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root/jsr166/jsr166/src/jsr166y/ForkJoinWorkerThread.java

Comparing jsr166/src/jsr166y/ForkJoinWorkerThread.java (file contents):
Revision 1.32 by dl, Sun Apr 18 12:51:18 2010 UTC vs.
Revision 1.61 by jsr166, Tue Nov 23 06:21:54 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	–	import java.util.concurrent.*;
10	–
9		import java.util.Random;
10		import java.util.Collection;
11		import java.util.concurrent.locks.LockSupport;
12	+	import java.util.concurrent.RejectedExecutionException;
13
14		/**
15	<	* A thread managed by a {@link ForkJoinPool}.  This class is
16	<	* subclassable solely for the sake of adding functionality -- there
17	<	* are no overridable methods dealing with scheduling or execution.
18	<	* However, you can override initialization and termination methods
19	<	* surrounding the main task processing loop.  If you do create such a
20	<	* subclass, you will also need to supply a custom {@link
21	<	* ForkJoinPool.ForkJoinWorkerThreadFactory} to use it in a {@code
22	<	* ForkJoinPool}.
15	>	* A thread managed by a {@link ForkJoinPool}, which executes
16	>	* {@link ForkJoinTask}s.
17	>	* This class is subclassable solely for the sake of adding
18	>	* functionality -- there are no overridable methods dealing with
19	>	* scheduling or execution.  However, you can override initialization
20	>	* and termination methods surrounding the main task processing loop.
21	>	* If you do create such a subclass, you will also need to supply a
22	>	* custom {@link ForkJoinPool.ForkJoinWorkerThreadFactory} to use it
23	>	* in a {@code ForkJoinPool}.
24		*
25		* @since 1.7
26		* @author Doug Lea
#	Line 83 | Line 83 | public class ForkJoinWorkerThread extend
83		* by the ForkJoinPool).  This allows use in message-passing
84		* frameworks in which tasks are never joined.
85		*
86	<	* Efficient implementation of this approach currently relies on
87	<	* an uncomfortable amount of "Unsafe" mechanics. To maintain
86	>	* When a worker would otherwise be blocked waiting to join a
87	>	* task, it first tries a form of linear helping: Each worker
88	>	* records (in field currentSteal) the most recent task it stole
89	>	* from some other worker. Plus, it records (in field currentJoin)
90	>	* the task it is currently actively joining. Method joinTask uses
91	>	* these markers to try to find a worker to help (i.e., steal back
92	>	* a task from and execute it) that could hasten completion of the
93	>	* actively joined task. In essence, the joiner executes a task
94	>	* that would be on its own local deque had the to-be-joined task
95	>	* not been stolen. This may be seen as a conservative variant of
96	>	* the approach in Wagner & Calder "Leapfrogging: a portable
97	>	* technique for implementing efficient futures" SIGPLAN Notices,
98	>	* 1993 (http://portal.acm.org/citation.cfm?id=155354). It differs
99	>	* in that: (1) We only maintain dependency links across workers
100	>	* upon steals, rather than use per-task bookkeeping.  This may
101	>	* require a linear scan of workers array to locate stealers, but
102	>	* usually doesn't because stealers leave hints (that may become
103	>	* stale/wrong) of where to locate them. This isolates cost to
104	>	* when it is needed, rather than adding to per-task overhead.
105	>	* (2) It is "shallow", ignoring nesting and potentially cyclic
106	>	* mutual steals.  (3) It is intentionally racy: field currentJoin
107	>	* is updated only while actively joining, which means that we
108	>	* miss links in the chain during long-lived tasks, GC stalls etc
109	>	* (which is OK since blocking in such cases is usually a good
110	>	* idea).  (4) We bound the number of attempts to find work (see
111	>	* MAX_HELP_DEPTH) and fall back to suspending the worker and if
112	>	* necessary replacing it with a spare (see
113	>	* ForkJoinPool.awaitJoin).
114	>	*
115	>	* Efficient implementation of these algorithms currently relies
116	>	* on an uncomfortable amount of "Unsafe" mechanics. To maintain
117		* correct orderings, reads and writes of variable base require
118		* volatile ordering.  Variable sp does not require volatile
119		* writes but still needs store-ordering, which we accomplish by
120		* pre-incrementing sp before filling the slot with an ordered
121		* store.  (Pre-incrementing also enables backouts used in
122	<	* scanWhileJoining.)  Because they are protected by volatile base
123	<	* reads, reads of the queue array and its slots by other threads
124	<	* do not need volatile load semantics, but writes (in push)
125	<	* require store order and CASes (in pop and deq) require
126	<	* (volatile) CAS semantics.  (Michael, Saraswat, and Vechev's
127	<	* algorithm has similar properties, but without support for
128	<	* nulling slots.)  Since these combinations aren't supported
129	<	* using ordinary volatiles, the only way to accomplish these
130	<	* efficiently is to use direct Unsafe calls. (Using external
131	<	* AtomicIntegers and AtomicReferenceArrays for the indices and
132	<	* array is significantly slower because of memory locality and
133	<	* indirection effects.)
122	>	* joinTask.)  Because they are protected by volatile base reads,
123	>	* reads of the queue array and its slots by other threads do not
124	>	* need volatile load semantics, but writes (in push) require
125	>	* store order and CASes (in pop and deq) require (volatile) CAS
126	>	* semantics.  (Michael, Saraswat, and Vechev's algorithm has
127	>	* similar properties, but without support for nulling slots.)
128	>	* Since these combinations aren't supported using ordinary
129	>	* volatiles, the only way to accomplish these efficiently is to
130	>	* use direct Unsafe calls. (Using external AtomicIntegers and
131	>	* AtomicReferenceArrays for the indices and array is
132	>	* significantly slower because of memory locality and indirection
133	>	* effects.)
134		*
135		* Further, performance on most platforms is very sensitive to
136		* placement and sizing of the (resizable) queue array.  Even
#	Line 126 | Line 155 | public class ForkJoinWorkerThread extend
155		private static final Random seedGenerator = new Random();
156
157		/**
158	<	* The timeout value for suspending spares. Spare workers that
159	<	* remain unsignalled for more than this time may be trimmed
160	<	* (killed and removed from pool).  Since our goal is to avoid
161	<	* long-term thread buildup, the exact value of timeout does not
162	<	* matter too much so long as it avoids most false-alarm timeouts
134	<	* under GC stalls or momentarily high system load.
158	>	* The maximum stolen->joining link depth allowed in helpJoinTask.
159	>	* Depths for legitimate chains are unbounded, but we use a fixed
160	>	* constant to avoid (otherwise unchecked) cycles and bound
161	>	* staleness of traversal parameters at the expense of sometimes
162	>	* blocking when we could be helping.
163		*/
164	<	private static final long SPARE_KEEPALIVE_NANOS =
137	<	5L * 1000L * 1000L * 1000L; // 5 secs
164	>	private static final int MAX_HELP_DEPTH = 8;
165
166		/**
167		* Capacity of work-stealing queue array upon initialization.
168	<	* Must be a power of two. Initial size must be at least 2, but is
168	>	* Must be a power of two. Initial size must be at least 4, but is
169		* padded to minimize cache effects.
170		*/
171		private static final int INITIAL_QUEUE_CAPACITY = 1 << 13;
172
173		/**
174		* Maximum work-stealing queue array size.  Must be less than or
175	<	* equal to 1 << 28 to ensure lack of index wraparound. (This
176	<	* is less than usual bounds, because we need leftshift by 3
177	<	* to be in int range).
175	>	* equal to 1 << (31 - width of array entry) to ensure lack of
176	>	* index wraparound. The value is set in the static block
177	>	* at the end of this file after obtaining width.
178		*/
179	<	private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 28;
179	>	private static final int MAXIMUM_QUEUE_CAPACITY;
180
181		/**
182		* The pool this thread works in. Accessed directly by ForkJoinTask.
#	Line 178 | Line 205 | public class ForkJoinWorkerThread extend
205		private int sp;
206
207		/**
208	+	* The index of most recent stealer, used as a hint to avoid
209	+	* traversal in method helpJoinTask. This is only a hint because a
210	+	* worker might have had multiple steals and this only holds one
211	+	* of them (usually the most current). Declared non-volatile,
212	+	* relying on other prevailing sync to keep reasonably current.
213	+	*/
214	+	private int stealHint;
215	+
216	+	/**
217		* Run state of this worker. In addition to the usual run levels,
218		* tracks if this worker is suspended as a spare, and if it was
219		* killed (trimmed) while suspended. However, "active" status is
220	<	* maintained separately.
220	>	* maintained separately and modified only in conjunction with
221	>	* CASes of the pool's runState (which are currently sadly
222	>	* manually inlined for performance.)  Accessed directly by pool
223	>	* to simplify checks for normal (zero) status.
224		*/
225	<	private volatile int runState;
225	>	volatile int runState;
226
227		private static final int TERMINATING = 0x01;
228		private static final int TERMINATED  = 0x02;
#	Line 191 | Line 230 | public class ForkJoinWorkerThread extend
230		private static final int TRIMMED     = 0x08; // killed while suspended
231
232		/**
233	<	* Number of LockSupport.park calls to block this thread for
234	<	* suspension or event waits. Used for internal instrumention;
196	<	* currently not exported but included because volatile write upon
197	<	* park also provides a workaround for a JVM bug.
198	<	*/
199	<	private volatile int parkCount;
200	<
201	<	/**
202	<	* Number of steals, transferred and reset in pool callbacks pool
203	<	* when idle Accessed directly by pool.
233	>	* Number of steals. Directly accessed (and reset) by
234	>	* pool.tryAccumulateStealCount when idle.
235		*/
236		int stealCount;
237
#	Line 218 | Line 249 | public class ForkJoinWorkerThread extend
249
250		/**
251		* True if use local fifo, not default lifo, for local polling.
252	<	* Shadows value from ForkJoinPool, which resets it if changed
222	<	* pool-wide.
252	>	* Shadows value from ForkJoinPool.
253		*/
254	<	private boolean locallyFifo;
254	>	private final boolean locallyFifo;
255
256		/**
257		* Index of this worker in pool array. Set once by pool before
#	Line 237 | Line 267 | public class ForkJoinWorkerThread extend
267		int lastEventCount;
268
269		/**
270	<	* Encoded index and event count of next event waiter. Used only
271	<	* by ForkJoinPool for managing event waiters.
270	>	* Encoded index and event count of next event waiter. Accessed
271	>	* only by ForkJoinPool for managing event waiters.
272		*/
273		volatile long nextWaiter;
274
275		/**
276	+	* Number of times this thread suspended as spare. Accessed only
277	+	* by pool.
278	+	*/
279	+	int spareCount;
280	+
281	+	/**
282	+	* Encoded index and count of next spare waiter. Accessed only
283	+	* by ForkJoinPool for managing spares.
284	+	*/
285	+	volatile int nextSpare;
286	+
287	+	/**
288	+	* The task currently being joined, set only when actively trying
289	+	* to help other stealers in helpJoinTask. Written only by this
290	+	* thread, but read by others.
291	+	*/
292	+	private volatile ForkJoinTask<?> currentJoin;
293	+
294	+	/**
295	+	* The task most recently stolen from another worker (or
296	+	* submission queue).  Written only by this thread, but read by
297	+	* others.
298	+	*/
299	+	private volatile ForkJoinTask<?> currentSteal;
300	+
301	+	/**
302		* Creates a ForkJoinWorkerThread operating in the given pool.
303		*
304		* @param pool the pool this thread works in
305		* @throws NullPointerException if pool is null
306		*/
307		protected ForkJoinWorkerThread(ForkJoinPool pool) {
252	–	if (pool == null) throw new NullPointerException();
308		this.pool = pool;
309	+	this.locallyFifo = pool.locallyFifo;
310	+	setDaemon(true);
311		// To avoid exposing construction details to subclasses,
312		// remaining initialization is in start() and onStart()
313		}
314
315		/**
316	<	* Performs additional initialization and starts this thread
316	>	* Performs additional initialization and starts this thread.
317		*/
318	<	final void start(int poolIndex, boolean locallyFifo,
262	<	UncaughtExceptionHandler ueh) {
318	>	final void start(int poolIndex, UncaughtExceptionHandler ueh) {
319		this.poolIndex = poolIndex;
264	–	this.locallyFifo = locallyFifo;
320		if (ueh != null)
321		setUncaughtExceptionHandler(ueh);
267	–	setDaemon(true);
322		start();
323		}
324
#	Line 295 | Line 349 | public class ForkJoinWorkerThread extend
349		/**
350		* Initializes internal state after construction but before
351		* processing any tasks. If you override this method, you must
352	<	* invoke super.onStart() at the beginning of the method.
352	>	* invoke {@code super.onStart()} at the beginning of the method.
353		* Initialization requires care: Most fields must have legal
354		* default values, to ensure that attempted accesses from other
355		* threads work correctly even before this thread starts
#	Line 305 | Line 359 | public class ForkJoinWorkerThread extend
359		int rs = seedGenerator.nextInt();
360		seed = rs == 0? 1 : rs; // seed must be nonzero
361
362	<	// Allocate name string and queue array in this thread
362	>	// Allocate name string and arrays in this thread
363		String pid = Integer.toString(pool.getPoolNumber());
364		String wid = Integer.toString(poolIndex);
365		setName("ForkJoinPool-" + pid + "-worker-" + wid);
#	Line 323 | Line 377 | public class ForkJoinWorkerThread extend
377		*/
378		protected void onTermination(Throwable exception) {
379		try {
380	+	ForkJoinPool p = pool;
381	+	if (active) {
382	+	int a; // inline p.tryDecrementActiveCount
383	+	active = false;
384	+	do {} while (!UNSAFE.compareAndSwapInt
385	+	(p, poolRunStateOffset, a = p.runState, a - 1));
386	+	}
387		cancelTasks();
388		setTerminated();
389	<	pool.workerTerminated(this);
389	>	p.workerTerminated(this);
390		} catch (Throwable ex) {        // Shouldn't ever happen
391		if (exception == null)      // but if so, at least rethrown
392		exception = ex;
#	Line 338 | Line 399 | public class ForkJoinWorkerThread extend
399		/**
400		* This method is required to be public, but should never be
401		* called explicitly. It performs the main run loop to execute
402	<	* ForkJoinTasks.
402	>	* {@link ForkJoinTask}s.
403		*/
404		public void run() {
405		Throwable exception = null;
#	Line 355 | Line 416 | public class ForkJoinWorkerThread extend
416		// helpers for run()
417
418		/**
419	<	* Find and execute tasks and check status while running
419	>	* Finds and executes tasks, and checks status while running.
420		*/
421		private void mainLoop() {
422	<	boolean ran = false; // true if ran task on previous step
422	>	boolean ran = false; // true if ran a task on last step
423		ForkJoinPool p = pool;
424		for (;;) {
425		p.preStep(this, ran);
426		if (runState != 0)
427	<	return;
428	<	ForkJoinTask<?> t; // try to get and run stolen or submitted task
368	<	if (ran = (t = scan()) != null || (t = pollSubmission()) != null) {
369	<	t.tryExec();
370	<	if (base != sp)
371	<	runLocalTasks();
372	<	}
427	>	break;
428	>	ran = tryExecSteal() || tryExecSubmission();
429		}
430		}
431
432		/**
433	<	* Runs local tasks until queue is empty or shut down.  Call only
434	<	* while active.
433	>	* Tries to steal a task and execute it.
434	>	*
435	>	* @return true if ran a task
436		*/
437	<	private void runLocalTasks() {
438	<	while (runState == 0) {
439	<	ForkJoinTask<?> t = locallyFifo? locallyDeqTask() : popTask();
440	<	if (t != null)
441	<	t.tryExec();
442	<	else if (base == sp)
443	<	break;
437	>	private boolean tryExecSteal() {
438	>	ForkJoinTask<?> t;
439	>	if ((t = scan()) != null) {
440	>	t.quietlyExec();
441	>	UNSAFE.putOrderedObject(this, currentStealOffset, null);
442	>	if (sp != base)
443	>	execLocalTasks();
444	>	return true;
445		}
446	+	return false;
447		}
448
449		/**
450	<	* If a submission exists, try to activate and take it
450	>	* If a submission exists, try to activate and run it.
451		*
452	<	* @return a task, if available
452	>	* @return true if ran a task
453		*/
454	<	private ForkJoinTask<?> pollSubmission() {
454	>	private boolean tryExecSubmission() {
455		ForkJoinPool p = pool;
456	+	// This loop is needed in case attempt to activate fails, in
457	+	// which case we only retry if there still appears to be a
458	+	// submission.
459		while (p.hasQueuedSubmissions()) {
460	<	if (active || (active = p.tryIncrementActiveCount())) {
461	<	ForkJoinTask<?> t = p.pollSubmission();
462	<	return t != null ? t : scan(); // if missed, rescan
460	>	ForkJoinTask<?> t; int a;
461	>	if (active || // inline p.tryIncrementActiveCount
462	>	(active = UNSAFE.compareAndSwapInt(p, poolRunStateOffset,
463	>	a = p.runState, a + 1))) {
464	>	if ((t = p.pollSubmission()) != null) {
465	>	UNSAFE.putOrderedObject(this, currentStealOffset, t);
466	>	t.quietlyExec();
467	>	UNSAFE.putOrderedObject(this, currentStealOffset, null);
468	>	if (sp != base)
469	>	execLocalTasks();
470	>	return true;
471	>	}
472		}
473		}
474	<	return null;
474	>	return false;
475	>	}
476	>
477	>	/**
478	>	* Runs local tasks until queue is empty or shut down.  Call only
479	>	* while active.
480	>	*/
481	>	private void execLocalTasks() {
482	>	while (runState == 0) {
483	>	ForkJoinTask<?> t = locallyFifo ? locallyDeqTask() : popTask();
484	>	if (t != null)
485	>	t.quietlyExec();
486	>	else if (sp == base)
487	>	break;
488	>	}
489		}
490
491		/*
492		* Intrinsics-based atomic writes for queue slots. These are
493	<	* basically the same as methods in AtomicObjectArray, but
493	>	* basically the same as methods in AtomicReferenceArray, but
494		* specialized for (1) ForkJoinTask elements (2) requirement that
495		* nullness and bounds checks have already been performed by
496		* callers and (3) effective offsets are known not to overflow
497		* from int to long (because of MAXIMUM_QUEUE_CAPACITY). We don't
498		* need corresponding version for reads: plain array reads are OK
499	<	* because they protected by other volatile reads and are
499	>	* because they are protected by other volatile reads and are
500		* confirmed by CASes.
501		*
502		* Most uses don't actually call these methods, but instead contain
#	Line 435 | Line 520 | public class ForkJoinWorkerThread extend
520		* range. This method is used only during resets and backouts.
521		*/
522		private static final void writeSlot(ForkJoinTask<?>[] q, int i,
523	<	ForkJoinTask<?> t) {
523	>	ForkJoinTask<?> t) {
524		UNSAFE.putObjectVolatile(q, (i << qShift) + qBase, t);
525		}
526
#	Line 447 | Line 532 | public class ForkJoinWorkerThread extend
532		* @param t the task. Caller must ensure non-null.
533		*/
534		final void pushTask(ForkJoinTask<?> t) {
450	–	int s;
535		ForkJoinTask<?>[] q = queue;
536		int mask = q.length - 1; // implicit assert q != null
537	<	UNSAFE.putOrderedObject(q, (((s = sp++) & mask) << qShift) + qBase, t);
538	<	if ((s -= base) <= 0)
539	<	pool.signalWork();
540	<	else if (s + 1 >= mask)
541	<	growQueue();
537	>	int s = sp++;            // ok to increment sp before slot write
538	>	UNSAFE.putOrderedObject(q, ((s & mask) << qShift) + qBase, t);
539	>	if ((s -= base) == 0)
540	>	pool.signalWork();   // was empty
541	>	else if (s == mask)
542	>	growQueue();         // is full
543		}
544
545		/**
546		* Tries to take a task from the base of the queue, failing if
547		* empty or contended. Note: Specializations of this code appear
548	<	* in scan and scanWhileJoining.
548	>	* in locallyDeqTask and elsewhere.
549		*
550		* @return a task, or null if none or contended
551		*/
#	Line 468 | Line 553 | public class ForkJoinWorkerThread extend
553		ForkJoinTask<?> t;
554		ForkJoinTask<?>[] q;
555		int b, i;
556	<	if ((b = base) != sp &&
556	>	if (sp != (b = base) &&
557		(q = queue) != null && // must read q after b
558	<	(t = q[i = (q.length - 1) & b]) != null &&
558	>	(t = q[i = (q.length - 1) & b]) != null && base == b &&
559		UNSAFE.compareAndSwapObject(q, (i << qShift) + qBase, t, null)) {
560		base = b + 1;
561		return t;
#	Line 480 | Line 565 | public class ForkJoinWorkerThread extend
565
566		/**
567		* Tries to take a task from the base of own queue. Assumes active
568	<	* status.  Called only by current thread.
568	>	* status.  Called only by this thread.
569		*
570		* @return a task, or null if none
571		*/
#	Line 490 | Line 575 | public class ForkJoinWorkerThread extend
575		ForkJoinTask<?> t;
576		int b, i;
577		while (sp != (b = base)) {
578	<	if ((t = q[i = (q.length - 1) & b]) != null &&
578	>	if ((t = q[i = (q.length - 1) & b]) != null && base == b &&
579		UNSAFE.compareAndSwapObject(q, (i << qShift) + qBase,
580		t, null)) {
581		base = b + 1;
#	Line 503 | Line 588 | public class ForkJoinWorkerThread extend
588
589		/**
590		* Returns a popped task, or null if empty. Assumes active status.
591	<	* Called only by current thread. (Note: a specialization of this
507	<	* code appears in scanWhileJoining.)
591	>	* Called only by this thread.
592		*/
593	<	final ForkJoinTask<?> popTask() {
510	<	int s;
593	>	private ForkJoinTask<?> popTask() {
594		ForkJoinTask<?>[] q = queue;
595	<	if (q != null && (s = sp) != base) {
596	<	int i = (q.length - 1) & --s;
597	<	ForkJoinTask<?> t = q[i];
598	<	if (t != null && UNSAFE.compareAndSwapObject
599	<	(q, (i << qShift) + qBase, t, null)) {
600	<	sp = s;
601	<	return t;
595	>	if (q != null) {
596	>	int s;
597	>	while ((s = sp) != base) {
598	>	int i = (q.length - 1) & --s;
599	>	long u = (i << qShift) + qBase; // raw offset
600	>	ForkJoinTask<?> t = q[i];
601	>	if (t == null)   // lost to stealer
602	>	break;
603	>	if (UNSAFE.compareAndSwapObject(q, u, t, null)) {
604	>	/*
605	>	* Note: here and in related methods, as a
606	>	* performance (not correctness) issue, we'd like
607	>	* to encourage compiler not to arbitrarily
608	>	* postpone setting sp after successful CAS.
609	>	* Currently there is no intrinsic for arranging
610	>	* this, but using Unsafe putOrderedInt may be a
611	>	* preferable strategy on some compilers even
612	>	* though its main effect is a pre-, not post-
613	>	* fence. To simplify possible changes, the option
614	>	* is left in comments next to the associated
615	>	* assignments.
616	>	*/
617	>	sp = s; // putOrderedInt may encourage more timely write
618	>	// UNSAFE.putOrderedInt(this, spOffset, s);
619	>	return t;
620	>	}
621		}
622		}
623		return null;
624		}
625
626		/**
627	<	* Specialized version of popTask to pop only if
628	<	* topmost element is the given task. Called only
527	<	* by current thread while active.
627	>	* Specialized version of popTask to pop only if topmost element
628	>	* is the given task. Called only by this thread while active.
629		*
630		* @param t the task. Caller must ensure non-null.
631		*/
632		final boolean unpushTask(ForkJoinTask<?> t) {
633		int s;
634		ForkJoinTask<?>[] q = queue;
635	<	if (q != null && UNSAFE.compareAndSwapObject
636	<	(q, (((q.length - 1) & (s = sp - 1)) << qShift) + qBase, t, null)){
637	<	sp = s;
635	>	if ((s = sp) != base && q != null &&
636	>	UNSAFE.compareAndSwapObject
637	>	(q, (((q.length - 1) & --s) << qShift) + qBase, t, null)) {
638	>	sp = s; // putOrderedInt may encourage more timely write
639	>	// UNSAFE.putOrderedInt(this, spOffset, s);
640		return true;
641		}
642		return false;
643		}
644
645		/**
646	<	* Returns next task or null if empty or contended
646	>	* Returns next task, or null if empty or contended.
647		*/
648		final ForkJoinTask<?> peekTask() {
649		ForkJoinTask<?>[] q = queue;
#	Line 582 | Line 685 | public class ForkJoinWorkerThread extend
685		* Computes next value for random victim probe in scan().  Scans
686		* don't require a very high quality generator, but also not a
687		* crummy one.  Marsaglia xor-shift is cheap and works well enough.
688	<	* Note: This is manually inlined in scan()
688	>	* Note: This is manually inlined in scan().
689		*/
690		private static final int xorShift(int r) {
691		r ^= r << 13;
#	Line 610 | Line 713 | public class ForkJoinWorkerThread extend
713		*/
714		private ForkJoinTask<?> scan() {
715		ForkJoinPool p = pool;
716	<	ForkJoinWorkerThread[] ws = p.workers;
717	<	int n = ws.length;            // upper bound of #workers
718	<	boolean canSteal = active;    // shadow active status
719	<	int r = seed;                 // extract seed once
720	<	int k = r;                    // index: random if j<0 else step
721	<	for (int j = -n; j < n; ++j) {
722	<	ForkJoinWorkerThread v = ws[k & (n - 1)];
723	<	r ^= r << 13; r ^= r >>> 17; r ^= r << 5; // xorshift
724	<	if (v != null && v.base != v.sp) {
725	<	if (canSteal ||       // ensure active status
726	<	(canSteal = active = p.tryIncrementActiveCount())) {
727	<	int b, i;         // inlined specialization of deqTask
728	<	ForkJoinTask<?> t;
729	<	ForkJoinTask<?>[] q;
730	<	if ((b = v.base) != v.sp &&  // recheck
731	<	(q = v.queue) != null &&
732	<	(t = q[i = (q.length - 1) & b]) != null &&
733	<	UNSAFE.compareAndSwapObject
734	<	(q, (i << qShift) + qBase, t, null)) {
735	<	v.base = b + 1;
736	<	seed = r;
737	<	++stealCount;
738	<	return t;
716	>	ForkJoinWorkerThread[] ws;        // worker array
717	>	int n;                            // upper bound of #workers
718	>	if ((ws = p.workers) != null && (n = ws.length) > 1) {
719	>	boolean canSteal = active;    // shadow active status
720	>	int r = seed;                 // extract seed once
721	>	int mask = n - 1;
722	>	int j = -n;                   // loop counter
723	>	int k = r;                    // worker index, random if j < 0
724	>	for (;;) {
725	>	ForkJoinWorkerThread v = ws[k & mask];
726	>	r ^= r << 13; r ^= r >>> 17; r ^= r << 5; // inline xorshift
727	>	ForkJoinTask<?>[] q; ForkJoinTask<?> t; int b, a;
728	>	if (v != null && (b = v.base) != v.sp &&
729	>	(q = v.queue) != null) {
730	>	int i = (q.length - 1) & b;
731	>	long u = (i << qShift) + qBase; // raw offset
732	>	int pid = poolIndex;
733	>	if ((t = q[i]) != null) {
734	>	if (!canSteal &&  // inline p.tryIncrementActiveCount
735	>	UNSAFE.compareAndSwapInt(p, poolRunStateOffset,
736	>	a = p.runState, a + 1))
737	>	canSteal = active = true;
738	>	if (canSteal && v.base == b++ &&
739	>	UNSAFE.compareAndSwapObject(q, u, t, null)) {
740	>	v.base = b;
741	>	v.stealHint = pid;
742	>	UNSAFE.putOrderedObject(this,
743	>	currentStealOffset, t);
744	>	seed = r;
745	>	++stealCount;
746	>	return t;
747	>	}
748		}
749	+	j = -n;
750	+	k = r;                // restart on contention
751		}
752	<	j = -n;           // reset on contention
752	>	else if (++j <= 0)
753	>	k = r;
754	>	else if (j <= n)
755	>	k += (n >>> 1) | 1;
756	>	else
757	>	break;
758		}
640	–	k = j >= 0? k + ((n >>> 1) | 1) : r;
759		}
760		return null;
761		}
#	Line 645 | Line 763 | public class ForkJoinWorkerThread extend
763		// Run State management
764
765		// status check methods used mainly by ForkJoinPool
766	<	final boolean isTerminating() { return (runState & TERMINATING) != 0; }
767	<	final boolean isTerminated()  { return (runState & TERMINATED) != 0; }
768	<	final boolean isSuspended()   { return (runState & SUSPENDED) != 0; }
769	<	final boolean isTrimmed()     { return (runState & TRIMMED) != 0; }
766	>	final boolean isRunning()    { return runState == 0; }
767	>	final boolean isTerminated() { return (runState & TERMINATED) != 0; }
768	>	final boolean isSuspended()  { return (runState & SUSPENDED) != 0; }
769	>	final boolean isTrimmed()    { return (runState & TRIMMED) != 0; }
770	>
771	>	final boolean isTerminating() {
772	>	if ((runState & TERMINATING) != 0)
773	>	return true;
774	>	if (pool.isAtLeastTerminating()) { // propagate pool state
775	>	shutdown();
776	>	return true;
777	>	}
778	>	return false;
779	>	}
780
781		/**
782	<	* Sets state to TERMINATING, also resuming if suspended.
782	>	* Sets state to TERMINATING. Does NOT unpark or interrupt
783	>	* to wake up if currently blocked. Callers must do so if desired.
784		*/
785		final void shutdown() {
786		for (;;) {
787		int s = runState;
788	+	if ((s & (TERMINATING|TERMINATED)) != 0)
789	+	break;
790		if ((s & SUSPENDED) != 0) { // kill and wakeup if suspended
791		if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
792		(s & ~SUSPENDED) |
793	<	(TRIMMED|TERMINATING))) {
663	<	LockSupport.unpark(this);
793	>	(TRIMMED|TERMINATING)))
794		break;
665	–	}
795		}
796		else if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
797		s | TERMINATING))
#	Line 671 | Line 800 | public class ForkJoinWorkerThread extend
800		}
801
802		/**
803	<	* Sets state to TERMINATED. Called only by this thread.
803	>	* Sets state to TERMINATED. Called only by onTermination().
804		*/
805		private void setTerminated() {
806		int s;
#	Line 681 | Line 810 | public class ForkJoinWorkerThread extend
810		}
811
812		/**
684	–	* Instrumented version of park. Also used by ForkJoinPool.awaitEvent
685	–	*/
686	–	final void doPark() {
687	–	++parkCount;
688	–	LockSupport.park(this);
689	–	}
690	–
691	–	/**
813		* If suspended, tries to set status to unsuspended.
814	<	* Caller must unpark to actually resume
814	>	* Does NOT wake up if blocked.
815		*
816		* @return true if successful
817		*/
818		final boolean tryUnsuspend() {
819		int s;
820	<	return (((s = runState) & SUSPENDED) != 0 &&
821	<	UNSAFE.compareAndSwapInt(this, runStateOffset, s,
822	<	s & ~SUSPENDED));
820	>	while (((s = runState) & SUSPENDED) != 0) {
821	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
822	>	s & ~SUSPENDED))
823	>	return true;
824	>	}
825	>	return false;
826		}
827
828		/**
829	<	* Sets suspended status and blocks as spare until resumed,
830	<	* shutdown, or timed out.
707	<	*
708	<	* @return false if trimmed
829	>	* Sets suspended status and blocks as spare until resumed
830	>	* or shutdown.
831		*/
832	<	final boolean suspendAsSpare() {
833	<	for (;;) {               // set suspended unless terminating
832	>	final void suspendAsSpare() {
833	>	for (;;) {                  // set suspended unless terminating
834		int s = runState;
835		if ((s & TERMINATING) != 0) { // must kill
836		if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
837		s | (TRIMMED | TERMINATING)))
838	<	return false;
838	>	return;
839		}
840		else if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
841		s | SUSPENDED))
842		break;
843		}
722	–	lastEventCount = 0;      // reset upon resume
844		ForkJoinPool p = pool;
845	<	p.releaseWaiters();      // help others progress
725	<	p.accumulateStealCount(this);
726	<	interrupted();           // clear/ignore interrupts
727	<	if (poolIndex < p.getParallelism()) { // untimed wait
728	<	while ((runState & SUSPENDED) != 0)
729	<	doPark();
730	<	return true;
731	<	}
732	<	return timedSuspend();   // timed wait if apparently non-core
733	<	}
734	<
735	<	/**
736	<	* Blocks as spare until resumed or timed out
737	<	* @return false if trimmed
738	<	*/
739	<	private boolean timedSuspend() {
740	<	long nanos = SPARE_KEEPALIVE_NANOS;
741	<	long startTime = System.nanoTime();
845	>	p.pushSpare(this);
846		while ((runState & SUSPENDED) != 0) {
847	<	++parkCount;
848	<	if ((nanos -= (System.nanoTime() - startTime)) > 0)
849	<	LockSupport.parkNanos(this, nanos);
850	<	else { // try to trim on timeout
851	<	int s = runState;
748	<	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
749	<	(s & ~SUSPENDED) |
750	<	(TRIMMED|TERMINATING)))
751	<	return false;
847	>	if (p.tryAccumulateStealCount(this)) {
848	>	interrupted();          // clear/ignore interrupts
849	>	if ((runState & SUSPENDED) == 0)
850	>	break;
851	>	LockSupport.park(this);
852		}
853		}
754	–	return true;
854		}
855
856		// Misc support methods for ForkJoinPool
#	Line 761 | Line 860 | public class ForkJoinWorkerThread extend
860		* used by ForkJoinTask.
861		*/
862		final int getQueueSize() {
863	<	return -base + sp;
864	<	}
766	<
767	<	/**
768	<	* Set locallyFifo mode. Called only by ForkJoinPool
769	<	*/
770	<	final void setAsyncMode(boolean async) {
771	<	locallyFifo = async;
863	>	int n; // external calls must read base first
864	>	return (n = -base + sp) <= 0 ? 0 : n;
865		}
866
867		/**
#	Line 776 | Line 869 | public class ForkJoinWorkerThread extend
869		* thread.
870		*/
871		final void cancelTasks() {
872	+	ForkJoinTask<?> cj = currentJoin; // try to cancel ongoing tasks
873	+	if (cj != null && cj.status >= 0) {
874	+	cj.cancelIgnoringExceptions();
875	+	try {
876	+	this.interrupt(); // awaken wait
877	+	} catch (SecurityException ignore) {
878	+	}
879	+	}
880	+	ForkJoinTask<?> cs = currentSteal;
881	+	if (cs != null && cs.status >= 0)
882	+	cs.cancelIgnoringExceptions();
883		while (base != sp) {
884		ForkJoinTask<?> t = deqTask();
885		if (t != null)
#	Line 803 | Line 907 | public class ForkJoinWorkerThread extend
907		// Support methods for ForkJoinTask
908
909		/**
910	+	* Gets and removes a local task.
911	+	*
912	+	* @return a task, if available
913	+	*/
914	+	final ForkJoinTask<?> pollLocalTask() {
915	+	ForkJoinPool p = pool;
916	+	while (sp != base) {
917	+	int a; // inline p.tryIncrementActiveCount
918	+	if (active ||
919	+	(active = UNSAFE.compareAndSwapInt(p, poolRunStateOffset,
920	+	a = p.runState, a + 1)))
921	+	return locallyFifo ? locallyDeqTask() : popTask();
922	+	}
923	+	return null;
924	+	}
925	+
926	+	/**
927	+	* Gets and removes a local or stolen task.
928	+	*
929	+	* @return a task, if available
930	+	*/
931	+	final ForkJoinTask<?> pollTask() {
932	+	ForkJoinTask<?> t = pollLocalTask();
933	+	if (t == null) {
934	+	t = scan();
935	+	// cannot retain/track/help steal
936	+	UNSAFE.putOrderedObject(this, currentStealOffset, null);
937	+	}
938	+	return t;
939	+	}
940	+
941	+	/**
942	+	* Possibly runs some tasks and/or blocks, until task is done.
943	+	*
944	+	* @param joinMe the task to join
945	+	* @param timed true if use timed wait
946	+	* @param nanos wait time if timed
947	+	*/
948	+	final void joinTask(ForkJoinTask<?> joinMe, boolean timed, long nanos) {
949	+	// currentJoin only written by this thread; only need ordered store
950	+	ForkJoinTask<?> prevJoin = currentJoin;
951	+	UNSAFE.putOrderedObject(this, currentJoinOffset, joinMe);
952	+	pool.awaitJoin(joinMe, this, timed, nanos);
953	+	UNSAFE.putOrderedObject(this, currentJoinOffset, prevJoin);
954	+	}
955	+
956	+	/**
957	+	* Tries to locate and help perform tasks for a stealer of the
958	+	* given task, or in turn one of its stealers.  Traces
959	+	* currentSteal->currentJoin links looking for a thread working on
960	+	* a descendant of the given task and with a non-empty queue to
961	+	* steal back and execute tasks from.
962	+	*
963	+	* The implementation is very branchy to cope with potential
964	+	* inconsistencies or loops encountering chains that are stale,
965	+	* unknown, or of length greater than MAX_HELP_DEPTH links.  All
966	+	* of these cases are dealt with by just returning back to the
967	+	* caller, who is expected to retry if other join mechanisms also
968	+	* don't work out.
969	+	*
970	+	* @param joinMe the task to join
971	+	* @param running if false, then must update pool count upon
972	+	*  running a task
973	+	* @return value of running on exit
974	+	*/
975	+	final boolean helpJoinTask(ForkJoinTask<?> joinMe, boolean running) {
976	+	/*
977	+	* Initial checks to (1) abort if terminating; (2) clean out
978	+	* old cancelled tasks from local queue; (3) if joinMe is next
979	+	* task, run it; (4) omit scan if local queue nonempty (since
980	+	* it may contain non-descendents of joinMe).
981	+	*/
982	+	ForkJoinPool p = pool;
983	+	for (;;) {
984	+	ForkJoinTask<?>[] q;
985	+	int s;
986	+	if (joinMe.status < 0)
987	+	return running;
988	+	else if ((runState & TERMINATING) != 0) {
989	+	joinMe.cancelIgnoringExceptions();
990	+	return running;
991	+	}
992	+	else if ((s = sp) == base || (q = queue) == null)
993	+	break;                            // queue empty
994	+	else {
995	+	int i = (q.length - 1) & --s;
996	+	long u = (i << qShift) + qBase;   // raw offset
997	+	ForkJoinTask<?> t = q[i];
998	+	if (t == null)
999	+	break;                        // lost to a stealer
1000	+	else if (t != joinMe && t.status >= 0)
1001	+	return running;               // cannot safely help
1002	+	else if ((running ||
1003	+	(running = p.tryIncrementRunningCount())) &&
1004	+	UNSAFE.compareAndSwapObject(q, u, t, null)) {
1005	+	sp = s; // putOrderedInt may encourage more timely write
1006	+	// UNSAFE.putOrderedInt(this, spOffset, s);
1007	+	t.quietlyExec();
1008	+	}
1009	+	}
1010	+	}
1011	+
1012	+	int n;                                    // worker array size
1013	+	ForkJoinWorkerThread[] ws = p.workers;
1014	+	if (ws != null && (n = ws.length) > 1) {  // need at least 2 workers
1015	+	ForkJoinTask<?> task = joinMe;        // base of chain
1016	+	ForkJoinWorkerThread thread = this;   // thread with stolen task
1017	+
1018	+	outer:for (int d = 0; d < MAX_HELP_DEPTH; ++d) { // chain length
1019	+	// Try to find v, the stealer of task, by first using hint
1020	+	ForkJoinWorkerThread v = ws[thread.stealHint & (n - 1)];
1021	+	if (v == null || v.currentSteal != task) {
1022	+	for (int j = 0; ; ++j) {      // search array
1023	+	if (j < n) {
1024	+	ForkJoinTask<?> vs;
1025	+	if ((v = ws[j]) != null &&
1026	+	(vs = v.currentSteal) != null) {
1027	+	if (joinMe.status < 0)
1028	+	break outer;
1029	+	if (vs == task) {
1030	+	if (task.status < 0)
1031	+	break outer; // stale
1032	+	thread.stealHint = j;
1033	+	break;        // save hint for next time
1034	+	}
1035	+	}
1036	+	}
1037	+	else
1038	+	break outer;          // no stealer
1039	+	}
1040	+	}
1041	+
1042	+	// Try to help v, using specialized form of deqTask
1043	+	for (;;) {
1044	+	if (joinMe.status < 0)
1045	+	break outer;
1046	+	int b = v.base;
1047	+	ForkJoinTask<?>[] q = v.queue;
1048	+	if (b == v.sp || q == null)
1049	+	break;                    // empty
1050	+	int i = (q.length - 1) & b;
1051	+	long u = (i << qShift) + qBase;
1052	+	ForkJoinTask<?> t = q[i];
1053	+	if (task.status < 0)
1054	+	break outer;              // stale
1055	+	if (t != null &&
1056	+	(running ||
1057	+	(running = p.tryIncrementRunningCount())) &&
1058	+	v.base == b++ &&
1059	+	UNSAFE.compareAndSwapObject(q, u, t, null)) {
1060	+	if (t != joinMe && joinMe.status < 0) {
1061	+	UNSAFE.putObjectVolatile(q, u, t);
1062	+	break outer;          // joinMe cancelled; back out
1063	+	}
1064	+	v.base = b;
1065	+	if (t.status >= 0) {
1066	+	ForkJoinTask<?> ps = currentSteal;
1067	+	int pid = poolIndex;
1068	+	v.stealHint = pid;
1069	+	UNSAFE.putOrderedObject(this,
1070	+	currentStealOffset, t);
1071	+	t.quietlyExec();
1072	+	UNSAFE.putOrderedObject(this,
1073	+	currentStealOffset, ps);
1074	+	}
1075	+	}
1076	+	else if ((runState & TERMINATING) != 0) {
1077	+	joinMe.cancelIgnoringExceptions();
1078	+	break outer;
1079	+	}
1080	+	}
1081	+
1082	+	// Try to descend to find v's stealer
1083	+	ForkJoinTask<?> next = v.currentJoin;
1084	+	if (task.status < 0 || next == null || next == task ||
1085	+	joinMe.status < 0)
1086	+	break;                 // done, stale, dead-end, or cyclic
1087	+	task = next;
1088	+	thread = v;
1089	+	}
1090	+	}
1091	+	return running;
1092	+	}
1093	+
1094	+	/**
1095	+	* Implements ForkJoinTask.getSurplusQueuedTaskCount().
1096		* Returns an estimate of the number of tasks, offset by a
1097		* function of number of idle workers.
1098		*
#	Line 854 | Line 1144 | public class ForkJoinWorkerThread extend
1144		}
1145
1146		/**
857	–	* Gets and removes a local task.
858	–	*
859	–	* @return a task, if available
860	–	*/
861	–	final ForkJoinTask<?> pollLocalTask() {
862	–	while (base != sp) {
863	–	if (active || (active = pool.tryIncrementActiveCount()))
864	–	return locallyFifo? locallyDeqTask() : popTask();
865	–	}
866	–	return null;
867	–	}
868	–
869	–	/**
870	–	* Gets and removes a local or stolen task.
871	–	*
872	–	* @return a task, if available
873	–	*/
874	–	final ForkJoinTask<?> pollTask() {
875	–	ForkJoinTask<?> t;
876	–	return (t = pollLocalTask()) != null ? t : scan();
877	–	}
878	–
879	–	/**
880	–	* Returns a popped or stolen task, if available, unless joinMe is done
881	–	*
882	–	* This method is intrinsically nonmodular. To maintain the
883	–	* property that tasks are never stolen if the awaited task is
884	–	* ready, we must interleave mechanics of scan with status
885	–	* checks. We rely here on the commit points of deq that allow us
886	–	* to cancel a steal even after CASing slot to null, but before
887	–	* adjusting base index: If, after the CAS, we see that joinMe is
888	–	* ready, we can back out by placing the task back into the slot,
889	–	* without adjusting index. The scan loop is otherwise the same as
890	–	* in scan.
891	–	*
892	–	*/
893	–	final ForkJoinTask<?> scanWhileJoining(ForkJoinTask<?> joinMe) {
894	–	ForkJoinTask<?> popped; // prefer local tasks
895	–	if (base != sp && (popped = popWhileJoining(joinMe)) != null)
896	–	return popped;
897	–	if (joinMe.status >= 0) {
898	–	ForkJoinPool p = pool;
899	–	ForkJoinWorkerThread[] ws = p.workers;
900	–	int n = ws.length;
901	–	int r = seed;
902	–	int k = r;
903	–	for (int j = -n; j < n && joinMe.status >= 0; ++j) {
904	–	ForkJoinWorkerThread v = ws[k & (n - 1)];
905	–	r ^= r << 13; r ^= r >>> 17; r ^= r << 5; // xorshift
906	–	if (v != null) {
907	–	int b = v.base;
908	–	ForkJoinTask<?>[] q;
909	–	if (b != v.sp && (q = v.queue) != null) {
910	–	int i = (q.length - 1) & b;
911	–	ForkJoinTask<?> t = q[i];
912	–	if (t != null && UNSAFE.compareAndSwapObject
913	–	(q, (i << qShift) + qBase, t, null)) {
914	–	if (joinMe.status >= 0) {
915	–	v.base = b + 1;
916	–	seed = r;
917	–	++stealCount;
918	–	return t;
919	–	}
920	–	UNSAFE.putObjectVolatile(q, (i<<qShift)+qBase, t);
921	–	break; // back out
922	–	}
923	–	j = -n;
924	–	}
925	–	}
926	–	k = j >= 0? k + ((n >>> 1) | 1) : r;
927	–	}
928	–	}
929	–	return null;
930	–	}
931	–
932	–	/**
933	–	* Version of popTask with join checks surrounding extraction.
934	–	* Uses the same backout strategy as scanWhileJoining. Note that
935	–	* we ignore locallyFifo flag for local tasks here since helping
936	–	* joins only make sense in LIFO mode.
937	–	*
938	–	* @return a popped task, if available, unless joinMe is done
939	–	*/
940	–	private ForkJoinTask<?> popWhileJoining(ForkJoinTask<?> joinMe) {
941	–	int s;
942	–	ForkJoinTask<?>[] q;
943	–	while ((s = sp) != base && (q = queue) != null && joinMe.status >= 0) {
944	–	int i = (q.length - 1) & --s;
945	–	ForkJoinTask<?> t = q[i];
946	–	if (t != null && UNSAFE.compareAndSwapObject
947	–	(q, (i << qShift) + qBase, t, null)) {
948	–	if (joinMe.status >= 0) {
949	–	sp = s;
950	–	return t;
951	–	}
952	–	UNSAFE.putObjectVolatile(q, (i << qShift) + qBase, t);
953	–	break;  // back out
954	–	}
955	–	}
956	–	return null;
957	–	}
958	–
959	–	/**
1147		* Runs tasks until {@code pool.isQuiescent()}.
1148		*/
1149		final void helpQuiescePool() {
1150	+	ForkJoinTask<?> ps = currentSteal; // to restore below
1151		for (;;) {
1152		ForkJoinTask<?> t = pollLocalTask();
1153		if (t != null || (t = scan()) != null)
1154	<	t.tryExec();
1154	>	t.quietlyExec();
1155		else {
1156		ForkJoinPool p = pool;
1157	+	int a; // to inline CASes
1158		if (active) {
1159	+	if (!UNSAFE.compareAndSwapInt
1160	+	(p, poolRunStateOffset, a = p.runState, a - 1))
1161	+	continue;   // retry later
1162		active = false; // inactivate
1163	<	do {} while (!p.tryDecrementActiveCount());
1163	>	UNSAFE.putOrderedObject(this, currentStealOffset, ps);
1164		}
1165		if (p.isQuiescent()) {
1166		active = true; // re-activate
1167	<	do {} while (!p.tryIncrementActiveCount());
1167	>	do {} while (!UNSAFE.compareAndSwapInt
1168	>	(p, poolRunStateOffset, a = p.runState, a+1));
1169		return;
1170		}
1171		}
#	Line 982 | Line 1175 | public class ForkJoinWorkerThread extend
1175		// Unsafe mechanics
1176
1177		private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1178	+	private static final long spOffset =
1179	+	objectFieldOffset("sp", ForkJoinWorkerThread.class);
1180		private static final long runStateOffset =
1181		objectFieldOffset("runState", ForkJoinWorkerThread.class);
1182	+	private static final long currentJoinOffset =
1183	+	objectFieldOffset("currentJoin", ForkJoinWorkerThread.class);
1184	+	private static final long currentStealOffset =
1185	+	objectFieldOffset("currentSteal", ForkJoinWorkerThread.class);
1186		private static final long qBase =
1187		UNSAFE.arrayBaseOffset(ForkJoinTask[].class);
1188	+	private static final long poolRunStateOffset = // to inline CAS
1189	+	objectFieldOffset("runState", ForkJoinPool.class);
1190	+
1191		private static final int qShift;
1192
1193		static {
#	Line 993 | Line 1195 | public class ForkJoinWorkerThread extend
1195		if ((s & (s-1)) != 0)
1196		throw new Error("data type scale not a power of two");
1197		qShift = 31 - Integer.numberOfLeadingZeros(s);
1198	+	MAXIMUM_QUEUE_CAPACITY = 1 << (31 - qShift);
1199		}
1200
1201		private static long objectFieldOffset(String field, Class<?> klazz) {

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