[ViewVC] Diff of: jsr166/jsr166/src/jsr166e/ForkJoinPool.java

Comparing jsr166/src/jsr166e/ForkJoinPool.java (file contents):
Revision 1.8 by dl, Mon Oct 29 17:23:26 2012 UTC vs.
Revision 1.27 by jsr166, Sat Dec 8 20:49:24 2012 UTC

#	Line 11 \| Line 11 \| import java.util.Arrays;
11		import java.util.Collection;
12		import java.util.Collections;
13		import java.util.List;
14	–	import java.util.Random;
14		import java.util.concurrent.AbstractExecutorService;
15		import java.util.concurrent.Callable;
16		import java.util.concurrent.ExecutorService;
17		import java.util.concurrent.Future;
18		import java.util.concurrent.RejectedExecutionException;
19		import java.util.concurrent.RunnableFuture;
21	–	import java.util.concurrent.ThreadLocalRandom;
20		import java.util.concurrent.TimeUnit;
23	–	import java.util.concurrent.atomic.AtomicInteger;
24	–	import java.util.concurrent.atomic.AtomicLong;
25	–	import java.util.concurrent.locks.AbstractQueuedSynchronizer;
26	–	import java.util.concurrent.locks.Condition;
21
22		/**
23		* An {@link ExecutorService} for running {@link ForkJoinTask}s.
#	Line 43 \| Line 37 \| import java.util.concurrent.locks.Condit
37		* ForkJoinPool}s may also be appropriate for use with event-style
38		* tasks that are never joined.
39		*
40	<	* <p>A static {@link #commonPool} is available and appropriate for
40	>	* <p>A static {@link #commonPool()} is available and appropriate for
41		* most applications. The common pool is used by any ForkJoinTask that
42		* is not explicitly submitted to a specified pool. Using the common
43		* pool normally reduces resource usage (its threads are slowly
44		* reclaimed during periods of non-use, and reinstated upon subsequent
45	<	* use). The common pool is by default constructed with default
52	<	* parameters, but these may be controlled by setting any or all of
53	<	* the three properties {@code
54	<	* java.util.concurrent.ForkJoinPool.common.{parallelism,
55	<	* threadFactory, exceptionHandler}}.
45	>	* use).
46		*
47		* <p>For applications that require separate or custom pools, a {@code
48		* ForkJoinPool} may be constructed with a given target parallelism
#	Line 61 \| Line 51 \| import java.util.concurrent.locks.Condit
51		* dynamically adding, suspending, or resuming internal worker
52		* threads, even if some tasks are stalled waiting to join
53		* others. However, no such adjustments are guaranteed in the face of
54	<	* blocked IO or other unmanaged synchronization. The nested {@link
54	>	* blocked I/O or other unmanaged synchronization. The nested {@link
55		* ManagedBlocker} interface enables extension of the kinds of
56		* synchronization accommodated.
57		*
#	Line 72 \| Line 62 \| import java.util.concurrent.locks.Condit
62		* {@link #toString} returns indications of pool state in a
63		* convenient form for informal monitoring.
64		*
65	<	* <p> As is the case with other ExecutorServices, there are three
65	>	* <p>As is the case with other ExecutorServices, there are three
66		* main task execution methods summarized in the following table.
67		* These are designed to be used primarily by clients not already
68		* engaged in fork/join computations in the current pool. The main
#	Line 107 \| Line 97 \| import java.util.concurrent.locks.Condit
97		* </tr>
98		* </table>
99		*
100	+	* <p>The common pool is by default constructed with default
101	+	* parameters, but these may be controlled by setting three {@link
102	+	* System#getProperty system properties} with prefix {@code
103	+	* java.util.concurrent.ForkJoinPool.common}: {@code parallelism} --
104	+	* an integer greater than zero, {@code threadFactory} -- the class
105	+	* name of a {@link ForkJoinWorkerThreadFactory}, and {@code
106	+	* exceptionHandler} -- the class name of a {@link
107	+	* java.lang.Thread.UncaughtExceptionHandler
108	+	* Thread.UncaughtExceptionHandler}. Upon any error in establishing
109	+	* these settings, default parameters are used.
110	+	*
111		* <p><b>Implementation notes</b>: This implementation restricts the
112		* maximum number of running threads to 32767. Attempts to create
113		* pools with greater than the maximum number result in
#	Line 193 \| Line 194 \| public class ForkJoinPool extends Abstra
194		* WorkQueues are also used in a similar way for tasks submitted
195		* to the pool. We cannot mix these tasks in the same queues used
196		* for work-stealing (this would contaminate lifo/fifo
197	<	* processing). Instead, we loosely associate submission queues
197	>	* processing). Instead, we randomly associate submission queues
198		* with submitting threads, using a form of hashing. The
199		* ThreadLocal Submitter class contains a value initially used as
200		* a hash code for choosing existing queues, but may be randomly
201		* repositioned upon contention with other submitters. In
202	<	* essence, submitters act like workers except that they never
203	<	* take tasks, and they are multiplexed on to a finite number of
204	<	* shared work queues. However, classes are set up so that future
205	<	* extensions could allow submitters to optionally help perform
206	<	* tasks as well. Insertion of tasks in shared mode requires a
207	<	* lock (mainly to protect in the case of resizing) but we use
208	<	* only a simple spinlock (using bits in field runState), because
209	<	* submitters encountering a busy queue move on to try or create
210	<	* other queues -- they block only when creating and registering
211	<	* new queues.
202	>	* essence, submitters act like workers except that they are
203	>	* restricted to executing local tasks that they submitted (or in
204	>	* the case of CountedCompleters, others with the same root task).
205	>	* However, because most shared/external queue operations are more
206	>	* expensive than internal, and because, at steady state, external
207	>	* submitters will compete for CPU with workers, ForkJoinTask.join
208	>	* and related methods disable them from repeatedly helping to
209	>	* process tasks if all workers are active. Insertion of tasks in
210	>	* shared mode requires a lock (mainly to protect in the case of
211	>	* resizing) but we use only a simple spinlock (using bits in
212	>	* field qlock), because submitters encountering a busy queue move
213	>	* on to try or create other queues -- they block only when
214	>	* creating and registering new queues.
215		*
216		* Management
217		* ==========
#	Line 229 \| Line 233 \| public class ForkJoinPool extends Abstra
233		* and their negations (used for thresholding) to fit into 16bit
234		* fields.
235		*
236	<	* Field "runState" contains 32 bits needed to register and
237	<	* deregister WorkQueues, as well as to enable shutdown. It is
238	<	* only modified under a lock (normally briefly held, but
239	<	* occasionally protecting allocations and resizings) but even
240	<	* when locked remains available to check consistency.
236	>	* Field "plock" is a form of sequence lock with a saturating
237	>	* shutdown bit (similarly for per-queue "qlocks"), mainly
238	>	* protecting updates to the workQueues array, as well as to
239	>	* enable shutdown. When used as a lock, it is normally only very
240	>	* briefly held, so is nearly always available after at most a
241	>	* brief spin, but we use a monitor-based backup strategy to
242	>	* block when needed.
243		*
244		* Recording WorkQueues. WorkQueues are recorded in the
245		* "workQueues" array that is created upon first use and expanded
#	Line 242 \| Line 248 \| public class ForkJoinPool extends Abstra
248		* by a lock but the array is otherwise concurrently readable, and
249		* accessed directly. To simplify index-based operations, the
250		* array size is always a power of two, and all readers must
251	<	* tolerate null slots. Shared (submission) queues are at even
252	<	* indices, worker queues at odd indices. Grouping them together
253	<	* in this way simplifies and speeds up task scanning.
251	>	* tolerate null slots. Worker queues are at odd indices. Shared
252	>	* (submission) queues are at even indices, up to a maximum of 64
253	>	* slots, to limit growth even if array needs to expand to add
254	>	* more workers. Grouping them together in this way simplifies and
255	>	* speeds up task scanning.
256		*
257		* All worker thread creation is on-demand, triggered by task
258		* submissions, replacement of terminated workers, and/or
#	Line 305 \| Line 313 \| public class ForkJoinPool extends Abstra
313		*
314		* Signalling. We create or wake up workers only when there
315		* appears to be at least one task they might be able to find and
316	<	* execute. When a submission is added or another worker adds a
317	<	* task to a queue that previously had fewer than two tasks, they
318	<	* signal waiting workers (or trigger creation of new ones if
319	<	* fewer than the given parallelism level -- see signalWork).
320	<	* These primary signals are buttressed by signals during rescans;
321	<	* together these cover the signals needed in cases when more
322	<	* tasks are pushed but untaken, and improve performance compared
323	<	* to having one thread wake up all workers.
316	>	* execute. However, many other threads may notice the same task
317	>	* and each signal to wake up a thread that might take it. So in
318	>	* general, pools will be over-signalled. When a submission is
319	>	* added or another worker adds a task to a queue that has fewer
320	>	* than two tasks, they signal waiting workers (or trigger
321	>	* creation of new ones if fewer than the given parallelism level
322	>	* -- signalWork), and may leave a hint to the unparked worker to
323	>	* help signal others upon wakeup). These primary signals are
324	>	* buttressed by others (see method helpSignal) whenever other
325	>	* threads scan for work or do not have a task to process. On
326	>	* most platforms, signalling (unpark) overhead time is noticeably
327	>	* long, and the time between signalling a thread and it actually
328	>	* making progress can be very noticeably long, so it is worth
329	>	* offloading these delays from critical paths as much as
330	>	* possible.
331		*
332		* Trimming workers. To release resources after periods of lack of
333		* use, a worker starting to wait when the pool is quiescent will
#	Line 323 \| Line 338 \| public class ForkJoinPool extends Abstra
338		* periods of non-use.
339		*
340		* Shutdown and Termination. A call to shutdownNow atomically sets
341	<	* a runState bit and then (non-atomically) sets each worker's
342	<	* runState status, cancels all unprocessed tasks, and wakes up
341	>	* a plock bit and then (non-atomically) sets each worker's
342	>	* qlock status, cancels all unprocessed tasks, and wakes up
343		* all waiting workers. Detecting whether termination should
344		* commence after a non-abrupt shutdown() call requires more work
345		* and bookkeeping. We need consensus about quiescence (i.e., that
#	Line 352 \| Line 367 \| public class ForkJoinPool extends Abstra
367		* method tryCompensate() may create or re-activate a spare
368		* thread to compensate for blocked joiners until they unblock.
369		*
370	<	* A third form (implemented in tryRemoveAndExec and
371	<	* tryPollForAndExec) amounts to helping a hypothetical
372	<	* compensator: If we can readily tell that a possible action of a
373	<	* compensator is to steal and execute the task being joined, the
374	<	* joining thread can do so directly, without the need for a
375	<	* compensation thread (although at the expense of larger run-time
376	<	* stacks, but the tradeoff is typically worthwhile).
370	>	* A third form (implemented in tryRemoveAndExec) amounts to
371	>	* helping a hypothetical compensator: If we can readily tell that
372	>	* a possible action of a compensator is to steal and execute the
373	>	* task being joined, the joining thread can do so directly,
374	>	* without the need for a compensation thread (although at the
375	>	* expense of larger run-time stacks, but the tradeoff is
376	>	* typically worthwhile).
377		*
378		* The ManagedBlocker extension API can't use helping so relies
379		* only on compensation in method awaitBlocker.
#	Line 380 \| Line 395 \| public class ForkJoinPool extends Abstra
395		* steals, rather than use per-task bookkeeping. This sometimes
396		* requires a linear scan of workQueues array to locate stealers,
397		* but often doesn't because stealers leave hints (that may become
398	<	* stale/wrong) of where to locate them. A stealHint is only a
399	<	* hint because a worker might have had multiple steals and the
400	<	* hint records only one of them (usually the most current).
401	<	* Hinting isolates cost to when it is needed, rather than adding
402	<	* to per-task overhead. (2) It is "shallow", ignoring nesting
403	<	* and potentially cyclic mutual steals. (3) It is intentionally
398	>	* stale/wrong) of where to locate them. It is only a hint
399	>	* because a worker might have had multiple steals and the hint
400	>	* records only one of them (usually the most current). Hinting
401	>	* isolates cost to when it is needed, rather than adding to
402	>	* per-task overhead. (2) It is "shallow", ignoring nesting and
403	>	* potentially cyclic mutual steals. (3) It is intentionally
404		* racy: field currentJoin is updated only while actively joining,
405		* which means that we miss links in the chain during long-lived
406		* tasks, GC stalls etc (which is OK since blocking in such cases
#	Line 393 \| Line 408 \| public class ForkJoinPool extends Abstra
408		* to find work (see MAX_HELP) and fall back to suspending the
409		* worker and if necessary replacing it with another.
410		*
411	+	* Helping actions for CountedCompleters are much simpler: Method
412	+	* helpComplete can take and execute any task with the same root
413	+	* as the task being waited on. However, this still entails some
414	+	* traversal of completer chains, so is less efficient than using
415	+	* CountedCompleters without explicit joins.
416	+	*
417		* It is impossible to keep exactly the target parallelism number
418		* of threads running at any given time. Determining the
419		* existence of conservatively safe helping targets, the
#	Line 414 \| Line 435 \| public class ForkJoinPool extends Abstra
435		* intractable) game with an opponent that may choose the worst
436		* (for us) active thread to stall at any time. We take several
437		* precautions to bound losses (and thus bound gains), mainly in
438	<	* methods tryCompensate and awaitJoin: (1) We only try
439	<	* compensation after attempting enough helping steps (measured
440	<	* via counting and timing) that we have already consumed the
441	<	* estimated cost of creating and activating a new thread. (2) We
442	<	* allow up to 50% of threads to be blocked before initially
443	<	* adding any others, and unless completely saturated, check that
444	<	* some work is available for a new worker before adding. Also, we
445	<	* create up to only 50% more threads until entering a mode that
446	<	* only adds a thread if all others are possibly blocked. All
447	<	* together, this means that we might be half as fast to react,
448	<	* and create half as many threads as possible in the ideal case,
449	<	* but present vastly fewer anomalies in all other cases compared
450	<	* to both more aggressive and more conservative alternatives.
451	<	*
452	<	* Style notes: There is a lot of representation-level coupling
453	<	* among classes ForkJoinPool, ForkJoinWorkerThread, and
454	<	* ForkJoinTask. The fields of WorkQueue maintain data structures
455	<	* managed by ForkJoinPool, so are directly accessed. There is
456	<	* little point trying to reduce this, since any associated future
457	<	* changes in representations will need to be accompanied by
458	<	* algorithmic changes anyway. Several methods intrinsically
459	<	* sprawl because they must accumulate sets of consistent reads of
460	<	* volatiles held in local variables. Methods signalWork() and
461	<	* scan() are the main bottlenecks, so are especially heavily
438	>	* methods tryCompensate and awaitJoin.
439	>	*
440	>	* Common Pool
441	>	* ===========
442	>	*
443	>	* The static commonPool always exists after static
444	>	* initialization. Since it (or any other created pool) need
445	>	* never be used, we minimize initial construction overhead and
446	>	* footprint to the setup of about a dozen fields, with no nested
447	>	* allocation. Most bootstrapping occurs within method
448	>	* fullExternalPush during the first submission to the pool.
449	>	*
450	>	* When external threads submit to the common pool, they can
451	>	* perform some subtask processing (see externalHelpJoin and
452	>	* related methods). We do not need to record whether these
453	>	* submissions are to the common pool -- if not, externalHelpJoin
454	>	* returns quickly (at the most helping to signal some common pool
455	>	* workers). These submitters would otherwise be blocked waiting
456	>	* for completion, so the extra effort (with liberally sprinkled
457	>	* task status checks) in inapplicable cases amounts to an odd
458	>	* form of limited spin-wait before blocking in ForkJoinTask.join.
459	>	*
460	>	* Style notes
461	>	* ===========
462	>	*
463	>	* There is a lot of representation-level coupling among classes
464	>	* ForkJoinPool, ForkJoinWorkerThread, and ForkJoinTask. The
465	>	* fields of WorkQueue maintain data structures managed by
466	>	* ForkJoinPool, so are directly accessed. There is little point
467	>	* trying to reduce this, since any associated future changes in
468	>	* representations will need to be accompanied by algorithmic
469	>	* changes anyway. Several methods intrinsically sprawl because
470	>	* they must accumulate sets of consistent reads of volatiles held
471	>	* in local variables. Methods signalWork() and scan() are the
472	>	* main bottlenecks, so are especially heavily
473		* micro-optimized/mangled. There are lots of inline assignments
474		* (of form "while ((local = field) != 0)") which are usually the
475		* simplest way to ensure the required read orderings (which are
#	Line 445 \| Line 477 \| public class ForkJoinPool extends Abstra
477		* declarations of these locals at the heads of methods or blocks.
478		* There are several occurrences of the unusual "do {} while
479		* (!cas...)" which is the simplest way to force an update of a
480	<	* CAS'ed variable. There are also other coding oddities that help
480	>	* CAS'ed variable. There are also other coding oddities (including
481	>	* several unnecessary-looking hoisted null checks) that help
482		* some methods perform reasonably even when interpreted (not
483		* compiled).
484		*
#	Line 494 \| Line 527 \| public class ForkJoinPool extends Abstra
527		* Default ForkJoinWorkerThreadFactory implementation; creates a
528		* new ForkJoinWorkerThread.
529		*/
530	<	static class DefaultForkJoinWorkerThreadFactory
530	>	static final class DefaultForkJoinWorkerThreadFactory
531		implements ForkJoinWorkerThreadFactory {
532	<	public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
532	>	public final ForkJoinWorkerThread newThread(ForkJoinPool pool) {
533		return new ForkJoinWorkerThread(pool);
534		}
535		}
536
537		/**
538	+	* Per-thread records for threads that submit to pools. Currently
539	+	* holds only pseudo-random seed / index that is used to choose
540	+	* submission queues in method externalPush. In the future, this may
541	+	* also incorporate a means to implement different task rejection
542	+	* and resubmission policies.
543	+	*
544	+	* Seeds for submitters and workers/workQueues work in basically
545	+	* the same way but are initialized and updated using slightly
546	+	* different mechanics. Both are initialized using the same
547	+	* approach as in class ThreadLocal, where successive values are
548	+	* unlikely to collide with previous values. Seeds are then
549	+	* randomly modified upon collisions using xorshifts, which
550	+	* requires a non-zero seed.
551	+	*/
552	+	static final class Submitter {
553	+	int seed;
554	+	Submitter(int s) { seed = s; }
555	+	}
556	+
557	+	/**
558		* Class for artificial tasks that are used to replace the target
559		* of local joins if they are removed from an interior queue slot
560		* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
561		* actually do anything beyond having a unique identity.
562		*/
563		static final class EmptyTask extends ForkJoinTask<Void> {
564	+	private static final long serialVersionUID = -7721805057305804111L;
565		EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
566		public final Void getRawResult() { return null; }
567		public final void setRawResult(Void x) {}
#	Line 528 \| Line 582 \| public class ForkJoinPool extends Abstra
582		*
583		* Field "top" is the index (mod array.length) of the next queue
584		* slot to push to or pop from. It is written only by owner thread
585	<	* for push, or under lock for trySharedPush, and accessed by
586	<	* other threads only after reading (volatile) base. Both top and
587	<	* base are allowed to wrap around on overflow, but (top - base)
588	<	* (or more commonly -(base - top) to force volatile read of base
589	<	* before top) still estimates size.
585	>	* for push, or under lock for external/shared push, and accessed
586	>	* by other threads only after reading (volatile) base. Both top
587	>	* and base are allowed to wrap around on overflow, but (top -
588	>	* base) (or more commonly -(base - top) to force volatile read of
589	>	* base before top) still estimates size. The lock ("qlock") is
590	>	* forced to -1 on termination, causing all further lock attempts
591	>	* to fail. (Note: we don't need CAS for termination state because
592	>	* upon pool shutdown, all shared-queues will stop being used
593	>	* anyway.) Nearly all lock bodies are set up so that exceptions
594	>	* within lock bodies are "impossible" (modulo JVM errors that
595	>	* would cause failure anyway.)
596		*
597		* The array slots are read and written using the emulation of
598		* volatiles/atomics provided by Unsafe. Insertions must in
599		* general use putOrderedObject as a form of releasing store to
600		* ensure that all writes to the task object are ordered before
601	<	* its publication in the queue. (Although we can avoid one case
602	<	* of this when locked in trySharedPush.) All removals entail a
603	<	* CAS to null. The array is always a power of two. To ensure
604	<	* safety of Unsafe array operations, all accesses perform
545	<	* explicit null checks and implicit bounds checks via
546	<	* power-of-two masking.
601	>	* its publication in the queue. All removals entail a CAS to
602	>	* null. The array is always a power of two. To ensure safety of
603	>	* Unsafe array operations, all accesses perform explicit null
604	>	* checks and implicit bounds checks via power-of-two masking.
605		*
606		* In addition to basic queuing support, this class contains
607		* fields described elsewhere to control execution. It turns out
608	<	* to work better memory-layout-wise to include them in this
609	<	* class rather than a separate class.
608	>	* to work better memory-layout-wise to include them in this class
609	>	* rather than a separate class.
610		*
611		* Performance on most platforms is very sensitive to placement of
612		* instances of both WorkQueues and their arrays -- we absolutely
#	Line 562 \| Line 620 \| public class ForkJoinPool extends Abstra
620		* trades off slightly slower average field access for the sake of
621		* avoiding really bad worst-case access. (Until better JVM
622		* support is in place, this padding is dependent on transient
623	<	* properties of JVM field layout rules.) We also take care in
623	>	* properties of JVM field layout rules.) We also take care in
624		* allocating, sizing and resizing the array. Non-shared queue
625	<	* arrays are initialized (via method growArray) by workers before
626	<	* use. Others are allocated on first use.
625	>	* arrays are initialized by workers before use. Others are
626	>	* allocated on first use.
627		*/
628		static final class WorkQueue {
629		/**
#	Line 588 \| Line 646 \| public class ForkJoinPool extends Abstra
646		*/
647		static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
648
649	<	volatile long totalSteals; // cumulative number of steals
649	>	// Heuristic padding to ameliorate unfortunate memory placements
650	>	volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
651	>
652		int seed; // for random scanning; initialize nonzero
653		volatile int eventCount; // encoded inactivation count; < 0 if inactive
654		int nextWait; // encoded record of next event waiter
655	<	int rescans; // remaining scans until block
596	<	int nsteals; // top-level task executions since last idle
597	<	final int mode; // lifo, fifo, or shared
655	>	int hint; // steal or signal hint (index)
656		int poolIndex; // index of this queue in pool (or 0)
657	<	int stealHint; // index of most recent known stealer
658	<	volatile int runState; // 1: locked, -1: terminate; else 0
657	>	final int mode; // 0: lifo, > 0: fifo, < 0: shared
658	>	int nsteals; // number of steals
659	>	volatile int qlock; // 1: locked, -1: terminate; else 0
660		volatile int base; // index of next slot for poll
661		int top; // index of next slot for push
662		ForkJoinTask<?>[] array; // the elements (initially unallocated)
#	Line 606 \| Line 665 \| public class ForkJoinPool extends Abstra
665		volatile Thread parker; // == owner during call to park; else null
666		volatile ForkJoinTask<?> currentJoin; // task being joined in awaitJoin
667		ForkJoinTask<?> currentSteal; // current non-local task being executed
609	–	// Heuristic padding to ameliorate unfortunate memory placements
610	–	Object p00, p01, p02, p03, p04, p05, p06, p07;
611	–	Object p08, p09, p0a, p0b, p0c, p0d, p0e;
668
669	<	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode) {
670	<	this.mode = mode;
669	>	volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
670	>	volatile Object pad18, pad19, pad1a, pad1b, pad1c, pad1d;
671	>
672	>	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode,
673	>	int seed) {
674		this.pool = pool;
675		this.owner = owner;
676	+	this.mode = mode;
677	+	this.seed = seed;
678		// Place indices in the center of array (that is not yet allocated)
679		base = top = INITIAL_QUEUE_CAPACITY >>> 1;
680		}
#	Line 626 \| Line 687 \| public class ForkJoinPool extends Abstra
687		return (n >= 0) ? 0 : -n; // ignore transient negative
688		}
689
690	<	/**
690	>	/**
691		* Provides a more accurate estimate of whether this queue has
692		* any tasks than does queueSize, by checking whether a
693		* near-empty queue has at least one unclaimed task.
#	Line 638 \| Line 699 \| public class ForkJoinPool extends Abstra
699		(n == -1 &&
700		((a = array) == null \|\|
701		(m = a.length - 1) < 0 \|\|
702	<	U.getObjectVolatile
703	<	(a, ((m & (s - 1)) << ASHIFT) + ABASE) == null)));
702	>	U.getObject
703	>	(a, (long)((m & (s - 1)) << ASHIFT) + ABASE) == null)));
704		}
705
706		/**
707	<	* Pushes a task. Call only by owner in unshared queues.
707	>	* Pushes a task. Call only by owner in unshared queues. (The
708	>	* shared-queue version is embedded in method externalPush.)
709		*
710		* @param task the task. Caller must ensure non-null.
711		* @throw RejectedExecutionException if array cannot be resized
#	Line 652 \| Line 714 \| public class ForkJoinPool extends Abstra
714		ForkJoinTask<?>[] a; ForkJoinPool p;
715		int s = top, m, n;
716		if ((a = array) != null) { // ignore if queue removed
717	<	U.putOrderedObject
718	<	(a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task);
717	>	int j = (((m = a.length - 1) & s) << ASHIFT) + ABASE;
718	>	U.putOrderedObject(a, j, task);
719		if ((n = (top = s + 1) - base) <= 2) {
720		if ((p = pool) != null)
721	<	p.signalWork();
721	>	p.signalWork(this);
722		}
723		else if (n >= m)
724	<	growArray(true);
724	>	growArray();
725		}
726		}
727
728	<	/**
729	<	* Pushes a task if lock is free and array is either big
730	<	* enough or can be resized to be big enough.
731	<	*
670	<	* @param task the task. Caller must ensure non-null.
671	<	* @return true if submitted
728	>	/**
729	>	* Initializes or doubles the capacity of array. Call either
730	>	* by owner or with lock held -- it is OK for base, but not
731	>	* top, to move while resizings are in progress.
732		*/
733	<	final boolean trySharedPush(ForkJoinTask<?> task) {
734	<	boolean submitted = false;
735	<	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
736	<	ForkJoinTask<?>[] a = array;
737	<	int s = top;
738	<	try {
739	<	if ((a != null && a.length > s + 1 - base) \|\|
740	<	(a = growArray(false)) != null) { // must presize
741	<	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
742	<	U.putObject(a, (long)j, task); // don't need "ordered"
743	<	top = s + 1;
744	<	submitted = true;
745	<	}
746	<	} finally {
747	<	runState = 0; // unlock
748	<	}
733	>	final ForkJoinTask<?>[] growArray() {
734	>	ForkJoinTask<?>[] oldA = array;
735	>	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
736	>	if (size > MAXIMUM_QUEUE_CAPACITY)
737	>	throw new RejectedExecutionException("Queue capacity exceeded");
738	>	int oldMask, t, b;
739	>	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
740	>	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
741	>	(t = top) - (b = base) > 0) {
742	>	int mask = size - 1;
743	>	do {
744	>	ForkJoinTask<?> x;
745	>	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
746	>	int j = ((b & mask) << ASHIFT) + ABASE;
747	>	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
748	>	if (x != null &&
749	>	U.compareAndSwapObject(oldA, oldj, x, null))
750	>	U.putObjectVolatile(a, j, x);
751	>	} while (++b != t);
752		}
753	<	return submitted;
753	>	return a;
754		}
755
756		/**
757		* Takes next task, if one exists, in LIFO order. Call only
758	<	* by owner in unshared queues. (We do not have a shared
696	<	* version of this method because it is never needed.)
758	>	* by owner in unshared queues.
759		*/
760		final ForkJoinTask<?> pop() {
761		ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
#	Line 748 \| Line 810 \| public class ForkJoinPool extends Abstra
810		else if (base == b) {
811		if (b + 1 == top)
812		break;
813	<	Thread.yield(); // wait for lagging update
813	>	Thread.yield(); // wait for lagging update (very rare)
814		}
815		}
816		return null;
#	Line 775 \| Line 837 \| public class ForkJoinPool extends Abstra
837
838		/**
839		* Pops the given task only if it is at the current top.
840	+	* (A shared version is available only via FJP.tryExternalUnpush)
841		*/
842		final boolean tryUnpush(ForkJoinTask<?> t) {
843		ForkJoinTask<?>[] a; int s;
#	Line 788 \| Line 851 \| public class ForkJoinPool extends Abstra
851		}
852
853		/**
791	–	* Version of tryUnpush for shared queues; called by non-FJ
792	–	* submitters after prechecking that task probably exists.
793	–	*/
794	–	final boolean trySharedUnpush(ForkJoinTask<?> t) {
795	–	boolean success = false;
796	–	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
797	–	try {
798	–	ForkJoinTask<?>[] a; int s;
799	–	if ((a = array) != null && (s = top) != base &&
800	–	U.compareAndSwapObject
801	–	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
802	–	top = s;
803	–	success = true;
804	–	}
805	–	} finally {
806	–	runState = 0; // unlock
807	–	}
808	–	}
809	–	return success;
810	–	}
811	–
812	–	/**
813	–	* Polls the given task only if it is at the current base.
814	–	*/
815	–	final boolean pollFor(ForkJoinTask<?> task) {
816	–	ForkJoinTask<?>[] a; int b;
817	–	if ((b = base) - top < 0 && (a = array) != null) {
818	–	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
819	–	if (U.getObjectVolatile(a, j) == task && base == b &&
820	–	U.compareAndSwapObject(a, j, task, null)) {
821	–	base = b + 1;
822	–	return true;
823	–	}
824	–	}
825	–	return false;
826	–	}
827	–
828	–	/**
829	–	* Initializes or doubles the capacity of array. Call either
830	–	* by owner or with lock held -- it is OK for base, but not
831	–	* top, to move while resizings are in progress.
832	–	*
833	–	* @param rejectOnFailure if true, throw exception if capacity
834	–	* exceeded (relayed ultimately to user); else return null.
835	–	*/
836	–	final ForkJoinTask<?>[] growArray(boolean rejectOnFailure) {
837	–	ForkJoinTask<?>[] oldA = array;
838	–	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
839	–	if (size <= MAXIMUM_QUEUE_CAPACITY) {
840	–	int oldMask, t, b;
841	–	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
842	–	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
843	–	(t = top) - (b = base) > 0) {
844	–	int mask = size - 1;
845	–	do {
846	–	ForkJoinTask<?> x;
847	–	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
848	–	int j = ((b & mask) << ASHIFT) + ABASE;
849	–	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
850	–	if (x != null &&
851	–	U.compareAndSwapObject(oldA, oldj, x, null))
852	–	U.putObjectVolatile(a, j, x);
853	–	} while (++b != t);
854	–	}
855	–	return a;
856	–	}
857	–	else if (!rejectOnFailure)
858	–	return null;
859	–	else
860	–	throw new RejectedExecutionException("Queue capacity exceeded");
861	–	}
862	–
863	–	/**
854		* Removes and cancels all known tasks, ignoring any exceptions.
855		*/
856		final void cancelAll() {
#	Line 884 \| Line 874 \| public class ForkJoinPool extends Abstra
874		return seed = r ^= r << 5;
875		}
876
877	<	// Execution methods
877	>	// Specialized execution methods
878
879		/**
880		* Pops and runs tasks until empty.
#	Line 913 \| Line 903 \| public class ForkJoinPool extends Abstra
903		}
904
905		/**
906	<	* If present, removes from queue and executes the given task, or
907	<	* any other cancelled task. Returns (true) immediately on any CAS
906	>	* If present, removes from queue and executes the given task,
907	>	* or any other cancelled task. Returns (true) on any CAS
908		* or consistency check failure so caller can retry.
909		*
910	<	* @return 0 if no progress can be made, else positive
921	<	* (this unusual convention simplifies use with tryHelpStealer.)
910	>	* @return false if no progress can be made, else true;
911		*/
912	<	final int tryRemoveAndExec(ForkJoinTask<?> task) {
913	<	int stat = 1;
925	<	boolean removed = false, empty = true;
912	>	final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
913	>	boolean stat = true, removed = false, empty = true;
914		ForkJoinTask<?>[] a; int m, s, b, n;
915		if ((a = array) != null && (m = a.length - 1) >= 0 &&
916		(n = (s = top) - (b = base)) > 0) {
#	Line 952 \| Line 940 \| public class ForkJoinPool extends Abstra
940		}
941		if (--n == 0) {
942		if (!empty && base == b)
943	<	stat = 0;
943	>	stat = false;
944		break;
945		}
946		}
#	Line 963 \| Line 951 \| public class ForkJoinPool extends Abstra
951		}
952
953		/**
954	+	* Polls for and executes the given task or any other task in
955	+	* its CountedCompleter computation
956	+	*/
957	+	final boolean pollAndExecCC(ForkJoinTask<?> root) {
958	+	ForkJoinTask<?>[] a; int b; Object o;
959	+	outer: while ((b = base) - top < 0 && (a = array) != null) {
960	+	long j = (((a.length - 1) & b) << ASHIFT) + ABASE;
961	+	if ((o = U.getObject(a, j)) == null \|\|
962	+	!(o instanceof CountedCompleter))
963	+	break;
964	+	for (CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;;) {
965	+	if (r == root) {
966	+	if (base == b &&
967	+	U.compareAndSwapObject(a, j, t, null)) {
968	+	base = b + 1;
969	+	t.doExec();
970	+	return true;
971	+	}
972	+	else
973	+	break; // restart
974	+	}
975	+	if ((r = r.completer) == null)
976	+	break outer; // not part of root computation
977	+	}
978	+	}
979	+	return false;
980	+	}
981	+
982	+	/**
983		* Executes a top-level task and any local tasks remaining
984		* after execution.
985		*/
986		final void runTask(ForkJoinTask<?> t) {
987		if (t != null) {
988	<	currentSteal = t;
989	<	t.doExec();
990	<	if (top != base) { // process remaining local tasks
988	>	(currentSteal = t).doExec();
989	>	currentSteal = null;
990	>	if (base - top < 0) { // process remaining local tasks
991		if (mode == 0)
992		popAndExecAll();
993		else
994		pollAndExecAll();
995		}
996		++nsteals;
997	<	currentSteal = null;
997	>	hint = -1;
998		}
999		}
1000
#	Line 987 \| Line 1004 \| public class ForkJoinPool extends Abstra
1004		final void runSubtask(ForkJoinTask<?> t) {
1005		if (t != null) {
1006		ForkJoinTask<?> ps = currentSteal;
1007	<	currentSteal = t;
991	<	t.doExec();
1007	>	(currentSteal = t).doExec();
1008		currentSteal = ps;
1009		}
1010		}
#	Line 1023 \| Line 1039 \| public class ForkJoinPool extends Abstra
1039
1040		// Unsafe mechanics
1041		private static final sun.misc.Unsafe U;
1042	<	private static final long RUNSTATE;
1042	>	private static final long QLOCK;
1043		private static final int ABASE;
1044		private static final int ASHIFT;
1045		static {
#	Line 1032 \| Line 1048 \| public class ForkJoinPool extends Abstra
1048		U = getUnsafe();
1049		Class<?> k = WorkQueue.class;
1050		Class<?> ak = ForkJoinTask[].class;
1051	<	RUNSTATE = U.objectFieldOffset
1052	<	(k.getDeclaredField("runState"));
1051	>	QLOCK = U.objectFieldOffset
1052	>	(k.getDeclaredField("qlock"));
1053		ABASE = U.arrayBaseOffset(ak);
1054		s = U.arrayIndexScale(ak);
1055		} catch (Exception e) {
#	Line 1045 \| Line 1061 \| public class ForkJoinPool extends Abstra
1061		}
1062		}
1063
1048	–	/**
1049	–	* Per-thread records for threads that submit to pools. Currently
1050	–	* holds only pseudo-random seed / index that is used to choose
1051	–	* submission queues in method doSubmit. In the future, this may
1052	–	* also incorporate a means to implement different task rejection
1053	–	* and resubmission policies.
1054	–	*
1055	–	* Seeds for submitters and workers/workQueues work in basically
1056	–	* the same way but are initialized and updated using slightly
1057	–	* different mechanics. Both are initialized using the same
1058	–	* approach as in class ThreadLocal, where successive values are
1059	–	* unlikely to collide with previous values. This is done during
1060	–	* registration for workers, but requires a separate AtomicInteger
1061	–	* for submitters. Seeds are then randomly modified upon
1062	–	* collisions using xorshifts, which requires a non-zero seed.
1063	–	*/
1064	–	static final class Submitter {
1065	–	int seed;
1066	–	Submitter() {
1067	–	int s = nextSubmitterSeed.getAndAdd(SEED_INCREMENT);
1068	–	seed = (s == 0) ? 1 : s; // ensure non-zero
1069	–	}
1070	–	}
1071	–
1072	–	/** ThreadLocal class for Submitters */
1073	–	static final class ThreadSubmitter extends ThreadLocal<Submitter> {
1074	–	public Submitter initialValue() { return new Submitter(); }
1075	–	}
1076	–
1064		// static fields (initialized in static initializer below)
1065
1066		/**
#	Line 1083 \| Line 1070 \| public class ForkJoinPool extends Abstra
1070		public static final ForkJoinWorkerThreadFactory
1071		defaultForkJoinWorkerThreadFactory;
1072
1073	+	/**
1074	+	* Per-thread submission bookkeeping. Shared across all pools
1075	+	* to reduce ThreadLocal pollution and because random motion
1076	+	* to avoid contention in one pool is likely to hold for others.
1077	+	* Lazily initialized on first submission (but null-checked
1078	+	* in other contexts to avoid unnecessary initialization).
1079	+	*/
1080	+	static final ThreadLocal<Submitter> submitters;
1081
1082	<	/** Property prefix for constructing common pool */
1083	<	private static final String propPrefix =
1084	<	"java.util.concurrent.ForkJoinPool.common.";
1082	>	/**
1083	>	* Permission required for callers of methods that may start or
1084	>	* kill threads.
1085	>	*/
1086	>	private static final RuntimePermission modifyThreadPermission;
1087
1088		/**
1089		* Common (static) pool. Non-null for public use unless a static
1090	<	* construction exception, but internal usages must null-check on
1091	<	* use.
1090	>	* construction exception, but internal usages null-check on use
1091	>	* to paranoically avoid potential initialization circularities
1092	>	* as well as to simplify generated code.
1093		*/
1094		static final ForkJoinPool commonPool;
1095
#	Line 1101 \| Line 1099 \| public class ForkJoinPool extends Abstra
1099		static final int commonPoolParallelism;
1100
1101		/**
1102	<	* Generator for assigning sequence numbers as pool names.
1102	>	* Sequence number for creating workerNamePrefix.
1103		*/
1104	<	private static final AtomicInteger poolNumberGenerator;
1104	>	private static int poolNumberSequence;
1105
1106		/**
1107	<	* Generator for initial hashes/seeds for submitters. Accessed by
1108	<	* Submitter class constructor.
1107	>	* Return the next sequence number. We don't expect this to
1108	>	* ever contend so use simple builtin sync.
1109		*/
1110	<	static final AtomicInteger nextSubmitterSeed;
1110	>	private static final synchronized int nextPoolId() {
1111	>	return ++poolNumberSequence;
1112	>	}
1113
1114	<	/**
1115	<	* Permission required for callers of methods that may start or
1116	<	* kill threads.
1117	<	*/
1118	<	private static final RuntimePermission modifyThreadPermission;
1114	>	// static constants
1115
1116		/**
1117	<	* Per-thread submission bookkeeping. Shared across all pools
1118	<	* to reduce ThreadLocal pollution and because random motion
1119	<	* to avoid contention in one pool is likely to hold for others.
1117	>	* Initial timeout value (in nanoseconds) for the thread
1118	>	* triggering quiescence to park waiting for new work. On timeout,
1119	>	* the thread will instead try to shrink the number of
1120	>	* workers. The value should be large enough to avoid overly
1121	>	* aggressive shrinkage during most transient stalls (long GCs
1122	>	* etc).
1123		*/
1124	<	private static final ThreadSubmitter submitters;
1126	<
1127	<	// static constants
1124	>	private static final long IDLE_TIMEOUT = 2000L * 1000L * 1000L; // 2sec
1125
1126		/**
1127	<	* Initial timeout value (in nanoseconds) for the thread triggering
1131	<	* quiescence to park waiting for new work. On timeout, the thread
1132	<	* will instead try to shrink the number of workers.
1127	>	* Timeout value when there are more threads than parallelism level
1128		*/
1129	<	private static final long IDLE_TIMEOUT = 1000L * 1000L * 1000L; // 1sec
1129	>	private static final long FAST_IDLE_TIMEOUT = 200L * 1000L * 1000L;
1130
1131		/**
1132	<	* Timeout value when there are more threads than parallelism level
1132	>	* Tolerance for idle timeouts, to cope with timer undershoots
1133		*/
1134	<	private static final long FAST_IDLE_TIMEOUT = 100L * 1000L * 1000L;
1134	>	private static final long TIMEOUT_SLOP = 2000000L; // 20ms
1135
1136		/**
1137		* The maximum stolen->joining link depth allowed in method
1138	<	* tryHelpStealer. Must be a power of two. This value also
1144	<	* controls the maximum number of times to try to help join a task
1145	<	* without any apparent progress or change in pool state before
1146	<	* giving up and blocking (see awaitJoin). Depths for legitimate
1138	>	* tryHelpStealer. Must be a power of two. Depths for legitimate
1139		* chains are unbounded, but we use a fixed constant to avoid
1140		* (otherwise unchecked) cycles and to bound staleness of
1141		* traversal parameters at the expense of sometimes blocking when
#	Line 1152 \| Line 1144 \| public class ForkJoinPool extends Abstra
1144		private static final int MAX_HELP = 64;
1145
1146		/**
1155	–	* Secondary time-based bound (in nanosecs) for helping attempts
1156	–	* before trying compensated blocking in awaitJoin. Used in
1157	–	* conjunction with MAX_HELP to reduce variance due to different
1158	–	* polling rates associated with different helping options. The
1159	–	* value should roughly approximate the time required to create
1160	–	* and/or activate a worker thread.
1161	–	*/
1162	–	private static final long COMPENSATION_DELAY = 1L << 18; // ~0.25 millisec
1163	–
1164	–	/**
1147		* Increment for seed generators. See class ThreadLocal for
1148		* explanation.
1149		*/
#	Line 1195 \| Line 1177 \| public class ForkJoinPool extends Abstra
1177		* scan for them to avoid queuing races. Note however that
1178		* eventCount updates lag releases so usage requires care.
1179		*
1180	<	* Field runState is an int packed with:
1180	>	* Field plock is an int packed with:
1181		* SHUTDOWN: true if shutdown is enabled (1 bit)
1182	<	* SEQ: a sequence number updated upon (de)registering workers (30 bits)
1183	<	* INIT: set true after workQueues array construction (1 bit)
1182	>	* SEQ: a sequence lock, with PL_LOCK bit set if locked (30 bits)
1183	>	* SIGNAL: set when threads may be waiting on the lock (1 bit)
1184		*
1185		* The sequence number enables simple consistency checks:
1186		* Staleness of read-only operations on the workQueues array can
1187	<	* be checked by comparing runState before vs after the reads.
1187	>	* be checked by comparing plock before vs after the reads.
1188		*/
1189
1190		// bit positions/shifts for fields
#	Line 1214 \| Line 1196 \| public class ForkJoinPool extends Abstra
1196		// bounds
1197		private static final int SMASK = 0xffff; // short bits
1198		private static final int MAX_CAP = 0x7fff; // max #workers - 1
1199	<	private static final int SQMASK = 0xfffe; // even short bits
1199	>	private static final int EVENMASK = 0xfffe; // even short bits
1200	>	private static final int SQMASK = 0x007e; // max 64 (even) slots
1201		private static final int SHORT_SIGN = 1 << 15;
1202		private static final int INT_SIGN = 1 << 31;
1203
#	Line 1239 \| Line 1222 \| public class ForkJoinPool extends Abstra
1222		private static final int E_MASK = 0x7fffffff; // no STOP_BIT
1223		private static final int E_SEQ = 1 << EC_SHIFT;
1224
1225	<	// runState bits
1225	>	// plock bits
1226		private static final int SHUTDOWN = 1 << 31;
1227	+	private static final int PL_LOCK = 2;
1228	+	private static final int PL_SIGNAL = 1;
1229	+	private static final int PL_SPINS = 1 << 8;
1230
1231		// access mode for WorkQueue
1232		static final int LIFO_QUEUE = 0;
1233		static final int FIFO_QUEUE = 1;
1234		static final int SHARED_QUEUE = -1;
1235
1236	+	// bounds for #steps in scan loop -- must be power 2 minus 1
1237	+	private static final int MIN_SCAN = 0x1ff; // cover estimation slop
1238	+	private static final int MAX_SCAN = 0x1ffff; // 4 * max workers
1239	+
1240		// Instance fields
1241
1242		/*
1243	<	* Field layout order in this class tends to matter more than one
1244	<	* would like. Runtime layout order is only loosely related to
1243	>	* Field layout of this class tends to matter more than one would
1244	>	* like. Runtime layout order is only loosely related to
1245		* declaration order and may differ across JVMs, but the following
1246		* empirically works OK on current JVMs.
1247		*/
1248
1249	+	// Heuristic padding to ameliorate unfortunate memory placements
1250	+	volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
1251	+
1252		volatile long stealCount; // collects worker counts
1253		volatile long ctl; // main pool control
1254	<	final int parallelism; // parallelism level
1255	<	final int localMode; // per-worker scheduling mode
1256	<	volatile int nextWorkerNumber; // to create worker name string
1264	<	final int submitMask; // submit queue index bound
1265	<	int nextSeed; // for initializing worker seeds
1266	<	volatile int mainLock; // spinlock for array updates
1267	<	volatile int runState; // shutdown status and seq
1254	>	volatile int plock; // shutdown status and seqLock
1255	>	volatile int indexSeed; // worker/submitter index seed
1256	>	final int config; // mode and parallelism level
1257		WorkQueue[] workQueues; // main registry
1258	<	final ForkJoinWorkerThreadFactory factory; // factory for new workers
1258	>	final ForkJoinWorkerThreadFactory factory;
1259		final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1260		final String workerNamePrefix; // to create worker name string
1261
1262	<	/*
1263	<	* Mechanics for main lock protecting worker array updates. Uses
1275	<	* the same strategy as ConcurrentHashMap bins -- a spinLock for
1276	<	* normal cases, but falling back to builtin lock when (rarely)
1277	<	* needed. See internal ConcurrentHashMap documentation for
1278	<	* explanation.
1279	<	*/
1280	<
1281	<	static final int LOCK_WAITING = 2; // bit to indicate need for signal
1282	<	static final int MAX_LOCK_SPINS = 1 << 8;
1262	>	volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
1263	>	volatile Object pad18, pad19, pad1a, pad1b;
1264
1265	<	private void tryAwaitMainLock() {
1266	<	int spins = MAX_LOCK_SPINS, r = 0, h;
1267	<	while (((h = mainLock) & 1) != 0) {
1268	<	if (r == 0)
1269	<	r = ThreadLocalRandom.current().nextInt(); // randomize spins
1265	>	/*
1266	>	* Acquires the plock lock to protect worker array and related
1267	>	* updates. This method is called only if an initial CAS on plock
1268	>	* fails. This acts as a spinLock for normal cases, but falls back
1269	>	* to builtin monitor to block when (rarely) needed. This would be
1270	>	* a terrible idea for a highly contended lock, but works fine as
1271	>	* a more conservative alternative to a pure spinlock. See
1272	>	* internal ConcurrentHashMap documentation for further
1273	>	* explanation of nearly the same construction.
1274	>	*/
1275	>	private int acquirePlock() {
1276	>	int spins = PL_SPINS, r = 0, ps, nps;
1277	>	for (;;) {
1278	>	if (((ps = plock) & PL_LOCK) == 0 &&
1279	>	U.compareAndSwapInt(this, PLOCK, ps, nps = ps + PL_LOCK))
1280	>	return nps;
1281	>	else if (r == 0) { // randomize spins if possible
1282	>	Thread t = Thread.currentThread(); WorkQueue w; Submitter z;
1283	>	if ((t instanceof ForkJoinWorkerThread) &&
1284	>	(w = ((ForkJoinWorkerThread)t).workQueue) != null)
1285	>	r = w.seed;
1286	>	else if ((z = submitters.get()) != null)
1287	>	r = z.seed;
1288	>	else
1289	>	r = 1;
1290	>	}
1291		else if (spins >= 0) {
1292		r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1293		if (r >= 0)
1294		--spins;
1295		}
1296	<	else if (U.compareAndSwapInt(this, MAINLOCK, h, h \| LOCK_WAITING)) {
1296	>	else if (U.compareAndSwapInt(this, PLOCK, ps, ps \| PL_SIGNAL)) {
1297		synchronized (this) {
1298	<	if ((mainLock & LOCK_WAITING) != 0) {
1298	>	if ((plock & PL_SIGNAL) != 0) {
1299		try {
1300		wait();
1301		} catch (InterruptedException ie) {
1302	<	Thread.currentThread().interrupt();
1302	>	try {
1303	>	Thread.currentThread().interrupt();
1304	>	} catch (SecurityException ignore) {
1305	>	}
1306		}
1307		}
1308		else
1309	<	notifyAll(); // possibly won race vs signaller
1309	>	notifyAll();
1310		}
1306	–	break;
1311		}
1312		}
1313		}
1314
1311	–	// Creating, registering, and deregistering workers
1312	–
1315		/**
1316	<	* Tries to create and start a worker
1316	>	* Unlocks and signals any thread waiting for plock. Called only
1317	>	* when CAS of seq value for unlock fails.
1318		*/
1319	<	private void addWorker() {
1320	<	Throwable ex = null;
1321	<	ForkJoinWorkerThread wt = null;
1319	<	try {
1320	<	if ((wt = factory.newThread(this)) != null) {
1321	<	wt.start();
1322	<	return;
1323	<	}
1324	<	} catch (Throwable e) {
1325	<	ex = e;
1326	<	}
1327	<	deregisterWorker(wt, ex); // adjust counts etc on failure
1319	>	private void releasePlock(int ps) {
1320	>	plock = ps;
1321	>	synchronized (this) { notifyAll(); }
1322		}
1323
1324		/**
1325	<	* Callback from ForkJoinWorkerThread constructor to assign a
1326	<	* public name. This must be separate from registerWorker because
1327	<	* it is called during the "super" constructor call in
1328	<	* ForkJoinWorkerThread.
1325	>	* Performs secondary initialization, called when plock is zero.
1326	>	* Creates workQueue array and sets plock to a valid value. The
1327	>	* lock body must be exception-free (so no try/finally) so we
1328	>	* optimistically allocate new array outside the lock and throw
1329	>	* away if (very rarely) not needed. (A similar tactic is used in
1330	>	* fullExternalPush.) Because the plock seq value can eventually
1331	>	* wrap around zero, this method harmlessly fails to reinitialize
1332	>	* if workQueues exists, while still advancing plock.
1333	>	*
1334	>	* Additionally tries to create the first worker.
1335		*/
1336	<	final String nextWorkerName() {
1337	<	int n;
1338	<	do {} while(!U.compareAndSwapInt(this, NEXTWORKERNUMBER,
1339	<	n = nextWorkerNumber, ++n));
1340	<	return workerNamePrefix.concat(Integer.toString(n));
1336	>	private void initWorkers() {
1337	>	WorkQueue[] ws, nws; int ps;
1338	>	int p = config & SMASK; // find power of two table size
1339	>	int n = (p > 1) ? p - 1 : 1; // ensure at least 2 slots
1340	>	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4; n \|= n >>> 8; n \|= n >>> 16;
1341	>	n = (n + 1) << 1;
1342	>	if ((ws = workQueues) == null \|\| ws.length == 0)
1343	>	nws = new WorkQueue[n];
1344	>	else
1345	>	nws = null;
1346	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1347	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1348	>	ps = acquirePlock();
1349	>	if (((ws = workQueues) == null \|\| ws.length == 0) && nws != null)
1350	>	workQueues = nws;
1351	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1352	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1353	>	releasePlock(nps);
1354	>	tryAddWorker();
1355		}
1356
1357		/**
1358	<	* Callback from ForkJoinWorkerThread constructor to establish its
1359	<	* poolIndex and record its WorkQueue. To avoid scanning bias due
1346	<	* to packing entries in front of the workQueues array, we treat
1347	<	* the array as a simple power-of-two hash table using per-thread
1348	<	* seed as hash, expanding as needed.
1349	<	*
1350	<	* @param w the worker's queue
1358	>	* Tries to create and start one worker if fewer than target
1359	>	* parallelism level exist. Adjusts counts etc on failure.
1360		*/
1361	<	final void registerWorker(WorkQueue w) {
1362	<	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1363	<	tryAwaitMainLock();
1361	>	private void tryAddWorker() {
1362	>	long c; int u;
1363	>	while ((u = (int)((c = ctl) >>> 32)) < 0 &&
1364	>	(u & SHORT_SIGN) != 0 && (int)c == 0) {
1365	>	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) \|
1366	>	((u + UAC_UNIT) & UAC_MASK)) << 32;
1367	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1368	>	ForkJoinWorkerThreadFactory fac;
1369	>	Throwable ex = null;
1370	>	ForkJoinWorkerThread wt = null;
1371	>	try {
1372	>	if ((fac = factory) != null &&
1373	>	(wt = fac.newThread(this)) != null) {
1374	>	wt.start();
1375	>	break;
1376	>	}
1377	>	} catch (Throwable e) {
1378	>	ex = e;
1379	>	}
1380	>	deregisterWorker(wt, ex);
1381	>	break;
1382	>	}
1383	>	}
1384	>	}
1385	>
1386	>	// Registering and deregistering workers
1387	>
1388	>	/**
1389	>	* Callback from ForkJoinWorkerThread to establish and record its
1390	>	* WorkQueue. To avoid scanning bias due to packing entries in
1391	>	* front of the workQueues array, we treat the array as a simple
1392	>	* power-of-two hash table using per-thread seed as hash,
1393	>	* expanding as needed.
1394	>	*
1395	>	* @param wt the worker thread
1396	>	* @return the worker's queue
1397	>	*/
1398	>	final WorkQueue registerWorker(ForkJoinWorkerThread wt) {
1399	>	Thread.UncaughtExceptionHandler handler; WorkQueue[] ws; int s, ps;
1400	>	wt.setDaemon(true);
1401	>	if ((handler = ueh) != null)
1402	>	wt.setUncaughtExceptionHandler(handler);
1403	>	do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed,
1404	>	s += SEED_INCREMENT) \|\|
1405	>	s == 0); // skip 0
1406	>	WorkQueue w = new WorkQueue(this, wt, config >>> 16, s);
1407	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1408	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1409	>	ps = acquirePlock();
1410	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1411		try {
1412	<	WorkQueue[] ws;
1413	<	if ((ws = workQueues) == null)
1414	<	ws = workQueues = new WorkQueue[submitMask + 1];
1415	<	if (w != null) {
1416	<	int rs, n = ws.length, m = n - 1;
1417	<	int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence
1362	<	w.seed = (s == 0) ? 1 : s; // ensure non-zero seed
1363	<	int r = (s << 1) \| 1; // use odd-numbered indices
1364	<	if (ws[r &= m] != null) { // collision
1365	<	int probes = 0; // step by approx half size
1366	<	int step = (n <= 4) ? 2 : ((n >>> 1) & SQMASK) + 2;
1412	>	if ((ws = workQueues) != null) { // skip if shutting down
1413	>	int n = ws.length, m = n - 1;
1414	>	int r = (s << 1) \| 1; // use odd-numbered indices
1415	>	if (ws[r &= m] != null) { // collision
1416	>	int probes = 0; // step by approx half size
1417	>	int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2;
1418		while (ws[r = (r + step) & m] != null) {
1419		if (++probes >= n) {
1420		workQueues = ws = Arrays.copyOf(ws, n <<= 1);
#	Line 1372 \| Line 1423 \| public class ForkJoinPool extends Abstra
1423		}
1424		}
1425		}
1426	<	w.eventCount = w.poolIndex = r; // establish before recording
1427	<	ws[r] = w; // also update seq
1377	<	runState = ((rs = runState) & SHUTDOWN) \| ((rs + 2) & ~SHUTDOWN);
1426	>	w.eventCount = w.poolIndex = r; // volatile write orders
1427	>	ws[r] = w;
1428		}
1429		} finally {
1430	<	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1431	<	mainLock = 0;
1382	<	synchronized (this) { notifyAll(); };
1383	<	}
1430	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1431	>	releasePlock(nps);
1432		}
1433	<
1433	>	wt.setName(workerNamePrefix.concat(Integer.toString(w.poolIndex)));
1434	>	return w;
1435		}
1436
1437		/**
1438		* Final callback from terminating worker, as well as upon failure
1439	<	* to construct or start a worker in addWorker. Removes record of
1440	<	* worker from array, and adjusts counts. If pool is shutting
1441	<	* down, tries to complete termination.
1439	>	* to construct or start a worker. Removes record of worker from
1440	>	* array, and adjusts counts. If pool is shutting down, tries to
1441	>	* complete termination.
1442		*
1443	<	* @param wt the worker thread or null if addWorker failed
1443	>	* @param wt the worker thread or null if construction failed
1444		* @param ex the exception causing failure, or null if none
1445		*/
1446		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1447		WorkQueue w = null;
1448		if (wt != null && (w = wt.workQueue) != null) {
1449	<	w.runState = -1; // ensure runState is set
1450	<	long steals = w.totalSteals + w.nsteals, sc;
1451	<	do {} while(!U.compareAndSwapLong(this, STEALCOUNT,
1452	<	sc = stealCount, sc + steals));
1453	<	int idx = w.poolIndex;
1454	<	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1455	<	tryAwaitMainLock();
1449	>	int ps;
1450	>	w.qlock = -1; // ensure set
1451	>	long ns = w.nsteals, sc; // collect steal count
1452	>	do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
1453	>	sc = stealCount, sc + ns));
1454	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1455	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1456	>	ps = acquirePlock();
1457	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1458		try {
1459	+	int idx = w.poolIndex;
1460		WorkQueue[] ws = workQueues;
1461		if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1462		ws[idx] = null;
1463		} finally {
1464	<	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1465	<	mainLock = 0;
1414	<	synchronized (this) { notifyAll(); };
1415	<	}
1464	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1465	>	releasePlock(nps);
1466		}
1467		}
1468
#	Line 1422 \| Line 1472 \| public class ForkJoinPool extends Abstra
1472		((c - TC_UNIT) & TC_MASK) \|
1473		(c & ~(AC_MASK\|TC_MASK)))));
1474
1475	<	if (!tryTerminate(false, false) && w != null) {
1475	>	if (!tryTerminate(false, false) && w != null && w.array != null) {
1476		w.cancelAll(); // cancel remaining tasks
1477	<	if (w.array != null) // suppress signal if never ran
1478	<	signalWork(); // wake up or create replacement
1479	<	if (ex == null) // help clean refs on way out
1480	<	ForkJoinTask.helpExpungeStaleExceptions();
1477	>	int e, u, i, n; WorkQueue[] ws; WorkQueue v; Thread p;
1478	>	while ((u = (int)((c = ctl) >>> 32)) < 0) {
1479	>	if ((e = (int)c) > 0) { // activate or create replacement
1480	>	if ((ws = workQueues) != null &&
1481	>	ws.length > (i = e & SMASK) &&
1482	>	(v = ws[i]) != null && v.eventCount == (e \| INT_SIGN)) {
1483	>	long nc = (((long)(v.nextWait & E_MASK)) \|
1484	>	((long)(u + UAC_UNIT) << 32));
1485	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1486	>	v.eventCount = (e + E_SEQ) & E_MASK;
1487	>	if ((p = v.parker) != null)
1488	>	U.unpark(p);
1489	>	break;
1490	>	}
1491	>	}
1492	>	else
1493	>	break;
1494	>	}
1495	>	else {
1496	>	if ((short)u < 0)
1497	>	tryAddWorker();
1498	>	break;
1499	>	}
1500	>	}
1501		}
1502	<
1503	<	if (ex != null) // rethrow
1504	<	U.throwException(ex);
1502	>	if (ex == null) // help clean refs on way out
1503	>	ForkJoinTask.helpExpungeStaleExceptions();
1504	>	else // rethrow
1505	>	ForkJoinTask.rethrow(ex);
1506		}
1507
1508		// Submissions
#	Line 1439 \| Line 1510 \| public class ForkJoinPool extends Abstra
1510		/**
1511		* Unless shutting down, adds the given task to a submission queue
1512		* at submitter's current queue index (modulo submission
1513	<	* range). If no queue exists at the index, one is created. If
1514	<	* the queue is busy, another index is randomly chosen. The
1444	<	* submitMask bounds the effective number of queues to the
1445	<	* (nearest power of two for) parallelism level.
1513	>	* range). Only the most common path is directly handled in this
1514	>	* method. All others are relayed to fullExternalPush.
1515		*
1516		* @param task the task. Caller must ensure non-null.
1517		*/
1518	<	private void doSubmit(ForkJoinTask<?> task) {
1519	<	Submitter s = submitters.get();
1520	<	for (int r = s.seed, m = submitMask;;) {
1521	<	WorkQueue[] ws; WorkQueue q;
1522	<	int k = r & m & SQMASK; // use only even indices
1523	<	if (runState < 0)
1524	<	throw new RejectedExecutionException(); // shutting down
1525	<	else if ((ws = workQueues) == null \|\| ws.length <= k) {
1526	<	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1527	<	tryAwaitMainLock();
1528	<	try {
1529	<	if (workQueues == null)
1530	<	workQueues = new WorkQueue[submitMask + 1];
1531	<	} finally {
1463	<	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1464	<	mainLock = 0;
1465	<	synchronized (this) { notifyAll(); };
1466	<	}
1467	<	}
1468	<	}
1469	<	else if ((q = ws[k]) == null) { // create new queue
1470	<	WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE);
1471	<	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1472	<	tryAwaitMainLock();
1473	<	try {
1474	<	int rs = runState; // to update seq
1475	<	if (ws == workQueues && ws[k] == null) {
1476	<	ws[k] = nq;
1477	<	runState = ((rs & SHUTDOWN) \| ((rs + 2) & ~SHUTDOWN));
1478	<	}
1479	<	} finally {
1480	<	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1481	<	mainLock = 0;
1482	<	synchronized (this) { notifyAll(); };
1483	<	}
1484	<	}
1485	<	}
1486	<	else if (q.trySharedPush(task)) {
1487	<	signalWork();
1518	>	final void externalPush(ForkJoinTask<?> task) {
1519	>	WorkQueue[] ws; WorkQueue q; Submitter z; int m; ForkJoinTask<?>[] a;
1520	>	if ((z = submitters.get()) != null && plock > 0 &&
1521	>	(ws = workQueues) != null && (m = (ws.length - 1)) >= 0 &&
1522	>	(q = ws[m & z.seed & SQMASK]) != null &&
1523	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock
1524	>	int b = q.base, s = q.top, n, an;
1525	>	if ((a = q.array) != null && (an = a.length) > (n = s + 1 - b)) {
1526	>	int j = (((an - 1) & s) << ASHIFT) + ABASE;
1527	>	U.putOrderedObject(a, j, task);
1528	>	q.top = s + 1; // push on to deque
1529	>	q.qlock = 0;
1530	>	if (n <= 2)
1531	>	signalWork(q);
1532		return;
1533		}
1534	<	else if (m > 1) { // move to a different index
1534	>	q.qlock = 0;
1535	>	}
1536	>	fullExternalPush(task);
1537	>	}
1538	>
1539	>	/**
1540	>	* Full version of externalPush. This method is called, among
1541	>	* other times, upon the first submission of the first task to the
1542	>	* pool, so must perform secondary initialization (via
1543	>	* initWorkers). It also detects first submission by an external
1544	>	* thread by looking up its ThreadLocal, and creates a new shared
1545	>	* queue if the one at index if empty or contended. The plock lock
1546	>	* body must be exception-free (so no try/finally) so we
1547	>	* optimistically allocate new queues outside the lock and throw
1548	>	* them away if (very rarely) not needed.
1549	>	*/
1550	>	private void fullExternalPush(ForkJoinTask<?> task) {
1551	>	int r = 0; // random index seed
1552	>	for (Submitter z = submitters.get();;) {
1553	>	WorkQueue[] ws; WorkQueue q; int ps, m, k;
1554	>	if (z == null) {
1555	>	if (U.compareAndSwapInt(this, INDEXSEED, r = indexSeed,
1556	>	r += SEED_INCREMENT) && r != 0)
1557	>	submitters.set(z = new Submitter(r));
1558	>	}
1559	>	else if (r == 0) { // move to a different index
1560	>	r = z.seed;
1561		r ^= r << 13; // same xorshift as WorkQueues
1562		r ^= r >>> 17;
1563	<	s.seed = r ^= r << 5;
1563	>	z.seed = r ^ (r << 5);
1564	>	}
1565	>	else if ((ps = plock) < 0)
1566	>	throw new RejectedExecutionException();
1567	>	else if (ps == 0 \|\| (ws = workQueues) == null \|\|
1568	>	(m = ws.length - 1) < 0)
1569	>	initWorkers();
1570	>	else if ((q = ws[k = r & m & SQMASK]) != null) {
1571	>	if (q.qlock == 0 && U.compareAndSwapInt(q, QLOCK, 0, 1)) {
1572	>	ForkJoinTask<?>[] a = q.array;
1573	>	int s = q.top;
1574	>	boolean submitted = false;
1575	>	try { // locked version of push
1576	>	if ((a != null && a.length > s + 1 - q.base) \|\|
1577	>	(a = q.growArray()) != null) { // must presize
1578	>	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
1579	>	U.putOrderedObject(a, j, task);
1580	>	q.top = s + 1;
1581	>	submitted = true;
1582	>	}
1583	>	} finally {
1584	>	q.qlock = 0; // unlock
1585	>	}
1586	>	if (submitted) {
1587	>	signalWork(q);
1588	>	return;
1589	>	}
1590	>	}
1591	>	r = 0; // move on failure
1592	>	}
1593	>	else if (((ps = plock) & PL_LOCK) == 0) { // create new queue
1594	>	q = new WorkQueue(this, null, SHARED_QUEUE, r);
1595	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
1596	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1597	>	ps = acquirePlock();
1598	>	if ((ws = workQueues) != null && k < ws.length && ws[k] == null)
1599	>	ws[k] = q;
1600	>	int nps = (ps & SHUTDOWN) \| ((ps + PL_LOCK) & ~SHUTDOWN);
1601	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1602	>	releasePlock(nps);
1603		}
1604		else
1605	<	Thread.yield(); // yield if no alternatives
1605	>	r = 0; // try elsewhere while lock held
1606		}
1607		}
1608
1500	–	/**
1501	–	* Submits the given (non-null) task to the common pool, if possible.
1502	–	*/
1503	–	static void submitToCommonPool(ForkJoinTask<?> task) {
1504	–	ForkJoinPool p;
1505	–	if ((p = commonPool) == null)
1506	–	throw new RejectedExecutionException("Common Pool Unavailable");
1507	–	p.doSubmit(task);
1508	–	}
1509	–
1510	–	/**
1511	–	* Returns true if the given task was submitted to common pool
1512	–	* and has not yet commenced execution, and is available for
1513	–	* removal according to execution policies; if so removing the
1514	–	* submission from the pool.
1515	–	*
1516	–	* @param task the task
1517	–	* @return true if successful
1518	–	*/
1519	–	static boolean tryUnsubmitFromCommonPool(ForkJoinTask<?> task) {
1520	–	// Peek, looking for task and eligibility before
1521	–	// using trySharedUnpush to actually take it under lock
1522	–	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
1523	–	ForkJoinTask<?>[] a; int t, s, n;
1524	–	int k = submitters.get().seed & SQMASK;
1525	–	return ((p = commonPool) != null &&
1526	–	(ws = p.workQueues) != null &&
1527	–	ws.length > (k &= p.submitMask) &&
1528	–	(q = ws[k]) != null &&
1529	–	(a = q.array) != null &&
1530	–	(n = (t = q.top) - q.base) > 0 &&
1531	–	(n > 1 \|\| (int)(p.ctl >> AC_SHIFT) < 0) &&
1532	–	(s = t - 1) >= 0 && s < a.length && a[s] == task &&
1533	–	q.trySharedUnpush(task));
1534	–	}
1535	–
1609		// Maintaining ctl counts
1610
1611		/**
#	Line 1544 \| Line 1617 \| public class ForkJoinPool extends Abstra
1617		}
1618
1619		/**
1620	<	* Tries to create one or activate one or more workers if too few are active.
1620	>	* Tries to create or activate a worker if too few are active.
1621	>	*
1622	>	* @param q the (non-null) queue holding tasks to be signalled
1623		*/
1624	<	final void signalWork() {
1625	<	long c; int u;
1626	<	while ((u = (int)((c = ctl) >>> 32)) < 0) { // too few active
1627	<	WorkQueue[] ws = workQueues; int e, i; WorkQueue w; Thread p;
1628	<	if ((e = (int)c) > 0) { // at least one waiting
1629	<	if (ws != null && (i = e & SMASK) < ws.length &&
1624	>	final void signalWork(WorkQueue q) {
1625	>	int hint = q.poolIndex;
1626	>	long c; int e, u, i, n; WorkQueue[] ws; WorkQueue w; Thread p;
1627	>	while ((u = (int)((c = ctl) >>> 32)) < 0) {
1628	>	if ((e = (int)c) > 0) {
1629	>	if ((ws = workQueues) != null && ws.length > (i = e & SMASK) &&
1630		(w = ws[i]) != null && w.eventCount == (e \| INT_SIGN)) {
1631		long nc = (((long)(w.nextWait & E_MASK)) \|
1632		((long)(u + UAC_UNIT) << 32));
1633		if (U.compareAndSwapLong(this, CTL, c, nc)) {
1634	+	w.hint = hint;
1635		w.eventCount = (e + E_SEQ) & E_MASK;
1636		if ((p = w.parker) != null)
1637	<	U.unpark(p); // activate and release
1637	>	U.unpark(p);
1638		break;
1639		}
1640	+	if (q.top - q.base <= 0)
1641	+	break;
1642		}
1643		else
1644		break;
1645		}
1646	<	else if (e == 0 && (u & SHORT_SIGN) != 0) { // too few total
1647	<	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) \|
1648	<	((u + UAC_UNIT) & UAC_MASK)) << 32;
1571	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1572	<	addWorker();
1573	<	break;
1574	<	}
1575	<	}
1576	<	else
1646	>	else {
1647	>	if ((short)u < 0)
1648	>	tryAddWorker();
1649		break;
1650	+	}
1651		}
1652		}
1653
#	Line 1584 \| Line 1657 \| public class ForkJoinPool extends Abstra
1657		* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1658		*/
1659		final void runWorker(WorkQueue w) {
1660	<	w.growArray(false); // initialize queue array in this thread
1661	<	do { w.runTask(scan(w)); } while (w.runState >= 0);
1660	>	w.growArray(); // allocate queue
1661	>	do { w.runTask(scan(w)); } while (w.qlock >= 0);
1662		}
1663
1664		/**
#	Line 1596 \| Line 1669 \| public class ForkJoinPool extends Abstra
1669		* contention, or state changes that indicate possible success on
1670		* re-invocation.
1671		*
1672	<	* The scan searches for tasks across a random permutation of
1673	<	* queues (starting at a random index and stepping by a random
1674	<	* relative prime, checking each at least once). The scan
1675	<	* terminates upon either finding a non-empty queue, or completing
1676	<	* the sweep. If the worker is not inactivated, it takes and
1677	<	* returns a task from this queue. On failure to find a task, we
1678	<	* take one of the following actions, after which the caller will
1679	<	* retry calling this method unless terminated.
1672	>	* The scan searches for tasks across queues (starting at a random
1673	>	* index, and relying on registerWorker to irregularly scatter
1674	>	* them within array to avoid bias), checking each at least twice.
1675	>	* The scan terminates upon either finding a non-empty queue, or
1676	>	* completing the sweep. If the worker is not inactivated, it
1677	>	* takes and returns a task from this queue. Otherwise, if not
1678	>	* activated, it signals workers (that may include itself) and
1679	>	* returns so caller can retry. Also returns for true if the
1680	>	* worker array may have changed during an empty scan. On failure
1681	>	* to find a task, we take one of the following actions, after
1682	>	* which the caller will retry calling this method unless
1683	>	* terminated.
1684		*
1685		* * If pool is terminating, terminate the worker.
1686		*
1610	–	* * If not a complete sweep, try to release a waiting worker. If
1611	–	* the scan terminated because the worker is inactivated, then the
1612	–	* released worker will often be the calling worker, and it can
1613	–	* succeed obtaining a task on the next call. Or maybe it is
1614	–	* another worker, but with same net effect. Releasing in other
1615	–	* cases as well ensures that we have enough workers running.
1616	–	*
1687		* * If not already enqueued, try to inactivate and enqueue the
1688		* worker on wait queue. Or, if inactivating has caused the pool
1689		* to be quiescent, relay to idleAwaitWork to check for
1690		* termination and possibly shrink pool.
1691		*
1692	<	* * If already inactive, and the caller has run a task since the
1693	<	* last empty scan, return (to allow rescan) unless others are
1694	<	* also inactivated. Field WorkQueue.rescans counts down on each
1625	<	* scan to ensure eventual inactivation and blocking.
1626	<	*
1627	<	* * If already enqueued and none of the above apply, park
1628	<	* awaiting signal,
1692	>	* * If already enqueued and none of the above apply, possibly
1693	>	* (with 1/2 probability) park awaiting signal, else lingering to
1694	>	* help scan and signal.
1695		*
1696		* @param w the worker (via its WorkQueue)
1697		* @return a task or null if none found
1698		*/
1699		private final ForkJoinTask<?> scan(WorkQueue w) {
1700	<	WorkQueue[] ws; // first update random seed
1701	<	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1702	<	int rs = runState, m; // volatile read order matters
1703	<	if ((ws = workQueues) != null && (m = ws.length - 1) > 0) {
1704	<	int ec = w.eventCount; // ec is negative if inactive
1705	<	int step = (r >>> 16) \| 1; // relative prime
1706	<	for (int j = (m + 1) << 2; ; r += step) {
1707	<	WorkQueue q; ForkJoinTask<?> t; ForkJoinTask<?>[] a; int b;
1708	<	if ((q = ws[r & m]) != null && (b = q.base) - q.top < 0 &&
1709	<	(a = q.array) != null) { // probably nonempty
1700	>	WorkQueue[] ws; int m;
1701	>	int ps = plock; // read plock before ws
1702	>	if (w != null && (ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1703	>	int ec = w.eventCount; // ec is negative if inactive
1704	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1705	>	int j = ((m + m + 1) \| MIN_SCAN) & MAX_SCAN;
1706	>	do {
1707	>	WorkQueue q; ForkJoinTask<?>[] a; int b;
1708	>	if ((q = ws[(r + j) & m]) != null && (b = q.base) - q.top < 0 &&
1709	>	(a = q.array) != null) { // probably nonempty
1710		int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1711	<	t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1711	>	ForkJoinTask<?> t = (ForkJoinTask<?>)
1712	>	U.getObjectVolatile(a, i);
1713		if (q.base == b && ec >= 0 && t != null &&
1714		U.compareAndSwapObject(a, i, t, null)) {
1715	<	if (q.top - (q.base = b + 1) > 0)
1716	<	signalWork(); // help pushes signal
1717	<	return t;
1718	<	}
1719	<	else if (ec < 0 \|\| j <= m) {
1720	<	rs = 0; // mark scan as imcomplete
1721	<	break; // caller can retry after release
1722	<	}
1723	<	}
1724	<	if (--j < 0)
1725	<	break;
1726	<	}
1727	<
1728	<	long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
1729	<	if (e < 0) // decode ctl on empty scan
1730	<	w.runState = -1; // pool is terminating
1731	<	else if (rs == 0 \|\| rs != runState) { // incomplete scan
1732	<	WorkQueue v; Thread p; // try to release a waiter
1733	<	if (e > 0 && a < 0 && w.eventCount == ec &&
1734	<	(v = ws[e & m]) != null && v.eventCount == (e \| INT_SIGN)) {
1735	<	long nc = ((long)(v.nextWait & E_MASK) \|
1736	<	((c + AC_UNIT) & (AC_MASK\|TC_MASK)));
1737	<	if (ctl == c && U.compareAndSwapLong(this, CTL, c, nc)) {
1738	<	v.eventCount = (e + E_SEQ) & E_MASK;
1739	<	if ((p = v.parker) != null)
1740	<	U.unpark(p);
1741	<	}
1742	<	}
1743	<	}
1677	<	else if (ec >= 0) { // try to enqueue/inactivate
1678	<	long nc = (long)ec \| ((c - AC_UNIT) & (AC_MASK\|TC_MASK));
1679	<	w.nextWait = e;
1680	<	w.eventCount = ec \| INT_SIGN; // mark as inactive
1681	<	if (ctl != c \|\| !U.compareAndSwapLong(this, CTL, c, nc))
1682	<	w.eventCount = ec; // unmark on CAS failure
1683	<	else {
1684	<	if ((ns = w.nsteals) != 0) {
1685	<	w.nsteals = 0; // set rescans if ran task
1686	<	w.rescans = (a > 0) ? 0 : a + parallelism;
1687	<	w.totalSteals += ns;
1688	<	}
1689	<	if (a == 1 - parallelism) // quiescent
1715	>	if ((q.base = b + 1) - q.top < 0)
1716	>	signalWork(q);
1717	>	return t; // taken
1718	>	}
1719	>	else if ((ec < 0 \|\| j < m) && (int)(ctl >> AC_SHIFT) <= 0) {
1720	>	w.hint = (r + j) & m; // help signal below
1721	>	break; // cannot take
1722	>	}
1723	>	}
1724	>	} while (--j >= 0);
1725	>
1726	>	long c, sc; int e, ns, h;
1727	>	if ((h = w.hint) < 0) {
1728	>	if ((ns = w.nsteals) != 0) {
1729	>	if (U.compareAndSwapLong(this, STEALCOUNT,
1730	>	sc = stealCount, sc + ns))
1731	>	w.nsteals = 0; // collect steals
1732	>	}
1733	>	else if (plock != ps) // consistency check
1734	>	; // skip
1735	>	else if ((e = (int)(c = ctl)) < 0)
1736	>	w.qlock = -1; // pool is terminating
1737	>	else if (ec >= 0) { // try to enqueue/inactivate
1738	>	long nc = ((long)ec \| ((c - AC_UNIT) & (AC_MASK\|TC_MASK)));
1739	>	w.nextWait = e; // link and mark inactive
1740	>	w.eventCount = ec \| INT_SIGN;
1741	>	if (ctl != c \|\| !U.compareAndSwapLong(this, CTL, c, nc))
1742	>	w.eventCount = ec; // unmark on CAS failure
1743	>	else if ((int)(c >> AC_SHIFT) == 1 - (config & SMASK))
1744		idleAwaitWork(w, nc, c);
1745		}
1746	<	}
1693	<	else if (w.eventCount < 0) { // already queued
1694	<	int ac = a + parallelism;
1695	<	if ((nr = w.rescans) > 0) // continue rescanning
1696	<	w.rescans = (ac < nr) ? ac : nr - 1;
1697	<	else if (((w.seed >>> 16) & ac) == 0) { // randomize park
1698	<	Thread.interrupted(); // clear status
1746	>	else if (w.eventCount < 0) { // block
1747		Thread wt = Thread.currentThread();
1748	+	Thread.interrupted(); // clear status
1749		U.putObject(wt, PARKBLOCKER, this);
1750	<	w.parker = wt; // emulate LockSupport.park
1751	<	if (w.eventCount < 0) // recheck
1750	>	w.parker = wt; // emulate LockSupport.park
1751	>	if (w.eventCount < 0) // recheck
1752		U.park(false, 0L);
1753		w.parker = null;
1754		U.putObject(wt, PARKBLOCKER, null);
1755		}
1756		}
1757	+	if (h >= 0 \|\| w.hint >= 0) // signal others before retry
1758	+	helpSignalHint(w);
1759		}
1760		return null;
1761		}
#	Line 1722 \| Line 1773 \| public class ForkJoinPool extends Abstra
1773		* @param prevCtl the ctl value to restore if thread is terminated
1774		*/
1775		private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1776	<	if (w.eventCount < 0 && !tryTerminate(false, false) &&
1777	<	(int)prevCtl != 0 && !hasQueuedSubmissions() && ctl == currentCtl) {
1776	>	if (w != null && w.eventCount < 0 &&
1777	>	!tryTerminate(false, false) && (int)prevCtl != 0) {
1778		int dc = -(short)(currentCtl >>> TC_SHIFT);
1779		long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1780	<	long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop
1780	>	long deadline = System.nanoTime() + parkTime - TIMEOUT_SLOP;
1781		Thread wt = Thread.currentThread();
1782		while (ctl == currentCtl) {
1783		Thread.interrupted(); // timed variant of version in scan()
#	Line 1741 \| Line 1792 \| public class ForkJoinPool extends Abstra
1792		if (deadline - System.nanoTime() <= 0L &&
1793		U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1794		w.eventCount = (w.eventCount + E_SEQ) \| E_MASK;
1795	<	w.runState = -1; // shrink
1795	>	w.qlock = -1; // shrink
1796		break;
1797		}
1798		}
#	Line 1749 \| Line 1800 \| public class ForkJoinPool extends Abstra
1800		}
1801
1802		/**
1803	+	* Scans through queues looking for work while joining a task; if
1804	+	* any present, signals. May return early if more signalling is
1805	+	* detectably unneeded.
1806	+	*
1807	+	* @param task return early if done
1808	+	* @param origin an index to start scan
1809	+	*/
1810	+	private void helpSignal(ForkJoinTask<?> task, int origin) {
1811	+	WorkQueue[] ws; WorkQueue w; Thread p; long c; int m, u, e, i, s;
1812	+	if (task != null && task.status >= 0 &&
1813	+	(u = (int)(ctl >>> 32)) < 0 && (u >> UAC_SHIFT) < 0 &&
1814	+	(ws = workQueues) != null && (m = ws.length - 1) >= 0) {
1815	+	outer: for (int k = origin, j = m; j >= 0; --j) {
1816	+	WorkQueue q = ws[k++ & m];
1817	+	for (int n = m;;) { // limit to at most m signals
1818	+	if (task.status < 0)
1819	+	break outer;
1820	+	if (q == null \|\|
1821	+	((s = -q.base + q.top) <= n && (n = s) <= 0))
1822	+	break;
1823	+	if ((u = (int)((c = ctl) >>> 32)) >= 0 \|\|
1824	+	(e = (int)c) <= 0 \|\| m < (i = e & SMASK) \|\|
1825	+	(w = ws[i]) == null)
1826	+	break outer;
1827	+	long nc = (((long)(w.nextWait & E_MASK)) \|
1828	+	((long)(u + UAC_UNIT) << 32));
1829	+	if (w.eventCount == (e \| INT_SIGN) &&
1830	+	U.compareAndSwapLong(this, CTL, c, nc)) {
1831	+	w.eventCount = (e + E_SEQ) & E_MASK;
1832	+	if ((p = w.parker) != null)
1833	+	U.unpark(p);
1834	+	if (--n <= 0)
1835	+	break;
1836	+	}
1837	+	}
1838	+	}
1839	+	}
1840	+	}
1841	+
1842	+	/**
1843	+	* Signals other workers if tasks are present in hinted queue.
1844	+	*
1845	+	* @param caller the worker with the hint
1846	+	*/
1847	+	private void helpSignalHint(WorkQueue caller) {
1848	+	WorkQueue[] ws; WorkQueue q, w; Thread p; long c; int h, m, u, e, i, s;
1849	+	if (caller != null && (h = caller.hint) >= 0 &&
1850	+	(u = (int)(ctl >>> 32)) < 0 && (u >> UAC_SHIFT) < 0 &&
1851	+	(ws = workQueues) != null && (m = ws.length - 1) >= 0 &&
1852	+	(q = ws[h & m]) != null) {
1853	+	caller.hint = -1;
1854	+	for (int n = 2;;) { // limit to at most 2 signals
1855	+	int idleCount = (caller.eventCount < 0) ? 0 : -1;
1856	+	if (((s = idleCount - q.base + q.top) <= n && (n = s) <= 0) \|\|
1857	+	(u = (int)((c = ctl) >>> 32)) >= 0 \|\|
1858	+	(e = (int)c) <= 0 \|\| m < (i = e & SMASK) \|\|
1859	+	(w = ws[i]) == null)
1860	+	break;
1861	+	long nc = (((long)(w.nextWait & E_MASK)) \|
1862	+	((long)(u + UAC_UNIT) << 32));
1863	+	if (w.eventCount == (e \| INT_SIGN) &&
1864	+	U.compareAndSwapLong(this, CTL, c, nc)) {
1865	+	w.hint = h;
1866	+	w.eventCount = (e + E_SEQ) & E_MASK;
1867	+	if ((p = w.parker) != null)
1868	+	U.unpark(p);
1869	+	if (--n <= 0)
1870	+	break;
1871	+	}
1872	+	}
1873	+	}
1874	+	}
1875	+
1876	+	/**
1877		* Tries to locate and execute tasks for a stealer of the given
1878		* task, or in turn one of its stealers, Traces currentSteal ->
1879		* currentJoin links looking for a thread working on a descendant
#	Line 1779 \| Line 1904 \| public class ForkJoinPool extends Abstra
1904		}
1905		if ((ws = workQueues) == null \|\| (m = ws.length - 1) <= 0)
1906		break restart; // shutting down
1907	<	if ((v = ws[h = (j.stealHint \| 1) & m]) == null \|\|
1907	>	if ((v = ws[h = (j.hint \| 1) & m]) == null \|\|
1908		v.currentSteal != subtask) {
1909		for (int origin = h;;) { // find stealer
1910		if (((h = (h + 2) & m) & 15) == 1 &&
#	Line 1787 \| Line 1912 \| public class ForkJoinPool extends Abstra
1912		continue restart; // occasional staleness check
1913		if ((v = ws[h]) != null &&
1914		v.currentSteal == subtask) {
1915	<	j.stealHint = h; // save hint
1915	>	j.hint = h; // save hint
1916		break;
1917		}
1918		if (h == origin)
#	Line 1835 \| Line 1960 \| public class ForkJoinPool extends Abstra
1960		}
1961
1962		/**
1963	<	* If task is at base of some steal queue, steals and executes it.
1963	>	* Analog of tryHelpStealer for CountedCompleters. Tries to steal
1964	>	* and run tasks within the target's computation.
1965	>	*
1966	>	* @param task the task to join
1967	>	* @param mode if shared, exit upon completing any task
1968	>	* if all workers are active
1969		*
1840	–	* @param joiner the joining worker
1841	–	* @param task the task
1970		*/
1971	<	private void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
1972	<	WorkQueue[] ws;
1973	<	if ((ws = workQueues) != null) {
1974	<	for (int j = 1; j < ws.length && task.status >= 0; j += 2) {
1975	<	WorkQueue q = ws[j];
1976	<	if (q != null && q.pollFor(task)) {
1977	<	joiner.runSubtask(task);
1978	<	break;
1971	>	private int helpComplete(ForkJoinTask<?> task, int mode) {
1972	>	WorkQueue[] ws; WorkQueue q; int m, n, s, u;
1973	>	if (task != null && (ws = workQueues) != null &&
1974	>	(m = ws.length - 1) >= 0) {
1975	>	for (int j = 1, origin = j;;) {
1976	>	if ((s = task.status) < 0)
1977	>	return s;
1978	>	if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) {
1979	>	origin = j;
1980	>	if (mode == SHARED_QUEUE &&
1981	>	((u = (int)(ctl >>> 32)) >= 0 \|\| (u >> UAC_SHIFT) >= 0))
1982	>	break;
1983		}
1984	+	else if ((j = (j + 2) & m) == origin)
1985	+	break;
1986		}
1987		}
1988	+	return 0;
1989		}
1990
1991		/**
1992		* Tries to decrement active count (sometimes implicitly) and
1993		* possibly release or create a compensating worker in preparation
1994		* for blocking. Fails on contention or termination. Otherwise,
1995	<	* adds a new thread if no idle workers are available and either
1996	<	* pool would become completely starved or: (at least half
1862	<	* starved, and fewer than 50% spares exist, and there is at least
1863	<	* one task apparently available). Even though the availability
1864	<	* check requires a full scan, it is worthwhile in reducing false
1865	<	* alarms.
1866	<	*
1867	<	* @param task if non-null, a task being waited for
1868	<	* @param blocker if non-null, a blocker being waited for
1869	<	* @return true if the caller can block, else should recheck and retry
1995	>	* adds a new thread if no idle workers are available and pool
1996	>	* may become starved.
1997		*/
1998	<	final boolean tryCompensate(ForkJoinTask<?> task, ManagedBlocker blocker) {
1999	<	int pc = parallelism, e;
2000	<	long c = ctl;
2001	<	WorkQueue[] ws = workQueues;
2002	<	if ((e = (int)c) >= 0 && ws != null) {
2003	<	int u, a, ac, hc;
2004	<	int tc = (short)((u = (int)(c >>> 32)) >>> UTC_SHIFT) + pc;
2005	<	boolean replace = false;
2006	<	if ((a = u >> UAC_SHIFT) <= 0) {
2007	<	if ((ac = a + pc) <= 1)
2008	<	replace = true;
2009	<	else if ((e > 0 \|\| (task != null &&
2010	<	ac <= (hc = pc >>> 1) && tc < pc + hc))) {
1884	<	WorkQueue w;
1885	<	for (int j = 0; j < ws.length; ++j) {
1886	<	if ((w = ws[j]) != null && !w.isEmpty()) {
1887	<	replace = true;
1888	<	break; // in compensation range and tasks available
1889	<	}
1890	<	}
1998	>	final boolean tryCompensate() {
1999	>	int pc = config & SMASK, e, i, tc; long c;
2000	>	WorkQueue[] ws; WorkQueue w; Thread p;
2001	>	if ((ws = workQueues) != null && (e = (int)(c = ctl)) >= 0) {
2002	>	if (e != 0 && (i = e & SMASK) < ws.length &&
2003	>	(w = ws[i]) != null && w.eventCount == (e \| INT_SIGN)) {
2004	>	long nc = ((long)(w.nextWait & E_MASK) \|
2005	>	(c & (AC_MASK\|TC_MASK)));
2006	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
2007	>	w.eventCount = (e + E_SEQ) & E_MASK;
2008	>	if ((p = w.parker) != null)
2009	>	U.unpark(p);
2010	>	return true; // replace with idle worker
2011		}
2012		}
2013	<	if ((task == null \|\| task.status >= 0) && // recheck need to block
2014	<	(blocker == null \|\| !blocker.isReleasable()) && ctl == c) {
2015	<	if (!replace) { // no compensation
2016	<	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
2017	<	if (U.compareAndSwapLong(this, CTL, c, nc))
2018	<	return true;
2019	<	}
2020	<	else if (e != 0) { // release an idle worker
2021	<	WorkQueue w; Thread p; int i;
2022	<	if ((i = e & SMASK) < ws.length && (w = ws[i]) != null) {
2023	<	long nc = ((long)(w.nextWait & E_MASK) \|
2024	<	(c & (AC_MASK\|TC_MASK)));
2025	<	if (w.eventCount == (e \| INT_SIGN) &&
2026	<	U.compareAndSwapLong(this, CTL, c, nc)) {
2027	<	w.eventCount = (e + E_SEQ) & E_MASK;
2028	<	if ((p = w.parker) != null)
1909	<	U.unpark(p);
2013	>	else if ((tc = (short)(c >>> TC_SHIFT)) >= 0 &&
2014	>	(int)(c >> AC_SHIFT) + pc > 1) {
2015	>	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
2016	>	if (U.compareAndSwapLong(this, CTL, c, nc))
2017	>	return true; // no compensation
2018	>	}
2019	>	else if (tc + pc < MAX_CAP) {
2020	>	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
2021	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
2022	>	ForkJoinWorkerThreadFactory fac;
2023	>	Throwable ex = null;
2024	>	ForkJoinWorkerThread wt = null;
2025	>	try {
2026	>	if ((fac = factory) != null &&
2027	>	(wt = fac.newThread(this)) != null) {
2028	>	wt.start();
2029		return true;
2030		}
2031	+	} catch (Throwable rex) {
2032	+	ex = rex;
2033		}
2034	<	}
1914	<	else if (tc < MAX_CAP) { // create replacement
1915	<	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
1916	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1917	<	addWorker();
1918	<	return true;
1919	<	}
2034	>	deregisterWorker(wt, ex); // clean up and return false
2035		}
2036		}
2037		}
#	Line 1931 \| Line 2046 \| public class ForkJoinPool extends Abstra
2046		* @return task status on exit
2047		*/
2048		final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
2049	<	int s;
2050	<	if ((s = task.status) >= 0) {
2049	>	int s = 0;
2050	>	if (joiner != null && task != null && (s = task.status) >= 0) {
2051		ForkJoinTask<?> prevJoin = joiner.currentJoin;
2052		joiner.currentJoin = task;
2053	<	long startTime = 0L;
2054	<	for (int k = 0;;) {
2055	<	if ((s = (joiner.isEmpty() ? // try to help
2056	<	tryHelpStealer(joiner, task) :
2057	<	joiner.tryRemoveAndExec(task))) == 0 &&
2053	>	do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
2054	>	joiner.tryRemoveAndExec(task)); // process local tasks
2055	>	if (s >= 0 && (s = task.status) >= 0) {
2056	>	helpSignal(task, joiner.poolIndex);
2057	>	if ((s = task.status) >= 0 &&
2058	>	(task instanceof CountedCompleter))
2059	>	s = helpComplete(task, LIFO_QUEUE);
2060	>	}
2061	>	while (s >= 0 && (s = task.status) >= 0) {
2062	>	if ((!joiner.isEmpty() \|\| // try helping
2063	>	(s = tryHelpStealer(joiner, task)) == 0) &&
2064		(s = task.status) >= 0) {
2065	<	if (k == 0) {
2066	<	startTime = System.nanoTime();
2067	<	tryPollForAndExec(joiner, task); // check uncommon case
1947	<	}
1948	<	else if ((k & (MAX_HELP - 1)) == 0 &&
1949	<	System.nanoTime() - startTime >=
1950	<	COMPENSATION_DELAY &&
1951	<	tryCompensate(task, null)) {
1952	<	if (task.trySetSignal()) {
2065	>	helpSignal(task, joiner.poolIndex);
2066	>	if ((s = task.status) >= 0 && tryCompensate()) {
2067	>	if (task.trySetSignal() && (s = task.status) >= 0) {
2068		synchronized (task) {
2069		if (task.status >= 0) {
2070		try { // see ForkJoinTask
#	Line 1966 \| Line 2081 \| public class ForkJoinPool extends Abstra
2081		(this, CTL, c = ctl, c + AC_UNIT));
2082		}
2083		}
1969	–	if (s < 0 \|\| (s = task.status) < 0) {
1970	–	joiner.currentJoin = prevJoin;
1971	–	break;
1972	–	}
1973	–	else if ((k++ & (MAX_HELP - 1)) == MAX_HELP >>> 1)
1974	–	Thread.yield(); // for politeness
2084		}
2085	+	joiner.currentJoin = prevJoin;
2086		}
2087		return s;
2088		}
#	Line 1984 \| Line 2094 \| public class ForkJoinPool extends Abstra
2094		*
2095		* @param joiner the joining worker
2096		* @param task the task
1987	–	* @return task status on exit
2097		*/
2098	<	final int helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
2098	>	final void helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
2099		int s;
2100	<	while ((s = task.status) >= 0 &&
2101	<	(joiner.isEmpty() ?
2102	<	tryHelpStealer(joiner, task) :
2103	<	joiner.tryRemoveAndExec(task)) != 0)
2104	<	;
2105	<	return s;
2100	>	if (joiner != null && task != null && (s = task.status) >= 0) {
2101	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2102	>	joiner.currentJoin = task;
2103	>	do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
2104	>	joiner.tryRemoveAndExec(task));
2105	>	if (s >= 0 && (s = task.status) >= 0) {
2106	>	helpSignal(task, joiner.poolIndex);
2107	>	if ((s = task.status) >= 0 &&
2108	>	(task instanceof CountedCompleter))
2109	>	s = helpComplete(task, LIFO_QUEUE);
2110	>	}
2111	>	if (s >= 0 && joiner.isEmpty()) {
2112	>	do {} while (task.status >= 0 &&
2113	>	tryHelpStealer(joiner, task) > 0);
2114	>	}
2115	>	joiner.currentJoin = prevJoin;
2116	>	}
2117		}
2118
2119		/**
#	Line 2001 \| Line 2121 \| public class ForkJoinPool extends Abstra
2121		* during a random, then cyclic scan, else null. This method must
2122		* be retried by caller if, by the time it tries to use the queue,
2123		* it is empty.
2124	+	* @param r a (random) seed for scanning
2125		*/
2126	<	private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
2006	<	// Similar to loop in scan(), but ignoring submissions
2007	<	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
2008	<	int step = (r >>> 16) \| 1;
2126	>	private WorkQueue findNonEmptyStealQueue(int r) {
2127		for (WorkQueue[] ws;;) {
2128	<	int rs = runState, m;
2128	>	int ps = plock, m, n;
2129		if ((ws = workQueues) == null \|\| (m = ws.length - 1) < 1)
2130		return null;
2131	<	for (int j = (m + 1) << 2; ; r += step) {
2132	<	WorkQueue q = ws[((r << 1) \| 1) & m];
2133	<	if (q != null && !q.isEmpty())
2131	>	for (int j = (m + 1) << 2; ;) {
2132	>	WorkQueue q = ws[(((r + j) << 1) \| 1) & m];
2133	>	if (q != null && (n = q.base - q.top) < 0) {
2134	>	if (n < -1)
2135	>	signalWork(q);
2136		return q;
2137	+	}
2138		else if (--j < 0) {
2139	<	if (runState == rs)
2139	>	if (plock == ps)
2140		return null;
2141		break;
2142		}
#	Line 2034 \| Line 2155 \| public class ForkJoinPool extends Abstra
2155		ForkJoinTask<?> localTask; // exhaust local queue
2156		while ((localTask = w.nextLocalTask()) != null)
2157		localTask.doExec();
2158	<	WorkQueue q = findNonEmptyStealQueue(w);
2158	>	// Similar to loop in scan(), but ignoring submissions
2159	>	WorkQueue q = findNonEmptyStealQueue(w.nextSeed());
2160		if (q != null) {
2161		ForkJoinTask<?> t; int b;
2162		if (!active) { // re-establish active count
#	Line 2055 \| Line 2177 \| public class ForkJoinPool extends Abstra
2177		}
2178		else
2179		c = ctl; // re-increment on exit
2180	<	if ((int)(c >> AC_SHIFT) + parallelism == 0) {
2180	>	if ((int)(c >> AC_SHIFT) + (config & SMASK) == 0) {
2181		do {} while (!U.compareAndSwapLong
2182		(this, CTL, c = ctl, c + AC_UNIT));
2183		break;
#	Line 2065 \| Line 2187 \| public class ForkJoinPool extends Abstra
2187		}
2188
2189		/**
2068	–	* Restricted version of helpQuiescePool for non-FJ callers
2069	–	*/
2070	–	static void externalHelpQuiescePool() {
2071	–	ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q;
2072	–	ForkJoinTask<?> t; int b;
2073	–	int k = submitters.get().seed & SQMASK;
2074	–	if ((p = commonPool) != null &&
2075	–	(ws = p.workQueues) != null &&
2076	–	ws.length > (k &= p.submitMask) &&
2077	–	(w = ws[k]) != null &&
2078	–	(q = p.findNonEmptyStealQueue(w)) != null &&
2079	–	(b = q.base) - q.top < 0 &&
2080	–	(t = q.pollAt(b)) != null)
2081	–	t.doExec();
2082	–	}
2083	–
2084	–	/**
2190		* Gets and removes a local or stolen task for the given worker.
2191		*
2192		* @return a task, if available
#	Line 2091 \| Line 2196 \| public class ForkJoinPool extends Abstra
2196		WorkQueue q; int b;
2197		if ((t = w.nextLocalTask()) != null)
2198		return t;
2199	<	if ((q = findNonEmptyStealQueue(w)) == null)
2199	>	if ((q = findNonEmptyStealQueue(w.nextSeed())) == null)
2200		return null;
2201		if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2202		return t;
#	Line 2099 \| Line 2204 \| public class ForkJoinPool extends Abstra
2204		}
2205
2206		/**
2207	<	* Returns the approximate (non-atomic) number of idle threads per
2208	<	* active thread to offset steal queue size for method
2209	<	* ForkJoinTask.getSurplusQueuedTaskCount().
2210	<	*/
2211	<	final int idlePerActive() {
2212	<	// Approximate at powers of two for small values, saturate past 4
2213	<	int p = parallelism;
2214	<	int a = p + (int)(ctl >> AC_SHIFT);
2215	<	return (a > (p >>>= 1) ? 0 :
2216	<	a > (p >>>= 1) ? 1 :
2217	<	a > (p >>>= 1) ? 2 :
2218	<	a > (p >>>= 1) ? 4 :
2219	<	8);
2220	<	}
2221	<
2222	<	/**
2223	<	* Returns approximate submission queue length for the given caller
2224	<	*/
2225	<	static int getEstimatedSubmitterQueueLength() {
2226	<	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
2227	<	int k = submitters.get().seed & SQMASK;
2228	<	return ((p = commonPool) != null &&
2229	<	p.runState >= 0 &&
2230	<	(ws = p.workQueues) != null &&
2231	<	ws.length > (k &= p.submitMask) &&
2232	<	(q = ws[k]) != null) ?
2233	<	q.queueSize() : 0;
2207	>	* Returns a cheap heuristic guide for task partitioning when
2208	>	* programmers, frameworks, tools, or languages have little or no
2209	>	* idea about task granularity. In essence by offering this
2210	>	* method, we ask users only about tradeoffs in overhead vs
2211	>	* expected throughput and its variance, rather than how finely to
2212	>	* partition tasks.
2213	>	*
2214	>	* In a steady state strict (tree-structured) computation, each
2215	>	* thread makes available for stealing enough tasks for other
2216	>	* threads to remain active. Inductively, if all threads play by
2217	>	* the same rules, each thread should make available only a
2218	>	* constant number of tasks.
2219	>	*
2220	>	* The minimum useful constant is just 1. But using a value of 1
2221	>	* would require immediate replenishment upon each steal to
2222	>	* maintain enough tasks, which is infeasible. Further,
2223	>	* partitionings/granularities of offered tasks should minimize
2224	>	* steal rates, which in general means that threads nearer the top
2225	>	* of computation tree should generate more than those nearer the
2226	>	* bottom. In perfect steady state, each thread is at
2227	>	* approximately the same level of computation tree. However,
2228	>	* producing extra tasks amortizes the uncertainty of progress and
2229	>	* diffusion assumptions.
2230	>	*
2231	>	* So, users will want to use values larger, but not much larger
2232	>	* than 1 to both smooth over transient shortages and hedge
2233	>	* against uneven progress; as traded off against the cost of
2234	>	* extra task overhead. We leave the user to pick a threshold
2235	>	* value to compare with the results of this call to guide
2236	>	* decisions, but recommend values such as 3.
2237	>	*
2238	>	* When all threads are active, it is on average OK to estimate
2239	>	* surplus strictly locally. In steady-state, if one thread is
2240	>	* maintaining say 2 surplus tasks, then so are others. So we can
2241	>	* just use estimated queue length. However, this strategy alone
2242	>	* leads to serious mis-estimates in some non-steady-state
2243	>	* conditions (ramp-up, ramp-down, other stalls). We can detect
2244	>	* many of these by further considering the number of "idle"
2245	>	* threads, that are known to have zero queued tasks, so
2246	>	* compensate by a factor of (#idle/#active) threads.
2247	>	*
2248	>	* Note: The approximation of #busy workers as #active workers is
2249	>	* not very good under current signalling scheme, and should be
2250	>	* improved.
2251	>	*/
2252	>	static int getSurplusQueuedTaskCount() {
2253	>	Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q;
2254	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
2255	>	int p = (pool = (wt = (ForkJoinWorkerThread)t).pool).config & SMASK;
2256	>	int n = (q = wt.workQueue).top - q.base;
2257	>	int a = (int)(pool.ctl >> AC_SHIFT) + p;
2258	>	return n - (a > (p >>>= 1) ? 0 :
2259	>	a > (p >>>= 1) ? 1 :
2260	>	a > (p >>>= 1) ? 2 :
2261	>	a > (p >>>= 1) ? 4 :
2262	>	8);
2263	>	}
2264	>	return 0;
2265		}
2266
2267		// Termination
#	Line 2145 \| Line 2281 \| public class ForkJoinPool extends Abstra
2281		* @return true if now terminating or terminated
2282		*/
2283		private boolean tryTerminate(boolean now, boolean enable) {
2284	+	if (this == commonPool) // cannot shut down
2285	+	return false;
2286		for (long c;;) {
2287		if (((c = ctl) & STOP_BIT) != 0) { // already terminating
2288	<	if ((short)(c >>> TC_SHIFT) == -parallelism) {
2289	<	synchronized(this) {
2288	>	if ((short)(c >>> TC_SHIFT) == -(config & SMASK)) {
2289	>	synchronized (this) {
2290		notifyAll(); // signal when 0 workers
2291		}
2292		}
2293		return true;
2294		}
2295	<	if (runState >= 0) { // not yet enabled
2295	>	if (plock >= 0) { // not yet enabled
2296	>	int ps;
2297		if (!enable)
2298		return false;
2299	<	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
2300	<	tryAwaitMainLock();
2301	<	try {
2302	<	runState \|= SHUTDOWN;
2303	<	} finally {
2304	<	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
2166	<	mainLock = 0;
2167	<	synchronized (this) { notifyAll(); };
2168	<	}
2169	<	}
2299	>	if (((ps = plock) & PL_LOCK) != 0 \|\|
2300	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
2301	>	ps = acquirePlock();
2302	>	int nps = SHUTDOWN;
2303	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
2304	>	releasePlock(nps);
2305		}
2306		if (!now) { // check if idle & no tasks
2307	<	if ((int)(c >> AC_SHIFT) != -parallelism \|\|
2307	>	if ((int)(c >> AC_SHIFT) != -(config & SMASK) \|\|
2308		hasQueuedSubmissions())
2309		return false;
2310		// Check for unqueued inactive workers. One pass suffices.
#	Line 2189 \| Line 2324 \| public class ForkJoinPool extends Abstra
2324		int n = ws.length;
2325		for (int i = 0; i < n; ++i) {
2326		if ((w = ws[i]) != null) {
2327	<	w.runState = -1;
2327	>	w.qlock = -1;
2328		if (pass > 0) {
2329		w.cancelAll();
2330		if (pass > 1)
#	Line 2208 \| Line 2343 \| public class ForkJoinPool extends Abstra
2343		if (w.eventCount == (e \| INT_SIGN) &&
2344		U.compareAndSwapLong(this, CTL, cc, nc)) {
2345		w.eventCount = (e + E_SEQ) & E_MASK;
2346	<	w.runState = -1;
2346	>	w.qlock = -1;
2347		if ((p = w.parker) != null)
2348		U.unpark(p);
2349		}
#	Line 2219 \| Line 2354 \| public class ForkJoinPool extends Abstra
2354		}
2355		}
2356
2357	+	// external operations on common pool
2358	+
2359	+	/**
2360	+	* Returns common pool queue for a thread that has submitted at
2361	+	* least one task.
2362	+	*/
2363	+	static WorkQueue commonSubmitterQueue() {
2364	+	ForkJoinPool p; WorkQueue[] ws; int m; Submitter z;
2365	+	return ((z = submitters.get()) != null &&
2366	+	(p = commonPool) != null &&
2367	+	(ws = p.workQueues) != null &&
2368	+	(m = ws.length - 1) >= 0) ?
2369	+	ws[m & z.seed & SQMASK] : null;
2370	+	}
2371	+
2372	+	/**
2373	+	* Tries to pop the given task from submitter's queue in common pool.
2374	+	*/
2375	+	static boolean tryExternalUnpush(ForkJoinTask<?> t) {
2376	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q; Submitter z;
2377	+	ForkJoinTask<?>[] a; int m, s;
2378	+	if (t != null &&
2379	+	(z = submitters.get()) != null &&
2380	+	(p = commonPool) != null &&
2381	+	(ws = p.workQueues) != null &&
2382	+	(m = ws.length - 1) >= 0 &&
2383	+	(q = ws[m & z.seed & SQMASK]) != null &&
2384	+	(s = q.top) != q.base &&
2385	+	(a = q.array) != null) {
2386	+	long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE;
2387	+	if (U.getObject(a, j) == t &&
2388	+	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2389	+	if (q.array == a && q.top == s && // recheck
2390	+	U.compareAndSwapObject(a, j, t, null)) {
2391	+	q.top = s - 1;
2392	+	q.qlock = 0;
2393	+	return true;
2394	+	}
2395	+	q.qlock = 0;
2396	+	}
2397	+	}
2398	+	return false;
2399	+	}
2400	+
2401	+	/**
2402	+	* Tries to pop and run local tasks within the same computation
2403	+	* as the given root. On failure, tries to help complete from
2404	+	* other queues via helpComplete.
2405	+	*/
2406	+	private void externalHelpComplete(WorkQueue q, ForkJoinTask<?> root) {
2407	+	ForkJoinTask<?>[] a; int m;
2408	+	if (q != null && (a = q.array) != null && (m = (a.length - 1)) >= 0 &&
2409	+	root != null && root.status >= 0) {
2410	+	for (;;) {
2411	+	int s, u; Object o; CountedCompleter<?> task = null;
2412	+	if ((s = q.top) - q.base > 0) {
2413	+	long j = ((m & (s - 1)) << ASHIFT) + ABASE;
2414	+	if ((o = U.getObject(a, j)) != null &&
2415	+	(o instanceof CountedCompleter)) {
2416	+	CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;
2417	+	do {
2418	+	if (r == root) {
2419	+	if (U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2420	+	if (q.array == a && q.top == s &&
2421	+	U.compareAndSwapObject(a, j, t, null)) {
2422	+	q.top = s - 1;
2423	+	task = t;
2424	+	}
2425	+	q.qlock = 0;
2426	+	}
2427	+	break;
2428	+	}
2429	+	} while ((r = r.completer) != null);
2430	+	}
2431	+	}
2432	+	if (task != null)
2433	+	task.doExec();
2434	+	if (root.status < 0 \|\|
2435	+	(u = (int)(ctl >>> 32)) >= 0 \|\| (u >> UAC_SHIFT) >= 0)
2436	+	break;
2437	+	if (task == null) {
2438	+	helpSignal(root, q.poolIndex);
2439	+	if (root.status >= 0)
2440	+	helpComplete(root, SHARED_QUEUE);
2441	+	break;
2442	+	}
2443	+	}
2444	+	}
2445	+	}
2446	+
2447	+	/**
2448	+	* Tries to help execute or signal availability of the given task
2449	+	* from submitter's queue in common pool.
2450	+	*/
2451	+	static void externalHelpJoin(ForkJoinTask<?> t) {
2452	+	// Some hard-to-avoid overlap with tryExternalUnpush
2453	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; Submitter z;
2454	+	ForkJoinTask<?>[] a; int m, s, n;
2455	+	if (t != null &&
2456	+	(z = submitters.get()) != null &&
2457	+	(p = commonPool) != null &&
2458	+	(ws = p.workQueues) != null &&
2459	+	(m = ws.length - 1) >= 0 &&
2460	+	(q = ws[m & z.seed & SQMASK]) != null &&
2461	+	(a = q.array) != null) {
2462	+	int am = a.length - 1;
2463	+	if ((s = q.top) != q.base) {
2464	+	long j = ((am & (s - 1)) << ASHIFT) + ABASE;
2465	+	if (U.getObject(a, j) == t &&
2466	+	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2467	+	if (q.array == a && q.top == s &&
2468	+	U.compareAndSwapObject(a, j, t, null)) {
2469	+	q.top = s - 1;
2470	+	q.qlock = 0;
2471	+	t.doExec();
2472	+	}
2473	+	else
2474	+	q.qlock = 0;
2475	+	}
2476	+	}
2477	+	if (t.status >= 0) {
2478	+	if (t instanceof CountedCompleter)
2479	+	p.externalHelpComplete(q, t);
2480	+	else
2481	+	p.helpSignal(t, q.poolIndex);
2482	+	}
2483	+	}
2484	+	}
2485	+
2486	+	/**
2487	+	* Restricted version of helpQuiescePool for external callers
2488	+	*/
2489	+	static void externalHelpQuiescePool() {
2490	+	ForkJoinPool p; ForkJoinTask<?> t; WorkQueue q; int b;
2491	+	if ((p = commonPool) != null &&
2492	+	(q = p.findNonEmptyStealQueue(1)) != null &&
2493	+	(b = q.base) - q.top < 0 &&
2494	+	(t = q.pollAt(b)) != null)
2495	+	t.doExec();
2496	+	}
2497	+
2498		// Exported methods
2499
2500		// Constructors
#	Line 2290 \| Line 2566 \| public class ForkJoinPool extends Abstra
2566		throw new NullPointerException();
2567		if (parallelism <= 0 \|\| parallelism > MAX_CAP)
2568		throw new IllegalArgumentException();
2293	–	this.parallelism = parallelism;
2569		this.factory = factory;
2570		this.ueh = handler;
2571	<	this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE;
2571	>	this.config = parallelism \| (asyncMode ? (FIFO_QUEUE << 16) : 0);
2572		long np = (long)(-parallelism); // offset ctl counts
2573		this.ctl = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
2574	<	// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2.
2300	<	int n = parallelism - 1;
2301	<	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4; n \|= n >>> 8; n \|= n >>> 16;
2302	<	this.submitMask = ((n + 1) << 1) - 1;
2303	<	int pn = poolNumberGenerator.incrementAndGet();
2574	>	int pn = nextPoolId();
2575		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2576		sb.append(Integer.toString(pn));
2577		sb.append("-worker-");
2578		this.workerNamePrefix = sb.toString();
2308	–	this.runState = 1; // set init flag
2579		}
2580
2581		/**
2582		* Constructor for common pool, suitable only for static initialization.
2583		* Basically the same as above, but uses smallest possible initial footprint.
2584		*/
2585	<	ForkJoinPool(int parallelism, int submitMask,
2585	>	ForkJoinPool(int parallelism, long ctl,
2586		ForkJoinWorkerThreadFactory factory,
2587		Thread.UncaughtExceptionHandler handler) {
2588	+	this.config = parallelism;
2589	+	this.ctl = ctl;
2590		this.factory = factory;
2591		this.ueh = handler;
2320	–	this.submitMask = submitMask;
2321	–	this.parallelism = parallelism;
2322	–	long np = (long)(-parallelism);
2323	–	this.ctl = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
2324	–	this.localMode = LIFO_QUEUE;
2592		this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2326	–	this.runState = 1;
2593		}
2594
2595		/**
#	Line 2332 \| Line 2598 \| public class ForkJoinPool extends Abstra
2598		* @return the common pool instance
2599		*/
2600		public static ForkJoinPool commonPool() {
2601	<	ForkJoinPool p;
2602	<	if ((p = commonPool) == null)
2337	<	throw new Error("Common Pool Unavailable");
2338	<	return p;
2601	>	// assert commonPool != null : "static init error";
2602	>	return commonPool;
2603		}
2604
2605		// Execution methods
#	Line 2359 \| Line 2623 \| public class ForkJoinPool extends Abstra
2623		public <T> T invoke(ForkJoinTask<T> task) {
2624		if (task == null)
2625		throw new NullPointerException();
2626	<	doSubmit(task);
2626	>	externalPush(task);
2627		return task.join();
2628		}
2629
#	Line 2374 \| Line 2638 \| public class ForkJoinPool extends Abstra
2638		public void execute(ForkJoinTask<?> task) {
2639		if (task == null)
2640		throw new NullPointerException();
2641	<	doSubmit(task);
2641	>	externalPush(task);
2642		}
2643
2644		// AbstractExecutorService methods
#	Line 2392 \| Line 2656 \| public class ForkJoinPool extends Abstra
2656		job = (ForkJoinTask<?>) task;
2657		else
2658		job = new ForkJoinTask.AdaptedRunnableAction(task);
2659	<	doSubmit(job);
2659	>	externalPush(job);
2660		}
2661
2662		/**
#	Line 2407 \| Line 2671 \| public class ForkJoinPool extends Abstra
2671		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2672		if (task == null)
2673		throw new NullPointerException();
2674	<	doSubmit(task);
2674	>	externalPush(task);
2675		return task;
2676		}
2677
#	Line 2418 \| Line 2682 \| public class ForkJoinPool extends Abstra
2682		*/
2683		public <T> ForkJoinTask<T> submit(Callable<T> task) {
2684		ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2685	<	doSubmit(job);
2685	>	externalPush(job);
2686		return job;
2687		}
2688
#	Line 2429 \| Line 2693 \| public class ForkJoinPool extends Abstra
2693		*/
2694		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2695		ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2696	<	doSubmit(job);
2696	>	externalPush(job);
2697		return job;
2698		}
2699
#	Line 2446 \| Line 2710 \| public class ForkJoinPool extends Abstra
2710		job = (ForkJoinTask<?>) task;
2711		else
2712		job = new ForkJoinTask.AdaptedRunnableAction(task);
2713	<	doSubmit(job);
2713	>	externalPush(job);
2714		return job;
2715		}
2716
#	Line 2468 \| Line 2732 \| public class ForkJoinPool extends Abstra
2732		try {
2733		for (Callable<T> t : tasks) {
2734		ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2735	<	doSubmit(f);
2735	>	externalPush(f);
2736		fs.add(f);
2737		}
2738		for (ForkJoinTask<T> f : fs)
#	Line 2507 \| Line 2771 \| public class ForkJoinPool extends Abstra
2771		* @return the targeted parallelism level of this pool
2772		*/
2773		public int getParallelism() {
2774	<	return parallelism;
2774	>	return config & SMASK;
2775		}
2776
2777		/**
#	Line 2528 \| Line 2792 \| public class ForkJoinPool extends Abstra
2792		* @return the number of worker threads
2793		*/
2794		public int getPoolSize() {
2795	<	return parallelism + (short)(ctl >>> TC_SHIFT);
2795	>	return (config & SMASK) + (short)(ctl >>> TC_SHIFT);
2796		}
2797
2798		/**
#	Line 2538 \| Line 2802 \| public class ForkJoinPool extends Abstra
2802		* @return {@code true} if this pool uses async mode
2803		*/
2804		public boolean getAsyncMode() {
2805	<	return localMode != 0;
2805	>	return (config >>> 16) == FIFO_QUEUE;
2806		}
2807
2808		/**
#	Line 2569 \| Line 2833 \| public class ForkJoinPool extends Abstra
2833		* @return the number of active threads
2834		*/
2835		public int getActiveThreadCount() {
2836	<	int r = parallelism + (int)(ctl >> AC_SHIFT);
2836	>	int r = (config & SMASK) + (int)(ctl >> AC_SHIFT);
2837		return (r <= 0) ? 0 : r; // suppress momentarily negative values
2838		}
2839
#	Line 2585 \| Line 2849 \| public class ForkJoinPool extends Abstra
2849		* @return {@code true} if all threads are currently idle
2850		*/
2851		public boolean isQuiescent() {
2852	<	return (int)(ctl >> AC_SHIFT) + parallelism == 0;
2852	>	return (int)(ctl >> AC_SHIFT) + (config & SMASK) == 0;
2853		}
2854
2855		/**
#	Line 2605 \| Line 2869 \| public class ForkJoinPool extends Abstra
2869		if ((ws = workQueues) != null) {
2870		for (int i = 1; i < ws.length; i += 2) {
2871		if ((w = ws[i]) != null)
2872	<	count += w.totalSteals;
2872	>	count += w.nsteals;
2873		}
2874		}
2875		return count;
#	Line 2741 \| Line 3005 \| public class ForkJoinPool extends Abstra
3005		qs += size;
3006		else {
3007		qt += size;
3008	<	st += w.totalSteals;
3008	>	st += w.nsteals;
3009		if (w.isApparentlyUnblocked())
3010		++rc;
3011		}
3012		}
3013		}
3014		}
3015	<	int pc = parallelism;
3015	>	int pc = (config & SMASK);
3016		int tc = pc + (short)(c >>> TC_SHIFT);
3017		int ac = pc + (int)(c >> AC_SHIFT);
3018		if (ac < 0) // ignore transient negative
#	Line 2757 \| Line 3021 \| public class ForkJoinPool extends Abstra
3021		if ((c & STOP_BIT) != 0)
3022		level = (tc == 0) ? "Terminated" : "Terminating";
3023		else
3024	<	level = runState < 0 ? "Shutting down" : "Running";
3024	>	level = plock < 0 ? "Shutting down" : "Running";
3025		return super.toString() +
3026		"[" + level +
3027		", parallelism = " + pc +
#	Line 2786 \| Line 3050 \| public class ForkJoinPool extends Abstra
3050		*/
3051		public void shutdown() {
3052		checkPermission();
3053	<	if (this != commonPool)
2790	<	tryTerminate(false, true);
3053	>	tryTerminate(false, true);
3054		}
3055
3056		/**
#	Line 2810 \| Line 3073 \| public class ForkJoinPool extends Abstra
3073		*/
3074		public List<Runnable> shutdownNow() {
3075		checkPermission();
3076	<	if (this != commonPool)
2814	<	tryTerminate(true, true);
3076	>	tryTerminate(true, true);
3077		return Collections.emptyList();
3078		}
3079
#	Line 2823 \| Line 3085 \| public class ForkJoinPool extends Abstra
3085		public boolean isTerminated() {
3086		long c = ctl;
3087		return ((c & STOP_BIT) != 0L &&
3088	<	(short)(c >>> TC_SHIFT) == -parallelism);
3088	>	(short)(c >>> TC_SHIFT) == -(config & SMASK));
3089		}
3090
3091		/**
#	Line 2831 \| Line 3093 \| public class ForkJoinPool extends Abstra
3093		* commenced but not yet completed. This method may be useful for
3094		* debugging. A return of {@code true} reported a sufficient
3095		* period after shutdown may indicate that submitted tasks have
3096	<	* ignored or suppressed interruption, or are waiting for IO,
3096	>	* ignored or suppressed interruption, or are waiting for I/O,
3097		* causing this executor not to properly terminate. (See the
3098		* advisory notes for class {@link ForkJoinTask} stating that
3099		* tasks should not normally entail blocking operations. But if
#	Line 2842 \| Line 3104 \| public class ForkJoinPool extends Abstra
3104		public boolean isTerminating() {
3105		long c = ctl;
3106		return ((c & STOP_BIT) != 0L &&
3107	<	(short)(c >>> TC_SHIFT) != -parallelism);
3107	>	(short)(c >>> TC_SHIFT) != -(config & SMASK));
3108		}
3109
3110		/**
#	Line 2851 \| Line 3113 \| public class ForkJoinPool extends Abstra
3113		* @return {@code true} if this pool has been shut down
3114		*/
3115		public boolean isShutdown() {
3116	<	return runState < 0;
3116	>	return plock < 0;
3117		}
3118
3119		/**
3120	<	* Blocks until all tasks have completed execution after a shutdown
3121	<	* request, or the timeout occurs, or the current thread is
3122	<	* interrupted, whichever happens first.
3120	>	* Blocks until all tasks have completed execution after a
3121	>	* shutdown request, or the timeout occurs, or the current thread
3122	>	* is interrupted, whichever happens first. Note that the {@link
3123	>	* #commonPool()} never terminates until program shutdown so
3124	>	* this method will always time out.
3125		*
3126		* @param timeout the maximum time to wait
3127		* @param unit the time unit of the timeout argument
#	Line 2872 \| Line 3136 \| public class ForkJoinPool extends Abstra
3136		return true;
3137		long startTime = System.nanoTime();
3138		boolean terminated = false;
3139	<	synchronized(this) {
3139	>	synchronized (this) {
3140		for (long waitTime = nanos, millis = 0L;;) {
3141		if (terminated = isTerminated() \|\|
3142		waitTime <= 0L \|\|
#	Line 2981 \| Line 3245 \| public class ForkJoinPool extends Abstra
3245		public static void managedBlock(ManagedBlocker blocker)
3246		throws InterruptedException {
3247		Thread t = Thread.currentThread();
3248	<	ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ?
3249	<	((ForkJoinWorkerThread)t).pool : null);
3250	<	while (!blocker.isReleasable()) {
3251	<	if (p == null \|\| p.tryCompensate(null, blocker)) {
3252	<	try {
3253	<	do {} while (!blocker.isReleasable() && !blocker.block());
3254	<	} finally {
3255	<	if (p != null)
3248	>	if (t instanceof ForkJoinWorkerThread) {
3249	>	ForkJoinPool p = ((ForkJoinWorkerThread)t).pool;
3250	>	while (!blocker.isReleasable()) { // variant of helpSignal
3251	>	WorkQueue[] ws; WorkQueue q; int m, u;
3252	>	if ((ws = p.workQueues) != null && (m = ws.length - 1) >= 0) {
3253	>	for (int i = 0; i <= m; ++i) {
3254	>	if (blocker.isReleasable())
3255	>	return;
3256	>	if ((q = ws[i]) != null && q.base - q.top < 0) {
3257	>	p.signalWork(q);
3258	>	if ((u = (int)(p.ctl >>> 32)) >= 0 \|\|
3259	>	(u >> UAC_SHIFT) >= 0)
3260	>	break;
3261	>	}
3262	>	}
3263	>	}
3264	>	if (p.tryCompensate()) {
3265	>	try {
3266	>	do {} while (!blocker.isReleasable() &&
3267	>	!blocker.block());
3268	>	} finally {
3269		p.incrementActiveCount();
3270	+	}
3271	+	break;
3272		}
2994	–	break;
3273		}
3274		}
3275	+	else {
3276	+	do {} while (!blocker.isReleasable() &&
3277	+	!blocker.block());
3278	+	}
3279		}
3280
3281		// AbstractExecutorService overrides. These rely on undocumented
#	Line 3014 \| Line 3296 \| public class ForkJoinPool extends Abstra
3296		private static final long PARKBLOCKER;
3297		private static final int ABASE;
3298		private static final int ASHIFT;
3017	–	private static final long NEXTWORKERNUMBER;
3299		private static final long STEALCOUNT;
3300	<	private static final long MAINLOCK;
3300	>	private static final long PLOCK;
3301	>	private static final long INDEXSEED;
3302	>	private static final long QLOCK;
3303
3304		static {
3305	<	poolNumberGenerator = new AtomicInteger();
3023	<	nextSubmitterSeed = new AtomicInteger(0x55555555);
3024	<	modifyThreadPermission = new RuntimePermission("modifyThread");
3025	<	defaultForkJoinWorkerThreadFactory =
3026	<	new DefaultForkJoinWorkerThreadFactory();
3027	<	submitters = new ThreadSubmitter();
3028	<	int s;
3305	>	int s; // initialize field offsets for CAS etc
3306		try {
3307		U = getUnsafe();
3308		Class<?> k = ForkJoinPool.class;
3032	–	Class<?> ak = ForkJoinTask[].class;
3309		CTL = U.objectFieldOffset
3310		(k.getDeclaredField("ctl"));
3035	–	NEXTWORKERNUMBER = U.objectFieldOffset
3036	–	(k.getDeclaredField("nextWorkerNumber"));
3311		STEALCOUNT = U.objectFieldOffset
3312		(k.getDeclaredField("stealCount"));
3313	<	MAINLOCK = U.objectFieldOffset
3314	<	(k.getDeclaredField("mainLock"));
3313	>	PLOCK = U.objectFieldOffset
3314	>	(k.getDeclaredField("plock"));
3315	>	INDEXSEED = U.objectFieldOffset
3316	>	(k.getDeclaredField("indexSeed"));
3317		Class<?> tk = Thread.class;
3318		PARKBLOCKER = U.objectFieldOffset
3319		(tk.getDeclaredField("parkBlocker"));
3320	+	Class<?> wk = WorkQueue.class;
3321	+	QLOCK = U.objectFieldOffset
3322	+	(wk.getDeclaredField("qlock"));
3323	+	Class<?> ak = ForkJoinTask[].class;
3324		ABASE = U.arrayBaseOffset(ak);
3325		s = U.arrayIndexScale(ak);
3326		ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
#	Line 3049 \| Line 3329 \| public class ForkJoinPool extends Abstra
3329		}
3330		if ((s & (s-1)) != 0)
3331		throw new Error("data type scale not a power of two");
3332	<	try { // Establish common pool
3333	<	String pp = System.getProperty(propPrefix + "parallelism");
3334	<	String fp = System.getProperty(propPrefix + "threadFactory");
3335	<	String up = System.getProperty(propPrefix + "exceptionHandler");
3336	<	ForkJoinWorkerThreadFactory fac = (fp == null) ?
3337	<	defaultForkJoinWorkerThreadFactory :
3338	<	((ForkJoinWorkerThreadFactory)ClassLoader.
3339	<	getSystemClassLoader().loadClass(fp).newInstance());
3340	<	Thread.UncaughtExceptionHandler ueh = (up == null)? null :
3341	<	((Thread.UncaughtExceptionHandler)ClassLoader.
3342	<	getSystemClassLoader().loadClass(up).newInstance());
3343	<	int par;
3344	<	if ((pp == null \|\| (par = Integer.parseInt(pp)) <= 0))
3345	<	par = Runtime.getRuntime().availableProcessors();
3346	<	if (par > MAX_CAP)
3347	<	par = MAX_CAP;
3348	<	commonPoolParallelism = par;
3349	<	int n = par - 1; // precompute submit mask
3350	<	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4;
3351	<	n \|= n >>> 8; n \|= n >>> 16;
3352	<	int mask = ((n + 1) << 1) - 1;
3353	<	commonPool = new ForkJoinPool(par, mask, fac, ueh);
3354	<	} catch (Exception e) {
3355	<	throw new Error(e);
3356	<	}
3332	>
3333	>	submitters = new ThreadLocal<Submitter>();
3334	>	ForkJoinWorkerThreadFactory fac = defaultForkJoinWorkerThreadFactory =
3335	>	new DefaultForkJoinWorkerThreadFactory();
3336	>	modifyThreadPermission = new RuntimePermission("modifyThread");
3337	>
3338	>	/*
3339	>	* Establish common pool parameters. For extra caution,
3340	>	* computations to set up common pool state are here; the
3341	>	* constructor just assigns these values to fields.
3342	>	*/
3343	>
3344	>	int par = 0;
3345	>	Thread.UncaughtExceptionHandler handler = null;
3346	>	try { // TBD: limit or report ignored exceptions?
3347	>	String pp = System.getProperty
3348	>	("java.util.concurrent.ForkJoinPool.common.parallelism");
3349	>	String hp = System.getProperty
3350	>	("java.util.concurrent.ForkJoinPool.common.exceptionHandler");
3351	>	String fp = System.getProperty
3352	>	("java.util.concurrent.ForkJoinPool.common.threadFactory");
3353	>	if (fp != null)
3354	>	fac = ((ForkJoinWorkerThreadFactory)ClassLoader.
3355	>	getSystemClassLoader().loadClass(fp).newInstance());
3356	>	if (hp != null)
3357	>	handler = ((Thread.UncaughtExceptionHandler)ClassLoader.
3358	>	getSystemClassLoader().loadClass(hp).newInstance());
3359	>	if (pp != null)
3360	>	par = Integer.parseInt(pp);
3361	>	} catch (Exception ignore) {
3362	>	}
3363	>
3364	>	if (par <= 0)
3365	>	par = Runtime.getRuntime().availableProcessors();
3366	>	if (par > MAX_CAP)
3367	>	par = MAX_CAP;
3368	>	commonPoolParallelism = par;
3369	>	long np = (long)(-par); // precompute initial ctl value
3370	>	long ct = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
3371	>
3372	>	commonPool = new ForkJoinPool(par, ct, fac, handler);
3373		}
3374
3375		/**

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Comparing jsr166/src/jsr166e/ForkJoinPool.java (file contents): Revision 1.8 by dl, Mon Oct 29 17:23:26 2012 UTC vs. Revision 1.27 by jsr166, Sat Dec 8 20:49:24 2012 UTC

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Comparing jsr166/src/jsr166e/ForkJoinPool.java (file contents):
Revision 1.8 by dl, Mon Oct 29 17:23:26 2012 UTC vs.
Revision 1.27 by jsr166, Sat Dec 8 20:49:24 2012 UTC