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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.118 by jsr166, Sat Jan 28 04:34:54 2012 UTC vs.
Revision 1.136 by dl, Mon Oct 29 17:23:34 2012 UTC

#	Line 21 \| Line 21 \| import java.util.concurrent.RunnableFutu
21		import java.util.concurrent.TimeUnit;
22		import java.util.concurrent.atomic.AtomicInteger;
23		import java.util.concurrent.atomic.AtomicLong;
24	<	import java.util.concurrent.locks.ReentrantLock;
24	>	import java.util.concurrent.locks.AbstractQueuedSynchronizer;
25		import java.util.concurrent.locks.Condition;
26
27		/**
#	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 203 \| Line 201 \| public class ForkJoinPool extends Abstra
201		* take tasks, and they are multiplexed on to a finite number of
202		* shared work queues. However, classes are set up so that future
203		* extensions could allow submitters to optionally help perform
204	<	* tasks as well. Pool submissions from internal workers are also
205	<	* allowed, but use randomized rather than thread-hashed queue
206	<	* indices to avoid imbalance. Insertion of tasks in shared mode
207	<	* requires a lock (mainly to protect in the case of resizing) but
208	<	* we use only a simple spinlock (using bits in field runState),
209	<	* because submitters encountering a busy queue try or create
212	<	* others so never block.
204	>	* tasks as well. Insertion of tasks in shared mode requires a
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 -- they block only when creating and registering
209	>	* new queues.
210		*
211		* Management
212		* ==========
#	Line 238 \| Line 235 \| public class ForkJoinPool extends Abstra
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
247	<	* scanning. To avoid flailing during start-up, the array is
248	<	* presized to hold twice #parallelism workers (which is unlikely
249	<	* to need further resizing during execution). But to avoid
253	<	* dealing with so many null slots, variable runState includes a
254	<	* mask for the nearest power of two that contains all current
255	<	* workers. All worker thread creation is on-demand, triggered by
256	<	* task submissions, replacement of terminated workers, and/or
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
250		* compensation for blocked workers. However, all other support
251		* code is set up to work with other policies. To ensure that we
252		* do not hold on to worker references that would prevent GC, ALL
#	Line 266 \| Line 259 \| public class ForkJoinPool extends Abstra
259		* both index-check and null-check the IDs. All such accesses
260		* ignore bad IDs by returning out early from what they are doing,
261		* since this can only be associated with termination, in which
262	<	* case it is OK to give up.
263	<	*
264	<	* All uses of the workQueues array check that it is non-null
265	<	* (even if previously non-null). This allows nulling during
266	<	* termination, which is currently not necessary, but remains an
267	<	* option for resource-revocation-based shutdown schemes. It also
275	<	* helps reduce JIT issuance of uncommon-trap code, which tends to
262	>	* case it is OK to give up. All uses of the workQueues array
263	>	* also check that it is non-null (even if previously
264	>	* non-null). This allows nulling during termination, which is
265	>	* currently not necessary, but remains an option for
266	>	* resource-revocation-based shutdown schemes. It also helps
267	>	* reduce JIT issuance of uncommon-trap code, which tends to
268		* unnecessarily complicate control flow in some methods.
269		*
270		* Event Queuing. Unlike HPC work-stealing frameworks, we cannot
#	Line 323 \| 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 383 \| 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 workers 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 395 \| 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 418 \| Line 433 \| public class ForkJoinPool extends Abstra
433		* managed by ForkJoinPool, so are directly accessed. There is
434		* little point trying to reduce this, since any associated future
435		* changes in representations will need to be accompanied by
436	<	* algorithmic changes anyway. All together, these low-level
437	<	* implementation choices produce as much as a factor of 4
438	<	* performance improvement compared to naive implementations, and
439	<	* enable the processing of billions of tasks per second, at the
440	<	* expense of some ugliness.
441	<	*
442	<	* Methods signalWork() and scan() are the main bottlenecks, so are
443	<	* especially heavily micro-optimized/mangled. There are lots of
444	<	* inline assignments (of form "while ((local = field) != 0)")
445	<	* which are usually the simplest way to ensure the required read
446	<	* orderings (which are sometimes critical). This leads to a
447	<	* "C"-like style of listing declarations of these locals at the
448	<	* heads of methods or blocks. There are several occurrences of
449	<	* the unusual "do {} while (!cas...)" which is the simplest way
435	<	* to force an update of a CAS'ed variable. There are also other
436	<	* coding oddities that help some methods perform reasonably even
437	<	* when interpreted (not compiled).
436	>	* algorithmic changes anyway. Several methods intrinsically
437	>	* sprawl because they must accumulate sets of consistent reads of
438	>	* volatiles held in local variables. Methods signalWork() and
439	>	* scan() are the main bottlenecks, so are especially heavily
440	>	* micro-optimized/mangled. There are lots of inline assignments
441	>	* (of form "while ((local = field) != 0)") which are usually the
442	>	* simplest way to ensure the required read orderings (which are
443	>	* sometimes critical). This leads to a "C"-like style of listing
444	>	* declarations of these locals at the heads of methods or blocks.
445	>	* There are several occurrences of the unusual "do {} while
446	>	* (!cas...)" which is the simplest way to force an update of a
447	>	* CAS'ed variable. There are also other coding oddities that help
448	>	* some methods perform reasonably even when interpreted (not
449	>	* compiled).
450		*
451		* The order of declarations in this file is:
452	<	* (1) statics
453	<	* (2) fields (along with constants used when unpacking some of
454	<	* them), listed in an order that tends to reduce contention
455	<	* among them a bit under most JVMs;
456	<	* (3) nested classes
457	<	* (4) internal control methods
458	<	* (5) callbacks and other support for ForkJoinTask methods
459	<	* (6) exported methods (plus a few little helpers)
448	<	* (7) static block initializing all statics in a minimally
449	<	* dependent order.
452	>	* (1) Static utility functions
453	>	* (2) Nested (static) classes
454	>	* (3) Static fields
455	>	* (4) Fields, along with constants used when unpacking some of them
456	>	* (5) Internal control methods
457	>	* (6) Callbacks and other support for ForkJoinTask methods
458	>	* (7) Exported methods
459	>	* (8) Static block initializing statics in minimally dependent order
460		*/
461
462	+	// Static utilities
463	+
464	+	/**
465	+	* If there is a security manager, makes sure caller has
466	+	* permission to modify threads.
467	+	*/
468	+	private static void checkPermission() {
469	+	SecurityManager security = System.getSecurityManager();
470	+	if (security != null)
471	+	security.checkPermission(modifyThreadPermission);
472	+	}
473	+
474	+	// Nested classes
475	+
476		/**
477		* Factory for creating new {@link ForkJoinWorkerThread}s.
478		* A {@code ForkJoinWorkerThreadFactory} must be defined and used
#	Line 477 \| Line 501 \| public class ForkJoinPool extends Abstra
501		}
502
503		/**
504	<	* Creates a new ForkJoinWorkerThread. This factory is used unless
505	<	* overridden in ForkJoinPool constructors.
506	<	*/
507	<	public static final ForkJoinWorkerThreadFactory
484	<	defaultForkJoinWorkerThreadFactory;
485	<
486	<	/**
487	<	* Permission required for callers of methods that may start or
488	<	* kill threads.
489	<	*/
490	<	private static final RuntimePermission modifyThreadPermission;
491	<
492	<	/**
493	<	* If there is a security manager, makes sure caller has
494	<	* permission to modify threads.
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
507	>	* actually do anything beyond having a unique identity.
508		*/
509	<	private static void checkPermission() {
510	<	SecurityManager security = System.getSecurityManager();
511	<	if (security != null)
512	<	security.checkPermission(modifyThreadPermission);
509	>	static final class EmptyTask extends ForkJoinTask<Void> {
510	>	EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
511	>	public final Void getRawResult() { return null; }
512	>	public final void setRawResult(Void x) {}
513	>	public final boolean exec() { return true; }
514		}
515
516		/**
503	–	* Generator for assigning sequence numbers as pool names.
504	–	*/
505	–	private static final AtomicInteger poolNumberGenerator;
506	–
507	–	/**
508	–	* Bits and masks for control variables
509	–	*
510	–	* Field ctl is a long packed with:
511	–	* AC: Number of active running workers minus target parallelism (16 bits)
512	–	* TC: Number of total workers minus target parallelism (16 bits)
513	–	* ST: true if pool is terminating (1 bit)
514	–	* EC: the wait count of top waiting thread (15 bits)
515	–	* ID: ~(poolIndex >>> 1) of top of Treiber stack of waiters (16 bits)
516	–	*
517	–	* When convenient, we can extract the upper 32 bits of counts and
518	–	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
519	–	* (int)ctl. The ec field is never accessed alone, but always
520	–	* together with id and st. The offsets of counts by the target
521	–	* parallelism and the positionings of fields makes it possible to
522	–	* perform the most common checks via sign tests of fields: When
523	–	* ac is negative, there are not enough active workers, when tc is
524	–	* negative, there are not enough total workers, when id is
525	–	* negative, there is at least one waiting worker, and when e is
526	–	* negative, the pool is terminating. To deal with these possibly
527	–	* negative fields, we use casts in and out of "short" and/or
528	–	* signed shifts to maintain signedness.
529	–	*
530	–	* When a thread is queued (inactivated), its eventCount field is
531	–	* negative, which is the only way to tell if a worker is
532	–	* prevented from executing tasks, even though it must continue to
533	–	* scan for them to avoid queuing races.
534	–	*
535	–	* Field runState is an int packed with:
536	–	* SHUTDOWN: true if shutdown is enabled (1 bit)
537	–	* SEQ: a sequence number updated upon (de)registering workers (15 bits)
538	–	* MASK: mask (power of 2 - 1) covering all registered poolIndexes (16 bits)
539	–	*
540	–	* The combination of mask and sequence number enables simple
541	–	* consistency checks: Staleness of read-only operations on the
542	–	* workers and queues arrays can be checked by comparing runState
543	–	* before vs after the reads. The low 16 bits (i.e, anding with
544	–	* SMASK) hold the smallest power of two covering all worker
545	–	* indices, minus one. The mask for queues (vs workers) is twice
546	–	* this value plus 1.
547	–	*/
548	–
549	–	// bit positions/shifts for fields
550	–	private static final int AC_SHIFT = 48;
551	–	private static final int TC_SHIFT = 32;
552	–	private static final int ST_SHIFT = 31;
553	–	private static final int EC_SHIFT = 16;
554	–
555	–	// bounds
556	–	private static final int MAX_ID = 0x7fff; // max poolIndex
557	–	private static final int SMASK = 0xffff; // mask short bits
558	–	private static final int SHORT_SIGN = 1 << 15;
559	–	private static final int INT_SIGN = 1 << 31;
560	–
561	–	// masks
562	–	private static final long STOP_BIT = 0x0001L << ST_SHIFT;
563	–	private static final long AC_MASK = ((long)SMASK) << AC_SHIFT;
564	–	private static final long TC_MASK = ((long)SMASK) << TC_SHIFT;
565	–
566	–	// units for incrementing and decrementing
567	–	private static final long TC_UNIT = 1L << TC_SHIFT;
568	–	private static final long AC_UNIT = 1L << AC_SHIFT;
569	–
570	–	// masks and units for dealing with u = (int)(ctl >>> 32)
571	–	private static final int UAC_SHIFT = AC_SHIFT - 32;
572	–	private static final int UTC_SHIFT = TC_SHIFT - 32;
573	–	private static final int UAC_MASK = SMASK << UAC_SHIFT;
574	–	private static final int UTC_MASK = SMASK << UTC_SHIFT;
575	–	private static final int UAC_UNIT = 1 << UAC_SHIFT;
576	–	private static final int UTC_UNIT = 1 << UTC_SHIFT;
577	–
578	–	// masks and units for dealing with e = (int)ctl
579	–	private static final int E_MASK = 0x7fffffff; // no STOP_BIT
580	–	private static final int E_SEQ = 1 << EC_SHIFT;
581	–
582	–	// runState bits
583	–	private static final int SHUTDOWN = 1 << 31;
584	–	private static final int RS_SEQ = 1 << 16;
585	–	private static final int RS_SEQ_MASK = 0x7fff0000;
586	–
587	–	// access mode for WorkQueue
588	–	static final int LIFO_QUEUE = 0;
589	–	static final int FIFO_QUEUE = 1;
590	–	static final int SHARED_QUEUE = -1;
591	–
592	–	/**
593	–	* The wakeup interval (in nanoseconds) for a worker waiting for a
594	–	* task when the pool is quiescent to instead try to shrink the
595	–	* number of workers. The exact value does not matter too
596	–	* much. It must be short enough to release resources during
597	–	* sustained periods of idleness, but not so short that threads
598	–	* are continually re-created.
599	–	*/
600	–	private static final long SHRINK_RATE =
601	–	4L * 1000L * 1000L * 1000L; // 4 seconds
602	–
603	–	/**
604	–	* The timeout value for attempted shrinkage, includes
605	–	* some slop to cope with system timer imprecision.
606	–	*/
607	–	private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
608	–
609	–	/**
610	–	* The maximum stolen->joining link depth allowed in tryHelpStealer.
611	–	* Depths for legitimate chains are unbounded, but we use a fixed
612	–	* constant to avoid (otherwise unchecked) cycles and to bound
613	–	* staleness of traversal parameters at the expense of sometimes
614	–	* blocking when we could be helping.
615	–	*/
616	–	private static final int MAX_HELP_DEPTH = 16;
617	–
618	–	/*
619	–	* Field layout order in this class tends to matter more than one
620	–	* would like. Runtime layout order is only loosely related to
621	–	* declaration order and may differ across JVMs, but the following
622	–	* empirically works OK on current JVMs.
623	–	*/
624	–
625	–	volatile long ctl; // main pool control
626	–	final int parallelism; // parallelism level
627	–	final int localMode; // per-worker scheduling mode
628	–	int nextPoolIndex; // hint used in registerWorker
629	–	volatile int runState; // shutdown status, seq, and mask
630	–	WorkQueue[] workQueues; // main registry
631	–	final ReentrantLock lock; // for registration
632	–	final Condition termination; // for awaitTermination
633	–	final ForkJoinWorkerThreadFactory factory; // factory for new workers
634	–	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
635	–	final AtomicLong stealCount; // collect counts when terminated
636	–	final AtomicInteger nextWorkerNumber; // to create worker name string
637	–	final String workerNamePrefix; // Prefix for assigning worker names
638	–
639	–	/**
517		* Queues supporting work-stealing as well as external task
518		* submission. See above for main rationale and algorithms.
519		* Implementation relies heavily on "Unsafe" intrinsics
#	Line 685 \| Line 562 \| public class ForkJoinPool extends Abstra
562		* avoiding really bad worst-case access. (Until better JVM
563		* support is in place, this padding is dependent on transient
564		* properties of JVM field layout rules.) We also take care in
565	<	* allocating and sizing and resizing the array. Non-shared queue
565	>	* allocating, sizing and resizing the array. Non-shared queue
566		* arrays are initialized (via method growArray) by workers before
567		* use. Others are allocated on first use.
568		*/
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 719 \| 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) {
730	<	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.
748	–	* @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 774 \| Line 673 \| public class ForkJoinPool extends Abstra
673		boolean submitted = false;
674		if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
675		ForkJoinTask<?>[] a = array;
676	<	int s = top, n = s - base;
676	>	int s = top;
677		try {
678	<	if ((a != null && n < a.length - 1) \|\|
678	>	if ((a != null && a.length > s + 1 - base) \|\|
679		(a = growArray(false)) != null) { // must presize
680		int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
681		U.putObject(a, (long)j, task); // don't need "ordered"
#	Line 791 \| 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. (We do not have a shared
695	>	* version of this method because it is never needed.)
696		*/
697	<	final ForkJoinTask<?> poll() {
698	<	ForkJoinTask<?>[] a; int b, i;
699	<	while ((b = base) - top < 0 && (a = array) != null &&
700	<	(i = (a.length - 1) & b) >= 0) {
701	<	int j = (i << ASHIFT) + ABASE;
702	<	ForkJoinTask<?> t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
703	<	if (t != null && base == b &&
697	>	final ForkJoinTask<?> pop() {
698	>	ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
699	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
700	>	for (int s; (s = top - 1) - base >= 0;) {
701	>	long j = ((m & s) << ASHIFT) + ABASE;
702	>	if ((t = (ForkJoinTask<?>)U.getObject(a, j)) == null)
703	>	break;
704	>	if (U.compareAndSwapObject(a, j, t, null)) {
705	>	top = s;
706	>	return t;
707	>	}
708	>	}
709	>	}
710	>	return null;
711	>	}
712	>
713	>	/**
714	>	* Takes a task in FIFO order if b is base of queue and a task
715	>	* can be claimed without contention. Specialized versions
716	>	* appear in ForkJoinPool methods scan and tryHelpStealer.
717	>	*/
718	>	final ForkJoinTask<?> pollAt(int b) {
719	>	ForkJoinTask<?> t; ForkJoinTask<?>[] a;
720	>	if ((a = array) != null) {
721	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
722	>	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
723	>	base == b &&
724		U.compareAndSwapObject(a, j, t, null)) {
725		base = b + 1;
726		return t;
#	Line 809 \| Line 730 \| public class ForkJoinPool extends Abstra
730		}
731
732		/**
733	<	* Takes next task, if one exists, in LIFO order.
813	<	* Call only by owner in unshared queues.
733	>	* Takes next task, if one exists, in FIFO order.
734		*/
735	<	final ForkJoinTask<?> pop() {
736	<	ForkJoinTask<?> t; int m;
737	<	ForkJoinTask<?>[] a = array;
738	<	if (a != null && (m = a.length - 1) >= 0) {
739	<	for (int s; (s = top - 1) - base >= 0;) {
740	<	int j = ((m & s) << ASHIFT) + ABASE;
741	<	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) == null)
742	<	break;
743	<	if (U.compareAndSwapObject(a, j, t, null)) {
824	<	top = s;
735	>	final ForkJoinTask<?> poll() {
736	>	ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t;
737	>	while ((b = base) - top < 0 && (a = array) != null) {
738	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
739	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
740	>	if (t != null) {
741	>	if (base == b &&
742	>	U.compareAndSwapObject(a, j, t, null)) {
743	>	base = b + 1;
744		return t;
745		}
746		}
747	+	else if (base == b) {
748	+	if (b + 1 == top)
749	+	break;
750	+	Thread.yield(); // wait for lagging update
751	+	}
752		}
753		return null;
754		}
#	Line 849 \| Line 773 \| public class ForkJoinPool extends Abstra
773		}
774
775		/**
852	–	* Returns task at index b if b is current base of queue.
853	–	*/
854	–	final ForkJoinTask<?> pollAt(int b) {
855	–	ForkJoinTask<?>[] a; int i;
856	–	ForkJoinTask<?> task = null;
857	–	if ((a = array) != null && (i = ((a.length - 1) & b)) >= 0) {
858	–	int j = (i << ASHIFT) + ABASE;
859	–	ForkJoinTask<?> t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
860	–	if (t != null && base == b &&
861	–	U.compareAndSwapObject(a, j, t, null)) {
862	–	base = b + 1;
863	–	task = t;
864	–	}
865	–	}
866	–	return task;
867	–	}
868	–
869	–	/**
776		* Pops the given task only if it is at the current top.
777		*/
778		final boolean tryUnpush(ForkJoinTask<?> t) {
#	Line 881 \| Line 787 \| public class ForkJoinPool extends Abstra
787		}
788
789		/**
790	+	* Version of tryUnpush for shared queues; called by non-FJ
791	+	* submitters after prechecking that task probably exists.
792	+	*/
793	+	final boolean trySharedUnpush(ForkJoinTask<?> t) {
794	+	boolean success = false;
795	+	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
796	+	try {
797	+	ForkJoinTask<?>[] a; int s;
798	+	if ((a = array) != null && (s = top) != base &&
799	+	U.compareAndSwapObject
800	+	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
801	+	top = s;
802	+	success = true;
803	+	}
804	+	} finally {
805	+	runState = 0; // unlock
806	+	}
807	+	}
808	+	return success;
809	+	}
810	+
811	+	/**
812		* Polls the given task only if it is at the current base.
813		*/
814		final boolean pollFor(ForkJoinTask<?> task) {
815	<	ForkJoinTask<?>[] a; int b, i;
816	<	if ((b = base) - top < 0 && (a = array) != null &&
817	<	(i = (a.length - 1) & b) >= 0) {
890	<	int j = (i << ASHIFT) + ABASE;
815	>	ForkJoinTask<?>[] a; int b;
816	>	if ((b = base) - top < 0 && (a = array) != null) {
817	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
818		if (U.getObjectVolatile(a, j) == task && base == b &&
819		U.compareAndSwapObject(a, j, task, null)) {
820		base = b + 1;
#	Line 898 \| Line 825 \| public class ForkJoinPool extends Abstra
825		}
826
827		/**
901	–	* If present, removes from queue and executes the given task, or
902	–	* any other cancelled task. Returns (true) immediately on any CAS
903	–	* or consistency check failure so caller can retry.
904	–	*
905	–	* @return false if no progress can be made
906	–	*/
907	–	final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
908	–	boolean removed = false, empty = true, progress = true;
909	–	ForkJoinTask<?>[] a; int m, s, b, n;
910	–	if ((a = array) != null && (m = a.length - 1) >= 0 &&
911	–	(n = (s = top) - (b = base)) > 0) {
912	–	for (ForkJoinTask<?> t;;) { // traverse from s to b
913	–	int j = ((--s & m) << ASHIFT) + ABASE;
914	–	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
915	–	if (t == null) // inconsistent length
916	–	break;
917	–	else if (t == task) {
918	–	if (s + 1 == top) { // pop
919	–	if (!U.compareAndSwapObject(a, j, task, null))
920	–	break;
921	–	top = s;
922	–	removed = true;
923	–	}
924	–	else if (base == b) // replace with proxy
925	–	removed = U.compareAndSwapObject(a, j, task,
926	–	new EmptyTask());
927	–	break;
928	–	}
929	–	else if (t.status >= 0)
930	–	empty = false;
931	–	else if (s + 1 == top) { // pop and throw away
932	–	if (U.compareAndSwapObject(a, j, t, null))
933	–	top = s;
934	–	break;
935	–	}
936	–	if (--n == 0) {
937	–	if (!empty && base == b)
938	–	progress = false;
939	–	break;
940	–	}
941	–	}
942	–	}
943	–	if (removed)
944	–	task.doExec();
945	–	return progress;
946	–	}
947	–
948	–	/**
828		* Initializes or doubles the capacity of array. Call either
829		* by owner or with lock held -- it is OK for base, but not
830		* top, to move while resizings are in progress.
#	Line 990 \| Line 869 \| public class ForkJoinPool extends Abstra
869		ForkJoinTask.cancelIgnoringExceptions(t);
870		}
871
872	+	/**
873	+	* Computes next value for random probes. Scans don't require
874	+	* a very high quality generator, but also not a crummy one.
875	+	* Marsaglia xor-shift is cheap and works well enough. Note:
876	+	* This is manually inlined in its usages in ForkJoinPool to
877	+	* avoid writes inside busy scan loops.
878	+	*/
879	+	final int nextSeed() {
880	+	int r = seed;
881	+	r ^= r << 13;
882	+	r ^= r >>> 17;
883	+	return seed = r ^= r << 5;
884	+	}
885	+
886		// Execution methods
887
888		/**
889	<	* Removes and runs tasks until empty, using local mode
997	<	* ordering.
889	>	* Pops and runs tasks until empty.
890		*/
891	<	final void runLocalTasks() {
892	<	if (base - top < 0) {
893	<	for (ForkJoinTask<?> t; (t = nextLocalTask()) != null; )
891	>	private void popAndExecAll() {
892	>	// A bit faster than repeated pop calls
893	>	ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t;
894	>	while ((a = array) != null && (m = a.length - 1) >= 0 &&
895	>	(s = top - 1) - base >= 0 &&
896	>	(t = ((ForkJoinTask<?>)
897	>	U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
898	>	!= null) {
899	>	if (U.compareAndSwapObject(a, j, t, null)) {
900	>	top = s;
901		t.doExec();
902	+	}
903		}
904		}
905
906		/**
907	+	* Polls and runs tasks until empty.
908	+	*/
909	+	private void pollAndExecAll() {
910	+	for (ForkJoinTask<?> t; (t = poll()) != null;)
911	+	t.doExec();
912	+	}
913	+
914	+	/**
915	+	* If present, removes from queue and executes the given task, or
916	+	* any other cancelled task. Returns (true) immediately on any CAS
917	+	* or consistency check failure so caller can retry.
918	+	*
919	+	* @return 0 if no progress can be made, else positive
920	+	* (this unusual convention simplifies use with tryHelpStealer.)
921	+	*/
922	+	final int tryRemoveAndExec(ForkJoinTask<?> task) {
923	+	int stat = 1;
924	+	boolean removed = false, empty = true;
925	+	ForkJoinTask<?>[] a; int m, s, b, n;
926	+	if ((a = array) != null && (m = a.length - 1) >= 0 &&
927	+	(n = (s = top) - (b = base)) > 0) {
928	+	for (ForkJoinTask<?> t;;) { // traverse from s to b
929	+	int j = ((--s & m) << ASHIFT) + ABASE;
930	+	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
931	+	if (t == null) // inconsistent length
932	+	break;
933	+	else if (t == task) {
934	+	if (s + 1 == top) { // pop
935	+	if (!U.compareAndSwapObject(a, j, task, null))
936	+	break;
937	+	top = s;
938	+	removed = true;
939	+	}
940	+	else if (base == b) // replace with proxy
941	+	removed = U.compareAndSwapObject(a, j, task,
942	+	new EmptyTask());
943	+	break;
944	+	}
945	+	else if (t.status >= 0)
946	+	empty = false;
947	+	else if (s + 1 == top) { // pop and throw away
948	+	if (U.compareAndSwapObject(a, j, t, null))
949	+	top = s;
950	+	break;
951	+	}
952	+	if (--n == 0) {
953	+	if (!empty && base == b)
954	+	stat = 0;
955	+	break;
956	+	}
957	+	}
958	+	}
959	+	if (removed)
960	+	task.doExec();
961	+	return stat;
962	+	}
963	+
964	+	/**
965		* Executes a top-level task and any local tasks remaining
966		* after execution.
1009	–	*
1010	–	* @return true unless terminating
967		*/
968	<	final boolean runTask(ForkJoinTask<?> t) {
1013	<	boolean alive = true;
968	>	final void runTask(ForkJoinTask<?> t) {
969		if (t != null) {
970		currentSteal = t;
971		t.doExec();
972	<	runLocalTasks();
972	>	if (top != base) { // process remaining local tasks
973	>	if (mode == 0)
974	>	popAndExecAll();
975	>	else
976	>	pollAndExecAll();
977	>	}
978		++nsteals;
979		currentSteal = null;
980		}
1021	–	else if (runState < 0) // terminating
1022	–	alive = false;
1023	–	return alive;
981		}
982
983		/**
#	Line 1036 \| Line 993 \| public class ForkJoinPool extends Abstra
993		}
994
995		/**
996	<	* Computes next value for random probes. Scans don't require
1040	<	* a very high quality generator, but also not a crummy one.
1041	<	* Marsaglia xor-shift is cheap and works well enough. Note:
1042	<	* This is manually inlined in several usages in ForkJoinPool
1043	<	* to avoid writes inside busy scan loops.
996	>	* Returns true if owned and not known to be blocked.
997		*/
998	<	final int nextSeed() {
999	<	int r = seed;
1000	<	r ^= r << 13;
1001	<	r ^= r >>> 17;
1002	<	r ^= r << 5;
1003	<	return seed = r;
998	>	final boolean isApparentlyUnblocked() {
999	>	Thread wt; Thread.State s;
1000	>	return (eventCount >= 0 &&
1001	>	(wt = owner) != null &&
1002	>	(s = wt.getState()) != Thread.State.BLOCKED &&
1003	>	s != Thread.State.WAITING &&
1004	>	s != Thread.State.TIMED_WAITING);
1005	>	}
1006	>
1007	>	/**
1008	>	* If this owned and is not already interrupted, try to
1009	>	* interrupt and/or unpark, ignoring exceptions.
1010	>	*/
1011	>	final void interruptOwner() {
1012	>	Thread wt, p;
1013	>	if ((wt = owner) != null && !wt.isInterrupted()) {
1014	>	try {
1015	>	wt.interrupt();
1016	>	} catch (SecurityException ignore) {
1017	>	}
1018	>	}
1019	>	if ((p = parker) != null)
1020	>	U.unpark(p);
1021		}
1022
1023		// Unsafe mechanics
#	Line 1075 \| Line 1045 \| public class ForkJoinPool extends Abstra
1045		}
1046
1047		/**
1048	<	* Class for artificial tasks that are used to replace the target
1049	<	* of local joins if they are removed from an interior queue slot
1050	<	* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
1051	<	* actually do anything beyond having a unique identity.
1052	<	*/
1053	<	static final class EmptyTask extends ForkJoinTask<Void> {
1054	<	EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
1055	<	public Void getRawResult() { return null; }
1056	<	public void setRawResult(Void x) {}
1057	<	public boolean exec() { return true; }
1058	<	}
1059	<
1060	<	/**
1061	<	* Per-thread records for (typically non-FJ) threads that submit
1092	<	* to pools. Cureently holds only psuedo-random seed / index that
1093	<	* is used to choose submission queues in method doSubmit. In the
1094	<	* future, this may incorporate a means to implement different
1095	<	* task rejection and resubmission policies.
1048	>	* Per-thread records for threads that submit to pools. Currently
1049	>	* holds only pseudo-random seed / index that is used to choose
1050	>	* submission queues in method doSubmit. In the future, this may
1051	>	* also incorporate a means to implement different task rejection
1052	>	* and resubmission policies.
1053	>	*
1054	>	* Seeds for submitters and workers/workQueues work in basically
1055	>	* the same way but are initialized and updated using slightly
1056	>	* different mechanics. Both are initialized using the same
1057	>	* approach as in class ThreadLocal, where successive values are
1058	>	* unlikely to collide with previous values. This is done during
1059	>	* registration for workers, but requires a separate AtomicInteger
1060	>	* for submitters. Seeds are then randomly modified upon
1061	>	* collisions using xorshifts, which requires a non-zero seed.
1062		*/
1063		static final class Submitter {
1064	<	int seed; // seed for random submission queue selection
1099	<
1100	<	// Heuristic padding to ameliorate unfortunate memory placements
1101	<	int p0, p1, p2, p3, p4, p5, p6, p7, p8, p9, pa, pb, pc, pd, pe;
1102	<
1064	>	int seed;
1065		Submitter() {
1066	<	// Use identityHashCode, forced negative, for seed
1067	<	seed = System.identityHashCode(Thread.currentThread()) \| (1 << 31);
1106	<	}
1107	<
1108	<	/**
1109	<	* Computes next value for random probes. Like method
1110	<	* WorkQueue.nextSeed, this is manually inlined in several
1111	<	* usages to avoid writes inside busy loops.
1112	<	*/
1113	<	final int nextSeed() {
1114	<	int r = seed;
1115	<	r ^= r << 13;
1116	<	r ^= r >>> 17;
1117	<	return seed = r ^= r << 5;
1066	>	int s = nextSubmitterSeed.getAndAdd(SEED_INCREMENT);
1067	>	seed = (s == 0) ? 1 : s; // ensure non-zero
1068		}
1069		}
1070
#	Line 1123 \| Line 1073 \| public class ForkJoinPool extends Abstra
1073		public Submitter initialValue() { return new Submitter(); }
1074		}
1075
1076	+	// static fields (initialized in static initializer below)
1077	+
1078		/**
1079	<	* Per-thread submission bookeeping. Shared across all pools
1079	>	* Creates a new ForkJoinWorkerThread. This factory is used unless
1080	>	* overridden in ForkJoinPool constructors.
1081	>	*/
1082	>	public static final ForkJoinWorkerThreadFactory
1083	>	defaultForkJoinWorkerThreadFactory;
1084	>
1085	>
1086	>	/** Property prefix for constructing common pool */
1087	>	private static final String propPrefix =
1088	>	"java.util.concurrent.ForkJoinPool.common.";
1089	>
1090	>	/**
1091	>	* Common (static) pool. Non-null for public use unless a static
1092	>	* construction exception, but internal usages must null-check on
1093	>	* use.
1094	>	*/
1095	>	static final ForkJoinPool commonPool;
1096	>
1097	>	/**
1098	>	* Common pool parallelism. Must equal commonPool.parallelism.
1099	>	*/
1100	>	static final int commonPoolParallelism;
1101	>
1102	>	/**
1103	>	* Generator for assigning sequence numbers as pool names.
1104	>	*/
1105	>	private static final AtomicInteger poolNumberGenerator;
1106	>
1107	>	/**
1108	>	* Generator for initial hashes/seeds for submitters. Accessed by
1109	>	* Submitter class constructor.
1110	>	*/
1111	>	static final AtomicInteger nextSubmitterSeed;
1112	>
1113	>	/**
1114	>	* Permission required for callers of methods that may start or
1115	>	* kill threads.
1116	>	*/
1117	>	private static final RuntimePermission modifyThreadPermission;
1118	>
1119	>	/**
1120	>	* Per-thread submission bookkeeping. Shared across all pools
1121		* to reduce ThreadLocal pollution and because random motion
1122		* to avoid contention in one pool is likely to hold for others.
1123		*/
1124	<	static final ThreadSubmitter submitters = new ThreadSubmitter();
1124	>	private static final ThreadSubmitter submitters;
1125	>
1126	>	// static constants
1127
1128		/**
1129	<	* Top-level runloop for workers
1129	>	* Initial timeout value (in nanoseconds) for the thread triggering
1130	>	* quiescence to park waiting for new work. On timeout, the thread
1131	>	* will instead try to shrink the number of workers.
1132		*/
1133	<	final void runWorker(ForkJoinWorkerThread wt) {
1137	<	// Initialize queue array and seed in this thread
1138	<	WorkQueue w = wt.workQueue;
1139	<	w.growArray(false);
1140	<	// Same initial hash as Submitters
1141	<	w.seed = System.identityHashCode(Thread.currentThread()) \| (1 << 31);
1133	>	private static final long IDLE_TIMEOUT = 1000L * 1000L * 1000L; // 1sec
1134
1135	<	do {} while (w.runTask(scan(w)));
1135	>	/**
1136	>	* Timeout value when there are more threads than parallelism level
1137	>	*/
1138	>	private static final long FAST_IDLE_TIMEOUT = 100L * 1000L * 1000L;
1139	>
1140	>	/**
1141	>	* The maximum stolen->joining link depth allowed in method
1142	>	* tryHelpStealer. Must be a power of two. This value also
1143	>	* controls the maximum number of times to try to help join a task
1144	>	* without any apparent progress or change in pool state before
1145	>	* giving up and blocking (see awaitJoin). Depths for legitimate
1146	>	* chains are unbounded, but we use a fixed constant to avoid
1147	>	* (otherwise unchecked) cycles and to bound staleness of
1148	>	* traversal parameters at the expense of sometimes blocking when
1149	>	* we could be helping.
1150	>	*/
1151	>	private static final int MAX_HELP = 64;
1152	>
1153	>	/**
1154	>	* Secondary time-based bound (in nanosecs) for helping attempts
1155	>	* before trying compensated blocking in awaitJoin. Used in
1156	>	* conjunction with MAX_HELP to reduce variance due to different
1157	>	* polling rates associated with different helping options. The
1158	>	* value should roughly approximate the time required to create
1159	>	* and/or activate a worker thread.
1160	>	*/
1161	>	private static final long COMPENSATION_DELAY = 1L << 18; // ~0.25 millisec
1162	>
1163	>	/**
1164	>	* Increment for seed generators. See class ThreadLocal for
1165	>	* explanation.
1166	>	*/
1167	>	private static final int SEED_INCREMENT = 0x61c88647;
1168	>
1169	>	/**
1170	>	* Bits and masks for control variables
1171	>	*
1172	>	* Field ctl is a long packed with:
1173	>	* AC: Number of active running workers minus target parallelism (16 bits)
1174	>	* TC: Number of total workers minus target parallelism (16 bits)
1175	>	* ST: true if pool is terminating (1 bit)
1176	>	* EC: the wait count of top waiting thread (15 bits)
1177	>	* ID: poolIndex of top of Treiber stack of waiters (16 bits)
1178	>	*
1179	>	* When convenient, we can extract the upper 32 bits of counts and
1180	>	* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
1181	>	* (int)ctl. The ec field is never accessed alone, but always
1182	>	* together with id and st. The offsets of counts by the target
1183	>	* parallelism and the positionings of fields makes it possible to
1184	>	* perform the most common checks via sign tests of fields: When
1185	>	* ac is negative, there are not enough active workers, when tc is
1186	>	* negative, there are not enough total workers, and when e is
1187	>	* negative, the pool is terminating. To deal with these possibly
1188	>	* negative fields, we use casts in and out of "short" and/or
1189	>	* signed shifts to maintain signedness.
1190	>	*
1191	>	* When a thread is queued (inactivated), its eventCount field is
1192	>	* set negative, which is the only way to tell if a worker is
1193	>	* prevented from executing tasks, even though it must continue to
1194	>	* scan for them to avoid queuing races. Note however that
1195	>	* eventCount updates lag releases so usage requires care.
1196	>	*
1197	>	* Field runState is an int packed with:
1198	>	* SHUTDOWN: true if shutdown is enabled (1 bit)
1199	>	* SEQ: a sequence number updated upon (de)registering workers (30 bits)
1200	>	* INIT: set true after workQueues array construction (1 bit)
1201	>	*
1202	>	* The sequence number enables simple consistency checks:
1203	>	* Staleness of read-only operations on the workQueues array can
1204	>	* be checked by comparing runState before vs after the reads.
1205	>	*/
1206	>
1207	>	// bit positions/shifts for fields
1208	>	private static final int AC_SHIFT = 48;
1209	>	private static final int TC_SHIFT = 32;
1210	>	private static final int ST_SHIFT = 31;
1211	>	private static final int EC_SHIFT = 16;
1212	>
1213	>	// bounds
1214	>	private static final int SMASK = 0xffff; // short bits
1215	>	private static final int MAX_CAP = 0x7fff; // max #workers - 1
1216	>	private static final int SQMASK = 0xfffe; // even short bits
1217	>	private static final int SHORT_SIGN = 1 << 15;
1218	>	private static final int INT_SIGN = 1 << 31;
1219	>
1220	>	// masks
1221	>	private static final long STOP_BIT = 0x0001L << ST_SHIFT;
1222	>	private static final long AC_MASK = ((long)SMASK) << AC_SHIFT;
1223	>	private static final long TC_MASK = ((long)SMASK) << TC_SHIFT;
1224	>
1225	>	// units for incrementing and decrementing
1226	>	private static final long TC_UNIT = 1L << TC_SHIFT;
1227	>	private static final long AC_UNIT = 1L << AC_SHIFT;
1228	>
1229	>	// masks and units for dealing with u = (int)(ctl >>> 32)
1230	>	private static final int UAC_SHIFT = AC_SHIFT - 32;
1231	>	private static final int UTC_SHIFT = TC_SHIFT - 32;
1232	>	private static final int UAC_MASK = SMASK << UAC_SHIFT;
1233	>	private static final int UTC_MASK = SMASK << UTC_SHIFT;
1234	>	private static final int UAC_UNIT = 1 << UAC_SHIFT;
1235	>	private static final int UTC_UNIT = 1 << UTC_SHIFT;
1236	>
1237	>	// masks and units for dealing with e = (int)ctl
1238	>	private static final int E_MASK = 0x7fffffff; // no STOP_BIT
1239	>	private static final int E_SEQ = 1 << EC_SHIFT;
1240	>
1241	>	// runState bits
1242	>	private static final int SHUTDOWN = 1 << 31;
1243	>
1244	>	// access mode for WorkQueue
1245	>	static final int LIFO_QUEUE = 0;
1246	>	static final int FIFO_QUEUE = 1;
1247	>	static final int SHARED_QUEUE = -1;
1248	>
1249	>	// Instance fields
1250	>
1251	>	/*
1252	>	* Field layout order in this class tends to matter more than one
1253	>	* would like. Runtime layout order is only loosely related to
1254	>	* declaration order and may differ across JVMs, but the following
1255	>	* empirically works OK on current JVMs.
1256	>	*/
1257	>
1258	>	volatile long stealCount; // collects worker counts
1259	>	volatile long ctl; // main pool control
1260	>	final int parallelism; // parallelism level
1261	>	final int localMode; // per-worker scheduling mode
1262	>	volatile int nextWorkerNumber; // to create worker name string
1263	>	final int submitMask; // submit queue index bound
1264	>	int nextSeed; // for initializing worker seeds
1265	>	volatile int mainLock; // spinlock for array updates
1266	>	volatile int runState; // shutdown status and seq
1267	>	WorkQueue[] workQueues; // main registry
1268	>	final ForkJoinWorkerThreadFactory factory; // factory for new workers
1269	>	final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1270	>	final String workerNamePrefix; // to create worker name string
1271	>
1272	>	/*
1273	>	* Mechanics for main lock protecting worker array updates. Uses
1274	>	* the same strategy as ConcurrentHashMap bins -- a spinLock for
1275	>	* normal cases, but falling back to builtin lock when (rarely)
1276	>	* needed. See internal ConcurrentHashMap documentation for
1277	>	* explanation.
1278	>	*/
1279	>
1280	>	static final int LOCK_WAITING = 2; // bit to indicate need for signal
1281	>	static final int MAX_LOCK_SPINS = 1 << 8;
1282	>
1283	>	private void tryAwaitMainLock() {
1284	>	int spins = MAX_LOCK_SPINS, r = 0, h;
1285	>	while (((h = mainLock) & 1) != 0) {
1286	>	if (r == 0)
1287	>	r = ThreadLocalRandom.current().nextInt(); // randomize spins
1288	>	else if (spins >= 0) {
1289	>	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1290	>	if (r >= 0)
1291	>	--spins;
1292	>	}
1293	>	else if (U.compareAndSwapInt(this, MAINLOCK, h, h \| LOCK_WAITING)) {
1294	>	synchronized (this) {
1295	>	if ((mainLock & LOCK_WAITING) != 0) {
1296	>	try {
1297	>	wait();
1298	>	} catch (InterruptedException ie) {
1299	>	Thread.currentThread().interrupt();
1300	>	}
1301	>	}
1302	>	else
1303	>	notifyAll(); // possibly won race vs signaller
1304	>	}
1305	>	break;
1306	>	}
1307	>	}
1308		}
1309
1310	<	// Creating, registering and deregistering workers
1310	>	// Creating, registering, and deregistering workers
1311
1312		/**
1313		* Tries to create and start a worker
1314		*/
1315		private void addWorker() {
1316		Throwable ex = null;
1317	<	ForkJoinWorkerThread w = null;
1317	>	ForkJoinWorkerThread wt = null;
1318		try {
1319	<	if ((w = factory.newThread(this)) != null) {
1320	<	w.start();
1319	>	if ((wt = factory.newThread(this)) != null) {
1320	>	wt.start();
1321		return;
1322		}
1323		} catch (Throwable e) {
1324		ex = e;
1325		}
1326	<	deregisterWorker(w, ex);
1326	>	deregisterWorker(wt, ex); // adjust counts etc on failure
1327		}
1328
1329		/**
#	Line 1169 \| Line 1333 \| public class ForkJoinPool extends Abstra
1333		* ForkJoinWorkerThread.
1334		*/
1335		final String nextWorkerName() {
1336	<	return workerNamePrefix.concat
1337	<	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1336	>	int n;
1337	>	do {} while(!U.compareAndSwapInt(this, NEXTWORKERNUMBER,
1338	>	n = nextWorkerNumber, ++n));
1339	>	return workerNamePrefix.concat(Integer.toString(n));
1340		}
1341
1342		/**
1343	<	* Callback from ForkJoinWorkerThread constructor to establish and
1344	<	* record its WorkQueue.
1343	>	* Callback from ForkJoinWorkerThread constructor to establish its
1344	>	* poolIndex and record its WorkQueue. To avoid scanning bias due
1345	>	* to packing entries in front of the workQueues array, we treat
1346	>	* the array as a simple power-of-two hash table using per-thread
1347	>	* seed as hash, expanding as needed.
1348		*
1349	<	* @param wt the worker thread
1349	>	* @param w the worker's queue
1350		*/
1351	<	final void registerWorker(ForkJoinWorkerThread wt) {
1352	<	WorkQueue w = wt.workQueue;
1353	<	ReentrantLock lock = this.lock;
1185	<	lock.lock();
1351	>	final void registerWorker(WorkQueue w) {
1352	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1353	>	tryAwaitMainLock();
1354		try {
1355	<	int k = nextPoolIndex;
1356	<	WorkQueue[] ws = workQueues;
1357	<	if (ws != null) { // ignore on shutdown
1358	<	int n = ws.length;
1359	<	if (k < 0 \|\| (k & 1) == 0 \|\| k >= n \|\| ws[k] != null) {
1360	<	for (k = 1; k < n && ws[k] != null; k += 2)
1361	<	; // workers are at odd indices
1362	<	if (k >= n) // resize
1363	<	workQueues = ws = Arrays.copyOf(ws, n << 1);
1364	<	}
1365	<	w.poolIndex = k;
1366	<	w.eventCount = ~(k >>> 1) & SMASK; // Set up wait count
1367	<	ws[k] = w; // record worker
1368	<	nextPoolIndex = k + 2;
1369	<	int rs = runState;
1370	<	int m = rs & SMASK; // recalculate runState mask
1371	<	if (k > m)
1372	<	m = (m << 1) + 1;
1373	<	runState = (rs & SHUTDOWN) \| ((rs + RS_SEQ) & RS_SEQ_MASK) \| m;
1355	>	WorkQueue[] ws;
1356	>	if ((ws = workQueues) == null)
1357	>	ws = workQueues = new WorkQueue[submitMask + 1];
1358	>	if (w != null) {
1359	>	int rs, n = ws.length, m = n - 1;
1360	>	int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence
1361	>	w.seed = (s == 0) ? 1 : s; // ensure non-zero seed
1362	>	int r = (s << 1) \| 1; // use odd-numbered indices
1363	>	if (ws[r &= m] != null) { // collision
1364	>	int probes = 0; // step by approx half size
1365	>	int step = (n <= 4) ? 2 : ((n >>> 1) & SQMASK) + 2;
1366	>	while (ws[r = (r + step) & m] != null) {
1367	>	if (++probes >= n) {
1368	>	workQueues = ws = Arrays.copyOf(ws, n <<= 1);
1369	>	m = n - 1;
1370	>	probes = 0;
1371	>	}
1372	>	}
1373	>	}
1374	>	w.eventCount = w.poolIndex = r; // establish before recording
1375	>	ws[r] = w; // also update seq
1376	>	runState = ((rs = runState) & SHUTDOWN) \| ((rs + 2) & ~SHUTDOWN);
1377		}
1378		} finally {
1379	<	lock.unlock();
1379	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1380	>	mainLock = 0;
1381	>	synchronized (this) { notifyAll(); };
1382	>	}
1383		}
1384	+
1385		}
1386
1387		/**
1388	<	* Final callback from terminating worker, as well as failure to
1389	<	* construct or start a worker in addWorker. Removes record of
1388	>	* Final callback from terminating worker, as well as upon failure
1389	>	* to construct or start a worker in addWorker. Removes record of
1390		* worker from array, and adjusts counts. If pool is shutting
1391		* down, tries to complete termination.
1392		*
#	Line 1222 \| Line 1397 \| public class ForkJoinPool extends Abstra
1397		WorkQueue w = null;
1398		if (wt != null && (w = wt.workQueue) != null) {
1399		w.runState = -1; // ensure runState is set
1400	<	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1400	>	long steals = w.totalSteals + w.nsteals, sc;
1401	>	do {} while(!U.compareAndSwapLong(this, STEALCOUNT,
1402	>	sc = stealCount, sc + steals));
1403		int idx = w.poolIndex;
1404	<	ReentrantLock lock = this.lock;
1405	<	lock.lock();
1406	<	try { // remove record from array
1404	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1405	>	tryAwaitMainLock();
1406	>	try {
1407		WorkQueue[] ws = workQueues;
1408		if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1409	<	ws[nextPoolIndex = idx] = null;
1409	>	ws[idx] = null;
1410		} finally {
1411	<	lock.unlock();
1411	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1412	>	mainLock = 0;
1413	>	synchronized (this) { notifyAll(); };
1414	>	}
1415		}
1416		}
1417
#	Line 1241 \| Line 1421 \| public class ForkJoinPool extends Abstra
1421		((c - TC_UNIT) & TC_MASK) \|
1422		(c & ~(AC_MASK\|TC_MASK)))));
1423
1424	<	if (!tryTerminate(false) && w != null) {
1424	>	if (!tryTerminate(false, false) && w != null) {
1425		w.cancelAll(); // cancel remaining tasks
1426		if (w.array != null) // suppress signal if never ran
1427		signalWork(); // wake up or create replacement
1428	+	if (ex == null) // help clean refs on way out
1429	+	ForkJoinTask.helpExpungeStaleExceptions();
1430		}
1431
1432		if (ex != null) // rethrow
1433		U.throwException(ex);
1434		}
1435
1436	+	// Submissions
1437	+
1438		/**
1439	<	* Tries to add and register a new queue at the given index.
1439	>	* Unless shutting down, adds the given task to a submission queue
1440	>	* at submitter's current queue index (modulo submission
1441	>	* range). If no queue exists at the index, one is created. If
1442	>	* the queue is busy, another index is randomly chosen. The
1443	>	* submitMask bounds the effective number of queues to the
1444	>	* (nearest power of two for) parallelism level.
1445		*
1446	<	* @param idx the workQueues array index to register the queue
1447	<	* @return the queue, or null if could not add because could
1448	<	* not acquire lock or idx is unusable
1449	<	*/
1450	<	private WorkQueue tryAddSharedQueue(int idx) {
1451	<	WorkQueue q = null;
1452	<	ReentrantLock lock = this.lock;
1453	<	if (idx >= 0 && (idx & 1) == 0 && !lock.isLocked()) {
1454	<	// create queue outside of lock but only if apparently free
1455	<	WorkQueue nq = new WorkQueue(null, SHARED_QUEUE);
1456	<	if (lock.tryLock()) {
1446	>	* @param task the task. Caller must ensure non-null.
1447	>	*/
1448	>	private void doSubmit(ForkJoinTask<?> task) {
1449	>	Submitter s = submitters.get();
1450	>	for (int r = s.seed, m = submitMask;;) {
1451	>	WorkQueue[] ws; WorkQueue q;
1452	>	int k = r & m & SQMASK; // use only even indices
1453	>	if (runState < 0)
1454	>	throw new RejectedExecutionException(); // shutting down
1455	>	else if ((ws = workQueues) == null \|\| ws.length <= k) {
1456	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1457	>	tryAwaitMainLock();
1458		try {
1459	<	WorkQueue[] ws = workQueues;
1460	<	if (ws != null && idx < ws.length) {
1461	<	if ((q = ws[idx]) == null) {
1462	<	int rs; // update runState seq
1463	<	ws[idx] = q = nq;
1464	<	runState = (((rs = runState) & SHUTDOWN) \|
1465	<	((rs + RS_SEQ) & ~SHUTDOWN));
1466	<	}
1459	>	if (workQueues == null)
1460	>	workQueues = new WorkQueue[submitMask + 1];
1461	>	} finally {
1462	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1463	>	mainLock = 0;
1464	>	synchronized (this) { notifyAll(); };
1465	>	}
1466	>	}
1467	>	}
1468	>	else if ((q = ws[k]) == null) { // create new queue
1469	>	WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE);
1470	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1471	>	tryAwaitMainLock();
1472	>	try {
1473	>	int rs = runState; // to update seq
1474	>	if (ws == workQueues && ws[k] == null) {
1475	>	ws[k] = nq;
1476	>	runState = ((rs & SHUTDOWN) \| ((rs + 2) & ~SHUTDOWN));
1477		}
1478		} finally {
1479	<	lock.unlock();
1479	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1480	>	mainLock = 0;
1481	>	synchronized (this) { notifyAll(); };
1482	>	}
1483		}
1484		}
1485	+	else if (q.trySharedPush(task)) {
1486	+	signalWork();
1487	+	return;
1488	+	}
1489	+	else if (m > 1) { // move to a different index
1490	+	r ^= r << 13; // same xorshift as WorkQueues
1491	+	r ^= r >>> 17;
1492	+	s.seed = r ^= r << 5;
1493	+	}
1494	+	else
1495	+	Thread.yield(); // yield if no alternatives
1496		}
1497	<	return q;
1497	>	}
1498	>
1499	>	/**
1500	>	* Submits the given (non-null) task to the common pool, if possible.
1501	>	*/
1502	>	static void submitToCommonPool(ForkJoinTask<?> task) {
1503	>	ForkJoinPool p;
1504	>	if ((p = commonPool) == null)
1505	>	throw new RejectedExecutionException("Common Pool Unavailable");
1506	>	p.doSubmit(task);
1507	>	}
1508	>
1509	>	/**
1510	>	* Returns true if the given task was submitted to common pool
1511	>	* and has not yet commenced execution, and is available for
1512	>	* removal according to execution policies; if so removing the
1513	>	* submission from the pool.
1514	>	*
1515	>	* @param task the task
1516	>	* @return true if successful
1517	>	*/
1518	>	static boolean tryUnsubmitFromCommonPool(ForkJoinTask<?> task) {
1519	>	// Peek, looking for task and eligibility before
1520	>	// using trySharedUnpush to actually take it under lock
1521	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
1522	>	ForkJoinTask<?>[] a; int t, s, n;
1523	>	int k = submitters.get().seed & SQMASK;
1524	>	return ((p = commonPool) != null &&
1525	>	(ws = p.workQueues) != null &&
1526	>	ws.length > (k &= p.submitMask) &&
1527	>	(q = ws[k]) != null &&
1528	>	(a = q.array) != null &&
1529	>	(n = (t = q.top) - q.base) > 0 &&
1530	>	(n > 1 \|\| (int)(p.ctl >> AC_SHIFT) < 0) &&
1531	>	(s = t - 1) >= 0 && s < a.length && a[s] == task &&
1532	>	q.trySharedUnpush(task));
1533		}
1534
1535		// Maintaining ctl counts
#	Line 1294 \| Line 1543 \| public class ForkJoinPool extends Abstra
1543		}
1544
1545		/**
1546	<	* Activates or creates a worker.
1546	>	* Tries to create one or activate one or more workers if too few are active.
1547		*/
1548		final void signalWork() {
1549	<	/*
1550	<	* The while condition is true if: (there is are too few total
1551	<	* workers OR there is at least one waiter) AND (there are too
1552	<	* few active workers OR the pool is terminating). The value
1553	<	* of e distinguishes the remaining cases: zero (no waiters)
1554	<	* for create, negative if terminating (in which case do
1555	<	* nothing), else release a waiter. The secondary checks for
1556	<	* release (non-null array etc) can fail if the pool begins
1557	<	* terminating after the test, and don't impose any added cost
1558	<	* because JVMs must perform null and bounds checks anyway.
1559	<	*/
1560	<	long c; int e, u;
1561	<	while ((((e = (int)(c = ctl)) \| (u = (int)(c >>> 32))) &
1562	<	(INT_SIGN\|SHORT_SIGN)) == (INT_SIGN\|SHORT_SIGN)) {
1314	<	WorkQueue[] ws = workQueues; int i; WorkQueue w; Thread p;
1315	<	if (e == 0) { // add a new worker
1316	<	if (U.compareAndSwapLong
1317	<	(this, CTL, c, (long)(((u + UTC_UNIT) & UTC_MASK) \|
1318	<	((u + UAC_UNIT) & UAC_MASK)) << 32)) {
1319	<	addWorker();
1320	<	break;
1549	>	long c; int u;
1550	>	while ((u = (int)((c = ctl) >>> 32)) < 0) { // too few active
1551	>	WorkQueue[] ws = workQueues; int e, i; WorkQueue w; Thread p;
1552	>	if ((e = (int)c) > 0) { // at least one waiting
1553	>	if (ws != null && (i = e & SMASK) < ws.length &&
1554	>	(w = ws[i]) != null && w.eventCount == (e \| INT_SIGN)) {
1555	>	long nc = (((long)(w.nextWait & E_MASK)) \|
1556	>	((long)(u + UAC_UNIT) << 32));
1557	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1558	>	w.eventCount = (e + E_SEQ) & E_MASK;
1559	>	if ((p = w.parker) != null)
1560	>	U.unpark(p); // activate and release
1561	>	break;
1562	>	}
1563		}
1564	<	}
1323	<	else if (e > 0 && ws != null &&
1324	<	(i = ((~e << 1) \| 1) & SMASK) < ws.length &&
1325	<	(w = ws[i]) != null &&
1326	<	w.eventCount == (e \| INT_SIGN)) {
1327	<	if (U.compareAndSwapLong
1328	<	(this, CTL, c, (((long)(w.nextWait & E_MASK)) \|
1329	<	((long)(u + UAC_UNIT) << 32)))) {
1330	<	w.eventCount = (e + E_SEQ) & E_MASK;
1331	<	if ((p = w.parker) != null)
1332	<	U.unpark(p); // release a waiting worker
1564	>	else
1565		break;
1334	–	}
1335	–	}
1336	–	else
1337	–	break;
1338	–	}
1339	–	}
1340	–
1341	–	/**
1342	–	* Tries to decrement active count (sometimes implicitly) and
1343	–	* possibly release or create a compensating worker in preparation
1344	–	* for blocking. Fails on contention or termination.
1345	–	*
1346	–	* @return true if the caller can block, else should recheck and retry
1347	–	*/
1348	–	final boolean tryCompensate() {
1349	–	WorkQueue[] ws; WorkQueue w; Thread p;
1350	–	int pc = parallelism, e, u, ac, tc, i;
1351	–	long c = ctl;
1352	–
1353	–	if ((e = (int)c) >= 0) {
1354	–	if ((ac = ((u = (int)(c >>> 32)) >> UAC_SHIFT)) <= 0 &&
1355	–	e != 0 && (ws = workQueues) != null &&
1356	–	(i = ((~e << 1) \| 1) & SMASK) < ws.length &&
1357	–	(w = ws[i]) != null) {
1358	–	if (w.eventCount == (e \| INT_SIGN) &&
1359	–	U.compareAndSwapLong
1360	–	(this, CTL, c, ((long)(w.nextWait & E_MASK) \|
1361	–	(c & (AC_MASK\|TC_MASK))))) {
1362	–	w.eventCount = (e + E_SEQ) & E_MASK;
1363	–	if ((p = w.parker) != null)
1364	–	U.unpark(p);
1365	–	return true; // release an idle worker
1366	–	}
1367	–	}
1368	–	else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) {
1369	–	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
1370	–	if (U.compareAndSwapLong(this, CTL, c, nc))
1371	–	return true; // no compensation needed
1566		}
1567	<	else if (tc + pc < MAX_ID) {
1568	<	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
1567	>	else if (e == 0 && (u & SHORT_SIGN) != 0) { // too few total
1568	>	long nc = (long)(((u + UTC_UNIT) & UTC_MASK) \|
1569	>	((u + UAC_UNIT) & UAC_MASK)) << 32;
1570		if (U.compareAndSwapLong(this, CTL, c, nc)) {
1571		addWorker();
1572	<	return true; // create replacement
1572	>	break;
1573		}
1574		}
1575	+	else
1576	+	break;
1577		}
1381	–	return false;
1578		}
1579
1580	<	// Submissions
1580	>	// Scanning for tasks
1581
1582		/**
1583	<	* Unless shutting down, adds the given task to a submission queue
1388	<	* at submitter's current queue index. If no queue exists at the
1389	<	* index, one is created unless pool lock is busy. If the queue
1390	<	* and/or lock are busy, another index is randomly chosen.
1583	>	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1584		*/
1585	<	private void doSubmit(ForkJoinTask<?> task) {
1586	<	if (task == null)
1587	<	throw new NullPointerException();
1395	<	Submitter s = submitters.get();
1396	<	for (int r = s.seed;;) {
1397	<	WorkQueue q; int k;
1398	<	int rs = runState, m = rs & SMASK;
1399	<	WorkQueue[] ws = workQueues;
1400	<	if (rs < 0 \|\| ws == null) // shutting down
1401	<	throw new RejectedExecutionException();
1402	<	if (ws.length > m && // k must be at index
1403	<	((q = ws[k = (r << 1) & m]) != null \|\|
1404	<	(q = tryAddSharedQueue(k)) != null) &&
1405	<	q.trySharedPush(task)) {
1406	<	signalWork();
1407	<	return;
1408	<	}
1409	<	r ^= r << 13; // xorshift seed to new position
1410	<	r ^= r >>> 17;
1411	<	if (((s.seed = r ^= r << 5) & m) == 0)
1412	<	Thread.yield(); // occasionally yield if busy
1413	<	}
1585	>	final void runWorker(WorkQueue w) {
1586	>	w.growArray(false); // initialize queue array in this thread
1587	>	do { w.runTask(scan(w)); } while (w.runState >= 0);
1588		}
1589
1416	–
1417	–	// Scanning for tasks
1418	–
1590		/**
1591		* Scans for and, if found, returns one task, else possibly
1592		* inactivates the worker. This method operates on single reads of
1593	<	* volatile state and is designed to be re-invoked continuously in
1594	<	* part because it returns upon detecting inconsistencies,
1593	>	* volatile state and is designed to be re-invoked continuously,
1594	>	* in part because it returns upon detecting inconsistencies,
1595		* contention, or state changes that indicate possible success on
1596		* re-invocation.
1597		*
1598	<	* The scan searches for tasks across queues, randomly selecting
1599	<	* the first #queues probes, favoring steals 2:1 over submissions
1600	<	* (by exploiting even/odd indexing), and then performing a
1601	<	* circular sweep of all queues. The scan terminates upon either
1602	<	* finding a non-empty queue, or completing a full sweep. If the
1603	<	* worker is not inactivated, it takes and returns a task from
1604	<	* this queue. On failure to find a task, we take one of the
1605	<	* following actions, after which the caller will retry calling
1606	<	* this method unless terminated.
1598	>	* The scan searches for tasks across a random permutation of
1599	>	* queues (starting at a random index and stepping by a random
1600	>	* relative prime, checking each at least once). The scan
1601	>	* terminates upon either finding a non-empty queue, or completing
1602	>	* the sweep. If the worker is not inactivated, it takes and
1603	>	* returns a task from this queue. On failure to find a task, we
1604	>	* take one of the following actions, after which the caller will
1605	>	* retry calling this method unless terminated.
1606	>	*
1607	>	* * If pool is terminating, terminate the worker.
1608		*
1609		* * If not a complete sweep, try to release a waiting worker. If
1610		* the scan terminated because the worker is inactivated, then the
#	Line 1441 \| Line 1613 \| public class ForkJoinPool extends Abstra
1613		* another worker, but with same net effect. Releasing in other
1614		* cases as well ensures that we have enough workers running.
1615		*
1444	–	* * If the caller has run a task since the last empty scan,
1445	–	* return (to allow rescan) if other workers are not also yet
1446	–	* enqueued. Field WorkQueue.rescans counts down on each scan to
1447	–	* ensure eventual inactivation, and occasional calls to
1448	–	* Thread.yield to help avoid interference with more useful
1449	–	* activities on the system.
1450	–	*
1451	–	* * If pool is terminating, terminate the worker.
1452	–	*
1616		* * If not already enqueued, try to inactivate and enqueue the
1617	<	* worker on wait queue.
1617	>	* worker on wait queue. Or, if inactivating has caused the pool
1618	>	* to be quiescent, relay to idleAwaitWork to check for
1619	>	* termination and possibly shrink pool.
1620	>	*
1621	>	* * If already inactive, and the caller has run a task since the
1622	>	* last empty scan, return (to allow rescan) unless others are
1623	>	* also inactivated. Field WorkQueue.rescans counts down on each
1624	>	* scan to ensure eventual inactivation and blocking.
1625		*
1626	<	* * If already enqueued and none of the above apply, either park
1627	<	* awaiting signal, or if this is the most recent waiter and pool
1458	<	* is quiescent, relay to idleAwaitWork to check for termination
1459	<	* and possibly shrink pool.
1626	>	* * If already enqueued and none of the above apply, park
1627	>	* awaiting signal,
1628		*
1629		* @param w the worker (via its WorkQueue)
1630	<	* @return a task or null of none found
1630	>	* @return a task or null if none found
1631		*/
1632		private final ForkJoinTask<?> scan(WorkQueue w) {
1633	<	boolean swept = false; // true after full empty scan
1634	<	WorkQueue[] ws; // volatile read order matters
1635	<	int r = w.seed, ec = w.eventCount; // ec is negative if inactive
1636	<	int rs = runState, m = rs & SMASK;
1637	<	if ((ws = workQueues) != null && ws.length > m) {
1638	<	ForkJoinTask<?> task = null;
1639	<	for (int k = 0, j = -2 - m; ; ++j) {
1640	<	WorkQueue q; int b;
1641	<	if (j < 0) { // random probes while j negative
1642	<	r ^= r << 13; r ^= r >>> 17; k = (r ^= r << 5) \| (j & 1);
1643	<	} // worker (not submit) for odd j
1644	<	else // cyclic scan when j >= 0
1645	<	k += (m >>> 1) \| 1; // step by half to reduce bias
1646	<
1647	<	if ((q = ws[k & m]) != null && (b = q.base) - q.top < 0) {
1648	<	if (ec >= 0)
1649	<	task = q.pollAt(b); // steal
1650	<	break;
1633	>	WorkQueue[] ws; // first update random seed
1634	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1635	>	int rs = runState, m; // volatile read order matters
1636	>	if ((ws = workQueues) != null && (m = ws.length - 1) > 0) {
1637	>	int ec = w.eventCount; // ec is negative if inactive
1638	>	int step = (r >>> 16) \| 1; // relative prime
1639	>	for (int j = (m + 1) << 2; ; r += step) {
1640	>	WorkQueue q; ForkJoinTask<?> t; ForkJoinTask<?>[] a; int b;
1641	>	if ((q = ws[r & m]) != null && (b = q.base) - q.top < 0 &&
1642	>	(a = q.array) != null) { // probably nonempty
1643	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1644	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1645	>	if (q.base == b && ec >= 0 && t != null &&
1646	>	U.compareAndSwapObject(a, i, t, null)) {
1647	>	if (q.top - (q.base = b + 1) > 0)
1648	>	signalWork(); // help pushes signal
1649	>	return t;
1650	>	}
1651	>	else if (ec < 0 \|\| j <= m) {
1652	>	rs = 0; // mark scan as imcomplete
1653	>	break; // caller can retry after release
1654	>	}
1655		}
1656	<	else if (j > m) {
1485	<	if (rs == runState) // staleness check
1486	<	swept = true;
1656	>	if (--j < 0)
1657		break;
1658	+	}
1659	+
1660	+	long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
1661	+	if (e < 0) // decode ctl on empty scan
1662	+	w.runState = -1; // pool is terminating
1663	+	else if (rs == 0 \|\| rs != runState) { // incomplete scan
1664	+	WorkQueue v; Thread p; // try to release a waiter
1665	+	if (e > 0 && a < 0 && w.eventCount == ec &&
1666	+	(v = ws[e & m]) != null && v.eventCount == (e \| INT_SIGN)) {
1667	+	long nc = ((long)(v.nextWait & E_MASK) \|
1668	+	((c + AC_UNIT) & (AC_MASK\|TC_MASK)));
1669	+	if (ctl == c && U.compareAndSwapLong(this, CTL, c, nc)) {
1670	+	v.eventCount = (e + E_SEQ) & E_MASK;
1671	+	if ((p = v.parker) != null)
1672	+	U.unpark(p);
1673	+	}
1674		}
1675		}
1676	<	w.seed = r; // save seed for next scan
1677	<	if (task != null)
1678	<	return task;
1679	<	}
1680	<
1681	<	// Decode ctl on empty scan
1682	<	long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
1683	<	if (!swept) { // try to release a waiter
1684	<	WorkQueue v; Thread p;
1685	<	if (e > 0 && a < 0 && ws != null &&
1686	<	(v = ws[((~e << 1) \| 1) & m]) != null &&
1687	<	v.eventCount == (e \| INT_SIGN) && U.compareAndSwapLong
1688	<	(this, CTL, c, ((long)(v.nextWait & E_MASK) \|
1689	<	((c + AC_UNIT) & (AC_MASK\|TC_MASK))))) {
1690	<	v.eventCount = (e + E_SEQ) & E_MASK;
1691	<	if ((p = v.parker) != null)
1692	<	U.unpark(p);
1693	<	}
1694	<	}
1695	<	else if ((nr = w.rescans) > 0) { // continue rescanning
1696	<	int ac = a + parallelism;
1697	<	if ((w.rescans = (ac < nr) ? ac : nr - 1) > 0 && w.seed < 0 &&
1698	<	w.eventCount == ec)
1699	<	Thread.yield(); // 1 bit randomness for yield call
1700	<	}
1701	<	else if (e < 0) // pool is terminating
1702	<	w.runState = -1;
1703	<	else if (ec >= 0) { // try to enqueue
1704	<	long nc = (long)ec \| ((c - AC_UNIT) & (AC_MASK\|TC_MASK));
1705	<	w.nextWait = e;
1520	<	w.eventCount = ec \| INT_SIGN; // mark as inactive
1521	<	if (!U.compareAndSwapLong(this, CTL, c, nc))
1522	<	w.eventCount = ec; // back out on CAS failure
1523	<	else if ((ns = w.nsteals) != 0) { // set rescans if ran task
1524	<	if (a <= 0) // ... unless too many active
1525	<	w.rescans = a + parallelism;
1526	<	w.nsteals = 0;
1527	<	w.totalSteals += ns;
1528	<	}
1529	<	}
1530	<	else{ // already queued
1531	<	if (parallelism == -a)
1532	<	idleAwaitWork(w); // quiescent
1533	<	if (w.eventCount == ec) {
1534	<	Thread.interrupted(); // clear status
1535	<	ForkJoinWorkerThread wt = w.owner;
1536	<	U.putObject(wt, PARKBLOCKER, this);
1537	<	w.parker = wt; // emulate LockSupport.park
1538	<	if (w.eventCount == ec) // recheck
1539	<	U.park(false, 0L); // block
1540	<	w.parker = null;
1541	<	U.putObject(wt, PARKBLOCKER, null);
1676	>	else if (ec >= 0) { // try to enqueue/inactivate
1677	>	long nc = (long)ec \| ((c - AC_UNIT) & (AC_MASK\|TC_MASK));
1678	>	w.nextWait = e;
1679	>	w.eventCount = ec \| INT_SIGN; // mark as inactive
1680	>	if (ctl != c \|\| !U.compareAndSwapLong(this, CTL, c, nc))
1681	>	w.eventCount = ec; // unmark on CAS failure
1682	>	else {
1683	>	if ((ns = w.nsteals) != 0) {
1684	>	w.nsteals = 0; // set rescans if ran task
1685	>	w.rescans = (a > 0) ? 0 : a + parallelism;
1686	>	w.totalSteals += ns;
1687	>	}
1688	>	if (a == 1 - parallelism) // quiescent
1689	>	idleAwaitWork(w, nc, c);
1690	>	}
1691	>	}
1692	>	else if (w.eventCount < 0) { // already queued
1693	>	int ac = a + parallelism;
1694	>	if ((nr = w.rescans) > 0) // continue rescanning
1695	>	w.rescans = (ac < nr) ? ac : nr - 1;
1696	>	else if (((w.seed >>> 16) & ac) == 0) { // randomize park
1697	>	Thread.interrupted(); // clear status
1698	>	Thread wt = Thread.currentThread();
1699	>	U.putObject(wt, PARKBLOCKER, this);
1700	>	w.parker = wt; // emulate LockSupport.park
1701	>	if (w.eventCount < 0) // recheck
1702	>	U.park(false, 0L);
1703	>	w.parker = null;
1704	>	U.putObject(wt, PARKBLOCKER, null);
1705	>	}
1706		}
1707		}
1708		return null;
1709		}
1710
1711		/**
1712	<	* If inactivating worker w has caused pool to become quiescent,
1713	<	* checks for pool termination, and, so long as this is not the
1714	<	* only worker, waits for event for up to SHRINK_RATE nanosecs.
1715	<	* On timeout, if ctl has not changed, terminates the worker,
1716	<	* which will in turn wake up another worker to possibly repeat
1717	<	* this process.
1712	>	* If inactivating worker w has caused the pool to become
1713	>	* quiescent, checks for pool termination, and, so long as this is
1714	>	* not the only worker, waits for event for up to a given
1715	>	* duration. On timeout, if ctl has not changed, terminates the
1716	>	* worker, which will in turn wake up another worker to possibly
1717	>	* repeat this process.
1718		*
1719		* @param w the calling worker
1720	+	* @param currentCtl the ctl value triggering possible quiescence
1721	+	* @param prevCtl the ctl value to restore if thread is terminated
1722		*/
1723	<	private void idleAwaitWork(WorkQueue w) {
1724	<	long c; int nw, ec;
1725	<	if (!tryTerminate(false) &&
1726	<	(int)((c = ctl) >> AC_SHIFT) + parallelism == 0 &&
1727	<	(ec = w.eventCount) == ((int)c \| INT_SIGN) &&
1728	<	(nw = w.nextWait) != 0) {
1729	<	long nc = ((long)(nw & E_MASK) \| // ctl to restore on timeout
1730	<	((c + AC_UNIT) & AC_MASK) \| (c & TC_MASK));
1565	<	ForkJoinTask.helpExpungeStaleExceptions(); // help clean
1566	<	ForkJoinWorkerThread wt = w.owner;
1567	<	while (ctl == c) {
1568	<	long startTime = System.nanoTime();
1723	>	private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1724	>	if (w.eventCount < 0 && !tryTerminate(false, false) &&
1725	>	(int)prevCtl != 0 && !hasQueuedSubmissions() && ctl == currentCtl) {
1726	>	int dc = -(short)(currentCtl >>> TC_SHIFT);
1727	>	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1728	>	long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop
1729	>	Thread wt = Thread.currentThread();
1730	>	while (ctl == currentCtl) {
1731		Thread.interrupted(); // timed variant of version in scan()
1732		U.putObject(wt, PARKBLOCKER, this);
1733		w.parker = wt;
1734	<	if (ctl == c)
1735	<	U.park(false, SHRINK_RATE);
1734	>	if (ctl == currentCtl)
1735	>	U.park(false, parkTime);
1736		w.parker = null;
1737		U.putObject(wt, PARKBLOCKER, null);
1738	<	if (ctl != c)
1738	>	if (ctl != currentCtl)
1739		break;
1740	<	if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
1741	<	U.compareAndSwapLong(this, CTL, c, nc)) {
1742	<	w.runState = -1; // shrink
1743	<	w.eventCount = (ec + E_SEQ) \| E_MASK;
1740	>	if (deadline - System.nanoTime() <= 0L &&
1741	>	U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1742	>	w.eventCount = (w.eventCount + E_SEQ) \| E_MASK;
1743	>	w.runState = -1; // shrink
1744		break;
1745		}
1746		}
#	Line 1596 \| Line 1758 \| public class ForkJoinPool extends Abstra
1758		* leaves hints in workers to speed up subsequent calls. The
1759		* implementation is very branchy to cope with potential
1760		* inconsistencies or loops encountering chains that are stale,
1761	<	* unknown, or of length greater than MAX_HELP_DEPTH links. All
1600	<	* of these cases are dealt with by just retrying by caller.
1761	>	* unknown, or so long that they are likely cyclic.
1762		*
1763		* @param joiner the joining worker
1764		* @param task the task to join
1765	<	* @return true if found or ran a task (and so is immediately retryable)
1765	>	* @return 0 if no progress can be made, negative if task
1766	>	* known complete, else positive
1767		*/
1768	<	final boolean tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1769	<	ForkJoinTask<?> subtask; // current target
1770	<	boolean progress = false;
1771	<	int depth = 0; // current chain depth
1772	<	int m = runState & SMASK;
1773	<	WorkQueue[] ws = workQueues;
1774	<
1775	<	if (ws != null && ws.length > m && (subtask = task).status >= 0) {
1776	<	outer:for (WorkQueue j = joiner;;) {
1777	<	// Try to find the stealer of subtask, by first using hint
1616	<	WorkQueue stealer = null;
1617	<	WorkQueue v = ws[j.stealHint & m];
1618	<	if (v != null && v.currentSteal == subtask)
1619	<	stealer = v;
1620	<	else {
1621	<	for (int i = 1; i <= m; i += 2) {
1622	<	if ((v = ws[i]) != null && v.currentSteal == subtask) {
1623	<	stealer = v;
1624	<	j.stealHint = i; // save hint
1625	<	break;
1626	<	}
1768	>	private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1769	>	int stat = 0, steps = 0; // bound to avoid cycles
1770	>	if (joiner != null && task != null) { // hoist null checks
1771	>	restart: for (;;) {
1772	>	ForkJoinTask<?> subtask = task; // current target
1773	>	for (WorkQueue j = joiner, v;;) { // v is stealer of subtask
1774	>	WorkQueue[] ws; int m, s, h;
1775	>	if ((s = task.status) < 0) {
1776	>	stat = s;
1777	>	break restart;
1778		}
1779	<	if (stealer == null)
1780	<	break;
1781	<	}
1782	<
1783	<	for (WorkQueue q = stealer;;) { // Try to help stealer
1784	<	ForkJoinTask<?> t; int b;
1785	<	if (task.status < 0)
1786	<	break outer;
1787	<	if ((b = q.base) - q.top < 0) {
1788	<	progress = true;
1789	<	if (subtask.status < 0)
1790	<	break outer; // stale
1791	<	if ((t = q.pollAt(b)) != null) {
1792	<	stealer.stealHint = joiner.poolIndex;
1793	<	joiner.runSubtask(t);
1779	>	if ((ws = workQueues) == null \|\| (m = ws.length - 1) <= 0)
1780	>	break restart; // shutting down
1781	>	if ((v = ws[h = (j.stealHint \| 1) & m]) == null \|\|
1782	>	v.currentSteal != subtask) {
1783	>	for (int origin = h;;) { // find stealer
1784	>	if (((h = (h + 2) & m) & 15) == 1 &&
1785	>	(subtask.status < 0 \|\| j.currentJoin != subtask))
1786	>	continue restart; // occasional staleness check
1787	>	if ((v = ws[h]) != null &&
1788	>	v.currentSteal == subtask) {
1789	>	j.stealHint = h; // save hint
1790	>	break;
1791	>	}
1792	>	if (h == origin)
1793	>	break restart; // cannot find stealer
1794		}
1795		}
1796	<	else { // empty - try to descend to find stealer's stealer
1797	<	ForkJoinTask<?> next = stealer.currentJoin;
1798	<	if (++depth == MAX_HELP_DEPTH \|\| subtask.status < 0 \|\|
1799	<	next == null \|\| next == subtask)
1800	<	break outer; // max depth, stale, dead-end, cyclic
1801	<	subtask = next;
1802	<	j = stealer;
1803	<	break;
1796	>	for (;;) { // help stealer or descend to its stealer
1797	>	ForkJoinTask[] a; int b;
1798	>	if (subtask.status < 0) // surround probes with
1799	>	continue restart; // consistency checks
1800	>	if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
1801	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1802	>	ForkJoinTask<?> t =
1803	>	(ForkJoinTask<?>)U.getObjectVolatile(a, i);
1804	>	if (subtask.status < 0 \|\| j.currentJoin != subtask \|\|
1805	>	v.currentSteal != subtask)
1806	>	continue restart; // stale
1807	>	stat = 1; // apparent progress
1808	>	if (t != null && v.base == b &&
1809	>	U.compareAndSwapObject(a, i, t, null)) {
1810	>	v.base = b + 1; // help stealer
1811	>	joiner.runSubtask(t);
1812	>	}
1813	>	else if (v.base == b && ++steps == MAX_HELP)
1814	>	break restart; // v apparently stalled
1815	>	}
1816	>	else { // empty -- try to descend
1817	>	ForkJoinTask<?> next = v.currentJoin;
1818	>	if (subtask.status < 0 \|\| j.currentJoin != subtask \|\|
1819	>	v.currentSteal != subtask)
1820	>	continue restart; // stale
1821	>	else if (next == null \|\| ++steps == MAX_HELP)
1822	>	break restart; // dead-end or maybe cyclic
1823	>	else {
1824	>	subtask = next;
1825	>	j = v;
1826	>	break;
1827	>	}
1828	>	}
1829		}
1830		}
1831		}
1832		}
1833	<	return progress;
1833	>	return stat;
1834		}
1835
1836		/**
#	Line 1663 \| Line 1839 \| public class ForkJoinPool extends Abstra
1839		* @param joiner the joining worker
1840		* @param task the task
1841		*/
1842	<	final void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
1842	>	private void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
1843		WorkQueue[] ws;
1844	<	int m = runState & SMASK;
1845	<	if ((ws = workQueues) != null && ws.length > m) {
1670	<	for (int j = 1; j <= m && task.status >= 0; j += 2) {
1844	>	if ((ws = workQueues) != null) {
1845	>	for (int j = 1; j < ws.length && task.status >= 0; j += 2) {
1846		WorkQueue q = ws[j];
1847		if (q != null && q.pollFor(task)) {
1848		joiner.runSubtask(task);
#	Line 1678 \| Line 1853 \| public class ForkJoinPool extends Abstra
1853		}
1854
1855		/**
1856	<	* Returns a non-empty steal queue, if one is found during a random,
1857	<	* then cyclic scan, else null. This method must be retried by
1858	<	* caller if, by the time it tries to use the queue, it is empty.
1856	>	* Tries to decrement active count (sometimes implicitly) and
1857	>	* possibly release or create a compensating worker in preparation
1858	>	* for blocking. Fails on contention or termination. Otherwise,
1859	>	* adds a new thread if no idle workers are available and either
1860	>	* pool would become completely starved or: (at least half
1861	>	* starved, and fewer than 50% spares exist, and there is at least
1862	>	* one task apparently available). Even though the availability
1863	>	* check requires a full scan, it is worthwhile in reducing false
1864	>	* alarms.
1865	>	*
1866	>	* @param task if non-null, a task being waited for
1867	>	* @param blocker if non-null, a blocker being waited for
1868	>	* @return true if the caller can block, else should recheck and retry
1869	>	*/
1870	>	final boolean tryCompensate(ForkJoinTask<?> task, ManagedBlocker blocker) {
1871	>	int pc = parallelism, e;
1872	>	long c = ctl;
1873	>	WorkQueue[] ws = workQueues;
1874	>	if ((e = (int)c) >= 0 && ws != null) {
1875	>	int u, a, ac, hc;
1876	>	int tc = (short)((u = (int)(c >>> 32)) >>> UTC_SHIFT) + pc;
1877	>	boolean replace = false;
1878	>	if ((a = u >> UAC_SHIFT) <= 0) {
1879	>	if ((ac = a + pc) <= 1)
1880	>	replace = true;
1881	>	else if ((e > 0 \|\| (task != null &&
1882	>	ac <= (hc = pc >>> 1) && tc < pc + hc))) {
1883	>	WorkQueue w;
1884	>	for (int j = 0; j < ws.length; ++j) {
1885	>	if ((w = ws[j]) != null && !w.isEmpty()) {
1886	>	replace = true;
1887	>	break; // in compensation range and tasks available
1888	>	}
1889	>	}
1890	>	}
1891	>	}
1892	>	if ((task == null \|\| task.status >= 0) && // recheck need to block
1893	>	(blocker == null \|\| !blocker.isReleasable()) && ctl == c) {
1894	>	if (!replace) { // no compensation
1895	>	long nc = ((c - AC_UNIT) & AC_MASK) \| (c & ~AC_MASK);
1896	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1897	>	return true;
1898	>	}
1899	>	else if (e != 0) { // release an idle worker
1900	>	WorkQueue w; Thread p; int i;
1901	>	if ((i = e & SMASK) < ws.length && (w = ws[i]) != null) {
1902	>	long nc = ((long)(w.nextWait & E_MASK) \|
1903	>	(c & (AC_MASK\|TC_MASK)));
1904	>	if (w.eventCount == (e \| INT_SIGN) &&
1905	>	U.compareAndSwapLong(this, CTL, c, nc)) {
1906	>	w.eventCount = (e + E_SEQ) & E_MASK;
1907	>	if ((p = w.parker) != null)
1908	>	U.unpark(p);
1909	>	return true;
1910	>	}
1911	>	}
1912	>	}
1913	>	else if (tc < MAX_CAP) { // create replacement
1914	>	long nc = ((c + TC_UNIT) & TC_MASK) \| (c & ~TC_MASK);
1915	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1916	>	addWorker();
1917	>	return true;
1918	>	}
1919	>	}
1920	>	}
1921	>	}
1922	>	return false;
1923	>	}
1924	>
1925	>	/**
1926	>	* Helps and/or blocks until the given task is done.
1927	>	*
1928	>	* @param joiner the joining worker
1929	>	* @param task the task
1930	>	* @return task status on exit
1931	>	*/
1932	>	final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
1933	>	int s;
1934	>	if ((s = task.status) >= 0) {
1935	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
1936	>	joiner.currentJoin = task;
1937	>	long startTime = 0L;
1938	>	for (int k = 0;;) {
1939	>	if ((s = (joiner.isEmpty() ? // try to help
1940	>	tryHelpStealer(joiner, task) :
1941	>	joiner.tryRemoveAndExec(task))) == 0 &&
1942	>	(s = task.status) >= 0) {
1943	>	if (k == 0) {
1944	>	startTime = System.nanoTime();
1945	>	tryPollForAndExec(joiner, task); // check uncommon case
1946	>	}
1947	>	else if ((k & (MAX_HELP - 1)) == 0 &&
1948	>	System.nanoTime() - startTime >=
1949	>	COMPENSATION_DELAY &&
1950	>	tryCompensate(task, null)) {
1951	>	if (task.trySetSignal()) {
1952	>	synchronized (task) {
1953	>	if (task.status >= 0) {
1954	>	try { // see ForkJoinTask
1955	>	task.wait(); // for explanation
1956	>	} catch (InterruptedException ie) {
1957	>	}
1958	>	}
1959	>	else
1960	>	task.notifyAll();
1961	>	}
1962	>	}
1963	>	long c; // re-activate
1964	>	do {} while (!U.compareAndSwapLong
1965	>	(this, CTL, c = ctl, c + AC_UNIT));
1966	>	}
1967	>	}
1968	>	if (s < 0 \|\| (s = task.status) < 0) {
1969	>	joiner.currentJoin = prevJoin;
1970	>	break;
1971	>	}
1972	>	else if ((k++ & (MAX_HELP - 1)) == MAX_HELP >>> 1)
1973	>	Thread.yield(); // for politeness
1974	>	}
1975	>	}
1976	>	return s;
1977	>	}
1978	>
1979	>	/**
1980	>	* Stripped-down variant of awaitJoin used by timed joins. Tries
1981	>	* to help join only while there is continuous progress. (Caller
1982	>	* will then enter a timed wait.)
1983	>	*
1984	>	* @param joiner the joining worker
1985	>	* @param task the task
1986	>	* @return task status on exit
1987	>	*/
1988	>	final int helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
1989	>	int s;
1990	>	while ((s = task.status) >= 0 &&
1991	>	(joiner.isEmpty() ?
1992	>	tryHelpStealer(joiner, task) :
1993	>	joiner.tryRemoveAndExec(task)) != 0)
1994	>	;
1995	>	return s;
1996	>	}
1997	>
1998	>	/**
1999	>	* Returns a (probably) non-empty steal queue, if one is found
2000	>	* during a random, then cyclic scan, else null. This method must
2001	>	* be retried by caller if, by the time it tries to use the queue,
2002	>	* it is empty.
2003		*/
2004		private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
2005	<	int r = w.seed; // Same idea as scan(), but ignoring submissions
2005	>	// Similar to loop in scan(), but ignoring submissions
2006	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
2007	>	int step = (r >>> 16) \| 1;
2008		for (WorkQueue[] ws;;) {
2009	<	int m = runState & SMASK;
2010	<	if ((ws = workQueues) == null)
2009	>	int rs = runState, m;
2010	>	if ((ws = workQueues) == null \|\| (m = ws.length - 1) < 1)
2011		return null;
2012	<	if (ws.length > m) {
2013	<	WorkQueue q;
2014	<	for (int n = m << 2, k = r, j = -n;;) {
2015	<	r ^= r << 13; r ^= r >>> 17; r ^= r << 5;
2016	<	if ((q = ws[(k \| 1) & m]) != null && q.base - q.top < 0) {
2017	<	w.seed = r;
1697	<	return q;
1698	<	}
1699	<	else if (j > n)
2012	>	for (int j = (m + 1) << 2; ; r += step) {
2013	>	WorkQueue q = ws[((r << 1) \| 1) & m];
2014	>	if (q != null && !q.isEmpty())
2015	>	return q;
2016	>	else if (--j < 0) {
2017	>	if (runState == rs)
2018		return null;
2019	<	else
1702	<	k = (j++ < 0) ? r : k + ((m >>> 1) \| 1);
1703	<
2019	>	break;
2020		}
2021		}
2022		}
#	Line 1714 \| Line 2030 \| public class ForkJoinPool extends Abstra
2030		*/
2031		final void helpQuiescePool(WorkQueue w) {
2032		for (boolean active = true;;) {
2033	<	w.runLocalTasks(); // exhaust local queue
2033	>	ForkJoinTask<?> localTask; // exhaust local queue
2034	>	while ((localTask = w.nextLocalTask()) != null)
2035	>	localTask.doExec();
2036		WorkQueue q = findNonEmptyStealQueue(w);
2037		if (q != null) {
2038	<	ForkJoinTask<?> t;
2038	>	ForkJoinTask<?> t; int b;
2039		if (!active) { // re-establish active count
2040		long c;
2041		active = true;
2042		do {} while (!U.compareAndSwapLong
2043		(this, CTL, c = ctl, c + AC_UNIT));
2044		}
2045	<	if ((t = q.poll()) != null)
2045	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2046		w.runSubtask(t);
2047		}
2048		else {
#	Line 1746 \| Line 2064 \| public class ForkJoinPool extends Abstra
2064		}
2065
2066		/**
2067	+	* Restricted version of helpQuiescePool for non-FJ callers
2068	+	*/
2069	+	static void externalHelpQuiescePool() {
2070	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q;
2071	+	ForkJoinTask<?> t; int b;
2072	+	int k = submitters.get().seed & SQMASK;
2073	+	if ((p = commonPool) != null &&
2074	+	(ws = p.workQueues) != null &&
2075	+	ws.length > (k &= p.submitMask) &&
2076	+	(w = ws[k]) != null &&
2077	+	(q = p.findNonEmptyStealQueue(w)) != null &&
2078	+	(b = q.base) - q.top < 0 &&
2079	+	(t = q.pollAt(b)) != null)
2080	+	t.doExec();
2081	+	}
2082	+
2083	+	/**
2084		* Gets and removes a local or stolen task for the given worker.
2085		*
2086		* @return a task, if available
2087		*/
2088		final ForkJoinTask<?> nextTaskFor(WorkQueue w) {
2089		for (ForkJoinTask<?> t;;) {
2090	<	WorkQueue q;
2090	>	WorkQueue q; int b;
2091		if ((t = w.nextLocalTask()) != null)
2092		return t;
2093		if ((q = findNonEmptyStealQueue(w)) == null)
2094		return null;
2095	<	if ((t = q.poll()) != null)
2095	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2096		return t;
2097		}
2098		}
#	Line 1778 \| Line 2113 \| public class ForkJoinPool extends Abstra
2113		8);
2114		}
2115
1781	–	// Termination
1782	–
2116		/**
2117	<	* Sets SHUTDOWN bit of runState under lock
2117	>	* Returns approximate submission queue length for the given caller
2118		*/
2119	<	private void enableShutdown() {
2120	<	ReentrantLock lock = this.lock;
2121	<	if (runState >= 0) {
2122	<	lock.lock(); // don't need try/finally
2123	<	runState \|= SHUTDOWN;
2124	<	lock.unlock();
2125	<	}
2119	>	static int getEstimatedSubmitterQueueLength() {
2120	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
2121	>	int k = submitters.get().seed & SQMASK;
2122	>	return ((p = commonPool) != null &&
2123	>	p.runState >= 0 &&
2124	>	(ws = p.workQueues) != null &&
2125	>	ws.length > (k &= p.submitMask) &&
2126	>	(q = ws[k]) != null) ?
2127	>	q.queueSize() : 0;
2128		}
2129
2130	+	// Termination
2131	+
2132		/**
2133	<	* Possibly initiates and/or completes termination. Upon
2134	<	* termination, cancels all queued tasks and then
2133	>	* Possibly initiates and/or completes termination. The caller
2134	>	* triggering termination runs three passes through workQueues:
2135	>	* (0) Setting termination status, followed by wakeups of queued
2136	>	* workers; (1) cancelling all tasks; (2) interrupting lagging
2137	>	* threads (likely in external tasks, but possibly also blocked in
2138	>	* joins). Each pass repeats previous steps because of potential
2139	>	* lagging thread creation.
2140		*
2141		* @param now if true, unconditionally terminate, else only
2142		* if no work and no active workers
2143	+	* @param enable if true, enable shutdown when next possible
2144		* @return true if now terminating or terminated
2145		*/
2146	<	private boolean tryTerminate(boolean now) {
2146	>	private boolean tryTerminate(boolean now, boolean enable) {
2147		for (long c;;) {
2148		if (((c = ctl) & STOP_BIT) != 0) { // already terminating
2149		if ((short)(c >>> TC_SHIFT) == -parallelism) {
2150	<	ReentrantLock lock = this.lock; // signal when no workers
2151	<	lock.lock(); // don't need try/finally
2152	<	termination.signalAll(); // signal when 0 workers
1810	<	lock.unlock();
2150	>	synchronized(this) {
2151	>	notifyAll(); // signal when 0 workers
2152	>	}
2153		}
2154		return true;
2155		}
2156	<	if (!now) {
2157	<	if ((int)(c >> AC_SHIFT) != -parallelism \|\| runState >= 0 \|\|
2156	>	if (runState >= 0) { // not yet enabled
2157	>	if (!enable)
2158	>	return false;
2159	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
2160	>	tryAwaitMainLock();
2161	>	try {
2162	>	runState \|= SHUTDOWN;
2163	>	} finally {
2164	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
2165	>	mainLock = 0;
2166	>	synchronized (this) { notifyAll(); };
2167	>	}
2168	>	}
2169	>	}
2170	>	if (!now) { // check if idle & no tasks
2171	>	if ((int)(c >> AC_SHIFT) != -parallelism \|\|
2172		hasQueuedSubmissions())
2173		return false;
2174		// Check for unqueued inactive workers. One pass suffices.
2175		WorkQueue[] ws = workQueues; WorkQueue w;
2176		if (ws != null) {
2177	<	int n = ws.length;
1822	<	for (int i = 1; i < n; i += 2) {
2177	>	for (int i = 1; i < ws.length; i += 2) {
2178		if ((w = ws[i]) != null && w.eventCount >= 0)
2179		return false;
2180		}
2181		}
2182		}
2183	<	if (U.compareAndSwapLong(this, CTL, c, c \| STOP_BIT))
2184	<	startTerminating();
2185	<	}
2186	<	}
2187	<
2188	<	/**
2189	<	* Initiates termination: Runs three passes through workQueues:
2190	<	* (0) Setting termination status, followed by wakeups of queued
2191	<	* workers; (1) cancelling all tasks; (2) interrupting lagging
2192	<	* threads (likely in external tasks, but possibly also blocked in
2193	<	* joins). Each pass repeats previous steps because of potential
2194	<	* lagging thread creation.
2195	<	*/
1841	<	private void startTerminating() {
1842	<	for (int pass = 0; pass < 3; ++pass) {
1843	<	WorkQueue[] ws = workQueues;
1844	<	if (ws != null) {
1845	<	WorkQueue w; Thread wt;
1846	<	int n = ws.length;
1847	<	for (int j = 0; j < n; ++j) {
1848	<	if ((w = ws[j]) != null) {
1849	<	w.runState = -1;
1850	<	if (pass > 0) {
1851	<	w.cancelAll();
1852	<	if (pass > 1 && (wt = w.owner) != null &&
1853	<	!wt.isInterrupted()) {
1854	<	try {
1855	<	wt.interrupt();
1856	<	} catch (SecurityException ignore) {
2183	>	if (U.compareAndSwapLong(this, CTL, c, c \| STOP_BIT)) {
2184	>	for (int pass = 0; pass < 3; ++pass) {
2185	>	WorkQueue[] ws = workQueues;
2186	>	if (ws != null) {
2187	>	WorkQueue w;
2188	>	int n = ws.length;
2189	>	for (int i = 0; i < n; ++i) {
2190	>	if ((w = ws[i]) != null) {
2191	>	w.runState = -1;
2192	>	if (pass > 0) {
2193	>	w.cancelAll();
2194	>	if (pass > 1)
2195	>	w.interruptOwner();
2196		}
2197		}
2198		}
2199	<	}
2200	<	}
2201	<	// Wake up workers parked on event queue
2202	<	int i, e; long c; Thread p;
2203	<	while ((i = ((~(e = (int)(c = ctl)) << 1) \| 1) & SMASK) < n &&
2204	<	(w = ws[i]) != null &&
2205	<	w.eventCount == (e \| INT_SIGN)) {
2206	<	long nc = ((long)(w.nextWait & E_MASK) \|
2207	<	((c + AC_UNIT) & AC_MASK) \|
2208	<	(c & (TC_MASK\|STOP_BIT)));
2209	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
2210	<	w.eventCount = (e + E_SEQ) & E_MASK;
2211	<	if ((p = w.parker) != null)
2212	<	U.unpark(p);
2199	>	// Wake up workers parked on event queue
2200	>	int i, e; long cc; Thread p;
2201	>	while ((e = (int)(cc = ctl) & E_MASK) != 0 &&
2202	>	(i = e & SMASK) < n &&
2203	>	(w = ws[i]) != null) {
2204	>	long nc = ((long)(w.nextWait & E_MASK) \|
2205	>	((cc + AC_UNIT) & AC_MASK) \|
2206	>	(cc & (TC_MASK\|STOP_BIT)));
2207	>	if (w.eventCount == (e \| INT_SIGN) &&
2208	>	U.compareAndSwapLong(this, CTL, cc, nc)) {
2209	>	w.eventCount = (e + E_SEQ) & E_MASK;
2210	>	w.runState = -1;
2211	>	if ((p = w.parker) != null)
2212	>	U.unpark(p);
2213	>	}
2214	>	}
2215		}
2216		}
2217		}
#	Line 1946 \| Line 2287 \| public class ForkJoinPool extends Abstra
2287		checkPermission();
2288		if (factory == null)
2289		throw new NullPointerException();
2290	<	if (parallelism <= 0 \|\| parallelism > MAX_ID)
2290	>	if (parallelism <= 0 \|\| parallelism > MAX_CAP)
2291		throw new IllegalArgumentException();
2292		this.parallelism = parallelism;
2293		this.factory = factory;
2294		this.ueh = handler;
2295		this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE;
1955	–	this.nextPoolIndex = 1;
2296		long np = (long)(-parallelism); // offset ctl counts
2297		this.ctl = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
2298	<	// initialize workQueues array with room for 2*parallelism if possible
2299	<	int n = parallelism << 1;
2300	<	if (n >= MAX_ID)
2301	<	n = MAX_ID;
2302	<	else { // See Hackers Delight, sec 3.2, where n < (1 << 16)
1963	<	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4; n \|= n >>> 8;
1964	<	}
1965	<	this.workQueues = new WorkQueue[(n + 1) << 1];
1966	<	ReentrantLock lck = this.lock = new ReentrantLock();
1967	<	this.termination = lck.newCondition();
1968	<	this.stealCount = new AtomicLong();
1969	<	this.nextWorkerNumber = new AtomicInteger();
2298	>	// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2.
2299	>	int n = parallelism - 1;
2300	>	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4; n \|= n >>> 8; n \|= n >>> 16;
2301	>	this.submitMask = ((n + 1) << 1) - 1;
2302	>	int pn = poolNumberGenerator.incrementAndGet();
2303		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2304	<	sb.append(poolNumberGenerator.incrementAndGet());
2304	>	sb.append(Integer.toString(pn));
2305		sb.append("-worker-");
2306		this.workerNamePrefix = sb.toString();
2307	<	// Create initial submission queue
2308	<	WorkQueue sq = tryAddSharedQueue(0);
2309	<	if (sq != null)
2310	<	sq.growArray(false);
2307	>	this.runState = 1; // set init flag
2308	>	}
2309	>
2310	>	/**
2311	>	* Constructor for common pool, suitable only for static initialization.
2312	>	* Basically the same as above, but uses smallest possible initial footprint.
2313	>	*/
2314	>	ForkJoinPool(int parallelism, int submitMask,
2315	>	ForkJoinWorkerThreadFactory factory,
2316	>	Thread.UncaughtExceptionHandler handler) {
2317	>	this.factory = factory;
2318	>	this.ueh = handler;
2319	>	this.submitMask = submitMask;
2320	>	this.parallelism = parallelism;
2321	>	long np = (long)(-parallelism);
2322	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) \| ((np << TC_SHIFT) & TC_MASK);
2323	>	this.localMode = LIFO_QUEUE;
2324	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2325	>	this.runState = 1;
2326	>	}
2327	>
2328	>	/**
2329	>	* Returns the common pool instance.
2330	>	*
2331	>	* @return the common pool instance
2332	>	*/
2333	>	public static ForkJoinPool commonPool() {
2334	>	ForkJoinPool p;
2335	>	if ((p = commonPool) == null)
2336	>	throw new Error("Common Pool Unavailable");
2337	>	return p;
2338		}
2339
2340		// Execution methods
#	Line 1996 \| Line 2356 \| public class ForkJoinPool extends Abstra
2356		* scheduled for execution
2357		*/
2358		public <T> T invoke(ForkJoinTask<T> task) {
2359	+	if (task == null)
2360	+	throw new NullPointerException();
2361		doSubmit(task);
2362		return task.join();
2363		}
#	Line 2009 \| Line 2371 \| public class ForkJoinPool extends Abstra
2371		* scheduled for execution
2372		*/
2373		public void execute(ForkJoinTask<?> task) {
2374	+	if (task == null)
2375	+	throw new NullPointerException();
2376		doSubmit(task);
2377		}
2378
#	Line 2026 \| Line 2390 \| public class ForkJoinPool extends Abstra
2390		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2391		job = (ForkJoinTask<?>) task;
2392		else
2393	<	job = ForkJoinTask.adapt(task, null);
2393	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2394		doSubmit(job);
2395		}
2396
#	Line 2040 \| Line 2404 \| public class ForkJoinPool extends Abstra
2404		* scheduled for execution
2405		*/
2406		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2407	+	if (task == null)
2408	+	throw new NullPointerException();
2409		doSubmit(task);
2410		return task;
2411		}
#	Line 2050 \| Line 2416 \| public class ForkJoinPool extends Abstra
2416		* scheduled for execution
2417		*/
2418		public <T> ForkJoinTask<T> submit(Callable<T> task) {
2419	<	if (task == null)
2054	<	throw new NullPointerException();
2055	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
2419	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2420		doSubmit(job);
2421		return job;
2422		}
#	Line 2063 \| Line 2427 \| public class ForkJoinPool extends Abstra
2427		* scheduled for execution
2428		*/
2429		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2430	<	if (task == null)
2067	<	throw new NullPointerException();
2068	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
2430	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2431		doSubmit(job);
2432		return job;
2433		}
#	Line 2082 \| Line 2444 \| public class ForkJoinPool extends Abstra
2444		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2445		job = (ForkJoinTask<?>) task;
2446		else
2447	<	job = ForkJoinTask.adapt(task, null);
2447	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2448		doSubmit(job);
2449		return job;
2450		}
#	Line 2092 \| Line 2454 \| public class ForkJoinPool extends Abstra
2454		* @throws RejectedExecutionException {@inheritDoc}
2455		*/
2456		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
2457	<	ArrayList<ForkJoinTask<T>> forkJoinTasks =
2458	<	new ArrayList<ForkJoinTask<T>>(tasks.size());
2459	<	for (Callable<T> task : tasks)
2460	<	forkJoinTasks.add(ForkJoinTask.adapt(task));
2461	<	invoke(new InvokeAll<T>(forkJoinTasks));
2462	<
2457	>	// In previous versions of this class, this method constructed
2458	>	// a task to run ForkJoinTask.invokeAll, but now external
2459	>	// invocation of multiple tasks is at least as efficient.
2460	>	List<ForkJoinTask<T>> fs = new ArrayList<ForkJoinTask<T>>(tasks.size());
2461	>	// Workaround needed because method wasn't declared with
2462	>	// wildcards in return type but should have been.
2463		@SuppressWarnings({"unchecked", "rawtypes"})
2464	<	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
2103	<	return futures;
2104	<	}
2464	>	List<Future<T>> futures = (List<Future<T>>) (List) fs;
2465
2466	<	static final class InvokeAll<T> extends RecursiveAction {
2467	<	final ArrayList<ForkJoinTask<T>> tasks;
2468	<	InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
2469	<	public void compute() {
2470	<	try { invokeAll(tasks); }
2471	<	catch (Exception ignore) {}
2466	>	boolean done = false;
2467	>	try {
2468	>	for (Callable<T> t : tasks) {
2469	>	ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2470	>	doSubmit(f);
2471	>	fs.add(f);
2472	>	}
2473	>	for (ForkJoinTask<T> f : fs)
2474	>	f.quietlyJoin();
2475	>	done = true;
2476	>	return futures;
2477	>	} finally {
2478	>	if (!done)
2479	>	for (ForkJoinTask<T> f : fs)
2480	>	f.cancel(false);
2481		}
2113	–	private static final long serialVersionUID = -7914297376763021607L;
2482		}
2483
2484		/**
#	Line 2142 \| Line 2510 \| public class ForkJoinPool extends Abstra
2510		}
2511
2512		/**
2513	+	* Returns the targeted parallelism level of the common pool.
2514	+	*
2515	+	* @return the targeted parallelism level of the common pool
2516	+	*/
2517	+	public static int getCommonPoolParallelism() {
2518	+	return commonPoolParallelism;
2519	+	}
2520	+
2521	+	/**
2522		* Returns the number of worker threads that have started but not
2523		* yet terminated. The result returned by this method may differ
2524		* from {@link #getParallelism} when threads are created to
#	Line 2175 \| Line 2552 \| public class ForkJoinPool extends Abstra
2552		int rc = 0;
2553		WorkQueue[] ws; WorkQueue w;
2554		if ((ws = workQueues) != null) {
2555	<	int n = ws.length;
2556	<	for (int i = 1; i < n; i += 2) {
2180	<	Thread.State s; ForkJoinWorkerThread wt;
2181	<	if ((w = ws[i]) != null && (wt = w.owner) != null &&
2182	<	w.eventCount >= 0 &&
2183	<	(s = wt.getState()) != Thread.State.BLOCKED &&
2184	<	s != Thread.State.WAITING &&
2185	<	s != Thread.State.TIMED_WAITING)
2555	>	for (int i = 1; i < ws.length; i += 2) {
2556	>	if ((w = ws[i]) != null && w.isApparentlyUnblocked())
2557		++rc;
2558		}
2559		}
#	Line 2228 \| Line 2599 \| public class ForkJoinPool extends Abstra
2599		* @return the number of steals
2600		*/
2601		public long getStealCount() {
2602	<	long count = stealCount.get();
2602	>	long count = stealCount;
2603		WorkQueue[] ws; WorkQueue w;
2604		if ((ws = workQueues) != null) {
2605	<	int n = ws.length;
2235	<	for (int i = 1; i < n; i += 2) {
2605	>	for (int i = 1; i < ws.length; i += 2) {
2606		if ((w = ws[i]) != null)
2607		count += w.totalSteals;
2608		}
#	Line 2254 \| Line 2624 \| public class ForkJoinPool extends Abstra
2624		long count = 0;
2625		WorkQueue[] ws; WorkQueue w;
2626		if ((ws = workQueues) != null) {
2627	<	int n = ws.length;
2258	<	for (int i = 1; i < n; i += 2) {
2627	>	for (int i = 1; i < ws.length; i += 2) {
2628		if ((w = ws[i]) != null)
2629		count += w.queueSize();
2630		}
#	Line 2274 \| Line 2643 \| public class ForkJoinPool extends Abstra
2643		int count = 0;
2644		WorkQueue[] ws; WorkQueue w;
2645		if ((ws = workQueues) != null) {
2646	<	int n = ws.length;
2278	<	for (int i = 0; i < n; i += 2) {
2646	>	for (int i = 0; i < ws.length; i += 2) {
2647		if ((w = ws[i]) != null)
2648		count += w.queueSize();
2649		}
#	Line 2292 \| Line 2660 \| public class ForkJoinPool extends Abstra
2660		public boolean hasQueuedSubmissions() {
2661		WorkQueue[] ws; WorkQueue w;
2662		if ((ws = workQueues) != null) {
2663	<	int n = ws.length;
2664	<	for (int i = 0; i < n; i += 2) {
2297	<	if ((w = ws[i]) != null && w.queueSize() != 0)
2663	>	for (int i = 0; i < ws.length; i += 2) {
2664	>	if ((w = ws[i]) != null && !w.isEmpty())
2665		return true;
2666		}
2667		}
#	Line 2311 \| Line 2678 \| public class ForkJoinPool extends Abstra
2678		protected ForkJoinTask<?> pollSubmission() {
2679		WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2680		if ((ws = workQueues) != null) {
2681	<	int n = ws.length;
2315	<	for (int i = 0; i < n; i += 2) {
2681	>	for (int i = 0; i < ws.length; i += 2) {
2682		if ((w = ws[i]) != null && (t = w.poll()) != null)
2683		return t;
2684		}
#	Line 2341 \| Line 2707 \| public class ForkJoinPool extends Abstra
2707		int count = 0;
2708		WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t;
2709		if ((ws = workQueues) != null) {
2710	<	int n = ws.length;
2345	<	for (int i = 0; i < n; ++i) {
2710	>	for (int i = 0; i < ws.length; ++i) {
2711		if ((w = ws[i]) != null) {
2712		while ((t = w.poll()) != null) {
2713		c.add(t);
#	Line 2362 \| Line 2727 \| public class ForkJoinPool extends Abstra
2727		* @return a string identifying this pool, as well as its state
2728		*/
2729		public String toString() {
2730	<	long st = getStealCount();
2731	<	long qt = getQueuedTaskCount();
2732	<	long qs = getQueuedSubmissionCount();
2368	<	int rc = getRunningThreadCount();
2369	<	int pc = parallelism;
2730	>	// Use a single pass through workQueues to collect counts
2731	>	long qt = 0L, qs = 0L; int rc = 0;
2732	>	long st = stealCount;
2733		long c = ctl;
2734	+	WorkQueue[] ws; WorkQueue w;
2735	+	if ((ws = workQueues) != null) {
2736	+	for (int i = 0; i < ws.length; ++i) {
2737	+	if ((w = ws[i]) != null) {
2738	+	int size = w.queueSize();
2739	+	if ((i & 1) == 0)
2740	+	qs += size;
2741	+	else {
2742	+	qt += size;
2743	+	st += w.totalSteals;
2744	+	if (w.isApparentlyUnblocked())
2745	+	++rc;
2746	+	}
2747	+	}
2748	+	}
2749	+	}
2750	+	int pc = parallelism;
2751		int tc = pc + (short)(c >>> TC_SHIFT);
2752		int ac = pc + (int)(c >> AC_SHIFT);
2753		if (ac < 0) // ignore transient negative
#	Line 2390 \| Line 2770 \| public class ForkJoinPool extends Abstra
2770		}
2771
2772		/**
2773	<	* Initiates an orderly shutdown in which previously submitted
2774	<	* tasks are executed, but no new tasks will be accepted.
2775	<	* Invocation has no additional effect if already shut down.
2776	<	* Tasks that are in the process of being submitted concurrently
2777	<	* during the course of this method may or may not be rejected.
2773	>	* Possibly initiates an orderly shutdown in which previously
2774	>	* submitted tasks are executed, but no new tasks will be
2775	>	* accepted. Invocation has no effect on execution state if this
2776	>	* is the {@link #commonPool}, and no additional effect if
2777	>	* already shut down. Tasks that are in the process of being
2778	>	* submitted concurrently during the course of this method may or
2779	>	* may not be rejected.
2780		*
2781		* @throws SecurityException if a security manager exists and
2782		* the caller is not permitted to modify threads
#	Line 2403 \| Line 2785 \| public class ForkJoinPool extends Abstra
2785		*/
2786		public void shutdown() {
2787		checkPermission();
2788	<	enableShutdown();
2789	<	tryTerminate(false);
2788	>	if (this != commonPool)
2789	>	tryTerminate(false, true);
2790		}
2791
2792		/**
2793	<	* Attempts to cancel and/or stop all tasks, and reject all
2794	<	* subsequently submitted tasks. Tasks that are in the process of
2795	<	* being submitted or executed concurrently during the course of
2796	<	* this method may or may not be rejected. This method cancels
2797	<	* both existing and unexecuted tasks, in order to permit
2798	<	* termination in the presence of task dependencies. So the method
2799	<	* always returns an empty list (unlike the case for some other
2800	<	* Executors).
2793	>	* Possibly attempts to cancel and/or stop all tasks, and reject
2794	>	* all subsequently submitted tasks. Invocation has no effect on
2795	>	* execution state if this is the {@link #commonPool}, and no
2796	>	* additional effect if already shut down. Otherwise, tasks that
2797	>	* are in the process of being submitted or executed concurrently
2798	>	* during the course of this method may or may not be
2799	>	* rejected. This method cancels both existing and unexecuted
2800	>	* tasks, in order to permit termination in the presence of task
2801	>	* dependencies. So the method always returns an empty list
2802	>	* (unlike the case for some other Executors).
2803		*
2804		* @return an empty list
2805		* @throws SecurityException if a security manager exists and
#	Line 2425 \| Line 2809 \| public class ForkJoinPool extends Abstra
2809		*/
2810		public List<Runnable> shutdownNow() {
2811		checkPermission();
2812	<	enableShutdown();
2813	<	tryTerminate(true);
2812	>	if (this != commonPool)
2813	>	tryTerminate(true, true);
2814		return Collections.emptyList();
2815		}
2816
#	Line 2483 \| Line 2867 \| public class ForkJoinPool extends Abstra
2867		public boolean awaitTermination(long timeout, TimeUnit unit)
2868		throws InterruptedException {
2869		long nanos = unit.toNanos(timeout);
2870	<	final ReentrantLock lock = this.lock;
2871	<	lock.lock();
2872	<	try {
2873	<	for (;;) {
2874	<	if (isTerminated())
2875	<	return true;
2876	<	if (nanos <= 0)
2877	<	return false;
2878	<	nanos = termination.awaitNanos(nanos);
2870	>	if (isTerminated())
2871	>	return true;
2872	>	long startTime = System.nanoTime();
2873	>	boolean terminated = false;
2874	>	synchronized(this) {
2875	>	for (long waitTime = nanos, millis = 0L;;) {
2876	>	if (terminated = isTerminated() \|\|
2877	>	waitTime <= 0L \|\|
2878	>	(millis = unit.toMillis(waitTime)) <= 0L)
2879	>	break;
2880	>	wait(millis);
2881	>	waitTime = nanos - (System.nanoTime() - startTime);
2882		}
2496	–	} finally {
2497	–	lock.unlock();
2883		}
2884	+	return terminated;
2885		}
2886
2887		/**
#	Line 2597 \| Line 2983 \| public class ForkJoinPool extends Abstra
2983		ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ?
2984		((ForkJoinWorkerThread)t).pool : null);
2985		while (!blocker.isReleasable()) {
2986	<	if (p == null \|\| p.tryCompensate()) {
2986	>	if (p == null \|\| p.tryCompensate(null, blocker)) {
2987		try {
2988		do {} while (!blocker.isReleasable() && !blocker.block());
2989		} finally {
#	Line 2614 \| Line 3000 \| public class ForkJoinPool extends Abstra
3000		// implement RunnableFuture.
3001
3002		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
3003	<	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
3003	>	return new ForkJoinTask.AdaptedRunnable<T>(runnable, value);
3004		}
3005
3006		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
3007	<	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
3007	>	return new ForkJoinTask.AdaptedCallable<T>(callable);
3008		}
3009
3010		// Unsafe mechanics
3011		private static final sun.misc.Unsafe U;
3012		private static final long CTL;
2627	–	private static final long RUNSTATE;
3013		private static final long PARKBLOCKER;
3014	+	private static final int ABASE;
3015	+	private static final int ASHIFT;
3016	+	private static final long NEXTWORKERNUMBER;
3017	+	private static final long STEALCOUNT;
3018	+	private static final long MAINLOCK;
3019
3020		static {
3021		poolNumberGenerator = new AtomicInteger();
3022	+	nextSubmitterSeed = new AtomicInteger(0x55555555);
3023		modifyThreadPermission = new RuntimePermission("modifyThread");
3024		defaultForkJoinWorkerThreadFactory =
3025		new DefaultForkJoinWorkerThreadFactory();
3026	+	submitters = new ThreadSubmitter();
3027		int s;
3028		try {
3029		U = getUnsafe();
3030		Class<?> k = ForkJoinPool.class;
3031	<	Class<?> tk = Thread.class;
3031	>	Class<?> ak = ForkJoinTask[].class;
3032		CTL = U.objectFieldOffset
3033		(k.getDeclaredField("ctl"));
3034	<	RUNSTATE = U.objectFieldOffset
3035	<	(k.getDeclaredField("runState"));
3034	>	NEXTWORKERNUMBER = U.objectFieldOffset
3035	>	(k.getDeclaredField("nextWorkerNumber"));
3036	>	STEALCOUNT = U.objectFieldOffset
3037	>	(k.getDeclaredField("stealCount"));
3038	>	MAINLOCK = U.objectFieldOffset
3039	>	(k.getDeclaredField("mainLock"));
3040	>	Class<?> tk = Thread.class;
3041		PARKBLOCKER = U.objectFieldOffset
3042		(tk.getDeclaredField("parkBlocker"));
3043	+	ABASE = U.arrayBaseOffset(ak);
3044	+	s = U.arrayIndexScale(ak);
3045	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3046	+	} catch (Exception e) {
3047	+	throw new Error(e);
3048	+	}
3049	+	if ((s & (s-1)) != 0)
3050	+	throw new Error("data type scale not a power of two");
3051	+	try { // Establish common pool
3052	+	String pp = System.getProperty(propPrefix + "parallelism");
3053	+	String fp = System.getProperty(propPrefix + "threadFactory");
3054	+	String up = System.getProperty(propPrefix + "exceptionHandler");
3055	+	ForkJoinWorkerThreadFactory fac = (fp == null) ?
3056	+	defaultForkJoinWorkerThreadFactory :
3057	+	((ForkJoinWorkerThreadFactory)ClassLoader.
3058	+	getSystemClassLoader().loadClass(fp).newInstance());
3059	+	Thread.UncaughtExceptionHandler ueh = (up == null)? null :
3060	+	((Thread.UncaughtExceptionHandler)ClassLoader.
3061	+	getSystemClassLoader().loadClass(up).newInstance());
3062	+	int par;
3063	+	if ((pp == null \|\| (par = Integer.parseInt(pp)) <= 0))
3064	+	par = Runtime.getRuntime().availableProcessors();
3065	+	if (par > MAX_CAP)
3066	+	par = MAX_CAP;
3067	+	commonPoolParallelism = par;
3068	+	int n = par - 1; // precompute submit mask
3069	+	n \|= n >>> 1; n \|= n >>> 2; n \|= n >>> 4;
3070	+	n \|= n >>> 8; n \|= n >>> 16;
3071	+	int mask = ((n + 1) << 1) - 1;
3072	+	commonPool = new ForkJoinPool(par, mask, fac, ueh);
3073		} catch (Exception e) {
3074		throw new Error(e);
3075		}

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents): Revision 1.118 by jsr166, Sat Jan 28 04:34:54 2012 UTC vs. Revision 1.136 by dl, Mon Oct 29 17:23:34 2012 UTC

Diff Legend

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.118 by jsr166, Sat Jan 28 04:34:54 2012 UTC vs.
Revision 1.136 by dl, Mon Oct 29 17:23:34 2012 UTC