[ViewVC] Diff of: jsr166/jsr166/src/jsr166y/ForkJoinPool.java

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.122 by jsr166, Tue Jan 31 01:51:13 2012 UTC vs.
Revision 1.139 by dl, Wed Oct 31 12:49:24 2012 UTC

#	Line 42 \| Line 42 \| import java.util.concurrent.locks.Condit
42		* ForkJoinPool}s may also be appropriate for use with event-style
43		* tasks that are never joined.
44		*
45	<	* <p>A {@code ForkJoinPool} is constructed with a given target
46	<	* parallelism level; by default, equal to the number of available
47	<	* processors. The pool attempts to maintain enough active (or
48	<	* available) threads by dynamically adding, suspending, or resuming
49	<	* internal worker threads, even if some tasks are stalled waiting to
50	<	* join others. However, no such adjustments are guaranteed in the
51	<	* face of blocked IO or other unmanaged synchronization. The nested
52	<	* {@link ManagedBlocker} interface enables extension of the kinds of
45	>	* <p>A static {@link #commonPool} is available and appropriate for
46	>	* most applications. The common pool is used by any ForkJoinTask that
47	>	* is not explicitly submitted to a specified pool. Using the common
48	>	* pool normally reduces resource usage (its threads are slowly
49	>	* reclaimed during periods of non-use, and reinstated upon subsequent
50	>	* use). The common pool is by default constructed with default
51	>	* parameters, but these may be controlled by setting any or all of
52	>	* the three properties {@code
53	>	* java.util.concurrent.ForkJoinPool.common.{parallelism,
54	>	* threadFactory, exceptionHandler}}.
55	>	*
56	>	* <p>For applications that require separate or custom pools, a {@code
57	>	* ForkJoinPool} may be constructed with a given target parallelism
58	>	* level; by default, equal to the number of available processors. The
59	>	* pool attempts to maintain enough active (or available) threads by
60	>	* dynamically adding, suspending, or resuming internal worker
61	>	* threads, even if some tasks are stalled waiting to join
62	>	* others. However, no such adjustments are guaranteed in the face of
63	>	* blocked IO or other unmanaged synchronization. The nested {@link
64	>	* ManagedBlocker} interface enables extension of the kinds of
65		* synchronization accommodated.
66		*
67		* <p>In addition to execution and lifecycle control methods, this
#	Line 94 \| Line 106 \| import java.util.concurrent.locks.Condit
106		* </tr>
107		* </table>
108		*
97	–	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
98	–	* used for all parallel task execution in a program or subsystem.
99	–	* Otherwise, use would not usually outweigh the construction and
100	–	* bookkeeping overhead of creating a large set of threads. For
101	–	* example, a common pool could be used for the {@code SortTasks}
102	–	* illustrated in {@link RecursiveAction}. Because {@code
103	–	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
104	–	* daemon} mode, there is typically no need to explicitly {@link
105	–	* #shutdown} such a pool upon program exit.
106	–	*
107	–	* <pre> {@code
108	–	* static final ForkJoinPool mainPool = new ForkJoinPool();
109	–	* ...
110	–	* public void sort(long[] array) {
111	–	* mainPool.invoke(new SortTask(array, 0, array.length));
112	–	* }}</pre>
113	–	*
109		* <p><b>Implementation notes</b>: This implementation restricts the
110		* maximum number of running threads to 32767. Attempts to create
111		* pools with greater than the maximum number result in
#	Line 177 \| Line 172 \| public class ForkJoinPool extends Abstra
172		* If an attempted steal fails, a thief always chooses a different
173		* random victim target to try next. So, in order for one thief to
174		* progress, it suffices for any in-progress poll or new push on
175	<	* any empty queue to complete.
175	>	* any empty queue to complete. (This is why we normally use
176	>	* method pollAt and its variants that try once at the apparent
177	>	* base index, else consider alternative actions, rather than
178	>	* method poll.)
179		*
180		* This approach also enables support of a user mode in which local
181		* task processing is in FIFO, not LIFO order, simply by using
#	Line 207 \| Line 205 \| public class ForkJoinPool extends Abstra
205		* lock (mainly to protect in the case of resizing) but we use
206		* only a simple spinlock (using bits in field runState), because
207		* submitters encountering a busy queue move on to try or create
208	<	* other queues, so never block.
208	>	* other queues -- they block only when creating and registering
209	>	* new queues.
210		*
211		* Management
212		* ==========
#	Line 233 \| Line 232 \| public class ForkJoinPool extends Abstra
232		* deregister WorkQueues, as well as to enable shutdown. It is
233		* only modified under a lock (normally briefly held, but
234		* occasionally protecting allocations and resizings) but even
235	<	* when locked remains available to check consistency. An
237	<	* auxiliary field "growHints", also only modified under lock,
238	<	* contains a candidate index for the next WorkQueue and
239	<	* a mask for submission queue indices.
235	>	* when locked remains available to check consistency.
236		*
237		* Recording WorkQueues. WorkQueues are recorded in the
238	<	* "workQueues" array that is created upon pool construction and
239	<	* expanded if necessary. Updates to the array while recording
240	<	* new workers and unrecording terminated ones are protected from
241	<	* each other by a lock but the array is otherwise concurrently
242	<	* readable, and accessed directly. To simplify index-based
243	<	* operations, the array size is always a power of two, and all
244	<	* readers must tolerate null slots. Shared (submission) queues
245	<	* are at even indices, worker queues at odd indices. Grouping
246	<	* them together in this way simplifies and speeds up task
251	<	* scanning. To avoid flailing during start-up, the array is
252	<	* presized to hold twice #parallelism workers (which is unlikely
253	<	* to need further resizing during execution). But to avoid
254	<	* dealing with so many null slots, variable runState includes a
255	<	* mask for the nearest power of two that contains all currently
256	<	* used indices.
238	>	* "workQueues" array that is created upon first use and expanded
239	>	* if necessary. Updates to the array while recording new workers
240	>	* and unrecording terminated ones are protected from each other
241	>	* by a lock but the array is otherwise concurrently readable, and
242	>	* accessed directly. To simplify index-based operations, the
243	>	* array size is always a power of two, and all readers must
244	>	* tolerate null slots. Shared (submission) queues are at even
245	>	* indices, worker queues at odd indices. Grouping them together
246	>	* in this way simplifies and speeds up task scanning.
247		*
248		* All worker thread creation is on-demand, triggered by task
249		* submissions, replacement of terminated workers, and/or
#	Line 325 \| Line 315 \| public class ForkJoinPool extends Abstra
315		*
316		* Trimming workers. To release resources after periods of lack of
317		* use, a worker starting to wait when the pool is quiescent will
318	<	* time out and terminate if the pool has remained quiescent for
319	<	* SHRINK_RATE nanosecs. This will slowly propagate, eventually
320	<	* terminating all workers after long periods of non-use.
318	>	* time out and terminate if the pool has remained quiescent for a
319	>	* given period -- a short period if there are more threads than
320	>	* parallelism, longer as the number of threads decreases. This
321	>	* will slowly propagate, eventually terminating all workers after
322	>	* periods of non-use.
323		*
324		* Shutdown and Termination. A call to shutdownNow atomically sets
325		* a runState bit and then (non-atomically) sets each worker's
#	Line 385 \| Line 377 \| public class ForkJoinPool extends Abstra
377		* (http://portal.acm.org/citation.cfm?id=155354). It differs in
378		* that: (1) We only maintain dependency links across workers upon
379		* steals, rather than use per-task bookkeeping. This sometimes
380	<	* requires a linear scan of workQueues array to locate stealers, but
381	<	* often doesn't because stealers leave hints (that may become
380	>	* requires a linear scan of workQueues array to locate stealers,
381	>	* but often doesn't because stealers leave hints (that may become
382		* stale/wrong) of where to locate them. A stealHint is only a
383		* hint because a worker might have had multiple steals and the
384		* hint records only one of them (usually the most current).
#	Line 397 \| Line 389 \| public class ForkJoinPool extends Abstra
389		* which means that we miss links in the chain during long-lived
390		* tasks, GC stalls etc (which is OK since blocking in such cases
391		* is usually a good idea). (4) We bound the number of attempts
392	<	* to find work (see MAX_HELP_DEPTH) and fall back to suspending
393	<	* the worker and if necessary replacing it with another.
392	>	* to find work (see MAX_HELP) and fall back to suspending the
393	>	* worker and if necessary replacing it with another.
394		*
395		* It is impossible to keep exactly the target parallelism number
396		* of threads running at any given time. Determining the
397		* existence of conservatively safe helping targets, the
398		* availability of already-created spares, and the apparent need
399		* to create new spares are all racy, so we rely on multiple
400	<	* retries of each. Currently, in keeping with on-demand
401	<	* signalling policy, we compensate only if blocking would leave
402	<	* less than one active (non-waiting, non-blocked) worker.
403	<	* Additionally, to avoid some false alarms due to GC, lagging
404	<	* counters, system activity, etc, compensated blocking for joins
405	<	* is only attempted after rechecks stabilize in
406	<	* ForkJoinTask.awaitJoin. (Retries are interspersed with
407	<	* Thread.yield, for good citizenship.)
400	>	* retries of each. Compensation in the apparent absence of
401	>	* helping opportunities is challenging to control on JVMs, where
402	>	* GC and other activities can stall progress of tasks that in
403	>	* turn stall out many other dependent tasks, without us being
404	>	* able to determine whether they will ever require compensation.
405	>	* Even though work-stealing otherwise encounters little
406	>	* degradation in the presence of more threads than cores,
407	>	* aggressively adding new threads in such cases entails risk of
408	>	* unwanted positive feedback control loops in which more threads
409	>	* cause more dependent stalls (as well as delayed progress of
410	>	* unblocked threads to the point that we know they are available)
411	>	* leading to more situations requiring more threads, and so
412	>	* on. This aspect of control can be seen as an (analytically
413	>	* intractable) game with an opponent that may choose the worst
414	>	* (for us) active thread to stall at any time. We take several
415	>	* precautions to bound losses (and thus bound gains), mainly in
416	>	* methods tryCompensate and awaitJoin: (1) We only try
417	>	* compensation after attempting enough helping steps (measured
418	>	* via counting and timing) that we have already consumed the
419	>	* estimated cost of creating and activating a new thread. (2) We
420	>	* allow up to 50% of threads to be blocked before initially
421	>	* adding any others, and unless completely saturated, check that
422	>	* some work is available for a new worker before adding. Also, we
423	>	* create up to only 50% more threads until entering a mode that
424	>	* only adds a thread if all others are possibly blocked. All
425	>	* together, this means that we might be half as fast to react,
426	>	* and create half as many threads as possible in the ideal case,
427	>	* but present vastly fewer anomalies in all other cases compared
428	>	* to both more aggressive and more conservative alternatives.
429		*
430		* Style notes: There is a lot of representation-level coupling
431		* among classes ForkJoinPool, ForkJoinWorkerThread, and
#	Line 449 \| Line 462 \| public class ForkJoinPool extends Abstra
462		// Static utilities
463
464		/**
452	–	* Computes an initial hash code (also serving as a non-zero
453	–	* random seed) for a thread id. This method is expected to
454	–	* provide higher-quality hash codes than using method hashCode().
455	–	*/
456	–	static final int hashId(long id) {
457	–	int h = (int)id ^ (int)(id >>> 32); // Use MurmurHash of thread id
458	–	h ^= h >>> 16; h *= 0x85ebca6b;
459	–	h ^= h >>> 13; h *= 0xc2b2ae35;
460	–	h ^= h >>> 16;
461	–	return (h == 0) ? 1 : h; // ensure nonzero
462	–	}
463	–
464	–	/**
465		* If there is a security manager, makes sure caller has
466		* permission to modify threads.
467		*/
#	Line 501 \| Line 501 \| public class ForkJoinPool extends Abstra
501		}
502
503		/**
504	–	* A simple non-reentrant lock used for exclusion when managing
505	–	* queues and workers. We use a custom lock so that we can readily
506	–	* probe lock state in constructions that check among alternative
507	–	* actions. The lock is normally only very briefly held, and
508	–	* sometimes treated as a spinlock, but other usages block to
509	–	* reduce overall contention in those cases where locked code
510	–	* bodies perform allocation/resizing.
511	–	*/
512	–	static final class Mutex extends AbstractQueuedSynchronizer {
513	–	public final boolean tryAcquire(int ignore) {
514	–	return compareAndSetState(0, 1);
515	–	}
516	–	public final boolean tryRelease(int ignore) {
517	–	setState(0);
518	–	return true;
519	–	}
520	–	public final void lock() { acquire(0); }
521	–	public final void unlock() { release(0); }
522	–	public final boolean isHeldExclusively() { return getState() == 1; }
523	–	public final Condition newCondition() { return new ConditionObject(); }
524	–	}
525	–
526	–	/**
504		* Class for artificial tasks that are used to replace the target
505		* of local joins if they are removed from an interior queue slot
506		* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
#	Line 592 \| Line 569 \| public class ForkJoinPool extends Abstra
569		static final class WorkQueue {
570		/**
571		* Capacity of work-stealing queue array upon initialization.
572	<	* Must be a power of two; at least 4, but set larger to
573	<	* reduce cacheline sharing among queues.
572	>	* Must be a power of two; at least 4, but should be larger to
573	>	* reduce or eliminate cacheline sharing among queues.
574	>	* Currently, it is much larger, as a partial workaround for
575	>	* the fact that JVMs often place arrays in locations that
576	>	* share GC bookkeeping (especially cardmarks) such that
577	>	* per-write accesses encounter serious memory contention.
578		*/
579	<	static final int INITIAL_QUEUE_CAPACITY = 1 << 8;
579	>	static final int INITIAL_QUEUE_CAPACITY = 1 << 13;
580
581		/**
582		* Maximum size for queue arrays. Must be a power of two less
#	Line 619 \| Line 600 \| public class ForkJoinPool extends Abstra
600		volatile int base; // index of next slot for poll
601		int top; // index of next slot for push
602		ForkJoinTask<?>[] array; // the elements (initially unallocated)
603	+	final ForkJoinPool pool; // the containing pool (may be null)
604		final ForkJoinWorkerThread owner; // owning thread or null if shared
605		volatile Thread parker; // == owner during call to park; else null
606	<	ForkJoinTask<?> currentJoin; // task being joined in awaitJoin
606	>	volatile ForkJoinTask<?> currentJoin; // task being joined in awaitJoin
607		ForkJoinTask<?> currentSteal; // current non-local task being executed
608		// Heuristic padding to ameliorate unfortunate memory placements
609	<	Object p00, p01, p02, p03, p04, p05, p06, p07, p08, p09, p0a;
609	>	Object p00, p01, p02, p03, p04, p05, p06, p07;
610	>	Object p08, p09, p0a, p0b, p0c, p0d, p0e;
611
612	<	WorkQueue(ForkJoinWorkerThread owner, int mode) {
630	<	this.owner = owner;
612	>	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode) {
613		this.mode = mode;
614	+	this.pool = pool;
615	+	this.owner = owner;
616		// Place indices in the center of array (that is not yet allocated)
617		base = top = INITIAL_QUEUE_CAPACITY >>> 1;
618		}
619
620		/**
621	<	* Returns number of tasks in the queue.
621	>	* Returns the approximate number of tasks in the queue.
622		*/
623		final int queueSize() {
624	<	int n = base - top; // non-owner callers must read base first
625	<	return (n >= 0) ? 0 : -n;
624	>	int n = base - top; // non-owner callers must read base first
625	>	return (n >= 0) ? 0 : -n; // ignore transient negative
626	>	}
627	>
628	>	/**
629	>	* Provides a more accurate estimate of whether this queue has
630	>	* any tasks than does queueSize, by checking whether a
631	>	* near-empty queue has at least one unclaimed task.
632	>	*/
633	>	final boolean isEmpty() {
634	>	ForkJoinTask<?>[] a; int m, s;
635	>	int n = base - (s = top);
636	>	return (n >= 0 \|\|
637	>	(n == -1 &&
638	>	((a = array) == null \|\|
639	>	(m = a.length - 1) < 0 \|\|
640	>	U.getObjectVolatile
641	>	(a, ((m & (s - 1)) << ASHIFT) + ABASE) == null)));
642		}
643
644		/**
645		* Pushes a task. Call only by owner in unshared queues.
646		*
647		* @param task the task. Caller must ensure non-null.
648	–	* @param p if non-null, pool to signal if necessary
648		* @throw RejectedExecutionException if array cannot be resized
649		*/
650	<	final void push(ForkJoinTask<?> task, ForkJoinPool p) {
651	<	ForkJoinTask<?>[] a;
650	>	final void push(ForkJoinTask<?> task) {
651	>	ForkJoinTask<?>[] a; ForkJoinPool p;
652		int s = top, m, n;
653		if ((a = array) != null) { // ignore if queue removed
654		U.putOrderedObject
655		(a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task);
656		if ((n = (top = s + 1) - base) <= 2) {
657	<	if (p != null)
657	>	if ((p = pool) != null)
658		p.signalWork();
659		}
660		else if (n >= m)
#	Line 691 \| Line 690 \| public class ForkJoinPool extends Abstra
690		}
691
692		/**
693	<	* Takes next task, if one exists, in FIFO order.
693	>	* Takes next task, if one exists, in LIFO order. Call only
694	>	* by owner in unshared queues.
695		*/
696	<	final ForkJoinTask<?> poll() {
697	<	ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t;
698	<	while ((b = base) - top < 0 && (a = array) != null) {
696	>	final ForkJoinTask<?> pop() {
697	>	ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
698	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
699	>	for (int s; (s = top - 1) - base >= 0;) {
700	>	long j = ((m & s) << ASHIFT) + ABASE;
701	>	if ((t = (ForkJoinTask<?>)U.getObject(a, j)) == null)
702	>	break;
703	>	if (U.compareAndSwapObject(a, j, t, null)) {
704	>	top = s;
705	>	return t;
706	>	}
707	>	}
708	>	}
709	>	return null;
710	>	}
711	>
712	>	final ForkJoinTask<?> sharedPop() {
713	>	ForkJoinTask<?> task = null;
714	>	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
715	>	try {
716	>	ForkJoinTask<?>[] a; int m;
717	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
718	>	for (int s; (s = top - 1) - base >= 0;) {
719	>	long j = ((m & s) << ASHIFT) + ABASE;
720	>	ForkJoinTask<?> t =
721	>	(ForkJoinTask<?>)U.getObject(a, j);
722	>	if (t == null)
723	>	break;
724	>	if (U.compareAndSwapObject(a, j, t, null)) {
725	>	top = s;
726	>	task = t;
727	>	break;
728	>	}
729	>	}
730	>	}
731	>	} finally {
732	>	runState = 0;
733	>	}
734	>	}
735	>	return task;
736	>	}
737	>
738	>
739	>	/**
740	>	* Takes a task in FIFO order if b is base of queue and a task
741	>	* can be claimed without contention. Specialized versions
742	>	* appear in ForkJoinPool methods scan and tryHelpStealer.
743	>	*/
744	>	final ForkJoinTask<?> pollAt(int b) {
745	>	ForkJoinTask<?> t; ForkJoinTask<?>[] a;
746	>	if ((a = array) != null) {
747		int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
748		if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
749		base == b &&
#	Line 708 \| Line 756 \| public class ForkJoinPool extends Abstra
756		}
757
758		/**
759	<	* Takes next task, if one exists, in LIFO order. Call only
712	<	* by owner in unshared queues. (We do not have a shared
713	<	* version of this method because it is never needed.)
759	>	* Takes next task, if one exists, in FIFO order.
760		*/
761	<	final ForkJoinTask<?> pop() {
762	<	ForkJoinTask<?> t; int m;
763	<	ForkJoinTask<?>[] a = array;
764	<	if (a != null && (m = a.length - 1) >= 0) {
765	<	for (int s; (s = top - 1) - base >= 0;) {
766	<	int j = ((m & s) << ASHIFT) + ABASE;
767	<	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) == null)
768	<	break;
769	<	if (U.compareAndSwapObject(a, j, t, null)) {
724	<	top = s;
761	>	final ForkJoinTask<?> poll() {
762	>	ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t;
763	>	while ((b = base) - top < 0 && (a = array) != null) {
764	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
765	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
766	>	if (t != null) {
767	>	if (base == b &&
768	>	U.compareAndSwapObject(a, j, t, null)) {
769	>	base = b + 1;
770		return t;
771		}
772		}
773	+	else if (base == b) {
774	+	if (b + 1 == top)
775	+	break;
776	+	Thread.yield(); // wait for lagging update
777	+	}
778		}
779		return null;
780		}
#	Line 749 \| Line 799 \| public class ForkJoinPool extends Abstra
799		}
800
801		/**
752	–	* Returns task at index b if b is current base of queue.
753	–	*/
754	–	final ForkJoinTask<?> pollAt(int b) {
755	–	ForkJoinTask<?> t; ForkJoinTask<?>[] a;
756	–	if ((a = array) != null) {
757	–	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
758	–	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
759	–	base == b &&
760	–	U.compareAndSwapObject(a, j, t, null)) {
761	–	base = b + 1;
762	–	return t;
763	–	}
764	–	}
765	–	return null;
766	–	}
767	–
768	–	/**
802		* Pops the given task only if it is at the current top.
803		*/
804		final boolean tryUnpush(ForkJoinTask<?> t) {
#	Line 780 \| Line 813 \| public class ForkJoinPool extends Abstra
813		}
814
815		/**
816	+	* Version of tryUnpush for shared queues; called by non-FJ
817	+	* submitters after prechecking that task probably exists.
818	+	*/
819	+	final boolean trySharedUnpush(ForkJoinTask<?> t) {
820	+	boolean success = false;
821	+	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
822	+	try {
823	+	ForkJoinTask<?>[] a; int s;
824	+	if ((a = array) != null && (s = top) != base &&
825	+	U.compareAndSwapObject
826	+	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
827	+	top = s;
828	+	success = true;
829	+	}
830	+	} finally {
831	+	runState = 0; // unlock
832	+	}
833	+	}
834	+	return success;
835	+	}
836	+
837	+	/**
838		* Polls the given task only if it is at the current base.
839		*/
840		final boolean pollFor(ForkJoinTask<?> task) {
#	Line 796 \| Line 851 \| public class ForkJoinPool extends Abstra
851		}
852
853		/**
799	–	* If present, removes from queue and executes the given task, or
800	–	* any other cancelled task. Returns (true) immediately on any CAS
801	–	* or consistency check failure so caller can retry.
802	–	*
803	–	* @return false if no progress can be made
804	–	*/
805	–	final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
806	–	boolean removed = false, empty = true, progress = true;
807	–	ForkJoinTask<?>[] a; int m, s, b, n;
808	–	if ((a = array) != null && (m = a.length - 1) >= 0 &&
809	–	(n = (s = top) - (b = base)) > 0) {
810	–	for (ForkJoinTask<?> t;;) { // traverse from s to b
811	–	int j = ((--s & m) << ASHIFT) + ABASE;
812	–	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
813	–	if (t == null) // inconsistent length
814	–	break;
815	–	else if (t == task) {
816	–	if (s + 1 == top) { // pop
817	–	if (!U.compareAndSwapObject(a, j, task, null))
818	–	break;
819	–	top = s;
820	–	removed = true;
821	–	}
822	–	else if (base == b) // replace with proxy
823	–	removed = U.compareAndSwapObject(a, j, task,
824	–	new EmptyTask());
825	–	break;
826	–	}
827	–	else if (t.status >= 0)
828	–	empty = false;
829	–	else if (s + 1 == top) { // pop and throw away
830	–	if (U.compareAndSwapObject(a, j, t, null))
831	–	top = s;
832	–	break;
833	–	}
834	–	if (--n == 0) {
835	–	if (!empty && base == b)
836	–	progress = false;
837	–	break;
838	–	}
839	–	}
840	–	}
841	–	if (removed)
842	–	task.doExec();
843	–	return progress;
844	–	}
845	–
846	–	/**
854		* Initializes or doubles the capacity of array. Call either
855		* by owner or with lock held -- it is OK for base, but not
856		* top, to move while resizings are in progress.
#	Line 892 \| Line 899 \| public class ForkJoinPool extends Abstra
899		* Computes next value for random probes. Scans don't require
900		* a very high quality generator, but also not a crummy one.
901		* Marsaglia xor-shift is cheap and works well enough. Note:
902	<	* This is manually inlined in several usages in ForkJoinPool
903	<	* to avoid writes inside busy scan loops.
902	>	* This is manually inlined in its usages in ForkJoinPool to
903	>	* avoid writes inside busy scan loops.
904		*/
905		final int nextSeed() {
906		int r = seed;
#	Line 902 \| Line 909 \| public class ForkJoinPool extends Abstra
909		return seed = r ^= r << 5;
910		}
911
912	<	// Execution methods
912	>	// Specialized execution methods
913
914		/**
915	<	* Removes and runs tasks until empty, using local mode
909	<	* ordering.
915	>	* Pops and runs tasks until empty.
916		*/
917	<	final void runLocalTasks() {
918	<	if (base - top < 0) {
919	<	for (ForkJoinTask<?> t; (t = nextLocalTask()) != null; )
917	>	private void popAndExecAll() {
918	>	// A bit faster than repeated pop calls
919	>	ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t;
920	>	while ((a = array) != null && (m = a.length - 1) >= 0 &&
921	>	(s = top - 1) - base >= 0 &&
922	>	(t = ((ForkJoinTask<?>)
923	>	U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
924	>	!= null) {
925	>	if (U.compareAndSwapObject(a, j, t, null)) {
926	>	top = s;
927		t.doExec();
928	+	}
929		}
930		}
931
932		/**
933	+	* Polls and runs tasks until empty.
934	+	*/
935	+	private void pollAndExecAll() {
936	+	for (ForkJoinTask<?> t; (t = poll()) != null;)
937	+	t.doExec();
938	+	}
939	+
940	+	/**
941	+	* If present, removes from queue and executes the given task, or
942	+	* any other cancelled task. Returns (true) immediately on any CAS
943	+	* or consistency check failure so caller can retry.
944	+	*
945	+	* @return 0 if no progress can be made, else positive
946	+	* (this unusual convention simplifies use with tryHelpStealer.)
947	+	*/
948	+	final int tryRemoveAndExec(ForkJoinTask<?> task) {
949	+	int stat = 1;
950	+	boolean removed = false, empty = true;
951	+	ForkJoinTask<?>[] a; int m, s, b, n;
952	+	if ((a = array) != null && (m = a.length - 1) >= 0 &&
953	+	(n = (s = top) - (b = base)) > 0) {
954	+	for (ForkJoinTask<?> t;;) { // traverse from s to b
955	+	int j = ((--s & m) << ASHIFT) + ABASE;
956	+	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
957	+	if (t == null) // inconsistent length
958	+	break;
959	+	else if (t == task) {
960	+	if (s + 1 == top) { // pop
961	+	if (!U.compareAndSwapObject(a, j, task, null))
962	+	break;
963	+	top = s;
964	+	removed = true;
965	+	}
966	+	else if (base == b) // replace with proxy
967	+	removed = U.compareAndSwapObject(a, j, task,
968	+	new EmptyTask());
969	+	break;
970	+	}
971	+	else if (t.status >= 0)
972	+	empty = false;
973	+	else if (s + 1 == top) { // pop and throw away
974	+	if (U.compareAndSwapObject(a, j, t, null))
975	+	top = s;
976	+	break;
977	+	}
978	+	if (--n == 0) {
979	+	if (!empty && base == b)
980	+	stat = 0;
981	+	break;
982	+	}
983	+	}
984	+	}
985	+	if (removed)
986	+	task.doExec();
987	+	return stat;
988	+	}
989	+
990	+	/**
991	+	* Version of shared pop that takes top element only if it
992	+	* its root is the given CountedCompleter.
993	+	*/
994	+	final CountedCompleter<?> sharedPopCC(CountedCompleter<?> root) {
995	+	CountedCompleter<?> task = null;
996	+	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
997	+	try {
998	+	ForkJoinTask<?>[] a; int m;
999	+	if ((a = array) != null && (m = a.length - 1) >= 0) {
1000	+	outer:for (int s; (s = top - 1) - base >= 0;) {
1001	+	long j = ((m & s) << ASHIFT) + ABASE;
1002	+	ForkJoinTask<?> t =
1003	+	(ForkJoinTask<?>)U.getObject(a, j);
1004	+	if (t == null \|\| !(t instanceof CountedCompleter))
1005	+	break;
1006	+	CountedCompleter<?> cc = (CountedCompleter<?>)t;
1007	+	for (CountedCompleter<?> q = cc, p;;) {
1008	+	if (q == root) {
1009	+	if (U.compareAndSwapObject(a, j, cc, null)) {
1010	+	top = s;
1011	+	task = cc;
1012	+	break outer;
1013	+	}
1014	+	break;
1015	+	}
1016	+	if ((p = q.completer) == null)
1017	+	break outer;
1018	+	q = p;
1019	+	}
1020	+	}
1021	+	}
1022	+	} finally {
1023	+	runState = 0;
1024	+	}
1025	+	}
1026	+	return task;
1027	+	}
1028	+
1029	+	/**
1030		* Executes a top-level task and any local tasks remaining
1031		* after execution.
921	–	*
922	–	* @return true unless terminating
1032		*/
1033	<	final boolean runTask(ForkJoinTask<?> t) {
925	<	boolean alive = true;
1033	>	final void runTask(ForkJoinTask<?> t) {
1034		if (t != null) {
1035		currentSteal = t;
1036		t.doExec();
1037	<	runLocalTasks();
1037	>	if (top != base) { // process remaining local tasks
1038	>	if (mode == 0)
1039	>	popAndExecAll();
1040	>	else
1041	>	pollAndExecAll();
1042	>	}
1043		++nsteals;
1044		currentSteal = null;
1045		}
933	–	else if (runState < 0) // terminating
934	–	alive = false;
935	–	return alive;
1046		}
1047
1048		/**
#	Line 1005 \| Line 1115 \| public class ForkJoinPool extends Abstra
1115		* submission queues in method doSubmit. In the future, this may
1116		* also incorporate a means to implement different task rejection
1117		* and resubmission policies.
1118	+	*
1119	+	* Seeds for submitters and workers/workQueues work in basically
1120	+	* the same way but are initialized and updated using slightly
1121	+	* different mechanics. Both are initialized using the same
1122	+	* approach as in class ThreadLocal, where successive values are
1123	+	* unlikely to collide with previous values. This is done during
1124	+	* registration for workers, but requires a separate AtomicInteger
1125	+	* for submitters. Seeds are then randomly modified upon
1126	+	* collisions using xorshifts, which requires a non-zero seed.
1127		*/
1128		static final class Submitter {
1129		int seed;
1130	<	Submitter() { seed = hashId(Thread.currentThread().getId()); }
1130	>	Submitter() {
1131	>	int s = nextSubmitterSeed.getAndAdd(SEED_INCREMENT);
1132	>	seed = (s == 0) ? 1 : s; // ensure non-zero
1133	>	}
1134		}
1135
1136		/** ThreadLocal class for Submitters */
#	Line 1025 \| Line 1147 \| public class ForkJoinPool extends Abstra
1147		public static final ForkJoinWorkerThreadFactory
1148		defaultForkJoinWorkerThreadFactory;
1149
1150	+	/** Property prefix for constructing common pool */
1151	+	private static final String propPrefix =
1152	+	"java.util.concurrent.ForkJoinPool.common.";
1153	+
1154	+	/**
1155	+	* Common (static) pool. Non-null for public use unless a static
1156	+	* construction exception, but internal usages must null-check on
1157	+	* use.
1158	+	*/
1159	+	static final ForkJoinPool commonPool;
1160	+
1161	+	/**
1162	+	* Common pool parallelism. Must equal commonPool.parallelism.
1163	+	*/
1164	+	static final int commonPoolParallelism;
1165	+
1166		/**
1167		* Generator for assigning sequence numbers as pool names.
1168		*/
1169		private static final AtomicInteger poolNumberGenerator;
1170
1171		/**
1172	+	* Generator for initial hashes/seeds for submitters. Accessed by
1173	+	* Submitter class constructor.
1174	+	*/
1175	+	static final AtomicInteger nextSubmitterSeed;
1176	+
1177	+	/**
1178		* Permission required for callers of methods that may start or
1179		* kill threads.
1180		*/
1181		private static final RuntimePermission modifyThreadPermission;
1182
1183		/**
1184	<	* Per-thread submission bookeeping. Shared across all pools
1184	>	* Per-thread submission bookkeeping. Shared across all pools
1185		* to reduce ThreadLocal pollution and because random motion
1186		* to avoid contention in one pool is likely to hold for others.
1187		*/
#	Line 1046 \| Line 1190 \| public class ForkJoinPool extends Abstra
1190		// static constants
1191
1192		/**
1193	<	* The wakeup interval (in nanoseconds) for a worker waiting for a
1194	<	* task when the pool is quiescent to instead try to shrink the
1195	<	* number of workers. The exact value does not matter too
1052	<	* much. It must be short enough to release resources during
1053	<	* sustained periods of idleness, but not so short that threads
1054	<	* are continually re-created.
1193	>	* Initial timeout value (in nanoseconds) for the thread triggering
1194	>	* quiescence to park waiting for new work. On timeout, the thread
1195	>	* will instead try to shrink the number of workers.
1196		*/
1197	<	private static final long SHRINK_RATE =
1057	<	4L * 1000L * 1000L * 1000L; // 4 seconds
1197	>	private static final long IDLE_TIMEOUT = 1000L * 1000L * 1000L; // 1sec
1198
1199		/**
1200	<	* The timeout value for attempted shrinkage, includes
1061	<	* some slop to cope with system timer imprecision.
1200	>	* Timeout value when there are more threads than parallelism level
1201		*/
1202	<	private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
1202	>	private static final long FAST_IDLE_TIMEOUT = 100L * 1000L * 1000L;
1203
1204		/**
1205	<	* The maximum stolen->joining link depth allowed in tryHelpStealer.
1206	<	* Depths for legitimate chains are unbounded, but we use a fixed
1207	<	* constant to avoid (otherwise unchecked) cycles and to bound
1208	<	* staleness of traversal parameters at the expense of sometimes
1209	<	* blocking when we could be helping.
1205	>	* The maximum stolen->joining link depth allowed in method
1206	>	* tryHelpStealer. Must be a power of two. This value also
1207	>	* controls the maximum number of times to try to help join a task
1208	>	* without any apparent progress or change in pool state before
1209	>	* giving up and blocking (see awaitJoin). Depths for legitimate
1210	>	* chains are unbounded, but we use a fixed constant to avoid
1211	>	* (otherwise unchecked) cycles and to bound staleness of
1212	>	* traversal parameters at the expense of sometimes blocking when
1213	>	* we could be helping.
1214		*/
1215	<	private static final int MAX_HELP_DEPTH = 16;
1215	>	private static final int MAX_HELP = 64;
1216	>
1217	>	/**
1218	>	* Secondary time-based bound (in nanosecs) for helping attempts
1219	>	* before trying compensated blocking in awaitJoin. Used in
1220	>	* conjunction with MAX_HELP to reduce variance due to different
1221	>	* polling rates associated with different helping options. The
1222	>	* value should roughly approximate the time required to create
1223	>	* and/or activate a worker thread.
1224	>	*/
1225	>	private static final long COMPENSATION_DELAY = 1L << 18; // ~0.25 millisec
1226	>
1227	>	/**
1228	>	* Increment for seed generators. See class ThreadLocal for
1229	>	* explanation.
1230	>	*/
1231	>	private static final int SEED_INCREMENT = 0x61c88647;
1232
1233		/**
1234		* Bits and masks for control variables
#	Line 1101 \| Line 1260 \| public class ForkJoinPool extends Abstra
1260		*
1261		* Field runState is an int packed with:
1262		* SHUTDOWN: true if shutdown is enabled (1 bit)
1263	<	* SEQ: a sequence number updated upon (de)registering workers (15 bits)
1264	<	* MASK: mask (power of 2 - 1) covering all registered poolIndexes (16 bits)
1263	>	* SEQ: a sequence number updated upon (de)registering workers (30 bits)
1264	>	* INIT: set true after workQueues array construction (1 bit)
1265		*
1266	<	* The combination of mask and sequence number enables simple
1267	<	* consistency checks: Staleness of read-only operations on the
1268	<	* workQueues array can be checked by comparing runState before vs
1110	<	* after the reads. The low 16 bits (i.e, anding with SMASK) hold
1111	<	* the smallest power of two covering all indices, minus
1112	<	* one.
1266	>	* The sequence number enables simple consistency checks:
1267	>	* Staleness of read-only operations on the workQueues array can
1268	>	* be checked by comparing runState before vs after the reads.
1269		*/
1270
1271		// bit positions/shifts for fields
#	Line 1119 \| Line 1275 \| public class ForkJoinPool extends Abstra
1275		private static final int EC_SHIFT = 16;
1276
1277		// bounds
1122	–	private static final int POOL_MAX = 0x7fff; // max #workers - 1
1278		private static final int SMASK = 0xffff; // short bits
1279	+	private static final int MAX_CAP = 0x7fff; // max #workers - 1
1280		private static final int SQMASK = 0xfffe; // even short bits
1281		private static final int SHORT_SIGN = 1 << 15;
1282		private static final int INT_SIGN = 1 << 31;
#	Line 1148 \| Line 1304 \| public class ForkJoinPool extends Abstra
1304
1305		// runState bits
1306		private static final int SHUTDOWN = 1 << 31;
1151	–	private static final int RS_SEQ = 1 << 16;
1152	–	private static final int RS_SEQ_MASK = 0x7fff0000;
1307
1308		// access mode for WorkQueue
1309		static final int LIFO_QUEUE = 0;
#	Line 1165 \| Line 1319 \| public class ForkJoinPool extends Abstra
1319		* empirically works OK on current JVMs.
1320		*/
1321
1322	+	volatile long stealCount; // collects worker counts
1323		volatile long ctl; // main pool control
1324		final int parallelism; // parallelism level
1325		final int localMode; // per-worker scheduling mode
1326	<	int growHints; // for expanding indices/ranges
1327	<	volatile int runState; // shutdown status, seq, and mask
1326	>	volatile int nextWorkerNumber; // to create worker name string
1327	>	final int submitMask; // submit queue index bound
1328	>	int nextSeed; // for initializing worker seeds
1329	>	volatile int mainLock; // spinlock for array updates
1330	>	volatile int runState; // shutdown status and seq
1331		WorkQueue[] workQueues; // main registry
1174	–	final Mutex lock; // for registration
1175	–	final Condition termination; // for awaitTermination
1332		final ForkJoinWorkerThreadFactory factory; // factory for new workers
1333		final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1178	–	final AtomicLong stealCount; // collect counts when terminated
1179	–	final AtomicInteger nextWorkerNumber; // to create worker name string
1334		final String workerNamePrefix; // to create worker name string
1335
1336	<	// Creating, registering, deregistering and running workers
1336	>	/*
1337	>	* Mechanics for main lock protecting worker array updates. Uses
1338	>	* the same strategy as ConcurrentHashMap bins -- a spinLock for
1339	>	* normal cases, but falling back to builtin lock when (rarely)
1340	>	* needed. See internal ConcurrentHashMap documentation for
1341	>	* explanation.
1342	>	*/
1343	>
1344	>	static final int LOCK_WAITING = 2; // bit to indicate need for signal
1345	>	static final int MAX_LOCK_SPINS = 1 << 8;
1346	>
1347	>	private void tryAwaitMainLock() {
1348	>	int spins = MAX_LOCK_SPINS, r = 0, h;
1349	>	while (((h = mainLock) & 1) != 0) {
1350	>	if (r == 0)
1351	>	r = ThreadLocalRandom.current().nextInt(); // randomize spins
1352	>	else if (spins >= 0) {
1353	>	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1354	>	if (r >= 0)
1355	>	--spins;
1356	>	}
1357	>	else if (U.compareAndSwapInt(this, MAINLOCK, h, h \| LOCK_WAITING)) {
1358	>	synchronized (this) {
1359	>	if ((mainLock & LOCK_WAITING) != 0) {
1360	>	try {
1361	>	wait();
1362	>	} catch (InterruptedException ie) {
1363	>	try {
1364	>	Thread.currentThread().interrupt();
1365	>	} catch (SecurityException ignore) {
1366	>	}
1367	>	}
1368	>	}
1369	>	else
1370	>	notifyAll(); // possibly won race vs signaller
1371	>	}
1372	>	break;
1373	>	}
1374	>	}
1375	>	}
1376	>
1377	>	// Creating, registering, and deregistering workers
1378
1379		/**
1380		* Tries to create and start a worker
#	Line 1205 \| Line 1400 \| public class ForkJoinPool extends Abstra
1400		* ForkJoinWorkerThread.
1401		*/
1402		final String nextWorkerName() {
1403	<	return workerNamePrefix.concat
1404	<	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1403	>	int n;
1404	>	do {} while (!U.compareAndSwapInt(this, NEXTWORKERNUMBER,
1405	>	n = nextWorkerNumber, ++n));
1406	>	return workerNamePrefix.concat(Integer.toString(n));
1407		}
1408
1409		/**
1410	<	* Callback from ForkJoinWorkerThread constructor to establish and
1411	<	* record its WorkQueue.
1410	>	* Callback from ForkJoinWorkerThread constructor to establish its
1411	>	* poolIndex and record its WorkQueue. To avoid scanning bias due
1412	>	* to packing entries in front of the workQueues array, we treat
1413	>	* the array as a simple power-of-two hash table using per-thread
1414	>	* seed as hash, expanding as needed.
1415		*
1416	<	* @param wt the worker thread
1416	>	* @param w the worker's queue
1417		*/
1418	<	final void registerWorker(ForkJoinWorkerThread wt) {
1419	<	WorkQueue w = wt.workQueue;
1420	<	Mutex lock = this.lock;
1221	<	lock.lock();
1418	>	final void registerWorker(WorkQueue w) {
1419	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1420	>	tryAwaitMainLock();
1421		try {
1422	<	int g = growHints, k = g & SMASK;
1423	<	WorkQueue[] ws = workQueues;
1424	<	if (ws != null) { // ignore on shutdown
1425	<	int n = ws.length;
1426	<	if ((k & 1) == 0 \|\| k >= n \|\| ws[k] != null) {
1427	<	for (k = 1; k < n && ws[k] != null; k += 2)
1428	<	; // workers are at odd indices
1429	<	if (k >= n) // resize
1430	<	workQueues = ws = Arrays.copyOf(ws, n << 1);
1431	<	}
1432	<	w.eventCount = w.poolIndex = k; // establish before recording
1433	<	ws[k] = w;
1434	<	growHints = (g & ~SMASK) \| ((k + 2) & SMASK);
1435	<	int rs = runState;
1436	<	int m = rs & SMASK; // recalculate runState mask
1437	<	if (k > m)
1438	<	m = (m << 1) + 1;
1439	<	runState = (rs & SHUTDOWN) \| ((rs + RS_SEQ) & RS_SEQ_MASK) \| m;
1422	>	WorkQueue[] ws;
1423	>	if ((ws = workQueues) == null)
1424	>	ws = workQueues = new WorkQueue[submitMask + 1];
1425	>	if (w != null) {
1426	>	int rs, n = ws.length, m = n - 1;
1427	>	int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence
1428	>	w.seed = (s == 0) ? 1 : s; // ensure non-zero seed
1429	>	int r = (s << 1) \| 1; // use odd-numbered indices
1430	>	if (ws[r &= m] != null) { // collision
1431	>	int probes = 0; // step by approx half size
1432	>	int step = (n <= 4) ? 2 : ((n >>> 1) & SQMASK) + 2;
1433	>	while (ws[r = (r + step) & m] != null) {
1434	>	if (++probes >= n) {
1435	>	workQueues = ws = Arrays.copyOf(ws, n <<= 1);
1436	>	m = n - 1;
1437	>	probes = 0;
1438	>	}
1439	>	}
1440	>	}
1441	>	w.eventCount = w.poolIndex = r; // establish before recording
1442	>	ws[r] = w; // also update seq
1443	>	runState = ((rs = runState) & SHUTDOWN) \| ((rs + 2) & ~SHUTDOWN);
1444		}
1445		} finally {
1446	<	lock.unlock();
1446	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1447	>	mainLock = 0;
1448	>	synchronized (this) { notifyAll(); };
1449	>	}
1450		}
1451		}
1452
#	Line 1257 \| Line 1463 \| public class ForkJoinPool extends Abstra
1463		WorkQueue w = null;
1464		if (wt != null && (w = wt.workQueue) != null) {
1465		w.runState = -1; // ensure runState is set
1466	<	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1466	>	long steals = w.totalSteals + w.nsteals, sc;
1467	>	do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
1468	>	sc = stealCount, sc + steals));
1469		int idx = w.poolIndex;
1470	<	Mutex lock = this.lock;
1471	<	lock.lock();
1472	<	try { // remove record from array
1470	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1471	>	tryAwaitMainLock();
1472	>	try {
1473		WorkQueue[] ws = workQueues;
1474	<	if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w) {
1474	>	if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1475		ws[idx] = null;
1268	–	growHints = (growHints & ~SMASK) \| idx;
1269	–	}
1476		} finally {
1477	<	lock.unlock();
1477	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1478	>	mainLock = 0;
1479	>	synchronized (this) { notifyAll(); };
1480	>	}
1481		}
1482		}
1483
#	Line 1287 \| Line 1496 \| public class ForkJoinPool extends Abstra
1496		}
1497
1498		if (ex != null) // rethrow
1499	<	U.throwException(ex);
1291	<	}
1292	<
1293	<	/**
1294	<	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1295	<	*/
1296	<	final void runWorker(ForkJoinWorkerThread wt) {
1297	<	// Initialize queue array and seed in this thread
1298	<	WorkQueue w = wt.workQueue;
1299	<	w.growArray(false);
1300	<	w.seed = hashId(Thread.currentThread().getId());
1301	<
1302	<	do {} while (w.runTask(scan(w)));
1499	>	ForkJoinTask.rethrow(ex);
1500		}
1501
1502		// Submissions
#	Line 1307 \| Line 1504 \| public class ForkJoinPool extends Abstra
1504		/**
1505		* Unless shutting down, adds the given task to a submission queue
1506		* at submitter's current queue index (modulo submission
1507	<	* range). If no queue exists at the index, one is created unless
1508	<	* pool lock is busy. If the queue and/or lock are busy, another
1509	<	* index is randomly chosen. The mask in growHints controls the
1510	<	* effective index range of queues considered. The mask is
1511	<	* expanded, up to the current workerQueue mask, upon any detected
1512	<	* contention but otherwise remains small to avoid needlessly
1316	<	* creating queues when there is no contention.
1507	>	* range). If no queue exists at the index, one is created. If
1508	>	* the queue is busy, another index is randomly chosen. The
1509	>	* submitMask bounds the effective number of queues to the
1510	>	* (nearest power of two for) parallelism level.
1511	>	*
1512	>	* @param task the task. Caller must ensure non-null.
1513		*/
1514		private void doSubmit(ForkJoinTask<?> task) {
1319	–	if (task == null)
1320	–	throw new NullPointerException();
1515		Submitter s = submitters.get();
1516	<	for (int r = s.seed, m = growHints >>> 16;;) {
1517	<	WorkQueue[] ws; WorkQueue q; Mutex lk;
1516	>	for (int r = s.seed, m = submitMask;;) {
1517	>	WorkQueue[] ws; WorkQueue q;
1518		int k = r & m & SQMASK; // use only even indices
1519	<	if (runState < 0 \|\| (ws = workQueues) == null \|\| ws.length <= k)
1519	>	if (runState < 0)
1520		throw new RejectedExecutionException(); // shutting down
1521	<	if ((q = ws[k]) == null && (lk = lock).tryAcquire(0)) {
1522	<	try { // try to create new queue
1523	<	if (ws == workQueues && (q = ws[k]) == null) {
1524	<	int rs; // update runState seq
1525	<	ws[k] = q = new WorkQueue(null, SHARED_QUEUE);
1526	<	runState = (((rs = runState) & SHUTDOWN) \|
1527	<	((rs + RS_SEQ) & ~SHUTDOWN));
1521	>	else if ((ws = workQueues) == null \|\| ws.length <= k) {
1522	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1523	>	tryAwaitMainLock();
1524	>	try {
1525	>	if (workQueues == null)
1526	>	workQueues = new WorkQueue[submitMask + 1];
1527	>	} finally {
1528	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1529	>	mainLock = 0;
1530	>	synchronized (this) { notifyAll(); };
1531	>	}
1532	>	}
1533	>	}
1534	>	else if ((q = ws[k]) == null) { // create new queue
1535	>	WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE);
1536	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1537	>	tryAwaitMainLock();
1538	>	try {
1539	>	int rs = runState; // to update seq
1540	>	if (ws == workQueues && ws[k] == null) {
1541	>	ws[k] = nq;
1542	>	runState = ((rs & SHUTDOWN) \| ((rs + 2) & ~SHUTDOWN));
1543		}
1544		} finally {
1545	<	lk.unlock();
1545	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1546	>	mainLock = 0;
1547	>	synchronized (this) { notifyAll(); };
1548	>	}
1549		}
1550		}
1551	<	if (q != null) {
1552	<	if (q.trySharedPush(task)) {
1553	<	signalWork();
1554	<	return;
1555	<	}
1556	<	else if (m < parallelism - 1 && m < (runState & SMASK)) {
1557	<	Mutex lock = this.lock;
1346	<	lock.lock(); // block until lock free
1347	<	int g = growHints;
1348	<	if (g >>> 16 == m) // expand range
1349	<	growHints = (((m << 1) + 1) << 16) \| (g & SMASK);
1350	<	lock.unlock(); // no need for try/finally
1351	<	}
1352	<	else if ((r & m) == 0)
1353	<	Thread.yield(); // occasionally yield if busy
1354	<	}
1355	<	if (m == (m = growHints >>> 16)) {
1356	<	r ^= r << 13; // update seed unless new range
1357	<	r ^= r >>> 17; // same xorshift as WorkQueues
1551	>	else if (q.trySharedPush(task)) {
1552	>	signalWork();
1553	>	return;
1554	>	}
1555	>	else if (m > 1) { // move to a different index
1556	>	r ^= r << 13; // same xorshift as WorkQueues
1557	>	r ^= r >>> 17;
1558		s.seed = r ^= r << 5;
1559		}
1560	+	else
1561	+	Thread.yield(); // yield if no alternatives
1562	+	}
1563	+	}
1564	+
1565	+	/**
1566	+	* Submits the given (non-null) task to the common pool, if possible.
1567	+	*/
1568	+	static void submitToCommonPool(ForkJoinTask<?> task) {
1569	+	ForkJoinPool p;
1570	+	if ((p = commonPool) == null)
1571	+	throw new RejectedExecutionException("Common Pool Unavailable");
1572	+	p.doSubmit(task);
1573	+	}
1574	+
1575	+	/**
1576	+	* Returns true if the given task was submitted to common pool
1577	+	* and has not yet commenced execution, and is available for
1578	+	* removal according to execution policies; if so removing the
1579	+	* submission from the pool.
1580	+	*
1581	+	* @param task the task
1582	+	* @return true if successful
1583	+	*/
1584	+	static boolean tryUnsubmitFromCommonPool(ForkJoinTask<?> task) {
1585	+	// If not oversaturating platform, peek, looking for task and
1586	+	// eligibility before using trySharedUnpush to actually take
1587	+	// it under lock
1588	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q;
1589	+	ForkJoinTask<?>[] a; int ac, s, m;
1590	+	if ((p = commonPool) != null && (ws = p.workQueues) != null) {
1591	+	int k = submitters.get().seed & p.submitMask & SQMASK;
1592	+	if ((m = ws.length - 1) >= k && (q = ws[k]) != null &&
1593	+	(ac = (int)(p.ctl >> AC_SHIFT)) <= 0) {
1594	+	if (ac == 0) { // double check if all workers active
1595	+	for (int i = 1; i <= m; i += 2) {
1596	+	if ((w = ws[i]) != null && w.parker != null) {
1597	+	ac = -1;
1598	+	break;
1599	+	}
1600	+	}
1601	+	}
1602	+	return (ac < 0 && (a = q.array) != null &&
1603	+	(s = q.top - 1) - q.base >= 0 &&
1604	+	s >= 0 && s < a.length &&
1605	+	a[s] == task &&
1606	+	q.trySharedUnpush(task));
1607	+	}
1608	+	}
1609	+	return false;
1610	+	}
1611	+
1612	+	/**
1613	+	* Tries to pop and run a task within same computation from common pool
1614	+	*/
1615	+	static void popAndExecCCFromCommonPool(CountedCompleter<?> cc) {
1616	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; int m, ac;
1617	+	CountedCompleter<?> par, task;
1618	+	if ((p = commonPool) != null && (ws = p.workQueues) != null) {
1619	+	while ((par = cc.completer) != null) // find root
1620	+	cc = par;
1621	+	int k = submitters.get().seed & p.submitMask & SQMASK;
1622	+	if ((m = ws.length - 1) >= k && (q = ws[k]) != null &&
1623	+	(ac = (int)(p.ctl >> AC_SHIFT)) <= 0) {
1624	+	if (ac == 0) {
1625	+	for (int i = 1; i <= m; i += 2) {
1626	+	if ((w = ws[i]) != null && w.parker != null) {
1627	+	ac = -1;
1628	+	break;
1629	+	}
1630	+	}
1631	+	}
1632	+	if (ac < 0 && q.top - q.base > 0 &&
1633	+	(task = q.sharedPopCC(cc)) != null)
1634	+	task.exec();
1635	+	}
1636		}
1637		}
1638
#	Line 1371 \| Line 1647 \| public class ForkJoinPool extends Abstra
1647		}
1648
1649		/**
1650	<	* Tries to activate or create a worker if too few are active.
1650	>	* Tries to create one or activate one or more workers if too few are active.
1651		*/
1652		final void signalWork() {
1653		long c; int u;
#	Line 1405 \| Line 1681 \| public class ForkJoinPool extends Abstra
1681		}
1682		}
1683
1684	+	// Scanning for tasks
1685	+
1686		/**
1687	<	* Tries to decrement active count (sometimes implicitly) and
1410	<	* possibly release or create a compensating worker in preparation
1411	<	* for blocking. Fails on contention or termination.
1412	<	*
1413	<	* @return true if the caller can block, else should recheck and retry
1687	>	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1688		*/
1689	<	final boolean tryCompensate() {
1690	<	WorkQueue w; Thread p;
1691	<	int pc = parallelism, e, u, ac, tc, i;
1418	<	long c = ctl;
1419	<	WorkQueue[] ws = workQueues;
1420	<	if ((e = (int)c) >= 0) {
1421	<	if ((ac = ((u = (int)(c >>> 32)) >> UAC_SHIFT)) <= 0 &&
1422	<	e != 0 && ws != null && (i = e & SMASK) < ws.length &&
1423	<	(w = ws[i]) != null) {
1424	<	long nc = (long)(w.nextWait & E_MASK) \| (c & (AC_MASK\|TC_MASK));
1425	<	if (w.eventCount == (e \| INT_SIGN) &&
1426	<	U.compareAndSwapLong(this, CTL, c, nc)) {
1427	<	w.eventCount = (e + E_SEQ) & E_MASK;
1428	<	if ((p = w.parker) != null)
1429	<	U.unpark(p);
1430	<	return true; // release an idle worker
1431	<	}
1432	<	}
1433	<	else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) {
1434	<	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
1435	<	if (U.compareAndSwapLong(this, CTL, c, nc))
1436	<	return true; // no compensation needed
1437	<	}
1438	<	else if (tc + pc < POOL_MAX) {
1439	<	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
1440	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1441	<	addWorker();
1442	<	return true; // create replacement
1443	<	}
1444	<	}
1445	<	}
1446	<	return false;
1689	>	final void runWorker(WorkQueue w) {
1690	>	w.growArray(false); // initialize queue array in this thread
1691	>	do { w.runTask(scan(w)); } while (w.runState >= 0);
1692		}
1693
1449	–	// Scanning for tasks
1450	–
1694		/**
1695		* Scans for and, if found, returns one task, else possibly
1696		* inactivates the worker. This method operates on single reads of
1697	<	* volatile state and is designed to be re-invoked continuously in
1698	<	* part because it returns upon detecting inconsistencies,
1697	>	* volatile state and is designed to be re-invoked continuously,
1698	>	* in part because it returns upon detecting inconsistencies,
1699		* contention, or state changes that indicate possible success on
1700		* re-invocation.
1701		*
1702	<	* The scan searches for tasks across queues, randomly selecting
1703	<	* the first #queues probes, favoring steals over submissions
1704	<	* (by exploiting even/odd indexing), and then performing a
1705	<	* circular sweep of all queues. The scan terminates upon either
1706	<	* finding a non-empty queue, or completing a full sweep. If the
1707	<	* worker is not inactivated, it takes and returns a task from
1708	<	* this queue. On failure to find a task, we take one of the
1709	<	* following actions, after which the caller will retry calling
1467	<	* this method unless terminated.
1702	>	* The scan searches for tasks across a random permutation of
1703	>	* queues (starting at a random index and stepping by a random
1704	>	* relative prime, checking each at least once). The scan
1705	>	* terminates upon either finding a non-empty queue, or completing
1706	>	* the sweep. If the worker is not inactivated, it takes and
1707	>	* returns a task from this queue. On failure to find a task, we
1708	>	* take one of the following actions, after which the caller will
1709	>	* retry calling this method unless terminated.
1710		*
1711		* * If pool is terminating, terminate the worker.
1712		*
#	Line 1475 \| Line 1717 \| public class ForkJoinPool extends Abstra
1717		* another worker, but with same net effect. Releasing in other
1718		* cases as well ensures that we have enough workers running.
1719		*
1478	–	* * If the caller has run a task since the last empty scan,
1479	–	* return (to allow rescan) if other workers are not also yet
1480	–	* enqueued. Field WorkQueue.rescans counts down on each scan to
1481	–	* ensure eventual inactivation and blocking.
1482	–	*
1720		* * If not already enqueued, try to inactivate and enqueue the
1721	<	* worker on wait queue.
1721	>	* worker on wait queue. Or, if inactivating has caused the pool
1722	>	* to be quiescent, relay to idleAwaitWork to check for
1723	>	* termination and possibly shrink pool.
1724	>	*
1725	>	* * If already inactive, and the caller has run a task since the
1726	>	* last empty scan, return (to allow rescan) unless others are
1727	>	* also inactivated. Field WorkQueue.rescans counts down on each
1728	>	* scan to ensure eventual inactivation and blocking.
1729		*
1730	<	* * If already enqueued and none of the above apply, either park
1731	<	* awaiting signal, or if this is the most recent waiter and pool
1488	<	* is quiescent, relay to idleAwaitWork to check for termination
1489	<	* and possibly shrink pool.
1730	>	* * If already enqueued and none of the above apply, park
1731	>	* awaiting signal,
1732		*
1733		* @param w the worker (via its WorkQueue)
1734	<	* @return a task or null of none found
1734	>	* @return a task or null if none found
1735		*/
1736		private final ForkJoinTask<?> scan(WorkQueue w) {
1737	<	boolean swept = false; // true after full empty scan
1738	<	WorkQueue[] ws; // volatile read order matters
1739	<	int r = w.seed, ec = w.eventCount; // ec is negative if inactive
1740	<	int rs = runState, m = rs & SMASK;
1741	<	if ((ws = workQueues) != null && ws.length > m) { // consistency check
1742	<	for (int k = 0, j = -1 - m; ; ++j) {
1743	<	WorkQueue q; int b;
1744	<	if (j < 0) { // random probes while j negative
1745	<	r ^= r << 13; r ^= r >>> 17; k = (r ^= r << 5) \| (j & 1);
1746	<	} // worker (not submit) for odd j
1747	<	else // cyclic scan when j >= 0
1748	<	k += 7; // step 7 reduces array packing bias
1749	<	if ((q = ws[k & m]) != null && (b = q.base) - q.top < 0) {
1750	<	ForkJoinTask<?> t = (ec >= 0) ? q.pollAt(b) : null;
1751	<	w.seed = r; // save seed for next scan
1752	<	if (t != null)
1737	>	WorkQueue[] ws; // first update random seed
1738	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1739	>	int rs = runState, m; // volatile read order matters
1740	>	if ((ws = workQueues) != null && (m = ws.length - 1) > 0) {
1741	>	int ec = w.eventCount; // ec is negative if inactive
1742	>	int step = (r >>> 16) \| 1; // relative prime
1743	>	for (int j = (m + 1) << 2; ; r += step) {
1744	>	WorkQueue q; ForkJoinTask<?> t; ForkJoinTask<?>[] a; int b;
1745	>	if ((q = ws[r & m]) != null && (b = q.base) - q.top < 0 &&
1746	>	(a = q.array) != null) { // probably nonempty
1747	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1748	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1749	>	if (q.base == b && ec >= 0 && t != null &&
1750	>	U.compareAndSwapObject(a, i, t, null)) {
1751	>	if (q.top - (q.base = b + 1) > 0)
1752	>	signalWork(); // help pushes signal
1753		return t;
1754	<	break;
1754	>	}
1755	>	else if (ec < 0 \|\| j <= m) {
1756	>	rs = 0; // mark scan as imcomplete
1757	>	break; // caller can retry after release
1758	>	}
1759		}
1760	<	else if (j - m > m) {
1515	<	if (rs == runState) // staleness check
1516	<	swept = true;
1760	>	if (--j < 0)
1761		break;
1518	–	}
1762		}
1763
1521	–	// Decode ctl on empty scan
1764		long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
1765	<	if (e < 0) // pool is terminating
1766	<	w.runState = -1;
1767	<	else if (!swept) { // try to release a waiter
1768	<	WorkQueue v; Thread p;
1769	<	if (e > 0 && a < 0 && (v = ws[e & m]) != null &&
1770	<	v.eventCount == (e \| INT_SIGN)) {
1765	>	if (e < 0) // decode ctl on empty scan
1766	>	w.runState = -1; // pool is terminating
1767	>	else if (rs == 0 \|\| rs != runState) { // incomplete scan
1768	>	WorkQueue v; Thread p; // try to release a waiter
1769	>	if (e > 0 && a < 0 && w.eventCount == ec &&
1770	>	(v = ws[e & m]) != null && v.eventCount == (e \| INT_SIGN)) {
1771		long nc = ((long)(v.nextWait & E_MASK) \|
1772		((c + AC_UNIT) & (AC_MASK\|TC_MASK)));
1773	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1773	>	if (ctl == c && U.compareAndSwapLong(this, CTL, c, nc)) {
1774		v.eventCount = (e + E_SEQ) & E_MASK;
1775		if ((p = v.parker) != null)
1776		U.unpark(p);
1777		}
1778		}
1779		}
1780	<	else if ((nr = w.rescans) > 0) { // continue rescanning
1539	<	int ac = a + parallelism;
1540	<	if (((w.rescans = (ac < nr) ? ac : nr - 1) & 3) == 0 &&
1541	<	w.eventCount == ec)
1542	<	Thread.yield(); // occasionally yield
1543	<	}
1544	<	else if (ec >= 0) { // try to enqueue
1780	>	else if (ec >= 0) { // try to enqueue/inactivate
1781		long nc = (long)ec \| ((c - AC_UNIT) & (AC_MASK\|TC_MASK));
1782		w.nextWait = e;
1783	<	w.eventCount = ec \| INT_SIGN;// mark as inactive
1784	<	if (!U.compareAndSwapLong(this, CTL, c, nc))
1785	<	w.eventCount = ec; // unmark on CAS failure
1786	<	else if ((ns = w.nsteals) != 0) {
1787	<	w.nsteals = 0; // set rescans if ran task
1788	<	w.rescans = a + parallelism;
1789	<	w.totalSteals += ns;
1783	>	w.eventCount = ec \| INT_SIGN; // mark as inactive
1784	>	if (ctl != c \|\| !U.compareAndSwapLong(this, CTL, c, nc))
1785	>	w.eventCount = ec; // unmark on CAS failure
1786	>	else {
1787	>	if ((ns = w.nsteals) != 0) {
1788	>	w.nsteals = 0; // set rescans if ran task
1789	>	w.rescans = (a > 0) ? 0 : a + parallelism;
1790	>	w.totalSteals += ns;
1791	>	}
1792	>	if (a == 1 - parallelism) // quiescent
1793	>	idleAwaitWork(w, nc, c);
1794		}
1795		}
1796	<	else { // already queued
1797	<	if (parallelism == -a)
1798	<	idleAwaitWork(w); // quiescent
1799	<	if (w.eventCount == ec) {
1800	<	Thread.interrupted(); // clear status
1801	<	ForkJoinWorkerThread wt = w.owner;
1796	>	else if (w.eventCount < 0) { // already queued
1797	>	int ac = a + parallelism;
1798	>	if ((nr = w.rescans) > 0) // continue rescanning
1799	>	w.rescans = (ac < nr) ? ac : nr - 1;
1800	>	else if (((w.seed >>> 16) & ac) == 0) { // randomize park
1801	>	Thread.interrupted(); // clear status
1802	>	Thread wt = Thread.currentThread();
1803		U.putObject(wt, PARKBLOCKER, this);
1804	<	w.parker = wt; // emulate LockSupport.park
1805	<	if (w.eventCount == ec) // recheck
1806	<	U.park(false, 0L); // block
1804	>	w.parker = wt; // emulate LockSupport.park
1805	>	if (w.eventCount < 0) // recheck
1806	>	U.park(false, 0L);
1807		w.parker = null;
1808		U.putObject(wt, PARKBLOCKER, null);
1809		}
#	Line 1572 \| Line 1813 \| public class ForkJoinPool extends Abstra
1813		}
1814
1815		/**
1816	<	* If inactivating worker w has caused pool to become quiescent,
1817	<	* checks for pool termination, and, so long as this is not the
1818	<	* only worker, waits for event for up to SHRINK_RATE nanosecs.
1819	<	* On timeout, if ctl has not changed, terminates the worker,
1820	<	* which will in turn wake up another worker to possibly repeat
1821	<	* this process.
1816	>	* If inactivating worker w has caused the pool to become
1817	>	* quiescent, checks for pool termination, and, so long as this is
1818	>	* not the only worker, waits for event for up to a given
1819	>	* duration. On timeout, if ctl has not changed, terminates the
1820	>	* worker, which will in turn wake up another worker to possibly
1821	>	* repeat this process.
1822		*
1823		* @param w the calling worker
1824	+	* @param currentCtl the ctl value triggering possible quiescence
1825	+	* @param prevCtl the ctl value to restore if thread is terminated
1826		*/
1827	<	private void idleAwaitWork(WorkQueue w) {
1828	<	long c; int nw, ec;
1829	<	if (!tryTerminate(false, false) &&
1830	<	(int)((c = ctl) >> AC_SHIFT) + parallelism == 0 &&
1831	<	(ec = w.eventCount) == ((int)c \| INT_SIGN) &&
1832	<	(nw = w.nextWait) != 0) {
1833	<	long nc = ((long)(nw & E_MASK) \| // ctl to restore on timeout
1834	<	((c + AC_UNIT) & AC_MASK) \| (c & TC_MASK));
1592	<	ForkJoinWorkerThread wt = w.owner;
1593	<	while (ctl == c) {
1594	<	long startTime = System.nanoTime();
1827	>	private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1828	>	if (w.eventCount < 0 && !tryTerminate(false, false) &&
1829	>	(int)prevCtl != 0 && !hasQueuedSubmissions() && ctl == currentCtl) {
1830	>	int dc = -(short)(currentCtl >>> TC_SHIFT);
1831	>	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1832	>	long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop
1833	>	Thread wt = Thread.currentThread();
1834	>	while (ctl == currentCtl) {
1835		Thread.interrupted(); // timed variant of version in scan()
1836		U.putObject(wt, PARKBLOCKER, this);
1837		w.parker = wt;
1838	<	if (ctl == c)
1839	<	U.park(false, SHRINK_RATE);
1838	>	if (ctl == currentCtl)
1839	>	U.park(false, parkTime);
1840		w.parker = null;
1841		U.putObject(wt, PARKBLOCKER, null);
1842	<	if (ctl != c)
1842	>	if (ctl != currentCtl)
1843		break;
1844	<	if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
1845	<	U.compareAndSwapLong(this, CTL, c, nc)) {
1846	<	w.eventCount = (ec + E_SEQ) \| E_MASK;
1847	<	w.runState = -1; // shrink
1844	>	if (deadline - System.nanoTime() <= 0L &&
1845	>	U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1846	>	w.eventCount = (w.eventCount + E_SEQ) \| E_MASK;
1847	>	w.runState = -1; // shrink
1848		break;
1849		}
1850		}
#	Line 1622 \| Line 1862 \| public class ForkJoinPool extends Abstra
1862		* leaves hints in workers to speed up subsequent calls. The
1863		* implementation is very branchy to cope with potential
1864		* inconsistencies or loops encountering chains that are stale,
1865	<	* unknown, or of length greater than MAX_HELP_DEPTH links. All
1626	<	* of these cases are dealt with by just retrying by caller.
1865	>	* unknown, or so long that they are likely cyclic.
1866		*
1867		* @param joiner the joining worker
1868		* @param task the task to join
1869	<	* @return true if found or ran a task (and so is immediately retryable)
1869	>	* @return 0 if no progress can be made, negative if task
1870	>	* known complete, else positive
1871		*/
1872	<	final boolean tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1873	<	ForkJoinTask<?> subtask; // current target
1874	<	boolean progress = false;
1875	<	int depth = 0; // current chain depth
1876	<	int m = runState & SMASK;
1877	<	WorkQueue[] ws = workQueues;
1878	<
1879	<	if (ws != null && ws.length > m && (subtask = task).status >= 0) {
1880	<	outer:for (WorkQueue j = joiner;;) {
1881	<	// Try to find the stealer of subtask, by first using hint
1642	<	WorkQueue stealer = null;
1643	<	WorkQueue v = ws[j.stealHint & m];
1644	<	if (v != null && v.currentSteal == subtask)
1645	<	stealer = v;
1646	<	else {
1647	<	for (int i = 1; i <= m; i += 2) {
1648	<	if ((v = ws[i]) != null && v.currentSteal == subtask) {
1649	<	stealer = v;
1650	<	j.stealHint = i; // save hint
1651	<	break;
1652	<	}
1872	>	private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1873	>	int stat = 0, steps = 0; // bound to avoid cycles
1874	>	if (joiner != null && task != null) { // hoist null checks
1875	>	restart: for (;;) {
1876	>	ForkJoinTask<?> subtask = task; // current target
1877	>	for (WorkQueue j = joiner, v;;) { // v is stealer of subtask
1878	>	WorkQueue[] ws; int m, s, h;
1879	>	if ((s = task.status) < 0) {
1880	>	stat = s;
1881	>	break restart;
1882		}
1883	<	if (stealer == null)
1884	<	break;
1885	<	}
1886	<
1887	<	for (WorkQueue q = stealer;;) { // Try to help stealer
1888	<	ForkJoinTask<?> t; int b;
1889	<	if (task.status < 0)
1890	<	break outer;
1891	<	if ((b = q.base) - q.top < 0) {
1892	<	progress = true;
1893	<	if (subtask.status < 0)
1894	<	break outer; // stale
1895	<	if ((t = q.pollAt(b)) != null) {
1896	<	stealer.stealHint = joiner.poolIndex;
1897	<	joiner.runSubtask(t);
1883	>	if ((ws = workQueues) == null \|\| (m = ws.length - 1) <= 0)
1884	>	break restart; // shutting down
1885	>	if ((v = ws[h = (j.stealHint \| 1) & m]) == null \|\|
1886	>	v.currentSteal != subtask) {
1887	>	for (int origin = h;;) { // find stealer
1888	>	if (((h = (h + 2) & m) & 15) == 1 &&
1889	>	(subtask.status < 0 \|\| j.currentJoin != subtask))
1890	>	continue restart; // occasional staleness check
1891	>	if ((v = ws[h]) != null &&
1892	>	v.currentSteal == subtask) {
1893	>	j.stealHint = h; // save hint
1894	>	break;
1895	>	}
1896	>	if (h == origin)
1897	>	break restart; // cannot find stealer
1898		}
1899		}
1900	<	else { // empty - try to descend to find stealer's stealer
1901	<	ForkJoinTask<?> next = stealer.currentJoin;
1902	<	if (++depth == MAX_HELP_DEPTH \|\| subtask.status < 0 \|\|
1903	<	next == null \|\| next == subtask)
1904	<	break outer; // max depth, stale, dead-end, cyclic
1905	<	subtask = next;
1906	<	j = stealer;
1907	<	break;
1900	>	for (;;) { // help stealer or descend to its stealer
1901	>	ForkJoinTask[] a; int b;
1902	>	if (subtask.status < 0) // surround probes with
1903	>	continue restart; // consistency checks
1904	>	if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
1905	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1906	>	ForkJoinTask<?> t =
1907	>	(ForkJoinTask<?>)U.getObjectVolatile(a, i);
1908	>	if (subtask.status < 0 \|\| j.currentJoin != subtask \|\|
1909	>	v.currentSteal != subtask)
1910	>	continue restart; // stale
1911	>	stat = 1; // apparent progress
1912	>	if (t != null && v.base == b &&
1913	>	U.compareAndSwapObject(a, i, t, null)) {
1914	>	v.base = b + 1; // help stealer
1915	>	joiner.runSubtask(t);
1916	>	}
1917	>	else if (v.base == b && ++steps == MAX_HELP)
1918	>	break restart; // v apparently stalled
1919	>	}
1920	>	else { // empty -- try to descend
1921	>	ForkJoinTask<?> next = v.currentJoin;
1922	>	if (subtask.status < 0 \|\| j.currentJoin != subtask \|\|
1923	>	v.currentSteal != subtask)
1924	>	continue restart; // stale
1925	>	else if (next == null \|\| ++steps == MAX_HELP)
1926	>	break restart; // dead-end or maybe cyclic
1927	>	else {
1928	>	subtask = next;
1929	>	j = v;
1930	>	break;
1931	>	}
1932	>	}
1933		}
1934		}
1935		}
1936		}
1937	<	return progress;
1937	>	return stat;
1938		}
1939
1940		/**
#	Line 1689 \| Line 1943 \| public class ForkJoinPool extends Abstra
1943		* @param joiner the joining worker
1944		* @param task the task
1945		*/
1946	<	final void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
1946	>	private void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
1947		WorkQueue[] ws;
1948	<	int m = runState & SMASK;
1949	<	if ((ws = workQueues) != null && ws.length > m) {
1696	<	for (int j = 1; j <= m && task.status >= 0; j += 2) {
1948	>	if ((ws = workQueues) != null) {
1949	>	for (int j = 1; j < ws.length && task.status >= 0; j += 2) {
1950		WorkQueue q = ws[j];
1951		if (q != null && q.pollFor(task)) {
1952		joiner.runSubtask(task);
#	Line 1704 \| Line 1957 \| public class ForkJoinPool extends Abstra
1957		}
1958
1959		/**
1960	<	* Returns a non-empty steal queue, if one is found during a random,
1961	<	* then cyclic scan, else null. This method must be retried by
1962	<	* caller if, by the time it tries to use the queue, it is empty.
1960	>	* Tries to decrement active count (sometimes implicitly) and
1961	>	* possibly release or create a compensating worker in preparation
1962	>	* for blocking. Fails on contention or termination. Otherwise,
1963	>	* adds a new thread if no idle workers are available and either
1964	>	* pool would become completely starved or: (at least half
1965	>	* starved, and fewer than 50% spares exist, and there is at least
1966	>	* one task apparently available). Even though the availability
1967	>	* check requires a full scan, it is worthwhile in reducing false
1968	>	* alarms.
1969	>	*
1970	>	* @param task if non-null, a task being waited for
1971	>	* @param blocker if non-null, a blocker being waited for
1972	>	* @return true if the caller can block, else should recheck and retry
1973	>	*/
1974	>	final boolean tryCompensate(ForkJoinTask<?> task, ManagedBlocker blocker) {
1975	>	int pc = parallelism, e;
1976	>	long c = ctl;
1977	>	WorkQueue[] ws = workQueues;
1978	>	if ((e = (int)c) >= 0 && ws != null) {
1979	>	int u, a, ac, hc;
1980	>	int tc = (short)((u = (int)(c >>> 32)) >>> UTC_SHIFT) + pc;
1981	>	boolean replace = false;
1982	>	if ((a = u >> UAC_SHIFT) <= 0) {
1983	>	if ((ac = a + pc) <= 1)
1984	>	replace = true;
1985	>	else if ((e > 0 \|\| (task != null &&
1986	>	ac <= (hc = pc >>> 1) && tc < pc + hc))) {
1987	>	WorkQueue w;
1988	>	for (int j = 0; j < ws.length; ++j) {
1989	>	if ((w = ws[j]) != null && !w.isEmpty()) {
1990	>	replace = true;
1991	>	break; // in compensation range and tasks available
1992	>	}
1993	>	}
1994	>	}
1995	>	}
1996	>	if ((task == null \|\| task.status >= 0) && // recheck need to block
1997	>	(blocker == null \|\| !blocker.isReleasable()) && ctl == c) {
1998	>	if (!replace) { // no compensation
1999	>	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
2000	>	if (U.compareAndSwapLong(this, CTL, c, nc))
2001	>	return true;
2002	>	}
2003	>	else if (e != 0) { // release an idle worker
2004	>	WorkQueue w; Thread p; int i;
2005	>	if ((i = e & SMASK) < ws.length && (w = ws[i]) != null) {
2006	>	long nc = ((long)(w.nextWait & E_MASK) \|
2007	>	(c & (AC_MASK\|TC_MASK)));
2008	>	if (w.eventCount == (e \| INT_SIGN) &&
2009	>	U.compareAndSwapLong(this, CTL, c, nc)) {
2010	>	w.eventCount = (e + E_SEQ) & E_MASK;
2011	>	if ((p = w.parker) != null)
2012	>	U.unpark(p);
2013	>	return true;
2014	>	}
2015	>	}
2016	>	}
2017	>	else if (tc < MAX_CAP) { // create replacement
2018	>	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
2019	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
2020	>	addWorker();
2021	>	return true;
2022	>	}
2023	>	}
2024	>	}
2025	>	}
2026	>	return false;
2027	>	}
2028	>
2029	>	/**
2030	>	* Helps and/or blocks until the given task is done.
2031	>	*
2032	>	* @param joiner the joining worker
2033	>	* @param task the task
2034	>	* @return task status on exit
2035	>	*/
2036	>	final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
2037	>	int s;
2038	>	if ((s = task.status) >= 0) {
2039	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2040	>	joiner.currentJoin = task;
2041	>	long startTime = 0L;
2042	>	for (int k = 0;;) {
2043	>	if ((s = (joiner.isEmpty() ? // try to help
2044	>	tryHelpStealer(joiner, task) :
2045	>	joiner.tryRemoveAndExec(task))) == 0 &&
2046	>	(s = task.status) >= 0) {
2047	>	if (k == 0) {
2048	>	startTime = System.nanoTime();
2049	>	tryPollForAndExec(joiner, task); // check uncommon case
2050	>	}
2051	>	else if ((k & (MAX_HELP - 1)) == 0 &&
2052	>	System.nanoTime() - startTime >=
2053	>	COMPENSATION_DELAY &&
2054	>	tryCompensate(task, null)) {
2055	>	if (task.trySetSignal()) {
2056	>	synchronized (task) {
2057	>	if (task.status >= 0) {
2058	>	try { // see ForkJoinTask
2059	>	task.wait(); // for explanation
2060	>	} catch (InterruptedException ie) {
2061	>	}
2062	>	}
2063	>	else
2064	>	task.notifyAll();
2065	>	}
2066	>	}
2067	>	long c; // re-activate
2068	>	do {} while (!U.compareAndSwapLong
2069	>	(this, CTL, c = ctl, c + AC_UNIT));
2070	>	}
2071	>	}
2072	>	if (s < 0 \|\| (s = task.status) < 0) {
2073	>	joiner.currentJoin = prevJoin;
2074	>	break;
2075	>	}
2076	>	else if ((k++ & (MAX_HELP - 1)) == MAX_HELP >>> 1)
2077	>	Thread.yield(); // for politeness
2078	>	}
2079	>	}
2080	>	return s;
2081	>	}
2082	>
2083	>	/**
2084	>	* Stripped-down variant of awaitJoin used by timed joins. Tries
2085	>	* to help join only while there is continuous progress. (Caller
2086	>	* will then enter a timed wait.)
2087	>	*
2088	>	* @param joiner the joining worker
2089	>	* @param task the task
2090	>	* @return task status on exit
2091	>	*/
2092	>	final int helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
2093	>	int s;
2094	>	while ((s = task.status) >= 0 &&
2095	>	(joiner.isEmpty() ?
2096	>	tryHelpStealer(joiner, task) :
2097	>	joiner.tryRemoveAndExec(task)) != 0)
2098	>	;
2099	>	return s;
2100	>	}
2101	>
2102	>	/**
2103	>	* Returns a (probably) non-empty steal queue, if one is found
2104	>	* during a random, then cyclic scan, else null. This method must
2105	>	* be retried by caller if, by the time it tries to use the queue,
2106	>	* it is empty.
2107		*/
2108		private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
2109	<	int r = w.seed; // Same idea as scan(), but ignoring submissions
2109	>	// Similar to loop in scan(), but ignoring submissions
2110	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
2111	>	int step = (r >>> 16) \| 1;
2112		for (WorkQueue[] ws;;) {
2113	<	int m = runState & SMASK;
2114	<	if ((ws = workQueues) == null)
2113	>	int rs = runState, m;
2114	>	if ((ws = workQueues) == null \|\| (m = ws.length - 1) < 1)
2115		return null;
2116	<	if (ws.length > m) {
2117	<	WorkQueue q;
2118	<	for (int k = 0, j = -1 - m;; ++j) {
2119	<	if (j < 0) {
2120	<	r ^= r << 13; r ^= r >>> 17; k = r ^= r << 5;
2121	<	}
1723	<	else
1724	<	k += 7;
1725	<	if ((q = ws[(k \| 1) & m]) != null && q.base - q.top < 0) {
1726	<	w.seed = r;
1727	<	return q;
1728	<	}
1729	<	else if (j - m > m)
2116	>	for (int j = (m + 1) << 2; ; r += step) {
2117	>	WorkQueue q = ws[((r << 1) \| 1) & m];
2118	>	if (q != null && !q.isEmpty())
2119	>	return q;
2120	>	else if (--j < 0) {
2121	>	if (runState == rs)
2122		return null;
2123	+	break;
2124		}
2125		}
2126		}
#	Line 1741 \| Line 2134 \| public class ForkJoinPool extends Abstra
2134		*/
2135		final void helpQuiescePool(WorkQueue w) {
2136		for (boolean active = true;;) {
2137	<	w.runLocalTasks(); // exhaust local queue
2137	>	ForkJoinTask<?> localTask; // exhaust local queue
2138	>	while ((localTask = w.nextLocalTask()) != null)
2139	>	localTask.doExec();
2140		WorkQueue q = findNonEmptyStealQueue(w);
2141		if (q != null) {
2142	<	ForkJoinTask<?> t;
2142	>	ForkJoinTask<?> t; int b;
2143		if (!active) { // re-establish active count
2144		long c;
2145		active = true;
2146		do {} while (!U.compareAndSwapLong
2147		(this, CTL, c = ctl, c + AC_UNIT));
2148		}
2149	<	if ((t = q.poll()) != null)
2149	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2150		w.runSubtask(t);
2151		}
2152		else {
#	Line 1773 \| Line 2168 \| public class ForkJoinPool extends Abstra
2168		}
2169
2170		/**
2171	+	* Restricted version of helpQuiescePool for non-FJ callers
2172	+	*/
2173	+	static void externalHelpQuiescePool() {
2174	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, sq;
2175	+	ForkJoinTask<?>[] a; int b;
2176	+	ForkJoinTask<?> t = null;
2177	+	int k = submitters.get().seed & SQMASK;
2178	+	if ((p = commonPool) != null &&
2179	+	(ws = p.workQueues) != null &&
2180	+	ws.length > (k &= p.submitMask) &&
2181	+	(q = ws[k]) != null) {
2182	+	while (q.top - q.base > 0) {
2183	+	if ((t = q.sharedPop()) != null)
2184	+	break;
2185	+	}
2186	+	if (t == null && (sq = p.findNonEmptyStealQueue(q)) != null &&
2187	+	(b = sq.base) - sq.top < 0)
2188	+	t = sq.pollAt(b);
2189	+	if (t != null)
2190	+	t.doExec();
2191	+	}
2192	+	}
2193	+
2194	+	/**
2195		* Gets and removes a local or stolen task for the given worker.
2196		*
2197		* @return a task, if available
2198		*/
2199		final ForkJoinTask<?> nextTaskFor(WorkQueue w) {
2200		for (ForkJoinTask<?> t;;) {
2201	<	WorkQueue q;
2201	>	WorkQueue q; int b;
2202		if ((t = w.nextLocalTask()) != null)
2203		return t;
2204		if ((q = findNonEmptyStealQueue(w)) == null)
2205		return null;
2206	<	if ((t = q.poll()) != null)
2206	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2207		return t;
2208		}
2209		}
#	Line 1805 \| Line 2224 \| public class ForkJoinPool extends Abstra
2224		8);
2225		}
2226
2227	+	/**
2228	+	* Returns approximate submission queue length for the given caller
2229	+	*/
2230	+	static int getEstimatedSubmitterQueueLength() {
2231	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
2232	+	int k = submitters.get().seed & SQMASK;
2233	+	return ((p = commonPool) != null && (ws = p.workQueues) != null &&
2234	+	ws.length > (k &= p.submitMask) &&
2235	+	(q = ws[k]) != null) ?
2236	+	q.queueSize() : 0;
2237	+	}
2238	+
2239		// Termination
2240
2241		/**
#	Line 1822 \| Line 2253 \| public class ForkJoinPool extends Abstra
2253		* @return true if now terminating or terminated
2254		*/
2255		private boolean tryTerminate(boolean now, boolean enable) {
1825	–	Mutex lock = this.lock;
2256		for (long c;;) {
2257		if (((c = ctl) & STOP_BIT) != 0) { // already terminating
2258		if ((short)(c >>> TC_SHIFT) == -parallelism) {
2259	<	lock.lock(); // don't need try/finally
2260	<	termination.signalAll(); // signal when 0 workers
2261	<	lock.unlock();
2259	>	synchronized (this) {
2260	>	notifyAll(); // signal when 0 workers
2261	>	}
2262		}
2263		return true;
2264		}
2265		if (runState >= 0) { // not yet enabled
2266		if (!enable)
2267		return false;
2268	<	lock.lock();
2269	<	runState \|= SHUTDOWN;
2270	<	lock.unlock();
2268	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
2269	>	tryAwaitMainLock();
2270	>	try {
2271	>	runState \|= SHUTDOWN;
2272	>	} finally {
2273	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
2274	>	mainLock = 0;
2275	>	synchronized (this) { notifyAll(); };
2276	>	}
2277	>	}
2278		}
2279		if (!now) { // check if idle & no tasks
2280		if ((int)(c >> AC_SHIFT) != -parallelism \|\|
#	Line 1959 \| Line 2396 \| public class ForkJoinPool extends Abstra
2396		checkPermission();
2397		if (factory == null)
2398		throw new NullPointerException();
2399	<	if (parallelism <= 0 \|\| parallelism > POOL_MAX)
2399	>	if (parallelism <= 0 \|\| parallelism > MAX_CAP)
2400		throw new IllegalArgumentException();
2401		this.parallelism = parallelism;
2402		this.factory = factory;
2403		this.ueh = handler;
2404		this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE;
1968	–	this.growHints = 1;
2405		long np = (long)(-parallelism); // offset ctl counts
2406		this.ctl = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
2407	<	// initialize workQueues array with room for 2*parallelism if possible
2408	<	int n = parallelism << 1;
2409	<	if (n >= POOL_MAX)
2410	<	n = POOL_MAX;
2411	<	else { // See Hackers Delight, sec 3.2, where n < (1 << 16)
1976	<	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4; n \|= n >>> 8;
1977	<	}
1978	<	this.workQueues = new WorkQueue[(n + 1) << 1]; // #slots = 2 * #workers
1979	<	this.termination = (this.lock = new Mutex()).newCondition();
1980	<	this.stealCount = new AtomicLong();
1981	<	this.nextWorkerNumber = new AtomicInteger();
2407	>	// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2.
2408	>	int n = parallelism - 1;
2409	>	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4; n \|= n >>> 8; n \|= n >>> 16;
2410	>	this.submitMask = ((n + 1) << 1) - 1;
2411	>	int pn = poolNumberGenerator.incrementAndGet();
2412		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2413	<	sb.append(poolNumberGenerator.incrementAndGet());
2413	>	sb.append(Integer.toString(pn));
2414		sb.append("-worker-");
2415		this.workerNamePrefix = sb.toString();
2416	+	this.runState = 1; // set init flag
2417	+	}
2418	+
2419	+	/**
2420	+	* Constructor for common pool, suitable only for static initialization.
2421	+	* Basically the same as above, but uses smallest possible initial footprint.
2422	+	*/
2423	+	ForkJoinPool(int parallelism, int submitMask,
2424	+	ForkJoinWorkerThreadFactory factory,
2425	+	Thread.UncaughtExceptionHandler handler) {
2426	+	this.factory = factory;
2427	+	this.ueh = handler;
2428	+	this.submitMask = submitMask;
2429	+	this.parallelism = parallelism;
2430	+	long np = (long)(-parallelism);
2431	+	this.ctl = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
2432	+	this.localMode = LIFO_QUEUE;
2433	+	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2434	+	this.runState = 1;
2435	+	}
2436	+
2437	+	/**
2438	+	* Returns the common pool instance.
2439	+	*
2440	+	* @return the common pool instance
2441	+	*/
2442	+	public static ForkJoinPool commonPool() {
2443	+	ForkJoinPool p;
2444	+	if ((p = commonPool) == null)
2445	+	throw new Error("Common Pool Unavailable");
2446	+	return p;
2447		}
2448
2449		// Execution methods
#	Line 2004 \| Line 2465 \| public class ForkJoinPool extends Abstra
2465		* scheduled for execution
2466		*/
2467		public <T> T invoke(ForkJoinTask<T> task) {
2468	+	if (task == null)
2469	+	throw new NullPointerException();
2470		doSubmit(task);
2471		return task.join();
2472		}
#	Line 2017 \| Line 2480 \| public class ForkJoinPool extends Abstra
2480		* scheduled for execution
2481		*/
2482		public void execute(ForkJoinTask<?> task) {
2483	+	if (task == null)
2484	+	throw new NullPointerException();
2485		doSubmit(task);
2486		}
2487
#	Line 2034 \| Line 2499 \| public class ForkJoinPool extends Abstra
2499		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2500		job = (ForkJoinTask<?>) task;
2501		else
2502	<	job = ForkJoinTask.adapt(task, null);
2502	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2503		doSubmit(job);
2504		}
2505
#	Line 2048 \| Line 2513 \| public class ForkJoinPool extends Abstra
2513		* scheduled for execution
2514		*/
2515		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2516	+	if (task == null)
2517	+	throw new NullPointerException();
2518		doSubmit(task);
2519		return task;
2520		}
#	Line 2058 \| Line 2525 \| public class ForkJoinPool extends Abstra
2525		* scheduled for execution
2526		*/
2527		public <T> ForkJoinTask<T> submit(Callable<T> task) {
2528	<	if (task == null)
2062	<	throw new NullPointerException();
2063	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
2528	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2529		doSubmit(job);
2530		return job;
2531		}
#	Line 2071 \| Line 2536 \| public class ForkJoinPool extends Abstra
2536		* scheduled for execution
2537		*/
2538		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2539	<	if (task == null)
2075	<	throw new NullPointerException();
2076	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
2539	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2540		doSubmit(job);
2541		return job;
2542		}
#	Line 2090 \| Line 2553 \| public class ForkJoinPool extends Abstra
2553		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2554		job = (ForkJoinTask<?>) task;
2555		else
2556	<	job = ForkJoinTask.adapt(task, null);
2556	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2557		doSubmit(job);
2558		return job;
2559		}
#	Line 2112 \| Line 2575 \| public class ForkJoinPool extends Abstra
2575		boolean done = false;
2576		try {
2577		for (Callable<T> t : tasks) {
2578	<	ForkJoinTask<T> f = ForkJoinTask.adapt(t);
2578	>	ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2579		doSubmit(f);
2580		fs.add(f);
2581		}
#	Line 2156 \| Line 2619 \| public class ForkJoinPool extends Abstra
2619		}
2620
2621		/**
2622	+	* Returns the targeted parallelism level of the common pool.
2623	+	*
2624	+	* @return the targeted parallelism level of the common pool
2625	+	*/
2626	+	public static int getCommonPoolParallelism() {
2627	+	return commonPoolParallelism;
2628	+	}
2629	+
2630	+	/**
2631		* Returns the number of worker threads that have started but not
2632		* yet terminated. The result returned by this method may differ
2633		* from {@link #getParallelism} when threads are created to
#	Line 2236 \| Line 2708 \| public class ForkJoinPool extends Abstra
2708		* @return the number of steals
2709		*/
2710		public long getStealCount() {
2711	<	long count = stealCount.get();
2711	>	long count = stealCount;
2712		WorkQueue[] ws; WorkQueue w;
2713		if ((ws = workQueues) != null) {
2714		for (int i = 1; i < ws.length; i += 2) {
#	Line 2298 \| Line 2770 \| public class ForkJoinPool extends Abstra
2770		WorkQueue[] ws; WorkQueue w;
2771		if ((ws = workQueues) != null) {
2772		for (int i = 0; i < ws.length; i += 2) {
2773	<	if ((w = ws[i]) != null && w.queueSize() != 0)
2773	>	if ((w = ws[i]) != null && !w.isEmpty())
2774		return true;
2775		}
2776		}
#	Line 2366 \| Line 2838 \| public class ForkJoinPool extends Abstra
2838		public String toString() {
2839		// Use a single pass through workQueues to collect counts
2840		long qt = 0L, qs = 0L; int rc = 0;
2841	<	long st = stealCount.get();
2841	>	long st = stealCount;
2842		long c = ctl;
2843		WorkQueue[] ws; WorkQueue w;
2844		if ((ws = workQueues) != null) {
#	Line 2407 \| Line 2879 \| public class ForkJoinPool extends Abstra
2879		}
2880
2881		/**
2882	<	* Initiates an orderly shutdown in which previously submitted
2883	<	* tasks are executed, but no new tasks will be accepted.
2884	<	* Invocation has no additional effect if already shut down.
2885	<	* Tasks that are in the process of being submitted concurrently
2886	<	* during the course of this method may or may not be rejected.
2882	>	* Possibly initiates an orderly shutdown in which previously
2883	>	* submitted tasks are executed, but no new tasks will be
2884	>	* accepted. Invocation has no effect on execution state if this
2885	>	* is the {@link #commonPool}, and no additional effect if
2886	>	* already shut down. Tasks that are in the process of being
2887	>	* submitted concurrently during the course of this method may or
2888	>	* may not be rejected.
2889		*
2890		* @throws SecurityException if a security manager exists and
2891		* the caller is not permitted to modify threads
#	Line 2420 \| Line 2894 \| public class ForkJoinPool extends Abstra
2894		*/
2895		public void shutdown() {
2896		checkPermission();
2897	<	tryTerminate(false, true);
2897	>	if (this != commonPool)
2898	>	tryTerminate(false, true);
2899		}
2900
2901		/**
2902	<	* Attempts to cancel and/or stop all tasks, and reject all
2903	<	* subsequently submitted tasks. Tasks that are in the process of
2904	<	* being submitted or executed concurrently during the course of
2905	<	* this method may or may not be rejected. This method cancels
2906	<	* both existing and unexecuted tasks, in order to permit
2907	<	* termination in the presence of task dependencies. So the method
2908	<	* always returns an empty list (unlike the case for some other
2909	<	* Executors).
2902	>	* Possibly attempts to cancel and/or stop all tasks, and reject
2903	>	* all subsequently submitted tasks. Invocation has no effect on
2904	>	* execution state if this is the {@link #commonPool}, and no
2905	>	* additional effect if already shut down. Otherwise, tasks that
2906	>	* are in the process of being submitted or executed concurrently
2907	>	* during the course of this method may or may not be
2908	>	* rejected. This method cancels both existing and unexecuted
2909	>	* tasks, in order to permit termination in the presence of task
2910	>	* dependencies. So the method always returns an empty list
2911	>	* (unlike the case for some other Executors).
2912		*
2913		* @return an empty list
2914		* @throws SecurityException if a security manager exists and
#	Line 2441 \| Line 2918 \| public class ForkJoinPool extends Abstra
2918		*/
2919		public List<Runnable> shutdownNow() {
2920		checkPermission();
2921	<	tryTerminate(true, true);
2921	>	if (this != commonPool)
2922	>	tryTerminate(true, true);
2923		return Collections.emptyList();
2924		}
2925
#	Line 2498 \| Line 2976 \| public class ForkJoinPool extends Abstra
2976		public boolean awaitTermination(long timeout, TimeUnit unit)
2977		throws InterruptedException {
2978		long nanos = unit.toNanos(timeout);
2979	<	final Mutex lock = this.lock;
2980	<	lock.lock();
2981	<	try {
2982	<	for (;;) {
2983	<	if (isTerminated())
2984	<	return true;
2985	<	if (nanos <= 0)
2986	<	return false;
2987	<	nanos = termination.awaitNanos(nanos);
2979	>	if (isTerminated())
2980	>	return true;
2981	>	long startTime = System.nanoTime();
2982	>	boolean terminated = false;
2983	>	synchronized (this) {
2984	>	for (long waitTime = nanos, millis = 0L;;) {
2985	>	if (terminated = isTerminated() \|\|
2986	>	waitTime <= 0L \|\|
2987	>	(millis = unit.toMillis(waitTime)) <= 0L)
2988	>	break;
2989	>	wait(millis);
2990	>	waitTime = nanos - (System.nanoTime() - startTime);
2991		}
2511	–	} finally {
2512	–	lock.unlock();
2992		}
2993	+	return terminated;
2994		}
2995
2996		/**
#	Line 2612 \| Line 3092 \| public class ForkJoinPool extends Abstra
3092		ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ?
3093		((ForkJoinWorkerThread)t).pool : null);
3094		while (!blocker.isReleasable()) {
3095	<	if (p == null \|\| p.tryCompensate()) {
3095	>	if (p == null \|\| p.tryCompensate(null, blocker)) {
3096		try {
3097		do {} while (!blocker.isReleasable() && !blocker.block());
3098		} finally {
#	Line 2629 \| Line 3109 \| public class ForkJoinPool extends Abstra
3109		// implement RunnableFuture.
3110
3111		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
3112	<	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
3112	>	return new ForkJoinTask.AdaptedRunnable<T>(runnable, value);
3113		}
3114
3115		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
3116	<	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
3116	>	return new ForkJoinTask.AdaptedCallable<T>(callable);
3117		}
3118
3119		// Unsafe mechanics
3120		private static final sun.misc.Unsafe U;
3121		private static final long CTL;
3122		private static final long PARKBLOCKER;
3123	+	private static final int ABASE;
3124	+	private static final int ASHIFT;
3125	+	private static final long NEXTWORKERNUMBER;
3126	+	private static final long STEALCOUNT;
3127	+	private static final long MAINLOCK;
3128
3129		static {
3130		poolNumberGenerator = new AtomicInteger();
3131	+	nextSubmitterSeed = new AtomicInteger(0x55555555);
3132		modifyThreadPermission = new RuntimePermission("modifyThread");
3133		defaultForkJoinWorkerThreadFactory =
3134		new DefaultForkJoinWorkerThreadFactory();
3135		submitters = new ThreadSubmitter();
3136	+	int s;
3137		try {
3138		U = getUnsafe();
3139		Class<?> k = ForkJoinPool.class;
3140	+	Class<?> ak = ForkJoinTask[].class;
3141		CTL = U.objectFieldOffset
3142		(k.getDeclaredField("ctl"));
3143	+	NEXTWORKERNUMBER = U.objectFieldOffset
3144	+	(k.getDeclaredField("nextWorkerNumber"));
3145	+	STEALCOUNT = U.objectFieldOffset
3146	+	(k.getDeclaredField("stealCount"));
3147	+	MAINLOCK = U.objectFieldOffset
3148	+	(k.getDeclaredField("mainLock"));
3149		Class<?> tk = Thread.class;
3150		PARKBLOCKER = U.objectFieldOffset
3151		(tk.getDeclaredField("parkBlocker"));
3152	+	ABASE = U.arrayBaseOffset(ak);
3153	+	s = U.arrayIndexScale(ak);
3154	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3155	+	} catch (Exception e) {
3156	+	throw new Error(e);
3157	+	}
3158	+	if ((s & (s-1)) != 0)
3159	+	throw new Error("data type scale not a power of two");
3160	+	try { // Establish common pool
3161	+	String pp = System.getProperty(propPrefix + "parallelism");
3162	+	String fp = System.getProperty(propPrefix + "threadFactory");
3163	+	String up = System.getProperty(propPrefix + "exceptionHandler");
3164	+	ForkJoinWorkerThreadFactory fac = (fp == null) ?
3165	+	defaultForkJoinWorkerThreadFactory :
3166	+	((ForkJoinWorkerThreadFactory)ClassLoader.
3167	+	getSystemClassLoader().loadClass(fp).newInstance());
3168	+	Thread.UncaughtExceptionHandler ueh = (up == null) ? null :
3169	+	((Thread.UncaughtExceptionHandler)ClassLoader.
3170	+	getSystemClassLoader().loadClass(up).newInstance());
3171	+	int par;
3172	+	if ((pp == null \|\| (par = Integer.parseInt(pp)) <= 0))
3173	+	par = Runtime.getRuntime().availableProcessors();
3174	+	if (par > MAX_CAP)
3175	+	par = MAX_CAP;
3176	+	commonPoolParallelism = par;
3177	+	int n = par - 1; // precompute submit mask
3178	+	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4;
3179	+	n \|= n >>> 8; n \|= n >>> 16;
3180	+	int mask = ((n + 1) << 1) - 1;
3181	+	commonPool = new ForkJoinPool(par, mask, fac, ueh);
3182		} catch (Exception e) {
3183		throw new Error(e);
3184		}

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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents): Revision 1.122 by jsr166, Tue Jan 31 01:51:13 2012 UTC vs. Revision 1.139 by dl, Wed Oct 31 12:49:24 2012 UTC

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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.122 by jsr166, Tue Jan 31 01:51:13 2012 UTC vs.
Revision 1.139 by dl, Wed Oct 31 12:49:24 2012 UTC