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Comparing jsr166/src/jsr166y/ForkJoinWorkerThread.java (file contents):
Revision 1.44 by jsr166, Wed Sep 1 20:15:43 2010 UTC vs.
Revision 1.69 by dl, Mon Feb 20 18:20:06 2012 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
6
7		package jsr166y;
8
9	–	import java.util.concurrent.*;
10	–
11	–	import java.util.Random;
12	–	import java.util.Collection;
13	–	import java.util.concurrent.locks.LockSupport;
14	–
9		/**
10	<	* A thread managed by a {@link ForkJoinPool}.  This class is
11	<	* subclassable solely for the sake of adding functionality -- there
12	<	* are no overridable methods dealing with scheduling or execution.
13	<	* However, you can override initialization and termination methods
14	<	* surrounding the main task processing loop.  If you do create such a
15	<	* subclass, you will also need to supply a custom {@link
16	<	* ForkJoinPool.ForkJoinWorkerThreadFactory} to use it in a {@code
17	<	* ForkJoinPool}.
10	>	* A thread managed by a {@link ForkJoinPool}, which executes
11	>	* {@link ForkJoinTask}s.
12	>	* This class is subclassable solely for the sake of adding
13	>	* functionality -- there are no overridable methods dealing with
14	>	* scheduling or execution.  However, you can override initialization
15	>	* and termination methods surrounding the main task processing loop.
16	>	* If you do create such a subclass, you will also need to supply a
17	>	* custom {@link ForkJoinPool.ForkJoinWorkerThreadFactory} to use it
18	>	* in a {@code ForkJoinPool}.
19		*
20		* @since 1.7
21		* @author Doug Lea
22		*/
23		public class ForkJoinWorkerThread extends Thread {
24		/*
30	–	* Overview:
31	–	*
25		* ForkJoinWorkerThreads are managed by ForkJoinPools and perform
26	<	* ForkJoinTasks. This class includes bookkeeping in support of
27	<	* worker activation, suspension, and lifecycle control described
35	<	* in more detail in the internal documentation of class
36	<	* ForkJoinPool. And as described further below, this class also
37	<	* includes special-cased support for some ForkJoinTask
38	<	* methods. But the main mechanics involve work-stealing:
39	<	*
40	<	* Work-stealing queues are special forms of Deques that support
41	<	* only three of the four possible end-operations -- push, pop,
42	<	* and deq (aka steal), under the further constraints that push
43	<	* and pop are called only from the owning thread, while deq may
44	<	* be called from other threads.  (If you are unfamiliar with
45	<	* them, you probably want to read Herlihy and Shavit's book "The
46	<	* Art of Multiprocessor programming", chapter 16 describing these
47	<	* in more detail before proceeding.)  The main work-stealing
48	<	* queue design is roughly similar to those in the papers "Dynamic
49	<	* Circular Work-Stealing Deque" by Chase and Lev, SPAA 2005
50	<	* (http://research.sun.com/scalable/pubs/index.html) and
51	<	* "Idempotent work stealing" by Michael, Saraswat, and Vechev,
52	<	* PPoPP 2009 (http://portal.acm.org/citation.cfm?id=1504186).
53	<	* The main differences ultimately stem from gc requirements that
54	<	* we null out taken slots as soon as we can, to maintain as small
55	<	* a footprint as possible even in programs generating huge
56	<	* numbers of tasks. To accomplish this, we shift the CAS
57	<	* arbitrating pop vs deq (steal) from being on the indices
58	<	* ("base" and "sp") to the slots themselves (mainly via method
59	<	* "casSlotNull()"). So, both a successful pop and deq mainly
60	<	* entail a CAS of a slot from non-null to null.  Because we rely
61	<	* on CASes of references, we do not need tag bits on base or sp.
62	<	* They are simple ints as used in any circular array-based queue
63	<	* (see for example ArrayDeque).  Updates to the indices must
64	<	* still be ordered in a way that guarantees that sp == base means
65	<	* the queue is empty, but otherwise may err on the side of
66	<	* possibly making the queue appear nonempty when a push, pop, or
67	<	* deq have not fully committed. Note that this means that the deq
68	<	* operation, considered individually, is not wait-free. One thief
69	<	* cannot successfully continue until another in-progress one (or,
70	<	* if previously empty, a push) completes.  However, in the
71	<	* aggregate, we ensure at least probabilistic non-blockingness.
72	<	* If an attempted steal fails, a thief always chooses a different
73	<	* random victim target to try next. So, in order for one thief to
74	<	* progress, it suffices for any in-progress deq or new push on
75	<	* any empty queue to complete. One reason this works well here is
76	<	* that apparently-nonempty often means soon-to-be-stealable,
77	<	* which gives threads a chance to set activation status if
78	<	* necessary before stealing.
79	<	*
80	<	* This approach also enables support for "async mode" where local
81	<	* task processing is in FIFO, not LIFO order; simply by using a
82	<	* version of deq rather than pop when locallyFifo is true (as set
83	<	* by the ForkJoinPool).  This allows use in message-passing
84	<	* frameworks in which tasks are never joined.
85	<	*
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	<	* 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
137	<	* though these queues don't usually become all that big, the
138	<	* initial size must be large enough to counteract cache
139	<	* contention effects across multiple queues (especially in the
140	<	* presence of GC cardmarking). Also, to improve thread-locality,
141	<	* queues are initialized after starting.  All together, these
142	<	* low-level implementation choices produce as much as a factor of
143	<	* 4 performance improvement compared to naive implementations,
144	<	* and enable the processing of billions of tasks per second,
145	<	* sometimes at the expense of ugliness.
146	<	*/
147	<
148	<	/**
149	<	* Generator for initial random seeds for random victim
150	<	* selection. This is used only to create initial seeds. Random
151	<	* steals use a cheaper xorshift generator per steal attempt. We
152	<	* expect only rare contention on seedGenerator, so just use a
153	<	* plain Random.
154	<	*/
155	<	private static final Random seedGenerator = new Random();
156	<
157	<	/**
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 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 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).
178	<	*/
179	<	private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 28;
180	<
181	<	/**
182	<	* The pool this thread works in. Accessed directly by ForkJoinTask.
183	<	*/
184	<	final ForkJoinPool pool;
185	<
186	<	/**
187	<	* The work-stealing queue array. Size must be a power of two.
188	<	* Initialized in onStart, to improve memory locality.
189	<	*/
190	<	private ForkJoinTask<?>[] queue;
191	<
192	<	/**
193	<	* Index (mod queue.length) of least valid queue slot, which is
194	<	* always the next position to steal from if nonempty.
195	<	*/
196	<	private volatile int base;
197	<
198	<	/**
199	<	* Index (mod queue.length) of next queue slot to push to or pop
200	<	* from. It is written only by owner thread, and accessed by other
201	<	* threads only after reading (volatile) base.  Both sp and base
202	<	* are allowed to wrap around on overflow, but (sp - base) still
203	<	* estimates size.
204	<	*/
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 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	<	volatile int runState;
226	<
227	<	private static final int TERMINATING = 0x01;
228	<	private static final int TERMINATED  = 0x02;
229	<	private static final int SUSPENDED   = 0x04; // inactive spare
230	<	private static final int TRIMMED     = 0x08; // killed while suspended
231	<
232	<	/**
233	<	* Number of steals, transferred and reset in pool callbacks pool
234	<	* when idle Accessed directly by pool.
235	<	*/
236	<	int stealCount;
237	<
238	<	/**
239	<	* Seed for random number generator for choosing steal victims.
240	<	* Uses Marsaglia xorshift. Must be initialized as nonzero.
241	<	*/
242	<	private int seed;
243	<
244	<	/**
245	<	* Activity status. When true, this worker is considered active.
246	<	* Accessed directly by pool.  Must be false upon construction.
247	<	*/
248	<	boolean active;
249	<
250	<	/**
251	<	* True if use local fifo, not default lifo, for local polling.
252	<	* Shadows value from ForkJoinPool.
253	<	*/
254	<	private final boolean locallyFifo;
255	<
256	<	/**
257	<	* Index of this worker in pool array. Set once by pool before
258	<	* running, and accessed directly by pool to locate this worker in
259	<	* its workers array.
26	>	* ForkJoinTasks. For explanation, see the internal documentation
27	>	* of class ForkJoinPool.
28		*/
261	–	int poolIndex;
29
30	<	/**
31	<	* The last pool event waited for. Accessed only by pool in
265	<	* callback methods invoked within this thread.
266	<	*/
267	<	int lastEventCount;
268	<
269	<	/**
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 helpStealer. Written only by current thread, but read by
290	<	* 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 current thread, but read by
297	<	* others.
298	<	*/
299	<	private volatile ForkJoinTask<?> currentSteal;
30	>	final ForkJoinPool.WorkQueue workQueue; // Work-stealing mechanics
31	>	final ForkJoinPool pool;                // the pool this thread works in
32
33		/**
34		* Creates a ForkJoinWorkerThread operating in the given pool.
#	Line 305 | Line 37 | public class ForkJoinWorkerThread extend
37		* @throws NullPointerException if pool is null
38		*/
39		protected ForkJoinWorkerThread(ForkJoinPool pool) {
40	<	this.pool = pool;
309	<	this.locallyFifo = pool.locallyFifo;
40	>	super(pool.nextWorkerName());
41		setDaemon(true);
42	<	// 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
317	<	*/
318	<	final void start(int poolIndex, UncaughtExceptionHandler ueh) {
319	<	this.poolIndex = poolIndex;
42	>	Thread.UncaughtExceptionHandler ueh = pool.ueh;
43		if (ueh != null)
44		setUncaughtExceptionHandler(ueh);
45	<	start();
45	>	this.pool = pool;
46	>	pool.registerWorker(this.workQueue = new ForkJoinPool.WorkQueue
47	>	(pool, this, pool.localMode));
48		}
49
325	–	// Public/protected methods
326	–
50		/**
51		* Returns the pool hosting this thread.
52		*
#	Line 343 | Line 66 | public class ForkJoinWorkerThread extend
66		* @return the index number
67		*/
68		public int getPoolIndex() {
69	<	return poolIndex;
69	>	return workQueue.poolIndex;
70		}
71
72		/**
73		* Initializes internal state after construction but before
74		* processing any tasks. If you override this method, you must
75	<	* invoke super.onStart() at the beginning of the method.
75	>	* invoke {@code super.onStart()} at the beginning of the method.
76		* Initialization requires care: Most fields must have legal
77		* default values, to ensure that attempted accesses from other
78		* threads work correctly even before this thread starts
79		* processing tasks.
80		*/
81		protected void onStart() {
359	–	int rs = seedGenerator.nextInt();
360	–	seed = rs == 0? 1 : rs; // seed must be nonzero
361	–
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);
366	–
367	–	queue = new ForkJoinTask<?>[INITIAL_QUEUE_CAPACITY];
82		}
83
84		/**
#	Line 376 | Line 90 | public class ForkJoinWorkerThread extend
90		* to an unrecoverable error, or {@code null} if completed normally
91		*/
92		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	–	p.workerTerminated(this);
390	–	} catch (Throwable ex) {        // Shouldn't ever happen
391	–	if (exception == null)      // but if so, at least rethrown
392	–	exception = ex;
393	–	} finally {
394	–	if (exception != null)
395	–	UNSAFE.throwException(exception);
396	–	}
93		}
94
95		/**
96		* This method is required to be public, but should never be
97		* called explicitly. It performs the main run loop to execute
98	<	* ForkJoinTasks.
98	>	* {@link ForkJoinTask}s.
99		*/
100		public void run() {
101		Throwable exception = null;
102		try {
103		onStart();
104	<	mainLoop();
104	>	pool.runWorker(workQueue);
105		} catch (Throwable ex) {
106		exception = ex;
107		} finally {
412	–	onTermination(exception);
413	–	}
414	–	}
415	–
416	–	// helpers for run()
417	–
418	–	/**
419	–	* Find and execute tasks and check status while running
420	–	*/
421	–	private void mainLoop() {
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	–	break;
428	–	ran = tryExecSteal() || tryExecSubmission();
429	–	}
430	–	}
431	–
432	–	/**
433	–	* Try to steal a task and execute it
434	–	*
435	–	* @return true if ran a task
436	–	*/
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 run it;
451	–	*
452	–	* @return true if ran a task
453	–	*/
454	–	private boolean tryExecSubmission() {
455	–	ForkJoinPool p = pool;
456	–	while (p.hasQueuedSubmissions()) {
457	–	ForkJoinTask<?> t; int a;
458	–	if (active || // inline p.tryIncrementActiveCount
459	–	(active = UNSAFE.compareAndSwapInt(p, poolRunStateOffset,
460	–	a = p.runState, a + 1))) {
461	–	if ((t = p.pollSubmission()) != null) {
462	–	UNSAFE.putOrderedObject(this, currentStealOffset, t);
463	–	t.quietlyExec();
464	–	UNSAFE.putOrderedObject(this, currentStealOffset, null);
465	–	if (sp != base)
466	–	execLocalTasks();
467	–	return true;
468	–	}
469	–	}
470	–	}
471	–	return false;
472	–	}
473	–
474	–	/**
475	–	* Runs local tasks until queue is empty or shut down.  Call only
476	–	* while active.
477	–	*/
478	–	private void execLocalTasks() {
479	–	while (runState == 0) {
480	–	ForkJoinTask<?> t = locallyFifo ? locallyDeqTask() : popTask();
481	–	if (t != null)
482	–	t.quietlyExec();
483	–	else if (sp == base)
484	–	break;
485	–	}
486	–	}
487	–
488	–	/*
489	–	* Intrinsics-based atomic writes for queue slots. These are
490	–	* basically the same as methods in AtomicObjectArray, but
491	–	* specialized for (1) ForkJoinTask elements (2) requirement that
492	–	* nullness and bounds checks have already been performed by
493	–	* callers and (3) effective offsets are known not to overflow
494	–	* from int to long (because of MAXIMUM_QUEUE_CAPACITY). We don't
495	–	* need corresponding version for reads: plain array reads are OK
496	–	* because they protected by other volatile reads and are
497	–	* confirmed by CASes.
498	–	*
499	–	* Most uses don't actually call these methods, but instead contain
500	–	* inlined forms that enable more predictable optimization.  We
501	–	* don't define the version of write used in pushTask at all, but
502	–	* instead inline there a store-fenced array slot write.
503	–	*/
504	–
505	–	/**
506	–	* CASes slot i of array q from t to null. Caller must ensure q is
507	–	* non-null and index is in range.
508	–	*/
509	–	private static final boolean casSlotNull(ForkJoinTask<?>[] q, int i,
510	–	ForkJoinTask<?> t) {
511	–	return UNSAFE.compareAndSwapObject(q, (i << qShift) + qBase, t, null);
512	–	}
513	–
514	–	/**
515	–	* Performs a volatile write of the given task at given slot of
516	–	* array q.  Caller must ensure q is non-null and index is in
517	–	* range. This method is used only during resets and backouts.
518	–	*/
519	–	private static final void writeSlot(ForkJoinTask<?>[] q, int i,
520	–	ForkJoinTask<?> t) {
521	–	UNSAFE.putObjectVolatile(q, (i << qShift) + qBase, t);
522	–	}
523	–
524	–	// queue methods
525	–
526	–	/**
527	–	* Pushes a task. Call only from this thread.
528	–	*
529	–	* @param t the task. Caller must ensure non-null.
530	–	*/
531	–	final void pushTask(ForkJoinTask<?> t) {
532	–	ForkJoinTask<?>[] q = queue;
533	–	int mask = q.length - 1; // implicit assert q != null
534	–	int s = sp++;            // ok to increment sp before slot write
535	–	UNSAFE.putOrderedObject(q, ((s & mask) << qShift) + qBase, t);
536	–	if ((s -= base) == 0)
537	–	pool.signalWork();   // was empty
538	–	else if (s == mask)
539	–	growQueue();         // is full
540	–	}
541	–
542	–	/**
543	–	* Tries to take a task from the base of the queue, failing if
544	–	* empty or contended. Note: Specializations of this code appear
545	–	* in locallyDeqTask and elsewhere.
546	–	*
547	–	* @return a task, or null if none or contended
548	–	*/
549	–	final ForkJoinTask<?> deqTask() {
550	–	ForkJoinTask<?> t;
551	–	ForkJoinTask<?>[] q;
552	–	int b, i;
553	–	if (sp != (b = base) &&
554	–	(q = queue) != null && // must read q after b
555	–	(t = q[i = (q.length - 1) & b]) != null && base == b &&
556	–	UNSAFE.compareAndSwapObject(q, (i << qShift) + qBase, t, null)) {
557	–	base = b + 1;
558	–	return t;
559	–	}
560	–	return null;
561	–	}
562	–
563	–	/**
564	–	* Tries to take a task from the base of own queue. Assumes active
565	–	* status.  Called only by current thread.
566	–	*
567	–	* @return a task, or null if none
568	–	*/
569	–	final ForkJoinTask<?> locallyDeqTask() {
570	–	ForkJoinTask<?>[] q = queue;
571	–	if (q != null) {
572	–	ForkJoinTask<?> t;
573	–	int b, i;
574	–	while (sp != (b = base)) {
575	–	if ((t = q[i = (q.length - 1) & b]) != null && base == b &&
576	–	UNSAFE.compareAndSwapObject(q, (i << qShift) + qBase,
577	–	t, null)) {
578	–	base = b + 1;
579	–	return t;
580	–	}
581	–	}
582	–	}
583	–	return null;
584	–	}
585	–
586	–	/**
587	–	* Returns a popped task, or null if empty. Assumes active status.
588	–	* Called only by current thread.
589	–	*/
590	–	private ForkJoinTask<?> popTask() {
591	–	ForkJoinTask<?>[] q = queue;
592	–	if (q != null) {
593	–	int s;
594	–	while ((s = sp) != base) {
595	–	int i = (q.length - 1) & --s;
596	–	long u = (i << qShift) + qBase; // raw offset
597	–	ForkJoinTask<?> t = q[i];
598	–	if (t == null)   // lost to stealer
599	–	break;
600	–	if (UNSAFE.compareAndSwapObject(q, u, t, null)) {
601	–	sp = s; // putOrderedInt may encourage more timely write
602	–	// UNSAFE.putOrderedInt(this, spOffset, s);
603	–	return t;
604	–	}
605	–	}
606	–	}
607	–	return null;
608	–	}
609	–
610	–	/**
611	–	* Specialized version of popTask to pop only if topmost element
612	–	* is the given task. Called only by current thread while
613	–	* active.
614	–	*
615	–	* @param t the task. Caller must ensure non-null.
616	–	*/
617	–	final boolean unpushTask(ForkJoinTask<?> t) {
618	–	int s;
619	–	ForkJoinTask<?>[] q = queue;
620	–	if ((s = sp) != base && q != null &&
621	–	UNSAFE.compareAndSwapObject
622	–	(q, (((q.length - 1) & --s) << qShift) + qBase, t, null)) {
623	–	sp = s; // putOrderedInt may encourage more timely write
624	–	// UNSAFE.putOrderedInt(this, spOffset, s);
625	–	return true;
626	–	}
627	–	return false;
628	–	}
629	–
630	–	/**
631	–	* Returns next task or null if empty or contended
632	–	*/
633	–	final ForkJoinTask<?> peekTask() {
634	–	ForkJoinTask<?>[] q = queue;
635	–	if (q == null)
636	–	return null;
637	–	int mask = q.length - 1;
638	–	int i = locallyFifo ? base : (sp - 1);
639	–	return q[i & mask];
640	–	}
641	–
642	–	/**
643	–	* Doubles queue array size. Transfers elements by emulating
644	–	* steals (deqs) from old array and placing, oldest first, into
645	–	* new array.
646	–	*/
647	–	private void growQueue() {
648	–	ForkJoinTask<?>[] oldQ = queue;
649	–	int oldSize = oldQ.length;
650	–	int newSize = oldSize << 1;
651	–	if (newSize > MAXIMUM_QUEUE_CAPACITY)
652	–	throw new RejectedExecutionException("Queue capacity exceeded");
653	–	ForkJoinTask<?>[] newQ = queue = new ForkJoinTask<?>[newSize];
654	–
655	–	int b = base;
656	–	int bf = b + oldSize;
657	–	int oldMask = oldSize - 1;
658	–	int newMask = newSize - 1;
659	–	do {
660	–	int oldIndex = b & oldMask;
661	–	ForkJoinTask<?> t = oldQ[oldIndex];
662	–	if (t != null && !casSlotNull(oldQ, oldIndex, t))
663	–	t = null;
664	–	writeSlot(newQ, b & newMask, t);
665	–	} while (++b != bf);
666	–	pool.signalWork();
667	–	}
668	–
669	–	/**
670	–	* Computes next value for random victim probe in scan().  Scans
671	–	* don't require a very high quality generator, but also not a
672	–	* crummy one.  Marsaglia xor-shift is cheap and works well enough.
673	–	* Note: This is manually inlined in scan()
674	–	*/
675	–	private static final int xorShift(int r) {
676	–	r ^= r << 13;
677	–	r ^= r >>> 17;
678	–	return r ^ (r << 5);
679	–	}
680	–
681	–	/**
682	–	* Tries to steal a task from another worker. Starts at a random
683	–	* index of workers array, and probes workers until finding one
684	–	* with non-empty queue or finding that all are empty.  It
685	–	* randomly selects the first n probes. If these are empty, it
686	–	* resorts to a circular sweep, which is necessary to accurately
687	–	* set active status. (The circular sweep uses steps of
688	–	* approximately half the array size plus 1, to avoid bias
689	–	* stemming from leftmost packing of the array in ForkJoinPool.)
690	–	*
691	–	* This method must be both fast and quiet -- usually avoiding
692	–	* memory accesses that could disrupt cache sharing etc other than
693	–	* those needed to check for and take tasks (or to activate if not
694	–	* already active). This accounts for, among other things,
695	–	* updating random seed in place without storing it until exit.
696	–	*
697	–	* @return a task, or null if none found
698	–	*/
699	–	private ForkJoinTask<?> scan() {
700	–	ForkJoinPool p = pool;
701	–	ForkJoinWorkerThread[] ws;        // worker array
702	–	int n;                            // upper bound of #workers
703	–	if ((ws = p.workers) != null && (n = ws.length) > 1) {
704	–	boolean canSteal = active;    // shadow active status
705	–	int r = seed;                 // extract seed once
706	–	int mask = n - 1;
707	–	int j = -n;                   // loop counter
708	–	int k = r;                    // worker index, random if j < 0
709	–	for (;;) {
710	–	ForkJoinWorkerThread v = ws[k & mask];
711	–	r ^= r << 13; r ^= r >>> 17; r ^= r << 5; // inline xorshift
712	–	ForkJoinTask<?>[] q; ForkJoinTask<?> t; int b, a;
713	–	if (v != null && (b = v.base) != v.sp &&
714	–	(q = v.queue) != null) {
715	–	int i = (q.length - 1) & b;
716	–	long u = (i << qShift) + qBase; // raw offset
717	–	int pid = poolIndex;
718	–	if ((t = q[i]) != null) {
719	–	if (!canSteal &&  // inline p.tryIncrementActiveCount
720	–	UNSAFE.compareAndSwapInt(p, poolRunStateOffset,
721	–	a = p.runState, a + 1))
722	–	canSteal = active = true;
723	–	if (canSteal && v.base == b++ &&
724	–	UNSAFE.compareAndSwapObject(q, u, t, null)) {
725	–	v.base = b;
726	–	v.stealHint = pid;
727	–	UNSAFE.putOrderedObject(this,
728	–	currentStealOffset, t);
729	–	seed = r;
730	–	++stealCount;
731	–	return t;
732	–	}
733	–	}
734	–	j = -n;
735	–	k = r;                // restart on contention
736	–	}
737	–	else if (++j <= 0)
738	–	k = r;
739	–	else if (j <= n)
740	–	k += (n >>> 1) | 1;
741	–	else
742	–	break;
743	–	}
744	–	}
745	–	return null;
746	–	}
747	–
748	–	// Run State management
749	–
750	–	// status check methods used mainly by ForkJoinPool
751	–	final boolean isRunning()     { return runState == 0; }
752	–	final boolean isTerminating() { return (runState & TERMINATING) != 0; }
753	–	final boolean isTerminated()  { return (runState & TERMINATED) != 0; }
754	–	final boolean isSuspended()   { return (runState & SUSPENDED) != 0; }
755	–	final boolean isTrimmed()     { return (runState & TRIMMED) != 0; }
756	–
757	–	/**
758	–	* Sets state to TERMINATING. Does NOT unpark or interrupt
759	–	* to wake up if currently blocked. Callers must do so if desired.
760	–	*/
761	–	final void shutdown() {
762	–	for (;;) {
763	–	int s = runState;
764	–	if ((s & (TERMINATING|TERMINATED)) != 0)
765	–	break;
766	–	if ((s & SUSPENDED) != 0) { // kill and wakeup if suspended
767	–	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
768	–	(s & ~SUSPENDED) |
769	–	(TRIMMED|TERMINATING)))
770	–	break;
771	–	}
772	–	else if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
773	–	s | TERMINATING))
774	–	break;
775	–	}
776	–	}
777	–
778	–	/**
779	–	* Sets state to TERMINATED. Called only by onTermination()
780	–	*/
781	–	private void setTerminated() {
782	–	int s;
783	–	do {} while (!UNSAFE.compareAndSwapInt(this, runStateOffset,
784	–	s = runState,
785	–	s | (TERMINATING|TERMINATED)));
786	–	}
787	–
788	–	/**
789	–	* If suspended, tries to set status to unsuspended.
790	–	* Does NOT wake up if blocked.
791	–	*
792	–	* @return true if successful
793	–	*/
794	–	final boolean tryUnsuspend() {
795	–	int s;
796	–	while (((s = runState) & SUSPENDED) != 0) {
797	–	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
798	–	s & ~SUSPENDED))
799	–	return true;
800	–	}
801	–	return false;
802	–	}
803	–
804	–	/**
805	–	* Sets suspended status and blocks as spare until resumed
806	–	* or shutdown.
807	–	*/
808	–	final void suspendAsSpare() {
809	–	for (;;) {                  // set suspended unless terminating
810	–	int s = runState;
811	–	if ((s & TERMINATING) != 0) { // must kill
812	–	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
813	–	s | (TRIMMED | TERMINATING)))
814	–	return;
815	–	}
816	–	else if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
817	–	s | SUSPENDED))
818	–	break;
819	–	}
820	–	ForkJoinPool p = pool;
821	–	p.pushSpare(this);
822	–	while ((runState & SUSPENDED) != 0) {
823	–	if (p.tryAccumulateStealCount(this)) {
824	–	interrupted();          // clear/ignore interrupts
825	–	if ((runState & SUSPENDED) == 0)
826	–	break;
827	–	LockSupport.park(this);
828	–	}
829	–	}
830	–	}
831	–
832	–	// Misc support methods for ForkJoinPool
833	–
834	–	/**
835	–	* Returns an estimate of the number of tasks in the queue.  Also
836	–	* used by ForkJoinTask.
837	–	*/
838	–	final int getQueueSize() {
839	–	int n; // external calls must read base first
840	–	return (n = -base + sp) <= 0 ? 0 : n;
841	–	}
842	–
843	–	/**
844	–	* Removes and cancels all tasks in queue.  Can be called from any
845	–	* thread.
846	–	*/
847	–	final void cancelTasks() {
848	–	ForkJoinTask<?> cj = currentJoin; // try to cancel ongoing tasks
849	–	if (cj != null) {
850	–	currentJoin = null;
851	–	cj.cancelIgnoringExceptions();
108		try {
109	<	this.interrupt(); // awaken wait
110	<	} catch (SecurityException ignore) {
111	<	}
112	<	}
113	<	ForkJoinTask<?> cs = currentSteal;
114	<	if (cs != null) {
859	<	currentSteal = null;
860	<	cs.cancelIgnoringExceptions();
861	<	}
862	<	while (base != sp) {
863	<	ForkJoinTask<?> t = deqTask();
864	<	if (t != null)
865	<	t.cancelIgnoringExceptions();
866	<	}
867	<	}
868	<
869	<	/**
870	<	* Drains tasks to given collection c.
871	<	*
872	<	* @return the number of tasks drained
873	<	*/
874	<	final int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
875	<	int n = 0;
876	<	while (base != sp) {
877	<	ForkJoinTask<?> t = deqTask();
878	<	if (t != null) {
879	<	c.add(t);
880	<	++n;
881	<	}
882	<	}
883	<	return n;
884	<	}
885	<
886	<	// Support methods for ForkJoinTask
887	<
888	<	/**
889	<	* Gets and removes a local task.
890	<	*
891	<	* @return a task, if available
892	<	*/
893	<	final ForkJoinTask<?> pollLocalTask() {
894	<	ForkJoinPool p = pool;
895	<	while (sp != base) {
896	<	int a; // inline p.tryIncrementActiveCount
897	<	if (active ||
898	<	(active = UNSAFE.compareAndSwapInt(p, poolRunStateOffset,
899	<	a = p.runState, a + 1)))
900	<	return locallyFifo ? locallyDeqTask() : popTask();
901	<	}
902	<	return null;
903	<	}
904	<
905	<	/**
906	<	* Gets and removes a local or stolen task.
907	<	*
908	<	* @return a task, if available
909	<	*/
910	<	final ForkJoinTask<?> pollTask() {
911	<	ForkJoinTask<?> t = pollLocalTask();
912	<	if (t == null) {
913	<	t = scan();
914	<	// cannot retain/track/help steal
915	<	UNSAFE.putOrderedObject(this, currentStealOffset, null);
916	<	}
917	<	return t;
918	<	}
919	<
920	<	/**
921	<	* Possibly runs some tasks and/or blocks, until task is done.
922	<	*
923	<	* @param joinMe the task to join
924	<	*/
925	<	final void joinTask(ForkJoinTask<?> joinMe) {
926	<	// currentJoin only written by this thread; only need ordered store
927	<	ForkJoinTask<?> prevJoin = currentJoin;
928	<	UNSAFE.putOrderedObject(this, currentJoinOffset, joinMe);
929	<	if (sp != base)
930	<	localHelpJoinTask(joinMe);
931	<	if (joinMe.status >= 0)
932	<	pool.awaitJoin(joinMe, this);
933	<	UNSAFE.putOrderedObject(this, currentJoinOffset, prevJoin);
934	<	}
935	<
936	<	/**
937	<	* Run tasks in local queue until given task is done.
938	<	*
939	<	* @param joinMe the task to join
940	<	*/
941	<	private void localHelpJoinTask(ForkJoinTask<?> joinMe) {
942	<	int s;
943	<	ForkJoinTask<?>[] q;
944	<	while (joinMe.status >= 0 && (s = sp) != base && (q = queue) != null) {
945	<	int i = (q.length - 1) & --s;
946	<	long u = (i << qShift) + qBase; // raw offset
947	<	ForkJoinTask<?> t = q[i];
948	<	if (t == null)  // lost to a stealer
949	<	break;
950	<	if (UNSAFE.compareAndSwapObject(q, u, t, null)) {
951	<	/*
952	<	* This recheck (and similarly in helpJoinTask)
953	<	* handles cases where joinMe is independently
954	<	* cancelled or forced even though there is other work
955	<	* available. Back out of the pop by putting t back
956	<	* into slot before we commit by writing sp.
957	<	*/
958	<	if (joinMe.status < 0) {
959	<	UNSAFE.putObjectVolatile(q, u, t);
960	<	break;
961	<	}
962	<	sp = s;
963	<	// UNSAFE.putOrderedInt(this, spOffset, s);
964	<	t.quietlyExec();
965	<	}
966	<	}
967	<	}
968	<
969	<	/**
970	<	* Unless terminating, tries to locate and help perform tasks for
971	<	* a stealer of the given task, or in turn one of its stealers.
972	<	* Traces currentSteal->currentJoin links looking for a thread
973	<	* working on a descendant of the given task and with a non-empty
974	<	* queue to steal back and execute tasks from.
975	<	*
976	<	* The implementation is very branchy to cope with potential
977	<	* inconsistencies or loops encountering chains that are stale,
978	<	* unknown, or of length greater than MAX_HELP_DEPTH links.  All
979	<	* of these cases are dealt with by just returning back to the
980	<	* caller, who is expected to retry if other join mechanisms also
981	<	* don't work out.
982	<	*
983	<	* @param joinMe the task to join
984	<	*/
985	<	final void helpJoinTask(ForkJoinTask<?> joinMe) {
986	<	ForkJoinWorkerThread[] ws;
987	<	int n;
988	<	if (joinMe.status < 0)                // already done
989	<	return;
990	<	if ((runState & TERMINATING) != 0) {  // cancel if shutting down
991	<	joinMe.cancelIgnoringExceptions();
992	<	return;
993	<	}
994	<	if ((ws = pool.workers) == null || (n = ws.length) <= 1)
995	<	return;                           // need at least 2 workers
996	<
997	<	ForkJoinTask<?> task = joinMe;        // base of chain
998	<	ForkJoinWorkerThread thread = this;   // thread with stolen task
999	<	for (int d = 0; d < MAX_HELP_DEPTH; ++d) { // chain length
1000	<	// Try to find v, the stealer of task, by first using hint
1001	<	ForkJoinWorkerThread v = ws[thread.stealHint & (n - 1)];
1002	<	if (v == null || v.currentSteal != task) {
1003	<	for (int j = 0; ; ++j) {      // search array
1004	<	if (j < n) {
1005	<	ForkJoinTask<?> vs;
1006	<	if ((v = ws[j]) != null &&
1007	<	(vs = v.currentSteal) != null) {
1008	<	if (joinMe.status < 0 || task.status < 0)
1009	<	return;       // stale or done
1010	<	if (vs == task) {
1011	<	thread.stealHint = j;
1012	<	break;        // save hint for next time
1013	<	}
1014	<	}
1015	<	}
1016	<	else
1017	<	return;               // no stealer
1018	<	}
1019	<	}
1020	<	for (;;) { // Try to help v, using specialized form of deqTask
1021	<	if (joinMe.status < 0)
1022	<	return;
1023	<	int b = v.base;
1024	<	ForkJoinTask<?>[] q = v.queue;
1025	<	if (b == v.sp || q == null)
1026	<	break;
1027	<	int i = (q.length - 1) & b;
1028	<	long u = (i << qShift) + qBase;
1029	<	ForkJoinTask<?> t = q[i];
1030	<	int pid = poolIndex;
1031	<	ForkJoinTask<?> ps = currentSteal;
1032	<	if (task.status < 0)
1033	<	return;                   // stale or done
1034	<	if (t != null && v.base == b++ &&
1035	<	UNSAFE.compareAndSwapObject(q, u, t, null)) {
1036	<	if (joinMe.status < 0) {
1037	<	UNSAFE.putObjectVolatile(q, u, t);
1038	<	return;               // back out on cancel
1039	<	}
1040	<	v.base = b;
1041	<	v.stealHint = pid;
1042	<	UNSAFE.putOrderedObject(this, currentStealOffset, t);
1043	<	t.quietlyExec();
1044	<	UNSAFE.putOrderedObject(this, currentStealOffset, ps);
1045	<	}
1046	<	}
1047	<	// Try to descend to find v's stealer
1048	<	ForkJoinTask<?> next = v.currentJoin;
1049	<	if (task.status < 0 || next == null || next == task ||
1050	<	joinMe.status < 0)
1051	<	return;
1052	<	task = next;
1053	<	thread = v;
1054	<	}
1055	<	}
1056	<
1057	<	/**
1058	<	* Returns an estimate of the number of tasks, offset by a
1059	<	* function of number of idle workers.
1060	<	*
1061	<	* This method provides a cheap heuristic guide for task
1062	<	* partitioning when programmers, frameworks, tools, or languages
1063	<	* have little or no idea about task granularity.  In essence by
1064	<	* offering this method, we ask users only about tradeoffs in
1065	<	* overhead vs expected throughput and its variance, rather than
1066	<	* how finely to partition tasks.
1067	<	*
1068	<	* In a steady state strict (tree-structured) computation, each
1069	<	* thread makes available for stealing enough tasks for other
1070	<	* threads to remain active. Inductively, if all threads play by
1071	<	* the same rules, each thread should make available only a
1072	<	* constant number of tasks.
1073	<	*
1074	<	* The minimum useful constant is just 1. But using a value of 1
1075	<	* would require immediate replenishment upon each steal to
1076	<	* maintain enough tasks, which is infeasible.  Further,
1077	<	* partitionings/granularities of offered tasks should minimize
1078	<	* steal rates, which in general means that threads nearer the top
1079	<	* of computation tree should generate more than those nearer the
1080	<	* bottom. In perfect steady state, each thread is at
1081	<	* approximately the same level of computation tree. However,
1082	<	* producing extra tasks amortizes the uncertainty of progress and
1083	<	* diffusion assumptions.
1084	<	*
1085	<	* So, users will want to use values larger, but not much larger
1086	<	* than 1 to both smooth over transient shortages and hedge
1087	<	* against uneven progress; as traded off against the cost of
1088	<	* extra task overhead. We leave the user to pick a threshold
1089	<	* value to compare with the results of this call to guide
1090	<	* decisions, but recommend values such as 3.
1091	<	*
1092	<	* When all threads are active, it is on average OK to estimate
1093	<	* surplus strictly locally. In steady-state, if one thread is
1094	<	* maintaining say 2 surplus tasks, then so are others. So we can
1095	<	* just use estimated queue length (although note that (sp - base)
1096	<	* can be an overestimate because of stealers lagging increments
1097	<	* of base).  However, this strategy alone leads to serious
1098	<	* mis-estimates in some non-steady-state conditions (ramp-up,
1099	<	* ramp-down, other stalls). We can detect many of these by
1100	<	* further considering the number of "idle" threads, that are
1101	<	* known to have zero queued tasks, so compensate by a factor of
1102	<	* (#idle/#active) threads.
1103	<	*/
1104	<	final int getEstimatedSurplusTaskCount() {
1105	<	return sp - base - pool.idlePerActive();
1106	<	}
1107	<
1108	<	/**
1109	<	* Runs tasks until {@code pool.isQuiescent()}.
1110	<	*/
1111	<	final void helpQuiescePool() {
1112	<	ForkJoinTask<?> ps = currentSteal; // to restore below
1113	<	for (;;) {
1114	<	ForkJoinTask<?> t = pollLocalTask();
1115	<	if (t != null || (t = scan()) != null)
1116	<	t.quietlyExec();
1117	<	else {
1118	<	ForkJoinPool p = pool;
1119	<	int a; // to inline CASes
1120	<	if (active) {
1121	<	if (!UNSAFE.compareAndSwapInt
1122	<	(p, poolRunStateOffset, a = p.runState, a - 1))
1123	<	continue;   // retry later
1124	<	active = false; // inactivate
1125	<	UNSAFE.putOrderedObject(this, currentStealOffset, ps);
1126	<	}
1127	<	if (p.isQuiescent()) {
1128	<	active = true; // re-activate
1129	<	do {} while (!UNSAFE.compareAndSwapInt
1130	<	(p, poolRunStateOffset, a = p.runState, a+1));
1131	<	return;
1132	<	}
1133	<	}
1134	<	}
1135	<	}
1136	<
1137	<	// Unsafe mechanics
1138	<
1139	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1140	<	private static final long spOffset =
1141	<	objectFieldOffset("sp", ForkJoinWorkerThread.class);
1142	<	private static final long runStateOffset =
1143	<	objectFieldOffset("runState", ForkJoinWorkerThread.class);
1144	<	private static final long currentJoinOffset =
1145	<	objectFieldOffset("currentJoin", ForkJoinWorkerThread.class);
1146	<	private static final long currentStealOffset =
1147	<	objectFieldOffset("currentSteal", ForkJoinWorkerThread.class);
1148	<	private static final long qBase =
1149	<	UNSAFE.arrayBaseOffset(ForkJoinTask[].class);
1150	<	private static final long poolRunStateOffset = // to inline CAS
1151	<	objectFieldOffset("runState", ForkJoinPool.class);
1152	<
1153	<	private static final int qShift;
1154	<
1155	<	static {
1156	<	int s = UNSAFE.arrayIndexScale(ForkJoinTask[].class);
1157	<	if ((s & (s-1)) != 0)
1158	<	throw new Error("data type scale not a power of two");
1159	<	qShift = 31 - Integer.numberOfLeadingZeros(s);
1160	<	}
1161	<
1162	<	private static long objectFieldOffset(String field, Class<?> klazz) {
1163	<	try {
1164	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1165	<	} catch (NoSuchFieldException e) {
1166	<	// Convert Exception to corresponding Error
1167	<	NoSuchFieldError error = new NoSuchFieldError(field);
1168	<	error.initCause(e);
1169	<	throw error;
1170	<	}
1171	<	}
1172	<
1173	<	/**
1174	<	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1175	<	* Replace with a simple call to Unsafe.getUnsafe when integrating
1176	<	* into a jdk.
1177	<	*
1178	<	* @return a sun.misc.Unsafe
1179	<	*/
1180	<	private static sun.misc.Unsafe getUnsafe() {
1181	<	try {
1182	<	return sun.misc.Unsafe.getUnsafe();
1183	<	} catch (SecurityException se) {
1184	<	try {
1185	<	return java.security.AccessController.doPrivileged
1186	<	(new java.security
1187	<	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1188	<	public sun.misc.Unsafe run() throws Exception {
1189	<	java.lang.reflect.Field f = sun.misc
1190	<	.Unsafe.class.getDeclaredField("theUnsafe");
1191	<	f.setAccessible(true);
1192	<	return (sun.misc.Unsafe) f.get(null);
1193	<	}});
1194	<	} catch (java.security.PrivilegedActionException e) {
1195	<	throw new RuntimeException("Could not initialize intrinsics",
1196	<	e.getCause());
109	>	onTermination(exception);
110	>	} catch (Throwable ex) {
111	>	if (exception == null)
112	>	exception = ex;
113	>	} finally {
114	>	pool.deregisterWorker(this, exception);
115		}
116		}
117		}
118		}
119	+

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