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Comparing jsr166/src/jsr166e/ForkJoinPool.java (file contents):
Revision 1.4 by jsr166, Fri Oct 12 16:46:37 2012 UTC vs.
Revision 1.9 by dl, Tue Oct 30 14:23:03 2012 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166e;
8	+
9		import java.util.ArrayList;
10		import java.util.Arrays;
11		import java.util.Collection;
#	Line 17 | Line 18 | import java.util.concurrent.ExecutorServ
18		import java.util.concurrent.Future;
19		import java.util.concurrent.RejectedExecutionException;
20		import java.util.concurrent.RunnableFuture;
21	+	import java.util.concurrent.ThreadLocalRandom;
22		import java.util.concurrent.TimeUnit;
23		import java.util.concurrent.atomic.AtomicInteger;
24		import java.util.concurrent.atomic.AtomicLong;
#	Line 41 | Line 43 | import java.util.concurrent.locks.Condit
43		* ForkJoinPool}s may also be appropriate for use with event-style
44		* tasks that are never joined.
45		*
46	<	* <p>A {@code ForkJoinPool} is constructed with a given target
47	<	* parallelism level; by default, equal to the number of available
48	<	* processors. The pool attempts to maintain enough active (or
49	<	* available) threads by dynamically adding, suspending, or resuming
50	<	* internal worker threads, even if some tasks are stalled waiting to
51	<	* join others. However, no such adjustments are guaranteed in the
52	<	* face of blocked IO or other unmanaged synchronization. The nested
53	<	* {@link ManagedBlocker} interface enables extension of the kinds of
46	>	* <p>A static {@link #commonPool} is available and appropriate for
47	>	* most applications. The common pool is used by any ForkJoinTask that
48	>	* is not explicitly submitted to a specified pool. Using the common
49	>	* pool normally reduces resource usage (its threads are slowly
50	>	* reclaimed during periods of non-use, and reinstated upon subsequent
51	>	* use).  The common pool is by default constructed with default
52	>	* parameters, but these may be controlled by setting any or all of
53	>	* the three properties {@code
54	>	* java.util.concurrent.ForkJoinPool.common.{parallelism,
55	>	* threadFactory, exceptionHandler}}.
56	>	*
57	>	* <p>For applications that require separate or custom pools, a {@code
58	>	* ForkJoinPool} may be constructed with a given target parallelism
59	>	* level; by default, equal to the number of available processors. The
60	>	* pool attempts to maintain enough active (or available) threads by
61	>	* dynamically adding, suspending, or resuming internal worker
62	>	* threads, even if some tasks are stalled waiting to join
63	>	* others. However, no such adjustments are guaranteed in the face of
64	>	* blocked IO or other unmanaged synchronization. The nested {@link
65	>	* ManagedBlocker} interface enables extension of the kinds of
66		* synchronization accommodated.
67		*
68		* <p>In addition to execution and lifecycle control methods, this
#	Line 93 | Line 107 | import java.util.concurrent.locks.Condit
107		*  </tr>
108		* </table>
109		*
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	–	*
110		* <p><b>Implementation notes</b>: This implementation restricts the
111		* maximum number of running threads to 32767. Attempts to create
112		* pools with greater than the maximum number result in
#	Line 239 | Line 236 | public class ForkJoinPool extends Abstra
236		* when locked remains available to check consistency.
237		*
238		* Recording WorkQueues.  WorkQueues are recorded in the
239	<	* "workQueues" array that is created upon pool construction and
240	<	* expanded if necessary.  Updates to the array while recording
241	<	* new workers and unrecording terminated ones are protected from
242	<	* each other by a lock but the array is otherwise concurrently
243	<	* readable, and accessed directly.  To simplify index-based
244	<	* operations, the array size is always a power of two, and all
245	<	* readers must tolerate null slots. Shared (submission) queues
246	<	* are at even indices, worker queues at odd indices. Grouping
247	<	* them together in this way simplifies and speeds up task
251	<	* scanning.
239	>	* "workQueues" array that is created upon first use and expanded
240	>	* if necessary.  Updates to the array while recording new workers
241	>	* and unrecording terminated ones are protected from each other
242	>	* by a lock but the array is otherwise concurrently readable, and
243	>	* accessed directly.  To simplify index-based operations, the
244	>	* array size is always a power of two, and all readers must
245	>	* tolerate null slots. Shared (submission) queues are at even
246	>	* indices, worker queues at odd indices. Grouping them together
247	>	* in this way simplifies and speeds up task scanning.
248		*
249		* All worker thread creation is on-demand, triggered by task
250		* submissions, replacement of terminated workers, and/or
#	Line 320 | Line 316 | public class ForkJoinPool extends Abstra
316		*
317		* Trimming workers. To release resources after periods of lack of
318		* use, a worker starting to wait when the pool is quiescent will
319	<	* time out and terminate if the pool has remained quiescent for
320	<	* SHRINK_RATE nanosecs. This will slowly propagate, eventually
321	<	* terminating all workers after long periods of non-use.
319	>	* time out and terminate if the pool has remained quiescent for a
320	>	* given period -- a short period if there are more threads than
321	>	* parallelism, longer as the number of threads decreases. This
322	>	* will slowly propagate, eventually terminating all workers after
323	>	* periods of non-use.
324		*
325		* Shutdown and Termination. A call to shutdownNow atomically sets
326		* a runState bit and then (non-atomically) sets each worker's
#	Line 504 | Line 502 | public class ForkJoinPool extends Abstra
502		}
503
504		/**
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	–	/**
505		* Class for artificial tasks that are used to replace the target
506		* of local joins if they are removed from an interior queue slot
507		* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
#	Line 717 | Line 692 | public class ForkJoinPool extends Abstra
692
693		/**
694		* Takes next task, if one exists, in LIFO order.  Call only
695	<	* by owner in unshared queues. (We do not have a shared
721	<	* version of this method because it is never needed.)
695	>	* by owner in unshared queues.
696		*/
697		final ForkJoinTask<?> pop() {
698		ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
#	Line 736 | Line 710 | public class ForkJoinPool extends Abstra
710		return null;
711		}
712
713	+	final ForkJoinTask<?> sharedPop() {
714	+	ForkJoinTask<?> task = null;
715	+	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
716	+	try {
717	+	ForkJoinTask<?>[] a; int m;
718	+	if ((a = array) != null && (m = a.length - 1) >= 0) {
719	+	for (int s; (s = top - 1) - base >= 0;) {
720	+	long j = ((m & s) << ASHIFT) + ABASE;
721	+	ForkJoinTask<?> t =
722	+	(ForkJoinTask<?>)U.getObject(a, j);
723	+	if (t == null)
724	+	break;
725	+	if (U.compareAndSwapObject(a, j, t, null)) {
726	+	top = s;
727	+	task = t;
728	+	break;
729	+	}
730	+	}
731	+	}
732	+	} finally {
733	+	runState = 0;
734	+	}
735	+	}
736	+	return task;
737	+	}
738	+
739	+	/**
740	+	* Version of pop that takes top element only if it
741	+	* its root is the given CountedCompleter.
742	+	*/
743	+	final ForkJoinTask<?> popCC(CountedCompleter<?> root) {
744	+	ForkJoinTask<?>[] a; int m;
745	+	if (root != null && (a = array) != null && (m = a.length - 1) >= 0) {
746	+	for (int s; (s = top - 1) - base >= 0;) {
747	+	long j = ((m & s) << ASHIFT) + ABASE;
748	+	ForkJoinTask<?> t =
749	+	(ForkJoinTask<?>)U.getObject(a, j);
750	+	if (t == null || !(t instanceof CountedCompleter) ||
751	+	((CountedCompleter<?>)t).getRoot() != root)
752	+	break;
753	+	if (U.compareAndSwapObject(a, j, t, null)) {
754	+	top = s;
755	+	return t;
756	+	}
757	+	if (root.status < 0)
758	+	break;
759	+	}
760	+	}
761	+	return null;
762	+	}
763	+
764	+	/**
765	+	* Shared version of popCC
766	+	*/
767	+	final ForkJoinTask<?> sharedPopCC(CountedCompleter<?> root) {
768	+	ForkJoinTask<?> task = null;
769	+	if (root != null &&
770	+	runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
771	+	try {
772	+	ForkJoinTask<?>[] a; int m;
773	+	if ((a = array) != null && (m = a.length - 1) >= 0) {
774	+	for (int s; (s = top - 1) - base >= 0;) {
775	+	long j = ((m & s) << ASHIFT) + ABASE;
776	+	ForkJoinTask<?> t =
777	+	(ForkJoinTask<?>)U.getObject(a, j);
778	+	if (t == null || !(t instanceof CountedCompleter) ||
779	+	((CountedCompleter<?>)t).getRoot() != root)
780	+	break;
781	+	if (U.compareAndSwapObject(a, j, t, null)) {
782	+	top = s;
783	+	task = t;
784	+	break;
785	+	}
786	+	if (root.status < 0)
787	+	break;
788	+	}
789	+	}
790	+	} finally {
791	+	runState = 0;
792	+	}
793	+	}
794	+	return task;
795	+	}
796	+
797		/**
798		* Takes a task in FIFO order if b is base of queue and a task
799		* can be claimed without contention. Specialized versions
#	Line 813 | Line 871 | public class ForkJoinPool extends Abstra
871		}
872
873		/**
874	+	* Version of tryUnpush for shared queues; called by non-FJ
875	+	* submitters after prechecking that task probably exists.
876	+	*/
877	+	final boolean trySharedUnpush(ForkJoinTask<?> t) {
878	+	boolean success = false;
879	+	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
880	+	try {
881	+	ForkJoinTask<?>[] a; int s;
882	+	if ((a = array) != null && (s = top) != base &&
883	+	U.compareAndSwapObject
884	+	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
885	+	top = s;
886	+	success = true;
887	+	}
888	+	} finally {
889	+	runState = 0;                         // unlock
890	+	}
891	+	}
892	+	return success;
893	+	}
894	+
895	+	/**
896		* Polls the given task only if it is at the current base.
897		*/
898		final boolean pollFor(ForkJoinTask<?> task) {
#	Line 1086 | Line 1166 | public class ForkJoinPool extends Abstra
1166		public static final ForkJoinWorkerThreadFactory
1167		defaultForkJoinWorkerThreadFactory;
1168
1169	+
1170	+	/** Property prefix for constructing common pool */
1171	+	private static final String propPrefix =
1172	+	"java.util.concurrent.ForkJoinPool.common.";
1173	+
1174	+	/**
1175	+	* Common (static) pool. Non-null for public use unless a static
1176	+	* construction exception, but internal usages must null-check on
1177	+	* use.
1178	+	*/
1179	+	static final ForkJoinPool commonPool;
1180	+
1181	+	/**
1182	+	* Common pool parallelism. Must equal commonPool.parallelism.
1183	+	*/
1184	+	static final int commonPoolParallelism;
1185	+
1186		/**
1187		* Generator for assigning sequence numbers as pool names.
1188		*/
#	Line 1113 | Line 1210 | public class ForkJoinPool extends Abstra
1210		// static constants
1211
1212		/**
1213	<	* The wakeup interval (in nanoseconds) for a worker waiting for a
1214	<	* task when the pool is quiescent to instead try to shrink the
1215	<	* number of workers.  The exact value does not matter too
1119	<	* much. It must be short enough to release resources during
1120	<	* sustained periods of idleness, but not so short that threads
1121	<	* are continually re-created.
1213	>	* Initial timeout value (in nanoseconds) for the thread triggering
1214	>	* quiescence to park waiting for new work. On timeout, the thread
1215	>	* will instead try to shrink the number of workers.
1216		*/
1217	<	private static final long SHRINK_RATE =
1124	<	4L * 1000L * 1000L * 1000L; // 4 seconds
1217	>	private static final long IDLE_TIMEOUT      = 1000L * 1000L * 1000L; // 1sec
1218
1219		/**
1220	<	* The timeout value for attempted shrinkage, includes
1128	<	* some slop to cope with system timer imprecision.
1220	>	* Timeout value when there are more threads than parallelism level
1221		*/
1222	<	private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
1222	>	private static final long FAST_IDLE_TIMEOUT =  100L * 1000L * 1000L;
1223
1224		/**
1225		* The maximum stolen->joining link depth allowed in method
#	Line 1247 | Line 1339 | public class ForkJoinPool extends Abstra
1339		* empirically works OK on current JVMs.
1340		*/
1341
1342	+	volatile long stealCount;                  // collects worker counts
1343		volatile long ctl;                         // main pool control
1344		final int parallelism;                     // parallelism level
1345		final int localMode;                       // per-worker scheduling mode
1346	+	volatile int nextWorkerNumber;             // to create worker name string
1347		final int submitMask;                      // submit queue index bound
1348		int nextSeed;                              // for initializing worker seeds
1349	+	volatile int mainLock;                     // spinlock for array updates
1350		volatile int runState;                     // shutdown status and seq
1351		WorkQueue[] workQueues;                    // main registry
1257	–	final Mutex lock;                          // for registration
1258	–	final Condition termination;               // for awaitTermination
1352		final ForkJoinWorkerThreadFactory factory; // factory for new workers
1353		final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1261	–	final AtomicLong stealCount;               // collect counts when terminated
1262	–	final AtomicInteger nextWorkerNumber;      // to create worker name string
1354		final String workerNamePrefix;             // to create worker name string
1355
1356	+	/*
1357	+	* Mechanics for main lock protecting worker array updates.  Uses
1358	+	* the same strategy as ConcurrentHashMap bins -- a spinLock for
1359	+	* normal cases, but falling back to builtin lock when (rarely)
1360	+	* needed.  See internal ConcurrentHashMap documentation for
1361	+	* explanation.
1362	+	*/
1363	+
1364	+	static final int LOCK_WAITING = 2; // bit to indicate need for signal
1365	+	static final int MAX_LOCK_SPINS = 1 << 8;
1366	+
1367	+	private void tryAwaitMainLock() {
1368	+	int spins = MAX_LOCK_SPINS, r = 0, h;
1369	+	while (((h = mainLock) & 1) != 0) {
1370	+	if (r == 0)
1371	+	r = ThreadLocalRandom.current().nextInt(); // randomize spins
1372	+	else if (spins >= 0) {
1373	+	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1374	+	if (r >= 0)
1375	+	--spins;
1376	+	}
1377	+	else if (U.compareAndSwapInt(this, MAINLOCK, h, h | LOCK_WAITING)) {
1378	+	synchronized (this) {
1379	+	if ((mainLock & LOCK_WAITING) != 0) {
1380	+	try {
1381	+	wait();
1382	+	} catch (InterruptedException ie) {
1383	+	Thread.currentThread().interrupt();
1384	+	}
1385	+	}
1386	+	else
1387	+	notifyAll(); // possibly won race vs signaller
1388	+	}
1389	+	break;
1390	+	}
1391	+	}
1392	+	}
1393	+
1394		//  Creating, registering, and deregistering workers
1395
1396		/**
#	Line 1288 | Line 1417 | public class ForkJoinPool extends Abstra
1417		* ForkJoinWorkerThread.
1418		*/
1419		final String nextWorkerName() {
1420	<	return workerNamePrefix.concat
1421	<	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1420	>	int n;
1421	>	do {} while(!U.compareAndSwapInt(this, NEXTWORKERNUMBER,
1422	>	n = nextWorkerNumber, ++n));
1423	>	return workerNamePrefix.concat(Integer.toString(n));
1424		}
1425
1426		/**
#	Line 1301 | Line 1432 | public class ForkJoinPool extends Abstra
1432		*
1433		* @param w the worker's queue
1434		*/
1304	–
1435		final void registerWorker(WorkQueue w) {
1436	<	Mutex lock = this.lock;
1437	<	lock.lock();
1436	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1437	>	tryAwaitMainLock();
1438		try {
1439	<	WorkQueue[] ws = workQueues;
1440	<	if (w != null && ws != null) {          // skip on shutdown/failure
1441	<	int rs, n = ws.length, m = n - 1;
1439	>	WorkQueue[] ws;
1440	>	if ((ws = workQueues) == null)
1441	>	ws = workQueues = new WorkQueue[submitMask + 1];
1442	>	if (w != null) {
1443	>	int rs, n =  ws.length, m = n - 1;
1444		int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence
1445		w.seed = (s == 0) ? 1 : s;          // ensure non-zero seed
1446		int r = (s << 1) | 1;               // use odd-numbered indices
#	Line 1328 | Line 1460 | public class ForkJoinPool extends Abstra
1460		runState = ((rs = runState) & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN);
1461		}
1462		} finally {
1463	<	lock.unlock();
1463	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1464	>	mainLock = 0;
1465	>	synchronized (this) { notifyAll(); };
1466	>	}
1467		}
1468	+
1469		}
1470
1471		/**
#	Line 1342 | Line 1478 | public class ForkJoinPool extends Abstra
1478		* @param ex the exception causing failure, or null if none
1479		*/
1480		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1345	–	Mutex lock = this.lock;
1481		WorkQueue w = null;
1482		if (wt != null && (w = wt.workQueue) != null) {
1483		w.runState = -1;                // ensure runState is set
1484	<	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1484	>	long steals = w.totalSteals + w.nsteals, sc;
1485	>	do {} while(!U.compareAndSwapLong(this, STEALCOUNT,
1486	>	sc = stealCount, sc + steals));
1487		int idx = w.poolIndex;
1488	<	lock.lock();
1489	<	try {                           // remove record from array
1488	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1489	>	tryAwaitMainLock();
1490	>	try {
1491		WorkQueue[] ws = workQueues;
1492		if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1493		ws[idx] = null;
1494		} finally {
1495	<	lock.unlock();
1495	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1496	>	mainLock = 0;
1497	>	synchronized (this) { notifyAll(); };
1498	>	}
1499		}
1500		}
1501
#	Line 1376 | Line 1517 | public class ForkJoinPool extends Abstra
1517		U.throwException(ex);
1518		}
1519
1379	–
1520		// Submissions
1521
1522		/**
#	Line 1394 | Line 1534 | public class ForkJoinPool extends Abstra
1534		for (int r = s.seed, m = submitMask;;) {
1535		WorkQueue[] ws; WorkQueue q;
1536		int k = r & m & SQMASK;          // use only even indices
1537	<	if (runState < 0 || (ws = workQueues) == null || ws.length <= k)
1537	>	if (runState < 0)
1538		throw new RejectedExecutionException(); // shutting down
1539	+	else if ((ws = workQueues) == null || ws.length <= k) {
1540	+	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1541	+	tryAwaitMainLock();
1542	+	try {
1543	+	if (workQueues == null)
1544	+	workQueues = new WorkQueue[submitMask + 1];
1545	+	} finally {
1546	+	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1547	+	mainLock = 0;
1548	+	synchronized (this) { notifyAll(); };
1549	+	}
1550	+	}
1551	+	}
1552		else if ((q = ws[k]) == null) {  // create new queue
1553		WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE);
1554	<	Mutex lock = this.lock;      // construct outside lock
1555	<	lock.lock();
1556	<	try {                        // recheck under lock
1554	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1555	>	tryAwaitMainLock();
1556	>	try {
1557		int rs = runState;       // to update seq
1558		if (ws == workQueues && ws[k] == null) {
1559		ws[k] = nq;
1560		runState = ((rs & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN));
1561		}
1562		} finally {
1563	<	lock.unlock();
1563	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1564	>	mainLock = 0;
1565	>	synchronized (this) { notifyAll(); };
1566	>	}
1567		}
1568		}
1569		else if (q.trySharedPush(task)) {
#	Line 1424 | Line 1580 | public class ForkJoinPool extends Abstra
1580		}
1581		}
1582
1583	+	/**
1584	+	* Submits the given (non-null) task to the common pool, if possible.
1585	+	*/
1586	+	static void submitToCommonPool(ForkJoinTask<?> task) {
1587	+	ForkJoinPool p;
1588	+	if ((p = commonPool) == null)
1589	+	throw new RejectedExecutionException("Common Pool Unavailable");
1590	+	p.doSubmit(task);
1591	+	}
1592	+
1593	+	/**
1594	+	* Returns true if caller is (or may be) submitter to the common
1595	+	* pool, and not all workers are active, and there appear to be
1596	+	* tasks in the associated submission queue.
1597	+	*/
1598	+	static boolean canHelpCommonPool() {
1599	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
1600	+	int k = submitters.get().seed & SQMASK;
1601	+	return ((p = commonPool) != null &&
1602	+	(int)(p.ctl >> AC_SHIFT) < 0 &&
1603	+	(ws = p.workQueues) != null &&
1604	+	ws.length > (k &= p.submitMask) &&
1605	+	(q = ws[k]) != null &&
1606	+	q.top - q.base > 0);
1607	+	}
1608	+
1609	+	/**
1610	+	* Returns true if the given task was submitted to common pool
1611	+	* and has not yet commenced execution, and is available for
1612	+	* removal according to execution policies; if so removing the
1613	+	* submission from the pool.
1614	+	*
1615	+	* @param task the task
1616	+	* @return true if successful
1617	+	*/
1618	+	static boolean tryUnsubmitFromCommonPool(ForkJoinTask<?> task) {
1619	+	// Peek, looking for task and eligibility before
1620	+	// using trySharedUnpush to actually take it under lock
1621	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
1622	+	ForkJoinTask<?>[] a; int s;
1623	+	int k = submitters.get().seed & SQMASK;
1624	+	return ((p = commonPool) != null &&
1625	+	(int)(p.ctl >> AC_SHIFT) < 0 &&
1626	+	(ws = p.workQueues) != null &&
1627	+	ws.length > (k &= p.submitMask) &&
1628	+	(q = ws[k]) != null &&
1629	+	(a = q.array) != null &&
1630	+	(s = q.top - 1) - q.base >= 0 &&
1631	+	s >= 0 && s < a.length &&
1632	+	a[s] == task &&
1633	+	q.trySharedUnpush(task));
1634	+	}
1635	+
1636	+	/**
1637	+	* Tries to pop a task from common pool with given root
1638	+	*/
1639	+	static ForkJoinTask<?> popCCFromCommonPool(CountedCompleter<?> root) {
1640	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
1641	+	ForkJoinTask<?> t;
1642	+	int k = submitters.get().seed & SQMASK;
1643	+	if (root != null &&
1644	+	(p = commonPool) != null &&
1645	+	(int)(p.ctl >> AC_SHIFT) < 0 &&
1646	+	(ws = p.workQueues) != null &&
1647	+	ws.length > (k &= p.submitMask) &&
1648	+	(q = ws[k]) != null && q.top - q.base > 0 &&
1649	+	root.status < 0 &&
1650	+	(t = q.sharedPopCC(root)) != null)
1651	+	return t;
1652	+	return null;
1653	+	}
1654	+
1655	+
1656		// Maintaining ctl counts
1657
1658		/**
#	Line 1435 | Line 1664 | public class ForkJoinPool extends Abstra
1664		}
1665
1666		/**
1667	<	* Tries to activate or create a worker if too few are active.
1667	>	* Tries to create one or activate one or more workers if too few are active.
1668		*/
1669		final void signalWork() {
1670		long c; int u;
#	Line 1519 | Line 1748 | public class ForkJoinPool extends Abstra
1748		* awaiting signal,
1749		*
1750		* @param w the worker (via its WorkQueue)
1751	<	* @return a task or null of none found
1751	>	* @return a task or null if none found
1752		*/
1753		private final ForkJoinTask<?> scan(WorkQueue w) {
1754		WorkQueue[] ws;                       // first update random seed
#	Line 1536 | Line 1765 | public class ForkJoinPool extends Abstra
1765		t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1766		if (q.base == b && ec >= 0 && t != null &&
1767		U.compareAndSwapObject(a, i, t, null)) {
1768	<	if (q.top - (q.base = b + 1) > 1)
1768	>	if (q.top - (q.base = b + 1) > 0)
1769		signalWork();    // help pushes signal
1770		return t;
1771		}
#	Line 1582 | Line 1811 | public class ForkJoinPool extends Abstra
1811		}
1812		}
1813		else if (w.eventCount < 0) {      // already queued
1814	<	if ((nr = w.rescans) > 0) {   // continue rescanning
1815	<	int ac = a + parallelism;
1816	<	if (((w.rescans = (ac < nr) ? ac : nr - 1) & 3) == 0)
1817	<	Thread.yield();       // yield before block
1589	<	}
1590	<	else {
1814	>	int ac = a + parallelism;
1815	>	if ((nr = w.rescans) > 0)     // continue rescanning
1816	>	w.rescans = (ac < nr) ? ac : nr - 1;
1817	>	else if (((w.seed >>> 16) & ac) == 0) { // randomize park
1818		Thread.interrupted();     // clear status
1819		Thread wt = Thread.currentThread();
1820		U.putObject(wt, PARKBLOCKER, this);
#	Line 1605 | Line 1832 | public class ForkJoinPool extends Abstra
1832		/**
1833		* If inactivating worker w has caused the pool to become
1834		* quiescent, checks for pool termination, and, so long as this is
1835	<	* not the only worker, waits for event for up to SHRINK_RATE
1836	<	* nanosecs.  On timeout, if ctl has not changed, terminates the
1835	>	* not the only worker, waits for event for up to a given
1836	>	* duration.  On timeout, if ctl has not changed, terminates the
1837		* worker, which will in turn wake up another worker to possibly
1838		* repeat this process.
1839		*
#	Line 1617 | Line 1844 | public class ForkJoinPool extends Abstra
1844		private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1845		if (w.eventCount < 0 && !tryTerminate(false, false) &&
1846		(int)prevCtl != 0 && !hasQueuedSubmissions() && ctl == currentCtl) {
1847	+	int dc = -(short)(currentCtl >>> TC_SHIFT);
1848	+	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1849	+	long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop
1850		Thread wt = Thread.currentThread();
1621	–	Thread.yield();            // yield before block
1851		while (ctl == currentCtl) {
1623	–	long startTime = System.nanoTime();
1852		Thread.interrupted();  // timed variant of version in scan()
1853		U.putObject(wt, PARKBLOCKER, this);
1854		w.parker = wt;
1855		if (ctl == currentCtl)
1856	<	U.park(false, SHRINK_RATE);
1856	>	U.park(false, parkTime);
1857		w.parker = null;
1858		U.putObject(wt, PARKBLOCKER, null);
1859		if (ctl != currentCtl)
1860		break;
1861	<	if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
1861	>	if (deadline - System.nanoTime() <= 0L &&
1862		U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1863		w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
1864		w.runState = -1;   // shrink
#	Line 1915 | Line 2143 | public class ForkJoinPool extends Abstra
2143		}
2144		}
2145
1918	–
2146		/**
2147		* Runs tasks until {@code isQuiescent()}. We piggyback on
2148		* active count ctl maintenance, but rather than blocking
#	Line 1958 | Line 2185 | public class ForkJoinPool extends Abstra
2185		}
2186
2187		/**
2188	+	* Restricted version of helpQuiescePool for non-FJ callers
2189	+	*/
2190	+	static void externalHelpQuiescePool() {
2191	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, sq;
2192	+	ForkJoinTask<?>[] a; int b;
2193	+	ForkJoinTask<?> t = null;
2194	+	int k = submitters.get().seed & SQMASK;
2195	+	if ((p = commonPool) != null &&
2196	+	(int)(p.ctl >> AC_SHIFT) < 0 &&
2197	+	(ws = p.workQueues) != null &&
2198	+	ws.length > (k &= p.submitMask) &&
2199	+	(q = ws[k]) != null) {
2200	+	while (q.top - q.base > 0) {
2201	+	if ((t = q.sharedPop()) != null)
2202	+	break;
2203	+	}
2204	+	if (t == null && (sq = p.findNonEmptyStealQueue(q)) != null &&
2205	+	(b = sq.base) - sq.top < 0)
2206	+	t = sq.pollAt(b);
2207	+	if (t != null)
2208	+	t.doExec();
2209	+	}
2210	+	}
2211	+
2212	+	/**
2213		* Gets and removes a local or stolen task for the given worker.
2214		*
2215		* @return a task, if available
#	Line 1990 | Line 2242 | public class ForkJoinPool extends Abstra
2242		8);
2243		}
2244
2245	+	/**
2246	+	* Returns approximate submission queue length for the given caller
2247	+	*/
2248	+	static int getEstimatedSubmitterQueueLength() {
2249	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
2250	+	int k = submitters.get().seed & SQMASK;
2251	+	return ((p = commonPool) != null &&
2252	+	p.runState >= 0 &&
2253	+	(ws = p.workQueues) != null &&
2254	+	ws.length > (k &= p.submitMask) &&
2255	+	(q = ws[k]) != null) ?
2256	+	q.queueSize() : 0;
2257	+	}
2258	+
2259		//  Termination
2260
2261		/**
#	Line 2007 | Line 2273 | public class ForkJoinPool extends Abstra
2273		* @return true if now terminating or terminated
2274		*/
2275		private boolean tryTerminate(boolean now, boolean enable) {
2010	–	Mutex lock = this.lock;
2276		for (long c;;) {
2277		if (((c = ctl) & STOP_BIT) != 0) {      // already terminating
2278		if ((short)(c >>> TC_SHIFT) == -parallelism) {
2279	<	lock.lock();                    // don't need try/finally
2280	<	termination.signalAll();        // signal when 0 workers
2281	<	lock.unlock();
2279	>	synchronized(this) {
2280	>	notifyAll();                // signal when 0 workers
2281	>	}
2282		}
2283		return true;
2284		}
2285		if (runState >= 0) {                    // not yet enabled
2286		if (!enable)
2287		return false;
2288	<	lock.lock();
2289	<	runState |= SHUTDOWN;
2290	<	lock.unlock();
2288	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
2289	>	tryAwaitMainLock();
2290	>	try {
2291	>	runState |= SHUTDOWN;
2292	>	} finally {
2293	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
2294	>	mainLock = 0;
2295	>	synchronized (this) { notifyAll(); };
2296	>	}
2297	>	}
2298		}
2299		if (!now) {                             // check if idle & no tasks
2300		if ((int)(c >> AC_SHIFT) != -parallelism ||
#	Line 2155 | Line 2427 | public class ForkJoinPool extends Abstra
2427		// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2.
2428		int n = parallelism - 1;
2429		n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
2430	<	int size = (n + 1) << 1;        // #slots = 2*#workers
2159	<	this.submitMask = size - 1;     // room for max # of submit queues
2160	<	this.workQueues = new WorkQueue[size];
2161	<	this.termination = (this.lock = new Mutex()).newCondition();
2162	<	this.stealCount = new AtomicLong();
2163	<	this.nextWorkerNumber = new AtomicInteger();
2430	>	this.submitMask = ((n + 1) << 1) - 1;
2431		int pn = poolNumberGenerator.incrementAndGet();
2432		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2433		sb.append(Integer.toString(pn));
2434		sb.append("-worker-");
2435		this.workerNamePrefix = sb.toString();
2169	–	lock.lock();
2436		this.runState = 1;              // set init flag
2437	<	lock.unlock();
2437	>	}
2438	>
2439	>	/**
2440	>	* Constructor for common pool, suitable only for static initialization.
2441	>	* Basically the same as above, but uses smallest possible initial footprint.
2442	>	*/
2443	>	ForkJoinPool(int parallelism, int submitMask,
2444	>	ForkJoinWorkerThreadFactory factory,
2445	>	Thread.UncaughtExceptionHandler handler) {
2446	>	this.factory = factory;
2447	>	this.ueh = handler;
2448	>	this.submitMask = submitMask;
2449	>	this.parallelism = parallelism;
2450	>	long np = (long)(-parallelism);
2451	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
2452	>	this.localMode = LIFO_QUEUE;
2453	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2454	>	this.runState = 1;
2455	>	}
2456	>
2457	>	/**
2458	>	* Returns the common pool instance.
2459	>	*
2460	>	* @return the common pool instance
2461	>	*/
2462	>	public static ForkJoinPool commonPool() {
2463	>	ForkJoinPool p;
2464	>	if ((p = commonPool) == null)
2465	>	throw new Error("Common Pool Unavailable");
2466	>	return p;
2467		}
2468
2469		// Execution methods
#	Line 2344 | Line 2639 | public class ForkJoinPool extends Abstra
2639		}
2640
2641		/**
2642	+	* Returns the targeted parallelism level of the common pool.
2643	+	*
2644	+	* @return the targeted parallelism level of the common pool
2645	+	*/
2646	+	public static int getCommonPoolParallelism() {
2647	+	return commonPoolParallelism;
2648	+	}
2649	+
2650	+	/**
2651		* Returns the number of worker threads that have started but not
2652		* yet terminated.  The result returned by this method may differ
2653		* from {@link #getParallelism} when threads are created to
#	Line 2424 | Line 2728 | public class ForkJoinPool extends Abstra
2728		* @return the number of steals
2729		*/
2730		public long getStealCount() {
2731	<	long count = stealCount.get();
2731	>	long count = stealCount;
2732		WorkQueue[] ws; WorkQueue w;
2733		if ((ws = workQueues) != null) {
2734		for (int i = 1; i < ws.length; i += 2) {
#	Line 2554 | Line 2858 | public class ForkJoinPool extends Abstra
2858		public String toString() {
2859		// Use a single pass through workQueues to collect counts
2860		long qt = 0L, qs = 0L; int rc = 0;
2861	<	long st = stealCount.get();
2861	>	long st = stealCount;
2862		long c = ctl;
2863		WorkQueue[] ws; WorkQueue w;
2864		if ((ws = workQueues) != null) {
#	Line 2595 | Line 2899 | public class ForkJoinPool extends Abstra
2899		}
2900
2901		/**
2902	<	* Initiates an orderly shutdown in which previously submitted
2903	<	* tasks are executed, but no new tasks will be accepted.
2904	<	* Invocation has no additional effect if already shut down.
2905	<	* Tasks that are in the process of being submitted concurrently
2906	<	* during the course of this method may or may not be rejected.
2902	>	* Possibly initiates an orderly shutdown in which previously
2903	>	* submitted tasks are executed, but no new tasks will be
2904	>	* accepted. Invocation has no effect on execution state if this
2905	>	* is the {@link #commonPool}, and no additional effect if
2906	>	* already shut down.  Tasks that are in the process of being
2907	>	* submitted concurrently during the course of this method may or
2908	>	* may not be rejected.
2909		*
2910		* @throws SecurityException if a security manager exists and
2911		*         the caller is not permitted to modify threads
#	Line 2608 | Line 2914 | public class ForkJoinPool extends Abstra
2914		*/
2915		public void shutdown() {
2916		checkPermission();
2917	<	tryTerminate(false, true);
2917	>	if (this != commonPool)
2918	>	tryTerminate(false, true);
2919		}
2920
2921		/**
2922	<	* Attempts to cancel and/or stop all tasks, and reject all
2923	<	* subsequently submitted tasks.  Tasks that are in the process of
2924	<	* being submitted or executed concurrently during the course of
2925	<	* this method may or may not be rejected. This method cancels
2926	<	* both existing and unexecuted tasks, in order to permit
2927	<	* termination in the presence of task dependencies. So the method
2928	<	* always returns an empty list (unlike the case for some other
2929	<	* Executors).
2922	>	* Possibly attempts to cancel and/or stop all tasks, and reject
2923	>	* all subsequently submitted tasks.  Invocation has no effect on
2924	>	* execution state if this is the {@link #commonPool}, and no
2925	>	* additional effect if already shut down. Otherwise, tasks that
2926	>	* are in the process of being submitted or executed concurrently
2927	>	* during the course of this method may or may not be
2928	>	* rejected. This method cancels both existing and unexecuted
2929	>	* tasks, in order to permit termination in the presence of task
2930	>	* dependencies. So the method always returns an empty list
2931	>	* (unlike the case for some other Executors).
2932		*
2933		* @return an empty list
2934		* @throws SecurityException if a security manager exists and
#	Line 2629 | Line 2938 | public class ForkJoinPool extends Abstra
2938		*/
2939		public List<Runnable> shutdownNow() {
2940		checkPermission();
2941	<	tryTerminate(true, true);
2941	>	if (this != commonPool)
2942	>	tryTerminate(true, true);
2943		return Collections.emptyList();
2944		}
2945
#	Line 2686 | Line 2996 | public class ForkJoinPool extends Abstra
2996		public boolean awaitTermination(long timeout, TimeUnit unit)
2997		throws InterruptedException {
2998		long nanos = unit.toNanos(timeout);
2999	<	final Mutex lock = this.lock;
3000	<	lock.lock();
3001	<	try {
3002	<	for (;;) {
3003	<	if (isTerminated())
3004	<	return true;
3005	<	if (nanos <= 0)
3006	<	return false;
3007	<	nanos = termination.awaitNanos(nanos);
2999	>	if (isTerminated())
3000	>	return true;
3001	>	long startTime = System.nanoTime();
3002	>	boolean terminated = false;
3003	>	synchronized(this) {
3004	>	for (long waitTime = nanos, millis = 0L;;) {
3005	>	if (terminated = isTerminated() ||
3006	>	waitTime <= 0L ||
3007	>	(millis = unit.toMillis(waitTime)) <= 0L)
3008	>	break;
3009	>	wait(millis);
3010	>	waitTime = nanos - (System.nanoTime() - startTime);
3011		}
2699	–	} finally {
2700	–	lock.unlock();
3012		}
3013	+	return terminated;
3014		}
3015
3016		/**
#	Line 2830 | Line 3142 | public class ForkJoinPool extends Abstra
3142		private static final long PARKBLOCKER;
3143		private static final int ABASE;
3144		private static final int ASHIFT;
3145	+	private static final long NEXTWORKERNUMBER;
3146	+	private static final long STEALCOUNT;
3147	+	private static final long MAINLOCK;
3148
3149		static {
3150		poolNumberGenerator = new AtomicInteger();
#	Line 2845 | Line 3160 | public class ForkJoinPool extends Abstra
3160		Class<?> ak = ForkJoinTask[].class;
3161		CTL = U.objectFieldOffset
3162		(k.getDeclaredField("ctl"));
3163	+	NEXTWORKERNUMBER = U.objectFieldOffset
3164	+	(k.getDeclaredField("nextWorkerNumber"));
3165	+	STEALCOUNT = U.objectFieldOffset
3166	+	(k.getDeclaredField("stealCount"));
3167	+	MAINLOCK = U.objectFieldOffset
3168	+	(k.getDeclaredField("mainLock"));
3169		Class<?> tk = Thread.class;
3170		PARKBLOCKER = U.objectFieldOffset
3171		(tk.getDeclaredField("parkBlocker"));
3172		ABASE = U.arrayBaseOffset(ak);
3173		s = U.arrayIndexScale(ak);
3174	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3175		} catch (Exception e) {
3176		throw new Error(e);
3177		}
3178		if ((s & (s-1)) != 0)
3179		throw new Error("data type scale not a power of two");
3180	<	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3180	>	try { // Establish common pool
3181	>	String pp = System.getProperty(propPrefix + "parallelism");
3182	>	String fp = System.getProperty(propPrefix + "threadFactory");
3183	>	String up = System.getProperty(propPrefix + "exceptionHandler");
3184	>	ForkJoinWorkerThreadFactory fac = (fp == null) ?
3185	>	defaultForkJoinWorkerThreadFactory :
3186	>	((ForkJoinWorkerThreadFactory)ClassLoader.
3187	>	getSystemClassLoader().loadClass(fp).newInstance());
3188	>	Thread.UncaughtExceptionHandler ueh = (up == null)? null :
3189	>	((Thread.UncaughtExceptionHandler)ClassLoader.
3190	>	getSystemClassLoader().loadClass(up).newInstance());
3191	>	int par;
3192	>	if ((pp == null || (par = Integer.parseInt(pp)) <= 0))
3193	>	par = Runtime.getRuntime().availableProcessors();
3194	>	if (par > MAX_CAP)
3195	>	par = MAX_CAP;
3196	>	commonPoolParallelism = par;
3197	>	int n = par - 1; // precompute submit mask
3198	>	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4;
3199	>	n |= n >>> 8; n |= n >>> 16;
3200	>	int mask = ((n + 1) << 1) - 1;
3201	>	commonPool = new ForkJoinPool(par, mask, fac, ueh);
3202	>	} catch (Exception e) {
3203	>	throw new Error(e);
3204	>	}
3205		}
3206
3207		/**

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