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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 1.139 by dl, Wed Oct 31 12:49:24 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		/**
740		* Takes a task in FIFO order if b is base of queue and a task
741		* can be claimed without contention. Specialized versions
#	Line 813 | Line 814 | public class ForkJoinPool extends Abstra
814
815		/**
816		* Version of tryUnpush for shared queues; called by non-FJ
817	<	* submitters. Conservatively fails to unpush if all workers
817	<	* are active unless there are multiple tasks in queue.
817	>	* submitters after prechecking that task probably exists.
818		*/
819	<	final boolean trySharedUnpush(ForkJoinTask<?> task, ForkJoinPool p) {
819	>	final boolean trySharedUnpush(ForkJoinTask<?> t) {
820		boolean success = false;
821	<	if (task != null && top != base && runState == 0 &&
822	<	U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
821	>	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
822		try {
823	<	ForkJoinTask<?>[] a; int n, s;
824	<	if ((a = array) != null && (n = (s = top) - base) > 0 &&
825	<	(n > 1 || p == null || (int)(p.ctl >> AC_SHIFT) < 0)) {
826	<	int j = (((a.length - 1) & --s) << ASHIFT) + ABASE;
827	<	if (U.getObjectVolatile(a, j) == task &&
828	<	U.compareAndSwapObject(a, j, task, null)) {
830	<	top = s;
831	<	success = true;
832	<	}
823	>	ForkJoinTask<?>[] a; int s;
824	>	if ((a = array) != null && (s = top) != base &&
825	>	U.compareAndSwapObject
826	>	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
827	>	top = s;
828	>	success = true;
829		}
830		} finally {
831		runState = 0;                         // unlock
#	Line 913 | Line 909 | public class ForkJoinPool extends Abstra
909		return seed = r ^= r << 5;
910		}
911
912	<	// Execution methods
912	>	// Specialized execution methods
913
914		/**
915		* Pops and runs tasks until empty.
#	Line 992 | Line 988 | public class ForkJoinPool extends Abstra
988		}
989
990		/**
991	+	* Version of shared pop that takes top element only if it
992	+	* its root is the given CountedCompleter.
993	+	*/
994	+	final CountedCompleter<?> sharedPopCC(CountedCompleter<?> root) {
995	+	CountedCompleter<?> task = null;
996	+	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
997	+	try {
998	+	ForkJoinTask<?>[] a; int m;
999	+	if ((a = array) != null && (m = a.length - 1) >= 0) {
1000	+	outer:for (int s; (s = top - 1) - base >= 0;) {
1001	+	long j = ((m & s) << ASHIFT) + ABASE;
1002	+	ForkJoinTask<?> t =
1003	+	(ForkJoinTask<?>)U.getObject(a, j);
1004	+	if (t == null || !(t instanceof CountedCompleter))
1005	+	break;
1006	+	CountedCompleter<?> cc = (CountedCompleter<?>)t;
1007	+	for (CountedCompleter<?> q = cc, p;;) {
1008	+	if (q == root) {
1009	+	if (U.compareAndSwapObject(a, j, cc, null)) {
1010	+	top = s;
1011	+	task = cc;
1012	+	break outer;
1013	+	}
1014	+	break;
1015	+	}
1016	+	if ((p = q.completer) == null)
1017	+	break outer;
1018	+	q = p;
1019	+	}
1020	+	}
1021	+	}
1022	+	} finally {
1023	+	runState = 0;
1024	+	}
1025	+	}
1026	+	return task;
1027	+	}
1028	+
1029	+	/**
1030		* Executes a top-level task and any local tasks remaining
1031		* after execution.
1032		*/
#	Line 1112 | Line 1147 | public class ForkJoinPool extends Abstra
1147		public static final ForkJoinWorkerThreadFactory
1148		defaultForkJoinWorkerThreadFactory;
1149
1150	+	/** Property prefix for constructing common pool */
1151	+	private static final String propPrefix =
1152	+	"java.util.concurrent.ForkJoinPool.common.";
1153	+
1154	+	/**
1155	+	* Common (static) pool. Non-null for public use unless a static
1156	+	* construction exception, but internal usages must null-check on
1157	+	* use.
1158	+	*/
1159	+	static final ForkJoinPool commonPool;
1160	+
1161	+	/**
1162	+	* Common pool parallelism. Must equal commonPool.parallelism.
1163	+	*/
1164	+	static final int commonPoolParallelism;
1165	+
1166		/**
1167		* Generator for assigning sequence numbers as pool names.
1168		*/
#	Line 1136 | Line 1187 | public class ForkJoinPool extends Abstra
1187		*/
1188		private static final ThreadSubmitter submitters;
1189
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	–
1190		// static constants
1191
1192		/**
1193	<	* Initial timeout value (in nanoseconds) for the tread triggering
1193	>	* Initial timeout value (in nanoseconds) for the thread triggering
1194		* quiescence to park waiting for new work. On timeout, the thread
1195		* will instead try to shrink the number of workers.
1196		*/
#	Line 1281 | Line 1319 | public class ForkJoinPool extends Abstra
1319		* empirically works OK on current JVMs.
1320		*/
1321
1322	+	volatile long stealCount;                  // collects worker counts
1323		volatile long ctl;                         // main pool control
1324		final int parallelism;                     // parallelism level
1325		final int localMode;                       // per-worker scheduling mode
1326	+	volatile int nextWorkerNumber;             // to create worker name string
1327		final int submitMask;                      // submit queue index bound
1328		int nextSeed;                              // for initializing worker seeds
1329	+	volatile int mainLock;                     // spinlock for array updates
1330		volatile int runState;                     // shutdown status and seq
1331		WorkQueue[] workQueues;                    // main registry
1291	–	final Mutex lock;                          // for registration
1292	–	final Condition termination;               // for awaitTermination
1332		final ForkJoinWorkerThreadFactory factory; // factory for new workers
1333		final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1334	<	final AtomicLong stealCount;               // collect counts when terminated
1335	<	final AtomicInteger nextWorkerNumber;      // to create worker name string
1336	<	String workerNamePrefix;                   // to create worker name string
1334	>	final String workerNamePrefix;             // to create worker name string
1335	>
1336	>	/*
1337	>	* Mechanics for main lock protecting worker array updates.  Uses
1338	>	* the same strategy as ConcurrentHashMap bins -- a spinLock for
1339	>	* normal cases, but falling back to builtin lock when (rarely)
1340	>	* needed.  See internal ConcurrentHashMap documentation for
1341	>	* explanation.
1342	>	*/
1343	>
1344	>	static final int LOCK_WAITING = 2; // bit to indicate need for signal
1345	>	static final int MAX_LOCK_SPINS = 1 << 8;
1346	>
1347	>	private void tryAwaitMainLock() {
1348	>	int spins = MAX_LOCK_SPINS, r = 0, h;
1349	>	while (((h = mainLock) & 1) != 0) {
1350	>	if (r == 0)
1351	>	r = ThreadLocalRandom.current().nextInt(); // randomize spins
1352	>	else if (spins >= 0) {
1353	>	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1354	>	if (r >= 0)
1355	>	--spins;
1356	>	}
1357	>	else if (U.compareAndSwapInt(this, MAINLOCK, h, h | LOCK_WAITING)) {
1358	>	synchronized (this) {
1359	>	if ((mainLock & LOCK_WAITING) != 0) {
1360	>	try {
1361	>	wait();
1362	>	} catch (InterruptedException ie) {
1363	>	try {
1364	>	Thread.currentThread().interrupt();
1365	>	} catch (SecurityException ignore) {
1366	>	}
1367	>	}
1368	>	}
1369	>	else
1370	>	notifyAll(); // possibly won race vs signaller
1371	>	}
1372	>	break;
1373	>	}
1374	>	}
1375	>	}
1376
1377		//  Creating, registering, and deregistering workers
1378
#	Line 1322 | Line 1400 | public class ForkJoinPool extends Abstra
1400		* ForkJoinWorkerThread.
1401		*/
1402		final String nextWorkerName() {
1403	<	return workerNamePrefix.concat
1404	<	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1403	>	int n;
1404	>	do {} while (!U.compareAndSwapInt(this, NEXTWORKERNUMBER,
1405	>	n = nextWorkerNumber, ++n));
1406	>	return workerNamePrefix.concat(Integer.toString(n));
1407		}
1408
1409		/**
#	Line 1336 | Line 1416 | public class ForkJoinPool extends Abstra
1416		* @param w the worker's queue
1417		*/
1418		final void registerWorker(WorkQueue w) {
1419	<	Mutex lock = this.lock;
1420	<	lock.lock();
1419	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1420	>	tryAwaitMainLock();
1421		try {
1422	<	WorkQueue[] ws = workQueues;
1423	<	if (w != null && ws != null) {          // skip on shutdown/failure
1424	<	int rs, n = ws.length, m = n - 1;
1422	>	WorkQueue[] ws;
1423	>	if ((ws = workQueues) == null)
1424	>	ws = workQueues = new WorkQueue[submitMask + 1];
1425	>	if (w != null) {
1426	>	int rs, n =  ws.length, m = n - 1;
1427		int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence
1428		w.seed = (s == 0) ? 1 : s;          // ensure non-zero seed
1429		int r = (s << 1) | 1;               // use odd-numbered indices
#	Line 1361 | Line 1443 | public class ForkJoinPool extends Abstra
1443		runState = ((rs = runState) & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN);
1444		}
1445		} finally {
1446	<	lock.unlock();
1446	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1447	>	mainLock = 0;
1448	>	synchronized (this) { notifyAll(); };
1449	>	}
1450		}
1451		}
1452
#	Line 1375 | Line 1460 | public class ForkJoinPool extends Abstra
1460		* @param ex the exception causing failure, or null if none
1461		*/
1462		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1378	–	Mutex lock = this.lock;
1463		WorkQueue w = null;
1464		if (wt != null && (w = wt.workQueue) != null) {
1465		w.runState = -1;                // ensure runState is set
1466	<	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1466	>	long steals = w.totalSteals + w.nsteals, sc;
1467	>	do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
1468	>	sc = stealCount, sc + steals));
1469		int idx = w.poolIndex;
1470	<	lock.lock();
1471	<	try {                           // remove record from array
1470	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1471	>	tryAwaitMainLock();
1472	>	try {
1473		WorkQueue[] ws = workQueues;
1474		if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1475		ws[idx] = null;
1476		} finally {
1477	<	lock.unlock();
1477	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1478	>	mainLock = 0;
1479	>	synchronized (this) { notifyAll(); };
1480	>	}
1481		}
1482		}
1483
#	Line 1406 | Line 1496 | public class ForkJoinPool extends Abstra
1496		}
1497
1498		if (ex != null)                     // rethrow
1499	<	U.throwException(ex);
1499	>	ForkJoinTask.rethrow(ex);
1500		}
1501
1502		// Submissions
#	Line 1426 | Line 1516 | public class ForkJoinPool extends Abstra
1516		for (int r = s.seed, m = submitMask;;) {
1517		WorkQueue[] ws; WorkQueue q;
1518		int k = r & m & SQMASK;          // use only even indices
1519	<	if (runState < 0 || (ws = workQueues) == null || ws.length <= k)
1519	>	if (runState < 0)
1520		throw new RejectedExecutionException(); // shutting down
1521	+	else if ((ws = workQueues) == null || ws.length <= k) {
1522	+	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1523	+	tryAwaitMainLock();
1524	+	try {
1525	+	if (workQueues == null)
1526	+	workQueues = new WorkQueue[submitMask + 1];
1527	+	} finally {
1528	+	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1529	+	mainLock = 0;
1530	+	synchronized (this) { notifyAll(); };
1531	+	}
1532	+	}
1533	+	}
1534		else if ((q = ws[k]) == null) {  // create new queue
1535		WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE);
1536	<	Mutex lock = this.lock;      // construct outside lock
1537	<	lock.lock();
1538	<	try {                        // recheck under lock
1536	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1537	>	tryAwaitMainLock();
1538	>	try {
1539		int rs = runState;       // to update seq
1540		if (ws == workQueues && ws[k] == null) {
1541		ws[k] = nq;
1542		runState = ((rs & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN));
1543		}
1544		} finally {
1545	<	lock.unlock();
1545	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1546	>	mainLock = 0;
1547	>	synchronized (this) { notifyAll(); };
1548	>	}
1549		}
1550		}
1551		else if (q.trySharedPush(task)) {
#	Line 1462 | Line 1568 | public class ForkJoinPool extends Abstra
1568		static void submitToCommonPool(ForkJoinTask<?> task) {
1569		ForkJoinPool p;
1570		if ((p = commonPool) == null)
1571	<	p = ensureCommonPool();
1571	>	throw new RejectedExecutionException("Common Pool Unavailable");
1572		p.doSubmit(task);
1573		}
1574
#	Line 1476 | Line 1582 | public class ForkJoinPool extends Abstra
1582		* @return true if successful
1583		*/
1584		static boolean tryUnsubmitFromCommonPool(ForkJoinTask<?> task) {
1585	<	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
1586	<	int k = submitters.get().seed & SQMASK;
1587	<	return ((p = commonPool) != null &&
1588	<	(ws = p.workQueues) != null &&
1589	<	ws.length > (k &= p.submitMask) &&
1590	<	(q = ws[k]) != null &&
1591	<	q.trySharedUnpush(task, p));
1585	>	// If not oversaturating platform, peek, looking for task and
1586	>	// eligibility before using trySharedUnpush to actually take
1587	>	// it under lock
1588	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q;
1589	>	ForkJoinTask<?>[] a; int ac, s, m;
1590	>	if ((p = commonPool) != null && (ws = p.workQueues) != null) {
1591	>	int k = submitters.get().seed & p.submitMask & SQMASK;
1592	>	if ((m = ws.length - 1) >= k && (q = ws[k]) != null &&
1593	>	(ac = (int)(p.ctl >> AC_SHIFT)) <= 0) {
1594	>	if (ac == 0) { // double check if all workers active
1595	>	for (int i = 1; i <= m; i += 2) {
1596	>	if ((w = ws[i]) != null && w.parker != null) {
1597	>	ac = -1;
1598	>	break;
1599	>	}
1600	>	}
1601	>	}
1602	>	return (ac < 0 && (a = q.array) != null &&
1603	>	(s = q.top - 1) - q.base >= 0 &&
1604	>	s >= 0 && s < a.length &&
1605	>	a[s] == task &&
1606	>	q.trySharedUnpush(task));
1607	>	}
1608	>	}
1609	>	return false;
1610	>	}
1611	>
1612	>	/**
1613	>	* Tries to pop and run a task within same computation from common pool
1614	>	*/
1615	>	static void popAndExecCCFromCommonPool(CountedCompleter<?> cc) {
1616	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; int m, ac;
1617	>	CountedCompleter<?> par, task;
1618	>	if ((p = commonPool) != null && (ws = p.workQueues) != null) {
1619	>	while ((par = cc.completer) != null) // find root
1620	>	cc = par;
1621	>	int k = submitters.get().seed & p.submitMask & SQMASK;
1622	>	if ((m = ws.length - 1) >= k && (q = ws[k]) != null &&
1623	>	(ac = (int)(p.ctl >> AC_SHIFT)) <= 0) {
1624	>	if (ac == 0) {
1625	>	for (int i = 1; i <= m; i += 2) {
1626	>	if ((w = ws[i]) != null && w.parker != null) {
1627	>	ac = -1;
1628	>	break;
1629	>	}
1630	>	}
1631	>	}
1632	>	if (ac < 0 && q.top - q.base > 0 &&
1633	>	(task = q.sharedPopCC(cc)) != null)
1634	>	task.exec();
1635	>	}
1636	>	}
1637		}
1638
1639		// Maintaining ctl counts
#	Line 1956 | Line 2107 | public class ForkJoinPool extends Abstra
2107		*/
2108		private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
2109		// Similar to loop in scan(), but ignoring submissions
2110	<	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	<	}
2110	>	int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
2111		int step = (r >>> 16) | 1;
2112		for (WorkQueue[] ws;;) {
2113		int rs = runState, m;
#	Line 2025 | Line 2171 | public class ForkJoinPool extends Abstra
2171		* Restricted version of helpQuiescePool for non-FJ callers
2172		*/
2173		static void externalHelpQuiescePool() {
2174	<	ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q;
2175	<	ForkJoinTask<?> t; int b;
2174	>	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, sq;
2175	>	ForkJoinTask<?>[] a; int b;
2176	>	ForkJoinTask<?> t = null;
2177		int k = submitters.get().seed & SQMASK;
2178		if ((p = commonPool) != null &&
2179		(ws = p.workQueues) != null &&
2180		ws.length > (k &= p.submitMask) &&
2181	<	(w = ws[k]) != null &&
2182	<	(q = p.findNonEmptyStealQueue(w)) != null &&
2183	<	(b = q.base) - q.top < 0 &&
2184	<	(t = q.pollAt(b)) != null)
2185	<	t.doExec();
2181	>	(q = ws[k]) != null) {
2182	>	while (q.top - q.base > 0) {
2183	>	if ((t = q.sharedPop()) != null)
2184	>	break;
2185	>	}
2186	>	if (t == null && (sq = p.findNonEmptyStealQueue(q)) != null &&
2187	>	(b = sq.base) - sq.top < 0)
2188	>	t = sq.pollAt(b);
2189	>	if (t != null)
2190	>	t.doExec();
2191	>	}
2192		}
2193
2194		/**
#	Line 2077 | Line 2230 | public class ForkJoinPool extends Abstra
2230		static int getEstimatedSubmitterQueueLength() {
2231		ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
2232		int k = submitters.get().seed & SQMASK;
2233	<	return ((p = commonPool) != null &&
2081	<	p.runState >= 0 &&
2082	<	(ws = p.workQueues) != null &&
2233	>	return ((p = commonPool) != null && (ws = p.workQueues) != null &&
2234		ws.length > (k &= p.submitMask) &&
2235		(q = ws[k]) != null) ?
2236		q.queueSize() : 0;
#	Line 2102 | Line 2253 | public class ForkJoinPool extends Abstra
2253		* @return true if now terminating or terminated
2254		*/
2255		private boolean tryTerminate(boolean now, boolean enable) {
2105	–	Mutex lock = this.lock;
2256		for (long c;;) {
2257		if (((c = ctl) & STOP_BIT) != 0) {      // already terminating
2258		if ((short)(c >>> TC_SHIFT) == -parallelism) {
2259	<	lock.lock();                    // don't need try/finally
2260	<	termination.signalAll();        // signal when 0 workers
2261	<	lock.unlock();
2259	>	synchronized (this) {
2260	>	notifyAll();                // signal when 0 workers
2261	>	}
2262		}
2263		return true;
2264		}
2265		if (runState >= 0) {                    // not yet enabled
2266		if (!enable)
2267		return false;
2268	<	lock.lock();
2269	<	runState |= SHUTDOWN;
2270	<	lock.unlock();
2268	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
2269	>	tryAwaitMainLock();
2270	>	try {
2271	>	runState |= SHUTDOWN;
2272	>	} finally {
2273	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
2274	>	mainLock = 0;
2275	>	synchronized (this) { notifyAll(); };
2276	>	}
2277	>	}
2278		}
2279		if (!now) {                             // check if idle & no tasks
2280		if ((int)(c >> AC_SHIFT) != -parallelism ||
#	Line 2250 | Line 2407 | public class ForkJoinPool extends Abstra
2407		// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2.
2408		int n = parallelism - 1;
2409		n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
2410	<	int size = (n + 1) << 1;        // #slots = 2*#workers
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();
2410	>	this.submitMask = ((n + 1) << 1) - 1;
2411		int pn = poolNumberGenerator.incrementAndGet();
2412		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2413		sb.append(Integer.toString(pn));
2414		sb.append("-worker-");
2415		this.workerNamePrefix = sb.toString();
2264	–	lock.lock();
2416		this.runState = 1;              // set init flag
2266	–	lock.unlock();
2417		}
2418
2419		/**
2420	<	* Returns the common pool instance
2420	>	* Constructor for common pool, suitable only for static initialization.
2421	>	* Basically the same as above, but uses smallest possible initial footprint.
2422	>	*/
2423	>	ForkJoinPool(int parallelism, int submitMask,
2424	>	ForkJoinWorkerThreadFactory factory,
2425	>	Thread.UncaughtExceptionHandler handler) {
2426	>	this.factory = factory;
2427	>	this.ueh = handler;
2428	>	this.submitMask = submitMask;
2429	>	this.parallelism = parallelism;
2430	>	long np = (long)(-parallelism);
2431	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
2432	>	this.localMode = LIFO_QUEUE;
2433	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2434	>	this.runState = 1;
2435	>	}
2436	>
2437	>	/**
2438	>	* Returns the common pool instance.
2439		*
2440		* @return the common pool instance
2441		*/
2442		public static ForkJoinPool commonPool() {
2443		ForkJoinPool p;
2444	<	return (p = commonPool) != null? p : ensureCommonPool();
2445	<	}
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	<	}
2444	>	if ((p = commonPool) == null)
2445	>	throw new Error("Common Pool Unavailable");
2446		return p;
2447		}
2448
#	Line 2558 | Line 2708 | public class ForkJoinPool extends Abstra
2708		* @return the number of steals
2709		*/
2710		public long getStealCount() {
2711	<	long count = stealCount.get();
2711	>	long count = stealCount;
2712		WorkQueue[] ws; WorkQueue w;
2713		if ((ws = workQueues) != null) {
2714		for (int i = 1; i < ws.length; i += 2) {
#	Line 2688 | Line 2838 | public class ForkJoinPool extends Abstra
2838		public String toString() {
2839		// Use a single pass through workQueues to collect counts
2840		long qt = 0L, qs = 0L; int rc = 0;
2841	<	long st = stealCount.get();
2841	>	long st = stealCount;
2842		long c = ctl;
2843		WorkQueue[] ws; WorkQueue w;
2844		if ((ws = workQueues) != null) {
#	Line 2826 | Line 2976 | public class ForkJoinPool extends Abstra
2976		public boolean awaitTermination(long timeout, TimeUnit unit)
2977		throws InterruptedException {
2978		long nanos = unit.toNanos(timeout);
2979	<	final Mutex lock = this.lock;
2980	<	lock.lock();
2981	<	try {
2982	<	for (;;) {
2983	<	if (isTerminated())
2984	<	return true;
2985	<	if (nanos <= 0)
2986	<	return false;
2987	<	nanos = termination.awaitNanos(nanos);
2979	>	if (isTerminated())
2980	>	return true;
2981	>	long startTime = System.nanoTime();
2982	>	boolean terminated = false;
2983	>	synchronized (this) {
2984	>	for (long waitTime = nanos, millis = 0L;;) {
2985	>	if (terminated = isTerminated() ||
2986	>	waitTime <= 0L ||
2987	>	(millis = unit.toMillis(waitTime)) <= 0L)
2988	>	break;
2989	>	wait(millis);
2990	>	waitTime = nanos - (System.nanoTime() - startTime);
2991		}
2839	–	} finally {
2840	–	lock.unlock();
2992		}
2993	+	return terminated;
2994		}
2995
2996		/**
#	Line 2970 | Line 3122 | public class ForkJoinPool extends Abstra
3122		private static final long PARKBLOCKER;
3123		private static final int ABASE;
3124		private static final int ASHIFT;
3125	+	private static final long NEXTWORKERNUMBER;
3126	+	private static final long STEALCOUNT;
3127	+	private static final long MAINLOCK;
3128
3129		static {
3130		poolNumberGenerator = new AtomicInteger();
#	Line 2978 | Line 3133 | public class ForkJoinPool extends Abstra
3133		defaultForkJoinWorkerThreadFactory =
3134		new DefaultForkJoinWorkerThreadFactory();
3135		submitters = new ThreadSubmitter();
2981	–	initializationLock = new Mutex();
3136		int s;
3137		try {
3138		U = getUnsafe();
#	Line 2986 | Line 3140 | public class ForkJoinPool extends Abstra
3140		Class<?> ak = ForkJoinTask[].class;
3141		CTL = U.objectFieldOffset
3142		(k.getDeclaredField("ctl"));
3143	+	NEXTWORKERNUMBER = U.objectFieldOffset
3144	+	(k.getDeclaredField("nextWorkerNumber"));
3145	+	STEALCOUNT = U.objectFieldOffset
3146	+	(k.getDeclaredField("stealCount"));
3147	+	MAINLOCK = U.objectFieldOffset
3148	+	(k.getDeclaredField("mainLock"));
3149		Class<?> tk = Thread.class;
3150		PARKBLOCKER = U.objectFieldOffset
3151		(tk.getDeclaredField("parkBlocker"));
3152		ABASE = U.arrayBaseOffset(ak);
3153		s = U.arrayIndexScale(ak);
3154	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3155		} catch (Exception e) {
3156		throw new Error(e);
3157		}
3158		if ((s & (s-1)) != 0)
3159		throw new Error("data type scale not a power of two");
3160	<	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3000	<
3001	<	// Establish configuration for default pool
3002	<	try {
3160	>	try { // Establish common pool
3161		String pp = System.getProperty(propPrefix + "parallelism");
3162		String fp = System.getProperty(propPrefix + "threadFactory");
3163		String up = System.getProperty(propPrefix + "exceptionHandler");
3164	+	ForkJoinWorkerThreadFactory fac = (fp == null) ?
3165	+	defaultForkJoinWorkerThreadFactory :
3166	+	((ForkJoinWorkerThreadFactory)ClassLoader.
3167	+	getSystemClassLoader().loadClass(fp).newInstance());
3168	+	Thread.UncaughtExceptionHandler ueh = (up == null) ? null :
3169	+	((Thread.UncaughtExceptionHandler)ClassLoader.
3170	+	getSystemClassLoader().loadClass(up).newInstance());
3171		int par;
3172		if ((pp == null || (par = Integer.parseInt(pp)) <= 0))
3173		par = Runtime.getRuntime().availableProcessors();
3174	+	if (par > MAX_CAP)
3175	+	par = MAX_CAP;
3176		commonPoolParallelism = par;
3177	<	if (fp != null)
3178	<	commonPoolFactory = (ForkJoinWorkerThreadFactory)
3179	<	ClassLoader.getSystemClassLoader().loadClass(fp).newInstance();
3180	<	else
3181	<	commonPoolFactory = defaultForkJoinWorkerThreadFactory;
3015	<	if (up != null)
3016	<	commonPoolUEH = (Thread.UncaughtExceptionHandler)
3017	<	ClassLoader.getSystemClassLoader().loadClass(up).newInstance();
3018	<	else
3019	<	commonPoolUEH = null;
3177	>	int n = par - 1; // precompute submit mask
3178	>	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4;
3179	>	n |= n >>> 8; n |= n >>> 16;
3180	>	int mask = ((n + 1) << 1) - 1;
3181	>	commonPool = new ForkJoinPool(par, mask, fac, ueh);
3182		} catch (Exception e) {
3183		throw new Error(e);
3184		}

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