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

Comparing jsr166/src/jsr166e/ForkJoinPool.java (file contents):
Revision 1.2 by jsr166, Mon Aug 13 18:25:53 2012 UTC vs.
Revision 1.11 by dl, Wed Oct 31 12:49:13 2012 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166e;
8	+
9		import java.util.ArrayList;
10		import java.util.Arrays;
11		import java.util.Collection;
#	Line 17 | Line 18 | import java.util.concurrent.ExecutorServ
18		import java.util.concurrent.Future;
19		import java.util.concurrent.RejectedExecutionException;
20		import java.util.concurrent.RunnableFuture;
21	+	import java.util.concurrent.ThreadLocalRandom;
22		import java.util.concurrent.TimeUnit;
23		import java.util.concurrent.atomic.AtomicInteger;
24		import java.util.concurrent.atomic.AtomicLong;
#	Line 41 | Line 43 | import java.util.concurrent.locks.Condit
43		* ForkJoinPool}s may also be appropriate for use with event-style
44		* tasks that are never joined.
45		*
46	<	* <p>A {@code ForkJoinPool} is constructed with a given target
47	<	* parallelism level; by default, equal to the number of available
48	<	* processors. The pool attempts to maintain enough active (or
49	<	* available) threads by dynamically adding, suspending, or resuming
50	<	* internal worker threads, even if some tasks are stalled waiting to
51	<	* join others. However, no such adjustments are guaranteed in the
52	<	* face of blocked IO or other unmanaged synchronization. The nested
53	<	* {@link ManagedBlocker} interface enables extension of the kinds of
46	>	* <p>A static {@link #commonPool} is available and appropriate for
47	>	* most applications. The common pool is used by any ForkJoinTask that
48	>	* is not explicitly submitted to a specified pool. Using the common
49	>	* pool normally reduces resource usage (its threads are slowly
50	>	* reclaimed during periods of non-use, and reinstated upon subsequent
51	>	* use).  The common pool is by default constructed with default
52	>	* parameters, but these may be controlled by setting any or all of
53	>	* the three properties {@code
54	>	* java.util.concurrent.ForkJoinPool.common.{parallelism,
55	>	* threadFactory, exceptionHandler}}.
56	>	*
57	>	* <p>For applications that require separate or custom pools, a {@code
58	>	* ForkJoinPool} may be constructed with a given target parallelism
59	>	* level; by default, equal to the number of available processors. The
60	>	* pool attempts to maintain enough active (or available) threads by
61	>	* dynamically adding, suspending, or resuming internal worker
62	>	* threads, even if some tasks are stalled waiting to join
63	>	* others. However, no such adjustments are guaranteed in the face of
64	>	* blocked IO or other unmanaged synchronization. The nested {@link
65	>	* ManagedBlocker} interface enables extension of the kinds of
66		* synchronization accommodated.
67		*
68		* <p>In addition to execution and lifecycle control methods, this
#	Line 93 | Line 107 | import java.util.concurrent.locks.Condit
107		*  </tr>
108		* </table>
109		*
96	–	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
97	–	* used for all parallel task execution in a program or subsystem.
98	–	* Otherwise, use would not usually outweigh the construction and
99	–	* bookkeeping overhead of creating a large set of threads. For
100	–	* example, a common pool could be used for the {@code SortTasks}
101	–	* illustrated in {@link RecursiveAction}. Because {@code
102	–	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
103	–	* daemon} mode, there is typically no need to explicitly {@link
104	–	* #shutdown} such a pool upon program exit.
105	–	*
106	–	*  <pre> {@code
107	–	* static final ForkJoinPool mainPool = new ForkJoinPool();
108	–	* ...
109	–	* public void sort(long[] array) {
110	–	*   mainPool.invoke(new SortTask(array, 0, array.length));
111	–	* }}</pre>
112	–	*
110		* <p><b>Implementation notes</b>: This implementation restricts the
111		* maximum number of running threads to 32767. Attempts to create
112		* pools with greater than the maximum number result in
#	Line 239 | Line 236 | public class ForkJoinPool extends Abstra
236		* when locked remains available to check consistency.
237		*
238		* Recording WorkQueues.  WorkQueues are recorded in the
239	<	* "workQueues" array that is created upon pool construction and
240	<	* expanded if necessary.  Updates to the array while recording
241	<	* new workers and unrecording terminated ones are protected from
242	<	* each other by a lock but the array is otherwise concurrently
243	<	* readable, and accessed directly.  To simplify index-based
244	<	* operations, the array size is always a power of two, and all
245	<	* readers must tolerate null slots. Shared (submission) queues
246	<	* are at even indices, worker queues at odd indices. Grouping
247	<	* them together in this way simplifies and speeds up task
251	<	* scanning.
239	>	* "workQueues" array that is created upon first use and expanded
240	>	* if necessary.  Updates to the array while recording new workers
241	>	* and unrecording terminated ones are protected from each other
242	>	* by a lock but the array is otherwise concurrently readable, and
243	>	* accessed directly.  To simplify index-based operations, the
244	>	* array size is always a power of two, and all readers must
245	>	* tolerate null slots. Shared (submission) queues are at even
246	>	* indices, worker queues at odd indices. Grouping them together
247	>	* in this way simplifies and speeds up task scanning.
248		*
249		* All worker thread creation is on-demand, triggered by task
250		* submissions, replacement of terminated workers, and/or
#	Line 320 | Line 316 | public class ForkJoinPool extends Abstra
316		*
317		* Trimming workers. To release resources after periods of lack of
318		* use, a worker starting to wait when the pool is quiescent will
319	<	* time out and terminate if the pool has remained quiescent for
320	<	* SHRINK_RATE nanosecs. This will slowly propagate, eventually
321	<	* terminating all workers after long periods of non-use.
319	>	* time out and terminate if the pool has remained quiescent for a
320	>	* given period -- a short period if there are more threads than
321	>	* parallelism, longer as the number of threads decreases. This
322	>	* will slowly propagate, eventually terminating all workers after
323	>	* periods of non-use.
324		*
325		* Shutdown and Termination. A call to shutdownNow atomically sets
326		* a runState bit and then (non-atomically) sets each worker's
#	Line 504 | Line 502 | public class ForkJoinPool extends Abstra
502		}
503
504		/**
507	–	* A simple non-reentrant lock used for exclusion when managing
508	–	* queues and workers. We use a custom lock so that we can readily
509	–	* probe lock state in constructions that check among alternative
510	–	* actions. The lock is normally only very briefly held, and
511	–	* sometimes treated as a spinlock, but other usages block to
512	–	* reduce overall contention in those cases where locked code
513	–	* bodies perform allocation/resizing.
514	–	*/
515	–	static final class Mutex extends AbstractQueuedSynchronizer {
516	–	public final boolean tryAcquire(int ignore) {
517	–	return compareAndSetState(0, 1);
518	–	}
519	–	public final boolean tryRelease(int ignore) {
520	–	setState(0);
521	–	return true;
522	–	}
523	–	public final void lock() { acquire(0); }
524	–	public final void unlock() { release(0); }
525	–	public final boolean isHeldExclusively() { return getState() == 1; }
526	–	public final Condition newCondition() { return new ConditionObject(); }
527	–	}
528	–
529	–	/**
505		* Class for artificial tasks that are used to replace the target
506		* of local joins if they are removed from an interior queue slot
507		* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
#	Line 717 | Line 692 | public class ForkJoinPool extends Abstra
692
693		/**
694		* Takes next task, if one exists, in LIFO order.  Call only
695	<	* by owner in unshared queues. (We do not have a shared
721	<	* version of this method because it is never needed.)
695	>	* by owner in unshared queues.
696		*/
697		final ForkJoinTask<?> pop() {
698		ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m;
#	Line 736 | Line 710 | public class ForkJoinPool extends Abstra
710		return null;
711		}
712
713	+	final ForkJoinTask<?> sharedPop() {
714	+	ForkJoinTask<?> task = null;
715	+	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
716	+	try {
717	+	ForkJoinTask<?>[] a; int m;
718	+	if ((a = array) != null && (m = a.length - 1) >= 0) {
719	+	for (int s; (s = top - 1) - base >= 0;) {
720	+	long j = ((m & s) << ASHIFT) + ABASE;
721	+	ForkJoinTask<?> t =
722	+	(ForkJoinTask<?>)U.getObject(a, j);
723	+	if (t == null)
724	+	break;
725	+	if (U.compareAndSwapObject(a, j, t, null)) {
726	+	top = s;
727	+	task = t;
728	+	break;
729	+	}
730	+	}
731	+	}
732	+	} finally {
733	+	runState = 0;
734	+	}
735	+	}
736	+	return task;
737	+	}
738	+
739	+
740		/**
741		* Takes a task in FIFO order if b is base of queue and a task
742		* can be claimed without contention. Specialized versions
#	Line 813 | Line 814 | public class ForkJoinPool extends Abstra
814		}
815
816		/**
817	+	* Version of tryUnpush for shared queues; called by non-FJ
818	+	* submitters after prechecking that task probably exists.
819	+	*/
820	+	final boolean trySharedUnpush(ForkJoinTask<?> t) {
821	+	boolean success = false;
822	+	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
823	+	try {
824	+	ForkJoinTask<?>[] a; int s;
825	+	if ((a = array) != null && (s = top) != base &&
826	+	U.compareAndSwapObject
827	+	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
828	+	top = s;
829	+	success = true;
830	+	}
831	+	} finally {
832	+	runState = 0;                         // unlock
833	+	}
834	+	}
835	+	return success;
836	+	}
837	+
838	+	/**
839		* Polls the given task only if it is at the current base.
840		*/
841		final boolean pollFor(ForkJoinTask<?> task) {
#	Line 887 | Line 910 | public class ForkJoinPool extends Abstra
910		return seed = r ^= r << 5;
911		}
912
913	<	// Execution methods
913	>	// Specialized execution methods
914
915		/**
916		* Pops and runs tasks until empty.
#	Line 966 | Line 989 | public class ForkJoinPool extends Abstra
989		}
990
991		/**
992	+	* Version of shared pop that takes top element only if it
993	+	* its root is the given CountedCompleter.
994	+	*/
995	+	final CountedCompleter<?> sharedPopCC(CountedCompleter<?> root) {
996	+	CountedCompleter<?> task = null;
997	+	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
998	+	try {
999	+	ForkJoinTask<?>[] a; int m;
1000	+	if ((a = array) != null && (m = a.length - 1) >= 0) {
1001	+	outer:for (int s; (s = top - 1) - base >= 0;) {
1002	+	long j = ((m & s) << ASHIFT) + ABASE;
1003	+	ForkJoinTask<?> t =
1004	+	(ForkJoinTask<?>)U.getObject(a, j);
1005	+	if (t == null || !(t instanceof CountedCompleter))
1006	+	break;
1007	+	CountedCompleter<?> cc = (CountedCompleter<?>)t;
1008	+	for (CountedCompleter<?> q = cc, p;;) {
1009	+	if (q == root) {
1010	+	if (U.compareAndSwapObject(a, j, cc, null)) {
1011	+	top = s;
1012	+	task = cc;
1013	+	break outer;
1014	+	}
1015	+	break;
1016	+	}
1017	+	if ((p = q.completer) == null)
1018	+	break outer;
1019	+	q = p;
1020	+	}
1021	+	}
1022	+	}
1023	+	} finally {
1024	+	runState = 0;
1025	+	}
1026	+	}
1027	+	return task;
1028	+	}
1029	+
1030	+	/**
1031		* Executes a top-level task and any local tasks remaining
1032		* after execution.
1033		*/
#	Line 1047 | Line 1109 | public class ForkJoinPool extends Abstra
1109		ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
1110		}
1111		}
1112	+
1113		/**
1114		* Per-thread records for threads that submit to pools. Currently
1115		* holds only pseudo-random seed / index that is used to choose
#	Line 1085 | Line 1148 | public class ForkJoinPool extends Abstra
1148		public static final ForkJoinWorkerThreadFactory
1149		defaultForkJoinWorkerThreadFactory;
1150
1151	+	/** Property prefix for constructing common pool */
1152	+	private static final String propPrefix =
1153	+	"java.util.concurrent.ForkJoinPool.common.";
1154	+
1155	+	/**
1156	+	* Common (static) pool. Non-null for public use unless a static
1157	+	* construction exception, but internal usages must null-check on
1158	+	* use.
1159	+	*/
1160	+	static final ForkJoinPool commonPool;
1161	+
1162	+	/**
1163	+	* Common pool parallelism. Must equal commonPool.parallelism.
1164	+	*/
1165	+	static final int commonPoolParallelism;
1166	+
1167		/**
1168		* Generator for assigning sequence numbers as pool names.
1169		*/
#	Line 1112 | Line 1191 | public class ForkJoinPool extends Abstra
1191		// static constants
1192
1193		/**
1194	<	* The wakeup interval (in nanoseconds) for a worker waiting for a
1195	<	* task when the pool is quiescent to instead try to shrink the
1196	<	* number of workers.  The exact value does not matter too
1118	<	* much. It must be short enough to release resources during
1119	<	* sustained periods of idleness, but not so short that threads
1120	<	* are continually re-created.
1194	>	* Initial timeout value (in nanoseconds) for the thread triggering
1195	>	* quiescence to park waiting for new work. On timeout, the thread
1196	>	* will instead try to shrink the number of workers.
1197		*/
1198	<	private static final long SHRINK_RATE =
1123	<	4L * 1000L * 1000L * 1000L; // 4 seconds
1198	>	private static final long IDLE_TIMEOUT      = 1000L * 1000L * 1000L; // 1sec
1199
1200		/**
1201	<	* The timeout value for attempted shrinkage, includes
1127	<	* some slop to cope with system timer imprecision.
1201	>	* Timeout value when there are more threads than parallelism level
1202		*/
1203	<	private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
1203	>	private static final long FAST_IDLE_TIMEOUT =  100L * 1000L * 1000L;
1204
1205		/**
1206		* The maximum stolen->joining link depth allowed in method
#	Line 1246 | Line 1320 | public class ForkJoinPool extends Abstra
1320		* empirically works OK on current JVMs.
1321		*/
1322
1323	+	volatile long stealCount;                  // collects worker counts
1324		volatile long ctl;                         // main pool control
1325		final int parallelism;                     // parallelism level
1326		final int localMode;                       // per-worker scheduling mode
1327	+	volatile int nextWorkerNumber;             // to create worker name string
1328		final int submitMask;                      // submit queue index bound
1329		int nextSeed;                              // for initializing worker seeds
1330	+	volatile int mainLock;                     // spinlock for array updates
1331		volatile int runState;                     // shutdown status and seq
1332		WorkQueue[] workQueues;                    // main registry
1256	–	final Mutex lock;                          // for registration
1257	–	final Condition termination;               // for awaitTermination
1333		final ForkJoinWorkerThreadFactory factory; // factory for new workers
1334		final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1260	–	final AtomicLong stealCount;               // collect counts when terminated
1261	–	final AtomicInteger nextWorkerNumber;      // to create worker name string
1335		final String workerNamePrefix;             // to create worker name string
1336
1337	+	/*
1338	+	* Mechanics for main lock protecting worker array updates.  Uses
1339	+	* the same strategy as ConcurrentHashMap bins -- a spinLock for
1340	+	* normal cases, but falling back to builtin lock when (rarely)
1341	+	* needed.  See internal ConcurrentHashMap documentation for
1342	+	* explanation.
1343	+	*/
1344	+
1345	+	static final int LOCK_WAITING = 2; // bit to indicate need for signal
1346	+	static final int MAX_LOCK_SPINS = 1 << 8;
1347	+
1348	+	private void tryAwaitMainLock() {
1349	+	int spins = MAX_LOCK_SPINS, r = 0, h;
1350	+	while (((h = mainLock) & 1) != 0) {
1351	+	if (r == 0)
1352	+	r = ThreadLocalRandom.current().nextInt(); // randomize spins
1353	+	else if (spins >= 0) {
1354	+	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1355	+	if (r >= 0)
1356	+	--spins;
1357	+	}
1358	+	else if (U.compareAndSwapInt(this, MAINLOCK, h, h | LOCK_WAITING)) {
1359	+	synchronized (this) {
1360	+	if ((mainLock & LOCK_WAITING) != 0) {
1361	+	try {
1362	+	wait();
1363	+	} catch (InterruptedException ie) {
1364	+	try {
1365	+	Thread.currentThread().interrupt();
1366	+	} catch (SecurityException ignore) {
1367	+	}
1368	+	}
1369	+	}
1370	+	else
1371	+	notifyAll(); // possibly won race vs signaller
1372	+	}
1373	+	break;
1374	+	}
1375	+	}
1376	+	}
1377	+
1378		//  Creating, registering, and deregistering workers
1379
1380		/**
#	Line 1287 | Line 1401 | public class ForkJoinPool extends Abstra
1401		* ForkJoinWorkerThread.
1402		*/
1403		final String nextWorkerName() {
1404	<	return workerNamePrefix.concat
1405	<	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1404	>	int n;
1405	>	do {} while (!U.compareAndSwapInt(this, NEXTWORKERNUMBER,
1406	>	n = nextWorkerNumber, ++n));
1407	>	return workerNamePrefix.concat(Integer.toString(n));
1408		}
1409
1410		/**
#	Line 1300 | Line 1416 | public class ForkJoinPool extends Abstra
1416		*
1417		* @param w the worker's queue
1418		*/
1303	–
1419		final void registerWorker(WorkQueue w) {
1420	<	Mutex lock = this.lock;
1421	<	lock.lock();
1420	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1421	>	tryAwaitMainLock();
1422		try {
1423	<	WorkQueue[] ws = workQueues;
1424	<	if (w != null && ws != null) {          // skip on shutdown/failure
1423	>	WorkQueue[] ws;
1424	>	if ((ws = workQueues) == null)
1425	>	ws = workQueues = new WorkQueue[submitMask + 1];
1426	>	if (w != null) {
1427		int rs, n =  ws.length, m = n - 1;
1428		int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence
1429		w.seed = (s == 0) ? 1 : s;          // ensure non-zero seed
#	Line 1327 | Line 1444 | public class ForkJoinPool extends Abstra
1444		runState = ((rs = runState) & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN);
1445		}
1446		} finally {
1447	<	lock.unlock();
1447	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1448	>	mainLock = 0;
1449	>	synchronized (this) { notifyAll(); };
1450	>	}
1451		}
1452		}
1453
#	Line 1341 | Line 1461 | public class ForkJoinPool extends Abstra
1461		* @param ex the exception causing failure, or null if none
1462		*/
1463		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1344	–	Mutex lock = this.lock;
1464		WorkQueue w = null;
1465		if (wt != null && (w = wt.workQueue) != null) {
1466		w.runState = -1;                // ensure runState is set
1467	<	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1467	>	long steals = w.totalSteals + w.nsteals, sc;
1468	>	do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
1469	>	sc = stealCount, sc + steals));
1470		int idx = w.poolIndex;
1471	<	lock.lock();
1472	<	try {                           // remove record from array
1471	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1472	>	tryAwaitMainLock();
1473	>	try {
1474		WorkQueue[] ws = workQueues;
1475		if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1476		ws[idx] = null;
1477		} finally {
1478	<	lock.unlock();
1478	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1479	>	mainLock = 0;
1480	>	synchronized (this) { notifyAll(); };
1481	>	}
1482		}
1483		}
1484
#	Line 1372 | Line 1497 | public class ForkJoinPool extends Abstra
1497		}
1498
1499		if (ex != null)                     // rethrow
1500	<	U.throwException(ex);
1500	>	ForkJoinTask.rethrow(ex);
1501		}
1502
1378	–
1503		// Submissions
1504
1505		/**
#	Line 1393 | Line 1517 | public class ForkJoinPool extends Abstra
1517		for (int r = s.seed, m = submitMask;;) {
1518		WorkQueue[] ws; WorkQueue q;
1519		int k = r & m & SQMASK;          // use only even indices
1520	<	if (runState < 0 || (ws = workQueues) == null || ws.length <= k)
1520	>	if (runState < 0)
1521		throw new RejectedExecutionException(); // shutting down
1522	+	else if ((ws = workQueues) == null || ws.length <= k) {
1523	+	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1524	+	tryAwaitMainLock();
1525	+	try {
1526	+	if (workQueues == null)
1527	+	workQueues = new WorkQueue[submitMask + 1];
1528	+	} finally {
1529	+	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1530	+	mainLock = 0;
1531	+	synchronized (this) { notifyAll(); };
1532	+	}
1533	+	}
1534	+	}
1535		else if ((q = ws[k]) == null) {  // create new queue
1536		WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE);
1537	<	Mutex lock = this.lock;      // construct outside lock
1538	<	lock.lock();
1539	<	try {                        // recheck under lock
1537	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1538	>	tryAwaitMainLock();
1539	>	try {
1540		int rs = runState;       // to update seq
1541		if (ws == workQueues && ws[k] == null) {
1542		ws[k] = nq;
1543		runState = ((rs & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN));
1544		}
1545		} finally {
1546	<	lock.unlock();
1546	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1547	>	mainLock = 0;
1548	>	synchronized (this) { notifyAll(); };
1549	>	}
1550		}
1551		}
1552		else if (q.trySharedPush(task)) {
#	Line 1423 | Line 1563 | public class ForkJoinPool extends Abstra
1563		}
1564		}
1565
1566	+	/**
1567	+	* Submits the given (non-null) task to the common pool, if possible.
1568	+	*/
1569	+	static void submitToCommonPool(ForkJoinTask<?> task) {
1570	+	ForkJoinPool p;
1571	+	if ((p = commonPool) == null)
1572	+	throw new RejectedExecutionException("Common Pool Unavailable");
1573	+	p.doSubmit(task);
1574	+	}
1575	+
1576	+	/**
1577	+	* Returns true if the given task was submitted to common pool
1578	+	* and has not yet commenced execution, and is available for
1579	+	* removal according to execution policies; if so removing the
1580	+	* submission from the pool.
1581	+	*
1582	+	* @param task the task
1583	+	* @return true if successful
1584	+	*/
1585	+	static boolean tryUnsubmitFromCommonPool(ForkJoinTask<?> task) {
1586	+	// If not oversaturating platform, peek, looking for task and
1587	+	// eligibility before using trySharedUnpush to actually take
1588	+	// it under lock
1589	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q;
1590	+	ForkJoinTask<?>[] a; int ac, s, m;
1591	+	if ((p = commonPool) != null && (ws = p.workQueues) != null) {
1592	+	int k = submitters.get().seed & p.submitMask & SQMASK;
1593	+	if ((m = ws.length - 1) >= k && (q = ws[k]) != null &&
1594	+	(ac = (int)(p.ctl >> AC_SHIFT)) <= 0) {
1595	+	if (ac == 0) { // double check if all workers active
1596	+	for (int i = 1; i <= m; i += 2) {
1597	+	if ((w = ws[i]) != null && w.parker != null) {
1598	+	ac = -1;
1599	+	break;
1600	+	}
1601	+	}
1602	+	}
1603	+	return (ac < 0 && (a = q.array) != null &&
1604	+	(s = q.top - 1) - q.base >= 0 &&
1605	+	s >= 0 && s < a.length &&
1606	+	a[s] == task &&
1607	+	q.trySharedUnpush(task));
1608	+	}
1609	+	}
1610	+	return false;
1611	+	}
1612	+
1613	+	/**
1614	+	* Tries to pop and run a task within same computation from common pool
1615	+	*/
1616	+	static void popAndExecCCFromCommonPool(CountedCompleter<?> cc) {
1617	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; int m, ac;
1618	+	CountedCompleter<?> par, task;
1619	+	if ((p = commonPool) != null && (ws = p.workQueues) != null) {
1620	+	while ((par = cc.completer) != null) // find root
1621	+	cc = par;
1622	+	int k = submitters.get().seed & p.submitMask & SQMASK;
1623	+	if ((m = ws.length - 1) >= k && (q = ws[k]) != null &&
1624	+	(ac = (int)(p.ctl >> AC_SHIFT)) <= 0) {
1625	+	if (ac == 0) {
1626	+	for (int i = 1; i <= m; i += 2) {
1627	+	if ((w = ws[i]) != null && w.parker != null) {
1628	+	ac = -1;
1629	+	break;
1630	+	}
1631	+	}
1632	+	}
1633	+	if (ac < 0 && q.top - q.base > 0 &&
1634	+	(task = q.sharedPopCC(cc)) != null)
1635	+	task.exec();
1636	+	}
1637	+	}
1638	+	}
1639	+
1640		// Maintaining ctl counts
1641
1642		/**
#	Line 1434 | Line 1648 | public class ForkJoinPool extends Abstra
1648		}
1649
1650		/**
1651	<	* Tries to activate or create a worker if too few are active.
1651	>	* Tries to create one or activate one or more workers if too few are active.
1652		*/
1653		final void signalWork() {
1654		long c; int u;
#	Line 1518 | Line 1732 | public class ForkJoinPool extends Abstra
1732		* awaiting signal,
1733		*
1734		* @param w the worker (via its WorkQueue)
1735	<	* @return a task or null of none found
1735	>	* @return a task or null if none found
1736		*/
1737		private final ForkJoinTask<?> scan(WorkQueue w) {
1738		WorkQueue[] ws;                       // first update random seed
#	Line 1535 | Line 1749 | public class ForkJoinPool extends Abstra
1749		t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1750		if (q.base == b && ec >= 0 && t != null &&
1751		U.compareAndSwapObject(a, i, t, null)) {
1752	<	if (q.top - (q.base = b + 1) > 1)
1752	>	if (q.top - (q.base = b + 1) > 0)
1753		signalWork();    // help pushes signal
1754		return t;
1755		}
#	Line 1581 | Line 1795 | public class ForkJoinPool extends Abstra
1795		}
1796		}
1797		else if (w.eventCount < 0) {      // already queued
1798	<	if ((nr = w.rescans) > 0) {   // continue rescanning
1799	<	int ac = a + parallelism;
1800	<	if (((w.rescans = (ac < nr) ? ac : nr - 1) & 3) == 0)
1801	<	Thread.yield();       // yield before block
1588	<	}
1589	<	else {
1798	>	int ac = a + parallelism;
1799	>	if ((nr = w.rescans) > 0)     // continue rescanning
1800	>	w.rescans = (ac < nr) ? ac : nr - 1;
1801	>	else if (((w.seed >>> 16) & ac) == 0) { // randomize park
1802		Thread.interrupted();     // clear status
1803		Thread wt = Thread.currentThread();
1804		U.putObject(wt, PARKBLOCKER, this);
#	Line 1604 | Line 1816 | public class ForkJoinPool extends Abstra
1816		/**
1817		* If inactivating worker w has caused the pool to become
1818		* quiescent, checks for pool termination, and, so long as this is
1819	<	* not the only worker, waits for event for up to SHRINK_RATE
1820	<	* nanosecs.  On timeout, if ctl has not changed, terminates the
1819	>	* not the only worker, waits for event for up to a given
1820	>	* duration.  On timeout, if ctl has not changed, terminates the
1821		* worker, which will in turn wake up another worker to possibly
1822		* repeat this process.
1823		*
#	Line 1616 | Line 1828 | public class ForkJoinPool extends Abstra
1828		private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1829		if (w.eventCount < 0 && !tryTerminate(false, false) &&
1830		(int)prevCtl != 0 && !hasQueuedSubmissions() && ctl == currentCtl) {
1831	+	int dc = -(short)(currentCtl >>> TC_SHIFT);
1832	+	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1833	+	long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop
1834		Thread wt = Thread.currentThread();
1620	–	Thread.yield();            // yield before block
1835		while (ctl == currentCtl) {
1622	–	long startTime = System.nanoTime();
1836		Thread.interrupted();  // timed variant of version in scan()
1837		U.putObject(wt, PARKBLOCKER, this);
1838		w.parker = wt;
1839		if (ctl == currentCtl)
1840	<	U.park(false, SHRINK_RATE);
1840	>	U.park(false, parkTime);
1841		w.parker = null;
1842		U.putObject(wt, PARKBLOCKER, null);
1843		if (ctl != currentCtl)
1844		break;
1845	<	if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
1845	>	if (deadline - System.nanoTime() <= 0L &&
1846		U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1847		w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
1848		w.runState = -1;   // shrink
#	Line 1914 | Line 2127 | public class ForkJoinPool extends Abstra
2127		}
2128		}
2129
1917	–
2130		/**
2131		* Runs tasks until {@code isQuiescent()}. We piggyback on
2132		* active count ctl maintenance, but rather than blocking
#	Line 1957 | Line 2169 | public class ForkJoinPool extends Abstra
2169		}
2170
2171		/**
2172	+	* Restricted version of helpQuiescePool for non-FJ callers
2173	+	*/
2174	+	static void externalHelpQuiescePool() {
2175	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q, sq;
2176	+	ForkJoinTask<?>[] a; int b;
2177	+	ForkJoinTask<?> t = null;
2178	+	int k = submitters.get().seed & SQMASK;
2179	+	if ((p = commonPool) != null &&
2180	+	(ws = p.workQueues) != null &&
2181	+	ws.length > (k &= p.submitMask) &&
2182	+	(q = ws[k]) != null) {
2183	+	while (q.top - q.base > 0) {
2184	+	if ((t = q.sharedPop()) != null)
2185	+	break;
2186	+	}
2187	+	if (t == null && (sq = p.findNonEmptyStealQueue(q)) != null &&
2188	+	(b = sq.base) - sq.top < 0)
2189	+	t = sq.pollAt(b);
2190	+	if (t != null)
2191	+	t.doExec();
2192	+	}
2193	+	}
2194	+
2195	+	/**
2196		* Gets and removes a local or stolen task for the given worker.
2197		*
2198		* @return a task, if available
#	Line 1989 | Line 2225 | public class ForkJoinPool extends Abstra
2225		8);
2226		}
2227
2228	+	/**
2229	+	* Returns approximate submission queue length for the given caller
2230	+	*/
2231	+	static int getEstimatedSubmitterQueueLength() {
2232	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
2233	+	int k = submitters.get().seed & SQMASK;
2234	+	return ((p = commonPool) != null && (ws = p.workQueues) != null &&
2235	+	ws.length > (k &= p.submitMask) &&
2236	+	(q = ws[k]) != null) ?
2237	+	q.queueSize() : 0;
2238	+	}
2239	+
2240		//  Termination
2241
2242		/**
#	Line 2006 | Line 2254 | public class ForkJoinPool extends Abstra
2254		* @return true if now terminating or terminated
2255		*/
2256		private boolean tryTerminate(boolean now, boolean enable) {
2009	–	Mutex lock = this.lock;
2257		for (long c;;) {
2258		if (((c = ctl) & STOP_BIT) != 0) {      // already terminating
2259		if ((short)(c >>> TC_SHIFT) == -parallelism) {
2260	<	lock.lock();                    // don't need try/finally
2261	<	termination.signalAll();        // signal when 0 workers
2262	<	lock.unlock();
2260	>	synchronized (this) {
2261	>	notifyAll();                // signal when 0 workers
2262	>	}
2263		}
2264		return true;
2265		}
2266		if (runState >= 0) {                    // not yet enabled
2267		if (!enable)
2268		return false;
2269	<	lock.lock();
2270	<	runState |= SHUTDOWN;
2271	<	lock.unlock();
2269	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
2270	>	tryAwaitMainLock();
2271	>	try {
2272	>	runState |= SHUTDOWN;
2273	>	} finally {
2274	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
2275	>	mainLock = 0;
2276	>	synchronized (this) { notifyAll(); };
2277	>	}
2278	>	}
2279		}
2280		if (!now) {                             // check if idle & no tasks
2281		if ((int)(c >> AC_SHIFT) != -parallelism ||
#	Line 2154 | Line 2408 | public class ForkJoinPool extends Abstra
2408		// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2.
2409		int n = parallelism - 1;
2410		n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
2411	<	int size = (n + 1) << 1;        // #slots = 2*#workers
2158	<	this.submitMask = size - 1;     // room for max # of submit queues
2159	<	this.workQueues = new WorkQueue[size];
2160	<	this.termination = (this.lock = new Mutex()).newCondition();
2161	<	this.stealCount = new AtomicLong();
2162	<	this.nextWorkerNumber = new AtomicInteger();
2411	>	this.submitMask = ((n + 1) << 1) - 1;
2412		int pn = poolNumberGenerator.incrementAndGet();
2413		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2414		sb.append(Integer.toString(pn));
2415		sb.append("-worker-");
2416		this.workerNamePrefix = sb.toString();
2168	–	lock.lock();
2417		this.runState = 1;              // set init flag
2418	<	lock.unlock();
2418	>	}
2419	>
2420	>	/**
2421	>	* Constructor for common pool, suitable only for static initialization.
2422	>	* Basically the same as above, but uses smallest possible initial footprint.
2423	>	*/
2424	>	ForkJoinPool(int parallelism, int submitMask,
2425	>	ForkJoinWorkerThreadFactory factory,
2426	>	Thread.UncaughtExceptionHandler handler) {
2427	>	this.factory = factory;
2428	>	this.ueh = handler;
2429	>	this.submitMask = submitMask;
2430	>	this.parallelism = parallelism;
2431	>	long np = (long)(-parallelism);
2432	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
2433	>	this.localMode = LIFO_QUEUE;
2434	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2435	>	this.runState = 1;
2436	>	}
2437	>
2438	>	/**
2439	>	* Returns the common pool instance.
2440	>	*
2441	>	* @return the common pool instance
2442	>	*/
2443	>	public static ForkJoinPool commonPool() {
2444	>	ForkJoinPool p;
2445	>	if ((p = commonPool) == null)
2446	>	throw new Error("Common Pool Unavailable");
2447	>	return p;
2448		}
2449
2450		// Execution methods
#	Line 2343 | Line 2620 | public class ForkJoinPool extends Abstra
2620		}
2621
2622		/**
2623	+	* Returns the targeted parallelism level of the common pool.
2624	+	*
2625	+	* @return the targeted parallelism level of the common pool
2626	+	*/
2627	+	public static int getCommonPoolParallelism() {
2628	+	return commonPoolParallelism;
2629	+	}
2630	+
2631	+	/**
2632		* Returns the number of worker threads that have started but not
2633		* yet terminated.  The result returned by this method may differ
2634		* from {@link #getParallelism} when threads are created to
#	Line 2423 | Line 2709 | public class ForkJoinPool extends Abstra
2709		* @return the number of steals
2710		*/
2711		public long getStealCount() {
2712	<	long count = stealCount.get();
2712	>	long count = stealCount;
2713		WorkQueue[] ws; WorkQueue w;
2714		if ((ws = workQueues) != null) {
2715		for (int i = 1; i < ws.length; i += 2) {
#	Line 2553 | Line 2839 | public class ForkJoinPool extends Abstra
2839		public String toString() {
2840		// Use a single pass through workQueues to collect counts
2841		long qt = 0L, qs = 0L; int rc = 0;
2842	<	long st = stealCount.get();
2842	>	long st = stealCount;
2843		long c = ctl;
2844		WorkQueue[] ws; WorkQueue w;
2845		if ((ws = workQueues) != null) {
#	Line 2594 | Line 2880 | public class ForkJoinPool extends Abstra
2880		}
2881
2882		/**
2883	<	* Initiates an orderly shutdown in which previously submitted
2884	<	* tasks are executed, but no new tasks will be accepted.
2885	<	* Invocation has no additional effect if already shut down.
2886	<	* Tasks that are in the process of being submitted concurrently
2887	<	* during the course of this method may or may not be rejected.
2883	>	* Possibly initiates an orderly shutdown in which previously
2884	>	* submitted tasks are executed, but no new tasks will be
2885	>	* accepted. Invocation has no effect on execution state if this
2886	>	* is the {@link #commonPool}, and no additional effect if
2887	>	* already shut down.  Tasks that are in the process of being
2888	>	* submitted concurrently during the course of this method may or
2889	>	* may not be rejected.
2890		*
2891		* @throws SecurityException if a security manager exists and
2892		*         the caller is not permitted to modify threads
#	Line 2607 | Line 2895 | public class ForkJoinPool extends Abstra
2895		*/
2896		public void shutdown() {
2897		checkPermission();
2898	<	tryTerminate(false, true);
2898	>	if (this != commonPool)
2899	>	tryTerminate(false, true);
2900		}
2901
2902		/**
2903	<	* Attempts to cancel and/or stop all tasks, and reject all
2904	<	* subsequently submitted tasks.  Tasks that are in the process of
2905	<	* being submitted or executed concurrently during the course of
2906	<	* this method may or may not be rejected. This method cancels
2907	<	* both existing and unexecuted tasks, in order to permit
2908	<	* termination in the presence of task dependencies. So the method
2909	<	* always returns an empty list (unlike the case for some other
2910	<	* Executors).
2903	>	* Possibly attempts to cancel and/or stop all tasks, and reject
2904	>	* all subsequently submitted tasks.  Invocation has no effect on
2905	>	* execution state if this is the {@link #commonPool}, and no
2906	>	* additional effect if already shut down. Otherwise, tasks that
2907	>	* are in the process of being submitted or executed concurrently
2908	>	* during the course of this method may or may not be
2909	>	* rejected. This method cancels both existing and unexecuted
2910	>	* tasks, in order to permit termination in the presence of task
2911	>	* dependencies. So the method always returns an empty list
2912	>	* (unlike the case for some other Executors).
2913		*
2914		* @return an empty list
2915		* @throws SecurityException if a security manager exists and
#	Line 2628 | Line 2919 | public class ForkJoinPool extends Abstra
2919		*/
2920		public List<Runnable> shutdownNow() {
2921		checkPermission();
2922	<	tryTerminate(true, true);
2922	>	if (this != commonPool)
2923	>	tryTerminate(true, true);
2924		return Collections.emptyList();
2925		}
2926
#	Line 2685 | Line 2977 | public class ForkJoinPool extends Abstra
2977		public boolean awaitTermination(long timeout, TimeUnit unit)
2978		throws InterruptedException {
2979		long nanos = unit.toNanos(timeout);
2980	<	final Mutex lock = this.lock;
2981	<	lock.lock();
2982	<	try {
2983	<	for (;;) {
2984	<	if (isTerminated())
2985	<	return true;
2986	<	if (nanos <= 0)
2987	<	return false;
2988	<	nanos = termination.awaitNanos(nanos);
2980	>	if (isTerminated())
2981	>	return true;
2982	>	long startTime = System.nanoTime();
2983	>	boolean terminated = false;
2984	>	synchronized (this) {
2985	>	for (long waitTime = nanos, millis = 0L;;) {
2986	>	if (terminated = isTerminated() ||
2987	>	waitTime <= 0L ||
2988	>	(millis = unit.toMillis(waitTime)) <= 0L)
2989	>	break;
2990	>	wait(millis);
2991	>	waitTime = nanos - (System.nanoTime() - startTime);
2992		}
2698	–	} finally {
2699	–	lock.unlock();
2993		}
2994	+	return terminated;
2995		}
2996
2997		/**
#	Line 2829 | Line 3123 | public class ForkJoinPool extends Abstra
3123		private static final long PARKBLOCKER;
3124		private static final int ABASE;
3125		private static final int ASHIFT;
3126	+	private static final long NEXTWORKERNUMBER;
3127	+	private static final long STEALCOUNT;
3128	+	private static final long MAINLOCK;
3129
3130		static {
3131		poolNumberGenerator = new AtomicInteger();
#	Line 2844 | Line 3141 | public class ForkJoinPool extends Abstra
3141		Class<?> ak = ForkJoinTask[].class;
3142		CTL = U.objectFieldOffset
3143		(k.getDeclaredField("ctl"));
3144	+	NEXTWORKERNUMBER = U.objectFieldOffset
3145	+	(k.getDeclaredField("nextWorkerNumber"));
3146	+	STEALCOUNT = U.objectFieldOffset
3147	+	(k.getDeclaredField("stealCount"));
3148	+	MAINLOCK = U.objectFieldOffset
3149	+	(k.getDeclaredField("mainLock"));
3150		Class<?> tk = Thread.class;
3151		PARKBLOCKER = U.objectFieldOffset
3152		(tk.getDeclaredField("parkBlocker"));
3153		ABASE = U.arrayBaseOffset(ak);
3154		s = U.arrayIndexScale(ak);
3155	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3156		} catch (Exception e) {
3157		throw new Error(e);
3158		}
3159		if ((s & (s-1)) != 0)
3160		throw new Error("data type scale not a power of two");
3161	<	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3161	>	try { // Establish common pool
3162	>	String pp = System.getProperty(propPrefix + "parallelism");
3163	>	String fp = System.getProperty(propPrefix + "threadFactory");
3164	>	String up = System.getProperty(propPrefix + "exceptionHandler");
3165	>	ForkJoinWorkerThreadFactory fac = (fp == null) ?
3166	>	defaultForkJoinWorkerThreadFactory :
3167	>	((ForkJoinWorkerThreadFactory)ClassLoader.
3168	>	getSystemClassLoader().loadClass(fp).newInstance());
3169	>	Thread.UncaughtExceptionHandler ueh = (up == null) ? null :
3170	>	((Thread.UncaughtExceptionHandler)ClassLoader.
3171	>	getSystemClassLoader().loadClass(up).newInstance());
3172	>	int par;
3173	>	if ((pp == null || (par = Integer.parseInt(pp)) <= 0))
3174	>	par = Runtime.getRuntime().availableProcessors();
3175	>	if (par > MAX_CAP)
3176	>	par = MAX_CAP;
3177	>	commonPoolParallelism = par;
3178	>	int n = par - 1; // precompute submit mask
3179	>	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4;
3180	>	n |= n >>> 8; n |= n >>> 16;
3181	>	int mask = ((n + 1) << 1) - 1;
3182	>	commonPool = new ForkJoinPool(par, mask, fac, ueh);
3183	>	} catch (Exception e) {
3184	>	throw new Error(e);
3185	>	}
3186		}
3187
3188		/**

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