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root/jsr166/jsr166/src/jsr166e/ForkJoinPool.java

Comparing jsr166/src/jsr166e/ForkJoinPool.java (file contents):
Revision 1.7 by dl, Sun Oct 28 22:35:45 2012 UTC vs.
Revision 1.10 by jsr166, Tue Oct 30 16:05:35 2012 UTC

#	Line 44 | Line 44 | import java.util.concurrent.locks.Condit
44		* tasks that are never joined.
45		*
46		* <p>A static {@link #commonPool} is available and appropriate for
47	<	* most applications. The common pool is constructed upon first
48	<	* access, or upon usage by any ForkJoinTask that is not explictly
49	<	* submitted to a specified pool. Using the common pool normally
50	<	* reduces resource usage (its threads are slowly reclaimed during
51	<	* periods of non-use, and reinstated upon subsequent use).  The
52	<	* common pool is by default constructed with default parameters, but
53	<	* these may be controlled by setting any or all of the three
54	<	* properties {@code
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		*
#	Line 237 | 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
249	<	* 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 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 814 | Line 872 | public class ForkJoinPool extends Abstra
872
873		/**
874		* Version of tryUnpush for shared queues; called by non-FJ
875	<	* submitters. Conservatively fails to unpush if all workers
818	<	* are active unless there are multiple tasks in queue.
875	>	* submitters after prechecking that task probably exists.
876		*/
877	<	final boolean trySharedUnpush(ForkJoinTask<?> task, ForkJoinPool p) {
877	>	final boolean trySharedUnpush(ForkJoinTask<?> t) {
878		boolean success = false;
879	<	if (task != null && top != base && runState == 0 &&
823	<	U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
879	>	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
880		try {
881	<	ForkJoinTask<?>[] a; int n, s;
882	<	if ((a = array) != null && (n = (s = top) - base) > 0 &&
883	<	(n > 1 || p == null || (int)(p.ctl >> AC_SHIFT) < 0)) {
884	<	int j = (((a.length - 1) & --s) << ASHIFT) + ABASE;
885	<	if (U.getObjectVolatile(a, j) == task &&
886	<	U.compareAndSwapObject(a, j, task, null)) {
831	<	top = s;
832	<	success = true;
833	<	}
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
#	Line 1113 | 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 1137 | Line 1207 | public class ForkJoinPool extends Abstra
1207		*/
1208		private static final ThreadSubmitter submitters;
1209
1140	–	/** Common default pool */
1141	–	static volatile ForkJoinPool commonPool;
1142	–
1143	–	// commonPool construction parameters
1144	–	private static final String propPrefix =
1145	–	"java.util.concurrent.ForkJoinPool.common.";
1146	–	private static final Thread.UncaughtExceptionHandler commonPoolUEH;
1147	–	private static final ForkJoinWorkerThreadFactory commonPoolFactory;
1148	–	static final int commonPoolParallelism;
1149	–
1150	–	/** Static initialization lock */
1151	–	private static final Mutex initializationLock;
1152	–
1210		// static constants
1211
1212		/**
1213	<	* Initial timeout value (in nanoseconds) for the tread triggering
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		*/
#	Line 1282 | 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
1292	–	final Mutex lock;                          // for registration
1293	–	final Condition termination;               // for awaitTermination
1352		final ForkJoinWorkerThreadFactory factory; // factory for new workers
1353		final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1354	<	final AtomicLong stealCount;               // collect counts when terminated
1355	<	final AtomicInteger nextWorkerNumber;      // to create worker name string
1356	<	String workerNamePrefix;                   // 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
#	Line 1323 | 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 1337 | Line 1433 | public class ForkJoinPool extends Abstra
1433		* @param w the worker's queue
1434		*/
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
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
#	Line 1362 | 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 1376 | 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) {
1379	–	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 1427 | 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 1463 | Line 1586 | public class ForkJoinPool extends Abstra
1586		static void submitToCommonPool(ForkJoinTask<?> task) {
1587		ForkJoinPool p;
1588		if ((p = commonPool) == null)
1589	<	p = ensureCommonPool();
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
#	Line 1477 | Line 1616 | public class ForkJoinPool extends Abstra
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	<	q.trySharedUnpush(task, p));
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 1957 | Line 2124 | public class ForkJoinPool extends Abstra
2124		*/
2125		private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
2126		// Similar to loop in scan(), but ignoring submissions
2127	<	int r;
1961	<	if (w == null) // allow external callers
1962	<	r = ThreadLocalRandom.current().nextInt();
1963	<	else {
1964	<	r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1965	<	}
2127	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
2128		int step = (r >>> 16) | 1;
2129		for (WorkQueue[] ws;;) {
2130		int rs = runState, m;
#	Line 2026 | Line 2188 | public class ForkJoinPool extends Abstra
2188		* Restricted version of helpQuiescePool for non-FJ callers
2189		*/
2190		static void externalHelpQuiescePool() {
2191	<	ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q;
2192	<	ForkJoinTask<?> t; int b;
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	<	(w = ws[k]) != null &&
2200	<	(q = p.findNonEmptyStealQueue(w)) != null &&
2201	<	(b = q.base) - q.top < 0 &&
2202	<	(t = q.pollAt(b)) != null)
2203	<	t.doExec();
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		/**
#	Line 2103 | Line 2273 | public class ForkJoinPool extends Abstra
2273		* @return true if now terminating or terminated
2274		*/
2275		private boolean tryTerminate(boolean now, boolean enable) {
2106	–	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 2251 | 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
2255	<	this.submitMask = size - 1;     // room for max # of submit queues
2256	<	this.workQueues = new WorkQueue[size];
2257	<	this.termination = (this.lock = new Mutex()).newCondition();
2258	<	this.stealCount = new AtomicLong();
2259	<	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();
2265	–	lock.lock();
2436		this.runState = 1;              // set init flag
2267	–	lock.unlock();
2437		}
2438
2439		/**
2440	<	* Returns the common pool instance
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	<	return (p = commonPool) != null? p : ensureCommonPool();
2465	<	}
2279	<
2280	<	private static ForkJoinPool ensureCommonPool() {
2281	<	ForkJoinPool p;
2282	<	if ((p = commonPool) == null) {
2283	<	final Mutex lock = initializationLock;
2284	<	lock.lock();
2285	<	try {
2286	<	if ((p = commonPool) == null) {
2287	<	p = commonPool = new ForkJoinPool(commonPoolParallelism,
2288	<	commonPoolFactory,
2289	<	commonPoolUEH, false);
2290	<	// use a more informative name string for workers
2291	<	p.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2292	<	}
2293	<	} finally {
2294	<	lock.unlock();
2295	<	}
2296	<	}
2464	>	if ((p = commonPool) == null)
2465	>	throw new Error("Common Pool Unavailable");
2466		return p;
2467		}
2468
#	Line 2559 | 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 2689 | 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 2827 | 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		}
2840	–	} finally {
2841	–	lock.unlock();
3012		}
3013	+	return terminated;
3014		}
3015
3016		/**
#	Line 2971 | 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 2979 | Line 3153 | public class ForkJoinPool extends Abstra
3153		defaultForkJoinWorkerThreadFactory =
3154		new DefaultForkJoinWorkerThreadFactory();
3155		submitters = new ThreadSubmitter();
2982	–	initializationLock = new Mutex();
3156		int s;
3157		try {
3158		U = getUnsafe();
#	Line 2987 | 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);
3001	<
3002	<	// Establish configuration for default pool
3003	<	try {
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	<	if (fp != null)
3198	<	commonPoolFactory = (ForkJoinWorkerThreadFactory)
3199	<	ClassLoader.getSystemClassLoader().loadClass(fp).newInstance();
3200	<	else
3201	<	commonPoolFactory = defaultForkJoinWorkerThreadFactory;
3016	<	if (up != null)
3017	<	commonPoolUEH = (Thread.UncaughtExceptionHandler)
3018	<	ClassLoader.getSystemClassLoader().loadClass(up).newInstance();
3019	<	else
3020	<	commonPoolUEH = null;
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		}

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