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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.126 by jsr166, Tue Feb 21 00:44:53 2012 UTC vs.
Revision 1.139 by dl, Wed Oct 31 12:49:24 2012 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	+
9		import java.util.ArrayList;
10		import java.util.Arrays;
11		import java.util.Collection;
#	Line 41 | Line 42 | import java.util.concurrent.locks.Condit
42		* ForkJoinPool}s may also be appropriate for use with event-style
43		* tasks that are never joined.
44		*
45	<	* <p>A {@code ForkJoinPool} is constructed with a given target
46	<	* parallelism level; by default, equal to the number of available
47	<	* processors. The pool attempts to maintain enough active (or
48	<	* available) threads by dynamically adding, suspending, or resuming
49	<	* internal worker threads, even if some tasks are stalled waiting to
50	<	* join others. However, no such adjustments are guaranteed in the
51	<	* face of blocked IO or other unmanaged synchronization. The nested
52	<	* {@link ManagedBlocker} interface enables extension of the kinds of
45	>	* <p>A static {@link #commonPool} is available and appropriate for
46	>	* most applications. The common pool is used by any ForkJoinTask that
47	>	* is not explicitly submitted to a specified pool. Using the common
48	>	* pool normally reduces resource usage (its threads are slowly
49	>	* reclaimed during periods of non-use, and reinstated upon subsequent
50	>	* use).  The common pool is by default constructed with default
51	>	* parameters, but these may be controlled by setting any or all of
52	>	* the three properties {@code
53	>	* java.util.concurrent.ForkJoinPool.common.{parallelism,
54	>	* threadFactory, exceptionHandler}}.
55	>	*
56	>	* <p>For applications that require separate or custom pools, a {@code
57	>	* ForkJoinPool} may be constructed with a given target parallelism
58	>	* level; by default, equal to the number of available processors. The
59	>	* pool attempts to maintain enough active (or available) threads by
60	>	* dynamically adding, suspending, or resuming internal worker
61	>	* threads, even if some tasks are stalled waiting to join
62	>	* others. However, no such adjustments are guaranteed in the face of
63	>	* blocked IO or other unmanaged synchronization. The nested {@link
64	>	* ManagedBlocker} interface enables extension of the kinds of
65		* synchronization accommodated.
66		*
67		* <p>In addition to execution and lifecycle control methods, this
#	Line 93 | Line 106 | import java.util.concurrent.locks.Condit
106		*  </tr>
107		* </table>
108		*
96	–	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
97	–	* used for all parallel task execution in a program or subsystem.
98	–	* Otherwise, use would not usually outweigh the construction and
99	–	* bookkeeping overhead of creating a large set of threads. For
100	–	* example, a common pool could be used for the {@code SortTasks}
101	–	* illustrated in {@link RecursiveAction}. Because {@code
102	–	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
103	–	* daemon} mode, there is typically no need to explicitly {@link
104	–	* #shutdown} such a pool upon program exit.
105	–	*
106	–	*  <pre> {@code
107	–	* static final ForkJoinPool mainPool = new ForkJoinPool();
108	–	* ...
109	–	* public void sort(long[] array) {
110	–	*   mainPool.invoke(new SortTask(array, 0, array.length));
111	–	* }}</pre>
112	–	*
109		* <p><b>Implementation notes</b>: This implementation restricts the
110		* maximum number of running threads to 32767. Attempts to create
111		* pools with greater than the maximum number result in
#	Line 239 | Line 235 | public class ForkJoinPool extends Abstra
235		* when locked remains available to check consistency.
236		*
237		* Recording WorkQueues.  WorkQueues are recorded in the
238	<	* "workQueues" array that is created upon pool construction and
239	<	* expanded if necessary.  Updates to the array while recording
240	<	* new workers and unrecording terminated ones are protected from
241	<	* each other by a lock but the array is otherwise concurrently
242	<	* readable, and accessed directly.  To simplify index-based
243	<	* operations, the array size is always a power of two, and all
244	<	* readers must tolerate null slots. Shared (submission) queues
245	<	* are at even indices, worker queues at odd indices. Grouping
246	<	* them together in this way simplifies and speeds up task
251	<	* scanning.
238	>	* "workQueues" array that is created upon first use and expanded
239	>	* if necessary.  Updates to the array while recording new workers
240	>	* and unrecording terminated ones are protected from each other
241	>	* by a lock but the array is otherwise concurrently readable, and
242	>	* accessed directly.  To simplify index-based operations, the
243	>	* array size is always a power of two, and all readers must
244	>	* tolerate null slots. Shared (submission) queues are at even
245	>	* indices, worker queues at odd indices. Grouping them together
246	>	* in this way simplifies and speeds up task scanning.
247		*
248		* All worker thread creation is on-demand, triggered by task
249		* submissions, replacement of terminated workers, and/or
#	Line 320 | Line 315 | public class ForkJoinPool extends Abstra
315		*
316		* Trimming workers. To release resources after periods of lack of
317		* use, a worker starting to wait when the pool is quiescent will
318	<	* time out and terminate if the pool has remained quiescent for
319	<	* SHRINK_RATE nanosecs. This will slowly propagate, eventually
320	<	* terminating all workers after long periods of non-use.
318	>	* time out and terminate if the pool has remained quiescent for a
319	>	* given period -- a short period if there are more threads than
320	>	* parallelism, longer as the number of threads decreases. This
321	>	* will slowly propagate, eventually terminating all workers after
322	>	* periods of non-use.
323		*
324		* Shutdown and Termination. A call to shutdownNow atomically sets
325		* a runState bit and then (non-atomically) sets each worker's
#	Line 504 | Line 501 | public class ForkJoinPool extends Abstra
501		}
502
503		/**
507	–	* A simple non-reentrant lock used for exclusion when managing
508	–	* queues and workers. We use a custom lock so that we can readily
509	–	* probe lock state in constructions that check among alternative
510	–	* actions. The lock is normally only very briefly held, and
511	–	* sometimes treated as a spinlock, but other usages block to
512	–	* reduce overall contention in those cases where locked code
513	–	* bodies perform allocation/resizing.
514	–	*/
515	–	static final class Mutex extends AbstractQueuedSynchronizer {
516	–	public final boolean tryAcquire(int ignore) {
517	–	return compareAndSetState(0, 1);
518	–	}
519	–	public final boolean tryRelease(int ignore) {
520	–	setState(0);
521	–	return true;
522	–	}
523	–	public final void lock() { acquire(0); }
524	–	public final void unlock() { release(0); }
525	–	public final boolean isHeldExclusively() { return getState() == 1; }
526	–	public final Condition newCondition() { return new ConditionObject(); }
527	–	}
528	–
529	–	/**
504		* Class for artificial tasks that are used to replace the target
505		* of local joins if they are removed from an interior queue slot
506		* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
#	Line 629 | Line 603 | public class ForkJoinPool extends Abstra
603		final ForkJoinPool pool;   // the containing pool (may be null)
604		final ForkJoinWorkerThread owner; // owning thread or null if shared
605		volatile Thread parker;    // == owner during call to park; else null
606	<	ForkJoinTask<?> currentJoin;  // task being joined in awaitJoin
606	>	volatile ForkJoinTask<?> currentJoin;  // task being joined in awaitJoin
607		ForkJoinTask<?> currentSteal; // current non-local task being executed
608		// Heuristic padding to ameliorate unfortunate memory placements
609		Object p00, p01, p02, p03, p04, p05, p06, p07;
#	Line 717 | Line 691 | public class ForkJoinPool extends Abstra
691
692		/**
693		* Takes next task, if one exists, in LIFO order.  Call only
694	<	* by owner in unshared queues. (We do not have a shared
721	<	* version of this method because it is never needed.)
694	>	* by owner in unshared queues.
695		*/
696		final ForkJoinTask<?> pop() {
697	<	ForkJoinTask<?> t; int m;
698	<	ForkJoinTask<?>[] a = array;
726	<	if (a != null && (m = a.length - 1) >= 0) {
697	>	ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
698	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
699		for (int s; (s = top - 1) - base >= 0;) {
700	<	int j = ((m & s) << ASHIFT) + ABASE;
701	<	if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) == null)
700	>	long j = ((m & s) << ASHIFT) + ABASE;
701	>	if ((t = (ForkJoinTask<?>)U.getObject(a, j)) == null)
702		break;
703		if (U.compareAndSwapObject(a, j, t, null)) {
704		top = s;
#	Line 737 | Line 709 | public class ForkJoinPool extends Abstra
709		return null;
710		}
711
712	+	final ForkJoinTask<?> sharedPop() {
713	+	ForkJoinTask<?> task = null;
714	+	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
715	+	try {
716	+	ForkJoinTask<?>[] a; int m;
717	+	if ((a = array) != null && (m = a.length - 1) >= 0) {
718	+	for (int s; (s = top - 1) - base >= 0;) {
719	+	long j = ((m & s) << ASHIFT) + ABASE;
720	+	ForkJoinTask<?> t =
721	+	(ForkJoinTask<?>)U.getObject(a, j);
722	+	if (t == null)
723	+	break;
724	+	if (U.compareAndSwapObject(a, j, t, null)) {
725	+	top = s;
726	+	task = t;
727	+	break;
728	+	}
729	+	}
730	+	}
731	+	} finally {
732	+	runState = 0;
733	+	}
734	+	}
735	+	return task;
736	+	}
737	+
738	+
739		/**
740		* Takes a task in FIFO order if b is base of queue and a task
741		* can be claimed without contention. Specialized versions
#	Line 814 | Line 813 | public class ForkJoinPool extends Abstra
813		}
814
815		/**
816	+	* Version of tryUnpush for shared queues; called by non-FJ
817	+	* submitters after prechecking that task probably exists.
818	+	*/
819	+	final boolean trySharedUnpush(ForkJoinTask<?> t) {
820	+	boolean success = false;
821	+	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
822	+	try {
823	+	ForkJoinTask<?>[] a; int s;
824	+	if ((a = array) != null && (s = top) != base &&
825	+	U.compareAndSwapObject
826	+	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
827	+	top = s;
828	+	success = true;
829	+	}
830	+	} finally {
831	+	runState = 0;                         // unlock
832	+	}
833	+	}
834	+	return success;
835	+	}
836	+
837	+	/**
838		* Polls the given task only if it is at the current base.
839		*/
840		final boolean pollFor(ForkJoinTask<?> task) {
#	Line 830 | Line 851 | public class ForkJoinPool extends Abstra
851		}
852
853		/**
833	–	* If present, removes from queue and executes the given task, or
834	–	* any other cancelled task. Returns (true) immediately on any CAS
835	–	* or consistency check failure so caller can retry.
836	–	*
837	–	* @return false if no progress can be made
838	–	*/
839	–	final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
840	–	boolean removed = false, empty = true, progress = true;
841	–	ForkJoinTask<?>[] a; int m, s, b, n;
842	–	if ((a = array) != null && (m = a.length - 1) >= 0 &&
843	–	(n = (s = top) - (b = base)) > 0) {
844	–	for (ForkJoinTask<?> t;;) {           // traverse from s to b
845	–	int j = ((--s & m) << ASHIFT) + ABASE;
846	–	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
847	–	if (t == null)                    // inconsistent length
848	–	break;
849	–	else if (t == task) {
850	–	if (s + 1 == top) {           // pop
851	–	if (!U.compareAndSwapObject(a, j, task, null))
852	–	break;
853	–	top = s;
854	–	removed = true;
855	–	}
856	–	else if (base == b)           // replace with proxy
857	–	removed = U.compareAndSwapObject(a, j, task,
858	–	new EmptyTask());
859	–	break;
860	–	}
861	–	else if (t.status >= 0)
862	–	empty = false;
863	–	else if (s + 1 == top) {          // pop and throw away
864	–	if (U.compareAndSwapObject(a, j, t, null))
865	–	top = s;
866	–	break;
867	–	}
868	–	if (--n == 0) {
869	–	if (!empty && base == b)
870	–	progress = false;
871	–	break;
872	–	}
873	–	}
874	–	}
875	–	if (removed)
876	–	task.doExec();
877	–	return progress;
878	–	}
879	–
880	–	/**
854		* Initializes or doubles the capacity of array. Call either
855		* by owner or with lock held -- it is OK for base, but not
856		* top, to move while resizings are in progress.
#	Line 936 | Line 909 | public class ForkJoinPool extends Abstra
909		return seed = r ^= r << 5;
910		}
911
912	<	// Execution methods
912	>	// Specialized execution methods
913
914		/**
915	<	* Removes and runs tasks until empty, using local mode
943	<	* ordering. Normally called only after checking for apparent
944	<	* non-emptiness.
915	>	* Pops and runs tasks until empty.
916		*/
917	<	final void runLocalTasks() {
918	<	// hoist checks from repeated pop/poll
919	<	ForkJoinTask<?>[] a; int m;
920	<	if ((a = array) != null && (m = a.length - 1) >= 0) {
921	<	if (mode == 0) {
922	<	for (int s; (s = top - 1) - base >= 0;) {
923	<	int j = ((m & s) << ASHIFT) + ABASE;
924	<	ForkJoinTask<?> t =
925	<	(ForkJoinTask<?>)U.getObjectVolatile(a, j);
926	<	if (t != null) {
927	<	if (U.compareAndSwapObject(a, j, t, null)) {
928	<	top = s;
929	<	t.doExec();
930	<	}
917	>	private void popAndExecAll() {
918	>	// A bit faster than repeated pop calls
919	>	ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t;
920	>	while ((a = array) != null && (m = a.length - 1) >= 0 &&
921	>	(s = top - 1) - base >= 0 &&
922	>	(t = ((ForkJoinTask<?>)
923	>	U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
924	>	!= null) {
925	>	if (U.compareAndSwapObject(a, j, t, null)) {
926	>	top = s;
927	>	t.doExec();
928	>	}
929	>	}
930	>	}
931	>
932	>	/**
933	>	* Polls and runs tasks until empty.
934	>	*/
935	>	private void pollAndExecAll() {
936	>	for (ForkJoinTask<?> t; (t = poll()) != null;)
937	>	t.doExec();
938	>	}
939	>
940	>	/**
941	>	* If present, removes from queue and executes the given task, or
942	>	* any other cancelled task. Returns (true) immediately on any CAS
943	>	* or consistency check failure so caller can retry.
944	>	*
945	>	* @return 0 if no progress can be made, else positive
946	>	* (this unusual convention simplifies use with tryHelpStealer.)
947	>	*/
948	>	final int tryRemoveAndExec(ForkJoinTask<?> task) {
949	>	int stat = 1;
950	>	boolean removed = false, empty = true;
951	>	ForkJoinTask<?>[] a; int m, s, b, n;
952	>	if ((a = array) != null && (m = a.length - 1) >= 0 &&
953	>	(n = (s = top) - (b = base)) > 0) {
954	>	for (ForkJoinTask<?> t;;) {           // traverse from s to b
955	>	int j = ((--s & m) << ASHIFT) + ABASE;
956	>	t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
957	>	if (t == null)                    // inconsistent length
958	>	break;
959	>	else if (t == task) {
960	>	if (s + 1 == top) {           // pop
961	>	if (!U.compareAndSwapObject(a, j, task, null))
962	>	break;
963	>	top = s;
964	>	removed = true;
965		}
966	<	else
967	<	break;
966	>	else if (base == b)           // replace with proxy
967	>	removed = U.compareAndSwapObject(a, j, task,
968	>	new EmptyTask());
969	>	break;
970	>	}
971	>	else if (t.status >= 0)
972	>	empty = false;
973	>	else if (s + 1 == top) {          // pop and throw away
974	>	if (U.compareAndSwapObject(a, j, t, null))
975	>	top = s;
976	>	break;
977	>	}
978	>	if (--n == 0) {
979	>	if (!empty && base == b)
980	>	stat = 0;
981	>	break;
982		}
983		}
984	<	else {
985	<	for (int b; (b = base) - top < 0;) {
986	<	int j = ((m & b) << ASHIFT) + ABASE;
987	<	ForkJoinTask<?> t =
988	<	(ForkJoinTask<?>)U.getObjectVolatile(a, j);
989	<	if (t != null) {
990	<	if (base == b &&
991	<	U.compareAndSwapObject(a, j, t, null)) {
992	<	base = b + 1;
993	<	t.doExec();
994	<	}
995	<	} else if (base == b) {
996	<	if (b + 1 == top)
984	>	}
985	>	if (removed)
986	>	task.doExec();
987	>	return stat;
988	>	}
989	>
990	>	/**
991	>	* Version of shared pop that takes top element only if it
992	>	* its root is the given CountedCompleter.
993	>	*/
994	>	final CountedCompleter<?> sharedPopCC(CountedCompleter<?> root) {
995	>	CountedCompleter<?> task = null;
996	>	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
997	>	try {
998	>	ForkJoinTask<?>[] a; int m;
999	>	if ((a = array) != null && (m = a.length - 1) >= 0) {
1000	>	outer:for (int s; (s = top - 1) - base >= 0;) {
1001	>	long j = ((m & s) << ASHIFT) + ABASE;
1002	>	ForkJoinTask<?> t =
1003	>	(ForkJoinTask<?>)U.getObject(a, j);
1004	>	if (t == null || !(t instanceof CountedCompleter))
1005		break;
1006	<	Thread.yield(); // wait for lagging update
1006	>	CountedCompleter<?> cc = (CountedCompleter<?>)t;
1007	>	for (CountedCompleter<?> q = cc, p;;) {
1008	>	if (q == root) {
1009	>	if (U.compareAndSwapObject(a, j, cc, null)) {
1010	>	top = s;
1011	>	task = cc;
1012	>	break outer;
1013	>	}
1014	>	break;
1015	>	}
1016	>	if ((p = q.completer) == null)
1017	>	break outer;
1018	>	q = p;
1019	>	}
1020		}
1021		}
1022	+	} finally {
1023	+	runState = 0;
1024		}
1025		}
1026	+	return task;
1027		}
1028
1029		/**
1030		* Executes a top-level task and any local tasks remaining
1031		* after execution.
989	–	*
990	–	* @return true unless terminating
1032		*/
1033	<	final boolean runTask(ForkJoinTask<?> t) {
993	<	boolean alive = true;
1033	>	final void runTask(ForkJoinTask<?> t) {
1034		if (t != null) {
1035		currentSteal = t;
1036		t.doExec();
1037	<	if (top != base)        // conservative guard
1038	<	runLocalTasks();
1037	>	if (top != base) {       // process remaining local tasks
1038	>	if (mode == 0)
1039	>	popAndExecAll();
1040	>	else
1041	>	pollAndExecAll();
1042	>	}
1043		++nsteals;
1044		currentSteal = null;
1045		}
1002	–	else if (runState < 0)      // terminating
1003	–	alive = false;
1004	–	return alive;
1046		}
1047
1048		/**
#	Line 1106 | Line 1147 | public class ForkJoinPool extends Abstra
1147		public static final ForkJoinWorkerThreadFactory
1148		defaultForkJoinWorkerThreadFactory;
1149
1150	+	/** Property prefix for constructing common pool */
1151	+	private static final String propPrefix =
1152	+	"java.util.concurrent.ForkJoinPool.common.";
1153	+
1154	+	/**
1155	+	* Common (static) pool. Non-null for public use unless a static
1156	+	* construction exception, but internal usages must null-check on
1157	+	* use.
1158	+	*/
1159	+	static final ForkJoinPool commonPool;
1160	+
1161	+	/**
1162	+	* Common pool parallelism. Must equal commonPool.parallelism.
1163	+	*/
1164	+	static final int commonPoolParallelism;
1165	+
1166		/**
1167		* Generator for assigning sequence numbers as pool names.
1168		*/
#	Line 1124 | Line 1181 | public class ForkJoinPool extends Abstra
1181		private static final RuntimePermission modifyThreadPermission;
1182
1183		/**
1184	<	* Per-thread submission bookeeping. Shared across all pools
1184	>	* Per-thread submission bookkeeping. Shared across all pools
1185		* to reduce ThreadLocal pollution and because random motion
1186		* to avoid contention in one pool is likely to hold for others.
1187		*/
#	Line 1133 | Line 1190 | public class ForkJoinPool extends Abstra
1190		// static constants
1191
1192		/**
1193	<	* The wakeup interval (in nanoseconds) for a worker waiting for a
1194	<	* task when the pool is quiescent to instead try to shrink the
1195	<	* number of workers.  The exact value does not matter too
1139	<	* much. It must be short enough to release resources during
1140	<	* sustained periods of idleness, but not so short that threads
1141	<	* are continually re-created.
1193	>	* Initial timeout value (in nanoseconds) for the thread triggering
1194	>	* quiescence to park waiting for new work. On timeout, the thread
1195	>	* will instead try to shrink the number of workers.
1196		*/
1197	<	private static final long SHRINK_RATE =
1144	<	4L * 1000L * 1000L * 1000L; // 4 seconds
1197	>	private static final long IDLE_TIMEOUT      = 1000L * 1000L * 1000L; // 1sec
1198
1199		/**
1200	<	* The timeout value for attempted shrinkage, includes
1148	<	* some slop to cope with system timer imprecision.
1200	>	* Timeout value when there are more threads than parallelism level
1201		*/
1202	<	private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
1202	>	private static final long FAST_IDLE_TIMEOUT =  100L * 1000L * 1000L;
1203
1204		/**
1205		* The maximum stolen->joining link depth allowed in method
#	Line 1160 | Line 1212 | public class ForkJoinPool extends Abstra
1212		* traversal parameters at the expense of sometimes blocking when
1213		* we could be helping.
1214		*/
1215	<	private static final int MAX_HELP = 32;
1215	>	private static final int MAX_HELP = 64;
1216
1217		/**
1218		* Secondary time-based bound (in nanosecs) for helping attempts
#	Line 1170 | Line 1222 | public class ForkJoinPool extends Abstra
1222		* value should roughly approximate the time required to create
1223		* and/or activate a worker thread.
1224		*/
1225	<	private static final long COMPENSATION_DELAY = 100L * 1000L; // 0.1 millisec
1225	>	private static final long COMPENSATION_DELAY = 1L << 18; // ~0.25 millisec
1226
1227		/**
1228		* Increment for seed generators. See class ThreadLocal for
#	Line 1267 | Line 1319 | public class ForkJoinPool extends Abstra
1319		* empirically works OK on current JVMs.
1320		*/
1321
1322	+	volatile long stealCount;                  // collects worker counts
1323		volatile long ctl;                         // main pool control
1324		final int parallelism;                     // parallelism level
1325		final int localMode;                       // per-worker scheduling mode
1326	+	volatile int nextWorkerNumber;             // to create worker name string
1327		final int submitMask;                      // submit queue index bound
1328		int nextSeed;                              // for initializing worker seeds
1329	+	volatile int mainLock;                     // spinlock for array updates
1330		volatile int runState;                     // shutdown status and seq
1331		WorkQueue[] workQueues;                    // main registry
1277	–	final Mutex lock;                          // for registration
1278	–	final Condition termination;               // for awaitTermination
1332		final ForkJoinWorkerThreadFactory factory; // factory for new workers
1333		final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1281	–	final AtomicLong stealCount;               // collect counts when terminated
1282	–	final AtomicInteger nextWorkerNumber;      // to create worker name string
1334		final String workerNamePrefix;             // to create worker name string
1335
1336	+	/*
1337	+	* Mechanics for main lock protecting worker array updates.  Uses
1338	+	* the same strategy as ConcurrentHashMap bins -- a spinLock for
1339	+	* normal cases, but falling back to builtin lock when (rarely)
1340	+	* needed.  See internal ConcurrentHashMap documentation for
1341	+	* explanation.
1342	+	*/
1343	+
1344	+	static final int LOCK_WAITING = 2; // bit to indicate need for signal
1345	+	static final int MAX_LOCK_SPINS = 1 << 8;
1346	+
1347	+	private void tryAwaitMainLock() {
1348	+	int spins = MAX_LOCK_SPINS, r = 0, h;
1349	+	while (((h = mainLock) & 1) != 0) {
1350	+	if (r == 0)
1351	+	r = ThreadLocalRandom.current().nextInt(); // randomize spins
1352	+	else if (spins >= 0) {
1353	+	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1354	+	if (r >= 0)
1355	+	--spins;
1356	+	}
1357	+	else if (U.compareAndSwapInt(this, MAINLOCK, h, h | LOCK_WAITING)) {
1358	+	synchronized (this) {
1359	+	if ((mainLock & LOCK_WAITING) != 0) {
1360	+	try {
1361	+	wait();
1362	+	} catch (InterruptedException ie) {
1363	+	try {
1364	+	Thread.currentThread().interrupt();
1365	+	} catch (SecurityException ignore) {
1366	+	}
1367	+	}
1368	+	}
1369	+	else
1370	+	notifyAll(); // possibly won race vs signaller
1371	+	}
1372	+	break;
1373	+	}
1374	+	}
1375	+	}
1376	+
1377		//  Creating, registering, and deregistering workers
1378
1379		/**
#	Line 1308 | Line 1400 | public class ForkJoinPool extends Abstra
1400		* ForkJoinWorkerThread.
1401		*/
1402		final String nextWorkerName() {
1403	<	return workerNamePrefix.concat
1404	<	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1403	>	int n;
1404	>	do {} while (!U.compareAndSwapInt(this, NEXTWORKERNUMBER,
1405	>	n = nextWorkerNumber, ++n));
1406	>	return workerNamePrefix.concat(Integer.toString(n));
1407		}
1408
1409		/**
#	Line 1322 | Line 1416 | public class ForkJoinPool extends Abstra
1416		* @param w the worker's queue
1417		*/
1418		final void registerWorker(WorkQueue w) {
1419	<	Mutex lock = this.lock;
1420	<	lock.lock();
1419	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1420	>	tryAwaitMainLock();
1421		try {
1422	<	WorkQueue[] ws = workQueues;
1423	<	if (w != null && ws != null) {          // skip on shutdown/failure
1424	<	int rs, n;
1425	<	while ((n = ws.length) <            // ensure can hold total
1426	<	(parallelism + (short)(ctl >>> TC_SHIFT) << 1))
1333	<	workQueues = ws = Arrays.copyOf(ws, n << 1);
1334	<	int m = n - 1;
1422	>	WorkQueue[] ws;
1423	>	if ((ws = workQueues) == null)
1424	>	ws = workQueues = new WorkQueue[submitMask + 1];
1425	>	if (w != null) {
1426	>	int rs, n =  ws.length, m = n - 1;
1427		int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence
1428		w.seed = (s == 0) ? 1 : s;          // ensure non-zero seed
1429		int r = (s << 1) | 1;               // use odd-numbered indices
1430	<	while (ws[r &= m] != null)          // step by approx half size
1431	<	r += ((n >>> 1) & SQMASK) + 2;
1430	>	if (ws[r &= m] != null) {           // collision
1431	>	int probes = 0;                 // step by approx half size
1432	>	int step = (n <= 4) ? 2 : ((n >>> 1) & SQMASK) + 2;
1433	>	while (ws[r = (r + step) & m] != null) {
1434	>	if (++probes >= n) {
1435	>	workQueues = ws = Arrays.copyOf(ws, n <<= 1);
1436	>	m = n - 1;
1437	>	probes = 0;
1438	>	}
1439	>	}
1440	>	}
1441		w.eventCount = w.poolIndex = r;     // establish before recording
1442		ws[r] = w;                          // also update seq
1443		runState = ((rs = runState) & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN);
1444		}
1445		} finally {
1446	<	lock.unlock();
1446	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1447	>	mainLock = 0;
1448	>	synchronized (this) { notifyAll(); };
1449	>	}
1450		}
1451		}
1452
#	Line 1356 | Line 1460 | public class ForkJoinPool extends Abstra
1460		* @param ex the exception causing failure, or null if none
1461		*/
1462		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1359	–	Mutex lock = this.lock;
1463		WorkQueue w = null;
1464		if (wt != null && (w = wt.workQueue) != null) {
1465		w.runState = -1;                // ensure runState is set
1466	<	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1466	>	long steals = w.totalSteals + w.nsteals, sc;
1467	>	do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
1468	>	sc = stealCount, sc + steals));
1469		int idx = w.poolIndex;
1470	<	lock.lock();
1471	<	try {                           // remove record from array
1470	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1471	>	tryAwaitMainLock();
1472	>	try {
1473		WorkQueue[] ws = workQueues;
1474		if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1475		ws[idx] = null;
1476		} finally {
1477	<	lock.unlock();
1477	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1478	>	mainLock = 0;
1479	>	synchronized (this) { notifyAll(); };
1480	>	}
1481		}
1482		}
1483
#	Line 1387 | Line 1496 | public class ForkJoinPool extends Abstra
1496		}
1497
1498		if (ex != null)                     // rethrow
1499	<	U.throwException(ex);
1499	>	ForkJoinTask.rethrow(ex);
1500		}
1501
1393	–
1502		// Submissions
1503
1504		/**
#	Line 1408 | Line 1516 | public class ForkJoinPool extends Abstra
1516		for (int r = s.seed, m = submitMask;;) {
1517		WorkQueue[] ws; WorkQueue q;
1518		int k = r & m & SQMASK;          // use only even indices
1519	<	if (runState < 0 || (ws = workQueues) == null || ws.length <= k)
1519	>	if (runState < 0)
1520		throw new RejectedExecutionException(); // shutting down
1521	+	else if ((ws = workQueues) == null || ws.length <= k) {
1522	+	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1523	+	tryAwaitMainLock();
1524	+	try {
1525	+	if (workQueues == null)
1526	+	workQueues = new WorkQueue[submitMask + 1];
1527	+	} finally {
1528	+	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1529	+	mainLock = 0;
1530	+	synchronized (this) { notifyAll(); };
1531	+	}
1532	+	}
1533	+	}
1534		else if ((q = ws[k]) == null) {  // create new queue
1535		WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE);
1536	<	Mutex lock = this.lock;      // construct outside lock
1537	<	lock.lock();
1538	<	try {                        // recheck under lock
1536	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1537	>	tryAwaitMainLock();
1538	>	try {
1539		int rs = runState;       // to update seq
1540		if (ws == workQueues && ws[k] == null) {
1541		ws[k] = nq;
1542		runState = ((rs & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN));
1543		}
1544		} finally {
1545	<	lock.unlock();
1545	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1546	>	mainLock = 0;
1547	>	synchronized (this) { notifyAll(); };
1548	>	}
1549		}
1550		}
1551		else if (q.trySharedPush(task)) {
#	Line 1438 | Line 1562 | public class ForkJoinPool extends Abstra
1562		}
1563		}
1564
1565	+	/**
1566	+	* Submits the given (non-null) task to the common pool, if possible.
1567	+	*/
1568	+	static void submitToCommonPool(ForkJoinTask<?> task) {
1569	+	ForkJoinPool p;
1570	+	if ((p = commonPool) == null)
1571	+	throw new RejectedExecutionException("Common Pool Unavailable");
1572	+	p.doSubmit(task);
1573	+	}
1574	+
1575	+	/**
1576	+	* Returns true if the given task was submitted to common pool
1577	+	* and has not yet commenced execution, and is available for
1578	+	* removal according to execution policies; if so removing the
1579	+	* submission from the pool.
1580	+	*
1581	+	* @param task the task
1582	+	* @return true if successful
1583	+	*/
1584	+	static boolean tryUnsubmitFromCommonPool(ForkJoinTask<?> task) {
1585	+	// If not oversaturating platform, peek, looking for task and
1586	+	// eligibility before using trySharedUnpush to actually take
1587	+	// it under lock
1588	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q;
1589	+	ForkJoinTask<?>[] a; int ac, s, m;
1590	+	if ((p = commonPool) != null && (ws = p.workQueues) != null) {
1591	+	int k = submitters.get().seed & p.submitMask & SQMASK;
1592	+	if ((m = ws.length - 1) >= k && (q = ws[k]) != null &&
1593	+	(ac = (int)(p.ctl >> AC_SHIFT)) <= 0) {
1594	+	if (ac == 0) { // double check if all workers active
1595	+	for (int i = 1; i <= m; i += 2) {
1596	+	if ((w = ws[i]) != null && w.parker != null) {
1597	+	ac = -1;
1598	+	break;
1599	+	}
1600	+	}
1601	+	}
1602	+	return (ac < 0 && (a = q.array) != null &&
1603	+	(s = q.top - 1) - q.base >= 0 &&
1604	+	s >= 0 && s < a.length &&
1605	+	a[s] == task &&
1606	+	q.trySharedUnpush(task));
1607	+	}
1608	+	}
1609	+	return false;
1610	+	}
1611	+
1612	+	/**
1613	+	* Tries to pop and run a task within same computation from common pool
1614	+	*/
1615	+	static void popAndExecCCFromCommonPool(CountedCompleter<?> cc) {
1616	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; int m, ac;
1617	+	CountedCompleter<?> par, task;
1618	+	if ((p = commonPool) != null && (ws = p.workQueues) != null) {
1619	+	while ((par = cc.completer) != null) // find root
1620	+	cc = par;
1621	+	int k = submitters.get().seed & p.submitMask & SQMASK;
1622	+	if ((m = ws.length - 1) >= k && (q = ws[k]) != null &&
1623	+	(ac = (int)(p.ctl >> AC_SHIFT)) <= 0) {
1624	+	if (ac == 0) {
1625	+	for (int i = 1; i <= m; i += 2) {
1626	+	if ((w = ws[i]) != null && w.parker != null) {
1627	+	ac = -1;
1628	+	break;
1629	+	}
1630	+	}
1631	+	}
1632	+	if (ac < 0 && q.top - q.base > 0 &&
1633	+	(task = q.sharedPopCC(cc)) != null)
1634	+	task.exec();
1635	+	}
1636	+	}
1637	+	}
1638	+
1639		// Maintaining ctl counts
1640
1641		/**
#	Line 1449 | Line 1647 | public class ForkJoinPool extends Abstra
1647		}
1648
1649		/**
1650	<	* Tries to activate or create a worker if too few are active.
1650	>	* Tries to create one or activate one or more workers if too few are active.
1651		*/
1652		final void signalWork() {
1653		long c; int u;
#	Line 1483 | Line 1681 | public class ForkJoinPool extends Abstra
1681		}
1682		}
1683
1486	–
1684		// Scanning for tasks
1685
1686		/**
#	Line 1491 | Line 1688 | public class ForkJoinPool extends Abstra
1688		*/
1689		final void runWorker(WorkQueue w) {
1690		w.growArray(false);         // initialize queue array in this thread
1691	<	do {} while (w.runTask(scan(w)));
1691	>	do { w.runTask(scan(w)); } while (w.runState >= 0);
1692		}
1693
1694		/**
#	Line 1534 | Line 1731 | public class ForkJoinPool extends Abstra
1731		* awaiting signal,
1732		*
1733		* @param w the worker (via its WorkQueue)
1734	<	* @return a task or null of none found
1734	>	* @return a task or null if none found
1735		*/
1736		private final ForkJoinTask<?> scan(WorkQueue w) {
1737		WorkQueue[] ws;                       // first update random seed
#	Line 1551 | Line 1748 | public class ForkJoinPool extends Abstra
1748		t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1749		if (q.base == b && ec >= 0 && t != null &&
1750		U.compareAndSwapObject(a, i, t, null)) {
1751	<	q.base = b + 1;       // specialization of pollAt
1751	>	if (q.top - (q.base = b + 1) > 0)
1752	>	signalWork();    // help pushes signal
1753		return t;
1754		}
1755	<	else if ((t != null || b + 1 != q.top) &&
1558	<	(ec < 0 || j <= m)) {
1755	>	else if (ec < 0 || j <= m) {
1756		rs = 0;               // mark scan as imcomplete
1757		break;                // caller can retry after release
1758		}
#	Line 1563 | Line 1760 | public class ForkJoinPool extends Abstra
1760		if (--j < 0)
1761		break;
1762		}
1763	+
1764		long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
1765		if (e < 0)                        // decode ctl on empty scan
1766		w.runState = -1;              // pool is terminating
#	Line 1596 | Line 1794 | public class ForkJoinPool extends Abstra
1794		}
1795		}
1796		else if (w.eventCount < 0) {      // already queued
1797	<	if ((nr = w.rescans) > 0) {   // continue rescanning
1798	<	int ac = a + parallelism;
1799	<	if (((w.rescans = (ac < nr) ? ac : nr - 1) & 3) == 0)
1800	<	Thread.yield();       // yield before block
1603	<	}
1604	<	else {
1797	>	int ac = a + parallelism;
1798	>	if ((nr = w.rescans) > 0)     // continue rescanning
1799	>	w.rescans = (ac < nr) ? ac : nr - 1;
1800	>	else if (((w.seed >>> 16) & ac) == 0) { // randomize park
1801		Thread.interrupted();     // clear status
1802		Thread wt = Thread.currentThread();
1803		U.putObject(wt, PARKBLOCKER, this);
#	Line 1619 | Line 1815 | public class ForkJoinPool extends Abstra
1815		/**
1816		* If inactivating worker w has caused the pool to become
1817		* quiescent, checks for pool termination, and, so long as this is
1818	<	* not the only worker, waits for event for up to SHRINK_RATE
1819	<	* nanosecs.  On timeout, if ctl has not changed, terminates the
1818	>	* not the only worker, waits for event for up to a given
1819	>	* duration.  On timeout, if ctl has not changed, terminates the
1820		* worker, which will in turn wake up another worker to possibly
1821		* repeat this process.
1822		*
#	Line 1630 | Line 1826 | public class ForkJoinPool extends Abstra
1826		*/
1827		private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1828		if (w.eventCount < 0 && !tryTerminate(false, false) &&
1829	<	(int)prevCtl != 0 && ctl == currentCtl) {
1829	>	(int)prevCtl != 0 && !hasQueuedSubmissions() && ctl == currentCtl) {
1830	>	int dc = -(short)(currentCtl >>> TC_SHIFT);
1831	>	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1832	>	long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop
1833		Thread wt = Thread.currentThread();
1635	–	Thread.yield();            // yield before block
1834		while (ctl == currentCtl) {
1637	–	long startTime = System.nanoTime();
1835		Thread.interrupted();  // timed variant of version in scan()
1836		U.putObject(wt, PARKBLOCKER, this);
1837		w.parker = wt;
1838		if (ctl == currentCtl)
1839	<	U.park(false, SHRINK_RATE);
1839	>	U.park(false, parkTime);
1840		w.parker = null;
1841		U.putObject(wt, PARKBLOCKER, null);
1842		if (ctl != currentCtl)
1843		break;
1844	<	if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
1844	>	if (deadline - System.nanoTime() <= 0L &&
1845		U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1846		w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
1847		w.runState = -1;   // shrink
#	Line 1665 | Line 1862 | public class ForkJoinPool extends Abstra
1862		* leaves hints in workers to speed up subsequent calls. The
1863		* implementation is very branchy to cope with potential
1864		* inconsistencies or loops encountering chains that are stale,
1865	<	* unknown, or so long that they are likely cyclic.  All of these
1669	<	* cases are dealt with by just retrying by caller.
1865	>	* unknown, or so long that they are likely cyclic.
1866		*
1867		* @param joiner the joining worker
1868		* @param task the task to join
1869	<	* @return true if found or ran a task (and so is immediately retryable)
1869	>	* @return 0 if no progress can be made, negative if task
1870	>	* known complete, else positive
1871		*/
1872	<	private boolean tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1873	<	WorkQueue[] ws;
1874	<	int m, depth = MAX_HELP;                // remaining chain depth
1875	<	boolean progress = false;
1876	<	if ((ws = workQueues) != null && (m = ws.length - 1) > 0 &&
1877	<	task.status >= 0) {
1878	<	ForkJoinTask<?> subtask = task;     // current target
1879	<	outer: for (WorkQueue j = joiner;;) {
1880	<	WorkQueue stealer = null;       // find stealer of subtask
1881	<	WorkQueue v = ws[j.stealHint & m]; // try hint
1882	<	if (v != null && v.currentSteal == subtask)
1883	<	stealer = v;
1884	<	else {                          // scan
1885	<	for (int i = 1; i <= m; i += 2) {
1886	<	if ((v = ws[i]) != null && v.currentSteal == subtask &&
1887	<	v != joiner) {
1888	<	stealer = v;
1889	<	j.stealHint = i;    // save hint
1890	<	break;
1872	>	private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
1873	>	int stat = 0, steps = 0;                    // bound to avoid cycles
1874	>	if (joiner != null && task != null) {       // hoist null checks
1875	>	restart: for (;;) {
1876	>	ForkJoinTask<?> subtask = task;     // current target
1877	>	for (WorkQueue j = joiner, v;;) {   // v is stealer of subtask
1878	>	WorkQueue[] ws; int m, s, h;
1879	>	if ((s = task.status) < 0) {
1880	>	stat = s;
1881	>	break restart;
1882	>	}
1883	>	if ((ws = workQueues) == null || (m = ws.length - 1) <= 0)
1884	>	break restart;              // shutting down
1885	>	if ((v = ws[h = (j.stealHint | 1) & m]) == null ||
1886	>	v.currentSteal != subtask) {
1887	>	for (int origin = h;;) {    // find stealer
1888	>	if (((h = (h + 2) & m) & 15) == 1 &&
1889	>	(subtask.status < 0 || j.currentJoin != subtask))
1890	>	continue restart;   // occasional staleness check
1891	>	if ((v = ws[h]) != null &&
1892	>	v.currentSteal == subtask) {
1893	>	j.stealHint = h;    // save hint
1894	>	break;
1895	>	}
1896	>	if (h == origin)
1897	>	break restart;      // cannot find stealer
1898		}
1899		}
1900	<	if (stealer == null)
1901	<	break;
1902	<	}
1903	<
1904	<	for (WorkQueue q = stealer;;) { // try to help stealer
1905	<	ForkJoinTask[] a; ForkJoinTask<?> t; int b;
1906	<	if (task.status < 0)
1907	<	break outer;
1908	<	if ((b = q.base) - q.top < 0 && (a = q.array) != null) {
1909	<	progress = true;
1910	<	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1911	<	t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1912	<	if (subtask.status < 0) // must recheck before taking
1913	<	break outer;
1914	<	if (t != null &&
1915	<	q.base == b &&
1916	<	U.compareAndSwapObject(a, i, t, null)) {
1917	<	q.base = b + 1;
1918	<	joiner.runSubtask(t);
1900	>	for (;;) { // help stealer or descend to its stealer
1901	>	ForkJoinTask[] a;  int b;
1902	>	if (subtask.status < 0)     // surround probes with
1903	>	continue restart;       //   consistency checks
1904	>	if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
1905	>	int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
1906	>	ForkJoinTask<?> t =
1907	>	(ForkJoinTask<?>)U.getObjectVolatile(a, i);
1908	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1909	>	v.currentSteal != subtask)
1910	>	continue restart;   // stale
1911	>	stat = 1;               // apparent progress
1912	>	if (t != null && v.base == b &&
1913	>	U.compareAndSwapObject(a, i, t, null)) {
1914	>	v.base = b + 1;     // help stealer
1915	>	joiner.runSubtask(t);
1916	>	}
1917	>	else if (v.base == b && ++steps == MAX_HELP)
1918	>	break restart;      // v apparently stalled
1919	>	}
1920	>	else {                      // empty -- try to descend
1921	>	ForkJoinTask<?> next = v.currentJoin;
1922	>	if (subtask.status < 0 || j.currentJoin != subtask ||
1923	>	v.currentSteal != subtask)
1924	>	continue restart;   // stale
1925	>	else if (next == null || ++steps == MAX_HELP)
1926	>	break restart;      // dead-end or maybe cyclic
1927	>	else {
1928	>	subtask = next;
1929	>	j = v;
1930	>	break;
1931	>	}
1932		}
1716	–	else if (q.base == b)
1717	–	break outer;        // possibly stalled
1718	–	}
1719	–	else {                      // descend
1720	–	ForkJoinTask<?> next = stealer.currentJoin;
1721	–	if (--depth <= 0 || subtask.status < 0 ||
1722	–	next == null || next == subtask)
1723	–	break outer;        // stale, dead-end, or cyclic
1724	–	subtask = next;
1725	–	j = stealer;
1726	–	break;
1933		}
1934		}
1935		}
1936		}
1937	<	return progress;
1937	>	return stat;
1938		}
1939
1940		/**
#	Line 1828 | Line 2034 | public class ForkJoinPool extends Abstra
2034		* @return task status on exit
2035		*/
2036		final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
2037	<	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2038	<	joiner.currentJoin = task;
2039	<	long startTime = 0L;
2040	<	for (int k = 0, s; ; ++k) {
2041	<	if ((joiner.isEmpty() ?                  // try to help
2042	<	!tryHelpStealer(joiner, task) :
2043	<	!joiner.tryRemoveAndExec(task))) {
2044	<	if (k == 0) {
2045	<	startTime = System.nanoTime();
2046	<	tryPollForAndExec(joiner, task); // check uncommon case
2047	<	}
2048	<	else if ((k & (MAX_HELP - 1)) == 0 &&
2049	<	System.nanoTime() - startTime >= COMPENSATION_DELAY &&
2050	<	tryCompensate(task, null)) {
2051	<	if (task.trySetSignal() && task.status >= 0) {
2052	<	synchronized (task) {
2053	<	if (task.status >= 0) {
2054	<	try {                // see ForkJoinTask
2055	<	task.wait();     //  for explanation
2056	<	} catch (InterruptedException ie) {
2037	>	int s;
2038	>	if ((s = task.status) >= 0) {
2039	>	ForkJoinTask<?> prevJoin = joiner.currentJoin;
2040	>	joiner.currentJoin = task;
2041	>	long startTime = 0L;
2042	>	for (int k = 0;;) {
2043	>	if ((s = (joiner.isEmpty() ?           // try to help
2044	>	tryHelpStealer(joiner, task) :
2045	>	joiner.tryRemoveAndExec(task))) == 0 &&
2046	>	(s = task.status) >= 0) {
2047	>	if (k == 0) {
2048	>	startTime = System.nanoTime();
2049	>	tryPollForAndExec(joiner, task); // check uncommon case
2050	>	}
2051	>	else if ((k & (MAX_HELP - 1)) == 0 &&
2052	>	System.nanoTime() - startTime >=
2053	>	COMPENSATION_DELAY &&
2054	>	tryCompensate(task, null)) {
2055	>	if (task.trySetSignal()) {
2056	>	synchronized (task) {
2057	>	if (task.status >= 0) {
2058	>	try {                // see ForkJoinTask
2059	>	task.wait();     //  for explanation
2060	>	} catch (InterruptedException ie) {
2061	>	}
2062		}
2063	+	else
2064	+	task.notifyAll();
2065		}
1853	–	else
1854	–	task.notifyAll();
2066		}
2067	+	long c;                          // re-activate
2068	+	do {} while (!U.compareAndSwapLong
2069	+	(this, CTL, c = ctl, c + AC_UNIT));
2070		}
1857	–	long c;                          // re-activate
1858	–	do {} while (!U.compareAndSwapLong
1859	–	(this, CTL, c = ctl, c + AC_UNIT));
2071		}
2072	+	if (s < 0 || (s = task.status) < 0) {
2073	+	joiner.currentJoin = prevJoin;
2074	+	break;
2075	+	}
2076	+	else if ((k++ & (MAX_HELP - 1)) == MAX_HELP >>> 1)
2077	+	Thread.yield();                     // for politeness
2078		}
1862	–	if ((s = task.status) < 0) {
1863	–	joiner.currentJoin = prevJoin;
1864	–	return s;
1865	–	}
1866	–	else if ((k & (MAX_HELP - 1)) == MAX_HELP >>> 1)
1867	–	Thread.yield();                     // for politeness
2079		}
2080	+	return s;
2081		}
2082
2083		/**
#	Line 1882 | Line 2094 | public class ForkJoinPool extends Abstra
2094		while ((s = task.status) >= 0 &&
2095		(joiner.isEmpty() ?
2096		tryHelpStealer(joiner, task) :
2097	<	joiner.tryRemoveAndExec(task)))
2097	>	joiner.tryRemoveAndExec(task)) != 0)
2098		;
2099		return s;
2100		}
#	Line 1922 | Line 2134 | public class ForkJoinPool extends Abstra
2134		*/
2135		final void helpQuiescePool(WorkQueue w) {
2136		for (boolean active = true;;) {
2137	<	if (w.base - w.top < 0)
2138	<	w.runLocalTasks();  // exhaust local queue
2137	>	ForkJoinTask<?> localTask; // exhaust local queue
2138	>	while ((localTask = w.nextLocalTask()) != null)
2139	>	localTask.doExec();
2140		WorkQueue q = findNonEmptyStealQueue(w);
2141		if (q != null) {
2142		ForkJoinTask<?> t; int b;
#	Line 1955 | Line 2168 | public class ForkJoinPool extends Abstra
2168		}
2169
2170		/**
2171	+	* Restricted version of helpQuiescePool for non-FJ callers
2172	+	*/
2173	+	static void externalHelpQuiescePool() {
2174	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, sq;
2175	+	ForkJoinTask<?>[] a; int b;
2176	+	ForkJoinTask<?> t = null;
2177	+	int k = submitters.get().seed & SQMASK;
2178	+	if ((p = commonPool) != null &&
2179	+	(ws = p.workQueues) != null &&
2180	+	ws.length > (k &= p.submitMask) &&
2181	+	(q = ws[k]) != null) {
2182	+	while (q.top - q.base > 0) {
2183	+	if ((t = q.sharedPop()) != null)
2184	+	break;
2185	+	}
2186	+	if (t == null && (sq = p.findNonEmptyStealQueue(q)) != null &&
2187	+	(b = sq.base) - sq.top < 0)
2188	+	t = sq.pollAt(b);
2189	+	if (t != null)
2190	+	t.doExec();
2191	+	}
2192	+	}
2193	+
2194	+	/**
2195		* Gets and removes a local or stolen task for the given worker.
2196		*
2197		* @return a task, if available
#	Line 1987 | Line 2224 | public class ForkJoinPool extends Abstra
2224		8);
2225		}
2226
2227	+	/**
2228	+	* Returns approximate submission queue length for the given caller
2229	+	*/
2230	+	static int getEstimatedSubmitterQueueLength() {
2231	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
2232	+	int k = submitters.get().seed & SQMASK;
2233	+	return ((p = commonPool) != null && (ws = p.workQueues) != null &&
2234	+	ws.length > (k &= p.submitMask) &&
2235	+	(q = ws[k]) != null) ?
2236	+	q.queueSize() : 0;
2237	+	}
2238	+
2239		//  Termination
2240
2241		/**
#	Line 2004 | Line 2253 | public class ForkJoinPool extends Abstra
2253		* @return true if now terminating or terminated
2254		*/
2255		private boolean tryTerminate(boolean now, boolean enable) {
2007	–	Mutex lock = this.lock;
2256		for (long c;;) {
2257		if (((c = ctl) & STOP_BIT) != 0) {      // already terminating
2258		if ((short)(c >>> TC_SHIFT) == -parallelism) {
2259	<	lock.lock();                    // don't need try/finally
2260	<	termination.signalAll();        // signal when 0 workers
2261	<	lock.unlock();
2259	>	synchronized (this) {
2260	>	notifyAll();                // signal when 0 workers
2261	>	}
2262		}
2263		return true;
2264		}
2265		if (runState >= 0) {                    // not yet enabled
2266		if (!enable)
2267		return false;
2268	<	lock.lock();
2269	<	runState |= SHUTDOWN;
2270	<	lock.unlock();
2268	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
2269	>	tryAwaitMainLock();
2270	>	try {
2271	>	runState |= SHUTDOWN;
2272	>	} finally {
2273	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
2274	>	mainLock = 0;
2275	>	synchronized (this) { notifyAll(); };
2276	>	}
2277	>	}
2278		}
2279		if (!now) {                             // check if idle & no tasks
2280		if ((int)(c >> AC_SHIFT) != -parallelism ||
#	Line 2152 | Line 2407 | public class ForkJoinPool extends Abstra
2407		// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2.
2408		int n = parallelism - 1;
2409		n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
2410	<	int size = (n + 1) << 1;        // #slots = 2*#workers
2156	<	this.submitMask = size - 1;     // room for max # of submit queues
2157	<	this.workQueues = new WorkQueue[size];
2158	<	this.termination = (this.lock = new Mutex()).newCondition();
2159	<	this.stealCount = new AtomicLong();
2160	<	this.nextWorkerNumber = new AtomicInteger();
2410	>	this.submitMask = ((n + 1) << 1) - 1;
2411		int pn = poolNumberGenerator.incrementAndGet();
2412		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2413		sb.append(Integer.toString(pn));
2414		sb.append("-worker-");
2415		this.workerNamePrefix = sb.toString();
2166	–	lock.lock();
2416		this.runState = 1;              // set init flag
2417	<	lock.unlock();
2417	>	}
2418	>
2419	>	/**
2420	>	* Constructor for common pool, suitable only for static initialization.
2421	>	* Basically the same as above, but uses smallest possible initial footprint.
2422	>	*/
2423	>	ForkJoinPool(int parallelism, int submitMask,
2424	>	ForkJoinWorkerThreadFactory factory,
2425	>	Thread.UncaughtExceptionHandler handler) {
2426	>	this.factory = factory;
2427	>	this.ueh = handler;
2428	>	this.submitMask = submitMask;
2429	>	this.parallelism = parallelism;
2430	>	long np = (long)(-parallelism);
2431	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
2432	>	this.localMode = LIFO_QUEUE;
2433	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2434	>	this.runState = 1;
2435	>	}
2436	>
2437	>	/**
2438	>	* Returns the common pool instance.
2439	>	*
2440	>	* @return the common pool instance
2441	>	*/
2442	>	public static ForkJoinPool commonPool() {
2443	>	ForkJoinPool p;
2444	>	if ((p = commonPool) == null)
2445	>	throw new Error("Common Pool Unavailable");
2446	>	return p;
2447		}
2448
2449		// Execution methods
#	Line 2341 | Line 2619 | public class ForkJoinPool extends Abstra
2619		}
2620
2621		/**
2622	+	* Returns the targeted parallelism level of the common pool.
2623	+	*
2624	+	* @return the targeted parallelism level of the common pool
2625	+	*/
2626	+	public static int getCommonPoolParallelism() {
2627	+	return commonPoolParallelism;
2628	+	}
2629	+
2630	+	/**
2631		* Returns the number of worker threads that have started but not
2632		* yet terminated.  The result returned by this method may differ
2633		* from {@link #getParallelism} when threads are created to
#	Line 2421 | Line 2708 | public class ForkJoinPool extends Abstra
2708		* @return the number of steals
2709		*/
2710		public long getStealCount() {
2711	<	long count = stealCount.get();
2711	>	long count = stealCount;
2712		WorkQueue[] ws; WorkQueue w;
2713		if ((ws = workQueues) != null) {
2714		for (int i = 1; i < ws.length; i += 2) {
#	Line 2551 | Line 2838 | public class ForkJoinPool extends Abstra
2838		public String toString() {
2839		// Use a single pass through workQueues to collect counts
2840		long qt = 0L, qs = 0L; int rc = 0;
2841	<	long st = stealCount.get();
2841	>	long st = stealCount;
2842		long c = ctl;
2843		WorkQueue[] ws; WorkQueue w;
2844		if ((ws = workQueues) != null) {
#	Line 2592 | Line 2879 | public class ForkJoinPool extends Abstra
2879		}
2880
2881		/**
2882	<	* Initiates an orderly shutdown in which previously submitted
2883	<	* tasks are executed, but no new tasks will be accepted.
2884	<	* Invocation has no additional effect if already shut down.
2885	<	* Tasks that are in the process of being submitted concurrently
2886	<	* during the course of this method may or may not be rejected.
2882	>	* Possibly initiates an orderly shutdown in which previously
2883	>	* submitted tasks are executed, but no new tasks will be
2884	>	* accepted. Invocation has no effect on execution state if this
2885	>	* is the {@link #commonPool}, and no additional effect if
2886	>	* already shut down.  Tasks that are in the process of being
2887	>	* submitted concurrently during the course of this method may or
2888	>	* may not be rejected.
2889		*
2890		* @throws SecurityException if a security manager exists and
2891		*         the caller is not permitted to modify threads
#	Line 2605 | Line 2894 | public class ForkJoinPool extends Abstra
2894		*/
2895		public void shutdown() {
2896		checkPermission();
2897	<	tryTerminate(false, true);
2897	>	if (this != commonPool)
2898	>	tryTerminate(false, true);
2899		}
2900
2901		/**
2902	<	* Attempts to cancel and/or stop all tasks, and reject all
2903	<	* subsequently submitted tasks.  Tasks that are in the process of
2904	<	* being submitted or executed concurrently during the course of
2905	<	* this method may or may not be rejected. This method cancels
2906	<	* both existing and unexecuted tasks, in order to permit
2907	<	* termination in the presence of task dependencies. So the method
2908	<	* always returns an empty list (unlike the case for some other
2909	<	* Executors).
2902	>	* Possibly attempts to cancel and/or stop all tasks, and reject
2903	>	* all subsequently submitted tasks.  Invocation has no effect on
2904	>	* execution state if this is the {@link #commonPool}, and no
2905	>	* additional effect if already shut down. Otherwise, tasks that
2906	>	* are in the process of being submitted or executed concurrently
2907	>	* during the course of this method may or may not be
2908	>	* rejected. This method cancels both existing and unexecuted
2909	>	* tasks, in order to permit termination in the presence of task
2910	>	* dependencies. So the method always returns an empty list
2911	>	* (unlike the case for some other Executors).
2912		*
2913		* @return an empty list
2914		* @throws SecurityException if a security manager exists and
#	Line 2626 | Line 2918 | public class ForkJoinPool extends Abstra
2918		*/
2919		public List<Runnable> shutdownNow() {
2920		checkPermission();
2921	<	tryTerminate(true, true);
2921	>	if (this != commonPool)
2922	>	tryTerminate(true, true);
2923		return Collections.emptyList();
2924		}
2925
#	Line 2683 | Line 2976 | public class ForkJoinPool extends Abstra
2976		public boolean awaitTermination(long timeout, TimeUnit unit)
2977		throws InterruptedException {
2978		long nanos = unit.toNanos(timeout);
2979	<	final Mutex lock = this.lock;
2980	<	lock.lock();
2981	<	try {
2982	<	for (;;) {
2983	<	if (isTerminated())
2984	<	return true;
2985	<	if (nanos <= 0)
2986	<	return false;
2987	<	nanos = termination.awaitNanos(nanos);
2979	>	if (isTerminated())
2980	>	return true;
2981	>	long startTime = System.nanoTime();
2982	>	boolean terminated = false;
2983	>	synchronized (this) {
2984	>	for (long waitTime = nanos, millis = 0L;;) {
2985	>	if (terminated = isTerminated() ||
2986	>	waitTime <= 0L ||
2987	>	(millis = unit.toMillis(waitTime)) <= 0L)
2988	>	break;
2989	>	wait(millis);
2990	>	waitTime = nanos - (System.nanoTime() - startTime);
2991		}
2696	–	} finally {
2697	–	lock.unlock();
2992		}
2993	+	return terminated;
2994		}
2995
2996		/**
#	Line 2827 | Line 3122 | public class ForkJoinPool extends Abstra
3122		private static final long PARKBLOCKER;
3123		private static final int ABASE;
3124		private static final int ASHIFT;
3125	+	private static final long NEXTWORKERNUMBER;
3126	+	private static final long STEALCOUNT;
3127	+	private static final long MAINLOCK;
3128
3129		static {
3130		poolNumberGenerator = new AtomicInteger();
#	Line 2842 | Line 3140 | public class ForkJoinPool extends Abstra
3140		Class<?> ak = ForkJoinTask[].class;
3141		CTL = U.objectFieldOffset
3142		(k.getDeclaredField("ctl"));
3143	+	NEXTWORKERNUMBER = U.objectFieldOffset
3144	+	(k.getDeclaredField("nextWorkerNumber"));
3145	+	STEALCOUNT = U.objectFieldOffset
3146	+	(k.getDeclaredField("stealCount"));
3147	+	MAINLOCK = U.objectFieldOffset
3148	+	(k.getDeclaredField("mainLock"));
3149		Class<?> tk = Thread.class;
3150		PARKBLOCKER = U.objectFieldOffset
3151		(tk.getDeclaredField("parkBlocker"));
3152		ABASE = U.arrayBaseOffset(ak);
3153		s = U.arrayIndexScale(ak);
3154	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3155		} catch (Exception e) {
3156		throw new Error(e);
3157		}
3158		if ((s & (s-1)) != 0)
3159		throw new Error("data type scale not a power of two");
3160	<	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3160	>	try { // Establish common pool
3161	>	String pp = System.getProperty(propPrefix + "parallelism");
3162	>	String fp = System.getProperty(propPrefix + "threadFactory");
3163	>	String up = System.getProperty(propPrefix + "exceptionHandler");
3164	>	ForkJoinWorkerThreadFactory fac = (fp == null) ?
3165	>	defaultForkJoinWorkerThreadFactory :
3166	>	((ForkJoinWorkerThreadFactory)ClassLoader.
3167	>	getSystemClassLoader().loadClass(fp).newInstance());
3168	>	Thread.UncaughtExceptionHandler ueh = (up == null) ? null :
3169	>	((Thread.UncaughtExceptionHandler)ClassLoader.
3170	>	getSystemClassLoader().loadClass(up).newInstance());
3171	>	int par;
3172	>	if ((pp == null || (par = Integer.parseInt(pp)) <= 0))
3173	>	par = Runtime.getRuntime().availableProcessors();
3174	>	if (par > MAX_CAP)
3175	>	par = MAX_CAP;
3176	>	commonPoolParallelism = par;
3177	>	int n = par - 1; // precompute submit mask
3178	>	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4;
3179	>	n |= n >>> 8; n |= n >>> 16;
3180	>	int mask = ((n + 1) << 1) - 1;
3181	>	commonPool = new ForkJoinPool(par, mask, fac, ueh);
3182	>	} catch (Exception e) {
3183	>	throw new Error(e);
3184	>	}
3185		}
3186
3187		/**

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