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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.135 by dl, Sun Oct 28 22:36:01 2012 UTC vs.
Revision 1.137 by dl, Tue Oct 30 14:23:11 2012 UTC

#	Line 43 | Line 43 | import java.util.concurrent.locks.Condit
43		* tasks that are never joined.
44		*
45		* <p>A static {@link #commonPool} is available and appropriate for
46	<	* most applications. The common pool is constructed upon first
47	<	* access, or upon usage by any ForkJoinTask that is not explictly
48	<	* submitted to a specified pool. Using the common pool normally
49	<	* reduces resource usage (its threads are slowly reclaimed during
50	<	* periods of non-use, and reinstated upon subsequent use).  The
51	<	* common pool is by default constructed with default parameters, but
52	<	* these may be controlled by setting any or all of the three
53	<	* properties {@code
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		*
#	Line 236 | 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
248	<	* 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 503 | Line 501 | public class ForkJoinPool extends Abstra
501		}
502
503		/**
506	–	* A simple non-reentrant lock used for exclusion when managing
507	–	* queues and workers. We use a custom lock so that we can readily
508	–	* probe lock state in constructions that check among alternative
509	–	* actions. The lock is normally only very briefly held, and
510	–	* sometimes treated as a spinlock, but other usages block to
511	–	* reduce overall contention in those cases where locked code
512	–	* bodies perform allocation/resizing.
513	–	*/
514	–	static final class Mutex extends AbstractQueuedSynchronizer {
515	–	public final boolean tryAcquire(int ignore) {
516	–	return compareAndSetState(0, 1);
517	–	}
518	–	public final boolean tryRelease(int ignore) {
519	–	setState(0);
520	–	return true;
521	–	}
522	–	public final void lock() { acquire(0); }
523	–	public final void unlock() { release(0); }
524	–	public final boolean isHeldExclusively() { return getState() == 1; }
525	–	public final Condition newCondition() { return new ConditionObject(); }
526	–	}
527	–
528	–	/**
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 716 | 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
720	<	* version of this method because it is never needed.)
694	>	* by owner in unshared queues.
695		*/
696		final ForkJoinTask<?> pop() {
697		ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
#	Line 735 | 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	+	* Version of pop that takes top element only if it
740	+	* its root is the given CountedCompleter.
741	+	*/
742	+	final ForkJoinTask<?> popCC(CountedCompleter<?> root) {
743	+	ForkJoinTask<?>[] a; int m;
744	+	if (root != null && (a = array) != null && (m = a.length - 1) >= 0) {
745	+	for (int s; (s = top - 1) - base >= 0;) {
746	+	long j = ((m & s) << ASHIFT) + ABASE;
747	+	ForkJoinTask<?> t =
748	+	(ForkJoinTask<?>)U.getObject(a, j);
749	+	if (t == null || !(t instanceof CountedCompleter) ||
750	+	((CountedCompleter<?>)t).getRoot() != root)
751	+	break;
752	+	if (U.compareAndSwapObject(a, j, t, null)) {
753	+	top = s;
754	+	return t;
755	+	}
756	+	if (root.status < 0)
757	+	break;
758	+	}
759	+	}
760	+	return null;
761	+	}
762	+
763	+	/**
764	+	* Shared version of popCC
765	+	*/
766	+	final ForkJoinTask<?> sharedPopCC(CountedCompleter<?> root) {
767	+	ForkJoinTask<?> task = null;
768	+	if (root != null &&
769	+	runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
770	+	try {
771	+	ForkJoinTask<?>[] a; int m;
772	+	if ((a = array) != null && (m = a.length - 1) >= 0) {
773	+	for (int s; (s = top - 1) - base >= 0;) {
774	+	long j = ((m & s) << ASHIFT) + ABASE;
775	+	ForkJoinTask<?> t =
776	+	(ForkJoinTask<?>)U.getObject(a, j);
777	+	if (t == null || !(t instanceof CountedCompleter) ||
778	+	((CountedCompleter<?>)t).getRoot() != root)
779	+	break;
780	+	if (U.compareAndSwapObject(a, j, t, null)) {
781	+	top = s;
782	+	task = t;
783	+	break;
784	+	}
785	+	if (root.status < 0)
786	+	break;
787	+	}
788	+	}
789	+	} finally {
790	+	runState = 0;
791	+	}
792	+	}
793	+	return task;
794	+	}
795	+
796		/**
797		* Takes a task in FIFO order if b is base of queue and a task
798		* can be claimed without contention. Specialized versions
#	Line 813 | Line 871 | public class ForkJoinPool extends Abstra
871
872		/**
873		* Version of tryUnpush for shared queues; called by non-FJ
874	<	* submitters. Conservatively fails to unpush if all workers
817	<	* are active unless there are multiple tasks in queue.
874	>	* submitters after prechecking that task probably exists.
875		*/
876	<	final boolean trySharedUnpush(ForkJoinTask<?> task, ForkJoinPool p) {
876	>	final boolean trySharedUnpush(ForkJoinTask<?> t) {
877		boolean success = false;
878	<	if (task != null && top != base && runState == 0 &&
822	<	U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
878	>	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
879		try {
880	<	ForkJoinTask<?>[] a; int n, s;
881	<	if ((a = array) != null && (n = (s = top) - base) > 0 &&
882	<	(n > 1 || p == null || (int)(p.ctl >> AC_SHIFT) < 0)) {
883	<	int j = (((a.length - 1) & --s) << ASHIFT) + ABASE;
884	<	if (U.getObjectVolatile(a, j) == task &&
885	<	U.compareAndSwapObject(a, j, task, null)) {
830	<	top = s;
831	<	success = true;
832	<	}
880	>	ForkJoinTask<?>[] a; int s;
881	>	if ((a = array) != null && (s = top) != base &&
882	>	U.compareAndSwapObject
883	>	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
884	>	top = s;
885	>	success = true;
886		}
887		} finally {
888		runState = 0;                         // unlock
#	Line 1112 | Line 1165 | public class ForkJoinPool extends Abstra
1165		public static final ForkJoinWorkerThreadFactory
1166		defaultForkJoinWorkerThreadFactory;
1167
1168	+
1169	+	/** Property prefix for constructing common pool */
1170	+	private static final String propPrefix =
1171	+	"java.util.concurrent.ForkJoinPool.common.";
1172	+
1173	+	/**
1174	+	* Common (static) pool. Non-null for public use unless a static
1175	+	* construction exception, but internal usages must null-check on
1176	+	* use.
1177	+	*/
1178	+	static final ForkJoinPool commonPool;
1179	+
1180	+	/**
1181	+	* Common pool parallelism. Must equal commonPool.parallelism.
1182	+	*/
1183	+	static final int commonPoolParallelism;
1184	+
1185		/**
1186		* Generator for assigning sequence numbers as pool names.
1187		*/
#	Line 1136 | Line 1206 | public class ForkJoinPool extends Abstra
1206		*/
1207		private static final ThreadSubmitter submitters;
1208
1139	–	/** Common default pool */
1140	–	static volatile ForkJoinPool commonPool;
1141	–
1142	–	// commonPool construction parameters
1143	–	private static final String propPrefix =
1144	–	"java.util.concurrent.ForkJoinPool.common.";
1145	–	private static final Thread.UncaughtExceptionHandler commonPoolUEH;
1146	–	private static final ForkJoinWorkerThreadFactory commonPoolFactory;
1147	–	static final int commonPoolParallelism;
1148	–
1149	–	/** Static initialization lock */
1150	–	private static final Mutex initializationLock;
1151	–
1209		// static constants
1210
1211		/**
1212	<	* Initial timeout value (in nanoseconds) for the tread triggering
1212	>	* Initial timeout value (in nanoseconds) for the thread triggering
1213		* quiescence to park waiting for new work. On timeout, the thread
1214		* will instead try to shrink the number of workers.
1215		*/
#	Line 1281 | Line 1338 | public class ForkJoinPool extends Abstra
1338		* empirically works OK on current JVMs.
1339		*/
1340
1341	+	volatile long stealCount;                  // collects worker counts
1342		volatile long ctl;                         // main pool control
1343		final int parallelism;                     // parallelism level
1344		final int localMode;                       // per-worker scheduling mode
1345	+	volatile int nextWorkerNumber;             // to create worker name string
1346		final int submitMask;                      // submit queue index bound
1347		int nextSeed;                              // for initializing worker seeds
1348	+	volatile int mainLock;                     // spinlock for array updates
1349		volatile int runState;                     // shutdown status and seq
1350		WorkQueue[] workQueues;                    // main registry
1291	–	final Mutex lock;                          // for registration
1292	–	final Condition termination;               // for awaitTermination
1351		final ForkJoinWorkerThreadFactory factory; // factory for new workers
1352		final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1353	<	final AtomicLong stealCount;               // collect counts when terminated
1354	<	final AtomicInteger nextWorkerNumber;      // to create worker name string
1355	<	String workerNamePrefix;                   // to create worker name string
1353	>	final String workerNamePrefix;             // to create worker name string
1354	>
1355	>	/*
1356	>	* Mechanics for main lock protecting worker array updates.  Uses
1357	>	* the same strategy as ConcurrentHashMap bins -- a spinLock for
1358	>	* normal cases, but falling back to builtin lock when (rarely)
1359	>	* needed.  See internal ConcurrentHashMap documentation for
1360	>	* explanation.
1361	>	*/
1362	>
1363	>	static final int LOCK_WAITING = 2; // bit to indicate need for signal
1364	>	static final int MAX_LOCK_SPINS = 1 << 8;
1365	>
1366	>	private void tryAwaitMainLock() {
1367	>	int spins = MAX_LOCK_SPINS, r = 0, h;
1368	>	while (((h = mainLock) & 1) != 0) {
1369	>	if (r == 0)
1370	>	r = ThreadLocalRandom.current().nextInt(); // randomize spins
1371	>	else if (spins >= 0) {
1372	>	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1373	>	if (r >= 0)
1374	>	--spins;
1375	>	}
1376	>	else if (U.compareAndSwapInt(this, MAINLOCK, h, h | LOCK_WAITING)) {
1377	>	synchronized (this) {
1378	>	if ((mainLock & LOCK_WAITING) != 0) {
1379	>	try {
1380	>	wait();
1381	>	} catch (InterruptedException ie) {
1382	>	Thread.currentThread().interrupt();
1383	>	}
1384	>	}
1385	>	else
1386	>	notifyAll(); // possibly won race vs signaller
1387	>	}
1388	>	break;
1389	>	}
1390	>	}
1391	>	}
1392
1393		//  Creating, registering, and deregistering workers
1394
#	Line 1322 | Line 1416 | public class ForkJoinPool extends Abstra
1416		* ForkJoinWorkerThread.
1417		*/
1418		final String nextWorkerName() {
1419	<	return workerNamePrefix.concat
1420	<	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1419	>	int n;
1420	>	do {} while(!U.compareAndSwapInt(this, NEXTWORKERNUMBER,
1421	>	n = nextWorkerNumber, ++n));
1422	>	return workerNamePrefix.concat(Integer.toString(n));
1423		}
1424
1425		/**
#	Line 1336 | Line 1432 | public class ForkJoinPool extends Abstra
1432		* @param w the worker's queue
1433		*/
1434		final void registerWorker(WorkQueue w) {
1435	<	Mutex lock = this.lock;
1436	<	lock.lock();
1435	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1436	>	tryAwaitMainLock();
1437		try {
1438	<	WorkQueue[] ws = workQueues;
1439	<	if (w != null && ws != null) {          // skip on shutdown/failure
1440	<	int rs, n = ws.length, m = n - 1;
1438	>	WorkQueue[] ws;
1439	>	if ((ws = workQueues) == null)
1440	>	ws = workQueues = new WorkQueue[submitMask + 1];
1441	>	if (w != null) {
1442	>	int rs, n =  ws.length, m = n - 1;
1443		int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence
1444		w.seed = (s == 0) ? 1 : s;          // ensure non-zero seed
1445		int r = (s << 1) | 1;               // use odd-numbered indices
#	Line 1361 | Line 1459 | public class ForkJoinPool extends Abstra
1459		runState = ((rs = runState) & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN);
1460		}
1461		} finally {
1462	<	lock.unlock();
1462	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1463	>	mainLock = 0;
1464	>	synchronized (this) { notifyAll(); };
1465	>	}
1466		}
1467	+
1468		}
1469
1470		/**
#	Line 1375 | Line 1477 | public class ForkJoinPool extends Abstra
1477		* @param ex the exception causing failure, or null if none
1478		*/
1479		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1378	–	Mutex lock = this.lock;
1480		WorkQueue w = null;
1481		if (wt != null && (w = wt.workQueue) != null) {
1482		w.runState = -1;                // ensure runState is set
1483	<	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1483	>	long steals = w.totalSteals + w.nsteals, sc;
1484	>	do {} while(!U.compareAndSwapLong(this, STEALCOUNT,
1485	>	sc = stealCount, sc + steals));
1486		int idx = w.poolIndex;
1487	<	lock.lock();
1488	<	try {                           // remove record from array
1487	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1488	>	tryAwaitMainLock();
1489	>	try {
1490		WorkQueue[] ws = workQueues;
1491		if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1492		ws[idx] = null;
1493		} finally {
1494	<	lock.unlock();
1494	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1495	>	mainLock = 0;
1496	>	synchronized (this) { notifyAll(); };
1497	>	}
1498		}
1499		}
1500
#	Line 1426 | Line 1533 | public class ForkJoinPool extends Abstra
1533		for (int r = s.seed, m = submitMask;;) {
1534		WorkQueue[] ws; WorkQueue q;
1535		int k = r & m & SQMASK;          // use only even indices
1536	<	if (runState < 0 || (ws = workQueues) == null || ws.length <= k)
1536	>	if (runState < 0)
1537		throw new RejectedExecutionException(); // shutting down
1538	+	else if ((ws = workQueues) == null || ws.length <= k) {
1539	+	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1540	+	tryAwaitMainLock();
1541	+	try {
1542	+	if (workQueues == null)
1543	+	workQueues = new WorkQueue[submitMask + 1];
1544	+	} finally {
1545	+	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1546	+	mainLock = 0;
1547	+	synchronized (this) { notifyAll(); };
1548	+	}
1549	+	}
1550	+	}
1551		else if ((q = ws[k]) == null) {  // create new queue
1552		WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE);
1553	<	Mutex lock = this.lock;      // construct outside lock
1554	<	lock.lock();
1555	<	try {                        // recheck under lock
1553	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1554	>	tryAwaitMainLock();
1555	>	try {
1556		int rs = runState;       // to update seq
1557		if (ws == workQueues && ws[k] == null) {
1558		ws[k] = nq;
1559		runState = ((rs & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN));
1560		}
1561		} finally {
1562	<	lock.unlock();
1562	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1563	>	mainLock = 0;
1564	>	synchronized (this) { notifyAll(); };
1565	>	}
1566		}
1567		}
1568		else if (q.trySharedPush(task)) {
#	Line 1462 | Line 1585 | public class ForkJoinPool extends Abstra
1585		static void submitToCommonPool(ForkJoinTask<?> task) {
1586		ForkJoinPool p;
1587		if ((p = commonPool) == null)
1588	<	p = ensureCommonPool();
1588	>	throw new RejectedExecutionException("Common Pool Unavailable");
1589		p.doSubmit(task);
1590		}
1591
1592		/**
1593	+	* Returns true if caller is (or may be) submitter to the common
1594	+	* pool, and not all workers are active, and there appear to be
1595	+	* tasks in the associated submission queue.
1596	+	*/
1597	+	static boolean canHelpCommonPool() {
1598	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
1599	+	int k = submitters.get().seed & SQMASK;
1600	+	return ((p = commonPool) != null &&
1601	+	(int)(p.ctl >> AC_SHIFT) < 0 &&
1602	+	(ws = p.workQueues) != null &&
1603	+	ws.length > (k &= p.submitMask) &&
1604	+	(q = ws[k]) != null &&
1605	+	q.top - q.base > 0);
1606	+	}
1607	+
1608	+	/**
1609		* Returns true if the given task was submitted to common pool
1610		* and has not yet commenced execution, and is available for
1611		* removal according to execution policies; if so removing the
#	Line 1476 | Line 1615 | public class ForkJoinPool extends Abstra
1615		* @return true if successful
1616		*/
1617		static boolean tryUnsubmitFromCommonPool(ForkJoinTask<?> task) {
1618	+	// Peek, looking for task and eligibility before
1619	+	// using trySharedUnpush to actually take it under lock
1620		ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
1621	+	ForkJoinTask<?>[] a; int s;
1622		int k = submitters.get().seed & SQMASK;
1623		return ((p = commonPool) != null &&
1624	+	(int)(p.ctl >> AC_SHIFT) < 0 &&
1625		(ws = p.workQueues) != null &&
1626		ws.length > (k &= p.submitMask) &&
1627		(q = ws[k]) != null &&
1628	<	q.trySharedUnpush(task, p));
1628	>	(a = q.array) != null &&
1629	>	(s = q.top - 1) - q.base >= 0 &&
1630	>	s >= 0 && s < a.length &&
1631	>	a[s] == task &&
1632	>	q.trySharedUnpush(task));
1633		}
1634
1635	+	/**
1636	+	* Tries to pop a task from common pool with given root
1637	+	*/
1638	+	static ForkJoinTask<?> popCCFromCommonPool(CountedCompleter<?> root) {
1639	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
1640	+	ForkJoinTask<?> t;
1641	+	int k = submitters.get().seed & SQMASK;
1642	+	if (root != null &&
1643	+	(p = commonPool) != null &&
1644	+	(int)(p.ctl >> AC_SHIFT) < 0 &&
1645	+	(ws = p.workQueues) != null &&
1646	+	ws.length > (k &= p.submitMask) &&
1647	+	(q = ws[k]) != null && q.top - q.base > 0 &&
1648	+	root.status < 0 &&
1649	+	(t = q.sharedPopCC(root)) != null)
1650	+	return t;
1651	+	return null;
1652	+	}
1653	+
1654	+
1655		// Maintaining ctl counts
1656
1657		/**
#	Line 1956 | Line 2123 | public class ForkJoinPool extends Abstra
2123		*/
2124		private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
2125		// Similar to loop in scan(), but ignoring submissions
2126	<	int r;
1960	<	if (w == null) // allow external callers
1961	<	r = ThreadLocalRandom.current().nextInt();
1962	<	else {
1963	<	r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
1964	<	}
2126	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
2127		int step = (r >>> 16) | 1;
2128		for (WorkQueue[] ws;;) {
2129		int rs = runState, m;
#	Line 2025 | Line 2187 | public class ForkJoinPool extends Abstra
2187		* Restricted version of helpQuiescePool for non-FJ callers
2188		*/
2189		static void externalHelpQuiescePool() {
2190	<	ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q;
2191	<	ForkJoinTask<?> t; int b;
2190	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, sq;
2191	>	ForkJoinTask<?>[] a; int b;
2192	>	ForkJoinTask<?> t = null;
2193		int k = submitters.get().seed & SQMASK;
2194		if ((p = commonPool) != null &&
2195	+	(int)(p.ctl >> AC_SHIFT) < 0 &&
2196		(ws = p.workQueues) != null &&
2197		ws.length > (k &= p.submitMask) &&
2198	<	(w = ws[k]) != null &&
2199	<	(q = p.findNonEmptyStealQueue(w)) != null &&
2200	<	(b = q.base) - q.top < 0 &&
2201	<	(t = q.pollAt(b)) != null)
2202	<	t.doExec();
2198	>	(q = ws[k]) != null) {
2199	>	while (q.top - q.base > 0) {
2200	>	if ((t = q.sharedPop()) != null)
2201	>	break;
2202	>	}
2203	>	if (t == null && (sq = p.findNonEmptyStealQueue(q)) != null &&
2204	>	(b = sq.base) - sq.top < 0)
2205	>	t = sq.pollAt(b);
2206	>	if (t != null)
2207	>	t.doExec();
2208	>	}
2209		}
2210
2211		/**
#	Line 2102 | Line 2272 | public class ForkJoinPool extends Abstra
2272		* @return true if now terminating or terminated
2273		*/
2274		private boolean tryTerminate(boolean now, boolean enable) {
2105	–	Mutex lock = this.lock;
2275		for (long c;;) {
2276		if (((c = ctl) & STOP_BIT) != 0) {      // already terminating
2277		if ((short)(c >>> TC_SHIFT) == -parallelism) {
2278	<	lock.lock();                    // don't need try/finally
2279	<	termination.signalAll();        // signal when 0 workers
2280	<	lock.unlock();
2278	>	synchronized(this) {
2279	>	notifyAll();                // signal when 0 workers
2280	>	}
2281		}
2282		return true;
2283		}
2284		if (runState >= 0) {                    // not yet enabled
2285		if (!enable)
2286		return false;
2287	<	lock.lock();
2288	<	runState |= SHUTDOWN;
2289	<	lock.unlock();
2287	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
2288	>	tryAwaitMainLock();
2289	>	try {
2290	>	runState |= SHUTDOWN;
2291	>	} finally {
2292	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
2293	>	mainLock = 0;
2294	>	synchronized (this) { notifyAll(); };
2295	>	}
2296	>	}
2297		}
2298		if (!now) {                             // check if idle & no tasks
2299		if ((int)(c >> AC_SHIFT) != -parallelism ||
#	Line 2250 | Line 2426 | public class ForkJoinPool extends Abstra
2426		// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2.
2427		int n = parallelism - 1;
2428		n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
2429	<	int size = (n + 1) << 1;        // #slots = 2*#workers
2254	<	this.submitMask = size - 1;     // room for max # of submit queues
2255	<	this.workQueues = new WorkQueue[size];
2256	<	this.termination = (this.lock = new Mutex()).newCondition();
2257	<	this.stealCount = new AtomicLong();
2258	<	this.nextWorkerNumber = new AtomicInteger();
2429	>	this.submitMask = ((n + 1) << 1) - 1;
2430		int pn = poolNumberGenerator.incrementAndGet();
2431		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2432		sb.append(Integer.toString(pn));
2433		sb.append("-worker-");
2434		this.workerNamePrefix = sb.toString();
2264	–	lock.lock();
2435		this.runState = 1;              // set init flag
2266	–	lock.unlock();
2436		}
2437
2438		/**
2439	<	* Returns the common pool instance
2439	>	* Constructor for common pool, suitable only for static initialization.
2440	>	* Basically the same as above, but uses smallest possible initial footprint.
2441	>	*/
2442	>	ForkJoinPool(int parallelism, int submitMask,
2443	>	ForkJoinWorkerThreadFactory factory,
2444	>	Thread.UncaughtExceptionHandler handler) {
2445	>	this.factory = factory;
2446	>	this.ueh = handler;
2447	>	this.submitMask = submitMask;
2448	>	this.parallelism = parallelism;
2449	>	long np = (long)(-parallelism);
2450	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
2451	>	this.localMode = LIFO_QUEUE;
2452	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2453	>	this.runState = 1;
2454	>	}
2455	>
2456	>	/**
2457	>	* Returns the common pool instance.
2458		*
2459		* @return the common pool instance
2460		*/
2461		public static ForkJoinPool commonPool() {
2462		ForkJoinPool p;
2463	<	return (p = commonPool) != null? p : ensureCommonPool();
2464	<	}
2278	<
2279	<	private static ForkJoinPool ensureCommonPool() {
2280	<	ForkJoinPool p;
2281	<	if ((p = commonPool) == null) {
2282	<	final Mutex lock = initializationLock;
2283	<	lock.lock();
2284	<	try {
2285	<	if ((p = commonPool) == null) {
2286	<	p = commonPool = new ForkJoinPool(commonPoolParallelism,
2287	<	commonPoolFactory,
2288	<	commonPoolUEH, false);
2289	<	// use a more informative name string for workers
2290	<	p.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2291	<	}
2292	<	} finally {
2293	<	lock.unlock();
2294	<	}
2295	<	}
2463	>	if ((p = commonPool) == null)
2464	>	throw new Error("Common Pool Unavailable");
2465		return p;
2466		}
2467
#	Line 2558 | Line 2727 | public class ForkJoinPool extends Abstra
2727		* @return the number of steals
2728		*/
2729		public long getStealCount() {
2730	<	long count = stealCount.get();
2730	>	long count = stealCount;
2731		WorkQueue[] ws; WorkQueue w;
2732		if ((ws = workQueues) != null) {
2733		for (int i = 1; i < ws.length; i += 2) {
#	Line 2688 | Line 2857 | public class ForkJoinPool extends Abstra
2857		public String toString() {
2858		// Use a single pass through workQueues to collect counts
2859		long qt = 0L, qs = 0L; int rc = 0;
2860	<	long st = stealCount.get();
2860	>	long st = stealCount;
2861		long c = ctl;
2862		WorkQueue[] ws; WorkQueue w;
2863		if ((ws = workQueues) != null) {
#	Line 2826 | Line 2995 | public class ForkJoinPool extends Abstra
2995		public boolean awaitTermination(long timeout, TimeUnit unit)
2996		throws InterruptedException {
2997		long nanos = unit.toNanos(timeout);
2998	<	final Mutex lock = this.lock;
2999	<	lock.lock();
3000	<	try {
3001	<	for (;;) {
3002	<	if (isTerminated())
3003	<	return true;
3004	<	if (nanos <= 0)
3005	<	return false;
3006	<	nanos = termination.awaitNanos(nanos);
2998	>	if (isTerminated())
2999	>	return true;
3000	>	long startTime = System.nanoTime();
3001	>	boolean terminated = false;
3002	>	synchronized(this) {
3003	>	for (long waitTime = nanos, millis = 0L;;) {
3004	>	if (terminated = isTerminated() ||
3005	>	waitTime <= 0L ||
3006	>	(millis = unit.toMillis(waitTime)) <= 0L)
3007	>	break;
3008	>	wait(millis);
3009	>	waitTime = nanos - (System.nanoTime() - startTime);
3010		}
2839	–	} finally {
2840	–	lock.unlock();
3011		}
3012	+	return terminated;
3013		}
3014
3015		/**
#	Line 2970 | Line 3141 | public class ForkJoinPool extends Abstra
3141		private static final long PARKBLOCKER;
3142		private static final int ABASE;
3143		private static final int ASHIFT;
3144	+	private static final long NEXTWORKERNUMBER;
3145	+	private static final long STEALCOUNT;
3146	+	private static final long MAINLOCK;
3147
3148		static {
3149		poolNumberGenerator = new AtomicInteger();
#	Line 2978 | Line 3152 | public class ForkJoinPool extends Abstra
3152		defaultForkJoinWorkerThreadFactory =
3153		new DefaultForkJoinWorkerThreadFactory();
3154		submitters = new ThreadSubmitter();
2981	–	initializationLock = new Mutex();
3155		int s;
3156		try {
3157		U = getUnsafe();
#	Line 2986 | Line 3159 | public class ForkJoinPool extends Abstra
3159		Class<?> ak = ForkJoinTask[].class;
3160		CTL = U.objectFieldOffset
3161		(k.getDeclaredField("ctl"));
3162	+	NEXTWORKERNUMBER = U.objectFieldOffset
3163	+	(k.getDeclaredField("nextWorkerNumber"));
3164	+	STEALCOUNT = U.objectFieldOffset
3165	+	(k.getDeclaredField("stealCount"));
3166	+	MAINLOCK = U.objectFieldOffset
3167	+	(k.getDeclaredField("mainLock"));
3168		Class<?> tk = Thread.class;
3169		PARKBLOCKER = U.objectFieldOffset
3170		(tk.getDeclaredField("parkBlocker"));
3171		ABASE = U.arrayBaseOffset(ak);
3172		s = U.arrayIndexScale(ak);
3173	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3174		} catch (Exception e) {
3175		throw new Error(e);
3176		}
3177		if ((s & (s-1)) != 0)
3178		throw new Error("data type scale not a power of two");
3179	<	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3000	<
3001	<	// Establish configuration for default pool
3002	<	try {
3179	>	try { // Establish common pool
3180		String pp = System.getProperty(propPrefix + "parallelism");
3181		String fp = System.getProperty(propPrefix + "threadFactory");
3182		String up = System.getProperty(propPrefix + "exceptionHandler");
3183	+	ForkJoinWorkerThreadFactory fac = (fp == null) ?
3184	+	defaultForkJoinWorkerThreadFactory :
3185	+	((ForkJoinWorkerThreadFactory)ClassLoader.
3186	+	getSystemClassLoader().loadClass(fp).newInstance());
3187	+	Thread.UncaughtExceptionHandler ueh = (up == null)? null :
3188	+	((Thread.UncaughtExceptionHandler)ClassLoader.
3189	+	getSystemClassLoader().loadClass(up).newInstance());
3190		int par;
3191		if ((pp == null || (par = Integer.parseInt(pp)) <= 0))
3192		par = Runtime.getRuntime().availableProcessors();
3193	+	if (par > MAX_CAP)
3194	+	par = MAX_CAP;
3195		commonPoolParallelism = par;
3196	<	if (fp != null)
3197	<	commonPoolFactory = (ForkJoinWorkerThreadFactory)
3198	<	ClassLoader.getSystemClassLoader().loadClass(fp).newInstance();
3199	<	else
3200	<	commonPoolFactory = defaultForkJoinWorkerThreadFactory;
3015	<	if (up != null)
3016	<	commonPoolUEH = (Thread.UncaughtExceptionHandler)
3017	<	ClassLoader.getSystemClassLoader().loadClass(up).newInstance();
3018	<	else
3019	<	commonPoolUEH = null;
3196	>	int n = par - 1; // precompute submit mask
3197	>	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4;
3198	>	n |= n >>> 8; n |= n >>> 16;
3199	>	int mask = ((n + 1) << 1) - 1;
3200	>	commonPool = new ForkJoinPool(par, mask, fac, ueh);
3201		} catch (Exception e) {
3202		throw new Error(e);
3203		}

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