2452		}
#	Line 2248 | Line 2465 | public class ForkJoinPool extends Abstra
2465		int count = 0;
2466		WorkQueue[] ws; WorkQueue w;
2467		if ((ws = workQueues) != null) {
2468	<	int n = ws.length;
2252	<	for (int i = 0; i < n; i += 2) {
2468	>	for (int i = 0; i < ws.length; i += 2) {
2469		if ((w = ws[i]) != null)
2470		count += w.queueSize();
2471		}
#	Line 2266 | Line 2482 | public class ForkJoinPool extends Abstra
2482		public boolean hasQueuedSubmissions() {
2483		WorkQueue[] ws; WorkQueue w;
2484		if ((ws = workQueues) != null) {
2485	<	int n = ws.length;
2486	<	for (int i = 0; i < n; i += 2) {
2271	<	if ((w = ws[i]) != null && w.queueSize() != 0)
2485	>	for (int i = 0; i < ws.length; i += 2) {
2486	>	if ((w = ws[i]) != null && !w.isEmpty())
2487		return true;
2488		}
2489		}
#	Line 2285 | Line 2500 | public class ForkJoinPool extends Abstra
2500		protected ForkJoinTask<?> pollSubmission() {
2501		WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2502		if ((ws = workQueues) != null) {
2503	<	int n = ws.length;
2289	<	for (int i = 0; i < n; i += 2) {
2503	>	for (int i = 0; i < ws.length; i += 2) {
2504		if ((w = ws[i]) != null && (t = w.poll()) != null)
2505		return t;
2506		}
#	Line 2315 | Line 2529 | public class ForkJoinPool extends Abstra
2529		int count = 0;
2530		WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2531		if ((ws = workQueues) != null) {
2532	<	int n = ws.length;
2319	<	for (int i = 0; i < n; ++i) {
2532	>	for (int i = 0; i < ws.length; ++i) {
2533		if ((w = ws[i]) != null) {
2534		while ((t = w.poll()) != null) {
2535		c.add(t);
#	Line 2336 | Line 2549 | public class ForkJoinPool extends Abstra
2549		* @return a string identifying this pool, as well as its state
2550		*/
2551		public String toString() {
2552	<	long st = getStealCount();
2553	<	long qt = getQueuedTaskCount();
2554	<	long qs = getQueuedSubmissionCount();
2342	<	int rc = getRunningThreadCount();
2343	<	int pc = parallelism;
2552	>	// Use a single pass through workQueues to collect counts
2553	>	long qt = 0L, qs = 0L; int rc = 0;
2554	>	long st = stealCount.get();
2555		long c = ctl;
2556	+	WorkQueue[] ws; WorkQueue w;
2557	+	if ((ws = workQueues) != null) {
2558	+	for (int i = 0; i < ws.length; ++i) {
2559	+	if ((w = ws[i]) != null) {
2560	+	int size = w.queueSize();
2561	+	if ((i & 1) == 0)
2562	+	qs += size;
2563	+	else {
2564	+	qt += size;
2565	+	st += w.totalSteals;
2566	+	if (w.isApparentlyUnblocked())
2567	+	++rc;
2568	+	}
2569	+	}
2570	+	}
2571	+	}
2572	+	int pc = parallelism;
2573		int tc = pc + (short)(c >>> TC_SHIFT);
2574		int ac = pc + (int)(c >> AC_SHIFT);
2575		if (ac < 0) // ignore transient negative
#	Line 2377 | Line 2605 | public class ForkJoinPool extends Abstra
2605		*/
2606		public void shutdown() {
2607		checkPermission();
2608	<	enableShutdown();
2381	<	tryTerminate(false);
2608	>	tryTerminate(false, true);
2609		}
2610
2611		/**
#	Line 2399 | Line 2626 | public class ForkJoinPool extends Abstra
2626		*/
2627		public List<Runnable> shutdownNow() {
2628		checkPermission();
2629	<	enableShutdown();
2403	<	tryTerminate(true);
2629	>	tryTerminate(true, true);
2630		return Collections.emptyList();
2631		}
2632
#	Line 2457 | Line 2683 | public class ForkJoinPool extends Abstra
2683		public boolean awaitTermination(long timeout, TimeUnit unit)
2684		throws InterruptedException {
2685		long nanos = unit.toNanos(timeout);
2686	<	final ReentrantLock lock = this.lock;
2686	>	final Mutex lock = this.lock;
2687		lock.lock();
2688		try {
2689		for (;;) {
#	Line 2571 | Line 2797 | public class ForkJoinPool extends Abstra
2797		ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ?
2798		((ForkJoinWorkerThread)t).pool : null);
2799		while (!blocker.isReleasable()) {
2800	<	if (p == null || p.tryCompensate()) {
2800	>	if (p == null || p.tryCompensate(null, blocker)) {
2801		try {
2802		do {} while (!blocker.isReleasable() && !blocker.block());
2803		} finally {
#	Line 2588 | Line 2814 | public class ForkJoinPool extends Abstra
2814		// implement RunnableFuture.
2815
2816		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
2817	<	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
2817	>	return new ForkJoinTask.AdaptedRunnable<T>(runnable, value);
2818		}
2819
2820		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
2821	<	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
2821	>	return new ForkJoinTask.AdaptedCallable<T>(callable);
2822		}
2823
2824		// Unsafe mechanics
2825		private static final sun.misc.Unsafe U;
2826		private static final long CTL;
2601	–	private static final long RUNSTATE;
2827		private static final long PARKBLOCKER;
2828	+	private static final int ABASE;
2829	+	private static final int ASHIFT;
2830
2831		static {
2832		poolNumberGenerator = new AtomicInteger();
2833	+	nextSubmitterSeed = new AtomicInteger(0x55555555);
2834		modifyThreadPermission = new RuntimePermission("modifyThread");
2835		defaultForkJoinWorkerThreadFactory =
2836		new DefaultForkJoinWorkerThreadFactory();
2837	+	submitters = new ThreadSubmitter();
2838		int s;
2839		try {
2840		U = getUnsafe();
2841		Class<?> k = ForkJoinPool.class;
2842	<	Class<?> tk = Thread.class;
2842	>	Class<?> ak = ForkJoinTask[].class;
2843		CTL = U.objectFieldOffset
2844		(k.getDeclaredField("ctl"));
2845	<	RUNSTATE = U.objectFieldOffset
2617	<	(k.getDeclaredField("runState"));
2845	>	Class<?> tk = Thread.class;
2846		PARKBLOCKER = U.objectFieldOffset
2847		(tk.getDeclaredField("parkBlocker"));
2848	+	ABASE = U.arrayBaseOffset(ak);
2849	+	s = U.arrayIndexScale(ak);
2850		} catch (Exception e) {
2851		throw new Error(e);
2852		}
2853	+	if ((s & (s-1)) != 0)
2854	+	throw new Error("data type scale not a power of two");
2855	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
2856		}
2857
2858		/**

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