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root/jsr166/jsr166/src/jsr166y/ForkJoinPool.java

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.122 by jsr166, Tue Jan 31 01:51:13 2012 UTC vs.
Revision 1.144 by jsr166, Sun Nov 18 18:03:10 2012 UTC

#	Line 11 | Line 11 | import java.util.Arrays;
11		import java.util.Collection;
12		import java.util.Collections;
13		import java.util.List;
14	–	import java.util.Random;
14		import java.util.concurrent.AbstractExecutorService;
15		import java.util.concurrent.Callable;
16		import java.util.concurrent.ExecutorService;
#	Line 19 | Line 18 | import java.util.concurrent.Future;
18		import java.util.concurrent.RejectedExecutionException;
19		import java.util.concurrent.RunnableFuture;
20		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.AbstractQueuedSynchronizer;
25	–	import java.util.concurrent.locks.Condition;
21
22		/**
23		* An {@link ExecutorService} for running {@link ForkJoinTask}s.
#	Line 42 | Line 37 | import java.util.concurrent.locks.Condit
37		* ForkJoinPool}s may also be appropriate for use with event-style
38		* tasks that are never joined.
39		*
40	<	* <p>A {@code ForkJoinPool} is constructed with a given target
41	<	* parallelism level; by default, equal to the number of available
42	<	* processors. The pool attempts to maintain enough active (or
43	<	* available) threads by dynamically adding, suspending, or resuming
44	<	* internal worker threads, even if some tasks are stalled waiting to
45	<	* join others. However, no such adjustments are guaranteed in the
46	<	* face of blocked IO or other unmanaged synchronization. The nested
47	<	* {@link ManagedBlocker} interface enables extension of the kinds of
40	>	* <p>A static {@link #commonPool} is available and appropriate for
41	>	* most applications. The common pool is used by any ForkJoinTask that
42	>	* is not explicitly submitted to a specified pool. Using the common
43	>	* pool normally reduces resource usage (its threads are slowly
44	>	* reclaimed during periods of non-use, and reinstated upon subsequent
45	>	* use).
46	>	*
47	>	* <p>For applications that require separate or custom pools, a {@code
48	>	* ForkJoinPool} may be constructed with a given target parallelism
49	>	* level; by default, equal to the number of available processors. The
50	>	* pool attempts to maintain enough active (or available) threads by
51	>	* dynamically adding, suspending, or resuming internal worker
52	>	* threads, even if some tasks are stalled waiting to join
53	>	* others. However, no such adjustments are guaranteed in the face of
54	>	* blocked IO or other unmanaged synchronization. The nested {@link
55	>	* ManagedBlocker} interface enables extension of the kinds of
56		* synchronization accommodated.
57		*
58		* <p>In addition to execution and lifecycle control methods, this
#	Line 59 | Line 62 | import java.util.concurrent.locks.Condit
62		* {@link #toString} returns indications of pool state in a
63		* convenient form for informal monitoring.
64		*
65	<	* <p> As is the case with other ExecutorServices, there are three
65	>	* <p>As is the case with other ExecutorServices, there are three
66		* main task execution methods summarized in the following table.
67		* These are designed to be used primarily by clients not already
68		* engaged in fork/join computations in the current pool.  The main
#	Line 94 | Line 97 | import java.util.concurrent.locks.Condit
97		*  </tr>
98		* </table>
99		*
100	<	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
101	<	* used for all parallel task execution in a program or subsystem.
102	<	* Otherwise, use would not usually outweigh the construction and
103	<	* bookkeeping overhead of creating a large set of threads. For
104	<	* example, a common pool could be used for the {@code SortTasks}
105	<	* illustrated in {@link RecursiveAction}. Because {@code
106	<	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
107	<	* daemon} mode, there is typically no need to explicitly {@link
108	<	* #shutdown} such a pool upon program exit.
109	<	*
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>
100	>	* <p>The common pool is by default constructed with default
101	>	* parameters, but these may be controlled by setting three {@link
102	>	* System#getProperty properties} with prefix {@code
103	>	* java.util.concurrent.ForkJoinPool.common}: {@code parallelism} --
104	>	* an integer greater than zero, {@code threadFactory} -- the class
105	>	* name of a {@link ForkJoinWorkerThreadFactory}, and {@code
106	>	* exceptionHandler} -- the class name of a {@link
107	>	* java.lang.Thread.UncaughtExceptionHandler
108	>	* Thread.UncaughtExceptionHandler}. Upon any error in establishing
109	>	* these settings, default parameters are used.
110		*
111		* <p><b>Implementation notes</b>: This implementation restricts the
112		* maximum number of running threads to 32767. Attempts to create
#	Line 177 | Line 174 | public class ForkJoinPool extends Abstra
174		* If an attempted steal fails, a thief always chooses a different
175		* random victim target to try next. So, in order for one thief to
176		* progress, it suffices for any in-progress poll or new push on
177	<	* any empty queue to complete.
177	>	* any empty queue to complete. (This is why we normally use
178	>	* method pollAt and its variants that try once at the apparent
179	>	* base index, else consider alternative actions, rather than
180	>	* method poll.)
181		*
182		* This approach also enables support of a user mode in which local
183		* task processing is in FIFO, not LIFO order, simply by using
#	Line 194 | Line 194 | public class ForkJoinPool extends Abstra
194		* WorkQueues are also used in a similar way for tasks submitted
195		* to the pool. We cannot mix these tasks in the same queues used
196		* for work-stealing (this would contaminate lifo/fifo
197	<	* processing). Instead, we loosely associate submission queues
197	>	* processing). Instead, we randomly associate submission queues
198		* with submitting threads, using a form of hashing.  The
199		* ThreadLocal Submitter class contains a value initially used as
200		* a hash code for choosing existing queues, but may be randomly
201		* repositioned upon contention with other submitters.  In
202	<	* essence, submitters act like workers except that they never
203	<	* take tasks, and they are multiplexed on to a finite number of
204	<	* shared work queues. However, classes are set up so that future
205	<	* extensions could allow submitters to optionally help perform
206	<	* tasks as well. Insertion of tasks in shared mode requires a
207	<	* lock (mainly to protect in the case of resizing) but we use
208	<	* only a simple spinlock (using bits in field runState), because
209	<	* submitters encountering a busy queue move on to try or create
210	<	* other queues, so never block.
202	>	* essence, submitters act like workers except that they are
203	>	* restricted to executing local tasks that they submitted (or in
204	>	* the case of CountedCompleters, others with the same root task).
205	>	* However, because most shared/external queue operations are more
206	>	* expensive than internal, and because, at steady state, external
207	>	* submitters will compete for CPU with workers, ForkJoinTask.join
208	>	* and related methods disable them from repeatedly helping to
209	>	* process tasks if all workers are active.  Insertion of tasks in
210	>	* shared mode requires a lock (mainly to protect in the case of
211	>	* resizing) but we use only a simple spinlock (using bits in
212	>	* field qlock), because submitters encountering a busy queue move
213	>	* on to try or create other queues -- they block only when
214	>	* creating and registering new queues.
215		*
216		* Management
217		* ==========
#	Line 229 | Line 233 | public class ForkJoinPool extends Abstra
233		* and their negations (used for thresholding) to fit into 16bit
234		* fields.
235		*
236	<	* Field "runState" contains 32 bits needed to register and
237	<	* deregister WorkQueues, as well as to enable shutdown. It is
238	<	* only modified under a lock (normally briefly held, but
239	<	* occasionally protecting allocations and resizings) but even
240	<	* when locked remains available to check consistency. An
241	<	* auxiliary field "growHints", also only modified under lock,
242	<	* contains a candidate index for the next WorkQueue and
239	<	* a mask for submission queue indices.
236	>	* Field "plock" is a form of sequence lock with a saturating
237	>	* shutdown bit (similarly for per-queue "qlocks"), mainly
238	>	* protecting updates to the workQueues array, as well as to
239	>	* enable shutdown.  When used as a lock, it is normally only very
240	>	* briefly held, so is nearly always available after at most a
241	>	* brief spin, but we use a monitor-based backup strategy to
242	>	* blocking when needed.
243		*
244		* Recording WorkQueues.  WorkQueues are recorded in the
245	<	* "workQueues" array that is created upon pool construction and
246	<	* expanded if necessary.  Updates to the array while recording
247	<	* new workers and unrecording terminated ones are protected from
248	<	* each other by a lock but the array is otherwise concurrently
249	<	* readable, and accessed directly.  To simplify index-based
250	<	* operations, the array size is always a power of two, and all
251	<	* readers must tolerate null slots. Shared (submission) queues
252	<	* are at even indices, worker queues at odd indices. Grouping
253	<	* them together in this way simplifies and speeds up task
254	<	* scanning. To avoid flailing during start-up, the array is
255	<	* presized to hold twice #parallelism workers (which is unlikely
253	<	* to need further resizing during execution). But to avoid
254	<	* dealing with so many null slots, variable runState includes a
255	<	* mask for the nearest power of two that contains all currently
256	<	* used indices.
245	>	* "workQueues" array that is created upon first use and expanded
246	>	* if necessary.  Updates to the array while recording new workers
247	>	* and unrecording terminated ones are protected from each other
248	>	* by a lock but the array is otherwise concurrently readable, and
249	>	* accessed directly.  To simplify index-based operations, the
250	>	* array size is always a power of two, and all readers must
251	>	* tolerate null slots. Worker queues are at odd indices Shared
252	>	* (submission) queues are at even indices, up to a maximum of 64
253	>	* slots, to limit growth even if array needs to expand to add
254	>	* more workers. Grouping them together in this way simplifies and
255	>	* speeds up task scanning.
256		*
257		* All worker thread creation is on-demand, triggered by task
258		* submissions, replacement of terminated workers, and/or
#	Line 314 | Line 313 | public class ForkJoinPool extends Abstra
313		*
314		* Signalling.  We create or wake up workers only when there
315		* appears to be at least one task they might be able to find and
316	<	* execute.  When a submission is added or another worker adds a
317	<	* task to a queue that previously had fewer than two tasks, they
318	<	* signal waiting workers (or trigger creation of new ones if
319	<	* fewer than the given parallelism level -- see signalWork).
320	<	* These primary signals are buttressed by signals during rescans;
321	<	* together these cover the signals needed in cases when more
322	<	* tasks are pushed but untaken, and improve performance compared
323	<	* to having one thread wake up all workers.
316	>	* execute. However, many other threads may notice the same task
317	>	* and each signal to wake up a thread that might take it. So in
318	>	* general, pools will be over-signalled.  When a submission is
319	>	* added or another worker adds a task to a queue that is
320	>	* apparently empty, they signal waiting workers (or trigger
321	>	* creation of new ones if fewer than the given parallelism level
322	>	* -- see signalWork).  These primary signals are buttressed by
323	>	* signals whenever other threads scan for work or do not have a
324	>	* task to process. On most platforms, signalling (unpark)
325	>	* overhead time is noticeably long, and the time between
326	>	* signalling a thread and it actually making progress can be very
327	>	* noticeably long, so it is worth offloading these delays from
328	>	* critical paths as much as possible.
329		*
330		* Trimming workers. To release resources after periods of lack of
331		* use, a worker starting to wait when the pool is quiescent will
332	<	* time out and terminate if the pool has remained quiescent for
333	<	* SHRINK_RATE nanosecs. This will slowly propagate, eventually
334	<	* terminating all workers after long periods of non-use.
332	>	* time out and terminate if the pool has remained quiescent for a
333	>	* given period -- a short period if there are more threads than
334	>	* parallelism, longer as the number of threads decreases. This
335	>	* will slowly propagate, eventually terminating all workers after
336	>	* periods of non-use.
337		*
338		* Shutdown and Termination. A call to shutdownNow atomically sets
339	<	* a runState bit and then (non-atomically) sets each worker's
340	<	* runState status, cancels all unprocessed tasks, and wakes up
339	>	* a plock bit and then (non-atomically) sets each worker's
340	>	* qlock status, cancels all unprocessed tasks, and wakes up
341		* all waiting workers.  Detecting whether termination should
342		* commence after a non-abrupt shutdown() call requires more work
343		* and bookkeeping. We need consensus about quiescence (i.e., that
#	Line 359 | Line 365 | public class ForkJoinPool extends Abstra
365		*      method tryCompensate() may create or re-activate a spare
366		*      thread to compensate for blocked joiners until they unblock.
367		*
368	<	* A third form (implemented in tryRemoveAndExec and
369	<	* tryPollForAndExec) amounts to helping a hypothetical
370	<	* compensator: If we can readily tell that a possible action of a
371	<	* compensator is to steal and execute the task being joined, the
372	<	* joining thread can do so directly, without the need for a
373	<	* compensation thread (although at the expense of larger run-time
374	<	* stacks, but the tradeoff is typically worthwhile).
368	>	* A third form (implemented in tryRemoveAndExec) amounts to
369	>	* helping a hypothetical compensator: If we can readily tell that
370	>	* a possible action of a compensator is to steal and execute the
371	>	* task being joined, the joining thread can do so directly,
372	>	* without the need for a compensation thread (although at the
373	>	* expense of larger run-time stacks, but the tradeoff is
374	>	* typically worthwhile).
375		*
376		* The ManagedBlocker extension API can't use helping so relies
377		* only on compensation in method awaitBlocker.
#	Line 385 | Line 391 | public class ForkJoinPool extends Abstra
391		* (http://portal.acm.org/citation.cfm?id=155354). It differs in
392		* that: (1) We only maintain dependency links across workers upon
393		* steals, rather than use per-task bookkeeping.  This sometimes
394	<	* requires a linear scan of workQueues array to locate stealers, but
395	<	* often doesn't because stealers leave hints (that may become
394	>	* requires a linear scan of workQueues array to locate stealers,
395	>	* but often doesn't because stealers leave hints (that may become
396		* stale/wrong) of where to locate them.  A stealHint is only a
397		* hint because a worker might have had multiple steals and the
398		* hint records only one of them (usually the most current).
#	Line 397 | Line 403 | public class ForkJoinPool extends Abstra
403		* which means that we miss links in the chain during long-lived
404		* tasks, GC stalls etc (which is OK since blocking in such cases
405		* is usually a good idea).  (4) We bound the number of attempts
406	<	* to find work (see MAX_HELP_DEPTH) and fall back to suspending
407	<	* the worker and if necessary replacing it with another.
406	>	* to find work (see MAX_HELP) and fall back to suspending the
407	>	* worker and if necessary replacing it with another.
408	>	*
409	>	* Helping actions for CountedCompleters are much simpler: Method
410	>	* helpComplete can take and execute any task with the same root
411	>	* as the task being waited on. However, this still entails some
412	>	* traversal of completer chains, so is less efficient than using
413	>	* CountedCompleters without explicit joins.
414		*
415		* It is impossible to keep exactly the target parallelism number
416		* of threads running at any given time.  Determining the
417		* existence of conservatively safe helping targets, the
418		* availability of already-created spares, and the apparent need
419		* to create new spares are all racy, so we rely on multiple
420	<	* retries of each.  Currently, in keeping with on-demand
421	<	* signalling policy, we compensate only if blocking would leave
422	<	* less than one active (non-waiting, non-blocked) worker.
423	<	* Additionally, to avoid some false alarms due to GC, lagging
424	<	* counters, system activity, etc, compensated blocking for joins
425	<	* is only attempted after rechecks stabilize in
426	<	* ForkJoinTask.awaitJoin. (Retries are interspersed with
427	<	* Thread.yield, for good citizenship.)
428	<	*
429	<	* Style notes: There is a lot of representation-level coupling
430	<	* among classes ForkJoinPool, ForkJoinWorkerThread, and
431	<	* ForkJoinTask.  The fields of WorkQueue maintain data structures
432	<	* managed by ForkJoinPool, so are directly accessed.  There is
433	<	* little point trying to reduce this, since any associated future
434	<	* changes in representations will need to be accompanied by
435	<	* algorithmic changes anyway. Several methods intrinsically
436	<	* sprawl because they must accumulate sets of consistent reads of
437	<	* volatiles held in local variables.  Methods signalWork() and
438	<	* scan() are the main bottlenecks, so are especially heavily
420	>	* retries of each.  Compensation in the apparent absence of
421	>	* helping opportunities is challenging to control on JVMs, where
422	>	* GC and other activities can stall progress of tasks that in
423	>	* turn stall out many other dependent tasks, without us being
424	>	* able to determine whether they will ever require compensation.
425	>	* Even though work-stealing otherwise encounters little
426	>	* degradation in the presence of more threads than cores,
427	>	* aggressively adding new threads in such cases entails risk of
428	>	* unwanted positive feedback control loops in which more threads
429	>	* cause more dependent stalls (as well as delayed progress of
430	>	* unblocked threads to the point that we know they are available)
431	>	* leading to more situations requiring more threads, and so
432	>	* on. This aspect of control can be seen as an (analytically
433	>	* intractable) game with an opponent that may choose the worst
434	>	* (for us) active thread to stall at any time.  We take several
435	>	* precautions to bound losses (and thus bound gains), mainly in
436	>	* methods tryCompensate and awaitJoin.
437	>	*
438	>	* Common Pool
439	>	* ===========
440	>	*
441	>	* The static commonPool always exists after static
442	>	* initialization.  Since it (or any other created pool) need
443	>	* never be used, we minimize initial construction overhead and
444	>	* footprint to the setup of about a dozen fields, with no nested
445	>	* allocation. Most bootstrapping occurs within method
446	>	* fullExternalPush during the first submission to the pool.
447	>	*
448	>	* When external threads submit to the common pool, they can
449	>	* perform some subtask processing (see externalHelpJoin and
450	>	* related methods).  We do not need to record whether these
451	>	* submissions are to the common pool -- if not, externalHelpJoin
452	>	* returns quickly (at the most helping to signal some common pool
453	>	* workers). These submitters would otherwise be blocked waiting
454	>	* for completion, so the extra effort (with liberally sprinkled
455	>	* task status checks) in inapplicable cases amounts to an odd
456	>	* form of limited spin-wait before blocking in ForkJoinTask.join.
457	>	*
458	>	* Style notes
459	>	* ===========
460	>	*
461	>	* There is a lot of representation-level coupling among classes
462	>	* ForkJoinPool, ForkJoinWorkerThread, and ForkJoinTask.  The
463	>	* fields of WorkQueue maintain data structures managed by
464	>	* ForkJoinPool, so are directly accessed.  There is little point
465	>	* trying to reduce this, since any associated future changes in
466	>	* representations will need to be accompanied by algorithmic
467	>	* changes anyway. Several methods intrinsically sprawl because
468	>	* they must accumulate sets of consistent reads of volatiles held
469	>	* in local variables.  Methods signalWork() and scan() are the
470	>	* main bottlenecks, so are especially heavily
471		* micro-optimized/mangled.  There are lots of inline assignments
472		* (of form "while ((local = field) != 0)") which are usually the
473		* simplest way to ensure the required read orderings (which are
#	Line 431 | Line 475 | public class ForkJoinPool extends Abstra
475		* declarations of these locals at the heads of methods or blocks.
476		* There are several occurrences of the unusual "do {} while
477		* (!cas...)"  which is the simplest way to force an update of a
478	<	* CAS'ed variable. There are also other coding oddities that help
478	>	* CAS'ed variable. There are also other coding oddities (including
479	>	* several unnecessary-looking hoisted null checks) that help
480		* some methods perform reasonably even when interpreted (not
481		* compiled).
482		*
#	Line 449 | Line 494 | public class ForkJoinPool extends Abstra
494		// Static utilities
495
496		/**
452	–	* Computes an initial hash code (also serving as a non-zero
453	–	* random seed) for a thread id. This method is expected to
454	–	* provide higher-quality hash codes than using method hashCode().
455	–	*/
456	–	static final int hashId(long id) {
457	–	int h = (int)id ^ (int)(id >>> 32); // Use MurmurHash of thread id
458	–	h ^= h >>> 16; h *= 0x85ebca6b;
459	–	h ^= h >>> 13; h *= 0xc2b2ae35;
460	–	h ^= h >>> 16;
461	–	return (h == 0) ? 1 : h; // ensure nonzero
462	–	}
463	–
464	–	/**
497		* If there is a security manager, makes sure caller has
498		* permission to modify threads.
499		*/
#	Line 501 | Line 533 | public class ForkJoinPool extends Abstra
533		}
534
535		/**
504	–	* A simple non-reentrant lock used for exclusion when managing
505	–	* queues and workers. We use a custom lock so that we can readily
506	–	* probe lock state in constructions that check among alternative
507	–	* actions. The lock is normally only very briefly held, and
508	–	* sometimes treated as a spinlock, but other usages block to
509	–	* reduce overall contention in those cases where locked code
510	–	* bodies perform allocation/resizing.
511	–	*/
512	–	static final class Mutex extends AbstractQueuedSynchronizer {
513	–	public final boolean tryAcquire(int ignore) {
514	–	return compareAndSetState(0, 1);
515	–	}
516	–	public final boolean tryRelease(int ignore) {
517	–	setState(0);
518	–	return true;
519	–	}
520	–	public final void lock() { acquire(0); }
521	–	public final void unlock() { release(0); }
522	–	public final boolean isHeldExclusively() { return getState() == 1; }
523	–	public final Condition newCondition() { return new ConditionObject(); }
524	–	}
525	–
526	–	/**
536		* Class for artificial tasks that are used to replace the target
537		* of local joins if they are removed from an interior queue slot
538		* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
539		* actually do anything beyond having a unique identity.
540		*/
541		static final class EmptyTask extends ForkJoinTask<Void> {
542	+	private static final long serialVersionUID = -7721805057305804111L;
543		EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
544		public final Void getRawResult() { return null; }
545		public final void setRawResult(Void x) {}
#	Line 550 | Line 560 | public class ForkJoinPool extends Abstra
560		*
561		* Field "top" is the index (mod array.length) of the next queue
562		* slot to push to or pop from. It is written only by owner thread
563	<	* for push, or under lock for trySharedPush, and accessed by
564	<	* other threads only after reading (volatile) base.  Both top and
565	<	* base are allowed to wrap around on overflow, but (top - base)
566	<	* (or more commonly -(base - top) to force volatile read of base
567	<	* before top) still estimates size.
563	>	* for push, or under lock for external/shared push, and accessed
564	>	* by other threads only after reading (volatile) base.  Both top
565	>	* and base are allowed to wrap around on overflow, but (top -
566	>	* base) (or more commonly -(base - top) to force volatile read of
567	>	* base before top) still estimates size. The lock ("qlock") is
568	>	* forced to -1 on termination, causing all further lock attempts
569	>	* to fail. (Note: we don't need CAS for termination state because
570	>	* upon pool shutdown, all shared-queues will stop being used
571	>	* anyway.)  Nearly all lock bodies are set up so that exceptions
572	>	* within lock bodies are "impossible" (modulo JVM errors that
573	>	* would cause failure anyway.)
574		*
575		* The array slots are read and written using the emulation of
576		* volatiles/atomics provided by Unsafe. Insertions must in
577		* general use putOrderedObject as a form of releasing store to
578		* ensure that all writes to the task object are ordered before
579	<	* its publication in the queue. (Although we can avoid one case
580	<	* of this when locked in trySharedPush.) All removals entail a
581	<	* CAS to null.  The array is always a power of two. To ensure
582	<	* safety of Unsafe array operations, all accesses perform
567	<	* explicit null checks and implicit bounds checks via
568	<	* power-of-two masking.
579	>	* its publication in the queue.  All removals entail a CAS to
580	>	* null.  The array is always a power of two. To ensure safety of
581	>	* Unsafe array operations, all accesses perform explicit null
582	>	* checks and implicit bounds checks via power-of-two masking.
583		*
584		* In addition to basic queuing support, this class contains
585		* fields described elsewhere to control execution. It turns out
586	<	* to work better memory-layout-wise to include them in this
587	<	* class rather than a separate class.
586	>	* to work better memory-layout-wise to include them in this class
587	>	* rather than a separate class.
588		*
589		* Performance on most platforms is very sensitive to placement of
590		* instances of both WorkQueues and their arrays -- we absolutely
#	Line 586 | Line 600 | public class ForkJoinPool extends Abstra
600		* support is in place, this padding is dependent on transient
601		* properties of JVM field layout rules.)  We also take care in
602		* allocating, sizing and resizing the array. Non-shared queue
603	<	* arrays are initialized (via method growArray) by workers before
604	<	* use. Others are allocated on first use.
603	>	* arrays are initialized by workers before use. Others are
604	>	* allocated on first use.
605		*/
606		static final class WorkQueue {
607		/**
608		* Capacity of work-stealing queue array upon initialization.
609	<	* Must be a power of two; at least 4, but set larger to
610	<	* reduce cacheline sharing among queues.
609	>	* Must be a power of two; at least 4, but should be larger to
610	>	* reduce or eliminate cacheline sharing among queues.
611	>	* Currently, it is much larger, as a partial workaround for
612	>	* the fact that JVMs often place arrays in locations that
613	>	* share GC bookkeeping (especially cardmarks) such that
614	>	* per-write accesses encounter serious memory contention.
615		*/
616	<	static final int INITIAL_QUEUE_CAPACITY = 1 << 8;
616	>	static final int INITIAL_QUEUE_CAPACITY = 1 << 13;
617
618		/**
619		* Maximum size for queue arrays. Must be a power of two less
#	Line 606 | Line 624 | public class ForkJoinPool extends Abstra
624		*/
625		static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
626
609	–	volatile long totalSteals; // cumulative number of steals
627		int seed;                  // for random scanning; initialize nonzero
628		volatile int eventCount;   // encoded inactivation count; < 0 if inactive
629		int nextWait;              // encoded record of next event waiter
613	–	int rescans;               // remaining scans until block
614	–	int nsteals;               // top-level task executions since last idle
630		final int mode;            // lifo, fifo, or shared
631	+	int nsteals;               // cumulative number of steals
632		int poolIndex;             // index of this queue in pool (or 0)
633		int stealHint;             // index of most recent known stealer
634	<	volatile int runState;     // 1: locked, -1: terminate; else 0
634	>	volatile int qlock;        // 1: locked, -1: terminate; else 0
635		volatile int base;         // index of next slot for poll
636		int top;                   // index of next slot for push
637		ForkJoinTask<?>[] array;   // the elements (initially unallocated)
638	+	final ForkJoinPool pool;   // the containing pool (may be null)
639		final ForkJoinWorkerThread owner; // owning thread or null if shared
640		volatile Thread parker;    // == owner during call to park; else null
641	<	ForkJoinTask<?> currentJoin;  // task being joined in awaitJoin
641	>	volatile ForkJoinTask<?> currentJoin;  // task being joined in awaitJoin
642		ForkJoinTask<?> currentSteal; // current non-local task being executed
643		// Heuristic padding to ameliorate unfortunate memory placements
644	<	Object p00, p01, p02, p03, p04, p05, p06, p07, p08, p09, p0a;
644	>	Object p00, p01, p02, p03, p04, p05, p06, p07;
645	>	Object p08, p09, p0a, p0b, p0c, p0d, p0e;
646
647	<	WorkQueue(ForkJoinWorkerThread owner, int mode) {
630	<	this.owner = owner;
647	>	WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode) {
648		this.mode = mode;
649	+	this.pool = pool;
650	+	this.owner = owner;
651		// Place indices in the center of array (that is not yet allocated)
652		base = top = INITIAL_QUEUE_CAPACITY >>> 1;
653		}
654
655		/**
637	–	* Returns number of tasks in the queue.
638	–	*/
639	–	final int queueSize() {
640	–	int n = base - top; // non-owner callers must read base first
641	–	return (n >= 0) ? 0 : -n;
642	–	}
643	–
644	–	/**
656		* Pushes a task. Call only by owner in unshared queues.
657	+	* Cases needing resizing or rejection are relayed to fullPush
658	+	* (that also handles shared queues).
659		*
660		* @param task the task. Caller must ensure non-null.
648	–	* @param p if non-null, pool to signal if necessary
661		* @throw RejectedExecutionException if array cannot be resized
662		*/
663	<	final void push(ForkJoinTask<?> task, ForkJoinPool p) {
664	<	ForkJoinTask<?>[] a;
665	<	int s = top, m, n;
666	<	if ((a = array) != null) {    // ignore if queue removed
663	>	final void push(ForkJoinTask<?> task) {
664	>	ForkJoinPool p; ForkJoinTask<?>[] a;
665	>	int s = top, n;
666	>	if ((a = array) != null && a.length > (n = s + 1 - base)) {
667		U.putOrderedObject
668	<	(a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task);
669	<	if ((n = (top = s + 1) - base) <= 2) {
670	<	if (p != null)
671	<	p.signalWork();
660	<	}
661	<	else if (n >= m)
662	<	growArray(true);
668	>	(a, (((a.length - 1) & s) << ASHIFT) + ABASE, task);
669	>	top = s + 1;
670	>	if (n <= 1 && (p = pool) != null)
671	>	p.signalWork(this, 1);
672		}
673	+	else
674	+	fullPush(task, true);
675		}
676
677		/**
678		* Pushes a task if lock is free and array is either big
679	<	* enough or can be resized to be big enough.
679	>	* enough or can be resized to be big enough. Note: a
680	>	* specialization of a common fast path of this method is in
681	>	* ForkJoinPool.externalPush. When called from a FJWT queue,
682	>	* this can fail only if the pool has been shut down or
683	>	* an out of memory error.
684		*
685		* @param task the task. Caller must ensure non-null.
686	<	* @return true if submitted
686	>	* @param owned if true, throw RJE on failure
687		*/
688	<	final boolean trySharedPush(ForkJoinTask<?> task) {
689	<	boolean submitted = false;
690	<	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
691	<	ForkJoinTask<?>[] a = array;
692	<	int s = top;
693	<	try {
694	<	if ((a != null && a.length > s + 1 - base) ||
695	<	(a = growArray(false)) != null) { // must presize
696	<	int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
697	<	U.putObject(a, (long)j, task);    // don't need "ordered"
698	<	top = s + 1;
699	<	submitted = true;
688	>	final boolean fullPush(ForkJoinTask<?> task, boolean owned) {
689	>	ForkJoinPool p; ForkJoinTask<?>[] a;
690	>	if (owned) {
691	>	if (qlock < 0) // must be shutting down
692	>	throw new RejectedExecutionException();
693	>	}
694	>	else if (!U.compareAndSwapInt(this, QLOCK, 0, 1))
695	>	return false;
696	>	try {
697	>	int s = top, oldLen, len;
698	>	if ((a = array) == null)
699	>	a = array = new ForkJoinTask<?>[len=INITIAL_QUEUE_CAPACITY];
700	>	else if ((oldLen = a.length) > s + 1 - base)
701	>	len = oldLen;
702	>	else if ((len = oldLen << 1) > MAXIMUM_QUEUE_CAPACITY)
703	>	throw new RejectedExecutionException("Capacity exceeded");
704	>	else {
705	>	int oldMask, b;
706	>	ForkJoinTask<?>[] oldA = a;
707	>	a = array = new ForkJoinTask<?>[len];
708	>	if ((oldMask = oldLen - 1) >= 0 && s - (b = base) > 0) {
709	>	int mask = len - 1;
710	>	do {
711	>	ForkJoinTask<?> x;
712	>	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
713	>	int j    = ((b &    mask) << ASHIFT) + ABASE;
714	>	x = (ForkJoinTask<?>)
715	>	U.getObjectVolatile(oldA, oldj);
716	>	if (x != null &&
717	>	U.compareAndSwapObject(oldA, oldj, x, null))
718	>	U.putObjectVolatile(a, j, x);
719	>	} while (++b != s);
720	>	}
721	>	}
722	>	U.putOrderedObject
723	>	(a, (((len - 1) & s) << ASHIFT) + ABASE, task);
724	>	top = s + 1;
725	>	} finally {
726	>	if (!owned)
727	>	qlock = 0;
728	>	}
729	>	if ((p = pool) != null)
730	>	p.signalWork(this, 1);
731	>	return true;
732	>	}
733	>
734	>	/**
735	>	* Takes next task, if one exists, in LIFO order.  Call only
736	>	* by owner in unshared queues.
737	>	*/
738	>	final ForkJoinTask<?> pop() {
739	>	ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
740	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
741	>	for (int s; (s = top - 1) - base >= 0;) {
742	>	long j = ((m & s) << ASHIFT) + ABASE;
743	>	if ((t = (ForkJoinTask<?>)U.getObject(a, j)) == null)
744	>	break;
745	>	if (U.compareAndSwapObject(a, j, t, null)) {
746	>	top = s;
747	>	return t;
748		}
686	–	} finally {
687	–	runState = 0;                         // unlock
749		}
750		}
751	<	return submitted;
751	>	return null;
752		}
753
754		/**
755	<	* Takes next task, if one exists, in FIFO order.
755	>	* Takes a task in FIFO order if b is base of queue and a task
756	>	* can be claimed without contention. Specialized versions
757	>	* appear in ForkJoinPool methods scan and tryHelpStealer.
758		*/
759	<	final ForkJoinTask<?> poll() {
760	<	ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t;
761	<	while ((b = base) - top < 0 && (a = array) != null) {
759	>	final ForkJoinTask<?> pollAt(int b) {
760	>	ForkJoinTask<?> t; ForkJoinTask<?>[] a;
761	>	if ((a = array) != null) {
762		int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
763		if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
764		base == b &&
#	Line 708 | Line 771 | public class ForkJoinPool extends Abstra
771		}
772
773		/**
774	<	* Takes next task, if one exists, in LIFO order.  Call only
712	<	* by owner in unshared queues. (We do not have a shared
713	<	* version of this method because it is never needed.)
774	>	* Takes next task, if one exists, in FIFO order.
775		*/
776	<	final ForkJoinTask<?> pop() {
777	<	ForkJoinTask<?> t; int m;
778	<	ForkJoinTask<?>[] a = array;
779	<	if (a != null && (m = a.length - 1) >= 0) {
780	<	for (int s; (s = top - 1) - base >= 0;) {
781	<	int j = ((m & s) << ASHIFT) + ABASE;
782	<	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) == null)
783	<	break;
784	<	if (U.compareAndSwapObject(a, j, t, null)) {
724	<	top = s;
776	>	final ForkJoinTask<?> poll() {
777	>	ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t;
778	>	while ((b = base) - top < 0 && (a = array) != null) {
779	>	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
780	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
781	>	if (t != null) {
782	>	if (base == b &&
783	>	U.compareAndSwapObject(a, j, t, null)) {
784	>	base = b + 1;
785		return t;
786		}
787		}
788	+	else if (base == b) {
789	+	if (b + 1 == top)
790	+	break;
791	+	Thread.yield(); // wait for lagging update (very rare)
792	+	}
793		}
794		return null;
795		}
#	Line 749 | Line 814 | public class ForkJoinPool extends Abstra
814		}
815
816		/**
752	–	* Returns task at index b if b is current base of queue.
753	–	*/
754	–	final ForkJoinTask<?> pollAt(int b) {
755	–	ForkJoinTask<?> t; ForkJoinTask<?>[] a;
756	–	if ((a = array) != null) {
757	–	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
758	–	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
759	–	base == b &&
760	–	U.compareAndSwapObject(a, j, t, null)) {
761	–	base = b + 1;
762	–	return t;
763	–	}
764	–	}
765	–	return null;
766	–	}
767	–
768	–	/**
817		* Pops the given task only if it is at the current top.
818	+	* (A shared version is available only via FJP.tryExternalUnpush)
819		*/
820		final boolean tryUnpush(ForkJoinTask<?> t) {
821		ForkJoinTask<?>[] a; int s;
#	Line 780 | Line 829 | public class ForkJoinPool extends Abstra
829		}
830
831		/**
832	<	* Polls the given task only if it is at the current base.
832	>	* Removes and cancels all known tasks, ignoring any exceptions.
833		*/
834	<	final boolean pollFor(ForkJoinTask<?> task) {
835	<	ForkJoinTask<?>[] a; int b;
836	<	if ((b = base) - top < 0 && (a = array) != null) {
837	<	int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
838	<	if (U.getObjectVolatile(a, j) == task && base == b &&
839	<	U.compareAndSwapObject(a, j, task, null)) {
840	<	base = b + 1;
841	<	return true;
834	>	final void cancelAll() {
835	>	ForkJoinTask.cancelIgnoringExceptions(currentJoin);
836	>	ForkJoinTask.cancelIgnoringExceptions(currentSteal);
837	>	for (ForkJoinTask<?> t; (t = poll()) != null; )
838	>	ForkJoinTask.cancelIgnoringExceptions(t);
839	>	}
840	>
841	>	/**
842	>	* Computes next value for random probes.  Scans don't require
843	>	* a very high quality generator, but also not a crummy one.
844	>	* Marsaglia xor-shift is cheap and works well enough.  Note:
845	>	* This is manually inlined in its usages in ForkJoinPool to
846	>	* avoid writes inside busy scan loops.
847	>	*/
848	>	final int nextSeed() {
849	>	int r = seed;
850	>	r ^= r << 13;
851	>	r ^= r >>> 17;
852	>	return seed = r ^= r << 5;
853	>	}
854	>
855	>	/**
856	>	* Provides a more accurate estimate of size than (top - base)
857	>	* by ordering reads and checking whether a near-empty queue
858	>	* has at least one unclaimed task.
859	>	*/
860	>	final int queueSize() {
861	>	ForkJoinTask<?>[] a; int k, s, n;
862	>	return ((n = base - (s = top)) < 0 &&
863	>	(n != -1 ||
864	>	((a = array) != null && (k = a.length) > 0 &&
865	>	U.getObject
866	>	(a, (long)((((k - 1) & (s - 1)) << ASHIFT) + ABASE)) != null))) ?
867	>	-n : 0;
868	>	}
869	>
870	>	// Specialized execution methods
871	>
872	>	/**
873	>	* Pops and runs tasks until empty.
874	>	*/
875	>	private void popAndExecAll() {
876	>	// A bit faster than repeated pop calls
877	>	ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t;
878	>	while ((a = array) != null && (m = a.length - 1) >= 0 &&
879	>	(s = top - 1) - base >= 0 &&
880	>	(t = ((ForkJoinTask<?>)
881	>	U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
882	>	!= null) {
883	>	if (U.compareAndSwapObject(a, j, t, null)) {
884	>	top = s;
885	>	t.doExec();
886		}
887		}
795	–	return false;
888		}
889
890		/**
891	<	* If present, removes from queue and executes the given task, or
892	<	* any other cancelled task. Returns (true) immediately on any CAS
891	>	* Polls and runs tasks until empty.
892	>	*/
893	>	private void pollAndExecAll() {
894	>	for (ForkJoinTask<?> t; (t = poll()) != null;)
895	>	t.doExec();
896	>	}
897	>
898	>	/**
899	>	* If present, removes from queue and executes the given task,
900	>	* or any other cancelled task. Returns (true) on any CAS
901		* or consistency check failure so caller can retry.
902		*
903	<	* @return false if no progress can be made
903	>	* @return false if no progress can be made, else true;
904		*/
905		final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
906	<	boolean removed = false, empty = true, progress = true;
906	>	boolean stat = true, removed = false, empty = true;
907		ForkJoinTask<?>[] a; int m, s, b, n;
908		if ((a = array) != null && (m = a.length - 1) >= 0 &&
909		(n = (s = top) - (b = base)) > 0) {
#	Line 833 | Line 933 | public class ForkJoinPool extends Abstra
933		}
934		if (--n == 0) {
935		if (!empty && base == b)
936	<	progress = false;
936	>	stat = false;
937		break;
938		}
939		}
940		}
941		if (removed)
942		task.doExec();
943	<	return progress;
943	>	return stat;
944		}
945
946		/**
947	<	* Initializes or doubles the capacity of array. Call either
948	<	* by owner or with lock held -- it is OK for base, but not
849	<	* top, to move while resizings are in progress.
850	<	*
851	<	* @param rejectOnFailure if true, throw exception if capacity
852	<	* exceeded (relayed ultimately to user); else return null.
947	>	* Polls for and executes the given task or any other task in
948	>	* its CountedCompleter computation
949		*/
950	<	final ForkJoinTask<?>[] growArray(boolean rejectOnFailure) {
951	<	ForkJoinTask<?>[] oldA = array;
952	<	int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
953	<	if (size <= MAXIMUM_QUEUE_CAPACITY) {
954	<	int oldMask, t, b;
955	<	ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size];
956	<	if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
957	<	(t = top) - (b = base) > 0) {
958	<	int mask = size - 1;
959	<	do {
960	<	ForkJoinTask<?> x;
961	<	int oldj = ((b & oldMask) << ASHIFT) + ABASE;
962	<	int j    = ((b &    mask) << ASHIFT) + ABASE;
963	<	x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj);
964	<	if (x != null &&
965	<	U.compareAndSwapObject(oldA, oldj, x, null))
966	<	U.putObjectVolatile(a, j, x);
967	<	} while (++b != t);
950	>	final boolean pollAndExecCC(ForkJoinTask<?> root) {
951	>	ForkJoinTask<?>[] a; int b; Object o;
952	>	outer: while ((b = base) - top < 0 && (a = array) != null) {
953	>	long j = (((a.length - 1) & b) << ASHIFT) + ABASE;
954	>	if ((o = U.getObject(a, j)) == null ||
955	>	!(o instanceof CountedCompleter))
956	>	break;
957	>	for (CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;;) {
958	>	if (r == root) {
959	>	if (base == b &&
960	>	U.compareAndSwapObject(a, j, t, null)) {
961	>	base = b + 1;
962	>	t.doExec();
963	>	return true;
964	>	}
965	>	else
966	>	break; // restart
967	>	}
968	>	if ((r = r.completer) == null)
969	>	break outer; // not part of root computation
970		}
873	–	return a;
874	–	}
875	–	else if (!rejectOnFailure)
876	–	return null;
877	–	else
878	–	throw new RejectedExecutionException("Queue capacity exceeded");
879	–	}
880	–
881	–	/**
882	–	* Removes and cancels all known tasks, ignoring any exceptions.
883	–	*/
884	–	final void cancelAll() {
885	–	ForkJoinTask.cancelIgnoringExceptions(currentJoin);
886	–	ForkJoinTask.cancelIgnoringExceptions(currentSteal);
887	–	for (ForkJoinTask<?> t; (t = poll()) != null; )
888	–	ForkJoinTask.cancelIgnoringExceptions(t);
889	–	}
890	–
891	–	/**
892	–	* Computes next value for random probes.  Scans don't require
893	–	* a very high quality generator, but also not a crummy one.
894	–	* Marsaglia xor-shift is cheap and works well enough.  Note:
895	–	* This is manually inlined in several usages in ForkJoinPool
896	–	* to avoid writes inside busy scan loops.
897	–	*/
898	–	final int nextSeed() {
899	–	int r = seed;
900	–	r ^= r << 13;
901	–	r ^= r >>> 17;
902	–	return seed = r ^= r << 5;
903	–	}
904	–
905	–	// Execution methods
906	–
907	–	/**
908	–	* Removes and runs tasks until empty, using local mode
909	–	* ordering.
910	–	*/
911	–	final void runLocalTasks() {
912	–	if (base - top < 0) {
913	–	for (ForkJoinTask<?> t; (t = nextLocalTask()) != null; )
914	–	t.doExec();
971		}
972	+	return false;
973		}
974
975		/**
976		* Executes a top-level task and any local tasks remaining
977		* after execution.
921	–	*
922	–	* @return true unless terminating
978		*/
979	<	final boolean runTask(ForkJoinTask<?> t) {
925	<	boolean alive = true;
979	>	final void runTask(ForkJoinTask<?> t) {
980		if (t != null) {
981	<	currentSteal = t;
928	<	t.doExec();
929	<	runLocalTasks();
930	<	++nsteals;
981	>	(currentSteal = t).doExec();
982		currentSteal = null;
983	+	if (++nsteals < 0) {     // spill on overflow
984	+	ForkJoinPool p;
985	+	if ((p = pool) != null)
986	+	p.collectStealCount(this);
987	+	}
988	+	if (top != base) {       // process remaining local tasks
989	+	if (mode == 0)
990	+	popAndExecAll();
991	+	else
992	+	pollAndExecAll();
993	+	}
994		}
933	–	else if (runState < 0)            // terminating
934	–	alive = false;
935	–	return alive;
995		}
996
997		/**
#	Line 941 | Line 1000 | public class ForkJoinPool extends Abstra
1000		final void runSubtask(ForkJoinTask<?> t) {
1001		if (t != null) {
1002		ForkJoinTask<?> ps = currentSteal;
1003	<	currentSteal = t;
945	<	t.doExec();
1003	>	(currentSteal = t).doExec();
1004		currentSteal = ps;
1005		}
1006		}
#	Line 977 | Line 1035 | public class ForkJoinPool extends Abstra
1035
1036		// Unsafe mechanics
1037		private static final sun.misc.Unsafe U;
1038	<	private static final long RUNSTATE;
1038	>	private static final long QLOCK;
1039		private static final int ABASE;
1040		private static final int ASHIFT;
1041		static {
#	Line 986 | Line 1044 | public class ForkJoinPool extends Abstra
1044		U = getUnsafe();
1045		Class<?> k = WorkQueue.class;
1046		Class<?> ak = ForkJoinTask[].class;
1047	<	RUNSTATE = U.objectFieldOffset
1048	<	(k.getDeclaredField("runState"));
1047	>	QLOCK = U.objectFieldOffset
1048	>	(k.getDeclaredField("qlock"));
1049		ABASE = U.arrayBaseOffset(ak);
1050		s = U.arrayIndexScale(ak);
1051		} catch (Exception e) {
#	Line 1002 | Line 1060 | public class ForkJoinPool extends Abstra
1060		/**
1061		* Per-thread records for threads that submit to pools. Currently
1062		* holds only pseudo-random seed / index that is used to choose
1063	<	* submission queues in method doSubmit. In the future, this may
1063	>	* submission queues in method externalPush. In the future, this may
1064		* also incorporate a means to implement different task rejection
1065		* and resubmission policies.
1066	+	*
1067	+	* Seeds for submitters and workers/workQueues work in basically
1068	+	* the same way but are initialized and updated using slightly
1069	+	* different mechanics. Both are initialized using the same
1070	+	* approach as in class ThreadLocal, where successive values are
1071	+	* unlikely to collide with previous values. Seeds are then
1072	+	* randomly modified upon collisions using xorshifts, which
1073	+	* requires a non-zero seed.
1074		*/
1075		static final class Submitter {
1076		int seed;
1077	<	Submitter() { seed = hashId(Thread.currentThread().getId()); }
1077	>	Submitter(int s) { seed = s; }
1078		}
1079
1080	<	/** ThreadLocal class for Submitters */
1081	<	static final class ThreadSubmitter extends ThreadLocal<Submitter> {
1082	<	public Submitter initialValue() { return new Submitter(); }
1017	<	}
1080	>	/** Property prefix for constructing common pool */
1081	>	private static final String propPrefix =
1082	>	"java.util.concurrent.ForkJoinPool.common.";
1083
1084		// static fields (initialized in static initializer below)
1085
#	Line 1026 | Line 1091 | public class ForkJoinPool extends Abstra
1091		defaultForkJoinWorkerThreadFactory;
1092
1093		/**
1094	<	* Generator for assigning sequence numbers as pool names.
1094	>	* Common (static) pool. Non-null for public use unless a static
1095	>	* construction exception, but internal usages null-check on use
1096	>	* to paranoically avoid potential initialization circularities
1097	>	* as well as to simplify generated code.
1098		*/
1099	<	private static final AtomicInteger poolNumberGenerator;
1099	>	static final ForkJoinPool commonPool;
1100
1101		/**
1102		* Permission required for callers of methods that may start or
#	Line 1037 | Line 1105 | public class ForkJoinPool extends Abstra
1105		private static final RuntimePermission modifyThreadPermission;
1106
1107		/**
1108	<	* Per-thread submission bookeeping. Shared across all pools
1108	>	* Per-thread submission bookkeeping. Shared across all pools
1109		* to reduce ThreadLocal pollution and because random motion
1110		* to avoid contention in one pool is likely to hold for others.
1111	+	* Lazily initialized on first submission (but null-checked
1112	+	* in other contexts to avoid unnecessary initialization).
1113	+	*/
1114	+	static final ThreadLocal<Submitter> submitters;
1115	+
1116	+	/**
1117	+	* Common pool parallelism. Must equal commonPool.parallelism.
1118	+	*/
1119	+	static final int commonPoolParallelism;
1120	+
1121	+	/**
1122	+	* Sequence number for creating workerNamePrefix.
1123		*/
1124	<	private static final ThreadSubmitter submitters;
1124	>	private static int poolNumberSequence;
1125	>
1126	>	/**
1127	>	* Return the next sequence number. We don't expect this to
1128	>	* ever contend so use simple builtin sync.
1129	>	*/
1130	>	private static final synchronized int nextPoolId() {
1131	>	return ++poolNumberSequence;
1132	>	}
1133
1134		// static constants
1135
1136		/**
1137	<	* The wakeup interval (in nanoseconds) for a worker waiting for a
1138	<	* task when the pool is quiescent to instead try to shrink the
1139	<	* number of workers.  The exact value does not matter too
1140	<	* much. It must be short enough to release resources during
1141	<	* sustained periods of idleness, but not so short that threads
1142	<	* are continually re-created.
1137	>	* Initial timeout value (in nanoseconds) for the thread
1138	>	* triggering quiescence to park waiting for new work. On timeout,
1139	>	* the thread will instead try to shrink the number of
1140	>	* workers. The value should be large enough to avoid overly
1141	>	* aggressive shrinkage during most transient stalls (long GCs
1142	>	* etc).
1143	>	*/
1144	>	private static final long IDLE_TIMEOUT      = 2000L * 1000L * 1000L; // 2sec
1145	>
1146	>	/**
1147	>	* Timeout value when there are more threads than parallelism level
1148		*/
1149	<	private static final long SHRINK_RATE =
1057	<	4L * 1000L * 1000L * 1000L; // 4 seconds
1149	>	private static final long FAST_IDLE_TIMEOUT =  200L * 1000L * 1000L;
1150
1151		/**
1152	<	* The timeout value for attempted shrinkage, includes
1153	<	* some slop to cope with system timer imprecision.
1152	>	* The maximum stolen->joining link depth allowed in method
1153	>	* tryHelpStealer.  Must be a power of two.  Depths for legitimate
1154	>	* chains are unbounded, but we use a fixed constant to avoid
1155	>	* (otherwise unchecked) cycles and to bound staleness of
1156	>	* traversal parameters at the expense of sometimes blocking when
1157	>	* we could be helping.
1158		*/
1159	<	private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
1159	>	private static final int MAX_HELP = 64;
1160
1161		/**
1162	<	* The maximum stolen->joining link depth allowed in tryHelpStealer.
1163	<	* Depths for legitimate chains are unbounded, but we use a fixed
1068	<	* constant to avoid (otherwise unchecked) cycles and to bound
1069	<	* staleness of traversal parameters at the expense of sometimes
1070	<	* blocking when we could be helping.
1162	>	* Increment for seed generators. See class ThreadLocal for
1163	>	* explanation.
1164		*/
1165	<	private static final int MAX_HELP_DEPTH = 16;
1165	>	private static final int SEED_INCREMENT = 0x61c88647;
1166
1167		/**
1168		* Bits and masks for control variables
#	Line 1099 | Line 1192 | public class ForkJoinPool extends Abstra
1192		* scan for them to avoid queuing races. Note however that
1193		* eventCount updates lag releases so usage requires care.
1194		*
1195	<	* Field runState is an int packed with:
1195	>	* Field plock is an int packed with:
1196		* SHUTDOWN: true if shutdown is enabled (1 bit)
1197	<	* SEQ:  a sequence number updated upon (de)registering workers (15 bits)
1198	<	* MASK: mask (power of 2 - 1) covering all registered poolIndexes (16 bits)
1197	>	* SEQ:  a sequence lock, with PL_LOCK bit set if locked (30 bits)
1198	>	* SIGNAL: set when threads may be waiting on the lock (1 bit)
1199		*
1200	<	* The combination of mask and sequence number enables simple
1201	<	* consistency checks: Staleness of read-only operations on the
1202	<	* workQueues array can be checked by comparing runState before vs
1110	<	* after the reads. The low 16 bits (i.e, anding with SMASK) hold
1111	<	* the smallest power of two covering all indices, minus
1112	<	* one.
1200	>	* The sequence number enables simple consistency checks:
1201	>	* Staleness of read-only operations on the workQueues array can
1202	>	* be checked by comparing plock before vs after the reads.
1203		*/
1204
1205		// bit positions/shifts for fields
#	Line 1119 | Line 1209 | public class ForkJoinPool extends Abstra
1209		private static final int  EC_SHIFT   = 16;
1210
1211		// bounds
1122	–	private static final int  POOL_MAX   = 0x7fff;  // max #workers - 1
1212		private static final int  SMASK      = 0xffff;  // short bits
1213	<	private static final int  SQMASK     = 0xfffe;  // even short bits
1213	>	private static final int  MAX_CAP    = 0x7fff;  // max #workers - 1
1214	>	private static final int  EVENMASK   = 0xfffe;  // even short bits
1215	>	private static final int  SQMASK     = 0x007e;  // max 64 (even) slots
1216		private static final int  SHORT_SIGN = 1 << 15;
1217		private static final int  INT_SIGN   = 1 << 31;
1218
#	Line 1146 | Line 1237 | public class ForkJoinPool extends Abstra
1237		private static final int E_MASK      = 0x7fffffff; // no STOP_BIT
1238		private static final int E_SEQ       = 1 << EC_SHIFT;
1239
1240	<	// runState bits
1240	>	// plock bits
1241		private static final int SHUTDOWN    = 1 << 31;
1242	<	private static final int RS_SEQ      = 1 << 16;
1243	<	private static final int RS_SEQ_MASK = 0x7fff0000;
1242	>	private static final int PL_LOCK     = 2;
1243	>	private static final int PL_SIGNAL   = 1;
1244	>	private static final int PL_SPINS    = 1 << 8;
1245
1246		// access mode for WorkQueue
1247		static final int LIFO_QUEUE          =  0;
#	Line 1164 | Line 1256 | public class ForkJoinPool extends Abstra
1256		* declaration order and may differ across JVMs, but the following
1257		* empirically works OK on current JVMs.
1258		*/
1259	<
1259	>	volatile long stealCount;                  // collects worker counts
1260		volatile long ctl;                         // main pool control
1261		final int parallelism;                     // parallelism level
1262		final int localMode;                       // per-worker scheduling mode
1263	<	int growHints;                             // for expanding indices/ranges
1264	<	volatile int runState;                     // shutdown status, seq, and mask
1263	>	volatile int indexSeed;                    // worker/submitter index seed
1264	>	volatile int plock;                        // shutdown status and seqLock
1265		WorkQueue[] workQueues;                    // main registry
1174	–	final Mutex lock;                          // for registration
1175	–	final Condition termination;               // for awaitTermination
1266		final ForkJoinWorkerThreadFactory factory; // factory for new workers
1267		final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1178	–	final AtomicLong stealCount;               // collect counts when terminated
1179	–	final AtomicInteger nextWorkerNumber;      // to create worker name string
1268		final String workerNamePrefix;             // to create worker name string
1269
1270	<	//  Creating, registering, deregistering and running workers
1271	<
1272	<	/**
1273	<	* Tries to create and start a worker
1274	<	*/
1275	<	private void addWorker() {
1276	<	Throwable ex = null;
1277	<	ForkJoinWorkerThread wt = null;
1278	<	try {
1279	<	if ((wt = factory.newThread(this)) != null) {
1280	<	wt.start();
1281	<	return;
1270	>	/*
1271	>	* Acquires the plock lock to protect worker array and related
1272	>	* updates. This method is called only if an initial CAS on plock
1273	>	* fails. This acts as a spinLock for normal cases, but falls back
1274	>	* to builtin monitor to block when (rarely) needed. This would be
1275	>	* a terrible idea for a highly contended lock, but works fine as
1276	>	* a more conservative alternative to a pure spinlock.  See
1277	>	* internal ConcurrentHashMap documentation for further
1278	>	* explanation of nearly the same construction.
1279	>	*/
1280	>	private int acquirePlock() {
1281	>	int spins = PL_SPINS, r = 0, ps, nps;
1282	>	for (;;) {
1283	>	if (((ps = plock) & PL_LOCK) == 0 &&
1284	>	U.compareAndSwapInt(this, PLOCK, ps, nps = ps + PL_LOCK))
1285	>	return nps;
1286	>	else 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, PLOCK, ps, ps | PL_SIGNAL)) {
1294	>	synchronized (this) {
1295	>	if ((plock & PL_SIGNAL) != 0) {
1296	>	try {
1297	>	wait();
1298	>	} catch (InterruptedException ie) {
1299	>	try {
1300	>	Thread.currentThread().interrupt();
1301	>	} catch (SecurityException ignore) {
1302	>	}
1303	>	}
1304	>	}
1305	>	else
1306	>	notifyAll();
1307	>	}
1308		}
1195	–	} catch (Throwable e) {
1196	–	ex = e;
1309		}
1198	–	deregisterWorker(wt, ex); // adjust counts etc on failure
1310		}
1311
1312		/**
1313	<	* Callback from ForkJoinWorkerThread constructor to assign a
1314	<	* public name. This must be separate from registerWorker because
1204	<	* it is called during the "super" constructor call in
1205	<	* ForkJoinWorkerThread.
1313	>	* Unlocks and signals any thread waiting for plock. Called only
1314	>	* when CAS of seq value for unlock fails.
1315		*/
1316	<	final String nextWorkerName() {
1317	<	return workerNamePrefix.concat
1318	<	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1316	>	private void releasePlock(int ps) {
1317	>	plock = ps;
1318	>	synchronized (this) { notifyAll(); }
1319		}
1320
1321	+	//  Registering and deregistering workers
1322	+
1323		/**
1324	<	* Callback from ForkJoinWorkerThread constructor to establish and
1325	<	* record its WorkQueue.
1324	>	* Callback from ForkJoinWorkerThread constructor to establish its
1325	>	* poolIndex and record its WorkQueue. To avoid scanning bias due
1326	>	* to packing entries in front of the workQueues array, we treat
1327	>	* the array as a simple power-of-two hash table using per-thread
1328	>	* seed as hash, expanding as needed.
1329		*
1330	<	* @param wt the worker thread
1330	>	* @param w the worker's queue
1331		*/
1332	<	final void registerWorker(ForkJoinWorkerThread wt) {
1333	<	WorkQueue w = wt.workQueue;
1334	<	Mutex lock = this.lock;
1335	<	lock.lock();
1332	>	final void registerWorker(WorkQueue w) {
1333	>	int s, ps; // generate a rarely colliding candidate index seed
1334	>	do {} while (!U.compareAndSwapInt(this, INDEXSEED,
1335	>	s = indexSeed, s += SEED_INCREMENT) ||
1336	>	s == 0); // skip 0
1337	>	if (((ps = plock) & PL_LOCK) != 0 ||
1338	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1339	>	ps = acquirePlock();
1340	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1341		try {
1342	<	int g = growHints, k = g & SMASK;
1343	<	WorkQueue[] ws = workQueues;
1344	<	if (ws != null) {                       // ignore on shutdown
1345	<	int n = ws.length;
1346	<	if ((k & 1) == 0 || k >= n || ws[k] != null) {
1347	<	for (k = 1; k < n && ws[k] != null; k += 2)
1348	<	;                           // workers are at odd indices
1349	<	if (k >= n)                     // resize
1350	<	workQueues = ws = Arrays.copyOf(ws, n << 1);
1351	<	}
1352	<	w.eventCount = w.poolIndex = k;     // establish before recording
1353	<	ws[k] = w;
1354	<	growHints = (g & ~SMASK) | ((k + 2) & SMASK);
1355	<	int rs = runState;
1356	<	int m = rs & SMASK;                 // recalculate runState mask
1357	<	if (k > m)
1358	<	m = (m << 1) + 1;
1359	<	runState = (rs & SHUTDOWN) | ((rs + RS_SEQ) & RS_SEQ_MASK) | m;
1342	>	WorkQueue[] ws;
1343	>	if (w != null && (ws = workQueues) != null) {
1344	>	w.seed = s;
1345	>	int n = ws.length, m = n - 1;
1346	>	int r = (s << 1) | 1;               // use odd-numbered indices
1347	>	if (ws[r &= m] != null) {           // collision
1348	>	int probes = 0;                 // step by approx half size
1349	>	int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2;
1350	>	while (ws[r = (r + step) & m] != null) {
1351	>	if (++probes >= n) {
1352	>	workQueues = ws = Arrays.copyOf(ws, n <<= 1);
1353	>	m = n - 1;
1354	>	probes = 0;
1355	>	}
1356	>	}
1357	>	}
1358	>	w.eventCount = w.poolIndex = r;     // establish before recording
1359	>	ws[r] = w;
1360		}
1361		} finally {
1362	<	lock.unlock();
1362	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1363	>	releasePlock(nps);
1364		}
1365		}
1366
1367		/**
1368		* Final callback from terminating worker, as well as upon failure
1369	<	* to construct or start a worker in addWorker.  Removes record of
1370	<	* worker from array, and adjusts counts. If pool is shutting
1371	<	* down, tries to complete termination.
1369	>	* to construct or start a worker.  Removes record of worker from
1370	>	* array, and adjusts counts. If pool is shutting down, tries to
1371	>	* complete termination.
1372		*
1373	<	* @param wt the worker thread or null if addWorker failed
1373	>	* @param wt the worker thread or null if construction failed
1374		* @param ex the exception causing failure, or null if none
1375		*/
1376		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1377		WorkQueue w = null;
1378		if (wt != null && (w = wt.workQueue) != null) {
1379	<	w.runState = -1;                // ensure runState is set
1380	<	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1381	<	int idx = w.poolIndex;
1382	<	Mutex lock = this.lock;
1383	<	lock.lock();
1384	<	try {                           // remove record from array
1379	>	int ps;
1380	>	collectStealCount(w);
1381	>	w.qlock = -1;                // ensure set
1382	>	if (((ps = plock) & PL_LOCK) != 0 ||
1383	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1384	>	ps = acquirePlock();
1385	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1386	>	try {
1387	>	int idx = w.poolIndex;
1388		WorkQueue[] ws = workQueues;
1389	<	if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w) {
1389	>	if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1390		ws[idx] = null;
1268	–	growHints = (growHints & ~SMASK) | idx;
1269	–	}
1391		} finally {
1392	<	lock.unlock();
1392	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1393	>	releasePlock(nps);
1394		}
1395		}
1396
#	Line 1281 | Line 1403 | public class ForkJoinPool extends Abstra
1403		if (!tryTerminate(false, false) && w != null) {
1404		w.cancelAll();                  // cancel remaining tasks
1405		if (w.array != null)            // suppress signal if never ran
1406	<	signalWork();               // wake up or create replacement
1406	>	signalWork(null, 1);        // wake up or create replacement
1407		if (ex == null)                 // help clean refs on way out
1408		ForkJoinTask.helpExpungeStaleExceptions();
1409		}
1410
1411		if (ex != null)                     // rethrow
1412	<	U.throwException(ex);
1412	>	ForkJoinTask.rethrow(ex);
1413		}
1414
1415		/**
1416	<	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1417	<	*/
1418	<	final void runWorker(ForkJoinWorkerThread wt) {
1419	<	// Initialize queue array and seed in this thread
1420	<	WorkQueue w = wt.workQueue;
1421	<	w.growArray(false);
1422	<	w.seed = hashId(Thread.currentThread().getId());
1423	<
1424	<	do {} while (w.runTask(scan(w)));
1416	>	* Collect worker steal count into total. Called on termination
1417	>	* and upon int overflow of local count. (There is a possible race
1418	>	* in the latter case vs any caller of getStealCount, which can
1419	>	* make its results less accurate than usual.)
1420	>	*/
1421	>	final void collectStealCount(WorkQueue w) {
1422	>	if (w != null) {
1423	>	long sc;
1424	>	int ns = w.nsteals;
1425	>	w.nsteals = 0; // handle overflow
1426	>	long steals = (ns >= 0) ? ns : 1L + (long)(Integer.MAX_VALUE);
1427	>	do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
1428	>	sc = stealCount, sc + steals));
1429	>	}
1430		}
1431
1432		// Submissions
#	Line 1307 | Line 1434 | public class ForkJoinPool extends Abstra
1434		/**
1435		* Unless shutting down, adds the given task to a submission queue
1436		* at submitter's current queue index (modulo submission
1437	<	* range). If no queue exists at the index, one is created unless
1438	<	* pool lock is busy.  If the queue and/or lock are busy, another
1439	<	* index is randomly chosen. The mask in growHints controls the
1440	<	* effective index range of queues considered. The mask is
1314	<	* expanded, up to the current workerQueue mask, upon any detected
1315	<	* contention but otherwise remains small to avoid needlessly
1316	<	* creating queues when there is no contention.
1437	>	* range). Only the most common path is directly handled in this
1438	>	* method. All others are relayed to fullExternalPush.
1439	>	*
1440	>	* @param task the task. Caller must ensure non-null.
1441		*/
1442	<	private void doSubmit(ForkJoinTask<?> task) {
1443	<	if (task == null)
1444	<	throw new NullPointerException();
1445	<	Submitter s = submitters.get();
1446	<	for (int r = s.seed, m = growHints >>> 16;;) {
1447	<	WorkQueue[] ws; WorkQueue q; Mutex lk;
1448	<	int k = r & m & SQMASK;          // use only even indices
1449	<	if (runState < 0 || (ws = workQueues) == null || ws.length <= k)
1450	<	throw new RejectedExecutionException(); // shutting down
1451	<	if ((q = ws[k]) == null && (lk = lock).tryAcquire(0)) {
1452	<	try {                        // try to create new queue
1453	<	if (ws == workQueues && (q = ws[k]) == null) {
1454	<	int rs;              // update runState seq
1455	<	ws[k] = q = new WorkQueue(null, SHARED_QUEUE);
1456	<	runState = (((rs = runState) & SHUTDOWN) |
1333	<	((rs + RS_SEQ) & ~SHUTDOWN));
1334	<	}
1335	<	} finally {
1336	<	lk.unlock();
1337	<	}
1442	>	final void externalPush(ForkJoinTask<?> task) {
1443	>	WorkQueue[] ws; WorkQueue q; Submitter z; int m; ForkJoinTask<?>[] a;
1444	>	if ((z = submitters.get()) != null && plock > 0 &&
1445	>	(ws = workQueues) != null && (m = (ws.length - 1)) >= 0 &&
1446	>	(q = ws[m & z.seed & SQMASK]) != null &&
1447	>	U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock
1448	>	int s = q.top, n;
1449	>	if ((a = q.array) != null && a.length > (n = s + 1 - q.base)) {
1450	>	U.putObject(a, (long)(((a.length - 1) & s) << ASHIFT) + ABASE,
1451	>	task);
1452	>	q.top = s + 1;                     // push on to deque
1453	>	q.qlock = 0;
1454	>	if (n <= 1)
1455	>	signalWork(q, 1);
1456	>	return;
1457		}
1458	<	if (q != null) {
1459	<	if (q.trySharedPush(task)) {
1460	<	signalWork();
1461	<	return;
1458	>	q.qlock = 0;
1459	>	}
1460	>	fullExternalPush(task);
1461	>	}
1462	>
1463	>	/**
1464	>	* Full version of externalPush. This method is called, among
1465	>	* other times, upon the first submission of the first task to the
1466	>	* pool, so must perform secondary initialization: creating
1467	>	* workQueue array and setting plock to a valid value. It also
1468	>	* detects first submission by an external thread by looking up
1469	>	* its ThreadLocal, and creates a new shared queue if the one at
1470	>	* index if empty or contended. The lock bodies must be
1471	>	* exception-free (so no try/finally) so we optimistically
1472	>	* allocate new queues/arrays outside the locks and throw them
1473	>	* away if (very rarely) not needed. Note that the plock seq value
1474	>	* can eventually wrap around zero, but if so harmlessly fails to
1475	>	* reinitialize.
1476	>	*/
1477	>	private void fullExternalPush(ForkJoinTask<?> task) {
1478	>	for (Submitter z = null;;) {
1479	>	WorkQueue[] ws; WorkQueue q; int ps, m, r, s;
1480	>	if ((ps = plock) < 0)
1481	>	throw new RejectedExecutionException();
1482	>	else if ((ws = workQueues) == null || (m = ws.length - 1) < 0) {
1483	>	int n = parallelism - 1; n |= n >>> 1; n |= n >>> 2;
1484	>	n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
1485	>	WorkQueue[] nws = new WorkQueue[(n + 1) << 1]; // power of two
1486	>	if ((ps & PL_LOCK) != 0 ||
1487	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1488	>	ps = acquirePlock();
1489	>	if ((ws = workQueues) == null)
1490	>	workQueues = nws;
1491	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1492	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1493	>	releasePlock(nps);
1494	>	}
1495	>	else if (z == null && (z = submitters.get()) == null) {
1496	>	if (U.compareAndSwapInt(this, INDEXSEED,
1497	>	s = indexSeed, s += SEED_INCREMENT) &&
1498	>	s != 0) // skip 0
1499	>	submitters.set(z = new Submitter(s));
1500	>	}
1501	>	else {
1502	>	int k = (r = z.seed) & m & SQMASK;
1503	>	if ((q = ws[k]) == null && (ps & PL_LOCK) == 0) {
1504	>	(q = new WorkQueue(this, null, SHARED_QUEUE)).poolIndex = k;
1505	>	if (((ps = plock) & PL_LOCK) != 0 ||
1506	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
1507	>	ps = acquirePlock();
1508	>	WorkQueue w = null;
1509	>	if ((ws = workQueues) != null && k < ws.length &&
1510	>	(w = ws[k]) == null)
1511	>	ws[k] = q;
1512	>	else
1513	>	q = w;
1514	>	int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
1515	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
1516	>	releasePlock(nps);
1517		}
1518	<	else if (m < parallelism - 1 && m < (runState & SMASK)) {
1519	<	Mutex lock = this.lock;
1520	<	lock.lock();             // block until lock free
1521	<	int g = growHints;
1522	<	if (g >>> 16 == m)       // expand range
1349	<	growHints = (((m << 1) + 1) << 16) | (g & SMASK);
1350	<	lock.unlock();           // no need for try/finally
1351	<	}
1352	<	else if ((r & m) == 0)
1353	<	Thread.yield();          // occasionally yield if busy
1354	<	}
1355	<	if (m == (m = growHints >>> 16)) {
1356	<	r ^= r << 13;                // update seed unless new range
1357	<	r ^= r >>> 17;               // same xorshift as WorkQueues
1358	<	s.seed = r ^= r << 5;
1518	>	if (q != null && q.qlock == 0 && q.fullPush(task, false))
1519	>	return;
1520	>	r ^= r << 13;                // same xorshift as WorkQueues
1521	>	r ^= r >>> 17;
1522	>	z.seed = r ^= r << 5;        // move to a different index
1523		}
1524		}
1525		}
#	Line 1371 | Line 1535 | public class ForkJoinPool extends Abstra
1535		}
1536
1537		/**
1538	<	* Tries to activate or create a worker if too few are active.
1539	<	*/
1540	<	final void signalWork() {
1541	<	long c; int u;
1542	<	while ((u = (int)((c = ctl) >>> 32)) < 0) {     // too few active
1543	<	WorkQueue[] ws = workQueues; int e, i; WorkQueue w; Thread p;
1544	<	if ((e = (int)c) > 0) {                     // at least one waiting
1545	<	if (ws != null && (i = e & SMASK) < ws.length &&
1538	>	* Tries to create (at most one) or activate (possibly several)
1539	>	* workers if too few are active. On contention failure, continues
1540	>	* until at least one worker is signalled or the given queue is
1541	>	* empty or all workers are active.
1542	>	*
1543	>	* @param q if non-null, the queue holding tasks to be signalled
1544	>	* @param signals the target number of signals.
1545	>	*/
1546	>	final void signalWork(WorkQueue q, int signals) {
1547	>	long c; int e, u, i; WorkQueue[] ws; WorkQueue w; Thread p;
1548	>	while ((u = (int)((c = ctl) >>> 32)) < 0) {
1549	>	if ((e = (int)c) > 0) {
1550	>	if ((ws = workQueues) != null && ws.length > (i = e & SMASK) &&
1551		(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
1552		long nc = (((long)(w.nextWait & E_MASK)) |
1553		((long)(u + UAC_UNIT) << 32));
1554		if (U.compareAndSwapLong(this, CTL, c, nc)) {
1555		w.eventCount = (e + E_SEQ) & E_MASK;
1556		if ((p = w.parker) != null)
1557	<	U.unpark(p);                // activate and release
1558	<	break;
1557	>	U.unpark(p);
1558	>	if (--signals <= 0)
1559	>	break;
1560		}
1561	+	else
1562	+	signals = 1;
1563	+	if ((q != null && q.queueSize() == 0))
1564	+	break;
1565		}
1566		else
1567		break;
1568		}
1569	<	else if (e == 0 && (u & SHORT_SIGN) != 0) { // too few total
1569	>	else if (e == 0 && (u & SHORT_SIGN) != 0) {
1570		long nc = (long)(((u + UTC_UNIT) & UTC_MASK) |
1571		((u + UAC_UNIT) & UAC_MASK)) << 32;
1572		if (U.compareAndSwapLong(this, CTL, c, nc)) {
1573	<	addWorker();
1573	>	ForkJoinWorkerThread wt = null;
1574	>	Throwable ex = null;
1575	>	boolean started = false;
1576	>	try {
1577	>	ForkJoinWorkerThreadFactory fac;
1578	>	if ((fac = factory) != null &&
1579	>	(wt = fac.newThread(this)) != null) {
1580	>	wt.start();
1581	>	started = true;
1582	>	}
1583	>	} catch (Throwable rex) {
1584	>	ex = rex;
1585	>	}
1586	>	if (!started)
1587	>	deregisterWorker(wt, ex); // adjust counts on failure
1588		break;
1589		}
1590		}
#	Line 1405 | Line 1593 | public class ForkJoinPool extends Abstra
1593		}
1594		}
1595
1596	+	// Scanning for tasks
1597	+
1598		/**
1599	<	* Tries to decrement active count (sometimes implicitly) and
1410	<	* possibly release or create a compensating worker in preparation
1411	<	* for blocking. Fails on contention or termination.
1412	<	*
1413	<	* @return true if the caller can block, else should recheck and retry
1599	>	* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
1600		*/
1601	<	final boolean tryCompensate() {
1602	<	WorkQueue w; Thread p;
1603	<	int pc = parallelism, e, u, ac, tc, i;
1604	<	long c = ctl;
1419	<	WorkQueue[] ws = workQueues;
1420	<	if ((e = (int)c) >= 0) {
1421	<	if ((ac = ((u = (int)(c >>> 32)) >> UAC_SHIFT)) <= 0 &&
1422	<	e != 0 && ws != null && (i = e & SMASK) < ws.length &&
1423	<	(w = ws[i]) != null) {
1424	<	long nc = (long)(w.nextWait & E_MASK) | (c & (AC_MASK|TC_MASK));
1425	<	if (w.eventCount == (e | INT_SIGN) &&
1426	<	U.compareAndSwapLong(this, CTL, c, nc)) {
1427	<	w.eventCount = (e + E_SEQ) & E_MASK;
1428	<	if ((p = w.parker) != null)
1429	<	U.unpark(p);
1430	<	return true;             // release an idle worker
1431	<	}
1432	<	}
1433	<	else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) {
1434	<	long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
1435	<	if (U.compareAndSwapLong(this, CTL, c, nc))
1436	<	return true;             // no compensation needed
1437	<	}
1438	<	else if (tc + pc < POOL_MAX) {
1439	<	long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
1440	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1441	<	addWorker();
1442	<	return true;             // create replacement
1443	<	}
1444	<	}
1445	<	}
1446	<	return false;
1601	>	final void runWorker(WorkQueue w) {
1602	>	// initialize queue array in this thread
1603	>	w.array = new ForkJoinTask<?>[WorkQueue.INITIAL_QUEUE_CAPACITY];
1604	>	do { w.runTask(scan(w)); } while (w.qlock >= 0);
1605		}
1606
1449	–	// Scanning for tasks
1450	–
1607		/**
1608		* Scans for and, if found, returns one task, else possibly
1609		* inactivates the worker. This method operates on single reads of
1610	<	* volatile state and is designed to be re-invoked continuously in
1611	<	* part because it returns upon detecting inconsistencies,
1610	>	* volatile state and is designed to be re-invoked continuously,
1611	>	* in part because it returns upon detecting inconsistencies,
1612		* contention, or state changes that indicate possible success on
1613		* re-invocation.
1614		*
1615	<	* The scan searches for tasks across queues, randomly selecting
1616	<	* the first #queues probes, favoring steals over submissions
1617	<	* (by exploiting even/odd indexing), and then performing a
1618	<	* circular sweep of all queues.  The scan terminates upon either
1619	<	* finding a non-empty queue, or completing a full sweep. If the
1620	<	* worker is not inactivated, it takes and returns a task from
1621	<	* this queue.  On failure to find a task, we take one of the
1622	<	* following actions, after which the caller will retry calling
1623	<	* this method unless terminated.
1615	>	* The scan searches for tasks across a random permutation of
1616	>	* queues (starting at a random index and stepping by a random
1617	>	* relative prime, checking each at least once).  The scan
1618	>	* terminates upon either finding a non-empty queue, or completing
1619	>	* the sweep. If the worker is not inactivated, it takes and
1620	>	* returns a task from this queue. Otherwise, if not activated, it
1621	>	* signals workers (that may include itself) and returns so caller
1622	>	* can retry. Also returns for trtry if the worker array may have
1623	>	* changed during an empty scan.  On failure to find a task, we
1624	>	* take one of the following actions, after which the caller will
1625	>	* retry calling this method unless terminated.
1626		*
1627		* * If pool is terminating, terminate the worker.
1628		*
1471	–	* * If not a complete sweep, try to release a waiting worker.  If
1472	–	* the scan terminated because the worker is inactivated, then the
1473	–	* released worker will often be the calling worker, and it can
1474	–	* succeed obtaining a task on the next call. Or maybe it is
1475	–	* another worker, but with same net effect. Releasing in other
1476	–	* cases as well ensures that we have enough workers running.
1477	–	*
1478	–	* * If the caller has run a task since the last empty scan,
1479	–	* return (to allow rescan) if other workers are not also yet
1480	–	* enqueued.  Field WorkQueue.rescans counts down on each scan to
1481	–	* ensure eventual inactivation and blocking.
1482	–	*
1629		* * If not already enqueued, try to inactivate and enqueue the
1630	<	* worker on wait queue.
1631	<	*
1632	<	* * If already enqueued and none of the above apply, either park
1633	<	* awaiting signal, or if this is the most recent waiter and pool
1634	<	* is quiescent, relay to idleAwaitWork to check for termination
1635	<	* and possibly shrink pool.
1630	>	* worker on wait queue. Or, if inactivating has caused the pool
1631	>	* to be quiescent, relay to idleAwaitWork to check for
1632	>	* termination and possibly shrink pool.
1633	>	*
1634	>	* * If already enqueued and none of the above apply, possibly
1635	>	* (with 1/2 probability) park awaiting signal, else lingering to
1636	>	* help scan and signal.
1637		*
1638		* @param w the worker (via its WorkQueue)
1639	<	* @return a task or null of none found
1639	>	* @return a task or null if none found
1640		*/
1641		private final ForkJoinTask<?> scan(WorkQueue w) {
1642	<	boolean swept = false;               // true after full empty scan
1643	<	WorkQueue[] ws;                      // volatile read order matters
1644	<	int r = w.seed, ec = w.eventCount;   // ec is negative if inactive
1645	<	int rs = runState, m = rs & SMASK;
1646	<	if ((ws = workQueues) != null && ws.length > m) { // consistency check
1647	<	for (int k = 0, j = -1 - m; ; ++j) {
1648	<	WorkQueue q; int b;
1649	<	if (j < 0) {                 // random probes while j negative
1650	<	r ^= r << 13; r ^= r >>> 17; k = (r ^= r << 5) | (j & 1);
1651	<	}                            // worker (not submit) for odd j
1652	<	else                         // cyclic scan when j >= 0
1653	<	k += 7;                  // step 7 reduces array packing bias
1654	<	if ((q = ws[k & m]) != null && (b = q.base) - q.top < 0) {
1655	<	ForkJoinTask<?> t = (ec >= 0) ? q.pollAt(b) : null;
1656	<	w.seed = r;              // save seed for next scan
1657	<	if (t != null)
1658	<	return t;
1659	<	break;
1660	<	}
1661	<	else if (j - m > m) {
1662	<	if (rs == runState)      // staleness check
1663	<	swept = true;
1517	<	break;
1518	<	}
1519	<	}
1520	<
1521	<	// Decode ctl on empty scan
1522	<	long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
1523	<	if (e < 0)                       // pool is terminating
1524	<	w.runState = -1;
1525	<	else if (!swept) {               // try to release a waiter
1526	<	WorkQueue v; Thread p;
1527	<	if (e > 0 && a < 0 && (v = ws[e & m]) != null &&
1528	<	v.eventCount == (e | INT_SIGN)) {
1529	<	long nc = ((long)(v.nextWait & E_MASK) |
1530	<	((c + AC_UNIT) & (AC_MASK|TC_MASK)));
1531	<	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1532	<	v.eventCount = (e + E_SEQ) & E_MASK;
1533	<	if ((p = v.parker) != null)
1534	<	U.unpark(p);
1642	>	WorkQueue[] ws; WorkQueue q;           // first update random seed
1643	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1644	>	int ps = plock, m;                     // volatile read order matters
1645	>	if ((ws = workQueues) != null && (m = ws.length - 1) > 0) {
1646	>	int ec = w.eventCount;             // ec is negative if inactive
1647	>	int step = (r >>> 16) | 1;         // relatively prime
1648	>	for (int j = (m + 1) << 2;  ; --j, r += step) {
1649	>	ForkJoinTask<?> t; ForkJoinTask<?>[] a; int b, n;
1650	>	if ((q = ws[r & m]) != null && (b = q.base) - q.top < 0 &&
1651	>	(a = q.array) != null) {   // probably nonempty
1652	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1653	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1654	>	if (q.base == b && ec >= 0 && t != null &&
1655	>	U.compareAndSwapObject(a, i, t, null)) {
1656	>	if ((n = q.top - (q.base = b + 1)) > 0)
1657	>	signalWork(q, n);
1658	>	return t;              // taken
1659	>	}
1660	>	if (j < m || (ec < 0 && (ec = w.eventCount) < 0)) {
1661	>	if ((n = q.queueSize() - 1) > 0)
1662	>	signalWork(q, n);
1663	>	break;                 // let caller retry after signal
1664		}
1665		}
1666	<	}
1667	<	else if ((nr = w.rescans) > 0) { // continue rescanning
1668	<	int ac = a + parallelism;
1669	<	if (((w.rescans = (ac < nr) ? ac : nr - 1) & 3) == 0 &&
1670	<	w.eventCount == ec)
1671	<	Thread.yield();          // occasionally yield
1672	<	}
1673	<	else if (ec >= 0) {              // try to enqueue
1674	<	long nc = (long)ec | ((c - AC_UNIT) & (AC_MASK|TC_MASK));
1675	<	w.nextWait = e;
1676	<	w.eventCount = ec | INT_SIGN;// mark as inactive
1677	<	if (!U.compareAndSwapLong(this, CTL, c, nc))
1678	<	w.eventCount = ec;       // unmark on CAS failure
1679	<	else if ((ns = w.nsteals) != 0) {
1680	<	w.nsteals = 0;           // set rescans if ran task
1681	<	w.rescans = a + parallelism;
1682	<	w.totalSteals += ns;
1683	<	}
1684	<	}
1685	<	else {                           // already queued
1686	<	if (parallelism == -a)
1687	<	idleAwaitWork(w);        // quiescent
1688	<	if (w.eventCount == ec) {
1689	<	Thread.interrupted();    // clear status
1690	<	ForkJoinWorkerThread wt = w.owner;
1691	<	U.putObject(wt, PARKBLOCKER, this);
1692	<	w.parker = wt;           // emulate LockSupport.park
1693	<	if (w.eventCount == ec)  // recheck
1565	<	U.park(false, 0L);   // block
1566	<	w.parker = null;
1567	<	U.putObject(wt, PARKBLOCKER, null);
1666	>	else if (j < 0) {              // end of scan
1667	>	long c = ctl; int e;
1668	>	if (plock != ps)           // incomplete sweep
1669	>	break;
1670	>	if ((e = (int)c) < 0)      // pool is terminating
1671	>	w.qlock = -1;
1672	>	else if (ec >= 0) {        // try to enqueue/inactivate
1673	>	long nc = ((long)ec |
1674	>	((c - AC_UNIT) & (AC_MASK|TC_MASK)));
1675	>	w.nextWait = e;
1676	>	w.eventCount = ec | INT_SIGN; // mark as inactive
1677	>	if (ctl != c ||
1678	>	!U.compareAndSwapLong(this, CTL, c, nc))
1679	>	w.eventCount = ec; // unmark on CAS failure
1680	>	else if ((int)(c >> AC_SHIFT) == 1 - parallelism)
1681	>	idleAwaitWork(w, nc, c);  // quiescent
1682	>	}
1683	>	else if (w.seed >= 0 && w.eventCount < 0) {
1684	>	Thread wt = Thread.currentThread();
1685	>	Thread.interrupted();  // clear status
1686	>	U.putObject(wt, PARKBLOCKER, this);
1687	>	w.parker = wt;         // emulate LockSupport.park
1688	>	if (w.eventCount < 0)  // recheck
1689	>	U.park(false, 0L);
1690	>	w.parker = null;
1691	>	U.putObject(wt, PARKBLOCKER, null);
1692	>	}
1693	>	break;
1694		}
1695		}
1696		}
#	Line 1572 | Line 1698 | public class ForkJoinPool extends Abstra
1698		}
1699
1700		/**
1701	<	* If inactivating worker w has caused pool to become quiescent,
1702	<	* checks for pool termination, and, so long as this is not the
1703	<	* only worker, waits for event for up to SHRINK_RATE nanosecs.
1704	<	* On timeout, if ctl has not changed, terminates the worker,
1705	<	* which will in turn wake up another worker to possibly repeat
1706	<	* this process.
1701	>	* If inactivating worker w has caused the pool to become
1702	>	* quiescent, checks for pool termination, and, so long as this is
1703	>	* not the only worker, waits for event for up to a given
1704	>	* duration.  On timeout, if ctl has not changed, terminates the
1705	>	* worker, which will in turn wake up another worker to possibly
1706	>	* repeat this process.
1707		*
1708		* @param w the calling worker
1709	+	* @param currentCtl the ctl value triggering possible quiescence
1710	+	* @param prevCtl the ctl value to restore if thread is terminated
1711		*/
1712	<	private void idleAwaitWork(WorkQueue w) {
1713	<	long c; int nw, ec;
1714	<	if (!tryTerminate(false, false) &&
1715	<	(int)((c = ctl) >> AC_SHIFT) + parallelism == 0 &&
1716	<	(ec = w.eventCount) == ((int)c | INT_SIGN) &&
1717	<	(nw = w.nextWait) != 0) {
1718	<	long nc = ((long)(nw & E_MASK) | // ctl to restore on timeout
1719	<	((c + AC_UNIT) & AC_MASK) | (c & TC_MASK));
1720	<	ForkJoinWorkerThread wt = w.owner;
1593	<	while (ctl == c) {
1594	<	long startTime = System.nanoTime();
1712	>	private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1713	>	if (w.eventCount < 0 &&
1714	>	(this == commonPool || !tryTerminate(false, false)) &&
1715	>	(int)prevCtl != 0) {
1716	>	int dc = -(short)(currentCtl >>> TC_SHIFT);
1717	>	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1718	>	long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop
1719	>	Thread wt = Thread.currentThread();
1720	>	while (ctl == currentCtl) {
1721		Thread.interrupted();  // timed variant of version in scan()
1722		U.putObject(wt, PARKBLOCKER, this);
1723		w.parker = wt;
1724	<	if (ctl == c)
1725	<	U.park(false, SHRINK_RATE);
1724	>	if (ctl == currentCtl)
1725	>	U.park(false, parkTime);
1726		w.parker = null;
1727		U.putObject(wt, PARKBLOCKER, null);
1728	<	if (ctl != c)
1728	>	if (ctl != currentCtl)
1729		break;
1730	<	if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
1731	<	U.compareAndSwapLong(this, CTL, c, nc)) {
1732	<	w.eventCount = (ec + E_SEQ) | E_MASK;
1733	<	w.runState = -1;          // shrink
1730	>	if (deadline - System.nanoTime() <= 0L &&
1731	>	U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1732	>	w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
1733	>	w.qlock = -1;   // shrink
1734		break;
1735		}
1736		}
#	Line 1612 | Line 1738 | public class ForkJoinPool extends Abstra
1738		}
1739
1740		/**
1741	+	* Scans through queues looking for work while joining a task;
1742	+	* if any are present, signals.
1743	+	*
1744	+	* @param task to return early if done
1745	+	* @param origin an index to start scan
1746	+	*/
1747	+	final int helpSignal(ForkJoinTask<?> task, int origin) {
1748	+	WorkQueue[] ws; WorkQueue q; int m, n, s;
1749	+	if (task != null && (ws = workQueues) != null &&
1750	+	(m = ws.length - 1) >= 0) {
1751	+	for (int i = 0; i <= m; ++i) {
1752	+	if ((s = task.status) < 0)
1753	+	return s;
1754	+	if ((q = ws[(i + origin) & m]) != null &&
1755	+	(n = q.queueSize()) > 0) {
1756	+	signalWork(q, n);
1757	+	if ((int)(ctl >> AC_SHIFT) >= 0)
1758	+	break;
1759	+	}
1760	+	}
1761	+	}
1762	+	return 0;
1763	+	}
1764	+
1765	+	/**
1766		* Tries to locate and execute tasks for a stealer of the given
1767		* task, or in turn one of its stealers, Traces currentSteal ->
1768		* currentJoin links looking for a thread working on a descendant
#	Line 1622 | Line 1773 | public class ForkJoinPool extends Abstra
1773		* leaves hints in workers to speed up subsequent calls. The
1774		* implementation is very branchy to cope with potential
1775		* inconsistencies or loops encountering chains that are stale,
1776	<	* unknown, or of length greater than MAX_HELP_DEPTH links.  All
1626	<	* of these cases are dealt with by just retrying by caller.
1776	>	* unknown, or so long that they are likely cyclic.
1777		*
1778		* @param joiner the joining worker
1779		* @param task the task to join
1780	<	* @return true if found or ran a task (and so is immediately retryable)
1780	>	* @return 0 if no progress can be made, negative if task
1781	>	* known complete, else positive
1782		*/
1783	<	final boolean tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1784	<	ForkJoinTask<?> subtask;    // current target
1785	<	boolean progress = false;
1786	<	int depth = 0;              // current chain depth
1787	<	int m = runState & SMASK;
1788	<	WorkQueue[] ws = workQueues;
1789	<
1790	<	if (ws != null && ws.length > m && (subtask = task).status >= 0) {
1791	<	outer:for (WorkQueue j = joiner;;) {
1792	<	// Try to find the stealer of subtask, by first using hint
1793	<	WorkQueue stealer = null;
1794	<	WorkQueue v = ws[j.stealHint & m];
1795	<	if (v != null && v.currentSteal == subtask)
1796	<	stealer = v;
1797	<	else {
1798	<	for (int i = 1; i <= m; i += 2) {
1799	<	if ((v = ws[i]) != null && v.currentSteal == subtask) {
1800	<	stealer = v;
1801	<	j.stealHint = i; // save hint
1802	<	break;
1783	>	private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1784	>	int stat = 0, steps = 0;                    // bound to avoid cycles
1785	>	if (joiner != null && task != null) {       // hoist null checks
1786	>	restart: for (;;) {
1787	>	ForkJoinTask<?> subtask = task;     // current target
1788	>	for (WorkQueue j = joiner, v;;) {   // v is stealer of subtask
1789	>	WorkQueue[] ws; int m, s, h;
1790	>	if ((s = task.status) < 0) {
1791	>	stat = s;
1792	>	break restart;
1793	>	}
1794	>	if ((ws = workQueues) == null || (m = ws.length - 1) <= 0)
1795	>	break restart;              // shutting down
1796	>	if ((v = ws[h = (j.stealHint | 1) & m]) == null ||
1797	>	v.currentSteal != subtask) {
1798	>	for (int origin = h;;) {    // find stealer
1799	>	if (((h = (h + 2) & m) & 15) == 1 &&
1800	>	(subtask.status < 0 || j.currentJoin != subtask))
1801	>	continue restart;   // occasional staleness check
1802	>	if ((v = ws[h]) != null &&
1803	>	v.currentSteal == subtask) {
1804	>	j.stealHint = h;    // save hint
1805	>	break;
1806	>	}
1807	>	if (h == origin)
1808	>	break restart;      // cannot find stealer
1809	>	}
1810	>	}
1811	>	for (;;) { // help stealer or descend to its stealer
1812	>	ForkJoinTask[] a;  int b;
1813	>	if (subtask.status < 0)     // surround probes with
1814	>	continue restart;       //   consistency checks
1815	>	if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
1816	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1817	>	ForkJoinTask<?> t =
1818	>	(ForkJoinTask<?>)U.getObjectVolatile(a, i);
1819	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1820	>	v.currentSteal != subtask)
1821	>	continue restart;   // stale
1822	>	stat = 1;               // apparent progress
1823	>	if (t != null && v.base == b &&
1824	>	U.compareAndSwapObject(a, i, t, null)) {
1825	>	v.base = b + 1;     // help stealer
1826	>	joiner.runSubtask(t);
1827	>	}
1828	>	else if (v.base == b && ++steps == MAX_HELP)
1829	>	break restart;      // v apparently stalled
1830	>	}
1831	>	else {                      // empty -- try to descend
1832	>	ForkJoinTask<?> next = v.currentJoin;
1833	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1834	>	v.currentSteal != subtask)
1835	>	continue restart;   // stale
1836	>	else if (next == null || ++steps == MAX_HELP)
1837	>	break restart;      // dead-end or maybe cyclic
1838	>	else {
1839	>	subtask = next;
1840	>	j = v;
1841	>	break;
1842	>	}
1843		}
1844		}
1845	<	if (stealer == null)
1845	>	}
1846	>	}
1847	>	}
1848	>	return stat;
1849	>	}
1850	>
1851	>	/**
1852	>	* Analog of tryHelpStealer for CountedCompleters. Tries to steal
1853	>	* and run tasks within the target's computation
1854	>	*
1855	>	* @param task the task to join
1856	>	* @param mode if shared, exit upon completing any task
1857	>	* if all workers are active
1858	>	*
1859	>	*/
1860	>	private int helpComplete(ForkJoinTask<?> task, int mode) {
1861	>	WorkQueue[] ws; WorkQueue q; int m, n, s;
1862	>	if (task != null && (ws = workQueues) != null &&
1863	>	(m = ws.length - 1) >= 0) {
1864	>	for (int j = 1, origin = j;;) {
1865	>	if ((s = task.status) < 0)
1866	>	return s;
1867	>	if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) {
1868	>	origin = j;
1869	>	if (mode == SHARED_QUEUE && (int)(ctl >> AC_SHIFT) >= 0)
1870		break;
1871		}
1872	+	else if ((j = (j + 2) & m) == origin)
1873	+	break;
1874	+	}
1875	+	}
1876	+	return 0;
1877	+	}
1878
1879	<	for (WorkQueue q = stealer;;) { // Try to help stealer
1880	<	ForkJoinTask<?> t; int b;
1881	<	if (task.status < 0)
1882	<	break outer;
1883	<	if ((b = q.base) - q.top < 0) {
1884	<	progress = true;
1885	<	if (subtask.status < 0)
1886	<	break outer;               // stale
1887	<	if ((t = q.pollAt(b)) != null) {
1888	<	stealer.stealHint = joiner.poolIndex;
1889	<	joiner.runSubtask(t);
1879	>	/**
1880	>	* Tries to decrement active count (sometimes implicitly) and
1881	>	* possibly release or create a compensating worker in preparation
1882	>	* for blocking. Fails on contention or termination. Otherwise,
1883	>	* adds a new thread if no idle workers are available and pool
1884	>	* may become starved.
1885	>	*/
1886	>	final boolean tryCompensate() {
1887	>	int pc = parallelism, e, u, i, tc; long c;
1888	>	WorkQueue[] ws; WorkQueue w; Thread p;
1889	>	if ((e = (int)(c = ctl)) >= 0 && (ws = workQueues) != null) {
1890	>	if (e != 0 && (i = e & SMASK) < ws.length &&
1891	>	(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
1892	>	long nc = ((long)(w.nextWait & E_MASK) |
1893	>	(c & (AC_MASK|TC_MASK)));
1894	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1895	>	w.eventCount = (e + E_SEQ) & E_MASK;
1896	>	if ((p = w.parker) != null)
1897	>	U.unpark(p);
1898	>	return true;   // replace with idle worker
1899	>	}
1900	>	}
1901	>	else if ((short)((u = (int)(c >>> 32)) >>> UTC_SHIFT) >= 0 &&
1902	>	(u >> UAC_SHIFT) + pc > 1) {
1903	>	long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
1904	>	if (U.compareAndSwapLong(this, CTL, c, nc))
1905	>	return true;    // no compensation
1906	>	}
1907	>	else if ((tc = u + pc) < MAX_CAP) {
1908	>	long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
1909	>	if (U.compareAndSwapLong(this, CTL, c, nc)) {
1910	>	Throwable ex = null;
1911	>	ForkJoinWorkerThread wt = null;
1912	>	try {
1913	>	ForkJoinWorkerThreadFactory fac;
1914	>	if ((fac = factory) != null &&
1915	>	(wt = fac.newThread(this)) != null) {
1916	>	wt.start();
1917	>	return true;
1918		}
1919	+	} catch (Throwable rex) {
1920	+	ex = rex;
1921		}
1922	<	else { // empty - try to descend to find stealer's stealer
1672	<	ForkJoinTask<?> next = stealer.currentJoin;
1673	<	if (++depth == MAX_HELP_DEPTH || subtask.status < 0 ||
1674	<	next == null || next == subtask)
1675	<	break outer;  // max depth, stale, dead-end, cyclic
1676	<	subtask = next;
1677	<	j = stealer;
1678	<	break;
1679	<	}
1922	>	deregisterWorker(wt, ex); // adjust counts etc
1923		}
1924		}
1925		}
1926	<	return progress;
1926	>	return false;
1927		}
1928
1929		/**
1930	<	* If task is at base of some steal queue, steals and executes it.
1930	>	* Helps and/or blocks until the given task is done.
1931		*
1932		* @param joiner the joining worker
1933		* @param task the task
1934	+	* @return task status on exit
1935		*/
1936	<	final void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
1937	<	WorkQueue[] ws;
1938	<	int m = runState & SMASK;
1939	<	if ((ws = workQueues) != null && ws.length > m) {
1940	<	for (int j = 1; j <= m && task.status >= 0; j += 2) {
1941	<	WorkQueue q = ws[j];
1942	<	if (q != null && q.pollFor(task)) {
1943	<	joiner.runSubtask(task);
1944	<	break;
1936	>	final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
1937	>	int s = 0;
1938	>	if (joiner != null && task != null && (s = task.status) >= 0) {
1939	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
1940	>	joiner.currentJoin = task;
1941	>	do {} while ((s = task.status) >= 0 &&
1942	>	joiner.queueSize() > 0 &&
1943	>	joiner.tryRemoveAndExec(task)); // process local tasks
1944	>	if (s >= 0 && (s = task.status) >= 0 &&
1945	>	(s = helpSignal(task, joiner.poolIndex)) >= 0 &&
1946	>	(task instanceof CountedCompleter))
1947	>	s = helpComplete(task, LIFO_QUEUE);
1948	>	while (s >= 0 && (s = task.status) >= 0) {
1949	>	if ((joiner.queueSize() > 0 ||           // try helping
1950	>	(s = tryHelpStealer(joiner, task)) == 0) &&
1951	>	(s = task.status) >= 0 && tryCompensate()) {
1952	>	if (task.trySetSignal() && (s = task.status) >= 0) {
1953	>	synchronized (task) {
1954	>	if (task.status >= 0) {
1955	>	try {                // see ForkJoinTask
1956	>	task.wait();     //  for explanation
1957	>	} catch (InterruptedException ie) {
1958	>	}
1959	>	}
1960	>	else
1961	>	task.notifyAll();
1962	>	}
1963	>	}
1964	>	long c;                          // re-activate
1965	>	do {} while (!U.compareAndSwapLong
1966	>	(this, CTL, c = ctl, c + AC_UNIT));
1967		}
1968		}
1969	+	joiner.currentJoin = prevJoin;
1970		}
1971	+	return s;
1972		}
1973
1974		/**
1975	<	* Returns a non-empty steal queue, if one is found during a random,
1976	<	* then cyclic scan, else null.  This method must be retried by
1977	<	* caller if, by the time it tries to use the queue, it is empty.
1975	>	* Stripped-down variant of awaitJoin used by timed joins. Tries
1976	>	* to help join only while there is continuous progress. (Caller
1977	>	* will then enter a timed wait.)
1978	>	*
1979	>	* @param joiner the joining worker
1980	>	* @param task the task
1981		*/
1982	<	private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
1983	<	int r = w.seed;    // Same idea as scan(), but ignoring submissions
1982	>	final void helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) {
1983	>	int s;
1984	>	if (joiner != null && task != null && (s = task.status) >= 0) {
1985	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
1986	>	joiner.currentJoin = task;
1987	>	do {} while ((s = task.status) >= 0 &&
1988	>	joiner.queueSize() > 0 &&
1989	>	joiner.tryRemoveAndExec(task));
1990	>	if (s >= 0 && (s = task.status) >= 0 &&
1991	>	(s = helpSignal(task, joiner.poolIndex)) >= 0 &&
1992	>	(task instanceof CountedCompleter))
1993	>	s = helpComplete(task, LIFO_QUEUE);
1994	>	if (s >= 0 && joiner.queueSize() == 0) {
1995	>	do {} while (task.status >= 0 &&
1996	>	tryHelpStealer(joiner, task) > 0);
1997	>	}
1998	>	joiner.currentJoin = prevJoin;
1999	>	}
2000	>	}
2001	>
2002	>	/**
2003	>	* Returns a (probably) non-empty steal queue, if one is found
2004	>	* during a random, then cyclic scan, else null.  This method must
2005	>	* be retried by caller if, by the time it tries to use the queue,
2006	>	* it is empty.
2007	>	* @param r a (random) seed for scanning
2008	>	*/
2009	>	private WorkQueue findNonEmptyStealQueue(int r) {
2010	>	int step = (r >>> 16) | 1;
2011		for (WorkQueue[] ws;;) {
2012	<	int m = runState & SMASK;
2013	<	if ((ws = workQueues) == null)
2012	>	int ps = plock, m;
2013	>	if ((ws = workQueues) == null || (m = ws.length - 1) < 1)
2014		return null;
2015	<	if (ws.length > m) {
2016	<	WorkQueue q;
2017	<	for (int k = 0, j = -1 - m;; ++j) {
2018	<	if (j < 0) {
2019	<	r ^= r << 13; r ^= r >>> 17; k = r ^= r << 5;
2020	<	}
1723	<	else
1724	<	k += 7;
1725	<	if ((q = ws[(k | 1) & m]) != null && q.base - q.top < 0) {
1726	<	w.seed = r;
1727	<	return q;
1728	<	}
1729	<	else if (j - m > m)
2015	>	for (int j = (m + 1) << 2; ; r += step) {
2016	>	WorkQueue q = ws[((r << 1) | 1) & m];
2017	>	if (q != null && q.queueSize() > 0)
2018	>	return q;
2019	>	else if (--j < 0) {
2020	>	if (plock == ps)
2021		return null;
2022	+	break;
2023		}
2024		}
2025		}
#	Line 1741 | Line 2033 | public class ForkJoinPool extends Abstra
2033		*/
2034		final void helpQuiescePool(WorkQueue w) {
2035		for (boolean active = true;;) {
2036	<	w.runLocalTasks();      // exhaust local queue
2037	<	WorkQueue q = findNonEmptyStealQueue(w);
2036	>	ForkJoinTask<?> localTask; // exhaust local queue
2037	>	while ((localTask = w.nextLocalTask()) != null)
2038	>	localTask.doExec();
2039	>	// Similar to loop in scan(), but ignoring submissions
2040	>	WorkQueue q = findNonEmptyStealQueue(w.nextSeed());
2041		if (q != null) {
2042	<	ForkJoinTask<?> t;
2042	>	ForkJoinTask<?> t; int b;
2043		if (!active) {      // re-establish active count
2044		long c;
2045		active = true;
2046		do {} while (!U.compareAndSwapLong
2047		(this, CTL, c = ctl, c + AC_UNIT));
2048		}
2049	<	if ((t = q.poll()) != null)
2049	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2050		w.runSubtask(t);
2051		}
2052		else {
#	Line 1779 | Line 2074 | public class ForkJoinPool extends Abstra
2074		*/
2075		final ForkJoinTask<?> nextTaskFor(WorkQueue w) {
2076		for (ForkJoinTask<?> t;;) {
2077	<	WorkQueue q;
2077	>	WorkQueue q; int b;
2078		if ((t = w.nextLocalTask()) != null)
2079		return t;
2080	<	if ((q = findNonEmptyStealQueue(w)) == null)
2080	>	if ((q = findNonEmptyStealQueue(w.nextSeed())) == null)
2081		return null;
2082	<	if ((t = q.poll()) != null)
2082	>	if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
2083		return t;
2084		}
2085		}
2086
2087		/**
2088	<	* Returns the approximate (non-atomic) number of idle threads per
2089	<	* active thread to offset steal queue size for method
2090	<	* ForkJoinTask.getSurplusQueuedTaskCount().
2091	<	*/
2092	<	final int idlePerActive() {
2093	<	// Approximate at powers of two for small values, saturate past 4
2094	<	int p = parallelism;
2095	<	int a = p + (int)(ctl >> AC_SHIFT);
2096	<	return (a > (p >>>= 1) ? 0 :
2097	<	a > (p >>>= 1) ? 1 :
2098	<	a > (p >>>= 1) ? 2 :
2099	<	a > (p >>>= 1) ? 4 :
2100	<	8);
2088	>	* Returns a cheap heuristic guide for task partitioning when
2089	>	* programmers, frameworks, tools, or languages have little or no
2090	>	* idea about task granularity.  In essence by offering this
2091	>	* method, we ask users only about tradeoffs in overhead vs
2092	>	* expected throughput and its variance, rather than how finely to
2093	>	* partition tasks.
2094	>	*
2095	>	* In a steady state strict (tree-structured) computation, each
2096	>	* thread makes available for stealing enough tasks for other
2097	>	* threads to remain active. Inductively, if all threads play by
2098	>	* the same rules, each thread should make available only a
2099	>	* constant number of tasks.
2100	>	*
2101	>	* The minimum useful constant is just 1. But using a value of 1
2102	>	* would require immediate replenishment upon each steal to
2103	>	* maintain enough tasks, which is infeasible.  Further,
2104	>	* partitionings/granularities of offered tasks should minimize
2105	>	* steal rates, which in general means that threads nearer the top
2106	>	* of computation tree should generate more than those nearer the
2107	>	* bottom. In perfect steady state, each thread is at
2108	>	* approximately the same level of computation tree. However,
2109	>	* producing extra tasks amortizes the uncertainty of progress and
2110	>	* diffusion assumptions.
2111	>	*
2112	>	* So, users will want to use values larger, but not much larger
2113	>	* than 1 to both smooth over transient shortages and hedge
2114	>	* against uneven progress; as traded off against the cost of
2115	>	* extra task overhead. We leave the user to pick a threshold
2116	>	* value to compare with the results of this call to guide
2117	>	* decisions, but recommend values such as 3.
2118	>	*
2119	>	* When all threads are active, it is on average OK to estimate
2120	>	* surplus strictly locally. In steady-state, if one thread is
2121	>	* maintaining say 2 surplus tasks, then so are others. So we can
2122	>	* just use estimated queue length.  However, this strategy alone
2123	>	* leads to serious mis-estimates in some non-steady-state
2124	>	* conditions (ramp-up, ramp-down, other stalls). We can detect
2125	>	* many of these by further considering the number of "idle"
2126	>	* threads, that are known to have zero queued tasks, so
2127	>	* compensate by a factor of (#idle/#active) threads.
2128	>	*
2129	>	* Note: The approximation of #busy workers as #active workers is
2130	>	* not very good under current signalling scheme, and should be
2131	>	* improved.
2132	>	*/
2133	>	static int getSurplusQueuedTaskCount() {
2134	>	Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q;
2135	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
2136	>	int b = (q = (wt = (ForkJoinWorkerThread)t).workQueue).base;
2137	>	int p = (pool = wt.pool).parallelism;
2138	>	int a = (int)(pool.ctl >> AC_SHIFT) + p;
2139	>	return q.top - b - (a > (p >>>= 1) ? 0 :
2140	>	a > (p >>>= 1) ? 1 :
2141	>	a > (p >>>= 1) ? 2 :
2142	>	a > (p >>>= 1) ? 4 :
2143	>	8);
2144	>	}
2145	>	return 0;
2146		}
2147
2148		//  Termination
#	Line 1822 | Line 2162 | public class ForkJoinPool extends Abstra
2162		* @return true if now terminating or terminated
2163		*/
2164		private boolean tryTerminate(boolean now, boolean enable) {
2165	<	Mutex lock = this.lock;
2165	>	if (this == commonPool)                     // cannot shut down
2166	>	return false;
2167		for (long c;;) {
2168		if (((c = ctl) & STOP_BIT) != 0) {      // already terminating
2169		if ((short)(c >>> TC_SHIFT) == -parallelism) {
2170	<	lock.lock();                    // don't need try/finally
2171	<	termination.signalAll();        // signal when 0 workers
2172	<	lock.unlock();
2170	>	synchronized (this) {
2171	>	notifyAll();                // signal when 0 workers
2172	>	}
2173		}
2174		return true;
2175		}
2176	<	if (runState >= 0) {                    // not yet enabled
2176	>	if (plock >= 0) {                       // not yet enabled
2177	>	int ps;
2178		if (!enable)
2179		return false;
2180	<	lock.lock();
2181	<	runState |= SHUTDOWN;
2182	<	lock.unlock();
2180	>	if (((ps = plock) & PL_LOCK) != 0 ||
2181	>	!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
2182	>	ps = acquirePlock();
2183	>	int nps = SHUTDOWN;
2184	>	if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
2185	>	releasePlock(nps);
2186		}
2187		if (!now) {                             // check if idle & no tasks
2188		if ((int)(c >> AC_SHIFT) != -parallelism ||
#	Line 1860 | Line 2205 | public class ForkJoinPool extends Abstra
2205		int n = ws.length;
2206		for (int i = 0; i < n; ++i) {
2207		if ((w = ws[i]) != null) {
2208	<	w.runState = -1;
2208	>	w.qlock = -1;
2209		if (pass > 0) {
2210		w.cancelAll();
2211		if (pass > 1)
#	Line 1879 | Line 2224 | public class ForkJoinPool extends Abstra
2224		if (w.eventCount == (e | INT_SIGN) &&
2225		U.compareAndSwapLong(this, CTL, cc, nc)) {
2226		w.eventCount = (e + E_SEQ) & E_MASK;
2227	<	w.runState = -1;
2227	>	w.qlock = -1;
2228		if ((p = w.parker) != null)
2229		U.unpark(p);
2230		}
#	Line 1890 | Line 2235 | public class ForkJoinPool extends Abstra
2235		}
2236		}
2237
2238	+	// external operations on common pool
2239	+
2240	+	/**
2241	+	* Returns common pool queue for a thread that has submitted at
2242	+	* least one task.
2243	+	*/
2244	+	static WorkQueue commonSubmitterQueue() {
2245	+	ForkJoinPool p; WorkQueue[] ws; int m; Submitter z;
2246	+	return ((z = submitters.get()) != null &&
2247	+	(p = commonPool) != null &&
2248	+	(ws = p.workQueues) != null &&
2249	+	(m = ws.length - 1) >= 0) ?
2250	+	ws[m & z.seed & SQMASK] : null;
2251	+	}
2252	+
2253	+	/**
2254	+	* Tries to pop the given task from submitter's queue in common pool.
2255	+	*/
2256	+	static boolean tryExternalUnpush(ForkJoinTask<?> t) {
2257	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q; Submitter z;
2258	+	ForkJoinTask<?>[] a;  int m, s; long j;
2259	+	if ((z = submitters.get()) != null &&
2260	+	(p = commonPool) != null &&
2261	+	(ws = p.workQueues) != null &&
2262	+	(m = ws.length - 1) >= 0 &&
2263	+	(q = ws[m & z.seed & SQMASK]) != null &&
2264	+	(s = q.top) != q.base &&
2265	+	(a = q.array) != null &&
2266	+	U.getObjectVolatile
2267	+	(a, j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE) == t &&
2268	+	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2269	+	if (q.array == a && q.top == s && // recheck
2270	+	U.compareAndSwapObject(a, j, t, null)) {
2271	+	q.top = s - 1;
2272	+	q.qlock = 0;
2273	+	return true;
2274	+	}
2275	+	q.qlock = 0;
2276	+	}
2277	+	return false;
2278	+	}
2279	+
2280	+	/**
2281	+	* Tries to pop and run local tasks within the same computation
2282	+	* as the given root. On failure, tries to help complete from
2283	+	* other queues via helpComplete.
2284	+	*/
2285	+	private void externalHelpComplete(WorkQueue q, ForkJoinTask<?> root) {
2286	+	ForkJoinTask<?>[] a; int m;
2287	+	if (q != null && (a = q.array) != null && (m = (a.length - 1)) >= 0 &&
2288	+	root != null && root.status >= 0) {
2289	+	for (;;) {
2290	+	int s; Object o; CountedCompleter<?> task = null;
2291	+	if ((s = q.top) - q.base > 0) {
2292	+	long j = ((m & (s - 1)) << ASHIFT) + ABASE;
2293	+	if ((o = U.getObject(a, j)) != null &&
2294	+	(o instanceof CountedCompleter)) {
2295	+	CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;
2296	+	do {
2297	+	if (r == root) {
2298	+	if (U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2299	+	if (q.array == a && q.top == s &&
2300	+	U.compareAndSwapObject(a, j, t, null)) {
2301	+	q.top = s - 1;
2302	+	task = t;
2303	+	}
2304	+	q.qlock = 0;
2305	+	}
2306	+	break;
2307	+	}
2308	+	} while ((r = r.completer) != null);
2309	+	}
2310	+	}
2311	+	if (task != null)
2312	+	task.doExec();
2313	+	if (root.status < 0 || (int)(ctl >> AC_SHIFT) >= 0)
2314	+	break;
2315	+	if (task == null) {
2316	+	if (helpSignal(root, q.poolIndex) >= 0)
2317	+	helpComplete(root, SHARED_QUEUE);
2318	+	break;
2319	+	}
2320	+	}
2321	+	}
2322	+	}
2323	+
2324	+	/**
2325	+	* Tries to help execute or signal availability of the given task
2326	+	* from submitter's queue in common pool.
2327	+	*/
2328	+	static void externalHelpJoin(ForkJoinTask<?> t) {
2329	+	// Some hard-to-avoid overlap with tryExternalUnpush
2330	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; Submitter z;
2331	+	ForkJoinTask<?>[] a;  int m, s, n; long j;
2332	+	if (t != null && t.status >= 0 &&
2333	+	(z = submitters.get()) != null &&
2334	+	(p = commonPool) != null &&
2335	+	(ws = p.workQueues) != null &&
2336	+	(m = ws.length - 1) >= 0 &&
2337	+	(q = ws[m & z.seed & SQMASK]) != null &&
2338	+	(a = q.array) != null) {
2339	+	if ((s = q.top) != q.base &&
2340	+	U.getObjectVolatile
2341	+	(a, j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE) == t &&
2342	+	U.compareAndSwapInt(q, QLOCK, 0, 1)) {
2343	+	if (q.array == a && q.top == s &&
2344	+	U.compareAndSwapObject(a, j, t, null)) {
2345	+	q.top = s - 1;
2346	+	q.qlock = 0;
2347	+	t.doExec();
2348	+	}
2349	+	else
2350	+	q.qlock = 0;
2351	+	}
2352	+	if (t.status >= 0) {
2353	+	if (t instanceof CountedCompleter)
2354	+	p.externalHelpComplete(q, t);
2355	+	else
2356	+	p.helpSignal(t, q.poolIndex);
2357	+	}
2358	+	}
2359	+	}
2360	+
2361	+	/**
2362	+	* Restricted version of helpQuiescePool for external callers
2363	+	*/
2364	+	static void externalHelpQuiescePool() {
2365	+	ForkJoinPool p; ForkJoinTask<?> t; WorkQueue q; int b;
2366	+	int r = ThreadLocalRandom.current().nextInt();
2367	+	if ((p = commonPool) != null &&
2368	+	(q = p.findNonEmptyStealQueue(r)) != null &&
2369	+	(b = q.base) - q.top < 0 &&
2370	+	(t = q.pollAt(b)) != null)
2371	+	t.doExec();
2372	+	}
2373	+
2374		// Exported methods
2375
2376		// Constructors
#	Line 1959 | Line 2440 | public class ForkJoinPool extends Abstra
2440		checkPermission();
2441		if (factory == null)
2442		throw new NullPointerException();
2443	<	if (parallelism <= 0 || parallelism > POOL_MAX)
2443	>	if (parallelism <= 0 || parallelism > MAX_CAP)
2444		throw new IllegalArgumentException();
2445		this.parallelism = parallelism;
2446		this.factory = factory;
2447		this.ueh = handler;
2448		this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE;
1968	–	this.growHints = 1;
2449		long np = (long)(-parallelism); // offset ctl counts
2450		this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
2451	<	// initialize workQueues array with room for 2*parallelism if possible
1972	<	int n = parallelism << 1;
1973	<	if (n >= POOL_MAX)
1974	<	n = POOL_MAX;
1975	<	else { // See Hackers Delight, sec 3.2, where n < (1 << 16)
1976	<	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8;
1977	<	}
1978	<	this.workQueues = new WorkQueue[(n + 1) << 1]; // #slots = 2 * #workers
1979	<	this.termination = (this.lock = new Mutex()).newCondition();
1980	<	this.stealCount = new AtomicLong();
1981	<	this.nextWorkerNumber = new AtomicInteger();
2451	>	int pn = nextPoolId();
2452		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2453	<	sb.append(poolNumberGenerator.incrementAndGet());
2453	>	sb.append(Integer.toString(pn));
2454		sb.append("-worker-");
2455		this.workerNamePrefix = sb.toString();
2456		}
2457
2458	+	/**
2459	+	* Constructor for common pool, suitable only for static initialization.
2460	+	* Basically the same as above, but uses smallest possible initial footprint.
2461	+	*/
2462	+	ForkJoinPool(int parallelism, long ctl,
2463	+	ForkJoinWorkerThreadFactory factory,
2464	+	Thread.UncaughtExceptionHandler handler) {
2465	+	this.parallelism = parallelism;
2466	+	this.ctl = ctl;
2467	+	this.factory = factory;
2468	+	this.ueh = handler;
2469	+	this.localMode = LIFO_QUEUE;
2470	+	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2471	+	}
2472	+
2473	+	/**
2474	+	* Returns the common pool instance.
2475	+	*
2476	+	* @return the common pool instance
2477	+	*/
2478	+	public static ForkJoinPool commonPool() {
2479	+	return commonPool; // cannot be null (if so, a static init error)
2480	+	}
2481	+
2482		// Execution methods
2483
2484		/**
#	Line 2004 | Line 2498 | public class ForkJoinPool extends Abstra
2498		*         scheduled for execution
2499		*/
2500		public <T> T invoke(ForkJoinTask<T> task) {
2501	<	doSubmit(task);
2501	>	if (task == null)
2502	>	throw new NullPointerException();
2503	>	externalPush(task);
2504		return task.join();
2505		}
2506
#	Line 2017 | Line 2513 | public class ForkJoinPool extends Abstra
2513		*         scheduled for execution
2514		*/
2515		public void execute(ForkJoinTask<?> task) {
2516	<	doSubmit(task);
2516	>	if (task == null)
2517	>	throw new NullPointerException();
2518	>	externalPush(task);
2519		}
2520
2521		// AbstractExecutorService methods
#	Line 2034 | Line 2532 | public class ForkJoinPool extends Abstra
2532		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2533		job = (ForkJoinTask<?>) task;
2534		else
2535	<	job = ForkJoinTask.adapt(task, null);
2536	<	doSubmit(job);
2535	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2536	>	externalPush(job);
2537		}
2538
2539		/**
#	Line 2048 | Line 2546 | public class ForkJoinPool extends Abstra
2546		*         scheduled for execution
2547		*/
2548		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
2549	<	doSubmit(task);
2549	>	if (task == null)
2550	>	throw new NullPointerException();
2551	>	externalPush(task);
2552		return task;
2553		}
2554
#	Line 2058 | Line 2558 | public class ForkJoinPool extends Abstra
2558		*         scheduled for execution
2559		*/
2560		public <T> ForkJoinTask<T> submit(Callable<T> task) {
2561	<	if (task == null)
2562	<	throw new NullPointerException();
2063	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
2064	<	doSubmit(job);
2561	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task);
2562	>	externalPush(job);
2563		return job;
2564		}
2565
#	Line 2071 | Line 2569 | public class ForkJoinPool extends Abstra
2569		*         scheduled for execution
2570		*/
2571		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
2572	<	if (task == null)
2573	<	throw new NullPointerException();
2076	<	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
2077	<	doSubmit(job);
2572	>	ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result);
2573	>	externalPush(job);
2574		return job;
2575		}
2576
#	Line 2090 | Line 2586 | public class ForkJoinPool extends Abstra
2586		if (task instanceof ForkJoinTask<?>) // avoid re-wrap
2587		job = (ForkJoinTask<?>) task;
2588		else
2589	<	job = ForkJoinTask.adapt(task, null);
2590	<	doSubmit(job);
2589	>	job = new ForkJoinTask.AdaptedRunnableAction(task);
2590	>	externalPush(job);
2591		return job;
2592		}
2593
#	Line 2112 | Line 2608 | public class ForkJoinPool extends Abstra
2608		boolean done = false;
2609		try {
2610		for (Callable<T> t : tasks) {
2611	<	ForkJoinTask<T> f = ForkJoinTask.adapt(t);
2612	<	doSubmit(f);
2611	>	ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t);
2612	>	externalPush(f);
2613		fs.add(f);
2614		}
2615		for (ForkJoinTask<T> f : fs)
#	Line 2156 | Line 2652 | public class ForkJoinPool extends Abstra
2652		}
2653
2654		/**
2655	+	* Returns the targeted parallelism level of the common pool.
2656	+	*
2657	+	* @return the targeted parallelism level of the common pool
2658	+	*/
2659	+	public static int getCommonPoolParallelism() {
2660	+	return commonPoolParallelism;
2661	+	}
2662	+
2663	+	/**
2664		* Returns the number of worker threads that have started but not
2665		* yet terminated.  The result returned by this method may differ
2666		* from {@link #getParallelism} when threads are created to
#	Line 2236 | Line 2741 | public class ForkJoinPool extends Abstra
2741		* @return the number of steals
2742		*/
2743		public long getStealCount() {
2744	<	long count = stealCount.get();
2744	>	long count = stealCount;
2745		WorkQueue[] ws; WorkQueue w;
2746		if ((ws = workQueues) != null) {
2747		for (int i = 1; i < ws.length; i += 2) {
2748		if ((w = ws[i]) != null)
2749	<	count += w.totalSteals;
2749	>	count += w.nsteals;
2750		}
2751		}
2752		return count;
#	Line 2366 | Line 2871 | public class ForkJoinPool extends Abstra
2871		public String toString() {
2872		// Use a single pass through workQueues to collect counts
2873		long qt = 0L, qs = 0L; int rc = 0;
2874	<	long st = stealCount.get();
2874	>	long st = stealCount;
2875		long c = ctl;
2876		WorkQueue[] ws; WorkQueue w;
2877		if ((ws = workQueues) != null) {
#	Line 2377 | Line 2882 | public class ForkJoinPool extends Abstra
2882		qs += size;
2883		else {
2884		qt += size;
2885	<	st += w.totalSteals;
2885	>	st += w.nsteals;
2886		if (w.isApparentlyUnblocked())
2887		++rc;
2888		}
#	Line 2393 | Line 2898 | public class ForkJoinPool extends Abstra
2898		if ((c & STOP_BIT) != 0)
2899		level = (tc == 0) ? "Terminated" : "Terminating";
2900		else
2901	<	level = runState < 0 ? "Shutting down" : "Running";
2901	>	level = plock < 0 ? "Shutting down" : "Running";
2902		return super.toString() +
2903		"[" + level +
2904		", parallelism = " + pc +
#	Line 2407 | Line 2912 | public class ForkJoinPool extends Abstra
2912		}
2913
2914		/**
2915	<	* Initiates an orderly shutdown in which previously submitted
2916	<	* tasks are executed, but no new tasks will be accepted.
2917	<	* Invocation has no additional effect if already shut down.
2918	<	* Tasks that are in the process of being submitted concurrently
2919	<	* during the course of this method may or may not be rejected.
2915	>	* Possibly initiates an orderly shutdown in which previously
2916	>	* submitted tasks are executed, but no new tasks will be
2917	>	* accepted. Invocation has no effect on execution state if this
2918	>	* is the {@link #commonPool}, and no additional effect if
2919	>	* already shut down.  Tasks that are in the process of being
2920	>	* submitted concurrently during the course of this method may or
2921	>	* may not be rejected.
2922		*
2923		* @throws SecurityException if a security manager exists and
2924		*         the caller is not permitted to modify threads
#	Line 2424 | Line 2931 | public class ForkJoinPool extends Abstra
2931		}
2932
2933		/**
2934	<	* Attempts to cancel and/or stop all tasks, and reject all
2935	<	* subsequently submitted tasks.  Tasks that are in the process of
2936	<	* being submitted or executed concurrently during the course of
2937	<	* this method may or may not be rejected. This method cancels
2938	<	* both existing and unexecuted tasks, in order to permit
2939	<	* termination in the presence of task dependencies. So the method
2940	<	* always returns an empty list (unlike the case for some other
2941	<	* Executors).
2934	>	* Possibly attempts to cancel and/or stop all tasks, and reject
2935	>	* all subsequently submitted tasks.  Invocation has no effect on
2936	>	* execution state if this is the {@link #commonPool}, and no
2937	>	* additional effect if already shut down. Otherwise, tasks that
2938	>	* are in the process of being submitted or executed concurrently
2939	>	* during the course of this method may or may not be
2940	>	* rejected. This method cancels both existing and unexecuted
2941	>	* tasks, in order to permit termination in the presence of task
2942	>	* dependencies. So the method always returns an empty list
2943	>	* (unlike the case for some other Executors).
2944		*
2945		* @return an empty list
2946		* @throws SecurityException if a security manager exists and
#	Line 2481 | Line 2990 | public class ForkJoinPool extends Abstra
2990		* @return {@code true} if this pool has been shut down
2991		*/
2992		public boolean isShutdown() {
2993	<	return runState < 0;
2993	>	return plock < 0;
2994		}
2995
2996		/**
2997	<	* Blocks until all tasks have completed execution after a shutdown
2998	<	* request, or the timeout occurs, or the current thread is
2999	<	* interrupted, whichever happens first.
2997	>	* Blocks until all tasks have completed execution after a
2998	>	* shutdown request, or the timeout occurs, or the current thread
2999	>	* is interrupted, whichever happens first. Note that the {@link
3000	>	* #commonPool()} never terminates until program shutdown so
3001	>	* this method will always time out.
3002		*
3003		* @param timeout the maximum time to wait
3004		* @param unit the time unit of the timeout argument
#	Line 2498 | Line 3009 | public class ForkJoinPool extends Abstra
3009		public boolean awaitTermination(long timeout, TimeUnit unit)
3010		throws InterruptedException {
3011		long nanos = unit.toNanos(timeout);
3012	<	final Mutex lock = this.lock;
3013	<	lock.lock();
3014	<	try {
3015	<	for (;;) {
3016	<	if (isTerminated())
3017	<	return true;
3018	<	if (nanos <= 0)
3019	<	return false;
3020	<	nanos = termination.awaitNanos(nanos);
3012	>	if (isTerminated())
3013	>	return true;
3014	>	long startTime = System.nanoTime();
3015	>	boolean terminated = false;
3016	>	synchronized (this) {
3017	>	for (long waitTime = nanos, millis = 0L;;) {
3018	>	if (terminated = isTerminated() ||
3019	>	waitTime <= 0L ||
3020	>	(millis = unit.toMillis(waitTime)) <= 0L)
3021	>	break;
3022	>	wait(millis);
3023	>	waitTime = nanos - (System.nanoTime() - startTime);
3024		}
2511	–	} finally {
2512	–	lock.unlock();
3025		}
3026	+	return terminated;
3027		}
3028
3029		/**
#	Line 2609 | Line 3122 | public class ForkJoinPool extends Abstra
3122		public static void managedBlock(ManagedBlocker blocker)
3123		throws InterruptedException {
3124		Thread t = Thread.currentThread();
3125	<	ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ?
3126	<	((ForkJoinWorkerThread)t).pool : null);
3127	<	while (!blocker.isReleasable()) {
3128	<	if (p == null || p.tryCompensate()) {
3129	<	try {
3130	<	do {} while (!blocker.isReleasable() && !blocker.block());
3131	<	} finally {
3132	<	if (p != null)
3125	>	if (t instanceof ForkJoinWorkerThread) {
3126	>	ForkJoinPool p = ((ForkJoinWorkerThread)t).pool;
3127	>	while (!blocker.isReleasable()) { // variant of helpSignal
3128	>	WorkQueue[] ws; WorkQueue q; int m, n;
3129	>	if ((ws = p.workQueues) != null && (m = ws.length - 1) >= 0) {
3130	>	for (int i = 0; i <= m; ++i) {
3131	>	if (blocker.isReleasable())
3132	>	return;
3133	>	if ((q = ws[i]) != null && (n = q.queueSize()) > 0) {
3134	>	p.signalWork(q, n);
3135	>	if ((int)(p.ctl >> AC_SHIFT) >= 0)
3136	>	break;
3137	>	}
3138	>	}
3139	>	}
3140	>	if (p.tryCompensate()) {
3141	>	try {
3142	>	do {} while (!blocker.isReleasable() &&
3143	>	!blocker.block());
3144	>	} finally {
3145		p.incrementActiveCount();
3146	+	}
3147	+	break;
3148		}
2622	–	break;
3149		}
3150		}
3151	+	else {
3152	+	do {} while (!blocker.isReleasable() &&
3153	+	!blocker.block());
3154	+	}
3155		}
3156
3157		// AbstractExecutorService overrides.  These rely on undocumented
#	Line 2629 | Line 3159 | public class ForkJoinPool extends Abstra
3159		// implement RunnableFuture.
3160
3161		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
3162	<	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
3162	>	return new ForkJoinTask.AdaptedRunnable<T>(runnable, value);
3163		}
3164
3165		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
3166	<	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
3166	>	return new ForkJoinTask.AdaptedCallable<T>(callable);
3167		}
3168
3169		// Unsafe mechanics
3170		private static final sun.misc.Unsafe U;
3171		private static final long CTL;
3172		private static final long PARKBLOCKER;
3173	+	private static final int ABASE;
3174	+	private static final int ASHIFT;
3175	+	private static final long STEALCOUNT;
3176	+	private static final long PLOCK;
3177	+	private static final long INDEXSEED;
3178	+	private static final long QLOCK;
3179
3180		static {
3181	<	poolNumberGenerator = new AtomicInteger();
3182	<	modifyThreadPermission = new RuntimePermission("modifyThread");
3183	<	defaultForkJoinWorkerThreadFactory =
3184	<	new DefaultForkJoinWorkerThreadFactory();
3185	<	submitters = new ThreadSubmitter();
3181	>	// Establish common pool parameters
3182	>	// TBD: limit or report ignored exceptions?
3183	>
3184	>	int par = 0;
3185	>	ForkJoinWorkerThreadFactory fac = null;
3186	>	Thread.UncaughtExceptionHandler handler = null;
3187	>	try {
3188	>	String pp = System.getProperty(propPrefix + "parallelism");
3189	>	String hp = System.getProperty(propPrefix + "exceptionHandler");
3190	>	String fp = System.getProperty(propPrefix + "threadFactory");
3191	>	if (fp != null)
3192	>	fac = ((ForkJoinWorkerThreadFactory)ClassLoader.
3193	>	getSystemClassLoader().loadClass(fp).newInstance());
3194	>	if (hp != null)
3195	>	handler = ((Thread.UncaughtExceptionHandler)ClassLoader.
3196	>	getSystemClassLoader().loadClass(hp).newInstance());
3197	>	if (pp != null)
3198	>	par = Integer.parseInt(pp);
3199	>	} catch (Exception ignore) {
3200	>	}
3201	>
3202	>	int s; // initialize field offsets for CAS etc
3203		try {
3204		U = getUnsafe();
3205		Class<?> k = ForkJoinPool.class;
3206		CTL = U.objectFieldOffset
3207		(k.getDeclaredField("ctl"));
3208	+	STEALCOUNT = U.objectFieldOffset
3209	+	(k.getDeclaredField("stealCount"));
3210	+	PLOCK = U.objectFieldOffset
3211	+	(k.getDeclaredField("plock"));
3212	+	INDEXSEED = U.objectFieldOffset
3213	+	(k.getDeclaredField("indexSeed"));
3214		Class<?> tk = Thread.class;
3215		PARKBLOCKER = U.objectFieldOffset
3216		(tk.getDeclaredField("parkBlocker"));
3217	+	Class<?> wk = WorkQueue.class;
3218	+	QLOCK = U.objectFieldOffset
3219	+	(wk.getDeclaredField("qlock"));
3220	+	Class<?> ak = ForkJoinTask[].class;
3221	+	ABASE = U.arrayBaseOffset(ak);
3222	+	s = U.arrayIndexScale(ak);
3223	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3224		} catch (Exception e) {
3225		throw new Error(e);
3226		}
3227	+	if ((s & (s-1)) != 0)
3228	+	throw new Error("data type scale not a power of two");
3229	+
3230	+	/*
3231	+	* For extra caution, computations to set up pool state are
3232	+	* here; the constructor just assigns these values to fields.
3233	+	*/
3234	+	ForkJoinWorkerThreadFactory defaultFac =
3235	+	defaultForkJoinWorkerThreadFactory =
3236	+	new DefaultForkJoinWorkerThreadFactory();
3237	+	if (fac == null)
3238	+	fac = defaultFac;
3239	+	if (par <= 0)
3240	+	par = Runtime.getRuntime().availableProcessors();
3241	+	if (par > MAX_CAP)
3242	+	par = MAX_CAP;
3243	+	long np = (long)(-par); // precompute initial ctl value
3244	+	long ct = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
3245	+
3246	+	commonPoolParallelism = par;
3247	+	commonPool = new ForkJoinPool(par, ct, fac, handler);
3248	+	modifyThreadPermission = new RuntimePermission("modifyThread");
3249	+	submitters = new ThreadLocal<Submitter>();
3250		}
3251
3252		/**

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